Abstract:
A descender system, typically for use in a fall arrest system, for enabling a suspended body to be lowered includes a rotatable descent line drum, and a release element arranged in a restraint configuration to inhibit the descent line from being deployed and in a release configuration to permit the descent line to be deployed. A rotating brake applies a braking force to the rotatable descent line drum; a gear train connects the brake to the drum. The gear train is provided in a substantially watertight sealed space. Typically, a substantially watertight seal is provided between a backplate of the rotating drum and a chassis of the device. Typically, the substantially watertight seal is of a material that is deformable/compressible, preferably at temperatures at or below −20 Celsius.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from PCT/GB/2011/052256 filed on Nov. 18, 2011, GB 1019462.9 filed on Nov. 18, 2010, GB 1112334.6 filed on Jul. 18, 2012, and GB 1112332.0 filed on Jul. 18, 2011, all of which are hereby incorporated by reference in their entireties. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a rescue descender system primarily, but not exclusively for use in fall arrest or fall safety systems for personnel safety when working at height. 
         [0004]    2. State of the Art 
         [0005]    Fall arrest or fall safety systems are known in which personnel working at height are secured to a safety line in order to arrest a fall, should this occur. Such safety lines can comprise a self retracting lifeline which includes a safety block secured to an anchor point and a safety line which pays out as the user moves away from the safety block. A brake device engages to prevent paying out of the safety line in the event of a fall. Typically the system includes an energy absorption device arranged to absorb the energy of the fall when the line payout stops in order to arrest the fall. 
         [0006]    Typically, in the circumstances of a fall, the user can be left suspended in mid air. In order to be rescued, the user can be hooked from above by a rescuer (if in reach and accessible), or a rescuer can descend to the individual to attach them to a rescue line. Alternatively, devices have been proposed to enable a suspended user to self instigate lowering to ground or rescue level. Such arrangements are disclosed in, for example, GB2414005 and WO2009/027619. Such systems can be referred to as self rescue devices. WO2009/027619 discloses a self rescue device that has a rescue line drum connected to a brake arrangement in order to control the rate of descent. This is achieved by means of a gear train connecting the drum and the brake. In very cold climates moisture present in the gear train can freeze and cause malfunction of the apparatus. 
         [0007]    An improved arrangement has now been devised. 
       SUMMARY OF THE INVENTION 
       [0008]    According to a first aspect, the present invention provides a descender device for enabling a suspended body to be lowered, the descender system comprising:
       a rotatable descent line drum,   a release element arranged in a restraint configuration to inhibit the descent line from being deployed and in a release configuration to permit the descent line to be deployed;   a brake arrangement to apply a braking force to the rotatable descent line drum; the brake arrangement comprising a rotating brake and a gear train connecting the brake to the drum; wherein the gear train is provided in a substantially watertight sealed envelope or environment.       
 
         [0012]    It is preferred that a substantially watertight seal is provided between a backplate of the rotating drum and a chassis of the device. 
         [0013]    Beneficially, the substantially watertight seal is of a material that is deformable/compressible, preferably at temperatures at or below −20 Celsius. 
         [0014]    In a preferred embodiment the substantially watertight seal comprises a silicon gasket. 
         [0015]    It is preferred that the brake is provided in a walled enclosure having an end cap fitted; a seal being provided between the end cap and the wall of the enclosure. 
         [0016]    In a preferred embodiment, the drum is mounted with an axial bolt, the axial bolt having a circumferential seal (such as an O′ ring seal). 
         [0017]    In a preferred embodiment, the device is provided with a back cover mounted to the chassis; the back cover and chassis being provided with an intermediate seal. 
         [0018]    The action of providing the seals as described provides a substantially watertight chamber or envelope about the gear train that is robust enough to be maintained even in extreme cold conditions. The flexible resilient seal positioned between the backplate surface of the drum and the chassis is particularly important in this regard. 
         [0019]    It is preferred that the descender device includes a clamp arrangement arranged prior to deployment of the descent line, to clamp or pinch the descent line, and/or a length of release line connected to the descent line, at one or more points intermediate the opposed ends of the line and spaced from the release means, the clamp arrangement being reconfigurable when, the release element is in the release configuration, to permit the line to pass; and/or
       the release element is connected to a pull tether, which pull tether extends in a harness over a shoulder portion of the harness; and/or   the release element secures through a loop or ring, which loop or ring is attached to a flexible line.       
 
         [0022]    In a preferred realisation of the invention, moving of the release means to the release configuration permits, or causes, the clamp arrangement to reconfigure from the clamping position, to permit the line to pass. 
         [0023]    In one embodiment, the clamp arrangement may comprise a plurality of bars spaced on a rack, the descent line passing serpentine-wise through the bars in the rack. 
         [0024]    Beneficially, the spacing of the bars on the rack can reduce or diminish to clamp the descent line between the bars, and also preferably expand or increase to permit the descent line to pass via the bars in the rack. 
         [0025]    It is preferred in this embodiment that moving of the release means to the release configuration permits or causes the spacing between the bars on the rack to expand from the reduced spacing configuration. 
         [0026]    It is preferred that the release means comprises a pin. The release mans is preferably connected to a tether line which can be pulled by the user to dislodge the pin from the restraint position in appropriate circumstances 
         [0027]    According to a further aspect, the present invention provides a fall arrest system incorporating a descender system as defined herein. 
         [0028]    The invention will now be further described, by way of example only, and with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]      FIGS. 1A and 1B  are face and side views respectively of a first embodiment of a rescue descender device  1  in accordance with the invention in an initial or first configuration. 
           [0030]      FIG. 2  is a schematic perspective exploded view of the rescue descender device  1  of figure; 
           [0031]      FIGS. 3A and 3  B are face and side views of the rescue descender device  1  of the preceding figures in an alternative configuration; 
           [0032]      FIGS. 4A and 4  B are face and side views of the rescue descender device  1  of the preceding figures in a further configuration; 
           [0033]      FIGS. 5A and 5  B are face and side views of the rescue descender device  1  of the preceding figures in a final configuration; 
           [0034]      FIGS. 6A to 6D  are alternative views showing the descender device of the invention mounted to a harness worn by a user; 
           [0035]      FIG. 7  is a perspective view of the parts making up an alternative embodiment of a descender device according to the invention; 
           [0036]      FIGS. 8   a  and  8   b  are side and face views of the embodiment of  FIG. 10 ; 
           [0037]      FIG. 9  is a face view of the embodiment in an alternative configuration; 
           [0038]      FIGS. 10   a  and  10   b  are side and face views of the embodiment in an alternative configuration; 
           [0039]      FIGS. 11   a  to  11   c  are perspective views of a further embodiment of the invention in various sequential stages of operation; 
           [0040]      FIG. 12  is a sectional view of the chassis drum and brake arrangement also shown in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0041]    Referring to the drawings there is shown a rescue descender device  1  in accordance with the invention. As shown in  FIGS. 6A to 6D , the rescue descender device  1  is arranged to be worn on the back of a user mounted to a body harness  30  and be connected to a fall arrest lifeline  31 , such as a self retracting lifeline as are known in the art. 
         [0042]    The rescue descender device  1  comprises, a first length of binding webbing  2  comprising an upper loop  3 , a lower loop  4  and an intermediate webbing length  5  which is stitched together to form a double thickness between the upper and lower loops  3 , 4 . The upper loop  3  of the first length of webbing is arranged to be connected to a fall arrest lifeline such as the self retracting lifeline  30  as are known in the art. 
         [0043]    The first length of binding webbing  2  is wrapped, serpentine fashion, around a restraint device  6  which comprises a U shaped frame  7  having spaced limbs  8 , at their upper ends joined by a curved crosspiece, and at their lower ends connected to a fixing bracket  9  connected to a descent line store device  10 . 
         [0044]    A series of movable pinch bars  11  are mounted on the spaced limbs  8  and the first length of binding webbing  2  is wrapped around the movable pinch bars  11  as shown in the figures in serpentine fashion. The movable bars  11  can slide up and own the spaced limbs  8 , upward movement being limited by a load arm mounting component  12  that is fixed relative to the U shaped frame  7 . The movable pinch bars  11  are provided with respective bores to accommodate the limbs  8 . The load arm mounting component  12  carries a pivotally mounted pivoting load arm  13  which has a cross bar  14  and a pair of spaced arms mounting arms  15   a    15   b . The pivoting load arm  13  is connected by a webbing loop harness connector  16  to the safety harness (not shown) worn by a user. The webbing loop harness connector  16  is looped around the cross bar  14  of load arm  13 . 
         [0045]    The pivoting load arm  13  is provided with an abutment piece  17  such that when the pivoting load arm  13  is biased to its normal at rest position (as shown in  FIGS. 1A and 1B ) by the biasing torsion spring  18 , the abutment piece  17  is positioned to lie adjacent the head of a release pin  19 , which is mounted in respective receiving bores  20  of the mounting component  12 . The head of the release pin  19  is connected to an end of a pin release tether  21 . The lower loop  4  of the first length of webbing  2  is connected via a connector clasp  22  to a descent line  23 . The descent line  23  is fixed at its other end and is wound on a descent line drum  24 . 
         [0046]    As shown most clearly with reference to  FIGS. 2 and 12 , the descent line drum  24  is mounted to a support chassis  25 . A brake device  26  is also mounted to the support chassis  25 . The brake device  26  is coupled to rotation of the descent line drum  24 , by means of a gear arrangement comprising a main gear  27  which rotates with the brake device  26  and is connected to a brake pinion gear  28  by means of an idler gear  29 . As the brake device  26  rotates to deploy the descent line  23 , the brake pinion gear  28  is activated by the main gear  27  in order to brake the rotation of the descent line drum  24  and slow deployment of the descent line  23 . 
         [0047]    The speed of rotation of the drum  24  is controlled by the centrifugal servo brake mechanism  26  which is attached the chassis  25  an provided in its own walled housing  30  attached to the chassis and which is closed by au end cap  3 . A watertight seal  32  is provided between the end cap  31  and the housing  30 . A drum retaining bolt  35  has a hexagonal head that is constrained within a hexagonal recess in the drum such that bolt and drum are constrained to rotate together about the central axis of the drum. Drum retaining bolt  35  has a threaded region that is engaged in a mating threaded region in a specially formed boss  36 . Boss  36  is secured to the gear  27  by means of an intervening corrugated tolerance ring  37 . 
         [0048]    A bearing  39  is provided in order to facilitate rotation of the gear  27  with respect to the chassis  25 . 
         [0049]    When the drum  24  and bolt  35  rotate in the direction of tightening of the mating screw surfaces between bolt and boss  36 , boss  36  will tend to unwind with respect to bolt. Therefore, as drum rotates with respect to the chassis, drive gear  27  will also tend to rotate in the same direction. 
         [0050]    Drive gear  27  intermeshes with one or more further gears  29  to drive pinion gear  28  that is constrained to rotate with drive shaft  40  that drives centrifugal brake shoes  41  against cylindrical friction brake lining. As brake shoes  41  rotate, the mass and rotational velocity of each shoe will determine the magnitude of the radial resistance between each brake shoe and cylindrical friction brake lining  43  thereby applying tangential rotational resistance that is translated back through the gear train to drive gear. The resultant rotational drag on drive gear  27  will also apply a rotational drag on boss  36  such that ongoing rotation of drum will tend to tighten bolt into the mating thread in boss  36 . Friction material pads  44  are mounted on the drum positioned between opposing conical surfaces of drum  24  and chassis  25 . As boss  36  moves along the bolt, the drum  24  is also is also drawn towards the frusto-conical bearing surface  47  of the chassis thereby reducing the rotational speed of drum. As the rotational speed of drum reduces further, the rotational speed of drive gear  27  and ultimately the rotational speed of centrifugal brake shoes reduces thereby also reducing the tendency to tighten the boss  36  onto bolt  35 . Eventually, the centrifugal drag from brake shoes will reduce to an extent whereby the thread of the boss  36  tends to unwind with respect to the bolt  35  allowing the drum  24  to move away from the frusto-conical bearing surface  47  of the chassis thereby freeing the drum  24  so that its rotational speed can increase again. In this way, the centrifugal brake  26  acts as a dynamic servo mechanism to regulate the braking force between drum and friction material dependent on the rotational speed of drum thereby also controlling the speed of deployment of the descent line from the drum. 
         [0051]    The use of respective conical surfaces on chassis  25  and drum  24  has several important advantages compared with a conventional arrangement using parallel flat interconnecting braking surfaces. The conical form is significantly stronger in compression along its central axis than parallel flat interconnecting surfaces and the braking resistance is also significantly greater for a given axial compression loading. The mating conical surfaces also tend to assist radial location between the drum and the chassis helping to resist contrary radial loading. Since the height rescue apparatus is normally carried attached to a person&#39;s harness, it is critically important that the weight and size of the apparatus is as small as possible. In practice, it has been found that the conical bearing arrangement enables the drum to be made from lightweight and low cost plastic materials instead of the heavier and more costly metal alternatives. The amount of material in the chassis can also be minimised. The friction material may be provided in one or more conical or part-conical portions or segments thereof disposed around the periphery of the drum or chassis. 
         [0052]    The bolt  35  is provided with an O ring seal  51  sealing on the axial bore of the drum to prevent fluid ingress via the axial bore of the drum. 
         [0053]    Between the backplate surface of the drum  24  and the chassis  25  is positioned a compressible/deformable silicon gasket seal  55 . This seal prevents fluid passing into the gear train of the device via the gap between the backplate surface of the drum  24  and the chassis  25 . It can be beneficial that the gasket seal  55  remains flexible in cold ambient conditions (at least up to −20 Celsius). This is to take up the variation in the separation between the frustoconical bearing surfaces of the drum  24  and the chassis  25  under the braking action as described earlier, even in extreme cold weather conditions. 
         [0054]    The device is provided with a back cover  61  mounted to the chassis  25 . The back cover  61  and chassis  25  are provided an intermediate seal. 
         [0055]    The action of providing the seals as described provides a substantially watertight chamber or envelope about the gear train that is robust enough to be maintained even in extreme cold conditions. The flexible resilient silicon gasket seal  55  positioned between the backplate surface of the drum  24  and the chassis  25  is particularly important in this regard. 
         [0056]    As shown in  FIGS. 1A and 1B , when the rescue descender device  1  is ready for use, it is in the configuration shown. The webbing loop harness connector  16  is connected to the users harness and the upper loop  2  is connected via the safety line  30  (for example a standard self retracting lifeline) to an anchor point. In this way the user is securely anchored to an anchor point via the rescue descender device  1 . In this configuration, the release pin  19  cannot be removed from the receiving bores  20  of the load arm mounting component  12 . This is because the abutment piece  17  of the pivoting load arm  13  is positioned adjacent the head of the release pin  19  and prevents removal of the release pin  19 . In the embodiment shown the torsion spring  18  biases the pivoting load arm  13  to this ‘normal’ position, although the shape of the pivoting load arm  13  is such that the pivoting moment normally biases the pivoting load arm  13  to this position under gravity in any case. In this configuration the user can move about their business unhindered, but the release pin  19  cannot be removed either intentionally or un-intentionally. 
         [0057]    In the event of a fall arrest event, the rescue descender device  1  reconfigures from the position shown in  FIGS. 1A and 1B  to the position shown in  FIGS. 4A and 4B  via the intermediate position shown in  FIGS. 3A and 3B . As the user becomes suspended from the anchor point via the safety line connected to the upper loop  3  of the first length of the binding webbing  2 , the intermediate webbing length  5  pulls up on the series of movable bars  11  causing the movable bars  11  to slide upwardly and pinch the intermediate webbing length  5  securely. This ensures that the intermediate webbing length  5  and the movable bars  11  are held fast. The main upward force acts via the lowermost of the movable bars  11  and the intermediate binding webbing length  5  which is wrapped around the lowermost of the movable bars  11 . This configuration is shown in  FIGS. 3A and 3B . 
         [0058]    Simultaneously, under the weight of the user now suspended from the anchor point, the pivoting load arm  13  pivots downwardly (arrow A). In so doing, the abutment piece  17  of the pivoting load arm  13  pivots out of its blocking position adjacent with the head of release pin  19 . Therefore once the fall arrest event occurs and the pivoting load arm  13  is loaded by the user&#39;s suspended weight, the abutment piece  17  moves such that the release pin  19  can be pulled out of the receiving bores  20  of the load arm mounting component  12 . 
         [0059]    In this embodiment the release pin  19  can only be removed from its home position secured in the receiving bores  20  of the load arm mounting component  12  when the pivoting load arm  13  is moved from its normal position. Furthermore the arrangement ensures that the pivoting load arm  13  moves from its home position automatically as a result of a fall arrest event. The pin release tether  21  is connected to the release pin  19  and has an end accessible to be pulled by the user to enable the release pin  19  to be removed when ready. 
         [0060]    As shown in  FIGS. 6A to 6C  the release tether  21  can be secured to the harness  30  ready for use. In the embodiment shown the release tether is secured to a shoulder strap  30   a  on the front of the user and a toggle  31  is connected to the tether line  21  to be pulled by the user in order to release the release pin  19 . The tether line  21  is provided with a Velcro type band  32  to secure to the shoulder strap  30   a . An over cover  33  is provided to prevent accidental release. 
         [0061]    Once the user has fallen and his fall has been arrested, he is suspended by the device  1  which is attached to the harness  30  on the back of the user. As shown in  FIGS. 6C and 6D , when the user is ready he opens the over cover  33 , peels back the band  32  and pulls on the pin release tether  21  to remove the release pin  19  from its home position. The resultant operation is shown in  FIGS. 5A and 5B . The release pin  19  releases from the lower loop  4  of the first length of the binding webbing  2 . As a result of releasing the lower loop  4  of the first length of webbing, the lower loop  4  can drop down releasing the tension on the intermediate webbing length  5  wound around the lowermost one of the movable pinch bars  11 . As a result the series of movable bars  11  can drop downwardly (see the arrows in  FIG. 5B ) becoming spaced out on the U shaped frame  7 . The intermediate webbing length  5  is no longer bound fast by the movable pinch bars  11  and as a result the intermediate webbing length  5  can feed through the pinch bars  11  in an upward direction of the U shaped frame  7 . 
         [0062]    The closed end of the lower loop  4  catches on the connector clasp  22  and pulls the connector clasp  22  through the movable bars  11  along a serpentine path in an upward direction of the U shaped frame  7 . In so doing the descent line  23  is also pulled from the descent line drum  24  along the same path. As a result loop  2  moves away from the U shaped frame  7 , and the U shaped frame  7  and the user attached via the webbing loop harness connector  16  descends relative to the upper loop  2 .  FIGS. 4A and 4B  show the connector clasp  22  pulled completely through the U shaped frame  7  and bars  11  together with the upper end of the connector clasp  22 . The brake device  26  acts to slow the rate of descent in accordance with a preset desired descent rate. 
         [0063]    In this embodiment, the release pin  19  is not a primary load supporting member of the rack restraint device  6 . The main vertical load is taken up by the intermediate webbing length  5  folded under the lowermost pinch bar  11 . The length  5  is clamped between the pinch bars  11 , such that the downward pulling force exerted by the loop  4  on the pin  19  is negligible when compared with the impulse weight or force as a result of the suspended user. Accordingly the force required to remove the pin  19  (when the abutment piece  17  is moved clear of the path of the release pin  19 ) is sufficiently low to enable the user to remove the pin  19  manually by pulling on the release pin tether  21 . The pivoting load arm  13  moves automatically as a result of the load applied by the suspended user to clear the abutment piece  17  from obstructing removal of the release pin  19 . The load of the suspended user imparted between the length of webbing  2  (connected to the safety line  30 ) and the descender device is not transmitted primarily via the release pin  19 . The load on the release pin  19  is substantially independent of the load imparted by the suspended user. The first length of webbing  2  is connected to the descent line  23  by the clasp  22 . These can be considered effectively as a single line as they act as such when deployed. The webbing  2  is connected to the safety line  31 . 
         [0064]    Referring now to  FIGS. 10 to 14 , there is shown a further embodiment of a descender device  101 , which is similar in general terms to the device  1  of  FIGS. 1 to 5 . In this embodiment a restraint rack device  106  has a U shaped frame comprising spaced limbs  108  and two pinch bars  111  which are slidably mounted on the limbs  108 . The main difference of this embodiment over the first described embodiment is in relation to the connection between the binding webbing  102  and the descent line  123 . 
         [0065]    In the previously described embodiment the lower loop  4  of the binding webbing  2  was secured to the upper end of the descent line  23  by means of the clasp  22 . This requires the clasp  22  to be pulled through the bars  11  when the descent line is being deployed. In practice the clasp can foul or become trapped resulting in non-ideal deployment or even malfunction. 
         [0066]    In the embodiment of  FIGS. 10 to 14 , the binding webbing  102  and the release line are connected at a D ring  170  which is positioned downstream of the restraint rack device  106  and which therefore does not need to be pulled through the rack during deployment of the release line  123 . The upper portion of the release line  123  is threaded serpentine fashion through the pinch bars  111 . The binding webbing is likewise threaded serpentine fashion through the pinch bars  111  and the lower loop  104  is secured about a release pin  119  which is secured in a cradle  118  provided on a platform  112  by means of a breakable clip  171 . The platform  112  is provided with mounting apertures top enable mounting on the limbs  8  and is secured in position the rack frame device limbs  108  by means of a pin  175  passing through bores  181 , and also the mating plugs  185 . The swing arm  113  is pivotally mounted on the plugs  185  and provides for securing to the users harness. 
         [0067]    As shown most clearly in  FIG. 11   b , the release pin  119  is secured by the breakable clip  171  in a specific orientation in the cradle  118 . When the device is loaded as a result of a fall arrest event, the binding webbing  102  is pulled tight resulting in the pinch bars  111  being pulled upwardly towards the top of the rack device  106 . The release line  123  is pinched by the pinch bars preventing the release line  123  from being pulled through the device. In the loaded condition, the loop  104  of the binding webbing  102  is secured over the release pin  119 . The webbing  102  extends downwardly from the pin  119  via an opening  190  in the cradle  118 . Therefore in the loaded condition, the tension in the webbing  102  tends to securely hold the release pin  119  in the cradle. The end of the pin  119  rests on a ledge  195  adjacent the opening  190 . When the user is suspended and wishes to deploy the release line  123 , the user tugs sharply on the release line tether  12 . In doing so the release pin ruptures the clip  171  and pivots from the position shown in  FIG. 10   b  to the position shown in  FIG. 11 . In the position shown in  FIG. 11  the end of the release pin  119  is no longer supported on the ledge  195  and the downward force acting on the pin by means of the loop  104  causes the loop  104  to be pulled downwardly off the end of pin  119  and through the opening  190 . In so doing the binding action exerted by the binding webbing  102  on the pinch bars  111  is released and they are able to move apart on the limbs  108 . This enables the binding webbing  102  and the release line  123  to be drawn simultaneously through the pinch bars  111 . This situation is shown in  FIGS. 12   a  and  12   b.    
         [0068]    A variation on this theme is shown in the embodiment of  FIGS. 14   a  to  14   c , in which like items are referred to with the same reference numbers as the previous embodiment. In this embodiment the opening  190  is replaced by a slot  290  downwardly through which the end loop  104  of the binding webbing  102  is pulled when the release pin breaks free from the clip  171 . A guide frame  199  is provided for the release pin tether  121  in order to ensure