Abstract:
An elevator including a cage configured to ascend and descend along a guide rail in an elevator shaft, a drive unit configured to move the cage up and down, and an emergency stop device configured to urgently stop the cage when the cage descends at an extraordinary speed. The emergency stop device including an emergency stop mechanism provided at a lower end portion of the cage and configured to engage the guide rail, thereby urgently stopping the cage, a link mechanism provided at the lower end portion of the cage so as to be located close to the emergency stop mechanism and configured to actuate the emergency stop mechanism on receiving an external input, and a speed detector configured to detect the descent of the cage at the extraordinary speed and correspondingly to apply the external input to the link mechanism.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims benefit of priority to Japanese Patent Application No. JP10-252681 filed Sep. 7, 1998, the entire disclosure of which is incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relate, to an elevator provided with an emergency stop device. 
     2. Description of the Background 
     A conventional elevator apparatus is composed of an elevator shaft extending vertically in a building, and a machine room (penthouse) located right over the shaft and having a motor and the like. This elevator apparatus further includes a sheave located in the machine room and driven by the motor, a cage disposed in the shaft and connected to one portion of a cable that is wound on the sheave, and a counterweight connected to another portion of the cable and balanced with the cage. The cage is moved up and down by rotating the sheave in the machine room. The cage and the counterweight are guided by means of guide rails arranged in the elevator shaft. 
     With the increased construction of high-rise buildings, the operating speed of elevators is becoming higher and higher, thus requiring a satisfactory safe measure. To cope with this, the conventional elevator apparatus is provided with an emergency stop device that can stop the cage safely and securely in case the cage for any reason suddenly descends at a speed higher than its rated speed. One example of the emergency stop device is disclosed in U.S. Pat. No. 5,377,786. 
     The emergency stop device is composed of a governor, a cable passed through the governor and adapted to be restricted in motion when the cage descends at a speed higher than its rated speed, and a stop mechanism attached to the cage and capable of braking and stopping the cage. The stop device further has a link mechanism, which connects the cable and the stop mechanism and actuates the stop mechanism through the medium of the relative movements of the cable and the cage when the cable is restricted in motion. 
     The emergency stop mechanism, which is located at the lower end portion of the cage, includes a holding member having a V-shaped slit gradually spreading downward and a stopper member slidable in the slit. The emergency stop device brakes the cage in a manner such that the stopper member moves up to cause each guide rail to be held tight in the slit of the holding member by an wedge effect. 
     The link mechanism includes a driving lever, which is attached to the upper part of the cage and fixed to the cable extending from the governor, and a lift rod connecting the driving lever and the slit member of the stop mechanism. The lift rod extends along the height direction of the cage, and serves to pull up the slit member of the stop mechanism at the lower end of the cage thereby actuating the stop mechanism. 
     Further, the link mechanism is provided with a limit switch, which detects the actuation of the link mechanism and outputs a hoisting machine stop command signal. Once the limit switch detects a shift of the driving lever and delivers the stop command signal to a control device, it continues to output the command signal. 
     In canceling an emergency stop state and restarting the elevator apparatus, the guide rail is released from the hold in the slit by means of the stopper member by, for example, pulling up the cage, whereby the restraint on the ascent and descent of the cage by the emergency stop device is removed. An operator gets on the cage and manually resets the limit switch to its initial state, thereby enabling the elevator apparatus to be restarted. 
     In the conventional elevator apparatus described above, the link mechanism is attached to the upper end portion of the cage, so that a relatively long member is used as the lift rod for connecting the stopper member of each emergency stop device and the driving lever. It is difficult, therefore, to keep the lift-mechanism in an assembled state when it is shipped from the factory. Thus, the lift mechanism must be assembled during installation of the elevator in the building. 
     Since the elevator shaft is relatively narrow, assembling the link mechanism in the building requires much time and labor. Since the lift rod is a relatively long member, moreover, each link mechanism must be finely adjusted as it is assembled, in order to assure normal operation. Thus, the installation work entails high costs. 
     If the link mechanism is attached to the lower end portion of the cage with the lift rod shortened so that the mechanism can be in the assembled state as it is shipped from the factory, furthermore, the limit switch must be also attached to the lower end portion of the cage. 
     If the limit switch is attached to the lower end portion of the cage, it is difficult for the operator to reset the limit switch manually to the initial state in restarting the elevator apparatus after once actuating the emergency stop device. Thus, the elevator apparatus cannot be restarted with ease. 
     SUMMARY OF THE INVENTION 
     Accordingly, one object of the present invention is to provide an elevator characterized by reduced installation costs and the like. 
     Another object of this invention is to provide an elevator apparatus capable of being easily restarted after an emergency stop device is once actuated to restrain a cage from ascending or descending. 
     These and other objects are achieved according to the present invention by providing a novel elevator including a cage configured to ascend and descend along a guide rail in an elevator shaft, a drive unit for moving the cage up and down, and an emergency stop device configured to urgently stop the cage when the cage descends at an extraordinary speed and including an emergency stop mechanism provided at a lower end portion of the cage and configured to engage the guide rail, thereby urgently stopping the cage, a link mechanism provided at the lower end portion of the cage so as to be located close to the emergency stop mechanism and configured to actuate the emergency stop mechanism on receiving an external input, and a speed detector configured to detect the descent of the cage at the extraordinary speed and correspondingly to apply the external input to the link mechanism. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
     FIG. 1A is a schematic view showing an elevator according to an embodiment of the present invention; 
     FIG. 1B is a front view showing the lower end portion of a cage; 
     FIG. 2A is a view showing an arrangement of an elevator apparatus according to a first embodiment of the invention and 
     FIG. 2B is a view of a modification of the first embodiment in which the reset switch  18  is located at an upper end portion of the cage; 
     FIG. 3 is a side view showing a portion of the emergency stop device of the elevator apparatus according to the first embodiment; 
     FIG. 4 is a side view showing a limit switch according to the first embodiment; 
     FIG. 5 is a side view showing an emergency stop device according to the first embodiment; 
     FIG. 6 is a side view illustrating operation of the emergency stop device shown in FIG. 5; 
     FIG. 7 is a side view showing a portion of the emergency stop device of an elevator apparatus according to a second embodiment of the invention; and 
     FIG. 8 is a side view showing a modification of the elevator apparatus according to the second embodiment. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, where like reference numerals designate the same or corresponding parts throughout the several views, and more particularly to FIG. 1A the general construction of a machine-room-less elevator according to the present invention will be described. 
     As shown in FIG. 1A, in an elevator shaft  1  provided in a building, a cage  2  and a counterweight  3  are suspended and balanced by means of a cable  4 . Guide rails  5  and  6  for vertically guiding the cage  2  are arranged on the right- and left-hand sides, respectively, of the shaft  1 , while counterweight guide rails  7  and  8  for guiding the counterweight  3  for up-and-down motion are arranged behind the left-hand guide rail  6 . 
     On the left-hand side of the upper part of the interior of the elevator shaft  1 , a drive unit  9  (a hoisting device or traction machine) is set in a narrow space between an inner wall of the shaft  1  and a side wall of the cage  2 . The drive unit  9 , which is fixed to the guide rails  6  and  7 , can wind up the cable  4 , thereby relatively moving the cage  2  and the counterweight  3  up and down. The drive unit  9  may be fixed to the guide rails  7  or  8 . 
     One end portion of the cable  4 , which is wound up by the drive unit  9 , is fixed to a cable hitch  10  that is attached to the upper end portion of the guide rail  5 , while the other end portion is fixed to a cable hitch  11  that is attached to the upper end portion of the counterweight guide rail  8 . The middle portion of the cable  4  is passed around lower sheaves  12  that are attached to the lower part of the cage  2 , extends through the drive unit  9 , and is then passed around a counterweight sheave  13  that is attached to the upper part of the counterweight  3 . 
     As shown in FIG. 1B, emergency stop mechanisms  14  are provided on the bottom portion of the cage  2 . The emergency stop mechanisms  14  serve to stop the cage  2  safely and securely in case the cage  2  suddenly falls at a speed higher than its rated speed for any reason. As described in detail later, the emergency stop mechanisms  14  brake and compulsorily stop the cage  2  in a manner such that stopper members are driven like wedges between the cage  2  and the guide rails  5  and  6 . 
     Referring now to FIG. 2, there will be described an arrangement of an emergency stop device  20  that includes the emergency stop mechanisms  14 . 
     The emergency stop device  20  is composed of a governor  23  held on the guide rails  5  or  6  for the cage  2  by means of a bracket or the like in the elevator shaft  1 , an endless cable  24  passed around a sheave  22  of the governor  23  and a tensioner  25  attached to the lower end of the cable  24  and capable of applying a predetermined tension to the cable  24 . The device  20  further has a link mechanism  28 , which is attached to the lower end portion of the cage  2  and connects the cable  24  and the emergency stop mechanisms  14 , and a limit switch  29  for detecting a stop state produced by the operation of the link mechanism  28 . 
     In normal operation, as the cage  2  ascends or descends, the cable  24 , which is connected to the cage  2  by means of the link mechanism  28 , moves at the same speed as the cage  2 , whereupon the sheave  22  of the governor  23  rotates. If the cage  2  descends at an extraordinary speed from any cause, however, the governor  23  is actuated to restrain the action of the cable  24 . 
     Thereupon, one end portion of the link mechanism  28  is pulled up relatively, so that the emergency stop mechanisms  14  are actuated. 
     FIGS. 5 and 6 are enlarged views showing one of the emergency stop mechanisms  14 . 
     The emergency stop mechanism  14  includes a holding member  33 , which is attached to a support base  31  on the lower end of the cage  2  and has an inverted V-shaped slit  33   a  opens downwardly. The guide rail  5  (or  6 ) is passed through the slit  33   a  of the member  33 . A stopper member  34  is caught between the slit  33   a  and the guide rail  5  so that the cage  2  is braked on the rail  5  by an wedge effect. The stopper member  34  is held by a support member  35  shown in FIG.  5 . Braking action is caused by pulling up the support member  35  by means of the link mechanism  28 . 
     As shown in FIGS. 2A and 3, the link mechanism  28  is composed of a driving lever  41  that is fixed to the cable  24  for actuating the one emergency stop mechanism  14 , a drive lever  42  that is connected to the lever  41  by means of a connecting rod  43  for actuating the other emergency stop mechanism  14 , and relatively short connecting members  44  connecting the levers  41  and  42  and the respective support members  35  of the two emergency stop mechanisms  14 . 
     The driving lever  41  and the driven lever  42  are rockable in the vertical direction around points A and B, respectively. The connecting rod  43 , which connects the levers  41  and  42 , is allowed only to move in its axial direction by a guide member  45  that is fixed to the support base  31 . Inserted in the axial middle portion of the rod  43 , moreover, is a spring  46  for urging the levers  41  and  42  to lower the connecting members  44  (in a direction so as not to actuate the emergency stop mechanisms  14 ). 
     As shown in FIG. 4, the limit switch  29 , which is attached to the link mechanism  28 , includes a switch body  51  and a contact  52  that can project from and draw back into the body  51 . In an initial state, the contact  52  projects from the switch body  51 . The limit switch  29  is mounted on the support base  31  in a manner such that the contact  52  touches the driving lever  41  in the initial state. As the lever  41  rocks, the contact  52  of the switch  29  projects from or draws back into the switch body  51 . 
     The limit switch  29  is connected to a control device  21  shown in FIG.  2 A. When the contact  52  recedes for a predetermined displacement or farther, the switch  29  delivers a stop command signal for the drive unit  9  to the control device  21 . Preferably, the predetermined displacement of the contact  52  by which the switch  29  outputs the stop command signal should be a displacement obtained immediately before the stopper member  34  comes into contact with the inner surface of the slit  22   a  of the holding member  33  (see FIG.  6 ). 
     The limit switch  29  ceases to deliver the stop command signal when the stopper member  34  is moved away from the inner surface of the slit  33   a  toward the region under the cage  2  after the switch  29  once delivers the stop command signal to the control device  21  as the driving lever  41  is shifted. 
     Preferably, the limit switch  29  should be provided with a display, such as an illuminant  53  shown in FIG. 4 that glows as it delivers the stop command signal. In this case, an operator or the like can easily visually determine whether or not the stop command signal is delivered from the switch  29 . 
     On the other hand. the control device  21  is a processor provided with a microprocessor or the like, and serves to control the whole elevator apparatus. The control device  21  includes a drive unit stop command section  54  for stopping the drive unit  9  and a drive unit operation prohibiting section  55  for maintaining the stop state of the drive unit  9 . 
     The command section  54  disconnects the drive unit  9  from the power supply in response to the stop command signal from the limit switch  29 . Once the command section  54  cuts off the power supply, prohibiting section  55  maintains the resulting state. 
     Thus, even when the limit switch  29  ceases to deliver the stop command signal, the prohibiting section  55  keeps the drive unit  9  disconnected from the power supply and stopped until the reset switch  18  is operated. 
     When the operator operates the reset switch  18  (drive unit operation prohibition canceling means) to apply a canceling command signal to the input of the control device  21 , the device  21  supplies electric power to the drive unit  9 , thereby enabling the elevator apparatus to be restarted. 
     Thus, summarizing the restarting of the elevator apparatus, first, the cage  2  is pulled up, for example, to release the guide rail  5  from the hold between the stopper member  34  and the slit  33   a,  thereby removing the restraint of the emergency stop mechanism  14  on the up-and-down motion of the cage  2 . When the mechanism  14  is released in this manner, the contact  52  of the limit switch  29  is reset to its initial state, so that the switch  29  ceases to deliver the stop command signal. In this state, however, the drive unit  9  is disabled by the action of the prohibiting section  55 . 
     Thereupon, the operator carries out various inspections and then operates the reset switch  18  to enable restart of the drive unit  9 . The switch  18  is set on a control panel in the door box of a hall door  47  on the uppermost floor, for example. Alternatively, the reset switch  18  is located at an upper end portion of the cage as shown in FIG.  2 B. 
     Since the link mechanism  28  can be located at the lower end portion of the cage  2 , moreover, it can be in an assembled state when it is shipped from the factory. Thus, the installation cost can be lowered. 
     The limit switch  29  delivers the stop command signal immediately before the emergency stop mechanisms  14  restrain the cage  2  from moving. If the mechanisms  14  operate wrongly due to vibration attributable to ascent or descent of the cage  2 , for example, the drive unit  9  can be prevented from being actuated to loosen the cable  4  that suspends the cage  2  or to cause the cable  4  to slip out of a traction sheave of the drive unit  9 . 
     Since the connecting rod  43  that connects the two emergency stop mechanisms  14  is guided in axial slide by the guide member  45 , moreover, the mechanisms  14  can securely operate in association with each other. 
     FIGS. 7 and 8 show a second embodiment of the invention, wherein a driving lever  41  of a link mechanism  28  is connected to a governor cable  24  by means of an extension lever  60 . The lever  60  is a belt-shaped plate, one end portion  60   a  of which is rockably connected to the driving lever  41 , and the other end portion  60   b  of which extends above the one end portion  60   a  and is rockably connected to the cable  24  in a position higher than the position of connection with the lever  41 . 
     Preferably, the extension lever  60  should be connected to the governor cable  24  by means of a first connecting portion  61  at the other end portion  60   b  and a second connecting portion  62  at the central portion, as shown in FIG.  7 . The first and second connecting portions  61  and  62  connect the lever  60  and the cable  24  for rocking motion. 
     According to the second embodiment, the driving lever  41  of the link mechanism  28  is connected to the governor cable  24  by means of the extension lever  60  that extends vertically from the lever  41 . Accordingly, a space  49  between the cage  2  at its bottom dead center and the floor surface of the elevator shaft  1  can be restricted. Thus, the depth of a pit for the shaft  1  can be reduced, so that the construction cost of the elevator apparatus can be restrained from increasing. 
     In the case where the extension lever  60  and the governor cable  24  are connected to each other by means of the first and second connecting portions  61  and  62  that are rockable, as shown in FIG. 7, the lever  60  can be prevented from falling so that erroneous operation of the emergency stop device is securely prevented if the lever  60  is urged to fall by a tension on the cable  24  and the mass of the lever  60 , as shown in FIG.  8 . 
     Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims the present invention can be practiced other than as specifically described herein.