Passive restraint for prevention of uncontrolled motion

A passive restraint strut apparatus for restraining uncontrolled linear movement between a first member and a second member and comprising:

• (a) a hydraulic cylinder connected to said first member, said cylinder having a closed end and an opposite open end and including an internal cylinder surface;
• (b) a piston rod connected to said second member and extending into said cylinder through said open end and slidably sealing said open end, said piston rod having a flange at an end thereof within said cylinder and a stop spaced axially from said flange;
• (c) a piston sleeved on said piston rod to enable movement between said flange and said stop, said piston sealingly engaging said internal cylinder surface and having a piston passage extending therethrough between opposite ends thereof, said piston passage being sized and positioned in such a manner as to be restricted upon engagement of said piston with said flange and to otherwise enable relatively unrestricted flow therethrough, said piston dividing said cylinder into a first chamber and a second chamber;
• (d) a hydraulic fluid filling said cylinder on opposite sides of said piston, said fluid flowing between said first and second chamber through said piston passage during relative movement between said cylinder and said piston;
• (e) a spring engaged between said piston and said piston rod, said spring having a spring force sufficient to urge said piston in a direction away from said flange during substantially gradual movement between said cylinder and said piston rod;
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• (f) said spring force being of such a strength as to be overcome in response to uncontrolled relative movement between said first and second members thereby enabling movement of said piston into engagement with said flange and restricting flow through said piston passage to thereby restrain relative movement between said cylinder and said piston rod in response to said uncontrolled relative movement between said first and second members.

A dynamically damped pneumatic lift apparatus for gradually lifting a load and for preventing uncontrolled extension of said lift apparatus in response to loss of said load from said lift apparatus at any location along an operating stroke of said lift apparatus and comprising:

• (a) a floor engaging base;
• (b) an elongated pneumatic piston rod upstanding from said base and terminating in a pneumatic piston;
• (c) a pneumatic cylinder sleeved onto said pneumatic piston in sliding and sealing engagement therewith to form a pneumatic chamber with said pneumatic piston;
• (d) a lift carriage connected to said pneumatic cylinder and adapted to engage a load to be lifted;
• (e) said pneumatic cylinder cooperating with said pneumatic piston to lift said carriage in response to entry of compressed gas into said pneumatic chamber and to lower said carriage in response to exhaustion of said gas from said chamber to thereby define an operating stroke of said lift device;
• (f) a hydraulic damper including a hydraulic cylinder and a hydraulic piston rod, said damper being connected between said pneumatic cylinder and said pneumatic piston rod;
• (g) a floating piston member mounted on said hydraulic piston rod within said hydraulic cylinder and slidably engaging said hydraulic cylinder to divide said hydraulic cylinder into a pair of hydraulic chambers;
• (h) a hydraulic fluid positioned within said hydraulic chambers;
• (i) said floating piston member cooperating with said hydraulic piston rod and said hydraulic cylinder to enable substantially unrestricted flow of said fluid between said hydraulic chambers in response to gradual relative movement between said pneumatic cylinder and said pneumatic piston rod;
• and
• (j) said floating piston member cooperating with said hydraulic piston rod and said hydraulic cylinder to restrict flow of said fluid between said hydraulic chambers in response to initiation of sudden relative movement between said pneumatic cylinder and said pneumatic piston rod to thereby prevent said sudden relative movement and to thereby enable only said gradual relative movement between said pneumatic cylinder and said pneumatic piston rod.