Double acting apparatus and method for ejecting workpieces from forming machines

A resilient element is used to eject a workpiece from a machine, such as a lidded container from a seaming chuck. The resilient element dual acting since it is formed of a flexible compressible material in a manner so that a first portion of the element applies a first ejecting force and a different, second portion applies a second ejecting force after completion of a task on the workpiece. This can be by a combination of flexion and compression. The resilient element can have a central panel portion of flexible resilient material and a margin portion of compressible material. A head can be formed on the central panel portion. The invention includes a chuck assembly provided with such resilient element. The invention also includes a method of ejecting workpieces from machines with the dual restorative forces.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS The present invention is directed generally to the metal forming machines that include forming stations operative to receive workpieces for performing a machining function thereon. Of particular concern of the present invention are improvements to the method and apparatus for ejecting a workpiece from such a forming station. Thus, the present invention is directed to new and useful embodiments of resilient ejectors that may retrofit onto existing chuck assemblies for such machines and, furthermore, to the combination of improved chuck elements with improved resilient ejectors. Thus, the present invention provides both retrofit capability for existing machines as well as to the improvements to original (O.E.M.) equipment. The present invention is particularly directed to ejector apparatus and methods for use with lid seaming machines of the type operative to seam or join lids or other end caps onto containers such as used in the food and beverage industry. Thus, for purposes of example only and not for limitation as to the overall scope, this invention will be described hereinafter in conjunction with a lid seaming apparatus for a container, such as a container that has a fiberboard, metal or plastic sidewall. An example of a type of product is a can for frozen juice concentrate. It is to be clearly understood from the outset, though, that the exemplary embodiments of the present invention and the methods employed could be utilized on other types of machine forming equipment, especially those incorporating ejector rods. Moreover, while the container body is shown to be cylindrical with the end closure (or lid) correspondingly circular, it should be understood that rectangular (including square), oval or other shaped containers and closures as now known or later developed are within the scope of this invention requiring modifications within the skill of the artisan. In order to better understand the present invention; it is first helpful to review a standard-type of forming station used in the beverage can industry. Thus, with reference to FIG. 1 , it may be seen that a standard lid seamer 10 includes an elongated spindle 12 that is fixedly mounted to the machine such as by a housing or turret (not shown). A chuck element 14 is threadably mounted on a distal end of spindle 12 and includes a working surface 16 that interacts with a forming roller 18 to seam a lid 20 onto a container, such as concentrated juice container 22 . Chuck element 14 and forming roller 18 thus define a forming station, and lids 20 are delivered to this forming station by means of gravity feed 24 . Unlidded containers 22 are moved into position with the forming station, for example, by star wheel 26 (shown in phantom). A push pad 28 reciprocates in the direction of arrow “A” and thus provides a positioning mechanism operative to first advance so as to move container 22 into a engaged position with the forming station and then to retract whereby the lidded container is ejected from the forming station. To assist in ejecting the lidded can from the forming station, it is common practice to form a longitudinal passageway 30 through spindle 12 to reciprocally mount a knock-out rod 32 therein by means of suitable bearings and bushings. Accordingly, chuck element 14 has a central, axial opening 34 that registers in axially alignment with longitudinal passageway 30 so that head 36 of knock-out rod 32 may protrude through opening 34 so as to selectively contact lid 20 thereby to assist in ejecting the lidded beverage can from the workstation. To supply the knock-out or ejection force, an end 38 of knock-out rod 32 opposite head 36 is connected to a mounting block 40 which in turn is secured to a cam follower 42 . Cam follower 42 includes a roller 44 received in a camming groove 46 formed in turret portion 48 so that, as the forming station revolves around stationary turret portion 48 in the direction of arrow “B”, block 40 and thus knock-out rod 32 reciprocates in the direction of arrow “C” according to the amplitude of undulating camming groove 46 , as is known in the art. As noted in the background of the description, the use of a knock-out rod 32 has disadvantages. The impact of head 36 on the lid 20 of container 22 caused by the reciprocating mounting block 40 can scratch or dent the lid or even rupture the seal of the lid thus exposing the contents of container 22 to contamination. This contamination can be in the form of intrusive materials, including bacteria or other microbes. Additionally, longitudinal passageway 30 is necessarily supplied with a lubricating medium, such as oil or the like. Any leakage through the bearings, seals or bushings associated with spindle 12 and knock-out rod 32 can contaminate the outer surface of lid 20 and, where the edge seal is violated, can possibly contaminate the contents of container 22 . The present invention contemplates elimination of the entire push rod assembly, including push rod 32 , mounting block 40 and cam follower 42 . This also can possibly permit faster machine speed by eliminating the inertial mass of the knock-out rod and its associated mechanical linkages. The present invention further helps control the lid/end closure during registration with the container body. Accordingly, it should be appreciated that the invention can be employed either in the manufacture of original equipment or as a retrofit structure, explained more thoroughly below. With reference to FIGS. 2 - 5 , therefore, a first exemplary embodiment of the present invention is shown in the form of a chuck assembly 110 including a chuck element 120 and a resilient element 150 . With reference first to FIGS. 2 and 3 , it may be seen that chuck element 120 is in the form of a generally cylindrical tool having a surrounding sidewall 122 so that a longitudinally extending passageway 124 is formed therethrough. Chuck element 120 is constructed identically to that described in my U.S. Pat. No. 5,533,853, the contents of which are incorporated herein by reference. It should be understood, however, that differently configured chuck assemblies could be used. For example, lid seaming machines with chuck assemblies are used for rectangular (including square) cans and oval cans, such as those used to package meat products. Other seaming machines employ chuck assemblies for cans provided with pull tab openers (such as beverage cans, some pet food cans, sardine cans, etc.). In any event, an inner wall of sidewall 122 is threaded at 126 so as to be threadably received on the threaded end of spindle 12 . Returning again to FIGS. 2 and 3 , it may be seen that sidewall 122 includes a plurality of spanner ports 128 so that a wrench may be engaged with chuck element 120 so as to allow loosening and tightening of chuck element 120 onto spindle 12 . A distal end 130 of chuck element 120 includes recess 132 surrounded by an upstanding peripheral rim 134 . Recess 132 communicates with a central opening 136 by way of passageway 124 centered about longitudinal central axis “X”. Thus, peripheral rim 134 extends around one end of chuck element 120 . Where the chuck element 120 is circular, then, the rim 134 extends circumferentially around the end with rim 134 having an exterior forming surface 138 which cooperates with forming roller 18 to join or “seam” a lid 20 onto an upper rim of container 22 . An annular groove 140 is formed (such as by machining) in recess 132 along the periphery thereof proximate to upstanding rim 134 . Annular groove 140 thus has an inner groove wall 141 with an exposed support surface 143 . Rim 134 and inner groove wall 141 together bound groove 140 . Resilient element 150 is best shown in FIGS. 3 - 5 . As is shown in these Figures, resilient element 150 includes a compressible, resilient, flexible body 152 having a first portion in the form of central panel section 153 generally having a first thickness “t 1 ”. An annular ridge structure 154 projects away from a first side 156 of central panel 153 . Ridge structure 154 is sized and adapted to be matably received in annual groove 140 of chuck element 120 thereby to secure resilient element 150 in a fastened state in a recess 132 of chuck element 120 . Ridge structure 154 has a wall 158 formed at a large acute angle relative to the plane “P” of central panel 153 . This allows ridge structure 154 to be snap-fitted into engagement with annular groove 140 . Resilient element 150 includes a second or margin portion defined by a radially outwardly projecting peripheral lip 160 that extends around an outer, exposed perilmeter edge of central panel 153 . An annular shoulder 162 extends around the interior 155 of resilient element 150 adjacent to but radially inwardly of ridge structure 154 . Accordingly, resilient member 150 provides an active spring region 164 located between annular edge 168 of central portion 153 and shoulder 162 as a margin portion of resilient element 150 . A spring region 164 is formed of a thickness “t 2 ” that is greater than “t 1 ”. Spring region 164 provides an ejecting force, when compressed, as described more thoroughly below. An annular ring 170 is located on the exterior surface of central portion 153 of resilient element 150 and has an axial bore 172 through which a shaft 174 of plug 180 is inserted for mounting. With reference to FIG. 4 , the construction and assembly of resilient element 150 may be seen in greater detail. Here, it may be seen that resilient flexible body 152 is sandwiched between plug 180 and a locking washer 190 . Flexible body 152 is preferably formed of a polymer material such as neoprene, EPDM or other durable, flexible, compressible, and resilient material. Further, body 152 is constructed to have the configuration described above. Plug 180 has an elongated axial shaft 174 provided with a plurality of radially projecting, resilient vanes 182 and an enlarged button or head 184 constructed as an annular disk. Plug 180 is integrally molded as a single piece out of nylon or other polymer, but is should be understood that it is preferable to use a hard, stiff, lubricious plastic. In any event, shaft 174 of plug 180 is inserted through axial bore 172 and resilient body 152 so that head 184 abuts a stanchion in the form of annular ring 170 . Plug 180 is held in position by means of a locking washer 190 that is press-fit onto shaft 174 so as to be engaged and held in position by vanes 182 . To this end, washer 190 is provided with a central opening 192 to receive shaft 174 . Plug 180 , along with the flexibility of central portion 153 , provides a second active spring region to eject a container 22 from chuck assembly 130 . As is also shown in this FIG. 4 , as well as in FIG. 3 , central panel 153 has a plurality of equiangularly spaced, longitudinally extending vent passageways 157 that provide vents such that the interior of chuck element 130 may be vented when resilient element 150 is mounted on the end thereof. The use of vents 157 is desirable, on one hand, to prevent resilient element 150 from forming a suction cup when pressed against a lid 20 . Should this happen, the suction force would act to resist ejection of the seamed container. Use of vents 157 does increase the possibility, however, of a small amount of lubricant leakage. Accordingly, depending on the application and risks involved, vents 157 may or may not be employed without departing from the scope of this invention. The action of resilient element 150 on a container 22 can now be more fully appreciated with reference to FIGS. 6 ( a )- 6 ( c ) and FIGS. 7 ( a )- 7 ( c ). Referring first to FIG. 6 ( a ), it may be seen that container 22 and lid 20 engage chuck 120 in a fully engaged position. Here, the active first spring region 164 is compressed against lid 20 while central portion 153 of resilient element 150 is inwardly deflected because of the contact of plug 180 with lid 20 . The amount of deflection is controlled by the thickness of head 184 and the thickness of ring 170 . FIG. 6 ( a ) corresponds, diagrammatically, to a dual spring equivalent of resilient element 150 as is shown in FIG. 7 ( a ). In FIG. 7 ( a ), it may be seen that a spring 210 is fully compressed between a first plate 220 and a second plate 230 spaced at a distance “I 1 ”. Another spring 250 is fully compressed between plate 230 and a third plate 240 a distance “I 2 ”. FIG. 6 ( b ) shows the resilient element of chuck assembly 120 in an intermediate position. Here, the spring region 164 is decompressed thus partially ejecting, that is, disengaging, lid 20 of container 22 from chuck assembly 120 . However, central region 153 remains substantially deflected. This, then, corresponds to the two spring equivalent diagram in FIG. 7 ( b ). In FIG. 7 ( b ), spring 250 remains fully compressed between plates 240 and 230 at a distance “I 2 ”. However, spring 210 is decompressed so that plates 230 and 240 are spaced from one another a distance “I 3 ”. Finally, with respect to FIG. 6 ( c ), chuck assembly 120 and resilient element 150 are in a fully disengaged state or release state. Here, spring region 164 is fully expanded. Moreover, the spring region formed by the deflection of central portion 153 is now in its undeflected, or normal position. This, then, corresponds to the mechanical equivalent spring structure shown in FIG. 7 ( c ). In FIG. 7 ( c ), it may be seen that spring 210 is fully open so that plates 220 and 230 are spaced the distance “I 3 ” apart from one another. Spring 250 remains fully expanded so that plates 230 and 240 are spaced-apart an expanded distance “I 4 ”. From the foregoing, and in particular reference to FIGS. 7 ( a )- 7 ( c ), it may be seen that, as container 22 and unseamed lid 20 are advanced into engagement with chuck assembly 120 , spring 250 first compresses at a first spring force “F 1 ” that is equal to k 1 (I 4 -I 2 ) where “k 1 ” is the spring constant of spring 250 . This compression occurs because “k 1 ” is much less than the spring constant of spring 210 , that is, “k 2 ”. Moreover, the compression of spring 250 corresponds to the deflecting of central wall portion 153 between the released position shown in FIG. 6 ( c ) to the intermediate position in FIG. 6 ( b ). Further advancement of container 22 and lid 20 into engagement with chuck 120 now results in the compression of spring 210 . This corresponds to the compression of spring region 164 of resilient element 150 . This second force exerted by this second compression, then, equals k 2 (I 3 -I 1 ). With the spring equivalent diagrams of FIGS. 7 ( a )- 7 ( c ) in mind and with further consideration of the structure of resilient element 150 , it may now be appreciated that resilient element 150 provides a dual action on a container 22 and its lid 20 both during engagement as well as for purposes of ejecting the assembled container from the forming station. When in the fully engaged position, spring region 164 exerts the larger spring force on lid 20 over a relatively short distance. It may be desirable that this force be approximately twenty to sixty pounds acting over a distance of approximately 0.010 to 0.060 inches. This force is provided by the compression of region 164 and acts to initially disengage the assembled container from the engaged position shown in FIG. 6 ( a ) to the intermediate position shown in FIG. 6 ( b ). Upon the expansion of region 164 , however, a smaller force acts over a longer distance. Here, the spring force is preferred to be approximately five to fifteen pounds acting over a distance of approximately 0.1 to 0.5 inches. This longer throw with less force accelerates the seamed container downwardly and helps overcome the frictional engagement of container 22 with the star-wheel apparatus. A first alternative embodiment of the present invention is shown in FIG. 8 . In FIG. 8 , resilient element 350 is adapted to again mount in chuck assembly 120 . Here, however, resilient element 350 is formed as integral one-piece molding of flexible, resilient, compressible polymer material. Accordingly, plug 180 is eliminated. Instead, central portion 353 has a head structure in the form of an enlarged external nub 360 with rounded surface 361 that is axially disposed so as to bear against lid 20 . Vents, such as vent 357 , are provided. A third exemplary embodiment of the present is shown in FIG. 9 . Here, resilient element 450 is again formed as a single molded piece. However, central portion 453 is thickened to provide a greater ejection force and the axial nub 460 has a flattened top surface 462 instead of being rounded. In this embodiment, the vent ports are eliminated. From the foregoing, it should be appreciated that the amount of the dual acting forces may be altered as should be readily apparent to those ordinarily skilled in the art. This can be accomplished, for example by changing the dimensions of shoulder 162 both in thickness and in radial dimension, by changing the thickness of region 164 and by changing the thickness of central region 153 . The distance of throw for the second spring force can be varied by changing the dimensions of plug 180 as well as annular ring 170 . The amount of force can be altered by changing the thickness or dimensions of central region 153 . In addition, cuts or other weakening structures such as annular channels could be used to alter the spring constant of the second spring force, all as should be apparent to the ordinarily skilled artisan. Also based on the foregoing, it should be appreciated that the present invention contemplates a dual acting method of ejecting workpieces from forming stations. This method would be that contemplated by the steps performed by all of the structures heretofore described. Broadly, however, the method would entail providing a first and a second ejection force, of different magnitudes, such that the seamed container is ejected by applying a first force over a first distance and a second force over a second distance. In the exemplary embodiment, the second force would be a greater force for a lesser distance while the first force would be a lesser force for a longer distance. Broadly, the method of the present invention comprises the steps of securing a resilient element in fixed relation relative to the chuck element in a manner such that a central portion of the resilient element will by contacted by deflected by the workpiece when the workpiece is moved into the intermediate position thereby to exert a first restorative force on the workpiece tending to eject it from the chuck element. Next, the positioning mechanism is advanced whereby the workpiece is moved from the intermediate position to the engaged position simultaneously compressing a margin portion of the resilient element thereby to exert a second restorative force tending to eject the workpiece from the chuck element. The workpiece is then held in the engaged position against the restorative forces until the machining function is completed. Thereafter, the positioning mechanism retracts to allow the resilient element to rebound to eject the workpiece. The resilient element is constructed in such the first and the second restorative forces applied thereby are sufficient to eject the workpiece from the forming station after the machining function is preformed thereof. For example, the machine may be a lid seamer and the machining function according to this method is seaming a lid or other end enclosure onto a container body. Accordingly, the present invention has been described with some degree of particularity directed to the exemplary embodiment of the present invention. It should be appreciated, though, that modifications or changes may be made to the exemplary embodiments of the present invention without departing from the inventive concepts contained herein.