Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Having structure to restrict rotation of threaded – mating... – Comprising a thread lock
Reexamination Certificate
1999-05-21
2001-04-17
Wilson, Neill (Department: 3627)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Having structure to restrict rotation of threaded, mating...
Comprising a thread lock
C411S296000, C411S949000
Reexamination Certificate
active
06217269
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention is a mechanical locking device for threaded connectors.
(2) Description of the Problems and the Prior Art
A number of connections utilize threaded components, including nuts and bolts, threaded pipes and couplings, soda bottles and caps, and medical connectors. Such connections are simple to mate and can be attached and disconnected many times. This simplicity comes with two side effects which are undesirable in certain applications. First, the presence of angled threads creates the possibility of the connection self-loosening under axial loading—a term referred to as “backdriving”. The greater the angle or “pitch” of the threads, the more likely that axial loading will cause backdriving. In some cases, users can add additional components such as lockwashers to prevent backdriving. In other cases, such additions are impractical or too expensive. Hence a need exists to provide backdriving resistance as an integral feature of the threaded connector. Secondly, very little torque is often required to disassemble the connections. This can be a problem when child-proofing is desired, or when one wants to discourage tampering with an assembly. The present invention may be used to overcome either of these shortcomings. An added advantage of the present invention is that it does not interfere with the ordinary function of threaded connections, and requires both mating sides to incorporate the described changes to operate. Components can be manufactured incorporating the feature, and only when assembled with a mating component also incorporating the feature would the user obtain the desired benefit. Hence a bolt with the features on the threads could still use a regular nut with no noticeable impact; a nut with the features on its threads could use a regular bolt with no noticeable impact; but a nut and bolt combined, with the mating features described herein, would demonstrate the desired characteristics.
SUMMARY OF THE INVENTION
The present invention provides features on both portions of a threaded connector to create an interference mechanism, leading to a “ratchet” effect. The extent of this interference can be determined by the designer to provide the degree of backdriving resistance desired for a given application. At modest levels of resistance the feature is not damaged by repeated assembly and disassembly. At high levels of resistance the features become permanently damaged and thereby may be used to indicate tampering.
The locations of these features can be selected so that they become engaged as assembly is started, only upon completion of assembly, or throughout the entire mating process. If the feature is engaged only at the start of assembly, one has, for instance, a nut which may be freely positioned anywhere along the length of a bolt, but resists having the nut fall all the way off the end of the bolt. If the feature is engaged only at the end of the assembly, it can be used to “lock” the nut in place, yet, once the strength of the “lock” is overcome, nut can be easily removed by hand. A bolt with the features along the length of the shaft would act like a ratchet, allowing the nut to be placed anywhere along its length and still require increased amounts of force to disassemble.
The amount of interference between the two components and the materials used in the interfering elements determines the amount of unscrewing resistance. It may range from being barely detectable, all the way through something which is nearly impossible to disassemble.
REFERENCES:
patent: 1881749 (1932-10-01), Llewellyn
patent: 2730154 (1956-01-01), Aspey
patent: 2869881 (1959-01-01), Smith
patent: 4475858 (1984-10-01), Benjamin et al.
patent: 5700122 (1997-12-01), Korpi
patent: 2183769 (1987-06-01), None
Wilson Neill
Winstead Sechrest & Minick P.C.
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