Abstract:
A plate gripper mechanism attachable to a robotic arm structure for transferring a sheet metal plate to or from a work station, e.g., stamping press, welding machine, milling machine, rivet machine, etc. The gripper mechanism utilizes a small commercially available fluid motor actuator in direct drive connection with a rotary shaft in the gripper mechanism, whereby the mechanism is relatively small and light. The mechanism is preferably constructed from bar stock, plate and tube stock; no special castings, stampings or forgings are used in preferred practice of the invention.

Description:
BACKGROUND OF THE INVENTION 
     1. Field Of The Invention 
     This invention relates to a side panel clamp mechanism adapted to grip an edge area of a metal plate or other workpiece so that the plate can be moved from place to place or manipulated into or out of a machining mechanism, such as a stamping press. The improved gripper mechanism can be carried on a robotic arm or other transfer device designed to move the gripper mechanism bodily from place to place. 
     2. Description Of The Prior Art 
     Various other types of plate gripper mechanisms are known. U.S. Pat. No. 4,448,056 to Baba shows a plate gripper mechanism wherein a fluid cylinder 130 is connected to a cam mechanism 116 for operating a movable jaw 104 between an unclamped position and a clamped position engaged with a workpiece W. The mechanism has a relatively long dimension along the axis of the cylinder 130. It is, therefore, difficult for this mechanism to move into or out of small clearance spaces. 
     U.S. Pat. No. 3,497,255 to Sindelar shows a gripper mechanism for gripping a workpiece W. The mechanism includes a fluid cylinder 14 having a slidable member 17 linked to a jaw 28 for gripment of the workpiece W. This mechanism is somewhat similar to the mechanism in U.S. Pat. No. 4,448,056 in that overall length of the mechanism is relatively great in a direction parallel to the axis of the fluid cylinder. 
     U.S. Pat. No. 4,752,094 to Tabeau shows a robotic gripping device wherein a piston 19 moves within a fluid cylinder to rotate a shaft 23 via a toothed rack 20. A work gripment jaw 42 is carried on the shaft. The mechanism shown in this patent utilizes a specially designed fluid cylinder actuator, which would be fairly expensive if produced in small volume quantities. 
     The Danly Machine Corporation of Chicago, Ill. manufactures a plate gripper mechanism wherein an air cylinder is connected to the shaft of a swingable jaw member via a pin-slot connection. The piston rod of the air cylinder is connected to a linear guide having two spiral slots in its inner surface. A rotary shaft is disposed within the linear guide so that a transverse pin extends from the shaft into two spiral slots. As the piston moves in the air cylinder the spiral slots exert cam actions on the end areas of the transverse pin to rotate the shaft around its axis, thereby producing a swinging motion of the associated jaw. The mechanism has a relatively long length in the direction of the rotary shaft. Also, the mechanism utilizes special castings which would be relatively expensive when produced in small volume quantities. This type of gripper mechanism provides limited output and is subject to degradation of the output force due to eventual wear of the spiral slots in the shaft. 
     SUMMARY OF THE INVENTION 
     The invention relates to a side panel gripper mechanism wherein a jaw or lifter arm is attached to a rotary shaft that is directly connected to a rotary fluid motor. The mechanism is designed to have a relatively small overall dimension along the shaft axis. Also, the mechanism is designed to utilize a commercial off the shelf fluid motor having a relatively small overall size and high torque output, whereby the associated lifter arm is able to exert a relatively strong clamping force on the metal plate or other workpiece being gripped by the gripper mechanism. 
     One object of the invention is to provide a side panel gripper mechanism having a relatively small overall size. 
     Another object of the invention is to provide a gripper mechanism that is relatively light in weight, such that the mechanism can be carried on the free end of a long length robotic arm structure without overloading the arm structure or requiring the arm structure to have a thick beefed-up cross-section in order to carry the weight of the gripper mechanism. 
     A further object of the invention is to provide a plate gripper mechanism that can be formed or manufactured without using specially stamped components, castings or forgings that might require special tooling or long lead times for part procurement. 
     The invention contemplates a gripper mechanism that is formed out of commercially available parts, such as bar stock, plates or tube stock. 
     A further general object of the invention is to provide a gripper mechanism that can be manufactured in small volume quantities using conventional machining practices. It is a further object of the invention to avoid the use of high cost tooling or special manufacturing equipment that would excessively add to the manufacturing cost of small volume quantities. 
     These and many other objects and features of the invention will become more apparent upon a reading of the following detailed description in conjunction with the drawings appended hereto. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view taken along line 1--1 in FIG. 2, and illustrating one form that the invention can take; 
     FIG. 2 is a sectional view taken along line 2--2 in FIG. 1; 
     FIG. 3 is a sectional view taken along line 3--3 in FIG. 1; and 
     FIG. 4 is a schematic illustration showing how the improved gripper mechanism can be connected to a transfer device to transport a metal sheet from one place to another. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 4 shows two side plate clamp gripper mechanisms 10 suspended or otherwise attached to an overhead bar structure 11 for gripping of a sheet metal plate 12. Each gripper mechanism includes a pivotable lifter arm 30 designed to be swung into engagement with the edge 32 of the undersurface 31 of the plate 12 to exert a clamp action thereon. The bar structure 11 would be connected to a non-illustrated power device for moving the bar structure and, hence, the clamped plate 12. The invention is primarily directed to the construction of a gripper mechanism 10, as shown more particularly in FIGS. 1, 2 and 3. 
     The gripper mechanism 10 of FIG. 1 includes a rotary fluid motor 24 attached to a carrier body 14. The carrier body has an elongated rectangular block structure 40 having side faces 41, 42, 43, and 44. An end face 82 of the block structure 40 is welded or otherwise permanently secured to a face plate 83. As best seen in FIG. 3, the face plate 83 has a greater face area than the block structure 40 such that peripheral face areas of the face plate extend laterally beyond the block side faces 41, 42, 43 and 44. The peripheral face areas of the face plate are, thus, usable to affix the carrier body 14 to the fluid motor 24. 
     The fluid motor 24 has attachment openings that are spaced closer together than the profile dimension of the block structure 40. Therefore, it is necessary to provide an adapter plate 85 between the fluid motor 24 and the face plate 83. The adapter plate 85 has a set of openings 86 that accommodate screws 87 for securing the adapter plate to the base surface of the fluid motor 24. The adapter plate 85 has a second set of threaded openings 84 alignable with openings 88 in the aforementioned face plate 83, whereby screws 89 can be extended through the openings 88 into the threaded openings 84 to secure the face plate 83 to the adapter plate 85. In this manner, the carrier body 14 is attached to the fluid motor 24 even though the attachment openings in the fluid motor are within the profile dimension of the block structure 40. The aforementioned fluid motor 24 has a circular piston 35 movable back and forth in a cylinder 36. The intermediate section of the piston 35 is cut away to form a toothed rack 38. A corresponding section of a square male rotary output member 26 is formed with gear teeth 39 thereon, whereby linear motion of the piston is translated into rotary motion of the square male output member 26. Pressurized air is emitted to opposite ends of the cylinder 36 via threaded fittings 28. The fluid motor 24 is preferably a commercially available motor obtainable from the Dynaquip Controls Co. of Fenton, Mo. 
     Formed in the elongated block structure 40 is a rectangular groove 46 cut transversely through the block at right angles to the axis 19 of a rotary shaft 18, to define a flat rear groove face 47 extending parallel to the shaft axis 19 and two groove side faces 48 and 49 extending normal to the shaft axis. The rotary shaft 18 extends through the groove 46 so that circular areas of the shaft on both sides of the groove are supported by the elongated block structure 40. The aforementioned lifter arm 30 is attached to the shaft in the space defined by the groove 46 so that the lifter arm can swing in a plane between and parallel to the groove side faces 48 and 49. 
     The lifter arm 30 includes a flat plate 51 having a flat surface recess 52 extending therealong. As seen in FIG. 2, the recess 52 fits around approximately one-half the perimeter of the square cross-sectioned shaft area 50. A retainer bar 53 has a second flat surface recess 55 extending therealong to fit around the remaining half of the square cross-section shaft area 50. Bolts 57 extend through openings in the retainer bar 53 and plate 51 to ri%idly clamp the lifter arm 30 to the shaft 18. 
     Adjacent its lower end, the plate 51 has a rectangular slot 60 in one of its faces. An additional flat plate 59 is arranged with an edge area 61 snugly fitted into the slot 60, as shown in FIG. 2. Bolts 63 extend through the slotted zone of the plate 51 into the edge area of the plate 59 to rigidly connect the two plates together. 
     As seen in FIG. 1, the width of the groove 46 is approximately one-half the total length of the block structure 40. The block area to the right of the groove 46 serves as a suspension point for the block structure, i.e., the point from which the block structure is suspended from the overhead bar structure 11 (FIG. 4) or other robotic arm system. A suspension bracket 67 is attached to the side face 44, as shown in FIGS. 1 and 2. The suspension bracket has an angle member 75 which has a leg 77 positioned against the block side face 44 and a leg 76 extending at a right angle to the leg 77. Bolts 70 extend through the leg 77 into threaded openings 69 in the block to rigidly but detachably connect the angle member 75 to the block structure. A reinforcement plate 79 is welded to the legs 76 and 77 to form an attachment surface for a tubular element 71. The tubular element 71 has a circular cross-section, as best seen in FIG. 2. Opposed arms 73 and 74 are welded to the tubular element 71 at the split 72 in the tubular element. Pressure applying screws 80 extend through openings in the opposed arms to provide a means for tightening the tubular element 71 onto a non-illustrated rod-like support member. This arrangement enables the gripper mechanism 10 to be suspended from a support structure. Also the gripper mechanism can be adjustably mounted for rotary adjustment around the axis of the tubular element 71. Additionally, the mechanism can be adjusted to a limited extent along the axis of the tubular element 71. 
     In FIG. 3 additional openings 69 in the side face 41 of the block 40 are shown. These additional openings provide an alternate mounting mechanism for the aforementioned suspension bracket 67. Thus, the suspension bracket can be attached to either the face 44 or the face 41 of the block structure 40, as might be most appropriate for a particular application of usage of the gripper mechanism. 
     A clamp structure 27 is shown in detail in FIG. 2. The clamp structure includes ar L-shaped bar 90 having a leg 91 abutted against the side face 42 of the block structure 40 and a second leg 92 abutted against the side face 43 of the block structure. Bolts 93 extend through the leg 91 to secure the bar 90 to the block structure 40. A thickened plate 94 is welded to the L-shaped bar 90 so that the lower face of the plate 94 is in planar alignment with the lower face of the second leg 92. The clamp structure is designed to engage an upper face 29 of the sheet metal plate 12. The lifter arm 30 is swingable from the dash line position in FIG. 2 to the full line position in FIG. 2 to exert a lifter force on the plate 12, to thereby tightly clamp the plate between the lifter arm and the clamp structure. The clamp structure 27 may be reinforced by a gusset 96 suitably welded to the plate 94 and the L-shaped bar 90. As seen in FIG. 1, the plate 94 extends leftwardly beyond the gusset 96. The associated plate 59 on the lifter arm 30 extends leftwardly a corresponding distance, as required for any particular usage or installation. The clamp structure 27 is detachable from the block structure 40 to permit different clamp structure configurations to be selectively utilized with a given block structure construction. 
     The gripper mechanism shown in FIGS. 1, 2, and 3 is formed out of easily available materials, i.e., flat plates, bar stock or tube stock. Conventional machining operations can be utilized to form the component parts. Welding operations can be utilized to connect the permanently connect the components. Many of the components are detachably connected so that alternate component constructions can be selectively or interchangeably used, as required to meet particular customer needs. 
     FIG. 4 shows one particular arrangement wherein two gripper mechanisms 10 are arranged at opposite edge areas of the sheet metal plate 12. The component parts in the mechanisms 10 are left-handed and right-handed. However, the structure shown in FIGS. 1, 2 and 3 is designed to be symmetrical such that many of the components can be used for both the left-handed and right-handed positions. In this regard, the block structure 40 is constructed to be symmetrical about a longitudinal plane extending through the shaft axis 19 and normal to the rear face 47 of the groove 46, such that the block structure 40 can be used interchangeably in gripper mechanisms at opposite side edges of any given sheet metal plate 12. 
     The FIG. 1 gripper mechanism advantageously uses a conventional fluid motor 24 having a minimum dimension along the axis of the shaft 18. The overall size of the gripper mechanism is relatively small. Also, the mechanism is relatively light in weight. Accordingly, the gripper mechanism can be located on the free end of a robotic arm structure without unduly overloading the structure. The shaft 18 has a direct drive connection by the use of a square female cavity 22 with the square male rotary output member 26, such that there are no sliding or frictional engagements that could cause premature wear during normal service. 
     The drawings show one particular form that the invention can take. However, it will appreciated that other forms can be utilized while still practicing the invention. 
     Having, thus, described the present invention by way of an exemplary embodiment, it will be apparent to those skilled in the art that many modifications may be made from the exemplary embodiment without departing from the spirit of the present invention or the scope of the claims appended thereto.