Abstract:
Stripping a workpiece from a punch using a plurality of pivotally mounted segments that in an open position have a diameter greater than the outside diameters of the workpiece and the punch but in a closed position have a diameter greater than the outside diameter of the punch but less than the outside diameter of the workpiece.

Description:
FIELD OF THE INVENTION 
     This invention relates to apparatus and method for stripping a cylindrical workpiece from a cylindrical forming member, and, more particularly, to stripping apparatus employed in a one-piece can drawn and iron type body making machine for stripping a one-piece can body from a punch member. 
     BACKGROUND OF THE INVENTION 
     Conventional can body making machines employ a removable tool pack assembly and a removable stripper assembly which are removably mounted in a forming cavity in the machine as generally shown and described in U.S. Pat. Nos. 3,167,044; 3,289,453; 3,312,097; 3,314,274; 3,353,394; 3,359,775; 3,379,153; 3,390,565; 3,399,558; 3,457,766; and 3,469,432. Conventional stripper assemblies comprise annular ring support structure mounting a plurality of separate circumferentially spaced gripping finger members mounted in side by side abutting arrangement in a circular array. The gripping finger members are individually radially inwardly and outwardly displaceable by force of engagement with either the punch member during retraction of the punch after a forming stroke or the can body member on the punch member during the forward forming stroke. Each gripping finger member is provided with a radially innermost machined and hardened edge along which contact is made with the punch or the can. The finger members are held in position by O-ring or garter spring type resiliently deflectable devices which exert a force causing the finger members to be biased toward a radially innermost location defining a more or less circular opening having a diameter less than the outside diameter of the punch and the outside diameter of the can body. These devices also enable the finger members to be radially outwardly displaced to accommodate passage of the punch and the can body through the opening. When the can body on the punch is pushed through the opening, a portion of the inner edge of each finger member rides on the outer surface of the can body until the rim of the can body has passed beyond the inner edges. Then the finger members are moved radially inwardly by the resiliently deflectable devices to cause engagement with the outer peripheral surface of the punch. When the punch is retracted, the finger members engage the end of the can body to prevent rearward movement thereof with the punch. At the same time, compressed air applied through an axial passage in the punch blows the can body away from finger members. 
     The engagement of the finger members with the can body and the punch causes wear of the finger members, the outer surface of the can body and the outer surface of the punch. The finger members and the punches may be repaired by machining when the amount of wear causes manufacturing problems. The machining causes a reduction in diameter of the punch and an increase in the diameter of the opening formed by the finger members. When the difference between the diameter of the punch and the diameter of the opening reaches a certain amount, the stripping apparatus is no longer operative and the finger members and/or the punch must be replaced. The foregoing problems have led to the practice of keeping a large supply of sets of variable diameter finger members and variable diameter punches so that different diameter combinations of sets of finger members and punches may be employed to obtain a minimum diameter differential suitable for satisfactory manufacturing operations. Even so, at some point in time, the worn finger members and the worn punches must be discarded and replaced with new finger members and new punches. The repair and replacement of finger members and punches constitutes a substantial cost of manufacture. 
     SUMMARY OF THE INVENTION 
     The present invention provides a solution to the foregoing problems by eliminating contact between the finger members and the outer peripheral surfaces of both the can body and the punch. The finger members are biased toward a radially outermost retracted position defining an opening of larger diameter than either the can body or the punch. A compressed air operated actuating means is associated with the finger members to exert a force only at the end of the punch stroke causing radial inward movement of the finger members toward the punch to locate the edge portions of the finger members radially inwardly beyond the end of the can body without engagement with the outer peripheral surface of the punch but capable of contacting a surface of the can body to prevent relative movement between the can body and the finger member. The finger members are mounted in a manner providing very accurate positioning and defining a punch-can body opening which is concentric with the punch and the can body. When compressed air is removed from the actuating means during retraction of the punch, a resiliently compressible spring means associated with the finger members causes radial outward movement to the maximum diameter opening position. In addition, opening diameter adjustment means are associated with the finger members to enable the opening diameter to be adjusted. 
     Additional objects, advantages, and novel features of the invention are set forth in part in the description which follows which will be understood by those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a partial cross-sectional side elevational view of a conventional stripper assembly; 
     FIG. 2 is a partial end view of the stripper assembly of FIG. 1; 
     FIG. 3 is a partial cross-sectional side elevational view of a portion of a conventional punch and a portion of a conventional can body showing initial engagement with a stripper finger segment; 
     FIG. 4 is a partial cross-sectional side elevational view of the apparatus of FIG. 3 at the end of the punch stroke; 
     FIG. 5 is a partial cross-sectional view of the apparatus of FIG. 3 during the return stroke of the punch; 
     FIG. 6 is an end view, partially in cross-section, of one embodiment of a stripper assembly employing the present invention; 
     FIG. 7 is an enlarged cross-sectional side elevational view of a portion of the apparatus of FIG. 6; 
     FIG. 8 is an end view, partially in section, of the outer housing means; 
     FIG. 9 is a cross-sectional view of the housing means; 
     FIG. 10 is an end view, partially in section, of an alternative embodiment; 
     FIG. 11 is an enlarged cross-sectional view of the embodiment of FIG. 10; 
     FIG. 12 is a partial cross-sectional view similar to FIG. 11 but using another form of biasing means; and 
     FIG. 13 is a transverse cross-sectional view of the biasing means in FIG. 12. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 and 2 illustrate a conventional prior art stripper assembly comprising an outer retainer ring member 20 having a plurality of circumferentially spaced bolt holes 22 for attachment to a can body maker machine (not shown). A plurality of circumferentially spaced finger gripping segment members 24 are mounted about the inner periphery of retainer member 20 by an annular inner ring member 26, an annular resilient O-ring member 28 and an annular resilient garter-type wire spring member 30. 
     Each segment member 24 has inclined flat radially extending side surfaces 32, 34 which abut similar side surfaces of circumferentially adjacent segment members. Opposite end surfaces 36, 38 are flat with an annular O-ring groove 40 formed in surface 38. The outer surface of each segment comprises an axially extending side surface 42 connected to a radially extending surface 44 to provide a seat for the garter spring 30, and an inclined side surface 46. The radially innermost portion of each segment is provided with a pair of generally arcuate intersecting inclined surfaces 48, 50. Surface 50 intersects surface 36 at an angle to provide a generally arcuate edge 52. During the course of manufacture of the segments, the original radius of each arcuate edge 52 is slightly changed so that a central portion 54 of each arcuate edge is located further radially inwardly than any other portion. The central radially innermost portions of each segment edge define a generally circular opening 56 having a diameter less than the diameter of an annular punch member 58 and a can body member 60 which pass through the opening during reciprocable operation of the punch between a retracted position and an extended position. It is intended that the central axis 62 of opening 56 be concentrically aligned with the longitudinal axis of the punch and the can body carried thereon, but in practice, the desired condition of concentricity is difficult to achieve and to maintain during continuous high speed operation. 
     In operation, the segments are normally floatably resiliently deflectably supported by O-ring 28 and garter spring 30 in a radially innermost location, as shown in FIG. 1, whereat edge portions 52 are located along a circle of lesser diameter than the diameter of either of the punch 58 or the can body 60 which has a cylindrical side wall portion 62, an end wall portion 64 and an open rim portion 66. During the initial portion of the forward stroke of the punch, the can body is formed by passage through dies in a tool pack (not shown) and then engages the segments 56 as illustrated in FIG. 3 during a subsequent portion of the punch stroke to force the segments radially outwardly away from the can body. When the can body passes beyond the segments, the segments move radially inwardly into engagement with the peripheral surface 68 of the punch as shown in FIG. 4. During the return stroke of the punch, the segment side surfaces 36 engage can rim surface 66 to prevent return movement of the can while compressed air is blown into the open end of the can body through a passage 70 in the punch. As shown in FIG. 5, the segments remain in engagement with the punch during the entire return stroke. 
     Referring now to FIGS. 6 and 7, one embodiment of the present invention comprises annular outer housing ring means 100, an inner annular pivot ring means 102, an inner annular adjustment retainer ring means 104, a plurality of circumferentially spaced finger segment means 106, an annular O-ring type flexible resilient biasing ring means 108, an annular air expandable and contractable resilient actuating tube means 110, an annular force transfer ring means 112, an air supply means 114 and an adjustment locking means 116. 
     As shown in FIGS. 8 and 9, outer retainer ring means 100 comprises an annular ring member 120 made of one-piece of suitable machined steel material with an annular outermost wall portion 122 connected to a side wall portion 124 having a central opening 125 defined by a flange portion 126. A plurality of circumferentially spaced bolt holes 128, 130 are provided in portions 122, 124, respectively. Portions 122, 124 and 126 define an annular cavity 132 having a threaded inner surface portion 134 axially adjacent a flat annular inner abutment surface portion 136 and a radially inwardly extending side abutment surface portion 138. A pair of tube passages 140, 142 extend through portion 122 opposite surface 136. Side surfaces 144, 145, 146 are accurately machined. 
     Referring to FIG. 7, pivot ring means 102 comprises a radially innermost axially extending annular flange portion 150 and a radially outwardly extending flange portion 152 having accurately machined side surfaces 154, 156 which are held in abutting engagement with retainer ring side surfaces 138, 144 by a plurality of circumferentially spaced bolt members 158. Annular inner peripheral surface 160 has a diameter substantially greater than the diameter of either the can body or the punch. An annular rib portion 162 extends axially outwardly from side surface 164 and has an accurately machined finished semi-circular peripheral surface 166 providing pivotal support means for each of the segments. 
     Each of the segment means 106, FIG. 6 and 7, has opposite inclined side surfaces 170, 172 to enable abutting supporting engagement with circumferentially adjacent ones of the segment means. A radially innermost head portion 174 has a flat side surface 176, which intersects an inclined inner peripheral annular surface 178 to provide an edge portion 180. A second inclined inner peripheral annular surface 182 intersects a side surface 184 opposite pivot ring surface 160. A V-shape groove 186 having machine finished side surfaces 188, 190 is formed in side surface 184 for rocking pivotal engagement with pivot rib means 162. A radially outwardly extending flange portion 192, having the same width as the head portion, provides spaced oppositely facing flat side surfaces 194, 196 which are continuously engaged by O-ring means 108 and force transfer ring means 112 at radially spaced locations 198, 200. 
     Adjustable retainer ring means 104 has an inner peripheral surface 202 defining an opening 204 of sufficient diameter to receive the segment head portions 174. The outer peripheral surface 206 is threaded for engagement with threaded portion 134 of outer retainer ring means 100. Thus, the axial location of ring means 104 may be adjustably varied and spanner wrench slots 208 are provided in side surface 210 for that purpose. In order to prevent rotation during operation, outer end portion 212 of locking flange means 116 is suitably fixed to the side by a bolt (not shown) and resiliently deflectable axially offset inner end portion 214 enables a portion 216 to be releasably engaged with one of the spanner wrench slots 208. An annular slot 218 in side surface 220 holds O-ring means 108. 
     Force applying ring means 112 has flat oppositely facing side surfaces 230, 232 and inner and outer peripheral surfaces 234, 236 such as to provide sufficient clearance. Surfaces 230, 232 are relatively wide to provide maximum contact with the segments 174 and the expandable tube means 110 which is held against surfaces 136, 138 and 155. 
     In operation, in a pre-adjusted position, as illustrated in FIG. 7, compressed air is injected into the tube means 110 to expand the tube means to cause uniform axial movement of the force ring means 112 and uniform pivotal movement of the segments 106 until side surface 194 abuts side surface 220 whereby all segment edges 180 of all segments are moved equal radial inward distances to define a circle of sufficient diameter to engage only the can end surface 66 during inflation of tube means 110. The distance of pivotal movement of the segments to the extended position is precisely controlled and positively limited by the axial location of surface 220. In order to set the pre-adjusted position of FIG. 7, adjustment ring means 104 is adjusted while tube means 110 is in the expanded condition so as to adjustably vary the diameter of the circle formed by the segment edges 180 when the segments 104 are pivoted about the pivot rib means 162. The adjustment ring means 104 is thus located at a position whereat the diameter of the innermost circle formed by the segment edges 180 is larger than the outside diameter of the punch but smaller than the outside diameter of the can body. Then, adjustment ring means 104 is locked in the pre-adjusted position. Thereafter when the application of the compressed air is stopped, the force of the O-ring bisasing means 108 will cause sufficient reverse uniform pivotal movement of the segments 106 so as to cause radially outward movement of the segment edges 180 to an open position whereat the outermost circle defined by the segment edges 180 is greater than the outside diameter of the can body. The amount of contraction of tube means 110 is exaggerated in FIG. 7 for purposes of illustration. In use in a can body stripping operation, the segment edges 180 will be in the open position of FIG. 7 as the can body 60 and punch 58 are moved through the circle formed by the segment edges 180 with no contact being made by the can body or punch with the segment edges 180. After the edge of the open end of the can body has moved past the circle defined by the segment edges 180, the compressed air will be injected into the tube means 110 to cause pivotal movement of the segments 106, as described above, to the preset closed stripping position whereat surfaces 194 and 220 are in abutting engagement to provide positive stop means so that the segment edges 180 define a circle having a diameter larger than the outside diameter of the punch but smaller than the outside diameter of the can body. Therefore, the segment edges 180 will contact only the edge 66 of the open end of the can body and strip it off the punch as the punch is retracted without engagement with either the peripheral side surface of the can body or the punch. 
     FIGS. 10 and 11 show an alternative and presently preferred embodiment of the invention which comprises annular outer housing ring means 300, an inner annular pivot ring means 302, an inner annular adjustment retainer ring means 304, a plurality of circumferentially spaced finger segment means 306, an annular flexible resilient biasing ring means 308, an annular air expandable and contractable resilient actuating tube means 310, an annular force transfer ring means 312, an air supply and control means 314, and an adjustment locking means 316. 
     The construction, arrangement and operation of the apparatus of FIGS. 10 and 11 is substantially the same as the apparatus of FIGS. 6-9 except as otherwise hereafter described. 
     Each of the segment means 306 are separately mounted in circumferentially spaced non-contacting relationship in separate circumferentially spaced segment slot means 320 provided in retainer ring member 322. Each segment has an L-shape cross-sectional configuration and comprises a pair of accurately machined and finished opposite parallel axially extending side surfaces 323, 324, which are slidably abuttably supported by accurately machined and finished slot side surfaces 325, 326. 
     In another embodiment, surfaces 178, 182 of segment members 106, FIG. 7, may be replaced by a single inclined inner peripheral surface 334 which intersects side surface 176 to provide the radially innermost edge portion 80. In addition, biasing ring means 308 may comprise a one piece metallic wave-type ribbon spring member 340, FIGS. 12 and 13, having circumferentially spaced axially displaced portions 341, 342 on one or more coils 344, 346 with a flat end coil 348 adapted to abut the side surface 349 of segment means 306. End portion 350 of wave form end coil 342 extends axially to provide a tang portion 352 located in a slot 354 in retainer ring member 304 to prevent rotation of spring member 340 and retainer ring member 304 during operation while enabling threaded rotative adjustment of retainer ring member 304 by force applied by a spanner wrench in wrench holes 356. 
     It is contemplated that the inventive concepts herein described may be variously otherwise embodied and it is intended that the appended claims be construed to include alternative embodiments of the invention except insofar as limited by the prior art.