FORCE DISTRIBUTION AND ATTENUATION DEVICE FOR USE IN A ROOF ANCHOR SAFETY SYSTEM
An anchor-to-lanyard adjustable riser cable with a choke and bearing plate. The device is positioned between a roof truss and a safety anchor system to better distribute the weight of a roofer on the truss in the event the roofer falls. The bearing plate is configured to engage a portion of the truss and to distribute forces into this structural member, thereby leading to attenuation of those forces. The bearing plate is provided with a non-skid surface to resist movement of the same along the structural member. Guide channels are provided on the bearing plate to receive portions of the cable from the cable choke therethrough. The bearing plate aids in protecting the structural member from being damaged by a lanyard extending to the safety harness in response to forces generated by the falling roofer.
1. Technical Field
This invention generally relates to safety systems. More particularly, the invention relates to a safety system for a roof anchor. Specifically, the invention relates to device that is engaged between a roof truss and a roof anchor safety system for distributing and attenuating the forces that would be applied to the truss and roof sheathing in the event of a roofer falling while being secured to the truss by a safety harness.
2. Background Information
There are a variety of roof anchor safety systems that are used by roofers to ensure their safety while they are working on a roof. The safety harness is worn on the body and is connected by a steel cable to an anchor that is temporarily or permanently mounted on some region of the roof truss system. Should the roofer slip or fall, the cable connected to the anchor will tend to prevent them from falling off the roof and being severely injured.
One of the problems in previously known safety systems is that the anchor is typically mounted on the peak or on the opposite side of the truss from where the roofer is working. This means that the steel cable extending between the anchor and the safety harness lanyard worn by the roofer is typically fed over the wood that forms the peak of the roof truss and is in direct contact with the sheathing that forms the base of the roof between the trusses. Since the cable is made from steel, it can cause substantial damage to the truss peak and to the plywood sheets that are used as sheathing in the event that the roofer slips or falls. This damage is essentially caused as the steel cable slams with force into the wood or plywood when the cable connected to the safety harness lanyard suddenly has to bear the roofer's full weight. The impact of the cable can slice and splinter the wood or sheathing and potentially damage the structural integrity of the same.
There is therefore a need in the art for an improved safety anchor system that will tend to distribute and attenuate the forces involved in the event of this type of accident and which will thereby tend to minimize the potential damage to the wooden components of the roof.
BRIEF SUMMARY OF THE INVENTIONThe present invention is an anchor-to-lanyard adjustable riser cable with a choke and bearing plate that is positioned between a roof truss and a safety anchor system for distributing and attenuating the forces that would be applied to the truss and roof sheathing in the event of a roofer falling while being secured to the truss by a safety harness. In addition, the device transfers the energy force from the bottom of the truss rafter and the anchor connector plate to the top of the truss rafter when an attached workman slips or falls from the roof. This force transfer is important, creating a direction of force that favorably compresses the peak truss rafter joint rather than causing a horizontal pulling force on the lower portion of the truss connector plate. The device thus better distributes a roofer's weight and attenuates forces generated by the roofer falling than would be the case if the roofer's safety harness was directly secured by a cable or lanyard to a roof anchor on the truss. The bearing plate is configured to engage a portion of the truss and is provided with a non-skid surface to resist movement therealong. The bearing plate distributes the forces over a wider region of the truss than if only a cable connected the truss and harness. The plate protects the truss and roof ridge from possible damage when the lanyard suddenly is pulled taut and also aids in protecting the sheathing on the opposite side of the roof ridge. The choke is used to adjust the riser length.
The device of the present invention does not aid the anchor system in arresting the fall of the roofer. It does, however, offer a measure of protection to the structural members of the roof in the event of a roofer's fall so that those structural members remain capable of performing as intended for the useful life of the building.
Preferred embodiments of the invention, illustrated of the best modes in which Applicant contemplates applying the principles, are set forth in the following description and are shown in the drawings and are particularly and distinctly pointed out and set forth in the appended claims.
Referring to
Each roof truss 18 is comprised of a plurality of wood rafters 22 that are secured together by a plurality of steel plates 24. In particular, roof truss 18 includes an anchor plate 26 that is engaged with rafters 22 adjacent the peak 28. Anchor plate 26 is preferably a plate such as those disclosed in U.S. Pat. Nos. 7,380,373 and 7,832,153 issued to the present inventor.
As shown in
Referring now to
First leg 42 is a generally planar member having a first face 42a and a second face 42b. First leg 42 defines a pair of spaced-apart apertures 46 therein that extend between first face 42a and second face 42b. The planar member may be reinforced in the regions immediately surrounding apertures 46. Second leg 44 is also a generally planar member having a first face 44a and a second face 44b.
In accordance with a specific feature of the present invention, first face 44a is provided with a non-skid surface 48 thereon. When force distribution device 36 is used, second leg 44 of bearing plate 38 is positioned in abutting contact with an upper surface 22a of one of the rafters 22 of truss 18. Non-skid surface 48 is provided to improve the traction between bearing plate 38 and the upper surface 22a of truss rafter 22. Non-skid surface 48 may be provided on first face 44a in a number of ways. Firstly, a plurality of grooves and ridges may be milled into the smooth original metal surface of first face 44a. Alternatively, a compound such as a gripping polymer may be applied to first face 44a or an abrasive aggregate may be bonded to the metal of first face 44a with an adhesive. Any other suitable methodology and substances may be utilized or applied to first face 44a to produce the non-skid surface 48 and these other methodologies and substances are considered to fall within the scope of the present invention. Additionally, it should be understood that bearing plate 38 may be produced in shapes other than the L-shape illustrated herein without departing from the scope of the present invention provided that the differently configured bearing plate is able to distribute force over a greater area of rafter 22 than would be the case if a cable directly connected the safety harness on the roofer to the rafter.
Preferably, the exterior edges 50 of one or both of first and second legs 42, 44 on bearing plate 38 are beveled or rounded so as to present a curved surface for contact by cable choke 40 and so as to reduce the possibility of bearing plate 38 cutting into the wood of rafter 22 and thereby damaging the same.
Cable choke 40 preferably is a steel cable that is of sufficient strength so as not to break in the event of an impact due to a roofer falling. A free end of the cable 39 of cable choke 40 is threaded into a first one of the apertures 46 in bearing plate 38 in the direction indicated by arrow “A” in
Force distribution device 36 is used in the following manner. A clip 60 secured to a lanyard 62 is engaged with third looped region 58 on force distribution device 36. Although not shown herein, it is to be understood that lanyard 62 may itself be directly connected to a safety harness worn by the roofer or it may be connected to a cable that is secured to the safety harness. Bearing plate 38 is positioned on an upper surface 22a of an appropriate one of rafters 22. The rafter is selected based on which side of the roof the roofer will be working. Bearing plate 38 should be positioned on the rafter disposed on the opposite side of the roof from the roofer. Non-skid surface 48 of bearing plate 38 is therefore positioned on upper surface 22a of rafter 22A adjacent peak 28 and in such a way that third looped region 58 is disposed between the roofer and bearing plate 38. Additionally, a first portion of cable 39 and first looped area 54 are positioned adjacent a first side wall of rafter 22A and a second portion of cable 39 and second looped area 56 are positioned adjacent an opposed second side wall of rafter 22A. An anchor plate pin 64 is inserted through one of the holes 34 in anchor plate 26 and the aligned first and second looped areas 54, 56 on cable choke 40. (Pin 64 will be removed when it is desired to disengage force distribution device 36 from rafter 22A.). The roofer secures his safety harness (not shown) to lanyard 62. Non-skid surface 48 on bearing plate 38 aids in substantially immobilizing bearing plate 38 on rafter 22A. Consequently, if the roofer should fall, the impact thereof will be transmitted from the harness (not shown) through lanyard 62 and clip 60 to force distribution device 36. The force is then transmitted through cable choke 40 to bearing plate 38 and is thereby transmitted to a region of rafter 22A in abutting contact with bearing plate 38. The traction of bearing plate 38 on rafter 22A afforded by non-skid surface 48 substantially prevents bearing plate 38 from sliding along rafter 22 under the impact of the force. Bearing plate 38 aids in distributing the force due to the impact more evenly into the upper surface 22a of rafter 22 and thereby aids in attenuating that force and reducing potential damage to rafter 22 and sheathing 20. Additionally, at least a portion of the steel cable 39 of cable choke 40 is in contact with the metal of bearing plate 38 instead of being in direct contact with the wood of rafter 22A. The metal disposed between cable 39 and the wood of rafter 22A also substantially reduces the potential damage to rafter 22A. As illustrated in
The features of bearing plate 138 are shown in greater detail in
First leg 142 of bearing plate 138 is a generally planar member having a first face 142a and a second face 142b. In accordance with a specific feature of the present invention, first leg 142 is a generally U-shaped member comprising first and second arms 165, 167 that define a gap 166 there between. Gap 166 is sized and shaped to be complementary to the cross-sectional size and shape of at least a top region of a roof rafter 122. First leg 142 defines a first portion 168a that will abut a first side surface (not shown) of rafter 122 when plate 138 is engaged therewith, a second portion 168b that will abut an upper surface 122a of rafter 122, and a third portion 168c that will abut a second side surface 122b of rafter 122.
In accordance with yet another feature of the present invention, a pair of tubular conduits 170, 172 is welded or otherwise secured to second face 142b of bearing plate 138. Tubular conduit 170 is provided on first leg 165 of bearing plate 138 and tubular conduit 172 is provided on second leg 167 thereof. Tubular conduits 170, 172 each define a bore 170a, 172a there through that is of any cross-sectional shape suitable to receive a portion of cable 139 of cable choke 140 there through.
Second leg 144 of bearing plate 138 is a generally planar member having a first face 144a and a second face 144b. In accordance with the present invention, first face 144a is provided with a non-skid surface and is adapted to abut upper surface 122a of truss rafter 122 when force distribution device 136 is engaged therewith. The non-skid surface provided on first face 144a is shown in
In accordance with yet another feature of the present invention, second leg 144 of bearing plate 136 further includes a pair of spaced apart tubular conduits 178, 180. Tubular conduits 178, 180 are welded or otherwise secured to second face 144b of bearing plate 138. Tubular conduits 178, 180 each define a bore 178a, 180a there through that is configured to have a cross-sectional shape through which cable choke 140 may be threaded. Tubular conduit 178 is generally aligned with tubular conduit 170 and tubular conduit 180 is generally aligned with tubular conduit 172. A first portion of cable 139 is threaded through tubular conduits 172 and 178 in a first direction, and a second portion of cable choke 140 is threaded through tubular conduits 174 and 180 in the opposite direction so that a looped region is formed in cable 139 as was the case with cable choke 40. The free ends of cable 139 are then looped back onto themselves and swages 152 are used to secure the same. Cable choke 140 therefore includes first, second and third looped regions as was the case with cable choke 40, except that in
Force distribution device 136 is used in the following manner. Bearing plate 138 is positioned on upper surface 122a of rafter 122 as illustrated in
Bearing plate 238 comprises a generally L-shaped bracket having a first leg 242 and a second leg 244. First and second legs 242, 244 are disposed at an angle relative to each other that is between 80° and 100° and preferably is 90°. Bearing plate 238 is manufactured from a strong, rigid material such as metal, preferably steel.
First leg 242 of bearing plate 238 is a generally planar member having a first face 242a and a second face 242b. In accordance with a specific feature of the present invention, first leg 242 is a generally U-shaped member comprising first and second arms 265, 267 that define a gap 266 there between. Gap 266 is sized and shaped to be complementary to the cross-sectional size and shape of at least a top region of a roof rafter 222. First leg 242 defines a first portion 268a that will abut a first side surface (not shown) of rafter 222 when plate 238 is engaged therewith, a second portion 268b that will abut an upper surface 222a of rafter 222, and a third portion 268c that will abut a second side surface 222b of rafter 222.
In accordance with yet another feature of the present invention, a pair of apertures 290, 292 is defined in first leg 242 of bearing plate 238. Aperture 290 is defined in first arm 265 and aperture 292 is defined in second arm 267. Apertures 290, 292 extend between first and second faces 242a, 242b of first leg 242 and preferably are positioned adjacent the region 294 where first leg 242 is joined to second leg 244, i.e., the apertures are positioned close to the corner of bearing plate 238. Preferably, apertures 290, 292 are horizontally aligned with each other.
Second leg 244 of bearing plate 238 is a generally planar member having a first face 244a and a second face 244b. In accordance with the present invention, first face 244a is provided with a non-skid surface and is adapted to abut upper surface 222a of truss rafter 222 when force distribution device 236 is engaged therewith. The non-skid surface provided on first face 244a is substantially identical to the non-skid surface provided on first face 144a of bearing plate 138. As such, the non-skid surface comprises a plurality of alternating grooves 274 and ridges 276 that are milled into first face 244a. The possible variations in the grooves and ridges have been described with reference to bearing plate 138 and will therefore not be discussed further herein. It should be understood that other suitable non-skid surfaces may be provided on first face 244a without departing from the scope of the present invention.
In accordance with yet another feature of the present invention, a pair of apertures 296, 298 is defined in second leg 244 of bearing plate 238. Aperture 296 is defined adjacent a first edge 244c and extends between first and second faces 244a, 244b of first leg 244. Aperture 296 is substantially longitudinally aligned with aperture 290 in first leg 242. Aperture 298 is defined adjacent a second edge 244d of second leg 244 and extends between first and second faces 244a, 244b. Aperture 298 is substantially longitudinally aligned with aperture 294 in first leg 242. Aperture 296 is generally horizontally aligned with aperture 298.
A first portion of cable 239 of cable choke 240 is threaded through aligned apertures 290 and 296 in a first direction, and a second portion of cable choke 240 is threaded through aligned apertures 298, 294 in the opposite direction so that a looped region is formed in cable 239 as was the case with cable choke 40. As illustrated in
Force distribution device 236 is used in the following manner. Bearing plate 238 is positioned on upper surface 222a of rafter 222 as illustrated in
Force distribution device 236 has been found to be adaptable to a range of different roof pitches that might be encountered by a roofer. Device 236 has a lower center of gravity than devices 36 and 136 and therefore tends to hold better on roof trusses having a steeper pitch.
It should be noted that one of the advantages of the present invention is that the force geometry relating to securing a lanyard to a roof anchor has been improved over devices that were previously known. In particular, the force geometry is improved by cabling the resistance from under the rafter to the top of the rafter through the bearing plate. Devices 36, 136 and 236 transfer the energy force from the bottom of truss rafter 22, 122, 222 and anchor plate 26, 126, 226 to the top of truss rafter 222 when an attached roofer slips or falls from the roof. This force passes through the slide adjustable bearing plate 38, 138, 238. The force transfer is important in that it creates a direction of force that favorably compresses the peak truss rafter joint (indicated at 300 in
In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed.
Moreover, the description and illustration of the invention are an example and the invention is not limited to the exact details shown or described.
Claims
1. A force distribution device for securement between a structural member disposed a distance vertically above the ground and a safety harness lanyard worn by a person, said device comprising;
- a cable choke adapted to engage the safety harness lanyard; and
- a bearing plate engaged with the cable choke and adapted to engage a portion of the structural member; said bearing plate being configured to distribute forces into the structural member that are generated by the weight of the person falling toward the ground.
2. The force distribution device as defined in claim 1, wherein the bearing plate is a bracket having a first leg and a second leg, wherein the first and second legs are disposed at an angle to each other, and wherein the second leg is adapted to abut the structural member.
3. The force distribution device as defined in claim 2, further comprising:
- a first face provided on the second leg and adapted to abut the structural member; and
- a non-skid surface provided on the first face.
4. The force distribution device as defined in claim 3, wherein the non-skid surface comprises at least one groove or ridge provided on the first face.
5. The force distribution device as defined in claim 4, wherein the bearing plate has a longitudinal axis that is adapted to be aligned with a longitudinal axis of the structural member, and wherein the at least one groove or ridge is disposed substantially at right angles to the longitudinal axis of the bearing plate.
6. The force distribution device as defined in claim 4, wherein the second leg extends outwardly from the first leg and terminates in an edge disposed substantially parallel to the first leg, and a plurality of alternating grooves and ridges are provided in the first face of second leg between the first leg and the edge thereof.
7. The force distribution device as defined in claim 6, wherein the plurality of grooves and ridges cover substantially the entire first face.
8. The force distribution device as defined in claim 4, wherein the second leg extends outwardly from the first leg and terminates in an edge disposed substantially parallel to the first leg, and wherein the second leg further has opposing sides extending between the first leg and the edge, and wherein the at least one groove or ridge extends for at least a partial distance between the opposing sides.
9. The force distribution device as defined in claim 3, wherein the non-skid surface comprises a gripping compound or an abrasive compound applied to the first face of the second leg.
10. The force distribution device as defined in claim 2, further comprising:
- a first guide channel provided on the first leg of the bearing plate, and
- a cable provided in the cable choke, and wherein a first portion of the cable is received through the first guide channel.
11. The force distribution device as defined in claim 10, wherein the first guide channel comprises one of a first aperture defined in the first leg and a first tubular element disposed on the first leg, where the first aperture extends between a first face and a second face of the first leg, and the first tubular element is disposed on the second face of the first leg and generally parallel to a longitudinal axis of the bearing plate.
12. The force distribution device as defined in claim 10, further comprising:
- a second guide channel provided on the first leg of the bearing plate a spaced distance from the first guide channel, and wherein a second portion of the cable is received through the second guide channel.
13. The force distribution device as defined in claim 12, wherein the second guide channel comprises one of a second aperture defined in the first leg and a second tubular element disposed on the first leg, where the second aperture extends between the first face and the second face of the first leg, and the second tubular element is disposed on the second face of the first leg and generally parallel to the longitudinal axis of the bearing plate.
14. The force distribution device as defined in claim 10, further comprising:
- a second guide channel provided on the second leg of the bearing plate, said second guide channel being generally aligned with the first guide channel on the first leg, and wherein a second portion of the cable is received through the second guide channel.
15. The force distribution device as defined in claim 14, further comprising:
- a third guide channel provided on the first leg of the bearing plate a spaced distance from the first guide channel, and wherein a third portion of the cable is received through the third guide channel; and
- a fourth guide channel provided on the second leg of the bearing plate, said fourth guide channel being generally aligned with the third guide channel on the first leg, and wherein a fourth portion of the cable is received through the fourth guide channel.
16. The force distribution device as defined in claim 15, wherein the third guide channel comprises a third aperture defined in the first leg and extending between the first and second faces thereof; and the fourth guide channel comprises a fourth aperture defined in the second leg and extending between the first and second faces thereof.
17. The force distribution device as defined in claim 15, wherein the third guide channel comprises a third tubular element provided on the second face of the first leg and the fourth guide channel comprises a fourth tubular element provided on the second face of the second leg
18. The force distribution device as defined in claim 3, wherein the first leg of the bearing plate further comprises:
- a first arm disposed generally at right angles to the second leg of the bearing plate;
- a second arm disposed generally at right angles to the second leg of the bearing plate; and
- a gap defined between the first and second arms, and wherein the bearing plate is adapted to receive a portion of the structural member in the gap.
19. A safety anchor system for a person comprising:
- a harness adapted to be worn on the body of the person;
- a force distribution device adapted to engage a structural member disposed a distance vertically above the ground; and
- a lanyard extending between the harness and the force distribution device; and wherein the force distribution device comprises: a cable choke selectively engageable with the lanyard; and a bearing plate engaged with the cable choke and adapted to engage a portion of the structural member; said bearing plate being configured to distribute forces into the structural member that are generated by the weight of the person falling toward the ground.
20. In combination,
- a roof truss including a truss rafter, said roof truss being disposed a distance above the ground;
- an anchor plate secured to the roof truss;
- a harness adapted to be worn on the body of a roofer;
- a force distribution device selectively engageable with a portion of the roof truss; said force distribution device comprising: a cable choke secured to the anchor plate; a bearing plate engaged with the cable choke and disposed in abutting contact with truss rafter; and a lanyard extending between the harness and the force distribution device; wherein said bearing plate is configured to distribute forces into the truss rafter that are generated by the roofer falling toward the ground.
21. The combination as defined in claim 20, further comprising a non-skid surface provided on the bearing plate, said non-skid surface resisting movement of the bearing plate along the truss in the event the roofer falls toward the ground.
22. The combination as defined in claim 21, wherein the cable choke and bearing plate transfer a load on the lanyard from the anchor plate to a top region of the truss rafter.
Type: Application
Filed: Mar 4, 2011
Publication Date: Sep 6, 2012
Inventor: Lawrence A. Crookston (Barberton, OH)
Application Number: 13/040,644
International Classification: E04G 21/32 (20060101); E04D 13/12 (20060101);