GB2214479A - Belt conveyor and pallets - Google Patents

Abstract

A conveyor system comprises a belt conveyor 118 and pallets 106 having complementary profiles 140, 142 allowing the pallets to be positively located in driven engagement with the belt conveyor and yet to be lifted clear for or by shot-bolting at a work station as at 110, 112. A guide system is also described to maintain contact between belt and pallet diving passage from an upper to a lower run (or vice versa) of the conveyor. <IMAGE>

Description

CONVEYOR SYSTEM The present invention relates to conveyor systems, particularly but not exclusively to those for use in production lines where operations are carried out on items along their transport path.

In some known such systems each item or workpiece is carried on a construction jig in the form of a pallet, the pallets being linked by or connected to chains or similar. At each station where an operation is to be carried out, the conveyor stops and the pallets are locked in place (by shot-bolting for example).

The latter systems have a number of inherent problems. In use, the chains tend to stretch with the result that the spacing between adjacent pallets becomes uneven and problems arise with aligning them at work stations. Shot-bolting can only locate the pallets (by engagement with appropriate recesses therein) if the pallets are relatively close to their desired position. Once the chain has become stretched, some if not all of the pallets will not align so that the system may jam. Maintenance is complex and costly with the system having to be shut down and partially dismantled for inspection and repair of chains and pallets.

The present invention provides a conveyor system having pallets for transporting workpieces between stations or delivery and collection areas, the pallets being positively located on, but not fixed to, a driven belt by which they are carried along. The pallets sit on the belt in positive driven engagement therewith but can be lifted clear. The location of the pallets on belt may suitably be achieved by complementary profiles on the belt and pallets, the engagement of the two surfaces preventing the pallet from moving longitudinally relative to the belt whilst allowing it to be lifted directly from the belt. These profiles may take the form of projections such as ribs, studs or similar with complementary recesses for them to engage on the other surface. The projections preferably taper to narrower free ends (with corresponding shaping of the recesses).The profiles may be shaped or arranged assymetrically to ensure that all pallets are placed on the belt the right way round.

The use of locating profiles to engage the pallets allows them to be lifted for or by shot-bolting. They are preferably shot-bolted from below (either directly or obliquely) e.g. through suitable gaps in the belt or outboard of the belt. Thus the belt may have two separate parallel runs with a continuous gap therebetween; or it may have longitudinally spaced gaps at the pallet location regions and/or the pallets may extend laterally beyond the belt edges. When the pallet reaches a work station, shot-bolting from below may lift it clear of the belt and hold it in place against overhanging ledges or lugs.

This action of lifting clear during operations on the workpiece allows the pallet to be moved into position without stretching the belt. The fact that the pallets are not fixed to the belt also provides a great advantage in terms of maintenance. The belt itself will need to be inspected far less frequently than in the present system with a consequent reduction in down time, since stretching is much less likely to occur. Additionally, the individual pallets may be removed or substituted for maintenance without stopping the belt running for long periods.

In order to provide a continuously running system, provision can be made for return of the pallets. At the end of the upper run and lower return of the belt, the belt and pallets pass round end rolls, the end rolls and lower run having guides which guide the pallets and keep them in contact with the belt. These guides may be a rail at either side of the path of the pallets in these sections.

The pallets may suitably be provided with projections in the form of rollers which run on the rails to keep the pallets in place relative to the belt, also providing smooth travel around the end rolls and along the lower run.

The guide rails used in the mechanism may suitably be in the form of open slots or channels in side walls of the conveyor assembly, with the corresponding rollers on the sides of each pallet running in the channels. There may be, for example, rollers arranged near each end of the opposing sides of the pallet. Between the entrance to and exit from the curved travel path around each end roll, one guide channel follows a curved path substantially constantly spaced from the surface of the end roll; from the entrance a linear guide channel also extends as a chord of the curved path, and a corresponding chordal linear channel extends to the exit. On entering the curved path at the end of the upper or lower run, the forward rollers of a pallet enter the linear path, whilst the trailing rollers enter the curved path; the reverse is the case at the exit from the end roll.This arrangement allows the pallet to move easily and continuously around the conveyor being held in contact with the belt at all times.

It will be noted that the conveyor system as described comprises a number of novel aspects, each of which may be used on its own or in combination with the others. The invention provides a conveyor system in which the pallets are accurately located on a driven belt from which they may be simply lifted off for maintenance or repair. Also provided is a conveyor system having a guide mechanism to enable pallets to be returned to the start of the line in a continuous run by maintaining them in contact with the conveyor or belt around the end rolls and along the lower run.These two features may be used alone or together and either or both may be used with the appropriate pallets as described above and having one or more of the following features: means for being shot-bolted from below; a profile base to co-operate with a profiled drive belt, and projections (such as rollers) at either side to co-operate with a guide rail adjacent to the belt. The pallet per se is also one of the novel aspects which may be used on its own or in combination with the other aspects described above.

One preferred embodiment will now be described by way of example and with reference to the accompanying drawings in which FIGURE 1 is a side view of a conveyor system according to the present invention with the nearest side plates removed for the sake of clarity; FIGURE 2 is an enlarged view of part of the upper run showing a pallet in a shot-bolted position.

Fig.l is a general view of the conveyor system 100 with a pallet 106 on the upper run 102. The pallets are moved along the conveyor 100 by a pair of parallel laterally spaced profiled drive belts 118.

The profiles 140 are formed at regular intervals along each of the two belts 118 and are in the form of ridges running transverse to the direction of travel of the belts. Both belts 118 pass around end rolls 126, one or both rolls 126 being powered. The two belts 118 run parallel and as such, act as a single belt with an opening down the centre. This opening is straddled by the pallets, each of which features an open slot 142 in its base, the slot running transverse to the direction of motion of the belts. These slots 142 engage the profiles 140 of the belts, locating the pallets and carrying them along with the belts 118.

In Fig.2 the pallet 106 shown on the upper run 102 in Fig.l is further shown locked in position as it would be at a work station (not shown). Shot-bolts 110 from below are raised and engage corresponding recesses 112 in the base of the pallet 106. The pallet 106 is lifted clear of the belt 118 and held against overhanging lugs 120 by the pressure exerted by the shot-bolts 110.

In operation, the system could operate in steps with a line of pallets being processed in sequence, the belt 118 carrying each pallet into position at a work station then stopping. The pallet is then shot-bolted, the operation carried out and the pallet released, following which the belt restarts to carry the pallets onto the next work station.

It can be seen from Fig.2 that the profile 140 on the belt tapers to a narrower free end, and the slot 142 in the base of the pallet 106 is of corresponding shape. If the pallet 106 is not perfectly aligned for shot-bolting, the engagement of the tapering heads of the shot-bolts 110 with the corresponding recesses 112 will pull the pallet 106 into place. Since, once the pallet 106 is lifted clear of the belt 118, there is some freedom of movement of the slot 142 in the base of the pallet relative to the profile 140, the limited movement along the length of the belt caused by the shot-bolting will not put pressure on the profile 140. Thus there is no tendency to stretch the belt 118.

Adjacent the shot-bolted pallet 106 in Fig.2 can be seen another pallet 206 located on the adjacent projection on the belt 118.

Since, at this point there are no overhanging lugs, the pallet 206 may simply be lifted clear for repair or maintenance as described earlier.

Referring back now to Fig.l, the arrangement for carrying the pallets back to the beginning of the line in a continuous run may be seen. Each pallet 106 features two rollers 130 projecting from each of its side faces, transverse to the direction of travel of the belt. At the end of the upper run 102 these rollers 130 enter slots or channels 150 in the side plates 124 of the conveyor assembly 100 and running adjacent to the belt 118. Initially the track is split into two channels 152, 154 with the leading roller passing along a horizontal channel 154 whilst the trailing roller passes along a curved channel 152 concentric to the circumference of the end roll 126. These two channels then unite and the single channel 150 (again concentric to the circumference of the end roll 126) carries the pallet around the roll 126.The separation of the leading and trailing rollers on each pallet and the layout and dimensions of the channels 150 around the end rolls 126 is such that the profile 140 on the belt and the corresponding slot 142 in the pallet are kept in engagement as the pallet passes around the end roll 126. Prior to the pallet reaching the lower run 104, the channel 150 splits as before although the leading roller now follows the curved track 152 and the trailing roller follows the horizontal track 154, as described previously. The two channels then unite and run into a straight horizontal channel 156. The channel 156 continues along the lower run 104 of the conveyor, still keeping the profile 140 and slot 142 engaged.At the end of the lower run 104 is a similar curved channel 150 with split portions as described above which enables the pallet to be conveyed around the other end roll 126, being lifted to the start of the top run 102 at the end of the channel 150, to follow the belt around once again.

The conveyor system as described has many potential applications, not the least of which would be as a replacement for chain-linked conveyor systems in operational use at present. Belts strengthened with steel cables are preferably used and the problems and resulting necessary maintenance due to the normal stretching of a chain under tension may be largely avoided. The profiles may be formed on both surfaces of the belt with those on the inside engaging corresponding recesses in the surface of the end rolls.

The use of removable pallets greatly reduces the problems associated with pallet maintenance and repair. With a few spare pallets, those on the conveyor may simply be substituted, checked/repaired and replaced on the line. In this way all the pallets may undergo a routine maintenance without the need to take the line out of service.

With the use of belts and, for example, nylon rollers on the pallets, the problems of lubrication of the system, including contamination of workpieces by lubricants used can also be greatly reduced.

It will be noted that the new conveyor system described above is ideal for use in the production system of our co-pending British Patent Application No.8710374. With the processes to be carried out arranged st shot-bolting points on the upper run (and similarly bolted intermediate checking stations) and the facility of the lower run for mounting the selective rejection stations (all as described in 8710374), the present conveyor system would provide an automatic production line requiring less maintenance than conventional production lines. The pallets described in 8710374, e.g. with spring bolts for retaining items during construction, may have one or more of the features described herein.

Claims (9)

CLAIMS:

1. A conveyor system comprising a belt conveyor and pallets to be carried thereby, the belt conveyor and pallets being adapted so that the pallets can be positively located on the belt conveyor in driven engagement therewith but are unfixed so that they can be lifted clear.

2. A conveyor system according to claim 1 wherein the belt conveyor and pallets have complementary profiles for effecting said engagement whilst allowing the pallets to be lifted clear.

3. A conveyor system according to claim 1 or 2 including means for lifting a pallet clear of the conveyor belt for or by shot-bolting at one one or more stations along the conveyor run.

4. A conveyor system according to claim 3 having means, at one or more stations along the conveyor run, for shot-bolting a pallet from below to lift it and fix it in work position clear of the conveyor belt.

5. A conveyor system according to any preceding claim having guide means for maintaining a pallet in driven engagement with the belt conveyor as it travels from the end of the upper run, along the lower return run and back to the beginning of the upper run.

6. A conveyor system comprising a conveyor having an upper run and a lower return run, and guide means extending from the end of the upper run, along the return run and back to the start of the upper run for engagement with a pallet on the conveyor to maintain it in contact with the conveyor over the length of said guide means.

7. A pallet adapted for use with a conveyor system according to any one of claims 1 to 6.

8. A conveyor system substantially as hereinbefore described with reference to the accompanying drawings.

9. A pallet substantially as hereinbefore described with reference to the accompanying drawings.