GB2207081A

GB2207081A - Moulding corrugations

Info

Publication number: GB2207081A
Application number: GB08815608A
Authority: GB
Inventors: Dennis Herbert Bowen
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 1987-07-22
Filing date: 1988-06-30
Publication date: 1989-01-25
Also published as: GB8815608D0; GB8717277D0

Abstract

An apparatus 10 for forming a long sheet 12 of a fibre-reinforced thermosetting plastic material into corrugations transverse to its length comprises a mould 14 with sections A, B, 20 arranged to close onto the sheet and form a single corrugation, a second section of the mould to the right of line CC curing the resin and so fixing the shape of the corrugations, and means 24, for moving the corrugated sheet from the first section to the second and then out of the mould 14. <IMAGE>

Description

Moulding Corrugations This invention relates to a moulding apparatus and process for forming a corrugated sheet, for example of a plastics material or of a fibre-reinforced plastics material.

One such process is the technique known as sequential moulding, in which a long strip of a material is passed through an open-ended die or mould of constant crosssection in a series of discrete steps; the mould is alternately opened and closed, and when it is open the material is moved a step forward through a distance much less than the length of the mould. Typically the material is of a thermosetting type, and is subjected to heat while the mould is closed, so that when the material finally emerges from the mould it has been cured. Hitherto this process has only been applied to produce straight lengths of a constant cross-section, and so is not applicable where the desired product has corrugations extending in a direction other than along its length.A technique for producing corrugations transverse to the length of a long strip is to pass the strip between mating grooved rollers, but this technique (though suitable for metals) is not readily applicable to thermosetting resins which must cure for a certain time before they hold their shape.

According to the present invention there is provided an apparatus for forming a corrugated sheet from a long feedstock, the corrugations extending transverse to the length of the sheet, comprising a first mould section with opposed members arranged to close onto the feedstock and to form an integral number of corrugations, a second mould section arranged to cure the corrugations and to ensure the corrugations lie in a desired plane, the first mould section and the second mould section being arranged alternately to open and to close onto the sheet, and to be open simultaneously, and means for moving the corrugated sheet from the first mould section to the second mould section, the moving means being arranged to move the sheet relative to the mould sections by a distance equal to the length of the said integral number of pitches of the corrugations whenever the mould sections are open.

The first mould portion, which forms the said integral number of pitches of the corrugations, preferably comprises a plurality of side-by-side parts which close onto the feedstock in succession so as to minimize friction or stretching as the pitches are formed. Desirably the number of said parts is at least twice the said integral number of corrugations.

The invention will now be further described by way of example only and with reference to the accompanying drawing which shows a diagrammatic sectional view of an embodiment of the invention.

Referring to the drawing an apparatus 10 is shown for forming transverse corrugations across the width of a long sheet 12 of a fibre-reinforced plastics material. The sheet incorporates a thermo-setting resin which impregnates the fibre-reinforcement; the fibres extend in several different directions, but predominantly along the length of the sheet 12. The apparatus 10 comprises a mould 14 mould 14 consisting of an upper mould portion 16, a mating lower mould portion 18, and an auxiliary lower mould portion 20 which can be slid relative to the portion 18.

All three mould portions 16, 18 and 20 are electrically heated so as to gel and then cure the resin after the sheet 12 has been deformed to their shape, and they are supported by drive means for moving them alternately towards and away from each other. The apparatus 10 also includes means 22 to support the sheet 12 being fed to the mould 14, and means 24 to support and to drive the corrugated sheet produced by the mould 14.

Operation of the apparatus 10 involves a cyclically repeated sequence of operations as follows (starting with the position shown in the drawing): (a) the upper mould portion 16 is closed onto the lower mould portion 18, so forming half of a new pitch of the corrugations (corresponding to the section of portion 16 marked A); (b) the auxiliary mould portion 20 is slid upwardly to close onto the upper mould portion 16, so forming another half of a new pitch of the corrugations (corresponding to the section marked B); (c) the mould portions 16, 18 and 20 remain closed long enough to ensure the resin in the newly formed pitch has gelled; (d) the mould 14 is opened, the upper mould portion 16 being moved upwardly, the lower mould portion 18 being moved downwardly, and the auxiliary mould portion 20 being slid downwardly relative to the lower mould portion 18;; (e) the drive means 24 is activated to move the sheet 12 through the mould 14 by a distance equal to the length of a pitch of the corrugations; and (f) the lower mould portion 18 is raised to support the sheet 12.

Thus the sections of the mould 14 to the left (as shown) of the line C-C form each new pitch, while the sections to the right of the line C-C cure the pitches so formed. The sequence (a) to (f) is continuously repeated, an additional pitch of the corrugations being formed at each cycle. The length of the mould 14 and its temperature are such that the resin in the sheet 12 is sufficiently cured to enable the shape of the corrugations to be maintained by the time the sheet 12 emerges from the mould 14. If necessary, the corrugated material can then be post-cured in an oven to maximise the desired mechanical or physical properties.

It will be appreciated that because each pitch of the corrugations is formed in two stages, any sliding of the sheet relative to the mould as the sheet 12 is deformed is much less than if one or more pitches were to be formed simultaneously - consequently the stretching forces to which the sheet 12 is subjected are much less. It will be understood that the mould 14 might consist of a larger number of portions than that described, closed together in sequence so as to form one new pitch in for example four stages instead of two, forming a quarter of the new pitch at each stage, and reducing the stretching forces still further. It will also be understood that the mould 14 might be longer than shown so as to provide more time for the resin to cure in the mould 14.

The corrugated sheet can then be cut into desired lengths for example to form springs, similar to the springs described in GB 2 155 144. For example a strip of fibre reinforced plastics material of width 50 mm and thickness 4 mm might be cut into springs of length 220 mm, each spring consisting of, for example, two complete corrugations. It will be appreciated that the spring might be of a different width, for example about five times the sheet thickness, and might consist of a greater number of corrugations.

Claims

1. An apparatus for forming a corrugated sheet from a long feedstock, the corrugations extending transverse to the length of the sheet, comprising a first mould section with opposed members arranged to close onto the feedstock and to form an integral number of corrugations, a second mould section arranged to cure the corrugations and to ensure the corrugations lie in a desired plane, the first mould section and the second mould section being arranged alternately to open and to close onto the sheet, and to be open simultaneously, and means for moving the corrugated sheet from the first mould section to the second mould section and then out of the second mould section, the moving means being arranged to move the sheet relative to the mould sections by a distance equal to the length of the said integral number of pitches of the corrugations whenever the mould sections are open.

2. An apparatus as claimed in Claim 1 wherein the first mould section comprises a plurality of side-by-side parts which close onto the feedstock in succession so as to minimize friction or stretching.

3. An apparatus as claimed in Claim 2 wherein each part is no longer than half the length of a pitch of the corrugations.

4. An apparatus for forming a corrugated sheet from a long feedstock substantially as hereinbefore described with reference to, and as shown in, the accompanying drawing.

5. A method of forming a corrugated sheet from a long feedstock, the corrugations extending transverse to the length of the sheet, the method comprising feeding the feedstock into a mould comprising a first mould section with opposed members arranged to close onto the feedstock to form an integral number of corrugations, and a second mould section arranged to cure the corrugations and to ensure the corrugations lie in a desired plane, alternately opening and closing the first mould section and the second mould section onto the sheet, and when both mould sections are open moving the sheet relative to the mould sections a distance equal to the length of the said integral number of pitches of the corrugations, the sheet being moved from the first mould section to the second mould section and then out of the mould.

6. A method as claimed in Claim 5 wherein the first mould section comprise a plurality of side-by-side parts, and the method comprises closing the parts in succession onto the feedstock so as to minimize friction or stretching.

7. A method of forming a spring comprising performing the method as claimed in Claim 5 or Claim 6, and subsequently cutting the sheet to form the springs.

8. A method of forming å corrugated sheet from a long feedstock substantially as hereinbefore described with reference to, and as shown in, the accompanying drawing.