Chain guide

Details Chain guide Chain guide

2000-03-06

2001-11-27

Hannon, Thomas R. (Department: 3682)

Endless belt power transmission systems or components

Belt guide has surface in sliding contact with belt

C474S111000, C474S101000

Reexamination Certificate

active

06322471

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a chain guide adapted to be mounted to a mount surface of an engine block, for example, for guiding the travel of a chain, and more particularly to an improvement in and relating to a joining structure between a guide shoe and a guide base of the chain guide.
2. Description of the Related Art
Conventionally, in a chain transmitting apparatus used in an automobile engine, as shown in
FIG. 6
hereof, a chain A
4
is trained around a drive sprocket Al and two driven sprockets A
2
and A
3
, and a chain guide A
5
is disposed on an exterior side of a longitudinal portion of the chain A
4
which constitutes a tension run (also called “tension side”) of the chain A
4
.
The chain guide A
5
has a function to suppress vibrations of the chain A
4
while running, in cooperation with a tensioner device A
6
which is disposed on the exterior side of a slack run (also called “slack side”) of the chain A
4
to remove a slack of the chain A
4
.
The conventional chain guide A
5
is generally composed of a guide shoe A
7
formed from a synthetic resin and having a shoe surface S adapted to be held in sliding contact with the rear surface of each plate P of the chain A
4
(i.e., an outer circumferential surface of the chain A
4
), and a guide base A
9
made of metal and firmly secured by a plurality of bolts A
8
to a mount surface of an engine block, for example, of the automobile engine.
As shown in
FIG. 7
, the guide shoe A
7
includes a plurality (two being shown) of pairs of hook-shaped locking prongs A
10
arranged along opposite longitudinal edges of the guide shoe A
7
at longitudinal intervals. The locking prongs A
10
project perpendicularly from a rear surface of the guide shoe A
7
which is opposite to the shoe surface S. The guide shoe A
7
further has a pair of locking portions A
11
and A
12
provided at both longitudinal ends of the guide shoe A
7
thereof (which correspond to a forward end and a backward end of the guide shoe A
7
when viewed from the direction of travel of the chain A
4
, as shown in FIG.
6
). The locking portions A
11
, A
12
are engageable with forward and backward ends of the guide base A
9
.
The guide base A
9
is made of metal and has a plurality of pairs of recessed portions A
13
formed in opposite side surfaces (upper and lower surfaces) of the guide base A
9
at a position corresponding to the position of the locking prongs A
10
for receiving therein respective pairs of the locking prongs A
10
.
Mounting flanges A
14
project from both longitudinal ends of the guide base A
9
in a direction toward an inner circumferential surface of the chain A
4
(FIG.
6
). The mounting flanges A
14
have bolt holes h formed at the same pitch as threaded holes (not shown) formed in the mount surface of the engine block. The bolts A
8
extend through the holes h in the mounting flanges A
14
and are threaded into the threaded holes in the mount surface to fasten the guide base A
9
to the mount surface of the engine block, as shown in FIG.
6
.
The conventional chain guide A
5
of the foregoing construction is assembled as follows. While the locking prongs A
10
of the guide shoe A
7
are held in alignment with the corresponding recessed portions A
13
of the guide base A
9
, the guide shoe A
7
is pressed or forced toward the guide base A
9
. Forward movement of the guide shoe A
7
relative to the guide base A
9
causes the opposed locking prongs A
10
to spread out against the resiliency thereof until front locking noses T (
FIG. 8
) of the locking prongs A
10
move into a corresponding pair of recessed portions A
13
of the guide base A
9
. Continuing forward movement of the guide shoe A
7
causes the front locking noses T of the locking prongs A
10
to project from a rear surface B of the guide base A
9
whereupon the locking prongs A
10
are allowed to spring back to restore their original shape. Thus, the locking noses T of the locking prongs A
10
are interlocked with the rear surface B of the guide base A
9
to thereby assemble together the guide shoe A
7
and the guide base A
9
, as shown in FIG.
8
. At the same time, the locking portions A
12
(
FIG. 7
) provided at the forward and backward ends of the guide shoe A
7
are brought into abutment with the forward and backward end faces of the guide base A
9
to thereby position the guide shoe A
7
relative to the guide base A
9
.
In the conventional chain guide A
5
shown in
FIGS. 6 through 8
, since the mounting flanges A
14
of the guide base A
9
are bolted to the mount surface of the engine at a side adjacent to an inner circumferential surface of the chain A
4
, a free space defined by the inner circumferential surface of the chain A
4
can be used efficiently.
However, since one locking prong of each pair of locking prongs A
10
is inserted between the mount surface E (
FIG. 8
) and a lower surface of the guide block A
9
, it is practically impossible to integrate the two mounting flanges A
14
into a single, relatively large mounting flange. Additionally, due to the presence of the recessed portions A
13
formed in the guide base A
9
for receiving therein the locking prongs A
10
of the guide shoe A
7
, the guide base A
9
is structurally weakened at such recessed portions and hence stiffness and rigidity of the guide base A
9
are relatively low. Accordingly, while the chain A
4
is traveling, the guide base A
9
tends to vibrate in resonance with the chain A
4
, thus forming a source of undesired vibration and noises.
In view of the foregoing problem, an attempt has been made to provide a guide base with a single mounting flange designed to extend along the entire length of the guide base for the purpose of increasing the mechanical strength, stiffness and rigidity of the guide base. However, the prior attempt is not successful because the resultant mounting flange is disposed on an exterior side of the guide shoe. The mounting flange requires a large installation space provided on the exterior side of a path of travel of the chain, which will lead to enlargement of the overall size of the engine.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a chain guide including structural features which can increase the mechanical strength, stiffness and rigidity of a chain guide to thereby reduce vibration and noises produced while a chain is running, and which enable compact accommodation of a mounting flange of the guide base within a space defined by an inner circumferential surface of the chain.
To attain the foregoing object, the present invention provides a chain guide for guiding an endless chain trained around a plurality of sprockets rotatably mounted on a fixed support member with a space defined between the chain and a mount surface of the fixed support member. The chain guide comprises a guide shoe having a shoe surface held in slide contact with an outer circumferential surface of the chain, and a guide base mounted to a mount surface of the fixed support member and supporting thereon the guide shoe. The guide base includes a single mounting portion bolted to the mounting surface of the fixed support member on an interior side of the endless chain and projecting to an exterior side of the endless chain through the space defined between the chain and the mounting surface, and a shoe supporting portion projecting from an end of the mounting portion located on the exterior side of the endless chain in a direction perpendicular to and away from the mounting surface and extending in a direction of travel of the chain. The shoe supporting portion has a plurality of locking edges spaced in the direction of travel of the chain and formed on a side of the shoe supporting portion facing away from the chain. The guide shoe has a rear surface opposite to the shoe surface and a plurality of resiliently deformable hook-shaped locking prongs formed on said rear surface. The locking prongs are interlocked with the locking edges of the guide base to secure the guide shoe t

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