PIPE FORMING APPARATUS FOR VOLUME OF PLASTIC ALONG THE PIPE WALL

Abstract: Apparatus for forming continuous products as an extruder die (21) with a supply channel which terminates with a channel mouth feeding plastic to a moving mold tunnel (23). The mold tunnel (23) comprises mold blocks (25, 27) of different mold block shapes which move past the channel mouth (31, 39) to form the wall of the product with a varying configuration. The channel mouth (31, 39) has an adjustable mouth gap which automatically adjusts in gap size according to which one of the mold block (25, 27) shapes is moving past the channel mouth (31, 39) to adjust plastic flow through the channel mouth so as to affect changes in thickness of the plastic along the product wall.

Description: TITLE: PIPE FORMING APPARATUS FOR VOLUME OF PLASTIC ALONG THE PIPE WALL FIELD OF THE INVENTION The present invention relates to product forming apparatus for forming a continuous length of plastic products such as plastic pipe or the like. BACKGROUND OF THE INVENTION In an .apparatus designed to produce a continuous length of product such as plastic pipe it is often desirable to vary the amount of plastic deposited at certain regions along the wall of the product. Apparatus for making this type of product typically includes a moving mold tunnel . In an effort to vary the amount of material fed to the moving mold tunnel, attempts have been made to either speed up or slow down the plastic feed from the extruder to the mold tunnel. This however creates a very serious potential safety hazard within the extrusion equipment . SUMMARY OF THE PRESENT INVENTION The present invention relates to apparatus for varying thickness in the wall of a continuous length of product made in a plastic forming apparatus using an extruder feeding to a moving mold tunnel . The apparatus does not contemplate the speeding up or slowing down of the plastic flow from the extruder to the mold tunnel and therefore avoids the prior art safety concerns. More particularly, the product forming apparatus of the present invention includes an extruder die with a supply channel which terminates with a channel mouth feeding plastic to a moving mold tunnel . The mold tunnel comprises mold blocks of different mold block shapes which move past the channel mouth to form a product wall of varying configuration. The channel mouth has an adjustable gap which automatically adjusts in gap size according to which particular mold block shape is moving past the channel mouth. This adjustment of the channel mouth adjusts the plastic flow through from the channel to affect changes in thickness of the plastic along the product wall . According to a particular aspect of the present invention, the apparatus comprises a pipe forming apparatus and the mouth gap is adjusted in size to maintain a constant volume to axial length ratio of the plastic along the pipe wall as to be described later in detail . 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 cross sectional view of a corrugated region of a pipe wall made in accordance with the present invention; Figure 2 is a view similar to Figure 1 with the exception that it shows the straightened length of the corrugated region indicated at 2-2 in Figure 1. Figure 3 is a sectional view of a pipe wall including a coupling region made in accordance with a prior art apparatus and labelled prior art; Figure 4 is a further sectional view of a pipe wall including a coupling region made in accordance with the present invention; Figure 5 is a sectional view of the plastic feed to moving mold tunnel region of a pipe molding apparatus according to a preferred embodiment of the present invention; Figures 6 through 8 are enlarged sectional views showing the channel mouth in various different operating positions for feeding plastic to the moving mold tunnel of Figure 5 ; Figures 9 through 11 are further enlarged sectional views of the channel mouth showing different operating devices for affecting adjustment of the channel mouth. DETAILED DESCRIPTION ACCORDING TO THE PREFERRED EMBODIMENTS OF THE PRESENT INVENTION IN WHICH: Figure 1 shows a corrugated section of a pipe wall generally indicated at 1 and made in accordance with the present invention. This corrugated pipe wall section comprises a plurality of alternating crests and troughs 3,5 respectively. Lines 2-2 designate the axial length of the pipe covered by two of the troughs and one of the crests between those two troughs. Figure 2 indicates at area 7, the axial length of the pipe region between the lines 2-2 of Figure 1 when this pipe region is straightened out. Area 7 is bordered by end lines 8-8. The separation between lines 8-8 is much greater than the separation between lines 2-2 as can be seen in comparing Figures 1 and 2. Figure 3 shows a section of pipe wall generally indicated at la. This pipe wall includes a substantially straight coupling indicated at 9 formed in the pipe wall. Coupling 9 is bordered to its opposite ends by lines 10- 10. In comparing Figures 1 and 3, it will be seen that the axial length of the pipe wall between lines 2-2 spanning the two troughs and the one crest is identical to the axial length of the pipe wall between the lines 10-10 spanning the coupling 9. It will also be seen in comparing Figures 2 and 3 that the straightened length of the two troughs and the single crest between the lines 8- 8 is substantially greater than the axial length of the pipe wall at the coupling between lines 10-10. The purpose of describing all of the above dimensions is to show that substantially more material is required to form the corrugations than is required • to form the coupling if the two have the same wall thickness. This is because the straightened length of the corrugations is substantially greater than the already substantially straight length of the coupling. Figure 4 once again shows a section of the pipe wall 1 from Figure 1 formed with the crests and troughs 3 and 5 respectively and also formed with a coupling region 11. This coupling region is bordered by the end lines 12-12 having the same separation as the end lines 10-10 bordering the coupling 9 of pipe la in Figure 3. However, in Figure 4, the coupling region 11 has a much greater volume of plastic in the pipe wall 1 than is found in the coupling 9 of pipe wall la of Figure 3, i.e. the wall of coupling 11 is thicker than the wall of coupling 9. Specifically, the thickness of the plastic in coupling 11 in Figure 4 is such that the volume of plastic used is the same as the volume of plastic used to make the two troughs and the single crest between the lines 2-2 in Figure 1. Accordingly, there is a constant volume to axial length ratio of plastic along the pipe wall of Figure 4. This is achieved by thickening the plastic at the coupling relative to the corrugated region of the pipe wall or conversely by thinning the plastic in the corrugated region in the pipe wall relative to the coupling region of the pipe wall. The means to produce the varying of the thickness along the pipe wall is described having reference to Figures 5 through 11 of the drawings. More particularly, Figure 5 shows die equipment 21 which is fed from an extruder not shown in the drawings. Die equipment 21 designed to make double wall pipe has a first plastic feed channel 29 terminating with a channel mouth 31 and a second plastic feed channel 38 terminating with a channel mouth 39. These two channel mouths guide the feed of plastic through the plastic flow channels to a moving mold tunnel generally indicated at 23. This mold tunnel is formed from mold block sections 25 and 27. The two mold block sections have varying configurations in that mold block section 25 has an interior surface to form the corrugations in the pipe wall while mold block section 27 is shaped to form the coupling in the pipe wall. Channel mouth 31 is bordered to its downstream side by guide 33 and to its upstream side by guide 35. Guide 33 includes a tip portion 34, while guide 35 includes its own tip portion 37. Channel mouth 39 is bordered to its downstream side by a guide 41 and to its upstream side by a guide 43 having a tip portion 45. As will be seen in comparing Figures 6, 7 and 8, the tip portion 37 of guide 35 (as is also the case with the tip portion 45 of guide 43) is adjustable to vary the size of the gap between the upstream and the downstream guides to the opposite side of channel mouth 31. This adjustment which produces a variation in the size of the mouth gap of the channel changes the amount of plastic exiting the channel. In accordance with a preferred feature of the present invention, the gap size change occurs automatically according to which particular mold block shape is passing by the channel mouth. In comparing Figures 6 and 7, it will be seen that the tip portion 37 of guide 35 has moved to a more downstream position which reduces the mouth gap which in turn reduces the amount of plastic exiting the channel mouth. This is to be compared to the Figure 8 position in which the guide tip 37 is moved to a more upstream position where the gap of the channel mouth has been increased. With this increased gap, more plastic is allowed to flow out of the channel mouth. By way of example only, Figure 7 might well be the normal position of the upstream channel mouth guide used to form the corrugations in the pipe wall. However, as the coupling part of the pipe wall is produced the tip guide would move to the Figure 6 position to allow more plastic to flow to the thickened pipe coupling. However, the volume of plastic to axial length ratio of the plastic used in forming the coupling in the corrugations will end up being the same between the corrugated and the coupling region of the pipe. Once again, this occurs because the actual, i.e. the straightened length of the thinner walled corrugations is substantially greater than the already substantially straight length of the thicker coupling. In accordance with the present invention, the varying of the channel mouth gap occurs automatically according to pipe wall shape changes. This can be done in a number of different ways. For example, the apparatus can simply be programmed to increase the channel mouth size as the coupling forming mold block sections pass the channel mouth and to decrease the coupling mouth size as the corrugation forming mold block sections pass the channel mouth. In the alternative, sensing means such as sensor 41 can be provided in the apparatus to sense the particular type of mold block section approaching the channel mouth which will then be adjusted accordingly. It is to be understood that the operation of the guide at the mouth of the downstream channel 39, when it is required to vary the thickness in the inner wall of the pipe, is identical to that described immediately above. It is also to be understood that the upstream channel mouth size can be varied through the use of movable guide tip 34 on the downstream guide 33 either alone or in conjunction with the operation of guide tip 37 as already described. Figures 9 through 11 show various different set ups which can be used for operating any one of the movable guide tips. More particularly, Figure 9 shows a cantilever device generally indicated at 51. This cantilever device comprises a pair of pivotally attached rod members 53 and 55 attached respectively to fixed rod support 57 and tip guide 37. A piston member 59 also supported at one end by support 57 has its other end attached to the two pivotal rod members. When piston member 59 is extended, it causes a folding action between rod members 53 and 51 to move them to the dotted line position of Figure 9 pulling in an upstream direction on guide tip 37. This causes an opening in the channel mouth . When piston member 59 is retracted, it pulls rod member 51 and 53 to a more straightened position to produce a downstream pushing on guide tip 37 to decrease the gap of the channel mouth. Figure 10 shows a plunger member 61 which attaches directly to guide tip 37. This plunger member, which is preferably electrically activated operates to either push the guide tip in a downstream direction to narrow the channel mouth or to pull the guide tip in an upstream direction to open the channel mouth. Figure 11 shows a further set up for moving the guide tip 37 comprising a fixed length rod 63 extending from a rotary gear 65 coupled to a fixed gear 67. Rod 63 has a downstream end 69 which is threadably engaged with guide tip 37. The rotation of the rod by .the gear combination 65 and 67 produces a threading action in one direction of rotation of the rod and an unthreading action in the other direction of rotation of the rod relative to the guide tip to either widen or narrow the channel mouth. It is to be understood that the three set ups described immediately above in Figures 9 through 11 are only some of many different types of adjustment arrangements which can be used to adjust or vary the positioning of the guide tip. Another way of varying the thickness of the plastic laid at different locations on the wall of product is to adjust the speed of the corrugator, i.e. the moving mold blocks. At a constant plastic flow from the channel mouth the wall thickness decreases with ' increasing corrugator speed and the wall thickness increases with decreasing corrugator speed. Further adjustments can be made by changing the corrugator speed while simultaneously adjusting the size of the mouth gap. It is also to be understood that although the above description does refer to maintaining a constant volume to axial length ratio of the plastic along the product wall, there may be cases in which it is desirable to either increase or decrease the volume of plastic at a specific region of the product wall relative to the other regions of the product wall. This is once again achieved by varying the gap of the channel mouth, by varying the speed of the moving mold tunnel or by a combination of varying the gap of the channel mouth while at the same time varying the speed of the moving mold tunnel. 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 .

Claims: THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS: 1. Pipe forming apparatus having an extruder die with a supply channel which terminates with a channel mouth feeding plastic to a moving mold tunnel comprising mold blocks of different mold block shapes which move past said channel mouth to form a pipe wall of varying configuration, said channel mouth having an adjustable mouth gap which automatically adjusts in gap size according to which one of the mold block shapes is moving past the channel mouth to provide a plastic flow through the gap mouth to maintain a constant volume to axial length ratio of the plastic along the pipe wall. 2. Pipe forming apparatus as claimed in Claim 1, wherein said channel mouth has upstream and downstream mouth guides to opposite sides of said mouth gap, said upstream mouth guide having a movable part to adjust the mouth gap . 3. Pipe forming apparatus as claimed in Claim 2, wherein said movable part of said upstream mouth guide is adjusted by a length adjustable member. 4. Pipe forming apparatus as claimed in Claim 2, wherein said movable part of said upstream mouth guide is adjusted by a threaded member. 5. Pipe forming apparatus as claimed in Claim 1, wherein said apparatus is preprogrammed to provide the adjustment of said mouth gap. 6. Pipe forming apparatus as claimed in Claim 1, wherein said apparatus includes sensing means to sense the different mold block shapes and to provide for the adjustment of the mouth gap. 7. Pipe forming apparatus as claimed in Claim 1, including means to adjust speed of the moving mold tunnel which cooperates with the adjustable mouth gap to maintain the constant volume to axial length ratio of the plastic along the pipe wall . 8. Product forming apparatus having an extruder die with a supply channel which terminates with a channel mouth feeding plastic to a moving mold tunnel comprising mold blocks of different mold block shapes which move past said channel mouth to form a product wall of varying configuration, said channel mouth having an adjustable mouth gap which automatically adjusts in gap size according to which one of the mold block shapes is moving past the channel mouth to adjust plastic flow through the channel mouth to affect changes in thickness of the plastic along the product wall . 9. Product forming apparatus having an extruder die with a supply channel which terminates with a channel mouth feeding plastic to a moving mold tunnel, said channel mouth having an adjustable mouth gap which adjusts in gap size to adjust plastic flow through the channel mouth to affect changes in thickness of the plastic along the product wall. 10. Product forming apparatus having an extruder die with a supply channel which terminates with a channel mouth feeding plastic to a moving mold tunnel, said mold tunnel being speed adjustable to vary thickness of the plastic along the product wall.

Inventors: LUPKE MANFRED A A, LUPKE STEFAN A, LUPKE, MANFRED, A., A., LUPKE, STEFAN, A.
Applicants: LUPKE MANFRED ARNO ALFRED, LUPKE STEFAN A, LUPKE, MANFRED, A., A., LUPKE, STEFAN, A.
Application year: 2001
Main classification: B29D
IPC codes: B29C47, B29C53