Patent Application
20080298960
The invention relates to a micro-air motor with a casing comprising a guide bore and a rotor rotatably mounted therein, wherein the rotor is provided with slots substantially oriented radially outwards, in which plate-shaped vanes are mounted radially displaceable outwards through the centrifugal force and a collector axially following the rotor with inlet and outlet apertures and with channels connected to external connections for the compressed air, wherein the collector (6) is rotatably arranged about the axis of rotation of the rotor (2) or about an axis parallel to said rotor or about the longitudinal axis of the casing (1) by means of an actuation sleeve (4).
Air motors with radially displaceable vanes are built and used in different sizes and for quite different applications. The devices designated “micro-air motors” as a rule have a casing diameter of less than two centimetres and are predominantly used in medical equipment, more preferably surgery and neurosurgery. The plurality of the devices known and employed to date can only be operated in one direction of rotation. This is due to the cross sections of the inlet and outlet apertures usually differing in size in order to achieve optimum speed and performance characteristics. If the inlet and outlet apertures are identically dimensioned direction of rotation reversal is possible but the device does not generate the optimum but only a limited output in both directions of rotation.
From WO 81/03520 a vacuum motor is known that can be operated in both directions of rotation. Here, the handle connected to a vacuum line can be twisted about the casing towards both sides into fixed end positions. Thus the handle additionally has the function of a rotary valve. Thus, the one or the other aperture of the casing can be connected to the vacuum line or the ambient air.
However the inlet and outlet apertures are thus always identical in size. Optimum operation of the motor is thus not possible in both directions of rotation.
A vane motor known from GB 1 578 364, which likewise is used in medical equipment, comprises a total of three connection apertures, wherein the one aperture always serves as outlet and the other two apertures, depending on the direction of rotation, optionally serve as inlet or outlet. This device thus has improved performance characteristics in both directions of rotation compared with a device having only two apertures. However, a special external valve is necessary for the control which is not disclosed in this publication.
From U.S. Pat. No. 4,708,210 a pneumatically operable hand tool is known which comprises a collector that can be twisted by means of an actuation ring. In both its end positions the collector serves for the reversal of the direction of rotation of the motor. The speed is controlled via a separate throttle valve. This design is involved and not very user-friendly.
The invention is based on the object of creating a micro-air motor which is reversible and has optimum speed and performance characteristics in both directions of rotation.
According to the invention this is achieved in that the collector (6) can be brought from a central neutral position stopping the rotor (2) towards both sides as far as an end position limited through stops, so that the rotor (2)—under compressed air—rotates anti-clockwise or clockwise.
The collector is a device-internal component which is practically present in different form in any air or micro-air motor. The rotatability of the collector can for example be achieved in a simple manner in that the collector on its outside is substantially designed cylindrically and is rotatably mounted in a corresponding bore of the casing.
A practical embodiment consists in that the collector can be brought from a central neutral position rotationally locking the rotor—under compressed air—to both sides into an end position limited through stops, in which the rotor—under compressed air—rotates anti-clockwise or clockwise. Thus the rotor is fixed in the neutral position of the collector and thus not freely rotatable. This produces substantial advantages for example during the tool change in that an additional locking device for the rotor is not required. A separate shut-off organ for stopping the air motor is not per se necessary either.
For controlling or regulating the air motor it is advantageous that the collector is continuously rotatable as far as the end positions. The speed of the air motor can thus be controlled practically continuously from zero to the maximum speed by enlarging the flow cross section.
For actuating the collector it is practically coupled with an actuation sleeve. Coupling can be effected for example by means of key, pin or screw-type fasteners. These fasteners can simultaneously interact also with corresponding guides or cranks and control or limit the twisting path of the collector.
The inlet and outlet apertures advantageously have different cross sections. As a result, these can be optimally adapted to the requirements, i.e. the outlet apertures in the region of the outflowing exhaust air can be dimensioned substantially larger than the inlet apertures in the region of the supply air inflowing with high pressure. Thus the air resistance can be optimally maintained over the entire flow path.
Practically the inlet and/or outlet apertures are designed kidney-shaped. In interaction with the working chamber of the air motor which is usually ring or wedge-shaped this produces favourable flow conditions at the transition points of the collector to the rotor in all positions of twist of the collector.
Since the compressed air to the rotor is supplied and discharged usually axially, it is advantageous that at least one channel is oriented coaxially or parallel to the axis of the rotor. Such an arrangement also makes possible a compact and slim design of the compressed air motor or the entire device. This is more preferably highly desirable and of great advantage with devices employed in medical equipment.
A further advantageous embodiment consists in that in the region of the vanes between the outside of the rotor and the guide bore of the casing a freely rotatable floating sleeve enveloping the outside of the vanes is arranged, which, on its shell, comprises at least one passage bore arranged on the circumference and/or irregularly distributed over the length of the floating sleeve substantially oriented radially or designed as slots substantially oriented in longitudinal direction of the floating sleeve or helically. Through the floating sleeve, contact of the vanes with the guide bore or the casing and thus wear of the vanes on their outside is avoided.
The floating sleeve and/or the vanes practically consist of plastic, preferentially of phenolic resin fabric. Such materials have a relatively low specific weight, good temperature resistance and favourable friction conditions.
The longitudinal slots for the vanes are advantageously arranged in the radial planes through the rotor. Thus the rotor has the same running characteristics in both directions of rotations.
Practically at least two to six, preferentially four vanes are provided. The higher the number of vanes the more even are the running characteristics and the torque curve of an air motor over one rotation.
The invention is explained in more detail in the following by means of the drawings exemplarily representing the invention. It shows:
The micro-air motor shown in
The collector 6 comprises longitudinal bores 7 and channels 8 oriented in axial direction which are open towards the outside for the compressed air supply and discharge. An adapter 9 is securely connected with the housing 1. The adapter 9 is provided with a central bore 10 as well as with transverse bores 11 terminating in the central bore 10. Through milled portions 12 the connection between the transverse bores 11 and the longitudinal bores 7 of the collector 6 is established.
As is evident from
In longitudinal slots 20 of the rotor 2 vanes 15 mounted radially displaceably are arranged. The vanes 15 on their outer side are surrounded by a floating sleeve 16. The floating sleeve 16 is provided with passage apertures 17 for the compressed air. Thus the same pressure exists on both sides of the floating sleeve 16 and the floating sleeve 16 is thus mounted in a floating manner and practically free of friction. The longitudinal bores 7 terminate in an inlet aperture 18 and the channels 8 in an outlet aperture 19.
In the position shown in
If the collector 6 is twisted in anti-clockwise direction as far as the other end position shown in
As is evident from
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 01225/05 | Jul 2005 | CH | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB2006/002000 | 7/21/2006 | WO | 00 | 6/16/2008 |
