Combination transfer/turnover machine
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     This invention relates to an apparatus and method for inverting and transferring parts between two workstations and, more particularly, for inverting the parts as well as transferring them. 
     2. Discussion 
     Transfer machines are used to automatically transfer parts between two workstations. These workstations can, for example, be two metal stamping presses which perform sequential operations on a workpiece. In some instances it is preferable for one of the presses to operate on an opposite side of the workpiece. Thus, it becomes necessary to turnover or invert the workpiece 180° about a horizontal axis. 
     Various attempts to accomplish this function have been made. U.S. Pat. No. 3,921,822 to Dickson generally discloses a machine having jaws which pick up a part at a loading station and place the part at a delivery station. The machine may be adapted to turn the part over, end over end, during its transfer between the stations. In U.S. Pat. No. 2,904,192 to Reynolds et al a transfer device is disclosed for light bulbs that inverts the bulb during its travel. U.S. Pat. No. 3,941,240 discloses grippers which engage and invert the workpiece. U.S. Pat. No. 4,493,450 to Yuzui likewise discloses machinery that inverts the part. The patent to Wenzel (U.S. Pat. No. 730,424) generally discloses a rack and gear arrangement for inverting bottles. 
     U.S. Pat. No. 3,342,125 to Curran generally discloses apparatus for reversing a workpiece in an automated press line. Some of the disadvantages of the approach taken in this patent are that the turnover equipment is connected to the presses in such a manner that it cannot be easily removed to obtain access to the presses for die changeover purposes and the like. In addition, this prior approach is not easily modified to accommodate different parts nor is it easily moveable to different locations within the production plant. 
     SUMMARY OF THE INVENTION 
     In accordance with the teachings of the preferred embodiment of this invention, a transfer machine is provided for transferring a part between two machines. The apparatus includes a horizontal bar connected to a vertically and horizontally moveable carriage. A first transfer means on one end of the bar is provided for picking up a part in one machine and depositing it at a first deposit station located between the machines. A second transfer arm on the other end of the bar serves to pick up the part from a second deposit station and place it into the second machine. Third means, carried by the bar between the two transfer arms, is provided for picking up a part at the first deposit station and depositing it at the second deposit station. In one embodiment, the third means is adapted to invert the part while transferring it between the two deposit stations. As will appear, the machine is easily moved within the production plant as necessary and can be readily modified for use with different parts. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. is a front plan view of apparatus made in accordance with the teachings of the preferred embodiment of this invention; 
     FIG. 2 is a perspective, somewhat schematic view taken from the rear of the apparatus shown in FIG. 1; 
     FIG. 3 is also a perspective view taken from the rear of the apparatus as viewed from one side, this view including many of the details of the pneumatic hose connections not shown in FIG. 2; 
     FIG. 4 is a partial perspective view of parts of the rear of the apparatus when viewed from a side opposite to that viewed in FIG. 3; 
     FIGS. 5-9 schematically illustrate a sequence of steps during operation of the apparatus; 
     FIGS. 10 and 11 illustrate a sequence of steps during the operation of another embodiment of this invention that does not incorporate the turnover feature; 
     FIG. 12 is a cross-sectional view taken along the lines 12--12 of FIG. 5; and 
     FIG. 13 is a cross-sectional view taken along the lines 13--13 of FIG. 6. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The details of the combination transfer/turnover machine 10 are illustrated in FIGS. 1-4. Many of the details, such as pneumatic hose connections, mounting brackets and the like are self explanatory and therefore need not be described in this text in order for the person of ordinary skill in the art to understand the invention. 
     Provision is made for vertically and horizontally moving a carriage 12 under control of a suitable programmable controller. The movement of carriage 12 is preferably provided by way of a drive mechanism that can be suspended between the two machines between which the parts are to be transferred by the apparatus 10. In this embodiment, an electric chain drive 14 is employed. The chain drive 14, per se is of conventional design such as that provided by an ULTIMAX II dual motion programmable loader/unloader made by Clearing Mfg. Co. of Chicago, Ill. Thus, the details of the chain drive 14 need not be discussed herein. Suffice it to say that the drive 14 includes electric motors under programmable control that drive suitable gearing arrangements cooperating with the chains to cause the desired vertical and/or horizontal movement of the carriage 12. In FIGS. 1-4, the drive 14 is suspended between frames 16 and 18. However, it is preferable that the entire apparatus 10 be suspended from an overhead gantry as commonly found in a production factory as illustrated, for example, in FIG. 5. 
     A horizontal bar 20 is connected to the carriage 12 and moves with it. A pair of transfer arms 22 and 24 are located on opposite lower ends of the bar 20. Means are provided on each transfer arm to pick up and carry the workpiece. In this embodiment, each arm includes a plurality of fingers having vacuum suction cups 26 thereon for temporarily gripping the workpiece. As is known in the art, when vacuum is applied to cups 26, they operate to hold the part onto the arm so that it can be carried by it, and when the vacuum ceases, the part is released. 
     Apparatus advantageously includes a double-acting feature for each of the transfer arms 22 and 24. In other words, each of the arms can be moved along with the bar 20 and, in addition, they can move relative to the bar 20 under the control of actuators 28 and 30, respectively. The purpose of actuators 28 and 30 is to enable the arms 22 and 24 to be moved very quickly. As will appear, this will enable more efficient transfer of the parts between the two workstations. Various actuating designs may be employed. FIGS. 12 and 13 illustrate an acceptable pneumatic design. Here, air pressure selectively applied to ports 32 or 34 cause piston 36 to move to the right or left carrying with it bracket 38 connected to the transfer arm 22. On the other hand, the actuators may be driven by a ball/screw drive which is currently presently preferred. 
     Transfer bar 20 also carries a turnover mechanism 40. Turnover mechanism 40 is connected to lower portions of the bar 20 between the two arms 22 and 24. Turnover mechanism 40 is perhaps best shown in FIG. 4 as including a gripper 42 having a pair of gripping jaws 44, 46 which open and close about the workpiece in any suitable manner. As illustrated, the jaws operate in a scissors like action, each being pivoted at an intermediate point 48 under the control of the cylinder 50. Other suitable drive arrangements for the jaws can also be used such as a rack and pinion type mechanism. The gripping jaws are designed for a particular part configuration and can be easily replaced by another jaw design to accommodate differently shaped parts. In most other respects the machine 10 need not be modified even though the part changes. 
     Means are provided for driving the gripper 42 in such manner that it will rotate 180° during horizontal movement of transfer bar 20 to thereby invert the part being gripped. The gripper drive includes a vertically extending rack 52 having a wheel at one end serving as a cam follower 54. Rack 52 is suitably connected to the arm 20 via bracket 56 so that it moves horizontally with the bar 20. During a portion of its horizontal travel, the cam follower 54 enters and follows a stationary cam track 58. As shown best in FIG. 2, cam track 58 includes a pair of open ended inclined rails 60 and 62 which are stationarily fixed via brackets to the chain drive 14. When the cam follower 54 is in the cam track 58, rack 52 moves vertically as the bar 20 moves horizontally. The lower portion of rack 52 engages a drive pinion 64. Vertical movement of rack 52 causes pinion 64 to turn shaft 66 which, in turn, is connected to gripper 42. As will appear, turnover mechanism 40 thus operates to invert the part held by gripper 42 as the bar 20 moves horizontally. If desired, a suitable brake can be employed to ensure exact 180° rotation. A selectively energizable piston rod 68 engaging an appropriately shaped block 70 on shaft 66 is illustrated in FIG. 4 for this purpose. 
     The method of operating the apparatus 10 will now be described with reference to FIGS. 5-9. Apparatus 10 is shown in FIG. 5 as a one-piece unit that can be suspended from an electric bridge 72 that rides on the overhead beams 76 normally found in production factories. The apparatus 10 thus can be easily placed at desired locations in the factory, as well as being easily removed by energizing the bridge 72 to carry the apparatus along the beam 76 to the desired location. Removal may be necessary, for example, to provide access to the presses to change the dies therein or for other purposes. In the drawings, apparatus 10 is shown positioned between two metal stamping presses 78 and 80. Presses 78 and 80 operate in a predetermined sequence to perform sequential operations on a part. The presses 78, 80 and apparatus 10 are all suitably programmed to perform the following method. 
     In FIG. 5, the press 78 is shown as just opening. The carriage 12 has moved transfer bar 20 to the left so that arm 22 is positioned as close as possible to the press 78 without interfering with its operation. Turnover mechanism 40 is located above a first deposit station 82 for temporarily holding a part. Similarly, transfer arm 24 is positioned above a second deposit station 84. Deposit stations 82 and 84 are preferably platforms which are stationarily connected via struts 83, 85 to the housing of the chain drive 14 so that they also form a one-piece unit and nothing is permanently mounted on the floor of the factory. 
     As soon as the press 78 opens, actuator 28 is energized to quickly move transfer arm 22 into the press over the part P1. Then, the drive 14 is energized to lower carriage 12 and thus all of the appendages connected to bar 20. This operation brings the finger suction cups of transfer arms 22 and 24 into contact with parts P1 and P3, respectively. Substantially simultaneously therewith, the turnover mechanism 40 is lowered so that its jaws 44 and 46 are in the plane of part P2. The jaws 44, 46 then close about the edges of part P2. Note in FIGS. 5 and 6 that the cam follower 54 is not yet restrained by the track 58. Accordingly, there is no rotation of drive pinion 64 to cause rotation of the gripper 42. 
     After the parts P1, P2 and P3 have been engaged, transfer bar 20 is moved upwardly and to the right towards the second press 80. As shown in FIG. 7, the horizontal movement of bar 20 causes the cam follower 52 to enter the mouth of the track 58 and begin its downward trek defined by the inclined rails of the track 58. This causes the rack 54 to move downwardly rotating pinion 64 and, thus, gripper 42. 
     This action continues as illustrated best in FIGS. 8-9. When the transfer bar 20 has moved completely to the right, the cam follower 54 has traversed the track 58 to such an extent that a complete 180° rotation of the part P2 is made and it is positioned over the second deposit station 84. The transfer arm 24 is poised immediately adjacent press 80. When press 80 opens, actuator 30 is energized to quickly move part P3 into the open press over the lower die. As illustrated in FIG. 9, the transfer bar 20 is then moved downwardly. This action simultaneously places part P3 in the press 80, part P2 at deposit station 84 and part P1 at deposit station 82. The vacuum on the transfer arms is stopped and the gripper 42 opened to release the respective parts at these locations. Then, the transfer bar 20 is moved leftwardly to the position shown in FIG. 5 for a repeat of the foregoing sequence. 
     Various modifications of the preceding embodiment can be made. For example, FIGS. 10-11 illustrate the substantially identical apparatus except that no provision is made to turn over the part during transfer between the presses. Instead, an intermediate transfer arm 90 is used. Transfer arm 90 is similar to transfer arms 22 and 24 but it does not include horizontal actuators. In all other respects the embodiment of FIGS. 10 and 11 is the same as the previously described embodiment. Various other modifications will become apparent to those skilled in the art after having the benefit of studying the specification, drawings and following claims.