GB2147848A

GB2147848A - Moulding thermoplastic sheet material

Info

Publication number: GB2147848A
Application number: GB08425613A
Authority: GB
Inventors: Gunther Kiefer
Original assignee: Adolf Illig Maschinenbau GmbH and Co KG
Current assignee: Adolf Illig Maschinenbau GmbH and Co KG
Priority date: 1983-10-14
Filing date: 1984-10-10
Publication date: 1985-05-22
Also published as: FR2553336B4; FR2553336A4; DE3337406A1; DE3337406C2; GB8425613D0; GB2147848B

Abstract

Moulding apparatus for moulding plates or film web portions of thermoplastic plastics material through differential pressure comprises a moulding station, a fixed clamping frame (6), a movable clamping frame (7), a mould table for the reception of a deep-drawing mould, a charging station and transport means. Let into the fixed clamping frame is a cutting band which protrudes by a fraction of the plate thickness (not shown). Provided opposite thereto at the other clamping frame is a first pipe (28) for conducting a heating medium. In order to be able to also perform cooling of the clamped rim portion of the plate without intermixing of the heating and cooling media, a second pipe (42) is arranged above the first pipe (28) and serves to conduct a cooling medium. The media flow through the pipes takes place alternatingly. <IMAGE>

Description

SPECIFICATION Moulding apparatus for moulding thermoplastic sheet material The present invention relates to moulding apparatus for moulding thermoplastic sheet material especially plates or film web portions, previously cut to shape, of thermoplastic plastics material by means of differential pressure.

In the specification of German (Fed. Rep.) patent application No. p 32 20 416.7-16 (UK specification 2 121 349 A) there is disclosed moulding apparatus with a moulding station in which heating of a clamped plate of film web portion takes place and in which a fixed and a movable clamping frame as well as a vertically movable mould table for the reception of a deep-drawing mould are arranged, a charging station being arranged upstream of the moulding station and transport means extending between the two stations. A cutting band is let into the lower clamping frame and protrudes by a fraction of the plate thickness, while a pipe which is arranged at the upper clamping frame and communicates with a heating circuit. It is also possible for this pipe to alternately conduct a heated and a cooling medium.

On heating of the plate, the clamped rim portion thereof is warmed so as to avoid distortion. In order to avoid distortion during the cooling of the deformed part, it was proposed to conduct cold medium through the pipe during the cooling process.

The disclosed connection of heating and cooling device provides intermixing of the heating medium and the cooling medium. This can be disadvantageous when temperatures of above 1 00"C are used during the heating. In this case, the heating medium stands under an increased pressure of 3 to 4 bar when water is employed. During the change-over, the cold medium impinges on the hot heating medium mostly under a different pressure. Disturbances due to vapour formation and degasification of the oxygen dissolved in the cooling liquid are the consequence.

It would thus be desirable to provide for heating and cooling of the clamping frames without intermixing of the media and to allow use of different heating and cooling media in orderto be able to adapt them to the requirements.

According to the present invention there is provided moulding apparatus for moulding thermoplastic sheet material of given thickness, comprising an upper and a lower clamping frame in a moulding station of the apparatus for clamping such thermoplastic sheet material therebetween and means in the moulding station for heating and pressure moulding of the clamped sheet material, the lower clamping frame being provided with a cutting edge to cut into the clamped sheet material by a fraction of its thickness and in the zone of clamping thereof and the upper clamping frame being provided with a first and a second pipe which are secured together and which are arranged to conduct a heating medium and a cooling medium respectively in separate flows to effect heating and cooling of the clamped sheet material in the clamping zone.

In a preferred embodiment, the two pipes are arranged one above the other at the clamping frame, one pipe to conduct a heated medium and the other a cooling medium in alternation. It has proved that, although during heating by way of the first pipe the cooling medium in the second pipe is warmed up and conversely, this occurs surprisingly quickly in the relatively small pipe cross-section. It has proved to be advantageous at the upper clamping frame to arrange the lower pipe as the heating pipe and to use a copper pipe because of its good thermal conductivity. It is also advantageous to arrange the upper pipe to be connected only locally with the clamping frame so that too strong a heating/cooling of the lower region of the clamping frame does not take place here.

An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Figure 1 is a sectional view of part of the clamping frames in the moulding station of moulding apparatus embodying the invention; Figure 2 is a side elevation of part of the clamping frames of Figure 1; and Figure 3 is a diagram of heating and cooling circuits for the clamping frames.

Referring now to the drawings, there is shown part of moulding apparatus which, apart from the heating and cooling arrangements described in greater detail in the following, is substantially the same as the apparatus described in the afore-mentioned German and United Kingdom specifications, the content of which is hereby incorporated to the extent necessary for understanding of general aspects of the construction and operation of the apparatus.

In the case of the apparatus embodying the present invention, an upper movable clamping frame 7 has a first pipe 28 for a heating medium and a second pipe 42 for a cooling medium, the pipe 42 being closely secured to the pipe 28 by, for example, soldering. In order to avoid too strong temperature transition to the clamping frame 7, the pipe 42 lies thereagainst only locally by means of webs 44, i.e.

recesses 43 are milled out of the frame to form the webs 44.

The fixed lower clamping frame 6 of the apparatus has a first pipe 41 for the heating medium and a second pipe 45 for the cooling medium. As shown in Figure 3, a heating device 40 is connected with the pipes 28 and 41 and a valve 31' in a feed circuit serves for the selectable switching on and off of the heated medium flow.

A cooling device 35 conducts cooling medium to the pipes 42 and 45 and a valve 30' in a feed circuit makes possible the switching on and off of the cooling medium flow.

Although the positions of the pipes 28 and 42 are transposable, as are the positions of the pipes 41 and 45, it is advantageous if the heating pipe in each case is the one closer to the sheet material clamped by the clamping frames.

During heating of the clamped rim portion of the sheet by way of this pipe, wherein the valve 30' is closed and valve 31' opened, the medium in the pipe 42 warms up. During cooling of the rim portion, the valve 30' is opened and the valve 31' closed. Now, the medium in the pipe 28 is cooled. It has proved that this mutual influencing has no negative effects and can be accepted.

The lower clamping frame 6 possesses a cutting edge (not shown) as described and illustrated in the afore-mentioned German and United Kingdom specifications.

Claims

1. Moulding apparatus for moulding thermoplastic sheet material of given thickness, comprising an upper and a lower clamping frame in a moulding station of the apparatus for clamping such thermoplastic sheet material therebetween and means in the moulding station for heating and pressure moulding of the clamped sheet material, the lower clamping frame being provided with a cutting edge to cut into the clamped sheet material by a fraction of its thickness and in the zone of clamping thereof and the upper clamping frame being provided with a first and a second pipe which are secured together and which are arranged to conduct a heating medium and a cooling medium respectively in separate flows to effect heating and cooling of the clamped sheet material in the clamping zone.

2. Apparatus as claimed in claim 1, comprising transport means extending between a charging station and the moulding station for selectably transporting plates of plastics material or portions of a film web of plastics material.

3. Apparatus as claimed in either claim 1 or claim 2, wherein the cutting edge is provided by cutting band recessed into the lower clamping frame.

4. Apparatus as claimed in any one of the preceding claims, wherein the second pipe is arranged between the first pipe and the upper clamping frame.

5. Apparatus as claimed in any one of the preceding claims, wherein the upper clamping frame is provided with a plurality of recesses and an upper one of the pipe is connected to the frame by way of webs between the recesses.

6. Apparatus as claimed in any one of the preceding claims, wherein the lower clamping frame is provided with a respective such first pipe and a respective such second pipe.

7. Moulding apparatus substantially as hereinbefore described with reference to the accompanying drawings.