MXPA00003065A - Temperature respnonsive switch with shape memory actuator - Google Patents

Abstract

A temperature actuated switch having a resilient switch blade that is movable between open and closed positions and extends perpendicular to an elongated actuator of shape memory alloy. The actuator has an elongated deformed shape at normal temperatures and a contracted recovered shape at an elevated temperature. An end portion of the actuator is attached to the switch blade to provide movement of same between open and closed positions as the actuator changes between its deformed and recovered shapes.

Description

TEMPERATURE SENSITIVE SWITCH WITH ACTUATOR WITH FORM MEMORY BACKGROUND OF THE INVENTION This invention relates to the art of switches and more particularly, with temperature-activated switches that use alloy actuators with shape memory. This invention can be applied particularly in very small relays or thermostats having a resilient switching blade that extends generally perpendicularly to an elongated shape memory alloy actuator and will be specifically described by reference. However, it will be appreciated that the invention has broader aspects, and that it can be used in other types of temperature-activated switches that have other arrangements between the actuator and the switch sheet. Relays and extremely small thermostats are very complicated because of the use of a relatively large number of parts and the difficulty of reliably producing the parts in very small sizes. The same considerations make such developers and thermostats relatively difficult to manufacture and assemble, and make them relatively expensive. It would be desirable to have a temperature activated switch that could be manufactured in extremely small sizes with a minimum number of parts, and that could be manufactured and assembled relatively efficiently and reliably. SUMMARY OF THE INVENTION A polymeric housing for a relay has a cavity therein that receives a resilient switching blade and an elongated shape memory alloy actuator that provides movement of the switching blade between closed and open positions. A pair of end members have fixed terminal contacts placed in the cavity and terminal lines extending outwardly from the housing of the terminal contacts. The switching blade has a moving blade contact to cooperate with one of the fixed terminal contacts as the switching blade moves between its open and closed positions. The elongated shape memory alloy actuator has a deformed and extended shape at normal temperatures and a retracted form and recovered at an elevated temperature. An end portion of the actuator is fixed to the switch blade to provide movement of the switch blade between its open and closed positions with variations in the length of the actuator as the actuator changes between its deformed and recovered shapes. In a preferred embodiment, the relay is normally closed with the movable contact being inclined to engage with a terminal contact by the force of the bending stress in the resilient switching blade. When the actuator changes to its recovered shape at an elevated temperature, the length of the actuator contracts and pulls the switching blade in one direction to move the moving contact away from the fixed terminal contact. Upon cooling, the actuator preferably returns to its deformed and extended shape to allow the switching blade to return to its closed position with the mobile contact engaging the fixed terminal contact. In one embodiment, the commutating sheet extends generally perpendicular to the elongated shape memory alloy actuator, and the actuator is fixed to the commutating sheet at an intermediate point between its opposite ends. In another embodiment, the actuator is in the form of a spiral spring with a plurality of spiral turns and the spring actuator is fixed to the resilient switching blade by extending the blade between adjacent turns in an end portion of the spring actuator.

In another embodiment, an anchor projection in the housing cavity is fixed to a remote end portion of the actuator remotely to the commutating sheet. In a preferred embodiment, the anchor projection is integrally molded in one piece with the housing and extends between adjacent turns in the distal end portion of the spring actuator. According to another aspect of the application, the resilient switching blade is on a switch blade member with a general U shape having a pair of substantially parallel arms connected by a base portion. One arm is longer than the other and defines the resilient switching blade, and the other arm engages the other terminal contact. The polymeric housing has opposite ends, opposite sides, and opposite front and back surfaces. The cavity includes opposite portions of end cavities located adjacent the opposite ends of the housing and a cavity joining portion that is adjacent one of the sides of the housing and extends between the end cavity portions. The arms are received to the switching blade member with U-shaped in the end cavity portions and its base portion in the cavity joining portion.

The cavity includes a portion with a general T-shape having a crossover portion with a leg portion extending therefrom in a longitudinal direction between the opposite ends of the polymeric housing. The resilient switching blade is received in the cavity crossing portion while the actuator is received in the leg cavity portion. The front surface of the housing has a pair of notches extending between the cavity and the opposite end portions of the housing to receive the terminal lines. The notches are located centrally between the opposite sides of the housing although it is possible to place them in other places. A plurality of spherical projections are ultrasonically welded to the front surface of the housing and extend up therefrom to be received in a plurality of fastener receiving recesses in a flat cover to secure the cover to the flat front surface of the housing. housing to close the cavity and secure the terminals to the housing. It is a primary object of the present invention to provide a temperature activated switch having an actuator in the form of a shape memory alloy. It is another object of the present invention to provide a switch having a minimum number of parts and which is relatively simple to manufacture and assemble. It is also an object of the present invention to provide a switch that allows the use of a thicker and stronger switch sheet material to minimize fatigue failure. BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a planar top view of a relay or thermostat constructed in accordance with the present invention and with a switch sheet shown in a closed position; Figure 2 is a view similar to that of Figure 1 showing the leaf of an open position; Figure 3 is a side elevation view of a housing cover used with the relay of Figures 1 and 2; and Figure 4 is an elevated side view of the relay or thermostat of Figures 1 and 2. DESCRIPTION OF A PREFERRED MODE With reference now to the figure, wherein what is shown is only for the purpose of illustrating a preferred embodiment of the invention. and is not intended to limit the same, a relay or thermostat A includes a polymeric housing B having opposite ends 10, 12, opposite sides 14, 16 and opposite front and rear surfaces 18, 20. Although the housing B is illustrated in A preferred shape as a rectangular solid, with the ends, sides and opposite surfaces flat and parallel, it will be recognized that other shapes are possible. The housing B has a cavity extending inwardly from the flat front surface 18, and includes opposite end cavity portions 30, 32 located adjacent the opposite ends 10, 12 and a cavity attachment portion 34 extending between the end cavity portions 30, 32 adjacent to the side 14. The cavity in the housing 16 further includes a receiving leg portion of the actuator 36 extending from the end cavity portion 30 to the end cavity portion 32. and ends just before the end cavity portion 32. The end cavity portion 30 and the leg cavity portion 36 together form a cavity portion with a general shape of T within the end portion 30 which is the portion of cross-section of the T-shaped cavity and the cavity portion 36 is the leg portion thereof. A pair of terminals C, D has terminal contacts 40, 42 positioned within the end cavity portions 30, 32 and terminal lines 44, 46 extend from terminal contacts 40, 42 outwardly from the housing ends 10, 12. The front surface 18 of the housing B has central notches 48, 50 extending from the end cavity portions 30, 32 towards the opposite housing ends., 12. The terminal lines 44, 46 are received in the notches 48, 50 and the depth of the notches is substantially equal to the thickness of the terminal lines AA, 46. A switching leaf member E has a configuration with a general shape of U including a pair of generally parallel spaced arms 60, 62 connected by a base portion 64. Arms 60 and 62 are received in the end cavity portions 30, 32 while the base portion 64 is received in the portion 2. The arm 62 of the switching blade member E flexes under tension by engaging the terminal contact 42. The arm 60 in a one-piece switching blade member E is longer than the arm 62 and defines a resilient switching blade having a movable contact 70 there to cooperate with the fixed terminal contact 40. An elongated actuator F of shape memory alloy is received in the leg cavity portion 36. In the arrangement shown and described, the actuator F is in the form of a spiral spring having a plurality of turns of turns. An end portion 72 is fixed to the resilient switching blade 60 by extending the switching blade 60 between adjacent turns in the end portion 72. The actuator F has a opposite end portion 74 that is anchored in the housing B. In a preferred embodiment, an anchor projection 76 integrally molded in one piece with the housing B extends upwardly from the bottom of the leg cavity portion 36 in spaced relationship with the distal end portion of the leg cavity 78. and is received between adjacent turns of the actuator F in the remote end portion 74 thereof. The elongated actuator F of shape memory alloy has an extended shape and deformed at normal temperatures where the contacts 40, 70 close as shown in Figure 1 and a shrunk and recovered form at an elevated temperature where the contacts 40 70 open as shown in Figure 2. When the actuator F changes from its deformed shape to its recovered shape, it pulls the resilient switching blade 60 from the position of Figure 1 to the position of Figure 2 and moves the mobile contact 70 out of engagement with the fixed terminal contact 40. Upon cooling, the actuator F preferably returns to its extended and deformed shape to allow inverse movement of the switch sheet 60 back to the position of Figure 1 to return to close the contacts 40, 70. It will be recognized that the switch can be designed to be normally open instead of normally closed. For example, the normal position of the switch could be as shown in Figure 2 with the shape memory actuator F having a reduced length in its shape deformed at normal temperatures to keep the switch sheet 60 open and flexed by tension. At the austenisic transformation temperature of the shape memory alloy, the actuator F would revert to its elongated shape recovered to allow the movement of the switch sheet 60 to the left in Figure 2 to close the contacts. In an alternative, the fixed contact 70 could be on the opposite side of the switching sheet in Figure 1 and the movable contact could be moved to the other surface of the switching sheet. The configuration in Figure 1 would then normally be open. By moving to the position in Figure 2, the relocated fixed and mobile contacts would be closed. Although the actuator is preferably in the form of a spiral spring, it will be recognized that other configurations are possible to provide a contraction and expansion while the actuator changes between its deformed and recovered shapes. For example, the actuator may be wavy similar to a sine wave or with an inverse configuration similar to a bellows or accordion but with soft folds instead of pronounced bends.

The switching blade member E can be made of beryllium copper or other suitable materials. The large force provided by the shape memory actuator F allows the use of thicker and stronger flat material for the switching blade member E so that the resilient switching blade 60 can be subjected to more opening and closing cycles without suffering failures due to fatigue. In addition, the thicker material allows the commutating sheet 60 to self-polarize the movable contact 70 into engagement with the fixed terminal contact 40 with a relatively large force to minimize the resistance. In manufacturing the shape memory actuator F, a wire is wound in the form of a spiral spring and heated to the austenisic temperature of transformation of the shape memory alloy. After cooling to its martenisic temperature, the actuator F is stretched to its desired length to be used in the application shown in Figure 1. When the actuator F is reheated to its austenisic transformation temperature, it shrinks or shrinks. to the length it had before it was stretched as shown in Figure 2. The stretched length is commonly referred to as the deformed shape that the shape memory actuator has at normal temperatures. The contracted or shrunken configuration of the actuator is known as the recovered form it takes at the austenisic temperature of transformation. Preferably the actuator is processed so that when it is cooled to its martenic state it is lengthened to allow the contacts to close again. Preferably, the actuator F is an alloy with a nickel-titanium shape memory. However, it will be appreciated that it is possible to use other alloys with shape memory such as copper-based ternary including copper-zinc-aluminum, and copper-nickel-aluminum. The range of transition temperature at which the alloy changes from its deformed shape to its recovered shape can be varied by selecting different alloy compositions with shape memory and by varying the heat treatment process. The housing B has a plurality of clamping projections 80-83 integrally formed in one piece therewith, and projecting upwards from the flat front surface 18. A flat and rectangular polymeric housing cover G in Figure 3 has a plurality of recesses for receiving fasteners therein, of which only two are shown by 92 and 93 in Figure 3. There are an equal number of recesses than clamping projections 80-83 and are positioned to receive the clamping projections 80-83 a through the holes in the cover. The clamping projections 80-83 are deformed to secure the cover G to the external surface 18 of the housing B to completely close the cavity of the housing and to secure the terminals C, D to the housing assembly. Strictly as an example and not to serve as a limitation, the accommodation member B may have a length between opposite ends 10, 12 of about 1.43 cm (0.562 inches), a width between opposite sides 14, 16 of about 0.8636 cm (0.340) inches) and a thickness between the front and back surfaces 18, 20 of about 0.282 cm (0.111 inches). The projections 80-83 extend upward from the front surface 18 approximately 0.0254 cm (0.010 inches). The length of the spring F in its relaxed and unsettled condition is about 0.6985 cm (0.275 inches) measured between its opposite ends. Spring F is made of circular wire with a diameter around 0.0254 cm (0.010 inches), and is formed into a cylindrical spiral with an internal diameter of about 0.1778 cm (0.070 inches). The switching blade member E has a thickness of 0.1778 cm (0.070 inches). The length of the switching member E between the outward facing surfaces of the switch sheet 60 and arm 62 is about 1.0033 cm (0.395 inches). Although the invention has been shown and described with reference to a preferred embodiment, it is obvious that equivalent alterations and modifications will occur to those skilled in the art when reading and understanding the specifications. The present invention includes such alterations and equivalent modifications, and is limited only by the scope of the clauses.

Claims (7)

1. CLAIMS 1.- A temperature activated switch characterized in that it comprises a polymeric housing having a cavity therein, a pair of terminals having terminal contacts in the cavity and terminal lines extending outwardly from the housing from the terminal contacts, a sheet of resilient switching having a moving blade contact which normally engages one of the terminal contacts, the switching blade is connected in electrically conductive relationship with the other terminal contact, an elongated shape memory alloy actuator placed in the cavity and having an actuator end portion attached to the switch blade and an opposite actuator end portion fixed to the housing, the actuator having an extended and deformed shape at normal temperatures where the blade contact engages one of the terminal contacts, and the actuator having a contracted and recovered form at a temperature elevated condition wherein the actuator flexes the switching blade in a direction away from said terminal contact to separate the blade contact from the terminal contact. 2. - The switch according to clause 1 characterized in that the actuator has the shape of a spiral spring. 3. The switch according to clause 2 characterized in that the spiral spring has a plurality of spiral turns and the switching blade is received between turns of adjacent turns in an end portion of the actuator. 4. The switch according to clause 3, characterized in that the cavity has an anchor projection therein and the anchor projection is received between turns of adjacent turns in the end portion of the actuator. 5. The switch according to clause 1 characterized in that the housing has opposite ends of housing and the terminal lines extend outwardly from the housing at opposite ends of the housing. 6. The switch according to clause 1 characterized in that the cavity includes a portion with a general shape of T having a crossing portion and a leg portion extending from the crossing portion, the switching blade and the terminal contact being in the crossover portion of the cavity and the actuator being in the leg portion thereof. 7. - The switch according to clause 1 characterized in that the leg portion of the cavity has a distal end portion remote from the crossover portion, an anchor projection in the distal end portion of the cavity, and the opposite portion of the cavity is fixed. end of the actuator to the anchor projection. 8. The switch according to clause 7 characterized in that the actuator is in the form of a spiral spring having a plurality of turns of turns, the switch sheet extends between turns of adjacent turns in an end portion of the actuator, and the projection Anchor extends between turns of adjacent turns in the opposite end portion of the actuator. 9. - The switch according to clause 1 characterized in that it includes a one-piece switching blade member having a generally U-shaped configuration with a pair of separate arms that are connected by a base portion, the switching blade is defined by one of the arms, and the other arm is coupled with the other terminal contact. 10. The switch according to clause 9, characterized in that one of the arms has a length that is substantially greater than the length of the other arm. 11. - The switch according to clause 1 characterized in that the housing has opposite ends and opposite sides, the terminals are located adjacent to the opposite ends, the terminal lines extend outwardly from the housing at the opposite ends thereof, the cavity has a portion of generally U-shaped cavity with end cavity portions located adjacent the end portions of the housing and the end cavity portions are connected by a cavity joining portion extending between the end cavity portions adjacent to one from the sides of the housing, the cavity has a leg cavity portion separated from the cavity joining portion and extends from one end cavity portion to the other end cavity portions, the leg cavity portion having a portion at the distant end located adjacent to, but spaced apart from the other end cavity portion, the switch blade is part of a switch blade member with a general U-shape having switch blade member arms that are received at end cavity portions and a base portion of commutating sheet member that is received in the cavity joining portion, the commutating blade is defined by means of one arm of the commutating blade member, the other arm of the switching blade member engages with the other terminal contact, and the actuator is positioned in the leg cavity portion. 12. The switch according to clause 11 characterized in that the actuator has the shape of a spiral spring having a plurality of turns of turns, the switching sheet is received between turns of adjacent turns in an end portion of the actuator, and the distal end portion of the leg portion of the cavity has an anchor projection that is received between turns of adjacent turns in the other end portion of the actuator. 13. The switch according to clause 1 characterized in that it includes a cover that closes the cavity, the housing has a plurality of integrated fastening protections extending therefrom, and the cover has gaps to receive the fasteners through which they extend the fixing projections to fix the cover to the housing. 14. A switch assembly characterized in that it comprises a polymeric housing having opposite ends, opposite sides and opposite front and rear surfaces, a cavity in the front surface, notches in the front surface extending between the cavity and the opposite ends, a pair of terminals having terminal lines that are received in the notches and terminal contacts placed in the cavity, a switching blade placed in the cavity and having a blade contact that normally couples one of the terminal contacts, the switching blade is connected in an electrically conductive relationship with the other terminal contact, an elongate shaped memory alloy actuator having an end portion fixed to the switching blade, the actuator has an extended shape and deformed at normal temperatures where the contact one of the terminal contacts is engaged, and the actuator has a contracted shape and recovers at an elevated temperature where the switch blade moves to an open position with the blade contact separated from one of the terminal contacts. 15. The switch according to clause 14 characterized in that the notches have a notch depth and the terminal lines have a thickness of terminal lines, and the notch depth is substantially the same as the thickness of the terminal lines. 16. The switch according to clause 15 characterized in that it includes a cover fixed to the a distant end opposite the end portion thereof, and an anchor projection in the cavity that is received between adjacent turns in the far end portion. 21. A switch assembly characterized in that it includes an elongated actuator of shape memory alloy that extends along an actuator shaft, a resilient switching blade that extends transversely to the actuator shaft, the switch assembly has a fixed contact and the switch blade has a movable contact, the switch blade can be moved between closed contact and open contact positions, the actuator has an end portion fixed to the switch blade, the actuator has an extended shape and deformed at normal temperatures and a retracted and recovered form at an elevated temperature, and the contacts are in a closed position when the actuator is in one of said shapes and are in the open position when the actuator is in the other of said shapes. 22. The switch according to clause 21 characterized in that the actuator has the shape of a spiral spring. 23. The switch according to clause 22 characterized in that the spiral spring has a front surface to close the cavity and secure the terminals to the housing. 17. The switch according to clause 16 characterized in that it includes fastening projections extending upwards from the front surface of the housing, and the cover has gaps to receive fasteners there through which the fastening projections extend to fix the cover To the accommodation. 18. The switch according to clause 14 characterized in that the actuator extends in a direction between the opposite ends and has a distal end portion separated from an end portion thereof that is fixed to the commutating sheet, an anchor projection in the cavity that is a single piece integral with the housing, and the far end portion is fixed to the anchor projection. 19. The switch according to clause 14 characterized in that the actuator has the shape of a spiral spring having a plurality of turns, and the actuator extends through one of the plurality of adjacent turns in the end portion of the actuator to fix the actuator to the switching sheet. 20. - The switch according to clause 19 characterized in that the spring has a portion of plural turns of turns and the switch sheet is received between turns of adjacent turns in an end portion of the actuator. 24. The switch according to clause 23 characterized in that the cavity has an anchor projection therein and the anchor projection is received between turns of adjacent turns in the opposite end portion of the actuator. 25. The switch according to clause 21 characterized in that the housing has opposite ends of housing and the terminal lines extend outwardly from the housing at opposite ends of accommodation. 26.- The switch according to clause 21 characterized in that the cavity includes a portion with a general shape of T having a crossing portion and a leg portion extending from the crossing portion, the switching blade and one of the contacts terminals are in the crossover portion of the cavity and the actuator is in the leg portion thereof. 27. The switch according to clause 21 characterized in that the leg portion of the cavity has a far end portion remote from the crossover portion, an anchor projection in the far end portion of the cavity, and the portion is fixed opposite end of the actuator to the anchor projection. 28. - The switch according to clause 27 characterized in that the actuator has the form of a spiral spring having a plurality of turns of turns, the switching sheet extends between turns of adjacent turns in an end portion of the actuator, and the anchor projection extends between turns of adjacent turns in the opposite end portion of the actuator. 29. The switch according to clause 21 characterized in that it includes a one-piece switching blade member having a generally U-shaped configuration with a pair of separate arms that are connected by a base portion, the switching blade is defined by one of the arms, and the other arm is coupled with the other terminal contact.