GB2184059A - Heatable platen - Google Patents

Abstract

A heatable platen comprises a plurality of heat-conductive strips (10) side by side. Each strip (10) has holes (11) from side to side along its length. These holes (11) coincide with holes in at least one adjacent strip to form sets of coinciding holes. Means (12), for example hollow tubes for passage of steam, extend through at least some of the sets of coincident holes to supply heat to the platen. Means (13) such as nuts are provided to maintain the strips (10) in side by side relationship so that the platen surface is formed by one set of corresponding edge faces of the strips. <IMAGE>

Description

SPECIFICATION Heatable platen Heated platens are used in many industries in processes in which pressure must be applied to materials being processed at the same time as heat is transferred to them. Such platens usually need to be strong to withstand the pressure used in the process. They may also provide a heat sink so that fluctuations in processing temperature are minimised when heat is given up by the platen to the materials being processed at a rate greater than the platen itself is being heated. An effective means of heat transfer from the heat source must also be provided often with a means of temperature control and measurement.

Small platens can usually by provided having satisfactory characteristics by known methods of manufacture typically being cast in various metals with ducts cast into them through which a heat transfer fluid can flow or in which a heat source can be mounted. Other platens may be machined from blocks of metal incorporating machined ducts to facilitate the heat transfer. Often the surface of such platens is machined to a form determined by the purpose for which it is used.

Difficulty is encountered in manufacturing large platens by these and other known means because the resources for handling large components are unavailable or too costly to employ. An example of a platen which is difficult to manufacture by traditional means is one used in the rubber processing industry which needs to present a flat surface to the components it is pressed against, and be several metres long and over two metres wide.

Such a platen is presently made from 25 mm.

thick steel plate and has hollow square section ducts clamped against its underside to carry high pressure steam. Diffulty is encountered in obtaining large enough sufficiently flat steel plate, in obtaining sufficient heat transfer since three sides of the duct are not in contact with the platen, in supporting the platen without crushing the ducts, in minimising the temperature gradient through the thick platen because the heat source is removed from the materials by at least the thickness of the platen and in servicing for steam leaks.

The present invention provides a means of construction which reduces the scale of the above problems and can improve the performance of such a platen whilst maintaining a low production cost. This invention can be applied to the manufacture of heated platens of a variety of types and sizes where its simplicity can produce a lower cost platen.

According to the present invention there is provided a heatable platen comprising a plurality of heat-conductive strips side by side, each strip having holes from side to side along its length, said holes coinciding with holes in at least one adjacent strip to form sets of coinciding holes, means extending through at least some of the sets of coinciding holes for supplying heat to the platen, and means maintaining the strips in side by side relationship, whereby the platen surface is formed by one set of corresponding edge faces of the strips.

In a preferred embodiment the platen comprises a plurality of metal strips side by side, each of said strips having holes at intervals along their length, said holes coinciding with holes in at least a number of adjacent strips, hollow metal sections passing through coinciding holes from side to side of the strips, heating means inside said hollow metal sections and means by which said strips are maintained in side to side contact.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which: Figure 1 shows a section through the platen along the length of a hollow section.

Figure 2 shows a section through part of the platen across a number of hollow sections.

Referring to the drawing the platen comprises a number of bright steel strips 10 through which coincident holes 11 have been punched, hollow sections 12 in the form of mild steel tubes which are a close fit in the holes 11 pass through the strips 10 the tubes 12 being threaded on their extremities and fitted with nuts 13 by means of which the strips are clamped together to form a rigid platen. Connection of ducts carrying steam under pressure is made to the ends of the tubes 12 by means not shown as is provision for the drainage and removal of condense.

The surface of the platen may be flat enough for many practical purposes without being dressed after assembly but may be machined as necessary for its conditions of use.

The quality of the strips 10 and the precision with which the holes are made will determine the flatness of the unprocessed surface and the fit of the tubes 12 in the holes 11 will influence the heat exchange efficency. The strips 10 need not be of a length to span the whole length of the platen one or more strips, together equalling the length of the platen, being laid end to end, preferably so that the joins in adjacent strips do not coincide and joins are so positioned in the platen that its strength is sufficiently maintained for its purpose.

Electric heaters may be enclosed in holow metal sections and inserted in the coinciding holes in which the fit of the section may be such as to permit removal and replacement with the platen assembled, in this case the means to hold the assembly together may not be associated with the hollow metal sections which may form the casing of the heating element, but be by tie rods passing through other coinciding holes or other known means.

Means for support or suspension of the platen may be incorporated by forming recesses in the back of the platen by making shaped cut outs in the edge of the strips where they form the rear surface of the platen such cut outs may, by coinciding with those in other strips, form pockets or keyways into which supporting or suspending means may be mounted. Two examples of supporting keyways are shown in Fig. 2 cutouts 16 and 17 being associated with supports 14 and 15 respectively, In the case of cutout 17 it can be used for suspension of the platen in association with a hanger of co-operating shape.

Holes 11 may be open sided forming a cavity in the strip or platen so that heating elements in their appropriate hollow sections may be inserted into such cavities other than through the side of the platen or to provide means for location, support or fixing of the platen which may be associated with the hollow sections.

Claims (8)

1. A heatable platen comprising a plurality of heat-conductive strips side by side, each strip having holes from side to side along its length, said holes coinciding with holes in at least one adjacent strip to form sets of coinciding holes, means extending through at least some of the sets of coinciding holes for supplying heat to the platen, and means maintaining the strips in side by side relationship, whereby the platen surface is formed by one set of corresponding edge faces of the strips.

2. A heatable platen as claimed in claim 1, wherein hollow heat-conductive sections extend through at least some of the sets of coinciding holes from side to side of the strips for the supply of heat from inside the hollow sections to the platen surface.

3. A heatable platen comprising a plurality of metal strips side by side, each of said strips having holes at intervals along its length, said holes coinciding with holes in at least a number of adjacent strips, hollow metal sections passing through coinciding holes from side to side of the strips, heating means inside said hollow metal sections, and means by which said strips are maintained in side by side contact whereby the platen surface is formed by one edge of each of said strips.

4. A platen as claimed in claim 2 or 3, wherein the hollow sections are steel tubes which are a close fit in the coinciding holes and extend from one side to the other of the -plurality of strips.

5. A platen as claimed in any of claims 2 to 4, designed for the supply of heat to the platen by means of steam under pressure passing through the hollow sections from and to ducts connected to the hollow sections.

6. A platen as claimed in any of claims 1 to 4, wherein the means for supplying heat comprises electrical heaters.

7. A platen as claimed in any of claims 1 to 6, wherein the platen surface has a length greater than the length of the individual strips, two or more strips being laid end to end in each row to constitute the full length of the platen surface, the join(s) in the platen surface between said two or more strips in each row being staggered from the join(s) in adjacent rows and being positioned so as to provide a load-bearing platen surface.

8. A platen substantially as hereinbefore specifically described with reference to the accompanying drawing.