Fall-protection apparatus comprising multi-stage friction brake

Abstract

A multi-stage friction brake assembly that includes a primary rotor and a secondary rotor that is rotatable relative to the primary rotor. The primary and secondary rotors are configured so that in ordinary use of the multi-stage brake assembly, the secondary rotor remains in a first rotational position relative to the primary rotor. The primary and secondary rotors are further configured so that if a rotational force above a predetermined threshold is encountered, the secondary rotor will rotate relative to the primary rotor through a predetermined rotational travel distance. The multi-stage friction brake assembly may be installed in a fall-protection apparatus.

Description

[0001] FALL-PROTECTION APPARATUS COMPRISING MULTI-STAGE FRICTION BRAKE ASSEMBLY

[0002] Background

[0003] Fall-protection apparatus such as e.g. self-retracting lifelines have often found use in applications such as building construction and the like.

[0004] Summary

[0005] In broad summary, herein is disclosed a multi-stage friction brake assembly that comprises a primary rotor and a secondary rotor that is rotatable relative to the primary rotor. The primary and secondary rotors are configured so that in ordinary use of the multi-stage friction brake assembly, the secondary rotor remains in a first rotational position relative to the primary rotor. The primary and secondary rotors are further configured so that if a rotational force above a predetermined threshold is encountered, the secondary rotor will rotate relative to the primary rotor through a predetermined rotational travel distance. In some embodiments, the multi-stage friction brake assembly may be installed in a fall-protection apparatus such as a self-retracting lifeline. These and other aspects will be apparent from the detailed description below. In no event, however, should this broad summary be construed to limit the claimable subject matter, whether such subject matter is presented in claims in the application as initially filed or in claims that are amended or otherwise presented in prosecution.

[0006] Brief Description of the Drawings

[0007] Fig. 1 is a perspective view of an exemplary fall-protection apparatus in which a multi-stage friction brake assembly as disclosed herein may be installed.

[0008] Fig. 2 is a perspective exploded view of various components of an exemplary fall-protection apparatus.

[0009] Fig. 3 is a perspective exploded view of various additional components of an exemplary fallprotection apparatus.

[0010] Fig. 4 is an perspective exploded view of various components of an exemplary multi-stage friction brake assembly of the fall-protection apparatus of Fig. 3.

[0011] Fig. 5 is a side view of various components of the exemplary multi-stage friction brake assembly of Fig. 4.

[0012] Fig. 6 is a perspective view of various components of the exemplary multi-stage brake assembly of Fig. 4, with a secondary rotor of the multi-stage friction brake assembly in a first rotational position relative to a primary rotor of the multi-stage friction brake assembly.

[0013] Fig. 7 is a perspective view of various components of the exemplary multi-stage friction brake assembly of Fig. 4, with a secondary rotor of the multi-stage friction brake assembly in a second rotational position relative to a primary rotor of the multi-stage friction brake assembly.

[0014] Fig. 8 is a perspective exploded view of various components of another exemplary fall-protection apparatus comprising a multi-stage friction brake assembly. Fig. 9 is a perspective exploded view of various components of an exemplary friction multi-stage brake assembly of the fall-protection apparatus of Fig. 8.

[0015] Fig. 10 is a side view of various components of the exemplary multi-stage friction brake assembly of Fig. 9.

[0016] Fig. 11 is a perspective view of various components of the exemplary multi-stage friction brake assembly of Fig. 9, with a secondary rotor of the multi-stage friction brake assembly in a first rotational position relative to a primary rotor of the multi-stage friction brake assembly.

[0017] Fig. 12 is a perspective view of various components of the exemplary multi-stage friction brake assembly of Fig. 9, with a secondary rotor of the multi-stage friction brake assembly in a second rotational position relative to a primary rotor of the multi-stage friction brake assembly.

[0018] Like reference numbers in the various figures indicate like elements. Some elements may be present in identical or equivalent multiples; in such cases only one or more representative elements may be designated by a reference number but it will be understood that such reference numbers apply to all such identical elements. Unless otherwise indicated, all figures and drawings in this document are not to scale and are chosen for the purpose of illustrating different embodiments of the invention. In particular the dimensions of the various components are depicted in illustrative terms only, and no relationship between the dimensions of the various components should be inferred from the drawings, unless so indicated. Although terms such as “front”, “back”, “outward”, “inward”, and “first” and “second” may be used in this disclosure, it should be understood that those terms are used in their relative sense unless otherwise noted.

[0019] As used herein as a modifier to a property or attribute, the term “generally”, unless otherwise specifically defined, means that the property or attribute would be readily recognizable by a person of ordinary skill but without requiring a high degree of approximation (e.g., within + / - 20 % for quantifiable properties). The term “configured to” and like terms is at least as restrictive as the term “adapted to”, and requires actual design intention to perform the specified function rather than mere physical capability of performing such a function.

[0020] Detailed Description

[0021] Disclosed herein is a multi-stage friction brake assembly. In many embodiments, such an assembly can be installed in, and used as a component of, a fall-protection apparatus, by which is meant an apparatus that acts to controllably decelerate a human user of the apparatus in the event of a user fall. In many embodiments, such a fall-protection apparatus is a self-retracting lifeline (SRL). By this is meant a deceleration apparatus that comprises a housing containing a drum-wound safety line that can be automatically extended from the housing and retracted into the housing during ordinary movement of a human user of the apparatus, and which, upon a user fall, automatically actuates a brake assembly that arrests the fall of the user.

[0022] An exemplary fall-protection apparatus 1 of the self-retracting lifeline type is depicted in Fig. 1 with portions of the apparatus being shown in exploded view in Figs. 2 and 3. Exemplary apparatus 1 has a housing 2 comprising a major housing piece 11 and first and second housing covers 12 and 22 that are assembled and fastened together. Any such pieces, covers, and other components of apparatus 1 may be fastened together e.g. by bolts or by any other suitable fasteners. In some embodiments, housing 2 may be load-bearing; in some embodiments, a load-bearing bracket or similar component may be present and may provide at least a portion of a load-bearing path of the apparatus. In some embodiments, housing 2 may comprise a connector 7 (e.g. a cab-mount bracket or the like) configured so that housing 2 can be connected to a secure anchorage.

[0023] The exemplary fall-protection apparatus 1 as shown in Figs. 1-3 is configured so that housing 2 defines two main interior portions 14 and 24 as indicated respectively in Figs. 2 and 3. In the depicted embodiment, a first main interior portion 14, shown in Fig. 2, houses a drum 15 with a proximal end 6 of a safety line 4 connected thereto. In some embodiments, a distal end 5 of safety line 4 may comprise a connector 3 (e.g. a gated hook, carabiner, etc.) configured to be attached e.g. to a fall-protection safety harness worn by a user of the fall-protection apparatus. In the depicted embodiment, a second main interior portion 24, shown in Fig. 3, houses a motor spring 30 for biasing drum 15 in a winding direction as discussed below, along with a friction brake assembly 100, a ratchet 25, and other associated components. A shaft 31 upon which drum 15 and friction brake assembly 100 are mounted, extends through both of the main interior portions 14 and 24 of housing 2 and is rotatably mounted in housing 2 (various bearings 18 and 28 may facilitate the rotatable mounting of shaft 31). Other components (e.g. one or more isolation discs 27 and 29, gaskets 13 and 23, and so on) may be present. It is noted that various components such as e.g. one or more nuts, bolts, screws, shafts, washers, bushings, gaskets, retainers, labels, and the like, are omitted from the Figures herein for ease of presentation of items of main interest; ordinary artisans will readily appreciate that any such items may be present as needed for the functioning of apparatus 1.

[0024] Ordinary artisans will appreciate that the exemplary fall-protection apparatus 1 depicted in Figs. 1-

[0025] 3 is a type of fall-protection apparatus often referred to as a “sealed-block” self-retracting lifeline, in which a partitioned arrangement (in particular, including a seal 19 that is resistant to oil and water) is used so that the second, brake-side interior portion 24 of the housing is isolated from the first, drum-side interior portion 14 of the housing. Fall-protection apparatus of this general type are often used in environments that are subject to contamination by moisture, grease, dust, and so on, as discussed e.g. in U.S. Patent 9925400. However, it is emphasized that a multi-stage friction brake assembly as disclosed herein can be used with any type of fall-protection apparatus; it is not limited to being used with a “sealed-block” self-retracting lifeline.

[0026] As noted above, apparatus 1 will comprise a drum 15, upon which is wound a length of safety line

[0027] 4 (with the term line broadly encompassing any elongated windable load-bearing member, including e.g. webbing, cable, rope, etc., made of any suitable synthetic or natural polymeric material, metal, etc., or any combination thereof). In the illustrated embodiment, drum 15 comprises a main body 16 and a sidewall 17, which, when joined to the main body, defines a space within which safety line 4 can be received and spiralwound. A proximal end 6 of safety line 4 is connected to drum 15. In various embodiments, such a drum (e.g. a main body and / or flange thereof) may be made of metal (e.g. machined or cast metal), molded plastic, or any other suitable material. In some embodiments such a drum may be made of a single unitary piece of material, which may be e.g. a molded polymeric piece or a machined or cast metal piece. Drum 15 is non- rotatably mounted on shaft 31, e.g. by way of a key 33 which resides in suitable cavities provided in drum 15 and shaft 31 for this purpose.

[0028] Various items, features and geometric relationships of fall-protection apparatus 1 and components thereof will be described herein in relation to the axial direction of the apparatus. By axial is mean a direction generally aligned with the long axis of shaft 31 upon which drum 15, motor spring 30, friction brake assembly 100, and so on, are mounted. By axially inward is meant a direction toward the axially centermost region of the apparatus; by axially outward is meant an opposing direction, i.e. toward the walls of the housing of the apparatus. The axial direction (A), and axially inward and outward directions (i and o), are denoted in various Figures. Various items, features and geometric relationships are also described in relation to a radial direction, by which is meant any direction perpendicular to the axial direction as established by shaft 31. Various items, features and geometric relationships are also described in relation to unwind and wind directions. By an unwind direction is meant a direction that drum 15, shaft 31, friction brake assembly 100, and associated components will rotate when safety line 4 is unwound from drum 15 (i.e., the direction that such items rotate in the event of a fall). The unwind direction (U) is denoted in various Figures. A wind direction is the opposite direction, i.e. the direction that such items turn when safety line 4 is wound upon drum 15. Terms such as leading and trailing are also used and are straightforwardly associated with the unwind direction and the wind direction.

[0029] Apparatus 1 comprises a brake assembly 100 as noted above. By a brake assembly is meant an assembly that is configured to arrest the rotation of a drum upon rotation of the drum above a predetermined threshold value of speed and / or acceleration. With reference to Fig. 4, such a brake assembly may rely on one or more pawls 111 that are disposed on a pawl-support plate 121 that is rotatably mounted on a brake hub 101. Brake hub 101 is non-rotatably mounted on shaft 31, e.g. by way of a key 32 which resides in suitable cavities provided in brake hub 101 and shaft 31 for this purpose. Pawl 111 will be biased so that in ordinary use of the fall-protection apparatus, an engaging end 112 of pawl 111 is urged into, and maintained in, a disengaged position in which it does not engage with any component (e.g. a ratchet tooth) that would limit the rotation of drum 15. (In the depicted embodiment, this biasing is performed by use of a biasing spring 113 having one end 114 attached to pawl 111 and a second, opposing end 114 is attached to pawlsupport plate 121).

[0030] Such an arrangement allows drum 15 to rotate (relatively slowly) back and forth in an unwind direction and a wind direction to automatically extend and retract safety line 4 in response to ordinary movements of a user to which the distal end 5 of the safety line is connected. During this use, pawl 111 will remain in its disengaged position. If drum 15 begins to rotate in the unwind direction above a predetermined value of velocity and / or acceleration (e.g. in the event of a user fall), pawl 111 will be motivated (overcoming the biasing force of spring 113) to an engaged position in which an engaging end 112 of the pawl engages a tooth 26 of a ratchet 25, which causes the rotation of the drum to be slowed or stopped as discussed in detail later herein.

[0031] In many embodiments, pawl 111 will be configured so that centrifugal force provides the motivation for the pawl to move to an engaged position. In many embodiments, pawl 111 may be pivotally disposed (e.g. on a pawl-support plate 121) so as to be able to pivotally move between a disengaged position and an engaged position. In some embodiments, pawl 111 will be configured so that the engaging end 112 of the pawl moves generally radially outward in moving from a disengaged position to an engaged position. Various parameters (e.g. the weight, shape, position and / or orientation of the pawl(s), the spring constant of the biasing spring(s), and so on) may be chosen so that the engaging of the pawl(s) with a ratchet occurs at a predetermined rotational velocity and / or acceleration of the drum.

[0032] In some embodiments, a pawl 111 may be attached to a pawl-support plate. In other embodiments pawl 111 may not be attached to a pawl-support plate but rather may simply be held in place in the desired location. For example, in the depicted embodiment of Fig. 4, each pawl 111 includes a pawl-stem 116 that is seated in a receiving aperture 123 of pawl-support plate 121. Such a pawl can be maintained in position by being axially sandwiched between the pawl-support plate 121 on one axial side of the pawls and by some other component (e.g. an interior surface of housing 2, or a surface of some item provided for that purpose) on the other axial side of the pawls. In some embodiments, receiving apertures 123 may be slightly elongated in the winding / unwinding direction as evident in Fig. 4, e.g. for reasons discussed in U.S. Patents 4877110 and 9925400, which are incorporated by reference in their entirety herein.

[0033] A brake assembly as disclosed herein can operate in concert with any suitable ratchet 25 that presents at least one tooth 26 that can be engaged by an engaging end 112 of a pawl 111. Such a ratchet may be made of any material that exhibits sufficient strength to withstand the forces that develop in the engaging / braking process; in some embodiments such a ratchet may be comprised of stainless steel, e.g. chosen from the 300 Series (austenitic) category of stainless steel. In some embodiments such a ratchet may be a separately-made component that is installed in, and non-movably (i.e., non-rotatably) affixed to, housing 2 of the apparatus, as in the exemplary arrangement depicted in Fig. 3. In some embodiments, a ratchet may be provided as an integral feature of the housing itself (e.g. a housing may be produced by injection molding, with features that will provide a ratchet being formed in the housing in the process of molding the housing).

[0034] Brake assembly 100 as disclosed herein is a friction brake assembly. A friction brake assembly will, when actuated, bring a safety -line-bearing drum to a halt in a relatively gradual manner by way of frictional forces as described in detail below. This canbe contrasted to brake assemblies that, when actuated, bring a drum to a halt in a near-instantaneous manner, and that consequently typically rely on a so-called shock absorber (e.g. a tear web or tear strip that is incorporated into the safety line) to minimize the force experienced by a user as the user is brought to a halt. (Fall-protection apparatus comprising brake assemblies that do not include a friction brake and that bring a drum to a near-instantaneous halt are disclosed e.g. in U.S. Patent 9488235.) A friction brake assembly will comprise at least one layer (often, several layers) of friction material that provides the frictional forces that cause the braking action. Such a layer of friction material will be referred to herein as a brake pad; a major surface of such a layer (that provides the actual frictional interface) will be termed a frictional surface. A brake pad may be made of any suitable material; various materials which may be suitable are disclosed and discussed in U.S. Patent 11504557, which is incorporated by reference in its entirety herein. Typically, a brake pad will be supported by a brake pad support (e.g. a rigid metal plate to which the brake pad is permanently affixed by adhesive bonding); the combination of one or more brake pads and a brake pad support will be referred to herein as a brake pad subassembly. In some embodiments, at least one brake pad of a friction brake assembly may not necessarily be fixedly attached to a brake pad support, but rather may simply be held in place by the axially -compressive forces.

[0035] A friction brake assembly will further comprise at least one rotor, meaning an item that has a platelike portion with a planar area that provides a surface (often, a rotor will have two such surfaces, in opposing relation) that a frictional surface of a brake pad is in constant contact with. Such a surface of a rotor will be termed a friction surface. It will be understood that language herein such as a brake pad being abutted against a rotor denotes that the frictional surface of the brake pad is pressed against the friction surface of the rotor. In the depicted embodiment of Figs. 2-5, the above-described pawl-support plate 121 serves as a rotor, which can be a convenient arrangement; however, it will be understood that a rotor does not necessarily have to serve as a pawl-support plate, nor does a pawl-support plate necessarily have to serve as a rotor. Thus for example, a pawl-support plate may be used in conjunction with a rotor that is separate from the pawl-support plate but is e.g. connected or otherwise coupled to the pawl-support plate so that the rotor is non-rotatable relative to the pawl-support plate.

[0036] A rotor of a friction brake assembly will have one or more brake pads abutted against it; in many embodiments, a rotor may be sandwiched between two brake pads. The abutting of the brake pad against the rotor provides sufficient static frictional holding power that as a human user moves in ordinary use of the apparatus (so that the drum, shaft, etc. rotate at a relatively slow speed) there is no relative motion or slippage between the brake pad(s) and the rotor(s). However, upon a fall event that causes the engaging of a pawl with a ratchet as described above, sufficient differential torque can be generated to overcome the static frictional force, such that relative motion of the brake pad and the rotor occurs. In some embodiments, this may occur by way of a rotor that is in the form of a pawl-support plate, being brought to a near- instantaneous stop while the brake pad (and thus the shaft, drum, etc.) continues to rotate relative to the stopped rotor. This relative rotation will be slowed and / or brought to a halt by the frictional forces between the frictional surface of the brake pad and the friction surface of the rotor. The slowing of this relative rotation will serve to slow (e.g. halt) the rotation of a drum bearing a safety line in a gradual manner. (Even this gradual arresting of dmm rotation will still occur relatively quickly, e.g. in less than a second.) The above description is phrased in terms of a single brake pad and rotor; however, it will be understood that in many cases, multiple brake pads and / or rotors will be used. With reference to the exemplary arrangement of Figs. 2-7, drum 15 is non-rotatably fixed to shaft 31 (e.g. by way of key 33) so drum 15 and shaft 31 will rotate in lockstep with each other. Brake hub 101 of brake assembly 100, likewise being non-rotatably fixed to shaft 31 (e.g. by way of key 32), will likewise rotate in lockstep with shaft 31. The various brake pads, all being provided as brake pad subassemblies in which the brake pads are fixedly attached to brake pad supports that are non-rotatably mounted on brake hub 101 , will likewise rotate in unison with brake hub 101 and thus with shaft 31.

[0037] Certain other components of brake assembly 100 (in particular, pawl-support plate 121) are not non-rotatably fixed to shaft 31 (or to any item that is non-rotatably fixed thereto) in the manner of drum 15 and brake hub 101. However, in ordinary use of apparatus 1, these components of brake assembly 100 (in particular, pawl-support plate 121, which in this instance will serve as a rotor, as discussed in detail below) will be frictionally constrained by the various brake pads so that these components likewise rotate in lockstep with shaft 31, drum 15, and brake hub 101 and the brake pads thereon.

[0038] In the event of a user fall, at least one pawl 111 is urged into an engaged position in which it engages with a tooth 26 of ratchet 25, causing pawl-support plate 121 to be brought to a near-instantaneous full stop. (In other words, pawl-support plate (rotor) 121 will cease rotating and will now be stationary with reference to housing 2.) However, the frictional forces exerted by the brake pads on the pawl-support plate (rotor) will not be sufficient to prevent the brake pads from slipping relative to pawl-support plate 121 under the forces that develop from the user fall. This slippage will allow the brake pads, brake hub 101, shaft 31, and dmm 15, to continue to rotate to a limited extent until the frictional forces exerted by the brake pads on the pawl-support plate bring them all to a halt. This will typically be accomplished within only a few rotations (e.g., less than one full rotation) of drum 15, which serves to bring the falling user to a halt as quickly as possibly without subjecting the user to high fall-arrest forces.

[0039] The specific exemplary friction brake assembly 100 as depicted in Figs. 3-7 will now be described in further detail. Friction brake assembly 100 comprises a brake hub 101 that has an axially-extending stem 107 with a cross-sectional shape (when viewed along the axial direction) that is a symmetrically -truncated circle with two opposing arcuate sections 102 that are co-circular with radially -outward surfaces of axially - outward portions of the two opposing arcuate sections being threaded to accept a locknut 105. Stem 107 further comprises two opposing flat sections 103. An axially -inward end of brake hub 101 comprises a flange 104.

[0040] Friction brake assembly 100 comprises a first brake pad subassembly 151 that comprises a first brake pad 152 that is immovably fixed (e.g. by adhesive bonding) to a major surface of a first brake pad support 154. As evident from Fig. 4, brake pad support 154 comprises a central through-opening 155 whose shape is complementary with the symmetrically-truncated circular cross-sectional shape of stem 107 of brake hub 101, so that brake pad support 154, thus first brake pad 152 and brake pad subassembly 151 as a whole, is non-rotatable with respect to brake hub 101 and thus with respect to shaft 31 and dmm 15. An axially -inward surface of brake pad support 154 abuts an axially -outward face of flange 104 of brake hub 101, and an axially -outward frictional surface 153 of brake pad 152 is abutted against an axially -inward friction surface 128 of pawl-support plate (rotor) 121. The axially-inward side of brake pad support 154, that faces flange 104 of brake hub 101, thus does not comprise a brake pad; brake pad subassembly 151 is thus a “single-sided” brake pad subassembly The axially-outward frictional surface of brake pad 152 is denoted by reference number 153 in Fig. 4; other brake pads will have similar frictional surfaces but these are not denoted by reference numbers in the Figures herein.

[0041] Proceeding in an axially outward direction, the next item that is mounted on brake hub 101 is pawlsupport plate 121, which, as noted above, also serves as a rotor. Pawl-support plate 121 comprises an axially-inward friction surface 128 as noted above, and similarly comprises an axially-outward friction surface 129. Pawl-support plate 121 comprises two slots 123 configured to accept stems 116 of pawls 111. Each pawl 111 comprises an engaging end 112 as described earlier; biasing springs 113 are provided, with a first end 114 of biasing spring 113 being connected to pawl 111 at a location near the engaging end 112 of pawl 111 and with a second, opposing end 115 of biasing spring 115 being connected to pawl-support plate 121. This is facilitated by pawl-support plate 121 being provided with two flanges 124 in generally radially -opposing locations. Each flange 124 includes a portion that extends in a generally axially-outward direction and that includes one or more connection features 125 (in the depicted arrangement, orifices) to which end 115 of biasing spring 113 can be connected. Pawl-support plate (rotor) 121 comprises a central through-opening 122 that is circular so that pawl-support plate 121 (in contrast to brake pad subassembly 151 and to other brake pad subassemblies described below) is able to rotate relative to stem 107 of brake hub 101.

[0042] Proceeding in an axially outward direction, the next item that is mounted on brake hub 101 is a second brake pad subassembly 161. Brake pad subassembly 161 comprises a second brake pad support 164 that is configured (i.e., comprises a shaped central through-opening 165) to be non-rotatably mounted on brake hub stem 107 in similar manner as described above for first brake pad support 154. Brake pad subassembly 161 comprises a second brake pad 162 that is immovably fixed to an axially-inward major surface of second brake pad support 164, and a third brake pad 163 that is similarly fixed to an axially- outward major surface of second brake pad support 164. (Second brake pad subassembly 161 is thus a “double-sided” brake pad subassembly.) Second brake pad 162 is abutted against the above-mentioned axially-outward friction surface 129 of pawl-support plate (rotor) 121. Pawl-support plate (rotor) 121 is thus sandwiched between first and second brake pads 152 and 162. In order for item 121 to serve as both a pawl-support plate and as a rotor, second brake pad subassembly 161 is configured (i.e., sized and shaped) so that all components of second brake pad subassembly 161 are positioned radially inward of pawls 111, biasing springs 113, etc., so that brake pad subassembly 161 does not interfere with the functioning of the pawls.

[0043] Continuing in an axially outward direction, the next item that is mounted on brake hub 101 is a rotor 141. Rotor 141 will be termed a “secondary” rotor, with the above-described pawl-support plate (rotor) 121 being termed a “primary” rotor. Secondary rotor 141 comprises a central through-opening 142 that is circular, so that secondary rotor 141 is able to rotate relative to brake hub 101. Secondary rotor 141 comprises a first, axially-inward-facing friction surface 148 that is abutted by the above-described third brake pad 163, and comprises a second, axially -outward-facing friction surface 149. Secondary rotor 141 comprises first and second generally radially -outwardly -extending tabs 143 and 144 whose function will be described in detail below. In the depicted embodiment, tabs 143 and 144 differ slightly in size; however, this is not required. In various embodiments, such tabs may be identical or each may be individually configured as desired.

[0044] Continuing in an axially outward direction, the next item that is mounted on brake hub 101 is a third brake pad subassembly 171. Brake pad subassembly 171 comprises a third brake pad support 174 that is configured (i.e., comprises a shaped central through-opening 175) to be non-rotatably mounted on brake hub stem 107 in similar manner as described above for first and second brake pad supports 154 and 164. Brake pad subassembly 171 comprises a single, fourth brake pad 172 that is immovably fixed to an axially- inward major surface of third brake pad support 174. (Third brake pad subassembly 171 is thus a singlesided brake pad subassembly.) Fourth brake pad 172 is abutted against the above-mentioned axially- outward-facing friction surface 149 of secondary rotor 141. Secondary rotor 141 is thus sandwiched between third and fourth brake pads 163 and 172.

[0045] The final items that are mounted on brake hub 101 are locknut 105 and Belleville washer 106. These items are configured so that when locknut 105 is threadably tightened onto threaded portions 102 of stem 107 ofbrake hub 101, the entire “stack” of primary and secondary rotors, and brake pad subassemblies, is held in axial compression. The amount of axial compression can be controlled by the degree to which the locknut is tightened, and can be set to provide the desired frictional braking force. In general, the braking force may be chosen so that the fall of a human user will be arrested within a suitably short time and / or within a suitably short distance of falling, while not subjecting the user to undesirably high fall-arrest forces. The particular configuration (e.g. the specific frustoconical shape, stiffness of the material of construction, etc.) of the Belleville washer can be chosen to operate in combination with the locknut as desired. In some situations, a stack of multiple (e.g., two, three, or more) Belleville washers may be used. In many embodiments a threaded locknut may be convenient; however, in general, any suitable fastener that can achieve the desired axial compression (alone or in combination with some other entity such as a Belleville washer) may be used.

[0046] Multi-stage friction brake assembly

[0047] Friction brake assembly 100 as disclosed herein is a multi-stage friction brake assembly. This is achieved by configuring secondary rotor 141 to be rotatable relative to pawl-support plate (primary rotor) 121. That is, rotors 121 and 141, respectively comprising central through-openings 122 and 142 that are circular, are not non-rotatably mounted on stem 107 ofbrake hub 101 but rather are able to rotate relative to brake hub 101 and thus relative to each other. In ordinary use of apparatus 1 and of multi-stage friction brake assembly 100, secondary rotor 141 will be in a first, “home” rotational position relative to primary rotor 121. (The rotational position of secondary rotor 141 relative to primary rotor 121 can most easily be evaluated by examining the position of tabs 143 and 144 of secondary rotor 141 in relation to the flanges 124 of primary rotor 121.)

[0048] Secondary rotor 141 is shown in the home rotational position in the side view of Fig. 5 and in the perspective view of Fig. 6; secondary rotor 141 is also in the home position in the exploded view of Fig. 4. (The locknut, pawls and springs are omitted from Figs. 5-7 so that various other items can be more easily viewed.) Secondary rotor 141 will remain in the home position in ordinary use of apparatus 1, with multistage friction brake assembly 100, in particular the primary and secondary rotors 121 and 141 and all brake pads thereof, rotating back and forth in lockstep with dmm 15 and shaft 31 as a user of apparatus 1 moves about. In the event of a user fall, drum 15 (and thus shaft 31 and the rotors and brake pad subassemblies) will rotate rapidly in the unwind direction causing a pawl 111 to engage a ratchet 25 thus bringing the rotation of primary rotor (pawl-support plate) 121 to a near-instantaneous halt. If the resultant forces are sufficiently high, first and second brake pads 152 and 162 will slip relative to primary rotor 121, so that these brake pads, their respective brake pad subassemblies, brake hub 101, shaft 31, and dmm 15, will all continue to rotate in the unwind direction.

[0049] During this first stage of the friction-braking operation, secondary rotor 141, being sandwiched between brake pads 163 and 172 and held in axial compression by these brake pads, will likewise rotate in the unwind direction in lockstep with brake hub 101, primary rotor 121, and so on, since there is nothing to impede secondary rotor 141 from rotating along with brake pads 163 and 172 between which it is held. So, during this first stage of friction-braking, third and fourth brake pads 163 and 172 will not contribute any frictional forces to the braking action since these brake pads are rotating in unison with secondary rotor 141. Rather, during this first stage, the only friction-braking is provided by the frictional action of first and second brake pads 152 and 162 on primary rotor 121.

[0050] In some instances, the frictional action of the first and second brake pads 152 and 162 on primary rotor 121 may be sufficient to fully arrest a user fall without secondary rotor 141 playing any part in the frictional braking operation. In such a case, secondary rotor 141 may, e.g., remain its first, home position relative to primary rotor 121 during the fall arrest.

[0051] However, in some instances (e.g. in the event of higher fall-arrest forces being developed) secondary rotor 141 may, e.g. during a latter portion of the first stage of the braking operation, move from its first, home position, through a predetermined rotational travel distance relative to primary rotor 121 to a second position, at which second position secondary rotor 141 is brought to a full stop relative to primary rotor 121. This rotational movement of secondary rotor 141 away from its first, home position toward its second position is indicated by arrows 181 of Fig. 6; secondary rotor 141 is shown in the second rotational position in Fig. 7.

[0052] In the exemplary arrangement depicted in Figs. 4-6, the stopping of secondary rotor 141 in its second rotational position is achieved by way of a contact surface 145 of a contact member (in this case, tab 143 and / or 144) of secondary rotor 141, moving (relative to primary rotor 121) along a rotation path until contact surface 145 impinges on, and is brought to a halt by, a stop surface 127 of primary rotor 121. In the depicted embodiment, this is achieved by providing an above-described flange 124 of primary rotor 121 with a stop member 126. Stop member 126 extends generally axially outward so that stop surface 127 of primary rotor 121 lies in the plane of rotation of contact surface 145 of secondary rotor 141 as secondary rotor 141 rotates relative to primary rotor 121. Tab 143 and / or tab 144 of secondary rotor 141 can similarly serve as a contact member that provides a contact surface 145.

[0053] During the first stage of friction-braking, any rotational movement of secondary rotor 141 relative to primary rotor 121 (as well as the “absolute” rotation of secondary rotor relative to the entire apparatus) will be the unwind direction. Accordingly, contact surface 145 of secondary rotor 141 faces generally in the unwind direction. Stop surface 127 of primary rotor 121 faces in the wind direction so that it can be impinged on by contact surface 145 of secondary rotor 141.

[0054] Once a contact surface 145 of secondary rotor 141 has impinged on a stop surface 127 of primary rotor 121, secondary rotor 141 is now physically blocked from rotating any further in the unwind direction relative to primary rotor 121. The rotation of secondary rotor 141 relative to primary rotor 121 is thus brought to a halt. This initiates a second stage of the friction-braking operation, in which secondary rotor 141 has come to a full stop relative to primary rotor 121 (and in which primary rotor 121 remains at a full stop relative to the overall apparatus) but in which third and fourth brake pads 163 and 172 continue to rotate in lockstep with brake hub 101, shaft 31 , drum 15 , and first and second brake pads 152 and 162. The continued rotation of these items will be opposed by the frictional forces between brake pads 163 and 172 and friction surfaces 148 and 149 of secondary rotor 141. So, in this second stage of the friction-braking operation, frictional forces applied to secondary rotor 141 by third and fourth brake pads 163 and 172 will operate in addition to, and in combination with, frictional forces applied to primary rotor 121 by first and second brake pads 152 and 162 (which will continue to be applied during this second stage of the frictionbraking). The user fall will thus be arrested by the combined frictional forces of all of these items.

[0055] An ongoing need in fall-protection lies in the fact that many conventional friction brakes do not provide a braking force that is uniform over the duration of the braking operation. Rather, the braking force may vary considerably over the duration of the braking operation and in particular may exhibit an initial peak or spike in braking force that is substantially higher than the braking force during subsequent portions of the braking operation. Consequently, it has sometimes been necessary to configure friction brakes so that the average braking force over the duration of the braking operation is lower than might otherwise be desired (e.g. in order to achieve an arrest distance that is as small as possible), in order to ensure that the initial, peak braking force remains below a desired level.

[0056] A multi-stage friction brake assembly as disclosed herein can allow a first, initial stage of braking that relies only on the frictional action of a first set of brake pads on a primary rotor. In some instances, this may be sufficient to entirely arrest a user fall. However, in some instances, a second, subsequent stage of braking may commence in which the frictional action of an additional set of brake pads on a secondary rotor is used in combination with the frictional action of the first set of brake pads on the primary rotor. This temporal delay in the onset of the maximum possible frictional braking can allow a high level of frictional braking to be achieved when needed, without developing a high initial braking peak. Such arrangements can enable a fall-protection apparatus to be compatible with a wider range of fall-arrest conditions and in particular may allow a fall-protection apparatus to be compatible with users of a wider variety of weights, with a wider variety of safety-line lengths, and so on.

[0057] A multi-stage friction brake assembly of the general type described herein can be arranged in any suitable manner. One parameter of interest is the amount of rotational travel that a secondary rotor will undergo in rotating from the first, home position to the second position, which will be referred to as an “activated” position of the secondary rotor. (This rotational travel is relative to the primary rotor and should not be confused with the overall rotation of the entire brake assembly.) This amount of rotational travel (characterized in degrees) can be any suitable amount, e.g. up to nearly a full rotation of 360 degrees. However, the present investigations have revealed that even a relatively short temporal delay between the start of the first stage of the frictional braking and the start of the second stage of the frictional braking may be sufficient to substantially mitigate any initial peak in braking force. So, a large amount of rotational travel may not be necessary. Accordingly, in some embodiments a multi-stage friction brake assembly may be configured so that the amount of rotational travel that a secondary rotor undergoes in moving from a first, home position to a second, activated position, can be less, e.g. considerably less, than 360 degrees.

[0058] Thus in various embodiments, a multi-stage friction brake assembly may be configured so that the amount of rotational travel of a secondary rotor relative to a primary rotor in moving from a first, home position to a second, activated position, is less than 270, 180, 90, 60, 40, 30, or 25 degrees. In further embodiments, a multi-stage friction brake assembly may be configured so that this amount of rotational travel is at least 5, 10, 15, or 20 degrees.

[0059] The upper limit on the amount of rotational travel that the secondary rotor can undergo can be established when the multi-stage friction brake assembly is assembled. (This will occur in production of the friction brake assembly or in servicing of the assembly; it will not be done e.g. in the field by a user.) For example, a secondary rotor 141 may be held in a chosen rotational position relative to primary rotor 121 (i.e., held in the above-discussed first, home position) while locknut 105 is tightened, so that in the thus-produced multi-stage friction brake assembly a predetermined arcuate gap (e.g. of at least 5, 10, 15 or 20 degrees) is present between the above-described contact surface 145 of secondary rotor 141 and the stop surface 127 of primary rotor 121. This arcuate gap will correspond to the arcuate distance over which secondary rotor 141 will travel in order to each the second, activated rotational position and be brought to a full stop. By way of a specific example, the arrangement depicted in Figs. 4-7 exhibits a gap between contact surface 145 and stop surface 127 (and thus a predetermined rotational distance that secondary rotor 141 will travel to reach its second, activated position) of approximately 20 degrees.

[0060] Many variations of the above arrangements can be envisioned, all of which are encompassed within the herein-disclosed concept of a multi-stage friction brake assembly that has a secondary rotor that is rotatable through a predetermined rotational travel distance to a second position at which it is brought to a full stop relative to a primary rotor. For example, the exemplary arrangement depicted in Figs. 3-7 uses the above-described flanges 124 of pawl-support plate 121 to provide stop members 126 and stop surfaces 127, and also to provide a connection point (in the form of apertures 125) for biasing springs 113. This does not necessarily have to be the case; for example, a pawl-support plate may have a spring-connection point that is provided by an entirely different component than one which provides a stop member and a stop surface.

[0061] As noted, contact members 143 and 144 do not necessarily have to be identical, nor must they be positioned exactly 180 degrees apart along the circumference of secondary rotor 141. Any number of contact members and contact surfaces may be used (along with a commensurate number of stop members and stop surfaces); for example one, two, three, or more. (Two stop members and surfaces, and two contact members and surfaces, are used in the exemplary designs shown herein.) In many embodiments, the contact members may take the form of tabs that protrude generally radially outward from secondary rotor 141. Exemplary tabs 143 and 144 as seen e.g. in Figs. 4 and 6 comprise an angular “width” in the circumferential direction of secondary rotor 141, of respectively approximately 12 degrees and 7 degrees. However, as will be demonstrated later, in some embodiments a contact member may exhibit a much larger angular width.

[0062] Other arrangements and variations may be envisioned. In particular, a multi-stage friction brake assembly is not limited to having two rotors (e.g. a primary rotor and a secondary rotor) and associated brake pads. Figs. 8-12 depict an exemplary fall-protection apparatus (a self-retracting lifeline) 201 that has a multi-stage friction brake assembly 300 that comprises three rotors and six brake pads. Some components and functionalities of fall-protection apparatus 201 will be similar to those of the previously -described fallprotection apparatus 1 and will only be briefly described. In fact, Fig. 8 depicts only the brake-side of apparatus 201, and depicts components such as a main housing piece 211 of a housing 202, and a safety line 204 and a connector 203 at a distal end 205 thereof. The drum-side of apparatus 201 (containing the safety -line-bearing drum and associated items) is not depicted in a Figure, but it will be understood that it may be very similar to that shown in Fig. 2 and discussed earlier herein. Also, various other items (e.g. retainers, bearings, fasteners, and so on) are omitted from Fig. 8 so that items of interest may be more easily viewed.

[0063] The brake-side of exemplary apparatus 201 as shown in Fig. 8 comprises a main housing piece 211 and a brake-side cover 222 (that collectively define a brake-side interior space 224), a gasket 223, a ratchet 225 with teeth 226, and two motor springs 230 (as may be convenient e.g. in the case of a self-retracting lifeline that has a relatively long safety line 204) and associated isolation disks 227 and a spacer disk 229. Apparatus 201 comprises a shaft 231 that is rotatably mounted in housing 202 e.g. by way of bearings (not shown); a brake hub 301 of a multi-stage friction brake assembly 300 is non-rotatably mounted on shaft 231 by way of key 232. The safety -line-bearing drum (not shown) will likewise be non-rotatably mounted on shaft 231 e.g. by way of a similar key (not shown).

[0064] Exemplary multi-stage friction brake assembly 300 of apparatus 201 is depicted in exploded perspective view in Fig. 9 and in side view in Fig. 10. (Pawls 311 and springs 313, as visible in Fig. 8, are omitted from Fig. 9; similarly, the pawls and springs, and locknut 305 and Belleville washer 306, are omitted from Fig. 10 so that other items may be more easily seen.) Friction brake assembly 300 comprises a brake hub 301 with an axially -oriented stem 307 with a cross-sectional shape that is a symmetrically- truncated circle with two opposing arcuate sections 302 that are co-circular with radially -outward surfaces of axially-outward portions of the two opposing arcuate sections being threaded to accept a locknut 305. Stem 307 further comprises two opposing flat sections 303. An axially -inward end of brake hub 301 comprises a flange 304.

[0065] Friction brake assembly 300 comprises a first brake pad subassembly 351 that comprises a first brake pad 352 that is immovably fixed to a major surface of a first brake pad support 354. Brake pad support 354 comprises a central through-opening 355 whose shape is complementary with the cross-sectional shape of stem 307 of brake hub 301, so that brake pad support 354, thus first brake pad 352 and brake pad subassembly 351 as a whole, are non-rotatable with respect to brake hub 301 and thus with respect to shaft 231 and the safety -line bearing drum that is non-rotatably mounted on shaft 231. An axially -inward surface of brake pad support 354 abuts an axially-outward face of flange 304 of brake hub 301, and an axially- outward frictional surface 353 of brake pad 352 is abutted against an axially -inward friction surface 328 of pawl-support plate (primary rotor) 321. The axially -inward side of brake pad support 354, that faces flange 304 of brake hub 301, thus does not comprise a brake pad; brake pad subassembly 351 is thus a “singlesided” brake pad subassembly. The axially-outward frictional surface of brake pad 352 is denoted by reference number 353 in Fig. 8; other brake pads of assembly 300 will have similar frictional surfaces but these are not denoted by reference numbers in the Figures herein.

[0066] Proceeding in an axially outward direction in Fig. 9, the next item that is mounted on brake hub 301 is pawl-support plate 321 which also serves as a primary rotor. Pawl-support plate 321 comprises an axially-inward friction surface 328 as noted above, and similarly comprises an axially-outward friction surface 329. Pawl-support plate 321 comprises two slots 323 configured to accept stems of pawls 311. Each pawl 311 comprises an engaging end in similar manner as described earlier herein for pawls 111; biasing springs 313 are similarly configured as described earlier herein. Each pawl 311 is thus supported by pawlsupport plate 321. Pawl-support plate 321 comprises side-flanges 324. Each flange 324 includes a portion that extends in a generally axially-outward direction and that includes a connection feature (in the depicted arrangement, an orifice) 325 that an end of biasing spring 313 can be connected to. Pawl-support plate (primary rotor) 321 comprises a central through-opening 322 that is circular so that pawl-support plate 321 (in contrast to brake pad subassembly 351 and to other brake pad subassemblies described below) is able to rotate relative to brake hub 301.

[0067] Continuing in an axially outward direction in Fig. 9, the next item that is mounted on brake hub 301 is a second brake pad subassembly 361. Brake pad subassembly 361 comprises a second brake pad support 364 that is configured with a shaped central through-opening 365 to be non-rotatably mounted on brake hub stem 307 in similar manner as described above for first brake pad support 354. Brake pad subassembly 361 comprises a second brake pad 362 that is immovably fixed to an axially-inward major surface of second brake pad support 364. Second brake pad 362 is abutted against the above-mentioned axially-outward friction surface 329 of pawl-support plate (primary rotor) 321. Pawl-support plate (rotor) 321 is thus sandwiched between first and second brake pads 352 and 362. In order for item 321 to serve as both a pawl-support plate and as a rotor, second brake pad subassembly 361 is configured so that all components of subassembly 361 are positioned radially inward of pawls 311, biasing springs 313, etc., so that brake pad subassembly 361 does not interfere with the functioning of the pawls. Brake pad subassembly 361 is double-sided, with another brake pad 363 that is fixed to an axially -outward major surface of second brake pad support 364. This brake pad will be termed a fifth brake pad for reasons that will become clear below.

[0068] Switching to the axially-outward end of multi-stage friction brake assembly 300, the final items that are mounted on the axially-outward end of brake hub 301 are locknut 305 and Belleville washer 306. These are configured in similar manner as described earlier herein, so that the entire stack of rotors and brake pad subassemblies is held in axial compression. Continuing in an axially inward direction from this end of assembly 300, the next item that is mounted on brake hub 301 is a third brake pad subassembly 371. Brake pad subassembly 371 comprises a third brake pad support 374 that is configured (i.e., comprises a shaped central through-opening 375) to be non-rotatably mounted on brake hub stem 307. Brake pad subassembly 371 is single-sided with a brake pad 372 that is immovably fixed to an axially-inward major surface of third brake pad support 374. This brake pad is abutted against an axially-outward friction surface 349 of secondary rotor 341 as described below, and will be termed a fourth brake pad for reasons that will become clear below.

[0069] Continuing in an axially inward direction in Fig. 9, the next item that is mounted on brake hub 301 is a secondary rotor 341. Although rotor 341 as seen e.g. in Fig. 9 differs in appearance from secondary rotor 141 as seen in Fig. 4, secondary rotor 341 is configured to function in a similar way as secondary rotor 141. Secondary rotor 341 comprises a central through-opening 342 that is circular, so that secondary rotor 341 is able to rotate relative to brake hub 301. Secondary rotor 341 comprises an axially-outward friction surface 349 that is abutted by the above-described fourth brake pad 372, and comprises an axially-inward friction surface 348 that is abutted by a third brake pad 393 as described below. Secondary rotor 341 is thus sandwiched between third and fourth brake pads 393 and 372. Secondary rotor 341 comprises contact members 343 with contact surfaces 345 that will impinge on stop surfaces 327 of stop members 326 of primary rotor 321 in similar manner as with the contact members and surfaces and stop members and surfaces described earlier herein. Other features of secondary rotor 341 are discussed below.

[0070] Continuing in an axially inward direction, the next item that is mounted on brake hub 301 is a fourth brake pad subassembly 391. Brake pad subassembly 391 comprises a fourth brake pad support 394 that is configured with a shaped central through-opening 395 so as to be non-rotatably mounted on brake hub stem 307. Brake pad subassembly 391 comprises a third brake pad 393 that is immovably fixed to an axially- outward major surface of brake pad support 394, and that is abutted against the axially-inward friction surface 349 of secondary rotor 341 as mentioned above. Brake pad subassembly 391 is double-sided, with another brake pad 392 that is fixed to an axially-inward major surface of fourth brake pad support 394. This brake pad will be termed a sixth brake pad for reasons that will become clear below. Continuing in an axially inward direction, the next item that is mounted on brake hub 301 is a rotor 381. Although rotor 381 is similar in shape and appearance to rotor 141 as shown in Fig. 4, rotor 381 and pawl-support plate (primary rotor) 321 are configured so that they interact differently than rotor 141 and pawl-support plate 121 of the Fig. 4 design, so that rotor 381 performs a different function than rotor 141.

[0071] Rotor 381 will be termed a “tertiary” rotor to distinguish it from secondary rotor 141 of Fig. 4 (and from secondary rotor 341 of Fig. 8). Tertiary rotor 381 comprises a first, axially-inward-facing friction surface 388 that is abutted by the above-described fifth brake pad 363, and comprises a second, axially- outward-facing friction surface 389 that is abutted by the above-described sixth brake pad 392. Tertiary rotor 381 comprises a central through-opening 382 that is circular, so that in theory tertiary rotor 381 would be able to rotate relative to brake hub 301 and thus able to rotate relative to primary rotor 321. However, tertiary rotor 381 comprises first and second generally radially -outwardly -extending protruding members (e.g., tabs) 383 and 384. In friction brake assembly 300 as assembled, tabs 383 and 384 are seated, and remain, in notches 331 of flanges 324 of pawl-support plate (primary rotor) 321, as can be seen from inspection of Figs. 10-12. With tabs 383 and 384 of tertiary rotor 381 seated in notches 331 of primary rotor 321 in this manner, tertiary rotor 381 is substantially unable to rotate relative to primary rotor 321. A tertiary rotor will thus be termed a “fixed” rotor, meaning that it cannot substantially rotate relative to the primary rotor. In contrast, a secondary rotor (e.g. rotor 141 or rotor 341), that is able to rotate relative to the primary rotor, will be termed a “traveling” rotor.

[0072] The numbering of the brake pads in friction brake assembly 300 can now be appreciated. First and second brake pads are those that sandwich, and operate in conjunction with, a primary rotor (e.g., a pawlsupport plate); third and fourth brake pads are those that sandwich, and operate in conjunction with, a secondary / traveling rotor, in exact correspondence to the counterpart brake pads in friction brake assembly 100. Fifth and sixth brake pads are those that sandwich, and operate in conjunction with, a tertiary / fixed rotor (and have no equivalents in friction brake assembly 100).

[0073] In the above-described arrangement, the tertiary / fixed rotor basically serves as an extension of the primary rotor. That is, it allows the total rotor surface area available for friction-braking to be increased without having to increase the radial size of the primary rotor. The presence of a tertiary / fixed rotor will thus increase the frictional forces that can be applied in a first, initial stage of friction-braking and in a second stage of friction-braking.

[0074] The operation of multi-stage friction brake assembly 300 can now be considered. In an initial stage, with secondary rotor 341 in its first, home position as shown in Figs 10 and 11, the friction-braking is performed by way of the first and second brake pads acting on the primary rotor and the fifth and sixth brake pads acting on the tertiary rotor. If forces arise that cause secondary rotor 341 to travel from the first, home position to the second, activated position (as indicated by arrow 281 of Fig. 11), secondary rotor 341 will be halted at this activated position by way of contact surface 345 of secondary rotor 341 impinging on stop surface 327 of stop member 326 of primary rotor 321. The second stage of friction-braking will now commence with the friction-braking now including a contribution from the third and fourth brake pads acting on secondary / traveling rotor 341 , along with the continued action of the other brake pads on primary rotor 321 and tertiary rotor 381.

[0075] The modularity and generality of the herein-disclosed multi-stage friction-braking concept can now be appreciated. A multi-stage friction brake assembly can include a primary rotor and e.g. one, two, or three or more tertiary / fixed rotors, the number of tertiary rotors being chosen in view of the desired overall friction-braking. In some embodiments, all such tertiary rotors may be held stationary relative to the primary rotor by way of the protruding members of the tertiary rotors being seated in a common notch of the primary rotor; or, each additional tertiary rotor may have a protruding member that is held in a feature (e.g. a notch) provided in the preceding tertiary rotor. Similarly, any number of secondary rotors may be used, e.g. one, two, three, or more, in any combination with a desired number of tertiary rotors. It will thus be appreciated that a multi-stage friction brake assembly as disclosed herein allows a modular approach in which any desired number and combination of various rotors, and their associated brake pads, may be used in order to provide a desired overall friction-braking capability and to tailor the manner in which additional frictionbraking is sequentially added in stages (by way of the activation of one or more secondary rotors) to the initially-achieved friction-braking as provided by the primary rotor and e.g. one or more tertiary rotors. Such an approach may, for example, allow a variety of fall-protection apparatus to be produced with a variety of safety-line lengths (e.g. ranging from 15 feet up to 175 feet), the apparatus all using brake assemblies that draw from a common set of component parts. This can be contrasted with fall-protection apparatus that each require a friction-brake assembly that includes parts that are custom-made for that particular apparatus.

[0076] In the exemplary depicted arrangement, the above-discussed notches 331 in which protruding members 383 and 384 of tertiary rotor 381 are permanently seated, and stop members 326 with stop surfaces 327 that interact with the contact surfaces of secondary rotor 341, are all provided by flanges 324 of primary rotor 321. (In the depicted arrangement, notches 331 are positioned axially inward of stop members 326 with portions of stop members 326 defining portions of notches 331.) However, this does not necessarily have to be the case. For example, a notch of primary rotor 321 (or any other feature or item that is arranged to securely hold a protruding member of a tertiary rotor so that the tertiary rotor cannot rotate relative to the primary rotor) can be provided separately from a feature or item that provides a stop member of primary rotor 321.

[0077] Astute observers will note e.g. from Figs. 11 and 12 that the notches 331 of primary rotor 321 are very slightly oversized (along the circumferential direction of primary rotor 321) in relation to the protruding members (tabs, in this case) 383 and 384 of tertiary rotor 381 that are permanently seated in notches 331. This may be done e.g. for ease of mating the tertiary rotor to the primary rotor. Accordingly, a very slight amount of relative rotational motion of tertiary rotor 381 relative to primary rotor 321 (e.g., less than 5, 3, 2 or 1 degrees) may be possible. This accounts for the above-used terminology that a tertiary rotor will be “substantially” prevented from moving relative to a primary rotor, with the term “substantially” denoting less than 5 degrees of total possible rotational motion. A tertiary / fixed rotor is thus distinguished from a secondary / traveling rotor that is purposefully configured to be able to move through a predetermined rotational travel distance of at least 5 degrees relative to a primary rotor.

[0078] As noted above, secondary rotor 341 as shown in Figs. 9-12 functions similarly to secondary rotor 141 as shown in Figs. 4-8 (and is configured to have a predetermined amount of rotational motion relative to primary rotor of approximately 20 degrees, which is very similar to that of secondary rotor 141). However, certain differences exist, which help illustrate various design options that are available. For example, contact members 343 of secondary rotor 341 as seen in Fig. 9 occupy a far greater angular extent around the circumference of secondary rotor 341 than do contact members 143 and 144 of secondary rotor 141 as seen in Fig. 4 (contact members 143 and 144 respectively occupy an angular extent of approximately 12 degrees and 7 degrees). In the depicted embodiment of Fig. 9, each contact member 343 occupies an angular extent of the perimeter of secondary rotor 341 of approximately 145 degrees; contact members 343 are separated by two radially -outwardly -open-ended, circumferentially -extending slots 291 that each occupy an angular extent of approximately 35 degrees. (Each stop member 326 of primary rotor 321 will be seated within a slot 291 of secondary rotor 341, as evident e.g. from Fig. 11.) The angular extent of a contact member of a secondary rotor may thus vary widely. In various embodiments, a contact member of a secondary rotor may occupy an angular extent of the circumference of a secondary rotor of at least 5, 10, 20, 40, 60, 80, 100, 120, or 140 degrees. In further embodiments, such a contact member may occupy an angular extent of less than 160, 130, 110, 90, 70, 50, 30, or 15 degrees. In some embodiments, a contact member of a secondary rotor may be positioned and sized (in particular, may comprise a fairly large angular extent) so that in the assembled multi-stage friction brake, the contact member axially overlap a pawl or pawl so as to help keep the pawl(s) 311 in place on a pawl-support plate. (In other words, in some embodiments, pawls 311 may be axially sandwiched between contact members 343 of secondary rotor 341, and pawl-support plate (primary rotor) 341.) In the depicted arrangement, secondary rotor 341 is configured to have a radially -outward perimeter that is thicker (in the axial direction) than the radially -interior portions of rotor 341, as most easily seen in the side view of Fig. 10.

[0079] Primary rotor 121 of multi-stage friction brake assembly 100 comprises stop members 126 with stop surfaces 127 that define the second, activated position at which the secondary rotor will cease rotation relative to the primary rotor. However, rotor 121 does not comprise any member that is configured to define the first, home position of the secondary rotor. So, in the production of assembly 100, the first, home position of secondary rotor 141 may have to be established by visual observation and measurement of the previously-described arcuate gap between contact surface 145 of secondary rotor 141 and stop surface 127 of primary rotor 121 as secondary rotor 141 is installed onto the brake hub 101.

[0080] Primary rotor 321 and secondary rotor 341 of multi-stage friction brake assembly 200 do comprise features that can allow secondary rotor 341 to be more easily installed in its first, home position. Secondary rotor 341 comprises circumferentially -extending slots 291 as described above, with stop members 326 of primary rotor 321 being seated in slots 291. Each slot 291 of secondary rotor 341 has a trailing end defined by a surface 345 of contact member 343. Surface 345 faces in the unwind direction and serves as a contact surface that will cause the secondary rotor 341 to halt at its second, activated position relative to the primary rotor as described above. Each slot 291 of secondary rotor 341 also has an opposing, leading end defined by a surface 344 (as seen e.g. in Fig. 11) of contact member 343. Surface 344 of secondary rotor 341 faces in the wind direction and can be abutted against a datum surface 333 (that faces in the unwind direction) of stop member 326 of primary rotor 321 in the manner depicted in Fig. 11 to establish the first, home position of secondary rotor 341. In other words, in the installation of secondary rotor 341 onto the brake hub 101, rotor 341 can be rotated so that its surface 344 is abutted against datum surface 333 of stop member 326, which will correspond to secondary rotor 341 being in its first, home position. With the secondary rotor positioned in this manner, the arcuate distance from contact surface 345 of secondary rotor 341 to stop surface 327 of primary rotor 321, will define the above-described predetermined rotational travel distance that secondary rotor 341 travels from its first, home position to its second, activated position, as discussed previously.

[0081] Observers will also note (e.g. in Figs. 11 and 12) apertures 292 in secondary rotor 341 and similar apertures 293 in primary rotor (pawl-support plate) 321. These features, while not necessarily serving any particular purpose in the operation of multi-stage friction brake assembly 300, may facilitate the manufacturing of assembly 300. Specifically, the amount of axial compression that is placed on the rotors and brake pad subassemblies will govern the friction-braking power that the assembly achieves. This axial compression will be imparted by tightening the locknut 305 (or other fastener) on the brake hub, but does not necessarily correlate exactly with the degree of tightening of the locknut (as measured or established e.g. by a torque wrench). Accordingly, in manufacturing of a friction-brake assembly, the assembly may be temporarily put into a test fixture that enables evaluation of the amount of force required to cause the rotor(s) to slip relative to the brake pads (or vice versa); the locknut can then be tightened so that this force, as measured in the test fixture, is in the desired range. Apertures 292 of secondary rotor 341 and apertures 293 of primary rotor 321 can thus accept members of a test fixture to facilitate the tightening of locknut 305 to a point that the friction-braking forces are in the desired range.

[0082] Numerous variations of the general concept of a multi-stage friction brake assembly and its implementation e.g. in a fall-protection apparatus may be envisioned. For example, ordinary artisans will be aware that the operational readiness of a fall-protection apparatus such as a self-retracting lifeline is often checked by a user in the field, by way of a “lock-up” test in which the user gives a quick pull on the safety line to engage the pawl(s) with the ratchet to confirm that the brake assembly is able to “lock up” as needed. In some embodiments, a multi-stage friction brake assembly as disclosed herein may be configured so that the forces that develop in such a procedure are insufficient to cause the secondary rotor 141 to move out of its first, home position. (Thus, in such “lock-up” testing, substantially all of the frictional forces may be from the action of brake pads on the primary rotor of the brake assembly.) However, in some embodiments a fall-protection apparatus may be configured so that it may encounter a situation in which the forces developed in a lock-up test may be sufficiently high to cause the secondary rotor to move out of the home position. In some such embodiments, one or more ancillary items may be optionally included in the multi-stage brake assembly to limit the ability of the secondary rotor to move out of the home position e.g. of the course of numerous lock-up tests over extended periods of time.

[0083] Such an item might take the form of e.g. a member that is positioned and configured to prevent secondary rotor 141 from rotating relative to primary rotor 121, the member being deflectable so that if a sufficiently high force is encountered, the member will deflect to a configuration in which it allows secondary rotor 141 to rotatably move relative to primary rotor 121. The force required to deflect the deflectable member may be set in an appropriate range so that secondary rotor 141 will not move from the first, home position during a lock-up test, but will move from the first, home position in the case of a higher- force event such as a user fall. Such a deflectable member may, for example, take the form of a deflectable pin comprised by primary rotor 121, the deflectable pin being located immediately in front (in the unwind direction) of a tab 143 or 144 of secondary rotor 141 when secondary rotor 141 is in its home position. Such a deflectable member can block rotation of secondary rotor in the unwind direction unless the force of secondary rotor 141 on the deflectable member is sufficient to cause the member to be deflected into a nonblocking configuration (shape, position, etc.). Other arrangements to achieve similar functioning can be envisioned, e.g. providing a secondary rotor with one or more detent features that interact with complementary features of e.g. the primary rotor. If desired, in some embodiments a primary rotor and a secondary rotor may be configured so that it is possible to ascertain whether the secondary rotor is still in its first, home position relative to the primary rotor. For example, a housing of a fall-protection apparatus may be equipped with a transparent window through which indicia on the rotors may be inspected, with the relative position of these indicia providing an indication of the position of the secondary rotor with respect to the primary rotor. In a more general sense, any sort of positional-sensing item (e.g. an optoelectronic device) may be used to provide a similar indication.

[0084] The herein-disclosed general concept of a multi-stage friction brake with at least one primary rotor, with at least one “traveling’Vsecondary rotor, and optionally with at least one “fixed’Vtertiary rotor, can be implemented in various ways. For example, any number of pawls may be used, e.g. one, two, three, four, or more. The exemplary arrangements presented herein have dealt with pawls 111 that are configured so that an increased speed of rotation causes an engaging end of 112 of the pawl to move radially outward. However, a multi-stage friction brake assembly may implemented with a pawl or pawls configured so that the engaging ends of the pawl(s) move radially inward (rather than outward as described earlier herein) to an engaged position. Such pawls may be used in conjunction with a ratchet that has radially -outward-facing teeth rather than having radially -inward-facing teeth as with ratchets 25 and 225 depicted herein. A ratchet of this general type is depicted e.g. inFig. 3 of U.S. Patent 11504557. In some embodiments, a pawl- biasing spring may act in compression rather than in extension, and / or a biasing spring may be seated on a pawlsupport plate without necessarily being attached to the pawl-support plate an / or the pawl. Arrangements of this type are disclosed e.g. in U.S. Patent 9488235, which is incorporated by reference in its entirety herein.

[0085] U.S. Patent 9488235 also discloses an arrangement in which a ratchet takes the form of a single, radially inwardly -facing tooth that is provided as an integral part of a bracket (e.g., a load-bearing bracket) of a fall-protection apparatus. The apparatus described in the ‘235 patent is one in which a rotationally- actuated braking device brings a safety -line-bearing drum to a near-instantaneous full stop upon engaging a pawl with the single ratchet tooth; that is, the ‘235 rotationally -actuated braking device does not comprise a friction brake. (Instead, a shock absorber is provided in the safety line of the apparatus.) The ‘235 patent thus does not include a friction brake and is cited herein merely to illustrate permissible variations in ratchet design with which a herein-disclosed multi-stage friction brake assembly can be used with. It is noted in passing that the term “ratchet” is used for convenience of description; use of this term does not require that the ratchet and pawl(s) must necessarily be arranged e.g. so that relative rotation of these components is permitted in one direction but is precluded in the opposite direction. (However, the ratchet and pawl(s) can be arranged so that such functionality is provided if desired.) Various pawl designs and configurations are described e.g. in U.S. Patents 7281620, 8430206, 8430208, and 9925400; a multi-stage friction brake assembly as disclosed herein may be used with any such arrangement of pawls and / or ratchets.

[0086] Still other variations may be envisioned. For example, in some embodiments a multi-stage friction brake assembly may be used in an apparatus in which a ratchet is able to rotate relative to a housing of apparatus rather than being fixed in position in the housing as with ratchets 25 and 225 in the Figures herein. (A ratchet of this general type is depicted in Fig. 4 of U.S. Patent 8430206.) In such cases, a ratchet (e.g. in the form of a ring or disk) may serve as primary rotor whose rotation is opposed by first and second brake pads. If the primary rotor (ratchet) rotates sufficiently far, this may cause activation of a secondary (traveling) rotor whose rotation is opposed by third and fourth brake pads. The ratchet (primary rotor) may thus comprise a stop member and a stop surface, with the secondary rotor comprising a contact member and a contact surface, and so on, in the general manner discussed herein.

[0087] Still other variations may be envisioned. For example, in some embodiments a multi-stage friction brake assembly may be used in an apparatus in which a shaft (e.g. similar to shaft 31) is non-rotatably fixed to a housing of the apparatus rather than being rotatably attached to the housing, and in which a safety linebearing drum, a multi-stage friction brake assembly, and so on, are rotatably mounted on the fixed shaft. And, as mentioned earlier herein, a pawl-support plate need not necessarily serve as a primary rotor, and vice versa. Thus in some embodiments, a primary rotor may be provided that is a separate entity from a pawl-support plate. In still other variations, a multi-stage friction brake assembly need not necessarily be positioned and / or oriented in the exact manner shown e.g. in Fig. 3. For example, in some embodiments the axial orientation of a multi-stage friction brake assembly may be reversed e.g. so that the flange of the brake hub of the assembly is at an axially outward location and a fastener (e.g. a locknut) of the assembly is at an axially inward location. In such embodiments, the particular locations, orientations, etc. of the various components of the multi-stage friction brake assembly as provided earlier herein, may be axially reversed.

[0088] In still more permissible variations, if a multi-stage friction brake assembly includes a tertiary (fixed) rotor in the general manner described earlier herein, a secondary, traveling rotor may be configured so that it is brought to a full stop at a second, activated rotational position by impinging on a stop member that is provided by the tertiary rotor rather than a stop member that is provided by the primary rotor. Since the tertiary rotor is itself mated to the primary rotor so that the tertiary rotor is substantially non-rotatable relative to the primary rotor, the same functioning will be achieved. In some embodiments, a tertiary rotor may comprise features (e.g. one or more generally radially-outwardly-extending flanges) that axially overlie one or more pawls to keep the pawl(s) axially “sandwiched” in position in the general manner referred to earlier.

[0089] In many embodiments a multi-stage friction brake assembly as disclosed herein will be a limiteduse item. By limited-use is meant that the friction brake assembly is not actuated during ordinary use of the fall-protection apparatus (e.g., while a human user of the device is performing workplace operations and / or moving about a workplace). Rather, the friction brake assembly will remain in a state of readiness, but will only be actuated upon the onset of a fall (and, as discussed earlier, in an occasional lock-up test). A limiteduse friction brake assembly as disclosed herein is thus distinguished from friction brakes of movable vehicles, from centrifugal brakes, clutches, torque converters, and so on, of vehicles and other motorized machinery.

[0090] In many embodiments a multi-stage friction brake assembly as disclosed herein will be a constantcontact brake. By this is meant that during ordinary use of the fall-protection apparatus, the frictional surface of each brake pad will remain constantly in direct, intimate contact with the friction surface of the rotor that the brake pad operates in conjunction with. Such a constant-contact brake may be contrasted with e.g. vehicular brakes, transmissions, etc. in which a layer of friction material is frequently retracted away from a “rotor” (or vice versa) so that a gap is often present between the frictional surface of the friction material and the friction surface of the rotor.

[0091] The arrangements disclosed herein may be advantageously used in any fall-protection apparatus; for example, in a self-retracting lifeline. Fall-protection apparatus such as e.g. self-retracting lifelines in which the arrangements disclosed herein may be advantageously utilized, are described in U.S. Patents 8181744, 8256574, 8430206, 8430207, 8511434, 9488235, and 9925400, and in U.S. Published Patent Application 2016 / 0096048. In many embodiments, such a fall-protection apparatus will be a non-motorized apparatus. By this is meant that a safety line of the apparatus is not moved (i.e., extended or retracted from a housing of the apparatus) by way of an electrically powered motor; in other words, the disclosed multistage friction brake assembly will not be used as part of a system (e.g., an elevator, a hoist, etc.) that uses one or more motors to raise or lower a load. It will be understood that a fall-protection apparatus that is “non-motorized” may still include such items as one or more electrically-powered sensors, monitors, communication units, actuators, and the like.

[0092] In some embodiments the fall-protection apparatus is a self-retracting lifeline which meets the requirements of ANSI Z359.14-2021. In general, the arrangements disclosed herein may be used in any fall-protection apparatus in which there is a desire to slow or arrest the fall of a human user while e.g. minimizing an initial braking force relative to the average braking force. In some embodiments, the arrangements disclosed herein may be used in fall-protection products that, at least in some modes of operation, can function as descenders (e.g. that can allow self-rescue capability) or rope adjusters. For example, the fall-protection apparatus may comprise both a full-arrest (halt) mode and a descending mode, e.g. as described in U.S. Published Patent Application 2010 / 0226748.

[0093] In various embodiments, a fall-protection apparatus as described herein may be used in concert with, or as part of, any suitable fall-protection system such as e.g. a horizontal lifeline or retractable horizontal lifeline, a positioning lanyard, a shock-absorbing lanyard, a rope adjuster or rope grab, a vertical safety system (such as e.g. a flexible cable, rigid rail, climb assist, or fixed ladder safety system), a confined- space rescue system or hoist system, and so on. In some cases a fall-protection apparatus as disclosed herein may be suited for use in so-called “leading edge” workplace environments. It is still further noted that the discussions herein have primarily concerned apparatus (e.g. self-retracting lifelines) that comprise a housing that is e.g. mounted to an overhead anchorage and that comprises a safety line with a distal end that can be attached to a harness of a human user. It will be understood that the arrangements disclosed herein may also be used in e.g. “personal” self-retracting lifelines that comprise a housing that is mountable to a harness of a human user and that comprises a safety line with a distal end that can be attached e.g. to an overhead anchorage. Such apparatus are exemplified by the product line available from 3M Fall Protection under the trade designation NANO-LOK.

[0094] It will be understood that any such fall-protection apparatus may include, or be used with, various ancillary items which are not described in detail herein. Such items may include, but are not limited to, one or more of lanyards, shock absorbers, tear strips, harnesses, belts, straps, paddings, tool holsters or pouches, impact indicators, carabiners, D-rings, anchorage connectors, and the like. Many such apparatus, products, and components are described in detail e.g. in the 3M DBI-SALA Fall Protection Full-Line Catalog (2022). Although in many embodiments it may not be necessary due to the presence of the friction brake, in some embodiments the safety line of the apparatus may comprise a shock absorber e.g. of the type described earlier herein. In other embodiments, no such shock absorber will be present.

[0095] Still further, the arrangements disclosed herein are not necessarily limited to being used in fallprotection apparatus. Rather, a multi-stage friction brake assembly, as a general concept, may be implemented in any of a variety of non-fall-protection apparatus. Furthermore, a rotor of a multi-stage friction brake assembly need not necessarily be sandwiched between brake pads; rather, in some embodiments, a rotor may operate in conjunction with a single brake pad that abuts only one friction surface of the rotor. All such variations being encompassed within the general concept of a multi-stage friction brake assembly, herein is disclosed an apparatus comprising a shaft and a multi-stage friction brake assembly that is mounted on the shaft, the friction brake assembly comprising: a brake hub that is non- rotatably mounted on the shaft; a primary rotor that is rotatably mounted on the brake hub and that comprises at least one friction surface; a secondary rotor that is rotatably mounted on the brake hub and that comprises at least one friction surface; at least one primary brake pad that is non-rotatably mounted on the brake hub and that axially abuts the at least one friction surface of the primary rotor; at least one secondary brake pad that is non-rotatably mounted on the brake hub and that axially abuts the at least one friction surface of the secondary rotor, with the primary and secondary rotors and the brake pads being held in axial compression, wherein the secondary rotor is rotatable relative to the primary rotor and with the primary and secondary rotors being configured so that in a first condition of use of the apparatus, the secondary rotor remains in a first, home rotational position relative to the primary rotor, the primary and secondary rotors being further configured so that if a rotational force above a predetermined threshold is applied to the shaft, the secondary rotor will rotate relative to the primary rotor through a predetermined rotational travel distance, to a second, activated rotational position relative to the primary rotor.

[0096] It will be apparent to those skilled in the art that the specific exemplary elements, structures, features, details, configurations, etc., that are disclosed herein can be modified and / or combined in numerous embodiments. All such variations and combinations are contemplated by the inventor as being within the bounds of the conceived invention, not merely those representative designs that were chosen to serve as exemplary illustrations. Thus, the scope of the present invention should not be limited to the specific illustrative structures described herein, but rather extends at least to the structures described by the language of the claims, and the equivalents of those structures. Any of the elements that are positively recited in this specification as alternatives may be explicitly included in the claims or excluded from the claims, in any combination as desired. Any of the elements or combinations of elements that are recited in this specification in open-ended language (e.g., comprise and derivatives thereof), are considered to additionally be recited in closed-ended language (e.g., consist and derivatives thereof) and in partially closed-ended language (e.g., consist essentially, and derivatives thereof). To the extent that there is any conflict or discrepancy between this specification as written and the disclosure in any document that is incorporated by reference herein but to which no priority is claimed, this specification as written will control.

Claims

What is claimed is:

1. A fall-protection apparatus comprising: a housing and a shaft that is rotatably mounted in the housing; a drum that is non-rotatably mounted on the shaft and that has a safety line connected thereto; a multi-stage friction brake assembly that is mounted on the shaft, the friction brake assembly comprising: a brake hub that is non-rotatably mounted on the shaft; a pawl-support plate that is rotatably mounted on the brake hub, the pawl-support plate serving as a primary rotor of the friction brake assembly and comprising first and second axially- opposing friction surfaces; at least one pawl that is supported on the pawl-support plate; a secondary rotor that is rotatably mounted on the brake hub and that comprises first and second axially -opposing friction surfaces; first and second brake pads that are non-rotatably mounted on the brake hub and that axially bracket the pawl-support plate so as to respectively abut the first and second axially-opposing friction surfaces of the pawl-support plate; third and fourth brake pads that are non-rotatably mounted on the brake hub and that axially bracket the secondary rotor so as to respectively abut the first and second axially -opposing friction surfaces of the secondary rotor; and, a fastener that is attached to the brake hub so as to hold the pawl-support plate, the secondary rotor, and the brake pads, in axial compression; wherein the secondary rotor is rotatable relative to the pawl-support plate with the pawl-support plate and the secondary rotor being configured so that in ordinary use of the fall-protection apparatus, the secondary rotor remains in a first rotational position relative to the pawl-support plate, the pawl-support plate and the secondary rotor being further configured so that if a rotational force above a predetermined threshold is applied to the drum and the shaft, the secondary rotor will rotate relative to the pawl-support plate through a predetermined rotational travel distance that is at least 10 degrees and that is less than 180 degrees, to a second rotational position relative to the pawl-support plate.

2. The apparatus of claim 1 wherein the friction brake assembly is configured so that during the rotation of the secondary rotor through the predetermined rotational travel distance to the second rotational position relative to the pawl-support plate, rotation of the shaft, drum and secondary rotor is opposed by frictional action of the first and second friction pads on the first and second axially -opposing frictionsurfaces of the pawl-support plate and is not opposed by frictional action of the third and fourth friction pads on the first and second axially -opposing friction surfaces of the secondary rotor.

3. The apparatus of claim 2 wherein the friction brake assembly is configured so that after the secondary rotor has reached the second rotational position relative to the pawl-support plate, further rotation of the shaft, drum and secondary rotor is opposed by frictional action of the first and second friction pads on the first and second axially -opposing friction surfaces of the pawl-support plate and is also opposed by frictional action of the third and fourth friction pads on the first and second axially -opposing friction surfaces of the secondary rotor.

4. The apparatus of claim 1 wherein the secondary rotor comprises a contact member with a contact surface and the pawl-support plate comprises a stop member with a stop surface, and wherein the friction brake assembly is configured so that when the secondary rotor reaches the second rotational position relative to the pawl-support plate, the secondary rotor is brought to a full stop relative to the pawl-support plate by way of the contact surface of the contact member of the secondary rotor coming into contact with the stop surface of the stop member of the pawl-support plate, the stop member serving to physically block the secondary rotor from rotating any further relative to the pawl-support plate.

5. The apparatus of claim 4 wherein the contact member of the secondary rotor protmdes generally radially outwardly from the secondary rotor and wherein the stop member of the pawl-support plate extends generally axially outwardly from the pawl-support plate so that at least a portion of the stop surface of the stop member of the pawl-support plate resides in a plane of rotation of the contact surface of the contact member of the secondary rotor; wherein when the secondary rotor is in the first rotational position relative to the pawl-support plate the contact member of the secondary rotor is at a first, home position relative to the stop member of the pawl-support plate, and wherein the angular distance from the contact surface of the contact member of the secondary rotor to the stop surface of the stop member of the pawl-support plate when the contact member is in the first, home position, defines the predetermined rotational travel distance that the secondary rotor is able to rotate relative to the pawl-support plate.

6. The apparatus of claim 5 wherein the contact member of the secondary rotor comprises a radially - outwardmost arcuate section of the secondary rotor that extends through an arcuate extent of at least 20 degrees and that comprises a circumferentially -extending notch that extends through an arcuate extent of from at least 10 to at most 90 degrees and within which the stop member of the pawl-support plate is permanently seated, the contact surface of the contact member defining a trailing end of the arcuately- extending notch.

7. The apparatus of claim 6 wherein the pawl-support plate comprises a generally axially -outwardly extending flange, a leading portion of which comprises the stop member of the pawl-support plate, the stop surface of the stop member being a trailing surface of the leading portion of the generally axially -outwardly extending flange.

8. The apparatus of claim 1 wherein the at least one pawl is configured so that rotation of the shaft, drum and pawl-support plate above a threshold rotational velocity causes an engaging end of the pawl to pivotally move to an engaging position; and, wherein the apparatus comprises a ratchet that is non-rotatably fixed to the housing of the apparatus and that comprises at least one tooth that is configured to be engaged by the engaging end of the at least one pawl when the at least one pawl is in the engaging position.

9. The apparatus of claim 8 wherein the apparatus is configured so that when the engaging end of the pawl engages the at least one tooth of the ratchet, the pawl-support plate is brought to a full stop while the shaft, the drum, and the secondary rotor all continue to rotate until the secondary rotor has rotated through the predetermined rotational travel distance and has reached its second rotational position relative to the pawl-support plate, during time which the rotation of the shaft, drum and secondary rotor is opposed by frictional action of the first and second friction pads on the first and second axially -opposing friction surfaces of the pawl-support plate and is not opposed by frictional action of the third and fourth friction pads on the first and second axially -opposing friction surfaces of the secondary rotor; and, wherein the apparatus is configured so that when the secondary rotor has reached its second rotational position, the secondary rotor is brought to a full stop by way of a contact surface of a contact member of the secondary rotor contacting a stop surface of a stop member of the pawl-support plate; and, wherein the apparatus is configured so that after the secondary rotor has reached the second rotational position, further rotation of the shaft and drum is opposed by frictional action of the first and second friction pads on the first and second axially -opposing friction surfaces of the pawl-support plate and is also opposed by frictional action of the third and fourth friction pads on the first and second axially -opposing friction surfaces of the secondary rotor.

10. The apparatus of claim 9 wherein the apparatus is configured so that if rotation of the shaft, drum and pawl-support plate exceeds the threshold rotational velocity so as to cause the engaging end of the pawl to engage the ratchet tooth and to bring the pawl-support plate to a full stop, but the rotational force is not above the predetermined threshold that will cause the secondary rotor to rotate relative to the pawl-support plate, the secondary rotor will remain in the first rotational position relative to the pawl-support plate with the rotation of the shaft, dmm and secondary rotor being brought to a halt only by way of frictional action of the first and second friction pads on the first and second axially -opposing friction surfaces of the pawl-support plate and not by way of frictional action of the third and fourth friction pads on the first and second axially -opposing friction surfaces of the secondary rotor.

11. The apparatus of claim 1 wherein the friction brake assembly comprises: a first brake pad subassembly that is a single-sided brake pad subassembly mounted on the brake hub axially inward of the pawl-support plate, the first brake pad subassembly comprising a first brake pad support that is non-rotatably mounted on the brake hub and with the first brake pad being bonded to an axially outward surface of the first brake pad support; a second brake pad subassembly that is a double-sided brake pad subassembly mounted on the brake hub axially outward of the pawl-support plate and axially inward of the secondary rotor, the second brake pad subassembly comprising a second brake pad support that is non-rotatably mounted on the brake hub and with the second brake pad being bonded to an axially inward surface of the second brake pad support and with the third brake pad being bonded to an axially outward surface of the second brake pad support; and, a third brake pad subassembly that is a single-sided brake pad subassembly mounted on the brake hub axially outward of the secondary rotor, the third brake pad subassembly comprising a third brake pad support that is non-rotatably mounted on the brake hub and with the fourth brake pad being bonded to an axially inward surface of the third brake pad support.

12. The apparatus of claim 1 wherein the fastener that is attached to the brake hub to hold the pawlsupport plate, the secondary rotor, and the brake pads in axial compression, is a locknut, and wherein at least one Belleville washer is mounted on the brake hub axially inward of the locknut and axially outward of the pawl-support plate, the secondary rotor, and the brake pads.

13. The apparatus of claim 12 wherein the brake hub comprises a stem with a cross-sectional shape that is a symmetrically -truncated circle with two opposing arcuate sections that are co-circular with radially - outward surfaces of axially -outward portions of the two opposing arcuate sections being threaded to accept the locknut, the stem further having two opposing flat sections; and, wherein an axially-inward end of the brake hub stem comprises a flange that axially -inwardly abuts an axially-inward surface of a first brake pad support to whose axially -outward surface the first brake pad of the friction brake assembly is bonded.

14. The apparatus of claim 13 wherein all of the brake pads of the friction brake assembly are supported on, and immovably fixed to, respective brake pad supports, and wherein all of the brake pad supports of the brake assembly comprise through-openings through which the stem of the brake hub passes, with the through-openings of the brake pad supports being complementary with the cross-sectional shape of the stemof the brake hub so that all of the brake pads of the friction brake assembly are non-rotatably mounted on the brake hub.

15. The apparatus of claim 1 wherein the friction brake assembly comprises first and second pawls with stems that reside in first and second slots of the pawl-support plate with each pawl being configured so that an engaging end of the pawl can pivotally move to an engaging position, and with each pawl being biased by a biasing spring with one end connected to the pawl and with a second, opposing end connected to the pawl-support plate, the biasing spring serving to keep the engaging end of the pawl from pivotally moving to the engaging position unless the shaft, drum, and pawl-support plate rotate above a threshold rotational velocity.

16. The apparatus of claim 1 wherein the friction brake assembly comprises a tertiary rotor that is rotatably mounted on the brake hub and is configured to be non-rotatable relative to the pawl-support plate, the tertiary rotor being mounted on the brake hub in a position axially between the pawl-support plate and the secondary rotor and the tertiary rotor comprising first and second axially -opposing friction surfaces, the brake assembly further comprising fifth and sixth brake pads that respectively abut the first and second axially -opposing friction surfaces of the tertiary rotor and that are non-rotatably mounted on the brake hub.

17. The apparatus of claim 16 wherein the tertiary rotor comprises a first radially -outwardly protruding member and wherein the pawl-support plate comprises a first generally outwardly -axially -extending flange that comprises a first gap, and wherein the first radially -outwardly protruding member of the tertiary rotor is permanently seated within the first gap of the pawl-support plate, with the first gap of the pawl-support plate and the first radially-outwardly protruding member of the tertiary rotor being sized and shaped so that the tertiary rotor is substantially unable to rotate relative to the pawl-support plate.

18. The apparatus of claim 17 wherein the apparatus is configured so that upon at least one tooth of the at least one pawl of the friction brake assembly engaging at least one tooth of a ratchet that is non-rotatably fixed to the housing of the apparatus, the pawl-support plate and the tertiary rotor will come to a full stop while the shaft, the drum, all of the brake pads, and the secondary rotor, all continue to rotate through the predetermined rotational travel distance, during which the rotation of the shaft, drum, and secondary rotor is opposed by frictional action of the first and second friction pads on the first and second axially -opposing friction surfaces of the pawl-support plate and by frictional action of the fifth and sixth friction pads on first and second axially -opposing friction surfaces of the tertiary rotor, and is not opposed by frictional action of the third and fourth friction pads on the first and second axially -opposing friction surfaces of the secondary rotor.

19. The apparatus of claim 18 wherein the apparatus is configured so that when the secondary rotor has reached its second rotational position, the secondary rotor is brought to a full stop by way of a contact surface of a contact member of the secondary rotor contacting a stop surface of a stop member of the pawlsupport plate; and, wherein the apparatus is configured so that after the secondary rotor has reached the second rotational position, further rotation of the shaft and drum is opposed by frictional action of the first and second friction pads on the first and second axially-opposing friction surfaces of the pawl-support plate, by frictional action of the fifth and sixth friction pads on first and second axially -opposing friction surfaces of the tertiary rotor, and by frictional action of the third and fourth friction pads on the first and second axially -opposing friction surfaces of the secondary rotor.

20. The apparatus of claim 19 wherein the first generally axially-outwardly-extending flange of the pawl-support plate, that comprises the first gap within which the protruding member of the tertiary rotor is permanently seated, comprises a leading portion that comprises the stop member of the pawl-support plate, the stop surface of the stop member being a trailing surface of the leading portion of the first generally axially -outwardly-extending flange of the pawl-support plate and at least a portion of the stop surface of the stop member of the pawl-support plate being in a plane of rotation of the contact surface of the contact member of the secondary rotor.

21. The apparatus of claim 1 wherein the apparatus is a self-retracting lifeline in which the safety line comprises a distal end that is attachable to a harness of a human user of the apparatus or to an anchorage of a workplace, and wherein the housing of the apparatus comprises a motor spring that is biased to rotate the drum in a winding direction.

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