Butera, Francesco (Corso Vittorio Emanuele II 22, Torino, I-10100, IT)
Zanella, Alessandro (Via Tirreno, 139, Torino, I-10100, IT)
Capretti, Gianluca c/o Società, Consortile Per Azioni C. R. F. (Strada Torino 50, Orbassano, I-10043, IT)
Alacqua, Stefano (Corso Einaudi, 115/A, Rivoli Cascine Vica, I-10090, IT)
Butera, Francesco (Corso Vittorio Emanuele II 22, Torino, I-10100, IT)
Zanella, Alessandro (Via Tirreno, 139, Torino, I-10100, IT)
Capretti, Gianluca c/o Società, Consortile Per Azioni C. R. F. (Strada Torino 50, Orbassano, I-10043, IT)
| 1. | Lock device (1) comprising at least a first controlled element (7), in par ticular a bolt, which can be shifted with respect to a stationary structure (2) between an operating and a nonoperating position, actuating means which can be actuated in order to shift the first controlled element (7) from its op erating to its nonoperating position, comprising a flexible shape memory element (14) that can take an ex tended and a shortened configuration, constraint means (P, 10,17 ; P', 10", 17) for determining the arrangement at least a first intermedi ate portion of the shape memory element (14), within which portion the element is operatively associated to the first controlled element (7), means (1720) for obtaining the heating up the shape memory element (14), so as cause its passage from the extended configuration to the shortened configura tion and thus shift the first controlled element (7) from the operating position to the nonoperating posi tion, characterized in that the constraint means (P, 10, 17; P', 10", 17) are in such relative positions that said first intermediate portion of the shape memory element (14) takes a substantially Vshaped structure at least when the first controlled element (7) is in its operating position. |
| 2. | Device according to claim 1, characterized in that the constraint means (P, 10,17 ; P', 10", 17) com prise at least two points (P, 17; P') between which ex tends the first intermediate portion, where during the passage of the shape memory element (14) from the ex tended configuration to the shortened configuration, the first intermediate portion tends to take a recti linear development, in order to generate a traction in a substantially transversal or perpendicular direction with respect to an ideal straight line joining the two constraint points (P, 7; P'). |
| 3. | Device according to claim 2, characterized in that at least one of the two points belongs to a re spective constraint element (P'), which can make a shift (c) during the passage of the shape memory ele ment (14) from its extended to its shortened configura tion. |
| 4. | Device according to claim 2, characterized in that each of the two points belongs to a respective constraint element (P'), which can make a shift (c), the constraints elements (P') being mechanically con nected to one another and to the controlled element (7). |
| 5. | Device according to claim 2, characterized in that the first controlled element (7) linearly slides between the operating position and the nonoperating position, and that the passage of the shape memory ele ment (14) from the extended configuration to the short ened configuration results in a traction on the first controlled element (7) according to a direction basi cally perpendicular to the sliding direction of the first controlled element (7). |
| 6. | Device according to claim 1, characterized in that elastic means (12) are provided, designed to con stantly push the first controlled element (7) towards the operating position. |
| 7. | Device according to claim 1, characterized in that the constraint means (P, 10,17 ; P', 10", 17) com prise means (17) for anchoring a first and a second end (14') of the shape memory element (14) to the station ary structure (2). |
| 8. | Device according to claim 7, characterized in that the constraint means (P, 10,17 ; P', 10", 17) com prise transmission means (P, 10; P', 10") on which a stretch of the shape memory element (14) rests, said stretch being intermediate with respect to the ends (14') of the shape memory element. |
| 9. | Device according to claim 1, characterized in that the constraint means (P, 10,17 ; P', 10", 17) com prise means (10; 10") for guiding the shape memory ele ment (14), being associated to the first controlled element (7). |
| 10. | Device according to claim 9, characterized in that the guiding means comprise a groove (10) made in the first controlled element (7), said groove (10) hav ing at least a surface (10') with a substantially V shape on which at least part of said first intermediate portion of the actuating element (14) rests when the first controlled element (7) is in its operating posi tion. |
| 11. | Device according to claim 1, characterized in that the means for heating the shape memory element (14) comprise means (1720) for electric supply, in cluding at least a switch (18) having a switching ele ment (18') that can be actuated by the first controlled element (7) when shifting from the operating to the nonoperating condition. |
| 12. | Device according to claim 1, characterized in that the shape memory element (14) is provided with a coating made of synthetic material adhering to it, said coating (15) being elastically deformed when the shape memory element (14) shifts from the extended configura tion to the shortened configuration, said coating (15) favouring the return of the shape memory element (14) to its extended structure by virtue of its elastic re covery and of the fact that it accelerates the cooling of the shape memory element (14) when the supply of electric current ceases. |
| 13. | Device according to claim 12, characterized in that the shape memory element (14) is Ubent within the coating (15), so as to have a going and a return portion that are parallel and close to one another, and with its two ends (14') close to one another. |
| 14. | Device according to claim 1, characterized in that manual actuating means (27; 3034) are present, for shifting the first controlled element (7) from the operating position to the nonoperating position. |
| 15. | Device according to claim 1, characterized in that a second controlled element (7) is present, in particular a bolt, which can be shifted with respect to the stationary structure (2) between a respective oper ating position and a respective nonoperating position, through the shape memory element (14) and simultane ously to the first controlled element (7). |
| 16. | Device according to claim 15, characterized in that the constraint means (P, 10,17 ; P', 10", 17) operative for determining a substantially Vshape ar rangement of at least a second intermediate portion of the shape memory element (14), within said second in termediate portion the shape memory element (14) being operatively associated to the second controlled element (7). |
| 17. | Device according to claim 16, characterized in that elastic means (12) are provided, operatively placed between the first and second controlled element (7), so as to constantly push them towards their oper ating position. |
| 18. | Device according to claim 16, characterized in that the guiding means comprise a groove (10) made in the second controlled element (7) and having at least a surface (10') with a substantially Vshape. |
| 19. | Lock device (1) comprising at least a first controlled element (7), in par ticular a bolt, which can be shifted with respect to a stationary structure (2) between an operating and a nonoperating position, actuating means which can be actuated in order to shift the first controlled element (7) from its op erating to its nonoperating position, comprising a flexible shape memory element (14) that can take an ex tended and a shortened configuration, constraint means (P, 10,17 ; P', 10", 17) for determining the arrangement at least a first intermedi ate portion of the shape memory element (14), within which portion the element is operatively associated to the first controlled element (7), means (1720) for obtaining the heating up the shape memory element (14), so as cause its passage from the extended configuration to the shortened configura tion and thus shift the first controlled element (7) from the operating position to the nonoperating posi tion, characterized in that the passage of the shape memory element (14) from the extended configuration to the shortened configuration is operative for causing a traction on the first controlled element (7) according to a direction basically perpendicular to a sliding di rection of the first controlled element (7). |
A lock as mentioned above is described in US-A- 6,310, 411. In said solution the lock is equipped with a bolt moving between a blocked position and a released position, and with a coil-shaped wire made of a shape memory alloy, the two wire ends being connected to a first and a second electric supply terminal, respec- tively; the lock comprises at least a first and a sec- ond connection element for the wire, between which an intermediate portion of the latter is arranged in rec- tilinear direction, parallel to the direction of move- ment of the bolt. On said intermediate portion the shape memory wire is mechanically fastened to the bolt and is electrically connected to a third supply termi-
nal.
Shape memory actuating elements have been known for a long time and used in various fields in which simple and cheap actuating means are required. They are made for instance of shape memory metal alloys that can deform above a given transition temperature. In gen- eral, heating can be achieved since the actuating ele- ment directly detects a variable temperature, or by supplying an electric current through the actuating element so as to heat it by Joule effect.
Going back to the lock described in US-A- 6,310, 411, when an electric current is applied between the first and third terminal, the wire portion extend- ing between them gets shorter, including a part of the aforesaid rectilinear portion, thus shifting the bolt towards the release position of the lock; such shift also results in the switching of a spring bistable mechanism; when the electric supply between the first and third terminal is interrupted, the shape memory wire taking again its extended structure, the bistable mechanism keeps the bolt in the position it has reached. On the other hand, by applying an electric voltage between the second and third terminal, the shape memory wire portion extending between said termi- nal shrinks, thus causing a bolt shift opposed to the previous one, i. e. towards the blocked position of the lock; here again, the bolt shift results in the switch- ing of the bistable mechanism which, once the electric supply between the second and third terminal has been interrupted, keeps the bolt in the position it has reached, although the shape memory wire has taken again in the meanwhile its extended structure.
Basically, therefore, according to the solution described in US-A-6,310, 411, the shrinkage of the shape memory wire is used to generate a traction of the bolt
developing alternatively towards the first or second connection element, between which the aforesaid recti- linear wire portion is defined. The bolt is thus pulled in one direction or the other and the bistable cine- matic mechanism keeps the bolt in the position it has reached.
The presence of several terminals for supplying the shape memory wire with current, as well as the coil-shaped arrangement of said wire, with a rectilin- ear intermediate portion, makes lock production more complex and increases the size of said lock; the same can apply to the presence of the bistable system re- quired for keeping the position reached by the bolt without electric supply. Moreover, the shape memory wire should have a considerable length, which affects lock manufacturing costs. The electric control system of the lock is further complicated in that the shape memory wire is operatively divided into two portions which should be supplied selectively with current.
The present invention aims at carrying out a lock as referred to above, which is simpler and cheaper with respect to the prior art mentioned above. Another aim of the invention is to indicate such a lock with an ex- tremely small size. An additional aim of the invention is to indicate such a lock in which the return of the bolt from its non-operating to its operating position takes place rapidly, after the electric supply to wire made of shape memory material has ceased.
One or more of said aims are achieved according to the present invention by a lock device as referred to above, characterized in that the aforesaid constraint means are in such relative positions that the aforesaid first intermediate portion of the shape memory element takes a substantially V-shaped arrangement at least when the first controlled element is in its operating
position.
Thus, when the shape memory element gets shorter after heating, the aforesaid intermediate portion tends to take a rectilinear or less prominent V-like arrange- ment; the shape memory element thus generates a trans- versal or basically perpendicular traction with respect to an ideal straight line joining two connection points between which extends the intermediate portion.
The aforesaid traction can thus be obtained by supplying the shape memory element, which is preferably wire-shaped, on its two ends with current, without the need for intermediate electric terminals; the wire can thus have a small length and a reduced size. Prefera- bly, the return of the controlled element to its non- operating position is achieved through elastic means, when the electric supply of the shape memory element is interrupted. In a preferred embodiment of the inven- tion, the same shape memory element is arranged so as to control also the shift of a second controlled ele- ment towards its non-operating position, with movement in opposite direction with respect to the first con- trolled element.
Further preferred characteristics of the invention are indicated in the appended claims, which are an in- tegral and substantial part of the present invention.
The invention shall be described with reference to the accompanying drawings, provided as a mere non- limiting example, in which: - Figure 1 is a perspective view of a lock accord- ing to the invention; - Figures 2 and 3 are front views of the lock of Figure 1, in a first and second operating condition, respectively; - Figures 4 and 5 are front views of a lock made in accordance with a possible variant of the invention,
in operating conditions resembling those of Figures 2 and 3, respectively; - Figures 6 and 7 are schematic views of a cine- matic mechanism which a lock made in accordance with a further possible variant of the invention is equipped with, in different operating conditions; - Figure 8 is a schematic perspective view of a lock made in accordance with a further possible variant of the invention; - Figure 9 is a schematic plan view designed to explain the operating principle of the lock in Figure 8.
In Figure 1 number 1 globally refers to a lock made in accordance with the teachings of the present invention. Said lock 1 comprises a box-shaped body 2, made for instance of molded thermoplastic material, having a rear wall 3, an upper wall 4, two side walls 5 and a lower wall with a central opening; a closing lid, not shown in Figure 1, can be fastened onto the body 2.
In the case shown by way of example, each side wall 5, has in an intermediate portion, a passage delimited by parallel guides 6 for a respective sliding bolt 7. Each bolt 7 has a head portion 8, basically tooth-shaped or however delimited by at least an inclined plane, and an inner portion 9, within which a groove 10 is defined, delimited on one side by a surface 10'whose length has a basically V-like development. At least the left bolt 7 (with reference to the figures) has on its lower edge a protuberance or a step 11, whose functions shall be disclosed below.
Between the two opposite bolts 7 an elastic ele- ment is mounted, here represented by a coil spring 12, whose elastic reaction pushes the bolts 7 in opposite directions, towards the outside of the body 2, through the passages defined between the respective pairs of
guides 6. Each end of the spring 12 is inserted into a hollow seating having a circular section, extending to- wards the inside of the portion 9, starting from the edge of the latter opposite the head portion 8.
Number 13 globally indicates a shape memory actu- ating element. Said actuating element 13 is shaped like a flexible cable, comprising a core consisting of a wire 14 made at least partially with a shape memory ma- terial. Onto the wire 14 a layer of elastic coating 15 is molded, which adheres to said wire and is chosen in an elastomer/silicone or synthetic material; as shall be evident from the following, the coating 15 helps both the wire 14 to cool down after current has ceased to pass through the latter, and the wire 14 to go back to a rest condition, as a consequence of the elastic recovery of the coating 15. The coating 15 is prefera- bly molded onto the wire 14 by simultaneously extruding the material which the wire 14 is made of and the mate- rial which the coating 15 is made of. In other words, during the manufacturing process, the wire 14 and its coating 15 are obtained simultaneously by a co- extrusion process, which is advantageous in that it en- ables to obtain the desired structure with one opera- tion, without any additional assembling operation. The coating 15 adhering to the wire 14 acts like a longitu- dinally ditributed spring, which undergoes compression when the wire 14 gets shorter after activation and, therefore, helps said wire to go back to its rest posi- tion thanks to its elastic recovery.
The cable actuator 13 basically has the configura- tion of an upside-down U, so that the two ends of the wire 14, referred to with 14'in Figure 1, are close to one another. In the embodiment shown by way of example, the cable actuator 13 comprises an upper section and two opposite side sections; each side section is par-
tially inserted into a groove 10 of a respective bolt 7, so that the two side sections take a V-like arrange- ment, following the side surface 10'of the respective groove 10.
From the rear wall 3 of the body 2 at least a sta- tionary transmission element P for the cable actuator 13 protrudes, which operates basically between the up- per rectilinear section of said actuator and its two V- like side sections; the two ends of the coating 15 are inserted each into a corresponding bushing 16, from which the ends 14'of the wire made of shape memory ma- terial protrude, said ends being electrically and me- chanically connected to a printed circuit board 17. The cable actuator 13 thus has a global development like a hexagon opened on its base. Onto the board 17, to which the two ends 14'of the wire 14 are electrically and mechanically connected, a micro-switch 18 is mounted, said switch being of NC type (normally closed), from whose shell a sensing head 18'protrudes upwards; the micro-switch 18 is substantially placed between the two bolts 7, slightly below the latter, so that the step 11 of the bolt 7 shown on the left in Figure 1 can push the sensing head 18'when said bolt gets into the body 2, as shall be evident in the following. Still onto the board 17 the following are mounted: a component 19 con- trolling the electric supply of the wire 14, such as a MOSFET (being represented in Figure 1 only), and a con- ventional connector 20 connecting the electric circuit to a suitable supply source, not shown. The board 17 and the components thereto associated (micro-switch 18, MOSFET 19 and connector 20) make up globally the supply means for applying an electric voltage to both ends 14' of the wire 14, so as to heat the latter by Joule ef- fect and, therefore, shorten it.
The operation of the lock 1 shall now be described
assuming that said lock is mounted onto a glove com- partment door within the instrument panel of a motor vehicle.
In Figure 2 the lock 1 is shown in its operating condition, resembling the one of Figure 1. The spring 12 constantly pushes in opposite directions the bolts 7, so that their portions 8 protrude outside the body 2 and engage into corresponding seatings defined on the instrument panel body, not shown. Under these circum- stances, the cable actuator 13 is not supplied electri- cally and thus the wire 14 is in its extended condi- tion; as can be seen, under these circumstances, the sensing head 18'freely protrudes from the shell of the micro-switch 18.
When the door equipped with the lock 1 has to be opened, and thus said lock has to be led to its non- operating position, the connector 20 is supplied with electric current by means of suitable conductors, not shown; supply can be actuated for instance by acting upon a pushbutton. Thus, the MOSFET 19 checks that a suitable electric voltage is applied to the ends 14'of the wire 14, which is thus progressively heated by Joule effect; above a given transition temperature the wire starts getting shorter; the shrinkage of the wire 14 also results in the compression of the coating 15, so that the whole cable actuator 13 tends to take a shortened configuration.
As a consequence of said shrinkage, the two oppo- site V-shaped sections of the wire 14 tend to take a rectilinear development, without however necessarily achieving the latter (see Figure 3). Given the engage- ment of the V-shaped sections of the actuator 13 into their respective grooves 10, the shrinkage of the actu- ating element 13 thus results in a traction on the sur- faces 10', such as to overcome the elastic reaction of
the spring 12 and to cause a corresponding sliding of the bolts 7 one towards the other; as can be inferred, said traction is exerted in transversal or basically perpendicular direction with respect to an ideal straight line joining two connection points between which extends each V-shaped section, i. e. the anchoring point of the corresponding end 14'of the wire and the corresponding return portion P. The fact that the two bolts 7 get closer to one another results in the com- pression of the spring 12, which is thus inserted al- most completely into its end housings defined on the opposite edges of said bolts. Thus the operating condi- tion as in Figure 3 is achieved, in which the bolts 7 are almost completely back into the body 2; the respec- tive head portions 8 thus get released from the afore- said seatings within the instrument panel body, and the door to which the lock 1 is associated can be opened.
At a certain moment during the stroke of the bolts 7, the step 11 of the left bolt causes the compression of the sensing head 18'of the micro-switch 18, and thus the opening of the latter. Said opening actuates the opening of the electric circuit, or anyway the inter- ruption of the supply to the wire 14, which then starts to cool down and thus to extend; while the wire 14 and the cable actuator 13 as a whole tend to reach their extended configuration, the elastic reaction of the spring 12 results in the linear sliding of the bolts 7 towards the outside of the body 2, in opposite direc- tions, until they go back to the condition as in Figure 2.
As previously mentioned, the coating 15 adhering to the wire 14 acts like a longitudinally distributed spring. Indeed, the elastomer/silicone material of the coating 15 on the wire 14 is chosen so as to obtain a double advantage. On one hand, said material, which is
no electric conductor, does not heat up, as conversely happens for the wire 14 when an electric current gets through it during the activation of the cable actuator 13; as a consequence, the material which the coating 15 is made of helps and accelerates the cooling of the wire 14 at the end of the electric supply stage. On the other hand, the coating 15, being made of elastic mate- rial, acts like a distributed spring which is com- pressed when the wire 14 gets shorter as a result of its activation; as a consequence, the coating 15 helps a swift return of the cable actuator 13 to its rest condition, at the end of an electric supply stage, not only since it accelerates cooling but also because it pushes the cable actuator 13 towards its rest condition thanks to its elastic recovery, when the electric sup- ply to the wire 14 ceases.
The door equipped with the lock 1 can then be led manually to its closing position. In this way, the in- clined planes of the head portions 8 of the bolts 7 get in contact with the edge of the aforesaid seatings of the instrument panel body; a light closing pressure on the door, such as to overcome the strength of the spring 12, then makes the bolts 7 get back into the body 2; when the ends of the portions 8 get beyond the edge of said seatings, the recovery of the spring 12 makes the bolts 7 get back and engage into said seat- ings. It should be pointed out that the aforesaid me- chanical return of the bolts 7 is enabled also thanks to the shape of the grooves 10, which have an enlarge- ment on the opposite side with respect to their sur- faces 10', and thanks to the presence of the transmis- sion element P; this allows the cable actuator 13, which is in any case flexible, to change its shape tem- porarily, even when it is in its extended condition, and then take it again at the end of the mechanical
stress.
From the above it is possible to infer how the control carried out onto the cable actuator 13 is con- tinuous and how each bolt 7, after the electric supply to the wire 14 has ceased, can automatically go back to its operating position, however enabling to close manu- ally the door to which the lock 1 is associated.
In the case described above, the lock 1 is led to its non-operating or opened position by electric sup- ply. In a possible execution variant, however, the lock 1 can be equipped with means enabling also a manual opening. Such a case is shown by way of example in Fig- ures 4 and 5, where a body 2, basically resembling the one as in the previous figures, is associated to a lid 25, defining two front passages 26 through which two parallel extensions 27 protrude, each extension 27 pro- truding upwards from a respective bolt 7.
Figure 4 shows an operating condition resembling the one as in Figure 2, in which the head portions 8 of the bolts 7 protrude from the body 2; by acting manu- ally upon the extensions 27, i. e. by placing them closer to one another, the bolts 7 can be shifted to- wards the inside of the body 2, so as to take the non- operating position of the lock 1 as in Figure 5. The position of Figure 5 can thus be reached without sup- plying the shape memory wire 14 with electric current, only by acting manually upon the extensions 27 so as to place them closer to one another, thus overcoming the reaction of the spring 12; such position can be reached also thanks to the width of the grooves 10, as ex- plained above.
In the case of Figures 4 and 5, the extensions 27 can be manually actuated in a direct manner, since they are visible. As an alternative, said extensions 27 can be part of a controlled actuating cinematic mechanism,
for instance a single handle or a key block as known per se. An example of said cinematic mechanism is shown schematically in Figures 6 and 7. In said figures, num- ber 30 refers to an actuating element, which can be shifted angularly around a corresponding hinging pin 31; as previously mentioned, the element 30 can be part of a rotating handle, to be actuated manually by a user, or it can be associated to a key mechanism, as known per se. Number 32 refers to two basically L- shaped levers, opposed to one another and between which the actuating element 30 is mounted; said levers 32 can be shifted angularly around respective hinging points 33 ; number 34 then refers to the end portions of exten- sions resembling extensions 27 as in Figures 4 and 5, i. e. each integral with a corresponding bolt 7.
The actuating element 30 can take a non-operating position, as shown by the hatched line of Figure 6, in which it is in a basically perpendicular position with respect to the extensions 34, and not in contact with the levers 32. The element 30 can be rotated counter- clockwise, starting from its non-operating position, so that its end portions get each in contact with first ends of the levers 32, as shown by the full line of Figure 6. The further angular movement of the element 30 then results in the progressive angular shift of each lever 32, so that its second end gets in contact with a corresponding extension 34, causing its shift towards the hinging pin 31 of the element 30 ; said sec- ond ends of the levers 32 slide on the surface of the extensions 34 as far as the position of Figure 7, in which said extensions are closer to one another, i. e. in a position resembling the one of Figure 5. By lead- ing the actuating element 30 back to the position shown by a hatched line in Figure 6, the levers 32 are then free to go back to their starting positions, as a re-
sult of the thrust of the extensions 34 in a direction opposed to the previous one, thanks to the elastic ac- tion of the spring 12 operating between the bolts 7 with which said extensions are integral.
Figures 8 and 9 show a further execution variant of the invention; in said figures the same numbers as in the previous figures are used for indicating techni- cally equivalent elements as the ones previously re- ferred to.
In accordance with said variant, the lock 1 com- prises a body 2 defining an embedded seating 6'for one bolt 7; at the bottom of said seating 6'a micro-switch 18 is located; between the bottom of the seating 6'and the end portion of the bolt 7 operate two coil springs 12 basically parallel to one another.
The body 2 is associated in a stationary way to a board 17, to which the micro-switch 18 is electrically connected and which has its supply connector, referred to with 20 in Figure 8; as in the embodiment of Figure 1, the board 17 is mechanically and electrically con- nected to the ends of the shape memory wire 14, which can be provided with its coating 15, if necessary, so as to obtain the cable actuating element previously re- ferred to with 13. P'refers to the peg-shaped portions of two transmission elements for the wire 14; in the present variant, the aforesaid transmissions P'can shift and in particular slide linearly within corre- sponding guides P", defined in parallel directions within opposite portions of the body 2; in the case shown by way of example, the guides P"extend longitu- dinally in the same direction as the movement of the bolt 7, as shall be evident from the following. Number 10"refers to a peg protruding from the bolt 7 and con- stituting a connection point for the wire 14 onto the bolt 7. It should be pointed out that the wire 14 can
be arranged as a coil on a corresponding peg P', as can be seen in Figure 8, or simply rest onto the pegs P', as in Figure 9.
Number 40 refers to a connection plate, having substantially a triangular shape and with respective passages into which the pegs P'are inserted; the plate 40, shown only in Figure 8, also has a slot or passage 41 into which the pegg 10"associated to the bolt 7 is inserted; the slot 41 extends longitudinally in the same direction as the movement of the bolt 7. The plate is placed above the wire 14.
The lock as in Figures 8 and 9 works as follows.
The springs 12 constantly push the bolt 7, so that its portion 8 protrudes outside the body 2. Under these circumstances, the wire 14 is not supplied with elec- tric current and therefore has an extended configura- tion; under these circumstances, the transmission pegs P'are in a first position within their guides P" ; said condition is shown with a full line in Figure 9.
When said lock 1 has to be led to its non- operating position, the connector 20 is supplied with electric current. Thus an electric voltage is applied to the ends of the shape memory wire 14, which then progressively heats up by Joule effect; above its tran- sition temperature, said wire 14 starts getting shorter and thus takes a shortened configuration.
The shrinkage of the portions of the wire 14 ex- tending between the board 17 and a corresponding peg P' results in a traction on the latter, such as to over- come the elastic reaction of the springs 12; the pegs P', connected to one another through the plate 40, shift towards the board 17 on the stroke referred to with"c"in Figure 9. The plate 40 transfers the move- ment of the pegs P'to the peg 10"of the bolt 7, which is thus given a"c"stroke towards the inside of the
seating 6'.
At the same time, the shrinkage of the portions of the wire 14 extending between the pegs P'and the peg 10"results in a further traction on the bolt 7, and thus in a shift of the latter added to the previous"c8 stroke; the total stroke of the bolt 7 is thus basi- cally of"2C", as schematically shown in Figure 9; as can be inferred, here again the traction on the bolt 7 is exerted in a transversal or basically perpendicular direction with respect to an ideal straight line join- ing two connection points between which extends the concerned V-shaped section of the wire 14, i. e. the pegs P'.
Thus, the operating condition shown with a hatched line in Figure 9 is achieved, in which the bolt 7 is almost completely got back into the seating 6'and within the body 2; at a certain moment during the stroke of the bolts 7, the latter opens the micro- switch 18, thus interrupting the electric supply to the wire 14, which then starts to cool down and thus to ex- tend; while the wire 14 tends to reach its extended structure, the elastic reaction of the springs 12 re- sults in the linear sliding of the bolt 7 towards the outside of the body 2, until it goes back to the condi- tion shown with a full line in Figure 9. If necessary, the presence of the slot 41 then allows to lead the bolt 7 back into its corresponding seating 6', if the door with the lock 1 has to be closed manually, as pre- viously described with reference to the embodiment as in Figures 1-3.
Practical tests have shown that the lock according to the invention enables to obtain the intended aims.
Indeed, said lock is simple and cheap and has an easy control, both in case of electric and manual actuation.
The particular arrangement enables to minimize the size
of the lock 1; by the way, the outer size of the body 2 can be of 4 x 4 0.5 cm.
Obviously, though the basic idea of the invention remains the same, construction details and embodiments can widely vary with respect to what has been described and shown by mere way of example, however without leav- ing the framework of the present invention.
In accordance with a first variant, the lock could be equipped with one bolt 7, with one or more springs 12 mounted between said bolt and a stationary surface of the body 2, which would have in this case a smaller size than the case shown in the figures. In case of one bolt, the cable actuating element could have a develop- ment resembling the one shown in the previous figures, with suitable guides, or be V-shaped, i. e. be shaped like one of the side sections of the actuator previ- ously referred to with 13; in the latter case, a first end of the wire 14 can be connected directly and me- chanically to the board 17, as in the accompanying fig- ures, whereas the second end can be mechanically fas- tened to the body 2 on the side longitudinally opposed to the one in which the board is present; through an electric conductor said second end can then be electri- cally connected to the board 17.
A second variant, applying in particular to the case in which the lock 1 is equipped with one bolt 7, consists in making the cable actuator 13 with a U-like shape memory wire, having a going and return portion immersed in a common coating made of elastomer/silicone material, as referred to above; thus, the two ends of the wire, close to one another, protrude from a longi- tudinal end of the common coating, for the electrical and mechanical connection to the same base of the sup- ply circuit; conversely, the arc-shaped portion of the shape memory wire protruding from the other longitudi-
nal end of the coating builds a sort of ring, which is fitted onto a peg protruding from the bottom wall 3 of the body 2; said peg thus builds a mechanical connec- tion for an end of the cable actuator, the opposite end of the latter being mechanically and electrically con- nected to the base. Such an arrangement, in which the actuator has a general V-shape, is advantageous because both ends of the shape memory wire are close to one an- other and can thus be connected directly to the same board, without the need for the electric conductor as in the previous variant.
The invention also applies to the case in which the bolt or bolts are shaped like rocking arm hooks in- stead of moving linearly.
In some applications of the lock device according to the invention, the shape memory element 14 could di- rectly detect the temperature to which it is subject, for instance the temperature of a gas or a liquid, so as to be actuated by said temperature at a transition value that can be adjusted when preparing the shape memory material used; in said light, for instance, the device 1 could be designed to keep a partition closed, against the action of elastic means, and be directly subject to a fluid to be controlled. When said fluid shifts from a first to a second given temperature, the wire 14, here without the coating 15, shifts from its extended to its shortened structure, so as to switch automatically the lock to its opened position.