SILENT CHAIN

Abstract: A silent chain (12) has articulated sets (P<u1>u, P<u2>u) of links (24, 26, 28) with teeth (20) adapted for operative engagement with sprocket teeth (18). Each link (26, 28) has two teeth (20) that define at least one surface (36, 37, 38, 39) adapted to come into intimate physical working contact with sprocket teeth (18). A plurality of link sets (P<u1>u, P<u2>u) that have similar working contact surfaces (39) are arranged consecutively in series. One link set (P<u2>u) having links (28f) working contact surfaces (37) that differ from the similar working contact surfaces of the plurality of link sets (P<u1>u, P<u2>u) is arranged in series therewith, to vary the type of contact between the chain teeth (20) and the sprocket teeth (18). The links (24, 26, 28) within the link sets (P<u1>u, P<u2>u) are arranged laterally and longitudinally in a weave pattern to achieve a balance between the link sets (P<u1>u, P<u2>u) for optimum tensile strength, fatigue strength and wear life of the chain (12).

Description: SI ENT CHAIN Technical Field This invention relates to silent chain having laterally positioned links that form sets. These link sets are arranged in a series throughout the length of the chain. Background Art Silent chain has been used to drive vehicles - having either four wheel drive or front wheel drive- Such chain is formed by links that have two teeth for contact¬ ing a sprocket. In conventional silent chain, each set of links making contact with sprocket teeth have identical working contact surfaces. These link sets are arranged consecutively in a series that extends throughout the length of the chain. Known chains have utilized various types of working contact surfaces, such as inside face, interior surface or crotch contact and outside face, ex¬ terior surface or flank contact. However, these working contact surfaces that are defined by the link teeth are the same for all sets of links in the chain. In automotive drives operating at high speed, silent chain has been known to create noise, such as a whine. This noise may be due to the type of tooth contact that is made between the chain and the sprocket. Such noise may be caused by a whipping action of the drive chain that runs under tension. The drive chain is sub¬ jected to a series of impulses which time with explosions T∑E O P in the cylinders or with torsionai vibration of a rotating shaft. These impulses may create resonant vibrations of the chain, sprockets and drive casing to further enhance both the vibrations and the noise level. DISCLOSURE OF INVENTION The present invention reduces noise and provides a longer wear life for an automotive chain of the silent type. Such chains create noise when periodic vibrations develop during operation of the chain. When such chains become loose due to elongation, noise results from both chain vibration and chain contact with adjacent structure, such as a drive housing. According to the present invention there is pro¬ vided a silent chain having articulated link sets with teeth' adapted for operative engagement with sprocket teeth-. Each link in a set has two teeth that define at least one surface that is " adapted to come into intimate physical working contact with sprocket teeth. - A plurality of link sets that have similar working contact surfaces are arranged consecutively in series throughout the length of the chain. At least one link set,. having working con¬ tact surfaces that differ from those of the plurality of link sets, is arranged in series with the plurality of link sets to vary the type of tooth contact between the chain and the sprocket teeth. In * a preferred embodiment of the invention, an automotive drive chain has similar links positioned later¬ ally of each other in link sets. These link sets are arranged in series throughout the length of the chain. Pins extend transversely of the links through openings therein. The links that are positioned laterally of each other extend between adjacent pins forming discrete link sets within the chain. Alternate link sets within the series of link sets have outer guide links secured near the outer ends of the pins. The link sets which include the outer guide links have less links than the link sets which do not include outer guide links. The outer guide links and links within the same link set are in strei balance with the link sets which include a greater number of similar links. Preferably, the links within the link sets are arranged in a weave pattern to achieve a balance between the link sets for optimum tensile strength, fatigue strength and wear life of the chain. BRIEF DESCRIPTION OF DRAWINGS Figure 1 is a broken perspective view of a silent chain drive embodying the present invention. Figure 2 is a plan view of the silent chain shown in Figure 1, with parts broken away to show the cylindrical pins. Figure 3 is a section in elevation of a drive sprocket portion having trained thereabout a length of the silent chain shown in Figure 1. Figure 4 is a side elevation view of a flank contact link superimposed upon a crotch contact link to illustrate the difference between the two types of links-. BEST MODES OF CARRYING OUT THE INVENTION Looking now at Figure 1, a drive 10 has an end- less silent chain.12 that is trained about a drive sprocket 14 and a driven sprocket 16. These sprockets have out¬ wardly extending teeth 18, while the chain has inwardly extending teeth 20 that mesh with the sprocket teeth. With reference to Figure 2, cylindrical pins 22 extend transversely of the chain 12. All links that are positioned laterally of each other and that extend between two pins form a set of links within the chain. Link sets P. have outer guides 24 secured near the outer ends of the pins. Individual links 26 are spaced laterally inwardly from the outer guides, and four groups of double links 26 are spaced therebetween. Link sets P_ include a middle group of three links 28, one individual link 28 spaced outwardly on each side of the middle group, and two groups of double links 28 spaced outwardly from each individual link. While Figure 2 represents but one weave pattern, various lateral lacing arrangements can be utilized to achieve a balance between the guided link sets P. and the non-guided link sets P . This balance is desired to ^ .^s x'p"^ achieve optimum tensile strength, fatigue strength and wear life of the silent chain. Such balance enables each link set to have about the same tensile strength, provides a higher concentration of link material at the outer pσr- tioπs of the link sets where fatigue failure generally occurs, and minimizes unit bearing stresses that affect wear rates- The solid cylindrical pins 22 are received in aligned openings 30 and 32 of both the links 26 and 28. These pins are slightly smaller in diameter than the link openings, but the pins are slightly larger in diameter than openings in the outer guides 24. Thus, the links are pivotal with respect to the pins, while the outer guides are pressed on the pins. The pins may be peened at their outer ends to assure that no outer guide is accidentally stripped from a pin. Thus, the pins pivotally connect ad¬ jacent link, sets P_ and P_. The outer guides hold the links on the pins and engage the sides of the sprocket teeth 18 to maintain the chain 12 on the sprockets 14 and „ 16. These outer guides also carry a proportional amount of the tensile stress within the chain. The guided link set P, has ten links 26 plus the two outer guides 24. The pivotal link set P_ includes thirteen links 28. The two outer guides 24 provide strength equal to three links 28 because the depth of the outer guide is not reduced by a crotch section as in the links 26 and 28. Thus, the link sets P, and P_ have sub¬ stantially the same tensile strength. Only links 28 pivot about the pins 22. These links occupy more of the sprocket width and have a greater overall bearing area upon the pins because of the larger number of these links in the weave pattern. Thus, this weave pattern provides excellent long-term durability by minimizing unit bearing stresses that affect wear rates between the links and the pins. By eliminating bushings and using cylindrical pins that fill the link openings, smaller link openings are required. The weave pattern shown in the drawi defined by new claims 17 and 22 provides that the link sets that pivot upon the pins have at least two links positioned between each outer guide and any other link within the outer guide link set. These features enable a higher concentration of link material at the outer por¬ tions of the links and link sets where fatigue failure generally occurs. Thus, the fatigue strength of the chain is improved. Maximum strength is obtained for the silent chain 12 by providing pins 22 that completely fill the link openings 30 and 32. Only slight clearance is allowed in the openings between the pins and the links so that the links can pivot on the pins. The links 26 and 28, outer guides 24 and pins 22 carry the load applied to the chain. This silent chain is a significantly stronger chain than a conventional chain of comparable size with bushings that require enlargement of the link openings. As shown ' in Figure 3, a length of the silent chain 12 is trained about a portion of the drive sprocket 14. This chain includes link sets P, and P_ that are arranged alternately in series throughout the length of the chain. The sets P. include outer guides 24 and links 26, while the sets P include links 28. These links may be similar to each other or they may be differentiated from each other by the type of contact that they are de¬ signed for making with the sprocket teeth 18. Those links designed for crotch contact are further designated by the letter c, while the link designated for flank contact is further designated by the letter f. Figure 4 shows a flank contact link 28f super¬ imposed upon a crotch contact link 28σ. Both of these links have a straight edge 34 at one side. This edge is desirable to enable the use of a tensioner member (not shown) to engage the chain 12 and take up the slack there— in. Near one end of each link is a circular opening 30, and a circular opening 32 is located near the other end of the link. An imaginary center line L may be drawn between the two openings 30 and 32. Both of these links longitudinally spaced teeth 20 projecting on the link side opposite from the straight edge. - The teeth of link 28f have outside, exterior or flank contact surfaces 36, while link 28c has such sur- faces 37. The flank contact link has inside, interior or crotch contact surf ces 38, while the crotch contact link has such surfaces 39. Both links have an uninterrupted span of metal between the openings 30 and 32 on the tooth side of the imaginary center line L drawn between the open- ings. Looking again at Figure 3, when the silent chain 12 travels about the drive sprocket 14, the sprocket teeth 18 make contact with the link sets P. and P^. The sprock¬ et teeth contact of the links 26c and 28c is made at the crotch contact surfaces 39. When a sprocket tooth fits between the teeth of the link 28f, there may be con¬ tact either at the crotch contact surface 38 of that link or at the flank contact surface 37 of the preceding link 26c. The next sprocket tooth 18 engages the rear flank contact surface 36 of the link 28f. This link has a tendency to either pivot upwardly at the front due to con¬ tact upon the rear flank, or else slide forward and down¬ ward into meshing engagement with the sprocket teeth. The following links 26c and 28c are contacted at their crotch contact surfaces 39 by the sprocket teeth. This varia¬ tion in the types of tooth contact made by different link sets results in a reduction of noise. From the foregoing description, it will be seen that an automotive drive of the silent chain type can be quieted by introducing into a series of sets of links throughout the length of the chain, at least one link set having working contact surfaces that differ from those of other link sets in the series. By using link sets having different types of tooth contact, there is variation in the manner in which such links contact, pivot and slide into meshing engagement with the sprocket teeth. Thus, periodic vibrations are broken up by varying the type of tooth contact that link sets within a series make wit_ ^„„ sprocket teeth. The links within the link sets are arranged in a weave pattern to achieve a balance between the link sets for optimum tensile strength, fatigue strength and wear life of the chain. Although the best mode contemplated for carrying out the present invention has been herein shown and des¬ cribed, it will be apparent that modification and varia¬ tion may be made without departing from what is regarded to be the subject matter of the invention. JWΞrsmb

Claims: What is claimed is: 1. A silent chain having articulated sets of links with teeth adapted for operative engagement with sprocket teeth, each link set having two teeth that define at least one surface adapted to come into intimate physi¬ cal working contact with sprocket teeth, a plurality of link sets having similar working contact surfaces arranged consecutively in series throughout the length of the chain, characterized by at least one link set having working con- tact surfaces that differ from those of the plurality of link sets arranged in the same series to vary the type of tooth contact between the chain and the sprocket teeth. 2. The silent chain described in claim 1 further characterized by said plurality of link sets hav- ing similar working contact surfaces located at single points on the interior side faces of the link set teeth. 3. The silent chain described in claim 1 further characterized by said plurality of link sets hav¬ ing similar working contact surfaces located at the crotch between the two teeth of each link set. 4. The silent chain described in claim 1 further characterized by said one link set having working contact surfaces located at each end of the link set on the two exterior side faces of the link set teeth. 5. The silent chain described in claim 1 further characterized by said one link set having working contact surfaces located at the flanks of the two teeth of each link. 6. The silent chain described in claim 1 further characterized by said plurality of link sets hav¬ ing similar working contact surfaces located at the crotch between the two teeth of each link and said one link set has working contact surfaces located at the flanks of the two teeth of each link. 7. The silent chain described in claim 6 further characterized by said link sets composed of similar links arranged laterally of each other, said lii having circular openings near each end and having an un¬ interrupted span of metal between said openings on the tooth, side of an imaginary center line drawn between the openings, individual links within adjacent link sets being staggered in lateral spacing to align the openings near one end of the links within one link set for registration with openings near the adjacent end of the links of the adjacent link set, and cylindrical pins received in the openings of the links to pivotally join the links of one link set to the links of an adjacent link set, said pins filling the openings in the links. 8. The silent chain described in claim 7 further characterized by outer guides secured on each of said pins. 9. A drive having a toothed sprocket and a silent chain, said chain having articulated link sets with teeth adapted for operative engagement with sprocket teeth, each set of links having two teeth that define at least ' one surface adapted to come into intimate physical working contact with sprocket teeth, a plurality of link sets hav¬ ing similar working contact surfaces arranged consecutive¬ ly in series throughout the length of the chain, charac¬ terized by at least one link set having working contact surfaces that differ from those of the plurality of link sets arranged in the same series to vary the type of tooth contact made as the chain travels about the sprocket. 10. The drive described in claim 9 further char¬ acterized in that said plurality of link sets having similar working contact surfaces that are located at the crotch between the two teeth of each link. 11. The drive , described in claim 10 further characterized by said one link set having working contact surfaces located at the flanks of the two teeth of each link. 12. The silent chain described in claim 1 fur¬ ther characterized in that said links within each link set have circular openings near each end, said links within each link set being arranged laterally of each other, said links within adjacent link sets being staggered in lateral spacing to align the openings near one end of the links within one link set for registration with openings near the adjacent end of the links of the adjacent link set, cylindrical pins received within and filling the openings of the links to pivotally join the links of one link set to the links of an adjacent link set, and outer guides press fitted on each of said pins on opposite sides of every other link set, said link sets adjacent to the outer guide link sets being free to pivot on the pins while said links within the outer guide link sets being held in a fixed position by the two pins and outer guides, said links within the link sets being arranged in a weave pat¬ tern to achieve a balance between the link sets for opti— mum tensile strength, fatigue strength and wear life of the chain. 13. The silent chain described in claim 12 further characterized in that there are more links within the link sets that pivot on the pins than within the outer guide link sets. 14. The silent chain described in claim 13 further characterized in that there are three more links within the link sets that pivot on the pins than within the outer guide link sets, and there are two outer guides within the outer guide link sets that compensate in ten¬ sile strength for the three extra lengths. 15. A chain having articulated sets of links with teeth adapted for operative engagement with sprocket teeth, said links having circular openings near each end, links within each link set arranged laterally of each other, links within adjacent link sets being staggered in lateral spacing to align the openings near one end of the links within one link set for registration with openings near the adjacent end of the links of the adjacent link set, cylindrical pins received within and filling the openings of the links to pivotally join the links of one link set to the links of an adjacent link set, and outer guides press fitted on each of said pins on opposite of every other link set, said link sets adjacent to the outer guide link sets being free to pivot on the pins while said links within the outer guide link sets being held in a fixed position by the two pins and outer guides, characterized in that said links within the link sets being arranged in a weave pattern to achieve a balance between the link sets for optimum tensile strength, fa¬ tigue strength and wear life of the chain. 16. The chain described in claim 15 further characterized in that there are more links within the link sets that pivot on the pins than within the outer guide link sets. 17. The chain described in claim 15 further characterized in that the link sets that pivot upon the pins have at least two links positioned between each outer guide and any other link within the outer guide link set. 18. The chain described in claim 16 further characterized in that there are three more links within the link sets that pivot on the pins than within the outer guide link sets, and there are two outer guides within the outer guide link sets that compensate in tensile strength for the three extra links. 19. The chain described in claim 17 further characterized by each link set having two teeth that de— fine at least one surface adapted to come into intimate physical working contact with sprocket teeth, a plurality of link sets having similar working contact surfaces arranged consecutively in series throughout the length of the chain, and at least one link set having working con- tact surfaces that-differ from those of the plurality of link sets arranged in the same series to vary the type of tooth contact between the chain and the sprocket teeth. 20. An automotive drive chain having similar links positioned laterally of each other in link sets, characterized by said link sets being of balanced strength and being arranged in series throughout the length of said chain, pins extending transversely of said links and through openings therein, said links positioned laterally σf each other' and which extend between adjacent pins form¬ ing discrete link sets within said chain, alternate link sets within said series of link sets having outer guide links secured near the outer ends of said pins, said link sets which include said outer guide links having less links than said link sets which do not include outer guide links, said outer guide links and links within the same link set being in strength balance with said link sets which include a great number of similar links. 21. The chain described in claim 20 further characterized in that there are three more links within the link sets which do not include outer guide links than within the outer guide link sets " which include two outer guide links in addition to the other links therein. 22. The chain described in claim 20 further characterized in that the link sets which do not include outer guide links have at least two links positioned on the pins between each outer guide link and any other link within the outer guide link set. 23. The chain described in claim 20, each link set having two teeth that define at least one surface adapted to come into intimate physical working contact with sprocket teeth, a plurality of link sets having similar working contact surfaces arranged consecutively in series throughout the length of the chain, and further- characterized by at least one link set having working con¬ tact surfaces that differ from those of the plurality of link sets arranged in the same series to vary the type of tooth contact between the chain and the sprocket teeth. -TWE-smb

Inventors: AVRAMIDIS S
Applicants: FMC CORP
Application year: 1981
Main classification: F16H7
IPC codes: B62D55, F16G13, F16H7