Abstract:
An automatic Braking system for an elevator car ( 10 ) is designed to stop it when it reaches or exceeds a speed limit of movement within an elevator shaft. A stop mechanism ( 40 ) is mounted on car ( 10 ), or a part thereof, so as to lock a stop pulley ( 41 ) which then moves relative to the car in a direction substantially parallel to the direction of the car ( 10 ) movement. A control mechanism ( 11 ) reacts to responsive to the stop pulley ( 41 ) movement to apply the brakes ( 12, 13 ).

Description:
BACKGROUND 
     The present invention concerns a system for the automatic braking of an elevator car designed to stop it when it reaches or exceeds a limit speed of movement within a lift shaft. 
     Such automatic braking systems are already known which generally consist of a stop mechanism comprising a stop pulley designed to be driven in rotation at the same time as said car moves. Said stop pulley is designed to rotate freely when its speed of rotation is less than a threshold speed of rotation and to lock when its speed of rotation is equal to or greater than said threshold speed of rotation. They also comprise a mechanism for controlling the action of said brakes when said stop pulley is locked. 
     FIG. 1 shows an elevator installation equipped with a braking system according to the known state of the art. This installation consists essentially of an elevator car  10  which is moved between the different floors of an elevator shaft (not shown), for example by means of a machinery  20  acting on a cable or a cluster of traction cables  21  and having a counterweight  22 . The elevator car  10  is guided in its movement by lateral rails extending vertically in the elevator shaft and on which the car  10  bears through guides  31 . For reasons of clarity, only one of these rails  30  has been depicted in FIG.  1 . 
     The elevator car  10  has a control mechanism  11  provided for controlling the action of the brakes  10  and  13  depicted here schematically in the form of simple wedges, The brakes  12  and  13  act generally on the rails  30  of the elevator car  10 . These brakes  12  and  13  are also known in the art as “safety stop clamps”. They act one in one direction of movement of the car  10 , the other in the other direction. 
     As for the automatic braking system, this includes a stop pulley  50  which is mounted on the masonry in the top part of the elevator shaft and an endless cable  60  wound between the stop pulley  50  and a return pulley  51 . The endless cable  60  is tensioned by means of a tension weight  52  acting on the return pulley  51 . 
     A control mechanism  53  is fixed on the one hand to the endless cable  60  and on the other hand to the car  53 . In normal operation, that is to say when the speed of movement of the car  10  is less than a limit speed, the car  10  drives the cable  60 . The mechanism  53  is not stressed and therefore does not act on the control mechanism  11  of the brakes  12  and  13 . 
     On the other hand, when the speed of the car  10  reaches or exceeds a limit speed, the stop pulley  50  locks and the cable  60  is immobilised. The mechanism  53  is stressed since it is on the one hand immobilised by the cable  60  and on the other hand fixed to the car  10 , which is still moving. The effect of this stressing of the mechanism  53  is to actuate the control mechanism  11 , which then acts on the brakes  12  and  13 . These in return act on the rails  30 , which has the effect of immobilising the car  10 . 
     One of the drawbacks of the braking system of the state of the art presented above is its relatively large bulk because notably of the use of an endless cable, which has two parallel lengths for which it is necessary to reserve space in the elevator shaft. 
     The other drawback of this braking system lies in the fact that the stop pulley is necessarily mounted in the top part of the elevator shaft, generally on the same piece of masonry as that on which the drive motor  20  rests. The risks of accident related to this piece are therefore not covered by the braking system. 
     SUMMARY OF THE INVENTION 
     The aim of the present invention is to propose a braking system which does not have the drawbacks of the braking systems of the prior art, notably those disclosed above, and which is consequently more compact compared with those of the state of the art and which is not mounted on the same piece of masonry as that on which the drive motor rests. 
     To do this, according to one characteristic of the present invention, said stop mechanism is mounted on said car, said stop mechanism or part thereof being designed so as, in reaction to the movement of said car when said stop pulley is locked, to move relatively to said car in a direction substantially parallel to the direction of said car. Said control mechanism then acts on said brakes when said stop mechanism or said part thereof moves relatively to said car. 
     Advantageously, said stop pulley is driven by a control cable suspended vertically in the elevator shaft and passing through its groove. 
     According to a first embodiment of the present invention, said stop mechanism comprises two pulleys, one of which is said stop pulley, said control cable having its top vertical length passing through the bottom part of a first groove in one of said pulleys, then passing through the groove in the second pulley and then passing once again through the top part of the second groove in said first pulley. 
     Said first pulley can then constitute the part of the stop mechanism which, in reaction to the movement of said car when said stop pulley is locked, moves relatively to said car. 
     According to a second embodiment of the present invention, said stop mechanism comprises at least two pulleys, one of which is said stop pulley, said control cable passing through each of said grooves in said pulleys. 
     Said upstream pulley and said downstream pulley constitute the part of the stop mechanism which, in reaction to the movement of said car when said stop pulley is locked, moves relatively to the car. 
     According to another characteristic of the present invention, said stop mechanism or said part of said stop mechanism are mounted at the end of a pivoting arm, said arm, when moving away from its idle position, stressing the control mechanism, which then acts on said brakes. 
     According to another characteristic of the present invention, said stop mechanism or said part of said stop mechanism are mounted on channels extending substantially in the direction of movement of said car, said channel, moving away from its idle position, stressing the control mechanism, which then acts on said brakes. 
     According to another characteristic of the present invention, said stop mechanism or said part of said stop mechanism are provided with a retractable rod which can, when it is not retractable, come into contact with stops provided in said elevator shaft, which has the effect of moving said stop mechanism or said part of said stop mechanism relative to said car and to stress the control mechanism, which then acts on said brakes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The characteristics of the invention mentioned above, and others, will emerge more clearly from a reading of the following description of an example embodiment, said description being given in relation to the accompanying drawings, amongst which: 
     FIG. 1 is a schematic view of an elevator installation provided with an automatic braking system according to the state of the art, 
     FIG. 2 is a schematic view of an elevator installation provided with an automatic braking system according to a first embodiment of the present invention, said arm, referred to as a stop mechanism, being situated in its idle position, 
     FIG. 3 is a schematic view of an elevator installation provided with an automatic braking system according to a first embodiment of the present invention, said arm, referred to as a stop mechanism, being situated in a working position, 
     FIG. 4 is a schematic view of an elevator installation provided with an automatic braking system according to the second embodiment of the present invention, 
     FIG. 5 is a schematic view of an elevator installation provided with an automatic braking system according to the third embodiment of the present invention, 
     FIG. 6 is a schematic view of an elevator installation which is identical to that of FIG.  2  and which also has a safety device. 
    
    
     DETAILED DESCRIPTION OF INVENTION 
     The elevator installation depicted in FIG. 2 consists essentially of an elevator car  10  which is moved between the different floors of an elevator shaft (not shown), for example by means of a machinery  20  acting on a traction cable or on a cluster of cables  21  and having a counterweight  22 . This machinery  20  is for example mounted on the masonry constituting the top part of the elevator shaft. 
     The elevator car  10  is guided in its movement by lateral guides extending vertically in the elevator shaft. For reasons of clarity, only one of these rails  30  has been depicted. 
     The elevator car  10  has a control mechanism  11  (depicted schematically by a simple dotted line) designed to control the action of brakes  12  and  13  depicted schematically in FIG. 2 in the form of wedges. The brakes  12  and  13  act on the guides of the elevator car  10 . These brakes  12  and  13  are also known in the art as “safety stop clamps”. One of them acts in one direction of movement of the car  10 , the other in the other direction. 
     The elevator car  10  has a stop mechanism  40  consisting here of a stop pulley  41  and a return pulley  42 . The stop pulley  41  is of the type which turns freely as long as its speed of rotation does not exceed a threshold speed, and which locks when its speed of rotation exceeds said threshold speed of rotation. 
     It will be noted that in the example embodiment depicted the system  40  is mounted underneath the car  10 , for example on the frame thereof. However, it will be understood, notably hereinafter, that it could be mounted, for example, on the same frame, in the top part of the car  10 , or elsewhere provided that it is secured to the car  10 . 
     A control cable  60 , which extends vertically in the elevator shaft in which the said elevator car  10  moves, passes through the bottom part of a first groove in the return pulley  42 , then passes through the groove in the stop pulley  41  in order to be able to drive it in rotation as the same time as the car  10  moves in the elevator shaft, and finally through the top part of a second groove in the return pulley  42 . Its bottom end has a tension system such as a weight  61  (or a spring or the like), whilst its top end is connected to the roof of the shaft by means of an elastic system  62 . The tension weight  61  and the elastic system  62  are designed to ensure the tension of the control cable  60 . 
     In the example embodiment depicted in FIG. 2, the return pulley  42  is mounted so as to rotate freely at the free end of an arm  43  designed to pivot about a pivot axis  44 . The stop pulley  41  and return pulley  42  have rotation axes parallel to each other and parallel to the pivot axis  44  of the arm  43 . 
     The arm  43  acts on the control mechanism  11  as follows. When the arm  43  is in a substantially horizontal position, referred to as the idle position, such as the one depicted in FIG. 2, the control mechanism  11  is not stressed and the brakes  12  and  13  are inactive. On the other hand, when it takes an inclined position, referred to as the working position, in one direction or the other, the mechanism  11  is stressed, which has the effect of making the brakes  12  and  13  active, thus stopping the car  10  on its rails  30 . 
     In normal operation, that is to say when the elevator car  10  does not exceed a limit speed, the cable  60  runs between the return pulley  42  and stop pulley  41 , notably driving the latter. The arm  43  is then in its idle position, as depicted in FIG.  2 . It therefore does not act on the control mechanism  11 , so that the brakes  12  and  13  do not act on the rails  30 . 
     It should be noted that the arm  43  can be acted on in this idle position, for example by means of elastic elements, such as springs (not shown). 
     When the elevator car  10  reaches and exceeds a limit speed, the speed of rotation of the stop pulley  41  becomes greater than its threshold speed of rotation. Consequently it locks, making it impossible for the control cable  60  to run through the stop mechanism  40 . The return pulley  42  is then immobilised with respect to the control cable  60  and with respect to the shaft (except for the movement of the cable  60  permitted by the elastic means  62 ). In reaction to the advancement of the car  10  which, through inertia, is still moving, the arms  43  pivots about its pivot axis  44 . The result is an action on the control mechanism  11 , which has the effect of locking the brakes  12  and  13  on the rails  30 . The elevator car  10  is then stopped. 
     The stop pulley  41  and return pulley  42  constitute together a stop mechanism  40  which therefore enables the movement cable  60  to run when its running speed is below a limit speed, which locks the control cable  60  when this limit speed is reached or exceeded. Moreover, the arm  43  constitutes a means allowing the movement of the stop mechanism  40  or a part of this mechanism  40  in the direction of travel of the car  10  when the control cable  60  is locked by the stop pulley  41 , and the car  10 , by inertia, still has movement. 
     It will be understood that the stop mechanism  40  could include a plurality of pulleys (at least two), where one would be a stop pulley  41  and at least one other would be mounted so as to be able to move in the direction of travel of the car, for example at the end of an arm such as the arm  43 . 
     Advantageously, it is the upstream pulley (the one which receives the top vertical length) and the downstream pulley (the one which returns the bottom vertical length) which are mounted so as to be able to move in the direction of travel of the car  10 . 
     In FIGS. 2 and 3, the return pulley  42  is a pulley with two grooves designed on the one hand to receive the top vertical length of the cable  60  and to return it to the stop pulley  41  and on the other hand to receive the length issuing from the stop pulley  41  and to return it as a bottom vertical length. 
     FIG. 4 depicts a variant embodiment where the arm  43  depicted in FIGS. 1 and 2 is replaced by a channel  46  parallel to the direction of travel of the car  10  in which the rotation axis  47  of the return pulley  43  can move when the control cable  60  is locked in the stop pulley  41 . In FIG. 4, the return pulley  42  is depicted in its idle position in which the rotation axis is substantially at the centre of the channel  46 . The mechanism  11  is stressed when the axis  47  is no longer in its central idle position, but is separated therefrom. 
     FIG. 5 is a variant embodiment which has two return pulleys  42   a  and  42   b  which are mounted so as to be free to rotate at the ends of a slider  48  designed so as to be able to move in translation in a direction parallel to the direction of movement of the elevator car  10 . The slider  48  is for this purpose mounted in a channel  49  extending vertically in the direction of travel of the car  10 . The slider  48  is here shown in its idle position. 
     It should be noted that the embodiments depicted are designed to trigger the action of the brakes  12  and  13  when the car  10  reaches or exceeds a limit speed fixed by the stop pulley  41 , whatever the direction of movement of the car  10 . 
     It will have been understood that, in all the examples depicted, the stop pulley  41  could be put in place of a return pulley  42 ,  42   a  or  42   b , and that it would then be replaced by a return pulley. 
     In FIG. 6 an elevator installation is shown which is identical to that which is already depicted in FIG.  2  and which also has a safety device  90 . This safety device  90  consists essentially of a rod  91  which is retractable under the action of a control device such as an electromagnetic  92 , which is mounted on the pivoting arm  43 . In FIG. 6, the retractable position of the rod  91  is depicted in bold lines, whilst its deployed position is depicted in dotted lines. 
     When the rod  91  is in the non-retracted position, it can come into contact with one or more stops  93  which are provided in the elevator shaft. On the other hand, in the retracted position, it can no longer come into contact with these stops  93 . 
     When the rod  91  comes into contact with a stop  93  by reaction to the travel of the car  10 , the arm  43  pivots on its axis, which has the effect of acting on the control mechanism  11  and actuating the brakes  12  and  13 . The car is the immobilised.