Rotary shafts – gudgeons – housings – and flexible couplings for ro – Torque transmitted via flexible element – Nonmetallic element
Reexamination Certificate
1999-06-17
2001-09-04
Browne, Lynne H. (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Torque transmitted via flexible element
Nonmetallic element
C464S903000, C156S137000
Reexamination Certificate
active
06283868
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a flexible shaft coupling element and flexible couplings incorporating such element. The flexible shaft coupling element is in the form of a flexible sleeve-shaped body comprising an annular portion and two coupling receiving portions on opposing sleeve ends at either end of the annular portion. Each of the coupling receiving portions includes a plurality of axially extending ribs or teeth along at least a portion of the inner periphery of the sleeve-shaped body for slidably meshing with grooves in oppositely disposed hubs or end pieces. Such couplings are used to connect two rotating shafts which may be coupled to the end pieces. The flexible shaft coupling of the present invention is useful for accommodating misalignment of two shafts to be coupled together, and for providing a silently operating driving connection between the shafts by virtue of its flexible annular portion or band and the resiliency of its ribs or teeth.
Heretofore, flexible shaft couplings comprising a flexible load carrying band or annular portion and coupling receiving portions having axially extending ribs for engaging axially extending grooves on oppositely disposed hubs or end pieces were characterized in that such ribs typically possessed a trapezoidal profile or contour, and mated with complementary contoured grooves in the generally rigid end pieces. The ribs of such elements are characteristically elastomeric and the end pieces against which the ribs bear are characteristically formed of metal, resulting in a disproportionate amount of strain on the elastomeric ribs vis-a-vis the end piece grooves.
Improvements in the design of these coupling elements have generally been directed toward strengthening the load carrying band to withstand ever greater torsional loading. Because the load bearing capability of such load carrying bands has steadily increased as a result of such improvements, the elastomeric ribs have been required to bear ever-increasing torsional strain.
Flexible shaft coupling devices of the prior art thus generally exhibit a characteristic failure mode, consisting of the ripping or shearing-off of one or more of the teeth from the inner periphery of the sleeve body due to the effect of torsional stress or applied load. Typically, not just one of the teeth would be sheared off in this way, but the entire tooth profile would be sheared away from the much higher strength load carrying backing of the coupling element, leaving a smooth, empty sleeve-shaped shell in the area of one or both coupling receiving portions. Thus, despite the increased strength of prior art coupling element sleeve bodies, such elements generally experienced premature failure due to the effects of torsional loading on the teeth.
This failure mode is moreover particularly troublesome since such shearing-off of the teeth is not apparent from a view of the outer surface of the coupling. One cannot ascertain the levels of torque being transmitted or the proportion of useful life remaining in the coupling without first stopping the drive, removing the elastomeric sleeve, and then performing a visual inspection of the tooth portion of the coupling element. At minimum, this decreases production output and increases engineering costs. Worse yet, very often the first indication of failure may be the total destruction of the coupling element.
SUMMARY OF THE INVENTION
Accordingly, it is a primary object of the present invention to provide a flexible shaft coupling element which exhibits increased load capacity over prior art designs, and which substantially avoids premature failure of the ribs due to torsional loading.
It is a further object of the present invention to provide such a device which exhibits improved resistance to slippage during operation.
It is yet another object of the present invention to provide such a device which provides an early indication of the condition of the coupling without the requirement of halting of coupling operation or removal and subsequent inspection of the coupling.
To achieve the foregoing and other objects and in accordance with a purpose of the present invention as embodied and broadly described herein, flexible shaft coupling elements, and flexible shaft coupling devices incorporating such elements are provided. A flexible shaft coupling element of the present invention is in the form of a substantially flexible sleeve-shaped body comprising an annular portion; at least two coupling receiving portions, each such receiving portion being coaxial with said annular portion and terminating at one of two opposing ends thereof, a sleeve body inner periphery or surface and a sleeve body outer periphery or surface. The coupling receiving portions each comprise a plurality of axially extending teeth or ribs arranged along at least a portion of the inner periphery of the sleeve-shaped body. Each tooth has a circumferential width spanning a portion or arc of the coupling receiving portion's inner surface.
Each of the teeth has an active axial length which, in conjunction with each circumferential width, defines a tooth shear area. The sum of these areas, or cumulative tooth shear area, possesses a cumulative tooth shear capacity. The annular portion also possesses a shear capacity, which is primarily torsional in nature and is distinct from the cumulative tooth shear capacity. The invention is characterized in that the cumulative tooth shear capacity exceeds the annular portion torsional shear capacity.
What is meant by the term “shear capacity” in this context is the resistance of a given material to the combined effects of the applied load (both torsional and non-torsional), vibration, frequency, amplitude, high and low temperature and time, as manifested in the material's ability to substantially maintain its structural integrity sufficiently to operate successfully in its intended application. Thus, in comparing the shear capacity of two materials subject to similar torsional loading, vibration, etc., the material having a lesser shear capacity would generally exhibit failure prior to the material having a greater shear capacity. This characteristic is discussed in greater detail below.
By exhibiting a cumulative tooth shear capacity greater than an annular portion torsional shear capacity, the flexible coupling elements of the present invention overcome disadvantages posed by prior art; premature failure of the teeth is substantially avoided. The flexible coupling elements moreover exhibit improved load capacities over prior art couplings. What is meant by the term, “load capacity” in this context is the capacity of the device to withstand or resist the overall applied force to which it is subjected in use. Load capacity in this context moreover includes both torque transmission, amplitude and frequency components.
In a further embodiment, a flexible coupling assembly is provided, comprising an element as described above, and moreover comprising at least two end pieces having grooves complementary to the teeth of the flexible coupling element coupling receiving portions for mating therewith, one each of such end pieces being engaged in a coupling receiving portion for further engagement to one of at least two shafts.
In yet another embodiment, a flexible coupling element is provided as noted above, moreover comprising means on the outer surface of the sleeve-shaped body for indicating the level of torque being transmitted to the coupling element at a given time.
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patent: 63-072940
Clarke Arthur Jack
Whitfield Kevin John Francis
Austin, Esq. S. G.
Browne Lynne H.
Castleman, Esq. C. H.
Dunwoody Aaron M.
Olson, Esq. M. S.
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