Rocker joint for chain

Abstract: An improved rocker joint for a chain in which each pin of a pair of pins (16,18) is substantially identical in cross-sectional shape. Each pin (16,18) has a front and working surface (34) defined by a first radius and a back surface (38) defined by a single and smaller radius. Planar surfaces diverging from front to back join the front and back surfaces of the pins. The links are provided with openings to receive the pins, each opening being generally circular and having inwardly directed lugs (44), the lugs (44) defining a first arc and a second and larger arc. One of the pins of the rocker joint is held against rotation in some of the links with its back surface contacting the smaller arc and also the walls of the defining lugs.

Description: This invention relates to power transmission chains and particularly to rocker joints for such chains. Power transmission chains of the "silent" or inverted tooth variety usually comprise a plurality of sets of transversely aligned links which are interleaved with other sets of links. Each link has a body with a pair of spaced openings and the openings of one set of links are arranged and aligned with the openings of the next adjacent set of interleaved links. To join the interleaved sets of links, a pivot means is inserted into each group of aligned openings. As taught in the prior art, round pins and rocker joints have been used, the rocker joints comprising a pair of pins, or a pin and a rocker, each with a front face which contacts and rocks on the other. Each link of a silent chain, with the exception of guide links which do not mesh with sprocket teeth, has a body and a pair of depending toes separated by a crotch, each toe being defined by flanks which diverge toward the body. It is also conceivable to construct a chain with links similar to those of the American or British standard roller chain, but with interleaved links. The ultimate use of a chain dictates its construction. When constructing a power transmission chain, it is common practice to make one of the pins of a rocker joint longer than the other. The shorter pin is trapped in position by the guide links which flank the sides of the chain while the longer pins are press-fitted or otherwise secured in the guide links. In other chains, the guide link's are located centrally of the links. In any event, the guide links are used to maintain the engagement of the chain with the sprocket or sprockets with which the chain meshes and do not serve to transmit power to or from the sprockets. Rocker joints for chains are well known in the prior art, see for example, US-A-1 534 494, US-A-3 540 302, US-A-3 742 776, US-A-4 010 656 and US-A-4 507 106. The aforementioned US-A-1 534 494 teaches a power transmission chain in which the links have generally circular openings, each with a pair of inwardly directed tabs defining a pair of arcs of different lengths, and each set of openings receiving a pair of pins having generally curved backs and ogee fronts which rock on one another as the chain articulates. The aforementioned US-A-3 540 302 shows a chain having a rocker joint comprising a pair of like members, each member having a rocking surface in rocking contact with the other. The rocking surface of each is defined by a a first radius, while the remainder of the member is defined by a surface of a second and smaller radius. Both surfaces are convex. The openings in the links for receiving each member are generally rectangular, and each joint member has spaced notches in which the link members seat to transmit the working load to the assembly. The aforementioned US-A-3742776 discloses a silent chain with a rocker joint comprising a pair of like members, each having a rocking surface engaging the other. The rocking surfaces are defined by a first radius, while the back surfaces of each member are defined by a second and smaller radius. The rocking and back surfaces are joined by planar or straight surfaces. The links of the chain have openings formed of inner and outer circular segments joined by wall segments which define straight chords of a circle. The members of the rocker joint are wedged into the openings of a set of links, such that a space is left between the back surface of the joint members and the walls of those openings. The aforementioned US-A-4010656 relates to a chain constructed of sets of interleaved links, each link having a pair of spaced, smooth walled, ovoid openings. The rocker joint comprises a pair of members each with a hypotrochoidal cross-sectional shape, i. e., they are generally three sided, each side having a convex surface. The members substantially match the shape of parts of the openings and engage those parts with a pair of its defining convex surfaces. Finally, the aforementioned US-A-4507106 teaches a rocker joint in which each pin or rocker of a pair has the identical cross-section, and in which each is defined by a front working surface of one radius and a back surface defined by second and third radii. Both of the radii defining the back surfaces are progressively smaller than the first radius, and an even smaller radius joins the front and back surfaces. The openings in the links are essentially round with smooth uninterrupted walls. While the rear surface matches a portion of the wall of the openings, the pins at times have a tendency to rotate relative to the opening which is not desirable. The present invention seeks to provide an improved rocker joint construction for use in power transmission claims. In accordance with the present invention as claimed this object is accomplished in that there is provided a power transmission chain comprising a plurality of sets of links interleaved with other sets of links, and pivot means forming a rocker joint between the interleaved sets of links, each link having ends, a central body portion and a pair of generally round and spaced openings each of which has a wall defined by a pair of arcs separated by spaced and generally inwardly extending lugs, each lug being defined by a pair of diverging substantially planar walls, the lugs being spaced such that one of the arcs is smaller than the other arc, the pivot means forming the rocker joint comprising a pair of pins having substantially identical cross-sectional shapes with their front working surfaces engaging and rocking on one another, each pin of a pair of pins having the working front surface defined only by a first radius, and a back surface defined only by a second radius matching that of the smaller arc of the respective opening, the first radius being larger than the second radius, the front and back surfaces being joined by generally planar surfaces which diverge from the front surface to the back surface, one of a pair of pins being received in the openings of one set of links between a pair of the lugs thereof such that its back surface engages the surface defined by the smaller arc and its planar surfaces engage the planar wall surfaces of the adjacent lugs, thereby preventing rotation of that pin relative to the links of that set, the other pin of the pair of pins being received in the openings of the interleaved set of links with the same relative relationship with the openings as said one set of links, the back surfaces of the pins being movable in the other openings of the links as the working front surfaces move relative to one another when the chain articulates about its joints. In order that the present invention may be well understood there will now be described an embodiment thereof, given by way of example, reference being made to the accompanying drawings, in which Fig. 1 is a longitudinal view of a portion of a power transmission chain embodying the present invention with parts broken away to show details; Fig. 2 is a plan view of a typical chain link in the same chain; Fig. 3 is an enlarged end view of a rocker joint comprising a pair of pins and within the openings in the interleaved sets of links of the same chain; and Fig. 4 is an view of a portion of the same chain on an enlarged scale showing the rocker joint thereof. Referring first particularly to Fig. 1, there is illustrated a chain 10 of the "silent" variety which comprises interlaced sets of links 12 joined by pivot means 14, the pivot means comprising a rocker joint having a pair of pins 16 and 18, (sometimes referred to as a pin and a rocker). The links 12 (see Fig. 2) have a body 13, a pair of spaced openings 20 to receive the pivot means 14, and a pair of toes 22 defined by outside and inside flanks 24, 26, respectively, the inside flanks being joined by a crotch 28. Guide links 30 flank the sides of the sets of links and function to maintain the chain on the sprocket or sprockets (not shown) with which the chain meshes. In this construction, the pins 16 extend through openings 32 and are usually peened over or upset at their ends, while the pins 18 are shorter in length and are trapped by the guide links. The guide links can be centrally located in a chain, if so desired. In such construction the central guide links ride in a central groove in the sprockets to ensure the meshing of the chain and the sprockets and both the pin and rocker are peened over, upset at their ends, or otherwise secured in the assembly. As illustrated in Fig. 3 and 4, the cross-sectional shape of the pins 16 and 18 is substantially identical. The pins can be cut from an extruded length of metal stock. As previously stated, the pin 16 may be longer than the pin 18. Each pin 16 and 18 has a front or working convex surface 34 defined only by a first radius 36, a back or rear convex surface 38 defined only by a second radius 40 smaller than the radius 36, and generally planar surfaces 42, 43 which diverge from the front surface to the back surface, thus joining the front and back surfaces. The surfaces 42, 43 are substantially alike in their lengths and angular relationship relative to an imaginary centerline passing through the centres of the back and front surfaces. The openings 20 in each link are mirror images of one another and are generally circular with a pair of inwardly extending lugs 44, 46, each defined by converging wall surfaces 48, 50 and 52, 54. The lugs are separated by a pair of arcs 56, 58, the arc 56 being smaller than the arc 58 and positioned outwardly of the centre of the link toward the ends thereof. The radius 60 of the smaller arc 56 substantially matches the radius 40 of the pin 16, and the surfaces 48, 50 substantially match the surfaces 42, 43 of a pin. When a pair of pins 16 and 18 is inserted in an opening 20, as illustrated in Figs. 3 and 4, the back surface of one pin engages the arc 56 and also the planar surfaces 42, 43 contact the surfaces 48, 50. Because of the fit of the pin in the opening, that pin does not and cannot rotate relative to the link in the opening. The other arc 58 and lug surfaces 52, 54 permit the other pin of the pair of pins to rock on the pin 16 held against rotation, to thus permit articulation of the chain without permitting back-bending of the chain. The pin 18 has the same relationship with the openings 20 in the next adjacent interlaced set of links, it being held against rotation with respect to that set of links but movable with respect to the next adjacent set of interlaced links.

Claims: A power transmission chain comprising a plurality of sets of links (12) interleaved with other sets of links (12), and pivot means (14) forming a rocker joint between the interleaved sets of links (12), each link (12) having ends, a central body portion (13) and a pair of generally round and spaced openings (20) each of which has a wall defined by a pair of arcs (56, 58) separated by spaced and generally inwardly extending lugs (44, 46), each lug (44; 46) being defined by a pair of diverging substantially planar walls (48, 50; 52, 54), the lugs (44, 46) being spaced such that one (56) of the arcs (56, 58) is smaller than the other arc (58), the pivot means (14) forming the rocker joint comprising a pair of pins (16, 18) having substantially identical cross-sectional shapes with their front working surfaces (34) engaging and rocking on one another, each pin (16; 18) of a pair of pins (16, 18) having the working front surface (34) defined only by a first radius (36), and a back surface (38) defined only by a second radius (40) matching that of the smaller arc (56) of the respective opening (20), the first radius (36) being larger than the second radius (40), the front (34) and back (38) surfaces being joined by generally planar surfaces (42, 43) which diverge from the front surface (34) to the back surface (38), one (16) of a pair of pins (16, 18) being received in the openings (20) of one set of links (12) between a pair of the lugs (44, 46) thereof such that its back surface (38) engages the surface defined by the smaller arc (56) and its planar surfaces (42, 43) engage the planar wall surfaces (48, 50) of the adjacent lugs (44, 46), thereby preventing rotation of that pin (16) relative to the links (12) of that set, the other pin (18) of the pair of pins (16, 18) being received in the openings (20) of the interleaved set of links (12) with the same relative relationship with the openings (20) as said one set of links (12), the back surfaces (38) of the pins (18) being movable in the other openings (20) of the links (12) as the working front surfaces (34) move relative to one another when the chain (10) articulates about its joints. A power transmission chain as claimed in claim 1, wherein the planar surfaces (42, 43) of the pins (16, 18) are substantially equal in length. A power transmission chain as claimed in claim 1 or claim 2, wherein the smaller arc (56) is positioned outwardly of the centre of the links (12), the lengths of the smaller and larger arcs (56, 58) are defined by the defining walls (48, 50; 52, 54) of the lugs (44, 46) which are substantially identical and extend inwardly of the openings (20) and short of the centre thereof, one set of the openings (20) of one set of links (12) being transversely aligned with the openings (20) in another set of openings (20) in the next adjacent set of interleaved links (12) to thus form groups of aligned openings (20), a pair of the pins (16, 18) being positioned in each such group of aligned openings (20) to both join the sets of links (12) and to permit articulation of the chain (10), each pin (16; 18) having a convex said front working surface (34) and a convex said back surface (38), each back surface (38) having a shape matching that of the smaller arc (56) of the openings (20) so as to engage the wall of the openings (20) in one set of links (12) which have the smaller radius and with the planar walls (42, 43) of the pin (16) engaging the planar walls (48, 50) of the lugs (44, 46) defining the smaller arc (56), thus preventing rotation of the pins (16) so engaged when the chain (10) articulates, the other (18) of the pair of pins (16, 18) being free of engagement with the walls of the openings (20) engaged by the other pin (18) of the pair of pins (16, 18), the pins (16, 18) of the pair of pins (16, 18) having the same relationship with the openings (20) in the next adjacent set of links (12) which is interleaved with said one set of links (12). A power transmission chain as claimed in any of the preceding claims, wherein the walls (52, 54) of the lugs (44, 46) defining the larger arc (58) limit the rotational movement of the other pin (18) of the pair of pins (16, 18). A power transmission chain as claimed in any of the preceding claims, wherein the pin-opening configuration limits the back-bending ability of the chain (10).

Inventors: ZIMMER GEORGE A, ZIMMER, GEORGE A.
Applicants: BORG WARNER AUTOMOTIVE, BORG-WARNER AUTOMOTIVE TRANSMISSION AND ENGINE COMPONENTS CORPORATION
Application year: 1989
Main classification: F16G13
IPC codes: F16G13