Abstract:
An apparatus for transferring a relatively flat object from a work station along a transfer path includes an upper tooling within the work station for locating the object in a ready position by causing an upper surface of the object to adhere to the tooling. The object is thus unsupported along its lower surface. A manifold forming an orifice is located adjacent to and directed toward the ready position, and is connected to a source of compressed gas. A valve initiates and discontinues flow of pressurized gas through the orifice. A control system controls the valve to direct a stream of pressurized gas through the orifice when an object is located in the ready position, thereby causing the transfer of the object in free flight from the work station.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a method and apparatus for the transfer of relatively flat objects from a first work station and, more particularly, to the means by which the object to be transferred is propelled from the work station. The present invention is especially adapted for use within equipment for the manufacture of shells used to close the ends of metal cans. 
     One common way of packaging liquids, particularly such as beer, softdrinks, juices and the like, is within cans typically formed from aluminum. In such cans, the can body is either manufactured to include both the can side walls and an attached bottom end, or the bottom end is formed separately and subsequently joined to the side walls. The upper end, which includes the means by which the can is later opened, is manufactured separately and attached to the can body after the can has been filled. The can ends, often referred to within the art as shells, are generally manufactured within ram presses. While various particular methods of shell formation are known and available, it is often necessary as a part of these methods to transfer the shells from a first to a succeeding work station. In any case, it is also necessary to transfer the shells from a work station out of the press. In view of the large quantities of cans and shells that are manufactured, it is desirable to be able to form quantities of the shells very rapidly. This necessitates a transfer system that is both quick and reliable. 
     Various types of transfer systems for shells are known. In one approach, the shell is partially formed within the first tooling station and then positioned for transfer. A device is actuated to strike the shell with an edgewise blow that propels the shell outwardly from the tooling. The shell moves laterally along a transfer path either out of the press for further processing, or to a second station within the press for additional operations. 
     An example of this type of transfer system may be seen in U.S. Pat. No. 4,561,280. There, a driver extends an actuator to provide the blow for moving the shell along the transfer path. Ideally, the shell moves in free flight without contacting the restraining structure defining the path until the shell is captured at the second station. This system has been found to work well. However, it is not unusual for shell forming presses to be operated at speeds in excess of 10,000 strokes per hour. Such rapid and repetitive action takes a significant toll on mechanical devices. Thus, while the driver described above is specifically designed for speed and reliability, failures of the mechanical drivers would not be totally unexpected. Moreover, it would not be unusual for the driver mechanism to develop an unwanted shocking effect, whereby extension or retraction of the shell driving actuator could be slightly delayed. 
     Particularly where a shell is being transferred into a second work station within the same press, speed and consistency in transfer times is of great importance. Thus, it is not only necessary that the shell drivers continue to function, but that they continue to operate with optimum performance. Otherwise, shells could be delayed in being discharged from the press work station. While it might be possible to provide detectors for determining the occasional late arrival of shells at a second station, there is no practical way of delaying operations in the stations since such operations are under the control of the press drive. With the press running at speeds of several hundred strokes per minute, the timing of individual strokes cannot be altered. Thus, a late arriving shell could be subjected to forming or other work steps prior to proper positioning within the tooling. At best, this result in a deformed workpiece, but could also cause disruption of the manufacturing process requiring restarting of the press, removal of lodged workpieces, or even repair to damage to the press tooling itself. 
     It can be seen, therefore, that any improvement in the transfer mechanism for moving shells from a press tooling and directing them into a transfer path is advantageous. Such improvements that increase either the speed or reliability of the transfer process will be reflected in a smaller number of defective shells and greater reliability of the press operation as a whole. 
     SUMMARY OF THE INVENTION 
     In meeting the foregoing needs, the present invention provides an apparatus for transferring a relatively flat object from a work station along a transfer path. Means located within the work station locates the object in a ready position by causing an upper surface of the object to adhere to the locating means, whereby the object is unsupported along a lower surface thereof. An orifice defining means is located adjacent to the ready position for defining an orifice directed toward the ready position. Supply means connected to the orifice defining means connects the orifice defining means to a source of compressed gas. Valve means disposed within the supply means initiates and discontinues flow of pressurized gas through the orifice defining means. A control means controls the valve means to direct a stream of pressurized gas through the orifice when an object is located in the ready position, thereby causing the transfer of the object in free flight from the work station. 
     The object locating means may include a lower surface, the lower surface defining therein a vacuum opening, and a source of vacuum connected to the vacuum opening. The object is caused to adhere to the lower surface by application of vacuum thereto. 
     The orifice defining means defines an outlet orifice having a cross-sectional area. The cross-sectional area may be circular or, alternatively, oblong having rounded ends. The cross-sectional area is within the range 0.060-0.140 inches (0.150-0.350 cm), and preferably is 0.120 inches (0.305 cm). 
     The source of compressed gas may supply air under pressure. The air may be supplied at a pressure within the range of 50-85 psi (3.5 to 6.0 kg/cm 2 ) and, more preferably, within the range of 60-85 psi (4.2 to 6.0 kg/cm 2 ). 
     The valve means may be a solenoid-actuated valve having a solenoid and defining a flow path therethrough. The flow path is normally closed to gas flow therethrough, opening to gas flow therethrough upon energizing of the solenoid. The valve is mounted at the work station adjacent to the ready position, the orifice defining means being mounted to the valve and extending outwardly therefrom. 
     The invention is preferably incorporated within a reciprocating ram press having a vertically-operating tooling set within a work station for separating a blank from a sheet of stock material and forming the blank into a relatively flat object. The invention, means for transferring the object from the work station along a transfer path, then includes the tooling set, which has an upper tooling including means for locating the object in a ready position by causing an upper surface of the object to adhere to the upper tooling. The object is thus unsupported along its lower surface. An orifice defining means is located adjacent to the ready position, and defines an orifice directed toward the ready position. Supply means is connected to the orifice defining means for connecting the orifice defining means to a source of compressed gas. Valve means disposed within the supply means initiates and discontinues flow of pressurized gas through the orifice. Control means controls the valve means to direct a stream of pressurized gas through the orifice defining means when an object is located in the ready position, thereby causing the transfer of the object in free flight from the work station. 
     The method for transferring a relatively flat object from a work station along a transfer path includes the step of locating the object within the work station in a ready position by securing an upper surface of the object, whereby the object is unsupported along a lower surface thereof. When the object is located in the ready position, a flow of pressurized gas is initiated through an orifice located adjacent to and directed toward the ready position, thereby causing the transfer of the object in free flight from the work station. The flow of pressurized gas through the orifice is then discontinued. 
     Accordingly, it is an object of the present invention to provide a method and apparatus for transferring a relatively flat object from a work station along a transfer path; to provide such a method and apparatus that is particularly adapted for use within a reciprocating ram press; to provide such a method and apparatus that is particularly adapted to transfer shells used for closing metal cans; to provide such a method and apparatus that is usable to transfer shells either from a first partial forming station to a second, succeeding forming station, or from a forming station out of the press; to provide such a method and apparatus that can increase the speed with which transfers of such shells are made; to provide such a method and apparatus that can increase the reliability with which transfers of such shells are made; to provide such a method and apparatus that can increase the output of shells from the press; and to provide such a method and apparatus that can decrease the number of shells damaged as a result of improper transfer. 
     Other objects and advantages of the invention will be apparent from the following description, the accompanying drawings, and the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 and 2 are, respectively, front and side views of a typical single acting ram press as utilized in the present invention; 
     FIG. 3 is a cross-sectional view illustrating the tooling of a first station within the shell-forming apparatus with which the present invention is used; 
     FIGS. 4, 5, 6 and 7 are partial sectional views of a portion of the preferred first station tooling, illustrating operation of the tooling for separating a blank and partially forming the blank into a shell; 
     FIG. 8 is a side view of a first tooling station and entrance into the transfer path, showing the air assist mechanism of the present invention; 
     FIG. 9 is a schematic plan view of the first station, transfer path, and a second station, along with the air assist mechanism; and 
     FIG. 10 is a diagram illustrating schematically the control system for operation of the press. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, a typical ram press used in the manufacturing of shells for can ends is shown generally in FIGS. 1 and 2. The press includes a drive motor 10 coupled to a flywheel 12 on the press crankshaft 14 which reciprocates the ram 16 along jibs 18 that are mounted to posts 20 extending upwards from the press bed 22. Upper tooling is fixed at 24 to the bottom of ram 16, and cooperating lower tooling is fixed at 26 to the top of bed 22. The relatively thin metal stock 28 from which the shells are formed is fed incrementally from a roll 29 into the front of the press. 
     The present invention is not dependent upon any specific method of shell formation, so long as the shells are at least partially formed with the ram press and transferred from the forming tooling. Thus, any one of a variety of methods may be used. In one preferred method, a two-step process requiring two separate toolings for each shell to be formed is used. At the first tooling, a blank is punched from the sheet of stock material. Into the blank is formed a substantially flat central panel and an upwardly extending chuckwall about the edge of the panel to produce a partially formed shell. The partially formed shell is then transferred to a second tooling within the same press, where the shell is captured and located. At this tooling, a countersink is formed into the shell at the base of the chuckwall by moving the panel upward relative to the chuckwall to produce a completed shell. Portions of this method and the necessary apparatus are described in detail below; further details may be found in commonly-assigned U.S. Pat. No. 4,561,280 of Bachmann et al, issued Dec. 31, 1985, which is hereby incorporated by reference. 
     However, it is not necessary that the two-step method disclosed in the above-referenced patent be used. For example, a method in which the forming that occurs within the press takes place at only a single station would also be appropriate, as is shown in either U.S. Pat. No. 4,382,737 of Jensen et al, or U.S. Pat. No. 3,537,291 of Hawkins. With such a method, finishing of the shells is performed following their ejection from the press. 
     For the preferred shell-making method and apparatus, the press tooling for each of the first stations 30 (or first stage of the method) is shown generally in FIG. 3. The upper tooling 32 is connected for operation by the press ram, while the lower tooling 34 is fixedly mounted to the press frame. 
     Lower tooling 34 includes die cut edge 36, over which the metal stock enters the tooling at a level generally indicated by line 38. Die cut edge 36, along with die form ring 40 are solidly supported by block member 41 which is in turn supported by base member 43. Additionally, lower tooling 34 includes draw ring 42, positioned between die form ring 40 and die cut edge 36. A center pressure pad 44 is located concentrically within form ring 40. Draw ring 42 is supported by four springs 45 (only one shown) mounted in base member 43. Springs 45 are shown in FIG. 3 in a compressed condition, caused by pressure exerted upon draw ring 42 when the tooling is closed. The center pressure pad 44 is supported by spring 47 mounted within pressure pad 44 and base member 43 central to the first station tooling. Spring 47 is also shown in a compressed condition from force exerted by the upper tooling 32. 
     When the tooling is open, draw ring 42 and center pressure pad 44 are retained in the lower tooling 34 by flanges 49 and 51 integrally machined on the respective tooling portions with draw ring 42 bottoming against die cut edge 36 and center pressure pad 44 against form ring 40. In such case, the uppermost surface of draw ring 42 is at a position some distance below the lowest point of shear on the die cut edge 36, while the uppermost surface of the center pressure pad 44 is some distance above draw ring 42 and below lowest point of shear on die cut edge 36. 
     Upper tooling 32 is provided with blank punch 46 which is positioned to cooperate with draw ring 42 for compression of spring 45 as the tooling is closed. A knockout and positioner 48 is located above die form ring 40, and punch center 50 is provided with an appropriate configuration to produce the partially completed shell, as well as to clamp a blank in cooperation with center pressure pad 44. Blank punch 46, knockout and positioner 48, and punch center 50 are all closed simultaneously upon lower tooling 34 as the press ram is lowered. 
     The operation of the first station tooling 30 to produce the blank from the stock and partially form a shell is shown in detail in FIGS. 4-7. In FIG. 4, the tooling is shown already partially closed. The stock 28 initially entered the tooling along a line indicated at 38, and as the press ram is lowered, a flat blank 58 is produced by shearing the stock material between die cut edge 36 and blank punch 46. 
     As the press ram continues downward, the blank punch 46, support ring 48, and punch center 50 all continue to move simultaneously. At the point illustrated in FIG. 5, the blank 58 is still pinched between blank punch 46 and draw ring 42, and between punch center 50 and center pressure pad 44, beginning the formation of the shell over die form ring 40. As the blank 58 is formed over form ring 40, it is pulled from between blank punch 46 and draw ring 42. 
     Referring now to FIG. 6, the press ram continues to move downward as the punch center 50 begins to form the panel of shell 58 (heretofore referred to as blank 58). The shell material is no longer held between the blank punch 46 and the draw ring 42, but is still contained between punch center 50 and center pad 44, and the draw ring 42 no longer controls the formation of the shell. The clearance between the inside diameter of the blank punch 46 and the outside diameter of the die form ring 40 is selected to provide an appropriate amount of drag or resistance on the shell 58 to insure proper formation. The upward-extending chuckwall 54 of the completed shell begins to be formed. 
     In FIG. 7, the tooling is shown in its closed position with the press ram bottomed against appropriate stop blocks. The first portion of the shell formation operation is completed, with a shell 58 being formed having a flat panel 60 terminating at a relatively large radius area 62. The large radius area 62 forms the junction region of chuckwall 54 with the panel 60, and will later form the shell countersink and panel form radius. A much tighter radius will later be provided for the shell countersink. 
     The shell is further provided with a lip 64 extending generally outwardly and upwardly from the chuckwall 54, but having general downward curvature. Lip 64 is provided with two distinct curvatures, with the portion adjacent chuckwall 54 having only slight relative curvature and thus providing the upward extension of lip 64. The outermost portion is provided with a relatively sharp downward curvature by die center form ring 40, although the lowermost portion of the outer edge of lip 64 is formed to at least even with, if not above, the point where lip 64 connects with the shell chuckwall 54. 
     It will be noted that upon closure of the tooling, knockout and positioner 48 does not contact shell 58. Once the forming operation has been completed, the press ram is raised to open the tooling. As the tooling is opened, shell 58 is held within blank punch 46 by the tight fit of shell 58 therein caused during its formation and is carried upward by upper tooling 32. For reasons that will be described in detail below, once the lowermost portion of shell 58 has cleared the stock level indicated in FIG. 4 at 38, knockout and positioner 48 halts its upward movement, while blank punch 46 and punch center 50 continue to rise with the press ram toward the uppermost portion of the press stroke shown in FIG. 8. When the upward movement of knockout and positioner 48 is stopped, shell 58 will contact knockout and positioner 48 which knocks out, or pushes, shell 58 from within the still-moving blank punch 46. 
     The shell 58 is then held in position on knockout and positioner 48, as shown in FIG. 8, through application of a vacuum to shell 58. A vacuum passage 66 connects with a conventional shop vacuum supply to provide the vacuum to the surface of punch center 50. This vacuum then causes the shell 58 to adhere to the surface of knockout and positioner 48. 
     Upon completion of the first operation upon the shell, it is moved by the transfer means of the present invention, to be described in detail below, either out of the press or to a corresponding one of a plurality of second stations for completion of the formation process. 
     At the second station tooling (not shown), the partially completed shell is captured and located within the tooling. The complete transfer and repositioning operation occurs between successive strokes of the press, so that as the press ram is next lowered, the tooling of the second station acts to work the partially completed shell into a finished shell. In carrying out this operation, the tooling clamps, the chuckwall of the shell, whereafter a raised central panel is formed into the shell to define a countersink at the base of the chuckwall. Further, the lip is given additional downward curl to properly configure the lip for later seaming to the upper end of a can body. The details regarding this operation, which are not necessary to understand the present invention, may be found by reference to the above incorporated U.S. Pat. No. 4,561,280. 
     Returning now to FIG. 8, once the shell which has been formed within the first station tooling is positioned, the shell 58 is ready to be transferred either to a subsequent tooling station or out of the press. The mechanism through which shell transfer occurs is the impinging of a directed blast of air directed against the chuckwall 54. The blast is sufficient to propel the shell from the tooling in the direction indicated by arrow 68. 
     The air stream is caused to emerge from manifold 70 which includes an air passage therethrough which defines a nozzle or orifice opening from manifold 70. The air stream is initiated by an air valve mechanism 71. Valve mechanism 71 is provided with an air inlet 72, to which is connected an inlet conduit 73 which is in turn connected to a remote source of compressed air. An outlet 75 is formed in valve mechanism 71, to which manifold 70 may be attached. The mechanism 71 is secured to the press bed with manifold 70 positioned near the location for partially completed shells which are supported for transfer. 
     The valve mechanism 71 may be any appropriate relatively quick acting valve, and is preferably a direct acting solenoid valve such as those manufactured by Schrader-Bellows Divison of Scovill Mfg. Co. of Akron, Ohio. 
     Also in FIG. 8, a transfer mechanism is shown for moving a partially completed shell from a first station tooling into a transfer path for delivery to a second tooling station where formation is completed. Only upper tooling 32 is shown, it being understood that the cooperating lower tooling is disposed beneath base plate 74 with tooling 32 lowered by the press ram through an opening (not shown) in the base plate. An air driver 71 is positioned adajcent tooling 32, so that manifold 70 will be in position to direct a stream of air against a shell 58 positioned on the lower, working surface of tooling 32. 
     Referring also to FIG. 9, the shell 58 will be propelled in substantially free flight into the entrance to a transfer path 82 leading to a second tooling station 84. There, the shell is captured and located within appropriate capturing mechanism 86 prior to being operated upon by the second station tooling. Details of the capturing mechanism 86 may be seen by reference to U.S. Pat. No. 4,561,280, which has been incorporated hereinto by reference. 
     Transfer path 82 is partially enclosed, and is defined by a pair of side walls 88 mounted to base plate 74. A pair of cross members 90 and 92 are connected between walls 88, and a pair of polished rails 94 are connected to the underside of each member 90 and 92 to define a top for the transfer path. Because the shell is propelled to travel substantially in free flight along the path, walls 88, plate 74 and rails 94 are provided only to occasionally guide a shell and to prevent shells from inadvertently leaving the transfer path. Normally, a shell does not travel in contact with these surfaces. 
     A typical length for transfer path 82 from the first station tooling to the second station tooling is in the order of approximately 10-30 inches (25 to 75 cm). 
     It is preferred that the compressed air supplied to air driver mechanism 71 be supplied at a pressure of approximately 60-85 psi (4.2 to 6.0 kg/cm 2 ). However, it has also been found that pressures as low as approximately 50 psi (3.5 kg/cm 2 ) are usable. The orifice for manifold 70 has a preferred dimension of 0.120 inches (0.305 cm), but it has been found that adequate transfer can be obtained with an orifice size ranging from 0.060-0.140 inches (0.150-0.350 cm). The manifold orifice is preferably circular, but also may be oblong with rounded ends. 
     Of course, it will be recognized that the air stream for propelling the shells can be produced through means other than the manifold shown herein. For example, a nozzle or other conduit extending from air driver mechanism 71 and capable of defining the air orifice could be substituted for manifold 70. 
     The duration for which air driver mechanism 71 is energized to direct air through manifold 70 is dependant upon the distance over which the shell is to be transferred, as well as the size of the shell. Thus, this duration may vary over a relatively wide range. However, for several working embodiments of the apparatus disclosed herein, duration times vary between approximately 0.040 and 0.105 seconds. 
     Control of air driver mechanism 71 will be described in detail below. 
     It has been found to be helpful to use, as part of the transfer apparatus, an air assist mechanism along the transfer path. An air valve mechanism 96 similar in construction to air valve mechanism 71 is mounted to plate 90 above and near the entrance to transfer path 82. An air inlet 98 (FIG. 9) connects with an inlet conduit 100 extending away from the transfer path. Conduit 100 connects with a reduced source of compressed air, preferably a source of 25 to 50 p.s.i. (1.7 to 3.5 kg/cm 2 ). Valve 96 may be any appropriate quick-acting valve for controlling compressed air flow, but is preferably a direct acting solenoid valve identical to valve mechanism 71. 
     A fitting 102 is threadingly engaged into an outlet for valve 96, and connects with an outlet conduit 104 extending downwardly along the exterior of one side wall 88. Conduit 104 curves around the end of wall 88 to the entrance to transfer path 82, where conduit 104 terminates in an open end. At the open end, a nozzle 106 is formed consisting preferably of simply a flattened portion of conduit for focusing the air emerging from the conduit. Nozzle 106 is positioned adjacent the inner surface of wall 88 and against base plate 74, and is directed down path 82 in the direction of shell movement. 
     Valve 96 is actuated to permit air flow through conduit 104 just after a shell has entered into the transfer path 82, and air flow is continued until the shell has completed its movement along the path to the second tooling station. It has been found that the air supplied in such a manner provides a pushing force behind the shell as the shell effectively rides the air stream, as well as some turning motion to the shell as a result of the application of air at one side of the transfer path. Further, it is believed that the air stream provides a cushion upon which the shell is at least partially supported. These effects have been found to be beneficial in facilitating shell movement along path 82 for transfer. Specifically, shell speed is increased, and the direction of the moving shell is more closely regulated to decrease contact with the structure defining the transfer path. 
     The transfer mechanism as shown in FIGS. 8 and 9, particularly the air driver mechanism, is specifically adapted to carry out the transfer of a shell from a first station tooling to a second station tooling within the same press. Of course, the present invention is not limited solely for such a transfer, but rather can be used for any shell transfer, or for transfers of other relatively flat objects moving in edgewise fashion. In a shell press having a two-stage tooling arrangement, such as that shown in FIG. 9, it is anticipated that a similar air assist mechanism will be used in conjunction with the shell transfer mechanism moving shells from the second station tooling station out of the press. 
     The electrical control means for controlling operation of the press for the manufacture of shells is shown schematically in FIG. 10. Power is supplied to main drive motor 110 through lines L1, L2 and L3 for driving the press ram to open and close the tooling of the first and second stations. A series of operator controls 112, which may be mounted on one or more conveniently located control panels, enable the press operator to control stopping, starting and speed of the press, as well as to control and monitor various other press functions. 
     A number of press functions are controlled by a programmable rotary position switch 114 that provides a variety of separate switching functions, each of which may be adjusted to open and close switching contacts at predetermined angular positions of the press crank. Rotary switch 114 is mounted for operation to the press frame, and is coupled to the rotary press ram drive through a drive chain or the like, and hence is coupled indirectly to motor 110 as indicated in FIG. 10. The switch is connected to the ram drive so that the switch position designated 0° coincides with the uppermost position of the press ram stroke. The electrically operated functions of the press are directed by a microprocessor 116 which interfaces with operator controls 112 and rotary position switch 114. The microprocessor 116 is programmed to control various press functions in proper timing and sequence. 
     As has been described, each partially completed and completed shell formed by the press is transferred from a press tooling station by directing a stream of air against the shell through manifold 70. Manifold 70 is in turn controlled by air driver mechanism 71, two such mechanisms 71 being shown in FIG. 10 for purposes of example. The solenoids of the valves incorporated in mechanisms 71 are energized at the appropriate points in each press stroke by microprocessor 116 in response to signals received from rotary position switch 114. In this way, the shell is transferred only when the press toolings are in correct position for transfer. 
     Microprocessor 116 causes each of mechanisms 71 to be energized whenever rotary switch 114 reaches an appropriate rotational position with respect to selected actuation times. For example, in one working embodiment of the invention, mechanisms 71 are actuated whenever rotary switch 114 reaches the position of 277°. It should be noted that this position for rotary switch 114 will occur when the press ram has completed most of its upward stroke and the shell has been properly positioned. Each shell will then be struck with a blast of air from manifold 70 and will be transferred away from its respective tooling station. 
     The mechanism 71 is controlled to discontinue the air stream emerging from manifold 70 at a crank position of 0°. At a typical press speed of 300 strokes per minute, this represents an actuated time for the mechanism of approximately 0.046 sec. 
     While the forms of apparatus herein described constitute preferred embodiments of this invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.