Sprocket

Details Sprocket Sprocket

2001-08-16

2003-07-29

Charles, Marcus (Department: 3682)

Endless belt power transmission systems or components

Positive drive pulley or guide roll

C474S158000, C474S162000

Reexamination Certificate

active

06599210

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a sprocket for a power transmission device of a winding type to transmit power or any other force through a chain. More particularly, the present invention relates to a sprocket having a reduced volume, weight or the like by using material for a thin plate or the like, that can realize an appropriate engagement of the sprocket with a chain by bringing the position of the sprocket into agreement with the position of the chain, and that can prevent an occurrence of a flat curvature or warp upon hardening.
BACKGROUND TECHNOLOGY
Generally, a transmission unit of a winding type using a chain and a sprocket has been adopted for extensive use in a power transmission system of motorcycles, bicycles or industrial machines. The shapes and sizes of the chain and the sprocket for use in this transmission unit are specified and defined as JIS (Japanese Industrial Standards) B1801.
As conventional sprockets, there is provided, for example, a normal sprocket product as shown in FIG.
32
(
a
). This drawing (FIG.
32
(
a
)) depicts a sectional view of a side portion of a normal sprocket product, a sectional view of the sprocket on a longitudinally central plane extending through and over the center of the sprocket, when looked at from direction A and from direction B, a sectional view of the side portion thereof when mounted on a wheel, and a sectional view of the side portion thereof showing a status of warp upon hardening the sprocket. FIGS.
32
(
b
) and
32
(
c
) depict the same illustrations for different sprocket products. In the drawings, a hatched portion in each of the sectional view of the side portions and the sectional view on the longitudinally central plane indicates the presence of material or a member.
As shown in FIG.
32
(
a
), the conventional sprocket product can be mounted on a wheel in a state in which the bottommost end surface (or the uppermost end surface) of the sprocket is engaged with the surface of a flange of the wheel. Therefore, the position of the sprocket is brought into agreement with the position of the chain upon mounting on the wheel, so that the teeth sections of the sprocket can be engaged with the chain in an appropriate fashion. Further, as the upper half portion and the lower half portion of the sprocket from the longitudinally central plane are symmetrical with each other with respect to the longitudinally central plane, the sprocket can present the advantages that it does not cause or causes little warp or curving upon hardening for improving durability.
For the conventional sprocket product as shown in FIG.
32
(
a
), however, it suffers from the defects that it is heavy and expensive in cost of production for the sprocket due to high costs for material because it is filled in with such material over the entire area extending from the bottommost end surface to the uppermost end surface, simply excluding hole portions. In order to render the sprocket lightweight, it is considered as a matter of course to render the entire area of the sprocket thinner. On the other hand, a chain engageable with the sprocket is configured such that two sheets of a pin ring plate and a roller ring plate are disposed alternately, which are disposed parallel to each other and they are mechanically connected to each other with pins. Therefore, the acceptable tensile strength of the chain has its own limits. If a chain having a narrower width than the one currently in use would be used, their may be problems with strength of the chain. The sprocket, however, has no mechanical connecting portion therein. Moreover, it has recently been proposed that the sprocket be made of material having high strength and rigidity. In this case, even if the thickness of the sprocket is half of that of the conventional sprocket, substantially the same strength and rigidity can be achieved as a sprocket prepared by using conventional material.
It is further proposed to provide a sprocket, as shown in FIG.
32
(
b
), which is depressed on upper and lower sides and is provided with a corrugated section having an amplitude in the thickness direction at the outer peripheral part of the sprocket and further with teeth at least at the outer edge portions of the top fold parts of the corrugated section (Laid-open Japanese Patent Application No. 8-214,529). This sprocket can dramatically reduce an amount of material to be used for the production of the sprocket and, even if the material would be used in an amount of from a half to one third the conventional sprocket made of a conventional material, the sprocket can achieve substantially the same strength as the conventional sprocket. Moreover, the teeth formed on the corrugated section are disposed alternately in the thickness direction, so that the sprocket can be used in combination with a chain having a conventional width. Furthermore, as the upper half portion and the lower half portion of the sprocket are symmetrical to each other with respect to the longitudinally central plane extending through and over the center of the sprocket, the sprocket can sustain the advantages that no or little warp or curvature may be caused upon hardening.
When the sprocket in this configuration is mounted on an existing wheel, however, the mounting surface at which the sprocket is mounted on the wheel is located above the bottommost end surface of the corrugated section, as shown in FIG.
32
(
b
). Therefore, a new problem may arise that the position of the sprocket is not brought into agreement with the position of a chain.
In order to solve this problem, it is considered to provide a sprocket with one side depressed therein, as shown in FIG.
32
(
c
), in which its mounting surface for mounting on the wheel is thinned, like in the embodiment shown in FIG.
32
(
b
). In this configuration, the sprocket is configured such that the mounting surface of the sprocket for mounting on the wheel can be brought into agreement with the bottommost end surface of the sprocket by placing the mounting surface of the sprocket eccentrically toward one side with respect to the longitudinally central plane extending through the center of the sprocket. Therefore, this configuration can bring the position of the sprocket into agreement with the position of the chain upon mounting on the wheel.
For the sprocket as shown in FIG.
32
(
c
), however, the material is distributed in an asymmetrical manner with respect to the longitudinally central plane extending over and through the center of the sprocket. This asymmetrical distribution of the material over he sprocket may cause warp or curving during the hardening process, and these defects may eventually lead to disagreement of the position of the sprocket with the position of the chain.
SUMMARY OF THE INVENTION
In order to solve the problems as specifically set forth under the above description of the background technology as shown in FIGS.
32
(
a
) to
32
(
c
), the present invention has the object to provide a sprocket that can reduce volume and weight by using material for use in preparing thin plates or the like, that can realize an appropriate state of engagement of the sprocket with a chain by agreeing the position of the sprocket with the position of a chain, and that causes no or little warp or curving on a surface of the sprocket upon hardening the sprocket.
In order to achieve the object, the present invention provides a sprocket comprising at least a mounting part for mounting on a rotary member and an outer peripheral part at which teeth engageable with a chain are formed, wherein the mounting part comprises a first raised section raised toward a first plate surface side and a second raised section raised towards a second plate surface side opposite to said first plate surface side. The term “rotary member” referred to herein is intended to mean any rotary member that can transmit a drive force through a chain, when the sprocket is mounted on the rotary member. Such a rotary member includes, for example, a wheel for use with two-wheel vehicles, bicycles, motorcycles, and

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