Patent Publication Number: US-7708116-B2

Title: Fall arrester as part of a fall protection system for ladders and similar climbing routes

Description:
This application is a national stage application under 35 USC 371 of International Application No. PCT/EP2004/052144, filed Sep. 13, 2004, the international Application being published in German. The application also claims priority of German Application No. 203 14 230.6, filed Sep. 12, 2003, the contents of each application hereby being incorporated by reference in their entirety for all purposes. 
   The invention relates to a fall arrester which forms part of a fall protection system for ladders and similar climbing routes and can be inserted into a guide rail with a C-profile. The fall arrester has a body and two pairs of rolls which are arranged on the body so that they run inside the guide rail. 
   Such a fall arrester is known from EP 0 168 021. Both pairs of rolls are arranged swivellably about an axis which runs at right angles to the longitudinal axis of the guide rail and to the axis of rotation of this pair of rolls. Due to the swivellable arrangement of the pair of rolls the fall arrester can be inserted into the guide rail at any point. For insertion the pairs of rolls are swivelled so that the axis of rotation of the rolls points in the longitudinal direction of the rail. After insertion of the fall arrester into the guide rail the pairs of rolls are then swivelled into their normal or secure position and secured in this position. 
   A fall arrester is known from DE 27 36 037 in which the parts which grip around one guide flange of the guide rail are swivellable about an axis which runs parallel to the guide rail. These parts can thereby be moved in the direction of the parts of the fall arrester gripping around the other guide flange, whereby the fall arrester can then be removed from the guide rail. To lock the fall arrester in the secure position a threaded bolt is tightened by means of a box spanner or an additional locking pin is provided. 
   The object of the invention is to simplify the design of the fall arrester and at the same time to increase the operational safety. 
   According to the invention this object is achieved in that one pair of rolls is arranged rigid against the body and the other pair of rolls is arranged swivellable about an axis which runs at right angles to the longitudinal axis of the guide rail and to the axis of rotation of this pair of rolls. 
   By having one pair or rolls arranged rigid, a possible source of errors is excluded and the design is simplified at the same time. 
   The swivellable pair of rolls can preferably be fixed in the secure position. The fixing can take place in that the swivellable pair of rolls is attached to a shank housed rotatable in the body and the end of the shank projects from the body and has a diametral indent. Articulated to the body is a lever which can be inserted into the indent and locked in this position by a stop bolt. 
   The lever which can be inserted into the indent is preferably one leg of a U-shaped suspended ratchet. The suspended ratchet is preferably articulated to the body at the base of its U-shape. On the free leg of the U-shape, an eyelet is provided for securing the safety belt of the personal safety equipment. If the fall arrester engages in the guide rail in the event of a fall, the U-shape of the suspended ratchet is bent upwards, whereby the catching impact is additionally attenuated. 
   Above the rigid pair of rolls a third pair of rolls is preferably arranged, which is also rigid. This pair of rolls runs on the outside of the guide rail so that the two guide flanges which delimit the opening of the C-profile lie between the two rigid pairs of rolls. A largely frictionless movement of the fall arrester in the guide rail is thereby achieved. 
   The two rigid pairs of rolls are usually arranged at the front end of the fall arrester, while the swivellable pair of rolls are arranged approximately in the middle of the fall arrester. The rear end is formed as a catching pawl, which is integral with the body. The axis of rotation of the swivellable pair of rolls is loaded towards the body by a compression spring so that, in the normal case, and during forward movement, the catching pawl is pushed towards the catching stop which is formed in the back of the guide rail. In the event of a fall, if the fall arrester is pulled backwards, the catching pawl impacts against the catching stop and the fall arrester is thereby locked in the guide rail. 
   The catching pawl can also be formed in the body as a movable element under spring tension, the swivellable pair of rolls expediently being arranged at the rear end of the body, while the catching pawl is then articulated in the middle of the body. 
   To insert the fall arrester into the guide rail, the fall arrester is first held at right angles to the guide rail and inserted with the front, lower, rigid pair of rolls into the opening of the C-profile of the guide rail. The fall arrester is then with its rear end swivelled down by 90° C., so that the swivellable pair of rolls and the catching pawl can also be inserted into the opening of the C-profile. The swivellable pair of rolls is located in its inserted position, in which the axis of rotation of the pair of rolls points in the longitudinal direction of the guide rail. After the insertion of the swivellable pair of rolls and the catching pawl into the opening of the guide rail the swivellable pair of rolls is swivelled by 90° C., so that it now lies across in the guide rail. In this position it is locked in the manner already mentioned above. 
   The guide rail is generally vertical. In order to prevent the fall arrester from being inserted upside down, with the front end pointing downwards, a device is provided which in this case prevents the swivelling of the swivellable pair of rolls into the secure position and the swinging shut of the suspended ratchet. This device consists of two opposed longitudinal grooves, facing the rolls, milled in the shank of the swivellable pair of rolls. In the inserted position one of the two longitudinal grooves points towards the rear end of the fall arrester. From the bore in which the shank of the swivellable pair of rolls is housed, a longitudinal bore a few millimeters thick leads to the rear end of the fall arrester. A cylindrical pin loosely slides in this longitudinal bore. If the fall arrester is inserted upside down, i.e. head first, the cylindrical pin drops through the action of gravity into the longitudinal groove of the shank and thereby locks the shank against rotation. 
   The body of the fall arrester is expediently made from aluminium or stainless steel. The suspended ratchet, which must bend upwards in the event of a fall, expediently consists of steel with a tensile strength of 480 to 600 N/mm 2 . 

   
     An embodiment of the invention is explained below with reference to the drawings. These show: 
       FIG. 1  a perspective representation of the fall arrester inserted into a guide rail, part being broken away; 
       FIG. 2  the fall arrester inserted into a guide rail in section; 
       FIG. 3  a representation similar to that of  FIG. 2 , the suspended ratchet being open; 
       FIG. 4  a representation similar to that of  FIG. 2 , but with the fall arrester inserted head first and 
       FIGS. 5 to 8  in four steps the insertion of the fall arrester into the guide rail. 
   

   According to  FIGS. 1 and 2  the fall arrester  10  is guided in a guide rail  12 . The guide rail  12  is normally vertical. It has a C-profile open to the front, i.e. towards the user, the opening being laterally delimited by two guide flanges  14 . In the back of the guide rail catching stops  16  are pressed out, protruding into the guide rail  12 . 
   The fall arrester  10  has a body  20 , oblong overall, extending in the direction of the guide rail with a catching pawl  18 . At the front end of the body  20 , two pairs of rolls  22 ,  24  are provided. The inner pair of rolls  22  run on the inside of the guide flange  14 , while the outer pair of rolls  24  run on the outside of the guide flange  14 . The rolls  22 ,  24  are housed on journals which are attached rigidly to the body  20 . The inner rolls  22  are at a distance from the outer rolls  24 , which is somewhat greater than the material thickness of the guide flange  14 . 
   Housed rotatable in a bore  26  of the body  20  is a shank  28 , the axis of rotation lying approximately perpendicular to the front of the guide rail  12 . At the end of the shank  28  projecting towards the guide rail  12 , a rear pair of rolls  30  with an axis of rotation lying across the shank axis is arranged. By rotating the shank  28 , the axis of rotation of the pair of rolls  30  can be swivelled parallel to the longitudinal direction of the guide rail  12 , the pair of rolls  30  then being located in the inserted position. The pair of rolls  30  can also be swivelled across the guide rail  12 , so that its axis of rotation lies parallel to the axes of rotation of the inner and outer rolls  22 ,  24 . The pair of rolls  30  is then in the secure position. The end of the shank  28  projecting on the upper side of the body  20  has a transverse indent  32 . On the upper side of the body  20  a suspended ratchet  34  is also articulated to the rear end of the body  20 . The suspended ratchet  34  is U-shaped, its centre of rotation lying in the region of the bend of the U-shape. The lower leg  36 , lying closer to the body  20 , lies in a milled recess in the upper side of the body  20 . The upper leg  38  is longer than the lower leg  36  and extends beyond the shank  28 . At its front end an eyelet  40  is provided for securing the safety belt of the user&#39;s personal safety equipment. If the swivellable pair of rolls  30  is in the secure position, the indent  32  points in the longitudinal direction and the upper leg  38  of the suspended ratchet  34  can be inserted into this indent  32 . The shank  28  and the swivellable pair of rolls  30  are thus locked against swivelling. The suspended ratchet  34  is secured in this shut position by a stop bolt  42 . The stop bolt  42  is attached laterally against the body  20  and pierces the lower leg  36  of the suspended ratchet  34 . The stop bolt  42  slopes at its front end so that it is pushed out when the suspended ratchet  34  swings shut and then engages in a bore  44  provided for this purpose at the front end of the lower leg  36 . 
   A catching pawl  18  is formed at the rear end of the body  20  integral with the latter. It slopes rearward, so that upon a forward movement of the fall arrester it travels over the catching stops  16  sloping in the same direction. In the event of a fall the catching pawl would move backwards, so that the catching pawl  18  then strikes the catching stop  16 , and thereby locks the fall arrester  10  in the guide rail  12 . 
   In order to ensure that the fall arrester  10  acts as a catch in the event of a fall, the fall arrester  10  must be inserted into the guide rail  12  correctly aligned. As usual, for this a pin  50  projects laterally to the right from the body  20  of the fall arrester. On the opposite side, i.e. on the left in the present case, of the guide rail a corresponding stop is provided, which the pin  50  strikes if the fall arrester  10  is incorrectly inserted into the guide rail  12 . This stop is usually provided only at the upper and lower ends of the guide rail, as the fall arrester is customarily inserted only at these points. As the fall arrester  10  according to the invention can be inserted at any point of the guide rail  12 , an additional device is provided which warns the user of incorrect insertion of the fall arrester  10 . This device consists of a cylindrical pin  52  and two longitudinal grooves  54  which are cut into the cylinder surfaces of the shank  28  at opposite points. The cylindrical pin  52  slides freely in a bore  56  which extends from the bore  26  for the shank  28  to the rear end of the body  20 . The rear opening of the longitudinal bore  56  is sealed by a grub screw  57  ( FIG. 3 ). If the fall arrester  10  is inserted wrongly aligned into the guide rail  12 , the cylindrical pin  52  drops under its own weight into one of the longitudinal grooves  54 , thereby blocking swivelling of the pair of rolls  30  ( FIG. 4 ). The longitudinal grooves  54  are attached to the sides facing the rolls  30 , so that the pair of rolls  30  cannot then be swivelled into the secure position and the suspended ratchet  34  cannot be swung shut. The user is thereby warned of an incorrect alignment of the fall arrester. 
   A nose  58  projects from the front end of the lower leg  36  of the suspended ratchet  34 , engaging in an indent  60  at the upper end of the shank  28  if the swivellable pair of rolls  30  is in the secure position. In the event of a fall the U-shape of the suspended ratchet  34  is bent upwards, the catching impact thereby being attenuated. The upper leg  38  is pulled out of the indent  32  in the process. The engagement of the nose  58  in the indent  60 , ensures that the swivellable pair of rolls  30  remains in the secure position even if the upper leg  38  is pulled out of the indent  32 . 
   The bore  26  has a shoulder  62  and is widened in the upper section. The shank  28  has a corresponding counter-shoulder  64  and a widened head  66 , in which the indent  32  is provided. A compression spring  68  is supported between the shoulder  62  and counter-shoulder  64 . The swivellable pair of rolls  30  are therefore pulled towards the inside of the guide flange  14 , whereby the catching pawl  18  is pushed towards the back of the guide rail  12  and thus towards the catching stops  16 . It is thereby guaranteed that in the event of a fall the fall arrester will be safely caught in the guide rail  12 . 
   The insertion of the fall arrester  10  is now explained with reference to  FIGS. 5-8 : 
   As shown in  FIG. 5 , the fall arrester  10  is held across the guide rail  12  and the inner, rigid rolls  22  are inserted through the opening of the C-profile of the guide rail  12  in the process. The suspended ratchet  34  is swung open and the swivellable pair of rolls  30  swivelled into the inserted position, in which the axis of rotation of the rolls  30  points in the longitudinal direction of the fall arrester  10 . 
   The fall arrester  10  is then swivelled into the position shown in  FIG. 6 , care needing to be taken that the guide flange  14  comes to rest between the inner rolls  22  and the outer rolls  24  in the process. The rear end of the fall arrester  10  is further raised somewhat from the guide rail  12 . In order to make this raised position possible, the inner rolls  22  are offset slightly forwards vis-à-vis the outer rolls  24 . The fall arrester  10  is then swivelled with its rear end towards the guide rail  12 , so that the swivellable pair of rolls  30  and the catching pawl  18  are now also inserted through the opening of the C-profile into the guide rail  12 , as shown in  FIG. 7 . 
   The shank  28  and thus the pair of rolls  30  are then swivelled by 90°, so that the pair of rolls  30  are transversely aligned and lie parallel to the rolls  22 ,  24 . Finally the suspended ratchet  34  swings shut, the upper leg  38  coming to rest in the indent  32  in the head of the shank  28 . On the swinging shut of the suspended a ratchet  34 , the stop bolt  42  engages in the bore  44  on the lower leg  36  of the suspended ratchet  34 , see  FIG. 8 . The fall arrester  10  is then ready for use. 
   LIST OF REFERENCES 
   
       
         10  Fall arrester 
         12  Guide rail 
         14  Guide flange 
         16  Catching stops 
         18  Catch 
         20  Body 
         22  Inner rolls 
         24  Outer rolls 
         26  Bore 
         28  Shank 
         30  Pair of rolls 
         32  Indent 
         34  Suspended ratchet 
         36  Lower leg 
         38  Upper leg 
         40  Eyelet 
         42  Stop bolt 
         44  Bore 
         50  Pin 
         52  Cylindrical pin 
         54  Longitudinal grooves 
         56  Longitudinal bore 
         57  Grub screw 
         58  Nose 
         60  Indent 
         62  Shoulder 
         64  Counter-shoulder 
         66  Head 
         68  Spring