Abstract:
An improvement for lift equipment having a lift cage and a counterweight movable in a lift shaft with travel buffers at at least one end permits override of safety brake operation when buffer travel occurs. The invention comprises a blocking device which blocks operation of the safety brake, and may include a blocking lever connected to a trip lever mechanism of the safety brake and a blocking element which controls the movement of the blocking lever.

Description:
The present invention relates to lift equipment with a lift cage movable in a lift shaft and with a counterweight movable in the lift shaft, wherein the speed of the lift cage or the counterweight is monitored by means of a speed limiter device and the speed limiter device stops the lift cage or the counterweight by means of a safety brake in the case of excess speed of the lift cage or the counterweight. 
     BACKGROUND OF THE INVENTION 
     In the case of lift equipment with a lift cage and counterweight movable in a shaft the speed of the lift cage or the counterweight is monitored. When excess speed occurs the lift cage or the counterweight is stopped by means of a safety brake. If, for example, the lift cage travels beyond the bottom story in the downward direction with less than an excess speed the lift cage is, on further travel thereof, caught by buffers. In that case, the safety brake can be tripped due to the inertia of the speed limiter and the limiter cable, whereby the braking elements of the safety brake wedge with the guide rails. 
     A disadvantage of known equipment resides in the fact that the lift cage has to be released from the brake. The safety brake has to be reset and the guide rails checked at the braking location and the surface processed. Evacuation of the lift passengers can be undertaken only by expert personnel. 
     The present invention addresses the disadvantages of the known equipment. The invention includes a speed monitor which applies a safety brake when excess speed of the lift cage or counterweight occurs. A blocking device is associated with the safety brake to block brake action when buffer travel of the lift cage or counterweight occurs. 
     The advantages achieved by the invention are essentially to be seen in that the safety brake is not tripped in the case of buffer travel. The lift passengers are thus not needlessly exposed to extreme decelerations of the lift cage. Moreover, expert personnel are not needed for carrying out evacuation of the lift passengers. 
     The lift cage can, after buffer travel, be manually moved to the next story so that the lift passengers can leave the lift cage. Moreover, the mechanical components of the safety brake, and the speed limiter and the guide rails are treated gently. In the case of buffer tests, the safety brake is not tripped and the considerable effort needed for release of the brake is avoided. In the case of approval tests, the safety brake is usually blocked, so that no instances of braking can occur in the shaft end regions in the event of out-of-the-ordinary test travels. With the equipment according to the invention, safety is guaranteed over the entire shaft height even in the case of approval tests. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is explained in more detail by reference to the accompanying figures, in which: 
     FIG. 1 is a diagrammatic view of lift equipment with a safety brake for stopping a lift cage incorporating the invention; and 
     FIG. 2 is a schematic diagram presenting the details of the blocking device for blocking the safety brake. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows lift equipment with a lift cage  2  movable in a lift shaft and connected with a counterweight  4  by way of a cable  3 . The cable  3  is driven in the operational case by means of a drive pulley of a drive unit  6 . Lift cage  2  and counterweight  4  are guided by means of guide rails  7  extending over the shaft height. The lift equipment comprises a top story with a top story door  8 , a second-to-top story with a second-to-top story door  10 , further stories with further story doors  10  and a bottom story with a bottom story door  11 . The drive unit  6  and a speed limiter  13 , which monitors the speed of the lift cage  2  and stops the lift cage  2  if excess speed occurs, are arranged in a shaft head  12 . A respective double lever  14 , which is pivotably mounted at a fulcrum  15  of the lift cage  2 , is provided at each side of the lift cage  2 . A safety brake  16  for stopping the lift cage  2  is connected by means of a linkage  17  with one side  14 . 1  of the double lever  14 , which side  14 . 1  is also connected to limiter cable  19  of the speed limiter  13 . The other side  14 . 2  of one double lever  14  is connected by means of a linkage  18  with the other double lever. If one side  14 . 1  of the double lever  14  is moved upwardly, then the safety brake  16  engaged, whereby braking elements wedging with the guide rails  7  stop the lift cage in the case of emergency. In the operational case, the lift cage  2  drives the limiter cable  19  by means of the one side  14 . 1  of the double lever  14 . In the case of excess speed of the lift cage  2 , the speed limiter  13  blocks the limiter cable  19 . The one side  14 . 1  of the double lever  14  is thereby deflected upwardly and the safety brake engaged at both sides of the lift cage  2 . 
     The endless limiter cable  19  is tensioned by means of a deflecting roller  21  arranged in a shaft pit  20 , wherein a roller support  22  is pivotably mounted at one end at a fulcrum  23  and carries a tensioning weight  24  at the other end. 
     A blocking lever  25  is connected at the fulcrum  15  with one double lever  14 . In the event of tripping as mentioned above, side  14 . 1  of one double lever  14  is deflected upwardly. At the same time, the blocking lever  25  is deflected in the anticlockwise sense. 
     FIG. 1 shows the lift cage  2 , which has set off at the top story, on the way down, wherein a stop at the second-from-bottom story and subsequently at the bottom story is provided. If, for example, the travel from the second-to-bottom story to the bottom story runs at less than excess speed and the lift cage  2  does not halt at the bottom story, the lift cage  2  on its further travel downwardly is caught by buffers  26 . In that case, the safety brake  16  can, due to the inertia of the speed limiter  13  and the limiter cable  19 , be tripped, whereby the braking elements of the safety brake  16  wedge with the guide rails  7 . In order to avoid undesired tripping of the safety brake  16  in the case of buffer travel of the lift cage  2  or the counterweight  4 , there is provided in the lift shaft  1  at the top and bottom a blocking element  27  which blocks the movement of the blocking lever  25  as soon as the lift cage  2  or the counterweight  4  has travelled downwardly past the bottom story. When the counterweight  4  impinges on the buffer (not illustrated), the lift cage  2  hangs in the cable  3 . The lower blocking element  27  prevents tripping of the safety brake  16  at the lower shaft end. The blocked blocking lever  25  blocks one double lever  14  and, by way of the linkage  18 , the other double lever  14 . Tripping of the safety brake  16  is thus precluded. 
     If the counterweight is monitored by means of a safety brake, a blocking lever and a blocking element with the above-illustrated effect are similarly provided. 
     At least one blocking element  27  is also provided at the upper shaft end if the upper shaft end also has buffers. 
     FIG. 1 shows lift equipment without a machine room. The equipment according to the invention for evacuation of lift passengers can also be used on lift equipment with a machine room. 
     FIG. 2 shows details of the blocking device, which is formed from the blocking lever  25  on the lift cage and blocking element  27 , for blocking the safety brake  16  in the case of buffer travel. The blocking lever  25  illustrated by solid lines is shown in the position in which the lift cage stands normally at the bottom story. The blocking lever  25  illustrated by dot-dashed lines is shown in the position in which the safety brake  16  is engaged. Normally, the movement of the blocking lever  25  is not blocked by the first end of blocking element  27  which may be in the form of a curved or angled track. The blocking lever  25  illustrated by dashed lines is shown in the position in which the lift cage  2  has travelled down past the bottom story. The movement of the blocking lever  25  is blocked by the second end of the blocking element  27 . The movement of the double lever  14  connected with the blocking lever  25  at the fulcrum  15  is thus also blocked. Tripping of the safety brake  16  is thus prevented.