High speed shutdown device for electric actuator

Patent metadata

Field	Value
Publication number	US-10024450-B2
Application number	US-201615332314-A
Country	US
Kind code	B2
Filing date	Oct 24, 2016
Priority date	Nov 25, 2015
Publication date	Jul 17, 2018
Grant date	Jul 17, 2018

Abstract

A high speed, fail-safe device for an electric actuator that can be independently triggered in the event of an emergency shutdown is provided. An electromagnetic brake is attached to the roller nut of the screw actuator. When actuated, the brake prevents rotation of the roller nut, and therefore enables linear movement of the roller nut upon rotation of the lead screw to linearly move an output shaft to actuate the valve. During actuation a return spring is compressed to enable retraction of the output shaft upon system failure. During such failure, the electric break is de-energized, which allows the roller nut to rotate and linearly move under force of the return spring to retract the output shaft to its fail-safe condition. A soft-stop/over-travel system is provided to limit the impact loads on the lead screw.

First claim

What is claimed is:

1. A high speed shutdown device for an electric actuator, comprising:
an electric motor;
a lead screw drivably coupled to the electric motor;
a lead screw nut threadably coupled to the lead screw;
a drive body operably coupled to the lead screw nut and configured to linearly translate in conjunction with the lead screw nut but not to rotate in conjunction with the lead screw nut;
a brake operatively coupled between the drive body and the lead screw nut such that the brake enables and prevents rotation of the lead screw nut;
an output shaft drivably coupled to the drive body; and
a return spring in contact with one of the output shaft or the drive body and configured to apply a return force on one of the output shaft or drive body to position the output shaft in a failsafe position;
wherein the lead screw nut is allowed to rotate when the brake does not apply a braking force;
wherein the lead screw nut is allowed to linearly translate along the lead screw under operation of the return force from the return spring when the lead screw is not being rotated by the electric motor in order to return the output shaft to the failsafe position; and
further comprising a soft stop spring positioned to engage one of the drive body or output shaft to slow its linear translation over-travel beyond the return of the output shaft to the failsafe position.

2. The device of claim 1 , wherein the soft stop spring linearly translates at least one of the drive body or the output shaft after it has reached over-travel to at most eliminate the over-travel.

3. The device of claim 2 , wherein the brake is energized to limit an amount of bounce seen as the drive body rebounds off the soft stop spring.

4. The device of claim 1 , wherein the soft stop spring is compressed during the linear translation over-travel.

5. A high speed shutdown device for an electric actuator, comprising:
an electric motor;
a lead screw drivably coupled to the electric motor;
a lead screw nut threadably coupled to the lead screw;
a drive body operably coupled to the lead screw nut and configured to linearly translate in conjunction with the lead screw nut but not to rotate in conjunction with the lead screw nut;
a brake operatively coupled between the drive body and the lead screw nut such that the brake enables and prevents rotation of the lead screw nut;
an output shaft drivably coupled to the drive body; and
a return spring in contact with one of the output shaft or the drive body and configured to apply a return force on one of the output shaft or drive body to position the output shaft in a failsafe position;
wherein the lead screw nut is allowed to rotate when the brake does not apply a braking force;
wherein the lead screw nut is allowed to linearly translate along the lead screw under operation of the return force from the return spring when the lead screw is not being rotated by the electric motor in order to return the output shaft to the failsafe position; and
wherein a soft stop spring engages the drive body via a soft stop spring land.

6. A high speed shutdown device for an electric actuator, comprising:
an electric motor;
a lead screw drivably coupled to the electric motor;
a lead screw nut threadably coupled to the lead screw;
a drive body operably coupled to the lead screw nut and configured to linearly translate in conjunction with the lead screw nut but not to rotate in conjunction with the lead screw nut;
a brake operatively coupled between the drive body and the lead screw nut such that the brake enables and prevents rotation of the lead screw nut;
an output shaft drivably coupled to the drive body; and
a return spring in contact with one of the output shaft or the drive body and configured to apply a return force on one of the output shaft or drive body to position the output shaft in a failsafe position;
wherein the drive body is operably coupled to the lead screw nut via a thrust bearing.

7. The device of claim 6 , wherein the lead screw nut is prevented from rotating but is allowed to linearly translate along the lead screw during rotation of the lead screw by the electric motor when the brake applies a braking force.

8. The device of claim 6 , wherein the lead screw nut is allowed to rotate when the brake does not apply a braking force.

9. The device of claim 8 , wherein the lead screw nut is allowed to linearly translate along the lead screw under operation of the return force from the return spring when the lead screw is not being rotated by the electric motor in order to return the output shaft to the failsafe position.

10. The device of claim 8 , wherein the lead screw nut is prevented from linearly translating along the lead screw when the lead screw is being rotated by the electric motor by operation of the return force from the return spring in order to maintain the output shaft in a failsafe position.

11. The device of claim 6 , wherein the brake is one of a disc brake, a drum brake, a band brake, or a wrap spring brake/clutch.

12. The device of claim 6 , wherein the return spring is in contact with the output shaft and configured to apply the return force on the output shaft to position the output shaft in a retracted state.

13. The device of claim 6 , wherein the return spring is in contact with the drive body and configured to apply the return force on the output shaft to position the output shaft in an extended state.

14. The device of claim 6 , wherein the brake applies a static torque to prevent rotation of the lead screw nut.

15. The device of claim 6 , wherein actuation of the brake and energization of the motor results in linear translation of the lead screw nut, drive body, and output shaft under rotation of the lead screw and compresses the return spring.

16. The device of claim 6 , wherein reversing the energization of the motor reverses the rotation of the lead screw.

17. A high speed shutdown device for an electric actuator, comprising:
an electric motor;
a lead screw drivably coupled to the electric motor;
a lead screw nut threadably coupled to the lead screw;
a drive body operably coupled to the lead screw nut and configured to linearly translate in conjunction with the lead screw nut but not to rotate in conjunction with the lead screw nut;
a brake operatively coupled between the drive body and the lead screw nut such that the brake enables and prevents rotation of the lead screw nut;
an output shaft drivably coupled to the drive body; and
a return spring in contact with one of the output shaft or the drive body and configured to apply a return force on one of the output shaft or drive body to position the output shaft in a failsafe position;
wherein the brake includes a caliper mounted on the drive body and a rotor mounted on the lead screw nut such that the brake enables and prevents rotation of the lead screw nut.

18. The device of claim 17 , wherein when the electric brake is de-energized the brake caliper releases the brake rotor to allow rotation of the lead screw nut along the lead screw that is not rotating.

19. The device of claim 17 , wherein the brake may be de-energized such that the brake rotor is free to rotate with the brake caliper so that the lead screw nut is not linearly driven along the lead screw and the output shaft is not deployed.

Assignees

• Been John J
• Woodward Inc

Inventors

• Been John J

Classifications

• F16K31/047 Primary

  characterised by mechanical means between the motor and the valve, e.g. lost motion means reducing backlash, clutches, brakes or return means (F16K31/043 takes precedence) · CPC title

• F16K31/50

  with screw-spindle {or internally threaded actuating means} · CPC title

• F16K31/046

  with electric means, e.g. electric switches, to control the motor or to control a clutch between the valve and the motor (F16K31/041 takes precedence) · CPC title

• F16H25/20

  Screw mechanisms (with automatic reversal F16H25/12) · CPC title

• F16H2025/2075

  Coaxial drive motors · CPC title