Torque limiting wrench for an ultrasonic medical device

Details Torque limiting wrench for an ultrasonic medical device Torque limiting wrench for an ultrasonic medical device

2003-01-15

2004-10-26

Smith, James G. (Department: 3723)

Tools

Wrench, screwdriver, or driver therefor

Responsive to torque on work

C081S483000

Reexamination Certificate

active

06807885

ABSTRACT:

RELATED APPLICATIONS
None.
FIELD OF THE INVENTION
The present invention relates to a torque limiting wrench, and more particularly to an apparatus and method of transferring an applied torque from a wrench to an ultrasonic medical device wherein the wrench is set to a predetermined torque to allow a user to supply an appropriate amount of torque to the ultrasonic medical device to not damage the medical device.
BACKGROUND OF THE INVENTION
Torque limiting wrenches are used in many different applications of adjusting various components including, but not limited to, bolts, nuts and fasteners. Torque limiting wrenches are used for applications where transmission of a consistent level of torque is needed. A consistent level of torque is important for a number of reasons. A torque limiting wrench assures that components are fully tightened. If a component is not fully tightened, the component can become loose wherein the component can become unengaged. A component that is not fully tightened can further adversely affect the functionality of the device as a whole. In addition, a torque limiting wrench prevents overtorqueing a component. Overtorqueing a component can lead to localized overstressing of the component, which can result in damage to various parts of the component. For example, overtorqueing a component that has threads can lead to damaged threads or stripped threads.
The efficiency of a torque limiting wrench is affected by the mechanics of the torque limiting wrench. It is important in the design of a torque limiting wrench that the mechanics are designed so that the functionality is not affected by the number of uses, environment in which the torque limiting wrench will be used or environments in which the torque limiting wrench will be subjected to. Torque limiting wrenches used with medical devices are often required to be subjected to a sterilization process. For many applications, the sterilization process comprises an autoclave. The sterilization process subjects the components of the torque limiting wrench to increased wear and tear. The integrity of any lubricants or parts that require lubricants may be compromised in the sterilization process.
Medical devices are often delicate, precise and sensitive instruments. The functionality and reliability of a medical device may be dependent upon all components of the medical device being fastened properly, all components of the medical device being tightened to the correct torque limit, and the surface conditions being devoid of scratches, burrs, nicks or other surface residue. These conditions allow the medical device to be tuned properly.
Use of a torque limiting wrench often requires that a part of the torque limiting wrench engage a component of the device that is to be tightened. In other cases, there is not direct contact between a part of the torque limiting wrench and the device that is to be tightened. In the case where a part of the torque limiting wrench physically contacts a component of the device that is to be tightened, the contacting part of the torque limiting wrench must not alter the surface conditions of the device that is being tightened. Some altering of the surface conditions of the device being tightened include, but are not limited to, scratching, nicking, burring or leaving residue on the surface of the device being tightened.
There have been several attempts in the prior art for providing a device that prevents overtightening of components. Many prior art devices are complicated, bulky and can adversely affect the components that are being tightened. Many of the prior art devices utilize external power sources and various lubricants in the mechanics and require that the torque limiting wrench move over the component to be tightened. Some prior art devices utilize external mechanisms to physically contact the component that is being tightened.
U.S. Pat. No. 3,955,662 to Thackston discloses a power tool having an adjustable torque-limiting coupling and a shut off means. The torque responsive coupling operates in response to a selected torque load to stop the driving connection between a driving member and a driven member. The power tool has a unit that couples a driving shaft to a driven shaft by means of a coil of variable cross section, with the release force a direct function of the cross sectional area of the coil that overlies the interface between the driving and driven members. The power tool uses a fluid motor with materials that would not be able to withstand a sterilization process that includes an autoclave. The power tool is expensive, complicated, large, requires an air power supply and has a fluid in the motor. It can be costly, difficult and cumbersome to provide pneumatic lines to environments where the power tool is to be used. The power tool requires that the power tool be moved over the component to be tightened and can alter the surface conditions of the component to be tightened. Altering the surface conditions of the component to be tightened can damage the component and adversely affect the functionality of the component. Since medical devices are sensitive instruments that require precise and accurate tightening and must be devoid of scratches, burrs, nicks or other surface residue, the power tool could not be used to tighten a medical device. Therefore, a need remains in the art for an apparatus and method of transmitting torque of a predetermined value to a component, the apparatus and method of which is compact, not complicated, does not require external power sources, moves on and off of the device to be tightened, comprises materials that will withstand an autoclave operation, does not damage and/or affect the device to be tightened and can be used on a medical device.
U.S. Pat. No. 5,467,674 to Thorn discloses a combined part marking and force limiting device. The Thorn device has a marking mechanism that marks a part when the part has been manipulated to a desired torque level. The Thorn mechanism includes a force applying handle, a housing pivotally mounted to the handle and a part-marking mechanism mounted within the housing. The force applying handle moves a linkage arm, which moves a pivotable cam to allow for the part marking mechanism to mark the part. The Thorn device is complex and uses a complicated method of tightening the component. The use of a part marking mechanism to physically contact a part and apply a liquid mark to a part can lead to undesirable effects of the surface of the part being manipulated and may affect the functionality of the part. Since medical devices are sensitive instruments that require precise, accurate tightening and must be devoid of scratches, burrs, deformations, nicks or other surface residue, the Thorn device could not be used to tighten a medical device. The Thorn device requires that the wrench be moved over the component to be tightened. Often times it is impossible or inconvenient to move a wrench over the component to be tightened. Therefore, a need remains in the art for an apparatus and method of transmitting torque of a predetermined value to a component that is simple, compact, moves on and off of the device to be tightened, does not leave a residue on a part to be tightened, does not damage and/or affect the functionality of the part to be tightened and can be used on a medical device.
U.S. Pat. No. 4,572,041 to Rissmann discloses a wrench wherein the force is limited to a set value. The Rissmann wrench has an input member and an output member coupled to each other, with the coupling formed by a collar on the input member with a plurality of axially directed, circumferentially disposed catches and a plurality of spring rods associated with each catch. The spring rods are bent outwardly by the flanks of the catches and out of the range of the catches once a force is reached. The Rissmann wrench has a head comprised of a hollow hexagonal member which receives the hexagonal head of the element to be tightened. The Rissmann wrench comprises catches and spring rods and the interactions of the catches and spring rods

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