Concentricity-optimized tool clamping system for dental angle handpieces and dental turbines

Abstract

A clamping device for clamping a dental tool in a dental turbine handpiece, comprising a housing (12) in which a collet chuck (14) is arranged, which has at least one clamping lever (16, 18) that can be elastically deflected and extends along the axis (A) of a tool shank to be clamped, and is designed and arranged such that the tool shank can be clamped by means of the clamping lever (16, 18), and a push-button mechanism (28, 30) displaceably arranged in the housing (12) is provided with a pressure piece (28) that acts in the axial direction on the clamping levers (16, 18) of the collet chuck (14), wherein the tool shank to be clamped is guided and aligned in the housing (12) by means of first and second guide surfaces (14b, 22a; 26a) spaced apart from one another along the axis (A). which are arranged in a fixed position relative to the housing (12), wherein the second guide surface (26a) is formed by an inner peripheral surface of a support ring (26) which is firmly connected to the housing (12), characterized in that that the support ring (26) is fastened in an opening (20) of the housing (12) and at the same time is arranged in an opening (34) of the pressure piece (28), wherein the opening (34) of the pressure piece (28) has a larger dimension in the direction of the axis (A) than the axially effective length of the support ring (26), so that the pressure piece (28) is axially movable relative to the support ring (26).

Description

[0001] The invention relates to a clamping device for clamping a dental tool in a dental turbine handpiece according to the preamble of patent claim 1, in particular for high-speed air turbines operating at high speeds of approximately 200,000 to 500,000 rpm. State of the art

[0002] Fundamentally, a clamping device for a dental tool in a dental turbine handpiece must be able to change the dental tool with the least possible actuation force, without the need for additional tools. However, the actuation force must not be too low, as this creates the risk of unintentional actuation. The holding force must be sufficient to clamp the dental tool firmly and securely under all operating conditions. Therefore, a clamping system that is quick and easy to use and has sufficient holding force to securely clamp a dental tool is desired.

[0003] Since today's dental tools always have a cylindrical shaft according to standards, a positive clamping of the shaft of the dental tool to secure it against axial displacement and rotation is not possible. Instead, it is necessary to hold the dental tool in position using frictional locking and the resulting frictional forces. The clamping device must be designed to reliably hold the dental tool even under the centrifugal forces acting at very high speeds of several hundred thousand rpm.

[0004] Dental handpieces powered by air turbines feature a turbine rotor supported within a housing via a plain or ball bearing. The turbine rotor has turbine blades around its periphery and a clamping device for clamping the shaft of a dental tool within a housing, on the outside of which the turbine blades are attached. The current standard for changing drilling and grinding tools in dental angle handpieces and dental turbines is push-button clamping systems. With this system, no tool is required to change the bur. A clamping system that is quick and easy to use, yet has sufficient holding power to securely clamp the bur, is advantageous.

[0005] Improvements to push-button clamping systems have been proposed repeatedly in the past. For example, DE 10 2010 037 791 A1 demonstrates an improvement in clamping systems by utilizing centrifugal force. This centrifugal force, which in the prior art counteracts the clamping effect on the tool, is used to enhance the clamping effect by modifying the collet and modifying the installation.

[0006] US 2002 / 0 105 149 A1 discloses a centrifugal clamping mechanism for holding dental instruments in an air turbine handpiece. The air turbine handpiece contains a sleeve into which the dental instrument can be inserted with one hand and is held securely until rotation begins. As the air turbine cartridge rotates, the instrument is fixed in position by centrifugal forces.

[0007] US 2007 / 0 243 499 A1 discloses a rotating spindle assembly for a dental handpiece and a hollow cylindrical collet chuck for applying a variable gripping force to reliably hold a dental tool. The collet chuck comprises a pair of collet elements that hold the tool with the aid of spring force and are movable into an open position by actuating a push button to release the tool.

[0008] US 5 833 704 A discloses a clamping device with a centrifugal chuck for axially clamping a dental tool, wherein the centrifugal chuck has a centrifugal locking element provided with a mass part, which receives a rear tool shank and radially clamps and holds it during faster rotation of the chuck.

[0009] For dental handpieces, and especially for dental turbines, precise concentricity of the rotating parts and even mass distribution are extremely important due to the very high speeds of 200,000 - 500,000 rpm. Vibrations due to imbalance in the system lead to high, unpleasant noise levels and also significantly reduce the service life of the bearings. In general, a sufficiently even mass distribution in the motors of dental handpieces and dental turbines can be achieved using standard balancing technology. Particular attention should be paid to the replaceable tool. Replacing the tool using the push-button clamping system can change the mass distribution in the rotor, which can lead to a reduction or an increase in the residual imbalance remaining after balancing.

[0010] The replaceable tool extends significantly beyond the clamping system and, once clamped, can assume a position at an angle to the rotor's rotational axis. During operation, the tool wobbles when clamped at an angle to the rotational axis. This causes an imbalance moment, which cannot be accounted for in advance with conventional balancing technology. Disclosure of the invention

[0011] The object of the invention is to provide a clamping device for a dental tool for dental turbine handpieces, which allows a more precise relative position and improved concentricity of the dental tool after clamping.

[0012] This object is achieved by a clamping device having the features of claim 1.

[0013] Preferred embodiments of the invention and further advantageous features are specified in the subclaims.

[0014] The clamping device for clamping a dental tool in a dental turbine handpiece comprises a housing in which a collet is arranged, which has at least one clamping lever that can be elastically deflected and extends along the axis A of the tool shank to be clamped. The clamping lever is designed and arranged such that the tool shank can be clamped by means of the clamping lever. Provided in the housing is an axially displaceable push-button mechanism with a pressure piece that acts in the axial direction on the clamping lever of the collet. The tool shank to be clamped is guided and aligned in the housing by means of first and second guide surfaces spaced apart from one another along the axis, wherein the guide surfaces are arranged stationary relative to the housing, and the second guide surface is formed by an inner circumferential surface of a support ring that is firmly connected to the housing.

[0015] According to the invention, the support ring is fastened in an opening in the housing and at the same time is arranged in an opening in the pressure piece, wherein the opening in the pressure piece has a larger dimension in the direction of the axis A than the axially effective length of the support ring, so that the pressure piece is axially movable relative to the support ring.

[0016] For the guide surfaces, it is necessary to produce a precise bore with a close tolerance for the insertion of the tool shank in order to ensure a precise clearance fit with as little radial play as possible between the tool shank and the guide surface.

[0017] Previously, it was known to arrange a guide surface in a corresponding guide bushing in the housing for axial movement. The guide bushing was part of the actuating mechanism for clamping the tool shank and was therefore arranged in an axially movable manner within the housing. As a result, the tool shank was guided relative to the housing in this guide bushing via two clearance fits. Depending on the component tolerances, this resulted in a relatively large radial play. In the worst case, the tool was very poorly centered, resulting in a significant imbalance in the rotating part of the clamping device containing the tool.

[0018] To improve this, the invention provides for both guide surfaces to be firmly mounted on the housing, so that only a clearance fit is required between the tool shank and the guide surface. Both guide surfaces offer closed guide surfaces, so that the tool shank is supported and guided over its entire circumferential surface.

[0019] This means that the tool shank is aligned much more accurately and precisely in the clamping device.

[0020] In particular, the invention provides a support ring which is fixedly arranged on or in the housing between the actuating device and the collet.

[0021] In a first preferred embodiment of the invention, the collet is fixed in the housing and itself forms a first guide surface for the tool shank.

[0022] In this embodiment of the invention, the first guide surface is formed by an inner circumferential surface of a sleeve-shaped portion of the collet.

[0023] The second guide surface is preferably formed by an inner peripheral surface of the support ring adjacent to the collet, which is firmly connected to the housing.

[0024] The tool shank to be clamped is thus guided by the two guide surfaces of the sleeve-shaped section of the collet and the support ring, which are arranged at an axial distance from each other, and is precisely aligned relative to the housing.

[0025] To clamp the tool shank, the collet preferably comprises two or more opposing clamping levers. Clamping surfaces are arranged on an inner circumference of the clamping levers, allowing the tool shank to be clamped and secured.

[0026] The clamping and release of the tool shank in the clamping device is carried out by a push-button mechanism with a pressure piece that acts axially on the clamping levers of the collet and enables the clamping levers to be released and locked.

[0027] In particular, the pressure piece has expansion elements that, upon axial displacement of the pressure piece, come to rest against the clamping levers and exert a circumferential force, i.e., a radial force, on the clamping levers. In particular, the expansion elements are pushed axially between adjacent clamping levers and push them apart radially, whereby the clamping surfaces arranged on the clamping levers release the clamped tool shank or allow the tool shank to be inserted.

[0028] When the expansion elements are retracted, for example by spring force, the clamping levers return to their original radial position, whereby the clamping surfaces clamp the tool shank and clamp it.

[0029] In another embodiment of the invention, no guide surface is arranged on the collet, but the collet is mounted in the housing so that it can move in the axial direction.

[0030] In this embodiment of the invention, the first guide surface is formed by an inner circumferential surface of a separate guide bushing, which is adjacent to the collet and fixed in the housing.

[0031] The second guide surface is still formed by the support ring, which is located on the other side of the collet and connected to the housing.

[0032] In one embodiment of this preferred embodiment, the spreading elements of the pressure piece can in turn be inserted axially between adjacent clamping levers of the collet and press them apart radially, whereby clamping surfaces arranged on the clamping levers release the tool shank to be clamped or allow the tool shank to be inserted.

[0033] In another embodiment of this design, a two-armed clamping lever can be used, with first and second lever arms that can be deflected around a virtual pivot point. The tool shank can be clamped by means of the first lever arms, with the first lever arms having corresponding clamping surfaces. The second, longer lever arms can be radially expanded by the expansion elements of the pressure piece, whereby the first, shorter lever arms are correspondingly pressed radially inward around the virtual pivot point and clamp the tool shank.

[0034] The first and second lever arms are configured such that when the clamping device rotates, the second lever arms are additionally deflected radially outwards by the effect of the centrifugal force, so that the clamping force of the first lever arms is increased.

[0035] In all embodiments of the invention, a push-button mechanism is provided in the clamping device for loosening and clamping the tool shank, which mechanism acts on the collet in the axial direction and moves the clamping levers elastically and in the radial direction as required.

[0036] In one embodiment of the invention, the corresponding spreading elements of the pressure piece of the push-button mechanism are pushed axially between the clamping levers and have inclined sliding surfaces which convert the axial movement into a radial movement and press the clamping levers radially outwards in order to reduce the clamping force of the clamping levers and to release the tool shank.

[0037] When the push button is released, the expansion elements slide out of the clamping levers due to the elasticity of the clamping levers and the clamping levers exert the required clamping force on the tool shank.

[0038] In a further advantageous embodiment, in the rest position of the push-button mechanism, a clamping force is already exerted on the clamping levers by means of the spreading elements and the tool shank is clamped between the clamping levers.

[0039] When the push-button mechanism is operated, the expansion elements reduce their force on the clamping levers so that they elastically return to their rest position and reduce the clamping force on the tool shank so that a tool change can be carried out.

[0040] Further features and advantages of the invention will become apparent from the preferred embodiments of the invention described in the following drawings. Short description of the drawings Fig. 1 is a perspective view of a dental turbine according to the invention; Fig. 2 shows an exploded view of a clamping device according to a first embodiment; Fig. 3 shows a section of the clamping device of Fig. 2 in tensioned state. Fig. 4 shows an exploded view of a clamping device according to a second embodiment. Fig. 5 shows a section of the clamping device of Fig. 4 in tensioned state. Fig. 6 shows an exploded view of a clamping device according to a third embodiment; Fig. 7 shows a section of the clamping device of Fig. 6 in tensioned state Fig. 8 shows a section of the clamping device along the line BB of Fig. 7. Description of preferred embodiments of the invention

[0041] Fig. Figure 1 shows a perspective view of a dental turbine incorporating a clamping device for a dental tool according to the invention. The dental turbine comprises a drive wheel 10 with turbine blades, which is seated on a housing 12 surrounding the clamping device. The housing 12 is preferably cylindrical or substantially cylindrical and fits within the inner diameter of the drive wheel 10. The housing 12 can be rotatably mounted in a dental turbine handpiece (not shown) via ball bearings. The clamping device and the housing 12 rotate together with the turbine drive wheel 10. Dental turbines are operated at very high speeds, for example in the range of 200,000 to 500,000 rpm. Thus, when the dental turbine rotates, a considerable centrifugal force acts on the clamping device.

[0042] The Fig. 2 and Fig. 3 shows a first embodiment of the clamping device according to the invention. The clamping device comprises a collet 14, which is fixedly arranged in the housing 12. A pressure piece 28, which is arranged axially displaceably in the housing 12, acts on the collet 14 by actuating a push button 30. The pressure head 30 can preferably be formed integrally with the pressure piece 28. According to the invention, a support ring 26 is arranged in an opening 34 of the pressure piece 28 and fastened in an opening 20 of the housing 12.

[0043] The collet 14 has a sleeve-shaped portion 14a that is attached to an inner circumference of the housing 12. Opposing first and second clamping levers 16, 18 are arranged on the sleeve-shaped portion 14a and are directed axially into the interior of the housing 12. The clamping levers 16, 18 are elastically deformable and radially deflectable. The clamping levers 16, 18 extend substantially parallel to the axis A of the tool shank to be clamped. The collet 14 is preferably made of metal, e.g., stainless steel. The lever arms of the clamping levers 16, 18 have clamping surfaces 16a, 18a on the inner circumference, which serve to clamp or hold the tool shank.

[0044] The sleeve-shaped section 14a of the collet 14 and the support ring 26 are arranged at the greatest possible mutual distance and form guide surfaces for guiding and centering the tool shank to be clamped.

[0045] The collet 14 is arranged and fixed at one end of the housing 12. The tool shank of the tool to be clamped is inserted from the direction of the sleeve-shaped portion 14a of the collet 14.

[0046] Adjacent to the free clamping levers 16, 18 of the collet 14, a pressure piece 28 with a push button 30 protruding from the housing 12 is arranged axially displaceably in the housing, wherein corresponding spreading elements 24 at the end of the pressure piece 28 can be brought into contact with the clamping levers 16, 18 of the collet 14.

[0047] The thrust piece 28 has an opening 34 in which the support ring 26 is arranged. The opening 34 has a larger dimension in the axial direction (in the direction of axis A) than the axially effective length of the support ring 26, so that the thrust piece 28 is axially movable relative to the support ring 26, while the support ring 26 is firmly connected to the housing.

[0048] For installation of the support ring 26, the housing 12 preferably also has an opening 20 into which the support ring 26 is inserted and firmly connected to the housing, for example by welding.

[0049] The support ring 26 is thus fixed relative to the housing 12, while the pressure piece 28 is axially movable relative to the housing and the support ring 26 in the direction of the axis A.

[0050] Fig. 3 shows the clamping device in the clamped state, ie corresponding clamping surfaces 16a and 18a, which are arranged on the inner circumference of the clamping levers 16, 18, define a clamping diameter D, which in the clamped state rests against the outer diameter of the tool shank, so that the tool shank is clamped in the region of the clamping surfaces 16a, 18a.

[0051] By pressing the push button 30, the pressure piece 28 can be moved axially in the direction of the arrow in the direction of the collet 14.

[0052] The obliquely or conically shaped spreading elements 24 of the pressure piece 28 thus reach the space between the two clamping levers 16, 18 of the collet 14. Due to the correspondingly bevelled surfaces of the spreading elements 24, the axial movement of the spreading elements 24 is converted into a radial movement of the two clamping levers 16, 18.

[0053] This means that the clamping diameter D increases by spreading the two clamping levers 16, 18 and the clamping surfaces 16a and 16b detach from the tool shank or allow a tool shank to be inserted into the clamping device due to the larger clamping diameter D.

[0054] The tool shank is inserted into the device from the right, i.e. from the side of the sleeve-shaped section 14a of the collet 14, through the collet 14 into the bore of the support ring 26, wherein the support ring can have an end stop which determines the end position of the tool shank.

[0055] The tool shank is guided by the first guide surface 14b on the sleeve-shaped section 14a and the second guide surface 26a of the support ring 26 and centered with respect to the rotation axis A.

[0056] Since the collet 14, ie also its sleeve-shaped section 14a, as well as the support ring 26 are fixed on or in the housing 12 and aligned accordingly, the tool shank is guided and centered in the tool in the area of ​​the manufacturing tolerances of the contact surfaces 14b and 26a.

[0057] If the actuating button 30 is released, the spreading elements 24 slide out of the space between the two clamping levers 16, 18 in the opposite direction to the arrow due to the radial preload of the clamping levers 16, 18 and their inclined surfaces, and the clamping levers move radially inwards in the direction of the axis A into their original position due to their elasticity. This reduces the clamping diameter D, and the clamping surfaces 16a and 18a rest against the outer circumference of the tool shank and clamp it firmly in the collet 14.

[0058] The support ring 26 is flattened on two opposite sides so that there is still space between the housing 12 and the support ring 26 for corresponding parts of the pressure piece 28, i.e. the pressure piece remains axially movable around the support ring.

[0059] The Fig. 4 and Fig. 5 show a further embodiment of a tool clamping system, which essentially corresponds in its functionality to the first embodiment according to the Fig. 2 and Fig. 3 matches.

[0060] For the designs in the Fig. 4 and Fig. 5, the same reference numerals are used for identical components. Reference is made to the above description of the individual components.

[0061] The second embodiment according to the Fig. 4 and Fig. 5 differs from the first embodiment in the shape of the individual components, in particular the shape of the collet 14, the support ring 26 and the pressure piece 28.

[0062] The collet 14 in turn defines a sleeve-shaped section 14a, which forms the first guide surface 14b for the tool shank.

[0063] Furthermore, the two clamping levers 16, 18 can be seen, which are directed in the direction of the pressure piece 28 parallel to the axis A and form a free space between them.

[0064] The legs of the clamping levers 16, 18 form the clamping diameter D, which is defined by corresponding clamping surfaces 16a, 18a.

[0065] The support ring 26 is fixedly arranged in the housing and is sleeve-shaped and forms two defined guide surfaces 26a, which are arranged opposite one another on the inner circumference of the support ring.

[0066] The pressure piece 28 is movably arranged in the support ring 26, with corresponding expansion elements 24 extending through the support ring 26 and extending into the space between the two clamping levers 16, 18. The expansion elements 24, in turn, are designed with inclined expansion surfaces. A push button 30 is arranged at the end of the pressure piece.

[0067] The functionality is again the same as in the Fig. 2 and Fig. 3. By pressing the push button 30 in the direction of the arrow, the expansion elements 24 slide between the two lever arms 16, 18, whereby the clamping diameter D increases and the clamped tool shank is released or can be inserted.

[0068] After releasing the push button 30, the two clamping levers 16, 18 return radially inwards to their starting position, whereby the clamping surfaces 24 are pushed against the direction of the arrow and the pressure piece 28 returns to its starting position.

[0069] Finally, in the Fig. 6 to 8 show a further embodiment of the invention.

[0070] To the extent that this third embodiment corresponds to the first two embodiments, the same reference numerals are used.

[0071] Reference is made to the above description of the individual components and their functionality.

[0072] The essential difference to the embodiments of the previous examples is that the collet 14 is not firmly fixed in the housing 12, but is arranged in the housing so as to be slightly axially movable.

[0073] In contrast to the first two embodiments of the invention, the collet 14 also has no guide function for the tool shank, ie the collet 14 does not comprise any guide surfaces for the tool shank.

[0074] Furthermore, this version differs from the previous versions in the design and arrangement of the collet 14.

[0075] The collet 14 comprises two clamping levers 16, 18 with opposing longer lever arms 16" and 18" as well as two opposing, shorter lever arms 16' and 18' extending in the other direction.

[0076] The two longer lever arms 16" and 18" of the collet 14 are directed toward the pressure piece 28, while the shorter lever arms 16', 18' are directed toward a guide bushing 22, which has a corresponding first guide surface 22a for guiding the tool shank. The guide bushing 22 is arranged on the side of the clamping device into which the tool shank is inserted.

[0077] The collet 14 is limited in the housing 12 by the guide bush 22 and by the pressure piece 28 and is actuated by the pressure piece.

[0078] The collet 14 has projections directed in the direction of the guide bush 22, which engage in corresponding recesses in the guide bush 22 and thus form an anti-twist device for the collet 14, since the guide bush 22 is fixedly arranged in the housing.

[0079] The pressure piece 28 features expansion elements 24 that engage between the two longer lever arms 16", 18", in correspondingly shaped dovetail grooves with inclined sliding surfaces. The expansion elements 24 are also dovetail-shaped with corresponding inclined sliding surfaces.

[0080] The collet 14 is actuated via a push button 30, which is part of the pressure piece 28, and a compression spring 36 arranged between the pressure piece 28 and the fixed support ring 26.

[0081] The compression spring 36 forms a return mechanism, which is described below.

[0082] The Fig. 7 and Fig. 8 show the clamping device in the clamped state, i.e. when the push button 30 is not actuated.

[0083] The compression spring 36 pushes the pressure piece 28 away from the support ring 26 in the opposite direction to the arrow, whereby the dovetail-shaped spreading elements 24 are pulled out of the dovetail-shaped recesses between the two longer lever arms 16'' and 18'' of the spreading pliers 14.

[0084] Due to the beveled surfaces of the expansion elements 24, which are inclined towards the pressure piece 28, and the correspondingly beveled counter surfaces on the recesses of the lever arms 16'', 18'', the longer lever arms 16'' and 18'' are pressed apart radially outwards by the expansion elements. This elastic pressure on the longer lever arms 16'', 18'' is passed on to the shorter lever arms 16' and 18', which are now pressed radially inwards in the direction of axis A against this force, so that the clamping diameter D is reduced. As a result, the clamping surfaces 16'a, 18'a arranged on the shorter lever arms 16' and 18' rest against the tool shank and clamp it. This is the clamped state.

[0085] By actuating the push button 30, the pressure piece 28 is moved in the direction of the arrow towards the collet 14, whereby the support ring 26 remains stationary and forms a stop for the push button of the pressure piece 28.

[0086] During this pressure movement, the expansion elements 24 move into the dovetail-shaped cavity between the longer lever arms 16'' and 18'', whereby the radial pressure on the longer lever arms 16'', 18'' is removed and the longer lever arms 16'' and 18'' can move elastically radially inward into their relaxed state.

[0087] As a result, the shorter lever arms 16', 18' move radially outwards around a virtual pivot point, whereby the clamping diameter D increases and the clamping surfaces 16'a and 18'a lift off and release from the tool shank. It can be provided that, in the non-preloaded state, the clamping diameter D of the collet is smaller than the diameter of the tool shank and the opening of the collet is effected by wedge-shaped inner surfaces 32 of the pressure piece 28. For this purpose, the pressure piece 28 has wedge-shaped inner surfaces 32 and when, upon actuation of the pressure piece, the wedge-shaped inner surfaces 32 slide along the bevels 38 of the longer lever arms 16'', 18'' of the clamping levers 16, 18, the longer lever arms 16'', 18'' are pressed in the direction of the axis of the tool shank to be clamped and the clamping diameter D on the shorter lever arms 16', 18' is opened.

[0088] Once the tool has been removed or replaced, the pressure on the push button 30 can be released, causing the pressure piece 28 to move back to its leftmost position under the spring force of the spring 36. As a result, the sliding surfaces of the expansion elements 24 again slide along the sliding surfaces of the longer lever arms 16" and 18" of the collet 14 and spread them, so that the clamping is reactivated, as described above.

[0089] In the embodiment of the invention according to the Fig. 4 and Fig. 5, the support ring 26 with its guide surfaces is not closed. This creates two opposing guide surfaces. The support ring can be mounted axially in the housing.

[0090] In the two solutions according to the Fig. 2 and Fig. 3 and the Fig. 6-8, a closed support ring with a closed guide surface is used, which is mounted radially through an opening in the housing 12 of the clamping system.

[0091] According to an advantageous embodiment of the invention, the second guide surface in the support ring can be slightly conical, whereby the tool is centered when the tool shank is inserted into the conically tapered guide bore.

[0092] The latter embodiment of the Fig.6-8 is a centrifugal force-assisted clamping system, meaning that when the housing and collet rotate, the longer lever arms 16" and 18" of the collet can spread further from the A axis of the tool shank to be clamped due to the centrifugal force acting on the lever arms 16" and 18". This centrifugal force-assisted spreading increases the clamping force acting on the shorter lever arms 16' and 18' as the clamping system speed increases. List of reference symbols 10 Drive wheel 12 housings 14 Collet 14a Sleeve-shaped section 14b Guide surface 16 clamping levers 16a clamping surface 18 clamping levers 18a clamping surface 16', 18' first, shorter lever arm 16'a, 18'a clamping surface 16'', 18'' second, longer lever arm 20 Breakthrough 22 Guide bushing 22a Guide surface 24 Spreader element 26 Support ring 26a Guide surface 28 Pressure piece 30 push button 32 inner surface 34 Breakthrough 36 compression spring 38 Bevel A axis of the tool shank to be clamped D clamping diameter

Claims

[1] Clamping device for clamping a dental tool in a dental turbine handpiece, comprising a housing (12) in which a collet chuck (14) is arranged, which has at least one clamping lever (16, 18) which can be elastically deflected and extends along the axis (A) of a tool shank to be clamped and is designed and arranged such that the tool shank can be clamped by means of the clamping lever (16, 18), and a push-button mechanism (28, 30) displaceably arranged in the housing (12) is provided with a pressure piece (28) which acts in the axial direction on the clamping levers (16, 18) of the collet chuck (14), wherein the tool shank to be clamped is guided and aligned in the housing (12) by means of first and second guide surfaces (14b, 22a; 26a) spaced apart from one another along the axis (A), which are arranged in a fixed position relative to the housing (12), wherein the second guide surface (26a) is formed by an inner peripheral surface of a support ring (26) which is firmly connected to the housing (12), characterized by , that the support ring (26) is fastened in an opening (20) of the housing (12) and at the same time is arranged in an opening (34) of the pressure piece (28), wherein the opening (34) of the pressure piece (28) has a larger dimension in the direction of the axis (A) than the axially effective length of the support ring (26), so that the pressure piece (28) is axially movable relative to the support ring (26). [2] Clamping device according to claim 1, characterized by that the collet (14) has two or more opposing clamping levers (16, 18). [3] Clamping device according to one of claims 1 or 2, characterized bythat the pressure piece (28) has spreading elements (24) which, upon axial displacement of the pressure piece (28), come to rest against the clamping levers (16, 18) and exert a force acting in the radial direction on the clamping levers (16, 18). [4] Clamping device according to one of claims 1 to 3, characterized by that the collet (14) is fixed in the housing (12). [5] Clamping device according to one of claims 1 to 4, characterized by that the first guide surface (14b) is formed by an inner peripheral surface of a sleeve-shaped portion (14a) of the collet (14). [6] Clamping device according to one of claims 1 to 5, characterized by that the spreading elements (24) come to lie between adjacent clamping levers (16, 18) and press them radially apart, whereby clamping surfaces (16a, 18a) arranged on the clamping levers (16; 18) release the clamped tool shank. [7] Clamping device according to one of claims 1 to 6, characterized by that the collet (14) is mounted in the housing so that it can move in the axial direction. [8] Clamping device according to one of claims 1 to 3 and 7, characterized by that the first guide surface (22a) is formed by an inner peripheral surface of a guide bush (22) which is adjacent to the collet (14) and is fixed in the housing (12). [9] Clamping device according to one of claims 1 to 3, 7 and 8, characterized by that the collet (14) has two clamping levers (16, 18), each with a first and a second lever arm (16', 18', 16'', 18'') which can be deflected about the virtual pivot point, wherein the tool shank can be clamped by means of the first lever arms (16', 18'), and the spreading elements (24) of the pressure piece (28) come to lie between the two second lever arms (16'', 18'') and press them radially apart, whereby clamping surfaces (16'a, 18'a) arranged on the first lever arms (16', 18') clamp the tool shank. [10] Clamping device according to one of claims 1 to 3, 7 to 9, characterized by that the first and second lever arms (16', 18', 16'', 18'') are configured such that upon rotation of the clamping device, the second lever arms (16'', 18'') are deflected about the virtual pivot point (20) by the action of centrifugal force and increase the clamping force of the first lever arms (16', 18').

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