Patent Application
20070102175
Not applicable
Not applicable
This invention relates to a surgical motor used for sawing and the like and includes mechanism for converting rotary motion to linear motion. In particular, this invention is characterized as utilizing a drive shaft and eccentric shaft that are parallel to the driven shaft.
There are a sundry of motor mechanisms in the medical field as well as the construction field that are designed to convert rotary motion to linear or rectilinear motion necessary to operate a motorized saw. The mechanism for making the conversion in both the medical and non-medical field typically use a wobble plate or an angularly mounted drive shaft that converts the rotary motion of the motor to the linear motion necessary to power the saw blade. While such mechanism are generally efficient, they have the propensity of wearing prematurely and inducing a great deal of vibratory motion. Obviously, the reciprocating electric saw used for non-medical purposes need not concern itself over the vibratory motion, size and feel of the mechanism. On the other hand these conditions and characteristics of the non-medical saws are far different than the parameters necessary for the power saws utilized by surgeons. In accordance with this invention, we have provided conversion mechanism that is characterized as providing less vibrations and noise hereto known in both the prior art medical power saws and commercial power saws. We have found that by virtue of this invention the power saw enhances the feel of the motor in the hands of a surgeon, is small and light weight and has an increased life. It is quite apparent that a motor that generates less noise and vibration provides an improved feel in the hands of a surgeon who typically is performing intricate work during the surgical procedure performed on a patient. Of course, in the interest of economy it is abundantly important to increase the useable life of the motor.
U.S. Pat. No. 5,555,626 granted to Fuchs on Sep. 17, 1996 entitled RECIPROCATING DRIVE MECHANISM exemplifies a motion conversion motor that utilizes a wobble plate which as is typical in these designs uses an angularly or oblique angle mechanism disposed shaft between the driving and driven members. Such devices are capable of being hand held and are portable.
Saws for medical purposes are exemplified in U.S. Pat. Nos. 4,827,615, 5,916,218, 5,606,603, and 6,302,406 granted to Graham on May 9, 1989, entitled MICROSURGERY SAW DRIVE, granted to Hagen et al on Jun. 29, 1999 entitled SAW FOR SURGICAL PURPOSES, granted to Linden on Mar. 11, 1997 entitled SURGICAL CUTTING DEVICE WITH SAFETY INTERLOCK, granted to Ventura on Oct. 16, 2001 entitled CONNECTOR ASSEMBLY FOR A SURGICAL SAW BLADE. As in the teachings of these patents and the non-medical patents the mechanism for converting the rotary motion developed by the motor is obtain by mechanism that includes a member that is angularly disposed relative to the driving and or driven mechanism. We have found that the problem with the converting mechanism is that it adversely affects the life of the medical saw. Moreover, typically these heretofore known devices are prone to have vibrations in the handle and produce unwanted noise.
We have found that we can obviate the problems alluded to in the above paragraph by disposing the driving, driven and conversion mechanism parallel to each other. Not only has this arrangement shown to enhance the longevity of the instrument, it also provides an improved “feel” to the surgeon as it eliminates or reduces vibrations and eliminates or at least lowers the noise level.
An object of this invention is to provide an improved saw for use in medical procedures.
Another object of this invention is to provide mechanism that converts rotary motion to linear motion with the use of parallel shafts for a saw or other medical instrument and is characterized as reducing noise levels, reducing vibrations, is lighter in weight and increasing the useful life of the saw.
The foregoing and other features of the present invention will become more apparent from the following description and accompanying drawings.
This invention details, in the preferred embodiment, mechanism for converting rotary motion to linear motion for driving a saw used in medical procedures. While in the preferred embodiment the mechanism powers the saw in a rectilinear motion, as one skill in this art will appreciate, the actuating mechanism can be designed by relocating the cam and with minor changes to the structure to produce an oscillating motion for medical instruments where an up and down motion, rather than in and out motion is desired.
As best seen in
The lock adapter 14 is secured to the main body or casing 12 by the threaded bushing 32 that threaded to the inner surface enlarged bore 34 formed in the casing 12. The lock adapter carries flange 40 that extends outwardly toward the inner diameter of the enlarged bore portion 42 formed on the aft end of the casing 12. This flange is forced against the shoulder 42 and bears there against and is locked into position by the threaded bushing 32.
The stub shaft portion 50 is formed on fore end of the offset shaft 22 and is oriented eccentrically relative but parallel thereto. Bearing 52 is snugly fitted to the end of stub shaft 50 which in turn is mounted in the yoke 54 between the bifurcated arms 56 and 58. Yoke 54 is rotatably mounted to casing 12 by pin 60 that fits through the opposed drilled holes 62 formed in the casing 12 and is rotary supported by a pair of bearings 52 made from a ceramic material and includes roller or bushing 59 mounted therein. The yoke 54 carries a laterally extending projection 66 that serves as a cam as will be explained in detail herein below. Mechanically connected to the yoke 54 is the drum 68 that carries enlarged hollow portion 70 formed on the end thereof and may be formed integrally therewith or mechanically coupled thereto. Aperture 72 formed on the end of the enlarged portion 70 serves to receive the projection 66 and the dynamics of the system serves to convert the rotary motion of the offset shaft 22 to a linear motion of the drum 68 by virtue of the action between the rotary motion of bearing 52, yoke 54, projection 66 and drum 68. To assure a smooth transition from the rotary motion to the linear motion, the spherical ring 74 is fitted between the bearing 52 and arms 56 and 58 of yoke 54.
Drum 68 is supported to casing 12 by the linear bearing 76 which consists of a cylindrical cage 78 and a plurality of balls 80 fitted into predetermined holes 82. Obviously, the drum rides on the inner surface of the balls so as to effectually provide a smooth and efficient rectilinear motion. The collet 16 is threadably fitted on the end of drum 68 by virtue of the threads 84 formed on the drum 68 and the inner threads 86 formed on the aft end of collet nut 88. The fore end of drum 86 includes the axial slot 90 that serves to receive the removably mounted saw blade (not shown). The inner surface 92 of the collet nut 88 is conically shaped so that as the nut is threaded on the drum 84 in an aft direction, the end of the collet nut 88 drives the gap in the slot 90 toward a closed position, urging the surfaces of the slot 90 against the saw blade for securing the same to the drum for rectilinear movement. Snap ring 94 serves to prevent the collet nut 88 from inadvertently become dislodged by overturning the collet nut.
Pin 96 serves to orient the lock adapter 14 to casing 12 and fits into hole 98 in lock adapter 14 and the slot 100 formed on the inner surface of the casing 12. Retaining ring 102 serves to hold the linear bearing 76 securely in place in the casing 12 as does the snap rings 104 and 106 that support the offset shaft 22 in place.
In operation the rotary motion imparted to the offset shaft 22 is converted to linear motion of the drum 86 by virtue of the dynamics of the eccentric stub shaft driving the bearings and spherical ring against the arms 56 and 58 of the yoke 54 rotating the same about the pin 60.
The projection 66 of yoke 54 defines a cam that drives the drum 68 that defines the follower.
The back and forth motion of the cam essentially defines the linear motion that is ultimately carried to the collet 16. It will be appreciated that the offset shaft 22, the stub shaft 50, and drum 68 are all parallel to each other. It has been found that this arrangement not only effectively produces a surgical saw that has improved the operating life of those heretofore known surgical saws, but also operates with virtually no vibratory motion and noiseless which provides a better feel in the hands of the surgeon.
Although this invention has been shown and described with respect to detailed embodiments thereof, it will be appreciated and understood by those skilled in the art that various changes in form and detail thereof may be made without departing from the spirit and scope of the disclosed invention.
