Chucks or sockets – Socket type – Radially reciprocating jaws
Reexamination Certificate
2000-05-16
2001-08-07
Bishop, Steven C. (Department: 3722)
Chucks or sockets
Socket type
Radially reciprocating jaws
C408S226000, C408S23900A, C433S128000, C606S079000
Reexamination Certificate
active
06270087
ABSTRACT:
BACKGROUND
FIELD OF THE INVENTION
The invention relates to methods and apparatus for reversibly coupling rotating shafts.
Coupling Tools to High-Speed Motors
Many types of rotary tools are preferably coupled to a driving shaft with a safe and reliable coupler which is also reversible (allowing for the rapid removal of a tool from the coupling and/or the coupling of one tool in place of another to a driving shaft). Applications in which there are particularly stringent safety and reliability requirements for couplers include the drilling, grinding, polishing and related material-removal operations which are inherent in many medical and dental treatment plans. Rotary tools (e.g., drills, burs, grinding wheels and cutting wheels) reversibly coupled to high-speed motors can precisely shape tooth, bone, or biocompatible implant material during certain surgical procedures. Such shaping operations often require precise tool positioning and as many as thirty tool changes in the course of a single operation. Thus, each rotating tool shaft would preferably be lockable securely into its coupler (i.e., substantially preventing its accidental disconnection from the coupler), but the lock would preferably be easily and surely reversed to allow tool insertion or removal or tool changes.
Surgical applications of a tool shaft coupler include a requirement to keep the total time under anesthesia as short as possible for each patient. Thus, connecting and disconnecting tools via a reversibly locking tool shaft coupler should preferably be quick and simple, even for a person wearing surgical gloves. Required motions to lock or unlock the connector, or to insert or remove a tool should be relatively uncomplicated. Further, because tools may reach rotational speeds in excess of 20,000 revolutions per minute, positive (and separate) indications would preferably be provided to clearly signify to a human operator either improper placement of a tool shaft within a coupler or inoperability of a coupler shaft lock. Moreover, once connected, a tool shaft and tool shaft coupler should not be subject to accidental unlocking (which could allow disconnection of the tool), either due to operator error or mechanical failure. Thus, a tool shaft coupler lock release mechanism would preferably comprise a separate coupler unlocking component which would be required to release the lock but which would normally be removed before the motor applies torque to the tool. Accidental failure of the operator to remove the unlocking component should not, however, pose a safety hazard during relatively brief operation of the motor. Further, accidental application of motor power to a tool shaft coupler during changing of a tool should not result in driving shaft rotation before the tool is securely locked in the coupler.
Tool shaft couplers should be capable of transmitting axial forces (i.e., tension or compression forces acting substantially parallel to the tool shaft longitudinal axis) alone or in combination with torque (i.e., rotational forces acting substantially about the tool shaft longitudinal axis). All such forces should be effectively transmitted, i.e., without substantial axial displacement of the tool shaft with respect to the driving shaft, without substantial rotational slippage of the driving shaft with respect to the tool shaft, and without substantial distortion of the driving shaft, tool shaft or coupler. Any tool shaft coupling failure leading to shaft displacement, deformation, distortion or slippage could lead to whipping of the tool shaft, increased vibration, tool overheating and/or tool shaft breakage. In turn, any of these events could lead to accidental uncoupling of the tool shaft from the driving shaft, leading to a risk of patient injury and possible difficulty in removing a damaged tool shaft from a coupler. These problems would be particularly acute in coupler and tool designs wherein both torque and axial forces are transmitted by substantially identical tool shaft surfaces. Hence, improved tool shaft couplers and mating tool shafts would comprise surfaces used to transmit torque which would preferably be different from those used to transmit axial forces. Even more preferably, at least some surfaces transmitting torque and axial forces would preferably be spaced apart to avoid or reduce potentially damaging stress concentrations within a tool shaft and/or driving shaft.
Additional sources of stress in tool and driving shafts or couplers are various vibration modes due, for example, to unbalance in couplers, tools and/or tool shafts. Vibration can also be induced by distortion of the shafts and non-concentricity of driving shafts, tool shafts and/or coupler components due to lateral and/or angular misalignment.
SUMMARY OF THE INVENTION
The invention comprises reversibly locking tool shaft couplers and mating tool shafts, and methods of using the couplers to drivingly couple a driving shaft and a mating tool shaft drivingly (effectively) engaged therewith. The couplers and mating tool shafts incorporate design improvements to enhance safety and ease of operation, and comprise surfaces and/or structures for drivingly coupling (i.e., for transmitting torque and axial forces between) a driving shaft and a mating tool shaft. Note that a driving shaft to which a tool shaft coupler of the present invention could be applied would be a driving shaft (substantially rigid or flexible) which is rotatable about a substantially longitudinal axis within a driving shaft housing. Note also that a mating tool shaft may comprise a portion of a tool itself (e.g., the shank of a drill bit or burr), or a shaft which itself is drivingly coupled with a tool shaft (e.g., a flexible or geared shaft tipped with a tool or coupled to a tool shaft).
A tool shaft coupler of the present invention comprises at least one torque transmission surface fixedly coupled to the driving shaft for axially slidingly mating with a mating tool shaft to transmit torque between the mating tool shaft and the driving shaft. Additionally, the coupler comprises at least one compression transmission surface as well as tension transmission means, the tension transmission means being spaced apart from the at least one compression transmission surface and the at least one torque transmission surface, and comprising at least one tension transmission surface and at least one movable tension-resisting member, the at least one tension-resisting member being reversibly and slidingly movable to a tension-resisting position to couple the driving shaft and a mating tool shaft to reversibly limit maximum axial movement of the mating tool shaft with respect to the driving shaft under an axial tension load (i.e., a force substantially parallel to the tool shaft longitudinal axis which tends to pull the driving and mating tool shafts apart).
The at least one compression transmission surface is fixedly coupled to the driving shaft for substantially limiting maximum axial movement of a mating tool shaft with respect to the driving shaft under an axial compression load. For reversibly locking said at least one tension-resisting member in a tension-resisting position, the invention comprises shaft locking means having an (optionally high-friction and/or mechanically engaging) engagement surface (for slidably engaging safety lock release means), the shaft locking means being slidably coupled to the driving shaft. The slidable coupling of the shaft locking means to the drive shaft may also include guide means which act to substantially prevent rotation of the shaft locking means with respect to the drive shaft while allowing substantially free sliding coupling as described herein.
Preferred embodiments of tool shaft couplers of the present invention may also comprise substantially toroidal safety lock release means and attachment means, the attachment means being reversibly coupled (e.g., as be screw threads or a twist-lock connector) to the driving shaft housing and serving one or more functions, as in guiding a mating tool shaft during connection to or disconnecti
Mickel Thomas J.
Willason Stewart W.
Bishop Steven C.
Mednext Inc.
Woodard Emhardt Naughton Moriarty & McNett
LandOfFree
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