Patent GB-190004279-A (GB)
Title: Improvements in Dental Chairs.
Inventor: SIBLEY GIDEON
Filed: 1900-03-06
Granted: 1900-06-02
Abstract: 4279. Sibley, G. March 6. Chairs, dental. The seat frame screws at 6a to the upper end of a telescopic guide in two parts 5, 6, the outer of which slides in the cylinder a, which is flanged at 3 and which can rotate on the pedestal 1. A wedge-shaped shoe B working in a housing on the cylinder a is pressed by a spring a<3>, adjustable in strength by set-screws a<2>, into a corresponding groove b in the part 5. A similar shoe A carried by the part 5 works in a groove in the part 6. The spring shoes hold the parts steady, but yield to the weight of the chair or to pressure produced by the pump. The chair is raised by a telescopic plunger 10, 11, 12. The outer part 10 is screwed into the base 9 of the cylinder a, and has at the top a head 14 accommodating two gasket rings which are secured by an intermediate L-shaped ring 25 and a screwed cover. The innermost part 12 is packed at its lower end by the gasket 24 in a similar manner, and bears at its upper end on the screw 6<a>. A fixed rod 28 projects into the part 12 ; its enlarged end fits the upper end of the tube 12, and produces a cushioning effect when the seat has nearly reached its lowest position. On depressing a pedal on the shaft 17<a>, against the action of a spring 17<b>, the pump plunger 15<a> descends and forces oil through the passage 20 and valve 21 into the tube 12, which is thereby raised ; when it reaches the top of the tube 11, it carries this with it. The guide 6 first rises, and then, by its shoulder d acting on the pin d<1>, carries up the part 5. When the pump plunger rises, by the action of the spring 17<b> the valve 14 opens and the valve 21 closes. By means of a release valve 31 acted on by a pedal and by a spring 33 the oil may be allowed to return to the reservoir while the chair descends. The arm-rest supports are removable and adjustable ; at their lower ends they have gapped bearings 69, which may be engaged with shafts 70, having two flats, and they also have hoods 67 fitting over slotted segments 68. By means of spring pins 71 engaging the holes 72 the angle of the arm-rests can be adjusted, whilst by turning the arm-rests down till the gaps 74 register with the flats on the shaft 70 they can be removed altogether. The back support is pivoted to lugs on the seat frame. A pair of rods 77, also pivoted to the seat frame, pass through guides 75 on the back. Between the rods 77 are a pair of wedge-shaped blocks 78, one of which is grooved at 78<b>. Three rollers 82, two of which bear on one block 78 and one on the other, run loosely on an axle carried on lugs on a nut 79. By turning a bolt 80, the rollers cause the blocks 78 to be wedged apart and so clamp the rods 77, and consequently the back support, firmly in place. The back support has a grooved guide-way in which slides a bar to which the back pad is pivoted. This bar is split at the lower end, and is clamped in its guide by a roller arrangement similar to the one above described. The rollers are carried on a rod 90 pressed upwards by a spring. By means of a handle or lever 95, the rod 90 can be depressed and the split bar unclamped. The head-rest pad plates 121 are pivoted at 119, 120 to pairs of arms 114, 115 pivoted on a yoke 111 having a stem 110 with a ball at its lower end. By means of a screw 112<a> and plate 113 the joints of the bars 114, 115 can be clamped in place ; a pin 117 and segmental groove on the yoke 111 limits the motion of the arms 114, 115. The ball 109 on the stem 110 is held between the ends of an outer hollow arm 106 and an inner arm 105. The arm 105 has cut-away inclines 105<b> and a disc 104 which fits in a recess in the hollow arm 100. A shoe 107 with inclined edges 107<a> is held in the hollow arm 106 by a screw. Rollers 105<c> are interposed between the inclined faces 105<b>, 107<a>. A bolt 108, with a head at each end, passes loosely through the arms 106, 105, 100 and through the inner arm 101. The inner arm 101 has two teats bearing on the washer 102<a>. A headed pin 98 with an internal thread engages a screw 97. By turning a handle 94 the screw 97 is rotated and the pin 98 drawn down, and by this one motion the ball 109 and the arms 106, 100 are all simultaneously clamped or wedged in their adjusted positions.