GB2108457A - Assembly stage having a plurality of individual operator positions - Google Patents

Abstract

An assembly stage for assembling and machining or treating products has a plurality of work stations each with an individual operator position for manual assembly, each of which stations comprises a round table (15) which revolves before an operative at the operator position (25), and is controlled by the operative. In a plurality of revolutions a plurality of successive assembly operations can be carried out. The workpieces (40) are assembled on workpiece carriers (21) of which a large number is disposed and positioned on the round table. After completion of the assembly step at one work station, the workpiece carriers (21) are ejected from the round table and replaced by new workpiece carriers if required. A transport section (13) connects the work stations (12) and includes buffers or stores (28) which can be constructed as conveyor belts disposed one above another, thereby increasing the buffer storage capacity of the round table and of the transport section itself. The work stations (12) can be connected in any desired arrangement by the transport section (13) and storage containers (24) can be provided for the components to be assembled or for tools within easy reach of the operator position in the central region. <IMAGE>

Description

SPECIFICATION Assembly stage having a plurality of individual operator positions This invention relates to an assembly stage having a plurality of individual operator positions in which numerous individual workpiece carriers can be moved past the operator positions.

Assembly stages of this type are used for assemb ling, machining, adjusting and testing workpieces.

Among the commonest assembly methods is that of conveyor line assembly which makes possible a high output, but is very inflexible since its speed is dependent upon the longest cycle time. There is moreover a dependence upon the number of oper ator positions and, if only one operator position is out of use, the conveyor line must be stopped or else reserve operatives would need to be continually kept available. Conveyor line work is, furthermore, becoming increasingly unpopular as a highly cycledependent type of work.

Fully automatic assembly apparatus presuppose, however, large numbers of items and a long product life because they demand high investment costs and investment period. Two and a half years normally need to be allowed from planning until fully automatic assembly is achieved.

In the watch and clock-making industry, assembly apparatus have already been disclosed on which plate-like carriers comprising a plurality of fixed workpiece seatings are used. These circular workpiece carriers can be advanced by hand. They are limited to small, light components and only one side is ever accessible for assembly.

It is an object of the present invention to create a flexible, adaptable assembly system which largely eliminates idle times, permits individual arrangement of the operator positions, and in spite of the interlinking of operator positions, is independent of cycles.

According to the present invention there is provided an assembly stage comprising a plurality of work stations each having an individual operator position, a rotatable transport device associated with at least one work station adapted to support a plurality of workpiece carriers and to advance such supported workpiece carriers past the operator position of the associated work station, transport means extending between the associated work station and another work station and transfer means for transferring workpiece carriers from the rotatable transport device to the transport means.

By the seating of the workpiece in a workpiece support, which is automatically transported from one work station to another and can be positioned there, all the secondary assembly operations, i.e. all the operations which do not directly serve to increase the value of the product such as turning over, positioning, taking up again, etc., are restricted to a minimum.By the circulating or rotatable transport device, which is preferably a round table comprising a rotating transport ring for the workpiece carriers, but can also be formed from other circulating transport devices, a greater concentration of work stations and operator positions is possible, i.e., a plurality of operations can be carried out on a specific number of workpieces in succession at one work station and operator position before the work pieces, sometimes treated or machined in several operating steps, are ejected on their workpiece carriers and replaced by new workpiece carriers. By the clear separation and independent controllability of the circulating transport device at each work station and operator position and of the transport section interconnecting the work stations, the trans port section itself constitutes a buffer or store.

Additional buffer or storage devices may be provided, preferably constructed in the form of a plurality of storage transport sections situated one above another.

The individual work station having a circulating transport device in the form of a round table is especially advantageous because such a round table is simple to manufacture and control and the storage containers or bins for the components required for assembly and also possibly for tools can be disposed at the centre of the round table within easy reach of the operator position.

By arranging the workpieces on individual workpiece carriers, it is also immediately possible to machine or treat the workpieces from different sides.

Without turning the workpieces round it is possible to machine or treat them from the opposite side if at least one of the operator positions or work stations is located at the side of the transport section opposite to another. The workpiece carriers are fed to this operator position in an alignment changed through 1800.

The assembly stage of this invention makes it possible to create an especially flexible and adaptable assembly system which can be set up in a very short period for the assembly of new workpieces. A modification or new construction of the workpiece carriers and possibly also new positioning of some operator positions is usualiy all that is required to enable a new workpiece to be assembled. A particu laradvantage is the independence of working cycles or independence of synchronization. The operative can assemble and machine or treat the individual workpieces according to his personal working rhythm and, due to the buffering at his working position and in the transport section, an adequate personal delay allowance becomes available, i.e., a short pause by an operative does not lead to shutdown of the entire assembly section.Due to the buffering, moreover, the possibility exists, if one operative should be completely out of action, or if the supply of items should be temporarily reduced, of causing several operator positions to be served by one person in succession. On the other hand, an adaptive possibility exists also in the other direction in that, if the rate of production of items should be increased, the output can be raised by doubling the operator positions. The operative has the choice between continuous or intermittent operation and between manual and automatic passing on to the next workpiece, this possibility of choice being retained independently for every operator position of the same assembly section. It is furthermore possible to combine the assembly stage with automatic partial operator stations, e.g., for the application of metered quantities, pressing operations or the like.

The assembly stage is distinguished especially by independence of space. It can be arranged in any desired manner, for example, in series arrangement one behind another or in ring arrangement, say in a four-sided figure, by which a recycling of the empty workpiece carriers can in certain circumstances be omitted.

The use of individual workpiece carriers which are not permanently associated with the transport devices make possible optimum accessibility to the workpiece and are largely independent of the form of the workpiece, so that they may in certain circumstances be used also to carry a plurality of workpieces by appropriate adjusting of the stops, etc. They may, for example, be simple plastics blocks with depressions formed in them or webs formed on them.

The possibility of concentrating the work stations and operator positions permits also simple adaptation to the particular operative and allowance for knowledge which only becomes available during operation. Thus, for example, for a new worker requiring training, the number of assembly operations to be carried out successively on the same workpiece can be reduced without the assembly section being reduced in its total output and, in the same manner, allowance could be made if it is found in the course of operation that one operation takes longer than planned or, e.g., an additional testing operation is necessary. The susceptibility to failure is less than with automatic assembly devices.

Further advantages and features of the invention will become apparent from the following description of the attached drawings. Some forms of embodiment are illustrated as examples in the drawings are are explained in more detail below.

Figure lisa diagrammatic plan view of an assembly stage comprising three operator positions, Figure2 is a section on the line ll-ll in Figure 1, Figure 3 is an exploded view of a workpiece to be assembled as an example on the assembly stage according to Figures 1 and 2 and of the associated workpiece carrier, Figure 4 is the workpiece carrier and components shown in Figure 3 in the assembled condition, Figure 5 is an arrangement of four operator positions of an assembly stage in a rectangular arrangement, and Figure 6 is a further arrangement of operator positions.

The assembly stage 11 illustrated in Figures 1 and 2 has three work stages 12 each with an operator position 25. The work stages 12 are disposed alongside one another and operatively associated by a transport section 13. The end of the transport section 13 constitutes a discharge and packing station 14, not illustrated in more detail, which may be of any form but can be constructed similarly to a work stage 12.

Each work stage 12 is constructed in the form of a circulating or rotating transport device and possesses a round table 15 rotatably mounted on a frame 16. The round table 15 can be driven continuously or intermittently by a diagrammatically illustrated motor 17 via a gear and can be controlled by the operator, i.e., started or stopped, by means of a foot switch 18. The rotatable round table 15 has, at its outer periphery, an annular transport zone 19 which may be formed with ribs or depressions 20 arranged in a sector pattern which correspond to the maximum size of a workpiece carrier 21 to be seated and located thereby. This annular zone 19 is freely accessible at least in the region of the working or front side 22 of the work stage 12 atthe operator position 25.

The central zone of the round table 15 is covered by a bridge 23 on which storage containers 24 are disposed within easy reach of the operative at position 25 who sits at the front side of the work station. The bridge may also have a central mounting, so that the entire annular zone 19 can be freely accessed all around.

At a position diametrically opposite the front side 22, the transport section 13 extends substantially tangentially to the outer side of the round table 15, this transport section being equipped with conveyor means 26 such as belts or roller tracks. From Figure 2, it can be seen that the transport section 13 contains three conveyor belts 26 one above another which each extend from one work station to the next and form a buffer 28 in which a large quantity of workpiece carriers 21 can be stored. Preferably, the capacity of the buffer is equal to several times the acceptance capacity of a round table 15 for the workpiece carriers. Since one round table 15 can receive numerous workpiece carriers 21 (in every case more than 10 and, in the example illustrated, 24), a buffer having a capacity to store 50 workpiece carriers is advantageous.

The three conveyor belts 26 (or roller tracks) are journalled on a support 27 which is vertically movable and has a vertical lifting drive in the form of a threaded spindle 29 which can be moved up and down by a screw motor 30 driven via a worm gear.

The worm 31 of the worm gear is driven from a motor 32.

Instead of this store or buffer 28 having a plurality of vertical levels, other types of buffer may be used, for example, buffers with helically arranged storage tracks or fixed stores.

At the position at which the transport section 13, which is rectilinear in the example illustrated, approaches tangentially the round table 15, transfer means 33,33' is disposed operable to transfer the workpiece carriers from the transport section to the adjacent round table and from the round table to the transport section. The station at such position contains, in the course of the transport section 13, a table 34 at the same level as the annular transport zone 19 of the round table 15, which enables the workpiece carriers 21 to be pushed on to and off the round table.For this purpose, in the example illustrated, pneumatic cylinders are provided, that is to say in all three work stations 12 pneumatic cylinders 35 are disposed on the bridge 23 for pushing out or ejecting workpieces from the tables 15 (transfer means 33') and in the case of the second and third work stations, additional pneumatic cylinders 36 are provided which can push workpiece carriers 21 situated on the table 34 on to the round table 15 (transfer means 33). Furthermore, pneumatic cylinders 37 are provided which push the workpiece carriers 21 from the table 34 on to the conveyor belt 26, situated at the appropriate level, by actuation in each case of the motor.Each buffer or store 28 of each transport section 13 extends from one work station to the one adjacent to it and can be actuated independently of the other, i.e., not only the lifting apparatus but also the drive of the conveyor belts can be operated independently. To obtain a complete decoupling of the method of functioning of mutually adjacent work stations, the two ends of the support 27 constituting the buffer could be capable of being raised and lowered independently of each other so that, for example, workpiece carriers 21 could be ejected from the first work station on to the upper buffer track (conveyor belt 26), whereas the next succeeding operator position locks in or displaces work pieces from the middle or lower conveyor belt to the table 15.

From the discharge station 14, the workpiece carriers 21 are recycled by a conventional transport device 38, indicated in broken line, back to the first work station 12 and stored there in a separate container 39. The recycling or return of the workpiece carriers 21 could also be carried out from time to time manually, especially in the case of small workpiece carriers.

In Figure 3, ten different components A to K are shown by way of example, for assembly to form a workpiece 40, i.e., joined and screwed together. At the same time, the associated workpiece carrier 21, made from plastics injection moulded material, is illustrated. Figure 4 shows the fully assembled workpiece 40 in the workpiece carrier 21. The working sequence in the assembly stage, comprising three work stations according to Figure 1, could be such that at the work station at the left in Figure 1, the workpiece carriers 21 from the storage container 39 are first laid out in a first revolution of the round table 15 and thereafter, in two further revolutions, the components A to C could be laid in the corresponding recesses of the workpiece carrier.The operator himself can determine whether the round table 15 shall be moved by steps or continuously, a decision which can be made in advance in different ways for different procedures (for example, continuously for the laying out of the workpiece carriers 21 and by steps forthe placing of the nuts A and B).

During the last revolution (in which the operator places the component C) the workpiece carriers 21 can each be ejected by actuation of the pneumatic cylinder 35 on each occasion on to the table 34 of the transport section 13 and then pushed on to one of the conveyor belts 26 of the buffer 28 by the pneumatic cylinder 37. If one of the conveyor belts is full, then by actuation of the motor 32 the next upper or lower conveyor belt is automatically brought to the level of the transfer table 34. It may be commented that the manual operation of laying out the workpiece carriers 21 on the round table can be dispensed with by the workpiece carriers 21 being brought automatically on to a feed conveyor belt, not illustrated, of the transport section (adjoining the left side) and being automatically displaced on to the round table by a pneumatic cylinder 36.

This takes place in each case at the following operator positions 12, simultaneously with or follow- ing the ejection. At the second, central operator position, the components D, E, F and G are positioned, i.e., four further components are assembled again in several operations. In each case the operator himself can choose whether he will carry out the assembly of several components in successive revolutions or, for example, can so easily pick up two components that they can be attached simultaneously or in succession, such as the two nuts A, B orthescrewsj. K.

At the second work station 12, ejection is again effected on to a buffer 28. If one conveyor belt of a buffer has filled up, this is detected by a signal transmitter and the motor 32 switches on, in order to bring the next upper or lower conveyor belt to the level of the transfer table 34.

The third work station (at the right in Figure 1) is the same as the central one. Here the component H and the screws I and K are inserted and finally tightened up with a screwdriver.

After ejection from the associated round table 15, transfer takes place on to a single conveyor belt which leads to the packaging and discharge station 14.

In Figure 5, an assembly stage 11' comprising four work stations 12 is illustrated in which the work stations and the transport section portions (bUff61.Z 28) can be the same as those according to Figures and 2. The only difference is that here the arrangement chosen is rectangular or square so that two operators at positions 25 sit opposite to each other and the transport section 13 constitutes a square, closed loop. As a consequence, separate workpiece carrier recycling is dispensed with, since these always remain in continuous circulation. Afree choice exists here of the position at which assembly is commenced so that this arrangement is an especially flexible standard arrangement which can be modified to any desired number by the introduction of further operator positions.

In the arrangement according to Figure 6, a more complicated working sequence is presented diagrammatically in which at a first, linear portion three work stations are situated alongside each other, opposite three further work stations 12. Each of these work stations operates on an independent portion (buffer 28) of the transport section 13, which portions run parallel to one another so that the same components are assembled at each two mutually opposite operator positions. In this manner the assembly capacity of the six operatives is fully utilized, without making them work one after the other on a conveyor line, which on the one hand presents problems of cycle-dependence (cycle time is too short for slow operations and too long for short operations) and in the case of failure or absence of one person, would bring the entire line to a stop.At the end of the three work stations 12 of double construction, the flows of the workpiece carriers on the two partial transport sections are brought together on one common transport section and, if necessary, the workpiece carriers 21 are turned round on one of the partial sections, if assembly can only favourably be carried out from one side. If, in the case of successive partial assembly operations, the assembly side should need to be changed over each time, then a cross-over arrangement of the transport sections, for example, would be possible, in that the first work station as seen from the left would give up its workpiece carriers to the upper, central one, etc.

Into the now combined transport section, two automatic work stations 41 are introduced which may carry out easily automated operations, such as pressing, riveting, screwing, bolting, etc. Adapting to the automatic method of operation is very easy because the workpieces are accurately positioned on the workpiece carriers 21 and, accordingly, positioning for automatic machining or treatment is possible by means of simple stops. The same applies natural ly for the hand assembly stations, in which accurate positioning facilitates also the manual work. Each workpiece in any case only has to be positioned once on the workpiece carrier during the entire treatment and handling in the course of assembly.In Figure 6, following the automatic work stations 41, two further work station positions 12 are shown which are each situated on mutually opposite sides of the transport section 13 and where operations may be carried out which on the one hand require less time (so that as compared with the initial operator positions twice the quantity can be passed through) and on the other hand, demand accessibility from two different sides of the workpiece. This is provided automatically by the opposed arrangement. Following then in the assembly direction (from left to right) a work station 42 is provided, which is not equipped with a circulating transport device and in which, therefore, work is carried out cyclically dependently in one pass.Operations which can be carried out in an extremely short time in sequence are suitable for this purpose such as the securing of screws or bolts with a securing lacquer or the like.

Finally, a packaging station 14 completes the assembly section. From this point on, the finished components taken from the workpiece carriers are packed and the workpiece carriers again recycled to the start of the assembly section.

It will be recognised that by the invention an assembly stage is created which consists of a few, like standard components (operator position and transport section) and which can be easily adapted to extremely varied requirements. It may be used for a very large variety of different and differently sized products, for larger products, for example, only the divisions of the round table would need to be changed. It can also be realised, according to the desired size, cycle number, etc., with the most varied components (for example, for the purpose of pushing transfer instead of the pneumatic cylinders illustrated), any kind of mechanical or electrical pusher apparatus can be used and, instead of the conveyor belts, other transport means such as roller tracks, chains, grabs, etc., may be used.

It is also possible optionally to control the round table 15 so that on each occasion it advances by two workpiece carriers 21, if the operator can readily carry out two operations in succession. Although preferably each workpiece will have its own workpiece carrier 21 associated with it, it is also possible, especially in the case of very small workpieces, to arrange two or three workpieces or, for example, two individual component assemblies of the same product on the same workpiece carrier.

It is also possible to cause automatic operations to be performed at a work station 12 instead of or in addition to the operative. Thus, for example, an automatic screwing or welding device could connect together the components which have been assembled manually, possibly also in several revolutions.

Claims (17)

1. An assembly stage comprising a plurality of work stations each having an individual operator position, a rotatable transport device associated with at least one work station adapted to support a plurality of workpiece carriers and to advance such supported workpiece carriers past the operator position of the associated work station, transport means extending between the associated work station and another work station and transfer means for transferring workpiece carriers from the rotatable transport device to the transport means.

2. An assembly stage according to claim 1 in which the rotatable transport device comprises an annular transport zone adapted to support the workpieces.

3. An assembly stage according to claim 1 or 2 in which the transfer means is disposed at a location substantially diametrically opposite to the operator position.

4. An assembly stage according to claim 1,2 or 3 including further transfer means for transferring workpiece carriers from the transport means to the rotatable transport device.

5. An assembly stage according to claims 3 and 4 in which the transfer means and the further transfer means are disposed at locations substantially diametrically opposite to'the operator position.

6. An assembly stage according to any one of the preceding claims in which the rotatable transport device is arranged to advance the workpiece carriers past the operator position a plurality of times before the transfer means operates.

7. An assembly stage according to any one of the preceding claims in which the transport means includes buffer or storage means for the workpiece carriers.

8. An assembly stage according to claim 7 in which the transport means comprises a plurality of transport sections disposed one above the other together with means for adjusting the level of such sections with respect to the rotatable transport device.

9. An assembly stage according to any one of the preceding claims in which storage containers for components to be assembled are disposed in or above a non-rotatable central zone of the transport device.

10. An assembly stage according to any one of the preceding claims in which at least two of the work stages are disposed on opposite sides of the direction of advance of the transport means.

11. An assembly stage according to any one of the preceding claims including control means operable to control the advance of the workpiece carriers supported on the rotatable transport device past the associated operator position in a continuous or stepwise manner.

12. An assembly stage according to any one of the preceding claims including means for recycling workpiece carriers from the end of the assembly stage to the beginning thereof.

13. An assembly stage according to any one of claims 1 to 11 in which the transport means is arranged as a closed loop extending between the work stations of the stage.

14. An assembly stage according to any one of the preceding claims in which a separate workpiece carrier is provided for each workpiece to be assembled, machined or treated.

15. An assembly stage according to any one of the preceding claims including automatic means disposed at at least one operator position for performing an operation on the workpiece.

16. An assembly stage according to claim 1 in which a separate rotatable transport device is associated with each of the plurality of work stations, the transport means is arranged to transport workpiece carriers in a predetermined sequence from each work station to the next in the sequence, first transfer means is associated with each rotatable transport device to transfer workpiece carriers therefrom to the transport means and is disposed substantially diametrically opposite the operator position of each work station and second transfer means is provided for at least all the work stations except the first in the sequence for transferring workpiece carriers from the transport means to the associated rotatable transport device.

17. An assembly stage constructed, arranged and adapted to operate substantially as herein described with reference to Figures 1 and 2, Figure 5 or Figure 6 of the accompanying drawings.