Temperature compensated electron beam convergence apparatus

Claim 1

In a static convergence apparatus for establishing a substantially constant magnetic flux field across paths traversed by electron beams in a color producing cathode ray tube, the apparatus including separate sections adapted to be positioned at spaced points about the neck of the tube opposite the respective beams thereof, each section of the apparatus including a pair of core members of a predetermined configuration and having ends adapted to be positioned adjacent to the neck of the cathode ray tube so magnetic flux passing between said ends extends into the tube in the path of the associated electron beam, and portions spaced from said core member ends and in closely spaced confronting relation to one another to provide a small gap therebetween, a manually movable adjustable magnetic flux producing means positioned on one side of said gap of the associated core members for producing magnetic flux in a first path which extends through said core members and between the ends thereof and in a second shunt leakage flux path passing across said air gap, the magnetic flux produced by said movable adjustable magnetic flux producing means having a tendency to vary according to the variation in the ambient temperature thereof, the improvement comprising: a U-shaped flux-permeable compensating magnetic member extending part way around said closely confronting portions of said core members to bridge said gap therebetween and having a magnetic reluctance which varies with temperature so as to vary the amount of leakage flux across said gap to maintain the flux in said first path fiarly constant with variation in the ambient temperature, said U-shaped compensating magnetic member having a bridging portion extending across said gap on the side of said core members opposite the side on which said movable adjustable magnetic flux producing means is located and a pair of opposite legs extending from said bridging portion thereof in the direction of said movable adjustable magnetic flux producing means and passing acroSs the gap along the adjacent sides of said core members so the shunt effect of the compensating member varies with the length of said opposite legs thereof.