TANK FOR SWIMMING AGAINST AN ARTIFICIAL CURRENT

Abstract: A swim tank (11) is provided that is slightly longer than a human and slightly wider than the maximum spread between fingertips. It is divided into upper (13) and lower channels (14) by members extending across the width of the tank and having a rectangular outlet (14) at the top front through which water is expelled. A vaned wheel (15) at the rear is driven by an induction motor (19) from a power source of controlled frequency and the tanked is bowed or rearwardly inwardly tapered.

Description: The present invention relates in general to flow controlling and more particularly concerns novel apparatus and techniques for controlling fluid flow, such as water in a tank, to establish a range of relative velocities between the flowing fluid and an object in it, such as a swimmer, while the object remains substantially stationary relative to earth. An embodiment of the invention provides a compact environment for a swimmer to attain all the exercise and fun of swimming at the swimmer's pace. Thus, the invention may be said to provide the environment of a swimming pool of infinite length in a structure slightly longer and wider than a swimmer while providing a form of exercise that cannot be achieved in a conventional bounded swimming pool with stationary water. It is known in the prior art to provide spas or tubs that create a flow through jets to allow a swimmer to swim upstream against the water jets. A difficulty with these prior art structures is that the jets create a turbulent current that often exerts sideward and up and downward forces on the swimmer and makes swimming against the longitudinal component of the current difficult. Examples of these prior devices are the swim-jet spa commercially available from Curtis Plastics of Huntington Beach, California, and the model AS-Sl-SL3 swim spa available from Wiedemann Industries, Inc. of Muscatine, Iowa. A search of subclasses 71 and 72 of class 272 and subclassed 488, 491 and 509 of class 4 uncovered US-A-520,342, US-A-1,285.259, US-A-1,331,270, US-A-1,630,797, US-A-1,796,291, US-A-1,992,891, US-A-2,035,835 and US-A-3,534,413. US-A-2,035,835 discloses confined flow channels in a tank; however, this patent does not disclose water driving means truly transverse to the length of the channel; therefore, the disclosed structure would create undesired turbulence. Furthermore, this patent discloses straight end walls having a tendency to create a head which would then empty wastefully into the swim channel and turbulently induce air and noise instead of contributing to establishing the desired current. US-A-1,285,259 and US-A-1,331,270 disclose paddle wheels used for surface movement only and could not establish a current along the length of the channel having negligible velocity gradient along the width. EP-A-0218527 discloses flow controlling apparatus comprising, a tank for supporting a fluid, upper and lower channels in the tank for allowing fluid flow in upper and lower opposed directions, and drive means for propelling the fluid through the upper and lower channels with substantially uniform velocity of fluid across substantially the entire width of the tank at the top of the tank, The present invention is characterised over EP-A-0218327 by the tank having a bowed shape or being rearwardly inwardly tapered so as to provide a substantially uniform water velocity gradient along the length of the tank. It is an important object of this invention to provide improved apparatus and techniques for flow controlling. Preferably, the vaned rotor is driven by an induction motor of electronically controlled frequency that controls the speed of rotation from substantially zero to maximum to allow a swimmer to set the current speed at any value from zero to maximum. In a most preferred embodiment, the apparatus comprises a plurality of sections, each section being sized to fit through a 850mm (34") door. Even more preferably the apparatus comprises four sections; the tank has a bowed shaped or is rearwardly inwardly tapered; the tank comprises a floor, wherein the floor is sloped to enhance drainage of the tank; the apparatus further comprises a bottom, below the floor, wherein the underside of the floor is sloped to promote venting of entrapped air; and the apparatus comprises fiberglass. Other advantages of the invention will be apparent from the following description of the preferred embodiments and from the claims. The drawings will first briefly be described. Fig. 1 is a perspective view of an embodiment of the invention; Fig. 1A is a longitudinal sectional view of this embodiment; Fig. 1B is a transverse sectional view; Figs. 1C and 1D are sectional views taken at A-A and B-B respectively; Fig. 1E is a section through a bolt used to hold sections of the tank together; and Figs. 2 and 3 are diagrammatic side and partial top views of an embodiment of the invention, with the vented rotor driven by jets. With reference to the drawings, a tank, slightly longer than a swimmer, typically 2.7-3m (9 - 12 feet) long and slightly wider than the maximum spread between fingertips of a swimmer, typically 1.5-2.1m (5 - 7 feet) wide, is filled with water. The tank 40 includes a number of plastic (polypropylene and polycarbonate) panels extending the width of the tank curved as shown for defining a lower channel 12 with water moving forward and an upper channel 13 with water flowing rearward. The upper portion of the curved conduit is formed with a rectangular baffled opening 14 through which water is expelled to the upper channel 13 to create a flow of substantially uniform velocity along the width of the tank 40 at the top of the tank. A vaned rotor 15 is rotatably supported at the rear of tank 40 and rotates counterclockwise to draw water through baffle 17 and propel the water into the tapered inlet at the rear end of lower channel 12. Vaned rotor 15 is shrouded closed by shroud 42 at the rear semicircular cross section and open shrouded by baffle 17 along most of the front. Rotation of vaned rotor 15 thus creates the current flow. In a specific embodiment of the invention, there are six vanes on vaned rotor 15 equiangularly spaced about the rotor axis, driven by a 3.7kW (five horsepower) three-phase induction motor through a conventional gear reduction transmission, such as a worm gear reducer 20. Typically, a 1160 rpm motor 19 drives vaned rotor 15 through a 15:1 gear ratio-reducer 20 that is shaft mounted. The motor is energized by an electronic inverter that provides three-phase power at controlled frequency to allow the vaned rotor to rotate from 0 to 77 rpm depending on the energizing frequency. This power source is typically a commercially available Graham inverter whose frequency is controlled by a potentiometer energized by a 24 volt a-c supply that minimizes the danger of electrical shock to a swimmer. In a specific embodiment of the invention a 3.7kW (five-horsepower) Leroy-Somers Power Block induction motor having a nominal rpm of 1160 when energized by 220 volts three-phase energy drove vaned rotor 15 through a belt drive with 1.8:1 reduction and a driving gear on the input shaft of a 10:1 Boston worm gear reducer with the output shaft of the latter coupled through a chain coupling to the main shaft of vaned rotor 15 controllable from 0-64 rpm. A Graham inverter energized by 220 volts single-phase at a maximum of 35 amperes provided three-phase output power to the induction motor at a controllable frequency from 1 to 102 Hz with a maximum current of 15 amperes per leg. Alternatively, other driving means may be provided. For example, vaned rotor 15 may be driven by water jets coupled to the shaft with driving water being furnished to the shaft through a suitable coupling from a pump supplying sufficient energy to drive vaned rotor 15 with sufficient rotational velocity to achieve the desired current, typically 0 to 64 rpm for the specific embodiment described having six vanes. The jets may be located on the tips of the vanes perpendicular to the vane surfaces. It is preferable that the shroud be as close to the vane ends as practical without introducing friction therebetween so as to optimize efficient transfer of power from the rotating vanes to the water. Preferably the angle between vanes corresponds to the angle subtended by a vertical plane passing through the axis of vaned rotor 15 and a plane passing through that axis and an extension of the top of lower channel 12 and a plane tangential to vaned rotor 15 at the forward side of vaned rotor 15. A tapered inlet allows fluid in the form of an escape flume flowing outside the perimeter of vaned rotor 15 having an upward component to be guided forward into lower channel 12. The outer tank is preferably made of stainless steel, and the baffles and channel dividers preferably made of polypropylene plastic. Other materials may be used. For example, the tank may be inground or above ground and made of concrete or vinyl-lined wood or metal. The invention may be located in a small portion of a conventional pool, such as in a corner at the shallow end using two walls of the pool and walls made of plastic or other material. Preferably, the power source for driving paddle wheel 15 is water jets when located in an inground tank or pool. Conventional pool filter, chlorinating or other purifying equipment and techniques may be used to keep the water clean and free of bacteria. Conventional heating equipment may be used to heat the water, such as a heat pump or gas or oil heater. Having described the structure, it is appropriate to discuss principles of operation and some modifications to the structure described above that may be desirable. The preferred embodiment of the invention comprises a transverse vane pump with working clearances to eliminate wear problems between the shroud and vanes, the rotor axis being substantially parallel to the width dimension of the tank. The vaned rotor is of diameter about equal to the depth of the tank. While the vane rotor could be constructed with vanes equiangularly disposed about a central shaft or tube embracing the rotor axis to define sectoral chambers isolated from each other by the vanes, it is more practical to secure the vanes to the rotor shaft with clamps with a gap between to allow access to the clamps which secure the vanes to the rotor shaft. The migration of water about the rotor shaft through these gaps is relatively insignificant because the outside diameter of the rotor at the vane edges is much larger than that of the shaft diameter, the outside diameter typically being 1.15m (46") and the shaft diameter typically 59mm (2.375"). The rear end of the swimming tank has for substantially the entire depth a transverse vane pump with a semicircular closed shroud. The rotor and shroud are completely submerged in water to prevent the induction of air and noisy churning turbulence that would accompany such induction. For river-like swimming comfort it is desirable to minimize noise and turbulence. As the vaned rotor rotates, it pushes water over its entire length, nearly equal to the tank width, between the vane chambers and shroud and into the lower channel 12 formed between the plastic false bottom and the tank bottom. The vaned rotor expels the water tangentially directly into the lower channel 12, or preferably into a tapering transition zone as shown. The transition zone is not absolutely required but tends to reduce turbulence in the water above the floor because water that might otherwise be thrust upward against the flow in the upper or swim portion of the tank is captured by the transition zone and directed to the lower channel. The false bottom or transition zone bottom edge is preferably placed in close proximity to the vanes as a control point for flow down the lower channel. Lower channel 12 is typically 225-250mm (9-10 inches) deep and may include a longitudinal septum to divide it into parallel rectangular channels that provide increased structural strength. These long parallel channels may further function as flow straighteners and turbulence dampers to coact with the transverse vane pump in delivering fluid exiting from the pump in large volumes at the front or delivery end of the tank at relatively low pressure. Thus, fluid inducted at the entrance to the vane pump at the top is delivered at low pressure down the enclosed lower channel 12 where it is forced to gradually reverse direction 180° and undergo a velocity reduction at the top front of the tank through the exit mouth, of height typically 125-200mm (5-8") higher than the lower channel depth. Alternatively, the exit mouth could be of height the same as the lower channel depth and deliver fluid to the top of the tank at greater velocity over a lesser depth. Water at fairly high velocity, typically between 1,5-3,1 m/s (3-6 knots) or more, is thereby forced into the swimming section at the top of the tank across the entire width substantially uniformly with negligible velocity gradient along the width and with little noise or turbulence. This stream extends downward from the top for 375-450mm (15-18") typically. The water traveling rearward in the open channel loses several knots in velocity vertically in the process of merging into the deeper open channel, typically 1.2m (4.8") of the swim tank, but the flow is steadily maintained by the vane pump as it continuously draws water arriving at the rear end of the tank. The relatively high water velocity in the lower channel 12 tends to keep this channel naturally clean so that it may be permanently enclosed without access. The limited depth of the lower channel allows continuous flow without wasting appreciable tank depth. It may be desirable to create wave action to provide a swimmer with additional challenge and fun. This may be accomplished by placing a barrier plate extending several inches into the stream across the entire width of the tank at the upper portion of the exit mouth. The exiting water is then forced to suddenly flow downward and under the barrier plate and will tend to immediately rise to the surface in the form of a wavelet of adjustable height. This effect may be created without the barrier blade at high velocities typically greater than two knots or more arising from natural surface agitation resulting from water delivery to the open channel. The use of a variable speed induction motor saves considerable energy because the required power increases with vane speed. The induction motor delivers and draws power only at the levels required for a particular rate of flow. The following table sets forth the relationship between input current, motor current, the speed dial setting and current flow. Input Amps. Motor Amps. Speed Dial Set Flow mS⁻¹ 2 4.5 20 0 3 8.5 30 0.3 4 9.75 40 0.47 6 10.5 50 0.57 8 11.5 60 0.64 11 13.5 70 0.79 19.5 15 80 0.92 25 17 90 1.2 Referring to Figs. 2 and 3 there are shown diagrammatic side and partial top views of the embodiment of the invention in which the vaned rotor is driven by jets. Vaned rotor 15 is mounted on a stationary hollow shaft 15B surrounded by a sealed manifold and bearing 15C. A pump 31 provides fluid under pressure, typically water, through pipe 32 to hollow shaft 15B formed with ports that communicate through manifold 15C wih radial tubes, such as 15D connected to a nozzle such as 15E at the end of a vane, such as 15A. Fig. 5 shows a diagrammatic partial top view of feeding shaft 15B through pipe 32 that branches into a U-shaped pipe assembly having branches 32A and 32B for feeding the ends of hollow shaft 15B. The fluid, typically water from the tank, may be delivered by one or two large pipes to the stationary hollow shaft coming in from above to simplify tank burial, or from either or both ends of hollow shaft 15B. The fluid is delivered through ports in hollow shaft 15B to manifolds 15C rotating with vaned rotor 15 and sealed to the shaft. These seals could leak somewhat without concern because they are in the tank water. The wheel manifolds may also function as bearings and by means of PVC tubing, such as 15D, connected to the nozzles, such as 15E mounted to the vanes, such as 15A, at their periphery. The invention not only has value for recreational and exercising purposes, but may also be used for therapeutic purposes. A physician or therapist could easily observe and aid a patient while immersed partially in the tank from a point outside the tank while standing on a platform. The patient might execute simple body motions in opposition to the current at a speed controlled by the therapist. Additionally, the patient could walk or push objects of varying fluid resistance through the flow stream to increase the load on muscles and skeletal structure while immersed in a relatively low velocity current that would create relatively little discomfort. Furthermore, the moving water could be warmed and/or salted, to any degree desired for deep muscle therapy, all conducted while the body is under very little load because of the buoyancy effects that could be further enhanced by flotation devices attached to the patient. While the speed of current flow is preferably controlled by adjusting the vaned rotor speed, speed may also be adjusted by varying the effective cross sectional area of the flow channel beteen inlet and outlet. For example, a vane may be introduced into this channel with controllable penetration. Angularly adjustable venetian-blind-like vanes may be interposed, preferably at the outlet. Other means for selectively introducing flow impedance into the stream may be used. A number of exemplary dimensions have been set forth above. The length of the swim channel between baffle 17 and outlet 14 is typically substantially (12 feet) 3,7 m. The curvature of the outer wall of the curved transition portion at the front is typically 594mm (23.75") radius and that of the inner wall substantially 287.5 mm (11.5") radius to form a substantially semicircular cylinder having an annular passage of substantially 180°. The top of shroud 42 is typically 254 mm (10") below the top of tank 11. The Swim-in-place pool tank 40 is constructed in four sections 42, 44, 46 and 48 from fiberglass. Section 42 forms the housing for paddle 15, sections 44 and 46 the rear and front compartments respectively of the tank, and section 48 the return channel from paddle 15 to the tank. Also provided are front and rear floor sections 52, 50. Rear section 50 has steps to facilitate entry to the tank. Further, hand rails 54 are provided and attached to section 44. Sections 44 and 46 are shaped so that the tank has a bowed shape, being wider in the area where a swimmer moves his arms (a distance O from the front of tank 40) and narrower at the rear of the tank near grille 17. The width of section 46 at the center of the tank is M, about 2.2m (88"), its depth is N, about 1.47m (59") while the minimum internal width at the rear end of the tank is Q, about 1.37m (55"). The maximum internal width of section 46 is about 1.87m (75") at a distance O, about 1.05m (42") from the front of the tank near baffled opening 14, where the width is P, about 1.67m (67"). The length S of both sections 44, 46 is about 1.85m (74"); and the depth T,U of sections 44, 48 respectively is about 0.85m (34") and 0.6m (24"), to give an overall length V, about 5.15m (206"). water 56 can be placed within the tank 40 to a depth R, about 1m (40"). Each section 42, 44, 46, 48 is bolted to another section with a bolt 60, such as shown in Fig. 1E. A seal cord 62 and sealant 64 are secured within channels 66 provided in each section to ensure sealing of the sections. Also provided in the tank are grille 17, controls 68, grate 70, and enclosure 72 for motor 20. Further, two pads 74, 76, having a drain slope 78 are provided. Drain slope 78 is about 1/4°. The floor sections 50, 52 of the tank are also sloped, decreasing in height from X, about 0.3m (13"), to Y, about 0.25 (10"). Thus, the underneath, or bottom 53, of floors 50, 52 is similarly sloped. By using fiberglass, tank 40 can be shaped to provide added features. The four bolted sections 42, 44, 46 and 48 are designed so that they can be moved through a 0.9m (36") wide door opening, or with care even through 0.85m (34") wide opening. The center sections 44, 46 are moved by standing them upright and walking them through and around door panels. The tank 40 is also provided with full width intake and outlet grilles 66 and 17 so that no dead zones are created at corners of the tank. Further, arm room of about 1.87m (75") (at a distance O from the front of tank 40) is provided and tank 40 is bowed so that it is narrower from this point, to create a rearward tapering shape in which a swimmer can comfortably swim. The shape also causes an increase in water velocity, as water flows toward grille 17, and thus compensates for velocity losses encountered as water flows along the length of tank 40. Thus, a more uniform longitudinal water velocity gradient results. The upwardly inclined floor in sections 50, 52 further enhances this effect by reducing the volume of the rear section of the tank. The slight slope 78 of the bottom (pads 74, 76) promotes drainage, slots (not shown) are also present to promote such drainage to forward section 46. The underside of the sloped floor 53 enhances escape of entrapped air in the turnabout duct, or lower channel 12, to vent holes (not shown) in the rear section 44, thus reducing turbulence in the recycled water. This slope, and the wedge action of the water flow, tends to work the bubbles backward where they rise at the paddle wheel grille. The specific embodiments described herein are by way of example only. Numerous variations may be practiced by those skilled in the art. For example, the driving means might comprise a row of pumps at either the front or rear of the tank, or in between, with outlets spaced across the width so as to maintain the velocity gradient substantially zero along the width of the tank in the stream at the top of the tank. Numerous other variations will be suggested to those skilled in the art. It is evident that those skilled in the art may now make numerous uses and modifications of and departures from the specific embodiments described herein without departing from the inventive concepts.

Claims: Flow controlling apparatus comprising, a tank (40) for supporting a fluid, upper (13) and lower (12) channels in the tank for allowing fluid flow in upper and lower opposed directions, and drive means (19,20,75) for propelling the fluid through the upper (13) and lower (12) channels with substantially uniform velocity of fluid across substantially the entire width of the tank (40) at the top of the tank (40), characterised by the tank (40) having a bowed shape or being rearwardly inwardly tapered so as to provide a substantially uniform water velocity gradient along the length of the tank (40). Apparatus according to claim 1, wherein the drive means comprises a vaned rotor (15) with vanes (15A) angularly spaced about the rotor axis rotatably supported in the tank (40) at one end thereof, the rotor axis being substantially parallel to the width dimension of the tank. Apparatus according to claim 2, wherein the diameter of the vaned rotor (15) is slightly less than the depth of the tank (40). Apparatus according to claim 2 or claim 3, wherein the length of the vanes corresponds substantially to the width of the tank (40). Apparatus according to any of claims 2 to 4, further comprising a shroud (42) of substantially semicircular cross-section surrounding the outside portion of the vaned rotor (15) and coating therewith to form a vane pump with working clearance between the shroud (42) and the outside edges of the vanes (15A). Apparatus according to any of claims 2 to 5, further comprising entry deflector means angled upward from the lower channel (12) toward the vaned rotor (15) for capturing an escape flume from the vaned rotor and directing the escape flume along the lower channel (12). Apparatus according to any of claims 2 to 6, wherein the drive means further comprises pump means (31) for providing fluid under pressure, the vanes (15A) including nozzle means (15E) for ejecting fluid under pressure in a direction tangential to the outer perimeter of the vanes, and means (32) for coupling fluid under pressure from the pump means (31) to the nozzle (15E) means to cause rotation of the vaned rotor (15). Apparatus according to any of claims 2 to 6, wherein the drive means further comprises, an induction motor (19) mechanically coupled to the vaned rotor (15) inverter means for converting input energy into A-C energy of controlled frequency, and means for coupling said energy of controlled frequency to the induction motor to control the speed of rotation of the vaned rotor. Apparatus according to any of claims 1 to 8, further comprising means defining a transition channel intercoupling the upper (13) and lower (12) channels and characterised by a curved longitudinal cross-section with a substantially rectangular opening (14) at the top. Apparatus according to claim 9, wherein the height of the rectangular opening (14) is greater than the depth of the lower channel (12). Apparatus according to any of claims 1 to 10, wherein the upper channel (13) is of length slightly greater than the length of a human being and of width slightly greater than the tip-to-tip span between fingers of outstretched opposed arms of a human being. Apparatus according to any of claims 1 to 11, wherein the tank has a floor which is sloped to enhance drainage of the tank. Apparatus according to claim 12, wherein the floor has an underside shaped to promote venting of entrapped air. Apparatus according to any of claims 1 to 13, formed from a plurality of sections, each of which is sized to fit through a 864 mm (34 inch) wide doorway. Apparatus according to claim 14, wherein there are four sections. Apparatus according to any of claims 1 to 15, wherein the tank is made of fibreglass.

Inventors: MERMELSTEIN, SEYMOUR
Applicants: SWIMEX SYSTEMS, INC.
Application year: 1988
Main classification: A47K3
IPC codes: E04H4, A63B69