ENHANCED SOUND REPRODUCTION TECHNICAL FIELD
The invention concerns the alleviation of the adverse effects of electrostatic charges present on gramophone 5. records.
DISCLOSURE OF THE INVENTION
According to the present invention there is proposed a method for the alleviation, during the playing of a record, of the adverse effects of the static charge on 10. the record and the electrostatic field arising from such charge, which method comprises the neutralisation or substantial neutralisation of the said field by means of positively and negatively charged ions.
According to a preferred feature, th'e positively 15. charged and negatively charged ions are emitted by respective emission means, and are emitted continuously' and simultaneously by such means.
The invention also includes apparatus for practising the method as aforesaid and which comprises emission means 20. adapted to create positively charged and negatively charged ions. BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described further, by way of example only, with reference to the accompanying drawing 25. illustrating one embodiment thereof, and in which:-
Fig. 1 is a diagrammatic side elevation of a device constructed in accordance with the invention as positioned for use relative to a record
disc on a gramophone turntable; Fig. 2 is a perspective view of the device shown in
Fig. 1; and Fig. 3 is a diagrammatic perspective view of the 5. pins of the device of Figs. 1 and 2.
BEST MODE OF CARRYING OUT THE INVENTION
Referring now to the drawings, a device for the neutralisation or substantial neutralisation of the electrostatic field arising from an electrostatic charge 10. at the surface of a record disc 11 on a gramophone turn¬ table 12 comprises spaced electrodes 13, 14 arranged in side-by-side disposition within a box 15 mounted adjacen the said turntable, the electrodes 13, 14 being connecte with respective high voltage sources via leads 16, 17. 15. The electrodes 13, 14 each comprise a pin of 38*s gauge wire, such pins being approximately two and a half centimetres long and being mounted in parallel dispositi at one and a half centimetres centres in a perspex block to extend forwardly therefrom by approximately three- 20. quarters of their length. The rearward ends of the pins are connected with the respective leads 16, 17 directl adjacent the back of the block.
The box 15, which box is conveniently fabricated from synthetic plastics material, for example ABS, is of 25. rectangular form, and has a window at its forward end, the pins being arranged perpendicular to the plane of the window and the perspex block being secured to the box with the forward ends of the pins positioned rear- wardly of the window respectively to emit positive and 30. negative ions therethrough.
In order to provide for the ready vertical adjust¬ ment of the box relative to the plane of the record disc, such box is mounted on a base plate 18 by means of an articulated linkage 19, such linkage being so connected 35. with the base plate 18 or box 15 as to provide for a
relative rotation between the box and base plate if desired. The device may be free-standing relative to the turntable 12 or may be secured in position relative thereto, the base plate in the former case, preferably 5. being weighted for stability purposes.
In a typical situation the device is positioned adjacent the periphery of the record disc 11, say two and a half centimetres from the line of such periphery, with the common plane of the electrodes 13, 14 approximately
10. one and a quarter centimetres above the plane of the disc, and the electrodes 13, 14 are connected with a positive source of 4.43 KV and a negative source of 3.55 KV respectively. The electrode emitting the positive ions is preferably placed forwardly of that electrode
15. emitting the negative ions in the direction of disc rotation so as to be met first by any particular part of the disc periphery, it having been found that such disposition gives an improved performance as compared with the alternative disposition.
20. We have found that by means of the device as herein¬ before described we are able to create a space above the revolving disc of substantially neutral charge, and accordingly are able effectively to inhibit the ingress of dust and the like to such space, and thus to the
25. surface of the record.
The disposition of the device in relation to the plane of the disc does not appear to be critical, and indeed advantageous effects have been achieved when the plane as defined by the pins is below the plane of the disc,
30. although it is preferred that the pins be positioned to define a plane parallel to the plane of the record disc and slightly above such plane.
It has been established that the pins will produce satisfactory effects if arranged one above the other,
35. rather than in the side-by-side disposition shown, and thus
the invention is not to be considered limited to the disposition of pins shown.
Whilst the device as hereinbefore described represents a convenient, effective and aesthetically 5. pleasing structure for reducing contamination of the playing surface of the revolving disc by dust, for minimising variations in the weight trackability of the pick-up arm and stylus and for alleviating other problems arising from any electrostatic charge at the record
10. surface, such device represents but one of a variety of means embodying the invention.
Thus, for example, instead of providing a single pair of pins emitting positive or negative ions, alternative forms of emitter may be used. In one
15. arrangement, there may be a row of from two to twelve pins arranged at say, two and a half centimetres centres for the emission of positive ions and a further similar row of pins for the emission of negative ions, the two rows being arranged in parallel disposition and lying in
20. respective, planes parallel or perpendicular to the plane of the disc and, in the former case, tangential to such disc.
In another arrangement, each emitter takes the form of a rod or wire arranged tangentially of the disc or
25. perpendicular to the plane thereof and in spaced dis¬ position relative to the periphery of the disc, wire lengths of between two and a half and thirty centimetres having given satisfactory results.
It may be found convenient, and indeed economically
30. advantageous to build the device into the turntable deck, thereby minimising or eliminating the need for additional structure specifically to support the emitters.
Like voltages to those referred to in connection with the device illustrated in the drawing,, and indeed a
35. range of voltages at either side thereof, will give
O Pi
substantial neutralisation of an electrostatic field arising from the disc surface to provide satisfactory results, although it may be that a lesser voltage differential as between the respective sources is 5. preferred.
Whilst the invention has been disclosed in the context of the simultaneous emission of positive and negative ions, such invention is not limited to simul¬ taneous emission in the sense of continuous emission
10. both of positive and negative ions at one and the same time as in the case of the embodiment hereindisclosed. In its broadest sense the inventive concept is seen to lie in the use both of positive and negative ions to neutralise the field arising from the electrostatic
15. charge present on the record.