Shock damping device for flush valve mechanism

A flush valve mechanism for controlling the flushing action of water through the water outlet of a flush cistern, comprising, in combination:

• a) a water outlet valve liftable off said water outlet to effect said flushing action, said water outlet valve having a valve disk for sealing a valve seat of the water outlet and an upwardly extending valve stem, and further having an effectively negative overall buoyancy when the cistern is at least partially full;
• b) buoyant means associated with said water valve for exerting a maintaining force on said water outlet valve at the completion of the lifting thereof and to hold it open while the cistern is emptying and until the completion of a predetermined flushing action;
• and
• c) a shock damping device, comprising an inverted cup-shaped member and a body member, said body member being configured to freely move with the inner surface of said cup, said cup-shaped member and said body member defining therebetween a changeable volume of substantially surrounded space and having restricted openings for the passage of water into and out of said space, one of said members being provided with means for attachment to said water outlet valve, and the remaining member being provided with means for attachment to a stationary component of said cistern, and being located so that said body member may reciprocate inside said cup-shaped member, whereby, upon the emptying of the cistern to a predetermined level of water below said buoyant means and the consequent completion of the exertion of said maintaining force on said water outlet valve by said buoyant means, impact shock of the reseating of said valve disk on said valve seat is reduced by the resistance of the water forced through said restricted openings as a result of the final descent of said valve attached member towards said cistern attached member, wherein said body member is a plate-and-stem member, wherein the plate of said plate-and-stem member is provided with at least one aperture, and further being provided with a cover plate axially mounted to afford reciprocal movement on top of said plate-and-stem member, said cover plate sealing said aperture when in contact with said plate and allowing substantially free passage for fluid when in space relationship to said plate.