Brake device for an elevator with monitoring capabilities

An elevator drive has a brake device with compression springs to actuate brake levers, and brake linings on a brake drum creating a braking force. A sensor is provided to detect the movement of a brake magnet armature tappet. A bracket is attached to the brake magnet tappet on one end and a distance piece carrying the sensor housing is arranged on the other end. A restoring lug is attached to the existing mechanical indicator. A monitor evaluates the sensor signal and turns off the elevator drive in the event of dangerous operational states via a safety circuit. The system allows the state of the brake device to be monitored. The more the brake linings wear off due to abrasion, the smaller the distance between the armature and the brake magnet housing. If the armature is in contact with the brake magnet housing, the braking ability of the brake linings is completely void.

The invention relates to a device and a method for monitoring a brake device for an elevator drive consisting of brake levers with compression springs which exert on the latter a spring force, whereby brake linings cause a braking force on a brake drum and at least one brake magnet lifts the brake levers against the spring force.

BACKGROUND OF THE INVENTION

From patent specification EP 1 156 008 B1 a brake device for a drive machine has become known. The brake device consists of a first brake lever and a second brake lever, arranged on each of which is a brake shoe that acts on a brake drum. At their lower ends the brake levers are supported in swivel bearings on a bearing pedestal and at their upper ends guided on a bar. For the purpose of actuating the brake shoes, a compression spring is provided for each brake lever. For the purpose of lifting the brake shoes, provided on each brake lever is a magnet which acts against the compression spring. The magnets are arranged on a frame which is joined to the bearing pedestal. Arranged on the inside of each magnet support is a microswitch. A tappet of the microswitch is actuated by means of a cam that is arranged on a plunger disk. The switching status of the microswitch indicates to the control of the elevator whether by means of the magnets the brake is released or lifted, or whether the brake is not released or not lifted.

The present invention provides a device and a method for a safely acting brake device which prevents states that are dangerous for the users of the elevator.

The main advantages derived from the invention are that not only, as hitherto, is the end-position of the brake levers in the released state as brought about by the brake magnet monitored, but also the position of the movable brake-magnet part, such as the brake-magnet tappet, and of the plunger of the brake magnet. By this means it is possible to avoid the movable brake-magnet part such as, for example, the brake-magnet tappet or brake magnet plunger coming into contact with the fixed brake-magnet part such as, for example, the brake-magnet housing, through gradual abrasion of the brake linings and thereby reducing, or in the extreme case eliminating, the braking capacity of the brake device. The elevator drive can hence be directly switched off before the brake fails, or before a state that is dangerous for the users of the elevator can occur.

A further advantage is the simple construction of the device according to the invention, which can be realized by means of, for example, the use of a variety of sensors, such as a sensor proximity switch, linear emitter, etc.

With the invention, an elevator drive can be advantageously constructed and also an existing elevator drive advantageously retrofitted. The sensor can be arranged in the fixed brake-magnet part as, for example, inside or outside the brake magnet housing, in either case the relative movement of the movable brake part as, for example, the brake-magnet tappet or the plunger, relative to the fixed brake-magnet part as, for example, the brake-magnet housing, being registered.

With the simple construction of the position monitor, existing elevator systems can be retrofitted with the position monitor according to the invention without great outlay, for example by mounting the sensor on the brake-magnet tappet.

BRIEF DESCRIPTION OF THE INVENTION

In accordance with the foregoing purposes and advantages, an elevator drive according to the invention has a brake device with brake levers to which a spring force is applied by means of compression springs. Brake linings cause a braking force on a brake drum, and at least one brake magnet lifts the brake levers against the spring force. At least one sensor is provided that monitors a movement or a distance between a plunger of the brake magnet and a brake magnet housing. With the sensor signal, not only a signal for the end-position of the brake magnet tappet or brake magnet plunger can be generated, but also further signals as, for example, a signal for brake travel, a signal for brake lining wear, or a signal for brake drum heating. The safety for the elevator users can thereby be additionally increased, since the operating states of the brake device that lead to dangerous situations are promptly recognizable.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1shows diagrammatically a brake device1with a first compression spring2, a second compression spring3, a first brake lever5, a second brake lever6, and a brake magnet4. The first compression spring2exerts a spring force on the first brake lever5. The second compression spring3exerts a spring force on the second brake lever6. The first compression spring2is guided by means of a first bar7which at one end is joined to a machine housing8and at the other end has a first adjusting element9, for example nuts with locknuts mounted on threads of the bar7, the braking force and the opening of the first brake lever5being settable with the adjusting element9. This second compression spring3is guided by means of a second bar10which at one end is joined to the machine housing8and at the other end has a second adjusting element11, for example nuts with locknuts mounted on threads of the bar10, the braking force and the opening of the second brake lever6being settable with the adjusting element11. Arranged on the first brake lever5is a first brake shoe12that carries a first brake lining13, the first brake lining13creating a braking force on a brake drum14. Arranged on the second brake lever6is a second brake shoe15that carries a second brake lining16, the second brake lining16creating a braking force on the brake drum14. The first brake lever5is mounted in swiveling manner on a first lever axle17that is supported on the machine housing8. The second brake lever6is mounted in swiveling manner on a second lever axle18that is supported on the machine housing8. The brake drum14is usually joined to a motor axle that is not shown.

The brake magnet4consists of a magnet coil20which is arranged in a fixed brake-magnet part as, for example, a brake-magnet housing19which, when carrying electric current, acts through its magnetic field on a movable brake-magnet part such as, for example, a plunger21. The brake-magnet housing19with the magnet coil20and the plunger21repel each other and act against the spring forces of the compression springs2,3. The movable brake-magnet part executes a relative movement relative to the fixed brake-magnet part. At a first joint22, the brake-magnet housing19is connected to the first brake lever5. The plunger21is connected to a brake-magnet tappet23which in turn, at a second joint24, is connected with a third bar25. By means of third adjustment elements26, the third bar25is connected to the second brake lever6.

The more the brake linings13,16wear due to abrasion, the smaller the distance d of the plunger21from the brake-magnet housing19becomes. Should the plunger21rest against the brake magnet housing, the braking capacity of the brake linings13,16is completely eliminated. So that this operating state that is dangerous for elevator users cannot occur, at least one sensor27is provided that detects the movement or the distance d. Sensor27can be, for example, a proximity switch, for example with analog output, or a linear emitter. The sensor27can be arranged on the plunger21and register the distance d from the brake-magnet housing19. The sensor27can also be arranged on the brake-magnet housing19and register the distance d from the plunger21. The sensor27can also be arranged on the brake-magnet tappet23and execute the relative movement of the brake-magnet tappet23relative to the brake-magnet housing19, the sensor27registering the relative position of the brake-magnet tappet23relative to the brake-magnet housing19. Details are explained more fully inFIGS. 4 to 6. The sensor arrangement according toFIGS. 4 to 6is preferred for retrofitting in existing elevator installations. For new installations, a sensor arrangement according toFIGS. 4 to 6, or a brake magnet4with a built-in sensor27, can be used.

FIG. 2shows diagrammatically a brake device1with a double brake magnet4consisting of a first magnet coil20.1, a second magnet coil20.2, a first plunger21.1, a second plunger21.2, a first brake-magnet tappet23.1, and a second brake-magnet tappet23.2. The first brake-magnet tappet23.1is connected in swiveling manner (joint22.1) to the first brake lever5. The second brake-magnet tappet23.2is connected in swiveling manner (joint22.2) to the second brake lever6. The brake-magnet housing19is joined to the machine housing8. A first sensor27.1monitors, or registers, the movement or the distance dl between the first plunger21.1and the brake-magnet housing19. A second sensor27,2monitors, or registers, the movement or the distance d2between the second plunger21.2and the brake-magnet housing19. The first sensor27.1can also be arranged on the swivel joint22.1. The second sensor27.2can also be arranged on the swivel joint22.2.

FIG. 3shows a variant embodiment of a brake device1with only one compression spring2and one brake magnet4. The compression spring2rests against the second brake lever6and against a fourth bar28which at its other end is connected to the first brake lever5. The compression spring3thus exerts a spring force on both brake linings13,16. The brake magnet4functions as explained inFIG. 1, it being possible for at least one sensor27to be built into the brake magnet4or, as shown inFIGS. 4 to 6, mounted on the second swivel joint24. The brake magnet4acts against the spring force of the compression spring3and releases the brake linings13,16from the brake drum14. The force of the brake magnet4can also be created manually by means of a brake-release lever29. A fifth bar32limits the displacement of the brake levers5,6by the magnet4or by the brake-release lever29. Arranged on a gear output shaft31, and referenced with30, is a traction sheave over which suspension and traction means of the elevator car and of the counterweight are guided.

FIG. 4shows details of the connection of the brake-magnet tappet23with the second brake lever6. By means of a pin33that penetrates through the brake-magnet tappet23, the third bar25is connected in swiveling manner to the brake-magnet tappet23, spring rings38securing the pin at both ends. The end37of the brake-magnet tappet23may be fork-shaped. Provided at the free end of the third bar25is a thread34which, together with nuts35, serves as third adjusting element26. At least one brake lever switch40can be provided to monitor whether the brake levers5,6, and thus the brake linings13,16, have been released from the brake drum14.

As shown inFIG. 4, the brake-lever switch40can monitor the position of the brake lever6, or be arranged in such manner that the former monitors the position of the pin33relative to the brake-magnet housing19. Normally arranged on the brake-magnet housing19is a sixth bar41, provided on which is a first vane42. With the relative position of the pin33relative to the first vane42, the distance of the plunger21from the brake-magnet housing19can be determined. The sixth bar41together with the first vane42is also referred to as a “mechanical indicator”. The more the brake linings13,16wear through abrasion, the less the pin33is distant from the first vane42. As shown inFIG. 6, in the present exemplary embodiment the sixth bar41and the pin33are used as a mechanical reference point for the sensor27.

FIG. 5shows diagramatically the sensor27for registering the movement or the distance d of the plunger21from the brake-magnet housing19, or the relative movement of the brake-magnet tappet23relative to the brake-magnet housing19. In the present exemplary embodiment, provided as sensor27is an inductive proximity switch with an analog output which responds to ferromagnetic objects. The sensor27has a sensor housing43with a second thread44onto which a locking nut45can be screwed. The sensor housing43is screwed into a magnetically neutral distance piece46of, for example, plastic, and by means of the locking nut45secured against turning, the distance piece46on the end-face47of the sensor27having a defined wall thickness48, for example 1 mm. Referenced with49is an air gap between a second vane50and the distance piece46. Wall thickness48plus air gap49yields the sensor gap51from the second vane50. InFIG. 7and inFIG. 7athe sensor gap51is referenced as “s.” With the distance piece46, setting work on site is avoided. As shown inFIG. 6and inFIG. 6a, the distance piece46serves also as a support for the sensor27. The sensor27can at the factory be completely screwed into the distance piece46and installed on site without settings in the axial direction. Power supply to the sensor27, and the signal output of the sensor27, take place via a connecting cable52.

FIG. 6,FIG. 6ashow details of arrangements of the sensor27on the brake-magnet tappet23. A stirrup53is fastened onto one end of the existing pin33, and arranged on the other end is the distance piece46that bears the sensor housing43. InFIG. 6, with the aid of elongated slots54and screws55, the distance piece46can be aligned perpendicular to the direction of movement of the brake-magnet tappet23on the exisiting sixth bar41. The second vane50is fastened to the sixth bar41. A setting of the brake-magnet tappet23in the direction of movement is not necessary.

InFIG. 6a, the stirrup53is fastened by means of screws55ato the fork-shaped end37of the brake-magnet tappet23. As shown inFIG. 6a, the second vane50is arranged coaxial to the axis of the sixth bar41and of the sensor27. The second vane50is embodied in a spring-returning manner.

By this means it is possible to avoid the suffering of damages by sensor27and/or the vane50should a collision occur between the sensor27and the second vane50, either because of incorrect mechanical settings or because of a travel of the brake magnet4that deviates from the norm.

FIGS. 6band6cshow details of the second vane50. A cylindrical base body50.1is connected with the sixth bar41and serves as a support for guides50.2which slide along pins50.6of a cap50.3with disk50.4. A spring50.5rests at one end on the base body50.1and at the other end on the disk50.4and holds the cap50.3with the disk50.4in the end-position shown inFIGS. 6aand6c. In the case of a collision of the sensor27with the vane50, the cap50.3with the disk50.4is moved against the spring force of the compression spring50.5.

FIG. 7,FIG. 7ashow the output signal of the sensor27as it depends on the registered distance, sensor gap51, or relative movement of the brake magnet tappet33relative to the brake-magnet housing19. The varying distance of the end-face47of the sensor27from the second vane50is referenced inFIG. 7,FIG. 7aas “s.” The proximity switch with analog output that is used as sensor27may have a current output between 0 and 20 mA, which is robust against electromagnetic interference signals as shown inFIG. 7, or a current output signal between 0 and 5 mA as shown inFIG. 7aat a sensor gap51, or s, of between 0 and 10 mm.FIG. 7,FIG. 7ashow the characteristic of the current I as a function of the travel s or of the sensor gap51. Of interest is the linear area of the curve between 8 mA and 17 mA as shown inFIG. 7, or between 2 mA and 4.3 mA as shown inFIG. 7a, and a sensor gap51, or s, between 3 mm and 7.5 mm. The analog current output signal is fed to an analog/digital converter64of a monitor60that is shown inFIG. 8and by which it is evaluated.

On elevators with many short trips and/or that stop at many floors, the brake linings13,16can wear more quickly than usual. Elevators that are halted by the brake in the area of the story (so-called two-speed elevators), have higher wear of the brake linings. A defective state of the brake can be promptly deduced from the diminishing leveling accuracy of the elevator car on the story. With drives with releveling, the leveling accuracy is always the same, and a defective state of the brake does not manifest itself visibly.

A further cause of excessive wear of the brake linings13,14can be an at least partial failure of the magnet coil20, as a consequence of which the magnet coil20no longer produces the full force for releasing the brake lever5,6, and the motor moves the traction sheave30with closed brake levers5,6. As shown inFIG. 4, to avoid this state with the resultant excessive wear of the brake linings13,16, a brake-lever switch40is provided which monitors the position of the brake levers5,6when the brake is perceived by the elevator control to be lifted, and determines whether on a travel command the brake levers5,6, and thus the brake linings13,16, have been released from the brake drum14. Should the brake-lever switch40not be present, or not supported by the elevator control, travel without lifted brake cannot be avoided, but the monitor60nonetheless detects and prevents a total failure of the brake.

FIG. 8shows a block circuit diagram of the monitor60for analyzing the sensor signal of the sensor27and for indicating the state of the brake device1. A processor61of the monitor60operates according to a program that is stored in a program memory62, the processor placing data into a working memory63or fetching it from thence. The analog sensor signal of the sensor27is fed to the analog/digital converter64of the monitor60. Converter64, memory63, memory62, and the processor61communicate via a bus system65. By means of a diagnosis instrument66, the program or parameters can be modified or data read out. A first power-supply device67supplies the monitor60with electrical energy, for example with a voltage of 5 V. The first power-supply device67is supplied by a monitor-external second power-supply device68, for example with alternating voltage from the power supply network at 220 V or, for example, with direct voltage at 24 V from the not-shown elevator control.

Depending on the sensor signal of the sensor27, a relay69is triggered. In the normal operating state of the brake device1, the relay69is activated and a potential-free contact70that belongs to the relay69is closed. To visualize the state of the closed contact, a first indicator71, for example a green-lit LED, can be provided. In the safety circuit72of the not-shown elevator control, the potential-free contact70is connected in series. A second potential-free contact can also be connected in series, and on failure of the relay69the safety circuit can be opened by means of the second potential-free relay-operable contact. The safety circuit of the elevator control is a series circuit of contacts that monitor important functions of the elevator operation as, for example, doors closed, brake lifted, normal speed of the elevator car, normal load, etc., and if at least one contact is open no car travel is executed.

Depending on the sensor signal of the sensor27, different operating states are detected and indicated. The normal operating state is made visible by means of a second indicator73, for example by means of a green-lit LED. The operating state corresponding to excessively worn brake linings13,16is made visible by means of a third indicator74, for example by means of a red-lit LED. A further operating state that corresponds to the stroke of the brake device1or of the brake-magnet tappet23is visualized by means of a fourth indicator75, for example by means of a red-lit LED. A further operating state corresponding to heating of the brake drum14is visualized by means of a fifth indicator76, for example by means of a red-lit LED. A further operating state corresponding to a failure detected by electronic tests is visualized by means of a sixth display77, for example by means of a red-lit LED. A further operating state of the brake corresponding to the closed position, or to the open position, of the brake levers5,6is visualized by means of a seventh indicator79, for example by means of an orange-lit LED. The monitor60can be equipped with all, or with a selection of, the said indicators.

With a push-button78, on electronic initialization of the monitor60, measurement values of the sensor27that were saved in the non-volatile working memory63(EEPROM) can be reset. After mechanical setting work on the brake device1, the push-button78must be pressed. For example, the processor61calculates the mean value of a plurality of measurement values of the sensor signal for the closed position of the brake levers5,6, or for the brake that has been activated by means of compression springs2,3, and the mean value of a plurality of measurement values of the sensor signal for the open position of the brake levers5,6, or of the brake levers5,6that have been lifted by means of the brake magnet4. After resetting of the mean values, mean values of new measurement values are calculated and saved.

The sixth bar41with the first vane42and the tappet pin33are used as mechanical reference point for the sensor27, there being provided as sensor gap51, for example, 3 mm, or as air gap49, 2 mm. As shown inFIG. 7, at 3 mm sensor gap51the linear area of the sensor signal, or of the output current I, begins. With an air gap49of 2 mm, collision of the sensor27with the second vane50can normally also be avoided at maximum wear of the brake linings13,16.

In normal operation with closed position of the brake levers5,6and with open position of the brake levers5,6, the sensor gap51in the present exemplary embodiment is greater than 3 mm. In the closed position of the brake levers5,6, the sensor gap51is given. Deviations are caused by wear of the brake linings13,16or by heating of the brake drum14. The monitor60can differentiate between the deviations. As the brake linings13,14wear, the brake-magnet tappet23moves relative to the brake-magnet housing19. On heating of the brake drum14, the brake magnet tappet23moves relatively away from the brake-magnet housing19.

Based on the analog/digital transformed sensor signal, the processor61of the monitor60calculates the speed and the direction of the brake magnet tappet23. To determine the closed position and the open position of the brake levers5,6, signal values or measurement values are allocated to the corresponding position if the brake-magnet tappet23does not, for example, move more than 0.01 mm in 100 ms. For the closed position, a sensor gap51of, for example, between 3 m and 5.5 mm is possible, and for the open position, for example, a sensor gap51of between 5 mm and 7.5 mm is possible.

With each car travel the speed and the direction of the brake-magnet tappet23changes, whereby the number of trips is detected and saved in the working memory63.

During the first, for example, 8 trips, the indicator73flashes at, for example, 10 Hz, with, for example, 8 signal values of the sensor27, or measurement values, being assigned to the corresponding closed position or open position and therefrom the corresponding mean values formed and saved in the working memory63. The closed position and open position learned on the brake device1serve as a starting point for the operating state of excessive wear of the brake linings13,16or for the operating state of excessive heating of the brake drum14. Thereafter, the second indicator73flashes at, for example, 1 Hz and indicates a fully functional capability of the brake device1. Monitoring of the closed position and of the open position can be continued. Should the mean values of the measured signal values deviate by more than, for example, 0.5 mm, the saved mean values are overwritten with the current mean values. Alternatively, the aforementioned closed position and open position can be learned once only with a plurality of measurement values.

With increasing wear of the brake linings13,16, for example 0.5 mm before the critical point, the third indicator74, is switched on and switched off with, for example, a frequency of 10 Hz. On attaining the critical point (sensor gap51=3 mm), the relay69is switched off with a time delay and the potential-free contact70is opened. The time delay is of such magnitude that the elevator car can complete the current trip and the transported persons can leave the elevator car. The operating state of excessive wear of the brake linings13,16is then signaled with the continuously switched-on third indicator74.

Should the stroke or distance between the closed position and the open position be smaller than, for example, 2 mm during, for example, 3 seconds, the monitor60assumes a fault, for example an incorrect mechanical setting or a mechanical blocking. A further fault that can be detected from the stroke is the number of open positions in relation to the maximum travel time of the elevator car. On occurrence of a stroke fault, the relay69is switched off with a time delay and the potential-free contact70is opened. The time delay is of such magnitude that the elevator car can complete the current trip and the transported persons can leave the elevator car. The fourth indicator75is initially, for example, switched on and switched off with a frequency of 10 Hz and then continuously switched on.

If, due to failure of the brake magnet, or due to software faults, or due to hardware faults in the electronic switching circuits, the brake device1is not lifted, or if the brake linings13,16are not released from the brake drum14, the monitor60can also not detect a stroke fault. In the case of car travel with a closed brake, the brake drum14and the brake linings13,16heat. Upon heating, brake drum14and brake linings13,16expand and cause a movement of the brake-magnet tappet23relative to the brake-magnet housing19opposite in direction to the movement caused by wear. The deviation is evaluated in relation to the distance of the closed position from the critical point. The more advanced the wear of the brake linings13,16is, or the thinner the brake linings13,14are, the smaller is the deviation that causes switching-off. The deviation can lie in the range of, for example, 0.7 mm to 1.5 mm. On occurrence of an impermissible deviation, the relay69is switched off with time delay and the potential-free contact70is opened. The time delay is of such magnitude that the elevator car can complete the current trip and the transported persons can leave the elevator car. The fifth indicator76is initially switched on and off with a frequency of 10 Hz and then switched on continuously.

The monitor60itself can also prevent switching-on of the relay69or effect switching-off of the relay69and an opening of the potential-free contact70. Reasons therefor are negative plausibility tests during electronic initiation or operation of the monitor60. Further reasons for switching-off are a missing sensor27, or a brake device1which has not been lifted for a long period of time, for example three months. This type of fault is visualized by means of the sixth indicator77.