The present invention provides a production line method and apparatus in which work pieces are operated on or manipulat-ed, or assemblies or sub-assemblies are formed or operated on or manipulated, on respective pallets mounted on an endless conveyor which carries the pallets along an upper operating run sequentially through a series of work and checking stations and then inverted along a lower return run for the selective release of reject items. Satisfactorily completed Items will usually be released and removed from their pallets at the end of the upper operating run. Usually, the first work station, at the beginning of the upper operating run, is for the positioning and releasable securing to the pallet of the initial work piece or of the first element(s) of the eventual assembly; at subsequent work stations various pre-determined manipulations or assembly or other operations are carried out on the items carried by the pallets. After each work station (or after at least some work stations) the pallet moves to a checking station for checking (e.g. by probing) that the previous operation(s) has/have been performed satisfactorily so that the subsequent steps can be performed.

It is one aspect of the invention that the production line is automatically controlled so that, when a check is failed, then according to the nature of the fault at least some succeeding operations and checks are not applied to that pallet and/or the pallet when it reaches the appropriate predetermined reject station on the return run releases the faulty item to be collected with others of the same type. For example, if the first check shows that the initial work piece or element is incorrectly positioned on the pallet for the subsequent operations, then the pallet concerned may pass untouched through the remaining work and checking stations and release the mis-positioned item at the appropriate reject station on the return run to join other rejects of the same nature; where a manipulation or operation is not performed at all, or an element

which should have been supplied and incorporated in the assembly is missing, then the check revealing this could programme for suspension of some or all succeeding operations on this pallet with release of the faulty item at a pre-selected different reject station on the return run - or with retention of the faulty item throughout the return run and back _o the work station where the omission occurred, operations already successfully performed on the item in the first operating run being suspended for the pallet concerned; where two or more sub-assemblies are to be built up at different locations on the pallet, any one failing a check may be rejected as described with the other(s) being recycled on the pallet back to the upper operating run. This automatic programming and sorting of rejects into types by fault detection gives economy of operation, reducing the number of unnecessary rejects and facilitating the use of some rejects - in many cases the fault is simply remedied and the cured reject can be fed back to the production line, but it would be uneconomic to identify and select these from an unsorted mixture of many different types of reject.

The endless conveyor preferably moves stepwise, with the work, checking and reject etc stations being occupied simultaneously by respective different pallets, the working, checking and rejecting etc operations being conducted simultaneously, and the pallets then moving in unison to the respective next stations along the line.

It is a feature of the invention that each pallet is secured to the endless conveyor, so as to be moved positively and directly from station to station along the production line; preferably, each pallet Is resiliently mounted on the conveyor to allow a little movement ahout its optimum operating position, and after entering a work or checking station is fixedly secured (e.g. by shot-bolting) in its precise position for the work or checking operation to be conducted, the pallet being released for passage to the next station after the operation Is completed.

Items located on the pallets are preferably clamped thereto so that if they are to be rejected or returned to the beginning of the cycle

they remain attached to the inverted pallet as it travels along the lower return run unless or until the clamping is released at a pre¬ arranged rejection station where the Item concerned then simply falls under gravity into the corresponding pre-determined reject bin. Reεiliently biassed clamps are preferably employed, so that the same pallet can accommodate items of different size and configuration. One especially preferred pallet according to the invention has at its receiving face two upright datum surfaces extending at an angle to one another and respective clamping members each moveable towards and away from and resiliently biassed towards its datum surface to clamp a work piece or like item against the datum surfaces; the clamping members can for example be upright pins moveable in horizontal slots; the clamping provided by the datum surfaces and clamping members can thus accommodate items of a variety of sizes and configurations - though to maintain correct centering of the item for operations on the production line it may be necessary to insert a spacer or spacers between at least one datum surface and the item. A pallet according to the invention can have means for separately clamping different items at different locations, e.g. so that different sub-assemblies can be built up on the same pallet for subsequent combination on the pallet.

Below and overlapping the beginning of the return run of the endless conveyor there is preferably located a second conveyor for taking away (e.g. to a reject bin) loose components from the endless conveyor. Thus where an item fails to be securely located on a pallet, it will drop off onto, or be wiped off by, the second conveyor.

A satisfactorily completed assembly or work piece will usually be released and removed from its pallet at the end of the operating room - e.g. onto a product conveyor on which it may be subjected to further tests and treatments.

The invention is illustrated, by way of example only, by the following description to be taken in conjunction with the accompanying drawings, in which :-

FIGURE 1 is a plan view of a preferred pallet according to the invention:

FIGURES 2, 3 and 4 are sectional views of the pallet along lines 2- 2, 3-3 and 4-4 respectively of Fig.l; and

FIGURES 5 and 6 are schematic side elevation and plan views respectively of an assembly line according to the Invention.

The pallet according to the invention shown in Fig.l is suitable for use In the assembly method and apparatus of Figs.5 and 6. The pallet 2 Is a body of metal having recesses 4 in opposed narrow sides for receiving shot bolts by which It is accurately positioned for operations on the assembly line. In its upper face 6 it has a tray-like depression 8 for receiving a work piece or a basic component of an assembly to be formed - e.g. the connector body of the connector assembly considered in connection with Figs.5 and 6. The depression R has two vertical datum surfaces 10 and respective clamping pins 12, one opposite each surface 10 and moveable towards and away from this surface In slot 14, each pin being resiliently biassed towards its surface 10. In this particular embodiment, a separate portion 16 of the receiving surface 6 of the pallet provides clamping means for a sub-assembly operation. Another clamping pin 18 moveable in slot 20 and resiliently biassed towards stops 22 provides for clamping of a jumper bar against stops 22 for assembly with yoke and screw terminals to be inserted and accommodated in spaces 24 and 26 respectively. The sub-assembly of terminals connected by the jumper bar can subsequently be transferred to and assembled with the main connector body clamped between surfaces 10 and pins 12. A range of sizes and configurations of connector body can be accommodated by the surfaces 10 and 12.

Figs.5 and 6 Illustrate schematically an assembly line procedure and apparatus according to the invention for an electrical terminal or connector assembly comprising a plastics connector body

accommodating (a) a pair of yoke and screw terminals connected by a jumper bar and (b) a spring clip by means of which a number of the connectors can be clamped together in a bank or stack. In the drawings the connector body is indicated symbolically at 30; the spring clip at 32; the jumper bar at 34; and the yoke, screw and terminal sub-assembly at 36, 38 and 40 respectively. Similar symbols are employed in connection with the various reject bins R2- R9.

The assembly line has an endless conveyor 50 with an upper operating run 52 and a lower return run 54, on which pallets such as that of Fig.l are mounted at longitudinally spaced intervals with receiving faces exposed. The pallets are positively mounted on the conveyor 50 by resilient means (not shown) allowing a pallet a degree of movement about a pre-determined operation position. The conveyor 50 moves stepwise to carry each pallet sequentially through stations SI to S16 (including checkpoints Cl to C8) of the operating run and over the various reject bins R2-R7 on the return run. The pallets are so spaced and movement of the conveyor so synchronised that pallets will be at each station and checkpoint simultaneously where they remain stationary for the working and checking operations before moving on in unison to the next station or checkpoint. When a pallet enters a station or checkpoint it is automatically shot- bolted for precise positioning, the shot-bolts being withdrawn after completion of each operation. The supply, assembly and manipulation operations at the various work stations are effected automatically, as is the checking at each check point. The checking is for presence, correct positioning, and assembly of the component or components on the pallet, and is suitably carried out by probes lowered onto the pallet which readily detect when a component is missing or out of position. Detection of a fault automatically alters the programme of succeeding operations for the pallet concerned so that, according to the circumstances, some or all of the work operations (including transfer from the endless conveyor at the end of the operating run) are suspended and/or the system is primed to unclamp the faulty or deficient item at the appropriate pre-determined reject station so that it falls into the appropriate

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reject bin. Programming and setting-up of the operations can be caarried out (often by a single operator) at control panel 60. The sequence of work operations is as follows :-

S2A- visual inspection of connector body 30;

S2 - supply of connector body 30 and clamping on pallet 2 by pins 12 and surfaces 10;

54 - supply of spring clip and insertion in connector body;

55 - twisting of spring clip to operative position;

S7 - supply of jumper bar and clamping on pallet between pin 18 and stops 22;

S9 and Sll - supply and assembly of terminal sub-assemblies 40 with jumper bar, terminals 40.being assembled off-line at S9A and S11A from yokes and screws 36 and 38;

S13 - remo-val of jumper bar and terminals assembly from region 16 of the pallet and transfer Into the adjacent connector body on the pallet;

S15 - unclamping of completed connector from pallet and lateral shifting onto product conveyor 56.

Checkpoints Cl and C8 (SI and SI6) are to ascertain what, if anything, is carried by the pallet; checkpoint C2 (S3) is for correct positioning of the connector body; checkpoint C3 (S6) is for the presence and correct location of the spring clip; checkpoint C4 (S8) is for the presence and correct positioning of the jumper bar on the pallet; checkpoints C5 and C6 (S10 and S12) are for the presence and correct positioning of the terminals in the terminal/jumper bar sub- assembly; and checkpoint C7 (S14) is for the presence and correct location of the latter sub-assembly in the connector body.

Items rejected at checkpoints C2 to C7 will be deposited in the respective reject bins R2 to R7.

As indicated above detection of a fault or deficiency at a checkpoint will reprogram e the system for the pallet concerned, e.g. to retain a reject item on the pallet through to the return run and to unclamp the item so that it falls into the appropriate reject bin, and/or to recycle back to the appropriate work εtation(s) an incompletely finished pallet load - e.g. when an operation such as supply of a component. or manipulation of a component or sub-assembly has been omitted altogether; in either case there will also be reprogramming to suspend any redundant or inappropriate operations. On the product conveyor 56 the finished assembly can be subjected as indicated to flash test (S17), visual inspection (S18), demagnetization(S19) etc, with satisfactory complete terminal assemblies being collected at the end of the conveyor 56 and rejects dropping into a bin R9.

Loose components on the endless conveyor 50 drop or are wiped onto conveyor 58 and dropped into another reject bin R8.

The invention thus has a number of aspects of merit and advantage which can be employed independently or in any combination. Included amongst these features are the use of an endless conveyor with upper and lower runs and the release of reject items into preselected receivers below the lower run according to type of reject. Whether or not the conveyor is endless with upper and lower runs, the invention covers independently, or in any combination of two or more, the use of fault detection to reprogramme the subsequent operations for the pallet concerned, the options being selected from suspension of at least some subsequent operations on the pallet, rejection of faulty or deficient items at selected rejection stations, and recycling of incompletely finished items back to the work stations concerned; the use of pallets permanently attached to and positively guided and carried by the conveyor, preferably with precise positioning (e.g. by shot-bolting) at work and checking stations; stepwise advance of the conveyor to synchronise movements of pallets to the work and checking stations and provide simultaneous performance of the various work and checking operations along the line; the provision of a subsidiary conveyor to collect

and carry away loose components from the production line; and the provision for effecting sub-assembly operations at more than one location on the pallet, preferably with subsequent final assembly on the pallet. The invention also provides pallets per se, in particular those having more than one location for receiving work pieces or components; and those having the preferred adjustable clamping provided by datum faces at an angle to one another and provided with respective resiliently biassed clamping members.

The production line method and apparatus of the Invention has great advantages compared to prior proposals in saving space, providing ready access for Intervention, and from the safety aspect. It is also very versatile; whilst illustrated in terms of assembling a connector, it could evidently be employed in like manner, with appropriate changes In the operations employed, for assembling a great variety of other multi-component articles, or for carrying out a succession of operations (e.g. drilling, milling, reaming, etc., etc. on work pieces of various materials.

The invention thus provides a production line in which work pieces are operated on or manipulated, or assemblies or sub-assemblies are formed or operated on or manipulated, on respective pallets mounted on an endless conveyor which carries the pallets along an upper operating run sequentially through a series of work and checking stations and then inverted along a lower return run sequentially through a plurality of reject stations, with reject items being releasable from their pallets at pre-selected reject stations according to reject type. Preferred features which maybe used Individually or In any combination of any two or more are

(a) reject Items released at the pre-selected reject stations to fall into reject receivers for rejects of respective different types;

(b) automatic control means so that failure of a check reprogrammes the system for the pallet concerned to effect, according to the nature of the failure, one or more of suspension of at least some subsequent operations on the pallet, release of a reject item from the pallet at a pre-selected rejection station, and

recycling of a faulty item on the pallet back to the appropriate work station(ε);

(c) stepwise advance of the conveyor to synchronise movements of pallets to the work and checking stations and to provide simultaneous performance of the work and checking operations along the line;

(d) pallets permanently attached to and positively guided and carried by the conveyor, e.g. resiliently secured to the conveyor and fixedly and precisely positioned thereon at work and checking stations;

(e) sub-assembly operation effected at more than one location on a pallet, preferably with subsequent final assembly on the pallet;

(f) below and overlapping the beginning of the return run of the endless conveyor, a second conveyor for taking away loose components from the en less conveyor; and

(g) satisfactorily completed items released and removed from their pallets at the end of the upper operating run.