GB2180787A

GB2180787A - Encapsulating process

Info

Publication number: GB2180787A
Application number: GB08613765A
Authority: GB
Inventors: Norman Perry David Darby
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-09-10
Filing date: 1986-06-06
Publication date: 1987-04-08
Also published as: GB8522421D0; GB8613765D0; GB2180787B

Abstract

A method of encapsulating a lamina in transparent resin encapsulant comprises supporting the lamina 4 in a mould space 3 formed between mould elements 2. The lamina is supported by a supporting means 15 in an upright position. The faces of the mould may be provided with a release coating 18 and the bottom and side edges of the mould may be sealed by a synthetic gasket material 17. After the encapsulant has set the supporting means 15, which in Fig. 6 is a nylon line, remains in the encapsulant but is invisible therein. In further embodiments (not shown) the lamina supporting means may comprise V-shaped members of the same material as the encapsulating material, or double sided tapes which secure the lamina is spaced relation to a mould wall, or glass fibre tissue bags which are porous to the encapsultant. The lamina may be a road sign. <IMAGE>

Description

SPECIFICATION Encapsulating method This invention relates to a method of encapsulating a lamina, such as a sheet or panel, displaying information in a transparent covering and is more particularly, although not exclusively, concerned with a method of encapsulating a sign in a transparent polymer material thereby to render the sign substantially vandal and weather proof.

Methods are known in which a sheet or panel bearing information is covered with a transparent coat by laying the sheet or panel on a surface and applying a resin and suitable reinforcing material, such as glass fibre, to the exposed surface using a conventional laying-up technique. The resulting panel has a rough back. The laying-up process is a manual technique which is not readily adaptable to mass production.

According to the present invention there is provided a method of encapsulating, in a transparent covering, a lamina displaying information which method comprises: supporting the lamina substantially upright in a mould by a supporting means; introducing a flowable encapsulant into the mould to enclose the body; permitting the encapsulant to solidify to form the transparent covering; and removing the encapsulated body from the mould; wherein, after encapsulation, the supporting means remains in the transparent covering but is substantially invisible in the transparent covering.

The encapsulant may be any material (liquid or powder) which is flowable and which sets, cures or hardens to provide a transparent finish. When a catalyst is used, this may be a peroxide. If a hardener is used, it may be of the cobalt variety. Particularly preferred encapsulants are the polyester resins, most preferably, the cryitic polyester resins. However, any liquid polymer which sets to provide a transparent finish may be used. Such cryitic polyesters resins are made up in a liquid form and, on hardening with the appropriate catalyst, give a highly durable, transparent finish.

At present, it is envisaged that the mould will be formed as a stack of spaced-apart elements, conveniently melamine faced chipboard elements. The spaces between the elements form separate mould cavities into which respective laminae displaying information are disposed for encapsulation. The open edges between the elements may be sealed along three edges to prevent egress of the flowable encapsulant as the encapsulant is introduced into the mould.

Preferably, the lamina displaying information is made of PVC. Alternatively, the lamina is fibreglass. If the lamina is fibreglass, the encapsulant may be fibreglass resin.

The lamina may be supported in the mould by several different alternative supporting means. The presently preferred method of supporting the lamina is by a catgut or nylon line which loops around the lamina and supports the lamina hanging in the mould. Once the encapsulant has been introduced into the mould and has solidified, the catgut or nylon becomes visually undetectable.

Alternatively, the supporting means may be a fibreglass tissue "bag" in which the lamina is supported in the mould. The lamina is hung in the mould by the bag and the encapsulant, upon introduction into the mould, permeates the bag eventually to surround the lamina entirely. Upon hardening of the encapsulant, the bag becomes an integral part of the transparent covering formed by the encapsulant and is visually undetectable.

In this embodiment, in which a bag is suspended in the mould, the lamina may either be supported in the bag or, by virtue of doublesided tape, be supported on an outer surface of the bag.

It is to be appreciated that the fibreglass tissue bag can be replaced by straps of fibreglass slung around the lamina.

In yet another embodiment, the supporting means may simply be double-sided tape which secures the lamina to one face of the mould, the double-sided tape additionally acting as a spacer for spacing the lamina away from the wall of the mould.

In another embodiment, the supporting means may take the form of two pre-cast members, each member being provided with an elongate groove which is adapted to accommodate an edge of the lamina to be encapsulated. The pre-cast members act as spacers between opposite walls of the mould as well as acting as supports for the lamina to be encapsulated. The members should be made of a material which is transparent and which bonds with the encapsulant material.

Preferably, but not essentially, the materal from which the members are cast is the same as the encapsulant material. Once the encapsulant is introduced into the mould, it flows around the lamina and the pre-cast members and subsequentally hardens to provide a transparent covering which includes the members.

The supporting members may desirably be used in association with the above-described technique in which the lamina or laminae are hung in the mould by means of catgut or nylon.

In the present invention the side of the mould may be provided with a release element which separates the side of the mould from the encapsulant. The release element is preferably a melanex (pvc) sheet. This may be useful in providing an extra smooth finish to the encapsulant, once solidified. The release sheet may alternatively be provided with a matt surface such that the surface of the encapsulated product is matt, and therefore nonreflective. Such a matt finish may be suitable for road signs.

To act as a seal between the edges of the elements from which the mould is constructed, a gasket material may be provided between the mould elements along three edges. The gasket may be made of a synthetic polymer material.

In the method of this invention, once the lamina displaying information has been supported in the mould, the encapsulant may be poured or pumped into the mould at the edge of each mould cavity. This ensures that each mould cavity fills from the bottom and reduces the likelihood of bubble formation in the encapsulant.

For a better understanding of the present invention and to show how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 shows, in elevation, a cross-section through a mould in which bodies displaying invention are being encapsulated in accordance with the process of the present invention; Figure 2 shows a mould for producing a supporting means in accordance with one apect of this invention and for use in the mould illustrated in Fig. 1; Figure 3 shows, in elevation, a cross-section through a mould cavity of the mould shown in Fig. 1; Figure 4 shows a view in the direction lV-lV of Fig. 3; Figure 5 shows a similar arrangement to that shown in Fig. 1; Figure 6 shows a mould for use in the method of the present invention employing a catgut or nylon line as a supporting means;; Figures 7 and 8 show a fibreglass sheet being encapsulated in accordance with the present invention; Figure 9 shows an alternative arrangement in which double-sided tape is used as the supporting means; Figure 10 shows the mould of Fig. 9 partially broken away; Figures 11, 12 and 13 illustrate a mould for use in the method of the present invention employing a glass fibre tissue bag as a supporting means; Figure 14 shows a perspective view of a mould stack employed in the method of the present invention; and Figure 15 illustrates the method by which the mould stack shown in Fig. 14 is used in the method of the present invention.

In Fig. 1 a mould comprises an outer casing 1 which may be made of a wood-based material, for example chipboard. The outer casing 1 is sub-divided by melamine faced chipboard elements 2 into a series of mould cavities 3.

In each space 3 a panel 4 displaying information has been encapsulated in a transparent resin covering 5. Although the transparent covering 5 is, in the finished product, a continuous, homogeneous covering, it is formed, in one aspect of the method of this invention, by supporting the panel 4 by supporting means 6, each supporting means 6 being provided with a groove which seats the panel 4 at the bottom and caps the panel 4 at the top. Each supporting means 6 is made of the same transparent resin material as the encapsulant used to form the covering 5.

The encapsulated lamina is formed by the following method. Firstly, the mould is constructed employing the elements 2 to define mould cavities 3 in which the encapsulated panel is to be formed. At the foot of each mould cavity 3, one or more of the supporting means 6 is placed. The panel 4 is then supported in the lower supporting means 6 and another one or more supporting means 6 is placed over the panel 4 such that the top and bottom edges of the panel 4 lie in the grooves of the supporting means 6. The supporting means thus serve to space apart the two elements 2 of the mould and to support the panel 4. Into the mould cavities 3, a resin, preferably a cryitic polyester resin is poured and allowed to solidify. The resin should be carefully poured down the side of the mould cavity 3 so that the mould space is filled from the bottom upwards, thereby avoiding the formation of bubbles.On hardening, the joint between the supporting means 6 and the encapsulant poured into the mould becomes invisible, and a continuous covering around the panel 4 is formed. The mould is subsequently broken open and the encapsulated panels removed.

In Fig. 2, a mould 10 in which a supporting means 6 as shown in Fig. 1 is formed. The mould 10 is shown in cross-section to have two upstanding side portions 11 and a base portion 12 which has an inverted V-shape to form the groove in the supporting element 6.

The supporting element 6 is cast in the same resin as the resin used to form the covering 5, as shown in Fig. 1.

In Fig. 3, the positioning of the supporting elements 6 in the mould 1 to support the panel 4 is illustrated. Fig. 4 illustrates a section on the line IV-IV of Fig. 3 and is selfexplanatory.

The embodiment of Fig. 5 is very similar to that shown in Fig. 1. However, on each face of the elements 2 of the mould there is provided a release coating 18 to ensure that the surface of the encapsulated panel is of a very smooth finish. In addition, a synthetic gasket 17 is laid around the bottom and side edges of the mould cavity 3.

In Fig. 6, the panel 4 displaying information is hung in the mould cavity 3 by a catgut or nylon line 15. The line is suspended from support bar 16. To give a seal at the bottom of the mould, a synthetic gasket 17 is provided along the bottom and the two side edges of the mould. Moreover, a melanex "(RTM)" (PVC) sheet 18 or other suitable release material is provided in the cavity 3 on the elements 2 defining the mould cavity 3. The liquid resin is then poured over the panel 4 displaying information and allowed to harden.

On hardening, the catgut or nylon line 15 becomes invisible in the resin. In this embodiment, small pads of glassfibre tissue may be inserted between the loop of catgut or line 15 to act as spacers holding the panel 4 upright.

Finally, the encapsulated panel is then removed from the mould and the release sheets 18 are peeled away from the encapsulated body to provide a very smooth surface to the encapsulated panel.

Figs. 7 and 8 show a fibreglass lamina 4 being encapsulated in a space 3 formed between the faces of elements 2 of the mould, each face being provided with a release element 18. The bottom of the space 3 is sealed by a synthetic gasket 17. In the embodiment shown in Fig. 7, the fibreglass lamina 4 has swelled, absorbing the resin, to fill about half of the space 3. The remainder of the space is filled by resin. In the embodiment of Fig. 8, the fibreglass lamina 4 has absorbed the resin and swelled to fill the whole space 3. The fibreglass lamina 4 is still considered to be encapsulated by the resin encapsulant.

In the mould shown in Fig. 9, the panel 4 displaying information is secured to a fibre glass sheet 20 by double-sided tape 21, the fibreglass sheet 20 further being secured, by double-sided tape 21 to a release element 18 on the face of one of the mould elements 2.

The liquid encapsulant is poured over the panel 4 and fibre glass sheet 20 and is allowed to harden. On hardening, the double sided tape 21 is invisible in the encapsulated product.

Fig. 10 shows, broken away, several components of the mould shown in Fig. 9. In particular, the synthetic gasket 17 can be seen to run along three edges of the mould cavity 3, thereby creating a pocket in which the resin is poured to form the covering 5 for the panel 4.

In Figs. 11, 12 and 13, the supporting means for the panel 4 is a fibre glass tissue bag 25 which is hung in the gap 3 of the mould. In Figs. 11 and 13, the panel 4 is supported inside the bag 25. The tissue bag 25 in Fig. 11 has its upper ends 26 secured together whereas in Fig. 13, the upper ends 26 are secured separately to opposite sides of the mould cavity 3 in which the encapsulated panel is being formed. In Fig. 12, the panel 4 is secured, by double-sided tape 21, to the outside of the bag 25. In these three embodiments, the liquid resin, on pouring into the mould, flows around the bag 25 which is porous to the resin and the mould cavity 3 becomes filled with the resin which subsequently hardens.

In the embodiments described above, the mould elements 2 may be held apart by wooden spacer elements which, in the embodiments employing the gasket 17, would determine the degree of compression of the gasket.

Fig. 14 shows a view of a complete mould for use in the present invention. The mould comprises outer case members 30, 31 at right angles to each other. Supported by the outer case members 30, 31 are stacked elements 2 defining the mould cavities 3 in which encapsulated bodies are to be formed by a method as described above.

In Fig. 15, the arrangement of Fig. 14 has been supplemented with a further wooden element 32 which is placed over the stack of elements 2. A clamp 33 clamps the elements 2 together, it being appreciated that the elements 2 will be spaced apart according to the different supporting means being used. Thus, the mould can be built up in a horizontal position, first by arranging an element 2, then placing on the element 2 the components to be encapsulated, then placing another element 2 over the components to be encapsulated, and so on. Finally, the arrangement is clamped together and turned through 900 so that the panels are upright. The resin is then poured into the mould and, under the action of gravity surrounds the panels 4 displaying information to encapsulate those panels 4.

After encapsulation, the edges of the hardened resin may be machined to provide a smooth finish. It will be appreciated that the panels 4 themselves will be spaced inwardly from the edges of the hardened resin all around the product, so that no part of the panels will be exposed.

Claims

1. A method of encapsulating, in a transparent covering, a lamina displaying information which method comprises: supporting the lamina substantially upright in a mould by a supporting means; introducing a flowable encapsulant into the mould to enclose the body; permitting the encapsulant to solidify to form the transparent covering; and removing the encapsulated body from the mould; wherein, after encapsultion, the supporting means remains in the transparent covering but is substantially invisible in the transparent covering.

2. A method according to Claim 1, wherein the encapsulant is a flowable material which sets, cures or hardens to provide the transparent covering.

3. A method according to Claim 1 or 2, wherein the lamina is made of a polymeric material.

4. A method according to Claim 3, wherein the polymeric material is polyvinyl chloride.

5. A method according to any preceding claim, wherein the encapsulant is a polyester resin.

6. A method according to Claim 5, wherein the polyester resin is a cryitic polyester resin.

7. A method according to Claim 1 or 2, wherein the lamina is made of fibreglass.

8. A method according to Claim 7, wherein the encapsulant is fibreglass resin.

9. A method according to any preceding claim, wherein the mould is formed of spacedapart elements.

10. A method according to Claim 9, wherein the spaced-apart elements are made of chipboard having a smooth face.

11. A method according to Claim 9 or 10, wherein each element is provided, on at least one of its faces, with a release element.

12. A method according to Claim 11 wherein the release element is melanex.

13. A method according to any preceding claim, wherein the supporting means comprises a loop of material, which material is invisible in the finished product, by which loop the lamina is hung in the mould.

14. A method according to Claim 13, wherein the material is a catgut or nylon line.

15. A method according any one of Claims 1 to 12, wherein the supporting means comprises a bag in which the lamina is hung in the mould.

16. A method according to Claim 15, wherein the bag is made of fibreglass.

17. A method according to Claim 15 or 16, wherein the lamina is supported inside the bag.

18. A method according to Claim 15 or 16, wherein the lamina is supported, by means of double-sided tape, on an outer surface of the bag.

19. A method according to any one of Claims 1 to 12, wherein the supporting means is double-sided tape which secures the lamina to one face of an element of the mould.

20. A method according to any one of Claims 1 to 12, wherein the supporting means comprises at least two pre-cast members, each member being provided with an elongate groove adapted to accommodate an edge of the lamina to be encapsulated and each precast member being fabricated of a material which, in the finished product, will be transparent, said pre-cast members being disposed at the top and bottom edges of the lamina to support and space the lamina regularly in the mould.

21. A method according to Claim 20, wherein a nylon or catgut line is further used to hang the lamina in the mould.

22. A method according to any preceding claim, wherein a synthetic gasket is provided in the mould space to seal the bottom and side edges of the mould space.

23. a method of encapsulating a lamina in a transparent covering substantially as hereinbefore described, with reference to the accompanying drawings.