Patent Description:
Spas, also commonly known as hot tubs, are popular fixtures that are used in many homes. They generally include a deep, vacuum formed tub having a smooth acrylic liner that is filled with heated water and which is used for soaking and relaxation. Spas typically include water jets for massage purposes.

Typically, the acrylic liner is formed into shapes that provide a variety of seating arrangements within the tub. Each seat is usually equipped with hydrotherapy jets that allow a pressurized flow of water to be directed at various parts of a user's body. The water flow may be aerated for additional effect, and some or all of the jets may also automatically move or rotate, causing the changing pressure of the water on the body to provide a massage like effect.

Because many spas/hot tubs are located outdoors, they are often equipped with covers for enclosing the tub when not in use. These covers help prevent dirt, leaves and other debris from entering the water, and provide a safety function by preventing children and animals from falling into the water. Moreover, spa covers are often insulated so as to limit heat loss from the water when the spa is not in use, for purposes of energy efficiency and readiness of use.

Both soft and hard covers are known in the art. Typical hard covers generally consist of a hollow plastic shell that can be filled with an insulating foam. Typical hard covers may be formed using a variety of molding methods, such as through rotational molding and blow molding, as well as vacuum forming. These hard covers, and even some soft covers, typically require some sort of lift mechanism to remove them from the spa. Many existing lift mechanisms are outfitted to the external cabinet or base of the spa, and can be cumbersome to operate, are unsightly, and contain a number of exposed components that can impede free movement around the spa.

<CIT> describes an improved automated spa cover lifting device and thermally efficient, foldable spa cover, the lifting device having a motorized expandable and retractable strut attachable to a spa housing and to at least one of two pivotal side arms that connect or support a folded spa cover to the spa housing during displacement with the preferred spa cover having a bevel at the fold to improve the thermal efficiency of the cover.

In view of the above, there remains a need for a cover lifter system for a spa that has improved performance properties, repeatability, structural integrity, and ease of use.

It is an object of the present invention to provide a cover lift system for a spa.

It is another object of the present invention to provide an automated cover lift system for a spa.

It is another object of the present invention to provide an automated cover lift system having a clutch and release mechanism.

It is another object of the present invention to provide an automated cover lift system having a passive lifter mechanism.

These and other objects are achieved by the present invention.

A lift system for a spa cover includes a fist lift assembly associated with a first side of a spa, and a second lift assembly associate with an opposed, second side of the spa. The first lift assembly includes a motor for applying an uncovering force to a spa cover. The second lift assembly includes a compression spring exerting a generally downward force on the cover when the cover is in the closed position, and a generally upwards force on the cover when the cover is moved towards an open position to assist in an uncovering operation. The second lift assembly also includes a tension spring configured to exert an upward force on the cover when the cover is in the open position to assist the first lift assembly in a covering operation.

According to yet another embodiment of the present invention, a method of installing a cover lift system on a spa includes the steps of connecting a first end of a first lifter handle to a cover of a spa at a first side of the spa, connecting a second end of the first lifter handle a motor-driven lift assembly positioned interior to a sidewall of the spa at the first side, connecting a first end of a second lifter handle to the cover of the spa at a second side of the spa, and connecting a second end of the second lifter handle to a non-motorized lift-assist device positioned interior to the sidewall of the spa at the second side, the non-motorized lift-assist device including a compression spring configured to exert a generally downward force on the cover when the cover is in a closed position atop the spa to maintain the cover in the closed position and a generally upwards force on the cover during movement of the cover from the closed position towards an open position.

Referring to <FIG>, a spa <NUM> (also referred to as a hot tub) having a cover lift system according to an embodiment of the present invention is shown. The spa <NUM> includes sidewalls <NUM> and a bottom <NUM>, which collectively define an interior chamber <NUM> (not shown) for containing a volume of water and one or more user occupants. The chamber <NUM> includes an open upper end <NUM> for user entry and exit.

Sidewalls <NUM> and bottom <NUM> may be configured to provide any suitable interior chamber <NUM>. In the illustrated example, sidewalls <NUM> and bottom <NUM> define a rectangular footprint. In other embodiments, sidewalls <NUM> and bottom <NUM> may define a circular, triangular or other regular or irregularly-shaped footprint. In the illustrated example, the interior chamber is further defined by an inner tub positioned above bottom <NUM> between sidewalls <NUM> and is preferably contoured to provide seating for user occupants of spa <NUM>, as is known in the art. Further, spa <NUM> may include one or more jets which extend through tub for injecting air and water into chamber below the water level inside the spa <NUM>.

Spa <NUM> includes covers <NUM>a and <NUM>b, also referred to herein as cover members. Each cover <NUM> is positionable over the open upper end <NUM> of the chamber <NUM> for covering at least a portion of the open upper end <NUM>. In the illustrated example, each cover <NUM> is equally sized and shaped to cover one half of the open upper end <NUM> of chamber. In alternative embodiments, each cover <NUM> may be differently sized and/or shaped to cover differently sized and/or shaped portions of the open upper end <NUM> of chamber <NUM>. In some embodiments (not shown), spa <NUM> may include just one cover <NUM> sized to cover the entire open upper end <NUM>. Each cover <NUM> may be movable between a closed position (shown by example in <FIG>), in which the cover <NUM> rests on the open upper end <NUM>, and an open position (shown by example in <FIG>), in which the cover <NUM> is displaced from the open upper end <NUM>. For example, covers <NUM> may be moved to their respective open positions to provide user access to chamber <NUM> through upper end <NUM>, and moved to their respective closed positions after all users have exited the chamber <NUM>.

In the closed position, covers <NUM> may substantially seal chamber <NUM>, and the water contained therein, from the external environment to mitigate entry of dirt/debris and loss of heat. Further, the water inside may be heated to temperatures of up to <NUM> or higher. The energy consumption required to heat such volumes of water is significant. Therefore, a spa cover may be configured to provide insulation against heat loss, thus accelerating water heating and conserving water temperature for future usage.

With further reference to <FIG>, each cover <NUM> is connected to at least one lift system which are used for selectively removing and replacing covers <NUM> over the upper end <NUM> of chamber <NUM>. Preferably, lift assemblies <NUM> reduce the force required from a user to move covers <NUM> from the open position to the closed position, and optionally from the closed position to the open position. According to the invention, each lift system includes a primary lift assembly <NUM> associated with a first side <NUM> of the spa <NUM>, and a secondary or auxiliary lift assembly <NUM> associated with a second, opposing side <NUM> of the spa. In the preferred embodiment, the first and second lift assemblies <NUM>, <NUM> are located interior to the sidewalls <NUM> of the spa, between the sidewalls <NUM> and the interior chamber <NUM>.

As exemplified, each lift system includes a lever arm <NUM> for directing the movement of the connected cover <NUM> between the open and closed positions. Lever arm <NUM> is shown including a first end pivotally connected to a sidewall <NUM> of spa <NUM>, and a second end spaced apart from the first end <NUM> and connected to a cover <NUM>. In use, the second end may be rotated about the first end for moving the connected cover in an arcuate motion between the open and closed positions.

As shown, lever arm <NUM> may extend from the first end pivotally connected to sidewall <NUM> to an opposite second end connected to cover <NUM>. In the illustrated example, the lever arm <NUM> includes a connecting portion or connecting rod <NUM> that extends through the cover <NUM> and connects the opposed primary and secondary lift assemblies <NUM>, <NUM> (e.g. through the first ends of opposed lever arms <NUM>). As shown, connecting portion <NUM> may penetrate cover <NUM> to form a rotatable connection with cover <NUM>.

Optionally, lever arm <NUM> may further include a handle <NUM> that a user may grasp while manipulating lever arm <NUM> between the closed and open positions, in an optional manual mode of operation.

Each cover <NUM> may extend in width across spa <NUM> from a first cover side <NUM> to an opposite second cover side <NUM>. As shown, the primary lift assembly <NUM> may be connected to cover <NUM> at first cover side <NUM>, through the lever arm <NUM>. In some embodiments, second lift assembly <NUM> may be connected to cover <NUM> at second cover side <NUM> (such as through an opposing lever arm). In particular lever arms <NUM> of first and second lift assemblies <NUM>, <NUM> are joined through cross rod <NUM> that extends across a full width of the spa cover <NUM>.

Lever arm <NUM> is preferably sized and positioned relative to sidewall <NUM> and cover <NUM> to provide clearance for cover <NUM> to move between the open and closed positions. As shown, cover <NUM> may be oriented substantially horizontally over chamber <NUM> in the closed position, and substantially vertically outboard of sidewall <NUM> in the open position.

Referring now to <FIG>, more detailed views of the primary lift assembly <NUM> are shown. The primary lift assembly <NUM> is a motor-driven lift assembly of the type described in <CIT>. As illustrated in <FIG>, the primary lift assembly <NUM> includes a first sprocket <NUM> operatively connected to the lever arm <NUM>, a second sprocket <NUM> being generally coplanar with the first sprocket <NUM> and spaced from the first sprocket <NUM>, and a drive chain <NUM> drivingly connecting the first sprocket <NUM> and the second sprocket <NUM>. It is contemplated that the first and second sprockets <NUM>, <NUM>, and drive chain <NUM> may be positioned at any suitable location and, preferably, hidden behind sidewall <NUM>.

The primary lift assembly <NUM> further includes an actuator configured to rotate at least one of the first sprocket <NUM> and second sprocket <NUM>. For example, in an embodiment, the actuator may be a linear actuator <NUM> comprising a linear motor and linear drive shaft <NUM> connected to the drive chain <NUM>. This configuration allows the first sprocket <NUM> to be driven by manipulating chain <NUM>. In particular, in operation, extension of the linear drive shaft <NUM> causes the first sprocket <NUM> to rotate in the direction of arrow, A, while retraction of the linear drive shaft <NUM> causes the first sprocket <NUM> to rotate in the opposite direction, as indicated by arrow, B. In other embodiments, the first sprocket <NUM> may be rotated/ driven by directly rotating the second sprocket <NUM> (e.g., by a motor having a rotational output), which is connected to the first sprocket <NUM> via chain <NUM>. As discussed in detail below, rotation of the first sprocket <NUM> effects rotation of the lever arm <NUM>, which is operatively connected thereto, thereby opening or closing the cover <NUM> to which the lever arm <NUM> is connected.

With particular reference to <FIG>, the primary lift assembly <NUM> includes a clutch assembly drive mechanism <NUM> that, importantly, functions to automatically decouple the drive mechanism (i.e., the motor <NUM> and sprockets <NUM>, <NUM>) from the lever arm <NUM> and spa cover <NUM> in the event loads in excess of prescribed loads are seen during a covering or uncovering operation. In particular, as shown therein, the first sprocket <NUM> is fixedly/ rigidly connected to, such as via welding, a central hub <NUM>. An opposite end of the hub <NUM> is fixedly/ rigidly connected to a drive plate <NUM> having a first surface that faces the first sprocket <NUM> and an opposing second surface <NUM> that faces away from the first sprocket <NUM>. As best shown in <FIG>, the drive plate <NUM> includes a plurality of recesses or apertures <NUM>, the purpose of which is described hereinafter. While the drive plate <NUM> is shown as being spaced from the sprocket <NUM> by the hub <NUM>, it is contemplated that the first sprocket <NUM>, itself, may include the plurality of recesses or apertures on the second surface <NUM> thereof (in which case a separate drive plate may not be necessary; that is, the first sprocket <NUM> can be driven directly by drive chain <NUM>, as well as transmit rotational force directly to a clutch plate of the lift assembly <NUM>).

As further shown in <FIG>, and as referenced above, the primary lift assembly <NUM> includes a clutch plate <NUM> axially aligned with the drive plate <NUM> and first sprocket <NUM>. The clutch plate <NUM> carriers a plurality of ball bearings <NUM> on a drive plate-facing, first surface <NUM> thereof that are configured to be received in the corresponding recesses <NUM> on the second surface <NUM> of the drive plate <NUM>. In this manner, the clutch plate <NUM> and the ball bearings <NUM> thereof, and the drive plate <NUM> and the recesses <NUM> thereof, for a ball-detent like mechanism, the function of which is hereinafter described. With further reference to <FIG>, the primary lift assembly <NUM> also includes an end plate <NUM> axially aligned with the first sprocket <NUM>, the drive plate <NUM> and the clutch plate <NUM>, and one or more spring elements <NUM> sandwiched between the end plate <NUM> and a second surface <NUM> of the clutch plate <NUM>. In an embodiment, the spring elements <NUM> may be a plurality of stacked wave springs. As discussed hereinafter, the wave springs <NUM> function to bias the clutch plate <NUM> towards the drive plate <NUM>, thereby urging the ball bearings <NUM> carried by the clutch plate <NUM> into the corresponding recesses <NUM> in the drive plate <NUM>.

Importantly, the lever arm <NUM> is drivingly connected to the clutch plate <NUM> via a coupling member <NUM> for rotation for rotation of the lever arm <NUM> with the clutch plate <NUM>. The coupling member <NUM> is slidably received through a central recess in the first sprocket <NUM>, hub <NUM> and drive plate <NUM>, but is not connected thereto, such that the first sprocket <NUM>, hub <NUM> and drive plate <NUM> may be rotated without causing a corresponding rotation of the coupling member <NUM> and lever arm <NUM>, for the purposes hereinafter described.

In operation, to effect covering or uncovering of the cover <NUM>, the motor <NUM> is actuated to extend or retract the drive shaft <NUM>, which moves the drive chain <NUM> upwardly or downwardly, causing the first sprocket <NUM> to rotate (pushing the chain upwardly causes the first sprocket <NUM> to rotate in the direction of arrow, A, in <FIG>, while pulling downwardly on the chain <NUM> causes the first sprocket <NUM> to rotate in the direction of arrow, B, in <FIG>. Importantly, because the drive plate <NUM> is fixedly connected to the first sprocket <NUM> via the hub <NUM>, the drive plate <NUM> rotates along with the first sprocket <NUM>. Rotation of the drive plate <NUM> causes a corresponding rotation of the clutch plate <NUM> via frictional engagement of the ball bearings <NUM> in the recesses <NUM> in the drive plate <NUM>. In particular, the wave springs <NUM> bias the ball bearings <NUM> into the recesses <NUM> in the drive plate <NUM>, creating a frictional engagement between the ball bearings <NUM> of the clutch plate <NUM> and the drive plate <NUM>. This frictional engagement allows rotational forces to be transferred from the drive plate <NUM> to the clutch plate <NUM>, effecting rotation of the clutch plate <NUM>. As the lever arm <NUM> is fixedly connected to the clutch plate <NUM> via the coupling member <NUM>, rotation of the clutch plate <NUM> thereby effects a corresponding rotation of the lever arm <NUM>. Moreover, as the second end of the lever arm <NUM> is connected to the cover <NUM> via crossbar <NUM>, rotation of the lever arm <NUM> thereby effects movement of the cover <NUM> between the open and closed positions (depending on the direction of rotation of the first sprocket <NUM>).

As alluded to above, the wave springs <NUM> and clutch plate <NUM> form a clutch assembly <NUM> that serves to limit the forces seen by the drive mechanism (including at least the drive plate <NUM>, first sprocket <NUM>, and motor <NUM>) during a covering or uncovering operation. In particular, in the event of an overload condition (e.g., a person or object is atop the cover <NUM>), the ball bearings <NUM> will disengage from their seated positions within the recesses <NUM> in the drive plate <NUM>, causing slippage between the drive plate <NUM> and the clutch plate <NUM>, thereby preventing the drive mechanism (including the motor <NUM>) from seeing excess loads that could damage components thereof, such as the motor. Indeed, if the torque exerted by the drive plate <NUM> (under rotational urging by the motor through the first sprocket) exceeds the frictional holding force exerted by the ball bearings <NUM> on the drive plate <NUM>, then the drive plate <NUM> will 'slip' (it will rotate without imparting a corresponding rotation of the clutch plate <NUM>).

In particular, if the torque exerted by the drive plate <NUM> exceeds the frictional force between the ball bearings <NUM> of the clutch plate <NUM> and the recesses <NUM> in the drive plate <NUM>, then the drive plate <NUM> will rotate relative to the clutch plate <NUM>, causing the ball bearings <NUM> to rise up out of the recesses/holes <NUM> in the drive plate <NUM>. As the ball bearings <NUM> become unseated, the drive plate <NUM> exerts an axial force on the clutch plate <NUM> (through the ball bearings <NUM>), causing the clutch plate <NUM> to move away from the drive plate <NUM> against the spring bias of the wave springs <NUM>, thereby allowing the drive plate <NUM> to 'slip' relative to the clutch plate <NUM>. This essentially decouples the cover <NUM> from the drive mechanism and motor <NUM> thereof if the cover sees an external load such as a snow load bank during opening, or somebody laying across the spa while the cover is closing.

Importantly, the ball bearings <NUM> become disengaged from the holes <NUM> at a preselected torque, which disconnects the cover from the actuator drive. In an embodiment, the stack of wave springs <NUM> is selected to provide the proper axial force to hold the drive balls <NUM> in the holes <NUM> for normal operation. In an embodiment, however, the axial force exerted by the wave springs <NUM> on the clutch plate <NUM> (which controls the toque at which disengagement will occur) may be selectively set or varied by tightening or loosening nut <NUM> received on threaded shaft <NUM> of the coupling member <NUM>. In particular, tightening the nut <NUM> will push the end plate <NUM> towards the clutch plate <NUM>, which compresses the wave springs <NUM> between the end plate <NUM> and clutch plate <NUM>, causing the wave springs <NUM> to exert a greater axial fore on the clutch plate <NUM>. This causes the balls <NUM> to more forcefully engage the recesses <NUM> in the drive plate <NUM>, increasing the amount of torque necessary for disconnection. Similarly, loosening the nut <NUM> will move the end plate <NUM> away from the clutch plate <NUM>, which lessens the biasing force the wave springs <NUM> exert on the clutch plate <NUM>. This causes the balls <NUM> to less forcefully engage the recesses <NUM> in the drive plate <NUM>, decreasing the amount of torque necessary for disconnection. In this respect, the biasing force exerted by the wave springs <NUM> controls/ determines the 'sensitivity' of the breakaway mechanism.

The clutch assembly of the present invention is reversible and auto resetting by simply running the cover through an opening and closing cycle (after which the clutch assembly will reset itself and start moving the cover again). As indicated above, the wave spring stack allows <NUM> for axial movement of the clutch plate <NUM> as the balls <NUM> climb up out of the holes <NUM> in the drive plate <NUM> under overload conditions. This allows for disconnection of the clutch from the linear actuator drive system which protects both the mechanism itself from incurring any damage and safety for anyone who might be in the way of the moving cover. The wave springs <NUM> are used because they provide the above-mentioned functionality in a very small package that can fit inside the cramped conditions of the underside of a spa. Also, it is envisioned that the diameter of the holes <NUM> in which the balls <NUM> sit will be precisely controlled so that the force against the wave springs is the properly designed value.

As indicated above, the clutch <NUM> has a dual purpose: (<NUM>) to drive the handle <NUM> and cross bar <NUM> rotation to open and close the cover <NUM> and (<NUM>) to provide a safety brake mechanism in case someone or something is obstructing the cover movement. In particular, the ball bearings <NUM> disengage from their drive holes and protect the drive mechanism <NUM> and the person obstructing the cover. It can then be easily reengaged to normal functioning. The spring stack <NUM> (shown in <FIG>, <FIG> and <FIG>) allows for adjustment of brake torque.

Further to the above, the drive plate <NUM> is manufactured with a Hardness Rockwell C in the range of about <NUM> to about <NUM> to provide the proper edge condition to interact with the ball bearings <NUM> and to provide sufficient surface strength so that excessive deformation does not occur when the ball bearings <NUM> ride up out of the holes <NUM> and roll across the second side surface <NUM> during over-torqueing.

As indicated above, the linear actuator <NUM> drives the chain and sprocket mechanism by pushing and pulling on the chain. This provides a constant radial torque lever (distance from the chain sprocket to the center of rotation) so that the actuator creates constant torque on the lever arm <NUM> throughout its rotation. The present invention further provides an adjustable chain tensioner (i.e., an adjustable chain bracket allowing for ¼ link adjustment by simply moving bolt position).

As illustrated in <FIG>, the coupling member <NUM> includes a square socket/coupling to effectively transmit torque to the lever arm <NUM>. This configuration also facilitates assembly and disassembly. In an embodiment, the lever arm <NUM> and/or coupling member <NUM> may be received in a steel bushing that extends through the sidewall of the spa, to bear lifting forces, and pin bearings may be utilized to bear the side loading forces of any small tilt in the cover.

The primary lift assembly <NUM> therefore provides for an automated, motor-driven means to open and close the cover <NUM>. Importantly, the primary lift assembly <NUM> also includes a clutch and release system/ mechanism, as described above, that allows for transmission of opening and closing torque to the handle <NUM> and cover <NUM>, and provides a safety brake/ release mechanism in case the cover <NUM> does not smoothly open or close such as due to an obstruction.

Turning now to <FIG>, detailed views of the secondary lift assembly <NUM> are shown. The secondary lift assembly <NUM>, as described above, is located on an opposite side of the spa <NUM> from the primary lift assembly <NUM>, and includes a disk <NUM> rigidly connected to the lever arm <NUM> (associated with the secondary lift assembly <NUM>) and/or cross rod <NUM> behind sidewall <NUM> for common rotation with the lever arm <NUM> and/or connecting rod <NUM>. The secondary lift assembly <NUM> further includes first and second lift-assist devices <NUM>, <NUM> operatively connected to disk <NUM> adjacent to an outer periphery thereof. As illustrated in <FIG>, the first lift-assist device <NUM> is directly coupled to the disk <NUM>, while the second lift-assist device <NUM> is coupled to the disk <NUM> via a linkage <NUM>. In particular, the second lift device <NUM> is pivotally connected to a first end of linkage <NUM>, while the second end of the linkage <NUM> is pivotally connected to the disk <NUM>. Respective distal ends of the first and second lift-assist devices <NUM>, <NUM> are configured to secure and rigid coupling to sidewall <NUM> of the spa. In an embodiment, a mounting bracket (identified by reference numeral <NUM> in <FIG>) may be utilized to connect the lift-assist devices <NUM>, <NUM> to the sidewall <NUM> of the spa <NUM>.

Importantly, the first lift-assist device <NUM> is a compression spring that is loaded so that that when the cover <NUM> is closed, the first lift-assist device <NUM> provides rotational torque on the disk to provide downward force on the cover <NUM>, thus providing for a positive seal of the cover <NUM> when it is closed. This position is best illustrated in <FIG>. In operation, as the automatic drive mechanism of the primary lift assembly <NUM> opens the cover <NUM>, the compression spring (i.e., first lift-assist device <NUM>) provides lift that helps keep the cover <NUM> level and set it down gently towards the ground. In particular, the first lift-assist device <NUM> provides an upward force on the cover <NUM> as it rotates past vertical to help lower it gently, as well as aids in lifting the cover <NUM> from the ground during a closing operation. <FIG> and <FIG> illustrate the position of the secondary lift assembly <NUM> (and the position of the first and second lift-assist devices <NUM>, <NUM>) as the cover moves towards the fully open position.

With reference to <FIG>, in the fully open position of the cover <NUM>, the compression spring (i.e., first lift-assist device <NUM>) is fully compressed, and is almost directly under the center of rotation of the disk <NUM>. In this position, there is substantially no appreciable side vector to provide for a rotational torque on the disk <NUM>. That is where the second lift-assist device <NUM>, configured as a traction spring or tension spring, comes into play.

As discussed above, the second lift-assist device <NUM> is attached to the linkage <NUM> that is free to rotate and it provides no torque on the system until the linkage <NUM> comes in contact with a bolt head or protrusion <NUM> on the side of the disk <NUM>. In particular, the linkage <NUM> rotates freely until predetermined angle of rotation of disk <NUM> is reached, while the cover <NUM> is opening. As the cover <NUM> advances downward vertically, the linkage <NUM> engages the position stop <NUM> and then applies a load to the traction spring <NUM> attached to it. This creates positive torque that acts to slow the decent of the cover <NUM>. In particular, as the cover <NUM> falls over the side of the spa, the disk rotates <NUM> to the position where the lever/ linkage <NUM> contacts the bolt <NUM>, and the traction spring (i.e., second lift-assist device <NUM>) starts to stretch and provide significant torque to the system helping set the cover down gently.

In addition, when the cover <NUM> comes to rest adjacent the side of the spa, the second lift-assist device <NUM> provides a constant upward force (torque) that aids in lifting the cover back up onto the spa (this lever mechanism divides the load between itself and the linear actuator of the primary lift assembly <NUM>, reducing the force the actuator has to produce by half). In particular, when the drive mechanism of the primary lift assembly <NUM> reverses to close the cover <NUM>, this traction spring (i.e., second lift-assist device <NUM>) provides significant torque to help the drive pick the cover up off the ground. In particular, it provides enough torque to level the cover <NUM> during lifting so that no binding occurs due to cover tilt and overloads the drive mechanism.

The second lift-assist device <NUM> continues to help the actuator lift the cover until the compression air spring <NUM> rotates into position to provide similar torque at which time the linkage <NUM> disengages and the actuator and compression spring <NUM> complete the rotation to closure of the cover. This lever mechanism (i.e., lift-assist device <NUM> and linkage <NUM>) engages to assist the control of the decent of the cover and disengages halfway during the ascent of the cover so that the forces and torques can be controlled within acceptable limits, from the downforce on the closed cover, to a strong force to resist freefall while opening but allowing full travel to fully open, then to a strong assist force to help the actuator lift the cover back on the spa. Importantly, the second lift-assist device <NUM> is designed to disengage during the closing cycle so that it doesn't add to the closing torque and provide too much closing force.

Importantly, the compression spring (i.e., first lift-assist device <NUM>) and traction spring (i.e., second lift-assist device <NUM>) of the secondary lift assembly <NUM> work in concert with one another to provide steady rotational torque during the entire opening and closing operations. This passive, secondary lift assembly <NUM> allows the cover to be lowered and raised evenly with the active actuator. This way the cover does not tilt to either side creating too much side loading of the lift system resulting in binding of the entire cover lift system.

In an embodiment, the first and second lift-assist devices <NUM>, <NUM> may be air springs (configured as compression and traction/tension air springs, respectively), although other lift-assist devices such as hydraulic devices, mechanical springs and the like may also be utilized without departing from the broader aspects of the invention. In some embodiments, it is contemplated that a double-damping air spring may be employed, which functions as a sort of shock to smooth out the entire motion of the cover.

The present invention therefore provides both 'active' (i.e., the primary lift assembly) and 'passive' (i.e., the secondary lift assembly <NUM>) lift assemblies that work in tandem to facilitate smooth opening and closing of a spa cover. In particular, while the primary lift assembly <NUM> provides active, i.e., motor-driven force for opening the spa cover <NUM>, the secondary lift assembly <NUM> provides an auxiliary opening and closing force to supplement the force provided by the primary lift assembly <NUM>. In addition, the secondary lift assembly <NUM> provides for smooth and leveling movement of the cover <NUM> between the open and closed position, and vice versa. The present invention therefore minimizes the likelihood of an uneven torque being applied to the over, which could result in uneven movement and/or binding of the cover.

Claim 1:
A lift system for a spa cover (<NUM>), comprising:
a first lift assembly (<NUM>) configured for coupling to a first side of a spa (<NUM>), the first lift assembly (<NUM>) including a motor (<NUM>) operable to move a spa cover (<NUM>) between an open position and a closed position; and
a second lift assembly (<NUM>) configured for coupling to a second side of the spa, the second lift assembly (<NUM>) including at least one non-motorized lift-assist device configured to assist moving the cover (<NUM>) from at least one of the closed position to the open position, and/or the open position to the closed position;
characterized in that the second lift assembly (<NUM>) includes a compression spring (<NUM>) exerting a generally downward force on the cover (<NUM>) when the cover (<NUM>) is in the closed position to maintain the cover (<NUM>) in the closed position, and a generally upwards force on the cover (<NUM>) during movement of the cover (<NUM>) towards the open position.