INTEGRATED PLANAR SMA DEVICE AND METHOD

Abstract

This disclosure relates generally to a reusable actuating device utilizing multiple integrated planar shape memory alloy elements integrated with independent driver circuits and at least one return spring integrated onto a single multi-layer PCB with a novel layout to create an electrically and mechanically redundant integrated actuator solution uniquely suited for use in low-profile devices that can be utilized by themselves or as an initiator in a staged device to release higher loads. The apparatus of the invention is particularly useful for spacecraft and other vehicular actuation devices.

Claims

1-2. (canceled)

3. An integrated planar shape memory alloy (SMA) device, comprising: a multi-layer printed circuit board (PCB); SMA elements; an output latch; bridge components; a return spring; and driver circuits; where said SMA elements, said output latch, said bridge components, said return spring and said driver circuits are mounted on said PCB, and wherein said SMA elements cause said output latch to actuate when a current is applied to said SMA elements.

4. The integrated planar SMA device of claim 3, wherein said output latch is split into at least two output latch halves to mount said PCB and to capture said return spring between said two output latch halves and said bridge components.

5. The integrated planar SMA device of claim 4, wherein said bridge components comprise bridge wires and bridge plates.

6. The integrated planar SMA device of claim 5, wherein said bridge plates clamp fixed ends of said SMA elements to said PCB fixing them and causing them to contact conductive patches which in turn connect said SMA elements to said driver circuits.

7. The integrated planar SMA device of claim 5, further comprises end-of-travel pins, wherein said end-of-travel pins attach to said PCB, and wherein said bridge wires attach to said output latch halves.

8. The integrated planar SMA device of claim 3, wherein said SMA elements are collocated with said PCB such that each SMA element of said SMA elements is a mirror of the other, resulting in two SMA elements that retract the same amount when heated to their transition temperature electrically through said driver circuits and actuate said output latch.

9. The integrated planar SMA device of claim 4, wherein said return spring is pre-compressed to a predetermined load and sized such that said return spring applies a nearly constant load to said SMA elements during cooling to re-stretch said SMA element to its original length, causing said integrated planar SMA device to reset itself once power is no longer applied or once said driver circuits are in a latched state.

10. The integrated planar SMA device of claim 4, wherein said return spring sits in a cut-out in said PCB such that said return spring pushes said output latch halves tensioning said SMA elements.

11. The integrated planar SMA device of claim 5, wherein said SMA elements are heated to or beyond their transition temperature by current applied through said driver circuits.

12. The integrated planar SMA device of claim 11, wherein said output latch halves retract due to the force exerted by said SMA elements when said SMA elements reach their transition temperature.

13. The integrated planar SMA device of claim 11, wherein said bridge wires contact end-of-travel pins attached to said PCB and close a switching circuit in said driver circuits and cut power to said SMA elements to prevent annealing.

14. The integrated planar SMA device of claim 3, wherein said integrated planar SMA device mounts in a housing having a secondary output latch connected by a secondary spring, and wherein said secondary output latch connects said output latch.

15. The integrated planar SMA device of claim 14, wherein said secondary output latch is pressed against said output latch with the help of said secondary spring to press said output latch causing said SMA elements to heat to or beyond their transition temperature by current applied through said driver circuits.

16. A method of providing an integrated planar shape memory alloy (SMA) device, said method comprising the steps of: providing a multi-layer printed circuit board (PCB); mounting SMA elements, an output latch, bridge components, a return spring, and driver circuits on said PCB; and actuating said output latch via said SMA elements by applying current through said SMA elements.

17. The method of claim 16, further comprising splitting said output latch into at least two output latch halves to mount said PCB and to capture said return spring between said two output latch halves and said bridge components.

18. The method of claim 16, providing said bridge components having bridge wires and bridge plates.

19. The method of claim 18, further comprising clamping said bridge plates to fixed ends of said SMA elements to said PCB fixing them and causing them to contact conductive patches which in turn connect said SMA elements to said driver circuits.

20. The method of claim 16, further comprising collocating said SMA elements with said PCB such that each SMA element of said SMA elements is a mirror of the other, resulting in two SMA elements that retract the same amount when heated to their transition temperature electrically through said driver circuits and actuate said output latch.

21. The method of claim 17, further comprising pre-compressing said return spring to a predetermined load and sized such that said return spring applies a nearly constant load to said SMA elements during cooling to re-stretch said SMA element to its original length, causing said integrated planar SMA device to reset itself once power is no longer applied or once said driver circuit is in a latched state.

22. The method of claim 18, further comprising heating said SMA elements beyond their transition temperature by current applied through said driver circuits.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] A more complete understanding of the invention and the many attendant advantages thereof will be readily appreciated as the same becomes better understood by reference to the following detailed description, when considered in connection with the accompanying drawings wherein:

[0018] FIG. 1a is an isometric view of the first embodiment while static.

[0019] FIG. 1B is an isometric view of the first embodiment while actuated.

[0020] FIG. 1c is a side view of the first embodiment while static.

[0021] FIG. 1d is a cutaway view of the first embodiment while static.

[0022] FIG. 2a is a cutaway view of the second embodiment while static.

[0023] FIG. 2b is a cutaway view of the second embodiment after actuation.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0024] In FIG. 1a the inventive device utilizes a single printed circuit board 100 to collocate the SMA elements 101 with bridge plates 105, driver circuits 106, output latch 102, end-of-travel pins 103. Bridge plate 105 clamp the SMA elements 101 to conductive pads (not shown) embedded in the printed circuit board 100 which are connected via traces (not shown) on an interior layer of the printed circuit board 100 to the driver circuits 106. End-of-travel pins 103 are connected to the driver circuits 106 via traces (not shown) on an interior layer of the printed circuit board. Output latch 102 is fastened to circuit board 100. Bridge wires 104 are attached to output latch halves 102. Return spring 108 is captured between output latch halves 102 and sits in a cutout in printed circuit board 100. It is pushing on output latch halves 102, tensioning SMA elements 101.

[0025] In FIG. 1b SMA elements 101 have been heated to or beyond their transition temperature by current applied through driver circuits 106. Output latch halves 102 have retracted due to force exerted by SMA elements 101 reaching their transition temperature. Bridge wires 104 have contacted end-of-travel pins 103 closing the switching circuit in the driver circuits 106 and cutting power to SMA elements 101 to prevent annealing.

[0026] In FIG. 1c the inventive device is in its static state and SMA elements 101 can be seen on both sides of printed circuit board 100 captured between output latch halves 102, printed circuit board 100, and are clamped to the printed circuit board 100 by bridge plates 105. End-of-travel pins 103 are attached to printed circuit board 100. Bridge wires 104 are attached to output latch halves 102. A portion of return spring 108 is visible between bridge plates 105 and output latch halves 102.

[0027] In FIG. 1d the inventive device is in its static state. Return spring 108 can be seen in printed circuit board 100 cutout being captured between bridge plates 105 and output latch halves 102.

[0028] In FIG. 2a the inventive device utilizes a printed circuit board 100 mounted inside housing 200, collocating it with secondary output latch 201 which is pressed against output latch halves 102 by secondary spring 202 in its compressed state. Output latch halves 102 are held in their static state by return spring 108. Printed circuit board 100 collocates SMA elements 101 with bridge plates 105, driver circuits 106, output latch 102, end-of-travel pins 103. Bridge plate 105 clamp the SMA elements 101 to conductive pads (not shown) embedded in the printed circuit board 100 which are connected via traces (not shown) on an interior layer of the printed circuit board 100 to the driver circuits 106. End-of-travel pins 103 are connected to the driver circuits 106 via traces (not shown) on an interior layer of the printed circuit board. Output latch 102 is fastened to circuit board 100. Bridge wires 104 are attached to output latch halves 102. Return spring 108 is captured between output latch halves 102 and sits in a cutout in printed circuit board 100. It is pushing on output latch halves 102, tensioning SMA elements 101.

[0029] In FIG. 2b SMA elements 101 have been heated to or beyond their transition temperature by current applied through driver circuits 106. Output latch halves 102 have retracted due to forced exerted by SMA elements 101 reaching their transition temperature. Bridge wires 104 have contacted end-of-travel pins 103 closing the switching circuit in the driver circuits 106 and cutting power to SMA elements 101 to prevent annealing. Secondary latch 201 has been retracted by force exerted by secondary spring 202 due to latch halves 102 being retracted beyond interfering with secondary latch 201.

[0030] The inventive device enables the creation of mechanically simple, yet highly reliable integrated devices that can be built on a single multi-layer printed circuit board 100 with integral driver circuits 106 creating an electrically and mechanically redundant, lightweight, low-profile solution that can be readily adapted to a variety of applications.

[0031] It will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.