Dental handpieces and axial groove ball bearings

Abstract

The present invention relates to a dental handpiece for rotating a rotating dental tool. The dental handpiece consists of a housing with a handle and a turbine that can be operated by 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, and 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. The protrusions 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 a radial groove ball bearing. Compared with a dental handpiece with a radial groove ball bearing, the proposed dental handpiece design exhibits little power loss or friction loss, and in particular can practically completely prevent sliding and drilling friction components. Therefore, in addition to reducing noise emissions when the dental tool is driven, the service life of the dental handpiece can also be extended.

Description

Technical Field

[0001] The present invention relates to a dental handpiece which can be equipped with a large number of different dental tools for dental treatment. For example, these include drills, milling cutters, files, polishers, smoothers and / or trimmers. Before dental treatment, the tools are clamped into the dental handpiece and a pneumatic drive is used to rotate them. The drive is implemented by a turbine, which is operated by compressed gas or compressed air. The gas or driving air is usually supplied to the turbine through a channel in the dental handpiece. The turbine and the associated rotational motion of the dental tools it drives are characterized by high speeds of up to 500,000 revolutions per minute.

[0002] The practical requirements of dental handpieces, especially high speeds, pose many challenges to the storage of rotating parts in dental handpieces and the dental tools clamped therein. Therefore, storage is usually carried out with the aid of roller bearings, such as ball bearings. They implement bearings that ensure safe and low-vibration use of the dental handpiece, even at high speeds. The roller bearings support the rotor of the pneumatic drive or the hollow shaft, in which the dental tools can be clamped with the aid of a chuck or collet.

[0003] Roller bearings must not only ensure permanent and smooth or silent operation at high speeds, they must also cope with the often very high accelerations and decelerations of the rotor shaft and the dental tools. The associated stresses arise, for example, when the dental handpiece is put into operation or during the dental treatment itself when the dental tools are pressed against the teeth with the forces required for the treatment.

[0004] The forces applied during treatment not only lead to friction losses and the associated deceleration and acceleration of the dental tool, but also to a tilting of the tool in the dental handpiece or a corresponding tilting moment, which is introduced directly from the tool into the roller bearing via the rotor or hollow shaft. Depending on the intensity of the forces used, this can lead to an overload of the bearing.

[0005] Tilting of the shaft (e.g., the bearing shaft and / or the tool shaft) occurs not only in dental treatment, but it is often the result of a narrow installation space in a dental handpiece. The installation space is severely limited by the specifications of the dental equipment manufacturers. Therefore, in most cases, the inner diameter of the roller bearing is fixed at 3.175 mm (1 / 8 inch), the outer diameter is fixed at 6.35 mm (1 / 4 inch), and the width is fixed at 2.779 or 2.38 mm. Since the ball bearings used for vibration reduction are preferably supported in the housing on O-rings and preloaded relative to each other in the axial direction by wave spring disks, the rotor shaft can assume a tilted position when the drilling tool is loaded. Even a slight imbalance, which causes considerable vibration and noise due to the high speed, is considered to reduce quality.

[0006] Another problem is the discharge of lubricants by compressed gas or compressed air, which is led through the pneumatic drive or turbine and the dental handpiece. Some of the exhaust gas from the turbine flows through the ball bearings and conveys lubricants to the outside, so that insufficient lubrication occurs after a short time. After each dental treatment, the handpiece is cleaned by rinsing it with water and / or alkaline detergent, lubricating it and sterilizing it with superheated steam to ensure hygiene. Background Art

[0007] Some of the problems just raised have already been solved in US 4,249,896 A. This document proposes a dental handpiece with two radial groove ball bearings, which are arranged on the upper and lower regions of the rotor shaft of a dental handpiece with a chuck. The ball bearings can thus exert a lever action on the chuck, thereby stabilizing the chuck and the tool clamped therein against tilting. In a sectional view, the associated tilting axis or load axis connects the two ball bearings to each other in an X shape, which is why this arrangement is also called an X arrangement. In addition, the ball bearings are mounted in a housing with the aid of elastic O-rings to dampen vibrations transmitted to the housing.

[0008] DE 10 2015 012 332 A1 represents a further development of such a dental handpiece. Here, further measures for compensating for the tilting effect are proposed, the main purpose of which is to reduce the elliptical characteristics of the running track in the case of tilting by equipping the outer ring raceway with three different zones. This prevents or compensates for the balls of the ball set running at different speeds in the case of tilting and premature wear of the ball bearing cage due to the restraining forces from the ball set and thus failure of the ball bearing.

[0009] The problem of lubricant being discharged by compressed gas or compressed air is compensated by an adhesion promoter layer, which is described in DE 10 2014 220 872 A1. This layer attracts the lubricant and is conveniently applied to the surface 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 in the prior art still have many problems. They arise from the nature of these friction systems. In particular, radial groove ball bearings indicate power losses and wear due to drilling friction and sliding. In this way, not only a considerable part of the drive energy may be consumed, but the service life of the ball bearings may also be significantly reduced.

[0011] Purpose

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

[0013] Solution

[0014] This object is achieved by the subject-matter of the independent claims. Preferred further developments are specified in the dependent claims. Unless otherwise stated, the use of the singular does not intend to exclude the plural and vice versa.

[0015] To achieve this purpose, a dental handpiece for rotating a rotary dental tool is proposed. The rotary dental tool can be a tool for drilling, milling, grinding, filing, polishing and / or finishing or smoothing. The dental handpiece consists of a housing with a handle, which usually has a channel for supplying and removing compressed gas or compressed air. The housing also includes a chuck and a turbine for receiving the dental tool. The turbine has a turbine impeller and a rotor shaft connected to the turbine impeller, and the turbine is connected to the chuck of the dental handpiece via the rotor shaft. For this purpose, the rotor shaft can be designed as a hollow shaft, which accommodates the chuck in its cavity.

[0016] The turbine can be driven by compressed gas or compressed air, which for this purpose can be led to the turbine via inlet and outlet air ducts in the handle. In the turbine, the compressed gas or compressed air hits the turbine impeller and drives it. The rotational movement and the corresponding torque of the turbine impeller are transmitted to the chuck and, if necessary, to the dental tool clamped therein by means of a rotor shaft connected to the turbine impeller. In this way, the chuck and the dental tool that may be clamped therein can be driven rotationally.

[0017] The design of the dental handpiece also provides at least one axial groove ball bearing with a plurality of rolling elements. The axial groove ball bearing is housed in a housing and supports the rotor shaft both when rotating and when not in use. To this end, the axial groove ball bearing has a shaft disc, which is connected to the rotor shaft; and a housing disc, which is used to mount or fix the bearing in the housing of the dental handpiece. In the case of a commonly used ball bearing, the rolling elements represent balls.

[0018] Compared with radial groove ball bearings, axial groove ball bearings have lower power losses or friction losses. In particular, sliding parts can be almost completely avoided or even eliminated. Therefore, in addition to reducing noise emissions when the dental tool is driven, the service life of the dental handpiece can also be extended.

[0019] Due to the axial arrangement of the shaft disc, rolling elements and housing disc, axial groove ball bearings have an axial load direction due to their construction. They are generally suitable for absorbing axial forces, but in many cases have insufficient stiffness or resistance to radial forces. Therefore, the prejudice that axial groove ball bearings are not suitable for use in dental handpieces has been established, where tilting or tilting moments of dental tools are inevitable when radial forces are generated by highly asymmetric external loads during drilling, milling, grinding, filing, polishing and / or finishing or smoothing, etc. Therefore, the skilled person would not consider using axial groove ball bearings in dental handpieces, because the radial stiffness of axial groove ball bearings is poor compared to radial groove ball bearings used for dental handpieces, but would 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.

[0020] The proposed dental handpiece equipped with axial groove ball bearings can be constructed using commercially available components, thereby keeping production costs low. In addition, the design according to the invention is able to absorb higher loads in the axial direction, especially when static loads act on the ball bearings when the collet is actuated to change the drill.

[0021] 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, housing disc and cage with the ball set do not form a closed unit and can disintegrate during assembly or disassembly, which makes handling very complicated. However, in order to better accommodate the bearing in the dental handpiece, in particular for the larger outer bearing surface of the housing disc, it is advantageous if the housing disc of the axial groove ball bearing has a projection extending in the axial direction of the bearing. The projection is designed in such a way that it covers 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 rolling element cage that may be present and the shaft disc.

[0022] The protrusions also reduce the amount of lubricant that is discharged from the axial groove ball bearing, particularly the portion of lubricant discharge that occurs when compressed gas or air flows through the dental handpiece.

[0023] The radial stiffness of the axial groove ball bearing can be improved, for example, by increasing the axial preload, for example from 2 N, which is typical for radial bearings in dental turbines, to a higher value of greater than or equal to 3 N and less than or equal to 8 N, but preferably 5 N (N represents the unit of force, Newton). By this increased preload, the resistance or radial stiffness of the conventional axial groove ball bearing can also be increased relative to the radial force to the level required for the dental handpiece.

[0024] For a better understanding, the components of the proposed dental handpiece are shown only as individual components. In one embodiment, these components can be embodied as individual components. In a preferred embodiment, two or more of these individual components can also be made in one piece. For example, this applies to the shaft disc of at least one axial groove ball bearing and the turbine impeller of the dental handpiece, which can not only be obtained as individual components, but can also be made in one piece. Similarly, the shaft disc and the rotor shaft and / or the turbine impeller can be made in one piece. In these cases, the raceway of the shaft disc is already integrated into the corresponding plane of the turbine impeller or rotor shaft. Therefore, such embodiments according to the invention do not have separate bearings, but rather have a design in which the bearings are integrated into the turbine impeller or rotor shaft. This enables simplified assembly of the dental handpiece.

[0025] The object is also achieved by an axial groove ball bearing comprising a plurality of rolling elements. Furthermore, the axial groove ball bearing has a shaft disc which can be connected to a shaft, and a housing disc for mounting or fixing the bearing in a housing. The rolling elements are arranged between the raceways of the shaft disc and the raceways of the housing disc, similar to radial groove ball bearings. However, the associated raceways are not arranged in the radial direction but in the axial direction.

[0026] Compared to commercially available axial groove ball bearings, the axial groove ball bearing according to the invention has a housing disk with a projection extending in the axial direction of the bearing. The projection is designed in such a way that it covers the rolling elements of the axial groove ball bearing. The projection increases the outer surface area or bearing surface, which can be used to preload the bearing and / or to mount or fix the bearing in a housing.

[0027] The protrusions also reduce the emission of lubricant from the axial groove ball bearing, particularly the portion of lubricant emission that occurs when compressed gas or air flows through the bearing.

[0028] 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 makes sense in many cases for the housing disk (including the projections) to extend over 95% to 105% of the width of the bearing.

[0029] In contrast to many radial groove ball bearings, axial groove ball bearings are not protected from disintegration due to the axial arrangement. This can be particularly problematic during assembly. In contrast, radial groove ball bearings are protected from disintegration due to their design.

[0030] In order to simplify assembly, an axially overlapping axial groove ball bearing with a housing disc having a projection comprising 95% to 105% of the bearing width can also be equipped with protection against falling out. To this end, the projection is provided with a groove, wherein the groove is formed on the inner side of the projection, i.e. the side of the projection closest to the rolling elements. In addition, the shaft disc can be provided with a step in the region 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 a smaller outer diameter is arranged in such a way that a snap ring can be inserted into the bearing from the outside in order to snap it into the groove of the projection. Therefore, the second part of the shaft disc is designed in such a way that the snap ring snapped into the groove locks the shaft disc against axial displacement. It can thus be ensured that the axial groove ball bearing is fixed against disintegration. This greatly simplifies the assembly of the axial groove ball bearing on the rotor shaft and on the housing of the turbine head.

[0031] The proposed axial groove ball bearing with a cantilever offers another possibility of protecting the bearing from disintegration. To this end, a ring is attached to the flat surface of the projection (e.g. welded) and the shaft disc is provided with a step in the region of the ring, 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 smaller outer diameter is arranged in such a way that, after the ring has been fixed to the projection, the ring engages in the step formed by the two parts. The second part of the shaft disc is designed in such a way that the ring attached to the projection locks the shaft disc against axial displacement and thereby protects the axial groove ball bearing from disintegration.

[0032] In addition to the protrusions on the housing disc, the axial groove ball bearing according to the invention can also be designed with protrusions on the shaft disc. The protrusions are designed in such a way that they cover the rolling elements of the axial groove ball bearing. The protrusions increase the width (inner diameter) or the inner contact surface of the hole that can be used to connect the bearing to the shaft. In this way, the fitting of the axial groove ball bearing on the shaft can be improved.

[0033] As mentioned above, the rolling elements do not have to be completely covered by the projections of the shaft disk. However, in order to further improve the assembly on the rotor shaft, it is expedient for the shaft disk including the projections to extend over 95% to 105% of the width of the bearing.

[0034] In a particularly preferred embodiment, the housing disk including the protrusions and the shaft disk including the protrusions extend over 95% to 105% of the width of the bearing. Furthermore, as described above, the axial groove ball bearing is secured against disintegration by means of a snap ring and a corresponding groove or step. In these cases, when viewed from the outside, the axial groove ball bearing looks like a radial groove ball bearing and can be mounted on the rotor shaft or in the turbine head like a radial groove ball bearing. Despite the fact that the rolling elements are radially covered on both sides, the axial groove ball bearing takes up only a minimal amount of space or no more space than a comparable radial groove ball bearing.

[0035] In the axial groove ball bearing according to the invention, the raceways of the rolling elements can be machined into the shaft disc or housing disc using suitable grinding or honing techniques. In order to make grinding in the raceways easier, the rolling elements can be arranged on the outer edge of the shaft disc 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 disc and other components such as a possible ball bearing cage. This is particularly advantageous when the shaft disc is provided with projections on its inner edge. The projections and the raceways on the shaft disc are separated as far as possible so that more space is available for the use of corresponding grinding or honing tools.

[0036] The rolling elements can also be arranged on the inner edge of the shaft disk of an axial groove ball bearing. The raceway thus has a small radius, so that the rolling elements have to cover as little distance as possible with each rotation of the shaft. This arrangement of the rolling elements offers additional advantages if the housing disk is equipped with projections on its outer edge. The projections and the raceway of the rolling elements on the housing disk are separated as far as possible, so that more space is available for the use of corresponding grinding or honing tools.

[0037] The rolling elements may be located in a rolling element cage which separates the rolling elements from one another. In particular, the rolling element cage keeps the rolling elements at the same distance from one another and thereby prevents the rolling elements from sliding in the raceways or from contacting and / or interfering with one another. This enables more reliable operation, for example at high speeds. In many cases, the rolling element cage keeps the balls evenly spaced. Alternatively, the axial groove ball bearing can also be operated without a rolling element cage as a fully complementary variant.

[0038] If the rolling element cage does not completely surround the rolling elements on the outside, the raceways of the rolling elements can be displaced to a larger diameter. In this case, the rolling element cage is closed only on the inside, and the outer diameter of the axle disc is given by the raceway diameter and the rolling element diameter.

[0039] If the rolling element cage does not completely surround the rolling elements on the inside, the raceways of the rolling elements can be displaced to a smaller diameter. In this case, the rolling element cage is only closed on the outside.

[0040] Further details and features will emerge from the following description of preferred exemplary embodiments in conjunction with the accompanying drawings. Here, the respective features can be implemented individually or in combination with one another. The possibilities for achieving this object are not limited to the exemplary embodiments. For example, the specified ranges therefore always include all intermediate values ​​(not specified) and all conceivable subranges.

[0041] Exemplary embodiments are schematically illustrated in the accompanying drawings. Like reference numerals in individual drawings represent one or more similar or functionally similar elements that correspond to each other in terms of function. In the drawings:

[0042] Figure 1 A dental handpiece having an axial groove ball bearing is shown;

[0043] Figure 2 An axial groove ball bearing according to the prior art is shown;

[0044] Figure 3 An axial groove ball bearing with a protrusion on the housing disk is shown;

[0045] Figure 4 An axial groove ball bearing with protrusions on the housing and the shaft disc is shown;

[0046] Figure 5 An axial groove ball bearing with a ring on a protrusion of the housing disk is shown;

[0047] Figure 6 A dental handpiece having a turbine impeller with an integrated shaft disk having axial groove ball bearings is shown; and

[0048] Figure 7 A turbine wheel with an integrated shaft disk is shown.

[0049] Figure 1 A dental handpiece 100 is shown with a housing 105 and a dental tool 110. The dental tool 110 is clamped in a chuck 120 located in the housing 105 of the dental handpiece 100. The chuck 120 is firmly connected to a rotor shaft 130 and is connected to a turbine impeller 140 via the rotor shaft 130. Due to the fixed connection, the rotor shaft 130 is able to transmit the rotational movement and torque of the turbine impeller 140 to the chuck 120 and the dental tool 110 clamped therein. When the turbine impeller 140 is driven by means of compressed air, a rotational movement or torque is generated. For this purpose, the compressed air is guided via the turbine impeller 140 via a channel 150 in a handle 160 of the dental handpiece 100. The turbine impeller 140 and the rotor shaft 130 represent a turbine or 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.

[0050] 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 when stationary and when the rotor shaft rotates. The axial groove ball bearings 170 are arranged on the upper region and on the lower region of the rotor shaft 130.

[0051] The axial groove ball bearing 170 is usually fixed or supported by means of an additional elastic element in order to suppress or reduce the vibration and the associated noise of the turbine in the dental handpiece operated by compressed gas or compressed air. For this purpose, the elastic element is composed of, for example, an elastic material or an elastomer and can be annular, designed as an O-ring 180, etc. The axial groove ball bearing 170 is also mounted in the housing 105 of the dental handpiece 100 by means of a wave spring disk 190.

[0052] The arrangement of axial groove ball bearings 170 on the upper and lower regions of rotor shaft 130 counteracts the tilting of the tool axis in dental handpiece 100 and thus stabilizes dental tool 110 and rotor shaft 130 in dental handpiece 100. This prevents ball bearings 170 from being overloaded due to dental tool 110 tilting.

[0053] The O-ring 180 supports the ball bearing 170 in the radial direction. The wave spring disk 190 supports the bearing 170 in the axial direction. The elastic or resilient mounting in the radial direction dampens oscillations and vibrations of the pneumatic drive, in particular the turbine wheel 140 and the rotor shaft 130.

[0054] Wave spring disk 190 preloads axial groove ball bearing 170 with an axial force. The preload creates a radial stiffness of axial groove ball bearing 170 sufficient for use with dental handpiece 100.

[0055] Figure 2 A conventional or commercially available axial groove ball bearing 200 is shown.

[0056] The axial groove ball bearing 200 is composed 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 each other by a ball bearing cage 240 and are kept at the same distance from each other.

[0057] If the axial groove ball bearing 200 is used in the dental handpiece, the shaft disc 220 protrudes slightly inwardly beyond the housing disc 210. Likewise, the housing disc 210 protrudes slightly beyond the shaft disc 220.

[0058] 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 contacting, rubbing against each other, moving against each other and / or impeding their circulation. This is critical for high-speed operation of the ball bearing, especially under load, thereby preventing the ball bearing from overloading and wearing.

[0059] Figure 3An axial groove ball bearing 300 is shown which, in contrast to the axial groove ball bearing 200, has a housing disc 310 with a protrusion 370 and a shaft disc 320 with a step 340. The protrusion 370 is located on the outside of the housing disc 310 and covers the balls 230 of the axial groove ball bearing 300. Furthermore, the protrusion 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 installed 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.

[0060] The protrusion 370 increases the area available for mounting the axial groove ball bearing 300, for example, in the housing 105 of the dental handpiece 100. Therefore, it can be mounted more stably than, for example, the axial groove ball bearing 200.

[0061] The protrusions also reduce the emission of lubricant from the axial groove ball bearing 300, for example caused by compressed air flowing into the axial groove ball bearing 300. The protection lies 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 which forces the medium to flow through at least one, two or even three changes of direction. The compressed air must pass through this labyrinth in order to have an effect on the balls and their lubrication. In this way, negative external influences can be avoided or at least mitigated.

[0062] After mounting the snap ring 350 , the axial groove ball bearing 300 is protected from falling out and can be mounted on the rotor shaft or in the housing of the turbine head like a radial groove ball bearing.

[0063] Compared with the cage 240, the ball bearing cage 360 ​​does not completely surround the balls 230. It is open to the outside. Therefore, compared with the conventional axial groove ball bearing 200, the raceway of the balls 230 in the axial groove ball bearing 300 is further outward, that is, the raceway has a larger diameter.

[0064] and Figure 3 An alternative embodiment (not shown) which is very similar to the embodiment shown has a longer protrusion of the housing disc compared to the protrusion 370. In this extended protrusion, there is again a groove 330, into which a snap ring 350 can be inserted. This is designed in such a way that when it engages in the groove, it secures the shaft disc against axial displacement of the shaft disc. By extending the protrusion, the formation of a step 340 in the shaft disc can be omitted.

[0065] Figure 4An axial groove ball bearing 400 is shown, which comprises 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, which is similar to the housing disc 310. Compared to the housing disc 310, the protrusion 470 is arranged on the inner side of the shaft disc and covers the balls 230. Compared to the cage 370, the ball bearing cage 470 is adapted to the developed shaft disc 420, i.e., its inner diameter has been slightly increased in order to create space for the protrusion 470.

[0066] The balls 230 of the axial groove ball bearing 400 are covered on both sides, namely by the protrusions 370 of the housing disk 310 and by the protrusions 470 of the shaft disk. Figure 3 The balls 230 are better protected from lubricant discharge in the axial groove ball bearing 400 than in the axial groove ball bearing 300 of FIG. Additional protection is also provided by the fact that the projections 470 together with the housing disk 310 and the shaft disk 420 form a labyrinth system which forces the air flow through it to undergo multiple changes of 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 can be avoided or at least mitigated.

[0067] Furthermore, the axial groove ball bearing 400 looks like a radial groove ball bearing from the outside due to the two protrusions 370 and 470. Furthermore, due to the anti-collision protection formed by the groove 330, the step 340 and the snap ring 350, it can be handled like a radial groove ball bearing.

[0068] Figure 5 An axial groove ball bearing 500 is shown with a housing disk 510 and an axle disk 420. Compared to the axial groove ball bearing 400, the axial groove ball bearing 500 has an alternative protection against damage. The bearing 500 is not protected from disintegration by a snap ring (as in the case of the bearing 400), but by a ring 550. The ring 550 is laterally fixed to a projection 570 of the housing disk 510. For this purpose, the ring 550 can be welded to the projection, for example, after assembly.

[0069] In order that the bearing 500 is not widened by the attachment ring, the projection 570 is designed to be somewhat shorter than the projection 470 in the axial groove ball bearing 400. However, this only represents a preferred embodiment, i.e. such a ring can also be applied to a housing disk with a non-shortened projection which, together with the housing disk, extends over the entire width of the bearing.

[0070] Similar 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 so that the ring 550 engages in the step in the assembled state and the shaft disc 420 is thus blocked from axial displacement. In the above case with unshortened protrusions, such a step 340 can be omitted.

[0071] To protect the axial groove ball bearing according to the invention from disintegration, not only the protrusion of the housing disk can be used. In embodiments in which the shaft disk has a protrusion, equivalent protection against damage can be achieved by a similar device at the end of the protrusion of the shaft disk. For this purpose, the housing disk can then have a step.

[0072] Figure 6 A dental handpiece 600 is shown having a turbine impeller 640 with an integrated shaft disk in contrast to dental handpiece 100. Turbine impeller 640 represents an integral embodiment of turbine impeller 140 and a shaft disk of an axial groove ball bearing.

[0073] Figure 7 A combination of a turbine wheel 640 with an integrated shaft disk is shown. Figure 7 The roller bearing 230 and the housing disk 310 are shown again on a larger scale, which can also be seen in FIG. Figure 6 The assembly can be assembled outside the dental handpiece 600 and, in the assembled state, can be mounted on the rotor shaft and inserted into the housing 105.

[0074] In addition to the integral design of the turbine impeller and the shaft disk, the shaft disk and the rotor shaft can also be integrally designed. This applies not only to the turbine impeller 140, the rotor shaft 130 and the shaft disk 320, but also to other embodiments of these three components.

[0075] Glossary

[0076] Protrusion

[0077] A protrusion refers to a protruding portion of a component that protrudes or projects from the component.

[0078] Axial groove ball bearings

[0079] An axial groove ball bearing is a ball bearing in which the housing disk, the balls and the shaft disk are arranged one behind the other in the axial direction.

[0080] Drilling friction

[0081] Drilling friction occurs at the support points of the body rotating on a plane about a vertical axis.

[0082] Ball bearings

[0083] A ball bearing is a roller bearing in which the rolling elements are balls.

[0084] Radial bearings

[0085] 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. On the other hand, the inner ring usually has a smaller circumference.

[0086] slide

[0087] Slip generally refers to the deviation in velocity of machine elements in frictional contact with each other and the associated relative displacement of the machine elements associated with frictional or power losses.

[0088] Chuck

[0089] A chuck is a device that holds a tool such as a drill or milling cutter on a tool (eg, a dental handpiece).

[0090] Roller bearings

[0091] Roller bearings are bearings for rotating parts, such as spindles or shafts, in which between at least a first ring, which is connected to the housing and is therefore also called the outer ring, and at least a second ring, which is connected to the rotating part and is therefore called the inner ring, rolling elements or rolling bodies reduce the frictional resistance between the rings or disks. Roller bearings can have one or more rows of rolling elements, which can be separated from each other by additional rings or disks. For example, the rolling elements roll on a hardened steel surface 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.

[0092] Rolling elements

[0093] 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 in a roller bearing can be balls, rollers, cylinders, needles, sleeves or cones.

[0094] Rolling element cage

[0095] A rolling element cage is an annular component which can accommodate the rolling elements of a roller bearing and hold them at a fixed, preferably equal distance from one another. A rolling element cage can be made in one or two pieces.

[0096] Wave spring disc

[0097] A wave spring disc is a wave spring or annular disc which produces a spring effect by being conical, curved on both sides or wavy. Wave spring discs are used for defined axial preload of roller bearings, mainly miniature and small ball bearings.

[0098] Reference Numbers

[0099] 100 Dental Handpiece

[0100] 105 Housing

[0101] 110 Dental Tools

[0102] 120 Chuck

[0103] 130 Rotor shaft

[0104] 140 Turbine impeller

[0105] 150 channels

[0106] 160 Handle

[0107] 170 Axial groove ball bearing

[0108] 180 O-ring

[0109] 190 Wave Spring Disc

[0110] 200 Axial groove ball bearings

[0111] 210 Shell plate

[0112] 220 Shaft disc

[0113] 230 Ball

[0114] 240 Ball bearing cage

[0115] 300 Axial groove ball bearings

[0116] 310 Shell plate

[0117] 320 Shaft Plate

[0118] 330 Grooves

[0119] 340 steps

[0120] 350 Snap ring

[0121] 360 Ball Bearing Cage

[0122] 370 protrusion

[0123] 400 Axial groove ball bearings

[0124] 420 Shaft Plate

[0125] 460 Ball Bearing Cage

[0126] 470 protrusion

[0127] 500 Axial groove ball bearings

[0128] 510 Shell plate

[0129] 550 rings

[0130] 570 protrusion

[0131] 600 Dental Handpiece

[0132] 640 Turbine impeller with integrated shaft disk

[0133] Citations

[0134] Citations of patent documents

[0135] US 4,249,869 A

[0136] DE 10 2014 220 872 A1

[0137] DE 10 2015 012 332 A1

Claims

1. A dental handpiece (100; 600) for rotating a rotary dental tool (110), comprising: A housing (105) having a handle (160) and a chuck (120), wherein the chuck is used to receive the dental tool (110) in the dental handpiece (100); A turbine capable of being driven by compressed gas and / or compressed air and having a turbine wheel (140; 640) and a rotor shaft (130) connected to the turbine wheel (140; 640); in, The rotor shaft (130) is connected to the chuck (120) to transmit the rotation of the turbine impeller (140; 640) to the chuck (120); Two axial groove ball bearings (170; 200; 300; 400; 500), the two axial groove ball bearings are arranged on the upper area and the lower area of ​​the rotor shaft (130), respectively, each of the axial groove ball bearings has a respective shaft disk (220; 320; 420), a housing disk (210; 310; 510) and a rolling element (230), wherein the rolling element (230) is arranged between the shaft disk (220; 320; 420) and the housing disk (210; 310; 510); wherein the shaft disc (220; 320; 420) of the axial groove ball bearing (170; 200; 300; 400; 500) acts on the rotor shaft (130); wherein the housing disk (210; 310; 510) of the axial groove ball bearing (170; 200; 300; 400; 500) is installed in the housing (105); wherein the housing disk has a protrusion (370; 570) extending in the axial direction of the axial groove ball bearing; wherein the protrusion (370; 570) covers the rolling element (230) of the axial groove ball bearing on the outside, wherein: a. A groove (330) is provided in the protrusion, wherein the groove (330) is formed on the inner side of the protrusion; A step (340) is provided in the shaft disc (320; 420), wherein the step (340) is arranged on the outer side of the shaft disc (320; 420) in the region of the groove (330); A snap ring (350) capable of being snapped into the groove (330) is provided; wherein the step (340) and the snap ring (350) in the shaft disc (320; 420) are formed such that the snap ring (350) engages with the step (340) when the snap ring is engaged in the groove (330), thereby ensuring that the axial groove ball bearing is secured against disintegration, or b. A ring (550) is provided, wherein the ring (550) can be fixed to the protrusion; A step (340) is provided in the shaft disk (320; 420), wherein the step (340) is arranged on the outer side of the shaft disk (320; 420) in the region of the ring (550); and The ring (550) on the protrusion and the step (340) in the shaft disc (320; 420) are formed so that the ring (550) engages with the step (340) when the ring is fixed on the protrusion, thereby ensuring that the axial groove ball bearing is fixed and prevented from disintegrating.

2. The dental handpiece (100; 600) according to claim 1, Features The axial groove ball bearing (170; 200; 300; 400; 500) is preloaded with a force greater than or equal to 3N and less than or equal to 8N in the axial direction.

3. The dental handpiece (100; 600) according to claim 1 or 2, Features The turbine impeller and / or the rotor shaft (130) and / or the shaft disk (220; 320; 420) of the axial groove ball bearing (170; 200; 300; 400; 500) are manufactured in one piece.

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