Devices for holding intermediate positions and articles that contain the same

Abstract

Disclosed herein is a strut assembly 10 comprising a locking device 11 in operative communication with a piston 3 , wherein the locking device 11 comprises an active material operative to resist motion of the piston 3 in response to an activation signal. Disclosed herein too is a method of operating a strut assembly 10 comprising displacing a suspended body 60 in mechanical communication with a piston 3 ; activating an active material in operative communication with the piston 3 ; and controlling the motion of the suspended body 60.

1 . A strut assembly comprising:
 a piston in slideable communication with a housing;   a locking device in operative communication with the piston, wherein the locking device comprises:   an active material in operative communication with the device; wherein the device is operative to control the motion of the piston and/or the motion of the housing.   
     
     
         2 . The strut assembly of  claim 1 , wherein the locking device further comprises a sleeve, and the active material is in operative communication with the sleeve, such that the sleeve is operative to control the motion of the piston and/or the motion of the housing. 
     
     
         3 . The strut assembly of  claim 2 , wherein the active material is a shape memory alloy. 
     
     
         4 . The strut assembly of  claim 2 , wherein the sleeve is in operative communication with a return spring. 
     
     
         5 . The strut assembly of  claim 1 , wherein the piston includes a piston head and a piston rod, the locking device comprises a plate in operative communication with the piston head, wherein the plate is in slideable communication with the piston rod, a spring stack disposed between the plate and the piston head, and the active material is in operative communication with the plate, such that the active material upon activation is operative to control the motion of the piston. 
     
     
         6 . The strut assembly of  claim 1 , wherein the piston includes a piston head and a piston rod, the piston rod is in slideable communication with the housing, and the locking device includes a protrusion fixedly attached to the piston head and a wave-like tubular guide comprising the active material, such that the wave-like tubular guide is in slideable communication with the protrusion and operative to control the motion of the piston. 
     
     
         7 . The strut assembly of  claim 6 , wherein the active material comprises a shape memory alloy polymer layer disposed on opposing surfaces of a shape memory alloy layer. 
     
     
         8 . The strut assembly of  claim 1 , wherein the piston includes a piston head and a piston rod in slideable communication with the housing, and the piston head further includes a portion having one or more elastic members, one or more brake shoes in operative communication with the elastic members, and an active material in operative communication with the brake shoes and operative to control the motion of the piston. 
     
     
         9 . The strut assembly of  claim 1 , wherein the piston includes a piston head and a piston rod in slideable communication with the housing, the housing includes an electrorheological fluid or a magnetorheological fluid, the piston head includes an optional permanent magnet and an electromagnet, and the optional permanent magnet and the electromagnet are operative to control the motion of the piston. 
     
     
         10 . The strut assembly of  claim 9 , wherein the optional permanent magnet and the electromagnet are concentrically arranged. 
     
     
         11 . A locking device comprising:
 a pivot pin having disposed thereon a ball disk comprising balls;   a long arm and a short arm in rotary communication with a pivot pin; wherein the short arm comprises detents disposed upon a surface that is opposed to a surface in contact with a surface of the long arm; and   a cylindrical housing in communication with a surface of the long arm in opposition to a surface in contact with the short arm, wherein the housing comprises an actuator, a piston and a spring, and wherein the actuator comprises a shape memory material operative to disengage the balls from the detents.   
     
     
         12 . A method of operating a strut assembly comprising:
 displacing a suspended body in mechanical communication with a piston;   activating an active material in operative communication with the piston; and   controlling the motion of the suspended body.   
     
     
         13 . The method of  claim 12 , wherein the activating of the active material occurs by the application of an external stimulus to shape memory material, and wherein the external stimulus is an electrical stimulus, a magnetic stimulus, a thermal stimulus, a chemical stimulus, a mechanical stimulus, an ultrasonic stimulus or a combination comprising at least one of the foregoing external stimuli. 
     
     
         14 . The method of  claim 12 , wherein the activating of the active material resists the motion of the piston. 
     
     
         15 . The method of  claim 12 , wherein controlling the motion of the suspended body comprises locking the suspended body.