Force transmitting coupling for stamping and forming machine
FIELD OF THE INVENTION 
     This invention relates to force transmitting couplings and particularly to couplings between a ram assembly which reciprocates along a rectilinear path and an actuator which oscillates along an arcuate path. 
     BACKGROUND OF THE INVENTION 
     U.S. Pat. No. 4,497,196 describes a stamping and forming machine having aligned opposed ram assemblies which move towards and away from each other along rectilinear paths. The ram assemblies have stamping and forming tooling on their opposed faces which performs stamping and forming operations on strip material which is fed along a strip feed path that extends between the ram assemblies. The ram assemblies are reciprocated by levers which oscillate along arcuate paths and which are coupled to the ram assemblies. The couplings must be such that they are capable of accommodating the arcuate movement of the levers and transmitting forces from the levers to the ram assemblies as they reciprocate along their straight line paths. The above identified U.S. Patent describes a machine in which universal joints are used in the couplings and good service has been obtained with universal joints although they tend to wear out with time and with prolonged usage because of the friction generated or developed during operation of the machine. Application Ser. No. 915,79 filed Jul. 16, 1992 (15343) describes an improved coupling which has cylindrical bearing surfaces with the axes of the cylindrical surfaces extending normally of the path of reciprocation of the ram assembly and normally of the plane of oscillation of the actuator lever. Couplings of the type shown in that application are an improvement over universal joint type couplings for the reason that the friction is greatly reduced and longer life in the coupling is obtained. 
     The present invention is directed oo the achievement of an improved force transmitting coupling which applies force transmitted from an arcuately moving actuator to the axis of a ram which reciprocates along a rectilinear path. The invention is further directed to the achievement of a coupling which is essentially frictionless so that the necessity for lubricating the coupling is avoided and to the achievement of a &#34;fail safe&#34; coupling. 
     THE INVENTION 
     The invention comprises force transmitting means or transmitting force from an actuator assembly, which moves to-and-fro along an actuator path, to a ram assembly which reciprocates along a rectilinear path between a retracted position and a forward position. The force transmitting mean comprises a flexible member which extends between the actuator assembly and the ram assembly and which has first and second ends. The first end of the flexible member is against the ram assembly and the second end is proximate the actuator assembly. The flexible member and the ram assembly are connected to each other by oppositely facing shoulder portions on the ram and flexible member. The flexible member and the actuator assembly are connected to each other by a lost motion connection. The actuator assembly has actuator driving surface portions which are adjacent to, and movable against, the second end of the flexible member. Supporting surfaces are provided which extend parallel to the flexible member. These supporting surfaces permit a limited amount of flexure in the flexible member and prevent flexure by an amount greater than the limited amount. During operation, the ram assembly is pushed from its retracted position to its forward position by the actuator driving surface portions and the ram assembly is pulled from its forward position to its retracted position by the actuator acting through the opposed shoulder portions and the lost motion connection. When the ram is pushed from its retracted position to its forward position, the flexible member is placed under compression and flexes by the amount permitted by the supporting surfaces. When the ram assembly is pulled back to its retracted position, the flexible member functions as a tensioned member. 
    
    
     THE DRAWING FIGURES 
     FIG. 1 is an end view of a stamping and forming machine. 
     FIG. 2 is a sectional view, on an enlarged scale, of the upper portion of the actuator lever and the coupling between the actuator and the ram assemblies. 
     FIG. 3 is a sectional side view on an enlarged scale of the coupling. 
     FIG. 4 is a top plan view of the coupling looking in the direction of the arrows 4--4 of FIG. 3. 
     FIG. 5 is a simplified diagramatic side view of the coupling. 
     FIG. 6 is a diagramatic view looking in the direction of the arrows 6--6 of FIG. 5. 
     FIG. 7 is a view similar to FIG. 5 showing the positions of the parts when the ram assembly is being pushed from its retracted position to its forward position. 
     FIG. 8 is a view similar to FIG. 5 showing the positions of the parts when the ram assembly is being pulled from its forward position to its retracted position. 
    
    
     THE DISCLOSED EMBODIMENT 
     A machine 2 of the type described in U.S. Pat. No. 4,497,196 has a base portion 4 on which one or more machine modules 6 are supported. The machine module has an upper surface 8 on which a ram housing 10 is supported. Opposed ram assemblies 12, 12&#39; are sideably contained in the housing 10 and strip material is fed along a strip feed path which extends through aligned slots 14 in the housing. When the ram assemblies 12, 12&#39; move towards each other, tooling on the opposed ends of the rams perform punching and forming operations on the strip material. 
     The ram assemblies are reciprocated by levers which oscillate along arcuate paths. These levers have upper ends 16, 16&#39; which are coupled by coupling assemblies 44, 44&#39; to the ram assemblies. Each lever is pivoted at its lower end 15 and is connected by an eccentric 17 intermediate its ends to a power shaft 19. 
     The lever assemblies and the couplings are substantially identical and in the description which follows, only the lever assembly shown on the left in FIG. 1 will be described in detail. 
     An opening 18 extends through the upper end 16 of the lever from the left side 20 to the right side 22 thereof. This opening is counterbored on the right side as shown at 24 and a fixed sleeve 26 is contained in the bore. The sleeve 26 has a flange that is received in the counterbore and is secured to the lever by fasteners 28. An adjustable sleeve 30 is received in the left hand portion of the bore and has a flange 32 on its end. Fasteners 34 extend through the flange and bear against the surface 20 of the lever. An adjusting rod 36 extends through the sleeves 26, 30 and has a reduced diameter right hand end 38. The left hand end 40 of the rod is enlarged and is non-circular so that it can be turned with a wrench. 
     The external surface of the rod and the internal surface of the adjustable sleeve are provided with threads 42 so that the rod 36 can be adjusted rightwardly or leftwardly as viewed in FIG. 2 thereby to adjust the extreme positions of the ram assembly. 
     The coupling 44 which couples the upper end 16 of the lever to the ram assembly 12 will be described with reference to FIGS. 5-8. These Figures are diagramatic and do not show all of the parts in the actual embodiment of the coupling showing in FIGS. 2-4. The clearances between parts in FIGS. 5-8 are highly exaggerated for purposes of illustration and in some instances clearances are shown where they do not exist. 
     The coupling assembly 44 comprises first and second collar assemblies 46, 48 and a flexible plate-like member 50. The first collar assembly 46 is secured by fasteners 54 to an adaptor plate 56 which is received in a recess 58 in the ram assembly 12 and which is secured to the ram assembly by a screw 60. The ram assembly 12 is therefore secured rigidly to the first collar assembly 46. The adaptor is received in a recess 62 in the rightwardly facing surface 64 of the collar assembly 46. 
     The flexible member 50 is a thin plate-like member having a substantial width as viewed in FIG. 6 relative to its thickness and has laterally extending arms 66 at its first end 65. A T-shaped recess 68 is provided in the collar assembly 46 and the flexible member 50 is contained in this recess. The right hand edge 72 of the first end 65 of the flexible member 50 is against the surface 74 of the adaptor 56 and the second end 80 of the flexible member extends beyond the left hand end 70 of collar assembly 46. The flexible member is supported, when it is in a flexed condition, by supporting surfaces 76, 78 in the collar assembly which extend parallel to the upper and lower surfaces of the flexible member 50. Adjacent to the first end 65 of the flexible member, these supporting surfaces converge as shown at 79 so that the first end of the flexible member 50 is more closely confined than the intermediate portion. The surfaces 76, 78 permit the flexible member to flex by a predetermined amount but prevent flexure by an amount greater than the predetermined amount. 
     The second end 80 of flexible member 50 extends into a recess 82 that extends inwardly in the second collar assembly 48. The inner end 86 of this recess is immediately adjacent to the trailing edge 88 of the flexible member. The surface 86 functions as a driving surface when the ram is pushed from its retracted position to its forward position. A hole 90 is provided in the flexible member and is in alignment with holes 92 in the collar assembly 48. A pin 94 extends through the hole 90 and is received in the holes 92 in the collar assembly. These holes and the pin 94 function as a lost motion connection between the flexible member and the collar assembly. The pin 94 is designed such that it functions as a shear pin so that in the event of the development of unduly high forces, the pin will shear and thereby prevent damage to the machine. The operation of the coupling 44 is as follows. 
     Assuming that the ram assembly 12 is in its retracted position and the actuator is at the leftward limit of its stroke as viewed in the drawing, the ram assembly is first pushed by the actuator rightwardly from the position showed in FIG. 5. The surface 86 of the collar assembly 48 moves against the edge 88 of the flexible member 50 and the flexible member in turn moves against the surface 74 of the adaptor 56. The flexible member flexes during this portion of the operating cycle as shown in FIG. 7 and the intermediate portion of the flexible member moves against, and is supported by, the surfaces 76, 78. Because of the fact that the intermediate portion of the flexible member is supported, it can function as a compression member notwithstanding its tendency to flex and its extreme thinness. During the forward stroke of the actuator 16, the flexible member will first flex in one direction toward one of the surfaces 76 or 78 and then towards the other surface. This reversal in the flexure of the member 50 is caused by the fact that the lateral force component transmitted from the actuator is upwardly, as viewed in FIG. 5, during one portion of the stroke and downwardly during the other portion. The constricted portions 79 of the supporting surfaces ensure that the leading or first end of the flexible member is closely confined and flexure will take place in a predictable manner. 
     At the beginning of the return stroke, when the ram assembly 12 is pulled by the actuator leftwardly, the lost motion connection between the collar assembly 48 and the second end 80 of the flexible member becomes effective and the pin moves relatively leftwardly of the left hand side of the hole 90. The flexible member 50 is thereby pulled leftwardly and the opposed shoulders or edges 81, 83 on the arms 66 of the flexible member 50 and the edges of the recess 68 function as a coupling between the flexible member 50 and the first collar assembly 46. During this portion of the cycle, the flexible member is placed in tension and extends axially as shown in FIG. 8. 
     The actual coupling 46 as shown in FIG. 3 differs in some respects from the diagramatic views of FIGS. 5-8. The second collar assembly 48 is connected to the reduced end portion 38 of the rod 36 by a connection which permits rotation of the rod relative to the collar assembly. The reduced end 38 of the rod is provided with a circumferential groove 98 and coupling pins 100 extend through the collar and are received in this groove. The rod 36 can thus be rotated without affecting the collar assembly 48. 
     The recess 82 in the collar assembly 48 is relatively wider than the recess shown in FIG. 5 and two spacers or adaptors 102 are contained in the recess on each side of the flexible member. These spacers or adaptors are provided only for purposes of manufacturing convenience. 
     The first collar assembly 46 is a composite member having upper and lower sections 104, 106 which are secured to each other by fasteners 108. The T-shaped recess 68 in which flexible member 50 is contained is formed by recesses in the opposed surfaces of the two sections 104, 106. 
     Flexible member has an overall length of about 31 mm and a thickness of about 2.38 mm. This flexible member can be formed with two or more thin stampings, rather than as a single piece, in order to reduce the maximum bending stresses developed when the member is repeatedly flexed and in order to avoid metal fatigue. 
     The clearances between the flexible member 50 and the collar sections 46, 45 are very small and are greatly exaggerated in FIGS. 5-8 for purposes of explanation. For example, the clearance between the shear pin 94 and the hole 90 in flexible member 50 is only about 0.002 mm. The connection between the second end 80 of flexible member 50 and the second collar section 48 is nonetheless a lost motion connection and the pin is stressed only when the ram assembly 12 is pulled from its forward position to its retracted position. The ram is pushed by the surface 86 when the ram is moved from its retracted position to its forward position, and the pin is not stressed during that portion of the cycle. 
     Many of the advantages of the invention will be obtained if the ends 65, 80 of flexible member 50 are secured tot he ram and the actuator with rigid connections, however the advantages obtained by the use of the shear pin will not be obtained. Also, the disclosed construction of the coupling is believed to be the best known at present from the standpoint of manufacturing convenience. 
     One advantage of the invention is that in the event of the development of excessive forces in the coupling 44, as a result of galling or a jam in the tooling, the shear pin will fail and damage to the machine will be avoided. Another advantage is that frictional losses are minimized and little or no lubrication is required.