AU1115395A

AU1115395A - Die casting machine

Info

Publication number: AU1115395A
Application number: AU11153/95A
Authority: AU
Inventors: Peter Harrison
Original assignee: REDMAN E M B Ltd
Current assignee: Emb-Redman Ltd
Priority date: 1993-12-03
Filing date: 1994-12-02
Publication date: 1995-06-19
Also published as: GB9324820D0; EP0682573A1; WO1995015235A1

Description

DIE CASTING MACHINE

This invention relates to a die casting machine, and in particular to an "inclined", pressure die casting machine.

In this specification, the pressure die casting machine is considered in two parts; the "mould side" refers to the platens, tie bars and dies, the "injection side" refers to the reservoir for the molten metal, the nozzle, the gooseneck, and the plunger and ram assembly for delivering the molten metal to the mould.

BACKGROUND TO THE INVENTION

Pressure die casting is the injection of molten metal or plastic under high pressure into a mould cavity. For simplicity, the following description concerns apparatus and method to produce metal castings; the apparatus and method to form plastics castings is similar.

Prior to injection of the molten metal into the cavity, the mould is "closed" i.e. the two halves of the mould, called dies, are brought together; thereafter the dies are held together whilst the molten metal is forced into the cavity they form. The metal is allowed to solidify, to the shape of the mould cavity; and then the dies are pulled apart so that the solidified object can be ejected and the cycle repeate .

To simplify the clamping arrangement for holding the dies together, known apparatus utilises a die casting machine which has one die mounted upon a fixed platen, so that it remains stationary relative to the machine, and the second die is mounted to a movable platen, so that it is movable into and out of engagement with the fixed die.

The movable platen has the movement and control apparatus; the fixed platen has the injection apparatus.

Aluminium and copper alloys which attack and erode machine parts with which they are in constant contact are usually made in a so-called cold chamber machine, whilst tin, lead and zinc die castings are usually produced in a so-called hot chamber machine. This invention will principally be used on a hot chamber pressure die casting machine, and the use on such a machine is discussed below.

A class of hot chamber machines, hereinafter referred to as "inclined" pressure die casting machines are becoming increasingly common. In these machines, the mould side is mounted to the machine base at an incline (typically five degrees), the fixed platen being lower than the movable platen. The reasons for an incline are {1} since the cast article is typically ejected from the die attached to the movable platen, which die faces slightly downwardly at the inclined angle, the action of gravity increases the tendency of the article to become free of the die, so that the incline allows a more reliable ejection of a cast article; and {2} that it reduces the likelihood of molten metal dripping from the nozzle as the mould is opened, since the axis of the nozzle, and the path of molten metal through the nozzle, is directed upwardly at the inclined angle.

However, the injection side of these machines is not inclined; the surface of the molten metal in the reservoir will always remain horizontal, and furthermore it is advantageous to retain the vertical action of the injection ram assembly.

Amongst the many requirements which a pressure die casting machine must satisfy is a first requirement to provide accessibility to the nozzle, and this can only be achieved by separating the nozzle from the fixed platen. It is necessary to access the nozzle, both for maintenance of the nozzle and to replace it if necessary.

Manufacturers of inclined pressure die casting machines have come to recognise the problem associated with this first requirement, since the nozzle is connected to the injection side, which is not inclined, and yet fits into an aperture in the fixed platen, which is inclined.

It is known that the standard injection-efficient conical form of the nozzle requires that the nozzle may not only be separated from, but also brought together with, the fixed platen along the path of its axis i.e. at the inclined angle of the machine.

A second requirement for pressure die casting machines is a facility for alteration in the vertical position of the nozzle relative to the fixed platen i.e. relative to the dies. Some moulds require central molten metal injection, whereas other moulds require below-centre molten metal injection.

Thus, for a multi-mould facility it is necessary that the height of the nozzle can be altered, and thus that the height of injection side relative to the dies, can be altered.

DESCRIPTION OF THE PRIOR ART

Known inclined pressure die casting machines achieve the first and second requirements outlined above by moving the mould side, whilst the injection side, including the nozzle, remains stationary relative to the machine base. In order to access the nozzle, for repair or replacement, the fixed platen must be moved. In the known machines this is achieved by moving not just the fixed platen, but the whole of the mould side of the machine. The first and second fixed platens are mounted upon inclined rails, so that these platens, the tie bars connected therebetween, and the movable platen carried by the tie bars, can be moved, as a single unit, towards and away from the nozzle.

This known arrangement thus requires the movement of a large and heavy section of the machine, which is expensive both in terms of time and energy. The manufacture of the rails, and of the cooperating mounting parts of the fixed platens, requires considerable accuracy to prevent any potentially damaging distortion of the tie bars during movement of the mould side.

The second requirement is achieved in the known machines by having a machine base to which the injection side and the mould side are independently connected; the mould side, mounted upon its inclined rails, can be moved vertically up or down relative to the injection side, as required. This again has the disadvantage that the movement of a large and heavy section of the machine is necessary, and must be strictly controlled. Another disadvantage is that the independent connections of the injection side and the mould side to the machine base must be essentially rigid, since the high pressure of molten metal entering the mould will act to force the injection side away from the mould side.

STATEMENT OF THE INVENTION

In order to overcome or reduce the effect of the disadvantages outlined above, we disclose an inclined pressure die casting machine wherein the mould side remains in place, and part of the injection side, including the nozzle, is able to move relative to the machine base, i.e "towards and away from" the mould side.

Thus we provide an inclined pressure die casting machine having a base, securement means for mounting a set of dies, movement means for moving the dies relative to one another, a reservoir for molten metal, and an injection means for injecting molten metal between the dies, characterised by driving means for moving the injection means relative to the base, the driving means having a first part fixed relative to the machine base and a second part engageable with a part of the injection means.

Preferably, the injection means comprises an injection unit mounted upon at least one carrier. Preferably also the injection unit comprises a plunger, a ram assembly, a gooseneck and a nozzle; in use the ram assembly acts upon the plunger to force molten metal around the gooseneck and through the nozzle. Desirably, the injection unit is mounted upon a pair of carriers, one carrier being to each side of the injection unit, each carrier being slidably engaged by a fabricated assembly fixed relative to the machine base, the carrier and fabricated assembly having sliding engagement parts oriented at the inclined angle of the machine.

Usefully, the driving means comprises a pair of piston and cylinder assemblies and pair of levers, the piston rod of each piston and cylinder assembly being connected to one of the opposed ends of a respective lever, the other of the opposed ends of the lever engaging one of the carriers, each lever being pivotable about an axis between its opposed ends. Usefully also the cylinder is secured to the machine base. Whilst the piston and cylinder assemblies are usefully hydraulic, pneumatic operation is alternatively possible.

Conveniently, the injection unit is mountable upon the carriers at a plurality of (vertically) spaced positions, so that the injection unit may be mounted at differing (vertical) positions relative to the carrier, and thus relative to the machine base. BRIEF DESCRIPTION OF THE DRAWINGS

Fig.l is a schematic side view of an inclined pressure die casting machine;

Fig.2 is a side view, partly in section, of part of the machine of Fig.l

Fig.3 is a fabricated assembly for the machine of Fig.l; and

Fig.4 is an end view of part of the injection unit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The pressure die casting machine 10 of Fig.l comprises an end wall carrying a first fixed platen 12, a second fixed platen 14, and a movable platen 16. Rigidly connected between the fixed platens 12,14 are tie bars 20, upon which the movable platen is slidably guided.

The movement means of this embodiment is a toggle mechanism 22 arranged between the first fixed platen 12 and the movable platen 16, and which drive the movable platen towards and away from the second fixed platen 14 in known fashion. The dies are replaceably attached by securement means (not shown). Thus attached to the movable platen is a first die 24, whilst attached to the second fixed platen is a second die 26. When the dies are clamped together they form a mould cavity into which molten metal may be injected, and allowed to cool and solidify into the die-cast article.

The molten metal is contained in a reservoir 30; an injection unit 32, comprising a ram assembly 42, a plunger 40, a gooseneck 44 and a nozzle 46 (Fig.2), is adapted to force molten metal into the mould cavity, in known fashion.

Thus, in the embodiment shown, the "mould side" comprises the fixed platens 12,14, the movable platen 16, the tie bars 20, toggle mechanism 22, and the fitted dies 24,26; the "injection side" comprises the reservoir 30, the ram assembly 42, plunger 40, gooseneck 44 and nozzle 46.

The machine 10 has a inclined mould side, i.e. the mould side is at an inclined angle α to the horizontal, and to the injection side.

As particularly shown in Fig.2, the reservoir 30 contains the molten metal to be cast; the reservoir though shown open can be a covered container. The molten metal will flow through aperture 34 into chamber 36; in this preferred embodiment the aperture 34 is below the surface level of the molten metal, so that floating scum and the like is inhibited from entering the chamber 36. A plunger 40, driven downwardly by ram assembly 42, forces molten metal around the gooseneck 44, through the nozzle 46, and into the mould (not shown in this figure).

In accordance with the invention, the injection unit 32 comprising the nozzle 46, gooseneck 44, and ram assembly 42, is mounted upon a carrier 50, the carrier having a projecting portion 52 (see also Fig.4) inclined at the angle α to the machine base 11 i.e. to the horizontal.

The projecting portion 52 has a lateral recess 54, which accepts one end 60 of an operating lever 62. In an alternative embodiment the body part of carrier 50 receives the lever 62. The lever can rotate about pivot 63, which is secured to a bracket 64; the bracket 64 is fixed relative to the machine as described below. The arcuate movement of the lever end engaging the recess 54 can follow the inclined movement of projecting portion 52 so that this projecting portion can be of reduced vertical dimension.

The opposed end of the lever 62 is pivotally connected to a piston rod 66, the piston of which is slidably mounted inside a hydraulic operating cylinder 68 positioned adjacent the upper edge of the second fixed platen 14, and thus is secured to the machine base 11. It will be understood that the cylinder 68 is some distance above the reservoir 30, and so is substantially unaffected by heat (radiant and convective) from the molten metal contained therein.

Thus, the piston and cylinder assembly and lever comprise the driving means, the cylinder 68 being the first part of the driving means, connected to the machine base 11, the end 60 of the lever 62 being the second part, engageable with the carrier 50 of the injection means.

A fabricated assembly 70 (Fig.3) is secured to each side of the fixed platen 14, one to either side of the injection unit (see Fig.4). Each fabricated assembly carries a channel member 72 with a channel 73 inclined at the angle α, and adapted to be slidably engaged by the projection 52 of the injection unit. The channel member 72 is secured to the fabricated assembly 70 by recessed bolts 74; in an alternative embodiment, the channel member is welded to the fabricated assembly; and in yet a further embodiment the recessed bolts 74 secure a low friction material to the channel member, to assist in the sliding movement of the projection 52.

In the embodiment shown, the fabricated assembly 70 carries the bracket 64 to which the lever 62 is pivotally attached; in other embodiments, the bracket is secured directly to the machine base. It will be understood therefore that the only structural connection between the injection unit and the remainder of the machine is by way of the pair of inclined projections

52 which are slidably received in the respective inclined channel members 72.

The introduction of working fluid into, or the removal of working fluid from, the hydraulic operating cylinder 68 will cause pivoting of the lever 62 (about pivot 63), driving the whole of the injection unit respectively up or down (as drawn) the inclined channel 72. Since the axis of nozzle 46 is inclined at the angle α, and the nozzle projects through a similarly inclined aperture 15 in the fixed platen 14, the movement of the injection unit "down" the channel (i.e. towards the bottom right in Fig.2 and 3), will permit withdrawal of the nozzle 46 from the platen aperture, permitting nozzle maintenance or replacement.

It will be understood that the reservoir 30 is not part of the injection unit, i.e. it is connected to the machine base and not to the carrier 50. Thus, the lower portion of the injection unit (the chamber 36 and part of the gooseneck 44), is submerged in the reservoir, and free to move therein (between predetermined limits of travel).

As seen from Fig.4, one fabricated assembly 70 is mounted to either side of the injection unit 32, with the respective channel members 72 facing towards one another, the projections 52 of each of the two carriers 50 facing outwardly, each engaging a respective channel member. In accordance with a further feature of this invention, each carrier 50 has two recesses 76 in its face opposed to the projection 52. The recesses 76 are of square section, and are sized to accept a lip 78 attached to a part of the ram assembly 42.

The opposed lips 78 can be located respectively in either of the facing pair of recesses 76, so that the hydraulic ram assembly, and thus the injection unit, can be mounted at a different vertical position relative to the carrier. This may be necessary if a different second fixed platen or second die is used, with the nozzle required to enter the mould at a different height. In other embodiments, more recesses 76 can be provided, as required.

In the embodiment shown, pressure is required to be maintained in the hydraulic operating cylinder 68 in order to retain the nozzle 46 in its normal condition i.e. in engagement with and/or projecting through the second fixed platen 14; the pressure required may be considerable, for instance to withstand the forces from molten metal in the mould, and the piston seals may leak without the operator becoming aware of this failure. In another embodiment therefore, the injection unit after positioning may be locked into position e.g. into the normal "moulding" position shown in Fig.2, as by bolts securing the injection unit relative to the machine base; the hydraulic operating cylinder is in this embodiment only required to be placed under pressure for nozzle maintenance or replacement.

Claims

1. A pressure die casting machine (10) which includes a base (11), and a nozzle (46) for supplying working fluid between a pair of dies (24,26) mounted to the base, characterised by driving means (62,66,68) to move the nozzle relative to the base.

2. An inclined pressure die casting machine (10) which includes a base (11), securement means for mounting a set of dies to the base, movement means (22) carried by the base adapted to move the dies relative to one another, a reservoir (30) carried by the base to hold working fluid, and injection means including a nozzle (46) for injecting working fluid between the dies characterised by driving means (62,66,68) to move the injection means relative to the base and at an inclined angle (α) relative thereto, the driving means having a first part (68) connected to the base and a second part (62) in driving engagement with the injection means.

3. An inclined pressure die casting machine (10) according to claim 2 characterised in that the injection means comprises an injection unit which includes a chamber (36), a connection (44) between the chamber and the nozzle, a plunger (40) movable in the chamber to eject working fluid into said connection and to the nozzle and a ram assembly (42) adapted to operate the plunger.

4. An inclined pressure die casting machine (10) according to claim 3 characterised in that part of the chamber is within the reservoir, in that said part of the chamber has an opening (34) to the reservoir closable by the plunger (40), and in that the chamber has a connection to the nozzle by way of a goose-neck (44).

5. An inclined pressure die casting machine (10) according to claim 3 characterised in that the ram assembly (42) is moved by said driving means (62,66,68), in that the driving means comprises a pair of piston (66) and cylinder (68) assemblies and a pair of levers (62), the levers having opposed ends, the piston rod of each piston and cylinder assembly being connected to one of the opposed ends of a respective lever, the other (60) of the opposed ends of the lever being engageable with the injection unit.

6. An inclined pressure die casting machine (10) according to claim 3 in which the injection unit is mounted to a pair of carriers (50), one carrier being to each side of the injection unit, each carrier being slidably engaged with the machine base at said inclined angle.

7. An inclined pressure die casting machine (10) according to claim 6 characterised in that the machine base carries a pair of facing channel members (72), each channel member having a channel (73) at said inclined angle, each carrier having a projecting portion (52) engaged within a respective channel, and in that the driving means is in driving engagement with said projecting portion.

8. An inclined pressure die casting machine (10) according to claim 6 or claim 7 characterised in that the carrier has first and second recesses (76) providing vertically spaced mounting positions for the injection unit, the injection unit having opposed lips (78) mounted in said first and second mounting positions to alter the height position of the nozzle relative to the machine base.

9. An inclined pressure die casting machine (10) according to claim 2 in which the working fluid is molten metal, and in that the machine is a hot chamber machine.

10. An inclined pressure die casting machine (10) according to claim 2 in which the inclined angle is in the range three to seven degrees, preferably five degrees.