Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Torque responsive nut or bolt driving connection – Resilient connection
Reexamination Certificate
1999-10-18
2001-10-30
Saether, Flemming (Department: 3627)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Torque responsive nut or bolt driving connection
Resilient connection
C081S475000
Reexamination Certificate
active
06309154
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to torque-limiting devices. More particularly, the invention provides an assembly that transfers a limited amount of torque between a wrenching device and a fitting.
BACKGROUND OF THE INVENTION
Mechanical fittings are often coupled to another component (a “mating component”) through the use of threads disposed on the fitting and the mating component. Typically, the threads of the fitting and the mating component are securely joined by applying a torque to the fitting. The inadvertent application of excessive torque can damage the threads of the fitting or the mating component. Such damage can prevent the effective mating of the fitting and the mating component, and may necessitate repair or replacement of the fitting or the mating component. Torque-limiting devices are utilized to prevent this type of damage. Torque-limiting devices facilitate the transfer of a limited amount of torque between a torque-applying device, e.g., a wrench or a socket, and the fitting.
Torque-limiting devices typically limit torque in one of two ways. One type of torque-limiting device relies exclusively on friction. In particular, one or more sliding surfaces within these types of devices generate a frictional force as the surfaces translate in response to the applied torque. The frictional force limits the amount of torque that can be transferred to the fitting.
Another type of torque-limiting device relies on mechanical interference. Specifically, a component within the device is placed in contact against another component in a manner that facilitates the transfer of torque between the components. A spring-loaded mechanism holds the components in contact while the applied torque is below a particular value. The spring-loaded mechanism allows the components to separate when the applied torque exceeds a predetermined value, thereby preventing the transmission of torque levels above that value.
Commonly-used torque-limiting devices have a number of substantial drawbacks. For example, the limiting torque produced by such devices usually changes after repeated use of the device. This characteristic is due to wear of the friction-producing surfaces, or permanent stretching of the springs that facilitate the torque-limiting function. Hence, an optimum limiting torque is difficult to maintain throughout the useful life of such devices.
In addition, the springs utilized in spring-loaded devices are usually large, and cannot be integrated into the device in a manner that minimizes the overall dimensions of the device. Furthermore, spring-loaded devices usually have a high parts count, and rely on relatively complicated mechanical interactions between their individual component parts. These characteristics add size and weight to the device, and tend to decrease reliability. Furthermore, spring-loaded devices usually incorporate a number of relatively fragile components. Hence, spring-loaded devices are not particularly suited for use in high-vibration, high-temperature, or corrosive environments.
Both friction-based and spring-loaded torque-limiting devices are susceptible to contamination by foreign materials. Specifically, friction-based devices are particularly susceptible to contamination by grease, oil, and other commonly-used lubricants, as these types of materials alter the coefficients of friction on the friction-producing surfaces. Spring-loaded devices can be affected by foreign materials that collect on the torque-transferring surfaces within the device. In particular, the presence of such materials can reduce the effective contact area of the surfaces, and thereby alter the limiting torque.
Thus, a need exists for a torque-limiting device of compact size and low complexity. In addition, it is desirable that the device be suitable for use under harsh operating conditions, e.g., in high-vibration or high-temperature environments. Furthermore, the device should be capable of producing a limiting torque that changes minimally over the useful life of the device. Also, the device should be capable of satisfactory operation in the presence of common contaminants such as lubricating materials. The present invention is directed to these and other goals.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an assembly for limiting an amount of torque transferred between a torque-applying device and a fitting. A presently-preferred embodiment of the torque-limiting assembly comprises a collar rotatably and coaxially coupled to the fitting. The collar has a plurality of circumferentially-disposed surfaces for engaging the torque-applying device. The torque-limiting assembly also includes a sleeve member non-rotatably coupled to at least one of the collar and the fitting. The sleeve member has a plurality of contact surfaces disposed along a circumference of the sleeve member.
The presently-preferred embodiment of the torque-limiting assembly also includes a locking ring non-rotatably coupled to at least one of the collar and the fitting. The locking ring has a plurality of elongate tangs that extend from a portion of the ring. The tangs are radially spaced from an axis of rotation of the fitting. The tangs are adapted to securely engage the sleeve-member contact surfaces on a selective basis.
Preferably, the tangs are adapted to securely engage the sleeve-member contact surfaces when a torque about equal to or less than a predetermined amount is applied to the collar. The secure engagement of the tangs and the contact surfaces causes torque levels about equal to or less that the predetermined amount to be transferred to the fitting. The tangs are preferably adapted to slip over the sleeve-member contact surfaces when a torque greater than the predetermined amount is applied to the collar. The slipping of the tangs prevents torque levels greater than the predetermined amount from being transferred to the fitting.
A further object of the present invention is to provide a housing for removably coupling a probe to a mounting structure. A presently-preferred embodiment of the housing comprises a main portion having a central passage for removably receiving the probe. The housing main portion also includes a plurality of threads for engaging the mounting structure in response to an installation torque. The housing also includes a collar rotatably and coaxially coupled to the main portion. The collar has a plurality of circumferentially-disposed surfaces for transferring the installation torque. The housing further includes a sleeve member non-rotatably coupled to at least one of the collar and the main portion. The sleeve member has a plurality of contact surfaces disposed along a circumference of the sleeve member.
The presently-preferred embodiment of the housing also comprises a locking ring non-rotatably coupled to at least one of the collar and the main portion. The locking ring has a plurality of elongate tangs extending from a portion of the ring. The tangs are radially spaced from a central axis of the main portion. Preferably, the tangs are adapted to non-rotatably engage the sleeve-member contact surfaces when the installation torque is about equal to or less than a predetermined limit. The non-rotatable engagement of the tangs and the contact surfaces causes the installation torque to be transferred to the main portion when the installation torque is about equal to or less than the predetermined limit.
The tangs are preferably adapted to flex and ratchet over junctures between the sleeve-member contact surfaces when the installation torque is greater than the predetermined limit. The flexing and ratcheting of the tangs prevents the installation torque from being transferred to the main portion when the installation torque is greater than the predetermined limit.
Another object of the present invention is to provide a chip-detector assembly for use with a machine having a lubrication system. A presently-preferred embodiment of the chip-detector assembly comprises a probe having a chip-detecting element.
The presently-preferred embodiment
Saether Flemming
Vibro-Meter S.A.
Woodcock Washburn Kurtz Mackiewicz & Norris LLP
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