Gyroscopic stabilizer

Abstract

A gyroscopic stabiliser for stabilising motion of an object includes a support for attaching to the object, a gimbal rotatably supported by the support to be rotatable around a first axis, a flywheel rotatably supported by the gimbal to be rotatable around a second axis relative to the gimbal, orthogonal to the first axis, and a rotary damper. The rotary damper has a chamber containing a damping fluid a vane that is rotatable within the chamber and that is coupled to the gimbal and a flow passage allowing flow of the damping fluid from the chamber on one side of the vane to the chamber on the other side of the vane when the vane is rotated.

Claims

1. A gyroscopic stabiliser for stabilising motion of an object, the gyroscopic stabiliser comprising: a support for attaching to the object whose motion is to be stabilised; a gimbal rotatably supported by the support to be rotatable around a first axis relative to the support; a flywheel rotatably supported by the gimbal to be rotatable around a second axis relative to the gimbal, the second axis being orthogonal to the first axis; and a rotary damper for damping rotation of the gimbal around the first axis relative to the support; wherein the rotary damper comprises: a chamber containing a damping fluid; a vane that is rotatable within the chamber and that is coupled to the gimbal; and a flow passage allowing flow of the damping fluid from the chamber on one side of the vane to the chamber on the other side of the vane when the vane is rotated, wherein the flow passage comprises a flow valve configured to provide substantially the same flow rate of fluid through the flow passage for different torques applied to rotate the vane; and wherein the flow valve comprises a fixed orifice and a variable orifice in series in the flow passage, wherein a change in a pressure differential across the fixed orifice causes a change in a size of the variable orifice.

2. The gyroscopic stabiliser according to claim 1, wherein: the vane partitions the chamber into a first sub-chamber and a second sub-chamber on opposite sides of the vane; and the flow passage is between the first sub-chamber and the second sub-chamber.

3. The gyroscopic stabiliser according to claim 1, wherein the flow passage is located in a body of a housing that houses the chamber.

4. The gyroscopic stabiliser according to claim 1, wherein the gyroscopic stabiliser further comprises a plurality of valves for connecting either: the chamber on a first side of the vane to an upstream side of the flow valve and the chamber on a second side of the vane to a downstream side of the flow valve; or the chamber on the second side of the vane to the upstream side of the flow valve and the chamber on the first side of the vane to the downstream side of the flow valve.

5. The gyroscopic stabiliser according to claim 4, wherein the rotary damper comprises: a first flow passage connecting the chamber on the first side of the vane to the upstream side of the flow valve; a second flow passage connecting the chamber on the second side of the vane to the upstream side of the flow valve; a third flow passage connecting the chamber on the first side of the vane to the downstream side of the flow valve; and a fourth flow passage connecting the chamber on the second side of the vane to the downstream side of the flow valve.

6. The gyroscopic stabiliser according to claim 5, wherein the plurality of valves comprises a valve provided in each of the first to fourth flow passages.

7. The gyroscopic stabiliser according to claim 6, wherein the fixed orifice is upstream of the variable orifice.

8. The gyroscopic stabiliser according to claim 1, wherein: the flow valve comprises a displaceable member to which the pressure differential across the fixed orifice is applied; the pressure differential causes a force to act on the displaceable member that acts to displace the displaceable member in a first direction; the displaceable member is biased in a second direction opposite to the first direction, and displacement of the displaceable member changes a size of the variable orifice.

9. The gyroscopic stabiliser according to claim 8, wherein the displaceable member is linearly displaceable.

10. The gyroscopic stabiliser according to claim 8, wherein: the fixed orifice is between a first region and a second region of the flow passage; and the displaceable member is displaceable within a channel that connects the first region and the second region of the flow passage in parallel to the fixed orifice.

11. The gyroscopic stabiliser according to claim 8, wherein the variable orifice comprises a gap between an edge of the displaceable member and another surface, and displacement of the displaceable member changes the size of the gap.

12. The gyroscopic stabiliser according to claim 8, wherein the variable orifice comprises a fixed opening, and displacement of the displaceable member changes an extent to which the displaceable member covers the fixed opening.

13. The gyroscopic stabiliser according to claim 8, wherein the displaceable member has a first surface to which a pressure upstream of the fixed orifice is applied, and an opposite second surface to which a pressure downstream of the fixed orifice is applied.

14. The gyroscopic stabiliser according to claim 8, wherein the flow valve comprises a biasing element that applies a biasing force to the displaceable member.

15. The gyroscopic stabiliser according to claim 14, wherein: the displaceable member has a first surface to which a pressure upstream of the fixed orifice is applied, and an opposite second surface to which a pressure downstream of the fixed orifice is applied; and the biasing element applies the biasing force to the second surface of the displaceable member.

16. The gyroscopic stabiliser according to claim 14, wherein the biasing element comprises a spring.

17. The gyroscopic stabiliser according to claim 14, wherein the biasing force applied by the biasing element is adjustable.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the present invention will now be discussed, by way of example only, with reference to the accompanying Figures, in which:

(2) FIG. 1 is an illustration of a typical gyroscopic stabiliser;

(3) FIG. 2 is an illustration of a gyroscopic stabiliser according to an embodiment of the present invention;

(4) FIG. 3 is an illustration of a cross-sectional view of a first rotary damper that can be used in a gyroscopic stabiliser according an embodiment of the present invention;

(5) FIG. 4 is an illustration of a perspective view of the first rotary damper;

(6) FIG. 5 is an illustration of a cross-sectional view of a second rotary damper that can be used in a gyroscopic stabiliser according an embodiment of the present invention;

(7) FIG. 6 is an illustration of a perspective view of the second rotary damper.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS AND FURTHER OPTIONAL FEATURES OF THE INVENTION

(8) Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art.

(9) Gyroscopic stabilisers according to embodiments of the present invention can be used to stabilise motion of an object. In one example application, the gyroscopic stabiliser may be used to reduce rolling or pitching motion of a marine vehicle, such as a boat or ship. However, the gyroscopic stabiliser may instead be used to stabilise motion of other types of vehicle, such as land or air vehicles, or other objects that may be subject to unwanted oscillations or movement.

(10) FIG. 2 is an illustration of a gyroscopic stabiliser 19 according to an embodiment of the present invention. As shown in FIG. 2, the gyroscopic stabiliser 19 in this embodiment is the same as the gyroscopic stabiliser 1 in FIG. 1 with the exception that the rotary dampers 17 are replaced with the rotary dampers 21 in the present invention.

(11) Parts of the gyroscopic stabiliser 19 in this embodiment that are the same as parts of the gyroscopic stabiliser 1 are indicated using the same reference numbers. These parts may therefore have any of the features described above with reference to FIG. 1. This description is not repeated here for conciseness.

(12) More generally, the gyroscopic stabiliser 19 in this embodiment may have any of the features of the gyroscopic stabiliser 1 described above, unless incompatible with the features discussed below. This description is not repeated here for conciseness.

(13) The rotary dampers 21 in the present invention each include a flow passage allowing flow of the damping fluid from the chamber on one side of the vane to the chamber on the other side of the vane when the vane is rotated, wherein the flow passage comprises a flow valve configured to provide substantially the same flow rate of fluid through the flow passage for different torques applied to rotate the vane.

(14) Therefore, the rotary dampers 21 in the present invention provide a substantially uniform angular velocity of the vane for different torques applied to rotate the vane, and therefore a substantially uniform angular velocity of the gimbal 5 for different rolling torques applied to the gyroscopic stabiliser 19.

(15) The precession rate ψ of the gyroscopic stabiliser 19 is therefore substantially the same for different rolling torques applied to the gyroscopic stabiliser 19.

(16) Furthermore, the precession rate ψ of the gyroscopic stabiliser 19 being substantially the same for different rolling torques applied to the gyroscopic stabiliser 19 means that the stabilising torque provided by the gyroscopic stabiliser 19 will be substantially the same for different rolling torques applied to the gyroscopic stabiliser 19.

(17) Of course, the configuration of the gyroscopic stabiliser 19 is not limited to the specific arrangement illustrated in FIG. 2.

(18) For example, the shape of the frame (support) 3 and/or the gimbal 5 and/or the flywheel 11 may be different to those illustrated in FIG. 2. The shapes of the frame 3, gimbal 5 and flywheel 11 are not particularly limited in the present invention.

(19) Furthermore, the manner in which the gimbal 5 is rotatably supported by the frame 3 may be different to that illustrated in FIG. 2. For example, the shafts 7 may be omitted and one or more bearings may be provided directly between the gimbal 5 and the frame 3. In one embodiment a slewing ring bearing may be provided between the gimbal 5 and the frame 3.

(20) Furthermore, the manner in which the flywheel 11 is rotatably mounted in the gimbal 5 may be different to that illustrated to FIG. 2. For example, in some embodiments the flywheel shaft 13 may be omitted and one or more bearings may be provided directly between the flywheel 11 and the gimbal 5.

(21) Furthermore, the positioning of the rotary dampers 21 may be different to that illustrated in FIG. 2. For example, the rotary dampers 21 may instead be positioned between the gimbal 5 and the frame 3, or inside the gimbal 5.

(22) It is also not essential in the present invention for there to be two rotary dampers 21 as illustrated in FIG. 2. Instead, in an alternative embodiment only a single rotary damper 21 may be provided.

(23) Where two rotary dampers 21 are provided, it is not essential for the two rotary dampers 21 to be identical, although this is preferred.

(24) A first example of a rotary damper 21a that can be used as the rotary damper 21 in the present invention is illustrated in FIG. 3.

(25) As shown in FIG. 3, the rotary damper 21a comprises a housing 23 that encloses a chamber 25. The chamber 25 contains a damping fluid.

(26) A vane 27 is rotatably mounted within the chamber 25 in the housing 23. In particular, the vane 27 is rotatably mounted at a first end 29 of the vane 27.

(27) The first end 29 of the vane 27 has a substantially circular outer shape.

(28) The first end 29 of the vane 27 is located adjacent to a first internal surface 31 of the housing 23 that has a curved shape that is complementary to (or that corresponds to) the substantially circular outer shape of the first end 29 of the vane 27.

(29) The first internal surface 31 of the housing 23 and the first end 29 of the vane 27 are positioned close together, so that fluid flow between the first end 29 of the vane 27 and the first internal surface 31 of the housing 23 is substantially prevented. The complementary shapes of the first internal surface 31 and the first end 29 mean that the first end 29 can rotate relative to the first internal surface 31 while still substantially preventing fluid flow therebetween.

(30) The vane 27 further comprises a blade portion 33 that extends from the first end 29. The blade portion 33 may be substantially flat.

(31) The blade portion 33 extends from the first end 29 to a point adjacent to a second internal surface 35 of the housing 23.

(32) The second internal surface 35 has a circular shape that corresponds to a circular shape swept out by a tip of the blade portion 33 when the vane 27 is rotated in the chamber 25.

(33) The tip of the blade portion 33 and the second internal surface 35 are positioned close together, so that fluid flow between the tip of the blade portion 33 and the second internal surface 35 is substantially prevented as the vane 27 is rotated within the chamber 25.

(34) As shown in FIG. 4, the housing 23 may have substantially flat (or planar) front and back faces 37, 39 (the two main faces of the housing 23). The vane 27 may also have substantially flat top and bottom edges (surfaces perpendicular to an axis of rotation of the vane 27). The substantially flat top and bottom edges of the vane 27 may be positioned close to the substantially flat front and back faces 37, 39 respectively of the housing 23, so that fluid flow between the top edge of the vane 27 and the front face 37 of the housing 23 is substantially prevented as the vane 27 is rotated within the chamber 25, and so that fluid flow between the bottom edge of the vane 27 and the back surface 39 of the housing 23 is substantially prevented as the vane 27 is rotated within the chamber 25.

(35) Therefore, fluid flow between the outside of the vane 27 and the housing 23 as the vane 27 is rotated in the chamber 25 may be substantially prevented.

(36) More generally, the edges of the vane and the internal surfaces of the housing may have complementary or corresponding shapes.

(37) In some embodiments, one or more seals may be provided to restrict fluid flow around the outside of the vane 27 as the vane 27 is rotated in the chamber 25.

(38) Of course, in other embodiments the shape of the vane may be different to that illustrated in FIG. 3.

(39) The vane 27 partitions the chamber 25 into a first sub-chamber 25a on one side of the vane 27 and a second sub-chamber 25b on the other side of the vane 27.

(40) As shown in FIG. 4, a rotary shaft 40 extends from the housing 23. The rotary shaft 40 is fixed or connected to the vane 27, so that the rotary shaft 40 rotates with the vane 27 relative to the housing 23. The rotary shaft 40 is coupled or connected to the gimbal 5, so that the gimbal 5 rotates with the vane 27.

(41) As shown in FIG. 3, the rotary damper 21a comprises a flow passage 42 that connects the first sub-chamber 25a and the second sub-chamber 25b, so that the damping fluid can flow from the first sub-chamber 25a to the second sub-chamber 25b when the vane 27 is rotated towards the first sub-chamber 25a, and so that the damping fluid can flow from the second sub-chamber 25b to the first sub-chamber 25a when the vane 27 is rotated towards the second sub-chamber 25b.

(42) In particular, when the vane 27 is rotated within the chamber 25 towards the first sub-chamber 25a, the vane 27 will apply pressure to the damping fluid in the first sub-chamber 25a. This pressure will cause the damping fluid in the first sub-chamber 25a to flow through the flow passage 42 to the second sub-chamber 25b, which will be at a lower pressure than the first sub-chamber 25a. The greater the torque applied to rotate the vane 27 towards the first sub-chamber 25a, the greater the pressure will be in the first sub-chamber 25a.

(43) The flow passage 42 is formed inside the housing 23.

(44) The flow passage 42 includes a constant flow valve 43 that provides a constant flow of fluid through the flow passage 42 when the vane 27 is rotated in either direction, for different torques applied to rotate the vane 27.

(45) The constant flow valve 43 includes a first constant flow valve 43a and a second constant flow valve 43b.

(46) The first constant flow valve 43a provides a constant flow of fluid through the flow passage 42 when the vane 27 is rotated towards the first sub-chamber 25a.

(47) The second constant flow valve 43b provides a constant flow of fluid through the flow passage 42 when the vane 27 is rotated towards the second sub-chamber 25b.

(48) As shown in FIG. 3, the first constant flow valve 43a includes a fixed orifice 45 and a variable orifice 47 arranged in series along the flow passage 42. When fluid is flowing from the first sub-chamber 25a to the second sub-chamber 25b, the fixed orifice 45 is upstream of the variable orifice 47.

(49) The fixed orifice 45 is a narrowing in the flow passage 42 formed by an annular protrusion in the flow passage 42. The fixed orifice 45 may be formed by an orifice plate.

(50) The fixed orifice 45 is located between a first region A and a second region B on the flow path. The first region A is upstream of the fixed orifice 45 and the second region B is downstream of the fixed orifice 45 when the fluid is flowing from the first sub-chamber 25a to the second sub-chamber 25b.

(51) When damping fluid flows through the flow passage 42 from the first sub-chamber 25a to the second sub-chamber 25b, the flow of damping fluid through the fixed orifice 45 causes the fluid pressure in the first region A to be higher than the fluid pressure in the second region B.

(52) The first constant flow valve 43a further comprises a piston 49 that is linearly moveable along a channel that extends between the first region A and the second region B in parallel to the flow passage through the fixed orifice 45.

(53) The channel is formed between a first housing part 51 and a second housing part 53.

(54) The piston 49 substantially seals the channel, such that the damping fluid cannot flow from the first region A to the second region B along the channel around the piston 49.

(55) A first surface of the piston 49 is in fluid communication with the first region A, and therefore the fluid pressure in the first region A acts on the first surface of the piston 49. An opposite second surface of the piston 49 is in fluid communication with the second region B, and therefore the fluid pressure in the second region B acts on the second surface of the piston 49.

(56) Since the pressure in the first region A is greater than the pressure in the first region B when the vane 27 is rotated towards the first sub-chamber 25a, a pressure differential exists between the first surface of the piston 49 and the second surface of the piston 49. This pressure differential causes a force to be applied to the piston 49 that acts in a first direction from the first surface towards the second surface. This force acts to displace the piston 49 along the channel in the first direction.

(57) As shown in FIG. 3, the first constant flow valve 43a comprises a spring 55 that is positioned between a bottom surface 57 of the housing and the second surface of the piston 49.

(58) The spring 55 applies a biasing force to the second surface of the piston 49 that acts to displace the piston 49 in a second direction from the second surface towards the first surface, that is opposite to the first direction.

(59) The biasing force applied to the second surface of the piston 49 by the spring 55 increases as the piston 49 is displaced in the first direction, and decreases as the piston is displaced in the second direction, due to a changing amount of compression of the spring 55.

(60) When the vane 27 is being rotated towards the first sub-chamber 25a with a constant torque applied to the vane 27, the pressure differential across the fixed orifice 45, and therefore the pressure differential between the first and second surfaces of the piston 49, will be constant. The force acting to displace the piston 49 in the first direction due to the pressure differential will therefore also be constant.

(61) In this case, the piston 49 will be displaced along the channel in the first direction until the biasing force applied to the piston 49 by the spring 55 in the second direction balances the force acting to displace the piston 49 in the first direction.

(62) As shown in FIG. 3, the variable orifice 47 is formed between a bottom edge of the piston 49 and an internal surface of the housing 23. As the piston 49 is displaced in the second direction, the size of the variable orifice 47 is increased (because the bottom edge of the piston 49 and the internal surface of the housing 23 move further apart). Conversely, as the piston 49 is displaced in the first direction, the size of the variable orifice 47 is decreased (because the bottom edge of the piston 49 and the internal surface of the housing 23 move closer together).

(63) When the torque applied to rotate the vane 27 is increased, the pressure differential across the fixed orifice 45 will increase. In other words, the pressure difference between the first region A and the second region B will increase.

(64) In isolation, this increased pressure difference would increase the flow rate of the fluid through the fixed orifice 45.

(65) However, the increased pressure difference between the first region A and the second region B also causes a greater force to act on the piston 49 in the first direction. This greater force causes the piston 49 to be displaced in the first direction until the biasing force applied to the piston 49 in the second direction by the spring 55 increases to balance the greater force in the first direction. Displacement of the piston 49 in the first direction causes the size of the variable orifice 47 to decrease, because the bottom edge of the piston 49 moves closer to the internal surface of the housing 23.

(66) The reduction in size of the variable orifice 47 reduces the flow rate through the variable orifice 47, which increases the pressure in region B downstream of the fixed orifice 45 and therefore decreases the pressure drop across the fixed orifice 45.

(67) This decrease in the pressure difference between the first region A and the second region B causes the piston 49 to move back in the first direction to increase the size of the variable orifice 47, thereby increasing the size of the variable orifice 47.

(68) The first constant flow valve 43a reaches an equilibrium when the force acting on the piston 49 in the first direction due to the pressure differential and the force acting on the piston 49 in the second direction due to the spring 55 are in balance.

(69) The constant flow rate provided by the first constant flow valve 43a, and therefore the constant angular velocity of the vane 27, are therefore controlled by the tension in the spring 55.

(70) As shown in FIG. 3, the first constant flow valve 43a further includes an adjustment mechanism in the form of knob or nut 59 that can be manually rotated to change the tension in the spring 55.

(71) As shown in FIG. 3, when fluid flows through the flow passage 42 from the second sub-chamber 25b to the first sub-chamber 25a, the fluid flows through the fixed orifice 45 in the opposite direction, so that the pressure in the second region B is therefore greater than the pressure in the first region A.

(72) Therefore, the pressure applied to the second surface of the piston 49 is greater than the pressure applied to the first surface of the piston 49, and the force due to the pressure differential therefore acts in the second direction, which is the same direction as the force applied to the piston 49 by the spring.

(73) The piston 49 is therefore displaced to its maximum extent in the second direction so that the size of the variable orifice 47 is a maximum.

(74) As such, the first constant flow valve 43a essentially does not restrict flow of the fluid from the second sub-chamber 25b to the first sub-chamber 25a.

(75) As shown in FIG. 3, the second constant flow valve 43b includes the same parts as the first constant flow valve 43a. These parts are given the same reference numbers but with the addition of “b” to help differentiate them. These parts may have any of the features of corresponding parts of the first constant flow valve 43a discussed above.

(76) Essentially, the second constant flow valve 43b corresponds to the first constant flow valve 43a connected the opposite way around, i.e. with the fixed orifice 45b closer to the second sub-chamber 25b on the flow passage 42 than to the first sub-chamber 25a.

(77) This means that when the vane 27 is rotated towards the second sub-chamber 25b, the second constant flow valve 43b functions in exactly the same way that the first constant flow valve 43a operates when the vane 27 is rotated towards the first sub-chamber 25a.

(78) The second constant flow valve 43b therefore provides a constant flow of fluid through the flow passage 42 when the vane 27 is rotated towards the second sub-chamber 25b, for different torques applied to rotate the vane 27.

(79) In addition, similarly to the first constant flow valve 43a, when the vane 27 is rotated towards the first sub-chamber 25a the piston 49b is displaced to its maximum extent in the second direction so that the size of the variable orifice 47b is a maximum.

(80) As such, the second constant flow valve 43b essentially does not restrict flow of the fluid from the first sub-chamber 25a to the second sub-chamber 25b.

(81) As shown in FIG. 3, the pistons 49 and 49b of the first and second constant flow valves 43a, 43b are arranged on opposite sides of the same fixed opening.

(82) A second example of a rotary damper 21b that can be used as the rotary damper 21 in the present invention is illustrated in FIG. 5 and FIG. 6.

(83) The rotary damper 21b differs from the rotary damper 21a in terms of the configuration of the flow passage and constant flow valve. The other features of the rotary damper 21b are the same as for the rotary damper 21a, but are not repeated here for conciseness. The rotary damper 21b may therefore have any of the features of the rotary damper 21a described above, where compatible with the description below.

(84) The rotary damper 21b includes a constant flow valve 43 that in practice is the same as the first constant flow valve 43a in FIG. 3, and that includes the same features as the first constant flow valve 43a. Description of those features is not repeated here for conciseness.

(85) The rotary damper 21b provides the same flow rate of fluid through the flow passage for different torques applied to the vane 27 both when the vane 27 rotates towards the first sub-chamber 25a and when the vane 27 rotates towards the second sub-chamber 25b using the single constant flow valve 43.

(86) This is achieved by providing a plurality of sub-flow passages and valves that can be used to either (i) connect the first sub-chamber 25a to (only) the upstream side of the constant flow valve 43 (the fixed orifice 45 side) and the second sub-chamber 25b to (only) the downstream side of the constant flow valve 43 (the variable orifice 47 side), or (ii) connect the second sub-chamber 25b to (only) the upstream side of the constant flow valve 43 and the first sub-chamber 25a to (only) the downstream side of the constant flow valve 23.

(87) In particular, as illustrated in FIG. 5, the rotary damper 21b includes a flow passage that comprises a first sub-flow passage 42a connecting the first sub-chamber 25a to the upstream side of the constant flow valve 43, a second sub-flow passage 42b connecting the second sub-chamber 25b to the upstream side of the constant flow valve 43, a third sub-flow passage 42c connecting the first sub-chamber 25a to the downstream side of the constant flow valve 43, and a fourth sub-flow passage 42d connecting the second sub-chamber 25b to the downstream side of the constant flow valve 43.

(88) As shown in FIG. 5, a one-way flow valve 61a, 61b, 61c, 61d is positioned in each of the sub-flow passages 42a, 42b, 42c, 42d.

(89) The one-way flow valves 61a-61d are passive one-way flow valves, that automatically allow fluid flow in one direction but prevent fluid flow in the opposite direction.

(90) One-way flow valve 61a positioned in the first sub-flow passage 42a allows fluid flow in the first sub-flow passage 42a only in the direction from the first sub-chamber 25a to the upstream side of the flow valve 43.

(91) One-way flow valve 61b positioned in the second sub-flow passage 42b allows fluid flow in the second sub-flow passage 42b only in the direction from the second sub-chamber 25b to the upstream side of the flow valve 43.

(92) One-way flow valve 61c positioned in the third sub-flow passage 42c allows fluid flow in the third sub-flow passage 42c only in the direction from the downstream side of the flow valve 43 to the first sub-chamber 25a.

(93) One-way flow valve 61d positioned in the fourth sub-flow passage 42d allows fluid flow in the fourth sub-flow passage 42d only in the direction from the downstream side of the flow valve 43 to the second sub-chamber 25b.

(94) When the vane 27 is rotated towards the first sub-chamber 25a, the higher pressure in the first sub-chamber 25a causes valve 61a to open and valve 61c to close. The higher pressure at the upstream side of the constant flow valve 43 also causes valve 61b to close. The fluid that flows through the constant flow valve 43 from the first sub-chamber causes the valve 61d to open, so that the fluid can flow into the second sub-chamber 25b. A corresponding process occurs when the vane 27 is rotated towards the second sub-chamber 25b.

(95) Therefore, when the vane 27 is rotated in either direction in the chamber 25, the flow rate of the flow of fluid between the two sub-chambers 25a, 25b is controlled to be substantially the same for different torques applied to rotate the vane 27. The angular velocity of the vane 27 will therefore also be substantially the same for different torques applied to rotate the vane 27.

(96) Of course, a different arrangement of sub-flow passages and valves could be used than the specific arrangement illustrated in FIG. 5.

(97) FIG. 6 is an illustration of a perspective view of the second rotary damper.

(98) The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

(99) While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

(100) For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

(101) Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

(102) Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

(103) It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example +/−10%.