Chain – staple – and horseshoe making – Chain making – Roller chain
Reexamination Certificate
2000-06-13
2001-07-17
Jones, David (Department: 3725)
Chain, staple, and horseshoe making
Chain making
Roller chain
C474S215000, C059S078000
Reexamination Certificate
active
06260345
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a silent chain including a number of link plates articulately connected by double rocker joint pins, and more particularly to a silent chain having double rocker joint pins each composed of two pins having different lengths and cross sections.
2. Description of the Related Art
Silent chains include guide links and articular links alternately arranged in the longitudinal direction of the chain and articulately connected together by pivot pins. The guide links each include a pair of laterally spaced guide plates and one or more guide link plates disposed between the guide plates. The articular links each include two or more articular link plates whose number is one more than the number of the guide link plate in each guide link. The guide plates, guide link plates and articular link plates each have a pair of pin holes at opposite ends thereof (or leading and trailing ends as viewed in the direction of movement of the silent chain). The pivot pins are inserted through the pin holes so that power can be transmitted between two adjacent links.
In one type of such silent chains, a double rocker joint pin is used as a pivot pin. The double rocker joint pin is composed of a longer pin and a shorter pin used in combination. The longer pin is located at respective leading and trailing ends of the guide plates and respective leading and trailing ends of the guide link plates, while the shorter pin is located at respective leading and trailing ends of the articular link plate.
The longer pin is fitted in two laterally aligned pin holes in the guide plates and has opposite ends projecting outwardly from the guide plates, the projecting opposite ends being swaged or riveted. The longer pin and shorter pin of each double rocker joint pin are movably received in laterally aligned pin holes of the guide and articular link plates for rocking motion relative to the link plates.
In the currently manufactured silent chains, the longer pin and the shorter pin have the same cross section, these pins of the same cross section are arranged in mirror symmetry within the same pin hole. From the viewpoint of manufacturing cost, the identical cross-sectional shape is advantageous because both pins can be manufactured by cutting off desired lengths from a single drawn wire of a certain uniform cross section. However, form the viewpoint of manufacturing process and power-transmitting operation, the longer pin and the shorter pin should preferably have different functions.
In the manufacture of the silent chain, opposite ends of the longer pins projecting outwardly from opposite outside surfaces of the guide plates are swaged or riveted. On the other hand, the shorter pin is not subjected to such swaging or riveting process. The rocker joint pin is generally elongated in shape and has a length much greater than the cross section. The longer pin has a generally semicircular cross section and hence is likely to bend when subjected to a great axial force applied during swaging of the opposite ends. Bending of the longer pin would give rise to a problem in that the overall length of the silent chain is changed and the longer pin itself may be broken during use of the silent chain.
The longer pin and shorter pin are so designed as to maintain a desired strength when they are used in combination. Accordingly, the longer pin when used alone can only provide insufficient flexural rigidity and bending strength and hence is likely to be broken. In the silent chains of the type using the rocker joint pins, only the longer pins are engaged with the guide plates. Accordingly, each longer pin is subjected to a bending force and a shear force both acting on a part of the longer pin engaged with the guide plates. Thus, during power-transmitting operation of the silent chain, the longer pin is used with more severe conditions than the shorter pin. An attempt has been made to cut down the thickness of the guide plates below the thickness of the link plates for the purpose of protecting the longer pin against undue force. However, the attempted reduction of the guide plate thickness has failed to achieve the desired purpose.
In addition, since the longer pin and the shorter pin have the same cross-sectional shape, the silent chain has a uniform pitch throughout the length thereof. This arrangement may cause a problem that secondary noise is produced due to resonance.
SUMMARY OF THE INVENTION
With the foregoing drawbacks of the prior art in view, it is an object of the present invention to provide a silent chain including structural features which can reduce loads acting on longer pins of double rocker joint pins during manufacture and power-transmitting operation of the silent chain.
To achieve the foregoing object, the present invention provides a silent chain comprising: guide links and articular links articulately connected by double rocker joint pins in an alternate fashion along the length of the chain. Each of the double rocker joint pins is composed of a longer pin and a shorter pin smaller in length than the longer pin. Each of the guide links has a pair of laterally spaced guide plates and at least one guide link plate disposed between the guide plates. Each of the articular links has at least two laterally aligned articular link plates. The guide plates each have a pair of first pin holes at opposite ends thereof, and the longer pin of each of the double rocker joint pins is fitted in each of the first pin holes. The guide link plate and each of the articular link plates have a pair of second pin holes at opposite ends thereof, and each of the double rocker joint pins composed of one pair of longer and shorter pins is inserted through each of the second pin holes. The longer pin and the shorter pin each have a different cross-sectional shape, and a thickness of the longer pin as measured in a direction parallel to a pitch line of the chain is greater than that of the shorter pin.
The longer pin preferably has a cross-sectional area greater than that of said shorter pin. It is preferable that the difference in thickness between the longer pin and the shorter pin in the chain pitch line direction is in the range of from about 0.3 to about 5% of a pitch of the silent chain.
The double rocker joint pins of the silent chain are fitted in the first and second pin holes of the plates in such a manner that the longer and shorter pins are rockably received in pair within the second pin holes of the link plates. Considering that only the longer pins are subjected to a swaging or riveting process during the manufacture of the silent chain, the cross-sectional shape of the longer pins is made different from that of the shorter pins, and the thickness of the longer pins in the direction of a pitch line of the silent chain is made greater than that of the shorter pins, whereby the cross-sectional area of the longer pins is made larger than that of the shorter pins. By thus arranging the double rocker joint pins, the longer pins are protected from becoming bent when subjected to an axial impact force during the swaging or riveting process.
During power-transmitting operation of the silent chain, the longer pins are subjected to a bending force because opposite end portions thereof are secured to the guide plates forming a cantilever. The opposite end portions of the longer pins are also subjected to a shear force in the same manner as the shorter pins. The bending force acts in the direction of the pitch line of the silent chain. According to the present invention, the thickness of the longer pins as measured in the direction of the chain pitch line is made greater than that of the shorter pins, so that the longer pins are able to withstand severe operating conditions than those of the shorter pins. Thus, the overall lifetime of the silent chain can be lengthened.
REFERENCES:
patent: 2067243 (1937-01-01), Perry
patent: 2096061 (1937-10-01), Perry
patent: 2725755 (1955-12-01), Riopelle
patent: 3043154 (1962-07-01), Karig et al.
paten
Fukuda Shigekazu
Funamoto Takayuki
Horie Hiroshi
Kanehira Makoto
Kusunoki Yoshihiro
Howson & Howson
Jones David
Tsubakimoto Chain Co.
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