The invention relates to an underwater propulsion device which is attachable to the human body.

The concept of a propulsion system which is attachable to the body for underwater use is already known from the prior art. Such systems are designed to be used in the diving sector as underwater propulsion device for individual divers. An advantage of propulsion systems which are attachable to the body is the fact that they permit the user a large degree of freedom of movement because the user does not have to hold on to anything and does not have to sit on anything or support himself on anything.

However, the abovementioned propulsion systems also face several technical challenges, as a result of which their practical application has hitherto been limited. These technical challenges are largely related to the need to keep the system manageable and user-friendly. After all, the user has to be able to wear the system both in the water and, to a limited degree, also outside the water and has to be able to move with the system. The ease of handling of the system is in this case not only determined by the dimensions and the mass of the system which should preferably be kept as low as possible. The ergonomics of the system play an important part in this. When wearing the system, the freedom of movement of a user should not be inhibited or as little as possible by the system. In this case, the control of the system should preferably be intuitive for the sake of ease of use and in order to keep the time required to learn how to control the system as short as possible. In addition, the system has to be usable in combination with a conventional diving outfit.

In short, propulsion systems for underwater use which are attachable to the body will only become widely used when such systems have become sufficiently user- friendly. It is therefore an object of this invention to provide an underwater propulsion device for attaching to the human body which is more ergonomic and more user-friendly than the systems known until now. To this end, the invention provides an underwater propulsion device which is attachable to the human body comprising at least one propulsion unit which is configured to be attached to at least a part of a lower leg, wherein the propulsion unit comprises at least one electric motor and at least one propeller which is drivable by the electric motor, and at least one battery which is electrically connected to at least one electric motor, wherein the underwater propulsion device comprises at least one upper leg belt, which upper leg belt is configured to be attached to at least a part of an upper leg, and wherein the upper leg belt is configured to hold the at least one battery.

The underwater propulsion device is adapted to displace water, as a result of which a propelling force is generated. Therefore, the underwater propulsion device, or at least the propeller, will have to be situated at least partly underwater during normal use in order to be able to achieve the desired water displacement. The propeller is for example a drive screw. Because the lower legs and feet will generally always be under the water surface, even when moving forward on the water surface, the propulsion unit will also always be underwater when it is attached to a lower leg, ankle and/or foot, thus ensuring continuous propulsion. Where reference is made to the lower leg, this also includes the ankle and/or foot. Therefore, the part of the leg below the knee may be regarded as the lower leg as intended in the present invention. In addition, the part of the leg below the knee is not usually an attaching location for standard diving equipment, as a result of which an underwater propulsion device which is attachable to this part of the leg can be used in combination with standard diving equipment without any problem. The battery is configured to provide electrical energy, such as current, to at least one electric motor. The use of an upper leg belt to attach the at least one battery to the body at the location of the upper leg has a beneficial effect on a good weight distribution of the underwater propulsion device. Where reference is made to an upper leg belt, it is also possible to use the term upper leg belt. Because the propulsion unit, due to its attachment below the knee, already adds weight to the lower leg, the ankle or the foot, it is advantageous to fit the at least one battery at another location on the body. In this case, a belt around the upper leg offers sufficient space to be able to attach the one or more batteries to the body, considering that the batteries have quite a significant mass and dimensions due to the battery power which is required to be able to provide energy to the electric motor of the propulsion unit for a prolonged period of time. Arranging the at least one battery on the lower body, in particular the upper leg, in addition prevents the weight and the bulk of the equipment form being concentrated around the waist of the diver when using the underwater propulsion device in combination with regular diving equipment. The upper leg belt is not in the way of regular diving equipment which often comprises a diving vest (trim vest) with an incorporated weight belt, to which the cylinder(s) containing respiratory air (compressed air) are also attached. Conventionally, a separate weight belt is attached around the waist and this is thus not inhibited by an upper leg belt. In this case, it is even conceivable, in practice, to omit the use of a weight belt due to the additional weight of the at least one battery. As the underwater propulsion device according to the invention is at least substantially fitted to the lower body, whereas conventional diving equipment is attached to the torso, the weight of the total equipment of a diver, consisting of the regular diving equipment and the underwater propulsion device, is distributed proportionally over the torso and the lower body. This prevents the diver from sagging at the waist when he or she is in a horizontal position in the water.

Where appropriate, the underwater propulsion device, and in particular the at least one upper leg belt, comprises an electronic speed controller which is connected between the at least one battery and the electric motor of the at least one propulsion unit. The electronic speed controller serves for the commutation of the electric motor and for regulating the motor output. Where appropriate, the electronic speed control is formed by an electronic circuit which is able to regulate the speed of the electric motor. By making the electronic speed control form part of the upper leg belt, the propulsion unit can be kept more compact and the weight on the lowest part of the leg is limited. This benefits the ease of handling and the streamline of the underwater propulsion device when it is attached to a user. In a further possible embodiment, it is also conceivable for the electronic speed controller to form an integral part of a propulsion unit. An advantage of this embodiment is that cooling of the electronic speed controller can be achieved in a relatively simple manner, for example by means of water cooling.

In a preferred embodiment, the underwater propulsion device may comprise two propulsion units, wherein each propulsion unit is configured to be attached to at least a part of a (separate) lower leg, and the underwater propulsion device may comprise two upper leg belts, wherein each upper leg belt is configured to be attached to at least a part of a (separate) upper leg and wherein each upper leg belt is configured to hold at least one battery. More preferably, the underwater propulsion device are substantially symmetrical. It is, for example, conceivable for the underwater propulsion device to comprise a left upper leg belt and a right upper leg belt, as well as a left propulsion unit and a right propulsion unit. Preferably, at least one electric motor of the left propulsion unit is then electrically connected to at least one battery which is held in the left upper leg belt and/or at least one electric motor of the right propulsion unit is electrically connected to at least one battery which is held in the right upper leg belt. This embodiment may contribute further to a stable positioning of the underwater propulsion device and/or to a good weight distribution of the underwater propulsion device. Therefore, this embodiment may also provide a positive contribution to the possibility of the diver to assume a desired streamlined, preferably substantially horizontal, posture while diving.

Using two propulsion units which are each attached to a different leg, the stability of the propulsion mechanism is improved during use. In addition, using two propulsion units makes it possible to control the underwater propulsion device by varying the thrust supplied by the individual propulsion units with respect to each other. Finally, the use of two propulsion units also benefits the maximum thrust and/or efficiency. By distributing the batteries across two upper leg belts, the weight of the batteries is distributed across both legs, which is advantageous for the balance of the diver in the water, but also when wearing them outside the water. Usually, the batteries of an upper leg belt will in this case provide the power for the electric motor of the propulsion unit which is configured to be attached to the same leg as this upper leg belt.

In a further possible embodiment, it is conceivable for the underwater propulsion device to comprise at least one secondary propulsion unit which comprises at least one electric motor and at least one propeller which is drivable by the electric motor. Said secondary propulsion unit is preferably an independent propulsion unit and/or is configured to be attached to an external component. A non-limiting example of an external component is, for example, a parcel which is carried along by the diver. In a possible embodiment, it is also conceivable for the at least one propulsion unit to be a stand-alone propulsion unit which comprises at least one electric motor and at least one propeller which is drivable by the electric motor, wherein the propulsion unit may optionally be configured to be attached to at least a part of a lower leg.

The upper leg belts may be mutually connected to each other via a waist belt. In this way, an underwater system may be obtained whose components are all connected to each other. This is advantageous, for example, if the electronic components in the propulsion unit and upper leg belt which are configured to be attached to a left leg and/or a right leg have to be electrically connected to each other. The cabling for this connection may run via the waist belt. By means of a waist belt, attachment of the underwater propulsion device to the body is also further ensured. In addition, the waist belt may comprise one or more operating elements for operating the propulsion units. If the underwater propulsion device, and in particular the waist belt, comprise several operating elements, it is conceivable for every operating element to be configured to operate an individual propulsion unit. Such an operating element may comprise, for example, an on/off switch. An advantage of placing an operating element on the waist belt is that it is readily accessible to the hands. However, when placing such components on the waist belt, the compatibility with standard diving equipment should be taken into account, so that the waist belt is not in the way of this diving equipment. It is also conceivable for an upper leg belt to comprise at least one operating element. It is also conceivable for the underwater propulsion device, and in particular the upper leg belt, to comprise at least one user interface. The user interface may comprise, for example, a display and/or at least one visual indicator, such as an LED.

In a possible embodiment of the underwater propulsion device, the upper leg belts may each comprise an electronic speed controller, wherein the electronic speed controller of each of the upper leg belts is connected between the at least one battery which is also comprised by the respective upper leg belt and the electric motor of one of the two propulsion units. The propulsion unit whose electric motor is connected to the electronic speed controller is preferably the propulsion unit which is configured to be attached to the same leg as the upper leg belt which comprises the aforementioned speed controller. This prevents the unnecessary diversion of cables across the body in order to connect the electronic speed controllers to the propulsion units. The waist belt may comprise cabling which electrically connects the electronic speed controller of the first upper leg belt to the electronic speed controller of the second upper leg belt. In this way, the motor output of the two propulsion units can be controlled in dependence on each other. In addition, the cabling of the waist belt which connects the upper leg belts to each other makes it possible to connect both electronic speed controllers to the same electronic components of the underwater propulsion device. Thus, it is possible, for example, for the cabling of the waist belt to electrically connect the electronic speed controllers to an operating element on the waist belt as described above. It is also possible for the batteries from the two upper leg belts to be electrically connected to each other so that both propulsion units can be supplied with energy from one central cluster of batteries. When used in practice, there will be a difference in the energy consumption of the propulsion units, as a result of which the batteries supplying energy thereto will discharge at different rates. When connecting the batteries to each other and creating a battery cluster, the propulsion units will only stop working when all batteries are discharged. Optionally, it is also possible to connect and/or disconnect further external batteries in order to extend the life.

In order to protect the electronic speed controller and the cable connections as well as the structural integrity of the upper leg belt, the at least one electronic speed controller may be accommodated in a frame having a rigidity which is greater than the rigidity of the at least one upper leg belt. If a (pulling) force is exerted on the upper leg belt which results in a deformation (stretching) of the upper leg belt, the aforementioned rigid frame may prevent electrical cabling which is connected to the electronic speed controller from becoming disconnected. In addition, a frame may provide impact protection to delicate or critical electronic components, such as an electronic speed controller.

The frame may also serve to connect the electronic speed controller to other components of the underwater propulsion device. More particularly, the frame may comprise at least one connection which is configured to couple at least one cable connected to the propulsion unit in a detachable and/or adjustable way from an outer side of the upper leg belt in order to electrically connect the propulsion unit to the electronic speed controller. By connecting the propulsion unit to the electronic speed controller via connections in the frame, it becomes possible to protect the electronic speed controller, as a result of which it can be packed water-tight. At the same time, it becomes possible to design this connection to be detachable, as a result of which the upper leg belt of the propulsion unit can be uncoupled. This has the advantage that the underwater propulsion device can be fitted to the body or removed from the body more easily. This also benefits the ease of handling of the underwater propulsion device before and after use. It is also conceivable for the aforementioned connection to be an adjustable connection, so that it can be adapted to the user, in particular the height of the user. It is for example also conceivable for the aforementioned cable to be adjustable in order to achieve the aforementioned adjustability.

In a further possible embodiment, it is conceivable for two or more electronic components of the underwater propulsion device to be wirelessly connected to each other. It is for example conceivable for two or more electronic components to be connected to each other via Bluetooth or the like.

Preferably, the size of the upper leg belt is adjustable in such a way that it can be attached to upper legs of different sizes. It is for example conceivable for at least one upper leg belt to be provided with a hook and loop fastener, (press-)buttons, a zip, buckle connection, click-fit connection and/or other connecting means by means of which the dimensions of the upper leg belt can be adjusted. It is also conceivable for the propulsion unit to comprise attachment means by means of which it can be attached to a lower leg, which attachment means are preferably detachable and/or adjustable.

The upper leg belt may comprise, for example, at least one holder for holding at least one battery. It is also conceivable for the upper leg belt to comprise at least one receiving space for receiving at least a part of a battery. It is preferred if the battery can be detachably connected to the upper leg belt. This is advantageous, for example, if a battery has to be replaced or in case the upper leg belt has to be cleaned. In a possible embodiment, at least one upper leg belt is configured to hold one or more batteries.

In an advantageous case, at least one upper leg belt may be provided with a housing which surrounds the at least one battery in a water-tight manner. Usually, the upper leg belt will be configured in such a way that it not only surrounds the batteries, but also all other electronic components which are comprised in the upper leg belt in a water-tight manner. In this case, the upper leg belt therefore not only serves to arrange electronic components, such as the batteries and electronic speed controllers, around the upper leg, but also serves to pack these components in a water-tight manner. If one or more external batteries are used in combination with the underwater propulsion device according to the present invention, it is also conceivable for each of these to be provided externally with its own external water tight housing and wherein each external water-tight housing can be attached to the underwater device, for example an upper leg belt, by way of attachment means. Non-limiting examples of attachment means are a hook and loop fastener, (press-)buttons and/or a click-fit connection.

In one possible embodiment, the housing may be formed by at least one sealed rubber cell. This cell surrounds the electronic components of the upper leg belt, as a result of which these are protected in a water-tight manner. In one possible embodiment, the upper leg belt may comprise several interconnected rubber cells which each surround a part of the electronic components of the upper leg belt in a water-tight manner. The advantages of using such a construction with one or more rubber cells are innumerable. Firstly, the construction can be produced in a simple manner, because the rubber can easily be adhesively bonded to the electronic components arranged therein, which results in a water-tight construction. Also, the rubber is robust and impact-proof, absorbing the force of any impact due to the inherent elasticity of the material. Furthermore, the at least one rubber cell provides a degree of flexibility to the upper leg belt, as a result of which a good connection of the upper leg belt around the body is achieved. Because rubber also has a relatively high coefficient of friction, the upper leg belt will remain securely fixed around the upper leg during use. Finally, the at least one sealed rubber cell may provide a positive contribution to the buoyancy, as a result of which the weight of the enclosed components and/or the propulsion element may be compensated for.

If the upper leg belts are connected to each other by means of a waist belt, it is also conceivable for the waist belt to form part of this at least one sealed rubber cell, so that the upper leg belts and the waist belt form one flexible unit in which all cabling, batteries, electronic speed controllers and any other electronic components are retained in a water-tight manner. In an advantageous embodiment of the underwater propulsion device, the propeller of the at least one propulsion unit is formed by an impeller which is coupled to an output shaft of the electric motor via a toothed-belt transmission, wherein the impeller is provided with external toothing on a peripheral side for engagement by the toothed belt. The specific design of the impeller in which the toothing is incorporated on the peripheral side is crucial in making a compact and lightweight embodiment of the underwater propulsion device possible, which in turn benefits the ease of handling of the underwater propulsion device overall. Usually, the transmission ratio between the output shaft of the electric motor and the impeller is greater than 1 , with the output shaft of the electric motor performing more than a complete revolution for every complete revolution of the impeller. In order to provide the impeller with a sufficiently great torque and to achieve an efficiency of the electric motor which is as large as possible while aiming for an electric motor with a relatively good streamline, a relatively low mass and a relatively limited volume, it was found that the output shaft of the electric motor has to rotate at a higher rotary speed than the impeller. By means of the impeller with toothing, the water displacement function and the transmission function are achieved by a single component, which is advantageous with regard to both the weight and the dimensions of the drive unit. In addition, the peripheral wall provided with teeth gives additional reinforcement to the impeller, as a result of which the impeller can be made more light-weight and is also able to withstand relatively large forces which are due to high rotary speeds. The use of a toothed-belt transmission has the advantage that it does not require any lubrication in order to function well, as a result of which direct exposure of the toothed-belt transmission to water is not a problem. In addition, a toothed-belt transmission is resistant to wear and suitable for high rotary speeds. By means of the combination of this impeller with a toothed- belt transmission and an electric motor, an efficient, compact and lightweight underwater propulsion device is obtained which is eminently suitable for direct attachment to the body in the light of the requirements which are placed on a propulsion system which is attachable to the body.

Where appropriate, the at least one propulsion unit of the underwater propulsion device may comprise an operating member for actuating the propulsion device, the operating member being configured to be operated by means of the foot. To this end, the operating member may comprise a foot-retaining element for attaching to the foot. As such an operating member makes operation by foot possible, the hands of the operator are free to perform other tasks. In a specific embodiment, the operating member may be configured for increasing the thrust delivered by the electric motor by means of a plantar flexion of the foot and for decreasing the thrust delivered by the electric motor by means of a dorsal flexion of the foot. Due to its similarity to a standard accelerator pedal, the operator of the propulsion device finds this way of regulating the motor power very intuitive. In addition, this way of regulating causes minimal drag in the water at maximum thrust and maximum drag at minimal thrust. It is furthermore conceivable for the operating member to be configured to reverse the jet by means of dorsal flexion of the foot beyond the neutral position of the foot.

The invention will be explained by non-limiting exemplary embodiments illustrated in the following figures, in which:

- Fig. 1 shows a side view of an underwater propulsion device according to the invention in a position attached to a user,

- Fig. 2 shows a top view of an underwater propulsion device as illustrated in Fig. 1 , again in a position attached to a user,

- Fig. 3 shows a combination of two upper leg belts and a waist belt as provided in an underwater propulsion device according to the invention, and

- Fig. 4 shows a cross section of a propulsion unit as provided in an underwater propulsion device according to the present invention.

Figs. 1 and 2 show a side view and a top view, respectively, of an underwater propulsion device 1 according to the invention in a position attached to a diver 2. The illustrated underwater propulsion device 1 comprises two propulsion units 3 which are provided with attachment means in order to be attached to the body. In the case illustrated, the attachment means are formed by a number of belts 5 which are attached to a housing 4 of the propulsion units 3 and by means of which each of the propulsion units 3 is attached to a leg 8 of the diver 2 at the location of the lower leg 6 and the ankle 7. It is also conceivable for attachment means other than belts 5 to be used. In addition, the location of attachment to the body may differ from the positions illustrated here. In the illustrated embodiment, the propulsion units 3 are provided with an operating member 9 which is configured to be operated by means of the foot 10. In the illustrated embodiment, the operating member 9 comprises a foot-retaining element 25 provided with attachment members. Furthermore, the propulsion units 3 are each provided with an electric motor 11 and a propeller 12 which is driven by the electric motor 11 , which are diagrammatically shown in the drawing by dashed lines. By means of cables 13, the electric motors 11 of the propulsion units 3 are connected to electronic speed controllers 14 which are each accommodated in a different one of two upper leg belts 15. The electronic speed controllers 14 are in turn electrically connected to batteries 16 which are likewise accommodated in the upper leg belts 15. The upper leg belts 15 are mutually connected via a waist belt 17 which is arranged around the waist of the diver 2. Due to the fact that (the majority of) the electronic components for controlling and actuating the propulsion units 3 are connected to the upper leg belts 15, the waist belt 17 may have a low profile. Consequently, the combination of waist belt 17, upper leg belts 15 and propulsion units 3 connected to the lower legs 6 is not in the way of the regular diving equipment of the diver 2, formed by a diving vest 18 and cylinders of respiratory air 19 and a(n integrated) weight belt 20.

Fig. 3 shows a combination of two upper leg belts 30 and a waist belt 31 as provided in an underwater propulsion device according to the invention. In the illustrated embodiment, each upper leg belt 30 is provided with two batteries 32, which are electrically connected to an electronic speed controller 34 via cables 33. The upper leg belt 30 may also be provided with additional cables 43 for connecting an optional external battery (not shown). The electronic speed controller 34 is accommodated in a frame 35 which, for the sake of rigidity, may be made of, for example, a metal or a fiber-reinforced polymer. The frame 35 is provided with a few detachable and/or adjustable connections 36 which project out of the upper leg belt 30 and are connected to contacts of the electronic speed controller 34. Detachable and/or adjustable cabling which is connected to the electric motor of a propulsion unit of an underwater propulsion device according to the invention may be connected to these connections 36 from an outer side of the upper leg belt 30. In this way, the propulsion unit may be electrically connected to the electronic speed controller 34 and, by way of the electronic speed controller 34, to the batteries 32 situated behind. Furthermore, connections 36 may be accommodated in the frame which serve to connect external electronics, such as sensors. The upper leg belts 30 are connected to each other via a waist belt 31 . The waist belt 31 furthermore comprises cabling 37 by means of which the electronic speed controllers 34 of both upper leg belts 30 are electrically connected to each other. The waist belt 31 additionally comprises an operating element for operating the propulsion units, and more particularly a switch 38 for switching the underwater propulsion device on and off. This switch 38 is connected to a circuit board 39 which circuit board is connected to the cabling 37 coming from the upper leg belts 30 which electrically connect the electronic speed controllers 34 to each other. The illustrated assembly of the upper leg belts 30 and waist belt 31 forms one unit, the outer side of which is formed by a sealed rubber cell 40 which keeps the components held in the upper leg belts 30 and waist belt 31 together and packs them in a water-tight manner. In the illustrated embodiment, the upper leg belts 30 and waist belt 31 are attached by means of hook and loop fastener 41 . However, other attachment means, such as belts, may also be used to attach the belts 30, 31 around the body of the user.

Finally, Fig. 4 shows a cross section of a propulsion unit 50 as provided in the underwater propulsion device according to the present invention, wherein the propulsion unit 50 is partly shown in perspective. In the illustrated embodiment, the propulsion unit 50 is surrounded on an outer side by a housing 51 which protects the internal mechanism of the propulsion unit 50 from the user. This internal mechanism comprises an electric motor 52 with an output shaft 53. A gear wheel 54 is arranged on the output shaft 53 of the electric motor 52 which is engaged by a toothed belt 55. The toothed belt 55 in turn engages with an impeller 56 which is provided with external toothing 57 on a peripheral side to this end. The impeller 56 is placed in a jet pipe 59, an upstream part 60 of which is formed by the housing 51 in the illustrated embodiment. This part of the jet pipe 59 serves to guide the flow 61 of water in the direction of the impeller 56. In a downstream part 62 of the jet pipe 59, several stator blades 63 are provided which are positioned in the jet pipe 59 so as to be rotationally symmetrical and extend in the radial direction up to the inner side of the jet pipe 59, as a result of which de facto several ducts are created for the outflowing water flow 64. In this embodiment, the downstream part 62 of the jet pipe 59 is furthermore formed in such a way that the diameter of this part 62 of the jet pipe 59 tapers in a direction facing away from the impeller 56. The housing 51 also forms the engagement point for attachment means by means of which the propulsion unit 50 can be attached to the user 65. These attachment means are formed by belts 66 by means of which the propulsion unit 50 can be attached to the body of the user 65 at the location of the ankles and lower legs. In addition thereto, the propulsion unit 50 is provided with a foot-retaining element 67 which engages around the foot and is connected to an operating member 68 of the propulsion unit 50. This operating member 68 is configured to actuate the electric motor 52 of the propulsion unit 50 and also configured to be operated by means of the foot using the aforementioned foot-retaining element 67. It is possible, for example, for the operating member 68 to regulate actuation of the electric motor 52 by way of an electronic speed controller. In the illustrated embodiment, the foot-retaining element 67 is provided with attachment members 85 which, in an advantageous embodiment, may be provided with a hook and loop fastener. In the illustrated embodiment of the propulsion unit 50, actuation of the electric motor 52 takes place by rotating the operating member 68. This rotation is made possible by a rotation of the foot-retaining element 67 which is coupled to the operating member. In particular, it is preferred if the actuation of the electric motor 52 coupled to the turning direction of the operating member 68 is chosen in such a way that a rotation caused by a plantar flexion of the foot leads to an increase in the thrust delivered by the electric motor 52 and a rotation caused by a dorsal flexion of the foot leads to a decrease or even a reversal of the thrust delivered by the electric motor 52.

It will be clear that the invention is not limited to the exemplary embodiments illustrated and described here, but that numerous variants are possible without departing from the scope of the attached claims which are obvious to the person skilled in the art. In this case, it is conceivable that different inventive concepts and/or technical measures of the above-described embodiments can be combined in part or in their entirety without departing from the scope as described in the attached claims.