FR2506041A1 - CONTROL DEVICE FOR THE HYDRAULIC CIRCULATION OF A MACHINE FOR MOLDING SYNTHETIC INJECTION MATERIALS - Google Patents

Abstract

IN A CONTROL DEVICE FOR INJECTION MOLDING MACHINES THE FLOW RATE AND DISCHARGE PRESSURE OF THE REGULATOR PUMP ARE SUITABLE FOR THE DIFFERENT CONDITIONS REQUIRED OF THE RECEIVER USING A SINGLE PROPORTIONAL FLOW DISTRIBUTOR 12, A PILOT RETURN DUCT 22 ADJUSTING THE REGULATOR PUMP FOR THIS PURPOSE 16. TO PROGRAM ADJUSTMENT OF THE FLOW OF THE PROPORTIONAL FLOW DISTRIBUTOR 12 IS SUBSTITUTED, UNDER DETERMINED PRESSURE CONDITIONS, AUTOMATICALLY THROUGH A PRESSURE SENSOR 24 A PROGRAM ADJUSTMENT . THE REGULATOR PUMP 16 IS ALWAYS CONTROLLED, DEPENDING ON THE PRESSURE IN THE RECEIVER DUCT 13 BEFORE DISTRIBUTOR 12, AS IT EXISTS BETWEEN THE REGULATOR PUMP 16 AND THE RECEIVER DUCT 13 DOWNSTREAM OF DISTRIBUTOR 12 A GRADIENT CONSTANT WORKING PRESSURE.

Description

Control device for the hydraulic circulation of a

  injection molding machine for synthetic materials.

  The present invention relates to a device for

  - request for the hydraulic circulation of a plastic injection molding machine, allowing the flow rate and the discharge pressure of the regulating pump to be adapted to the varied conditions required by the receiver during the different phases of a cycle working using a proportional distributor system whose passage section is adjustable by electrical input signals, device in which a return pilot duct is provided which downstream of the proportional distributor system extends bypass from the receiver duct and readjust the regulating pump and the

  proportional valve is in a regulated circuit

  tor with at least one displacement detector by means of the

  which a setting of the proportional valve system that does not correspond to the nominal value can be reduced to the

  nominal value fixed in advance by the program.

  In a known control device of this kind

  (French patent No. 2 317 084 (7 619 502)) the distribution system

  proportional tributary includes both a distributor

  proportional flow and a pressure distributor

  portable in the regulator circuit of each of which is a displacement detector Such a control device provides a geometrical quantity, the position of the

  body of each proportional valve being adjustable.

  This gives for the operating intervals, in

  especially the pressures and speeds at the reception

  a qualitatively very satisfactory control thanks to which the energy consumption by the regulating pump is adapted, at a lower limit,

  to the actual performance required of the receiver.

  The present invention aims, starting from this

  state of the art, perfecting a device for

  demand of the kind mentioned above in such a way that it can satisfy the most diverse forms of programs much better, especially also with regard to a pressure program control directly adapted to the receiver, and at the same time the pump regulator to operate in a way that reduces consumption

energy to a minimum.

  This object is achieved according to the invention, with regard to

  relates to a control device for hy-

  hydraulics of a plastic molding machine

  by injection, allowing flow and pressure

  flow of the regulating pump to be adapted to the condi-

  various requirements of the receiver during the different

  phases of a work cycle using a distribution system

  proportional distributor whose cross section is

  adjustable by electrical input signals, device in which a return pilot duct is provided which downstream of the proportional distributor system extends in bypass from the receiver duct and readjusts the

  regulating pump, and proportionate distributor system

  nel is in a regulator circuit with at least one

  displacement sensor by means of which a system setting

  proportional valve not corresponding to

  the nominal value can be reduced to the nominal value fi-

  xed in advance by the program, by the fact that with the program setting of the flow rate of the proportional distributor system can be substituted according to at least one criterion (route, time, pressure), for determined required pressure conditions (by example the subsequent pressure phase during injection and the safety phases of the tool when closing the mold), via a pressure sensor automatically a pressure program setting during which the sensor pressure takes the

  position of the displacement detector in the regulated circuit

  proportional distributor system, and that as long

  in the case of flow program adjustment than in the case of adjustment

  ge with pressure program the regulating pump can be

  controlled via the pilot line in re-

  tower, depending on the pressure prevailing in the section of the

  receiver duct located downstream of the distribution system

  proportional stopper, so that in the case of flow program adjustment and in the case of pressure program adjustment there is between the regulating pump and said section of the receiver duct a pressure gradient of

constant service.

  By the term "servideal pressure gradient" is meant here a gradient which is in any case essential for the operation and control of the

  regulating pump and constitutes in this respect the lower limit

better.

  In a device thus designed, the adjustment can also

  Lement take place directly according to the pressure of the hydraulic fluid Of course, the position of the body

  of the distributor in the proportional distributor system

  nel is also adjusted in this case, using a sensor

  displacement sensor cooperating with the electromagnet

  order, so as to obtain a variation in cross-section

  Dedicated by program and repeating cyclically The power delivered by the regulating pump is now however determined according to the evolution of the pressure in the receiver duct downstream of the proportional flow distributor, for a minimum discharge pressure

  constant of the circulation pump, which is essential

  thinkable for maximum energy savings.

  From a design point of view, the

  control according to the invention also fulfills the conditions

  relatively simple and therefore inexpensive construction, because it can operate at high speed with a

  only proportional flow distributor.

  To allow various speed levels the circuit

  cooked proportional distributor system regulator

  may include, in addition to the pressure sensor, a transducer

  tension-tread which is mounted directly on the level

of the receiver.

  The invention is explained in more detail below

  using an exemplary embodiment illustrated in the drawing an-

  attached. The single figure schematically shows the circuit

  hydraulic control device.

  The control device comprises an assembly 10 formed by a distributor and additional components, a motor-pump unit 11 and a set 50 comprising a path-voltage transducer S / UZ 6 for speed adjustment concerning speed levels very varied, which is equivalent to a

flow program setting.

  From the regulating pump 16 equipped with a

  control unit 17 and forming part of the motor-pump group It a conduit 25 leads to the oil filter 18 from which a conduit opens into the reservoir 19 A conduit 14 extending

  from the assembly 10 formed by a distributor and or-

  auxiliary ganes also opens into the tank 19 The regulating pump, which can for example be a radial piston pump, an axial piston pump or a pump

  multicellular with pallets, is provided with a regulating organ

  tor 20 o leads a return pilot pipe 22

  extending from the assembly 10 formed by a distributor

tor and related bodies.

  Set 10 includes a flow distributor

  portable 12 at high working speed which has a part 12 a interposed in the conduit 13 which extends through

  shot from the regulating pump 16 to the receiver and presents

  te a section 13 a located upstream of the flow distributor

  proportional 12 and a section 13 b located downstream of the distribution

  stopper 12 The return pilot duct 22 extends in bypass from section 13 b of the receiver duct

  13, i.e. from a point downstream of the

  proportional flow regulator 12, in order to be able to

  apply the regulating pump 16 as a function of the pressure

  prevailing in the receiver duct.

  In the return pilot duct 22 is inserted a damping diaphragm 21 A pressure relief valve 15 is located in a duct 23 connecting the section 13a of the duct 13 of the receiver to the duct 14 leading to the tank The elec-1 three-magnet of command 12 d provided on the pilot stage 12 b of the

  proportional flow distributor 12 cooperates with a

  displacement sensor 12 c The displacement sensor 12 c is therefore in a regulating circuit by means of which

  values of the proportional flow distributor which differs

  face value can be reduced to this

  nominal value The pilot stage 12 b can be supplied al-

  ternatively by an external hydraulic oil source 27 via a conduit 29 or else from a

  internal hydraulic oil source consisting of a

  sampling line 28 from the receiver duct 13

at section 13 a.

  If varying speed levels are controlled, follow

  before a preset program based on an appropriate setting

  required from the body of the proportional flow distributor 12

  using the 12 c displacement detector via

  re from the pilot stage 12 bla pressure can be taken by the return pilot pipe 22 at the same place of the section 13b of the receiver pipe 13 as that where the

  pressure 24 detects the pressure in the event of a command to pro-

gram of pressure.

  The voltage-path transducer 26 of the assembly

  designed to regulate various speed levels,

  that is to say to regulate flows, comprises a part under tension

  sion U As a transducer can be used by

  example a linear or rotary potentiometer.

  The control device can be used for multi-

many ways.

  Adjusting the proportional flow valve

  12, preset in the computer and realized by con-

  sequent according to a program, constitutes the basis of the

  tif control according to the invention in the sense that a

  flow or pressure setting established at the distributor

  proportional flow stopper 12 and not corresponding to

  the nominal value can be reduced to this nominal value

  alternatively by means of the displacement detector 12 c, the voltage-path transducer 26 or the

  pressure 24 participating in the regulator circuit The perfor-

  mances, for example constantly variable speeds and pressures required at the receiver during the working cycle are taken into account by a corresponding control pump control via

  of the return pilot duct 22 as a function of the pressure

  reign prevailing in section 13 b of the receiver duct 13 downstream of the proportional flow distributor 12 TO

  In this respect, the pressure gradient between the regulated pump

  16 and the receiver duct 13 at the section

  Lesson 13 b located downstream of the proportional flow distributor

  nel 12 is always kept constant The pressure difference can for example be close to 11 bars This value represents a lower limit for which the regulating pump is still capable of operating and

  likely to be controlled -The command is therefore essential-

  also a flow control which provides by means of the detector

  displacement sensor 12 c a geometrical quantity, namely the adjustment of the body of the proportional flow distributor being carried out during the injection cycle according to a program This flow control is superimposed with a pressure program control Depending on level requirements

  from the receiver the control device switches automatically-

  from the flow control to the program control of

  pressure This change is made according to certain criteria.

  res, for example according to the distance traveled at the level of the receiver, or as a function of time or, by means of the pressure sensor 24, as a function of the pressure of the oil in the receiver duct or also by a pressure sensor

  mounted directly at the receiver For each cry-

  the transition from control to flow program to the

  pressure program control occurs in the event of

  passing of a determined signal amplitude fixed at a-

  vance in the computer A pressure program command takes place for example in the pressure maintenance phase after the injection of the plastic material into the injection mold and during the closing of the mold during

  the sareness phase of the tool At this command

  gram pressure can again, depending on a large

  date fixed in advance in the computer, replace a flow program control oriented directly to the

  level of the receiver and which is realized on the basis of the

  seems 50 comprising the path-voltage transducer for speed adjustment In this sense, the so-called pressure program command is a combined program command

  flow and pressure program in which the

  proportional flow regulator is no longer controlled by the displacement detector 12 c but for example directly by the voltage-path transducer 26 or by the pressure sensor 24 In all cases, the pilot line

  return 22 however ensures a readjustment of the regulated pump

  latrice 16 so that the pressure gradient between

  the regulating pump 16 and the section 13 b of the return duct

  sensor has a constant minimum value.

  In the embodiment shown in the figure

  gure single the pressure sensor 24 samples, as shown

  above, the pressure in the same place of the receiver duct 13 as that where the pilot pipe returns

  22 takes the pressure The pressure sensor 24 can

  during also be mounted directly on the receiver

in conduit 13.

  In many cases it may be useful to plan, or-

  be the pressure sensor 24, another pressure sensor

  pressure which takes the pressure in the cavity of the mold

  jection This other pressure sensor is intended and suitable, as part of a pressure adjustment, for controlling the

  pressure in the mold cavity It cannot therefore replace

  place the pressure sensor 24 which is suitable for

  very areas of pressure control, whether it's

  for example to use the maximum pressure or to close the

  injection mold under low pressure.

  The additional pressure sensor can be carried by a bolt passing through the wall of the injection mold II

  can then be easily removed from the injection mold and

  placed in it The addition pressure sensor

  However, it can also be mounted on the rear side of an injection mold ejection pin since this ejection pin limits with its front side before the mold cavity and is therefore able to transmit pressure data from the cavity. from mold to pressure sensor

mounted on the rear c 8 tee.

  The additional pressure sensor is therefore an ele

  essential constituent of a superimposed mode of adjustment

  with the usual pressure adjustment carried out by means of the

pressure sensor 24.

  A work cycle adjusted by means of the

  order takes place for example, starting from the mold

  open jection, in several successive phases:

  1) The injection mold closes the iron movement

  necessary steps can be taken at different speeds

  The essential debit program for this

  is adjusted via the displacement sensor

  12 c or the 26 Au voltage-transducer

  during the closing movement we pass through an inter-

  safety valve for the injection mold during

  which a pressure adjustment via the cap-

  pressure sensor 24 is superimposed on the speed control.

  This means that when the limiting pressure ad-

  missile planned by the program is reached it spreads

  automatically blit a pressure setting.

  2) the injection nozzle is placed on the injection mold; this is done by means of a speed program to which a program is superimposed

  pressure During this phase the adjustment

  reads respectively through the

  displacement 12 c and of the pressure sensor 24.

  3) The plastic is injected into the mold.

  The injection is carried out via a program-

  speed me which is equivalent to a flow program Ce

  flow program is set via the

  displacement sensor 12 c or of the transducer

  voltage 26 The flow program is superimposed for

  safety reasons pressure adjustment via

  diary of the pressure sensor 24 As soon as a pressure predicted by the program is reached in the injection mold, there is a transition to a pressure maintenance program This is done by means of a pressure sensor in the injection mold or a

  pressure sensor in the hydraulic circuit,

  ie preferably in the flow dispenser pro-

  portional 12 or on the injection cylinder.

  4) The plastic is plasticized using the plasticizing screw in the plasticizing cylinder

  (injection cylinder) via a program-

  speed me The drive of the plastic screw

  tion is effected by means of a hydro-

  The necessary program flow adjustment in this respect is carried out by means of the

  displacement 12 c or of the voltage-path transducer 26.

  5) Then the injection nozzle is removed from the injection mold

  jection through a speed program

(debit program).

  6) Then the injection mold opens The necessary opening movement can be carried out at different speeds The flow program necessary for this

  regard is set via the detection sensor

  placement 12 ó or of the voltage-path transducer 26.

  7) The finished molded part is ejected The hy-

  hydraulics is controlled during the forward movement as during the backward movement by means of a speed program to which a program is superimposed

  pressure In this respect the adjustment is carried out by the

  12 c displacement sensor or trans-

  path-voltage conductor 26 as well as the

pressure 24.

Claims (9)

  1 Control device for hy-   hydraulics of a plastic molding machine   by injection, allowing flow and pressure   flow of the regulating pump to be adapted to the con-   various editions required of the receiver during the different   annuities phases of a work cycle using a proportional distributor system including the passage section   is adjustable by electrical input signals, available   sitive in which a pilot line is provided in re-   tower which downstream of the proportional distributor system extends in bypass from the receiver duct and   readjusts the regulating pump and the distribution system   proportional sensor is in a regulating circuit with at least one displacement detector by means of which a setting of the proportional valve system which does not correspond to the nominal value can be brought back to   the nominal value fixed in advance by the program, ie   characterized in that at the program setting of the system flow   proportional distributor may replace the following   with at least one criterion (course, time, pressure), for   determined required pressure conditions (e.g.   the pressure maintenance phase during injection and the safety phases of the tool when the mold is closed), via a pressure sensor (24) automatically a program pressure adjustment at neck Is   from which the pressure sensor (24) takes the place of the   displacement sensor (12 c) in the regulator circuit of the proportional valve system, and in that   in the case of flow program adjustment than in the case of adjustment   ge pressure program the regulating pump (16) can be controlled via the return pilot line (22), depending on the pressure prevailing in the section (13 b) of the receiver line (13) located in downstream of the proportional distributor system, so   only in case of flow program adjustment and in case of   pressure program setting there is between the pump   gulator (16) and the section (13 b) of the receiver duct   a constant operating pressure gradient.   2 control device according to claim   1, characterized in that the distributor system provides   is made up of a single professional flow distributor   portable (12) at high operating speed.   3 control device according to claim   1 or 2, characterized in that to allow different ni-   speed calves there is in the regulator circuit of the proportional distributor system, in addition to the pressure sensor (24), a voltage-path transducer (26) which   is mounted directly on the receiver.   4 Control device according to any one   of claims 1 to 3, characterized in that, for the re-   flow program setting used to obtain different speed levels with regard to the receiver, it can be interconnected in the regulator circuit of the proportional distributor system alternatively the displacement detector (12 c) or a voltage-path transducer (26).   Control device according to any one   claims 1 to 4, characterized in that the amplifiers   signal studies planned within the framework of each criterion and triggering the transition from the setting to flow program to setting to pressure program are fixed in advance   in the computer for a given work cycle.   6 Control device according to any one   of claims 1 to 5, characterized in that a diaphragm   cushioning (21) is interposed in the pilo- return step (22).   7 to Control device according to any one   of claims 1 to 6, -characterized in that the system   proportional valve is selectively supplied by an internal (28) or external hydraulic oil source (27).   8 Control device according to any one   claims 1 to 7, characterized in that a limiter   pressure (15) is mounted in the section (13 a) of the duct   receiver (13) upstream of the proportional flow distributor tional (12).   9 Control device according to any one   claims 1 to 8, characterized in that the sample   pressure through the return pilot line   (22) in the case of flow program adjustment and the sample   pressure sensor by the pressure sensor (24) in the event of   pressure program adjustment takes place at the same   right of the receiver duct (13).   Control device according to any one   claims 1 to 8, characterized in that the sensor   pressure (24) is mounted directly at the receiver   tor in the conduit (13), in that it is provided, in addition to the   pressure sensor (24), an additional pressure sensor   pressure sampling in the cavity of the injection mold   tion, and in that the additional pressure sensor is carried by a bolt passing through the wall of the injection mold, the additional pressure sensor being mounted on a spindle injection mold ejection.