Magnetic torque-limiting device and method

Abstract

In a torque-limiting device, a first end engages a fastener, a second end receives an applied torque, and a magnetic torque limiter transmits the applied torque from the second end to the first end to rotate the first end in conjunction with the second end when the applied torque is less than a predetermined limit.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority to U.S. Provisional Patent Application Ser. No. 60 / 799,650, filed on May 12, 2006, titled “MAGNETIC TORQUE LIMITING DEVICE AND METHOD,” the disclosure of which is incorporated herein by reference in its entirety.FIELD OF THE INVENTION[0002]The present invention generally relates to a magnetic torque-limiting device and method. More particularly, the present invention pertains to a device and method for limiting an amount of torque applied by the device.BACKGROUND OF THE INVENTION[0003]In various manufacturing, construction, and medical industries, fasteners are utilized that are threaded or screwed into place. These fasteners may include a predetermined amount of torque that has been determined to be optimal for a given fastening situation. In addition, the fastener may include a predetermined amount of torque that has been determined to fatigue or break the fastener. Often, these predetermined torque valu...

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Benefits of technology

[0012]Yet another embodiment of the present invention relates to a torque-limiting device. The torque-limiting device includes a shaft, first magnetic assembly, housing and second magnetic assembly. The shaft includes a distal end to engage a fastener and a proximal end. The first magnetic assembly is secured to the proximal end. The first magnetic assembly includes a first plurality of magnets. Each one of the first plurality of magnets has a North side adjacent to a South side of another one of the first plurality of magnets. The housing is pivotally secured to the proximal end. The housing includes an outer surface to receive an applied torque. The second magnetic assembly is secured to the housing. The second magnetic assembly includes a second plurality of magnets. Each one of the second plurality of magnets having a North side adjacent to a South side of another one of the second plurality of magnets. Each of the North and South sides of the second magnetic assembly is juxtaposed in attractive cooperative alignment with respective opposite South and North sides, respectively of, the first magnetic assembly to generate an array of attractive magnetic forces between the shaft and the housing.

[0013]Yet another embodiment of the present invention pertains to a torque-limiting device. The torque-limiting device includes a shaft, housing, first magnet, second magnet, first gear, and second gear. The shaft includes a distal end to engage a fastener and a proximal end. The shaft defines an axis of rotation along which a rotation vector is aligned towards the distal end. The housing is pivotally secured to the proximal end. The housing includes an outer surface and an inner surface. The inner surface includes at least a first toothed region having teeth protruding radially inwardly into the housing and at least a second toothed region having teeth protruding radially inwardly into the housing. The first magnet is disposed within the housing. The first magnet is secured to the proximal end. The first magnet includes a first toothed carrier. The second magnet is juxtaposed in attractive cooperative alignment with the first magnet. The second magnet includes a second toothed carrier. The first magnet is aligned with the second magnet with an attractive magnetic force between them. The first gear is pivotally secured to the proximal end. The first gear has teeth to engage the first toothed region and the first toothed carrier. A clockwise external torque applied to the outer surface urges the first toothed region to engage the first gear and clockwise rotate the first gear. The clockwise urging of the first gear urges the first magnet to laterally slide out of alignment with the second magnet. The second gear is pivotally secured to the proximal end. The second gear has teeth to engage the second toothed region and the second toothed carrier. The clockwise external torque applied to the outer surface urges the second toothed region to engage the second gear and clockwise rotate the second gear. The clockwise urging of the second gear urges the second magnet to laterally slide out of alignment with the first magnet and wherein rotation of the housing relative to the shaft is impeded until the first magnet and the second magnet laterally slide past each other by exceeding the attractive magnetic force between them.

[0014]Yet another embodiment of the present invention relates to a torque-limiting device. The torque-limiting device includes a shaft, housing, first magnet, second magnet and lever. The shaft includes a distal end to engage a fastener and a proximal end. The shaft defines an axis of rotation along which a rotation vector is aligned towards the distal end. The housing is pivotally secured to the proximal end. The housing includes an outer surface and an inner surface. The inner surface includes at least one lug protruding radially inwardly into the housing. The first magnet is disposed within the housing. The first magnet is secured to the proximal end. The second magnet is slidably secured to the proximal end and juxtaposed in attractive cooperative alignment with the first magnet. The second magnet includes a magnet bearing surface. The first magnet is urg

Problems solved by technology

In addition, the fastener may include a predetermined amount of torque that has been determined to fatigue or break the fastener.

Unfortunately, as components within these conventional torque-limiting devices slide by one another, wear may alter the torque setting of the conventional torque-limiting device.

This could lead to over-torqueing, an unsafe condition.

An additional aspect of conventional torque-limiting devices is that the torque-limiting event occurs through the same axis as the tool shaft thereby sending shock waves along the tool axis and into the fastener.

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