EP2743225A2

EP2743225A2 - Elevator system

Info

Publication number: EP2743225A2
Application number: EP13178244.3A
Authority: EP
Inventors: Asmo Tenhunen; Harri Hakala; Nithil Karimpanackal Natarajan; Pekka Rantanen; Pekka Vuoti; Riku Lampinen; Risto Jokinen; Sakari Korvenranta; Tuukka Kauppinen; Ari Pikivirta; Marko Saarinen; Petteri Valjus
Original assignee: Kone Corp
Current assignee: Kone Corp
Priority date: 2011-03-11
Filing date: 2012-03-12
Publication date: 2014-06-18
Anticipated expiration: 2032-03-12
Also published as: EP2665669A1; FI20115248A; EP2665669B1; ES2566790T3; ES2906236T3; FI123239B; WO2012123635A1; EP2743225A3; FI20115248A0; FI20115246A0; EP2743225B1; EP2665669A4

Abstract

The invention relates to an elevator system and also to a method for ensuring the safety of an elevator system. The elevator system comprises a driving member (1) and also a hoisting means (3), which engages with the aforementioned driving member (1) by frictional traction. The elevator system comprises traction determination means (4, 5, 6A, 6B, 7) for determining the traction of the driving member (1), and the elevator system comprises a control circuit (4), which is configured to start a procedure ensuring the safety of the elevator system after the traction determination means (4, 5, 6A, 6B, 7) have detected that the traction of the driving member (1) has weakened.

Description

Field of the invention

The invention relates to solving the problems caused by a weakening of traction in an elevator system.

Background of the invention

An elevator system can comprise a motor drive for moving an elevator car. The motor drive usually comprises a hoisting machine of the elevator and also a power supply device, such as a frequency converter, of the hoisting machine. The elevator car is moved in the elevator hoistway with elevator ropes, which travel in the grooves of the traction sheave of the hoisting machine. The elevator car and the counterweight are suspended in the elevator hoistway such that their weight difference produces a force difference in the elevator ropes on the different sides of the traction sheave. The friction force between the grooves of the traction sheave and the elevator ropes in the grooves compensates the aforementioned force difference caused by the weight difference of the elevator car and the counterweight. In addition, the friction force transmits driving torque to the elevator ropes from the motor drive, i.e., the torque with which the elevator car is driven in the elevator hoistway. Also the force effect produced by the drive torque is different in the elevator ropes on the different sides of the traction sheave.
Since elongation of an elevator rope is proportional to the rope force according to a spring constant, rope elongation in the elevator ropes is different on the different sides of the traction sheave since the rope forces differ from each other on the different sides of the traction sheave. In this case also the speed of the elevator rope traveling in a rope groove from one side of the traction sheave to the other differs from the speed of the rope groove, i.e. the elevator rope slips in the rope groove. The magnitude of the slip can also vary slightly, depending on by how much the rope forces on the different sides of the traction sheave differ from each other. This slip is, however, normal; problems are caused only if the traction of the traction sheave weakens such that the friction force between the elevator ropes and the traction sheave is no longer able to compensate in its entirety the force difference acting in the elevator ropes on the different sides of the traction sheave. To illustrate this point, Fig. 1 presents a situation in which the rope forces T1, T2 acting in the elevator ropes 3 on the different sides of the traction sheave 1 are of different magnitudes, such that T2 > T1. The indicator 11 presents the distribution on the traction sheave of the amplitude of the friction force between the elevator ropes 3 and the rope grooves 2 of the traction sheave, said friction force compensating the difference of the rope forces T1, T2. The amplitude is at its greatest at the point 12A, where the section of rope having the greater rope force T2 arrives in the rope groove 2 of the traction sheave, and at its smallest at the point 12B, where the section of rope having the smaller rope force T2 diverges from the rope groove 2. The rope elongation changes in relation to the rope groove 2 of the traction sheave such that the rope elongation is at its greatest at the point 12A and at its smallest at the point 12B. The slip caused from rope elongation is normal, and the traction of the traction sheave fails only if the friction force 11 is no longer able to compensate the force difference acting in the elevator ropes 3 on the different sides of the traction sheave. When the traction fails, slipping of the elevator rope 3 in the rope groove 2 increases uncontrollably. In the situation according to Fig. 1, this uncontrolled slip would be noticed in the indicator of the amplitude of friction force 11 such that the amplitude would go to zero in the area of the rope groove 2 already before the point 12B, where the elevator rope 3 diverges from the rope groove 2.
Slip of the traction sheave might increase e.g. owing to damage of the coating of a coated traction sheave. In addition, the traction of the traction sheave can vary as a function of, among other things, the temperature of the traction sheave and of the elevator rope.
Instead of elevator ropes, e.g. a belt can also be used, inside the matrix supporting the structure of which belt tractive strands, such as fibers or metal strands, are fitted.
Uncontrolled slip of the elevator ropes on the traction sheave causes problems. Uncontrolled slip is a potential safety risk, e.g. to a serviceman working in the elevator hoistway. In addition, slip during a run might affect the stopping accuracy of the elevator car.

Aim of the invention

The aim of the invention is to solve the problems caused by a weakening of traction in an elevator system. To achieve this aim the invention discloses an elevator system according to claim 1, an elevator system according to claim 2, a safety arrangement of an elevator according to claim 22, a method according to claim 23, and a method according to claim 24. The preferred embodiments of the invention are described in the dependent claims. Various inventive embodiments and inventive combinations of the different embodiments are also presented in the descriptive section and in the drawings of the present application.

Summary of the invention

The elevator system according to the invention comprises a driving member and also a hoisting means, which engages with the aforementioned driving member by frictional traction. The elevator system also comprises traction determination means for determining the traction of the driving member. The elevator system comprises a control circuit, which is configured to start a procedure ensuring the safety of the elevator system after the traction determination means have detected that the traction of the driving member has weakened. Consequently, the safety of the elevator system can be improved and the safety risk caused from a weakening of traction can be eliminated with the method according to the invention.
The invention relates to an elevator system, which comprises a hoisting means and also a driving member engaging with the hoisting means by frictional traction for moving the elevator car according to a movement profile to be determined for the movement of the elevator car. The elevator system also comprises traction determination means for determining the traction of the driving member. The elevator system comprises a control circuit for adapting the movement profile of the elevator car to the prevailing traction by changing the value of the movement magnitude of the elevator car in the movement profile of the elevator car on the basis of the determined traction. Consequently, by adapting the movement profile of the elevator car uncontrolled slip can be prevented, in which case operation of the elevator can, if necessary, also be continued despite a weakening of the traction. On the other hand, when the traction improves the transportation capacity of the elevator system can be increased by adapting the movement profile. By the aid of the control circuit, the movement profile of the elevator car can be adapted to the prevailing traction automatically, and immediately it is detected that the traction has changed, without a manual resetting of the parameters of the elevator system performed by a serviceman.
A driving member refers in the invention to a structure that transfers the force effect produced by a drive device, such as by an electric motor of a hoisting machine of an elevator, into a force driving the hoisting means. This type of driving member according to the invention is e.g. the traction sheave of an elevator. The term hoisting means refers to a means that exerts a force on a load to be lifted, such as on an elevator car or on a structure moving along with the elevator car, for supporting and/or moving the load to be lifted. This type of hoisting means is e.g. an elevator rope or belt traveling in a rope groove of a traction sheave and engaging by frictional traction with the traction sheave.
In a preferred embodiment of the invention maximum values and minimum values for acceleration and deceleration are preset in the system. In a preferred embodiment of the invention the control circuit is configured to decrease acceleration and/or deceleration in the movement profile of the elevator car after the traction determination means have detected that the traction of the driving member has weakened. By decreasing the acceleration and/or deceleration the force difference acting on the different sides of the driving member, such as of the traction sheave, can be reduced and consequently the amount of traction needed for driving the elevator decreases. The traction of the driving member can also weaken gradually e.g. when the lubricant of the elevator ropes wears away from the contact surface between the elevator ropes and the rope grooves.
In a preferred embodiment of the invention the control circuit is configured to increase acceleration and/or deceleration in the movement profile of the elevator car after the traction determination means have detected that the traction of the driving member has improved. By increasing the acceleration/deceleration the door-to-door time of the elevator car can be reduced, which increases the transportation capacity of the elevator system.
In a preferred embodiment of the invention the traction determination means are configured to determine the traction of the driving member regularly while the elevator is in use. In this way the risk caused by a weakening of traction in an elevator system can be essentially reduced. When the risk decreases, the safety of the elevator system can also be better maintained by means of the traction of the traction sheave. Consequently, better safety than is known can also be achieved with a machinery brake braking the movement of a driving member, such as of a traction sheave, when using a machinery brake as a safety device braking the movement of an elevator car. In a preferred embodiment of the invention the machinery brake is used as a safety device in an elevator system, which comprises a measuring device, which is arranged to measure and/or to forecast the presence of an elevator car in a temporary safety space to be formed in the elevator hoistway. The elevator system comprises a control circuit of a machinery brake, which is configured to activate the machinery brake when the measuring device detects and/or forecasts the presence of an elevator car in a temporary safety space formed in the elevator hoistway. The aforementioned safety space can be formed in the proximity of an end of the elevator hoistway, in which case a serviceman can perform servicing work or installation work from a servicing space. In a preferred embodiment of the invention a temporary safety space is formed in the top part of the elevator hoistway. In a preferred embodiment of the invention a machinery brake is used as a confirmative safety device of the temporary safety space in the top part of the elevator hoistway, said machinery brake braking upward movement of an elevator car when the elevator car proceeds into the temporary safety space in the top part of the elevator hoistway. Correspondingly, the safety gear, i.e. the wedge brake, of the elevator car is used as a safety device of a temporary safety space to be formed in the bottom part of the elevator hoistway, which wedge brake wedging to a guide rail of the elevator car brakes downward movement of the elevator car in the elevator hoistway, when the elevator car proceeds into a temporary safety space in the bottom part of the elevator hoistway.
In a second preferred embodiment of the invention the machinery brake is used as a safety device to brake the movement of the elevator car when upward overspeed of an ascending elevator car is detected. In a third preferred embodiment of the invention the machinery brake is used as a safety device when it is detected that an elevator is moving away from the door zone monitored by the door zone sensors of a stopping floor while the door of the elevator car and/or the landing door is open.
In a preferred embodiment of the invention the aforementioned control circuit is configured to transfer the elevator out of use, when the traction determination means have detected that the traction of the driving member has weakened. The elevator car can In this case be driven closer to the stopping floor at reduced acceleration and/or deceleration, after which the doors of the elevator car can still be opened before the elevator is switched to run prevention mode. When transferring to run prevention mode, the control of the elevator switches into a mode in which a run with the elevator is prevented. In the same connection, the elevator car is locked into its position in the elevator hoistway by activating the machinery brake. In addition, the power supply to the hoisting machine of the elevator is disconnected.
In a preferred embodiment of the invention the traction determination means comprise a sensor detecting the presence of an elevator car, which sensor is arranged to indicate information about the presence of an elevator car at a specified point of the elevator hoistway. The traction determination means are configured to determine the value of a travel magnitude of the elevator car. The travel magnitude can be e.g. the travel time of the elevator car or the position data of the elevator car, said position data to be determined on the basis of a measurement of the movement of the elevator car. The traction determination means are configured to determine one or more limit values for a travel magnitude, such as estimated travel time or estimated position data, said limit value(s) to be determined on the basis of the normal traction of the driving member and to be connected to a certain measuring point in the elevator hoistway of a sensor detecting the presence of an elevator car, when the elevator car arrives at the measuring point in the elevator hoistway of the sensor detecting the presence of an elevator car. The traction determination means are arranged to compare the aforementioned one or more limit values for a travel magnitude of the elevator car to the value for the travel magnitude of the elevator car that is the limit value specified for that travel magnitude at the corresponding point of the elevator hoistway, and the traction determination means are configured to deduce that the traction of the driving member has weakened when it is detected that a specified travel magnitude deviates by the limit value for the travel magnitude/from the permitted values specified with limit values. In this way the traction of the driving member can be determined regularly also during normal operation of the elevator, e.g. always when the elevator car arrives in the door zone of a stopping floor.
In a preferred embodiment of the invention the traction determination means comprise an identifier in connection with the hoisting means. The identifier can be e.g. an RFID identifier or a readable plate, or corresponding, fixed to the hoisting means, which plate indicates the type of the hoisting means, such as of the elevator rope, the lubricant used on the elevator rope, et cetera. In a preferred embodiment of the invention the traction determination means are configured to determine the traction of the driving member on the basis of the aforementioned identifier. For achieving sufficient traction, e.g. the elevator rope or the lubricant of the rope can be selected to be of a certain type; in a preferred embodiment of the invention the lubricant of the rope must be of a specified composition for achieving sufficient traction between a groove of the traction sheave and an elevator rope lubricated with rope grease traveling in the groove.
In a preferred embodiment of the invention the elevator system comprises a control unit, which is configured to start a testing run for testing the traction of the driving member. The traction determination means are configured to determine the traction of the driving member in connection with the testing run. The elevator car is preferably configured for moving at an increased acceleration and/or deceleration in connection with the testing run. In this case a larger than normal force difference can be formed in the hoisting means on the different sides of the driving member, owing to which a weakening of the traction of the driving member can be detected in time before it has an effect on the normal operation of the elevator.
The invention also relates to a method, in which frictional traction is directed between the driving member and the hoisting means, for moving the elevator car, the traction of the driving member is determined and also a procedure ensuring the safety of the elevator system is started, when it is detected that the traction of the driving member has weakened.
The invention also relates to a method, in which frictional traction is directed between the driving member and the hoisting means, for moving the elevator car according to a movement profile to be determined for the movement of the elevator car. In the method the traction of the driving member is determined and also the movement profile of the elevator car is adapted to the prevailing traction by changing the value of a movement magnitude of the elevator car in the movement profile of the elevator car on the basis of the determined traction.
In a preferred embodiment of the invention an identifier is fitted in connection with the hoisting means and also the traction of the driving member is determined on the basis of the identifier fitted in connection with the hoisting means.
In a preferred embodiment of the invention one or more limit values for a travel magnitude are determined, said limit value(s) to be determined on the basis of the normal traction of the driving member and to be connected to a certain measuring point in the elevator hoistway of a sensor detecting the presence of an elevator car, the presence of the elevator car at a specified point of the elevator hoistway is measured, a value for a travel magnitude of the elevator car is determined, the aforementioned one or more limit values for the travel magnitude of the elevator car are compared to the value for the travel magnitude of the elevator car that is specified as the limit value for that travel magnitude at the corresponding point of the elevator hoistway, and if it is detected that the specified travel magnitude deviates by the limit value/from permitted values specified with limit values, it is deduced that the traction of the driving member has weakened.
Taking the preceding into account, or alternatively, the invention relates to a safety arrangement of an elevator for forming a temporary safety space in an elevator hoistway. The safety arrangement comprises a measuring device moving along with the elevator car and also an identifier, which is configured to cover in the vertical direction the part of the elevator hoistway intended to be a temporary safety space. The measuring device moving along with the elevator car is configured to detect the presence of an elevator car in a temporary safety space when the measuring device is situated in the horizontal direction at the point of the identifier in the elevator hoistway.
By means of the invention safety relating to the traction of the driving member can also be improved in elevator systems in which the elevator mechanics to be moved, such as the elevator car, the elevator ropes, et cetera, are designed to be lighter than prior art. In this case sufficient traction can be achieved while at the same time utilizing the advantages derived from the reduction of the moving masses, such as energy saving and also reduction of the acceleration currents and deceleration currents of the hoisting machine.
The aforementioned summary, as well as the additional features and additional advantages of the invention presented below, will be better understood by the aid of the following description of some embodiments, said description not limiting the scope of application of the invention.

Brief explanation of the figures

Fig. 1: illustrates the force distribution on the traction sheave of the hoisting machine
Fig. 2: presents as a block diagram an elevator system according to the invention,
Fig. 3: presents as a block diagram one arrangement according to a third embodiment of the invention
Fig. 4: presents as a block diagram a temporary safety space in an elevator system according to the invention
Fig. 5: illustrates the concept of a travel magnitude and of a limit value for the travel magnitude

More detailed description of preferred embodiments of the invention

Embodiment

1

The elevator system of Fig. 2 comprises an elevator car 10 and also an electric drive for moving the elevator car in the elevator hoistway 16 according to a speed reference 8 of the elevator car, which profile is formed by the elevator control unit 4. The electric drive comprises a hoisting machine disposed in the top part of the elevator hoistway 16, which hoisting machine comprises an alternating current motor as the power producing part. In addition, the electric drive comprises a frequency converter 17 for supplying variable-amplitude and variable-frequency current to the alternating current motor of the hoisting machine.
The elevator car 10 is suspended in the elevator hoistway 16 with elevator ropes 3 traveling in the rope grooves 2 of the traction sheave 1 integrated into the rotor of the hoisting machine. The hoisting machine is, in this embodiment of the invention, fixed to the guide rail (not in figure) of the elevator car, in a space between the guide rail and the wall part of the elevator hoistway 16. The hoisting machine could, however, also be fixed e.g. to a machine bedplate, and the hoisting machine could also be disposed elsewhere in the elevator hoistway, such as in the bottom part of the elevator hoistway. In an elevator system with machine room, the hoisting machine can be disposed in the machine room.
The elevator control unit 4 sends a speed reference 8 formed by it for the elevator car to the frequency converter 17 via a data transfer bus between the elevator control unit 4 and the frequency converter 17. The frequency converter 17 measures the speed of rotation of the traction sheave 1 with a pulse encoder 5 and adjusts the torque of the alternating-current motor by adjusting the current flowing in the motor such that the speed of the traction sheave 1, and thereby of the elevator car 10, approaches the aforementioned speed reference 8 for the elevator car.
The hoisting machine comprises two machinery brakes 14, each of which comprises a brake frame conjoined with the frame part of the hoisting machine and a brake shoe (not in figure) movably supported on the brake frame. Between the brake frame and the brake shoe are thruster springs, which when the brake is activated press the brake shoe to engage with the braking surface on the traction sheave to brake the movement of the traction sheave. The machinery brake is opened by supplying current to the electromagnet in the brake frame, which then pulls the brake shoe off the braking surface of the traction sheave by resisting the thrusting force of the thruster springs. The current supply to the electromagnets of the machinery brakes occurs with a current supply circuit 15.
The machinery brakes 14 are used as a safety device to prevent uncontrolled movement of the elevator car in the elevator hoistway, e.g. in an overspeed situation of an ascending elevator car 10 and also when it is detected that an elevator car 10 is moving away from the door zone monitored by the door zone sensors 6B of a stopping floor 9 while the door of the elevator car10 and/or the landing door is open.
In order for the machinery brakes 14 to be used as a safety device to prevent uncontrolled movement of the elevator car, it must be possible to solve the safety problem relating to uncontrolled slipping of the elevator ropes 3 in the rope grooves of the traction sheave 1. Uncontrolled slipping might occur if the traction of the traction sheave weakens, i.e. the friction between the elevator ropes 3 and the rope grooves 2 is not for some reason sufficient. For solving the problem the elevator system of Fig. 2 is provided with a safety arrangement, wherein the traction of the traction sheave 1 is determined regularly, and a procedure ensuring the safety of the elevator system is performed if it is detected that the traction of the traction sheave 1 has weakened.
A measuring device 6A moving along with the elevator car is fitted in connection with the elevator car. The measuring device 6A detects the identifier 6B in the elevator hoistway when the measuring device 6A arrives at the point on the horizontal plane of the identifier 6B in the elevator hoistway. Information about the identifier can be conveyed to the measuring device e.g. as electromagnetic radiation or via a magnetic field. Each identifier 6B is also individualized either on the basis of identification, such as RFID identification, in the identifier 6B or by inference from the consecutive succession of the identifiers 6B. The identifiers 6B are disposed to indicate the presence of an elevator car 10 at a stopping floor in a door zone 9 of the elevator hoistway, i.e. at a point at which passengers are able to arrive in the elevator car 10 and leave from the elevator car 10. When it is serving passengers, the elevator car 10 always starts moving from the departure floor from the point of an identifier 6B and correspondingly always stops at the destination floor at the point of a second identifier 6B.
The elevator control unit 4 calculates the distance traveled by the traction sheave 1 by integrating the pulses given by a pulse encoder 5. The distance that the elevator car 10 traveled while the traction sheave 1 rotates is evaluated on the basis of the integral. A learning run is driven with the elevator car 10, in which run the elevator car travels the elevator hoistway 16 from end to end and simultaneously the distance traveled by the elevator car 10 is calculated from the pulses of the pulse encoder 5. Always when the elevator car 10 arrives at the point of a new identifier 6B, the elevator control unit 4 records in memory the distance to the previous identifier calculated from the pulses of the pulse encoder 5. On the basis of these distances that are measured/recorded in memory, the elevator control unit 4 forms a reference that predicts the position data of the elevator car when the elevator car arrives at the point of a determined identifier 6B in the elevator hoistway 16. The elevator control unit 4 specifies a permitted fluctuation range in the environs of each reference, within the scope of which the position data of the elevator car 10 can vary inside the scope of normal traction of the traction sheave.
While the elevator drives and serves passengers, the elevator control unit 4 determines the distance traveled by the elevator car from the encoder pulses. The elevator control unit 4 also calculates the position data of the elevator car by summing the distance traveled with the position reference that is specified at the point of the identifier 6B identifying the presence of an elevator car at the departure floor of a run. When the measuring device 6A fitted in connection with the elevator car arrives at the point of a specified identifier 6B in the elevator hoistway, the elevator control unit 4 compares the calculated position data to the position reference specified by the identifier 6B in question, taking into account the aforementioned permitted fluctuation range. If the calculated position data deviates from the reference by more than the permitted fluctuation range, the elevator control unit 4 deduces that the traction of the traction sheave 1 has weakened. Fig. 5 presents by way of illustration the value 14 of a position calculation for an elevator car during a run of the elevator car and also at the moment 20 when the elevator car arrives at the point of the identifier 6B in the elevator hoistway. A permitted fluctuation range with the limit values 13A, 13B is specified at the point of the identifier 6B in question for the position data of the elevator car, within the scope of which fluctuation range the calculated position data 14 of the elevator car can vary at the point of the identifier 6B inside the scope of normal traction of the traction sheave. If at the moment 20 the position data 14 at the point of the identifier 6B were to deviate to outside the permitted range specified with the limit values 13A, 13B, it would be deduced that the traction of the traction sheave 1 had weakened and a procedure for ensuring the safety of the elevator system would be performed.
If weakening of the traction of the traction sheave is detected at the end of a run after the elevator car has arrived at the destination floor, the software of the elevator control unit 4 activates the machinery brakes 14 and disconnects with the frequency converter 17 the power supply occurring to the hoisting machine. In addition, the software of the elevator control unit 4 switches into the run prevention mode, in which the elevator in question stops serving passengers.
If weakening of the traction of the traction sheave is detected in the middle of a run, i.e. when the elevator car is driving past an identifier 6B disposed between the departure floor and the destination floor, the elevator control unit 4 changes the run to occur to the nearest possible stopping floor 9, such that the elevator car is driven to the nearest possible stopping floor 9 in question at a reduced deceleration for ensuring sufficient traction. If the elevator car is situated so close to the end that attaining the floor 9 at a reduced deceleration is no longer possible, the elevator control unit 4 activates an emergency stop, in which case the machinery brakes are activated and the power supply to the hoisting machine is disconnected essentially immediately. If the machinery brakes are unable, owing to weakened traction of the traction sheave, to stop the elevator car with a sufficiently short braking distance, the safety gear of the elevator car is also activated, which safety gear stops the elevator car by tractionping to the guide rails.
In some embodiments a number of limit values are specified for a travel magnitude for ascertaining fault situations of differing degrees, such that when the value of a travel magnitude exceeds a first fluctuation range specified with limit values 13A, 13B the elevator control unit changes the run to occur to the nearest floor in the manner described above, and if the value of the travel magnitude exceeds a second fluctuation range, specified with second limit values, that is greater than the first fluctuation range the elevator control unit 4 activates the machinery brakes 14 and also disconnects the power supply to the hoisting machine essentially immediately.

Embodiment 2

In embodiment 2 a safety arrangement is fitted into the elevator system of Fig. 2, which safety arrangement differs from the safety arrangement according to embodiment 1 such that determination of the traction of the traction sheave is implemented using the travel time of the elevator car, instead of the position data of the elevator car, as the travel magnitude 14.
When the elevator car is driving a learning run from end to end of the elevator hoistway the elevator control unit 4 measures and records in memory the time that it takes the elevator car 10 to drive at a speed according to the speed reference 8 from one identifier 6B to the next. On the basis of these distances that are measured/recorded in memory, the elevator control unit 4 forms a reference for the travel time of the elevator car that is estimated to be needed to drive the elevator car from one identifier 6B to another in the elevator hoistway. The elevator control unit 4 specifies a permitted fluctuation range in the environs of each reference, within the scope of which the travel time of the elevator car 10 can vary inside the scope of normal traction of the traction sheave.
The elevator control unit 4 measures the travel time of the elevator car 10, i.e. the time that has passed since the run started. The elevator control unit 4 compares the measured travel time to the aforementioned reference for travel time, and if the time taken for the elevator car 10 at arrive at the point of a certain identifier 6B deviates to outside the permitted fluctuation range for the reference for travel time, the elevator control unit 4 deduces that the traction of the traction sheave 1 has weakened and performs some procedure described in embodiment 1 for ensuring the safety of the elevator system. One advantage of the solution is that a weakening of traction can be detected already before the arrival of the elevator car 10 at the identifier 6B, when the measured travel time of the elevator car 10 exceeds that permitted.

Embodiment 3

In embodiment 3 a safety arrangement is fitted into the elevator system of Fig. 2, which safety arrangement differs from the safety arrangement according to embodiment 1 or 2 such that determination of the traction of the traction sheave 1 is implemented in the manner presented in the following. The solution of embodiment 3 is also illustrated in Fig. 3.
An identifier 7 is fixed in connection with the elevator rope 3, which identifier indicates the type of the elevator rope or e.g. the type of the lubricant of the rope. The identifier 7 can be e.g. an RFID identifier or a readable plate. The elevator control unit 4 reads the identifier e.g. with an RFID reader; in one embodiment the information of a plate 7 is entered manually into the elevator control unit 4 with a user interface. The elevator control unit 4 checks the type of the elevator rope/lubricant on the basis of the information of the identifier 7, and determines the traction of the traction sheave on the basis of the aforesaid information. With certain types of elevator ropes special procedures are required for achieving sufficient traction of the traction sheave; in certain cases, for example, the lubricant of the rope must be of the right type for achieving sufficient traction. For example, a solution is known from publication EP1963543 A1 wherein a substance containing magnesium oxide is spread on the elevator rope, owing to which the corrosion resistance of the rope and also the traction on the traction sheave 1 improve.
If the elevator control unit 4 determines on the basis of the identifier 7 the type of rope 3/lubricant to be such with which high traction is achieved on the traction sheave 1, the elevator control unit 4 forms a speed reference 8 for the elevator car for a greater acceleration and deceleration of the elevator car 10 than in the case that the type of rope/lubricant indicated by the identifier 7 differs from the aforementioned.
In one embodiment of the invention the elevator control unit completely prevents operation of the elevator if the type of rope 3/lubricant determined on the basis of the identifier 7 is incorrect.

Embodiment 4

In embodiment 4 a safety arrangement is fitted into the elevator system of Fig. 2, which safety arrangement differs from the safety arrangements according to embodiments 1 and 2 in the following manner.
When it is detected that the traction of the traction sheave has weakened, operation of the elevator is continued, but the speed reference 8 of the elevator car is adapted to the prevailing traction. Elevator passengers will then be served by driving with the elevator car from the departure floor to the destination floor at a reduced acceleration and deceleration. For implementing this the elevator control unit 4 recalculates the speed reference of the elevator car for implementing the reduced acceleration and deceleration after the elevator control unit 4 has detected that the traction has weakened. In the same connection, the speed reference must be adapted by selecting e.g. the starting point of the deceleration phase of the elevator car such that the elevator car starts to decelerate earlier owing to the reduced deceleration. One advantage is that, despite the weakening of the traction, a run with the elevator can be continued at least temporarily, which improves the transportation capacity of the elevator system. However, information about the weakening of the traction can also be sent in all the embodiments 1 - 4 to a service center so that the necessary servicing procedures can be performed for returning the traction of the traction sheave 1 to the normal level.

Embodiment 5

In this embodiment of the invention the elevator control unit 4 regularly starts a special testing run, during which the traction of the traction sheave is tested e.g. with a method according to embodiment 1 or 2. For performing the test run, the elevator control unit 4 forms a speed reference 8 for driving the elevator car 10 at an increased acceleration and deceleration. In this case the difference in the rope forces of the elevator ropes 3 on the different sides of the traction sheave 1 forms to be larger than normal, owing to which a weakening of the traction of the traction sheave 1 can be detected already before it has an effect on the normal operation of the elevator at the normal acceleration/deceleration of the elevator car 10.
A weakening of the traction of the traction sheave can also be tested by performing an emergency stop in connection with a testing run by stopping a moving elevator car by activating the machinery brakes. The greater-than-normal deceleration of the elevator car during the emergency stop facilitates the detection of a weakening of traction. In addition, in some elevators greater braking force can be exerted with the machinery brakes on the traction sheave of the hoisting machine of the elevator than by braking with the electric motor of the hoisting machine. Consequently, a weakening of traction can also be detected more easily in an emergency stop than by driving the elevator car with the hoisting machine.
In one preferred embodiment of the invention, in an elevator system with counterweight the traction of the traction sheave is tested by driving the elevator car according to the multiphase testing process being presented in the following. When performing the testing, an empty elevator car is first driven upwards so that the elevator car will be situated a sufficient distance from the top end of the elevator hoistway before the start of the testing. A serviceman starts the testing process from a manual user interface of the elevator control unit 4; alternatively, the testing process could be also started by sending a starting signal to the elevator control unit 4 from the service center of the elevator. For the start of the testing process, a run with an empty elevator car upwards is started. When the elevator car /the measuring device 6A moving along with the elevator car arrives at the point of the identifier 6B situated in the top part of the elevator hoistway, the machinery brakes are activated to brake the movement of the elevator car. What is essential in the selection of the identifier 6B/the starting point of braking is that the location of the elevator car must be sufficiently accurately known at the moment of starting the braking. In connection with the braking, the traction sheave stops first after which the elevator ropes, and at the same time also the elevator car, still continue their movement upwards while the elevator ropes are slipping on the traction sheave. After braking, when movement both of the traction sheave and of the elevator ropes has stopped and the elevator car is standing in its position in the elevator hoistway, a new run is started for driving the elevator car downwards in the elevator hoistway. The elevator car is driven back downwards until the measuring device 6A moving along with the elevator car arrives back at the point of the identifier 6B in the elevator hoistway. The distance S₁, which the traction sheave rotates before it stops during braking, and also on the other hand the distance S₂ rotated in the opposite direction by the traction sheave during the run of the elevator car downwards back to the identifier 6B, is measured with a pulse encoder 5. The traction of the traction sheave/slipping of the elevator ropes on the traction sheave is determined by comparing the aforementioned distances S₁, S₂ to each other. This comparison is based on the fact that when the traction weakens slipping of the elevator ropes on the traction sheave during braking increases, and at the same time also the difference between the distances travelled by the traction sheave and the elevator car during braking increases. Consequently, a weakening of traction is detected such that the distance S₂ traveled by the elevator car from the identifier 6B/back to the identifier 6B increases in relation to the distance S₁ traveled by the traction sheave.
The aforementioned testing method of the traction of the traction sheave is advantageous because the force difference acting in the elevator ropes 3 on the different sides of the traction sheave 1 is at its greatest when braking an upward-moving empty elevator car situated in the top part of the elevator hoistway with the machinery brakes, in which case also possible weakening of traction can be clearly detected. This is because when the elevator car is situated in the top part of the elevator hoistway, the weight of the counterweight and also of the elevator ropes produce the greatest possible force difference on the different sides of the traction sheave; in addition, the weight of the counterweight/elevator ropes in this case acts in the direction of movement of the upward-traveling elevator car.

Embodiment 6

Fig. 4 presents an addition according to embodiment 6 in the elevator system of Fig. 2. As presented in Fig. 4, a temporary safety space 21 for the working space of a serviceman has been formed in the top part, in connection with the top end, of the elevator hoistway 16.
The elevator control unit 4 determines the traction of the traction sheave 1, in a manner according to any of embodiments 1 - 5, regularly while the elevator is in use. In this case the machinery brakes 14 are used as a safety device braking the movement of the elevator car 10.
A lengthened identifier 6C is disposed in the elevator hoistway by the side of the path of movement of the elevator car, which identifier can be one identifier or which, on the other hand, can be composed of a number of shorter identifiers disposed consecutively, such as of identifiers 6B indicating the location of a stopping floor 9. The identifier 6C covers in the vertical direction the part of the elevator hoistway intended to be a temporary safety space 21. The measuring device 6A moving along with the elevator car detects the presence of an elevator car 10 in the temporary safety space 21 when the measuring device is situated in the horizontal direction at the point of the identifier 6C in the elevator hoistway 16.
A temporary safety space 21 of the elevator hoistway is formed in a situation in which a serviceman moves into the elevator hoistway in order to work from the temporary safety space 21. A temporary safety space 21 is taken into use in the top part of the elevator hoistway 16 when it is detected that any of the other entrances of the elevator hoistway 16 than the entrance leading to the pit of the elevator hoistway 16 is opened with a service key. Consequently, a temporary safety space is taken into use e.g. when it is detected that the landing door of the topmost stopping floor 9 is opened with a service key in a situation in which the elevator car 10 is located below the topmost stopping floor 9. When a temporary safety space 21 is in use the elevator control unit 4, or an electronic monitoring unit (not presented in the figure) separate to it, reads the measuring data of the measuring device 6A, and when it detects the presence of an elevator car in the temporary safety space the elevator control unit 4/electronic monitoring unit sends to the control circuit 15 of the machinery brakes 14 a signal for activating the machinery brakes 14. In the same connection the elevator control unit 4/electronic monitoring unit sends to the frequency converter 17 a control signal for disconnecting the power supply of the hoisting machine. The elevator system is also transferred into a control mode in which a run with the elevator is prevented. Recovery from this control mode is only possible with a special procedure, e.g. with a separate manual reset apparatus.
In the second safety arrangement of Fig. 6 above, the elevator car 10 is pulled with one or more toothed belts traveling via the traction sheave of the hoisting machine instead of with an elevator rope or with a smooth belt. Grooves for the teeth are made in the traction sheave. The grooves and the teeth are formed to be so deep that the toothed belt/toothed belts are not able to slip on the traction sheave. In this preferred embodiment of the invention a machinery brake is used as a mechanical safety device of the elevator without the traction of the toothed belt on the traction sheave being separately monitored.
In some preferred embodiments of the invention a safety gear is used as a mechanical safety device, in addition to or instead of a machinery brake, which safety gear brakes the movement of the elevator car by tractionping to the guide rail of the elevator car.
The frictional traction of the elevator rope 3 or belt can also be implemented in other ways than taking an elevator rope/belt into a rope groove 2 of the traction sheave; frictional traction can also be implemented e.g. with drive belts that connect to the opposite sides of the elevator rope/belt.
The preferred embodiments of the invention described above can also be combined with each other for improving safety. For example, the methods for determining the traction of a traction sheave 1 according to embodiments 1 and 2 can be used simultaneously, in which case the traction of the traction sheave 1 can be determined both on the basis of the position data of the elevator car and on the basis of the travel time of the elevator car.
In the preceding the invention is described in connection with an elevator system with counterweight; it is, however, obvious to a person skilled in the art that the invention is suited also to elevator systems without counterweight.
The invention is not only limited to be applied to the embodiments described above, but instead many variations are possible within the scope of the inventive concept defined by the claims.

Claims

Elevator system, comprising:
a driving member (1);

a hoisting means (3), which engages with the aforementioned driving member (1) by frictional traction;

characterized in that the elevator system comprises traction determination means (4, 5, 6A, 6B, 7) for determining the traction of the driving member (1); and in that the elevator system comprises a control circuit (4), which is configured to start a procedure ensuring the safety of the elevator system after the traction determination means (4, 5, 6A, 6B, 7) have detected that the traction of the driving member (1) has weakened, and in that the elevator system comprises a measuring device (6A), which is arranged to measure and/or to forecast the presence of an elevator car (10) in a temporary safety space to be formed in the elevator hoistway (16).
Elevator system, comprising:
a hoisting means (3);

a driving member (1) engaging with the hoisting means (3) by frictional traction for moving the elevator car (10) according to a movement profile (8) to be determined for the movement of the elevator car;

characterized in that the elevator system comprises traction determination means (4, 5, 6A, 6B, 7) for determining the traction of the driving member (1); and in that the elevator system comprises a control circuit (4) for adapting the movement profile (8) of the elevator car to the prevailing traction, and in that the elevator system comprises a measuring device (6A), which is arranged to measure and/or to forecast the presence of an elevator car (10) in a temporary safety space to be formed in the elevator hoistway (16).
Elevator system according to claim 1 or 2, characterized in that the elevator system comprises a control circuit (15) of a machinery brake, which control circuit is configured to activate the machinery brake when the measuring device (6A) detects and/or forecasts the presence of an elevator car (10) in the aforementioned temporary safety space formed in the elevator hoistway (16).
Elevator system according to any of the preceding claims, characterized in that a temporary safety space is formed in the top part of the elevator hoistway (16).
Elevator system according to claim 4, wherein a machinery brake is used as a confirmative safety device of the temporary safety space in the top part of the elevator hoistway, said machinery brake braking upward movement of an elevator car when the elevator car proceeds into the temporary safety space in the top part of the elevator hoistway.
Elevator system according to one of the preceding claims, wherein a safety gear, i.e. a wedge brake, of the elevator car is used as a safety device of a temporary safety space to be formed in the bottom part of the elevator hoistway, which wedge brake wedging to a guide rail of the elevator car brakes downward movement of the elevator car in the elevator hoistway, when the elevator car proceeds into a temporary safety space in the bottom part of the elevator hoistway.
Safety arrangement of an elevator for forming a temporary safety space in an elevator hoistway (16), which safety arrangement comprises:
a measuring device (6A) moving along with an elevator car;

characterized in that the safety arrangement comprises:
a n identifier (6C), which is configured to cover in the vertical direction the part of the elevator hoistway (16) intended to be a temporary safety space (21);

and in that the measuring device (6A) moving along with the elevator car is configured to detect the presence of an elevator car (10) in the temporary safety space (21) when the measuring device (6A) is situated in the horizontal direction at the point of the identifier (6C) in the elevator hoistway (16).