The invention concerns in general the technical field of elevators. More particularly, the invention concerns a monitoring solution of a machinery brake in an elevator.
An elevator comprises an elevator hoisting machine into which a machinery brake is implemented. The machinery brake engages mechanically with a rotating part of the hoisting machine causing the braking effect. The machinery brake may e.g. be a shoe brake, a drum brake or a disc brake.
A structure of the machinery brake is typically such that it comprises an armature part provided with a brake pad and a frame part comprising an electromagnet. Between the armature part and the frame part is arranged one or more springs. The operation of the machinery brake is based on a utilization of the springs that are arranged to push the armature part provided with a brake pad against the braking surface of a rotating part of the hoisting machine in order to achieve the braking effect i.e. holding the elevator car stationary in the shaft when the control of the motor is inactivated. By means of the electromagnet when provided with an electric current it is possible to pull a magnetic core of the armature part, and thus the armature part, against the spring force of the springs so that the brake may be released away from the braking surface. Hence, the control of the machinery brake between the activated and inactivated states may be achieved by controlling the current supply of the electromagnet and, thus, the force of attraction of the electromagnet may be controlled.
As is clear the machinery brake of an elevator hoisting machine is under heavy forces when used. Additionally, the elevator is affected by great number of environmental variables, such as constant change in load, vibration caused by the hoisting motor among others, thermal expansion due to ambient temperature and temperature generated by elevator operation. All these have also effect on elevator brake and the elevator parts in general and in the worst case may cause displacement of parts even so that the elevator starts to misoperate or stop operation in full. As regards to elevator brake it is important to detect that the brake parts have such mutual positions that they do not prevent the operation of the elevator brake.
In known solutions so called micro switches are used for detecting mutual positions of at least two objects, and especially a change in positions of the objects. However, the problem in the use of micro switches is that they cannot be used in every application areas because there is no possibility to arrange a space for them and/or the operational environment is such that it prevents the use of the micro switches. For example, an electromagnetic field of the electromagnets may cause challenges in using the micro switches, which is the case in elevator brakes. Moreover, one problem with micro switches is that they are unreliable by default and their accuracy is inadequate in many application areas. For example, in elevator brakes the mutual motion of the armature part and the frame part is in scale of 0.15 mm, but the micro switches cannot detect such a small motion with acceptable reliability. Further, manufacturing of the micro switches is challenging.
Hence, there is need to develop solutions by means of which it is at least partly possible to improve a monitoring of an operational state of elevator brakes.
The following presents a simplified summary in order to provide basic understanding of some aspects of various invention embodiments. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying embodiments of the invention.
An objective of the invention is to present a solution for monitoring an operational state of a machinery brake for elevators. Alternatively or additionally, it is an object of the present invention to provide a solution by means of which the operational state monitoring is achieved by a sophisticated sensor arrangement implemented in the machinery brake.
The objectives of the invention are reached by a machinery brake for an elevator and a method as defined by the respective independent claims.
According to a first aspect, a machinery brake for an elevator is provided, wherein the machinery brake comprises: a frame part comprising an electromagnet, an armature part; wherein the machinery brake further comprising an inductive proximity sensor mounted to one of the following: the frame part, the armature part and a target mounted to the other of the following: the frame part, armature part, wherein the inductive proximity sensor and the target are mounted with respect to each other so that in a normal state of the machinery brake the target resides within an operational area of the inductive proximity sensor and in an abnormal state of the machinery brake the target resides at least partly outside the operational area of the inductive proximity sensor.
The proximity sensor may be configured to generate a first output signal when the machinery brake is in the normal state and a second output signal when the machinery brake is in the abnormal state.
The target may comprise a planar surface facing the proximity sensor wherein the planar surface is arranged perpendicularly to a center axis of a coil in the proximity sensor. A boundary defining the planar surface of the target may comprise rounded shapes. The planar surface may be a circle.
Further, a ratio of an outer diameter of the coil with respect to a shortest diameter of the target surface may be 1:3.
The inductive proximity sensor and the target may be mounted with the respective parts so that a direction of a central axis of a coil residing in the inductive proximity sensor deviates from a normal of the surface of the armature part facing the frame part.
The target may be brought to the operational area of the inductive proximity sensor through a through hole arranged in the part into which the inductive proximity sensor is mounted to.
The target may at least partly be made of ferromagnetic material.
The machinery brake may further comprise a control unit that is configured to generate an alarm signal in response to a detection that the machinery brake is in the abnormal state.
According to a second aspect, a method for monitoring an operational state of a machinery brake of an elevator is provided, wherein the machinery brake comprises a frame part comprising an electromagnet and an armature part, the method comprising: monitoring an output signal of an inductive proximity sensor that is mounted to one of the following: the frame part, the armature part wherein the output signal is dependent on a mutual position of the inductive proximity sensor and a target mounted to the other of the following: the frame part, armature part; and in response to detection that the output signal of the inductive proximity sensor is changed a control unit of the machinery brake is configured to generate an alarm signal.
Various exemplifying and non-limiting embodiments of the invention both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying and non-limiting embodiments when read in connection with the accompanying drawings.
The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of unrecited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of “a” or “an”, i.e. a singular form, throughout this document does not exclude a plurality.
The embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings.
The specific examples provided in the description given below should not be construed as limiting the scope and/or the applicability of the appended claims. Lists and groups of examples provided in the description given below are not exhaustive unless otherwise explicitly stated.
The present invention is at least partly based on a utilization of at least one proximity sensor in elevator solutions and especially in a machinery brake of the elevator. The proximity sensor is a type of sensor that is configured to detect a presence or an absence of a target within an operational area of the sensor. There are different types of proximity sensors available. For example, the operation of the proximity sensors may be based on a capacitance between the sensor and the target or an inductance between the sensor and the target. Further, photoelectric sensors may also be considered as proximity sensors as a reflection of a transmitted light may be monitored and analyzed in order to detect the presence or the absence of the target. Also other types of proximity sensors are known. A selection of the type of proximity sensor is typically dependent on an application area in which the proximity sensor is applied to. More specifically, the selection depends heavily on a material of the target. As an example, if the target is metal an inductive proximity sensor is applicable.
The proximity sensor, and especially the inductive proximity sensor, comprises an inductive coil made of numerous turns of conductive wire, such as copper, and a capacitor for storing electrical charge. An input current is provided to an oscillator that generates an alternating current to the coil, which, in turn, generates a magnetic field in front of the proximity sensor. Now, when a target made of conductive metal is brought in a zone defined by boundaries of the magnetic field, some of the energy is transferred into the target causing eddy currents flowing in the target surface. Thus, the power loss affects to current flow in the internal LC resonance circuit of the proximity sensor, and when the target moves away from the zone at some point the state of the sensor changes. In other words, the sensor may indicate the presence of the target within the magnetic field for example by outputting a signal and when the target moves enough away from the boundaries of the magnetic field, the proximity sensor changes its state and the output signal is not present anymore.
In order to monitor an operational state of the machinery brake, according to an embodiment of the invention, an inductive proximity sensor is arranged in the machinery brake as schematically illustrated in
At least some aspects of the present invention relate to a utilization of the arrangement, as illustrated e.g. in
For sake of clarity one may consider that in
Next the at least some aspects of the invention relating to the monitoring the lateral displacement is described by referring to
By combining the coordination system with the switching point consideration in three dimensional space the advantages of the invention may be explained in more detail. As already mentioned the switching point in the context of the inductive proximity sensors refers to a distance between the sensor and the target at which the sensor changes its state due to the fact that magnetic field traveling through the target changes over a limit, i.e. sensor's detection circuit detects a reduced strength in an oscillating magnetic field. The change of the state in sensor refers to output signal from the proximity sensor.
According to an embodiment of the invention it may be desirable that the monitoring of the lateral displacement is arranged to be symmetric in every direction. Such an embodiment is schematically illustrated in
The shape of the planar surface facing the proximity sensor may vary from the circle one as depicted in
Next the operation of the arrangement as disclosed is described in more detail. Namely, the proximity sensor 122 and the target 124 mounted to the actuating part i.e. armature part 110 are initially mutually positioned so that the central axis of the coil 210 in the proximity sensor 122 travels, at least essentially, through the center of the circular surface of the target 124. The coil generates the magnetic field when supplied with current which magnetic field travels from a first end of the coil through the metallic target and the air gap back to the other end of the coil 210. The volume of the metallic conductive target material defines, at least partly, the resistance, i.e. reluctance, for the magnetic field. As at least one aim of the present invention is to monitor the operational state of the machinery brake, and specifically to detect permanent changes in the mutual positions of the proximity sensor 122 and the target 124, the target surface is advantageously symmetric and changes in the magnetic field are to be monitored. At some point the magnetic field experienced in the sensor may change due to a change in mutual positions of the mentioned elements. This is because the magnetic field does not travel anymore in the same manner as originally due to displacement that causes an increase in the reluctance of the magnetic circuit. In other words the mutual lateral displacement of the elements is that large that the target does not anymore provide a path for the magnetic field to travel so that the reluctance remains within limits defined by the structure. The change in the magnetic field is detected in the proximity sensor and the sensor changes it state. One additional inventive aspect of the arrangement as described is that when the state of the sensor changes it does not return to the original state at the same displacement point where the change of the sensor state happened if the elements return towards their original positions (i.e. when the sensor was at the first state (“normal state”)). This is due to the fact that the coil in the proximity sensor aims to resist the change in the magnetic field. The phenomenon is known as hysteresis. Due to hysteresis in the monitoring arrangement the machinery brake may be driven to a state that it is not allowed to return to operative state without maintenance. The maintenance may comprise an alignment of the frame part and the armature part, with respect to each other, so that the operation of the proximity sensor may be brought to a normal state. Naturally, the alignment may relate to an alignment of the proximity sensor and the target, especially in case if it is concluded that the frame part and the armature part has not laterally displaced with each other. An advantage of the invention is that the monitoring of the elevator brake operation with the proximity sensor as described reveals displacement of the armature part with respect to the frame part, but also if either or both the proximity sensor and the target are displaced. The result is that a need for service is detected.
The operation of the monitoring arrangement may at least partly be adjusted by dimensioning sizes of the coil 210 of the proximity sensor 122 and the target 124 optimally for the application area. According to an embodiment of the invention the optimal dimensioning in the machinery brake may be such that a ratio of an outer diameter of the coil 210 with respect to a diameter of the circular target surface is 1:3. In case the target is not circular, but another shape with rounded shape, such as any of the ones illustrated in
An aspect of the present invention is that the coil in the proximity sensor and a coil of the electromagnet residing in the frame part preferably does not interfere each other. The interference may be mitigated by optimal selection of the proximity sensor so that a frequency of the magnetic field generated by the coil in the proximity sensor differs from any other magnetic field frequency existing in the environment of the machinery brake. For example, it is possible to optimize the operation of the electromagnet in the frame part 120 so that the operation does not generate frequencies overlapping the operational frequency of the proximity sensor. For example, the operational frequency of the proximity sensor 122 may e.g. be >100 kHz, whereas the frequencies of the magnetic fields originating from machinery brake, due to disturbances among other, remain <50 KHz.
Some further embodiment of the present invention may be implemented so that the proximity sensor 122 and the target 124 are mounted in a slanted position with respect to an axis of motion of the armature part 110. More specifically, the central axis of the coil 210 in the proximity sensor 122 travels slanted with respect to the axis of a normal motion of the armature part 110 i.e. wherein the armature part 110 is configured to move essentially along a normal of the surface of the armature part 110 facing the frame part. Such an implementation is schematically illustrated in
The embodiments as described above are implemented so that the proximity sensor 122 is mounted in the frame part 120 and the target is mounted, or arranged, in the armature part 110 of the machinery brake. However, the inventive idea of the present invention may also be applied so that the proximity sensor 122 is mounted in the armature part 110 and the target 124 is mounted in the frame part 120. In such an implementation the cable supplying current to the proximity sensor 122 shall be brought to the sensor so that arrangement enable the movement of the armature part 110 in such a manner that the cable does not prevent the motion nor it is possible that the cable, or any part of it, ends up to any un-allowed location, such as between the frame part and the armature part, in the machinery brake. Hence, the mounting arrangement of the cable is important. Alternatively or in addition, the cable shall be protected so that it may stand the stress caused by the motion.
As already mentioned the target material shall be made of conductive metal. Advantageously, the target for the proximity sensor is a flat piece of ferrous metal, but non-ferrous metals may also be used. Generally speaking some non-limiting examples of the target materials may be: steel (Fe360), stainless steel, aluminum, brass, copper. Especially, in elevator environment and in the application area of machinery brakes for elevators, ferromagnetic material is used as the target material at least partly, such as coated with the ferromagnetic material. This is due to the fact that as the ferromagnetic material maintains the magnetic characteristic it has a further effect in the elevator environment. Namely, they may collect at least part of the dust from the elevator shaft around the target. That forms a protection layer to the target against other dirt ending up between the target and the proximity sensor. Hence, the operation of the present invention is also improved by using the ferromagnetic material as the target material, such as iron or any other applicable.
The proximity sensor and the target may be mounted to the entities, such as to the frame part or to the armature part, with any known method. For example, any applicable mounting device, such as screw, bolt or similar may be used. As well, gluing, welding or any similar may be used either both or one of the mountable parts.
Some aspects of the invention relate to a method for monitoring an operational state of a machinery brake of an elevator, wherein the machinery brake comprises a frame part 120 comprising an electromagnet and an armature part 110. In the method an output signal of an inductive proximity sensor 122 is monitored. The inductive proximity sensor 122 is mounted either to the frame 120 part or the armature part 110. The output signal of the inductive proximity switch is dependent on a mutual position of the inductive proximity sensor and a target 124 that is mounted to the other of the frame part 120 or armature part (110) i.e. to the other of the one into which the sensor 122 is mounted to. According to the method, in response to detection that the output signal of the inductive proximity sensor 122 is changed a control unit of the machinery brake is configured to generate an alarm signal.
As described the proximity sensor generates an output signal having typically two states. The solution according to the invention is based on an idea that when the machinery brake operates normally, i.e. the parts of the machinery brake are mutually positioned in an acceptable way, the proximity sensor is configured to generate a first output signal. In case the proximity sensor changes its state due to a change in mutual positions of the parts exceeding the limit defined by the arrangement according to the invention the proximity sensor is configured to generate a second output signal. A control unit may be configured to monitor the output signal and in response to a detection of a change from the first output signal to a second output signal the control unit may be configured to perform predetermined tasks. The predetermined tasks may e.g. comprise, but are not limited to, one or more of the following: controlling of operation of the elevator, controlling of a maximum travel speed of the elevator, controlling of access to the elevator.
The monitoring of an operational state of the machinery brake comprises at least to detecting with sensor arrangement if the machinery brake is operating normally or if it is misoperating. The misoperation may e.g. be due to misalignment, or un-allowed displacement, of parts of the machinery brake with respect to each other.
The specific examples provided in the description given above should not be construed as limiting the applicability and/or the interpretation of the appended claims. Lists and groups of examples provided in the description given above are not exhaustive unless otherwise explicitly stated.
Number | Date | Country | Kind |
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16167492.4 | Apr 2016 | EP | regional |