GB2200074A

GB2200074A - A hot line sheet forming machine

Info

Publication number: GB2200074A
Application number: GB08629701A
Authority: GB
Inventors: Edward Darcy
Original assignee: Weston Hyde Products Ltd
Current assignee: Weston Hyde Products Ltd
Priority date: 1986-12-12
Filing date: 1986-12-12
Publication date: 1988-07-27
Anticipated expiration: 2006-12-12
Also published as: GB8629701D0; GB2200074B

Abstract

A plastics sheet e.g. of rigid P.V.C., is intermittently advanced through sequential heating and forming stations of the machine, at which it is respectively heated by a plurality of heating elements (8, 10) along lines at which it is then formed e.g. into corrugations, between male and female formers (20, 21, Fig 5). The heating elements (8 and 10) are arranged on respective opposite sides of the sheet to heat the sheet along the lines against unheated supporting saddle strips (9 and 11), so that heat is applied along each line along only one side of the sheet to facilitate forming. The heating elements (8, 10) are formed to concentrate heat at the tips and include heat sensors to permit monitoring and heat control. Interchangeable spacers (31) are provided between adjacent elements (8, 10) to enable a variety of spacings to be precisely determined. <IMAGE>

Description

A HOT LINE FORMING MACHINE The present invention relates to a hot line forming machine. The machine is intended primarily, but not exclusively, for moulding flat, substantially rigid polyvinylchloride sheets to provide corrugated profiles.

The profile may be any one of a number.

One such machine is already generally known from United Kingdom Patent Specification No. 2,044,168A.

However, the machine has certain disadvantages. Corrugated sheets produced on the machine have poor impact performance. Also, the machine is difficult to adjust for different corrugations. Further, it is difficult to concentrate the heat in the areas in which it is most needed.

According to the present invention, there is provided a hot line forming machine comprising upper and lower heating elements disposed on opposite sides respectively of a plane in which a sheet to be heated is in operation disposed, and unheated supports corresponding to each heating element and disposed adjacent to the element but on the opposite side of the plane to that element whereby in operation heat is applied directly to one side only of the material along the or each desired line.

In order that the invention may be more clearly understood, one embodiment thereof will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic perspective partial view of a hot line forming machine according to the invention, Figure 2 is a diagrammatic side elevational view of the machine of Figure 1, Figure 3A is a detail view of a part of the machine illustrating the spacing of heater blades and their settings.

Figure 3B is a sectional view of part of Figure 3A along the line X-X, Figure 4A is a diagrammatic sketch of a heater blade forming part of Figure 1, Figure 4B is a cross section through the heater blade of Figure 4A, Figure 5 is a detail view in section of part of the machine of Figures 1 and 2 illustrating positioning of the mould and tool, Figure 6A is a side view of the heater blades of the machine of Figures 1 and 2 showing the blades hangers and expansion tees which are designed to cater for the expansion of the heater blades and eliminate bowing,and Figure 6B is a partial side elevational view taken in the direction of the arrow B in Figure 6A.

Referring to Figures 1 and 2 of the drawings, the machine comprises a frame 1 on which upper and lower beams 2 and 3 are pivotally mounted. The frame 1 comprises two free standing, welded fabricated, side frames 1A an#d 1B, adapted to be bolted to the floor. The frames are set approximately 5.2 metres apart and tied together by five bolt-on channel ties. On two of the ties, at the working height and to the rear of the machine is a flat wooden bedplate running the full 5.2 metre width of the machine.

The bedplate is supported at mid-span by two additional free standing frames 1C and 1D bolted to the floor. The structure is braced by angle corner braces at six points between the ties and side frames. Figure 1 shows the beams in an operational position. The beams 3 and 2 are moved between the operative and inoperative positions, by means of pressure fluid operable (pneumatic) piston and cylinder devices 5 and further cylinders behind 4 (not visible in Figure 2). Beam 22 is operated by cylinder 4.

The ends of the upper beam 2 are supported on two pivot arms 6 (Figure 1) which raise and lower it during the normal running cycle under the action of piston and cylinder devices behind 4 as previouisly explained.

On the underside of the beam 2 are seven pads 7 welded to it, equally spaced over the full length. To each of these pads is mounted an assembly for supporting two full length heater elements 8 (5 metres plus) and two full length saddle strips 9. Built into the support strips are facilities for lateral adjustment of each individual heater element or saddle strip, so that spacing between each can be varied. This is to suit differing profiles to be formed on the machine, and will be described in more detail later. The strip supports utilise stainless steel and PTFE which helps to minimize heat losses. Furthermore, the provision of longitudinal brackets supporting the strips allows for expansion thus inhibiting warping.This is achieved by 18 stainless steel Tee pieces, supporting each of the four heated blades, which are free to slide longitudinally in slots in brass brackets (see Figure 6B).

The lower beam 3 is generally similar to upper beam 2 and is sited directly below it and below the working height of the machine. Heater elements 10 and saddle strips 11 (Figure 3a) are supported on the top side of the beam 3 rather than being suspended from the underside as they are on the top support beam 2.

The beam 3 itself is slightly shorter than the top beam 2 (5 metres approximately) and is stationary during normal operation of the machine. However, the beam is mounted on pivot arms 12 so that it can be lowered when setting up the machine for different profiles of sheet.

Pivot arms 12 are in turn connected to piston and cylinder devices 5.

As described above four heater element strips are provided two (referenced 8) on the upper beam 2 and two (referenced 10) on the lower beam 3 (figure 3a). These heater element strips cooperate in operation of the machine with complementary saddle strips respectively, referenced 9 on the upper beam 2 and 11 on the lower beam 3. Referring to Figures 4A and 4B, each strip is made up by sandwiching inconnel sheathed heating elements 13 between aluminium strip bars and end nose plates 14. The sandwich is approximately 16mm wide with a 3mm wide tip where heat is to be transferred to the flat PVC sheet. At mid-span along each heating element (five elements per heater blade), there is a heating sensing probe fitted as near to the 3mm wide transfer tip as possible.These thermocouples relay information to separate heat control boxes, (that is one control box per heating element,) so that the full length strip temperature can be regulated as evenly as possible.

Each saddle strip comprises an aluminium bar equal in length to the corresponding heater element strip and forms, in operation of the machine a saddle or support for the PVC sheet being formed as the heater element contacts the sheet from the other side.

Downstream of the heater element strips 8 and 10 and saddle strips 9 and 11 are complementary male and female wooden forming tools 20 and 21 (Figure 5). The mould position is fixed by reference to a metal key insert 23 in the baseplate 24. Steel screw inserts are employed in the wooden tool and base plate to ease securing. The male tool 20 running the full length of the machine is mounted on a machined steel plate suspended from beam 22 by channel platforms. The ends of the beam are suported on two pivot arms 25 which raise and lower it during the normal running cyle. The beam can be laterally adjusted on the pivot arm mountings to vary its position relative to the heater elements. Pressure fluid operable piston and cylinder devices (pneumatic) are provided to raise and lower the beam 22.

As described above the two pairs of pneumatic cylinders control the movement of the top heater element support beam and forming tool mounting beam. Both these beams pivot up or down to leave or contact the PVC sheet, as required, during normal running of the machine As each beam, that is, element or tool function, requires a dwell time of contact, the cylinders are linked to timers and are controlled by electropneumatic valves in an automatic cycle.

The third pair of pneumatic cylinders 5 controls the movement of the bottom heater element support beam.

This beam is normally fixed and held to the underside of the PVC sheet during normal machine operation. The beam is lowered for access to the heater elements only for a product change. This pair of cylinders can therefore be controlled manually by pneumatic valves.

To achieve an even and controlled movement of all beams it may be desirable to fit additional cushioning facilities to those provided by the cylinders.

Referring particularly to Figures 3A and 3B the spacing of the heater elements may be varied as required.

For this purpose the heater element strips and forming strips are mounted on lateral suports 30. Between adjacent heater or saddle strips, U-shaped spacers 31 are disposed. The width of the spacer precisely determines the spacing between adjacent strips. If a different spacing is required the strips and spacers which are clamped on their corresponding supports are released and the spacers replaced with those of desired width. This greatly facilitates adjustment of the machine to a different required corrugation and reduces machine downtime.

Thus in operation of the machine, after setting up the machine, PVC sheets are fed onto the heater strips 10 and saddle strips 11 on the lower beam 3. The upper beam 2 is brought down on the sheet and heat supplied for a predetermined length of time after which the upper beam is raised to allow the sheet to be advanced through the machine and accurately positioned beneath the forming tool, referencing against stops at the front of the machine.

This determines the correct alignment of the heated lines with the female forming tool 21 underneath. The male forming tool 20 is then brought down to produce the corrugation. This process is repeated the desired number of times to produce the desired number of corrugations.

It will be appreciated that the above embodiment has been described by way of example only and that many variations are possible without departing from the scope of the invention.

Claims

1. A hot line forming machine comprising upper and lower heating elements disposed on opposite sides respectively of a plane in which a sheet to be heated is, in operation, disposed, and unheated supports corresponding to each heating element and disposed adjacent to the element but on the opposite side of the plane to that element whereby in operation heat is applied directly to one side only of the material along the or each desired line.

2. A hot line forming machine as claimed in claim 1, in which each heating element is supported on saddle strips.

3. A hot line forming machine as claimed in claim 2, in which each saddle strip incorporates means enabling lateral adjustment of the element supported on it so that spacing between adjacent heating elements can be adjusted.

4. A hot line forming machine as claimed in claim 3, in which the means enabling lateral adjustment comprises interchangeable spacers disposed between adjacent saddle strips.

5. A hot line forming machine as claimed in claim 4, in which the interchangeable spacers are U-shaped and of predetermined width to precisely determine the corresponding spacing.

6. A hot line forming machine as claimed in any of claims 2 to 5, in which each strip is mounted on a suport including stainless steel and polytetrafluoroethylene to minimize heat losses.

7. A hot line forming machine as claimed in any of claims 2 to 6, in which each strip is mounted on a support and the support comprises slidable members to accommodate expansion of the heating elements being supported.

8. A hot line forming machine as claimed in any preceding claim,in which means are provided for raising and lowering the upper heating elements.

9. A hot line forming machine as claimed in claim 8, in which the means comprises piston and cylinder devices.

10. A hot line forming machine as claimed in any preceding claim, in which means are provided for raising and lowering the lower heating elements.

11. A hot line forming machine as claimed in claim 10 in which the means comprises pressure fluid operable piston and cylinder devices.

12. A hot line forming machine as claimed in any preceding claim, in which each heating element is sheathed in a thermally conductive material.

13. A hot line forming machine as claimed in claim 12, in which each sheathed heating element is sandwiched between strips and nose plate.

14. A hot line forming machine as claimed in claim 11 or 12, in which the sheath is made of inconnel.

15. A hot line forming machine as claimed in claim 12, 13 or 14, in which the strips are made of aluminium.

16. A hot line forming machine substantially as hereinbefore described with reference to the accompanying drawings.

16. A hot line forming machine as claimed in any preceding claim, in which each heater element is provided with a heat sensor and. sensors are connected to control means enabling the temperature of the elements to be controlled and monitored.

17. A hot line forming machine as claimed in any preceding claim, in which complementary forming tools are disposed downstram of the heating elements by means of which plastics sheet heated by the heating elements may be formed into a desired shape.

18. A hot line forming machine as claimed in claim 17, in which the position of the forming tools is adjustable.

19. A hot line forming machine substantially as hereinbefore described with reference to the accompanying drawings.

Amendments to the claims have been filed as follows CLAIMS 1. A hot line forming machine comprising upper and lower heating elements disposed on opposite sides respectively of a plane in which a sheet to be heated is, in operation, disposed, and unheated supports corresponding to each heating element and disposed adjacent to the element but on the opposite side of the plane to that element whereby in operation heat is applied directly to one side only of the material along the or each desired line, each heating element being supported on saddle strips and each saddle strip incorporating means comprising interchangeable spacers disposed between that strip and the or each adjacent saddle strip enabling lateral adjustment of the element supported on it so that spacing between adjacent heating elements can be adjusted.

2. A hot line forming machine as claimed in claim 1, in which the interchangeable spacers are U-shaped and of predetermined width to precisely determine the corresponding spacing.

3. A hot line forming machine as claimed in claims 1 or 2, in which each strip is mounted on a suport including stainless steel and polytetrafluoroethylene to minimize heat losses.

4. A hot line forming machine as claimed in claims 1, 2 or 3 in which each strip is mounted on a support and the support comprises slidable members to accommodate expansion of the heating elements being supported.

5. A hot line forming machine as claimed in any preceding claim,in which means are provided for raising and lowering the upper heating elements.

6. A hot line forming machine as claimed in claim 5, in which the means comprises piston and cylinder devices.

7. A hot line forming machine as claimed in any preceding claim, in which means are provided for raising and lowering the lower heating elements.

8. A hot line forming machine as claimed in claim 7 in which the means comprises pressure fluid operable piston and cylinder devices.

9. A hot line forming machine as claimed in any preceding claim, in which each heating element is sheathed in a thermally conductive material.

10. A hot line forming machine as claimed in claim 9, in which each sheathed heating element is sandwiched between strips and nose plate.

11. A hot line forming machine as claimed in claim 9 in which the sheath is made of inconnel.

12. A hot line forming machine as claimed in claim 9, 10 or 11, in which the strips are made of aluminium.

13. A hot line forming machine as claimed in any preceding claim, in which each heater element is provided with a heat sensor and sensors are connected to control means enabling the temperature of the elements to be controlled and monitored.

14. A hot line forming machine as claimed in any preceding claim, in which complementary forming tools are disposed downstram of the heating elements by means of which plastics sheet heated by the heating elements may be formed into a desired shape.

15. A hot line forming machine as claimed in claim 14, in which the position of the forming tools is adjustable.