Abstract:
A brake mechanism for a device for hauling up/down by rope, in particular one for the safe hauling up and down by rope of persons and loads. The device has a pulley which preferably has a back stop that prevents the pulley from turning during the roping down. The rope brake mechanism has a rope speed measuring device that cooperate with a rope brake, which acts upon the rope to exert a braking force onto the rope when the rope speed increases above a maximum predetermined speed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority of European Patent Application No. 97810359.6 filed Jun. 9, 1997, the subject matter of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a brake mechanism for a device for hauling up/down by rope, in particular one for the safe hauling up and down by rope of persons and loads. The device has a pulley which preferably has a back stop that prevents the pulley from turning during the roping down. 
     In accordance with the European published patent EP-A-0 480 117 by the applicant, such devices for hauling up/down by rope are preferably used for hauling persons or loads up and down on a rope. The preferred area of application is for rescue services or in general as mobile equipment. The devices for hauling up/down by rope essentially function to reduce the retaining force during the roping down in connection with a safety to prevent an uncontrolled dropping of the person or load attached to the rope. 
     These known devices for hauling up/down by rope have a large-volume pulley equipped with a back stop. In most cases, a rope is placed with 2.5 windings around this pulley. The device is operated such that when pulling up, the pulley is running freely and represents only a low resistance. During the roping down, on the other hand, the pulley is blocked by the back stop and the rope slides over the surface of the pulley. The resulting friction takes over a large portion of the load attached to the rope. 
     As a safeguard during the roping down, the International Patent Application WO-A-9 717 107 suggests providing a self-activating rope stop on the pull side of the device for hauling up/down by rope. The advantage of this arrangement is that the rope stop only needs to take over a portion of the load since the device for roping up/down accepts the largest portion of the pull. 
     However, the disadvantage of this solution is that upon reaching the critical roping down speed, the roping down operation is stopped completely. In particular if a roping down speed near the permissible limit, e.g. 2 m/s, is required, a brief exceeding of this speed limit can trigger the stopping of the rope. 
     SUMMARY OF THE INVENTION 
     It is the object of the present invention to specify a device, which prevents an increase in the roping down speed above a predetermined limit value during the roping down operation. 
     In accordance with the present invention, the rope brake mechanism comprises rope speed measuring means that cooperates with a rope brake, which acts upon the rope to exert a braking force onto the rope when the rope speed increases above a maximum predetermined speed. 
     A brake mechanism is installed on the pull side of a device for hauling up/down by rope, which mechanism forces the engagement of a frictional brake on the rope, preferably only during the roping down, if a predetermined rope speed is exceeded. In particular, the brake mechanism increases the braking effect of the frictional brake with increasing rope speed, so that the roping down speed does not reach an unacceptable, uncontrollable speed, even for heavy loads. 
     The present invention relates to a device for raising and lowering a load, and the device includes a pulley and a brake mechanism. A rope is wound about the pulley, and the brake mechanism acts upon the rope to exert a braking force on the rope when the rope speed increases above a maximum predetermined speed. The break mechanism includes at least two flyweights and at least one bearing surface. The rotatable arrangement of flyweights is operatively connected to the pulley and rotates about an axis in response to rotation of the pulley. The bearing surface is operatively connected to the flyweights and is movable against the rope in response to rotation of the flyweights. When the pulley is rotated, the centrifugal force exerted on the flyweights is transferred axially to the bearing surface, which causes an increased braking effect on the rope. The braking effect increases with increasing rotational speed. 
     The flyweights surround a rotatable core in a symmetrical arrangement, and from the core originates a radial guide means. The radial guide means holds the flyweights such that they can be moved radially. The arrangement of flyweights is surrounded peripherally by a spring-elastic element, which biases the flyweights toward the core. In addition, a frictional wheel bears against the rope and is linked to the flyweights, and a gear is arranged between the frictional wheel and the flyweights in order to establish a gear ratio, as well as a rotational link. 
     The rope moves through an essentially tube-shaped rope guide proximate the pulley, and the width of the rope guide can be changed. The rope guide includes convexities and concavities to force the rope into an increasingly S-shaped course during the reduction of the width so as to increase the braking effect on the rope. At least a section of the rope guide is movable so as to allow the change in width for the rope guide, and the movable section can be moved by a coupling means. The coupling means include contact zones that are angled relative to the rotational axis of the flyweights to convert radial movement of the flyweights to a movement of the coupling means directed along the rotational axis. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top view from above of a device for hauling up/down by rope, which device has the brake mechanism according to the invention; 
     FIG. 2 is a section through the brake mechanism according to II—II in FIG.  1 . 
     FIG. 3 is a top view of a brake jaw for the rope brake of the brake mechanism. 
     FIG. 4 is a top view of the centrifugal unit. 
     FIG. 5 is a section along the rope guide formed by the brake jaws, according to V—V in FIG. 3, in the position where the brake jaws are pressed together. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The design of the actual device for hauling up/down by rope corresponds to the design described in the WO-A-9 717 107, the subject matter of which is incorporated into the description by reference. 
     FIG. 1 shows a rope brake mechanism  1  according to the invention on a device  2  for hauling up/down by rope, e.g. a device according to the WO-A-9 717 107. The rope brake mechanism  1  comprises a frictional wheel  3  with knurled running surface, which is pressed against a rope  4 . The frictional wheel  3  moves in roping up  5  direction as well as roping down  6  direction. The pull end  7  of the rope passes through a rope guide  8  (see FIG.  2 ), which consists of two jaws  9 ,  10 , having an essentially mirror-inverted design (FIG.  3 ). The stationary jaw  9  in this case is fixedly connected to the housing  11 , while the other jaw  10  can be moved. 
     In the position shown here, the two jaws  9 ,  10  are pushed by a spring  12  into the opened resting position. In this position, the guide  8  is opened to the maximum and has the largest cross section, so that the rope  7  essentially glides without resistance through the guide. 
     The jaws  9 ,  10  are held on the one hand by a fixed cone  13  or a cone  15  that can be displaced along the axis  14  and is coupled with the centrifugal unit  16  while, on the other hand, the jaws are secured against turning by a screw  17 . A bolt  18  with internal thread is screwed onto the screw  17 , which bolt extends through the bore at the back end of the brake jaws  9 ,  10 , near the plateaus  19 , and has a slightly conical shape to allow a movement of the brake jaw  10 . During the braking operation, the movable jaw  10  tilts slightly over the front edges of the plateau if the movable cone  15  is moved by the centrifugal unit in the direction of the fixed cone  13 . 
     The centrifugal unit  16  consists of the frictional wheel  3 , inside of which a shaft  20  is positioned such that it can rotate. A planet pinion  21  fits on the outer end of shaft  20  and meshes with a fixed toothed ring  22  with internal toothing. An additional, inside planet pinion  23  fits on the other end of the shaft  20  and meshes with the central gear  24 . This planet pinion  23  is attached to the shaft  20  by means of a freewheel mechanism  25 . The freewheel mechanism blocks during the roping down, so that the center gear  24  is put in motion via the frictional wheel  3  and the planet gear, consisting of toothed ring  22  and the toothed gears  21  and  23 . 
     In roping up direction, the freewheel mechanism  25  uncouples the two toothed gears  21  and  23 , so that the center gear  24  is not driven and the frictional wheel can move freely, without problems and at any speed without causing a braking of the rope. 
     As a rule and to prevent the parts  26  that react to the centrifugal force from being too heavy or too large, it is advantageous to have a transmission, so that the speed of the center gear, for example, is 8 times higher than that of the frictional wheel  3 . 
     The center gear  24  is fixedly connected to the core  27 , into which core radially outward-pointing pins  28  are inserted. A sector-shaped flyweight  26  is positioned on each pin  28 , in such a way that it can glide. The flyweights have respectively one bore  29  for one pin  28  for this. 
     The 4 flyweights  26  surround the core  27  in a symmetrical arrangement (FIG.  4 ), wherein each covers a 90° sector. A spiral spring  31 , positioned inside groove  30  on the outside, keeps the flyweights pushed against the core  27  and forms the antagonistic force to the centrifugal force. 
     Respectively two pins  32  are inserted at an angle into the flyweights  26  and project from the flyweights  26  in the direction of axis  14 . The pins  32  glide inside bores  33  in the thrust collar  34 . Finally, the movable cone  15 , positioned rotatably on a rolling bearing  35 , sits on the thrust collar. 
     All rotating parts of the centrifugal unit are positioned with little friction in suitable bearings  36  on the axis  14 . Shaft  20  is positioned in the same way inside frictional wheel  3 . Pins  32  and pins  28  are composed of steel, which ensures good gliding qualities in the flyweights  26  of brass and the thrust ring  34  that is also made of brass. 
     During the roping down, the rope  4  puts into motion the frictional wheel  3  and, via the planet gear, also the core  27  and the surrounding flyweights  26  since the freewheel mechanism  25  blocks in this direction. Starting with a certain speed, the flyweights  26  start to move toward the outside, against the force of spiral spring  31 , or to exert a net force directed toward the outside onto the pins  32 . The pins  32  convert this movement and force, directed toward the outside, into an axially directed force onto the pressure disk and thus the cone  15 . The cone  15  pushes the movable jaw  10  in the direction of the fixed jaw  9  and thus narrows the cross section of guide  8 , as a result of which an increasingly stronger frictional braking force is exerted onto the pull end  7  that is positioned inside the guide  8 . In addition, convexities  38  are located inside grooves  37  in jaws  9 ,  10 , which jaws together form the guide  8 , so that the rope  7  is forced into an increasingly S-shaped course inside the guide  8  (FIG.  5 ), which further increases the friction. 
     It is a common design criteria for the brake mechanism to avoid roping down speeds exceeding 2 m/s for a load of 150 kg. The operating threshold and strength of the brake is achieved through a suitable selection of the various component parts, such as transmission of the planet gear  21 - 24 , weight of the flyweights  26 , strength and characteristic of the spiral spring  31 , form of the brake jaws  9 ,  10  and the guide  8 , etc. 
     It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptions, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims. 
     For example, it is conceivable to use a combination of conical and tapered surfaces in place of the angled pins  32 , possibly by also using roll bodies. With higher requirements, e.g. for higher loads, the blocking effect of the freewheel mechanism  25  can be overtaxed. However, it is possible to provide more than one planetary shaft  20  with, respectively, one freewheel mechanism  25 , as a result of which the load will be distributed over the existing freewheel mechanisms. It is furthermore conceivable to have a different number of flyweights with a different form or different angle. Also, a different material can be selected for producing the flyweights and pins  32  and pins  28 , as long as displacement on the latter is ensured.