Automatic shearing method
PATENTEBFIPR 1 5 sum 8 or A/R SOL/FEE Fig E6.  
  AUTOMATIC SI-IEARING METHOD This is a continuation of application Ser. No. 286,898, filed Sept. 7, 1972, which is a division of original application Ser. No. 42,047, filed June 1, 1970, now U.S. Pat. No. 3,691,887 issued Sept. 19, 1972.  
 BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to machine tools, and more particularly to a shearing machine wherein cuts are made simultaneously on intersecting lines to produce a finished blank from a sheet positioned and held by power driven carriage means.  
 2. Description of the Prior Art Conventional metal shearing practice involves a pair of power-driven shears capable of cutting a sheet along a single line at a time. As the sheet is manually or machine fed through the plane of the shears, blanks are cut from the sheet and fall behind the blades.  
  It is quite common for the shear operator, or his assistant, to collect blanks from behind the shear blades and carry them around to the front to be passed through the blades individually for shearing into smaller blanks of the desired size. This procedure involves considerable time and handling, and sometimes involves considerable effort, before the collection of blanks cut to the desired sizes is completed. The present invention is directed toward reduction of time, effort and expense of producing sheared blanks of specified sizes from sheet or plate material.  
  In addition to conventional well known and widely used shears, there are some patents pertaining to various types of notching presses, coupon cutters, and sheet or web cutting equipment. For example, U.S. Pat. Nos. 3,405,583 and 3,446,105 issued to J. H. Herzog, describe notching equipment for use on presses. The Detjen U.S. Pat. No. 1,416,800 describes a device for cutting coupons or tabs from a sheet. The Duenke U.S. Pat. No. 2,897,892 describes adjustable die structure for cutting materials such as those used for transformer core laminations. The Biel U.S. Pat. No. 2,850,090 describes a method for trimming, cutting and cornering folded paper articles. The Bielert U.S. Pat. No. 3,405 ,880 discloses a method and apparatus for punching blanks from relatively wide and long webs of sheet stock, the web normally being stored on reels.  
  Although the aforementioned patents deal with various methods and forms of apparatus for punching or cutting paper or metal materials, none of them is intended for shearing blanks of assorted sizes from metal sheet or plate material. Accordingly, the prior art notwithstanding, there remains a need for equipment capable of economically and accurately shearing metal sheet or plate material into finished blanks of desired sizes.  
 SUMMARY OF THE INVENTION Described briefly, in a typical embodiment of the present invention, the shearing machine has two pairs of shears intersecting at right angles to enable the making of a right-angle cut in sheet or plate stock with a single stroke of the shearing machine. A positioning carriage incorporating sheet grippers energized by a pneumatic tube, is driven by pneumatic cylinders in both the X-axis and Y-axis directions with respect to the shears. Hydraulic means are provided for control of the positioning, as well as appropriate programming means for operating mode selection and predetermination of finished part dimensions. Conveyor means are provided behind the blades for bearing off-fall to appropriate collection stations for the scrap and finished blanks.  
 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration of prior art sheet shearing procedure.  
  FIG. 2 is a diagram of the same type as FIG. 1, but illustrating the shearing according to one embodiment of the present invention.  
  FIG. 3 is a view of a sheet with areas designated thereon in such manner to be virtually impossible to remove by shearing on typical conventional shearing machines.  
  FIG. 4 is a perspective view of a shearing machine according to a typical embodiment of the present invention.  
  FIG. 5 is an enlarged view of the machine taken generally at line 5--5 in FIG. 4.  
  FIG. 6 is a further enlarged section taken at line 66 in FIG. 4 and viewed in the direction of the arrows, showing some details of the grippers, carriage, and X axis and Y axis drive means therefor, portions being broken out as indicated to conserve space in the drawmg.  
  FIG. 7 is a section taken at line 77 in FIG. 6 showing the X axis carriage drive cylinder block, motion multiplier.  
 1 FIG. 8 is a section similar to FIG. 7 but taken at line 88 in FIG. 6.  
  FIG. 9 is a combination pneumatic-hydraulic schematic diagram of the Y-axis drive apparatus and compensating system for the positioning carriage.  
  FIG. 10 is a top plan view of a portion of the righthand ends of the table top slats, with a portion of the top extension broken away to show details of the slat support track and plates and the operating cam therefor.  
  FIG. 11 is a section taken at line 11-11 in FIG. 10 and viewed in the direction of the arrows.  
  FIG. 12 is a schematic view of the lower edges of the upper shear blades, the view being taken in the direction of the arrows 12-12 in FIG. 2 and showing the rake on the blades.  
  FIG. 13 is a schematic diagram of the hydraulic stroke control.  
 FIG. 14 is a block diagram of the operating system.  
  FIG. 15 is a schematic diagram of various actuators and valves for them.  
  FIG. 16 is a schematic plan view of the conveyor shift, and scrap slot arrangement.  
 DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the FIG. 1 representation of prior art, a metal sheet 21 is shown in position for advancement in the direction of the arrow 22 toward a pair of shears 23. Assuming for simplicity, that the sheet is a rectangle, and requires no trimming to square it up, the various areas thereon designated by the letters of the alphabet represent the finished blanks which are desired. These are to be produced by shearing the sheet.  
  The normal procedure in order to obtain the blanks designated is to move the sheet in the direction of arrow 22, stopping and shearing at each of the lines designated by numerals l, 2, 3 and 4. This produces three finished blanks A, B, C, and two additional blanks, all behind the shears in the area 24. The two unfinished blanks must then be carried around to the front of the shears. One of these is passed through the shears in the direction of arrow 22 for shearing along the lines 5 and 6. This produces the finished blanks, D and E behind the blades, and the finished blank F in front of the blades. Then the other blank is passed through the shears in the same direction for shearing along the lines 7, 8 and 9, producing the finished blanks G, H, and I behind the shears, and an unfinished blank in front of the shears. This unfinished blank is then shorn along the line 10 to produce the finished blank J behind the shears, and the finished blank K in front of the shears.  
  The foregoing description of the prior art practice illustrates that even for a comparatively simple arrangement of blanks on a sheet, blanks of finished and unfinished dimensions will be deposited behind the shears, so some bearing of off-fall is necessary to pass blanks of unfinished size through the shears in order to obtain the blanks of the desired size. The present invention overcomes this problem as illustrated in FIG. 2 wherein a pair of shears is provided at 26 and another pair at 27, these being arranged for simultaneous operation to shear on intersecting lines. For purposes of illustration, the sheet is given the same reference numeral 21. However it is inverted so that the order of cuts is somewhat different. However, it will be appreciated that this particular order of cuts described with reference to FIG. 2, is not essential, as they can be made in various other orders.  
  With the carriage means gripping the sheet adjacent the lower marginal edge 28, the X and Y axes drives thereof are able to move the sheet in an X axis direction 22 or 29, and in a Y axis director 31 or 32. With the sheet oriented as shown in FIG. 2, the sheet will be moved as needed to place the sheet portion D within the corner of the two pairs of shears 26 and 27 for shearing the sheet along the lines 1 1, to thereby remove the blank D from the sheet. Then the sheet may be moved in the direction of arrow 31, and stopped for shearing along the lines 12 to remove blank E. Then it is moved again in the direction of arrow 31 for shearing along the line 13 to remove blank F.  
  Then the sheet is moved in the direction of arrow 32 and arrow 22 for shearing blank G away from the sheet along lines 14. Then it is moved in the direction of arrow 32 for shearing blank H from the sheet along the lines 15. Then it is moved again for shearing blank I from the sheet along lines 16. Then it is moved in the direction of arrow 29 and arrow 31 for removing blank K by shearing along line 17. Then it is moved in the direction of arrow 22 for removing blank J by shearing along line 18. Then it is moved in the direction of arrow 22 for removal of blank C by shearing along line 19, and then it is moved once again in the direction of arrow 22 for removal of blank B by shearing along line 20.  
  It should be apparent from the foregoing description, that each blank sheared from the sheet is deposited behind the blades, and the only blank which, in its finished form, remains in front, is the last one. Moreover, all blanks which fall behind the shears are of finished size.  
  It will be recognized from the foregoing description, that as a practical matter it will likely be necessary to allow a gripping margin of about inch along the lower edge of the sheet, or to shift the grippers along the sheet as certain portions are removed from the right-hand end thereof, such as the blanks F, K, J, C and B. Means for accomplishing this will be described hereinafter.  
  Referring now to FIG. 3, wherein each of the blanks on sheet 33 is given a prime sign, brief consideration will make it apparent that only blank A can be removed by the prior art practice described above. There is no easy way to remove the rest of the blanks from the sheet with conventional power driven shears. Nevertheless, the particular arrangement illustrated may be the most satisfactory arrangement consistent with optimum usage of the area of material available for the collection of blanks needed. Further consideration in view of the present invention will make it apparent that the blanking from a sheet arranged as shown in FIG. 3 can be accomplished readily.  
  Referring now to FIG. 4, illustrating a typical embodiment of the present invention, the machine includes a positioning support table including a slide top portion 34 and slatted top portion 35, the latter being partially rolled down under a positioning support carriage, this carriage having an extemal housing 36 disposed below the level of the top surfaces of the table. The carriage has a plurality of sheet grippers 38 spaced along the marginal edge 28 of the sheet 21 supported on the table top.  
  Left and right gap frame members 39 and 41 with cross members 40 and 84 affixed between them, (FIG. 5) are provided to support a ram on which the upper blades 26U and 27U of the shears 26 and 27 are mounted at right angles. A holddown assembly 42 is mounted to the left-hand frame member 39 by a hinge assembly 43, and has a plurality of holddown feet 44 spaced therealong immediately in front of upper shear 26U and immediately to the left of upper shear 27U.  
  There is a torsion bar 46 mounted in bearings in the frame members 39 and 41. Near each end of the torsion bar 46, an equalizer torque arm 47 is affixed to the bar, (only one of these being visible in FIG. 4) and it has a pivotal connection at 48 to the piston rod 49 of a power stroke control hydraulic cylinder 51, trunnion mounted to the ram housing top cross member 40 to permit limited pivoting on the trunnions at 52. The equalizer arm also has a pivotal connection at 53 to a bar 54 extending down to a pivotal connection at with ram cross member 86 (FIG. 5).  
  As shown on the left hand side of the gap frame member 39, in FIG. 4, a handle 56 is provided on a plate 57 pivotally mounted in the member 39 and having a ram pivot shaft (79 in FIG. 5) eccentrically mounted thereon. The plate has the slots 58 therein and cap screws 59 passing through each slot, whereby the position of the plate can be affixed to determine the eccentric position desired for the ram pivot shaft.  
  Endless belt conveyor 61 extends out to the right from behind the blades 26 and 27, to convey completed blanks in the direction of arrow 63.  
  A control console 64 is provided at any desired convenient location adjacent to the machine, and may include a tape reader 66 therein, with program tape passing therethrough at 67. The operators control panel 68 contains a plurality of switches and indicators which will be described hereinafter. The positioning carriage housing 36 may also have indicators thereon, but more likely it will merely have a cycle start button 69, a gripper clamping button 71, and a gripper unclamping button 72.  
  To provide Y axis motions of the carriage in the direction of arrows 31 and 32, y axis drive means are provided in housings 73A, 73B, and 73C. The housing 36 is supported on three pedestals, one extending up from each of the drive means in housings 73 through accordian type bearing way covers 74 atop the housings. The X axis motions in the directions of the arrows 29 and 22 are effected by drive means within the housing 36 as will become apparent as the description proceeds.  
  Referring now to FIG. 5, the left-hand gap frame member 39 is omitted as are the Y axis drive units in housings 73A and 73B, and the left-hand wall of a lefthand table slot track, in order to show interior details of the ram, holddown assembly, and to show the conveyor location and the slat end assembly. The ram 76 has a pair of support arms, the left-hand arm 77 and right hand arm 78 (FIG. 4) being mounted on the pivot shaft 79, the left-hand end of which is affixed to the plate 57 (FIG. 4) previously described, whereby the shaft can be moved from the position shown in the solid outline in FIG. 5 to the position shown in the dotted outline 80 in FIG. 5 by appropriate adjustment of the arm 56 in FIG. 4. The right-hand end of shaft 79 may be supported in like manner. Gibs are provided at the left-and right-hand sides of the ram, near the front, and about half-way between the front and the pivot axis. The right-hand gibs are shown at 81 and 82 in FIGS. 4 and 5. A pneumatic bag 83 may be provided between an upper support frame 84 therefor and the ram cross member 86. Ram return springs are provided such as at 80, encircling the piston rod projecting from the rear of cylinder 51, and retained between the cylinder end and the seat plate 85 bolted in the rear end of the piston rod.  
  A front cross member 87 is provided across the front of the gap frame members 39 and 41 and affixed thereto. The front cross member 88 of the ram is disposed immediately behind it. The front portion of the holddown assembly is immediately in front of it and includes a top plate 91, a pneumatic actuator tube 92, each holddown foot 44, holddown foot guides 93 and guide pins 94, and return springs 96 between the side guide plates 93 and the lower face of the holddown foot headplate 97. These holddown feet are disposed immediately above the lower front shear blade, shown at 26L, the lower side shear blade being omitted from FIG. 5 in order to permit showing the conveyor 61.  
  In order that the handling of stock while loading it onto the machine be unimpeded by superstructure, the housing 36 is, for the most part, below the level of the cutting edge of the lower shear blades 26L and 27L. To permit the housing, thus depressed, to move inward in the direction of arrow 31, the slats 35A are linked together by links as at 45, and the first slat 50 is pinned to the machine frame at 50A. The same pins that serve to connect links to the slats, have rollers on the ends thereof as at 45A. These rollers, at the left-hand ends of the slats are received and supported in track 55 which is affixed to the carriage housing 36 as by brackets 55A and 55B (FIG. 5). The underside of the front end portion of the track can be supported by roller 60 mounted to the machine frame and supporting the track adjacent the plane of the shears 26 as the track moves in and out in the direction of arrows 31 and 32 respectively with the carriage housing.  
  The track support rollers 45A at the right-hand (FIGS. 11 and 12) ends of the slats are normally supported on a series of plates mounted on vertical pivot shafts 452 which may be fixed in the table top 351 with their upper ends flush with the upper face thereof and projecting downwardly from the underside thereof. These plates are normally urged in the counterclockwise direction by springs 452 and rest against stops in the normal supporting position as at 453. However, these plates are pivotal in the clockwise direction by cam 454 to a position such as at 456 and 457.  
  Cam 454 has a leading edge 458 on a portion extending from the lower surface of a track 553 mounted to plate 101 in the same manner as track 55 as shown in FIG. 5. However, track 553 differs from track 55 in that it terminates at a point 554 about in line with the forward edges of the gripping fingers, to avoid entering the plane of the shears 26 as the carriage moves toward the shears 26.  
  With the left and right-hand rollers thus supported, as the carriage housing 36 is driven toward the shears 26, the track 55 moves in unison with the carriage. As the downwardly curved portion of the track encounters successive slat support rollers, it permits the rollers (and thereby the slats) to descend. At the right-hand end of the slats, as the front end 554 of the track 553 approaches the support rollers, the cam face 458 pushes the support plates 453 out of the way as at 456 and the top of the cam leads the track 553 into rolling supporting engagement with the roller. As the cam passes each support plate, the return spring will return it to initial position. The rear face 459 of the cam will ease the plates back out of the way as the carriage retracts.  
  As the tracks move in toward the shears, and the slat support rollers are deposited out the ends 55C of the tracks, the slats may rest on rails secured to and projecting parallel to the housings 73. As the tracks move out with the carriage housing, they lift the slats and restore them to their original table top forming level.  
  Referring now to FIG. 6, the positioning carriage includes the upper housing 36 affixed to plates 101 of the three Y axis drive units. Each plate 101 is mounted for movement in the Y axis sense in the direction of arrows 31 and 32 on a pair of horizontally spaced rods 102. Ball bushings or other appropriate bearing means in blocks. 103 may be provided for low friction traversal. The ends of bars 102 are received in and affixed to end plates such as shown at 105A and 1058 in FIGS. 4 and 5.  
  The carriage housing 36 encloses the gripper carriage 104 including upper and lower bearing mounts 106 and 107, each having suitable bearings to run on the upper and lower guide rails 108 and 109 respectively of the carriage housing. Ball bushings may be employed in this instance also, for low-friction movement of the gripper carriage 104 in the X axis sense of arrows 22 and 29 of FIG. 4.  
  The sheet grippers 38 include the upper fingers 111 affixed to the carriage, and the lower fingers 112 pivotably mounted to the upper fingers at pins 114. An elongated pneumatic actuator tube 116 is mounted on the lower finger plates 117 and is disposed under the upper finger plates 113. Inflation thereof serves to close the fingers on the edge of the sheet 21 to be sheared.  
  To drive the carriage 104 in the X direction, a cylinder block 118 is employed, (FIGS. 6 and 7), this block having a pair of cylinders therein, side-by-side, with piston rods 119 and 119A extending out from the left and right ends, respectively, of the one cylinder, and the piston rods 121 and 121A extending out from the left and right ends, respectively, of the other cylinder. This cylinder block has one pulley 122 on the bottom wall thereof, and another pulley 123 on the top wall thereof, each being mounted for rotation on an axis perpendicular to the plane of the piston rods and each having a chain passing therearound. In the case of the chain 126 on the pulley 122, one end thereof is affixed to a block 124 connected by adjusting screw 124A to end plate 125 of the carriage housing (FIG. 7). The other end of the chain 126 is connected to an inwardly projecting arm 127 of the carriage 104 at 127A. Piston rods 119a and 121A are received in and affixed with respect to manifold block 125A affixed to the wall 125, while rods 119 and 121 are received in and affixed with respect to manifold block 128A affixed to the end plate 128.  
  As shown in FIG. 8, the pulley 123 has the chain 120 thereon, with one end thereof connected to the block 131 fastened by adjusting screw 131A to end plate 128. The other end of chain 130 is connected to the arm 132 of the carriage 104. By providing this chain and pulley arrangement, travel multiplication is obtained so that, because of pulley 122 and chain 126, a given increment of travel of the cylinder block 118 in the direction of arrow 29, will result in travel of the carriage 104 in the same direction twice the distance. Similarly, in FIG. 8, travel of the cylinder block 118 a given increment in the direction of arrow 22, will result in travel of the carriage a distance twice as great.  
  Because of the travel multiplication feature employed with the cylinder block 118, it is not necessary that the piston rods extend the entire length from one end 124 to the other end 128 of the housing, if it is found desirable to use some other structural members at a lesser spacing. At this point it might also be mentioned that the piston rods 119 and 119A are colinear and extend in opposite directions from a single piston in one cylinder in the housing, this cylinder containing hydraulic fluid or oil. Similarly, piston rods 121 and 121A extend in opposite directions from a piston in the other cylinder in the block, this cylinder being divided into two chambers by the piston, these chambers being pressurized with air. Further details and the operation of such structure is described hereinafter.  
  It will become apparent as the description proceeds, that for automatic operation it is essential to know the extent of linear travel of the carriage, both in the X axis and in the Y axis directions. The X axis travel may be detected by a rotary encoder 133 mounted over the cylinder block 118. This encoder has a cylindrical encoder wheel 134 projecting therefrom and having its circumference engaging the longitudinally extending bar 136 projecting up from and affixed to the cylinder block 118. The encoder is pivoted at 137 and a compression spring 138 between the encoder and the carriage housing continuously urges the encoder wheel against the track 136 so that, as linear motion takes place in the X axis direction, the extent of travel will be precisely transmitted into the encoder by the rolling of the wheel 134 on the track 136. While pinion teeth on the wheel, and rack teeth on the bar 136 could be employed, or pins and holes or some similar positive displacement arrangement, such details have been found unnecessary for proper precise and accurate operation of rotary encoders.  
  Referring now to FIGS. 4 and 6, the Y axis drive apparatus for the positioning carriage is shown. End plates A and 1058 serve to support the opposite ends of the bearing rods 102. Each of the rods 102, supports the bearing housings 103, each of which is affixed to the bar 101 which extends the length of the housing 36 and to which the housing is affixed. The Y axis drive is provided by essentially the same type of apparatus as described above for the X axis drive. It includes the cylinder block 142 coupled to the housing through travel multiplying chain and sprocket means of the type described above, and which need not be described in detail at this point. Such an arrangement is provided for each of the units 73 of FIG. 4. The cylinder block 142 is mounted on piston rods 144A, 144B, 146A and 146B, each of the rods 144A and 146A having one end affixed to the member 105A, and each of the rods 144B and 1463 having one end affixed to the cross member 1058. The other end of each of the rods is connected to a piston as will be described hereinafter, one piston for the rods 144A and 1443 and another piston for the rods 146A and 146B, these pistons being disposed in a pair of cylinders in the block 142.  
  In a manner much like that described above with reference to FIGS. 6 and 8, cylinder block 142 has a rotary encoder 149 pivotally mounted thereto on a hinge axis 151 and having an encoder wheel 152 extending therefrom and rotatable on the axis 153. The circumferential surface of this encoder wheel rides on the top surface 154 of a rail extending from one end of the cylinder block to the opposite end thereof, and a spring may be employed at 156 to urge the wheel continuously into engagement with the surface 154 so that the linear travel of the cylinder block 142 is reliably detected. Each encoder may be arranged to complete one revolution during one inch of travel of the carriage, and produce 1,000 pulses per revolution. It should produce two output signals in quadrature so that direction may be determined. Other outputs may also be provided.  
  Referring now to the schematic pneumatic and hydraulic diagram of the Y axis drive cylinders in FIG. 9, cylinder block 142 has a pair of cylinders, the first cylinder being divided into two chambers 157A and 157B by a piston 158. This piston is connected to the piston rods 146A and 146B affixed to end plates 105A and.  
 105B, respectively. The second cylinder in the cylinder block 142 is divided into the chambers 159a and 1598 by the piston 161. This piston is mounted to the rods 144A and 1448 affixed to the end plates 105A and 1058, respectively. A cam assembly 162 is mounted to the cylinder block 142 and has a ramp surface 163 engaged by follower roller 164 on a piston rod 166 in a compensating cylinder 167 which is affixed to a portion of the Y axis drive housing 73A. Of course, the housing 73A is affixed with respect to the end plates 105A and 1058. A cam ramp inclination adjusting screw 162A is provided for a purpose to be described hereinafter.  
  Cylinder block 143 of the Y axis drive unit 738, has a cylinder therein with piston 168 dividing the cylinder into chambers 169A and 1693. Piston rods 148A and 1488 are affixed to the respective end plates for this drive unit, just as the corresponding piston rods were connected to the end plates for the drive unit 73A. Similarly, the other cylinder in cylinder block 143 is divided by the piston 171 into the chambers 172A and 1728. Piston rods 147A and 1478, connected to the piston 171, are affixed respectively to the opposite end plates of the unit. Cylinder block 143 is provided with a cam assembly 173 thereon, having a ramp surface 174 of inclination determined by the setting of adjustment screw 173A. Follower roller 176 engages the ramp surface and is connected to the follower piston shaft 177 connected to a piston in the compensating cylinder 178 affixed to the housing 73B.  
  Cylinder block 196 has a pair of cylinders therein, the first being divided into chambers 197A and 1978 by the piston 197. Piston rods 198A and 1988 are connected to the piston and are affixed to end plates at the opposite ends of the drive unit. The second cylinder is divided into chambers 199A and 199B by the piston 199. Piston rods 201A and 201B are connected to the piston and their opposite ends are affixed to the opposite end plates of the drive unit. A cam assembly 202 includes the ramp 203 and adjusting screw 202A. A follower roller 204 engages the ramp surface and is connected to a shaft 206 which is in turn connected to a piston in the compensating cylinder 207 affixed to the drive unit housing 73C.  
  A source of air is indicated at 179 and may be a shop supply at 90 pounds per square inch (p.s.i.) for example. A three position solenoid-operated valve 181 is connected between the air source 179 and the chambers of the first cylinder of each of the three cylinder blocks. Accordingly, line pressure is normally applied through valve 181 to the chambers 157A, 157B, 169A, 1698, 197A, and 1978.  
  An accumulator is provided at 182 and, by means of the one-way check valves 183, 184, and 208, is able to maintain a full condition of hydraulic fluid (typically oil) in hydraulic lines 186, 209, and 211. Line 186 normally communicates with hydraulic chambers 1598 and 172A. Line 209 normally communicates with chamber 172B and 199A. Line 211 normally communicates with chamber 1998 and is communicable with chamber 159A. Oil control solenoid valves S05, S06 and S07 are provided in line 211 for motion control and lock-up, and will be described. Solenoid operated oil valves S08 and S010 are provided for balancing, as will become apparent. A manually-operated normallyopen valve 192 is provided between the compensating cylinder 167 and the line 186. The pressure relief valve is provided at 193 between the line 186 and the accumulator, enabling return of hydraulic fluid to the accumulator in the event of rise of pressure in line 186 over the setting of the relief valve.  
  In operation, in order to drive the X carriage 36 in the Y axis direction of arrow 31 toward the shear, it is necessary to vent air chambers 157B, 1698, and 1973. It is also necessary to permit departure of oil from the hydraulic cylinder chambers 159B, 172B and 1998, and admit oil to cylinder chambers 159A, 172A and 199A. Then the cylinder blocks can move in the direction of arrow 31. For uniformity of operation it is necessary that all three cylinder blocks move in like manner. In order to achieve the venting of the air chambers, while applying pressure to the others, solenoid valve assembly 181 is shifted in the direction of arrow 32, activating the SA3 portion thereof in the circuit. In order to permit departure of oil from hydraulic chamber 1998 and admission of oil to hydraulic chamber 159A, solenoid valves S05, S06, and S07 may be shifted to provide communication between these chambers. In the illustrated embodiment, chamber 159B is constantly in communication with chamber 172A, permitting the shuttling of oil between these two chambers as needed. Similarly, hydraulic chamber 1728 is constantly in communication with hydraulic cylinder chamber 199A through the line 209, permitting the shuttling of oil back and forth between these chambers as needed. It is possible, however, to incorporate solenoid valves between the respective chambers in the lines 186 and 209, matching valves S05, S06 and S07 in line 211 if this desired for equalization of pressure rise, flow restriction, and temperature effects in the three lines, or for any other desired reason. Accordingly, with the appropriate air chambers supplied by line pressure, and the appropriate communication between the hydraulic chambers of the respective hydraulic cylinders, the three cylinder blocks move simultaneously in the direction of arrow 31, driving the X carriage 36 in the same direction at twice the speed and distance due to the travel multiplying chain and pulley structure incorporated in the Y axis drive units.  
  As the carriage travel approaches the desired termination point, valve S05 can be closed, permitting hydraulic communication between chambers 1998 and 159A only through valves S06 and S07, thus slowing the speed of travel materially. At a further point in travel, valve S06 is closed, whereupon the speed is further reduced to a creep rate. At a further point, valve S07 is closed and cylinder travel is terminated due to the hydraulic lock-up thus achieved. This sequence of speed, fast, slow and creep, is used whenever distances to be moved are significant. For lesser distances, it may be that valve S05 would not be activated, whereupon only the slow and creep speeds would be used. If desired the capacity of the valves would differ, or orifices could be used in lines associated with them, as needed, to obtain the flow rates needed for the speeds desired with the various valves activated.  
  In order to drive the X carriage outward in the direction of arrow 32, the three cylinder blocks must be driven in the same direction. For this purpose, the solenoid valve 181 is shifted from its spring-centered position, in the direction of arrow 31, to activate the SA4 portion and thereupon exhaust the air cylinder chambers 157A, 169A, and 197A. Then upon opening the solenoid valvesSOS, S06, and S07, oil can leave chamber 159A and enter chamber 1998. Oil can shuttle from chamber 172A through line 186 to chamber 159B. Similarly, oil can shuttle from chamber 199A through line 209 to chamber 1728. At a point near the desired travel termination point, valve S05 will be closed to reduce the speed. At a further point valve S06 will be closed to reduce the speed to a creep, subsequent to which valve S07 will be closed to terminate travel. Thereupon solenoid valve 181 will be allowed to return to center to balance the pressure on both sides of the air pistons.  
  Accumulator 182 can be pressurized to the extent needed to adequately pressurize the hydraulic circuits and compress the air trapped therein, thus causing the system to be stiffer when everything is at rest, than might otherwise be possible. If any oil leakage occurs, the accumulator can provide make-up oil continuously.  
  The accumulator 182 is also useful for balancing. This can be accomplished by applying the air pressure to one side of the piston in all three air cylinders, to drive the cylinders against the stops therefor. Then the solenoid valves S08 and S010 are opened momentarily, while one or all of the valves S05, S06, and S07 are open. This enables the necessary communication throughout the hydraulic lines to enable all cylinders to fully engage their stops, such as end plates or other suitable stop means. At this time, oil can move from the accumulator as needed to provide a completely filled condition in all lines and cylinders. Then the valves S05, S06, S07, S08, and S010 are closed, and normal operation can be resumed. Such balancing can occur within seconds.  
  For precise synchronizm of time and distance of movement of the three cylinder blocks to obtain the precise linear positioning desired, the three oil cylinders must normally have exactly the same bore size and shape. As a practical matter, this cannot be accomplished through conventional manufacturing techniques, so I have provided a self-compensating feature. Assuming the diameter of the oil cylinders in blocks 142 and 143 is smaller than the diameter of the oil cylinder in block 196, if the cylinders are driven in the direction of arrow 31, there will not be sufficient oil dis played from hydraulic cylinder chamber 1728 to fill the chamber 199A at a rate sufficient to establish equal distances of travel of the two cylinder blocks. To compensate, the inclined plane 174 of the cam assembly 173 is adjusted by the screw 173A to incline upwardly to the right. Therefore, as the cylinder block 143 moves to the left, the follower roller 176 drives the piston upwardly and displaces oil from the compensating cylinder 178 into the line 209 at a rate compensating for the difference between volumes displaced in chambers 172B and 199A during an equal amount of travel of the two cylinder blocks 143 and 196.  
  At the same time as compensating cylinder 178 is furnishing make-up oil to chamber 199A, a greater amount of oil is being expelled from chamber 1998 than can be accepted in chamber 159A of the first cylinder block 142 during a given distance of travel. Therefore, the adjusting screw 202A of the cam assembly 202 is set to establish an incline downward and to the right in the ramp 203 thereof. As the cylinder block 196 moves to the left, the follower roller 204 decends the ramp, withdrawing the piston in the compensating cylinder 207 to admit that amount of oil from chamber 199B which exceeds that which can be accepted in chamber 159A.  
  A compensating cylinder and cam assembly 162 is provided in association with cylinder block 142 and, by appropriate adjustment of each of the three assemblies, depending upon the size relationships between the hydraulic cylinders of the three cylinder blocks, precise tracking of the cylinder blocks can be accomplished. It should be understood that variation in location and arrangements of the cams and compensating cylinders can be made, depending upon size and space requirements and convenience of use. For example, all three cams and associated compensating cylinders can be incorporated in one of the three drive units, with appropriate hydraulic connections as needed.  
  Referring now to FIG. 12, there is illustrated schematically a significant feature of the present invention. As indicated in FIG. 2, the direction in which the shear is viewed to produce FIG. 12, is along a line bisecting the degree angle between the blades of the shear. Although it will be observed that the upper edges of the lower shears 26L and 27L are co-planar, the lower edges of the upper shear blades have an upward rake, which is continuous from the righthand end corner 26R to the intersection of the blades and then to the lefthand end corner 27? of the blade 27U. This makes it possible to shear along the lower edge of the blade 26U throughout its length (56 inches, for example) without engagement of the blade 27U with the stock. Then, if desired, the stock can be shifted along the length of the blade 26U, followed by another closure, so that this nibbling approach, cutting only along the X axis, a cut longer than the length of the blade 26U can be achieved, before a cross cut by blades 27U and 27L is performed.  
  Referring now to FIG. 13, the ram stroke control cylinder 51 is shown with the piston thereof dividing it into two chambers. A hydraulic path between the two chambers is provided by means of the line 216 having a pair of adjustable orifices 217 and 218 therein, and a normally closed solenoid valve S09 therein. An accumulator 221 is associated with the line to maintain a complete fill of hydraulic fluid at all times under pressure. It should be understood that the adjustable orifices are such that one of them is useful to restrict flow in one direction, and the other is useful to restrict flow in the other direction. In this manner, the force required to move the piston in one direction can be different from that required in the other direction. The solenoid valve S09 provides means for easy and accurate control of the ram. When it is closed as it normally is, the ram is locked, so that it can move neither up nor down from the position in which it is disposed when the valve S09 is closed. Check valve 220 prevents flow from the cylinder into the accumulator.  
  Referring now to FIG. 14, there is shown a general block diagram of the control apparatus. It includes the tape reader 66, the manual control block 226, and the interlock and alarm block 227. In addition, there are the X-axis rotary encoder 133, and the Y-axis rotary encoder 149. Manually operated, mode determining switches for the controller and shear are provided in the block 226. Situation indication signals are provided to the controller by the pressure switches and limit switches through the interlock and alarm block 227.  
  The X axis position display is at 228 and the Y axis position display is at 229, Nixie tubes or other indicator means being provided for this purpose. Code converters are provided at 231 and 232 for the inputs from the rotary encoders and provide outputs respectively to the binary comparators 233 and 234 which may have 17 bit capacity each. Other inputs to the binary comparators are derived from the X axis and Y axis position control blocks 236 and 237, respectively, which have inputs from the binary adder and control block 238, the inputs of which are derived from the part size X axis dimension thumbwheel switches in block 239 and the part size Y axis dimension thumbwheel switches in block 241, both of which typically have a capacity for five decimal digits. Another input from the machine constants block 242 is also provided. The reference dimension for the X axis is provided by thumbwheel switches in block 243, and the reference dimension for the Y axis is provided by thumbwheel switches in block 244 coupled respectively to the X and Y position controls 236 and 237. The binary comparators provide outputs to the speed control drivers in block 247 and 248 for the X axis and Y axis carriage drive speed control valve solenoids respectively. The drives from the controller 246 to the other valve solenoids are represented in block 249.  
 OPERATION A. Operation in the Automatic Mode The program tape 67 is loaded into the reader 66. The selector switch 252 is placed in the Auto position. The shear mode selector switch 253 for the shear is placed in the Auto position. The reset button 254 is pushed. The manual mutiple cut switch 256 is turned off.  
  The stock to be sheared is manually placed within the jaws of the grippers and, before the grippers are closed, the stock is manually pulled against the lowered endlocator gauge 251. Clamp button 71 is pressed to energize solenoid valve SA to cause inflation of the pneumatic tube 116, whereupon the grippers clamp the stock and pressure switch PS1 is closed. The endlocator gauge is then raised to space it from the end of the stock and operate limit switch LS1.  
  Then the cycle start button 257 is pushed, whereupon the Nixie tube sets 258 and 259 display the position of the carriage in the X axis and Y axis directions, respectively. The tape reader advances the tape to the information block containing the data for the first cut, and reads it. The carriages fully retract. Then the controller calculates the direction of carriage motion and the initial carriage speed needed, based on the distance to be moved. This causes activation of the appropriate direction control solenoid drivers in block 249 (FIG. 14) and the appropriate speed control solenoid drivers in blocks 247 and 248 (FIG. 14). The carriages are thereby moved toward the coordinates dictated by the program tape. The rotary encoders feed to the comparators the travel information and, as the desired point is approached, the comparator outputs will begin the speed control sequence to slow, creep and halt travel. Speed constants for valve selection may be predetermined by programmable circuit boards with, for example, four digits for fast speed, three digits for slow speed, and two digits for creep.  
  Once the carriages are properly positioned, the control activates a driver in block 249 for air solenoid valve SA6 to inflate the holddown tube 92 and clamp the sheet at the shears. Inflation of the holddown tube 92 will close pressure switch PS2, activating air solenoid valve SA7 to inflate the ram bellows 83, and activating oil solenoid valve S09 in the hydraulic stroke control circuit, whereupon the ram is driven downward.  
  Descent of the ram will close limit switch LS4 at half stroke, and will close limit switch LS3 at full stroke. Closure of one or the other of these switches, depending upon the mode dictated by the tape, will deenergize air solenoid valve SA7, whereupon the ram bellows will be vented and the springs will retract the ram. When the ram reaches the top of the return stroke, it closes limit switch LS2, causing deenergization of the oil solenoid valve S09 to lock-up the stroke control, and de-energization of the air solenoid valve SA6 to release the holddowns.  
  The closure of pressure switch PS2, or some other event associated with actuation of the ram can be used to restart to program tape and move it to the next data block for reading data for the next cut by the shears. The sequence of events will be repeated for each cut to be made, and will terminate upon reading an end of program character on the tape. A visual display designating the block of data being read, can be provided.  
 B. Operation In the Manual Multiple Cut Mode In this mode, multiple parts of the same size are cut automatically, following initial manual establishment of dimensions. The controller mode switch 252 is placed in the manual position. The manual multiple cut switch 256 is turned on. The shear mode switch 253 is turned to manual. Six thumbwheel switches in the X group 243 and five thumbwheel switches in the Y group 244 are used to dial in reference decimal dimensions corresponding to the size of the sheet stock to be used. Two sets of thumbwheel switches 263 and 264 are used to dial in the number of cuts (up to a maximum of 99) to be made on the X and Y axes, respectively. Switch 266 is moved to the X first or Y first position, depending upon whether the cuts are to be made on the X axis first or on the Y axes first. The five part size thumbwheel switches in the X group 239 and the five in the Y group 241 are positioned to define the size of the parts to be out. Then the cycle start button 257 is pressed.  
  The first cut will produce the part nearest the reference corner on the stock (farthest from the end gauge 251). The next cut will be made with movement occurring only on the X axis of Y axis, depending on the position of the switch 266. After cuts are made on the first designated axis according to the number established by switches 263 or 264, the carriages will retract to the reference corner, advance one part size increment on the other axis, and begin the next succession of cuts on the first axis. This process continues until all parts designated by the number-of-cut switches 263 and 264 have been cut.  
  The program tape may be eight level one inch tape punches with EIA RS-244-A code. It will contain a start of program character to clear the block counter and prepare the controller for receipt of information. The next character will be a start of information block which is followed by twelve information characters, followed by an end of block character. An example of the significance of character in a block is as follows:  
  Any characters inserted between blocks of information, i.e., between end of block and start of block will not be recognized. Therefore information such as block number may be inserted between blocks. Any delete characters that appear in the block information will be ignored and not counted as part of the information.  
 Therefore if any error is made in preparing the tape only the errored character need be changed to a delete character. The entire tape or block of information need not be destroyed.  
  The auxiliary function character may be used to cause any one of the following functions to take place:  
 a. full cut-causes the shear to make a full stroke, cutting on both the X axis and Y axis, and closing limit switch LS3.  
 b. half cutcauses the shear to make a stroke only to its mid-position as terminated by closure of limit switch LS4, to cut only on the X axis for a slitting (nibbling) effect.  
 c. gripper shift start-causes the carriages to move to the position specified in the data block, whereupon the hold-downs clamp the part and the grippers release. The shear does not function. The completion of the gripper shift function can be accomplished in the next information block.  
 (I. gripper shift finish-causes the carriages to move to the location where the grippers are to regrip the stock, anad the hold-downs then unclamp. The shear does not function.  
 e. scrapenergizes solenoid SA8 to move conveyor 61 aside and open the scrap door 262 (FIG. 15) as the shearing is done.  
  Obviously there are limit switches and interlocks, error signals and alarms as desired to prevent damage and for the safety of the operator, but a large variety of choices and possibilities exist in this area and need not be described here.  
  A trim function can be provided. For this purpose a trim switch 261 is turned on. In the following description, it should be understood to be an example where the X axis shear is 56 inches long, and the Y axis shear is 50 inches long. If the trim function is turned on, the first movement of the machine will be to a position so that the stock sheet of metal can be trimmed to the demensions given by the reference thumbwheels. It may be necessary to trim in more than one stroke along each axis. This will automatically be determined by the reference dimensions dialed into the thumbwheels. Any X dimension greater than 52 inches but less than 105 inches, will require two cuts along the X axis for trimming. The first cut will be made at X equals 48 inches and Y equals reference and the second cut will be made at a point past X equals zero, Y equals reference. In the case of the X dimension being greater than 105 inches, the X trim must take place in three strokes.  
 The first cut will occur at X equal 96 inches, Y equals reference and the second cut will occur at X equals 48 inches, Y equals reference. The final X trim cut would occur at X equals zero, Y equals reference.  
  For any Y dimension greater than 49 inches, trim must occur in two cuts. The first cut would occur at X equals reference, Y equals 48 inches. The second cut will occur at X equals reference, Y equals 0.750 inches. No more than two cuts for Y trim are permissible. All cuts during trim are full strokes. If the trim cut is turned off the shearing will occur as described above. The scrap slot will be automatically opened during trimming. After trimming the machine will move to the first cut to be made which will be that piece nearest the reference corner.  
  The above described trim function implemented by moving the trim switch 261 to on position, is available only in the manual multiple cut mode. Any trimming operations needed in the automatic mode must be provided by suitable instructions on the tape. Appropriate interlocks may be provided to disable the manual trim function in the automatic mode.  
  Referring to FIG. 16, the scrap slot is an L-shaped slot 268 immediately behind the blades 26L and 27L and produced by moving the conveyor assembly 61 in the direction of arrow 269 from the position in solid outline to the position in dotted outline so that there is an L-shaped space between a vertical projection of the blades and a vertical projection of the margins of said conveyor belt as indicated at 268 in FIG. 16. Air cylinder 271, when activated, by solenoid valve 8A8, serves this purpose. In this manner trim strips may fall through the slot and be directed by a door 262 or other means into a bin or scrap conveyor. As an alternative, the door may be deleted altogether. Y  
  A shear jog pushbutton 267 is provided. When th shear mode selector switch 253 is in the off or manual position the controller is disabled from affecting shear operation. Pushing the jog button opens the solenoid $09 as long as the button is depressed, so that the ram descends if air solenoid SA7 is energized. This solenoid SA7 normally is energized when the shear mode switch is in manual position.  
 The invention claimed is:  
  l. A method of power shearing comprising the steps of:  
 gripping a portion of a member to be sheared;  
 moving the gripped portion toward a pair of power operated shears and stopping movement at a location of the gripped portion remote from said shears, thereby placing another portion of the member in position for shearing by said shears; and shearing said member on intersecting lines while holding said member in one position, beginning the shearing at one edge of the member and continuing along one of said lines to a point of intersection of the lines, and continuing the shearing from said point along the other of said lines to another edge of said member, thereby removing a corner blank from said member at a location thereon remote from the gripped portion.  
 2. The method of claim 1 and further comprising the steps of:  
 moving the gripped portion toward the shears in a sequence of steps, and shearing said member on intersecting lines at each step in the sequence,  
 thereby shearing another corner blank from said member at each step in the sequence, to remove from said member successive blanks of finished size;  
 pre-programming the sequence of steps to remove blanks of various desired sizes;  
 and power driving the gripped portion toward the shears automatically according to the programmed sequence.  
 3. The method of claim 2 and further comprising the step of:  
 power driving two pairs of shears simultaneously and automatically during each of said steps in the sequence to thereby shear along the intersecting lines during each step.  
 4. The method of claim 2 wherein:  
 the shearing is performed along different percentages of the length of the shears at certain different steps of said sequence to remove blanks of different sizes. 5. The method of claim 1 and further comprising the step of:  
 producing a notch in said member by shearing a corner therefrom. 6. The method of claim 5 and further comprising the steps of:  
  successively moving said member and closing said shears, and thereby extending and enlarging said notch. 7. The method of claim 1 and further comprising the steps of:  
 moving the gripped portion toward the shears in a sequence of steps, and shearing said member on intersecting lines at each step in the sequence, thereby shearing another corner blank from said member at each step in the sequence, to remove from said member successive blanks of finished size. 8. The method of claim 7 and further comprising the steps of:  
  depositing said blanks behind said shears. 9. The method of claim 8 and further comprising the steps of:  
 conveying said blanks away from the vicinity of said shears. 10. The method of claim 1 and further comprising the steps of:  
  clamping said member alongside both lines outside the corner during the shearing of said member. 11. The method of claim 1 and further comprising the step of:  
  clamping said member in front of the shears along a second pair of intersecting lines adjacent and in front of the intersecting lines of shearing, during the shearing of said member. 12. The method of claim 1 wherein the step of shearing on intersecting lines comprises:  
 first contacting said one edge with the cutting edge of a movable blade of the pair of shears while supporting the member with the cutting edge of the other blade of the pair and then closing the movable blade with the other blade to commence a cut of said member at said one edge and progressively extend the cut of said member along the one of the lines to said point, and then contact the member at said point with the cutting edge of a movable blade of a second pair of shears while supporting the member with the cutting edge of the other blade of the second pair of shears and closing the movable blade of the second pair with the other blade of the second pair to commence a second cut of said member at said point and progressively extend said second out along the other of said lines to said another edge, to sever the blank from the member. 13. The method of claim 12 wherein: the contacting and closing to out along the one line, and the contacting and closing to out along the other line are done during one continuous movement of the movable blades. 14. A method of power shearing comprising the steps of:  
 gripping a member to be sheared, at first locations along a line parallel to a first pair of shears; successively partially closing on said member a first pair of power operated shears and then opening said first pair and then moving said member longitudinally of said first pair between said closures thereof, to shear said member along a first line of greater length than the length of said shears;  
 and then completely closing on said member said first pair of shears, and simultaneously therewith closing on said member a second pair of shears along a line intersecting said first line, to thereupon shear from said member a blank having at least one dimension exceeding the length of said first pair of shears.  
  15. The method of claim 14 and further comprising the step of:  
 clamping said member adjacent said first pair of shears while gripping said member at said first locations, and while shearing said member.  
  16. The method of claim 15 and further comprising the step of:  
 ungripping said member at said first location while continuing to clamp said member adjacent said first pair of shears, and regripping said member at second locations along said line, said second locations being more distant from a reference edge of said member than are said first locations with respect to said reference edge.  
  17. The method of claim 15 and further comprising the step of:  
 clamping said member adjacent said second pair of shears while shearing said member.  
  18. The method of claim 17 wherein the step of clamping said member adjacent said first and second pairs of shears comprises clamping in front of said first pair of shears and in front of said second pair of shears.  
  19. A method of power shearing comprising the steps of:  
 establishing a shearing step program in a shear control unit;  
 placing a member to be sheared atop a table associated with power shears and against locating and gripping means and gripping the member with the gripping means;  
 starting a series of member positioning and shear operating steps according to said program, causing the locating and gripping means to horizontally move to position said member and causing said shears to shear blanks from said member automatically in a variety of finished blank sizes predetermined according to said program, and for at least some of said blanks, causing the shears to shear edges square to each other in the member to sever the blank from the member whereby at least some of said blanks are corner blanks;  
 and returning said locating and gripping means to a starting position after completion of said series.  
 20. The method of claim 19 wherein:  
 said program is established by loading tape into a tape reader in said control unit.  
 21. The method of claim 19 wherein:  
 said program is established by manual setting of a plurality of switches.  
  22. The method of claim 19 and further comprising the steps of:  
 conveying from behind said shears, the blanks sheared from said member.  
 23. The method of claim 19 wherein:  
 the step of causing the shears to shear blanks, further comprises for each of the corner blanks, the step of shearing along first and second intersecting lines which extend to different edges of said member.  
  24. The method of claim 23 wherein the step of shearing along first and second intersecting lines further comprises:  
 shearing along the first line between one edge of the 32. A method of power shearing sheet or plate material to shear it into finished pieces of various desired final dimensions, the method comprising the steps of:  
 operating gripping means so as to grip a portion of a member to be sheared;  
 power moving the gripping means in discreate steps member and a point, and shearing along the second line perpendicular to the first line between the point and a different edge of the member, and  
 for the member positioning and shear operating steps for at least some of the corner blanks, the member is moved horizontally relative to both of said intersecting lines during the movement from said one position to said another position.  
 29. The method of claim 27 wherein: for each of the member positioning and shear operating steps for each of the corner blanks, clamping force is applied to the member adjacent both the first and second intersecting lines, outside the corner defined by the intersection of said lines, and the blank is separated from the clamped member without unclamping.  
 30. The method of claim 29 wherein: the separated blanks are deposited and conveyed away from within the corner defined by the intersection of said lines, behind the shears.  
 31. The method of claim 19 wherein: the step of causing the shears to shear edges square to each other in the member for each blank of said 6 at least some of the blanks, is performed while said member is held in one position during the shearing of the blank from the member.  
 of predetermined different amounts of mmovement for certain ones of said steps so as to move the gripped portion towards two pairs of power opidi h i b d h point on any f i 10 erated shears having blades which extend along li two intersecting lines, and for each step, stopping 25. The method of l i 23 h i movement of the gripping means with the gripped the step of shearing along first and second intersect- Pemon at a Posltlon Femote from the blades, as ing lines consists of beginning to shear along the to Place enother POrtlon of the member Posltlon first line at one edge of the member and continuing for Shearmg y the blades; to shear along the first line to a point of intersecand each p P h l the member tion of the lines, and then shearing along the secmanually on e mtersectmg by PP Shear 0nd line beginning at said point and continuing mg along lme and along the other e so to along Said Second line to a different edge of the remove a finished corner piece of final dimensions member from the member at a location thereon remote 26. The method of claim 23 wherein the step of from the gnPped porno f beh1nd the blades; shearing along first and second intersecting lines furwhereby f of szfud comer pleces ther comprises, moved with dimensions different from others in acshearing along the first line between one edge of the 25 cordance Sald dlfferent amounts of movemember and a point, and shearing along the second i h d l 32 h line perpendicular to the first line between a differth f 0 i fg to 6 mm w erem&#39; d ent edge of the member and the point, and avoiding 6 etermme, l f amounts r pre etershearing along said line beyond the point on the mmed by applymg tanglbfe pmgrammmg to member, until the member is moved from one posia and contronmg Sald power moving of tion to another position for shearing the next blank the gnppmg l by the controller accordmg to from the member the programming means.  
  34. The method of claim 32 wherein: 27. The method of claim 23 wherein:  
 . the shearing performed at said certain ones of said for each of the member positioning and shear operatsteps is performed along differentpercentages of mg steps for each of the comer blanks, the member 3 5 the lengths of said blades in accordance with said different amounts of movement affected by said power moving of said gripping means.  
 35. The method of claim 32 wherein certain ones of the steps of power moving are further characterized by:  
 power moving the gripping means and thereby the member in directions having components in directions generally parallel to said intersecting lines.  
 36. The method of claim 35 wherein:  
 the shearing performed at said certain ones of said steps is performed along different percentages of the lengths of said blades in accordance with said different amounts of movement affected by said &#39;power moving of said gripping means, said shearing along blades of said one pair extending up to 56 inches at 100% of the length of the blades of the one pair, and up to inches at of the length of the blades of the other pair.  
 37. A method of power shearing sheet or plate material comprising the steps of:  
 operating gripping means so as to grip a portion of a member to be sheared; power moving the gripping means so as to move the gripped portion towards two pairs of power operated shears having blades which extend along two intersecting lines, and stopping movement of the gripping means with the gripped portion at a position remote from the blades, so as to place another portion of the member in position for shearing by the blades;  
 and shearing the member substantially on the intersecting lines while holding the member in one position, by shearing along one line and along the other point of intersection, the shearing being continued from the said point along the other line to another edge of the member.  
 =l l l