Pneumatic Motor For Medical Instruments

Abstract

The invention relates to a small pneumatic motor for a rotating medical instrument, especially for drilling or milling instruments. A shaft with a turbine is supported in a housing with the gas inlet end of the turbine arranged towards the output end of the motor. The driving gas flows to the turbine inlet side via channels arranged longitudinally in the housing along the periphery of the turbine and then back to the input end of the housing. Discharge of driving gas at the output end of the housing toward the patient is avoided in this way.

Description

BACKGROUND OF THE INVENTION

The invention relates to a hand-actuated pneumatic motor for a drilling and/or milling instrument for medical application. It relates especially to a small turbine used for driving a precision drilling or precision milling instrument. The speed of such precision drill or precision milling instrument is very high. It is possible, for instance, with such motor driven precision drilling instruments or precision milling instruments to impart to the instrument shaft a speed of about 100,000 rpm without a speed transmission gear being arranged between the turbine and the shaft. With known turbine-driven precision drilling or milling instruments the air discharged from the turbine leaves the cylindrical housing on the side of the rotating instrument which, in the case of operations with open wounds increases the danger of infection. Another danger existing additionally is that of an air emboly. The use of nitrogen instead of air as a driving fluid does not completely eliminate this danger and suffers from additional shortcomings.

Also, precision drilling instruments and precision milling instruments have become known which are not driven by means of a compressed air driven turbine but by means of a compressed air driven piston sickle motor, the pistons of which consist of individual discs rotating eccentrically with respect to the axis of rotation. With such piston motor driven precision drilling instruments or precision milling instruments it is possible to supply and to discharge the air at the drive end of the housing, i.e. to the end facing away from the tool. Such compressed-air motors, however, in case of high speeds tend to produce disturbing noises. In addition, with such motors the fineness of the work is not guaranteed under all conditions. Finally, such compressed air motors develop a higher torque than compressed-air turbines which might induce the doctor to demand a higher torque by exerting a pressure on the drill or the milling instrument which might impair the precision of the work.

SUMMARY OF THE INVENTION

It is the object of the invention to provide a turbine driven rotating instrument for medical application in which the gas leaving the turbine is discharged away from the area of the instrument.

The hand operated pneumatic motor for a drilling or milling instrument comprises a cylindrical housing, a shaft supported in the housing and projecting from one front side thereof and a compressed gas driven turbine adapted to drive the shaft.

In accordance with the invention the compressed gas is supplied and discharged at the end (input end) of the housing facing away from the shaft projecting end (output end) with the fluid gas inlet end of the turbine facing toward the output end of the housing and the fluid gas exit end of the turbine facing toward the input end of the housing, and the compressed gas is supplied to the inlet end of the turbine through channels arranged along the outer periphery of the turbine.

Thus, the flow direction of the compressed air is reversed within the housing. The compressed air flows from the input end of the housing toward the output end thereof until it approximately arrives at the inlet nozzles of the turbine. Within the turbine the air flows in the opposite direction to the exit end of the turbine which is arranged towards the input end of the housing.

Small amounts of air might still escape at the inlet end of the turbine towards the tool because the air at the exit from the nozzles, i.e. directly before entering the blades of the turbine rotor, is subjected to an impact pressure, i.e. a certain overpressure which might drive small amounts of air through the output end towards the instrument. Here it must be taken into consideration that a certain running clearance must necessarily be provided between the exit end of the nozzles and the inlet end of the blades of the turbine rotor.

To avoid also the exit of these small amounts of air, the nozzle member with the nozzles is provided with a bushing extending towards the turbine exit end, said bushing having a small running clearances with both the instrument shaft and the turbine rotor. These small running clearances constitute additional flow resistance which prevent these small amounts of air from escaping at the output end of the housing towards the instrument. The suction effect of the gaseous jet leaving the nozzles is so great that even a vacuum is formed which draws in a certain amount of air from the output end of the housing and drives it through the turbine to the turbine exit end.

The invention in addition offers the advantage that it is possible without any difficulties to dimension the channels for the gas leaving the turbine so amply that practically the entire gas pressure available may be transformed into a high velocity and thus into turbine energy.

In a preferred embodiment of the invention, the turbine is constructed to have two stages with a stator arranged between the two stages.

Suitably, the two stages of the turbine are arranged on a turbine rotor common to both stages, said stator being constructed in two stages in the form of two annular halves. After having pushed the two annular halves of the stator into a corresponding annular groove of the turbine rotor, the stator is fixed on its outer periphery inside the housing by means of correspondingly designed bushings. This is a very simple manner of fixing the stator, however, other constructions are not excluded.

It is recommendable to supply the pressure gas at the input end of the housing through a centrically arranged line and to lead off the exhaust gas at the input end via a likewise approximately centrically disposed conduit of larger diameter which surrounds the pressure gas line.

Suitably, a manually operated control valve or a manually actuated control slide is arranged in the housing near the input end thereof.

An element to actuate the control valve or control slide is adapted to act on a brake member, which with a closed control valve or the control slide brakes the instrument shaft.

Suitably, the brake member is held in its brake release position by means of a spring and is movable into its braking position in dependence on the closing of the control valve or the control slide. A positive actuation and braking of the tool is obtained in this manner independently of the respective extent of wear on the brake surface.

The brake member is suitably constructed as a centrally arranged bolt with a pivotal lever arranged between the bolt and a spring-biased slide by means of which the control valve or control slide, respectively, is movable.

With a brake air pressure of 5-6 kp/cm.sup.2 and a direct drive of the tool shaft by means of the turbine rotor the invention secures a speed of about 100,000 rpm. The construction according to the invention is distinguished by its low noise at that speed and in that it allows the finest precision work with safety. Air consumption in this operation is 200 to 300 l/min.

BRIEF DESCRIPTION OF THE DRAWING

Further improvements and features of the invention are described by way of the enclosed drawing which shows one embodiment of the invention on an enlarged scale. In practice, the diameter of the cylindrical housing only is about 20 mm.

In the drawings,

FIG. 1 shows a longitudinal sectional view of a pneumatic motor constructed in accordance with the invention, and

FIG. 2 a partial sectional view taken on line II--II of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The cylindrical housing 1 comprises an output member 2 and an input member 3, with a sleeve 4 being fastened on the output member 2 by shrinking or pressing, for example. The input member 3 is provided with an external thread 5 which may be threaded into a corresponding internal thread 6 of the sleeve 4.

The instrument shaft 7 is supported in the ball bearings 8, 9 and 10.

The turbine rotor consists of the rotor member 11 with the two blade rings 12 and 13. A stator 14 is stationarily arranged between the blade rings. On the left-hand side of the blade ring 12 as shown in FIG. 1, a nozzle member 15 is stationarily arranged in which blowing nozzles 16 are provided. Compressed air flows to the blowing nozzles 16 via an annular chamber 17 and channels 18 provided in the output member 2. An intermediate member 20 is provided between the sleeve-shaped end 19 of the output member 2 and the left-hand end of the input member 3. The intermediate member 20 is provided with a projecting sleeve 21. The outer periphery of the stator 14 is fixedly clamped between sleeve 21 and a shoulder 22 formed on the output member 2. The clamping action is effected by pressing the input member 3 against the intermediate member 20 with the aid of screw connection 5, 6.

Compressed air enters the input member 3 via the centric bore 23. It is supplied through a hose (not shown) which is screwed to the bore 24 of the input member 3. The compressed air flows through the radial bore 27 via a control slide 25 which will be described herebelow in more detail, through an axial bore 26 and an oblique bore 28 of the input member 3 to an annular chamber 29, which is provided between the sleeve 4 on the one side and the left-hand end of the input member 3 and the right-hand end of the intermediate member 20 on the other side. The sleeve shaped end 19 of the output member 2 is provided with radial projections 30 by means of which this end is centrally guided within the sleeve 4. Wide channels remain open between these projections 30 for the passage of the compressed-air from the annular chamber 29 to an annular chamber 31 which is provided between the remaining part of the sleeve 19 and the output member 2 on the one side and the sleeve 4 on the other side.

The compressed air flows from this annular chamber 31 into the annular chamber 17 via channels 18. Then it passes via the blowing nozzles 16 into the first blade ring 12. It is deviated in the stator 14 after having left the first blade ring 12. Then the air flows through the second blade ring 13 of the turbine rotor. From here it flows through the chamber 32 to a plurality of exit bores 33 which are provided in the intermediate member 20 (see FIG. 2). The exit bores 33 open into bores 34 of the input member 3 which terminate in a chamber 35. This chamber 35 is connected with a hose or pipe 36 arranged centrally with respect to the bore 24 and through which the exhaust air is discharged into the atmosphere, for example.

In the shown embodiment, there are altogether six of the bores 33 and 34 arranged in such a way to leave sufficient space between them for the bores 26, 28 through which compressed air is supplied. A running clearance 37 is provided between the right-hand end of the nozzle member 15 and the left-hand end of the turbine rotor 11. The nozzle member 15 is provided with a bushing 38 extending a considerable length towards the input member 3. The bushing 38 is formed integrally with the nozzle member 15. The running clearance 37 passes over into a small running clearance 39 provided between the bushing 38 and a bore 40 of the turbine rotor 11. On the other side there is a small running clearance 41 between the bushing 38 and the instrument shaft 7. The gap 37 thus communicates with the bearing 9 and thus with the free atmosphere at the instrument end only through the long narrow gaps 39 and 41. It has been found that this construction suffices to prevent the exit of very small quantities of air towards the instrument end.

The shaft 7 is provided with a bore 42 to receive the instrument. The instrument is clamped in the bore 42 by three centrally arranged wedges 43, for example. These wedges are retained by a resilient sleeve 44 consisting of rubber, for example, which is rigidly connected with a metallic outer sleeve 45 by vulcanization. When the instrument spindle is being plugged into the bore 42 the wedges 43 are slightly pressed outwardly stressing the elasticity of the sleeve 44, thereby clamping the instrument spindle.

A circular plate-shaped control slide 25 is supported in a corresponding recess 46 of the input member 3, said control slide being provided with a sickle-shaped control opening 47. In the position shown in FIG. 1 the control opening 47 connects the bore 23 through which compressed air is supplied, with the radial bore 27. The control slide is sealed by sealings 48 and is supported in its position by a disc 49. A pin 50 fixedly connected with the slide 25 serves to actuate said slide, said pin 50 being pivotally supported in an actuating slide 51. The actuating slide 51 is forced by means of a spring 52 into a position in which the control slide 25 is closed. Towards the outside, the actuating slide 51 is closed by means of a sleeve 53 which surrounds the input member 3. A slot 54 is provided in the sleeve 53 with a projection 55 of the actuating slide 51 engaging therethrough. The slot 54 constitutes an elongated hole which serves to guide the projection 55 of the actuating slide. On the projection 55, there is mounted by means of a screw 56 an actuating rod 57 with a grip projection 58 by means of which the control slide 25 may be operated. The actuating rod 57 is in addition guided by means of an elongated slot 59 provided therein and being in engagement with a pin 60, said pin being fastened on the input member 3.

A nut 61 lies close to the inner race of the ball bearing 10 which race rotates with the shaft 7, said nut being screwed onto a threaded end 62 of the shaft 7. A brake member 63 formed as a concentric bolt is adapted to lie close to said threaded end and is provided with a head 64. The brake member is axially movably guided in a bushing 65 and has its head 64 pressed against a swivel beam 67 by means of a spring 66 which swivel beam 67 is pivotally supported in a bore 68 of the input member 3. The swivel beam 67 outer end is located in a recess in the actuating slide 51 and passes through a slot 71 of a cover plate 69 which separates the control slide 25 from the actuating slide 51. The slot 71 serves to guide both the swivel beam 67 and the pin 50 of the control slide 25.

In the left-hand end position (not shown) the actuating slide 51 forces the outer end of the swivel beam 67 to the left. In this way the brake member 63 is also forced to the left on the front side of the threaded end 62 of the shaft 7 against the tension of the spring 66. Accordingly, with the control slide 25 closed, the shaft 7 is braked by means of the brake member 63. The bore 26 is closed by means of a plug 72 near its left hand end (FIG. 1). Plug 72 separates the bore 26 supplying the compressed air from an annular chamber 70 on the left-hand side of the input member 3 into which the exhaust air bores 33 of the intermediate member 20 open.

Claims

What we claim is:

1. A pneumatic turbine powered surgical motor apparatus for rotating a medical instrument comprising, in combination, an elongated housing having a longitudinal axis, an input end and an output end, a shaft rotatably mounted in said housing concentric with said axis and projecting from said output end adapted to drive a cutting instrument, a pressurized gas connection and an exhaust gas connection defined on said housing at said input end, an axial flow turbine having a rotor rotatably mounted in said housing concentric thereto and drivingly connected to said shaft, said turbine having an inlet disposed toward said housing output end and an exit disposed toward said housing input end, first passage means longitudinally defined in said housing concentrically extending about the periphery of said turbine and communicating with said pressurized gas connection and said turbine inlet, and second passage means defined in said housing communicating with said exhaust gas connection and said turbine exit whereby pressurized gas entering said pressurized gas connection and first passage flows toward said housing output end to said turbine inlet, enters said turbine inlet and reverses its direction of flow to flow through said turbine toward said housing input end and from said turbine exit to said exhaust gas connection.

2. In a pneumatic turbine powered surgical motor apparatus as in claim 1, a nozzle member within said housing located adjacent said turbine inlet, nozzles defined in said nozzle member for directing pressurized gas into said turbine, said nozzle member including an annular bushing circumscribing said shaft and extending toward said turbine exit and being radially spaced from said shaft and turbine rotor by small running clearances.

3. In a pneumatic turbine powered surgical motor apparatus as in claim 1 wherein said first passage means comprises an annular chamber concentrically disposed about said turbine and said second passage means comprises a plurality of passages axially defined in said housing extending between said turbine exit and said exhaust gas connection.