RELEASE AND BRAKE MECHANISM FOR ELECTRIC ACTUATOR

Abstract

An electric fail-safe actuator includes a speed reducer/gear assembly housing arranged between one or more electric motors, and a rotation to linear transformer including a roller or ball nut and a screw, or a nut and a roller or ball screw. The speed reducer/gear assembly housing is connected to an actuator housing via a counter hold release mechanism, allowing the speed reducer/gear assembly housing to co-rotate with a rotational side of the rotation to linear transformer when the counter hold release mechanism is released.

Claims

1.-19. (canceled)

20. An electric fail-safe actuator comprising: a speed reducer/gear assembly housing arranged between one or more electric motors; and a rotation to linear transformer comprising a roller or ball nut and a screw, or a nut and a roller or ball screw, wherein the speed reducer/gear assembly housing is connected to an actuator housing via a counter hold release mechanism, allowing the speed reducer/gear assembly housing to co-rotate with a rotational side of the rotation to linear transformer when the counter hold release mechanism is released.

21. The electric actuator according to claim 20, wherein the electric fail-safe actuator further comprises one or more brake mechanisms for controlling a return speed of the electric fail-safe actuator.

22. The electric actuator according to claim 21, wherein the one or more brake mechanisms is activated by a returning force conducting member.

23. The electric actuator according to claim 21, wherein the one or more brake mechanisms is arranged between a first non-rotating member and a force conducting member, wherein the force conducting member is arranged for interaction with a return movement of the actuator resulting in a movement towards a brake assembly and wherein said movement engaging the first non-rotating member resulting in a brake activation force responding to the speed and force of engagement, causing a brake effect between the first non-rotating member and the rotating force conducting member and between the surface of a second non-rotating member connected to the housing and a rotating member.

24. The electric actuator according to claim 23, wherein the brake activating force is regulated by an elastic member.

25. The electric actuator according to claim 23, wherein the brake activating force is regulated by a fluid damper.

26. The electric actuator according to claim 21, wherein said one or move brake mechanisms comprises a friction material on the non-rotating member and a force conducting element pressing said friction material of the non-rotating member towards a circular surface of the conducting member rotationally coupled to the speed reducer/gear assembly housing.

27. The electric actuator according to claim 21, wherein said one or more brake mechanisms comprises one or more stacked segments and where a multitude of said segments are rotationally connected to the speed reducer/gear assembly housing and the actuator housing in an alternating arrangement.

28. The electric actuator according to claim 21, wherein said one or more brake mechanisms comprises a fluid shear effect between two or more members with relative rotational speed relative to each other.

29. The electric actuator according to claim 21, wherein said one or more brake mechanisms comprises a fluid pump and nozzle(s).

30. The electric actuator according to claim 21, wherein said one or more brake mechanisms is activated by centripetal forces activating a radial expanding brake pad assembly.

31. The electric actuator according to claim 20, wherein release by the release mechanism is instigated by receiving electrical signals and/or current and/or potential.

32. The electric actuator according to claim 20, wherein release by the release mechanism is instigated by the absence of an electrical signals and/or current and/or potential.

33. The electric actuator according to claim 20, wherein release by the release mechanism is instigated by a change to fluid pressure and/or flow.

34. The electric actuator according to claim 20, wherein release by the release mechanism is instigated by a defined torque threshold to the release mechanism.

35. The electric actuator according to claim 20, wherein the rotational energy represented in the speed reducer/gear assembly housing rotation, is at hand for the rotational to linear transformer to complete a fail-safe return in addition to a linear force stored by an elastic element.

36. The electric actuator according to claim 25, wherein said brake activation force is multiplied by the use of a difference in the fluid exposed area of plunger(s) and piston(s) transforming the brake activation force from a returning force conducting member.

37. The electric actuator according to claim 20, wherein an axle with a toothed wheel at one end engages opposing teeth connected to a transformer housing and/or a carrier of the transformer, wherein an opposing end of said axle is arranged for application of an external override torque or a static holding lock out force.

38. The electric actuator according to claim 21, wherein the fluid is gaseous, and wherein a movement towards the speed reducer of a toroidal member results in an increased pressure in a volume, wherein an increased pressure acting on a surface of a brake piston results in a brake activation force.

39. The electric actuator according to claim 22, wherein said one or move brake mechanisms comprises a friction material on the non-rotating member and a force conducting element pressing said friction material of the non-rotating member towards a circular surface of the conducting member rotationally coupled to the speed reducer/gear assembly housing.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0056] FIG. 1 shows a typical general assembly of an electrical actuator A, according to prior art, into which the current invention could be integrated. The actuator A comprises the following components. One or several electric rotational motor(s) 11, a counter hold mechanism in form of a release clutch 2 for the speed reducer/gear assembly housing 100 and a rotational to linear transformer 4 in the shape of a roller or ball screw. In addition, the actuator A comprises a safety return spring (not shown) and a housing (not shown) in addition to a connection for the linear output force. An electrical controller (not shown) is also a part of the actuator A. A speed reducing function is integrated to dampen the impact speed at the end of the return movement of the actuator A.

[0057] As used herein, an impact speed at the end of the return movement of the actuator A should be understood to be the speed of the stem of actuator as it reaches its inner end position driven by the spring and external load from the valve.

[0058] FIG. 2 shows a typical general assembly of an electric actuator according to the present invention, where the electric actuator comprises a speed reducer/gear assembly housing 1 arranged in the actuator housing 106 of the actuator A and a release mechanism 2 in form of a clutch allowing the speed reducer/gear assembly housing 1 to co-rotate with the rotational side of the rotation to linear transformer 4 when releasing the release clutch 2. The release mechanism 2 comprises in a typical embodiment an electrical release clutch mechanism, and the electrical release mechanism 2 may be activated by the absence of electrical potential. The toque transfer member in form of a hollow axel 3 is connected to the output side of the electric actuator A via the rotational to linear transformer 4.

[0059] As the electrical potential holding the release mechanism is interrupted, the whole gear box housing is allowed to start spinning as a result of the torque from the rotational to linear transformer originating from the spring and external load. The whole gear box housing is co-rotating with the nut of the rotational to linear transformer, as if the gearbox would be one solid part. As the nut and the gearbox housing co-rotates, the internal members of the gearbox are not rotating due to the self-locking effect/internal friction of the gearbox and the lack of counter hold for the gearbox housing.

[0060] FIG. 3 shows an embodiment where a brake mechanism 109 is used to brake the speed reducer/gear assembly housing 1. The speed reducer/gear assembly housing 1 is axially supported by bearings 108 and thus cannot move axially relative the actuator housing 106. The returning force conducting member 107, for instance in form of a bar, rod or the like, activates the braking mechanism.

[0061] FIG. 3 also shows members of the counter hold mechanism comprising a cogged ring 102, a cogwheel 103, an axel 104 and the release mechanism 105.

[0062] FIG. 4 shows how the brake is activated trough the linearly free sliding speed reducer/gear assembly housing 300. This embodiment shows how the speed reducer/gear assembly housing 300 can move axially relative the actuator housing 302 engaged by the member 301 that activates the brake mechanism 303 via a toroidal contact member 304 arranged on the edge of the speed reducer/gear assembly housing 300. The movement and force of the member (301) originates from the spring return force and/or the external load on the actuator for instance from the valve. Said movement and force is conducted via the reducer/gear assembly housing 300 and via contact member 304 at its edge. The brake mechanism 303 is activated by contact forces resulting in a rotational brake forces activated by from the linear force and movement of the edge 304 and towards the rigid wall on the opposite end of 303. The brake function 303 comprising a lamellar brake assembly 305 and 306, the lamellar brake assembly 305 and 306 comprises a number of stacked elements 305, where the number of stacked elements 305 are rotationally connected to the actuator housing 307, and similar discs 306 are connected to the speed reducer/gear assembly housing 300 in an alternating arrangement.

[0063] FIG. 5 shows how the speed reducer/gear assembly housing 300 is activated by force and/or speed.

[0064] A representation of this embodiment shows how the activation force for the braking function is achieved and/or regulated by the speed and/or force whereby a force conducting member 201 is engaging by the return movement of the actuator represented by the returning member 107. The force conducting member 201 is arranged adjacent to the brake assembly 207. Said force conducting member 201 is arranged for interaction with the return movement of the actuator resulting in a movement towards the brake assembly 207. The surface 208 compresses the fluid media of the chamber 202 resulting in a pressure engaging the right surface of the brake piston 203 resulting in a leftward movement. Said movement engaging the non-rotating member 204 resulting in a brake activation force responding to the speed and/or force of engagement. The brake effect occurs between the non-rotating member 204 and the rotating force conducting member 210 and between the surface of a non-rotating member 209 connected to the housing and the rotating member 211.

[0065] The characteristics of the force generated are set by the fluid in a chamber 202 and the relative pressure exposed areas of brake piston 203 and surface 208 towards said chamber 202. In combination or in an alternative embodiment, said resulting brake activation force resulting from the engagement with the force conducting member 201 is characterized by the elastic properties and design of the elastic member 206.

[0066] FIG. 6 shows how the speed reducer/gear assembly housing rotation is reduced by lamellar brake discs.

[0067] This embodiment shows a lamellar brake assembly 305 and a friction material disc 306 or a steel disc comprising a number of stacked elements 305, where the number of stacked elements 305 are rotationally connected to the actuator housing 307 and the speed reducer/gear assembly housing 300 in an alternating arrangement. The speed reducer/gear assembly housing 300 is allowed to move along the longitudinal axis of the actuator housing 307 and said movement originating from the brake piston 301 forwarding brake activation force from the return movement of the actuator A.

[0068] The movement and force of the member 301 originates from the spring return force and/or the external load on the actuator for instance from the valve. Said movement and force is conducted via the reducer/gear assembly housing 300 and via contact member 304 at its edge. The brake mechanism 303 is activated by contact forces resulting in a rotational brake forces activated by from the linear force and movement of the edge 304 and towards the rigid wall on the opposite end of 303.

[0069] FIG. 7 shows a damper assembly with a gaseous fluid filled volume 702 arranged between a toroidal member 701 linearly movable by engagement by the returning member 107 (see FIG. 1). When activated by the returning member 107 the toroidal member 701 slides in the direction of the piston(s) 702 increasing the pressure in the gaseous filled volume 702. The increased pressure acts on the exposed surfaces of brake piston 703 generating a linear brake activation force conducted to a force conducting ring 704 attached to the speed reducer/gear assembly housing. The force is conducted via and the along the main axis of the speed reducer/gear assembly housing 300 and activates the brake assembly 705.

[0070] FIG. 8 shows a typical fluid-shear brake assembly where the fluid shear effect absorbs the energy absorbed from the rotation converting said energy to heat.

[0071] Such fluid shear brakes are of a wet or hydro viscous type and transmits torque between drive plates and friction surfaces. A fluid is used for cooling and provides a hydro viscous fluid film between the friction disc and the drive plate during the dynamic phase of engagement.

[0072] The transmission fluid in shear transmits torque between the two components increasing as the clamping pressure increases until mechanical lock up occurs.

[0073] FIG. 9 shows a hydraulic piston pump, where the hydraulic pump will convert rotational input to a fluid flow.

[0074] The hydraulic piston pump 500 comprises a disk 501 connected to a drive shaft 502, a cylinder block 503 comprising a number of openings 504 for reception of pistons 505, where each opening 504 for reception of a piston 505 is provided with a throughgoing opening 506. A valve plate 507 arranged adjacent the cylinder block 503 is provided with an inlet port 508 and an outlet port 509 for a fluid.

[0075] The disk 501 is mounted at an oblique angle to the drive shaft 502, where this arrangement will cause the disk's 501 edge to describe a path that oscillates along the drive shaft's 502 length as observed from a non-rotating point of view away from the drive shaft 502. The pistons 505 will follow the path of the disk 501, where this will result in that the openings 504 can be filled with a fluid through the inlet port 508 and emptied through the outlet port 509.

[0076] FIG. 10 shows schematically an orifice 600 arranged in a pipe 601 or the like, where the orifice 600 will have the ability to convert the energy in a fluid flow in head of the orifice 600 and thereby generate a braking effect in combination with a hydraulic piston pump as shown in FIG. 9.

DESCRIPTION OF EMBODIMENTS

[0077] In a first embodiment of the present invention the speed reducer/gear assembly housing 100 is mounted in an actuator housing 106 of the actuator A in a manner that allows rotation of said speed reducer/gear assembly housing 100 around a longitudinal axis of the actuator housing 106. The speed reducer/gear assembly housing 100 is connected to the actuator housing 106 via a counter hold release mechanism 105. When altered by an external input or the lack thereof, the counter hold release mechanism 105 would no longer provide the counter hold effect for the speed reducer/gear assembly housing 100 and said speed reducer/gear assembly housing 100 would co-rotate with the rotation originating from the return movement of the actuator A.

[0078] In a second embodiment of the present invention the resulting rotational speed of the speed reducer/gear assembly housing 100 is controlled by means of a braking mechanism. The activation and regulating means for said braking mechanism is regulated by the fail-safe speed of and/or the linear force of the actuator A. The returning linear movement represented by the returning force conducting member 107 connected to the returning movement of the actuator A engaging the force conducting member 201 resulting in an increased pressure in the chamber 202 acting on a surface of a larger piston 203 resulting in an amplified brake force engaging a non-rotating but free member 204 engaging the rotating force conducting member 210 and the rotating member 211 delivering the brake force to generate a second braking effect towards the non-rotating member 209, thereby reducing the rotational speed of the speed reducer/gear assembly housing 100.

[0079] In a third embodiment of the present invention the engaging brake force is conducted from the returning member represented by (107) via an elastic element 206 for instance a spring. The movement and force of the returning member originates from the spring return force and/or the external load on the actuator for instance from the valve. The resulting force from said dampening mechanism engages the spinning speed reducer/gear assembly housing forcing it towards the brake function 303 comprising a lamellar brake assembly 305 and 306, the lamellar brake assembly 305 and 306 comprises a number of stacked elements 305, where the number of stacked elements 305 are rotationally connected to the actuator housing 307, and similar discs 306 are connected to the speed reducer/gear assembly housing 300 in an alternating arrangement. The stiffness of the elastic member 206 regulates the resulting force conducted from the return movement towards the braking mechanism 303.

[0080] In a fourth embodiment of the present invention the speed of the moving member (returning member) 107 towards the speed reducer/gear assembly housing 300 determines the brake activation force. The dampening effect and the resulting brake activation force can be realized by a variety of different dampers, all with a stiffening effect resulting from the compression speed from the returning member 107. The speed reducer/gear assembly housing 300 is mounted in a manner that allows linear movement along the axis of the actuator A. The engaging brake force is conducted from the returning member represented by 107 via a dampening mechanism 202, 203, 208 comprising chamber 202, brake piston 203 and surface 208. The resulting force from said dampening mechanism engages the spinning speed reducer/gear assembly housing 300 forcing it towards the brake function 303 on the opposite side. The braking effect occurs between the speed reducer/gear assembly housing edge 304 and the stationary actuator housing. Alternatively, the brake effect occurs between the members 204 and 201 in addition to the braking effect between 201 and 209.

[0081] In a fifth embodiment of the present invention a fluid-based damper comprising the chamber 202 and an orifice 600 (see FIG. 10) is used to achieve said stiffening effect resulting from the speed of the returning member represented by 107.

[0082] In yet another embodiment of the present invention a piston or plunger pump energizing a fluid and an orifice would be used to reduce the rotational speed and dissipate the energy.

[0083] Piston or plunger pumps and associated hydraulic components such as orifices are assumed to be known for a person skilled in the art and will not be further described herein. The characteristics of the fluid filled (gas and/or liquid) damper is regulated by selection of fluid media and the associated characteristics in combination with the sizes of orifices placed in the flow loop.

[0084] In yet another embodiment of the present invention a centripetal force activated clutches and brakes would be utilized to engage and/or execute the braking and dissipation of energy. Centripetal force activated clutches and brakes are assumed to be known for a person skilled in the art and will not be further described herein.

[0085] In yet another embodiment of the present invention the braking effect is achieved by the use of the fluid shear effect. The fluid shear effect and the utilization in braking are assumed to be known for a person skilled in the art and will not be further described herein.

[0086] In yet another embodiment of the present invention the braking effect is achieved by the use of the fluid shear effect. The fluid shear effect and the utilization in braking are assumed to be known for a person skilled in the art and will not be further described herein.

[0087] In yet another embodiment of the present invention, the brake activation force is generated by compression of a fluid in a gaseous state. The returning movement of the actuator engages the toroidal member 701. The movement of the toroidal member 701 in the direction of the piston(s) 703 increases the pressure in the volume between 701 and said pistons. The increased pressure acts on the surface of 703 exposed to said pressure resulting in a brake activation force from the piston 703.

[0088] It should be noted that several embodiments of the electrical actuator according to the present invention are possible. The scope of the invention is limited by the claims, and a person of skill in the art will be able to make numerous changes to the aforementioned examples without departing from the scope of the invention as defined in the enclosed set of claims.