Endless belt power transmission systems or components – Means for adjusting belt tension or for shifting belt,... – Tension adjuster has surface in sliding contact with belt
Reexamination Certificate
2002-10-11
2004-12-21
Charles, Marcus (Department: 3682)
Endless belt power transmission systems or components
Means for adjusting belt tension or for shifting belt,...
Tension adjuster has surface in sliding contact with belt
C474S140000
Reexamination Certificate
active
06832966
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority from Japanese patent application 325529/2001, filed in Japan on Oct. 23, 2001.
FIELD OF THE INVENTION
This invention relates to a plastic movable guide for a power transmission in which an endless chain transmits power from a driving sprocket to a driven sprocket or an endless belt transmits power from a driving pulley to a driven pulley. The guide may be used, for example, as a fixed guide, or as a pivotally mounted tensioner lever.
BACKGROUND OF THE INVENTION
Many engines, and other machines in which mechanical power is transmitted from one shaft to another, include a circulating transmission device, comprising a chain, a belt, or the like as shown in
FIG. 10. A
movable guide Ga, on which the transmission medium C slides, may be used, in cooperation with a tensioner T, to impart appropriate tension to the transmission medium, and also to prevent vibration in the plane of circulation of the transmission medium and also transverse vibration. The movable guide Ga is ordinarily attached to a frame E of the engine or other machine by a supporting shaft P, which may be a mounting bolt, a pin, or the like. In
FIG. 10
, an endless, circulating transmission medium is engaged with a driving sprocket S
1
, driven sprockets S
2
, and a fixed guide Gb for guiding, and limiting the traveling path of, the circulating transmitting medium C.
FIGS. 8 and 9
show a plastic movable guide
300
, used as a tensioner lever in a transmission device utilizing a chain, as described in present inventors' previously filed Japanese Patent Application No. 2000-382798.
In this plastic movable guide
300
, a guide body
301
includes a shoe
302
. A transmitting medium C, such as a traveling chain, belt or the like, is in sliding contact with a surface of the shoe. A plate-receiving portion
303
, provided on the back of the shoe
302
, and extending along the longitudinal direction of the guide, is molded of synthetic resin as a unit with the shoe. A reinforcing plate
308
, composed of a rigid material which reinforces the guide body
301
, fits into a slot
307
, which opens in an edge of the plate-receiving portion
303
along the longitudinal direction of the guide, and faces in a direction opposite to the direction in which the chain-engaging surface of the shoe faces. A mounting hole
305
, for mounting on the frame of an engine, or other machine, is provided at a fixed end of the plate-receiving portion
303
. A through hole
308
A is also provided at one end of the reinforcing plate
308
. The through hole is positioned and fastened, together with the mounting hole
305
in the guide body
301
, on a shaft such as a mounting bolt or the like, with the reinforcing plate
308
fitting into the slot
307
.
In the above-described plastic movable guide
300
, the shoe
302
and the plate-receiving portion
303
are integrally molded as a unit from a synthetic resin. The guide body
301
itself performs a sliding function, and it is not necessary to provide a separate shoe member. Therefore, the number of the parts and the number of production steps is minimized. Furthermore, since a slot
307
opens at an edge of the plate-receiving portion
303
in the guide body
301
along the longitudinal direction of the guide, and the reinforcing plate
308
fits into the slot
307
, the strength of the plastic movable guide in the pivoting direction is increased, and its bending rigidity, toughness, strength are significantly improved.
A mounting hole, for mounting the guide on a frame of an engine, a drive, or the like, is provided adjacent a fixed end of the guide body, and a through hole, which is positioned in register with the mounting hole of guide body, is provided adjacent one end of the reinforcing plate, so that the guide body and reinforcing plate can be fastened together on a supporting shaft, such as a mounting bolt, pin, or the like, which extends through both holes. Thus, both the guide body and the reinforcing plate can be pivotally rotated about a mounting axis while cooperating with each other without the reinforcing plate becoming disassembled from the guide body. Furthermore, since the reinforcing plate is only connected to the guide body by the supporting shaft adjacent one end of the reinforcing plate, and fits into the slot of the guide body, even if there is a difference between the coefficients of thermal expansion of the guide body and the reinforcing plate, the reinforcing plate and guide body are free to move relative to each other in the longitudinal direction of the guide, and thermal shape deformation and resulting breakage are avoided.
In the conventional plastic movable guide
300
, the relationships between the respective sizes and shapes of the mounting hole
305
bored in the guide body
301
and the through hole
308
A bored in the reinforcing plate
308
, are not considered, and the diameter of the mounting hole
305
is set to be the same as that of the through hole
308
A by design. However, a variation in working accuracy in production, and a difference between the coefficients of thermal expansion of the materials made the diameter of the hole
308
A in the reinforcing plate smaller than the diameter of the hole
305
in the guide body, causing the edge of the through hole
308
A to protrude inward past the inner periphery of the hole
305
.
When the conventional plastic movable guide is attached to the frame of an engine and used as a tensioner lever, objectionable metallic noise and transverse vibration are generated, both exceeding the noise and vibration generated when a plastic movable guide composed only of resin was used. A solution to these problems is desirable in view of requirements for reduced engine noise.
Furthermore, in the conventional plastic movable guide, the reinforcing plate can seize on its supporting shaft due to friction. Friction between the reinforcing plate and its supporting shaft can also cause wear, generating metal powder, the presence of which inside an engine can lead to engine failure. Thus, it has been necessary to subject the reinforcing plate to a preliminary strengthening process such as heat treatment in order to enhance its wear resistance. The necessity of preliminary treatment results in an increase in production cost. Furthermore, subjecting the reinforcing plate to a strengthening process such as heat treatment or the like, causes distortion of the reinforcing plate, impairing the ability of the reinforcing plate to fit easily into the slot of the guide body, and potentially reducing assembly efficiency. Thus, improvements are also desirable to avoid seizing, wear, increased production cost and reduced efficiency of assembly.
The inventors have studied and analyzed the causes of metallic noise generation, transverse vibration, wear of the reinforcing plate and seizing of the plate on its supporting shaft. As a result of their studies, the inventors have unexpectedly found that these problems do not occur in all plastic movable guides, but occur only where the diameter of the through hole bored in the reinforcing plate is smaller than that of the mounting hole bored in the guide body, or in where a part of the inner periphery of the through hole in the reinforcing plate protrudes inwardly past the inner periphery of the mounting hole in the guide body. Thus, the inventors have determined that the above-mentioned problems result from direct contact between the support shaft, that is the mounting bolt, pin, or the like, and the inner periphery of the through hole bored in the reinforcing plate.
Accordingly, the objects of the invention are to solve the above-mentioned problems encountered in the production and use of prior art plastic movable guides, and to provide a plastic movable guide having excellent quietness, improved assembly efficiency, and reduced production cost.
SUMMARY OF THE INVENTION
The guide in accordance with the invention comprises an elongated guide body composed of an elongated shoe having a front surface for sliding contact with
Kawano Atsushi
Konishi Tatsuya
Kurohata Junya
Charles Marcus
Howson and Howson
Tsubakimoto Chain Co.
LandOfFree
Plastic movable guide for transmission device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Plastic movable guide for transmission device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Plastic movable guide for transmission device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3311522