Dental handpieces

Claim 2

A dental handpiece for mounting a dental tool and driving the same in oscillatory partial rotation about its axis, said handpiece comprising a handle (12) incorporating a drive shaft (20), a head (14) incorporating a tool holder (30) mounted for rotation about an axis (Y) perpendicular to the axis (X) of the drive shaft, and a drive pin (26) extending from the drive shaft, at a location laterally offset from the shaft axis, into an axially extending slot (40) in the tool holder so as to drive the latter in oscillatory partial rotation upon rotation of the drive shaft, characterised in that the face of the tool holder in which the said slot (40) is defined is convex in the direction of the length of the slot.

Claim 3

A dental handpiece as claimed in claim 1, wherein the convexity of the said slot (40) is such that-the said drive pin extends into the slot to substantially the same extent at all positions of rotation of the drive shaft.

Claim 4

A dental handpiece as claimed in claim 1 or 2, wherein the said face (32) of the tool holder in which the said slot (40) is defined is part-spherical with its geometric centre on the axis (Y) of the tool holder at the point where that axis and the axis (X) of the drive shaft intersect.

Claim 5

A dental handpiece as claimed in claim 3, wherein the said drive pin (26) is located adjacent the perimeter of a circular end face (24) of the drive shaft face, said end face being of concave part-spherical shape concentric with, and closely adjacent, the said part-spherical face (32) of the tool holder.

Claim 6

A dental handpiece as claimed in claim 4, wherein the said drive pin (26) is circular cylindrical and has its axis passing through the intersection (0) of the drive shaft and tool holder axes.

Claim 7

A dental handpiece as claimed in any preceding claim, wherein the floor (41) of the said slot (40) is outwardly concave.

Claim 8

A dental handpiece as claimed in any of the preceding claims, wherein the means for securing a dental tool in the said tool holder comprises a pair of slots (50, 52) in the said head (14), a pair of bores (54, 56) in the head, one such bore (56) forming an extension of a tool-receiving bore (38) in the tool holder and the other being screw-threaded (55), a locking plate (60) slidably mounted in said slots (50, 52) and formed with a pair of openings (62, 64) alignable with said bores (54, 56), a screw (58) engageable in said threaded bore (55) to secure the locking plate in position, the dental tool being held against withdrawal by a terminal screw (66) thereof received in the unthreaded bore (56) and having its head engaging said locking plate.