FR2656245A1 - METHOD AND DEVICE FOR MANUFACTURING MOLDED PARTS COMPRISING CAVITIES. - Google Patents

Abstract

This device comprises a nozzle (2) mounted in the mold (1) and connected by means of a first valve (7) which can be controlled and of a regulator (8) to the compressed air tank (9), the nozzle being connected by means of a second controllable valve (4), to the sealed chamber (5) containing the reservoir for the melt, and a level sensor (12) is mounted on the pipe (11) of the machine, which conveys matter. Application in particular in the field of foundry machines used to perform counter-pressure molding.

Description

i 2656245

  Method and apparatus for making molded parts

  The invention relates to a method and a device for manufacturing molded articles having cavities, and in particular shaped moldings used

in the foundry industry.

  A process for making hollow articles using silicate melts (Bulgarian Patent No. 17,065) is known in which the silicate melt is introduced into a prepared shell mold which can be flattened at a desired temperature. moment, we introduce the rest of the

  melt by flipping the die, turning its

  A hollow article is formed from the shell-shaped molded material having a configuration reproducing the molding surfaces of the matrix used. The thickness of the wall of the finished article is a function of the time of the mold. stay of the melt in the mold. A disadvantage of this method lies in the fact that the overturning of the mold implies a consumption in

additional energy.

  Another disadvantage is the increased duration of the process since the rollover -should be performed slowly with smooth starting and stopping due to the presence of high inertia forces while

  that the exit of the melt is impeded by the displacement

antagonistic to the air.

  There is known a device for producing, with the application of a low pressure, thin-walled molded parts comprising cavities, and in which, under

  the action of a pressure higher than the atmospheric pressure

  the melt from the reservoir, which contains it and is arranged in a sealed chamber, circulates

  in a conduit to enter a chamber under pres-

  with two conical cavities that are connected

  to one another and to the said channel The first

  Conicality is connected at the extreme end

  on the mold while the other cavity is

  corded by means of a pipe to a faucet that

  carries at least four positions The first position of the

  faucet establishes a connection to a gas source

  awarded, the second position establishes a communication with

  the volume of gas in the closed chamber

  the third position establishes a connection with the pipe of the second conical cavity of the pressure chamber and the fourth position establishes a connection

  to the atmosphere (French Patent No. 02 147 827).

  The two conical cavities of the pressure chamber have almost identical volumes and are interconnected by a passage whose cross section is equal to that of the pipe used to convey the material The volume of the conical cavity, which is connected to the tap , is such that when the mold is

  the level of the melt in this category.

  must be below a certain level.

  In its upper part, at the beginning of the canali-

  connecting the one of the conical cavities to the valve, the pressure chamber comprises a device stopping the flow of gas entering this cavity, when the

  melt has reached a determined level.

  A disadvantage of this device lies in the

  fact that it allows for the molding of unique articles-

  under a low pressure, and which is particularly suitable for molding thin-walled hollow workpieces,

  which imposes the presence of an intermediate chamber

  pressure and a valve controlling the

molding phases.

  Another disadvantage is that the evacuation of the melt out of the cavity area

  in the molded part is achieved by means of the

  gravity pleating with a bubbling, by counter-current circulation, of the air which occupies the volume released by the

  melt This mode of evacuation of the melt

  This considerably prolongs the duration of this evacuation and therefore also lengthens the molding cycle and reduces the accuracy of obtaining the dimensions of the cavity. Additional oxidation and additional gasification of the melt also takes place. outside of this, the machine presents a weak

  yield since the mold is removed after

  melting process, which requires an inter-

  much longer than the duration of the operation.

molding.

  Also known is a method and apparatus for making molded parts from metals and alloys by means of counter pressure molding (patent

Bulgarian 38,717).

  A disadvantage of this process is that it is unsuitable for molding shaped moldings having cavities having a complex configuration since the melt can not solidify at the surface in the mold.

  the upper end of the cavity of the matrix.

  Another disadvantage of this process lies in

  the fact that, to push the melt out of the body,

  it is necessary to increase the pressure in the

  It appears from the chamber in which the mold is located, resulting in increased gas consumption at a higher pressure, which gives the process greater inertia. A disadvantage of this device lies in the fact that we can not detect the passage of the surface

  free of the melt, which leaves the matrix under the control of

  gas placed under increased pressure in space

  extending from the bottom level to the bottom end

  the channel of the pouring gate, so that the risk of an escape of this gas under increased pressure through the melt located in the crucible and the overflow of the molten mass can not be avoided.

  along the walls and the oven lid.

  Another disadvantage lies in the fact that this device does not make it possible to control the process of solidarity.

  which produces the blank in the matrix.

  The object of the present invention is to provide a method and a device for manufacturing molded parts having cavities, and thanks to which, after the complete filling of the cavity in the mold by the melt, the latter is repressed only

  out of the cavity area in the casting.

  This object is achieved using a method for making molded articles having cavities,

  in which, under the action of the pressure or the dif-

  As a result of the pressure difference between the sealed chamber and the reservoir housing the melt and the chamber equipped with the mold for forming the molded part, the melt circulates in a pipe so as to fill the cavity of the mold and begins to solidify. The solidification process continues until the molded part is obtained with its configuration. Next, the melt is forced back into the tank by means of

  direct introduction into the areas of the cavities

  in the molded part, a gas having a pressure equal to or greater than the pressure acting on the mass

melted in the tank.

  The object of the invention is also achieved by means of a device for manufacturing molded parts having cavities, connected to a machine used to

  back-pressure molding, this device

  taking a nozzle mounted in the mold and connected via a first controllable valve and a pressure reducer to the compressed air reservoir, the nozzle being connected via a second controllable valve, to the sealed chamber containing the tank for the melt, and a level sensor is mounted on

  the channeling of the machine, which conveys the material.

  An advantage of this method lies in the fact that it creates conditions improving the structure of the

  molded piece due to the careful training and com-

  plete of the molded part by means of a solidification of

  controllable mass of the melt and a compensation

  the lack of volume from the free phase.

  which fills the cavity area of the molded part.

  Another advantage lies in the fact that, when one avoids the use of single nuclei, one can

  to save material, energy and labor

  for the production of cores and the elimination of the cores of molded parts.

  the work of the operator working on the machine

  and increases productivity because of the removal of

  In addition, this reduces the prerequisites for the creation of rejects since the risks associated with the possibility of breakage or crushing of cores of

  sand and exhaust gas are removed.

  The advantages of this process can be obtained

  and to this device, by applying them to an existing machine

  aunt used for back pressure molding.

  Another advantage of the device lies in the

  that the setting of the temperature conditions of the machine

  trice, by which the solidification is controlled

  of the molded part and the formation of cavities in

  this room, can be controlled by a micro-ordina-

tor.

  Other features and advantages of the pre-

  invention will emerge from the description given below.

  after making reference to the accompanying drawing, which shows a diagram of the device according to the invention and a machine

counter-pressure molding.

  The device shown in the figure comprises a nozzle 2 which is mounted in the mold and one end of which is connected to the zone of the cavity 3 located in the molded part, while its other end is connected by means of a controllable valve 4, to the sealed chamber 5, in which is placed a tank for the melt 6 The mold is connected via a first controllable valve 7 and a pressure reducer 8 to a tank 9 for the gas under pressure, to which is connected

  the pressure gauge 10 A sensor 12, which serves to detect the

  calf of the melt and is connected to the microcomputer

  13, is mounted on the pipe 11 conveying the material.

  On the microcomputer are connected controllable valves

  14, to which are connected, via the channels

  for coolant, cores

  movable metals 15 and the cooling devices

  The computer is also connected to the

  17 which controls the electric heating elements 18 which are inserted in the mold 1, and the thermocouples 19 and 20 The tank 9 housing the gas under pressure is connected via the valves 21, 22 and 23 to the two sealed chambers 5 and 24 of the machine, which are connected to each other by the valve 25 A valve

  exhaust pipe 26 is connected to the chamber 24.

  The operating mode of the device is the

  In the case where the valves 21,22,23 and 25 are

  green and where valve 7 is closed, the filling of both

  sealed chambers 5 and 24 by the pressurized gas

  tank 9 starts when the operating pressure

  Preset, which is equal in both chambers, is reached, the valves 22, 23 are closed and the valve 26 is opened and the working gas exiting the chamber 24 escapes into the atmosphere and pressure. the interior of this chamber begins to decrease until it reaches a preset value, following which

  the valve 26 closes under the action of the initial pressure.

  in room 5, the mass

  due from the reservoir 6 completely fills the mold 2, circulating in the pipe 11 conveying the material According to a preset program and based on

  information received from the thermocouple 19 which de-

  the temperature of the melt in the tank 6 as well as on the basis of the information received from

  of the thermocouple system 20 which record the temperature

  in the separate areas of the mold, the microcomputer

  13 opening or closing, by means of valves 14, the sending of

  cooling element to the moving metal cores 15 and the cooling device 16, while

  through switch 17, it switches on or off

  connect the electric heating elements 18

  the microcomputer 13 carries out the control of the con-

  temperature conditions in the mold and, through this

  the control of the solidification of the mass

  due to the fact that after the lapse of the determined time interval, the melt takes the configuration of the molded part Then the microcomputer sends a signal to open the valve 7 The working gas at a higher pressure at the pressure prevailing in the chamber 5 and the values of which are preset by means of a pressure reducer 8, penetrates through the valve 7 and through the nozzle 2 into the region of the molding cavity 3

  the effect of the working gas with this higher pressure

  The melt is forced out of the cavity 3 area of the molded part. When the free surface of the melt reaches the level detector 12, the detector sends a signal to the microcomputer 13, which sends a signal.

  closing command of the valve 7 so that the

  Working gas at a higher pressure is

  interrupted, and sends an opening order of one second

  controllable valve 4 In this way, the pressure at

  the calf of the free surface of the melt present in the circulation pipe of the material is made equal to the pressure prevailing in the chamber 5, and consequently the melt continues to return to the tank 16, but under the sole effect of its own weight This avoids

an overflow of the melt.

Claims (2)

  1 Process for manufacturing molded parts   carrying cavities, in which, under the action of the pressure or pressure difference between the sealed chamber and the reservoir housing the melt and the chamber equipped with the mold for forming the molded part, the melt circulates in a pipe so as to fill the cavity of the mold and begins to solidify, characterized in that after the formation of the   the molded part, the melt is   stride into the tank through a di-   in the areas of the cavities formed in the molded part, a gas having a pressure equal to or greater than   the pressure acting on the melt in the tank.   2 Device for producing moving parts   with cavities according to claim 1,   corded to a machine for counter-molding   pressure, characterized in that it comprises a nozzle (2) mounted in the mold (1) and connected via   a first controllable valve (7) and a   tensioner (8) to the compressed air reservoir (9), the nozzle being connected via a second valve   controllable (4), to the sealed chamber (5) containing the   melting tank, and that a level sensor (12) is mounted on the pipe (11) of the machine, which vehicle the material.