Patent GB-427975-A (GB)
Title: Improvements in or relating to phonographic pickups
IPC: H04R11/08
Filed: 1933-11-03
Abstract: 427,975. Gramophone pick-ups. COMPARE, M., Via Quintino Sella, Milan, Italy. Nov. 3, 1933, No. 30591. Convention date, Nov. 3, 1932. [Class 40 (iv)] [See also Group XXXVIII] A gramophone pick-up comprising an armature 6 surrounded by a coil 1 has one end semi-elastically mounted by means of a fork-like joint on the neutral pole 4 of an electromagnet 2 whilst its other end is connected by an arm 7 provided with a small loop 9 to the needle holder 11. The volume of sound may be adjusted by shunting coil 1 by an adjustable resistance or by modifying the current flowing through the energizing coils 3. The Specification as open to inspection under Sect. 91 comprises also a construction of pick-up in which the needle holder is mounted directly on the armature which, together with the magnet poles, is arranged obliquely with respect to the main magnet body so that the pick-up as a whole can be accommodated in the curved end of the pick-up arm 16, Figs. 10 and 11 (Cancelled). The pick-up assembly also carries contact blades 45 electrically connected wth the coils and adapted to engage fixed contacts 70 in the arm 16. This arm is pivoted at 65 on a base member provided with a slot 24 through which a pin 31 on the arm 16 projects. Mounted within the base is a centrally pivoted arm carrying weights K, a freely revolving gear wheel controlled by a spring 69 being mounted on the same pivot and engaged by teeth on one end of a pivoted lever 54, the other end of this lever being in the path of pin 31. The natural frequency of oscillation of the weights K is tuned to 78 periods per minute and when the pick-up needle enters the eccentric groove at the end of playing the record, the pin 31 in moving backwards and forwards strikes the lever 54 and sets the arm carrying the weights into oscillation. A projecting pin 55 then rocks the lever 56 about its pivot 57 thereby allowing the roller 72 on the spring- controlled pivoted lever 60 to be withdrawn from engagement with the contact blades 62 and opening the motor circuit. Fig. 5 (Cancelled) shows a modification in which the pin 31 engages one end 23 of a lever 19 pivoted at 29, the toothed end of this lever engaging a gear wheel 20 mounted on a pivot which also carries a spring-controlled plate 18 and an arm 27 carrying weights K. In order to close the motor circuit the arm 16 is moved away from the turntable so as to cause the pin 31 to press on the spring-controlled pivoted lever 30 till the latter is engaged by the tooth 28 on plate 18 and is held in that position and maintains the roller 25 between the contact blades 35. As the arm 16 during playing moves across the record the pin 31 is brought into contact with arm 23 to which it imparts a slow rotary movement which is conveyed to arm 27. On the needle entering the run-out groove, the pin 31 is given a sudden accentuated movement which cannot be followed by weights K owing to their inertia and a pressure is therefore exercised on plate 18 which is then turned through a small angle, thus releasing the lever 30 and opening the motor circuit. The button 32 is provided to brake the turntable by direct pressure. This subject-matter does not appear in the Specification as accepted.