SILLCOCK INCORPORATING AN ANTI-SIPHON AND BACKFLOW PREVENTER

摘要

Disclosed is an improved sillcock valving mechanism that employs a valving element carried on a piston that is slidably mounted on a valve stem and a valve seat engageable by the valving element. A handle is operated to close the sillcock and to open the sillcock. Normal line pressure holds the valving mechanism open, when so permitted by the position of the valve stem, but when the line pressure drops below a predetermined value a spring that applies continuous biasing pressure on the piston forces the valving element into sealing engagement with the valve seat (irrespective of the position of the valve stem) to prevent backflow through the sillcock and into the supply line. A second valving mechanism controls communication between the first passageway and a second passageway which extends within the valve stem and opens to atmosphere. The second valving mechanism opens to preclude siphoning in response to that closure of the first valving mechanism effected by the pressure of the fluid supply line dropping below a predetermined value. Because the piston is rotatable with respect to the valve stem, relative rotation between the valving element and the valve seat is precluded with an attendant reduction in deleterious wear to the valving element.