Gas spring

A gas compression spring for moving a substantially horizontally pivotted closure member on an automobile body from a fully closed position corresponding to compression of the spring to a fully open position, comprising:

• a cylinder having a first, closed-off, end carrying a fixture for connecting the cylinder to one of the body and the closure member and a second, opposite, end;
• a piston rod sealingly protruding through the opposite end of the cylinder and carrying a fixture for connecting the piston rod to the other of the body and the closure member,
• the piston rod being connected to a piston slidable within the cylinder, the piston having a head defining a first chamber in the cylinder between the head of the piston and the first cylinder end, the piston defining a second chamber through which the piston rod extends;
• means in the cylinder defining a third chamber nearer to the second end of the cylinder than the second chamber;
• the third chamber having an open mouth communicating with the second chamber and through which mouth the piston rod extends;
• the interior of the cylinder being charged with gas under pressure so that the force of the gas moves the piston rod from a retracted position inwardly of the cylinder towards an extended position;
• first gas flow means providing a first restricted gas flow path allowing gas to flow from the second chamber to the first chamber to facilitate such movement;
• a sealing ring mounted to extend sealingly round the piston rod and means defining a smooth interior wall surface portion forming part of the interior surface of the third chamber, the smooth interior wall surface portion being so positioned that it and the sealing ring act mutually to form a temporary seal which seals off the interior of the third chamber from the second chamber when the piston rod in moving towards the extended position has reached a predetermined intermediate position between the retracted and extended positions, whereby the resulting build-up of gas pressure within the third chamber stops further movement of the piston rod towards the extended position;
• and
• means defining a longitudinally extending groove in a second interior wall portion of the third chamber, the second interior wall portion being positioned closer to the second end of the cylinder than the smooth interior wall surface portion, the groove providing a second restricted gas flow path which connects the interior of the third chamber to the second chamber when the piston rod has been moved beyond the predetermined position towards the extended position by an externally applied farce, whereby gas flow from the third chamber to the second chamber is permitted by the second gas flow means and causes the gas pressure within the interior of the cylinder to move the piston rod into the extended position.

A gas compression spring for moving a member relative to a body from a first position corresponding to compression of the spring to a second position, comprising

• a piston-cylinder arrangement with a piston rod slidingly and sealingly extending outwardly of a first one of the two ends of the cylinder and terminating in a distal end outside the cylinder;
• the distal end of the piston rod and the second one of the ends of the cylinder being adapted for connection between the body and the member;
• the interior of the cylinder being filled with gas under pressure;
• piston means carried by the piston rod and slidable within the cylinder;
• first gas flow means providing a restrictive gas flow path permitting limited flow of gas from one side of the piston means to the other as the gas pressure exerted on the piston rod moves the piston rod from an inner piston rod position towards an outer piston rod position more outwardly from the cylinder, whereby to move the member towards the second position;
• gas flow blocking means operated by the piston means when the piston rod has reached an intermediate position between the inner and outer piston rod positions to cause a block in the said gas flow path and thereby to cause a pressure build-up halting movement of the piston rod at the intermediate position;
• second gas flow means operative when a change in an external force applied to the piston rod has caused the piston rod to move further outwardly of the cylinder to unblock the said gas flow path whereby to allow the piston rod to move into the said outer piston rod position;
• the piston means comprising first and second pistons, the first piston dividing the interior of the cylinder into a first chamber closed by the head of the first piston and a second chamber through which the piston rod extends and in which the second piston is positioned;
• means defining a third chamber in which the second piston reaches a predetermined position when the piston rod has reached the intermediate position;
• the first gas flow means including first interconnection means interconnecting the third chamber and the second chamber and second interconnection means interconnecting the second and first chambers;
• the gas flow blocking means comprising sealing means carried by the second piston to form a gas-tight seal which seals off the third chamber from the second chamber when the second piston reaches the predetermined position within the third chamber thereby blocking the passage of gas through the first interconnection means, whereby to produce the said pressure build-up in the third chamber and thus a corresponding force opposing the force which is produced by the gas pressure in the first and second chambers and which tends to move the piston rod to the outer piston rod position;
• and
• pressure release means carried by the second piston and operative when the piston rod is moving inwardly of the cylinder from the outer piston rod position under the application of an externally applied force to provide a by-pass flow path by-passing the sealing means when the second piston moves into the predetermined position, whereby to prevent pressure build-up opposing such movement;
• the pressure release means comprising groove means carried by the second piston and extending from the side of the sealing means closer to the third chamber to the side thereof closer to the second chamber, the sealing means being movable between a first position in which it closes the groove means and a second position in which it opens the groove means, the sealing means being urged into its first position by frictional contact between the sealing means and the first wall surface portion of the third chamber when the piston rod is moving from the inner piston rod position towards the outer piston rod position, the sealing means being urged into its second position by frictional contact between the sealing means and the first wall surface portion of the third chamber when the piston rod is moving from the outer piston rod position towards the inner piston rod position.