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
2001-12-17
2003-11-11
Charles, Marcus (Department: 3681)
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
active
06645102
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pivotally movable guide for use in a power transmission device including an endless chain trained around a driving sprocket and a driven sprocket, or a similar power transmission device including an endless belt trained around a driving pulley and a driven pulley. More particularly, it relates to a pivotally movable plastic guide used as a tensioner lever or a guide lever pivotally mounted on a single shaft in the power transmission device.
2. Description of the Related Art
In general, an engine or a driving unit includes a power transmission device for transmitting power by means of a chain or a belt. In the chain or belt power transmission device, a pivotally movable guide having slip function is used. The movable guide is mounted to a body of the engine or driving unit by means of a mounting bolt or a pin.
In use, the movable guide is held in slide contact with an endless chain or belt while running so as to apply an appropriate tension to the chain, or to prevent whipping and lateral oscillation of the chain or belt during travel.
FIGS. 16
to
18
show a conventional movable plastic guide
100
used in a chain drive system, the guide taking the form of a tensioner lever. The guide
100
has a one-piece structure molded of a single synthetic resin material and includes a curved shoe
101
for slide contact with a chain C, a thin plate-like guide body
102
disposed on the back side of the shoe
101
along the length thereof and extending perpendicularly to a front surface (shoe surface) of the shoe
101
, a side flange
103
disposed on and along a side edge of the guide body
101
opposite to the shoe
101
, and a boss
105
formed at one end of the guide body
102
and having a mount hole
104
for attachment of the guide
100
to the body of an engine or a driving unit. Reference numeral
102
′ denotes reinforcement ribs formed on front and rear surfaces of the thin plate-like guide body
102
.
Due to the one-piece structure molded of a single synthetic resin material, the conventional movable plastic guide
100
is unable to maintain its slip properties, wear resistance, strength properties at high levels in a compatible manner. For instance, when a synthetic resin material with excellent slip properties and wear resistance is used, the resulting movable guide has an insufficient mechanical strength. Alternatively, enlarging the cross section to recover the insufficient mechanical strength results in a guide with undue thickness, which requires a large space for installation of the guide to the body of the engine or driving unit.
To deal with this problem, several improvements have been proposed. According to one improvement disclosed in Japanese Patent No. 2,818,795, a plastic guide is formed by a support member of fiber reinforced plastic and a lining member of high wear-resistant plastic, wherein the support member and the lining member are produced in a progressive molding cycle and are interconnected via one or several dovetailed connections. According to another improvement disclosed in Japanese Patent Laid-open Publication No. 8-254253, a plastic guide is formed by insert molding, wherein an extruded steel core or insert is molded with synthetic resin. Both the progressive molding process and the insert molding process require a complicated molding die assembly, which increases manufacturing cost of the plastic guides. Additionally, due to the difference in thermal expansion coefficient between two different plastic materials or between the plastic material and the steel core, the guide is likely to deform or sometimes break.
Still another prior improvement is shown here in
FIGS. 19
to
21
, wherein a movable plastic guide
110
is formed by a curved plastic shoe
111
, a plastic guide body
111
integrally molded with the shoe
111
and a reinforcement plate
118
of steel or iron fitted in a groove
117
formed in a front surface of the molded shoe
111
. The guide body
112
has reinforcement ribs
112
′ and a side flange
113
. The reinforcement plate
118
is arranged in parallel with a curved shoe surface of the molded guide body
111
, so that the modulus of section of the movable guide
110
is relatively small and this deteriorates the rigidity and strength of the movable guide
110
. Especially, since a mount hole
114
extending through a boss of the molded guide body
111
is distant from, and hence is not reinforced by, the reinforcement plate
118
, as shown in
FIGS. 19 and 20
, the strength of a molded guide body portion extending around the boss is very low. Additionally, the curved reinforcement plate
118
made of metal requires a punching process followed by a bending process, which increases the manufacturing cost of the movable guide
110
.
According to another prior improvement, a movable guide is formed by a guide body made of metal or fiber reinforced plastic and a plastic shoe that are formed separately and are interconnected via a mechanical connection such as hooks formed on the shoe (see Japanese Utility Model Publication No. 7-36201, Japanese Utility Model Registration No. 2,519,476 and Japanese Patent Laid-open Publication No. 9-324839). The two-piece guide is complicated in construction, is not readily adapted to an automated assembling process, requires relatively high manufacturing cost, and may cause accidental separation of the guide body and the shoe due to a damage at the mechanical connection.
According to still another prior improvement, a guide has a plastic guide body sandwiched between metal plates (see Japanese Patent Laid-open Publications Nos. 11-2012249, 11-22790 and 2000-220706). The guide of the laminated structure is costly to manufacture due to parts variety and increased assembling man-hours.
SUMMARY OF THE INVENTION
It is, accordingly, an object of the present invention to provide a pivotally movable plastic guide for a power transmission device, which includes a plastic guide body of a simple configuration and a reinforcement plate of a simple configuration arranged to enlarge the modulus of section of the guide to thereby increase the flexural rigidity and strength of the guide without increasing the cross-sectional dimensions and overall weight and size of the guide, which occupies a relatively small space for installation with respect to a fixed support member such as an engine body, and which is free from break or rupture caused due to the difference in thermal expansion coefficient between the guide body and the reinforcement plate.
To achieve the foregoing object, according to the present invention, there is provided a guide for a power transmission device including an endless chain or belt, the lever comprising: an elongated one-piece guide body molded of synthetic resin, the guide body having a shoe at one longitudinal edge thereof and a plate-like carrier integral with the shoe. The shoe has a shoe surface for slide contact with the chain or belt, and the carrier extends from the shoe in a direction perpendicularly away from the shoe surface and has a longitudinal groove extending along the length thereof and opening to a longitudinal edge of the carrier facing away from the shoe surface. The carrier further has a mount hole formed at one end thereof for attachment of the guide to a stationary mount base. The guide further comprises a reinforcement plate fitted in the longitudinal groove of the carrier and having a through-hole at one end thereof, the through-hole being aligned the mount hole of the carrier.
The guide body including a shoe and a carrier integrally molded from synthetic resin into a one-piece structure has slip function. The carrier has a longitudinal groove extending along the length thereof and opening to a longitudinal edge thereof facing away from the shoe surface. With the reinforcement plate fitted in the longitudinal groove of the carrier, the guide has high flexural rigidity and strength. The reinforcement plate can readily be assembled with the guide body merely by being in
Charles Marcus
Dann Dorfman Herrell and Skillman
Skillman Henry H.
Tsubakimoto Chain Co.
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