Hydraulic contouring means for a hot or cold leveler machine
BACKGROUND OF THE INVENTION 
     This invention relates broadly to the art of flatening or leveling of metal webs or strip by passing the same between opposed groups of offset rollers. Such machines for this purpose are referred to in the art as levelers, flatteners, or straighteners and all perform essentially the same function in the same general manner. 
     For the purposes of background, the following U.S. patents may be referred to: Peterson U.S. Pat. No. 2,852,065; Krynytzky U.S. Pat. No. 2,963,071; Bearer U.S. Pat. No. 3,301,031; Thompson et al U.S. Pat. No. 3,638,326; Talbot 3,657,913; Ihle U.S. Pat. No. 4,107,970; and Matsui U.S. Pat. No. 4,380,921. 
     The basic operation theory of a leveler machine is well known. Metal is formed into strip form from a heated or cold billet or slab by passing the material between a pair of work rolls in a rolling mill to reduce the cross-section and to elongate the same. When the final thickness is achieved, and the strip exits from the mill, it is occasionally wrapped convolutely to form a coil. When it is desired to uncoil the material, a certain curvature or set remains which of course varies dependent on the radius of the portion of the strip in the coil. 
     It will of course be apparent that the outermost convolution will have less curvature than the innermost convolution. The leveler is designed to remove this curvature so that the strip is perfectly flat and suitable for other machining and manufacturing steps. 
     While the present invention could be used for removing curvature from rolled sheet material, its principal utility is for working relatively thick sheet or plate that has not been convolutely wound. 
     In addition to coil curvature, the sheet could have other defects such as edge waves caused by the edges being rolled thinner than its center, or &#34;oil canning&#34; when the reverse is true because the center was rolled thinner than the edges. In most prior art levelers, the strip is passed through a combination of rollers which provide a predetermined amount of reverse flexure sequentially diminishing as the web passes through the leveler to remove curvature and other shape defects. 
     In operation of the conventional leveler, as the strip passes between the rolls, a very high pressure is generated and this results in the strip tending to wedge the roll pairs apart. Accordingly, back-up rolls are provided. 
     Heretofore, it has been necessary for the leveler operator to carefully monitor the work roller position during the material pass, and high quality product was, to a large degree, dependent upon the skill of the individual operator. 
     Almost all prior art levelers include an upper and a lower series of work rollers which extend across the machine from one side frame to the other. Each series of rollers are positioned in parallel from the entry to the exit point. The upper and lower rollers are offset with respect to each other so that the web or strip passes in a tortuous path from entry to exit. In the prior art the adjustment of the vertical spacing between the upper and lower rollers is accomplished by means of wedges, jack screws or the like. 
     Very little development has been made to date in the field of automation of strip levelers. Two examples, however, are Buta U.S. Pat. No. 4,454,738 and Ball U.S. Pat. No. 3,596,489. 
     DESCRIPTION OF THE INVENTION 
     In order to provide at least semi-automatic operation of a leveler for strip metal, I have mounted the upper back-up rolls on a partially flexible beam support extending parallel to the axes of the rolls which in turn is mounted to the leveler rigid frame through a plurality of piston-cylinder units with the piston members thereof in contact with the flexible beam support and the cylinders mounted on the rigid leveler frame. A position feedback transducer in each cylinder senses the position of the respective piston and sends a position feedback signal to a summing amplifier which compares this to a reference position signal and by actuation of a servo valve, can inject or allow outflow of hydraulic fluid into or out of the cylinder so as to maintain the proper preset piston position of the system if set for operation in the &#34;position mode.&#34; 
     With my invention, a sheet having a width of about 3.66 meters, a length of 15 meters, and a thickness of between approximately 4.76 mm to 50.8 mm may be worked hot and a thickness of 4.76 mm to 25.4 mm may be worked in the cold state. 
     OBJECTS OF THE INVENTION 
     The principal object of my invention is to provide a leveler for sheet metal having means to detect back-up roller beam deflection and to produce a counter force on the beam to automatically resist such deflection in order to produce a substantially flat sheet product. 
     Another important object of my invention is to provide a plurality of hydraulic piston-cylinder units for mounting the back-up roller support beam on the main frame of a leveler wherein means are provided to automatically maintain piston position in the cylinder by injecting or venting hydraulic fluid into or out of the respective cylinder. 
     An object of my invention is to improve sheet or plate levelers by mounting the upper backing rolls on an intermediate frame which may be partially deflected in use and which is supported on the main frame of the leveler across its length by a plurality of contouring hydraulic cylinder units which are individually position controlled by servo valves and which can be adjusted to work the sheet metal across its width to different degrees dependent on flatness of the sheet or plate. 
     A further object is to provide a safe reliable, control system for levelers which utilizes commercially available components and which produces a high quality level of final product consistently and which requires a minimum of maintenance. 
    
    
     These and further objects will be readily apparent to those skilled in the art of metal rolling from a study of the detailed descriptions of the specification and drawings which follow. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional side elevation of a preferred embodiment of the leveler of my invention. 
     FIG. 2 is a front elevational view of the invention shown in FIG. 1. 
     FIG. 3 is a detailed enlarged view of one of the piston-cylinder beam mounting assemblies shown in FIG. 2, and 
     FIG. 4 is a schematic presentation of the electrical and hydraulic control circuits of my new leveler. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to the drawings, wherein like parts are designated with the same reference characters, the basic leveler is shown generally at 10 and includes a heavy steel base frame 11 and upstanding steel side frame members 12. A top frame assembly 13 is secured to the side frame members as is common in the art. The upper frame supports a screw adjustment assembly 14 which may be actuated by a worm gear 15 via a drive shaft 16 rotated by the electric motor 17. This arrangement permits vertical adjustment of rigid top subframe 18 which is engaged with the foot 19 of screw 20. A piston assembly serves to force the rigid top subframe 18 against the foot 19 of screw 20. In FIG. 1 this piston assembly is shown somewhat schematically at 24 where it reacts against the base frame 11 and the rigid subframe 18. This arrangement is shown in greater detail in Thompson et al U.S. Pat. No. 3,638,326. 
     The sheet or plate to be worked passes into the leveler from the right in FIG. 1 as shown at P and moves along the pass line L. After passing beneath an entry roll 25 it passes between an upper and lower series of work rollers 26 and 27. Each of these rollers are separately driven by a motor, not shown, through drive shafts 28 and 29 and universal joints 30 and 31. Each of the upper and lower work rollers 26 and 27 are journalled in bearings 32. 
     At the exit point on pass line L, a delivery roll 33 is mounted, which, like entry roll 25, may be larger in diameter than the work rolls 26 and 27, and is not necessarily backed up. 
     While three upper work rolls 26 and four lower rolls 27 are shown, it will be apparent that a greater or lesser number may be selected dependent on the particular situation. The upper and lower rollers are offset with respect to each other and may be adjusted so that they may be brought into substantially nesting relationship with each other. The spacing between the upper and lower rollers, referred to as the gap or roller &#34;plunge&#34; is adjustable and each bank of rollers can even be tilted as required to provide an increasing or decreasing gap from front to back. This is accomplished by electro-mechanical screws or hydraulic cylinders. 
     Because of the high working pressures encountered, each of the working rolls 26 and 27 is provided with a backing roll 40 and 41. Hydraulic cylinders 34 and 35 serve to hold the working rolls 26, 27 snugly against the backing rolls. The lower work rolls 27 and their backing rolls are mounted in a roll change cassette 42 as is known in the art, which rests on the leveler base frame 11. The upper backing rolls 40 are journalled and supported by a flexible intermediate beam 43 which extends across the width of the machine (FIG. 2) parallel to the working rolls and which in turn is mounted by means of piston-cylinder units shown generally at 50 to the top subframe 18. Similar piston-cylinder assemblies are also provided to back-up the entry roll 25 and the delivery roll 33 although these are not provided with backing rollers. 
     In FIGS. 1 and 2, a hydraulic-actuated pivoted lever 21 is shown acting on links 22 which in turn are secured to the flexible beam 43 at 23 for the purpose of forcing the flexible beam upwardly. 
     The cylinders 51 are machined into the subframe 18 or provided by sleeving, see FIG. 3. A piston 52 is received in each cylinder and has its piston rod or shaft 53 in contact with the beam 43 as at 54, so that any flexure of the beam 43 caused by the pressure imparted to the rolls 26, 40 will cause concurrent movement of the rod 53 and the piston 52 within the cylinder 51. 
     A hydraulic inlet and outlet line 55 extends from the servo valve of the control circuit into each of the cylinders. The cylinders are otherwise closed but are each provided with a fluid pressure transducer 56 and a linear position-displacement transducer 57. 
     The fluid pressure transducer 56 may be of any conventional design, although the model P563 manufactured by George Kelk Limited of Don Mills, Ontario, Canada has been found to be ideal for this application and is fitted into the cylinder side wall with the four conductor shielded cable 58 extending to a video display unit 59 for graphic depiction of the cylinder fluid pressure. This type of transducer operates in the manner of a strain gauge which permits the use of D.C. excitation ensuring rapid response and providing good linearity and low hysteresis. 
     The linear position-displacement transducer is also a component available on the commercial market and is installed in the top of each cylinder. I have found that the units manufactured by Temposonics Division, MTS Systems Corporation of Plainview, N.Y. (U.S. Pat. No. 3,898,555) are suitable for this purpose. These devices utilize a waveguide and external magnet as described in detail in the above patent. The hollow transducer tube 44 having a wire therein extends into the cylinder and into a bore 45 formed in the head of piston 52. 
     An annular ring magnet 46 surrounds bore 45 in the piston head in a manner known in the art. When a current pulse is sent through the wire, the resulting magnetic field is concentratedin tube 44 which acts as a waveguide. This causes an interaction with the field from magent 46 and a local rotary strain. This strain continues for the duration of the current pulse. The rotary strain travels along the waveguide element at ultrasonic speed and can be detected at the end of the tube. By measuring the time from the generation of the initial electrical pulse until the ultrasonic pulse is detected, determination may be made of the distance from the reference point. Devices of this type are commercially available as noted, supra. 
     Any apparent piston movement, as for example would occur from deflection of beam 43, will result in an analog output signal in the lead 61. Using this system, a pulse generator produces a series of pulses, each also used to set a bistable flip flop. Setting the flip flop closes a switch, permitting the application of a D.C. reference voltage to the input of a summing amplifier 62 (FIG. 4). A base reference position or null adjusting potentiometer 63 is used to provide a bias voltage to a second input 64 of the summing amplifier 62 to provide a voltage subtraction. The D.C. output voltage is preferably filtered and may be further amplified before it is fed to the servo valve. 
     If desired, the output from the position-displacement transducer 57 may also be fed through cable 66 to a piston position video display console 67 located adjacent to the pressure video display 59. Here the operator will have a graphic presentation of both pressure and piston position in each of the piston-cylinder units 50. 
     The hydraulic system includes a fluid supply resevoir or tank, a motor-driven pump, line filter and system pressure gauge 70. A manifold 71 is used to direct fluid flow into and out of each of the servo valves in the system, only one being shown in FIG. 5 for purposes of simplicity. The servo valve also is provided with a capped port 72. 
     In order to operate the system in a &#34;pressure mode&#34;; the reference position potentiometers 63 are adjusted so that the pistons are all at the same level in the cylinders 51 and the pressure display screen 59 and the piston position screen 67 will each show the individual lines at the same level. As sheet material advances into the leveler, any forces created by the material against the work rollers 26 should ideally be the same, however, if variations in thickness or buckling is present, there will be a variation in the pressures against the working roll nearest the defect which will be transferred to its backing roll and then tend to deform or flex the beam 43. This flexure causes concurrent movement upwardly of the piston 52 adjacent the effected portion of the beam. Piston movement is sensed immediately by the position-displacement transducer 57 sending a position feedback analog signal to the summing amplifier 62 which compares this input to that at 64 from the reference position signal. The output from the amplifier then actuates the servo valve and the pump motor to direct hydraulic fluid under pressure to the effected cylinder or vent cylinder pressure via the line 55 thereby varying the fluid pressure above the piston, restoring it to its initial position to counter the loading on the work roll from the sheet material. 
     If, on the other hand, it is desired to work the material in a same special manner, as for example, to provide a narrow dishing effect the system can be operated in a &#34;position mode.&#34; Here the operator, by manually controlling the reference position potentiometers, can select the appropriate piston position as seen on the graphic display 67 in the example shown in FIG. 4. Thereafter, the system will apply or remove hydraulic pressure as needed to maintain the desired product configuration. 
     It will be apparent from the above description that I have provided for substantially automatic leveler operation by a new and simple mechanical and electrical means which will produce a high quality product at lower cost than prior art machines. Other modifications, embodiments and improvements will be readily apparent to those skilled in the art based upon these teachings. Such further modifications, embodiments and improvements are deemed to be within the spirit and scope of the invention as defined in the following claims: