AU2015249060A1 - Swim Spa With Efficient Water Circulation System - Google Patents

Abstract

A water circulation system for a swim spa or swim-in-place swimming pool comprising: a vertical discharge trunk; one or more inlet trunks connected to the base of said discharge trunk; a discharge section 5 formed at the upper end of said discharge trunk to receive a flow of water from said discharge trunk; one or more discharge apertures formed at the outlet of said discharge section; an impeller shaft driven by an electric motor and arranged coaxially with said discharge trunk; one or more axial-flow impellers driven by said impeller shaft, said 10 impellers being situated more or less level with the base of said swim spa or swim-in-place swimming pool and acting to accelerate the flow of water from said inlet trunks; flow straighteners to ensure the maintenance of an orderly, streamline flow in the zone downstream of said impellers and guide vanes in zones of directional change. Sheet 5 of 8 .- -o

Description

2015249060 26 Oct 2015

ORIGINAL

Australia

Patents Act 1990

Complete Specification for the Invention Entitled SWIM SPA WITH EFFICIENT WATER CIRCULATION SYSTEM

The invention is described in the following statement: 2 2015249060 26 Oct 2015

SWIM SPA WITH EFFICIENT WATER CIRCULATION SYSTEM

This invention relates to methods and apparatus employed to create sustained horizontal water flows or currents in swim spas or swim-in-place swimming pools. In particular, it relates to such methods and 5 apparatus which incorporate means to provide an efficient system of water circulation.

Swimming has long been recognised as an excellent form of exercise and is commonly included in many physical fitness programmes. However, for the urban dweller not having a swimming pool or ready 10 access to one, swimming is often neglected due to inconvenience and time constraints. To render swimming more attractive as a form of exercise for the urban dweller, the swim spa or swim-in-place swimming pool has been developed. Swim spas or swim-in-place swimming pools are compact and readily accommodated in the home, whether house or 15 apartment. In the swim spa or swim-in-place swimming pool, suitable means, including water jets and propellers, situated at the head of the pool act to generate a sustained circulation of water in which a current flows rearwardly along the upper levels of the pool to descend at the foot and pass back along the lower levels of the pool to return to the head. A 2 0 swimmer swims in the upper level current, the velocity of flow of which is adjusted as required to maintain the swimmer positioned within a swimming zone of the pool at the swimming speed selected. Provision is normally made to increase or decrease the velocity of flow of the current, by increasing or decreasing pump output, by decreasing or increasing the 3 2015249060 26 Oct 2015 size of the orifices through which said jets of water are discharged, or by increasing or decreasing the rate of working of propellers, where they are used.

In addition to the simple, linear circulating flow described above, 5 Lior teaches in US 4,845,787 and 5,315,720 a form of circular swim-inplace pool in which the pool proper is enclosed within a concentric channel. Vanes rotating within the concentric channel cause a continuous circulation of water, the circulation being led through suitable openings at the head and foot of said pool proper to provide a circulation therethrough. 10 The arrangement taught by Lior is mechanically complex, is costly to manufacture and install and imposes a substantial maintenance requirement. For the purpose of generating a linear water circulation in a swim-in-place pool, the use of submerged propellers is well known. Two examples are those taught by Weihe et al in US 5,298,003 and Shannon in 15 US 5,662,558. The Michael Phelps Signature Swim Spas manufactured by Master Spas of Fort Wayne, Indiana, USA utilise what is described as the Wave Propulsion™ Technology Propulsion System. From images and information provided in the promotional material of Master Spas, water is drawn in through two laterally-located grilles in the head wall of a 20 swim spa and passed via an external conduit to a centrally-located propeller to generate a flow of water which is discharged through a grille into the swim spa In the cited prior art, a submerged, power-driven propeller is located at the head of a pool, operation of the propeller resulting in a strong current of water. The propeller is enclosed within a 4 2015249060 26 Oct 2015 suitable enclosure or housing which, where propellers are situated within a pool, acts to protect swimmers from contact with the propeller blades. The housing is optionally provided with vanes which prevent cavitation and ensure that the flow of water from the propeller is substantially 5 laminar. The shortcomings of these arrangements are several. When located within a pool, they are unsightly, they unnecessarily occupy space within the pool, and their discharge flow is localised and more or less fixed. Location of the propeller at a relatively shallow water depth may lead to the development of cavitation if the propeller is driven at high 10 rotational speed. Many forms exist of adjustable water jets for use in spas and pools, examples being those taught by Moreland et al in US 4,671,463, Henkin et al in US 4,731,887 and 4,813,086, Howard in US 5,095,558, Spears et al in US 5,269,029, Leaverton et al in US 5,495,627, Dongo in US 5,915,849 and Buck in US6,691,336. Most of these are 15 similar in arrangement and comprise, variously, a discharge nozzle which is adjustable for direction, a rotor to provide a pulsing or intermittent flow and means to control influent air and water streams. The principal shortcomings of these water jets are that they are mechanically complex, are therefore costly to manufacture and are not adaptable to remote 2 0 adjustment. More importantly, they are poorly adapted for use as means to generate a large-scale water current. In all prior art, little attention is directed towards maximisation of water flow efficiency and efficient use of electrical energy.

The object of the present invention is to provide a swim spa or 5 2015249060 26 Oct 2015 swim-in-place swimming pool in which the speed of the swimming current is readily regulated via variation of the pumped, circulating water flow, a high level of efficiency of the pumped water flow and electric motor function being maintained throughout all phases of operation, 5 thereby minimising energy requirements.

According to the present invention, in a swim spa or swim-in-place swimming pool, water is drawn off via one or more deeply-located offtake openings, accelerated through one or more deeply-located, axial-flow impellers and discharged through one or more discharge apertures located 10 in one end wall. Water is discharged from said discharge apertures along the axis of said swim spa or pool in coherent, parallel streams of suitable width at a suitable depth below water level in order to generate and maintain a sustained swimming current for a swimmer to swim through. Attention is given to ensuring the maintenance of an efficient flow of 15 water by ensuring that all directional and cross-sectional changes in the area between said off-take openings and said discharge apertures are made in a properly graduated way. Where unacceptably sharp directional and cross-sectional shape changes are necessary, flow straighteners are provided downstream of said impellers and suitable guide vanes are 20 provided to ensure the maintenance of a more or less even flow distribution. Attention is given to ensuring efficient operation of electric motors driving said impellers during all phases of operation of said swim spa or pool. Provision is optionally made to heat and aerate the flow of water discharged from said discharge apertures. A secondary flow of 6 2015249060 26 Oct 2015 water drawn off from the swim spa or pool by means of a secondary pump is filtered and/or heated and/or sanitised in the conventional way and returned to said swim spa or pool. While said swimming current is sustained, a continuous water circulation passes along the upper levels of 5 the swim spa or pool, descending at the foot of the pool and returning along the lower levels of the swim spa or pool to said intakes. The speed of said swimming current is regulated by controlling the output of the pumps with provision made to effect such control remotely.

The various aspects of the present invention will be more readily 10 understood by reference to the following description of preferred embodiments given in relation to the accompanying drawings in which:

Figure 1 is an exploded, partial view of an embodiment of the present invention;

Figure 2 is an isometric view of a tee piece forming part of 15 the water circulation means of the present invention;

Figure 3 is an isometric view of a combination flow straightener and bearing support, and an impeller shroud of the present invention;

Figure 4 is a partial, longitudinally-sectioned, anterior view 2 0 of the embodiment of the present invention depicted in Figure 1;

Figure 5 is a partial, longitudinally-sectioned, posterior view of the embodiment of the present invention depicted in Figure 1;

Figure 6 is a side view of certain internal components of 2015249060 26 Oct 2015 7 the embodiment of the present invention depicted in Figure 1;

Figure 7 is a longitudinal cross-sectional view of the components of Figure 6;

Figure 8 is a diagrammatic, partial, longitudinally-5 sectioned view of the impeller and flow straightener of a typical axial impeller pump;

Figure 9 is an end view of a swim spa incorporating an embodiment of the present invention;

Figure 10 is a longitudinal cross-sectional view of the 10 impeller compartment and associated structure of an embodiment of the present invention;

Figure 11 is a longitudinal cross-sectional view of means to connect an embodiment of the present invention to water circulation means; 15 Figure 12 is a longitudinal cross-sectional view of a swim spa incorporating an embodiment of the present invention;

Figure 13 is an end view of a swim spa incorporating the embodiment of the present invention depicted in Figure 12;

Figures 14a to 14d are transverse cross-sectional views of 2 0 water ducts of the embodiment of the present invention depicted in

Figures 12 and 13.

No inference should be taken from the fact that the various figures are drawn to differing scales. 8 2015249060 26 Oct 2015

With reference to Figures 9 and 12, a swim spa or swim-in-place swimming pool 1 comprising head wall 2, foot wall 3, side walls 4, 5 and floor 6 is substantially filled with water 15. In the preferred embodiment, said swim spa or pool is surrounded by a more or less horizontal coping 5 panel 7. Water drawn off from said swim-spa or pool via one or more deeply-located off-take openings 8 is conducted via inlet trunks 9 to one or more axial-flow impellers 10 where it is accelerated and conveyed via discharge trunk 11 to discharge apertures 12 located in said head wall. Water is discharged from said discharge apertures along the axis of said 10 swim spa or pool in coherent, parallel streams of suitable width at a suitable depth below the water surface 14 in order to generate and maintain a sustained swimming current for a swimmer to swim through. Attention is given to ensuring that all directional and cross-sectional changes in the area between said off-take openings and said discharge 15 apertures are made in a properly graduated way, Where unacceptably sharp directional and cross-sectional shape changes are necessary, flow straighteners 13 are provided downstream of said impellers and suitable guide vanes (depicted as 47 in Figure 1 and 66 to 70 in Figure 13) are provided to ensure the maintenance of a more or less even flow 2 0 distribution. In the preferred embodiment, changes in the cross-sectional area of said discharge trunk are limited to 15% per unit length, a unit length being taken as the original diameter of said discharge trunk. Attention is given to ensuring efficient operation of electric motors 15 driving said impellers during all phases of operation of said swim spa or 9 2015249060 26 Oct 2015 pool. Provision is optionally made to heat or aerate the flow of water discharged from said discharge apertures. While said swimming current is sustained, a continuous water circulation 16 passes along the upper levels of the swim spa or pool, descending at the foot of the pool and returning 5 along the lower levels of the swim spa or pool to said off-take openings.

The speed of said swimming current is regulated by controlling the output of the pumps with provision made to effect such control remotely. In the preferred embodiment, said off-take openings and said pump impellers are located as deeply as possible in said swim spa or pool to minimise the 10 possibility of cavitation. As depicted in the figures, said take-off openings are optionally located in the floor of said swim spa or pool or at the lower edges of the side walls and are covered by suitable grilles to prevent ingestion of articles likely to choke or damage said axial-flow impellers.

With addition reference to Figures 1 to 7, in a first preferred 15 embodiment, discharge trunk 11 is made in two parts divided along the longitudinal centreline, said parts being sealingly fixed together at flanges 17 using a plurality of suitable fasteners (not shown). Said discharge trunk is optionally moulded from a suitable polymer material or cast from a suitable metal alloy material. At the upper end of said discharge trunk, the 2 0 circular internal cross-sectional shape transitions to a discharge section 53 of more or less fan-shaped plan form with a rectangular transverse cross-sectional shape, said discharge section terminating in discharge aperture 49. The cross-sectional area of said discharge aperture is reduced as required to further accelerate the water flow. Said discharge section 10 2015249060 26 Oct 2015 terminates at its outer end in attachment flange 48 which is sealingly fixed over a suitable aperture in said swim spa or pool head wall using a plurality of suitable fasteners (not shown). Said discharge section is provided with a plurality of suitable guide vanes 47, the ends of which are 5 captured in complementary recesses in the side walls of said discharge section during assembly of the two parts of said discharge trunks. The relative spacing 49 of said guide vanes is adjusted to ensure a uniform flow of water throughout the whole area of said discharge aperture. Said discharge trunk is made with an integral upper part 27 which is filled by 10 plug 18, a curved lower face 42 of said plug, in opposition to a curved transitional surface 43 between said discharge trunk circular internal cross-sectional shape and the inner floor of said fan-shaped discharge section, acting to create a throat which efficiently carries the flow of water through the directional change with a minimum of shearing and disturbance. The 15 upper surface of said plug is expanded to create circumferential flange 29 which is sealingly fixed to flange 28 formed on the upper edge of said discharge trunk upper part using a plurality of suitable fastenings (not shown).

Impeller shaft 22 passes collinearly through said discharge trunk, 20 accommodated coaxially within support tube 23. The upper end of said support tube is fixed in bore 30 of plug 18, said support tube supporting flow straightener 13 by its lower end being fixed in bore 32 of said flow straightener. Said flow straightener is provided with a plurality of radially-arranged vanes 61 which act to correct the spiral discharge of water from 11 2015249060 26 Oct 2015 said impeller into more or less streamline flow. In the preferred embodiment, the thickness of the cylindrical outer wall of said flow straightener is neatly accommodated within a recessed area of said discharge trunk such that its lower edge provides no impediment to the 5 flow of water from said impeller. In an alternative embodiment (not shown), in order to more positively locate said flow straightener within said discharge trunk, three or more grub screws are screwed through threaded bosses (not shown) in said discharge trunk to engage a circumferential groove or discrete recesses in said outer wall of said flow 10 straightener. Impeller shroud 34 is optionally made integral with the outer wall of said flow straightener or, as depicted in Figure 3, is made separately and accommodated within said discharge trunk upstream of said flow straightener immediately adjacent said impeller, said shroud acting to prevent erosion or ablation of the inner wall surface of said discharge 15 trunk. In the preferred embodiment, said impeller shroud is made split and is installed by elastically partially collapsing it and then allowing it to spring out into place into recessed area 55 of said discharge trunk. Shaft 22 is rotationally supported at its upper end in suitable bearing 60 accommodated within housing 25 which is, in turn, accommodated within 2 0 recess 26 formed in the upper part of plug 18. In the embodiment depicted in Figures 1 to 7, the lower end of said shaft is rotationally supported in water-lubricated bearing 33 accommodated within said flow straightener. Suitable lubricating water ingress apertures 24 are provided in said support tube. In the embodiment depicted in Figure 12, said shaft is rotationally 12 2015249060 26 Oct 2015 supported in water-lubricated bearing 50 supported in bearing housing 51 formed in the floor of inlet trunk 9. Said water-lubricated bearings are of the well-known type typified by those manufactured by Dynamax Industrial Products, of Hiram, Ohio, USA. Driven pulley 19 is secured to 5 the threaded upper end 56 of said shaft by nut 31 and connected by belt 21 to driving pulley 20 of electric motor 15. Said electric motor is supported from the head wall of said swim spa or pool by suitable support means (not shown) and is controllable in speed to vary the rate of flow from said impeller and, thereby, the velocity of flow of water discharged from said 10 discharge aperture. In the embodiment depicted in Figure 12, shaft 22 extends out upwardly through sealed tube 44, said tube being supported by integral sturdy fins 45 fixed to said discharge trunk.

Impeller boss 40 is secured to the threaded lower end 57 of said shaft by nut 58. The blades of said impeller are able to take a variety of 15 configurations and have been deleted from said impeller boss for clarity of illustration. Said impeller boss is optionally made more or less solid, as depicted in Figure 12, or hollow and closed with a removable, streamlined cap 59, ;is depicted in Figure 7. In the preferred embodiment, where accessibility is possible, removable drainage plugs 52 are provided in the 2 0 lowest parts of said inlet trunks to facilitate removal of sediment or small articles accumulating in said trunks.

The flow of water from said swim spa or pool passes via inlet trunks 9 to tee piece 35. Flange 37 formed around the central opening 41 of said tee piece is sealingly fixed to flange 36 formed on the lower edge 13 2015249060 26 Oct 2015 of said discharge trunk using a plurality of suitable fastenings (not shown). The opposed ends 38 of said tee piece are optionally made in several forms, including female sockets, as depicted in Figures 2, 4 and 5, and compression fittings, as depicted in Figures 9 and 11. 5 With additional reference to Figures 13 to 14d, in an alternative embodiment, said discharge trunk is expanded out to form a more or less fan-shaped discharge section 39 commencing from a point immediately downstream of said impeller, the cross-sectional shapes of said discharge trunk and said discharge section at planes 62, 63, 64, 65 being shown, 10 respectively as figures 14a, 14b, 14c, 14d. Because of the rapid expansion in width of fan-shaped discharge section 46, a plurality of guide vanes (positions indicated in broken line as 66, 67, 68, 69, 70) are provided within said discharge section to ensure a uniform flow of water throughout the whole area of said discharge aperture. The relative positions of the 15 upstream ends of said guide vanes are adjusted to ensure said uniform water flow. The small depth of said discharge section obviates the need for horizontal guide vanes of the type depicted in Figure 1.

With additional reference to Figure 9, in an alternative embodiment, said impeller and flow straightener are accommodated 20 within a separate cylindrical compartment 71, the upper and lower edges 73, 74 of which are formed into flanges, said flanges being sealingly fixed, respectively, to flange 36 of said discharge trunk and flange 37 of said tee piece. In the preferred embodiment, all said flanges are urged into sealing cooperation by a plurality of long bolts (positions indicated in broken line 14 2015249060 26 Oct 2015 as 76) passing through all. Where a said swim spa or pool is set into the ground, said tee piece, said cylindrical compartment, said discharge trunk, said discharge section and said electric motor are accommodated in a suitable pit 72 positioned at the head end of said swim spa or pool, the 5 area outside said pit, including part of said inlet trunks, being buried (buried area indicated by hatching 75). Feet 54 of said tee piece are secured to a supporting surface by suitable fastenings (not shown).

With additional reference to Figure 11, an inlet trunk 9 is sealingly connected to tee piece 35 by urging of the flat face of a tapered collar 79 10 formed on the end of said trunk into sealing cooperation with the flat face of a complementary tapered collar 77 formed on the end of said tee piece by means of the tightening (and, thereby, the contraction) of a tapered clamping band 90, suitable elastically-compliant sealing means 78 being compressed between said flat faces. Said sealing means are optionally 15 partially accommodated in a circumferential groove or channel formed in one or other of said flat faces. In the preferred embodiment, said clamping band incorporates one or more elongated, axially-extending straps 80, each being provided with a longitudinally-arranged slot. Slidingly accommodated within each said slot is a peg 83 fixed to a band 82 tightly 2 0 clamped around said tee piece end. Said slotted strap and peg arrangement acts to locate said tapered collar circumferentially while permitting it to be loosened and withdrawn from said tapered collars, permitting said inlet trunk to be separated from said tee piece end. Where said inlet trunk is partially buried, means (not shown) are provided in the exposed part of 15 2015249060 26 Oct 2015 said trunk to permit a small degree of elastic compliance, such that said flat face of said tapered collar on the end of said trunk is able to be drawn into contact with said flat face of said complementary tapered collar on said tee piece end. In the preferred embodiment, said compliance means 5 take the form of a deeply corrugated section or of a short insert of a suitable elastomeric material.

With additional reference to Figure 10, said impeller and said flow straightener are accommodated within a cylindrical compartment 84 accommodated within the lower part of said discharge trunk. Flange 92 10 formed on the lower end of said compartment is sandwiched between flange 36 formed on the lower end of said discharge trunk and flange 37 formed around opening 41 of said tee piece, said flanges being maintained in sealing cooperation by a plurality of suitable fasteners (positions indicated in broken line as 85). Depending upon the internal diameter of 15 the lower end of said discharge trunk, an annular void 91 may exist between it and said cylindrical compartment. In the preferred embodiment, a sealing band 86 made from a suitable elastomeric material is accommodated within a groove in said discharge trunk adjacent the upper end of said cylindrical compartment, said band acting to locate said 20 cylindrical compartment and to seal it to said discharge trunk. If necessary, the external thickness of said discharge trunk is increased in a circumferential band 93 adjacent said groove. Also in the preferred embodiment, a suitably-located, tapered shoulder 88 is provided in the internal surface of said discharge trunk, said shoulder being engaged by 16 2015249060 26 Oct 2015 the complementary tapered upper edge 87 of said cylindrical compartment, said engagement acting to positively locate the upper end of said cylindrical compartment. A small degree of protrusion of the inner, upper edge 89 of said cylindrical compartment is acceptable, causing little 5 disturbance of the flow of water over it.

With reference to Figure 8, a typical axial flow impeller comprises hub 103 supporting a plurality of blades 97, said impeller turned by a shaft (not shown) passing through guide tube 95. Said guide tube is supported from duct 94 by a plurality of blades 96 of a flow straightener. The 10 arrangement depicted is broadly representative of those incorporated into the embodiments depicted in Figures 1, 2, 3, 6, 7, 12. In operation, the gross inflow of water to said impeller may be represented by vector 98, while the effect of rotation of said impeller may be represented by vector 99, the resultant vector 100 representing the actual inflow of water to said 15 impeller blades at a small angle of attack. Vector 101 represents the spiral motion of the flow of water downstream of said impeller, vector 102 representing the corrected (straightened), streamline, axial flow downstream of said flow straightener. The use of one or more axial flow pumps is suitable for the swim spa or pool application because of the 2 0 ability of this type of pump to efficiently move large volumes of water at low heads. In combination with efficient duct design, the embodiment permits the movement of the greatest volume of water with the least expenditure of energy. In an alternative embodiment (not shown), in order to match the operational characteristics of electric motor 15 to the 17 2015249060 26 Oct 2015 pumping characteristics of said axial-flow impeller throughout all phases of operation, variable pitch impeller blades are employed. In this embodiment, shaft 22 is made hollow and a push-pull control rod is slidingly accommodated coaxially within it. Said impeller blades are 5 rotationally supported at their roots in suitable bearings formed in hub 40 and are provided within said hub with short levers orientated normal to their axes. The free ends of said levers are pivotally engaged by a spider fixed to the end of said push-pull rod and displacement of said rod in the appropriate sense causes a simultaneous increase or decrease in the blade 10 angle of all said impeller blades. In the preferred embodiment, said push-pull rod is displaced by a suitable actuator in the form of a stepper motor driving a screw jack, operation of said stepper motor being controlled by a microprocessor-based controller referencing the selected setting for said swimming current. In the preferred embodiment, said push-pull rod, said 15 screw jack and said stepper motor rotate with said shaft. Those skilled in the art will appreciate that other methods may be employed to vary the pitch of the blades of said impeller. In another alternative embodiment (not shown), where the use of variable-pitch impeller blades is impractical, variable inlet guide vanes are employed. Said inlet guide vanes are located 2 0 immediately upstream of said impeller and, by appropriately defecting the inlet water flow, alter the direction of vector 98. Those skilled in the art will appreciate that a number of mechanisms may be employed to vary the angle of said inlet guide vanes. In the preferred embodiment, the mechanism employed to vary the angle of said inlet guide vanes is 18 2015249060 26 Oct 2015 actuated by a suitable actuator in the form of a stepper motor driving a screw jack, operation of said stepper motor being controlled by a microprocessor-based controller referencing the selected setting for said swimming current. Where said impeller blade pitch angle is constant, 5 movement of vector 98 has the affect of altering the angle of attack of said blades. As a general rule, said impeller blades will require a coarser pitch at lower RPM and a finer pitch at higher RPM, the optimum number of blades and their pitch angles for a particular configuration being determined by practical testing. In all said embodiments, said impeller 10 blades are shaped to have an efficient, aerodynamically-formed, transverse cross-sectional shape, between two and ten blades being used in each said impeller.

In an alternative embodiment (not shown), said discharge trunk or, where made separately, said impeller compartment, is made from a 15 magnetically permeable polymer material. Said impeller is rotationally supported on a fixed shaft and is provided with a suitable strong, permanent magnet at the end of each of its said blades, said magnets being made curved to conform to the inner wall shaping of said discharge trunk or said impeller compartment. To minimise obstruction of the water flow, 20 said magnets are optionally accommodated in a circumferential channel formed in said discharge trunk or impeller compartment. A plurality of electromagnetic coils is positioned around the exterior of said discharge trunk or said impeller compartment, said coils being arranged radially with the axes of their cores arranged to be coincident with the plane of rotation 19 2015249060 26 Oct 2015 of said impeller. In this embodiment, said impeller effectively becomes the rotor of a radial-flux electric motor, said electromagnetic coils being electronically commutated to cause said impeller to rotate. The speed of rotation of said rotor is determined by the number, pattern and frequency 5 of energisation of said electromagnetic coils, controlled by a microprocessor-based controller referencing the selected speed setting for said swimming current.

In the preferred embodiment, said electric motor takes the form of a brushless, direct current, axial-flux electric motor incorporating 10 electronic commutation. By varying the number of electromagnetic coils energised and their pattern and frequency of energisation, such electric motors are able to operate in an energy-efficient way over an extended RPM range with a wide range of power outputs. In alternative embodiments, said electric motor takes the form of an interior permanent 15 magnet synchronous motor or switched-reluctance motor or other similar electrical machine providing electrical efficiency with flexibility of operation. Operation of said electric motor is controlled by a microprocessor-based controller referencing the selected speed setting for said swimming current. 20 In the preferred embodiment, to minimise the possibility of cavitation at said impeller, a water level sensor is provided, said sensor transmitting a signal to said electric motor controller to automatically interrupt operation of said electric motor should the water in said swim spa or pool fall to a minimum acceptable level. 20 2015249060 26 Oct 2015

In the preferred embodiment, said electric motor is electrically isolated from said discharge trunk through the use of an isolated electric motor supporting structure, a non-conductive drive belt and, if necessary, driving and driven pulleys made from a suitable dielectric material. 5 In an alternative embodiment (not shown), an efficient heat exchange unit is provided, positioned either in said discharge trunk or upstream of said impeller. Said heat exchange unit is either heated directly by electricity or by circulating a hot fluid through it. Said heat exchange element is preferably located in said inlet trunks or other area of 10 enlarged cross-sectional area upstream of said impeller, where said water flow has a longer residence time. In an alternative embodiment, said water flow is heated directly by microwave energy radiated into it through a radio-transparent part of said discharge trunk or said impeller compartment. 15 In the preferred embodiment, a secondary flow of water drawn off from the body of water in said swim spa or pool by means of a secondary pump, said secondary flow being filtered and/or heated and/or sanitised in the conventional way and returned to said swim spa or pool. The operation of said secondary pump is controlled by timing means in 20 accordance with a pre-set program, or a timed cycle automatically triggered by recent use of said swim spa or pool.

In the preferred embodiment, the speed setting for said swimming current is variable by voice command. A swimmer wishing to vary the speed of said swimming current speaks clearly the commands, ‘Command 21 2015249060 26 Oct 2015 up’ or ‘Command down’ (or similar commands easily discriminated one from the other) to achieve, respectively, an increase or decrease in speed. In this embodiment, a microphone captures the spoken command and transmits it to a microprocessor-based control unit where the wave form of 5 the signal generated by said microphone is compared with a library of waveforms for the command words spoken by a range of male and female speakers. If the command is recognised, an appropriate increase or decrease in speed is generated. In the preferred embodiment, said increase is in the range 5% to 10% and an audible tone is generated to signal to the 10 swimmer that the change in speed has been made. Also in the preferred embodiment, a time interval of at least five seconds must elapse before another command can be processed. In another alternative embodiment (not shown), a pendant speed control unit is permitted to float in the swimming current adjacent the swimming position. In another alternative 15 embodiment (not shown), a machine vision system incorporating a camera located above the ideal swimming position continuously monitors the position of the envelope occupied by a swimmer and compares it to the ideal position. Should, at any time, the swimmer be detected as falling back from the ideal swimming position, the speed of the swimming 2 0 current is reduced by a predetermined margin. Should the swimmer be detected as drawing ahead of the ideal swimming position, the speed of the swimming current is increased by a predetermined margin.

In an alternative embodiment (not shown), two separate axial-flow pumps are located in two separate said discharge ducts, separate flows of 22 2015249060 26 Oct 2015 water being discharged through separate discharge apertures positioned side-by-side in said head wall of said swim spa or pool. In this embodiment, operation of the two pumps allows two swimmers to swim side by side, only one pump being operated for a single swimmer. 5 In an alternative embodiment (not shown), two separate axial-flow pumps are located in two separate said discharge ducts, separate flows of water being discharged through separate discharge apertures positioned one above the other in said head wall of said swim spa or pool. In this embodiment, one said pump is operated to generate a low to medium-10 speed swimming current and the second pump is additionally operated to generate a medium to high-speed swimming current. In a variation of this embodiment (not shown), said discharge apertures are optionally positioned low down in the water body of said swim spa or pool an appropriate distance ahead of said swimming position and inclined 15 upwardly at an angle between 10 and 45 degrees. The flow of water discharged from said discharge apertures generates said swimming current, but simultaneously generates an upwelling of water which acts to overcome the lack of buoyancy felt by swimmers in fresh water.

In an alternative embodiment (not shown), part of said discharge 2 0 trunk is moulded into said head wall of said swim spa or pool as a channel of more or less semi-circular transverse cross-sectional shape, said channel being closed by a cover of more or less semi-circular transverse cross-sectional shape to create the complete said discharge trunk.

In an alternative embodiment (not shown), short lengths are 23 2015249060 26 Oct 2015 inserted into or removed from said discharge trunk to vary its length for differing configurations.

In the preferred embodiment, a removable hatch (not shown) is provided in said discharge trunk adjacent said impeller to permit 5 inspection of said impeller or removal of debris entangled in said impeller blades.

In the preferred embodiment, said rotor hub is made with a suitable streamlined longitudinal shape and the zone of said discharge duct adjacent said hub is expanded in diameter to maintain the cross-sectional 10 area of said trunk.

In an alternative embodiment (not shown), said pump rotor is made with two or more stages, said stages preferably being separated by suitable fixed stator blades.

In an alternative embodiment (not shown), the position of said 15 discharge aperture or of said guide vanes within said discharge aperture are made adjustable to permit control of the direction of said discharged stream of water.

In an alternative embodiment (not shown), said stream of water from said discharge aperture is discharged into the throat of an elongated 2 0 flow augmentor supported from said swim spa or pool head wall. Said augmentor has a venturi-shaped transverse cross-sectional shaping and acts to increase the volume of water accelerated over what would be accelerated solely by said stream of water discharged from said discharge aperture. 24 2015249060 26 Oct 2015

In an alternative embodiment (not shown), two discrete jets of water emitted from said discharge aperture are directed towards the two sides of said swim spa or pool, said jets acting to prevent the development of a counterflow along the upper sides of the water body. 5 In an alternative embodiment (not shown), two or more flexible blocking panels, of more or less vertical arrangement and located a suitable distance behind said swimming position, extend into the body of water from the side walls of said swim spa or pool. Said panels each extend downwardly from the water surface for between 10% and 50% of 10 the depth of the water body and inwardly for between 10% and 25% of the width of said swim spa or pool, said panels acting to prevent the development of a counterflow along the upper sides of the water body. In the preferred embodiment, said panels take the form of elastic frames of metal wire or polymer rod, each supporting a sheet of a suitable film or 15 fabric material.

In an alternative embodiment (not shown), a flow of compressed air from a suitable source is discharged from a plurality of nozzles in said discharge section, thereby aerating the flow of water discharged into said swim spa or pool. 20 In an alternative embodiment (not shown), shaft 22 is arranged horizontally beneath said floor of said swim spa or pool with said electric motor extending beyond said head wall. The flow of water generated by said impeller is optionally led up through a discharge trunk and discharge section of the arrangements depicted in Figures 1 and 12, or is discharged 2015249060 26 Oct 2015 25 from saicl discharge aperture located at the base of said head wall or between the base and 50% of the height of said head wall and inclined upwardly at an angle between 10 and 45 degrees, the flow of water discharged from said discharge aperture generating said swimming 5 current, but simultaneously generating an upwelling of water which acts to overcome the lack of buoyancy felt by swimmers in fresh water.

In an alternative embodiment (not shown), suitable deflectors are provided pivotally supported from the upper and lower edges of said discharge apertures, the positions of said deflectors being adjustable to 10 adjust the effective width of said discharge apertures and, thereby, the velocity of the water flow discharged therefrom.

The scope of the present invention should be taken to include any feasible combination of any one or more of the disclosed features with any one or more of the other disclosed features. 15

Claims (61)

1. A water circulation system for a swim spa or swim-in-place pool comprising: a vertical discharge trunk situated outside of, parallel to and centrally positioned in relation to the head wall of said swim spa or swim-in-place pool, said trunk having very gradual cross-sectional area and directional changes; one or more inlet trunks taking a flow of water from off-take openings deeply-located at the base of said swim spa or swim-in-place pool and being connected to the base of said discharge trunk; a discharge section formed at the upper end of said discharge trunk to receive a flow of water from said discharge trunk; one or more discharge apertures formed at the outlet of said discharge section and supported in said head wall just below the water line; an impeller shaft arranged coaxially with said discharge trunk and rotationally supported on bearings at its upper and lower ends; one or more axial-flow impellers driven by said impeller shaft and situated more or less level with the base of said swim spa or swim-in-place pool and acting to accelerate the flow of water from said inlet trunks; flow straighteners to ensure the maintenance of an orderly, streamline flow in the zone downstream of said impellers; guide vanes in zones of directional change in said discharge trunk or said discharge section to ensure the maintenance of an orderly flow and even distribution of water flow across said discharge apertures; an electric motor positioned adjacent said head wall, one or more drive pulleys of said electric motor shaft being connected by belts to complementary driven pulleys at the upper end of said impeller shaft; and control means to control the rotational speed of said electric motor and, thereby, the speed of the swimming current generated in said swim spa or swim-in-place pool by the flow of water discharged from said discharge apertures.

2. The water circulation system of Claim 1 in which all directional and cross-sectional changes in the duct area between said off-take openings and said discharge apertures are made in a smooth and gradual way,

3. The water circulation system of Claim 1 in which changes in the cross-sectional area of said discharge trunk are limited to 15% per unit length, with a unit length being taken as the original diameter of said discharge trunk.

4. The water circulation system of Claim 1 in which said electric motor takes the form of a brushless, direct current, axial-flux electric motor incorporating electronic commutation, allowing operation in an energy-efficient way over an extended RPM range and with a wide range of power outputs.

5. The water circulation system of Claim 1 in which said electric motor takes the form of an interior permanent magnet synchronous motor or switched-reluctance motor or other similar electrical machine providing electrical efficiency with flexibility of operation.

6. The water circulation system of Claim 1 in which operation of said electric motor is controlled by a microprocessor-based controller referencing the selected speed setting for said swimming current.

7. The water circulation system of Claim 1 in which provision is made to heat the flow of water discharged from said discharge apertures, a heat exchange unit being provided positioned either in said discharge trunk or upstream of said impeller, said heat exchange unit being either heated directly by electricity or by circulating a hot fluid through it.

8. The water circulation system of Claim 1 in which said water flow is heated directly by microwave energy radiated into it through a radio-transparent part of said discharge trunk or said impeller compartment.

9. The water circulation system of Claim 1 in which said discharge trunk is made in two parts dividing along a longitudinal centreline, said parts being sealingly fixed together at abutting flanges using a plurality of suitable fasteners, said discharge trunk being moulded from a suitable polymer material or cast from a suitable metal alloy material.

10. The water circulation system of Claim 1 in which the upper end of said discharge trunk transitions from a circular internal cross-sectional shape to a discharge section of more or less fan-shaped plan form with a rectangular transverse cross-sectional shape, said discharge section terminating in one or more discharge apertures.

11. The water circulation system of Claim 10 in which the cross-sectional area of said discharge aperture is reduced as required to provide a further acceleration of the water flow.

12. The water circulation system of Claim 1 in which said discharge section terminates at its outer end in a peripheral attachment flange which is sealingly fixed over a suitable aperture in said swim spa or swim-in-place pool head wall using a plurality of suitable fasteners.

13. The water circulation system of Claim 1 in which said discharge section is provided with a plurality of suitable guide vanes, the ends of which are captured in complementary recesses in the side walls of said discharge section during assembly of said discharge trunk, the relative spacing of said guide vanes being adjusted to ensure a uniform flow of water throughout the whole area of said discharge apertures.

14. The water circulation system of Claim 1 in which said discharge trunk is made with an integral upper part which is filled by a removable plug in which the upper end of said impeller shaft is rotationally supported, said plug having a curved lower face which, in opposition to a curved transitional surface between said discharge trunk and said discharge section, acts to create a curved throat which efficiently carries the flow of water through the directional change with a minimum of shearing and disturbance.

15. The water circulation system of Claim 14 in which the upper surface of said plug is expanded to create a circumferential flange which is sealingly fixed to a complementary flange formed on the upper end of said discharge trunk upper part using a plurality of suitable fastenings.

16. The water circulation system of Claims 1 and 14 in which said impeller shaft passes coaxially through said discharge trunk, accommodated within a support tube having its upper end fixed in said plug and its lower end fixed in said flow straightener, suitable water ingress apertures being provided in said support tube.

17. The water circulation system of Claim 1 in which said flow straightener is provided with a plurality of radially-arranged vanes, the thickness of the cylindrical outer wall of said flow straightener being neatly accommodated within a recessed area of said discharge trunk such that its lower edge provides no impediment to the flow of water from said impeller.

18. The water circulation system of Claim 1 in which an impeller shroud enclosing said impeller blades is optionally made integral with the outer wall of said flow straightener or made separately and accommodated within said discharge trunk upstream of said flow straightener and immediately adjacent said impeller, said shroud acting to prevent erosion or ablation of the inner wall surface of said discharge trunk.

19. The water circulation system of Claim 18 in which said impeller shroud is made split and is installed by elastically partially collapsing it and then allowing it to spring out into place in a recessed area of said discharge trunk.

20. The water circulation system of Claims 1 and 14 in which said impeller shaft is rotationally supported at its upper end in one or more suitable bearings accommodated within a bearing housing which is, in turn, accommodated within a recess formed in the upper part of said plug, the lower end of said shaft being rotationally supported in one or more water-lubricated bearings accommodated within said flow straightener.

21. The water circulation system of Claim 1 in which said impeller shaft is rotationally supported at its lower end in one or more water-lubricated bearings accommodated within a bearing housing formed in the floor of said inlet trunk.

22. The water circulation system of Claims 20 and 21 in which said water-lubricated bearings are of the type typified by those manufactured by Dynamax Industrial Products, of Hiram, Ohio, USA.

23. The water circulation system of Claim 1 in which said discharge trunk is expanded to form a more or less fan-shaped discharge section commencing from a point immediately downstream of said impeller, a plurality of guide vanes being provided within said discharge section to ensure a uniform and orderly flow of water through the rapidly expanding zone of said discharge section and the whole area of said discharge apertures.

24. The water circulation system of Claim 1 in which said impeller and said flow straightener are accommodated within a separate cylindrical compartment, the upper and lower edges of which are flanged, said flanges being urged into sealing cooperation with complementary flanges of said discharge trunk and said inlet trunks by a plurality of long bolts passing between said discharge trunk and said inlet trunk flanges.

25. The water circulation system of Claims 1 and 24 in which, where a said swim spa or swim-in-place pool is set into the ground, said cylindrical compartment accommodating said impeller and said flow straightener, said discharge trunk, said discharge section, a tee piece connecting said inlet trunks to said discharge section and said electric motor are accommodated within a suitable pit positioned at the head of said swim spa or swim-in-place pool, said tee piece being secured to a supporting surface by suitable fastenings, said inlet trunk parts outside of said pit being buried.

26. The water circulation system of Claims 1 and 25 in which a said inlet trunk is sealingly connected to said tee piece by the urging of the flat face of a tapered collar formed on the end of said inlet trunk into sealing cooperation with the flat face of a complementary tapered collar formed on the end of an arm of said tee piece by means of the tightening (and, thereby, the contraction) of a tapered clamping band, suitable elastically-compliant sealing means being compressed between said flat faces.

27. The water circulation system of Claim 26 in which a slotted strap and peg arrangement is provided to locate said tapered collar circumferentially while permitting it to be loosened and withdrawn from said tapered collars, permitting said inlet trunk to be separated from said tee piece arm.

28. The water circulation system of Claims 1 and 25 in which, where said inlet trunks are partially buried, means are provided in their exposed parts to permit a small degree of elastic compliance such as to permit the flat face of said tapered collar of said inlet trunk to be able to be drawn into contact with said flat face of said complementaiy tapered collar of said tee piece arm, said compliance means taking the form of a deeply corrugated section or a short insert of a suitable elastomeric material.

29. The water circulation system of Claim 1 in which axial-flow water pumping is employed because of the ability of this type of pump to efficiently move large volumes of water at low heads, which attribute, in combination with efficient duct design, permitting movement of the greatest volume of water with the least expenditure of energy.

30. The water circulation system of Claim 1 in which, in order to match the operational characteristics of said electric motor to the pumping characteristics of said axial-flow impeller throughout all phases of operation, variable pitch impeller blades are employed, said impeller shaft being made hollow with a push-pull control rod slidingly accommodated coaxially within it, said impeller blades being rotationally supported at their roots in suitable bearings formed in an impeller hub and are provided within said hub with short levers orientated normal to their axes, the fiee ends of said levers being pivotally engaged by a spider fixed to the end of said push-pull rod, displacement of said rod in the appropriate sense causing a simultaneous increase or decrease in the blade angle of all said impeller blades.

31. The water circulation system of Claim 30 in which said push-pull rod is displaced by a suitable actuator in the form of a stepper motor driving a screw jack, operation of said stepper motor being controlled by a microprocessor-based controller referencing the selected setting for said swimming current, said push-pull rod, said screw jack and said stepper motor rotating with said impeller shaft.

32. The water circulation system of Claims 30 and 31 in which said push-pull rod is displaced by means of any suitable actuator.

33. The water circulation system of Claim 1 in which, where the use of variable-pitch impeller blades is impractical, variable inlet guide vanes are employed, said inlet guide vanes being located immediately upstream of said impeller.

34. The water circulation system of Claim 33 in which the positions of said variable inlet guide vanes are adjusted by means of a suitable actuator in the form of a stepper motor driving a screw jack, operation of said stepper motor being controlled by a microprocessor-based controller referencing the selected setting for said swimming current.

35. The water circulation system of Claims 33 and 34 in which, where said impeller blade angle is constant, displacement of the water flow inlet vector by means of inlet guide vanes has the affect of altering the angle of attack of said impeller blades, said impeller blades requiring a coarser pitch at lower RPM and a finer pitch at higher RPM, the optimum number of impeller blades and their pitch angles for a particular configuration being determined by practical testing; all said impeller blades being shaped to have an efficient, aerodynamically-formed, transverse cross-sectional shape with between two and ten blades being used in each said impeller.

36. The water circulation system of Claims 33 and 34 in which the angles of said inlet guide vanes is adjusted by means of any suitable actuator.

37. The water circulation system of Claim 1 in which, where said discharge trunk or, where it is made separately, said impeller compartment, is made from a magnetically permeable polymer material, said impeller being rotationally supported on a fixed shaft and provided with a suitable strong, permanent magnet at the end of each of its said blades, said magnets being made curved to conform to the inner wall shaping of said discharge trunk or said impeller compartment and accommodated in a circumferential channel formed in said discharge trunk or impeller compartment; a plurality of electromagnetic coils being positioned around the exterior of said discharge trunk or said impeller compartment, said coils being arranged radially with the axes of their cores arranged coincidently with the plane of rotation of said impeller such that said impeller effectively becomes the rotor of a radial-flux electric motor, said electromagnetic coils being electronically commutated to cause said impeller to rotate, the speed of rotation of said rotor being determined by the number, pattern and frequency of energisation of said electromagnetic coils, said functions being controlled by a microprocessor-based controller referencing the selected speed setting for said swimming current.

38. The water circulation system of Claim 1 in which, to minimise the possibility of cavitation at said impeller, a water level sensor is provided, said sensor transmitting a signal to said electric motor controller to automatically interrupt operation of said electric motor should the water in said swim spa or swim-in-place pool fall to a minimum acceptable level.

39. The water circulation system of Claim 1 in which said electric motor is electrically isolated from said discharge trunk through the use of an isolated electric motor supporting structure, a non-conductive drive belt and, if necessary, driving and driven pulleys made from a suitable dielectric material.

40. The water circulation system of Claim 1 in which a secondary flow of water drawn off from the body of water in said swim spa or swim-in-place pool by means of a secondary pump is filtered and/or heated and/or sanitised in the conventional way and returned to said swim spa or swim-in-place pool, the operation of said secondary pump being controlled by timing means in accordance with a pre-set program, or a timed cycle automatically triggered by recent use of said swim spa or pool.

41. The water circulation system of Claim 1 in which the speed setting for said swimming current is variable by voice command, a swimmer wishing to vary the speed of said swimming current speaking a command, a microphone capturing said spoken command and transmitting it to said microprocessor-based control unit where the wave form of the signal generated by said microphone is compared with a library of waveforms for the specified command words spoken by a range of male and female speakers, an appropriate increase or decrease in speed being generated if a command is recognised, an audible tone being generated to signal to the swimmer that the commanded change in speed has been made.

42. The water circulation system of Claim 1 in which a pendant speed control unit is permitted to float in the swimming current adjacent the swimming position, said pendant being employed to input swimming current speed variation commands.

43. The water circulation system of Claim 1 in which a machine vision system incorporating a camera located above the ideal swimming position continuously monitors the position of the envelop» occupied by a swimmer and compares it to the ideal position, should a swimmer be detected as departing from the ideal swimming position, the speed of the swimming current is increased or reduced, as appropriate, to correct the excursion.

44. The water circulation system of Claim 1 in which two separate axial-flow pumps are located in two separate said discharge ducts, separate flows of water being discharged through separate discharge apertures positioned side-by-side in said head wall of said swim spa or swim-in-place pool, operation of said embodiment, allowing two swimmers to swim side by side, with only one pump being operated to accommodate the needs of a single swimmer.

45. The water circulation system of Claim 1 in which two separate axial-flow pumps are located in two separate said discharge ducts, separate flows of water being discharged through separate discharge apertures positioned one above the other in said head wall of said swim spa or swim-in-place pool, one said pump being operated to generate a low to medium-speed swimming current with the second pump being additionally operated to generate a medium to high-speed swimming current.

46. The water circulation system of Claim 1 in which said discharge apertures are positioned low down in the water body of said swim spa or swim-in-place pool, located an appropriate distance ahead of said swimming position and inclined upwardly at an angle between 10 and 45 degrees, the flow of water discharged from said discharge apertures generating said swimming current and simultaneously generating an upwelling of water which acts to overcome the lack of buoyancy felt by swimmers in fresh water.

47. The water circulation system of Claim 1 in which half of said discharge trunk is moulded into the exterior of said head wall of said swim spa or swim-in-place pool as a channel of more or less semi-circular transverse cross-sectional shape, said channel being closed by a cover of more or less semi-circular transverse cross-sectional shape, said cover being fixed to said head wall and shaped to create the circular cross-sectional shape of the complete said discharge trunk.

48. The water circulation system of Claim 1 in which short lengths are inserted into or removed from said discharge trunk to vary its length for differing configurations.

49. The water circulation system of Claim 1 in which a removable hatch is provided in said discharge trunk adjacent said impeller to permit inspection of said impeller blades or removal of debris entangled in said impeller blades.

50. The water circulation system of Claim 1 in which the hub of said impeller is made with a suitable streamlined longitudinal shape and the zone of said discharge trunk adjacent said hub is expanded in diameter to maintain a constant cross-sectional area of said trunk.

51. The water circulation system of Claim 1 in which two or more impeller stages are employed, said impeller stages being separated by suitable fixed stator blades.

52. The water circulation system of Claim 1 in which the position of said discharge aperture or of said guide vanes within said discharge aperture are made adjustable to permit control of the direction of said discharged stream of water.

53. The water circulation system of Claim 1 in which the stream of water from said discharge aperture is discharged into the throat of an elongated flow augmentor supported from said swim spa or swim-in-place pool head wall, said augmentor having a venturi cross-sectional shaping in the direction of water flow and acting to increase the volume of water accelerated over that accelerated solely by said stream of water discharged from said discharge aperture.

54. The water circulation system of Claim 1 in which two discrete jets of water emitted from said discharge aperture are directed towards the two sides of said swim spa or swim-in-place pool, said jets acting to prevent the development of a counterflow along the upper sides of the water body.

55. The water circulation system of Claim 1 in which two or more flexible blocking panels, of more or less vertical arrangement are located a suitable distance behind said swimming position, extending into the body of water from the side walls of said swim spa or swim-in-place pool, said panels each extending downwardly from the water surface for between 10% and 50% of the depth of the water body and inwardly for between 10% and 25% of the width of said swim spa or swim-in-place pool, said panels acting to prevent the development of a counterflow along the upper sides of the water body.

56. The water circulation system of Claim 55 in which said panels take the form of elastic frames of metal wire or polymer rod, each supporting a sheet of a suitable film or fabric material.

57. The water circulation system of Claim 1 in which a flow of compressed air from a suitable source is discharged from a plurality of nozzles in said discharge section, thereby aerating the flow of water discharged into said swim spa or swim-in-place pool.

58. The water circulation system of Claim 1 in which said impeller shaft is arranged horizontally beneath said floor of said swim spa or swim-in-place pool with said electric motor extending beyond said head wall, the flow of water generated by said impeller passing horizontally and thence up through said discharge trunk and said discharge section, or being discharged from said discharge aperture located at the base of said head wall or between said base and 50% of the height of said head wall and inclined upwardly at an angle between 10 and 45 degrees, said upwardly- inclined flow of water generating said swimming current, and simultaneously generating an upwelling of water which acts to overcome the lack of buoyancy felt by swimmers in fresh water.

59. The water circulation system of Claim 1 in which suitable deflectors are provided pivotally supported from the upper and lower edges of said discharge apertures, the positions of said deflectors being adjustable to adjust the effective width of said discharge apertures and, thereby, the velocity of the water flow discharged therefrom.

60. The water circulation system of Claim 1 in which any feasible combination of any one or more of the described features with any one or more of the other described features is employed.

61. A method of generating a swimming current in a swim spa or swim-in-place pool consisting of providing a vertical discharge trunk situated outside of, parallel to and centrally positioned in relation to the head wall of said swim spa or swim-in-place pool, said trunk having very gradual cross-sectional area and directional changes; one or more inlet trunks taking a flow of water from offtake openings deeply-located at the base of said swim spa or swim-in-place pool and being connected to the base of said discharge trunk; a discharge section formed at the upper end of said discharge trunk to receive a flow of water from said discharge trunk; one or more discharge apertures formed at the outlet of said discharge section and supported in said head wall just below the water line; an impeller shaft arranged coaxially with said discharge trunk and rotationally supported on bearings at its upper and lower ends; one or more axial-flow impellers driven by said impeller shaft and situated more or less level with the base of said swim spa or swim-in-place pool and acting to accelerate the flow of water from said inlet trunks; flow straighteners to ensure the maintenance of an orderly, streamline flow in the zone downstream of said impellers; guide vanes in zones of directional change in said discharge trunk or said discharge section to ensure the maintenance of an orderly flow and even distribution of water flow across said discharge apertures; an electric motor positioned adjacent said head wall of said swim spa or swim-in-place pool, one or more drive pulleys of said electric motor shaft being connected by belts to complementary driven pulleys at the upper end of said impeller shaft; and control means to control the rotational speed of said electric motor and, thereby, the speed of the water current generated in said swim spa or swim-in-place pool by the flow of water discharged from said discharge apertures.