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CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application is related to and claims priority to U.S. patent application Ser. No. 60/231,910, filed Sep. 11, 2000, entitled MOVEABLE SWIMMING POOL FLOOR, the entirety of which is incorporated herein by reference. 
     
    
     
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
         [0002]    n/a  
         FIELD OF THE INVENTION  
         [0003]    This invention relates to an apparatus for swimming pools, namely, a vertically moveable swimming pool floor.  
         BACKGROUND OF THE INVENTION  
         [0004]    Swimming pools present serious dangers to small children, the elderly, the disabled, and others who do not have the ability to swim. Because most pools are configured to accommodate both diving and swimming, the depth of a pool must be adequate to safely allow users to dive into the pool. Yet, even very shallow water can be deadly to those incapable of swimming.  
           [0005]    Pools often provide a shallow, wading depth at one end, safe enough for non-swimmers, and provide a deeper swimming and diving depth at the opposite end. This requires greater time, effort and expense in laying out and constructing the swimming pool floor, as a sloped floor is inherently more difficult to construct than a flat one.  
           [0006]    Nevertheless, the swimming pool presents a serious drowning hazard to small children or the disabled who may accidentally fall into the pool. Another hazard exists when the pool itself is emptied of water for cleaning or maintenance, presenting a dangerous structural cavity or pit.  
           [0007]    It is desirable therefore, to provide a device which may effectively vary the depth of a swimming pool, without requiring the construction of a curved, sloped, or otherwise complex swimming pool shell, and which may effectively minimize the depth of a pool when such pool is emptied of water.  
           [0008]    Furthermore, the planform area of a swimming pool may significantly decrease the usable area of a yard or other space where the pool is located. For personal and home applications, this decrease in usable planform area can be significant. Conventional devices and methods for covering a swimming pool generally use flexible thin covers such as tarpaulins. Unless a sufficiently rigid device is used to cover the pool, the planform area of the swimming pool is not effectively usable for any other purpose than as a swimming pool.  
           [0009]    It is desirable therefore to provide a device which may render the planform area of a swimming pool usable for a purpose other than swimming or diving, where the pool is covered by a rigid medium suitable for walking, sitting, or playing thereupon.  
         SUMMARY OF THE INVENTION  
         [0010]    A vertically moveable swimming pool floor apparatus includes a rigid planar platform configured to fit the panform area of a swimming pool, and a plurality of hydraulically powered hoists coupled to the platform to raise and lower the platform. A number of depth indicators are attached to the platform. A control system is coupled to the hoists to monitor and control the movement and position of the platform. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:  
         [0012]    [0012]FIG. 1 is a diagram of the moveable swimming pool floor apparatus system;  
         [0013]    [0013]FIG. 2 is a perspective view of the apparatus inside a swimming pool;  
         [0014]    [0014]FIGS. 3A, 3B, and  3 C are cross-sectional views of the apparatus with the platform at varying depths; and  
         [0015]    [0015]FIG. 4 is a cutaway perspective view of a hydraulic hoist assembly.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    [0016]FIG. 1 illustrates the moveable swimming pool floor apparatus as integrated with a power and control system, labeled generally as  10 . The moveable swimming pool floor apparatus and system includes a platform  100 , a plurality of hoists or hoist assemblies  105 , a hydraulic power unit  110 , a control unit  115 , a user panel  120 , a depth sensor  125 , communications media  130 , and a number of hydraulic power lines  135 .  
         [0017]    The platform  100  is coupled to a number of hoists  105 . In FIG. 1, four such hoists  105  are positioned around a rectangular platform  100 . The platform  100  may be of any shape suitable to conform to the particular planform area of the swimming pool into which the apparatus is to be installed. The hoists  105  are hydraulically powered rotary hoists, configured to generate torque to power a strap or other mechanical pulling medium (not shown) coupled to the platform. The platform  100  is configured to be moved by the action of the hoists  105  in a direction into and out of the plane of platform  100 .  
         [0018]    The hoists  105  are coupled via power lines  135  to the hydraulic power unit  110 . The power unit  110  is any suitable hydraulic or pneumatic power assembly, capable of providing sufficient hydraulic power through lines  135  to meet the loads presented.  
         [0019]    The hydraulic power unit  110  is in turn coupled via communications medium  130  to the control unit  115 , which may also be coupled to a depth sensor  125  via another, separate communications medium. The communications media  130  are any device capable of sending or receiving data in electronic form, either analog or digital, wired or wireless, suitable to allow control system  115  to send and receive electronic commands and responses from the power unit  110  or depth sensor  125 .  
         [0020]    The hoist assemblies  105  also comprise an automatic braking system (not shown) configured to detect undesired movements of the platform  100 , or individual hoists  105 , such that the actuation of one or all of the hoists  105 , and hence the movement of platform  100 , is arrested in response to the detection of an undesired movement characteristic of the platform  100 . This undesired movement characteristic may be predetermined based on any number of criteria, such as excessive movement speed of the platform  100  when it is being raised or lowered by the hoists  105 , or the detection of an obstruction or hazard around the apparatus.  
         [0021]    The user panel  120  contains a number of switches, gauges, and indicators to allow a user to independently control and monitor each or all of the hoists  105 , as well as to monitor the relative depth of the platform  100  as measured and communicated by depth sensor  125 . The user panel  120  is connected to the control unit  115 , which receives commands and input from the user panel  120  to relay to the power unit  110 . The control unit has mechanical, electrical, or electromechanical components capable of controlling (i) the starting and stopping of each of the individual hoists  105 ; (ii) the speed at which each of the individual hoists  105  are actuated, such that the platform  100  is movable at a nominal speed of about one foot per minute; (iii) additional air-powered shut-off devices located in the apparatus, capable of arresting the action of an individual hoist  105 , platform  100 , or both, when the platform is positioned at a predetermined point, such as near the very top of its range of motion near the top or coping of the swimming pool, or near the very bottom of its range of motion near the floor of the swimming pool.  
         [0022]    [0022]FIG. 2 illustrates the apparatus  10  as installed in a swimming pool of characteristic size and shape. In addition to the platform  100 , FIG. 2 shows the layout and positioning of a number of elements incorporated into the apparatus  10 , namely, a number of depth indicators  140 , each including an elongate member or pole  145  topped with a warning sign  150  and coupled to each of the four corners of the platform  100 , and a number of hoist assembly covers  155 , each covering a hydraulic hoist  105  (not shown). The hoists  105  are positioned opposite each other at two lateral lines across the shorter side of the platform  100 . Coping  160  circumscribes the platform and pool cavity (not shown).  
         [0023]    The platform  100  is shown in FIG. 2 at its uppermost position, wherein it may effectively function as a swimming pool cover and may be usable floor space for a number of applications. The platform is moved up in the direction U and down in the direction L, as shown in FIG. 2. The platform is constructed of lightweight materials having a high modulus of elasticity, having a normal compressive strength that is sufficient to withstand the load of several people as well as commonly used objects such as tables, lawn chairs, barbeques, and the like. The platform  100  may be constructed of any materials suitable and robust enough to meet the foregoing criteria, such as PVC, structural aluminum, stainless steel, carbon fiber, or other rigid, workable material.  
         [0024]    The depth indicators  140  are constructed with at least one elongate pole  145 , having a number of markings affixed longitudinally thereon to show linear dimension in the directions U and L. A sign  150  having a suitable warning message is fixed to the top of each pole  145 . The poles  145  are detachably fixed to the platform  100  in the corners as shown, and may be rigid or semi-rigid. As the platform  100  is actuated up or down in the directions U or L, respectively, the depth indicators  140  move with the platform  100  in such direction. An observer may ascertain the depth at which the platform  100  is lowered into the pool cavity relative to a reference level by viewing the position of such reference level next to the dimensional markings affixed on any of the poles  140 . The reference level may be the pool coping  160 , or any other reference height chosen by the user so generally correspond with the maximum height of the water level in the swimming pool.  
         [0025]    In the alternative, the pole  145  may be a telescoping pole, such that the signs  150  are configured to be indicator gauges, coupled to a depth sensor disposed inside of the poles  145 . The signs  150  are then fixed at a reference height relative to the pool, and do not move as the platform  100  is moved. Instead, as the platform  100  is lowered into the pool, the poles  145  telescope downwards with the platform  100  and relay a depth indication to the signs  150 , which are then observed to ascertain pool depth.  
         [0026]    [0026]FIGS. 3A, 3B, and  3 C show the platform  100  in its uppermost, intermediate, and lowermost stages, respectively, as it descends into a swimming pool cavity  200 . At its upper most stage, the platform  100  is at a depth D 1  above the swimming pool floor  210 , as shown in FIG. 3A. At such a position, a nominal clearance C exists between the platform  100  surface and the very top of the coping  160 . FIG. 3A shows the platform  100  at its uppermost position when the device is used as a pool cover or usable floor space, and no water is in the pool cavity  200 .  
         [0027]    As the platform is lowered in the direction L, it reaches an intermediate position D 2  above the floor  210 , as shown in FIG. 3C. Here the water level  220  is shown at a level corresponding to a height D 1  above the floor  210 , such that the effective depth of water (and hence the usable swimming pool) is: (D 1 -D 2 ). The vertical position of platform  100  is continuously variable by the action of the hoists  105  and control unit  115  as indicated in FIG. 1, such that the effective swimming pool depth (D 1 -D 2 ) is continuously variable.  
         [0028]    When the platform  100  is lowered the maximum amount into cavity  200 , the top surface of platform  100  rests at a small clearance D 3  above the floor  210  (including the thickness of the platform  100  itself), such that the effective swimming pool depth is at its maximum amount: (D 1 -D 3 ).  
         [0029]    A flexible, resilient seal (not shown), made of a material such as rubber, is disposed around the platform  100 , in the plane of the platform  100 , and mates the edges of the platform  100  with the sides  230  of pool cavity  220 . The platform  100  itself is also constructed to have a number of fluid-permeable joints and seals (not shown), such that water can easily travel through such joints and seals to allow the platform  100  to be moved without encountering excessive compressive, expansive, or drag resistance from the water  220  as the platform  100  moves therethrough.  
         [0030]    Not shown in FIGS. 3A, 3B, and  3 C are the hydraulically actuated shutoff mechanisms positioned near the top and bottom of the pool cavity  200 , such that each mechanism is activated when the platform  100  is in its uppermost position, as in FIG. 3A, and its lowermost position, as in FIG. 3C. In such cases, when the platform  100  has been moved to such a position, the action of the hoists  105 , and hence the platform  100 , is halted for safety and efficiency considerations.  
         [0031]    [0031]FIG. 4 shows a cut-away view of a hoist assembly  105 , with the hoist assembly cover  155  cut-away to show detail. The hoist assembly  105  includes an actuation unit  310 , coupled to the hydraulic power lines  135 , and engaged to a rotary spindle  320 , which houses and wraps a strap  330 , connected at its distal end to the platform  100 . The entire hoist assembly  105  and cover  155  are fixedly attached to the coping  160 , wherein the strap  330  is positioned to run vertically very near to the edge of the swimming pool sides  230 . The hoist assembly  105  is hydraulically powered via power lines  135 , such that when the actuator unit  310  engages the spindle to rotate in the direction R shown in FIG. 4, the platform  100 , moves up in the direction U. The mere force of gravity, coupled with a possible resistive drag from the actuation of the hoist  105  and spindle  320  in the direction opposite R, allows the platform  100  to be lowered in the direction L at a safe, controlled speed.  
         [0032]    It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the invention, which is limited only by the following claims.

Summary:
A vertically moveable swimming pool floor apparatus includes a rigid planar platform configured to fit the planform area of a swimming pool, and a plurality of hydraulically powered hoists coupled to the platform to raise and lower the platform. The hoists are controlled by a control system operated by the user. The hoists controllably actuate the platform into and out of a swimming pool cavity, such that effective depth of the swimming pool is variable in a continuous range. The platform is equipped with depth indicators to allow users to observe the effective depth of the pool.