Sprocket

Details Sprocket Sprocket

1999-06-07

2001-03-20

Bucci, David A. (Department: 3682)

Endless belt power transmission systems or components

Positive drive pulley or guide roll

Having nonmetallic component

C474S156000, C474S160000

Reexamination Certificate

active

06203462

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a sprocket associated with a chain in a power transmission system to transmit power.
BACKGROUND ART
A combination of a chain and sprocket as a power transmission system is widely employed in a motorcycle, bicycle or other various industrial machines. The shape and size of the chain and sprocket are defined in JISB1801 and JISB1802 of the Japan Industrial Standards.
To reduce the amount of material or the production cost, or to reduce the weight of a motorcycle and improve response during acceleration, a predetermined pattern of weight reduction holes are formed in the sprocket. A sprocket which is mounted on a rear wheel of a motorcycle is, in many cases, exposed to ambient atmosphere. Such holes have an effect on the aesthetics of the motorcycle. To this end, there have been proposed holes of various shapes and sizes.
As mentioned above, such holes are effective for reducing the weight of the sprocket to some extent. The holes can not, however, be formed at the outer periphery of the sprocket since it is necessary to maintain the strength and rigidity of the teeth. Thus, a further reduction in the weight of the sprocket is not possible. It should be noted that to improve response during acceleration, it is preferable to reduce the weight of the outer periphery of the sprocket. However, the weight of the outer periphery of the sprocket can not be reduced by the holes as mentioned above.
A chain is typically composed of two pin link plates and roller link plates extending parallel to each other and arranged in an alternate fashion, and mechanically connected by pins. This arrangement inevitably places limits on tensile strength. As such, the use of a narrower chain creates a problem as to strength. In contrast, the sprocket has no mechanical connection. Various materials have recently been proposed to increase the strength and rigidity of a sprocket. A sprocket made of such materials enjoys the same strength and rigidity if the thickness is reduced by one-half that of a conventional sprocket.
There may be employed a combination of a thin and lightweight sprocket and a conventional chain with a sufficient degree of strength. Such a combination may, however, create rattling in the thickness direction of the sprocket. Such vibration or rattling, it occurs, results in improper engagement of the sprocket with the chain, produces noise, and causes irregular wear of the sprocket and the chain and twisting of the sprocket and chain due to application of uneven loads.
It is, therefore, an object of the present invention to provide a sprocket which is thin, but enables smooth engagement of the sprocket with an associated chain, which provides a sufficient degree of torsional strength, and which has an aesthetically pleasing appearance.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, there is provided a sprocket comprising a wavy region formed at least at its outer periphery, and a plurality of teeth. The wavy region extends in an undulating fashion along the circumference of the sprocket and includes a plurality of convex joint portions. The teeth are formed at least at the outer end of the wavy region.
In its preferred form, the sprocket includes a central opening. The wavy region extends between the central opening and the outer periphery of the sprocket. The wavy region may also be located only at or near the outer periphery of the sprocket.
In its preferred form, the sprocket includes a plurality of holes adapted to reduce the weight of the sprocket. The holes are circular in shape, or may be oblong in shape. The sprocket has a central opening, and the holes are connected to the central opening.
In its preferred form, the convex joint portions extend radially of the sprocket. Alternatively, the convex joint portions are inclined relative to the radial direction of the sprocket. The convex joint portions may be curved, may have flat surfaces, or may be bent.
In its preferred form, the teeth are in the form of flat plates. A pitch between one pair of adjacent convex joint portions is different from a pitch between the other pairs of adjacent convex joint portions.
The teeth are formed at the outer end of the convex joint portions or slant portions between adjacent convex joint portions.
According to another aspect of the present invention, there is provided a sprocket comprising an annular wavy region formed at least at its outer periphery, and a plurality of teeth. The wavy region extends in an undulating fashion in a direction radially of the sprocket. The teeth are formed at the outer periphery of the wavy region.
According to a further aspect of the present invention, there is provided a sprocket comprising thick and thin portions formed at its outer periphery and arranged alternately along the circumference of the sprocket, and a plurality of teeth are formed at the outer end of the wavy region.
In its preferred form, there is provided a means for reducing noise arising from contact between the sprocket and an associated chain. The means for reducing noise is mounted to roots formed between adjacent teeth, and may comprise a cushion element. The means for reducing noise may also comprise an annular resilient element and may extend along the teeth so as to position part of the resilient element in the roots. The means for reducing noise may also extend over the roots, or may be located in part of the roots, located adjacent to the roots, located radially outwardly of the roots, located at one side of the roots, or located at opposite sides of the roots.
In its preferred form, the means for reducing noise comprises cushion elements, and the sprocket includes through-holes adjacent to the roots. The cushion elements extend through the through-holes and are interconnected so that the cushion elements are disposed along the roots.
The sprocket according to the present invention comprises a wavy region formed at least at its outer periphery, and a plurality of teeth. The wavy region extends in an undulating fashion along the circumference of the sprocket and includes a plurality of convex joint portions. The teeth are formed at least at the outer end of the convex joint portions. The teeth of the sprocket are engaged with opposite sides of chain rollers so as to constantly provide an appropriate amount of axial play between the sprocket and a chain. The wavy region enables a reduction in the thickness of the sprocket. The teeth of such a thin sprocket appear to have a nominal thickness identical to those of a typical sprocket and can thus be maintained in proper engagement with an associated chain. Also, the wavy region provides a higher degree of torsional strength and rigidity to the entire sprocket. Advantageously, the wavy region promotes the flow of air during rotation of the sprocket so as to prevent an increase in the temperature of the sprocket. As the sprocket is rotated, the resulting centrifugal force causes mud and other foreign substances, which may be attached to the outer surface of the sprocket during use, to be moved to a part where the sprocket is engaged with the chain. The wavy region, formed at least at the outer periphery of the sprocket, is effective for allowing such mud to flow along the grooves of the wavy region and then out of the sprocket. Thus, the sprocket is substantially free from mud and other foreign substances.
In the sprocket, one pitch between adjacent convex joint portions may be different from the other pitches between the other convex joint portions. With this arrangement, an odd number of teeth can be formed by providing an odd number of convex joint portions.
The sprocket according to the present invention comprises an annular wavy region formed at least at its outer periphery, and a plurality of teeth. The wavy region extends in an undulating fashion in a direction radially of the sprocket. The teeth are formed at the outer periphery of the wavy region. This arrangement provides an appropriate amount of axial play between the sprocket and the chain. The wavy region wh

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