GB2071561A

GB2071561A - A moulding tool

Info

Publication number: GB2071561A
Application number: GB8106913A
Authority: GB
Original assignee: Adolf Illig Maschinenbau GmbH and Co KG
Current assignee: Adolf Illig Maschinenbau GmbH and Co KG
Priority date: 1980-03-12
Filing date: 1981-03-05
Publication date: 1981-09-23
Also published as: DE8006678U1; FR2481190A1

Abstract

A moulding tool, for the production of beakers (4) from heated thermoplastic synthetic material film (3) by deep drawing, comprises an upper part provided with a matrix (11), a presser foot (12) and a head plate (13) and a lower part provided with the actual mould (5) of the beaker and a severing device (6, 7). An encircling sealed-off chamber (18) is provided between the presser foot (12) and the matrix (11) and is connected by transverse bores (17) to bores (15, 16) for the supply and removal of coolant medium. The transverse bore (17) from the bore (15) to the chamber (18) opens into a lower region thereof, while the other transverse bore (17) to the bore (16) opens into an upper region of the chamber (18). A further encircling chamber (21) may be provided between the matrix (11) and the presser foot (12) underneath the chamber (18) and be in communication through bores (22) with the interior space of the moulding tool. Alternatively or preferably in addition to the chamber (21), a further encircling chamber (23) between the presser foot (12) and the matrix (11) above the chamber (18) may be in communication with a feed duct (25) as well as through bores (24) with the interior space.

Description

SPECIFICATION A molding tool The present invention relates to a molding tool for the production of articles, such as cups or beakers of heated thermoplastic material, preferably in the form of a file web, by deep drawing.

Known tools of that kind generally comprise an - upper part and a lower part, these parts being displaceable relative to each other. The lower part contains the actual mould and is usually provided with a cutting edge, while the upper part includes the matrix and a sprung presser foot. The published Federal Republic of Germany patent application No. 21 45 250 shows a moulding tool of this species by the example of the manufacture of a beaker with a so-called flat rim. Since the rim thickness in such a case corresponds to about the film thickness, the beaker wall itself becoming relatively thin through the deep drawing and therefore cooling down more rapidly, the cooling time of this rim influences significantly the cycle time required for the manufacture of a beaker.

When the removal of the beaker from the mould takes place before the rim has cooled sufficiently, an unacceptable distortion of the rim takes place.

To obtain a shortening of the cycle time, it has previously already been proposed to provide the matrix with a cooling bore and to feed cooling water through it. Hereby, a cooling of the presser foot, holding down the rim during the moulding operation, was attained through the matrix and a slight shortening of the cycle time gained.

According to the present invention, there is now provided a moulding tool for the production of articles from heated thermoplastic material by deep drawing, the tool comprising a lower part provided with a mould and an upper part provided with a matrix, a presser foot disposed with the matrix, a chamber surrounding the presser foot and disposed between the presser foot and the matrix, and duct means provided within the matrix for feeding coolant medium through the chamber.

This arrangement allows cooling water to flow all round the presser foot so that a substantially better cooling of the film rim may be obtained in this manner when the cooling effect is transmitted through the matrix to the presser foot, where an air gap would have to be overcome.

Since the presser foot moves vertically in each cycle and a relative movement consequently takes place between it and the matrix, a sealing of the chamber is required. To provide additional security against downward leakage of the water, a small annular chamber may be provided between matrix and presser foot underneath the lower chamber seal and be connected with the interior space of the mould. In order substantially to prevent an upward leakage, an annular chamber, through which the mould air is supplied, may also be provided above the upper chamber seal. The mould air then flows through this upper chamber into the interior space of the mould.In this manner, a pressure builds up externally of the firstmentioned chamber flowed through by the cooling water and, in the case of a potential leakage of the seals, presses the water back into this chamber, since the pressure of the mould air is generally rather greater than the pressure of the cooling water.

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 shows a cross-section through a moulding tool embodying the present invention, Figure 2 shows a plan view onto a matrix of the moulding tool and Figure 3 shows an enlarged cross-sectional illustration of a portion of the tool in the region of its presser foot.

Referring now to the drawings, these illustrate a moulding tool comprising an upper part 1 and a lower part 2, which are displaceable relative to each other and in co-operation deep-draw a portion of a film 3 of thermoplastic plastics material into a beaker 4 and stamp this out by severing the finished article from surrounding portions of the thermoplastic material. For this purpose, the lower part 2 is provided with the actual mould insert 5 with a cutting edge 6, a stripper member 7, a receptable 8 and a base plate 9 and with a vertically movable mould bottom 10. The upper part 1 comprises a matrix 11, a presser foot 12, a head plate 13 and a stretching aid 14.

As figure 2 shows, production tools are usually equipped with several mould nests in one row (3 mould nests in the example), a multi-row arrangement of such mould nests also being possible.

The matrix is traversed by duct means comprising bores 15 and 16. Transverse bores 17 extend from these bores to the pressure foot 12, which is surrounded by a chamber 18. When cooling water is now supplied through the bore 1 5, this flows through each of the chambers 18 of the individual mould nests and away through the bore 16.

Since air is likely to be in the bores 15 and 16 and the chamber 18 at least during initial operation of the tool, the transverse bores 1 7 leading from the bore 15 open into the lower region of the chamber 18 and the transverse bores 17 leading to the bore 16 open into the upper region of the chamber 18. In this manner, possibly included air is conducted out when the cooling water flows through. The uniformity of the cooling is also improved in this manner, since a greater uniformity of flow around the pressure foot is achieved by a reduced tendency to formation of regions of stationary or only slowly moving cooling liquid. A sealing of the chamber 1 8 and an issuing of cooling liquid is prevented by seals 19 and 20, for example O-rings.Nevertheless, slight leakages are always likely to appear in practice even if only through wear in the course of time, because a wear is readily given by the relative movement between presser foot and matrix at about 20 to 40 cycles per minute. Such leakages are very disadvantageous because any leaking cooling water would then drip directly into the beakers. Since this cooling water is often dirty and generally provided with rust protection agents, the consequence of such a dripping can be significant.

To reduce any tendency to such issuing of cooling liquid, an encircling chamber 21 is provided for this reason between presser foot 12 and matrix 1 1 and stands in communication through one or more bores 22 with the interior space, as is evident particularly from figure 3.

A further chamber 23, into which the mould air is supplied through the feed duct 25, extends around the upper region of the presser foot 12.

The mould air flows through bores 24 into the interior of the mould and from there also into the annular space 21. Consequently, an air pressure builds up on both sides of the chamber 18 during each operating cycle of the moulding and is greater than the pressure of the coolant. In case of leakages, the cooling water is urged by the air pressure back into the chamber 18 or cannot even escape at all.

The scope of the present invention of course also extends to moulding tools which only mould the beaker which is then to be stamped out in a succeeding station. The chambers may be formed equally well in the matrix wall instead of the wall of the presser foot.

Claims

1. A moulding tool for the production of articles from heated thermoplastic material by deep drawing, the tool comprising a lower part provided with a mould and an upper part provided with a matrix, a presser foot disposed with the matrix, a chamber surrounding the presser foot and disposed between the presser foot and the matrix, and duct means provided within the matrix for feeding coolant medium through the chamber.

2. A moulding tool as claimed in claim 1, the tool further being provided with cutting means movable to sever a finished article from surrounding portions of the thermoplastic material.

3. A moulding tool as claimed in either claim 1 or claim 2, the duct means comprising a first duct for leading coolant into the chamber and a second duct for leading coolant out of the chamber at a level higher than that, at which coolant is being led into the chamber through the first duct.

4. A moulding tool as claimed in any one of the preceding claims, the tool being provided with a further chamber extending below the firstmentioned chamber, the further chamber surrounding the presser foot and being disposed between the presser foot and the matrix, and with bore means to connect the further chamber with the space enclosed by the mould.

5. A moulding tool as claimed in any one of claims 1 to 3, the tool being provided with a further chamber extending above the firstmentioned chamber, the further chamber surrounding the presser foot and being disposed between the presser foot and the matrix, and with bore means to connect the further chamber with the space enclosed by the mould.

6. A moulding tool as claimed in claim 5, comprising a feed duct provided for feeding a gaseous medium under pressure into the space enclosed by the mould, the feed duct extending through the matrix and opening into the further chamber.

7. A moulding tool for the production of articles from heated thermoplastic material by deep drawing, the tool being substantially as hereinbefore described with reference to and as illustrated by figures 1 and 3 of the accompanying drawings.

8. A moulding tool as claimed in claim 7, the tool being substantially as hereinbefore described with reference to and as illustrated by figure 2 of the accompanying drawings.