IL252166B

IL252166B - Centrifugal brake

Info

Publication number: IL252166B
Application number: IL252166A
Authority: IL
Original assignee: Skysaver Rescue Ltd
Priority date: 2017-05-08
Filing date: 2017-05-08
Publication date: 2022-08-01
Also published as: IL252166A

Description

252166/ - 1 - CONTROLLED CABLE RELEASE MECHANISM TECHNOLOGICAL FIELD The present invention is generally in the field of centrifugal brakes usable for controlled descent devices.

BACKGROUND In today’s urban environments, many people live or work in multi-storied buildings such as sky-scrapers. In case of a fire or terrorist attack, rapid descent from upper floors of such buildings may be necessary. In such emergency situations, use of an elevator may be unsafe. Emergency stairwells may become blocked by fire or smoke, making rapid escape difficult. Descent devices may be used in such emergency situations to allow a rescuee to be safely lowered to the ground. Some patent publications relating to brake mechanisms usable for CDD applications are briefly described below. US Patent publication No. 2004/245048 describes a rappelling device for permitting persons to be rescued from high buildings, towers, and the like, having a suspension strap, suspension vest, or the like, to be worn by the person in question, wherein a rope container having a device to release the rope length is provided on the suspension strap, which solution is supposed to be easy to operate, on the one hand, and to be made available to the persons in question at any time, and easy to handle for them, whereby the person using the device can essentially move both hands freely, in a stable rappelling position. This is achieved in that the rope drum that forms the rope container, in the wearing position on the back of the person using the device, is provided with a rope guide device for passing the rope to a release position in the chest region of the person using the device. International Patent Publication No. WO 03/055560 discloses an abseiling device used as rescue equipment in disaster situations, particularly fires in buildings or tall buildings, comprising a harness for supporting particularly a person, a housing provided with a rope drum and an automatic braking device, and a rope, one end of which is fixed to the building and the other end of which is fixed to the housing. The housing is connected to the harness so as to form a unit. 30 252166/ - 2 - International Patent Publication No. WO 89/00063 describes a lowering device particularly for assisting persons to escape from multi-storied buildings in an emergency situation, and adapted to engage a cable or rope of twisted configuration. The device comprises an inner rotatable sleeve surrounding and engaging the cable to follow the twist therein and rotate about the cable as it descends down the cable. The inner sleeve is contained within an outer housing which, in turn, supports a person, and the speed of rotation of the inner sleeve and thus the rate of descent of the device down the cable is controlled by a centrifugal brake having bell cranks carried by the inner sleeve and each pivotable against tension springs under centrifugal force to cause eccentrics on the ends of the cranks to act on brake shoes which engage a brake surface on part of the outer housing. Also disclosed is a device which as an alternative, involves braking by utilizing a hydraulic system with a closed circuit gear pump driven by the inner sleeve and containing a variable constricted orifice to control the speed of the pump and therefore the rate of descent of the device. The slow descender described in US Patent No. 3,946,989 includes a rope pulley and a braking apparatus which restricts the rotation speed of the rope pulley. The braking apparatus includes a mechanical braking device containing a centrifugal brake which has centrifugal weights, a V-shaped lining part cooperating with the weights, and a speed multiplying gearing device connecting the rope pulley and the centrifugal friction brake. The slow descender further includes an oil hydraulic braking device of the vane pump type or of the inscribed gear pump type. US Patent No. 4,986,390 describes a small and light slow-descending device that anybody can easily carry in a traveling bag, or the like. Therefore, it is useful as an emergency evacuation device which enables to escape from a fire in a hotel, apartment house, office building, etc., or from a disaster in a high level road or highway, etc.

GENERAL DESCRIPTION There is a need in the art for compact and efficient centrifugal brake mechanisms capable of rapidly damping angular velocity of a rotating body (e.g., a wheel, drum, or cable reel), and that can be accommodated inside said rotating body. Embodiments of the centrifugal brake mechanism of the present invention are particularly beneficial for drum devices of controlled descent devices (CDDs) to allow regulating the speed release of a cable spooled in the drum device, and guarantee 252166/ - 3 - continuous cable release from the device until reaching safe ground, and thereby preventing suspension trauma. The centrifugal brake mechanism of the present invention is configured to allow substantial reduction of the geometrical dimensions of the drum device by compactly arranging its components inside a circular central cavity formed inside a cable reel, of the drum device, on which the cable is spooled. Brake elements (e.g., brake shoes arrangements) mounted inside the central cavity are slidably coupled to a rotatable axle/shaft coaxially mounted inside the cable reel, and a planetary gear system is used to transfer rotations of the cable reel into counter-rotations of the axle. This configuration causes the breaking elements to rotate inside the central cavity in a direction opposite to the direction of the rotation of the cable reel, and responsively to radially slide outwardly towards an inner wall of the cable reel encircling the cavity due to centrifugal forces applied over them. As the breaking elements distally slide they become pressed against the inner wall of the cavity due to the centrifugal forces, and apply friction forces thereover and thereby damp the angular velocity of the cable reel and consequently the descent speed. In some embodiments the brake mechanism is adapted to permit rapid speed damping by increasing the contact surface area of the breaking elements used to apply the friction forces. For example, one or more of the brake elements may comprise a curved groove and the inner wall may comprise one or more circular rails radially protruding inwardly from the inner wall of the cavity, each circular rail configured to become engaged inside one of the curved grooves while the respective brake elements contacts the inner wall. In one aspect there is provided a centrifugal brake mechanism comprising a support structure, a circular wheel having a circular central cavity and being attached to the support structure to allow it to be rotated about an axis of rotation of the wheel, an axle mounted inside the central cavity and configured and operable to rotate about the axis of the wheel thereinside, a gear system configured and operable to transfer rotations of the wheel into counter-rotations of the axle, and one or more brake elements slidably coupled to the axle inside the central cavity and configured and operable to radially slide towards an inner wall of the wheel encircling the cavity in response to the counter-rotations of the axle and contact and apply friction forces over the inner wall. 252166/ - 4 - In some possible embodiments each brake element comprises one or more curved grooves and the inner wall encircling the cavity comprises one or more circular rails each configured and operable to be received inside one of the curved grooves when the brake element contact the inner wall, to thereby increase the applied friction forces. For example, and without being limiting, geometrical shapes of at least one of the curved grooves and of a respective one of the circular rails configured to be received in it, may be adapted to progressively increase the contact surface area of the respective brake element according to the speed of rotation of the wheel, to thereby increase the friction forces responsive to increase in angular velocity of the wheel. Additionally or alternatively, one of the one or more curved grooves may comprise a tapering groove section in which opposing sides of the groove taper towards the axis of rotation, and at least one of the one or more circular rails may comprise a corresponding tapering rail section configured to be received inside the tapering groove section. The brake mechanism may comprise one or more shaft rods attached to the axle substantially perpendicular to the axis of rotation, where each brake element is being mounted over at least one of the shaft roads and configured and operable to radially slide over it. One or more return springs, each mounted over one of the one or more shaft rods, may be used to mechanically couple between the axle and the brake element mounted over the shaft rod. Optionally, and in some embodiments preferably, the gear system is a planetary gear comprising a sun-gear fixedly attached to the axle, one or more planet gears attached to said support member and meshing with the sun-gear, and a ring-gear formed over a portion of the inner wall of the cavity and meshing with said one or more planet gears. For example, and without being limiting, a speed ratio of the gear system may be about 1 to 5.3. In another aspect there is provided a drum device for controlled release of a spooled cable, comprising a housing having a cable release opening for passage of released cable portions therethrough, a cable reel on which the cable is spooled where the cable reel has a circular central cavity and is being mounted inside the housing for rotation about an axis thereof during the release of the cable through the opening, an axle mounted inside the central cavity and configured and operable to rotate thereinside about the axis of the wheel, a gear system configured and operable to transfer rotations of said cable reel into counter-rotations of said axle, and one or more brake elements 252166/ - 5 - slidably coupled to the axle inside the central cavity and configured and operable to radially slide towards an inner wall of the cable reel encircling the cavity in response to the counter-rotations of the axle, and to contact and apply friction forces over the inner wall. The brake elements may comprise one or more curved grooves, and the inner wall encircling the cavity may comprise one or more circular rails, as described hereinabove and hereinbelow. Similarly, geometrical shapes of at least one of the curved grooves and of a respective one of the circular rails may be adapted to progressively increase the contact surface area of the respective brake element according to the speed of rotation of the wheel, to increase the friction forces responsive to increase in angular velocity of the wheel. At least one of the one or more curved grooves may comprise a tapering groove section, and at least one of the one or more circular rails may comprise a corresponding tapering rail section, as described hereinabove and hereinbelow. The drum device may comprise one or more shaft rods attached to the axle substantially perpendicular to the axis of rotation, and each brake element may be mounted over at least one of the shaft roads and configured and operable to radially slide thereover. One or more return springs, each spring being mounted over one of said one or more shaft rods, may be used to mechanically couple between the axle and the brake element mounted over the shaft rod. In some embodiments a cable-release system is used to direct the released cable portions in an outward direction towards the cable release opening of the drum device, and prevent backward movement of the released cable into the housing. For example, and without being limiting, the cable-release system may comprise a first cable-release unit mounted above the cable reel and having a slender opening defined between two rotatable roller shafts for passage of the released cable portions therethrough. Optionally, and in some embodiments preferably, the two rotatable roller shafts of the first cable-release unit are set with substantially different diameters according to a predetermined bend radius of the cable. The cable-release system may comprise at least one additional cable-release unit having a slender opening defined between two rotatable roller shafts for passage of the released cable portions therethrough, where the at least one additional cable-release unit is being mounted above and substantially in parallel to the first cable-release unit. 252166/ - 6 - Optionally, and in some embodiments preferably, orientation of the two rotatable roller shafts of the first cable-release unit is substantially perpendicular to orientation of the two rotatable roller shafts of the at least one additional cable-release unit.

BRIEF DESCRIPTION OF THE DRAWINGS In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings. Features shown in the drawings are meant to be illustrative of only some embodiments of the invention, unless otherwise implicitly indicated. In the drawings like reference numerals are used to indicate corresponding parts, and in which: Fig. 1 exemplifies use of a CDD by a rescuee descending from a multi-storied building according to some possible embodiments; Fig. 2 shows a perspective view of a drum device of the CDD according to some possible embodiments; Fig. 3 shows a perspective view of the drum device without one of its covering plates; Fig. 4 shows a sectional view of the drum device without its covering plate; Figs. 5 A and 5B are exploded views showing internal components of the drum device from two different sides thereof; Fig. 6 shows an elevated perspective view of a cable reel of the drum device and internal components thereof mounted thereinside; Fig. 7 shows a top perspective view of the drum device without one of its side cover plates and the cable reel; Fig. 8 shows a sectional side view of the inner wall of the cable reel and of a brake shoe according to some possible embodiments; Fig. 9 shows a perspective view of a possible arrangement of the drum device according to some possible embodiments; and Figs. 10A and 10B shows another possible embodiment of drum device, wherein Fig. 10A is a perspective view of the drum device accommodated inside a housing and Fig. 10B shows an exploded perspective view of the drum device without the housing. 30 252166/ - 7 - DETAILED DESCRIPTION OF EMBODIMENTS The various embodiments of the present invention are described below with reference to the drawings, which are to be considered in all aspects as illustrative only and not restrictive in any manner. Elements illustrated in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention. This invention may be provided in other specific forms and embodiments without departing from the essential characteristics described herein. Fig. 1 exemplifies use of a CDD 9 according to some possible embodiments. In this non-limiting example, a rescuee 7 escaping a high structure 3 (e.g., building) safely descends from the structure by controlled release of a cable 4 spooled in the CDD 9 . The CDD 9 comprises a harness 6 (e.g., type of adjustable quick fit harness) worn by the rescuee 7 , and a drum device 5 attached to the backside of the harness 6 , at the upper back area of the rescuee 7 (e.g., between the shoulder blades of the rescuee 7 ). The drum device 5 includes a spooled cable 4 , a cable reel 47 on which the cable 4 is spooled, and a centrifugal brake mechanism 5m configured to regulate the rate of cable release from the drum device 5 and thereby guarantee safe descent of the rescuee 7 to the ground 2 . The spooled cable 4 is attached at one end to the cable reel 47 and includes an anchor fastener 4h (e.g., a snap hook) attached to its free end. As shown in Fig. 1 , in order to escape the structure 3 (e.g., in an emergency situation, such as spreading fire) the rescuee 7 wears the harness 6 , secures the anchor fastener 4h to an anchor member 3r , preferably an anchor fixture fixedly attached to the structure 3 (e.g., anchor ring), and exits the structure 3 e.g., through an opening 3wsuch as a window, exit/escape door, or the like. After exiting the structure 3 the rescuee 7 is pulled downwardly by gravity (shown by arrow 1 ) towards the ground 2 and the spooled cable 4 is progressively released from the drum device 5 as the rescuee 7 descends downwardly towards the ground 2 . In this non-limiting example the harness 6 and drum device 5 arrangement guarantees that orientation of the body of the rescuee 7 during the fall is substantially vertical relative to the ground 2 . The brake mechanism 5m provided in the drum device 5 is configured to controllably release the spooled cable 4 within predefined release rates and thereby maintain a substantially controlled descent speed (e.g., of about 0.7 to 2 m/sec for rescuee weighting between 30 to 1Kg) of the rescuee 7 , until safely reaching the ground 2 . 252166/ - 8 - The CDD 9 shown in Fig. 1 exemplifies a possible embodiment wherein the drum device 5 is mounted substantially perpendicular to a back piece of the harness 6 , such that the plane of rotation of the cable reel 47 substantially resides in (or parallel to) a median plane of the rescuee 7 . It is however noted that other arrangements of the harness 6 and the drum device 5 are also possible, without departing from the scope and spirit of the present invention. For example, and without being limiting, in some possible embodiment the drum device 5 may be mounted substantially parallel to the back piece (i.e., such that the plane of rotation of the cable reel 47 is substantially parallel to a frontal plane of the rescuee 7 ) and/or over a lower back area of the harness (e.g., below the shoulder blades of the user). Alternatively, in some possible embodiments the drum device 5 is mounted over a frontal piece of the harness such that the rotation plane of the cable reel 47 is substantially parallel (or perpendicular) to a frontal plane of the rescuee 7 . Fig. 2 shows a perspective view of the drum device 5 according to some possible embodiments. In this non-limiting example the drum device 5 comprises a cable reel 47 mechanically coupled to an axle (shaft) 60 passing along the axis of rotation 47a of the cable reel 47 . The axle 60 is operably mounted for rotations inside a support structure 45 of the drum device 5 . The support structure 45 comprises two tear-like shaped side cover plates, 45f and 45r , and upper and lower support elements (e.g., rods), 45b and 45a , respectively, fixedly attached at their ends to the cover plates, 45f and 45r . The length of the support elements, 45b and 45a , is configured to define a gap g between the two side cover plates, 45f and 45r , sufficiently wide to accommodate the cable reel 47 and permit free undisturbed rotations thereof inside the support structure 45 . The extremities of the axle 60 are attached to the side cover plates 45f and 45r by bearings 45x allowing it to freely rotate inside the support structure 45 in a plane substantially parallel to the side cover plates. The upper portion of the tear-like shaped support structure 45 includes a cable release mechanism for directing the release of the cable 4 from the drum device 5 and preventing backward movement of the cable 4 into the support structure. In this non-limiting example the cable release mechanism comprises two cable release units, 48 and 49 , accommodated one on top of the other between the upper portions of the cover plates, 45f and 45r . The cable release mechanism 48 and/or 49 is configured and operable to direct the cable release in an outward direction towards a cable release 252166/ - 9 - opening Pc of the drum device 5 , and prevent backward movement of the released cable 4 into the drum device 5 . In this specific and non-limiting example the cable release opening Pc is defined by an opening of the upper cable release unit 48 . As best seen in Fig. 3 , the bottom cable release mechanism 49 comprises two roller shafts rotatably mounted one parallel to the other between, and perpendicular, to the cover plates 45f and 45r . As demonstrated in Fig. 3 , in possible embodiments the bottom cable release mechanism 49 comprises two rollers shafts which may be of different diameters and configured to provide a desired bend radius. For example, and without being limiting, for a cable 4 having a diameter of about 3 mm and a bend diameter of about 32 mm, a first roller shaft 49u of the bottom cable release mechanism 49 may be of a smaller diameter (e.g., about 16 mm) relative to a second roller shaft 49v thereof having a greater diameter (e.g., about 32 mm). The parallel roller shafts 49u and 49v are mounted slightly spaced-apart above the cable reel 47 , leaving a slender gap between them sufficient for passage of the cable 4 therethrough, while contacting the roller shafts and rotating them in predetermined directions due to friction forces evolving therebetween. The parallel roller shafts, 49u and 49v , may be configured to prevent movement of the cable ( 4 ) towards the cable reel 47 (i.e., to prevent the cable from returning back into the support structure 45 ), for example and without being limiting, by using a ratchet mechanism (not shown) configured to prevent rotations of the shaft rollers in a counter direction. Additionally or alternatively, backward movement of the cable 4 into the support structure may be prevented by properly setting the elasticity of the cable 4 to a desired suitable level (e.g., allowing cable deformations to occur when passed between the roller shafts and quick restoration of its shape upon leaving the roller shafts), applying adhesive material(s) between the cable 4 and the roller shafts of the cable release mechanism 49 , and/or by setting friction of the surface of the rollers contacting the cable 4 to a desire suitable level. The upper cable release mechanism 48 comprises two rollers shafts 48s and 48t rotatably mounted one parallel to the other inside a flat frame 48f . In this specific and non-limiting example the roller shafts 48s and 48t of the upper cable release mechanism 48 have substantially the same diameter (e.g., about 16 mm). The frame 48f of the upper cable release mechanism 48 is mounted above the bottom cable release mechanism 49 , between and perpendicular to the cover plates, 45f and 45r . The frame 48f is mounted 252166/ - 10 - inside the support structure 45 in a plane being substantially parallel to a plane in which the shaft rollers 49u and 49v , of the bottom cable release mechanism 49 , reside. As seen in Fig. 3 , in this non-limiting example the axes of rotations of roller shafts 48s and 48t of the upper cable release mechanism 48 are substantially perpendicular to the axes of rotations of the shaft rollers 49u and 49v of the bottom cable release mechanism 49 . The roller shafts 48s and 48t are mounted spaced-apart inside the frame 48f leaving a slender gap between them sufficient for passage of the cable ( 4 ) therethrough, while contacting the roller shafts and rotating them in predetermined directions due to friction forces evolving therebetween. The roller shafts, 48s and 48t , may be configured to prevent movement of the cable ( 4 ) towards the cable reel 47 (i.e., to prevent the cable from moving into the support structure 45 ), using one or more of the techniques described hereinabove with reference to the bottom cable release mechanism 49(e.g., using a ratchet mechanism configured to prevent rotations of the shaft rollers in a counter direction). In some embodiments a fastening element 5s (e.g., shackle), attached to the support structure 45 , is used to fixedly attach the drum device 5 to the harness ( 6 ). The fastening element 5s may be attached to the support structure 45 by a fastening member 5r (e.g., metal ring or holed piece) suitable for attaching the fastening element 5s to the lower support element 45a , while permitting some rotary movement of the fastening element 5s thereabout. Fig. 3 shows the drum device 5without its side cover plate 45f , thus exposing the arrangement of cable reel 47 , and its reel flanges 47f , inside the support structure 45 . Fig. 4 is a sectional view of the drum device, without the covering plate 45f and the reel flange 47f located beside it, thus showing elements mounted inside the cable reel 47 . As best seen in Figs. 5A and 5B , the axle 60 comprises a sun-gear 64 fixedly attached to it, the cover plate 45r comprises a planetary gear system 65 (e.g., comprising three planet-gear wheels) rotatably attached to it, and a ring-gear 67 is formed on a portion of the inner wall 47w of the cable reel 47 adjacent to the cover plate 45r . Each planet-gear 65 , attached over the cover plate 45r free to rotate about its central axis, is mechanically coupled to the sun-gear 64 fixedly mounted on the axle 60 , and to the ring-gear 67 formed on the inner wall 47w of the cable reel 47 . Optionally, and in some embodiments preferably, the planetary gear system 65 is designed to transfer the rotations of the cable reel 47 to the axle 60 during the cable 252166/ - 11 - release and cause counter rotations (i.e., in opposite direction) of the axle 60 in an angular velocity ( Vx in Fig. 6 ) that is greater than the angular velocity ( Vr ) of the cable reel 47 . For example, in use, as the cable 4 is released from the drum device 5 , the cable reel 47 rotates about the rotation axis 47a and the ring-gear 67 formed over the inner wall 47w of the cable reel 47 rotates the planet-gears 65 mechanically coupled to it in the same direction of rotations. In effect, the planet-gears 65 coupled to the sun-gear 64 rotates the axle 60 in a direction opposite to the direction of rotation of the cable reel 47 . Optionally, and in some embodiments preferably, the planetary gear system 65 may be configured and operable to rotate the axle 60 during the cable release and cause counter rotations (i.e., in opposite direction) of the axle 60 in an angular velocity ( Vx in Fig. 6 ) which magnitude is greater than (or equal to) the magnitude of the angular velocity ( Vr ) of the cable reel 47 . For example, and without being limiting, the planetary gear system 65 may be configured to provide a gear ratio of about 1 to 5.3. In possible embodiments the diameter of the ring-gear 67 may be about 140 to 150 mm, the diameter of the planet-gears 65 may be about 50 to 70 mm, and the diameter of the sun-gear 64 may be about 25 to 35 mm. The axle 60 , rod arms 67r , gear elements and cable reel 47 , and other parts of the CDD 9 , may be manufactured from any suitable metallic or plastic type of material capable of withstanding the forces evolving in the device during the descent. For example, and without being limiting, in possible embodiments the brake shoes 62 may be manufactured from Iron, Aluminum, Brass, Stainless Steel, or combinations thereof, the cable reel 47 may be manufactured from Aluminum, plastic, fiberglass reinforced Nylon, or combinations thereof, and the cogwheels of the gear system may be manufactured from any suitable metal or plastic material. The cable 4 may be made from a fireproof material, such as a metal, for example, steel. Alternately it may be made of engineering plastics, such as Kevlar®, carbon fiber, or other high strength cable material. The length of the cable may be about 50-500 meters (m) and having a diameter of about 1 to 4 millimeters mm. For example, and without being limiting, in some possible embodiments: the weight of a drum device and about 50 m of cable may be about 5 kilograms, the weight of a drum device and about 100 m of cable may be about 7.5 kilograms; the weight of a drum device and about 200 m of cable may be about 12 kilograms. The drums device having these weight ranges may be suitable weights for a user to lift and put on his or her back using a CDD according to embodiments of the invention. 252166/ - 12 -

Claims

252166/3- 17 - CLAIMS

1. A drum device for controlled release of a cable spooled therein the drum device comprising:a support structure having a cable release opening for passage of released cable portions therethrough;a circular wheel located inside said support structure and configured and operable to rotate about an axis of rotation thereof, said circular wheel comprising a circular central cavity and an inner wall encircling the cavity;a brake mechanism comprising one or more brake elements mounted to slidably move inside said central cavity, said one or more brake elements being configured and operable to slide towards the inner wall of the wheel encircling said cavity and apply friction forces thereon;a friction enhancement mechanism of said brake mechanism being configured for increasing friction forces responsive to increase in angular velocity of said circular wheel, said friction enhancement mechanism being configured to provide additional engagement between the circular wheel and the brake element and comprising one or more circular rails formed by respective two or more circular grooves and corresponding one or more curved grooves configured to form shoulder structures, each circular groove being configured to receive one of said shoulder structures when said brake element contacts the inner wall, to thereby progressively increase friction between said brake elements and the inner wall of the wheel responsive to increase in angular velocity of the wheel; anda cable-release system configured and arranged to receive released cable portions from the circular wheel and direct the released cable portions in an outward direction towards the cable release opening of the drum device, and prevent backward movement of the released cable into the drum device.

2. The drum device of claim 1 wherein the cable-release system comprises a first cable-release unit mounted above the circular wheel and having a slender opening defined between two rotatable roller shafts thereof for passage of the released cable portions therethrough. 252166/3- 18 -

3. The drum device of claim 2 wherein diameters of the two rotatable roller shafts of the first cable-release unit are different, and wherein the diameter of one of said rotatable roller shafts is set according to a predetermined bend radius of the cable.

4. The drum device of claim 2 or 3 wherein the cable-release system comprises at least one additional cable-release unit having a slender opening defined between two rotatable roller shafts for passage of the released cable portions therethrough, said at least one additional cable-release unit being mounted above and in parallel to the first cable-release unit.

5. The drum device of claim 4 wherein the orientation of the two rotatable roller shafts of the first cable-release unit is perpendicular to orientation of the two rotatable roller shafts of the at least one additional cable-release unit.

6. The drum device of any one of the preceding claims comprising: an axle mounted inside said central cavity of the circular wheel, said axle extending along and rotatable about the axis of rotation inside said central cavity; and two or more parallel shaft rods attached to the axle and extending perpendicular to the axis of rotation inside said central cavity.

7. The drum device of claim 6 comprising a gear system configured and operable to transfer rotations of the circular wheel into counter-rotations of the axle.

8. The drum device of claim 7 wherein the gear system is a planetary gear system configured and operable to rotate the axle during rotation of the wheel in an angular velocity whose magnitude is greater than the magnitude of the angular velocity of the wheel.

9. The drum device of claim 8 wherein the planetary gear system is configured to guarantee a cable release speed of 1 to 2 m/s.

10. The drum device of any one of the preceding claims wherein geometrical shapes of at least one of the curved grooves and of a respective one of the circular rails configured to be received in it, are adapted to progressively increase the friction forces responsive to increase in angular velocity of the wheel. 252166/3- 19 -

11. The drum device of claim 10 wherein at least one of the one or more curved grooves comprises a tapering groove section in which opposing sides of the groove taper towards the axis of rotation, and at least one of the one or more circular rails comprises a corresponding tapering rail section configured to be received inside said tapering groove section.

12. The drum device of any one of the preceding claims wherein the spooled cable is configured to be anchored to an external support by a free end of said cable, and wherein said drum device is configured and operable to be harnessed to a descending user for guaranteeing continuous descent of the user while preventing suspension trauma.

13. A controlled descent device comprising:a wearable harness;a drum device comprising a spooled cable and a brake mechanism configured to regulate speed of release of the cable from the drum device, said brake mechanism comprising a circular wheel having a circular central cavity and configured to rotate about an axis of rotation thereof and one or more brake elements configured for sliding motion inside said central cavity towards the inner wall of the wheel encircling said cavity;a friction enhancement mechanism of said brake mechanism being configured for increasing friction forces responsive to increase in angular velocity of said circular wheel, said friction enhancement mechanism being configured to provide additional engagement between the circular wheel and the brake elements and comprising one or more circular rails formed by respective two or more circular grooves and corresponding one or more curved grooves configured to form shoulder structures, each circular groove being configured to receive one of said shoulder structures when said brake element contacts the inner wall, to thereby progressively increase friction between said brake elements and the inner wall of the wheel responsive to increase in angular velocity of the wheela cable release opening for passage of portions of the released cable therethrough; anda cable-release system configured and arranged to receive the portions of the cable from the cable release opening and direct the released cable portions in an 252166/3- 20 - outward direction from the cable release opening of the drum device, and prevent backward movement of the released cable into the drum.

14. The controlled descent device of claim 13 wherein the cable-release system comprises a first cable-release unit mounted above the circular wheel and having a slender opening defined between two rotatable roller shafts thereof for passage of the released cable portions therethrough.

15. The controlled descent device of claim 14 wherein diameters of the two rotatable roller shafts of the first cable-release unit are different, and wherein the diameter of one of said rotatable roller shafts is set according to a predetermined bend radius of the cable.

16. The controlled descent device of claim 14 or 15 wherein the cable-release system comprises at least one additional cable-release unit having a slender opening defined between two rotatable roller shafts for passage of the released cable portions therethrough, said at least one additional cable-release unit being mounted above and in parallel to the first cable-release unit.

17. The controlled descent device of claim 16 wherein the orientation of the two rotatable roller shafts of the first cable-release unit is perpendicular to orientation of the two rotatable roller shafts of the at least one additional cable-release unit.

18. The controlled descent device of any one of claims 13 to 17 wherein said brake mechanism comprises: an axle extending along and rotatable about said axis of rotation inside said central cavity; two or more parallel shaft rods attached to the axle and extending perpendicular to the axis of rotation inside the cavity; a gear system configured to transfer rotations of said wheel into counter-rotations of said axle; wherein the one or more brake elements are mounted on said two or more parallel shaft rods, each brake element having two or more pass-through bores for slidably moving along said two or more parallel shaft rods inside said central cavity, and two or more springs mounted over at least one of said shaft rods between the brake element and the axle, said one or more brake elements being configured and operable to radially slide over the parallel shaft rods towards the inner wall of the wheel encircling said cavity in response to the counter-rotations of said axle.