GB1567919A

GB1567919A - Method and apparatus for filling a mould of a foaming machine with foamable plastics

Info

Publication number: GB1567919A
Application number: GB41852/76A
Authority: GB
Original assignee: Haendle & Soehne Maschf Karl
Current assignee: Haendle & Soehne Maschf Karl
Priority date: 1975-10-11
Filing date: 1976-10-08
Publication date: 1980-05-21
Also published as: ES452223A1; FR2327069A1; FR2327069B1

Description

(54) METHOD AND APPARATUS FOR FILLING A MOULD OF A FOAMING MACHINE WITH FOAMABLE PLASTICS (71) Wc, KARL HÄNDLI. & SÖHNE MAS IINENFABRIK u. EISENGIES StiREI, a Wcst German Komman ditgesellschaft, of Industricstrasse 47, 7130 Muhlacker, Wcst Germany, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a method and apprattIs for filling a mould of a moulding machine with foamable plastics, in particular granular polystyrene.

With hitherto known method and apparatus of this type with thin-walled articles having wall thicknesses below 3mm, considerable wastage of material may arise due to faults occurring during the filling of the mould.

One object of the present invention is to provide a method and apparatus with which such faults can be substantially avoided and with which the filling time can be substantially reduced so that very short time cycles for the filling procedure can be achieved.

According to one aspect of the present invention therefore there is provided a method for filling a mould of a moulding machine with foamable plastics, particularly polystyrene, comprising the steps of: deliverying said plastics from a supply container into a pressure silo, admitting pressure medium to the silo to pressurise same to a predetermined pressure, and admitting plastics from said silo to the mould under the influence of said pressure, wherein, after filling the mould with the said plastics, excess plastics fed to the mould is blown back to the pressure silo with pressure medium.

According to a second aspect of the present invention there is provided apparatus for carrying out the above method comprising a supply container for plastics, a pressure silo connected to the supply container via a first passage provided with a closure device whereby plastics can be delivered from the supply container to the pressure silo only when the closure device is in an open state, a foaming mould having a mould filling device connected to the pressure silo via a second passage provided with an openable and closable control valve whereby plastics can be delivered from the pressure silo to the mould filling device only when the control valve is open, said mould filling device comprising a piston and cylinder assembly the piston of which is movable between an open position at which it permits admission of plastics via a filling tube of the filling device through a mould inlet into the mould and a closed position at which it covers said inlet, a pressurising system which is connected to the pressure silo via a supply pipe for admitting pressure medium thereto so as to pressurise same to a predetermined pressure, and means for applying pressure medium to the said filling tube after filling of the mould and whilst the piston of the filling device is in the open position thereof for blowing back excess plastics in said filling tube to said pressure silo.

If the above mentioned blow-back procedure of the method of the invention is effected, when performing said method with the aforesaid apparatus of the invention, simultaneously with movement of the piston of the filling device to the closed position it may occur that not all of the excess plastics can be removed from the filling device. In this case, material may build up in front of the piston so as to prevent the piston from reaching a desired end position in which it closes the mould inlet flush with the inner surface of the mould. This possibility is especially problematical with thin-walled mould parts and with a view to avoiding this problem, with one embodiment of the apparatus of the invention a timing device is provided which delays movement of the piston of the filling device to the closed position thereof after filling of the mould for a pre-adjustable delay time, to allow time for performance of the blow-back procedure.

The invention will now be described further by way of example only, and with reference to the accompanying drawings in which: Figure 1 shows one form of apparatus according to the present invention with a mould filling device belonging to the apparatus shown in axial longitudinal section and in a position corresponding to the end of a filling procedure; Figure 2 shows the mould filling device in a position corresponding to a filling procedure; Figure 3 shows the mould filling device in a position corresponding to a blow-back procedure; Figure 4 shows the mould filling device in a fault position; Figure 5 shows a modified form of the apparatus; Figure 6a shows a part of a feed device slide valve used in the apparatus of Figure 5 in the open position; and Figure 6b shows the valve in the half open position.

The apparatus shown in Figure 1 serves for the filling of foamable plastics, in particular polystyrene, in one of several foaming moulds of an automatic foaming maching (not shown). One of the various foaming moulds is shown in Figure 1 and consists of essentially two mould parts 1 and 2 which are placed against one another and define between them a hollow space 3 which is to be filled with the plastics material to be processed, such space 3 during the following foaming procedure determining the shape of the formed blank.

The foaming procedure is effected with the influence of heat. For this two heating chambers 5 and 6 connect respectively with the two mould parts. In the heating chambers there is introduced in usual manner steam with which the two mould parts 1 and 2 are heated during the foaming procedure. After termination of the foaming procedure the two mould parts 1 and 2 are cooled with the aid of cooling water introduced into the chambers 5 and 6. Then the mould part 2 together with its heating chamber 6 can be moved away in axial direction from the mould part 1 so that the formed article 4 can be removed from the mould.

The apparatus shown serves to accelerate the filling-in procedure of the plastics to be processed in the hollow space 3 between the two mould parts 1 and 2 and to ensure that no filling fault leading to waste can result.

In detail the apparatus shown has a tank 7 which receives the plastics to be processed, for example, pre-foamed pearl-like polystyrene, and at its lower conically tapered end section merges into a connecting pipe 8 which leads to a pressure silo 10 made of sheet metal. This takes the plastics indicated in Figure 1 at 11 in a quantity sufficient for several successive foaming procedures when a pneumatic silo closure 12 arranged in the connecting pipe 8 is pivotted with the aid of a pneumatic adjusting cylinder 13 from its closed position shown, by 90 " and then opens the path from the tank 7 to the pressure silo for the plastics.

In order to be able to introduce the plastics 11 stored in the pressure silo 10 rapidly into the hollow space 3 between the two mould parts 1 and 2 there is provided a supply pipe 14 leading from a pressurising system into the connecting pipe 8 for supplying compressed air at a pressure of 6 Bar as indicated with the arrow 15. This compressed air flows into the pressure silo 10 when a shut-off valve 16 is opened. This valve may be actuated hydraulically, pneumatically or electromagnetically by remote control. The shut-off valve may be spring loaded to its closed position and is preferably a shut-off slide valve. To the bottom region of the pressure silo 10 there is connected a flexible pressure pipe 17 which in the simplest case as shown in Figures 1 to 3 is connected via a mould filling apparatus 18 (which may be of conventional form) a mould inlet in the centre of the mould part 1.

Under the influence of the compressed air 15 effective in the pressure silo 10 when the shut-off valve 16 is opened the plastics 11 is forced out of the pressure silo 10 and applied via the pressure pipe 17 and via the mould filling apparatus 18 into the hollow space 3 of the closed mould parts 1 and 2 in a quantity sufficient to fill completely this hollow space.

In the embodiment shown there is arranged in addition between the pressure pipe 17 and the pressure silo 10 an openable and closable control valve 20 which may consist of a ball cock or a rotating flap valve the valve flap 21 of which can be pivotted from the closed position shown by 90" into the open position with the aid of a switch lever 22. For actuating the lever 22 there is provided a pneumatic adjusting cylinder (not shown).

The mould filling device consists of a filling tube 25 connected to the mould inlet and along which one end 29 of a piston is movable under the control of pressure medium applied to an opposite end of the piston within a pneumatic cylinder 26. The pressure pipe 17 is connected to the filling tube via a connection piece 23.

In the embodiment shown there is provided between the automatically actuated shut-off valve 16 and the supply pipe 14 for the compressed air 15 a preferably spring loaded pressure reduction valve 33 the regulating range of which is from 0 to 6 Bar.

This pressure reduction valve is advantageously so adjusted that when the silo closure 12 is closed there is during the filling procedures in the pressure silo 10 a predetermined pressure necessary for the filling.

In operatlng the apparatus shown the following procedures running cyclically result: First of all by opening the silo closure 12 plastics from the supply tank 7 is filled into the pressure silo 10 in a quantity sufficient for several following foaming procedures.

When the silo closure 12 is brought into the closed position shown in Figure 1 the shut-off valve 16 opcns and the compressed air 15 is admitted to the pressure silo 10. As soon as the adjusted pressure is attained in the pressurc silo then with the aid of the adjusting apparatus, not shown, the valve 20 is opened so that the plastics can be introduced in the manner as can be seen in Figure 2 by the compressed air into the hollow space 3 of the mould 3, the piston end 29 of the mould filling apparatus 18 being in a retracted position in the filling tube 25 and thereby permitting feed of plastics along the connection piece 23, along the tube 25 and through the mould inlet. When sufficient plastics has been introduced into the mould, pressure medium is admitted to the cylinder 26 of the mould filling apparatus 18 so that the piston end 29 is forced into the end position shown in Figure 1 in which it closes the mould inlet flush with the inner surface of the mould.

A blow-back procedure is effected with the piston of the mould filling apparatus 18 in the retracted position as shown in Figure 3 and with the shut-off valve 16 closed and with at the same time the silo closure 12 opened, by applying compressed air to the tube 25 so that excess plastics located in the tube 25, the pressure pipe 17 and the connecting piece 23 is conveyed back into the pressure silo via the still open valve 20.

In order to avoid the condition shown in Figure 4 in which a build up of material 30 is formed in front of the mould inlet 31 and the piston end 29 is prevented from reaching its end position as shown in Figure 1 in which it closes the inlet 3 flush with the inner surface of the mould, it is arranged that pressure medium is admitted to the cylinder 26 a predetermined period of time after the blowback procedure has been initiated. The time delay is so selected that during the blow-back procedure all excess plastics is blown back fore the advance of the piston end 29 commences. For this time delay there is provided a timing device in the form of an electronic time relay known per se not shown in the drawing which after the expiry of the set delay automatically effects admission of pressure medium to the cylinder 26.

If the pressure in the pressure silo 10 provided for the filling of the plastics into the foaming mould is selected too high there is the danger that via the pressure pipe 17 in the hollow space 3 plastics will arrive in too large a quantity and with thin mould parts thickenings and bridge formations can occur inside the foaming mould. In order to avoid this and furthermore to prevent the mould inlet 31 being blocked by a material plug before the mould has been filled, in the embodiment according to Figure 5 it is arranged that in the pressure silo 10 for each mould filling apparatus 18 (up to ten may be used), a respective feed device 35 is provided with which the plastics feed pressure can be adjusted. Each feed device comprises a tube having an upper inlet 36 which is exposed to the compressed air within the silo 10 above the level of the plastics. The inlets 36 of the devices 35 have a slide valve 37 with which the cross-section of openings 38 at the inlets 36 can be varied as shown in Figures 6a and 6b. Figures 6a and 6b show the use of the valve 37 to adjust the openings 38 for three of the feed devices 35 simultaneously and uniformly. The smaller the cross-section of the openings 38 the more plastics can be drawn in at the lower pick up ends 39 of the tubes 40 which ends 39 open beneath the level of the plastics in the silo. In the position of the slide valve 37 shown in Figure 6b the openings 38 are only half open. In this case substantially less plastics is introduced into the foaming mould than in the case not shown in the drawing in which the slide valve completely covers the openings 38. In the position of the slide valve 37 shown in Figure 6a practically none or only very little plastics is picked up and introduced into the foaming mould. The slide valve 37 is coupled to a set of rods which is not shown in the drawing and is accessible externally of the pressure silo 10.

WHAT WE CLAIM IS: 1. A method for filling a mould of a moulding machine with foamable plastics, particularly polystyrene, comprising the steps of: delivering said plastics from a supply container into a pressure silo, admitting pressure medium to the silo to pressurise same to a predetermined pressure, and admitting plastics from said silo to the mould under the influence of said pressure, wherein, after filling the mould with the said plastics, excess plastics fed to the mould is blown back to the pressure silo with pressure medium.

2. A method according to claim 1, characterised in that the plastics is delivered into the pressure silo in a quantity sufficient for several mould-filling procedures.

3. A method according to claim 1 or 2, characterised in that the said admission of pressure medium to the silo to pressurise same is arrested during the said blow-back procedure.

4. A method according to claim 3,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. This pressure reduction valve is advantageously so adjusted that when the silo closure 12 is closed there is during the filling procedures in the pressure silo 10 a predetermined pressure necessary for the filling. In operatlng the apparatus shown the following procedures running cyclically result: First of all by opening the silo closure 12 plastics from the supply tank 7 is filled into the pressure silo 10 in a quantity sufficient for several following foaming procedures. When the silo closure 12 is brought into the closed position shown in Figure 1 the shut-off valve 16 opcns and the compressed air 15 is admitted to the pressure silo 10. As soon as the adjusted pressure is attained in the pressurc silo then with the aid of the adjusting apparatus, not shown, the valve 20 is opened so that the plastics can be introduced in the manner as can be seen in Figure 2 by the compressed air into the hollow space 3 of the mould 3, the piston end 29 of the mould filling apparatus 18 being in a retracted position in the filling tube 25 and thereby permitting feed of plastics along the connection piece 23, along the tube 25 and through the mould inlet. When sufficient plastics has been introduced into the mould, pressure medium is admitted to the cylinder 26 of the mould filling apparatus 18 so that the piston end 29 is forced into the end position shown in Figure 1 in which it closes the mould inlet flush with the inner surface of the mould. A blow-back procedure is effected with the piston of the mould filling apparatus 18 in the retracted position as shown in Figure 3 and with the shut-off valve 16 closed and with at the same time the silo closure 12 opened, by applying compressed air to the tube 25 so that excess plastics located in the tube 25, the pressure pipe 17 and the connecting piece 23 is conveyed back into the pressure silo via the still open valve 20. In order to avoid the condition shown in Figure 4 in which a build up of material 30 is formed in front of the mould inlet 31 and the piston end 29 is prevented from reaching its end position as shown in Figure 1 in which it closes the inlet 3 flush with the inner surface of the mould, it is arranged that pressure medium is admitted to the cylinder 26 a predetermined period of time after the blowback procedure has been initiated. The time delay is so selected that during the blow-back procedure all excess plastics is blown back fore the advance of the piston end 29 commences. For this time delay there is provided a timing device in the form of an electronic time relay known per se not shown in the drawing which after the expiry of the set delay automatically effects admission of pressure medium to the cylinder 26. If the pressure in the pressure silo 10 provided for the filling of the plastics into the foaming mould is selected too high there is the danger that via the pressure pipe 17 in the hollow space 3 plastics will arrive in too large a quantity and with thin mould parts thickenings and bridge formations can occur inside the foaming mould. In order to avoid this and furthermore to prevent the mould inlet 31 being blocked by a material plug before the mould has been filled, in the embodiment according to Figure 5 it is arranged that in the pressure silo 10 for each mould filling apparatus 18 (up to ten may be used), a respective feed device 35 is provided with which the plastics feed pressure can be adjusted. Each feed device comprises a tube having an upper inlet 36 which is exposed to the compressed air within the silo 10 above the level of the plastics. The inlets 36 of the devices 35 have a slide valve 37 with which the cross-section of openings 38 at the inlets 36 can be varied as shown in Figures 6a and 6b. Figures 6a and 6b show the use of the valve 37 to adjust the openings 38 for three of the feed devices 35 simultaneously and uniformly. The smaller the cross-section of the openings 38 the more plastics can be drawn in at the lower pick up ends 39 of the tubes 40 which ends 39 open beneath the level of the plastics in the silo. In the position of the slide valve 37 shown in Figure 6b the openings 38 are only half open. In this case substantially less plastics is introduced into the foaming mould than in the case not shown in the drawing in which the slide valve completely covers the openings 38. In the position of the slide valve 37 shown in Figure 6a practically none or only very little plastics is picked up and introduced into the foaming mould. The slide valve 37 is coupled to a set of rods which is not shown in the drawing and is accessible externally of the pressure silo 10. WHAT WE CLAIM IS:

1. A method for filling a mould of a moulding machine with foamable plastics, particularly polystyrene, comprising the steps of: delivering said plastics from a supply container into a pressure silo, admitting pressure medium to the silo to pressurise same to a predetermined pressure, and admitting plastics from said silo to the mould under the influence of said pressure, wherein, after filling the mould with the said plastics, excess plastics fed to the mould is blown back to the pressure silo with pressure medium.

4. A method according to claim 3,

wherein the mould is filled with the said plastics through an inlet to the mould and said inlet is closed after the said blow-back procedure.

5. Apparatus for use in performing the method of claim 1 comprising a supply container for plastics, a pressure silo connected to the supply container via a first passage provided with a closure device whereby plastics can be delivered from the supply container to the pressure silo only when the closure device is in an open state, a foaming mould having a mould filling device connected to the pressure silo via a second passage provided with an openable and closable control valve whereby plastics can be delivered from the pressure silo to the mould filling device only when the control valve is open, said mould filling device comprising a piston and cylinder assembly the piston of which is movable between an open position at which it permits admission of plastics via a filling tube of the filling device through a mould inlet into the mould and a closed position at which it covers said inlet, a pressurising system which is connected to the pressure silo via a supply pipe for admitting pressure medium thereto so as to pressurise same to a predetermined pressure, and means for applying pressure medium to the said filling tube after filling of the mould and whilst the piston of the filling device is in the open position thereof for blowing back excess plastics in said filling tube to said pressure silo.

6. Apparatus according to claim 5, characterised in that in said supply pipe for the pressure medium there is disposed a shut-off valve.

7. Apparatus according to claim 6, wherein the said shut-off valve is a slide valve actuated by remote control.

8. Apparatus according to claim 6 or 7, characterised in that the shut-off valve is spring-loaded to its closed position.

9. Apparatus according to any one of claims 6 to 8 characterised in that between the shut-off valve and the pressure silo there is arranged a pressure reduction valve.

10. Apparatus according to claim 9, characterised in that the pressure reduction valve has a regulating range of 0 to 6 Bar.

11. Apparatus according to any one of claims 5 to 10, characterised in that a timing device is provided which delays movement of the piston of the filling device to the closed position thereof after filling of the mould for a pre-adjustable delay time.

12. Apparatus according to any one of claims 5 to 11, characterised in that in the pressure silo there is disposed at least one feed device via which the said second passage is in communication with the pressure silo, said feed device having a pick-up tube with a lower pick-up end which opens beneath the level of plastics in the silo and an upper inlet thereto which is provided with an adjustable shut-off valve and is exposed to pressure medium above the level of plastics in the pressure silo.

13. An apparatus according to claim 12, characterised in that in the pressure silo there are disposed several said feed devices each connected via a respective said second pipe to a respective mould filling device, the said upper inlets of said feed devices being provided with a common said adjustable shut-off valve.

14. Apparatus according to claim 13, characterised in that said common valve is a slide valve operated via a set of rods which are accessible externally of the pressure silo.

15. A method and apparatus substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.