The head drum assembly for use in a tape recorder comprises a rotating shaft divided arbitrarily into an upper and a lower parts, a rotary drum pressed in and fixed to the upper part of the rotating shaft, the rotary drum having a protruding cylindrical portion with its center coinciding with that of the rotating shaft, a stationary drum attached at the lower part of the rotating shaft through a plurality of bearings, the stationary drum being hollowed out thereby being provided with an inside bottom surface, the stationary drum further including a bottom surfaces, a rotary transformer bonded to the protruding cylindrical portion, a stationary transformer fixed to and installed on inside bottom surface of the stationary drum, the rotary transformer and the stationary transformer being aligned and separated by a gap, and a transferrer for adjusting the gap between the rotary transformer and the stationary transformer. The transferrer includes a set screw and a feed ring with a matching tapped hole and is located at the bottom surface of the stationary drum and the top of the set screw is in a physical contact with the bottom of the rotating shaft in such a way that the rotary drum is moved vertically by turning the set screw, thereby allowing the gap between the rotary transformer and the stationary transformer to be adjusted.
According to a first aspect the present invention is related to a head drum arrangement allowing a much easier mounting of the rotary transformer. The head drum arrangement comprises a non-rotating lower drum and a rotating upper drum, which are connected by a shaft fixed in the lower drum. The upper drum is mounted on the shaft by a bearing and preferably by two ball bearings. A rotary transformer is arranged between the lower drum and the upper drum having a fixed stator and a rotor rotating jointly with the upper drum. The rotor is non-positively held in its position by the magnetic force of a permanent magnet accommodated in the upper drum.
