GB2111010A

GB2111010A - Buffer chain conveyor

Info

Publication number: GB2111010A
Application number: GB08232773A
Authority: GB
Inventors: Gerhard Obenland
Original assignee: Duerr Automation and Fordertechnik GmbH
Current assignee: Duerr Automation and Fordertechnik GmbH
Priority date: 1981-12-08
Filing date: 1982-11-17
Publication date: 1983-06-29
Also published as: FR2517648A1; DE8135650U1; BR8207101A; ES8307649A1; ES517615A0; MX154546A

Abstract

A buffer chain conveyor for conveying workpieces, for example, motor vehicle parts, comprises a revolving endless conveyor chain (5) carrying rotatably mounted rollers (6) and constituting a conveying track. A stop (9) at one end of the conveying track is selectively movable into the conveying track to retain the workpieces. A contact rail (11) is applied against the rollers when located adjacent the end of the conveying track so that the conveying speed is higher than the speed of revolution of the endless conveyor chain. The contact rail and the stop are moved together in such a way that either the stop is disengaged from the conveying track and the contact rail is engaged with the rollers or vice versa. <IMAGE>

Description

SPECIFICATION Buffer chain conveyor This invention relates to buffer chain conveyors for conveying workpieces, for example, motorvehicle parts.

Buffer chain conveyors are used in industry, for example, in relatively large numbers and are arranged in side-by-side relationship for the purpose of intermediate storage of workpieces advanced by a conveying device running perpendicular to the conveying direction of the buffer chain conveyor and in order to transfer them subsequently onto another conveying device also running perpendicularly to the conveying direction of the buffer chain conveyor.

During this time, the workpieces are transported along the buffer chain conveyor, so that the workpieces first delivered onto the buffer chain conveyor are also discharged first from it. Thus a large number of workpieces can be stored along the buffer chain conveyor.

Known buffer chain conveyors of this type comprise at least one endless conveyor chain on which rotatable rollers are mounted to support workpieces directly or via a support or pallets on which the workpieces are placed. The rollers are mounted in a freely rotatable manner on the endless conveyor chain. During rotation of the endless conveyor chain, the rollers carry the workpieces or pallets but essentially do not rotate. At the upstream and downstream ends of the buffer chain conveyor it is necessary for the workpieces to be transferred onto and from the buffer chain conveyor at a speed which is higher than the speed of rotation of the endless conveyor chain. Driven rotatable rollers are therefore provided at the upstream and downstream ends of the known buffer chain conveyor, and the endless conveyor chain with its rollers is made correspondingly shorter.Conventionally special drive units are provided for these driven rollers so that they can be driven art a desired speed. The provision of these special drive units complicates the buffer chain conveyor and makes it more expensive to manufacture.

The present invention seeks to provide a buffer chain conveyor where a workpiece located at the downstream end of the buffer chain conveyor can, if required, be conveyed at an increased speed, without the need for complicated and expensive drive unitsforthe rollers.

According to the present invention there is provided a buffer chain conveyor for conveying workpieces comprising: at least one revolving endless conveyor chain carrying a plurality of rotatably mounted rollers and constituting a conveying track; a stop at one end of the conveying track selectively movable into the conveying track to retain the workpieces; a contact rail which can be applied against the rollers when located adjacent said one end of the track so that the conveying speed is higher than the speed of revolution of the endless chain conveyor; and transmission means for moving the contact rail and the stop together in such a way that either the stop is disengaged from the conveying track and the contact rail is engaged with the rollers, or vice versa.

Thus, in the first operrating state, the workpiece advanced by the rollers is halted by the stop projecting into the conveying track. Following workpieces are likewise halted against the first workpiece.

During revolution of the endless conveyor chain, the rollers engage and roll on the underside of the workpiece or its support, and the workpiece and the succeeding workpieces remain stationary.

The stop can be moved out of the conveying track, the contact rail being engaged against the underside of the rollers at the same time. During revolution of the endless conveyor chain, the rollers roll on the contact rail, that is to say the relative speed increases in relation to the workpiece, this relative speed arising as a result of combining the speed of revolution of the endless conveyor chain and the rotational speed of the individual rollers. In this way, the leading workpiece is discharged from the buffer chain conveyor at an increased speed, whereas the succeeding workpieces are conveyed at a lower speed, namely at the speed of revolution of the endless conveyor chain.

As soon as the workpiece has left the buffer chain conveyor, the stop is moved into the conveying track again and at the same time the contact rail is moved out of engagement with the rollers so that the succeeding workpiece is moved against the stop at the normal speed of revolution of the endless conveyor chain.

Preferably a further contact rail permanently engages against the rollers at said other end of the conveying track. In this way, the rollers located at the upstream end of the conveying track are rotated in addition to their linear advance by means of the endless conveyor chain, so that the workpieces entering the buffer chain conveyor are taken from a conveyor device at an increasing conveying speed and transported on the buffer chain conveyor. The length of the region with rotating rollers is determined by the length of the further contact rail, and following this the workpieces are advanced at the speed of the endless conveyor chain until they come up against the workpieces located in front and are halted.

The invention is illustrated, merely by way of example, in the accompanying drawings, in which: Figure lisa diagrammatic plan view of a workpiece store with three buffer chain conveyors according to the present invention arranged side by side.

Figure 2 is a diagrammatic side view of one of the buffer chain conveyors of Figure 1; and Figure 3 is a diagrammatic enlarged side view of the region of the downstream end of the buffer chain conveyor of Figure 2.

Aworkpiece store is shown very diagrammatically in Figure 1 and has a first conveying track 1 on which are advanced sledge-shaped supports or pallets 2 which carry workpieces, for example, motor vehicle bodies, coming from a machining station (not shown). Arranged next to one another, perpendicu marly to the longitudinal direction of the conveying track 1, are three buffer chain conveyors 3 according to the present invention, onto which the pallets 2 transported by the conveying track 1 can be pushed.

Conventionally, there are, for this purpose, between the conveying track 1 and the buffer chain conveyor 2 special devices, for example lifting tables, which have been omitted from Figure 1 so as to simplify the illustration. The pallets can be pushed, as desired, onto one of the three buffer chain conveyors arranged side by side.

Located at the opposite end of the three buffer chain conveyors is a further track 4 which has essentially the same construction as the conveying track 1 and is arranged parallel to it. The pallets 2 can be pushed from the buffer chain conveyors on to the conveying track 4 which transports the pallets to, for example, a further machining station (not shown).

The construction of one of the buffer chain conveyors shown in Figure 1 will be described below with reference to Figures 2 and 3. Essentially, each buffer chain conveyor incorporates an endless conveyor chain 5 which revolves over the entire length of the buffer chain conveyor and on which freely rotatable rollers 6 are mounted on horizontal pivot pins arranged transversely to the conveying direction. The rollers can be mounted, for example, between side plates of the individual links of the endless conveyor chain, so that, as a whole, they are no wider than the endless conveyor chain. In such a construction, illustrated in Figure 1, the buffer chain conveyor 3 incorporates a parallel sliding rail, the distance between it and the endless conveyor chain 5 being selected so that one runner of the pallet 2 rests on the rollers and the other on the sliding rail.

it is also possible to provide, instead of a sliding rail, a second endless conveyor chain with rollers or two endless conveyor chains revolving in parallel between which rollers extending transversely over the entire buffer chain conveyor are mounted so as to be freely rotatable. The further description refers exclusively to a construction in which an endless conveyor chain with rollers mounted between the chain links is used, a sliding rail being provided parallel to it.

The endless conveyor chain 5 is guided around two rollers 7, 8, the roller 7, which is downstream, being driven, while the roller 8, which is upstream, forms part of a tensioning station which can be displaced in the conveying direction and fixed so as to tension the endless conveyor chain.

At the downstream end, there is a stop 9 located on the free end of a lever which is pivotable about a horizontal pivot pin 10 fixed to the buffer chain conveyor and extending transversely to the conveying direction.

Located in front of the stop 9, underneath the upper run of the endless conveyor chain 5, is a contact rail 11 which extends essentially parallel to the latter and which is mounted at one end for pivotal movement about a horizontal pivot pin 12 extending transversely to the conveying direction and fixed to the buffer chain conveyor.

Located at the free end of the contact rail 11, on its underside, is a cam lever 13 which is pivotable about a pivot pin 14 extending parallel to the pivot pin 12 and fixed to the buffer chain conveyor. This cam lever 13 is fixed to a drive lever 15 which engages with a freely rotatable connecting rod 16. The other end ofthe connecting rod 16 is articulated to a cam 17 of a gear servo-motor 18. The arrangement is such that the connecting rod 16 is displaceable by means of the gear servo-motor 18 essentially parallel to its longitudinal direction, so that the cam lever 13 is rotated and, at the same time, the contact rail 11 is pivoted upwardly until the contact rail engages or comes to rest against the underside of the rollers 6 of the endless conveyor chain 5.Conversely, during the opposite movement of the connecting rod and the cam lever, the contact rail is pivoted away from the rollers, so that the engagement between the contact rail and the rollers is terminated.

Mounted at the connection point between the connecting rod 16 and the drive lever 15 is a further connecting rod 19 which is pivoted to the free end of a further drive lever 20. This drive lever 20 is mounted for pivotal movement about a pin extending parallel to the pivot pin 14 and fixed to the buffer chain conveyor. The drive lever 20 carries a cam lever 21 to which it is fixed, and which engages, by means of a journal, an open ended slot 22 in the lever carrying the stop 9.

The movements of the contact rail 11, on the one hand, and of the stop 9, on the other hand, are thus coupled, in such a way that when the contact rail is lowered the stop is pivoted into the feed track, whilst when the contact rail engages against the underside of the rollers it is pivoted out of the feed track.

As will be seen from Figure 2, there is, at the upstream end of the buffer chain conveyor, underneath the upper side of the latter, a contact rail 23 which is fixed to the buffer chain conveyor and which rests permanently against the underside of the rollers 6.

During operation of the buffer chain conveyor, the endless conveyor chain 5 revolves at a constant speed, the upper run moving in the direction indicated by arrow A. At the upstream end, the rollers 6 roll against the contact rail 23 so that superimposed on the translatory movement of the rollers is a rotary movement about their respective pivot pins.

As a result, pallets carrying the workpieces are received at the upstream end of the buffer chain conveyor from the conveying track 1 at a speed which is higher than the speed of revolution of the endless conveyor chain 5. This is essential for ensuring that the cycle times of the conveying track 1 are maintained.

As soon as the pallets carrying the workpieces have left the upstream end of the buffer chain conveyor, they are conveyed along the latter at a speed corresponding to the speed of revolution of the endless conveyor chain 5. During this time, the rollers 6 scarcely rotate about their respective pivot pins.

Conveying takes place until the leading pallet comes against the stop 9 which consequently stops movement of the leading pallet and the following pallets as they come against one another. When the stop 9 is pivoted into the conveying track, the contact rail 11 is lowered, that is to say the rollers 6 roll freely on the underside of the pallets.

As soon as it is desired that a pallet is transferred from the buffer chain conveyor onto the conveying track 4, the gear servo-motor 18 is actuated. As a result, simultaneously the stop 9 is lowered out of the feed track and the contact rail 11 is pressed against the underside of the rollers 6. Thereupon, because of the translatory movement of the endless conveyor chain 5, the rollers roll on the contact rail, that is to say, the translatory speed and the rotational speed are superimposed and applied to the pallet.

At the start, the rollers still slide against the underside of the pallet but because of the relatively high frictional forces, the pallet is quickly accelerated to a speed corresponding to the combined translatory and rotational speed of the rollers, this speed being substantially higher than the speed of revolution of the endless conveyor chain 5. The pallet is transferred to the conveying track 4 at this increased speed.

However, the succeeding pallet is advanced only at a speed corresponding to the speed of revolution of the endless conveyor chain 5, and a gap therefore is produced between the leading pallet and the next pallet. As soon as the leading pallet has left the buffer chain conveyor, the gear servo-motor is actuated again, so that the contact rail is lowered and the stop is pivoted into the feed track between the pallet being transferred to the conveyor track 4 and the following pallet. As a result of the lowering of the contact rail 11, it is possible again, during the subsequent retention of the pallets, for the rollers to roll freely on the underside of the pallets, thus effectively preventing sliding and therefore increased abrasion.

Because of the relatively simple arrangement of the stop, which can be selectively moved into and out of the feed track and of the contact rail, as well as the coupling therebetween, it is possible to achieve an increased conveying speed of pallets at the downstream end of the buffer chain conveyor without expensive special drive units being necessary for this purpose. The movements of the stop and of the contact rail can also be achieved in other ways, the essential feature being merely that the movements should be coupled to one another. The contact rail can, for example, be displacable parallel to the conveying direction.

To increase the friction between the contact rail and the rollers, it may be advantageous to coat the contact rail with a covering having a high coefficient of friction, for example, with a plastics material similarto, for example, rubber.

Claims

1. A buffer chain conveyor for conveying workpieces comprising: at least one revolving endless conveyor chain carrying a plurality of rotatably mounted rollers and constituting a conveying track; a stop at one end of the conveying track selectively movable into the conveying track to retain the workpieces; a contact rail which can be applied against the rollers when located adjacent said one end of the track so that the conveying speed is higher than the speed of revolution of the endless chain conveyor; and transmission means for moving the contact rail and the stop together in such a way that either the stop is disengaged from the conveying track and the contact rail is engaged with the rollers, or vice versa.

2. A buffer chain conveyor as claimed in claim 1 in which a further contact rail permanently engages against the rollers at said other end of the conveying track.

3. A buffer chain conveyor substantially as herein described with reference to and as shown in the accompanying drawings.

4. Buffer chain conveyor for conveying workpieces, especially motor vehicle parts, from a first conveyor unit to a second conveyor unit, in which the workpieces rest directly or by means of a support on rollers which are mounted rotatably on at least one revolving endless chain, and the rollers at the end of the conveying track can be driven in their mounting so that the conveying speed is higher than the speed of revolution of the chain, characterised in that a disengageable stop retaining the workpieces (support) is provided at the end of the conveying track, in that a contact rail which can be applied against the rollers is located at the end of the conveying track underneath the rollers, and in that the contact rail and the stop are movable together via transmission means, in such a way that either the stop is disengaged from the conveying track and the contact rail is applied against the rollers, or vice versa.