Separation fastener with frangible nut

Abstract

A separation fastener assembly includes a housing defining a cavity. A frangible nut is disposed in the cavity. The nut includes a plurality of nut segments. The one-piece frangible nut greatly reduces existing assembly problems and difficulties. Adjacent nut segments are interconnected at fracture lines. A bolt has an end coupled to the nut. A movable element is disposed in the housing and movable from a first position to a second position. In the first position, the nut segments are restrained from radial expansion. In the second position the nut segments are permitted to radially expand for releasing the fastener assembly.

1 . A separation fastener assembly comprising:
 a housing defining a cavity;   a frangible nut disposed in the cavity, the nut including a plurality of nut segments, adjacent segments interconnected at fracture lines;   a bolt having an end coupled to the frangible nut; and   a movable element disposed in the housing and movable from a first position in which the nut segments are restrained from radial expansion to a second position in which the nut segments are permitted to radially expand.   
   
   
       2 . The separation fastener assembly of  claim 1 , wherein the movable element is a piston radially surrounding the nut. 
   
   
       3 . The separation fastener assembly of  claim 2 , further comprising a reactive charge for pressurizing the cavity to displace the piston from the first position to the second position 
   
   
       4 . The separation fastener assembly of  claim 1 , wherein the housing includes an input port in fluid communication with the cavity for introducing a source of pressurized gas to displace the movable element from the first position to the second position. 
   
   
       5 . The separation fastener assembly of  claim 4 , wherein the housing includes a generally cylindrical sidewall defining the input port. 
   
   
       6 . The separation fastener assembly of  claim 1 , wherein the bolt includes a head opposite the end coupled to the nut and the movable element moves in a direction away from the head from the first position to the second position. 
   
   
       7 . The separation fastener assembly of  claim 1 , wherein the nut includes a plurality of nut segments. 
   
   
       8 . A separation fastener assembly comprising:
 a housing defining a cavity;   a bolt having an end coupled to the nut and a head opposite the end; and   a movable element disposed in the housing and radially surrounding the nut, the movable element movable in a direction away from the head between a first position in which the nut is restrained from radial expansion to a second position in which the nut is permitted to radially expand.   
   
   
       9 . The separation fastener assembly of  claim 8 , wherein the nut includes a plurality of discrete nut segments. 
   
   
       10 . The separation fastener assembly of  claim 8 , wherein the nut is a frangible nut including a plurality of nut segments, adjacent nut segments interconnected at fracture lines. 
   
   
       11 . The separation fastener assembly of  claim 8 , wherein the movable element is a piston. 
   
   
       12 . The separation fastener assembly of  claim 11 , further comprising a pyrotechnic actuator for pressurizing a portion of the cavity to displace the piston from the first position to the second position. 
   
   
       13 . The separation fastener assembly of  claim 8 , further comprising a spacer member for normally retaining the movable element in the first position. 
   
   
       14 . The separation fastener assembly of  claim 13 , wherein the spacer member includes a deflectable leg, the leg being inelastically deflectable upon movement of the movable element from the first position to the second position. 
   
   
       15 . The separation fastener assembly of  claim 8 , wherein the housing includes an open end for receiving the end of the bolt and a closed end, the movable element movable toward the closed end between the first position and the second position. 
   
   
       16 . A separation fastener assembly comprising:
 a housing defining a cavity;   a nut disposed in the cavity;   a bolt having an end coupled to the nut;   a piston radially surrounding at least a portion of the nut to restrain the nut from radial expansion; and   an actuator for pressurizing a portion of the cavity to displace the piston from a first position to a second position in which the nut is free to radially expand in response to a load on the bolt.   
   
   
       17 . The separation fastener assembly of  claim 16 , wherein the actuator is a pyrotechnic actuator. 
   
   
       18 . The separation fastener assembly of  claim 16 , wherein the bolt includes a head opposite the end coupled to nut, the piston movable away from the head from the first position to the second position. 
   
   
       19 . The separation fastener assembly of  claim 16 , wherein the nut is a frangible nut. 
   
   
       20 . The separation fastener assembly of  claim 16 , wherein the housing includes an open end for receiving the end of the bolt and a closed end, the piston movable toward the closed end upon pressurization of the portion of the cavity. 
   
   
       21 . A method of releasing at least one secured component, the method comprising:
 providing a separation fastener having a housing defining a cavity, a frangible nut and a bolt;   inserting the frangible nut into the housing as a single piece;   threadably engaging an end of the nut with the frangible nut to secure the at least one component; and   fracturing the nut into a plurality of discrete segments.   
   
   
       22 . The method of  claim 21 , wherein fracturing the frangible nut into a plurality of discrete segments includes applying a torque to the bolt to fracture the frangible nut within the housing during assembly. 
   
   
       23 . The method of  claim 21 , further comprising radially restraining the frangible nut, and wherein fracturing the nut into a plurality of segments includes removing the radial restraint from the frangible nut in response to a predetermined event.