Swimming pool with automatic pool cover arrangement and method of operating a swimming pool cover

Abstract: A drive and control system for controlling the movement of a pool cover comprised of interconnected rigid buoyant slats. The system relies upon a hydraulic drive section including a hydraulic motor drive which may be initially provided with fluid under pressure by a remote electric drive section. The hydraulic drive section is also provided with an effective means of controlling movement of the pool cover, both in a winding direction on a cover drum, which may be submerged, and/or in an unwinding direction where the pool cover is being unwound from the drum. Various mechanisms to control the movement of the cover are described herein.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention: This invention relates to a swimming pool in combination with an automatic pool cover arrangement according to the preamble of Claim 1. 2. Brief Description of Related Art The present applicant recognized the problems inherent in the use of an electric drive system for operating pool covers. Aside from the numerous safety factors, the electric motors had to be completely insulated from the water environment. Nevertheless, many pool cover drives are located in a subterranean environment. Consequently, the overall costs of construction and costs of installation were considerable. Notwithstanding, even rain water and ground water tended to collect in subterranean compartments housing the electric motors and their associated electrical components. In fact, it has been recognized that at least fifty percent of the failures of most automatic pool cover systems is due to the inherent problem of water damage. In order to overcome this problem, the present applicant had proposed and provided, as hereinafter described, pool cover systems which rely totally upon a hydraulic drive located at or near the swimming pool. An electric drive could be provided to operate a pump for pumping the hydraulic fluid. However, an electric drive and the pump could be located at a remote location and even housed in a building of the like. Automatic pool cover systems utilizing interconnected rigid buoyant slats which roll up on a submerged or elevated drum as described by U.S. Pat. No. 3,613,126, which represents the prior as described in the preamble of appended claim 1 to R. Granderath, are popular in Europe. These pool cover systems utilize passive forces arising from buoyancy or gravity for propelling, the cover to extend the cover across a pool. With either buoyancy or gravity, there must be some mechanism to prevent a retracted cover from unwinding responsive to the passive force. Such passive force systems also have a disadvantage in that the passive force must be overcome during retraction. Granderath suggests a worm gear drive mechanism for winding the cover and preventing cover drum rotation when not powered. The slats for these are further described in U.S. Patent No. 4,577,352, to Gautheron. Pool covers which employ floating slats or like materials, and which use buoyant forces to propel the cover across the pool, necessarily wind the cover onto a roller drum which is positioned below the water surface. Buoyant covers, which rely on buoyant or gravitational force to propel the cover across the pool, need to move at a low linear speed, and accordingly a low drum rotational speed, so as to prevent buckling of the cover as it moves across the water surface. A low rotational velocity is also necessary to prevent excess unwinding of the cover still wound onto the drum. Automatic covers of the buoyant type described above typically locate the reducer and electric drive motor exterior the pool wall. The drive shaft of the cover drum passes through an orifice or opening in the pool side wall and incorporates a bearing and several seals and gaskets to prevent pool water from leaking or seeping from the pool around the drive shaft. Considerable expertise and skill is required to prepare and locate the bearing seal arrangement. Furthermore, a separate excavation and structure of sufficient size to house the drum shaft drive mechanism and to facilitate service is required next to the pool wall. BRIEF SUMMARY OF THE INVENTION A desirable solution for the buoyant slat type, buoyant membrane or even the gravity type of cover, would be to use a hydraulic motor drive system to move the pool cover drum and thereby alleviate the moisture problems, flooding and electrical shock hazard associated with electric pool cover drive systems. The advantage of hydraulic systems is that the power pack pump system can be placed some safe distance away from the pool and in a covered building area. Only two hydraulic lines are required to power the cover system. Little use has been made of hydraulic motors in the buoyant type of cover to date. One object of this invention is therefore to provide a swimming pool according to the preamble of Claim 1 which comprises means to control the flow of fluid under pressure to the hydraulic motor to limit the travel of the cover. Another object is to enable using a hydraulic motor to drive the cover system without the use of a worm gear reducer as an unwinding braking force. To achieve the aforementioned objects, the present invention provides a swimming pool in combination with an automatic pool cover arrangement with the features of Claim 1. Preferred embodiments of the inventive swimming pool are characterized in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS Reference will now be made to the accompanying drawings in which: Figure 1 represents a flow diagram which shows possible combinations of components forming part of various gravity/buoyant slat-membrane pool cover systems; Figure 2 is a somewhat schematic fragmentary exploded perspective view of one form of hydraulic drive operated pool cover system forming part of the present invention; Figure 3 is a side elevational view of an arrangement for mounting a pool cover in a submerged position and the associated drive mechanism associated therewith; Figure 4 is a schematic side elevational view showing the arrangement of the pool cover of Figure 3 in a submerged position; Figure 5 is a fragmentary perspective view, partially broken away and in section, showing the operative arrangement of a travel limiting control mechanism with a pool cover drum forming part of the automatic pool cover system of the invention; Figure 6 is a vertical sectional view showing one form of travel limiting control mechanism for use with the present invention; Figure 7 is a sectional view taken along line 7-7 of Figure 6; Figure 8 is a sectional view taken along line 8-8 of Figure 6; Figure 9 is a schematic perspective view showing a one way clutch mechanism which may used in the control system of the present invention; Figure 10 is a fragmentary schematic side elevational view showing a cam-wedging arrangement for controlling unwinding of a cover from a cover drum; Figure 11 is a fragmentary schematic side elevational view, similar to Figure 10, and showing the cams forming part of the arrangement of Figure 10 in a different position; Figure 12 is a schematic view showing one form of fluid drive control system for use in the present invention; Figure 13 is a schematic view showing an alternate form of fluid drive control system for use in the present invention; Figure 14 is a schematic view showing still a further form of fluid drive control system for use in the present invention; Figure 15 is a schematic perspective view of a further modified form of automatic cover drive system which can be used in accordance with the present invention; Figure 16 is a schematic side elevational view of a mechanical limit switch actuator used with the control circuit of Figure 15 and showing the actuator in one position; Figure 17 is a schematic side elevational view, similar to Figure 16, and showing the mechanical limit switch actuator in an alternate position; and Figure 18 is a fragmentary schematic side elevational view showing another modified form of travel limiting device using a type of one way clutch mechanism in place of a hydraulic motor with a holding brake. OVERALL SYSTEM COMBINATIONS Referring now more particularly to Figure 1, there is schematically illustrated various combinations of components which form various embodiments of the present invention. By referring to Figure 1, some of the major components which can be used in various combinations are schematically identified. Initially, it can be observed that there is provided a floating cover with slats moved by the buoyant force, that is, the force imposed on a submerged cover drum which tends to force the slats upwardly to thereby unwind from the drum. In effect, some means must be provided to control that movement for the cover slats when the cover is moving to the fully covered position or closed position. A major component of the system of the present invention is a hydraulic motor. Moreover, a hydraulic motor with an internal brake may also be employed. This can be effective because a brake on the motor shaft can be used to reduce any problems of slippage of the hydraulic motor. A holding brake can prevent rotation of the drive shaft and can also be provided with a counter balance circuit to provide counter balance force. The hydraulic motor system eliminates the hazards associated with electrical power in close proximity to a swimming pool. In order to control end point movements of the cover, that is, to cause the cover to stop movement at one end of the swimming pool when moving to the closed position and in order to stop movement of the cover when it is fully wound upon the drum, a rotary encoder limit switch or an electrical limit switch could be used. Furthermore, a worm gear drive coupled to a motor or drum shaft could be incorporated to control end points of travel. In contrast, a braking means effectively serves the function to stop movement of a cover. The braking means could operate as a type of rate movement mechanism to control the rate of movement of the cover, whereas the travel limiting means will stop the movement of the cover at specific end points. Various types of devices can be used for this purpose and including a hydraulic pump with an adjustable pressure transducer. Open and closing control switches can be used. In addition, a hydraulic counter balance valve can also be employed for this purpose. Other components which can be used to provide the braking action and to provide a limit of travel are also disclosed in Figure 1 of the drawings. In addition to the foregoing, other embodiments to control limits of movement include a hydraulic pump with an adjustable pressure switch or transducer switch generating a signal to break electrical power. Referring now in more detail to Figure 1, it can be seen that there is initially an electric power pack 20 which includes, for example, an electric motor, and which may be used for operating a hydraulic system, a main component of which is a hydraulic motor 22. In this case, the hydraulic motor 22 and the associated components, with the exception of the power pack 20, could be located in close proximity to a swimming pool since they are all hydraulically operated. The electric power pack 20 is located at a remote position with respect to the hydraulic motor and connected that hydraulic motor. A simple drive system which uses a hydraulic motor 22 in combination with the power pack 20 would employ a worm gear reducer 24 on the output of the hydraulic motor in order to control buoyant forces which tend to unwind a cover from the cover drum. In order to preclude hard impact of the cover or buckling of a cover at an end of travel position, either when opening and, particularly, when closing, encoders of the type described above can be used including, for example, a rotary shaft encoder. A rotary shaft encoder 26 could be connected directly to a pool cover drive shaft 28, as schematically shown in Figure 1. In accordance with this system, the main electrical component, such as the power pack, still would be in a position remote from the swimming pool. The hydraulic motor 22 could be located at or in close proximity to the drum shaft for the pool cover. The only electrical component at or near the swimming pool would be the encoder 26. However, the encoder could be designed to operate with very low current levels to minimize any electrical hazard. The power pack 20 could also be operated with a pressure relief valve. Moreover, the power pack 20 operates in conjunction with a relay 32 and a number of other components, as illustrated in Figure 1. As an example, the relay 32 would operate in conjunction with a timer 34 and a mechanical over travel stop system 27, in turn, connected to the pool cover drive shaft 28. The power pack 20 and the hydraulic motor 22 could also operate with an external holding brake 36 constituting at least a one way brake action, and which would, in turn, operate with a hydraulic counter balance or brake valve 37. However, some travel limiting mechanism of the type described herein would necessarily have to be employed. This travel limiting mechanism could be the mechanical over travel stop system 27, or otherwise a travel limiter 38 with a hydraulic flow blocking valve, or otherwise a travel limiter with a flow diverter valve 41 used at the output of the hydraulic counter balance and brake valve 37. It can be observed that this system can rely upon a positive pressure switch 43 to shut down a pump operating with the power pack 20 or, alternatively, rely upon the pressure relief valve forming part of the power pack 20 to bypass pressurized flow to a sump tank. The timer 34 would be then controlled to automatically shut down the pump on a predetermined time basis. Another possible combination of the components illustrated in Figure 1 would be the power pack 20 and hydraulic motor 22 operating with an external holding and counter balance brake 42. This could be a one way component, as well. Moreover, these three components could operate in combination with a mechanical over travel stop system 27, but more preferably with a travel limiter with a hydraulic flow blocking valve. This arrangement would operate to close or trigger a switch sending an electrical pulses to a latching relay to thereby cut power to an electrical motor and, hence, flow of hydraulic fluid to the hydraulic motor. Furthermore, the system could also be operated with a flow diverter travel limiter 41 operating in conjunction with a timer 34. Another possible combination of the components illustrated in Figure 1 would be the power pack 20 along with a hydraulic motor with internal holding brake 44. On the output of the hydraulic motor would be a hydraulic counter balance brake valve 37 and the travel limiter either with a hydraulic flow blocking valve 38 or other control. It would be possible to use a combination of the travel limiter with the hydraulic flow diverter valve 41. In essence, this system is similar to the combination of the power pack 20, the hydraulic motor 22 and the external holding brake 42 along with a mechanical over travel stop system 27. The various components in Figure 1 can also be operated with latching relays 50 and operator control start/stop switches 52, as shown. The power pack may include a reversible motor, if desired, in order to reverse flow or, otherwise, it can incorporate a directional valve to reverse flow, if desired. In like manner, a pressure transducer switch (not shown) could also be used to break power to a pump forming part of the power pack. Although it is not so illustrated in Figure 1, an electrical limit switch could be used in place of the encoder 26. Moreover, the encoder limit switch or electrical limit switch could be used to stop movement of the cover drum and, therefore, prevent unwinding of the cover from the drum. In like manner, a mechanical over travel stop system could be employed, if desired. Further, a worm gear reducer can also be used to control unwinding movement of the cover drum. Again, and although not illustrated, it is possible to use a time-out circuit in conjunction with the open/close switches in order to break the circuit to the pump forming part of the power pack after a predetermined time period, regardless of the action of the manually operable control switch. It is also possible to use a pressure relief valve in combination with the hydraulic motor 22 and in combination with the power pack (20,100). The pressure relief valve, along with a pressure transducer, could be used to break power to the pump forming part of the hydraulic motor drive system after pressure has been built-up to a predetermined pressure level. This would, in turn, cause cessation of the operation of the hydraulic motor 22. The travel limiters, such as the travel limiter 38 and the travel limiter 40, are described hereinafter in more detail. They are primarily used for controlling the movement of the cover and to prevent a hard impact of the cover at a fixed end position. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 1. Overall System Referring now to Figures 2-4, there is illustrated a pool deck 70 surrounding a swimming pool wall 72 and which provides an interior swimming pool cavity 74 containing water therein. The automatic pool cover mechanism is located in a separate subterranean compartment 76 formed by a subterranean wall 78, as shown. A pool cover lid 80 is disposed over the compartment 76 and provides access thereto. A hydraulic drive mechanism 82 is provided for operation of a cover drum 84 and the drive mechanism 82 may be located in a separate compartment 86. The cover is located in its own compartment 81 formed by an enclosing wall 83. Generally, the hydraulic drive mechanism and braking means 82 is also located in its own separate compartment for easy access for purposes of cleaning and repair. The compartment 86 is formed by a separate enclosing subterranean located wall 88. By further reference to Figures 2 and 4, it can be seen that the cover drum 84 is mounted on a drum shaft 90 which projects through a sealed aperture 91 in the wall 78, and which is also hereinafter described in more detail. A buoyant slat type cover 92 is wound upon the cover drum and may be unrolled therefrom to extend over the upper surface 93 of a swimming pool body of water. 2. Hydraulic Drive Mechanism and Brake Means The drive mechanism 82 comprises a hydraulic drive motor 94 and is provided with hydraulic hoses 95 and 96 for connection to a suitable hydraulic pump 98 forming part of a power pack 100. By further reference to Figure 2, it can be observed that a power pack 100 may be located in its own separate compartment 102 formed by an enclosing wall 104, as shown. The power pack 100 is generally conventional and typically includes, in addition to the pump 98, a suitable electric motor 101 mechanically connected to the pump 98 for operation of same. In the embodiment of the invention as shown in Figures 2-4, the pump 98 provides fluid under pressure to the inlet hose 95 at the hydraulic motor 94 to cause rotation of same. As the slatted cover is wound onto the cover drum 84, the diameter of the drum increases. The torque on the motor shaft is the product of the upward buoyant force of the slat area unwound from the cover drum and submerged below the surface of the water, multiplied by the instant radius of the cover drum. Consequently, the torque or pressure required from the pumping source must increase as the cover 92 winds up onto the drum 84. A means to brake the cover drum in the unwinding direction is provided to counteract the buoyant force of the cover, as hereinafter described. A one-way brake as described U.S. Patent 5,930,848 may be used for this purpose. This may either be directly coupled to the output shaft or indirectly coupled via a chain drive or other suitable power transmission means. The drive shaft 90, which is coupled to the hydraulic motor 94, is also provided with a sprocket 110 coupled to a sprocket 112 forming part of a brake mechanism 114. The two sprockets are driven together by means of a drive chain 116, as shown in Figures 2 and 5. The sprocket 112 is also connected to and operates in conjunction with a travel limiter 118, hereinafter described in more detail. However, the sprocket 112 is also mounted on a brake shaft 115 which carries a brake disc 117 forming part of a brake mechanism. This braking mechanism may have a brake shoe device 120 to apply a braking pressure to the disc 117. Brake pads (not shown in Figure 2) engage and provide a frictional braking force against the brake disc 117. 3. Travel Limiter Referring to Figures 5-8, there is illustrated a first embodiment of a hard stop travel limiting device 170 or so-called "travel limiter" or "travel limiting device". The travel limiting device 170 is designed to provide hard stops representing the equivalent of a stop position for the swimming pool cover at either end of the swimming pool. The travel limiting device 170 comprises a cylindrically shaped elongate outer housing 172 and which is hollow forming an interior central bore 174 extending axially therethrough. An end cap 176 is mounted at the left-hand end of the housing 172 and is secured thereto by means of screws 178. In like manner, an end cap 180 is secured to the right-hand end of the housing 172 and is secured thereto by means of screws 182. Extending axially through the housing 172 is a partially threaded shaft 184 containing an acme threaded section 186. A traveling nut 188 or so-called traveler has an internally threaded bore matching the threaded section 186 and, therefore, as the shaft 184 rotates, as hereinafter described, the traveling nut 188 will shift axially along the shaft 184. The nut 188 is constrained from rotating by a pair of keys 190 which are secured to the shaft by screws 192 and which keys 190 fit into key ways 194 formed in the internally threaded bore 174. The set screws 192 are preferably recessed in the manner as shown. As the shaft 184 rotates, the traveling nut 188 will shift to one end position, such as, for example, a left-hand end position, and will make contact with a face of an adjustable "stop nut" 195, threaded into the end cap 176, in the manner as shown. A lock nut 198 holds the adjustable stop nut in position within the housing. Moreover, by releasing the threaded lock nut 198, it is possible to rotate the adjustable end nut 196 and thereby provide an adjustment of the end position. For this purpose, the stop nut or end nut is provided with an outer knurled finger engaging surface 200. When the traveling nut 188 reaches the left-hand end position, it will engage an inner surface of the lock nut 196. Inasmuch as there is a counter force, the shaft 186 will actually exert a force to the right, reference being made to Figure 6, and which force will be imposed on the bearing 202. When the shaft 184 is rotated in the opposite direction, the traveling nut 188 will shift to the right and exert a force against annular retaining ring 202 and thrust bearing 206 held in a recessed section of the shaft 184. This will, in turn, stop rotation of the shaft 184. The power pack will sense a pressure increase as a result of the cessation of rotation of the shaft 186 and, hence, the movement of the traveler 188. This pressure increase causes a pressure switch to initiate a current to the coil of a latching circuit to cease operation of the hydraulic motor. The travel of the traveling nut or so-called "traveler" 188 can be adjusted at the right-hand end of the housing 172 by allowing the outer housing 172 to rotate in housing clamps 208 and 210, as best shown in Figure 8 of the drawings. When the outer bolts 212 are loosened, the clamps 208 and 210 are released and thereby allow for rotation of the outer housing 172. Accordingly, the body of the device is free, along with the traveling nut, when the latter has engaged an end position. In this way, when a proper end position is achieved, the clamps 208 and 210 can be retightened by tightening the nuts 212. When the nut 188 abuts the left-hand end position, the nut becomes engaged against that left-hand end wall 176 and the stop nut 195. This is equivalent to one end position of the cover. When the nut is rotated to the opposite end position and abuts against the end wall, that represents the opposite end position for the movement of the cover. By further reference to Figure 6, it can be observed that the sprocket 112, as also shown in Figure 2, is keyed to an outer end of the shaft 184 extending beyond the housing 172. This sprocket 112 will receive the chain or pulley 116 (not shown in Figure 6). One effective means for accomplishing this result is more fully illustrated in Figures 5 and 6 and comprises a combination of a one way clutch device 220 as well as a brake mechanism 222. The clutch device 220 includes a braking disc 224 mounted on an outer hub 226 which is, in turn, keyed to an outer end of the rotating shaft 184, as best shown in Figures 5 and 6. In this way, when the cable drum rotates in a clockwise direction to move the cover from the pool to the wound position on the drum, the sprocket on the drum shaft will rotate, but the one way clutch is not set to rotate and the brake 222 will remain stationary and inactive, that is, not in a braking condition. The braking mechanism 222 comprises a pair of brake pads 228 which are shiftable into and out of engagement by means of a brake arm 230 held by an outer locking nut 232 and which can be biased into engagement by means of a compression spring 234. Thus, when the shaft 184 rotates in that opposite direction, it will cause rotation of the brake disc 224 and the disc will be engaged by the brake pads 228 in the manner as shown in Figure 6. Moreover, the pads will be held into braking engagement with the disc 224 by the spring 234 to thereby counteract the buoyant force of the cover as it tends to unwind off of the drum in the pool covering direction. One effective brake mechanism which can be used is that which operates with an overrunning one way clutch. One type of conventional overrunning one way clutch is a sprague type overrunning one way clutch 290, which is more fully illustrated in Figures 9-11 of the drawings. Sprag overrunning clutches 290 typically include a sprag cage 292 for maintaining orientation of a plurality of spragues 294 in concentricity between an outer cylindrical engagement raceway 296 and an inner cylindrical engagement raceway 298. The inner engagement raceway 298 typically comprises or otherwise engages the surface of a shaft 300 which would be in the pool cover drive. As indicated by the arrows in Figure 10, relative rotation between the respective inner and outer raceways 296 and 298 in one direction rotates the spragues 294 into wedging engagement between the respective raceways coupling the rotation of one raceway to the other raceway. Relative rotation of the respective raceways 296 and 298 in the opposite direction as indicated by the arrow in Figure 11 rotates the spragues out of engagement with the respective raceways de-coupling rotation of the raceways allowing the outer raceway to overrun. Such sprag type overrunning clutch mechanisms may also include ball and/or needle bearings confined by the sprag cage 292 to facilitate overrunning rotation of the respective raceways. 4. Control Systems Figures 12-14 illustrate several control systems which may be used with the travel limiting mechanisms and the automatic pool cover system of the invention. Referring to Figure 12, a broken line, designated by reference numeral 310, separates a power pack 312 from the hydraulic drive section 314 of an automatic pool cover system in accordance with the present invention. In essence, all of the electrical components are located within the power pack 312 or at least associated with the power pack 312 in a position remote from a swimming pool. The hydraulic drive system 314 is located at or in close proximity to a cover drum which holds the cover for the swimming pool. When it is desired to start operation and to either open or close the swimming pool cover, the operator will actuate either a close switch 314 or an open switch 316, as shown in Figure 12. Actuation of the open switch 316 will cause a current flow to a latching relay designated as 318, thereby closing the latch. This closed latch will thereupon allow a current flow to a relay 320 and thereby start the rotation of a reversible electric motor 322. This motor 322 is coupled mechanically by a mechanical link schematically designated as 324 in Figure 12 to a reversible hydraulic pump 326. This combination of the electric motor 322 and the hydraulic pump 326 are frequently referred to as "the hydraulic power pack". In the arrangement as shown in Figure 12, when the start switch 316 has been actuated, hydraulic fluid under pressure will flow from the power pack through a pressure switch 328. Another pressure switch 330, operating in conjunction with the pressure switch 328, also has its set point pressure above the normal pool cover operating pressure. Therefore, pressurized fluid flows to a hydraulic brake motor 332. The brake motor 332 preferably has an internal mechanical brake retained by spring pressure and which is releasable when hydraulic motor pressure is applied to the motor. However, the motor will not begin to rotate until there is sufficient pressure to release the brake of that motor and, secondly, a higher pressure is achieved in a pilot pressure line 334 to open a counter balance valve 336. The pilot pressure on the motor, which is actually a back pressure, is set sufficiently high to counteract the buoyant force of the pool cover as it unwinds to cover the pool. It is well recognized that manufacturers of hydraulic brake motors frequently recommend that the brake be used only as a holding brake. However, with the arrangement of the present invention, it is desirable to set the counter balance valve pilot line pressure, that is, the pressure in the line 334, well above the brake release pressure. Therefore, as the hydraulic motor 326 is mechanically coupled to a travel limiting device, such as a travel limiting device 328, as shown in Figure 16, it will continue to move the mechanical traveling nut 340 of that travel limiting device until it reaches an end position of travel. At this point, the hydraulic motor 326 will sense the high resistance and the pressure will build until it reaches the set point pressure of the pressure valve 336. This will then close the normally open switch and send a current to an unlatching side of another relay 340, as also shown in Figure 12. This will, in turn, break the circuit to the relay 320 to stop current flow to the electric motor 322 and, hence, stop operation of the pump 326. A check valve 335 across the pressure valve 336 allows the brake 332 to be open in the wind-up direction of the pool cover. The check valve 335 will allow flow in the opposite direction. Even minimal flow is desirable to enable the nut to start moving again. Otherwise, there would be no force sufficient to start movement of the nut 340 after it stopped. Further, it may be desirable to add a cross-piloted load check circuit on the output side of the power pack to assist in preventing rotation of the hydraulic motor 326 when at rest. It can also be observed that the operator can also push an emergency stop switch 342 at any point during travel of the cover in order to immediately stop the cover. A relay switch 344 also operates in conjunction with the relay switch 320 and on the opposite side of the electric motor 322 with respect to the relay switch 320. A latching or unlatching of the latching relay 318 would allow the relay 344 to close and thereby cause operation of the motor 322 in the opposite direction. It can be observed that the travel limiting means 338 operates in the same manner as each of the previously described travel limiting means, in that when the nut 340 reaches an end position, it will cause an end position engagement and thereby physically cause the motor 322 to stop. The motor will effectively stop because of the resistance to travel created by the travel limiting means 338. In effect, the power pack will reach the relief pressure on the pressure switches 320 and 330. Figure 13 is a schematic illustration of a control circuit similar to Figure 12. In this respect, like components described in Figure 12 will carry the same reference numerals as their corresponding components in Figure 13. This circuit arrangement of Figure 13 is similar to that of Figure 12, except that the counter balance valve 336 of Figure 12 has been replaced by a one way braking device 350, as shown in Figure 13. This braking device 350 is mechanically coupled to the hydraulic motor 332 by means of a mechanical linkage 352, as shown in Figure 13. In the embodiment as illustrated, the braking device 350 comprises a ratchet 354 and a pawl 356 which allows only one way rotation of the brake mechanism coupled to the hydraulic motor 332. In the embodiment as shown, the ratchet 354 can only operate freely in the counter-clockwise direction but would be precluded from rotation in the clockwise direction, unless the pawl 356 was released. It should be recognized that the ratchet and pawl arrangement, as illustrated in Figure 13, is only one of numerous one way brake devices which would be used. Another version of a hydraulic system which can be used for this purpose is that hydraulic system 360 as illustrated in Figure 14. In this case, the arrangement of the circuit is similar to that of Figure 12. However, a mechanical two way - two position hydraulic valve 364 is used and is hydraulically interposed between the travel limiting device and the power pack 312. In this embodiment, the travel limiter 338 does not actually provide for a jamming of the traveling nut 340. Rather, the traveling nut 340 is provided with a probe or upstanding actuating element 366 for activating a plunger 368 on the hydraulic valve 362 or otherwise a plunger 370 on the hydraulic valve 364. By further reference to Figure 14, it can be observed that the valve 362 and the valve 364 each has a check valve position 372, and each of which would block flow of hydraulic fluid to the hydraulic motor 332. In like manner, each of the valves 362 and 364 would be normally biased to a normal flow position, that is, positions 374 and 376, respectively, allowing normal flow of hydraulic fluid to the motor 332. In effect, this arrangement constitutes a bypass shut-off circuit around the two position valve 364. When either of the valves 362 or 364 are in the check valve position, they will almost instantaneously build up pressure to either of the pressure switches 330 or 328 causing these pressure switches to reach a set point and trigger the unlatching side of the latching relays 318 and 340. This will, in turn, stop power from the power pack to the cover. Thus, the cover can now move in the opposite or reverse direction, since the valves 362 and 364 allow flow in the normal flow position, that is, in a direction opposite to that of the check valve. This occurs while the valve is being held in position initially until the valve is shifted back to a two way flow position by the traveling nut 340 moving in an opposite direction. Referring now to Figure 15, there is illustrated another form of travel limiting control mechanism which will control movement of the cover when moving both to the open and closed positions. For better appreciation of the control circuit of Figure 15, reference can also be made to Figure 2 showing an overall schematic illustration of the components forming part of the automatic pool cover system of the invention. In this particular case, like reference numerals will be used with respect to the previously described embodiments of the invention to designate like components. Referring again in more detail to Figure 15, it can be observed that the slatted pool cover 92 is mounted on the drum 84 and which is, in turn, supported on a drum shaft 90. However, in place of the drive system as shown in Figure 2, the hydraulic motor 94 is connected to a worm gear reducer 384 of generally conventional construction in the manner as shown. The hydraulic motor 94 similarly receives the hydraulic hoses 95 and 96, as shown. The worm gear reducer has an input shaft 386 which is connected through a coupling 388 to a input shaft 390 of a limit switch actuator 392, and the latter of which is hereinafter described in more detail. Also by reference to Figure 15, it can be observed that the hydraulic lines 95 and 96, which are used for operation of the hydraulic motor 94, are connected to the limit switch actuator 392 and which, in turn, receives the hydraulic fluid through alternate fluid supply and return lines 394 and 396, as shown. Turning now to Figures 16 and 17, the mechanical limit switch actuator is more fully illustrated in detail. It should be noted that the mechanical limit switch actuator 392 carries many of the details of construction of a device for limiting rotation of a rotating shaft, as set forth in U. S. Patent No. 3 718 215 dated February 27, 1973, to Mimeur. However, the device of the present invention is a valve operated limit switch actuator and which uses electrical limit switches in combination with the hydraulic valves 362 and 364. Thus, and to this extent, the arrangement as shown in Figures 15-17 is still a further improvement over the arrangement as shown in Figure 14, although both are quite viable in the present invention. The mechanical limit switch actuators 392 operate in a manner quite similar to that described in the aforesaid U.S. Patent No. 3,718,295 to Mimeur, except that in this case, electrical limit switches of Mimeur are not employed. In the embodiment of the invention as shown in Figure 15, the reducer is a hollow shaft type reducer and the cover drive shaft effectively passes directly through the reducer and thereby connects to the coupling 388 and the shaft 390 of the limit switch actuator 392. The mechanical limit switch actuators of the invention as shown in Figures 16 and 17 generally comprises non-rotatable screw shafts 400 and 402, as shown. However, each of the screw shafts 400 and 402 are provided with opposite hand screw threads, as best shown in Figures 16 and 17. There is also provided a rotatable splined drive shaft 404 which has a reduced end shaft 405 connected to the coupling 388 and which is, in turn, connected to the gear reducer output 386. The screw shafts 400 and 402 engage with opposite end plates 406 and 408 which support the screw shafts 400 and 402. When the splined shaft rotates, it will cause the nuts 410 and 412 to move along the stationary screw shafts 400 and 402, respectively, due to the threaded engagement therebetween. As the splined shaft 404 rotates, the two nuts 410 and 412 will rotate in the same direction. However, because the screw shafts 400 and 402 have opposite threads, the nuts 410 and 412 will move to the opposite ends of the screws 400 and 402. The traveling nuts 410 and 412 are limited at the ends of travel by unthreaded portions 415 and 417, as shown in Figures 16 and 17. Thus, when the traveling nuts 410 and 412 reach the ends of the screws, they will effectively free-wheel on the ends of the screws 400 and 402 in a manner as hereinafter described. The nuts 410 and 412 actually operate as types of switches. In this case, valve actuator arms 414 and 416 are mounted on the ends of the threaded shafts 400 and 402 and will similarly engage valve stems 420 and 422 on the respective valves 362 and 364. Thus, when the actuator arms 414 and 416 engage the respective valve stems 420 and 422, they will open check valves 424 and 426, respectively, against the action of springs 440 and 442, also as shown in Figures 16 and 17. When one nut 410 reaches its right-hand end point position, it slidably shifts the arm 414 to the right, as shown in Figure 16, and this allows the check valve 424 to literally close and thereby block flow. This causes a pressure increase in the line from the power pack causing actuation of the pressure switch. In this way, the spring loaded ball of the check valve literally operates as a one way check valve. The check valve 335 allows for a short interval of motion for the nut 410 and 412 which causes a sufficient bypass to start movement. The limit switch actuator of the invention is effectively fail safe. Each of the threaded screws 400 and 402 have unthreaded end sections 416 and 417 at each of the opposite ends. In this way, if the splined shaft 404 should keep rotating, the nuts would reach the unthreaded ends of the shafts 416 and 417 and thereby free-wheel on the ends of the shafts. Thus, no damage would result to the swimming pool cover. The springs 444 and 446 on one end and 440 and 442 on the opposite end would bias the nuts back onto the threaded portions of the shaft when the splined shaft again starts rotating. Even though the splined shaft, and even the pinions, may continue to rotate, there will be no damage to the device if the valve should fail to block fluid flow. As the splined shaft continues to rotate in the opposite direction, the nut 410 will move to the left and is urged by the strength of the spring 444 back against the shoulder of the left-hand threaded section of the shaft. A similar spring 446 is also provided on the opposite screw. The various screws on the screw shafts 400 and 402 are generally angularly fixed. However, they can be turned manually, if desired, by means of gears 450 and 452 mounted on the ends of each of the screw shafts 400 and 402, as shown in Figures 20 and 21. Thus, the distance between each of the respective traveling nuts 410 and 412 and, hence, the arms 414 and 416, can thereby be slightly adjusted. Normally, the initial setting of each of the end positions for movement of the traveler, which is effectively operating as a type of limit switch, results from a trial and error situation. With the device situated next to a swimming pool, it is relatively inaccessible and, particularly, inconvenient to attempt to adjust. With a trial and error situation, the operator must necessarily continuously adjust the threaded rods 400 and 402 in order to allow the traveling nuts 410 and 412 to stop in the right position, that is, timed to shut off at the exact points. Two bypass circuits 471 and 473 along with logic valves 470 and 472, respectively, allow the user of the system to initially set the limit switch to cut off early and thereby activate the arms 414 and 416 to close the valves 362 and 364. At this point, the user would then have to open the bypass valves 362 and 364 to allow the cover to manually continue to reach the end position. At this point, the nut 410 has been driven to the non-threaded section 415 for free-wheeling and held against the thread by means of one of the springs 440 or 444. The user would then be forced to stop the cover by using the emergency stop switch. The user would then close the logic valve and allow the valve 362 to pick up the end stop automatically in the next operation of the cover. In accordance with this system, there is provided a type hydraulic control circuit in which the circuit is self-programming so as to properly stop the cover in the next cycle. It is possible to also use a hydraulic motor, such as the motor 332, in the form of a regular dual rotation motor in place of a motor with an internal holding brake, such as the type illustrated in Figure 14. This arrangement would use a ratchet and pawl operating as a type of one way clutch in place of the hydraulic motor and the holding brake. In this case, the pool cover 92 is unspooled from a cover drum, such as the drum 84, and the latter of which is mounted on a drum shaft 90. A ratchet 460 is mounted on the drum shaft 90, in the manner as best shown in Figure 18 of the drawings. A pawl 462 is spring biased to be engaged against the ratchet when the system is not pressurized with hydraulic fluid and to become disengaged when the pressure is delivered to the hydraulic motor. A spring 464 biases the pawl to be engaged with the ratchet, in the manner as illustrated in Figure 18. A hydraulic cylinder 466 is also provided to act upon the pawl 462 and is supplied with hydraulic fluid under pressure by means of a hydraulic line 468. Hydraulic fluid under pressure would be delivered to the cylinder 466 when the cover is unwinding from the cover drum, that is, in the clockwise direction, reference being made to Figure 18. This would permit disengagement of the pawl from the ratchet 460. It can be observed that the pawl actually pushes against a plunger 470 inside of the hydraulic cylinder 466 and, thus, opposes the action of the pawl lever 462 pivoting on a pivot pin 472. When the system has reached a stop position, the pressure in the cylinder 466 effectively drops and the spring 464 pushes against the pawl 462 to engage against the ratchet 460. This will effectively lock the pool cover from turning in the clockwise direction. The ratchet and pawl arrangement also overcomes the hydraulic motor internal leakage and would preclude any creep therefrom.

Claims: A swimming pool (74) in combination with an automatic pool cover arrangement (82) incorporating a slat type cover (92) comprised of a plurality of interconnected and preferably relatively rigid buoyant slats or a buoyant membrane or a gravity type of cover and a rotatable cover drum (84) for winding the cover (92) onto said cover drum (84) and allowing unwinding of the cover (92) from the cover drum (84) to a closed position so that the cover (92) may extend across and cover the swimming pool, wherein the movement of the cover (92) is controlled in both opening and closing movements of said cover (92) relative to the swimming pool (74), and which pool cover arrangement (82) further comprises: a) a motor (94) for causing driving movement of the cover (92) across a swimming pool to an open position and winding the cover (92) onto the cover drum (84); b) movement control means (114) operatively coupled to said cover drum (84) to control a rate of movement due to a gravitational or a buoyant force respectively of the cover (92) from the cover drum (84) to extend the cover (92) over the swimming pool (74); characterized in that the motor (94) is a hydraulic motor, which is operated by an electrical power pack (100) remote from the hydraulic motor and from the swimming pool (74). The swimming pool (74) in combination with the automatic pool cover arrangement (82) of claim 1 further comprising a travel limiting means (170) for controlling the limits of movement of the cover (92) to preclude hard contact of a cover at an end of travel to the closed position. The swimming pool (74) in combination with the automatic pool cover arrangement (82) of Claim 2 further characterized in that said hydraulic motor (94) provides a positive driving action for moving the cover (92) to the opened position and winding the pool cover (92) about the drum (84), but operates in reverse to provide a braking action preventing unwinding to restrain tendency of the cover(92) to unwind from the drum (84). The swimming pool (74) in combination with the automatic pool cover arrangement (82) of Claim 2 further characterized in that said movement control means for controlling movement is a one way brake device (36). The swimming pool (74) combination with the automatic pool cover arrangement (82) of Claim 2 further characterized in that the travel limiting means (170) is a hard stop travel limiter (170). The swimming pool (74) in combination with the automatic pool cover arrangement (82) of Claim 2 further characterized in that said hydraulic motor (94) is provided with an internal brake (44). The swimming pool (74) in combination with the automatic pool cover arrangement (82) of Claim 2 further characterized in that the travel limiting means (170) is a hydraulic pump (98) with an adjustable pressure relief valve. The swimming pool (74) in combination with the automatic pool cover arrangement (82) of Claim 2 further characterized in that the travel limiting means (170) is a hydraulic pump (98) with an adjustable pressure transducer switch for controlling electrical power to a means (95, 96) for driving the hydraulic motor (94). The swimming pool (74) in combination with the automatic pool cover arrangement (82) of one of the preceding claims further comprising hydraulic line means (95, 96) carrying only hydraulic fluid connected between said power pack and said hydraulic motor (94) and with no electrical current connected between the power pack (100) and the hydraulic motor (94) or drum (84), such that said automatic pool cover system can operate a subaqueous cover drum (84) and can be hydraulically operated, thereby electrically insulating the power pack from the hydraulic drive motor and thereby eliminating any electrical hazard at or in proximity to the swimming pool (74). The swimming pool (74) in combination with the automatic pool cover arrangement (82) of Claim 9 further characterized in that said power pack includes a hydraulic pump in close proximity to said electric motor for operation by said electric motor. The swimming pool (74) in combination with the automatic pool cover arrangement (82) of Claim 10 further characterized in that said drum (84) is mounted on a drum shaft (90) powered for rotation by said hydraulic motor (94) in at least the wind-up direction to wind the pool cover onto the drum (84), and a brake means (114) is operable with respect to said shaft (90) when said pool cover (92) is being unwound from said drum (84) to move the cover (92) to the closed position. The swimming pool (74) in combination with the automatic pool cover arrangement (82) of Claim 11 further characterized in that said travel limiting device (170) has a traveler rotatable shaft (184), and brake means (222) is operable to control speed of rotation of the drum (84) when the cover (92) is unwound from the drum (84) from the same traveler rotatable shaft (184) forming part of said travel limiting device. The swimming pool (74) in combination with the automatic pool cover arrangement (82) of Claim 12 wherein the travel limiting device controls (170) movement of the pool cover (92) so that it does engage a fixed obstruction at least at one end position with a hard impact, said travel limiting device (170) having an element (188) moving between two end positions representative of end positions of the cover (92) and proportional to the distance of movement of the cover between the end positions, said moving element (188) engaging with moving element end positions to represent the cover end positions and thereby precluding any hard impact of the cover (92) at either of the fully opened position or fully closed position. The swimming pool (74) in combination with the automatic pool cover arrangement (82) of one of the preceding claims characterized in that the travel limiting device (392) for controlling movement of the pool cover (92) between a closed end position and an opened end position, said travel limiting device (392) comprising: a) a housing (172); b) a travel limiter shaft (400, 402) extending through said housing (172); c) an element (410, 412) movable on said travel limiter shaft (400, 402) and translating movement therealong in response to rotation of said shaft; d) A first fixed contact element (406) in said housing (172) representing one end position of travel of the pool cover (92) and which traveler contacts the first fixed element (406) when the cover (92) reaches a first end position of travel across the swimming pool (74); and e) a second fixed contact element (408) in said housing (172) representing an opposite end position of travel of the pool cover (92) and which traveler contacts the second fixed element when the cover (92) reaches a second end position of travel across the swimming pool (74). The swimming pool (74) in combination with the automatic pool cover arrangement (82) of claim 14 further characterized in that said pool cover (92) is wound upon a drum (84) and said travel limiter shaft (400, 402) is mechanically coupled to a shaft which supports said drum (432) so that movement of the drum is directly coupled to and proportional to movement of the travel limiter shaft and movement of the traveler (410, 412) thereon. The swimming pool (74) in combination with the automatic pool cover arrangement (82) of claim 15 further characterized in that said traveler (410, 412) translates axially along said shaft (400, 402) through threaded engagement of said traveler with said travel limiter shaft and which is keyed with respect to said housing to preclude rotation of said traveler (410, 412). The swimming pool (74) in combination with the automatic pool cover arrangement (82) of claim 15 further characterized in that first adjustment means (406) is provided for adjusting one end position of the traveler (410) to coincide with a first end position of the pool cover (92), and second adjustment means (408) is provided for adjusting the second end position of the traveler (410, 412) to coincide with a second end position of the pool cover (92). The swimming pool (74) in combination with the automatic pool cover arrangement (82) of claim 17 further characterized in that said housing (172) is cylindrically shaped and provided with an axially extending cylindrically shaped bore (174) and said traveler (188) is shiftable within said housing (172) in close proximity to the interior of said bore (174). The swimming pool (74) in combination with the automatic pool cover arrangement (82) of claim 17 further characterized in that said first contact element (406) operates control valves to control the operation of said hydraulic motor. A method of operating a swimming pool cover (92) comprised of a plurality of interconnected buoyant slats (92) which is capable of extending to a closed position over a swimming pool (74) and to an opened position where it is wound upon a cover drum (84) and where the rate of movement of the cover is controlled at least to the closed position, and in which rotating power is provided to said cover drum (84) for rotating same at least in a wind-up direction to rotate the pool cover (92) about the drum (84) rotatable only from a hydraulic power source (94) at or in proximity to said swimming pool (74), said hydraulic power source comprising a hydraulic motor (94) which is operated by an electrical power pack (100) remote from the hydraulic motor (94) and from the swimming pool (74), the method comprising: a) providing a braking action (114) to said drum (84) when the cover (92) is moving due to a gravitational or a buoyant force from the wind-up position on the drum (84) to a closed position across the swimming pool (74) to thereby control the rate of movement of the cover (92); and b) controlling the limits of movement of the cover (92) to the fully opened position and the full closed position through a member (170) associated with the drum (84) and capable of being moved a distance proportional to the limits of movement of the cover (92) from the fully opened position to the fully closed position to thereby preclude hard impact of the cover (92) into either end position. The method of Claim 20 further characterized in that said method comprises making a determination of an end position of movement of the cover (92) at a remote location simultaneously with the providing of a braking action (114), such that the limit of travel of the cover (92) to the closed position is directly coordinated with the braking action (114) therefor. The swimming pool (74) in combination with the automatic pool cover arrangement (82) of one of the claims 1 to 19 further comprising a control system (312) for controlling operation of the automatic pool cover arrangement (82) and which controls movement of the pool cover (92) having a plurality of interconnected preferably relatively rigid buoyant slats (92) across said swimming pool (74), said control system comprising: a) a fluid operated motor (94) for providing powered movement to the pool cover (92); b) a travel limiting mechanism (170) for controlling the movement of the pool cover (92) in at least one direction to preclude hard impact of the pool cover (92) against a fixed obstruction when the pool cover (92) reaches an end position; c) a power pack (100) remotely located with respect to said pool cover (92) and said fluid operated motor (94) and providing fluid power to said fluid motor (94); d) latching means (318, 340) operatively connected to the electric motor of said power pack (100) in response to actuation of a manual control therefor; and e) a relay means (328, 330) operatively connected to said latching means (318, 340) for controlling operation of said fluid motor (94) in response to actuation of a manual control therefor. The swimming pool (74) in combination with the automatic pool cover arrangement (82) of claim 22 with the control system (312) is further characterized in that a ratchet and pawl mechanism (350) is connected to said fluid operated motor (94) in order to preclude operation in one direction but to allow operation in the opposite direction. The swimming pool (74) in combination with the automatic pool cover arrangement (82) of claim 22 with the control system (312) is further characterized in that a two way-two position hydraulic valve is operatively connected to the travel limiting mechanism (170), such that flow of hydraulic fluid to the motor (94) can be blocked when the valve is in one position and fluid flow resumed when the valve is in the other position. The swimming pool (74) in combination with the automatic pool cover arrangement (82) of claim 2 further characterized in that said movement control means (112) comprises: a) a rotatably located ratchet (350) operatively connected to said drum (84); b) a pawl (356) engageable with recesses on said ratchet (350) and being biased to a first position or a second position and where one is a position of engagement and the other position is a position of disengagement with the ratchet (350); and c) a fluid actuator (332) operatively connected to said pawl (356) and causing movement of the pawl (356) to the position other than that to which it is biased upon receipt of a fluid signal. The swimming pool (74) in combination with the automatic pool cover arrangement (82) of claim 25 is further characterized in that the ratchet (350) and pawl (356) mechanism is used with an automatic pool cover system for moving a slatted type buoyant pool cover (92) and provides a releasable braking action to a cover drum (84) for the pool cover (92).

Inventors: LAST HARRY J, LAST, HARRY J.
Applicants: LAST HARRY J, LAST, HARRY J.
Application year: 2001
Main classification: E04H4
IPC codes: E04H4