Electric Propulsion Device for Surfboard with Flexible Shaft Drive

Abstract

An electric propulsion device for surfboard with a flexible shaft drive is disclosed. A motor, batteries, and electronic control equipment is enclosed in a box assembly that is embedded in the tail end of a conventional surfboard to assist a surf rider in paddling, propulsion, and catching a wave. A fin with a propeller is attached to the box. Rotational power from the motor is delivered via a flexible shaft from the box to the propeller. By placing the motor in the outside environment and within the profile of the board, the device improves cooling, reduces drag, and achieves superior performance.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 63 / 761,878, filed Feb. 21, 2025, of which the entire contents thereof are hereby incorporated by reference into the present disclosure.BACKGROUND OF THE INVENTION

[0002] Surfing is a sport that is traditionally accomplished by a rider positioning himself in line with the direction of travel of the wave. As the wave approaches, the rider accelerates with a spurt of paddling so that the board gains enough momentum to slide down the face of the wave and the rider may “stand up” on the board and commence the riding session. However, many factors such as wave size, water choppiness, and rider ability influence this critical process of catching a wave.

[0003] Additionally, most riders must be able to paddle from the beach to the “lineup,” the area where the wave reaches the ideal shape to be ridden. In order to do so, the rider must be able to have sufficient strength to paddle beyond the “break zone” where the waveform collapses into whitewater and the choppiness is a significant barrier for riders with less upper body strength.

[0004] To these ends, Applicant has previously filed and been granted U.S. Pat. No. 11,459,068 “Motorized surfboard fin and remote control” and U.S. Pat. No. 12,434,794 “Extended range motorized surfboard fin and remote control.” These disclosures seek to resolve the common issue of a rider failing to paddle to the lineup or catching a wave by providing a boost of propulsion at the critical moment where acceleration is most desired.

[0005] Many assistive devices in the prior art consume large amounts of power and a high-capacity battery is required, adding significant weight to the device. These devices are difficult to use because of the weight added by housing a large battery in a separate compartment in the surfboard or building the motor and propellers into the surfboard. The wire connection in some of these prior art devices is a large hollow elongated rod or a mast. Others extend the drive shaft from dry compartments into wet areas. In addition to weight distribution that change board performance and handling, these devices suffer from salt water intrusion or breakdown from other environmental factors.BRIEF SUMMARY OF THE INVENTION

[0006] Herein disclosed is an electric propulsion device for surfboard with a flexible shaft drive. A motor, batteries, and electronic control equipment is enclosed in a box-in-board that is embedded in the tail end of a conventional surfboard. A fin with a propeller is attached to the box. Rotational power from the motor is delivered via a flexible shaft from the box to the propeller.

[0007] The invention couples the electrical components with the propeller fin using a flexible drive shaft which is protected by a shaft tube. A flat motor is embedded in the box-in-board. In a preferred embodiment, the invention comprises the propeller fin and the box-in-board, which can be used by surfboard shapers and manufacturers to incorporate into their own board designs. The box is attached to the board via serviceable screws and can be swapped from board to board.

[0008] The invention is superior over the prior art by embedding a larger motor and more battery capacity near the tail end of the surfboard. The propeller fin is smaller compared to the prior art. The motor can be positioned with its rotational axis orthogonal to the board surface, which reduces the total amount of parts that protrude into the current. Together, these features optimize water flow and improve performance.

[0009] All moving parts of the invention are located in wet areas, which improve heat dissipation and ensure no moving parts traverse into dry / sealed areas. Better antenna reception for user remote control is contemplated. The box is additionally used as an anchor and attachment point to secure the motorized fin. The invention removes the electronic components from the fin itself and eliminates the need to waterproof the moving parts of the fin.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which like numbers refer to like parts throughout, and in which:

[0011] FIG. 1 is an exploded view of the components of the electric propulsion device.

[0012] FIG. 2 is an cross-sectional view of the components of the electric propulsion device.

[0013] FIG. 3A is a front right perspective view of the electric propulsion device.

[0014] FIG. 3B is a right elevational view of the electric propulsion device.

[0015] FIG. 3C is a rear elevational view of the electric propulsion device.

[0016] FIG. 3D is a top plan view electric propulsion device.

[0017] FIG. 3E is a rear right perspective view of the electric propulsion device.DETAILED DESCRIPTION

[0018] FIG. 1 is an exploded view of the various components of the electric propulsion device for surfboard. Box-in-board 102 is a base to house the major components, and forms a secure attachment with surfboard 101, by being placed in a preformed cavity within surfboard 101.

[0019] Box bottom 103 and box top 104 together have an external surface, which faces the environment, and an internal surface which faces an internal cavity. They form a watertight compartment to house electronic components, exclusive of the motor 120.

[0020] A second cavity formed by box bottom and box top is for the placement of the motor, which is exposed to water.

[0021] The electric propulsion device moves water by motor and propeller means. Motor 120 mounted to box bottom 103 connects to the propeller 131 via flexible shaft 121 that is protected by shaft tube 122, which is then passed within the fin 130. In one embodiment, the flexible shaft may be made from “316 stainless steel.” The shaft tube may be made from, or coated with polytetrafluoroethylene / PTFE (Teflon™).

[0022] The flexible shaft is not a solid steel shaft. It is an approximate tubular shape formed by a wound spring, retaining its durability and flexibility as it makes angled rotations. It is shaped like a square at its ends to securely attach to other rotating parts without slipping. The shaft tube serves as its bearing, keeping its approximate shape while it delivers rotational torque and protects the shaft from creating friction with the interior of fin 130, which the shaft and tube passes through. An oil or silicone-based lubricant / grease can be applied to the flexible shaft within the tube.

[0023] One end of flexible shaft 121 is connected to motor 120. The motor is disposed within a cavity formed by box top 104 and box bottom 103, which is exposed to water via a plurality of holes 105 disposed within the box top and box bottom. These holes allow water to flush through the motor compartment and remove heat. In addition, no moving parts traverse the interior cavity and exterior environment, reducing potential water intrusion failures.

[0024] The other end of flexible shaft 121 connects to propeller 131 via propeller adapter 123, which provides a matching square hole for the square terminus of the flexible shaft. When motor 120 is on, the spinning motion of the motor rotates flexible shaft which spins the propeller. The propeller assembly is adapted to spin freely when unpowered and further reduces drag, such as when the rider is paddling under his own power or when riding a wave.

[0025] Propeller 131 is protected by propeller duct 132, which focuses water flow toward the propeller surface, separating the flow to be accelerated from ambient flow and thereby reducing drag. The propeller duct 132 also protects large pieces of debris from becoming entangled with moving parts, and also protects the rider from encountering moving parts.

[0026] Regarding the electronic components, batteries 113 supply, in an exemplary embodiment, 25V DC to the system. The batteries are charged by charging port 114 and are monitored by battery monitoring system (BMS) 111. 25V DC is directly supplied to electronic speed controller (ESC) 110 which controls the speed of the motor 120, as well as to other components, which are located on a printed circuit board (PCB) 112. Silicone plug connector 115 protects the charging port.

[0027] Box top additionally serves as a connection surface and anchor point for the fin and propeller. Different sizes and shapes based on user needs are contemplated.

[0028] It is noted that saltwater intrusion may, over time, irreversibly damage the electronic components. The arrangement of parts enables speedy replacement or user-accessible repair.

[0029] FIG. 2 is a cross-sectional view of the major components as assembled. The assembled components are attached to the board-in-box via serviceable screws and can be swapped from board to board, as long as the board itself has a similar cut-out adapted to fit the device.

[0030] The box top 104 sits flush with the water-facing (bottom) surface of surfboard 101. In this configuration, the motor lies entirely within the profile of the surfboard, and the larger internal cavity compared to the prior art enables higher battery capacity as well as more standard / inexpensive batteries to be used. In an exemplary embodiment, the batteries used may be the 21700 lithium-ion cylindrical cell.

[0031] FIGS. 3A, 3B, 3C, 3D, and 3E show assembled components of the electric propulsion device 100 and illustrate the external look-and-feel of the design.

[0032] All publications and patent applications cited in this specification are herein incorporated byreference as if each individual publication or patent application were specifically, and individually, indicated to be incorporated by reference.

[0033] While the invention has been described with reference to exemplary embodiments, it will beunderstood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. An electric propulsion device for a surfboard comprising:a watertight electronics compartment configured to be embedded within a cavity in a surfboard;a motor compartment, separate from the watertight electronics compartment, configured to be exposed to water, the motor compartment having an external surface with a plurality of holes formed therethrough;an electric motor disposed within the motor compartment;at least one battery and an electronic speed controller disposed within the watertight electronics compartment and operatively connected to the electric motor;a fin assembly attachable to the external surface of the motor compartment, the fin assembly comprising a propeller; anda flexible drive shaft having a first end operatively connected to the electric motor and a second end operatively connected to the propeller, the flexible drive shaft being configured to transmit rotational power from the motor to the propeller.

2. The electric propulsion device of claim 1, wherein:the motor compartment comprises a box top and a box bottom, the box top being configured to sit flush with a bottom surface of the surfboard and to serve as an anchor point for the fin assembly.

3. The electric propulsion device of claim 1, further comprising a protective tube encasing the flexible drive shaft, wherein the protective tube is constructed from PTFE.

4. The electric propulsion device of claim 3, wherein the protective tube serves as a bearing for the flexible drive shaft.

5. The electric propulsion device of claim 3, wherein the flexible drive shaft is lubricated by oil or silicone grease.

6. The electric propulsion device of claim 1, wherein the flexible drive shaft comprises a wound spring construction having a square-shaped terminus for engaging with the propeller.

7. The electric propulsion device of claim 1, further comprising a propeller duct at least partially surrounding the propeller.

8. The electric propulsion device of claim 1, wherein the motor compartment and the watertight electronics compartment are removably attached to the surfboard with serviceable screws.

9. The electric propulsion device of claim 1, wherein the fin assembly is removably attached to the motor compartment.

10. The electric propulsion device of claim 1, wherein the at least one battery comprises a plurality of 21700 lithium-ion cylindrical cells.

11. The electric propulsion device of claim 1, wherein the motor compartment is adapted to be exposed to water for heat dissipation.

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