EP1936344A1

EP1936344A1 - Temperature-sensor and actuator device

Info

Publication number: EP1936344A1
Application number: EP07024478A
Authority: EP
Inventors: Romano Gualandris; Francesco Stortiero
Original assignee: Technosprings Italia Srl
Current assignee: Technosprings Italia Srl
Priority date: 2006-12-22
Filing date: 2007-12-18
Publication date: 2008-06-25
Also published as: ITVA20060083A1

Abstract

Provided herein is a temperature-sensor and actuator device, comprising: a supporting body (4); an actuator lever (5), which is constrained to the supporting body (4) and can turn with respect to the supporting body (4) itself about an axis of rotation (5a), the rotation of the actuator lever (5) being linked to the rotation of an actuator shaft (2); a return torque acting on the control lever (5) about said axis of rotation (5a); and at least one elastic element (3) made of shape-memory material, designed to vary its elastic constant at at least two different operating temperatures, and constrained to the supporting body (4) and to the actuator lever (5) in such a way that its elastic deformation is such as to determine a torque acting on the actuator lever (5) about the axis of rotation (5a) and opposing the return torque.

Description

The subject of the present invention is a temperature-sensor and actuator device of the type comprising an elastic element made of shape-memory material and described in the preamble of Claim 1.
Currently known are different types of temperature-sensor and actuator devices that are used for different applications.
In particular, sensors and actuators are known, based upon the use of shape-memory materials.
As is known, in fact, shape-memory materials have at least two different phases of crystalline structure at temperatures close to the temperatures of operation and use thereof, at which they assume different mechanical and/or geometrical characteristics.
Thanks to said peculiarity, it is possible to vary the geometry or the mechanical characteristics of an element made of shape-memory material by varying its temperature.
The elements made of shape-memory material can hence constitute a temperature sensor and at the same time a mechanical actuator.
It is in fact possible simply to form a shape-memory sensor/actuator element having a given length at a certain temperature and a smaller or greater length at a different temperature, or a spring having different elastic constants at different temperatures.
Said sensors/actuators are very appreciated above all for their own simplicity: just one element made of shape-memory material replaces, in fact, complicated actuator devices and sensor devices with advantages in terms of costs, weights, and reliability.
Alongside the considerable advantages, the known art referred to above presents certain important drawbacks.
In fact, the actuators made of shape-memory material enable movements that are difficult to regulate and rather limited.
It is in practice necessary to design a different actuator made of shape-memory material for each different application.
Another important disadvantage is represented by the fact that the force exerted by the actuator is not adjustable in a simple way.
Not the least drawback is the fact that shape-memory sensors/actuators are used for performing only movements of translation. It is in fact not simple to obtain shape-memory actuators that perform angular movements, if it is taken into account that the materials in question present linear variations in their dimensions.
In this situation, the technical task of the present invention is to develop a sensor and actuator device capable of overcoming substantially the drawbacks mentioned above.
In the framework of said technical task, an important purpose of the invention is to provide a sensor and actuator device comprising an elastic element made of shape-memory material that is versatile and will enable the movement of the actuator to be varied easily.
Another important purpose of the invention is to obtain a sensor and actuator device comprising an elastic element made of shape-memory material capable of actuating angular movements accurately.
Not the least important purpose of the invention is to develop a sensor and actuator device comprising an elastic element made of shape-memory material that is able to exert an adjustable force.
The technical task and the purposes specified above are achieved by a sensor and actuator device that is characterized in that it comprises one or more of the new technical solutions described and claimed hereinafter.
Illustrated by way of example in the attached drawings are preferred embodiments of the invention. In particular:

Figure 1a shows, in the horizontal plane, the device according to the invention in a first position;
Figure 1b illustrates, in the horizontal plane, the device according to the invention in a second position;
Figure 2 represents the device according to the invention in the vertical plane; and
Figure 3 presents a different embodiment of the device according to the invention.

With reference to the figures, the device according to the invention is designated as a whole by the number 1.
It sets itself in at least two different configurations at at least two different operating temperatures. Said different configurations entail different angular positions of an actuator shaft 2 or the like, about a principal axis of rotation 2a.
The device 1 comprises, broadly speaking: a supporting body 4; an actuator lever 5, such as to move the actuator shaft 2; an elastic element 3 made of shape-memory material; and a return torque, acting on the actuator lever 5.
In particular, the supporting body 4 is designed to support the elastic element 3, the actuator lever 5, and other components of the device 1 described hereinafter.
It moreover presents a prevalently plane development lying in a plane of development 4a that is preferably substantially perpendicular to the principal axis of rotation 2a.
The actuator lever 5 is constrained to the supporting body 4 and can turn with respect to the supporting body 4 itself about an axis of rotation 5a, preferably parallel to the principal axis of rotation 2a.
In particular, the actuator lever 5 is substantially constituted by a rod lying in the plane of development 4a of the supporting body 4, and constrained at one end to a rotational hinge 6, fixed to the body 4 and such as to enable rotation of the lever 5 about the axis 5a.
The device 1 then comprises the elastic element 3 made of shape-memory material and designed to exert a force proportional to its elongation in at least one direction of action 3a.
In particular, said elastic element 3 can be constituted by a helical spring, the length of which varies in a linearly proportional way with the force applied thereto in the direction of the axis of the helicoid coinciding with the direction of action 3a.
In particular, the force applied by an elastic element 3 can be simply obtained from the product between the elongation of the spring and an elastic constant.
Alternatively, there can exist different proportions between the elongation of the spring and the force applied thereby. However, in the present text only a linear approximation of the relation between force and elongation will be taken into account, so that the elastic constant alone will basically determine the totality of the characteristics of the elastic element 3.
The elastic element 3 made of shape-memory material is moreover designed to vary its own elastic constant at at least two different operating temperatures.
It is in fact preferably made of a shape-memory metal alloy.
Said alloys are known as SMAs (Shape Memory Alloys) and present at least two different phases of crystalline structure at temperatures close to the operating temperatures.
In particular, the two different phases of one and the same SMA material have two different elastic moduli, or Young's moduli.
For example, the alloy Ni_xTi_100-X, with 49at%<X<51at% at appropriate compositions and after appropriate thermal treatments at temperatures of between 300°C and 700°C can present at 20°C an elastic modulus of approximately 30 GPa and at 40°C an elastic modulus of approximately 70 GPa.
As is known, proportionally to the elastic modulus of the material, the elastic constant of the elastic element 3 made of the same material varies.
Consequently, an elastic element 3 made of shape-memory material has two different elastic constants, for example, a first value at a temperature of 20°C and a second value at a temperature of 40°C.
It should be emphasized that substantially all the materials present slight differences of elastic modulus as a function of temperature, in particular in the proximity of the melting points. However, said differences of elastic modulus cannot be used for the purpose of the device 1 in so far as they are too contained.
Instead, shape-memory materials present elastic moduli having values that vary markedly at the transition between the crystalline phases, which occurs in narrow temperature intervals, as in the case mentioned above.
The shape-memory elastic element 3 is constrained to the supporting body 4 and to the actuator lever 5, not in an area coinciding with the axis of rotation 5a.
It presents a direction of action 3a conveniently parallel to the plane of development 4a and is preferably constrained at its ends to two supports 8, in particular to a control support 8a, fixed with respect to the supporting body 4, and to a control support 8b, fixed with respect to the actuator lever 5.
Said supports 8 conveniently comprise two rotational hinges, designed to enable the loading of the elastic element 3 to occur always in the direction of action 3a.
In particular, if the elastic element 3a is constituted by a helical spring, its ends are preferably constituted by two circular hooks having an axis in a direction perpendicular to the direction of action 3a, and the supports 8 are preferably constituted by two circular pins arranged on the supporting body 4 and on the lever 5 and having a principal direction of development perpendicular to the plane of development 2a, as illustrated in the figures listed. Said circular pins enable, in fact, a rotation of the circular hooks about them.
Said embodiment is illustrated in the figures listed.
The elastic element 3 is then designed to exert a twisting torque acting on the actuator lever 5 about the axis of rotation 5a.
Said twisting torque varies as a function of the distance of the control support 8b from the axis of rotation 5a and of the force exerted by the element 3 in a way proportional to its elastic constant.
The twisting torque then varies also as a function of the operating temperature of the device 1 and in particular assumes two different values at temperatures that determine two different phases of crystalline structure of the shape-memory material that forms the elastic element 3.
The device 1 then comprises a return torque acting on the actuator lever 5 about the axis of rotation 5a and opposing the twisting torque determined by the elastic element 3 made of shape-memory material.
Said return torque is preferably substantially constant as the temperature varies in the proximity of said operating temperatures. It can be produced by a further elastic element or, alternatively, by a magnetic force, a gravitational force, or the like.
In particular, in the present figures the return torque is constituted by an elastic contrast element 7, consisting of a helical spring, partially constrained to the supporting body 4 and to the actuator lever 5.
More in particular, the contrast element 7 is constituted by a helical spring made of steel or the like having an elastic constant that remains substantially constant as the temperature varies.
Also the elastic contrast element 7 is preferably constrained at its ends to two supports 8, in particular to a control support 8a, fixed with respect to the supporting body 4, and to a control support 8b, fixed with respect to the actuator lever 5.
The supports 8 and the ends of the elastic contrast element 7 are preferably altogether similar to the supports 8 of the elastic element 3 and to the ends thereof, and moreover the control support 8b of the elastic contrast element 7 can coincide with the control support 8b of the elastic element 3, as illustrated in the figures listed.
The supporting body 4 and the actuator lever 5 further comprise conveniently a plurality of seats 9 designed to house the supports 8.
In particular, said seats 9 can be set at regular intervals along the axis of the lever 5 and circularly along two arcs of a circumference having as centre the principal axis of rotation 2a or the axis of rotation 5a of the lever 2.
Said seats 9 can be constituted by simple holes in which the supports 8 can be constrained by means of screws or the like.
Alternatively, the supports 8 can be constituted by sleeves or the like, which can be arranged in a preferred position along the actuator lever 5 or the supporting body 4. In this case, the seats 9 can be constituted by notches or the like designed to indicate the position of the supports 8.
The supporting body 4 can finally comprise a transmission device 10 designed to link the rotation of the actuator lever 5, about the axis 5a, to the rotation of the actuator shaft 2, about the principal axis of rotation 2a.
The transmission device 10 appropriately increases or reduces the torque acting on the actuator lever 5 and resulting from the difference between the twisting torque and the return torque.
Said transmission device 10 can be, for example, constituted by a gear pair having selectable dimensions, as illustrated in Figure 3.
Alternatively, it is possible for no transmission device 10 to be present, and the axis of the lever 5a and the principal axis of rotation 2a can coincide, as illustrated in Figures 1a, 1b and 2.
Operation of a sensor and actuator device made of shape-memory material, described above from the structural standpoint, is outlined in what follows.
At a first operating temperature, the shape-memory material is in a first phase, and the elastic element 3 has a first elastic constant. The elastic element 3 hence exerts a certain twisting torque opposing the return torque. The difference between the twisting torque and the return torque gives rise to a resultant torque, which causes rotation of the lever 5 and hence of the actuator shaft 2.
Said rotation is stopped by the equilibrium of the torques being reached or simply at the end of travel of an elastic element 3 or 7, as illustrated in Figures 1a, 1b and 3.
At a second operating temperature, the shape-memory material is in a second phase, and the elastic element 3 has a second elastic constant. The elastic element 3 hence exerts a different twisting torque, once again opposing the return torque.
The difference between the new twisting torque and the return torque gives rise to a new resultant torque, different from the previous one.
Said new resultant torque has, for example, a direction opposite to the direction of the first resultant torque and causes rotation in an opposite direction of the lever 5 and hence of the actuator shaft 2. This situation arises in particular when the elastic constant of the elastic element 3 has values higher or lower than the elastic constant of the elastic element 7 according to whether the material constituting it is in the first phase or in the second phase.
The resultant torque and the angular range of the actuator shaft 2 are selectable.
It is, in fact, possible to arrange the elastic elements 3 and 7 in preferred positions along the seats 9 and hence adjust the arm of the torques or the elongation of the elastic elements 3 and 7.
It is moreover possible to select the transmission device 10 and apply then to the shaft 2 a desired resultant torque or a desired angular range.
The device 1 is hence connected to apparatuses and the like that require angular adjustments according to the temperature, in particular to air conditioners, refrigerating apparatuses, water heaters, and the like.
The invention enables important advantages.
The device 1 is in fact capable of performing angular movements as a function of the temperature and by means of shape-memory elements.
The device 1 is moreover versatile and enables ease of variation of the movement of the actuator, in particular thanks to the plurality of seats 9 and to the transmission device 10.
As has been mentioned, it is in fact possible to regulate very easily and precisely, by mere positioning of the supports 8 in the seats 9 or a mere replacement of the gears that make up the transmission device 10, the arm of the torques or the elongation of the elastic elements 3 and 7, and consequently the angular position of the actuator shaft 2 at the two different temperatures and the resultant torque with which the shaft 2 performs said rotation.
The device 1 can then be applied on different apparatuses and adapted thereto via simple adjustments. It is not then necessary to design a new sensor/actuator based upon the use of shape-memory materials for each application, and the costs of production and use of said sensors/actuators are considerably reduced.
The invention may undergo modifications and variations, all of which fall within the scope of the inventive idea.
All the items can be replaced by equivalent elements, and the materials, shapes, and dimensions may be any whatsoever.

Claims

A temperature-sensor and actuator device comprising at least one elastic element (3) made of shape-memory material, designed to vary its own elastic constant in the presence of different operating temperatures, and a body (4) for supporting said elastic element (3), and being characterized in that it comprises an actuator lever (5), which is constrained to said supporting body (4) and can turn with respect to said supporting body (4) about an axis of rotation (5a), and a return torque acting on said control lever (5) about said axis of rotation (5a), and in that said at least one elastic element (3) is constrained to said supporting body (4) and to said actuator lever (5) in such a way that its elastic deformation is such as to determine a torque acting on said actuator lever (5) about said axis of rotation (5a) and opposing said return torque.
The device according to one or more of the preceding claims, in particular Claim 1, comprising an actuator shaft (2) having a principal axis of rotation (2a) coinciding with said axis of rotation (5a).
The device according to one or more of the preceding claims, in particular Claim 1, comprising an actuator shaft (2) having a principal axis of rotation (2a), and a transmission device (10) designed to link the rotation of said actuator lever (5) about said axis (5a) with the rotation of said actuator shaft (2) about said principal axis of rotation (2a).
The device according to one or more of the preceding claims, in particular Claim 3, in which said transmission device (10) is designed to vary the torque exerted by the actuator lever (5).
The device according to one or more of the preceding claims, in particular Claim 4, in which said transmission device (10) is constituted by gears.
The device according to one or more of the preceding claims, in particular Claim 1, in which said elastic element (3) is constrained to two supports (8), fixed with respect to said supporting body (4) and to said actuator lever (5) and in which said actuator lever (5) comprises a plurality of seats (9) designed to house one of said supports (8).
The device according to one or more of the preceding claims, in particular Claim 1, in which said elastic element (3) is constrained to two supports (8), one fixed with respect to said supporting body (4) and the other to said actuator lever (5) and in which said supporting body (4) comprises a plurality of seats (9) designed to house one of said supports (8).
The device according to one or more of the preceding claims, in particular Claim 1, in which said elastic element (3) made of shape-memory material is constituted by a helical spring.
The device according to one or more of the preceding claims, in particular Claim 1, in which said return torque is constituted by an elastic contrast element (7), constrained to said supporting body (4) and to said actuator lever (5) in such a way that its elastic deformation is such as to determine said return torque.
The device according to one or more of the preceding claims, in particular Claim 9, in which said elastic contrast element (7) is constrained to two supports (8), one fixed with respect to said supporting body (4) and the other to said actuator lever (5) and in which said actuator lever (5) comprises a plurality of seats (9) designed to house one of said supports (8).
The device according to one or more of the preceding claims, in particular Claim 9, in which said elastic contrast element (7) is constrained to two supports (8), one fixed with respect to said supporting body (4) and the other to said actuator lever (5) and in which said supporting body (4) comprises a plurality of seats (9) designed to house one of said supports (8).