Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
  • B22D17/20—Accessories: Details
  • B22D17/2015—Means for forcing the molten metal into the die

Definitions

• injection unit for a hydraulic die-casting machine provided with a device for the elimination of pressure peaks at injection.
• the present invention relates to an injection unit for a hydraulic die-casting machine, provided with a device for the elimination of pressure peaks at injection.
• such injection units comprise an injection cylinder, an inject.on piston slidably housed in the cylinder and valve means suitable for sequentially placing in communication with the cylinder first a fluid supply pump for a possible slow advancement stage of the injection piston and subsequently a fluid accumulator for a second fast advancement stage of the injection piston.
• Such units also comprise a pressure multiplier which has the function of subsequently raising the pressure of the fluid acting on the injection piston for a third short advancement stage at slow speed and high pressure. The latter stage allows the molten metal to reach and fill with adequate compactness the most distant and difficult interstices of the casting cavity.
• the object of the present invention is to overcome this drawback by accomplishing an injection unit in which such pressure peak is eliminated.
• an injection unit for a hydraulic die-casting machine comprising an injection cylinder, a hydraulically-operated injection piston, a fluid accumulator for the operation at high speed of the injection piston during the injection stroke and a pressure multiplier for the operation at low speed and high pressure of the piston at the end of the injection stroke of the piston, characterized in that it further comprises an auxiliary cylinder/piston unit interposed between the injection piston and the accumulator to allow the advancement of the auxiliary piston under the action of the accumulator and the advancement of said injection piston in accordance with that of said auxiliary piston, the cross-section of said auxiliary cylinder being larger than the cross-section of said injection cylinder.
• the difference between the cross-sections of the injection piston and of the auxiliary piston is such that the auxiliary piston moves at a speed that is lower than that of the injection piston and reaches the end of the stroke in a controlled manner so as to avoid the creation of pressure peaks on the injected metal.
• Fig. 1 illustrates the unit at rest in one embodiment
• Fig. 2 illustrates the unit during the injection stage
• Fig. 3 illustrates the unit during the pressure multiplication stage
• Fig. 4 illustrates the unit during the return stage from the injection;
• Fig.s 5 - 8 illustrate another embodiment according to the invention in the same operating stages of Fig.s 1 - 4.
• the injection unit comprises a high-speed accumulator 1 consisting of a cylindrical chamber 14 in which a piston 15 slides.
• the upper part of the cylindrical chamber 14 is filled with nitrogen 2 under pressure from a cylinder 19, while the lower part is filled with fluid 30 which, pushed by the piston 15, through a connecting conduit 5, under the action of valve means constituted by a valve shell 31 and by a variable-action breech 32, causes the advancement of a piston 7 of an auxiliary cylinder/piston unit 6, 7 provided with a Linear speed transducer 71.
• the cylindrical chamber 6 is filled in the front with fluid 40 which, pushed in a conduit 8 provided with a unidirectional valve 60 by the movement of the piston 7, causes the advancement of an injection piston 10 into a corresponding injection cylinder 9 provided with a rapid discharge valve 65 (of a type known in itself).
• a pressure multiplier 12 With the injection cylinder/piston unit 9, 10, provided with an injection stem 42, there is connected through a line 11, provided with a unidirectional valve 61, a pressure multiplier 12.
• the latter comprises an accumulator 13 consisting of a cylinder/piston 16, 17.
• the upper part of the cylindrical chamber 16 is filLed with nitrogen under pressure 18 which causes the sliding action of the piston 17, while the lower part of the chamber 16 is filled with fluid 50 which, pushed by the piston 17, through the line 51 under the action of valve means constituted by a valve shell 20 and a variable- action breech 21, causes the advancement of a cylinder/piston pair 53, 52 which in turn with fluid 54 causes the sliding action of the injection piston 10 in the corresponding cylinder 9.
• the molten mass present in the injection cylinder 9 is compressed by the stem 42 in the proximity of the injection mouth (not shown).
• the Larger diameter of the auxiliary cylinder 6 with respect to the injection cylinder 9 causes the speed of the auxiliary piston 7 during its stroke to be Lower than that of the injection piston 10 and thus easily controllable.
• the action of the pressure multiplier 12 then follows in a controlled manner.
• the piston 17, pushed by the nitrogen under pressure 18 present in the upper part of the cylinder 16 starts its stroke and pushes the fluid 50 into the line 51 under the action of the valve means 20, 21 and, through the cylinder/piston pair 53, 52 and the corresponding control fluid 54, causing the sliding action with the multiplication of the pressure of the injection piston 10 in the corresponding cylinder 9.
• the increase in ' pressure that occurs during this stage does not create undesired pressure peaks on the injection piston 10 and thus on the molten mass to be injected.
• at the end of this stage there is the restoration of the initial conditions for the pistons 15, 7, 10, 52, 17 in the respective cylinders 14, 6, 9, 53, 16.
• auxiliary piston 7 also operates in the ambit of the pressure multiplier 12.
• the piston 7 has a part with a smaller diameter which co-operates with the cylinder 6 supplied with fluid 30 from the accumulator 1 through a unidirectional valve 85 and communicating with the injection cylinder 9 through a valve 87 with a floating breech 88 and a part with a larger diameter which co-operates with a cylinder 86 supplied with fluid 50 from the accumulator 13 through the valve 20 with controlled breech 21 and communicating with the injection cylinder 9 through the unidirectional valve 61.
• Fig.s 5 - 8 also show two unidirectional valves 91 and 92 destined to the supply of fluid under pressure for recharging the accumulators 1 and 13 and a valve 93 with a floating breech 94 for discharging the fluid sent back by the injection piston 10 during the stages when it returns to the at rest position.
• the movement of opening of the breech 32 causes the supply of fluid 30 through the unidirectional valve 85 into the cylinder 6, where the piston 7 is thus caused to move forward so that, in turn, through the unidirectional valve 61, it causes the advancement of the injection piston 10 inside the injection cylinder 9 (with the valve 65 open ) for the stage of injection of the metal into the casting cavity (Fig. 6).
• the breech 21 is caused to open, allowing the transfer of high- pressure fluid from the accumulator 13 to the auxiliary cylinder 86, where the above fluid causes the auxiliary piston 7 to move backward and, due to the difference in area, the consequent creation of a multiplied pressure in the cylinder 6, which opens the valve 87 and goes to supply the injection piston 10 (Fig. 7). This creates the pressure multiplier effect on the molten metal pushed by the piston stem 42.
• valves 31, 32 and 21, 10 close again and thanks to the valve 65 the injection piston 10 is caused to return, thus discharging fluid through the valve 93 (Fig. 8).

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Injection Moulding Of Plastics Or The Like (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)
• Molds, Cores, And Manufacturing Methods Thereof (AREA)
• Fluid-Pressure Circuits (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=11166319

Family Applications (1)

Country Status (7)

Cited By (3)

Families Citing this family (1)

Citations (3)

• 1990
  • 1990-05-22 IT IT02039490A patent/IT1248476B/it active IP Right Grant
• 1991
  • 1991-05-15 WO PCT/EP1991/000913 patent/WO1991017850A1/en not_active Ceased
  • 1991-05-15 DE DE69116361T patent/DE69116361T2/de not_active Expired - Fee Related
  • 1991-05-15 EP EP91909466A patent/EP0530244B1/en not_active Expired - Lifetime
  • 1991-05-15 ES ES91909466T patent/ES2080948T3/es not_active Expired - Lifetime
  • 1991-05-15 AT AT91909466T patent/ATE132781T1/de active
  • 1991-05-22 CN CN91103431.5A patent/CN1056643A/zh active Pending

Patent Citations (3)

Non-Patent Citations (1)

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