WO1990007414A1

WO1990007414A1 - Apparatus and method for the production of molded articles

Info

Publication number: WO1990007414A1
Application number: PCT/US1989/005556
Authority: WO
Inventors: Heinrich B. Dickhut; John S. Berns
Original assignee: Cullom Machine Tool & Die, Inc.
Priority date: 1988-12-27
Filing date: 1989-12-13
Publication date: 1990-07-12
Also published as: AU4827690A

Abstract

An apparatus and method for the continuous production of discrete molded articles including an extrusion nozzle (10) for forming an extrudate (18), and a plurality of mold assemblies (30) continuously circulating and moving past the extrusion nozzle along a molding section. Each mold assembly comprises a pair of mold blocks (26, 28) including an interior molding surface (34) profiled in accordance with the shape of a molded article. A Vacuum is introduced through passages (44, 46, 48) in the interior surface of the mold blocks and/or a gas is introduced within the extrudate to cause the extrudate to conform to the shape of the interior molding surface.

Description

APPARATUS AND METHOD FOR THE PRODUCTION OF MOLDED ARTICLES

Field of the Invention

This invention relates to an apparatus and method for the production of molded articles, and more particularly, to an apparatus and method for the continuous production of discrete molded articles.

Background of the Invention

It is customary in the art to manufacture separate or discrete molded articles by a process which involves: a) the introduction of extrudate within an interior surface of a mold assembly, b) blowing the extrudate into shape by applying pressure within the tube of extrudate or by using a vacuum to draw the air from around the inner surface of the mold assembly, c) opening the mold assembly to remove the molded article, and d) repeating steps a-c with the same mold assembly for as many times as is necessary to make the desired number of molded articles. The above process, being sequential in manner with each step being discretely practiced for each article (i.e. _r each step begun then stopped, over and over) , is inefficient in its use of the molding equipment and mold assemblies, and therefore is also slow and/or expensive (by, for example, requiring the purchase of more equipment to reach a required manufacturing capacity) .

The present invention is directed toward overcoming one or more of the problems with the prior art as set forth above.

Summary of the Invention

In an exemplary embodiment of the present invention, an- apparatus for the continuous production of discrete molded articles is provided which includes an extrusion nozzle for forming an extrudate, and a plurality of mold assemblies continuously circulating and moving past the extrusion nozzle along a molding section. Each mold assembly comprises a pair of mold blocks including an interior molding surface which is profiled in accordance with the shape of the molded article. The apparatus further includes means for causing the tube of extrudate to conform to the profile of the molding surface.

In another aspect of the present invention, the extrudate is conformed to the profile of the molding surface by a vacuum through passages in the interior surface of the pair of mold blocks.

In yet another aspect of the present invention, the extrudate is pinched-off into discrete pockets within the mold blocks, which pockets are conformed to the profile of the molding surface by pressurized gas introduced into the extrudate. The gas, such as air, may be introduced by a fixed or cam actuated gas injection needle located within one of the pair of mold blocks.

The present invention provides a fast, efficient, and inexpensive method of manufacturing discrete articles.

Brief Description ofthe Drawinσs Fig. 1 is a cross-sectional view of an exemplary embodiment of the present invention (taken along line 1-1 of Fig. 2) , showing a pair of mold blocks at the beginning of the molding section; and

Fig. 2 is a cross-sectional view of a mold assembly taken along line 2-2 of Fig. 1.

Description of the Preferred Embodiment

An exemplary embodiment of the present invention is shown in Fig. 1. The assembly shown therein is intended for use in an apparatus for the continuous production of discrete molded articles. Although not shown in Fig. 1, the apparatus further includes an extruder, a tube extrusion die, and a plurality of mold assemblies continuously circulating along a molding section. Apparatuses having the above-described elements are well-known in the art. For example, U.S. Patent Nos. 4,199,314 and 4,439,130 disclose such an apparatus for making continuous articles such as corrugated tubing, and their disclosures are hereby incorporated by reference.

It should be understood that the apparatus may be oriented horizontally or vertically depending upon the particular application. However, it is preferable to orient the apparatus vertically such that the mold blocks comprising the mold assemblies move about a vertical path and molding section.

As shown in Fig. 1, the apparatus according to the present invention includes a tube extrusion nozzle 10 having inner surfaces 12, 14 defining a passage 16 for the continuous flow of a tube of extrudate 18. An additional inner surface 20, centrally located within the nozzle 10, comprises a passage 22 for air. Although not shown in Fig. 1, it is understood that the tube extrusion nozzle may, alternatively, be configured for the continuous flow of extrudate 18 in forms other than a tube.

Fig. 1 further shows two mold blocks 24, 26 in coaxial abutment with each other along the molding section. As shown in Fig. 2, each mold block 26 cooperates with a mating mold block 28 along the molding section (Fig. 1) to comprise a mold assembly 30 as described in greater detail below. Further, it should be understood that each pair of mold blocks 26, 28 may be brought together either by mounting them on clamshell-type carriages following a continuous path such as disclosed in U.S. Patent No. 4,439,130, or by mounting each block of the pair on opposite continuous tracks which bring the blocks 26, 28 together through the molding section such as shown in U.S. Patent No. 4,199,314.

Referring back to Fig. 1, each of the mold blocks 24, 26 includes an interior face 32 and an interior molding surface 34 which is profiled in accordance with the shape of a particular article to be molded. Although Fig. 1 shows the interior molding surface 34 profiled in the shape of a bottle, it is to be understood that the interior molding surface 34 may be profiled in the shape of a variety of discrete articles.

As profiled in the shape of a bottle, the interior molding surface 34 includes a neck portion 36 and a main body portion 38. Additionally, each of the mold blocks 24, 26 include a leading portion 40 and a trailing portion 42 for pinching off or crimping the tube of extrudate 18.

The interior molding surface 34 of each of the mold blocks 24, 26 also includes passages 44, 46, 48 through which a vacuum may be introduced. As shown in Fig. 1, one vacuum passage 44 is located at the neck portion 36 of the profiled interior molding surface 34 while the other vacuum passages 46, 48 are located at the main body portion 38 of the profiled interior molding surface 34. Of course, still other configurations for providing a vacuum in the molding surface could be used, such as the combination of slits, bores and grooves shown in my U.S. Patent No. 4,439,130. As shown in Figs. 1 and 2, a vacuum plenum

50 is disposed adjacent the openings of the vacuum passages 44, 46, 48 in the mold blocks 24, 26 through the molding section. The vacuum plenum 50 defines a passage 56 which is connected to a conduit 58 providing a vacuum source, thereby drawing a vacuum through the passages 44, 46, 48.

As shown in Fig. 2, each of the mold blocks 24, 26 also allow for introduction of a gas within the interior of the tube of extrudate to further assist in conforming the tube of extrudate 18 to the mold block surfaces 34. Specifically, an injection needle 60 (through which pressurized gas is injected as described below) is fixed to a cam member 62 located within a recessed portion 64 of the mold block 26. A compression spring 66 located within the recessed portion 64 biases the cam member 62 and needle 60 radially away from the mold block surface 34. A cam plate 70 suitably fixed relative to the molding section is configured so as to force the cam member 62 and attached needle 60 radially inwardly along the portion of the molding section at which the trailing portion 42 has pinched off the tube of extrudate 18 (essentially forming a bubble of the extrudate 18) . The end of the needle 60 will puncture the extrudate 18 as shown in Fig. 2.

The cam plate 70 includes a passage 72 suitably connected to a source of pressurized air or the like, and which communicates with passages 74, 76 through the cam member 62 and needle 60. Accordingly, when the cam plate 70 forces the needle 60 through the tube of extrudate 18 in the location of the bottle neck 36, the pressurized air is introduced into the bubble of the extrudate to help in conforming the extrudate to the mold surface 34.

Alternatively, it is noted that the gas injection needle 60 may be rigidly fixed within the mold block 26, rather than cam actuated. In a preferred method of operation of the exemplary embodiment of the present invention, the tube of extrudate 18 is first formed at the extrusion nozzle 10. As the mold block 24 moves past the extrusion nozzle 10 along the molding section, the tube of extrudate 18 is crimped and trapped at the leading pinch off portion 40.

. As the mold block 24 moves further along the molding section, as the extrudate 18 is stretched, air is introduced to the interior of the tube of extrudate 18 through the passage 22 in the extrusion nozzle 10 to prevent the collapse thereof. As the mold block 24 moves still further along the molding section, the tube of extrudate 18 will be trapped and crimped at the trailing pinch off portion 42 to form a bubble. At this point in the process, the extrudate 18 is positioned within the interior molding surface 34 of mold block 24, as shown in Fig. 1. The vacuum is then introduced through the passages 44, 46, 48 located in the interior molding surface 34 of the mold block 24, to the area between the interior surface 34 and the tube of extrudate 18 to form and hold the tube of extrudate 18 to the interior mold surface 34.

As the mold block 24 moves along the molding section, the piercing cam member 62 also comes into contact with the cam plate 70, which forces the cam 62 into the recessed portion 64 of the mold block 24 against the bias of the return spring 66, as shown in Fig. 2. Since the injection needle 60 is mounted to the cam 62, the movement of the cam 62 also causes the injection needle 60 to pierce the tube of extrudate 18. Once the tube of extrudate 18 has been pierced, air flowing through the passages 72, 74, 76 is forced into the interior of the tube of extrudate 18 to further assist in conforming it to the shape of the interior molding surface 34. At the end of the molding section, the cam plate 70 is spaced back from the molding blocks 24, 26 to allow the spring 66 to force the cam 62 out of the recessed portion 64 and withdraw the attached needle 60 from the extrudate 18. Finally, when the mold blocks 26, 28 reach the end of the molding section, they are themselves separated to return around their continuous path to the beginning of the molding section and the profiled tube of extrudate 18 is thus freed and allowed to cool. Depending upon the particular article being molded, suitable finishing operations may then be performed on the articles (for example, with the bottles as shown, the pinched off portions at the bottom of each bottle would be removed as well as that portion of the bottle neck having the puncture of the needle 60) .

While the above described embodiment uses both vacuum and pressurized air to conform the extrudate 18 to the molding surface 34, it will be understood by a skilled artisan having knowledge of the present invention that any combination of the two could be used as well. For example, only air injection could be used, with the passages 44, 46, 48 being open to the atmosphere for venting only. Alternatively, particularly where it is undesirable to puncture the article being molded, only vacuum around the outside of the extrudate 18 can be used to conform the extrudate 18 to the molding surface 34.

It should be understood that the steps described sequentially above are, in fact, not sequential, but rather are continuously occurring all at the same time (though at different parts of the apparatus) . For example, the extrusion nozzle 10 is continuously creating extrudate 18, the mold blocks 26, 28 are continuously being mated as they enter the molding section, and are continuously separating as they reach the end of the molding section, etc. This process and apparatus thus produces a continuous string of identical, discrete articles, without any undesirable starting and stopping of each process. In particular, by following this process, there is no need to create separate, discrete amounts of extrudate — rather, continuous and identical amounts of extrudate may be created for each molded article. Other aspects, objects and advantages of the invention can be obtained from a study of the drawings, the specification and the appended claims.

Claims

1. An apparatus for the continuous production of discrete molded articles comprising: an extrusion nozzle for forming an extru¬ date; a plurality of mold assemblies continuously circulating and moving past said extrusion nozzle along a molding section, each mold assembly comprising a pair of mold blocks including an interior molding surface which is profiled in accordance with the shape of the molded article; and means for causing the extrudate to conform to the profile of the molding surface.

2. The apparatus of claim 1 wherein said gas is air.

3. The apparatus of claim 1 wherein the means for causing the extrudate to conform to the profile of the molding surface comprises means for introducing a vacuum through passages in the interior surface of said pair of mold blocks.

4. The apparatus of claim 3 wherein the molding surface is profiled in the shape of a bottle and includes a neck portion and a main body portion.

5. The apparatus of claim 4 wherein the vacuum is introduced through passages in the neck portion of the interior molding surface of said pair of mold blocks.

6. The apparatus of claim 1, said mold assemblies further including a pinch-off portion, wherein the means for causing the extrudate to conform to the profile of the molding surface comprises means for introducing a gas within the extrudate once the extrudate has been pinched off.

7. The apparatus of claim 6, wherein said air which is trapped between the extrudate and the mold block interior surface is expelled through passages in the interior surface of said pair of mold blocks.

8. The apparatus of claim 6 wherein the means for introducing a gas within the extrudate comprises a gas injection needle located within one of the pair of mold blocks.

9. The apparatus of claim 8 wherein said gas injection^"needle is cam actuated.

10. An apparatus for the continuous production of discrete molded articles comprising: an extrusion nozzle for forming an extru¬ date; a plurality of mold assemblies continuously circulating and moving past said extrusion nozzle along a molding section, each mold assembly comprising a pair of mold blocks including an interior molding surface which is profiled in accordance with the shape of the molded article, said mold assemblies further including a pinch-off portion; means for introducing a vacuum through passages in the interior surface of said pair of mold blocks to form and hold said extrudate to said surface; and means for introducing a gas within the the extrudate once the extrudate has been pinched off, said gas causing the extrudate to conform to the profile of the molding surface.

11. The apparatus of claim 10 wherein said gas is air.

12. The apparatus of claim 10 wherein the molding surface is profiled in the shape of a bottle and includes a neck portion and a main body portion.

13. The apparatus of claim 12 wherein the vacuum is introduced through passages in the neck portion of the interior molding surface of said pair of mold blocks.

14. The apparatus of claim 10 wherein the means for introducing a gas within the extrudate comprises a gas injection needle located within one of the pair of mold blocks.

15. The apparatus of claim 14 wherein said gas injection needle is cam actuated.

16. An apparatus for the continuous production of discrete molded articles comprising: an extrusion nozzle for forming an extru¬ date; a plurality of mold assemblies continuously circulating about a path and moving past said extrusion nozzle along a molding section, each mold assembly comprising a pair of mold blocks including an interior molding surface which is profiled in accordance with the shape of the molded article; and means for introducing a vacuum through passages in the interior surface of said pair of mold blocks to form and hold said extrudate to said surface.

17. The apparatus of claim 16 further including: a pinch-off section with the molding assemblies; and an air injection needle located within one of the pair of mold blocks for introducing a gas within the extrudate to cause the extrudate to conform to the profile of the molding surface.

18. The apparatus of claim 17 wherein said air injection needle is cam actuated.

19. The apparatus of claim 16 wherein the molding surface is profiled in the shape of a bottle and includes a neck portion and a main body portion.

20. The apparatus of claim 19 wherein the vacuum is introduced through passages in the neck portion of the interior molding surface of said pair of mold blocks.

21. An apparatus for the continuous production of discrete molded articles comprising: an extrusion nozzle for forming an extru¬ date; a plurality of mold assemblies continuously circulating about a path and moving past said extrusion nozzle along a molding section, each mold assembly comprising a pair of mold blocks including an interior molding surface which is profiled in accordance with the shape of the molded article, said mold blocks further including a pinch-off portion; and an air injection needle located within one of the pair of mold blocks for introducing a gas within the pinched-off extrudate to cause the extrudate to conform to the profile of the molding surface, said air which is trapped between the extrudate and the mold block interior surface being expelled through passages in the interior surface of said pair of mold blocks.

22. The apparatus of claim 21 further including means for introducing a vacuum through said passages in the interior surface of said pair of mold blocks to form and hold said extrudate.

23. The apparatus of claim 22 wherein the molding surface is profiled in the shape of a bottle and includes a neck portion and a main body portion.

24. The . apparatus of claim 23 wherein the vacuum is introduced through passages in the neck portion of the interior molding surface of said pair of mold blocks.

25. A method for the continuous production of molded articles comprising the steps of: forming an extrudate at an extrusion nozzle; continuously moving a plurality of contiguously arranged mold assemblies about a path along a molding section located past said extrusion nozzle, each mold assembly comprising a pair of mold blocks which are brought together along a molding section to present an interior molding surface which is profiled in accordance with the shape of the molded article; pinching off the extrudate as said mold assembly moves past said extrusion nozzle; and causing the extrudate to conform to the profile of the molding surface.

26. The method of claim 25 wherein the extrudate is caused to conform to the profile of the molding surface by introducing a vacuum through passages in the interior surface of said pair of mold blocks.

27. The method of claim 26 wherein the molding surface is profiled in the shape of a bottle and includes a neck portion and a main body portion.

28. The method of claim 27 wherein the vacuum is introduced through passages in the neck portion of the interior molding surface of said pair of mold blocks.

29. The method of claim 25 wherein the extrudate is caused to conform to the profile of the molding surface by introducing a gas within the extrudate, said air which is trapped between the extrudate and the mold block interior surface being expelled through passages in the interior surface of said pair of mold blocks.

30. The method of claim 29, wherein a vacuum is also introduced in the passages in the interior surface of said pair of mold blocks.

31. The method of claim 29 wherein said gas is introduced within the extrudate by means of a gas injection needle located within one of the pair of mold blocks comprising said mold assembly.

32. The method of claim 31 wherein said gas injection needle is cam actuated.

33. A method for the continuous production of molded articles comprising the steps of: forming an extrudate at an extrusion nozzle; continuously moving a plurality of contiguously arranged mold assemblies along a molding section located past said extrusion nozzle, each mold assembly comprising a pair of mold blocks including an interior molding surface which is profiled in accordance with the shape of the molded article, said mold blocks further including a pinch-off portion; pinching off the extrudate as said mold assembly moves past said extrusion nozzle; introducing a vacuum through passages in the interior surface of said pair of mold blocks to form and hold said extrudate to said surface; and introducing a gas within the extrudate to cause said extrudate to conform to the profile of the molding surface.

34. The method of claim 33 wherein said gas is air.

35. The method of claim 33 wherein the molding surface is profiled in the shape of a bottle and includes a neck portion and a main body portion.

36. The method of claim 34 wherein the vacuum is introduced through passages in the neck portion of the interior molding surface of said pair of mold blocks.

37. The method of claim 33 wherein gas is introduced within the extrudate by means of a gas injection needle located within one of the pair of mold blocks comprising said mold assembly.

38. The method of claim 37 wherein said gas injection needle is cam actuated.

39. A method for the continuous production of discrete molded articles comprising the steps of: forming an extrudate at an extrusion nozzle; continuously moving a plurality of contiguously arranged mold assemblies along a molding section located past said extrusion nozzle, each mold assembly comprising a pair of mold blocks including an interior molding surface which is profiled in accordance with the shape of the molded article; and introducing a vacuum through passages in the interior surface of said pair of mold blocks to form and hold said extrudate to said surface.

40. The method of claim 39 further including the step of introducing air within the extrudate by means of a gas injection needle located within one of the pair of mold blocks to cause said extrudate to conform to the profile of the molding surface.

41. The method of claim 40 wherein said gas injection needle is cam actuated.

42. The method of claim 39 wherein the molding surface is profiled in the shape of a bottle and includes a neck portion and a main body portion.

43. The method of claim 42 wherein the vacuum is introduced through passages in the neck portion of the interior molding surface of said pair of mold blocks.

44. The method for the continuous production of molded articles comprising the steps of: forming an extrudate at an extrusion nozzle; continuously moving a plurality of contiguously arranged mold assemblies along a molding section located past said extrusion nozzle, each mold assembly comprising a pair of mold blocks including an interior molding surface which is profiled in accordance with the shape of the molded article, said mold blocks further including a leading and trailing crimp area; crimping the extrudate as the leading crimp area of said mold assembly moves past said extrusion nozzle; crimping the extrudate as the trailing crimp area of said mold assembly moves past said extrusion nozzle to form a bubble between crimps; and introducing air within the bubble by means of a gas injection needle located within one of the pair of mold blocks to cause said extrudate to conform to the profile of the molding surface, said air which is trapped between the extrudate and the mold block interior surface being expelled through passages in the interior surface of said pair of mold blocks.

45. The method of claim 44 further including the step of introducing a vacuum through said passages in the interior surface of said pair of mold blocks to form and hold said extrudate to said surface.

46. The method of claim 44 wherein the molding surface is profiled in the shape of a bottle and includes a neck portion and a main body portion.

47. The method of claim 46 wherein the vacuum is introduced through passages in the neck portion of the interior molding surface of said mold blocks.

48. The apparatus of claim 1 wherein the apparatus is arranged in a vertical orientation.

49. The method of claim 25 wherein said plurality of contiguously arranged mold assemblies are moved about a vertical path along a vertical molding section.