Apparatus for loading and/or unloading industrial presses
RELATED APPLICATION 
     This application is a continuation of Ser. No. 368,914, filed Apr. 16, 1982. 
    
    
     BACKGROUND 
     This invention is concerned with improvements in or relating to work pick-up and/or handling apparatus such as may be used in automatically picking up, moving, and releasing workpieces with respect to different positions or stations in a repetitive manufacturing process. For example, such apparatus may be used in loading and/or unloading a press in the manufacture of metal pressings or stampings. In particular, the invention relates to such apparatus which is arranged to impart to work-supporting means of the apparatus, and so to a workpiece when held, a reciprocable linear movement. 
     One such apparatus is described in U.K. patent specification No. 1,395,058. That known apparatus comprises a linearly-reciprocable wheeled carriage for supporting any one of a variety of work-handling attachments. The carriage is constrained by guide rails to remain in a constant orientation as it is reciprocated to and fro along a linear path. The carriage is pivotally connected to a crank level which in turn is pivotally connected to a crank arm, the three pivot axes being in parallel and the effective lengths of the crank arm and crank lever, measured between the pivot axes, being equal. By means of a geared connection in the ratio 2:1 from a stationary gear on the pivot axis of the crank arm to a gear which is fast with the crank lever and on the pivot axis of the crank lever, it is provided that linear motion is imparted to the carriage upon rotation of the crank arm about its pivot axis, the linear path of the carriage being intersected by the pivot axis of the crank arm. 
     BRIEF SUMMARY 
     It is an object of the present invention to provide work handling apparatus for industrial presses which comprises work-supporting means that is arranged to be linearly reciprocated without the need for guide rails in order to determine its path of movement and which, preferably, also maintains the orientation of the work-supporting means constant. 
     A preferred form of the invention provides in one of its aspects, work handling apparatus comprising mounting means, a first arm pivotally mounted on said mounting means for movement about a first pivot axis, a second arm pivotally mounted on said first arm for movement about a second pivot axis parallel to said first pivot axis, and work-supporting means pivotally mounted on said second arm for movement about a third pivot axis parallel to said first and second pivot axes, said first and third pivot axes preferably being substantially equi-distant from said second pivot axis and the apparatus comprising first coordinating means arranged to so coordinate movements of the arms about the first and second pivot axes that said work-supporting means moves substantially linearly, and with preferably a second coordinating means comprising a geared connection of a desired ratio between said first arm and said work-supporting means whereby a desired orientation of said work-supporting means is obtained, such as no angular change despite linear movement. 
     Preferably, the first arm is pivotally mounted on a linearly-reciprocable carriage of the mounting means, the carriage being reciprocable relative to a carrier of the mounting means in a direction perpendicular to the direction in which the work-supporting means is arranged to move. The work-supporting means is preferably arranged to move generally horizontally (upon movement of the two arms) and the carriage arranged to move generally vertically on the carrier. The carriage and the carrier may be telescopically arranged, and in a preferred construction the carriage is suspended from the carrier by means comprising a plurality of pneumatic balancer cylinders and guided in its movements by rollers mounted on one of the carriage and the carrier and arranged to roll against the other. 
     The work-supporting means may be arranged to carry any one of a variety of work-holding attachments for picking-up, moving and releasing workpieces, such as vacuum cups, jaws, gripping fingers, magnets, etc. An electrical and/or fluid control system (not shown) may be employed to synchronise operation of the apparatus and a work-holding attachment with operation of a press, for example, which the apparatus is to load and/or unload automatically. The mounting means of the work handling apparatus may be secured in any of various positions, such as directly on a press frame, on a powered transfer carriage across a press, or on a transfer system or conveyor. The absence of guide rails for the work-supporting means provides more floor clearance around the press and thereby encourages efficient operation at high speed. 
     There now follows a detailed description, to be read with reference to the accompanying drawings, of a presently preferred embodiment which illustrates the invention by way of example. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of the apparatus, taken in section along a vertical midplane with the machine in extended position; 
     FIG. 2 is a partial view similar to FIG. 1 which shows the mounting means of the apparatus to a larger scale; and 
     FIG. 3 is a partial plan view in section on the line III--III of FIG. 2. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Apparatus illustrating a preferred form of the invention comprises mounting means 10 which could be secured, for example, to the frame of a large industrial press used to fabricate shapes in large steel workpieces, such as roofs of automobiles. A first arm 12 (hereinafter referred to as the crank or upper arm) is pivotally mounted on the mounting means for movement about a first vertical pivot axis 14. A second arm 16 (hereinafter referred to as the crank lever or lower arm) is pivotally mounted on the crank arm 12 for movement about a second vertical pivot axis 18. Work-supporting means 20 is pivotally mounted on the crank lever 16 for movement about a third vertical pivot axis 22. The first and third pivot axes 14 and 22 are equi-distant from the second pivot axis 18. The apparatus 1 comprises also first coordinating means, comprising a first geared connection 24, arranged to so coordinate movements of the crank arm 12 and the crank lever 16 about the first and second pivot axes 14 and 18 that the work-supporting means 20 moves linearly along a horizontal path. The apparatus 1 also comprises second coordinating means, comprising a second geared connection 26, whereby the orientation of the work-supporting means 20 is maintained constant throughout swinging movements of the crank arm and crank lever. 
     The mounting means 10 (see FIGS. 2 and 3) comprises a linearly-reciprocable carriage 28 on which the crank arm 12 is pivotally mounted, the carriage being reciprocable vertically relative to a carrier 30 of the mounting means. The carriage and carrier are telescopically arranged, with the carriage 28 mounted within the carrier 30. The carriage comprises a straight, vertically aligned, tubular frame 32 of a generally octagonal cross-section, bearing an internal cross-plate 34. Secured to the bottom end of the tubular frame 32, and aligned coaxially with the frame, are a first pulley 36 and an inner race of a first slewing or turnable bearing 38 of the machine. 
     The carrier 30 also comprises a generally octagonal tubular frame 40, coaxially arranged around the carriage and depending from an annular, horizontal, top plate 42. A cylindrical skirt 44 depends from the outer periphery of the top plate to shield the frame 40 of the carrier. 
     The carriage 28 is guided for vertical movements within the carrier 30 by means of sixteen rollers 46 mounted on the carrier frame 40 and arranged to roll against linear tracks 48 secured to outer surfaces of the carriage frame 32. There are four sets 50, 52, 54, 56 of four rollers, each set extending longitudinally of the carriage and the sets being arranged in two pairs of opposed sets, the line of action of one pair of sets 50 and 54 being perpendicular to the line of action of the other pair of sets 52 and 56. Each set comprises an upper and a lower pair of rollers, the two pairs being spaced apart longitudinally of the carriage and the rollers in each pair of rollers being spaced apart transversely of the carriage. As shown in FIG. 3, the rollers 46 of each pair of rollers are pivotally mounted on the side walls of a radially-inwardly facing channel-shaped portion of the carrier frame 40, the two rollers being positioned between the side walls. 
     The carriage 28 is suspended from the carrier 30 by means of two pneumatic balancer cylinders 58 and 60 which act between the carrier and the carriage to take the weight of the carriage and its load. Supplies of air under pressure to the cylinders are regulated by suitable means to maintain the pressure within the cylinders constant as the carriage moves. The cylinders extend vertically, on opposite sides of the carriage axis, between top brackets 62 and 64 secured to the top plate 42 of the carrier and bottom brackets 66 and 68 secured to the carriage frame 32 adjacent its bottom end. The cylinders 58 and 60 are arranged equi-distant from, and on opposite sides of, the carriage/carrier axis, which it will be understood is also the first pivot axis 14, each cylinder extending from the top plate 42 down between the upper rollers and between the lower rollers of the two pairs of rollers of a roller set. 
     The apparatus 1 includes a nut-and-screw arrangement which determines the vertical position of the carriage 28 relative to the carrier 30, one of the nut and the screw being non-rotatably secured to one of the carriage and the carrier and the other of the nut and the screw being arranged to be rotated by vertical movement actuating means comprising a motor 70 mounted on the other side of the carriage and the carrier. The lite motor 70 is shown mounted on the carrier 30, being mounted in a well 72 of the carrier, and comprises an output shaft 74 arranged for rotation about the first pivot axis 14. By means of a coupling 76, a screw 78 is secured to the shaft 74, the screw being in threaded engagement with a recirculating ball nut 80 mounted on the cross-plate 34 of the carriage. An encoder and tachometer unit 82 and a brake unit 84 are associated with the motor 70. 
     The crank arm 12 is affixed (as by bolts, not shown) to the outer race of the first turntable bearing 38 beneath the carriage frame 32 (FIG. 2). The arm 12 is of a hollow, tubular, fabricated, sheet metal construction. Adjacent an outer end of the crank arm 12, the crank lever 16 is pivotally mounted for rotation beneath the crank arm 12 about the second pivot axis 18. The lever 16 is mounted on arm 12 by means of a second slewing or turntable bearing 86 of the apparatus. An outer race of the bearing 86 is affixed as by bolts (not shown) to the crank arm 12 and the inner race is affixed to the crank lever 16. 
     Actuating means for horizontal movement is coupled to the crank lever 16 to rotate it about the second pivot axis 18 on the second turntable bearing 86 and comprises a second motor 88 of the apparatus. The motor 88 is mounted on the crank arm 12 (housed within the arm) in association with a gear reducer 89 secured fast to the arm 12. It has a vertical output shaft 90 arranged for rotation about the second pivot axis 18. The crank lever 16 is of a hollow, tubular, fabricated sheet steel construction. The gear reducer 89 and the output shaft 90 project from the crank arm into the interior of the crank lever. The shaft 90 is secured to the lever 16 by means of a sleeve 92 affixed as by welding to a bottom inside face of the lever 16. An encoder and tachometer unit 94 and a brake unit 96 are associated with the motor 88 to provide for accurate control of angular positions of the two arms and therefore of the linear position of the work support 20. 
     The first coordinating means, comprising the first geared connection 24, includes in addition to the pulley 36 of the carriage 28 a second pulley 98. The second pulley 98 coaxial with axis 18 is secured fast as part of the crank lever 16, and projects upwardly into space within the crank arm 12. The geared connection 24 comprises a toothed timing-belt 100 which extends around the two toothed pulleys 36 and 98 and through the crank arm 12 therebetween. The pulleys are sized to provide a geared connection in the ratio of 2:1 from the carriage 28 to the crank lever 16. 
     Adjacent an outer end of the crank lever 16, the work-supporting means 20 is pivotally mounted on the crank lever 16 for rotation about the third pivot axis 22. The work-supporting means comprises a third pulley 102 of the machine, affixed as by bolts (not shown) to an inner race of a third slewing or turntable bearing 104. An outer race of the bearing 104 is secured fast to a top inside face of the hollow crank lever 16, so that the pulley is housed substantially wholly within the crank lever. Adjustable attachment-holding means 106 for connection to a suitable specific workpiece pick-up device (not shown) is secured fast with the pulley 102 to depend beneath the crank lever 16. 
     The second coordinating means, comprising the second geared connection 26, includes in addition to the pulley 102 of the work-supporting means 20 a fourth pulley 108 of the apparatus 1. The fourth pulley 108 is secured fast as part of the crank arm 12, being secured generally beneath the motor 88, coaxially with the second pivot axis 18, and projecting downwardly into the interior of the crank lever 16. The second geared connection 26 comprises a toothed timing-belt 110 which extends around the two toothed pulley 108 and 102 and through the crank lever 16 therebetween. The pulleys 108 and 102 and the timing belt provide a geared connection in the ratio of 1:2 from the crank arm 12 to the work-supporting means 20. 
     Preferably, idlers 112 for each reach of each belt 110 and 100 are used to apply balanced pressure to opposite sides of the respective belts and take-up slack in each. 
     In operation of the apparatus 1, power for horizontal movement is supplied by motor 88. The motor 88, by way of reducer 89, is secured to crank arm 12 to move with it. The rotary output shaft of the motor is secured to crank lever 16 to move with it. Thus, when the motor 88 is energized, the arm 12 and lever 16 move angularly relative to each other about axis 18. The amount of such relative movement equals the degree of rotation of the output shaft 90. If the shaft rotates 90°, for example, the included angle between the two arms changes by 90°. 
     When the motor 88 is energized, there is also pivotal movement of the crank arm 12 about the axis 14. This occurs because pulley 98 is rotated about axis 18 with arm 16. The amount of the movement is determined by the 1:2 ratio of diameters of pulley 98 to pulley 36. Pulley 36 is stationary so motion of belt 100 by pulley 98 cannot move it. Instead, the entire arm 12 will pivot about axis 14 and the degree of angular movement will be one half the degree of rotation of shaft 90. If the shaft 90 rotates 90°, for example, the arm 12 will pivot 45° about axis 14. 
     Considering the apparatus 1 in the condition of FIG. 1, all three axes 14, 18, and 22 lie in the same vertical plane. If shaft 90 is rotated, axis 18 will be moved out of this vertical plane. Axis 14 is fixed in the vertical plane and does not move. Axis 22 stays in the vertical plane but moves to the left, i.e., it is retracted from its fully extended stroke position of FIG. 1. It stays in the same vertical plane because (a) axis 18 is always midway between axes 14 and 22 since the distance 14-18 equals the distance 18-22 and (b) and the 1:2 ratio of pulleys 98 and 36 insures that the angle of displacement of axis 18 out of the vertical plane (i.e. the angle made by arm 12 between its position in FIG. 1 and its displaced position) is one half that of the included angle between arm 12 and lever 16. If distance 14-18 is unequal to distance 18-22 (especially if the inequality is small), the difference in distance can be counteracted by corresponding change in the ratio of the diameters of pulleys 98 and 36 in order to maintain movement of axis 22 in the same vertical plane, i.e., straight line, horizontal motion. Alternatively, if a variation from straight line motion is desired, it can, within limits, be accomplished by variations in the distances 14-18 and 18-22 accompanied by appropriate sizing of pulleys 98 and 36. The isosceles relationship in which 14-18 substantially equals 18-22 is ordinarily preferable because it gives the maximum straight line stroke (i.e. four times the distance 14-18 or 18-22) and involves simpler relationships of lengths and pulley diameters. 
     Orientation of the work attachment 106 about the axis 22 is controlled by the coordinating means 26. With the 1:2 ratio between pulleys 108 and 102 that has been described, rotation of the work attachment 106 will be equal to angular movement by arm 12 about the axis 14 so that it remains straight even though it is moved horizontally. Alternatively, different orientations can be automatically achieved by varying the pulley ratios; or, even further, the coordinating means 26 can be eliminated and the work attachment 106 simply allowed to rotate freely and manually on bearing 104, or not at all by eliminating the bearing. 
     In conjunction with horizontal motion, or separately, vertical movement of the work-holding attachment 106 can be achieved by appropriately energizing lite motor 70. While this motor has been illustrated in alignment with axis 14, it and the vertical movement actuating and support mechanism could be located elsewhere; for example, at axis 18. Similarly, while the rotary, horizontal drive motor is shown on axis 18, it could also be located elsewhere, on axis 14, for example, since the two coordinating systems 24 and 26 will maintain the desired relationship among the various parts. 
     While toothed pulleys and timing belts are presently preferred for the geared connections 24 and 26, in other embodiments other suitable forms of geared connection (e.g. using chains, V belts, wire ropes or gear trains) could be used. Similarly, instead of electric motors 70 and 88 hydraulic or fluid motors may be used depending upon the application, etc. 
     For use as production equipment, operation of the two motors 70 and 88 can be controlled and coordinated by any suitable control system and may be programmed by use of a computerised numerical control system to secure a desired sequence or combination of horizontal and vertical movements and a desired automatically repeatable path of movement of the work-holding attachment 106. Work-holding attachments such as jaws as shown in U.S. Pat. No. 3,975,992, for example, or controllable magnets or vacuum cups, etc., can therefore be secured to the attachment holding means 106 and operated in harmony with the apparatus 1 to pick-up, move, load and/or unload, and release workpieces (not shown) with respect to industrial presses, conveyors, etc. 
     Thus, the invention provides a heavy duty workpiece handling device which by virtue of the large turntable bearings (especially bearing 38) and other features described above eliminates the need for a guide track (such as used in British Pat. No. 1,395,085) and uses articulated and controlled cantilever action to impart a desired motion to a workpiece. 
     Modifications in the specific structure shown can be made without departing from the spirit and scope of the invention.