Patent Description:
An elevator may comprise a car, a shaft, hoisting machinery, ropes, and a counterweight. A separate or an integrated car frame may surround the car.

The hoisting machinery may be positioned in the shaft. The hoisting machinery may comprise a drive, an electric motor, a traction sheave, and a machinery brake. The hoisting machinery may move the car upwards and downwards in the shaft. The machinery brake may stop the rotation of the traction sheave and thereby the movement of the elevator car.

The car frame may be connected by the ropes via the traction sheave to the counterweight. The car frame may further be supported with gliding means at guide rails extending in the vertical direction in the shaft. The guide rails may be attached with fastening brackets to the side wall structures in the shaft. The gliding means keep the car in position in the horizontal plane when the car moves upwards and downwards in the shaft. The counterweight may be supported in a corresponding way on guide rails that are attached to the wall structure of the shaft.

The car may transport people and/or goods between the landings in the building. The shaft may be formed so that the wall structure is formed of solid walls or so that the wall structure is formed of an open steel structure.

The elevator may be controlled by a controller.

<CIT> discloses a method for detecting a stuck car or a stuck counterweight in an elevator system having a machine for imparting motion to the car and a counterweight. The method includes sensing a car side suspension member tension, T1, sensing a counterweight side suspension member tension, T2, determining a traction ratio in response to a relationship between TI and T2, and determining a stuck car or a stuck counterweight if the traction ratio violates a limit.

An object of the present invention is an improved method for controlling an elevator.

The method for controlling the elevator according to the invention is defined in claim <NUM>.

The method for controlling the elevator may use the same Load Weighing Device (LWD) sensors and interfaces which can be used also for overload detection and drive starting torque (balance) setting. There is thus no need for additional switches in terminals or rope & tension weight switch systems.

LWD sensors positioned in connection with the bedplate of the hoisting machinery may measure the total masses acting on the bedplate. The masses hanging from the car side and the counterweight (CWT) side of the traction sheave may be determined based on the measurements. This means that stalling of the car and the CWT can be detected with the same system and sensors used for overload detection and drive starting torque (balance) setting.

The method can be applied in an elevator with any suspension ratio, e.g. a <NUM>:<NUM> suspension ratio or a <NUM>:<NUM> suspension ratio due to the fact that the method is based on traction sheave axial hanging masses.

In the method, the weight of the hoisting ropes on the car side and on the CWT side of the traction sheave are measured, which means that hoisting rope compensation factors are not needed in the method. Only travelling cable compensation factors may be needed in the method.

The measurement of the total masses acting on bedplate of the hoisting machinery may be done continuously or only when needed.

A continuous measurement of the masses acting on the bedplate of the hoisting machinery makes it possible also to determine acceleration, deceleration and constant speed of the car.

The invention will in the following be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which.

<FIG> shows a side view of a first elevator.

The elevator may comprise a car <NUM>, an elevator shaft <NUM>, hoisting machinery <NUM>, hoisting ropes <NUM>, and a counterweight <NUM>. A separate or an integrated car frame <NUM> may surround the car <NUM>.

The hoisting machinery <NUM> may be positioned in the shaft <NUM>. The hoisting machinery may comprise a drive <NUM>, an electric motor <NUM>, a traction sheave <NUM>, and a machinery brake <NUM>. The hoisting machinery <NUM> may move the car <NUM> in a vertical direction Z upwards and downwards in the vertically extending elevator shaft <NUM>. The machinery brake <NUM> may stop the rotation of the traction sheave <NUM> and thereby the movement of the elevator car <NUM>.

The car frame <NUM> may be connected by the ropes <NUM> via the traction sheave <NUM> to the counterweight <NUM>. The car frame <NUM> may further be supported with gliding means <NUM> at guide rails <NUM> extending in the vertical direction in the shaft <NUM>. The gliding means <NUM> may comprise rolls rolling on the guide rails <NUM> or gliding shoes gliding on the guide rails <NUM> when the car <NUM> is moving upwards and downwards in the elevator shaft <NUM>. The guide rails <NUM> may be attached with fastening brackets <NUM> to the side wall structures <NUM> in the elevator shaft <NUM>. The gliding means <NUM> keep the car <NUM> in position in the horizontal plane when the car <NUM> moves upwards and downwards in the elevator shaft <NUM>. The counterweight <NUM> may be supported in a corresponding way on guide rails that are attached to the wall structure <NUM> of the shaft <NUM>.

The car <NUM> may transport people and/or goods between the landings in the building. The elevator shaft <NUM> may be formed so that the wall structure <NUM> is formed of solid walls or so that the wall structure <NUM> is formed of an open steel structure.

The suspension ratio is <NUM>:<NUM> in this first elevator. When the electric motor <NUM> lifts or lowers the car <NUM> in this first elevator by X meters, then X meters of lifting rope <NUM> passes over the traction sheave <NUM>.

The elevator may be controlled by a controller <NUM>.

<FIG> shows a side view of a second elevator.

The suspension ratio in this second elevator is <NUM>:<NUM> compared to the suspension ratio <NUM>:<NUM> in the first elevator shown in <FIG>. When the electric motor <NUM> lifts or lowers the car <NUM> in this second elevator by X meters, then 2X meters of lifting rope <NUM> passes over the traction sheave <NUM>.

Both ends of the hoisting rope <NUM> are fixed in fixing points A1, A2 to the shaft <NUM> in an upper end portion of the shaft <NUM>. The hoisting rope <NUM> passes from a first fixing point A1 vertically downwards in the shaft <NUM> towards the lower end of the car <NUM>. The hoisting rope <NUM> is then turned on a first deflection roll <NUM> positioned below the car <NUM> into a horizontal direction. The hoisting rope <NUM> passes then in the horizontal direction to a second deflection roll <NUM> positioned below the car <NUM> at an opposite side of the car <NUM> in relation to the first deflection roll <NUM>. The car <NUM> is supported on the first deflection roll <NUM> and on the second deflection roll <NUM>. The hoisting rope <NUM> passes after the second deflection roll <NUM> again vertically upwards in the shaft <NUM> towards the traction sheave <NUM>. The hoisting rope <NUM> is then again turned on the traction sheave <NUM> into a vertically downwards directed direction in the shaft <NUM> towards a third deflection roll <NUM>. The counterweight <NUM> is supported on the third deflection roll <NUM>. The hoisting rope <NUM> passes then after the third deflection roll <NUM> again vertically upwards in the shaft <NUM> to the second fixing point A2. Rotation of the traction sheave <NUM> in a clockwise direction moves the car <NUM> upwards, whereby the counterweight <NUM> moves downwards and vice a versa. The friction between the hoisting rope <NUM> and the traction sheave <NUM> eliminates slipping of the hoisting rope <NUM> on the traction sheave <NUM> in normal operational conditions.

The electric motor <NUM> in the hoisting machinery <NUM> may comprise a motor frame <NUM> for supporting the hoisting machinery <NUM> at a motor bed frame <NUM>. An isolation pad <NUM> and a load transfer plate <NUM> may be positioned between the motor frame <NUM> and the motor bed <NUM>. The motor bed <NUM> may be supported on a guide rail <NUM> in the shaft <NUM>. The hoisting machinery <NUM> could be supported on the guide rail <NUM> in any height position along the guide rail <NUM>. The traction sheave <NUM> and the electric motor <NUM> could also be separated. The traction sheave <NUM> could be supported on the guide rail <NUM> in the shaft <NUM> and the electric motor <NUM> could be positioned e.g. at the bottom of the pit in the shaft <NUM>. A power transmission would thus be needed between the traction sheave <NUM> and the electric motor <NUM>.

<FIG> shows a side view of a first support arrangement of the elevator machinery.

The support arrangement between the motor frame <NUM> of the hoisting machinery <NUM> and the motor bed <NUM> may comprise the isolation pad <NUM>, the load transfer plate <NUM> and at least one sensor <NUM> for measuring continuously the forces acting on the traction sheave <NUM>.

The sensor(s) <NUM> may be positioned between the load transfer plate <NUM> and the motor bed <NUM>. Another possibility is to position the sensor(s) <NUM> in connection with the shaft of the traction sheave <NUM>. The sensors could in the latter situation be positioned in connection with the bearing of the shaft of the traction sheave <NUM>, whereby the sensors <NUM> would measure the force acting on the shaft of the traction sheave <NUM>.

Any sensors <NUM> capable of measuring continuously the forces acting on the traction sheave <NUM> may be used.

The sensor may be formed of a load cell i.e. a transducer which converts force into a measurable electric output. Strain gauge load cells, which are the most common in industry, could be used in this first support arrangement. Strain gauge load cells are particularly stiff, have very good resonance values, and tend to have long life cycles in application. Strain gauge load cells work on the principle that the strain gauge (a planar resistor) deform when the material of the load cells deforms appropriately. Deformation of the strain gauge changes its electrical resistance, by an amount that is proportional to the strain. The change in the resistance of the strain gauge provides an electric value change that is calibrated to the load placed on the load cell. A load cell usually consists of four strain gauges in a Wheatstone bridge configuration. Also piezoelectric load cells, hydraulic load cells, pneumatic load cells could be used in this first support arrangement.

The elevator is controlled by a controller <NUM>.

<FIG> shows a side view of a second support arrangement of the elevator machinery.

The difference between this second support arrangement and the first support arrangement is in the sensor <NUM> that is used.

The sensor <NUM> may be positioned between the frame support and the isolation pad <NUM> or between the isolation pad <NUM> and the load transfer plate <NUM> or between the load transfer plate <NUM> and the frame structure <NUM>.

<FIG> shows a side view of a third support arrangement of the elevator machinery.

The sensor <NUM> may be positioned between two vibration isolation pads <NUM>, two vibration isolation pads <NUM> being positioned between the motor frame <NUM> and the motor bed <NUM>.

<FIG> shows a side view of a fourth support arrangement of the elevator machinery.

The sensor <NUM> may be positioned between the vibration isolation pad <NUM> and the motor bed <NUM> or between the lower ends of the legs of the motor bed <NUM> and the floor of the machine room.

<FIG> shows an axonometric view, <FIG> shows a plan view and <FIG> shows a cross sectional view of a sensor.

The sensor is a strain gauge sensor <NUM>. Three sensor assemblies <NUM>, <NUM>, <NUM> are embedded between a bottom plate <NUM> and a top plate <NUM>. The second sensor <NUM> may be positioned between two planar surfaces e.g. between the machinery and the bed plate.

A strain gauge load cell is particularly stiff, has a very good resonance value, and tend to have a long life cycle in application. The strain gauge load cell work on the principle that the strain gauge (a planar resistor) deform when the material of the load cells deforms appropriately. Deformation of the strain gauge changes its electrical resistance, by an amount that is proportional to the strain. The change in the resistance of the strain gauge provides an electric value change that is calibrated to the load placed on the load cell.

The further sensor may be formed of a capacitive sensor. The capacitive sensor may be formed of an electrically non-conducting first layer. The first layer may be elastic i.e. it returns to its original shape when unloaded. The first layer should thus be reversibly compressible. At least one electrically conductive electrode may be provided at a first surface of the first layer. An electrically conductive layer may be provided on the second opposite surface of the first layer. A pressure on the first material layer caused by a weight will cause compression of the first layer, whereby the distance between the at least one electrically conductive electrode and the electrically conductive layer will change. The change in the distance will change the capacitance between the at least one electrode and the electrically conductive layer. The weight acting on the first layer is thus proportional to the change in the capacitance between the at least one electrode and the electrically conductive layer.

The sensor <NUM> may comprise a first layer <NUM>. The first layer <NUM> may be an elastic and stretchable layer of an electrically non-conducting material. The first layer <NUM> may be formed as one single layer or as two or more different layers. At least two stretchable electrodes <NUM>, <NUM> may be provided on a first surface of the first layer <NUM>. The electrodes <NUM>, <NUM> may be attached form a first surface to the first surface of the first layer <NUM> so that the electrodes <NUM>, <NUM> are positioned at a distance apart from each other. A flexible foil <NUM> may further be provided. An electrically conductive wiring <NUM>, <NUM> may be connected to the flexible foil <NUM> and via connections <NUM>, <NUM> to the electrodes <NUM>, <NUM>. The electrically conductive wiring <NUM>, <NUM> may be attached to a second surface of the electrodes <NUM>, <NUM>. The second surface of the electrodes <NUM>, <NUM> is opposite to the first surface of the electrodes <NUM>, <NUM>. An electrically conducting layer <NUM> may further be provided on a second surface of the first layer <NUM>. The second surface of the first layer <NUM> is opposite to the first surface of the first layer <NUM>.

The sensor <NUM> may form a capacitive sensor, whereby the capacitance between each electrode <NUM>, <NUM> and the electrically conductive layer <NUM> may be measured. The distance between the electrodes <NUM>, <NUM> and the electrically conductive layer <NUM> varies is response to the force F acting on the sensor <NUM>.

The first layer has a first Young's modulus Y311 and a first yield strain ε311. The first yield stain ε311 is at least <NUM> percent.

Young's modulus is a mechanical property that measures the stiffness of a solid material. It defines the relationship between stress (force per unit area) and strain (proportional deformation) in a material in the linear elasticity regime of a uniaxial deformation.

The yield point is the point on a stress-strain curve that indicates the limit of elastic behavior and the beginning of plastic behavior. Yield strength or yield stress is a material property defining the stress at which a material begins to deform plastically whereas yield point is the point where nonlinear (elastic + plastic) deformation begins. Prior to the yield point the material will deform elastically and will return to its original shape when the applied stress is removed. Once the yield point is passed, some fraction of the deformation will be permanent and non-reversible. Yield strain is a strain value corresponding to yield stress. The yield strain can be read from a material's stress-strain curve for yield point. The yield strain defines the material's elongation limit before plastic deformation occurs.

The first layer <NUM> may comprise at least one of polyurethane, polyethylene, poly(ethylene-vinyl acetate), polyvinyl chloride, polyborodimethylsiloxane, polystyrene, acrylonitrile-butadiene-styrene, styrene-butadienestyrene, ethylene propylene rubber, neoprene, cork, latex, natural rubber, silicone and thermoplastic gel.

The stretchable electrodes <NUM>, <NUM> may comprise electrically conductive particles, such as flakes or nanoparticles, attached to each other in an electrically conductive manner. The electrical conductive particles may comprise at least one of carbon copper, silver and gold.

The electrically conductive layer <NUM> may comprise at least one of electrically conductive material from conductive ink, electrically conductive fabric and electrically conductive polymer.

The connection <NUM>, <NUM> may be made from electrically conductive adhesive, i.e. an adhesive comprising cured electrically conductive adhesive. Such adhesives include isotropically conductive adhesives and anisotropically conductive adhesives.

The flexible foil <NUM> has a second Young's modulus Y350. The first Young's modulus Y311 is smaller than the second Young's modulus Y350.

The flexible foil <NUM> may comprise at least one of polyester, polyamide, polyethylene, naphthalate, and polyetheretherketone.

The second sensor <NUM> may measure the force acting on the machine bed.

An electrically conductive material means in this application a material of which the resistivity (specific electric resistivity) is less than <NUM>Ωm at the temperature of <NUM> degrees Celsius. An electrically non-conductive material means in this application a material of which the resistivity (specific electric resistivity) is more than <NUM>Ωm at the temperature of <NUM> degrees Celsius.

<FIG> shows forces acting on the traction sheave in an elevator.

The figure shows masses M1 and M2 hanging from each side of the traction sheave <NUM> and a mass M3 of the hoisting machinery <NUM>. The masses M1, M2, M3 cause corresponding forces F1, F2, F3 acting on the machinery bedplate of the hoisting machinery <NUM>. The first force F1 is caused by the masses M1 hanging with the hoisting ropes <NUM> on the first side of the traction sheave <NUM>. The masses M1 hanging on the first side of the traction sheave <NUM> is formed of at least the car <NUM> and the load Q in the car <NUM>. The second force F2 is caused by the masses M2 hanging with the hoisting ropes <NUM> on the second opposite side of the traction sheave <NUM>. The masses M2 hanging on the second side of the traction sheave <NUM> is formed of at least the counterweight <NUM>. The third force F3 is caused by the masses M3 of the hoisting machinery <NUM> acting on the machinery bed plate. The total force FΣ acting on the machinery bedplate hanging from the traction sheave <NUM> is formed of the sum of the forces F1, F2 and F3 i.e. FΣ = F1 + F2 + F3.

The total force FΣ acting on the machinery bedplate may be measured with the sensor(s) arrangements disclosed in <FIG>.

The situation is exemplified with the following example. The starting point in the example is a <NUM>% balancing ratio in an elevator with a <NUM>:<NUM> suspension ratio. The car weight KT is <NUM>, the weight of the maximum load in the car is Qmax = <NUM>. The weight of the counterweight (CWT) is thus KT + <NUM> Qmax = <NUM> + <NUM>*<NUM> = <NUM>.

The total minimum axial hanging mass with an empty car <NUM> may be calculated in the following way in an elevator with a <NUM>:<NUM> suspension ratio: <MAT> <MAT>.

The total minimum axial hanging mass with an empty car <NUM> is thus the sum of the masses F1 and F2 i.e. <NUM> + <NUM> = <NUM>.

The total actual axial hanging mass with a full car <NUM> may be calculated in the following way in an elevator with a <NUM>:<NUM> suspension ratio: <MAT> <MAT>.

The total actual axial hanging mass with a full car <NUM> is thus the sum of the masses F1 + F2 i.e. <NUM> + <NUM> = <NUM>.

Three different stalling situations may occur:.

In order to improve the reliability and in order to enable stalling detection also with a smaller balancing percentage and/or in an overload (e.g. <NUM>% load) situation (when the total actual axial hanging mass KT + Qact is greater than the allowed total minimum axial hanging mass), a predetermined stalling limit weight reduction tolerance may be used in the stalling detection activation. The predetermined stalling limit weight should be divided by the elevator suspension ratio SPR. The weight KT of the car may be used as one possible stalling limit weight reduction tolerance. The stalling limit weight reduction tolerance in an elevator with a <NUM>:<NUM> suspension ratio would thus be KT/<NUM>. The stalling detection may be activated:.

In this case, the elevator stalling detection can determine a total minimum axial hanging mass FΣmin after the car doors have been closed but before the actual start of the elevator based on the total actual axial hanging mass FΣact.

This makes it possible to use axial force LWD based stalling detection also for CWT stalling i.e. there is no need e.g. for stalling detection switches on the CWT side of the suspension terminal.

<FIG> shows a flow diagram of a method for controlling an elevator.

The elevator car <NUM> is first loaded and/or unloaded on a landing in step <NUM>.

The car <NUM> doors are fully closed or the car doors are not fully open i.e. the loading and/or the unloading of the car <NUM> has been completed in step <NUM>.

The total actual axial hanging mass FΣact is measured in step <NUM>. The total actual axial hanging mass FΣact may be measured by one or more load sensors. The total actual axial hanging mass FΣact = (F1act + F2 + F3)/SPR = [(KT+Qact) + (KT+Bal% * Qmax) + F3(Machinery)]/SPR. SPR is the suspension ratio of the elevator i.e. <NUM> in case the suspension ratio of the elevator is <NUM>:<NUM>.

A total minimum axial hanging mass FΣmin is then determined for the elevator in step <NUM>. The total minimum axial hanging mass FΣmin may be determined by deducting a stalling weight reduction tolerance (a tolerance weight) divided by the elevator suspension ratio SPR. The weight KT of the car is one possible reduced stalling weight when determining the total minimum axial hanging mass FΣmin = FΣact - KT/SPR. The total minimum axial hanging mass FΣmin may in an elevator with a <NUM>:<NUM> suspension ratio be determined as FΣmin = FΣact - KT and in an elevator with a <NUM>:<NUM> suspension ration be determined as FΣmin = FΣact - KT/<NUM>.

A possible reopening of the car <NUM> doors is then detected in step <NUM>. The car <NUM> doors may be reopened e.g. in case the load in the car <NUM> exceeds the maximum load. The car <NUM> doors may also be reopened e.g. in case somebody presses the call button on the landing when the car doors are closing or the car doors have closed, but the car has not yet started.

I the answer is yes i.e. the car <NUM> doors are reopened, then the method starts again from the beginning.

If the answer is no i.e. the car <NUM> doors are not reopened, then start of the elevator is permitted in step <NUM>. The start of the elevator may be permitted e.g. by permitting opening of the machinery brake. The car may also be kept in place by the machinery, whereby start of the elevator may be permitted by permitting drive of the machinery.

Then it is determined whether the elevator operates in a normal drive LWD (Load Weighing Device) profile in step <NUM>. The normal drive LWD profile is based on the determined total minimum axial hanging mass FΣmin i.e. the stalling limit.

The answer is yes, i.e. the elevator is operating in the normal drive LWD profile, when the total actual axial hanging mass FΣact is equal to or greater than the determined stalling limit total minimum axial hanging mass FΣmin in step <NUM>.

The elevator car <NUM> may now be moved in a normal run to the next landing in step <NUM>.

The answer is no, i.e. the elevator is not operating within the normal drive LWD profile, when the total actual axial hanging mass FΣact is smaller than the stalling limit total minimum axial hanging mass FΣmin. The counterweight <NUM> is stuck when F2 = <NUM> in step <NUM>. The car <NUM> is stuck when F1 = <NUM> in step <NUM>.

The answer is thus no when the counterweight <NUM> is stuck or the car <NUM> is stuck, whereby stalling is detected and the hoisting machinery is immediately stopped <NUM>.

The analytics that process the measurement results may be able to determine which of the two i.e. the counterweight <NUM> or the car <NUM> is stalling. This may be done based on the forces acting on each side of the traction sheave <NUM>. The moment acting on the shaft of the traction sheave <NUM> will change when the forces acting on each side of the traction sheave <NUM> changes. Several sensors or a sensor with several pressure cells may be needed in order to be able to measure forces on each side of the traction sheave <NUM>.

The term force and weight are used more or less as synonyms in this application. The weight of a body is W = M*g, where W denotes weight, M denotes mass and g denotes acceleration due to gravity. The value of the acceleration g due to gravity on the earth is <NUM>,<NUM>/s<NUM>. The unit of mass M is kg and the unit of weight W (force) is N. A mass M of <NUM> causes a force of <NUM>,<NUM> N on the earth.

The use of the invention is not limited to the elevators disclosed in the figures. The invention can be used in any type of elevator e.g. an elevator comprising a machine room or lacking a machine room, an elevator comprising a counterweight or lacking a counterweight. The counterweight could be positioned on either side wall or on both side walls or on the back wall of the elevator shaft. The drive, the motor, the traction sheave, and the machine brake could be positioned in a machine room or somewhere in the elevator shaft. The car guide rails could be positioned on opposite side walls of the shaft or on a back wall of the shaft in a so called ruck-sack elevator.

The use of the invention is not limited to the weight measuring devises and/or sensors disclosed in the figures. The invention can be used in connection with any kind of weigh measuring device and/or sensor being capable of measuring the total actual axial hanging weight FΣact.

Claim 1:
A method for controlling an elevator comprising
a first step in which the car (<NUM>) is on a landing with car doors open for loading and/or unloading the car (<NUM>),
a second step in which it is determined whether the car doors are fully closed or the car doors are not fully open after the loading and/or unloading is completed,
a third step in which the total actual axial mass hanging from the traction sheave (<NUM>) is measured,
a fourth step in which a stalling limit total minimum axial mass hanging from the traction sheave (<NUM>) is determined by deducting from the total actual axial mass measured in the third step a predetermined stalling weight reduction tolerance, said predetermined stalling weight reduction tolerance being determined as the weight of the car (<NUM>) divided by the suspension ratio of the elevator,
a fifth step in which reopening of the car (<NUM>) doors is checked,
whereby if the car (<NUM>) doors are reopened, then return to the first step, else, continue to the next step,
a sixth step in which start of the elevator is permitted,
a seventh step in which the total actual axial mass measured in the third step is compared with the stalling limit total minimum axial mass determined in the fourth step, whereby
if the total actual axial mass measured in the third step is equal to or greater than the stalling limit total minimum axial mass determined in the fourth step, then normal run of the elevator car (<NUM>) to the next landing is permitted, else, the elevator is stopped.