GB2024696A - Apparatus and method for the manufacture of moulded parts from foamable thermoplastic synthetic material - Google Patents

Abstract

Apparatus for moulding foamable thermoplastic synthetic materials comprises a mould having a vapour chamber (5, 5') in each half, which half- moulds (1, 2) are relatively movable apart (arrow A) and each contains a mould lining (11, 12) into which the foamable material is received, wherein each vapour chamber is closable by a plate (8, 8') movable therefrom to form a gap connecting the chamber inner space with atmosphere for heat dissipation. One or both vapour chamber frames (5, 5') may be separated from the corresponding mould frame (6, 6') for further heat dissipation. A cooling medium spray tube (3, 3') may be provided inside one or both half- moulds, preferably within the vapour chambers, and directed onto the mould linings, and also a suction blower may create cooling on one or both half- moulds. <IMAGE>

Description

SPECIFICATION Apparatus and method for the manufacture of moulded parts from foamable thermoplastic synthetic material The invention relates to a method of and apparatus for the manufacture of moulded parts from foamable synthetic thermoplastic material.

In known automatic foaming machines heat must be supplied to the mould inserts determining the outer shape of the moulded part to be made in such an amount that the foamable plastics material present in the hollow space of the mould inserts can rapidly inflate and fill up the inner hollow space. For this purpose hot vapour is introduced into the vapour chamber provided behind the mould inserts so that such inserts can be heated. For the next working cycle, firstly the halves of the mould must be closed and then the plastics materials necessary for the next foaming procedure must be blown into the hollow space of the mould. Hot vapour is then supplied to the vapour chamber of the mould and such mould can again be heated.

The invention is based on the problem of providing an apparatus for use in manufacturing foamed moulded parts having a low moisture content, wherein the heat stored in the mould halves of the mould upon termination of the heating stage can be dissipated as quickly as possible, the acceleration of the foaming procedure requiring that high moulding temperatures, and thus very hot apparatus, be utilised.

According to the invention there is proposed an apparatus for the manufacture of moulded parts from foamable thermoplastic synthetic material, with two mould halves each containing a vapour chamber, which mould halves are movable axially relative to one another, and in their closed position contact on one another on a separating plane running crosswise to the axial direction of displacement, and with two mould inserts for receiving the work material during the foaming procedure determining the outer shape of the moulded parts; characterised in that for the front side closure of the vapour chambers a cross wall is provided which forms a gap connecting the inner space of each vapour chamber with the surrounding air thereby increasing the speed of cooling and is movable axially away from the halves of the vapour chamber.

Due to the gap openable outwards it is possible to provide that the heat stored in the halves of the mould is dissipated in the shortest period of time to the surrounding air, thereby however, ensuring that the mould is already dry and sufficiently pre-heated before the next working cycle, which leads to a considerable saving of energy in respect of the media (preferably water vapour, cooling water and compressed air). In another construction of the invention, a particularly simple constructional solution follows if, for the formation of the gap, one of the two halves of the mould is divided, crosswise to its axial direction of displacement, into a moulded frame connected to one of the two mould inserts and into a vapour chamber frame closable on the front side.This front side closing of the vapour chamber frame may be achieved in a simple manner by means of a plate axially movable in respect of the vapour chamber frame. For shortening the time necessary for the cooling up to the next working cycle, there may be arranged, in a further construction of the invention, inside at least one of the two halves of the mould, preferably in both vapour chambers of the mould, a cooling medium spray pipe which contains several spray bores directed towards the separating plane of the halves of the mould; and according to a preferred method for the operation of the apparatus according to the invention, for a short time cooling water is sprayed continuously or pulsatingly onto the halves of the mould.In order to increase the expulsion, the working cycles following one another may, in a further construction of the invention, be shortened such that with one of the two halves of the mould a cooling blower is associated, which may be formed as a suction blower or pressure blower and is connected via respectively one of two valves to the inner space of the halves of the mould, preferably to the inner space of the two mould frames.

The invention is described and explained in more detail in the following with reference to embodiments which are illustrated very schematically in the drawings.

Figure 1 shows a side elevation, partly in axial section, of a first embodiment of the invention; Figures la to 6 are views similar to Figure 1, but drawn to a smaller scale, of the arrangement shown therein and in different positions thereof; Figure 7shows a side elevation, partly in axial section, of a second embodiment of the invention; Figures 8to 12 are views similar to Figure 1, but drawn to a smaller scale, and show the structure in the different operating positions thereof; and Figures 13 to 16 show the method of operation of a still further embodiment of the invention.

The foaming apparatus illustrated in Figure 1 serves for the manufacture of moulded parts from foamable thermoplastic synthetic material and has two mould halves 1 and 2 located on a rigid mould carrier, not shown. These are guided on parallel supporting rods indicated at 13 in Figure 1 and axially movable in the direction A, indicated with arrows, with the aid of piston cylinder units (main cylinder) actuated pneumatically, hydropneumatically or hydraulically, not shown, in the drawings.

In the closed position shown in Figure 1 the two mould halves 1 and 2 lie on one another with their front sides along a separating plane T running crosswise to the axis direction of displacement, A.

The left half of the mould 1 is divided into a front side closable vapour chamberframe 5 and into a mould frame 6 which at its front side facing the separating plane T receives as a press-in, not shown, the mould insert indicated at 11. To this belongs a second mould insert 12. The hollow space enclosed by the two mould inserts 11 and 12 are to be filled with the foamable thermoplastic synthetic material during a further foaming procedure described in more detail below, and-this determines the outer shape of the moulded part to be made in the two mould inserts 11 and 12.

The right hand mould insert 12 is fitted into the front side of the right hand mould frame 6' facing the separating plane T the right hand vapour chamber frame 5' contacts against this. For the front side closure of the two vapour chamber frames 5 and 5', two plates 8 and 8' are provided which extend crosswise to the direction of displacement A and may be removed from the vapour chamber frames by respectively one of two hydraulically, pneumatically, hydropneumatically or mechanically operable adjusting devices 7 and 7'.

Inside the wall of vapour chamber 5 belonging to the left half of the mould 1, is arranged a cooling medium injection pipe 3 which contains several injection bores, not shown in more detail, individually directed towards the separating plane T and the floor of the mould insert 11.

When the two halves of the mould 1 and 2 are driven towards one another foamable synthetic material from a silo, not shown, is pressed via a filling device, preferably a filling injector 14, into the inner hollow space existing between the two mould inserts 11 and 12; and the excess synthetic material is drawn back into the silo from the filling hoses, not shown. For the heating of the mould, hot vapour is introduced into the two mould vapour chambers 5, 5' by means of which it is effected that the synthetic material foams until it has filled the whole hollow space between the mould inserts 11 and 12. For the mould part which, not shown in the drawing, produced in this way there can be removed from the mould the two halves of the mould 1, 2 and the mould inserts 11, 12 respectively must be greatly cooled.

In order to accelerate considerably this cooling procedure, and thereby to be able to shorten the cycle time up to the next working cycle, cooling water is sprayed for a short time continuously or pulsatingly from the injection pipe 3, 3'. For this water cooling as shown in Figure 1 a there is connected a draining face which is effected as indicated in Figure 2 when the mould halves 1 and 2 are closed. Thereby the cooling water still contained in the mould halves 1 and 2, so far as it has not already changed into steam, is led off from the mould halves. The two mould vapour chambers 5, 5' are then removed from their appropriate mould frames 6, 6' by means of a lifting movement of the main closing cylinder.The mould frames 6, 6' are held tensioned against one another by means of the cylinder 4,4'. By the separation of the mould vapour chambers 5, 5' from their mould frames 6, 6' a larger axial annular gap is opened in the manner as can be seen in Figure 3, from which in the shortest time the quantity of heat stored in the mould half concerned can be led off to the surrounding air.

The described method brings about the further advantage that work can be done with higher mould temperature and that upon commencement of the next working cycle the phases "pre-vapouring" and "pre-blowing" can be omitted because the mould is already dry and sufficiently pre-heated, which leads to saving in energy of the media used, preferably water vapour cooling water and compressed air.

Deviating from the method described with reference to Figures 1a to Figure 3, the apparatus constructed according to the invention also, see Figure 4, allows only the right hand vapour chamber frame 5' to be removed from its mould frame 6' by means of the lifting movement of the main cylinder, whilst the two mould frames 6, 6' are held together on the left hand vapour chamber half 5 by the left hand cylinder 4. With the separation of the right hand vapour chamber 5' from its mould frame 6' then at the same time the left hand movable plate 8 is removed from the other vapour chamber half 5 by means of the left hand adjusting cylinder 7 provided therefor.By means of these annular gaps, achieved in this manner, between the right hand vapour chamber half 5' and the mould frame 6' as well as the left hand mould vapour chamber 5 and the plate 8 a delivery for a short time of the stored quantity of heat from the mould halves to the surrounding air is achieved.

In Figure 5 a reversal of the above-described method is illustrated. There, the annular groove between the left hand mould vapour chamber 5 and the mould frame 6, provides for the delivery of the heat from the left hand mould half 1. The air gap provided for the cooling of the right hand half of the mould is formed there in that the right hand plate 8' is removed from the mould vapour chamber 5' by means of the adjusting cylinder 7'.

In Figure 6 a further method for the operating of the apparatus according to Figure 1 is illustrated.

There for a short period delivery of the stored quantity of heat from the two halves of the mould 1 and 2, the right hand half of the mould 2 is held tensioned againstthe left hand half of the mould 1, whereby the two front side plates 8 and 8' are removed from the halves of the mould by means of the two adjusting cylinders 7, 7'. It is expressly pointed out however, that the method shown in Figures 4to 6 can be used in combination with water cooling according to Figure 1 and Figure la respectively, whereby the cooling phase shown there can follow a draining phase according to Figure 2, which in its time duration may be greater than or equal to zero.Furthermore, it is possible, proceeding from the cooling position illustrated in Figure 3, additionally to remove from their mould vapour chambers 5, 5' respectively the two front plates 8, 8' with the aid of the adjusting devices 7, 7' associated with them and thereby accelerate the cooling.

With the embodiments according to Figures 7 to 12, the cooling action is increased in that a common cooling blower 9 is associated with the two halves of the mould 1 and 2.

This may be formed as a suction blower or pressure blower and via two remote operable valves 10, 10' is in communication with the inner chamber of the halves of the moulds 1 and 2. In the embodiment illustrated the two valves 10, 10' are located respectively on the mould frames 6, 6'. For the remote operation of the valves 10,10' these may be coupled to existing means, not shown in detail, in the drawing, which are operable electromagnetically, hydraulically or pneumatically. With a particularly effective method for the operation of the foaming apparatus shown, with the water cooling to be carried out with the aid of the injection pipes 3, 3', a stabilizing phase may be connected in which the valves 10, 10' are opened and the blower 9 is stopped or in operation (see Figure 8).

For increasing the cooling action the two mould vapour chambers 5, 5' may be removed respectively from their mould frames 6, 6' in the manner which can be seen in Figure 9. The blower 9 then connected causes, in the opened halves of the mould, a strong turbulence with correspondingly increased cooling action.

Instead of such an opening of the two halves of the mould 1,2 or in combination with such an opening on both sides, as in Figure 9 or only a one-sided opening as in Figures 10 and 11, it is possible to raise from their mould vapour chambers 5, 5' the two front side plates 8, 8' respectively by means of the adjusting cylinders 7, 7', and to draw in with the aid of the blower 9 the ambient air in the halves of the mould through the gap thereby formed, and to draw off after taking the quantity of heat to be led off.

The foaming apparatus shown in Figure 13 corresponds in its essential parts to those previously described and serves for illustration of a further method in accordance with the invention.

In the position shown in Figure 13, directly before the initiation of the filling phase, the two half moulds 1 and 2 lie contacting one another along a separating plane T running crosswise to the axial direction of displacement A. The left hand half of the mould is divided into a front side closable vapour chamber 5, and a mould frame 6 which, upon its front side facing the separating plane T, receives as a press-in, not shown in detail, a mould insert indicated at 11.

To this belongs a second mould insert 12. The hollow space enclosed by the two mould inserts 11 and 12 are to be filled, during the further filling procedure described in more detail below, with foamable thermoplastic synthetic material, and this determines after the foaming procedure the outer shape of the moulded part, not shown in the drawing, to be produced in the two mould inserts 11 and 12.

The right hand mould insert 12 is fitted into the front side of the right hand mould frame 6' facing the separating plane T. Against this the right hand vapour chamber frame 5', which is illustrated in Figure 13 in the raised position, is brought into contact. For the front side closing of the two vapour chamber frames 5, 5' two plates 8, 8' are provided which extend crosswise to the direction of displacement A and by means of respectively one of two adjusting devices 7, 7', operable hydraulically, pneumatically, hydropneumaticaly or mechanically, are removed from the vapour chamber frames 5 and 5' or held tensioned against these.Inside the vapour chamber frame 5 belonging to the left hand half of the mould 1, is arranged a cooling injection pipe 3 which contains several injection bores, not shown individually, in more detail, directed towards the separating plane T and the bottom of the mould insert 11.

For initiating a filling phase for the two mould inserts 11 and 12 both vapour chamber frames 5, and 5', until reaching the position shown in Figure 13, are lifted from their mould frames 6 and 6' by means of a lifting movement of the main closing cylinder mentioned above. Thereby the mould frames 6, 6' are held tensioned against one another by cylinders 4 and 4' respectively with hydraulic, hydropneumatic, pneumatic or mechanical operation. Two condensation valves 16, 16' arranged on the underside of the two mould frames 5, 5' flow into their closed position. Then from a silo, not shown, the foamable synthetic material is blown in via a filling apparatus, preferably a filling injector 14, with the use of synthetic materials in bead form with filling air in the inner hollow space existing between the two mould inserts 11, 12.Due to the gap opened outwards between the vapour chamber frame 5 and the mould frames 6, 6' respectively and the vapour chamber frame 5' it is possible to allow the released filling air to flow off. Hence by suitable choice of the axial width of this gap it is possible directly, and in a simple manner, to be able to control the filling air stream laden with foamable synthetic material. In order to be able to effect the escape of the filling air from the closed mould inserts 11 and 12, there are provided in the mould inserts ventilation bores which are kept substantially smaller than the size of grain of the plastics inserted.

By means of the method described, the following further advantages are achieved over the abovementioned advantages of the unobstructed flowingoff of the released filling air; work can be done with less compressed air; a more uniform and more rapid filling of the hollow space of the mould inserts is achieved; irregular wall thicknesses inside the hollow space of the mould inserts ensure a uniform filling; with the filling of the hollow space of the mould inserts in thin wall technology, with thin wall thicknesses, the released filling air can flow off unobstructed; with the filling of the hollow space of the mould inserts, work can be done without gap at the separating joint T (Figure 1) whereby an unnecessary impression of the foamed plastic is prevented.The unobstructed flowing-off of the release filling air is advantageous in particular with the use of a pressure filling apparatus.

The method shown in Figures 14 and 15, which is based on the principle that only one of the halves of the mould 1 and 2 is opened by the lifting off of its appropriate vapour chamber frame 5 and 5' respec tivelyfrom the mould frames 6 and 6' for the forming of a gap between these two parts.

In detail according to Figure 14 it is arranged that there only the right handvapourchamberframe 5' is removed from the mould frame 6' belonging to the right hand half of the mould 2, by means of a lifting movement of the main cylinderforthe initiation of a filling phase. Thereby the mould frames 6, 6' are kept in contact on the other vapour chamber frame 5 by means of a cylinder 4 whilst at least approximately simultaneously a movable plate 8 arranged on the front side of the vapour chamber frame 5 is removed from the left hand half of the mould 1, preferably by means of an adjusting cylinder 7. The condensation valves 16, 16' remain, in contradistinction to the known method, closed.

Contrary thereto, the method for the operation of an apparatus of the above mentioned type according to Figure 15 may be carried out in the manner such that for the initiation of a filling phase, the left hand vapour chamber 5 is removed from the left hand mould frame 6 for the forming of an air gap by means of a lifting movement of the main cylinder, not shown, whereby at the same time the two mould frames 6, 6' are kept in contact on the vapour chamber frame 5' belonging to the right hand half of the mould 2 by means of a cylinder 4', whilst at the same time the movable plate 8 belonging to the right hand half of the mould 2 is removed from the vapour chamber frame 5' with the aid of the adjusting cylinder 7'. Also in this case the condensation valves 16, 16' remain closed.

The method illustrated in Figure 16 represents a modification of that according to Figure 13 in so far that with the method according to Figure 16the inner space of both halves of the moulds 1 and 2 is ventilated simultaneously, but not by mutual removal of the outer lying vapour chamber frames 5, 5', from their moulded frames 6, 6' remaining in contact with one another, but with the two movable plates 8, 8' arranged on the front side of the halves of the mould are removed by means of adjusting cylinders 7, 7' associated with them.

Claims (21)

1. An apparatus, for the manufacture of moulded parts from foamable thermoplastic synthetic material, with two mould halves each containing a vapour chamber, which mould halves are movable axially relative to one another, and in their closed position contact on one another on a separating plane running crosswise to the axial direction of displacement, and with two mould inserts for receiving the work material during the foaming procedure determining the outer shape of the moulded parts; characterised in that for the front side closure of the vapour chambers a cross wall is provided which forms a gap connecting the inner space of each vapour chamber with the surrounding air thereby increasing the speed of cooling and is movable axially away from the halves of the vapour chamber.

2. An apparatus according to claim 1, characterised in that, for the forming of the gap, at least one of the two halves of the mould, crosswise to the axial direction of displacement, is divided into a mould frame connected to one of the mould inserts and into a vapour chamber frame closable on the front side.

3. Apparatus according to claim 2, characterised in that, for the front side closing of the vapour chamber frame, a plate, movable axially in respect of this, is provided.

4. An apparatus according to claim 3, characterised in that, for the removing of the plate from the vapour chamber frame, an adjusting device operable hydraulically, pneumatically or mechanically is provided.

5. An apparatus according to claim 3 or4, characterised in that inside at least one of the two parts of the mould, preferably inside the two mould vapour chambers, a cooling medium spray tube is provided which contains several spray bores directed towards the separating plane.

6. An apparatus according to any one of claims 1 to 4, characterised in that a cooling blower is associated with at least one of the two halves of the mould.

7. An apparatus according to claim 6, characterised in that the cooling blower is formed as a suction blower.

8. An apparatus according to claim 7, characterised in that the suction blower is connected to the inner space of the halves of the mould, in particular the mould frames via respectively one of,two valves.

9. An apparatus according to claim 8, characterised in that the valves, for their remote control actuation, are coupled to adjusting means operating electromagnetically, hydraulically or pneumatically.

10. An apparatus according to any one of claims 1 to 9, characterised in that the halves of the mould are movable relative to one another on parallel supporting rods by means of pneumatic, hydropneumatic distance cylinder units.

11. A method for the operation of an apparatus according to any one of the preceding claims, characterised in that, during a cooling phase, cooling water, preferably from the spray pipe or spray pipes, is sprayed onto the halves of the mould, in particular on the mould inserts, for a short time continuously or pulsatingly.

12. A method according to claim 11, characterised in that, following the cooling phase, a draining phase is carried out which in its time course may be greater than or equal to zero, and with closed mould halves takes place according to Figure 2.

13. A method for the operating of an apparatus according to claim 3, characterised in that the mould vapour chambers are removed from the mould frames by means of the lifting movement of the main closing cylinders, for the initiation of a cooling phase, whereby the mould frames are held tensioned against one another by the cylinders with hydraulic, hydropneumatic, pneumatic or mechanical operation.

14. A method for the operating of an apparatus according to claim 3, characterised in that only one of the vapour chamber frames is removed from its mould frame by means of alifting movement of a main cylinder, whereby the mould frames are held on the vapour chamber half by means of the cylinder, and whereby at least approximately at the same time a movable plate is removed from the other vapour chamber half contacting on its mould frame preferably by means of an adjusting cylinder (see Figures 5, 6).

15. An apparatus for the operating of an apparatus according to claim 6, characterised in that, additionally to the separation, at least one of the mould vapour chambers is withdrawn from its mould frame, and/or the separation of the plate from its mould vapour chamber the stored heat is drawn off by the blower via the open valve (Figures 7-12).

16. A method for the operating of an apparatus according to any one of the claims 2 to 10, characterised in that one of the vapour chamber frames is removed from its mould frame by means of a lifting movement of a main cylinder for the initiation of a filling phase for the mould inserts, whereby both mould frames are held on the other vapour chamber frame by means of a cylinder whilst at least approximately at the same time a movable plate is removed from the other vapour chamber frame contacting on its appropriate mould frame, preferably by means of an adjusting cylinder.

17. A method according to claim 16,characterised in that both vapour chamber frames are removed from their mould frames by means of a lifting movement of the main closing cylinder for the initiation of the filling phase, whereby the mould frames are held tensioned against one another by cylinders with hydraulic, hydropneumatic, pneumatic or mechanical actuation.

18. A method for the operation of an apparatus according to claim 2, characterised in that the front side plates are removed from the halves of the mould by means of a lifting movement of adjusting devices associated with them for the initiation of the filling phase for the mould insert, whereby the two halves of the mould are held in the separating plane in mutual contact.

19. A method according to any one of claims 16 to 18, with an apparatus in which the mould halves are each provided with a condensation valve, characterised in that the two condensation valves are held closed during the filling procedure.

20. An apparatus for the manufacture of moulded parts from foamable thermoplastic synthetic material substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 6 or Figures 7 to 12, or Figures 13to 16 of the accompanying drawings.

21. A method for the manufacture of moulded parts from foamable thermoplastic synthetic material substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 6, or Figures 7 to 12, or Figures 13 to 16 of the accompanying drawings.