Stock material or miscellaneous articles – Structurally defined web or sheet – Including variation in thickness
Reexamination Certificate
1999-03-18
2001-03-20
Morris, Terrel (Department: 1771)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including variation in thickness
C428S163000, C428S168000
Reexamination Certificate
active
06203886
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a toothed belt, and more particularly to a skew-toothed belt for power transmission and to a method for manufacturing the skew-toothed belt.
2. Description of the Related Art
FIGS. 3A and 3B
are a perspective view showing the appearance of a conventional toothed belt, and a bottom view showing the arrangement of the weft f as viewed from the teeth side. The toothed belt includes core yarns, or tension members
11
, a tooth portion
12
, and a back portion
13
. The tooth portion
12
and the back portion
13
are located on opposite sides of an array of the tension members
11
and are formed of tooth rubber and back rubber, respectively. The side of the toothed belt on which teeth are formed is called the tooth side. The tooth side is covered with a tooth cloth
14
. The warp and the weft f, which are multifilament yarns of polyamide or a like material, are woven into the tooth cloth
14
. The tooth cloth
14
is usually arranged such that the warp extends in the width direction of the belt and such that the weft f extends in the longitudinal direction of the belt.
FIG. 4
shows a portion of a process for manufacturing such a toothed belt. As shown in
FIG. 4
, in a cutting step for cutting out the tooth cloth
14
, an elongated tooth cloth material
14
a
impregnated with rubber dough is cut in the width direction thereof, i.e., along the weft arrangement, thereby obtaining a tooth cloth sheet
14
b
. The opposite end portions of the tooth cloth sheet
14
b
extending along the warp are bonded together to form a cylindrical tooth cloth
14
c
. The cylindrical tooth cloth
14
c
is fitted onto a cylindrical die
20
′, on the circumference of which are formed axially-extending tooth-profiled grooves
21
′. Then, the adhesive-applied tension members (not shown but see the one
11
shown in
FIG. 3A
) are wound onto the cylindrical tooth cloth
14
c
. Further, an unvulcanized rubber compound sheet, which will become tooth rubber and back rubber, is wound onto the wound tension members. The resultant assembly is subjected to forming and vulcanization in a pressure chamber. Subsequently, the resultant cylindrical body is cut into annular toothed belts, each having a predetermined width.
In the thus-obtained annular toothed belt, as shown in
FIG. 3B
, the weft f extends in the longitudinal direction of the belt. Thus, the warp interlaced with the weft f extends in the width direction of the belt. Accordingly, the stretchability of the weft f itself helps the tooth cloth
14
follow the tooth profile intimately.
Thus, in the case of a toothed belt whose tooth trace direction is perpendicular to the longitudinal direction of the belt, i.e., whose teeth are not skewed, the tooth cloth
14
follows the tooth profile intimately, so that the teeth are profiled to a high degree of accuracy, thereby establishing good engagement with a pulley.
However, in
FIG. 6
, in order to manufacture a toothed belt whose tooth trace direction is oblique to the longitudinal direction thereof, i.e., a skew-toothed belt, the method for cutting the tooth cloth
14
b
as shown in
FIG. 4
is combined with a cylindrical die
20
on the circumference of which are formed tooth-profiled grooves
21
extending obliquely to the axis thereof. In such a case, the weft f extends in the longitudinal direction of the belt, but obliquely to the tooth trace direction, as shown in FIG.
5
B. As a result, the stretchability of the weft f becomes insufficient during forming and vulcanization in a pressure chamber, and thus the tooth cloth follows the tooth profile poorly.
Therefore, the skewed teeth fail to be profiled as desired, resulting in a potential failure to smoothly engage a pulley and thus raising various problems in terms of ability to reduce the size of a skew-toothed belt, power transmission rate, durability, applications, and reliability.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a skew-toothed belt whose teeth are profiled to a high degree of accuracy and establish smooth engagement, as well as a method for manufacturing the skew-toothed belt capable of profiling teeth to a high degree of accuracy.
To achieve the above object, the present invention provides a skew-toothed belt comprising a tooth cloth attached to skewed teeth. The tooth cloth is woven of warp thread and a weft thread. The weft thread of the tooth cloth extends substantially perpendicular to the tooth trace direction of each skewed tooth.
Through employment of such arrangement of the weft, the skewed teeth are uniformly profiled to a high degree of accuracy. Also, a force to be transmitted is imposed on the skewed tooth without generation of a shear force on the surface of the tooth cloth, and the force is uniformly transmitted along the tooth trace direction. Thus, smooth engagement is established between the skewed teeth and a pulley without transmission loss.
The present invention further provides a method for manufacturing a skew-toothed belt, comprising the steps of: sequentially winding a tooth cloth sheet woven of warp threads and a weft thread, a tension member, and an unvulcanized rubber compound sheet onto a die on the circumference of which are formed tooth-profiled grooves extending obliquely to the axis of the die; subjecting the resultant assembly to forming and vulcanization in a pressure chamber; and cutting the resultant article into an annular form. The weft thread of the tooth cloth sheet and the tooth groves intersect substantially perpendicular to each other.
Through employment of the above relationship between the orientation of the weft and that of the tooth-profiled grooves, during forming and vulcanization in the pressure chamber, the weft stretches intimately along the profile of the tooth-profiled groove, thereby profiling the outer surface of the skewed tooth as desired. Since the warp threads extend substantially parallel to the tooth trace direction of each skewed tooth, the skewed teeth are formed uniformly in terms of tooth profile along the tooth trace direction. Thus, the skewed teeth can be profiled to a high degree of accuracy.
Even in the case of a skew-toothed belt in which a dimple is formed on the crest of each skewed tooth in order to absorb collision energy generated in association with engagement between the skewed teeth and a pulley, the weft follows the profile of the dimple intimately, so that the dimpled skewed teeth can also be profiled to a high degree of accuracy.
REFERENCES:
patent: 0309653 (1989-04-01), None
patent: 0571887 (1993-12-01), None
patent: 2665737 (1992-02-01), None
patent: 2686959 (1993-08-01), None
patent: 10184808 (1998-07-01), None
Fujiwara Tooru
Itou Yoshinori
Kasahara Mitsuo
Kikuchi Hiroshi
Dann Dorfman Herrell and Skillman
Morris Terrel
Pratt Christopher C.
Skillman Henry H.
Tsubakimoto Chain Co.
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