Surgical Air Drill

Abstract

An improved surgical air drill having a novel, detachable hand piece assembly with an integral cutting burr. The hand piece is interchangeable with others having different burrs or cutting heads and may be removed and replaced while the drill motor is operating at full speed. The particular configuration of the coupling between the motor and the hand piece permits such interchanging to be accomplished with ease while assuring that the burr remains axially true.

Description

FIELD OF THE INVENTION

This invention relates in general to tools operated by rotary air driven motors and more particularly concerns a novel surgical air drill having interchangeable hand piece assemblies which include integral burrs, bearings and couplings.

DISCUSSION OF THE PRIOR ART

Tools of many types employing air driven rotary motors are currently available. They are widely used for dentists' drills and have been used to some extent in the field of surgery, primarily for bone cutting and shaping.

Surgical drills normally use a larger and more powerful motor together with a larger cutting tool or burr than is normal with dental drills. Furthermore, due to the locations which must be reached by the operating cutter head of the surgical drill it is often necessary that the cutting head be spaced a significant distance from the handle which normally contains the air motor. Burrs of many different shapes and sizes are likely to be needed, even during a single operation and it is thus necessary to provide for ready interchangeability of the cutting tools. It is also necessary to maintain the burr and its shaft absolutely axially true so that the cutting head remains centered without any tendency to deviate during operation in order to provide the precision required for delicate surgical procedures.

Many of the prior art devices have provided an interchangeable cutting tool which has a shank for removable engagement by some type of chuck coupled to the motor. Other such instruments have an interchangeable outboard support where extra length is necessary. In such a device, an elongated tool shank is supported near its outer end by a bearing in the outboard support and the inner end is supported in the normal manner by a chuck coupled to the air motor. It may be appreciated that most known types of chucks are somewhat flexible and often will permit the burr to rotate slightly offcenter, particularly when a sideward force is applied, as when the burr is in actual surgical use. Furthermore, with an elongated cutting tool of the type which must employ an outboard support, it is not unlikely that the shank of the cutting tool could become longitudinally warped to some small degree, thereby causing the burr to generate a small circle, somewhat larger than its own diameter, as it rotates. This, of course, would normally be unacceptable for surgical or any other precision use.

It is a primary object of this invention to provide an interchangeable hand piece assembly which not only supports its integrally constructed cutting head in truly centered fashion, but may be interchanged even while the air motor is operating at full speed.

SUMMARY OF THE INVENTION

This invention generally concerns an improved surgical instrument powered by an air motor and having an interchangeable hand piece and cutting head assembly. A splined shaft, which is coupled to and rotates with the air motor, has an interior splined sleeve secured to its forward end. The hand piece also includes a splined shaft configured to mate with the interior splines of the sleeve. The end of the sleeve and the splined end of the hand piece shaft are configured so as to mate the respective splined elements easily and positively, even while the motor is rotating. The cutting tool which comprises a burr and a shank is secured to the hand piece shaft in a semi-permanent manner such as by brazing and at least two sets of bearings are provided in the assembly to insure that the burr remains truly centered at all times. While the hand piece may have different lengths, the shank of the burr is short to avoid the possibility of lateral deformation.

An advantage of this device is that even though the burr is operating at full speed, the outboard assembly may be removed and another one inserted in its place within a very few seconds without the need of stopping the air motor. This enables the surgeon to maintain a preferred speed setting for the air motor and at the same time change to different burrs as necessary.

BRIEF DESCRIPTION OF THE DRAWING

The objects, features and advantages of this invention will become more clearly evident from the following detailed description when taken in conjunction with the accompanying drawing in which:

FIG. 1 is a perspective view of a fully assembled surgical instrument constructed in accordance with this invention;

FIG. 2 is an enlarged broken away exploded perspective of the coupling used in the instrument of FIG. 1; and

FIG. 3 is a sectional view of the hand piece and the forward end of the housing constructed in accordance with this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference now to the drawing there is shown in FIG. 1 a surgical instrument 11 having a main housing 12 enclosing a conventional air motor (not shown) powered by air supplied through tube 13. Hand piece 14 with its integrally constructed burr 16 is shown attached to the forward end of the main housing 12. By opening appropriate valves (not shown) the air supplied through tube 13 causes the motor within housing 12 to rotate, the speed normally being variably controllable. A shaft within hand piece assembly 14 is coupled between the motor and shank 15 for rotation of burr 16 as necessary for use by the operator.

The operative coupling between the air motor and the hand piece is shown in detail in FIG. 2. Within housing 12 is shaft 17 which is directly coupled to the air motor. The forward end of shaft 17 is formed with splines 21. Sleeve 22 having an interior splined surface 23 configured to mate with splines 21 is secured to the end of shaft 17 by conventional means such as pin or screw 24. This sleeve rotates with shaft 17 and is firmly fixed thereto. The forward end of sleeve 22 is formed with surfaces or lands 25 separated by arcuate cutouts 26. The purpose of this configuration will become apparent from the detailed description hereinbelow of the hand piece shaft.

The rearward end of shaft 27 in hand piece 14 is also formed with a splined outer surface 31, similar to that of shaft 17. These splines are configured to mate with the splined configuration of sleeve 22. The rearward end of shaft 27 is formed with radially arranged wedge-shaped ridges 32 separated by radial grooves 33. If sleeve 22 and shaft 27 are aligned properly when they are brought together, the outwardly projecting splines 34 on shaft 27 will mate with the outwardly projecting grooves 35 in the inner surface of sleeve 22. However, it is not possible to always have the shafts in such perfect coupling alignment and it is manifestly impossible if shaft 17 is rotating. To accommodate this fact the particular end configurations of shaft 27 and sleeve 22 have been devised. If outwardly projecting splines 34 are aligned with inwardly projecting splines 36 in sleeve 22, ridges 32 will abut surfaces 25 on the forward end of the sleeve. If shaft 17 is rotating, ridges 32 will very quickly drop off the adjacent edge of surface 25 in the vicinity of arcuate cutouts 26. However, when this occurs splines 34 are in alignment with grooves 35 and shaft 27 may then enter and become rotatably coupled with sleeve 22 and shaft 17. It will be observed that with the tapered shape of ridges 32 on the end of shaft 27, a force urging the hand piece and main housing together will cause these ridges to immediately drop between surfaces 25 when they are in alignment with grooves 35. The particular configuration of the rearward end of hand piece 14 and the forward end of housing 12 facilitates this coupling as will become apparent from the further description hereinbelow.

The hand piece assembly 14 is shown in detail in FIG. 3. Housing 41 is formed with internal threads 42 at its rearward end for coupling with correspondingly threaded connector 43. Sleeve 44 is secured within the forward end of housing 41 and in turn retains forward cone 45. These elements may be secured together by any appropriate means. Anti-friction bearing 46 is mounted within the forward end of sleeve 44 adjacent cone 45. A rearward facing shoulder 47 provides a seat for the forward end of the beaing while an internal taper 51 is provided within sleeve 44 to maintain the bearing at its proper location. It should be noted that the bearing could be maintained in its position by means of retaining rings at either end thereof if desired rather than using the particular structure shown.

Shaft 27, having rearward splined end 31 and forward end 52 of reduced diameter, is rotatably mounted within hand piece 14. The forward end of the shaft terminates adjacent the forward end of the hand piece and has a bore 53 for receiving shank 15 of the cutting tool. This particular configuration permits shank 15 to be relatively short compared with the total length of the hand piece and cutting tool and therefore less likely to become axially misaligned than would a cutting tool having a longer shaft. The tool shank is secured within end 52 of the hand piece shaft by any suitable means such as brazing or sweating and is centered and trued when so assembled. The rearward end of shaft 27 is centered by means of anti-friction bearing 54 which is retained in place on the shaft by retaining rings 55 and 56. The shaft and bearing are prevented from moving rearwardly beyond their normal position as shown by means of shoulder 57 in connector 43. Rearward facing shoulder 61 within housing 41 and located forward of threads 42 provides a seat for spring retaining ring 62. Compression spring 63 is provided between ring 62 and bearing 54 and thereby biases shaft 27 rearwardly.

The forward end of air motor housing 12 is provided with tapered entry 64 and the rearward end of connector 43 is formed with bevel 65 to facilitate entry of the connector into the main housing. When the connector is fully inserted, locking ring 66 engages bevel 67 within the main housing and removably retains the hand piece in place. The inner diameter of the forward end of housing 12 is slightly larger than the outer diameter of connector 43 to permit free entry and rotation of the connector. Bevel 68 is provided on connector 43 to seat on tapered entry 64. Through the action of locking ring 66, connector 43 is thus seated tightly against housing 12 to assure that the cutting head maintains its axial alignment while permitting the hand piece to swivel freely. This swivelling feature is important because the surgeon must manipulate the instrument at various angles during an operation. By permitting such relative rotation, he does not have to be concerned with the angle and direction at which the hose connects to the instrument because it will always tend toward one orientation from the work area. Another advantage of this feature is that no rotational alignment is necessary when the hand piece and main housing are assembled.

As previously described, splined end 31 of the hand piece shaft enters sleeve 22 so that the main shaft 17 and the hand piece shaft 27 are caused to rotate together. Spring 63 is provided to facilitate engagement of the two shafts when the motor is rotating. It will be appreciated that with sleeve 22 rotating very rapidly and shaft 27 not rotating, a perfect match is not likely immediately upon insertion of the hand piece into the main housing. In this manner, when ridges 32 of the rearward end of shaft 27 make initial engagement with the rotating sleeve, it is likely that the hand piece shaft will lag slightly the rearward motion of the hand piece housing, thereby compressing spring 63. However, under the continuous biasing effect of the spring, shaft 27 is urged rearwardly and will very quickly mate properly with sleeve 22. It is of course possible to secure the sleeve to the hand piece shaft and reverse the coupling configuration if desired.

It will now be appreciated how this instrument provides a much more convenient means for exchanging cutting burrs during surgery. Because the burrs have short shafts and are mounted to the hand piece as an integral part thereof they remain centered indefinitely. This structure eliminates the need for a flexible chuck which could permit the burr to stray from its true axis of rotation. Furthermore, the ability to remove a hand piece and insert another within seconds while the motor is operating at the desired speed is a significant advantage during surgery. The high speed connection is further facilitated by the fact that the air motor has a very low rotational inertia thereby permitting its speed to momentarily change upon contacting the hand piece shaft and facilitating the desired coupling. It is also possible to replace a worn burr in a hand piece. Since this would be a factory type service, centering would be accomplished anew at that time, so that the user always has a trued integral hand piece and burr.

In light of the above description it is likely that changes and improvements will occur to those skilled in the art which are within the scope of this invention.

Claims

What is claimed is:

1. A rotary surgical instrument comprising:

a main housing having an air motor mounted therewithin;

means for supplying air under pressure to said motor to cause controlled rotation thereof;

a forwardly extending shaft coupled to said air motor for rotation therewith;

a hand piece removably coupled to said main housing, said hand piece comprising;

a housing;

a shaft rotatably mounted within said hand piece housing; and

a cutting tool having a shaft secured to the forward end of said hand piece shaft for rotation therewith; and

means for removably coupling said hand piece shaft to said air motor shaft for rotation together of said shafts;

said coupling means comprising a sleeve secured to the forward end of said air motor shaft for receiving the rearward end of said hand piece shaft, the forward end of said air motor shaft and the rearward end of said hand piece shaft having similarly splined external surfaces, the internal surface of said sleeve having mating splines;

the forward end of said sleeve being formed with lands at the ends of the inwardly projecting ridges of said splined surface and depressions between said lands at the ends of the grooves between said ridges;

the rearward end of said hand piece shaft being formed with radial ridges at the ends of the outwardly projecting splines and depressions between said ridges at the ends of the grooves between said splines.