Note: Descriptions are shown in the official language in which they were submitted.
CA 02625746 2008-03-14
Attorney Docket No. 442005-00210
MOLDED POLYMER CAP WITH CONFORMABLE INTERNAL STRUCTURE
BACKGROUND
[0001] This application is directed to a cap for reinforcement members and
reinforcement
placement accessories used in concrete construction and, more particularly, to
molded polymer
caps for attachment to rebar, metal slab bolsters, and other reinforcement-
related items, where
the cap includes a conformable internal structure for frictionally engaging an
end or leg of the
item.
[0002] During the construction of buildings, bridges, and other structures
using reinforced
concrete it is common to place a plurality of metal slab bolsters on grade or
within forming
molds to position steel reinforcement bars (a.k.a. "rebar") within the mold
cavity prior to the
pouring of wet concrete. Such slab bolsters become embedded within the cured
concrete but
include support legs that intersect the lower surface of the cured concrete
element. The exposed
support leg ends may corrode due to exposure to the environment, creating an
expanded, porous
oxide that fractures the concrete and permits the infiltration water, oxygen,
salts, and the like,
potentially leading to corrosion of the embedded rebar and compromise of the
design strength of
the concrete element. Molded polymer caps may be placed over the ends of such
support legs to
minimize the potential for corrosion and infiltration. Such caps typically
include an internal
cavity sized to match the end of the slab bolster support leg and frictionally
engage that leg
through an interference-type fit. However, such caps are vulnerable to
cracking, splitting, and
retention failure due to the means of attachment as well as differential
expansion/contraction
between the polymer cap and metal support leg end during temperature swings at
the
construction site. The interference fit between the cap and the metal support
leg generates
substantial hoop stresses that are magnified by the dynamic heating and
cooling of the connected
materials during the day/night cycle and during changes in the weather.
[0003] During the intermediate stages of construction, portions of the rebar
emplaced in an
earlier-constructed structural element, such as a footing or a slab, may
project outward or
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upwards from the element to leave a free end for interconnection with rebar in
other structural
elements. The projecting rebar may be spliced or otherwise connected to rebar
that will be
emplaced within a later-constructed structural element, such as a load bearing
wall. However
until construction commences on the later-constructed element, the free end of
the rebar presents
a hazard to workers who may fall onto it or otherwise contact it while
performing other
construction activities. To prevent worker injuries various rebar protective
caps or rebar safety
caps having large, sometimes flexible or collapsible heads may be placed over
the free end of the
rebar to alter impact forces and prevent impalement. Such rebar protective
caps may include
conformable internal fins permitting the caps to be used on a range of rebar
sizes, however these
designs require a worker to simultaneously twist and press the cap onto the
rebar end in order to
deflect the fins and bring them into contact with the side surfaces of the
rebar. An example of a
rebar protective cap is illustrated in U.S. Pat. No. 6,857,235, the entire
contents of which are
incorporated herein by reference.
[0004] There is a need for a molded polymer cap for slab bolsters and other
reinforced concrete
construction accessories which does not rely upon an internal cavity creating
an interference-type
fit with as a means for retention upon the accessory, and which reduces the
hoop stresses within
the cap to reduce the incidence of cracking, splitting, and retention failure
in such caps. There is
a further need for a molded polymer cap that may be applied by workers or
automated machinery
while preserving the simple, linear application method used with the above-
described prior art
molded polymer caps. There is also a need for a rebar protective cap or rebar
safety cap having
conformable internal structure that does not require a twisting motion for
proper application of
the cap over rebar.
SUMMARY
[0005] An aspect of the disclosure relates to a molded polymer cap generally
including a
hollow body defining a central channel, a closed cap end, an open receiving
end, and a plurality
of resilient internal fins. A first portion of each internal fin runs
longitudinally down the body
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from the closed cap end toward the open receiving end, extending laterally
inward from the body
into the central channel. These first portions resiliently deflect toward the
body to contact to the
side surfaces of an inserted object, with the broad sides of the fins
frictionally engaging the side
surfaces of the object to retain the cap on the object. A second portion of
each internal fin runs
partially longitudinally and partially laterally down the body from the end of
the first portion
toward the receiving end of the device, extending laterally inward from the
body into the central
channel. The configuration of the second portion exposes a broad side of each
fin to the
advancing end of an inserted object, enabling the forward motion of the object
to deflect the fins
toward the body for engagement with the sides of the object. The first and
second portions of
each internal fin are connected to each other, so that the deflection will
propagate ahead of the
advancing end of the object, eliminating the potential for a blocking
interference between an end
of a fin and the end of the object.
[0006] A further aspect of the disclosure relates to a slab bolster
incorporating the molded
polymer cap.
[0007] A further aspect of the disclosure relates to a rebar protective cap
generally including a
collar defining a central channel, a protective cap end, an open receiving
end, and a plurality of
resilient internal fins. A first portion of each internal fin runs
longitudinally down the collar
from the closed cap end toward the open receiving end, extending laterally
inward from the
collar into the central channel. These first portions resiliently deflect
toward the collar to contact
to the side surfaces of inserted rebar, with the broad sides of the fins
frictionally engaging the
side surfaces of the rebar to retain the cap on the end of the rebar. A second
portion of each
internal fin runs partially longitudinally and partially laterally down the
collar from the end of
the first portion toward the receiving end of the device, extending laterally
inward from the collar
into the central channel. The configuration of the second portion exposes a
broad side of each
fin to inserted rebar, enabling the forward motion of the rebar to deflect the
fins toward the body
for engagement with the sides the rebar. The first and second portions of each
internal fin are
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connected to each other, so that the deflection will propagate ahead of the
rebar, eliminating the
potential for a blocking interference between an end of a fin and the end of
the rebar.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Fig. 1 is an entry view of a molded polymer cap illustrating internal
fins having a
partially helical configuration;
[0009] Fig. 2 is a cross-sectional view of the molded polymer cap of Fig. 1
illustrating internal
fins first running longitudinally down the cap and second running helically
down the cap toward
the receiving end;
[0010] Fig. 3 is an entry view of a rebar protective cap illustrating internal
fins having a
partially helical configuration;
[0011] Fig. 4 is a cross-sectional view of the rebar protective cap of Fig. 3
illustrating internal
fins first running longitudinally down the cap and second running helically
down the cap toward
the receiving end; and
[0012] Fig. 5 is a perspective view of a slab bolster combinable with the
molded polymer cap
of Figs. 1 and 2.
DETAILED DESCRIPTION
[0013] A first aspect of a molded polymer cap, generally designated 50, is
shown in Figs. I and
2. The molded polymer cap 50 includes a hollow body 52 defining a central
channel 60, a closed
cap end 54, an open receiving end 56, and a plurality of resilient internal
fins 58 each having at
least two different alignments for releasably engaging the sides of an
inserted object such as a
slab bolster leg end or a rebar end.
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[0014] The plurality of resilient internal fins 58 comprises a first portion
62 running
longitudinally down the body 52 from the cap end 54 toward the receiving end
56 and extending
laterally inward from the body 52 into the central channel 60; and a second
portion 64 running
partially longitudinally and partially laterally down the body 52 from the
first portion 62 toward
the receiving end 56 and extending laterally inward from the body 52 into the
central channel 60.
The second portion 64 may be said to have a helical configuration. The first
portion 62
preferably, but not necessarily, extends laterally but not radially inward
into the central channel
60 to maximize the useful range of distortion of the fins 58 while
accommodating a
predetermined range of sizes and shapes of inserted material. The body may
preferably, but not
necessarily, define a frusto-conical entry 68 at the receiving end to ease the
automated
application of the cap on an object such as a slab bolster leg end when a
single size or narrow
range of sizes of inserted material will be capped by the device.
[0015] The first portion 62 of each internal fin 58 resiliently deflects
toward the body 52 to
conform to sides of an inserted object, with the broad sides of the fins of
the first portion 62
frictionally engaging the side surfaces of the object. This means for
retention enables the cap 50
to be placed over various sizes and shapes of inserted material, e.g., slab
bolsters constructed
from different sizes of metal rod, and also causes the stresses caused by
thermal
expansion/contraction in the cap material and inserted material to be
distributed primarily as
elastic deformation stress within the internal fins 58 rather than as hoop
stress within the body 52
of the cap.
[0016] The helical configuration of the second portion 64 of each internal fin
58 exposes a
broad side of each fin to the advancing end of an inserted object, thereby
allowing the forward
motion of the object to deflect the second portion 64 toward the body 52. The
second portion 64
and first portion 62 of each internal fin 58 are connected to each other so
that the deflection of
the second portion 64 will cause a deflection of the first portion 62,
enabling the deflection to
propagate ahead of the advancing object, thereby eliminating the potential for
a blocking
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interference between an end of a fin 58 and the end of object. This
configuration permits a
molded polymer cap to be placed over the end of an object such as a slab
bolster support leg
using automated, linearly reciprocating machinery like that used with molded
polymer caps
lacking an internal fin structure. In molded polymer caps lacking fins with a
helical
configuration, such automated machinery would need to simultaneously twist and
press the cap
onto the slab bolster support leg end to create an initial deflection of the
fins 58, or risk crushing,
tearing, or otherwise damaging the fins, therevy increasing the risk of
retention failure and the
time spent by construction workers in assuring that a molded polymer cap is
still in place at
various stages in the construction process.
[0017] A second aspect of a molded polymer cap, generally designated 150, is
shown in Figs. 3
and 4. The molded polymer cap 150 includes a hollow collar 152 defining a
central channel 160,
a protective cap end 154, an open receiving end 156, and a plurality of
resilient internal fins 158
each having at least two different alignments for releasably engaging the
sides of projecting end
of rebar.
[0018] The plurality of resilient internal fins 158 comprises a first portion
162 running
longitudinally down the collar 152 from the protective cap end 154 toward the
receiving end 156
and extending laterally inward from the collar 152 into the central channel
160; and a second
portion 164 running partially longitudinally and partially laterally down the
collar 152 from the
first portion 162 toward the receiving end 156 and extending laterally inward
from the collar 152
into the central channel 160. The second portion 164 may be said to have a
helical
configuration. The first portion 162 preferably, but not necessarily, extends
laterally but not
radially inward into the central channel 160 to maximize the useful range of
distortion of the fins
158 while accommodating a predetermined range of sizes of rebar.
[0019] The first portion 162 of each internal fin 158 resiliently deflects
toward the collar 152 to
conform to sides of inserted rebar, with the sides of the fins of the first
portion 162 frictionally
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engaging the side surfaces of the rebar. This means for retention enables the
cap 150 to be
placed over various sizes of rebar, e.g., #4 to #9 rebar.
[0020] The helical configuration of the second portion 164 of each internal
fin 158 exposes a
broad side of each fin to the inserted rebar, thereby allowing the forward
motion of the rebar to
deflect the second portion 164 toward the collar 152. The second portion 164
and first portion
162 of each internal fin 158 are connected to each other so that the
deflection of the second
portion 164 will cause a deflection of the first portion 162, enabling the
deflection to propagate
ahead of the rebar end, thereby eliminating the potential for a blocking
interference between an
end of a fin 158 and the rebar end. This configuration permits a rebar
protective cap to be placed
over the end of rebar using a single-handed, generally linear pushing motion,
rather than a
single-handed, combined twisting and pushing motion or a two-handed, combined
twisting and
pushing motion that may be disfavored as being significantly slower than a
single-handed
placement technique.
[0021] The protective cap end 154 of the device may include any of a number of
rebar
protective cap or rebar safety cap top constructions known in the art. Such
protective caps most
typically include cap portion 170 oriented substantially perpendicularly to
the collar structure
and extending laterally beyond the collar structure, preferably defining a top
surface having an
area of at least 16 square inches, and a barrier 172 embedded within or
coupled to the cap portion
170 to prevent rebar from penetrating the protective cap end 154 and impaling
a falling worker.
[0022] These molded polymer caps 50, 150 described herein may be made from a
wide variety
of injection moldable polymer materials, including materials containing
colorants, UV inhibitors,
and various non-polymer additives, depending on the specific physical,
chemical, and electrical
properties desired for a particular application.
[0023] While the present invention has been described in detail and with
particular reference to
illustrated embodiments, it is to be understood that other variations in the
form and details which
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are within the spirit and scope of the invention are not specifically
addressed. Therefore the
invention is to be limited only by the appended claims.
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