Joints and connections – Interfitted members – Radially interposed shim or bushing
Patent
1998-11-13
2000-08-08
Kim, Harry C.
Joints and connections
Interfitted members
Radially interposed shim or bushing
4033744, F16D 106
Patent
active
060991992
DESCRIPTION:
BRIEF SUMMARY
The invention involves a conical clamping set of a type that corresponds to the characterizing clause of claim 1.
Clamping sets of this type are known in many cases both as simple clamping sets and as double-cone clamping sets, e.g. from DE-GM 71 33 914, 77 27 308 and 75 12 290, as well as from U.S. Pat. No. 3,958,888.
The invention's problem resulted from clamping sets that correspond to FIG. 4 of U.S. Pat. No. 3,958,888. The double-cone ring is the external cone ring there, and it fits in a hub bore hole with its cylindrical outer-circumference surface. The conical inner-circumference surfaces are arranged in such a way that the largest wall thickness of the double-cone ring is in the center. A centering crosspiece is provided in the middle, which extends up to the shaft, and consequently makes a centering of the hub possible vis-a-vis the shaft. The clamping screws axially reach through the two individual conical rings; the screws reach through the clearance holes in the one conical ring and in the centering crosspiece, and reach into the threaded holes of the opposite conical ring. The individual conical rings have, on the whole, a larger wall thickness than the double-cone ring in a radial direction in the transfer area of the clamping forces because they take in the clamping screws, so the double-cone ring changes dimensions easily and readily fits into the inner circumference of the recess in the external component. "Thin-walled" should mean, here and in further contexts, that the radial wall thickness at every point in the zone in which the radial forces are transferred is at most half of the radial wall thickness of the internal conical ring, in general, however, only one-third or one-fourth of this wall thickness.
If, for example, a belt driving drum for belt conveyors is attached to a shaft with a conical clamping set of this type, the shaft experiences a substantial bending stress through the pull of the conveyor belt; the bending stress can lead to a noticeable deflection of the shaft. This in turn has the consequence that the outer-circumference surface of the external double-cone ring can slightly move away from the inner-circumference surface of the hub on the external side of the bending, even if the conical clamping set was initially completely tight when the bracing at the edge took place.
This intermittent movement of the external double-cone ring away from the hub bore hole suffices to allow moisture to penetrate at this point, which leads to the feared frictional corrosion there that can make later disassembly of the conical clamping set impossible because the joint surfaces are rusted together. In the case of the example of the belt driving drum, the water comes from the axially external side, which is exposed to the weather.
The point at which the moving away occurs circulates around with the rotation of the shaft, so a ring-shaped rust zone forms.
The penetration of the moisture and the subsequent formation of frictional corrosion primarily arises on the outside of the conical clamping set, so in a zone lying on the axial edge of it, on the radially external circumferential surface fitting into the hub, because lower surface pressure prevails there, and the forces arising because of the bending exceed the clamping forces at this point to begin with.
The problem of avoiding an appearance of frictional corrosion of this type is at the root of the invention.
This problem is solved by the measure described in claim 1.
The axial zones in which the radial clamping forces are transferred are normally approximately equal at the inner component, for example the shaft, and the external component, for example the hub. This leads to the surface pressure on the outside being lower than that on the inside, i.e. on the shaft, because of the larger radius and the corresponding larger surface available for transferring force. The idea that is at the root of the invention consists in reducing the axial zones on the outside that are available for the transfer of the radial forces and to artificially
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International Preliminary Examination Report, dated Aug. 7, 1998.
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