Title of Invention

A CONTROL CIRCUIT FOR CONTROLLING AN ELECTROMECHANICAL ELEVATOR BRAKE

Abstract A control circuit for controlling an electromechanical elevator brake, said control circuit comprising at least one brake coil (L1), a direct-voltage source (BR1), a semiconductor switch arrangement and a control unit (CO1) for controlling the circuit, and which circuit further comprises a current measuring unit (IM1) producing current data that can be passed to the control unit (CO1). The circuit comprises at least two semiconductor switches (SW1, SW2), and these can be controlled by the control unit (CO1) in an alternate manner such that the working condition of each switch can be checked in its turn on the basis of feedback data obtained from the current measurement.
Full Text A Control Circuit For Controlling An Electromechanical Elevator Brake
The present invention relates to a circuit for controlling an electromechanical
elevator brake.
The operation of an electromechanical brake of an elevator is such that when
the brake coil is currentless, the brake remains closed as a brake pad is
pressed against a braking surface by the force generated by a mechanical
pressure means, e.g. a spring. When a sufficient current is conducted to the
brake coil, the force produced by the magnetic field thus set up acts in a direc-
tion opposite to the force transmitted from the pressure element to the brake
pad and releases the brake, permitting rotation of the traction sheave and
movement of the elevator. The brake coil current needed to release the brake,
the so-called operating current, is larger than the holding current, which is
needed to keep the brake in the released state after it has already been re-
leased. The brake is said to be in an energized state when released, and corre-
spondingly in a de-energized state when the brake is closed. For operating
safety, it is essential to have a possibility to get the brake into the de-energized
state when necessary, which can be reliably implemented by interrupting the
supply of current to the brake coil.
To control the supply of electricity to electromechanical elevator brakes, contac-
tors connected to a direct-current circuit controlling the brake are generally
used. A direct voltage is obtained e.g. by means of a rectifier from an alternat-
ing-current circuit. As the contactor works on the direct-current side, it has to be
relatively large. Moreover, the contactor is a mechanical element subject to
wear with time. To ensure that a failure of the contactor in the direct-current cir-
cuit will not lead to a dangerous situation, the brake is additionally controlled by
contactors connected to the alternating-current side, which, however, is a rela-
tively slow process. A prior-art brake works in such manner that when the eleva-
tor stops, the control unit of the elevator drive controls a switch on the direct-


current side so as to cause the brake to start braking, whereupon the control
unit removes the torque from the elevator motor. After that, the contactors on
the alternating-current side are opened. If the control of the direct-current side
does not work or the switch has been damaged, the elevator will bound when
stopping, which involves a safety risk and gives the elevator passengers a feel-
ing of inconvenience. In addition, the control system of the elevator drive re-
ceives no feedback information regarding brake control.
In some prior-art elevator brake control circuits the contactor in the direct-
current circuit is replaced by a controlled semiconductor switch, such as a tran-
sistor. A control circuit of this type for controlling an electromagnetic brake is
disclosed in specification JP 2001278554. It describes a control circuit which
contains a direct-current circuit comprising a brake coil, a current measuring
circuit in series with it and a transistor controlling the brake coil. The direct-
current circuit receives a voltage via a rectifier from an alternating-current net-
work. In this specification, the brake is controlled by comparing the brake coil
current to a reference value and controlling the transistor using the comparison
value thus obtained. This arrangement is designed to reduce the noise, losses
and costs of the brake system. A drawback with the brake system according to
the specification in question is that the brake circuit comprises only one transis-
tor, which means that a failure of the transistor involves a safety risk. In addition,
the working condition of the transistor cannot be checked.
The object of the present invention is to overcome the drawbacks of prior art
and create an elevator brake that is more reliable than earlier brakes and a new
type of elevator brake control circuit wherein a possible failure of the switches
will be detected and whereby the brake can be reliably closed even in the event
of failure of a switch.
Accordingly, the present invention provides a control circuit for controlling an
electromechanical elevator brake, said control circuit comprising at least one


brake coil, a direct-voltage source, a semiconductor switch arrangement and a
control unit, and which circuit further comprises a current measuring unit pro-
ducing current data that can be passed to the control unit, characterized in that
the circuit comprises at least two semiconductor switches; and that the current
of each brake coil is controlled by two semiconductor switches; and that these
semiconductor switches can be controlled by the control unit in an alternate
manner such that the working condition of each switch can be checked in its
turn on the basis of feedback data obtained from the curent measurement.
The present invention also provides an electromechanical elevator brake, com-
prising at least a brake coil, a pressure element, a brake pad pressed towards a
braking surface by the pressure element, said brake pad being movable by the
action of the force effects of a magnetic field set up by a current flowing in the
brake coil, and a brake control circuit, characterized in that the current supplied
to the brake coil can be controlled by a control cicuit having a direct-current cir-
cuit with at least two semiconductor switches connected to it, and the brake coil
current can be completely interrupted by one semiconductor switch controlling it.
The supply of current to the brake coil can be completely interrupted by means
of one semiconductor switch connected to the direct-current circuit. The current
flowing through the brake coil can be measured by the current measuring unit.
The direct-voltage source is preferably a rectifier bridge, and the current in the
alternating-current network feeding the direct-voltage bridge can be measured
by the current measuring unit. The working condition of the semiconductor
switches can be monitored on the basis of the current measurement data both
when the brake is in a released state and when the brake is in a closed state.
The circuit comprises a voltage measuring unit arranged in parallel with the
brake coil and producing data that can be passed to the control unit. The state
of the brake can be determined continuously on the basis of measurement data
obtained from the circuit. The semiconductor switches have been arranged to
be opened when the safety circuit of the elevator is interrupted. The circuit is


preferably provided with a voltage measuring unit producing voltage data that
can also be used to control the semiconductor switches. The brake can be
closed at two different speeds. The control circuit comprises flywheel diodes
connected to it.
Inventive embodiments are also presented in the description part of and drawings
attached to the present application. The inventive content disclosed in the applica-
tion can also be defined in other ways than is done in the claims below. The in-
ventive content may also consist of several separate inventions, especially if the
invention is considered in the light of explicit or implicit sub-tasks or in respect of
advantages or sets of advantages achieved. In this case, some of the attributes
contained in the claims below may be superfluous from the point of view of sepa-
rate inventive concepts. Features of different embodiments of the invention can
be applied in connection with other embodiments within the framework of the
basic inventive concept.
The electromechanical elevator brake of the invention comprises at least a
brake coil, a pressure element, a brake pad pressed towards a braking surface
by the pressure element, said brake pad being movable by the force effects
produced by the magnetic field generated by a current flowing in the brake coil,
and a brake control circuit used to control the current supplied to the brake coil.
In respect of its mechanical structures, the brake may be e.g. like the brake dis-
closed in specification EP1294632. The brake control circuit contains two semi-
conductor switches connected to a direct-voltage circuit, and the brake coil cur-
rent can be completely switched off by a single functional semiconductor switch
connected to the direct-voltage circuit regardless of the operative condition of
the other switch.
The control circuit of the invention for controlling an electromechanical elevator
brake contains at least one brake coil, a direct-current source, a semiconductor
switch arrangement and a control unit as well as a current measuring unit pro-


ducing current data, which can be input to the control unit. The number of semi-
conductor switches used is at least two, and these are controlled by the elevator
drive control unit by measuring the current flowing in the direct-current circuit
and monitoring the operation of the semiconductor switches. The current of
each brake coil is controlled by two semiconductor switches. The switches can
be controlled alternately by the control unit in such manner that the working
condition of each switch can be checked in its turn by utilizing feedback data
obtained from the current measurement. The brake can be reliably de-energized
independently of the failure of a semiconductor switch in the direct-current cir-
cuit. The current state of the brake can be continuously determined by utilizing
measurement data collected from the circuit.
The semiconductor switches in the brake control circuit can also be controlled
and their condition monitored on the basis of the current measured from the
alternating-current circuit feeding the direct-current circuit via the rectifier, and to
allow more accurate determination of the state of the brake coil it is possible, if
necessary, to separately supply the control unit with information regarding the
voltage of the brake coil or the current flowing through it. The semiconductor
switches can also be controlled by voltage supply, e.g. so that the switches are
opened when the safety circuit is interrupted. Thus, the operation of the semi-
conductor switches can be controlled both via current measurement and via
voltage supply. The use of two semiconductor switches per brake coil makes it
possible to ensure the operation of the circuit in the case of failure of the semi-
conductor switches so that, in the control circuit of the invention, the supply of
current to each brake coil can be completely interrupted by means of one semi-
conductor switch connected to the direct-current circuit after the other semicon-
ductor switch controlling the brake has been damaged.
The details of the features of the control circuit of the invention are presented in
the claims below.


In addition to what was stated above, the invention provides the following ad-
vantages:
- the control circuit is a non-wearing, simple and reliable circuit, and due to
the use of semiconductor switches it is quieter than control circuits im-
plemented using contactors
- a failure of the semiconductor switches of the control circuit can be de-
tected very quickly, so the brake and its control circuit are reliable and
safe to use
- using the information obtained from the current measurement, it is possi-
ble both to monitor the operation of the switches, to monitor the operation
of the brake and to control the operation of the switches
- the condition of the brake can be determined and the brake adjusted
more reliably on the basis of the current measurement data than on the
basis of voltage data because the resistance of the brake coil changes as
a function of temperature
- the closing of the brake can be implemented using two different speeds
- the control circuit can be compatible with existing control circuits
- the same control circuit can be used to control several brakes
In the following, the invention will be described in detail with reference to exam-
ples and the accompanying drawings, wherein:
Fig. 1 presents a brake control circuit according to the invention for controlling
the brake of an elevator
Fig. 2 presents a second brake control circuit according to the invention for con-
trolling the brake of an elevator
Fig. 3 presents a third brake control circuit according to the invention for control-
ling the brake of an elevator


Fig. 4 presents a control circuit according to the invention wherein the same
circuit is used for simultaneous control of two brakes.
Fig. 1 represents a elevator brake control circuit, which contains a direct-current
circuit comprising a brake coil L1, a rectifier bridge BR1 connected to an alter-
nating-current network AC1, which may be e.g. a 230 V safety circuit, and semi-
conductor switches, e.g. IGBTs, SW1 and SW2, which are controlled by an ele-
vator drive control unit C01, each via a separate channel CH1 and CH2. In ad-
dition, the direct-current circuit comprises flywheel diodes D1 and D2, through
which the current fed by the brake coil indutance flows when only one of the
semiconductor switches is in the conducting state. In addition, the circuit com-
prises
a series connection of a resistor R1 and a diode D3, which is connected in par-
allel with the brake coil L1 and through which the current generated by the large
inductance of the coil L1 in a braking situation can be passed.
Moreover, the circuit comprises a direct current measuring unit IM1 producing
current data, which is input to the drive control unit, as well as a voltage regula-
tor VREG1 connected to the rectifier and a voltage measuring unit VM1 produc-
ing voltage data that can also be used to control the semiconductor switches.
The circuit presented in Fig. 1 works as follows. When the switches SW1 and
SW2 are open, no current is flowing in the direct-current circuit and the brake is
closed. This can be verified via the current measurement IM1. When the brake
is to be opened, the switches SW1 and SW2 are closed. In the circuit of the
invention, the supply of current from the DC supply BR1 to the brake coil is
completely interrupted when one of the switches is open, and thus, before re-
leasing the brake, the operating condition of the switches can be verified by al-
ternately closing the switches for a moment and establishing via the current
measuring unit that no current is flowing in the circuit. If the current measuring
unit detects a current already after one (e.g. SW1) of the switches has been


closed, then the other switch (SW2) has been damaged, and the elevator can
be denied permission to depart.
After the brake has been released, it is kept in the energized state by supplying
a hold current to the coil. The current to be fed to the coil is controlled by means
of the switches SW1 and SW2 by alternately turning the switches off, so that
when one of the switches is in the non-conducting state, the current flows via
the flywheel diode D1 or D2. The current measurement data is used both to de-
termine the actual value of the current supplied to the brake coil, on the basis of
which the current state of the brake can be established, and to verify that the
switches are working according to control. Thus, condition monitoring of the
switches is a continuous process, and the operating condition of the switches
can be checked on the basis of the current measurement data both when the
brake is in the released state and when it is in the closed state.
When the elevator is to stop, the brake is closed either by a fast control routine
by opening the switches SW1 and SW2 simultaneously, causing the energy
stored in the coil inductance to be consumed in the resistor R3 and the brake
coil current to fall rapidly, or by a slower control routine, causing the brake coil
current to fall more slowly. In this case, first one switch, e.g. switch SW1 is
opened, with the result that the energy stored in the coil inductance causes the
current to flow by the route L1-SW2-D2-IM1-L1. Next, switch SW2 is also turned
off, whereupon the current flows by the route L1-R1-D3-L1. By using the slow
control routine, the mechanical noise of the brake can be reduced to a lower
level than when the fast control routine is used. Interruption of the current is
again established via current measurement. After this, the torque can be re-
moved from the motor by the control unit CO1.
Besides using control commands transmitted via the channels CH1 and CH2,
the switches SW1 and SW2 can be controlled by a supply produced by the volt-
age measuring unit VM1. Voltage control may work e.g. in such manner that the


switches are opened every time when the voltage reaches too low a value, e.g.
due to a disturbance in the electricity supply or an interruption of the safety cir-
cuit.
Alternatively, the circuit can be used in such manner that the current to be fed to
the brake coil is regulated by setting the supply voltage by means of the voltage
regulator VREG1 to a value corresponding to the desired state of the brake. The
working condition of the switches can now be tested by turns in connection with
the closing and releasing of the brake. For example, when the elevator is to
stop, after the first switch, e.g. SW1 has been opened, the current measure-
ment IM1 indicates that the current starts to fall. The current is interrupted com-
pletely when switch SW2 is opened as well. In the following braking situation
again, switch SW2 is sent a control signal first and only then switch SW1, in
other words, during each successive control cycle the functionality of each
switch can be tested alternately by using current feedback data. In this case,
too, the braking can be performed at two different speeds: in a normal situation
at a slow speed, producing a low mechanical noise, and in a failure situation at
a high speed. The switches can be normally controlled by the slow stopping
procedure, but if the safety circuit on the alternating-current side is open, in
which case no voltage data is received from the voltage measuring unit, then
the braking is performed by the fast procedure.
If one of the semiconductor switches fails, the circuit will go on working normally
so that the brake coil current can be interrupted completely, but because one of
the switches is disengaged, the negative voltage pulse produced when the cur-
rent is switched off by both switches is left out.
Fig. 2 presents a control circuit that can be used in situations where only one
channel CH11 leads out of the electric drive control unit. If only one channel
CH11 leads out of the electric drive control unit (Fig. 2), then the control of the
switches SW1 and SW2 can be implemented by dividing the control function


between two different control circuits CH21 and CH22 in a separate brake con-
troller BO1. The control circuit works on the same principle as the circuit pre-
sented in Fig. 1.
Fig. 3 presents a control circuit according to the invention wherein the alternat-
ing-current network AC1, rectifier bridge BR1, semiconductor switches SW1 and
SW2, control unit CO1 with control channels CH1 and CH2, flywheel diodes D1
and D2, resistor R1 and diode D3 as well as the brake coil L1 are disposed as
in figures 1 and 2. A current measuring unit IM2 is placed on the side of the al-
ternating-voltage network, so it measures the current of alternating-current cir-
cuit feeding the direct-current circuit. The current measuring unit can also be
placed in other ways in the circuit than in the ways illustrated in figures 1-3, and
the circuit may have more than one current measurement point. In addition,
various voltages may be measured from the circuit. Fig. 3 shows two points P1
and P2 as examples of alternative locations of the current measurement point. If
placed at point P2, the current measuring unit measures the current flowing
through the brake coil even when the current is generated by the energy stored
in the coil inductance and the current is flowing through resistor R1 and diode
D3. In addition, Fig. 3 shows a voltage measuring unit VM2 arranged to meas-
ure the voltage across the brake coil. The voltage data produced by the unit can
be passed to the control unit and used as a basis on which the state of the
brake coil prevailing at each instant can also be determined. Fig. 3 additionally
shows a safety circuit SC1, which may comprise as a part of it the alternating-
current network AC1 feeding the rectifier bridge. The control of the switches
SW1 and SW2 can be so arranged that an interruption of the safety circuit will
lead to the opening of the switches.
Fig. 4 presents a control circuit according to the invention which is used to con-
trol two brakes simultaneously. The circuit comprises a branch consisting of a
second brake coil L2, a series connection of a resistance R2 and a diode D5
connected in parallel with it and a switch SW3, said branch being connected in


parallel with the circuit part consisting of brake coil L1, resistance R1, diode D3
and switch SW2. From a point between coil L2 and switch SW3, flywheel diode
D4 provides a flow path for the current supplied by the inductance of coil L2
when switch SW3 is open, corresponding to the flow path provided by diode D1
for the current of coil L1. In the circuit in Fig. 4, the measurement of current has
been arranged in such manner that the current measuring unit IM1 measures
the current flowing through both brake coils. If the states of the brakes are to be
monitored separately, then it is possible to provide a separate current measur-
ing unit for each brake, from which units the current data can be passed to the
control unit. These can be placed e.g. at points P3 and P4. Resistors R1 and R2
may have either equal or unequal resistance values, and in the latter case, in a
fast stopping procedure, one of the brakes will work faster, the other more
slowly.
The circuit presented in Fig. 4 can be used in such manner that that the current
of the brake coils is only controlled by switches SW1 and SW3, in which case
each brake can be controlled independently regardless of the control of the
other brake. The condition of the switches SW2 and SW3 is monitored continu-
ously, and the condition of switch SW1 is monitored when both brakes are in
the closed state. If diode D2, depicted by a broken line in the figure, is also
added to the circuit, then the current of the brake coil L1 can be controlled by
switches SW1 and SW2 and the current of brake coil L2 by switches SW1 and
SW3. Thus, all three switches are controlled alternately in such manner that the
working condition of each switch can be checked via current measurement IM1
both when the brake is in the energized state and when it is in the de-energized
state. Furthermore, the states of brakes can be chosen independently of each
other, but the states of both brakes are taken into account in the control of the
switches. The supply of current to each brake coil can be interrupted completely
when necessary by means of the switch controlling the current of one of the
coils, e.g. when the other switch is damaged.

It is obvious to the person skilled in the art that different embodiments of the
invention are not limited to the embodiments described above by way of exam-
ple, but that many variations and applications of the invention are possible
within the scope of the inventive concept defined in the claims below.


WE CLAIM :
1. A control circuit for controlling an electromechanical elevator brake,
said control circuit comprising at least one brake coil (L1), a direct-voltage
source (BR1), a semiconductor switch arrangement and a control unit (CO1),
and which circuit further comprises a current measuring unit (IM1) producing
current data that can be passed to the control unit (CO1), characterized in that
the circuit comprises at least two semiconductor switches (SW1, SW2);
and in that the current of each brake coil is controlled by two semicon-
ductor switches (SW1, SW2);
and in that these semiconductor switches (SW1, SW2) can be con-
trolled by the control unit (CO1) in an alternate manner such that the working
condition of each switch can be checked in its turn on the basis of feedback
data obtained from the current measurement.
2. A control circuit as claimed in claim 1, wherein the supply of current to
the brake coil can be completely interrupted by means of one semiconductor
switch connected to the direct-current circuit.
3. A control circuit as claimed in claim 1 or 2, wherein the current flowing
through the brake coil can be measured by the current measuring unit.
4. A control circuit as claimed in any one of claims 1 to 3, wherein the di-
rect-voltage source (BR1) is a rectifier bridge, and the current in the alternating-
current network feeding the direct-voltage bridge can be measured by the cur-
rent measuring unit.
5. A control circuit as claimed in any one of claims 1 to 4, wherein the
working condition of the semiconductor switches can be monitored on the basis
of the current measurement data both when the brake is in a released state and
when the brake is in a closed state.


6. A control circuit as claimed in any one of claims 1 to 5, wherein the cir-
cuit comprises a voltage measuring unit (VM2) arranged in parallel with the
brake coil and producing data that can be passed to the control unit (CO1).
7. A control circuit as claimed in any one of claims 1 to 6, wherein the
state of the brake can be determined continuously on the basis of measurement
data obtained from the circuit.
8. A control circuit as claimed in any one of claims 1 to 7, wherein the
semiconductor switches have been arranged to be opened when the safety cir-
cuit of the elevator is interrupted.
9. A control circuit as claimed in any one of claims 1 to 8, wherein the cir-
cuit is provided with a voltage measuring unit (VM1) producing voltage data that
can also be used to control the semiconductor switches.
10. A control circuit as claimed in any one of claims 1 to 9, wherein the
brake can be closed at two different speeds.
11. A control circuit as claimed in any one of claims 1 to 10, wherein the
control circuit comprises flywheel diodes (D1 ,D2) connected to it.
12. An electromechanical elevator brake, comprising at least a brake coil, a
pressure element, a brake pad pressed towards a braking surface by the pres-
sure element, said brake pad being movable by the action of the force effects of
a magnetic field set up by a current flowing in the brake coil, and a brake control
circuit, characterized in that the current supplied to the brake coil can be con-
trolled by a control circuit having a direct-current circuit with at least two semi-
conductor switches connected to it, and the brake coil current can be completely
interrupted by one semiconductor switch controlling it.

Documents:

00720-kolnp-2006-abstract.pdf

00720-kolnp-2006-claims.pdf

00720-kolnp-2006-description complete.pdf

00720-kolnp-2006-drawings.pdf

00720-kolnp-2006-form 1.pdf

00720-kolnp-2006-form 3.pdf

00720-kolnp-2006-form 5.pdf

00720-kolnp-2006-international publication.pdf

00720-kolnp-2006-international search report.pdf

00720-kolnp-2006-pct request form.pdf

00720-kolnp-2006-priority document.pdf

720-KOLNP-2006-ABSTRACT.1.1.pdf

720-kolnp-2006-assignment.pdf

720-kolnp-2006-correspondence.pdf

720-KOLNP-2006-DESCRIPTION (COMPLETE).1.1.pdf

720-KOLNP-2006-DRAWINGS.1.1.pdf

720-KOLNP-2006-EXAMINATION REPORT REPLY RECIEVED.pdf

720-kolnp-2006-examination report.pdf

720-KOLNP-2006-FORM 1.1.1.pdf

720-kolnp-2006-form 18.pdf

720-KOLNP-2006-FORM 2.pdf

720-KOLNP-2006-FORM 3.1.1.pdf

720-kolnp-2006-form 3.pdf

720-kolnp-2006-form 5.pdf

720-KOLNP-2006-FORM-27-1.pdf

720-KOLNP-2006-FORM-27.pdf

720-kolnp-2006-gpa.pdf

720-kolnp-2006-granted-abstract.pdf

720-kolnp-2006-granted-claims.pdf

720-kolnp-2006-granted-description (complete).pdf

720-kolnp-2006-granted-drawings.pdf

720-kolnp-2006-granted-form 1.pdf

720-kolnp-2006-granted-form 2.pdf

720-kolnp-2006-granted-specification.pdf

720-KOLNP-2006-OTHERS DOCUMENTS.pdf

720-kolnp-2006-others.pdf

720-KOLNP-2006-PA.pdf

720-KOLNP-2006-PETETION UNDER RULE 137.pdf

720-kolnp-2006-reply to examination report.pdf

abstract-00720-kolnp-2006.jpg


Patent Number 247925
Indian Patent Application Number 720/KOLNP/2006
PG Journal Number 23/2011
Publication Date 10-Jun-2011
Grant Date 06-Jun-2011
Date of Filing 27-Mar-2006
Name of Patentee KONE CORPORATION
Applicant Address KARTANONTIE 1, FI-00330, HELSINKI
Inventors:
# Inventor's Name Inventor's Address
1 KATTAINEN ARI TIILITEHTAANTIE 9, FI-5830 HYVINKAA
2 SYRMAN TIMO PIHALAMMENTIE 4, FI-05460, HYVINKAA
PCT International Classification Number B66B 1/44
PCT International Application Number PCT/FI2004/000668
PCT International Filing date 2004-11-10
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 20031647 2003-11-12 Finland