Patent Description:
Known systems make use of a pump outside of the swimming pool (typically in the technical space). Water is transported though conducts. Drawbacks of these systems are the loss of power in the conducts and a too-narrow current from the circular outlet, making it difficult for the swimmer to stay in the correct position.

Another drawback is that such deeply integrated systems make it difficult and expensive to add counter-current swimming capability to an existing pool.

<CIT> discloses a system which can be used as an add-on box. The box has a motor in it and a straight tube is placed directly in front of the motor, with a <NUM>-bladed open propeller screw which pushes the water straight through the round outlet (of the same diameter as the propeller) into the pool. The water is sucked in through the grid over the entire front side of the cabinet (on installation) or via grids on several sides (surface).

Document <CIT> discloses a submersible jet stream device having inlet apertures and an outlet nozzle which creates a jet stream which can be located either in a first position at the water surface or a second position at a pool bottom.

Document <CIT> describes a counter-current swimming device with a motor positioned inside the housing.

Document <CIT> describes another counter-current swimming device with a motor positioned inside the housing.

Document <CIT> discloses a current providing device for a swimming pool and explicitly discloses that the device has an annular channel that is widened suddenly, so that when the circulated water flows through, a negative pressure can be created behind it.

Document <CIT> discloses a swimming pool design which make use of a pump outside of the swimming pool by transporting water through conducts. This pool design is not suitable for a use as a device that can be attached to an existing pool.

It is an object to provide an improved counter-current swimming device.

According to a first aspect, the invention provides a counter-current swimming device for installation in a swimming pool, as defined in claim <NUM>.

The invention provides a device with a compact cabinet with a motor powered propeller in which the (low-voltage) motor an, for example, a multi-bladed (four-bladed) overlapping screw (with specially developed blades and pitch) push the water through a narrower round tube, after which the water jet flows through a considerably narrower oval shaped water outlet and into the pool.

Due to the overlapping blades of the screw no water can leak back so that the pressure in the narrow (tapered) housing parts and outlet nozzle may be further increased.

The water jet has therefore gained a lot of speed when entering the pool. As a result, significantly less volume displacement of water is required for a high flow rate than with prior art devices (efficiency improvement).

The applied principle (compared to the operating principle of prior art devices) can be described as that of water displacement combined with a pressure increase instead of only water displacement.

By optionally placing the water outlet not directly in front of the motor and propeller, but sending it to the outlet via a bend, the device can be built more compactly than in the prior art systems. In addition, more efficient use is made of the naturally present water pressure in the basin for sufficient water supply.

The device's grates for the suction of water are located deeper under the water surface where the natural water pressure is higher. The water supply is more efficient by using this natural water pressure combined with the pressure-increasing principle that is used in the device (so less water displacement is required for a strong flow rate).

Due to more efficient water supply, smaller grids can be used for sufficient water intake, which makes a more compact device possible.

The dimensions of the new product may be L: <NUM> x W: <NUM> x D: <NUM>. This makes it applicable in practically every size of swimming pool. It will be clear to the skilled person that devices according the invention can deviate from the above given example dimensions. Dimensions could be in the ranges <NUM> < L < <NUM>, <NUM> < W < <NUM>. <NUM> < D < <NUM>.

A magnetic coupling can be used for transmission from motor to propeller screw. Normally use is made of a watertight bearing between motor and screw to realize water tightness of the motor. But the bearings rotate and that is a significant weak point in the water tightness. By using magnetic coupling, a completely sealed enclosure around the motor is made possible, so that the water resistance of the motor is no longer an issue. Moreover, the magnetic coupling has advantages in that it allows the coupling to slip to prevent damage to the motor if the propeller gets stuck and, particularly if electro magnets are used on the driving part of the coupling, it is possible to easily disengage the coupling for maintenance purposes.

In an optional example, the motor is included in a motor housing and said motor housing is filled with a cooling liquid. The motor housing is sealed so that the cooling liquid cannot mix with the environment of the device. In an embodiment, the motor inside the motor housing is also filled with the cooling liquid. The use of cooling liquid helps to prevent the motor from running to hot. Applicant has found that the use of cooling liquid allows for compacter designs, compared with traditional cooling means such as fins, without impairing the functioning of the motor.

The invention further provides an assembly of two, three, or four counter-current swimming devices as described above installed on a single fastening frame. The invention also provides a swimming pool with at least one counter-current swimming device as described above.

Embodiments of the present invention will be described hereinafter, by way of example only, with reference to the accompanying drawings which are schematic in nature and therefore not necessarily drawn to scale. Furthermore, like reference signs in the drawings relate to like elements.

<FIG> schematically shows a side view of a counter-current swimming device <NUM> according to an embodiment of the invention. The device can be installed against a side wall <NUM> of a swimming pool <NUM> (see <FIG>) using a fastening frame <NUM> attachable to the device <NUM>. The device <NUM> comprises a motor housing <NUM>, which comprises a motor <NUM> (<FIG>) coupled to propeller shaft <NUM>. The motor <NUM> may be an electric motor, more specifically a low voltage electric motor. The propeller shaft <NUM> has a propeller screw <NUM> (shown in <FIG>).

The device further comprises a lower housing part <NUM> connected to an upper housing part <NUM>, which is in turn connected to an outlet nozzle <NUM>. The lower housing part <NUM>, upper housing part <NUM>, and outlet nozzle <NUM> form a flow path for water from a swimming pool (when the device is installed in said pool). The upper housing part <NUM> is in the form of a bend <NUM>'. The device may be provided in a cabinet (not shown) with sufficient grids provided in the cabinet to let water into the flow path.

The upper housing part <NUM> has an entrance <NUM> cross section (see <FIG>), at the connection with the lower housing part <NUM>, and an exit <NUM> cross section at the connection with the outlet nozzle <NUM>. In an embodiment, the entrance cross section is larger than the exit cross section. In an embodiment, the exit cross section is oval in shape. In an embodiment, the major and minor axis of the exit cross section are both smaller than a diameter of the entrance cross section. In an embodiment, the entrance cross section is circular. In another embodiment, the entrance cross section is an oval, with a major axis that is larger than a major axis of the exit cross section. The outlet nozzle <NUM> provides a further narrowing of the flow path. The flow path is continuously becoming more narrow starting from just before the (optional) bend <NUM>' up to the outlet nozzle <NUM>.

Prior art counter-current swimming devices tend to widen the flow path as the path nears the outlet. This is done on the presumption that such a widening of the flow path would allow a swimmer to feel a wide counter-current rather than a narrow jet, making it easier to, literally, stay in the flow. Meanwhile, at the entrance the prior art systems tend to have a relatively narrow flow path to save space.

However, the applicant has surprisingly found that the counter-current is improved when at the entrance the flow path is relatively wide, and it is narrowed somewhat towards the end. This may be in part due to the pressure increase effects described earlier.

<FIG> schematically shows a perspective view of the counter-current swimming device <NUM> according to an embodiment of the invention.

<FIG> schematically shows a front view of a double configuration <NUM> comprising two counter-current swimming devices <NUM> according to an embodiment of the invention installed on a single fastening frame <NUM>'. In an embodiment (not shown in <FIG>), the devices are at a slight angle with respect to each other, so that each nozzle is pointing a little bit away from the other nozzle, thus widening the output current of the combined flows. This has the effect of allowing optimization of the output current profile.

The devices <NUM> can be used in a configuration with practically any number of devices. For most practical pool sizes, Applicant envisages configurations of <NUM>, <NUM>, <NUM> or <NUM> or more counter-current swimming devices <NUM>. The devices can be on a shared fastening frame <NUM>, <NUM>'. Outlet openings <NUM> of each device may be set so that the overall current outlet of the combined devices is optimized. In case of two or more devices, the outlet openings can be pointed in directions in a symmetric (seen from the point of view of a centreline through the pool) fashion, so that the centre device(s) are pointed mostly along the length of the pool and the outer device are pointed somewhat more towards the respective sides of the pool. In this manner, a broad counter-current profile can be achieved while still keeping the multiple counter-current swimming devices <NUM> in a central place. Vice versa, each of the multiple devices can be pointed more towards a centre line of the pool, again in a symmetric fashion, so that a more narrow but stronger current is created in the centre of the pool.

In an embodiment, the orientation of the multiple devices is user-adjustable to a degree, so that a user can change the orientation of the devices and thus optimize the current pattern for his/her use.

The outlet opening <NUM> in each device <NUM> has an oval cross section. The oval cross section has a horizontal (when in operation) major axis and a vertical minor axis. The minor axis of the oval cross section is smaller than the diameter of the circular cross section of the upper housing part <NUM> entrance <NUM>.

<FIG> schematically show side and perspective views with exposed inside details of a counter-current swimming device according to an embodiment of the invention. These figures show the propeller screw <NUM> connected to the propeller shaft <NUM> and configured to provide water into the flow path formed by the lower and upper parts <NUM>, <NUM> and outlet nozzle <NUM>. The propeller screw <NUM> can be a double-bladed screw to prevent water from being pushed back in the opposite direction of the flow path.

In an embodiment most clearly shown in <FIG>, the lower housing part <NUM> is tapering (having an increasingly smaller cross section) towards the upper housing part <NUM>.

<FIG> schematically show side views of a counter-current swimming device <NUM> having an (electro)magnetic coupling <NUM>, <NUM> according to an embodiment of the invention. The coupling comprises a lower coupling part <NUM>, mechanically connected to a motor shaft <NUM> (see <FIG>) and an upper coupling part <NUM>, mechanically connected to the propeller shaft <NUM>. The lower and/or upper coupling parts <NUM>, <NUM> comprise magnets to enable the (electro)magnetic coupling.

The magnets may be permanent magnets or electro magnets. However, given the fluid environment of the device <NUM>, at least on the upper coupling part <NUM> the use of permanent magnets is preferred. Between the lower and upper coupling parts a waterproof layer <NUM> is provided. On the motor (lower) side of the magnetic coupling, either permanent or electro magnets may be used. The use of electro magnets provides the additional advantage that it becomes possible to electrically disengage the coupling, for example for testing or maintenance purposes.

The use of the waterproof layer <NUM> makes it possible to completely encapsulate the motor housing <NUM> in a waterproof seal (of which the waterproof layer <NUM> can be a part), without any moving parts having to penetrate said seal. This improves both the safety and the robustness of the device <NUM> considerably.

An added benefit of the (electro)magnetic coupling is that it allows the lower coupling part <NUM> to slip with respect to the upper coupling part <NUM>. For example, in case the propeller screw becomes stuck on something, the coupling can be allowed to slip, thus preventing damage to the motor <NUM>. In case of a hard mechanical coupling between the motor shaft <NUM> and the propeller shaft <NUM>, it is much more likely that the motor <NUM> will become damaged when the propeller screw <NUM> is stuck.

<FIG> schematically show perspective views of the counter-current swimming device <NUM> having the (electro)magnetic coupling <NUM>, <NUM> according to an embodiment of the invention and <FIG> schematically shows a close up of the motor housing <NUM> and (electro)magnetic coupling <NUM>, <NUM>.

<FIG> shows a folded-open view of the magnetic coupling of <FIG>. The upper coupling part <NUM> is mechanically (rigidly) connected with the propeller shaft <NUM>. The lower coupling part <NUM> is mechanically (rigidly) driven by the motor <NUM> via motor shaft <NUM>. Permanent or electro magnets <NUM>, <NUM> are arranged both in the upper coupling part <NUM> and the lower coupling part <NUM>. Magnet <NUM> has opposed polarity to magnet <NUM>, and is thus attracted by the latter. In stable condition, each magnet <NUM> in part <NUM> is aligned with a magnet <NUM> in part <NUM> and vice versa. The waterproof layer <NUM> is provided between upper and lower coupling parts <NUM>, <NUM>.

<FIG> shows a top view of an alternative magnetic coupling. Here the upper coupling part <NUM>' is partly inside the lower coupling part <NUM>'. The upper coupling part <NUM>' is again mechanically (rigidly) connected with the propeller shaft <NUM>. The lower coupling part <NUM>' is again mechanically (rigidly) driven by the motor <NUM> via motor shaft <NUM> (not shown). In the horizontal plane (seen as the device is installed, with a vertical propeller shaft), the permanent or electro magnets <NUM>, <NUM> are arranged both in the upper/interior coupling part <NUM>' and the lower/exterior coupling part <NUM>'. The waterproof layer <NUM> is again provided between upper and lower coupling parts <NUM>', <NUM>'.

From <FIG>, <FIG> it will be clear that different types of magnetic coupling are possible. What is important is that the two sides of the coupling can be waterproof insulated from each other, so that the motor housing <NUM>, which comprises the motor <NUM> and the lower coupling part <NUM>, <NUM>', can be more easily waterproofed.

<FIG> schematically show the motor housing and coupling according to an embodiment of the invention. In <FIG>, the magnetic coupling is used (as in <FIG>) and in <FIG> the motor shaft <NUM> is directly connected to propeller shaft <NUM>, with sealing ring <NUM> provided to allow the shafts <NUM>, <NUM> to rotate without allowing swimming pool water into the motor housing <NUM>. In both <FIG>, the motor <NUM> comprises two parts, top motor part <NUM>' is rotating together with shaft <NUM> and bottom motor part <NUM>" is stable with respect to the motor housing <NUM>. The skilled person will realize that other arrangements of the motor <NUM> inside motor housing <NUM> are possible.

In the embodiments of <FIG>, the motor housing <NUM> and the top motor part <NUM>' (which can contain coils with empty space around the coils) are filled with a cooling liquid C. Optionally, bottom motor part <NUM>' (and therefore the entire motor <NUM>) is filled with cooling liquid C as well. Applicant has found that without the cooling liquid, the motor may run too hot, necessitating traditional cooling means such as cooling fins and the like which have a negative influence on the compactness of the design.

Experiments with the cooling liquid have shown that it is possible to have a mere <NUM> degree Centigrade difference between the temperature of the cooling liquid (and therefore, of the motor) and the swimming pool water. The cooling effect was surprisingly larger than anticipated and allows for a more compact design. In typical applications, the motor housing <NUM> and empty spaces in the motor <NUM> are filled with air. However, applicant has found that the working of the motor <NUM> is not impaired if a suitable cooling liquid C is used.

A suitable cooling liquid C may be a liquid with good heat conducting properties, while having no or very limited electrical conductivity. A suitable cooling liquid may have a low viscosity. Anti-foaming additives may be used in view of the fact that the rotation of the top motor part <NUM>' inside housing <NUM> causes flows in the cooling liquid C. Anti-corrosion additives may be used to protect the metal motor parts. The cooling liquid may be an oil, particularly a mineral oil. Based on the above requirements, a skilled person can find other suitable cooling liquids.

The cooling liquid is prevented, by the motor housing <NUM> including the waterproof layer <NUM>, from becoming mixed with the environment of the motor housing <NUM>, i.e. the swimming pool water. Obviously, with "waterproof" is also meant "cooling liquid proof".

<FIG> show one or more swimmers S and one or more counter-current swimming devices <NUM> according to an embodiment of the invention. The device <NUM> streams water from the outlet nozzle <NUM> which provides a current for the swimmer S to swim in without actually changing position. <FIG> also include an indication of what is meant with the device <NUM> dimensions D (depth), L (length/height) and W (width).

The <FIG> also show a swimming pool <NUM> with one or more a counter-current swimming devices <NUM> according to an embodiment of the invention and one or more swimmers S. In <FIG>, the surface current is mainly from left to right (with the counter-current swimming device <NUM> on the leftmost wall), while the lower currents are from right to left. The device <NUM> thus causes a flow circulation in the swimming pool. This is also a reason why it is advantageous that the inlet of the device <NUM> is provided below the outlet <NUM>.

<FIG> show that multiple devices <NUM> can be used to create a counter-current for one (<FIG>) or more (<FIG>) swimmers S in the pool <NUM>. The devices <NUM> will be fastened to the swimming pool wall <NUM>.

<FIG> schematically show side, front and perspective views of a counter-current swimming device according to an embodiment of the invention. This embodiment is the same as the embodiments of <FIG>, except that there is no bend <NUM>' in the upper housing part. The upper housing part <NUM> is formed by the tapering part on top of the lower housing part <NUM>, and the exit of said upper housing part <NUM> forms the outlet nozzle <NUM>. The flow path is continuously becoming more narrow starting from the exit of the lower housing <NUM> up to the exit of the upper housing <NUM>. As can also be seen in <FIG>, the propeller screw <NUM> is located in the lower housing <NUM>, so that the flow path is continuously becoming more narrow (that is, has a decreasing cross section) starting from the propeller screw <NUM> to the exit <NUM> of the upper housing <NUM>.

It is advantageous that the counter-current swimming devices <NUM> can be attached to an existing pool <NUM> rather than being installed as an integral part of such a pool.

In the foregoing description of the figures, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the scope of the invention as summarized in the attached claims.

In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

In particular, combinations of specific features of various aspects of the invention may be made. An aspect of the invention may be further advantageously enhanced by adding a feature that was described in relation to another aspect of the invention.

It is to be understood that the invention is limited by the annexed claims only. In this document and in its claims, the verb "to comprise" and its conjugations are used in their non-limiting sense to mean that items following the word are included, without excluding items not specifically mentioned. In addition, reference to an element by the indefinite article "a" or "an" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements. The indefinite article "a" or "an" thus usually means "at least one".

Claim 1:
Counter-current swimming device (<NUM>) for installation in an existing swimming pool, the device comprising:
- a lower housing part (<NUM>) of a housing, the lower housing part having an inlet (<NUM>) with a cross section,
- an upper housing part (<NUM>) of the housing, connected to the lower housing part
- an outlet nozzle (<NUM>) connected to an exit (<NUM>) of the upper housing part, the exit having an exit cross section, so that the lower housing part (<NUM>), the upper housing part (<NUM>) and the outlet nozzle (<NUM>) form a flow channel,
wherein the device further comprises:
- a propeller screw (<NUM>) positioned in the lower housing and configured to, when the device is installed in the swimming pool, accelerate water into the inlet, and characterized by:
- a motor (<NUM>) positioned outside the housing and coupled to the propeller
wherein the cross section of the inlet (<NUM>) is larger than the exit cross section (<NUM>) of the upper housing part (<NUM>) and the flow channel is continuously becoming more narrow starting from the propeller screw (<NUM>) to the outlet nozzle (<NUM>) of the upper housing part (<NUM>).