WO2008152665A1

WO2008152665A1 - Die casting machine with double injection cylinder

Info

Publication number: WO2008152665A1
Application number: PCT/IT2007/000425
Authority: WO
Inventors: Giorgio Benzi
Original assignee: Giorgio Benzi
Priority date: 2007-06-15
Filing date: 2007-06-15
Publication date: 2008-12-18

Abstract

The diecasting machine, by means of injection moulding, produces pieces of non- ferrous metal alloys melted to a liquid state; for example, aluminium, zinc, magnesium, etc. During moulding, the machines mould closing system sags with consequent opening and formation of burrs on the pieces produced. The new machine has a double cylinder injection system instead of only one: one operates as a pressure limiter and compactor, the other operates as transferer of liquid metal from the chamber to the mould cavity. This system eliminates pressure peaks inside the mould created by kinetic energy, which are the cause of unwanted burrs.

Description

DESCRIPTION

TITLE OF EWENTION

DIE CASTING MACHINE WITH DOUBLE INJECTION CYLINDER

TECHNICAL FTELD

The die casting machine ( in the following called only "machine") produces, by means of injection moulding, pieces of non ferrous metal alloys melted to a liquid state , such as aluminium, zinc, magnesium, copper, etc.

Fig. 1/10 shows a traditional horizontal cold chamber die casting machine.

Figs. 2/10, 3/10- 4/10 are diagrams of the traditional moulding process.

As can be seen in Figs. 2/10, 3/10 and 4/10, with the traditional injection system there is a piston activated by an oledynamic cylinder, which after loading Fig. 2/10, thrusts the liquid metal into the mould at high speed Fig. 3/10.

When the mould is full additional pressure is applied to the liquid metal to render it compact, Fig. 4/10, this latter phase is normally called intensification or multiple compression.

After a time allowed for solidification the machine opens the mould and the piece is extrated.

The injection system generates in the mould pressure in the range from 200-1200 bars plus overpressure caused by the discharge of kinetic energy of the masses in movement on the inj ected liquid metal.

The masses are formed by: injector piston, piston holder, injection cylinder stem, oil and accumulator pad Fig 1/10

This overpressure creates elastic subsidience in the closure system of the macchine with Consequent slight opening of the mould and formation of burrs ( flashes). BACKGROUND ART.

Current technology has enabled die casting machine manufacturers to attenuate the problem of burrs by slowing injection with and oledynamic system which intervenes upon completion of mould filling in extremely rapid times ( thousands of a second). In order to slow they must reduce the injection speed of the primary cylinder with consequent variations in the quality of the piece. In practice it is not possible to eliminate overpressure without reducing the speed of the primary piston.

DISCLOSURE OF INVENTION

We have previously mentioned the problem we intend to solve with the new double injection cylinder machine, that is: overpressure created in the mould by the kinetic energy of the masses of the injection system in movement, which causes burrs.

The machine mentioned in the title is very similar to a traditional machine for cold chamber die-casting.

The novelty in this machine lies in the fact that it has two independent cylinder injection systems, instead of only one. This injection system ehniinates the problem of overpressure or pressure peaks due to kinetic energy of the masses in movement of the machine itself ans is described in Figs 5/10 and 6/10

With the double cylinder system, filling and absorption of overpressure can be carried out without slowing the injection speed of the primary piston. Figs. 8/10 and 9/10

This result is obtained, after filling the mould, due to increase in volume of the injected metal which is created by withdrawal of the secondary piston Fig. 9/10. The same withdrawal is piloted by the pressure of metal injected by the primary cylinder and by the power of the secondary cylinder which is previously set and contrasts the withdrawal Fig. 9/10.

The power of thrust of the secondary cylinder is maintained constant during withdrawal, by the aid of one or two pressure limiters connected to the cylinder.

The result is that at the end of secondary cylinder withdrawal the primary cylinder will be at the end of the run on the mould with the effect of discharging all the kinetic energy in the system, no longer on the liquid metal but on the mould avoiding unwanter pressure increase.

In brief we have maintained the pressure inside the mould within a set range given by the thrust power- of the secondary cylinder.

In practice the secodary cylinder is used as a pressure limiting device in the mould. After the dampening (cushioning) phase, the secondary cylinder can, if necessary, immediately start the compression phase, applying higher power through an oledynamic/electric circuitwhose start is given by the position of the primary cylinder Fig. 10/10 to complete the production cycle.

BRIEF DESCRIPTION OF DRAWINGS

Figs. 5/10, 6/10, 7/10, 8/10, 9/10, 10/10 show diagrams of the new machine and the new moulding cycle.

Figs. 5/10 and 6/10 show two versions of the double cylinder die casting machine. Note that one is a traditionl cylinder which we have named primary, and the other is the new one which is named secondary.

Figs 2/10, 3/10, 4/10 show a traditionally performed moulding cycle. Fig 1/10 shows a traditional die casting machine with its essential parts indicated.

Claims

1) The dual cylinder injection machine is the only machine that has a cylinder that works as a shock absorber (dampener) of over pressure created by kinetic energy (fig 9/10) and a cylinder that performs injection (fig 5/10, fig 6/10)

2) It is the only machine whose injection and compression phases (multiple or intensification) are carried out respectively by two distinct cylinders in two distinct chambers, (fig 8/10, Fig 10/10)

3) It is the only|machine whic makes the pressure inside the mould indipendent of the injection speed of the primary piston , eliminating over pressure caused by kinetic energy , even in the case of errors in dosing the loaded metal.

4) It is the only machine that has two injection cylinders with connected pistons that enter the mould (direct contact) (fig 5/10 fig 6/10)

5) As claimed in 2) It is the only machine that has an oledynamic electric circuit especially for this purpose.