Joints and connections – Interfitted members – Rotary binding cam or wedge
Patent
1993-01-14
1995-04-18
Reese, Randolph A.
Joints and connections
Interfitted members
Rotary binding cam or wedge
403343, 403352, 403367, F16B 218
Patent
active
054072956
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a shaft-hub linkage which has a plurality of wedge-shaped projections on the peripheral surface of the shaft and a corresponding number of wedge-shaped recesses on the inner peripheral surface of the hub.
This invention is not restricted to rotary shaft-hub linkages, it also concerns fixed linkages between stationary members such as tubes and pins. In so far the term shaft is also understood to mean a pin or spigot or journal, and the term hub also includes a tube or pipe according to the present invention.
A known shaft-hub linkage of this kind (DE 95 101) has a plurality of wedge-shaped or key surfaces ascending in the peripheral direction of the shaft and cooperating with corresponding wedge-shaped surfaces provided in hubs. The plurality of wedge-shaped surfaces serves for achieving simple variation of the angular position of the eccentrics, lifting devices and similar supporting hubs on the shaft. The wedge-shaped surfaces follow eccentric circles or involutes towards the axis of the shaft. Thus, only line contact can be obtained which results in an extremely high surface pressure and limited torque transmittability or transferability. The gradient or ascent or taper of about 1:20 following from the dimensions indicated in this publication causes a certain jamming of the hub on the shaft, which suffices to prevent jumping of the hubs when lifts move beyond their support. However, it does not form a durable linkage between hub and shaft, which serves for transmitting almost equal torques in both directions of rotation.
Therefore, it was the object of this invention to further develop a shaft-hub linkage of the above-mentioned type in such a way that the support of the wedge-shaped surfaces is distributed over the entire surfaces thereof to achieve the highest possible transmittable torques and that a high degree of interlock is achieved in both directions of rotation to bring about the transmittability or transferability of at least almost equally high torques.
This problem is solved according to aspects of the invention as follows. Owing to mutual relative motion of the members shaft and hub provided with the wedge-shaped or key surfaces, particularly owing to the twisting and in special embodiments of the invention also to the displacement towards the shaft axis, shaft and hub are initially centered with respect to each other when the entire surfaces of opposite wedge-shaped surfaces get into contact, and interlocking frictional engagement occurs between the wedge-shaped surfaces and thus between shaft and hub when the movement is continued. The relative motion stops at the latest when the induced torque is no longer sufficient to overcome the frictional engagement and thus positive engagement is reached. The frictional engagement permits the shaft-hub linkage according to the invention to receive, in addition to torques, considerable axial forces in the direction of the shaft axis.
The logarithmic spiral is the even curve having equal gradient over the entire course thereof. In the present case, this results in the fact that, with mutual relative motion of thus designed wedge-shaped surfaces provided on a shaft and a hub about a joint axis, all points of the wedge-shaped surfaces start touching and supporting one another at the same time. The logarithmic spiral is the mathematically exact form of this curve. However, in practice the aspired result is also achieved by means of curves approximated more or less to the logarithmic spiral, since minor deviations from the perfect course are compensated by the elastic and/or plastic deformability of the material used for the wedge-shaped surfaces. Thus, arcs of a circle having radii, centers and central angles can be found which only lead to imperceptible deviations from the perfect case when wedge-shaped surfaces are designed in accordance therewith. Therefore, only a circular spline profile is usually mentioned below for the purpose of simplification.
The amount of interlocking of a key connection does not only depend on
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Kim Harry C.
Reese Randolph A.
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