Hinge mechanism and a hinge assembly

A hinge mechanism comprising:

• first and second members rotatable relative to one another about a hinge axis from a first to a second position, and
• a drive operative in an active mode to bias the first and second members into at least one relative position, the drive comprises a cam surface disposed on the first member and a piston contained in the second member, the piston being biased into an extended position and movable from the extended position against the bias, the piston including an engagement surface which is operative to contact the cam surface during relative rotation of the first and second members and, during at least one selected angular displacement between the first and second positions, the contact between the cam surface and the engagement surface causes the piston to move from the extended position,
• wherein when the piston is in the extended position the drive is in an inactive mode such that it does not provide bias to the first or second members to undergo relative rotation,
• wherein the engagement surface is profiled to include a recess to accommodate at least a portion of a cam having the cam surface to allow rotation of the cam relative to the engagement surface without biasing the piston from the extended position such that the drive remains in the inactive mode on relative rotation of the first and second members through a first selected angular displacement and is in the active mode to bias the first and second members into at least one relative position through a second selected angular displacement.

A hinge system comprising:

• first and second hinge mechanisms for a barrier, each hinge mechanism comprising first and second members rotatable relative to one another about a hinge axis, one of the first or second members of each hinge mechanism being connected to the barrier and the other of the first or second members being connected to a supporting structure such that the barrier can rotate about the hinge axis,
• the hinge mechanisms each including a drive operative in an active mode to bias their respective first and second members to rotate relative to one another into at least one relative position, the first hinge mechanism comprising
• the drive having a cam and a piston, the drive operative to adopt an active mode to bias the first and second members to rotate relative to one another into at least one relative position, and the drive operative to adopt an inactive mode where the drive permits free relative rotation between the first and second members without providing bias to the first or second members to undergo relative rotation,
• the cam having a cam surface disposed on the first member and the piston is provided on the second member, the piston being biased into an extended position and movable from the extended position against the bias, and the piston including an engagement surface which is operative to contact the cam surface during relative rotation of the first and second members,
• wherein the drive remains in the inactive mode on relative rotation of the first and second members through a first angular displacement between the first position and the second position, and is in the active mode on relative rotation of the first and second members through a second angular displacement between the first position and the second position,
• wherein during the first angular displacement of the first and second member between the first and second positions, the piston is in the extended position and the engagement surface is profiled to include a recess to accommodate at least a portion of the cam to allow the drive to be in the inactive mode and allow free rotation of the cam relative to the engagement surface without biasing the piston from the extended position, and during the second angular displacement of the first and second members between the first and second positions, the contact between the cam surface and the engagement surface allows the drive to be in the active mode and the piston moves from the extended position against the bias,
• wherein the first and second hinge mechanisms are configured such that on rotation of the barrier about the hinge axis from the first position to the second position, at least one of the hinges mechanisms remain active to bias the barrier to return to the first position and wherein through at least one of the angular displacements between the first position and the second position at least the first hinge mechanism remains inactive.