Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
  • F03G—SPRING, WEIGHT, INERTIA OR LIKE MOTORS; MECHANICAL-POWER PRODUCING DEVICES OR MECHANISMS, NOT OTHERWISE PROVIDED FOR OR USING ENERGY SOURCES NOT OTHERWISE PROVIDED FOR
  • F03G7/00—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for
  • F03G7/06—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like
  • F03G7/061—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like characterised by the actuating element
  • F03G7/0614—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like characterised by the actuating element using shape memory elements
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
  • F03G—SPRING, WEIGHT, INERTIA OR LIKE MOTORS; MECHANICAL-POWER PRODUCING DEVICES OR MECHANISMS, NOT OTHERWISE PROVIDED FOR OR USING ENERGY SOURCES NOT OTHERWISE PROVIDED FOR
  • F03G7/00—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for
  • F03G7/06—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like
  • F03G7/061—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like characterised by the actuating element
  • F03G7/0614—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like characterised by the actuating element using shape memory elements
  • F03G7/06143—Wires
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
  • F03G—SPRING, WEIGHT, INERTIA OR LIKE MOTORS; MECHANICAL-POWER PRODUCING DEVICES OR MECHANISMS, NOT OTHERWISE PROVIDED FOR OR USING ENERGY SOURCES NOT OTHERWISE PROVIDED FOR
  • F03G7/00—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for
  • F03G7/06—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like
  • F03G7/063—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like characterised by the mechanic interaction
  • F03G7/0634—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using expansion or contraction of bodies due to heating, cooling, moistening, drying or the like characterised by the mechanic interaction using cam gearings
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
  • F16K31/00—Actuating devices; Operating means; Releasing devices
  • F16K31/02—Actuating devices; Operating means; Releasing devices electric; magnetic
  • F16K31/025—Actuating devices; Operating means; Releasing devices electric; magnetic actuated by thermo-electric means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
  • F16K31/00—Actuating devices; Operating means; Releasing devices
  • F16K31/44—Mechanical actuating means

Definitions

• the present invention relates to shape memory actuators, i.e. actuators in which the actuating member consists of an element (for example a wire element) made from a shape memory alloy (indicated in the following as "SMA"), and in particular to an actuator in which the driven element is multistable, preferably bistable, i.e. it is moved by a driving element between at least two stable positions.
• SMA shape memory alloy
• the shape memory phenomenon consists in the fact that a mechanical piece made of an alloy that exhibits said phenomenon is capable of transitioning, upon a temperature change, between two shapes that are preset at the time of manufacturing, in a very short time and without intermediate equilibrium positions.
• a first mode in which the phenomenon may occur is called "one-way" in that the mechanical piece can change shape in a single direction upon the temperature change, e.g. passing from shape A to shape B, whereas the reverse transition from shape B to shape A requires the application of a mechanical force.
• a SMA wire has to be trained so that it can exhibit its features of shape memory element, and the training process of a SMA wire usually allows to induce in a highly repeatable manner a martensite/austenite (M/A) phase transition when the wire is heated and to induce an austenite/martensite (A/M) phase transition when the wire is cooled.
• M/A martensite/austenite
• A/M austenite/martensite
• This characteristic of SMA wires to contract upon heating and then to re-extend upon cooling has been exploited since a long time to obtain actuators that are very reliable and silent.
• this type of actuator is used in some valves to perform the movement of the shutter from a first stable position of closed valve to a second stable position of open valve, or to multiple stable positions of partially open valve, and vice versa.
• valves with SMA actuators can be found in US 6840257, US 6843465, US 7055793, US 2005/0005980 and US 2012/0151913. All these prior art documents disclose actuators that are quite complicated, bulky and rather expensive, usually involving the use of two SMA wires and/or mechanical stabilization elements such as a diaphragm for moving the shutter between the two (or more) stable positions. These types of known SMA actuators are therefore unsuitable to be scaled down in size and not fully reliable when used in harsh environments due their rather delicate and sophisticated operation.
• SMA actuators are used also in a variety of other devices in which their operation is quite different from the two-way operation mentioned above.
• US 2007/0028964 discloses a resettable bi-stable thermal control valve that closes when fluid conducted therethrough reaches a predetermined temperature, so as to act as over temperature shut-off valve. More specifically, the reaching of the threshold temperature causes a SMA wire to contract and exert a force on an inner piston body to move into a piston cap compressing an inner piston spring, until two apertures provided through sidewalls of the piston cap become aligned with cavities formed in the piston body thus allowing corresponding balls to move from the outer surface of the piston body into said cavities, which in turn permits a shutter-carrying member that was previously blocked by said balls to retract into the valve body under the force of a spring.
• This operation of the SMA wire causes an irreversible closure of the valve since the balls in the cavities are prevented by the shutter-carrying member from recovering their original position under the action of the inner piston spring even after deactivation of the SMA wire.
• This valve is therefore merely a safety device in which the SMA actuator is used only as a release mechanism, and such a device must be reset manually by pulling out the shutter-carrying member against the resistance of its spring until the apertures in the piston cap are cleared, such that the balls can recover their original position when the inner piston body moves out of the inner piston cap under the force of the compressed inner piston spring.
• a SMA wire is used to disengage the latch of a spring-loaded lid which is then re-closed manually.
• the tension on the SMA wire is provided by two spring-loaded rotating levers that engage the wire through a capstan and a plunger.
• a SMA wire is used to disengage the latch of a door or trunk and a mechanism is provided to make use of the user's force in closing the door or trunk to restore the martensitic state of the SMA wire through a stress-induced state change in case the ambient temperature is so high that the SMA wire does not cool to the martensite transition temperature upon deactivation.
• the object of the present invention is to provide a shape memory actuator which overcomes the above-mentioned drawbacks.
• This object is achieved by means of a shape memory actuator in which the driving element acted on by the SMA wire returns to its rest position upon deactivation of the SMA wire due to first resilient means, while the driven element stably remains in the operative position thanks to a reversible engagement with the supporting body and is then released from said engagement by a control system to return to its rest position due to second resilient means.
• a first advantage of the actuator according to the invention stems from the fact that the driven element is moved between two (or more) stable positions without requiring any extra-stroke of the driving element. This results in the SMA wire being sized precisely for the required stroke of the driven element thus minimizing its cost and bulkiness.
• a second significant advantage of this actuator is its capacity of using a single SMA wire to move the driven element between two (or more) stable positions, thus dispensing with the second SMA wire usually employed in prior art actuators. Also this factor, obviously, contributes to minimizing the cost and bulkiness of the actuator.
• Another advantage of the present actuator in two specific embodiments thereof, resides in the fact that the control system releases the driven element from the operative position without activating the SMA wire, which therefore enjoys a longer operational life since it is activated only every other actuation cycle.
• Still another advantage of the subject actuator derives from its simple and robust structure, which makes it reliable, inexpensive and suitable also for operation in harsh environments.
• Fig. l is a diagrammatic top plan view of the main elements of a first embodiment of the present actuator, in a starting position defined as rest position;
• Fig.2 is a vertical sectional view of the actuator of Fig. l, taken along the central plane A- A;
• Fig.3 is a view similar to Fig.1 of the same actuator at an intermediate moment of a first actuation cycle, with both the driving element and the driven element in an operative position;
• Fig.4 is a vertical sectional view of the actuator of Fig.3, taken along the central plane A- A;
• Fig.5 is a view similar to Fig.3 of the same actuator at a final moment of a first actuation cycle, with the driving element back to the rest position and the driven element remaining engaged in the operative position;
• Fig.6 is a vertical sectional view of the actuator of Fig.5, taken along the central plane A- A;
• Fig.7 is a view similar to Fig.5 of the same actuator at an intermediate moment of a second actuation cycle, with the driving element and the driven element in the operative position and ready to return both to the rest position of Fig. l since the driven element is disengaged;
• Fig.8 is a vertical sectional view of the actuator of Fig.7, taken along the central plane A- A;
• Fig.9 is a view similar to Fig.3 of a second embodiment of the actuator, with some elements omitted, which differs from the first embodiment in the engaging means;
• Fig.10 is a diagrammatic perspective view showing an exemplificative application of the actuator of Fig.1 to the shutter of a valve.
• an actuator includes a supporting body 1 that carries all the other components through suitable seats and couplings, these being different depending on the specific technical solutions adopted for the intended purpose of the actuator.
• the supporting body 1 is provided with a longitudinal guide la, closed at one end by an abutment lb, that slidably receives at the other end a horizontal shutter-carrier 3 which in turn slidably and coaxially carries a slider 5.
• the shutter-carrier 3 includes a threaded shaft 3a at a rear end, where a valve shutter can be mounted, an axial seat 3b at a front end, where a coil spring 7 is received, a longitudinally extending horizontal slot 3c at a middle portion, where a transverse sleeve 5a of slider 5 is slidably received, and a vertical disk 3d located between seat 3b and slot 3c.
• Two compressed coil springs 9 are arranged at diametrically opposite positions between shutter-carrier 3 and slider 5, although even a single spring could be used, said springs 9 being located on pegs 5b that project from the front side of slider 5 and enter corresponding seats formed in the rear side of shutter-carrier 3.
• a horizontal SMA wire 11 passes through the transverse sleeve 5a and reaches end fixing points (not shown) provided on the supporting body 1, where it is secured by locking members that preferably also provide the electrical supply and the connection to an electronic control unit that controls the activation and deactivation of the SMA wire 11.
• a coiled spring is coaxially arranged on the SMA wire 11 at an end portion thereof so that it can be compressed against the adjacent locking member upon contraction of the SMA wire 11.
• This spring serves as a mechanical safety in case shutter-carrier 3 and/or slider 5 cannot be moved for any reason, whereby the contraction of the SMA wire 11 would result in the rupture thereof because the shortening of the wire cannot be turned into a shortening of the path between the two locking members.
• the strength of said spring is selected such that in normal operation it remains uncompressed upon contraction of the SMA wire 11 thus causing the horizontal sliding of slider 5.
• a connecting member in the form of a substantially inverted U-shaped bridge 13 extends from the top of slider 5 to connect the latter with a rotating member 15 that rotates horizontally around a vertical pivot lc extending from the top of the longitudinal guide la, preferably in the central plane A-A of the actuator. More specifically, bridge 13 has a first end 13a pivotally mounted on slider 5 with a vertical pivoting axis and a second end 13b slidably engaged in a slot 17 formed in the rotating member 15 and shaped such that its ends 17a, 17b are always located on opposite sides of pivot lc in the horizontal plane throughout the rotational stroke of the rotating member 15.
• Slot 17 is substantially shaped like a square bracket with the short end sides oriented outwards a bit more than 90° to facilitate the entry and exit of the bridge end 13b into and from the slot ends 17a, 17b.
• the rotating member 15 is shaped like a circular sector and slot 17 extends to the left of the central plane A-A (considering abutment lb as the front of the actuator) when in the rest position illustrated in these figures the second bridge end 13b is in the corner facing the first slot end 17a.
• the second bridge end 13b is not aligned with the first bridge end 13a and with pivot lc, which are preferably coplanar with the central plane A-A, but is rather a little to the right with respect to them whereby bridge 13 is oriented a few degrees (e.g. 3°-5°) to the right of pivot lc for the reason that will be clear in the following.
• a permanent magnet 19 is secured on the curved vertical side of the rotating member 15 next to the second slot end 17b.
• the deactivation of the SMA wire 1 1 can be determined on the basis of a pre-set activation time, but is preferably determined by sensor means suitable to detect the engagement condition of the engaging means so as to obtain a positive feedback on the stability of the reached operative position.
• sensor means suitable to detect the engagement condition of the engaging means so as to obtain a positive feedback on the stability of the reached operative position.
• magnetic engaging means allows to exploit magnetic sensor means, such as a Hall effect sensor or switch or the like, to detect the engagement condition.
• it is possible to use other types of sensor means such as mechanical (e.g. micro-switch), optical (e.g. photo- detector) or electrical (e.g. potentiometer).
• the SMA wire 11 is the actuating member
• slider 5 is the driving element
• shutter-carrier 3 is the driven element
• springs 9 are the first resilient means
• spring 7 is the second resilient means
• the reversible engagement of the driven element with the supporting body 1 is indirectly achieved through the rotating member 15 by means of magnet 19 that engages disk 3d.
• the control system that controls this magnetic engagement is made up of bridge 13, rotating member 15 and slot 17 that bring the engaging means 3d and 19 into engagement and then out of engagement.
• Figure 9 shows a second embodiment of the actuator that differs from the above- described actuator only in the type of engaging means arranged on disk 3d and rotating member 15, namely mechanical means rather than magnetic means. More specifically, a first substantially L-shaped engagement member 21a is provided on disk 3d and a second substantially L-shaped engagement member 21b is provided on the rotating member 15. Said two members 21a, 21b are both arranged in the horizontal plane with their internal sides (i.e. the "concave" sides) facing each other so as to achieve the hooking illustrated in Fig.9, however it is clear that a suitable engagement could be achieved also with different orientations of members 21a, 21b (even in perpendicular planes) as long as their internal sides face each other.
• FIG.10 An example of a possible application of such an actuator is illustrated in Fig.10, showing an actuator A mounted on a valve V provided with two flow-conveying ducts Fl, F2 connected by a shutter case S in which the shutter is moved by shutter-carrier 3 between a closed position and an open position.
• the magnetic engaging means can be changed to simplify the structure of the control system by providing a reversible magnet either as a replacement of the permanent magnet or in combination therewith to obtain an electro- permanent magnet.
• a reversible magnet is a permanent magnet in which the polarization is easily inverted through the application of an electric impulse, it produces an orientable magnetic flux that can also orient the flux of a conventional non-reversible permanent magnet combined therewith, such as to short-circuit the two magnets to deactivate them or to put them in parallel to activate them.
• the magnetic engaging means consist of a permanent magnet, preferably arranged on the driven element, and a reversible magnet, preferably arranged on the supporting body
• the magnetic engagement is achieved by setting the polarization of the reversible magnet such that it attracts the permanent magnet.
• the magnetic engaging means consist of a ferromagnetic member (or a permanent magnet), preferably arranged on the driven element, and an electro-permanent magnet, preferably arranged on the supporting body
• the magnetic engagement is achieved by setting the polarization of the reversible magnet such that the electro-permanent magnet is activated and attracts the ferromagnetic member (or permanent magnet).
• control system for engaging and releasing the magnetic engagement is just the control unit that controls the polarization of the reversible magnet, since the mere reversal of the latter is sufficient to achieve the engagement and disengagement.
• SMA wire need not be activated to move the magnetic means out of engagement as in the first embodiment illustrated above, whereby bridge 13 and rotating member 15 could even be dispensed with.
• Another kind of modification that can be made is aimed at providing more than one operative position, e.g. if the actuator is used on a valve with multiple opening degrees or multiple outlets.
• a different amount of current is supplied to the SMA wire depending on the position to be reached and therefore on the required degree of contraction of the SMA wire and, correspondingly, engaging means are provided at each of the multiple operative positions.
• further SMA wires can be provided (e.g. each passing through a suitable slider transverse sleeve) to move the driving element according to the needs such that the selection of the SMA wire to be activated depends on the position to be reached.
• the rotating member 15 could take the shape of a cam of progressively reduced radius starting from the central plane A- A and provided with a plurality of magnets 19 along its rear side.
• a plurality of magnetic engaging means could be provided on the supporting body along the path travelled by the driven element.
• the multistable actuator is to be intended having continuously controlled stable positions located between two end positions. This kind of operation can be obtained, for example, by means of a Pulse Width Modulated (PWM) control signal.
• PWM Pulse Width Modulated
• control system can be of any other known type, such as those used in retractable pens, as long as it provides the required disengagement of the driven element.
• the symmetrical arrangement of springs 9, the alignment of the first bridge end 13a with pivot lc, etc. are preferable for a smooth operation of the actuator but not strictly indispensable, whereby an asymmetrical and/or out-of-alignment arrangement of these elements and/or the elimination of one of them (e.g. using only one spring 9) could be conceived.
• the arrangement of many elements could be reversed with substantial equivalence of operation, e.g. springs 7 and 9 could be arranged to be pulling springs.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• Reciprocating, Oscillating Or Vibrating Motors (AREA)
• Life Sciences & Earth Sciences (AREA)
• Physics & Mathematics (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Remote Sensing (AREA)
• General Physics & Mathematics (AREA)
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• Actuator (AREA)

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Cited By (6)

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Citations (8)

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• 2013
  • 2013-04-05 IT IT000512A patent/ITMI20130512A1/it unknown
• 2014
  • 2014-03-21 KR KR1020157026698A patent/KR20150137072A/ko not_active Withdrawn
  • 2014-03-21 JP JP2016505906A patent/JP6139014B2/ja active Active
  • 2014-03-21 US US14/780,466 patent/US9512829B2/en active Active
  • 2014-03-21 ES ES14716028.7T patent/ES2632621T3/es active Active
  • 2014-03-21 CN CN201480018515.2A patent/CN105164412B/zh active Active
  • 2014-03-21 PL PL14716028T patent/PL2959164T3/pl unknown
  • 2014-03-21 EP EP14716028.7A patent/EP2959164B1/en active Active
  • 2014-03-21 WO PCT/IB2014/060037 patent/WO2014162234A2/en not_active Ceased

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