GB2109455A

GB2109455A - Chain, articulated joint and method of manufacture

Info

Publication number: GB2109455A
Application number: GB08229915A
Authority: GB
Inventors: Lewis A Scott; Daryl L Mossman
Original assignee: Omark Industries Inc
Current assignee: Omark Industries Inc
Priority date: 1981-11-09
Filing date: 1982-10-20
Publication date: 1983-06-02
Also published as: SE8206324D0; JPS5882621A; SE8206324L; DE3241183A1; FR2515994A1

Abstract

The flat centre links (12) and flat side links (16) of a saw chain are pivotally connected by pins (28) of uniform cross section each extending between apertures in the side links and through an aligned aperture in a centre link. The pins (28) are joined by welding to the side links using a laser beam circularly directed around the edges of the apertures in the side links. The centre links form their own spacer thereby eliminating the need for a spacer hub on a rivet pivotally joining the links. The links may be provided with a temporary coating material for accurately spacing the links prior to welding of the side links to the aforementioned pin. <IMAGE>

Description

SPECIFICATION Chain. articulated joint and method of manufacture Description The invention relates to an articulated joint for a chain, to a chain incorporating such an articulated joint, and to a method of manufacture of such a joint and such a chain, which may be arranged for use as a saw chain.

Saw chains employed on known types of handheld chain saws conventionally cut a much wider kerf and a more erratic kerf than could be provided by a relatively thin circular saw blade. Although the cutter teeth of the chain saw can be formed or set so as to provide a narrower kerf, the limiting factor tends to be the mechanics of the chain itself and particularly the articulating joints between chain links.Reference is now made to the accompanying drawing, in which: Fig. 1A is a perspective view, partially broken away, of a prior art chain; Fig. 1 B is a perspective view of a rivet employed in a prior art chain; From Figs. 1 A and 1 B, it will be seen that the chain links of the illustrated prior art chain are pivotally connected together by rivets 34 each of which includes a central spacer hub 36 and elongate ends arranged to be formed into rivet heads 40 for holding the chain elements together.

Both the rivet heads 40 and the hub 36 are space consuming in a direction lateral of the chain and, of course, the chain side links 32 extend laterally outwardly on either side of the chain. The side links 32 of this prior art chain must also have a certain minimum thickness in order to withstand the conventional rivet spinning process because of the force imparted against the ends of the rivet.

The spacer hub 36 is used to prevent the side links from being tightly compressed against centre links 30 during the formation of the rivet heads so that articulation would be prevented altogether. The lateral extent of the chain parts not only widens the kerf but also decreases the chip capacity between the chain and the kerf walls.

When a spacer hub is required as indicated above, the tolerance in the manufacture of the chain parts usually results in a chain with a certain amount of side play. The spacer hub 36 must be wider than the centre link 30, within certain tolerance limits, to prevent interference and binding between the parts. The saw chain then typically tends to wobble and cut in a somewhat erratic and inefficient manner. This factor alone limits the reduction in width of the saw kerf. Of course, the rivets themselves have a fairly complex and therefore expensive shape and require separate heat treatment on the ends so the ends may be deformed into rivet heads while the central part of the rivet remains suitable for a bearing surface.

The invention accordingly provides a method of manufacturing an articulated joint for a chain, the method comprising the steps of: joining a cross connecting member to a first link of the chain by welding so that the cross connecting member extends in substantially perpendicular relation from the first link, forming an aperture in a second link of the chain for receiving the cross connecting member, and inserting the cross connecting member through the aperture in the second link for pivotal relation therewith.

The invention also provides a method of manufacturing a chain comprising centre links and side links arranged for articulated overlapping relation, the method comprising the steps of: providing apertures in overlapping parts of a centre link and a pair of side links, inserting a cross connecting member through the aperture in the centre link and at least into an aperture in one of the side links, with the centre link and the one of the side links positioned in substantially bearing relation with their apertures aligned, and non-compressingly joining the cross connecting member to the said one of the side links.

The invention also provides an articulating joint for a chain, the joint comprising: first and second links substantially aligned in a parallel and end-to-end but overlapping relation such that ends of the links overlap in laterally adjacent relation for a part of their total length, and a cross connecting member extending crossways of the first and second links and pivotally joining their overlapping ends, the cross connecting member being welded to the first link and being pivotally received in an aperture in the second link.

The invention also provides a chain comprising a plurality of successive longitudinally connected articulating links, the chain being arranged to be driven along a path longitudinal of the chain and comprising a plurality of cross connecting members extending generally crossways of the chain, the cross connecting members being welded td ones of the said links with respect to which others of the said links can pivot.

The invention also provides an articulating chain comprising: a plurality of centre links and a plurality of side links extending in end-to-end overlapping relation with the centre links such that an end of a centre link is positioned between ends of a pair of side links for articulation with respect thereto, and a cross connecting member extending between the pair of side links and defining a pivoting centre of the centre link with respect thereto, each of the side links and the centre link having an aperture for receiving the cross connecting member, and the cross connecting member being welded to each of the side links.

The invention makes it possible to produce a saw chain which can be substantially thinner than saw chains or the like heretofore provided. Both the rivet heads and the spacer hubs can be eliminated. The absence of a spacer hub allows the chain parts to be disposed in bearing relation whereby less side play occurs, and moreover the absence of a riveting process allows the side links to be substantially thinner, thus contributing to the reduced lateral dimension of the chain.

The parts of a chain embodying the present invention can be manufactured economically, and the chain can be lighter, quieter and have improved shock absorbing characteristics and chip capacity, as compared with prior art saw chains.

The invention is further explained below by way of example with reference to the remaining figures of the accompanying drawings, in which: Fig. 1 is a perspective and partly exploded view of a chain embodying the invention; Fig. 2 is a perspective view of a cross connecting member or pin employed in the chain of Fig. 1; Fig. 3 is a side view of the chain of Fig. 1; Fig. 4 is a side view on a larger scale of a portion of the chain of Figs. 1 and 3; Fig. 5 is a perspective view of a work station, including a rotating laser head device for manufacturing chain in accordance with the present invention, Fig. 6 is a partial transverse cross sectional view of an alternative chain articulating joint according to the invention; Fig. 7 is a partial cross sectional view of a further chain embodying the invention;; Fig. 8 is a fragmentary side view of a welded articulated joint according to the invention; and Fig. 9 is a transverse cross-sectional view of part of an articulated joint according to the present invention, showing the use of a temporary coating material for accurately spacing relatively movable parts.

Figs. 1 and 3 illustrate a chain 10 embodying the invention and having the particular form of a saw chain arranged to be driven along a path in a direction longitudinal thereof on a hand-held chain saw. The chain 10 includes a plurality of flat metal centre or drive links 12 having tangs 14 for passing along the groove of a saw bar and for engaging a driving sprocket at one end of such a saw bar. The links 12 are pivotally connected in overlapping relation to flat, metal, intermediate side links 10 comprising tie straps and allochiral cutter links 18 provided with upstanding cutter teeth 20. The cutter links 1 8 in the chain illustrated occur between every other pair of drive links and are alternately disposed on opposite sides of the chain.

The exploded portion of Fig. 1 illustrates the manner in which the chain links are connected for articulation. Side links 1 6a and 1 6b are provided at each end thereof with bores or apertures 21 and 22 respectively. Centre links 1 2a and 1 2b include bores or apertures 24 and 26 respectively which have substantially the same diameter as the apertures 21 and 22, with which they are aligned.

Metal cross connecting members or pins 28 extend through the aligned apertures and are of such diameter as to be slidably received through apertures 24, 26 in bearing relation. A pin 28a extends through an aperture 24 in the centre link .1 2a and also at least into apertures 21 and 22 on first ends of the side links 1 6a and 1 6b. A pin 28b passes through an aperture 26 in the centre link 1 2b and also at least into apertures 21 and 22 at second ends of the side links 1 6a and 1 6b. The pins 28 are disposed in substantially perpendicular relation to the links through which they pass and provide a bearing surface or axle for the centre links 1 2a and 1 2b to pivot or articulate with respect to the pins and with respect to the side links.Proceeding along the chain, a first pair of side links is disposed one on either side of each centre link while two other side links are disposed at either side of the same centre link at the remaining end thereof, the links being substantially aligned in a parallel, end-to-end and overlapping relation. The pins 28 as well as the apertures through which they pass are desirably of constant cross section and are suitably cylindrical, although other cross sections are possible.

The pins 28 are connected to the side links in a non-compressionai manner, preferably by welding to the side links around the edges of the apertures in the side links. Thus, the pins 28a and 28b are welded to the side links 1 6a and 1 6b around the edges of the apertures 21 and 22. Preferably, the welding is performed by an energy beam, for example a laser beam as more fully described below. The centre links and side links have substantially flat adjoining surfaces and are disposed in bearing relation to one another such that side play or wobble between chain links is minimized. The pins 28 are suitably approximately of a length equal to the combined thickness of the centre link and side links through which they extend, so that the ends of the pins are approximately flush with the outer side surfaces of the links 16.However, this factor is approximate and need not limit the tolerances achievable in the chain construction, that is, the ends of the pins 28 do not have to be exactly flush with the outer side surfaces of the side links. In any event, the pins 28 are somewhat shorter than conventional rivets because there is no need for material for forming rivet heads to hold the articulated joint together.

Since the chain of the present invention has no rivet heads extending outwardly beyond the surface of the side links 1 G, the cutting width of the chain can be substantially thinner than the prior art chain illustrated in Fig. 1A. As discussed above, the prior art chain, with its centre links 30 and side links 32, was provided with rivets 34 (see Fig. 1 B) for pivotally connecting the centre links with the side links. The rivets 34 each included a spacer hub 36 received within an aperture 38 of the centre link, which aperture was larger in diameter than the aligned apertures in the side links. The spacer hub supported the side links during a riveting operation during which an apparatus would spin the ends of the rivet to provide the heads 40. Without the prior art spacer hub 36, the pressure of the spinner would merely force the side links tightly against the centre link and result in a non-articulating joint.

According to the present invention, the spacer hub 36 is not needed because joining is accomplished without exerting any substantial pressure on the joint in a direction axially of the pins 28. Not only can a narrower cutting chain be constructed as the result of the absence of the rivet heads 40 protruding outwardly from the side links, but the absence of pressure employed in joining the links makes it possible to employ thinner links, for example thinner side links, to produce a narrower kerf. In a typical prior art chain, 1.07 mm (0.042 inch) thick side links or tie straps were employed. The similar chain according to the present invention can utilize 0.84 mm (0.033 inch) thick side links or tie straps for a substantial overall decrease in the cutting width of the chain especially when considered in combination with the absence of rivet heads.

About a fifty percent decrease in kerf width is possible. Of course, the cutter teeth 20 are formed or set in such manner that their lateral width (in the direction of pins 28) and particularly the extent to which they protrude laterally outwardly from the side of the chain on which they are mounted is less than in the case of the prior art chain. The combined lateral width or profile of the cutter teeth will determine the width of the saw kerf, but such width need be only slightly greater than the combined thickness of a centre link and a pair of side links without the rivet heads.

Fig. 4 illustrates in greater detail a noncompressional joint 42 between the pin 28 and a side link 16 for providing an articulate connection with the centre link 12. This non-compressional joint is accomplished by welding and preferably by welding with an energy beam such as a laser or electron beam. Fig. 5 illustrates a rotating laser head 44 mounted for receiving a laser beam or coherent light beam 46 which is deflected vertically downwardly by a mirror 48 through the bearing assembly 50 and a gas nozzle and rotating lens assembly 52 toward the work being welded.

The assembly 52 is rotated by a drive motor 54 to cause the exiting laser beam to execute a circular path and produce the weld 42 around the inside edge of the aperture in the side link for joining the side link to the pin 28. The assembly 52 is suitably rotated at a speed of 220 r.p.m. The pin 28 can be provided from wire stock fed directly to the laser work station. The laser head 44 may comprise a Model 440 boring head employed with a Model 1003, 1350 watt carbon dioxide laser manufactured by Photon Sources, Inc., Livonia, Michigan, the laser being operated at approximately 400 watts.

The components of the chain 10 are illustrated in Fig. 5 as disposed in assembly track 58 and are moved longitudinally in the track in the direction indicated by the arrow whereby successive pins 28 may be welded in place by means of the rotating laser head. After welding is completed for securing side links to the pins 28 on one side of the chain, the assembly is reversed or turned over to accomplish welding on the opposite side of the chain.

It will be noted the chain links are assembled with their flat surfaces disposed substantially horizontally and with the pins 28 disposed substantially vertically in the track 58 prior to welding whereby the links are positioned or located relative to one another by gravity. No physical pressure is necessary or desirable in securing the chain elements together, but rather the chain elements are disposed in substantially bearing relation by their own weight. When the complete chain is then joined by laser welding or the like it is found the respective centre links articulate or pivot with respect to the side links in a satisfactory manner, and moreover the chain parts are exactly positioned to restrain lateral movement or wobble of the chain and cutter teeth as used, for example, on a chain saw.Thus, the chain establishes its own tolerance with the centre link as the central articulating member acting as its own spacer without requiring the spacer hub 36 of the prior art rivet. With the construction according to the present invention, minimum and accurate clearances can easily be maintained between the flat link elements. The non-wobbling chain not only contributes toward a narrow kerf cut by the chain mounted on a chain saw, but also contributes to increased cutting accuracy and efficiency of the chain.

An additional but accurate clearance can be established between articulating parts by coating sides of the links to be disposed in bearing relation with a temporary coating material. The temporary coating material may be applied either to the outside surfaces of the centre link 12 or the inside surfaces of side links 1 6 as illustrated at 60 in Fig. 9. A suitable coating material comprises zinc plate which wears rapidly after application and assembly and also provides a lubricating function.

Other suitable coatings comprise water soluble plastics material or hydrocarbon soluble lacquer, either one of which may be dissolved after chain assembly. Also a burn-away or heat sensitive material which is dispelled during the welding process or subsequently during use of the chain may be employed. In any case, the thickness of the temporary coating layer 60 is of the order of 0.013 mm (one-half one thousandth of an inch) for providing a substantially accurate clearance or spacing between the sides of the centre link and the side links.

Other non-compressional joining methods may be employed. Thus, another form of welding such as gas welding with a jewellers torch is possible but this is relatively slow and apt to deleteriously affect the hardness of the link material as the result of excessive application of heat over too wide an area. Energy beam welding such as laser welding is preferred because of its accuracy and speed and also because of the small heat-affected zone. This zone is substantially immediately around the weld 42 as shown in Fig. 4 and does not affect the hardness or wear quality of the bearing surfaces, that is the central portions of the pins 28 and the metal surrounding apertures 24 and 26. The heat affected zones are confined to the edges of the apertures in the side links and the peripheries of pins 28 where the same are joined to the side links within said apertures.

Embrittlement or cracking of the chain elements is substantially avoided since heat input to the bulk of the material is minimized. While a laser beam is preferred, an electron beam can be employed instead for welding the articulated joints of the present invention.

The alternative cross connecting member illustrated in cross section in Fig. 6 comprises a tubular or hollow cylindrical pin 62 used in the same manner as pin 28 described above. The tubular pin 62 is welded to the side links 16 in the manner hereinbefore described, as indicated at 64 in Fig. 6, suitably by laser welding. The pin 62 provides the bearing surface for centre link 12.

Again, side links 16 are disposed in substantially bearing relation with the sides of the centre link 12. The pin 62 provides a number of advantages over the pin 28 including reduction in weight of the chain and consequent reduction in the impact of the chain on a saw bar with attendant decrease in noise. The tubular pin has improved shock absorbing qualities as well as additional heat dissipation surface and also aids in transporting lubrication to the various bearing surfaces of the chain. Furthermore, the tubular pin can be rolled to shape from flat stock on a multi-slide machine, reducing the amount of material required. The central hole in the tubular pin also can provide a convenient locating feature for assembly and welding purposes.Thus, a plurality of pegs or guide pins (not shown) can be provided in the assembly track 58 in Fig. 5 upon which the chain elements are conveniently assembled.

The alternative construction illustrated in cross section in Fig. 7 employs cup-shaped pins 66 welded to the side links 16 as indicated at 68 in the same manner as hereinbefore described.

These pins 66 are hollow or cupped at each end and are formed with a central web or internal hub 70 in approximate central alignment with the centre links 12. This construction provides an articulated joint configuration which is lighter than the full solid pin while supplying increased strength in the bearing area where the centre links 12 pivot with respect to the pins 66.

In the further embodiment illustrated in Fig. 7, the hollow pin 62 is welded to a side link 16 at a number of separate weld areas or regions 72 around the outer periphery of the pin where it extends within the aperture in the side link 16.

This intermittent welding can be accomplished by operating the welding laser on an intermittent basis or alternatively by providing a plurality of separate laser beams. This approach reduces the weld time per joint and can conserve energy as well as time in the overall welding operation.

The various chain constructions according to the invention have the advantage of enhanced reliability and integrity as compared with the prior art riveted chain construction. In the riveted chain construction as illustrated for example in Fig. 1 A, it is desired the rivets 34 securely engage the side links 32, with the rivet engaging the edge of the apertures in side links 32 by being formed into the apertures. This "hole fill" requires the rivet be deformed down into the aperture while spinning a head on the rivet. Sometimes, the spinning process results in insufficient hole fill and an improper joint. However, with the welded joint according to the present invention, a secure and strong connection is more uniformly achieved, resulting in a more reliable joint and a longer lasting chain.

The chain construction of the invention further results in overall simplification and economy in that the cross connecting elements need not have the complex shape illustrated for the prior art rivets of Fig. 1 B, but may be of substantially uniform cross section. Furthermore, the prior art rivets were heat treated in a complex manner to provide softer end zones for deformation during assembly. On the other hand, the cross connecting members or pins according to the present invention can be batch heat treated to a given hardness throughout. Tight tolerance problems associated with the correct thickness of the hub 36 (Fig. 1 B) relative to the thickness of the centre links are also eliminated in that the centre links act as their own spacer hubs.

The present invention not only provides a cutting chain for cutting a narrower kerf due to the absence of rivet heads, due to the allowable thinness of parts and the substantial absence of side play in the chain, but the same factors can result in increased chip capacity for a cutter chain.

Thus, the elimination of the rivet heads projecting from the surface of the side links allows more space for chips, in the alternative to providing a chain for cutting a narrower kerf.

Although a generally cylindrically shaped pin or cross connecting member has been indicated above, such a member or pin need not be circular in cross section, but, for special applications such as a silent power transmission chain or the like, the member or pin may be heart shaped.

Claims

1. A method of manufacturing an articulated joint for a chain, the method comprising the steps of: joining a cross connecting member to a first link of the chain by welding so that the cross connecting member extends in substantially perpendicular relation from the first link, forming an aperture in a second link of the chain for receiving the cross connecting member, and inserting the cross connecting member through the aperture in the second link for pivotal relation therewith.

2. A method as claimed in claim 1 including forming an aperture in the first link of substantially the same diameter as the aperture in the second link, the cross connecting member being joined to the first link by inserting the cross connecting member into the aperture in the first link and welding around the periphery of the aperture in the first link.

3. A method as claimed in claim 2 including providing an additional link on the opposite side of the second link from the first link and welding the cross connecting member to the additional link.

4. A method as claimed in claim 1, 2 or 3 wherein the welding is accomplished by use of an energy beam.

5. A method of manufacturing a chain comprising centre links and side links arranged for articulated overlapping relation, the method comprising the steps of: providing apertures in overlapping parts of a centre link and a pair of side links, inserting a cross connecting member through the aperture in the centre link and at least into an aperture in one of the side links, with the centre link and the one of the side links positioned in substantially bearing relation with their apertures aligned, and non-compressionally joining the cross connecting member to the said one of the side links.

6. A method as claimed in claim 5 including coating one of the sides of the links in bearing relation with a temporary coating material for spacing the links prior to the joining of the cross connecting member to the said one of the side links.

7. A method as claimed in claim 5 or 6 wherein at least one of the side links, the centre link and said cross connecting member have substantially flat opposing surfaces and are assembled with the flat surfaces disposed substantially horizontally and with the cross connecting member disposed substantially vertically prior to the joining whereby the links are positioned by gravity in the substantially bearing relation and the centre link acts as a bearing spacer.

8. A method as claimed in claim 5, 6 or 7, wherein a complete chain is assembled by joining plural centre links to plural side links employing plural cross connecting members, with a pair of side links disposed one on either side of each centre link and another pair of side links disposed one at either side of the same centre link at the remaining end thereof.

9. A method as claimed in claim 8 including batch heat treating the plural cross connecting members to provide them with a substantially uniform hardness prior to chain assembly.

10. A method as claimed in any one of claims 5 to 9 wherein the or each cross connecting member is welded to the one of the side links by means of an energy beam directed around the edge of the aperture in the said one of the side links.

11. A method as claimed in claim 4 or 10 wherein the beam comprises a coherent light beam.

12. A method as claimed in claim 4 or 10 wherein the beam comprises an electron beam.

13. A method as claimed in claim 4, 10, 11 or 12 wherein the or each cross connecting member is substantially circular in cross section and the beam is directed in a substantially circular path around the edge of a link aperture for joining the link to the cross connecting member.

14. An articulating joint for a chain, the joint comprising: first and second links substantially aligned in a parallel and end-to-end but overlapping relation such that ends of the links overlap in laterally adjacent relation for a part of their total length, and a cross connecting member extending crossways of the first and second links and pivotally joining their overlapping ends, the cross connecting member being welded to the first link and being pivotally received in an aperture in the second link.

15. An articulating joint as claimed in claim 14 wherein the cross connecting member is received in an aperture in the first link, the cross connecting member being welded around its periphery where it is received in the aperture in the first link to the edge of the aperture.

16. An articulating joint as claimed in claim 14 having an additional link on the opposite side of the second link from the first link, the cross connecting member being welded to the additional link.

17. A chain comprising a plurality of successive longitudinally connected articulating links, the chain being arranged to be driven along a path longitudinal of the chain and comprising a plurality of cross connecting members extending generally crossways of the chain, the cross connecting members being welded to one of the said links with respect to which others of the said links can pivot.

18. A chain as claimed in claim 17 wherein a cross connecting member extends crossways between a pair of links to which the member is welded and wherein another of the links is provided with an aperture for pivotally receiving the cross connecting member between the pair of links.

19. An articulating joint as claimed in claim 17 or 18 wherein the cross connecting member is received in an aperture in the or each link to which it is secured, the cross connecting member being welded around its periphery where it is received in such aperture or apertures.

20. An articulated chain comprising: a plurality of centre links and a plurality of side links extending in end-to-end overlapping relation with the centre links such that an end of a centre link is positioned between ends of a pair of side links for articulation with respect thereto, and a cross connecting member extending between the pair of side links and defining a pivoting centre of the centre link with respect thereto, each of the side links and the centre link having an aperture for receiving the cross connecting member, and the cross connecting member being welded to each of the side links.

21. A chain as claimed in claim 20 wherein the length of the cross connecting member is no greater than the combined width of the centre link and a pair of the side links, the centre link and the pair of side links having substantially bearing relation, with the centre link acting as a bearing spacer.

22. A chain as claimed in claim 20 or 21 wherein ones of the side links comprise cutter links supporting cutter teeth and wherein the centre links are arranged to be driven by a chain saw.

23. A chain as claimed in any one of claims 17 to 22 wherein the cross connecting members are of substantially constant cross section.

24. A chain as claimed in any one of claims 17 to 23 wherein the cross connecting members are of hollow tubular construction.

25. A chain as claimed in any one of claims 17 to 23 wherein the cross connecting members are formed of solid rod.

26. A chain as claimed in any one of claims 17 to 25 wherein the cross connecting members are of circular cross-section.

27. A method of manufacturing an articulated joint for a chain substantially as herein described with reference to Figures 1 to 5, Figure 6, Figure 7, Figure 8 or Figure 9 of the accompanying drawing.

28. An articulated joint for a chain when manufactured by the method of any one of claims 1 to4and27.

29. A method of manufacturing a chain substantially as herein described with reference to Figures 1 to 5, Figure 6, Figure 7, Figure 8 or Figure 9 of the accompanying drawing.

30. A chain when manufactured by the method claimed in any one of claims 5 to 13 and 29.

31. A joint for an articulated chain substantially as herein described with reference to Figures 1 to .4, Figure 6, Figure 7, or Figure 8 of the accompanying drawing.

32. A chain substantially as herein described with reference to Figures 1 to 4, Figure 6, Figure 7, Figure 8 or Figure 9 of the accompanying drawing.