GB2481847A

GB2481847A - A chain sprocket assembly with individual teeth

Info

Publication number: GB2481847A
Application number: GB1011560.8A
Authority: GB
Inventors: Torquil Edmund Meredith Pyper; Michael Charles Christmas; Christopher James Lodge
Original assignee: Renold PLC
Current assignee: Renold PLC
Priority date: 2010-07-09
Filing date: 2010-07-09
Publication date: 2012-01-11
Also published as: GB201011560D0

Abstract

A chain sprocket assembly, for a conveyor chain, has a hub 10 for rotation about a rotational axis and a plurality of tooth blocks 13 fixed to an outer periphery of the hub 10. The tooth blocks 13 have inner portions (13b, fig 2) by which they are fixed to the hub 10 and outer portions (13a) that define teeth for engagement with a chain (25, fig 4) and a recess for receipt of a roller (29) of the chain (25). Hub 10, tooth blocks 13 and hub plates 12 are fixed by a plurality of fixing pins 21 or bolts that extend through the hub plates 12 and the hub 10. The fixing pins 21 are an interference fit in apertures (19) and may be riveted. Tooth blocks 13 may be keyed into engagement with the hub plates 12 and the number of teeth may be varied so as to accommodate chains with different pitches.

Description

A CHAIN SPROCKET ASSEMBLY

The present invention relates to a chain sprocket assembly and more particularly to a chain sprocket assembly for use with a conveyor chain.

Conveyor chains are used to convey articles and comprise a plurality of interconnected links with attachments for connection to a conveying platform, receptacle or the like. An inner link comprises a pair of inner link plates disposed in parallel opposite one another. Each inner link plate has a pair of apertures that receive the ends of a pair of cylindrical bushes in a press-fit engagement. A roller is rotatably disposed on each bush between the inner link plates. An outer link extends between neighbouring inner links on each side and interconnects both by means of transverse pins that pass through the cylindrical bushes and are fixed to the outer link plates. The chain, which extends in a length along a chain axis, thus comprises inner links that articulate on the pins relative to the outer link plates.

A conveyor chain is typically arranged to wrap around at least one drive sprocket which comprises a thin disc with peripheral teeth for engagement between adjacent rollers of the chain. Rotation of the sprocket effects translation of the chain along its axis and thus translation of the conveying platform or the like.

For a given breaking load a conveyor chain is typically made available in a variety of different pitches (the pitch being the distance between the centres of adjacent pins).

The minimum possible pitch is governed by the strength of the teeth and the maximum available pitch by the rigidity of the plate and the chain as a whole. The pins, bushes and rollers are generally of identical size across the range of pitches with only the length of the chain link plates varying. However, for each pitch a different sprocket is required as the teeth pitch has to match the chain pitch; so many different sprockets have to be maintained in stock. The manufacture of sprockets is relatively expensive as each has to be cut accurately (e.g. by laser) from plate and is a major cost implication in a conveyor chain drive.

It is an object of the present invention to obviate or mitigate the aforementioned disadvantage.

It is an object of the present invention to provide for an improved or alternative chain sprocket.

According to the present invention there is provided a chain sprocket assembly for a conveyor chain comprising a hub for rotation about an axis and a plurality of teeth arranged around a periphery of the hub, each tooth being individually coupled to the hub in a fixed relationship.

The teeth may be coupled by any suitable fixing means such as, for example, pins or bolts or they may be coupled by means of frictional engagement. The teeth may be removable to allow for replacement after wear or to allow for rearrangement of angular spacing of the teeth relative to the hub so as to accommodate different pitches of chain. It will be appreciated that the teeth are separate components from the hub rather than being integrally formed. They may therefore be mass produced separately from the hub in any convenient manner.

Each tooth may have at least one aperture by which it is coupled to hub.

Each tooth may comprise a tooth block having a radially outer portion that defines at least one projection and a radially inner portion by which it is coupled to the hub.

The radially outer portion may have a recess for receipt of a roller of the conveyor chain.

Each tooth block may define a pair of projections separated by the recess.

In a preferred embodiment the plurality of tooth blocks are identical in form. This allows the teeth to be mass produced in a cost-effective operation. The tooth blocks may, for example, be cast or moulded from metal or plastics-based materials.

The tooth blocks may taper inwards in the inward radial direction.

The hub may comprise at least one hub plate to which the plurality of tooth blocks is coupled. The hub plate or plates preferably extends in a radial direction beyond a main portion of the hub. The main portion may have a stepped outer surface with at least one hub plate being fixed to the main portion. The main portion may define a central portion flanked by at least one axially outer portion on which at least one hub plate is supported and to which it may be fixed. The hub plate or plates may be integrally formed or may be separately fixed to the main portion of the hub.

The tooth blocks may be supported at their radially inner portions on a surface of the central portion of the hub.

There may be two hub plates axially spaced apart and between which the at least part of the radially inner portions of the tooth blocks are received. The inner portions may be coupled to the hub and they may be thinner in the axial direction compared to the outer portions.

Each tooth block may have a transition between the inner and outer portions of the tooth blocks which defines at least one radially inward facing surface for engagement with a radially outward facing surface on at least one of the hub plates. The radially inward facing surface and the radially outward facing surface may be substantially planar. At least one hub plate may have an outer edge that defines a plurality of the radially outward facing surfaces which may be planar.

The tooth blocks may be mounted over a peripheral edge of at least one hub plate and an inner portion of the tooth blocks may have a recess for receipt of the peripheral edge of the at least one hub plate.

The at least one hub plate is substantially annular with an inner opening for receipt of a rotary. An axially outer surface of at least one hub plate may be substantially flush with an axially outer surface of the tooth blocks.

The tooth blocks may be coupled to at least one hub plate by at least one key defined on the tooth blocks, the, or each, key being received in a corresponding aperture in at least one hub plate. There may be a pair of keys defined on the tooth blocks, one for receipt in an aperture in a first hub plate and the other for receipt in an aperture in a second hub plate.

The innermost edge of the tooth block may substantially planar or alternatively may be arcuate and may abut an external arcuate surface of the hub.

The tooth blocks may be mounted on a supporting chain. The tooth blocks may be fixed to pivoting links of the coupling chain and the coupling chain may be mounted over a periphery of the hub. The coupling chain is preferably arranged in a loop around the periphery of the hub and is placed under tension so that the tooth blocks are coupled to the hub by friction. Radially inward facing surfaces of the tooth blocks preferably bear against radially outward facing surfaces of the outer periphery of the hub plates. The radially outward and radially inward facing surfaces may be substantially planar.

The tooth blocks may have an inner portions with a slot for receipt of the outer periphery of the at least one hub plate or for receipt of a link of the coupling chain.

According to a second aspect of the present invention the chain drive assembly comprises at least one chain sprocket assembly as defined above and a conveyor chain comprising a plurality of interconnected link assemblies each having rotary roller.

When the chain is meshed with the sprocket the rotary rollers are received in the recesses of the tooth blocks.

Specific embodiments of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 is a perspective view of a first embodiment of a chain sprocket in accordance with the present invention; Figure 2 is a perspective view of the chain sprocket of figure 1 with components removed to leave only the teeth of the sprocket; Figure 3 is a perspective view of the chain sprocket of figure 1 but partially cut away to reveal hidden features; Figure 4 is a perspective view of the sprocket of figures 1 to 3 wrapped around two chain sprockets in an endless loop; Figure 5 is a perspective view of a second embodiment of a chain sprocket in accordance with the present invention; Figure 6 is a perspective view of the chain sprocket of figure 5 with components removed to leave only the teeth of the sprocket; Figure 7 is a perspective view of the chain sprocket of figure 5 but partially cut away to reveal hidden features; Figure 8 is a perspective view of the sprocket of figures 5 to 7 wrapped around two chain sprockets in an endless loop; Figure 9 is a perspective view of a third embodiment of a chain sprocket in accordance with the present invention; Figure 10 is a perspective view of the chain sprocket of figure 9 with components removed to leave only the teeth of the sprocket; Figure 11 is a perspective view of the chain sprocket of figure 9 but partially cut away to reveal hidden features; Figure 12 a perspective view of a fourth embodiment of a chain sprocket in accordance with the present invention; Figure 13 is a perspective view of the chain sprocket of figure 12 with components removed to leave only the teeth of the sprocket; Figure 14 is a perspective view of the chain sprocket of figure 12 but partially cut away to reveal hidden features; Figure 15 is a perspective view of the chain sprocket of figures 12 to 14 wrapped around two chain sprockets in an endless loop; Figure 16 is a perspective view of a fifth embodiment of a chain sprocket in accordance with the present invention; Figure 17 is a perspective view of the chain sprocket of figure 16 with components removed to leave only the teeth of the sprocket; Figure 18 is a perspective view of the chain sprocket of figure 16 but partially cut away to reveal hidden features; Figure 19 is a perspective view of the chain sprocket of figures 16 to 18 wrapped around two chain sprockets in an endless loop; Figure 20 is a perspective view of a sixth embodiment of a chain sprocket in accordance with the present invention; Figure 21 is a perspective view of the chain sprocket of figure 20 with components removed to leave only the teeth of the sprocket; Figure 22 is a perspective view of the chain sprocket of figure 20 but partially cut away to reveal hidden features; Figure 23 is a perspective view of the chain sprocket of figures 20 to 22 wrapped around two chain sprockets in an endless loop; Figure 24 is a perspective view of a seventh embodiment of a chain sprocket in accordance with the present invention; Figure 25 is a perspective view of the chain sprocket of figure 24 with components removed to leave only the teeth of the sprocket; Figure 26 is a perspective view of the chain sprocket of figure 24 but partially cut away to reveal hidden features; Figure 27 is a perspective view of an eight embodiment of a chain sprocket in accordance with the present invention; Figure 28 is a perspective view of the chain sprocket of figure 27 with components removed to illustrate the sprocket teeth and the chain on which they are mounted in more detail; and Figure 29 is a perspective view of the chain sprocket of figure 27 but partially cut away to reveal hidden features.

Referring now to figures 1 to 3 of the drawings, the exemplary sprocket has a central hub 10 with peripheral teeth 11 arranged around the hub and flanked by a pair of annular hub plates 12 that effectively form an extension of the hub 10.

The teeth are defined by tooth blocks 13 that are identical in form and are equi-angularly spaced around the periphery of the hub 10 where they are held in place between the pair of annular hub plates 12.

The hub 10 is generally cylindrical with a stepped external surface and a bore 14 by which the sprocket is mounted, in use, to a rotary shaft (not shown). The centre of the bore 14 is thus the rotational axis about which the sprocket rotates in use. The stepped external surface comprises a central section 15 of a first diameter which is flanked on each side by outer sections 16 of a second diameter that is smaller than the first. The tooth blocks 13 are supported on the central section 15 of the external surface and the hub plates 12 are supported on respective outer sections 16.

Each tooth block 13 has a radially outer portion 13a that defines two angularly spaced projections 17 separated by an arcuate recess 18 and a radially inner root portion 13b by which it is fixed between the hub plates 12. The outer portion 13a has a thickness that is substantially the same as the distance between the outward facing surfaces of the respective hub plates 12 whereas the inner root portion 13b is thinner such that it can be received between the two hub plates 12. This arrangement ensures that the outwardly facing surfaces of the hub plates 12 are substantially flush with the side faces of the tooth blocks 13.

The inner root portion 13b of each tooth block 13 is tapered inwardly in the direction towards the hub 10 and has two radially spaced apertures 19 by which the tooth block 13 is fixed in place. The innermost edge 20 of the inner portion is arcuate and matches the curvature of the central section 15 of the hub 10 which it abuts.

The central hub 10, tooth blocks 13 and hub plates 12 are fixed together by means of a plurality of fixing pins 21 that extend through the hub plates 12 and the hub 10 or through the hub plates 12 and the apertures 19 provided in the tooth blocks 13. The fixing pins 21 are an interference fit and may be riveted at their ends to secure the components together more firmly. In an alternative embodiment one or more fixing bolts may be used in place of one or more the pins.

Figure 4 shows two such sprockets meshed with an endless loop conveyor chain 25 which comprises a plurality of interconnected links. Although not shown in figure 4, the chain 25 is typically with attachments for connection to a conveying platform, receptacle or the like. An inner link comprises a pair of inner link plates 26 disposed in parallel and opposite to one another. Each inner link plate 26 has a pair of apertures that receive the ends of a pair of cylindrical bushes (hidden) 28 in a press-fit engagement. A roller 29 is rotatably disposed on each bush 28 between the inner link plates 26 and is designed to engage with the outer portion 13a of a sprocket tooth block 13. Outer link plates 30 interconnect neighbouring inner link plates 26 on each side by means of transverse pins 31 that pass through the cylindrical bushes 28 and are fixed to the outer link plates 30. The chain 25 thus comprises inner links (each provided by the pair of inner link plates 26, bush 28 and the roller 29) that articulate on the pins 31 relative to the outer link plates 30 so that the chain 25 can be wrapped around the sprockets.

The rollers 29 of the chain 25 are received in the recesses 18 between the projections 17 of each tooth block 13 and the link plates 26, 30 ride over the side surfaces of the outer portions 1 3a of the tooth blocks. There are seven tooth blocks 13 and therefore seven roller engagement points.

Figures 5 to 8 show a variation to the sprocket of figures 1 to 4. It comprises the same components except that more tooth blocks 13 are disposed around the periphery for use with a conveyor chain 25 of a different pitch. The diameter of the sprocket is the same as the one of figures 1 to 4 but it has ten tooth blocks 13 and therefore ten roller engagement points. In this particular embodiment the tooth blocks 13 butt up against one another rather than being spaced apart.

The two embodiments described above are just two examples that illustrate how the same core components including the same tooth blocks 13 can be used to provide a range of different sprocket designs each having the same diameter. Other than the number of teeth, the only difference between the sprockets in the range is the number of fixing pins 21 that are required and consequently the pattern of their arrangement around the hub plates 12. The ability to use the same tooth blocks 13 on a number of different sprockets means that the blocks can be manufactured in volume at a relatively low cost. For example, the tooth blocks 13 may be cast rather than using an expensive machining, blanking or cutting operation. It will be appreciated that the teeth may be produced from any suitable wear resistant metal or alternatively in some applications may be formed from a suitable plastics material.

It will be appreciated that the same principle can be used on sprockets of different diameters.

Figures 9 to 11 show an alternative sprocket embodiment in which the tooth blocks 113 are keyed into engagement with the hub plates 112. Each tooth block 113 differs from those described in previous embodiments in that its inner portion 113b is not of reduced thickness along all of its length but instead it has a short reduced thickness portion 132 and terminates in a wider portion 133 at its inner end. The wider portion 133 has a planar inwardly facing surface 120 and serves to define a key 134 on each side for engagement with the hub plates 112 which each have corresponding rectangular apertures 135 in which a respective key 134 is received in a secure friction fit engagement. The transition between the outer portion 11 3a of each tooth block 113 and the inner portion 11 3b on each side is marked by a first flat surface 136 that is substantially parallel to the inwardly facing surface 120 and similarly there is an opposite facing second flat surface 137 defined between the reduced thickness portion 132 and the wider portion 133. The outer peripheral edge 138 of the hub plates 112 has a plurality of flat surfaces 139 designed to abut the first flat surfaces 136 on the tooth blocks 113. In the embodiment of figures 9 to 11, seven tooth blocks 113 are shown so the outer peripheral edge 138 of each plate 112 has seven corresponding flat surfaces 139 spaced around the circumference of the sprocket. The hub plates 112 are fixed to the central hub 110 against relative rotation by means of a plurality of pins 121 as before.

The sprocket embodiment of figures 9 to 11 allows the same tooth blocks 113 to be used on sprockets of different diameters particularly as the inwardly facing surfaces are flat and are not designed to complement the outer surface of the hub 110.

Larger hub plates 112 and a larger central hub 110 are required which are relatively easy to manufacture. If a sprocket of the same diameter is required but for use with a chain of a different pitch the same hub 110 and tooth block 113 design may be used but the annular hub plates 112 have to be replaced by plates with an appropriate number of apertures 135 and peripheral flat surfaces 139.

The embodiment of figures 12 to 15 combines features of the immediately preceding embodiment with those of figures 1 to 8. The inner portion 213b of the tooth block 213 is of reduced width (compared to the outer portion 213a) for its full length but its innermost surface 220, facing the central portion 215 of the hub 210, is flat as are the inwardly facing surfaces 236 at transition between inner and outer portions 213b, 213a of the tooth block 213. As in the embodiment of figures 9 to lithe hub plates 212 have a plurality of flat surfaces 239 defined on their outer peripheral edges 238 for engagement with the flat surfaces 236 at the transition of each tooth block 213. This particular sprocket provides for seven tooth blocks 213 and therefore seven roller engagement points as illustrated in figure 15 where a conveyor chain 225 is wrapped around two such sprockets. This particular sprocket design can be adapted to accommodate more teeth for a smaller chain pitch as shown in figures 16 to 19 where the sprocket has ten tooth blocks 213 of identical design and ten roller engagement points. To accommodate the increased number of tooth blocks there is a correspondingly increased number of fixing pins 221 and the annular hub plates 212 have been replaced for plates with a greater number of flat surfaces 239 on the peripheral outer edges 238.

The same tooth block design used in the preceding two embodiments is also used in the sprocket design of figures 20 to 23. This sprocket is of larger diameter but is otherwise constructed in the same manner. It provides for sixteen tooth blocks 313 and sixteen roller engagement points with the hub plates 312 being shaped accordingly.

In the embodiment of figures 24 to 26 the tooth blocks 413 are mounted on the sprocket in a different manner. There is only a single annular plate 412 mounted on one of the outer sections 416 of the hub 410 and fixed by pins 421 to the central section 415. Thus rather than being sandwiched between two hub plates, the tooth blocks 413 are mounted on the outer periphery 138 of the single plate 412 at angularly spaced intervals. In order to achieve this arrangement the inner portion 413b of each tooth block 413 is bifurcated by a slot 440 that receives the peripheral edge 438 of the plate 412 so that the inner portion 413b extends over the side faces of the plate 412.

The peripheral edge 438 again has a plurality of flat surfaces 439 for abutment with flat surfaces 441 defined at the bottom of each slot 440. A single fixing pin 421 is used to secure each tooth block 413 to the plate 412. It will be appreciated that this design can be adapted to fit more tooth blocks 413 of identical design on to the same plate 412. If additional strength is required more that one plate may be used in which case the width of the slot 440 and potentially the thickness of the tooth blocks 413 would be increased.

In an alternative sprocket embodiment of figures 27 to 29 the tooth blocks 513 are mounted on a separate sprocket chain 542 that in turn is supported over the central hub 510 and a pair of annular hub plates 512. Each tooth block 513 has a slot 540 in its inner portion 513b in a similar manner to the tooth block embodiment of figures 24 to 26. The slot 540 receives a link 543 of the chain 542 which is fixed to the tooth block 513 by a pair of fixing pins 544 that extend across the slot 540. The chain 542 comprises a plurality of chain links 543 pivotally connected the pins 544 with tooth blocks 513 being mounted on every other link 543 in this particular embodiment (it will be appreciated that other arrangements may be used). The sprocket chain 542 is arranged into a loop that sits tightly between the annular hub plates 512 such that the inwardly facing flat surfaces 536 of each tooth block 513 rest on a corresponding flat surface 539 defined on the peripheral outer edge 538 of the plates 512. The tension in the sprocket chain 542 is designed so that the respective flat surfaces 536, 539 bear against each other with sufficient force to prevent slippage.

It will be appreciated that numerous modifications to the above described designs may be made without departing from the scope of the invention as defined in the appended claims. For example, the precise profile of the projections on each tooth block 13,113,213,313,413,513 may vary depending on the nature of the chain drive.

Moreover the manner of fixing the hub plates 12, 112, 212, 312, 412, 512 to the central hub 10, 110, 110, 210, 310, 410, 510 or the tooth blocks to the rest of the sprocket may be varied. In other examples the central hub and the annular hub plates are fixed to each by alternative fixings or are integrally formed from the same piece of material.

The described and illustrated embodiments are to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the scope of the inventions as defined in the claims are desired to be protected. It should be understood that while the use of words such as "preferable", "preferably", "preferred" or "more preferred" in the description suggest that a feature so described may be desirable, it may nevertheless not be necessary and embodiments lacking such a feature may be considered as within the scope of the invention as defined in the appended claims. In relation to the claims, it is intended that when words such as "a," "an," "at least one," or "at least one portion" are used to preface a feature there is no intention to limit the claim to only one such feature unless specifically stated to the contrary in the claim. When the language "at least a portion" and/or "a portion" is used the item can include a portion and/or the entire item unless specifically stated to the contrary.

Claims

CLAIMS1. A chain sprocket assembly for a conveyor chain comprising a hub for rotation about an axis and a plurality of teeth arranged around a periphery of the hub, each tooth being individually coupled to the hub in a fixed relationship.
2. A chain sprocket assembly according to claim 1, wherein each tooth comprises a tooth block having a radially outer portion that defines at least one projection and a radially inner portion by which it is coupled to the hub.
3. A chain sprocket assembly according to claim 2 wherein radially outer portion has a recess for receipt of a roller of the conveyor chain.
4. A chain sprocket assembly according to claim 3, wherein each tooth block defines a pair of projections separated by the recess.
5. A chain sprocket assembly according to claim 2, 3 or 4, wherein the plurality of tooth blocks are identical in form.
6. A chain sprocket assembly according to any one of claims 2 to 5, wherein the hub further comprises at least one hub plate to which the plurality of tooth blocks are coupled.
7. A chain sprocket assembly according to claim 6, wherein there are at least two hub plates spaced apart with respect to the rotational axis and between which the radially inner portions of the tooth blocks are received.
8. A chain sprocket according to 6 or 7, wherein there is a transition between the radially inner and outer portions of the tooth blocks which defines at least one radially inward facing surface for engagement with a radially outward facing surface on at least one of the hub plates.
9. A chain sprocket assembly according to claim 8, wherein the radially inward facing surface and the radially outward facing surface are substantially planar.
10. A chain sprocket assembly according to claim 6, wherein the tooth blocks are mounted over a peripheral edge of the at least one hub plate.
11. A chain sprocket assembly according to claim 10, wherein the radially inner portions of the tooth blocks have a recess for receipt of the peripheral edge of the at least one hub plate.
12. A chain sprocket assembly according to any one of claims 6 to 11, wherein the, or each, hub plate is substantially annular with an inner opening for receipt of a rotary shaft.
13. A chain sprocket according to claim 12, wherein an axially outer surface of the, or each, hub plate is substantially flush with an axially outer surface of the tooth blocks.
14. A chain sprocket according to any one of claims 6 to 13, wherein the tooth blocks are coupled to the at least one hub plate by at least one key defined on the tooth blocks, the at least one key being received in a corresponding apertures in the at least one hub plate.
15. A chain sprocket assembly according to any one of claims 2 to 14, wherein the innermost edge of the tooth block is substantially planar or is arcuate.
16. A chain sprocket assembly according to any one of claims 2 to 6, wherein the tooth blocks are arranged on a supporting chain, the tooth blocks being fixed to links of the chain and the chain mounted over a periphery of the hub.
17. A chain sprocket assembly according to claim 16, wherein each tooth block has at least one radially inward facing surface defined on the radially inner portion in abutment with a corresponding radially outward facing surface of the hub, the abutment serving to couple the tooth blocks to the hub.
18. A chain drive assembly comprising at least one sprocket assembly according to any preceding claim and a conveyor chain comprising a plurality of interconnected link assemblies each having rotary roller.