BACKGROUND
The present invention relates to elevator speed monitoring. Elevators have
electromechanical brakes that apply to a traction sheave or rotating axis of a
5 hoisting machine to stop movement of the hoisting machine and therefore an
elevator car driven by the hoisting machine. A hoisting machine normally has
two electromechanical brakes. The brakes have to be dimensioned to stop and
hold an elevator car with 125% load (25% overload) at standstill in the elevator
shaft. The brakes may be used in rescue situations and in emergency braking
10 to stop the elevator car if an operational fault occurs, such as an overspeed
situation of the elevator car or a power failure.
Traditionally elevator is driven with steel ropes running via the traction sheave
of the hoisting machine. When hoisting machinery brakes are closed to stop
elevator car movement, steel ropes slip on the traction sheave to reduce
15 deceleration of the elevator car, which deceleration might otherwise be
uncomfortable or even dangerous to the elevator passengers.
Recently new kind of coated hoisting ropes have been introduced. These may
be traditional round steel ropes with a high-friction coating, or belts with highfriction
coating, such as a polyurethane coating. Load-carrying parts of the belts
2 0 maybe steel cords or they can be made of synthetic fibers, such as glass fibers
or carbon fibers, for example.
These new kind of coated hoisting ropes cause a higher friction between the
ropes and the traction sheave. Reduction in slipping of the ropes on the traction
sheave may lead to increased deceleration of elevator car in the emergency
2 5 stopping situation, which is a non-desired condition for the elevator passengers.
SUMMARY
According to the invention, an elevator is provided. The elevator comprises: an
30 elevator shaft defined by surrounding walls and top and bottom end terminals;
1
an elevator car vertically movable in the elevator shaft; an elevator hoisting
machinery adapted to drive the elevator car; an electromechanical braking
apparatus configured to brake movement of the elevator car; a first measuring
device adapted to provide first position data and first speed data of the elevator
5 car; a second measuring device adapted to provide at least second position
data of the elevator car; and a safety monitoring unit communicatively
connected to the first measuring device and the second measuring device. The
safety monitoring unit is configured to determine a synchronized position of the
elevator car from the first and the second position data, and to determine an
10 elevator car slowdown failure in the proximity of the top or the bottom end
terminal from the first speed data and from the synchronized position of the
elevator car. The safety monitoring unit is adapted to cause braking of the
elevator car at least with the electromechanical braking apparatus upon
determination of the slowdown failure.
15 Synchronized position means position data provided by the first measuring
device and then verified and, if necessary, also corrected by means of
independent position data from the second measuring device, to improve
reliability and accuracy and thus safety of said position data. In an embodiment,
the first measuring device is a pulse sensor unit and the second measuring
20 device is a door zone sensor.
This can mean that a distributed electronic safety system with a programmable
safety monitoring unit and measuring devices communicatively connected to
the programmable safety monitoring unit is used to perform the safety-related
ETSL (emergency terminal speed limit) elevator braking function. The first
25 measuring device may be flexibly disposed in suitable positions in the elevator
system. For example, the first measuring device may be a pulse sensor unit
mounted to suitable elevator components, such as to an elevator car, to an
overspeed governor, to a guide roller of an elevator car and / or at one or more
elevator landings.
30 According to an embodiment, the pulse sensor unit is mounted to rope pulley
of an elevator car. Elevator car may be suspended on the hoisting ropes
through the rope pulley. The pulse sensor unit may be adapted to measure
2
rotation speed of the rope pulley. Rotation speed of the rope pulley indicates
speed of the hoisting ropes running via the rope pulley, and therefore speed of
the car.
According to an embodiment, the elevator comprises a safety buffer of an
5 elevator car associated with the bottom end terminal of the elevator shaft.
According to an embodiment, the safety monitoring unit is adapted to cause
braking of the elevator car with the electromechanical braking apparatus to
decelerate car speed to the terminal speed of the top or bottom end terminal
upon determination of the slowdown failure. Terminal speed of the top or bottom
10 end terminal means highest allowed speed at said top or bottom end terminal.
Highest allowed speed of the top end terminal may be zero speed, to avoid
collision at the top end terminal. If the elevator comprises a safety buffer of an
elevator car associated with the bottom end terminal of the elevator shaft,
terminal speed of the bottom end terminal may be the allowed buffer impact
15 speed, i.e. the highest allowed structural speed of the safety buffer for elevator
car to safely hit the buffer.
According to an embodiment, the elevator further comprises an inductive
braking apparatus configured to brake movement of the elevator car. The safety
monitoring unit is adapted to cause braking of the elevator car with the
20 electromechanical braking apparatus in tandem with the inductive braking
apparatus to decelerate car speed to the terminal speed of the top or bottom
end terminal upon determination of the slowdown failure. The inductive braking
apparatus means a braking apparatus operating on inductive power, such as a
dynamic braking apparatus which generates braking torque by short-circuiting
25 windings of a rotating hoisting machinery. Therefore braking current is
generated from the electromotive force caused by rotation of the hoisting
machinery.
According to an embodiment, the electromechanical braking apparatus is used
for the safety-related ETSL (emergency terminal speed limit) elevator braking
30 function.
3
According to another embodiment, an inductive braking apparatus is used in
tandem with an electromechanical braking apparatus for the safety-related
ETSL (emergency terminal speed limit) elevator braking function. A smaller
electromechanical braking apparatus, i.e. an electromechanical braking
5 apparatus dimensioned for smaller braking torque, may be used, for example,
in elevators in high-rise buildings, because the braking torque of the inductive
braking apparatus can be taken into account when dimensioning the overall
ETSL braking system. By means of this smaller electromechanical braking
apparatus deceleration of the elevator car may be reduced to an acceptable
10 level also in elevators with coated hoisting ropes, in particular in high-rise
elevators with coated hoisting ropes.
According to an embodiment, the safety monitoring unit is configured to
calculate from the current speed data onwards, with the maximum acceleration,
speed prediction for the elevator car speed after reaction time of the
15 electromechanical braking apparatus and to calculate from the current
synchronized position onwards, with the maximum acceleration, the closest
possible position of an approaching elevator car to the top or bottom end
terminal after reaction time of the electromechanical braking apparatus, to
calculate a maximum initial speed for the elevator car to decelerate from said
20 closest possible position to the terminal speed of said top or bottom end
terminal, and to determine an elevator car slowdown failure if said speed
prediction meets or exceeds said maximum initial speed. Maximum
acceleration means highest possible (constant or variable) acceleration of the
elevator car within capacity of the drive system. Reaction time of the
25 electromechanical braking apparatus means time delay from detection of fault
by the safety monitoring unit to the moment electromechanical braking
apparatus actually engages the rotating part of the hoisting machinery (in case
of hoisting machinery brakes) or elevator guide rail (in case of car brake) and
starts braking of the elevator car.
30 According to an embodiment, the electromechanical braking apparatus
comprises two electromechanical brakes adapted to apply a braking force to
brake movement of the elevator car. Thus braking action with adequate braking
4
force may be performed even if one electromechanical brake fails (fail-safe
operation).
According to an embodiment, the electromechanical braking apparatus
comprises two electromechanical hoisting machinery brakes.
5 According to an embodiment, the electromechanical braking apparatus
comprises one or more car brakes, which is / are mounted to elevator car and
adapted to brake elevator car movement by engaging (e.g. wedging or
pressing) against a longitudinal braking element(s), such as guide rail(s) of
elevator car and / or guide rail(s) of elevator counterweight.
10 According to an embodiment, the inductive braking apparatus comprises at
least one, preferably at least two inductive braking devices.
According to an embodiment, the elevator comprises: a first monitoring circuit
configured to indicate operation of the electromechanical braking apparatus; a
second monitoring circuit configured to indicate operation of the inductive
15 braking apparatus; and a control device communicatively connected to the first
monitoring circuit and to the second monitoring circuit, the control device
configured to cause a safety shutdown of the elevator on the basis of a
communication indicating a malfunction of at least one of the electromechanical
braking apparatus and the inductive braking apparatus. In a preferred
2 0 embodiment, the control device is the safety monitoring unit.
According to an embodiment, the first monitoring circuit comprises a sensor,
such as a switch or a proximity sensor for sensing position and / or movement
of an armature of the electromechanical brake.
According to an embodiment, the inductive braking device comprises a
25 mechanical contactor having at least two contacts adapted to short phases of
an elevator hoisting machinery, and wherein the second monitoring circuit
comprises at least two auxiliary contacts of the mechanical contactor, said
auxiliary contacts co-acting with the at least two contacts, respectively, to
indicate switching state of the at least two contacts.
5
According to an alternative embodiment, the inductive braking device
comprises at least two solid state switches adapted to short phases of the
elevator hoisting machinery. The solid state switches may belong to the inverter
which supplies electrical power to the elevator hoisting machinery.
5 According to an embodiment, the electromechanical braking apparatus is
dimensioned to stop the elevator car when it is travelling downward at nominal
speed and with a 25% overload.
According to an embodiment, the combination of the electromechanical braking
apparatus and the inductive braking apparatus is dimensioned to decelerate
10 car speed from the maximum initial speed to the terminal speed of said top or
bottom end terminal within the distance between the closest possible position
of an approaching elevator car and the top or bottom end terminal.
According to an embodiment, the safety monitoring unit is adapted to provide a
common control signal to control the electromechanical braking apparatus in
15 tandem with the inductive braking apparatus.
According to an embodiment, the safety monitoring unit is adapted to provide
separate control signals for the electromechanical braking apparatus and the
inductive braking apparatus.
The term "inductive braking apparatus" means a braking apparatus operated
20 by inductive power, e.g. power generated by the braking / regenerating motor
of the hoisting machinery. According to an embodiment, a motor inverter
operating in regenerative mode, receiving electrical power from the motor is an
"inductive braking apparatus".
2 5 According to an embodiment, the inductive braking apparatus is a dynamic
braking apparatus comprising an elevator hoisting motor and one or more
switches adapted to provide a short-circuit to windings of the elevator hoisting
motor. In some embodiments, the dynamic braking apparatus comprises two
elevator hoisting motors mounted to the same hoisting machinery. The dynamic
30 braking apparatus further comprises switches adapted to provide a short-circuit
to the winding of said two elevator hoisting motors.
6
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are included to provide a further
understanding of the invention and constitute a part of this specification,
5 illustrate embodiments of the invention and together with the description help
to explain the principles of the invention. In the drawings:
FIG. 1A illustrates a sideview of an elevator according to an embodiment.
10 FIG. 1B illustrates afrontview of an elevator hoisting machinery suitable to the
embodiment of Fig. 1A.
FIG. 2 illustrates implementation of speed prediction for elevator car speed
according to an embodiment.
15
FIG. 3 illustrates determination of elevator car slowdown failure according to an
embodiment.
DETAILED DESCRIPTION
20 The following description illustrates a solution that monitors elevator car
movement in the proximity of end terminals of elevator shaft. In case of
slowdown failure of the elevator car, emergency stop may be performed to bring
elevator to a safe state. This solution may constitute an ETSL (emergency
terminal speed limiting device) safety function required by elevator safety rules
25 (EN 81-20 2014 paragraph 5.12.1.3; A17.1 2016 paragraph 2.25.4.1).
Figure 1A illustrates an elevator having an elevator car 4 and a counterweight,
which are arranged to move vertically in an elevator shaft 1, which is defined
by surrounding walls 25 and top 3A and bottom 3B end terminals. Elevator
7
comprises a hoisting machinery 6 including a rotating sheave 8. Hoisting ropes
9 of the elevator car 4 run via the sheave 8. When the sheave 8 rotates, elevator
car 4 moves in a first vertical direction and the counterweight moves is a
second, opposite direction. As depicted in figure 1B, hoisting machinery 6 of
5 Fig. 1A may contain two permanent magnet motors 7A, 7B arranged on the
same rotating axis with the sheave 8. Electrical power to the permanent magnet
motors 7A, 7B is provided with a drive unit 10 (e.g. a frequency converter) from
the mains 11, as illustrated in Fig. 1A. Drive unit 10 performs speed regulation
of the elevator car 4 moving between the landings 16 to serve elevator
10 passengers. In some alternative embodiments, the hoisting machinery 6 may
contain only one permanent magnet motor. Instead of permanent magnet
motor(s), the hoisting machinery 6 may contain a suitable alternative, such as
an induction motor, a reluctance motor, a stator-mounted permanent magnet
(SMPM) motor or corresponding. Instead of rotating motor, a linear motor may
15 be used to provide propulsion force to the elevator car 4.
The elevator of Fig. 1A is provided with electromechanical hoisting machinery
brakes 12A, 12B, as safety devices to apply braking force, either directly to the
sheave 8 or via a rotating shaft, to brake movement of the hoisting machinery
6 and therefore the elevator car 4. There are normally two separate brakes 12A,
20 12B, as illustrated in the figure 1A. The brakes 12A and 12B are altogether
dimensioned to stop and hold an elevator car with 125% load (25% overload)
at standstill in the elevator shaft 1. Additionally or alternatively, elevator may
have electromechanical car brakes, which are mounted to the elevator car 4
and which act on guide rails of elevator car 4 to brake movement of the elevator
25 car 4.
Further, the elevator has dynamic braking contactors 13A, 13B. Contacts of the
dynamic braking contactors 13A, 13B are connected across the terminals of the
permanent magnet motors 7A, 7B of the hoisting machinery 6. When the
contacts are closed, they short the windings of the permanent magnet motors
30 7A, 7B. Shorting of the windings causes dynamic braking current in the
windings, when the permanent magnet motors rotate and generate
electromotive force (emf). This means that the dynamic braking contactors 13A,
8
13B together with the permanent magnet motors 7A, 7B act as inductive
braking devices. Contacts on the dynamic braking contactors 13A, 13B are NC
(normally closed) type, so they are closed when current supply is interrupted to
the control coils of the contactors.
5 In some alternative embodiments, solid state switches, such as bipolar
transistors, igbt -transistors, mosfet -transistors, silicon carbide (SiC)
transistors or gallium nitride transistors are used instead of mechanical dynamic
braking contactors 13A 13B.
According to the embodiment of Fig. 1A, the inductive braking devices 13A,
10 13B; 7A, 7B operate as an assistive brake for the electromechanical hoisting
machinery brakes 12A, 12B. When the elevator car 4 moves in the proximity of
the end terminal 3A, 3B (that is, in the shaft section where the speed of an
approaching elevator elevator car is decelerated from nominal speed to the
allowed terminal speed of the end terminal 3A, 3B), an ETSL (Emergency
15 Terminal Speed Limit) safety function is used for speed monitoring of the
elevator car. The inductive braking device 13A, 13B; 7A, 7B is used in tandem
with the electromechanical hoisting machinery brakes 12A, 12B to perform the
emergency stop actuated by the ETSL safety function. Thus, less braking force
is required from the electromechanical brakes, and the electromechanical
20 brakes may be dimensioned to be smaller. The ETSL safety function is
implemented in the safety program of the safety monitoring unit 17, which is a
programmable elevator safety device fulfilling safety integrity level 3 (SIL 3).
The elevator of Fig. 1A has a first measuring device 14A, 14B, 14C adapted to
provide first position data and first speed data of the elevator car. In some
25 embodiments the first measuring device is a pulse sensor unit 14A, 14B. Pulse
sensor unit 14A may comprise a magnet ring arranged in the overspeed
governor OSG 12. Alternatively, in the pulse sensor unit 14B the magnet ring
may be arranged in a roller guide RG of the elevator car 4. The pulse sensor
unit 14A, 14B may comprise at least one quadrature sensor, one or more
30 processors, one or more memories being volatile or non-volatile for storing
portions of computer program code and any data values, a communication
interface and possibly one or more user interface units. The mentioned
9
elements may be communicatively coupled to each other with e.g. an internal
bus. The at least one quadrature sensor is configured to measure incremental
pulses from the rotating magnet ring arranged in OSG or RG. The magnetic
ring may comprise alternating evenly spaced north and south poles around its
5 circumference. The at least one quadrature sensor may be a Hall sensor, for
example. Furthermore, the at least one quadrature sensor has an A/B
quadrature output signal for the measurement of magnetic poles of the magnet
ring. Furthermore, the at least one quadrature sensor may be configured to
detect changes in the magnetic field as the alternating poles of the magnet pass
10 over it. The output signal of the quadrature sensor may comprise two channels
A and B that may be defined as pulses per revolution (PPR). Furthermore, the
position in relation to the starting point in pulses may be defined by counting
the number of pulses. Since, the channels are in quadrature more, i.e. 90
degree phase shift relative to each other, also the direction the of the rotation
15 may be defined. The communication interface provides interface for
communication with the at least one quadrature sensor and with the safety
monitoring unit 17. The communication interface may be based on one or more
known communication technologies, either wired or wireless, in order to
exchange pieces of information as described earlier. Preferably, the
20 communication interface may be implemented as a safety bus with at least
partly duplicated communication means.
The processor of the pulse sensor unit is at least configured to obtain the
quadrature signal from the at least one quadrature sensor, define the pulse
position information based on the quadrature signals, define speed based on
25 pulse intervals and /or number of pulses per time unit, and to store the defined
pulse position information and speed into the memory. The processor is thus
arranged to access the memory and retrieve and store any information
therefrom and thereto. For sake of clarity, the processor herein refers to any
unit suitable for processing information and control the operation of the pulse
30 sensor unit, among other tasks. The operations may also be implemented with
a microcontroller solution with embedded software. Similarly, the memory is not
limited to a certain type of memory only, but any memory type suitable for
10
storing the described pieces of information may be applied in the context of the
present invention.
In an alternative embodiment, the first measuring device 14C may be
implemented with a tape extending along elevator car trajectory in the shaft 1.
The tape may contain readable markings. The readable markings may be for
example optically readable markings, such as a barcode or 2D barcode, or in
the form of variable magnetic field, which can be read with a suitable sensor,
such as one or more hall -sensors. Elevator car may have a suitable reader
device adapted to read the markings of the tape. The reader device may be
configured to determine first elevator car position from the markings of the tape,
as well as elevator car speed from the timely variation of the markings as
elevator car 4 passes them. The reader device may be communicatively
connected to the safety monitoring unit 17 via a suitable communication
channel, such as a safety bus.
Further, the elevator of Fig. 1A has a second measuring device 15A, 15B. In
the embodiment of Fig. 1A the second measuring device is a door zone sensor
comprising a reader device 15 A mounted to elevator car 4 and magnets 15B
mounted to each landing 16 to indicate door zone position, i.e. the position at
which landing floor and elevator car floor are at same level to allow entering or
exiting the car. The reader device has hall sensors and a processor. Reader
device 15A is adapted to read variation of magnetic field from the magnet 15B
and determine linear door zone position of the elevator car 4 therefrom. Each
magnet 15B may also comprise an identification of the magnet. Identification
may be included in the magnetic field pattern of the magnet 15B. Identification
may also be implemented with a separate portion, such as with an rfid tag. In
this case reader device 15A may comprise an rfid tag reader. With the
identification it is possible to determine absolute door zone position of the
elevator car 4 when car arrives to the magnet 15B. The reader device 15A is
communicatively connected to the safety monitoring unit 17 via a suitable
communication channel, such as a safety bus running in the travelling cable
between elevator car 4 and the safety monitoring unit 17.
11
Every time the elevator car 4 arrives to the landing magnet 15B (e.g. stops to
the magnet or passes it), absolute door zone position of elevator car 4 is
determined and sent to the safety monitoring unit 17. During normal operation,
safety monitoring unit 17 compares the first elevator car position received from
5 the first measuring device 14A, 14B, 14C with the absolute door zone position
received from the second measuring device 15A, 15B and synchronizes the
first position information with the absolute door zone position. Thus, if there is
only a minor difference between the compared positions, safety monitoring unit
17 corrects the first position information by adding a correction term to the first
10 position information such that the first position information corresponds to the
absolute door zone position of the second measuring device. If the comparison
leads to the conclusion that the difference between first position information and
absolute door zone position is too high to be allowable, safety monitoring unit
17 cancels normal elevator operation until a corrective measure, such as a
15 maintenance operation or a low-speed calibration run of the elevator car is
carried out.
Alternatively or in addition, the first position information and / or elevator car
speed and / or the absolute door zone position information of the elevator car
4 may be defined at two channels in order to certainly meet the SIL3 level
20 reliability. In order to define two-channel position / speed information the pulse
position information and door zone information may be obtained at two
channels. The two-channel pulse position and speed information may be
obtained from of the pulse sensor unit comprising one quadrature sensor and
at least one processor at each channel. Furthermore, the two-channel door
25 zone position information may be obtained from the door zone sensor unit
comprising at least one Hall sensor and at least one processor at each channel.
The above presented method safety control unit, and elevator system may be
implemented for two channels similarly as described above for one channel.
30 Next, figures 2 and 3 are used to illustrate how the ETSL safety monitoring
function is carried out by means of the safety monitoring unit 17.
12
As already mentioned above, the safety monitoring unit 17 receives first
position data of elevator car from the first measuring device 14A, 14B, 14C and
absolute door zone position information (second position data) from the door
zone sensor (second measuring device) and determines synchronized position
19 of the elevator car from the first and second position data.
Safety monitoring unit 17 receives also elevator car speed data from the first
measuring device 14A, 14B, 14C. By means of the synchronized position and
the elevator car speed data, safety monitoring unit 17 performs ETSL
monitoring. When the ETSL monitoring results in determining a slowdown
failure of an elevator car approaching the end terminal 3A, 3B of the elevator
shaft, safety monitoring unit 17 causes braking of the elevator car 4 with the
electromechanical hoisting machinery brakes 12A, 12B in tandem with the
inductive braking devices 13A, 13B; 7A, 7B. Next, more detailed
implementation of the ETSL monitoring is disclosed.
In figure 2 it is illustrated, how the safety monitoring unit 17 calculates from the
current speed data 20 (vo) onwards, with the maximum acceleration (amax),
speed prediction 21 (vP) for the elevator car speed after reaction time tr of the
electromechanical hoisting machinery brakes 12A, 12B:
VP= v0+ Camax(f)dt. (1)
Maximum acceleration amax means the highest possible constant or variable
acceleration of the elevator car within capacity of the drive system; in other
words the highest possible acceleration of elevator car in case of an operational
anomaly of the drive system. Therefore, the speed prediction 21 (vP) gives the
worst-case scenario for elevator car speed in case of an operational anomaly.
Reaction time tr means estimated time delay from detection of a fault by the
safety monitoring unit 17, to the moment that braking torque of the hoisting
machinery brakes 12A, 12B has increased to an adequate level, to decelerate
elevator car 4 movement. In some embodiments the adequate level is nominal
13
braking torque. In some other embodiments the adequate level may be lower,
for example 2/3 of the nominal braking torque.
Turning now to Figure 3, the safety monitoring unit 17 calculates from the
current synchronized position 19 (xo) onwards, with the maximum acceleration
5 amax, the closest possible position (xP) of an approaching elevator car 4 to the
top 3A or bottom 3B end terminal of the elevator shaft 1 after reaction time tr of
the electromechanical braking apparatus 12A, 12B:
xv= x0+ v0tr + JJ0
tr amax{t]dH (2)
10
Therefore, the calculated closest possible position xP gives the worst-case
scenario for the initial position when braking of the approaching elevator car
starts in case of an operational anomaly of the drive system.
The safety monitoring unit 17 calculates maximum initial speed 22 (viim) for the
15 elevator car 4 to decelerate, with the minimum average deceleration abr
resulting from the combined (average) braking torque of the hoisting machinery
brakes 12A, 12B and the inductive braking device 13A, 13B; 7A, 7B from said
closest possible position xP to the terminal speed vt of said top 3A or bottom 3B
end terminal:
20
vum = Jvt
2 + 2abr *xv- vs (3)
In the current embodiment terminal speed vt of top end terminal 3A is zero and
terminal speed vt of bottom end terminal 3B is highest allowed buffer impact
25 speed 18. Buffer impact speed depends on the dimensioning of the buffer and
it could be, for example a fixed value between 3.5 m/s and 1m/s. However the
value could be even higher or lower.
14
The safety monitoring unit 17 determines an elevator car slowdown failure if the
speed prediction 21 (worst-case scenario for elevator car speed) vp exceeds
the maximum initial speed 22 viim. In some embodiments, an applicationspecific
safety margin vs is also added to the equation (3) above to slightly lower
the slowdown failure tripping limit viim. The safety margin vs may be, for
example, 2 - 5% of the nominal travelling speed of the elevator car 4. Upon
determination of the slowdown failure, the safety monitoring unit 17 generates
safety control commands for the hoisting machinery brakes 12A, 12B and the
inductive braking device 13A, 13B; 7A, 7B. Safety control command may be,
for example, a data signal sent via a safety bus or it may be implemented by
cutting a safety signal, which is continuously active during normal elevator
operation. Responsive to the safety control command, hoisting machinery
brakes are actuated to brake movement of the elevator car 4 and the inductive
braking apparatus 13A, 13B; 7A, 7B starts assisting dynamic braking with the
motors 7A, 7B to decelerate car speed to the terminal speed of the top 3A or
bottom 3B end terminal. In some embodiments the safety monitoring unit 17
generates a common safety control command to control the electromechanical
braking apparatus 12A, 12B in tandem with the inductive braking apparatus
13A, 13B. In some alternative embodiments the safety monitoring unit 17
generates separate safety control commands for the hoisting machinery brakes
12A, 12B and the inductive braking devices 13A, 13B such that they may be
actuated separately and / or at different times.
Because the hoisting machinery brakes 12A, 12Band inductive braking devices
13A, 13B; 7A, 7B are ETSL safety devices, their operational condition is
monitored to assure high safety level. Thus a first monitoring circuit 23 in the
form of movement sensors is mounted to the hoisting machinery brakes.
Movement sensors may be, for example, switches or proximity sensors adapted
to measure movement or position of the hoisting machinery brake armature
12A, 12B relative to brake frame. A mismatch between a control command (e.g.
a safety control command), and measured brake armature movement indicates
malfunction of the hoisting machinery brake 12A, 12B. Further, a second
monitoring circuit is established by means of auxiliary contacts 24 of the
15
dynamic braking contactors 13A, 13B of the inductive braking devices 13A,
13B; 7A, 7B. Auxiliary contacts are normally closed (NC) type and they are
connected in series to form a chain that is closed when dynamic braking
contactors are de-energized. Thus an open chain of auxiliary contacts of a de-
5 energized contactor indicates a malfunction of the inductive braking apparatus.
The safety monitoring unit 17 is communicatively connected to the first
monitoring circuit 23 and to the second monitoring circuit 24 by means of a
suitable channel, such as with separate signal wires or a safety bus. The safety
monitoring unit 17 is configured to cause a safety shutdown of the elevator on
10 the basis of an indication of a malfunction received from the first 23 or the
second 24 monitoring circuit. Safety shutdown can mean that elevator is taken
out of operation immediately or after release of the passengers from the
elevator car. In an alternative embodiment, in case of indication of malfunction
received from the second 24 monitoring circuit, operation is continued with
15 degraded performance, such as with a lower speed.
In an alternative embodiment, the ETSL braking solution disclosed above is
implemented without the inductive braking devices 13A, 13B; 7A, 7B of Fig. 1
A and Fig. 1B. In this case the safety monitoring unit 17 is adapted to cause
braking of the elevator car 4 with the hoisting machinery brakes 12A, 12B to
20 decelerate car speed to the terminal speed of the top 3A or bottom 3B end
terminal upon determination of the slowdown failure. To enable this, the hoisting
machinery brakes 12A, 12B are dimensioned to decelerate car speed from the
maximum initial speed 22 (viim) to the terminal speed of said top 3 or bottom 3B
end terminal within the distance between the closest possible position xP of an
25 approaching elevator car 4 and the top 3A or bottom 3B end terminal. In this
embodiment the average deceleration at>r of equation (3) is the deceleration
caused by the braking torque of the hoisting machinery brakes 12A, 12B.
According to an embodiment, the electromechanical braking apparatus
comprises one or more car brakes, which is / are mounted to elevator car 4 and
30 adapted to brake elevator car 4 movement by engaging against a longitudinal
braking element(s), such as guide rail(s) of elevator car 4.
16
The invention can be carried out within the scope of the appended patent
claims. Thus, the above-mentioned embodiments should not be understood as
delimiting the invention.

CLAIMS
1. An elevator comprising:
an elevator shaft (1) defined by surrounding walls and top (3A) and bottom (3B)
end terminals;
5 an elevator car (4) vertically movable in the elevator shaft (1);
an elevator hoisting machinery (6) adapted to drive an elevator car (4);
an electromechanical braking apparatus (12A, 12B) configured to brake
movement of the elevator car (4);
a first measuring device (14A, 14B, 14C) adapted to provide first position data
10 and first speed data of the elevator car;
a second measuring device (15A, 15B) adapted to provide at least a second
position data of the elevator car (4);
a safety monitoring unit (17) communicatively connected to the first measuring
(14A, 14B, 14C) device and the second measuring device (15A, 15B) and
15 configured
to determine a synchronized position (19) of the elevator car (4) from the first
and the second position data, and
to determine an elevator car slowdown failure in the proximity of the top (3A) or
the bottom (3B) end terminal from the first speed, data (20) and from the
2 0 synchronized position (19) of the elevator car (4),
wherein the safety monitoring unit (17) is adapted to cause braking of the
elevator car (4) with the electromechanical braking apparatus (12A, 12B) upon
determination of the slowdown failure.
2. The elevator according to claim 1, wherein the safety monitoring unit (17) is
2 5 adapted to cause braking of the elevator car (4) with the electromechanical
braking apparatus (12A, 12B) to decelerate car speed to the terminal speed of
the top (3A) or bottom (3B) end terminal upon determination of the slowdown
failure.
18
3. The elevator according to claim 1 or 2, wherein the elevator comprises a
safety buffer (5) of an elevator car associated with the bottom end terminal (3B)
of the elevator shaft (1).
4. The elevator according to claim 3, wherein the safety monitoring unit (17) is
5 adapted to cause braking of the elevator car (4) with the electromechanical
braking apparatus (12A, 12B) to decelerate car speed to the allowed buffer
impact speed (18) upon determination of the slowdown failure in the proximity
of the bottom end terminal (3B).
5. The elevator according to any of the preceding claims, wherein the elevator
10 further comprises an inductive braking apparatus (13A, 13B) configured to
brake movement of the elevator car (4),
and wherein the safety monitoring unit (17) is adapted to cause braking of the
elevator car (4) with the electromechanical braking apparatus (12A, 12B) in
tandem with the inductive braking apparatus (13A, 13B) to decelerate car speed
15 to the terminal speed of the top (3A) or bottom (3B) end terminal upon
determination of the slowdown failure.
6. The elevator according to claim 5, wherein the safety monitoring unit (17) is
adapted to cause braking of the elevator car (4) with the electromechanical
braking apparatus (12A, 12B) in tandem with the inductive braking apparatus
20 (13A, 13B) to decelerate car speed to the allowed buffer impact speed (18)
upon determination of the slowdown failure in the proximity of the bottom end
terminal (3B).
7. The elevator according to any of the preceding claims, wherein the safety
monitoring unit (17) is configured
25 to calculate from the current speed data (20) onwards, with the maximum
acceleration, speed prediction (21) for the elevator car speed after reaction time
of the electromechanical braking apparatus (12A, 12B),
to calculate from the current (19) synchronized position onwards, with the
maximum acceleration, the closest possible position of an approaching
19
elevator car (4) to the top (3A) or bottom (3B) end terminal after reaction time
of the electromechanical braking apparatus (12A, 12B),
to calculate a maximum initial speed (22) for the elevator car (4) to decelerate
from said closest possible position to the terminal speed of said top (3A) or
5 bottom (3B) end terminal,
to determine an elevator car slowdown failure if said speed prediction (21)
meets or exceeds said maximum initial speed (22).
8. The elevator according to any of the preceding claims, wherein the
electromechanical braking apparatus (12A, 12B) comprises two
10 electromechanical brakes adapted to apply a braking force to brake movement
of the elevator car (4).
9. The elevator according to any or the preceding claims, wherein the
electromechanical braking apparatus (12A, 12B) comprises two
electromechanical hoisting machinery brakes.
15 10. The elevator according to any of claims 5 - 9 , wherein the inductive braking
apparatus (13A, 13B) comprises at least one, preferably at least two inductive
braking devices.
11. The elevator according to any of claims 5 - 1 0 , comprising:
a first monitoring circuit (23) configured to indicate operation of the
20 electromechanical braking apparatus (12A, 12B);
a second monitoring circuit (24) configured to indicate operation of the inductive
braking apparatus (13A, 13B);
wherein the safety monitoring unit (17) is communicatively connected to the first
monitoring circuit (23) and to the second monitoring circuit (24) and configured
25 to cause a safety shutdown of the elevator on the basis of an indication of a
malfunction of at least one of the electromechanical braking apparatus (12A,
12B) and the inductive braking apparatus (13A, 13B).
12. The elevator according to claim 11, wherein the first monitoring circuit (23)
comprises a sensor, such as a switch or a proximity sensor for sensing position
30 and / or movement of an armature of the electromechanical brake (12A, 12B).
20
13. The elevator according to claim 11 or 12, wherein the inductive braking
device comprises a mechanical contactor having at least two contacts (13A,
13B) adapted to short phases of an elevator hoisting machine (6), and wherein
the second monitoring circuit comprises at least two auxiliary contacts (24) of
5 the mechanical contactor, said auxiliary contacts (24) co-acting with the at least
two contacts (13A, 13B), respectively, to indicate switchincpstate of the at least
two contacts (13A, 13B).
14. The elevator according to any of the preceding claims, wherein the
electromechanical braking apparatus (12A, 12B) is dimensioned to stop the
10 elevator car (4) when it is travelling downward at nominal speed and with a 25%
overload.
15. The elevator according to claim 5, wherein the combination of the
electromechanical braking apparatus (12A, 12B) and the inductive braking
apparatus (13A, 13B) is dimensioned to decelerate car speed from the
15 maximum initial speed (22) to the terminal speed of said top (3A) or bottom (3B)
end terminal within the distance between the closest possible position of an
approaching elevator car and the top (3A) or bottom (3B) end terminal.
16. The elevator according to any of claims 5-15, wherein the safety monitoring
unit (17) is adapted to provide a common control signal to control the
20 electromechanical braking apparatus (12A, 12B) in tandem with the inductive
braking apparatus (13A, 13B).
1.6. The elevator according to any of claims 5 - 15; wherein the safety
monitoring unit (17) is adapted to provide separate control signals for the
electromechanical braking apparatus (12A, 12B) and the inductive braking
25 apparatus (13A.13B).