AU2017201540A1 - Spa With Adaptive Water Pumping Provisions - Google Patents

Abstract

A water circulation system for a spa or the like based upon the use of one or more centrifugal pumps close-coupled, singly or jointly, to a single electric motor, said electric motor being a brushless, direct current, axial 5 flux motor employing electronic commutation, said motor being under the control of a microprocessor-based control unit and capable of operation in an energy-efficient way over an extended RPM range with a wide range of power outputs. Sheet 2 of 3

Description

SPA WITH ADAPTIVE WATER PUMPING PROVISIONS

This invention relates generally to recreational spas and the like in which the water body Is heated for improved comfort. In particular, it relates to such recreational spas and the like In which the water body is continuously filtered and sanitized; in which the water body is maintained at ambient temperature or partially raised temperature during periods of non use and raised in temperature prior to a period of use; and in which recreational water jets may require large and rapid changes in water volume flow during use- in the operation of recreational spas and the like, it is common for associated filtration and sanitization means to be operated on a continuous or intermittent, but regular, basis during periods of non use. Said means maintain water quality by removal of suspended solids and microorganisms from the water body and by the circulation of Sterilization media. Also during periods of non use, the temperature of the water body in a spa may be permitted to fall to ambient or may be thermostatically maintained at a temperature above ambient but below that normally accepted as comfortable. Maintenance of the water body of a spa at an elevated temperature during periods of non use is undesirable, because of energy wastage and because warmth Is particularly favourable to the growth of microorganisms. Ideally, the temperature of the water body of a spa or the like is allowed to fall to ambient and is then raised rapidly only when required for use. To achieve this requires a large increase in water flow over that typically employed for filtration and sanitisation purposes. Similarly, when a spa is in use and groups of recreational water jets axe brought into or out of operation as seating positions are occupied or vacated, large and sharp changes in water flow are required. Similarly, large changes in water flow may also be required during heating of the water body of a spa. Such large changes in water flow have typically been achieved through the use of multiple pumps. For example, in US 4,322,297, Bajka teaches a recreational pool system that employs three separate pumps; the first for water circulation through gas-fired or solar heating means, the second to supply a flow of water to recreational water jets and the third to provide water flow to a pool sweeping device. Logic circuitry is used to control and co-ordinate the pumps and associated valve means. A plurality of sensing devices is provided and positioned to sense conditions in the pool system and actuating means are provided and coupled to electrically powered apparatus. Programmable means for the receipt and storage of time sequence inputs and temperature inputs produce logic signals based upon said sensing apparatus inputs. In US 6,444,129, Collins teaches a spa water treating system in which water is drawn from the spa by a pump and circulated through a heating unit and a filtration and sanitisation chemical dispenser before being returned to the water body. Water is circulated through said heating unit to maintain said water body at a pre-set temperature. A control system monitors the duration of water circulation for heating purposes and, where it exceeds that required for filtration and sanitisation purposes, restricts water circulation accordingly. Where die water circulation requirement for filtration and sanitisation purposes has not been met, circulation is continued as required. No information is given as to recreational water jets normally incorporated into a spa and it is presumed that this is performed by a separate pumping system based upon a second pump and separate control system. In US 7,236,692, Tran teaches a spa heater system and an associated electronic control system. Said spa heater system incorporates a first water circulation circuit incorporating a pump and filtration and heating means and a second water circulation circuit incorporating a pump to provide a flow of water to recreational water jets. An algorithm is employed to control said heating means and to monitor current levels drawn by them. In US 6,476,363, Authier et ai teach a fire protection system for a spa and associated equipment. A separate water circulation circuit incorporates a heating element to heat the water body of said spa and a first pump to circulate water through said circuit. A water level sensor triggers a heating element deactivation device to electrically deactivate said heating element when the water level around the heating element falls outside a predetermined level. A second pump is employed to provide a supply a flow of water to recreational water jets in said spa. In US 6,145,139, Bonn teaches an improved swimming pool/spa water heating system whereby a portion of the water flow into a main heater unit is preheated, thereby decreasing the time of operation of the main, combustion-type heater unit to raise the pool water body to the desired temperature. The system improvement includes an arrangement wherein pool water is drawn from the pool by a water pump and a portion of the water flow is diverted through a supplementary heater unit located in the combustion exhaust stream of the main heating unit. The diverted water is thus preheated in the supplementary heater unit by the residual heal in the main heater unit exhaust and is then directed back into the water system at a point prior to the inlet of the main heater unit. In OS 5,932,127, Maddox teaches a spa in which the water body is maintained at a ready-to--use temperature by a daily heating cycle initiated by a filter cycle clock, which traditionally has been used only for programming the circulation of the spa water through a filter. Heating of said water body is achieved through the use of an electrical resistance heater. Once a daily heating cycle has been initiated, it normally concludes only when the temperature of the spa water reaches a desired temperature that has been pre-set into a thermostat. However, for safety, the heating cycle is terminated immediately in die event that the heater temperature becomes excessive, since this event could result from lack of water or inadequate circulation. It is apparently necessary for the single pump of said spa to be operated at normal power during said heating cycle, which is inefficient in terms of energy usage when said spa is not in use. In US 5,226,408, Drysdale teaches a method and apparatus for heating water in a spa having a plurality of venturi jets, a hosing which includes a plurality of venturi jets and a single dual-speed pump which circulates water through die housing and the venturi jets in the spa and a water thermostat. The thermostat is positioned in the water of the spa and connected to the high speed pump such that the high speed pump is activated to propel water through the venturi jets at high speed and thus heat it whenever the water temperature falls below a preset level. Said spa has no separate heating unit, as such, and heating of its water body is achieved by running said pump at high speed such that the venturi effect of forcing water through a small orifice at high pressure results in an increase in the temperature of the water. Said dual-speed pump is apparently operated at low speed to provide a flow of water to recreational water jets in said spa. It is likely that a low flow of water through an efficient water heater of conventional arrangement would prove a more energy efficient method of heating the water body of said spa. In US 5,585,025, Tdland teached the use of a spa control circuit for regulating a water circulation and heating system in a spa or hot tub or the like. The control circuit comprises a thermostat circuit and a high temperature limit circuit, both of which receive a temperature signal from a common temperature sensor. A safety circuit responds to sensor failure to prevent operation of the circulation/heating system. A latching relay ensures system reset in the same operational state following a power outage. An arc suppression circuit substantially prevents arc damage to relay contacts subjected to frequent opening and closing in response to on-off cycling of the thermostat circuit In a preferred font), the control circuit components are mounted within a compact housing having a heat transfer member in heat exchange relation with circulating spa water. whereby the spa water is used to prevent overheating of the control circuit components. Heat exchange means are coiled spirally about the casing of the pump motor of said spa, taking up heat from said motor and said control circuit components. Thus, heating of the water body of said spa can only occur during full-power operation of said pump, which is inefficient in terms of energy usage when said spa is not in use. Further, said pump may not be able to be operated when the temperature of said spa water body exceeds that required. Although not stated, obviously, a second water pump and water circuit may be provided at additional cost to supply a flow of water to recreational water jets in said spa. In US 5,526,538, Rainwater teaches the use of a water circulation and heating system for spas which exhibits low power consumption for continuous circulation of the spa water while avoiding air entrapment in the water beating unit and comprises a low speed water pump, and a heater that is configured so that water flows through it generally vertically. The low speed pump circulates spa water through the heater at a low flow rate that would cause air entrapment in the heater if it were configured so that water flowed through it horizontally. In a preferred embodiment, a high speed water pump is also provided for operating the spa’s high speed jets when the spa is in use. The low and high speed pumps preferably form part of an interconnected water circulation system, so that the water flow rate through the heater is increased when the high speed jet pump is activated. In US 6,976,052, Tompkins et al teach the use of an improved spa control system which calculates the time required to heat the water in a spa system to a desired temperature. From that information, the heating rate of the spa system can be determined, and the heating element of the spa system can be activated at the proper time to raise the temperature of the water to a selected temperature by a desired time. The spa system also monitors information which might show errors in the operation of the spa system such as a blockage in the flow of water over the heating element in the spa system. Said system is microprocessor-based and connected to a system interconnection panel which is, in turn, connected to a power input, to various sensors which detect parameters such as flow rate, temperature and pH of the water, and also to mechanical and electrical components of the spa, such as the pump, heater, blower, and lights. The heater may be interlocked to the pump so that the pump is continuously pumping water over the heating clement of the heater while the heater is activated. This prevents a "hot spot" from developing in the spa system which could damage the components of the spa or give erroneous measurements. Said pump is operated at low speed, causing water to pass through a filter and heater prior to flowing into said spa. Said pump is operated at high speed to produce a high speed flow of water through recreational jets in said spa. Where an increased water volume flow is required in a spa to operate additional jet combinations, it is common for additional pumps to be brought into operation. This is particularly so in spas having large numbers of jets in groups, the operation of which is required only selectively. An example is the Model LSX 1000 spa manufactured by Master Spas, Inc., 6927 Lincoln Parkway. Fort Wayne, IN. 46804, USA which has up to 115 jets in a variety of separately controllable combinations in seven seating positions. The jets are supplied with water by five separate pumps in the form of two dual-speed pumps and two single-speed pumps, with a separate circulation pump in continuous operation for filtration, ozonation, and heating purposes, as needed. The total power output of the pump motors, with all spa jets operating, is approximately 15.75 kilowatts. The seating positions of the Model LX 1000 have various numbers and arrangements of jets which are selectable and adjustable to provide a variety of effects.

Many of the spa systems in the cited prior art utilize two or more water circulation pumps. While this may provide some improvement in efficiency of energy useage, it adds considerably to cost. Where a single water circulation pump is employed, there is little opportunity to integrate all water circulation functions in a way which confers efficiency of energy useage. What is required Is a water circulation system for a spa in which all functions, including heating, filtration and sanitization and the working of recreational water jets are all accomplished through the use of a single pump in an. energy-efficient manner.

Hitherto, when additional water flow was required in order to bring into operation additional water jets, the options available were to operate more pumps or to increase the output flow of an already operating pump. The latter option was limited to removing an inhibition imposed upon the output of a pump through discharge throttling or recycling of flow, both of which are inefficient and wasteful of energy. Although the operating principle of variable speed centrifugal pumps has been known for some time, the adoption of this innovation for smaller systems, such as spas has been largely neglected. The reasons for this have been several: resistance to new technology, technical difficulties with matching pump output to large changes in system flow requirements; and a reputation for unreliability of electronic components. Suitably designed installations can now be made to have very low failure rates and the body of knowledge and design skills necessary to create systems with the flexibility to seamlessly accommodate a broad range of flow configurations is now available, A first object of the present invention is to provide a spa incorporating a water circulation system based upon a single variable-speed pump driven by an electric motor, said pump and motor combination being operable over a "wide RPM range with high energy efficiency. A second object of the present invention is to provide a spa incorporating a water circulation system based upon a single variable-speed pump operable over a wide RPM range to provide a continuous or intermittent, low flow of water for filtration and sanitisation purposes, a high flow of water for heating purposes, and a rapidly variable flow of water to various jet combinations incorporated into a plurality of spa seating stations. A third object of the present invention is to provide a spa incorporating a water circulation system based upon a single variable-speed pump which is operable over a wide RPM range and controlled by a microprocessor-based control unit to respond automatically to pre-set functional commands, to respond automatically to commands resulting from the occupation by users of spa seating positions and to respond to commands deliberately initiated by spa users through functional selections at control panels.

According to the present invention, a spa is provided in which a single centrifugal pump of suitable maximum flow characteristics is driven at variable speeds to provide the pressures and flow rates necessary to deliver all said spa functions. Said pump is driven by an electric motor able to operate in an energy-efficient way over an extended RPM range and capable of meeting the maximum power requirement of said pump. These requirements are best provided by a brushless, direct current, axial-flux electric motor employing electronic commutation. Said electric motor is controlled in accordance with a stored program run in a microprocessor-based control unit which determines, for a particular selected configuration, the commencement of operation of said pump, the RPM at which said pump is operated and the duration of operation. Filtration and sanitisation functions are pre-set into said control unit and are initiated automatically in relation to lapsed time and spa useage. Selections of particular spa configurations made by spa users provide signals to said control unit which responds by initiating all appropriate functions. Other signals are provided to said control unit by water or air pressure sensors, water or air flow sensors, water or air temperature sensors and occupation sensors which detect the occupation of spa seating positions, said control unit similarly initiating all appropriate functions- In addition to the operation of said pump, said functions include the opening or closing valves to control water and air flows to specific parts of said spa.

The various aspects of the present invention will be more readily understood by reference to the following description of preferred embodiments given in relation to the accompanying drawings in which:

Figure 1 is a schematic diagram of a spa and associated water circulation system made according to the present invention;

Figure 2 is a side view of two centrifugal pumps selectively powered by a single electric motor;

Figure 3 is a fragmentary transverse cross-sectional view of an impeller vane partially accommodated within a complementary slot of the moveable impeller shroud;

Figure 4 is a longitudinal cross-sectional view of a variable capacity, shrouded impeller, centrifugal pump.

With reference to Figure 1, a spa 1 is provided in which all of the various operational functions are controlled by a microprocessor-based control unit 40. In a typical form of said spa, four seating positions 2,3,4, 5 of more or less identical arrangement incorporate water distribution manifolds (not shown) which deliver flows of water to a plurality of nozzles (not shown) in each said seating position. Different said seating positions optionally have their said nozzles arranged in a variety of arrays, said nozzles emitting water jets which impinge upon the bodies of persons seated therein. Said water jets are optionally larger or smaller, steady or pulsed flow, aerated and^r heated. Water is drawn off from the water body of said spa by a single pump 16 via a small sump 19 and supply line 18. In the preferred embodiment, said pump is a centrifugal pump of suitable capacity driven by a brushless, direct current, axial-flux electric motor incorporating electronic commutation, said electric motor able to operate in an energy-efficient way over an extended RPM range and with a wide range of power outputs. In alternative embodiments, said electric motor takes the form of an interior permanent magnet synchronous motor or switched-reluctance motor or other similar electrical machine. Control signals to said electric motor are depicted as 22.

The output of said pump is delivered via first delivery line 15 to first diversion valve 14. Control signals to said first diversion valve are depicted as 23. During periods of non-use of said spa, said first diversion valve directs a small, continuous or timed flow of water to said spa via second delivery line 32 incorporating filter unit 33 and sanitisaiion unit 34 and thence via return line 9 to one or more discharge points 11 in said spa. Status signals transmitted from said filter unit and said sterilisation unit to said control unit are depicted as 27, 28. Between periods of use, the temperature of the water body of said spa is permitted to fall to ambient Prior to periods of use of said spa, either by manual selection of pre-set timer, a flow of water is directed via first diversion val ve 14 and second diversion valve 17. Control signals transmitted to said second diversion valve are depicted as 24. Said second diversion valve directs a high flow of water to said spa via third delivery line 7 incorporating heater unit 21 and thence via return line 9 to said discharge points. In the preferred embodiment, said heater unit is an efficient, high capacity gas-fired unit, with auto ignition and capable of being rapidly brought into service as required using remote control. Examples of suitable heater units are the Hurlcon JX and HX series of gas pool and spa heaters supplied by Red Baron Pool Supplies, of Lambion, NSW 2299 and the Raypak series of heaters. Models 127 to 430, supplied by Raypak Australia, of Scoresby, VIC 3179. Investigations have shown that, in comparison with maintaining a continuously elevated temperature of the water body of a spa, permitting said temperature to fall to ambient and then relatively rapidly raising said temperature to a comfortable level immediately prior to use is more energy efficient. For example, where the daily filtration and sarutisation water flow for a spa is 38,000 litres, energy useage may be reduced from 1,870 kilowatt hours to 800 kilowatt hours. At the same time, noise levels may be reduced from 72.8 dBa to 5S.2 dBa. Using a heater unit with a nominal output of 24 kW, the temperature of a 3,000 litre water body may be raised at the rate of 7 degrees C per hour. A heater unit with a nominal output of 42 kW is able to raise the temperature of the same body of water by 14 degrees per hour. Control signals transmitted to said heater unit are depicted as 25. Signals from water pressure or flow sensors associated with said heater unit and transmitted to said control unit are depicted as 26. In the preferred embodiment, said control unit prevents commencement of operation of said heater unit until full water flow is established through it and maintains Ml water flow through said heater unit for a pm-determined period after cessation of its operation. One or more sensors are provided in said spa, temperature related signals transmitted to said control unit being depicted as 29. When said spa is in use, said first diversion valve directs a high flow of water to said spa via fourth delivery line 13 and thence via fifth delivery line 12 and distribution manifolds 10 to individual seating position feeder lines 6. Remotely controllable control valves 8 regulate the water flow to said feeder lines. Control signals transmitted to said control valves are depicted as 20. The lengths and diameters of said delivery lines connecting said pump to said seating positions are designed to ensure equal pressure drops between said pump and all said seating positions. A flow of air from a suitable source is delivered to said seating position jets by separate means (not shown). In the preferred embodiment, said flow of air is supplied from a suitable pressurised source (not shown). In an alternative embodiment (not shown) separate heating means are provided in lines supplying said flow of air to said seating positions and in feeder lines 6.

Each said seating position has conveniently located to it a control panel 35 incorporating controls (not shown) used to regulate any of water jet energy, water jet temperature, aeration air temperature, aeration level of water or lighting, or selection of all or specific groups of nozzles in that seating position. Operation of said controls generates signals (depicted as 39) which are transmitted to said microprocessor-based control unit Sensors (not shown) provided in said seating positions detect the presence of a seated user and provide an occupancy signal (depicted as 41) which is transmitted to said control unit In the preferred embodiment said sensors take the form of suitable pressure pads incorporated into the surface of said seating positions. In alternative embodiments, said sensors take the form of light-dark sensors, force sensing resistors, piezo film sensors or the like, adapted for the purpose. Signals received by said control unit are depicted as 52 and signals transmitted from said control unit are depicted as 53. At times during which said spa is unoccupied, said pump operates at low RPM, generating a continuous flow of water in the range 40 to 250 litres per minute. Said flow passes via diversion valve 14 which directs flow via filter unit 33 and sanitisation unit 34 and thence via second delivery line 32 and return line 9 to said spa. Said water flow acts to cycle most of the body of water contained in said spa through said filtration and sanitisation units, thereby removing suspended and dissolved material and sterilizing biological organisms. Said filtration and sanitisation water flow is optionally manually selected or, in the preferred embodiment, is initiated by said control unit at pre-set intervals for pre-set durations. In an alternative embodiment, in addition to said pre-set filtration and sanitisation water flow, when occupants leave said spa and are terminating a period of use, said control unit initiates said filtration and sanitisation water flow for a period proportional to the period of spa use and, optionally, the number of users during that period. In the preferred embodiment, said filtration unit and said sterilisation unit take any of the forms commonly used with spas, swimming pools and the like and which are well known in the art In alternative embodiments (not shown), any function normally occurring on the delivery side of said pump, such as sterilization, filtration or the like, optionally occurs on the suction side of said pump.

Said control unit contains a stored program which covers all possible configurations and combinations of occupied seating position, water nozzle combinations, water jet energy, water temperature, air temperature and degree of water aeration. Upon receiving configuration signals from a particular occupied seating position, said control unit refers to a look-up table and determines, for the totality of occupied seating positions and their selected configurations, the commencement of operation and speed of operation of said pump, the opening or closing of diversion valves 14, 17 the opening or closing of solenoid valves S, the operation of heater unit 21, the operation of said separate heating means in lines supplying said flow of air to said seating positions and in feeder lines 6, the opening or closing of solenoid valves in said seating position water distribution manifolds and the opening or closing of valves to admit or interrupt said aeration airflow. Said opening or closing of said solenoid valves in said seating position water distribution manifolds is optionally employed to direct water to nozzles emitting water jets in steady flow or to nozzles from which pulsed water jets are emitted.

Because of the greater magnitude of the advantage available in larger installations, variable speed pumps have hitherto been ignored for smaller applications. Improvement in the technology, largely as a result of developments in relation to electric vehicles, now permits smaller pumps suitable for use in a spa to be operated over suitable RPM ranges. In the preferred embodiment, said water pump is a variable speed centrifugal pump of suitable capacity driven by a brushless, direct current, axial-flux electric motor incorporating electronic commutation, said electric motor being able to operate in an energy-efficient way over an extended RPM range and with a wide range of power outputs. In alternative embodiments, said electric motor takes the form of an interior permanent magnet synchronous motor, 3witched-rductaD.ce motor or other similar electrical machine. In common with other synchronous designs, such electric motors may suffer from conduction and magnetic losses and heat generation during high power operation. Rotor cooling is more difficult than with brushless direct-current motors and peak point efficiency is generally lower. Generally speaking, induction machines ate more difficult to control, the control laws being more complex and less amenable to modelling. Achieving stability over the entire torque-speed range and controlling temperature is more difficult than with brushless direct-current motors. In alternating current electric motors, pump speed is controlled by varying the frequency and voltage supplied to the drive motor. This provides a relatively constant ratio of voltage to frequency as required by the characteristics of the AC motor to generate torque. In closed-loop control, a change in process demand is compensated by a change in power and frequency supplied to the motor, thereby producing a change in motor speed. A typical brushless, direct current, axial-flux electric motor, having electromagnetic cods arranged in circular arrays with the centre distances of adjacent pairs subtending an angle of 30 degrees or less and incorporating electronic commutation, has a separate motor control system permitting arbitrary switching of any one of said electromagnetic coils independently of all other coils in a said array. Using pulse-width modulation, any excitation waveform may be generated and used to drive said coil. A wide variety of coil drive profiles can be employed for the real-time maximisation of efficiency and power output over a wide range of RPM and operating temperatures. The back EMF characteristics of said coils are optionally analysed during run time for a specific velocity, power requirement and operating temperature, and an optimal or near optimal wave generated using pulse-width modulation to, as far as is possible, maximise the efficiency of said electric motor. In the preferred embodiment, such analysis is performed automatically and on a continuous basis. Pre-computed or partially pre-computed waveform patterns are stored in a look-up table and are recalled when specific velocity, power requirement, operating temperature, or any combination of these, is detected. Said look-up tables are optionally optimised through the use of meta-heuristic algorithms, evolutionary algorithms, traditional, deterministic algorithms or any other suitable optimisation technique.

Said optimisation techniques confer a high level of flow flexibility and a high level of energy efficiency. In a suitable electric motor and pump combination, water flow may be reduced to as low as 50 litres per minute and increased to in excess of 1,000 litres per minute.

With reference to Figure 2, in order to make use of the fact that axial flux electric motors are fully reversible, electric motor 30 is made with common shaft 31 extending to both sides. A first, smaller centrifugal pump 36 is connected to one end of said shaft and a second, larger centrifugal pump 37 is connected to the other end of said shaft. Said pumps are driven in opposite senses respectively through freewheel clutches 47,48. In the preferred embodiment, said freewheel clutches take the form of wedge-ramp-type overrunning clutches. Said electric motor and said pumps are fixed by suitable flanges 49, 50, 51 to supporting surface 38. Inlet flange 44 of said first pump is connected to a branch of supply line 18 and its outlet flange 44 is connected directly to second delivery line 32 and diversion valve 17 is deleted. Inlet flange 46 of said second pump is connected to a branch of supply line 18 and its outlet flange 46 is connected to delivery line 15. Where said spa requires said low water volume flow for filtration and sanitization purposes, said control system operates said electric motor in the appropriate rotational sense to drive said first pump al optimal speed. Where said spa requires said high water volume flow for beating purposes or supplying water to said jets, said control, system operates said electric motor in the opposite rotational sense to drive said second pump at optimal speed. In this way, water flow rates may be more precisely matched to pump characteristics. In an alternative embodiment, said freewheel clutches are replaced by electromagnetic clutches and said pumps are arranged to run in a common rotational sense, with either or both said pumps being operated, as required.

In an alternative embodiment (not shown), a system for the heating of water of the type taught by Griggs in US 5,385,298 is operated in conjunction with one or both said pumps. Said system generates a heating effect by causing severe turbulence of water within the cavity of a housing through rotation of a rotor closely received within said housing, the surface of said rotor being provided with a plurality of uniformly-spaced recesses oriented at a selected angle to said surface, and said rotor being supported on a shaft journalled in bearing assemblies and seal units at end walls of said housing.

In an alternative embodiment, diversion valve 17 is a proportional flow valve which maintains a reduced flow of water through said heater unit via third delivery line 7 while said jets are being supplied with water via fifth delivery line 12.

With reference to Figures 3 and 4, in an alternative embodiment, a said pump takes the form of a variable capacity, shrouded impeller, centrifugal pump. In this embodiment, the pump impeller comprises fixed shroud 58 and moving shroud 62. Said fixed shroud is rigidly connected to boss 56 by a plurality of vanes 57, in the preferred embodiment, said boss, vanes and fixed shroud being made in a single piece. Said vanes are shaped in radially-disposed volute curves, in the form well known in the art. Said moving shroud has formed on its outer face a plurality of generally radially arranged mouldings 74, each of which encloses a channel 73 open to the inner face of said shroud, each said channel being complementary to and able to closely accommodates a said vane for a substantial part of its axial depth. Boss 56 is fixed to shaft 55 which is rotationally supported in bearing and seal combination 65. The bearings of said bearing and seal combination act to locate and restrain said shaft in an axial seme. The bearings and sealing means of said bearing and seal combination take any of the forms well known in the art and they' are not depicted or described. The engagement of said vanes with said channels of said moving shroud cause said moving shroud to rotate in unison with said fixed shroud. Inlet housing 59 has inlet duct 76 formed on it, attachment flange 77 being formed on the outer end of said inlet duct. Annular recess 83 is formed m said inlet housing to accommodate forwardly projecting part 82 of fixed shroud 58. In the preferred embodiment, the forwardly projecting, free edges 84 of said vanes are deflected in the direction of motion, of said impeller, in the manner well known in the art, to provide more efficient entry flow to said impeller. In the preferred embodiment, a suitable seal (not shown) is provided at point 79 to seal said inlet housing to the outer surface of forwardly projecting part 82. Rear housing 60 meets and is joined to said inlet housing at annular plenum 75, a tangential outlet from said plenum (not shown) having attachment flange 78 formed on its outer end. The outer end parts 61 of mouldings 74 are covered by a circular plate 64 offering a flat surface to any water accumulating in space 81 between said circular plate and the inner surface of rear housing 60, thereby providing lower drag characteristics. Bearing housing 66 is formed on the outer surface of said rear housing and hydraulic cylinder 68 is rotationaliy supported in said bearing housing in bearing and seal combination 67. The bearings of said bearing and seal combination act to locate and restrain said cylinder in an axial sense and the sealing means of said bearing and seal combination act to prevent egress of water from space 81. Said bearings and sealing means take any of the forms well known in the art and they are not depicted or described. Said moving shroud is supported on sleeve 69 which is slidingly supported on shaft 55. The outer end part of said sleeve is formed into a piston which is sealingly and slidingly accommodated within the bore of cylinder 68. In the preferred embodiment, that part of said sleeve between said piston and said moving shroud is provided with splines or similar· shaped engagement surfaces (not shown) which engage complementary engagement surfaces at the mouth of said bore of said cylinder. Said engagement surfaces act to prevent differential rotary motion between sleeve 69 and said cylinder. Suitable seals (not shown) are provided on said piston or in the bore of said cylinder to prevent egress of hydraulic fluid from said cylinder. Suitable seals (not shown) are provided between said sleeve and said shaft to prevent the ingress of water from said impeller zone to said hydraulic cylinder. In the preferred embodiment, said fixed shroud is closed by circumferential flange 63 and a screw-back seal (not shown) is provided on the outer surface of said circumferential flange to minimise the ingress of water to space 81 via the clearance between the outer surface of said circumferential flange and the inner surface of said rear housing at point 80. Swivel joint 70 is rotationally fixed to the free end of said shaft and pressurised hydraulic fluid entering via inlet duct 71 passes via gallery' 72 formed in the end of said shaft to pressurise the interior of said cylinder. Said pressurisation of said cylinder acts to displace said piston and, thereby, said moveable shroud forwardly on said shaft such that said vanes enter channels 73 more deeply, thereby reducing the volume of the radially arranged space between said fixed and moving shrouds. Further, said deeper accommodation of said vanes within said channels effectively reduces the amount of work which said vanes may do upon water passing between said shrouds, the net effect thereby being to reduce the flow capacity of said pump. Said pressurised hydraulic fluid is supplied to inlet duct 71 by suitable pump via control valve means. In an alternative embodiment (not shown), sleeve 69 is axially displaced as required by suitable mechanical means operated by a small electric motor supplied with electric current via a suitable slip-ring and brush arrangement. Said swivel joint takes any of the forms well known in the art and its bearing and sealing arrangements are not depicted or described. When an increase in the flow capacity of said pump is required, hydraulic fluid is bled off from said hydraulic cylinder and water pressure generated between said fixed and moveable shrouds by dynamic forces acts to displace said moveable shroud rearwardly. In operation, said control unit refers to a look-up table and determines, for the totality of occupied seating positions and their selected configurations, the commencement of operation and speed of operation of said pump, the opening or closing of diversion valves 14, 17 the opening or closing of solenoid valves 8, the operation of heater unit 21, the operation of said separate heating means in lines supplying said flow of air to said seating positions and in feeder lines 6, the opening or closing of solenoid valves in said seating position water distribution manifolds and the opening or closing of valves to admit or interrupt said aeration airflow. Said control unit also determines the most efficient flow characteristics of said pump and adjusts them in the maimer described.

In an alternative embodiment (not shown), photovoltaic panels of suitable output are provided which optionally provide a supply of electric current to resistance heating means in third delivery line 7 or deliver their current output to the mains supply. In the preferred embodiment, provision is made to manually select on said control panel for the output of said photovoltaic panels to be automatically supplied to said resistance heating means whenever the output of said panels is sufficient or to be delivered to the main supply. Whenever the output of said photovoltaic panel is supplied to said resistance heating means, provision is made to lock other said beating means out of operation. Provision is also made to ensure that water is circulating past said resistance heating means before power is supplied to them. In the preferred embodiment, control signals are transmitted from said control panel to the control means of said photovoltaic panels via a Bluetooth connection or other radio-frequency means,

In another alternative embodiment (not shown), the downstream flow from said heater unit is optionally supplied to discharge points 11 in said spa or to fifth delivery line 12 to supply a flow of heated wafer to said jets. In this embodiment, a proportional diversion valve is preferably employed to direct said water flow as required.

The use of a single variable-speed pump operable in an energy-efficient way over a wide RPM range permits pump output to be precisely and almost instantaneously matched to the water flow7 requirements of a spa. As a result, it provides the greatest operational flexibility of spa operation, reduces electrical power consumption, reduces noise and reduces pump costs when compared with the use of fixed-speed or stepped-speed pumps.

The scope of the present invention should be taken to include any possible combination of any disclosed feature or features with any other disclosed feature or features.

Claims (19)

1. A water circulation system for a spa based upon the use of one or more centrifugal pumps close-coupled, singly or jointly, to a single electric motor, said electric motor being a brushless, direct current, axial-flux motor employing electronic commutation, said motor being under the control of a microprocessor-based control unit and capable of operation in an energy-efficient way over mi extended RPM range with a wide range of power outputs.

2. The water circulation system of Claim 1 in which said electric motor incorporates electromagnetic coils in circular arrays with the centre distances of adjacent pairs subtending an angle of 30 degrees or less.

3. The water circulation system of Claim 2 in which said electric motor has a separate control system permitting arbitrary switching of any one of said electromagnetic coils independently of all other coils in a said array.

4. The water circulation system of Claim 1 in which said electric motor is controlled using pulse-width modulation with a range of excitation waveforms.

5. The water circulation system of Claims 1 and 4 in which, to optimise energy efficiency and power output, the back EMF characteristics of the coil arrays of said electric motor are analysed automatically and on a continuous basis and an optimal or near optimal wave form generated for a specific rotational velocity, power and operating temperature,

6. The water circulation system of Claim 5 in which said precomputed or partially pre-computed waveform patterns are stored in a look-up table in said control unit and are recalled when any particular combination of rotational velocity, power, operating temperature or combination of them is detected,

7. The water circulation system of Claim 6 in which said look-up tables are optimised through the use of meta-hcuristic algorithms, evolutionary algorithms, traditional deterministic algorithms or other suitable optimisation technique.

S. The water circulation system of Claim 1 in which water flow may be reduced to as low as 50 litres per minute and increased to in excess of 1,000 litres per minute while maintaining a high level of energy efficiency.

9* The water circulation system of Claim 1 in which said electric motor is made reversible with a common shaft extending to both sides, a first, smaller centrifugal pump being connected to one end of said shaft and a second, larger centrifugal pump being connected to the other end of said shaft, said pumps being operable in opposing senses via freewheel clutches, the arrangement better enabling the high and low-volume water flow requirements of said circulation system to be delivered through the operation of a single electric motor.

10. The water circulation system of Claim 9 in which said freewheel clutches take the form of wedge-ramp-type overrunning clutches.

11. The water circulation system of Claim 9 in which said freewheel clutches are replaced by electromagnetic clutches, said pumps being jointly or separately operable in a common rotational sense as required to meet flow needs of said system.

12. The water circulation system of Claim 1 in which water heating means generate their effect by causing severe turbulence within die cavity of a housing through rotation of a rotor closely received within said housing, the surface of said rotor being provided with a plurality of uniformly-spaced recesses oriented at a selected angle to said surface, and said rotor being supported on a shaft journalled in bearing assemblies and seal units at end walls of said housing.

13. The water circulation system of Claim 1 in which a proportional flow control valve is employed to maintain a minor flow of water through water heating means while a larger flow of water is supplied to water jets of a spa

14. The water circulation system of Claim 1 in which a said pump takes the form of a variable capacity, shrouded impeller, centrifugal pump, the impeller of said pump comprising fixed and moving shrouds; said fixed shroud being rigidly connected to a boss fixed to the shaft of said impeller by a plurality of radially-disposed, volute-curve vanes; said moving shroud being having formed on its outer face a plurality of generally radially arranged mouldings, each of which encloses a channel open to the inner face of said shroud, each said channel being complementary to and able to closely accommodate a said vane for a substantial part of its axial depth, engagement of said vanes with said channels naming said moving shroud to rotate in unison with said fixed shroud; said moving shroud being supported on a sleeve slidingly supported on said impeller shaft, means being provided to axially displace said sleeve and, thereby, to displace said moveable shroud on said shaft such that said vanes enter said channels to a greater or lesser depth, with the effect of reducing or increasing the volume of the radially arranged space between said fixed and moving shrouds; said change in the volume of the radially arranged space between said shrouds effectively changing the amount of work which said vanes may do upon water passing between said shrouds and, thereby, reduce or increasing the flow capacity of said pump.

15. The water circulation system of Claims 1 and 14 in which said control unit refers to a look-up table and determines, for the totality of occupied seating positions and their selected configurations, the most efficient flow characteristics of said pump and adjusts the position of said moving shroud in the manner described to achieve said efficient flow characteristics.

16. The water circulation system of Claim 1 in which, a said electric motor takes the form of an interior permanent magnet synchronous motor, switched-reluctance motor or other similar synchronous electrical machine.

17. The water circulation system of Claim 1 in which a said electric motor is an alternating current motor in which pomp speed is controlled by variation of the frequency and voltage supplied to said drive motor.

18. The water circulation system of Claim 1 in which the temperature of water in a spa is permitted to fall to ambient during periods of non-use of said spa.

19. The water circulation system of Claim 1 in which the water temperature of a spa is raised rapidly when said spa is required for use, a water circulation rate of at least 30 per cent of total volume per minute and a heating capacity in the range 8 to 14 kilowatts per 1,000 litres of total capacity being employed for the purpose.