Dental handpiece

Abstract

Provided is an impeller-type dental handpiece that can improve cutting efficiency while reducing a generated sound volume. Among m×n (m=1, 2, ... and n=2, 3, …) blades (22-p) constituting an impeller (2) that is disposed rotatably about an axis in internal space of a housing (11) and that is for rotating a cutting blade tool (4) for teeth, the fluid resistance of a jth blade (1≤j≤n-1) constituting an ith blade group (1≤i≤m) is configured to be higher than, or lower than, the fluid resistance of a j+1th blade neighboring the jth blade on the downstream side.

Description

Dental Handpiece

[0001] The present invention relates to an impeller-type dental handpiece.

[0002] The present inventor has proposed a dental handpiece that includes a housing with an impeller for rotating a tooth-cutting tool, and a handle-side housing attached to the housing and incorporating an air supply passage for the impeller, the impeller being designed to emit ultrasonic vibrations by disrupting rotational balance (see Patent Document 1).

[0003] The rotor can be configured to emit ultrasonic vibrations of approximately 60 kHz by disrupting the rotational balance relative to smooth rotation. These ultrasonic vibrations are transmitted to the cutting tool, which is attached coaxially to the impeller. The rotating cutting tool acts as an ultrasonic horn, and is applied directly to the tooth that comes into contact with this horn. In other words, by bringing the cutting tool into contact with the tooth to remove the decayed area, the ultrasonic vibrations are transmitted to the decayed tooth, making it less painful for the patient.

[0004] For example, if an impeller has eight blades, seven of which are conventional and one blade is designed to have a smaller surface area exposed to the wind than the other seven, or one blade may be designed to have a curve that creates a higher air resistance, thereby providing an impeller with a desired degree of rotational imbalance that causes the rotating shaft to generate ultrasonic vibrations.

[0005] Japanese Patent Application Laid-Open No. 2023-162078

[0006] However, in a dental handpiece having such a configuration, compressed air from the compressor rotates the impeller inside the impeller at high speed, generating a high-pitched whine from the impeller, which is often unpleasant to the ears of dentists and patients. Although it is desirable for patients to feel at ease during dental treatment, this can frighten the patient.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an impeller-type dental handpiece that can reduce noise while improving cutting efficiency.

[0008] The dental handpiece of the present invention comprises a housing, an impeller rotatably arranged about an axis within the internal space of the housing for rotating a tooth-cutting tool, and a handle-side housing attached to the housing and having an air supply passage and an air exhaust passage for the impeller, wherein the impeller has m×n (m=1, 2, ..., n=2, 3, ...) blades, and the fluid resistance of the jth blade (1≦j≦n-1) constituting the ith blade group (1≦i≦m) is configured to be higher or lower than the fluid resistance of the j+1th blade adjacent to the jth blade on the downstream side.

[0009] In this dental handpiece, the impeller in the housing's internal space is driven to rotate by compressed air supplied from a compressor by the practitioner, and a cutting tool attached coaxially to the impeller shaft performs treatment such as cutting the patient's teeth. The multiple (n × m) blades (vanes) that make up the impeller each have a pattern of varying fluid resistance, which suppresses the generation of large vortices around the impeller and reduces noise. This suppresses the generation of vortices, which is one of the causes of reduced rotational efficiency of the impeller and, ultimately, the cutting tool.

[0010] FIG. 1 is an explanatory diagram of the configuration of a dental handpiece according to a first embodiment of the present invention. FIG. 2 is a schematic plan view of an impeller of the dental handpiece. FIG. 3 is a schematic side development view of the impeller of the dental handpiece. FIG. 4 is an explanatory diagram of the fluid resistance pattern of each blade of the impeller according to the first embodiment. FIG. 5 is an explanatory diagram of the fluid resistance pattern of each blade of the impeller according to the first modified example. FIG. 6 is an explanatory diagram of the fluid resistance pattern of each blade of the impeller according to the second modified example. FIG. 7 is an explanatory diagram of the fluid resistance pattern of each blade of the impeller according to the third modified example. FIG. 8 is an explanatory diagram of the fluid resistance pattern of each blade of the impeller according to the fourth modified example. FIG. 9 is an explanatory diagram of the configuration of a dental handpiece according to a second embodiment of the present invention. FIG. 10 is an explanatory diagram of the configuration of a toroidal blade according to the first embodiment of the present invention.

[0011] (First Embodiment) An impeller-type dental handpiece 1 according to a first embodiment of the present invention, shown in Fig. 1, includes a housing 11 having a substantially cylindrical internal space, an impeller 2 disposed in the internal space of the housing 11 for rotating a tooth-cutting tool 4, and a handle-side housing 12 attached to the housing 11 and provided with an air supply passage 121 and an exhaust passage 122 for the impeller 2. The handle-side housing 12 is designed to have an appropriate shape and size for easy gripping by a practitioner such as a dentist. As shown in Fig. 1, an air supply conduit 101 is connected to the air supply passage 121, and an exhaust conduit 102 is connected to the exhaust passage 122.

[0012] As shown in Fig. 1, the handle-side housing 12 is provided with an air supply passage 121 and an exhaust passage 122 for the impeller 2, as well as a water supply passage 124 that communicates with the external space of the handle-side housing 12 and opens downwardly from the housing 11. As shown in Fig. 3, the water supply conduit 104 is connected to the water supply passage 124, and the exhaust passage 122 is arranged to merge with the water supply passage 124. The water supply passage 124 may be omitted.

[0013] The upper part of the housing 11 may be formed by a cover member, and opening or removing the cover member may allow access to the internal space of the housing 11, thereby enabling replacement of the impeller 2.

[0014] As shown in FIG. 2, the impeller 2 includes a rotor 220 that is fixed to or detachably attached to a substantially cylindrical shaft 20, and P blades 22-1, 22-2, ... 22-P (P=12 in this embodiment) that extend radially from the rotor 220.

[0015] As shown in Fig. 1 , the shaft 20 is rotatably held relative to the housing 11 via upper ball bearings 111 and lower ball bearings 112 at the upper shaft portion 201 and the lower shaft portion 202, respectively. A cutting tool 4 is fixed to the lower shaft portion 202 coaxially with the shaft 20. The cutting tool 4 may be detachably attached to the lower shaft portion 202, for example, by fitting an upper portion of the cutting tool 4 into a hole at the bottom of the lower shaft portion 202. As shown in Fig. 1 , at least a portion of the cutting tool 4 including the file portion 40 protrudes downward from the housing 11 through a through-hole 114 provided in the bottom of the housing 11.

[0016] In this embodiment, the P blades 22-1, 22-2, ... 22-P protrude radially from the rotor 220 while gradually increasing the inclination angle relative to the radial direction (gradually tilting clockwise in FIG. 2). The P blades 22 are arranged to have P-fold rotational symmetry about the central axis of the shaft 20. The shaft 20 includes a shaft sheath 210 formed integrally with the P blades 22. The impeller 2 shown in FIG. 2 rotates clockwise about the central axis of the shaft 20 or the rotor 220. The impeller 2 shown in FIG. 2 may also rotate counterclockwise about the central axis of the shaft 20 or the rotor 220, in which case the P blades 22-1 to 22-P are numbered sequentially in the counterclockwise direction.

[0017] The number of blades 22-p constituting the impeller 2 may be any even number or non-prime odd number such as 12, 4, 6, 8, 12, 15, 16, 18, or 24.

[0018] The impeller 2 may be made of a light metal such as aluminum (specific gravity 2.7) or various aluminum alloys (specific gravity 2.6 to 2.8), such as duralumin (specific gravity 2.8). The blades 22 may be made of ceramics such as forsterite (2MgO·SiO2) (specific gravity 3.0), silicon carbide (SiC) (specific gravity 3.16), silicon nitride (Si3P4) (specific gravity 3.3), aluminum nitride (AlP) (specific gravity 3.4), alumina (Al2O3) (specific gravity 3.8), yttria (YO3) (specific gravity 4.9), or zirconia (ZrO2) (specific gravity 6.0), or a metal composite material such as cermet (TiC·TiP) (specific gravity 6.0). The impeller 2 may be made of a heavy metal such as iron (specific gravity 7.9), nickel (specific gravity 8.8), copper (specific gravity 8.9), or an alloy thereof. When the impeller 2 is made of chromium or lead, it is preferable that the entire impeller be plated with a harmless metal such as silver or nickel. Impellers 2 having complex shapes can be produced by a three-dimensional printer using raw material powder and / or by laser processing of the raw material.

[0019] Fig. 2 shows a schematic plan view of the impeller 2. As shown in Fig. 2, the protrusion amount or radial size Δr1 of each of the first blade 22-1, the third blade 22-3, the fifth blade 22-5, the seventh blade 22-7, the ninth blade 22-9, and the eleventh blade 22-11 from the rotor 220 is designed to be smaller than the protrusion amount or radial size Δr2 of each of the second blade 22-2, the fourth blade 22-4, the sixth blade 22-6, the eighth blade 22-8, the tenth blade 22-10, and the twelfth blade 22-12 from the rotor 220.

[0020] FIG. 3 shows a schematic side development view of the impeller 2. In this embodiment, as shown in FIG. 3, each blade 22-p (p = 1, 2, ... P) has a substantially circular arc or substantially elliptical arc shape, and both ends are positioned at substantially the same position in the circumferential direction. Each blade 22-i (i = 1, 2, ... P) may have both ends offset from each other in the circumferential direction, or may have various shapes, such as a substantially wing-like shape. As shown in FIG. 3, the axial size L1 of each of the first blade 22-1, the third blade 22-3, the fifth blade 22-5, the seventh blade 22-7, the ninth blade 22-9, and the eleventh blade 22-11 of the rotor 220 is designed to be smaller than the axial size L2 of each of the second blade 22-2, the fourth blade 22-4, the sixth blade 22-6, the eighth blade 22-8, the tenth blade 22-10, and the twelfth blade 22-12.

[0021] Due to the size or size and shape of each blade 22-p constituting the impeller 22 as shown in Figures 2 and 3, as shown in Figure 4, the fluid resistance R1 of each of the first blade 22-1, third blade 22-3, fifth blade 22-5, seventh blade 22-7, ninth blade 22-9 and eleventh blade 22-11 is designed to be smaller than the fluid resistance R2 of each of the second blade 22-2, fourth blade 22-4, sixth blade 22-6, eighth blade 22-8, tenth blade 22-10 and twelfth blade 22-12. In other words, of the m × n (m = 6, n = 2) blades 22-1 to 22-12 that make up the impeller 2 of this embodiment, the fluid resistance of the jth blade (j = 1 or j = 2i-1) that makes up the ith blade group (i = 1, 2, ... 6) is configured to be higher than the fluid resistance of the j+1th blade that is adjacent to the jth blade on the downstream side.

[0022] The fluid resistance between the blades 22-p may be adjusted by the surface roughness (particularly the surface roughness on the upstream side) of the blades 22-p instead of or in addition to the size and / or shape of the blades 22-p. The surface roughness of the blades 22-p is adjusted to, for example, Ra=10 μm to 200 μm, or 20 to 100 μm.

[0023] (Modification) As shown in FIG. 5, among the m×n (m=4, n=3) blades 22-1 to 22-12 that constitute the impeller 2 of the first modification, the fluid resistance of the jth blade (j=1, 2 or j=3i-2, 3i-1) that constitutes the ith blade group (i=1, 2, ... 4) may be configured to be higher than the fluid resistance of the j+1th blade that is adjacent to the jth blade on the downstream side.

[0024] As shown in Figure 6, of the m x n (m = 2, n = 6) blades 22-1 to 22-12 that make up the impeller 2 of the second modified example, the fluid resistance of the jth blade (j = 1, 2, ... 6 or j = 6i-5, 6i-4, ... 6i-1) that makes up the ith blade group (i = 1, 2) may be configured to be higher than the fluid resistance of the j+1th blade that is adjacent to the jth blade on the downstream side.

[0025] As shown in Figure 7, of the m x n (m = 2, n = 6) blades 22-1 to 22-12 that make up the impeller 2 of the third modified example, the fluid resistance of the jth blade (j = 1, 2, ... 6 or j = 6i-5, 6i-4, ... 6i-1) that makes up the first blade group (i = 1) may be configured to be higher than the fluid resistance of the j+1th blade that is adjacent to the jth blade on the downstream side, and the fluid resistance of the jth blade (j = 1, 2, ... 6 or j = 6i-5, 6i-4, ... 6i-1) that makes up the first blade group (i = 2) may be configured to be lower than the fluid resistance of the j+1th blade that is adjacent to the jth blade on the downstream side.

[0026] As shown in Figure 8, among the m x n (1 = 4, n = 12) blades 22-1 to 22-12 that make up the impeller 2 of the fourth modified example, the fluid resistance of the jth blade (j = 1, 2, ... 11) that makes up the ith blade group (i = 1) may be configured to be higher than the fluid resistance of the j+1th blade that is adjacent to the jth blade on the downstream side.

[0027] (Operation and Effect) With the dental handpiece 1 configured as described above, compressed air is supplied from the compressor to the interior space of the housing 11 through the air supply conduit 101 and the air supply passage 121 by operation by the practitioner. In the air supply circuit communicating with the compressor, the amount of compressed air supplied is adjusted by an air supply volume adjustment mechanism constituted by a pedal or the like of a chair unit. The impeller 2 in the interior space of the housing 11 is driven to rotate by the compressed air, and treatment such as cutting of the patient's teeth is performed by the cutting tool 4 coaxially attached to the shaft 20 of the impeller 2. The compressed air is exhausted from the interior space of the housing 11 to the outside of the dental handpiece 1 through the exhaust passage 122 and the exhaust conduit 102.

[0028] Because there is a pattern of differences in fluid resistance among the multiple (n × m) blades 22-1 to 22-P that make up the impeller 2 (see FIGS. 4 to 8), the generation of large vortexes around the impeller 2 in the internal space of the housing 11 is suppressed, thereby reducing the volume of sound generated. The generation of vortexes, which is one of the causes of reduced rotational efficiency of the impeller 2 and, in turn, the cutting tool 4, can be suppressed. Furthermore, high-frequency components are generated in the rotational torque of the impeller 2 and, in turn, the shaft 20, achieving the same effect as high-frequency vibration cutting, in which the tip or cutting edge of the cutting tool 4 is rapidly separated from the portion to be cut, such as a tooth root, thereby improving cutting efficiency.

[0029] Second Embodiment In an impeller-type dental handpiece 1 according to a second embodiment of the present invention, shown in Figure 9, an impeller 2 is composed of a first impeller 21 and a second impeller 22. Other configurations are substantially the same as those of the dental handpiece 1 of the first embodiment, and therefore the same components are denoted by the same reference numerals and detailed description thereof will be omitted.

[0030] As shown in Fig. 9, the first impeller 21 is disposed in the internal space of the housing 11, facing (or adjacent to) the air intake port communicating with the air intake passage 121. As shown in Fig. 10, the first impeller 21 includes a substantially cylindrical first rotor 210 and Q blades 21-q (q = 1, 2, ... Q) (for example, Q = 4; Q may also be 2, 3, 5 or more) extending radially from the first rotor 210. The first rotor 210 is fixed or detachably attached to the shaft 20. The Q blades 21-q are disposed to have Q-fold rotational symmetry about the central axis of the first rotor 210.

[0031] As shown in Figure 10, blade 21-q is composed of a first blade portion 211, a second blade portion 212, and a bridge portion 214. The first blade portion 211 extends radially and diagonally downward from the first rotor 210, then bends clockwise when viewed from above, and extends in a generally L-shape. The second blade portion 212 extends radially and diagonally upward from the first rotor 210, then bends counterclockwise when viewed from above, and extends in a generally L-shape. The bridge portion 214 is a portion where the distal portion of the first blade portion 211 (the portion bent clockwise) and the distal portion of the second blade portion 212 (the portion bent counterclockwise) are continuous.

[0032] The second blade portion 212 has a shape that includes the central axis of the first rotor 210 and is a mirror image of the first blade portion 211, with respect to a plane perpendicular to the direction in which the first blade portion 211 protrudes from the first rotor 210. The axial and circumferential relative positions (phase difference) and relative attitudes of the continuous portions or continuous regions of the first blade portion 211 and the second blade portion 212 relative to the first rotor 210 are adjusted so that the first blade portion 211 and the second blade portion 212 are connected by a bridge portion 214 at their distal portions. The blades may be configured so that the first blade portion 211 and the second blade portion 212 are continuous such that a portion of the distal portion of the first blade portion 211 overlaps or is common to a portion of the distal portion of the second blade portion 212. In this case, the overlapping portion forms the bridge portion 214.

[0033] Blade 21-q may be formed in a substantially semi-annular shape, with the twisted portion of a Möbius strip included in the middle portion. In this case, half of the substantially semi-annular portion (a substantially quarter-annular portion) constitutes first blade portion 211 and second blade portion 212, and the twisted portion constitutes bridge portion 214.

[0034] The first impeller 21 may be made of a light metal, ceramic, metal composite material, or heavy metal, similar to the impeller 2 of the first embodiment. The first impeller 21 having a complex shape can be produced by a three-dimensional printer using raw material powder and / or laser processing of the raw material.

[0035] The blade 21-q may be configured so that the specific gravity of the first blade portion 211, the second blade portion 212, and the bridge portion 214 is higher than the specific gravity of the first rotor 210. The blade 22 may be configured so that the specific gravity of the bridge portion 214 is higher than the specific gravity of the first rotor 210, the first blade portion 211, and the second blade portion 212. For example, the blade 21-q may be configured from a base material such as a light metal or ceramic, and a thermal sprayed film of ceramic having a higher specific gravity than the base material is formed on a portion of the blade 21-q, thereby producing a blade 21-q having different specific gravities depending on the region. Furthermore, the blade 21-q may be configured from a base material such as a heavy metal or ceramic, and a thermal sprayed film of ceramic having a lower specific gravity than the base material is formed on a portion of the blade 21-q, thereby producing a first impeller 21 having different specific gravities depending on the region.

[0036] 9, the second impeller 22 is disposed in the internal space of the housing 11 facing (or adjacent to) the exhaust port communicating with the exhaust passage 122. The second impeller 22 rotates around the central axis of the shaft 20 in the same manner as the first impeller 21, and rotates integrally with the first impeller 21. The second impeller 22 has a configuration similar to that of the impeller 2 in the first embodiment.

[0037] (Operation and Effect) With the dental handpiece 1 configured as described above, compressed air is supplied from the compressor to the interior space of the housing 11 through the air supply conduit 101 and the air supply passage 121 by operation by the practitioner. In the air supply circuit communicating with the compressor, the amount of compressed air supplied is adjusted by an air supply volume adjustment mechanism constituted by a pedal or the like of a chair unit. The impeller 2 in the interior space of the housing 11 is driven to rotate by the compressed air, and treatment such as cutting of the patient's teeth is performed by the cutting tool 4 coaxially attached to the shaft 20 of the impeller 2. The compressed air is exhausted from the interior space of the housing 11 to the outside of the dental handpiece 1 through the exhaust passage 122 and the exhaust conduit 102.

[0038] The first impeller 21 is equipped with toroidal blades 21-1 to 21-Q (blades in which the first blade portion 221 and the second blade portion 222 are connected at a bridge portion 224 (see FIG. 2 )). This prevents large vortexes from being generated around the first impeller 21 in the internal space of the housing 11, thereby reducing the volume of noise generated. This prevents vortexes from being generated at the blade ends, which is one of the causes of reduced rotational efficiency of the first impeller 21 and, ultimately, the cutting tool 4.

[0039] Because there is a pattern of differences in fluid resistance among the multiple (P = n × m) blades 22-1 to 22-P that make up the second impeller 22 (see FIGS. 4 to 8), the generation of large vortexes around the second impeller 22 in the internal space of the housing 11 is suppressed, thereby reducing the volume of generated sound. The generation of vortexes, which is one of the causes of reduced rotational efficiency of the second impeller 22 and, ultimately, the cutting tool 4, can be suppressed. Furthermore, high-frequency components are generated in the rotational torque of the second impeller 22 and, ultimately, the shaft 20, achieving the same effect as high-frequency vibration cutting, in which the tip or cutting edge of the cutting tool 4 is rapidly separated from the cutting target portion, such as a tooth root, thereby improving cutting efficiency.

[0040] The dental handpiece of the present invention reduces the sound volume generated by the high-speed rotation of the impeller caused by compressed air, thereby alleviating the anxiety felt by patients due to the generated sound and allowing dentists to have more technical and psychological freedom, thereby contributing to the development of the industry.

[0041] 1: Dental handpiece 101: Air intake conduit 102: Exhaust conduit 104: Water supply conduit 11: Housing 111: Upper ball bearing 112: Lower ball bearing 114: Through hole 12: Handle side housing 121: Air intake passage 122: Exhaust passage 124: Water supply passage 2: Impeller 20: Shaft 201: Upper shaft 202: Lower shaft 21: First impeller 21-q: Blades 211: First blade portion 212: Second blade portion 214: Bridge portion 22: Second impeller 22-1 to 22-12: Blades 4: Cutting tool 40: File portion.

Claims

1. A dental handpiece comprising: a housing; an impeller rotatably disposed about an axis within the interior space of said housing for rotating a tooth-cutting tool; and a handle-side housing attached to said housing and having an air supply passage and an air exhaust passage for said impeller, wherein, of the m x n (m = 1, 2, ..., n = 2, 3, ...) blades constituting said impeller, the fluid resistance of the jth blade (1 ≦ j ≦ n-1) constituting the ith blade group (1 ≦ i ≦ m) is configured to be higher or lower than the fluid resistance of the j+1th blade adjacent to said jth blade on the downstream side.

2. A dental handpiece as claimed in claim 1, wherein the fluid resistance of the jth blade in the ith blade group is configured to be lower than the fluid resistance of the j+1th blade, and the fluid resistance of the jth blade in the i+1th blade group adjacent to the ith blade group on the downstream side is configured to be lower than the fluid resistance of the j+1th blade.

3. A dental handpiece as claimed in claim 1, wherein the fluid resistance of the jth blade in the ith blade group is configured to be higher than the fluid resistance of the j+1th blade, and the fluid resistance of the jth blade in the i+1th blade group adjacent to the ith blade group on the downstream side is configured to be higher than the fluid resistance of the j+1th blade.

4. A dental handpiece as claimed in claim 1, wherein the fluid resistance of the jth blade in the ith blade group is configured to be lower than the fluid resistance of the j+1th blade, and the fluid resistance of the jth blade in the i+1th blade group adjacent to the ith blade group on the downstream side is configured to be higher than the fluid resistance of the j+1th blade.

5. A dental handpiece according to any one of claims 1 to 4, wherein the fluid resistance of the jth blade constituting the ith blade group is differentiated from the fluid resistance of the j+1th blade by at least one of the size, shape, and surface roughness of the jth blade and the j+1th blade.

6. A dental handpiece as defined in claim 1, wherein the impeller comprises: a first impeller whose blades are toroidal; and a second impeller having m x n blades, which is positioned in the internal space of the housing closer to the exhaust port communicating with the exhaust passage than the first impeller, is rotatable integrally with the first impeller around the same axis.

7. A dental handpiece according to claim 6, wherein the first impeller is disposed in the internal space of the housing, facing an air inlet port communicating with the air inlet passage, and the second turbine is disposed in the internal space of the housing, facing an exhaust port communicating with the exhaust passage.

8. A dental handpiece according to claim 1, wherein the blade is detachably mounted on the shaft of the impeller.

9. A dental handpiece according to claim 1, wherein the cutting tool is detachably mounted coaxially on the shaft of the impeller.

10. A dental handpiece according to claim 1, wherein the blade is made of at least one of an aluminum alloy, a ceramic, and a heavy metal.

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