BACKGROUND OF THE INVENTION

1. FIELD OF THE INVENTION

This application relates to power transmission chains and particularly to an improved rocker joint for such chains.

2. BACKGROUND DISCUSSION

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.

Rocker joints for chains are well known in the prior art, as for example, U.S. Pat. Nos. 1,534,494; 3,540,302; 3,747,776; 4,010,656 and 4,507,106.

U.S. Pat. No. 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.

U.S. Pat. No. 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 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.

U.S. Pat. No. 3,742,776 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.

U.S. Pat. No. 4,010,656 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.

U.S. Pat. No. 4,507,106 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.

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 links 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.

BRIEF SUMMARY OF THE INVENTION

The present invention comprises an improved rocker joint construction suitable for use in power transmission chains. The general construction of such chains has been described.

The improved rocker joint of this invention comprises a pair of pins having substantially identical cross-sectional shapes. A pair of these pins is received in each group of transversely aligned openings in the interlaced sets of links which make up the chain, the openings in one set of links retaining one pin against rotation relative to the links of that set while permitting limited movement and rotation of the other pin relative to the opening of that set of links. The other pin is retained against rotation in the aligned openings of the next adjacent interleaved set of links while permitting movement and rotation of the one pin relative to the openings in the latter set of links. With this fit, the front, working surfaces of the pair of pins engage and rock on the other.

The openings in the links each comprise a pair of arcs, one longer than the other, the arcs being separated by lugs extending inwardly of the openings and which are defined by generally planar converging surfaces. One pin of each pair of pins is held so that its back surface contacts the opening's shorter arc and the walls of the defining lugs, while the other pin does the same with the openings of the next adjacent and interleaved set of links.

Each pin is defined by four major surfaces, i.e., a front or working surface defined only by a first radius, a rear or back surface defined only by a single radius smaller than the first radius, and planar surfaces or walls diverging from front to back joining the front and rear surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal view of a portion of a chain constructed according to this invention with parts broken away to show details;

FIG. 2 is a plan view of a typical chain link according to this invention;

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 according to this invention; and

FIG. 4 is an view of a portion of a chain on an enlarged scale showing the joint of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Looking now at the drawings, and especially 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 insure 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 FIGS. 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 surface 34 defined only by a first radius 36, a back or rear surface 38 defined only by a single 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 centers 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 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 center 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.

The appended claims are intended to cover all reasonable equivalents and are to be interpreted as broadly as the prior art will permit.