Dental handpiece having a chuck with an integral plunger ball

Abstract

The present invention relates to a dental handpiece (1), the dental handpiece (1) comprising a head (4), a rotatable hollow shaft (15) rotatably disposed inside the head (4), drive means for rotating the hollow shaft (15), a chuck (26) having an elastic arm (27) for releasably clamping a dental drill (2), wherein the chuck (26) is fixed inside the hollow shaft (15) so as to rotate together with the hollow shaft (15), a ball (14) axially movably disposed inside the rotatable hollow shaft (15) and in direct contact with the elastic arm (27) of the chuck (26), wherein the ball (14) partially protrudes through an opening (17) at the upper end of the hollow shaft (15), the opening (17) being smaller than the size of the ball (14) and being disposed in the head (4) and, when pressed by the user, contacting the partially protruding ball (14) and configured to move the ball (14) downward between the elastic arms (27) so as to deflect the elastic arms (27) radially outward to release the dental drill (2), wherein the elastic arm (27) biases the ball (14) toward the opening (17) inside the rotatable hollow shaft (15) and biasing means for moving the push button (7) away from the ball (14), wherein the push button (7), when released, does not contact the ball (14).

Description

Technical Field

[0001] The present invention relates to a dental handpiece, and more particularly to a clamping mechanism of a dental handpiece for releasably clamping 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 a dental handpiece is usually provided with a clamping mechanism such as a chuck that allows a dentist to exchange dental tools according to the intended dental treatment by pressing a button.

[0003] Refer to EP0639354A2, EP1733696A1, EP2959860A1, JPH02130619U, EP0245692A2, each of which discloses a prior art dental handpiece.

[0004] To ensure proper operation of a dental handpiece, there are certain design requirements that must be met by the dental handpiece. For example, any excessive heating of the push button in the contact area with the clamping mechanism must be prevented as much as possible. For example, any excessive mechanical wear of the clamping jaws must be prevented as much as possible. For example, the size of the head should be reduced as much as possible so that it can easily reach a spatially limited location within the oral cavity. For example, the push button and the clamping mechanism must be operable in a reliable and easy manner.

Summary of the Invention

[0005] The inventor is not aware of any prior art dental handpiece in which the clamping / release of a dental drill can be affected through a plunging ball that is under the push button and in direct contact with the elastic arm of the chuck.

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

[0007] This object is achieved through the dental handpiece according to claim 1. The subject matter of the dependent claims relates to further developments and embodiments.

[0008] The dental handpiece of the present invention comprises a head; a rotatable hollow shaft rotatably disposed inside the head; drive means for rotating the hollow shaft; and a chuck having an elastic arm for releasably clamping a dental drill, wherein the chuck is fixed within the hollow shaft so as to rotate with the hollow shaft; a ball axially movably disposed inside the rotatable hollow shaft and in direct contact with the elastic arm of the chuck, wherein the ball partially protrudes through an opening at the upper end of the hollow shaft, the opening being smaller than the size of the ball; a push button disposed in the head and configured to move the ball downward between the elastic arms when pressed by the user, contacting the partially protruding ball and deflecting the elastic arm radially outward to release the dental drill, wherein the elastic arm biases the ball toward the opening inside the rotatable hollow shaft; and biasing means for moving the push button away from the ball, wherein the push button does not contact the ball when released.

[0009] A major advantageous effect of the present invention is that the chuck can be prevented from any excessive mechanical wear. This can be explained as follows: Since the ball rotates together with the hollow shaft, when the user presses the push button, it has no relative speed with respect to the elastic arm of the chuck. This also reduces the friction against the chuck and the heat dissipation during the pressing operation. Thereby, excessive mechanical wear and heating of the chuck can be prevented as much as possible. On the other hand, when the push button makes a point contact with the upper surface of the ball, the heat generated by the relative movement of the ball with respect to the push button will generally be dissipated radially by the push button. Furthermore, the lower surface of the ball generally causes only a point contact with the elastic arm of the chuck due to its spherical shape, which further reduces any heat transfer from the lower surface of the ball to the chuck.

[0010] Another major advantageous effect of the present invention is that the size of the head can be further reduced. This can be explained as follows: Since the ball is located immediately below the push button, the ball can be directly used to flex the elastic arm of the chuck when the push button moves downward to release the dental drill. Therefore, the number of parts required to clamp / release the dental drill is reduced. 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 to work more easily within the oral cavity.

[0011] Another major advantageous effect of the present invention is that the push button can operate in a more reliable and easier manner. This can be explained as follows: The ball is positioned directly between the push button and the chuck and operates like a plunger, so the ball will directly activate the release operation. Further, when the ball is pushed downward, the contact force generated between the chuck and the ball will gradually increase in the radial horizontal direction, and the elastic arms will be pushed apart by an increasing amount depending on the spherical curvature of the ball that intrudes between the elastic arms. As a result, the user can apply a relatively smaller force to clamp / release the dental drill. This gives a comfortable feel to the user's finger when pressing the button.

[0012] In one embodiment, the ball is preferably made of a ceramic material. Thereby, friction can be reduced and mechanical strength can be increased.

[0013] In the following description, the present invention will be described in more detail by using exemplary embodiments and with reference to the drawings.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2a

Figure 2b

Figure 2c

Figure 3

Figure 4a

Figure 4b

Figure 5a

Figure 5b

Figure 6a

Figure 6b

Figure 6c

Figure 6d

DETAILED DESCRIPTION OF THE INVENTION

[0015] The reference numbers 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 6. Female thread 7. Push button 8. Cap 9. Flange collar (hat-shaped) 9a. Claw 9b. Gap (thermal insulation) 9’ Cap 10. Contact surface (dot-shaped) 11. Spring (conical) 12. Guide 13. Clamping means 14. Ball 15. Hollow shaft 16. Gear 17. Opening 18. Stopping edge 19. Bearing 20. Outer ring 21. Inner ring 22. Ball 23. Cage 24. Thread ring 25. Protrusion (Nose) 26. Chuck 27. Arm 27a. Contact point 28. Notch 29. Large-diameter part 30. Small-diameter part 31. Contact edge (bar stop) 32. Driving shaft 33. Bearing 34. Outer ring 35. Inner ring 36. Ball 37. Cage 38. Crown gear A: Axial direction F: Actuating force

[0016] 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). The 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 the clamping means (13). As shown in Figure 4a, the clamping means (13) has a chuck (26) with 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 inside the hollow shaft (15) so as to rotate with the hollow shaft (15). The dental handpiece (1) has driving means such as a motor (not shown) for rotating the hollow shaft (15). As shown in Figure 2a, the driving means is coupled to a drive shaft (32), and the drive shaft (32) is rotatably held through 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 through a pair of bearings (19) attached inside the housing (5). The bearing (19) has an outer ring (20), an inner ring (21), a plurality of balls (22), and a cage (23).

[0017] As shown in FIG. 3, the clamping means (13) preferably has a ball (14) made of a ceramic material. This ball (14) is disposed axially movably inside a rotatable hollow shaft (15) and is in direct contact with the elastic arms (27) of the chuck (26). The ball (14) partially protrudes through an opening (17) at the upper end of the hollow shaft (15). The elastic arms (27) are long enough to bias the ball (14) toward the inside of the opening (17). The size of the opening (17) is smaller than the size of the ball (14), and as a result, the ball (14) is partially held within the hollow shaft (15). As shown in FIG. 3, the opening (17) has an annular retaining edge (18) formed integrally with the upper end of the hollow shaft (15), and this annular retaining edge (18) restricts the outward movement of the ball (14). As shown in FIGS. 2a and 2b, the dental handpiece (1) is disposed at the head (4) and, when pushed by the user, contacts the partially protruding ball (14) and is configured to move the ball (14) downward between the elastic arms (27) so as to elastically deflect the elastic arms (27) radially outward to release the dental drill (2). Even when the push button (7) is fully released, the ball (14) remains in direct contact with the upper portions of the two elastic arms (27). As shown in FIG. 5a, the chuck (26) has two diametrically opposed notches (28) at its upper portion to form the two elastic arms (27). As shown in FIG. 5b, a linear semi-cylindrical channel is formed inside the upper portion 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 deflected, the dental drill (2) can be further inserted into the small-diameter portion (30) until it abuts against the contact edge (31) (bar 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) towards the opening (17) inside the rotatable hollow shaft (15). As shown in Figure 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 point 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), to move the push button (7) away from the ball (14) and remove it from the ball (14). As shown in Figure 2a, when the push button (7) is released, the point contact surface (10) is not in contact with the ball (14). As shown in Figure 2b, when the push button (7) is pushed downward, the contact surface (10) makes point contact with the upper surface of the ball (15). The gap between the opening (17) of the shaft (15) and the elastic arms (27) functions directly as a guide for the plunging ball (14). Therefore, the ball (14) does not need to be fixed within a separate sleeve or bearing cylinder etc. to reciprocate inside the shaft (15).

[0018] Figure 2c shows an alternative embodiment where the cap (9’) is provided as a single part instead of two separate parts. That is, the cap (8) and the hat-shaped flange collar (9) of Figure 2a can also be provided in the form of a single part having the same functions. All other features remain the same. Thereby, the number of parts can be further reduced.

[0019] As shown in Fig. 2a, the housing (5) has an internal thread (6) for receiving a threaded ring (24). The threaded ring (24) has a protrusion (25) that is visible in Fig. 2c but not in Fig. 2a. The respective cross-sectional views of Figs. 2a and 2c are rotated approximately 90 degrees relative to each other. The cross-section of Fig. 2a is along line I-I shown in Fig. 1, and the cross-section of Fig. 2c is along line II-II shown in Fig. 1. As shown in Fig. 2c, the protrusion (25) extends radially inward and abuts from below against the claw (9a) of a hat-shaped flange collar (9) that extends radially outward, and can prevent the push button (7) from disengaging from the housing (5). The hat-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, a gap (9b) is formed below the cap (8), preferably to improve heat insulation. Alternatively, the gap (9b) can be filled with a material that is a low heat conductor.

[0020] As shown in Figs. 2a and 2c, the inner surface of the hat-shaped flange collar (9) slides on the outer surface of an outer ring (20) while being in contact with the outer ring (20) that constitutes a guide (12) for the movement of the push button (7). The protrusion (25) of the threaded ring (24) is disposed above the claw (9a) of the hat-shaped flange collar (9). The hat-shaped flange collar (9) does not contact the inner diameter surface of the threaded ring (24). The housing (5) has a gap (5a) directly above the threaded ring (24) and the protrusion (25), and this gap (5a) enables the cap (8; 9) to move upward or downward during the clamping / releasing operation. The cylindrical outer surface of the cap (8; 9') does not contact the inner surface of the housing (5) during its entire movement, thanks to a sufficient radial gap. Accordingly, the guide (12) functions as a guide contact surface for the up / down movement of the cap (8; 9). With the above configuration, the height and diameter of the head (4) can be further reduced.

Claims

1. a head (4); a rotatable hollow shaft (15) rotatably disposed inside the head (4); driving means for rotating the hollow shaft (15); a chuck (26) having an elastic arm (27) for releasably clamping a dental drill (2), wherein the chuck (26) is fixed within the hollow shaft (15) so as to rotate with the hollow shaft (15); a ball (14) axially movably disposed inside the rotatable hollow shaft (15) and in direct contact with the elastic arm (27) of the chuck (26), wherein the ball (14) partially protrudes through an opening (17) at the upper end of the hollow shaft (15), and the opening (17) is smaller than the size of the ball (14); a push button (7) disposed on the head (4) and configured to contact the partially protruding ball (14) when pushed by a user and move the ball (14) downward between the elastic arms (27) to deflect the elastic arms (27) radially outward to release the dental drill (2), wherein the elastic arms (27) bias the ball (14) toward the opening (17) inside the rotatable hollow shaft (15); biasing means for moving the push button (7) away from the ball (14), wherein the push button (7) does not contact the ball (14) when the push button (7) is released; A dental handpiece (1) comprising the above components.

2. The dental handpiece (1) according to claim 1, wherein the ball (14) is made of a ceramic material.

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