U.S. patent application number 11/756730 was filed with the patent office on 2008-12-04 for cable for use in safety barrier.
Invention is credited to Peter Bergendahl.
Application Number | 20080296546 11/756730 |
Document ID | / |
Family ID | 39672140 |
Filed Date | 2008-12-04 |
United States Patent
Application |
20080296546 |
Kind Code |
A1 |
Bergendahl; Peter |
December 4, 2008 |
CABLE FOR USE IN SAFETY BARRIER
Abstract
A cable for use in a safety barrier is provided. A cable for use
in a safety barrier may include a plastic core wire and a plurality
of metal wires disposed adjacent to and longitudinally to the
plastic core wire. The cable may be pre-stretched prior to
installation in the safety barrier. A method of making cable for
use in a safety barrier may include (a)providing a plastic core
wire, (b) disposing a plurality of metal wires, each metal wire
disposed adjacent to and longitudinally to the plastic core wire,
and (c) prestretching the cable prior to installation in the safety
barrier.
Inventors: |
Bergendahl; Peter;
(Angelholm, SE) |
Correspondence
Address: |
BAKER BOTTS L.L.P.
2001 ROSS AVENUE, SUITE 600
DALLAS
TX
75201-2980
US
|
Family ID: |
39672140 |
Appl. No.: |
11/756730 |
Filed: |
June 1, 2007 |
Current U.S.
Class: |
256/13.1 |
Current CPC
Class: |
D07B 2201/2066 20130101;
D07B 1/0693 20130101; D07B 2205/201 20130101; D07B 2201/2067
20130101; D07B 2201/2024 20130101; D07B 2801/14 20130101; D07B
2205/201 20130101; D07B 2201/2039 20130101; D07B 2201/2023
20130101; D07B 1/0673 20130101; E01F 15/065 20130101; D07B
2401/2005 20130101; E01F 15/06 20130101 |
Class at
Publication: |
256/13.1 |
International
Class: |
E01F 15/06 20060101
E01F015/06 |
Claims
1. A safety barrier installed adjacent to a roadway comprising: a
plurality of posts spaced from each other and disposed adjacent to
the roadway; and at least one pre-stretched cable releasably
engaged with and supported by the posts; and the cable having a
first plastic core wire, a first plurality of metal wires disposed
adjacent to and extending longitudinally along the first plastic
core wire.
2. The safety barrier of claim 1, further comprising the cable
pre-stretched using a force equal to between approximately 60% to
approximately 70% of the force required to break the cable.
3. The safety barrier of claim 1, wherein the first plastic core
wire comprises a polypropylene thread.
4. The safety barrier of claim 1, wherein the first plurality of
metal wires comprises six metal wires.
5. The safety barrier of claim 1, further comprising: a first wire
rope having the first plastic core and the first plurality of metal
wires; and a second wire rope and a third wire rope disposed
adjacent to and extending longitudinally along the first wire
rope.
6. The safety barrier of claim 5, wherein at least one of the
second wire rope and third wire rope comprises: a plastic core
wire; and a plurality of metal wires disposed adjacent to and
extending longitudinally along the plastic core wire.
7. The safety barrier of claim 5, wherein at least one of the
second wire rope and third wire rope comprises: a metal core wire;
and a plurality of metal wires disposed adjacent to and extending
longitudinally along the metal core wire.
8. A cable for use in a safety barrier comprising: a first plastic
core wire; a first plurality of metal wires disposed adjacent to
and longitudinally to the first plastic core wire; and the cable
pre-stretched prior to installation in the safety barrier.
9. The cable of claim 8, comprising the cable pre-stretched using a
force equal to between approximately 60% to approximately 70% of
the force required to break the cable.
10. The cable of claim 8, wherein the first plastic core wire
comprises a polypropylene thread.
11. The cable of claim 8, wherein the first plurality of metal
wires comprises six metal wires.
12. The cable of claim 8, further comprising: a first wire rope
having the first plastic core and the first plurality of metal
wires; and a second wire rope and a third wire rope disposed
adjacent to and extending longitudinally along the first wire
rope.
13. The cable of claim 12, wherein at least one of the second wire
rope and third wire rope comprises: a plastic core wire; and a
plurality of metal wires disposed adjacent to and extending
longitudinally along the plastic core wire.
14. The cable of claim 12, wherein at least one of the second wire
rope and third wire rope comprises: a metal core wire; and a
plurality of metal wires disposed adjacent to and extending
longitudinally along the metal core wire.
15. A method of making cable for use in a safety barrier
comprising: providing a first plastic core wire; and disposing a
first plurality of metal wires adjacent to and extending
longitudinally along the first plastic core wire; and prestretching
the cable prior to installation in the safety barrier.
16. The method of claim 15, further comprising prestretching the
cable using a force equal to between approximately 60% to
approximately 70% of the force required to break the cable.
17. The method of claim 15, further comprising forming the first
plastic core wire from a polypropylene thread.
18. The method of claim 15, further comprising wrapping six metal
wires adjacent to and extending along the first plastic core
wire.
19. The method of claim 15, further comprising forming a first wire
rope with the first plastic core and the first plurality of metal
wires, and disposing a second wire rope and a third wire rope
adjacent to and extending longitudinally relative to the first wire
rope.
20. The method of claim 19, further comprising: forming at least
one of the second wire rope and third wire rope using a second
plastic core wire; and disposing a plurality of metal wires
adjacent to and extending longitudinally relative to the second
plastic core wire.
Description
RELATED APPLICATION
[0001] This application is related to co-pending U.S. patent
application Ser. No. 11/207,239 entitled "Cable Safety System,"
filed Aug. 19, 2005.
TECHNICAL FIELD
[0002] The present disclosure is related to highway barriers and
safety systems and more particularly to cable safety systems and
associated cables.
BACKGROUND OF THE DISCLOSURE
[0003] Cable safety systems and cable barriers have been installed
along edges of roadways and highways for many years. Cable safety
systems and cable barriers have also been installed along medians
between roadways and/or highways. Cable safety systems generally
include one or more horizontal cables attached to support posts.
For some applications cable safety systems and cable barriers may
reduce damage to an impacting vehicle and/or injury to occupants of
the impacting vehicle as compared with other types of highway
safety systems and highway barriers.
[0004] Cable safety systems are often designed and installed with
at least one cable mounted horizontally on a plurality of generally
vertical support posts. Many cable safety systems include three
cables spaced vertically from each other on each support post. The
number of cables may vary depending on factors such as the type of
vehicles using the associated roadway and the hazard which requires
installation of the cable safety system. The length of a cable
safety system is generally determined based on the adjacent
roadside hazard. Each cable is typically installed at a selected
height relative to the ground and with selected vertical spacing
between adjacent cables.
[0005] During the past several years, cable safety systems have
been used as an alternative to traditional W-beam or thrie-beam
guardrail systems. Cable safety systems are often more
aesthetically appealing and minimize potential sight distance
problems as compared with W-beam and thrie beam guardrail systems.
Cable safety systems generally minimize snow accumulation on
adjacent highways and roadways.
[0006] As steel prices have increased, there has arisen a need to
manufacture cable safety systems with lesser amounts of steel.
However, an approach of lowering steel content by merely making
steel cables thinner may not be an appropriate solution, as such an
approach may lower the effectiveness of cable safety systems in
protecting occupants of an impacting vehicle. Accordingly,
solutions are needed in which steel content is reduced while at the
same time maintaining the effectiveness of the cable safety system
in reducing damage to impacting vehicles and/or the occupants
thereof.
SUMMARY OF THE DISCLOSURE
[0007] In accordance with teachings of the present disclosure, a
cable safety system may be provided which overcomes many
disadvantages and problems associated with prior cable safety
systems and cable barriers.
[0008] According to one embodiment of the present disclosure, a
safety barrier installed adjacent to a roadway comprising includes
a plurality of posts spaced from each other and disposed adjacent
to the roadway, and at least one cable releasably engaged with and
supported by the posts. The cable may include a plastic core wire
and a plurality of metal wires disposed adjacent to and
longitudinally to the plastic core wire. The cable may be
pre-stretched prior to installation in the safety barrier.
[0009] According to another embodiment of the present disclosure, a
cable for use in a safety barrier may include a plastic core wire
and a plurality of metal wires disposed adjacent to and
longitudinally to the plastic core wire. The cable may be
pre-stretched prior to installation in the safety barrier.
[0010] According to yet another embodiment of the present
disclosure, a method of making cable for use in a safety barrier is
provided. The method may include providing a plastic core wire. A
plurality of metal wires may each be disposed adjacent to and
longitudinally to the plastic core wire. The cable may be
pre-stretched prior to installation in the safety barrier.
[0011] Further technical benefits of the present disclosure may
include improved cables for use in safety barriers, wherein the
cables may be lighter than similar cables manufactured entirely
from metal, while at the same time remaining as effective against
impacting vehicles as similar cables manufactured entirely from
metal. Other technical advantages and benefits will be apparent to
those of ordinary skill in the art in view of the following
specification, claims, and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] A more complete and thorough understanding of the present
disclosure and advantages thereof may be acquired by referring to
the following description taken in conjunction with the
accompanying drawings, in which like reference numbers indicate
like features, and wherein:
[0013] FIG. 1a is a schematic drawing in elevation with portions
broken away of a cable safety system, in accordance with the
present disclosure;
[0014] FIG. 1b is a schematic drawing showing a plan view with
portions broken away of the cable safety system of FIG. 1a;
[0015] FIG. 1c is a schematic drawing in elevation with portions
broken away of another cable safety system incorporating teachings
of the present disclosure;
[0016] FIG. 1d is a schematic drawing in section and in elevation
with portions broken away of a below ground cable anchor assembly
satisfactory for use with the cable safety system of FIG. 1c;
[0017] FIG. 2 is a schematic drawing showing an isometric view with
portions broken away of a post and cables, in accordance with the
present disclosure;
[0018] FIG. 3a is a schematic drawing in section showing one
example of a cable formed using a seven strand metal wire rope, in
accordance with the present disclosure;
[0019] FIG. 3b is a schematic drawing in section depicting the
forces that may be applied during an impact to individual wires of
the wire rope of FIG. 3a;
[0020] FIG. 4a is a schematic drawing in section showing one
example of a cable formed using a plastic core wire surrounded by a
plurality of metal wires adjacent to and disposed longitudinally to
the plastic core wire, in accordance with the present
disclosure;
[0021] FIG. 4b is a schematic drawing in section depicting the
forces that may be applied during an impact to the individual wires
of the wire rope of FIG. 4a;
[0022] FIG. 5a is a schematic drawing in section showing one
example of a cable formed from three groups of seven strand metal
wire rope, in according with the present disclosure;
[0023] FIG. 5b is a schematic drawing in section showing one
example of a cable formed from three groups of wire rope, each of
the three groups formed using a plastic core wire surrounded by a
plurality of metal wires adjacent to and disposed longitudinally to
the plastic core wire, in accordance with the present disclosure;
and
[0024] FIG. 5c is a schematic drawing in section showing one
example of a cable formed from three groups of wire rope, wherein
one of the three groups is formed using a plastic core wire
surrounded by a plurality of metal wires adjacent to and disposed
longitudinally to the plastic core wire, in accordance with the
present disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[0025] Preferred embodiments of the invention and its advantages
are best understood by reference to FIGS. 1a-11 wherein like
reference numbers indicate like features.
[0026] The terms "safety system" or "safety systems", "safety
barrier" or "safety barriers," and "barrier" or "barriers" may be
used throughout this application to include any type of safety
system and/or barrier which may be formed at least in part using
cables and support posts incorporating teachings of the present
disclosure. The term "roadway" may be used throughout this
application to include any highway, roadway or path satisfactory
for vehicle traffic. Safety systems and barriers incorporating
teachings of the present disclosure may be installed in median
strips or along shoulders of highways, roadways or any other path
which is likely to encounter vehicular traffic.
[0027] Various aspects of the present disclosure will be described
with respect to cable safety systems 20 and 20a. However, teachings
of the present disclosure may be used to form a wide variety of
safety systems and barriers. Cable safety systems 20 and 20a may
have similar design features and characteristics except cable
safety system 20 includes above ground anchors 24 and 26. Cable
safety system 20a includes below ground anchors 24a and 26a. The
present disclosure is not limited to cable safety systems 20 and
20a as shown in FIGS. 1a-1d.
[0028] Cable safety systems 20 and 20a may be installed adjacent to
a roadway (not expressly shown) to prevent motor vehicles (not
expressly shown) from leaving the roadway and to redirect vehicles
away from hazardous areas without causing serious injuries to the
vehicle's occupants or other motorists. The general direction of
traffic flow along the roadway is illustrated by directional arrow
22.
[0029] Cable safety systems 20 and 20a may be satisfactorily used
as a median, a single barrier installation along the edge of a
roadway and at merge applications between adjacent roadways. For
some applications, cable safety systems 20 and 20a may
satisfactorily withstand a second impact before repairs have been
made after a first impact. For many applications, cable safety
systems 20 and 20a may be described as generally maintenance free
except for repairs required after a vehicle impact.
[0030] Cable safety systems 20 and 20a preferably include a
plurality of support posts 30 anchored adjacent to the roadway.
Posts 30 may be anchored with the ground using various techniques.
For some applications a concrete foundation (not expressly shown)
may be provided with holes to allow relatively quick and easy
insertion and removal of parts. The number, size, shape and
configuration of posts 30 may vary significantly among various
applications and installations. Optimum spacing between posts 30
may also vary among various applications and installations. See,
for example, U.S. Pat. No. 6,962,328, granted Nov. 8, 2005 and
entitled "Cable Safety Systems," which is incorporated by reference
herein for all purposes.
[0031] Various types of cables and/or wire ropes may be
satisfactorily used to form a cable safety system in accordance
with teachings of the present disclosure. Cables 160a, 160b and
160c may be substantially identical. However, for some applications
each cable of a cable safety system formed in accordance with
teachings of the present disclosure may have different
characteristics. Cable safety systems 20 and 20a may be generally
described as flexible, substantially maintenance free systems with
designed low deflection of cables 160a, 160b, and 160c during a
vehicle impact. Forming cable safety systems 20 and 20a in
accordance with teachings of the present disclosure minimizes
damage during a vehicle impact with posts 30 and/or cables 160a,
160b and 160c. For some applications cables 160a, 160b and 160c may
be formed from seven strand wire rope, e.g. cable 170 as depicted
in FIG. 3a. Other types of wire ropes and cables may also be used,
e.g., cable 175 as depicted in FIG. 4a, cable 180 depicted in FIG.
5a, cable 190 depicted in FIG. 5b, and/or cable 195 as depicted in
FIG. 5c.
[0032] A plurality of cables 160a, 160b and 160c may be attached to
support posts 30 in accordance with teachings of the present
disclosure. Support posts 30 generally maintain associated cables
160a, 160b and 160c in substantially horizontal positions extending
along an edge of the roadway. Support posts 30 often allow relative
quick and easy repair of cable safety systems 20 and 20a after a
vehicle impact.
[0033] Cable safety systems 20 and 20a are generally relatively
narrow as compared to conventional W-beam and thrie beam guardrail
systems. The length of cables 160a, 160b and 160c may be up to
3,000 meters between anchors 24 and 26 or anchors 24a and 26a. For
other applications the length of cable 160a, 160b and 160c may
exceed 3,000 meters without an intermediate anchorage. Support
posts 30 maintain desired vertical spacing between cables 160a,
160b and 160c and desired vertical spacing of each cable relative
to the ground. Cable safety system 20 and 20a including support
posts 30 formed in accordance with teachings of the present
disclosure may be designed in accordance with teachings of the
present disclosure to meet or exceed the criteria of NCHRP Report
350 Level 3 requirements.
[0034] Cable safety systems 20 and 20a preferably include cables
160a, 160b and 160c disposed in slot 40 of each post 30. Cable
160a, 160b and 160c are preferably disposed at different heights
relative to the ground and relative to each other. Varying the
vertical spacing between cables 160a, 160b and 160c often provides
a much wider lateral catch area for vehicles impacting with cable
safety systems 20 and 20a. The vertical spacing between cables
160a, 160b and 160c may be selected to satisfactorily contain both
pickups and, to some extent, even larger vehicles with a relatively
high center of gravity, as well as vehicles with a low front
profile and low center of gravity.
[0035] Cables 160a, 160b and 160c may be prefabricated in
approximately three hundred (300) meter lengths with desired
fittings attached with opposite ends of each cables 160a, 160b and
160c. Tailor made cables 160a, 160b and 160c may then be delivered
to a desired location for installation adjacent to a roadway.
[0036] Alternatively, cables 160a, 160b, and 160c may be formed
from a single cable stored on a large drum (not expressly shown).
Cables stored on drums may often exceed three thousand (3,000)
meters in length. Cables 160a, 160b, and 160c may be cut in desired
lengths from the cable stored on the drum. Appropriate fittings
(not expressly shown) may be swaged or otherwise attached with
opposite ends of the respective cable 160a, 160b and 160c at an
onsite location. Cables 160a, 160b and 160c may be installed
between anchors 24 and 26 or anchor 24a and 26a with approximately
twenty thousand Newtons of tension over a length of approximately
three thousand (3,000) meters.
[0037] FIG. 1d shows one example of a below ground anchor which may
be satisfactorily used with a cable safety system incorporating
teachings of the present disclosure. Respective holes 27 may be
formed in the ground at desired locations for anchors 24a and 26a.
A portion of each hole 27 may be filled with concrete foundation
28. Anchor plate 29 may be securely engaged with concrete
foundation 28 using various types of mechanical fasteners,
including, but not limited to, a plurality of bolts 23 and nuts 24.
Anchor plate 29 may be formed at an appropriate angle to
accommodate the design of cable safety system 20a. Also multiple
slots and/or openings (not expressly shown) may be formed in anchor
plate 29 to receive respective end fittings 64.
[0038] For the embodiment of the present disclosure as shown in
FIG. 1d, end fitting 64a of cable 160a is shown engaged with anchor
plate 29. Various types of anchor assemblies and cable end fittings
may be satisfactorily used with a cable safety system incorporating
teachings of the present disclosure. The present disclosure is not
limited to anchor 24a or end fittings 64a as shown in FIG. 1d.
[0039] One example of support posts 30 and cables 160a, 160b and
160c which may be satisfactorily used to form cable safety system
20 in accordance with teachings of the present disclosure is shown
in FIG. 2. Post 30 includes first end 31 and second end 32. For
this embodiment of the present disclosure, post 30 includes a
generally C-shaped cross section defined in part by web 34 with
respective legs 35 and 36 extending therefrom. As shown in FIG. 2,
the extreme edge of each leg 35 and 36 opposite from web 34 may be
rounded or bent inward to eliminate any sharp edges. Support post
30 may also have a generally "rounded" or "soft" profile. For some
applications post 30 may be formed using roll forming
techniques.
[0040] Slot 40 is preferably formed in web 34 extending from first
end 31 towards second end 32. The length of slot 40 may be selected
in part based on desired vertical spacing of cable 160c relative to
the adjacent roadway. The length of slot 40 may also be selected to
accommodate the number of cables which will be installed therein
and desired vertical spacing between each cable. Slot 40 may have a
generally elongated U-shaped configuration defined in part by first
edge 41, second edge 42 and bottom (not expressly shown). For the
embodiment of the present disclosure as shown in FIG. 2, first edge
41 and second edge 42 may have a generally smooth profile and
extend generally parallel with each other. Forming slot 40 within
web 34 of post 30 eliminates requirements for bolts, hooks or other
mechanical attachments to releasably secure cables 160a, 160b and
160c with post 30. Further examples of support posts 30 and cables
160a, 160b, and 160c that may be used to form cable safety system
in accordance with the present disclosure may be set forth U.S.
Pat. No. 6,962,328, discussed above.
[0041] FIG. 3a is a schematic drawing in section showing one
example of a cable 170 for use in cable barrier system 20. Cable
170, as depicted, may comprise a metal core wire 71, and a
plurality of metal wires 72 disposed adjacent to and longitudinally
to metal core wire 71. In some embodiments, cable 170 may comprise
a seven strand wire rope. In the same or alternative embodiments,
metal core wire 71 and/or metal wires 72 may comprise steel. FIG.
3b depicts the forces that may be applied during an impact to
individual wires 71, 72 of cable 170 during a vehicle impact to
cable safety system 20 comprising cable 170. As shown, a vehicle
impact to cable safety system 20 may cause metal wires 72 to be
forced towards metal core wire 71, thus decreasing the flexibility
of cable 170.
[0042] In order to increase the flexibility of cable 170 depicted
in FIG. 3a, a plastic core wire 73 may be substituted in place of
metal core wire 71, as depicted in FIG. 4a, forming cable 175. As
shown in FIG. 4a, cable 175 may include a plastic core wire 73 and
a plurality of metal wires 72 disposed adjacent to and
longitudinally to plastic core wire 73. In certain embodiments,
plastic core wire 73 may comprise polypropylene. In the same or
alternative embodiments, cable 175 may comprise six metal wires 72.
In addition, cable 175 may be manufactured or formed by methods
similar to that of cable 170.
[0043] FIG. 4b depicts the forces that may be applied during an
impact to individual wires 72, 73 of cable 175 during a vehicle
impact to cable safety system 20 comprising 175. As shown, a
vehicle impact to cable safety system 20 may cause some of metal
wires 72 (e.g. metal wires 72d, 72e and 72f) to be forced towards
plastic core wire 73, while other metal wires (e.g. metal wires
72a, 72b, and 72c) may be forced away from plastic core wire 73,
due to the flexible nature of plastic core wire 73. Accordingly,
cable 175 may remain more flexible during a vehicle impact with
cable safety system 20, and thus may be more resistant to breaking
than a similarly-sized metal-wire-only cable 170.
[0044] In certain embodiments, cables comprising three groups of
seven-strand wire, for example, cables 180, 190 and 195 depicted in
FIGS. 5a, 5b and 5c, respectively, may be used to form cable safety
system 20. FIG. 5a depicts a cable 180 formed from three groups of
seven strand metal wire rope, as is often used in conventional
cable safety systems. During a vehicle impact to cable safety
system 20 comprising cable 180, the metal wires 72 comprising each
wire rope of cable 180 may be forced towards the metal core wire 71
of their respective wire rope, as depicted in FIG. 3b, which may
result in decreased flexibility.
[0045] To increase the flexibility of a cable formed from three
groups of seven strand wire rope, a plastic core wire 73 may be
substituted in place each wire rope's metal core wire 71, as
depicted in FIG. 5b, forming cable 190. As shown in FIG. 5b, cable
190 may include three wire ropes, each including a plastic core
wire 73 and a plurality of metal wires 72 disposed adjacent to and
longitudinally to the respective plastic core wires 73. In a
vehicle impact to a cable safety system 20 comprising cable 190,
some of the metal wires 72 of each wire rope comprising cable 190
may be forced towards their respective plastic core wires 73, while
other metal wires 72 may be forced away from their respective
plastic cores wires, as depicted in FIG. 4b. Accordingly, cable 190
may remain more flexible during a vehicle impact with cable safety
system 20, and thus may be more resistant to breaking than a
similarly-sized metal-wire-only cable 180.
[0046] In addition to the embodiments depicted in FIGS. 5a and 5b,
cable safety system 20 may comprise three groups of seven strand
wire ropes, wherein some of the groups may include a plastic core
wire 73, while others may not, such as cable 195 depicted in FIG.
5c.
[0047] In conventional cable safety systems, cables are often
pre-stretched to about 50% of designed or rated breaking strength
in order to obtain a desired modulus of elasticity for the cable.
However, in accordance with the present disclosure, cables 170,
175, 180, 190 and 195 may be pre-stretched to between approximately
60% and approximately 70% of designed or rated breaking strength.
Such increased pre-stretching may reduce elasticity of the cable,
thus decreasing the amount of deflection of the cable during a
vehicle impact, as compared to a cable pre-stretched to 50% of its
breaking strength. In certain embodiments, increased prestretching
to between 60% and approximately 70% of designed or rated breaking
strength may permit use of smaller-diameter cables as compared to
that of conventional cable safety systems, thus potentially
reducing raw materials cost.
[0048] Some of the advantages of the various alternatives discussed
above may be illustrated in TABLE 1.
TABLE-US-00001 TABLE 1 20 steel 18 steel wires, 1 wires, 3 plastic
plastic 21 steel core core wires; wire; wires; 21 steel 60%-70%
60%-70% 60%-70% wires; 50% pre- pre- pre- pre-stretch stretch
stretch stretch force force force force (conventional) (FIG. 5a)
(FIG. 5c) (FIG. 5b) Wire 3.00 mm 2.81 mm 2.88 mm 3.06 mm diameter
Cable 19.00 mm 18.12 mm 18.58 mm 18.12 mm diameter Tensile 1370
N/mm.sup.2 1570 N/mm.sup.2 1570 N/mm.sup.2 1570 N/mm.sup.2 strength
Minimum 183.00 KN 184.00 KN 183.16 KN 183.69 KN breaking load
Weight 1.18 Kg/m 1.04 Kg/m 1.04 Kg/m 1.06 Kg/m of metal
[0049] The second column of TABLE 1 depicts the wire diameter,
cable diameter, tensile strength, minimum breaking load, and weight
of metal for an example conventional cable 180 comprising three
groups of seven-strand steel wire rope. The third, fourth, and
fifth each depict the same parameters for alternatively constructed
cables having a similar minimum breaking load. Specifically, the
third, fourth, and fifth columns respectively depict these same
parameters for each of: (a) a 21 steel wire strand cable 180
similar to that depicted in FIG. 5a pre-stretched to 60% to 70%,
(b) a 20 steel wire, 1 plastic core wire cable 195 similar to that
depicted in FIG. 5c pre-stretched to 60% to 70%, and (c) a 18 steel
wire, 3 plastic core wire cable 190 similar to that depicted in
FIG. 5b pre-stretched to 60% to 70%. From TABLE 1, it can be seen
that by using pre-stretched cables, lighter steel strands, and
plastic core wire strands, cables of similar minimum breaking load
to that of conventional cables may be constructed using less metal,
and therefore, may be less expensive to manufacture.
[0050] Although the present disclosure and its advantages have been
described in detail, it should be understood that various changes,
substitutions and alternations can be made herein without departing
from the spirit and scope of the disclosure as defined by the
following claims.
* * * * *