GB2209016A

GB2209016A - Die casting apparatus

Info

Publication number: GB2209016A
Application number: GB8819866A
Authority: GB
Inventors: Masakazu Sato; Keisuke Ban; Bakugo Fujito; Shigetada Suwabe; Katsunobu Nakamura
Original assignee: Honda Motor Co Ltd; TEISAN IND KK
Current assignee: Honda Motor Co Ltd; TEISAN IND KK
Priority date: 1987-08-24
Filing date: 1988-08-22
Publication date: 1989-04-26
Anticipated expiration: 2008-08-22
Also published as: DE3828741A1; GB2209016B; JPS6453751A; GB8819866D0

Description

1 DIE CASTING APPARATUS The present invention relates to a die casting

apparatus of the type that it is possible to exert a secondary pressurization force upon molten metal injected into and filled in a cavity of a mold.

A die casting method in which molten metal is poured into a cavity of a mold at a high pressure, has been widely employed and practiced as a method most suitable for massproduction in the casting technique for aluminium alloys.

this casting method, a thick wall portion that a crystalline mechanical strength In blow holes are liable to be produced in of a product, and there is a tendency structure would become coarse and a of the thick wall portion would be lowered. In order to resolve this problem, a secondary pressurization casting method, in which an additional pressurizing force (a secondary presurizing force) is applied to molten metal injected into and f illed in a cavity of a 20 mold, was proposed (for example, see Japanese Patent Publication No.48-7570(1973) and Japanese Patent Publication No.49-36093(1974)).

As the method for carrying out the secondary pressurization, a method of pushing a secondary pressurization pin into molten metal after completion of filling of molten metal, and a method of forwardly moving a secondary pressurization pin within a through-hole that is formed in a mold for the purpose of making the secondary pressurization pin advance or retreat and thereby pushing C m. --4 Z2 5 o' 0 1 b v back the molten metal entering into the through-hole, are known.

In these methods, the secondary pressurization pin would suffer a lot of heat in each of the respective casting works which are effected repeatedly, and adhesion by baking of molten metal (leght matals) ontoits outer circumference would arise, resulting in adverse influence upon the operation of the sescondary pressurization pin. As a countermeasure for that shortcoming, in the case where the secondary pressurization pin is large in diameter, a method of providing a coolant pessageway within the pin is known. However, in the case of a secondary pressurizaiton pin having a small diameter, leakage of a water coolant to the outside due to damage is worried.

is The present invention has been worked out under the above-mentioned technical backgroud, and one object of the present invention is to provide a die casting apparatus which can effectively perform cooling of a secondary pressurizaiotn pin, and also which can contemplate improvements in a productivity.

The aforementioned object can be achieved, in a die casting apparatus of the type that a secondary pressurization force is exerted upon moltan metal after completion of filling thereof, in which apparatus push-out pins and a secondary pressurization pin penetrate through a movable die forming a mold in cooperation with a fixed die, by mounting a secondary pressurization hydraulic cylinder for driving a secondary pressurization pin onto a push-out plate carrying 4 1 the push-out pins and adapted to advance or retreat relatively to the movable die as hydraulically driven.

Fig.1 shows steps in a common secondary pressurization casting process, and in the case of carrying out a casting work continuously, the illustrated steps are repeated. In the steps of Mry air ejectioC and "spraying of a mold releasing agenC forming the initial steps, the secondary pressurization pin is held retreated within the wall of the mold, hence cooling of the secondary pressurization pin is not effected, and therefore, in the illustrated example of steps, there is no chance for performing cooling ofthe secondary pressurizaiton pin and application of a mold releasing agent. In order to perform cooling of the secondary pressurization pin and application of a mold releasing agent, it is necessary to employ such control system that before performing spray of a mold releasing agent it may cause the seconadary pressurization pin to project and after the spray it may make the seconadary pressurization pin retreat and perform fastening of the dies.

The construcrion of such control system is complicated as compared to that of the conventional control system, the number of steps is also increased, and hence a productivity is lowered. Furthermore, even if such casting process steps were to be employed, effective cooling of the secondary pressurization pin would not be carried out because the stroke of advance or retreat of the secondary pressurization pin caused by the secondary pressurization hydraulic cylinder is small.

1 v Therefore, according to the present invention, it has been proposed that a secondary pressurization hydraulic cylinder for driving a secondary pressurization pin is mounted onto a pushu-out plate carrying the pushout pins and adapted to advance or retreat relatively to the movable die as hydraulically driven.

According to the above-mentioned construction, the secondary pressurization pin can be made to project by a length equal to the projection length of the push-out pins io when the mold is opened by moving the movable die and at the same time the push-out pins are made to project from the wall of the movable die. for the purpose of releasing a cast piece from the mold.

f rom the mold, Therefore, after the cast piece was taken out if spraying of a mold releasing agent is effected with the secondary pressurization pin kept projected, effective cooling of the secondary pressurization pin can be performed without increasing the number of steps of process nor without employing a special control system.

BRIEF DESCRIPTION OF THE DRAWINGS:

Fig.1 is a flow chart showing steps of a secondary pressurization casting process known in the prior art;

Fig.2 is a cross-section side view partly cut away showing an essential part of a die casting apparatus according to one preferred embodiment of the present invention, in which a mold is closed; Fig.3 is a cross-section view similar to Fig.2 of the same die casting apparatus but showing the state where the mold is opened.

Now description will be made on one prefered embodiment of the present invention illustrated in Fig. 2 and 3.

Fig.2 shows an essential part of a die casting apparatus in a cross-section view partly cut away. A mold 14 in this die casting apparatus consists of a fixed die 16 that is fixed to a stationary platen 10 and a movable die 18 that is fixed to a movable platen 12, and a cavity 20 is delimited by combining the fixed die 16 and the movable die 18.

The movable platen 12 carries, besides the movable die 18, a push-out hydraulic cylinder 24 whose piston rod 26 has its tip end fixed to the movable platen 12, push-out rods 28 secured to a base plate 22 of the push-out hydraulic cylinder 24 penetrate through the movable platen 12 and butt against a push-out plate 30 as will be described later (arrows A indicating the directions of advance and retreat of the movable platen 12). When the push-out hydraulic cylinder 24 operates, the push-out hydraulic cylinder 24 itself moves jointly with the base plate 22 towards the movable platen 12, and the push-out rods 28 penetrating through the movable platen 12 would push the push-out plate 30 to bring it close to the movable die 18.

The push-out plate 30 is provided with return pins 32 penetrating through the movable die 18, push-out pins 34 penetrating through the movable die 18 so as to face the cavity 20, a secondary pressurization hydraulic cylinder 36, and a secondary pressurization pin 38 connected to the piston of the secondary pressurization hydraulic cylinder 36 to be driven thereby. The push-out pins 34 can move relatively to the movable die 18 between a retreated position where its tip 1 end portion does not project into the cavity 20 and an advanced position where its tip end portion projects from the surface of the cavity 20 (the inner wall surface of the movable die 18), as shown in Fig.2 and 3, respectively.

The secondary pressurization pin 38 can move relatively to the movable die 18 between a retreated position (solid lines in Fig.2) where its front end portion does not project into the cavity 20 and an advanced position upon secondary pressurization (double-dot chain lines in Fig.2) where its front end portion projects from the surface ot the cavity 20 by a projecting amount less than the projecting amount shown in Fig.3 ( the projecting amount when a cast piece is pushed out by the pushu-out pins 34). The illustrated embodiment is constructed as described above, and during the period from the "mold fastening (making the movable die 18 butt against the fixed die 16)" step until the "injection" step shown in Fig.1, to say nothing of the push-out pins 14, the secondary pressurization pin 38 is held at the retreated position (Fig.2). And, after f illing of molten metal in the cavity 20 has completed through an injection sleeve, the secondary pressurization pin 38 advances into the cavity 20 at an immediate selected timing (double-dot chain lines in Fig.2), and thereby secondary pressurization for the molten metal is effcted. When the molten mdtal within the cavity 20 has finished to solidify, the secondary pressurization pin 38 retreats, the movable platen 12 moves to open the mold 14, the push-out plate 30 that was pushed by the push rods 28 is moved in the direction for approaching the movable die by actuating the push-out hydraulic cylinder 24, hence the push- A out pins 34 and the secondary prerssurization pin 38 project sufficiently largely from the retreated position with respect to the movable die 18, and thereby a cast piece is pushed out from the movable die 18 (Fig.3).

Thereafter, a spray gun 40 is inserted between the fixed die 16 and the movable die 18 as 'shown in Fig.3, then by ejection of air and subsequant spraying of a mold releasing agent, coolin of the fixed die 16, the movable die 18 and the secondary pressurization pin 38 as well as application of a mold releasing agent therto are effected, and the next casting process is commenced.

In the die casting apparatus according to the abovedescribed preferred embodiment, when the cast piece is removed from the movable die 18 by means of the push-out pins 34, since the secondary pressurization pin 38 also projects simultaneously by the same stroke as the push-out pins 34, if cooling of the mold 14 is carried out under such condition, cooling of the secondary poressurization pin. 38 can be effected over a sufficiently large scope exceeding the contact range with the molten metal, and so, generation of baking and adhesion of molten metal to the secondary pressurization pin 38 can be preliminarily inhibited. In addition, cooling and application of a mold releasing agent for the mold 14 and the secondary pressurization pin 38 can be carried out under the condition where a cast piece has been removed from the movable die 18 without employing a special control system, hence not only reduction of a manufacturing cost of an apparatus can be achieved, but also increase of the number of steps (the increase of the number 1 1 of steps in the meaning of projecting the secondary pressurization pin 38 after a cast piece has been push-out) can be suppressed, and thereby improvements in a productivity can be contemplated.

As will be apparent from the above description, a die casting apparatus in which a s.econdary pressurization hydraulic cylinder for driving a secondary pressurization pin is mounted to a push-out plate carrying push-out pins and adapted to advance or retreat relatively to a movable die as hydraulically driven, has been proposed.

In this die casting apparatus, since the secondary pressurization pin projects largely (by a projecting amount exceeding the secondary pressurization stroke) jointly with the push-out pins when a cast piece is pushed out f rom the mold, if cooling of the mold (and application of a mold releasing agent thereto) is carried out under such condition, cooling of the secondary pressurization pin (and application of a mold releasing agent thereto) can be performed effectively, moreover there is no need to employ a special control system, and there is no need to make the secondary pressurization pin project by actuating the secondary pressurization hydraulic cylinder except for that upon secondary pressurization.

4 t

Claims

1. A die casting apparatus capable of exerting a secondary pressurizing force upon molten metal after completion of filling thereof, which includes a movable die cooperating with a fixed die to form a mold, said movable die being provided with cast piece push-out pins and a secondary pressurization pin penetrating therethrough; characterized in that said apparatus comprises a push-out plate carrying said push-out pins and adapted to advance or retreat relatively to said movable die as hydraulically driven, and a secondary pressurizaion hydraulic cylinder mounted to said push-out plate for driving said secondary pressurization pin.

2. A die casting apparatus as claimed in Claim 1, wherein said push-out pins and said secondary pressurization pin extend from said push-out plate in parallel to each other.

3. A die casting apparatus as claimed in Claim 1 or 2, wherein the amount of movement of said push-out plate relative to said movable die is larger than the amount of movement of said secondary pressurization pin relative to said push-out plate.

4. A die casting apparatus as claimed in claim 3, wherein said apparatus comprises a movable platen to which said movable die is fixed, a hydraulic cylinder for driving pushout pins that is mounted to said movable platen with the tip end of its piston rod fixedly secured to said movable platen, and push rods connecting the base plate of said hydraulic cylinder with said push- out plate.

5. A die casting apparatus substantially as described with reference to, and as shown in, Figures 2 and 3 of the accompanying drawings.

1 i P,abhshed 1988 al The Pate.---Ot^ice. Stat. House- 66 71 High ndlbcrn. London WC1R 4TF_ Further copies may. be obtained The Patent Oflice Sales Branch. St Mary Cray. Orpington. Kent BR5 3RD. Printed by Multiplex techniques ltd. St Mary Cray, Kent. Con. 1187.