U.S. patent number 3,885,521 [Application Number 05/362,014] was granted by the patent office on 1975-05-27 for apparatus for coating the inner wall surface of a duct.
Invention is credited to Paul von Arx.
United States Patent |
3,885,521 |
von Arx |
May 27, 1975 |
Apparatus for coating the inner wall surface of a duct
Abstract
An apparatus for the application of a coating on the inner wall
surface of a duct comprising a forward and rearward piston, axially
displaceable and defining a space therebetween for a coating mass,
and further including a rotating polishing device upstream of both
pistons, and a guide cable attached to the polishing device and
passing through both pistons.
Inventors: |
von Arx; Paul (CH-4450 Sissach,
CH) |
Family
ID: |
4330431 |
Appl.
No.: |
05/362,014 |
Filed: |
May 21, 1973 |
Foreign Application Priority Data
|
|
|
|
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May 24, 1972 [CH] |
|
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7785/72 |
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Current U.S.
Class: |
118/105;
15/104.16; 118/408; 118/DIG.10; 118/112 |
Current CPC
Class: |
B05C
7/08 (20130101); Y10S 118/10 (20130101) |
Current International
Class: |
B05C
7/00 (20060101); B05C 7/08 (20060101); B05c
007/06 (); B05c 011/02 () |
Field of
Search: |
;117/95
;118/408,105,254,DIG.10 ;15/104.05,14.6R,104.09 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Martin; William D.
Assistant Examiner: Frenkel; Stuart D.
Attorney, Agent or Firm: Ross; Karl F. Dubno; Herbert
Claims
I claim:
1. An apparatus for the application of a coating on the inner wall
surface of a duct, comprising:
a forward and a rearward piston axially displaceable and spaced
apart inside said duct and jointly with a portion of said inner
wall surface forming therebetween a space for a coating mass, said
forward piston having first sealing means along said inner wall
surface for providing increased sealing when the pressure exerted
on said coating mass increases, and said rearward piston having
second sealing means along said inner wall surface which
increasingly yields with increasing pressure of said coating mass
and permits the issuance of said coating mass between said second
sealing means and said inner wall surface;
a polishing device upstream of both said pistons;
a guide cable attached to said polishing device and passing through
both said pistons;
respective means for sealing each piston against said guide cable,
respectively, said polishing device pushing both said pistons and
said coating mass enclosed therebetween through said duct when said
guide cable is pulled;
guide means for said polishing device for inducing rotary motion
thereto in said duct while said polishing device pushes said
pistons through said duct;
connecting means between said polishing device and said guide cable
for permitting said rotary motion without substantial twisting of
said guide cable, and
a swivel joint between said polishing device and said rearward
piston permitting relative pivotal movement thereof while
transmitting axial force from said polishing device to said
rearward piston.
2. The apparatus defined in claim 1 wherein said first and second
sealing means are sealing rings.
3. The apparatus defined in claim 2, wherein said sealing rings are
solid rings, further comprising respective means for holding said
solid rings and pressing the latter to effect increased sealing and
friction between said two pistons, respectively, and said inner
wall surface.
4. The apparatus defined in claim 2, further comprising two
ring-shaped flanges on said pistons, respectively; two hollow rings
restrained between said sealing rings and said ring-shaped flanges,
respectively; and two means for controlling the pressure in said
hollow rings, respectively, said hollow rings urging said sealing
rings, respectively, to increasingly press against the inner wall
surface of said duct, when said pressure controlling means are
actuated and the pressures in said ring-shaped hollow rings are
increased.
5. The apparatus defined in claim 1 wherein said second sealing
means includes a set of self-adjusting springy polishing members
which follow the cross-sectional irregularities of said duct while
in operation.
6. The apparatus defined in claim 1, further comprising means for
adjusting the contact pressure between said first sealing means and
said inner wall surface, thereby determining the friction between
said first sealing means and said inner wall surface and
consequently the pressure exerted on said coating means when said
pistons and said coating mass jointly are advanced.
Description
FIELD OF THE INVENTION
The present invention relates to an apparatus for and a method of
coating the inner wall surface of a duct, particularly a duct
already in place.
BACKGROUND OF THE INVENTION
It is frequently desired to provide sealing and corrosion-resistant
coatings along the inner wall of a duct, pipe or conduit, e.g., as
a rust removal or preventive measure in water mains. The duct can
also be a gas main. Such a duct must be cleaned out and joints and
areas penetrated by corrosion be sealed off before a coating of the
inner wall surface thereof can be undertaken. Likewise, the inner
wall surfaces of pipelines, the ducts of sewage systems, and
high-pressure conduits of power plants can be coated, after
thorough cleaning and removal of rust, to protect the same against
corrosion and decay. Suitable materials for coating masses to be
used on the inner wall surfaces of ducts are paint formulations as
well as synthetic resin materials which may contain fillers such as
glass fibers.
It is known in the art to coat the inner wall surface of ducts with
such materials. However, comparatively complicated apparatus and
techniques are used and seldom can the inner surfaces of ducts
having comparatively large diameters, say at least 400 mm, be
coated with conventional systems.
OBJECTS OF THE INVENTION
It is, therefore, an important object of my invention to provide a
method of and an apparatus for the application of a coating on the
inner wall surface of a duct which avoids the above-described
drawbacks, is simple and easy to operate and can be used in ducts
having large as well as small diameters.
Another object of my invention is to provide a method of and an
apparatus with which a coating of uniform and easily controllable
thickness can be applied.
Another object of the invention is to provide a method of and an
apparatus for the internal coating of a duct, tube, conduit, pipe
or other channel of closed cross section having cross-sectional
irregularities, and ducts having bends.
Still another object of the invention is to provide an improved
method and apparatus whereby a coating can be applied to the inner
wall surface of a duct laid in the ground.
SUMMARY OF THE INVENTION
These objects and others which will become apparent hereinafter are
attainable in accordance with my invention with a system for
coating the inner wall surface of a duct whereby a pair of pistons
are forced through a duct with the rearward piston being driven and
the forward piston frictionally retarded so that a coating mass
between the pistons is extruded under pressure around the trailing
piston onto the duct surface. More particularly the coating or
sealing mass of a viscous flamable material is disposed between
axially spaced pistons which are introduced into the duct and have
peripheries which form seals confronting the inner duct surface so
as to trap the mass between the pistons.
The apparatus thus comprises a forward and a rearward piston having
first and second sealing means, respectively, and means for
advancing the rearward piston through the duct. The two pistons and
the inner wall surface therebetween jointly define a space for a
coating mass. The first sealing means of the forward piston is so
constructed and arranged as to provide increased sealing when the
pressure exerted on the coating mass and consequently on the first
sealing means increases, and the second sealing means of the
rearward piston is so constructed and arranged as to increasingly
yield when the pressure exerted on the coating mass and
consequently on the second sealing means increases.
Thus, the coating mass is permitted to issue or escape (extrude)
between the second sealing means and the inner wall surface of the
duct, when the pressure on the coating mass increases.
According to a particularly advantageous feature of this invention,
the advancing means can be a guide cable. It is attached to the
rearward piston with a fastening device and caused to pass or be
drawn through a hole in the forward piston. Sealing means are
provided for the hole in the forward piston and the guide cable to
prevent the escape of coating mass to the area of the duct which is
downstream of the piston assembly. When the guide cable is pulled,
the pistons and the coating mass contained therebetween are
advanced through the duct, i.e., the trailing piston is drawn
forwardly and exerts an axial pressure upon the flowable but
viscous mass ahead of it. The hydraulic force exerted by the fluid
mass advances the leading piston and, at the same time, biases its
seal (first sealing means) outwardly against the wall of the duct
to prevent escape of the mass around the leading piston. The
resulting frictional retardation of the leading piston, in turn,
permits buildup of the pressure in the fluid mass and causes
deflection of the seal of the trailing piston (second sealing
means) to cause extrusion of the flowable mass therearound. The
pressure is thus a function of the rate at which the assembly is
drawn through the duct.
According to a further feature of my invention, the apparatus can
comprise a polishing device positioned in the duct upstream of the
piston assembly to smooth the coating. A guide cable is attached to
the polishing device and passes or is drawn through holes in the
rearward as well as the forward piston. Respective sealing means
for the two pistons and the guide cable, respectively, are provided
to prevent undesired escape of the coating mass to areas of the
duct outside the piston assembly. When the guide cable is pulled,
the polishing device pushes the rearward piston, which action
pressurizes the coating mass so that the entire piston assembly can
be advanced in the forward direction through the duct.
According to a particularly advantageous feature of my invention,
the above-described polishing device can be provided with guide
means for inducing rotary motion to the polishing device in the
duct while the guide cable is pulled and the piston assembly
thereby is pushed in the forward direction through the duct.
Connecting means between the guide means of the polishing device
and of the guide cable is provided for permitting such rotary
motion of the polishing device without imparting a substantial
twisting to the guide cable.
According to a further feature of my invention, the means for
advancing the pistons and the coating mass can include means for
providing pressurized air in the duct area which is upstream of the
two pistons. In other words the trailing piston may be urged
through the duct by an airpressure differential across the assembly
of the pistons.
According to a further feature of my invention, the first and
second sealing means for the forward and the rearward piston,
respectively, can be sealing rings, held or supported and pressed
between outer and inner rigid discs, to effect increased sealing
and friction between the two pistons and the duct surface,
respectively.
The sealing rings can be solid or hollow rings. In the case of a
hollow ring, means for controlling the pressure in the hollow ring
is provided for varying the contact pressure between the hollow
ring and a solid ring and then also the contact pressure between
the solid ring and the inner wall surface of the duct.
According to a particularly advantageous feature of my invention,
the second sealing means can be formed as a set of self-adjusting
springy polishing or coating-doctoring members. They follow the
cross-sectional irregularities of the duct when the coating
apparatus is advanced through the duct.
DESCRIPTION OF THE DRAWING
The above and other objects, features and advantages of the present
invention will become more readily apparent from the following
description, reference being made to the accompanying drawing in
which:
FIGS. 1-6 are longitudinal sections of portions of ducts and
partially longitudinal sections of coating apparatuses according to
the invention accommodated therein;
FIGS. 7-9 are transverse sections which show how the sealing means
of the second piston in FIG. 6 operates in a duct with a deformed
cross-section;
FIG. 10 is a longitudinal section which shows how a coating
apparatus according to FIG. 2 is adapted in a duct with a bend;
FIG. 11 is a vertical section which shows how a coating apparatus
according to the present invention can be used in a duct laid below
a street; and
FIG. 12 is an axial section which shows how a coating apparatus
according to the present invention can be driven with pressurized
air.
SPECIFIC DESCRIPTION
Reference will first be made to FIG. 1, which shows a coating
apparatus consisting of two pistons 1 and 2 and a polishing device
G in a duct R to be formed with a coating B. A guide cable Z drawn
through central holes in pistons 1 and 2 is attached to a driver 3
rotatably connected to polishing device G by means of swivel
coupling 5.
Piston 1 comprises a short intermediate tube portion 11 and two
disk-shaped inner flanges 12 rigidly fastened thereto. Two outer
flanges 13 and sealing means 15 hold and press two sets of first
sealing rings 14 made of tough rubber against inner flanges 12,
respectively. The sealing effectivity of rings 14 increases when
they are pressed harder by outer disks 13 and when the pressure
exerted by coating mass M enclosed between pistons 1 and 2
increases.
The first sealing means 14 comprises three horizontally stacked
rubber disks with at least the leading disk having a diameter in
excess of that of the duct and the flange 12 or disk 13 immediately
behind each stack of rubber disks. At least when the first or
leading piston 1 is inserted into the duct, therefore, the outer
periphery of the seal stacks is deflected rearwardly so as to be
conically rearwardly divergent. The coating mass acting upon the
rearwardly inclined lip of the rearmost stack of sealing disks
biases the lip against the inner wall of the duct.
Trailing piston 2 is similar in construction to piston 1 and
consists of short tube portion 21 with two axially spaced inner
flanges 22, two sets of second sealing rings or cuffs 24, made of a
material softer than the first sealing rings 14, outer flanges or
disks 23, and sealing and fastening means 25 preventing leakage
around the cables.
Polishing or smoothing device G comprises a central portion 60 and
a brush holder 41 rotatably mounted and axially offset from a
central portion on a common bar 42 and connected thereto by spring
means 63. Central portion 60 is provided with two sets of swingable
arms 61 and wheels mounted on the outer extremities of arms 61 and
touching the inner wall surface of duct R. Wheels 62 are aligned in
a direction which is slightly inclined in relation to the axis of
duct R. Brush holder 41 holds polishing brushes 4.
The brush holder comprises a pair of disks whose confronting faces
are inclined to the axis of the device so that the brush 4 likewise
assumes an inclination to the axis as has been shown in FIG. 1.
In operation, pistons 1 and 2 and coating mass M enclosed
therebetween and polishing device G are jointly advanced through
duct R by pulling guide cable Z from a location ahead of the
pistons. Polishing device G is pulled thereby and in its turn
pushes piston 2, coating mass M and piston 1. The pressure on the
coating mass M increases, the second sealing means 24 of piston 2
yield and coating material M is extruded between the seal 24 and
the inner wall surface of duct R to produce a layer B is formed on
the inner wall surface of duct R. However, the following
requirements must be met to obtain a continuous and uniform coating
B:
1. There must be a considerable friction between first sealing
rings 14 of piston 1 and the inner wall surface of duct R,
providing a braking action when piston 1 is pushed through duct R.
Then the necessary pressure will be exerted on coating mass M and
on the seal 24 of piston 2 so that the latter will yield and
coating mass M can issue around seal 24 as mentioned
previously.
2. The second seal 24 must have such characteristics and be so held
that the coating mass M does not escape when guide cable Z is not
pulled and substantially no external pressure is exerted on coating
mass M. However, when guide cable Z is pulled to the extent that
the coating apparatus advances in duct R, second sealing rings 24
must be so constructed that they yield and a ring-shaped body of
coating mass M is extruded between sealing rings 24 and the inner
wall surface of duct R and a coating of this shape is formed on the
inner wall surface of duct R. The direction of orientation of
sealing rings 24 and also sealing rings 14 in the areas where they
come in contact with or approach the inner wall surface is of
course of importance. The increased pressure of coating mass M
tends to lessen the contact pressure between sealing means 24 and
the inner wall surface of the duct because sealing rings 24 are
bent in an upstream direction and away from the coating mass M,
whereas the contact pressure between sealing rings 14 and the inner
wall surface of the duct tends to increase when the pressure of
coating mass M increases because sealing rings 14 also are bent in
an upstream direction but towards coating mass M and not away from
it.
3. The contact pressures between sealing rings 14 and 24 and the
innerwall surface of duct R, respectively, must be mutually
balanced so that the desired coating thickness can be obtained.
4. The amount of coating mass M fed between pistons 1 and 2 must be
calculated taking into consideration the desired thickness of the
coating B, the inner diameter of duct R, and the length of duct to
be coated.
Polishing and smoothing device G is rotated in duct R when the
coating apparatus is advanced therein due to the above-mentioned
inclined direction of wheels 62. Spring 63 is tensioned due to the
braking action of polishing brushes 4. Arms 61 are pivotally
connected to an extension brush holder 41, and arms 61 and wheels
62 are urged outwardly against the inner wall surface of duct R
when the distance between the central body 60 and brush holder 41
increases as a consequence of increasing speed of the advancing
coating apparatus in duct R and increasing friction between brushes
4 and the inner wall surface. This, and the fact that the wheels
lie at angles to the axis, i.e., along helical arcs, ensures
reliable rotation and improved smoothing by polishing device G as
the coating apparatus advances and the speed thereof varies. The
flanges or disks 23 are held away from flanges 22 by spacer tubes
through which the cable Z passes.
The polishing device G.sub.1 in FIG. 2 is nonrotating. It is
similar in construction to piston 2 as indicated in the figure.
However, piston 2 is provided with tightly held sealing rings
whereas polishing device G.sub.1 is provided with polishing brushes
141 which can be loosely held sealing rings.
In FIG. 2 the system makes use of a nonrotating polishing or wiping
assembly G.sub.1 which abuts directly upon and therefore pushes the
trailing piston 102. The smoothing assembly G.sub.1 may be
identical in all respects to the trailing piston 2 and hence the
latter may be provided on its leading disk with a sealing sleeve
125 having a forwardly concave surface conforming to a spherical
section. Its trailing sleeve may be provided with a spherically
convex portion 125a so that, when the spherically convex portion of
an upstream assembly abuts the spherically concave portion of a
downstream assembly or vice versa, a swivel joint will be formed at
the surfaces allowing the application of the driving force from the
upstream assembly while permitting the train of pistons to
negotiate bends in the duct. Of course, as shown in FIG. 10, both
abutting sleeves may be convex with comparable effect since the
surfaces roll upon one another.
FIG. 3 illustrates a particularly advantageous feature of my
invention wherein the end of guide cable Z is pulled around cable
pulley 127 mounted on piston 126 on its upstream side, urged back
through holes in piston 202 and is connected to an eye 126a mounted
on piston 201 on its upstream side. The result of this guide cable
arrangement is that the pressure on coating mass M is doubled when
the guide cable Z is pulled and the coating apparatus starts
advancing in duct R. Piston 126 is provided with forwardly
positioned tightly held sealing rings 224 and two rearwardly
positioned polishing means 241, e.g., two sets of polishing
brushes.
In the embodiment of FIG. 3, the piston assembly 126, carrying the
pulley 127 comprises the second or trailing piston 202 having the
function described for the piston 2 and a smoothing device 241
which is rigidly fixed to the piston 202.
In other words, the piston assembly 126 comprises a pair of rigid
drums 202a and 241a each provided with a small-diameter flange
202b, 241b in the forward direction, and a large diameter flange
202c, 241c at the trailing end of the drum. Ahead of the
small-diameter flange 202b of the piston portion 202, there is
provided a large diameter disk 202d carrying a seal 202e
surrounding the two passes of the cable Z which extend through the
piston and formed with rollers diagrammatically shown at 202f to
reduce frictional interengagement of the oppositely moving cable
passes and the piston. A spacer tube 202g is disposed between the
flange 202b to limit the compression upon the sealing lamella
224.
A larger diameter spacer tube 241d is provided between the leading
flange 241b and the trailing flange 202c to limit the compression
applied to the first set of polishing lamella 241 forming the
nonrotating brush and constituted in the form of elastomeric disks
of low stiffness which are readily deflected rearwardly and wipe
the coating B.
A similar spacer tube 241e is disposed between the trailing flange
241c and a small-diameter disk 241f carrying the pulley 127.
Rollers 24g upon the disk 241f reduce friction between the cable
and the piston assembly. It will be apparent that not only is there
a mechanical advantage of two by the use of the described cable
arrangement, to thereby increase the pressure upon the coating mass
M, but also a relative displacement of the two pistons 201, 202
toward one another as the entire assembly is drawn through the duct
in the direction of the arrow.
FIG. 4 shows means for controlling the contact pressure between the
sealing means 14 and 24 on pistons 1 and 2, respectively, and the
inner wall surface of duct R. An air-filled ring-shaped tube 16 is
accommodated between sealing means 14 and a ring-shaped flange 161
on tube portion 11. Tube 16 is connected to pressure controlling
means 170 over a monometer 17. When a higher friction between
sealing means 14 and the inner wall surface of duct R is desirable
the pressure in tube 16 is increased by actuating pressure
controlling means 170.
An air-filled ring-shaped tube 26 is accommodated between sealing
means 24 and a ring-shaped flange 261 on tube portion 21. Tube 26
is connected to pressure controlling means 270 over a monometer 27.
When a different friction between sealing means 24 and the inner
wall surface of duct R is desirable, the pressure in tube 26 is
increased by actuating pressure controlling means 270.
FIG. 5 shows a solid rubber ring 18 as sealing means. It is pressed
by ring-shaped flange 181 and ring-shaped pressure ring 191 mounted
on tube portion 11. Ring 191 increasingly presses sealing ring 18
when nut 19 is screwed in a forward direction and lock nut 192
locks nut 19 in a desirable position, i.e., when the contact
pressure between sealing means 18 and the inner wall surface is the
desired one. Piston 2 is provided with the same kind of sealing
means 28, and corresponding pressure ring 291, nut 29 and lock nut
292, the three latter elements being mounted on tube portion 21.
When the pressure on ring 28 is increased, the thickness of coating
B will decrease.
FIGS. 6 and 7 show a rearward piston 7 of quite different
construction. It is advantageous when highly viscous and pasty
coating masses M are to be applied to the inner wall of duct R.
Radially and also axially extending guide plates 72 are mounted on
an axially extending hub 71 and swingably held thereon by setting
ring 73. They are provided with fins 721, substantially normal to
guide plates 72. Fins 721 overlap each other to confine coating
mass M. They are pressed against the duct wall by two rubber plates
75 held in place and pressed by three support plates 74. Rubber
plates 75 and support plates 74 are also mounted on hub 71. Rubber
plates 75 individually urge fins 72 against the duct wall.
FIGS. 8 and 9 show two ducts having deformed cross-sections. Guide
plates 72 swing inwardly, towards the axis of the duct, where the
duct wall is bent inwardly and outwardly where the duct wall is
bent outwardly because rubber plates 75 urge fins 721, fastened to
guide plates 72, against the duct wall. Thus, coating mass M is
contained by an umbrella-like conical wall, its shape being adapted
after the duct wall against which it is pressed. Guide plates 72 do
not have dots for sake of clarity.
FIG. 10 shows the coating apparatus of FIG. 2 in operation in a
bent portion of a duct. Pistons 1 and 2 and polishing device
G.sub.1 adapt themselves very nicely to the curved duct wall when
they are advanced through the duct.
FIG. 11 shows a duct R laid in ground E under a street St. The
length A of the duct is for instance 700 m. Two pits X and Y have
been excavated to expose the duct. Portions of duct R in pits X and
Y can be sawed off to allow access to the interior thereof. An
auxiliary duct portion R.sub.1 has been adapted to duct R to
facilitate the feeding of coating mass M between pistons 1 and 2.
The necessary amount of coating mass M is calculated and an excess
thereof is introduced, by means of filling device F, to secure an
uninterrupted coating of the inner wall surface of the duct.
Filling device F is mounted on auxiliary duct portion R.sub.1. Care
must be taken not to introduce air in the coating mass when it is
fed into the space between pistons 1 and 2. Guide cable Z is reeled
in on cable winch over guide pulley 110 adapted on the duct end in
pit Y, pistons 1 and 2 and the coating mass M enclosed therebetween
advance through duct R, and a coating is formed from coating mass M
issuing between the sealing means of rearward piston 2 and the
inner wall surface of duct R.
FIG. 12 illustrates the use of an advancing means for the coating
apparatus which is quite different from guide cable Z, namely a
pressurized-air system. Cover 120 secures the necessary air-tight
condition in the upstream portion of duct R and pressurized air is
introduced through cock 121. The speed of the advancing coating
apparatus through the duct can be controlled by the amount of
pressurized air introduced through cock 121.
* * * * *