Cam operated toggle for securing a light fixture or the like to a tube

Claim 1

In an apparatus for affixing a body to the end of a tube having a uniform cross-section formed about an axis wherein the body includes a hub which extends into the tube from said end and has a distal end within said tube, and said apparatus includes a draw bolt means extending through said hub generally parallel to said axis, said draw bolt means having head means within the tube beyond said hub and means on the opposite side of the hub from said head means to draw said head means towards said hub, and a device between said hub and said head means for engaging said tube in response to said head means being so drawn towards said hub, the improvement wherein said device comprises: a rigid support centrally positioned within said tube and extending to opposite sides of said axis, said support being engaged by said head means so that as said head means is drawn toward said hub said support is moved correspondingly, said support being of generally "U" shaped configuration in cross-section and comprising a base and two sides integral with the base, said sides extending from the base towards the hub and at opposite sides of said axis; a pair of engaging arms each having a distal end and a proximal end, each arm including two sides and an integral connecting plate, the sides of the arm being in juxtaposition to the sides of the base respectively and pivotally connected thereto, the connecting plate extending approximately to the distal end of the arm and having an outer edge at the distal end, the arms being of a length such that the distance between the pivotal connections plus the length of each arm from the pivotal connection to the distal end of each arm is greater than the inside dimension of the tube normal to the axis in the direction corresponding to the measurement between the pivotal connections, said arms extending upwardly and outwardly to contact the hub and the inside of the tube, whereby as the head of the draw bolt means draws said support towards the hub the hub cams the arms outwardly so that the said outer edges of the plates are forced against the inside of the tube to engage the tube; and a spring having a base and arms at the respective ends thereof, said spring base being on the side of the support base adjacent the hubs and the spring arms extending at an angle to contact the arm plates respectively to hold the arms against the hub and, prior to the head of the draw bolt means being so drawn, to hold the arms in a position such that the distance between the distal ends of the arms is less than said inside dimension of the tube, the distal ends of the spring arms being closer to said axis than are the distal ends of the engaging arms.