Dental handpiece and axial groove ball bearing

Abstract

A dental handpiece for rotating rotary dental instruments has been proposed. The dental handpiece consists of a housing with a handle and a turbine that can be powered by compressed gas or compressed air. The rotational motion of the turbine, driven by compressed gas, is transmitted to the dental instrument via a rotor shaft and a chuck. The rotor shaft is rotatably supported by at least one axial groove ball bearing. The radial stiffness required for operating the dental handpiece is achieved by axially preloading the ball bearing. Protrusions on the housing and shaft disc of the at least one axial groove ball bearing allow the axial groove ball bearing to be used as a radial groove ball bearing. Compared to dental handpieces with radial groove ball bearings, the proposed dental handpiece design exhibits almost no power or friction losses, and can virtually completely prevent slippage and component drilling friction. Therefore, in addition to reducing noise emissions while the dental instrument is being driven, the service life of the dental handpiece can also be extended.

Description

[Technical field]

[0001] The present invention relates to a dental handpiece that can be fitted with a number of different dental instruments for dental treatment. These include, for example, drills, milling cutters, files, polishers, smoothers and / or finishers. Prior to dental treatment, the instruments are clamped to the dental handpiece and rotated using a pneumatic drive. The drive is provided by a turbine that runs on compressed gas or compressed air. The gas or drive air is generally supplied to the turbine through a channel in the dental handpiece. The associated rotational movement of the turbine and the dental instruments it drives is characterized by high speeds of up to 500,000 revolutions per minute.

[0002] The practical requirements of dental handpieces, especially the high speeds, bring many challenges to the storage of the rotating components of dental handpieces and the dental instruments clamped to them. Therefore, the storage is usually aided by roller bearings, such as ball bearings. These allow bearings that ensure a safe and low-vibration use of the dental handpiece, even at high speeds. The roller bearings support the rotor or hollow shaft of the pneumatic drive, where the dental instruments can be clamped with the aid of a chuck or collet.

[0003] The roller bearings not only have to ensure permanently smooth and quiet operation at high speeds, but also have to cope with the usually very high accelerations and decelerations of the rotor shaft and the dental instruments. The associated stresses arise, for example, when the dental handpiece is actuated or during the dental treatment itself, when the dental instruments are pressed against the teeth with the forces required for the treatment.

[0004] The forces applied during the procedure not only lead to friction losses and associated decelerations and accelerations of the dental instruments, but also to tilting of the instruments or corresponding tilting moments of the dental handpiece, which are transferred from the instruments via the rotor or hollow shaft directly to the roller bearings. Depending on the strength of the forces used, this can lead to overloading of the bearings.

[0005] Tilting of axes such as bearing and / or instrument axes not only occurs in dental treatment, but is often the result of the narrow installation space of dental handpieces, which is severely limited by the specifications of dental equipment manufacturers. Therefore, in most cases, the inner diameter of roller bearings is fixed at 3.175 mm (1 / 8 inch), the outer diameter at 6.35 mm (1 / 4 inch), and the width at 2.779 or 2.38 mm. Due to the fact that the vibration-damping ball bearings are supported in the housing, preferably with O-rings, and are axially preloaded against each other by wave spring disks, the rotor shaft can assume a tilted position when the drilling instrument is loaded. Even a slight imbalance, which results in considerable vibrations and noise due to high speeds, is recognized as degrading quality.

[0006] A further problem is the exhaust of lubricant through the compressed gas or air guided through the pneumatic drive or turbine and the dental handpiece. Part of the exhaust air from the turbine flows through the ball bearings and carries the lubricant to the outside, so that after a short time, a lack of lubrication occurs. After each dental treatment, the handpiece is cleaned for hygiene purposes by rinsing and lubricating with water and / or alkaline cleaners and sterilized with superheated steam. [Background technology]

[0007] Some of the problems just presented have already been solved in US Pat. No. 4,249,896. This document proposes a dental handpiece with two radial groove ball bearings arranged both in the upper and lower regions of the rotor shaft of the dental handpiece with a chuck. The ball bearings can thus exert a supporting action on the chuck, which stabilizes the chuck and the tool clamped therein against tilting. In cross section, the associated tilt or load axis connects the two ball bearings to each other in an X-shape, for this reason this configuration is also called X-configuration. Furthermore, the ball bearings are mounted in the housing with the help of elastic O-rings to damp vibrations transmitted to the housing.

[0008] DE 10,2015,012,332 A1 represents a further development of such a dental handpiece. There, further measures for compensating for the effect of tilting are presented, which are mainly aimed at reducing the elliptical character of the running path when tilting, by providing the raceway of the outer ring with three different zones. This prevents or compensates for the balls of the ball set advancing at different speeds when tilting and for premature wear of the ball bearing cage as a result of the binding forces from the ball set, with the resultant failure of the ball bearing.

[0009] The problem of lubricant evacuation by compressed gas or compressed air is compensated for by an adhesion promoter layer, which is described in DE 10 2014 220 872 A1, which attracts the lubricant and is advantageously applied to the surfaces of the balls, the inner ring and / or the outer ring of the proposed radial groove ball bearing.

[0010] Despite these advances, dental handpieces known from the prior art still suffer from a number of problems. These arise due to the nature of these tribological systems. In particular, radial groove ball bearings exhibit power losses and wear due to friction and slippage of the drillings. In this way, not only can a significant part of the drive energy be consumed, but also the life of the ball bearings can be significantly shortened. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] U.S. Pat. No. 4,249,896 [Patent Document 2] DE 10,2015,012,332 [Patent Document 3] DE 10,2014,220,872 Summary of the Invention [Problem to be solved by the invention]

[0012] It is therefore an object of the present invention to provide a dental handpiece with low power loss and low wear, which is also characterized by high resilience, low noise emission and smooth running. [Means for solving the problem]

[0013] This object is achieved by the subject matter of the independent claims. Preferred further developments are specified in the dependent claims. The use of the singular is not intended to exclude the plural and vice versa, unless specifically disclosed otherwise.

[0014] To this end, a dental handpiece has been proposed for rotating a rotary dental instrument. The rotary dental instrument may be an instrument for drilling, milling, grinding, scraping, polishing and / or finishing or smoothing. The dental handpiece consists of a housing with a handle, which usually has channels for supplying and removing compressed gas or compressed air. The housing also comprises a chuck and a turbine for receiving the dental instrument. The turbine has a turbine wheel and a rotor shaft connected to the turbine wheel and is connected via the rotor shaft to the chuck of the dental handpiece. For this purpose, the rotor shaft may be designed as a hollow shaft that accommodates the chuck in its cavity.

[0015] The turbine can be driven by compressed gas or compressed air, which for this purpose can be led to the turbine through inlet and outlet air ducts in the handle. In the turbine, the compressed gas or compressed air strikes a turbine wheel and drives it. The rotational movement of the turbine wheel and the corresponding torque are transmitted to the chuck and, if necessary, to the dental instruments clamped therein by means of a rotor shaft connected to the turbine wheel. In this way, the chuck and, optionally, the dental instruments clamped therein can be driven in rotation.

[0016] The design of the dental handpiece also provides for at least one axial groove ball bearing having a plurality of rolling elements. The axial groove ball bearing is accommodated in a housing and supports the rotor shaft both during rotation and when not in use. For this purpose, the axial groove ball bearing has a shaft disc connected to the rotor shaft and a housing disc used to mount or fix the bearing in the housing of the dental handpiece. In the case of commonly used ball bearings, the rolling elements represent balls.

[0017] Axial groove ball bearings have lower power or friction losses than radial groove ball bearings. In particular, slip components can be almost completely avoided or even eliminated. Thus, in addition to reducing noise emissions while the dental instrument is being driven, the service life of the dental handpiece can also be extended.

[0018] Due to the axial arrangement of the shaft disk, the rolling elements and the housing disk, axial groove ball bearings have an axial load direction due to their construction. They are generally suitable for absorbing axial forces, but often have insufficient stiffness or resistance to radial forces. For this reason, a preconception has been established that axial groove ball bearings are not suitable for use in dental handpieces, where radial forces are generated, in particular by high asymmetric external loads during drilling, milling, grinding, scraping, polishing and / or finishing or smoothing, and where tilting or tilting moments of dental instruments are unavoidable. Therefore, those skilled in the art do not consider using axial groove ball bearings in dental handpieces due to their lower radial stiffness compared to radial groove ball bearings for use in dental handpieces, and instead choose bearings with a radial load direction, in particular radial groove ball bearings. However, this has not been confirmed in simulations and calculations of dental handpieces with axial groove ball bearings, nor in practice.

[0019] The proposed dental handpiece with axial groove ball bearing can be constructed using commercially available components, keeping manufacturing costs low. Furthermore, the design according to the invention is able to absorb higher loads in the axial direction, especially when the collet is activated and the drilling tool is replaced, which exerts a static load on the ball bearing.

[0020] Commercially available groove ball bearings can be used in the dental handpiece according to the invention. However, these have the disadvantage that the shaft disc, the housing disc and the cage with the set of balls do not form a closed unit and collapse during assembly or disassembly, making handling very complicated. However, for a better seating of the bearing in the dental handpiece, in particular for a larger outer bearing surface of the housing disc, it is advantageous if the housing disc of the axial groove ball bearing has a protrusion extending in the axial direction of the bearing. The protrusion is designed to cover the rolling elements of the axial groove ball bearing. The remaining components of the bearing are simple and inexpensive bearing components. This applies in particular to the rolling elements, the possible rolling element cage and the shaft disc.

[0021] The protrusions also reduce the amount of lubricant that is expelled from the axial groove ball bearing, particularly the portion of lubricant that is expelled when compressed gas or compressed air flows through the dental handpiece.

[0022] The radial stiffness of an axial groove ball bearing can be improved, for example, by increasing the axial preload from, for example, 2 N, typical for radial bearings of dental turbines, to a higher value, between 3 and 8 N, but preferably 5 N, where N denotes the unit of force Newton. By such an increased preload, the resistance or radial stiffness of a conventional axial groove ball bearing can also be increased against radial forces, up to the level required for dental handpieces.

[0023] The components of the proposed dental handpiece are shown only as individual components for better understanding. In an embodiment, the components may be embodied as separate components. In a preferred embodiment, two or more of these individual components can also be made in one piece. This applies, for example, to the shaft disk of at least one axial groove ball bearing and the turbine wheel of the dental handpiece, which are not only available as separate components but can also be made in one piece. Similarly, the shaft disk and the rotor shaft and / or the turbine wheel can be made in one piece. In these cases, the raceways of the shaft disk are already integrated into the corresponding planes of the turbine wheel or rotor shaft. Such an embodiment according to the invention therefore does not have individual bearings, but has a design in which the bearings are integrated into the turbine wheel or rotor shaft. This simplifies the assembly of the dental handpiece.

[0024] This object is also achieved by an axial groove ball bearing with a plurality of rolling elements, which has a shaft disc connectable to the shaft and a housing disc used to mount or fasten the bearing to the housing. The rolling elements are arranged between the raceways of the shaft and the housing disc, similar to radial groove ball bearings. However, the associated raceways are arranged axially instead of radially.

[0025] In contrast to commercially available axial groove ball bearings, the axial groove ball bearing according to the invention has a housing disc with protrusions extending in the axial direction of the bearing. The protrusions are designed to cover the rolling elements of the axial groove ball bearing. The protrusions increase the outer surface area or bearing surface, which can be used to preload and / or seat or fix the bearing in the housing.

[0026] The protrusions also reduce some of the lubricant that is expelled from the axial groove ball bearing, particularly lubricant expulsion that occurs when compressed gas or compressed air flows through the bearing.

[0027] The rolling elements do not have to be completely covered by the projections: in order to protect or even shield them from external influences, it often makes sense for the housing disc, including the projections, to extend over 95% to 105% of the width of the bearing.

[0028] Due to their axial arrangement, axial groove ball bearings are not protected from collapse as many radial groove ball bearings are. This can be particularly problematic during assembly. In contrast, radial groove ball bearings are protected from collapse by their design.

[0029] To simplify assembly, axial groove ball bearings with an axial overlap of the housing disc with the projection of 95%-105% of the width of the bearing can also be provided with protection against falling out. For this purpose, the projection is provided with a groove, which is formed on the inside of the projection, i.e. on the side of the projection closest to the rolling elements. Furthermore, the shaft disc can be provided with a step in the area of ​​the groove, so that the shaft disc has a first part with a smaller outer diameter and a second part with a larger outer diameter. The part with the smaller outer diameter is arranged in such a way that a retaining ring can be inserted into the bearing from the outside in order to fit it into the groove of the projection. The second part of the shaft disc is thus designed in such a way that the retaining ring snapped into the groove locks the shaft disc against axial movement. The axial groove ball bearing can thus be free from any risk of collapse. This significantly simplifies the assembly of the axial groove ball bearing on the rotor shaft and in the housing of the turbine head.

[0030] The proposed axial groove ball bearing with a cantilever offers another possibility of protecting the bearing from collapse. To do this, a ring is attached, for example welded, to the flat face of the lug, and the shaft disk is provided with a step in the area of ​​the ring, so that the shaft disk has a first part with a smaller outer diameter and a second part with a larger outer diameter. The part with the smaller outer diameter is arranged in such a way that the ring engages in the step formed by the two parts after fastening to the lug. The second part of the shaft disk is designed in such a way that the ring attached to the lug locks the shaft disk against axial movements and thus protects the axial groove ball bearing from collapse.

[0031] In addition to the protrusions of the housing disc, the axial groove ball bearing according to the invention can also be designed with protrusions of the shaft disc. The protrusions are designed to cover the rolling elements of the axial groove ball bearing. The protrusions increase the width of the bore (inner diameter) or the inner contact surface that can be used to connect the bearing to the shaft. In this way, the fit of the axial groove ball bearing to the shaft can be improved.

[0032] As mentioned above, the rolling elements do not need to be completely covered by the projections of the shaft disc, however, to further improve the fit onto the rotor shaft, it makes sense if the shaft disc, including the projections, extends over 95% to 105% of the width of the bearing.

[0033] In a particularly preferred embodiment, the housing disk with the projections and the shaft disk with the projections extend over 95% to 105% of the width of the bearing. Furthermore, as mentioned above, the axial groove ball bearing is protected from the risk of collapse by the retaining ring and the corresponding groove or step. In these cases, the axial groove ball bearing looks like a radial groove ball bearing from the outside and can be installed on the rotor shaft or turbine head just like a radial groove ball bearing. Despite the fact that the rolling elements are radially covered on both sides, the axial groove ball bearing only occupies a minimal amount of space, or less than the space of a comparable radial groove ball shaft.

[0034] In the axial groove ball bearing according to the invention, the raceways of the rolling elements can be machined into the shaft or into the housing disk using suitable grinding or honing techniques. To make grinding the raceways easier, the rolling elements can be located on the outer edge of the shaft disk of the axial groove ball bearing, i.e. the raceways of the rolling elements have the largest possible diameter for a given size of the shaft disk and other components such as the ball bearing cage that may be present. This is particularly advantageous when the shaft disk is provided with protrusions on its inner edge. The protrusions and the raceways on the shaft disk are as far apart as possible, so that more space is available for the use of the corresponding grinding or honing tools.

[0035] The rolling elements can also be arranged on the inner edge of the shaft disc of the axial groove ball bearing. The raceways therefore have a smaller radius, so that the rolling elements have to cover as little distance as possible per revolution of the shaft. Such an arrangement of the rolling elements offers an additional advantage if the housing disc is equipped with projections on its outer edge: the projections and the raceways of the rolling elements on the housing disc are as far apart as possible, so that more space is available for the use of corresponding grinding or honing tools.

[0036] The rolling elements may be arranged in a rolling element cage, which separates them from each other. In particular, the rolling element cage keeps the rolling elements at the same distance from each other and thus prevents the rolling elements from slipping in the raceways or from contacting and / or interfering with each other. This allows for more reliable operation, for example at high speeds. In many cases the rolling element cage keeps the balls evenly spaced. Alternatively, axial groove ball bearings can also operate as a full complement without a rolling element cage.

[0037] If the rolling element cage does not completely surround the rolling elements on the outside, the raceways of the rolling elements can be shifted to a larger diameter: in this case, the rolling element cage is closed only on the inside and the outer diameter of the shaft disc is given by the diameter of the raceways and the diameter of the rolling elements.

[0038] If the rolling element cage does not completely surround the rolling elements on the inside, the raceways of the rolling elements can be shifted to a smaller diameter, in which case the rolling element cage is only closed on the outside.

[0039] Further details and features will become apparent from the following description of preferred exemplary embodiments in conjunction with the drawings, where each feature can be implemented individually or in combination with each other. The possibilities for achieving the objective are not limited to the exemplary embodiments. Thus, for example, a specified range always includes all intermediate values ​​(not specified) and all possible subranges.

[0040] Exemplary embodiments are illustrated diagrammatically in the drawings, in which like reference numbers in the individual figures indicate like or functionally similar elements or elements that correspond to one another in terms of their functionality. [Brief description of the drawings]

[0041] [Figure 1] 1 shows a dental handpiece having an axial groove ball bearing. [Diagram 2] 1 shows an axial groove ball bearing according to the prior art. [Diagram 3] 1 shows an axial groove ball bearing with protrusions on the housing disc. [Figure 4] 1 shows an axial groove ball bearing with protrusions on the housing and shaft disc. [Diagram 5] FIG. 2 shows an axial groove ball bearing with a ring on a projection of a housing disc. [Figure 6] 1 shows a dental handpiece with a turbine wheel having an integral shaft disc of an axial groove ball bearing. [Figure 7] 1 shows a turbine wheel with an integral shaft disc. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] FIG. 1 shows a dental handpiece 100 with a housing 105 and a dental instrument 110. The dental instrument 110 is clamped in a chuck 120 arranged in the housing 105 of the dental handpiece 100. The chuck 120 is rigidly connected to a rotor shaft 130 and via the rotor shaft 130 to a turbine wheel 140. Due to the rigid connection, the rotor shaft 130 can transmit the rotational movement and torque of the turbine wheel 140 to the chuck 120 and to the dental instrument 110 clamped therein. The rotational movement or moment is generated when the turbine wheel 140 is driven with the help of compressed air. For this purpose, the compressed air is delivered via the turbine wheel 140 through a channel 150 in a handle 160 of the dental handpiece 100. The turbine wheel 140 and the rotor shaft 130 represent the turbine or pneumatic drive of the dental handpiece 100 to which the compressed air is supplied via the inlet and outlet air channels 150 of the handle 160.

[0043] In this exemplary embodiment, the rotor shaft 130 is designed as a hollow shaft. It is rotatably 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 in the upper and lower regions of the rotor shaft 130.

[0044] The axial groove ball bearing 170 is typically fixed or supported with an additional elastic element to damp or reduce the vibrations of the turbine in dental handpieces operating with compressed gas or compressed air, and the associated noise. For this purpose, the elastic element may, for example, consist of an elastic material or elastomer, be ring-shaped, be designed as an O-ring 180, or the like. The axial groove ball bearing 170 is also mounted in the housing 105 of the dental handpiece 100 with a wave spring disc 190.

[0045] The placement of axial groove ball bearings 170 at the upper and lower regions of the rotor shaft 130 counteracts tilting of the instrument axis at the dental handpiece 100, thus stabilizing the dental instrument 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 instrument 110 being tilted.

[0046] An O-ring 180 radially supports the ball bearing 170. A wave spring disk 190 axially supports the bearing 170. The radial resilience or elastic mounting damps oscillations and vibrations of the pneumatic drive, particularly the turbine wheel 140 and rotor shaft 130.

[0047] The wave spring disc 190 preloads an axial force on the axial groove ball bearing 170. The preload creates sufficient radial stiffness in the axial groove ball bearing 170 for the dental handpiece 100.

[0048] FIG. 2 illustrates a conventional or commercially available axial groove ball bearing 200 .

[0049] The axial groove ball bearing 200 consists of a housing disk 210, a shaft disk 220, and a number of balls 230. The balls 230 are disposed between the housing disk 210 and the shaft disk 220. They are also separated from each other by a ball bearing cage 240, which keeps them at the same distance from each other.

[0050] When the axial groove ball bearing 200 is used in a dental handpiece, the shaft disc 220 protrudes inwardly slightly beyond the housing disc 210. Similarly, the housing disc 210 protrudes inwardly slightly beyond the shaft disc 220.

[0051] The ball bearing cage 240 ensures that the balls 230 are evenly spaced along the raceways of the ball bearing 200. It also prevents the balls from touching, rubbing against each other, moving against each other, and / or impeding their circulation, which is essential to prevent overloading and wear of the ball bearings during high speed operation of the ball bearings, especially under load.

[0052] FIG. 3 shows an axial groove ball bearing 300, which, in contrast to the axial groove ball bearing 200, has a housing disk 310 with a projection 370 and a shaft disk 320 with a step 340. The projection 370 is on the outside of the housing disk 310 and covers the balls 230 of the axial groove ball bearing 300. The projection 370 also has a groove 330. The groove 330 can receive a retaining ring 350. The retaining ring 350 can be introduced into the axial groove ball bearing 300 through the step 340. The step 340 is also designed to lock the shaft disk 320 against axial movement when the retaining ring 350 is seated 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 from each other.

[0053] The protrusions 370 increase the area over which the axial groove ball bearing 300 can be mounted, for example, in the housing 105 of the dental handpiece 100. Thus, the bearing can be mounted more stably than the axial groove ball bearing 200, for example.

[0054] The protrusions also reduce the draining of lubricant from the axial groove ball bearing 300, for example by compressed air entering the axial groove ball bearing 300. The protection consists in the fact that the protrusions 370 together with the housing disk 310, the shaft disk 320 and the retaining ring 350 form a labyrinth system that forces the medium to flow through at least one, two or even three changes of direction. To affect the balls and their lubrication, the compressed air must pass through this labyrinth. In this way, negative external influences are avoided or at least reduced.

[0055] After the retaining ring 350 is installed, the axial groove ball bearing 300 is protected from falling out and can be installed on a rotor shaft or turbine head housing like a radial groove ball bearing.

[0056] In contrast to the cage 240, the ball bearing cage 360 ​​does not completely surround the balls 230. It is open to the outside. Thus, the raceways of the balls 230 of the axial groove ball bearing 300 are further outward compared to the conventional axial groove ball bearing 200, i.e. the raceways have a larger diameter.

[0057] An alternative embodiment (not shown), very similar to the embodiment shown in Figure 3, has a longer protrusion of the housing disc compared to the protrusion 370. This extended protrusion also has a groove 330 into which a retaining ring 350 can be inserted, which is designed to secure the shaft disc against axial movement when the shaft disc is engaged in the groove. By lengthening the protrusion, it is possible to omit forming a step 340 in the shaft disc.

[0058] 4 shows an axial groove ball bearing 400 with a further developed shaft disc 420 and a further developed ball bearing cage 460 compared to the axial groove ball bearing 300. The shaft disc 420 has a protrusion 470 similar to the housing disc 310. In contrast to the housing disc 310, the protrusion 470 is arranged on the inside of the shaft disc and covers the balls 230. The ball bearing cage 470 is adapted to the shaft disc 420 which is developed compared to the cage 370, i.e. its inner diameter is slightly increased to make room for the protrusion 470.

[0059] The balls 230 of the axial groove ball bearing 400 are covered on both sides, i.e. by the projections 370 of the housing disc 310 and by the projections 470 of the shaft disc. The balls 230 are therefore much better protected from the expulsion of the lubricant in the axial groove ball bearing 400 than in the axial groove ball bearing 300 according to FIG. 3. An additional protection consists in that the projections 470 together with the housing disc 310 and the shaft disc 420 form a labyrinth system which causes a number of directional changes in the air flow through it. The compressed air must flow through this labyrinth to affect, for example, the balls 230, the ball bearing cage 460, their raceways and their lubrication. In this way, negative external influences are avoided or at least reduced.

[0060] Also, due to the two protrusions 370, 470, the axial groove ball bearing 400 appears to be a radial groove ball bearing from the outside. Furthermore, due to the anti-crash protection provided by the groove 330, the step 340 and the retaining ring 350, it can be treated like a radial groove ball bearing.

[0061] FIG. 5 shows an axial groove ball bearing 500 with a housing disc 510 and a shaft disc 420. In comparison with the axial groove ball bearing 400, the axial groove ball bearing 500 has an alternative protection against damping. The bearing 500 is protected from disassembly not by a retaining 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.

[0062] In order that the bearing 500 is not widened by the attached ring, the projections 570 are designed somewhat shorter than the projections 470 of the axial groove ball bearing 400. However, this only represents a preferred embodiment, i.e. such a ring can also be applied to housing discs with non-shortened projections that extend over the entire width of the bearing together with the housing disc.

[0063] Similar to the axial groove ball bearing 400, the shaft disc 420 of the axial groove ball bearing 500 has a step 340 designed to engage with the ring 550 in the assembled state and thus prevent the shaft disc 420 from moving axially. In the aforementioned case where the projection is not shortened, such a step 340 can be omitted.

[0064] To protect the axial groove ball bearing according to the invention from collapse, other than the protrusions of the housing disc can be used. In the embodiments in which the shaft disc has a protrusion, an equivalent protection against damping can be achieved by equivalent measures at the ends of the protrusions of the shaft disc. For this purpose, the housing disc may have a step.

[0065] 6 shows a dental handpiece 600, which, in comparison to dental handpiece 100, has a turbine wheel 640 with an integral shaft disc. Turbine wheel 640 represents an embodiment of the integral turbine wheel 140 and shaft disc of an axial groove ball bearing.

[0066] Figure 7 shows the combination of turbine wheel 640 and integral shaft disc. Additionally, Figure 7 shows roller bearing 230 and housing disc 310, which can also be seen on a larger scale in Figure 6. The assembly can be assembled outside of dental handpiece 600 and, once assembled, attached to the rotor shaft and inserted into housing 105.

[0067] In addition to the integral design of the turbine wheel and the shaft disk, the shaft disk and the rotor shaft can also be designed integrally. This applies to the turbine wheel 140, the rotor shaft 130 and the shaft disk 320, as well as to other embodiments of these three components. term

[0068] protrusion A protrusion refers to a protruding portion of a component that protrudes or projects from the component.

[0069] Axial groove ball bearing An axial groove ball bearing is a ball bearing in which a housing disc, balls and a shaft disc are arranged axially one behind the other.

[0070] Perforation friction Friction in drilling occurs at the support point of an object rotating about a vertical axis on a plane.

[0071] ball bearing A ball bearing is a roller bearing in which the rolling elements are balls.

[0072] Radial bearings A radial bearing is a roller bearing with an outer ring, rolling elements, and an inner ring arranged radially one behind the other. The outer ring usually has a larger circumference than the inner ring, while the inner ring usually has a smaller circumference.

[0073] slip Slip generally refers to the deviation in speed of mechanical elements in frictional contact with one another and the associated relative movement of the mechanical elements associated with friction or power losses.

[0074] Chuck A chuck is a device that houses an instrument, such as a drill or milling blade, on an instrument (eg, a dental handpiece).

[0075] Roller bearings A roller bearing is a bearing for rotating a component, such as an axle or shaft, in which the rolling elements or rolling bodies reduce the frictional resistance between the rings or discs between at least a first ring, connected to the housing and appropriately also called the outer ring, and at least a second ring, connected to the rotating component and appropriately called the inner ring. Roller bearings can have one or more rows of rolling elements, which may be separated from each other by additional rings or discs. The rolling elements roll, for example, on hardened steel surfaces, with optimized lubrication to keep the rolling friction low. They move on raceways or grooves ground into the rings. Depending on their design, roller bearings can absorb radial and / or axial forces.

[0076] Rolling elements The rolling elements are the parts of a roller bearing that reduce the frictional resistance between the rings or discs of the roller bearing. The rolling elements of a roller bearing can be balls, rollers, cylinders, needles, barrels or cones.

[0077] Rolling Element Cage A rolling element cage is an annular component that can accommodate the rolling elements of a roller bearing and keep them at a fixed, preferably equal, distance from each other. The rolling element cage can be made in one piece or in two pieces.

[0078] Wave Spring Disc A wave spring disc is a wavy spring or ring disc that produces its spring effect by being conical, curved or wavy on two sides. Wave spring discs are used for defined axial preload of roller bearings, mainly small and miniature ball bearings. [Explanation of symbols]

[0079] 100 Dental Handpieces 105 Housing 110 Dental instruments 120 Chuck 130 rotor shaft 140 Turbine Wheel 150 Duct 160 Handle 170 Axial groove ball bearing 180 O-ring 190 Wave Spring Disc 200 Axial groove ball bearing 210 Housing Disc 220 Shaft Disc 230 balls 240 Ball Bearing Cage 300 Axial groove ball bearing 310 Housing Disc 320 Shaft Disc 330 Groove 340 steps 350 retaining ring 360 Ball Bearing Cage 370 Protrusion 400 Axial groove ball bearing 420 Shaft Disc 460 Ball Bearing Cage 470 Protrusion 500 Axial groove ball bearing 510 Housing Disc 550 Ring 570 Protrusion 600 Dental Handpiece 640 Integrated shaft disc turbine wheel

Claims

1. A dental handpiece (100; 600) for rotating a rotary dental instrument (110), comprising: A housing (105), A handle (160); a housing having a chuck (120) for receiving the dental instrument (110) in the dental handpiece (100); A turbine capable of being driven by compressed gas and / or compressed air, comprising a turbine wheel (140; 640) and a rotor shaft (130) connected to said turbine wheel (140; 640), a turbine, the rotor shaft (130) being connected to the chuck (120) so as to transmit the rotation of the turbine wheel (140; 640) to the chuck (120); and Two axial groove ball bearings (170; 200; 300; 400; 500) arranged in the upper and lower regions of the rotor shaft (130), each axial groove ball bearing having: A shaft disc (220; 320; 420), A housing disk (210; 310; 510), A rolling element (230), The rolling element (230) comprises two axial groove ball bearings arranged between the shaft disc (220; 320; 420) and the housing disc (210; 310; 510), the shaft disc (220; 320; 420) of the axial groove ball bearing (170; 200; 300; 400; 500) acting on the rotor shaft (130), The housing disk (210; 310; 510) of the axial groove ball bearing (170; 200; 300; 400; 500) is mounted in the housing (105), The housing disk (310; 510) has a projection (370; 570) extending in the axial direction of the axial groove ball bearing (170; 300; 400; 500), The protrusion (370; 570) covers the rolling element (230) of the axial groove ball bearing (170; 300; 400; 500) from the outside, a. The axial groove ball bearing (170; 200; 300; 400; 500) A groove (330) in the projection (370), A groove (330) formed on the inner side of the protrusion (370); A step (340) in the shaft disc (320; 420), a step (340) arranged on the outside of the shaft disc (320; 420) in the region of the groove (330); A retaining ring (350), a retaining ring that can be fitted into said groove (330); the step (340) of the shaft disc (320; 420) and the retaining ring (350) are formed to engage with the step (340) when the retaining ring (350) engages with the groove (330); Thereby, the axial groove ball bearing (170; 300; 400) is not at risk of collapsing, or b. The axial groove ball bearing (170; 200; 300; 400; 500) A ring (550), a ring (550) capable of being secured to said projection (570); A step (340) in the shaft disc (320; 420), the step (340) being arranged outside the shaft disc (320; 420) in the region of the ring (550), said ring (550) on said projection (570) and said step (340) in said shaft disc (320; 420) are formed to engage said step (340) when said ring (550) is secured onto said projection (570); This ensures that the axial groove ball bearing (500) is not at risk of collapsing. Dental handpiece.

2. 2. Dental handpiece (100; 600) according to claim 1, characterized in that the axial groove ball bearing (170; 200; 300; 400; 500) is axially preloaded with a force of ≥ 3N and ≤ 8N.

3. 3. Dental handpiece (100; 600) according to claim 1 or 2, characterized in that the turbine wheel (640) and / or the rotor shaft (130) and / or the shaft disks (220; 320; 420) of the at least one axial groove ball bearing (170; 200; 300; 400; 500) are formed in one piece.

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