CA1290387C - Brake for a motor - Google Patents
Brake for a motorInfo
- Publication number
- CA1290387C CA1290387C CA000534642A CA534642A CA1290387C CA 1290387 C CA1290387 C CA 1290387C CA 000534642 A CA000534642 A CA 000534642A CA 534642 A CA534642 A CA 534642A CA 1290387 C CA1290387 C CA 1290387C
- Authority
- CA
- Canada
- Prior art keywords
- brake
- circuit
- switch
- coil
- 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.)
- Expired - Lifetime
Links
Classifications
-
- 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
- H02P3/00—Arrangements for stopping or slowing electric motors, generators, or dynamo-electric converters
- H02P3/02—Details
- H02P3/04—Means for stopping or slowing by a separate brake, e.g. friction brake, eddy-current brake
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
- H02K7/10—Structural association with clutches, brakes, gears, pulleys or mechanical starters
- H02K7/102—Structural association with clutches, brakes, gears, pulleys or mechanical starters with friction brakes
- H02K7/1021—Magnetically influenced friction brakes
- H02K7/1023—Magnetically influenced friction brakes using electromagnets
Abstract
ABSTRACT
A brake for a motor, particularly an alternating current motor with an electromagnet is proposed for improving the dynamic characteristics, without increasing the power loss, whereby the coil of electromagnet (2) is subdivided by an intermediate tap (6) into two partial coils (3, 4), one of which is arranged in a freewheeling circuit.
(Fig 1)
A brake for a motor, particularly an alternating current motor with an electromagnet is proposed for improving the dynamic characteristics, without increasing the power loss, whereby the coil of electromagnet (2) is subdivided by an intermediate tap (6) into two partial coils (3, 4), one of which is arranged in a freewheeling circuit.
(Fig 1)
Description
BRAKE FOR A MOTOR
The invention relates to a brake for a motor, particularly an alternating current motor with an electromagnet and a rectifier circuit. In such electromagnetic brakes, in which an armature disk or plate is generally moved counter to the tension of springs on switching onr high magnetomotive forces or potential differences must be built up on s~itching on in order to move the armature disk and in particular to achieve a momentary response or operation of the brake. Following the application of the brake the air gap between the armature disk and the electromagnet becomes smaller and consequently the magnetic resistance is reduced, so that lower potential differences and therefore lower holding currents are required for maintaining the brake.
It has already been proposed (US patent 3 614 565 ~ to initially subject the magnet for a short time following the switching on of the motor current to the action of a high voltage and therefore a correspondingly high current and then to reduce the current through the magnet coil by means of a control circuit to a low holding value. This can be more rapidly decreased following disconnection, so that the brake can then relatively rapidly be released again.
The problem of the present invention is to so further develop a brake according to the preamble, that the dynamic characteristics can be improved in a simple manner.
In the case of a brake with an electromagnet and a rectifier circuit, this problem is inventively solved in that the coil is subdivided by an intermediate tap into two partial coils, whereof one is located in a freewheeling circuit. The dynamic characteristics of the brake are improved in that the freewheeling circuit of the coil is only formed by a partial coil thereof.
As a result of the inventive brake construction the d~namic characteristics of a brake are improved, which can be constructed more cost-favourably, because less copper has to ~k be used for the winding, less iron for the armature and also less expensive iron can be use~, which more than compensates for the slightly increased costs of the switching electronics, which merely switch one coil into and out of the circuit. As a result of the inventive construction, the brake is subject to less wear and has a higher brake lining life, because the lining becomes less worn due to the rapid application of the brake through the high starting current in the case of electromagnetic production of the lifting force.
The short starti.ng ti.me i.s attai.ned by the small time constant of the accelerator coil. A high current flows far a short ti.me, but because of the smaller number of turns the current does not cause a over-saturati.on.
In addition, during starting, the motor is heated less due to the rapid removal of the brake.
According to the invention, for switching the branches or partial coils of the brake, one partial coil as the accelerating coil is in series with a switch which is in parallel to the other partial coil and which can be switched by an associated control element~ This inventive further development provides the possibility of applying the voltage to only one part of the coil during the switching on of the brake and consequently the current only flows through one part of the coil with a high value adequate for applying the armature disk, whereas for maintaining purposes the voltage decreases over the entire coil, so that as a result of the increased resistance there is automatically a lower holding current. The control element is preferably constructed as a time switch, to which is also connected in series one of the partial coils as a dropping resistor.
For as long as the switch, which is preferably constructed as an electronic switch, such as a thyristor is connected, the rectified current flows across one coil part, namely the accelerating coil part, as well as the thyristor. slocking the thyristor leads to a current flow through both partial coils and the increased resistance reduces the current passage. On switching off the motor, accompanied by the application of the brake, a freewheeling circuit with a freewheeling diode can be associated in conventional manner with the coil or one of its branches in order to decrease the ~2~ 87 magnetic energy of the coil following disconnection. In order to permit rapid application, in known manner the freewheeling circuit can be made high impedance in that an electronic switch is blocked, so that followiny disconnection the current flows across a resistor arranged in parallel to the switch and e.g. a varistor. The latter switch has hitherto been switched in known manner by the voltage at the motor. Following the disconnection of the motor, the latter produces a generator voltage, which delays the blocking of said switch.
In order to obtain immediate switching and therefore an improvernent to the dynamic behaviour of the brake, even on disconnecting the motor and on applying the brake, according to a preferred development it is proposed that a current transformer is located in the brake motor power supply and is connected to a control circuit for a switch arranged in the brake coil circuit. Thus, according to the invention, for switching the magnet the motor current and not the voltage is used as the control signal for opening the freewheeling circuit of the brake. Unlike the voltagel said motor current is also interrupted immediately after interrupting the supply to the motor, e.g. by switching a contactor, so that the disconnection times are further reduced. According to a further development, the control circuit has a Schmitt trigger circuit and with the circuit breaker is associated in antiparallel form a diode, which provides an additional protection for the switch, particularly a field effect transistor against confusion of the poles.
As an alternative to the per se known direct current-side high impedance switching of the freewheeling circuit, the invention further proposes countercurrent energizing, so that a preferred embodiment of the invention is characterized in that with the freewheeling circult is associated a counterenergizing branch with a switch for countercurrent application purposes. Thus, the residual induction voltage of the motor following the disconnection thereof is used to .~ .
~2~3~
supply countercurrent to the brake. It is also pointed out that, should the motor have no residual voltage after disconnection, so that no countercurrent action can be provided, this would correspond to an a.c. voltage-side disconnection, in which the brake would in any case be rapidly applied due to its inventive construction. An a.c.
voltage-side disconnection of a lifting magnet coil supplied with direct current is known per se, but the switch for carrying out switching belongs to a contactor used for switching on and off the mains voltage, whereby it is prejudicial that a motor contactor must have an additional switch contact for the brake coil and therefore additional connecting lines from the contactor to the circuit arrangement for the brake coil, so that d.c. side disconnections have been proposed as a result of the residual voltage of the motor and which have the aforementioned disadvantages. According to a further development, the invention proposes an a.c. side isolation in that on decreasing the switching signal across a current transformer located in the brake motor power supply, said switch is connected on the a.c. side in the power supply of the brake coil. The switch is a circuit breaker and in particular a triac.
Further advantages and features of the invention can be gathered from the claims and the following description of preferred embodiments of the inventive brake and with reference to the attached drawings, wherein show :
Fig 1, a first embodiment of the invention.
Fig 2, a diagrammatic representation of brake and motor with the circuit according to fig 1.
Fig 3, a circuit for further improving the dynamics.
Fig 4, another embodiment like that of fig 1.wi-th better removal dynamics by accelerator functi.on Fi.g 4a, a speci.fi.c circuit for controlling and moni.-toring of the emhodiment of Fig. ~.
Fi.g 5, another embodi.ment si.mi.lar to that of Fi.g. 3 Fi.q..6, an alternati.ve to the ci.rcui.t accordi.ng to Fi.g 3, particularly for the embodi.ment of Fi.g l.
Fi.g 7, a preferred fitting possibility for a swi.tch 9~ 87 according to figs 3 or 6.
According to fig 2, the inventive brake 1 has an electromagnet 2 with two partial coils 3, 4, as is shown diagrammatically in fig 1. An intermediate tap 6 is provided between the two partial coils 3, 4. The overall coil 2 is preferably constructed in such a way that the two partial coils are wound in radially superimposed manner and are led out at an appropriate point of the intermediate tap. Partial coil 3 has approximately / to / of the resistance of partial coil 4. There is also a one-way rectiEier circuit 7 with two rectifier diodes V1, V2, whereof diode V1 is positioned parallel to partial coil 4 in the form of a freewheeling diode. Varistors R1 and R2, as overvoltage protection means are connected in parallel to diodes V1, V2.
There is finally a third varistor R3, which will be explained with reference to fig 2 and which on disconnecting the brake is in series with the high impedance freewheeling circuit of the brake coil, as is shown by a comparison with fig 2.
The function of the embodiment of fig 1 is as follows. For one half-wave of the alternating current network, the current flows across both partial coils 3, 4 and diode V2. For the other half-wave diode V2 is blocked, whilst a freewheeling circuit is freed across diode V1 and across which the energy of the coil is reduced. This in itself leads to an improvernent in the dynamics of brake 1 compared with conventional brakes with the same production of heat and in particular the release time is reduced.
Fig 2 shows a motor 21 to be braked with connections L1, L2, L3 for phases R, S, T of an a.c. voltage network. In connection lines L1, L2, L3 is provided a motor contactor K1, via which the motor 21 can be connected to the mains. From two connections, in this L2, L3, leads 22, 23 pass to the brake of fig 1. The freewheeling circuit of lifting magnet 2 also contains a switch 24 switchable by the disconnection of the mains via contactor K1. Switch 24 can be switched in per se known manner by the voltage drop on switching off the motor across contactor K1 or by means of the control circuit 26 descri~ed relative to fig 3 by a motor current in the manner represented in fig 2. Switch 24 is shunted by varistor R3 contained in fig 1. With the disconnection of motor 21 from the mains, via contactor K1, the switch 24 shunted by varistor R3 is opened and consequently the freewheeling current flowing across the freewheeling diode V1 is reduced to a value limited by varistor R3, so that the lifting magnet leads to an even faster applicakion of brake 1.
As stated, according to the invention, switch 24 in the freewheeling circuit of the lifting magnet forms part of a control circuit 26, as shown in fig 3. Circuit 26 of fig 3 is preferably constructed as an additional device in a separate casing. The casing can be designed in the manner described with reference to fig 7.
The additional device with circuit 26 has four leads. With two leads 31, 32 it is connected into one of the connecting lines of the motor and in the embodiment according to fig 2 into line L3. Circuit 26 has as an essential element a current transformer T1, so that it deals with the motor current and not the voltage applied to motor 21. The additional device is switched in the freewheeling circuit of the lifting magnet by output terminals 33, 34 associated with electronic switch 24, which is a field effect transistor (EET) in the represented embodiment. To switch 24 can be connected an antiparallel-associated diode V8, in order to provide further protection against pole confusion during wlring. A field effect transi.stor (FET) has already incorporated such a di.ode (as parasi.ti.c elernent). Control circui.t 26 has a bri.dge recti.fier 37 with two diodes V4, V5 and two Zehner di.odes Z1, Z2 (the latter for voltaye limi.tation purposes), as well as a Schmi.tt tri.gger D1, whi.ch is formed by a correspondingly wired integrated component 4093. A fi.lter R4, R5, C1 is provi.ded, in order to filter out the ri.pple of the signal of current transformer T1 rectified by the rectifier. Schmi.tt tri.gger D1 i.s ~L2~
supplied by means of diodes V6 and capacitor C2 ensuring that there is always an adequate supply voltage for the Schmitt trigger. V7 is a protection diode. If the motor is now switched off, in that contactor K1 is opened then leads 22, 23 of brake 1 (fig 2) become dead, so that the brake should be released. However, such a rapid release i9 delayed by the generator voltage formed on disconnecting the motor. In addition, a freewheeling current is formed in the brake coil on disconnection and delays and application of brake 1. On disconnecting the motor across contactor K1, the power supply in leads L1 to L3 is immediately interrupted, so that via the control circuit 26 in lead L3, on dropping below the lower breakover voltage of the Schmitt trlgger, switch 24 is immediately transferred into the blocked state, so that (fig. 2) the freewheeling current of brake coil 2 must flow against the varistor voltage and~the magnetic energy is withdrawn from the brake system, what makes the brake be apply even faster.
As soon as the motor is switched on again, i.e. is connected to the mains and consequently current flows, switch 26 is again connected through.
Fig 4 shows another embodiment of the inventive brake. This construction is based on fig 1, so that reference should be made thereto in connection with coinciding features.
thyristor Th is connected to the intermediate tap 6 and in series with partial coil 3, so that the latter can be switched as an accelerating coil. The thyristor Th is switched and in particular started by a time switch 12, which has a not shown RC network, which applies the starting signal for a desired time to thyristor Th. A monitoring unit 13 is provided for retriggering time switch 12 in the case of undervoltages~ the use o~ said unit being a function of the dimensioning of the brake and will be explained in further detail hereinafter. Unit 13 operates in preferred manner according to the principle of relative voltage measurement, so that the function thereof is independent of the supply voltage. Compared with the construction according to fig 1, ~2~
the dimensioning of the coil and the partial coils 6 is such that without switching the current flowing through the complete coil 2, it is no longer possible to apply the brake.
Thus, in this construction, the same coil as in fig 1 can be used in the case of a "heavier" brake for a more powerful motor.
The function of the circuit shown in fig 4 is as follows. On applying mains voltage and therefore switching on motor 21, thyristor Th is switched through as an electronic switch, so that as a result of the small internal resistance compared with the complete coil 2 a high current flows through accelerating coil 3 and this brings about a high magnetic flux and consequently a rapid application action and a short response time. Following the response or operation of the brake magnet, the high magnetic flux is no longer necessary, because the air gap between armature and magnet coil and therefore the magnetic resistance is reduced. Thus, lower holding forces and consequently lower magnetic potential differences and lower holding current are required. Thus, after response or operation, the thyristor Th is blocked by time switch 12, so that mains current flows across the entire coil, i.e. both partial coils 3, 4 and is rectified by the oppositely directed diodes 8, 9 forming the rectifier. Due to the higher resistance of coil 3, 4, there is a lower holding current, which permits a lower energy consumption and a faster disconnection.
The above-described brake can be switched in the same way as a conventional brake (fig 5) like that of fig 1, in the manner shown in fig 2 ~or additional fast disconnection by means of a freewheeling circuit connected in high impedance manner by varistor 3.
For the rapid energizing or disconnection of the brake coil, a counter energizing can be provided, as indicated in broken line form in fig 4. For this purpose, a further thyristor Th' is connected in antiparallel to thyristor Th and with the g additional transistor is associated not shown switching electronics corresponding to electronics 12. Thyristor Th' switches the negative mains half-wave to accelerating coil 3. The voltage comes from the motor, so that a tirne control is not needed. Countercurrent application leads to rapid demagnetization of the system and therefore to rapid brake application. Thyristor Th' can be started in an appropriate manner, e.g. by a current sensor T1 according to fig 3. The circuit replaces the control line and the switching contact a "direct current-side isolation", e.g. according to fig 2.
As stated hereinbefore, as a functioning of the dimensioning of the brake in the case of a voltage "break", it may be the case that the holding force of the complete brake coil (both partial coils) is no longer adequate for holding the brake, so that the latter is applied. When the voltage is restored, it must be ensured that the brake is applied again and, as a function of the brake dimensioning, may not be achievable by the brake, in the case of a current flow through the complete coil (blocked thyristor Th). In this case, the thyristor Th must be momentarily switched through, so that there is an increased current flow through partial coil 3 which, as on switching on, leads to the re-application of the brake. A
specific circuit for this is shown in fig 4a. Monitoring circuit 13 is supplied from the mains across a dropping resistor 101 of e.g. approximately 180 K and brake coil 2.
The relative voltage is taken on the one hand at a capacitor 102 with 0.33 uF and on the other hand at time switch 12 with e.g. 220 K~n0.1 uF. In the case of a rise in the voltage (of a half-wave), due to the voltage difference which occurs a double transistor arrangement 103 (which can be looked upon as a thyristor) and then a FET 10~ is switched in such a way that thyristor Th is initially connected through, so that only accelerating coil 3 is applied between the mains terminals. If the voltage applied is then compensated across time switch 12, then the starting pulse is removed from thyristor Th, so that the latter is blocked. If voltage occurs, discharging takes place, so that on rising again ~.29~ o-there i.s again a voltage dlfference. The further elements are used for matchmg in the particular case.
If FET 104 is connected-through, there i.s no si.gnal at thyri.stor Th2accordi.ngly the Thyristor Th can tri.gger on at positive half wave.
If FET 104 i.s blocked the tri.gger si.gnal i.s present a~ the thyristor Th2. Which si.gnal makes the thyristor Th2 conductive with the posi.ti.ve half wave and accordingly withdraws the trigger voltage from the Thyri.stor Th. In the case of a voltage difference at the time switch 12 and the capacitor 102 is not connected through the double transi.stor (thyrlstor) definite, where by the translstor 104 becomes conducti.ve (self conductive FET) and the Thyristor Th can trigger on. Thus the voltage at capacities Cl and C2 equalize, the double transistor 103 blocks and so does the Transistor 104 whi.ch stops the accelerator function. After reducing the voltage di.fference to below a given limi.t, the thyris-tor must be switched , so that the FET blocks.
Corresponding to fig 2, fig 5 shows the circuit of a conventional brake through the current of motor 21 by means of a circuit 26 according to fig 3 for the direct current-side isolation for the high impedance switching of the freewheeling circuit. Once again are shown motor 21 with connections L1, L2, L3 for phases R, S, T of an a.c. voltage mains and motor contactor K1 located in connections L1, L2, L3 by means of which motor 21 can be connected to the mains.
From connection L2 and L3, once again leads 22, 23 lead to a circuit arrangement 41 which, as stated, in the embodiment according to fig 5 is a conventional circuit. Circuit 24 shown in fig 5 has a rectifier with two zero diodes in one-way connection. For controlling the high disconnection speeds of large inductors additional wiring with varistor R3 is provided. If with the disconnection of motor 21 from the mains switch 24 shunted by varistor R3 in the freewheeling circuit having a freewheeling diode the coil of brake 42 is opened, then the freewheeling current flowing across the freewheeling diode is reduced to a value li.mited by varistor R3, so that the lifting magnet permits a corresponding rapid application of brake 1. Thus, the circuit of fig 5 is known to the extent that it control circuit 41.
However, switch 24 in the freewheeling circuit of the lifting magnet forms part of the control circuit 27 of fig 3 connected with its leads 31, 32 in connecting line L3 of ~.2~ 37 motor 21, so that in this case switch 24 is inventively switched by the motor current.
The circuit according to fig 3 is preferably constructed as an additional device in a separate casing. The latter can be constructed by standard components, such as a conventional screwing part and a blind plug, so that the additional device can be fitted by screwing in the thread of a cable bushing on the motor terminal box, so that there is no need use a larger terminal box.
The inventive intermediate tap 6 on brake coil 2 and the arrangement of the freewheeling circuit across partial coil 4 with freewheeling diode V1 makes it possible, in place of the hitherto preferred d.c. side isolation, an identical result by a.c. side isolation, whilst involving lower costs. For this purpose a circuit 51 according to fig 6 is provided, whose connections 52, 53, as in the circuit according to fig 3, are connected in a lead L3 to motor 21~ By means of outputs 54, 56, the circuit is connected on the a.c. side into one of the supply lines 221 23 of brake coil 2 (fig 2)o Circuit 51 once again has a current transformer T11, followed by a rectifier with diodes V11, V12 and voltage limiting zener diodes V13, V14. A capacitor 10, 11 is provided for bringing the brief voltage drop of the alternating signal.
The voltage smoothed by current transformer T11 and capacitor C11 is supplied to the control input of a triac V15, with which a varistor R11 is connected in parallel. On switching off the motor power supply, across current sensor T11 the supply for brake coil 2 is immediately interrupted by blocking triac V15 or the varistor R11 is reduced to a value not adequate for holding the brake. As a result of this inventive construction, the own lines hitherto disadvantageously necessary in the case of alternating current-side isolation are rendered superfluous.
Fig 7 shows a construction for receiving additional circuits, particularly with current sensors, like those of figs 3 and ~ 2~ 37 6, without larger terminal boxes having to be provided.
Apart from its cover 62, a conventional terminal box 61 has a number of cable bushings 63 having an internal thread and closed by externally threaded blind plugs 64 when not in use.
Into such an opening 63 is screwed an additional casing 66 with a threaded attachment 67, which is frontally closed with a cover 68. In the represented embodiment the additional casing is a reducer or extender which is at the front of sealingly screwed an adapted blind plug, whilst interposing sealsr such as an O-ring (not shown). There is a clamping plate 71 brake rectifier 72, a clamping block 73r whilst the actual cabling is not shown in detail.
The invention relates to a brake for a motor, particularly an alternating current motor with an electromagnet and a rectifier circuit. In such electromagnetic brakes, in which an armature disk or plate is generally moved counter to the tension of springs on switching onr high magnetomotive forces or potential differences must be built up on s~itching on in order to move the armature disk and in particular to achieve a momentary response or operation of the brake. Following the application of the brake the air gap between the armature disk and the electromagnet becomes smaller and consequently the magnetic resistance is reduced, so that lower potential differences and therefore lower holding currents are required for maintaining the brake.
It has already been proposed (US patent 3 614 565 ~ to initially subject the magnet for a short time following the switching on of the motor current to the action of a high voltage and therefore a correspondingly high current and then to reduce the current through the magnet coil by means of a control circuit to a low holding value. This can be more rapidly decreased following disconnection, so that the brake can then relatively rapidly be released again.
The problem of the present invention is to so further develop a brake according to the preamble, that the dynamic characteristics can be improved in a simple manner.
In the case of a brake with an electromagnet and a rectifier circuit, this problem is inventively solved in that the coil is subdivided by an intermediate tap into two partial coils, whereof one is located in a freewheeling circuit. The dynamic characteristics of the brake are improved in that the freewheeling circuit of the coil is only formed by a partial coil thereof.
As a result of the inventive brake construction the d~namic characteristics of a brake are improved, which can be constructed more cost-favourably, because less copper has to ~k be used for the winding, less iron for the armature and also less expensive iron can be use~, which more than compensates for the slightly increased costs of the switching electronics, which merely switch one coil into and out of the circuit. As a result of the inventive construction, the brake is subject to less wear and has a higher brake lining life, because the lining becomes less worn due to the rapid application of the brake through the high starting current in the case of electromagnetic production of the lifting force.
The short starti.ng ti.me i.s attai.ned by the small time constant of the accelerator coil. A high current flows far a short ti.me, but because of the smaller number of turns the current does not cause a over-saturati.on.
In addition, during starting, the motor is heated less due to the rapid removal of the brake.
According to the invention, for switching the branches or partial coils of the brake, one partial coil as the accelerating coil is in series with a switch which is in parallel to the other partial coil and which can be switched by an associated control element~ This inventive further development provides the possibility of applying the voltage to only one part of the coil during the switching on of the brake and consequently the current only flows through one part of the coil with a high value adequate for applying the armature disk, whereas for maintaining purposes the voltage decreases over the entire coil, so that as a result of the increased resistance there is automatically a lower holding current. The control element is preferably constructed as a time switch, to which is also connected in series one of the partial coils as a dropping resistor.
For as long as the switch, which is preferably constructed as an electronic switch, such as a thyristor is connected, the rectified current flows across one coil part, namely the accelerating coil part, as well as the thyristor. slocking the thyristor leads to a current flow through both partial coils and the increased resistance reduces the current passage. On switching off the motor, accompanied by the application of the brake, a freewheeling circuit with a freewheeling diode can be associated in conventional manner with the coil or one of its branches in order to decrease the ~2~ 87 magnetic energy of the coil following disconnection. In order to permit rapid application, in known manner the freewheeling circuit can be made high impedance in that an electronic switch is blocked, so that followiny disconnection the current flows across a resistor arranged in parallel to the switch and e.g. a varistor. The latter switch has hitherto been switched in known manner by the voltage at the motor. Following the disconnection of the motor, the latter produces a generator voltage, which delays the blocking of said switch.
In order to obtain immediate switching and therefore an improvernent to the dynamic behaviour of the brake, even on disconnecting the motor and on applying the brake, according to a preferred development it is proposed that a current transformer is located in the brake motor power supply and is connected to a control circuit for a switch arranged in the brake coil circuit. Thus, according to the invention, for switching the magnet the motor current and not the voltage is used as the control signal for opening the freewheeling circuit of the brake. Unlike the voltagel said motor current is also interrupted immediately after interrupting the supply to the motor, e.g. by switching a contactor, so that the disconnection times are further reduced. According to a further development, the control circuit has a Schmitt trigger circuit and with the circuit breaker is associated in antiparallel form a diode, which provides an additional protection for the switch, particularly a field effect transistor against confusion of the poles.
As an alternative to the per se known direct current-side high impedance switching of the freewheeling circuit, the invention further proposes countercurrent energizing, so that a preferred embodiment of the invention is characterized in that with the freewheeling circult is associated a counterenergizing branch with a switch for countercurrent application purposes. Thus, the residual induction voltage of the motor following the disconnection thereof is used to .~ .
~2~3~
supply countercurrent to the brake. It is also pointed out that, should the motor have no residual voltage after disconnection, so that no countercurrent action can be provided, this would correspond to an a.c. voltage-side disconnection, in which the brake would in any case be rapidly applied due to its inventive construction. An a.c.
voltage-side disconnection of a lifting magnet coil supplied with direct current is known per se, but the switch for carrying out switching belongs to a contactor used for switching on and off the mains voltage, whereby it is prejudicial that a motor contactor must have an additional switch contact for the brake coil and therefore additional connecting lines from the contactor to the circuit arrangement for the brake coil, so that d.c. side disconnections have been proposed as a result of the residual voltage of the motor and which have the aforementioned disadvantages. According to a further development, the invention proposes an a.c. side isolation in that on decreasing the switching signal across a current transformer located in the brake motor power supply, said switch is connected on the a.c. side in the power supply of the brake coil. The switch is a circuit breaker and in particular a triac.
Further advantages and features of the invention can be gathered from the claims and the following description of preferred embodiments of the inventive brake and with reference to the attached drawings, wherein show :
Fig 1, a first embodiment of the invention.
Fig 2, a diagrammatic representation of brake and motor with the circuit according to fig 1.
Fig 3, a circuit for further improving the dynamics.
Fig 4, another embodiment like that of fig 1.wi-th better removal dynamics by accelerator functi.on Fi.g 4a, a speci.fi.c circuit for controlling and moni.-toring of the emhodiment of Fig. ~.
Fi.g 5, another embodi.ment si.mi.lar to that of Fi.g. 3 Fi.q..6, an alternati.ve to the ci.rcui.t accordi.ng to Fi.g 3, particularly for the embodi.ment of Fi.g l.
Fi.g 7, a preferred fitting possibility for a swi.tch 9~ 87 according to figs 3 or 6.
According to fig 2, the inventive brake 1 has an electromagnet 2 with two partial coils 3, 4, as is shown diagrammatically in fig 1. An intermediate tap 6 is provided between the two partial coils 3, 4. The overall coil 2 is preferably constructed in such a way that the two partial coils are wound in radially superimposed manner and are led out at an appropriate point of the intermediate tap. Partial coil 3 has approximately / to / of the resistance of partial coil 4. There is also a one-way rectiEier circuit 7 with two rectifier diodes V1, V2, whereof diode V1 is positioned parallel to partial coil 4 in the form of a freewheeling diode. Varistors R1 and R2, as overvoltage protection means are connected in parallel to diodes V1, V2.
There is finally a third varistor R3, which will be explained with reference to fig 2 and which on disconnecting the brake is in series with the high impedance freewheeling circuit of the brake coil, as is shown by a comparison with fig 2.
The function of the embodiment of fig 1 is as follows. For one half-wave of the alternating current network, the current flows across both partial coils 3, 4 and diode V2. For the other half-wave diode V2 is blocked, whilst a freewheeling circuit is freed across diode V1 and across which the energy of the coil is reduced. This in itself leads to an improvernent in the dynamics of brake 1 compared with conventional brakes with the same production of heat and in particular the release time is reduced.
Fig 2 shows a motor 21 to be braked with connections L1, L2, L3 for phases R, S, T of an a.c. voltage network. In connection lines L1, L2, L3 is provided a motor contactor K1, via which the motor 21 can be connected to the mains. From two connections, in this L2, L3, leads 22, 23 pass to the brake of fig 1. The freewheeling circuit of lifting magnet 2 also contains a switch 24 switchable by the disconnection of the mains via contactor K1. Switch 24 can be switched in per se known manner by the voltage drop on switching off the motor across contactor K1 or by means of the control circuit 26 descri~ed relative to fig 3 by a motor current in the manner represented in fig 2. Switch 24 is shunted by varistor R3 contained in fig 1. With the disconnection of motor 21 from the mains, via contactor K1, the switch 24 shunted by varistor R3 is opened and consequently the freewheeling current flowing across the freewheeling diode V1 is reduced to a value limited by varistor R3, so that the lifting magnet leads to an even faster applicakion of brake 1.
As stated, according to the invention, switch 24 in the freewheeling circuit of the lifting magnet forms part of a control circuit 26, as shown in fig 3. Circuit 26 of fig 3 is preferably constructed as an additional device in a separate casing. The casing can be designed in the manner described with reference to fig 7.
The additional device with circuit 26 has four leads. With two leads 31, 32 it is connected into one of the connecting lines of the motor and in the embodiment according to fig 2 into line L3. Circuit 26 has as an essential element a current transformer T1, so that it deals with the motor current and not the voltage applied to motor 21. The additional device is switched in the freewheeling circuit of the lifting magnet by output terminals 33, 34 associated with electronic switch 24, which is a field effect transistor (EET) in the represented embodiment. To switch 24 can be connected an antiparallel-associated diode V8, in order to provide further protection against pole confusion during wlring. A field effect transi.stor (FET) has already incorporated such a di.ode (as parasi.ti.c elernent). Control circui.t 26 has a bri.dge recti.fier 37 with two diodes V4, V5 and two Zehner di.odes Z1, Z2 (the latter for voltaye limi.tation purposes), as well as a Schmi.tt tri.gger D1, whi.ch is formed by a correspondingly wired integrated component 4093. A fi.lter R4, R5, C1 is provi.ded, in order to filter out the ri.pple of the signal of current transformer T1 rectified by the rectifier. Schmi.tt tri.gger D1 i.s ~L2~
supplied by means of diodes V6 and capacitor C2 ensuring that there is always an adequate supply voltage for the Schmitt trigger. V7 is a protection diode. If the motor is now switched off, in that contactor K1 is opened then leads 22, 23 of brake 1 (fig 2) become dead, so that the brake should be released. However, such a rapid release i9 delayed by the generator voltage formed on disconnecting the motor. In addition, a freewheeling current is formed in the brake coil on disconnection and delays and application of brake 1. On disconnecting the motor across contactor K1, the power supply in leads L1 to L3 is immediately interrupted, so that via the control circuit 26 in lead L3, on dropping below the lower breakover voltage of the Schmitt trlgger, switch 24 is immediately transferred into the blocked state, so that (fig. 2) the freewheeling current of brake coil 2 must flow against the varistor voltage and~the magnetic energy is withdrawn from the brake system, what makes the brake be apply even faster.
As soon as the motor is switched on again, i.e. is connected to the mains and consequently current flows, switch 26 is again connected through.
Fig 4 shows another embodiment of the inventive brake. This construction is based on fig 1, so that reference should be made thereto in connection with coinciding features.
thyristor Th is connected to the intermediate tap 6 and in series with partial coil 3, so that the latter can be switched as an accelerating coil. The thyristor Th is switched and in particular started by a time switch 12, which has a not shown RC network, which applies the starting signal for a desired time to thyristor Th. A monitoring unit 13 is provided for retriggering time switch 12 in the case of undervoltages~ the use o~ said unit being a function of the dimensioning of the brake and will be explained in further detail hereinafter. Unit 13 operates in preferred manner according to the principle of relative voltage measurement, so that the function thereof is independent of the supply voltage. Compared with the construction according to fig 1, ~2~
the dimensioning of the coil and the partial coils 6 is such that without switching the current flowing through the complete coil 2, it is no longer possible to apply the brake.
Thus, in this construction, the same coil as in fig 1 can be used in the case of a "heavier" brake for a more powerful motor.
The function of the circuit shown in fig 4 is as follows. On applying mains voltage and therefore switching on motor 21, thyristor Th is switched through as an electronic switch, so that as a result of the small internal resistance compared with the complete coil 2 a high current flows through accelerating coil 3 and this brings about a high magnetic flux and consequently a rapid application action and a short response time. Following the response or operation of the brake magnet, the high magnetic flux is no longer necessary, because the air gap between armature and magnet coil and therefore the magnetic resistance is reduced. Thus, lower holding forces and consequently lower magnetic potential differences and lower holding current are required. Thus, after response or operation, the thyristor Th is blocked by time switch 12, so that mains current flows across the entire coil, i.e. both partial coils 3, 4 and is rectified by the oppositely directed diodes 8, 9 forming the rectifier. Due to the higher resistance of coil 3, 4, there is a lower holding current, which permits a lower energy consumption and a faster disconnection.
The above-described brake can be switched in the same way as a conventional brake (fig 5) like that of fig 1, in the manner shown in fig 2 ~or additional fast disconnection by means of a freewheeling circuit connected in high impedance manner by varistor 3.
For the rapid energizing or disconnection of the brake coil, a counter energizing can be provided, as indicated in broken line form in fig 4. For this purpose, a further thyristor Th' is connected in antiparallel to thyristor Th and with the g additional transistor is associated not shown switching electronics corresponding to electronics 12. Thyristor Th' switches the negative mains half-wave to accelerating coil 3. The voltage comes from the motor, so that a tirne control is not needed. Countercurrent application leads to rapid demagnetization of the system and therefore to rapid brake application. Thyristor Th' can be started in an appropriate manner, e.g. by a current sensor T1 according to fig 3. The circuit replaces the control line and the switching contact a "direct current-side isolation", e.g. according to fig 2.
As stated hereinbefore, as a functioning of the dimensioning of the brake in the case of a voltage "break", it may be the case that the holding force of the complete brake coil (both partial coils) is no longer adequate for holding the brake, so that the latter is applied. When the voltage is restored, it must be ensured that the brake is applied again and, as a function of the brake dimensioning, may not be achievable by the brake, in the case of a current flow through the complete coil (blocked thyristor Th). In this case, the thyristor Th must be momentarily switched through, so that there is an increased current flow through partial coil 3 which, as on switching on, leads to the re-application of the brake. A
specific circuit for this is shown in fig 4a. Monitoring circuit 13 is supplied from the mains across a dropping resistor 101 of e.g. approximately 180 K and brake coil 2.
The relative voltage is taken on the one hand at a capacitor 102 with 0.33 uF and on the other hand at time switch 12 with e.g. 220 K~n0.1 uF. In the case of a rise in the voltage (of a half-wave), due to the voltage difference which occurs a double transistor arrangement 103 (which can be looked upon as a thyristor) and then a FET 10~ is switched in such a way that thyristor Th is initially connected through, so that only accelerating coil 3 is applied between the mains terminals. If the voltage applied is then compensated across time switch 12, then the starting pulse is removed from thyristor Th, so that the latter is blocked. If voltage occurs, discharging takes place, so that on rising again ~.29~ o-there i.s again a voltage dlfference. The further elements are used for matchmg in the particular case.
If FET 104 is connected-through, there i.s no si.gnal at thyri.stor Th2accordi.ngly the Thyristor Th can tri.gger on at positive half wave.
If FET 104 i.s blocked the tri.gger si.gnal i.s present a~ the thyristor Th2. Which si.gnal makes the thyristor Th2 conductive with the posi.ti.ve half wave and accordingly withdraws the trigger voltage from the Thyri.stor Th. In the case of a voltage difference at the time switch 12 and the capacitor 102 is not connected through the double transi.stor (thyrlstor) definite, where by the translstor 104 becomes conducti.ve (self conductive FET) and the Thyristor Th can trigger on. Thus the voltage at capacities Cl and C2 equalize, the double transistor 103 blocks and so does the Transistor 104 whi.ch stops the accelerator function. After reducing the voltage di.fference to below a given limi.t, the thyris-tor must be switched , so that the FET blocks.
Corresponding to fig 2, fig 5 shows the circuit of a conventional brake through the current of motor 21 by means of a circuit 26 according to fig 3 for the direct current-side isolation for the high impedance switching of the freewheeling circuit. Once again are shown motor 21 with connections L1, L2, L3 for phases R, S, T of an a.c. voltage mains and motor contactor K1 located in connections L1, L2, L3 by means of which motor 21 can be connected to the mains.
From connection L2 and L3, once again leads 22, 23 lead to a circuit arrangement 41 which, as stated, in the embodiment according to fig 5 is a conventional circuit. Circuit 24 shown in fig 5 has a rectifier with two zero diodes in one-way connection. For controlling the high disconnection speeds of large inductors additional wiring with varistor R3 is provided. If with the disconnection of motor 21 from the mains switch 24 shunted by varistor R3 in the freewheeling circuit having a freewheeling diode the coil of brake 42 is opened, then the freewheeling current flowing across the freewheeling diode is reduced to a value li.mited by varistor R3, so that the lifting magnet permits a corresponding rapid application of brake 1. Thus, the circuit of fig 5 is known to the extent that it control circuit 41.
However, switch 24 in the freewheeling circuit of the lifting magnet forms part of the control circuit 27 of fig 3 connected with its leads 31, 32 in connecting line L3 of ~.2~ 37 motor 21, so that in this case switch 24 is inventively switched by the motor current.
The circuit according to fig 3 is preferably constructed as an additional device in a separate casing. The latter can be constructed by standard components, such as a conventional screwing part and a blind plug, so that the additional device can be fitted by screwing in the thread of a cable bushing on the motor terminal box, so that there is no need use a larger terminal box.
The inventive intermediate tap 6 on brake coil 2 and the arrangement of the freewheeling circuit across partial coil 4 with freewheeling diode V1 makes it possible, in place of the hitherto preferred d.c. side isolation, an identical result by a.c. side isolation, whilst involving lower costs. For this purpose a circuit 51 according to fig 6 is provided, whose connections 52, 53, as in the circuit according to fig 3, are connected in a lead L3 to motor 21~ By means of outputs 54, 56, the circuit is connected on the a.c. side into one of the supply lines 221 23 of brake coil 2 (fig 2)o Circuit 51 once again has a current transformer T11, followed by a rectifier with diodes V11, V12 and voltage limiting zener diodes V13, V14. A capacitor 10, 11 is provided for bringing the brief voltage drop of the alternating signal.
The voltage smoothed by current transformer T11 and capacitor C11 is supplied to the control input of a triac V15, with which a varistor R11 is connected in parallel. On switching off the motor power supply, across current sensor T11 the supply for brake coil 2 is immediately interrupted by blocking triac V15 or the varistor R11 is reduced to a value not adequate for holding the brake. As a result of this inventive construction, the own lines hitherto disadvantageously necessary in the case of alternating current-side isolation are rendered superfluous.
Fig 7 shows a construction for receiving additional circuits, particularly with current sensors, like those of figs 3 and ~ 2~ 37 6, without larger terminal boxes having to be provided.
Apart from its cover 62, a conventional terminal box 61 has a number of cable bushings 63 having an internal thread and closed by externally threaded blind plugs 64 when not in use.
Into such an opening 63 is screwed an additional casing 66 with a threaded attachment 67, which is frontally closed with a cover 68. In the represented embodiment the additional casing is a reducer or extender which is at the front of sealingly screwed an adapted blind plug, whilst interposing sealsr such as an O-ring (not shown). There is a clamping plate 71 brake rectifier 72, a clamping block 73r whilst the actual cabling is not shown in detail.
Claims (12)
1. A brake for a motor, particularly an alternating current motor, with an electromagnet and a rectifier circuit, wherein the rectifier is a half-wave rectifier, an accelerating coil and a holding coil for the electromagnet forming a series connection, i.e. while the brake is being held, the voltage drops across the entire holding and accelerating coil, only the holding coil being located in a freewheeling circuit of the rectifier.
2. A brake according to claim 1 wherein the accelerating coil is arranged in series with a switch arranged in parallel to the hoilding coil, the switch being adapted to be operated by an associated control member.
3. A brake according to claim 1, wherein overvoltage protection elements are associated with the rectifier circuit.
4. A brake according to claim 3, wherein one overvoltage protection element is arranged in parallel to each diode of the rectifier circuit.
5. A brake according to one of claims 2 to 4, wherein a control element for the switch is connected in series with at least one of said partial coils as a dropping resistor.
6. A brake according to one of claims 2, 3 or 4, including a control element for said switch, said control element being a time switch.
7. A brake according to one of claims 1, 2 or 3, wherein the power supply for the motor brake is provided with a current transformer which is connected to a control circuit for a switch arranged in the circuit of the partial coils.
8. A brake according to claim 7, wherein the control circuit has a Schmitt trigger.
9. A brake according to claim 7 wherein a diode is associated in antiparallel manner with said switch arranged in the circuit of the partial coils.
10. A brake according to claim 7, wherein a voltage limiter is connected in parallel with said switch arranged in the circuit of the partial coils.
11. A brake according to claim 7, wherein said switch arranged in the circuit of the partial coils is connected on the dielectric current side of the power supply of the partial coils.
12. A brake according to one of claims 1, 2 or 3, wherein a counter energizing branch, including a switch for countercurrent energizing, is associated with the freewheeling circuit.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19863613294 DE3613294A1 (en) | 1986-04-19 | 1986-04-19 | BRAKE FOR A MOTOR |
| DEP3613294.2 | 1986-04-19 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1290387C true CA1290387C (en) | 1991-10-08 |
Family
ID=6299084
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000534642A Expired - Lifetime CA1290387C (en) | 1986-04-19 | 1987-04-14 | Brake for a motor |
Country Status (9)
| Country | Link |
|---|---|
| EP (1) | EP0242671B1 (en) |
| AT (1) | ATE79204T1 (en) |
| AU (1) | AU602685B2 (en) |
| BR (1) | BR8701854A (en) |
| CA (1) | CA1290387C (en) |
| DE (2) | DE3613294A1 (en) |
| DK (1) | DK171091B1 (en) |
| FI (1) | FI94688C (en) |
| ZA (1) | ZA872751B (en) |
Families Citing this family (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE59809932D1 (en) | 1997-07-04 | 2003-11-20 | Sew Eurodrive Gmbh & Co | ELECTRIC MOTOR AND METHOD FOR OPERATING AN ELECTRIC MOTOR |
| DE19730440A1 (en) * | 1997-07-16 | 1999-01-21 | Flender Himmelwerk Gmbh | Switchgear for electromagnetically operated assemblies |
| WO1999010975A1 (en) * | 1997-08-25 | 1999-03-04 | Sew-Eurodrive Gmbh & Co. | Method and circuit arrangement for operating an electromagnetically actuated mechanical brake of an electric motor |
| US5892341B1 (en) * | 1997-10-29 | 2000-06-27 | Rexnord Corp | Quick set electric motor brake control |
| DE19964437B4 (en) | 1999-02-24 | 2018-10-31 | Sew-Eurodrive Gmbh & Co Kg | distributor |
| DE102004013033B3 (en) * | 2004-03-16 | 2005-07-14 | Sew-Eurodrive Gmbh & Co. Kg | Drive for industrial use has brake(s) and electric motor supplied with alternating current from end stage via supply lines; brake is supplied from brake controller connected via capacitor(s) to supply line(s) and is supplied from this |
| DE102004022254B3 (en) | 2004-05-04 | 2005-06-30 | Sew-Eurodrive Gmbh & Co. Kg | Electrical coil e.g. electric motor braking coil, with coil former wound with winding coil connected to cable conductor or filament via sleeve with deformable tongue sections |
| DE102005027502B4 (en) * | 2004-10-22 | 2009-07-09 | Sew-Eurodrive Gmbh & Co. Kg | Electromagnetically actuated brake, device for safe control of an electromagnetically actuated brake, electric motor and brake |
| DE102005030085B4 (en) * | 2005-06-27 | 2007-06-06 | Sew-Eurodrive Gmbh & Co. Kg | Device and method for testing and / or monitoring of an electromagnetically actuated brake and electric motor with device |
| DE102006034049B4 (en) * | 2006-07-20 | 2014-08-07 | Sew-Eurodrive Gmbh & Co Kg | Electromagnetically actuated brake or clutch with air coil, method for operating the same and drive |
| JP5164875B2 (en) * | 2009-02-04 | 2013-03-21 | 株式会社日立製作所 | Electromagnetic brake control device for elevator |
| DE102009007961A1 (en) * | 2009-02-06 | 2010-08-19 | Sew-Eurodrive Gmbh & Co. Kg | Drive system, has energy storage and unipolar voltage, direct current link for supplying current to two inverters, respectively, and electric motor with stator windings that are inductively coupled with each other |
| EP2504600B1 (en) | 2009-11-26 | 2016-08-24 | SEW-EURODRIVE GmbH & Co. KG | Electromagnetically actuable brake and method for operating a brake |
| DE102010014860B4 (en) | 2010-04-13 | 2018-12-20 | Sew-Eurodrive Gmbh & Co Kg | Coil and brake |
| DE102020213640A1 (en) * | 2020-10-29 | 2022-05-05 | Maha Maschinenbau Haldenwang Gmbh & Co. Kg | Unlocking an electromagnetic brake of a motor |
| DE102022002146A1 (en) | 2021-07-12 | 2023-01-12 | Sew-Eurodrive Gmbh & Co Kg | Drive system with central module, distributors and drives |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3087104A (en) * | 1961-06-12 | 1963-04-23 | Gen Electric | Series brake system for alternating current motors |
| US3614565A (en) * | 1970-07-09 | 1971-10-19 | Harnischfeger Corp | Control for electromechanical brake |
| DE3045027C2 (en) * | 1980-11-28 | 1982-10-21 | Siemens AG, 1000 Berlin und 8000 München | Electrical circuit arrangement for an AC motor with an electromagnetically releasable spring pressure brake |
| DE3223260C2 (en) * | 1982-06-22 | 1984-10-25 | Eberhard Bauer Elektromotorenfabrik GmbH, 7300 Esslingen | Circuit arrangement for interrupting the freewheeling current for the release magnets of brake motors |
| JPS6013484A (en) * | 1983-07-01 | 1985-01-23 | Hitachi Ltd | Rotary electric machine with dc brake |
-
1986
- 1986-04-19 DE DE19863613294 patent/DE3613294A1/en active Granted
-
1987
- 1987-04-03 EP EP87104974A patent/EP0242671B1/en not_active Expired - Lifetime
- 1987-04-03 AT AT87104974T patent/ATE79204T1/en not_active IP Right Cessation
- 1987-04-03 DE DE8787104974T patent/DE3780850D1/en not_active Expired - Lifetime
- 1987-04-10 FI FI871579A patent/FI94688C/en not_active IP Right Cessation
- 1987-04-13 DK DK189087A patent/DK171091B1/en not_active IP Right Cessation
- 1987-04-14 CA CA000534642A patent/CA1290387C/en not_active Expired - Lifetime
- 1987-04-15 BR BR8701854A patent/BR8701854A/en not_active IP Right Cessation
- 1987-04-16 AU AU71768/87A patent/AU602685B2/en not_active Ceased
- 1987-04-16 ZA ZA872751A patent/ZA872751B/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| DK189087D0 (en) | 1987-04-13 |
| ZA872751B (en) | 1987-10-06 |
| DE3613294A1 (en) | 1987-10-22 |
| FI871579A (en) | 1987-10-20 |
| AU7176887A (en) | 1987-10-22 |
| FI94688B (en) | 1995-06-30 |
| FI94688C (en) | 1995-10-10 |
| DK171091B1 (en) | 1996-05-28 |
| EP0242671A2 (en) | 1987-10-28 |
| AU602685B2 (en) | 1990-10-25 |
| DE3780850D1 (en) | 1992-09-10 |
| DK189087A (en) | 1987-10-20 |
| BR8701854A (en) | 1988-01-26 |
| EP0242671A3 (en) | 1989-05-17 |
| ATE79204T1 (en) | 1992-08-15 |
| EP0242671B1 (en) | 1992-08-05 |
| DE3613294C2 (en) | 1991-05-23 |
| FI871579A0 (en) | 1987-04-10 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |