GB724471A - Counterbalancing mechanism - Google Patents

Abstract

724,471. Springs &c. RITTER CO., Inc. April 17, 1953 [Oct. 13, 1952], No. 10609/53. Class 108 (3). Weight-counterbalancing mechanism for an object 12 (as shown, a dentist's lamp), comprises a pair of parallel motion links, one A of which is a tubular member which encloses the other link 64, members 21, 46 to which the links are pivoted, and a compression spring 61 exerting pressure between the links and enclosed by the tubular member A. The member A is formed by two channel-sectioned members 51, 52 (Fig. 8) one, 52, of which is detachable to permit inspection and lubrication of the mechanism. The member 21 is pivoted about a vertical axis 19 to a fixed support 18, and is pivoted to the member A at 27. The member 46 carries the lamp 12 pivotally at 43 and is pivoted to the member A at 48. The link 64 comprises a tube having angularly offset end-portions 66, and is pivoted at 32 and 49 respectively, to the members 21 and 46. The spring 61 acts between a sleeve 59, adjustably threaded in a tubular member 56 rigid with the channelsectioned member 51, and a sleeve 63 slidable within the member 56. The sleeve 63 bears on the base of a member 69 which is of hollow truncated conical shape. The upper edge of the member 69 has notches which engage transversely projecting pins 68 rigid with the link 64. The base of the member 69 is not planar, but is formed with diametrically-opposed projections 72 which bear on the sleeve 63. The spring 61 thus acts between the member A and the link 64, tending to raise the lamp 12 about the pivot 27. The layout of the pivots 27, 48 and 32, 49 is such that the mechanism provides a constant counterbalancing force whatever the position of the lamp 12. The tubular member A may alternatively be of cylindrical crosssection.