192 clutches and power-stop control – Clutches – Torque responsive
Reexamination Certificate
1999-09-07
2001-04-24
Bonck, Rodney H. (Department: 3681)
192 clutches and power-stop control
Clutches
Torque responsive
C464S037000
Reexamination Certificate
active
06220415
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention provides a hold-down type fastener wherein the preload is set without extensive adjustments, and independent of the fastener axial load and wherein the number of fastener components are substantially reduced.
2. Description of the Prior Art
U.S. Pat. No. 4,534,234 discloses a hold-down type fastener for the insertion and extraction of modular units positioned on an airframe shelf. The fastener disclosed in this patent, although providing satisfactory results, uses a substantial number of components adding to the fastener weight. In addition, assembly time is increased with the attendant increase in labor costs. The fastener utilizes a clutching mechanism that requires numerous adjustments during assembly fabrication. In particular, all the components are first assembled together and then positioned on a fixture. By trial and error, the preload is adjusted on a machine recording the preload. Should further adjustment be required, due to unacceptable preload levels, the fastener is then disassembled with everything forward of the adjustable plate component
66
being removed. The adjustable plate
66
is then rotated clockwise or counterclockwise to the desired preload. The fastener is then reassembled, the preload measured and if the selected value is reached, set screws are locked. It should be noted that '234 fastener takes into account the entire axial component assembly in setting the preload which in turn causes the complicated preload setting procedure. Once assembled and used to secure the modular unit, the operator rotates the fastener sleeve clockwise. As the hold-down progresses towards its defined clutching load, the rotational resistance of the sleeve increases steadily until it finally “clutches out.” At that point the hold-down provides a fixed, non-adjustable prescribed load against the modular unit. In this case, the tightening torque increases as the hold down approaches the maximum clutch loading.
SUMMARY OF THE PRESENT INVENTION
The present invention provides an improved hold-down fastener with less parts, less weight, and a simplified preload prevailing torque adjustment technique. In particular, the two Belleville washers, three spacer washers and the two clutching plates positioned behind the adjuster plate used in the prior design are replaced with the simplified preload clutching mechanism of the present invention. The new clutching mechanism comprises an inner torque ring having a pair of split outer ring members with angled ends. A sloped surface at one of the angled ends is at a predetermined angle to the fastener longitudinal axis. The other end of the inner ring member may be integrally or separately joined to an adjacent sleeve/ring member which has two or more protruding rib members. The selected slope (angle) and the internal diameter of the angled surface for the specific material used, determines the amount of prevailing torque provided by the device itself.
The sleeve disclosed in the above-mentioned patent is modified by fabricating two or more rib members having an angled surface, on the interior sleeve surface, the rib angle corresponding to the angled surface formed on inner torque ring. An optional design is to incorporate a separate ring that is subsequently captivated to the internal portion of the sleeve. The inner torque ring and the inner sleeve surface are operatively connected such that when the connecting shaft is rotated, the rib members on the inner surface of the sleeve compresses the split ring members to the desired preload. In one embodiment, the inner torque ring is a single, integral member. In a second embodiment, the inner torque ring comprises a plurality of substantially identical torque rings.
The present invention thus provides an improved hold down fastener wherein the number of fastener components are reduced, which in turn reduces the overall weight of the fastener. The fastener preload is easily adjusted without requiring the extensive adjustment process currently required, reducing the fastener production costs and increasing reliability.
REFERENCES:
patent: 1865559 (1932-07-01), De Montgrand
patent: 4180990 (1980-01-01), Hill
patent: 4534234 (1985-08-01), Cosenza
patent: 4702122 (1987-10-01), Richard
patent: 4766641 (1988-08-01), Daglow
patent: 4878880 (1989-11-01), Williams
patent: 5183140 (1993-02-01), Nicoll
patent: 5601491 (1997-02-01), Chan et al.
patent: 6019708 (2000-02-01), Kaminski et al.
Bonck Rodney H.
Keschner Irving
The Fairchild Corporation
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