Dental handpiece with improved push button guidance

Abstract

The present invention relates to a dental handpiece (1), comprising a head (4), clamping means (13) rotatably arranged within a bearing (19) inside the head (4) and adapted to releasably clamp a dental drill (2), wherein the bearing (19) has an inner ring (21) fixed to the clamping means (13) and an outer ring (21) fixed to the housing (5) of the head (4), drive means for rotating the clamping means (13) around the axial direction of the dental drill (2), a push button (7) movably arranged axially within the head (4) and configured to actuate the clamping means (13) to release the dental drill (2), and biasing means for moving the push button (7) away from the clamping means (13), wherein the radially inner surface (7a) of the push button (7) is arranged to contact and slide on the radially outer surface (20a) of an outer ring (20) constituting a guide (12) for the moving push button (7), wherein the radial direction is perpendicular to the axial direction of the dental drill (2), and wherein a radial clearance (A) is arranged between the radially inner surface (5b) of the housing (5) and the radially outer surface (7b) of the push button (7).

Description

Technical Field

[0001] The present invention relates to a dental handpiece, and more particularly to a push button guidance of a dental handpiece for operating a clamping mechanism for a dental drill.

Background Art

[0002] A dental handpiece is a handheld device for performing various dental treatments that may require the use of various dental tools such as drills. The head of the dental handpiece is usually provided with a clamping mechanism such as a chuck that allows a dentist to replace the dental tool according to the intended dental procedure by pressing a button. The push button is movably held through a guide within the head of the dental handpiece.

[0003] Refer to EP0639354A2, EP1733696A1, EP2959860A1, EP3412244, which disclose respective prior art dental handpieces.

[0004] To ensure proper operation of the dental handpiece, there are specific design requirements that the dental handpiece must meet. For example, excessive heating of the push button in the contact area with the clamping mechanism should be prevented as much as possible. For example, excessive mechanical wear of the clamping jaw should be prevented as much as possible. For example, the size of the head should be made as small as possible so as to be easily accessible to the spatially limited areas within the oral cavity. For example, the push button and the clamping mechanism must be operable reliably and easily.

Summary of the Invention

[0005] The inventor is unaware of a prior art handpiece in which the radially inner surface of the push button is arranged to slide in direct contact with the radially outer surface of the outer ring of a bearing that rotatably holds a burr shaft. Thereby, the axis of the burr shaft can be accurately aligned with the axis of the push button, and the push button can be operated extremely smoothly.

[0006] An object of the present invention is to overcome one or more drawbacks of the prior art and to provide a dental handpiece that is mechanically compact and easy to use.

[0007] This object is achieved through the dental handpiece defined in claim 1.

[0008] The dental handpiece of the present invention includes a head, clamping means rotatably disposed within a bearing in the head and adapted to releasably clamp a dental drill, wherein the bearing has an inner ring fixed to the clamping means and an outer ring fixed to the housing of the head, drive means for rotating the clamping means about the axial direction of the dental drill, a push button movably disposed axially within the head and configured to actuate the clamping means to release the dental drill, and biasing means for moving the push button away from the clamping means. The radially inner surface of the push button is arranged to slide in contact with the radially outer surface of the outer ring that constitutes a guide for the push button moving axially, where the radial direction is perpendicular to the axial direction of the dental drill. A radial clearance is disposed between the radially inner surface of the housing and the radially outer surface of the push button.

[0009] The main advantageous effect of the present invention is that the size of the head can be reduced. This can be explained as follows. Also, since the radially outer surface of the outer ring constitutes an axial guide for the moving push button, there is no need to provide a separate guide member. This enables a compact mechanical configuration. The compact size of the head also allows the dentist to easily reach spatially limited locations within the oral cavity and work more easily within the oral cavity.

[0010] Another great effect of the present invention is that the push button can be operated more reliably and easily. This can be explained as follows: Since the radially outer surface of the outer ring constitutes a guide for the push button that moves along the axial direction, the movement can be properly aligned with the bearing surface and thus the drill of the clamping mechanism. This enables good alignment between the movable parts.

[0011] In an alternative embodiment of the present invention, the push button can be provided as a single-piece member or a two-piece member.

Brief Description of the Drawings

[0012] In the following description, exemplary embodiments are used and the present invention will be described in more detail by referring to the following drawings.

[0013]

Figure 1

Figure 2a

Figure 2b

Figure 2c

Figure 2d

Figure 3

Figure 4a

Figure 4b

Figure 5a

Figure 5b

Figure 6a

Figure 6b

Figure 6c

Figure 6d

Figure 7a

Figure 7b

Figure 7c

Figure 7d

DETAILED DESCRIPTION OF THE INVENTION

[0014] The reference numerals shown in the drawings indicate the elements listed below and are referred to in the following description of the exemplary embodiments. 1. Dental handpiece 2. Dental drill (bar) 3. Body 4. Head 5. Housing 5a. Gap 5b. Radial inner surface 6. Female thread 7. Push button 7a. Radial inner surface 7b. Radial outer surface 8. Cap 9. Flange collar (hat type) 9a. Claw 9b. Gap (thermal insulation) 9`. Cap 10. Contact surface (point-like) 11. Spring (conical) 12. Guide 13. Clamping means 14. Ball 15. Hollow shaft 16. Gear 17. Opening 18. Stop edge 19. 19’ Bearing 20. Outer ring 20a. Radial outer surface 21. Inner ring 22. Ball 23. Retainer 24. Thread ring 25. Nose 26. Chuck 27. Arm 27a. Contact point 28. Notch 29. Large diameter part 30. Small diameter part 31. Contact edge (burst stop) 32. Drive shaft 33. Bearing 34. Outer ring 35. Inner ring 36. Ball 37. Retainer 38. Crown gear A: Axial direction R: Radial direction S: Radial clearance F: Actuating force

[0015] Figure 1 shows a dental handpiece (1) according to an embodiment of the present invention. As shown in Figure 1, the dental handpiece (1) has a main body (3) and a head (4). A dental drill (2) is detachably attached to the head (4). Figure 2a shows an enlarged cross-sectional view of the head (4). As shown in Figure 2a, the head (4) has a housing (5) that houses clamping means (13). As shown in Figure 4a, the clamping means (13) has a chuck (26) that has an elastic arm (27) for releasably clamping the dental drill (2). A hollow shaft (15) is rotatably disposed inside the head (4). The chuck (26) is fixed within the hollow shaft (15) and rotates with the hollow shaft (15). The dental handpiece (1) has drive means such as a motor (not shown) for rotating the hollow shaft (15). The drive means is coupled to a drive shaft (32) as shown in Figure 2a, and the drive shaft (32) is rotatably held via a bearing (33) having an outer ring (34), an inner ring (35), a plurality of balls (36), and a cage (37). The end of the drive shaft (32) has a crown gear (38) that meshes with a gear (16) on the hollow shaft (15). As shown in Figure 3, the hollow shaft (15) is rotatably held via a pair of bearings (19; 19') attached within the housing (5). Each bearing (19; 19') has an outer ring (20) and an inner ring (21), a plurality of balls (22), and a retainer (23).

[0016] As shown in Fig. 3, the clamping means (13) preferably has a ball (14) made of a ceramic material, which ball is axially movably disposed inside a rotatable hollow shaft (15) and is in direct contact with the elastic arms (27) of the chuck (26). The ball (14) partially projects through an opening (17) at the upper end of the hollow shaft (15). The size of the opening (17) is smaller than the size of the ball (14), so that the ball (14) is partially held within the hollow shaft (15). As shown in Fig. 3, the opening (17) has an annular stop edge (18) formed integrally with the upper end of the hollow shaft (15), and this annular stop edge (18) limits the outward movement of the ball (14). As shown in Figs. 2a and 2b, the dental handpiece (1) is disposed on the head (4) and has a push button (7) configured to contact the ball (14) that partially projects when pushed by the user and move the ball (14) downward between the elastic arms (27) to bend the elastic arms (27) radially outward to release the dental drill (2). As shown in Fig. 5a, the chuck (26) has two diametrically opposed notches (28) at its upper part, forming two elastic arms (27). As shown in Fig. 5b, a linear semi-cylindrical channel is formed at the upper part of the chuck (26), and its edges form two diametrically opposed contact points (27a) for direct contact with the ball (14). As shown in Fig. 3, the chuck (26) has a large-diameter portion (29) and a small-diameter portion (30). When the elastic arms (27) are retracted, the dental drill (2) can only be manually inserted up to the upper end of the large-diameter portion (29). When the elastic arms (27) are bent via the ball (14), the dental drill (2) can be further inserted into the small-diameter portion (30) until it abuts against the contact edge (31) (burst stop). When the push button (7) is released, the elastic arms (27) retract and the dental drill (2) is clamped within the small-diameter portion (30) between the elastic arms (27). The elastic arms (27) also bias the ball (14) inside the rotatable hollow shaft (15) toward the opening (17).As shown in Fig. 2a, the push button (7) has a cap (8) and a hat-shaped flange collar (9) disposed inside the cap (8) and fixed to the cap (8). The hat-shaped flange collar (9) has a preferably planar dot contact surface (10) for direct contact with the ball (14). The push button (7) has a biasing means such as a spring (11), preferably a conical spring (11), for removing the push button (7) away from the ball (14). As shown in Fig. 2a, when the push button (7) is released, the dot contact surface (10) is not in contact with the ball (14). As shown in Fig. 2b, when the push button (7) is pushed downward, the contact surface (10) makes a point contact with the upper side of the ball (14).

[0017] Fig. 2c shows an enlarged view of the two-component push button (7) of Fig. 2a constituted by the cap (8) and the hat-shaped flange collar (9). Figs. 7a and 7b show the two-component push button (7) in more detail.

[0018] Fig. 2d shows an alternative embodiment in which the cap (9’) is provided as a single part instead of two separate parts. All other features remain the same. Thereby, the number of components can be further reduced. Figs. 7c and 7d show the single-part push button (7) in more detail.

[0019] According to the alternative embodiments shown in Figs. 2c and 2d, the radial inner surface (7a) of the push button (7) is directly in contact with and arranged to slide on the radial outer surface (20a) of an outer ring (20) that constitutes a guide (12) for the movable push button (7). The radial direction is perpendicular to the axial direction (A) of the dental drill (2). A radial clearance (s) is arranged between the radial inner surface (5b) of the housing (5) and the radial outer surface (7b) of the push button (7). The housing (5) is formed from a single part.

[0020] As shown in Fig. 2a, the housing (5) has an internal thread (6) for receiving a separate screw ring (24). The mounting flange of the upper bearing (19) is fixed in its mounting position via the screw ring (24). The mounting flange has an L-shaped cross-section and is formed integrally with the outer ring (20) of the bearing (19). The screw ring (24) has a nose (25) which is visible in Fig. 2d but not in Fig. 2a. The respective cross-sectional views of Figs. 2a and 2d are rotated approximately 90 degrees relative to each other. The cross-section of Fig. 2a is along the line I-I shown in Fig. 1, and the cross-section of Fig. 2d is along the line II-II shown in Fig. 1. As shown in Fig. 2d, the nose (25) extends radially inwards and can abut from below against the claw (9a) of a cap-shaped flange collar (9) which extends radially outwards, preventing the push button (7) from disengaging from the screw ring (24) and thus from the housing (5). The cap-shaped flange collar (9) can be provided separately from the cap (8; 9') or integrally with the cap (8; 9'). In the former case, as shown in Fig. 2a, in order to improve the thermal insulation, it is preferable that a gap (9b) is formed under the cap (8). Alternatively, the gap (9b) may be filled with a material which is a low heat conductor.

[0021] As shown in FIGS. 2a and 2d, the inner surface of the cap-shaped flange collar (9) slides directly on the outer surface of the outer ring (20) and is in contact with the outer ring (20) that constitutes a guide (12) for the movement of the push button (7). The nose (25) of the screw ring (24) is disposed above the claw (9a) of the cap-shaped flange collar (9). The cap-shaped flange collar (9) does not contact the inner radial surface of the screw ring (24). The flange collar (9) is inserted between the screw ring (24) and the outer ring (20). The housing (5) has a gap (5a) directly above the screw ring (24) and the nose (25), whereby the cap (8; 9') can move upward or downward during the clamping / releasing operation. The screw ring (24) is completely embedded / recessed inside the housing (5) and does not protrude outside the head (4). Thereby, the height of the head (4) can be reduced. Thereby, the diameter of the cap (8, 9') can also be increased, and the operating pressure applied to the finger is reduced. The cylindrical outer surface of the cap (8; 9') does not contact the inner surface of the housing (5) during its entire movement due to a sufficient radial clearance (S). Therefore, the guide (12) acts as a guide contact surface for the vertical movement of the cap (8; 9'). With the above configuration, the height and diameter of the head (4) can be further reduced.

Claims

【Claim 1】 a head (4), clamping means (13) rotatably arranged within a bearing (19) inside the head (4) and adapted to releasably clamp a dental drill (2), wherein the bearing (19) has an inner ring (21) fixed to the clamping means (13) and an outer ring (20) fixed to a housing (5) of the head (4), driving means for rotating the clamping means (13) about the axial direction of the dental drill (2), a push button (7) movably arranged along the axial direction within the head (4) and configured to actuate the clamping means (13) to release the dental drill (2), biasing means for moving the push button (7) away from the clamping means (13), characterized in that, in a dental handpiece (1) comprising: a radial inner surface (7a) of the push button (7) is arranged to contact and slide along a radial outer surface (20a) of the outer ring (20) constituting a guide (12) for the movable push button (7), wherein the radial direction is perpendicular to the axial direction of the dental drill (2), and a radial clearance (S) is arranged between a radial inner surface (5b) of the housing (5) and a radial outer surface (7b) of the push button (7).

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