Safety band longitudinal and transverse control
10221579 ยท 2019-03-05
Assignee
Inventors
Cpc classification
E04B7/024
FIXED CONSTRUCTIONS
Y10T29/49874
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
E04G21/3261
FIXED CONSTRUCTIONS
E04D15/06
FIXED CONSTRUCTIONS
E04D12/002
FIXED CONSTRUCTIONS
E04D13/1625
FIXED CONSTRUCTIONS
International classification
E04G21/32
FIXED CONSTRUCTIONS
E04D13/16
FIXED CONSTRUCTIONS
E04D12/00
FIXED CONSTRUCTIONS
E04D15/06
FIXED CONSTRUCTIONS
Abstract
This invention provides fall protection systems comprising a suspension fabric, supported by a grid-work of longitudinal and lateral bands, in metal building construction. The fall protection system uses safety clips to attach lateral bands to intermediate purlins, and also provides novel attachments of the lateral bands to eaves and ridges whereby the respective eave and/or the ridge absorbs an enhanced portion of the force of impact when an object falls onto the fall protection system. The invention further provides methods of installing such systems, and buildings embodying such systems.
Claims
1. A fall protection system in a roof structure of a building, said building roof structure including at least first and second rafters, a space between said first and second rafters defining a first distance between said first and second rafters, each said rafter having a top, and opposing first and second ends, said roof structure further comprising an eave, having a length, and extending between the first ends of said first and second rafters, a ridge, having a length, and extending between the second ends of said first and second rafters, and a second distance between said cave and said ridge, said cave and said ridge being disposed on, and extending transverse to, the tops of said first and second rafters, and a plurality of intermediate purlins extending from said first rafter to said second rafter, said fall protection system comprising: (a) a first set of support bands extending from said first rafter to said second rafter and being connected to said building, said first set of support bands being spaced along the lengths of said first and second rafters; (b) a second set of support bands extending from said cave toward said ridge and crossing under said intermediate purlins, said bands of said second set of support bands having first and second end portions and being spaced along the lengths of said cave and said ridge; and (c) a suspension fabric attached to said building roof structure, said suspension fabric underlying said intermediate purlins and overlying said first and second sets of support bands, said first and second sets of support bands supporting said suspension fabric, a first band of said second set of support bands being attached to said building, and crossing under respective ones of said intermediate purlins, said first band, at a given one of the respective said intermediate purlins so crossed, being restrained against at least one of lateral movement and vertical movement, and not being restrained against longitudinal movement.
2. A fall protection system as in claim 1 wherein said first band is attached to said building only at said first and second end portions.
3. A fall protection system as in claim 1, said given purlin having a top flange, a bottom flange, and a web extending between said top flange and said bottom flange, and wherein said first band is supported proximate, and spaced from, said bottom flange of said given purlin.
4. A fall protection system as in claim 1, said first band, when in a generally horizontally-extending orientation, having a generally horizontally-extending length, a generally horizontally-extending width, and a generally vertically-extending thickness, a safety clip being attached to a bottom flange of said given intermediate purlins, said safety clip, either alone or in combination with said given intermediate purlin, defining an opening at or adjacent said given intermediate purlin, said first band extending through such opening, said first band being restrained against lateral movement by said safety clip at sides of such opening, and being restrained against downward movement by said safety clip at a bottom of such opening, said safety clip accommodating generally unrestricted longitudinal movement of said first band through such opening.
5. A fall protection system as in claim 4, said first band being restrained against upward movement by one of (i) said safety clip at a top of such opening and (ii) the overlying said intermediate purlin.
6. A fall protection system as in claim 1, said purlins having top flanges and bottom flanges, and webs extending between said top flanges and said bottom flanges, and wherein said first band is supported at an elevation which approximates an elevation of the bottom flange of said given intermediate purlin, while being spaced from said given intermediate purlin.
7. A fall protection system as in claim 1, said cave having a top flange having a first remote edge remote from said ridge and a first distal edge relatively closer to said ridge, a bottom flange having a second remote edge remote from said ridge and a second distal edge relatively closer to said ridge, and a web extending between said top flange and said bottom flange, and wherein said first band extends under said bottom flange of said cave, and turns a first corner about the second remote edge of said bottom flange and extends upwardly from said bottom flange alongside said web, the first end portion of said first band being attached to said cave between the first corner and a remote end of said first band.
8. A fall protection system as in claim 1, said cave having a top flange having a first remote edge remote from said ridge and a first distal edge relatively closer to said ridge, a bottom flange having a second remote edge remote from said ridge and a second distal edge relatively closer to said ridge, and a web extending between said top flange and said bottom flange, and wherein said first band extends under said bottom flange of said cave, and turns a first corner about the second remote edge of said bottom flange and extends upwardly from said bottom flange to said top flange, turns a second corner about the first remote edge of said top flange, and extends, as the first end portion of said first band, toward said ridge, the first end portion of said first band being attached to said cave between the second corner and a remote end of said first band.
9. A fall protection system as in claim 1, said cave having a top flange having a first remote edge remote from said ridge and a first distal edge relatively closer to said ridge, a bottom flange having a second remote edge remote from said ridge and a second distal edge relatively closer to said ridge, and a web extending between said top flange and said bottom flange, and wherein said first band extends under said bottom flange of said cave, and turns a first corner about the second remote edge of said bottom flange and extends upwardly from said bottom flange to said top flange, turns a second corner about the first remote edge of said top flange, and extends, as the first end portion of said first band, toward said ridge, and wherein said eave further comprises a top flange return extending down from the distal edge of said top flange, and wherein said first band turns a third corner about the first distal edge of said top flange, and is attached to said eave between the third corner and a remote end of said top flange return.
10. A fall protection system as in claim 1, said fall protection system, as installed, being of sufficient strength to catch and support a weight of 400 pounds, distributed over a diameter of approximately 30 inches, when dropped from a height of about 50.5 inches.
11. A fall protection system in a roof structure of a building, said building roof structure including at least first and second rafters, a space between said first and second rafters defining a first distance between said first and second rafters, each said rafter having a top, and opposing first and second ends, said roof structure further comprising an eave, having a first length, and extending between the first ends of said first and second rafters, a ridge, having a second length, and extending between the second ends of said first and second rafters, and a second distance between said cave and said ridge, said eave and said ridge being disposed on, and extending transverse to, the tops of said first and second rafters, and a plurality of intermediate purlins extending from said first rafter to said second rafter, said fall protection system comprising: (a) a first set of support bands extending from said first rafter to said second rafter and being connected to said building, said first set of support bands being spaced along the lengths of said first and second rafters; (b) a second set of support bands extending from said cave toward said ridge and crossing under said intermediate purlins, said bands of said second set of support bands having first and second end portions and being spaced along the lengths of said cave and said ridge; and (c) a suspension fabric attached to said building roof structure, said suspension fabric underlying said intermediate purlins and overlying said first and second sets of support bands, said first and second sets of support bands supporting said suspension fabric, a first band of said second set of support bands being attached to said building and crossing under respective ones of said intermediate purlins, said first band, being restrained against at least one of lateral movement and vertical movement at each of the respective intermediate purlins so crossed, and being restrained against longitudinal movement at less than all of the respective intermediate purlins so crossed.
12. A fall protection system as in claim 11 wherein said first band is restrained against longitudinal movement only at said first and second end portions.
13. A fall protection system as in claim 11, said first band, when in a generally horizontally-extending orientation, having a generally horizontally-extending length, a generally horizontally-extending width, and a generally vertically-extending thickness, a safety clip being attached to a bottom flange of one of said intermediate purlins, said safety clip, either alone or in combination with said one intermediate purlin, defining an opening at or adjacent said intermediate purlin, said first band extending through such opening, said first band being restrained against lateral movement by said safety clip at the sides of such opening, said first band being restrained against downward vertical movement by said safety clip at a bottom of such opening, and being restrained against upward vertical movement by the overlying said intermediate purlin, said safety clip accommodating generally unrestricted longitudinal movement of said first band through such opening.
14. A fall protection system as in claim 13, said purlins having top flanges and bottom flanges, and webs extending between said top flanges and said bottom flanges, and wherein said first band is supported at an elevation which approximates an elevation of the bottom flange of a said intermediate purlin crossed by said first band, a space being present between said first band and the respective said intermediate purlin.
15. A fall protection system as in claim 11, said cave having a top flange having a first remote edge remote from said ridge and a first distal edge relatively closer to said ridge, a bottom flange having a second remote edge remote from said ridge and a second distal edge relatively closer to said ridge, and a web extending between said top flange and said bottom flange, and wherein said first band extends under said bottom flange of said cave, and turns a first corner about the second remote edge of said bottom flange and extends upwardly from said bottom flange alongside said web, the first end portion of said first band being attached to said cave between the first corner and a remote end of said first band.
16. A fall protection system as in claim 11, said cave having a top flange having a first remote edge remote from said ridge and a first distal edge relatively closer to said ridge, a bottom flange having a second remote edge remote from said ridge and a second distal edge relatively closer to said ridge, and a web extending between said top flange and said bottom flange, and wherein said first band extends under said bottom flange of said cave, and turns a first corner about the second remote edge of said bottom flange and extends upwardly from said bottom flange alongside said web to said top flange, turns a second corner about the first remote edge of said top flange, and extends, as the first end portion of said first band, toward said ridge, the first end portion of said first band being attached to said cave between the second corner and a remote end of said first band.
17. A fall protection system as in claim 16, said cave having a top flange having a first remote edge remote from said ridge and a first distal edge relatively closer to said ridge, a bottom flange having a second remote edge remote from said ridge and a second distal edge relatively closer to said ridge, and a web extending between said top flange and said bottom flange, and wherein said first band extends under said bottom flange of said cave, and turns a first corner about the second remote edge of said bottom flange and extends upwardly from said bottom flange alongside said web to said top flange, turns a second corner about the first remote edge of said top flange, and extends, as the first end portion of said first band, toward said ridge, and wherein said cave further comprises a top flange return extending down from the distal edge of said top flange, and wherein said first band turns a third corner about the first distal edge of said top flange, and is attached to said cave between the third corner and a remote end of said top flange return.
18. A fall protection system as in claim 11, said fall protection system, as installed, being of sufficient strength to catch and support a weight of 400 pounds, distributed over a diameter of approximately 30 inches, when dropped from a height of about 50.5 inches.
19. A fall protection system in a roof structure of a building, said building roof structure including at least first and second rafters, having respective first and second lengths, a space between said first and second rafters defining a first distance between said first and second rafters, each said rafter having a top, and opposing first and second ends, said roof structure further comprising an eave, having a third length, and extending between the first ends of said first and second rafters, a ridge, having a fourth length, and extending between the second ends of said first and second rafters, and a second distance between said cave and said ridge, said cave and said ridge being disposed on, and extending transverse to, the tops of said first and second rafters, and a plurality of intermediate purlins extending from said first rafter to said second rafter, said fall protection system comprising: (a) a first set of support bands extending from said first rafter to said second rafter and being connected to said building, and being spaced along the lengths of said first and second rafters; (b) a second set of support bands extending from said cave toward said ridge and crossing under said intermediate purlins, said bands of said second set of support bands having first and second end portions and being spaced along the lengths of said cave and said ridge; and (c) a suspension fabric attached to said building roof structure, said suspension fabric underlying said intermediate purlins and overlying said first and second sets of support bands, said first and second sets of support bands supporting said suspension fabric, a first band of said second set of support bands being attached to said building, for restraint of longitudinal movement of said band at less than all of said intermediate purlins.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Illustrative embodiments of the invention are described hereinafter, by way of examples only, with reference to the accompanying drawings.
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(19) The invention is not limited in its application to the details of construction, or to the arrangement of the components, or to the methods of construction, set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various other ways. Also, it is to be understood that the terminology and phraseology employed herein is for purpose of description and illustration and should not be regarded as limiting. Like reference numerals are used to indicate like components.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
(20)
(21) According to the embodiments illustrated in
(22) Ridge members 22, expressing Z-shaped cross-sections as illustrated in
(23) The ridge members and the eave members overlie, extend transverse to, and are attached to, the upper surfaces of the respective rafters 16, and are spaced from each other by distances which generally correspond to the lengths of the respective rafters.
(24) Intermediate purlins 24 express Z-shaped cross-sections. The intermediate purlins overlie, extend transverse to, and are attached to, upper surfaces 16A of the respective rafters. Purlins 24 are spaced from each other along the lengths of the rafters. The purlins extend parallel to each other and parallel to any ridges and eaves and, overall, span the length of the bay, whereby the purlins are displaced from each other and from any ridges and eaves along the spaces between the respective eave and the ridge.
(25) As shown in
(26) Support bands 26, 28 support a high strength fabric 32, the fabric being shown partially unfolded in
(27) Starting with the structural skeleton of the building as illustrated in
(28) A length of a given longitudinal band 26 extends across a given bay and is extended across the upper surface of each rafter overlain by the respective band, and is attached to the upper surfaces, or other surfaces, of the respective rafters. Where the longitudinal band 26 extends across multiple bays, the longitudinal band is secured, for restrained longitudinal movement, to the upper surfaces of those rafters which are most remote from one another. Optionally, but not necessarily, the longitudinal band may be secured to one or more intermediate rafters.
(29) Longitudinal bands 26 are fastened to the rafters or rake channels (not shown) which correspond with the end portions of the bands by conventional attachment means such as by self-drilling screws. Longitudinal bands 26 are pulled tight between the rafters so as to, in part, and at this stage of installation, begin to define the afore-mentioned band grid, and the imaginary plane of support provided by the band grid, immediately under the intermediate purlins. Band attachment tools, known in the art, may be used in attaching the bands, either temporarily or permanently, to the rafters or rake channels, thus to instill a suitable, conventionally known, level of tension in bands 26 as the bands are being installed.
(30) Each eave has a top flange 34, a bottom flange 36, and an upstanding web 38 extending between the top and bottom flanges, and connecting the top flange to the bottom flange. The top and bottom flanges are arranged such that the profile of the eave defines a C-shaped structure, perhaps best seen in
(31) While the eave profiles shown define generally perpendicular turns between the flanges 34 and 36, and upstanding web 38, actual eave profiles typically define a modest acute angle (not shown) between the bottom flange and the upstanding web and a corresponding modest obtuse angle (not shown) between the top flange and the upstanding web. Such acute and obtuse angles adapt the eave to the specific slope of the roof for which the eaves are designed, while providing that the upstanding web conform to the vertical orientation of the respective side wall of the building.
(32) Correspondingly, each ridge has a top flange 40, a bottom flange 42, and an upstanding web 44 extending between the top and bottom flanges, and connecting the top flange to the bottom flange. The top and bottom flanges are arranged such that the profile of the ridge defines a Z-shaped structure, illustrated in
(33) Similarly, each intermediate purlin has a top flange 46, a bottom flange 48, and an upstanding web 50 extending between the top and bottom flanges, and connecting the top flange to the bottom flange. The top and bottom flanges are arranged such that the profile of the respective purlin defines a Z-shaped structure, illustrated in
(34) Lateral bands 28 are installed after the longitudinal bands 26 are in place. Lateral bands 28 extend transverse to, typically perpendicular to, the longitudinal bands. Lateral bands 28 generally underlie and support longitudinal bands 26. Lateral bands 28 may be first attached to the respective ridge 22. Bands 28 may be attached to any suitable surface of the ridge which enables the band to pass, from the location of attachment, under and in tensioned contact with, the bottom flange of the ridge. For example, a lateral band can be attached to the bottom surface of the bottom flange of the ridge, with intervening fabric 32, and extend from there toward the eave.
(35) As an alternative, one end of a given lateral band can extend up alongside, and be fastened to, the surface of the upstanding ridge web which faces away from the eave on the respective slope of the roof. The band passes alongside, and turns about, the edge of the bottom flange of the ridge which faces away from the respective eave, and then passes under, and in general contact with, the bottom surface of the bottom flange, again with intervening fabric, and extends from there toward the eave.
(36) As a still further example of attachment of a lateral band to the ridge, the band can be attached to the top surface of the top flange, turn about the upper edge of the top flange which is away from the respective eave, extend from there down toward the bottom ridge flange, turn about the edge of the bottom flange and pass alongside, and in general contact with, the bottom surface of the bottom flange, and extend from there toward the eave, again with the fabric between the band and the ridge.
(37) The lateral bands are extended, from the bottom surface of the bottom flange of the ridge toward the respective eave, passing under the longitudinal bands, and pulled tight to minimize sag in both the lateral bands and the respective overlying longitudinal bands. The so-tightened lateral bands are in general contact, again with intervening fabric, with the bottom surface of the bottom flange of the respective eave. With the so-tightened lateral bands in contact with the bottom surface of the bottom flange of the respective eave, the lateral bands are fastened to the eave so as to maintain the tension in the lateral bands, thus to lift the lateral bands toward the bottom flanges of the overlying intermediate purlins.
(38) The number of lateral bands 28 to be used between a respective pair of next-adjacent rafters, and the spacing between the lateral bands, varies with the distance between the rafters. Typically, the lateral bands are 36 inches to 40 inches apart, optionally up to 48 inches apart in some cases.
(39) Traditional banding stock used for bands 26 and 28 is a hot-dip zinc/aluminum alloy-coated Grade 80 structural steel, 0.023 inch thick, having longitudinal tensile yield strength of at least 93 ksi, such Grade 80 banding sometimes being referred to in the industry as full hard. Such steel banding is typically about 1 inch wide and continuous length. Such traditional full hard steel banding is available from Steelscape, A BlueScope Steel Company, Kalarna, Wash. as ZINCALUME Steel Grade 80 (Class 1).
(40) Banding used in the invention is distinguished from steel bar stock in that steel bar stock is stiff and rigid. By contrast, the banding used in the invention is thin and flexible such that the banding is typically shipped to the user in rolls. When the banding stock is cut to the e.g. specified 1-inch width, and the resulting bands are loosely draped over rafters spaced e.g. 25 feet apart, mid-sections of the bands readily drape downwardly by multiple feet from the elevations of the rafters. Further, such banding is completely incapable of supporting itself or the overlying suspension fabric until substantial tensile force, which can be manually applied using hand tools, is applied to the banding.
(41) Certain fabrics are known in the art for use as suspension fabrics in roof insulation systems, and such fabrics may be acceptable in the fall protection systems of the invention, provided that the bands used in the band grid-work of the invention are sufficiently close together. An exemplary fabric, which the inventors have tested and found satisfactory for use with the band grid-work disclosed herein is available as Type 1070 Vapor Retarder fabric from Intertape Polymer Group, Bradenton, Fla. The Type 1070 fabric is a woven HDPE scrim having the following characteristics as specified by the fabric supplier:
(42) Nominal thickness9 mils (0.23 mm)
(43) Nominal weight4.3 oz/yd.sup.2 (149 g/m.sup.2)
(44) Grab TensileWarp 136 lb (605 N)/Weft 126 lb (559 N)
(45) Strip TensileWarp 100 lb/in (877)/Weft 90 lb/in (799)
(46) Tongue TearWarp 50 lb (222 N)/Weft 45 lb (200 N)
(47) Mullen Burst245 psi (1690 kPa)
(48) Moisture vapor transmission of 0.02 perms.
(49) A typical bay 18 is about 25 feet wide, between pairs of next-adjacent rafters. Within a given bay, lateral bands 28 extend parallel to each other, parallel to the respective rafters which define the bay, and are generally spaced apart by about 36 inches to 40 inches, but no more than 48 inches. Thus, a desired spacing between lateral bands 28 is 36-40 inches; but up to 48 inches is accepted where the increase from 40 inches e.g. up to 48 inches can reduce the number of bands.
(50) In the invention, the lateral bands which are closest to the opposing sides of the rafters are referred to as safety bands 28S, in part because the safety bands are the bands which are the most likely ones of the lateral bands to receive the stress of having a worker fall onto the suspension fabric used in the fall protection system. Further, the inventors have discovered that the safety bands, when stressed by a fall, absorb more of the force than when any other lateral band is stressed by a fall. The inventors contemplate that the force of a fall/drop test away from the rafters can be dispersed among at least four bands which surround the drop location; whereas by contrast, when such force is imposed close to the rafter, only 3 bands are disposed around the drop site, whereby those 3 bands, in that instance, do the work done by 4 bands at locations further away from the rafter.
(51) The safety bands 28S are graphically delineated in
(52) Known prior-art-alleged fall protection systems specify that each lateral band be attached by a Tek screw to the bottom flange of each intermediate purlin, whereby a substantial fraction of the force of a worker falling, or the force of a drop test, is transferred through the respective lateral bands to the next adjacent purlins. Where the force is applied at the lateral band which is next-adjacent a rafter, that force is transferred by a single such lateral band.
(53) It is known that, when a fall protection system of the prior art is tested using the government-mandated test procedure, even if the system successfully passes the test, namely catches and holds the falling object, the suspension fabric tears at the screws which fasten the fabric and bands to the purlins. Typically, the banding closest to the falling object also breaks.
(54) As a corrective measure, some commercially available alleged fall protection systems require the use of two Tek screws, at least two inches apart, into the bottom flange of each respective eave. The purpose of the second screw is believed to be to provide additional strength to the band, to prevent the band from tearing past the screws, or tearing diagonally out the side of the band, when the object impacts the fall protection system fabric.
(55) The determination of passing or failing the government-defined drop test is whether the falling object proceeds through the fabric, known as a test failure, or is successfully held and supported by the fabric, which is a successful, passing of the test.
(56) The inventors herein have discovered, by their experience, by their testing, that existing commercially available alleged fall protection systems, even those using the two-screw attachment, fail the government-defined drop test when the force is applied adjacent a rafter, or anywhere the impact is not absorbed by 4 bands surrounding the point of impact. Accordingly, the invention contemplates novel ways of using the lateral bands.
(57) As illustrated in
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(60) The safety clip is oriented relative to the ridge and eave such that opposing ends of opening 64 are disposed, respectively, toward the corresponding ridge 22 and eave 20. Accordingly, the passage which extends through opening 64 extends in the same direction as lateral bands 28.
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(62) However, safety clip 52 places no limitations on the ability of the lateral band 28 to move longitudinally with respect to the safety clip. Thus, other than incidental friction between the walls of the loop, such as at the bottom of the lateral band and the top of the lower leg of the safety clip, longitudinal movement of the lateral band relative to the safety clip is generally unhindered.
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(64) Safety clip 52A operates very similar to safety clip 52 in that the installation of safety clip 52A limits lateral movement of band 28 while providing generally unrestricted longitudinal movement of the lateral band relative to the safety clip.
(65) So, rather than building a fall protection system to transfer the impact force on the lateral band to the closest purlins by screwing the lateral band to the bottom flange of each purlin as in the prior art, the invention uses a longer length of banding, defined through the loop of at least one safety clip, on at least some of the lateral bands, to absorb some of the laterally-expressed energy of the impact force as well as, in some bands, to transfer a substantial portion of the laterally-expressed impact force to the ridge and eave of the roof, and/or to one or more of the intermediate purlins which are displaced from the point of impact by at least one purlin.
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(67) Thus, the safety band is secured against longitudinal movement of the band only at the ridge and at the eave. Between the ridge and the eave, the safety band is free to move longitudinally through each of the safety clips, while being restricted against lateral movement beyond the boundaries of loops 62 at the respective purlins/safety bands.
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(69) When a falling/dropping impact force arrives on the suspension fabric, the force received by the suspension fabric has a first directional force component and a second velocity/shock/suddenness component. The force component of the impact is resisted by, absorbed by, the deflection characteristics of the materials in the fall protection system. The velocity/shock/suddenness component of the impact addresses the rate at which the respective materials can deflect as the force of the impact is applied to the respective building elements.
(70) Where a safety band 28S, mounted to a purlin by a safety clip 52, is one of the closest lateral bands to the point of impact, a first portion of that force is transferred, as first tensile forces, into the full length of the longitudinally-mobile portion of the respective safety band and is absorbed by tensile elongation of the safety band.
(71) A second portion of that received force is transferred, by the safety band through the safety clips closest to the location of the impact, and thence to the purlins which are closest to the location of the impact.
(72) A third portion of that received force is transferred, by the safety band, to the purlins, the ridge, or the eave which are next adjacent the purlins which are closest to the location of the impact, such that greater than two, typically at least four, longitudinally-extending structural members of the roof participate in dissipating substantial portions of the impact of the fall/drop. A fourth portion of that received force to the eave and ridge.
(73) A fourth portion of that force is transferred to respective closest ones of the longitudinal bands, which transfer their received tensile forces to the respective next adjacent rafters.
(74) A fifth remainder portion of that force is distributed about the respective affected area of the suspension fabric. While choosing to not be bound by theory, the inventors herein contemplate that the fabric absorbs both a portion of the directional component of the force of the impact and a velocity/shock/suddenness component of the force of the impact.
(75) Turning again to the responses of the bands, the tensile forces so imposed on the longitudinal bands and the safety band are distributed along the full lengths of the respective longitudinal bands and the respective safety band, while the tensile forces imposed on the remaining ones of the lateral bands may be transferred directly to the closest ones of the intermediate purlins. Thus, the elongation properties of both the longitudinal bands and the safety band are utilized along the full lengths of such bands between their points of attachment at the ridge, the eaves, and the rafters, all of which are disposed at the edges of the respective bay.
(76) The benefit of using the full lengths of the safety bands to absorb the impact force of the fall/drop is that more of the force is dissipated by band elongation rather than that force being retained in the fabric or transferred to the next adjacent purlins. In addition, a portion of the force can be transferred, by the safety band, to additional ones of the purlins, and additional portions of the force can be transferred to the eave and to the ridge. Thus, the use of the safety clips to accommodate longitudinal mobility of the safety band results in dissipating more of the force of the impact in an increase number of elements of the roof structure. By increasing the number of elements of the roof structure which participate in dissipating the force of the impact, the amount of the force which must be dissipated by the fabric and by the bands is reduced. Such reduction in the amount of the force which must be dissipated by the bands and the fabric provides increased opportunity for the fabric to survive the force of the impact without catastrophic failure of the fabric which is, by definition, a failure of the fall protection system.
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(79) Referring again to
(80) In a second set of embodiments, illustrated in
(81) In a third set of embodiments, illustrated in
(82) In a fourth set of embodiments, illustrated in
(83) The common feature of the attachments in
(84) In addition, referring now to
(85) As an alternative to wrapping the fabric about the eave with the lateral band, the fabric can extend inside the eave instead of outside the eave. A leading edge of the fabric enters the eave above bottom flange 36, passes across the top of the bottom flange to web 38, passes along the inside surface of web 38 and up to upper flange 34 and thence toward the ridge to the opening which faces the ridge. By traversing such path inside the cavity defined inside the eave, the fabric can substantially encase the edge of any insulation which is to be installed on top of the fabric in the space between the eave and the next-adjacent purlin.
(86) Purlins 24, eave 20, and ridge 22 extend a few inches beyond the respective rafter. A rake channel defining a C-shaped cross-section, not shown, is commonly mounted over the ends of the purlins, the eave, and the ridge, at the end of the building. The invention also contemplates that, instead of the longitudinal bands being fastened to the top flange of the corresponding rafter, the longitudinal bands 26 can pass over the top of the upper flange of the rafter, under the lower flange of the rake channel, and wrap about at least one corner of the bottom flange of the rake channel, optionally about the top flange of the rake channel, as illustrated in
(87) At the eave, the embodiments of
(88) The embodiments of
(89) The embodiments of
(90) Thus, referring to the combination of
(91) Thus, in a given embodiment, the safety bands are suspended from the intermediate purlins by safety clips, and the ends of the safety bands turn at least one corner about the remote edge of the lower flange of the eave before being terminated at one or more screws 66; and the remaining lateral bands (non-safety bands) are fastened to the intermediate purlins, either directly through the suspension fabric through a washer, or fastened to some or all of the intermediate purlins using safety clips. The remaining lateral bands (non-safety bands) may be fastened to each of the intermediate purlins directly through the fabric to the lower flange of the purlin using a screw.
METHOD
(92) Installation of a fall protection system of the invention begins after the columns, rafters, ridges, eaves, and intermediate purlins are in place about at least a given bay. Typically, installation of the fall protection system begins after erection/emplacement of all of the columns, rafters, ridges, eaves, and purlins.
(93) Installation of the fall protection system begins by installing longitudinal bands 26. A given longitudinal band is installed by unwinding band material from a roll and extending the band material over the tops of the respective rafters and across a given bay or bays. At least one longitudinal band is extended, between each next-adjacent pair of purlins to at least the next rafter, and is cut to length. The longitudinal bands are manually stretched tight with hand tools, and the so-tightened bands are fastened to the respective rafters with Tek screws. As illustrated in the drawings, the longitudinal bands typically extend perpendicular to the rafters. The so-partially-installed, tightened, longitudinal bands extend from rafter to rafter at generally the height of the tops of the rafters, but some nominal amount of sag of the longitudinal bands exists between the rafters at this stage of installation.
(94) Typically, the purlins are spaced no more than 5 feet apart. In this invention, typically a single band is installed between each pair of next-adjacent purlins so long as the purlin spacing is no more than the typical maximum of 5 feet. Where the purlin spacing approaches, or exceeds, the typical 5-feet maximum, an additional longitudinal band 26 may be used in one or more of the spaces between the purlins.
(95) Once the longitudinal bands 26 have been emplaced and tightened, banding for lateral bands 28 is unrolled under the longitudinal bands, and one end of the banding is secured to the respective ridge or purlin, or to an opposing eave. The lateral banding material is extended to the eave and then tightened sufficiently to raise both the lateral band and the overlying longitudinal bands into close proximity with the intermediate purlins. This process is repeated along the width of the bay, e.g. between the rafters, until the desired number of lateral bands has been emplaced across the width of the bay.
(96) With the band grid system thus temporarily in place, a zigzag-folded roll of the suspension fabric is elevated to the height of the rafters, typically adjacent a rafter at an end of the building or bay. The fabric is then unrolled on top of the band grid in one of the spaces between next-adjacent ones of the purlins such that one end of the fabric faces the eave and the opposing end of the fabric faces the ridge. The ends of the fabric are then pulled, individually, toward the eave and the ridge, working the leading ends of the fabric under the intervening purlins and above the band grid. The initial phase of the process of so-extending the fabric is illustrated in
(97) Once the fabric has been generally extended the full length and width of the bay over which the fabric is to be suspended, over the band grid and under the intermediate purlins, the lateral bands are then attached to the intermediate purlins, beginning at the ridge and working toward the eave. The method of such attachment at each intersection of band and purlin is determined by the fall protection system which has been designed for, specified for, that particular building. In a typical design, the safety bands 28S are attached to each purlin using safety clips 52.
(98) For example, a safety clip such as that shown in
(99) Once the attachments to the intermediate purlins have been completed, the temporary attachments of the bands to the eave are released, and the fabric is worked up alongside the eave, such as alongside web 38, top flange 34, and/or top flange return 76, with the fabric thus between the eave and the respective lateral bands. With the fabric thus in place, each band is again stretched against the eave and permanently fastened to the eave at the respective location on the eave, according to the embodiment being implemented, whether the embodiment of
(100) Sides of the fabric are then cut around the purlins at each rafter, as known in the art, and edges of the fabric are secured to the top surfaces of the rafter such as by adhesive, also as known in the art.
(101) With both the longitudinal and lateral bands so secured to the roof structure; with the fabric so secured to the ridge and eave by the lateral bands and secured to the rafters by e.g. adhesive, installation of the fall protection system of the invention is thus complete and ready to protect workers who subsequently install other elements of the building while working at the roof elevation; such elements as the roof insulation and the roof panels.
(102) Suspension fabric 32, which in the preferred embodiment consists of a vapor barrier material, is trimmed to size before installation. The suspension fabric is installed one bay 18 at a time and, in the case of large buildings or buildings with high gables, fabric 32 for each half of the bay may be divided at ridge 22 and may be installed separately.
(103) The suspension fabric has been cut, prior to installation, to a size having a dimension a few inches longer than the dimensions of the bay to be overlaid, and is Z-folded for easy spreading above the band grid. For this purpose a zigzag type fold, as shown in
(104) The fall protection systems of the invention are designed to be of sufficient strength to catch and support a man's weight, generally between 250 and 400 pounds. The system is tested by dropping a 400 lb. weight with the center of gravity of the weight, before the weight is dropped, being 42 inches above a worker's walking height, thus 42 inches plus the height of the purlins, namely about 50.5 inches above the fabric. To pass the test, the system must stop the falling weight at any point in the bay which is so protected. In one test specified by OSHA, 400 lb. of washed gravel or sand is placed into a reinforced bag that can tolerate being dropped repeatedly. The test bag is 30 inches in diameter, plus or minus 2 inches. The 400 pound bag is hoisted above the fall protection system to a height of 42 inches above the plane of the intermediate purlins, measuring from the center of the so-filled bag. A cord supporting the weight of the bag is then released, allowing the weight to free fall in one concentrated load. The weight can be dropped onto any part of the fall protection system to test different areas.
(105) Although the invention has been described with respect to various embodiments, it should be realized this invention is also capable of a wide variety of further and other embodiments within the spirit and scope of the appended claims.
(106) Those skilled in the art will now see that certain modifications can be made to the apparatus and methods herein disclosed with respect to the illustrated embodiments, without departing from the spirit of the instant invention. And while the invention has been described above with respect to the preferred embodiments, it will be understood that the invention is adapted to numerous rearrangements, modifications, and alterations, and all such arrangements, modifications, and alterations are intended to be within the scope of the appended claims.
(107) To the extent the following claims use means plus function language, it is not meant to include there, or in the instant specification, anything not structurally equivalent to what is shown in the embodiments disclosed in the specification.