Headrest for medical treatment chair

Claim 1

A chair for human dental or medical treatment and having an improved adjustable headrest support, which comprises: a. a chair, said chair having a frame, b. a seat, mounted on said frame; c. a headrest; d. a bearing race rotatably mounted to a first transverse supporting shaft, e. a flat curved strip member, one end of said strip member being attached to said headrest, said strip member defining part of a circle, and means mounting said strip member for circular movement around the center of the circle, the other end of said strip member being attached to said bearing race, whereby movement of said strip member corresponds to the natural movement of a human neck, f. said mounting means comprising at least one pair of opposed cylindrical guide rollers on said frame, said rollers straddling said strip member and extending contiguously across the surface of said strip member substantially transverse to the linear longitudinal axis of said strip member, so as to guide the motion of said strip member along said longitudinal axis, g. a hydraulic mechanism, said hydraulic mechanism comprising a fluid pressure cylinder pivotally linked at one end to said frame by a second transverse supporting shaft, said cylinder containing a piston plunger having a piston head, the outer end of said piston plunger being pivotally attached to the other end of said strip member by said first transverse supporting shaft and said bearing race, wherein said piston plunger moves in a horizontal path causing said curved strip member to move in a circular path in conjunction with said bearing race, resulting in the different positioning of said headrest without placing of a human body in a strained position, h. means to pass a hydraulic fluid into said cylinder, so that said piston head and piston plunger may be displaced in said cylinder, and said headrest may be positioned in said way; i. a spring, said spring extending between said first shaft and said second shaft, to produce substantially smooth backdown of said piston plunger and piston head when fluid pressure in said cylinder is reduced.