Abstract:
A fall arrest apparatus comprising a brake assembly (comprising a main body and a clamping mechanism) and a lifeline comprising an elongate first lifeline member and an elongate second lifeline member, the lifeline members overlapping with each other along a section of the lifeline. The main body has a passage extending therethrough, the overlapping section of the lifeline extending through the passage. The configuration is such as to provide from opposite sides of the passage a clamping force to compress together opposed surfaces of the two overlapping lifeline members to prevent these from moving with respect to each other until pulled in relatively opposite directions by a fall of the worker, causing the compressed overlapping members to slidingly contact each other so that energy of the fall is dissipated by sliding friction between said opposed surfaces. The main body has first and second portions on opposite sides of the passage.

Description:
BACKGROUND 
       [0001]    a. Field of the Invention 
         [0002]    This invention relates to a fall arrest apparatus for use by a worker working at a height above the ground. 
         [0003]    b. Related Art 
         [0004]    While a worker is working at height, he will typically be connected to a secure mounting by means of a lifeline attached to a harness. Usually the lifeline is wound around a drum. In the event of a fall by the worker, fall arrest devices conventionally work by switching in a friction brake which slows down the rate at which the lifeline is unwound from the drum, while absorbing energy in doing so. 
         [0005]    One prior art fall arrest device is disclosed in US patent document 2005/0269153. This discloses a fall arrest device comprising a section of lifeline formed from two lengths of line sewn together. If a worker falls, the fall is broken by the ripping apart of these two lengths, which helps to dissipate energy. 
         [0006]    One problem with this device however, is that If the fall is severe enough, the full length of the sewn sections will be torn apart. For this reason, the prior art device also includes a fixed length lifeline in parallel with the torn sections and having a length longer than that of the sewn sections when torn apart. A problem remains, however, because the energy absorbing function ceases as the two sewn sections become fully separated. The document therefore proposes the inclusion of an additional third section of lifeline in the form of an elastic section which is fixed in parallel to the main lifeline. These multiple sections of lifeline create a complex and bulky fall arrest device. 
         [0007]    It is therefore an object of the present invention to provide a fall arrest device that is compact and able to controllably arrest the fall of a worker secured to a lifeline. 
       SUMMARY OF THE INVENTION 
       [0008]    According to the present invention, there is provided a fall arrest apparatus for protecting a worker working at height, comprising a brake assembly and a lifeline for tethering said worker, the lifeline comprising an elongate first lifeline member and an elongate second lifeline member, the first lifeline member extending along a first section of the lifeline and the second lifeline member extending along a second section of the lifeline, said first and second sections overlapping with each other along a third section of the lifeline, and the brake assembly comprising a main body and a clamping mechanism, the main body having a passage extending through the main body, the third section of the lifeline extending through the passage and the configuration of the main body and clamping mechanism being such as to provide from opposite sides of the passage a clamping force to compress together opposed surfaces of said first and second lifeline members in said third section to prevent said first and second lifeline members from moving with respect to each other until said members are pulled in relatively opposite directions by a fall of said tethered worker, causing said first and second lifeline members to move in sliding contact with each other under the compression of the brake assembly so that energy of the fall is dissipated by sliding friction between said opposed surfaces, wherein:
       the main body has on opposite sides of the passage a first portion and a second portion, said first portion providing inside the passage a static first clamping surface configured to bear against the first lifeline member; and   the clamping mechanism comprises a pressure plate, the pressure plate providing a second clamping surface inside the passage configured to bear against the second lifeline member to provide said compression of said first and second lifeline members, the pressure plate being dimensioned such that the pressure plate engages with said second portion of the main body and with the pressure plate being retained in the passage at least in part by the presence of the third section of the lifeline extending through the passage.       
 
         [0011]    In other words, whether or not other retention means are used to retain the pressure plate to the main body, the pressure plate has dimensions such that this can only be removed from the passage after at least one, and most preferably both of the lifeline members have been removed from the passage. Removal of the third section of lifeline from the passage is therefore a necessary precondition for removal of the pressure plate from the passage. 
         [0012]    In some embodiments, the sliding friction may further comprise friction between the second lifeline member and the second clamping surface. 
         [0013]    In a preferred embodiment of the invention, the main body is a unitary main body, that is, of one piece construction, such that first and second portions of the main body are formed from a single piece of material. 
         [0014]    Preferably the brake assembly, and in particular the unitary main body, completely surrounds the first and second lifeline members in the third section. Preferably the unitary main body is torus-like. 
         [0015]    In a preferred embodiment the first clamping surface is a first side wall of the passage and at least a part of the pressure plate, forming the second clamping surface, is located adjacent to a second opposing side wall of the passage. 
         [0016]    Preferably, the brake assembly comprises means for applying an adjustable force to the plate member so as to clamp the first and second lifeline members securely between the clamping surfaces. 
         [0017]    Typically the means for applying an adjustable force to the pressure plate comprises a screw, the screw extending through the second portion of the main body and a first end of the screw being in contact with the pressure plate. To prevent the lifeline catching or rubbing on the screw, a second end of the screw preferably does not protrude from an outer surface of the main body. 
         [0018]    In a preferred embodiment the pressure plate is U-shaped and comprises a central region that extends through the passage forming the second clamping surface and two arm portions, one at either end of the central region, that extend over a part of the outer surface of the second portion of the main body. Preferably one arm portion is shorter than the other arm portion and the shorter arm portion is dimensioned to pass through the passage in the main body when there are no lifelines in the passage. 
         [0019]    Preferably the clamping mechanism further comprises limiting means for limiting the movement of the pressure plate within the passage of the main body to prevent the pressure plate being removed from the passage even if the lifeline members are removed. Preferably the limiting means comprises a slot formed in one arm portion, typically a longer one of the two arm portions, and a pin extending from a part of the outer surface of the main body and through the slot. 
         [0020]    An end of the first lifeline member may be looped around the first portion of the main body of the brake assembly in order to secure the second lifeline member to the brake assembly. In this way, the brake assembly is located at a first end of the third section of the lifeline, and in use, in the event of a fall, the brake assembly moves from this first end to a second end of the third section of lifeline. During this movement of the brake assembly, the sliding friction between the two lifeline members dissipates the energy of the fall. 
         [0021]    Preferably, the first and second lifeline members are flexible straps, and typically these will be made of webbing. 
         [0022]    To prevent the end of the first strap flapping around and becoming caught or trapped while the worker is working, preferably the straps are sewn together with at least one stitch, or other joining means, in the third section of the lifeline. In the event of a fall, the at least one stitch is designed to break, allowing the first and second straps to slide relative to each other. The use of joining means in this way means that, when the first and second lifeline members are under tension, they are typically in touching contact with each other along the full length of the third section of the lifeline. 
         [0023]    Also according to the invention there is provided a method of assembling a fall arrest apparatus for protecting a worker working at height, the fall arrest apparatus comprising a brake assembly and a lifeline for tethering said worker, the lifeline comprising first and second lifeline members, and the method comprising the steps of:
       forming a main body of the brake assembly, the main body including a passage extending through the main body for receiving the first and second lifeline members, a first portion of the main body being on a first side of the passage and comprising a first side wall of the passage forming a first clamping surface, and a second portion of the main body being on a second opposing side of the passage;   inserting a pressure plate into the passage, the pressure plate being dimensioned such that the pressure plate engages with the second portion of the main body and cannot be removed from the passage once the lifeline members are positioned within the passage, the pressure plate forming a second clamping surface;   inserting an end of the first lifeline member through the passage so that a part of the first lifeline member bears directly against the first side wall of the passage;   inserting an end of the second lifeline member through the passage, between the first lifeline member and the pressure plate; and   applying a force to the pressure plate to clamp together the first and second lifeline members in contact with each other between the first and second clamping surfaces within the passage.       
 
         [0029]    The main body is most preferably formed as a unitary main body. 
         [0030]    In a preferred embodiment the pressure plate is U-shaped and comprises a central region and two arm portions, one at each end of the central region, and the method comprises the steps of:
       inserting the pressure plate into the passage so that the central region extends through the passage; and   engaging the pressure plate with the second portion of the main body such that the two arm portions extend over a part of the outer surface of the main body.       
 
         [0033]    To reduce the number of parts in the brake assembly and to ease assembly of the fall arrest apparatus, a first one of the two arm portions is preferably dimensioned to pass through the passage and a second one of the two arm portions is preferably dimensioned not to pass through the passage. Additionally the brake assembly comprises limiting means for limiting the movement of the pressure plate within the passage of the main body, and the method of assembly of the brake assembly comprises the steps of:
       inserting the pressure plate into the passage, from a first end of the brake assembly, so that the first arm portion passes through the passage and extends over a part of the outer surface of the main body at a second end of the brake assembly; and   engaging the second arm portion with the limiting means such that the pressure plate cannot be withdrawn from the passage.       
 
         [0036]    In embodiments in which the brake assembly includes limiting means, the method preferably comprises the steps of:
       forming an elongate slot in the second arm portion of the pressure plate;   forming a hole in an outer surface of the second portion of the main body at the first end of the brake assembly, the hole being dimensioned to receive an end of a pin; and   once the pressure plate has been inserted into the passage, aligning the slot with the hole and inserting the end of the pin into the hole so that the pin extends through the slot, thereby forming the limiting means.       
 
         [0040]    In a preferred embodiment the method further comprises the step of forming a loop around the first portion of the main body with the first end of the first lifeline member to secure the lifeline member to the brake assembly. 
         [0041]    Preferably, once the second lifeline member has been inserted through the passage, the method comprises the step of providing means at the first end of the second lifeline member to prevent the second lifeline member being withdrawn from the brake assembly. Typically the end of the second lifeline member will be folded and secured to create a length of double thickness lifeline at the end of the second lifeline member. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0042]    The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: 
           [0043]      FIG. 1  is a cross-sectional view of a fall arrest apparatus in accordance with a preferred embodiment of the invention, including a brake assembly and lifeline, and showing a pressure plate engaged with the lifeline; 
           [0044]      FIG. 2  shows the fall arrest assembly in an initial configuration, with ends of first and second lifeline members secured together and the brake assembly engaged with the lifeline; and 
           [0045]      FIG. 3  shows the fall arrest assembly under load during a fall of a worker, with the lifeline members separated. 
       
    
    
     DETAILED DESCRIPTION 
       [0046]      FIGS. 1 to 3  show a fall arrest apparatus  1  including a brake or clamp assembly  2  and a lifeline  4 , the lifeline comprising first and second elongate lifeline members  14 ,  16 . As shown schematically in  FIG. 2 , the first and second lifeline members  14 ,  16  extend along respective first and second sections of the lifeline  3 ,  5 . The first and second sections  3 ,  5  of lifeline overlap in a third section  7  of the lifeline  4  such that opposed inner surfaces  8 ,  9  of the lifeline members are in contact with each other. The brake assembly  2  is located around the third section  7  of the lifeline, where the lifeline passes through a passage  28  that extends fully through the brake assembly  2 . In this third section  7  of the lifeline, the first and second lifeline members  14 ,  16  overlap. The brake assembly  2  is arranged to grip and clamp together the first and second lifeline members  14 ,  16  inside the passage such that the two lifeline members  14 ,  16  are in contact with each other and cannot move relative to each other. 
         [0047]    Typically the elongate lifeline members  14 ,  16  will be flexible straps made of webbing or other suitable woven material. In other embodiments, the lifeline members  14 ,  16  may be made of any suitable strong material, as is well known in the art. 
         [0048]    In use, when a worker is working at height, either the first or second lifeline member or strap  14 ,  16  will be connected at a first end (not shown) remote from the brake assembly  2  to a secure fixed point on the building or other work area. The other lifeline member or strap is secured at a second end (not shown) remote from the brake assembly  2  to the worker&#39;s safety harness. 
         [0049]    If the worker falls from the area in which he is working, the fall arrest apparatus  1  works like a friction brake. The increased load applied to the end of the second strap  16  due to the fall causes the two lifeline members to slide relative to each other and through the brake assembly  2 . The brake assembly  2  is designed to apply a compressive force to the straps  14 ,  16  so that as the straps slip through the brake assembly  2  sliding friction between the straps dissipates the energy of the fall and slows the descent of the worker. 
         [0050]    The advantages of this invention over existing fall arrest devices are its small size and small number of parts, meaning that the device is simple to manufacture and assemble and is lightweight compared to current devices. 
         [0051]    As shown in  FIG. 1 , the brake assembly  2  comprises a unitary main body  18  and a clamping mechanism comprising a pressure plate  20  and a grub screw  50 . The unitary main body  18  has on opposite sides of the passage  28  a first portion  118  and a second portion  218 . The main body  18  has rounded outer surfaces and has in both the first and second portions a substantially circular cross-sectional shape in planes parallel to the width of the lifeline straps. In this example the length of main body  18  in a direction parallel with the length of the lifeline straps is less than its diameter such that the main body  18  is disc-shaped in a plane perpendicular to the length of the lifeline straps, having flat first and second outer faces  22 ,  24  of approximately circular periphery at front and rear sides of the main body  18 . The circumferential outer surface  26  of the second portion  218  of the main body  18  is curved, having a substantially convex profile. In other embodiments the outer surface  26  of the second portion  218  of the main body  18  may have a different profile, however, it is preferred if the outer surface  26  has a convex curvature as this reduces the likelihood of wear of the straps  14 ,  16  as they pass over this surface  26 . 
         [0052]    The passage  28  formed in the main body  18  extends fully through the main body  18  from the first face  22  to the second face  24  so that the main body  18  has a torus-like shape. The passage  28  has a rectangular cross-sectional shape having between the first and second portions  118 ,  218 , first and second opposing end walls, and on the first and second portions  118 ,  218 , respectively, first and second opposing side walls  30 ,  32 . The passage  28  is positioned centrally within the main body  18  so that, in this example, the unitary main body  18  extends completely around the passage  28 , and the end walls and side walls  30 ,  32  extend perpendicular to the faces  22 ,  24  of the main body  18 . The width of the passage  28  extends for almost the full diameter of the main body  18  such that narrow portions of the main body  18  extend around the ends of the passage  28 . 
         [0053]    A central region  38  of a pressure plate  20  is arranged to locate within the passage  28 . The pressure plate  20  includes first and second arm portions  34 ,  36  that extend perpendicularly from either end of the central region  38  of the pressure plate  20 , such that the pressure plate  20  has a U-shaped cross-section. The dimensions of the pressure plate  20  are such that when the pressure plate  20  is located in the passage  28 , the central region  38  spans the full length or thickness of the main body  18  and the arm portions  34 ,  36  extend away from the passage  28  and over respective first and second faces  22 ,  24  of the main body  18 . In this way, when the pressure plate  20  is located in the passage  28 , the central region  38  is positioned parallel to and proximate and adjacent one of the side walls  32  of the passage  28 . 
         [0054]    In a preferred embodiment, the first and second arm portions  34 ,  36  are of different lengths, the first arm portion  34  being shorter than the second arm portion  36 . As shown in  FIG. 1 , the first arm portion  34  extends only about halfway across the second face  24  of the main body  18 . The second arm portion  36  extends almost to the circumferential edge of the main body  18 , and the end  37  of the second arm portion  36  is curved so as to follow the shape of this edge. Both the first and second arm portions  34 ,  36  are in sliding engagement with the respective first and second outer faces  22 ,  24  of the main body  18 . 
         [0055]    The first arm portion  34  is short enough in a direction perpendicular to the plane of the lifeline straps, so that, with no lifeline inside the passage  28 , the first arm portion can be inserted into the passage to assemble the pressure plate with the main body  18 . Conversely, when at least one of the lifeline straps is subsequently inserted into the passage, the first arm portion  34  is long enough in a direction perpendicular to the plane of the lifeline straps, such that the lifeline straps prevent the first arm portion  34  from disengaging with the second outer face  24  of the main body  18 , even in the absence of other retaining means, such as a retaining pin  42  described below. The pressure plate  20  is therefore dimensioned such that the pressure plate engages with the second portion  218  of the main body with the pressure plate being retained in this engagement within the passage at least in part by the presence of the third section  7  of the lifeline extending through the passage  28 . Conversely, the pressure plate cannot be removed from the passage, even with the retaining pin removed, as long as at least one of the lifelines is present inside the passage. This provides security for the braking mechanism, so that even if the grub screw  50  is fully loosened so that this no longer bears on the pressure plate, the pressure plate cannot come loose from the main body. Additionally, when the main body is a unitary main body, it is impossible for the main body to come apart, for example into separately joined components, which ensures that the fall arrest apparatus cannot become dysfunctional owing to components of the main body becoming loose. 
         [0056]    A through slot  40  in the second arm portion  36  of the pressure plate  20  receives a retaining pin  42 , as will be described in more detail below. The longitudinal axis of the slot  40  is perpendicular to the plane of the central region  38 , such that the slot  40  extends along the length of the arm portion  36  from close to the end of the central region  38  of the pressure plate  20  to proximate the curved end  37  of the arm portion  36 . 
         [0057]    The retaining pin  42  sits within a hole  44  formed in the first face  22  of the main body  18 . The hole  44  and pin  42  are sized so that a first end  46  of the pin  42  fits tightly within the hole  44 . A second end  48  of the pin  42  protrudes from the first face  22  of the main body  18  and, when the pressure plate  20  is located within the passage  28 , the pin  42  extends into the slot  40 . In this way, the pin  42  and slot  40  form limiting means to limit the movement of the pressure plate  20  within the passage  28  as explained further below. 
         [0058]    The grub screw  50  of the clamping mechanism fits within a threaded bore  52  formed through the main body  18 . The bore  52  extends from the curved circumferential surface  26  of the main body  18  to one of the side walls  32  of the passage  28 . In this way, when the grub screw  50  is inserted into the bore  52 , an end  58  of the screw  50  is able to extend into the passage  28  and engage with the pressure plate  20 . Preferably an Allen key or Hex key is used to secure the grub screw  50  within the bore  52 . It is advantageous if the screw  50  does not have an end or head  51  that protrudes from the surface  26  of the main body  18 , when the screw  50  is fully inserted in the bore  52 , so that the lifeline  4  does not rub on the edges of the screw head in use. Preferably the end  51  of the screw  50  is substantially flush, or slightly recessed, with the outer surface  26  of the main body  18  when the screw  50  is fully inserted in the bore  52 . 
         [0059]    To assemble the brake assembly  2 , the pressure plate  20  is inserted through the passage  28 . The shorter length of the first arm portion  34  of the pressure plate  20  allows this end of the pressure plate  20  to be passed through the passage  28 . Once the pressure plate  20  is in position in the passage  28 , the retaining pin  42  is pushed through the slot  40  until the first end  46  of the pin  42  locates fully in the hole  44  in the main body  18 . Once the pin  42  is in place, the pressure plate  20  cannot be removed from the passage  28  without first removing the pin  42 . 
         [0060]    With the retaining pin  42  at a first end  54  of the slot  40  nearest the central region  38 , a rear face  56  of the central region  38  of the pressure plate  20  is in contact with the side wall  32  of the passage  28 . In this way, the side wall  30  of the passage  28  and a front face  68  of the pressure plate  20  form opposing clamping surfaces. The static side wall  30  and movable front face  68  of the pressure plate  20  will therefore be referred to below as, respectively, first and second clamping surfaces  30 ,  68 . The static first clamping surface  30  is configured to bear against the first lifeline member  14  and the movable second clamping surface  68  is configured to bear against the second lifeline member  16 . 
         [0061]    The grub screw  50  is screwed into the bore  52  in the main body  18 , and as the grub screw  50  is inserted further into the bore  52 , the end  58  of the grub screw  50  makes contact with the rear face  56  of the pressure plate  20 . As the grub screw  50  is tightened, the end  58  pushes against the rear face  56  of the pressure plate  20  and forces the central region  38  of the pressure plate  20  away from the side wall  32  of the passage  28 . In this way, the grub screw  50  provides means for applying an adjustable force to the pressure plate  2  to clamp the lifeline members  14 ,  16  as explained below. As the pressure plate  20  moves away from the side wall  32 , the retaining pin  42  moves towards a second end  60  of the slot  40 , and movement of the pressure plate  20  is limited by the length of the slot  40 . Because the movement of the second end  48  of the retaining pin  42  is confined by the bounds of the slot  40 , the pressure plate  20  is guided to move smoothly towards the centre of the passage  28  with the central region  38  of the pressure plate  20  remaining substantially parallel to the side wall  32 . 
         [0062]    Preferably, the brake assembly  2  including the main body  18  and the clamping mechanism is made from a non-corrosive metal, for example stainless steel. 
         [0063]    To fit the straps  14 ,  16  into the brake assembly  2 , the pressure plate  20  is initially located so that the central region  38  of the pressure plate  20  sits against the side wall  32  of the passage  28 . 
         [0064]    A first end  62  of the first strap  14  is passed through the passage  28  in a first direction, indicated by arrow A in  FIG. 2 . The end  62  of the first strap  14  is then wrapped around the main body  18  of the clamp assembly  2  so that a part of the strap  14  covers the first clamping surface  30  of the passage  28 , a part of the first face  22  of the main body  18  adjacent to the first clamping surface  30  and a part of the convex outer surface  26  of the main body  18 . In this way, the first and  62  of the first strap  14  doubles back on itself and a loop  64  is formed around one half of the brake assembly  2 . 
         [0065]    The end  62  of the first strap  14  is sewn securely to itself as indicated by the series of straight dashed lines  66  in  FIG. 3 . The end portion  62  may be securely fastened using other means, but any fastening means should be sufficient to prevent the end  62  of the first strap  14  coming apart when an increased load is applied during a fall. In this way, the first strap  14  remains securely attached to the brake assembly  2  at all times. 
         [0066]    The second strap  16  is then passed through the passage  28  in the brake assembly  2  in the opposite direction to the first strap  14 . This second strap  16  is, therefore, positioned between a portion of the first strap  14  and the second clamping surface  68  (see  FIG. 1 ) of the pressure plate  20 . 
         [0067]    An end  70  of this second strap  16  is folded back on itself to form a double-thickness end portion  72 . This end portion  72  is securely sewn together, or fastened together using any other suitable means, such that this end portion  72  will not separate even when an increased load is applied to the lifeline  4  during a fall. This secure fastening is indicated by the straight dashed lines  74  in  FIGS. 2 and 3 . 
         [0068]    The end region  72  of the second strap  16  is then loosely attached to a point on the first strap  14  at a distance from the brake assembly  2  so that the first and second straps  14 ,  16  overlap along their length between the brake assembly  2  and the end  70  of the second strap  16 . In this example, the two straps  14 ,  16  are sewn together as indicated by the zigzag stitches  76  in  FIGS. 2 and 3 . These stitches  76  pass through the double thickness end portion  72  of the second strap  16  and through the first strap  14 . In other embodiments, the two straps  14 ,  16  may be joined together using other means, however, the joining means must be such that the two straps  14 ,  16  separate easily when a load is applied to the lifeline in the event of a fall. With the straps  14 ,  16  arranged in this way, when the straps are under tension, for example at the start of a fall, the two straps  14 ,  16  are in touching contact with each other along the full length of the third section  7  of lifeline where the straps  14 ,  16  overlap. 
         [0069]    Once the two straps  14 ,  16  are in place in the passage  28  of the main body  18 , the grub screw  50  is tightened. The end  58  of the grub screw  50  pushes against the rear face  56  of the pressure plate  20  and presses the second clamping surface  68  of the pressure plate  20  against the second strap  16 . As the grub screw  50  is tightened further, a compressive force is applied and the two straps  14 ,  16  are clamped together in contact with each other within the passage  28 . 
         [0070]    In the event of a worker falling from a height, when an increased load is applied to the lifeline, the temporary stitches  76  joining the two straps  14 ,  16  break, as shown in  FIG. 3 . The two straps  14 ,  16  are then free to move with respect to each other. The brake assembly  2  slides along the second strap  16  towards the double thickness end region  72 , as indicated by the arrow in  FIG. 3 . 
         [0071]    Because the two straps  14 ,  16  are held tightly within the brake assembly  2 , there is a large frictional force generated between the two straps as the second strap  16  is pulled through the passage  28  of the brake assembly  2 . This sliding friction dissipates the energy of the fall and, therefore, acts to slow the descent of the worker. When the brake assembly  2  reaches the end region  72  of the second strap  16 , the increased thickness of the end region  72  means that the end  70  is unable to pass through the passage  28 , and the worker&#39;s fall is stopped. Preferably, a sufficient length of the second strap  16  has passed through the brake assembly  2  that the sliding friction has slowed the rate of falling such that little additional deceleration occurs when the brake assembly  2  reaches the end region  72  of the second strap  16 . 
         [0072]    Generally, the majority of the sliding friction will be generated between the two straps  14 ,  16 , however, in some embodiments it may be preferable if a significant frictional force is also generate between the straps  14 ,  16  and the second clamping surface  68  of the brake assembly  2 . This may be achieved by roughening the second clamping surface  68 . 
         [0073]    The amount of frictional force may be adjusted and controlled simply by varying the compressive force that is applied to the straps  14 ,  16  by the pressure plate  20 , which is in turn adjusted by tightening or loosening the grub screw  50  as required. 
         [0074]    The fall arrest apparatus  10  of the present invention, therefore, provides a compact and lightweight device, having relatively few components, that controllably dissipates the energy of a fall. 
         [0075]    It is to be recognized that various alterations, modifications, and/or additions may be introduced into the constructions and arrangements of parts described above without departing from the spirit or scope of the present invention, as defined by the appended claims.