Retraction mechanism for dental units and the like

Claim 1

A take up system for the utility lines of a dental unit or the like comprising: (a) a storage chamber for a utility line, said chamber defining an air cylinder wherein the utility line extends into said chamber through a front end wall thereof; (b) a piston within said chamber and operatively connected to said utility line such that movement of the utility line out of said chamber moves said piston towards said front end wall and retraction of the utility line is accomplished by pressurizing said chamber to move said piston away from said front end wall; (c) said chamber having a vent adjacent said front end wall to permit the free exhaust of air from said chamber as withdrawal of the utility line moves said piston towards said front end wall; (d) a pressure operated valve for sealing said vent including a valve housing fixed to the exterior of a side wall of said chamber about said vent, said housing having a plurality of elongated exhaust ports disposed about its periphery, the total area of said ports being at least substantially equal to the cross sectional area of said vent; (e) a flexible diaphragm in said valve housing, said diaphragm being normally spaced from said vent so as to define a free air passage between said vent and exhaust ports; and (f) means for introducing fluid under pressure simultaneously into said chamber and valve housing for moving said diaphragm against said side wall to a sealing position over said vent and for pressurizing said chamber to move said piston away from said front end wall.