Patent Publication Number: US-7905328-B2

Title: Brake device of an elevator car

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a brake device of an elevator car that, at least on occurrence of an inadmissibly high speed of the elevator car, brakes the elevator car. 
     From JP 06092568 such a brake device is known, in which an overspeed governor with a rope sheave activates via an overspeed governor rope a brake unit on an elevator car. In the form of a closed loop, the overspeed governor rope passes at one end round the rope sheave of the overspeed governor that is arranged in the upper area of the car travel path, and at the other end round a rope reversing sheave that is present in the lower area of the car travel path. One end of the rope loop is coupled to an actuating element of the brake unit that is mounted on the elevator car, and therefore also to the elevator car. The lower rope reversing sheave is arranged vertically movable and loaded in downward direction by a weight, so that the rope loop is tensioned by the lower rope reversing sheave. A monitoring device with a detector monitors the position of this lower rope reversing sheave so as to influence the elevator control system in case of breakage, or excessive elongation, of the overspeed governor rope. 
     In the mentioned state of the art, breakage or excessive elongation of the overspeed governor rope is detected by a detector, and corresponding safety measures initiated if necessary. However, failure of the coupling between the overspeed governor rope and the elevator car during operation of the elevator is not detected by the monitoring device. This has the consequence that, on failure of the coupling, the elevator system remains in operation even though the brake device on the elevator car, that is of utmost importance for the safety of the passengers, is not functioning. 
     Possible causes of such failure of the coupling between the overspeed governor rope and the brake unit, and thereby also the elevator car are, for example, a fallen-out or fractured connecting bolt, a fractured actuating lever (actuating element) of the brake unit, or a broken actuating shaft via which the actuating lever is connected to the brake unit and thereby also the elevator car. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a brake device of the type described above that does not possess the disadvantages of the device cited as the state of the art. In particular, a brake device for elevator cars shall be created in which, following failure of the coupling between the overspeed governor and the brake unit of the elevator car, the elevator system does not continue to remain in operation in an inadmissible condition of safety. 
     According to the invention, the object is fulfilled by means of a brake device for an elevator car, and an elevator system with the brake device, in which the brake device possesses the following characteristics:
         it contains at least one brake unit that is mounted on the elevator car and has an actuating element;   it contains at least two tension-means reversing-sheaves, of which one is installed in the area of the upper end, and one in the area of the lower end, of the car travel path;   it contains a flexible tension means that passes round the tension-means reversing sheave, at least one end of the tension means extending parallel to the travel path of the elevator car, being coupled to the actuating element of the brake unit and thereby to the elevator car, and in normal operation moving synchronously with the elevator car;   it contains a blocking device that at least on overspeed of the elevator car brakes the tension means, as a result of which the tension means, via the actuating element, activates the brake unit; and   it contains a monitoring device that detects failure of the coupling between the tension means and the elevator car.       

     The advantage achieved by the invention is mainly to be seen in that the operating safety of the elevator system is increased in that, on failure of the coupling (operating interaction) between the tension means and the elevator car, and thereby also the brake unit of the elevator car, an operating condition is avoided in which persons are transported with the elevator car even though the prescribed protection by the brake device is no longer capable of functioning. 
     According to a preferred embodiment of the invention, the tension means of the brake device forms a closed loop that passes round the tension-means reversing-sheaves. Both ends of the tension means are fastened to a coupling element that, at the same time, couples the tension means to the actuating element of the brake unit. The combination of the connection of the tension-means ends and the coupling into one single element has the advantages that two functions are fulfilled with the same component, that the weight is concentrated into one single component, and that thereby the greatest possible freedom for the arrangement of the tension-means reversing-sheave is achieved. 
     It is expedient for the coupling element to have a weight that, in the case of failure of the coupling between the tension means and the elevator car, is sufficient to set the tension means, along with the tension-means reversing-sheaves, in motion so that the coupling element falls. 
     A particularly simple and inexpensive embodiment of the invention is achieved through the monitoring device containing a detector that is mounted in the area of the lower tension-means reversing-sheave, that detects the coupling element should the coupling element, following failure of the coupling between the tension means and the brake unit, and thereby also the elevator car, fall to the level of the detector. 
     In a particularly preferred and functionally safe embodiment of the invention, the monitoring device contains a detector that is mounted on the elevator car and that, in normal operation, detects whether the coupling element is in its normal position relative to the elevator car, and signals failure of the coupling between the tension means and the elevator car as soon it no longer detects the coupling element. 
     In a particularly inexpensive embodiment of the brake device according to the invention, the detector is a switch with electrically conductive contacts that detects the presence of the coupling element with the aid of a mechanical sensing element. 
     A brake unit that is reliable and simple to install is obtained with a detector that contains a sensor that detects the presence of the coupling element touchlessly. For this purpose, it is advantageous for inductive sensors, capacitive sensors, or light sensors to be used. 
     It is expedient for the brake device according to the invention to be embodied in such manner that the detector of the monitoring device is in contact with an elevator control system which, in the case of a detected failure of the coupling between the tension means and the brake unit and thereby also the elevator car, interrupts operation of the elevator. 
     In a preferred embodiment of the invention, the elevator control system is conceived in such manner that, following detected failure of the coupling, it only interrupts operation of the elevator when the elevator car has reached a story, floor or landing. This avoids passengers remaining unnecessarily trapped in the elevator car and needing to be evacuated with third-party assistance. 
     Exemplary embodiments of the invention are explained below by reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Shown are in 
         FIG. 1  a cross section through an elevator system according to the invention with a first embodiment of the brake device according to the invention; and 
         FIG. 2  an enlarged cutout of the elevator system according to  FIG. 1  with a second embodiment of the brake device according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows diagrammatically an elevator system  1  with a brake device  2  according to the invention. The elevator system  1  essentially comprises the following components:
         an elevator hoistway  3  with car guide rails  4  fastened therein;   an elevator car  5  that is movable along the car guide rails  4 , that has a car frame  7  that is guided by car guide shoes  6  on the car guide rails  4 , and that has a car body  8  that is fastened in the car frame  7 ;   a counterweight  10  that is guided on counterweight guide rails  9 ;   a drive machine  11  that suspends and drives the elevator car  5  and the counterweight  10  via at least one flexible suspension means  12 ; and   the brake device  2  with two brake units  15  that are fastened on the car frame  7  on both sides of the elevator car  5 , an actuating lever  16  via which the brake units  15  are activated, a traveling flexible tension means  17  that is guided over an upper tension-means reversing-sheave  18  and a lower tension-means reversing-sheave  19 , a blocking device  20  that can block movement of the tension means  17 , a coupling element  23  that couples the tension means  17  with the actuating lever  16  of the brake unit  15 , and a tension-means tensioning device  24  that guides the lower tension-means reversing-sheave  19  in a vertical direction and, via the reversing-sheave  19 , tensions the tension means  17 .       

     The brake device  2  and its manner of functioning are described in greater detail below. 
     The brake units  15  that are mounted on the elevator car  5  can be embodied as normal elevator safety brakes. In such safety brakes, via an actuating lever  16  and a system of mechanical levers that is not shown here, brake wedges or eccentric disks, for example, are brought into frictional contact with the car guide rails  4 , whereupon, as a result of the relative movement and frictional effect between them and the car guide rails, the brake wedges or eccentric disks are brought into a position in which they themselves, or a brake body lying in between, are pressed so forcefully against the car guide rails  4  that the elevator car  5  is braked. 
     The brake units  15  can, for example, also contain hydraulically actuated brake pistons that press the brake plates against the car guide rails  4  and thereby brake the elevator car  5 . Preferably, the actuating lever  16  thereby acts on valves that control application to the brake pistons of pressure fluid, and thereby the brake plates&#39; are pressed against the guide rails. 
     Depending on the embodiment of the brake units, they can brake the travel of the elevator car in only one, or in both, direction(s) of travel. 
     An activation system activates the brake units  15  in case of inadmissibly high speed—hereinafter referred to as “overspeed”—or also in other situations that are detected by the elevator control system  30 , that necessitate immediate and safe braking of the elevator car  5 . The activation system contains the tension means  17  with two tension-means ends that extend parallel to the direction of travel of the elevator car  5 . The tension means  17  passes over at least one upper tension-means reversing-sheave  18  and one lower tension-means reversing-sheave  19  and is fastened at both of its ends to the coupling element  23 . This coupling element  23  is coupled to the actuating lever  16  of the brake unit  15  that is mounted on the elevator car  5 , and that in normal operation is held disengageably in its normal position by a centering device  25 . As a result thereof, in normal operation, one end of the traveling tension means  17  moves up and down synchronously with the elevator car  5 . Present in the area of the upper tension-means reversing-sheave  18  is the blocking device  20  that, on detected overspeed of the tension means  17  and the elevator car  5 , or on presence of a blocking signal generated by the elevator control system  30 , blocks the tension means  17 . The blocking is effected, depending on the embodiment, either by direct braking of the tension means  17  or by blocking of the upper tension-means reversing-sheave  18 . 
     Usable as the tension means  17  for the brake device  2  are, for example, wire ropes, flat belts, toothed belts, or roller chains of all types. 
     On occurrence of inadmissibly high speed—hereinafter referred to as “overspeed”—or also of other situations detected by the elevator control system that necessitate immediate and safe braking of the elevator car  5 , the tension means  17  is blocked by the blocking device  20 , with the result that the coupling element  23  disengages the actuating lever  16  of the brake units  15  out of the position in which it is disengageably centered by the centering device  25 , and thereby activates the brake units. 
     In case of failure as described above of the coupling between the coupling element  23  of the tension means  21  and the elevator car  5 , and thereby also the brake units  15  that are mounted on the elevator car, the coupling element  23 , along with the end of the tension means  17  that is fastened thereto, falls in the direction of the lower tension-means reversing-sheave  19 . For this purpose, the coupling element  23  is executed sufficiently heavily that, despite frictional losses, its weight force can set the tension means  17  and the two tension-means reversing-sheaves  18 ,  19  into motion. 
     According to a first embodiment of the brake device  2  according to the invention, shortly before the coupling element  23  has reached its lowest possible position slightly above the lower tension-means reversing-sheave  19 , it is detected by a detector  27  of a monitoring device  29 . This situation is shown in the lowest part of  FIG. 1 , where the detector  27  is shown as an electric switch with a mechanical sensing element  27 . 1 , and the fallen coupling element  23  is shown dotted. The detector  27  signals the presence of the coupling element  23  in its fallen position, and thereby failure of the coupling between the coupling element  23  of the tension means  17  and the elevator car  5 , to the elevator control system  30 , that brings the elevator system to a standstill preferably as soon as the elevator car has reached a floor. 
       FIG. 2  shows a second embodiment of the brake device  2  according to the invention, in which the position of the coupling element  23  relative to the elevator car  5  is monitored by a detector  28  that is connected to the car  5 . Advantageously, a detector  28  is used that detects the coupling element touchlessly, i.e. that contains, for example, an inductively or capacitively acting sensor or an infrared light sensor. Following failure of the coupling between the coupling element  23  and the elevator car  5 , as soon as the coupling element  23  moves out of the detecting area of the detector  28 , also in this embodiment the detector  28  signals the failure of the coupling to the elevator control system  30 , which brings the elevator system to a standstill preferably only when the elevator car has reached a story or floor. Advantageously, the service organization that is responsible for the elevator system is alarmed at the same time. 
     Particularly readily discernible in  FIG. 2  is the centering device  25  already mentioned in association with  FIG. 1 , which, in normal operation of the elevator system, fixes the actuating lever  16  of the brake unit  15  that is mounted on the elevator car  5  disengageably in its normal position to ensure that in normal operation one end of the traveling tension means  17  moves up and down synchronously with the elevator car. Centering of the actuating lever  16  in its normal position is realized by a ball that is guided in a drilled hole being pressed by a compression spring into a notch of a disk that monolithically with the actuating lever  16  is swivelable about a common lever axle  26 . 
     Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited but by the specific disclosure herein, but only by the appended claims.