GB2069383A - Moulding machine - Google Patents

Abstract

A moulding machine for producing shaped parts from a mixture of solid and liquid components, comprises a frame 1 mounting a hopper 4 for a filler component 5, and a mixing device 10 carrying a hopper with a dosing means 37 for a binder component and having a feed unit 14 for the liquid component. The mixing device 10 is a double-walled vessel, defining a fluid- tightly closable mixing chamber 11 heatable by a heating fluid 34 in a cavity formed between the vessel walls. The vessel outer walls 32 are at least partly thermally insulating. The mixing device 10 has orifices 12 and 13 for feeding the solid components of the moulding mass and a discharge orifice 16 closable by a member 15 on the end of a mixing shaft 22 and driven by a motor 24. A pressurised gas is introduced into the mixing chamber 11 to discharge the finished moulding mass, upon opening of the discharge orifice 16, into a mould 36 supported on a raisable and lowerable table 2. <IMAGE>

Description

SPECIFICATION Moulding machine This invention relates to a moulding machine for producing shaped bodies, for example moulds, cores and other constructional parts, which consists substantially of a granular or powdery filler and a binder agent. The invention relates particularly to a moulding machine for carrying out a method, in the course of which the moulding mass shaped in a mould is consolidated into a shaped body ready for use in a few seconds to minutes, and as described in detail in our British Patent No. 2045132.

As is known, shaped bodies of the type initially mentioned are produced from a moulding mass which consists mainly of a granular filler and a binder. After the shaping it is necessary for the moulding mass to be hardened so that the body retains its required shape. Depending upon the nature of the binder chosen, the procedures for hardening the moulding mass, and consequently the moulding machines, vary. In addition to the thermosetting moulding masses which have been known for a long time, and which require a thermal action in order to harden, in the recent past cold-hardening moulding masses, which have better energy economy, have become known, in which the binder is hardened by passing a catalyst gas through the required moulding body.

A typical example of the machines known for this purpose is described in U.S.A.

Patent 1,264,525. This core moulding machine consists substantially of a framework with a hopper for the moulding mass, and a blowing cylinder and a gassing head, which are both alternately movable into a position above a core box secured on a raisable and lowerable work table, for the purpose of first filling the core box with moulding mass and then passing a gas through the core, in order to harden it, by means of the gassing head. Since most of these gases are toxic and also frequently highly corrosive-with respect to many materials, and therefore necessitate extensive measures to avert danger to the operatives and to render the catalyst gas nontoxic, or to eliminate it, after use, it has recently been thought desirable to avoid the use of the catalyst gas.

The self-hardening binder systems are advantageous in this respect. They consist principally of the actual binder and a catalyst or accelerator. The hardening of the binder commences as soon as the components are mixed together and is complete, for example, within a period of from 5 to 60 seconds, depending upon the quantity of catalyst liquid added. This means that after all the components have been mixed the moulding mass must be introduced into the core box or moulding box quickly before it has an opportunity to harden inside the mixing device or the blowing cylinder or shooting cylinder of the moulding machine.

Since the moulding mass is sticky, a further problem is to keep all the machine parts which have come into contact with the moulding mass clean in order to prevent faults in the operating processes which may be caused by set particles of the moulding mass. German Offenlegungsschriften 2 830 630 and 2 834 721 describe two machines which are intended for a working method using self-hardening binder systems. In their essential features they consist of a mixer, transfer means for the moulding mass, when ready for use, from the mixer to a horizontally movable blowing cylinder, a blowing head connected to the blowing cylinder or connectable to it for a work process, and a raisable and lowerable machine table to accommodate a core box.In order to avoid faults due to set particles of the moulding mass, vibrators and air nozzles are arranged on various parts of the machine and in the zone of the blowing head cleaning devices are arranged which ensure that the particularly fault-prone machine parts are cleansed of the sticky moulding mass after each operating cycle. In spite of the substantial outlay the disadvantage of parts of the sticky moulding mass remaining adhering inside the machine, hardening there and causing faults in the operating cycle, is not completely eliminated. A problem in remedying the fault arises from the fact that the hardening of the moulding mass is irreversible. It is therefore necessary for the hardened moulding mass to be removed from the machine parts by means of tools.This is extremely onerous on the one hand, and on the other hand the machine parts are not always accessible without difficulty.

A further problem arises in the production of a core, for example for foundry purposes. It is necessary to ensure that a sufficient quantity of the moulding mass is mixed in each work cycle, so that the cavity of the core box can be completely filled and the finished core is not under size. For this purpose the sand and the binder components are mixed together in a quantity which is slightly greater than the quantity required for the core. The resulting excess volume is wasted and cannot be fed back into the operating cycle because the binder sets irreversibly in an extremely short time.

German Offenlegungsschrift 2 035 951 also describes an apparatus for producing foundry moulds and cores using a self-hardening binder system, which consists substantially of two mixing conveyors for the production of a sand-resin mixture on the one hand and a sand-catalyst mixture on the other hand, and a mixing chamber with rotary mixing elements for the production of the moulding mass ready for use, including the transfer means for the pre-mixes from the mixing conveyors to the mixing chamber, whilst the mixing chamber is connectible by pipes and a valve to a compressed air vessel in order to shoot the moulding mass by compressed air out of the mixing chamber into a moulding box or core box.

In principle, this apparatus has the same disadvantages as the moulding machines described in German Offenlegungsschriften 2 830 630 and 2 834 721, with the difference that in this apparatus fewer precautions are taken to clean the machine parts which come into contact with the sticky moulding mass after each operating cycle, and consequently faults in the operating cycle occur more frequently.

The invention proposes to produce shaped bodies in the same advantageously short time as by the methods which employ a moulding mass hardening by catalyst gas, or self-hardening, and on the other hand to avoid the disadvantages which are inherent in the machines intended for these methods.

The underlying aim of the invention is to provide a moulding machine for the production of shaped parts from essentially a filler and a soluble or dispersible binder or a binder mixture by means of the method described in detail in our British Patent No. 2045132.

Accordingly, the present invention consists in a moulding machine for producing shaped parts from a mixture of components, comprising storage containers for the mixture components, a raisable and lowerable machine table for supporting a mould and a mixing device arranged above said table and having exterior walls, the mixing device having orifices for feeding the mixture components, a pressurised gas inlet, a discharge orifice for the finished moulding mass and a vertical mixing shaft provided with mixing implements, wherein the mixing device has a fluid-tightly closable mixing chamber, the exterior walls of the mixing device are made at least partly thermally insulating and wherein means are provided for heating the mixing chamber.

According to an optional feature of the invention, the mixing shaft arranged vertically within the mixing chamber is movable in the direction of its longitudinal axis and has at its lower free end a closure member which is rotatable relatively to the mixing shaft about the longitudinal axis thereof and corresponds to the discharge orifice of the mixing device.

According to a particular development of the invention, the mixing device additionally comprises a blowing chamber or shooting chamber arranged beneath the mixing chamber, which is fluid-tightly closable with reference to the mixing chamber by a closure member, and with reference to the atmosphere by a further closure.

This blowing chamber or shooting chamber is made thermally insulated and/or heatable in analogous manner to the mixing chamber.

The walls of the hopper for the granular or pulverous filler may be thermally insulated with respect to the atmosphere.

In order that the invention may be more readily understood, reference is made to the accompanying drawings which illustrate diagrammatically and by way of example embodiments thereof, and in which: Fig. 1 is a partly sectioned side elevation of a moulding machine according to the invention in an embodiment having a mixing device without blowing chamber or shooting chamber, Fig. 2 is an elevation of the moulding machine illustrated in Fig. 1, Fig. 3 is a side elevation of the heating unit illustrated in Fig. 2, and Fig. 4 is a side elevation of another embodiment of the moulding machine having a mixing device with a blowing chamber or shooting chamber.

Figures 1 and 2 show, in a preferred embodiment of the invention, a frame 1 with a machine table 2 which is raisable and lowerabie by means of a working cylinder 3. On the upper part of the frame 1 is arranged a hopper 4 for a granular or pulverous, fire-proof filler 5, which has at its lower part a closure 6 which is operable by means of a working cylinder 7. The wall 8 of the hopper 4 is so constructed that the filler 5 stored in the hopper 4 is thermally insulated relative to the atmosphere. A mixing device 10 having a mixing chamber 11 is attached to the frame 1 by means of a bracket 9.The mixing device 10 also has a feed orifice 12 for the fireproof filler 5, a feed orifice 13 for a binder with a closure 21, an inlet with a feed unit 14 for a liquid component and a discharge orifice 1 6 closable by a closure member 1 5. An inlet 1 7 for a pressurised gas (Fig.

2) is connected by a duct 1 8 and via a controllable valve 19 to a pressurised gas cylinder 20.

A mixing shaft 22 with mixing members 23 is arranged vertically within the mixing device 1 0.

The upper end of the mixing shaft 22 is connected to a driving motor 24, which is screwed firmly to a cross-member 25, which is slidable by means of guide bushes 26 on guide rods 27. For this purpose the guide rods 27 are attached vertically on the bracket 9 and connected by a yoke 28 to form a rigid frame 9;27;28. A working cylinder 29 is also attached on the yoke 28, and its piston rod 30 is pivotably attached to a further yoke 31 which rigidly connects the upper ends of the guide bushes 26. The closure member 1 5 arranged at the lower end of the mixing shaft 22 is rotatable about the axis of the mixing shaft 22, for example by means of a bearing fixed inside the mixing shaft 22.

The mixing device 10 is provided with an insulating wall 32 which thermally insulates the mixing chamber 11 relative to the atmosphere, and has according to this embodiment a heating unit 33, by means of which a liquid heating medium 34 is heated to a required temperature.

The feed unit 14 has a working cylinder 35 to open and close the inlet for the liquid component and is also connected to a pump 36, so that by means of a control system known per se, the feeding of precisely measured quantities of the liquid component into the mixing chamber 11 is possible even when the pressure in the mixing chamber 11 is higher than the atmospheric pressure.

The operation of the moulding machine so far described is explained below: After the heating medium 34 surrounding the mixing chamber 11 has been heated to the required operating temperature by means of the heating unit 33, the closure 6 is opened by an appropriate actuation of the working cylinder 7, until a quantity of the filler 5 which is necessary to produce the required shaped part and which has previously likewise been heated to the operating temperature, has passed out of the hopper 4 into the mixing chamber 11. The closure 6 then recloses the mixing chamber 11 fluid-tightly with reference to the hopper 4.At the same time, by means of a dosing unit 37 and with the closure 21 open, a quantity of pulverous substances appropriate for the quantity of filler is charged into the mixing chamber 11, and after this feeding is complete the mixing chamber 11 is closed pressure-tightly by means of the closure 21. These pulverous substances may be soluble or dispersible binders or mixtures of these binders or mixtures of one or more binders with additives for specific purposes. According to another procedure, the feeding of the pulverous substances may occur after that of the filler, for example, if the filler stored in the hopper 4 is required to be heated to the required operating temperature in the mixing chamber 11 initially.

But it is also possible in this case to feed the two components simultaneously into the mixing device 10.

Immediately after the feeding of the filler and of the pulverous substance/s, the mixing chamber 11 is loaded with a pressurised gas from the pressurised cylinder 20 by controlling the valve 19, until the required operating pressure in the sense of the method described in our British Patent No. 2045132 has been adjusted in the mixing chamber 11. Then, or also at the commencement of the pressure loading, by switching on the pump 36 and simultaneously actuating the working cylinder 35 in the sense that the feed unit 14 is opened, the liquid component of the moulding mass is injected into the mixing chamber 11. The requisite quantity can be controlled by the duration of actuation of the pump 36 and of the working cylinder 35.After the feeding of the liquid component, which according to the procedure adopted is a solvent or a dispersing agent for the binder or binder mixture previously charged into the mixing chamber 11, is complete, the feed unit 14 is immediately closed in order to prevent the liquid from after-running, and the pump 36 is stopped.

In order to achieve a certain degree of distribution during the actual feeding of the individual components, and to reduce the time for the preparation of the moulding mass, it is convenient to set the mixing shaft 22 in rotation by means of the driving motor 24 from the commencement of feeding the individual components. During the operation of the moulding machine hitherto described, the mixing shaft 22 with its closure member 1 5 mounted rotatably in its lower end face occupies the vertical position illustrated in Fig. 1. In this position the closure member 1 5 fluid-tightly seals the discharge orifice 1 6 of the mixing device 10.

During the above-described work stages, a mould 38 fixed on the machine table 2 and having a mould cavity 39 which corresponds to a moulding 40 to be produced, has been raised by means of the working cylinder 3 from a lower position of readiness into the position illustrated in Fig. 1 and brought into sealing contact with the mixing device 10.

As soon as the components fed into the mixing chamber 11 have been mixed to form a moulding mass ready for use, the driving motor 24 is raised with the mixing shaft 22 and with the closure member 1 5 by the working cylinder 29, so that the moulding mass ready for use is blown or shot through the discharge orifice 16, which is now open, into the mould cavity 39 by the effect of the excess pressure prevailing in the mixing chamber 11. The valve 1 9 still connects the pressurised gas cylinder 20 to the mixing chamber 11 during this work stage. This is convenient, on the one hand in order to compensate possible pressure losses, and on the other hand in order to achieve a "shot-like" emptying of the mixing device 10.After this the valve 1 9 is switched so that the mixing chamber 11 communicates with the atmosphere and the pressurised gas can escape. The machine table 2 with the mould 38 can now be moved downwards, and the moulding 40 which has been consolidated in the meantime can be removed from the mould 38. For the next operating cycle, the driving motor 24 is moved down again with the mixing shaft 22 and with the closure member 15, and the discharge orifice 1 6 is closed.

Another embodiment of the moulding machine according to the invention is illustrated in Fig. 4. It is advantageous if the production of the moulding mass and the charging of the moulding mass ready for use into the mould are required to take place relatively mutually independently for operational reasons. This may be the case, for example, if the volume of the shaped part to be produced is greater than the volume of a mixing batch, and it is necessary to "collect" two or more batches of moulding mass ready for use in the first instance.

For this purpose a shooting vessel 41 is arranged beneath a mixing device 1 0a, with a fluid-tightly sealable shooting chamber 42 which can be shut off from a mixing chamber 11 a by a slide closure 43. This shooting chamber 42 tapers downwards towards a discharge orifice 44 and has a closure member 45 which corresponds to the discharge orifice 44 and is actuated by a working cylinder 46. The shooting chamber 42 is connectible to a pressurised gas cylinder 20a by a pressurised gas line 47 having a valve 48. The shooting vessel 41 is constructed as a doublewalled vessel with insulating external walls and with a jacketing space 49 surrounding the shooting chamber 42 and containing a heating fluid and a heating unit, not shown in detail.

In contrast to the embodiment of Figures 1 to 3, the mixing shaft 22a and also the driving motor 24a are fixed axially and the mixing shaft 22a has a free lower end. The operation corresponds substantially to that described for the exemplary embodiment of the invention illustrated in Figures 1 to 3. After the mixing process in the fluid-tightly sealed mixing chamber 11 a is complete, the moulding mass ready for use is charged, by opening the slide closure 43, into the shooting chamber 42, after a pressure which corresponds to the pressure prevailing in the mixing chamber 11 a has previously been generated in the shooting chamber 42 by appropriate actuation of the valve 48, and the required operating temperature has been adjusted in the shooting chamber 42 by appropriate heating of the heating liquid present in the jacketing space 49.The slide closure 43 is then moved back into the closed position. A batch of moulding mass ready for use can now be produced once more in the mixing chamber 11 a in accordance with the procedure already described and, if this is intended, charged into the shooting chamber 42 with the first batch by opening the slide closure 43. As soon as a quantity of the moulding mass sufficient for a shaped part is available in this way, after closing the slide closure 43 the closure member 45 is opened by means of the working cylinder 46, so that the moulding mass is charged by the action of the pressurised gas present in the shooting chamber 42 into the mould 38a pressed against the shooting vessel 41.

If the quantity of one batch of the moulding mass is sufficient to produce a shaped part, then the moulding mass may be charged directly into the mould after transfer into the shooting chamber 42 and closing the slide closure 43. This shows a further advantage of this embodiment of the invention. It permits an exchange of the moulds relatively independent of the size of the mixing device 1 Oa, and is suitable for plants which produce shaped parts of a wide range of sizes.

Claims (12)

1. A moulding machine for producing shaped parts from a mixture of components, comprising storage containers for the mixture components, a raisable and lowerable machine table for supporting a mould and a mixing device arranged above said table and having exterior walls, the mixing device having orifices for feeding the mixture components, a pressurised gas inlet, a discharge orifice for the finished moulding mass and a vertical mixing shaft provided with mixing implements, wherein the mixing device has a fluid-tightly closable mixing chamber, the exterior walls of the mixing device are made at least partly thermally insulating and wherein means are provided for heating the mixing chamber.

2. A moulding machine as claimed in claim 1, wherein the mixing device is constructed at least in part as a double-walled vessel and a heating unit is arranged in the cavity thereby formed.

3. A moulding machine as claimed in claim 2, wherein the cavity is filled with a heating fluid.

4. A moulding machine as claimed in any of the preceding claims, wherein the mixing chamber tapers downwards towards the discharge orifice of the mixing device.

5. A moulding machine as claimed in any of the preceding claims, wherein an inlet orifice with a feed unit for a liquid mixture component is arranged in the lower part of the wall of the mixing chamber adjacent the discharge orifice.

6. A moulding machine as claimed in any of the preceding claims, wherein the mixing shaft is axially movable and has at its lower end a closure member rotatable about the axis of the shaft and relatively thereto, said closure member corresponding to the discharge orifice of the mixing device.

7. A moulding machine as claimed in any of the preceding claims, wherein a shooting vessel, which has a fluid-tightly closable shooting chamber connectible to the mixing chamber and to a pressurised gas cylinder, is arranged beneath the mixing device and is firmly attached thereto.

8. A moulding machine as claimed in claim 7, wherein the shooting vessel is a double-walled vessel having a jacketing space surrounding the shooting chamber and filled with a heating fluid, said jacketing space containing a heating unit and the exterior walls of the shooting vessel being of insulating construction.

9. A moulding machine as claimed in claim 7 or 8, wherein the shooting chamber has a discharge orifice and tapers downwards towards the discharge orifice.

10. A moulding machine as claimed in any of claims 7 to 9, wherein a closure member which corresponds to the discharge orifice of the shooting chamber and is actuable by a working cylinder is arranged within the shooting chamber.

11. A moulding machine as claimed in any of the preceding claims, wherein one storage container serves for storing a filler component and is constructed as a thermally insulated container.

12. A moulding machine, substantially as herein described with reference to and as shown in Figs. 1 to 3 or Fig. 4 of the accompanying drawings.