US 2892898 A
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United States Patent DELAY APPARATUS Raymond Lubow, Los Angeles, Calif.
Application February 21, 1958, Serial No. 716,797
'14 Claims. (Cl. 179-1001) This invention relates to electrical delay apparatus and, more particularly, to improvements therein.
Electrostatic recording is a capacitive type of recording wherein a voltage is applied to a dielectric by means of an electrode. The dielectric retains the charge, and it can be subsequently removed from the dielectric by another electrode. This type of recording, although well known, has not found very great favor, especially in audio recording, since the previously known recording systems were either noisy, or could not provide sutficient reproduction fidelity, or would require high voltages for writing, or the dielectric material was poor and the stored charges would dissipate.
An object of the present invention is to provide an electrostatic storage arrangement suitable for use in high fidelity audio reproduction systems.
Another object of the present invention is the provision of a useful electrostatic storagesystem which is free from noise and does not require excessive recording voltages.
Yet another object of the present invention is the provision of a novel, useful, and simple delay device.
Another object of the present invention is the provision of a novel dielectric recording medium and novel dielectric recording electrodes.
These and other objects of the invention are achieved in an arrangement whereby a preferred dielectric is an oxide. of a metal, such as aluminum -or magnesium, which is supported by the metal itself. A novel recording electrode is provided which actually contacts the oxide. A readout electrode is provided, which also actually contacts the oxide. If desired, an erasing electrode is placed in contact with the oxide after. it has passed from under the readout electrode. In the preferredembodiment, these electrodes are made of a material which is conductive and has rubber-like characteristics. A preferred material is exemplified by neoprene impregmated with graphite. This arrangement may be employed for recording, for delay purposes, or to provide an artificial reverberation system which is inexpensive and yet produces the results which are obtainable from more complicated arrangements of apparatus.
The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in connection with the accompanying drawings, in which:
Figure 1 is a block diagram of a recording system in accordance with this invention;
Figure 2 shows in enlarged form the details of the invention;
Figure 3 is a block diagram of a reverberation system in accordance with this invention; and
Figure 4 is a block diagram of a binaural system in accordance with this invention.
Referring now to Figure 1, which is a block diagram of an arrangement for employing the embodiment of the invention in a delay system, signals for recording or delay are obtained from a signal source 10. These are applied to a recording electrode 12, which in accordance with this invention is actually in contact with the dielectric recording means being employed. By way of example of a suitable form for the medium, although not to be considered as a limitation thereon, there is shown a disc 14, supported by a shaft 16, which is rotatably driven by a motor 18. A readout, or pickup, electrode 20, which may be identical with the writing electrode 12, is positioned a distance therefrom to provide a desired delay interval. The signal read by the electrode 20 is applied to a signal utilization device 22.
The electrodes employed in accordance with this invention are commonly termed conductive rubber. As may be seen in Figure 2, this conductive rubber electrode 24 is supported by means of a metal holder 26, which can hold its position so that as in the case of carbon brushes, when the material in contact with the dielectric surface 28 wears out, the electrode can be moved to maintain contact with the'dielectric surface. In the preferred embodiment, the conductive rubber comprises neoprene in which there has been impregnated graphite. The dielectric material itself 28, in the preferred embodiment of the invention, comprises an oxide of a metal,
such as aluminum or magnesium. The dielectric is the oxide which normally forms on such metal. The metal 30, accordingly, would be the carrier for the oxide.
Heretofore, actual physical contact of the electrodes with the dielectric could not be employed first because of the factor of both dielectric and electrode wear, which soon rendered the storage system useless. Secondly, static charges generated by friction as the dielectric moved appears as unwanted noise signal in the output. To attempt to overcome this, the electrode was not actually brought in contact with the dielectric, but was brought as close to its as possible. However, this would require a voltage for writing of a substantially high value. Since the metal 30 serves as one electrode and the electrodes 12, 14 serve as 'the second electrode, the thinner the dielectric, the closer the opposite electrodes can be brought to each other, and, therefore, the greater the charge that can be deposited upon the dielectric for a given applied potential. Furthermore, the closer together that opposite electrodes are brought to the dielectric, the further the frequency response is extended. Accordingly, by employing direct contact, the highest frequency response obtainable for a given recording speed is provided.
In accordance with this invention, by employing the oxide of a metal, which oxide normally forms on such metal, a coating, or dielectric, which is only a few molecules thick is provided. Therefore, the capacitance or sensitivity is very great. Since such oxide coating constantly reforms when worn away, a directly contacting electrode may be used effectively without wearing out the dielectric. However, the requirements for the direct contacting electrode are that it be made of a material which will not penetrate the oxide layer. The conducting rubber, or neoprene impregnated with graphite, does not penetrate the oxide layer. Eifectively, the graphite provides a lubricant. In order to reduce the friction between the electrode and the dielectric and to obtain still better performance, an additional lubricant may be employed, such as a light oil, or, preferably, by impregnating the oxide coating with wax.
Figure 3 is a block diagram showing how the invention may be used as a reverberation-producing device. The signal source 10 provides signals for which a reverberation efiect is desired. Instead of directly connect a ing the signal source 10 with an audio reproducing device 32, as is customarily done, there is interposed, in accordance with this invention, a reverberation-producing structure. This will include a recording electrode 34, a reading electrode 3 6, and, if desired, an eras ng electrode 38. These all consist of the neoprene 1mpregnated graphite electrode previously descrlbed, or material having similar. properties. These are all m contact with the dielectric supported on the metal d1sc 40. The reading electrode 36 is connected to the audioreproducing device 32. A variable resistor 42 may be connected between the output of the reading electrode 36 and the grounded shaft 44, upon which the disc 40 is rotatably supported. The grounded shaft, of course, is in contact with the metal of the disc 40, and thus the resistor 42 is connected between the electrodes on opposite sides of dielectric storage material.
A signal from the source 10 will be recorded by the electrode 34 electrostatically on the dielectric medium on the disc 40. The signal will be read by the electrode 36 as the disc rotates. This signal will be reproduced by the audio-reproducing device 32. If the impedance of the discharge path between the reading electrode 36 and the metal of the disc 40 is high, charge will remain on the dielectric, and as the disc continues to rotate the reading electrode 36 will read this again and it will be reproduced again by the audio-reproducing device. This can continue until the amount of charge is sufficiently low, so that it is below thedetecting level of the audio-reproducing device 32. The number of. times the signal is read accordingly may be controlled by controlling the impedance of the discharge path by means of the variable resistor 42. Accordingly, the duration of the reverberation effect, or the decay of the signal, is controlled by this resistor 42. If desired, because of input-impedance consideration, an erasing electrode 38, which has connected between it and the shaft 44 a variable resistor 46, may be employed for performing the function ascribed to the variable resistor 42. Variations of resistor 46 can determine the number of times a recorded signal will be reproduced, and thus the extent of the reverberation effect.
The arrangement described can be simply eifectuated with any home record player by connecting the output of therecord-reproducing head, for example, to a writing electrode when in contact with a portion of the record turntable which is made of aluminum. The reading head 36 can contact this portion of the record turntable at a distance to provide a desired reverberation delay. Of course, in place of the record-reproducing head, the audio signal of the radio may be brought out and applied to the writing electrode 34, so that the reverberation elfect may be provided for the radio, as well as for the record player.
Reference is now made to Figure 4, which shows the embodiment of the inventionemployed for-providing a bmaural effect. The signalsource 10, as before, applies the signals to a recording electrode 50. A reading electrode. 52 is supported above the recording disc 54by an adjustable support 56, whereby it may be moved to provide a desired amount of. delay between thewriting of the signal by the electrode 50 and the. reading of the signal by the electrode 52.. A signal source It) is also directly connected to a first audio-reproducing'device 58. The readingelectrode 52 is connected to a secondaudio-reproducing device 60. The binaural effect is obtalnedby spacing the two audio-reproducing devices 58, 60 a suitable distance from one another and feeding them with signals directlyfrom the signal source and from the reading electrode 52 as. the disc 54 is rotatably driven- With the type of electrode-described, dielectrics of other types than an' oxide of metal may be employed which were not usable heretofore, in view of the possibrhty offragllity and wear thereof, or where penetration of. the dlelectric might otherwise occur. With these brushes, for example, thin layers of plastic, paint, acetate, and wax have been used as a dielectric. Best results were achieved, however, using an anodized alummum surface in which wax has been impregnated. The anodized surface is porous and thus absorbs the wax or oil. This provides excellent lubrication and is most effective. By providing a spiral groove 62 on a disc, any material which is otherwise accumulated under a brush is swept away, thus preserving the efiectiveness of the arrangement.
Although the dielectric storage medium has been shown and described in the application as a disc, this is by way of illustration and should not be a limitation upon the form of the storage. medium, since this may be any figure of revolution, or in the form of a ribbon, such as is commonly employed with magnetic tape. The dielectric recording arrangement described is simple, light, and inexpensive, and will record signals at low as well as at high voltage. It should'further be noted that although electrodes are shown in pairs, namely, a recording or writing electrode followed by a reproducing electrode, it is still within the scope of this invention to have a single electrode in contact with the dielectric recording medium which may be used for either recording on the medium, or forreproduction of signals recorded thereon in the manner of a single magnetic transducer head in contact with magnetic tape.
1. A signal delay device comprising a movable dielectric medium, a writing electrode, a reading electrode, each of said electrodes being. elastic, conductive, and comprised of a mixture of an insulating material and a conductive material, and means for holding said writing and reading electrodes in operative relationship with said movable dielectric medium and spaced apart a distance to provide a desired signal delay.
2. In a system for storing signals on a moving dielectric surface wherein signals are applied by an electrode to said surface and are read out from said dielectric surface by an electrode, the improvement in said system comprising making said electrodes of a material having conductive and rubberlike properties.
3. In a system as recited in claim 2 wherein said electrodes are made of neoprene impregnated with graphite.
4. A signal delay device comprising a movable dielec tric coating on a conductive backing, a writing electrode, a reading electrode, each of. said electrodes being made of a conductive elastic material, means for holding said writing and reading electrodes in operative relationship with said dielectric coating and spaced apart a distance to provide a desired delay, and a variable discharge means to provide a desired decay time for signals written on said dielectric medium.
5. A signal delay device as recited in claim 4 wherein said variable discharge means includes avariable resistor coupling one of said electrodes to said conductive backing.
6. A signal delay device as recited in claim 4 wherein said variable discharge means includes a discharge elec trode made of a conductive elastic material, means for holding said discharge electrode in operative relationship with said dielectric coating between said writing and reading electrodes, and a variable resistor coupling said discharge electrode to said conductive backing.
7. A dielectric signal recording arrangement comprising a recording medium comprising a metal oxide on a metal backing, and an electrode in contact with said medium, said electrode being made of a rubberlike conductive material.
8. A dielectric signal recording arrangement as recited in claim 7 wherein said metal oxide coating on a metal backing is aluminum oxide on aluminum.
9. A dielectric signal recording arrangement comprising an electrode of neoprene impregnated rubber and a recording surface comprising anodized aluminum impregnated with wax.
10. A signal delay device comprising a dielectric signal storage medium, means for movably supporting said dielectric signal storage medium, said signal storage medium comprising a coating of an oxide of a metal on a metal backing, a writing electrode, means supporting said writing electrode in contact with said storage medium, a reading electrode, means supporting said reading electrode spaced from said writing electrode and in contact with said storage medium, said electrodes being made of conductive rubberlike material, means to apply a signal to said writing electrode, and a variable resistance connected in series with said reading electrode to provide a desired decay on said storage medium of a signal applied by said means to apply a signal.
11. A signal delay device as recited in claim wherein said coating of an oxide of a metal supported by a metal is aluminum oxide on aluminum.
12. In an acoustic reverberation system of the type comprising a source of audio signals, an audio signal reproducing system, and a means for repetitively applying audio signals from said source to said audio signal reproducing system, the improvement in said means for repetitively applying audio signals comprising a rotatably supported dielectric medium, an input electrode made of a rubberlike, conductive material, means supporting said input electrode in contact with said dielectric medium, means connecting said input electrode to said source of audio signals, an output electrode made of a rubberlike, conductive material, means supporting said output electrode spaced from said input electrode and in contact with said dielectric medium, means connecting said output electrode to said audio signal reproducing system, and means including a variable impedance through which signals stored on said storage medium are discharged to provide a desired decay time and thus reverberation effect for said system.
13. In an acoustic reverberation system as recited in claim 12 wherein said rotatably supported dielectric medium is made of anodized aluminum in the form of a figure of rotation and said anodized surface is impregnated with wax.
14. In a binaural simulating system of the type comprising a source of audio signals, a first and a second audio signal reproducing system, a delay means connected to said second audio signal reproducing system, and means to apply signals from said source to said first audio signal reproducing system and to said delay means, the improvement in said delay means comprising a rotatably supported surface of revolution made of a coating of an oxide of a metal on a metal, an input electrode made of a rubberlike conductive material, means supporting said input electrode in contact with said oxide coating, means connecting said input electrode to said source of audio signals, an output electrode connected to said second audio signal reproducing means, said output electrode being made of a rubberlike conductive material, and means for movably supporting said output electrode in contact with said oxide coating.
References Cited in the file of this patent UNITED STATES PATENTS 2,197,050 Kellogg Apr. 16, 1940 2,200,741 Gray May 14, 1940 2,837,597 Lubow June 3, 1958