Method of positioning by means of an actuator having three bridges

Abstract

Method of positioning a part ( 43 ) in a device by means of an actuator ( 1 ). The actuator comprises two parts ( 3, 5 ) which extend in a main plane and are mutually connected by means of three bridges ( 7, 9, 11 ). The bridges can be shortened in respective shortening directions (Y 1 , Y 2 , Y 3 ) parallel to said main plane by local heating and subsequent cooling down of the bridges. According to the invention, the shortening directions of the three bridges are parallel, and the two parts of the actuator are rotated relative to one another about an axis of rotation ( 21, 23 ) extending perpendicularly to the main plane through alternate shortening of two adjacent bridges ( 7, 9 or 9, 11 ) of the three bridges. In this manner, a tensile stress can be built up in the bridges which exceeds a lowered yield point of the material of the bridges when heated, so that relatively high angle of rotation can be achieved between the two parts of the actuator. Besides, the two parts of the actuator can be rotated relative to one another in two opposite directions (R 1 , R 2 ). A preferred embodiment of an actuator ( 1 ) according to the invention comprises a blade spring ( 27 ) which extends parallel to an X-direction perpendicular to the shortening directions and which is coupled to one of the parts of the actuator. By means of the blade spring, a mutual rotation of the two parts of the actuator is transmitted into a translation of an end portion ( 31 ) of the blade spring in a direction parallel to the X-direction.

1 . A method of positioning a component in a device by means of an actuator, which actuator is provided with two parts which extend in a main plane and are interconnected by means of three bridges, which three bridges can each be shortened in a shortening direction which extends parallel to the main plane in that the bridge is locally heated and subsequently cooled down, in which method the two parts of the actuator are rotated relative to one another about an axis of rotation extending substantially perpendicularly to the main plane through shortening of at least one of said three bridges, the shortening directions of the three bridges are mutually substantially parallel, and the two parts of the actuator are rotated relative to one another by an alternate shortening of two mutually adjoining bridges of the three bridges.  
   
   
       2 . A method as claimed in  claim 1 , characterized in that the two parts of the actuator are rotated relative to one another in a first direction by an alternate shortening of a first and an adjacent second bridge of the three bridges, and in that the two parts of the actuator are rotated relative to one another in a second direction opposed to the first direction by an alternate shortening of the second and the adjacent third bridge.  
   
   
       3 . (cancelled)  
   
   
       4 . The method of  claim 1  wherein the bridges have a width, seen perpendicularly to the shortening direction, which is substantially smaller than twice a spot diameter of a laser beam used or designed to be used for shortening the bridges.  
   
   
       5 . The method of  claim 4 , wherein the width of the bridges is at most equal to the spot diameter.  
   
   
       6 . The method of  claim 1  wherein a distance present between the bridges and the width of the bridges have a same order of magnitude.  
   
   
       7 . The method of  claim 1  wherein a distance present between the bridges is substantially greater than the width of the bridges.  
   
   
       8 . The method of  claim 1  wherein the actuator is provided with a coupling member which is fastened to one of the two parts of the actuator at a distance from the bridges as seen parallel to the shortening direction and in a fixed position as seen in a displacement direction directed substantially perpendicularly to the shortening direction, which coupling member is uncoupled from the corresponding part when seen in the rotation direction of the actuator.  
   
   
       9 . The method of  claim 8 , wherein the coupling member comprises a blade spring which extends substantially parallel to the displacement direction and substantially perpendicularly to the main plane.  
   
   
       10 . The method of  claim 9 , wherein the two parts of the actuator, the three bridges, and the blade spring are manufactured from a single piece of sheeting, the blade spring being bent from the main plane into a position substantially perpendicular to the main plane.