DENTAL HANDPIECE AND AXIAL GROOVE BALL BEARING

Abstract

The dental handpiece consists of a housing with a handle and a turbine that can be operated with compressed gas or compressed air. The rotational movement of the turbine driven by compressed gas is transmitted to the dental tool via a rotor shaft and a chuck. The rotor shaft is rotatably supported by at least one axial groove ball bearing. The radial rigidity required for operating a dental handpiece is achieved by axially preloading the ball bearings. Projections on the housing and the shaft disc of the at least one axial groove ball bearing allow the axial groove ball bearing to be used as radial groove ball bearings. The proposed design of the dental handpiece exhibits little power loss or frictional loss in comparison to dental handpieces with radial groove ball bearings, and slip and drilling friction components can be virtually completely prevented in particular.

Claims

1. A dental handpiece for rotating a rotating dental tool, comprising: a housing that has a handle and a chuck for receiving the dental tool in the dental handpiece; a turbine which can be driven by compressed gas and/or compressed air and has a turbine wheel and a rotor shaft connected to the turbine wheel; wherein the rotor shaft is connected to the chuck to transmit the rotation of the turbine wheel to the chuck; and at least one axial groove ball bearing having a shaft disc, a housing disc and rolling elements, wherein the rolling elements are arranged between the shaft disc and the housing disc; wherein the shaft disc of the axial groove ball bearing acts on the rotor shaft; and wherein the housing disc of the axial groove ball bearing is mounted in the housing.

2. The dental handpiece according to claim 1, wherein the housing disc has a projection extending in an axial direction of the axial groove ball bearing and the projection covers the rolling elements of the axial groove ball bearing on the outside.

3. The dental handpiece according to claim 1, wherein the axial groove ball bearing is preloaded in an axial direction with a force greater than or equal to 3 N and less than or equal to 8 N.

4. The dental handpiece according to claim 1, wherein the turbine wheel and/or the rotor shaft and/or the shaft disc of the at least one axial groove ball bearing are made in one piece.

5. An axial groove ball bearing comprising: a shaft disc, a housing disc, and rolling elements, wherein the rolling elements are arranged between the shaft disc and the housing disc; wherein the shaft disc of the axial groove ball bearing is designed in such a way that it can be attached to a shaft; wherein the housing disc of the axial groove ball bearing is designed in such a way that the axial groove ball bearing can be fastened in a housing; wherein the housing disc has a projection extending in an axial direction of the axial groove ball bearing; and wherein the projection covers the rolling elements of the axial groove ball bearing on the outside.

6. The axial groove ball bearing according to claim 5, wherein the projection, together with the housing disc, extends over 95% to 105% of the width of the axial groove ball bearing.

7. The axial groove ball bearing according to claim 5, further comprising: a groove in the projection, wherein the groove is formed on the inside of the projection; a step in the shaft disc, wherein the step is arranged on the outside of the shaft disc in the region of the groove; and a snap ring, which can snap into the groove; wherein the step in the shaft disc and the snap ring are formed such that the snap ring engages the step when it is engaged in the groove, whereby the axial groove ball bearing is secured against disintegrating.

8. The axial groove ball bearing according to claim 5, further comprising: a ring, wherein the ring can be fixed to the projection; and a step in the shaft disc, wherein the step is arranged on the outside of the shaft disc in the region of the ring; wherein the ring on the projection and the step in the shaft disc are formed such that the ring engages the step when it is fixed on the projection, whereby the axial groove ball bearing is secured against disintegrating.

9. The axial groove ball bearing according to claim 5, wherein the shaft disc has a projection extending in the axial direction of the axial groove ball bearing, wherein the projection covers the rolling elements on the inside.

10. The axial groove ball bearing according to claim 9, wherein the projection together with the shaft disc extends over 95% to 105% of the width of the axial groove ball bearing.

11. The axial groove ball bearing according to claim 5, wherein the rolling elements are arranged on an outer edge of the axial groove ball bearing.

12. The axial groove ball bearing according to claim 5, wherein the rolling elements are arranged on an inner edge of the axial groove ball bearing.

13. The axial groove ball bearing according to claim 5, further comprising a rolling element cage wherein the rolling element cage separates the rolling elements from one another.

14. The axial groove ball bearing according to claim 13, wherein the rolling element cage is only closed on the inside; and the rolling elements are not completely surrounded on the outside by the rolling element cage.

15. The axial groove ball bearing according to claim 13, wherein the rolling element cage is only closed on the outside; and the rolling elements are not completely surrounded on the inside by the rolling element cage.

Description

[0039] The exemplary embodiments are shown schematically in the figures. Like reference signs in the individual figures denote like or functionally like elements or elements that correspond to one another in respect of their function. In the figures:

[0040] FIG. 1 shows a dental handpiece with axial groove ball bearings;

[0041] FIG. 2 shows an a axial groove ball bearing according to the prior art;

[0042] FIG. 3 shows an axial groove ball bearing with a projection on the housing disc;

[0043] FIG. 4 shows an axial groove ball bearing with projections on the housing and shaft disc;

[0044] FIG. 5 shows an axial groove ball bearing with a ring on the projection of the housing disc;

[0045] FIG. 6 shows a dental handpiece with a turbine wheel with integrated shaft discs of the axial groove ball bearings; and

[0046] FIG. 7 shows a turbine wheel with integrated shaft discs.

[0047] FIG. 1 shows a dental handpiece 100 with a housing 105 and a dental tool 110. The dental tool 110 is clamped in a chuck 120 that is located in the housing 105 of the dental handpiece 100. The chuck 120 is firmly connected to a rotor shaft 130 and via the rotor shaft 130 to a turbine wheel 140. Due to the fixed connection, the rotor shaft 130 can transmit rotational movements and torques of the turbine wheel 140 to the chuck 120 and the dental tool 110 clamped therein. The rotational movements or moments arise when the turbine wheel 140 is driven with the aid of compressed air. For this purpose, the compressed air is routed via channels 150 in a handle 160 of the dental handpiece 100 via the turbine wheel 140. The turbine wheel 140 and rotor shaft 130 represent the turbine or the pneumatic drive of the dental handpiece 100 which is supplied with compressed air via the inlet and outlet air channels 150 of the handle 160.

[0048] In this exemplary embodiment, the rotor shaft 130 is designed as a hollow shaft. It is rotationally supported by two axial groove ball bearings 170, i.e. the ball bearings support the rotor shaft both at rest and when the rotor shaft is rotating. The axial groove ball bearings 170 are arranged on an upper and on a lower area of the rotor shaft 130.

[0049] The axial groove ball bearing 170 is typically fixed or supported with the aid of an additional elastic element in order to dampen or reduce vibrations of the turbine in the dental handpiece, which is operated with compressed gas or compressed air, and the associated noise. For this purpose, the elastic element consists of, for example, an elastic material or elastomer and can be ring-shaped, designed as an O-ring 180 or the like. The axial groove ball bearings 170 are also mounted in the housing 105 of the dental handpiece 100 with the aid of wave spring discs 190.

[0050] The arrangement of the axial groove ball bearings 170 on an upper and on a lower area of the rotor shaft 130 counteracts tilting of the tool axis in the dental handpiece 100 and thus stabilises the dental tool 110 and the rotor shaft 130 in the dental handpiece 100. This prevents the ball bearings 170 from being overloaded as a result of the dental tool 110 tilting.

[0051] The O-rings 180 support the ball bearings 170 in the radial direction. The wave spring discs 190 support the bearings 170 in the axial direction. The elastic or resilient mounting in the radial direction dampens oscillations and vibrations of the pneumatic drive, in particular of the turbine wheel 140 and the rotor shaft 130.

[0052] The wave spring discs 190 preload the axial groove ball bearings 170 with an axial force. The preload produces a radial rigidity of the axial groove ball bearings 170 that is sufficient for dental handpieces 100.

[0053] FIG. 2 shows a conventional or commercially available axial groove ball bearing 200.

[0054] The axial groove ball bearing 200 consists of a housing disc 210, a shaft disc 220 and a plurality of balls 230. The balls 230 are arranged between the housing disc 210 and the shaft disc 220. They are also separated from one another by a ball bearing cage 240 and kept at the same distance from one another.

[0055] If the axial groove ball bearing 200 is used in a dental handpiece, the shaft disc 220 protrudes inwards slightly beyond the housing disc 210. Likewise, the housing disc 210 protrudes slightly beyond the shaft disc 220.

[0056] The ball bearing cage 240 ensures that the balls 230 are evenly arranged along their raceways in the ball bearing 200. It also prevents the balls from touching, rubbing against one another, moving one another and/or impeding their circulation. This is essential for high speed operation of the ball bearing, especially under load, to prevent ball bearing overload and wear.

[0057] FIG. 3 shows an axial groove ball bearing 300 which, in contrast to the axial groove ball bearing 200, has a housing disc 310 with a projection 370 and a shaft disc 320 with a step 340. The projection 370 is on the outside of the housing disc 310 and covers the balls 230 of the axial groove ball bearing 300. Furthermore, the projection 370 has a groove 330. The groove 330 can receive a snap ring 350. The snap ring 350 can be introduced into the axial groove ball bearing 300 via the step 340. The step 340 is also designed in such a way that the snap ring 350 locks the shaft disc 320 against axial displacement when it is mounted or engaged in the groove. The axial groove ball bearing 300 also has a ball bearing cage 360. The ball bearing cage 360 keeps the balls 230 evenly spaced apart from one another.

[0058] The projection 370 increases the area with which the axial groove ball bearing 300 can be mounted, e.g. in a housing 105 of a dental handpiece 100. It can therefore be mounted more stably than, for example, an axial groove ball bearing 200.

[0059] The projection also reduces the discharge of lubricant from the axial groove ball bearing 300, for example by compressed air flowing into the axial groove ball bearing 300. The protection consists in the fact that the projection 370 together with the housing disc 310, the shaft disc 320 and the snap ring 350 forms a labyrinthine system which forces the medium to flow through at least one, two or even three changes of direction. The compressed air has to get through this labyrinth in order to have an effect on the balls and their lubrication. In this way, negative external influences are avoided or at least mitigated.

[0060] After mounting the snap ring 350, the axial groove ball bearing 300 is protected against falling apart and can be mounted on the rotor shaft or in the housing of the turbine head like a radial groove ball bearing.

[0061] In contrast to the cage 240, the ball bearing cage 360 does not completely enclose the balls 230. It is open to the outside. Accordingly, the raceway of the balls 230 in the axial groove ball bearing 300 is further to the outside in comparison to the conventional axial groove ball bearing 200, i.e. the raceway has a larger diameter.

[0062] An alternative embodiment (not shown) very similar to the embodiment shown in FIG. 3 has a longer projection of the housing disc compared to projection 370. In this extended projection there is again a groove 330 into which the snap ring 350 can be inserted. This is designed in such a way that it secures the shaft disc against axial displacement when it is engaged in the groove. By lengthening the projection, the formation of a step 340 in the shaft disc can be omitted.

[0063] FIG. 4 shows an axial groove ball bearing 400 which, in comparison to the axial groove ball bearing 300, comprises a further developed shaft disc 420 and a further developed ball bearing cage 460. The shaft disc 420 has a projection 470 similar to the housing disc 310. In contrast to the housing disc 310, the projection 470 is arranged on the inside of the shaft disc and covers the balls 230. The ball bearing cage 470 is adapted to the developed shaft disc 420 in comparison to the cage 370, i.e. its inner diameter has been increased slightly in order to create space for the projection 470.

[0064] The balls 230 of the axial groove ball bearing 400 are covered on both sides, i.e. both of the projection 370 of the housing disc 310 as well as the projection 470 of the shaft disc. The balls 230 are therefore even better protected against lubricant discharge in the axial groove ball bearing 400 than in an axial groove ball bearing 300 according to FIG. 3. The additional protection also consists in that the projection 470 together with the housing disc 310 and the shaft disc 420 form a labyrinthine system that forces the air flow through it to make a multitude of changes in direction. The compressed air must flow through this labyrinth in order to have an effect, for example, on the balls 230, the ball bearing cage 460, their raceways and their lubrication. In this way, negative external influences are avoided or at least mitigated.

[0065] Furthermore, due to the two projections 370 and 470, the axial groove ball bearing 400 looks like a radial groove ball bearing from the outside. In addition, it can be handled like a radial groove ball bearing due to the anti-collision protection formed by the groove 330, the step 340 and the snap ring 350.

[0066] FIG. 5 shows an axial groove ball bearing 500 with a housing disc 510 and a shaft disc 420. In comparison to the axial groove ball bearing 400, the axial groove ball bearing 500 has an alternative protection against decay. The bearing 500 is not protected from disintegrating by a snap ring as in the case of the bearing 400, but by a ring 550. The ring 550 is fixed laterally to a projection 570 of the housing disc 510. For this purpose, the ring 550 can, for example, be welded onto the projection after assembly.

[0067] So that the bearing 500 is not widened by the attached ring, the projection 570 is designed somewhat shorter than the projection 470 in the axial groove ball bearing 400. However, this represents only a preferred embodiment, i.e. such a ring can also be applied to a housing disc with a non-shortened projection which, together with the housing disc, extends over the entire width of the bearing.

[0068] Similarly to the axial groove ball bearing 400, the shaft disc 420 of the axial groove ball bearing 500 has a step 340 which is designed such that the ring 550 engages in it in the assembled state and thus the shaft disc 420 is blocked against axial displacement. In the aforementioned case with the projection that is not shortened, such a step 340 can be omitted.

[0069] To protect an axial groove ball bearing according to the invention from disintegrating, not only the projection of the housing disc can be used. In embodiments in which the shaft disc has a projection, an equivalent protection against decay can be achieved with comparable means at the end of the protrusion of the shaft disc. For this purpose, the housing disc may then have a step.

[0070] FIG. 6 shows a dental handpiece 600 which, in comparison to the dental handpiece 100, has a turbine wheel 640 with integrated shaft discs. The turbine wheel 640 represents a one-piece embodiment of the turbine wheel 140 and the shaft discs of the axial groove ball bearings.

[0071] FIG. 7 shows the combination of turbine wheel 640 with integrated shaft discs. Furthermore, FIG. 7 shows the roller bearings 230 and housing discs 310, which can also be seen in FIG. 6, again on a larger scale. The assembly can be assembled outside of the dental handpiece 600 and, in the assembled state, can be mounted on the rotor shaft and inserted into the housing 105.

[0072] In addition to a one-piece design of the turbine wheel and the shaft discs, the shaft discs and the rotor shaft can also be designed in one piece. This applies not only to the turbine wheels 140, rotor shafts 130 and shaft discs 320, but also to other embodiments of these three components.

Glossary

Projection

[0073] A projection refers to a protruding part of a component that projects or protrudes from the component.

Axial Groove Ball Bearing

[0074] An axial groove ball bearing is a ball bearing in which a housing disc, balls and a shaft disc are arranged one behind the other in the axial direction.

Drilling Friction

[0075] Drilling friction occurs at the support point of a body rotating about the vertical axis on a plane.

Ball Bearing

[0076] A ball bearing is a roller bearing in which the rolling elements are balls.

Radial Bearing

[0077] A radial bearing is a roller bearing in which an outer ring, rolling elements and an inner ring are arranged one behind the other in the radial direction. The outer ring usually has a larger circumference than the inner ring. The inner ring, on the other hand, usually has a smaller circumference.

Slip

[0078] Slip generally refers to the deviation in the speeds of mechanical elements in frictional contact with one another and the associated relative displacement of the mechanical elements associated with friction losses or power losses.

Chuck

[0079] A chuck is a device that accommodates tools such as drills or milling cutters on tools (e.g. a dental handpiece).

Roller Bearing

[0080] A roller bearing is a bearing for rotating components such as axles or shafts in which between at least a first ring, which is connected to a housing and is accordingly also called the outer ring, and at least a second ring, which is connected to the rotating component and is accordingly called the inner ring, rolling elements or rolling bodies reduce the frictional resistance between the rings or discs. Roller bearings can have one or more rows of rolling elements, which may be separated from one another by additional rings or discs. The rolling elements roll, for example, on hardened steel surfaces with optimised lubrication to keep rolling friction low. They move on raceways or grooves that are ground into the rings. Depending on their design, roller bearings can absorb radial and/or axial forces.

Rolling Element

[0081] A rolling element is a part of a roller bearing that reduces the frictional resistance between the rings or discs of a roller bearing. Rolling elements in a roller bearing can be balls, rollers, cylinders, needles, barrels or cones.

Rolling Element Cage

[0082] A rolling element cage is an annular component that can accommodate the rolling elements of a roller bearing and keep them at fixed, preferably equal distances from one another. Rolling element cages can be made in one piece or in two pieces.

Wave Spring Disc

[0083] A wave spring disc is a wave-shaped spring or ring disc that produces its spring effect by being conical, bent on two sides, or wavy. Wave spring discs are used for defined, axial preloading of roller bearings, primarily miniature and small ball bearings.

REFERENCE NUMERALS

[0084] 100 Dental handpiece [0085] 105 Housing [0086] 110 Dental tool [0087] 120 Chuck [0088] 130 Rotor shaft [0089] 140 Turbine wheel [0090] 150 Duct [0091] 160 Handle [0092] 170 Axial groove ball bearing [0093] 180 O-ring [0094] 190 Wave spring disc [0095] 200 Axial groove ball bearing [0096] 210 Housing disc [0097] 220 Shaft disc [0098] 230 Ball [0099] 240 Ball bearing cage [0100] 300 Axial groove ball bearing [0101] 310 Housing disc [0102] 320 Shaft disc [0103] 330 Groove [0104] 340 Step [0105] 350 Snap ring [0106] 360 Ball bearing cage [0107] 370 Projection [0108] 400 Axial groove ball bearing [0109] 420 Shaft disc [0110] 460 Ball bearing cage [0111] 470 Projection [0112] 500 Axial groove ball bearing [0113] 510 Housing disc [0114] 550 Ring [0115] 570 Projection [0116] 600 Dental handpiece [0117] 640 Turbine wheel with integrated shaft disc

CITED LITERATURE

Cited Patent Literature

[0118] U.S. Pat. No. 4,249,869 A [0119] DE 10 2014 220 872 A1 [0120] DE 10 2015 012 332 A1