the controlled descent device 10 of the present invention shown in fig4 - 10 comprises a steel housing 1 containing a line 23 having a carabiner 5 or the like on one end wound on a drum 24 . a constant force retraction spring 6 provides a force on the drum 24 to retract the line 23 into the housing 1 . a centrifugal brake mechanism 7 like the braking mechanism of the dynescape ® descender is attached to the housing and engages the drum to produce a resisting force when the line is extracted . the preferred embodiment of the braking mechanism 7 includes a brake hub 13 , three spokes 14 , brake shoes 15 and brake housing 16 similar in form and function to the dynescape ® descender . a pinion gear with shaft 29 is supported on the brake housing 16 by two roller bearings 12 . the brake hub 13 is supported on the shaft by a one - way roller bear 21 and an additional bearing 12 a . this one - way bearing 21 may be one of several types of manufactured mechanisms such as those commercially available from morse and formsprag ®, that produce a rotational motion in one direction and a fixed motion in the opposite direction such as back stopping , clutch or indexing bearings , roller - ramp type bearings or sprag clutches and sprag clutch / roller bearing combinations . specifically , the one - way bearing permits rotation of its inner raceway relative to its outer raceway in one direction . when rotated in the opposite direction , the two raceways remain fixed with respect to one another , rotating in unison . the sprag type bearing 35 illustrated in fig6 contains a series of spring loaded sprags 36 that reside between , and are in contact with the inner 37 and outer 38 bearing raceways . when rotation of the outer raceway 38 , relative to the inner raceway 37 , is in one direction , these sprags 36 cam , locking the inner raceway 37 to the outer raceway 38 . when rotation is in the opposite direction , the sprags 36 uncam , permitting the inner raceway 37 to rotate relative to the outer raceway 38 . sprag type bearings 35 frequently have a set of rollers 42 situated next to the sprags as shown in fig5 . these rollers provide concentricity and produce smooth rolling motion between the raceways . the roller - ramp type bearing 40 illustrated in fig7 contains an array of balls or rollers 41 that reside between , and are in contact with the inner 37 and outer 38 raceways . the surface of the inner raceway 37 is ramped 39 , such that the balls or rollers 41 roll up the ramps 39 during rotation in one direction , and down the ramps 39 in the opposite direction . as the balls or rollers 41 roll up the ramps , they wedge between the inner 37 and outer 38 raceway , preventing relative rotation of the inner 37 and outer 38 raceways . as the balls or rollers rolls down the ramps 39 , they unwedge and provide clearance for the outer raceway 37 to roll relative to the inner raceway 37 , like a standard roller bearing . the one - way roller bearing 21 connecting the shaft 29 to the hub 13 permits engagement of the brake mechanism only during line extraction . during line retraction , the pinion with shaft 29 will rotate freely , while the hub 13 , spokes 14 and brake shoes 15 remain stationary . the line 23 of the present invention is formed from flat webbing , preferably of nylon material . the drum 24 on which the line 23 is wrapped has side walls spaced slightly wider than the webbing width , such that when line 23 is wrapped on the drum 24 the line 23 will stack in consecutive layers . the line 23 passes through a nozzle 25 as it leaves the housing 1 . the nozzle opening is dimensioned slightly larger than the webbing cross - section . this shape is designed to direct the webbing onto the drum 24 in consecutive layers . the webbing also passes across a cylindrical roller 26 between the nozzle 25 and drum 24 . the roller 26 helps redirect the webbing 23 and lay it flat on the drum 24 . the line 23 of the present invention may also be field replaceable as shown in fig8 - 10 . the field replaceable line comprises an internal portion of line 27 that is permanently attached to the drum , and a distal portion of line 28 that extracts from the housing and is replaceable . the ends of each portion are joined by a linkage . the ends of the webbing are sewn in loops 29 . in the preferred embodiment shown in fig8 the loops 29 each contain a steel cylinder 30 , oriented with their diameters supporting the webbing . a bolt 31 passes through a hole formed in the top of each loop 29 and through each cylinder . the linkage , including the two cylinders 30 , has a width identical to the width of the webbing . the shape of the linkage facilitates it fitting inside the drum , and laying flat and neatly on the drum beneath the other layers of webbing . to replace the line , a user removes the nozzle 25 , and extracts all of the line from the housing until the linkage is external to the housing . the user then disconnects the replaceable portion of line by removing the bolt 31 connecting the cylinders . a new nozzle 25 , line 23 , cylinders 30 and bolt 31 is then connected , replacing the worn components . the line 23 is then returned to the housing and the new nozzle 25 is re - attached . it is contemplated that any means of joining two portions of webbing that are attached using loops that contain hardware joined by a screw , bolt or other means or two loops attached using a screw lock link could be substituted for the above - described arrangement . alternate linkage mechanisms are illustrated in fig9 and 10 . in a second alternate embodiment illustrated in fig9 a steel plate 32 is threaded through each loop 29 . at least one screw 33 and preferably two screws pass through the loops 29 and plates 33 to anchor the two portions of webbing together . fig1 depicts a third alternate embodiment in which a screw lock link 34 is threaded through loops 29 . if not otherwise stated herein , it may be assumed that all components and / or processes described heretofore may , if appropriate , be considered to be interchangeable with similar components and / or processes disclosed elsewhere in the specification , unless an indication is made to the contrary . it should be appreciated that the apparatus and methods of the present invention may be configured and conducted as appropriate for the application . the embodiments described above are to be considered in all respects only as illustrative and not restrictive . the scope of the invention is defined by the following claims rather than by the foregoing description . all changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope .
a controlled descent device for use in industrial or recreational settings for controlled descent of a user from an upper level to a lower level . the device comprises principally a steel housing , an internal spring - loaded drum on which a webbing line is wound , and an attachment to a harness worn by a user . a centrifugal brake mechanism which acts upon the drum to limit the rate of descent includes a manufactured one - way bearing . the line constituent provides increased shock absorbing capabilities and is field replaceable .