Dental handpiece

Abstract

The present invention provides a dental handpiece capable of improving the wear resistance of a chuck mechanism and stably holding a dental treatment tool regardless of cutting conditions. The dental handpiece includes a sleeve (37) that is hollow and cylindrical, into which a dental treatment tool (15) is inserted and which is rotatably supported; a cylindrical slide member (45) that is housed in the sleeve (37); a plurality of divided movable pieces (47A, 47B) that are respectively arranged at different circumferential positions in the sleeve (37) and that hold the dental treatment tool (15); an elastic force applying member (41) that applies a force to the cylindrical slide member (45) in the direction of insertion of the dental treatment tool (15); and a stopper (49) that is fixed at least in part to the sleeve (37) and that restricts axial movement of the plurality of divided movable pieces (47A, 47B) in the direction of insertion.

Description

TECHNICAL FIELD

[0001] The present application relates to a dental handpiece. BACKGROUND

[0002] As a dental handpiece, an air turbine handpiece that performs cutting on a treatment site by the rotational force of an air turbine, and a motor handpiece that performs cutting on a treatment site by the driving force of a motor are known. These dental handpieces hold a dental treatment tool by a chuck mechanism housed in a head, and perform cutting on a treatment site by rotating the dental treatment tool at high speed.

[0003] With regard to the chuck mechanism that holds a dental treatment tool, a technology that suppresses a decrease in chucking force to prevent the dental treatment tool from falling off, idling, and the like is proposed (for example, Patent Documents 1 and 2).

[0004] Patent Document 1 discloses a configuration that chucks a dental treatment tool (chucked member) by a ball that is protruded and retracted in the radial direction from a cylindrical chuck shaft.

[0005] Patent Document 2 discloses a holding mechanism that has a tool holding member that holds a dental treatment tool, a tapered member that is disposed on the outside of the tool holding member, and a coil spring that exerts a force on the tool holding member in the upward direction. The holding mechanism has three slits that are engraved in the circumferential direction of the tool holding member, and a small piece is fitted in each slit. The outer circumferential surface of the small piece is brought into contact with the tapered member by the exertion of force from the coil spring through the tool holding member, and each small piece is pushed toward the radial inner side by the wedge effect of the tapered surface. Thus, each small piece is engaged with the dental treatment tool, and the dental treatment tool is held in the tool holding member.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT DOCUMENTS

[0008] Patent Document 1: Japanese Patent No. 3126887

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2006-122080

[0010] However, in the chuck mechanism of Patent Document 1, since the dental treatment tool is held by the ball in a local manner, there is a problem that wear is likely to occur, and the holding force is likely to decrease.

[0011] Further, in Patent Document 2, the holding force of the dental treatment tool depends on the frictional force of the tapered surface. Thus, for example, when a particularly strong vibration is applied to the tapered surface at the time of cutting, a gap is likely to occur between the dental treatment tool and the small piece, and the dental treatment tool is likely to fall off from the tool holding member. Further, the tapered member is thin-walled, and thus the taper of the tapered surface is shallow, and seizure is likely to occur in the tapered surface. As a result, the dental treatment tool is likely to be poorly attached and detached. SUMMARY

[0012] Therefore, an object of the present application is to provide a dental handpiece capable of improving the wear resistance of a tool mounting mechanism and stably holding a dental treatment tool at all times regardless of a cutting condition.

[0013] The present application includes the following configurations.

[0014] A dental handpiece having a tool mounting mechanism that mounts a dental treatment tool in a detachable manner, the dental handpiece rotating and driving the dental treatment tool mounted to the tool mounting mechanism, wherein

[0015] The tool mounting mechanism includes:

[0016] a hollow cylindrical sleeve into which the dental treatment tool is inserted and which is supported so as to be rotatable;

[0017] a cylindrical sliding member housed in the sleeve so as to be movable in the axial direction of the sleeve;

[0018] a plurality of divided movable pieces each disposed at a different circumferential position in the sleeve, each having an outer circumferential surface that abuts an inner circumferential surface of the cylindrical sliding member and an inner circumferential surface that abuts an outer circumferential surface of the dental treatment tool inserted into the sleeve, the plurality of divided movable pieces gripping the dental treatment tool;

[0019] a resilient biasing member biasing the cylindrical sliding member in the forward direction of the insertion direction of the dental treatment tool; and

[0020] a stopper, at least a portion of which is fixed to the sleeve, the stopper limiting the axial movement of the plurality of divided movable pieces in the forward direction of the insertion direction,

[0021] at least one of the outer circumferential surface of the plurality of divided movable pieces and the inner circumferential surface of the cylindrical sliding member abuts the other via a tapered fitting portion having a taper in the axial direction, and by the relative movement of the divided movable pieces and the cylindrical sliding member in the axial direction, the divided movable pieces move in the radial direction, and the fixing and the fixing release of the dental treatment tool are performed.

[0022] Effects of the Invention

[0023] According to the present application, the wear resistance of the tool mounting mechanism can be improved, and the dental treatment tool can be stably held at all times regardless of a cutting condition. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is an overall view of the dental handpiece of the present application.

[0025] Figure 2 is Figure 1Fig. 1 is a perspective view of a dental handpiece according to the present application.

[0026] Figure 3 Fig. 2 is a sectional view of the head of the dental handpiece shown in Fig. 1.

[0027] Figure 4 Fig. 3 is an exploded view of the components of the dental handpiece shown in Fig. 1.

[0028] Figure 5 Fig. 4 is a perspective view of the movable piece of the dental handpiece shown in Fig. 1.

[0029] Figure 6 Fig. 5 is a perspective view of the components of the dental handpiece shown in Fig. 1 in the assembled state. Figure 4 Fig. 6 is a sectional view along the line VI-VI of the dental handpiece shown in Fig. 1.

[0030] Figure 7 Fig. 7 is a sectional view along the line VII-VII of the dental handpiece shown in Fig. 1. Figure 3

[0031] Fig. 8 is a diagram showing the dental handpiece shown in Fig. 1 in the state in which the dental treatment tool is inserted into the chuck mechanism. Figure 8A

[0032] Fig. 9 is a diagram showing the dental handpiece shown in Fig. 1 in the state in which the dental treatment tool is inserted into the chuck mechanism. Figure 8B

[0033] Fig. 10 is a diagram showing the dental handpiece shown in Fig. 1 in the state in which the dental treatment tool is inserted into the chuck mechanism. Figure 8C

[0034] Fig. 11 is a diagram showing the dental handpiece shown in Fig. 1 in the state in which the dental treatment tool is inserted into the chuck mechanism. Figure 8D

[0035] Fig. 12 is a diagram showing the dental handpiece shown in Fig. 1 in the state in which the chucking of the dental treatment tool inserted into the chuck mechanism is released. Figure 9A

[0036] Fig. 13 is a diagram showing the dental handpiece shown in Fig. 1 in the state in which the chucking of the dental treatment tool inserted into the chuck mechanism is released. Figure 9B

[0037] Fig. 14 is a diagram showing the dental handpiece shown in Fig. 1 in the state in which the chucking of the dental treatment tool inserted into the chuck mechanism is released. Figure 9C

[0038] Fig. 15 is a diagram showing the dental handpiece shown in Fig. 1 in the state in which the chucking of the dental treatment tool inserted into the chuck mechanism is released. Figure 9D

[0039] Fig. 16 is a diagram showing the dental handpiece shown in Fig. 1 in the state in which the chucking of the dental treatment tool inserted into the chuck mechanism is released. Figure 10A Fig. 17 is a diagram showing the dental handpiece shown in Fig. 1 in the state in which an external force is applied to the chuck mechanism.

[0040] Figure 10B is a diagram showing the operation of the mounting mechanism in the case where an external force is applied to the mounting mechanism in stages.

[0041] Figure 10C is a diagram showing the operation of the mounting mechanism in the case where an external force is applied to the mounting mechanism in stages.

[0042] Figure 11 is a diagram showing the state in which the dental treatment tool is sandwiched by the split movable piece.

[0043] Figure 12 is a diagram showing the case where the taper angles of the first and second tapered surfaces are made different from the taper angles of the third and fourth tapered surfaces.

[0044] Figure 13 is a diagram showing the case where the taper angles of the first and second tapered surfaces are made different from the taper angles of the third and fourth tapered surfaces.

[0045] Figure 14 is a diagram showing the split movable piece having the second tapered surface on the outer peripheral surface and the cylindrical sliding member not having the first tapered surface on the inner peripheral surface.

[0046] Figure 15 is a diagram showing the split movable piece not having the second tapered surface on the outer peripheral surface and the cylindrical sliding member having the first tapered surface on the inner peripheral surface.

[0047] Figure 16 is a diagram showing the mounting mechanism having the split movable piece obtained by elongating the axial length.

[0048] Figure 17 is a diagram showing the mounting mechanism of the deformation example 2 having the split movable piece obtained by elongating the axial length.

[0049] Figure 18 is a diagram showing the mounting mechanism of the deformation example 3 obtained by integrally forming the protrusion portion with the split movable piece.

[0050] Figure 19 is a diagram showing the configuration of the mounting mechanism of the simplified deformation example 4.

[0051] Figure 20 is a diagram showing the configuration of the mounting mechanism of the other simplified deformation example 5.

[0052] Explanation of Reference Numerals

[0053] 11: head portion; 13: handle portion; 15: dental treatment tool; 21: head case; 23: head cap; 25: button; 27: urging spring; 29: cartridge case; 31A, 31B: rolling bearing; 33: outer ring; 35: inner ring; 37: sleeve; 37a: small diameter portion; 37b: large diameter portion; 38: step portion; 39: rotor; 41: coil spring (elastic urging member); 43, 43A, 43B, 43C, 43D, 43E: chucking mechanism; 45: cylindrical slide member; 47A, 47B, 48A, 48B, 49A, 49B, 50A, 50B, 52A, 52B: divided movable piece; 49: stopper; 51: first tapered surface; 53: second tapered surface; 55: third tapered surface; 57: cylindrical fixed member; 57A: tapered cylindrical member; 57B: remaining cylindrical member; 59: fourth tapered surface; 60: chamfered portion; 61: presser; 63: press piece; 65: restriction ring; 67: groove; 69, 71: groove wall; 73: circumferential end portion; 75: protrusion portion; 77: end surface; 81: protrusion portion; 83: groove portion; 100: dental handpiece. DETAILED DESCRIPTION

[0054] Hereinafter, an embodiment of the dental handpiece of the present application will be described in detail with reference to the drawings. Here, a configuration example of an air turbine handpiece will be described, but a motor handpiece or the like having other driving mechanisms can also be used.

[0055] Figure 1 is a whole view of the dental handpiece 100 of the present application.

[0056] The dental handpiece 100 has a head portion 11 and a handle portion 13 extending rearward from the head portion 11. The head portion 11 has a chucking mechanism to which a dental treatment tool 15 is attached in a detachable manner, and the head portion 11 rotationally drives the dental treatment tool 15 attached to the chucking mechanism. In the present configuration, a compressed air supply passage (not shown) and a discharge passage (not shown) are provided in the handle portion, and the dental treatment tool 15 is rotationally driven by compressed air supplied from the supply passage, and the compressed air for driving is discharged through the discharge passage.

[0057] Figure 2 is a cross-sectional view of the head portion 11 of the dental handpiece 100 shown in Figure 1 In the following description, the insertion and removal directions of the dental treatment tool 15 when the dental treatment tool 15 is attached to the head portion 11 will also be referred to as the up-down direction or the insertion direction, the front of the insertion direction will also be referred to as the upper side, and the rear of the insertion direction will also be referred to as the lower side.

[0058] The head 11 is configured to be surrounded by a head case 21 connected to the handle portion 13, covering the outer periphery of the head 11, a head cap 23 covering the upper portion of the head case 21, fixed to the head case 21, and a button 25 covering the upper portion of the head cap 23. A biasing spring 27 is provided between the button 25 and the head cap 23, and biases the button 25 upward.

[0059] A cartridge case 29 is housed inside the head case 21. The cartridge case 29 is fixed to the head case 21 as one body by mounting the head cap 23 from above the head case 21. An outer ring 33 of a pair of rolling bearings 31A, 31B is fixed to the inner periphery side of the cartridge case 29. A hollow cylindrical sleeve 37 is fitted to the outer peripheral surface of the inner ring 35 of the rolling bearings 31A, 31B.

[0060] The sleeve 37 is rotatably supported by the rolling bearings 31A, 31B, and the inside of the sleeve is for insertion of the dental treatment tool 15.

[0061] A rotor 39 is fixed between the rolling bearing 31A and the rolling bearing 31B in the sleeve 37. The rotor 39 is a rotating body having turbine blades, and generates a rotational force by compressed air supplied into the cartridge case 29, and rotationally drives the sleeve 37. That is, the sleeve 37 is supported to the head case 21 and the cartridge case 29 via the rolling bearings 31A, 31B, and thus the sleeve 37 is rotated by the rotational force generated by the rotor 39 as a driving source.

[0062] The sleeve 37 has a small-diameter portion 37a and a large-diameter portion 37b in the inner peripheral surface thereof. A coil spring 41 as an elastic biasing member that biases a cylindrical sliding member 45 forward in the insertion direction of the dental treatment tool 15 is arranged at the lower end of the large-diameter portion 37b. The coil spring 41 has an inner diameter through which the dental treatment tool 15 can be inserted along the axis Lc of the sleeve 37, and is formed in a configuration that improves the space efficiency in the sleeve 37. The sleeve 37 and the members housed in the large-diameter portion 37b of the sleeve 37 constitute a chucking mechanism 43 described later.

[0063] Figure 3 is a partially enlarged cross-sectional view showing the chucking mechanism 43 housed in the sleeve 37. Figure 4 is an exploded view of the members constituting the chucking mechanism 43. In the following description, the same members, the same portions are given the same reference numerals to omit or simplify the description thereof.

[0064] The chucking mechanism 43 mainly has the sleeve 37, the cylindrical sliding member 45, a plurality of (two in the present configuration) split movable pieces 47A, 47B, the above-described coil spring 41, and a stop portion 49 (see Figure 3 ).

[0065] The cylindrical slide member 45 is housed in the sleeve 37 in a manner capable of axial movement of the sleeve 37, and has a first tapered surface 51 that widens upward (in front of the insertion direction of the dental treatment tool 15) on the inner peripheral surface thereof. The divided movable pieces 47A, 47B have a second tapered surface 53 that is in sliding contact with the first tapered surface 51 on the outer peripheral surface thereof.

[0066] The pair of divided movable pieces 47A, 47B are arranged in opposition to each other in the diameter direction of the sleeve 37, and are independently rotatable with the presser 61 described later within the sleeve 37.

[0067] The stopper 49 is configured to include a cylindrical fixed member 57 having a third tapered surface 55 (third tapered surface) on the inner peripheral surface thereof, and a fourth tapered surface 59 provided to the divided movable pieces 47A, 47B. These tapered surfaces have a taper in the axial direction Lc, and thereby function as a tapered fitting portion that converts movement of the divided movable pieces 47A, 47B in the axial direction Lc to movement in the radial direction. The details of the stopper 49 will be described later, but at least a portion of the stopper 49 is fixed to the sleeve 37, and the stopper 49 restricts axial movement of the divided movable pieces 47A, 47B in the insertion direction.

[0068] Further, the presser 61 is arranged at a position higher than the divided movable pieces 47A, 47B, and is moved by the button 25 being pressed when the dental treatment tool 15 is removed from the chuck mechanism 43. The presser 61 has a pair of press pieces 63 that extend toward the cylindrical slide member 45 through the circumferential gap between the divided movable pieces 47A, 47B.

[0069] In addition, a ring-shaped restriction ring 65 that is fixed to the sleeve 37 is arranged below the cylindrical fixed member 57 (at the rear end in the insertion direction of the dental treatment tool 15). The restriction ring 65 is sandwiched between the stepped portion 38 formed on the inner peripheral surface of the sleeve 37 and the lower end of the cylindrical fixed member 57.

[0070] Figure 5 is a perspective view of the divided movable pieces 47A, 47B.

[0071] The divided movable pieces 47A, 47B are arranged at mutually different circumferential positions within the sleeve 37, and have the same shape. The divided movable pieces 47A, 47B are arranged so as to have an outer peripheral surface that abuts the inner peripheral surface of the cylindrical slide member 45 and an inner peripheral surface that abuts the outer peripheral surface of the dental treatment tool 15 inserted into the sleeve 37, and sandwich the dental treatment tool 15.

[0072] A second tapered surface 53 and a fourth tapered surface 59, whose radii gradually decrease toward the radially outer side in the axial direction, are formed on the axial one end side and the other end side of the split movable piece 47A, 47B. Further, a groove 67 along the circumferential direction is formed between the second tapered surface 53 and the fourth tapered surface 59. By this groove 67, a groove wall 69 on the second tapered surface 53 side and a groove wall 71 on the fourth tapered surface 59 side are formed. Also, as shown in Figure 3 the drawing, the restriction ring 65 is inserted inside the groove 67. Further, a chamfer portion 60, whose inner peripheral surface radius gradually increases toward the radially outer side in the axial direction, is formed on at least one end portion of the inner peripheral surface of the split movable piece 47A, 47B.

[0073] The split movable pieces 47A, 47B shown here are in a symmetrical shape, with an axial vertical surface passing through the axial center being taken as the symmetry plane. By being in a symmetrical shape, there is no need to be conscious of the directionality of the split movable pieces when assembling the chucking mechanism 43, and the assembly workability can be improved.

[0074] Figure 6 is a perspective view showing the state after assembly of each member shown in Figure 4 . In Figure 6 , the cylindrical fixed member 57 is omitted. In the presser 61, the tip end of the press piece 63 disposed between the pair of split movable pieces 47A, 47B abuts against the cylindrical sliding member 45. Also, by pressing the button 25 (refer to Figure 3 ), the cylindrical sliding member 45 is moved along the axis line Lc against the elastic force of the coil spring 41.

[0075] Figure 7 is a cross-sectional view along the line VII-VII shown in Figure 3 .

[0076] The radius Rs of the inner peripheral surface of the split movable piece 47A, 47B is smaller than the radius R0 of the outer peripheral surface of the dental treatment tool 15 to be held (Rs < R0). In this case, in the case where the split movable piece 47A, 47B holds the dental treatment tool 15, the circumferential end portion 73 of the inner peripheral surface of the split movable piece 47A, 47B is in line contact with the outer peripheral surface of the dental treatment tool 15. Thereby, the circumferential end portion 73 easily elastically bites into the dental treatment tool 15, and reliable chucking of the dental treatment tool 15 can be achieved.

[0077] <Chuck action>

[0078] Next, the chuck action of the dental treatment tool 15 by the chucking mechanism constituted as described above will be described.

[0079] Figure 8A to Figure 8D is a diagram showing the situation where the dental treatment tool is inserted into the chucking mechanism 43 to perform the chuck action in stages. Note that although not shown, the movement of the restriction ring 65 to the rear in the insertion direction isFigure 3 The stepped portion 38 provided on the inner circumferential surface of the sleeve 37 limits.

[0080] From Figure 8A From the state shown, the insertion of the dental treatment tool 15 into the sleeve 37 is performed by pressing the button 25, as shown in Figure 8B The tip of the pressing piece 63 of the presser 61 presses the end surface of the cylindrical slide member 45, and the presser 61 and the cylindrical slide member 45 are moved in the insertion opposite direction against the applied force of the coil spring 41. Thus, the divided movable pieces 47A, 47B are separated from the cylindrical slide member 45.

[0081] When the button 25 is further pressed, the end portion of the presser 61 in the insertion opposite direction abuts against the divided movable pieces 47A, 47B, and the divided movable pieces 47A, 47B are moved in the insertion opposite direction. Thus, the third tapered surface 55 slides with the fourth tapered surface 59, and the divided movable pieces 47A, 47B are expanded in the radial direction. Note that the pressing action of the button 25 is limited to the position where the groove wall 71 of the divided movable pieces 47A, 47B abuts against the limiting ring 65.

[0082] In this state, the dental treatment tool 15 is inserted into the sleeve 37 in the direction of the arrow K, as shown in Figure 8C The tip of the dental treatment tool 15 is inserted into the inner circumferential surface of the divided movable pieces 47A, 47B. At this time, the tip of the dental treatment tool 15 abuts against the chamfered portion 60 formed on the end portion of the inner circumferential surface of the divided movable pieces 47A, 47B, and the dental treatment tool 15 is inserted while the divided movable pieces 47A, 47B are pushed apart. The radial positions of the divided movable pieces 47A, 47B are adjusted by the sliding of the first tapered surface 51 and the second tapered surface 53 and the sliding of the third tapered surface 55 and the fourth tapered surface 59 accompanying the insertion action of the dental treatment tool 15.

[0083] That is, when the outer circumferential surface of the tip of the dental treatment tool 15 is inserted into the inner circumferential side of the divided movable pieces 47A, 47B, the divided movable pieces 47A, 47B are arranged at the radial positions corresponding to the outer diameter of the dental treatment tool 15. Note that the divided movable pieces 47A, 47B are arranged so as to be rotatable within the sleeve 37, and thus the alignment of the outer circumferential surface of the dental treatment tool 15 and the inner circumferential surface of the divided movable pieces 47A, 47B becomes easy, and it is difficult to cause the dental treatment tool 15 to be stuck when the dental treatment tool 15 is inserted.

[0084] The dental treatment tool 15 is inserted into the prescribed position within the sleeve 37, and the operator releases the pressing of the button. As shown in Figure 8DAs shown, by the exertion of force Fl from the coil spring 41, the cylindrical slide member 45 is moved in the direction of insertion of the dental treatment tool 15. By this, a wedge effect is produced between the first tapered surface 51 and the second tapered surface 53 and between the third tapered surface 55 and the fourth tapered surface 59. By this wedge effect, a fastening force Fc is produced from the divided movable pieces 47A, 47B toward the dental treatment tool 15. By this fastening force Fc, the dental treatment tool 15 is clamped in the sleeve 37.

[0085] <Clamping release action>

[0086] Next, the clamping release action will be described.

[0087] Figure 9A to Figure 9D is a diagrammatic view showing the action of releasing the clamping of the dental treatment tool inserted in the clamping mechanism 43 in stages.

[0088] From Figure 9A the state shown in which the dental treatment tool 15 is clamped, as shown in Figure 9B by pressing the button 25 to move the presser 61 in the direction opposite to the insertion of the dental treatment tool 15. Then, as described above, the presser 61 and the cylindrical slide member 45 are moved in the direction opposite to the insertion against the exertion of force of the coil spring 41, and the divided movable pieces 47A, 47B are separated from the cylindrical slide member 45.

[0089] When the button 25 is pressed further, as shown in Figure 9C the divided movable pieces 47A, 47B are moved in the direction opposite to the insertion, whereby the divided movable pieces 47A, 47B are expanded in the radial direction by the sliding of the third tapered surface 55 and the fourth tapered surface 59.

[0090] When the divided movable pieces 47A, 47B are expanded in the radial direction as described above, as shown in Figure 9D the clamping of the dental treatment tool 15 is released, and the dental treatment tool 15 can be pulled out.

[0091] That is, the outer peripheral surface of the divided movable pieces 47A, 47B and the inner peripheral surface of the cylindrical slide member 45 abut via the tapered fitting portion having the taper in the axial direction, and by the relative movement of the divided movable pieces 47A, 47B and the cylindrical slide member 45 in the axial direction, the divided movable pieces 47A, 47B are moved in the radial direction, and the fixing and the fixing release of the dental treatment tool 15 are performed.

[0092] <Exertion of external force from the dental treatment tool>

[0093] When the dental treatment tool is used, vibrations and axial forces from the dental treatment tool are transmitted to the clamping mechanism. Even in this case, the clamping mechanism 43 of the present configuration does not relax the clamping of the dental treatment tool 15, and a reliable clamping can be maintained.

[0094] Figure 10A to Figure 10C This is an explanatory diagram showing the action of the loading mechanism 43 when an external force is applied to it in stages.

[0095] When from Figure 10A The image shows the state of the dental treatment tool 15 being mounted, as shown. Figure 10B As shown, when an external force Fv is applied to the dental treatment tool 15, the dental treatment tool 15 is pushed forward toward the insertion direction of the sleeve 37, and the surface pressure between the third conical surface 55 of the cylindrical fixing member 57 and the fourth conical surface 59 of the movable dividing pieces 47A and 47B increases. As a result, the clamping force Fc from the movable dividing pieces 47A and 47B to the dental treatment tool 15 increases, and the dental treatment tool 15 is more securely fastened. At this time, the cylindrical sliding member 45 moves integrally with the movable dividing pieces 47A and 47B in a state of contact with them via the coil spring 41.

[0096] And, as Figure 10C As shown, when the external force Fv becomes stronger, the dental treatment tool 15 moves forward in the insertion direction, but the groove wall 69 of the dividing movable pieces 47A and 47B abuts against the limiting ring 65, thus limiting further axial movement.

[0097] Thus, even when vibration or axial force is applied to the dental treatment tool 15, the clamping mechanism 43 will always keep the dental treatment tool 15 in place and will not loosen the clamp.

[0098] Figure 11 This is a schematic cross-sectional view showing the state in which the dental treatment tool 15 is clamped by the segmented movable pieces 47A and 47B.

[0099] The aforementioned fastening force Fc generated by the conical fit (refer to...) Figure 8D , Figure 10B This can be converted into vertical resistance Fn for holding the dental treatment tool 15 via the segmented movable plates 47A. The larger the central angle θ formed by the pair of circumferential ends 73 of each segmented movable plate 47A, 47B and the center O of the dental treatment tool 15, the greater the vertical resistance Fn. When the radius of the inner circumferential surface of the segmented movable plates 47A, 47B is set as Rs, and the radius of the outer circumferential surface of the dental treatment tool 15 is set as R0, when Rs≥R0, the vertical resistance Fn at the circumferential ends 73 is almost 0, and the holding force (occlusion) of the dental treatment tool 15 is weakened. Therefore, the radius Rs of the inner circumferential surface of the segmented movable plates 47A, 47B that hold the dental treatment tool 15 is preferably set to be smaller than the radius R0 of the outer circumferential surface of the dental treatment tool 15.

[0100] Further, when the circumferential length of the split movable piece 47A, 47B is lengthened to approach a semicircle (position of the split movable piece 47A shown by the dotted line), although the vertical resistance Fn at the time of clamping increases, the split movable piece 47A approaches the split movable piece 47B and interferes with the pressing piece 63 (refer to FIG. 6). In the case where interference occurs, the tightening force Fc becomes a force that clamps the pressing piece 63, and the dental treatment tool 15 cannot be clamped any more. Further, depending on the size of the outer diameter of the dental treatment tool 15, the position of the split movable piece 47A, 47B at the time of clamping easily changes greatly, and thus the range of the outer diameter of the dental treatment tool 15 is limited. Figure 11 Figure 4 Further, when the circumferential length of the split movable piece 47A, 47B is lengthened to approach a semicircle (position of the split movable piece 47A shown by the dotted line), although the vertical resistance Fn at the time of clamping increases, the split movable piece 47A approaches the split movable piece 47B and interferes with the pressing piece 63 (refer to FIG. 6). In the case where interference occurs, the tightening force Fc becomes a force that clamps the pressing piece 63, and the dental treatment tool 15 cannot be clamped any more. Further, depending on the size of the outer diameter of the dental treatment tool 15, the position of the split movable piece 47A, 47B at the time of clamping easily changes greatly, and thus the range of the outer diameter of the dental treatment tool 15 is limited.

[0101] Therefore, it is good that the circumferential length of the split movable piece 47A, 47B is formed so that at least 1 / 6 or more of the circumference of the outer circumference of the dental treatment tool 15 is exposed, and it is preferable that 1 / 4 or more of the circumference is exposed, and it is more preferable that 1 / 3 or more of the circumference is exposed. That is, the central angle θ is preferably 165° or less, more preferably 152.5° or less, and further preferably 150° or less. By making the split movable piece 47A, 47B be within the above range, it is possible to expand the range of the outer diameter of the dental treatment tool 15 that can be clamped.

[0102] Further, the taper fitting of the split movable piece 47A, 47B and the cylindrical sliding member 45 and the cylindrical fixed member 57 needs to be set to a taper angle (angle formed by the axis of the sleeve 37 and the tapered surface) that enables reliable clamping and smooth clamping release. In order to make the pressing stroke of the button 25 be a small amount of 1 mm or less from the viewpoint of operability and to generate a sufficient clamping force, it is preferable that the taper angle be 5° or more, more preferably 7° or more, and further preferably 10° or more. Further, for the same reason, it is preferable that the taper angle be 30° or less, more preferably 20° or less, and further preferably 15° or less.

[0103] Figure 12 , Figure 13 is an explanatory view showing a case where the taper angles of the first tapered surface 51 and the second tapered surface 53 are different from the taper angles of the third tapered surface 55 and the fourth tapered surface 59.

[0104] The split movable piece 47A, 47B described above is in a symmetrical shape, and an axial vertical surface passing through the axial center is set as a symmetry plane, and the taper angles al of the first tapered surface 51 and the second tapered surface 53 are equal to the taper angles a2 of the third tapered surface 55 and the fourth tapered surface 59, but the taper angles are not limited thereto. It is also possible to make the taper angles be different from each other on one side and the other side in the axial direction with the axial vertical surface as the center.

[0105] As described above, the split movable piece 47A, 47B is formed so that the circumferential length of the split movable piece 47A, 47B is longer than the circumferential length of the split movable piece 47B, and the split movable piece 47A is formed so that the circumferential length of the split movable piece 47A is longer than the circumferential length of the split movable piece 47B. Figure 12 ​As shown, in the case where the taper angle al is smaller than the taper angle a2, the taper surface becomes less inclined with respect to the axial direction, and the applied force Fl from the coil spring 41 (see FIG. 2) can be converted into a larger vertical resistance Fn1. The tightening force Fc1 is a component of Fn1 in a direction perpendicular to the rotation axis, and thus the tightening force Fc1 can also be increased. Figure 3 ) of the coil spring 41 (see FIG. 2) can be converted into a larger vertical resistance Fn1. The tightening force Fc1 is a component of Fn1 in a direction perpendicular to the rotation axis, and thus the tightening force Fc1 can also be increased.

[0106] Further, as shown, in the case where the taper angle al is larger than the taper angle a2, the taper surface becomes more inclined with respect to the axial direction, and the vertical resistance Fn1 becomes smaller, and thus the frictional force generated by the taper surface can be reduced, and the occurrence of seizure can be suppressed. Figure 13

[0107] Note that the split movable pieces 47A and 47B are configured to be split into two parts in the circumferential direction, but the number of splits is not limited thereto. For example, the split movable pieces can be configured to be split into three parts or four parts in the circumferential direction. However, as the number of splits increases, the clamping force generated by the taper fitting of one split movable piece decreases, and thus in the case where the radial force generated by the taper fitting is small, it is preferable to reduce the number of splits.

[0108] According to the clamping mechanism 43 described above, by configuring the split movable pieces 47A and 47B to be split into two parts and providing taper surfaces respectively, a wedge effect can be produced, and a weak force in the rotation axis direction generated by the coil spring 41 can be converted into a larger force in the radial direction. Further, by providing taper surfaces at both ends of each of the split movable pieces 47A and 47B, even if a force in the insertion direction or the opposite direction (extraction direction) is applied to the dental treatment tool 15, the outer peripheral surface of the dental treatment tool 15 and the inner peripheral surfaces of the split movable pieces 47A and 47B do not separate, and the dental treatment tool 15 does not inadvertently fall off or become excessively inserted.

[0109] Further, the split movable pieces 47A and 47B are each provided with a taper surface at two locations, and the direction conversion effect of the force achieved by the tapering is doubled, and even if the taper angle is increased, a sufficient radial force can be obtained. Further, seizure that causes poor attachment and detachment of the dental treatment tool 15 is less likely to occur. Moreover, the dental treatment tool 15 is clamped in a manner in which the outer peripheral surface thereof is in line contact with the inner peripheral surfaces of the split movable pieces 47A and 47B, and thus the area in which clamping is facilitated is increased. As a result, a configuration that is strong against wear and has high durability can be achieved. Furthermore, in the clamping mechanism 43, the member that requires elasticity and the member that requires rigidity are separated, and the materials having the characteristics required for each can be freely selected, and the degree of freedom in design can be improved.

[0110] ​The sliding members (the divided movable pieces 47A, 47B, the cylindrical sliding member 45, and the cylindrical fixed member 57) that slide on the tapered surfaces are formed separately from the coil spring 41 that is the elastic biasing member. Therefore, compared to a case where each sliding member functions as an elastic biasing member, each sliding member can be formed of a material that is lower in elasticity and higher in hardness. Thus, the wear resistance of the divided movable pieces 47A, 47B, the cylindrical sliding member 45, and the cylindrical fixed member 57 can be further improved.

[0111] Further, regarding the above-described tapered fitting, the tapered surfaces can be provided on the divided movable pieces 47A, 47B, the cylindrical sliding member 45, and the cylindrical fixed member 57, respectively, but a configuration in which only either of the tapered surfaces that fit with each other is provided as a tapered surface can also be adopted. In the case of such a single tapered surface, the structure of the clamping mechanism 43 can be simplified.

[0112] Figure 14 is a schematic cross-sectional view that shows the divided movable pieces 47A, 47B having the second tapered surfaces 53 on the outer peripheral surfaces and the cylindrical sliding member 45 having no first tapered surface on the inner peripheral surface.

[0113] As shown in Figure 14 , a configuration in which the end portion 45a of the inner peripheral surface of the cylindrical sliding member 45 slides along the second tapered surface 53 can also be adopted without providing the first tapered surface on the cylindrical sliding member 45. Similarly, a configuration in which the end portion of the inner peripheral surface of the cylindrical fixed member 57 slides along the fourth tapered surface 59 of the divided movable piece 47A, 47B without providing the third tapered surface 55 on the inner peripheral surface of the cylindrical fixed member 57 can also be adopted as shown in Figure 3 . Even in such a case, the above-described clamping action can be performed.

[0114] Figure 15 is a schematic cross-sectional view that shows the divided movable pieces 47A, 47B having no second tapered surface 53 on the outer peripheral surfaces and the cylindrical sliding member 45 having a first tapered surface on the inner peripheral surface.

[0115] As shown in Figure 15 , a configuration in which one end portion 47a of the outer peripheral surface of the divided movable piece 47A, 47B slides along the first tapered surface 51 of the cylindrical sliding member 45 can also be adopted without providing the second tapered surface on the divided movable piece 47A, 47B. Similarly, a configuration in which the other end portion 47b of the outer peripheral surface of the divided movable piece 47A, 47B slides along the third tapered surface 55 of the inner peripheral surface of the cylindrical fixed member 57 can also be adopted without providing the fourth tapered surface on the divided movable piece 47A, 47B as shown in Figure 3 . Even in such a case, the above-described clamping action can be performed.

[0116] Moreover, the above-described configurations can also be combined as appropriate, such as not providing a tapered surface on either of the axial directions in which the movable pieces 47A, 47B are divided and providing a tapered surface only on the other. The above-described configurations can also be applied similarly to each of the modified examples described below.

[0117] <Other Configuration Example of the Mounting Mechanism> (Modified Example 1)

[0118] Figure 16 is a partial cross-sectional view of the mounting mechanism 43A of Modified Example 1 having a cylindrical fixed member 57 that is divided into two parts.

[0119] The cylindrical fixed member 57 of this mounting mechanism 43A is divided along the axial direction into a tapered cylindrical member 57A including the region of the third tapered surface 55 and a remaining cylindrical member 57B excluding the tapered cylindrical member 57A.

[0120] A third tapered surface 55 is formed on the inner peripheral surface of the cylindrical fixed member 57, and this third tapered surface 55 is required to have high machining precision and high wear resistance in order to be taperedly fitted with the fourth tapered surface 59. However, for regions other than the third tapered surface 55, such conditions are not required in most cases. Therefore, as shown in Figure 16 it is good to divide the cylindrical fixed member 57 into a region including the third tapered surface 55 that is required to have particularly high machining precision and wear resistance and a region other than this. In this case, for example, the tapered cylindrical member 57A can be formed by high-precision machining of a material having high wear resistance, and the remaining cylindrical member 57B can be formed using a material that is relatively inexpensive and has good machinability. That is, it is possible to make the cylindrical fixed member 57 into a configuration that can suppress material costs and can sufficiently exhibit necessary performance with little waste. Furthermore, the axial length of the tapered cylindrical member 57A is shortened, and thus its machinability can be improved.

[0121] <Modified Example 2>

[0122] Figure 17 is a cross-sectional view of the mounting mechanism 43B of Modified Example 2 having divided movable pieces 48A, 48B obtained by lengthening the axial length.

[0123] In the divided movable pieces 48A, 48B of this mounting mechanism 43B, the length from the groove 67 to the second tapered surface 53 is lengthened. According to this configuration, it is easy to secure a space for forming a tapered surface when the inclination of the second tapered surface 53 is set to be small. Thus, it is possible to become a configuration that can increase the contact area of the first tapered surface 51 and the second tapered surface 53 to reduce the surface pressure and can suppress wear. Furthermore, a configuration that lengthens the length from the groove 67 to the fourth tapered surface 59 to increase the contact area can also be adopted similarly.

[0124] <Modified Example 3>

[0125] Figure 18 is a sectional view showing a card attachment mechanism 43C of Modification 3 in which the protruding portion is formed integrally with the divided movable pieces 49A, 49B.

[0126] In the card attachment mechanism 43C, a protruding portion 81 is formed between the second tapered surface 53 and the fourth tapered surface 59 of the divided movable pieces 49A, 49B, and protrudes toward the radial outside in the circumferential direction. The protruding portion 81 can abut against the mutually opposed end portions of the cylindrical sliding member 45 and the cylindrical fixed member 57. Further, a ring-shaped groove portion 83 is formed in the sleeve 37 to prevent interference when the divided movable pieces 49A, 49B having the protruding portion 81 move toward the radial outside.

[0127] According to this configuration, the above-described limiting ring 65( Figure 3 ) can be omitted to simplify the configuration, and the axial movement of the divided movable pieces 49A, 49B can be limited.

[0128] (Modification 4)

[0129] The above-described card attachment mechanisms can also be configured to be further simplified.

[0130] Figure 19 is a schematic sectional view showing the configuration of a card attachment mechanism 43D of simplified Modification 4.

[0131] In the card attachment mechanism 43D, the axial movement of the divided movable pieces 50A, 50B having the second tapered surface 53 is limited by the protruding portion 75 protruding toward the radial inside from the inner circumferential surface of the sleeve 37. The other configurations can be configured in the same manner as the above-described card attachment mechanisms 43, 43A, 43B.

[0132] The divided movable pieces 50A, 50B have a tapered surface (second tapered surface 53) that is in sliding contact with the first tapered surface 51 of the cylindrical sliding member 45 on one end side in the axial direction, and an end surface 77 that abuts against the protruding portion 75 on the other end side. That is, the configuration does not have the above-described fourth tapered surface 59.

[0133] The protruding portion 75 can be formed on the inner circumferential surface of the sleeve 37 in a continuous manner in the circumferential direction, or can be a plurality of protrusions that are truncated in the circumferential direction. The protruding portion 75 only needs to abut against the respective end surfaces 77 of the divided movable pieces 50A, 50B to function as a stopper 49 that limits the axial movement of the divided movable pieces 50A, 50B.

[0134] According to the chucking mechanism 43D, reliable chucking of the dental treatment tool 15 can be performed by the taper fitting of the first taper surface 51 and the second taper surface 53. Also, the soft and resiliently required member such as the coil spring 41 and the member high in rigidity and superior in wear resistance taper-fitted to each other are separately configured, so that selection of the characteristics required for each member can be easily performed.

[0135] (Modified Example 5)

[0136] Figure 20 is a schematic cross-sectional view showing the configuration of another simplified modified example 5 of the chucking mechanism 43E.

[0137] The chucking mechanism 43E is provided with split movable pieces 52A and 52B provided with a taper surface on only one side in the axial direction, and the axial movement of the split movable pieces 52A and 52B is restricted by a restriction ring 65. Also, the end portion of the cylindrical fixed member 57 on the side of the restriction ring 65 does not have a taper surface (third taper surface 55) but is formed as an end surface in contact with the restriction ring 65. The other configurations are the same as those of the chucking mechanism 43 shown in Figure 3 .

[0138] According to the present configuration, as with the chucking mechanism 43D of the modified example 4, reliable chucking can be performed by the taper fitting of the first taper surface 51 and the second taper surface 53, and the machining of the sleeve 37 can be simplified.

[0139] The present application is not limited to the above-described embodiments, and can be appropriately modified, improved, or the like. Also, the material, shape, size, value, form, number, arrangement position, and the like of each component in the above-described embodiments are arbitrary as long as the present application can be achieved, and are not limited.

[0140] As described above, the following matters are disclosed in the present specification. (1) A dental handpiece 100 provided with a chucking mechanism 43 to which a dental treatment tool 15 is attached and detached in a detachable manner, the dental handpiece 100 performing rotational drive of the dental treatment tool 15 attached to the chucking mechanism 43, in which

[0141] The chucking mechanism 43 is provided with:

[0142] A hollow cylindrical sleeve 37 into which the dental treatment tool 15 is inserted and which is supported so as to be rotatable;

[0143] A cylindrical sliding member 45 accommodated in the sleeve so as to be movable in the axial direction of the sleeve;

[0144] The plurality of divided movable pieces 47A, 47B are arranged at different circumferential positions in the sleeve, have an outer circumferential surface abutting against an inner circumferential surface of the cylindrical sliding member 45 and an inner circumferential surface abutting against an outer circumferential surface of the dental treatment tool inserted into the sleeve, and hold the dental treatment tool 15;

[0145] The elastic force applying member 41 applies an elastic force to the cylindrical sliding member 45 in the direction of insertion of the dental treatment tool;

[0146] The stopper 49, at least a part of which is fixed to the sleeve, limits the axial movement of the plurality of divided movable pieces 47A, 47B in the direction of insertion,

[0147] At least one of the outer circumferential surface of the plurality of divided movable pieces 47A, 47B and the inner circumferential surface of the cylindrical sliding member 45 abuts against the other via a tapered fitting portion having a taper in the axial direction, and the divided movable pieces 47A, 47B move in the radial direction by the relative movement of the divided movable pieces 47A, 47B and the cylindrical sliding member 45 in the axial direction, thereby performing the holding and release of the dental treatment tool 15.

[0148] According to the dental handpiece, the movement of the divided movable pieces in the axial direction is converted to the movement in the radial direction by the tapered fitting portion, and the radial position of the inner circumferential surface of the divided movable pieces changes. Thus, the holding and release of the dental treatment tool by the divided movable pieces can be performed. Also, the dental treatment tool is reliably held by the inner circumferential surface of the plurality of divided movable pieces. Furthermore, even if an external force is applied to the dental treatment tool to push it in the direction of insertion, the stopper limits the axial movement of the dental treatment tool, so the tapered fitting portion does not loosen. Thus, the dental treatment tool can be stably held at all times.

[0149] (2) The dental handpiece according to (1), wherein

[0150] A pair of the divided movable pieces 47A, 47B are arranged in the diametrical direction of the sleeve 37 so as to face each other.

[0151] According to the dental handpiece, the pair of divided movable pieces sandwich the dental treatment tool in the diametrical direction, so the dental treatment tool can be held with high holding force.

[0152] (3) The dental handpiece according to (1) or (2), wherein

[0153] The cylindrical sliding member 45 has a first tapered surface 51 on the inner circumferential surface thereof, which expands in the direction of insertion,

[0154] The plurality of divided movable pieces 47A, 47B have a second tapered surface 53 on an outer peripheral surface thereof that is in sliding contact with the first tapered surface 51.

[0155] According to the dental handpiece, by the tapered fitting of the first tapered surface and the second tapered surface, radial movement of the divided movable pieces is enabled.

[0156] (4) The dental handpiece according to (3), wherein the stop portion 49 includes:

[0157] A cylindrical fixed member 57 is disposed at a position further forward in the insertion direction than the plurality of divided movable pieces 47A, 47B, and has a third tapered surface 55 on an inner peripheral surface thereof that is tapered to be reduced in diameter toward the front in the insertion direction; and

[0158] A fourth tapered surface 59 is provided on an outer peripheral surface of the plurality of divided movable pieces 47A, 47B, and is in sliding contact with the third tapered surface 55.

[0159] According to the dental handpiece, by the tapered fitting of the third tapered surface and the fourth tapered surface, axial movement of the divided movable pieces is restricted, and radial movement is enabled.

[0160] (5) The dental handpiece according to (4), wherein

[0161] The cylindrical fixed member 57 is divided along the axial direction into a tapered cylindrical member 57A including a region of the third tapered surface 55 and a remaining portion cylindrical member 57B excluding the tapered cylindrical member.

[0162] According to the dental handpiece, for example, the tapered cylindrical member can be formed by high-precision machining of a material having high wear resistance, and the remaining portion cylindrical member can be formed using a material that is relatively inexpensive and has good machinability. That is, the cylindrical fixed member can be configured to be wasteful to a small extent in that material costs are suppressed and necessary performance can be sufficiently exhibited. Furthermore, machinability of the tapered surface of the tapered cylindrical member can be improved.

[0163] (6) The dental handpiece according to any one of (1) to (5), wherein

[0164] The divided movable pieces 47A, 47B are provided with a protrusion portion 81 protruding to the radially outer side on an outer peripheral surface thereof further forward in the insertion direction than the tapered fitting portion,

[0165] The protrusion portion 81 can abut against an end portion of the cylindrical sliding member 45 that is forward in the insertion direction.

[0166] According to the dental handpiece, the configuration becomes simpler.

[0167] (7) The dental handpiece according to (4) or (5), wherein

[0168] The dental handpiece has a ring-shaped restriction ring 65 disposed at a rear end portion in the insertion direction of the cylindrical fixed member, fixed to the sleeve,

[0169] The outer diameter surface of the split movable piece 47A, 47B between the second tapered surface 53 and the fourth tapered surface 59 is formed with a groove 67 in the circumferential direction,

[0170] The restriction ring 65 has a radial thickness in which the inner peripheral surface of the restriction ring is inserted into the groove 67, and by movement of the split movable piece 47A, 47B in the axial direction, the groove wall in front of the insertion direction or the groove wall at the rear of the groove 67 abuts against the restriction ring 65.

[0171] According to the dental handpiece, the axial movement of the split movable piece can be restricted by the restriction ring.

[0172] (8) The dental handpiece according to any one of (4) to (7), wherein

[0173] The split movable piece 47A, 47B, the cylindrical sliding member 45, and the cylindrical fixed member 47 are made of a material having a higher hardness than the elastic biasing member 41.

[0174] According to the dental handpiece, the wear resistance of the split movable piece, the cylindrical sliding member, and the cylindrical fixed member that slide on the tapered surface can be improved.

[0175] (9) The dental handpiece according to any one of (4) to (8), wherein

[0176] In the axial cross section of the sleeve 37, the tapered angle formed by the second tapered surface 53 and the fourth tapered surface 59 of the split movable piece 47A, 47B and the axis of the sleeve 37 is 5° or more and 30° or less.

[0177] According to the dental handpiece, by appropriately setting the tapered angle, reliable chucking and smooth chucking release of the dental treatment tool can be performed.

[0178] (10) The dental handpiece according to any one of (1) to (9), wherein

[0179] The dental handpiece has a presser 61 disposed at a position in front of the split movable piece 47A, 47B in the insertion direction, which is depressed when the dental treatment tool 15 is removed from the chucking mechanism,

[0180] The presser 61 has a presser piece 63 extending toward the cylindrical slide member 45 through the circumferential gaps of the plurality of divided movable pieces from each other,

[0181] When the presser is pressed rearward of the insertion direction of the dental treatment tool 15, the presser piece 63 pushes the cylindrical slide member 45 rearward of the insertion direction, thereby releasing the clamping of the divided movable pieces 47A, 47B and the dental treatment tool 15.

[0182] According to the dental handpiece, the cylindrical slide member is pushed back by the presser, the fitting of the tapered fitting portion is released, and the divided movable pieces move to the radial outside. Thereby, the clamping of the dental treatment tool is released.

[0183] (11) The dental handpiece according to any one of (1) to (10), wherein

[0184] The radius of the inner circumferential surface of the divided movable pieces 47A, 47B is smaller than the radius of the outer circumferential surface of the dental treatment tool 15.

[0185] According to the dental handpiece, the circumferential end portions of the divided movable pieces abut the outer circumferential surface of the dental treatment tool in a line contact. Thereby, the circumferential end portions of the divided movable pieces easily elastically bite into the dental treatment tool, and reliable clamping of the dental treatment tool can be achieved.

[0186] (12) The dental handpiece according to any one of (1) to (11), wherein

[0187] The plurality of divided movable pieces 47A, 47B are configured to be rotatable around the axis of the sleeve within the sleeve.

[0188] According to the dental handpiece, by making the divided movable pieces rotatable, when the dental treatment tool is inserted, the feeling of being stuck is less, and smoother clamping can be performed.

[0189] (13) The dental handpiece according to any one of (1) to (12), wherein

[0190] The elastic force applying member 41 is a coil spring.

[0191] According to the dental handpiece, the dental treatment tool can be inserted along the central axis of the coil spring, which is a configuration with high space efficiency within the sleeve.

[0192] (14) The dental handpiece according to any one of (1) to (13), wherein

[0193] The divided movable pieces 47A, 47B are in a symmetrical shape, and an axial vertical surface passing through the axial center is set as a symmetry plane.

[0194] According to the dental handpiece, the tapered fitting portions formed on the outer circumferential surfaces of the split movable pieces are disposed at the same tapered angle on one side and the other side in the axial direction with the axial direction perpendicular surface as the center. Thus, the sliding of the tapered fitting portions becomes balanced and smooth. Furthermore, by making the split movable pieces symmetrical in shape, the directionality of the split movable pieces does not need to be considered at the time of assembly, and the assembly workability can be improved.

Claims

1. A dental handpiece having a chuck mechanism to which a dental treatment tool is attached in a detachable manner, the dental handpiece rotating and driving the dental treatment tool attached to the chuck mechanism, wherein the chuck mechanism has: a sleeve of a hollow cylindrical shape into which the dental treatment tool is inserted and which is supported so as to be rotatable; a cylindrical slide member housed in the sleeve so as to be movable in an axial direction of the sleeve; a plurality of divided movable pieces each disposed at a different circumferential position in the sleeve, each having an outer circumferential surface abutting an inner circumferential surface of the cylindrical slide member and an inner circumferential surface abutting an outer circumferential surface of the dental treatment tool inserted into the sleeve, the plurality of divided movable pieces gripping the dental treatment tool; an elastic force applying member applying a force to the cylindrical slide member in a direction of insertion of the dental treatment tool; and a stopper at least a portion of which is fixed to the sleeve, the stopper limiting axial movement of the plurality of divided movable pieces in the direction of insertion, at least one of the outer circumferential surface of the plurality of divided movable pieces and the inner circumferential surface of the cylindrical slide member abutting the other via a tapered fitting portion having a taper in the axial direction, the divided movable pieces moving in a radial direction by relative movement of the divided movable pieces and the cylindrical slide member in the axial direction, the divided movable pieces being gripped and un-gripped, the plurality of divided movable pieces being disposed so as to be rotatable about an axis of the sleeve in the sleeve.

2. The dental handpiece according to claim 1, wherein a pair of the divided movable pieces are disposed opposite each other in a diameter direction of the sleeve.

3. The dental handpiece according to claim 1, wherein the cylindrical slide member has a first tapered surface on the inner circumferential surface thereof expanding in the direction of insertion, and the plurality of divided movable pieces have a second tapered surface on the outer circumferential surface thereof in sliding contact with the first tapered surface.

4. The dental handpiece according to claim 2, wherein the cylindrical slide member has a first tapered surface on the inner circumferential surface thereof expanding in the direction of insertion, and the plurality of divided movable pieces have a second tapered surface on the outer circumferential surface thereof in sliding contact with the first tapered surface.

5. The dental handpiece according to claim 2, wherein the stopper includes: a cylindrical fixed member disposed at a position further in the direction of insertion than the plurality of divided movable pieces, the cylindrical fixed member having a third tapered surface on an inner circumferential surface thereof tapering in the direction of insertion; and a fourth tapered surface provided on the outer circumferential surface of the plurality of divided movable pieces in sliding contact with the third tapered surface.

6. The dental handpiece according to claim 5, wherein the cylindrical fixed member is divided along the axial direction into a tapered cylindrical member including a region of the third tapered surface and a remaining portion cylindrical member excluding the tapered cylindrical member.

7. The dental handpiece according to claim 5, wherein the cylindrical fixed member is divided along the axial direction into a tapered cylindrical member including a region of the third tapered surface and a remaining portion cylindrical member excluding the tapered cylindrical member. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 5. The dental handpiece of claim 3, wherein, ​ ​ ​ 6. The dental handpiece of claim 4, wherein, ​ ​ ​ ​ ​ 8. The dental handpiece according to claim 6, wherein the cylindrical fixed member is divided into a tapered cylindrical member including a region of the third tapered surface and a remaining cylindrical member excluding the tapered cylindrical member along the axial direction.

9. The dental handpiece according to any one of claims 1 to 8, wherein the divided movable piece is provided with a protruding portion protruding to the radially outer side at an outer peripheral surface in front of the tapered fitting portion in the insertion direction, the protruding portion is capable of abutting against an end portion in front of the insertion direction of the cylindrical sliding member.

10. The dental handpiece according to any one of claims 5 to 8, wherein the dental handpiece is provided with a ring-shaped restriction ring disposed at a rear end portion of the insertion direction of the cylindrical fixed member and fixed to the sleeve, a groove is formed in the outer diameter surface of the divided movable piece between the second tapered surface and the fourth tapered surface along the circumferential direction, the restriction ring has a radial thickness in which an inner peripheral surface of the restriction ring is inserted into the groove, and a groove wall in front of the insertion direction or a groove wall at the rear of the groove abuts against the restriction ring by movement of the divided movable piece in the axial direction.

11. The dental handpiece according to any one of claims 5 to 8, wherein the divided movable piece, the cylindrical sliding member, and the cylindrical fixed member are composed of a material having a higher hardness than the elastic biasing member.

12. The dental handpiece according to any one of claims 5 to 8, wherein in an axial cross section of the sleeve, a tapered angle formed by at least one of the second tapered surface and the fourth tapered surface of the divided movable piece and the axis of the sleeve is 5° or more and 30° or less.

13. The dental handpiece according to any one of claims 1 to 8, wherein the dental handpiece is provided with a presser disposed at a position in front of the insertion direction of the divided movable piece and depressed when the dental treatment tool is removed from the chuck mechanism, the presser has a presser piece extending to the cylindrical sliding member through the circumferential gaps of the plurality of divided movable pieces from each other, when the presser is depressed in the rear of the insertion direction of the dental treatment tool, the presser piece pushes the cylindrical sliding member back to the rear of the insertion direction, releasing the chucking of the divided movable pieces and the dental treatment tool.

14. The dental handpiece according to any one of claims 1 to 8, wherein a radius of an inner peripheral surface of the divided movable piece is smaller than a radius of an outer peripheral surface of the dental treatment tool.

15. The dental handpiece according to any one of claims 1 to 8, wherein the elastic biasing member is a coil spring.

16. The dental handpiece according to any one of claims 1 to 8, wherein the divided movable piece is in a symmetrical shape with an axial vertical surface passing through the axial center as a symmetrical surface.

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