Richard J. Mcclure

Magnetic head with versatile gap

Apparatus squeezes together, on selective command, the poles of a core having a gap of a given physical gap length, thereby to place the poles under stress. Stress decreases the permeability of the pole material. Attendantly, in response to the application of stress, the effective gap of the core lengthens. Release of the applied stress restores the effective gap length to that corresponding to the physical gap length. To increase pole stress, the invention employs a piezoelectric element that is bonded to the core across its gap. Application of an electrical signal (of predetermined polarity) to the piezoelectric element causes the element to contract, thereby squeezing the poles together.