GB2228890A

GB2228890A - Sheet forming

Info

Publication number: GB2228890A
Application number: GB9004794A
Authority: GB
Inventors: Roger Anthony James
Original assignee: James R A & Co Ltd
Current assignee: James R A & Co Ltd
Priority date: 1989-03-02
Filing date: 1990-03-02
Publication date: 1990-09-12
Also published as: GB8904734D0; GB9004794D0

Abstract

Heat mouldable sheet is worked by heating an area of the sheet and urging it away from the remainder of the sheet to form a raised portion. A preferred apparatus 10 for providing raised areas on a sheet 12 of heat mouldable material comprising a frame 16 defining a flat base 18 provided with a plurality of jet defining apertures 20 therethrough. The sheet 12 is locatable on the base 18 and a former 22 is locatable on the sheet 12 to restrain the latter on the base 18. Holes 24 are provided in the former 22 corresponding in position and size to the configuration of apertures 20 in the base 18. Heat is applied from above the former 22 to heat the sections 14 of the sheet 12 exposed through the holes 24. Air is subsequently blown through the apertures 20 to form raised areas in the sheet 12 corresponding to the sections 14. <IMAGE>

Description

Working Heat Mouldable Material This invention relates to a method of and apparatus for working heat mouldable materials and particularly but not exclusively for producing an area of raised relief on a sheet of plastics material.

In this specification the term "heat mouldable material" is to be understood as referring to a material which softens upon lahe application of heat permitting the material to be moulded to a required shape which is retained upon cooling.

Conventionally raised areas on plastics sheets have been produced by vacuum forming. This involves heating the whole of the plastics sheet and distortion of the unraised areas is oftn experienced.

According to the present invention there is provided a method ot working a sheet of heat mouldable material, the method comprising applying heat substantially to onLy an area of the sheet to be moulded and urging said area away from the remainder of the sheet to be a raised area relative thereto.

Preferably the remainder of the sheet is restrained during the urging oF said area. Desirably said remainder is also substantially insulated from the Iscat supplied, and the one means may provide both insulation and restraining.

The urging may be provided by one or more jets of fluid, preferably air. Desirably different rates or different periods of flow may be provided by different jets to produce a variation in height across the raised area.

The heat mouldable material preferably comprises a plastics material.

A curve may be applied to the sheet prior to said heat being applied.

The heat is preferably directed onto only one side of the sheet.

Also according to the present invention there is provided apparatus for working a sheet of heat mouldable material, the apparatus comprising means for locating the sheet, means for heating only one or more areas of the sheet which are to be moulded, and means for urging the or each area from the remainder of the sheet to produce one or more raised areas.

Preferably means are provided for restraining the remainder of the sheet, and the restraining means may be engagable with one side of the sheet.

Desirably means are provided for insulating all but the or each area of the sheet. The restraining means may provide the insulating means and may comprise a planar member, desirably with a hole corresponding to the or each area, and means for mounting the member on the locating means against the sheet.

The urging mean may comprise one or more jets of fluid, preferably air, directable onto the areas from the other side of the sheet. The flow of fluid to different jets may be variable to provide variations in height of the raised areas.

The heating means may comprise jets of hot air or one or more heating eJer:lents locatable adjacent to the one side of the sheet.

An embodiment of the present invention will now be described by way Df example only with reference to the single figure of th accompanying drawing which shows a diagrammatic perspective view of part of an apparatus according to the present: invention and a sheet of material to be moulded.

The drawing shows apparatus 10 suitable for producing a raised pattern on a sheet 12 of plastics material. The pattern comprises two sections 14, and for example, the areas of the sheet 12 corresponding to the sections 14 may be differently coloured from the remainder of the sheet.

The apparatus 10 comprises a frame 16 defining a recess 17 of a size to permit the sheet 12 to slidingly fit therein. A flat base 18 is provided in the frame recess 17. A plurality of jet defining apertures 20 are provided through the bacse 18, two groups of the apertures 20 being provided at locations corresponding respectively to the positions of the sections 14 on the sheet 12. The apertures 20 communicate with pipework (not shown) leading to a fan (also not shown). A former 22 is also provided and comprises a sheet of material also of a size to slidingly fit in the frame recess 17. Two holes 24 are provided in the former 22 each corresponding in position and size to a respective one of the sections 14.

eaìls are provided (not shown) for clamping the former 22 in the frame 16.

In use, the sheet 12 is slid into the frame recess 17, the former 22 is placed on top as shown by the arrows in the drawing and is clamped to the frame 16. Heat is applied for a fixed period of time above the former 22 and hence to the sections 14 of the sheet 12 exposed through the holes 24. The heat may be applied as a stream of warm air, or heating elements may be suitably positioned. Cold air is subsequently blown by the fan for a fixed period through the jet apertures 20. The air flow from the fan cue the heated parts of the sheet 12 to stretch into the hcles 24 producing the required raised areas.

The time for which heat is applied depends on the type of plastics used and the thickness of the sheet 12.

For example with the apparatus 10 a 0.25mm thick sheet of craylon requires a three second heating period.

With such relatively short heating times the former and frame can be made for example of wood, or steel or a similar metal. However, if a longer period of heating is required the former ard frame should be made of a heat insulating material.

The period of time for which air is blown through the jets is dependent on the required height of the rained portions. If required, air can be blown through different jets at different rates or for different periods of time, to give a variable height to differant raised portions or across the raised portions.

There is thus described a method and apparatus for producing raised areas in plastics sheeting without distorting the unraised areas of the sheet. This system is relatively simple and thus can be relatively inexpensively made and used. The system allows a considerable amount of flexibility in the different raised patterns which can be produced. With variable flow rates or variable periods of air flow through the jets the raised areas can be shaped to resemble a wide range of articles.

This method is particularly suited to the manufacture of reel bands for fruit machines with raised symbols. One problem experienced with reel bands is that a kink is often produced on either side of the raised symbols. One method of overcoming this is to reheat the reel band until pliable then to place it around a former of a similar diameter to the reel on which the band will be placed. An alternative method is to apply a gentle curve to the sheet of plastics material prior to forrrrntion of the raised symbols reducing stress on the b #iid when curved mo:-e tiglatly to form a reel band. Suitably modified apparatus with a curved base to the frame will obviously be required.

Various modifications may be made without departing from the scope of the invention. For example the number and shape of raised areas formed can be varied considerably. If required jets could be provided across the whole of the base of the frame and a further former could be placed thereon to cover all but the required jets. Different method of applying heat could be used.

This apparatus could be used with heat mouldable materials other tharl plastics, and may be used on plasticised paper. The system could be simultaneously used with a number cf sheets of plastics and could be incorporated into a production line.

Claims

Claims:

1. A method of working a sheet of heat mouldable material, the method comprising applying heat substantially to only an area of the sheet to be moulded and urging said area away from the remainder of the sheet to be a raised area relative thereto.

2. A method according to claim 1, in which the remainder of the sheet is restrained during the urging of said area.

3. A method according to claim 1 or 2, in which the remainder of the sheet is substantially insulated from the heat supplied.

4. A method according to claim 3 when dependent on claim 2, in which one means provides both insulation and restraining.

5. A method according to any of the preceding claims, in which the urging of said area is provided by one or more jets of fluid.

6. A method according to claim 5, in which the fluid is air.

7. A method according to claim 5 or 6, in which different rates of flow are provided by different jets to produce a variation in height across the raised area.

8. A method according to any of claims 5 to 7, in which different periods of flow are provided by different jets to produce a variation in height across the raised area.

9. A method according to any of the preceding claims, in which the heat moujdable material comprises a plastics material.

10. A method according to any of the preceding claims, in which a curve is applied to the sheet prior to said heat being applied.

11. A method according to any of the preceding claims, in which the heat is directed onto only one side of the sheet.

12. Apparatus for working a sheet of heat mouldable material, the apparatus comprising means for locating the sheet, means for heating only one or more areas of the sheet which are to be moulded, and means for urging the or each area from the rinder of the sheet to produce one or more raised areas.

13. Apparatus according to claim 12, in which means are provided for restraining the remainder of the sheet.

14. Apparatus according to claim 13, in which the restraining means are engagable with one side of the sheet.

15. Apparatus according to any of claims 12 to 14, in which means are provided for insulating all but the or each area of the sheet..

16. Apparatus according to claim 15 when dependent on claim 13, in which the restraining means provides the insulating means.

17. Apparatus according to any of claims 14 to 16 when dependent on claim -13. in which the restraining means comprise a planar member.

18. Apparatus according to claim 17, in which the restraining means comprises means for mounting the member on the locating means against the sheet.

19. Apparatus according to any of claims 14 to 18 when dependent on claim 13, in which the restraining means comprises a member with a hole corresponding to the or each area.

20. Apparatus according to any of claims 12 to 19, in which the urging means comprises one or more jets of fluid, directable onto the or each area from an other side of the sheet.

21. Apparatus according to claim 20, in which the flow of fluid to different jets is variable to provide variations in height of the raised areas.

22. Apparatus according to any of claims 12 to 21, in which the heating means comprises one or more jets of hot air.

23. Apparatus according to any of claims 12 to 21, in which the heating means comprises one or more heating elements locatable adJacent ad3aoent acentto a one side of the sheet.

24. A method of working a sheet of heat mouldable material substantially as hereinbefore described with reference to the accompanying drawing.

25. Apparatus for working a sheet of heat mouldable material substantially as hereinbefore described with reference to the accompanying drawing.

26. Any novel subject matter or combination including novel subject matter disclosed in the foregoing specification or claims and/or shown in the drawings, whether or not within the scope of or relating to the same invention as any of the preceding claims.