WO1994013444A1

WO1994013444A1 - A method in injection moulding

Info

Publication number: WO1994013444A1
Application number: PCT/SE1993/001065
Authority: WO
Inventors: Ernst Axelsson; Axel Svenson
Original assignee: Recon Pharmaceutical Ltd.
Priority date: 1992-12-11
Filing date: 1993-12-10
Publication date: 1994-06-23
Also published as: SE9203722D0; AU5663994A

Abstract

Method in injection moulding in a mould cavity, which is defined by fitted mould parts (13) enclosed in an outer casing (10) keeping the mould parts together.

Description

Λ METHOD IN INJECTION MOULDING The invention relates to a method in injection mould¬ ing in a mould cavity, which is defined by fitted mould parts enclosed in an outer casing keeping the mould parts together.

DE-C-397 198 discloses a method for moulding of porcelain material in a mould box, in which a mould for the moulding which is to be produced by the porcelain material is enclosed. The mould comprises three parts two of which are made in one piece while one part is composed of three parts. The mould parts are enclosed in a cavity in the mould box.

Also FR-A-2 608 963, US-A-2 097 658, US-A-3 764 101 and US-A- 4 066 236 show moulds for casting complicated objects, wherein the moulds are composed of several parts. In injection moulding the construction and design of the moulds are of great importance for the quality of the products as well as the production economy. However, split moulds are connected with the drawback that the joints between the mould parts give rise to unattractive and in many cases unacceptable burr on the injection moulded product.

The object of the invention is to overcome this pro- blem, and according to the invention this object is achieved by a method with the characterizing features of claim 1.

The invention will be further explained below by way of an illustrated embodiment thereof, reference being made to the accompanying drawings, in which

Fig. 1 is a perspective view of the lower part of a device which is used in the method according to the inven¬ tion having the upper part indicated by a dash- and dott- line, Fig. 2 is a perspective view of the mould parts which are used in the method according to the invention, Fig. 3 is a perspective view of an example of an object which is to be injection moulded by means of the method according to the invention,

Fig. 4 is an exploded perspective view of the mould parts which are to be used in the injection moulding of the object in Fig. 3,

Fig. 5 is a perspective view of the mould parts fitted together, the object in Fig. 3 being indicated by a dotted line, and Fig. 6 is a vertical cross sectional view of the mould device for working of a modification of the method according to the invention.

In injection moulding there are high demands on the mould which has to be heavily dimensioned such that damages or deformations do not arise at the high pressures which are required especially for viscous materials. In the figures there is shown a device to be used in the method of injection moulding according to the invention, comprising an outer casing 10 with a cavity 11 and an axial interface 12. In the cavity 11 mould parts are enclosed which consist of elements comprising e.g. discs, halves, and bars which when fitted together, have an outer shape with axial and radial dimensions corresponding to the measures of the cavity 11. This outer shape may for example be circular, hexagonal, square, or rectangular.

When a complicated object 14 is to be injection moulded, a mould cavity 15 is easily provided within the mould parts 13 by means of conventional workshop practice. The mould parts 13 having radial and axial interfaces 16 and 17 which are parallel with one or the other, respectively of two planes perpendicular to each other are subsequently placed within the cavity 11 and held pressed against each other at the radial interfaces 16 between an injection nozzle, acting at 18, and a support surface at 19 formed by the outer casing. The axial interfaces 17 are held pressed against each other by a clamp tie pressure exerted against the outer casing at 20 in order to press the parts together at the interface 12.

The interfaces are made with great accuracy as they are especially exposed to damages at the closing of the mould due to remaining burrs. The material of the mould parts is metal or metal alloy, preferably tool steel and can be varied depending on the injection pressures applied. It is possible to provide cores in the mould in order to form an apperture in the object which is to be moulded. In the arrangement of the mould according to Fig. 6, the pressure plates of the injection moulding device are shown at 20. Between the pressure plates the outer casing 10 with the interface 12 thereof is provided. The injection nozzle is to be applied at 18. The mould parts 13 are pro¬ vided within the outer casing.

An additional part 21 on the outer casing is fixed thereto by means of a screw connection 22, and a steel body is inserted into a cavity within the additional part, said steel body comprising a cylindrical portion 23 and a conical portion 24. The additional part 21 has an interface 12' coinciding with the interface 12. The cylindrical portion 23 abuts with the end surface thereof the mould parts 13. The angle V of the conical portion should be larger than the angle of an irreversable wedge (usually at least 6°). The conical portion is 0,01 - 0,02 mm larger than the corresponding conical cavity within the additional part 21, such that when a clamp tie pressure is applied between the pressure plates 20, said pressure is changed to an axial pressure against the mould parts by means of wedge action at the conical portion 24, said mould parts being compressed between the body 23, 24 and a support surface 25 in the outer casing 10.

Claims

1. Method in injection moulding into a mould cavity, which is defined by fitted mould parts (13) enclosed in an outer casing (10) keeping the mould parts together, c h a r a c t e r i z e d in that the mould parts, having interfaces (16, 17) which are parallel to one of two planes perpendicular to each other, pressed together at the interfaces parallel to one of the planes by a pressure which is coaxial with the injection nozzle, and at interfaces parallel to the other plane by clamp tie pressure exerted against the outer casing (10) which forms an interface in said second plane.

2. Method according to claim 1, c h a r a c t e r i z e d in that the pressure, which is coaxial with the injection nozzle, is applied between the injection nozzle and a support surface formed by the outer casing by engaging the nozzle with the mould parts.

3. Method according to claim 1 or 2, c h a r a c t e r i z e d in that the fitted mould parts (13) are inserted into a cavity (11) in the outer casing (10), the shape of said cavity corresponding to the outer shape of the fitted mould parts.

4. Method according to claim 1, c h a r a c t e r i z e d in that the pressure which is coaxial with the injection nozzle is applied against the mould parts between pressure areas, one of which is pressed against the mould parts by wedge action by means of the clamp tie pressure.

5. Method according to one of claims 1 or 4, c h a r a c t e r i z e d in that the outer shape of the fitted mould parts is circular, hexagonal, square or rectangular.

6. Method according to any of claims 1 - 5, c h a r a c t e r i z e d in that the number of mould parts (13), and the length and the width thereof is varied depending on the shape and size of the casting.