Patent Publication Number: US-9415973-B2

Title: Endless cable winch with safety cable

Description:
RELATED APPLICATIONS 
     This application is a continuation application of co-pending International Patent Application PCT/EP2012/062573 filed on Jun. 28, 2012 which claims priority of German patent application 10 2011 106 636.9 filed on Jul. 4, 2011 the contents of which is fully incorporated by reference herewith. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to an endless cable winch, in particular for a service lift, in particular for wind power plants, comprising a working cable and a safety cable, a driving cable pulley around at least a part of which the working cable is wrapped, a drive for driving the driving cable pulley, and further comprising a safety device for the safety cable. 
     Endless cable winches (also called “hoists”) of this type are widely used for person transport applications. It is generally the case here that a lift cage, a platform or the like for receiving one or more persons is moved in an upward or downward direction by means of the endless cable winch along a cable depending from a building or the like. To provide a fall arrestor in the event of a cable breakage of the working cable or in the event of a gearbox failure of the endless cable winch, the safety cable is provided which runs jointly with and independently of the working cable and which, if the safety cable moves downward at too high a speed, generates a blocking action at the safety device, such that the safety cable is abruptly halted and the lift cage, the platform etc. is caught. 
     The abrupt braking in the event of failure of the working cable however results in a high load being exerted on the safety cable, and furthermore, the persons situated in the lifting device moved by the cable winch are subjected to intense physical and psychological stress. 
     SUMMARY OF THE INVENTION 
     It is one aspect of the present invention to disclose an endless cable winch which overcomes one of the disadvantages described above. 
     It is another aspect of the invention to disclose an endless cable winch which allows for a relatively smooth braking of the endless cable winch in the event of failure of the working cable. 
     It is still another aspect of the invention to disclose an endless cable winch which is of simple construction. 
     It is still another aspect of the invention to disclose an endless cable winch which is highly reliable. 
     It is still another aspect of the invention to disclose an endless cable winch which is of compact design. 
     These and other objects of the invention are achieved by an endless cable winch, comprising:
         a housing;   a driving cable pulley received within said housing;   a working cable extending through said cable winch, at least partially being wrapped around said driving cable pulley;   a drive for driving said driving cable pulley;   a non-driven safety cable pulley being mounted rotatably;   a safety cable extending through said cable winch, at least partially being wrapped around said safety cable pulley;   a friction brake being coupled to said cable pulley; and   an arresting device coupled to said brake and configured for activating said brake for blocking and friction braking said safety cable when said safety cable reaches a predetermined threshold speed.       

     The object of the invention is hereby fully achieved. 
     Specifically, the fact that the arresting device blocks, and brakes the safety cable by means of the brake, when the predetermined speed is reached, has the result, during the catching of the safety cable by means of the safety device, of considerably slower braking of the safety cable as compared with the blocking arresting device used in the prior art, which acts directly on the safety cable. 
     Whereas it is the case in the prior art that braking accelerations of the order of magnitude of approximately 3 to 5 g arise during the direct catching of the safety cable by means of an arresting device, it is possible depending on the design of the brake device to realize a considerably lower braking acceleration, for example of the order of magnitude of approximately 2 g. This firstly has the result that the loading of the safety cable upon the response of the safety device is considerably reduced. Secondly, the physical and psychological stress on the personnel located in the person lifting device which is moved by means of the endless cable winch is reduced in this way. 
     In a preferred refinement of the invention, the arresting device comprises a ratchet wheel which interacts with a pawl mounted on the housing, in such a way that the pawl latches into the ratchet wheel at a predetermined speed of the safety cable. 
     In this way, an arresting device is provided which is highly robust and which is of simple and reliable design. 
     Here, in a preferred refinement of the invention, the pawl has a first pawl arm and a second pawl arm, between which the pawl is pivotably mounted on the housing, wherein the pawl is preloaded against the ratchet wheel in such a way that the first pawl arm can move along the ratchet wheel up to a predetermined speed, and latches with its second pawl arm into the ratchet wheel if the predetermined speed is exceeded in the downward direction of the safety cable. 
     In this way, it is possible to ensure reliable blocking of the ratchet wheel by means of the pawl. The predetermined speed at which the blocking takes place can be finely adjusted by means of the preload of the pawl. 
     In a further embodiment of the invention, a sensor is provided for detecting a blocking of the arresting device, which sensor outputs a signal which indicates a blocking of the arresting device. 
     In this way, the signal can be utilized, in the event of blocking of the arresting device, for example to shut off the drive and if appropriate implement further measures such as for example the transmission of a fault signal to a remote monitoring unit. 
     Furthermore, means for targetedly activating the arresting device may be provided, in particular a button for moving the pawl into a latching position for latching into the ratchet wheel. 
     In this way, the arresting device can be targetedly activated manually, mechanically, electrically or in some other way, for example in order, if a critical situation is detected, to activate the arresting device in order to generate a braking action. 
     Here, the arrangement may be such that the arresting device, after an activation, is automatically released again during a subsequent movement of the safety cable in the upward direction. 
     In a further embodiment of the invention, the ratchet wheel and the cable pulley are rotatable about a common axis of rotation, and the ratchet wheel forms a friction brake with the cable pulley. 
     A simple and reliable construction is ensured in this way. 
     In a further embodiment of the invention, the brake is in the form of a conical brake. 
     The design of the brake as a conical brake yields a particularly effective braking action with a relatively small installation size. 
     It is furthermore preferable for the friction brake to comprise a first friction partner composed of a bronze alloy and a second friction partner composed of a steel alloy. 
     It has been found that such a design of a friction brake for the application according to the invention yields particularly expedient configuration parameters which permit in particular a high braking force. It is alternatively possible for two friction partners to be used, at least one of which is provided with a friction lining. 
     Here, the brake preferably has a cone angle of approximately 4° to 10°. 
     A particularly expedient configuration of the brake can be attained in this way. 
     It is also alternatively possible for a friction lining to be provided on at least one of the friction partners. It is then generally the case here that a larger cone angle is also used, of the order of magnitude of approximately 10° to 40°. 
     This counteracts possible wear or seizing. 
     In a further preferred embodiment of the invention, the ratchet wheel has an external cone which is spring-loaded against an internal cone of the cable pulley. 
     Here, the ratchet wheel may be preloaded against the internal cone of the cable pulley for example by means of a plate spring, the preload of which is preferably adjustable. 
     These measures yield a simple and reliable construction. 
     The use of a plate spring makes it possible to impart a very high pressing force, such that high braking forces can be transmitted. 
     In a further embodiment of the invention, at least the working cable or the safety cable are wrapped around the driving cable pulley or the cable pulley with a wrap angle of less than 300°, preferably of approximately 260° to 280°, particularly preferably of approximately 270°. 
     Whereas it is the case in conventional endless cable winches that the wrap angle is normally 360°, it has been recognized according to the invention that a smaller wrap angle may also be adequate. With a smaller wrap angle of in particular approximately 270°, it is possible to dispense with a diverting roller if, in the case of the endless cable winch being used with a person lifting device, the cable should not be guided through the service lift itself but rather should be diverted laterally past the service lift and downwards by means of diverting rollers. 
     In a preferred refinement of the invention, the predetermined speed for the braking of the safety cable is 20 to 40 meters/minute, preferably 25 to 35 meters/minute, preferably approximately 30 meters/minute. 
     In this way, adherence to the triggering speed predefined by the European standard EN 1808 can be ensured. 
     In a further embodiment of the invention, the driving cable pulley and the cable pulley are mounted in a common housing. 
     In this way, it is possible for both the winch and also the safety device to be of compact construction in a common housing. 
     It would however basically also be conceivable for the safety device to be formed as a separate unit with the arresting device and the brake. 
     In a further embodiment of the invention, the cable pulley has a biasing device for biasing the safety cable against the cable pulley. 
     In a further embodiment of the invention, the driving cable pulley has a biasing device for biasing the working cable against the driving cable pulley. 
     Here, the biasing device may be for example a spring-loaded pressing roller. 
     These measures concern additional safety measures which are basically not necessary if both cables are preloaded or are loaded with a weight, but which lead to a further increase in safety. 
     Furthermore, the ratchet wheel may be mounted on a journal of the cable pulley. 
     Finally, a rotationally conjoint connection of the driving cable pulley and cable pulley to one another is also conceivable. 
     These measures yield a more simplified construction and a compact design of the safety device and of the endless cable winch as a whole. 
     The invention also provides a person lifting device, in particular a service lift, in particular for wind power plants, which has an endless cable winch of the type described above. 
     It is possible here for the working cable and the safety cable to be guided laterally out of the endless cable winch at an angle of approximately 90° relative to the upper strands, and diverted downward merely by means of in each case one diverting roller. 
     In this way, it is possible to attain simpler cable guidance while dispensing with further diverting rollers, and to attain a smaller structural height of the person lifting device, in particular of a hoisting cage. 
     It is self-evident that the features of the invention mentioned above and the features of the invention yet to be explained below can be used not only in the respectively specified combination but rather also in other combinations or individually, without departing from the scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the invention will be apparent from the following description of preferred exemplary embodiments with reference to the drawings, in which: 
         FIG. 1  shows, in a simplified side view, a person lifting device in the form of a service lift for a wind power plant; 
         FIG. 2  shows a perspective illustration of an endless cable winch according to the invention which is used in the person lifting device as per  FIG. 1 ; 
         FIG. 3  shows a front view of the endless cable winch as per  FIG. 2 ; 
         FIG. 4  shows a front view of the endless cable winch as per  FIG. 3  in an enlarged illustration and after the housing cover has been removed; 
         FIG. 5  shows a section through the endless cable winch as per  FIG. 2 ; and 
         FIG. 6  shows, in an enlarged illustration, a partial section as per  FIG. 5  in the region of the winch and safety device. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
       FIG. 1  shows, in a side view and in a simplified illustration, a person lifting device in the form of a service lift for wind power plants. 
     The person lifting device denoted as a whole by  10  has a lift cage  12  with a frame  18 , to the top end of which is fastened an endless cable winch  20 . 
     The lift cage  12  hangs on a working cable which is guided through the endless cable winch  20  and which, laterally, is diverted downwards by means of a roller  14 . Parallel to the working cable there runs a safety cable  16  which is likewise guided through the endless cable winch  20  and is guided laterally out of the endless cable winch  20  at an angle of 90° or 270° relative to the upper strand of the safety cable  16  and guided downwards by means of the diverting roller  14 . In  FIG. 1 , it is possible to see only the course of the safety cable  16 , because the working cable runs exactly parallel thereto and is thus hidden by the safety cable  16 . 
     The construction and mode of operation of the endless cable winch  20  will now be explained in more detail below on the basis of  FIGS. 2 to 6 . 
       FIG. 2  shows a perspective view of the endless cable winch  20 . The endless cable winch  20  moves the working part  28  upwards or downwards such that the lift cage  12  moves upwards or downwards on the working cable  28 . The winch  22  comprises a drive  24  with a motor and a gearbox, and also comprises a controller  26 . The endless cable winch  20  comprises a winch  22  which moves the working part  28 , and also a safety device  30  through which the safety cable  16  is guided. 
       FIG. 3  shows the endless cable winch  20  in a front view, whereas  FIG. 4  shows the endless cable winch  20  in a slightly enlarged front view after the housing cover of the safety device  30  has been removed. 
       FIG. 4  shows the construction of an arresting device  31  which is part of the safety device  30 . The arresting device  31  comprises a ratchet wheel  32  which interacts with a pawl  34  which is held so as to be pivotable about a pivot axis  36 . The pawl  34  has a first pawl arm  38  and a second pawl arm  40  which protrude in opposite directions from the pivot axis  36 . The pawl  34  is preloaded by a spring  46  in such a way that the first pawl arm  38  normally bears against the internal toothing of the ratchet wheel  32 . In this position, the ratchet wheel can be moved both clockwise and also anticlockwise without the pawl leading to blocking against the ratchet wheel  32 . If the ratchet wheel  32  moves anticlockwise as per the illustration in  FIG. 4 , the lift cage  12  moves downwards. Here, the pawl  34  runs with its first pawl arm  38  on the toothed inner surface of the ratchet wheel  32 . The stress of the spring  46  is now set such that, when the downward speed of the safety cable  16  reaches approximately  30  meters per minute, the interaction of the first pawl arm  38  with the toothed inner surface of the ratchet wheel  32  causes the pawl  34  to lift from the inner surface of the ratchet wheel  32  and turn over, such that the pawl latches with a latching lug  42  at the end of the second pawl arm into the inner surface of the ratchet wheel  32 , and the ratchet wheel  32  is thus blocked by means of the pawl  34  mounted in the housing  54 . The arresting device  31  is thus arrested and causes the rotatably mounted ratchet wheel  32  to be fixed at the pawl  34 . 
     In the arrested state, a switch  44  is actuated. The switch signals to the controller  26  that the drive  24  must be shut off. Furthermore, the switch  44  may also be utilized to output for example a fault signal, which is transmitted for example to a remote monitoring device, in the event of a response. 
       FIG. 4  also shows a pressing device  48  for a cable pulley over which the safety cable  16  is guided (cf.  FIG. 5 ). The pressing device  48  has a pressing roller  50  which is pressed by means of a spring  52  against the safety cable  16  in order to press the latter into an associated guide groove of the cable pulley  68  as per  FIG. 5 . 
       FIG. 5  furthermore shows the construction of the winch  22 . The winch  22  has, in a way which is basically known, a driving cable pulley  58  over which the working cable  28  is guided with a wrap angle of approximately 270°. The driving cable pulley  58  has a guide groove  59  in which the working cable  28  runs. A pressing device  56  is also provided for pressing the working cable  28  into the guide groove  59 . This pressing device involves a pressing roller combined with a spring. The working cable  28  emerges laterally out of the winch  22 , as can be seen from  FIG. 2 , after a wrap angle of approximately 270°, and is then diverted downwards by means of the diverting roller  14 . 
       FIG. 5  also shows the drive  24  which comprises an electric motor and a gearbox. The output shaft  70  of the gearbox drives the driving cable pulley  58  via a shaft-type pinion (not illustrated). 
     As can be seen from the enlarged illustration of  FIG. 6 , both the driving cable pulley and also the cable pulley are mounted in the common housing  54  of the winch  22  and of the safety device  30  by means of in each case two bearings  60 ,  62 ,  64 ,  66 . 
     The safety device  30  comprises the arresting device  31  discussed above on the basis of  FIG. 4 , this safety device being coupled by means of a brake, denoted as a whole by numeral  71 , to the cable pulley  68  over which the safety cable  16  is guided. The ratchet wheel  32  has an external cone  72  which bears against an internal cone  74  of the cable pulley  68 . The ratchet wheel  32  is preloaded against the cable pulley  68  by means of a plate spring  78  which is supported against a bearing ring  76  on a journal  73  of the cable pulley, such that there is frictional engagement between the external cone  72  of the ratchet wheel  32  and the internal cone  74  of the cable pulley  68 . The preload of the plate spring  78  can be adjusted by means of a nut  82  which is screwed onto a thread  80  on the journal  73 . 
     The function of the safety device  30  is as follows: 
     In the normal situation, the non-driven cable pulley  68  runs synchronously with the driving cable pulley  58 . The safety cable  16  thus moves at the same speed as the working cable  28  over the cable pulley  68 . 
     If, for any reason, the winch  22  fails, either as a result of breakage of the working cable  28  or gearbox failure in the drive  24 , which would cause the lift cage  12  to fall downwards, the lift cage  12  moves downwards initially at an increased speed until the triggering speed of the arresting device  31  is reached. At approximately  30  meters per minute, the pawl  34  blocks against the ratchet wheel  32 , such that the previously rotating cable pulley  68  is now braked by means of the conical brake  71  until the lift cage  12  finally comes to a standstill. 
     The triggering speed for the arresting device  31  is approximately  30  meters per minute. The preload of the plate spring  78 , the cone angle of the conical brake  71 , which is approximately 5° to 8°, and the friction pairing of the materials of the internal cone  74  and external cone  72  (bronze alloy/steel alloy) are coordinated with one another such that, proceeding from the triggering speed of approximately 30 meters per minute, the lift cage  12  is braked with approximately 2 g. This constitutes considerably smoother braking than with conventional safety devices, by means of which the safety cable was immediately blocked, which led to catching of the lift cage  12  with approximately 5 g. 
     Instead of the direct material pairing of two metals (bronze alloy/steel alloy), it would also be possible for a friction lining to be provided on at least one friction partner in order to counteract possible wear as a result of corrosion or seizing. Here, it would then generally also be necessary to use a larger cone angle of the order of magnitude of approximately 10° to 40°, for example of approximately 30°. 
     By means of a button  45 , the pawl  34  can also be moved into its arresting position manually, mechanically, electrically or in some other way (cf.  FIG. 5 ). For this purpose, the button  45  is actuated once in order to pivot the pawl  34 . The arresting position is automatically eliminated again if the safety cable  16  is moved in the upward direction again.