GB2097092A

GB2097092A - Sprocket wheel

Info

Publication number: GB2097092A
Application number: GB8211336A
Authority: GB
Original assignee: Gewerkschaft Eisenhutte Westfalia GmbH
Current assignee: Gewerkschaft Eisenhutte Westfalia GmbH
Priority date: 1981-04-22
Filing date: 1982-04-20
Publication date: 1982-10-27
Also published as: DE3115941C2; AU8290482A; GB2097092B; FR2504633A1; FR2504633B1; DE3115941A1; ZA822707B; AU549026B2; ES272723Y; ES272723U

Abstract

A sprocket wheel 10 has a plurality of equi-spaced circumferential teeth 11, and a plurality of pockets 12 positioned between the teeth. A central circumferential groove 14 in the sprocket wheel 10 divides each of the teeth 11 into two parts. Each of the pockets 12 is shaped to engage with a link 13 of a drive chain, each of the pockets being formed partially by flanks 16 provided on each of the two parts of each of the pair of adjacent teeth 11 defining that pocket. The flanks 16 constitute chain link bearing faces, and each of the flanks has an inner end zone 18 adjacent to the groove 14, and an outer end zone 19 remote from the groove. <IMAGE>

Description

SPECIFICATION Sprocket wheel This invention relates to a sprocket wheel for driving and/or guiding a drive chain for a scraper-chain conveyor or a mineral winning machine such as a coal plough. The invention is particularly concerned with a sprocket wheel for use with a drive chain having chain links made from rod of circular crosssection.

The sprocket wheel of this type has a plurality of equi-spaced circumferential teeth. The adjacent teeth define pocketsforthe reception of the links of a drive chain. Each of the teeth is of two-part construction, the sprocket wheel being formed with a central circumferential groove which passes through all the teeth thereby defining their two-part construction.

Alternate links of the chain lie within the pockets as the chain passes round the sprocket wheel, and the remaining links (which lie substantially at rightangles to the first-mentioned links) are accommodated in the groove. The two ends of each pocket are defined by flanks formed on the mutually-facing portions of the two parts of each of the teeth defining that pocket. The tooth flanks at the two ends of each pocket converge slightly, and define chain link bearing faces.

In a known sprocket wheel of this type, the tooth flanks formed at each end of each pocket are constituted by bearing surfaces which are inclined to one another at an angle of about 90 . The arrangement is such that the chain links contact the tooth flanks at points which are disposed at a predetermined distance from the central circumferential groove. In this way, it is possible to avoid excessively high punctiform loading of the tooth flanks immediately adjacent to the groove. If such loading were to occur, it would result in heavy wear of the chain links, and may lead to the formation of what are known as "parsons' noses".

The disadvantage of this sprocket wheel is that, owing to the unavoidable variations in chain link size which occur during manufacture of chains made from rod of circular cross-section, excessively high punctiform loading can still occur, and this can lead to dangerous notching of the chain links. Moreover, even where the points of contact of the chain links with the tooth flanks are intended to lie at the predetermined (safe) distance from the edge of the central circumferential groove in the sprocket wheel, the points of contact can move nearerthe groove for chain links of different sizes.

The aim of the invention is to provide a sprocket wheel which does not suffer from these disadvantages.

The present invention provides a sprocket wheel having a plurality of equi-spaced circumferential teeth, each of the teeth being of two-part construc- tion, the sprocket wheel being formed with a central circumferential groove which passes through the teeth thereby defining their two-part construction, each pair of adjacent teeth defining therebetween a pocket, the pockets being shaped to engage with the links of a drive chain, each part of each tooth being formed with flanks constituting chain link bearing faces, each of the pockets being formed partially by the flanks of the pair of adjacent teeth defining that pocket, each of the flanks having an inner end zone adjacent to the groove and an outer end zone remote from the groove, wherein each of the flanks is such that points on its inner and outer end zones lie on a respective imaginary circle, and wherein the radius of each imaginary circle is at least approximately 1.5 times as great as the radius of the curved end portion of a drive chain link, and the centre point of said circle lies on the opposite side of the longitudinal axis of the associated pocket to that flank. Advantageously, the radius of each imaginary circle is at least twice as great as the radius of the curved end portion of a drive chain link.

A sprocket wheel having tooth flanks of this form enables particularly favourable loading conditions to be achieved, whilst excessively high loading peaks can be avoided. Consequently, dangerous notching and heavy wear of the links can be prevented.

Moreover, irrespective of the unavoidable variation in the sizes of chain links that occur during manufacture, the points of contact between the chain links and the tooth flanks are always positioned sufficiently far away from the sprocket groove to ensure that excessively high edge pressures do not occur.

Thus, the formation of "parsons' noses" cannot take place.

In a preferred embodiment, each of the flanks is constituted by an arcuate bearing surface. Alternatively, each of the flanks is constituted by a pair of planar bearing surfaces which meet to define a line of indentation. In the latter case, the line of indentation of each flank may be positioned substantially midway between the inner end zone and the outer end zone of that flank. Advantageously, the two bearing surfaces of each flank are inclined to one another at an angle lying in the range of from 10 to 20 , and preferably at an angle of 15".

The invention will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a part-sectional side elevation of a sprocket wheel; Fig. 2 is a cross-section taken on the line A-B of Fig.

1, and shows a first preferred form of sprocket tooth construction and one link of a chain associated with the sprocket wheel; Fig. 3 is a cross-section similar two that of Fig. 2, but showing a slightly differently sized chain link; and Figs. 4 and 5 are views corresponding to Figs. 2 and 3, but showing a second preferred form of sprocket tooth construction.

Referring to the drawings, Fig. 1 shows a sprocket wheel 10 which is used for driving and/or guiding a drive chain for a scraper-chain conveyor or a mineral winning machine such as a coal plough. For example, the sprocket wheel 10 could befitted, in the manner of a crown wheel, to a hollow drum to form a sprocket drum for driving a scraper-chain con veyor.Thesprocketwheel 10 hasteeth 11 which define pockets 12 therebetween. The pockets 12 are shaped to conform with the links of the drive chain which are made from rod of circular cross-section.

Fig.1 shows the position of one link 13 of a drive chain, this link lying within a chain pocket 12. In the known manner, each of the teeth 11 is formed with a circumferential groove 14 (see Figs. 2 to 5), these grooves accommodating the chain links which lie at right-angles to the links (such as the link 13) which lie flat in the pockets 12.

The teeth 11 are profiled to define the pockets 12.

Thus, each pair of grooved adjacent teeth 11 have faces 15 forming the floor of the pocket 12 defined by those teeth, and flanks 16 which define the walls of that pocket. The flanks 16 engage the chain links 13 to transfer drive to the chain from the sprocket wheel 10. Each tooth face 15 merges with its flank 16 by way of a rounded face 17.

The shape of each of the tooth flanks 16 is of importance. In the embodiment shown in Figs. 2 and 3, each of the tooth flanks 16 is formed by an arcuate face having a radius R and a centre point M. The two flanks 16 of each tooth 11 which are associated with the same pocket 12 are disposed symmetrically relative to the axis X of that pocket. The inner and outer end points 18 and 19 respectivelyofeach of those tooth flanks 16 thus lie on a respective imaginary circle. The centre point M of each of these circles is laterally displaced relative to the axis X of the pocket 12, and the radius R of each circle is greater than the radius R1 of the chain link 13 (that is to say the radius of the arc forming the outer contour of the curved end portion of the link). The centre point M1 of the radius R1 lies on the axis X of the pocket 12.The radius R should be at least approximately 1.5 times as large as the radius F1, and preferably R should be approximately2 to 2.5 times Ri. In the embodiment shown in Figs. 2 and 3, R is approximately twice R1.

As can be seen from Fig. 2, the link 13 bears against each of the flanks 16 of the left-hand tooth 11 at the point 20. The bearing points 20 are positioned considerably closer to the outer end points 19 of the flanks 16 than to their inner end points 18. Consequently, the link 14 bears against the tooth flanks 16 at positions well away from the groove 14.

Fig. 3 shows the same situation as Fig. 2, except that here the link 13' has a curved end portion whose radius R1' is approximately3 millimetres less than the radius R1 of the curved end portion of the link 13 shown in Fig. 2. Such a variation in size between the two links 13 and 13' lies within the tolerances which are unavoidable in the manufacture of chain links of this type. As shown in Fig. 3, the link 13' bears against each of the flanks 16 of the left-hand tooth 11 at bearing points 20'. The points 20' are located slightly nearer the central regions of the flanks 16 than the bearing points 20. However, the bearing points 20' are still located at a relatively large (safe) distance from the groove 14.

In the embodiment shown in Figs. 4 and 5, each of the tooth flanks 16 has two bearing faces 16a and 16b. The bearing faces 16a and 16b of each flank 16 are angled relatively to one another, and meet at a line of indentation 21. Each line of indentation 21 is positioned approximately in the central region of its tooth flank 16. The angle a defined by the two bearing faces 16a of each tooth 11 is approximately 100 , and the angles defined by the two bearing faces 1 6b of that tooth is approximately 70 . Thus, the two bearing faces 16a and 16b of each tooth flank 16 are inclined to one another at an angle of about 15".

The inner and outer end points 18 and 19 respectively of each of the flanks 16 of each tooth 11 lie on a respective imaginary circle. The radius R of each of these circles is greater than the radius R1 of the curved end portion of the link 13, and the centre point M of each circle is laterally displaced relative to the axisX of the pocket 12. Thus, as with the embodiment of Figs. 2 and 3, the centre point M of each circle lies on the opposite side of the axis X to the associated tooth flank 16. As with the embodiment of Figs. 2 and 3, the radius R should be at least approximately 1.5 times as large as the radius R1, and preferably R should be approximately 2 to 2.5 times R1. In the embodiment shown in Figs. 4 and 5, R is approximately 1.5 times R1.

As can be seen from Fig. the link 13 (which is the same size as the link 13 of Fig. 2) bears against the left-hand tooth 11 at bearing points 20 which are positioned approximately at the central regions of the bearing faces 16a. Consequently, the bearing points 20 are positioned considerably closer to the outer end points 19 of the tooth flanks 16 than to their inner end points 18. Here again, therefore, the link 13 contacts the tooth flanks 16 at a relatively large (safe) distance from the groove 14. Similarly, as shown in Fig. 5 the link 13' (which is the same size as the link 13' of Fig. 3) bears againstthe bearing faces 16a and 16b atthe points 20'. In this case, therefore, a two-point contact occurs between each of the tooth flanks 16 and the link 13'. Consequently, excessively high punctiform loading is prevented.

Moreover, the bearing points 20' on the bearing faces 16b are located at sufficiently safe distance from the groove 14.

It will be apparent that the two forms of tooth constructions described above prevent excessively high punctiform loading occurring at positions adjacent to the groove, irrespective of differences in the sizes of the links that occur during manufacture. Consequently, optimum loading of the chain links in the pockets of the sprocket wheel is achieved, and the chain pockets are subjected to minimum wear.

Claims

1. A sprocket wheel having a plurality of equispaced circumferential teeth, each of the teeth being of two-part construction, the sprocket wheel being formed with a central circumferential groove which passes through the teeth thereby defining their two-part construction, each pair of adjacent teeth defining therebetween a pocket, the pockets being shaped to engage with the links of a drive chain, each part of each tooth being formed with flanks constituting chain link bearing faces, each of the pockets being formed partially by the flanks of the pair of adjacent teeth defining that pocket, each of the flanks having an inner end zone adjacent to the groove and an outer end zone remote from the groove, wherein each of the flanks is such that points on its inner and outer end zones lie on a respective imaginary circle, and wherein the radius of each imaginary circle is at least approximately 1.5 times as great as the radius of the curved end portion of a drive chain link, and the centre point of said circle lies on the opposite side ofthe longitudinal axis of the associated pocket to that flank.

2. Asprocketwheel as claimed in claim 1, wherein the radius of each imaginary circle is at least twice as great as the radius of the curved end portion of a drive chain link.

3. A sprocket wheel as claimed in claim 1 or claim 2, wherein each of the flanks is constituted by an arcuate bearing surface.

4. A sprocket wheel as claimed in claim 1 or claim 2, wherein each of the flanks is constituted by a pair of planar bearing surfaces which meet to define a line of indentation.

5. A sprocket wheel as claimed in claim 4, wherein the line of indentation of each flank is positioned substantially midway between the inner end zone and the outer end zone of that flank.

6. A sprocket wheel as claimed in claim 4 or claim 5, wherein the two bearing surfaces of each flank are inclined to one another at an angle lying in the range of from 10? to 20 .

7. A sprocket wheel as claimed in claim 6, wherein the two bearing surfaces of each flank are inclined to one another at an angle of 15O.

8. A sprocket wheel substantially as hereinbefore described with reference to, and as illustrated by, Figs. 1,2 and 3 or Figs. 1,4 and 5 of the accompanying drawings.