GB2254170A - Lift control system - Google Patents

Abstract

A lift control system includes a central control processor for controlling and monitoring the operation of a lift car, car and landing gate safety interlocks for preventing movement of the lift car whilst the doors are open, and monitoring means for monitoring the car and landing gate interlocks and upon detection of a bridged-out condition of the car and landing gate interlocks immobilising the operation of the lift car. A "bridged-out condition" occurs when a service engineer uses a jump wire to bridge car and landing gate interlock terminals during testing of lift operation. The car and landing doors may be closed in response to the detection of a bridged-out condition.

Description

IMPROVEMENT IN LIFT CONTROL SYSTEMS The present invention relates to a lift control system in which a central processor controls and monitors, amongst other things, the operation of the lift car and landing doors.

Various approaches to increase the safety of lifts have been incorporated into lift control systems, including relay proving techniques, direct monitoring of overspeed devices, over-travel sensors, etc., but the advent of the processor has allowed additional safety monitoring which previously would have been considered as too complicated or costly.

During servicing operations, the service engineer may bridge-out safety devices to enable testing of the operation of the lift, but in general terms, the majority of these would not, of themselves, create a lifethreatening situation, although they may cause an incident. However, experience has shown that it is not unusual for service engineers to bridge the car and landing gate lock terminals by the use of a jump wire, in order to facilitate the checking of door mechanisms whilst riding the top of the car under Inspection Control. In this condition, direct motion control of the lift is available to the service engineer, via the Car Top Test Unit, situated on the top of the lift car and to prevent the public having access to the lift car during testing, barriers are normally erected at every landing opening.

Following such an operation, it is necessary for the service engineer, when returning the lift to normal operation, to remove the jumper wite to reintroduce the safety interlocks for the doors to restore a safe operating condition to the lift control system. However, the possibility exists that the jumper lead, bridging the car and landing gate contacts, may accidentally be left in position, leading to a potentially life-threatening condition, in which the lift car may move, even if the landing doors are open, the safety barriers having been removed by the service engineer upon completion of testing.

It is the object of the present invention to provide an improved lift control system in which additional safety features are incorporated to detect the condition in which the car and landing gate contacts are bridged-out, and to thereby prohibit lift travel and, wherever possible, to close the car doors in order to leave the car in a user/safe condition.

According to the present invention there is provided an improved, life control system, using the central control processor for controlling and monitoring the operation of the lift car, including car and landing gate safety interlocks for preventing movement of the lift whilst the doors are open, wherein monitoring means are provided for monitoring the car and landing gate locks and immobilising the operation of the lift, if a bridged-out condition of the car and landing gate locks is detected.

Preferably, in addition to immobilising the lift in such a bridged-out condition of the safety interlocks, additional means are provided for automatically closing the car and landing doors, where possible. Further, all calls in the lift control system are cancelled and automatic parking of the lift car is disabled.

The functioning of the lift control system in relation to the door control can be summarised as follows: The lift doors will be opened under the control of the control system under the following conditions, providing the lift car is considered to be in a "door zone":- 1. Upon power up or reset on NORMAL service 2. Upon switching to NORMAL service from INSPECTION Control.

3. Upon resuming NORMAL service after a primary safety circuit failure.

In a lift control system utilising the present invention, the car and landing gate locks are monitored each time the door is opened. If, during the door opening cycle, the car and landing gate locks are deemed closed, then the gate locks will be assumed bridged.

Suitable precautions are taken to provide for circumstances in which there is a door malfunction, i.e.

stall close or part open.

Similar monitoring can be achieved in the door open stage, using additional door open limit inputs to ensure no bridges of the car and landing gate locks are on the system, whilst the door has been parked open.

Where this limit is not available, the controller will enforce a door cycle when the car and landing gate contacts can be monitored as previously described.

Where a door limit signal is available that operates before the car and landing gate locks, additional monitoring may be made in the door closing cycle. Should this door limit not be available, then the system may monitor the door close contacts to determine whether the lift should be instructed to move.

Upon detection of a bridge of the car and landing gate contacts, a fault is registered and retained in memory and the life is immobilised and, where possible the doors are parked closed. Additionally, all existing calls in the lift system are cancelled and automatic parking of the lift car is disabled. Restoring of normal operation of the lift can only be achieved once the detected condition has been remedied.

Thus, the present invention provide an improved lift control system which prevents operation of the lift car when the car and landing gate locks have been bridged and in which, in order to permit movement of the lift, following detection of such condition, the doors need to be recycled, whether by operation from the lift motor room at the controller, or, in the case of any lift user being in the lift, via the door open push, whereupon the aforementioned checking sequence is reinvoked.

The control sequence involved in the operation of the lift controller in the monitoring of the car and landing gate locks is illustrated in the accompanying flow diagram.

The present invention will now be described further with reference to the accompanying flow diagram illustrating the operation of the control system of the present invention.

In the control system of a lift, the central processor controls and monitors the operation of the lift car doors and the landing doors, amongst other functions.

In relation to the monitoring and control of the lift car doors and landing doors, the improvement of the present invention additionally provides monitoring of the car and landing gate safety interlocks to ensure that the car is immobilised if a bridged-out condition of the car and landing gate locks is detected. The monitoring and control of such function is performed by the central control processor of the lift control system according to the procedure as set forth in the accompanying flow diagram.

The procedure is set forth below: Firstly, the central processor, upon detecting that the left has stopped and is not in an advanced stage of "Fire Control" or is not on "Car Top Test" control, monitors the door open relay contactor after instructing the doors to open. The central processor having instructed the lift doors to open then monitors the gate lock signal. If, at any time during the door open cycle, a gate lock signal is sensed, then the condition is recorded in the current record. If during the door open cycle or the doors fully opened cycle, the gate lock signal is not present, the gate lock made condition is deleted from the current record, but may be entered in the systems event log of the central control system.

Upon checking the gate lock made current record is valid (indicating a gate lock signal present when it should not be), but not registered, as having corrective action taken, the system proceeds to cancel and disable landing calls, cancel and disable car calls, cancel and disable any timer initiated lift movement, enter the fault into the system event log, register the condition in the system memory and attempt to close the lift doors.

The procedure set out above is invoked at all times when the lift is stationary with the door opening or open.

If, however, the door open contactor is sensed to be requesting that the doors be opened after the CPU has instructed the doors to open, the central processor checks to determine if the doors are fully open. If the doors are determined as being fully open, then the procedure of checking the gate lock signal is initiated.

If the gate lock signal is present, when it should not have been, then the procedure as outlined above to cancel operation of the lift is followed.

If the doors are determined as not being fully open, the CPU checks to ensure the door open contactor has not released through inherent door protection procedures. Should this be the case, the normal recovery procedures are initiated with gate lock condition checking invoked at the door opening cycle.

Thus, the integrity of the gate lock signal is checked in the doors opening and the open cycle, protection is afforded in the closing cycle by the monitoring of the car door closing contactor signal precluding lift operation until this signal is no longer present.

The detailed procedure describing the operation of the control system for the present invention can be seen more clearly from the flow diagram.

Claims (4)

1. A lift control system using a central processor for controlling and monitoring the operation of a lift car, including car and landing gate safety interlocks for preventing movement of the lift whilst the doors are open, comprising monitoring means for monitoring the car and landing gate locks and upon detection of a bridged out condition of the car and landing gate locks immobilises operation of the lift car.

2. A lift control system as claimed in claim 1 in which means are provided for automatically closing the car and landing doors whenever a bridged-out condition of the safety interlocks is detected.

3. A lift control system as claimed in claim 1 or 2 in which the lift control system cancels all calls and any timer initiated lift movement such as automatic parking of the lift car.

4. A lift control system as claimed in any preceding claims in which all fault conditions are automatically recorded in the system log.