The gear-type motor 1 schematically illustrated in FIGS. 1 and 2 comprises a closed housing 2 formed by a ring 3 and two flat end plates 4, 5 located on the end faces of the ring. Two mutually parallel bearing shafts 7, 8 are rotatably mounted between the two end plates 4, 5 across the interior 6 of the housing 2, each said bearing shaft carrying a respective gear 9 and 10 which is fixed thereon. The two gears extend over the whole width of the interior 6 and interengage at their outer peripheries. The shape of the interior 6 is selected to be such that the inner wall 11 of the ring 3 at the upper and lower ends of the interior 6 i.e. at the points remote from the point of engagement of the gears 9, 10, borders the outer peripheries of the gears 9, 10 in a manner such as to form a very narrow gap.
An inlet 12 enters the interior 6 at one side thereof in the spandrel between the two interengaging gears 9, 10, whilst an outlet from the interior 6 emerges at the opposite side of the interior 6 although this is not illustrated in the drawing.
The part of the interior 6 adjoining the inlet 12 is, to a large extent, sealed relative to the part of the interior 6 adjoining the outlet by virtue of the fact that, in the vicinity of the inner wall 11, the two gears 9, 10 are moved past it in a manner such as to form a very small gap, moreover, that they extend sideways such as to leave a very narrow gap relative to the flat end plates 4, 5, and finally, that the flanks of their teeth abut very closely together at their points of engagement. The compressed air, at a pressure of 6 bar for example, entering through the inlet thus impinges on the flanks of the teeth of the two gears 9, 10 in the spandrel adjacent the point of engagement of the gears 9, 10 and thereby exerts a torque on the two gears. The effective surfaces are thereby different for the differing directions of rotation since, in one direction of rotation, pressure is applied to a full flank of each gear whereas, in the other direction of rotation, pressure is applied to only one flank face in the region of engagement of the flanks of the teeth. As a consequence, the gears 9, 10 rotate in opposite senses when compressed air is applied thereto as indicated by the direction of the arrows shown in FIG. 1. The compressed air is carried along in the space between the flanks of the teeth and escapes through the outlet into the surroundings after it has been reduced in pressure.
The gears 9, 10, which one could also refer to as toothed rollers, preferably have an outer diameter of less than 40 mm. The diameter to width ratio of the gear D/B preferably lies between 0.5 and 2, whilst the number of teeth amounts to at least 8. The modulus of the gears lies between 0.5 and 1.5.
The toothing on the gears may be straight or bevelled, whilst it is expedient if the gears 9, 10 consist of a self-lubricating material, for example, of polyoxymethylene (POM) or polyetheretherketone (PEEK).
A gear-type motor, such as is schematically illustrated in FIGS. 1 and 2, is illustrated in FIG. 3 in a housing 13 of a surgical apparatus although, in the embodiment illustrated, only the housing 13 of a tool holder of this surgical apparatus is illustrated without the supply arrangements and without a tool.
It can be perceived in the gear-type motor 1 of this embodiment that a bearing shaft 7 is mounted at each end in ball bearings 14, 15, one of these being disposed in one of the end plates 4 and the other in a terminating portion 16 directly adjoining the end plate 5.
The other bearing shaft 8 is likewise mounted in the terminating portion 16 by means of a ball bearing 17, but this shaft extends through the end plate 4 of the gear-type motor 1 into a cylindrical extension 18 of the housing 13 of the tool holder and is mounted therein by means of a ball bearing 19 which is somewhat distanced from the gear-type motor 1. The bearing shaft 8 is surrounded by a sleeve 20 in the region between the end plate 4 and the ball bearing 19, said sleeve being sealed relative to a sleeve-shaped insert 22 in the cylindrical extension 18 by means of an O-ring seal 21.
The free end of the bearing shaft 8 carries a coupling 23 in which a tool can be mounted in known manner by means of a chuck for example although this is not visible in the drawing. This tool may be a burr, a drill or a similar rotary tool.
The gear-type motor 1 can be withdrawn backwardly out of the open end of the housing 13 together with the bearing shaft 8 and the parts surrounding it i.e. the ball bearing 19, the sleeve 20, the seal 21 and the insert 22. This can be done after a plate-like closure member 24 has been unscrewed from the open end of the housing 13.
Conversely, the gear-type motor 1 can be reinserted into the housing 13 in a similar manner whereby the ball bearing 19 abuts against an annular shoulder 25 within the cylindrical extension 18 as the motor is pushed in, a resiliently compressible locking washer 26 possibly being provided as an intermediary. The requisite pressure in the direction towards the annular shoulder 25 is produced by the closure member 24 which abuts the rear end of the terminating portion 16 and pushes the gear-type motor 1 forward longitudinally of the housing 13 when it is screwed into the housing 13.
A central compressed air conduit 27 and a plurality of air extraction conduits 28 are disposed in the closure member 24. The compressed air conduit is connected to the inlet 12 although this is not visible in the drawing whilst the air extraction conduits 28 are in communication in the terminating portion 16 with the outlet from the interior 6 although this too is not visible in the drawing.
Thus, the gear-type motor 1 can be constructed in the form of a very compact independent module so that it is possible to remove it from the surgical apparatus in a simple manner for the purposes of cleaning and sterilisation for example. It is also readily possible to replace this motor by another motor having different operational properties when differing operational parameters are desired for alternative purposes.
In the embodiment of a gear-type motor illustrated in the drawing, the two gears 9 and 10 are rotatably mounted in the housing 2 by means of the bearing shafts 7 and 8, whereby, for their part, the bearing shafts 7, 8 are rigidly connected to the gears 9 and 10.
In a modified embodiment, it would also be possible for just the bearing shaft 8 to be rotatably mounted in this manner, said shaft then being rigidly connected to the appertaining gear 10. The other gear 9 could be mounted in freely rotatable manner on the bearing shaft 7 which, for its part, would then be mounted in non-rotational manner in the housing 2 as a fixed axle.