Actuation device with a drive element actuated by crawling

1. An actuation device for setting into motion an element to be driven, comprising:

a drive element able to be put into contact with the element to be driven; and

an actuation element comprising a fixed portion and a driving portion for the drive element;

wherein the fixed portion includes a crawling surface, the driving portion includes a flexible moveable blade with a given width positioned in parallel and at a distance from the crawling surface, the moveable blade having a free end and an end connected to the drive element;

wherein the moveable blade has a length which is selected so that, when a power supply voltage is applied between the moveable blade and the crawling surface, the free end will come into contact with the crawling surface and a contact area, between the moveable blade and the crawling surface, longitudinally delimited relatively to the moveable blade by the free end of the moveable blade and a crawling front, increases by propagation of the crawling front along the moveable blade, the propagation of the crawling front moving the moveable blade according to a first orientation, thus driving the drive element.

2. The actuation device according to claim 1 , wherein the fixed portion comprises a flexible balk having the crawling surface, so that when a power supply voltage is applied between the moveable blade and the crawling surface, the balk moves closer to the moveable blade.

3. The actuation device according to claim 1 , wherein the driving portion further comprises an elastic return element connected to the moveable blade and to a frame of the actuation device,

the moveable blade being able to be displaced along a first displacement sense according the first orientation by propagation of the crawling front under the effect of the power supply voltage, and

according to a second displacement sense according to the first orientation, opposite to the first displacement sense, under the effect of a return force generated by the elastic return element, so as to generate a reciprocal movement of the drive element.

4. The actuation device according to claim 3 , further comprising an abutment limiting the displacement of the driving portion along the second sense.

5. The actuation device according to claim 1 , wherein the fixed portion, includes a fixed gantry and a balk attached to the fixed gantry, the balk having the crawling surface,

wherein the driving portion includes a moveable gantry and a moveable blade attached to the moveable gantry through one of its ends.

6. The actuation device according to claim 5 , wherein the fixed portion includes a plurality of balks attached to the fixed gantry, each of the balks having a crawling surface,

wherein the driving portion comprises a plurality of moveable blades attached to the moveable gantry, and

wherein the plurality of balks and the plurality of moveable blades are positioned relatively to each other so as to form an assembly of interdigitating combs.

7. The actuation device according to claim 5 , wherein the moveable gantry comprises a support to which are attached the moveable blades and at least one arm connecting the support to a frame of the actuation device.

8. The actuation device according to claim 7 , wherein the arm of the moveable gantry forms an elastic return element connected to the moveable blade and to a frame of the actuation device,

the moveable blade being able to be displaced along a first displacement sense according the first orientation by propagation of the crawling front under the effect of the power supply voltage, and

according to a second displacement sense according to the first orientation, opposite to the first displacement sense, under the effect of a return force generated by the elastic return element, so as to generate a reciprocal movement of the drive element.

9. The actuation device according to claim 5 , wherein the drive element further comprises first and second beams,

the first beam including a first end connected to the moveable gantry and a second end connected to the drive element; and

the second beam including a first fixed end and a second end connected to the driving element;

so that the displacement of the moveable blades generates bending of both beams causing the displacement of the drive element according to a second orientation perpendicular to the first orientation.

10. The actuation device according to one of claim 1 , wherein, for a given width of the moveable blade and a given power supply voltage, the moveable blade has a length which is equal to the minimum length required for allowing formation of the crawling front.

11. The actuation device according to claim 1 , wherein, for a given length of the moveable blade and a given power supply voltage, the moveable blade has a width which is equal to the maximum width allowing formation of the crawling front.

12. A method for mounting an actuation device according to claim 1 , comprising steps of:

etching, in a block of semi-conducting material, the driving portion in the operating position, the fixed portion of the actuation element in a so-called initial position, a holding element comprising at least one abutment able to be engaged in order to displace and block the fixed portion in its operating position and a positioning abutment;

displacing the holding element until its abutment is engaged with the fixed portion thereby causing displacement of the fixed portion against the positioning abutment.

13. An actuation assembly comprising a first actuation device and a second actuation device, each of the first and second actuation device comprising:

a drive element able to be put into contact with the element to be driven; and

an actuation element comprising a fixed portion and a driving portion for the drive element;

wherein the fixed portion includes a crawling surface, the driving portion includes a flexible moveable blade with a given width positioned in parallel and at a distance from the crawling surface, the moveable blade having a free end and an end connected to the drive element;

wherein the moveable blade has a length which is selected so that, when a power supply voltage is applied between the moveable blade and the crawling surface, the free end will come into contact with the crawling surface and a contact area, between the moveable blade and the crawling surface, longitudinally delimited relatively to the moveable blade by the free end of the moveable blade and a crawling front, increases by propagation of the crawling front along the moveable blade, the propagation of the crawling front moving the moveable blade according to a first orientation, thus driving the drive element

the first actuation device and the second actuation device sharing a single and same finger,

the first actuation device being able to displace the finger according to a first orientation and the second actuation device being able to displace the finger according to a second orientation; and

the assembly further comprising a control simultaneously driving both actuation devices, so that:

in a first phase, the first actuation device displaces the finger according to the first orientation and in a first sense;

in a second phase, the second actuation device displaces the finger according to a second orientation and in a first sense;

in a third phase, the first actuation device displaces the finger according to the first orientation and in a second sense;

in a second phase, the second actuation device displaces the finger according to the second orientation and in a second sense.