GB2166178A - Cutting tooth - Google Patents

Abstract

A tooth of the point attack type comprises a cutting head (1) and a shank extending therefrom for mounting within a socket (3). The shank is provided with a plurality of longitudinally spaced peripheral grooves (4), each of which contains a resilient bearing ring (5). Each ring, in use, exerts a resilient retention force against the internal wall of the socket independently of the remaining rings. <IMAGE>

Description

SPECIFICATION Cutting tooth This invention relates to a cutting tooth of the point attack type for mounting in a socket of a cutting chain or wheel which would normally be used for cutting coal or railway ballast, for example, or for general excavating.

It is essential that such teeth be held securely in their sockets in order to avoid dislodgement and loss thereof under arduous working conditions and that they are, at the same time, free to revolve in their sockets so that a continuously changing part of the tooth cutting face is applied to the material being worked in orderto avoid premature wear of one face part only.

One conventional form of tooth is illustrated in Figure 1 and will be seen to have a cutting head 1 from which extends a shank2 shown mounted in a socket 3.

Towards its ends remote from the head, the shank has a peripheral groove4within which is received a radially split ring 5 of spring steel or similar material, the shank 2 being inserted in the socket 3 with the ring 5 in a radially inwardly compressed state so that, by resilient recovery within the socket, the ring exerts a retention force on the internal wall of the socket which resists axial movement ofthe tooth whilst permitting the tooth to rotate during cutting.This arrangement has been in useformanyyearsand,whilstbeing generally satisfactory, it can be prone to early wear of the engaged shank and socket surfaces atthe region thereof nearest to the head 1, due to the action of abrasive material entering the socket between these surfaces and causing initial wearwhich is aggravated by subsequent rocking of the tooth in the socket under the action of cutting forces in use. This can lead to unreliability of operation and lack of security of the tooth.

An attempt to solve this problem is illustrated in Figure 2. The tooth shown therein is essentially similar to that of Figure 1 butthe groove 4 is extended to the mouth ofthe socket to accommodate a ring 5 oftwo or three times the axial length of that used in Figure 1.

This is found to reduce the effect of abrasive wear, but forces encountered during cutting can produce distortion of the housing, particularyatthe mouth thereof, again permitting ingress of abrasive material between the tooth shank and socket, leading, as before to a reduction in the grip provided by the ring 4. The effects of this, including possible tooth loss can be particularly acute when the tooth is used on a cutting wheel and centrifugal forces are relatively high.

An object of the invention is to provide an improved cutting tooth of the point attack type which is less subject two the aforesaid problems than the aforesaid conventional teeth and which is consequently more secureand versatile in operation.

According to the present invention, a tooth of the point attacktype comprises a cutting head and a shank extending therefrom for mounting within a socket of a cutting chain orwheel,theshankhaving a plurality of the longitudinally spaced peripheral grooves each for the reception of a respective resilient bearing ring, each said ring, in use, exerting a resilient retention force againstthe internal wall of said socket independentlyofthe remaining rings.

Preferably, one of said rings is located adjacent the cutting head. In one convenient arrangement, at least one ofthe grooves, and preferably the one adjacent the cutting head, is provided with a plurality of rings arranged in axial succession within the groove. This arrangement is particularly advantageous forvery heavydutyapplications.

The invention will now be described by way of example, with reference to the accompanying drawings in which: Figure 3 illustrates part of a cutting chain with which the cutting tooth ofthe invention may be used, Figure 4 is a perspective view of one form of the cutting tooth ofthe invention; Figure 5 is a sideview, partly in cross-section, ofthe tooth of Figure 4, and Figures 6 to 10 illustrate alternative embodiments of the tooth of the invention.

Referring to Figure 3 ofthe drawings, this shows diagrammatically a cutting chain 6 consisting of a succession of links 7 interconnected by rollers 8 in conventional manner. Some ofthe links carry a socket 3 (only one being shown for illustrating purposes), each socket receiving a cutting tooth indicated generallyat8.

Afirst embodiment of the cutting tooth of the invention is illustrated in Figures 4and Sand, as in the conventional teeth of Figures 1 and 2, comprises a cutting head 1 andashank2,thecutting head being provided with a hardened cutting tip 1A. in this embodiment,theshank2 is provided with three longitudinally spaced peripheral grooves 4 defined by lands4B, each groove 4 containing a resilient ring 5 of spring steel for example, and each ring being resiliently splitto facilitate resilient deformation of the ring for the purpose to be described. As will be clearly seen from Figure 4, the end portions 5, 5A of each ring resulting from the splitting are angled transversely of the width of the ring.One ofthe grooves 4 is located at the head end ofthe shank and the remaining grooves are equi-distantly disposed along the shank, although the spacing of the grooves, as well as the number thereof, may be varied according to requirements.

The tooth is shown in Figure 4 priorto insertion in the chain socket 3 and it will be seen thatthe rings 5, then in their unstressed condition, are of a size such thattheir external surfaces lie slightly proud of the adjacent external surfaced ofthe lands 4B. In use, the tooth 8 is inserted within a socket 3 ofthe cutting chain (Figures 3 and 5), the tooth being inserted with the rings 5 radially inwardly compressed, partly by the action ofthe internal level 3A atthe mounth of the socket so that, resilient recovery of the rings against the internal wall of the socket will create a retention force to hold the tooth firmly within the socket. The three rings in the embodiment illustrated all act independently of each other so that each can conform to the size ofthe internal wall of the socket at its own particular location.It will be seen that, with this arrangement, should the ring 5 nearestto the cutting head 1 be subject to wear, as a result for example, of ingress of abrasive material between the ring and socket, the remaining rings will remain substantially unaffected by this so that rocking ofthe tooth in the socket is minimised and adequate retention of the tooth within the socket is likely to be maintained for a longer period of useful life of the tooth than can be expected with conventional arrangements.

When the tooth is initially inserted in the socket in the aforesaid manner, the lands 4B will be spaced fromtheinternalsocketwall or in only light contact therewith so that load applied generally radially ofthe tooth is borne entirely by the rings, or substantiallyso.

During a cutting operation performed bythetooth, rotation ofthetooth occurs within the rings, producing wear between the bases ofthe grooves and the inner surfaces ofthe rings therein. Because ofthe radial loading on the tooth, however, the largest part ofthe loading and corresponding weartakes place at the outermost ring. After a time, sufficient wear ofthe outermost ring will have occurred to enable the adjacent land 4B ofthe shank to contact the socket wall and thereby share part ofthe load. It will thus be seen thatfora time, a major part ofthewear occurs on the ring and/ortooth, rather than on the socket, so that wear one socket is minimised and the useful life thereof prolonged.

Whenthetooth cutting tip 1Aisworn outandthe tooth replaced, the new upper ring will againtakethe load initially and the upper land 4B is again spaced from the socket,the more so now since the first used ring will have produced some grooving ofthe socket wall. The process described above is repeated, eventually bringing the upper land back into contact with the socket. As ovalisation ofthe outer part of the sockettakes place during prolonged use, it would be possible to use a pair of narrower rings in at least the outer groove 4to obtain a further extension of socket life.

Such an arrangement is illustrated in Figure 6 in which a pair of rings 5' are located in the groove 4 adjacent to the cutting head 1. This can also be a particularly useful arrangement when excessively arduous work is contemplated, with a corresponding expectation of heavywear and ovalistion of the outer part ofthe socket.

In some circumstances, as for example when a chain equipped with teeth of the invention is called upon to rotate at high speeds around small diameter wheels, it can be advisable to provide additional positive means for retaining the teeth axially within the socket. in the embodiment of Figure 7,the innermost ring is omitted and a pin 10 is inserted axiallythrough a groove formed in the housingforthis purpose in axial register with the empty groove 4,the pin being of such a diameter as to project into the emptygroove 4, thereby positively limiting axial movement ofthe tooth within the socket, whilst at the same time permitting rotation ofthetooth, as is required forthe reasons referred to above.

Figure 8 shows an alternative configuration provided with a locking tooth, the tooth being, in this case, provided in the central groove 4, from which the ring is omitted.

In a further elternative arrangement (not shown), the pin 10 may be replaced by a screw inserted axially throughathreaded opening formed inthewall ofthe socket,the end ofthe screw projecting into an empty groove 4, left by omission of one of the rings, again to limit axial movement of the tooth whilst permitting its rotation.

Figure 9 shows a further alternative embodimentin which a part-circular groove 4A is machined in the internal wall ofthe socket and a spring ring 5B.

preferablyofcircularcross-section as shown is placed in the central groove 4 above the corresponding ring 5. When the tooth is inserted in the socket, the ring 5B is initially compressed inwardly, but expands outwardly into the groove 4Awhen it registers therewith in orderto retain the tooth axiallywithin the socket.

The groove 4A is made sufficiently deep axially in relation to the ring 5Bto accommodate some move mentofthetooth inwardly ofthe socket as wear occurs. Itwill be understood that the ring 5B may be provided in any one of the grooves 4 or such rings may be provided in a plurality of the grooves 4.

Figure 10 illustrates a further alternative embodi mentoftheinvention, particularlysuitablefor heavy duty use, in which the shank 2 has a larger diameter portion 2A adjacent to the head 1 and a smaller diameter portion 2B, the socket 3 being internally stepped in a corresponding mannerto acceptthe shank. The lengths ofthe different diameter shank portions, aswell as the number of grooves 4 provided in these portions and the number and type of rings in each groove may be varied as desired.

It is possible to fit radially thicker rings in at least the outermost groove when the socket is very worn and particularly, for example, when a worn conventional tooth is replaced by a tooth of the invention. By this means, even a badly ovalised bore resulting from the use of a conventional tooth can be given further useful life and its replacementthereby postponed. In all embodiments of the invention, the rings may each have a greater axial extentthan that of the lands between the ring-receiving grooves in orderto increase the bearing area provided bythe rings.

Claims (12)

1. Atooth of the pointattacktype comprising a cutting head and a shank extending therefrom for mounting within a socket of a cutting chain or wheel, the shank having a plurality of longitudinally spaced peripheral grooves each forthe reception of a respective resilient bearing ring, each said ring, in use, exerting a resilient retention force against the internal wall of said socket independently of the remaining rings.

2. Atooth according to Claim 1 wherein one ofthe rings is located adjacent the cutting head.

3. Atooth according to Claim 1 or Claim 2 wherein at least one ofthe grooves is provided with a plurality of rings arranged in axial succession within the groove.

4. Atooth according to Claim 2 wherein at leastthe groove located adjacent the cutting head is provided with a plurality of rings arranged in axial succession withinthe groove.

5. Atooth according to any one of the preceding claims wherein the grooves are equi-distantly disposed along the shank.

6. Atooth according to any one of the preceding claims wherein retention means is provided to retain the tooth axiallywithinthe socket.

7. Atooth according to Claim 6wherein said retention means comprises an elongate element housed in a groove in the housing in register with a empty peripheral groove of said shank, said element being of such a diameter as to project into the empty groove so as positively to limit axial movement of the tooth within the socket whilst permitting rotation of the tooth.

8. Atooth according to Claim 6wherein said retention means comprises a resilient ring, engaging in internal and external grooves formed respectively in the housing and shankto limit axial movement of the tooth within the socket whilst permitting rotation ofthe tooth.

9. Atooth according to Claim 1 wherein the shank has a larger diameter portion adjacent to its head.

10. Atooth according to any one ofthe preceding claims wherein the axial extent of the rings is greater than that ofthe lands between the ring-receiving grooves.

11. Atooth ofthe point attacktype substantially as hereinbefore described with reference to Figures 4 and 5, Figure 6, Figure 7, Figure 8, Figure 9or Figure 10 ofthe accompanying drawings.

12. Acutting chain or wheel incorporating one or more teeth according to any one of Claims 1 to 11.