U.S. patent number 3,895,085 [Application Number 05/393,190] was granted by the patent office on 1975-07-15 for process for preparing a synthetic floating pipe.
This patent grant is currently assigned to Maruhachi Kasei Kogyo Kabushiki Kaisha. Invention is credited to Hiroshi Maruyama, Todao Suzuki.
United States Patent |
3,895,085 |
Suzuki , et al. |
July 15, 1975 |
Process for preparing a synthetic floating pipe
Abstract
A method for preparing a synthetic pipe for use in a float is
disclosed. A first pipe is extruded by the use of a first extruding
means and separating plates are inserted and fixed in the pipe in a
tight manner at predetermined intervals in order to form chambers
within the pipe. While the pipe is still heated and in a soft state
from the extrusion, a perforating means perforates the wall of the
first pipe, between the plates thus forming a communication between
the atmosphere and the chamber. This eliminates the deformation of
the pipe which would be caused if the chamber were sealed from the
atmosphere. After the pipe has cooled, a second pipe is extruded
around the first pipe in contact therewith in order to cover the
first pipe and thus cover the perforations. In this manner, a
closed pipe is formed which is suitable for use as a float. The
insertion of the separating plates is conducted in such a manner
that a ridge is formed at the point of insertion. This is the
finished pipe, a plurality of circumferential ridges at
predetermined lengths giving an appearance similar to bamboo.
Inventors: |
Suzuki; Todao (Toyohashi,
JA), Maruyama; Hiroshi (Toyakawa, JA) |
Assignee: |
Maruhachi Kasei Kogyo Kabushiki
Kaisha (JA)
|
Family
ID: |
13921449 |
Appl.
No.: |
05/393,190 |
Filed: |
August 30, 1973 |
Foreign Application Priority Data
|
|
|
|
|
Aug 31, 1972 [JA] |
|
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47-87673 |
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Current U.S.
Class: |
264/154;
264/209.3; 264/210.1; 264/171.11; 264/171.12 |
Current CPC
Class: |
B29C
48/15 (20190201); B29C 48/21 (20190201); B29C
48/0016 (20190201); B29C 48/157 (20190201); B29C
48/154 (20190201); B29C 48/13 (20190201); B29C
48/09 (20190201) |
Current International
Class: |
B29C
47/06 (20060101); B29C 47/02 (20060101); B29d
023/04 (); B29f 003/00 () |
Field of
Search: |
;264/150,151,156,167,154,172,173,209,210,290 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: White; Robert F.
Assistant Examiner: Hoag; W. E.
Attorney, Agent or Firm: Armstrong, Nikaido & Wegner
Claims
1. A method of preparing a synthetic pipe for use in a float
comprising:
a. extruding a first pipe
b. inserting at least two plates into said first pipe at
predetermined intervals;
c. fixing said plates to the inner surface of said first pipe as
said first pipe is being extruded;
d. perforating the wall of said first pipe between said plates
while said first pipe is still heated and in a soft state from the
extrusion, whereby the space between said plates communicates with
the atmosphere;
e. extruding a second pipe around said first pipe and in contact
therewith whereby said second pipe covers said first pipe and
covers said
2. The method of claim 1 wherein fixing said plates includes
pinching said first pipe immediately after said separating plates
have been inserted.
3. The method of claim 1 wherein fixing said plates includes
heating the
4. The method of claim 1 further including drawing said first pipe
a faster rate after said plate is inserted than before said plate
is inserted whereby a ridge is formed on the outer surface of said
first pipe around
5. The method of claim 4 further including drawing said second pipe
at a rate faster than said first pipe whereby a corresponding ridge
is formed in said second pipe.
Description
BACKGROUND OF THE INVENTION
This invention relates to a process for preparing a synthetic
floating pipe which contains separating plates therein.
By a synthetic floating pipe which contains separating plates
therein is meant a pipe which has a structure resembling a bamboo,
i.e. a pipe having therein a number of compartments or chambers
which are air-tightly separated from each other by plates inserted
into the pipe. The compartments or chambers never permit water to
penetrate thereinto, and therefore the synthetic floating pipe has
the characteristic of considerable buoyancy in water.
The inventor has attempted to prepare the synthetic floating pipe
by inserting a number of separating plates into a thermoplastic
resin pipe in the process of extrusion. The inventor has filed a
utility model application in connection with an apparatus for
preparing the article in Japan, which was published under the
Japanese utility model publication No. 45-33897. Consequently, the
principle of a method for preparing the synthetic floating pipe has
already been known. The present invention has been made by adding
an improvement to the known principle.
Japanese utility model publication No. 45-33897 discloses an
apparatus which comprises mounting on the forward end of an
extruder a cross-head die for use in extruding a pipe, providing an
inner mold of said die with an aperture extending through the inner
mold in the extruding direction, mounting a means for inserting
separating plates on said die on the side opposite to the extruding
direction, communicating said aperture with an interior cavity of
the means, and providing a rod for inserting the plates which
reciprocate between the cavity of the means and the aperture. It is
possible to continuously prepare a pipe having separating plates
therein by means of said apparatus. This is especially true when
the separating plates are used, each of which has a perforation
extending through the wall thereof. An excellent pipe having
separating plates therein can be prepared by means of the apparatus
just described in the publication. However, when the separating
plate is used which has no perforations, special attention is
needed in order to prepare a quality pipe having separating plates
therein. This is because deformation occurs in the pipe when the
pipe is cooled, owing to formation of a number of chambers or
compartments which are air-tightly separated from each other on
account of close contact of the separating plates with the pipe.
That is, since the pipe is at a high temperature and in a softened
state at the time when the separating plates are provided with the
pipe, the interior of the compartments or chambers are brought into
a state of reduced pressure, and therefore the pipe has a tendency
to deform from its original shape. The bigger the diameter of the
pipe, the more conspicuous the tendency. Further, the higher an
extrusion speed, the more conspicuous the tendency. As a result,
said apparatus cannot produce with good efficiency a synthetic
floating pipe having the separating plates therein for use in
floats.
SUMMARY OF THE INVENTION
The present invention aims to produce the synthetic pipe for use in
floats by improving over the drawbacks and avoiding the
deficiencies and disadvantages of the past.
The present invention is based upon the principle that minute
perforations are provided in a pipe during a process of
manufacturing the pipe by extruding synthetic thermoplastic resin,
so that the air can penetrate into each of the airtight
compartments or chambers which are formed by fixing separating
plates to the inner surface of the pipe. Subsequently, the thus
obtained pipe is covered over the entire outer surface thereof,
with another synthetic thermoplastic pipe extruded from an extruder
so as to close the minute perforations.
The present invention provides a process and apparatus for
preparing a synthetic pipe containing separating plates therein for
use in floats and which comprises inserting a number of
thermoplastic resin plates into a thermoplastic resin pipe at
certain intervals and fixing the plates tightly to the inner
surface of the pipe, while the pipe is being extruded from a die
mounted on an extruder, providing the pipe with a plurality of
perforations having a minute diameter and extending through the
width of the pipe while the pipe is still heated and in a softened
state so that each of the compartments or chambers formed in the
pipe by the plates may be communicated with the outer atmosphere
through the perforations, extruding another thermoplastic resin
pipe around said pipe so as to cover said pipe, and contacting both
pipes closely so that the perforations are closed by the other
pipe.
By way of example, accompanying drawings show a process according
to the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematical plan view of one embodiment of the process
wherein extruders and pipes are partly cut away.
FIG. 2 is a sectional view of a die for extruding another
thermoplastic resin pipe around a perforated pipe, wherein
perforation is not shown.
FIG. 3 is a sectional view of a die for extruding a thermoplastic
resin pipe and inserting the separating plates in the pipe.
DETAILED DESCRIPTION OF THE DRAWINGS
In FIG. 1, cross-head die 2 is mounted on the forward end of
extruder 1, and inserting means 3 is mounted on cross-head die 2 in
order to transfer the separating plates to pipe a extruded from die
2. After being provided with the separating plates therein, pipe a
is perforated by piercing means 5 to have minute pin holes
extending through the thickness of the pipe. Pipe a is then cooled
in the air and pulled by take-up rolls 6. Thereafter, pipe a is
further introduced into cross-head die 8 mounted on extruder 7.
Thus, pipe a is covered with another pipe over the entire outer
surface of pipe a in cross-head die 8 to form one pipe b, as the
result the perforations are closed. Pipe b is cooled in cooling box
9, then is pulled by take-up rolls 10.
More particularly, according to the process shown in FIG. 1, a pipe
having separating plates therein is formed in the following manner:
Molten resin is extruded in the form of a pipe from cross-head die
2 mounted on extruder 1. Separating plates are preformed so as to
have such sufficient dimensions that the plates extend across the
diameter and are stored in inserting means 3. The separating plates
are intermittently transferred into the pipe through cross-head die
2 by means of inserting means 3. Since the pipe extruded from die 2
is in a softened state, the separating plates are allowed to
contact closely with inner surface of the pipe, and therefore there
are formed in the pipe a number of compartments or chambers which
are air-tightly separated by the separating plates. The pipe is
advanced onto rolls 4. In the meantime, the pipe is exposed to the
air, and is therefore gradually cooled.
Immediately after the compartments or chambers have been formed in
the pipe, the pipe is provided with perforations which have minute
diameters and extend through wall of the pipe. Thus, there is
formed pipe a. The perforations are produced by instantaneously
piercing the pipe with a needle mounted on the forward end of
piercing means 5. Thus, pipe a should have at least one perforation
in every compartment or chamber. These perforations have a diameter
almost equal to the outside diameter of the piercing needle. Pipe a
is cooled in the air to have such a hardness that it can maintain
its shape as a pipe, and then pipe a is caught between take-up
rolls 6. During the time period while pipe a is conveyed to the
rolls 6, the air penetrates into every compartment or chamber
through every perforation, and therefore the interior of all
compartments or chambers in pipe a are maintained at the
atmospheric pressure. As the result, even in the event wherein the
pipe a is further cooled, the pipe a does not collapse, though the
separating plates have been air-tightly fixed in the pipe.
After passing take up rolls 6, pipe a is introduced into cross-head
die 8 mounted on the second extruder 7. In cross-head die 8, pipe a
is covered with another pipe of thermoplastic resin extruded from
extruder 7. When this additional pipe covers pipe a over the entire
outer surface thereof, said perforations are closed by the
additional pipe, and thus is obtained pipe b which has separating
plates and no perforations on the outer surface thereof.
In cross-head die 8, it is preferable to discharge the air included
between pipe a and said additional pipe in order to contact closely
both pipes. FIG. 2 shows the mode of a preferable covering process.
In FIG. 2, thermoplastic resin is extruded from the second extruder
7 into passage 81, and then is extruded from die 8 in the form of
pipe 82. Pipe 82 is the other or additional pipe which is to cover
pipe a. Tube 83 is connected to a vacuum pump which is not shown,
and tube 83 is to discharge the air between pipe a and the inner
wall surrounding pipe a in crosshead die 8. Thus by evacuating the
air through tube 83 in die 8, covering pipe 82 is closely contacted
with pipe a immediately after pipe 82 has been extruded from die 8.
As the result, pipe b is formed. It should also be noted that
packing 84 is provided in order to prevent the air from flowing
into die 8 through the opening existing on the inlet side of pipe
a. Preferably, packing 84 is composed of several sheets of packing
materials which are arranged at short distances.
In the process for preparing pipe b, pipe a is at first prepared
such that a number of separating plates are closely fixed to the
inner surface of the pipe a. However, pipe a is then provided with
perforations in each of the compartments or chambers confined by
the separating plates, so that the air can penetrate into each of
the compartments. Consequently pipe a does not give rise to any
unexpected deformation. Thereafter the covering pipe is formed on
pipe a, and the resultant pipe b does not give rise to any
unexpected deformation even when pipe b is cooled by contacting
with water in cooling box 9 and pulled by take-up rolls 10, because
pipe a is able to maintain the shape of the combination pipe. Thus,
a pipe is obtained which has a number of separating plates
air-tightly fixed to the interior of the pipe, and is identified as
a synthetic floating pipe containing separating plates therein.
According to the present invention, the separating plates can be
firmly fixed to predetermined positions and the resultant pipe does
not give rise to any unexpected deformation, though the separating
plates are inserted into the pipe which is being extruded from the
die mounted on an extruder, and the plates are air-tightly fixed to
the inner surface of the pipe. Thus, the process enables the
production of a synthetic floating pipe containing separating
plates therein and which has a desired predetermined shape.
Further, two extrusion steps are carried out in this process, and
therefore material of the outer pipe may be varied from that of the
inner pipe, thus the resultant pipe product may be imparted with a
peculiar characteristic by combination of two materials. Moreover,
if a resin of the same kind is used in two extrusions, that is, the
first extrusion for preparing pipe a and the second extrusion for
preparing the covering pipe, both pipes can be adhered so
intimately that both pipes are never separated. The perforations
provided in pipe a are so minute in diameter that they can be
entirely closed by subsequently overlaying pipe a with a covering
pipe, and they thus, leave no observable trace or appearance.
Furthermore, immediately after the separating plates have been
fixed in pipe a in the first extrusion, if pipe a is pulled at a
slightly higher speed, then pipe a is allowed to protrude slightly
and outwardly in the portions wherein the separating plates have
been fixed in pipe a, and thus an article is produced which is
perforated and has the appearance of bamboo. Also, if pipe b is
pulled in the second extrusion at a slightly higher speed than that
of the first extrusion, then outward protrusions in the vicinity of
the separating plates can be maintained in the same state as they
were originally. Consequently, an article is obtained which has
outward protrusions in places at certain distances, as is similar
to bamboo. Such outward protrusions are useful when the pipe is
tied by strings because the protrusions act to prevent the strings
from slipping off. This invention has such advantages as stated
above, as well as others.
Insertion of the separating plates into the pipe are carried out by
means of the following die: in FIG. 3, molten resin is extruded
from extruder 1 and introduced into die 2. Die 2 is constructed
with outer mold 27 and inner mold 28, between which a tubular
passage is formed which starts from 23, through 24 and 25 and ends
at 26. Inner mold 28 is provided with aperture 29 which is to pass
the separating plates. Molten resin is introduced from portion 21,
passed through passage 22, and brought to tubular passage 23.
Passage 22 is composed of two portions, each of which goes round by
half of circumference of aperture 29 to communicate with passage
23, with gradually increasing the width and gradually changing the
advancing direction perpendicularly. Passage 23, 24 and 25 are
gradually decreased in thickness in the advancing direction.
Forward end of inner mold 28 is located inwardly in relation to
forward end of outer mold 27.
Separating plates are inserted into the pipe by the following
manner: in FIG. 3, separating plates x are at first stored in case
31, and are heated at the sides thereof by heater 32, and are
transferred one by one to inserting case 34 by transferring rod 33.
One separating plate x is fixed to suction disk 36 mounted on
inserting rod 35 in inserting compartment 34. Separating plate x
fixed to suction disk 36 is transferred to die 2 by inserting rod
35. While transferred, the separating plate x is further heated at
the sides in aperture 29. Thus, separating plate x is passed
through aperture 29 of inner mold 28 and is inserted into the pipe
which is still in contact with inner surface of outer mold 27. At
this time, suction from the suction disk is stopped by a means
which is not shown in FIG. 3. Thereafter, inserting rod 35 is
withdrawn from die 2. Thus, separating plates are provided with the
pipe at certain intervals by repeating motions as stated above.
The separating plates can be more firmly fixed to the inner surface
of the pipe in the following manner: one method is to pinch and
compress the pipe by paired rolls immediately after the pipe has
been provided with the separating plates. Further, another method
is to use the separating plates having the diameter a little larger
than inner diameter of the pipe and to forcibly insert the plate
into the pipe, or to heat the sides of the plate prior to the
insertion.
It is quite easy to provide the pipe with perforations of minute
diameter immediately after the separating plates have been fixed to
the pipe which is extruded by the first extrusion. The reason that
the pipe can be easily perforated by piercing the pipe with a
needle, is because the pipe is in a softened state at this time. A
perforating means may be, for example, constructed by providing the
forward end of a reciprocating rod with a needle, the needle
piercing the pipe when the rod is advanced to the pipe. In order to
reciprocate the rod, it is preferable to use electro-magnets or
combination of electro-magnets and springs. The perforations will
be sufficient, if only one or two perforations having 1-2 mm in
diameter are provided for each compartment, for example, having a 4
cm inside diameter and a 20 cm inside length.
The pipe a formed by the first extrusion (hereinafter referred to
as "the first pipe") is normally made to have a little larger
thickness than that of the pipe formed by the second extrusion
(hereinafter referred to as "the second pipe"). However, when the
first pipe is increased in the thickness, the pipe does not show
remarkable protrusions which occur on account of the separating
plates. Therefore, in order to make the protrusions more
noticeable, it is not advantageous to increase the first pipe too
much in thickness. Thus it is preferable that, for example, if the
first pipe is made to have 2 mm in thickness, then the second pipe
is made to have about 1 mm in thickness. By doing so, a final pipe
can be obtained which is about 3 mm in thickness, and has
remarkable and beautiful protrusions which give the appearance of
bamboo. Therefore, the final pipe obtained by this process is
superior to all pipes which are manufactured by conventional
methods.
The present invention may be embodied in other specific forms
without departing from the spirit or essential characteristics
thereof. The presently disclosed embodiments are therefore to be
considered in all respect as illustrative and not restrictive, the
scope of the invention being indicated by the appended claims
rather than the foregoing description, and all changes which come
within the meaning and range of equivalency of the claims are
therefore intended to be embraced therein.
* * * * *