192 clutches and power-stop control – Clutches – Operators
Reexamination Certificate
2000-01-21
2001-08-28
Bonck, Rodney H. (Department: 3681)
192 clutches and power-stop control
Clutches
Operators
C192S11000B
Reexamination Certificate
active
06279711
ABSTRACT:
FIELD OF THE INVENTION
This invention is directed to clutches, and more particularly to centrifugal clutches.
BACKGROUND OF THE INVENTION
Centrifugal clutches are well known in the art. In essence, these devices, sometimes known as frictional contact axial clutches, utilize mating frictional members to transfer torque from an input shaft to an output shaft. This is accomplished by harnessing the effects of centrifugal force upon pivoted weights to generate axial movement and ultimately axial thrust. This axial thrust is applied upon an output frictional member which, by interacting with an input shaft frictional member, effectively transmits the input shaft torque to the output or driven shaft.
In one such type of clutch, weights are attached to a support disc which is mounted for rotation with a rotating input shaft. The weights are mounted to pivot about an axis perpendicular to the rotational axis of a support disc. The weights are spring biased to a non-engaging position relative to a clutch plate. As the angular speed increases, the weights pivot as the centrifugal force of the pivoting weights overcome the force generated by the springs and engage the clutch plate. With increasing angular speed, the weights pivot more and the clutch plate engages a clutch disc which is splined to an output drum. The plurality of springs which are operative between the support disc and the clutch plate pull the clutch plate toward the support disc. Thus, as the angular speed decreases, the springs push against the pivoted weights to restore the weights to their non-engaging, i.e., non-pivoted, position. Consequently, the clutch plate disengages the clutch disc such that the output drum is not actively driven.
There are several disadvantages associated with the type of clutch described above. One particular problem associated with this centrifugal clutch is frictional induced hysteresis. Friction acting upon the springs and weights causes the clutch to engage at one speed yet disengage at another speed. Typically, the frictional induced hysteresis causes the clutch to engage at a higher speed but disengage at a lower speed. Preferably, the engagement and disengagement speeds are substantially equivalent to one another, allowing for smoother operation of the centrifugal clutch when used on motorized vehicles such as racing karts. Furthermore, prior centrifugal clutches are too complicated, costly, and relatively heavy. Additionally, adjusting the springs to achieve different engagement speeds is difficult, imprecise, and cumbersome.
What is needed, therefore, is a centrifugal clutch which is kinematically simpler so as to minimize frictional induced hysteresis during its operation to provide a centrifugal clutch with substantially equivalent engagement and disengagement speeds. This clutch should also be less complicated, less expensive, and relatively lightweight. Finally, the springs such be designed to be relatively simple to adjust and replace in order to allow for efficient adjustment of the engagement speed.
SUMMARY OF THE INVENTION
The present invention is directed to a kinematically simple centrifugal clutch which minimizes frictional induced hysteresis. The centrifugal clutch also provides an efficient manner to adjust the clutch's engagement speed. To that end and in accordance with the principles of the present invention, the centrifugal clutch includes a rotatable output driven member, at least one drive plate, and at least one clutch disc disposed adjacent to the drive plate. The clutch disc is mounted for rotation with the driven member. A drive hub is adapted to receive a rotational input such as that from an output shaft of a motor. The drive hub is mounted for rotation with the drive plate. At least one weighted member is pivotally mounted to the drive hub. At least one spring member is operative between the drive hub and the weighted member to apply a restoring force to the weighted members. Various types of spring members could be utilized to apply a restoring force to the weighted member. For example, the spring member may be a torsion spring, an extension spring, or a garter spring. Under the influence of centrifugal force generated by the rotation of the drive hub, the weighted member pivots against the resistance of the spring member so as to engage the drive plate and thereby urge the drive plate into engagement with the clutch disc to rotate the driven member in unison with the rotating drive hub. As the rotational speed of the drive hub decreases, the centrifugal force is overcome by the restoring force of the spring member and the weighted member pivots out of engagement with the drive plate, causing the drive plate to disengage the clutch disc. Consequently, the driven member is no longer actively driven by the clutch disc.
In one embodiment, the drive hub includes at least two attachment posts and the spring members are torsion springs mounted concentrically about the attachment posts. The drive hub also includes at least two adjustment holes associated with each attachment post. One end of the torsion spring can be selectively inserted into a desired adjustment hole to alter the restoring force exerted by the torsion spring onto the weighted members.
Although the centrifugal clutch of the present invention may be used in applications requiring a clutch mechanism intermediate to a drive motor and a drive wheel, it is specifically adapted for application in motorized carts, especially racing karts.
Various additional advantages, objects and features of the invention will become more readily apparent to those of ordinary skill in the art upon consideration of the following detailed description of the presently preferred embodiments taken in conjunction with the accompanying drawings.
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patent: 3291274 (1966-12-01), Wyman
patent: 3769905 (1973-11-01), Dishcler
patent: 4111291 (1978-09-01), Horstman
patent: 4856637 (1989-08-01), Gebhart
patent: 5070984 (1991-12-01), Fehring
patent: 5284234 (1994-02-01), Miglizzi
patent: 5638935 (1997-06-01), Fehring
patent: 5967286 (1999-10-01), Hokanson et al.
Bonck Rodney H.
Wood Herron & Evans L.L.P.
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