FR2650647A1 - Device with a worm - Google Patents

Abstract

A device with a worm comprises a first pair of worms 5 and 6 formed on the emerging part of a rotor shaft 2 with helix winding directions which are opposite from one another, a pair of worm wheels 9 and 10 engaged on the helix, a pair of gear wheels 11 and 12 fastened onto the worm wheels, and a straight-cut gear wheel (spur gear) engaged with these two gear wheels. The spur gear 13 is mounted on a shaft 14 of a windscreen wiper device in a motor vehicle in order to drive it. A pair of shock absorbers 15 and 16 each one made of an elastic material such as a rubber or a resin are set out respectively at the two axial ends of the rotor shaft 2 to reduce the vibration of the gear meshing.

Description

Worm device
The invention relates to worm devices, and more particularly to a technique for avoiding noise due to mechanical play. For example, the invention relates to a worm device which can be used in an apparatus for driving wiper blades of a motor vehicle.

In general, it is necessary in a wiper drive for a motor vehicle to carry out a sufficient reduction in the speed of rotation of an engine. Consequently, a worm gear device is used in the wiper drive apparatus.

Conventionally, a worm device is known which comprises a pair of screws mounted at the front end of the rotor shaft of an engine, and whose helical windings are opposite to each other, while that a pair of toothed wheels respectively engage with the pair of screws, and that a drive gear (return gear to the right wheel) is provided, which cooperates with the wheels of screws to reduce their respective speeds, and thereby transmit the reduced rotational speeds to a wiper blade. A possible reaction force from a load is canceled by the screw couple.

However, conventional worm devices have the following disadvantage. This is because any variation in the accuracy of each tooth profile, or any variation in the precision of assembly, introduces variations in the respective gears between the screws and the screw wheels, as well as in the gears between them. pinion wheels and the drive mechanism. Thus, the clearances in a first path which starts from one of the screws, and in a second path which leaves from the other screw are different from each other. Therefore, when the drive shaft is driven upside down, by the load for some time, the screw which is in the path with the smallest clearance will move the rotor shaft axially. produces the situation where the rotor shaft is again driven, this rotor shaft is moved in the opposite direction At this time, abrupt and sudden collisions appear between the faces of teeth, so that a noise of gear, which will hereinafter be called gear vibration, is generated.

One of the aims of the invention is to provide a worm device capable of reducing the appearance of the gear vibration, even if there are different clearances between the drive paths in the device.

A worm device according to the invention comprises a pair of screws placed at the front end of a rotor shaft, with helical windings which are opposite directions to each other, a pair of wheels screws which engage respectively on the screws, and a drive mechanism cooperating with the screw wheels to reduce the speed of rotation of the rotor shaft in order to transmit rotation to a load, characterized in that a pair of shock absorbing elements are arranged at the two axial ends of the rotor shaft, between the respective axial ends of the rotor shaft and the supports or housings.

According to the worm device of the invention defined above, even if the rotor shaft is driven for a certain time by a load during the rotation of the rotor shaft, so that the latter is subject to a reciprocal movement which applies impact forces between tooth faces, these impact forces are absorbed by shock absorbing elements, which are provided respectively at the two ends of the rotor shaft. Thus, it is possible to reduce the appearance of the gear vibration.

In addition, according to another aspect of the invention, a shock absorbing element is interposed between the drive mechanism and the output shaft. This shock absorbing element absorbs the impact forces between the faces of the teeth, so that it is possible to reduce the occurrence of the gear vibration.

In addition, according to yet another aspect of the invention, a shock absorbing element is interposed between at least one of the pairs of screw wheels and one of the gears of the pinions which is associated with this same screw wheel. With this arrangement the impact forces between the tooth faces are absorbed by the shock absorbing element. Thus, it is possible to reduce the gear vibration.

Other characteristics and advantages of the invention will appear on examining the description below, and the appended drawings, in which each element retains the same reference, and in which - Figure 1 is a top view in section showing a worm device according to an embodiment of the invention - Figures 2 to 9 are explanatory views of the operation of the worm device of Figure 1, Figures 2 to 7 being mechanical views for the explanation of the gear vibration problem, while Figure 8 is a graphical representation showing the characteristic of the motor current, and Figure 9 is a graphical representation showing the characteristic of the gear vibration - FIG. 10 is a graphical representation showing a characteristic of motor current in the conventional worm device, in which no shock absorbing element is provided on the ro shaft tor - Figure 11 is a graphical representation showing the vibration of the gear in the worm device corresponding to Figure 10; - Figure 12 is a top view. in section showing a worm device according to another embodiment of the invention - Figure 13 is a partial sectional view taken along line AA of Figure 12 - Figure 14 is an exploded perspective view showing the worm device as illustrated in Figure 13 - Figure 15 is a top view in section showing a worm device according to a third embodiment of the invention - Figure 16 is a section view partial taken along line BB in Figure 15; and FIG. 17 is an exploded perspective view showing the worm device as illustrated in FIG. 16.

The first embodiment will now be described with reference to FIG. 1. A worm device according to the invention is formed as a reduction drive mechanism in a wiper or wiper blade drive device. . The worm device comprises a motor housing 3 internally housing a motor 1 which serves as a drive source. A gear housing 4 is mounted on the motor housing 3, in series arrangement thereon, and with attachment to the motor housing 3. The motor 1 has a motor shaft 2, the terminal end of which is inserted into the housing d 'gear 4. And a pair of screws 5 and 6 are cut from the material of the rotor shaft 2. The screws 5 and 6 have helical windings which are opposite directions to each other.Ci -after, the screw 5 will be designated as "screw wound on the left", and the screw 6 will be designated as "screw wound on the right". A pair of support shafts 7 and 8 are arranged perpendicular to the rotor shaft 2, in respective positions which face the screws 5 and 6 respectively, and on either side of the rotor shaft 2. A pair of screw wheels 9 and 10 are fixed respectively on the support shafts 7 and 8, and are mounted for rotation thereon.

The two screw wheels 9 and 10 engage respectively with the screw wound on the left 5 and the screw wound on the right 6. A pair of pinion wheels 11 and 12 are provided respectively on one of the sides of the screw wheels 9 and 10, coming from matter with them, and in coaxial relationship with them. The pinion wheels 11 and 12 engage with a right return wheel 13 which serves as a drive wheel.

 The wheel 13 is fixed to the control shaft 14 of a wiper blade (not shown) to rotate jointly with this shaft 14. The shaft 14 is arranged on one side of the rotor shaft 2 , in a direction perpendicular to it, and it is rotatably supported by the gearbox 4.

In this embodiment, a pair of shock absorbers 15 and 16 each serving as a shock absorbing element are disposed respectively at the two end faces of the rotor shaft 2, and are interposed respectively between these two end faces of the rotor shaft 2 and the motor housing 3 on one side, and the gear housing 4 on the other.

The shock absorbers 15 and 16 are so arranged that they can absorb an axial impact force acting on the rotor shaft 2. Each of the shock absorbers 15 and 16 is integrally molded by an elastic or deformable material, such as a rubber, resin or the like. The shock absorbers 15 and 16 are mounted with respective elastic forces of a degree such that they can slightly push the rotor shaft 2 axially, from its two ends. That is, the elastic forces of the respective shock absorbers 15 and 16 are forces capable of defining a thrust equilibrium position on the rotor shaft 2. In addition, these elastic forces are established at such a level that the damping effects of the respective dampers 15 and 16 are the most significant.

Between the damper 15 and the end of the rotor shaft 2 which is on the left in FIG. 1, is interposed a spherical body 17 such as a steel ball, as well as a flat element 18. The spherical body 17 is rotatably inserted into a recess provided in the right end of the rotor shaft 2, and partly projects outward, axially, on this rotor shaft 2. The plate element 18 has a face, that which is on the right in FIG. 1, which abuts against the spherical body 17. Its other face, which is on the left in FIG. 1, abuts on the damper 15.

Similarly, between the damper 16 and the other end face of the rotor shaft, that is to say the one which is on the right in FIG. 1, a spherical body 19 such as a steel ball and a plate element 20. The spherical body 19 is rotatably inserted in a recess provided in the right end face of the rotor shaft 2, and has a part projecting outward, axially , on the rotor shaft 2. The plate element 20 has a face, that is to say its left face in FIG. 1, which abuts against the spherical body 19. The other face, that is to say the right face of ltélémentzplaque 20 in Figure 1, abuts against a damper-sseur 16.

The operation of the device will now be described.

When the motor 1 rotates, its rotation is transmitted to the gear wheel 13 by the worm screw wound on the left 5 and the worm screw wound on the right 6, formed by the rotor shaft 2, via respectively screw wheels 9 and 10 and pinion wheels 11 and 12. At this time, as the screw wheels 9 and 10 are engaged respectively on the worm screw wound on the left 5 and on the worm screw wound on the right 6, at locations or positions which are opposite to each other with respect to the axis of the rotor shaft 2, the reaction forces on the respective screw wheels 9 and 10 act on the shaft of rotor 2 in an equal or uniform manner, in other words in a manner which - compensates for the offset. Thus, the transmission of motion is practiced efficiently, and the durability or reliability of the rotor shaft 2 is improved.

When the output shaft 13 rotates, the rotation of this shaft 13 rotates the shaft 14. The rotation of the shaft 14 is converted into an alternating angular movement of a brush arm, by means of a crank, a rod, a link, and a broom shaft, which are not shown: The alternating angular movement of the broom shaft causes a squeegee (not shown) to sweep a window glass.

Now, a mechanism, in which the gear vibration occurs due to the rotation of the rotor shaft 2, will be described with reference to Figures 2 to 7.

First of all, FIG. 2 shows a situation where equal clearances occur respectively in the two paths which start from the rotor shaft 2 to end at the right wheel 13, when the rotor shaft 2 is driven. At this time, even if a situation arises such that the rotor shaft 2 is driven for a certain time from the load, the rotor shaft 2 is prevented from moving axially, and the impact between the flanks or tooth faces is weak.

On the other hand, as illustrated in FIG. 3, the case will now be considered where the play between the screw wheel 10 and the screw 6 is small, while the play between the screw wheel 9 and the screw 5 is tall. As will be described later, if a situation occurs where the rotor shaft 2 is driven for a certain time from the load, i.e. from downstream, for example when the brush shaft sees its angular movement reverse, then the rotor shaft 2 is moved axially.

As shown in Figure 4, when the right wheel 13 is driven from downstream, that is to say from the side of a linkage mechanism towards the wiper arm, such as when the shaft windscreen wiper sees its angular movement reverse, or similar circumstances, the right wheel 13 abuts against the pinion wheels 11 and 12 on the flanks of teeth which are opposite to those illustrated in FIG. 3.

Furthermore, as can be seen in FIG. 5, when the pinion wheels 11 and 12 are subject to rotation under the above condition, the screw wheel 10 is brought to a position such that it comes into abutment against the sides opposite teeth of the screw 6. However, the tooth faces of the screw wheel 9 are brought into a state such that they are spaced from the screw 5. For this reason, a pushing force towards the screw 6 occurs on rotor shaft 2.

Figure 6 shows a condition of this kind, where the rotor shaft is moved towards the screw 6. At the moment when the pinion wheels 11 and 12 come to be driven in this state, but from the motor 1, c '' i.e. from the shaft 2 itself, the driving force of the screw 6 serves as a reaction force on the load, and acts on the rotor shaft 2 so as to move the latter in motor direction 1.

At this time, as illustrated in FIG. 7, when the screws 5 and 6 are moved towards the motor 1 due to the rotation of the rotor shaft 2, a gear vibration occurs when the stop, which occurs- due to the meshing between the right wheel 13 and the pinion wheels 11 and 12, and the respective meshes between the screw wheels 9 and 10 and the screws 5 and 6, these meshes becoming close or intimate in a relatively brief moment or moment.

 In view of the above, in this embodiment, when the faces or flanks of teeth of the screw wheels 9 and 10 abut against the faces or flanks of teeth of the screws 5 and 6, the dampers 15 and 16 are arranged respectively at the two ends of the rotor shaft 2, at the same time as the spherical bodies 17 and 19 and the plate elements 18 and 20, so as to absorb the thrust impact force which acts on the rotor shaft 2. That is to say that when the axial thrust force acts on the rotor 2 in the manner of an impact, the elastic force of each of the dampers 15 and 16 acts as a reaction force to absorb this pushing force. Thus, the speed of striking or beating the gear is reduced, so that the occurrence of the gear vibration is suppressed or restricted.

The relationship between the drive current of the motor 1 and the noise level of the gear vibration due to the rotation of the motor shaft 2 was measured in the worm device according to this embodiment.

Then, the measurement results were obtained and are as illustrated in FIGS. 8 and 9.

In Figure 8, a high current flows at the time of switching (in both directions) the forward movement and the return movement of the wiper blade. The game intervenes at the time of switching. Even if the play occurs in the worm device, to the point that the pushing force acts on the rotor shaft 2 in a brutal manner by impact, however, as illustrated in FIG. 9, in this mode In one embodiment, the noise level of the gear vibration during the scanning operation is generally restricted.

Besides this, the same measurement was carried out on a conventional example of a device in which the dampers 15 and 16 were not provided. From there, the measurement results obtained were illustrated in FIGS. 10 and 11 .

It has been confirmed from FIGS. 10 and 11 that a high current of pupil in the motor 1 at the initial moment of movement of the wiper squeegee, and, at this time, the noise level of the gear vibration rises manifestly.

As described above, according to this embodiment, the worm device is arranged in such a way that shock absorbing elements are mounted respectively at opposite ends of the rotor shaft to absorb the impact force. thrust acting on this rotor shaft. With this arrangement, even if the clearances which exist in the path from one of the screws and in the path from the other screw are different from each other, and thus there is a pushing force which acts on the rotor shaft, the speed of movement of the rotor shaft is reduced so that the noise level of the gear vibration can be reduced.

A second embodiment of the invention will now be described with reference to FIGS. 12 to 14.

In this embodiment, the right wheel 13 is mounted on the shaft 14 of the scanning device (not illustrated) by means of a damping unit 115, which rotates with the shaft 14. The shaft 14 which serves as an output shaft is arranged on one side of the rotor shaft 2, and extends perpendicular to the latter. The rotor shaft 2 has its terminal end which is inserted into the gear housing 4 in a cantilevered state. The output shaft 14 is rotatably supported by the gear housing 4.

In this embodiment, the damping unit 115 comprises a damper 116, serving as a shock absorber element, a locking plate on the gear side 17, and a locking plate on the shaft side 118.

The damping unit 115 is interposed between the right wheel 113 and the shaft 14, and is so arranged that it absorbs an impact force which acts on them. The damper 116 which serves as a shock absorbing element is mounted by integral molding in the configuration of a circular or annular ring, using an elastic material such as rubber, resin or the like. The damper 116 has an elastic force of a degree such that it normally transmits the drive force from the right wheel 13, in an appropriate manner, to the shaft 14. That is to say that the elastic force of the shock absorber 116 is adjusted to be to such a degree that the damping effect of the shock absorber 116 is most significant at the time of the action of the impact force .

The gear side locking plate 117 is integrally formed, by suitable means such as press treatment or the like, to be presented as a plate element whose configuration is that of an annular or circular ring having a width in the radial direction which is a little narrower than that of the damper 116
The gear side locking plate 117 is pressed against an end face of the damper 116, on the lower side thereof, in a unitary manner. A plurality of engagement pieces 117a are formed on the locking plate 117, in a spaced apart relationship substantially equidistant from each other in the peripheral direction. These engagement pieces 117a are cut from the locking plate 117, and are placed vertically downwards. On the other hand, the shaft-side locking plate 118 is formed in one piece, by suitable means such as a press treatment or the like, to constitute a plate element whose configuration is that of an annular or circular ring having an outer diameter substantially equal to that of the damper 116, and an inner diameter smaller than the diameter outside of the shaft 14. A plurality of engagement bores 118a are formed in the locking plate 118, so as to pass through it in the direction of its thickness, and they are arranged in a spaced-apart relationship substantially equidistant from relative to each other in the peripheral direction. The locking plate 118 is locked on the end face of the damper 116 on the upper side thereof in a unitary manner , in a condition such that the engagement pieces 116a provided on the upper face of the shock absorber 116 respectively engage in the engagement bores 118a. A female flat 118b is formed in the center of the locking plate 118, and serves as a female engagement piece.

The damping unit 115 thus constructed is located in an annular attachment bore 13a, formed in the upper face of the right wheel 13, concentric # therewith, so that the shaft-side locking plate 117 is directed downward As a result, the engagement pieces 117a of the gear side locking plate 117 are engaged respectively in a plurality of engagement bores 13b, which are formed through the lower part of the fixing bore 13a. The female flat 118b of the shaft-side locking plate 118 is mounted on a male flat 14a, which is formed in the upper part of the drive shaft 14. Thus, a keying section 14b is formed at the upper end of the shaft 14, whereby the damping unit 115 is fixedly mounted on the right wheel 13, and on the shaft 14, in a condition such that the locking plates 117 and 118 prevent the damping unit 115 to be rotated relative to the right wheel 13 and relative to the shaft 14.

In this embodiment, since the damping unit 115 is interposed between the right wheel 13 and the shaft 14, any shock is lessened by the damping unit 115, when the impact force of the flanks of teeth is transmitted to the damping unit 115. As a result, the gear vibration is restricted. That is, when the impact force acts on the right wheel 13 and on the shaft 14, the elastic force of the damper 116 of the damping unit 115 acts and serves as reaction force to absorb the impact force Hence the restriction of the gear vibration
As described above, the worm device according to the second embodiment is arranged so that the shock absorbing means is interposed between the drive wheel and the output shaft to absorb the impact force .

With this arrangement, even if the clearances in the path from one of the screws and in the path from the other screw are different from each other, it becomes possible to reduce the level of noise due to the gear vibration which occurs due to the movement of the rotor shaft.

A third embodiment of the invention will now be described with reference to FIGS. 15 to 17.

In this embodiment, a pair of shock absorbers 215 each serving as shock absorbing means are interposed respectively between the screw wheels 9 and 10 and the pinion wheels 11 and 12, so as to absorb the impact forces acting there. -above. These shock absorbers 215 and 215 are formed in the same way both, and that is why they bear the same reference and the description of one of the two will be sufficient to define them both. The shock absorber 215 is made by molding in one piece, in the configuration of a generally circular or annular disc or ring, using an elastic material such as rubber, resin or the like. The shock absorber 215 has a force elastic of a degree such that the driving force of the screw wheel 9 or 10 is normally transmitted to the pinion wheel II or 12 in an appropriate manner. Also, the elastic force of the shock absorber 215 is adjusted to be to such a degree that the damping effect of the shock absorber 215 is most important when the impact force is applied. . A plurality of engagement projections 216 are formed by molding on the outer periphery of the damper 215, with the general shape of the configuration of a circular or annular disc or ring, in a spacing relationship substantially equidistant from one relative to each other in the peripheral direction. The engagement projections 216 project radially inwards. The female splines 217 are formed in the material, on the periphery of a central bore of the shock absorber 215, so as to be engaged with the inter-tooth spaces of the pinion wheels 11 and 12.

On the other hand, a fastening bore 218 of generally annular shape is formed in the material of the upper face of the screw wheel 9 or 10, concentrically thereto.

A plurality of engagement recesses 219 are formed in the material, on the periphery of the attachment bore 218, and extend radially outwards, so as to correspond respectively to the engagement projections 216 of the shock absorber 215.

When the damper 215 is arranged between the screw wheel 9 or 10 and the pinion wheel 11 or 12, the damper 215 is mounted in the fastening bore 218 of the screw wheel 9 or 10 in such a way that the engagement projections 216 are aligned respectiy respect and forcibly engaged respectively in the engagement recesses 219. The pinion wheel 11 or 12 is forcibly mounted in the damper 215, so that the teeth of the pinion wheels 11 or 12 respectively engage in the grooves 217. In doing so, the screw wheel 9 or 10 and the pinion wheel 11 or 12 are connected to each other by means of the damper on 215, so to shoot together.

In this embodiment, the shock absorber 215 is interposed between the specification wheel 9 or 10 and the pinion wheel 11 or 12. Consequently, when the force # of impact of each tooth flank is transmitted to the shock absorber 215 , the shock is lessened by the shock absorber 215. I1 as a result that the gear vibration is restricted. That is, when the impact force acts on the screw wheel 9 or 10 and on the pinion wheel 11 or 12, the elastic force of the shock absorber 215 acts as a reaction force to absorb the impact force, so that the occurrence of a gear vibration is restricted.

With regard to the above, the invention is not limited to the three embodiments described above, and it goes without saying that different variants and modifications can be made to the invention, in accordance with its scope, without move away from his mind.

For example, the arrangement of interposition of a shock absorber is not limited to the use of the abovementioned constructions in the embodiments described. As shown in Figure 17, the following construction can be used, like any other. That is, a plurality of grooves 220 and 221 each having a cross-sectional configuration of a half cylinder or half column can be formed at the junction surface between the screw wheel 10 and the pinion wheel. 12; and a plurality of shock absorbers 215a each formed in a cylinder or column configuration are forcibly mounted respectively in the plurality of hollow cylindrical or columnar sections 222, which are formed by the union of the two grooves in half-column 220 and 221. The shock absorbers 215 are made of elastic material.

Furthermore, the invention is not limited to an arrangement such that a pair of shock absorbers are interposed respectively between the two screw wheels and the two pinion wheels.
That is to say, the arrangement can be such that only one damper is interposed between one of the screw wheels and the corresponding pinion wheel.

As described above, the worm device according to the invention is arranged such that shock absorbing means are provided in the position where it can absorb the impact force due to mechanical play. With this arrangement, even if the clearances in the path from one of the screws and in the path from the other screw are different from each other, it becomes possible to reduce the noise level due to the gear vibration which occurs during the movement of the motor shaft.

Claims (10)

Claims. 1. A worm device comprising a pair of screws provided on an end section at the front of a rotor shaft, so as to present respective helical windings in opposite directions. to the other, a pair of screw wheels which respectively engage said screws, and a drive wheel cooperating with said screw wheels to reduce the speed of rotation of said motor shaft in order to transmit this reduced speed of rotation to a load, characterized in that a pair of shock absorbing means are located respectively at the two axial ends of the rotor shaft. 2. A worm device according to claim 1, characterized in that each of said pairs of shock absorbing means consists of an elastic material such as rubber or a resin. 3. Worm screw device according to one of claims 1 and 2, characterized in that a pair of spherical bodies and a pair of plate elements are interposed respectively between said pair of shock absorbing means and the opposite ends of said rotor shaft, said pair of spherical bodies being arranged respectively at the two opposite ends of the rotor shaft, and having respective parts which are projecting axially outwards relative to the end faces of the respective ends of said rotor shaft , said plate elements having respective faces abutting against these spherical bodies, and other respective faces abutting respectively towards said pair of shock absorbing means.  4. A worm device comprising a pair of screws provided on an end section at the front of a rotor shaft, so as to present respective helical windings in opposite directions to each other, a pair of screw wheels which engage respectively on said screws, and a drive wheel cooperating with said screw wheels to reduce the speed of rotation of said motor shaft in order to transmit this reduced speed of rotation to a load, characterized in that shock absorbing means are interposed between said drive wheel and said output shaft. 5. A worm device according to claim 4, characterized in that said shock absorbing means comprise a damping unit which is fixedly interposed between a straight wheel forming the drive wheel, and a shaft which forms the output shaft, in a manner preventing rotation, and in that said damping unit comprises a shock absorbing damper generally in the form of a circular annular disc made of elastic material, of a gear side closure plate formed on the bottom of said shock absorber in a unitary manner, and a shaft side closure plate formed on the top of said shock absorber in a unitary manner. 6. Worm screw device according to claim 5, characterized in that said damping unit is located in a fastening bore formed on an upper face of said straight wheel, in concentric relation thereon, in a condition such that said gear side closure plate is directed downward, and that this gear side closure plate has a plurality of engagement pieces which are engaged respectively in engagement bores formed in the bottom of said fastening bore. 7. A worm device comprising a pair of screws provided on an end section at the front of a rotor shaft, so as to present respective helical windings in opposite directions to each other, a pair of screw wheels which respectively engage on said screws, a pair of pinion wheels respectively cooperating with said screw wheels for rotation therewith, a drive wheel engaged with these two pinion wheels, and a output shaft cooperating with said drive wheel to reduce the speed of rotation of said rotor shaft and transmit the reduced speed of rotation to a load, characterized in that the shock absorbing means is interposed between at least one of said pairs of screw wheels and at least one of said pinion wheels, that which is associated with said screw wheel. 8. A worm screw device according to claim 7, characterized in that said shock absorbing means comprises a shock absorber generally in the form of a circular annular disc made of elastic material, in that a plurality of engagement projections project, coming from material, radially outwards, from the external periphery of said damper, and are arranged in a spacing relationship substantially equidistant from each other in the peripheral direction, in that a plurality of female grooves are formed integrally on the internal periphery of said damper, so as to be capable of fitting respectively in the spaces defined respectively between the flanks of gear teeth of said pinion wheel. 9. A worm device according to claim 8, characterized in that a fastening bore is formed, integrally formed, in an upper face of said screw wheel considered, concentrically thereto, and in that 'a plurality of engagement recesses are formed integrally in an internal peripheral surface of said engagement bore, at locations which respectively correspond to those of said engagement projections of said damper, said engagement recesses being oriented stiffly outwards. 10. Worm screw device according to claim 7, characterized in that said shock absorbing means comprise a plurality of shock absorbers each made of an elastic material and formed in a cylindrical or columnar configuration, in that a plurality of grooves each having a cross-sectional configuration of half-cylinder or half-column are formed at #respective junction surfaces between said screw wheels and pinion wheels considered, and which are associated with each other, and in that said cylindrical or column-shaped dampers are force-fitted respectively into a plurality of hollow cylindrical or columnar sections, formed by the respective union of the semi-circular or semi-cylindrical grooves formed in said screw wheel considered, and the semi-circular or semi-cylindrical grooves made in said pinion wheel considered.