GB1602579A

GB1602579A - Die casting machines

Info

Publication number: GB1602579A
Application number: GB2461678A
Authority: GB
Original assignee: Dynacast International Ltd
Current assignee: Dynacast International Ltd
Priority date: 1978-05-30
Filing date: 1978-05-30
Publication date: 1981-11-11
Also published as: CA1143131A

Description

(54) IMPROVEMENTS RELATING TO DIE CASTING MACHINES (71) We, DYNACAST INTER NATIONAL LIMITED, a British Company of Tything Road, Arden Forest Industrial Estate, Alcester, in the County of Warwick, do hereby declare the invention for which we pray that a Patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement:- This invention relates to a hot chamber pressure die casting machine of the type, hereinafter referred to as the type described, comprising a reservoir for molten metal, a gooseneck, one end of which, in use, being immersed in the molten metal and the other end of which provides a nozzle having an end surface which, in use, is brought into engagement with a back surface of a die assembly from which a runner passage extends to a die cavity defined by the die assembly and into which a shot of molten metal is injected by a pump in the gooseneck, the die assembly being mounted on a back plate and comprising a plurality of die parts movably mounted on the back plate for movement between a closed position in which the die cavity is defined and an open position in which an article cast within the cavity can be ejected and die closure means to effect said movement of the die parts.

In order to facilitate ejection of a cast article on the die set when the dies are in their open position we desire that the back plate should lie in a plane lying in, or inclined at not more than 25 (and preferably at less then 10 or 5 ) to a vertical plane. However we have found that if we adopt a back plate inclined at such an angle, which results in the back surface of the die assembly from which the feed passage extends also lying in a plane inclined at such an angle, with a gooseneck having a nozzle in which the passage for metal, adjacent the die assembly engaging end surface, extends in a plane lying in, or inclined at such an angle to a horizontal plane then metal tends to run out of the nozzle passage at the end surface when the end surface is moved out of engagement with the die set.

It is accordingly an object of the invention to provide a die casting machine of the type described from which cast articles can be easily ejected and in which the abovementioned problem of "metal dribble" is overcome or is reduced.

According to the invention we provide a die casting machine of the type described wherein the back plate lies in a plane lying in, or inclined at not more than 25 to a vertical plane and the gooseneck nozzle has a passage, part of which lies in a plane lying in, or inclined at not more than 25 to a horizontal plane, when the nozzle end surface is engaged with the back surface of the die assembly, and an end part which is inclined upwardly from said one part to the end surface of the nozzle.

This arrangement avoids metal dribbling out of the nozzle when the nozzle end surface is moved out of engagement of the back surface of the die assembly and also permits the provision of nozzle heating means including a conventional electrical heating jacket which is relatively bulky and which could not be provided if the whole of the nozzle were to be inclined upwardly.

One embodiment of the invention will now be described in more detail by way of example with reference to the accompanying drawings wherein: Figure 1 is a front elevation of a die casting machine embodying the invention, Figure 2 is a side elevation of the machine of Figure 1 looking in the direction of the arrow A in Figure 1, Figure 3 is a section on the line 3-3 of Figure 1, Figure 4 is a plan view of the machine ol Figure 1, Figure 5 is a fragmentary longitudinal cross-sectional view, to an enlarged scale, through the goose-neck nozzle of the machine of Figure 1, Figure 6 is a fragmentary longitudinal cross sectional view, to an enlarged scale, through the gooseneck closure means of the machine of Figure 1, Figure 7 is a section on the line 7-7 of Figure 2, and Figure 8 is a section on the line 8-8 of Figure 1.

Referring to the drawings a die casting machine for producing pressure die castings of zinc is illustrated generally at 10 and comprises a base part 11 which carries a crucible 12 which in use contains molten zinc and thus provides a reservoir for the zinc. The base part 11 also carries a circuit back plate 13 having a central opening 14 through which a nozzle 45 of a gooseneck 16 projects so that an end surface 17 of the nozzle 15 can be engaged with a back surface 18 of a die assembly indicated generally at 19 in Figure 5 so as to be in metal transmitting relationship with a runner passage 20 which extends from the back surface 18 to a cavity defined bv the die assembly. In the example illustrated the back plate lies in a vertical plane but may lie in other planes which are inclined to the vertical at up to25".

The die assembly 19 comprises four die parts mounted in die carriers 21 mounted on the back plate 13 so as to be slidable in the plane of the back plate at 90 to each other by means of die closing means indicated generally at 22. If desired the dies may be slidable in directions other than 90".

Referring now particularly to Figure 3 the gooseneck 16 is mounted for pivotal movement about an axis 23 so as to move the end surface 17 of the gooseneck nozzle 15 into and out of engagement with the back surface 18 of the die assembly. This movement is caused by a drive means 24, which includes a toggle mechanism 25 connected to the gooseneck.

The gooseneck 16 is mounted on the base part 11 by means of a generally square cross-section axle member 26 having cylindrical end bearing portions which are received in bearing apertures 27 formed in brackets 28 connected to arms 29 which are themselves carried at the upper ends of threaded rods 30. The rods 30 are mounted on the back plate 13 and the arrangement is such that rotation of a rod permits vertical adjustment of the bracket 28 connected thereto and thereby permits adjustment of the position of the end surface 17 of the nozzle 15 relative to the back surface 18 of the die assembly.

The gooseneck 16 contains a conventional pump arrangement whereby molten zinc contained within the crucible 12 is drawn from the crucible into the interior of the gooseneck and is then injected in the die cavity through the runner passage 20 by means of an internal passage 32 formed in the gooseneck and a passage 33 formed in the nozzle 15. The major length of the passage 33 in the gooseneck i.e. the part indicated at 34 extends in a horizontal direction when the end surface 17 and back surface 18 are in engagement as shown in Figure 5. A minor part 35 of the passage extends from the outer end of the major part 34 to the end surface 17 in a direction which is inclined upwardly from the part 34 to the end surface 17 at angle of 25". When the back plate is inclined to the vertical the major part 34 may also be inclined to the horizontal, for example, by an angle equal to the inclination of the back plate to the vertical.

The arrangement is such that the injection pump closes the passage 32 before the nozzle is withdrawn from the back of the die thereby preventing metal drawing back and keeping the part 34 of the passage full of molten metal and in addition, the part 34 is below the bottom of the aperture in the end surface 17 when the gooseneck is withdrawn out of contact with the back surface 18.

This is done to avoid molten zinc dribbling from the end surface 17 when the gooseneck is withdrawn out of contact with the back surface 18 which could otherwise be the case.

By providing that the major part 34 of the passage 33 extends in a horizontal direction then the general extent of the nozzle can also lie horizontally and the end surface 36 can lie in a vertical plane thereby permitting the fitting of a conventional electrical heating jacket 37 to the nozzle without interference with the die set 19 or back plate 13.

It will be appreciated that the precise angle of the minor part 35 and the relative extent of the parts 34 and 35 may be varied from that described hereinbefore whilst still achieving the objects described hereinbefore.

Referring to Figures 3 and 4 the gooseneck 16 is pivoted into and out of engagement with the die set about the axis 23 by means of a pneumatic piston and cylinder device 38 the cylinder of which is connected to the base part 11 of the apparatus whilst the piston rod of which is pivotally connected, at 39, to a toggle mechanism 25 which comprises a first link 40 one end of which is rigidly connected, at 41, to a rod 42 connected to the gooseneck 16 whilst the other end is connected to the piston rod at 39 and a pair of second links 43 one end of which are pivotally connected at 44 to the base part 11 of the apparatus through an air spring 45 and the other ends of which are connected to the piston rod at 40a.

Referring now particularly to Figure 6 the link 43 is connected, at 44 to a piston rod 46 of the air spring 45 which extends through a nose part 47 of the cylinder 48 of the air spring. The piston rod 46 has a shoulder 49 with which a washer 50 is engaged. Rotatably mounted on a reduced diameter part 51 of the piston rod 46 is a piston 52 having a boss 53 apertured to receive the part 51 and extending through a rear wall 54 of the cylinder 48.

Conventional O-ring seals 55 are provided between the wall 54 and the boss 53 and between the wall of the passage in the boss 53 and the reduced diameter part 51. Air under pressure is fed via a connector 56, axial passage 57, radial passages 58 and circumferential groove 59 in the part 51 of the piston rod 46 and a radial passage 60 in the boss 53 to the region 61 so as to act on one side 62 of the piston 52 and via a bleed aperture 63 to act on a reduced area part 64 of the other side 65 of the piston 52.

An exhaust passage 66 extends from the interior of the cylinder 48 adjacent the washer 49 to atmosphere. A microswitch 67 is mounted on a bracket 68 fixed to the end of the piston rod 46 and the operating member 69 of which is adapted to engage a surface 70 of the cylinder 48.

In use, when it is desired to move the end surface 17 of the gooseneck nozzle 15 into metal transferring relationship with the back surface 18 of the die assembly 19 the pneumatic piston and cylinder device 38 is actuated to move the piston rod thereof outwardly of the cylinder so as to tend to move the links 40 and 43 into axial alignment thereby moving the rod 42 to the left in Figure 3 and thus pivoting the gooseneck 16 about the axis 23. When the end surface 17 engages the back surface 18 so that the movement of the gooseneck 16 is prevented then whilst movement of the piston rod of the device 38 continues this causes only movement of the piston rod 46 of the air spring 45 to the left in Figure 6 thus engaging the washer 50 with the piston 52 to move the piston 52 to the left. This has two effects. One effect is that the air acting on the reduced cross sectional area parts 64 of the piston 62 is permitted to move past an O-ring seal 71 and hence be exhausted to atmosphere through the exhaust passage 66. As a result the whole of the side 65 of the piston will be subjected to only atmospheric pressure whilst the whole of the side 62 will be subjected to air under pressure fed via the connector 56 and passages 57. 58. groove 59 and passage 60.

As a result whilst the piston and cylinder device 38 is permitted to carry out its full stroke since the piston 52 can move to the left against the pressure of the air acting in the region 61 the force exerted by the drive means on the gooseneck is increased, once contact between the surfaces 17 and 18 has taken place, due to the air acting on the piston 52 as described hereinbefore and also the pressure pressing the surface 17 and 18 into contact can be maintained constant irrespective of any variation in the dimensions between the gooseneck and the connection of the toggle mechanism to the base 11 since the pressure is determined by the force exerted by the air on the piston 52.

The second thing which happens is that to cause the plunger 69 to operate the micro-switch so that it sends a signal to a control mechanism of the machine to permit the pump in the gooseneck to operate to feed a shot of metal since movement of the piston rod 46 to the left will have meant that the surfaces 17 and 18 are in metal transferring relationship.

As best shown in Figures 1 to 3 the back plate 13 is provided with a continuous circular track 72 the centre of the track being coincident with the center of the opening in the end surface 17 of the gooseneck, when the gooseneck is in position with the back surface 18. Mounted in the track 72 are four die closure means 22 (see Fig. 1). In Figures 1 and 2 only one closure means is shown in its entirety the other three being shown schematically but they are, in fact, identical to that shown in detail. Each die closure means comprises a pneumatic piston and cylinder device 73 pivotally mounted at 74 on a bracket 75 fixed to a shoe 76 engaged with the track 72 and provided with means such as clamping bolts to clamp it in a desired position circumferentially spaced from the track.

The piston rod 73a of the device 73 is pivotally connected at 77 to one end of a first link 78 of a toggle mechanism, the other end of the link 78 being connected at 79 to a die. A pair of second links 80 are connected at 81 intermediate the points 77 and 79 to the first link 78 and at 82 to an adjustment member 83 having a threaded rod. 84 in threaded engagement with an adjustment member 85 which abuts the end of a housing 86 so that rotation of the member 85 moves the rod 84 axially and hence the pivot 82 so that the closure position of the die can be adjusted.

The die parts are mounted for sliding movement in a cross head 87. It will be appreciated that the position of the die closure can be easily and conveniently adjusted to suit any particular die head which is clamped to the backing plate in conventional manner merely by moving the shoes 76 circumferentially of the track to the desired position. Also, if desired, additional closure may be providedi intermediate the four described hereinbefore; also a closure may be provided for one or more core members which may be required with any particular die assembly.

If desired the track or tracks can be provided on a member separate from the remainder of the back plate and fixed thereto.

Aspects of the machine described hereinbefore are claimed in our co-pending application No. 24618/78 (Serial No.

1602580).

WHAT WE CLAIM IS: 1. A pressure die casting machine lying in, or of the type described wherein the back plate lies in a plane inclined at not more than 25 to a vertical plane and the gooseneck nozzle has a passage, one part of which lies in a plane lying in, or inclined at not more than 250 to a horizontal plane, when the nozzle end surface is engaged with the back surface of the die assembly, and an end part of which is inclined upwardly from said one part to the end surface of the nozzle.

2. A machine according to Claim 1 wherein the back plate lies in a vertical plane.

3. A machine according to Claim 2 wherein said part of the passage is horizontal.

4. A machine according to any one of the preceding claims wherein said one, part of the passage comprises a major part of the length thereof.

5. A machine according to any one of the preceding claims wherein the nozzle is provided with a heating means.

6. A machine according to Claim 5 wherein the heating means comprises an electrical heating coil surrounding an end part of the nozzle adjacent the die assembly.

7. A machine according to any one of the preceding claims wherein the end part is inclined to said one part of the passage at an angle of 250.

8. A machine according to any one of the preceding claims wherein, in use, on withdrawal of the nozzle from the die assembly the level of liquid in the nozzle passage is above the top of said one part and below the bottom of the aperture formed in the end surface where said end portion intersects the end surface.

9. A machine according to any one of the preceding claims wherein the external configuration of the nozzle at least adjacent the die assembly is generally cylindrical and the end surface of said part of the nozzle extends parallel to the backing plate wherein, in use, the nozzle end surface is engaged with the back surface of the die assembly.

10. A machine according to any one of the preceding claims wherein said end portion is formed in an insert removably engageable with the remainder of the nozzle.

11. A machine according to any one of the preceding claims wherein the end surface of the nozzle which engages the back surface of the die assembly lies in a vertical plane when in engagement with the back surface.

12. A die casting machine according to any one of the preceding claims wherein the gooseneck is moved, to engage the end surface of the nozzle thereof with the back surface of the die assembly, by means of a toggle mechanism.

13. A machine according to Claim 12 wherein the toggle mechanism is anchored to a fixed part of the machine through a biasing means.

14. A machine according to Claim 13 wherein the biasing means is a resilient biasing means.

15. A machine according to Claim 14, wherein the resilient biasing means comprises an air spring.

16. A machine according to Claim 15 wherein the air spring applies an increased force to the gooseneck once the end surface thereof has engaged the back surface of the die assembly.

17. A machine according to any one of Claims 12 to 16 wherein the toggle mechanism comprises a first link connected at one end to the gooseneck and at the other end to a drive means and a second link pivotally connected at one end to a fixed part of the machine and at the other end to the first link adjacent to said connection to the drive means said links when the end and back surfaces are in engagement extending generally parallel to the direction of movement of the gooseneck and being generally axially aligned and said drive means being operative to cause movement thereof in a direction transverse to the direction of movement of the gooseneck to move the end surface out of engagement with the back surface.

18. A machine according to Claim 17 wherein the drive means comprises a fluid operated piston and cylinder device.

19. A machine according to Claim 18 wherein the piston has a piston rod which extends transversely to said direction of movement.

20. A machine according to Claim 19 wherein the piston rod has a head to which said other end of said first link is pivotally connected.

21. A machine according to any one of

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Claims

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additional closure may be providedi intermediate the four described hereinbefore; also a closure may be provided for one or more core members which may be required with any particular die assembly.

If desired the track or tracks can be provided on a member separate from the remainder of the back plate and fixed thereto.

Aspects of the machine described hereinbefore are claimed in our co-pending application No. 24618/78 (Serial No.

1602580).

WHAT WE CLAIM IS: 1. A pressure die casting machine lying in, or of the type described wherein the back plate lies in a plane inclined at not more than 25 to a vertical plane and the gooseneck nozzle has a passage, one part of which lies in a plane lying in, or inclined at not more than 250 to a horizontal plane, when the nozzle end surface is engaged with the back surface of the die assembly, and an end part of which is inclined upwardly from said one part to the end surface of the nozzle.
2. A machine according to Claim 1 wherein the back plate lies in a vertical plane.
3. A machine according to Claim 2 wherein said part of the passage is horizontal.
4. A machine according to any one of the preceding claims wherein said one, part of the passage comprises a major part of the length thereof.
5. A machine according to any one of the preceding claims wherein the nozzle is provided with a heating means.
6. A machine according to Claim 5 wherein the heating means comprises an electrical heating coil surrounding an end part of the nozzle adjacent the die assembly.
7. A machine according to any one of the preceding claims wherein the end part is inclined to said one part of the passage at an angle of 250.
8. A machine according to any one of the preceding claims wherein, in use, on withdrawal of the nozzle from the die assembly the level of liquid in the nozzle passage is above the top of said one part and below the bottom of the aperture formed in the end surface where said end portion intersects the end surface.
9. A machine according to any one of the preceding claims wherein the external configuration of the nozzle at least adjacent the die assembly is generally cylindrical and the end surface of said part of the nozzle extends parallel to the backing plate wherein, in use, the nozzle end surface is engaged with the back surface of the die assembly.
10. A machine according to any one of the preceding claims wherein said end portion is formed in an insert removably engageable with the remainder of the nozzle.
11. A machine according to any one of the preceding claims wherein the end surface of the nozzle which engages the back surface of the die assembly lies in a vertical plane when in engagement with the back surface.
12. A die casting machine according to any one of the preceding claims wherein the gooseneck is moved, to engage the end surface of the nozzle thereof with the back surface of the die assembly, by means of a toggle mechanism.
13. A machine according to Claim 12 wherein the toggle mechanism is anchored to a fixed part of the machine through a biasing means.
14. A machine according to Claim 13 wherein the biasing means is a resilient biasing means.
15. A machine according to Claim 14, wherein the resilient biasing means comprises an air spring.
16. A machine according to Claim 15 wherein the air spring applies an increased force to the gooseneck once the end surface thereof has engaged the back surface of the die assembly.
17. A machine according to any one of Claims 12 to 16 wherein the toggle mechanism comprises a first link connected at one end to the gooseneck and at the other end to a drive means and a second link pivotally connected at one end to a fixed part of the machine and at the other end to the first link adjacent to said connection to the drive means said links when the end and back surfaces are in engagement extending generally parallel to the direction of movement of the gooseneck and being generally axially aligned and said drive means being operative to cause movement thereof in a direction transverse to the direction of movement of the gooseneck to move the end surface out of engagement with the back surface.
18. A machine according to Claim 17 wherein the drive means comprises a fluid operated piston and cylinder device.
19. A machine according to Claim 18 wherein the piston has a piston rod which extends transversely to said direction of movement.
20. A machine according to Claim 19 wherein the piston rod has a head to which said other end of said first link is pivotally connected.
21. A machine according to any one of

Claims 12 to 20 wherein means are provided to sense engagement between the end and back surfaces and to permit of operation of the pump of the gooseneck only subsequent to such engagement.
22. A machine according to Claim 21 when dependant upon Claim 13 or any of Claims 14 to 20 when dependant on Claim 13 wherein said sensing is achieved by sensing movement of the biasing means.
23. A machine according to Claim 16 or any one of Claims 17 to 22 when dependant upon Claim 16 wherein the air spring comprises a cylinder, a piston movable in the cylinder, the piston being connected to one end of the toggle mechanism, means to supply air under pressure to act on one side of the piston and restricted passage means to permit said air to act on a smaller cross sectional area of the other side of the piston when the piston is in a first position wherein said end and back surfaces are not in engagement and exhaust means to connect said other side of the piston to atmosphere and valve means operated when the surfaces are moved into engagement to connect said exhaust means to other side of the piston.
24. A die casting machine according to any one of the preceding claims wherein the back plate is provided with a track along which the position of die closure means can be adjusted.
25. A machine according to Claim 24 wherein the machine includes a plurality of die closure means each of which is adjustable along a tank provided on the back plate.
26. A machine according to Claim 24 or Claim 25 wherein a single circular track is provided lying in the plane of the back plate the or each die closure means being adjustable along said single track.
27. An apparatus according to Claim 24 or Claim 25 wherein a plurality of separate tracks are provided each lying in the place of the back plate and there being at least one closure means associated with each track.
28. A machine according to any one of Claims 24 to 27 wherein the or each die closure means is operable to reciprocate the die part or parts between the open and - the,Qosition by a linkage from a drive means.
29. A machine according to Claim 28 wherein the axes of pivot of the linkage lie in a plane parallel to the plane of the back plate.
30. A machine according to Claim 28 or Claim 29 wherein the drive means comprises a fluid operated piston and cylinder device.
31. A machine according to Claim 29 or Claim 30 when dependant upon Claim 29 wherein the linkage is a toggle linkage.
32. A machine according to any one of Claims 24 to 31 having a core member and a closure means therefor.
33. A machine according to any one of Claims 24 to 32 wherein clamping means are provided to secure the or each die closure means in a desired position along its associated track.
34. A machine according to any one of Claims 24 to 33 wherein the or each track is integral with the back plate.
35. A machine according to any one of Claims 24 to 33 wherein the or each track is provided on or by a member or members separate from the remainder of the back plate and secured thereto.
36..A machine according to any one of Claims 24 to 35 wherein the or each track comprises a slideway and the or each die closure means comprises a shoe mounted on said slideway.
37. A die casting machine substantially as hereinbefore described with reference to and as shown in the accompanying drawings.