GB2115931A - Rotational speed detecting system for Hall motor - Google Patents
Rotational speed detecting system for Hall motor Download PDFInfo
- Publication number
- GB2115931A GB2115931A GB08300868A GB8300868A GB2115931A GB 2115931 A GB2115931 A GB 2115931A GB 08300868 A GB08300868 A GB 08300868A GB 8300868 A GB8300868 A GB 8300868A GB 2115931 A GB2115931 A GB 2115931A
- Authority
- GB
- United Kingdom
- Prior art keywords
- hall
- rotational speed
- signal
- voltage
- motor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
- G01P3/64—Devices characterised by the determination of the time taken to traverse a fixed distance
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
- H02P6/14—Electronic commutators
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
- G01P3/42—Devices characterised by the use of electric or magnetic means
- G01P3/44—Devices characterised by the use of electric or magnetic means for measuring angular speed
- G01P3/48—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage
- G01P3/481—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals
- G01P3/487—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals delivered by rotating magnets
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
- G01P3/64—Devices characterised by the determination of the time taken to traverse a fixed distance
- G01P3/66—Devices characterised by the determination of the time taken to traverse a fixed distance using electric or magnetic means
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K11/00—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection
- H02K11/30—Structural association with control circuits or drive circuits
- H02K11/33—Drive circuits, e.g. power electronics
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K29/00—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices
- H02K29/06—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices with position sensing devices
- H02K29/08—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices with position sensing devices using magnetic effect devices, e.g. Hall-plates, magneto-resistors
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Control Of Motors That Do Not Use Commutators (AREA)
- Brushless Motors (AREA)
Abstract
A rotational speed detecting system for a Hall-effect motor, which comprises a pair of Hall-effect elements 14, 15, a rotor magnet, (not shown) magnetised to present N and S poles alternately to the Hall-effect elements, and stator coils 13a-13d, comprises a signal forming circuit 31,32,34,35 for forming a signal when a specific point of the rotating rotor magnet opposes each of the Hall elements and a detection output signal obtaining circuit Q1,Q2,C3,C4,R5,37 for obtaining a speed-proportional output signal having a voltage derived in accordance with the time interval between signals formed by the signal forming circuit. <IMAGE>
Description
SPECIFICATION
Rotational speed detecting system for Hall motor
The present invention generally relates to rotational speed detecting system for Hall motors which use Hall elements, and more particularly to a rotational speed detecting system for Hall motor designed to detect the rotational speed of the Hall motor by using outputs of Hall elements which are originally provided in the Hall motor.
Generally, in order to control the rotation of a motor, it is necessary to detect the rotational speed of the motor and obtain a rotation control current or voltage according to the detected result. Conventionally, a frequency generator comprising a printed circuit provided with a multi-pole magnet mounted on a rotor and a coil arranged at a position opposing this multi-pole magnet, was used as a rotational speed detecting apparatus for Hall motor. A detecting device employing this frequency generator detected the frequency of an A.C. voltage waveform generated at the coil by rotating the magnet unitarilywith the rotor, and obtained the detected result of the rotational speed from this detected frequency.
However, in the above conventional rotational speed detecting apparatus, it was necessary to provide the frequency generator besides the main Hall motor body. Accordingly, there were disadvantages in that additional space was required for the detecting coil and the magnet making it impossible to downsize the whole Hall motor, and the manufacturing cost became high. In addition, if the magnetization of the magnet of the frequency generator is uneven, that is, if there is unevenness in the size, magnetic force intensity, and the like of the N-pole part and the S-pole part of the magnet, or when the surface of the magnet and the surface of the printed coil are not parallel and a gap therebetween varies, or if axis of the magnet is deviated from the axis of a rotary shaft of the rotor, there was a disadvantage in that the rotational speed of the motor could not be detected accurately.
Accordingly, it is a general object of the present invention to provide a novel and useful rotational speed detecting system for Hall motor, in which the above described disadvantages have been overcome.
The present invention provides a rotational speed detecting system for Hall motor comprising a pair of
Hall elements, a rotor magnet alternately magnetized of an N-pole and an S-pole, and stator coils, said system comprising, signal forming means for forming a signal at a time position of corresponding points on respective output waveforms of said Hall elements which are produced with a phase difference, and detection output signal obtaining means for obtaining a detection output signal having a voltage in accordance with a time interval of the signal formed by said signal forming means, the time position of the corresponding points on said output waveforms being a time position when a specific point of said rotating rotor magnet opposes each of said Hall elements.
Another and more specific object of the present invention is to provide a rotational speed control system for Hall motor, in which outputs of a pair of Hall elements originally provided in the Hall motor as detecting elements for switching a current applied to a motor coil are used, to obtain an output voltage in accordance with a time interval required for a specific position on a rotor magnet originally provided in the Hall motor for generating a magnetic field to rotate to a position opposing one Hall element from a position opposing the other Hall element, and detect the rotational speed of the Hall motor.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.
Figure 1 is a development showing a general Hall motor in principle;
Figure 2 is a graph showing the magnetic field intensity between a rotor and a yoke of the Hall motor shown in Figure 1;
Figures 3(A) and 3(B) are graphs respectively showing output voltage waveforms of respective Hall elements;
Figure 4 is a systematic circuit diagram showing a rotation control system employing an embodiment of a rotational speed detecting system according to the present invention; and
Figures 5(A) through 5(F) are graphs respectively showing signal waveforms at each part of the circuit system shown in Figure 3.
Figure 1 is a development showing a general 6-pole 2-phase Hall motor in principle, to which the rotational speed detecting system according to the present invention can be applied. Stator coils 13a through 13d and
Hall elements 14 and 15 arranged mutually separated from each other by an electrical angle of 90 , are respectively provided between a stator yoke 12 and a rotor magnet 11 of the 6-pole magnet which is alternately magnetized of the N-pole and the S-pole. In Figure 1, a symbol "x" within a circle indicates a current flowing in a direction towards the paper, and a black circular symbol within a circle indicates a current flowing away from the paper.When voltages from a coil driving circuit 33 shown in Figure 4 are applied between terminals 16a and 16b and terminals 16e and 16d so that currents flow through the coils 13a through 13d in directions indicated by the symbols, the rotor magnet 11 rotates in the direction of an arrow
A. Thereafter, the direction of the currents flowing to the coils 13a and 13b and the coils 1 3e and 13d are respectively switched over, so that the rotor magnet 11 continues to rotate in a constant direction. The above described construction and operation are the same as in the conventional Hall motor.
The magnetic field intensity between the rotor magnet 11 and the yoke 12 is as shown in Figure 2. In Figure 2, the vertical axis indicates the magnetic field intensity, and the horizontal axis indicates the distance along the longitudinal direction in the development of the rotor magnet 11 and the yoke 12.
An output voltage V1 shown in Figure 3(A) is obtained between output electrode terminals 17a and 17b of the Hall element 14, and an output voltage V2 shown in Figure 3(B) is obtained between output terminals 18a and 1 8b of the Hall motor 15, with a phase difference of 900 in electrical angle. An input voltage from an input voltage applying circuit 30 shown in Figure 4, is applied to input electrode terminals 1 9a and 1 9b of the Hall elements 14 and 15.A time t between a zero crossing point of the waveform of the output voltage V1 of the
Hall element during a rise from a negative peak to a positive peak and a zero crossing point of the waveform of the output voltage V2 of the Hall element 15 during a rise from a negative peak to a positive peak, is equal to a time required for a specific boundary point 20 between a certain N-pole and S-pole of the rotor magnet to reach a position opposing the Hall element 15 by the rotation of the rotor magnet 11 from a position opposing the Hall element 14.
The output terminals 1 7a and 1 7b of the Hall element 14 are respectively connected to a non-inverting input terminal and an inverting input terminal of a comparator 31 wherein the output voltage V1 is subjected to voltage comparison. Hence, a square wave voltage a shown in Figure 5(A) which rises and falls at the zero crossings during the rise from the negative peak to the positive peak and during the fall from the positive peak to the negative peak of the voltage V1, is obtained from the comparator 31. Similarly, the output terminals 18a and 18b of the Hall element 15 are respectively connected to a non- inverting input terminal and an inverting input terminal of a comparator 32.Thus, a square wave voltage b shown in Figure 5(B) which has a phase shift of 90 in electrical angle with the square wave voltage a, is obtained from the comparator 32. The output square wave voltages a and b are respectively supplied to the coil driving circuit 33, and formed into a coil driving voltage as in the conventional system. The output driving voltage of the coil driving circuit 33 is applied to the terminals 1 6a through 16d.
At the same time, the output voltage a of the comparator 31 is supplied to a differentiating circuit 34 comprising a capacitor C1, a diode D1, and a resistor R1, wherein the voltage is differentiated and formed into a differentiated pulse c shown in Figure 5(C). Similarly, the output voltage b of the comparator 32 is supplied to a differentiating circuit 35 comprising a capacitor C2, a diode D2, and a resistor R2, wherein the voltage is differentiated an formed into a differentiated pulse dshown in Figure 5(D). The pulse c is applied to the base of a transistor Ol through the resistor R2, and the pulse d is applied to the base of a transistor Q2 through a resistor R4.
The transistor Q1 becomes ON when applied with the pulse c, and at this instant, a capacitor C3 completes charging by a current from a stabilizing power source 36, and a collector voltage e of the transistor Q1 becomes zero at times tl,t3, t5, as as shown in Figure 5(E). Thereafter, the transistor Q1 becomes OFF, and the charge in the capacitor C3 is discharged through a resistor R5. Thus, the collector voltage e of the transistor Q1 rises between the times tl and t3, t3 and t5, with a time constant R5C3 determined by the resistor R5 and the capacitor C3, as shown in Figure 5(E).
During the rise of the voltage e, the pulse d is applied to the base of the transistor Q2 at times t2, t4, t6, --, and the transistor Q2 becomes ON at the instant when the pulse d is applied. When the transistor Q2 is turned ON, a capacitor C4 becomes charged, and a collector voltage fof the transistor Q2 while the transistor
Q2 is ON becomes substantially equal to the collector voltage e of the transistor Q1.This collectorvoltage fis supplied to a buffer amplifier 37. Because the input impedance of the buffer amplifier 37 is high, the collector voltage fof the transistor Q2 at the times t2, t4, during the OFF period of the transistor Q2 is held, and a held voltage fshown in Figure 5(F) is obtained from the buffer amplifier 37.Here, the voltage fcan be described by the following equation, where E is the voltage of the power source 36.
f = E - Eexp (-t/C3R5) In the above equation, E, C3, and R5 respectively are constants. Therefore, the time t is detected. That is, the rotational speed which is proportional to the reciprocal of the time t is detected, where the proportional constant is determined by the number of poles of the rotor magnet 11.
That is, as described before, the time interval t between the times tl and t2, t3 and t4, t5 and t6, corresponds to the time the specific point 20 of the rotor magnet 11 requires to pass between the Hall elements 14 and 15. This time interval t is inversely proportional to the rotational speed of the rotor magnet 11. On the other hand, the sampled and held voltage described previously is proportional to the time interval t. Therefore, the voltage fis inversely proportional to the rotational speed of the rotor magnet 11.
The output voltage fof the buffer amplifier 37 is obtained through an output terminal 38 as a rotation detection signal, and applied to a non-inverting input terminal of a comparison amplifier 39. A reference voltage from a terminal 40 is applied to an inverting input terminal of the comparison amplifier 39. The voltage fis thus compared with the reference voltage at the comparison amplifier 39 is amplified, and supplied to the coil driving circuit 33 as a rotation control signal.
In Figures 5(A) through 5(D), at an intermediate part on the time base where the intervals of waveforms are shortened, that is, where the time t is small, the rotation of the motor is high and the detection output voltage fdecreases. Rotation control is carried out according to the output control signal of the comparison amplifier 39 to control the rotation of the motor so that the detection output voltage fapproaches near the above reference voltage, that is, so that the time interval t becomes constant.
Examples of constants of the circuit elements in the circuit shown in Figure 4 are given below.
Resistor Resistance Capacitor Capacitance R1 1 kQ C1 1500pF
R2 10 kip C2 1500 pF
R3 1 kQ C3 0.1 'LF R4 10 kQ C4 0.01 yF R5 144 kQ The voltage Eof the power source 36 is 5V, and the reference voltage applied to the terminal 40 is 2.5V. In addition, when the rotational speed of the motor is 25 rps, the time interval t is approximately equal to 10 msec.
As described heretofore, according to the system of the present invention, the outputs of the Hall elements originally provided in the Hall motor as detecting elements for switching the currents applied to the motor coils are used to detect the rotational speed of the motor, and the originally provided Hall elements are also used as elements for speed detection. In addition, the rotor magnet which is originally provided in the Hall motor as a magnet for generating the magnetic field, is also used as a magnet for speed detection.
Accordingly, there is no need to additionally provide an independent detecting coil, a magnet, and the like as in the conventional frequency generator. Therefore, the construction of the system can be simplified, and the manufacturing cost is reduced. Furthermore, it is unnecessary to provide additional space for setting special additional devices, and the design of the system can be downsized.
Moreover, the rotational speed of the motor is detected from the time interval required for the specific point (the changing point from the N-pole to the S-pole in the embodiment described heretofore) of the rotor magnet to rotate to the position opposing the Hall element 15 from the position opposing the Hall element 14. Hence, even if there is unevenness in the size of the poles of the magnet, the magnetic field intensity, and the like, or eccentricity and the like in the rotor magnet, the detecting accuracy of the rotational speed is not affected, and the detection of the rotational speed can be carried out accurately. The specific point of the rotor magnet may be any determined position, as long as the position is the same. However, if the specific point of the rotor magnet is selected to be a changing point from the N-pole to the S-pole as in the embodiment described heretofore, the signals shown in Figures 5(A) through 5(D) may be obtained with ease by detecting the zero crossing points of the waveforms shown in Figures 3(A) and 3(B). For this reason, it is desirable to use this changing point as the specific point of the rotor magnet.
Further, the present invention is not limited to these embodiments, but various variations and modifications may be made without departing from the scope of the present invention.
Claims (5)
1. A rotational speed detecting system for Hall motor comprising a pair of Hall elements, a rotor magnet alternately magnetized of an N-pole and an S-pole, and stator coils, said system comprising:
signal forming means for forming a signal at a time position of corresponding points on respective output waveforms of said Hall elements which are produced with a phase difference, and
detection output signal obtaining means for obtaining a detection output signal having a voltage in accordance with a time interval of the signal formed by said signal forming means,
the time position of the corresponding points on said output waveforms being a time position when a specific point of said rotating rotor magnet opposes each of said Hall elements.
2. A rotational speed detecting system for Hall motor as claimed in claim 1 in which said signal forming means comprises a circuit for obtaining first and second square wave series from the output of each of said
Hall elements, and a circuit for differentiating each square wave of said first and second square wave series thus obtained to obtain first and second differentiated wave series, and said detection signal obtaining means comprises a charging and discharging circuit for starting charging after discharge is carried out by said first differentiated wave sires, and a circuit for sampling and holding a charged voltage in said charging and discharging circuit by said second differentiated wave series.
3. A rotational speed detecting system for Hall motor as claimed in claim 1 in which the specific point of said rotor magnet is a changing point between the N-pole and the S-pole, and the corresponding points on the output waveforms of said Hall elements are zero crossing points of of the output voltage waveforms of said Hall elements.
4. A rotational speed detecting system for Hall motor as claimed in claim 1 which further comprises stator coil driving means for driving said stator coils according to the outputs of said Hall elements, and rotation control signal forming means for obtaining a rotation control signal according to said detection output signal and supplying said rotation control signal to said stator coil driving means.
5. A rotational speed detecting system for Hall motor as claimed in claim 4 in which said rotation control signal forming means comprises a comparison amplifier for comparing said detection output signal with a reference voltage to produce said rotation control signal, and said rotor magnet is rotationally controlled so that said detection output signal becomes equal to said reference voltage.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP57004333A JPS58131571A (en) | 1982-01-14 | 1982-01-14 | Detection of speed of hall motor |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8300868D0 GB8300868D0 (en) | 1983-02-16 |
| GB2115931A true GB2115931A (en) | 1983-09-14 |
| GB2115931B GB2115931B (en) | 1985-09-25 |
Family
ID=11581519
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08300868A Expired GB2115931B (en) | 1982-01-14 | 1983-01-13 | Rotational speed detecting system for hall motor |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS58131571A (en) |
| KR (1) | KR860002000B1 (en) |
| DE (1) | DE3300990A1 (en) |
| FR (1) | FR2519765B1 (en) |
| GB (1) | GB2115931B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0687054A3 (en) * | 1994-06-07 | 1997-11-05 | Matsushita Electric Industrial Co., Ltd. | Three-phase brushless servo motor |
| EP0964506A2 (en) * | 1998-06-08 | 1999-12-15 | Matsushita Electric Industrial Co., Ltd. | Three-phase brushless servo motor |
| US6862415B2 (en) | 2001-06-27 | 2005-03-01 | Eastman Kodak Company | Device for treating the surface of an article in connection with printing |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5122075A (en) * | 1991-05-17 | 1992-06-16 | Amp Incorporated | Electrical connector with improved retention feature |
| CN110501516B (en) * | 2018-05-16 | 2022-02-08 | 中国航天科工飞航技术研究院（中国航天海鹰机电技术研究院） | Combined speed measuring system and method for ultra-high-speed linear motor |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2132783B2 (en) * | 1971-07-01 | 1972-10-05 | Siemens Ag | ARRANGEMENT FOR GENERATING THE CLOCK FOR THE RECORDING OF DIGITAL INFORMATION ON A DATA MEDIUM, IN PARTICULAR A MAGNETIC TAPE |
| JPS4938110A (en) * | 1972-08-16 | 1974-04-09 | ||
| DE2330309C3 (en) * | 1973-06-14 | 1978-04-13 | Siemens Ag, 1000 Berlin Und 8000 Muenchen | Circuit arrangement for speed control of a brushless DC motor |
| DE2534745C3 (en) * | 1975-08-04 | 1979-07-26 | Siemens Ag, 1000 Berlin Und 8000 Muenchen | Circuit arrangement for generating an actual speed value from the voltages induced in the stator windings of a speed-controlled electronic motor |
| DE2725502C2 (en) * | 1977-06-06 | 1984-10-18 | Papst-Motoren GmbH & Co KG, 7742 St Georgen | Arrangement for speed detection and preferably speed control |
| JPS5951941B2 (en) * | 1977-08-12 | 1984-12-17 | 大塚製薬株式会社 | carbostyril derivatives |
| JPS54107370A (en) * | 1978-02-10 | 1979-08-23 | Fujiya Audio | Method of detecting revolution speed of brushless motor |
| JPS57160065A (en) * | 1981-03-30 | 1982-10-02 | Secoh Giken Inc | Rotating speed detection device |
-
1982
- 1982-01-14 JP JP57004333A patent/JPS58131571A/en active Pending
-
1983
- 1983-01-10 KR KR1019830000069A patent/KR860002000B1/en not_active IP Right Cessation
- 1983-01-13 GB GB08300868A patent/GB2115931B/en not_active Expired
- 1983-01-13 FR FR8300426A patent/FR2519765B1/en not_active Expired
- 1983-01-14 DE DE19833300990 patent/DE3300990A1/en active Granted
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0687054A3 (en) * | 1994-06-07 | 1997-11-05 | Matsushita Electric Industrial Co., Ltd. | Three-phase brushless servo motor |
| US5942863A (en) * | 1994-06-07 | 1999-08-24 | Matsushita Electric Industrial Co., Ltd. | Three-phase brushless servo motor |
| EP0964506A2 (en) * | 1998-06-08 | 1999-12-15 | Matsushita Electric Industrial Co., Ltd. | Three-phase brushless servo motor |
| EP0964506A3 (en) * | 1998-06-08 | 2001-06-27 | Matsushita Electric Industrial Co., Ltd. | Three-phase brushless servo motor |
| US6862415B2 (en) | 2001-06-27 | 2005-03-01 | Eastman Kodak Company | Device for treating the surface of an article in connection with printing |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8300868D0 (en) | 1983-02-16 |
| FR2519765B1 (en) | 1986-07-11 |
| KR860002000B1 (en) | 1986-11-12 |
| JPS58131571A (en) | 1983-08-05 |
| GB2115931B (en) | 1985-09-25 |
| DE3300990A1 (en) | 1983-07-21 |
| KR840003361A (en) | 1984-08-20 |
| DE3300990C2 (en) | 1988-01-28 |
| FR2519765A1 (en) | 1983-07-18 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19930113 |