Abstract:
A safety brake device has a setting device moving an abutment or a housing to limit movement of brake wedges engaging a guide rail which limits a braking force applied by the brake wedges. The setting device can continuously adjust the braking force limit in dependence on a magnitude of a mass to be braked.

Description:
This is a continuation of application Ser. No. PCT/CH01/00386, filed Jun. 20, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to a safety brake device for the load receiving means of vertical conveying equipment, including at least one brake wedge, which is arranged in a housing and which on triggering of a braking action acts on a guide rail of the conveying vehicle, and an abutment, which limits the stroke of the at least one brake wedge and thus limits the maximum braking force during the braking process. Moreover, the invention relates to a method of adapting the braking force of this safety brake device to the masses which are to be braked and which act on the load receiving means. 
     Safety brake devices as described above are used for, for example, passenger elevators, goods elevators and cages in mine conveying installations, wherein the braking process is usually triggered by a limiter cable, which acts on the brake wedge, of a speed limiter when a permissible travel speed is exceeded. 
     There is shown in the Austrian patent specification No 297260 a safety brake device according to the description above, in which a sliding guide, which is fastened to the elevator car and consists of angle girders, is provided for a wedge housing. The wedge housing has a recess which extends conically in a vertical direction and in which two brake wedges are arranged and surround the guide rail of the elevator with a play. The brake wedges are mounted on balls in grooves of the recess to be rollable, so that only a low rolling resistance arises at the wedge surfaces of wedge housing and brake wedges during movement thereof. The two brake wedges can be moved by a double lever seated on a shaft which is rotated by way of a lever of the limiter cable of a speed limiter. When the permissible speed of the elevator is exceeded, the brake wedges are pressed against the guide rail and initiate the braking process. A support bracket, against which the wedge housing is supported by way of plate springs, is fastened above the wedge housing to project from the car. Setting screws serving as abutments for the brake wedges and secured by nuts are arranged at the support bracket. During the braking process the brake wedges are drawn into the wedge housing to an extent corresponding with the thickness of the guide rail. The braking forces thereby arising have the effect that the wedge housing is raised against the plate springs until the brake wedges abut against the setting screws, whereby a further increase in the braking forces is prevented. 
     The safety brake device described in the foregoing has the disadvantage that in the case of different masses to be braked, different retardation values are generated at the load receiving means. In the case of large loads in the load receiving means a too small retardation of the load receiving means can thus arise and in the case of small loads an unacceptably high retardation of the load receiving means can arise and thus lead to harm to persons and property. 
     SUMMARY OF THE INVENTION 
     The present invention therefore has the object of proposing a safety brake device according to the first paragraph of the preceding section, but without the disadvantages of the prior art devices. 
     This object is met by a setting device according to the present invention which, through displacement of at least one abutment or the housing, determines the spring deflection of spring elements occurring in the case of a safety braking and thus the spring forces resulting therefrom, wherein these spring elements press the brake wedges against the guide rails of the load receiving means by the stated spring forces. The at least one abutment or the housing can thus be adjusted by means of the setting device in dependence on the magnitude of the mass, which is to be braked, of the load receiving means and the braking force between the brake wedges and the guide rail can thereby be influenced. 
     The advantages achieved by the device according to the present invention are that independently of the size of the actual load present in the load receiving means a defined retardation of such a magnitude that harm to persons and property is avoided can be achieved during braking. 
     A further advantage of the device according to the present invention is that the adjustment of the abutment or of the housing can be undertaken continuously during travel. This is important in the case of vertical conveying equipment having counter-weights and equipped with compensating cables hanging between the underside of the load receiving means and that of the counter-weight. As the proportion of the mass, which additionally influences a safety braking, of the mentioned compensating cables changes during travel it is advantageous that the position of the abutment or of the housing, on which the braking force arising in the case of a safety braking depends, can be constantly adapted to this change. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which: 
         FIG. 1  is a cross-sectional view, in simplified schematic form, through a first safety brake device according to the present invention; 
         FIG. 2  is a cross section through the safety brake device according to the present invention along the line II—II in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view, similar to  FIG. 1 , through a safety brake device according to an alternate embodiment of the present invention; and 
         FIG. 4  is a schematic block diagram view of the setting device shown in  FIG. 1 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In  FIGS. 1 and 2 , there is shown a housing  1  fastened to a load receiving means L of vertical conveying equipment such as an elevator, and a guide rail  2  of the elevator. Brake wedges  3 ,  4  are arranged at both sides of the guide rail  2  in the housing  1 . The brake wedges  3 ,  4  are supported in the housing  1  by associated counter-shoes  5 ,  6  and spring elements  7 ,  8  respectively, wherein the counter-shoes and the spring elements are guided in recesses  9 ,  10  respectively of the housing  1 . Provided above the brake wedges  3 ,  4  is an abutment  11 , which abutment is guided in the housing  1  and can be moved up and down in the direction of a double-headed arrow  12 . For this purpose a setting device  13 , which stands in operative connection with the abutment  11  and by means of which the abutment can be positioned independently of the actual masses to be braked, is provided. These masses are composed principally of the load present in the load receiving means L, the weight of the elevator car and the actually effective weight proportion of the lower cables hanging at the load receiving means. The stroke of the brake wedges  3 ,  4  and in dependence thereon the compression travel of the spring elements  7 ,  8 , as well as the braking force resulting therefrom between the brake wedges  3 ,  4  and the guide rail  2 , can be influenced by the described measures in such a manner that independently of the magnitude of the masses to be braked a retardation arises, in the case of a safety braking, by which on the one hand the load receiving means L is safely stopped and on the other hand no harm to persons or property occurs. 
     The setting device  13  can include, for example, an adjusting drive that contains a servomotor driving a screw spindle by means of which the abutment  11  is positioned. The servomotor and screw spindle are conventional devices represented by the block  13  and a solid line connection C 1  respectively. The setting device  13  moreover includes a position regulating device which generates setting signals for the servomotor in dependence on several input signals. At least one input signal on a line S 1 , which reports the position of the abutment  11 , as well as a signal on a line S 2 , which is generated by a load measuring device and represents the size of the load in the load receiving means, are evaluated. In cases where the vertical conveying equipment is equipped as described in the foregoing with compensating cables, there can be taken into consideration a further input signal on a line S 3  which in dependence on the vertical position of the load receiving means represents the varying, actually effective mass of the compensating cables. 
     The setting device  13  of  FIG. 1  is shown in more detail in  FIG. 4 . The lines S 1 , S 2  and S 3  are connected to inputs of the position regulating device P which has an output connected to an input of the servomotor M. The servomotor M rotates the screw spindle C 1  that is connected to the abutment  11 . Obviously, setting devices of another kind can also be used for the abutment positioning, such as, for example, known hydraulically actuated servo setting cylinders or known motor-driven cam discs as represented by the block  13  and the line C 1  in  FIG. 1 . 
     As known per se, when a permissible speed is exceeded by the elevator car, the brake wedges  3 ,  4  are raised by way of a limiter cable of a speed limiter and a lever arrangement (not shown). Due to the wedge effect between the brake wedges  3 ,  4  and the counter-shoes  5 ,  6  the former are moved towards the guide rail  2  until they contact it. Due to the occurrence of friction forces between the brake wedges  3 ,  4  and the guide rail  2  the brake wedges  3 ,  4  are drawn upwardly as far as the abutment  11 , which causes a lateral displacement of the counter-shoes  5 ,  6  by the wedge effect and the spring deflection of the spring elements  7 ,  8 . The compressed spring elements  7 ,  8  now press the brake wedges  3 ,  4  against the guide rail  2 , whereby a braking force which is dependent on the position of the abutment  11  and counteracts movement of the load receiving means arises between the brake wedges and the guide rail. 
     By contrast to the equipment described in the foregoing in which the housing  1  is fixed to the load receiving means and the abutment  11  is displaced by the setting device  13 , in a variant embodiment the abutment  11  can be fixed to the load receiving means and the housing together with the brake wedges  3 ,  4 , the counter-shoes  5 ,  6  and the spring elements  7 ,  8  can be displaced. This arrangement is illustrated in  FIG. 1  by a dashed line connection C 2  between the setting device  13  and the housing  1  that replaces the solid line connection C 1 . In that case the triggering and the braking effect of the safety braking device remain practically unchanged. 
     An alternate embodiment according to  FIG. 3  has, instead of the abutment  11  determining the end setting of the brake wedge, two abutments  15  guided in the region of the recesses  9 ,  10  in the wall of the housing  1 . These abutments form adjustable supports for the spring elements  7 ,  9  movable in the direction of a double-headed arrow  16 , with the assistance of which the spring deflection of the spring elements  7 ,  8  arising, in the case of a safety braking, by the wedge effect of the brake wedges  3 ,  4  can be varied. Two setting devices  14  position associated ones of the abutments  15  before each travel and optionally also during travel, so that in the case of a safety braking the spring deflection of the spring elements  7 ,  8  and thus the spring forces resulting therefrom, by which the spring elements  7 ,  8  press the brake wedges  3 ,  4  against the guide rail  2 , are matched to the actual mass to be braked. The functional characteristics of the setting devices  14  correspond with those of the setting device  13  described in the foregoing. 
     In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.