the present invention is directed to a system for more efficiently draining water from a waterbed mattress 10 , illustrated in fig1 as including a bladder 12 having a top wall 14 , bottom wall 16 and peripheral sidewalls 18 , 19 , 20 and 21 . in its actual formation , the bladder 12 may have corner openings that are closed and sealed by corner caps 22 , but for purposes of the present invention , the top surface of the corner cap shall be regarded as part of the top wall 14 and each sidewall of a corner cap shall be regarded as part of the sidewall to which it is attached . in fig1 and 2 , there is shown a filler opening 24 through top wall 14 . the filler opening is defined by a threaded generally tubular collar 26 which extends upwardly from a flexible skirt 28 having an outer periphery 30 thermowelded to top wall 14 . the filler opening 24 is adapted to receive a removable plug and threaded cap 32 for closing it when the mattress is not being filled or drained . flexible skirt 28 enables the filler opening collar 26 to be pulled upwardly to the raised drain position of fig1 and 2 , or depressed into the bladder below the surface of top wall 14 during normal usage of the mattress . fig2 shows a conventional water hose 34 having one end 36 threaded onto the inlet port 38 of water pump 40 and the opposite end 42 threaded onto an elongated generally conical drain insert 44 which is adapted to be press fit into filler opening collar 26 to form a fluid tight connection therebetween for filling and draining the waterbed mattress . the outlet port 46 of pump 40 may be connected by a second hose 48 to any suitable drain . the pump 40 may be any of the commercially available water pumps manufactured and sold for draining waterbeds . fig6 illustrates a vacuum relief valve $ o sealed within a generally l - shaped tube 52 having a mounting flange 54 at the open top end thereof . the tube 52 is preferably formed of a flexible plastic and the flange 54 is thermowelded to top wall 14 . the l - shaped tube 52 minimizes protrusion of the vacuum relief valve below the surface of top wall 14 . the vacuum relief valve 50 is press fit and / or adhesively bonded within tube 52 so that fluid flow through the tube is controlled by the vacuum relief valve 50 . vacuum relief valve 50 may be of any commercially available type which is biased to a closed position , but which opens in response to vacuum pressure exceeding a predetermined level . the simple cylindrical shape of vacuum relief valve 50 is preferred , but valves of other shapes may be appropriately sealed and mounted relative to a mattress wall for use according to the invention . likewise , whereas a conventional spring biased valve is preferred for purposes of durability and economy , any other type of vacuum relief valve could be substituted . fig3 illustrates an alternate embodiment wherein the vacuum relief valve 50 is sealed within a tubular nipple 56 surrounding an opening through the sidewall of drain insert 44 . the nipple $ 6 and vacuum relief valve 50 are situated longitudinally on the insert 44 so as not to interfere with either the connection of the insert to the hose 34 or with full insertion of the insert into the filler opening collar 26 . in another embodiment of the invention , it is contemplated that the vacuum relief valve could be incorporated into the water pump 40 at a position to enable air to be bled back through the hose and into the filler opening in response to vacuum pressure within the bladder exceeding a predetermined level . the vacuum relief valve 50 is preferably such that it enables air to be bled into the waterbed bladder 12 when the vacuum pressure within the bladder exceeds a predetermined level between 5 and 15 &# 34 ; of mercury vacuum pressure . in one embodiment , the predetermined level of vacuum pressure for the vacuum relief valve was four pounds ( 4 lbs .) per square inch vacuum pressure . these levels enable the pump to induce sufficient vacuum for collapsing any foam , fiber , springs , or other inserts within the mattress bladder for compact shipping and storage . vacuum pressure beyond that required for collapsing the contents of the bladder tends to arrest drainage of water from the mattress , typically at a stage where perhaps ten ( 10 ) gallons of water remains within the mattress and the combination mattress and remaining water weigh approximately one hundred ten pounds ( 110 lbs .). in operation , draining the filled waterbed mattress 10 is accomplished by connecting the one end 36 of water hose 34 to the inlet port 38 of water pump 40 and connecting the opposite end 42 of the hose to the filler opening 24 of mattress 10 . that connection is facilitated by the use of drain insert 44 which enables a simple press fit of the hose into the filler opening 24 . the second hose 48 is connected between the outlet port 46 of pump 40 and any suitable drain , such as a sink , toilet , bathtub , shower , or the like . upon activation of pump 40 , water is drawn from the mattress through filler opening 24 , hose 34 , pump 40 and hose 48 to the drain . the bladder 12 collapses as water is withdrawn from it . as the mattress becomes substantially emptied , the internal vacuum pressure increases . vacuum relief valve 50 prevents that internal pressure from prematurely reaching the extent that drainage is arrested . rather , vacuum relief valve 50 bleeds sufficient air back into the mattress to enable continued drainage to an extent where only approximately one or two gallons of water may be left in the mattress and the combination mattress and any remaining water weigh approximately fifty pounds ( 50 lbs .). this represents a a substantial improvement over the approximately one hundred ten pound ( 110 lb .) weight of a mattress drained without any bleeding of air into the mattress and a still very substantial improvement over the approximately seventy pound ( 70 lb .) weight of a mattress drained by a skilled operator who manually lets air back into the mattress without losing the prime on pump 40 . an important feature of the present invention is that it operates automatically without any input from the one emptying the waterbed mattress . in fact , the vacuum relief valve 50 will operate effectively even if the operator doesn &# 39 ; t know it is there and connects the mattress to the pump in the conventional manner for draining waterbeds . as the mattress is emptied and the internal vacuum pressure increases above the predetermined level of the vacuum relief valve , the valve bleeds air back into the bladder until the vacuum pressure is lowered to the predetermined level , enabling continued drainage without interruption and without any skill , attention or handling by the operator . fig7 and 8 illustrate a simplified embodiment of the invention wherein the vacuum relief valve comprises a combination cap 58 and orifice 60 formed in the top wall 62 of a tubular collar 64 which merges with a flexible skirt 66 having a peripheral edge 68 thermowelded to the bladder top wall 14 , much like the conventional filler opening 24 . cap 58 has internal threads 70 which engage external thread 72 on collar 64 for closing and sealing cap 58 onto the collar when the orifice is to be covered and closed . orifice 60 has a diameter , on the order of approximately 1 / 16 &# 34 ; in one embodiment , that is matched to the pumping action of the drain pump to allow air to bleed back into the bladder through the orifice when vacuum pressure is built up within the mattress by the water pump . if the orifice diameter is matched with the pump capacity , it is anticipated that a waterbed mattress equipped with the orifice illustrated in fig7 and 8 can be drained in the same manner described in connection with the previous embodiments including the spring biased vacuum relief valve . the cap 58 is effective to close and seal the orifice so as to prevent fluid communication therethrough between the ambient atmosphere and bladder during normal usage of the mattress . whereas the invention has been shown and described in connection with preferred embodiments thereof , it is understood that many modifications , additions and substitutions may be made which are within the intended broad scope of the appended claims .
a waterbed draining system utilizes a vacuum relief valve operatively associated with a waterbed mattress bladder , or alternatively with the drain hose or water pump , to automatically provide air flow into the bladder upon the vacuum pressure within the bladder exceeding a predetermined level . the vacuum relief valve automatically bleeds air back into the bladder as needed to effect more complete drainage than was heretofore possible with conventional systems and without any need for operator assistance .