WO1991009720A1

WO1991009720A1 - Improvements relating to heating units

Info

Publication number: WO1991009720A1
Application number: PCT/GB1990/001976
Authority: WO
Inventors: John Michael Skalitzky
Original assignee: Elmatic (Cardiff) Limited
Priority date: 1989-12-22
Filing date: 1990-12-18
Publication date: 1991-07-11
Also published as: EP0508998A1; GB8929145D0

Abstract

A heating unit comprises a heat conductive block (3) with cooling fins (4). Grooves (6) are formed in the one face of the block (3) and these receive correspondingly shaped heating elements (7) whose outer faces are flush with the face of the block (3). Because the heating elements are situated directly on the face of the block desired heating effects can be readily achieved in extruded blocks which can adopt quite detailed design shapes.

Description

"Improvements Relating to Heatinσ Units"

Conventional heating units used, for example, in plastics injection and extrusion processes are conven¬ tionally formed by casting a suitably shaped block about a heat sealing element. The casting process puts constraints upon the shapes which can be created for the block and the heat transfer properties of the unit are somewhat restricted by the embedding of the heat element within the block.

It is an object of this invention to provide a heating unit of a more versatile form and which is capable of acheiving a more rapid heating response, than for the conventional type discussed above.

Accordingly this invention provides a heating unit comprising an extruded metal alloy block whose one face is formed with grooves in which are securely mounted heat transfer pipes whose inner faces bear against the wall surfaces of the grooves and whose outer faces are aligned with the said one face of the block.

Two significant advantages are acheived by a heating unit of this form in that the extrusion process allows for quite detailed design shapes and, because the heat transfer pipes are situated directly on one face of the block, heating effects are more readily acheived.

In the preferred arrangement grooves of the heating transfer pipes will be of square, rectangular or half-round cross-section. The edges of the grooves may be peened over to retain the heat transfer pipes. Another possibility would be to form the heat transfer pipes and the grooves in dovetail form so that the heat transfer pipes would be slid into place. The heat transfer pipes may incorporate heating elements or could provide fluid passageways for heating or cooling liquids.

The extruded blocks can be suitably shaped so that said one face forms a circular or part-circular internal surface. In the latter case several parts can be secured together to define a complete circle of a desired size. The extruded block can have dovetailed sections along edge walls enabling a number of such blocks to be linked together. A preferred material for the block is aluminium. For certain purposes the face of the block opposite to said one face may have fins formed thereon which could act, for example, as cooling fins.

The invention may be performed in various ways and a preferred example thereof will now be described with reference to the accompanying drawings, in which:- Figures 1 and 2 are end and side views respectively of a heating unit constructed in accordance with this invention;

Figure 3 is an enlarged detail of part of Figure 1; Figure 4 is a longitudinal section through part of the heating unit of Figures l and 2;

Figure 5 is a section through an enlarged detail of part of an alternative mounting arrangement for heating elements of the heating unit. The heating unit shown in Figures 1 to 4 of the drawings defines a cylindrical passageway 1 which can receive a tube 2 forming part of plastics injection or extrusion equipment. The main part of the heating unit is 5 defined by a ring-shaped block 3 formed from aluminium. This is formed by an extrusion process so as to define fins 4, the block being shaped subsequently to create the ring shape. In this instance two semi-circular parts are created which are held together by fixing bolts 5.

10 The ring 3 also incorporates square cross-section grooves 6 within which are fitted correspondingly shaped heating elements 7 whose ends 8 are brought out through the body of the block 3, as shown in Figures 1 and 3. As can be seen from Figures 2 and 3, three ring-shaped blocks 3 are

15 provided within the whole unit, the central one of these incorporating an access passageway 9 in which can be mounted temperature measuring devices, for example. The rings 3 are surrounded by an outer casing 10 provided with inlet and outlet passageways 11 and 12 through which air can be blown

20. for cooling purposes.

The design of heating unit illustrated in the drawings has a number of advantages over the conventional cast unit where the heating element is embedded in the block. Firstly the aluminium block can be formed by the extrusion process

25 with quite thin fins 4 as compared with those which can be created by the casting process. This enables the block to have a much faster cooling response because of the increase in the number and the decrease in the thickness of these cooling fins. The extruded design means that a fairly low weight block can be constructed. Furthermore, the heating elements could be positioned even closer to the,cooling fins 4 by adopting the design shown in Figure 5 so that cooling is more readily achieved. In this case a root enlargement of two adjacent fins 4 incorporates the groove 6 for a heating element 7.

The main advantage is the positioning of the heating element 7 directly on the inner face 1 of the equipment so that the heating is applied directly to the tube 2 rather than having to pass the heat through part of the block 3. The flat inner face of each heating element 7 permits the good heat transfer and there is also substantial surface contact between the heating element 7 and the body of the block 3 so that heat is rapidly transmitted through the block 3. An additional advantage is that the heating elements 7 are readily accessible and can therefore be replaced as required.

.It is envisaged that the corners of the opening 6 of the block 3 will be peened over to hold the heating elements 7 in place. The heating elements could have other forms of cross-sectional shape so as to fit into suitably defined grooves 6 in the block 3, with the exposed face of each heating element 7 lying flush with the inner face 1 of the block 3. Thus a heating element of semi-circular form could be used. Another possibility is to form the heating element of a dovetail shape which could then be slid into a complementary groove 6. Dovetail sections could be formed, as at 13 and 14

(Figure 4) in the side walls of the block 3 so that several blocks can be linked together to extend the length of the heating unit, prior to the formation of the blocks into the required circular form.

Claims

1. A heating unit comprising an extruded metal alloy block whose one face is formed with grooves in which are securely mounted heat transfer pipes whose inner faces bear against the wall surface of the grooves and whose outer faces are aligned with the said one face of the block.

2. A heating unit according to claim 1, wherein the edges of the grooves are peened over to retain the heat transfer pipes.

3. A heating unit according to claim 1 or claim 2, wherein the grooves and heat transfer pipes are of square, rectangular or half-round cross-section.

4. A heating unit according to any one of claims 1 to

3, wherein the heat transfer pipes incorporate heating elements or provide flow passageways for heating or cooling liquids.

5. A heating unit according to any one of claims l to

4, wherein the external block is shaped so that the said one face forms a circular or part-circular internal surface.

6. A heating unit according to any one of claims 1 to

5, wherein the extruded block has dovetail sections along edge walls enabling a number of such blocks to be linked together.

7. A heating unit according to any one of claims l to 6, wherein the face of the block opposite to said one face has fins formed thereon.

8. A heating unit according to any one of claims l to 7, wherein the block is formed from aluminium.

9. A heating unit substantially as herein described with reference to the accompanying drawings.