This invention relates to phonograph cartridge attachments. More particularly, this invention relates to an improved brush contact for the dynamic stabilizer of a phonograph cartridge.
In the phonograph cartridge industry before 1978, a device for damping unwanted vibration and simultaneously removing static electricity had long been sought. In 1978, Shure Brothers, Inc. introduced such a device in its V15 Type IV Cartridge, which is the subject of U.S. Pat. No. 4,275,888, issued on June 30, 1981 to Carl R. Anderson, et al. for a "Stabilizing and Static Removing Attachment For Phonograph Pickup Cartridge." As described in detail in this Anderson Patent (incorporated here by reference), a cartridge can be vibrationally stabilized and a phonograph record statically discharged by a device comprising a record-engaging, conductive brush; a biasing mass; a lever-mounted, conductive frame and frame-mounting bearings filled with a conductive, viscous fluid. As also described in the Anderson patent, at column 5, lines 6-15, and shown best in that patent's FIG. 10, the brush of this dynamic stabilizer has been formed in the shape of a broom, with a bundle of generally parallel bristles held together at one end by a clamp.
This brush arrangement has proven highly desirable. While the lateral damping ability of Anderson's dynamic stabilizer was not well understood in 1978, it is now believed a phenomenon of "locking" between the bristles and record grooves makes lateral damping possible. This locking occurs when the bristles, during record rotation, sort themselves into "V" shaped groups in record grooves. The locking results in interfiber friction of the bristles during lateral vibration. This friction affords the lateral damping of the cartridge.
The penetration and locking of the bristles in the grooves also results in effective record cleaning by the brush. In forming "V's", the bristles fan the record grooves, with some descending to the groove bottoms. So positioned, the bristles catch minute dust particles in the grooves and thereby prepare the grooves for the stylus.
In spite of these advantages, the Anderson brush is not perfection. Frequent cleaning of the brush is required. In addition, excess lateral force, as from manual error, causes the bristles to bend and possibly disengage from the groove, or cause side thrust on the stylus affecting the tracking of the stylus in the groove and increasing stylus and record wear.