Note: Descriptions are shown in the official language in which they were submitted.
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This is a divisional of Patent Application Serial
No. 2,038,019, filed March 12, 1991.
This invention relates to a pig for cleaning a pipe
or pipeline.
For the sake of simplicity, in the following, the
term "pipeline" is used to describe a conventional pipeline or
pipes used to convey fluids, e.g. in industrial heaters or
cooling systems.
Pipelines are commonly used to transport,
inter alia, a crude oil, gas, slurries or water. During use,
the interior of a pipeline becomes coated which decreases flow
through the pipeline. Typical coatings include paraffin,
asphaltene, sediments, silica, coke, calcium or other salts
and corrosion products which are often difficult or almost
impossible to remove. The standard method of cleaning a
pipeline is to drive a so-called pig through the pipeline
using fluid pressure as the driving force. Pigs can also be
used as dividers when transporting different materials through
the pipeline, the pig simultaneously cleaning the interior of
the pipeline.
Examples of pipeline cleaning pigs are described in
United States Patents Nos. 2,447,966, issued to D.K. Stephens
on August 24, 1948; 3,204,274, issued to M.M. Knapp on
September 7, 1965; 3,277,508, issued to M.M. Knapp et al on
October 1, 1968; 3,389,417, issued to M.M. Knapp et al on June
25, 1968; 3,538,531, issued to M.M. Knapp et al on November
10, 1970; 3,605,159, issued to H.J. Girard on September 20,
1971; 3,659,305, issued to M.D. Powers on May 2, 1972;
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3,725,968, is6ued to M.M. Knapp et al on April 10, 1973;
3,863,287, issued to K.M. Knapp et al on February 4, 1975;
4,077,079, issued to M.M. Knapp on March 7, 1978; 4,244,073,
issued to S. Sagawa on January 13, 1981; 4,509,222, issued to
K.M. Knapp on April 9, 1985 and 4,603,449, issued to K.M.
Knapp on August 5, 1986.
In general, many existing pipeline pigs are
incapable of cleaning deposits much harder than candle wax.
Those pigs which are adapted to clean hard deposits such as
sediment and scale are not able to maintain a seal between
separate products in a pipeline, and are prone to tearing on
welds or other irregularities on the interior of the pipeline.
An object of the present invention is to solve the
above problems by providing a relatively simple pipe or
pipeline pig, which can remove hard deposits from the interior
of a pipeline.
Another object of the invention is to provide a
pipeline pig which can maintain a seal between different
products in a pipeline, i.e. the pig can be used to clean only
or to clean a pipeline and simultaneously separate products in
the pipeline.
According to one aspect, the present invention
relates to a pipeline pig comprising:
a body formed of elastic material;
a plurality of sleeves anchored in the body;
a plurality of teeth disposed about and extending
radially outward from the sleeves;
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the teeth and the sleeves each having radially
accessible means cooperating with each other to detachably
secure each detachable tooth within a corresponding sleeve.
According to another aspect, the invention relates
to a detachable tooth for use in combination with a pipeline
pig having a central portion, the detachable tooth being
attachable to a sleeve radially disposed in the central
portion of the pipeline pig, for use in scraping scale from
the inside of pipes, the detachable tooth comprising:
a shank;
a head carried on the shank;
the head including a hexagonal base and a scraping
portion remote from the shank; and
means on the shank for cooperating with the sleeve
to detachably secure the detachable tooth within the sleeve.
The invention will be described in greater detail
with reference to the accompanying drawings, which illustrate
a preferred embodiment of the invention, and wherein:
Figure 1 is a side elevational view of a pig in
accordance with the present invention in a section of
pipeline;
Figure 2 is a longitudinal sectional view of the pig
taken generally along line II-II of Fig. 1;
Figure 3 is a cross section of the pig taken
generally along line III-III of Fig. 1;
Figure 4 is an isometric view of a tooth used in the
pig of Figs. 1 to 3;
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~igure 5 is an exploded, isometric view of the tooth
of Fig. 4; and
Figure 6 is a cross-sectional view of a portion of a
mold used to produce the pig of Figs. 1 to 3.
Referring to Figs. 1 to 3, the pig of the present
invention which is generally indicated at 1 is intended for
use in a pipeline, a section 2 of which is shown in Fig. 1 for
cleaning the interior 3 thereof. The pig 1 includes a one-
piece elongated, flexible, cylindrical body 4 with
hemispherical ends 5. The body is symmetrical, permitting
travel in both directions which is important when using the
pig in industrial heaters and similar pipelines. The body 4
is formed, e.g. of polyethylene, polypropylene, rubber or
polyurethane. The flexibility and hardness of the body 4 are
adapted to the intended use.
A wide annular rib 7 is provided at the center of
the body 4, and two narrower annular ribs 8 are provided
nearer to the ends 5 of the body. Thin, longitudinal ribs 10
extend between the ribs 7 and 8. The annular ribs 7 and 8,
and the longitudinal ribs 10 define the sides and ends of
square recesses 11, each of which contains a tooth 12.
Another circumferential row of recesses 13 is provided on each
side of the central ribs 7 ~only one row shown). Each of the
recesses 13 also contains a tooth 12. Additional ribs or
fingers 14 extend outwardly from the outer side edge of each
end rib 8. The fingers 14 are spaced equidistant apart around
the periphery of the body 4, and taper outwardly from a wide
inner end having the same thickness as the ribs 7 and 8 to a
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narrow outer end 16 (Fig. 1). The fingers 14 lend strength to
the ribs 8 in the longitudinal direction. The dimensions and
numbers of ribs 7, 8 and 10 and fingers 14 may vary depending
upon the use of the pig, e.g. the seal required for pig travel
through the pipeline. Moreover, the ribs and fingers can be
formed of different material and have a different hardness
from each other and from the remainder of the body 4. For
example, the use of harder end ribs 8 may be required because
of the fact that the end ribs define the leading ribs in the
direction of pig travel, and thus are subjected to higher
forces than the rib 7.
Each tooth 12 includes an internally threaded anchor
or sleeve 17 for mounting in the body 4, and a separate
threaded shank 18 (Fig. 5) carrying a head 19 for mounting in
the sleeve 17. The plates 21 and 22 may also be circular.
Hexagonal flanges or plates 21 and 22 are provided on the
bottom and top ends, respectively of the sleeve 17. The plate
21 anchors the sleeve 17 in the body 4, and the plate 22
limits movement of the sleeve into the body 4. The head 19
has a hexagonal base and a pyramidal pointed end 24. The
sleeve 17, and the shank 18 and head 19 are formed of metal,
but depending upon the intended use, can also be formed of
plastic.
With reference to Fig. 6, the sleeves 17 are molded
into the body using a mold (not shown), each half 25 of which
contains threaded holes for receiving threaded sleeve holders
26. The sleeves 17 are mounted on the holders 26 in the mold
cavity before the mold is closed. The mold is closed, and the
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body 4 is molded. The mold is opened, the holders 26 are
removed and the body 4 is removed from the mold. The shanks
18 are threaded into the sleeves 17 to complete the pig.
In use, the pig is inserted into a pipe, and is
S propelled therethrough by a fluid (gas or liquid) pressure
gradient within the pipe. Pressure acting on one end of the
pig body 4 causes expansion of the pig against the internal
surface of the pipe, so that the teeth 12 are caused to scrape
the interior surface of the pipe to dislodge material
therefrom. Although it is not shown in Fig. 1, the outer
diameter of the pig is normally equal to or slightly larger
than the interior diameter of the pipe, so that the outer
surface of the pig body 4 is forced against the internal
surface of the pipe. As they become worn, the heads 19 of the
teeth 12 can be moved outwardly by rotating the shank 18 in
the sleeve 17, or removed and replaced. The plates 21 and 22
resist removal of the teeth 12 from the body 4, and prevent
driving of the head 19 into the body 4.
Because the body 4 of the pig is symmetrical, the
pig can be caused to reciprocate in a pipe for removing scale
from an area with large accumulations. In cases where the pig
is used to separate different materials in a pipeline, the
teeth 12 can be omitted.
It will be appreciated that the recesses in the body
of the pig can be circular rather than square or rectangular.
Moreover, the top plate on the tooth sleeve can be cup shaped
or concavo/convex, so that it is recessed in the body for
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certain uses-. The geometry of the head 19 of each tooth can
also be different from that described above.
