Abstract:
A descender ( 10 ) comprises a rear or base plate ( 20 ), a front plate ( 22 ) which is fixedly mounted to the base plate, generally parallel to and spaced from the base plate and an arm ( 30 ) which is pivotally mounted to the base plate and/or the front plate for movement between the two plates. The arm ( 30 ) defines a generally curved channel ( 38 ) through which a rope ( 14 ) may pass. The channel is defined between a sheave ( 34 ) and a wall ( 37 ) of the arm and defines an entrance ( 38   a ) and an exit ( 38   b ) for the rope. The sheave ( 34 ) is pivotable about an axis, the sheave being lightly biased towards a first or rest position. Pivoting of the sheave about the axis in a first direction, away from the rest position, causes an increase in the friction applied to the rope passing through the channel, typically by causing the exit of the channel to narrow. A handle ( 46 ) is provided, operation of which may cause the sheave ( 34 ) to rotate towards its rest or neutral position thereby allowing faster passage of the rope through the descender. The descender ( 10 ) includes means for connecting the descender to a harness or the like.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority from Australian Provisional Patent Application No 2015900527 filed on 17 Feb. 2015, the content of which is incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The present application relates to a descender for use in abseiling and belaying and the like. 
       BACKGROUND 
       [0003]    Abseiling is a technique which is used to descend steep surfaces such as cliff faces and is often used by persons involved in activities such as mountain climbing, canyoning and caving. In order to abseil down a cliff face, one end of a rope is made fast at the top of the cliff and the person making the descent then slides down the rope. The rope is passed either around the body of the person or, more usually, through a descender attached to a harness worn by the person such that the passage of the rope around the body or through the descender provides sufficient friction to slow the rate of descent to a safe speed. These techniques are also used in the workplace e.g. by persons working at heights on roofs and buildings, and by rescue services. 
         [0004]    A descender defines rope engaging services around and between which the rope travels along a tortuous path, to provide frictional engagement between the rope and the descender. The rate of descent is normally controlled by holding the free or tail end of the rope to control the tension on the rope where it emerges from the descender thereby to control the degree of friction engagement between the rope and descender, which in turn controls the rate of descent. 
         [0005]    Descenders used in abseiling vary greatly in performance and complexity, there being a variety of relatively simple devices which rely on frictional engagement between the rope and metal rings or racks about which the rope is wrapped, and a number of more complex descenders which incorporate a braking mechanism which allows friction between the rope and descender to be varied other than by simply controlling the free or tail end of the rope. The earliest of these more complex devices have a handle or lever which, when operated, tended to increase the friction between the descender and the rope. This type of descender had the problem that the brake was not self-engaging and therefore, if the user was knocked unconscious, he or she would fall in the same way as a user of the earlier devices. 
         [0006]    A number of devices now include automatic braking mechanisms in which a handle is operated by a person using descender to control their speed of descent and if the handle is released, a brake actuates and prevents a user falling uncontrollably. Such a descender is disclosed in U.S. Pat. No. 4,596,314. 
         [0007]    It is known to provide a descender having a sheave around which a rope passes located between front and rear plates which pivot to open the descender to allow a rope to be threaded through. The sheave may be shaped and pivotable to control the resistance to the passage of the rope. One disadvantage to such descenders is that if the plates pivot open during use, the possibility exists that the descender could fall off the rope, if the plates are not locked in a closed position. 
         [0008]    Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application. 
       SUMMARY 
       [0009]    According to the present invention there is provided a descender comprising:
   a rear or base plate;   a front plate which is fixedly mounted to the base plate, generally parallel to and spaced from the base plate;   an arm which is pivotally mounted to the base plate and/or the front plate, wherein the arm defines a generally curved channel through which a rope may pass, the channel being defined between a sheave and a wall of the arm and defining an entrance and an exit for the rope, wherein the sheave is pivotable about an axis, the shave being, typically lightly, biased towards a first or rest position, and wherein pivoting of the sheave about the axis in a first direction, away from the rest position, causes an increase in the friction applied to the rope passing through the channel, typically by causing the exit of the channel to narrow; and   
 
         [0013]    wherein a handle is provided, operation of which may cause the sheave to rotate towards its rest or neutral position thereby allowing faster passage of the rope through the descender; and 
         [0014]    wherein the descender includes means for connecting the descender to a harness or the like. 
         [0015]    In use, when a rope passes through the descender under tension the friction caused by the rope passing through the descender causes the sheave to move away from the rest position, thus increasing the braking on the rope. Operation of the handle to pivot the shave back towards its rest position reduces the braking force on the rope, thus it is possible to control the rate of descent. The use of fixed front and rear plates and a pivoting arm which can be pivoted out from between the plates for loading rope into the descender makes the descender inherently safer than existing descenders where the front or rear plates pivot to load rope into the descender. 
         [0016]    In a preferred embodiment, a post/projection is mounted on the rear plate adjacent the exit to the channel. 
         [0017]    The post provided at the exit of the descender provides an additional element that can be used to further increase resistance and slow the movement of the rope through the descender. 
         [0018]    Typically, the means for connecting the descender to a harness or the like will be a through hole for receiving a karabiner. 
         [0019]    In one embodiment, the handle is able to pivot through a predetermined angle from one end position to a second end position and wherein in the end positions the sheave is either unaffected by the handle or turned towards a position where the rope is subject to increased friction and wherein movement of the handle to a position intermediate the end positions causes the sheave to move towards its rest position. 
         [0020]    Thus the operation of the handle is fail safe in the sense that at either extreme position, maximum friction is preferably applied to the rope so the fall of a user who falls unconscious and releases the handle will be braked while a user who might panic and push the lever too far would also have their fall braked. 
         [0021]    The sheave may define a bulge or projection which when the sheave is rotated under load, restricts the exit of the channel. 
         [0022]    The sheave may define an integral projection on its underside which passes through a typically arcuate slot in the base plate of the arm. The projection may engage in use with a projection associated with and moveable by operation of the handle, by means of which the handle is able to rotate the sheave. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0023]    A specific embodiment of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which: 
           [0024]      FIG. 1  is a front photographic view of a descender embodying the present invention, showing a rope passing through the descender, with the descender closed; 
           [0025]      FIG. 2  is a rear photographic view of the descender of  FIG. 1 ; 
           [0026]      FIG. 3  is a front photographic view of the descender of Figure, showing the descender open; 
           [0027]      FIG. 4  is a further photographic view of the descender of Figure, showing the descender open 
           [0028]      FIG. 5  is a front view of the descender of Figure, showing the descender open and without the rope; 
           [0029]      FIG. 6  is a side view of the descender of  FIG. 5 ; 
           [0030]      FIG. 7  is a rear view of the descender of Figure, showing the descender open; 
           [0031]      FIG. 8  is a schematic drawing of a handle of the descender; 
           [0032]      FIG. 9  is a schematic drawing of a connecting rod of the descender; 
           [0033]      FIG. 10  is a schematic drawing showing a rear plate of the descender and the handle showing hidden detail; 
           [0034]      FIG. 11  is a schematic drawing as shown in  FIG. 11  but further illustrating the interaction of the sheave with the handle via a connecting rod; 
           [0035]      FIG. 12  is a further schematic drawings illustrating the movement of the connecting rod. 
           [0036]      FIG. 13  illustrates the descender in use with a load attached to the descender using a karabiner; and 
           [0037]      FIG. 14  shows the descender in use in the opposite orientation to  FIG. 12 . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0038]    Referring to the drawings,  FIG. 1  shows a descender  10 , to which a karabiner  12  is attached, and through which a rope  14  passes. 
         [0039]    The descender includes a rear plate  20  (refer to  FIG. 2 ) and a front plate  22 . The front plate is mounted in a fixed arrangement relative to the rear plate on three fixed posts  24 ,  26  and  28 . The posts maintain the front plate parallel to, and a fixed distance from, the rear plate. A loop  27  is pivotally mounted attached to fixed post  26  and can be used for attaching a karabiner to the descender. 
         [0040]    With reference to  FIGS. 3 and 5  in particular, an arm  30  is pivotally mounted about the post  26 . The arm  30  defines a base plate  32  on which a shaped sheave  34  is mounted and around which a rope may pass. With reference to  FIG. 5 , the shaped sheave  34  is pivotally mounted about a pivot  36 . A wall  37  extends around the curved perimeter of the arm so as to define a generally U-shaped channel/rope guide  38 , having an entrance  38   a  and an exit  38   b , extending around three sides of the sheave through which the rope may pass in use. This assists in retaining the rope in the descender, in use. Also shown is a metal insert  40  which defines a shaped curved channel which guides the passage of the rope out of the rope guide  38 . The sheave is biased into the rest position shown in  FIG. 5  by a biasing means such as a spring (not shown). The sheave may pivot through up to about 45° in the direction of the arrow A (refer to  FIG. 5 ) which causes a narrowing of the exit channel from the descender. The sheave is generally oval but defines a bulge or salient  41  on that side of the sheave facing and adjacent the exit  38   b  from the channel  38 , and when the sheave pivots in the direction of the arrow A, the bulge  41  moves towards the insert  40  narrowing the channel and slowing the passage of the rope through the descender. 
         [0041]    As is best seen in  FIG. 7 , an arcuate slot is  42  defined in the base plate  32  whose arc is centred on the pivot pin  36 . A v-shaped projection  44  which is integral with the sheave  34  projects from the underside to the sheave into the slot  42 . The slot defines a first end  42   a  and a second end  42   b.  The spring associated with the sheave discussed in the paragraph above, biases the projection towards the end  42   a  of the slot. In use, when the sheave slides on a rope is passing through the channel  38  as is described in more detail below the sheave rotates by friction with the rope which overcomes the light biasing provided by the spring and the v-shaped projection  44  is moved towards and as far the other end of the slot  42   b  as is described in more detail below. Operation of the handle/lever  46  moves the projection  44  back towards end  42   a,  in which position minimum braking is applied to the rope. 
         [0042]    In use, the arm locates in between the two plates  20  and  22 , as shown in  FIGS. 1 and 2 . 
         [0043]    The arm also defines a depressible button/latch  50 . As is best seen in  FIG. 5 , the front plate defines a circular aperture  52 . When the arm is rotated about the pivot  26  into position between the plates  20  and  22 , the button/latch  50  locates in the aperture and retains the descender closed, until it is manually depressed to overcome the button&#39;s bias to release the arm  30 . 
         [0044]      FIG. 5  also shows an additional post  51  which in use is adjacent the exit of the channel and can be used to increase the twisting in the path along which the rope passes and hence can increase the friction applied to the rope when used. 
         [0045]    As is best seen in  FIG. 4 , the centre of the sheave co-axial with the pivot axis of the sheave defines a circular projection  54 , which extends above the height of the wall  37 . An arcuate guide slot  60  is defined in the plate  22  along which the projection passes as the descender is closed. The entry to the slot  60  is covered by a raised bridging portion  62 , which allows the projection to pass under it and helps maintain the strength and integrity of the top plate  22 . 
         [0046]    With reference to  FIGS. 4 and 6  in particular, it can be seen that there is a wide arcuate channel  70  defined in the surface of the lower plate  20  that faces the arm. The centre of curvature of the channel is the pivot  26 . The v-shaped projection  44  passes along that channel  70  when the arm  30  is pivoted between the plates to close the descender. Also visible in the channel is a projection  72  which locates in an arcuate slot in the rear plate of the descender, as is discussed below. 
         [0047]      FIG. 8  is a drawing showing the face of the handle  46  which in faces the rear plate  22  of the descender, illustrating detail which is hidden in the assembled descender. It can be seen that the handle has a generally circular portion  47  and an integral arm/lever portion  48 . The handle  46  pivots about a circular aperture  49 , which is mounted on a circular pin, bolt, or the like  49   a,  located in the generally circular portion  47 . Operation of the lever  48  rotates the handle about pivot  47 .  FIG. 8  also shows a generally arcuate channel  100 , located adjacent the aperture  49 . 
         [0048]      FIG. 9  shows a connecting rod  110  which is also hidden in the assembled descender. The rod comprises a generally planar member with the cylindrical projection  72  at one end and a cylindrical projection  112  at the other end which is located in the arcuate channel  100  of the handle  46 . 
         [0049]      FIG. 10  is a drawing showing just the rear plate of the descender omitting the arm and front plate but showing the outline of the hidden part of the handle  46  behind the plate  20 , in dashed lines 
         [0050]      FIG. 10  shows the channel  70  in detail and that the distal closed end  70   a  of the channel is enlarged relative to the channel entry  70   b.  An arcuate/curved through slot  74  is defined adjacent the end  70   a,  and the cylindrical post or projection  72  extends through that slot into the channel  70 . 
         [0051]      FIGS. 11 and 12  illustrate the interaction of the post  72  with the sheave, specifically the projection  44  on the underside of the sheave.  FIG. 11  shows the sheave at an intermediate position  44  and end positions  44   a  and  44   b  corresponding to end positions  42   a  and  42   b  of the channel  42  shown in  FIG. 7 . It will be appreciated that if the projection  72  travels along the channel in the direction of the arrow B, it will push the projection  44  from the end  44   b/   42   b  of the channel to the end  44   a/   42   a,  in which position, the least resistance is applied to the rope. It should also be noted that that position corresponds to the resting position of the sheave when it is unloaded due to the biasing spring and the sheave only rotates against the biasing when forces are applied to the sheave due to rope passing through the descender. (Clearly the descender only needs to function when in use and the resting position of the sheave when not in use is irrelevant to the safety of the device). It is also noted that the v-shaped projection  44  is constrained to move inside the channel  70 , but is not constrained by the slot  74   
         [0052]    With reference to  FIG. 10  turning the handle  46  in the direction B away from the body of the descender causes the post  72  to move along the slot in the direction C during the first  90 ° of movement and then moves it back in the opposite direction to its start position shown in  FIG. 10 . As the handle is turned, the projection  112  can move along the slot  100  in the direction of the arrow D. 
         [0053]    In use, with reference to  FIGS. 5 and 10 , when the rope  14  is passing through the descender and is under tension, for example because a person is using the descender to abseil down the rope, the forces on the rope cause the sheave to pivot against the biasing means and turn the sheave in the direction A which tends to slow the passage of the rope through the descender. As the sheave turns, the v-shaped projection  44  moves from the position  44   a  (rest) towards  44   b  where it engages with the projection  74 . Therefore movement of the post in the direction C causes movement of the v-shaped projection  44  in that same direction C, which in turn causes the sheave to pivot in the opposite direction to the arrow A, reducing the friction of the rope and allowing it to pass more freely through the descender. 
         [0054]    If the handle is moved too far in the direction B the projection  74  moves back in the opposite direction to arrow C and the sheave pivots back towards its rest position in the opposite direction to the arrow A, thus slowing down the passage of rope. 
         [0055]    The projection  112  is able to move along the slot  100 . With reference to  FIGS. 11 and 12  in particular due to the geometry of the connection and the arcuate slots  100  and  74 , after the handle has been turned through more than a particular angle (approximately 45° as shown but the exact angle is not critical) the, the projection  112  will move rapidly along the slot  100  in the direction of the arrow D to the distal end  100 B of the slot  100 . Depending on the geometry of the slots and the connector, this will occur when the when the projection  112  is about in the centre of the slot  100  as shown in  FIG. 12 . This will “lock” the apparatus in the braking position as a small movement of the handle will no longer release the braking and the handle will have to be turned to the rest position adjacent the body of the descender shown in  FIG. 10  before the pin is able to travel towards the first end  100 A of the slot. 
         [0056]    A further safety feature arising from the geometry of the connector projections and slots is that the geometry is arranged so that the position in which the descender is providing the minimum resistance, in particular, is unstable so that if the handle is released it will not remain in that position and will move thus activating the braking. 
         [0057]    Thus the operation of the handle is fail safe in the sense that at either extreme position maximum friction is applied to the rope so the fall of a user who falls unconscious and releases the handle will be braked while a user who might panic and push the lever too far would also have their fall braked. 
         [0058]    The post provided at the exit of the descender provides an additional element that can be used to further increase resistance and slow the movement of the rope through the descender. 
         [0059]    The use of fixed front and rear plates and a pivoting arm which can be pivoted from between the plates for loading rope into the descender makes the descender inherently safer than versions where the front or rear plates pivot to load rope into the descender. 
         [0060]      FIG. 13  illustrates the descender in use with a load attached to the descender by a karabiner attached to the post  28  or “anchor point A”. A hand  200  is shown holding the unloaded side of the rope. The rope slides through the descender to allow slack to be taken up. Pulling on the rope can be used to haul the load upwards. When hauling, pulleys can be used to create a mechanical advantage. 
         [0061]      FIG. 14  shows the descender in use in the opposite orientation to  FIG. 13 . In this case the karabiner is attached to the opposite end of the descender on loop  27  or “anchor point B” 
         [0062]    The descender is able to be used in either orientation for various different rigging purposes. Pulleys or pulley kits can be attached to the upper most anchor point for use in assisting in pulling up the load. If the pulley system is released, the descender will stop the load from falling. 
         [0063]    It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.