actuation. An extractor provides force to help extract the bolt and hold the segments in a release position  after actuation. The bolt is torqued to a preload value that prov ides an outward radial load on the  segments that are restricted by the load ring or collar.  Figure 1b shows the bolt release system during actuation. The load ring or collar is moved up by gas  pressure or spring. The threaded segments that are no longer restricted by the load ring or collar move  out, releasing the bolt. The bolt is extracted by a combination of force from the extractor and the preload. With some applications, an external spring loaded extractor may be required for a positive complete  extraction. This basic bolt release system, used in all of Hi-Shear’s separation nuts, provides a forty-year pedigree to  the new electrically powered devices.  Shock Produced by Separation Nuts  The shock produced by Hi-Shear separation nuts is due to several different factors. Not all of these  factors are present in all designs.   Pyro Shock  Pyro shock is produced by the rapid burning of the pyrotechnic in the initiator with its associated rapid  pressure increase. In pyro actuated separation nuts, pyro shock provides approximately 10 percent of the shock output. In electrically powered separation nuts, there are no initiators and therefore, no pyro shock.  Bolt Strain Energy Release This shock is produced by the rapid release of the preloaded bolt strain. In the standard pyro-actuated  separation nut, this shock accounts for approximately 60 percent of the shock output. This shock is  greatly reduced in Hi-Shear’s Ultra Low Shock Pyro and Electrically Powered separation nuts by the slow  release of the strain energy.  Mechanical Impact Mechanical impact shock is produced by the collision of parts in the nut during actuation. This shock  accounts for approximately 30 percent of the shock output in standard pyro-actuated separation nuts. The  electrically powered nut’s release is slow, ther efore low impact collision of internal parts.  Figure 2 shows the shock output of the electrically powered separation nut. The electrically powered  separation nut shock en ergy output is only 1% of the standard pyro-actuated nut.   Hi-Shear’s Electrically Powered Separation Nut The electrically powered sep aration nut in the fastened position without  the bolt torqued is shown in  Figure 3. The reset tool is used only at the time of installation and is removed after the bolt is torqued to the preload value. The leads come from the release motor that requires 28 VDC at 15 watts to actuate the  nut. The installation tool is temporarily holding the spring-loaded locking ring in place. When the bolt is  torqued, the radial force on segments holds the locking ring in place and then the installation tool is removed.  Figures 4 and 5 show the cam release assembly. In the locked position, the cam ring is forcing the rollers  through the slots in the outer helical ramp into the pockets in the inner helical ramp. When the cam ring is  allowed to rotate counter clockwise by the motor, the radial force on the rollers rotates the cam ring,  releasing the rollers from the pockets in the inner helical ramp. This allows the inner helical ramp to screw down in the outer helical ramp, releasing the strain  load on the bolt as shown in Figure 6 . With the bolt  load released, the radial force  on the segments is removed and the wave spring lifts the locking ring off of  the segments. The segments are driven outward, releasing the bolt. A bolt extractor is required to reliably  separate the bolt from the nut.    186