Description

The invention relates to a hoistway door, a safety circuit for a hoistway door and a door lock for a hoistway door. Furthermore, the invention relates to a method for operating a hoistway door.

Elevator systems usually have one or more hoistway doors in every floor, which protect from falling into the hoistway, when the elevator cabin is not in the respective floor. As a rule there are several safety systems that protect a hoistway door from unintentional opening and, in the case of a malfunction, the elevator system from operating. For example, there may be a mechanical switch, which senses, whether a door lock has closed or not. In the case, the door is not regularly locked, the elevator system may prevent the elevator cabin from moving away.

The contacts of such a switch may be susceptible to excessive wear and contamination by hoistway dust. It may be very time intensive and costly to regularly replace and/or clean contacts in order to avoid elevator malfunction and shutdown.

There may be a need for a more safe and a less service intensive elevator system.

Such a need may be met by the subject-matter of the independent claims. Further exemplary embodiments are evident from the dependent claims and the following description.

An aspect of the invention relates to a safety circuit for a hoistway door. A hoistway door may be an automatically opening and closing door that protects access to a hoistway. The hoistway door only may open, when an elevator cabin is behind the hoistway door. The safety circuit may be adapted for determining, whether the hoistway door is closed and locked. If this is not the case, the safety circuit may provide a safety signal, which may be received by a central controller of the elevator system, which then may prevent the elevator cabin from moving. According to an embodiment of the invention, the safety circuit comprises two reed switches, each reed switch being adapted for being switched between an inactive and an active state by a magnet moved by a locking bar of the hoistway door and a monitoring circuit adapted for determining whether one of the reed switches has a malfunction, by determining that the reed switches are in different states, wherein the monitoring circuit is adapted for providing a safety signal indicating, whether the reed switches have a malfunction. For example, the hoistway door may comprise a lock with a locking bar that may be moved by actuators of the hoistway door between a locked position, in which the hoistway door is locked, and an unlocked position, in which the hoistway door may be opened. Also the opening of the hoistway door may be performed by actuators of the hoistway door.

For detecting, whether the hoistway door is locked, the lock also may comprise a door lock sensor, which comprises a permanent magnet on the locking bar and two reed switches, which are actuated by the magnet. When the locking bar is in the locking position, the magnet may near (for example less than 5 mm) the reed switches, which are then switched both into an active state. When the locking bar is in the unlocked position, the magnet may be remote from the reed switches (for example more than 10 mm) and the reed switches are both in an inactive state.

A reed switch or magnet switch may be a switch that comprises at least two conductors, which attract each other and are in electrical contact, when they are in the vicinity (for example less than 5 mm) of a magnet, and which are otherwise not in electrical contact. It may be possible that a reed switch has a further conductor, which is in contact with one of the other conductors, when there is no magnet in the vicinity of the reed switch, i.e. that the reed switch may be a switch adapted to switch between two conducting paths. In general, the active state of a reed state may be the state, in which the reed switch is actuated by the magnet and provides a current path and the inactive state is the state, in which the reed switch is in its ground state, either providing no current path or a different current path. There may be the problem that a reed switch does not return to the inactive state, when the magnet is moved away, for example, when the respective conductors stick together. It also may be that the conductors of the reed switch do not generate a desired current path, when the magnet is moved towards the reed switch. These may be seen as malfunctions of the reed switch. In this case, the two reed switches may be in different states, i.e. one reed switch may be in the active state and the other one may be in the inactive state. The safety circuit is adapted for detecting such a malfunction of the reed switches.

When thee reed switches are in different states, it is not clear any more, whether the door is regularly locked or not. The safety circuit may provide a safety signal, which may be sent to a further controller, which may take further measures to ensure safety of the elevator system and which, for example, may stop the operation of the elevator system.

Since reed switches are used for detecting the door locking state, service time may be reduced, since reed switches are less impervious to both wear and contamination compared to an ordinary mechanical switch. Additionally, because two reed switches are used, the door lock is safer, since the safety circuit may monitor the door position and may open a safety chain, when the one of the reed switches fails with the door open. According to an embodiment of the invention, the safety circuit further comprises a disconnection relay adapted for supplying at least one of the reed switches with a voltage, wherein the disconnection relay is connected with the monitoring circuit, such that the disconnection relay is opened, when the safety signal indicates a malfunction of the reed switches. With the disconnection relay power may be prevented from flowing through the reed switches. Furthermore, in case of a malfunction, the disconnection replay may prevent the elevator from running without a monitoring of the reed switches status.

According to an embodiment of the invention, the safety circuit further comprises a switch state indicator for each reed switch comprising an LED indicating the switching state of the reed switch. For example, the monitoring circuit and/or the safety circuit may be integrated into the door lock. When a malfunction occurs, a service technician may look onto the LEDs on the door lock and immediately may see, which one of the reed switches stays in one state, i.e. may have the malfunction. According to an embodiment of the invention, the monitoring circuit is adapted for receiving a door signal of a door sensor, the door sensor signal indicating whether the hoistway door is open or closed, wherein the monitoring circuit is adapted for combining the door signal with reed switch signals from the reed switches to determine, whether the reed switches have a malfunction. For example, it may be possible, when the functionality of the reed switches is determined, when the door starts or intends to open, to prevent opening the door in the case of a malfunction.

According to an embodiment of the invention, the monitoring circuit comprises two AND elements, each AND element combining the door switch signal with one switch signal.

For each reed switch, the resulting signal is then the door switch signal, when a door open signal is present.

According to an embodiment of the invention, the safety circuit further comprises a memory circuit adapted for maintaining a safety signal indicating a malfunction of the reed switches, wherein the memory circuit providing a malfunction signal, when the reed switches have a malfunction. This may be beneficial, when a reed switch only sometimes has a malfunction. Once a malfunction occurs, the safety circuit stays in a state, in which it indicates a malfunction, also the reed switch may temporarily behaves correctly.

According to an embodiment of the invention, the malfunction signal is stored in a flip flop, which is set by the safety signal. Such a flip flop may be composed of two NAND elements, which also may be provided by the same electronics chip as the AND elements of the monitoring circuit. This may save electronic components.

According to an embodiment of the invention, the safety circuit further comprises a reset switch adapted for resetting the memory circuit, such as the flip flop. The reset switch may be a manually actuatable switch. Once a malfunction has occurred, only a service technician may reset the safety circuit.

A further aspect of the invention relates to a door lock for a hoistway door, such as described in the above and in the following. A door lock with a sensor based on two reed switches may be low-maintenance and safe. According to an embodiment of the invention, the door lock comprises a locking bar for locking the hoistway door, a magnet attached to the locking bar, and two reed switches, which are positioned such that the magnet is actuating the reed switches, when the locking bar is in a locked position. Such a door lock enables to use a safety circuit as described in the above and in the following.

A further aspect of the invention relates to a hoistway door, which comprises such a door lock. Furthermore, the hoistway door may additionally comprise a door sensor adapted for detecting, whether the hoistway door is opened or closed, which door signal is also used by the monitoring circuit to monitor a malfunction of the reed switches.

A further aspect of the invention relates to a method for operating a hoistway door. For example, the method may be performed by a controller, which is adapted for actuating the hoistway door and for sensing signals from sensors inside the hoistway door, i.e. which may comprise the monitoring circuit and/or the safety circuit.

According to an embodiment of the invention, the method comprises: moving, for example with an actuator of the hoistway door, a locking bar for locking the hoistway door between a locking position and an unlocking position, wherein a magnet attached to the locking bar is moved towards or away from two reed switches of a monitoring circuit; determining, with a monitoring circuit, whether the reed switches have a malfunction by determining that one of the reed switches is in an active state and that the other one of the reed switches is in an inactive state; and providing a safety signal indicating, whether the reed switches have a malfunction.

It has to be understood that features of the method as described in the above and in the following may be features of the system as described in the above and in the following.

Below, embodiments of the present invention are described in more detail with reference to the attached drawings.

Fig. 1 shows an elevator system with a hoistway door according to an embodiment of the invention, Fig. 2 shows a safety circuit for a hoistway door according to an embodiment of the invention.

The reference symbols used in the drawings, and their meanings, are listed in summary form in the list of reference symbols. In principle, identical parts are provided with the same reference symbols in the figures.

Fig. 1 shows an elevator system 8 with a hoistway door 10, through which access to a hoistway 12 is possible, in which an elevator cabin 14 is moving. Due to safety reasons, the hoistway door only may open and/or stay open, when the elevator cabin 14 is behind the hoistway door 10. Thus, it is very important that the hoistway door 10 is closed, when the elevator cabin 14 is moving.

The hoistway door 10 has a lock 16 for locking the hoistway door 10, for example, when the elevator 14 is not behind the hoistway door 10. The lock 16 has a safety circuit 18 for sensing, whether the lock 16 is in a locked state or an unlocked state. The safety circuit 18 comprises two reed switches 20a and 20b, which are actuated by a magnet 22, which is attached to a locking bar 24 of the lock 16. Both reed switches 20a, 20b may be activated, when the magnet 22, which may be located on a front part of the locking bar 24, reaches a sensing distance of, for example, 3 mm. This may be the case, when the locking bar 24 is moved to a locked state, in which it locks the hoistway door 10.

The safety circuit 18 is adapted for detecting, whether both reed switches 20a, 20b have been activated or deactivated. In this case, it may be assumed that the lock 16 is operating correctly and that in the case, when both reed switches 20a, 20b are activated, the lock 16 is locked and when both reed switches 20a, 20b are deactivated, the lock is unlocked.

The hoistway door 10 furthermore may comprise a door sensor 28, which is adapted for detecting, whether the hoistway door 10 is opened or closed. Also, the signal from the door sensor 28 may be provided to the safety circuit 18. When the door open sensor 28 indicates that the hoistway door 10 is open and the two reed switches 20 are activated or the door sensor 28 indicates that the hoistway door 10 is closed and the two reed switches 20 are deactivated, it may be assumed that there is a malfunction in the reed switches 20a, 20b. Furthermore, the safety circuit 18 is adapted for detecting, whether one of the reed switches is activated and the other one is deactivated. In this case, it also may be assumed that a malfunction of the reed switches 20a, 20b is occurred.

When a malfunction occurs, the safety circuit 18 generates a signal 26, indicating a malfunction, which, for example, may be provided to a central elevator controller, which may interrupt the operation of the elevator system 8. Fig. 2 shows the safety circuit 18 in more detail. The reed switches 20a, 20b, which may be located inside a door lock housing 30, in which also the safety circuit 18 or at least parts of may be located, may be SPDT (single pole, double throw) reed switches 20a, 20b being switchable between a first, deactivate state, in which an input COM is connected with a first input NC, and a second, active state, in which the input COM is connected with a second input NO. In Fig. 1, both reed switches 20a, 20b are shown in the deactivate state.

The reed switches are connected with their inputs COM and their inputs NO, NC with an interface 32 of the safety circuit 18 in the following way. Both reed switches 20a, 20b are connected with its input NO with a voltage supply indicated by VCC. The first reed switch 20a is connected via a relay 34 with the voltage supply VCC. The second reed switch 20b is connected directly with the voltage supply VCC. The other input NC of each reed switch 20a, 20b is connected with ground GND. (In the whole drawing, VCC indicates a supply of positive voltage and GND indicates ground, i.e. 0 V). In such a way, the output COM of each reed switch 20a, 20b is connected with ground (signal "low") in the deactivate state and with VCC (signal "high") in the active state (when both reed switches 20a, 20b are working properly).

Each reed switch 20a, 20b is connected with the input COM to a switch state indicator circuit 36a, 36b. Each switch state indicator circuit 36a, 36b comprises a green LED (light emitting diode) 38a, 38b and a transistor 40a, 40b that is connected with its base to the respective input COM. Thus, when the signal at the input COM is low, the respective LED 38a, 38b are on, i.e. illuminated. With the door 10 open and no failed reed switches 20a, 20b, the output of the circuits 36a and 36b is low. The transistors 40a, 40b are PNP transistor, thus an input of low turns on the transistors 49a, 40b, allowing conduction to ground and the output will be low. With the door 10 open, the green LEDs 38a, 38b will be on. With door 10 closed and no failed reed switch 20a, 20b the output of circuits 36a and 36b is high. The green LEDs 38a, 38b turn off when the reed switches 20a, 20b are correctly working and the door 10 is closed.

The logic circuit 42 also receives a signal from a circuit of the door sensor 28, which delivers a high signal, when the door is open and a low signal, when the door is closed. The door sensor 28 comprises a relay 44, which provides this signal and which is actuated by two light detectors 45 adapted for sensing the open and closed state of the hoistway door 10.

The logic circuit 40 firstly applies AND to one of the signals from the switch state indicator circuit 36a, 36b and the signal from the door sensor 28 (by applying NAND with a first NAND element and applying NOT with a second NAND element with interconnected inputs). The result signals are combined with OR and then inverted again to a safety signal 46.

The switch state indicator circuits 36a, 36b and the logic circuit 42 together form a monitoring circuit 48, which provides the safety signal 46 based on the signals from the two reed switches 20a, 20b and the door sensor 28.

The safety signal 46 is applied in reversed form to the relay 34. When the safety signal is low, the relay 34 is opened. When the safety signal is high, the relay 34 is closed.

Furthermore, the safety signal 46 is applied to a malfunction memory circuit 50, comprising a flip flop 52 of two NAND elements. The state of the flip flop 52 may be set to high, with a high safety signal 46, which is applied to the upper input of the flip flop 52. In this case, a red LED 54, which is connected to the output of the flip flop 52, which provides a malfunction signal 26, is illuminated.

The flip flop 52 may be reset (in which case the LED 54 is off and/or the malfunction signal 26 is low) with a switch 56 connected to the lower input of the flip flop 52. The safety circuit 8 and in particular the monitoring circuit 48 monitors both reed switches 20a, 20b and the door position to control the relay 34 and/or to generate the safety signal 46. The safety signal 46 is high and/or the relay 34 is only maintained in closed, i.e. conducting state, when power is supplied to the safety circuit 18 and both reed switches 18 are inactive, or, when the car door is closed.

Relay 34 de-energizes, i.e. opens, in case one or both reed switches 20a, 20b fail to deactivate with the door sensor 28 indicating the door 10 in the open state. Relay 34 also opens, if power is removed from the safety circuit 18.

When the hoistway door 10 is open, the reed switches 20a, 20b are inactive thus keeping the safety string open. With the door closed, the magnet 22 on the locking bar 24 causes both reed switches 20a, 20b to activate thereby completing the safety chain (NO contacts close).

When the door 10 is open, relay 34 is activated and reed switches 20a, 20b and relay 44 are deactivated. Safety circuit is open. Green LED 38a and green LED 38b is on indicating both reed switches 20a, 20b and door sensor 28 are operating normally. When the door 10 is closed, reed switches 20a, 20b are energized. Safety chain is closed through relay 32 and the reed switches 20a, 20b.

With the door 10 open, the magnet 22 is away from both reed switches 20a, 20b.

Therefore, both reed switches 20a, 20b should return to their inactive state. Should, for example, reeds switch 20a fail to return to its proper position, the monitoring circuit 48 output, i.e. the safety signal 46 goes low, which opens relay 32 thereby opening the safety chain. Once relay 32 is deactivated, the red LED 54 turns on and remains latched until the safety circuit 18 is manually reset with switch 56. While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art and practising the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or controller or other unit may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

List of reference symbols

8 elevator system

10 hoistway door

12 hoistway

14 elevator cabin

16 lock

18 safety circuit

20a first reed switch

20b second reed switch

22 magnet

24 locking bar

26 malfunction signal

28 door sensor

30 door lock housing

32 interface

34 relay

36a, 36b switch state indicator circuit

38a, 38b green LED

40a, 40b transistor

42 logic circuit

44 relay

46 safety signal

48 monitoring circuit

50 memory circuit

52 flip flop

54 red LED

56 reset switch