Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: PIPE MOLD WITH MULTIPLE SOURCES OF PLASTIC SUPPLY
FIELD OF THE INVENTION
The present invention relates to a pipe mold which
uses multiple sources of plastic to form a pipe.
BACKGROUND OF THE INVENTION
A conventional pipe mold is one which uses a single
source of plastic to form a pipe. If the pipe has a double
wall construction then the plastic supplied from the single
source is used to form both the outer and the inner wall of
the pipe. This leaves no opportunity to use different
materials or at least different grades of the same material
in the walls of the pipe.
SUMMARY OF THE PRESENT INVENTION
The present invention provides a pipe molding
apparatus which uses multiple supplies of plastic to form
double wall pipe. The apparatus includes die equipment
having first and second delivery passages delivering the
plastic from the multiple supplies to a pipe mold where the
pipe is formed with inner and outer walls. The die
equipment includes a plastic separator which separates the
plastic from the different supplies in advance of the
delivery passages to determine which particular supply of
plastic going to a particular delivery passage.
For example the apparatus may be fed with first and
second supplies of plastic. The separator may be set such
that all of the plastic from the first supply goes to the
first delivery passage and all of the plastic from the
second supply goes to the second delivery passage.
Alternatively, some of the plastic from the first supply
may go to the second delivery passage or some of the
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plastic from the second supply may go to the first delivery
passage.
BRIEF DESCRIPTION OF THE DRAWINGS
The above as well as other advantages and features
of the present invention will be described in greater
detail according to the preferred embodiments of the
present invention in which;
Figure 1 is a sectional view through a pipe molding
apparatus fed with multiple supplies of plastic according
to a preferred embodiment of the invention;
Figure 2 is an enlarged sectional view of the
delivery passage region of the apparatus of Figure 1;
Figure 3 is a further enlarged sectional view
through the delivery passage area showing the flow of
plastic therethrough;
Figures 4 through 6 are sectional views of pipe
wall constructions of double wall pipe made in accordance
with various different preferred embodiments of the
invention.
DETAILED DESCRIPTION ACCORDING TO THE PREFERRED EMBODIMENTS
OF THE PRESENT INVENTION IN WHICH:
Figure 1 shows a pipe molding apparatus generally
indicated at 1. This apparatus has die equipment 3 and an
actual molding region 5 where plastic pipe is formed. The
molding region may be formed by mold blocks moving through
a mold tunnel as is known in the art. The pipe formed is
double wall pipe having inner and outer pipe walls as will
be better described with respect to Figures 4 through 6.
Die equipment 3 is in accordance with the present
invention, fed plastic by multiple plastic supplies, namely
plastic supplies 7 and 9. As will be understood from
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Figure 1, the plastic supplied by supply 9 is externally
surrounded by the plastic supplied by supply 7.
By way of example only, supply 9 may feed a pure
grade of plastic, e.g. polyethylene while supply 7 may feed
a lower grade of plastic, e.g. recycled polyethylene to the
die equipment. For reasons to be described later in
detail, this will produce a pipe having an inner wall
comprising or at least substantially comprising the higher
grade plastic and an outer wall comprising or at least
substantially comprising the lower grade plastic. In the
alternative, the supplies can be reversed depending upon
the desired use of the pipe.
The plastic from both supplies enters a single
delivery passage 11 of the die equipment. This passage
delivers the plastic to first and second delivery passages
13 and 15 interiorly of the pipe mold 5. The plastic
delivered into the mold through passage 13 forms the outer
wall of the pipe while the plastic delivered through
passage 15 forms the inner wall of the pipe.
Located in advance of passages 13 and 15 is a
plastic separator 17. This separator determines which
plastic goes to which of the two delivery passages 13 and
15.
Again by way of example only, Figure 3 shows that
separator 17 is set up such that all of the plastic P1,
which is the plastic from supply 7, and some of the plastic
P2, which is the plastic from supply 9, is fed along
passage 13. The remainder of the plastic P2 is fed along
passage 15.
Figures 4 through 6 show different pipe wall
constructions which are possible when working with two
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separate supplies of plastic.
Figure 4 shows a double wall pipe 21 having an
outer pipe wall 23 formed by all of the plastic P1 and some
of the plastic P2. Pipe 21 also has an inner pipe wall
which is formed only by plastic P2 which is the remainder
of this particular plastic not taken up by the outer pipe
wall.
Pipe 21 is made in accordance with the separation
of plastic shown in Figure 3.
Figure 5 shows a double wall pipe 27 having outer
and inner walls 29 and 31 respectively.
To achieve the pipe construction of Figure 5, the
plastic separator is set up to completely separate the
individual supplies of plastic such that all of the plastic
P1 goes to passage 13 in forming the outer pipe wall and
all of the plastic P2 goes to passage 17 to form pipe wall
31.
Figure 6 shows a double wall pipe 33 with still a
different separation of plastic. More particularly the
separator is set up such that only some o the plastic P1
goes to the passage 13 to form the outer pipe wall 35,
while the rest o the plastic P1 and all of the plastic P2
goes to passage 15 to form the inner pipe wall 37.
It is to be understood that although only two
supplies of plastic are shown, the concept of the plastic
separation also applies to more than two supplies of
plastic. For example, a third supply of plastic could be
introduced interiorly of supply 9 and the separator could
be set that some or all of this supply goes to the inner
pipe wall with the outer supplies going to the outer pipe
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wall.
The description above relates to multiple sources
of different grades of plastic, i.e. one high grade plastic
and one lower grade of plastic that may be recycled and
that may contain fillers. The same concept equally applies
to other different sources of plastic where the pipe may be
formed for example by a combination of dense and foamed
plastics.
Although various preferred embodiments of the
present invention have been described in detail, it will be
appreciated by those skilled in the art that variations may
be made without departing from the spirit of the invention
or the scope of the appended claims.
