FR2530454A1 - Air motor with two distinct speed ranges for driving rotatory dental instruments - Google Patents

Abstract

The subject of the invention is a high speed motor with two distinct speed ranges, of the type in which a first turbine transmits, via a speed reducing unit, a rotation to a driven shaft. A second turbine 7 drives, via an epicycloidal speed reducing gear train 10, a shaft 13 which itself drives the driven shaft 20 via a second epicycloidal speed reducing gear train 16, and the turbine 7 can be locked. Application: driving of rotatory dental instruments.

Description

 The subject of the present invention is a high speed air motor, of the type comprising two distinct speed ranges, a turbine transmitting by means of a reduction unit a rotation to a driven shaft.

 High-speed air motors of this type are already known, the advantage of which is to allow the user to be able to choose, depending on the work to be performed, the low speed range or the high speed range. These motors can reach a rotation speed of up to about 35,000 rpm and have been the subject in particular of US patent 3,292,459.

 Despite the speed performance obtained, these motors, which essentially consist of a turbine with reducer by rings which are driven by friction, are fragile.

 On the other hand, simple air motors do not exceed 20,000 rpm.

 There is therefore a need for a high speed air motor, which is robust and allows to provide a significant torque over a wide range of rotational speeds.

 According to the invention, this result is obtained with a high speed motor, of the type comprising two distinct speed ranges, a turbine transmitting by means of a reduction unit, a rotation to a driven shaft, characterized in that 'It comprises a second turbine driving by a first reduction planetary gear train an intermediate shaft, said intermediate shaft driving by a second reduction planetary gear train said driven shaft, the second turbine being able to be locked.

 This device produces a high speed motor actually comprising two distinct speed ranges, which are selected by the user according to whether or not he locks the second turbine.

 The invention will be better understood using the description below of an embodiment given by way of nonlimiting example, with reference to the appended drawing which is a view in longitudinal section of a motor with double turbine air according to the invention.

The motor is arranged inside a body (1) of generally cylindrical shape, comprising for simple reasons of ease of assembly, for example four parts respectively
- (2): cap closing the body,
- (3,4): sockets supporting the bearings,
- (5): front sleeve supporting the bearings and closing the body (1) at its other end.

 The four elements (2,3,4,5) will for example be forced to force one inside the other. They could also be screwed.

 The engine comprises a first turbine (6) actuated by an air jet, with a variable speed capped at around 160,000 rpm.

 It also comprises a second turbine (7) rotating, when it is not locked, at the same speed as the turbine (6). It is internally provided with a toothed crown (8) which meshes with a pinion (9) of a reducing epicyeloldal train (10) comprising a plurality of pinions such as (9). The pinions (9) mesh on the other hand with a pinion (11) integral with the axis (12) of the first turbine (6).

 The planetary gear (10) is integral with an intermediate shaft (13) via a disc (14) rotated by said train.

 The intermediate shaft (13) has at its other end a pinion (15) which meshes internally with a reducing planetary gear train (16), which comprises a plurality of pinions (17) meshing externally with a fixed and integral toothed crown (18) of the part (5) of the engine body.

 By a disc (19), the train (16) drives a driven shaft (20> which ensures the connection and the training, for example with a handpiece of dentistry, not shown. coupling means between the shaft (20) and the handpiece, which are well known to the specialist.

 Likewise, the air supply and exhaust system for the turbines (6) and (7) has not been shown either. these are systems known in themselves and well known to the specialist.

 The different axes (12), (13) and (20) are conventionally supported by suitable bearings respectively (21,22), (23,24) and (25,26).

Finally, in accordance with an essential characteristic of the invention, the turbine (7) can be locked in rotation, that is to say locked, by a locking member (27),
for example a lug or the like, controlled from the outside by the utility
reader.

We will now explain the details of the movie channel
matic, taking as hypotheses two turbines (6) and (7)
turning at 160,000 revolutions per minute, with planetary gears
(10) and (16) 1/4 reducers.

When the turbine (7) is not locked, the two
turbines (6,7) and the ring gear (8) rotate at the same
speed, or 160,000 rpm. This has the effect of neutra
read the reduction of the planetary gear (10), and therefore the shaft
(13) also rotates at 160,000 rpm. At its end
the pinion (15) transmits the movement to the shaft (20), through the in
intermediate of the planetary gear (16), and the shaft (20) rotates
therefore at 40,000 revolutions / minute due to the reduction.

So you get a high speed with a couple
high, because the torques of the two turbines (6) and (7) staddi-
argue.

when the turbine (7) is locked, only the turbine
bine (6) rotates at 160,000 rpm. The axle (12) and the pinion
(11) also rotate at this speed, but the intermediate shaft
diaire (13) only rotates at 40,000 revolutions per minute due to the
epicycloidal reducer (10).

In the same way as before, the spur train
cycloidal (16) will further reduce the speed by four, the speed
of the driven shaft being finally only 10000 turns
minute.

The speeds obtained on the a-rbre (20) of 10,000 and
40,000 rpm are the speeds corresponding to the speed
maximum of turbines estimated at around 160,000 rpm.

 In these two cases the torque is maximum.

It is also possible to vary slightly
the air pressure on the turbines to reduce their speed
retaining sufficient torque. If we get to around 100,000
revolutions / minute at the turbines we obtain the handpiece approximately
6000 rpm and therefore all intermediate speeds
between 6,000 and 40,000 rpm.

 Many modifications can be made without departing from the scope of the invention. Thus, the force absorbed by the gears of the reduction trains being low, it is conceivable to produce an engine with several speed ranges by coupling in series as many turbines and planetary gear as the speed is desired, depending on the above design.

Claims (3)

CLAIMS. 1. High speed motor, of the type comprising two distinct speed ranges, a turbine transmitting, by means of a reduction unit, a rotation to a driven shaft, characterized in that it comprises a second turbine ( 7) driving an intermediate shaft (13) by a first reducing planetary gear train (10), said intermediate shaft (13) driving said driven shaft (20) by a second reducing gear epicyeloidal train (16), the second turbine (7) possibly being locked by a member (27). 2. Motor according to claim 1, characterized in that the first turbine (6) comprises a shaft (12) provided with a pinion (11), said pinion (11) meshing with pinions (9) of the planetary gear (10 ), the pinions (9) also meshing with a ring gear (8) integral with the turbine (7). 3. Motor according to any one of claims 1 and 2, characterized in that the intermediate shaft (13) has a pinion (15) which meshes internally with the reducing planetary gear train (16), the latter comprising a plurality of pinions (17) meshing externally with a toothed ring (18) fixed and integral with the part (5) of the engine body, the train (16) driving the driven shaft (20).