Safety screen for swimming pools

Claim 1

A SAFETY APPARATUS FOR A SWIMMING POOL HAVING AN ELONGATE INCLINED BOTTOM WALL AND UPWARDLY EXTENDING PERIPHERAL WALLS AND WITH ONE END OF THE POOL BEING DEEPER THAN ITS OTHER END, SAID SAFETY APPARATUS COMPRISING A SCREEN ADAPTED TO CONFORM TO THE CONFIGURATION OF THE POOL BOTTOM, MEANS FOR MOVING THE SCREEN TO AND BETWEEN A SUBMERGED POSITION ADJACENT THE BOTTOM WALL AND AN ELEVATED POSITION PROXIMATE THE TOP OF SAID POOL, SAID MEANS COMPRISING A VERTICALLY EXTENDING HYDRAULIC CYLINDER POSITIONED UNDER AND CENTRALLY OF THE POOL, A PISTON IN SAID CYLINDER, A SHAFT EXTENDING VERTICALLY FROM SAID PISTON TO SAID SCREEN, A PIVOT MOUNT SECURED UPON THE UPPER END OF THE SHAFT, A PIN FOR PIVOTALLY ATTACHING THE UNDERSIDE OF SAID SCREEN TO SAID MOUNT ALONG A PIVOTAL AXIS EXTENDING TRANSVERSELY OF THE SCREEN WHEREBY THE SCREEN IS SWINGABLE ON SAID PIVOTAL AXIS TO A POSITION PARALLELING THE SLANT OF SAID BOTTOM WALL WHEN THE SCREEN IS IN ITS LOWERED POSITION AND THE SCREEN IS SWINGABLE ON SAID PIVOTAL AXIS TO A POSITION EXTENDING HORIZONTALLY WHEN THE POOL IS IN ITS ELEVATED POSITION, MEANS ON THE SCREEN ENGAGEABLE WITH SAID MOUNT FOR PREVENTING TURNING OF THE SCREEN ON SAID AXIS BEYOND SAID HORIZONTAL POSITION WITH RESPECT TO SAID SLANT POSITION AND VALVE CONTROLLED FLUID SUPPLY SYSTEM CONNECTED TO SAID CYLINDER FOR ADMITTING FLUID PRESSURE TO SAID CYLINDER THEREBY TO DRIVE THE PISTON IN THE CYLINDER.