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

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 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 separate supplies of plastic.

Figure 4 shows a double wall pipe 21 having an outer pipe wall 23 formed by all of the. plastic PI 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 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.