The present invention relates generally to drivers that apply up to a predetermined torque to a device, such as a screw or bolt.
There are many torque limiting devices in the marketplace today, including the medical and automotive industries. Torque limiting wrenches, for example, are used in many different applications to adjust various components including, but not limited to, bolts and fasteners to a specified torque. Such a device can be important to prevent over-torquing.
Torque limiting wrenches used with medical devices are designed to be used multiple times, with re-sterilization after each use. The sterilization process subjects the wrench's components to increased wear and tear. Moreover, re-sterilization causes the accuracy of the device to decrease; thus, hospitals (and other health care providers) continually send instruments to manufacturers for recalibration.
Therefore, there is a need for a novel torque limiting device that overcomes these issues.
According to one aspect, the invention provides a torque limiting driver for applying up to a maximum torque to an associated driven member. In one embodiment, the driver includes first and second rotatable members with proximal and distal ends. A torque limiting assembly may be operatively coupling the distal end of the first rotatable member with the proximal end of the second rotatable member. The torque limiting assembly may include a plurality of torque limiting devices that are arranged to sequentially uncouple the second rotatable member from a torque load applied to the first rotatable member when the torque load exceeds the preselected maximum torque.
In some embodiments, the proximal end of the first rotatable member and/or the distal end of the second rotatable member includes a quick connect fastening portion. For example, the quick connect fastening portion could include an opening dimensioned to receive an external device. In some cases, an interference member could be disposed within the opening to frictionally engage the external device. Embodiments are contemplated in which the torque limiting assembly could include a frangible member that is configured to release the second rotatable member from a torque load applied to the first rotatable member when the torque load exceeds the preselected maximum torque. For example, the frangible member could be a shear pin.
According to another aspect, the invention provides a method for driving a device in a torque limited manner. The method includes the step of providing a torque limiting driver having a torque limiting assembly operatively coupling a first rotatable member with a second rotatable member. The torque limiting assembly could include a frangible portion that is configured to shear when a preselected maximum torque is applied to the first rotatable member. Another step could be applying a torque load to the first rotatable member. In response to the torque load on the first rotatable member exceeding the preselected maximum torque, the method includes the step of releasing the second rotatable member from the torque load applied to the first rotatable member by breaking the frangible member.
According to a further aspect, the invention provides a kit for use by a health care provider. In this embodiment, the kit includes at least one medical device. A single-use torque limiting driver is also provided that has an end adapted to be coupled with the medical device. Typically, the single-use torque limiting driver is capable of transferring torque to the medical device up to a preselected maximum torque. For purposes of example only, the health care provider could drive the single-use torque limiting device up to the maximum torque a certain number of times during a medical procedure and then dispose of the single-use torque limiting driver.
Additional features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrated embodiment exemplifying the best mode of carrying out the invention as presently perceived. It is intended that all such additional features and advantages be included within this description and be within the scope of the invention.
The present disclosure will be described hereafter with reference to the attached drawings which are given as non-limiting examples only, in which:
Corresponding reference characters indicate corresponding parts throughout the several views. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principals of the invention. The exemplification set out herein illustrates embodiments of the invention, and such exemplification is not to be construed as limiting the scope of the invention in any manner.
While the concepts of the present disclosure are susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the concepts of the present disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure.
In the embodiment shown, referring now to
As shown, the second end 28 of the input member 12 terminates with a fastener 40 (
In the example shown, a plurality of shear pins 14 are disposed in the pin retaining member 18. Although this example shows six shear pins 14 for purposes of example, there could be less shear pins 14 or more shear pins 14. The number of shear pins 14 could be chosen depending on the number of times that the torque limiting driver 10 is configured to reach its maximum torque. As discussed below, a single shear pin 14 shears each time the torque limiting driver reaches the maximum torque in one embodiment. Consider a medical procedure in which six bone screws were intended to be used. In this embodiment, a shear pin 14 would shear each time a bone screw is screwed into the maximum torque. At the end of this example procedure with six bone screws, each of the shear pins 14 would have sheared. Accordingly, after each shear pin 14 has sheared, the torque limiting driver 10 could be disposed of, which would eliminate the need for re-sterilization and recalibration of the torque limiting driver 10. Alternatively, embodiments are contemplated in which a new set of shear pins 14 could be loaded into the pin retaining member 18. For example, pins could be loaded similar to a revolver. Rotate the revolver and load one pin, break pin, and then rotate revolver to load a new pin. Other embodiments contemplate shear pins extending radially from circumferential slots into another structure that shears the pins upon reaching the desired torque. Embodiments are also contemplated in which other devices could be used to sequentially release a torque load between the input assembly and the output member without shearing any pins, including teeth and magnets.
As shown, the shear pins 14 include a head portion 44 and a pin portion 46. In this embodiment the head portion 44 is sized to be substantially tightly-fit between the second end 28 of the input member 12 and an interior surface 48 of the pin retaining member 18 (as best seen in
As best seen in
Other embodiments are contemplated for limiting the maximum torque for the torque limiting driver 10. For example, a single pin (longer than those shown in the drawings) could be spring loaded within the input assembly. Once the housing assembly is fit together, then the input member 12 would be rotated until the pin snapped into a bottom hole in the output member 20. The pin would be sheared, thus resulting in a pre-selected amount of torque. The input member 12 could be rotated until the pin drops into another hole and then the pin would be sheared again upon reaching the maximum torque. This procedure would be repeated using up the remainder of the pin and filling all holes with pin fragments. The breaking of the pin would be accomplished by a consistent force which would be dependent on pin geometry and diameter of rotation among other factors.
In another embodiment, the maximum torque could be established using the pull of magnets to determine a constant force. Breaking of magnetism would be accomplished at a consistent torque. For example, different size of magnets could be used depending on what torque needs to be accomplished.
In another embodiment, teeth similar to a ratchet-like device could be used to establish the maximum torque. For example, it would take a certain amount of torque to get up the incline of the teeth, thus resulting in a consistent torque. The teeth could be made in either direction and there would be no clockwise turning and then inadvertent counterclockwise turning in the process. In another embodiment, the gear teeth could be vertical with a pin backed by a spring and set screw (or all of this could be in the form of a ball plunger) to create a variable piece that engages the teeth. The torque could be adjusted by tweaking the spring via the set screw.
Referring again to
In the embodiment shown, the housing assembly is a clam-shell style design. In some embodiments, the housing assembly could be formed from plastic or metal (such as stainless steel). As shown, the first housing member includes hooks 60 that are received in slots (not shown) in the second housing member 24.
An embodiment shown in
Consider an example operation of the torque limiting driver 10 during a surgery in which six bone screws are intended to be secured at a predetermined torque. The surgeon could receive a kit with six bone screws, along with the torque limiting driver 10 configured with a preselected torque for the bore screws to be used during the surgery. In this example with six bore screws to be attached, the torque limiting driver 10 could include six shear pins 14. The surgeon would typically attach a medical instrument to the fastener portion 30, such as a handle. As discussed above, this could be with the use of the quick connect mechanism described with respect to
Although the present disclosure has been described with reference to particular means, materials, and embodiments, from the foregoing description, one skilled in the art can easily ascertain the essential characteristics of the invention and various changes and modifications may be made to adapt the various uses and characteristics without departing from the spirit and scope of the invention.
The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/109,539, filed on Oct. 30, 2008, the entire disclosure of which is hereby incorporated by reference.
Number | Date | Country | |
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61109539 | Oct 2008 | US |