GB2220829A

GB2220829A - Heating apparatus

Info

Publication number: GB2220829A
Application number: GB8816726A
Authority: GB
Inventors: Peter Bennell
Original assignee: Eastern Electricity PLC
Current assignee: Eastern Electricity PLC
Priority date: 1988-07-14
Filing date: 1988-07-14
Publication date: 1990-01-17
Anticipated expiration: 2008-07-14
Also published as: GB8816726D0; GB2220829B

Abstract

An apparatus for heating bulk foodstuffs comprises a resistively heated perforated screen on which material to be heated e.g. margarine, frozen fruit juice is placed. Melted material is collected in container 11. The screen may be heated by passing electric current through it and comprises a perforated sheet, an expanded metal sheet, a parallel array of rods or wires or a crossing array of rods or wires and may be flexible. <IMAGE>

Description

HEATING APPARATUS This invention relates to heating apparatus and in particular to heating apparatus adapted to provide melted material.

There is a requirement to melt low melting point materials, for instance waxes, polymers as well as many sorts of bulk foodstuffs. As an example, orange juice is generally frozen prior to transportation from the country of origin so that melting of the frozen juice is necessary before final packaging. Hitherto this has been achieved by placing drums containing the frozen juice into warmed ovens or tanks of warmed water, thus allowing the gradual thawing of the juice. This process may be extremely slow however.

Similarly, margarine, in bulk form has to be melted to allow final packaging. This is commonly achieved by placing the bulk quantities of margarine onto a heated platform, there being provided a blade for removing margarine which is sufficiently melted.

Such an apparatus is extremely costly, however.

It is an object of the present invention to provide a heating apparatus adapted to provide melted material which both allows for rapid heating of material and is economical to manufacture.

In accordance with the present invention a heating apparatus comprises a perforate means adapted to receive material to be heated and a means to heat the perforate means to heat said material.

Preferably, the perforated means is arranged to be resistively heated and the means to heat is arranged to supply electrical. current to flow in the perforate means.

The perforate means and the means to heat may be arranged to cause melted material to flow through the perforate means at a predetermined temperature and/or flow rate, and may be made of stainless steel formed as a perforate sheet, expanded metal sheet, cross wire screen, wire mesh screen or an arrangement of rods or wires with no cross connections. Such arrangements are particularly adventageous since the current density distribution across the perforate means will optimise for the most efficient heating of the material. Essentially, those regions of the perforate means on which there is material to be heated will be cooler than those regions in which there is no such material and will, consequently, have a lower resistivity and thus a higher current density.

It will be appreciated that the present invention will also be able to meet the need to heat materials and is not limited to melting materials.

In particular, the present apparatus may find particular applicability in heating very viscous liquids.

The invention will now be described with reference to the accompanying drawings in which Figure 1 is a schematic representation of an embodiment of the present invention utilising a perforated means having a given shape and Figure 2 is cross sectional schematic representation of a perforate means having another shape.

Referring now to the drawings, a heating apparatus is shown comprising a transformer 1, the primary of which is connected to a power supply 2 (not shown) via a pair of back to back connected thyristors 3 triggerable to provide a variable voltage to the primary of the transformer. A gate trigger 12 for the thyristors 3 provides phase angle or burst fire power control. Each of the outputs of the secondary of the transformer 1 are connected to a respective copper busbar 4, 5 across which is connected a stainless steel perforate mesh 6. The mesh 6 may be of non-flexible material formed into the required shape. Insulating spacers 7, 8 seperate the two aluminium busbars 4, 5 from stainless steel surrounds 9, 10 which allow quantities of material (not shown) to be loaded onto the perforate sheet without spillage. A collection container 11 for receiving the heated material is provided.

In operation, the material to be heated is loaded onto the perforate mesh 6 and a low voltage high current (generally up to 20,000 A although greater in some circumstances) derived from the transformer 1 is passed through the perforate mesh 6. Resistive heating of the mesh 6 results in heating of the material. For material which is to be melted, heating of solid portions of the material continues until those portions are sufficiently liquid to pass through the perforations of the mesh 6 and into the collection container 11. It will be appreciated that the residence time for which material is in thermal contact with the heated mesh 6 is relatively short so that burning of the material is substantially prevented.

Independant control of the flow rate from the mesh and the temperatue of material delivered from the mesh may be provided for by varying the current supplied to the mesh 6 and the shape of the mesh 6.

For instance, in Figure 2 there is shown a flexible mesh 6 which is elongated compared with that shown in Figure 1. Consequently, melted material has a tendency to run along the mesh, remaining in contact for longer than it would do with the mesh shown in Figure 1 and thus reaching a higher temperature before eventually running off. Adjustable bars 15 are provided to allow for the variation of the shape of the mesh 6. Conversely, increasing the current to the mesh 6 will increase the rate of melting and therefore the flow rate. In addition, varying the temperature of material delivered may also be achieved by changing the arrangement or material of the mesh.

Generally, material is gravity fed towards the mesh 6 although a varitey of pressure applying devices, such as pneumatic rams, may also be utilised when necessary.

In addition, some circumstances may require the provision of means for scraping unwanted material from the mesh 6 in particular from the underside of the mesh 6. This may be the case when very viscous liquids are being heated or when solid materials are being heated to the point at which they are only just beginning to melt.

Claims

CLAIMS:

1. Heating apparatus for heating material comprising perforate means adapted to receive material to be heated and means to heat the perforate means to heat said material received thereby.

2. Heating apparatus as claimed in Claim 1 wherein the perforate means is arranged to be resistively heated and the means to heat is arranged to supply electrical current to flow in the perforate means.

3. Heating apparatus as claimed in either Claim 1 or Claim 2 wherein the perforate and the means to heat are arranged to cause heated material to flow through the perforate means at a predetermined temperature and/or flow rate.

4. Heating apparatus as claimed in Claim 3 wherein the perforate means is flexible and there is provided means to arrange the perforated means into a predetermined shape.

5. Heating apparatus as claimed in any preceding claim further comprising supply means supplying material to said perforate means and being adapted to apply predetermined pressure on said material towards the perforate means.

6. Heating apparatus as claimed in any preceding claim further comprising scraping means adapted to remove adhering material which has passed through the perforate means.

7. Heating apparatus as claimed in any preceding claim wherein the perforate means is one of the following: perforate sheet; expanded metal sheet; cross wire screen; wire mesh screen; rod or wire arrangement with no cross connections.