Patent Publication Number: US-9422140-B2

Title: Endless cable winch with overload protection

Description:
RELATED APPLICATIONS 
     This application is a continuation application of co-pending International Patent Application PCT/EP2012/062841 filed on Jul. 2, 2012 which claims priority of German patent application 10 2011 106 635.0 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, comprising a working 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 an overload detection device for identifying an overload of the working cable. 
     Endless cable winches of this type (also called “hoists”) are widely used for transporting loads or people. Endless cable winches have, for safety reasons, an overload detection device which responds in the event of a certain passing of the rated load in order to shut off the endless cable winch and/or output a warning signal. 
     In the prior art, for an overload detection device, the load acting on the working cable is measured indirectly by means of a spring-loaded roller, by virtue of the travel of the roller being monitored. 
     The disadvantage of this principle is that the load acting on the working cable is influenced by the weight of the hanging-down strand of the working cable. As a result, the measurement result may deviate to a great extent in particular at relatively great heights, that is to say in the case of long hanging-down strands, and therefore an overload detection device based on this can be rather inaccurate. 
     SUMMARY OF THE INVENTION 
     It is a first aspect of the invention to disclose an endless cable winch which permits a reliable and highly precise overload detection. 
     It is a another aspect of the invention to disclose an endless cable winch which is of simple design. 
     It is a another aspect of the invention to disclose an endless cable winch that automatically shuts down the drive thereof in case of an overload detection. 
     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 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 are achieved according to the invention, in the case of an endless cable winch of the type mentioned at the outset, in that the housing is mounted so as to be pivotable about a pivot axis, and in that a sensor for detecting a pivoting movement of the housing is provided. 
     The fact that, according to the invention, a pivoting movement of the housing is monitored by means of a sensor results in particularly simple and reliable load monitoring for the force exerted on the working cable, which load monitoring is not influenced by a hanging-down strand of the working cable. 
     In a further embodiment of the invention, the housing is pivotably mounted at a first end, and is suspended at a second end on an elongation element. 
     The elongation element may be a spring element, an elongation cable or the like. 
     Particularly simple and sensitive adaptation of a certain triggering force at which the sensor responds is permitted in this way. 
     In a further embodiment of the invention, the sensor is in the form of a travel sensor, elongation sensor, contact sensor, piezo sensor or magnetic sensor. 
     All of these sensor types permit adequately accurate and reliable detection of the force acting on the working cable. 
     In a further embodiment of the invention, the drive is shut off when the sensor responds. 
     In addition or alternatively, a warning signal may be output when the sensor responds. 
     In this way, a malfunction is as far as possible eliminated or at least limited in the event of an overload. 
     In a further embodiment of the invention, a safety cable is provided with a safety device which has a non-driven cable pulley, which is rotatably mounted in a housing and around at least a part of which the safety cable is wrapped, and also has an arresting device which is coupled via a brake to the cable pulley and which blocks, and brakes the safety cable by means of the brake, at a predetermined speed of the safety cable at least in one direction. 
     The arresting device hereby blocks, and brakes the safety cable by means of the brake, when the predetermined speed is reached. The result, during the catching of the safety cable by means of the safety device, is relatively gentle braking of the safety cable with a braking acceleration for example of the order of magnitude of approximately 2 g. This has the result that a low loading of the safety cable upon the response of the safety device is achieved. Also, 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 further embodiment 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 metered by means of the preload of the pawl. 
     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. 
     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 used, of approximately 10° to 40°, e.g. approximately 30°. 
     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. 
     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. 
     This 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. A smaller wrap angle of in particular approximately 270° has space advantages, since it is hereby possible in certain cases to dispense with a diverting roller. 
     The predetermined speed for the braking of the safety cable is preferably 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 pressing the safety cable against the cable pulley. 
     In a further embodiment of the invention, the driving cable pulley has a biasing device for pressing 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, but which lead to a further increase in safety. 
     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 emerge from the following description of preferred exemplary embodiments with reference to the drawing, in which: 
         FIG. 1  shows a perspective illustration of an endless cable winch according to the invention; 
         FIG. 2  shows a front view of the endless cable winch as per  FIG. 1 ; 
         FIG. 3  shows a front view of the endless cable winch as per  FIG. 2  but without the crossbeam on which the endless cable winch is accommodated; 
         FIG. 4  shows a section through the endless cable winch as per  FIG. 1 ; and 
         FIG. 5  shows a rear view of the endless cable winch as per  FIG. 1 , but after removal of the housing cover of the safety device. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
       FIG. 1  shows a perspective view of the endless cable winch  10 . The endless cable winch  10  comprises a winch  22  which moves a working cable  28  upwards or downwards such that a load located thereon, e.g. lift cage, 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 . 
     In the situation illustrated here, in which people are conveyed, the endless cable winch  10  also comprises a safety device  30  through which a safety cable  16  is guided. If, by contrast, the endless cable winch  10  is used merely for transporting materials, it is possible to dispense with the safety cable  16  and the safety device  30 . The winch  22  and the safety device  30  are accommodated in a common housing  54 . 
     The endless cable winch  10  is designed for a certain rated load, for example 600 kg. To avoid overloading, or to avoid accidents in the event of overloading, the endless cable winch  10  has an overload detection device denoted as a whole by  11 . The overload detection device  11  monitors the force acting on the working cable  28 . If the rated load is exceeded, for example by 25%, the overload detection device  11  identifies an overload state. In this case, the drive is immediately stopped and a warning signal is output. 
       FIGS. 2 and 3  show the endless cable winch  10  in a front view. The endless cable winch  10  is fastened to two beams  21 ,  23 . Only the rear beam  23  is illustrated in  FIG. 2 , whereas  FIG. 3  shows the front beam  21  which faces toward the viewer. 
     For the purpose of monitoring the load acting on the working cable  28 , the housing  54  is held at a first end so as to be pivotable about a pivot axis  12 . At the opposite, second end, the housing  54  is held on a spring  14  which is held with one end in a housing recess  17  and which is fastened with its other end to a beam on which the housing  54  is held. The spring acts on the housing  54  of the endless cable winch. A sensor  13  is fastened to the housing  54 . A holder  15  comprises an adjusting screw  18  by means of which the value for the overload can be finely adjusted. The sensor  13  may for example be in the form of an electrical contact sensor which closes an electrical circuit when a contact-making end of the spring  14  makes contact. Various other embodiments of the sensor  13  are conceivable which respond when the housing  54  pivots about the pivot axis  12  by a certain pivot angle. This sensor could therefore for example also be a travel sensor in the form of a strain gauge or the like. 
     When the sensor  13  responds, the housing  54  has pivoted by a certain pivot angle as a result of the force acting on the working cable. The spring characteristic and the sensor are preferably coordinated with one another such that the sensor  13  responds when 125% of the rated load of the endless cable winch  10  is reached, that is to say at 750 kg in the case of a rated load of 600 kg. This corresponds to the EN1808 standard. 
     If the sensor  13  responds, the drive is automatically stopped and a warning signal, for example a visual warning signal and an acoustic warning signal, is output. Furthermore, the overload state may be transmitted electrically to further elements via a signal line. Since the overload generally occurs when the endless cable winch  10  is at a standstill, the drive cannot start in this case, and, as a result of the warning signal output, a user will generally immediately recognize the overload, such that he can correspondingly reduce the load. 
     The further construction of the winch  22  and of the safety device  30  can be seen from  FIG. 4 . 
     The winch  22  has 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 biasing device  56  is also provided for biasing or pressing the working cable  28  into the guide groove  59 . This biasing 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. 1 , after a wrap angle of approximately 270°, and can optionally then be diverted downwards by means of a diverting roller. 
       FIG. 4  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 also be seen from  FIG. 4 , both the driving cable pulley  58  and also the cable pulley  68  are each mounted in the common housing  54  of the winch  22  and of the safety device  30  by means of two bearings  60 ,  62 ,  64 ,  66 . 
     The safety device  30  comprises an arresting device  31 , the safety device being coupled by means of a brake, denoted as a whole by numeral  71 , to a cable pulley  68  over which the safety cable  16  is guided. If the arresting device  31  arrests the safety cable  16  when a certain speed is reached, the cable pulley  68  is braked via the brake  71 . 
     The arresting device  31  comprises a rotatably mounted ratchet wheel  32 , which interacts with a pawl  34  which is pivotably mounted on the housing  54 . 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 . A biasing device  48 , consisting of spring and pressing roller, is also provided for the cable pulley  68 , for pressing the safety cable  16  into the guide groove provided therefor. 
       FIG. 5  shows in more detail the construction of the arresting device  31  which is part of the safety device  30 . The pawl  34  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 , which is accommodated on a holder  44 , 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. 5 , a load accommodated on the endless cable winch  10 , for instance a lift cage, 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 . A response of the arresting device  31  is signalled by the switch  44 . 
     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 load accommodated on the endless cable winch  10  to fall downwards, the load 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 safety cable  16  finally comes to a standstill. 
     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. 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.