US2703822A - Phonograph pickup and the like - Google Patents

Description

March 8, 1955 H. c. WARNER 2,703,822

PHONOGRAPH PICKUP'AND THE LIKE Filed April 29, 1952 IN VEN TOR. 70 HA/PR) a. WARNER /K VW 2Q ATTORNEY United States Patent '0 PHONOGRAPH PICKUP AND THE LIKE Harry C. Warner, San Francisco, Calif.

Application April 29, 1952, Serial No. 284,865

Claims. (Cl. 179-100.41)

This invention relates to an improved phonograph pickup and the like, of the type employing a fluid current-modulating medium.

In the type of pickup to which this invention relates, the phonograph needle is mounted on an actuator member which is swung in a small are as the needle moves back and forth laterally in the record groove. The swinging of the actuator is used to modulate an electric current that flows between two or more electrodes through an electrolytic fluid contained in cavities or cells in a body member made of insulating material.

A preferred pickup construction divides the body member into three serially adjoining cavitieseach containing an electrode and liquid. The central cavity is joined to the other cavities by a pair of orifices whose areas are varied by the actuator member in response to the movement of the needle. Each orifice may be formed between a wall of the chambers and a flexible diaphragm which yields to pressure exerted by the movement of the actuator member and tends to resume its shape when the pressure is relaxed by movement of the actuator member in the opposite direction. Each time the orifice changes in size, the electrical resistance between adjacent chambers changes, varying the current flow and voltage between them. In a pickup having three chambers, a difference in electric potential can be set up across the electrodes in the end chambers, and a varying voltage can be obtained from the electrode in the central chamber. This variation, obtained by varying the areas of the orifices between the central chamber and the other two chambers, causes the voltage on the electrode in the central chamber to increase and decrease relatively to the potential of the other two electrodes, although voltage between these two electrodes remains constant.

The present invention is an improvement in this type of construction and solves several problems which had not been solved heretofore.

One problem has been caused by the fact that there are two different standard types of grooves for phonograph records. Those records adapted to rotate at approximately 33 R. P. M. or 45 R. P. M. have grooves that are substantially narrower than the grooves in the records which rotates at 78 R. P. M. For that reason, the needles which were best calculated to give ideal results with the 78 R. P. M. records are too large to give ideal results with the 33 R. P. M. and 45 R. P. M. records. It is therefore desirable to have two different sizes of needles available so that any type of record can be played with its proper needle. It is also desirable in a phonograph pickup of the modulating fluidtype to be able to use a permanently mounted needle which has a life approximately coterminous with that of the pickup cartridge, because this makes it possible to do away with the inconvenience, poor performance, and added weight of the type of needle-holding chuck in which a screw is tightened on the needle.

The present invention has solved this problem and, at the same time, has obtained other advantageous results, by providing an actuator that extends perpendicularly to the plane of the record. Also, the diaphragm is mounted in a plane generally perpendicular to the plane of the record. This structure contrasts with the type of structure heretofore in use where the actuator and diaphragm lay in a plane parallel to the record surface. Both ends of the actuator are, because of the present invention, now caused to project out beyond the cartridge body, and this new structure makes it possible to have a needle on one end of the actuator adapted to play 78 R. P. M. records and another needle on the opposite end of the same actuator arm adapted for playing 33 R. P. M. and 45 R. P. M. records. Since the needles project from opposite sides of the pickup, the change from one type to another may be made simply by rotating the pickup cartridge through degrees. The change in needles does not affect the response characteristics of the cartridge, and its operation remains the same.

This same structure may also be used in automatic coin-operated phonographs of the type where the records remain in a series of parallel vertical planes. The actuator and diaphragm will still be perpendicular to the record surface. In this type of phonograph, both needles will be the same, one being used to play from one side of the records and the other to play from the other side of the same records.

The vertical actuator (i. e., vertical with respect to the record) also minimizes needle scratch, because the actuator causes no electrical output due to any up-and-down movement of the needle, but only to the desired lateral movement.

This structure also makes it possible to use a very short actuator arm, a structural feature that simplifies the control of the amplitude-frequency responses of the pickup and allow the extension of the cartridges high frequency response to very high values-4o greater than .40 kilocycles per second, if desired.

Other objects and advantages of the invention will appear from the following description of a structure embodying its principles. Sufiicient description is made, in compliance with the statute, to set forth the features of my invention, but not to limit the invention except as defined in the appended claims.

In the drawings:

Fig. 1 is a view in perspective of a pickup cartridge embodying the principles of the invention, looking at the cartridge from the front. I

Fig. 2 is a view in perspective looking at the cartridge of Fig. 1 from the rear.

Fig. 3 is a view in section taken along the line 3-3 in Fig. 1.

Fig. 4 is a view in section taken along the line 44 of Fig. 3.

Fig. 5 is a view in section taken along the line 5-5 of Fig. 3.

Fig. 6 is a view in section taken along the line 6-6 of Fig. 3.

Fig. 7 is an enlarged view in section of one of the interior cells with its electrodes.

Fig. 8 is a view in elevation looking at Fig. 7 from the left.

Fig. 9 is a view in elevation and partly in section of a portion of a phonograph tone arm in which the pickup cartridge of Fig. 1 has been installed.

Fig. 10 is a top plan view of a portion of the tone arm of Fig. 9 showing the means for indicating which size of needle is in playing position. The alternative position taken by the indicator when the pickup cartridge is reversed is shown in dotted lines.

The pickup cartridge 10 may comprise a pair of parallel rigid plates 11 and 12 held together by a screw 13 and supporting between them a terminal plate 14 at the rear end of the cartridge 10 and a body member or master cell 15 at the forward end of the cartridge 10.

The cell 15 is preferably made from an electrical insulating material and is a hollow container, having a cavity 16 with its open face closed by a diaphragm 17 (which may be rubber or synthetic rubber) cemented and sealed thereon. The shape of the master cell 15 is optional. In this instance it is shown as generally rectangular in shape, but it may be made in any other desired shape.

Inside the hollow master cell 15 (see Figs. 3, 4 and 6) are two isolated hollow cells 20 and 21 (for details see Figs. 6, 7, and 8) each of which includes a respective wall member 22, 23 made from plastic or some other insulating material. Preferably, though not necessarily, the walls 22, 23 are tubular in shape. They may be formed integrally with the master cell 15, or they may be made separately and secured (as by cementing) to the forward wall 24 of the master cell 15. In considering the cartridge as a three-chamber sys tem, the master cell is the central chamber and the cells and 21 are the end or outer chambers.

Inside each hollow tubular member 22, 23 is an inner electrode 25, 26, which is preferably a hollow tube adhered to the inner wall of the member 22, 23. The electrodes may be metal plated on the inner wall of the tube 22, 23, or they may be formed separately and installed. Around the outer wall of each tubular member 22, 23 is an outer electrode 27, 28, which is also preferably tubular.

As is shown in Figs. 3 and 7, the open ends of the plastic tubular members 22, 23 extend beyond the electrodes '25, 26, 27, 28, and preferably the tubular members 22, 23 terminate in a sharp edge 29. The assembled inner cells 20, 21 are units whose three main parts are firmly adhered together with the proper tolerances allowed for, and the thicknesses of the two plastic members 22, 23 are preferably identical. The members 22, 23 are preferably secured firmly to the wall 24, as by cementing, so that there will be no leak at this closed end.

The bases 30, 31 of the inner electrodes 25, 26 may extend out through the wall 24. A wire 32 may lead from the inner electrode to one of the outer terminals on the terminal plate 25. A wire 33 may lead from the other inner electrode 26 to the other outer terminal 36. Preferably the two outer electrodes 27, 28 are connected together and a single wire 34 leads to the center terminal 37. Normally, a potential is impressed across the outer terminals 35, 36 and the output voltage is drawn off from the center terminal 37.

A suitable electrolytic liquid 40 fills not only the main cavity 16 but also the hollow interior of two inner cells 20, 21. The conductivity between the inner electrode 25 and its outer electrode 27 is changed by the change in size of the orifice 41 (see Fig. 3) formed between the sharp outer edge 29 of the plastic tube 22 and the diaphragm 17. When the adjacent portion of the diaphragm 17 is flexed so that it is moved closer to the sharp edge 29, the electrical resistance between the inner and outer electrodes 25, 27 of the cell 20 increases, until if the diaphragm 17 touches the sharp edge 29, the current flow will be cut off. The other cell 21 operates in the same manner to vary the orifice 42 and the current between its inner electrode 26 and its outer electrode 28. Since the outer electrodes 27 and 28 are connected together, they are always at the same potential.

The desired variation in current is brought about by an actuator member 50, which is substantially vertical (i. e. perpendicular to the record surface, as is also the diaphragm 17 and has styluses 51 and 52, one on each of its outer ends, and generally perpendicular to its axis, each stylus having its respective needle tip 53, 54. For some uses the needle tips 53 and 54 will be identical. However, with phonographs adapted to play both types of standard record grooves, the needle tip for playing 33 R. P. M. or R. P. M. records will be smaller than the needle for playing 78 R. P. M. records.

The actuator extends through openings 55 and 56 in the plates 11 and 12 and is mounted there in compliant tubular bearings 57, 58. These tubular bearings 57, 58, which may be made of latex, are preferably made with their outer diameter somewhat oversize, for a snug fit in the plates 11 and 12, and with a barely undersized inner diameter so that there will be some damping of the actuator 50. This damping action prevents the actuator 50 from swinging over too Wide a range and holds the operating characteristics of the pickup cartridge 10 within an optimum current range, where there will be greater freedom from distortion than would be the case without damping.

Mounted on the actuator 50 are a symmetric pair of arms 60 and 61 (see Figs. 4 and 5) which extend out an equal distance perpendicularly to the main axis of the actuator and have pads 62, 63 on their outer ends. The

pads 62, 63 are preferably round with a diameter somewhat larger than the outer diameter of the outer electrodes 27, 28, and the pads 62, 63 are preferably cemented to the diaphragm 17, so that the diaphragm moves with the pads 62, 63 both on tension and on relaxation.

When the pickup cartridge 10 is used for playinga record, the stylus being used swings radially back and fortlr'in the record groove. This causes the actuator 50 to be rotated across a small angle, swinging the actuator arms 60, 61 and thereby forcing one of the pads 62 in toward its corresponding inner cell 20, narrowing the orifice 41 between the inner and outer electrodes 25, 27 and thereby causing the current between them to decrease. Simultaneously, the other actuator pad 63 has moved the diaphragm 17 outwardly an amount which exactly balances the effect of the pad 62. The pad 63 widens the orifice 42, increasing the current flow between the inner and outer electrodes 26, 28 of its cell 21. Since the two outer electrodes 27, 28 are connected together, the eifect is always kept in perfect balance so that effects traceable to the vertical movement of the needle will be minimized. The potential across the terminal 35 and 36 remains substantially constant while the output through the terminal 37 varies. The fact that the actuator 50 itself is vertical means that vertical movement of the stylus is not transmitted to the pads 62, 63 nor to the orifices 41, 42. The vertical mounting of the actuator 50, together with the balanced three-chamber construction practically eliminates the transmission of record scratch.

Figs. 9 and 10 illustrate one type of mounting which is possible with the cartridge 10. In this instance the cartridge 10 is mounted on a phonographic tone arm by means of a bracket 71 and screws 72. A bearing 73 is provided in the tone arm 70 to receive a forwardlyprojecting shaft member 74 secured to the outer end of the cartridge 10, with an indicator 75 mounted on the forward end of the shaft 74. A spring 76 may be provided together with a stop member 77 so that the cartridge 10 is kept properly aligned. By turning the pickup cartridge 10 through an angle of the stylus 51 may be put in playing position instead of the stylus 52. This turning is done against the pressure of the spring 76 until the half-way point is passed, and then the spring 76 will help force the pickup 10 into the limit position against the stop 77 so that the stylus 51 is properly aligned. The indicator 75 shows which needle is in playing position. v Other types of mountings may be used with other types of tone arms. If desired both needles 53, 54 may be exposed at once, so that one needle 53 is always ready to play records on one side of the pickup arm and the other needle 54 is always ready to play records on the other side of the tone arm.

What is claimed is:

1. A phonograph pickup including in combination a body member of insulating material having three cavities, one cavity being joined to each of the other two cavities by separate variable orifice means; an actuator member for varying the size of said orifice means, said actuator extending linearly perpendicular to the surface of the phonograph record to be played, and each end of said actuator extending out of said body member; and a stylus secured at each extremity of said actuator.

2. A phonograph pickup cartridge for records having laterally-varied grooves, including in combination a body member of insulating material having a plurality of cavities therein open along a plane perpendicular to the playing surface of said grooves; a generally planar flexible diaphragm closing said cavities along said plane and providing orifice means between said cavities said orifice means being varied in response to the flexing of said diaphragm; actuator means perpendicular to the playing surface and having portions in contact with said diaphragm adjacent said orifice means for varying the area of said orifices by flexing said diaphragm in response to the movement of said actuator means around its vertical axis; and a phonographic needle mounted on at least one end of said actuator means.

3. A phonograph pickup cartridge including in combination a body member of insulating material having three serially adjoining cavities therein open along a plane perpendicular to the plane of the playing surface of the record; a flexible diaphragm closing said cavities, said diaphragm also lying along a plane perpendicular to said playing surface and providing orifice means between the center cavity and each of the two outer cavities, said orifice means being varied in size in response to the flexing of said diaphragm; an actuator having an axis of rotation in contact with said diaphragm opposite said orifice means for varying the area of said orifices by flexing said diaphragm in response to rotation of said actuator about its said axis, said presser members lying on opposite sides of said axis, said actuator extending at each end beyond said body member; and a phonographic needle at each end of said actuator.

4. A phonograph pickup cartridge including in combination a body member of insulating material recessed to provide three serially'adjoining cavities open at one end along a plane generally vertical to the record surface to be played; a diaphragm covering said open end of said cavities and providing variable sized orifices between said center cavity and each of the two outer cavities; a generally linear actuator rod with its axis vertical to the record surface to be played, said rod having a presser foot on each side of said axis adapted to press said diaphragm into' said orifices, so that when said rod is subjected to rotative movement about its vertical axis, said presser feet will open one orifice wider and close the other orifice to a narrower area; and a stylus at each outer end of said rod adapted to follow a record groove, said styluses having needles of different diameters, one to fit in each of two different sizes of grooves, so that said pickup cartridge will play both sizes of grooves, the change from one size to another being made by inverting said phonograph pickup.

5. A phonograph pickup cartridge for lateral-groove type records, including in combination a hollow body member of insulating material open only along one plane perpendicular to the surface to be played; a pair of hollow cells mounted on said body member and open along a plane parallel to said open plane; electrodes on the inner and outer walls of said cells; a flexible diaphragm perpendicular to said surface, closing said body member and providing orifice means between the hollow cells and said body member that are varied in response to the flexing of said diaphragm; actuator means outside said body member and perpendicular to said surface and having presser members in contact with said diaphragm opposite said cells for varying the area of said orifices by flexing said diaphragm in response to? rotation of said actuator means about its vertical axis, said actuator means extending at each end beyond said body member; and a phonographic needle on at least one end of said actuator means.

6. A phonograph pickup cartridge including in combination a hollow master cell of insulating material open along a plane perpendicular to the plane of the playing,

surface of the record; a pair of open tubular insulating cells in said master cell; a tubular electrode in each said tubular cell on its inner wall; a tubular electrode around each said tubular cell on its outer wall; a flexible diaphragm closing said master cell, said diaphragm also lying along a plane perpendicular to said playing surface and providing orifice means between said master cell and each of the two tubular cells, said orifice means being varied in size in response to the flexing of said diaphragm; an actuator having an axis of rotation parallel to said diaphragm and perpendicular to said playing surface, said actuator having presser members with pads secured to said diaphragm opposite said tubular cells for varying the area of said orifices by flexing said diaphragm in response to rotation of said actuator about its said axis, said presser members lying on opposite sides of said axis, said actu ator extending at each end beyond said body member; and a phonographic needle at each end of said actuator.

7. The device of claim 6 in which the cell wall extends closer to said diaphragm than said electrodes.

8. The device of claim 6 in which said outer tubular electrodes are connected to a common terminal.

9. A phonograph pickup cartridge including in combination a body member of insulating material having a plurality of adjoining cavities therein open along a plane perpendicular to the plane of the playing surface of the record; a generally flat flexible diaphragm closing said cavities, said diaphragm also lying along a plane perpendicular to said playing surface and providing orifice means between said cavities, said orifice means being varied in size in response to the flexing of said diaphragm; an actuator having an axis of rotation parallel to said diaphragm and perpendicular to said playing surface, said actuator having presser means secured to said diaphragm opposite said orifice means for varying the area of said orifices by flexing said diaphragm in response to rotation of said actuator about its said axis, said actuator extending at each end beyond said body member; and a phonographic needle at each end of said actuator.

10. A phonograph pickup cartridge including in combination a body member of insulating material recessed to provide a plurality of cavities open at one end along a plane generally vertical to the record surface to be played; a diaphragm covering said open end of said cavities and providing variable sized orifice means therebetween; a generally linear actuator rod with its axis vertical to the record surface to be played, said rod having presser foot means adapted to press said diaphragm into said orifice means, so that when said rod is subjected to rotative movement about its vertical axis, said presser foot means vary said orifice means; and a stylus at each outer end of said rod adapted to follow a record groove, said styluses having needles of dilferent diameters, one to fit in each of two different sizes of grooves, so that said pickup cartridge will play both sizes of grooves, the change from one size to another being made by inverting said phonograph pickup.

References Cited in the file of this patent UNITED STATES PATENTS 2,279,815 Dressel Apr. 14, 1942 2,403,696 Warner July 9, 1946 2,580,694 Munroe Jan. 1, 1952 2,648,726 Warner Aug. 11, 1953

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