Manipulator of flat sheet, in particular sheet metal plate

Abstract: The manipulator comprises a closed-ring conveyor device (3, 53), which comprises a succession of grasping organs (11, 61) having a fixed part (10, 84) and a movable part (14, 75). The path of the conveyor device (3, 53) comprises at least one rectilinear section along which suitable means (23; 76-81, 88, 89; 104, 96-101) act on the movable parts (14, 75) of grasping organs (11, 61) to allow the closing of same on the sheet to be manipulated.

Description: The present invention relates to a manipulator of flat sheet of any material, in particular sheet metal plate. Manipulators are widely used in different forms in machine tools, wherein the piece being machined must in succession assume different positions in the machine itself. Since such manipulators must exert strong accelerations to the piece being machined, their grasping organs have the form and function of clamps or pincers, capable of firmly holding the piece itself. In the case of manipulators of flat sheet, the clamps grasp the sheets in the proximity of one of their edges. Manipulators of flat sheet are known having one or two orthogonal axes, along each of which their grasping organs are capable of accomplishing a stroke equal to the maximum stroke which the sheet must perform along that axis or to accomplish a shorter stroke along the axis which is parallel to the grasped edge and, when necessary, to execute a "repositioning", that is, temporarily abandoning the sheet, returning along that axis and regrasping the sheet and then moving forward with it again. However, if the sheet is large or if long strokes must be accomplished, the manipulator must be of a large size, or it must execute one or more successive repositionings: in the first case it is expensive, heavy, bulky, slow and not very rigid; in the second case, time and accuracy are lost in the opening of the clamp (or clamps), in the return strokes and in reclosing the clamps. US-A-3100637 discloses a manipulator of flat sheets according to the preamble of claim 1, comprising at preset intervals supporting casings of grasping organs. In view of this state of the art, the object of the present invention is to accomplish a manipulator having one or two axes, of a size both small and independent of the stroke to be executed, light and rigid, capable of causing the sheet to accomplish, without repositionings, unlimited strokes along the axis parallel to the grasped edge. According to the invention, such object is attained with a manipulator of flat sheet as defined in claim 1. In this way, each grasping organ is capable of grasping a portion of the adjacent edge of the sheet at the start of the rectilinear section of its path so as to consequently give the sheet a corresponding rectilinear movement in co-operation with the other grasping organs which at that moment are moving along the same rectilinear section. At the end of the latter, each grasping organ opens again and releases the edge of the sheet, which, however, continues to be grasped and moved by the subsequent grasping organs, which successively replace those which are starting along the return section of their closed ring path. In this way a manipulator even of limited length, and thus light, rigid, of reduced size and not expensive, is capable of moving along a rectilinear axis flat sheets of a very great, practically unlimited, length. A second movement along an orthogonal axis is naturally obtainable by mounting the conveyor device with its corresponding grasping organs on a carriage movable along said orthogonal axis. An embodiment of the present invention will now be described in detail, as a non-limiting example, with reference to the drawings, wherein: Fig. 1 is a plan view from above of an one-axis manipulator according to the present invention; Fig. 2 is a vertical cross-sectional view of said manipulator taken along the line II-II of Fig. 1; Fig. 3 shows a front view of a clamp from the right hand side with respect to Fig. 2. The manipulator illustrated in Fig.s 1, 2 and 3 comprises on a base 51 a main housing 52 around which there runs a belt conveyor device 53, forming a closed ring with two parallel rectilinear sections (Fig. 1) between two vertical-axis pinions 54 and 55, of which the first is the driver and has a fixed axis and the second is the idler and has the axis which is movable in a direction parallel to itself in the plane wherein the two above axes lie and is operated by knob means to give tension to belt device 53. Belt 53 is of the type having internal teeth 57 (Fig. 2), so that its motion is perfectly synchronous with the motion of driving pinion 54. In addition to internal teeth 57, facing the pinions, belt 53 is provided with a certain number of external teeth 58 on its opposite face, equidistant one from the other, but with a longer pitch than that of teeth 57. Teeth 58 are used to anchor to belt 53 an equal number of grasping organs or clamps 61 (Fig.s 1, 2, and 3). Each clamp 61 is constituted by a housing 62, anchored to belt 53 by means of a tooth 58 and a metal tooth 59, replacing tooth 57 of the belt, opposite tooth 58, being the tooth 59 traversed by bolts 60 which bite into housing 62 and hold the belt tightly between tooth 59 and the housing itself (Fig. 2). At the upper and lower extremities of each housing 62 there are rotatably hinged two rollers 63 and two rollers 64 having a vertical axis, rolling in grooves 65 and 66 respectively of the main housing 52. At the lower extremity of each housing 62 there is also rotatably hinged a horizontal-axis roller 67, rolling on a track 68 of the main housing 52. Rollers 63 and 64 support the horizontal forces applied to clamp 61 and roller 67 supports the weight of clamp 61 itself. A vertical-axis roller 69, rolling on a track 70 of the main housing 52, is rotatably hinged on a small block 71 guided by two horizontal cylindrical pins 56 implanted in housing 62 of clamp 61, which block 71 is urged towards track 70 by two springs 72 resting against housing 62. This roller 69 has the function, co-operating with springs 72, of urging rollers 63 and 64 against the external faces 73 and 74 of grooves 65 and 66. On each housing 62 there is hinged at 120 a jaw 75 of clamp 61, on which there act two pistons 76 of hydraulic cylinders 77 obtained in the same housing 62 (in recess 78) having parallel and side-by-side axes. Recesses 78 of cylinders 77 communicate with the outside of clamp 61 by means of holes 79, 80 and 81. Two pivots 82 integral with jaw 75 are urged by springs 83 in the direction away from jaw 75 by a counterjaw 84 belonging to housing 62 and of returning pistons 76 in their seats 77. Between springs 83 and pivot 82 there is placed a piece 105 which is slipped with one of its cylindrical parts 106 into spring 83 and with one of its bored parts 107 on pivot 82; this piece 105 ensures the constant positioning of spring 83 with respect to pivot 82 even during rotation around the hinge of jaw 75. Coaxial with the driving pinion 54 and integral with it there is a pinion 85 (Fig. 1), which by means of toothed belt 86 transmits motion to a pulley 87 integral with a flanged bush 88, rotatable in a bush 89 located at the centre of the oblong ring formed by belt 53. The two bushes 88 and 89 may slide in a way parallel to their axis on a horizontal face 90 of the main housing 52, but are held in a precise position by a ring 91, which prevents its movement away from face 90, by a screw 92, which tightens belt 86, by belt 86 itself and by coaxial and opposite screws 93 and 94, which, by acting on a pin 95 implanted in bush 89, prevents its rotation around its vertical axis (Fig. 3). Along the periphery of the upper face of the flanged bush 88 there are made as many threaded holes 96 as there are clamps 61 integral with belt 53. Each hole 96 through holes 97, 98 and 99 ends up on the external cylindrical face of bush 88. On the internal cylindrical face of bush 89, which coincides with the external cylindrical face of bush 88, there are obtained two grooves 100 and 101 not communicating with one another, the first extending to just under the semi-circumference of the internal face of bush 88 facing one of the two rectilinear sections of belt 53 and the second extending to just over the semi-circumference facing the opposite rectilinear section. The groove 100 is in communication with a source of oil under pressure and the groove 101 is in communication with an oil tank not under pressure. The assembly 88, 89 thus operates as a rotating distributor which alternately connects holes 96 with either a supply or a discharge of oil. A given hole 99, if bush 88 rotates in bush 89, remains for just under half a revolution in communication with groove 100, and can thus receive oil under pressure, and for just over half a revolution in communication with hole 101, and can thus allow oil to flow towards the tank. Auxiliary grooves 103 diametrically opposed to groove 100, in communication with the latter but not reachable by holes 99, ensure a balance of the hydraulic forces acting on rotating bush 88, allowing for its easy rotation. Each hole 96 is connected by means of flexible hose 104 to hole 81 of the corresponding clamp 61. Holes 96 and 81 connected by hose 104 are in the same succession along the periphery of bush 88 and along the set of clamps 61 anchored to belt 53, respectively. The transmission ratio between pinion 85 and pulley 87 is such that bush 88 completes one revolution for each revolution of belt 53 and thus holes 96 and 81 connected together chase one another during the synchronous motion of bush 88 and belt 53, alternately getting closer to and moving away from one another and thus causing hose 104 to bend, but without ever twisting said hose 104. It follows that the movable jaw 75 of each clamp 61 forcefully approaches its respective counter-jaw 84, urged by its respective pistons 76 at the start of one of the two rectilinear sections of its path, because along that section its hydraulic cylinders 77 are in communication through conduits 79, 80, 81, 104, 96, 97, 98, 99 with groove 100 which is under pressure, and moves away from it under the action of springs 83 at the end of that section, because said communication closes and the communication is, on the other hand, opened between cylinders 77 and groove 101 which discharges the pressure. By turning screws 93 and 94, it is possible to adjust the points of starting and ending for closing clamps 61, by altering the peripheral position of grooves 100 and 101 of bush 89. When pressure from groove 100 is removed, all clamps remain open and the sheet to be manipulated (36) may be introduced into the jaws. The unit described above, completed with motor, codifier and driving and control units, may constitute a first axis of a two-axes manipulator, the other orthogonal axis being accomplished with known means. It appears obvious that the manipulator according to the invention is lighter and less bulky than any other known manipulator with long-stroke clamps. At the same time stops and repositionings are not necessary because the sheet metal plate is always grasped by the clamps, whatever its stroke and its dimensions.

Claims: Manipulator of flat sheets, comprising a conveyor device (53) forming a closed ring path with at least one rectilinear section and a succession of grasping organs (67) transported by said conveyor device (53) along said closed ring path, said grasping organs (61) having a fixed part (84) joined to said conveyor device (53) and a movable part (75) connected to said fixed part (84) so that it may be brought closer to and moved away from said fixed part (84) perpendicularly to the direction of movement of said conveyor device (53) for closing and opening said grasping organs (61), there being provided means for controlling the closing of said grasping organs (61) in said rectilinear section of said closed ring path, characterized in that said conveyor device (53) is constituted by a belt (53) to which there are joined at preset intervals supporting casings (62) for the grasping organs (61), which are provided with guide means (63, 64, 67) and have a portion defining the fixed part (84) of a grasping organ (61) and rotatably supporting the movable part (75) of the same grasping organ (61), and said means for controlling the closing of said grasping organs (61) comprise cylinder-piston assemblies (76, 77) supported by said supporting casings (62) and operating on the movable parts (75) of the grasping organs (61) and flexible hydraulic connections (104) between said cylinder-piston assemblies (76, 77) and a rotating distributor (88, 89) which, executing one rotation for each revolution of the belt (53), at the rectilinear section of said closed ring path puts into communication said flexible hydraulic connections (104) with a supply of oil under pressure.

Inventors: SALVAGNINI GUIDO, SALVAGNINI, GUIDO
Applicants: SALVAGNINI SPA, SALVAGNINI S.P.A.
Application year: 1989
Main classification: B65G17
IPC codes: B65G17, B65H5, B65G23, B29C31