Gas spring

An extendable and compressionable gas spring comprising:

• a hollow, elongate cylinder in which a seal and a guide member is contiguously arranged in an opening provided at one end of the cylinder for enclosing a gas therein, the other end of the cylinder being closed, the cylinder having an inner surface and an outer surface, said cylinder including an annular recession in said outer surface near said one end, thereby forming a stopper within said cylinder for stopping movement of a piston therein,
• said cylinder further including a cylinder groove formed by externally extending said inner cylinder surface in an axial direction of the cylinder, said groove extending between a pair of terminal ends, said cylinder defining three operating areas along the length of said cylinder in a direction from said closed end towards said stopper,
• a first area corresponding to an air-damping area, wherein said cylinder groove has a substantially square cross-section with a constant width and depth, said air-damping area terminating at said cylinder groove terminal end nearest said closed end,
• a second area corresponding to an air-damping reduction area, wherein said cylinder groove has a substantially square cross-section with a constant groove width and a changing groove depth, said groove depth becoming shallower in a direction from said closed end toward said stopper, said cylinder groove in said air-damping reduction area terminating at said terminal end nearest said stopper,
• a third area corresponding to an airlock area, wherein said airlock area is defined as the area of the cylinder extending between said stopper and said terminal end of said groove located within said air-damping reduction area, said airlock area free of said cylinder groove;
• a rod having a piston attached to one end thereof, said rod extending through the seal and guide members and slidably movable such that said piston travels within said cylinder between said closed end and said stopper, a movement of said rod and piston towards said closed cylinder end corresponding to a spring compression and movement towards said stopper corresponding to a spring extension, said piston dividing the cylinder into a rod-side chamber and a piston-side chamber, said piston a unitary member formed from a porous sintered alloy having open pores therein and defined by an outer peripheral edge, said piston including at least one passage formed between the inner surface of the cylinder and the outer edge of the piston for communicating the gas between each of the chambers on either side of the piston, said piston including an annular groove formed around the outer periphery, said annular groove intersecting said at least one passage and receiving therein an O-ring as a check valve for opening and closing said at least one passage during the spring compression and extension movements,
• wherein when said rod and piston is adapted to undergo spring compression, said check valve is in said open position, whereby gas within said piston-side chamber is simultaneously communicated under no damping force to said rod-side chamber through said at least one passage and said cylinder groove, and whereby when said rod and piston is adapted to undergo spring extension, said check valve is in said closed position, wherein gas within said rod-side chamber is communicated under a variably decreasing damping force to said piston-side chamber, wherein when said piston is in said air-damping area, said communication of gas occurs only through said cylinder groove such that said gas communicated in said piston-side chamber assists said spring extension into said air-damping reduction area, whereby said piston is gradually decelerated upon said piston travels through said air-damping reduction area into said airlock area, whereby when said piston is in said airlock area, said gas is solely communicated from said rod-side chamber to said piston-side chamber through said piston pores without said piston experiencing a damping rebound shock, said spring fully extended when said piston is in contact against said stopper.