Endless belt power transmission systems or components – Belt guide has surface in sliding contact with belt
Reexamination Certificate
2001-09-28
2003-04-29
Bucci, David A. (Department: 3681)
Endless belt power transmission systems or components
Belt guide has surface in sliding contact with belt
Reexamination Certificate
active
06554728
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
The present invention relates generally to a chain snubber for a power transmission chain such as an engine timing chain, transmission drive chain, or four-wheel drive transfer case chain. In particular, the present invention relates to a chain snubber that is positioned in and secured to a chain housing without the use of fasteners. Instead of fasteners, the snubber is positioned and secured by contact with the chain housing.
Power transmission chains are used in many automotive applications. For example, engine timing chains engage a sprocket on the crankshaft and a sprocket on a camshaft to drive the camshaft. Another important application is a four-wheel drive transfer case in which a power transmission chain engages and is driven by a drive sprocket and also engages and drives an output or driven sprocket. In these applications, it is often desirable to prevent or limit chain vibration and movement of the free span of chain between the sprockets. Tensioning devices or snubbers are conventionally used for these purposes. A snubber adjacent to a chain may be used to limit chain movement and vibration by contact with the chain.
Typically, chain snubbers are positioned and secured to a chain housing using fasteners. An example of a timing chain snubber using fasteners is shown in U.S. Pat. No. 4,193,314. This snubber includes a pair of guide shoes that are secured to a sheet metal snubber body. The snubber body is formed to be positioned against the engine block and defines holes through which fasteners secure the snubber body to the engine block. The guide shoes extend along chain runs between sprockets. The guide shoes prevent movement of the chain and limit chain oscillation or vibration.
The use of conventional fasteners, for example screws or bolts, to position and secure a snubber or guide to the chain housing is effective, but requires time for assembly and adds expense to chain systems. Thus, there has been a long-felt need in the automotive industry for a chain snubber that can be quickly positioned and secured economically, i.e. without the use of fasteners.
One attempt to position and secure a chain guide without the use of fasteners is understood to have been used commercially in the Oldsmobile Quad 4 engine. This chain guide was made from hard plastic and included separated mounting arms that were sized to fit loosely within slots in the chain housing. The slots were separated by a distance that required the mounting arms to be deflected away from each other to be positioned in the slots. The chain guide was held in place by a spring-like tension of the mounting arms towards each other and against surfaces of the slots in the housing. This chain guide limited chain vibration and movement. The flexibility and relatively loose fit of the mounting arms within the housing slots however permitted some movement of the guide due to contact with the moving chain. This movement of the guide and contact of the chain with the hard plastic surface of the guide generated undesirable levels of noise.
Flexibility of a chain snubber is also a concern, particularly where the snubber is relatively long, where the drive chain is heavy, or the snubber otherwise may deflect unacceptably. A chain snubber may be secured with additional fasteners to additionally support the snubber, or may be supported by a metal body that is secured by fasteners as shown by U.S. Pat. No. 4,193,314. Supporting a snubber by these methods also increases the cost of the chain assembly.
Automotive chain drives are subject to particularly stringent noise requirements. The noise created by prior guides having fastenerless mountings, such as the Quad 4 chain guide, was a significant disadvantage as compared to conventionally secured guides of earlier and later designs. A long felt need remains for a fastenerless chain snubber capable of limiting chain movement and vibration without producing objectionable levels of noise during chain movement.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to reduce the assembly time and costs of a power transmission chain by eliminating the use of fasteners to position and secure a chain snubber adjacent to the chain. It is also an object of the present invention to provide a snubber that limits the movement and vibration of a chain while avoiding objectionable chain system noise levels.
The present invention positions and secures a chain snubber with respect to a chain housing without the use of fasteners. The chain contact surface of the snubber may be an elastomer to prevent unacceptable noise levels due to chain contact with the snubber during operation.
A fastenerless chain snubber is provided that includes a snubber body and one or more attachment arms. The snubber is positioned by contact of the attachment arms against openings of a chain housing to retain, or trap contacting surfaces of the attachment arms of the snubber. The attachment arms of the snubber may be molded or cut into various geometries, including a tapered shape. The housing openings that contact the arms may be grooves, holes, or slots that are formed or cut into the chain housing to contact the attachment arms to secure the snubber to the housing. The geometry of the arms and the housing results in contact between the surface of the attachment arm and the surface of the housing opening that prevents movement of the attachment arm with respect to the housing.
Attachment arms having tapered attachment geometry is portrayed in the drawings, but other shapes of the arm or housing opening that trap the attachment arm within the housing opening are also contemplated. For example, a conical shape is contemplated that would provide a continuous surface for positioning.
The snubber can be firmly secured during chain operation by substantial contact between the snubber attachment arms and a chain cover. The arms may be contacted by one or more housing covers that secure the arms within housing openings. Contact of the arms against a cover limits the movement of the snubber and may additionally secure the snubber to the housing by urging the attachment arms against the housing openings. Compression of the attachment arms is only required to create substantial contact with the chain cover. The attachment arms need not be significantly deformed by the installation of the chain cover(s).
Compression that increases the amount of contact, the force of contact, or both between the attachment arm and the housing opening is contemplated with allowance for the elasticity of the attachment arm material. For example, the opening in the chain housing may or may not extend completely through the chain housing. If the openings do not extend completely through the housing, or the attachment arms engage the housing so as to extend beyond the chain housing on one side of the housing, the attachment arm can contact one cover and the opening of the housing. However, if the openings do extend through the housing and the attachment arms extend beyond the chain housing on opposed sides of the housing, the snubber can be secured by substantial contact with a chain cover on each side of the housing.
A snubber according to the present invention may also include a reinforcement that strengthens the snubber adjacent to a chain to limit snubber deflection. Use of such a reinforcement is particularly advantageous where the snubber body extends a relatively long distance between mounting arms, where the chain adjacent to the snubber body is particularly heavy, or both. A power transmission chain in a four-wheel drive transfer case is one such contemplated application of such a reinforcement.
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patent: 5045032 (1991-09-01), Suzuki et a
Butterfield Roger P.
Parks D. Laurence
Young, Jr. Roger G.
Borg-Warner Inc.
Bucci David A.
Dziegielweski Greg
Johnson Vicky A.
McAndrews Held & Malloy
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