Door check attachment

Claim 1

A latching device, for attachment to a door check unit having a cylinder element and a piston element, and serving releasably to secure a door in an open position, comprising: a pair of parallel elongated members comprising a cam carrying member attachable to one of the elements of the door check and a hook carrying member attachable to the other element of the door check, the two members being longitudinally slidable extendably or retractably one with respect to the other when the door check is extended or retracted; the cam carrying member having fixed thereon a planar cam having a sloping leading edge, a concave trailing edge, and a pair of lateral edges defining the cam width; the hook carrying member having an elongated hook element loosely mounted thereon for lateral pivotable movement with respect to the longitudinal sliding direction of the members against spring biasing means urging the hook member into a laterally offset position within the cam width, the hook element having a hook projecting laterally into the plane of the cam; whereby (1) on initially extending the members the hook engages and rides over the leading edge of the cam against the action of the hook biasing means and the spring biasing means urges the hook laterally to engage the concave trailing edge of the cam on retracting the members to restrain the members from further retracting, and (2) on extending the members again the hook emerges from the concave trailing edge of the cam and the spring biasing means urges the hook laterally therefrom allowing the members to be fully retracted; the latching device further including an elongated pin member lying in the plane of the cam and oriented in the sliding direction of the members, the pin being spaced rearwardly from the concave trailing edge of the cam, whereby the hook rides along the pin when overshooting the cam on the initial extension of the members and drops into the concave trailing edge of the cam on initial retraction of the members; the hook carrying member further comprising a channel and the cam carrying member a bar slidable along the base of the channel, the hook element being mounted on the channel above the base thereof by a transverse rivet passing loosely through the hook element, a compression coil spring being carried by the pin on one side of the hook element, the spring bearing against the hook element and against the side of the channel.