ELEVATOR SYSTEM
Field of the invention
The present invention relates to an elevator system as presented in the preamble
of claim 1 and a method for ensuring safety in an elevator system as presented in
the preamble of claim 10.
Prior art
In elevator systems it is important to endeavor to maximize the safety of
passengers. The elevator car may not move outside the landing zone when the
doors are open, the elevator car may not drop freely at any phase, nor may its
movement reach uncontrolled acceleration of movement or uncontrolled
deceleration of movement. For this reason elevator appliances contain
numerous safety and stopping devices, which take care of the stopping of the
elevator car in both normal situations and in fault situations.
The control system of the elevator handles the driving of the elevator from floor
to floor. During normal drive, in acceleration and deceleration the control system
of the elevator ensures that e.g. the speed of the elevator decreases and that
the elevator stops at the right point of the floor. The control system stops the
elevator smoothly also at the terminal floor. If normal stopping of the elevator by
means of the control system does not work, Normal Terminal Slowdown (NTS)
handles the smooth stopping of the elevator at the terminal floor.
If Normal Terminal Slowdown (NTS) does not succeed in stopping the elevator
when it arrives at the end of the shaft, ETSL (Emergency Terminal Speed
Limiting) stops the elevator by using the machinery brake. The machinery brake
is an electromechanical brake, which is generally arranged to connect if
necessary to the traction sheave of the elevator. If the deceleration of the
elevator is not adequate, ETSL can still use the brake of the elevator car or the
wedge brake, i.e. the safety gear, for stopping.
Fig. 1 presents the operation of the safety devices of a modern elevator system.
Graph 11 illustrates the travel of the elevator as a function of distance and
speed.
A mechanical overspeed governor (OSG) can be used as a safety device. The
overspeed governor monitors the speed of the elevator car in the elevator shaft
and if the speed of the elevator car exceeds a certain pre-set limit value (e.g. 6
m/s), the overspeed governor disconnects the safety circuit of the elevator, in
which case the machinery brake goes on (area 12). The elevator contains a
safety circuit, which is cut if any of the switches that are connected to it opens. If
the overspeed still increases from the previous, the overspeed governor uses
the safety gear (area 16) that is in connection with the elevator car, the wedge
of which grips the guide rails of the elevator and prevents the elevator car from
sliding. In other words, if the ropes or rope suspensions fail and the elevator car
starts to drop freely, the safety gear wedges and grips.
Overspeed can also be monitored electrically. For example, a solution is known
from publication WO00/39015, in which an electronic overspeed monitoring
appliance receives a signal indicating the speed of the car, compares the speed
of the car to the speed limit data stored in the memory of the monitoring
appliance, and if necessary produces an activation signal, by means of which
the brakes of the elevator can be engaged.
Near the end of the elevator shaft is a final limit switch. The position of the final
limit switch is marked x1 in Fig. 1. If the elevator has not stopped before the
final limit switch, the safety circuit of the elevator is again cut and the brake of
the elevator operates. The final limit switch uses the machinery brake to stop
the elevator car (area 12) if the elevator goes e.g. 100 mm past the terminal
station.
If the elevator continues onwards a few centimeters from the final limit switch,
the car (or correspondingly the counterweight) collides with the buffer 13, which
yields and finally stops the elevator. After the buffer there is still an empty space
14, after which the concrete end structure 15 of the shaft is encountered. Fig. 1
presents the shaft structure of especially an elevator system with counterweight.
In an elevator without counterweight the buffer structure of the top end of the
shaft can be lighter than the one below, because uncontrolled movement can
only occur downwards.
Even if the normal control system fails, full-length buffers have a stroke length
to the amount that in principle it is safe to drive onto the buffers at full speed,
nor does the acceleration inside the car go over the permitted limit before the
elevator car stops. Typically 1g is the kind of acceleration/deceleration that is
set in the safety regulations as bearable by a person.
There are also elevator systems in which so-called "reduced stroke buffers" are
used. In this case an electrical safety connection is used as an aid in stopping
the car, A switch is installed at a certain distance from the end of the shaft, the
speed limit of which is e.g. 90% of the nominal speed. A second switch is
installed slightly closer to the end of the shaft, the speed limit of which is e.g.
60% of the nominal speed. If the speed is over that permitted at the point of the
switch, the safety circuit is again cut and the machinery brake stops the elevator
car. If the overspeed still increases from the previous, the safety system of the
elevator uses the safety gear in connection with the elevator car to stop the car.
The authorities of different countries have different regulations concerning the
safety of elevators. The basic principle is that the elevator must contain the kind
of safety system that is able to stop the elevator in a fault situation. For
example, according to the elevator directive 95/16/EC issued by the European
Union, an elevator must contain an overspeed governor as well as a speed
monitoring system, The elevator may not reach uncontrolled acceleration of
movement or uncontrolled deceleration of movement. Furthermore, the situation
in which the elevator car starts to slide out of the landing zone when the doors
are open, owing e.g. to rope slipping or a fault situation in the machinery brake,
must be avoided.
Purpose of the invention
The purpose of the present invention is to present a new kind of method for
ensuring safety in an elevator system, and an elevator system that is safe and
reliable. In particular the purpose of the invention is to disclose a method for
ensuring safety in an elevator system without counterweight, by means of which
it is possible both to prevent unintended movement of the elevator car in the
floor zone and an overspeed situation of the elevator car as well as to ensure
controlled stopping of the elevator, and an elevator system without
counterweight in which stopping of the elevator car is ensured also when prior
art safety equipment malfunctions.
Characteristic features of the invention
The elevator system and the method according to the invention are
characterized by what is disclosed in the characterization parts of claims 1 and
10, Other embodiments of the invention are characterized by what is disclosed
in the other claims. Some inventive embodiments are also discussed in the
descriptive section and in the drawings of the present application. The inventive
content of the application can also be defined differently than in the claims
presented below. The inventive content may also consist of several separate
inventions, especially if the invention is considered in the light of expressions or
implicit sub-tasks or from the point of view of advantages or categories of
advantages achieved. In this case, some of the attributes contained in the
claims below may be superfluous from the point of view of separate inventive
concepts. The features of the various embodiments can be applied within the
scope of the basic inventive concept in conjunction with other embodiments,
Furthermore the features that are presented in conjunction with the method
according to the invention can be applied in an elevator system according to the
invention, and vice versa.
The present invention relates to an elevator system and a method for ensuring
safety in an elevator system.
The elevator system according to the invention comprises a safety arrangement
as well as the control of the safety arrangement The safety arrangement
according to the invention comprises at least one mechanical stopping
appliance and the control of the safety arrangement comprises at least one limit
value that sets the speed, deceleration or permitted vertical distance from the
door zone of the elevator car. The control of the safety arrangement also
comprises the measurement of time, and the limit value of the control of the
aforementioned safety arrangement is defined as a function of time.
In one elevator system according to the invention the limit value of the control of
the aforementioned safety arrangement is fitted to activate when the operating
mode of the elevator system changes.
In one elevator system according to the invention the safety arrangement
comprises means for receiving information about the direction of movement,
speed and/or deceleration of the elevator car, the status of the safety circuit of the
elevator, the status of the machinery brake of the elevator and/or the positioning of
the elevator car in the door zone, and monitoring means for monitoring that the
vertical distance from the door zone as well as the speed and/or deceleration of
the elevator car remain in the range defined by the limit value, and means to
control at least one stopping appliance if the vertical distance from the door zone,
speed and/or deceleration of the elevator car is outside the permitted range set by
the limit value. The safety arrangement further comprises means for setting the
operating mode of the elevator system utilizing the information about the direction
of movement, speed and/or deceleration of the elevator car, preliminary
information about arrival of the elevator in the door zone extrapolated from the
status of the safety circuit, information about the status of the machinery brake of
the elevator and/or the positioning of the elevator car in the door zone. A limit
value, which sets the limit for the permitted minimum deceleration of the elevator
car, is connected to at least one operating mode of the elevator system.
The safety arrangement can also comprise means for receiving information about
the service drive mode of the elevator and means to set the operating mode of the
elevator system utilizing the information about service drive mode, and/or means
for measuring time and for storing the time of the switching of the operating mode
of the elevator system. Preferably a limit value of the speed and/or minimum
deceleration of the elevator car connected to at least one operating mode of the
elevator system is defined as a function of time, and a limit value, which sets a
limit for the permitted maximum speed of the elevator car, is connected to at least
one operating mode of the elevator system. A limit value, which sets the limit for
the permitted speed of the elevator car, and at least one second limit value, which
sets the limit for the vertical distance of the elevator car from the door zone, can
be connected to at least one operating mode of the elevator system.
The elevator system also preferably comprises measuring means for constant
measuring of the direction of movement, the speed and/or the deceleration of the
elevator car. The means of the elevator system for controlling the stopping
appliance can comprise a control switch, for testing the operation of which are
further means in the elevator system. In one preferred embodiment the monitoring
means are integrated as a part of the control system of the elevator, and the
safety arrangement is fitted into the elevator system as supplementary safety, in
addition to the machinery brake, the mechanical overspeed monitoring and the
limit switches.
In the method for ensuring safety in an elevator system at least one mechanical
stopping appliance is fitted to the safety arrangement of the elevator system and
at least one limit value that sets the speed, deceleration or permitted vertical
distance from the door zone of the elevator car is set for the control of the safety
arrangement. In the method the passage of time is measured and at least one
limit value of the control of the aforementioned safely arrangement is set as a
variable function with respect to time.
In one method according to the invention at least one limit value of the control of
the safety arrangement is activated when the operating mode of the elevator
system changes.
In one method according to the invention the vertical distance of the elevator car
from the door zone, the direction of movement, speed and/or deceleration of the
elevator car, the status of the safety circuit of the elevator, the status of the
machinery brake of the elevator and/or the positioning of the elevator car in the
door zone, is checked, and it is monitored that the vertical distance of the elevator
car from the door zone as well as the speed and/or deceleration of the elevator
car remain within the permitted range defined by the limit values. If one of the
values monitored receives a value outside the permitted range, at least one
stopping appliance is controlled. According to the invention the operating mode of
the elevator system is set utilizing the information about the direction of
movement, the vertical distance from the door zone, the speed and/or the
deceleration of the elevator car, preliminary information about arrival of the
elevator in the door 2one extrapolated from the status of the safety circuit,
information about the status of the machinery brake of the elevator and/or the
positioning of the elevator car in the door zone, and a limit value, which sets the
limit for the minimum deceleration of the elevator car, is connected to at least one
operating mode of the elevator system. According to the invention it is also
possible to receive information about the service drive mode of the elevator and to
set the operating mode of the elevator system utilizing the information about
service drive mode. In one preferred embodiment the moment in time when the
operating mode of the elevator system changes is stored in memory, the passage
of time is measured, and it is monitored that the vertical distance of the elevator
car from the door zone as well as the speed and/or deceleration of the elevator
car remain within the permitted range defined by the limit values, of which limit
values at least one is defined as a function of time. The method can further
comprise the following phases: in at least one operating mode it is monitored that
the speed of the elevator car remains below a certain maximum speed, in at least
one operating mode of the elevator system it as monitored that the speed of the
elevator car remains below the permitted speed limit and that the elevator car
remains at a permitted distance from the door zone. Preferably the operation of
the control switch of the stopping appliance is tested according to the method at
regular intervals.
In the following the elevator system and the method of the invention are referred
to jointly as the solution according to the invention.
Advantages of the invention
By means of the solution according to the invention a safe elevator system is
achieved. With the solution according to the invention it is possible to avoid
hazardous situations produced by undesired movement caused by rope slip or
defective machinery brakes, and it is further possible with the solution to ensure
that the speed of the elevator remains controlled e.g. in a situation in which
dynamic braking does not succeed. With the solution according to the invention
it is further possible to ensure success of an emergency stop of the elevator
also in fast elevators without counterweight. The safety arrangement
incorporated in the elevator system according to the invention can easily be
applied for use in conjunction with prior art safety devices, in which case the
safety arrangement presented in the invention improves the safety level of the
elevator system with few extra components, and in the solution it is possible to
utilize the stopping appliances and measuring signals otherwise incorporated in
the elevator system.
Presentation of drawings
In the following, the invention will be described in more detail by the aid of one
of its embodiments with reference to the attached drawings, wherein
Fig. 1 presents the operation of one safety device according to prior art
Fig. 2 presents a block diagram of the operating modes of the elevator
system according to the invention and the switching between them
Fig. 3 presents some limit values of permitted movement according to the
invention, which set the limit for the deceleration of the elevator car.
The elevator system according to the invention comprises a safety arrangement
as well as the control of the safety arrangement. Preferably the safety
arrangement is used as a supplement to prior art safety devices, in which case
the safety arrangement presented in the invention stops movement of the
elevator car when the safety devices according to prior art for some reason do
not operate in the desired manner.
The safety arrangement of the elevator system according to the invention
comprises means for receiving and inspecting at least the direction of
movement, speed and/or deceleration of the elevator car, the status of the
machinery brake of the elevator, the status of the safety circuit of the elevator
and the door zone information of the elevator. In elevators without
counterweight the machinery brake is typically an asymmetrical brake, which is
fitted to brake movement directed downwards with a greater force than
movement directed upwards. The safety arrangement further comprises
monitoring means, with which it is possible to monitor that the vertical distance
of the elevator car from the door zone as well as the speed and/or deceleration
of the elevator car remain within the permitted range defined by the limit values
of movement, and means for setting the operating mode of the elevator system.
According to the invention, by means of the safety arrangement the vertical
distance of the elevator car from the door zone as well as the speed and/or
deceleration of the elevator car staying within the boundaries of the limit value
in certain operating modes of the elevator system is monitored. In different
operating modes the movement can be compared to different limit values, and
numerous limit values, which are monitored for non-exceedance of their
boundaries, can also be connected to a certain operating mode. If the
movement of the elevator car is not within the permitted range set by the limit
value, at least one stopping appliance is controlled, with which the elevator car
can be stopped.
An operating mode of an elevator system in this context means a certain status
n which the elevator system can be, and which operating mode is determined
by the status of the safety devices and/or actuating devices of the elevator
system and/or on the basis of the speed information and/or position information
of the elevator car. In the safety arrangement the operating modes to be set do
iot need to correspond to the other operating modes set for the safety devices
or control devices of the elevator system, although they can be the same. For
example, the statuses acceleration, uniform speed and braking that are
necessary for traffic control can from the viewpoint of the safety arrangement all
belong to operating mode 10 "elevator driving".
In the following the operation of the safety arrangement is described in
conjunction with the operating modes of the elevator system according to Fig. 2
and the method of the safety arrangement for setting the operating mode of the
elevator system and for switching from one operating mode to another. In the
embodiment the invention is applied in an elevator system without counterweight,
in which the safety arrangement comprises means for setting four different
operating modes. Different operating modes defined by the means of the safety
arrangement to which one or more supervisory limit values can be connected,
can however according to the invention also be more or less than this, and the
invention is suited for use also in elevator systems with counterweight.
Fig. 2 presents the switching of an elevator system from one operating mode to
another as a block diagram. Preferably a movement of the elevator car, such as
speed, deceleration and/or position as a function of time, is monitored constantly
irrespective of the operating mode of the elevator system, although it is also
possible that the safety arrangement is fitted to activate the stopping appliance
only in certain operating modes, to which a limit value of the motion is connected,
within which defined permitted range the movement of the elevator car must be. It
is also possible that a limit value is connected to all the operating modes of the
elevator system, compliance with which is monitored and exceedance of the
boundaries of which activates a stopping appliance. For example, in the solution
according to Fig. 2 the limit curve 11 presented in Fig. 1 could be used in
operating mode 10 (elevator driving), i.e. during normal driving of the elevator,
which describes the travel of the elevator in the elevator shaft as a function of
speed and position, or the electrical safety arrangement according to the invention
could be used to replace the mechanical overspeed governor, and a speed limit,
which movement of the elevator car may in no circumstances exceed, could be
set as the limit value for the mode 10.
In the solution according to Fig. 2, at least information about the status (on/off) of
the machinery brake, the status (open/cfosed) of the safety circuit of the elevator,
the door zones and the vertical distance of the elevator car from a door zone are
monitored, in addition to the speed and deceleration of the elevator car, which
information is monitored preferably constantly. On the basis of the information the
operating mode of the elevator system is defined. The safety arrangement
preferably also comprises means for measuring time and a memory, in which
information about the moment the elevator system switches from one operating
mode to another can be stored. The safety arrangement also comprises a
memory in which the limit values related to each operating mode of the elevator
system is stored.
Door zone information can be obtained e.g. by means of magnets fitted in the
elevator shaft in connection with each landing and by means of inductive switches
fitted to the elevator car or by means of other sensors suited to conveying door
zone information. Information about the movement of the elevator car can be
obtained e.g. with a speed sensor such as a pulse encoder or other applicable
speed measuring or position measuring method connected to the elevator car, the
overspeed governor, or the rope of the overspeed governor, The speed of the
elevator car can be calculated from the position information or, when the point of
departure is known, the position of the elevator car can be calculated by means of
the speed. Further, by means of the speed information it is possible to calculate
the acceleration/deceleration of the elevator car, and it is also possible that
acceleration sensors for determining deceleration data are connected to the
elevator car.
The safety arrangement can comprise means for receiving also other information
describing the status of the elevator system. For example, information about the
status of the main contactor of the elevator, about the status of the stopping
device, such as the switch of the OSG or other anti-creeping appliance and/or the
relay controlling this, and/or about manual opening of the machinery brake of the
elevator, about the load of the elevator car, or about the status of another switch
or actuator connected to the elevator system, can be received and monitored, and
these can be utilized in setting the operating mode of the elevator system. Further,
it is possible to monitor and utilize also other information in setting the operating
mode, such as information about the speed reference of the elevator, about
service drive mode, about inching mode or about another command relating to
control of the movements of the elevator.
In Fig. 2 the elevator system has four operating modes detected by
the safety arrangement, to three of which a limit value is connected, which sets
the limits for permitted movement of the elevator car, within the boundaries of
which the movement must remain, and if the movement exceeds the
boundaries of which a stopping appliance is activated. The stopping appliance
according to the invention can be e.g. a prior art anti-creeping device. It can be
e.g. a mechanical catch, guide rail brake or rope brake, which locks directly
against the hoisting ropes of the elevator. The stopping appliance used in the
solution according to the invention can also be a rope brake, which locks the
rope of the overspeed governor in its position, or an appliance that prevents or
brakes rotation of the rope pulley of the overspeed governor, in which case
when the elevator car moves a little distance downwards, the rope of the
overspeed governor activates the safety gear of the elevator and thus prevents
creeping of the elevator car downwards, in which case the mechanism that
stops the rope of the overspeed governor functions as the stopping appliance,
which thus can be formed from e.g. a rope brake or the safety gear.
The safety arrangement checks the operating mode of the elevator system
preferably continuously, and when the operating mode of the elevator system
changes it switches to compare the movement of the elevator car to the limit
value corresponding to the new operating mode. During normal driving 10 of the
elevator (elevator driving) the status of the safety circuit and of the machinery
brake is monitored. If the brake engages and the safety circuit opens, it is
interpreted as the end of elevator driving. If there is no fault situation in the
elevator system, the actual situation is one in which the elevator car is arriving
at a landing. Before the elevator system is interpreted as having switched to
mode 40 "car at door zone", the direction of movement and the speed of the
elevator car are checked. The directions of the magnitudes presented in Fig. 2
are defined such that the positive direction of the speed v is downwards, and
the deceleration g is positive when the elevator car moves downwards at a
decelerating speed.
If the elevator car is moving downwards and the speed is more than the set limit
speed vlim1, the elevator system is interpreted as having switched to the
operating mode 20 (preparing to stop, high speed), in which the elevator is
being stopped from a fast speed, e.g. because of a fault situation. If the elevator
car is moving upwards or its speed when moving downwards is at the highest
vlim1, it is checked whether information about the positioning of the elevator car
in the door zone has been received from the elevator. If the door zone
information indicates that the elevator car is in the door zone, operating mode
40 'car at door zone' is set. If the elevator car is not in the door zone, it is
determined that the elevator system has switched to the operating mode 30, in
which the elevator is being stopped from a slow speed (preparing to stop, low
speed).
When the elevator system is in the operating mode 20, (elevator preparing to
stop, high speed), the circumstance can be e.g. a situation in which the elevator
car is being stopped by means of ETSL. The objective is in this case to stop the
elevator by using different stopping appliances such that the elevator car is
brought to a stop reliably and quickly. It is not desirable, however, that the
stopping appliance used according to the invention is switched on when the
elevator is at full speed unless this is unavoidable, but rather in the safety
arrangement according to the invention the stopping appliance is activated only
if and when the other safety systems and stopping appliances incorporated in
the elevator system do not produce sufficient deceleration for the elevator car.
Especially in fast elevators without counterweight it is not desirable that the
elevator car ends up being stopped e.g. by the safety gear when its speed is too
great, because deceleration that is too great causes a risk to both the weilbeing
of the passengers and to the operation of the stopping appliance itself.
The safety arrangement according to the invention is thus applicable for use as
additional safety as a supplement to prior art safety devices. It is however
possible that other safety devices are replaced with the solution according to
the invention.
The limit values connected to the operating mode 20 set the limit for the
deceleration that at minimum the elevator car must have. Preferably the limit
values are defined as a function of time, e.g. in the manner described in Fig. 3,
When the elevator system switches to mode 20, the moment of time when the
switching occurs as well as the speed of the elevator car at the moment of
switching is recorded in the memory. After this the deceleration of the elevator
car is calculated as a function of time and it is monitored that the requirements
set by the limit value for movement of the elevator car are fulfilled. Here the
range of permitted movement is an area above the limit value, in which the
deceleration exceeds the limit glim(t), and the glim(t) on the curve and the area
below it, in which the deceleration is glim(t) or less than it, causes activation of the
stopping appliance.
In Fig. 3 the moment t=0 describes the moment when the elevator system has
switched to the operating mode 20. Between t=0...t1 the limit value glimo set for
deceleration is zero, because deceleration is not needed just when the elevator
system has switched to the operating mode 20. Between t1... t2 deceleration has
the limit value glim1, between t2... t3 the limit value of deceleration is glim2 and
after the moment t3 the limit value is glim3. Preferably glim3 > glim2 > glim1 > glimo
qualify for limit values, in which case it is possible to give to other safety
devices, such as to the machinery brake, time to stop the movement of the
elevator car in a controlled manner, and to use the stopping appliance of the
safety arrangement according to the invention only in fault situations of other
systems or e.g. when the ropes slip in conjunction with an emergency stop. In
elevators that move slowly, e.g. 0.6 m/s, success of an emergency stop could
be ensured by using a simple time delay, after which the stopping appliance is
activated. Purely using a time delay in activating the stopping appliance would
not however produce the desired result in fast elevators (speed e.g. 6 m/s)
without counterweight, because with prior art stopping appliances a time of
some seconds is spent on stopping movement of the elevator car, and the time
delay could not be set large enough to prevent the speed of the elevator car
growing excessively, If e.g. the machinery brake is defective. According to the
invention with a deceleration limit value defined to grow as a function of time it
is possible to ensure a safe emergency stop of the elevator car.
In mode 20 also the speed and the direction of the elevator car are constantly
monitored and compared to the speed limit vlim1. In this embodiment the limit
values for speed and deceleration are set only for movement directed
downwards, but according to the invention it is however possible to set limits
also for movement directed upwards. If the speed decreases below the value
vlim1 with sufficient deceleration, it is checked whether the elevator car is in the
door zone, and depending on the door zone information the elevator system is
determined to be either in the operating mode 30 or in the operating mode 40.
When movement of the elevator car occurs upwards or if the speed downwards
is small, below vlim1, there is a switch to mode 30 (elevator preparing to stop,
low speed), in which the speed of the elevator car is monitored comparing it to
the limit value that sets the speed limit. The limit value vlim2 of the greatest
permitted speed connected to the operating mode 30 sets the speed limit below
which the state of movement of the elevator is permitted at lower speeds. When
the speed is viim2 or greater than this, the stopping appliance is activated. In
addition, the velocity and the door zone Information of the elevator car is
monitored for setting the switching to the next operating mode. When the
elevator system Is In the operating mode 30, what is occurring can be e.g. a
fault situation, in which the electricity supply of the elevator system is defective,
and the speed of the elevator is restricted e.g. by means of dynamic braking of
the motor, or e.g. in the final stage of ETSL stopping. Further, it is possible that
what is occurring is an emergency stop in movement directed upwards, which in
an elevator without counterweight is, in itself, easy to Implement when gravity is
pulling the elevator car downwards, but in which there can be a risk of the brake
slipping after the emergency stop. In mode 30 it is monitored with the safety
arrangement that the brake does not start to slip downwards after a successful
emergency stop. Thus in the operating mode 30 of the elevator system
according to the invention, the stopping appliance is activated if the speed of
the elevator car exceeds the permitted limit, e.g. when dynamic braking does
not succeed, or if the ropes of the elevator slip - i.e. the friction between the
traction sheave and the hoisting roping is not sufficient to keep the elevator on
the desired path.
When the elevator is verified as having moved to the door zone, i.e. into
operating mode 40 (car at door zone), comparison of the movement of the
elevator car to both the speed limit and the position limits is started. In the door
zone it is ensured that the speed of the elevator car is not able, e.g. owing to
rope slip or failure of the brakes, to exceed the permitted speed. It is further
monitored in the door zone that the elevator car stays in the door zone, or that it
leaves the door zone by at the most the permitted distance. The distance can
be calculated when the information about the moment when the elevator car
leaves the door zone is recorded, and the speed of the elevator car is monitored
constantly. In the example according to Fig. 2 the speed of the elevator car is
compared to the same limit values irrespective of whether the doors of the
elevator car are open or closed, and whether the elevator is on the inching drive
setting or not. According to the invention it is possible, however, that separate
operating modes are set for these. Thus three limit values of movement are
connected to the operating mode 40: the limit value vlim2 sets the speed limit,
below which the state of movement of the elevator is permitted at lower speeds,
and the limit values hlim1 and hlim2 set the limit for the permitted distance of the
elevator car from the door zone. The permitted position h is between these, i.e.
when hlim1 =h =hlim2.
Fig. 2 presents the safety arrangement especially of an elevator system without
counterweight, in which uncontrolled accelerating movement can only occur
downwards. When using the solution according to the invention in an elevator
system with counterweight, in which a fault situation can cause uncontrolled
movement of the elevator car either downwards or upwards depending on the
state of loading of the elevator car, the criteria for making a decision about
switching from one operating mode to another and/or setting the operating
modes of the elevator system in the safety arrangement are preferably formed
such that the speed and the deceleration are monitored and limit values are set
for movement directed both upwards and downwards. It is possible that the limit
values are set to be the same for the magnitudes directed upwards and directed
downwards, but these can also differ from each other,
Fig. 2 presents the operation of an elevator system according to the invention
and of its safety arrangement with the aid of a simple embodiment. The safety
arrangement according to the invention can however comprise means for
setting also other operating modes of the elevator system. In one preferred
embodiment the safety arrangement comprises means for receiving information
about the manual opening of the machinery brake, and in this case the
machinery brakes can be opened manually such that the safety arrangement
does not activate the stopping appliance, in which case the elevator car can
drive to a floor also when the electrical circuits are disconnected. The safety
arrangement can further comprise means for testing the operation of the control
switch of the stopping appliance and for resetting the memory of a safety device
e.g. after malfunctionings of the elevator system. In one preferred embodiment
the operation of the control switch of the stopping appliance is tested at regular
intervals, e.g. once a day or after the 50th run.
The means for receiving information and for monitoring movement that are
incorporated in the arrangement according to the invention can be implemented
with a software program in conjunction with the control system of the elevator
such that for implementing the safety arrangement mainly a switch must be
added to the elevator control system according to prior art for an elevator
system, with which switch the stopping appliance can be activated when the
output of the control means so sets it. A prior art stopping appliance can be
used as a stopping appliance, which is fitted to operate also when controlled by
a safety device other than one according to the invention, e.g. a safety gear
functioning as the stopping appliance of a mechanical overspeed governor.
By means of the solution presented in Fig. 2 it is possible to implement at least
the following safety procedures: when the elevator car is situated in the door
zone either in normal mode or in inching mode, the stopping appliance is
activated if the elevator car moves away from the proximity of the door area or if
the speed of the elevator car is too great. The stopping appliance is activated in
an emergency stop downwards if the deceleration is not adequate, and in an
emergency stop upwards if the speed of the elevator car after stopping tries to
increase below the permitted limit. If the electricity of the elevator is
disconnected during a run, it is attempted to stop or limit movement of the
elevator car with the safety devices, and the stopping appliance of the solution
according to the invention is activated only if needed when the deceleration
remains too small.
By means of the safety arrangement according to the invention it is also possible
to implement the following functions: the means for controlling the stopping
appliance can be fitted to switch off when the machinery brake is opened
manually, in which case when the elevator car comes to a standstill outside the
door area it can be driven away without the stopping appliance of the safety
arrangement stopping elevator car. In order to implement this, a switch can be
fitted in connection with the machinery brake, which indicates the manual
opening of the brake, and the safety arrangement can comprise means for
receiving information about the status of this switch. The safety arrangement can
also be fitted to enable manual rescue both during an electricity power cut and
also when electricity is available.
It is obvious to the person skilled in the art that the invention is not limited solely
to the example described above, but that it may be varied within the scope of
the claims presented below. It is also obvious to a person skilled in the art that
the functional parts of the aforementioned safety arrangement do not
necessarily need to be separate but they can be integrated directly into the
control system of the elevator. The limit values of permitted movement
connected to the different operating modes can be stored in the memory of the
means incorporated in the safety arrangement. In one preferred embodiment,
the safety arrangement according to the invention is implemented in connection
with the control unit of the frequency converter incorporated In the electricity
supply equipment of the elevator, which in prior art also is fitted to receive
information, which is used in the safety arrangement to set the operating mode
of the elevator system. In this case no additional components at all are
necessarily needed alongside the prior art safety devices to implement the
safety appliance according to the invention, and the physical additional
components needed can be restricted to e.g. a relay, with which the stopping
appliance can be activated.
The invention is not limited to the embodiments described above, in which the
invention is described using examples, but rather many adaptations and
different embodiments of the invention are possible within the scope of the
inventive concept defined by the claims presented below.
CLAIMS
1. Elevator system, which incorporates a safety arrangement and a control of
the safety arrangement, in which the safety arrangement comprises at least
one mechanical stopping appliance and in which the control of the safety
arrangement comprises at least one limit value that sets the speed,
deceleration or permitted vertical distance from the door zone of the
elevator car, characterized in that the control of the aforementioned
safety arrangement comprises the measurement of time and in that the
limit value of the control of the aforementioned safety arrangement is
defined as a function of time.
2. Elevator system according to claim 1, characterized in that the limit value
of the control of the aforementioned safety arrangement is fitted to activate
when the operating mode (10,20, 30, 40) of the elevator system changes.
3. Elevator system according to claim 1 or 2, characterized in that the safety
arrangement comprises means for receiving information about the direction
of movement, speed and/or deceleration of the elevator car as well as its
vertical distance from the door zone, the status of the safety circuit of the
elevator, the status of the machinery brake of the elevator and/or the
positioning of the elevator car in the door zone, and monitoring means for
monitoring that the speed and/or deceleration as well as its vertical
distance from the door zone remain in the permitted range set by the limit
values, and means to control at least one stopping appliance if the speed
and/or deceleration of the elevator car as well as its vertical distance from
the door zone, are outside the permitted range set by the limit values, and
in that the safety arrangement comprises means for setting the operating
mode (10, 20, 30) of the elevator system utilizing information about the
speed and/or deceleration of the elevator car, the status of the machinery
brake of the elevator and/or the positioning of the elevator car in the door
zone, and in that a limit value is connected to at least one operating mode
of the elevator system, which sets the limit for the permitted minimum
deceleration of the elevator car, and in that the safety arrangement
comprises means for setting the operating mode (10, 20, 30) of the
elevator system utilizing information about the direction of movement of the
elevator car, the vertical distance of the elevator car from the door zone as
well as preliminary information about arrival in the door zone extrapolated
from the status of the safety circuit of the elevator.
4. Elevator system according to any of the claims above, characterized in
that the safety arrangement comprises means for receiving information
about the service drive mode of the elevator and means to set the
operating mode of the elevator system utilizing the information about
service drive mode.
5. Elevator system according to any of the claims above, characterized in
that a limit value, which sets the limit for the permitted maximum speed of
the elevator car, is connected to at least one operating mode of the
elevator system.
6. Elevator system according to any of the claims above, characterized in
that a limit value, which sets the limit for the permitted speed of the
elevator car, and at least one second limit value, which sets the limit for the
vertical movement of the elevator car in the proximity of the door zone, is
connected to at least one operating mode of the elevator system.
7. Elevator system according to any of the claims above, characterized in
that the elevator system also comprises measuring means for continuously
measuring the movement information of the elevator car.
8. Elevator system according to any of the claims above, characterized in
that the means of the elevator system for controlling the stopping
appliance comprise a control switch, and in that the elevator system further
comprises means for testing the operation of the control switch.
9. Elevator system according to any of the claims above, characterized in
that the monitoring means are integrated as a part of the control system of
the elevator.
10. Elevator system according to any of the claims above, characterized in
that the safety arrangement is fitted into the elevator system as
supplementary safety, in addition to the machinery brake, the mechanical
overspeed monitoring and the limit switches,
11. Method for ensuring safety in an elevator system, in which method:
- at least one mechanical stopping appliance is fitted to the safety
arrangement of the elevator system
- at least one limit value that sets the speed, deceleration or permitted
vertical distance from the door zone of the elevator car is set for the
control of the safety arrangement.
characterized in that:
- the passage of time is measured
- at least one limit value of the control of the aforementioned safety
arrangement is set as a variable function with respect to time
12, Method according to claim 11, characterized in that:
- at least one limit value of the control of the safety arrangement is
activated when the operating mode (10, 20, 30, 40) of the elevator
system changes
13. Method according to claim 11 or 12, characterized in that
- the direction of movement, speed and/or deceleration of the elevator
car as well as its vertical distance from the door zone, the status of
the safety circuit of the elevator, the status of the machinery brake of
the elevator and/or the positioning of the elevator car in the door
zone is checked
- it is monitored that the speed and/or deceleration of the elevator car
as well as its vertical distance from the door zone remain within the
permitted range defined by the limit values and at least one stopping
appliance is controlled if the movement of the elevator car is outside
the permitted range set by the limit values
- the operating mode of the elevator system is set utilizing the
information about the direction of movement, speed and/or
deceleration of the elevator car, as well as about the vertical
distance from the door zone, preliminary information about arrival of
the elevator in the door zone extrapolated from the status of the
safety circuit, information about the status of the machinery brake of
the elevator and/or the positioning of the elevator car in the door
zone
- in at least one operating mode it is monitored that the deceleration
of the elevator car remains within the permitted range set by the limit
value of movement, which limit value sets the limit for the permitted
minimum deceleration of the elevator car.
14. Method according to any of claims 11-13 above, characterized in that:
- information about the service drive mode of the elevator is received
and the operating mode of the elevator system is set utilizing the
information about service drive mode
15. Method according to any of claims 11-14 above, characterized in that:
- it is monitored that the speed of the elevator car remains within the
permitted range set by the limit value of movement, which limit value
sets the limit for the permitted maximum speed of the elevator car.
16. Method according to any of claims 11-15 above, characterized in that:
- it is monitored that in at least one operating mode of the elevator
system the speed of the elevator car remains within the permitted
range set by the limit value, which limit value sets the limit for the
permitted speed of the elevator car, and in addition to this at least
the position of the elevator car in the elevator shaft is monitored
such that vertical movement of the elevator car in the proximity of
the door zone remains within the permitted range set by the limit
value.
17, Method according to any of claims 11-16 above characterized in that the
means of the elevator system for controlling the stopping appliance
comprise a control switch, and in that the method further comprises the
phase:
the operation of the control switch is tested at regular intervals.

The invention relates to a safety arrangement of an elevator system and to a method for ensuring safety in an elevator system. The safety arrangement comprises at least one mechanical stopping appliance and the control of the
safety arrangement comprises at least one limit value that sets the speed, deceleration or permitted vertical distance from the door zone of the elevator car. In the method for ensuring safety in an elevator system at least one
mechanical stopping appliance is fitted to the safety arrangement of the elevator system and at least one limit value that sets the speed, deceleration or permitted vertical distance from the door zone of the elevator car is set for the
control of the safety arrangement.