GB1598829A

GB1598829A - Rolling chain conveyors

Info

Publication number: GB1598829A
Application number: GB1893677A
Authority: GB
Original assignee: Post Office
Current assignee: Post Office
Priority date: 1978-05-02
Filing date: 1978-05-02
Publication date: 1981-09-23

Description

(54) IMPROVEMENTS RELATING TO ROLLING CHAIN CONVEYORS (71) We, THE POST OFFICE, a British Corporation established by Statute of, 23 Howland Street, London W1P 6HQ do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a rolling chain conveyor in which an endless chain carries rollers which support and guide the chain in a guide; the chain, in use, carrying a load.

Such a conveyor is frequently used in the form of an overhead conveyor carrying items suspended from the chain to particular destinations of a work area.

An example of the use of such a conveyor is in a post sorting office in which it is used to carry mail bags from a loading bay to various predetermined positions within the post sorting office. The same conveyor, or further conveyor, may also carry mail bags from other positions within the sorting office to the loading bay. At present the chain used in such a system comprises a number of links connected one behind the other to form an endless chain. Each link includes at least one pair of rollers and the axis of rotation of the rollers on adjacent link are usually arranged in mutually perpendicular planes. The guide includes both upright roller engaging surfaces to guide the chain around the conveyor circuit, and load supporting surfaces having a horizontal component which support the rollers, the chain and any load carried thereby.The particular type of chain used at present in post sorting offices is known as E8 chain and it comprises a series of links each formed from a pair of perforated metal strips joined at each end by spindles, each spindle having a roller mounted on each of its ends. An articulator block which joins adjacent links together, comprises a block having two bores which are offset from one another and which lie in mutually perpendicular planes, and it is threaded onto spindles of adjacent ends of adjacent links. The articulator block is located between the strips of each link.

Thus adjacent links are arranged with their rollers generally at right angles. The articulator block between the adjacent links allows each link to pivot with respect to the next link about two mutually perpendicular axes. This type of chain runs through a guide having a generally cruciform section with an open slot running along its lowermost surface so that hanger carriers which are fixed to links having their rollers engaging the load supporting surfaces of the guide extend downwards through the slot beneath the guide.

This type of chain and all earlier chains can only pivot about two mutually perpendicular axes and consequently the track must always be arranged so that any curves in the track lie in a single plane. These earlier types of a chain cannot accommodate missalignments in the track and accordingly as the chain moves over a missaligned track torsional stresses are set up within the links of the chain. In E8 type chain these torsional stresses cause fretting of the perforations in the strips of each link through which the spindles pass and, eventually, this results in failure of the chain.

According to a first aspect of this invention a conveying chain for a rolling chain conveyor comprises a series of links connected one behind the other to form an endless band with each link including two pairs of rollers, each pair of rollers being mounted on a common axis and the two axes being located in two mutually perpendicular planes, the rollers, in use, engaging a track to support and guide the chain and any load carried by the chain, the connections between adjacent links including spherical bearings so that both pivotal and rotational movement between adjacent links is per mitted.

The spherical bearings between adjacent links may not allow total rotational freedom between adjacent links since it has been found that a limited rotational freedom of approximately 10 between adjacent links is sufficient to permit the chain to accommodate inaccuracies in the alignment of the guide and to allow the guide to be arranged along a path which is curved in two directions simultaneously. Thus, the guide may be arranged in a helix.

According to a second aspect of this invention a link for a chain of rolling chain conveyor comprises a cast or forged body having a forked jaw at one end, a first pair of rollers having a common axis of rotation and being mounted on the forked jaw, a second pair of rollers mounted on the other end of the body and having a common axis of rotation which is perpendicular to the axes of the first pair, one pair of a spherical bearing located at one end between the forked jaw, and the other part of the spherical bearing located at the other end of the body, so that the one end of the link is arranged to couple with the other end of an identical link, with the axes of the first part of rollers of the link intersecting the axes of the second pair of rollers of the identical link to form a chain having a spherical bearing between adjacent links.

The links may be cast or forged from steel or cast from an aluminium alloy. To reduce the number of subsequent machining steps the links are preferably cast by an investment casting process when they are made from steel and die-cast when made from an aluminium alloy. When the links are made from steel they may be of lighter gauge than when made from aluminium although a chain made from aluminium links is still lighter than a corresponding one made from steel. However, each link when it is made as an aluminium die-casting preferably includes steel inserts to carry the rollers whereas, when the link is investment cast in steel, these portions are formed as integral portions of the casting. Aluminium alloy is more expensive than steel although a diecasting process is cheaper than investment casting, once the mould has been constructed.Consequently, there are both advantages and disadvantages both in the use of steel and in the use of aluminium alloy. At present it is preferred to form the links as die-castings from an aluminium alloy.

Preferably the body of each link is provided with means for the attachment of a load and the means may include bosses to which a hanger can be attached.

When it is required that the conveyor be arranged to deliver items to various, different drop points along its length each hanger preferably includes a selector block containing a plurality of code pegs. These pegs each have two or more positions and are each arranged to move into and out of the selector blocks. A destination code is set up using these pegs by a person leading the items onto the conveyor. To set up the destination code the operator moves one or more of the pegs from its normal rest position into an active position.Sensing mechanisms are provided around the conveyor circuit immediately before their associated drop points and when a particular sensing mechanism detects that the selector block of a hanger passing through that particular sensing mechanism includes its own code, the sensor mechanism triggers a release mechanism at the associated drop point and this releases the load carried by the hanger as the hanger passes the drop point.

Our co-pending application No 45454/78, Serial No. 1598830 describes and claims a selector block for a rolling chain conveyor comprising a number of selector modules each having a coding peg which is movable into and out of the selector module, and a detent member arranged to hold the coding peg in one of two or more positions, the selector modules being arranged to stack one on top of the other to build up a selected block having the required number of coding pegs.

A particular example of a chain conveyor for use in a post sorting office will now be described with reference to the accompanying drawings; in which:- Figure 1 shows the general layout of the rolling chain conveyor circuit; Figure 2 is a partly sectioned side elevation of the chain; Figure 3 is a partly sectioned plan of the chain; Figure 4 is an end elevation of the chain and guide; Figure 5 is a scrap section taken along the lines A-A shown in Figure 2; Figure 6 is a plan of a link modified to take a conventional selector block; and Figure 7 is a side elevation of a modified link of longer pitch.

The general arrangement of the rolling chain conveyor system installed in a post sorting office is shown in Figure 1. Mail bags 1 are placed between the jaws of bag carriers 2 which are fixed to the chain of the rolling chain conveyor at a loading bay 3.

The bags 1 are moved from the loading bay 3 into the inside of the sorting office and they are deposited selectively in one of the chutes 4. 5, 6 and 7. The conveyor is driven by a driving unit 8. Combined sensor and bag release mechanisms 9. 10, 11 and 12 are associated with the chutes 4, 5, 6 and 7 respectively. An operator at the loading bay 3 identifies the contents of the mail bag from its destination label and, as the mail bag is attached to the bag carrier 2, the operator moves code pegs forming part of the bag carrier to set up a code for the required destination of that particular bag.The code registered by the pegs is read as the bag carrier passes through each of the sensor and release mechanisms 9, 10, 11 and 12 and when a sensor identifies the code carried by the bag carrier as its own particular code, the sensor responds and triggers its associated bag release mechanism, so that the bag carried by that carrier is released. The bag then drops into the chute associated with the sensor and release mechanism 9, 10, 11, or 12. The code pegs are returned to their normal state by a code normalizer unit 13 before they return to the loading bay 3.

The chain for use in such a conveyor is shown in more detail in Figures 2 and 3. The chain comprises a number of identical links connected one to another to form a continuous endless band. Each link includes a body 14 formed as a casting from a aluminium alloy. The body includes a forked jaw 15 at one end and a pair of spigots 16 at its other end. The other end of the link is arranged to fit beween the forked jaw of the one end of a following link. A bolt 17 passes through the forked jaw 15 and carries one part 18 of a spherical bearing, the other part 19 of the spherical bearing is housed in a sleeve 20 cast into the other end of the body 14 and retained in place by a circlip 21. The one part 18 of the spherical bearing is held in place by spacer tubes 22.The spherical bearing is shielded by flexible dust covers 23 and 24 and one part is provided with a wear face of sintered bronze impregnated with polytetrafluroethylene.

Rollers 25 and 26 are located on the ends of the bolt 17 and these rollers engage the upright roller engaging surfaces of the track 27, as shown in Figure 4. The rollers are held at a fixed distance from the forked jaw 15 by spacers 28 which are covered by a two thousandths of an inch thick coating of Klinger coat 50, a polytetrafluroethylene based plastics material. A hardened steel drive bush 29 surrounds the spacers 28 and is free to rotate on them. The drive bushes 29 are engaged by a pair of driven sprockets mounted one above the other in the drive unit 8. The spigots 16 have screw threaded studs 30 cast into them and rollers 31 and 32 are secured to the screw threaded studs 30 by nuts 33. The rollers 31 and 32 engage the generally horizontal surfaces of the guide 27 and support the chain and any load carried thereby.The rollers 25, 26, 31 and 32 are all identical and each preferably includes a single row deep groove sealed ballrace 34, a die cast hub 35 and a tyre 36 made from polyurethane. Alternatively the wheels may have a plain sintered bush type bearing. The polyurethane tyre 36 ensures a quiet operation and reduces the wear on the guide, particularly on the bends, but increases the power required to drive the conveyor. To overcome this, where noise levels are not critical, the rollers may not have a polyurethane tyre but, instead, have a solid metal tyre. In this case the bends in the guide are hardened to resist the wear caused by the metal tyres.

A limited rotational movement is allowed between adjacent links of the chain and, in this example, approximately 10 of rotational movement are allowed between each adjacent pair of links. This is sufficient to allow adjacent links to rotate with respect to one another to compensate for misalignments in the guide 27 and enables the chain to follow the guide 27 when it is formed into a path which is curved in two directions simultaneously, for example, the helical path 37 shown in Figure 1. The spherical bearing also enables adjacent links to pivot with respect to one another so that the chain can negotiate bends lying in a single plane.

The chain requires very little or no maintenance since the drive bush 29 runs on the coated spacer 28 and does not require any lubrication. The sealed ball race 34 or the plain sintered bearing when this is used instead does not require re-lubrication neither does the spherical bearing between adjacent links. Consequently this chain is substantially maintenance free.

Screw threaded studs 38 are inserted into a pair of bosses 39 and are secured by nuts 38' to the body 14 of some of the links.

Usually the links carrying the studs 38 will be pitched at four feet centres. Six selector modules 40 are threaded onto the studs 38 and the ends of the screw threaded studs 38 remote from the body 14 are screwed to a suspension fork 41. A bag carrier which is known as a hook and which includes a jaw, biassed into the closed position, is suspended by a clevis pin from the suspension fork 41. Each selector module 40 includes a code peg 42 which is moveable transversely of the chain through the selector module 40.

Each code peg 42 includes two grooves 43 and 44 and each selector module 40 includes a detent member 45 and a compression spring 46. The compresson spring 46 urges the detent member 45 into engagement with one of the grooves 43 and 44 in the code peg 42 to locate the code peg 42 in one of two alternative positions. The selector modules 40 are held spaced from the body 14 of the link by two sleeves 47 and 48.

The links and selector blocks are castings in an aluminium alloy and this results in a weight saving of some 11/2 tons per 1,000 feet of chain when this chain is compared with the conventional E8 chain and this, of course, reduces the power which is required to operate the conveyor.

The conventional selector units include a cast body usually containing eight code pegs and this cast body is arranged to be fixed to an existing E8 type chain by being bolted between the perforated strips forming each link of the chain. Figure 6 shows a body 48 for a modified link which is arranged to accommodate an existing selector block.

The selector block and the code pegs 49 are shown in chain dotted lines. This modified body will couple with similarly modified bodies but preferably the chain is mainly composed of normal links already described with a body 14 and merely has one of these links with a modified body included at the pitch of the selector blocks, for example every four feet. In this way, a chain including links with these modified bodies 48 can be used to replace the E8 chain in an existing system whilst still retaining the selector blocks, the guide and all the remaining accessories from the existing installation.

Figure 7 shows a further modification of the chain where it is required that the chain includes much longer links. In this modification, the body of each link is formed by a forked end piece 50 and a plain end piece 51 joined together by two strips 52 and 53 which are rivetted onto the pieces 50 and 51 by rivets 54. The two strips 52 and 53 are separated by spacers 55. The forked end piece 50 and the plain end piece 51 are substantially the same as the forked end 15 and the other end of the link 14 described above.

WHAT WE CLAIM IS: 1. A conveying chain for a rolling chain conveyor comprising a series of links connected one behind the other to form an endless band with each link including two pairs of rollers, each pair of rollers being mounted on a common axis and the two axes being located in two mutually perpendicular planes, the rollers, in use, engaging a track to support and guide the chain and any load carried by the chain, the connections between adjacent links including spherical bearings so that both pivotal and rotational movement between adjacent links is permitted.

2. A conveying chain according to claim 1, in which the spherical bearings between adjacent links alloy only a limited rotational freedom between adjacent links.

3. A conveying chain according to claim 2, in which substantially 10 of rotational freedom are allowed between adjacent links.

4. A link for a chain of rolling chain conveyor comprising a cast or forged body having a forked jaw at one end, a first pair of rollers having a common axis of rotation and being mounted on the forked jaw, a second pair of rollers mounted on the other end of the body and having a common axis of rotation which is perpendicular to the axis of the first pair, one part of a spherical bearing located at one end between the forked jaw, and the other part of the spherical bearing located at the other end of the body, so that the one end of the link is arranged to couple with the other end of an identical link, with the axes of the first pair of rollers of the link intersecting the axes of the second pair of rollers of the identical link to form a chain having a spherical bearing between adjacent links.

5. A link according to Claim 4, which is provided with means for the attachment of a load, the means including bosses to enable a hanger to be attached.

6. A conveying chain according to any one of Claims 1 to 3, or a link for a conveying chain according to Claim 4 or Claim 5, in which the or each link is cast or forged from steel, or cast from an aluminium alloy.

7. A conveying chain or a link according to any one of the preceding Claims, in which the rollers include polyurethane tyres.

8. razz A conveying chain for a rolling chain conveyor according to Claim 1, constructed substantially as described with reference to the accompanying drawings.

9. A link for a chain of a rolling chain conveyor according to Claim 4, constructed substantially as described with reference to Figures 2, 3 and 4, Figure 6, or Figure 7 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. to operate the conveyor. The conventional selector units include a cast body usually containing eight code pegs and this cast body is arranged to be fixed to an existing E8 type chain by being bolted between the perforated strips forming each link of the chain. Figure 6 shows a body 48 for a modified link which is arranged to accommodate an existing selector block. The selector block and the code pegs 49 are shown in chain dotted lines. This modified body will couple with similarly modified bodies but preferably the chain is mainly composed of normal links already described with a body 14 and merely has one of these links with a modified body included at the pitch of the selector blocks, for example every four feet. In this way, a chain including links with these modified bodies 48 can be used to replace the E8 chain in an existing system whilst still retaining the selector blocks, the guide and all the remaining accessories from the existing installation. Figure 7 shows a further modification of the chain where it is required that the chain includes much longer links. In this modification, the body of each link is formed by a forked end piece 50 and a plain end piece 51 joined together by two strips 52 and 53 which are rivetted onto the pieces 50 and 51 by rivets 54. The two strips 52 and 53 are separated by spacers 55. The forked end piece 50 and the plain end piece 51 are substantially the same as the forked end 15 and the other end of the link 14 described above. WHAT WE CLAIM IS:

1. A conveying chain for a rolling chain conveyor comprising a series of links connected one behind the other to form an endless band with each link including two pairs of rollers, each pair of rollers being mounted on a common axis and the two axes being located in two mutually perpendicular planes, the rollers, in use, engaging a track to support and guide the chain and any load carried by the chain, the connections between adjacent links including spherical bearings so that both pivotal and rotational movement between adjacent links is permitted.