US2088960A

US2088960A - Photoelectric sound pick-up

Info

Publication number: US2088960A
Application number: US44120A
Authority: US
Inventors: Johnson Edward Noel
Original assignee: Individual
Current assignee: Individual
Priority date: 1934-10-06
Filing date: 1935-10-08
Publication date: 1937-08-03
Anticipated expiration: 1954-08-03

Description

Aug. 3, 1937. E. N. JOHNSON PHOTOELECTRIC SOUND PICK-UP Filed Oct. 8, 19

Far 32 Patented Aug. 3, 1937 UNITED STATES 2,088,960 PHOTOELECTBJC SOUND PICK-UP Edward Noel Joh son, JohannesburgUnionof South Africa Application October 8, 1935, Serial No. 44,120 In the Union of South Africa October 6, 1934 12 Claims. (Cl. 179 -1011541) The present invention relates to sound pick-ups of the kind in which the oscillating stylus-carrier carries a mirror whereby a beam of light is oscillated correspondingly with the stylus and in turn actuates a photo-electric cell.

The object of the invention is to provide a stylus carrier for such a pick-up which has notably small mass and moment of inertia. and in which the centralizing force can be made low enough to permit the stylus to follow the sound track with extreme accuracy.

According to the invention there is provided a stylus carrier comprising a spindle mounted on the tone arm to oscillate about its axis and 5 comprising also means to secure a stylus in a position perpendicular to said axis, a mirror on said spindle, and means whereby the carrier is elastically centralized and its kinetic energy is absorbed.

The means for securing the stylus may comprise a socket arranged between the ends of the spindle, rigid with and perpendicular thereto, and a clamping screw entering one end of the spindle. The centralizing of the stylus carrier and its damping may be effected by separate means, but conveniently there is provided a hole in the tone arm through which the stylus socket extends and there is compressed within the hole and around the socket a sleeve of material such as rubber which acts as a spring to centralize the carrier and also as a damper for absorbing its kinetic energy.

' The means for mounting the spindle may comprise rubber sleeving on the spindle, opposite rigid half bearing members forced on to the sleeving to compress it, and means to fix said members in the compressing position. said bearing members may be pivoted to the tone arm and swung about their pivots to bring them into compressing contact with the sleeving. The half bearing members are surmounted by a cap plate, and bolts serve to position the halfbearings in their sleeve-compressing position and to clamp said cap plate and said members to the tone arm.

The invention further comprises the separate stylus carrier as hereafter described.

An example of the invention is shown in the accompanying drawing, in which:

Figure I is a dismembered view of the end of the tone arm and the parts associated there with.

Figure 11 is a end view of Figure I with the parts assembled.

Figure III is a vertical cross section on 111-,-

55 III, Figure I.

.IV illu trates th p rat n f t e de- I Vice. L

2 indicates the end tithe tone m? 3. 3 hal bearin members for the stylus. c rier; a d 4 a cap plate. by whichsaid members are s r d to the tone arm.

The stylus carrier comprises the spind e 5; the endsof which are adapted to act as the ournals of a rubber bearing and ar fitte with the rubber bearing sleeves 6, .6. :The members .3, 3 areformed with half round grooves I which engage and compress the sleeves 6, 6. To iacili tate such compression and the accurate positioning of the stylus carrier, the members 3, .3 are pivoted on pins Bprojecting up from the tone arm. The members 3 are first swung apart on said pivots sufliciently to admit the spindle 5 and-its sleeves 6. They are then pressed towardsone another suiiiciently to compress and grip thesleeves and are there held by the fitting bolts Ewhich pass through the tone arm, said members and the cap .4. The parts are finally secured by the nuts Ill. The rubber sleeves 6' permit the spindle to oscillate to the neces-. sary extent about its axis ll, without material lateral displacement from said axis. .One end I2 of the spindle is bored and screw threaded to receive the stylus clamping screw l3. At the.

other .end,and near to the axis ll, there is rigidly fixed the mirror l4 by which alight beam is deflected.

The stylus carrier further includes the stylus socket l 5, which is rigid with the spindle and projects at right angles to the latter. Said socket is formed witha bore [6 to receive the stylus llysaid bore I6 intersecting and extending upward beyond the bore for the clamping screw- 13* so that the stylus bears against the wall of.

its socket bot-h abovea-nd below the clamping screw. l r

The socket I5 passes through a hole l8-in the tone arm. Compressed in said hole and around the socket is a sleeve IQ of rubberor other material capable of functioning asa spring tocexitralize the stylusand as a damping medium to dissipate the kinetic energy which the stylus carrier and the stylus continually acquire when the pick-up is-in' o'peration'.

In use, the parts are assembled as indicated in Figures. II and III so that the stylus carrier can oscillate about its axis It, subject to the centralizing and damping effect of the sleeve l9; It is thus scillated by the y us follow n t e laterally out sound track of a gramophonerecord. A'stationary beam or lightTZ I. Fi u V; is irected onto the mirror l4 and by it is oscillated correspondingly with oscillations of the stylus. The oscillating beam after modulation, as by a fixed cut-01f 2|, is caused so to influence photoelectric apparatus 22 as to produce electric oscillations which in turn are converted into sound.

It will be noted that a large proportion of the mass of the stylus carrier is concentrated about the axis H and therefore has a lowmoment of inertia. The only members of which the moment of inertia is significant are the stylus I'I itself and the stylus socket IS. The moment of inertia of the latter is however very small and the centralizing and damping force can consequently be made small so that the stylus readily follows the full lateral range of the sound track without materially tending to oscillate the tone arm itself.

I claim:

1. In a photo-electric sound pick-upthe combination with a support, of a stylus carrier comprising a straights'pindle mounted in the support to oscillate about its longitudinal axis and comprising also a) transverse stylus socket, the spindle having an 'axial .bore intersecting the stylus socket and screw threaded to receive a stylus clamping screw, a mirror rigid with the spindle and having its reflecting surface approximately in a plane including the spindle axis, and means whereby the carrier iselastically centralized and its kinetic energy is absorbed.

2. In a photo-electric sound pick-up, thecom-v bination with a support of a stylus carrier comprising a spindle mounted on the support to oscillate about its axis and comprising also a stylus socket rigidly extending transversely from the spindle which is bored at one end to receive a clamping screw for securing the stylus in said socket; .amirror rigid with thespindle and having its reflecting surface approximately in a plane including the spindle axis, and means whereby the carrier is elastically centralized and its kinetic energy is absorbed.

3. In a photo-electric sound pick-up, the com l 4. In a photo-electric sound pick-up, the combination with a support of a stylus carrier comprising a spindle mounted on the support to 05 cillate about its axis, and comprising also a stylus socket rigidly extending transversely from the spindle which is bored at one end to receive a clamping screw for securing the stylus in said socket, amirror rigid with the spindle and having its reflecting surface approximately in a plane including the spindle axis, rubber sleeving on the spindle, opposite half bearing members forced onto the sleeving to compress it, means to fix said members in the compressing positio n, and furthermeans whereby the carrier is elastically centralized and its kinetic energy is absorbed.

5. In a photo-electric sound pick-up, the combination with a support of a stylus carrier comprising a spindle mounted on the support to oscillate about its axis and comprising also means to secure astylus 'ina position transverse toisaid axis, 'a mirror rigid with the'spiiidle and having .prising a spindlemounted on the support to oscillate about its axis and comprising also a stylus socket rigidly extending transversely from the spindle which is bored at one end to receive a clamping screw for securing the stylus in said socket, a mirror rigid with the spindle and having its reflecting surface approximately in a plane including the spindle axis/opposite half bearing members which are pivoted on the support and'are swung about their pivots to compress the sleeving, a cap plate, bolts serving to position the half bearing members in sleeve compressing relationship and to clamp said cap plate and said members to the support, and further means whereby the carrier is elastically centralized and its kinetic energy 'is absorbed.

7. In a photo-electric sound pick-up, the combination with a support .of a: stylus carrier comprisingv a spindle mounted on the support to oscillate about its axis and comprising also a stylus socket rigidly extending transversely from the spindle whichis bored at one end to receive a clamping screw for securing, the stylus in said socket, a mirror rigid with the spindle andhaving its reflecting surface approximately in a plane including the spindle axis, and means which bearson the socket at opposite sides in the direction of itsoscillation whereby the carrier is elastically centralized, and means whereby its kinetic energy is absorbed. c

8. In aphoto-electric sound pick-up, the combination with a support of a stylus carrier comprising a spindle mounted on the support to oscillate about its axis and comprising also a stylus socket rigidly extending transversely from the spindle which is bored at one end to receive a clamping screw for securing the stylus in said socket, a mirror rigid with the spindle and having its reflecting surface approximately in a plane including the spindle axis, rubber sleeving on the spindle, opposite half bearing members forced onto the sleeving to compress it, means to fix said members 'in the compressing position and means which bears on the socket at opposite sides in the direction of its oscillation whereby the carrier is elastically centralized, and means whereby its kinetic energy is absorbed.

9. In a photo-electric sound pick-up, the combination with a support of 'a'stylus carrier comprising a spindle mounted 'on the support to oscillate about its axis and comprising also a stylus socket rigidly extending transversely from the spindle whiclris bored at one end to receive aclamping screw for securing the stylus in said socket, a mirror rigid withthe spindle and having its reflecting surface approximately in a plane including the spindle axis, 'the' support having'a hole through which the stylus socket extends, and a sleeve compressed into thehole and 10. In a photo-electric sound pick-up," the comspindle which is bored at one end to receive a clamping screw for securing the stylus in said socket, a mirror rigid with the spindle and having its reflecting surface approximately in a plane including the spindle axis, rubber sleeving on the spindle, opposite half bearing members forced onto the sleeving to compress it, means to fix said members in the compressing position, the support having a hole through which the stylus socket extends, and a sleeve compressed into the hole and around the socket, said sleeve being of material having elastic and energyabsorbing properties.

11. A pick-up stylus carrier comprising a spindle, a stylus-receiving socket integral with the spindle and extending transversely therefrom, the spindle having an axial bore extending from one end to intersect the stylus socket and screw threaded suitably to receive a stylus clamping screw, and a mirror rigid with the spindle and. having its reflecting surface approximately in a plane including the spindle axis.

12. The carrier claimed in claim 11 in which the stylus-receiving socket is positioned at about the centre of the length of the spindle and the external surface of the spindle from said socket to its ends is: a plain cylindrical journal surface of uniform diameter.

EDWARD NOEL JOHNSON.