GB2157616A

GB2157616A - Injection moulding

Info

Publication number: GB2157616A
Application number: GB08509260A
Authority: GB
Inventors: Terence Pater Revill
Original assignee: Mardon Illingworth Ltd
Current assignee: Impress Sutton Ltd
Priority date: 1984-04-19
Filing date: 1985-04-11
Publication date: 1985-10-30
Also published as: EP0177538A1; ZA852508B; AU4211785A; GB2157616B; GB8410331D0; ES8700137A1; GB8509260D0; JPS60234815A; WO1985004836A1; ES542399A0

Abstract

A mould for use in an injection moulding machine, the mould having a body (20) with a mould cavity (21), a main core (22) and a collapsible core (23) supported by the main core, the main core being retractable relative to the collapsible core, to permit collapse of the latter in the mould cavity, and the collapsed core then being retractable. Hydraulic cylinders (30, 31) are provided for collapsing and retracting the collapsible core (23) and so switches are provided on the hydraulic cylinders and/or other relatively movable parts of the mould for providing signals (S1 to S10) when the mould parts are in predetermined positions for triggering the steps in a moulding sequence.

Description

SPECIFICATION Injection moulding method and mould This invention relates to a method and mould for injection moulding articles in which a collapsible core part is required.

It is usual to control the sequence of operations by the moulding machine. To control a mould of the complexity outlined by the invention it would be necessary to build a special moulding machine incorporating special electronics and hydraulics.

The invention seeks to avoid this problem and to provide a particularly efficient moulding method that can be run in standard injection moulding machines for e.g. a container of 180 mm diameter and 235 mm in height could run in a GKN Windsor 330 of a Klockner Ferromatik FD250 machine.

From one aspect, the present invention provides a method of injection moulding an article in a mould having a collapsible core part the method including in the moulding cycle the steps of retraction of a main core, collapse of a collapsible core and retraction of the collapsible core, wherein the steps of collapse and retraction of the collapsible core are effected by hydraulic and/or pneumatic means forming parts of the mould, said means being controlled by an electronic control circuit triggered by signals provided by the mould parts themselves when the parts reach given positions.

The invention also resides in a mould for use in an injection moulding machine, the mould having a body with a mould cavity, a main core and a collapsible core supported by the main core, the main core being retractable relative to the collapsible core, to permit collapse of the latter in the mould cavity, and the collapsed core then being retractable, and signal generating means on the relatively movable parts of the mould for providing signals when the mould parts are in predetermined positions for triggering the steps in a moulding sequence.

Reference is now made to the accompanying drawings, wherein: Figure 1 is a block diagram illustrating the basic control arrangement for a mould; Figures 2A to 2G diagrammatically illustrate the mould in various sequential stages of operation; and Figure 3 shows in block diagrammatic form the circuitry for the electronic control of Figure 1.

The mould is intended for Injection moulding containers such as described in U.K. Patent Application No. 8400431. The container 10 has a cylindrical wall 11 and a base 12. A circumferential channel 13 is formed at the rim and projects radially inwardly of the cylindrical wall. Sockets 14 are provided at diammetrically opposite sides of the container for receiving and mounting a yoke type handle (not shown). Each socket is defined by a hollow boss 15 projecting into the interior of the container, the socket being closed to the interior.

The mould comprises a body 20 having a cavity 21, a main core member 22 and an intermediate core 23.

The intermediate core 23 is made up of a series of fingers which extend into the cavity to form the container around the core. The fingers are supported by part 24 in slides, inward collapse is effected by relative movement along the mould axis between the intermediate core 23 and the annular part 19 provided with pins 18 inclined to the mould axis. In addition side cores 26 are provided which form the bosses 15 and these are mounted in the body for radial outward retraction.

The mould is mounted in the moulding machine of which only the main cylinder 29 is indicated, this cycling and thereby serving to open and close the mould by acting on the main core member 22.

The mould has first hydraulic means 30 which acts between the annular part and the core member 22.

The first hydraulic means 30 acts in synchronism with the main cylinder 29 and holds the rest of the mould closed as the core member is retracted.

Second hydraulic means 31 moves annular part 19 relative to the intermediate core 23 to cause radial collapse of the latter. Each of these hydraulic means comprises several cylinders spaced around the mould axis. Third hydraulic means 32 operates the side cores 26 and comprises one cylinder for each side core.

Figure 2A shows the mould fully closed having had the plastic material injected into the mould and allowed to set (cool). The injection and cooling time delays are determined in known manner by the size of the object to be moulded and the material used and form part of the injection moulding machine control EC1. An electronic control panel EC2 shown in detail in Figure 3 is interfaced with the electronic control of the injection machine EC1 as shown in Figure 1.

With reference now to Figures 1 and 3 the moulding machine MC comprises means MC1, MC2 for holding the mould M as illustrated in detail in Figures 2A-G. The moulding machine further comprises a hydraulic ram HR and an injector I and feed hopper FH for feeding the moulding material into the mould M. The moulding machine may for example be a GKN Windsor 330 or a Klockner Ferromatik FD 250. The electronic control panel EC1 for the moulding machine receives signals from the machine on line L1 and gives signals to the machine on line L2. The electronic control panel is basically of conventional design containing timing circuitry for timing the length of the moulding operations, e.g. injection and setting time and other controls related to monitoring the temperature of moulding etc. These are standard signals and are not therefore further described.

The electronic control circuitry provides output signals on lines L3 to the electronic mould control circuit EC2 and receives signals from the circuitry on lines L4. The electronic control circuitry EC2 provides output signals on lines L5 to operate the hydraulic and air circuit control HC and to operate the protection alarm PA the signals being generated as shown in greater detail in Figure 3 by input signals S1 to S10 received on lines L6 from the mould of Figures 2A-G.

With reference now to Figure 3, the electronic control circuit EC2 comprises an input filter 40 which receives signals from the switches S1-S10 and inputs from the moulding machine control EC1 on lines L3. The input filter serves to isolate the further electronics from voltage surges on the input lines which may occur for example on opening of a switch.

The outputs of the filter 40 are fed to a decoder 42 which provides an output for a step counter 44 and also an address output for a program memory 46. The output of program memory 46 is fed to an output buffer/driver circuit 48 which provides outputs 01 to 08 to control the hydraulic controls H1 to H6 and the core and cavity air circuits A7 and A8 and also outputs on lines L4 to the machine control EC1.

The hydraulic control circuit HA serves to open and close the hydraulic circuits Hia to Hib ... H6a, H6b to perform the machine operations as hereinafter described. The program memory 46 may be of any suitable form whereby a set of output signals are obtained in response to input addresses. It is possible for the program to be in the form of punched paper tape, a matrix, or complex relay contact arrangement. It is possible to use a programmable read only memory (PROM) since this may be more readily changed but this is not necessary since the steps for any particular mould will not normally change and therefore the operational sequence can be permanently fixed.

The electronic control EC2 commences its operation on receipt of a signal on lines L3 indicating the completion of the cooling time for the mould. The cooling time and temperature of moulding etc are controlled in the normal manner. They will vary for the type and size of object being moulded and do not form part of the present invention and will therefore not be described in detail.

The receipt of the output signal on completion of the coding time result in an output '0'1 from EC2 to hydraulic control HC and retracts side cores 26 by means of hydraulic circuits H1 and acting on cylinders 32a and 32b as shown in Figure 2B.

Upon retraction, switches S1 and S2 signal the electronic control EC2 and an output is fed to electronic control EC1 to enable mould opening to begin retracting main core member 22 as shown in Figure 2C, air is blown A7 into the mould to retain the moulding in position. EC2 also gives an output '0'3 to the hydraulic control HC circuit H3 to operate first hydraulic means 30 which keeps the core 23 and annular part 19 held in position as shown in Figure 2C. The main core continues to retract until cylinder 30 is fully extended at which point S5 signals electronic control EC2.Electronic control EC2 gives an output '0'5 to the hydraulic control HC circuit (H5 operating second hydraulic means 31) The mould continues to open as the intermediate core is collapsed by means of the separation of part 19 containing angle pins moving away from part 24 as shown in Figure 2D. When hydraulic means 31 is fully extended achieving full collapse of 23 S7 gives a signal to electronic control EC2, the output of which is fed to EC1 indicating that it is safe to continue to open. The whole core assembly 22, 23 is then fully retracted to the fully open position of the mould as shown in Figure 2E at which time S9 is made and sends a signal to EC2.

EC2 gives an output '0'6 to hydraulic control HC hydraulic circuit H6 of second hydraulic means 31 which re-expands the intermediate core 23 as shown in Figure 2F. When the intermediate core is fully expanded switch S8 is made and the resulting signal of which is fed to electronic control EC2 the output '0'4 of which is fed to hydraulic unit HC hydraulic circuit H4 of first hydraulic means 30. The first hydraulic means 30 closes up the intermediate core 23 onto the main core member 22. Air is introduced A8 to cavity 20 to eject the container as shown in Figure 2F.

When there is sufficient gap the container falls as shown in Figure 2G. A sensor SE1, SE2, (Figure 2G) detects the container has fallen clear of the mould and provides an input to EC1 on lines L1.

When intermediate core 23 is fully closed onto the main core member 22 the signal from S6 is fed to electronic control EC2. This signal along with signals S1, S2, S8 and the sensor gives an output on lines L4 from electronic control EC2 to the injection moulding machine control EC1 to close the mould.

When the mould is fully closed and high pressure is applied an output signal from electronic control EC1 indicating high pressure QON' is fed to electronic control EC2 output '0'2 to the hydraulic control HC circuits H2 of third hydraulic means 32 move the side cores in, when fully in S3, S7 are made these signals are fed to electronic control EC2 the output of which is fed to electronic control EC1 and instructs the machine to commence injection again.

The switch providing signal S10 is fed to electronic control EC2 and is a safety switch. It is imperative that there is no separation between the mould body 20 and the intermediate core 23 until the core 23 has been fully collapsed. If slight separation does occur, signal S10 triggers a mould open stop via an output from EC2 to the electronic control EC1 of the moulding machine. This is to prevent damage to the mould.

Claims

1. A method of injection moulding an article in a mould having a collapsible core part the method inciuding in the moulding cycle the steps of retraction of a main core, collapse of a collapsible core and retraction of the collapsible core, wherein the steps of collapse and retraction of the collapsible core are effected by hydraulic and/or pneumatic means forming parts of the mould, said means being controlled by an electronic control circuit triggered by signals provided by the mould parts themselves when the parts reach given positions.

2. A method according to Claim 1, wherein a side core is additionally provided, the moulding cycle includes the step of retracting the side core, and this step provides a signal to initiate retraction of the main core.

3. A mould for use in an injection moulding machine, the mould having a body with a mould cavity, a main core and a collapsible core supported by the main core, the main core being retractable relative to the collapsible core, to permit collapse of the latter in the mould cavity, and the collapsed core then being retractable, the mould including hydraulic and/or pneumatic means for effecting collapse and retraction of the collapsible core, and signal generating means on the relatively movable parts of the mould for providing signals when the mould parts are in predetermined positions for triggering the steps in a moulding sequence.

4. Apparatus for injection moulding an article, including a mould according to Claim 3, a hydraulic and/or pneumatic circuit for controlling operation of the mould, and an electronic circuit for controlling the hydraulic and/or pneumatic circuit, wherein the signals from the mould parts are fed to the electronic circuit.

5. Apparatus according to Claim 3 or 4, wherein the mould includes a side core and a hydraulic or pneumatic cylinder for extending the side core into the mould cavity and retracting the side core prior to retraction of the main core, the side core or its cylinder providing a signal when retracted to initiate retraction of the main core.