GB1492080A - Retraction device - Google Patents

Abstract

1492080 Supporting dental handpieces SIEMENS AG 9 Sept 1975 [13 Sept 1974] 37161/75 Heading A5R [Also in Division F2] A retractable linkage 2 for a supply line 3 of a dental handpiece 4 comprises a pair of links 8, 9 pivotally interconnected at 12, with the link 9 being pivoted at 10 on an elongate support member 11 carried on a dental fixture 1, the supply line 3 running from the handpiece 4 over a roller 6 which is freely rotatably journalled on an axis 7 on the free end of the arm 8. A torsion spring 13 at the pivot 12 biases the arm 8 to rotate anticlockwise towards the fully retracted position shown in full. A tension spring 14 is connected between the support 11 and the arm 9 and has an over-centre action which urges the arm 9 to rotate clockwise or anticlockwise when the arm 9 is inclined to the right or left respectively of the central i.e. vertical position of the arms 8, 9, shown chain-dotted. Thus both springs 13, 14 jointly serve to fully retract the mechanism once the arms 8, 9, pass the central position as the unit retracts towards the right; whilst, in use, i.e. with the linkage fully extended to the left for operation of the dental handpiece 4, the over-centre spring 14 now opposes and largely neutralises the bias of the torsion spring 13 such that there is little or no spring load acting on the supply line 3 of the dental handpiece 4. Additionally the spring 14. at all times, exerts a downward bias on the roller 6 to maintain it in contact with the support member 11. The supply line 3 leads back from the roller 6 through an aperture 16 in the member 11 to a supply arrangement 17 which makes available air, water and/or electric current for supplying the handpiece 4. and rests on the flat surface 18 of the support 11 or directly on the fixture 1, the handpiece 4, when not in use, resting on a cradle 5. Additional arms with associated spring means (not shown) could be used to increase the maximum extension length of the supply line.