U.S. patent number 3,671,622 [Application Number 05/089,335] was granted by the patent office on 1972-06-20 for method of forming seal for multi-wire strand.
This patent grant is currently assigned to Bethlehem Steel Corporation. Invention is credited to Darral V. Humphries.
United States Patent |
3,671,622 |
|
June 20, 1972 |
METHOD OF FORMING SEAL FOR MULTI-WIRE STRAND
Abstract
A short length of a multi-wire strand is surrounded with a mold
to provide an annular space about said length. Said space is filled
with a thermosetting plastic sealant and pressure is applied to
force said sealant into and along the interstices of said strand.
During said application of pressure, the strand is
circumferentially heated at the ends of said mold to provide a
radial temperature gradient across said ends. Pressure is applied
to said sealant until the ends of the seal are substantially
convex.
Inventors: |
Darral V. Humphries (Allentown,
PA) |
Assignee: |
Bethlehem Steel Corporation
(N/A)
|
Family
ID: |
22217101 |
Appl.
No.: |
05/089,335 |
Filed: |
November 13, 1970 |
Current U.S.
Class: |
264/263;
264/327 |
Current CPC
Class: |
E01D
19/16 (20130101); D07B 9/00 (20130101); B05D
7/20 (20130101) |
Current International
Class: |
E01D
19/00 (20060101); E01D 19/16 (20060101); B05D
7/20 (20060101); D07B 9/00 (20060101); B29c
006/00 (); B29g 007/00 () |
Field of
Search: |
;264/263,327,272
;174/23R,23C,26R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Robert F. White
Assistant Examiner: Richard H. Shear
Attorney, Agent or Firm: Joseph J. OKeefe
Parent Case Text
CROSS-REFERENCES TO RELATED APPLICATIONS
This application is a division of U.S. Pat. application Ser. No.
779,536, filed Dec. 27, 1968, by the present inventor, entitled
"Seal for Multi-Wire Strand and Method of Forming."
Claims
1. In a method of forming a seal in a multi-wire strand comprising:
I. surrounding a length of said strand with a mold to provide an
annular space about said length, Ii. filling said space with a
liquid sealant of thermosetting material settable at ambient
temperatures and capable of accelerated setting at temperatures
different from said ambient temperatures, and Iii. applying
pressure to said sealant within said mold to force said sealant
into and along the interstices of said strand, the improvement
comprising: a. during Step III. applying a radial temperature
gradient across those portions strand adjacent the ends of said
mold whereby substantially only said portions are at temperatures
at which there is accelerated setting of the sealant therein, said
temperatures being such that the rate of accelerated setting
progressively decreases as the distance from the center of the
strand decreases, and b. continuing to apply pressure to said
sealant until the ends of said seal
2. The improvement as recited in claim 1, in which said radial
temperature gradient is applied to said strand by circumferentially
heating said strand at the ends of said mold.
Description
The subject invention may be used to prevent or decrease corrosion
in the multi-wire strands and anchorage pipes disclosed in
copending application Ser. No. 614,651 to Durkee et al., filed Feb.
8, 1967.
This invention relates to a seal in a multi-wire strand, and more
particularly to a water deflector seal in a multi-wire bridge
strand.
Multi-wire strands exposed to the weather are subject to corrosion.
While it is relatively easy to inspect the exterior of a strand for
corrosion, no simple method of inspecting the interior of a strand,
or the strand anchorage, e.g. the anchorage pipes disclosed in the
above-referred-to Durkee et al. application, is known. It is
therefore desirable to prevent the ingress of water into the
interstices of a strand, particularly at the lowest point thereof,
which is the point where water will accumulate due to gravitational
forces.
In the past, attempts have been made to provide multiwire strands
with water-proof seals. Such seals have been formed, for example,
by placing a mold around a length of strand and injecting a sealant
into the interior of the strand by applying pressure to said
sealant. However, by reason of the decrease in pressure from the
outside to the center of the strand, the ends of the resultant seal
have been concave. A seal with concave ends tends to entrap, rather
than deflect, moisture, and probably accelerates corrosion of the
strand.
It is an object of this invention to provide a method of sealing a
multi-wire strand whereby the ends of the seal so formed are
substantially convex.
It is a further object to provide such a method which is relatively
simple and inexpensive.
I have discovered that the foregoing objects can be attained by a
method comprising the following five steps: (1) A length of
multi-wire strand is surrounded with a mold to provide an annular
space about said length. (2) Said space is filled with a liquid
sealant settable at ambient temperatures and capable of accelerated
setting at temperatures different from said ambient temperatures.
(3) Pressure is applied to said sealant within said mold to force
said sealant into and along the interstices of said strand. (4)
During said application of pressure, a radial temperature gradient
is applied across said strand at the ends of said mold whereby
across said ends the wires of said strand are at temperatures at
which said accelerated setting takes place, said temperatures being
such that the rate of setting progressively decreases as the
distance from the center of the strand decreases. (5) Pressure upon
said sealant is continued until the ends of said seal are
substantially convex.
FIG. 1 is an isometric view of a strand provided with apparatus for
forming a seal of the invention.
FIG. 2 is a sectional side elevation view of a sealed bridge strand
in a pipe anchorage.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 discloses a strand 10 consisting of a plurality of
zinc-coated parallel wires 12. A short length 14 of strand is to be
provided with a water deflecting seal.
The first step in providing said seal comprises coating a portion
16 of the length 14 with a wash primer, e.g. a mixture of
phosphoric acid, zinc tetroxychromate, and polyvinyl butyal. Said
primer may be applied with a brush, and dries in about 5 minutes.
The purpose of the primer is to improve the adhesion between the
seal and the zinc coating on the strand, and is desirable in cases
where there are shearing forces applied to the seal, e.g. in the
application which will be described in connection with FIG. 2. If
there are no shearing forces applied to the seal, this step may be
omitted.
After the wash primer has dried, a short length 18 of strand
contiguous to each end of the length 16 is wrapped with silicon
rubber tape. The purpose of the tape is to prevent the heating
elements, subsequently to be wrapped about the strand, from
contacting the sealant, as such contact may be damage the
elements.
Caulking tape 19 is next applied to the strand at points
overlapping the junction of the wash primer and the silicone rubber
tape, and a mold 20 is then pressed into place about the strand.
The mold 20 comprises two fiberglass half shells 22 and 24 which
are clamped together by hose clamps 26. The upper half shell 24 is
provided with openings 28 and 30 into which are inserted a
cartridge 32 and a vent nipple 34, respectively, the vent nipple 34
being disposed at substantially the uppermost point of the mold
20.
Prior to inserting the cartridge 32 into the mold 20, heating
elements 36, which may comprise silicon rubber tape containing
electrical resistance elements, are clamped about the strand at
each end of the mold 20. Said heating elements 36 are adapted to
heat the outermost interstices of the strand to a temperature of
about 260.degree. F. in about 7 minutes.
The cartridge 32 is next filled with a liquid sealant, e.g. the
polyether polyurethane sold under the trademark Conathane 1546. The
Conathane 1546 contained 0.5 percent by weight of
dibutyltindilaurate to accelerate the gel time of the sealant at
elevated temperatures, e.g. 260.degree. F. Conathane 1546 was
selected as a sealant for multi-wire bridge strand because it is
characterized by the following properties: (a) resistance to water,
air, ozone and fungus growth; (b) adequate resiliency, which does
not deteriorate with the passage of time, to accommodate flexing
and dimensional changes over a temperature range of -40.degree. F.
to +120.degree. F.; (c) a maximum viscosity of 3,000 centipoise, at
ambient temperatures, so that the interstices of the strand can be
impregnated at pressures of 15 psi. or less; (d) curability at
ambient temperatures without loss of volatiles; and (e) ease of
applicability, non-toxicity and low cost.
When the liquid sealant begins to emerge from the vent nipple 34,
the vent is closed with a cap 38 and a caulking gun is connected to
the cartridge 32. The heating elements 36 are then energized and
those sections of the strand beneath said elements are heated for
several minutes until the temperature of the outermost interstices
is about 260.degree. F. A pressure of about 7 psi. is then applied
to the caulking gun, forcing the sealant into and along the
interstices of the strand. The pressure is removed after the
sealant appears at the outer edge of the heating elements, the
heating elements 36 are removed, and the sealant is allowed to cure
at ambient temperatures for 16 to 24 hours. It has been found that
when the sealant appears at said outer edge, the sealant has
penetrated the interstices in such a manner that the ends of the
resultant seal are substantially convex. These results have been
obtained on multi-wire strand comprising both parallel and helical
wires.
FIG. 2 discloses a typical application of the above-described seal,
viz. as a water deflector in a bridge strand in a pipe anchorage.
The anchorage comprises an anchorage block 40 which is cast about a
pipe 42. The strand 44 passes through the pipe 42 and is suitably
anchored. The strand 44 is provided with a zinc fairlead 46 and the
forward section of the anchorage block 40 is provided with a
spacing plate 48.
A water deflecting seal 50, prepared in the same manner as the seal
shown in FIG. 1, is disposed in the strand 44 immediately above the
spacing plate 48. In this case, the mold 52 is not removed from the
strand, and a neoprene boot 54, in the shape of a conical frustum,
is sealed to the mold 52 and to a portion of the pipe 42 extending
beyond the spacing plate 48.
The arrows in FIG. 2 show the paths of water traveling along the
interstices of the strand. As can be seen, when water contacts the
end of the seal 50, it progressively moves to the outside of the
strand, around the mold 52, along the boot 54 and down the spacing
plate 48. As a result, the probability of corrosion within the
strand and the anchorage pipe is substantially reduced.
* * * * *