GB2263169A

GB2263169A - Electronic brake stopping distance tester

Info

Publication number: GB2263169A
Application number: GB9200534A
Authority: GB
Inventors: Robert Edwin Colebrooke
Original assignee: Otis Elevator Co
Current assignee: Otis Elevator Co
Priority date: 1992-01-10
Filing date: 1992-01-10
Publication date: 1993-07-14
Anticipated expiration: 2012-01-10
Also published as: GB2263169B; GB9200534D0

Abstract

A brake stopping distance tester for an escalator or other passenger conveyer includes means 1, 2 for generating pulses indicative of distances travelled by the escalator; means 4 for receiving the pulses and calculating the escalator running speed therefrom; and means for comparing the speed to a pre-programmed overspeed level and for providing a control signal when the running speed exceeds this level. In response to this control signal a brake is applied to the escalator and, at the same time a counter begins counting the number of pulses sensed until the escalator stops. The distance travelled by the escalator from the time it exceeds the overspeed level to the time it stops is displayed. <IMAGE>

Description

ELECTRONIC BRAKE STOPPING DISTANCE TESTER The present invention relates to an electronic brake stopping distance tester for a passenger conveyor, such as an escalator or the like.

Escalators are generally fitted with an overspeed device for slowing down the escalator if it is running too fast, a non-reversal switch or underspeed device for stopping the escalator when it slows, and one or two brakes which must stop the escalator, either acting together or individually, within a specified stopping distance. An escalator may have to be stopped in use because something has become trapped in it, e.g. part of a passenger's clothing, a bag etc., and it is important that the escalator is stopped as quickly as possible after the alarm is raised to avoid excessive damage or injury. Therefore, it is important to detect brake deterioration and failure as soon as possible so that the stopping distance does not become too great.

In known escalator systems the initial setting of the overspeed and underspeed devices and the testing of brakes are carried out prior to commissioning of the escalator. However, in such systems, it is not possible to alter the trip values of the overspeed and underspeed devices once the escalator has been installed and the stopping distance cannot be monitored at regular intervals after installation. Therefore, it is not possible to detect deterioration of the brakes or brake failure during the running of the escalator.

Previous escalators have been controlled by a mechanical governor as shown in Fig. 1. As the escalator runs, the escalator drives a sprocket with teeth around its circumference. A governor drive chain is looped around the sprocket, at one end, and a smaller governor drive sprocket at the other end. As the escalator drive sprocket rotates, the governor drive sprocket is also caused to rotate at a speed proportional to the speed of the escalator and by an amount proportional to the distance of travel of the escalator. The governor drive sprocket is mechanically connected to a governor containing mechanically operated switches. The switches produce an output, indicative of the escalator speed, to the escalator controls.

Such mechanically governed escalator systems have several disadvantages. The governor drive chain must be lubricated and adjusted regularly to allow it to run freely and to permit an accurate indication of the escalator speed to be conveyed to the governor. The mechanically operated switches on the governor are subject to mechanical wear and failure or nuisance tripping and the governor drive sprocket must be mechanically connected to the escalator drive driven sprocket and must be in line therewith thus limiting the possible position for location of the governor.

Further, the governor must be fixedly attached to the escalator and must, therefore, be specifically adapted to that particular escalator. It is difficult and time consuming to install and replace a mechanical governor and it is necessary to have a spare governor available for each individual escalator.

Therefore, there is a need to simplify the setting of the overspeed and non-reversal or underspeed devices and the testing of the brakes both during installation of the escalator and at regular intervals thereafter which overcomes the above-mentioned problems.

The present invention provides an electronic brake stopping distance tester for a passenger conveyor, comprising: means for generating pulses indicative of distance travelled by the conveyor; means for receiving said pulses and calculating the: spewed of travel therefrom; means for comparing said speed to a predetermined reference speed and for providing a control signal when said speed exceeds said reference speed; means responsive to the control signal for applying a brake when said speed exceeds said reference speed, counter means arranged to be activated on the occurrence of said control signal to count the number of pulses generated between the time said speed exceeds said reference speed and the time the brake causes the conveyor to stop, and means for displaying the distance travelled during that time as indicated by the number of pulses counted.

The brake stopping distance tester is preferably incorporated in an escalator governor which is capable of operating in a first, speed governing, mode in which it displays the running speed of the escalator and can be programmed with an overspeed threshold level whereby an output signal is provided to the escalator controls when the running speed exceeds the threshold level.

Preferably, in a second, brake stopping distance testing, mode, the predetermined threshold is provided by setting the overspeed threshold to the normal running speed of the escalator. In this mode the escalator is started up in the normal way and its running speed is displayed. As soon as the escalator reaches normal speed the control signal is provided to apply the brake and, at the same time, the display is switched to display distance travelled until the escalator stops.

Preferably, the pulses are generated by a proximity switch transducer which detects rotation of an escalator drive driven sprocket and the pulses are received and converted to speed or distance by an electronic programmable counter unit.

A preferred embodiment of the invention will now be described by way of example only and with reference to the accompanying drawings, wherein: Fig. 1 shows a mechanical governor commonly used in escalator systems; Fig. 2 shows the electronic governor and brake tester according to a preferred embodiment of the present invention; Fig. 3 shows a flow chart of the speed governing operation according to the preferred embodiment; and Fig. 4 shows a flow chart of the brake testing according to the preferred embodiment.

Referring to Fig. 2, a sprocket 1, driven by the escalator drive, has teeth around its circumference. A proximity switch transducer 2 detects each time a tooth passes it and emits a pulse each time a tooth is detected. The proximity switch transducer 2 is electrically connected to a programmable counter unit 4, mounted adjacent the escalator (not shown), via a flexible cable 3 connected to the proximity switch transducer 2 at one end and connected at its other end to the programmable counter unit 4 by means of a plug and socket arrangement 5. The programmable counter unit 4 includes a digital display 6 on a surface thereof, programming buttons 7, a reset button 9, a program enable/disable key switch 8, and ON/OFF switch 10. A lead 11 connects the counter unit 4 to a power supply (not shown) and another lead 12 connects the output of the unit 4 to the escalator control, remote indicators, etc. The leads 11 and 12 are connected to the counter unit 4 via plug/socket arrangements 13 and 14.

When the system is to be operated as an escalator speed governor, the counter unit 4 is switched on, via the ON/OFF switch 10 and programming is then enabled by switching the program enable/disable key switch 8. This ensures that the settings are tamper proof and, once programming has been completed, the key switch 8 is set to "disable". Only authorised users will have access to a key to set the switch 8 to "enable". The counter unit 4 is programmed, via the programming buttons 7, to calculate and display the running speed of the escalator in ft/min or m/s.

Operation of the system as an escalator speed governor is shown in the block diagram of Fig. 3. When the escalator is running, the proximity switch 2 detects the teeth of the sprocket 1 as it is rotated by the escalator drive. As each tooth passes the proximity switch transducer 2 a pulse is generated and the pulses thus indicate distance travelled. The pulse rate is proportional to the escalator speed and the circumference of the sprocket 1. The pulses are input to the programmable counter unit 4 through the flexible cable 3. This cable 3 permits freedom in the location of the counter unit 4 relative to the escalator. The pre-programmed counter unit 4 then converts the pulse rate into the speed of the escalator based on an internal timer such as a crystal oscillator, and the speed is displayed on the digital display 6 in ft/min.

or m/s. From the speed displayed, the desired overspeed and underspeed trip values can be calculated.

The unit 4 is then programmed, via the programming buttons 7, to de-energise an overspeed trip relay (not shown) at OUTPUT 1 if the calculated escalator speed exceeds the overspeed value, which may be set at a value greater than the normal speed by a predetermined amount, e.g. at 120% of the normal speed. The unit 4 is also programmed to energise an underspeed trip relay (not shown) at OUTPUT 2, only if the calculated escalator speed exceeds a predetermined lower threshold, e.g. only if the escalator is running at a speed greater than 80% of its normal speed. Outputs 1 and 2 are then fed to the escalator controls via a lead 12. Output 1 could for instance control the maintenance of motor drive to the escalator and output 2 holds off the brake(s).

Operation of the system as an escalator brake tester will now be described with reference to the flow chart of Fig. 4. The counter unit 4 is switched ON and enabled in the same way as for speed governing operation. The unit 4 is then programmed, via the programming buttons 7, to calculate and display speed in m/s or ft/min and linear travel distance in mm or inches. The trip value of OUTPUT 1 is then programmed via programming buttons 7 to be the same as the normal running speed of the escalator. The escalator is started normally with OUTPUT 1 ON. At step S1 a decision is made whether OUTPUT 1 is ON or OFF. If OUTPUT 1 is ON, as it is initially, the system goes to step S2, where the pulse rate is converted to the running speed of the escalator which is displayed on the digital display at step S3.At the same time the speed is compared with the preset overspeed value at step S4.

The overspeed value is preset to the normal speed of the escalator. When the speed reaches the overspeed value, i.e. normal running speed, after a short delay (e.g. 5 seconds) at step S5, to ensure the normal speed has actually been reached, the overspeed trip relay at OUTPUT 1 is de-energised at step S6 and, at the same time, OUTPUT 2 causes the escalator brakes to be applied at step S7. When OUTPUT 1 is switched OFF this initiates a changeover at step S1 and the counter unit changes to convert the pulse rate into linear travel of the escalator at step S8 which is displayed in inches or millimetres on the digital display at step S9. Thus, when the escalator stops, the distance shown on the display 6 will be the stopping distance, i.e. the distance taken for the escalator to come to a stop after the brakes have been applied. If the stopping distance is indicated as being greater than a predetermined acceptable distance the brakes are considered faulty and appropriate action can be taken.

The preferred embodiment has been described with respect to an escalator but it should be appreciated that the invention could be incorporated in other passenger conveyors such as a travelator.

Claims

1. An electronic brake stopping distance tester for a passenger conveyor, comprising: means for generating pulses indicative of distance travelled by the conveyor; means for receiving said pulses and calculating the speed of travel therefrom; means for comparing said speed to a predetermined reference speed and for providing a control signal when said speed exceeds said reference speed; means responsive to the control signal for applying a brake when said speed exceeds said reference speed, counter means arranged to be activated on the occurrence of said control signal to count the number of pulses generated between the time said speed exceeds said reference speed and the time the brake causes the conveyor to stop, and means for displaying the distance travelled during that time as indicated by the number of pulses counted.

2. The brake stopping distance tester of claim 1 wherein said predetermined reference speed is a programmed overspeed threshold level.

3. The brake stopping distance tester of claim 2 wherein said threshold level is set at the normal running speed of the escalator.

4. The brake stopping distance tester of any preceding claim wherein said pulses are generated by a proximity switch transducer which detects rotation of an escalator drive driven sprocket.

5. The brake stopping distance tester of any preceding claim wherein said pulses are received and converted to speed or distance by an electronic programmable counter unit.

6. An escalator governor incorporating the brake stopping distance tester of any preceding claim, said governor being operable in a first, speed governing, mode and a second, brake stopping distance testing, mode, wherein, during said first mode said pulses are converted to the running speed of the escalator and said speed is displayed, and said governor is programmed with an overspeed threshold level whereby an output signal is provided to the escalator controls when the running speed exceeds the threshold level; and wherein, during said second mode, a brake is applied to the escalator when said output signal is generated and, simultaneously, the display is switched to display the distance travelled until the escalator stops.

7. An escalator governor as claimed in claim 6 wherein, during said second mode, said overspeed threshold level is set at the normal running speed of the escalator.

8. A brake stopping distance tester substantially as hereinbefore described with reference to Figs. 2 to 4 of the accompanying drawings.