GB2287209A - Method and apparatus for producing pockets in plastics sheet material - Google Patents

Abstract

A water barrier (10), for protecting the surface trim within a motor vehicle door and for accommodating protrusions from that surface, comprises a sheet 12 of polypropylene material formed with one or more integral open-ended pockets whose openings lie within the plane of the sheet 12 and which are formed by compressing a corresponding area 16A between male and female tool parts formed with matching ridges and grooves so as to form partially folded and stretched corrugations or creases 50, which generally match the peripheral shape of the area 16A and are positioned one within the other. The tool parts apply a predetermined pressure to the polypropylene material for a predetermined time while the material is held to a predetermined elevated temperature. The creased area 16A can subsequently be erected to form the pocket. The pocket thus accommodates the protrusion in the door trim. <IMAGE>

Description

PRODUCTION OF PLASTIC ARTICLES The invention relates to the production of plastic articles. One example of such a plastic article is an article in sheet form but with open pockets extending out of the general plane of the sheet. An example of such an article, to be described in more detail below, is a sheet intended to act as a water shield or water barrier in a door of a motor vehicle.

According to the invention, there is provided a process for producing an open-ended pocket in a predetermined location in a sheet of plastics material with the open end of the pocket lying in the general plane of the sheet, comprising the step of forming a plurality of side-by-side corrugations by the application of predetermined elevated temperature and pressure to an area of the sheet which corresponds to the cross-sectional shape of the pocket and which is positioned at the predetermined location, such that the plastics material becomes stretched within the area permitting the corrugations to be subsequently unfolded to erect the material within the said area into the shape of the said pocket.

Methods according to the invention for making plastics articles in the form of water shields for motor vehicle doors will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which: Figure 1 is a plan view of one of the water shields; Figure 2 is a side elevation in the direction of the arrow II of Figure 1; Figure 3 is a scrap section taken on the line III-III of Figures 1 and 2; Figure 4 shows a plastic sheet during an early stage in manufacture of the article; Figure 5 shows the sheet of Figure 4 at a later stage in the manufacturing process; Figure 6 is a side view of several of the plastic sheets of Figure 5 during a stage in manufacture; Figure 7 is a side view of a stack of the sheets of Figure 6; Figure 8 is a cross-sectional view of a tool used in the process of manufacture of the article; Figure 9 is a plan view on the line IX of Figure 8; Figure 10 is a diagrammatic side view of apparatus used in implementing the process of manufacture; Figure 11 is a plan view of part of the apparatus of Figure 10; and Figure 12 is a plan view of the article after processing in the apparatus of Figures 8 and 9.

As shown in Figures 1,2 and 3, the plastics article 10 is a water shield for fitting in the door of a motor vehicle body to block the passage of water or moisture towards the interior of the vehicle. Water and moisture will inevitably enter the interior of a motor vehicle door through the waist-line gap through which the window glass can be raised or lowered (even though, of course, a seal is provided along this gap). Such water or moisture will thus be present in the hollow interior of the door. On the side of the door facing the interior of the vehicle, the hollow interior is closed off by the door trim. The water shield 10 is placed on the inner face of the door adjacent to the door trim, and thus the interior of the vehicle, from such water or moisture.

The water shield 10 comprises a sheet 12 made of plastics inaterial, such as . polypropylene for example, having adhesive layers 14 placed thereon and a formation 16 defining an open pocket extending outside the general plane of the sheet 12. As shown in Figures 2 and 3, this pocket 16 is positioned on the face 12B of the sheet 12, that is, the face opposite to the face 12A which carries the adhesive layer 14 (the sheet material is translucent, the adhesive layers 14 being visible through it in the Figures). Each pocket 16,18 is open to the face 12A. The purpose of the pocket 16 is to match and accommodate a corresponding shape or bulge in the door trim extending into the interior of the door, such as produced by a storage compartment formed in the outside of the door trim. The position and shape of the pocket 16 will of course depend on the design of the particular door to which the water shield 10 is to be fitted. More than one such pocket may be provided.

The water shield 10 is also provided with through holes and openings 20 through which, for example, the window winding mechanism (if of manual type) and the door handle may extend. Other holes 22 are also provided for a purpose to be described.

The sheet 12 is made of polypropylene. In a manner to be explained in more detail below, the pocket 16 is formed integrally from the material of the sheet.

Figure 4 shows the polypropylene sheet 12 at an early stage in the process of manufacture. At this stage, it has been cut to shape and the holes 20,22 formed. One face of the sheet has been coated with a release agent, and this face is the face 12B (Figure 2). By means of a silk screen process, the adhesive 14 has been applied to the face 12A of the sheet, as shown in Figure 5.

After this stage of the process, a stack 24 of several of the sheets 12 is then formed (see Figures 6 and 7). The sheets are stacked so that the face 12B of each sheet carrying the release agent is placed on top of the adhesive-carrying face 12A of the next sheet in the stack. The release agent on each face 12B prevents such face from being adhered to the next face by the adhesive 14; in other words, the release agent enables the sheets of the stack to be easily separated. Thus, each sheet in the stack thus acts as a protective layer for the adhesive 14 on the next sheet in the stack. The last sheet in the stack, that is, the sheet whose adhesive layers 14 are exposed, is covered by a separate protective sheet of polypropylene, that is, a sheet having a face carrying a release coating but with no adhesive on its opposite face.

Figure 6 shows the sheets 12 during the stacking process and Figure 7 shows the completed stack (but to an enlarged thickness).

The process of producing the pocket 16 (Figures 1 to 3) is carried out using a tool 25 shown diagrammatically in Figure 8 and 9 and comprising male and female metal parts 26,28. As shown in Figure 8, the part 26 comprises ridges 29, while the part 28 comprises matching grooves 30.

Figure 9 shows how the ridges 29 are arranged. It will be noted that they run around the periphery of the tool, being generally relatively close together, but also run across the general area of the tool where they are spaced at a greater distance from each other. The grooves 30 in the tool part 28 are correspondingly arranged. Thus, when the two parts of the tool 26,28 are brought together, each of the ridges 29 enters a corresponding one of the grooves 30. It will be noted that each of the ridges 29 is continuous; that is, it runs continuously around the general area of the tool part 26 so that the outermost ones of the ridges 29 match the peripheral shape of the tool part 26 more or less exactly, this match becoming generally less exact for the more innermost ones of the ridges 29. The grooves 30 are correspondingly arranged.

As shown in Figure 9, the ridges 29 of the tool part 26 (and, correspondingly, the grooves 30 of the tool part 28) are shaped and sized to match the shape and size of the pocket 16 to be formed in the sheet 12, as shown in Figure 1.

Figures 10 and 11 show one form of apparatus arranged to carry out the final stages of the process using the tool 25. As shown in Figure 8, the apparatus comprises a table 30 providing a platform 32. A platen 34 is supported on this platform by rotatable rollers 36 so that it can be moved to and fro in the direction of the arrows A. In this way, the platen 34 can be slid through an opening 38 into the interior of an enclosure 40 which is mounted on the platform 32. Inside the enclosure 40, the female part 28 of the tool is mounted on a movable platen 42 which is suspended from a mounting device 44.

Figure 11 shows a plan view of the platen 34 showing the male tool part 26 mounted in position (its ridges 29 being shown only diagrammatically). Upstanding from the platen 34 are a number of pegs 46.

In operation, a stack 24 of sheets (see Figures 6 and 7) is placed onto the platen 34 and is located accurately in position on the platen 34, in relation to the tool 26, by means of the pegs 46 which are positioned to engage the holes 22 in the sheets 12. The stack of sheets is thus so positioned that the tool part 26 on the platen 34 is aligned with the area of each sheet of the stack where the pocket 16 (Figure 1) is to be produced.

The platen 34, with the stack of sheets in position on it, is then moved into the interior of the enclosure 40. This may be done manually or automatically. The platen becomes so positioned within the enclosure 40 that the male part 26 of the tool 25 is accurately positioned in alignment with the corresponding female part 28. The interior of the enclosure is then heated, and the tool part 28 is then lowered towards the tool part 26. This lowering process is carried out by means of the press mechanism 44 which hydraulically (for example moves the platen 42 downwardly towards the platen 34.

In this way, the two parts of the tool 26,28 are brought towards each other, pressing the stacked polypropylene sheets 12 between them. The temperature of the tool parts is accurately held at a predetermined level (for example, 1000C) and a predetermined pressure (for example, 1,600 pounds per square inch or about 11 MPa) is maintained between the two parts of the tool for a predetermined time (for example, two seconds). The temperature, pressure and time have to be accurately selected and controlled in dependence on the thickness of the polypropylene sheets, the number of sheets in the stack, and the shape and size of the tool parts. The temperature, pressure and time have to be selected so that the material of the polypropylene is not damaged.

At the end of the predetermined time, the tool parts are separated, by raising the tool part 28, and the platen 34 is then removed from the enclosure 40, and the stack of sheets lifted off the platen. The platen is now ready to receive the next stack.

Figure 12 is a plan view of the uppermost one of the sheet 12 in the stack after removal from the platen 34. As shown, the ridges 29 and grooves 30 of the tool 25 have produced an area 16A in this sheet (and correspondingly in all of the sheets of the stack) where corrugations or creases 50 have been produced, matching the ridges and grooves of the tools. Each such corrugation or crease is a narrow region of the sheet where the polypropylene material has been subjected to localised stretching and thinning which produces permanent deformation. The peak of each corrugation is in the form of a sharply defined crease.

The stack of sheets can then be delivered to the vehicle manufacturer, the adhesive layers on each sheet in the stack (except the final one) being protected by the next sheet, the final one in the stack being protected by the protective sheet. On the production line, the fitter simply has to peel a sheet off the stack (this peeling process being facilitated by the release agent on the face 12B of the next sheet), and then press the corrugated area 50 from the face 12B, whereupon this corrugated area becomes erected into the form of the pocket 16 (Figure 1). The sheet can then be placed in position on the appropriate face of the door and secured thereto by means of the adhesive layers 14. In this way, the final shape of the pocket 16 is not formed until just before final mounting of the water shield 10. The water shields are thus delivered to the motor manufacturer in flat-form stacks. This considerably simplifies storage and transport - as compared with what would be the case if the water shields 10 had to be stored and delivered in their final form, with the erected pockets. The risk of damage to the pockets during storage or transit is eliminated.

Figure 12 also shows how corners of the sheets 12 can be modified if desired. The material of the sheet 12 at these corners has been partially cut through as shown by the lines 52 of intermittent serrations. When the sheet has been separated from the stack by the fitter, the lines of serrations 52 enable the fitter to tear off small corner portions 12C of the sheet. The fitter is thus provided with small pieces of polypropylene which carry adhesive 14. These pieces can be used to cover over predetermined holes in the door trim, or elsewhere within the interior of the door, such as holes which are used during the manufacturing process but are thereafter not required and need to be sealed against water or moisture.

This feature avoids the need to provide the fitter with separate small pieces of adhesive-covered material, which would be difficult to store, deliver and handle.

The polypropylene material may be replaced by any other suitable plastics material.

Claims (19)

1. A process for producing an open-ended pocket in a predetermined location in a sheet of plastics material with the open end of the pocket lying in the general plane of the sheet, comprising the step of forming a plurality of side-by-side corrugations by the application of predetermined elevated temperature and pressure to an area of the sheet which corresponds to the cross-sectional shape of the pocket and which is positioned at the predetermined location, such that the plastics material becomes stretched within the area permitting the corrugations to be subsequently unfolded to erect the material within the said area into the shape of the said pocket.

2. A method according to claim 1, in which the predetermined temperature and pressure are applied for a predetermined time.

3. A method according to claim 1 or 2, in which the corrugations generally match the peripheral shape of the cross-section of the pocket, successive corrugations further from the edge of the said area being of shorter peripheral length and each lying within the next adjacent corrugation.

4. A method according to claim 3, in which the corrugations close to-the edge of the said area are closer to each dther than the corrugations further within the area.

5. A method according to any preceding claim, in which each corrugation incorporates a crease or fold line running substantially centrally along it.

6. A method according to any preceding claim, including the step of applying adhesive to at least one predetermined region on one face of the sheet for adhesively securing it subsequently to the forming step in a mounting position in which the pocket covers a protrusion in a mounting surface to which the sheet is secured by the adhesive.

7. A method according to any one of claims 1 to 5, in which the forming step is applied to a stack of a plurality of the sheets so as to form the said corrugations simultaneously in corresponding said areas of all the sheets.

8. A method according to claim 7, including the step of applying adhesive to at least one predetermined region of a first one of the faces of each sheet before the sheets are stacked, applying a release coating to the second opposite, face of each stack before the sheets are stacked, and then stacking the sheets so that the release coating on each stack overlies the said first face of the next adjacent sheet in the stack, the release coatings preventing the sheets from adhering to each other and enabling them to be separated from each other after the forming step.

9. A method according to claim 8, including the step of applying a protective releasable layer over the exposed first face of the final one of the sheets in the stack.

10. A method according to any preceding claim, in which the forming step is carried out simultaneously in a plurality of said areas within the or each sheet, so as to form a corresponding plurality of open-ended pockets at predetermined locations within the or each sheet.

11. A method according to claim 10, in which each of the pockets of the said plurality have different cross-sectional shapes.

12. A method according to any preceding claim, in which the said corrugations are produced by placing the sheet or the stack of sheets between male and female tool parts respectively formed with ridges and grooves matching the corrugations in shape, size and relative position, and moving the tool parts relatively together with a predetermined pressure and raising them to the predetermined elevated temperature.

13. A method according to any preceding claim, including the step of forming one or more through holes in predetermined positions in the or each sheet.

14. A method according to any preceding claim, including the step of partially cutting through the or each sheet along a line lying within a said region thereon covered with the adhesive, the two ends of the line terminating in the edge of the sheet to provide a tear-off portion of the sheet for subsequent adhesive securing over a predetermined discontinuity in a mounting surface.

15. A method according to any preceding claim, in which the plastics material is polypropylene material.

16. Apparatus for carrying out the method of claim 12, comprising a substantially rigid platform carrying a first one of the said tool parts and locating means for locating the sheet or the stack thereof in a predetermined position on the platform relative to the said first tool part, and an enclosure sized to receive the said platform through an opening after location of the sheet or the stack on the platform, means movably mounting the second one of the tool parts within the enclosure in a predetermined position therein corresponding to and facing the first tool part on the platform when the platform is positioned within the enclosure, means for moving the second tool part into contact with the sheet or stack on the first tool part and applying the said predetermined pressure between the two tool parts, and means for heating the tool parts to the predetermined elevated temperature.

17. Apparatus according to claim 16, including timing means for maintaining the said pressure and temperature for the predetermined time.

18. A method of producing a formed sheet of plastics material, substantially as described with reference to the accompanying drawings.

19. Apparatus for producing formed sheets of plastics material, substantially as described with reference to the accompanying drawings.