GB2200802A

GB2200802A - Electric motor rotor comprising a propeller

Info

Publication number: GB2200802A
Application number: GB08715439A
Authority: GB
Inventors: James Ian Edwards
Original assignee: Sub Sea Offshore Ltd
Current assignee: Sub Sea Offshore Ltd
Priority date: 1986-12-19
Filing date: 1987-07-01
Publication date: 1988-08-10
Also published as: GB8715439D0; GB8630436D0

Abstract

A thruster motor suitable for propelling an underwater vehicle comprises a propeller (2) rotatably mounted within the interior of a Kort nozzle (1), the propeller blades (2) being fixed at their circumferential ends to a rotor (10) coaxial with respect to the nozzle (1), the rotor (10) or parts (100) of it being permanently magnetised and that region (15) of the Kort nozzle immediately adjacent the rotor circumference comprising an electrically or electronically commutated (12) stator, the rotary assembly being supported at tapered bearings 13 whereby in use propeller thrust can be transferred to the Kort nozzle and hence to any underwater vehicle attached thereto. <IMAGE>

Description

Improvements in or relating to motors This invention is concerned with an improved form of motor.

It is more particularly concerned with a thruster motor suitable for use on under-water vessels. Motors of this type comprise a rotatable propeller mounted within the interior of a Kort nozzle, the propeller situated between a plurality of radially extending supporting struts. Conventional electric or hydraulic thruster motors use a drive motor which is separate from the propeller.

The motor housing can obstruct flow of liquid through the thruster motor reducing efficiency. Additionally the motor must be housed in a waterproof casing to prevent ingress of water into the electrical or mechanical drive means. Such known thruster motors can also suffer problems in the use of a rotating seal on the propeller shaft. This seal is located generally within the motor housing in the immediate vicinity of the propeller, the propellershaft passing axially therethrough. This seal may be subject to excessive wear or premature failure and related problems. To overcome these seal problems some forms of thruster motor have used magnetic couplings and others have used oil-filled pressurecompensated housings for the electric motor. A typical conventional thruster motor is described and illustrated subsequently.

It is from a consideration of conventional thruster motors that has led to the development of the present invention.

According to this invention there is provided a thruster motor suitable for propelling an underwater vehicle and comprising a propeller rotatably mounted within the interior of a Kort nozzle, the propeller blades being fixed at their circumferential ends to a rotor coaxial with respect to the nozzle, the rotor or parts thereof being permanently magnetised and that region of the Kort nozzle immediately adjacent the rotor circumference comprising an electrically or electronically commutated stator, the propeller and/or rotor being bearing-supported whereby in use propeller thrust can be transferred to the Kort nozzle and hence to any underwater vehicle attached thereto. The Kort nozzle may include internal radial struts as in conventional thrusters.The propeller may be affixed to a bearing-support shaft or the rotor or parts thereof may be supported by bearing means located in the Kort nozzle.

In order that the invention may be illustrated and readily carried into effect an embodiment thereof will now be described by way of example only with reference to the accompanying drawings, also showing a typical conventional thruster motor, and in which: Figure 1 - is a typical conventional thruster in cross-section, Figure 2 - is a cross-sectional view of a thruster according to the invention, and Figure 3 - is an end elevation of the thruster shown in Figure 2.

Referring firstly to Figure 1 of the accompanying drawings, a rotatably mounted propeller 2 is located on a shaft within a conventional Kort nozzle 1. The nozzle 1 is supported on a plurality of radially extending struts 3 which extend radially from the shaft. An electric motor 5 is located within a specially adapted underwater housing 4, the rotating shaft of the motor being supported by bearing 6 and engaging reduction gears 7 at its other end. The propeller shaft extends from these reduction gears 7 through a rotary shaft seal 9 which has proved to be problematical in the past. Motive power for the motor 5 is supplied via electric supply.cables8. It can be seen that part of the housing 4 protrudes into the region of the Kort nozzle and a larger part thereof extends immediately adjacent the Kort nozzle.

Referring to Figures 2 and 3 of the accompanying drawings a thruster motor according to the invention is shown. The motor comprises a conventional Kort nozzle 1 and radially extending supporting struts 3, but an internal circumferential part 15 of the Kort nozzle has been hollowed into a channel and into this channel the propeller 2 is located. The circumferential ends 22 of the blades of the propeller 2 are affixed to an annular rotor 10 adapted to be located within the hollowed channel 15 of the Kort nozzle. The rotor 10 is magnetised over parts of its surface or over its entire surface. For example the rotor 10 or parts 100.

thereof may be magnetised by techniques which are known in the art of e.g linear motors. The region 11 of the Kort nozzle, immediately adjacent the magnetised rotor 2, is formed into an electrically/electronically commutated stator by a series of electromagnets 12. The rotor 10 and associated electromagnets 12 formed in the internal periphery of the Kort nozzle may be considered to be a form of linear motor, such as a rare earth motor, which has been formed into a ring configuration. The centre of the ring houses the propeller mechanism comprising the rotor, propeller and shaft and being the only moving part in the apparatus. Each end of the shaft 14 is supported in tapered bearings e.g. tapered roller bearings 13, which are designed to take up end thrust.

The magnetised rotor 10 is preferably coated with corrosion resistant composition and th el,ctronically commutated stator, being formed by the Kort nozzle as described above, may be "star" wound with e.g. three wires connecting it to an electronic control module. This control module for varying propeller speed and hence thrust may be,-for example, controlled digitally. When the stator is energised the magnetic rotor is caused to rotate and hence the propeller securely mounted thereon. This enables thrust to be transferred from the propeller, through the shaft and bearings to the radially extending struts 3 and then through the Kort nozzle 1 onto whichever vehicle the thruster motor is driving.

The embodiment of Figures 2 and 3 removes the need for a separate motor housing by incorporating the active drive means into the Kort nozzle itself.

This form of thruster motor has only one moving part and requires no other underwater housings therefor. Hydro-dynamic efficiency can be improved as there is very little obstruction to water flow into and out of the duct defined by the Kort nozzle. This embodiment employs a brushless, electronically commutated torque motor based on linear motor technology but formed into a ring configuration. There are also further advantages in the preset invention being capable of digital control.

Because the thruster according to the invention is simple to construct nd-maintain it represents a significant improvement over conventional thrusters. It can maintain a high output thrust compared to electrical input power, and these thrusters may be lighter weight than conventional thruster motors. Reliability and efficiency may be improved by virtue of the reductions in moving parts and elimination of additional underwater motor housings and reduction in the area of hydrodynamic obstructions. Thrusters according to the invention may require less maintenance because there is no shaft seal to be replaced.

Claims

1. A thruster motor suitable for propelling an underwater vehicle and comprising a propeller rotatably mounted within the interior of a Kort nozzle, the propeller blades being fixed at their circumferential ends to a rotor coaxial with respect to the nozzle, the rotor or parts thereof being permanently magnetised and that region of the Kort nozzle immediately adjacent the rotor circumference comprising an electrically or electronically commutated stator, the propeller and/or rotor being bearing-supported whereby in use propeller thrust can be transferred to the Kort nozzle.

2. A motor as claimed in Claim 1 in which the propeller is mounted between the ends of a supporting shaft which is mounted in bearings at both ends thereof.

3. A motor as claimed in Claim 1 or 2 wherein the bearings are located within the interior of the Kort nozzle.

4. A motor as claimed in any preceding claim in which an internal circumferential part of the Kort nozzle comprises an annular recess in which the propeller is located.

5. A motor as claimed in any preceding claim in which the commutated stator comprises a series of electromagnets.

6. A motor as claimed in Claim 5 in which the rotor and electromagnets comprise a ring configuration form of linear motor.

7. A motor as claimed in any preceding claim in which the only moving parts consist of the rotor, propeller and any associated shaft or bearing#.

8. A motor as claimed in any one of Claims 2 to 7 in which the supporting shaft is mounted at one or both ends in tapered bearings.

9. A motor as claimed in any preceding claim in which the rotor is coated to be corrosion resistant.

10. A motor as claimed in any preceding claim in which the stator is electronically commutated brushlessly.

11. A thruster motor as claimed in Claim 10 wherein the stator is star wound and connected to-a digitally operated control module.

12. A motor as claimed in any preceding claim substantially as herein described.

13. A thruster motor substantially as herein described and as illustrated in Figures 2 and 3 of the accompanying drawings.

15. An underwater vehicle to which is attached one or more thruster motors as claimed in any preceding claim.