Abstract:
A safety system which permits the free movement of the user, assists the ascent of the user and provides a reduced, controlled rate of descent in the event of an emergency descent or a fall, includes a cable attachable at one end to the user and secured at the other end to a moveable counterweight assembly. Intermediate its ends the cable passes over a pulley in a controlled descent device which also includes a centrifugally-actuated clutch coupling the pulley to a speed-multiplying gearing system and a centrifugally-operated braking assembly. Under normal-use conditions, the pulley is rotated at sufficiently low speeds to preclude engagement of the clutch, and the user has free movement, with a component of the counterweight assisting the ascent of the user. In the event of a rapid rate of descent, the increased rotational speed of the pulley is coupled to and actuates the braking assembly to reduce the rotation of the pulley and slow the descent to a lower, controlled rate. Descent may be vertically or at an angle with a spring pulley and an angled descent cable. The cable may be disposed on the pulley in different arrangements, and the pulley may be provided with alternate groove configurations. The pulley may be coupled to the braking assembly without an intervening clutch.

Description:
CROSS REFERENCE TO COPENDING APPLICATION 
     This application is a continuation-in-part of copending application Ser. No. 430,244, filed on Sept. 30, 1982 and now U.S. Pat. No. 4,458,781. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to safety equipment, and more particularly to such equipment used for the safe ascent and descent of the user. More specifically, the present invention relates to a safety system which assists the user during the ascent, permits free movement in ascent and descent during normal conditions and in the event of a too-rapid descent, such as a fall, the system operates to reduce the descent rate to a slower, controlled rate. 
     2. Prior Art 
     The following prior art is of record in the aforesaid copending application: 
     U.S. Pat. No. 511,896, Killeen, Jan. 2, 1894 
     U.S. Pat. No. 1,123,776, Meyer, Jan. 5, 1915 
     U.S. Pat. No. 1,849,725, Quick, Mar. 15, 1932 
     U.S. Pat. No. 2,280,396, Gentry, Apr. 21, 1942 
     U.S. Pat. No. 2,538,904, Herod, Jan. 23, 1951 
     U.S. Pat. No. 3,467,224, Curtis et al., Sept. 16, 1969 
     U.S. Pat. No. 3,826,335, Allen, July 30, 1974 
     U.S. Pat. No. 3,908,791, Kleine et al., Sept. 30, 1975 
     U.S. Pat. No. 3,946,989, Tsuda, Mar. 30, 1976 
     U.S. Pat. No. 4,111,281, Jacobs, Sept. 5, 1978 
     U.S. Pat. No. 4,130,176, Paulie, Dec. 19, 1978 
     U.S. Pat. No. 4,252,214, Miller, Feb. 24, 1981 
     U.S. Pat. No. 163,705 (Switz.), Dingeldein, Nov. 1, 1933 
     SUMMARY OF THE INVENTION 
     Among the objects of the invention are to provide an improved climbing aid and safety descent system for the safe ascent and descent between different elevations, to provide an improved system of the foregoing type which aids the ascent by counterbalancing a portion of the user&#39;s weight, to provide an improved system of the foregoing type having a controlled descent mechanism capable of reducing high rates of descent to a lower, controlled rate of descent, and to provide an improved system of the foregoing type which permits free movement of the user during normal use and which operates to provide a controlled rate of descent in the event of an emergency such as a fall or need for rapid descent. 
     Other objects of the invention are to provide a climbing aid and safety descent system of the foregoing type with an improved controlled descent device having a cable controller which permits free movement of the user during normal-use conditions and which operates in the event of a too-rapid descent to provide a controlled rate of descent, to provide an improved device of the foregoing type with a novel braking assembly, and to provide an improved device of the foregoing type with a centrifugally-actuated clutch coupling the cable controller with the braking assembly. 
     These and other objects of the invention are achieved in a climbing aid and safety descent system which includes a main cable attachable at one end to the safety harness of the user and attached at the other end to a counterweight assembly disposed for traversal along a guide wire. Intermediate its ends the cable passes over a cable pulley in a controlled descent device which also includes a centrifugally-actuated clutch coupling the pulley to a speed-multiplying gearing system and a centrifugally-operated braking assembly. Under normal-use conditions, the force of the counterweight assembly at one end of the cable and the weight of the user at the other end causes the cable to rotate the pulley at sufficiently low speeds to preclude engagement of the clutch, and the user has free movement with the system, with a component of the counterweight assisting the ascent of the user. 
     In the event of a rapid rate of descent, such as a fall or an emergency intentional rapid descent, the increased rotational speed of the pulley activates the clutch to couple the rotation of the pulley to the braking assembly, with the gearing system multiplying the rotational speed. The braking assembly reduces the rotation of the pulley and slows the descent to a lower, controlled rate. Descent may be vertically or at an angle along a second, angled guide cable. 
     Alternate embodiments of the controlled descent device include disposing the main cable at least one complete revolution around the cable pulley and, in cooperation with guide pulleys, disposing the cable less than a complete revolution around the pulley. The pulley itself may be provided with a straight-sided, flat bottomed groove, or a groove of U-shaped or V-shaped configuration. The V-chaped pulley may be provided with a friction enhancing surface at the base of the groove. The cable pulley may be directly coupled to the braking assembly by the gearing system, without an intervening clutch. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic illustration of one embodiment of the present invention; 
     FIG. 2 is a cross-sectional view of the invention, as along line 2--2 in FIG. 1; 
     FIG. 3 is a cross-sectional view of the invention, as seen along line 3--3 in FIG. 1; 
     FIG. 4 is an elevational cross-sectional view, on a reduced scale, as seen along line 4--4 in FIG. 3; 
     FIG. 5 is an elevational cross-sectional view, as seen along line 5--5 in FIG. 3; 
     FIG. 6 is an elevational cross-sectional view, as seen along line 6--6 in FIG. 3; 
     FIG. 7 is an elevational cross-sectional view, as seen along line 7--7 in FIG. 3; 
     FIG. 8 schematically illustrates another embodiment of the present invention; 
     FIG. 9 shows, to a larger scale, the controlled descent mechanism of FIG. 8; 
     FIG. 10 is a sectional view of the controlled descent mechanism, as seen along line 10--10 in FIG. 8; 
     FIG. 11 is a cross-sectional view of another embodiment of the pulley in the controlled descent mechanism; 
     FIG. 12 is a view similar to FIG. 11 showing yet another embodiment of the pulley; 
     FIG. 13 is a cross-sectional view showing a modification of the pulley of FIG. 12; 
     FIG. 14 is a sectional view of another embodiment of the cable and pulley arrangement in the controlled descent mechanism; 
     FIG. 15 illustrates an angled descent mode using the present invention; 
     FIG. 16 is a plan view of a pulley used in the angled descent mode of FIG. 15; 
     FIG. 17 is a view of the pulley as seen along line 17--17 in FIG. 16; and 
     FIG. 18 is a view similar to FIG. 16, showing an intermediate step in placing the pulley on a cable. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring more particularly to FIG. 1, the climbing aid and safety descent system of the present invention is shown to include a controlled descent mechanism, indicated generally at 10, which, together with a guide pulley 12, is mounted on a plate 14 securely but removably attached to a support 16. A main cable 18 passes over the controlled descent mechanism 10, passes over the guide pulley 12, and attaches at one end to a counterweight assembly or trolley indicated generally at 20. The counterweight assembly 20 includes a pair of frame members 22, one end of each being attached to a weight 24, with the other end rotatably supporting a roller 26. The end of the cable 18 is connected by conventional means to the weight 24. 
     A guide wire 28 is securely attached at its upper end to the support 16, such as at the point 30, and is anchored at its other end at an elevation (not shown) lower than the support. The rollers 26 of the counterweight assembly 20 traverse the guide wire 28 to move the counterweight assembly substantially parallel to the guide wire. The cross-sectional view of FIG. 2 shows more clearly the relationship between the counterweight assembly 20 and the rollers 26 moving along the guide wire 28. 
     With continuing reference to FIG. 1, the other end of the main cable 18 is provided with an eye 32 to which is connected a flexible member 34, such as a length of cable or a length of chain as shown, with a snap hook 36 or similar quick-connect fastener being attached to the free end of the flexible member. A worker W using the system of the present invention has a safety belt or harness 38 provided with a ring 40 to which the snap hook 36 may be readily connected. A second flexible member 42, which may also be a length of cable or a length of chain as shown, in connected at one end to the eye 32, with the remaining end being provided with another snap hook or similar quick-connect fastener 44. 
     A ladder 46 having a plurality of vertically-spaced rungs 48 is securely attached to the structure to which the support 16 is attached. As described more fully below, the climbing aid and safety descent system of the present invention permits the worker W to ascend the ladder 46 with greater ease and to descend quickly from the structure at a controlled rate in the event of an emergency. 
     Prior to use, both snap hooks 36 and 44 are connected to a ladder rung 48 or another convenient point. To use, the worker W wearing the safety harness 38 first attaches one end of the main cable 18 to the harness by connecting the snap hook 36 to the ring 40, with the snap hook 44 on the end of the flexible member 42 remaining connected to a rung 46 of the ladder 48 for safety reasons. When the worker W is ready to move, the snap hook 44 is then disconnected from the ladder rung 48 and conveniently attached to the ring 40. Attachment of the flexible member 42 to the ladder 48 when the worker W stops temporarily provides a safety connection to the ladder. With the counterweight assembly 20 provided in the system of the present invention, the ascent of the worker W is facilitated to the extent that a component of the weight 24 applies an upward pull to the worker by the main cable 18, thus counter-acting a portion of the worker&#39;s weight and making it easier for the worker to ascend the ladder 48. 
     The value of weight 24 need not be equal to the weight of the worker W for the present system to work properly and effectively, and in many applications weight 24 will be less than the worker&#39;s weight. However, if desired, or in order to comply with applicable regulations, e.g., OSHA Program Directive 100-103, the weight 24 may be equal to the weight of the worker W. 
     When the worker W has finished using the system, the foregoing procedure is reversed, by first detaching one of the snap hooks 36 and 44 from the ring 40 and connecting it to a ladder rung 48 or another convenient anchor point before disconnecting the remaining snap hook from the ring. 
     As shown in FIG. 3, the controlled descent mechanism 10 includes a housing or enclosure 50 open at both ends, with one end abutting against the plate 14 and the other end being closed by a plate 52 having a central aperture 54. A short distance inward, toward the plate 14, from the closure plate 52 the housing 50 is provided with an annular flange 56 which extends radially inwardly and terminates in a central opening. A shaft 58, which may conveniently have a threaded end portion, is passed through the central aperture 54 in the plate 52 and through the central opening in the annular flange 56, and through an opening in the plate 14, pass the back surface of the plate. A fastener, such as a nut 60, is threaded upon the shaft 58 to securely, but removably, mount the housing 50 and the controlled descent device 10 to the plate 14. 
     A pulley 62, rotatably supported on the shaft 58 by a tubular sleeve 64, has a groove or recess 66 around its peripheral surface to receive the main cable 18. As noted above, and as shown in FIG. 4, the cable 18 is wrapped one complete turn around the pulley 62, with the cable extending more than one turn from the point it makes initial contact with the pulley until it leaves the pulley. 
     Supported diametrically on one surface of the pulley 62, the surface facing away from the plate 14, is a pair of arcuate, pawl-like elements 68 rotatable about pivots 70. Each of the pawl elements 68 is rotatably supported off-center on the pivot 70 such that the pawl is unbalanced relative to the axis of the pivot. The end 68a of the pawl 68 furthest from the axis 70 is biased clockwise by a spring 72 attached at its ends by a pin 74 secured to the end of the pawl and a pin 76 fixed to the surface of the pulley 62, as shown in FIG. 5. This end 68a of the pawl 68 is smoothly contoured. The other end 68b of the pawl-like element 68, the end closer to the axis 70, is provided with an angular, plane surface 77. A disk 78, having a plurality of teeth-like projections 79 on its periphery, is securely attached to a hub 80 of a crown or ring gear 82. The pawl-like elements 68 and the disk 78 function as a clutch to selectively transmit rotational motion of the pulley 62 to the other portions of the controlled descent mechanism 10, as described below. 
     The ring gear 82 is provided with teeth 83 extending radially inwardly from its outer circumference, and is rotatably supported on the shaft 58 by a coaxial tubular sleeve 84 extending through the hub 80. An axial spacer 86 is disposed between the pulley 62 and the hub 80 to permit free, relative rotation between the pulley and the ring gear 82, and thus the free rotation of the disk 78 relative to the pulley and the pawl-like elements 68 supported on the pulley. 
     Two idler or planetary gears 88, rotatably supported by studs 90 fixed onto the annular flange 56, mesh with the teeth 83 of the ring gear 82 and with a center or sun gear 92 which is also rotatably supported on the shaft 58 by the sleeve 84. Note FIGS. 3 and 6. A brake holder 94, having adjacent its outer peripheral rim 96 a recessed channel or groove 98, has a central hub 100 which rotatably supports the brake holder on the shaft 58 by means of the tubular sleeve 84. Note FIGS. 3 and 7. Conveniently, the body of the center or sun gear 92 may be an axial extension of the hub 100 of brake holder 94, as shown in FIG. 3. 
     As shown in FIG. 6, with the meshing of the ring or crown gear 82 with the idler gears 88 and the center or sun gear 92, rotation of the ring gear is transmitted, at a multiplied rate, to the sun gear since the idler gears are fixed onto stationary annular flange 56 of the mechanism housing 50. This operation will be further described below. 
     Referring to FIGS. 3 and 7, the channeled or the grooved recess 98 in the outer periphery 96 of the brake holder 94 is joined to the hub 100 by an annular flange 102. As shown in FIG. 7, at regular intervals along the circumference, the channel 98 of the brake holder 94 is interrupted by radially-extending guides or dividers 104, to define annular receiving sectors or recesses in which are received brake elements 106 in the form of arcuate weights. The brake elements 106 can move freely radially outwardly and inwardly within the recesses under the influence of rotation of the brake holder 94, but can move only to a very limited extent in the circumferential direction of the brake holder. The outer surface of each of the brake elements 106 is covered with a layer 108 of friction material, such that upon rotation of the brake holder 94 and radial movement outwardly of each of the brake elements 106 under centrifugal force, the friction layer will engage the inner surface of the housing 50, thus creating a dragging or braking action between the brake holder and the stationary housing. 
     From the foregoing, it can be seen that the controlled descent mechanism 10 has two modes of operation. Under normal conditions, with the cable 18 passing slowly over the pulley 62 and the pulley rotating below a predetermined speed, there is no engagement between the pawl-like elements 68 and the disk 78. This permits the free, unhindered movement of the main cable 18 over the pulley 62, and the worker W is able to move freely up and down. In the arresting mode, when the cable passes rapidly over the pulley 62 to rotate the pulley above a predetermined speed, there is operative engagement between the pulley 62 and the brake holder 94. 
     More specifically, under normal conditions, as the worker W moves up and down on the ladder 46, his weight at one end of the cable 18 and the counterweight assembly 20 at the other end will cause the cable to rotate slowly the pulley 62, in either direction A (FIG. 5). Under these normal conditions, the force of the pawl spring 72 is sufficient to bias the shaped, plane end surfaces 77 of the pawls 68 out of engagement with the teeth-like elements 79 on the disk 78. The arcuate configuration of the inner edge surface of the pawl-like element 68 and the smooth contour of the end 68a causes each pawl to ride over the teeth-like elements 78 on the disk 78, against the bias of the springs 72, without engagement between these two structures. At the same time, the springs 72 bias the pawl ends 68b away from the teeth 79 on the disk 78. Thus, under normal operating conditions there is no coupling between the pulley 62 and the disk 78 and the brake holder 94. The brake holder 94 is inoperative, and the pulley 62 is freely rotatable. 
     However, in the event of a too-rapid descent of the worker W, such as a fall, the pulley 62 is rotated at a speed sufficient for the centrifugal force acting on the longer, off-centered portion 68a of the pawls 68 to overcome the restraint of the springs 72. The pawls 68 then rotate counterclockwise about the pivots 70, against the pull of the spring 72, causing the shaped ends 77 to engage the teeth 79 and mechanically coupling the rotating pulley 62 to the gearing system through the disk 78 fixed to the hub of the ring gear 82. The rotational speed imparted to the disk 78 by the rotating pulley 62 is multiplied by the arrangements of the ring gear 82, the idler gear 88 and the center or sun gear 92, which in turn transmits the rotational motion to the brake holder 94. 
     Rotation of the brake holder 94 causes the brake elements 106 to move radially outwardly to establish braking contact between the frictional material layer 108 and the inner surface of the enclosure 50. This braking force reduces the rapid rotation of the pulley 62, thus reducing the movement of the main cable 16 to a slower, controlled rate. The braking force is directly proportional to the rotational speed of the pulley 62, i.e., the rate of fall of the worker W, so that the more rapid the rate of fall of the worker, the greater is the rotational speed of the pulley, and the greater is the braking force produced by the controlled descent mechanism 10. The system will operate, in general, to safely lower the worker at a controlled descent rate of approximately 4 to 9 feet per second. 
     Once the rotating pulley 62 has slowed to a speed at which the centrifugal force exerted on the pawl-like elements 68 is not sufficient to overcome the restraint of the springs 72, then the springs rotate the pawl elements from the teeth 79 on the disk 78. This disengages the brake holder 94 and the gear assembly from the pulley, and the cable 18 again moves freely over the pulley 62. 
     An alternate embodiment of the climbing aid and safety descent system of the present invention is shown in FIG. 8. With the exception of the structure of the alternate embodiment of the controlled descent mechanism 210, the other elements in the system are substantially identical to that shown in FIG. 1, and the same reference characters are used. 
     As shown in FIGS. 8, 9 and 10, the portion of the main cable 18 extending from the counterweight assembly 20 passes between a pair of parallel, vertically-disposed guide rollers 212, and over a first guide pulley 214 rotatably supported on a horizontally-disposed axis, before passing over a main or drive pulley 216 which is operatively coupled to the clutching mechanism, the speed-multiplying gearing system and the brake holder disposed within the housing 50. The clutching mechanism, gearing system and brake holder are structurally and functionally identical to that described above relative to the embodiment shown in FIGS. 1-7. A second guide pulley 218 is positioned relative to the main pulley 216 to cause the cable 18 to wrap around the pulley less than one complete revolution. 
     The cable 18, after passing over the second guide pulley 218, passes downwardly through the controlled descent mechanism 216, between two pairs of orthogonally-disposed guide rollers 220 and 222, as best shown in FIGS. 8 and 10. As shown, the guide rollers 220 and 222 are preferably provided with concave-shaped or otherwise indented peripheral surfaces to center the cable 18 therebetween, and at the same time to provide maximum freedom of movement for the cable. 
     As shown in FIG. 9, the first guide pulley 214 is supported on the plate 14 so that the cable 18 passes over the groove of the guide pulley in a substantially horizontal orientation, and contacts the main pulley 216 in a tangential fashion. As the cable 18 passes between the lower portion of the main pulley 216 and the second guide pulley 218, the cable is wrapped around the main pulley less than one complete revolution, or with somewhat less than 360 degrees of engagement between the cable and the circumference of the main pulley. It has been found that by wrapping the cable around the main pulley 216 in this manner, operation of the controlled descent mechanism 210 is substantially identical in efficiency and performance as the controlled descent mechanism 10 shown in FIGS. 1-7, in which the main cable 18 is wrapped one complete revolution around the main pulley 62. 
     Shown in FIG. 8 is one suitable technique for attaching the main cable 18 to the weight 24. An eyebolt 120 is threaded into an internally-threaded hole tapped into an end of the weight 24. The cable 18 is passed through and secured to a cable vise or strand vise 122 of known construction, with the loop 124 of the cable vise passing through the eyebolt 120. 
     The remainder of the system shown in FIG. 8 is identical to that of FIG. 1, and further description of the structure is not deemed necessary. Similarly, the operation of the control descent mechanism 210 is identical to that of the control descent mechanism 10, and will not be further described. 
     The main pulley 216, preferably, is provided with a tapered or convergent groove which, in cross section, has straight convergent sides 224 terminating in a curved or arcuate trough 226, somewhat resembling a U, as shown in FIG. 11. Alternatively, the straight sides of the groove can intersect in a V-shaped groove 228, as shown in the pulley 216&#39; in FIG. 12. The groove configuration for the pulley 216 provides good, nonslip operating conditions up to a certain weight limit of the worker W, above which slippage may become evident. For heavier weights, the V-shaped groove shown in the main pulley 216&#39; is recommended. With this groove configuration, the heavier weight pulls the cable 18 further into the convergent groove 228, thereby increasing the contact between the cable and the pulley. The angle of the sides of groove 228 is appropriately selected for the size of the pulley and the size of the main cable to be used. 
     FIG. 13 illustrates a modification of the pulley having a V-shaped groove. Pulley 216&#34; has a V-shaped groove 228&#39; in which the base thereof has been provided with a recess 227 in which a member 229 is provided. The member 229 is of a material such as polyurethane or other suitable material which offers a high degree of slip resistance to the main cable 18. As shown, driving contact between the cable 18 and the pulley 216&#34; is principally via the member 229 which, due to material from which it is made, provides excellent rotating traction and negligible slippage of the cable regardless of the worker&#39;s weight. Any of the foregoing-described pulley groove configurations may be similarly provided with a traction-improving member. 
     An alternate embodiment of the single cable wrap configuration of the main pulley 216 is shown in FIG. 14, in which a main pulley 230 is rotatably disposed about a shaft 232 and the main cable 18 for the system is wrapped once around the peripheral groove of the pulley. The cable 18 passes between a pair of guide rollers 234 and 236 which are oriented along a common horizontally-disposed axis and positioned below the lowermost circumferential point of the pulley 230. As shown, preferably the guide pulleys 234 and 236 are smaller than the main pulley 230, with a guide pulley disposed on either side of an axis extending vertically through the main pulley, in the orientation of FIG. 14. The guide pulleys 234 and 236 are rotatably supported on a shaft 238 and 240, respectively, with the shafts spaced appropriately to permit the unencumbered passage of the cable 18 up, over, and down from the main pulley 230. While not specifically shown in FIG. 14, one portion of the cable 18 leads to the counterweight assembly 20 and the other portion leads to the safety harness 38 of the worker W. The pulley 230 may have the U-shaped groove of FIG. 11, or the V-shaped groove of FIG. 12 or FIG. 13. 
     It is understood that the combination of the main pulley 230 and the parallel-disposed guide pulleys 234 and 236 of FIG. 14 would be incorporated into the controlled descent mechanism 210, in place of the main pulley 216 and guide pulleys 214 and 218. The pulley 230 would be operatively coupled to the clutching, gearing and braking mechanisms already described to provide free, unencumbered passage of the cable 18 over the pulley during normal operation of the system, and to provide braked, controlled descent of the worker W during emergency situations. 
     In the invention described above, the descent, whether intentional or accidental, has been substantially vertical. It may be desired to descend from the structure at an angle away from the base thereof. As shown in FIG. 15, an angled descent at a controlled rate can be readily achieved with the system of the invention. A separate descent cable or wire 130 is securely anchored at its ends, at an appropriate angle and suitably convenient for access by the worker W. A descent pulley assembly 132, to which the main cable 18 can be readily connected, provides a rapid, controlled angled descent along the cable 130. 
     The structure and operation of the descent pulley assembly 132 can be appreciated by reference to FIGS. 16, 17 and 18. A pulley 134 is disposed between plates 136 and 138, and is rotatable about a shaft 140 extending through the plates. As shown the shaft 140 may have an enlarged head 142 at one end and threads on the remaining end to receive a nut 144. Each of the plates 136 and 138 has a circular portion 136a and 138a, respectively, located on opposite sides of the pulley 134. As shown clearly in FIGS. 16 and 18, the circular portion 138a of plate 138 has a peripheral segment removed to provide a straight surface 138b. 
     Each of the plates 136 and 138 is further provided with a tab 146 and 148, and a tongue 150 and 152 disposed diametrically relative to the tab. A hole 146a and 148a (FIG. 18) is provided in the respective tab 146 and 148, and a spacer 154 is positioned between the tabs and is fixed to tab 146. A bore 155 extends vertically through the spacer 154, as indicated by the broken lines in FIG. 17, the bore being aligned with the hole 146a in tab 146. At the other end of pulley assembly 132 a second spacer 156 is fixed to the tongue 152 and has a bore 158 extending transversely therethrough (FIG. 17). Spacers 154, 156 provide the correct separation between plates 136, 138 to ensure free rotation of the pulley 134 about the bolt 140. 
     Since the plate 138 is not fixed to spacers 154, 156, it is free to rotate about the bolt 140. To position plates 136, 138, hole 148a in tab 148 is aligned with bore 155 in spacer 154, and a beaded bolt 160 is inserted through the aligned apertures and held in place by a cotter pin 162 (FIGS. 1 and 17). Although not shown in the drawings, bolt 160 and cotter pin 162 are each attached to the descent pulley assembly 132, such as plate 136, by flexible elements to prevent their loss after separation. 
     An eyebolt 164, with an attachment ring 164a on one end, has an elongated body or rod portion 166 passing through the transverse bore 158 and terminates in an enlargement 168 at its interior end. A spring 170, compressed between enlargement 168 and the inner end surface of spacer 156, encircles rod portion 166 and biases the eyebolt 164 inwardly toward the pulley 134 (to the left in FIGS. 16-18). The body 166 of eyebolt 164 has a threaded portion 166a adjacent to the ring 164a meshing with a nut 172. Rod lengths 172a project transversely from nut 172 to facilitate rotation of the nut on the threaded portion 166a, similar to the &#34;wings&#34; on a wing nut. Under the urging of spring 170. eyebolt 164 is biased inwardly toward pulley 134, until nut 172 abuts the exterior surface of spacer 156. As is apparent from FIG. 17, the separation distance between pulley 134 and enlargement 168 may be adjusted by pulling on eyebolt 164 (to the right in FIGS. 16-18), adjusting the position of nut 172 on threaded portion 166a, and releasing the eyebolt. As long as any force on eyebolt 164 is less than or equal to the force of spring 170, the spring will maintain this separation distance. Since eyebolt rod 166 is slidable within transverse bore 158, eyebolt 164 freely reciprocates therein in response to such forces. 
     To install descent pulley assembly 132 onto descent cable 130 which, being anchored at both ends, does not permit installation via a cable end, the pulley assembly is &#34;opened&#34; by removing cotter pin 162 from bolt 160 and withdrawing the latter from bore 155 in the spacer 154, permitting plate 138 to be rotated, preferably counterclockwise, in the direction of arrow B in FIG. 16, to the position shown in FIG. 18. In this orientation, flat surface 138b along the periphery of plate 138 is substantially perpendicular to a horizontal line C extending through and joining the tab portion and the tongue of each plate 136, 138. By pulling on eyebolt 164, the descent cable 130 can be slipped between flat surface 138b and eyebolt enlargement 168, and onto pulley 134, after which the eyebolt is released. 
     To &#34;close&#34; pulley assembly 132, plate 138 is rotated clockwise (arrow D in FIG. 18) about pulley bolt 140, until hole 148a is aligned with spacer bore 155, and bolt 160 is reinserted and secured with cotter pin 162 to keep the pulley assembly on descent cable 130. Descent pulley assembly 132 may then be slid along cable 130 and held at a location convenient for use by worker W by adjusting the nut 172 in the manner described above until eyebolt enlargement 168 firmly engages cable 130. The force of spring 170 is sufficient to maintain this engagement. 
     In use, one of the flexible members 34, 42 attached to the end of main cable 18 is connected to ring 164a of eyebolt 164 and the remaining flexible member is connected to ring 40 on the worker&#39;s safety harness (FIG. 15). Then, as the worker W jumps or otherwise leaves his position, his weight will pull the eyebolt enlargement 168 away from the descent cable 130, compressing spring 170, permitting the descent pulley assembly 132 to move freely along the angled descent cable 130 to lower the worker at an angle away from the base of the structure. The controlled descent mechanism 10 or 210 operates as described above to lower the worker W at a controlled rate along the angled descent cable 130. 
     It is apparent from the drawings that since plate 138 is freely rotatable about bolt 140, it may be rotated either clockwise or counterclockwise during the foregoing procedure to place the pulley assembly 132 onto descent cable 130. The rotational directions described above result in the fastest procedure for mounting the pulley assembly. 
     It is within the comprehension of the invention that an alignment stop may be provided to quickly and mechanically align hole 148a in plate 138 with spacer bore 155 after pulley assembly 132 has been placed onto cable 130. As an example, a tang (not shown) or similar projection may extend vertically (outwardly from the place of the Figures) from tongue 150 of plate 136 and engage a lateral edge (the lower edge in FIGS. 16, 18) of tongue 152 on the rotatable plate 138 when hole 148a is aligned with bore 155. Equivalently, the tang may be carried on the tongue 152 of rotatable plate 138 to move therewith, and abut a lateral edge (e.g., the upper edge in FIGS. 16, 18) of the tongue 150 of the non-rotatable plate 138 when hole 148a is aligned with bore 155. Alternatively, instead of providing the stop tang on the tongue portions of the plates 136, 138, the tang may be provided on the tab portion of the plates, or the stop tang may otherwise be provided at a suitable location. Provision of an alignment stop will generally restrict unhindered, 360° rotation of the plate 138, and the location of the stop should be selected to permit the quickest &#34;opening&#34; and &#34;closing&#34; (as above described) of the pulley assembly 132 to place it onto the descent cable 130. 
     More than one eyebolt may be provided on descent pulley assembly 132 if desired and, for instance, may be secured to the spacer 156 and extend transversely therefrom to provide additional attachment points on the pulley assembly. 
     In the thus-described embodiments of the controlled descent mechanism of the present invention, the main or primary pulley over which the cable 18 passes, has been coupled to the centrifugally-operated brake system by a pawl-and-ratchet like clutch device. It is possible to directly couple the main pulley to the speed-multiplying gearing system and the centrifugally-operated braking mechanism, without an intervening clutch device. Due to the presence of the speed-multiplying gearing system, it is still possible for the cable 18 to pass through the controlled descent mechanism without undue restraint or hinderance of the worker W. The direct coupling of the main or drive pulley to the gearing system and the braking system may result in some additional wear of the braking element friction linings due to the possible constant engagement between the brake elements and the inner circumferential surface of the housing 50. Under normal operating conditions, the speed-multiplying gearing system will permit the cable 18 to pass through the controlled descent mechanism with a minimum of restraint resulting from this constant slight engagement between the brake elements and the housing surface. Under emergency or other rapid-descent conditions, the controlled descent mechanism operates as described above, to reduce the speed of descent to an acceptable, controlled rate. 
     Removal of the clutch mechanism and direct coupling of the drive pulley to the speed-multiplying gearing system and the brake system results in a controlled descent mechanism which is simpler mechanically, lighter in weight and less-expensive. This system is well suited for lighter weight ranges. Where heavier weights are anticipated during operation of the system, then the embodiments of the system which incorporate clutch coupling of the pulley to the gearing and brake systems is preferred. 
     Although the drive pulleys incorporating a U- or a V-shaped groove has been described in connection with the controlled descent mechanism in which the main cable 18 is wrapped around the drive pulley less than once, it is understood that either of these groove configurations could also be incorporated into the embodiment of FIGS. 1-7. Thus, for example, instead of the straight-sided and straight-bottom groove or recess for the pulley 62 shown in FIG. 2, a pair of U-shaped or V-shaped grooves could be provided for the pulley, with the cable wraps engaging the appropriate grooves. 
     The present invention offers many advantages over similar types of safety devices now in use. The main cable can be easily and quickly connected to the worker&#39;s safety harness, even with gloved hands, and thus encourages Since the present system can be quickly attached and detached from the safety harness, it is portable with the worker, and the same device can be used by different workers moving between different levels. 
     Another advantage is the easy maintenance and removal of foreign materials from the cable, the counterweight assembly, the controlled descent device and other components of the system. With the appropriate choices of sizes for the pulleys and rollers in the system, many different types and sizes of cables can be used. 
     With the system being designed for removable installation from the support, it may be removed relatively easily and stored when not in use to reduce exposure to adverse environments such as corrosive chemicals and seawater. This removability, combined with the use of corrosion-resistant materials, greatly prolongs the useful life of the system and significantly reduces maintenance requirements. 
     While the contemplated primary use of the present invention is not for the handling of working materials, in the event of an emergency, or if so desired, the system can be modified to raise and lower items of material by suitably providing the appropriate connections to the material and to both ends of the main cable. Although not specifically described herein or illustrated in the drawings, it is understood that all of the components described above are arranged and supported in an operative fashion to form a complete, operative system. Further, it is understood that all ancillary components have not been specifically described, but such components are known in the art and are appropriately incorporated into the operative system. 
     Of course, additional and other variations of the specific construction and arrangement of the climbing aid and safety descent system disclosed above can be made by those skilled in the art without departing from the invention as defined in the appended claims.