Endless belt power transmission systems or components – Friction drive belt – Including discrete embedded fibers
Reexamination Certificate
2001-02-27
2003-01-07
Bucci, David A. (Department: 3682)
Endless belt power transmission systems or components
Friction drive belt
Including discrete embedded fibers
Reexamination Certificate
active
06503164
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to power transmission belts having alternating cog crests and cog troughs on at least one side thereof. The invention is also directed to a method of manufacturing such a belt.
2. Background Art
It is known to use belts with cog crests and cog troughs alternating along the length thereof in various systems, such as in snowmobiles, other types of vehicles, and in general industry applications. In one such system, speed shifting is effected by altering the effective diameters of driving and driven pulleys around which the belt is trained. A conventional type belt used in this environment may have the alternating cog crest and cog trough configuration on one or both sides of a belt body in a compression rubber layer and/or a tension rubber layer. Load carrying cords are commonly embedded in the cushion rubber layer between the tension and compression rubber layers.
In a conventional manufacturing process for producing this type of belt, a cog pad is preliminarily formed. The cog pad is formed from a sheet consisting of a reinforcing cloth, a non-vulcanized rubber sheet forming a compression rubber layer, and a non-vulcanized rubber sheet forming a cushion rubber layer. Cog troughs and cog crests are formed by pressing the cog sheet against a mold having a shape that is complementary to that desired, with the cog sheet at an elevated temperature. The resultant cog pad is separated and placed around a cylindrical support having slots and ridges that are complementary to the cog troughs and cog crests. The ends of the cog pad are then butt joined to produce an endless cylindrical shape. Load carrying cords, non-vulcanized sheets forming an additional cushion rubber layer and an additional tension rubber layer are sequentially applied to the cog pad, after which the entire assembly is vulcanized and thereafter cut to separate belts of desired width.
The cog pad is a lamination of one or more plies of reinforcing cloth and an unvulcanized rubber sheet which has cog crests and cog troughs spaced at a predetermined pitch along the belt length. Typically, the cog pad is manually cut to produce the desired length. It is conventional to count the number of cogs to determine the desired circumferential length of the belts and use chalk to mark the cutting positions to produce that length. The cog pad is typically cut at both of its ends at the top of a cog crest, using conventional cutting equipment.
In cutting the cog pad ends, it is desired to cut from side to side along a line that is orthogonal to the belt length. The plane of the joint at which the ends are butted is biased, i.e. non-perpendicular to a line extending along the length of the belt. If the cog pad is cut at a location spaced from a cog crest, it becomes difficult to join the ends of the cog pad to produce a straight butt line. A gap may result at the butt joint, potentially leading to volumetric cracks, and potentially making a defective joint. Thus, with this defect, there is a risk of crack formation at the joint, particularly in the event of a change of load or heat generation as the belt is running in operation.
Conventionally, the planes of the joints, made even at the cog crests, may extend to an adjacent cog trough. This can be seen on the conventional cog belt at
10
, shown in FIG.
8
. The belt
10
has a body
12
with cog crests (C)
14
and cog troughs (T)
16
alternating at regular intervals along the length of the belt body
12
, as indicated by the doubled-headed arrow
18
. A reinforcing cloth layer
20
is applied on one side
22
of the belt body
12
over the cog crests
14
and cog troughs
16
. The other side
24
of the body
12
has alternating cog crests
26
and cog troughs
28
, likewise alternating along the length of the belt body
12
. At least one longitudinally extending load carrying cord
30
is embedded in cushion rubber layers
32
,
34
.
In this belt
12
, ends
36
,
38
of a rubber layer
40
are butt-connected to produce a bias joint
42
i.e. the plane thereof is non-perpendicular to a line extending lengthwise of the belt body
12
. The joint
42
penetrates from a cog crest
14
to a cog trough
16
, i.e. through to the region T. Rubber in the cushion rubber layer
34
tends to penetrate the trough
16
during the vulcanization process. This rubber migrates to the joint
42
at the end
44
thereof. A generally softer rubber in the cushion rubber layer
34
that has penetrated the rubber layer
40
, typically a compression rubber layer, may adversely affect the integrity of the layer
40
. This may result in the failure in the trough region due to fatigue resulting from repeated flexure. Cracks may generate at, or adjacent, the joint end
44
to thereby reduce the anticipated belt life. Cracks generated in the trough may propagate to the crest resulting in breakage thereof at the joint
42
.
In
FIG. 9
, the belt
10
of
FIG. 8
is shown with a joint
46
, corresponding to the joint
42
, wherein the joint
46
does not extend into the cog trough
16
. In this embodiment, the rubber in the cushion rubber layer
34
tends to migrate into the joint
46
at the joint end
48
in the crest region. This reduces the thickness Ti of the cushion rubber layer
34
at the cog trough
16
. As a result, the cog troughs
16
become more rigid, and are more prone to cracking as a result of fatigue from repeated flexing.
Short fibers in the rubber layer
40
orient, and conform to, the cog shape. With the belt
10
operated under high load, the belt side surfaces
50
(one shown) receive the sheering force from a cooperating pulleys. Crack-like grooves
52
following the cog contour may develop on the guide surfaces in contact with the pulleys. Crack-like grooves tend to also be developed at the joint
46
. These grooves can potentially grow into lengthwise cracks, which may cause the belt
10
to break.
SUMMARY OF THE INVENTION
In one form, the invention is directed to a power transmission belt having a body with a length, a first side, a second side, and laterally spaced side surfaces. The body has cog crests and cog troughs in at least a first layer on the first side of the body and alternating along the length of the body. The body further has at least one cushion rubber layer and at least one load carrying cord embedded in the at least one cushion rubber layer and extending lengthwise of the body between the cog crests and the second side of the body. The at least first layer has a first joint that is in a cog crest and does not extend into a cog trough. At least one cushion rubber layer is made from a first material, with the first material from the at least one cushion rubber layer not penetrating the first joint.
In one form, there is no joint in the at least first layer that extends into a cog trough.
In one form, the at least one cushion rubber layer has a thickness between the at least one load carrying cord and the first side of the body that is substantially uniform between adjacent cog crests and cog troughs. The thickness may be uniform over the entire length of the body.
In one form, the first joint resides in a first plane that is angularly oriented to a second plane orthogonal to a line extending lengthwise of the body and extending between the first and second sides.
The first plane may make an angle of at least 60° with respect to the second plane and may be in the range of 65° to 90°.
The first plane may be substantially orthogonal to a line extending lengthwise of the body.
In one form, the first joint extends along a first line between the laterally spaced side surfaces, and the first line is substantially orthogonal to a second line extending lengthwise of the body.
The power transmission belt may further include a reinforcing cloth layer over the cog troughs and cog crests on the first side of the body. The reinforcing cloth has ends that are lapped at a cog crest that is spaced from the cog crest in which the first joint is formed.
The at least first layer may be a compression rubber layer.
T
Bucci David A.
McAnulty Timothy
Mitsuboshi Belting Ltd.
Wood Phillips Katz Clark & Mortimer
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