An actuator and an assembly utilizing two or more actuators for vertically actuating a cover for a spa. In the lowered position the cover protects the spa and in the elevated position the cover acts as a roof over the spa. The actuator is either a rack and pinion assisted by a cable and pulley or a chain and a plurality of sprockets assisted by a cable and pulley which are connected to lift member which are generally shrouded by telescoping tubes to cover the actuators or to act as lift members themselves. The system can be further enhanced using a gas spring to assist in lifting the cover and reduce the load of the cover weight off the motor which is used to actuate the actuators.

CROSS REFERENCE TO RELATED APPLICATION 
   This application is a continuation in part of U.S. application Ser. No. 11/162,557 filed on Sep. 14, 2005, which is hereby incorporated by reference. 


   FIELD OF THE INVENTION 
   Embodiments of the invention relate to spa covers and more particularly to spa covers which are moveable vertically between a position directly atop the spa and a position elevated above the spa to act as a roof structure during spa use. 
   BACKGROUND OF THE INVENTION 
   It is known to cover hot tubs or spas to prevent contamination due to environmental debris, such as leaves, pollens and the like, to prevent excessive evaporation when the spa is not in use and to act as a safety measure to prevent animals, small children and the like from falling into the water when unsupervised. 
   Most conventional spa covers are fabric covered foam structures which rest atop the spa when the spa is not in use and which are removed, either by sliding off the tub or by folding at a middle and lifting to a position away from the top of the tub, such by a support frame wherein the cover is suspended vertically in the folded position adjacent a side of the tub. The fabric covers may be susceptible to chemical vapors, such as chlorine, are prone to tearing at seams exposing the foam layers to the elements and to the steam and vapors from the tub and are generally susceptible to normal wear and tear necessitating multiple replacements during the life of the average spa. 
   It is known to provide fixed structures built around the hot tub to provide an element of protection for use during inclement weather or to prevent excessive exposure to the sun. Most often the structure is independent of the cover and remains in a fixed position around the tub, the roof portion being fixed above the spa to permit use of the spa. While these structures may meet the needs of the user by providing a rigid or semi rigid roof structure, they add additional expense by requiring a spa cover to be used as well. 
   Conventional spa covers are not designed to handle the weight of a person or persons resting on the cover. As the spa covers are typically flat however, individuals may be encourage to walk or otherwise provide undue weight on the cover, such as when shoveling snow from a deck in which the spa is recessed, which results in damage not only to the cover but to the spa itself. 
   Others have attempted to provide domed rigid or semi-rigid cover structures which, like the conventional cover, reside atop the spa when in use and which are pivoted or slid laterally away from the spa when the spa is to be used. 
   It is known to provide a vertically actuable cover to a swimming pool or a spa. U.S. Pat. No. 3,566,420 to Peterson et al teaches hydraulic actuators used to raise and lower a cover from a swimming pool and U.S. Pat. No. 6,718,566 to Wilson teaches a plurality of telescoping and threaded sections which are used to raise and lower a cover over a spa. 
   There remains interest in the industry to find reliable, relatively simple and inexpensive lift systems for raising and lowering roof structures over spas, which can act to replace a conventional spa cover when in a lowered, spa engaging position and which act as a roof when in the raised position. 
   SUMMARY OF THE INVENTION 
   A cover assembly for a structure, such as a spa, is vertically actuated between a lowered position atop the spa to an elevated position above the spa where the cover acts as a roof over the spa. The actuation of the cover is accomplished using actuation members which support the cover and which employ unique lifting means, such as a rack and pinion system or a tension member and rotatable guides, powered by a motor. The lifting means are housed within telescoping tubular members which act to provide an aesthetic covering for the lifting means and which may or may not form a part of the lifting means structure. 
   In a broad aspect therefore, a vertically-actuable cover assembly for a structure comprises: a cover; and two or more actuation members for supporting the cover, the two or more actuation members being actuable between a lowered position atop the structure to an elevated position above the structure so as to act as a roof thereover, wherein the two or more actuation members further comprise: a first lift structure mounted on a base fixed relative to the structure; a second lift structure operatively connected to the first lift structure and actuable to be raised and lowered for raising and lowering the cover; a third upper lift structure operatively connected to the second lift structure; a rotatable guide supported adjacent a top end of the second lift structure; a cable connected between the first structure and extending about the rotatable guide for connection to a bottom end of the third lift structure; and drive means for driving the second lift structure to be lifted and lowered relative to the first lift structure, wherein the rotatable guide is lifted and lowered by the second lift structure so as to passively cause the cable to lift the upper lift structure relative to the second lift structure. 
   The cover is supported on a plurality of actuation members, typically one at each corner of the cover, having one or more motors. In a preferred embodiment, a plurality of electric motors are connected through a single circuit so as to co-ordinate the actuation members to support and vertically actuate the cover. 
   Preferably, stops are formed at top and bottom ends of the telescoping tubular members to limit the upward travel of the telescoping members within each other to prevent the telescoping members from becoming disconnected during elevation of the cover and to lift the intermediate member with the upper tubular member. 
   In one embodiment, a rack and pinion lifting system is used wherein the first lift structure is a pinion or worm gear mounted on a rotatable shaft, the second lift structure is a rack and the third lift structure is the upper telescoping member which supports the cover. An electric motor drives the shaft to rotate the worm gear which in turn engages the rack to be lifted and lowered along with the structures connected thereto. A cable is connected between the rack and an upper telescoping member, which forms part of the lifting structure and upon which the cover is supported, for assisting in raising and lowering cover. The cable is guided by a pulley which is connected at a top end of the rack. As the rack is moved so is the pulley at the top of the rack which causes the cable to passively lift or lower the upper telescoping member to raise and lower the cover. Limit switches act to stop the motor when the cover has reached the elevated or lowered position. 
   In an alternate embodiment, a tension cable and rotatable guide system is used wherein the first lift structure is a housing mounted on a base for telescopically housing a linearly extending member and the drive means is a tension member which is driven about a plurality of rotatable guides which are positioned at the top and bottom of the housing and the top and bottom of the second lift structure. One of the rotatable guides, preferably the guide at the bottom of the housing, is driven by a motor. The third lift structure is a linearly extending member telescopically housed in the second lift structure and to which the cover is connected 
   In a preferred embodiment the tension member is a chain or belt and the rotatable guide are sprockets. Further a biasing means, such as a hydraulic cylinder is provide to assist in lifting the second lift structure. The pulley over which the cable extends is rotatably connected by a bracket adjacent the top of the second lift structure and further to a hydraulic arm of the hydraulic cylinder. The cylinder arm is driven upwards as the chain lifts the second lift structure thus reducing the load on the motor. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a spa cover according to one embodiment, shown in a raised position; 
       FIG. 2  is a perspective view according to  FIG. 1  shown in a lowered position; 
       FIG. 3   a  is a longitudinal sectional side view of an actuation mechanism for raising and lowering the spa cover, shown in the lowered position; 
       FIG. 3   b  is a longitudinal sectional side view according to  FIG. 3   a , shown in the raised position; 
       FIG. 4   a  is a longitudinal sectional front view according to  FIG. 3   a , in the lowered position; 
       FIG. 4   b  is a longitudinal sectional front view according to  FIG. 3   a , in the raised position; 
       FIG. 5  is a detailed view of an embodiment of the actuation mechanism, more particularly a worm gear and rack; 
       FIG. 6  is a perspective view of the worm gear and rack of  FIG. 5  shown in the lowered position and illustrating an alternate embodiment for connection of the upper tubular member 
       FIG. 7  is a schematic sectional view of an embodiment of an actuation mechanism having two telescoping tubular members, the upper tubular member being connected to the rack; 
       FIG. 8  is a schematic section view of an embodiment of the invention according to  FIGS. 3   a - 4   b  having three telescoping tubular members, the upper tubular member being connected passively to the rack through a cable and pulley; 
       FIG. 9  is a schematic of a circuit for independently operating of a plurality of gear motors for rotationally powering worm gears; 
       FIG. 10  is a schematic of a circuit for operating the plurality of gear motors according to  FIG. 9 , in series; 
       FIG. 11  is a schematic of another embodiment of the actuation mechanism, more particularly a tension member and rotational guide system, shown in a raised position, the telescoping tubular members having been removed for clarity; 
       FIG. 12  is a schematic of the embodiment according to  FIG. 11 , in a lowered position; 
       FIG. 13  is a partial perspective view of the embodiment of  FIG. 11  illustrating the telescoping arrangement of the lift structures in the actuation means; and 
       FIG. 14  is an end view of the actuation means according to  FIG. 11 , the tension member removed for clarity. 
   


   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Having reference to  FIGS. 1 and 2 , a cover apparatus  1  for a structure  2 , such hot tub or spa, comprises a cover  3  supported on actuation members  4 , typically positioned at each corner of the spa  2 . The actuation members  4  elevate the cover  3  from a lowered position, wherein the cover  3  rests atop or adjacent a top edge  5  of the spa  2 , to a raised position, wherein the cover  3  is supported over the spa  2  to act as a roof. 
   As shown in  FIGS. 3   a ,  3   b  and  11 , the actuation members  4  comprise a first lift structure  30  mounted on a base  13  fixed relative to the structure  2 . A second lift structure  19  is operatively connected to the first lift structure  30  and is actuable to be raised and lowered relative thereto for raising and lowering the cover  3  supported thereon. A third upper lift structure  15  is operatively connected to the second lift structure  19  and actuable to be raised and lowered relative thereto. A rotatable guide, such as a pulley  23 , is supported adjacent a top end of the second lift structure  19  and a first flexible tension member such as a cable  16  is connected between the first structure  30  or the base  13  and extending about the rotatable guide  23  for connection to a lower end  21  of the third lift structure  15 . Drive means  40 , powered by a motor  31 , is provided for driving the second lift structure  19  to be lifted and lowered relative to the first lift structure  30  and in doing so lifts the rotatable guide  23  to passively cause the cable  16  to lift the upper lift structure  15  relative to the second lift structure  19 . 
   As shown in  FIGS. 3   a - 6  and in one embodiment, the actuation members  4  comprise a rack and pinion system  10  for raising and lowering the cover  3 . Each actuation member  4  is housed within two or more telescoping tubular members  11 . The tubular members  11  may be, but are not limited to being circular, rectangular or square in cross-section. Further, the tubular members can form a part or all of the lift structures  30 ,  19   15  or shroud same. Preferably, each actuation member  4  is housed within three telescoping tubular members  11 , a lower tubular member  12  secured to the base  13 , an intermediate tubular member  14  and an upper tubular member  15  upon which the cover  3  is supported. The rack and pinion system  10  is connected thereto for active actuation of at least the second lift structure  19  and with it the intermediate tubular member  14 . The upper tubular member acts is the third lift structure  15  and is connected thereto through cable  16  which is anchored, at a first end  17 , to the base  13  or to an upper end  18  ( FIG. 6 ) of a rack  19  of the rack and pinion system  10  for movement therewith and, at a second end  20 , to a lower end  21  of the upper tubular member  15 . The cable  16  is guided at an upper end  22  of the rack  19  by the pulley  23 . 
   With reference to  FIGS. 7 and 8 , preferably, a stop  24   a  is formed at an upper end  25  of the lower tubular member  12  for engaging a stop  24   b  at a lower end  26  of the intermediate tubular member  14  for retaining the intermediate telescoping tubular member  14  in the lower telescoping tubular member  12  and to prevent the intermediate tubular member  14  from being pulled out of the lower tubular member  12 , when the cover apparatus  1  is actuated to the raised position. Similarly, a stop  24   c  is formed at an upper end  28  of the intermediate member  14  for engaging a stop  24   d  at the lower end  21  of the upper tubular member  15  for retaining the upper tubular member  15  within the intermediate tubular member  14  during actuation to the elevated position. 
   Best seen in  FIGS. 6-8 , the rack and pinion system  10  comprises a worm gear  30  which is rotatably connected to the drive means  40 , such as an electric gear motor  31 , by a rod  32 . The worm gear  30  is rotated to raise and lower the rack  19 . For an actuation member  4  having two telescoping tubular members  11  ( FIG. 7 ), rack  19  directly raises upper telescoping member  15 . In the case of an actuation member  4  having three telescoping tubular members  11  ( FIG. 8 ), the rack  19  raises and lowers the upper telescoping member  15  via the cable  16 , the upper tubular member  15  raising and lowering the intermediate tubular member  14  through engagement of the stops  24   c,    24   d . As shown in  FIG. 6 , the cable  16  is connected at the second end  20  to a ring  33  which is used for mounting the cable  16  inside the lower end  21  of the upper tubular member  15 . 
   Preferably, each actuation member  4  is powered by an electric gear motor  31 . Most preferably, all of the gear motors  31   a ,  31   b ,  31   c ,  31   d  are connected through a single circuit so that when the circuit is activated, all of the actuation members  4  are caused to move at the same time. Limit switches  40  are positioned on the rack and pinion system  10  to stop the gear motor  31  when the cover  3  has reached the lowered or the raised position. As shown in  FIGS. 9 and 10 , the gear motor limit switches  40  may be independent ( FIG. 9 ) or in series ( FIG. 10 ). 
   In an alternate embodiment as shown in  FIGS. 11-14 , the first lift structure  30  is an upwardly linearly extending lower housing which is connected to the base  13 . Best seen in  FIG. 14 , the second lift structure  19  is an intermediate linearly extending member which is housed telescopically within the lower housing  30  and the third lift structure  15  is an upper, linearly extending member which is housed telescopically within the intermediate member  19 . 
   The drive means  40  comprises a durable, flexible tension member  41 , such as a chain or belt and a plurality of rotational guides  42 , such as sprockets or pulleys. At least one of the rotational guides is connected to a motor  31 , such as an electric gear motor for driving the tension member  41  thereabout. 
   The tension member  41  is arranged in a  FIG. 8  having two rotational guides  42  in one loop and two rotational guides  42  in the other loop. Actuation causes the one loop to be displaced relative to the other loop, raising one lift structure relative to the other. 
   As shown in  FIGS. 11 and 12 , the tension member  41 , such as a UNIFLEX™ belt available from Jason Industrial Inc. of Fairfield N.J., 07004, USA, is connected at either end  43 ,  44  to the intermediate member  19  and passes about rotational guides  42  positioned at a top  45  and bottom  46  of the lower housing  30  (a first loop) and at a top  47  and bottom  48  of the intermediate member  19  (A second loop). As the motor  31  drives the at least one rotational guide  42 , the intermediate member is raised ( FIG. 11 ) and lowered ( FIG. 12 ). 
   As in the previously described embodiment, the cable  16  is connected to the lower end  21  of the upper member  15 . The pulley  23  is connected to the intermediate member  19  through a bracket  49 . As the intermediate member  19  is raised and lowered, the pulley  23  is also raised and lowered causing the length of the cable  16  between the pulley  23  and lower end  21  to shorten as the intermediate member  19  raises, causing cable  16  to passively raise and lower the upper member  15 . 
   In a preferred embodiment, best seen in  FIGS. 13 and 14 , a slot  50  is formed along the length of the intermediate member  19  to accommodate connection of the cable  16  to the lower end  21  of the upper member  15  and to permit movement of the upper member  15  relative to the intermediate member  19  for telescoping therein. At least an upper stop  51  is formed along the slot  50  to assist in preventing the upper member  15  from lifting out of the intermediate member  19 . 
   As shown in  FIG. 14 , the actuation members  4  in this embodiment are housed within telescoping tubular members  11  so as to aesthetically cover the lift structures  30 ,  19  and  15 . An upper, lower and intermediate telescoping member (not shown) are connected to one or more of the lift structures  30 ,  19 ,  15  so as to move with the lift structures  30 ,  19 ,  15  as each are raised and lowered. For example, the upper telescoping member may be connected to the first lift structure  30  so that when the first lift structure  30  is lifted the upper telescoping member is raised at the same time. More preferably, the upper telescoping member is further connected to the intermediate telescoping member so that the intermediate telescoping member is passively raised to cover the second lift structure  19  when the first and second lift structures  30 ,  19  are raised. 
   Optionally, as shown in  FIGS. 11-14  and in a preferred embodiment, a biasing means  60 , such as a hydraulic cylinder, is connected between the lower housing  30  and the intermediate member  19  for assisting in lifting the intermediate member  19  to reduce load of the full weight of the cover  3  on the motor  31 . Preferably, an actuating arm  61  of the hydraulic cylinder  60 , such as a standard size 10 gas spring available from Industrial Gas Springs Ltd. of Mitcham, Surrey, CR4 4HR, United Kingdom, is connected to the intermediate member  19  through the bracket  49 . 
   In a preferred embodiment, the cover  3  is a substantially rigid, domed pyramidal-shaped cover manufactured of a foam core and having a fabric covering such as is known in the industry to provide protection and insulation as is also known with conventional spa covers. Further, the domed shape is particularly advantageous for spas which are enclosed in a deck structure to prevent persons or animals from walking or lying on the cover  3  and to minimize the amount of snow buildup on the cover  3  in snow-prone climates.