A cover assembly for a swimming pool and which can be raised and lowered, the cover assembly comprising a frame which is relatively rigid, a covering material which is supported by the frame, and a plurality of extendable and retractable leg members which are associated with the frame such that extension of the leg member causes the frame to be raised and lowering of the leg member causes the frame to be lowered, at least one leg member being powered to enable the leg member to the extended upon demand.

FIELD OF THE INVENTION 
       [0001]    The present invention is directed to a cover assembly which can be used to cover in ground swimming pools, above ground swimming pools, spas, but also sand pits and other open areas, and where the cover assembly can be lifted in a simple manner to provide shade and lowered in a simple manner to cover the swimming pool etc. 
       BACKGROUND OF THE INVENTION  
       [0002]    Numerous safety devices for swimming pools are known. Pool covers have been used in the past to prevent unsupervised use of the pool or for merely covering the pool to prevent objects such as leaves and sticks from falling into the pool. 
         [0003]    Some of the more recent types of pool covers or pool safety devices include a heat retaining swimming pool cover which is floatable on pool water in a swimming pool. The cover has an upper plastic film facing toward the atmosphere, a lower plastic film for facing toward the pool water, and sufficient spaced apart air pockets configured into the lower film for containing air such that the cover is floatable on the pool water. The upper and lower films have sealed land areas between the air pockets to seal the upper and lower films to each other. The lower film may contain an infrared absorbent material but the amount is insufficient to prevent sunlight from substantially penetrating the lower film and passing into the pool water. 
         [0004]    Another type of protective device used in the past is a rescue apparatus having a safety pool bottom substrate which has a periphery made of a buoyant material. The device also has at least one non-peripheral portion which is buoyant. The buoyant material is urged into a fixed position at the bottom of the pool by a retaining member. A lifting mechanism raises and lowers the safety pool bottom substrate. The lifting mechanism is coupled to a detection signal device for detecting the presence of a person in the pool, particularly if the person is underwater for an extended period of time. The electronic signal device has a trigger engaging the lifting mechanism to release the buoyant material from a fixed position at the bottom of the pool to a further position at an upper area above the water level of the pool. 
         [0005]    Yet another pool cover is used for covering an above ground swimming pool during periods of non-seasonal use. The cover device includes a plurality of pool cover brackets arranged about and on the railing of the swimming pool with each pool cover bracket including a hook for engaging the inner lip of the railing and a socket member which projects inwardly toward the swimming pool in order to receive the ends of pool cover supporting beams. Each supporting beam will extend across and above the swimming pool for attachment to oppositely arranged pairs of brackets thereby forming a cambered framework that supports a pool cover above and around the swimming pool. 
         [0006]    Still another cover device is an automatic swimming pool cover system. The system has a cover and a cover drive for extending and retracting the cover over the pool. The safety system also has at least one sensor for detecting the presence of a heat generating body in the pool and for generating a signal in response thereto. A controller is provided to receive the signal and activates a safety protocol in response to the sensor detecting the presence of a heat generating body in the pool. 
         [0007]    All of the above devices have their own particular disadvantages. Most of the devices are not only complex but may also be large. The necessity of having the devices positioned close to the pool means that the use and enjoyment of the pool and particularly the surround of the pool are diminished due to the presence of large devices close to the pool. 
         [0008]    The devices, particularly those that are adapted to extend and retract with respect to the pool are complex, and are therefore expensive. They require specialist knowledge to install and maintain and repairs may also be expensive. 
         [0009]    Simple pool covers that comprise a plastic sheet that floats on the surface of the water are effective in preventing evaporation and are also effective in reducing chlorine levels. However, these simple pool covers are extremely dangerous because if a child inadvertently steps on the pool cover, the child can easily slip underneath the pool cover and can drown without being seen. Also, a relatively large roller assembly is usually required to extend the pool cover or to roll up the pool cover when not required. These pool covers are also not particularly satisfactory in preventing debris from falling into the pool as the debris sits on top of the pool cover and as the pool cover is rolled up, the debris can fall into the pool. The pool covers do not have a long life as the cover sits directly on the chlorinated water and this will cause deterioration of the pool cover in a relatively short period. Thus, if a pool cover of this type is used, it is usually necessary to reduce the level of chlorine or, if a chlorinator is used, to reduce the run time of the chlorinator to avoid loss of warranty. 
         [0010]    The inventor of the present apparatus has created an easy to use, low-cost alternative to the complex, expensive prior art devices. The apparatus of the present invention also removes the cumbersome and sometimes intrusive equipment from the pool surrounds and provides a much less intrusive means for extending and retracting a pool cover allowing more complete use and enjoyment of a swimming pool and its surrounds. 
       BRIEF SUMMARY OF THE INVENTION  
       [0011]    The present invention is directed to a safety device for a swimming pool, which may at least partially overcome the abovementioned disadvantages or provide the consumer with a useful or commercial choice. 
         [0012]    In one form, the invention resides in a cover assembly which can be raised and lowered, the cover assembly comprising a frame which is relatively rigid, a covering material which is supported by the frame, and a plurality of extendable and retractable leg members which are associated with the frame such that extension of the leg member causes the frame to be raised and lowering of the leg member causes the frame to be lowered, at least one leg member being powered to enable the leg member to the extended upon demand. 
         [0013]    Typically, the powered leg member will comprise some form of ram that will typically comprise an outer cylindrical member that is fixed and an inner cylindrical member that can extend or retract relative to the outer cylindrical member. 
         [0014]    It is envisaged that more than one leg member will be powered and in a particular embodiment, each leg member is powered. 
         [0015]    It is preferred that the leg member is powered using pressurised water. The water may comprise swimming pool water, mains water, tank water or water from another source. 
         [0016]    In another form, the invention resides in a safety device for a swimming pool comprising a cover for closing the swimming pool, the cover mounted on a frame movable between a closed condition wherein access to said swimming pool is prevented, and a raised condition, said frame comprising a plurality of legs wherein said legs each have a ram portion disposed within a cylinder mounted adjacent the swimming pool, each said cylinder having an inlet and an outlet for a hydraulic fluid whereby on filling the cylinder with hydraulic fluid, the frame is moved to the raised condition and on draining said cylinder, the frame is lowered to the closed condition. 
         [0017]    In use, the cover for closing the swimming pool is adapted to move between a raised position wherein the cover is positioned above and spaced from the surface of the pool to allow swimmers to use the pool, and a closed position where the cover is positioned to prevent access to the swimming pool. The movement between the raised position and the closed position may generally be actuated at a user's convenience by providing a switch, button, or other actuation device associated with the plurality of legs. Preferably the actuator mechanism may be lockable to prevent movement of the cover. 
         [0018]    The hydraulic fluid may be any applicable fluid including water supplied from the garden or household tap. 
         [0019]    According to the invention, the swimming pool in relation to which the cover is used may be of any shape. In particular, the swimming pool may have a periphery and the periphery of the pool may be linear, arcuate or a combination of both. The swimming pool may be of an in-ground or above-ground type. The fluid contained in the swimming pool may also be of any type, for example, the swimming pool may be a salt water pool or it may be chlorinated. 
         [0020]    The cover for closing the swimming pool may preferably be at least partially rigid. Alternatively, the cover may comprise a fabric or the like stretched over or supported by, a support network. According to a particularly preferred embodiment, the support network may comprise a frame or support means. The cover may preferably be heavy or large enough to resist manual lifting of the cover, but also light enough to be raised by the legs. 
         [0021]    In some circumstances, it is envisaged that the cover may comprise somewhat rigid panel members which are preferably lightweight. Thus, these panel members may be made of relatively rigid plastic, metal and the like. It is envisaged that the panel members may be clear or translucent or completely opaque. 
         [0022]    There may be circumstances where the cover may comprise areas or zones of flexible material (e.g. shade cloth) and areas or zones of relatively rigid panel members. 
         [0023]    The frame or support means may preferably be securely attached to each of the legs. The frame or support means may suitably be manufactured using light but strong materials for example, of metal construction and in particular tubing of either the round or box type, or purlins and the like. The frame may preferably be shaped respectively to the swimming pool. The frame may preferably comprise a number of frame members, the frame members extending in different directions to maintain the rigidity of the cover. The frame members may preferably be permanently attached to each other for example, by welding, rivets, connecting plates and the like. 
         [0024]    The frame, and therefore the cover, may preferably have a shaped periphery. In a particularly preferred embodiment, the periphery of the frame and/or cover may preferably coincide with the shape of the periphery of the swimming pool. The shaped periphery of the frame may preferably be provided by round aluminium tubing. The fabric cover may preferably be attached relative to this shaped periphery. 
         [0025]    The periphery of the frame may preferably be weighted to ensure or enhance the closing of the pool and preventing entry to the pool. 
         [0026]    The frame may preferably comprise a plurality of main frame members extending lengthwise over the longer axis of the pool and a plurality of frame members extending substantially perpendicularly to the lengthwise frame members. All the frame members may be of a similar construction, comprising a lower member and an upper member spaced apart by one or more rung members extending between the upper and lower members. One or more than bracing members may extend from each main frame member toward the shaped periphery at an angle to provide support to the cover. The overall construction of the frame may preferably be of a dome shape, wherein the lower portion of the frame maybe substantially planar and the upper portion of the frame may have a contoured shape similar to that of a dome. 
         [0027]    The fabric used for the cover may preferably be at least partially resistant to ultraviolet light rays. The fabric used may preferably be a shade cloth, in which the fibers may be manufactured from a plastic material and woven to form a sheet. One or more sheets or layers of fabric may be used in the formation of the cover. 
         [0028]    There may preferably be a plurality of legs associated with the cover. The legs may suitably be spaced about the periphery of the swimming pool to allow the efficient raising and lowering of the cover. Each of the legs may preferably be substantially vertical in orientation allowing the swimming pool cover to remain in position substantially above the swimming pool when being raised and lowered. The legs may preferably be elongate members, and in particular be between approximately 2 m and 3 m in length when in their closed position. 
         [0029]    Each leg may preferably comprise a cylinder and at least one coaxial and concentric inner member extending at least partially into the cylinder. Each of the legs has a ram portion, and the ram portion may suitably be the inner member. The cylinder and the inner member may each suitably have an upper and a lower end when in the use position. The ram portion of each of the legs may be associated with the lower end of the inner member. 
         [0030]    The ram portion of each of the legs may comprise one or more annular members attached to the inner member and adapted to seal between the inner member and the cylinder. For example, the annular members may be a washer or bush type seal of a semi-rigid, but resilient material such as rubber or the like. 
         [0031]    In a particularly preferred embodiment, the ram portion of each of the legs may comprise at least two collar members sealed or attached to the lower end of the inner member. The two collar members may preferably be and upper and a lower collar member, the collar members attached to the inner member in a spaced apart relationship. Each of the collar members may preferably have one or more annular members extending therefrom to form a seal between the inner member and the cylinder. The lower collar member may preferably have more than one annular sealing members extending therefrom. 
         [0032]    Each leg may also comprise one or more guide members adapted to retain the inner member in a position wherein the inner member is substantially centered in the cylinder during the raising and lowering of the inner member. The guide members may preferably be spaced over the length of the inner member. 
         [0033]    Each inner member may preferably be manufactured from polyvinylchloride (PVC). Each inner member may suitably be cylindrical, but need not be. For instance, the inner member may be substantially square in cross-section and still function according to the invention within the cylinder, as long as the seal between the inner member and the cylinder is maintained. 
         [0034]    Each inner member may preferably be hollow with an upper end associated with the cover or the frame for the cover and a lower end which is sealed. The upper end of each in a member may preferably be adapted to attach to the frame or support means for the cover. Each inner member may alternatively comprise more than one telescopic member. 
         [0035]    Each inner member may generally be at least partially filled with a settable or cementitious material such as concrete or the like. The settable material may additionally comprise a reinforcing bar to add weight and/or stability to the leg, to bias the leg into the collapsed condition. 
         [0036]    It is particularly preferred that the outer surface of the inner member be smooth. 
         [0037]    When in use, it is preferable that the inner member is not raised so that the upper of the two collar members leaves the cylinder as this may interrupt the seal, and cause the legs to collapse. There will typically be stop means provided to prevent raising the inner member unduly. 
         [0038]    The cylinder may also preferably be manufactured from polyvinylchloride (PVC). Each cylinder may suitably be elongate. 
         [0039]    Preferably the cylinder may be sealed at a lower end. The seal may preferably be substantially fluid tight to prevent fluid leaking from the cylinder. The cylinder may preferably have an opening at the upper end through which the at least one inner member is raised and lowered. The upper end of the cylinder may be provided with an outwardly extending finishing collar to provide a flush fit with the surface into which the cylinder is fixed. 
         [0040]    Each cylinder may suitably be provided with a smooth bore, to enhance the seal created between the inner member and the cylinder. 
         [0041]    Each cylinder is provided with at least one inlet and at least one outlet and the designation as an inlet or outlet may be dependant upon the direction of flow into our out of the cylinder respectively. A single opening may therefore function as both an inlet and an outlet by reversing the flow direction. Preferably the inlet is positioned below the lower collar and seal on the inner member. In this position, the inlet may also suitably function as the outlet from the cylinder when the flow direction is reversed or the cylinder is allowed to drain. The inlet for each cylinder may suitably be associated with a pressurized fluid flow. 
         [0042]    Preferably the outlet may be positioned above or below the collars and seals on the inner member. The outlet may suitably be a drain-type outlet, allowing the release or drainage of the fluid disposed within the cylinder due to gravity alone. 
         [0043]    The inlet and the outlet of the cylinder may be associated with pump means to move fluid into or out of the cylinder. The pump means may be of any type or configuration. The outlet for each cylinder may provide for the reuse of the fluid drained from the cylinder during lowering of the leg, or alternatively may allow the fluid to drain away, for example into foliage or plants. When a pump is used, there may be an inlet/outlet at the upper end of the cylinder and an inlet/outlet at a lower portion of the cylinder. 
         [0044]    The safety device may preferably further comprise an equalization means for equalizing the pressure of the fluid distribution to each of the legs upon raising the cover. The equalization means may preferably comprise a fluid storage tank and one or more pump means. The fluid storage tank may suitably be associated with a fluid feed to ensure that the fluid tank contains fluid at all times. The fluid feed may be a garden hose or tap. 
         [0045]    In a particularly preferred embodiment, the equalization means may suitably comprise a fluid storage tank, the fluid storage tank having at least two solenoids associated with each leg. According to this preferred embodiment, one of the solenoids may be an inlet solenoid associated with the inlet to the cylinder, and the other solenoid may be an outlet solenoid associated with the outlet from the cylinder. Fluid piping may be provided to fluidly connect the fluid storage tank and the solenoids with the inlet and outlet for each leg. 
         [0046]    There may preferably be an additional solenoid associated with the fluid storage tank and the fluid feed adapted for operation as a safety valve to shut off the fluid feed to the tank and/or prevent the tank from overfilling. 
         [0047]    The equalization means may preferably create an equal distribution of pressurized fluid for each of the legs when the cover is being raised. The force distributed to each of the legs when the cover is being raised is preferably governed by the inlet solenoid for each leg in relation to the weight borne by respective legs. This configuration provides equalization such that if the legs bear different loads, the solenoids and fluid storage tank will provide the legs with suitable pressurized fluids to raise the cover in a substantially level configuration. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0048]    Two embodiments of the invention will be described With reference to the following drawings, in which: 
           [0049]      FIG. 1  is an elevation view of the safety device according to an aspect of the invention in the raised condition. 
           [0050]      FIG. 2  is a reverse elevation view of the safety device according to an aspect of the invention in a partially raised condition. 
           [0051]      FIG. 3  is an elevation view of the safety device according to an aspect of the invention in the closed condition. 
           [0052]      FIG. 4  is a view of a leg according to an aspect of the invention. 
           [0053]      FIG. 5  is a schematic sectional view of a lower portion of a leg according to an embodiment of the present invention. 
           [0054]      FIG. 6 . Illustrates another version of the device. 
           [0055]      FIG. 7 . Illustrates the  FIG. 6  version of the device from a different angle. 
       
    
    
     DETAILED DESCRIPTION  
       [0056]    According to the present invention, a safety device for a swimming pool, or other open area, is provided. 
         [0057]    The safety device as seen in  FIG. 1 to 3  includes a cover  10  for a swimming pool  11 . The cover  10  is mounted on a frame  12  which is movable vertically between a closed condition wherein access to the swimming pool  11  is prevented, and a raised condition. The frame comprises a plurality of water powered lifting and lowering legs  13 , each of the legs  13  adapted to move the cover between the raised and closed condition. 
         [0058]    In use, the cover is moved between a raised position wherein the cover  10  is positioned above and spaced from the surface of the pool  11  to allow swimmers to use the pool  11  ( FIG. 1 ), and a closed position where the cover  10  is positioned to prevent access to the swimming pool  11  ( FIG. 3 ). The movement between the raised position and the closed position will be actuated at a user's convenience by providing a switch, button, or other actuation device associated with the plurality of legs  13 . 
         [0059]    The swimming pool  11  illustrated has an edge  14 , which may be straight, curved or a combination of both. Although the swimming pool  11  illustrated is an in-ground type, the invention applies equally to an above-ground pool, a spa, a sand pit and the like 
         [0060]    The cover  10  for closing the swimming pool  11  comprises a fabric  15  (e.g. shadecloth) over the frame  12 . The cover  10  and frame is heavy or large enough to resist manual lifting of the cover ( e.g. by children), but is light enough to be raised by the legs  13 . 
         [0061]    The frame  12  comprises an assembly of frame members to provide a rigid supporting frame. In the particular embodiment, the frame members comprise a pair of spaced apart main support beams  17 , and a number of spaced apart cross beams  19 . A peripheral frame edge  18  is provided which can be made of metal, plastic or any suitable material. The length of the main support beams  17  should be sufficient to extend over the length of the pool and therefore it is envisaged that a typical length will be between 5-12 m. The main support beams may be formed with a “truss” type configuration which is quite well-known. 
         [0062]    The cross beams  19  should be of a length sufficient to extend over the width of the pool and it is therefore envisaged that a typical length of the cross beams will be between 3-6 m. The cross beams may also be formed with a “truss” type configuration which is quite well-known. 
         [0063]    The main support beams  17  and the cross beams  19  will typically be made of metal such as galvanised steel, although other metals such as aluminium may also be used. Under some circumstances, these beams may also be made from materials other than metal such as timber (particularly LVL-laminated veneer number), laminated plastic beams and the like. However, it is considered that galvanised metal may be the most suitable. The beams may be made of the box section, or may comprise purlins, or may be solid, tubular and the like depending inter alia on the type of material from which to beam is made. 
         [0064]    The frame is preferably shaped to allow water to drain from the cover  10 . Therefore, the uppermost part of the cross beams  19  may have a downwardly sloping portion to provide drainage. 
         [0065]    The fabric  15  of the cover  10  can be attached to the frame in any suitable manner. In a particular embodiment, the fabric will be attached to the edge  18  of the frame and is preferably somewhat stretched to provide a good taut cover. In the particular embodiment, the fabric may comprise a “shade cloth” type material which typically comprises a woven aspect material. Of course, the fabric may comprise other types of materials and may be porous or watertight. 
         [0066]    The design of the frame is such that leaves/debris that fall on the frame can be brushed off or blown off, and because the edge  18  of the frame extends past the edge  14  of the pool, the debris will not fall into the pool. If the fabric comprises a shade cloth type material, any rain will pass through the fabric to fill the pool. If the fabric comprises a watertight material, any rain will pass on to the pool surrounds. In a variation to the embodiments, it is envisaged that some form of collection means (e.g. a small gutter) might be provided to collect the water to a rainwater tank or something similar if the fabric comprises a watertight material. 
         [0067]    The frame can be raised above the pool or lowered by the water powered plurality of legs  13  associated with the frame  12  for the cover  10 . The legs are spaced about the periphery  14  of the swimming pool  11  to allow the efficient raising and lowering of the cover  10 . Each of the legs  13  are substantially vertical allowing the swimming pool cover  10  to remain in position substantially above the swimming pool  11  when being raised and lowered. 
         [0068]    The number of legs  13  will depend on the size of the pool, and other conditions such as wind loading etc. In the particular embodiment, the swimming pool illustrated can be covered using four legs  13 . 
         [0069]    As illustrated in  FIG. 5 , each leg comprises an outer cylinder member  23  and an inner member  24  extending at least partially into the cylinder  23 . The outer cylinder member  23  can be made of cylindrical tubular plastic material and will have a typical length of between 2-4 m and a diameter of between 50-200 mm. The outer cylinder member  23  is sunk into the pool surround area such that only an upper part  43  (see  FIG. 4 ) is flush or substantially flush with the pool surround area. A finishing collar  29  (see  FIG. 2 ) is fitted about the upper part  43 . The collar  29  can also function to ensure that the inner member remains centred as it comes out of or retracts into the outer member. Collar  29  can also function to prevent the inner member from extending too far out of the outer member. In the particular embodiment, the internal diameter of the outer member is 101 mm to give the lifting capacity at relatively low water pressure. 
         [0070]    The inner member  24  can be seen as the “ram” or “piston” and comprises a hollow cylindrical plastic tube having a length of between 2-4 m and a diameter which is sufficient to allow the inner member to slide into or out of the outer member  23 . The lower end of the inner member  24  is closed (see  FIG. 5 ) and the lower end can contain a weighted material  40  such as sand, cement, grout etc to provide the cover with sufficient weight to prevent the cover lifting unnecessarily during windy or breezy conditions. 
         [0071]    To allow inner member  24  to function as a ram or piston, a pair of spaced apart collar members are attached about the inner member  24  these comprising an upper collar member  26  and a lower collar member  27  (see  FIG. 5 ). These collar members are separated by 400 mm. To provide a good sealing between the inner member  24  and the outer member  23 , a sealing member  28  (typically an “O” ring) is fitted to the outside of upper collar member  26  (collar member  26  may be provided with a peripheral groove to accommodate the sealing member)  28 . A pair of sealing members  28  is fitted to lower collar member  27  to provide good sealing. 
         [0072]    The upper collar member  26  can also function as a “stop” to prevent excessive extension of the inner member from the outer member. For instance, the outer collar member  26  can contact the collar  29  to prevent further movement. 
         [0073]    An inlet  30 ,  31  (see  FIG. 5 ) is provided into outer member  23  and below the lower collar member  27 . The inlet can be attached to a pipe or something similar. Water can be pumped through the pipe and through the inlet and pressurised water will force in member  24  to rise out of the outer member  23  and therefore to lift the cover  10 . Loss of water pressure will cause the cover to move back to the lowered position. 
         [0074]    The inner member  24  and the outer member  23  can be made from PVC. Of course, other materials they also be used such as metal. 
         [0075]    The inner member  24  is provided with a bracket/cap  41  (see  FIG. 3 ) on the top of the inner member  24 . Thus, when the cover  10  is in the lowered position (see  FIG. 3 ), the bracket  41  is substantially flush with the pool paving. Conversely, when the cover is in the raised position, bracket  41  is raised above the pool surrounds. 
         [0076]    Bracket  41  is provided with a supporting arm  42  (see  FIG. 3 ). Supporting arm  42  is attached to the edge  18  and/or a cross beam  19  thereby operatively connecting the frame to the water powered leg members  13 . 
         [0077]    The inlet  30  in the bottom of outer member  23  can also function as the outlet  31 . 
         [0078]    A water pump (not illustrated) is provided to supply pressurised water to the water powered leg members. The pressurised water may comprise pool water, or mains water, tank water or water from any other source. The water pump may comprise the pool pump or a different pump. 
         [0079]    The outlet  31  is a drain-type outlet, allowing the release of the fluid disposed within the cylinder  23  due to gravity alone. 
         [0080]    The water which operates the water powered leg members can be reused and recycled. 
         [0081]    The size of the inlet pipe that supplies water to each leg member is preferably relatively narrow, or has a narrowed portion (typically no greater than 13 mm internal diameter). This provides a safety arrangement in the event that a pipe is fractured, the pool cover will fall slowly as opposed to suddenly because water will not be able to pass out of each leg member very quickly due to the relatively narrow pipe. 
         [0082]    All the pipes and fittings and parts of the water powered leg members are rated to twice the pressure at which the unit will be operated. All components are to be compatible with the national standards. 
         [0083]    The main pump that pressurises the system may comprise a stainless steel 240 V domestic pump and all other electrics for solenoids are 24 V and operated by a button (on a control panel) that must be held down to raise or lower the unit to ensure that a person is there at all times for safety reasons. 
         [0084]    A filter or strainer is positioned on the inlet side (or pickup side) of the pump to eliminate any foreign matter from entering into the valves on the electric solenoids. The pickup pipe with the strainer is the largest in diameter to give the volume for supply. 
         [0085]    In use, once the water is pressurised by the pump, it flows through one electric solenoid which is activated by a button on a control panel/device. The pressurised water than flows through a manifold with four outlets for each of the water operated leg members. Non-return valves (4) are provided to prevent backpressure which may occur due to one leg member having more weight than the others (which may occur because of the shape of the cover or the positioning of the leg members). The pressurised water than flows through four gate valves which are set to equalise the pressure and volume to each leg member according to the amount of weight on each leg member. At this point, the water flows through a T piece which houses a 24 V solenoid, one for each of the four lines/pipes , each of which are attached to the narrow diameter (13 mm) pipe and then into the lower end of each leg member. 
         [0086]    The cover can be lowered by activating the 4 24 V solenoids which opens the pressurised lines and lets the water flow back to the swimming pool through the 4 low pressure valves (one for each exhaust line) so as to control the lowering of the canopy so that it keeps the canopy level. These valves may be preset. 
         [0087]    The use of high-grade ultraviolet resistance shade cloth is preferred as the cover. The shade cloth is porous material so there is very little down draft or up draft. The material is very strong and long lasting and is strong enough to support an 80 kg person without tearing. 
         [0088]    The cover apparatus can be used domestically with home swimming pools, or at schools, etc. The cover apparatus need not be limited to swimming pools and may also be used for sand pits (for instance to reduce animal droppings, glass, etc) and supplying shade when in the raised position. 
         [0089]    A control panel is preferably provided which can operate the solenoids/pump etc. It is envisaged that the control panel can be locked using a key or something similar. Thus, when the cover is in the down position, and the key is removed from the control panel, the cover cannot be raised. 
         [0090]    The apparatus has a major safety aspect because when in the lowered position, it is almost impossible for a child etc to fall into the pool water. Even if the person falls onto the cover, the cover will not tear. The cover can also reduce evaporation from the pool when in the lowered position, and can also reduce build up of algae, and reduce the chlorine requirements. Leaves and debris falling into the swimming pool is reduced almost to zero and if the cover material is a poor a shade cloth material, water (e.g. rainwater) can still pass through the cover to fill the pool. The cover does not sit on the pool water. 
         [0091]    The apparatus has very few moving parts and uses low pressure water to power the leg members. 
         [0092]    The edge  18  of the cover may be made from relatively soft cushioning material such that when the cover is in the lowered position ( FIG. 3 , and also  FIG. 6  and  FIG. 7 ), the cushioning material can form a soft seal against the pool coping to prevent leaves/debris from blowing into the pool. 
         [0093]      FIGS. 6-7  illustrates another in embodiment of the invention, which is similar to the first embodiment described above. In this particular embodiment, a pair of leg members  50  is provided spaced from one edge of the pool and the cover  51  (which may be similar to that described above) is somewhat cantilevered from each leg member. An advantage of this embodiment is that there are few leg members spaced about the pool. 
         [0094]    In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted by those skilled in the art. 
         [0095]    Throughout the specification and the claims (if present), unless the context requires otherwise, the term “comprise”, or variations such as “comprises” or “comprising”, will be understood to apply the inclusion of the stated integer or group of integers but not the exclusion of any other integer or group of integers. 
         [0096]    Throughout the specification and claims (if present), unless the context requires otherwise, the term “substantially” or “about” will be understood to not be limited to the value for the range qualified by the terms. 
         [0097]    Any embodiment of the invention is meant to be illustrative only and is not meant to be limiting to the invention. Therefore, it should be appreciated that various other changes and modifications can be made to any embodiment described without departing from the spirit and scope of the invention.