PIEZOELECTRIC RECORD CUTTING STYLUS
United States Patent 3805100
For cutting mechanical recordings in a flat record carrier with a recording frequency of 20 to 200-400 kHz, a piezoelectric transducer arranged to undergo longitudinal oscillations to drive a cutting stylus, the transducer being constituted by a body of an amorphous piezo oxide composed of a mixture of oxides of lead, zirconium and titanium and having a coupling coefficient of at least about 0.6 and a mechanical resonant frequency above the highest frequency to be recorded, the transducer being connected to an electric signal supply circuit having a high electrical resistance such that the combination of the high electrical resistance and the high coupling coefficient of the transducer results in a maximum resonance gain in the transducer response of no more than 10 db.
US Patent References:
Means for recording and reproducing sound
Linsell - November 1929 - 1737253
Piezo-electric transmitter and recorder
Thomas - November 1934 - 1980888
Recording apparatus volume level indicator
Gay - September 1948 - 2449291
SOUND RECORDING METHOD AND APPARATUS
Bauer - January 1970 - 3490771
SYSTEM FOR REPRODUCING MECHANICALLY STORED SIGNALS INCLUDING CARRIER HAVING DEFORMABLE MEANS COACTING WITH PRESSURE-SENSITIVE PICKUP MEANS
Dickopp et al. - March 1972 - 3652809
Means for recording and reproducing sound
Linsell - November 1929 - 1737253
Piezo-electric transmitter and recorder
Thomas - November 1934 - 1980888
Recording apparatus volume level indicator
Gay - September 1948 - 2449291
SOUND RECORDING METHOD AND APPARATUS
Bauer - January 1970 - 3490771
SYSTEM FOR REPRODUCING MECHANICALLY STORED SIGNALS INCLUDING CARRIER HAVING DEFORMABLE MEANS COACTING WITH PRESSURE-SENSITIVE PICKUP MEANS
Dickopp et al. - March 1972 - 3652809
Inventors:
Klemp, Hans-joachim (Berlin, DT)
Redlich, Horst (Berlin, DT)
Redlich, Horst (Berlin, DT)
Application Number:
05/324407
Publication Date:
04/16/1974
Filing Date:
01/17/1973
View Patent Images:
Export Citation:
Assignee:
Ted Bildplatten Aktiengesellschaft Aeg-Telefunken (Teldec, Zurich, CH)
Primary Class:
Other Classes:
310/348, 310/328, 369/144, 369/132, 310/351
International Classes:
H04R1/16; H04R17/04; H04R1/00; H04R17/02; G11B3/00; H04R17/00
Field of Search:
310/8.3,8.1,9.4,8.2 179/1.4C,1.41P 274/38,46,42
US Patent References:
| 3691318 | PRESSURE PICKUP TRANSDUCERS FOR MECHANICALLY STORED SIGNALS | September 1972 | Schuller et al. |
Primary Examiner:
Miller J. D.
Assistant Examiner:
Budd, Mark O.
Attorney, Agent or Firm:
Spencer, George H.
Claims:
1. A piezoelectric transducer unit for driving a cutting stylus in a system for mechanically recording oscillations varying in frequency between 20 and 200-400 kHz, comprising a transducer constituting a longitudinal oscillator formed of a body of an amorphous piezo oxide having a high longitudinal coupling coefficient of at least about 0.6 and made of a mixture metal oxides, said body being dimensioned such that its natural mechanical resonant frequency lies above the highest frequency to be recorded and an electric signal supply circuit whose ohmic resistance is such that the natural resonance of said transducer in conjunction with the high coupling coefficient results in a maximum resonance gain of no more
2. A device as defined in claim 1 wherein said oxide is a mixture of oxides
3. A device as defined in claim 1 wherein said circuit includes a current supply source and the ohmic resistance of said current supply circuit is
4. A device as defined in claim 1 wherein said circuit comprises a high
5. A device as defined in claim 4 wherein the resistance of said resistor is substantially equal to the capacitive reactance of said transducer at a
6. A device as defined in claim 1 wherein said transducer is a cylinder and
7. A device as defined in claim 1 wherein said transducer is a cube and is
8. A device as defined in claim 1 wherein the relative dielectric constant
9. A device as defined in claim 1 wherein the Q factor of the piezo
10. A device as defined in claim 1, further comprising springs supporting
11. A device as defined in claim 10 wherein the natural resonance of the oscillating system constituted by the vibrating masses of said transducer and said springs, and the elasticity of said springs, lies below the
12. A device as defined in claim 11, further comprising a body of damping material supporting said transducer in the vicinity of its zero oscillation point for damping the natural resonance of said transducer.
13. A device as defined in claim 10 wherein said springs each comprise asymmetrical three-armed springs whose center arm is oriented at 90° with respect to the other two arms, which extend in respectively opposite directions, and holding said transducer at the point of intersection of said arms.
2. A device as defined in claim 1 wherein said oxide is a mixture of oxides
3. A device as defined in claim 1 wherein said circuit includes a current supply source and the ohmic resistance of said current supply circuit is
4. A device as defined in claim 1 wherein said circuit comprises a high
5. A device as defined in claim 4 wherein the resistance of said resistor is substantially equal to the capacitive reactance of said transducer at a
6. A device as defined in claim 1 wherein said transducer is a cylinder and
7. A device as defined in claim 1 wherein said transducer is a cube and is
8. A device as defined in claim 1 wherein the relative dielectric constant
9. A device as defined in claim 1 wherein the Q factor of the piezo
10. A device as defined in claim 1, further comprising springs supporting
11. A device as defined in claim 10 wherein the natural resonance of the oscillating system constituted by the vibrating masses of said transducer and said springs, and the elasticity of said springs, lies below the
12. A device as defined in claim 11, further comprising a body of damping material supporting said transducer in the vicinity of its zero oscillation point for damping the natural resonance of said transducer.
13. A device as defined in claim 10 wherein said springs each comprise asymmetrical three-armed springs whose center arm is oriented at 90° with respect to the other two arms, which extend in respectively opposite directions, and holding said transducer at the point of intersection of said arms.
Description:
BACKGROUND OF THE INVENTION
The present invention relates to record cutters, particularly for operation at recording frequencies of 20-400 kHz.
It is known to mechanically record sound oscillations having an upper frequency limit of about 20,000 Hz on an information carrier where the oscillations are recorded in the form of undulations provided on the surface of a recording groove of the carrier and constituting a spatial representation of the oscillations. It is also known to be possible, by using the so-called pressure-scanning technique, to mechanically scan stored signal oscillations which have much higher frequencies -- up to several MHz -- as required in the playback of video recordings. The pressure scanning system and the related "high density recording technique" form part of the prior art and are disclosed, for example, in the following publications:
"Radio Mentor," Issue No. 7, 1970, pages 451-452;
"VDI-Nachrichten," Issue No. 26, July 1, 1970, page 1;
"Radio Mentor," Issue No. 8, 1970, pages 513-516;
German Patent No. 1,574,489.
Because of the wide frequency range which must be covered in the recording of video signals, for example when recording a moving image, the playback of such a video recording must take place at relatively high playback speeds (up to 1,500 rpm for a 200 mm record) compared to the usual sound recordings.
It is obvious, however, that the recording of such video programs, which is effected with mechanically, electrodynamically or electrostatically controlled recording devices, cannot take place at the same speed because the member which produces the undulations in the recording groove to correspond to the signals could never follow the high frequencies (up to 4 MHz) to be recorded due to its inherent mass inertia. Thus a video record, or a matrix for such a video record, is produced with the aid of an intermediate recording of the signals, a technique known from the manufacture of sound records, for example on a magnetic carrier. This carrier is scanned at a speed reduced by about ten to 25 times, compared to the real-time speed, so that for an upper frequency limit of the playback signals of about 4 MHz, the recording device must be able to produce perfect recordings to about 160 to 400 kHz.
In spite of the substantially reduced recording speed, this upper frequency limit is still extremely high for an instrument which must produce mechanical undulations in the recording groove of a signal carrier. Even high-quality instruments built for special purposes presently have an upper recording frequency limit of about 30 to 40 kHz.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a recording device of the above-mentioned type which permits recording of a wide frequency range containing much higher frequencies than previously possible, i.e., frequencies up to about 400 kHz.
These and other objects according to the invention are achieved by a device for mechanically recording oscillations over a wide frequency range, e.g. 20 kHz to 200 or 400 kHz, in which the transducer for the longitudinal oscillations is composed of an amorphous piezo oxide having a high longitudinal coupling coefficient of about 0.6 or more and is made of a mixture of metal oxides, in particular oxides of lead, zirconium and titanium. Moreover, the transducer is so dimensioned that its natural mechanical resonant frequency lies somewhat above the highest frequency to be recorded and the ohmic resistance of the electrical current supply circuit for the transducer is selected so that the resonance gain due to the natural resonance of the transducer in conjunction with the high coupling coefficient will be no more than 10 db above the minimum gain occurring in the range of the frequencies to be recorded.
A piezo oxide suitable for this purpose is manufactured, for example, by the firm Philips under the name "Piezo Oxide PXE5" or by the firm Rosenthal under the name "Sonox 4." In the manufacture of this oxide, the powdery starting materials, i.e., the oxides of lead, zirconium and titanium, are mixed together and stirred in a finely ground wet state. After filtering and drying they are heated to 850° C so that the components react and form a bond. Thereafter, the mass is again wet ground until a certain grain size has been attained. After renewed filtering and drying, there is obtained a finished powder which can be brought into the desired shape, for example by pressing in matrices after the addition of small amounts of binder and some water. Then follows the sintering process at 1,100° C which lasts for several hours. Thereafter, the ceramic bodies are mechanically machined, i.e., ground or sawed, in order to obtain the desired shapes and dimensions. Finally, the bodies, which thus far have no piezoelectric properties, are polarized by a direct voltage, while at an increased temperature of 140°-300° C, with an electrical field strength of about 1 to 5 kV/mm, preferably 3 kV/mm.
The thus obtained piezoelectric bodies have a frequency constant of about 1,500 Hz . m, a longitudinal coupling coefficient between 0.6 and 0.7 and a relative dielectric constant of more than 1,000. This frequency constant for a cube with sides of 5 mm or for a cylinder with a diameter of 5 mm and a height of 5 mm results in a natural resonant frequency of about 300 kHz.
A high coupling coefficient, corresponding to the ratio of emitted mechanical output to the fed-in electrical power, is of great importance under consideration of the thermal stress on the oscillator and the attenuation of the resonance gain. The high dielectric constant is desired in order to be able to apply a lower voltage. A further advantage is the relatively high internal attenuation of the amorphous material. While an oscillator of a homogeneous material, such as quartz, may have a quality, Q, i.e., a resonance gain of 1,000 and more, the Q of the amorphous oscillator having the above-listed ingredients is only 50, for example.
By selecting the appropriate materials to be combined, it is possible, in contradistinction to naturally occurring homogeneous materials, to set the Q to any desired value, as has been done in the commercially available piezo oxides.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of an oscillator according to the invention with a cutting stylus attached thereto, to a scale being considerably larger than life size.
FIG. 2 is an elevational view of the mounting of the oscillator of FIG. 1.
FIG. 3 is a basic circuit diagram of the oscillator signal input.
FIG. 4 is a diagram used in explaining the contribution of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The structure shown in FIG. 1 includes a longitudinal oscillator 1 made of a piezo oxide with the above-mentioned composition of oxides of lead, zirconium and titanium. Its longitudinal oscillations are shown in the direction of the double arrow and result in movements of its top and bottom edges between the limits represented by the dashed lines. A stylus 2 is inserted in a tube 3 having high mechanical stability and good heat-conducting properties. Tube 3 is rigidly connected, e.g. by welding, with a metal plate 4 which is soldered to oscillator 1. Stylus 2 is commonly made of a diamond.
In order to facilitate the cutting process, the stylus 2 is heated to a relatively high temperature of about 100° C by means of a heating coil 8 which is fed by the heating current source H.
Oscillator 1 is held at its ends, according to the illustration shown to a somewhat smaller scale in FIG. 2, by means of springs 5. It is mounted to oscillate freely, to "float" so to speak. The natural resonance of the resonant system including the mass of the oscillator 1 and the mass of springs 5 as well as the elasticity of springs 5 must lie below the frequency range to be recorded. The information signal voltage to be recorded is fed in via springs 5 and silver electrodes at oscillator 1.
The springs are advisably asymmetric three-armed springs whose center arm is oriented at 90° with respect to the other two arms, the latter extending in respectively opposite directions and the transducer being held at the point of intersection of the arms. Instead of the springs, membranes can also be used.
The natural oscillation of this mechanical oscillating system can be attenuated by a damping ring 9 of a damping material, such as rubber or plastic, disposed in the vicinity of the zero oscillation point,or node, 10 of transducer 1.
Oscillator 1 is fed by a signal current source 7, as shown in FIG. 3, with a signal voltage of about 1.5 kV, via a relatively high resistance 6 of about 50 kΩ. This high resistance 6, together with the coupling coefficient, has the result that the natural resonance of the oscillator 1 which lies somewhat above the frequency range to be recorded is sufficiently attenuated so that the resonance gain will be no more than about 10 db.
It should be noted in this connection that the sum of this resistance 6 and the internal resistance of the current supply source must be considered for this attenuation effect. This sum must be greater than 50 kΩ. Under certain circumstances, and with an appropriate design of the circuit, a high internal resistance of the current supply source may be sufficient by itself, or only a relatively small resistance need be connected in series.
For reasons of circuitry it may be advantageous at times, however, to use a high resistance with the above given valve in the current supply circuit.
This resistance 6 also causes the oscillator 1 to be excited by a constant current (about 30 to 50 mA) practically over the entire frequency range. With the selected dimension of about 5 mm in the oscillation direction and with the material selected for the oscillator there results a capacitance of about 150 pF between the electrodes of the transducer at a natural resonance frequency in the range of 300 to 350 kHz.
These dimensions produces a mechanical oscillation amplitude vs. frequency response A at stylus 2, for a set resistance value 6, having the form shown in FIG. 4.
Due to the capacitive reactance which increases toward low frequencies, the voltage across transducer 1 increases and thus, due to the constant current, the energy which is fed to the transducer results in the illustrated gain in amplitude for stylus 2 toward the lower frequencies. This is particularly desired in frequency modulation recordings since it will inherently raise the lower sideband, which has favorable effects during playback.
The oscillation amplitude is between about 0.3 and 0.5 μ at about 150 kHz and increases again, due to the natural resonance, in the higher frequency range. This natural resonance, however, is sufficiently attenuated by the high electrical resistance provided according to the present invention in conjunction with the high coupling factor, as shown by the solid curve. The dashed curve R indicates the path that would exist without these attenuation measures.
It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.
The present invention relates to record cutters, particularly for operation at recording frequencies of 20-400 kHz.
It is known to mechanically record sound oscillations having an upper frequency limit of about 20,000 Hz on an information carrier where the oscillations are recorded in the form of undulations provided on the surface of a recording groove of the carrier and constituting a spatial representation of the oscillations. It is also known to be possible, by using the so-called pressure-scanning technique, to mechanically scan stored signal oscillations which have much higher frequencies -- up to several MHz -- as required in the playback of video recordings. The pressure scanning system and the related "high density recording technique" form part of the prior art and are disclosed, for example, in the following publications:
"Radio Mentor," Issue No. 7, 1970, pages 451-452;
"VDI-Nachrichten," Issue No. 26, July 1, 1970, page 1;
"Radio Mentor," Issue No. 8, 1970, pages 513-516;
German Patent No. 1,574,489.
Because of the wide frequency range which must be covered in the recording of video signals, for example when recording a moving image, the playback of such a video recording must take place at relatively high playback speeds (up to 1,500 rpm for a 200 mm record) compared to the usual sound recordings.
It is obvious, however, that the recording of such video programs, which is effected with mechanically, electrodynamically or electrostatically controlled recording devices, cannot take place at the same speed because the member which produces the undulations in the recording groove to correspond to the signals could never follow the high frequencies (up to 4 MHz) to be recorded due to its inherent mass inertia. Thus a video record, or a matrix for such a video record, is produced with the aid of an intermediate recording of the signals, a technique known from the manufacture of sound records, for example on a magnetic carrier. This carrier is scanned at a speed reduced by about ten to 25 times, compared to the real-time speed, so that for an upper frequency limit of the playback signals of about 4 MHz, the recording device must be able to produce perfect recordings to about 160 to 400 kHz.
In spite of the substantially reduced recording speed, this upper frequency limit is still extremely high for an instrument which must produce mechanical undulations in the recording groove of a signal carrier. Even high-quality instruments built for special purposes presently have an upper recording frequency limit of about 30 to 40 kHz.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a recording device of the above-mentioned type which permits recording of a wide frequency range containing much higher frequencies than previously possible, i.e., frequencies up to about 400 kHz.
These and other objects according to the invention are achieved by a device for mechanically recording oscillations over a wide frequency range, e.g. 20 kHz to 200 or 400 kHz, in which the transducer for the longitudinal oscillations is composed of an amorphous piezo oxide having a high longitudinal coupling coefficient of about 0.6 or more and is made of a mixture of metal oxides, in particular oxides of lead, zirconium and titanium. Moreover, the transducer is so dimensioned that its natural mechanical resonant frequency lies somewhat above the highest frequency to be recorded and the ohmic resistance of the electrical current supply circuit for the transducer is selected so that the resonance gain due to the natural resonance of the transducer in conjunction with the high coupling coefficient will be no more than 10 db above the minimum gain occurring in the range of the frequencies to be recorded.
A piezo oxide suitable for this purpose is manufactured, for example, by the firm Philips under the name "Piezo Oxide PXE5" or by the firm Rosenthal under the name "Sonox 4." In the manufacture of this oxide, the powdery starting materials, i.e., the oxides of lead, zirconium and titanium, are mixed together and stirred in a finely ground wet state. After filtering and drying they are heated to 850° C so that the components react and form a bond. Thereafter, the mass is again wet ground until a certain grain size has been attained. After renewed filtering and drying, there is obtained a finished powder which can be brought into the desired shape, for example by pressing in matrices after the addition of small amounts of binder and some water. Then follows the sintering process at 1,100° C which lasts for several hours. Thereafter, the ceramic bodies are mechanically machined, i.e., ground or sawed, in order to obtain the desired shapes and dimensions. Finally, the bodies, which thus far have no piezoelectric properties, are polarized by a direct voltage, while at an increased temperature of 140°-300° C, with an electrical field strength of about 1 to 5 kV/mm, preferably 3 kV/mm.
The thus obtained piezoelectric bodies have a frequency constant of about 1,500 Hz . m, a longitudinal coupling coefficient between 0.6 and 0.7 and a relative dielectric constant of more than 1,000. This frequency constant for a cube with sides of 5 mm or for a cylinder with a diameter of 5 mm and a height of 5 mm results in a natural resonant frequency of about 300 kHz.
A high coupling coefficient, corresponding to the ratio of emitted mechanical output to the fed-in electrical power, is of great importance under consideration of the thermal stress on the oscillator and the attenuation of the resonance gain. The high dielectric constant is desired in order to be able to apply a lower voltage. A further advantage is the relatively high internal attenuation of the amorphous material. While an oscillator of a homogeneous material, such as quartz, may have a quality, Q, i.e., a resonance gain of 1,000 and more, the Q of the amorphous oscillator having the above-listed ingredients is only 50, for example.
By selecting the appropriate materials to be combined, it is possible, in contradistinction to naturally occurring homogeneous materials, to set the Q to any desired value, as has been done in the commercially available piezo oxides.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of an oscillator according to the invention with a cutting stylus attached thereto, to a scale being considerably larger than life size.
FIG. 2 is an elevational view of the mounting of the oscillator of FIG. 1.
FIG. 3 is a basic circuit diagram of the oscillator signal input.
FIG. 4 is a diagram used in explaining the contribution of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The structure shown in FIG. 1 includes a longitudinal oscillator 1 made of a piezo oxide with the above-mentioned composition of oxides of lead, zirconium and titanium. Its longitudinal oscillations are shown in the direction of the double arrow and result in movements of its top and bottom edges between the limits represented by the dashed lines. A stylus 2 is inserted in a tube 3 having high mechanical stability and good heat-conducting properties. Tube 3 is rigidly connected, e.g. by welding, with a metal plate 4 which is soldered to oscillator 1. Stylus 2 is commonly made of a diamond.
In order to facilitate the cutting process, the stylus 2 is heated to a relatively high temperature of about 100° C by means of a heating coil 8 which is fed by the heating current source H.
Oscillator 1 is held at its ends, according to the illustration shown to a somewhat smaller scale in FIG. 2, by means of springs 5. It is mounted to oscillate freely, to "float" so to speak. The natural resonance of the resonant system including the mass of the oscillator 1 and the mass of springs 5 as well as the elasticity of springs 5 must lie below the frequency range to be recorded. The information signal voltage to be recorded is fed in via springs 5 and silver electrodes at oscillator 1.
The springs are advisably asymmetric three-armed springs whose center arm is oriented at 90° with respect to the other two arms, the latter extending in respectively opposite directions and the transducer being held at the point of intersection of the arms. Instead of the springs, membranes can also be used.
The natural oscillation of this mechanical oscillating system can be attenuated by a damping ring 9 of a damping material, such as rubber or plastic, disposed in the vicinity of the zero oscillation point,or node, 10 of transducer 1.
Oscillator 1 is fed by a signal current source 7, as shown in FIG. 3, with a signal voltage of about 1.5 kV, via a relatively high resistance 6 of about 50 kΩ. This high resistance 6, together with the coupling coefficient, has the result that the natural resonance of the oscillator 1 which lies somewhat above the frequency range to be recorded is sufficiently attenuated so that the resonance gain will be no more than about 10 db.
It should be noted in this connection that the sum of this resistance 6 and the internal resistance of the current supply source must be considered for this attenuation effect. This sum must be greater than 50 kΩ. Under certain circumstances, and with an appropriate design of the circuit, a high internal resistance of the current supply source may be sufficient by itself, or only a relatively small resistance need be connected in series.
For reasons of circuitry it may be advantageous at times, however, to use a high resistance with the above given valve in the current supply circuit.
This resistance 6 also causes the oscillator 1 to be excited by a constant current (about 30 to 50 mA) practically over the entire frequency range. With the selected dimension of about 5 mm in the oscillation direction and with the material selected for the oscillator there results a capacitance of about 150 pF between the electrodes of the transducer at a natural resonance frequency in the range of 300 to 350 kHz.
These dimensions produces a mechanical oscillation amplitude vs. frequency response A at stylus 2, for a set resistance value 6, having the form shown in FIG. 4.
Due to the capacitive reactance which increases toward low frequencies, the voltage across transducer 1 increases and thus, due to the constant current, the energy which is fed to the transducer results in the illustrated gain in amplitude for stylus 2 toward the lower frequencies. This is particularly desired in frequency modulation recordings since it will inherently raise the lower sideband, which has favorable effects during playback.
The oscillation amplitude is between about 0.3 and 0.5 μ at about 150 kHz and increases again, due to the natural resonance, in the higher frequency range. This natural resonance, however, is sufficiently attenuated by the high electrical resistance provided according to the present invention in conjunction with the high coupling factor, as shown by the solid curve. The dashed curve R indicates the path that would exist without these attenuation measures.
It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.