JPS6125453Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an increasing/decelerating mechanism for a dental handpiece that concentrically transmits the shaft rotational motion of a drive shaft connected to an electric or pneumatic drive motor to an operating shaft at variable speeds.

Conventionally, as an acceleration/deceleration mechanism for dental handpieces, the principle of a ball bearing, which consists of an inner ring, an outer ring, and balls held in between by a ball retainer, has been applied, and two rotating shafts in opposing relationship are connected to the inner ring and the outer ring, respectively. There is a ball planetary mechanism that can transmit the axial rotational motion of the drive shaft at variable speeds based on the rolling of the outer circumferential surface of the inner ring and the inner circumferential surface of the outer ring and the difference in circumferential speed due to the diameters of the inner and outer rings. . This is structurally simpler and has great cost advantages compared to systems that use planetary gears or planetary bearings, and is also recognized as an extremely superior mechanism with fewer mechanical problems because it is a gearless mechanism. has been done. However, this type of mechanism generally has the disadvantage that it is difficult to hold the ball during assembly, and therefore assembly requires skill and trouble.

The present invention was devised in view of the above, and is a new handpiece speed change that achieves extremely smooth coaxial speed change transmission of the rotational motion of two opposing rotating shafts, and also simplifies assembly. There is a mechanism to provide.

To illustrate the embodiment of the present invention, Fig. 1 is a partially cutaway vertical sectional view of a typical embodiment of the present invention, and Fig. 2
The figure is a sectional view taken along the line in FIG. 1, and FIG. 3 is an exploded perspective view of the main part of the portion taken along the line in FIG. That is, the present invention provides a dental handpiece in which two rotating shafts 2 and 3, which are rotatable coaxially and oppositely by ball bearings 11 and 12, are coupled in a main body 1 in a variable speed manner. In the transmission mechanism, the distal end side of one shaft 2 is provided with a plurality of split fork-shaped ball retainers 21 parallel to the circumferential direction and at equal intervals, and the rear end side 31 of the other shaft 3 is A circular ring 4 is fitted inside the main body 1 so as to surround the ball retainer 21 concentrically and to be non-rotatable in the circumferential direction but slidable in the axial direction. and the above axis 3
The balls 5 are brought into rolling contact between the ball retainer 21 and the outer periphery of the rear end side 31, and the elasticity of the spring 6 is always applied to the annular ring 4 in the axial direction, so that the balls 5 are held in the annular ring. 4 in the centripetal direction and the rear end side 31 of the shaft 3 in the centrifugal direction, and the axial rotation movement with either the shaft 2 or the shaft 3 as the driving side causes the balls 5 to rotate in a circle. This is a speed change mechanism for a dental handpiece characterized in that the speed is transmitted to the driven side by rolling the inner circumferential surface of the ring 4 and the outer circumferential surface of the shaft 3. In the figure, the shaft 2 is supported via ball bearings 11 in a case 10 that is fitted and fixed to the main body 1.
The ball retainers 21 are split into fork shapes parallel to the circumferential direction and at equal intervals, and a hollow part 22 with one end open is concentrically formed in the shaft 2 at the base of the ball retainers 21. The annular ring 4 is slidably fitted into the main body 1, and elasticity is applied in the direction of the axis 3 by a compression spring 6 interposed between the ring 4 and the case 10, and as shown in FIG. Rotation in the circumferential direction is made impossible due to the engagement between the axial protruding piece 101 of the case 10 fixed to the case 10 and the notch 41 of the cone 4. The inner circumferential surface of the ring 4 is composed of a large diameter portion 42 that closely circumscribes the balls 5 when the balls 5 are in rolling contact with each other, and a small diameter portion 43 that prevents the balls from moving toward the shaft 2. The space between the large diameter portion 42 and the small diameter portion 43 is a tapered or curved surface, and in the figure is an arcuate surface 44 that matches the curvature of the ball 5. Rear end side 3 of one shaft 3
The outer circumferential surface of the ball 1 consists of a small diameter part 311 that is in close contact with the balls 5 when the balls 5 are in rolling contact with each other, and a large diameter part 312 that prevents the balls from moving toward the shaft 3. A tapered or curved surface is provided between the large diameter portion 312 and the arcuate surface 313 which corresponds to the curvature of the ball 5 as described above.
It is said that The inner peripheral surface of such an annular ring 4 and the shaft 3
The configuration of the outer circumferential surface of the rear end side 31 and the elasticity of the spring 6 position the balls 5 in the axial direction, and the balls 5 are pressed in the centrifugal and centripetal directions to form the annular ring 4, the balls 5, and so on. and the rear end side 31 of the shaft 3 are maintained in a press-contact relationship.

The procedure for assembling the mechanism having the above structure will be described with reference to FIG. 1.A shaft 3 is inserted into the main body 1 from the left side in the figure and is supported via a ball bearing 12. As shown in FIG. then 3
Balls 5 are interposed between ball retainers 21 on the tip side of the shaft 2, and a ring 4 surrounds the balls 5. At this time, if a ball withdrawal prevention ring 7 is installed and fixed circumferentially on the tip side of the ball retainer 21 as shown in the figure, the balls 5 can be prevented from coming off in the axial direction, and at the same time, the ball retainer 21 can be prevented from coming off in the axial direction. By tapering the cross-sectional shape in the centripetal direction and making the inner distance between the ball retainers 21 smaller than the diameter of the balls 5 (see FIG. 2), the balls 5 do not slip out in the centripetal direction. In this state, the shaft 2 is inserted from the right side in the figure, so that the rear end side 31 of the shaft 3 is inscribed in the balls 5, and the balls 5 are brought into close contact with the circular arc surface 313 of the rear end side 31. Further, the case 10 is fitted into the main body 1 from the right side, the spring 6 is interposed, and the protrusion 101 and the notch 4 are attached to the ring 4.
The case 10 is engaged with the main body 1 by fitting with the cap 1 and pivotally supports the shaft 2 via the ball bearings 11 . In this way, the assembly of the transmission mechanism as shown in FIG. 1 is completed.

In the above configuration and assembly procedure, the balls 5 are closely circumscribed on the inner peripheral surface of the ring 4 by the elasticity of the spring 6, and are closely inscribed on the outer peripheral surface of the rear end side 31 of the shaft 3. Therefore, when the shaft 2 is used as the drive shaft, the rotational movement of the shaft 2 causes the balls 5 to roll on the inner peripheral surface of the ring 4, and also rolls on the outer peripheral surface of the rear end side 31 of the shaft 3. It will make you move. this ball 5
... The rolling of the outer peripheral surface of the rear end side 31 causes an axial rotation movement of the shaft 3, and the diameter of the large diameter portion 42 of the ring 4 and the ball 5
The rotation speed is also reduced in accordance with the ratio of the diameter of the small diameter portion 311 of the rear end side 31 inscribed in the rotation speed. Since this coaxial transmission of the rotational motion of the shaft utilizes the rolling motion of the balls 5, there is almost no heat generation due to friction, and it is carried out extremely smoothly without damage or vibration to the teeth unlike in a gear type. be. Moreover, since the balls 5, which are the direct speed transmission medium of the rotating shafts 2 and 3 facing each other, are surrounded by the elastic ring 4, the assembly is easy and requires no trouble during assembly. There is almost no sharpness. Further, in the above embodiment, a slip-off prevention ring 7 is installed on the tip side of the ball retainer 21 to prevent the balls from slipping out in the axial direction, and the ball retainer 21...
Since the cross-sectional shape is tapered in the centripetal direction to prevent the balls from falling out in the centripetal direction, troubles such as balls rolling out during assembly are completely prevented and assembly can be performed very easily.

It is obvious from the above that if the driving and driven sides in the above embodiment are reversed, that is, if the shaft 2 is used as the driven shaft and the shaft 3 is used as the driving shaft, this can be used as a speed reduction mechanism. It goes without saying that if an appropriate angle conversion mechanism is connected to the driven shaft and used in conjunction with this, it can also be applied to a contra handpiece speed change mechanism. Furthermore, as mentioned above, the rotational speed conversion ratio is determined by the large diameter portion 42 of the ring 4 and the small diameter portion 311 of the rear end side 31 of the shaft 3.
Since it is determined by the ratio of the diameter of Therefore, the diameter of the balls 5 is determined by these two diameters, and the number of balls 5 and ball retainers 21 is also calculated. Furthermore, it is also possible to adopt a tension spring between the ring 4 and the bearing 12 as the spring 6, and instead of disposing the ring 4 so as to impart elasticity to the shaft 3 side. do not have.

As mentioned above, since the actual speed change mechanism of the present invention is based on the rolling motion of balls, speed change transmission is carried out extremely smoothly, there are few mechanical troubles, and assembly is extremely easy. It is extremely suitable for precision mechanical parts such as handpieces.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway vertical sectional view of a typical embodiment of the present invention, FIG. 2 is a sectional view taken along the line in FIG. 1, and FIG. Explanation of symbols, 1... Main body, 11, 12... Ball bearing, 2... Rotating shaft, 21... Ball retainer, 3... Rotating shaft, 31... Rear end side, 4... Annular ring, 5...ball, 6...spring, 7...extraction prevention ring.

Claims (1)

[Claims for Utility Model Registration] 1. A dental clinic in which two rotating shafts 2 and 3, which are rotatable coaxially and oppositely by ball bearings 11 and 12, are connected in a variable speed manner in a main body 1. In the speed change mechanism of a handpiece, the tip side of one shaft 2 is provided with a plurality of split fork-shaped ball retainers 21 parallel to the circumferential direction and at equal intervals, and the rear end of the other shaft 3 is provided with a plurality of fork-shaped ball retainers 21... A ring 4 concentrically surrounds the end side 31 and surrounds the ball retainer 21, and is fitted into the main body 1 so as to be unrotatable in the circumferential direction but slidable in the axial direction. The balls 5 are brought into rolling contact between the ball retainer 21 between the inner periphery of the ring 4 and the outer periphery of the rear end side 31 of the shaft 3, and the elasticity of the spring 6 is constantly applied to the annular ring 4 in the axial direction. The balls 5 are pressed in the centripetal direction by the ring 4 and in the centrifugal direction by the rear end side 31 of the shaft 3, and the shaft has either the shaft 2 or the shaft 3 as the drive side. A speed change mechanism for a dental handpiece characterized in that rotational motion is transmitted to a driven side by rolling the inner circumferential surface of an annular ring 4 of balls 5 and the outer circumferential surface of a shaft 3. 2. The mechanism according to claim 1, wherein a ring 7 for preventing the balls 5 from being pulled out in the axial direction is installed and fixed in the circumferential direction on the distal end side of the ball retainer 21. 3 Utility model registration claim 1 in which the cross-sectional shape of the ball retainer 21 is tapered in the centripetal direction to prevent the balls 5 from coming off in the centripetal direction
Mechanism described in section. 4. The mechanism according to claim 1, wherein the shaft 2 is a driving shaft and the shaft 3 is a driven shaft as a speed increasing mechanism. 5. The mechanism according to claim 1, wherein the shaft 2 is a drive shaft and the shaft 3 is a drive shaft as a speed reduction mechanism.