FR2488822A1 - INJECTION UNIT FOR PRESSURE CASTING FOUNDRY MACHINES - Google Patents

Abstract

IN REPLACEMENT OF THE USUAL PISTON MULTIPLIER, A SECOND OIL ACCUMULATOR 29 IS PROVIDED, WHICH IS PUT INTO COMMUNICATION WITH THE INJECTION CYLINDER 1 AT THE END OF THE RAPID ADVANCE PHASE OF THE INJECTION PISTON 3.

Description

The present invention relates to a group of in-

  connection for die-casting foundry machines.

  The injection groups for machines of the kind in question which are currently known essentially comprise an injection cylinder, an injection piston slidably mounted in this cylinder and means

  shutters capable of successively putting in communication

  nication with this injection cylinder a fuel pump

  tation in oil, for a first phase of slow advance of the injection piston then an oil accumulator, for

  a second rapid advance phase of the injection piston.

  A pressure multiplier is further provided which has the function of then raising the pressure of the oil which acts on the injection piston during a brief third phase of advance of the piston which occurs under

  high pressure. This last phase allows the metal to melt.

  to safely reach the interstices of the empire-

  which are the most distant and the most diffi

access eyelashes.

  The pressure booster is usual-

  consisting of a piston element, equipped with means

  suitable shutters, which is arranged upstream of the cy-

  injection line and which, without intervening in the first two phases, is controlled in the third phase to partially introduce its rod into the injection cylinder until it is pressed against the injection piston, to quickly raise the pressure

  of oil exerted on this injection piston.

  It is well known to the pressure foundry technician that the multiplier is frequently in itself a source of problems and disadvantages, which range from its construction complexity to relatively long intervention times, to the practical impossibility of making

  vary at will the time of intervention of the multiplica-

  pressure rise time.

  The object of the invention is therefore to produce an injection group for foundry casting machines

  under pressure which does not present the problems and in-

  conveniences that characterize current multipliers.

  According to the invention, this object is achieved by means of an injection group characterized in that

  uses another accumulator as a pressure booster

  oil regulator which other sealing means put in communication with the injection cylinder at the end

  of the second advance phase of the injection piston.

  It is clear that the replacement

  of the traditional piston multiplier, of construction

  tion complicated, by a simple oil accumulator is all to the advantage, not only of the simplicity of

  construction but also functional convenience-

  the, in the sense that one can obviously obtain very short intervention times and also adjustable at will by a simple intervention of adjustment of the

  oil pressure supplied to the accumulator, i.e.

  say by means of a pressure regulator of the type habiti-

  tuel. By judiciously choosing the moment and the

  Methods of opening the shutter means which

  dent the communication between the oil accumulator and the injection cylinder, it is also possible to vary at will both the application time and the time of rise of the final advance pressure of the piston . Other features and benefits of

  the invention will be better understood on reading the

  following description of an example and

  referring to the attached drawing, which shows a group of information

  jection according to the invention in longitudinal section following

before the axis of the injection cylinder.

  As can be seen in the drawing, in an injection cylinder 1 having an internal cavity 2 is slidably mounted an injection piston 3 whose rod 4 ensures, in the usual way, the injection of the molten metal into the mold gaps mounted on the machine. To the injection cylinder 1 is fixed a head which is traversed by a hole 6 disposed after the interior cavity 2 of the cylinder 1. In this hole is lo

  has a fixed valve seat 7 which includes two openings

  diametrically opposite side tures 8 and 9 and a front axial opening 10. The latter is ordered

  by the front head 11 of a double-field valve -12

  gnon which is biased towards its closed position

  by a spring 35 acting on the rear head 13, la-

  what behaves like a piston in a chamber 14 defined inside a rear closing body

attached to head 5.

  The lateral opening 8 of the seat 7 communicates permanently with an internal passage 16 of the head which, in turn, can be connected alternately to

  a spout 17 (as in the case shown in the

  sin) or to an oil supply pump under pressure

  sion 18 (the usual pump for pressure casting machines) depending on the state of a control solenoid valve 19. This same solenoid valve connects the chamber 14 to the feed pump 18 or to the tank 17, in

  alternating with the aforementioned passage 15.

  The other lateral opening 9 communicates with its

  tower with another interior passage 20 that an electro-

  valve 21 keeps alternately closed (as shown

  tee in the drawing) or in communication with a loading and unloading opening 22 of an oil accumulator 23, said opening 22 being furthermore permanently connected to the feed pump 18 through

  a pressure reducer 24 and a non-return valve 25.

  The accumulator 23 includes an internal cavity

  eure 26 intended to contain oil and a piston of

  thrust 27 housed in this cavity 26 and stressed in per-

  manence, to cause the oil to exit, by a suitable gas, generally consisting of nitrogen, which is

contained in a bottle 28.

  Another accumulator 29 is also provided, the internal cavity 30 of which is subdivided by a

  3 piston 31 in an upper part containing a quantity

  predetermined nitrogen tee and a lower part contains

  oil from a high pressure (higher than that of the oil contained in the accumulator 23) supplied by the pump 18 via an adjustable pressure reducer 32 and a non-return valve 33. This

  inner part of the inner cavity of the accumu-

  lator 29 further communicates with the inner hole 6 of the head 5, downstream of the valve 12, through a

  solenoid valve 34 normally closed.

  In operation, the two accumulators

  23 and 29 are previously filled with oil under a pressure

  adequate pressure through the pressure reducers 24 and 32. iIn particular, through the latter,

  can adjust the pressure of the oil in the battery

  mulator 29 over the desired value for the final phase

injection piston 3.

  The start of the injection operation is determined

  undermined by a switching command transmitted to the electro-

  valve 19 which determines the cover of the chamber

  14, so that the spring 25 can cause the closing

  momentary ture of the valve 12, then the transmission of the oil from the pump 18 inside the cavity of the

  valve seat 7 through passage 16 and the opening

  re lateral 8. This oil transmission causes the

  reopening of the valve 12 and, consequently of the opening

  axial front 10 of seat 7, through which

  the oil can reach the injection piston 3 and pro-

  mention a first phase of slow advance of the piston,

  the speed determined by the pump flow.

  The solenoid valve 19 is then brought to rest while the valve 12 is kept open by the pressure thus restored behind its rear head 13 and on the contrary, the solenoid valve 21 is switched so that the oil accumulated in the accumulator 23 is pushed

  by the nitrogen from the bottle 28 to the injection piston

  tion 13 in order to give rise to a second rapid advance phase of the piston. The third phase is finally determined by the switching of the solenoid valve 34, which

  allows the oil under high pressure contained in the ac-

  accumulator 29, in which this oil has prestressed

  the nitrogen also contained in this accumulator,

  switch off the injection piston 3 (also closing the valve) e 12) to determine the short final advance

under high pressure.

  The value of this high pressure is determined as already said by the adjustment of the reduction valve.

  pressure 32, while the instant of application and the -

  pressure rise times are determined by proper setting of the solenoid valve 34. It is important

  note that in each case it is necessary to determine

  correctly mining the internal volume of the accumulator 29 in the project establishment phase so as to

  allow to enclose a very higher quantity of oil in it.

  to that which is necessary for the advance of the injection piston, so as to avoid pressure drops

during the injection stroke.

  Of course, various modifications may be made by those skilled in the art to the device which

  has just been described only by way of an unrelated example

  mitative without departing from the scope of the invention.

R E V E N D I CA TI 0 N S

  1 - Injection unit for underground machines -

  die casting, comprising a cylinder of in-

  jection (1), a sliding injection piston (3)

  in this cylinder, shutter means (i9, 21) intended

  born to successively put in communication with this cy-

  injection liner, first of all an oil supply pump (18), for a first phase of slow advance of the injection piston, then an oil accumulator (28),

  for a second rapid advance phase of the piston

  jection, and pressure multiplier means of-

  then apply a pressure to the injection piston

  higher oil pressure, for a brief third phase

  ahead of the piston under high pressure, this group of

  jection being characterized in that said multiple means

  pressure multipliers include another accumulator-

  oil leveler (29) and other sealing means (34)

  intended to put this other accumulator in communication

  tion with said injection cylinder at the end of said

  second phase of injection piston advance.

  2 - Injection unit according to claim 1, characterized in that said other accumulator (29)

  is supplied via a pressure reducer

  adjustable sion (32) and contains in its internal cavity

  a push piston (31) biased by pre-nitrogen

constrained.