Silent chain link plate with convex outer flank portion

Abstract: A silent chain link plate that has a pair of apertures and a plurality of teeth for engagement with a sprocket. Each tooth (21) has a protruding surface (24b) near its corresponding aperture, and thus, the durability of the link plate is increased.

Description: The present invention relates to a silent chain for transmitting power. Such chains are used in automotive transmissions, transfer cases, engine timing systems, and the like. More specifically, the present invention relates to a silent chain in which the outer flanks of each link plate have protruding surfaces near the apertures. The result is an increase in material at points of high stress, which improves the durability of the silent chain as compared with conventional silent chains. Silent chains are formed by an arrangement of link plates in lateral and longitudinal directions. The links are interlaced and joined by pins inserted into apertures in the link plates, forming a chain that is used in conjunction with a sprocket. A typical chain is composed of inner links, which contact the teeth of the sprocket to provide power transmission, and guide links, which do not provide power transmission. Guide links are employed to maintain the chain on the center of the sprocket. A row of link plates, arranged in the lateral direction, typically has a number of inner links combined with guide links in the center or at both edges of the row. conventional silent chains face design problems. In a conventional chain, tension acts to increase the distance between the apertures. As a result, cracks or breakage occur in the zone where the distance between the outside flank and the edge of the aperture is the smallest. In the past, there have been unsatisfactory attempts to solve this problem. Japanese Laid-Open Patent Application No. 4-312161 US-A-5 419 743 by Takeda and Kotera teaches a silent chain link plate with an outward protrusion on the flank of the tooth portion of the link plate. Thus, unlike the present invention, it does not improve the durability of the link plate in the vicinity of the aperture. In another design, the width of the entire outer flank of the link plate was increased. However, this resulted in a decrease in the distance between the teeth of adjacent link plates and thus necessitated a decrease in the width of the sprocket teeth. Such a decrease in width made the sprocket teeth highly vulnerable to fracture or breakage. The yet another design, the width of the outer flank was widened near the aperture by forming the edge of the flank as a straight surface that ran at an exaggerated slant of the vertical. The problem with this design was that it relied to a large extent on weak frictional forces to hold the sprocket teeth and link plate teeth in contact during engagement. As a result, slippage of teeth could not be prevented. US-A-5419743 discloses a silent chain comprising a plurality of link plates, each of said link plates having a pair of apertures and a pair of teeth depending below said apertures, said link plates being interconnected by pivot pins extending through said apertures, said pair of teeth being arranged to engage, in use, with the teeth of an associated sprocket, each of said teeth of said link plates being formed of an inside flank and an outside flank, the outside flank of each tooth tapering outwards towards the aperture. The present invention is directed to solving the above-described problems. It improves the durability of the link plate without decreasing the strength of the sprocket teeth or causing the sprocket teeth to slip when engaging with the chain. According to the present invention as claimed there is provided a silent chain comprising: a plurality of link plates each having a pair of apertures and a pair of teeth depending below said apertures said link plates being interconnected by pivot pins extending through said apertures, said pair of teeth being arranged to engage, in use, with the teeth of an associated sprocket, each of said teeth, of said link plates being formed of an inside flank and an outside flank, characterised in that said outside flanks have outwardly protruding convex surfaces near said apertures. The present invention increases the durability of silent chains. The outside flanks of the link plates have protruding surfaces near the apertures, thereby increasing the distance between the apertures and the edges of the outside flanks. Thus, the link plate is strengthened in an area susceptible to cracks and breakage, and the durability of the silent chain is improved. Because the thickness of the tip of the link plate tooth is not increased, the sprocket tooth need not be reduced in thickness and thus will not decrease in durability. In addition, since the slant of the link plate tooth edge does not increase, slippage of sprocket teeth does not increase. In order that the invention may be well understood, there will now be described some embodiments thereof, given by way of example, reference being made to the accompanying drawings, in which: FIG. 1 is a partially cut front elevational view of the silent chain in one embodiment of the invention; FIG. 2 is a plan view of the silent chain of FIG, 1; FIG. 3 is a front elevational view of a link plate that is part of the silent chain of FIG. 1; FIG. 4 is a front elevational view of the engagement of some of the link plates that are part of the silent chain of FIG. 1 with a sprocket; FIG. 5 is a front elevational view of a link plate in an alternative embodiment of the present invention; FIG. 6 is a front elevational view of the engagement of link plates of the type shown in FIG. 5 with a sprocket; and FIG. 7 is a front elevational view of a conventional silent chain link plate. Refering first to Figure 1, there is shown a partially cut front elevational view of the silent chain in one embodiment of the present invention; FIG. 2 is its plan view. As shown in both FIG. 1 and FIG. 2, silent chain 1 has multiple link plates 2 , each with a pair of teeth 21 and apertures or pinholes 22 . Connecting pins 3 are inserted in pinholes 22 to join link plates 2 . In addition, silent chain 1 has guide plates 4 on the outermost rows of link plates 2 . FIG. 3 is a front elevational view of a link plate that is part of the silent chain of FIG. 1. Tooth 21 has inside flank 23 , which has a straight or slightly curved edge, and outside flank 24 . Outside flank 24 has nearly straight edge 24a near the tip of tooth 21 and convex edge 24b near pinhole 22 . The dotted line shows a conventional outside flank. It is preferable to connect convex edge 24b and flat surface 24a with a small concave section. Convex surface 24b on outside flank 24 increases the material thickness near pinhole 22 , and thus, the strength of link plate 2 is increased. FIG. 4 is a front elevational view of the engagement of some of the link plates that are part of the silent chain of FIG. 1 with a sprocket. Engagement area C is near the center of flat surface 24a of outside flank 24 , and convex surface 24b is located near pinhole 22 . The engagement of sprocket tooth 51 below convex surface 24b allows space for sufficient material thickness t of sprocket tooth 51. Thus, the strength of sprocket tooth 51 is retained and the strength of link plate 2 is increased. FIG. 5 is a front elevational view of a back-driving link plate in an alternative embodiment of the present invention. Link plate 6 has teeth 61, 61' on both sides of center line L-L' drawn between pinholes 62 . Tooth 61 has inside flank 63 and outside flank 64, and tooth 61' has inside flank 63' and outside flank 64' . Inside flanks 63, 63' have straight or slightly curved surfaces. Outside flank 64 has nearly straight surface 64a at the tip of tooth 61 and convex surface 64b near pinhole 62. Similarly, outside flank 64' has nearly straight surface 64'a at the tip of tooth 61' and convex surface 64'b near pinhole 62. The dotted line indicates a conventional outside flank. Preferably, convex surfaces 64b, 64b' and flat surfaces 64a, 64a' are connected with a concave section. Convex surfaces 64b, 64'b increase the material thickness near pinhole 62 on outside flanks 64, 64' and thereby increase the strength of link plate 6 . FIG. 6 is a front elevational view of the engagement of link plates of the type shown in FIG. 5 with a sprocket. Engagement area C is near the center of straight surface 64a, and convex surface 64b is near pinhole 62 . Such positioning of engagement area C allows for sufficient material thickness t of sprocket tooth 81 . Thus, the strength of link plate 6 increases without any accompanying decrease in the strength of sprocket tooth 81 . Although not pictured, the engagement of tooth 61' with a sprocket is identical to the engagement of the sprocket with tooth 61 . FIG. 7 is a front elevational view of a conventional silent chain link plate.

Claims: A silent chain (1) comprising: a plurality of link plates (2) each having a pair of apertures (22) and a pair of teeth (21) depending below said apertures (22), said link plates (2) being interconnected by pivot pins (3) extending through said apertures (22), said pair of teeth (21) being arranged to engage, in use, with the teeth of an associated sprocket (5), each of said teeth (21) of said link plates (2) being formed of an inside flank (23) and an outside flank (24); characterised in that said outside flanks have outwardly protruding convex surfaces (24b) near said apertures (22). A silent chain according to claim 1, wherein said outside flank (24), in use, contacts said teeth of said sprocket (5) along said flank (24) at a point below said protruding surface (24b). A silent chain according to claim 1 or claim 2, wherein said convex surface (24b) is adjacent a substantially straight surface (24a) along said flank (24). A silent chain according to claim 3, wherein said convex surface (24b) and said substantially straight surface (24a) include a concave surface therebetween. A silent chain according to any of the preceding claims, wherein said link plate (6) includes teeth (61,61') on opposite sides of said apertures (62).

Inventors: MATSUDA AKIO, MATSUDA, AKIO
Applicants: BORGWARNER MORSE TEC JAPAN KK, BORGWARNER MORSE TEC JAPAN K.K.
Application year: 1998
Main classification: F16G13
IPC codes: F16G13