Abstract:
A computer-controlled system for transporting workpieces, in which each workpiece is placed on a load carrier, each workpiece and load carrier being marked with an identifier. A central computer is loaded with data relative to each given workpiece, its respective load carrier, and work to be performed on such workpiece, and predetermines a path to be followed by such load carrier. The load carrier is placed on a main path, its identifier is read, and if work is to be performed on a workpiece carried thereon, a switch is thrown to divert the load carrier to an auxiliary path and then to a work station. The load carrier may be diverted to the work station by a swing-out device or by a spur path, for example. After such work, the load carrier is returned to the main path and its identifier is read again to determine whether it again is to be diverted to an auxiliary path for performing further work on a workpiece carried thereon. Holding devices are provided on the main and auxiliary paths for performing sorting and accumulating functions to optimize passage times around the system.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a system for transporting workpieces and associated load carriers in manufacturing operations, and more particularly to a method and apparatus including main and auxiliary paths for the load carriers, and computer-controlled identifying, holding, and diverting devices for transferring load carriers from the main path to the auxiliary path and then to a work station, while optimizing the workpiece passage times around the system. 
     2. Description of the Related Art 
     An automatic workpiece transport and routing device is known (Federal Republic of Germany OS No. 17 81 310), which includes a power drag means and a conveyor, the load carriers which can travel on an endless main path being moved by the drivers provided at given distances apart on a continuously driven conveyor. Each load carrier has a respective coded address part which is scanned by scanning apparatus arranged alongside the main path. Beside the main path there are provided auxiliary paths over which the load carriers can travel via switchable switches. There are also buffer paths into which the load carriers are switched depending on their address code and, after the completion of the working of the workpiece carried by the load carrier, brought back into the main path. The known transport device has the following disadvantages: 
     1. Since one driver of the conveyor belt always moves only one load carrier, and as a result of the distance between each two drivers, intolerably long passage times result. 
     2. Since directly before the working of the workpiece transported by the load carrier said load carrier can neither be placed on or transferred from the auxiliary path, a simultaneous sorting operation is not possible during the working of the workpiece. 
     3. For the presorting of similar workpieces, a plurality of buffer paths will branch off from the main path and are arranged parallel to each other are provided in front of the work station, as a result of which the known device takes up a very large amount of space. 
     A principal object of the present invention is to provide a method by which shorter passage times during the course of manufacture can be obtained while, at the same time, the sorting of workpieces which have still not been worked can be carried out during the working of a given workpiece. A further object is to provide an apparatus for carrying out the method which takes up a minimum amount of space. 
     This object is achieved in a computer-controlled system in which each workpiece is placed on a load carrier, each workpiece and load carrier being marked with an identifier. A central computer is loaded with data relative to each given workpiece, its respective load carrier, and work to be performed on such workpiece, and predetermines a path to be followed by such load carrier. The load carrier is placed on a main path, its identifier is read, and if work is to be performed on a workpiece carrier thereon, a switch is thrown to divert the load carrier to an auxiliary path and then to a work station. The load carrier may be diverted to the work station by a swing-out device or by a spur path, for example. After such work, the load carrier is returned to the main path and its identifier is read again to determine whether it again is to be diverted to an auxiliary path for performing further work on a workpiece carried thereon. Holding devices are provided on the main and auxiliary paths for performing sorting and accumulating functions to optimize passage times around the system. 
     By the computer-assisted method of the invention it is now possible, for the desired shortening of the passage times, to assure an optimized flow of material to the individual work stations which substantially eliminates non-productive downtimes, the pieces of material to be worked being presented to the operator in optimal ergonomically favorable position for grasping, relative to the work center of each working station. For this purpose, the apparatus for the carrying out of the method permits automatic sorting, adapted to specific requirements, in the immediate vicinity of the corresponding work station, as well as the delay-free removal from said work station of the workpiece which has been worked. The computer-assisted method furthermore also permits the preferred working of rush orders and other special jobs by priority criteria stored in the central management computer, considerable efficiency being obtained by this method, particularly in the garment industry. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, features and advantages of the invention will be understood from the following detailed description of preferred embodiments of the invention, with reference to the drawings, in which: 
     FIG. 1 is a perspective view of a complete workpiece transport system including a work station; 
     FIG. 2 is a schematic plan view corresponding to FIG. 1 and showing movement of the swing-out device; 
     FIG. 3 is a sectional view of the swing-out device of FIG. 1; 
     FIG. 4 is a detail of the swing-out device with its mouth open; 
     FIG. 5 is a detail of the swing-out device with its mouth closed; 
     FIG. 6 is a side view of a portion of a load carrier for use with the embodiment of FIG. 1; and 
     FIG. 7 is a schematic plan view of an alternate embodiment of a complete apparatus having a spur path branching off from the auxiliary path. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a perspective view of a complete system, comprising a main path 4, an auxiliary path 9 which branches off from the main path, and a swing-out device 15. The main path 4 includes a suitable downward-sloping carrier rail 22 which has an elevated loading point 3 and a lower end point 5, and an upward-directed drag chain 6 which adjoins said end point and is driven by a controlled electric motor (not shown). A load carrier 2 (shown in part in FIG. 6), which is provided with gripper elements for the detachable gripping of workpieces 1, is raised from a lower level to an upper level by the drag chain 6. The drag chain 6 and load carriers 2 are sufficiently well known that they need not be described in further detail here. 
     Near its lower end point 5, the carrier rail 22 has a bridge 24 which is swinqable upward around a pivot point 25. In unloaded condition, the bridge 24 rests in such a manner that the upper edges of the carrier rail 22 and of the bridge 24 are aligned. A first holding device 11 is provided between the loading point 3 and the pivot point 25, which accumulates the on-coming load carriers 2 and, at the proper time, releases the accumulated load carriers 2 one at a time. Such a holding device 11 is known in conveyor technology and therefore need not be described in further detail here. 
     The carrier rail 22, the drag chain 6, the auxiliary path 9, and the swing-out device 15, as well as a buffer station 10 and a holding device 11a (discussed below), are all mounted on a stationary conveyor frame 28 which is merely indicated in FIG. 1. It can have the form of a suspended frame or a standing frame, for example. 
     Next to the upper end of the drag chain 6, at the starting end of a further carrier rail 22&#39;, is a reading device 7 for recognizing a code, preferably a bar code or another form of automatically detectable code, which is provided on the load carrier 2, preferably on its pulley 44. Arrangements for providing such coding as well as appropriate reading devices are known and need not be described in further detail here. 
     At the beginning of the further carrier rail 22&#39; is a switch 8 which can be switched in the horizontal plane, as shown in FIG. 1. Adjacent to the switch 8 is the starting point of an auxiliary path 9. By suitable switching of the switch 8, which can be effected by pressure-actuated means, for instance by a pneumatic cylinder or by a solenoid, a load carrier 2 which has been conveyed upward by the drag chain 6 may be guided onto the auxiliary path 9. In the overall downward-sloping course of the auxiliary path 9, there is first provided a buffer station 10 which can accumulate several oncoming load carriers 2, and at the proper moment release a first stored load carrier 2. 
     Further along the auxiliary path 9 are a swing-out device 15 and a second holding device 11a. As each load carrier 2 moves along the auxiliary path 9, the horizontal shaft portion 16 of the load carrier 2 moves into position where it may engage the swing-out device 15 by being received in its mouth 18 (see FIG. 4). The lowest point of the auxiliary path 9 discharges below the end point 5 of the carrier rail 22 into the main path 4. 
     The swing-out device 15 (FIG. 3) comprises a controlled electric motor 29 having a plate 30 fastened to its lower flange side. On the bottom of the plate are provided, as shown in FIG. 3, a plurality of switches 45 which correspond to respective positions into which the electric motor 29 can move an extension arm 37. A ring 31 is also firmly attached to the flange side of the electric motor 29. The lower edge of the ring 31 has a cam surface 32. Within its inner bore the ring 31 receives a low-friction bearing, for instance an anti-friction bearing 33. Within the inner ring of the latter there is arranged a bushing 34 which has a central bore 35 provided with a groove. The central bore 35 receives a stub shaft 36 of the electric motor 29 which is locked for rotation with it. Firmly attached to the bushing 34 is the extension arm 37, which is provided with a vertically adjustable switch pin 46. The switches 45 are actuated by the upper rounded end of the switch pin 46. 
     On the extension arm 37 there is a pivot 38, taking the known form of a horizontally arranged pin, which receives a swing arm 17, the latter being constructed as a double-armed lever. At the end of its shorter lever arm is a pin 39 having a roller 40 supported thereon with little friction. On the other end of the swing arm 17 is a hook 41, the lower portion of which forms the mouth 18. The bottom of the hook 41 includes a horizontally protruding nose 42, as shown in FIGS. 4 and 5. 
     A particularly advantageous feature of the invention, as shown in FIG. 7, is that a load carrier 2, after first being stored by the buffer station 10 and then released, may pass via a briefly closed switch 20 into a spur path 19. Then the switch 20 may be opened so that the spur path 19 is no longer functionally connected with the auxiliary path 9, for example for the duration of work on the workpiece 1. After such work, switch 20 is briefly actuated again, and the load carrier 2 is switched back onto the auxiliary path 9. 
     In order to minimize workpiece transport time around the system, each work station 12 should have means for storing and maintaining a plurality of given variable and fixed data which, to allow for necessary updating, must be able to be continuously supplemented, corrected, expanded and replaced. For this reason, each work station 12 is provided with a work-place computer 13 having an LCD display and several function keys, for example for controlling the forwarding of data or for starting predetermined automatic programs. A plurality of such work-place computers 13 are connected to a host management computer 14 in which, for example, fixed data necessary for the manufacture of a given product, such as product-related and operation-related data as well as customer-specific data, have been embodied in programs and stored. The management computer 14 controls the flow of material to and between the various work stations 12 in accordance with a program set up in this manner. It furthermore evaluates data received via the network of work-place computers 13 and then converts the data, practically without delay, into program-determining control signals. 
     The manner of operation of the system for minimizing workpiece transport time will now be described. 
     Code numbers associated with each load carrier 2 are entered into the management computer 14, for instance manually via a keyboard or by the reader 7. Furthermore, a code is placed on each workpiece 1 and is read into the computer 14, for example by a barcode reader or by manual keyboard entry. Following data entry, the course of movement of the load carrier 2 in question is continuously monitored during its manufacturing passage. The data obtained thereby are combined in accordance with predetermined criteria stored along with the programs in the computer 14 and form the basis for a desired flow of material with short passage times. 
     After entry of its code, each load carrier 2 is first placed at the loading place 3 on the carrier rail 22 and then rolls under the effect of gravity down to the first holding device 11. As each individual load carrier 2 is released from the latter, it rolls over the bridge 24 and down to the end point 5 of the carrier rail 22. Then it is carried by the drag chain 6 to the upper level. In this way, the load carrier 2 arrives at the reading device 7, which reads the code (preferably provided on the pulley 44) and transmits it to the management computer 14 together with the instantaneous position of the load carrier 2. 
     If, on the basis of the program which has been introduced, the management computer 14 determines that the load carrier 2 is to be brought to the work station 12 which lies closest to its instantaneous location, then the switch 8 is actuated to bring the load carrier 2 onto the auxiliary path 9, as shown in FIG. 1. It then rolls by gravity down to the buffer station 10 where it may be held. When the latter buffer 10 releases a stored load carrier 2, it rolls on the auxiliary path 9 until the horizontal shaft portion 16 of the load carrier 2 is caught by the mouth 18 of the swing-out device 15. The extension arm 37 is now swung through a defined angle, causing the roller 40, at the start of this swing, to rise on the raised portion of the cam surface 32. As a result of this, the swing arm 17 is swung in a clockwise direction as shown in FIG. 3, lifting the load carrier 2. In this way, at the very start of the swinging of the extension arm 37, the corresponding load carrier 2 is lifted off the auxiliary path 9. Since the mouth 18 is closed by the swinging of the swing arm 17, as shown in FIG. 5, the load carrier 2, as long as it is outside the auxiliary path 9, cannot be removed from the swing arm 17. 
     Then the swing-out device passes through an angle of rotation, for example 90 degrees, to bring the load carrier 2 and the workpiece 1 attached to it into the immediate vicinity of the work center 27 of the work station 12. (See position &#34;b&#34; in FIG. 2.) 
     As long as the load carrier in question is outside the auxiliary path 9, the sorting or recirculation of any other load carriers 2 on the auxiliary path 9 can continue, assuring, for example, that at least one similar workpiece 1 will be ready for the next work procedure at the work station 12. 
     After completion of the work, the extension 37 is again swung back to replace the load carrier 2 on the auxiliary path 9. The extension arm 37 is then swung up into the position &#34;c&#34; shown in FIG. 2, so as to permit the unimpeded passage of the just-replaced load carrier 2 along the auxiliary path 9. When the load carrier 2 has passed position &#34;c&#34;, then the extension 37 moves back again into its initial position &#34;a&#34;. 
     The load carrier 2 then rolls down to the second holding device 11a. When the latter releases the load carrier 2, it rolls to the end of the auxiliary path 9, the bridge 24 being moved upward and out of the way by the pulley 44 of the load carrier. The load carrier 2 is thus conveyed to the drag chain 6 for being conveyed upward, while the bridge 24, after being released by the pulley 44, again assumes its lower position, shown in FIG. 1. 
     Then the load carrier 2, having arrived at the upper level, thus arrives for the second time at the reader device 7 which again reads its code. In this way, for example, a time credit slip or other record corresponding to the operation just carried out may be produced for the operator in question. 
     If, in accordance with the program stored in the management computer 14, further operations are to be effected on the workpiece 1 that has just been worked upon and whose identification code has been read at the work station 12, the load carrier 2 thereof may be conducted onto the further carrier rail 22&#39;, and pass via a drag chain 1&#39;, and over an auxiliary path 9&#39; to another work station 12&#39; (not shown). 
     From the above description it is clear that a large number of different work stations 12 can be reached from the main path 4 in a very rational and efficient manner via auxiliary paths 9 branching off from it. In addition to the shortening of workpiece passage times, the method of the invention, due to the modular construction of the apparatus required, is very flexible since the apparatus can be adapted for either manufacturing or space requirements--even in the event of subsequent changes--in a relatively simple manner, and is capable of expansion at any time. 
     Although the present invention has been described in connection with preferred embodiments thereof, other variations and modifications may occur to those skilled in the art. It is to be understood, therefore, that the present invention is limited not by the specific disclosure herein, but only by the claims.