SI.EET

SHEET

3.689,797

1

AUTOMATIC TRANSPORT SYSTEM

BACKGROUND

a. Field of the Invention

The present invention relates to an automatic transport system, and more particularly to an automatic transport system which comprises a main conveyer which is freely and periodically driven and a plurality of intermittently driven sub-conveyers for carrying out a series of assembling or machining operations on workpieces composed on a number of small parts.

b. Prior Art

A conventional transport system is known which comprises a main conveyer for transporting workpieces, and sub-conveyers with automatic assembling or machining devices connected to the main conveyer. In this system, the workpieces transported by the main conveyer which are to receive different machining operations are fed to respective sub-conveyers, in accordance with classification methods effected in a wellknown manner. Each of the workpieces receives a series of predetermined assembling or machining operations. In this way, the workpieces are machined and again transported to the main conveyer.

This system has the advantage that different kinds of products can be machined by using sub-conveyers connected in parallel with the main conveyer. This system, however, is disadvantageous in that it is difficult to control the flow of workpieces, and in addition the system is complex. More particularly, it is difficult to collect and control the workpieces after they have been distributed and machined along their respective subconveyers. Moreover, much time is lost in repairing the sub-conveyer in the event of breakdown of the automatic assembling or machining devices. The greater the different kinds of products, the more time is lost.

There has also been proposed another automatic transport system on which workpieces transported by a sub-conveyer are machined and combined with other workpieces transported by another sub-conveyer by means of automatic assembling or machining devices. The thus machined workpieces are further combined with workpieces transported on the main conveyer to produce new workpieces by means of automatic assembling or machining devices. Additionally, further workpieces transported by another sub-conveyer are combined with these new workpieces to produce another new workpiece by means of automatic assembling or machining devices. In this way, various kinds of workpieces combined with the main workpiece are further transported and machined.

This automatic transport system is disadvantageous in that it requires at least one automatic assembling or machining device at the juncture between each subconveyer and the main conveyer. Moreover, in this system, it is difficult to drive the automatic assembling or machining devices in central controlling and to control the speed of each conveyer.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an automatic transport system in which the assembling or machining operation can be carried out completely automatically.

Another object of the invention is to provide an automatic transport system in which an automatic transport

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system is provided in which sub-conveyers are arranged around a main conveyer, the sub-conveyers being intermittently driven in succession to completely synchronize the advancing speed thereof with the working time

5 required for automatic assembling or machining operations, while the main conveyer is freely driven intermittently and independently of the sub-conveyers under control of a computer, so that the conventional problem due to accumulation or jamming of pallets caused

10 by a defect in the automatic assembling or machining devices or by the removal of defectively produced workpieces can be eliminated completely.

A further object of the present invention is to provide an automatic transport system in which a plurality of

15 intermittently driven sub-conveyers are connected in series along the freely and cyclically driven main conveyer, so that it is possible to minimize the working load of the computer. The automatic transport system according to the

20 present invention mainly comprises a main conveyer for transporting containers or pallets which are provided with memory elements and on which are stacked workpieces which are to receive the assembling or machining operation, and a plurality of sub-conveyers

25 connected to the main conveyer and including means for effecting the assembling or machining operations on the workpieces.

BRIEF DESCRIPTION OF THE DRAWING

30 FIG. 1 is a schematic arrangement of one embodiment of an automatic transport system according to the present invention;

FIG. 2 is a schematic arrangement of another embodiment of an automatic transport system according 35 to the present invention;

FIG. 3 is a schematic arrangement view of still another embodiment of an automatic transport system according to the present invention;

FIG. 4 is a schematic perspective view of a pallet 40 loaded with workpieces to be processed and conveyed by an automatic transport system according to the present invention;

FIG. 5 is a schematic perspective view of a container in which pallets are stacked; ^ FIG. 6 is a schematic view in section of a main conveyer employed in an automatic transport system according to the present invention;

FIG. 7 is a schematic view of a driving mechanism of the main conveyer; and

FIG. 8 is a schematic arrangement view of an automatically controlled warehouse used in the present invention.

DETAILED DESCRIPTION

^ Referring to FIG. 1 therein is seen a transport system which comprises a main conveyer 31 for transporting pallets on which workpieces are loaded and which are provided with a memory function. Intermittently driven

6Q sub-conveyers 32 to 35 are disposed in succession along main conveyer 31 and automatic assembling or machining devices 36 are mounted along subconveyers 32-35 to operate on the workpieces placed on the pallets. A computer COMP serves for control

^ ling the operation of the sub-conveyers 32-35.

Each pallet 51 (FIG. 4) serves as a workpiece carrier and is provided with memory elements such as the six magnets Mo as shown in FIG. 4. The pallets are coded 3

by selectively magnetizing the six magnets Mo on the pallet 51 in well-known manner at a starting sending station S of the main conveyer according to the kind of the workpieces to be processed. Then the pallet loaded with the workpieces is transported in the direction of arrow 41 along the main conveyer 31 and is stopped in front of the first sub-conveyer 32 by any suitable wellknown positioning means. The code on the pallet is read out by a reader Rs to send signals to the computer to discriminate the workpieces on the pallet. Then, the pallet on the main conveyer 31 is moved onto the subconveyer 32 by means of a conventional industrial robot or pusher operated by a signal from the computer. The workpieces on the pallet are then intermittently successively fed on the sub-conveyer 32 in the direction of arrow 42 and the workpieces are then assembled or machined at each step by means of the automatic assembling or machining devices 36.

After the pallet with the workpieces has been transported on the sub-conveyer 32 in the direction of arrow 43 the workpieces are detected by a detecting device D,, and the pallet is transferred back to the main conveyer 31 again by means of a conventional industrial robot or pusher for transportation on the main conveyer 31 in the direction of arrow 44. When the workpieces arrive at the reader R2 at the entrance to the second sub-conveyer 33, the memory elements on the pallet are read to send signals to the computer COMP. After confirming that the machining previously effected by automatic assembling or machining devices Wn, W12 etc. in the sub-conveyer 32 is satisfactory, the pallet loaded with the workpieces is then fed to the subconveyer 33 for assembling or machining at the working stations in succession in the same manner as in the sub-conveyer 32.

The workpieces can be fed to the sub-conveyer 33 only when they have been correctly processed by the assembling or machining devices disposed around the sub-conveyer 32. Otherwise the workpieces are carried in the direction of arrow 44 on the main conveyer 31 without being fed to the sub-conveyer 33. In a similar manner, the pallets loaded with the workpieces, after being subjected to similar processing along the subconveyers 34 and 35, are transported to the deliverystation E.

The present system has a buffer capability in that, when the intermittently driven sub-conveyer 32 is stopped, or when an automatic assembling or machining device 36 on the sub-conveyer 32 is stopped, the pallets loaded with the workpieces are stored and retained on the main conveyer 31 without being fed to the sub-conveyer 32. When the sub-conveyer 32 is stopped for a long time, an emergency conveyer having the same function as the sub-conveyer 32 is provided in replacement of the sub-conveyer 32. Further the provision of the by-pass on the main conveyer makes possible the selective feeding of the workpieces to the sub-conveyers according to the types or kinds of the workpieces.

The computer controls the pallets loaded with the workpieces through the memory elements, and the assembling or machining device through detectors (not shown) disposed in the automatic assembling and machining devices. The computer is connected to readers Rj, R2, R3 and R4, and detectors D,, D2, D3 and D4 for the reasons given previously. The computer is so connected to the respective control elements that it can in

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struct the automatic assembling or machining devices
whether processing of a workpiece on any pallet is to
be effected or not.
In FIG. 2 there is shown another embodiment of the

5 automatic transport system according to the present invention wherein main conveyer 31 serves for transporting a container in which a plurality of pallets (with memory elements) are loaded. In the embodiments of FIGS. 2 and 3 the sub-conveyers 32a and 33a are inter

10 mittently driven while sub-conveyer 34a is freely driven in periodic fashion. Automatic warehouses or storage stations are provided for storing defective workpieces and for receiving acceptable workpieces which can be delivered as completed products. The computer COMP

15 controls the system.

For convenience of the description of the above embodiments, it is assumed that one of the following is true:

I. All the containers fed from the sending station S 20 onto the main conveyer contain a plurality of pallets

each loaded with the same kind of workpieces (i.e., assembled, processed, and machined in the same manner).

II. The pallets are classified and accommodated in 25 the container at the sending station so that the same

container may contain the same workpieces in dependence upon where the workpieces are to be processed, i.e., along the sub-conveyer 32a, 33a or 34a.

III. Different types of workpieces are loaded in the 30 same container and are selectively processed in succession by the automatic assembling or machining devices along the corresponding sub-conveyer under the control of the computer.

Based on the above-mentioned three assumptions,

35 three operations will next be described.

In the case of assumption (I), containers 52 loaded with pallets 51 are provided with memory elements Mo, as shown in FIG. 5, and the memory elements are coded as regards where the workpieces are to be pro

40 cessed, and the containers advanced on the main conveyer 31 in succession. The container 52 is transported to sub-conveyer 32a and when the workpieces on the pallet of the container are to be processed along the sub-conveyer 32a, as detected by a reader R,, the con

4^ tainer 52 is halted by a positioning means S, (shown in FIG. 2). When the container 52 is stopped, a pusher Ptc is operated to push pallets loaded on the container 52 intermittently one by one so as to feed the pallets to

^ the subconveyer 32a. The workpieces on the pallet are intermittently advanced in the direction of arrow 42 along the sub-conveyer 32a. It is to be noted that all processes are controlled by the computer COMP.

The workpieces on the pallet are successively processed by the automatic assembling or machining devices W„, W12, WI3) W14 and W15. When the workpieces reach the corner of sub-conveyer, the pallets are contacted by a pusher P^b and advanced in a direction 43 by a second belt of the sub-conveyer 32a to arrive

^ at a location adjacent the main conveyer 31.

The container which has been emptied of the pallets due to unloading at the entrance of the sub-conveyer 32a is advanced along the main conveyer and waits at the juncture between the sub-conveyer 32a and the

^ main conveyer 31 at which the processed pallets are loaded from the sub-conveyer 32a into the waiting container in intermittent manner. When the container is filled with the processed pallets, the container is trans