IE83557B1 - A method and a mould for moulding an article - Google Patents

Description

“A method and a mould for moulding an article” The present invention relates to a method and a mould for moulding an article, and in particular, though not limited to a method and a mould for die casting an article using a pressure die casting method whereby the article may be die cast from aluminium, lead, zinc or any other suitable metal.

Methods and moulds for die casting articles from aluminium, lead and/or zinc are well known. In general, the mould is placed in a pressure die casting press which is provided with a pair of platens, one of which is moveable and the other is fixed. The mould, in general, comprise a pair of main dies, one of which may or may not carry a pair of secondary dies. The main dies are mounted one on the fixed platen, and one on the moveable platen. The die on the fixed platen is generally referred to as the fixed main die and the other the moveable main die. The secondary dies are generally slideably mounted on the moveable main die and are arranged so that as the moveable main die is moved towards the fixed main die by the moveable platen, the secondary dies which are located on the moveable main die between the two main dies are moveable towards each other into a closed position. In the closed position the secondary dies engage each other and the respective main dies, and define with the main dies a mould cavity. The mould cavity is then charged with molten aluminium, lead or zinc or other metal as the case may be for forming the article. On the article being moulded and solidifying within the mould cavity the moveable platen is moved for opening the mould so that the moveable main die with the secondary dies mounted thereon is moved apart from the fixed main die and the secondary dies are simultaneously moved apart for opening the mould for removing the article.

In general, one of the main dies, typically the moveable main die is a predominately more male die than the fixed main die, which generally is a predominately female die. In general, as the moulded article commences to solidify it contracts onto the predominately more male die. Thus, as the mould is opened the moulded article having contracted onto the predominately more male die remains thereon and moves with the male die. In order to remove the moulded article from the male die it is necessary to provide ejector pins in the male die which as the mould is approaching the fully open position are urged outwardly of the male die into engagement with the moulded article for urging the article from the male die.

While such ejector pins are adequate for removing the moulded article from the mould, they suffer from a number of disadvantages, firstly, by virtue of the fact that the ejector pins must be mounted in the male die for extending outwardly thereof, they in general, are slideably mounted in corresponding bores in the male die. In order to facilitate sliding of the ejector pins in the bores, a sliding clearance is required. Molten metal in the mould cavity being under ‘pressure is urged into the clearance around the ejector pins. This, thus, subsequently leads to the formation of a flash on the moulded article. A further problem with such ejector pins is that generally the mould is opened before the moulded article is completely cured, and when engaged by the ejector pins, distortion of the moulded article may occur or ejector pin marks may be formed in the moulded article. These are all significant disadvantages of current known moulding methods and moulds. The formation of a flash requires subsequent machining of the component to remove the flash where subsequent machining might not othenivise have been required. Furthermore, the flash, in general, having been formed by the male die, are formed on an inner surface of the moulded article, thus leading to difficulty in machining the flash from the moulded article. Additionally, since the flashes and ejector pin marks are generally formed on the inner surface of the moulded article, and in general, the inner surface is a high precision surface, high precision machining is required on the inner surface, which can be difficult to carry out and would not otherwise be required.

Distortion of a moulded article, in general leads to the article being subsequently rejected.

There is therefore a need for a method and a mould for moulding an article which overcomes these problems.

The present invention is directed towards providing such a moulding method and a mould.

According to the invention there is provided a method for moulding an article in a mould having a first main die which is a predominately male die, and a second main die which is a predominately female die co-operable with the first main die for forming a mould cavity which defines the moulded article, one of the first and second main dies being moveable relative to the other between a closed position of the mould with the two main dies forming the mould cavity and a spaced apart open position of the mould for facilitating removal of the moulded article from the mould cavity, the method comprising the steps of providing a grip means co-operable with a grip means accommodating bore extending into the second main die from the mould cavity, the grip means being slideable in the grip means accommodating bore between a gripping position corresponding to the closed position of the mould for gripping a portion of the moulded article and retaining the moulded article in the second main die, and a disengaging position corresponding to the open position of the mould for disengaging the moulded article, charging the mould cavity with the material to be moulded into the moulded article when the first and second main dies are in the closed position and the grip means is in the gripping position, urging the moveable one of the first and second main dies to the open position when the moulded article is just cured, and moving the grip means from the gripping position to the disengaging position as the moveable one of the first and second main dies is being urged from the closed position to the open position, so that as the moveable one of the first and second main dies commences movement from the closed to the open position, the moulded article is disengaged from the first main die, and on further movement of the moveable one of the first and second main dies towards the open position the moulded article disengages the second main die.

The terms “a predominately male die" and “a predominately female die” are used to describe dies which are mainly male type dies, or female type dies, respectively. For example, a predominately male die would be a die in which the majority of the characteristics, and overall general shape of the die would be male. Such a die could include female characteristics, however, the predominate characteristics however, the predominate characteristics would be of a male type nature. A predominately female die would be the opposite to a predominately male die, and could include some male characteristics, although, the predominate characteristics would be of a female nature.

In one embodiment of the invention the grip means disengages the moulded article from the second main die in the disengaging position. in one embodiment of the invention the grip means co—operates with the grip means accommodating bore for forming the portion of the moulded article to be gripped by the grip means in the grip means accommodating bore.

Preferably, the grip means is shaped adjacent the mould cavity for gripping the portion of the moulded article to be gripped.

Ideally, the grip means is hook-shaped adjacent the mould cavity for forming a corresponding hook-shaped portion on the moulded article in the grip means accommodating bore for co—operating with the hook-shaped portion of the grip means while the hook—shaped portion of the moulded article formed in the grip means accommodating bore is in the grip means accommodating bore.

Advantageously, the grip means comprises an elongated grip pin slideable in the grip means accommodating bore, the grip pin being moveable from the gripping position within the grip means accommodating bore to the disengaging position extending from the grip means accommodating bore into the mould cavity for disengaging the moulded article, and for acting as an ejector pin for disengaging the moulded article from the second main die.

In one embodiment of the invention the grip means accommodating bore is located in the second main die for forming the portion of the moulded article to be gripped by the grip means on a non-precision surface of the moulded article, or on a surface to be subsequently machined.

Additionally the invention provides a mould for moulding an article, the mould comprising a first main die which is a predominately male die, and a second main die which is a predominately female die co—operable with the first main die for forming a mould cavity which defines the article to be moulded, one of the first and second main dies being moveable relative to the other between a closed position of the mould with the two main dies forming the mould cavity, and a spaced apart open position of the mould for facilitating removal of the moulded article from the mould cavity, and a grip means co—operable with a grip means accommodating bore extending into the second main die from the mould cavity, and being slideable in the grip means accommodating bore from a gripping position corresponding to the closed position of the mould for gripping a portion of the moulded article and retaining the moulded article in the second main die, to a disengaging position corresponding to the open position of the mould for disengaging the moulded article, the grip means being moveable from the gripping position to the disengaging position as the moveable one of the first and second main dies is being moved from the closed position to the open position, so that as the moveable one of the first and second main dies commences movement from the closed position to the open position the moulded article is disengaged from the first main die, and on further movement of the moveable one of the first and second main dies towards the open position, the moulded article is disengages from the second main die by the grip means.

In one embodiment of the invention the grip means disengages the moulded article from the second main die when the grip means is in the disengaging position.

Ideally, the grip means co—operates with the grip means accommodating bore for forming the portion of the moulded article to be gripped by the grip means in the grip means accommodating bore.

In one embodiment of the invention the grip means is shaped adjacent the mould cavity for gripping the portion of the moulded article to be gripped.

Ideally, the grip means is hook—shaped adjacent the mould cavity for forming a corresponding hook—shaped portion on the moulded article in the grip means accommodating bore for co-operating with the hook—shaped portion of the grip means while the hook—shaped portion of the moulded article formed in the grip means accommodating bore is in the grip means accommodating bore.

In another embodiment of the invention the grip means comprises an elongated grip pin slideable in the grip means accommodating bore, the grip pin being moveable from the gripping position within the grip means accommodating bore to the disengaging position extending from the grip means accommodating bore into the mould cavity for disengaging the moulded article, and for acting as an ejector pin for disengaging the moulded article from the second main die.

Preferably, the grip means accommodating bore is located in the second main die for forming the portion of the moulded article to be gripped by the grip means on a non—precision surface of the moulded article, or on a surface to be subsequently machined.

In one embodiment of the invention the first main die is a fixed die, and the second main die is a moveable die.

In a further embodiment of the invention the method is for die casting the article, and ideally, is for die casting the article from zinc, lead and/or aluminium.

Further the invention provides an article moulded by the method according to the invention, and the invention also provides an article moulded in the mould according to the invention.

The invention will be more clearly understood from the following description of some preferred embodiments thereof which are given by way of example only with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of a component moulded using a mould, Fig. 2 is a transverse cross-sectional side elevational view of the component of Fig. ‘I, Fig. 3 is a side elevational view of a pressure die casting press for use in moulding the component of Fig. 1, (\J Uh Fig. 4 is a transverse cross-sectional side elevational view of a mould for moulding the component of Fig. 1, Fig. 5 is a transverse cross-sectional side elevational view of the mould of Fig. 4 in a different position, Fig. 6 is a transverse cross-sectional plan view of the mould of Fig. 4 on the line Vl—Vl of Fig. 4, Fig. 7 is a transverse cross-sectional plan view of the mould of Fig. 4 on the line Vll—Vll of Fig. 5, Fig. 8 is a view similar to Fig. 6 of the mould of Fig. 4 in a slightly different position to that of Fig. 6, Fig. 9 is a view similar to Fig. 6 of the mould of Fig. 4 in a still further different position, Fig. 10 is a perspective view of a part of the mould of Fig. 4, Fig. 11 is a perspective view of another part of the mould of Fig. 4, Fig. 12 is a front elevational view of the part of the mould of Fig. 10, Fig. 13 is a front elevational view of the part of the mould of Fig. 11, Fig. 14 is a transverse cross-sectional plan view of a detail of the mould of Fig. 4 on the line XIV-XIV of Fig. 4, Fig. 15 is an end elevational view of the detail of Fig. 14 of the mould of Fig.

Fig. 16 is a top perspective view of a component moulded in a mould according to a first embodiment of the invention, Fig. 17 is an underneath perspective view of the component of Fig. 16, Fig. 18 is a transverse cross—sectional side elevational view of the component of Fig. 15 on the line XVlll—XV||l of Fig. 17, Fig. 19 is a transverse cross—sectional side elevational view of a mould according to the invention for moulding the component of Fig. 16, Fig. 20 is a transverse cross-sectional plan view of the mould of Fig. 19, Fig. 21 is a front elevational view ofa part of the mould of Fig. 19, Fig. 22 is a transverse cross—sectional side elevational view of the part of the mould of Fig. 21 on the line XXII-XXII, Fig. 23 is a perspective view of the part of the mould of Fig. 21, Fig. 24 is a perspective view of another part of the mould of Fig. 19, Fig. 25 is a transverse cross—sectional side elevational view of a detail of the mould of Fig. 19, Fig. 26 is a view similar to Fig. 25 of the detail of the mould of Fig. 19 illustrating a part of the mould in a different position in use, Fig. 27 is a perspective view of a detail of the part of the mould of Fig. 19, Fig. 28 is a perspective view of a cast component which could be cast using a mould of the type illustrated in Figs. 1 to 15, but appropriately modified, Fig. 29 is another perspective view of the component of Fig. 28, Fig. 30 is a perspective view of another component which could be cast using the method according to the invention and a mould of the type illustrated in Figs. 16 to 27 but appropriately modified, and Fig. 31 is another perspective view of the component of Fig. 30.

Referring to the drawings and initially to Figs. 1 to 15 thereof, there is illustrated a mould which is not according to the invention indicated generally by the reference numeral 1 for mounting in a pressure die cast press indicated generally by the reference numeral 2, see Fig. 3, for die casting an article, namely, an aluminium component 3, see Figs. 1 and 2. Referring initially to Figs. 1 and 2 the component 3 is of circular transverse cross—section having a central body portion 4. A central circular bore 5 extends from one end 6 thereof into the component 3, and an annular groove 7 extends circumferentially around the component 3 towards the end 6. A radially extending flange 8 extends circumferentially around the component 3 at the other end 9.

Before describing the mould 1 in detail the relevant parts of the press 2 will first be described. The press 2 comprises a bed 10. An upwardly extending support member 11 extends upwardly from the bed 10 and supports a stationary platen 12 for receiving one part of the mould 1 as will be described below. A moveable platen 16 for carrying another part of the mould 1 as will also be described below is slideably carried on four parallel main support guide rods 13 which extend between the support member 11 and a support housing 14 which extends upwardly from the bed . A toggle mechanism 18 extending between the support housing 14 and the moveable platen 16 is operable by a ram 15 mounted on the support housing 14 for urging the moveable platen 16 towards and away from the fixed platen 12 along a longitudinally extending axis 17 in the direction of the arrows A and B for respectively closing and opening the mould 1 as will be described below. The toggle mechanism 18 under the action of the ram 15 also acts to secure the mould 1 in the closed position while the mould 1 is being charged with aluminium. The press 2 will not be described further, as such pressure die casting presses will be well known to those skilled in the art.

The mould 1 comprises a first main die 20 and a second main die 21. The first main die 20 is mounted on the fixed platen 12, and thus is a fixed main die, while the second main die 21 is mounted on the moveable platen 16, and thus is a moveable one of the two main dies 20 and 21. In this embodiment of the invention the mould 1 is a two cavity mould for moulding two of the components 3 in each shot. The first main die 20 is a predominately male die, and thus carries two spigots 24 extending therefrom for forming the respective bores 5 in the two components 3. The second main die 21 is a predominately female die, and defines two recesses 25 for forming the circumferential flange 8 of the component 3. A pair of secondary dies 30 are slideably carried on the second main die 21 for forming the body portion 4 of each of the two components 3. Two semi-cylindrical recesses 32 are formed in each secondary die 30 for forming the body portion 4 of the components 3. Semi-circular projecting ribs 33 extend into the recesses 32 for forming the corresponding grooves 7 in the respective components 3. The secondary dies 30 are slideably carried in tracks (not shown) in the second main die 21, and are slideable in the directions of the arrows C and D transversely of the longitudinal axis 17 for respectively closing and opening the mould 1. A pair of centring projections 34 in the first main die 20 co- operates with a corresponding pair of centring recesses 37 in the secondary dies 30 for centring the secondary dies 30 relative to the spigots 24 and the recesses 25 in the first and second main dies 20 and 21, respectively, as the secondary dies are being urged into the closed position.

Alignment means, namely, four parallel alignment pins 35 extend from the first main die 20 for engaging corresponding parallel alignment bores 36 in the second main die 21 for aligning the first and second main dies 20 and 21 as the second main die 21 is being moved from the open to the closed position. The alignment pins 35 and the bores 36 extend parallel to the longitudinal axis 17 when the first and second main dies 20 and 21 are mounted on the fixed and moveable platens 12 and 16, respectively.

A means for moving the secondary dies 30 in the direction of the arrows C and D between the closed and the open positions as the second main die 21 is being moved in the directions of the arrows A and B for closing and opening the mould 1, respectively, comprises six guide rods 38 extending from the first main die 20. Three of the guide rods 38 extend from the first main die 20 to one side of the spigots 24, and the other three guide rods 38 extend from the first main die 20 to the other side of the spigots 24. The guide rods 38 diverge outwardly away from each other and engage and co—operate with corresponding guide bores 39 in the secondary dies 30 which diverge and extend parallel to their corresponding guide rods 38. Thus, as the second main die 21 is being moved in the direction of the arrow A by the moveable platen 16 towards the first main die 20 for closing the mould 1, the guide rods 38 engage the corresponding guide bores 39 for urging the secondary dies 30 towards each other into the closed position of the mould 1, see Fig. 6. In the closed position the secondary dies 30 engage each other and are engaged by the first and second main dies 20 and 21 so that the main dies 20 and 21 and the secondary dies 30 form two mould cavities 40 each of which defines one of the components 3 and in which the components 3 are moulded. The second main die 21 is moveable in the direction of the arrow B by the moveable platen 16 from the closed to the open position, and as the second main die 21 is moving from the closed position, the guide rods 38 co- operate with the guide bores 39 for urging the secondary dies 30 apart, see Figs. 8 and 9, into an open position of the mould 1 for removing the respective moulded die cast components 3.

Ejector pins 41 are slideably located in corresponding ejector pin accommodating bores 42, which extend through the second main die 21, for ejecting the moulded components 3 from the cavity 25 of the second main die 21 when the mould is open.

The ejector pins 41 are operated by a ram 43 mounted on the moveabie platen 16, and the operation of the ram 43 is timed to operate the ejector pins 41 for engaging and ejecting the components 3 as the second main die 21 is moving into the open position.

A retaining means is provided by the secondary dies 30 for gripping and retaining the moulded components 3 in the second main die 21, during initial movement of the second main die 21 from the closed position for disengaging the components 3 from the first main die 20 as the second main die 21 commences movement from the closed position to the open position. In order to allow the secondary dies 30 to act as the retaining means the guide rods 38 co—operate with the guide bores 39 so that movement of the secondary dies 30 in the direction of the arrow D from the closed position for opening the secondary dies 30 is delayed until after initial movement of the second main die 21 in the direction of the arrow B from the closed position for opening the mould 1. This is achieved by providing side-ward clearance in the guide bores 39 with the guide rods 38. In other words, instead of the guide bores 39 being of circular transverse cross-section they are of an elongated type of cross-section having a central portion terminating in side portions of semi-circular transverse cross—section. The diameter of the semi-circular side portions corresponds to that of the guide rods 38, see Figs. 14 and 15. In general, to achieve the desired delay in opening of the secondary dies 30 typically, the width a of the guide bores 39 is of the order of 1.5 to 2 times the diameter b of the guide rods 39. This, thus, gives a side- ward clearance of (a—b). When the secondary dies 30 are in the closed position the guide rods 38 bear on side edges 39a of the guide bores 39 for maintaining the secondary dies 30 in the closed position. Accordingly, when the second main die 21 commences movement from the closed to the open position, the second main die 21 moves an initial distance in the direction of the arrow B from the closed position before the guide rods 38 cover the clearance (a-b) to make effective Contact with side edges 39b of the guide bores 39 for commencing opening of the secondary dies . During the time the guide rods cover the clearance (a-b) from the side edges 39a to 39b of the guide bores 39, the secondary dies 30 remain in their closed position gripping the components 3 while the second main die 21 has moved the initial distance in the direction of the arrow B from the first main die 20. This initial movement of the second main die 21 from the first main die 20 causes the components 3 to be disengaged from the spigots 24 of the first main die 20 while gripped by the secondary dies 30. The distance the second main die 21 moves during the initial movement is selected to be sufficient for disengaging the component or components from the first main die 20, and is determined by appropriately selecting the ratio of a/b.

The advantage of providing the secondary dies 30 on the second main die 21 which is a predominately female die is that the secondary dies 30 by acting as the retaining means disengage the components 3 from the spigots 24 of the first main die 20 which is a predominately male die as the second main die 21 is being initially moved from the closed to the open position. This significantly facilitates removal of the components 3 from the mould 1. By virtue of the fact that the components 3 are disengaged from the spigots 24 immediately the mould 1 is being opened, the danger of the components 3 contracting and shrinking onto the spigots 24 is minimised. The gripping action of the secondary dies 30 is enhanced by the engagement of the ribs 33 in the grooves 7 of the components 3, and by the engagement of the flange 8 by the secondary dies 30.

Additionally, since the second main die 21 is predominately female, and in this case, defines the flange 8 as the components 3 cool while the mould 1 is being opened the flange 8 shrinks in the recess 25 in the second main die 21, and thus when the secondary dies 30 are sufficiently spaced apart with the mould 1 approaching the open position, the components 3 are engaged by the ejector pins 41 under the action of the ram 43, and thus fall from the mould 1. Accordingly, the force required to eject the components 3 from the second main die 21 is minimal, and is significantly less than the force which would have been required in the ejector pins if the ejector pins were required to eject the components 3 from the spigots 24 of the first main die 20. Accordingly, by providing the second main die 21 as the female die, as well as reducing the force required in the ejector pins, and thus minimising any danger of distortion of the components during the engagement of the components by the ejector pins, marking of the components by the ejector pins is also significantly reduced if not eliminated. Furthermore, since the ejector pins act on an outer, rather than an inner surface of the components 3 in the event that flashing should occur on the components 3, such flashing can be readily removed by machining since the flashing is formed on an outer surface rather than an inner surface of the components.

In use, with the mould 1 mounted in the press 2 with the first main die 20 secured to the fixed platen 12 and the second main die 21 secured to the moveable platen 16 and aligned with each other, the press 2 is operated for closing the mould 1, in other words, for urging the second main die 21 in the direction of the arrow A towards the first main die 20. The co—operating action of the guide rods 38 and the guide bores 39 in turn urges the secondary dies 30 together. In this way the two mould cavities 40 are formed by the first and second main dies 20 and 21 and the secondary dies . The two mould cavities 40 are charged with molten aluminium, and as soon as the aluminium has just solidified the press 2 is operated for opening the mould 1. As the second main die 21 commences to move in the direction of the arrow B from the closed position the secondary dies 30 remain engaged with each other, thereby continuing to grip the components 3. The initial movement of the second main die 21 in the direction of the arrow B from the closed position causes the components 3 to disengage the corresponding spigots 24 of the first main die 20. Further movement of the second main die 21 in the direction of the arrow B causes the guide rods 38 to co-operate with the bores 39 thereby urging the secondary dies 30 apart.

The moveable platen 16 continues to urge the second main die 21 in the direction of the arrow B until the mould 1 is fully opened. As the second main die 21 is approaching the open position the ram 43 urges the ejector pins 41 into the recess for pushing the components 3 out of engagement with the second main die 21, and the components 3 thus fall from the mould 1.

Referring now to Figs. 16 to 27 there is illustrated a mould indicated generally by the reference numeral 50 according to the invention for casting a component 51 in the press 2. In this embodiment of the invention the component 51 is of aluminium. The component 51 is of square shape having a recess 52 extending inwardly from a top face 53. in this embodiment of the invention the mould 50 comprises only a first main die 60 and a second main die 61. The mould 50 does not comprise secondary dies. The first main die 60 is a predominately male die, and comprises a male projection 62 for forming the recess 52 of the component 51. The second main die 61 is a predominately female die and comprises a recess 63 which forms a substantial part of the component 51. The first main die 60 is mounted on the fixed platen 12, and is thus a fixed die, while the second main die 61 is mounted on the moveable platen 16 and is thus a moveable die. The second main die 61 is moveable in the direction of the arrows A and B by the moveable platen 16 for closing and opening the mould 50, respectively. The first and second main dies 60 and 61 when in the closed position engaging each other define and form a mould cavity 66 which defines the component 51 and within which the component 51 is cast.

Four alignment pins 68 extend from the first main die 60 and engage corresponding alignment bores 69 in the second main die 61 for aligning the first and second main dies 60 and 61, respectively, in similar fashion as the alignment pins 35 and bores 36 align the first and second main dies 20 and 21 of the mould 1. Since the mould 50 does not comprise secondary dies, guide rods and corresponding guide bores are not required.

In this embodiment of the invention the retaining means for retaining the component 51 in the second main die 61 during initial movement of the second main die 61 from the closed position for disengaging the component 51 from the first main die 60 is provided by two grip means, namely, two grip pins 70 which also act as ejector pins, and which are slideable in corresponding grip pin accommodating bores 71 in the second main die 61. The grip pins 70 are slideable under the action of the ram 43 in the corresponding bores 71 between a gripping position illustrated in Figs. 19 and 20 which corresponds to the closed position of the mould 50 for gripping the component , and a disengaging position illustrated in Fig. 26 extending into the recess 63 for disengaging and ejecting the component 51 from the second main die 61. In the gripping position the grip pins 70 terminate in the bores 71 just short of the recess 63 of the second main die 61. Each grip pin 70 is shaped at its end adjacent the recess 63 to form a hook type shape 73 which co-operates with the end of the corresponding bore 71 to form an extension of the mould cavity 66 for forming lugs 74 on the component 51. The lugs 74 are of hook shape corresponding to the hook shape 73 of the grip pins 70 so that the grip pins 70 and the lugs 74 interengage each other when the mould 50 is in the closed position. The operation of the ram 43 is timed for moving the grip pins 70 from the gripping position to the disengaging position as the second main die 21 is approaching the open position. in this way the grip pins 70 continue to grip the lugs 74 in the bores 71 until the component 51 has been disengaged from the first main die 60 during the initial movement of the second main die 61 in the direction of the arrow B from the closed position. As the ram 43 urges the grip pins 70 outwardly through the corresponding bores 71 into the recess 63 the grip pins 70 disengage the lugs 74 and eject the component 51 from the second main die 61.

Use of the mould 50 is substantially similar to that of the mould 1. The second main die 61 is urged into engagement with the first main die 60 for closing the mould 50.

In the closed position the grip pins 70 are located in the grip pin accommodating bores 71 in the gripping position illustrated in Figs. 19 and 20. The mould cavity 66 is then charged with molten aluminium which is allowed to solidify and just as the aluminium is solidifying the second main die 61 is urged in the direction of the arrow B for opening the mould 50. During initial movement of the second main die 61 in the direction of the arrow B from the closed position the grip pins 70 co-operate with the lugs 74 in the grip pin accommodating bores 71 for gripping the component 51, so that during initial movement of the second main die 61 in the direction of the arrow B from the closed position, the component 51 is disengaged from the male projection 62 of the first main die 60. As the second main die 61 moves further in the direction of the arrow B, the ram 43 urges the grip pins 70 from the gripping position to the disengaging position for urging the lugs 74 outwardly of the bores 71 towards the recess 63 for ejecting the component 51 from the second main die 61 and for disengaging the lugs 74 from the grip pins 70. On disengagement of the lugs 74 from the grip pins 70 the component falls from the mould 50.

The lugs 70 do not form part of the finished component 51 and are thus subsequently machined from the component. By virtue of the fact that the lugs 74 are formed on an outer male type surface, rather than an inner female type surface of the component 51 the lugs 74 can readily easily be subsequently machined off.

The mould 50 according to the invention and the method for moulding the component 51 according to the invention are particularly suitable for die casting thin walled components and components of relatively intricate and complex shapes. indeed, the mould 50 has been described for moulding relatively simple and non- complex components solely for the purpose of ease of illustrating and understanding of the invention.

Referring now to Figs. 30 and 31 the mould 50 described with reference to Figs. 16 to 27 is particularly suitable for moulding a heat sink plate 90 of the type illustrated in Figs. 30 and 31. The heat sink plate 90 comprises a plurality of fins 91 extending from a plate member 92. The fins 91 would be formed in the first fixed male main die of the mould 51, and the plate member 92 would be formed in the second moveable female main die. The lugs 93 projecting from the plate member 92 on the side opposite to that from which the fins 91 extend would be formed in the grip pin accommodating bores in co—operation with the grip pins.

Needless to say the moulds and methods according to the invention may be used for die casting components of many other shapes and configurations.

While the mould described with reference to Figs. 16 to 27 has been described as comprising retaining means formed by the grip pins, it is envisaged that in certain cases a mould similar to that described with reference to Figs. 1 to 15 may be provided with retaining means provided by both secondary dies and grip pins, both of which would be located and associated with the second main die.

It is also envisaged that the ejector pins could be arranged to engage runners associated with the cast component.

While the moulds and methods have been described for die casting a component of aluminium, it will be appreciated that the moulds may be used for die casting a component of any metal, and it will also be appreciated that the moulds may be used for injection moulding a plastics component or for moulding a component from any other suitable mouldable material.

Claims (14)

1. A method for moulding an article in a mould having a first main die which is a predominately male die, and a second main die which is a predominately female die co—operable with the first main die for forming a mould cavity which defines the moulded article, one of the first and second main dies being moveable relative to the other between a closed position of the mould with the two main dies forming the mould cavity and a spaced apart open position of the mould for facilitating removal of the moulded article from the mould cavity, the method comprising the steps of providing a grip means co—operable with a grip means accommodating bore extending into the second main die from the mould cavity, the grip means being slideable in the grip means accommodating bore between a gripping position corresponding to the closed position of the mould for gripping a portion of the moulded article and retaining the moulded article in the second main die, and a disengaging position corresponding to the open position of the mould for disengaging the moulded article, charging the mould cavity with the material to be moulded into the moulded article when the first and second main dies are in the closed position and the grip means is in the gripping position, urging the moveable one of the first and second main dies to the open position when the moulded article is just cured, and moving the grip means from the gripping position to the disengaging position as the moveable one of the first and second main dies is being urged from the closed position to the open position, so that as the moveable one of the first and second main dies commences movement from the closed to the open position, the moulded article is disengaged from the first main die, and on further movement of the moveable one of the first and second main dies towards the open position the moulded article disengages the second main die.

2. A method as claimed in Claim 1 in which the grip means disengages the moulded article from the second main die in the disengaging position.

3. A method as claimed in Claim 1 or 2 in which the grip means co—operates with the grip means accommodating bore for forming the portion of the moulded article to be gripped by the grip means in the grip means accommodating bore.

4. A method as claimed in any preceding claim in which the grip means is shaped adjacent the mould cavity for gripping the portion of the moulded article to be gripped.

5. A method as claimed in any preceding claim in which the grip means is hook shaped adjacent the mould cavity for forming a corresponding hook-shaped portion on the moulded article in the grip means accommodating bore for co—operating with the hook-shaped portion of the grip means while the hook-shaped portion of the moulded article formed in the grip means accommodating bore is in the grip means accommodating bore.

6. A method as claimed in any preceding claim in which the grip means comprises an elongated grip pin slideable in the grip means accommodating bore, the grip pin being moveable from the gripping position within the grip means accommodating bore to the disengaging position extending from the grip means accommodating bore into the mould cavity for disengaging the moulded article, and for acting as an ejector pin for disengaging the moulded article from the second main 25 die.

7. A method as claimed in any preceding claim in which the grip means accommodating bore is located in the second main die for forming the portion of the moulded article to be gripped by the grip means on a non—precision surface of the moulded article, or on a surface to be subsequently machined.

8. A method as claimed in any preceding claim in which the first main die is a fixed die.

9. A method as claimed in any preceding claim in which the second main die is a moveable die.

10. A method as claimed in any preceding claim in which the method is for die casting the article.

‘I1. A method as claimed in any preceding claim in which the method is for die casting the article from zinc.

12. A method as claimed in any preceding claim in which the method is for die casting the article from lead.

13. A method as claimed in any preceding claim in which the method is for die casting the article from aluminium. i0

14. A method for moulding an article, the method being substantially as described herein with reference to and as illustrated in