Patent GB-190000998-A (GB)
Title: Improvements in Dental Chairs.
Inventor: RITTER FRANK
Filed: 1900-01-16
Granted: 1900-12-01
Abstract: 998. Ritter, F. Jan. 16. Chairs, dental. A pedestal 2, containing a pump 4, oil reservoir 3, and plunger tube 5, is capable of rotation in a base 1. The plunger carrying the chair seat cross-frame 16<1> can be raised by working the pump by a treadle, and can be lowered by opening the valve 7, against the action of a spring 8. When the plunger reaches nearly to the top of its stroke, it hits against a turned-over part of a rod 10 connected to the valve 7, and thus automatically opens the valve and makes further pumping ineffective. The extent of the automatic opening is controlled by a set-screw 11<1>. A modified construction for automatically opening the valve, and also means for controlling the extent of opening, is shown and described. A pair of arms 15, some distance apart and connected by screws 19, project down from the chair seat crossframe 16', and each has two pairs of rollers 17 running on guides 13 on arms 12 rigid with the pedestal 2. The chair seat is pivoted to the frame 16<1>; its rocking can be adjusted by a rack 46 and pawl 47. The chair seat frame consists of two parts 20, 21, between which is a wooden filling-frame 20<111>; a child's foot-rest 30 can be slid in and out of the part 20. The part 21 is carried on a stem 22, and, when raised by means of a slotted lever 26 running on a fixed roller 27, forms a child's seat. The arms are carried on stems adjustable in sockets on the seat frame. The main back frame is pivoted to lugs 36 ; it has a sliding extension 38, to which is pivoted the upholstered part of the back adjusted by the rack and pawl 39. The sliding extension 38 is clamped to the back frame by an eccentric lever 40, which also simultaneously operates the spring rod or pawl 42, which engages the notched quadrant 44 and so holds the back at the required angle. The headrest pad 50 is pivoted to a split tube 52, which passes through a hole in a casing 58, 56, which contains thrust blocks and a ball screwed to the back extension 38 ; by means of a screw 60 the tube 52 and the ball-and-socket joint can be simultaneously clamped. By means of a nut 51 and a screwed rod, passing through the split tube 52 and connected to a wedge 53<11>, the head-rest pad pivot joint can be clamped in an adjusted position. A modified form of a head-rest support is shown in Fig. 16. In a trough-sectioned guide-block 62 fixed to the back slides a split guide-bar 63, having ribs working in grooves 65. By lifting a handle 74, the part 74<1> thereof presses down, against the action of a spring 77, a ferrule 76 and also a non-rotatable plug 72, in which is a cam-groove engaging a roller on a rod 69 ; this motion of the plug slightly rotates the rod, which is connected to the head 67 of a bolt having flats bearing against adjustable stops 68 on the split bar 63 ; the rotation of the bolt clamps the bar 63 in the guide-block 62. Rotation of the handle 74 acts through the bolt 79, wedges 84, 83, bolt 87, and slightly-rocking lever 89 in such a manner as to clamp the parts of the head pad ball-and-socket joint and the parts or arms 88, 82 rigidly together simultaneously. Fig. 25 shows a modified form for connecting the arms to the seat frame. The arm is carried on a stem 123, which passes through a split clamp 120 which is connected by a bolt 124 to a lug on the chair seat frame 118. By means of an eccentric 125, the stem 123 can be clamped at the same time that the clamp itself is clamped to the lug. By loosening the lever 125, the arm can be raised or lowered, or adjusted inwards or outwards, or turned completely down out of the way.