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Publication numberUS3825386 A
Publication typeGrant
Publication dateJul 23, 1974
Filing dateApr 19, 1973
Priority dateMay 25, 1972
Also published asDE2324839A1
Publication numberUS 3825386 A, US 3825386A, US-A-3825386, US3825386 A, US3825386A
InventorsBello W, Halma P, Van Der Meulen W
Original AssigneePhilips Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Pressing control device
US 3825386 A
Abstract
A pressing device for the pressing of synthetic resin materials in a mould, comprising an hydraulic motor which is provided with a piston which is movable in a cylinder, a piston rod being connected to the said piston. Hydraulic pressing liquid can be supplied to the spaces on both sides of this piston by means of a servo valve. The piston rod is provided with a force detector and a displacement detector. The signals supplied by these detectors are compared with adjusted values. As long as the pressing force remains below the adjusted value, the control unit controls the servo valve such that the piston moves at an adjusted speed. When the adjusted pressing force is reached, the control unit controls the servo valve such that the piston rod does not exceed the adjusted pressing force.
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Description  (OCR text may contain errors)

United States Patent [191 Bello et a1.

[ PRESSING CONTROL DEVICE [75] Inventors: Woltert Bello; Wijbren van der Meulen; Pieter Halma, all of Emmasingcl, Eindhoven, Netherlands [73] Assignee: U.S. Philips Corporation, New

York, NY.

[22] Filed: Apr. 19, 1973 [21] Appl. N0.: 352,585

[30] Foreign Application Priority Data May 25, 1972 Netherlands 7207024 [52] U.S. Cl 425/150, 425/135, 425/406 [51] Int. Cl. B29c 3/06 [58] Field of Search 425/150, 149, 135, 406; 100/48, 53

[56] References Cited UNITED STATES PATENTS 2,441,925 5/1948 Wege 425/150 UX 2,983,956 5/1961 Vogel, Jr. et al.. 425/135 [451 July 23, 1974 Mader, Jr. et al. 425/150 X Gaffney et al. 425/150 [5 7 ABSTRACT A pressing device for the pressing of synthetic resin materials in a mould, comprising an hydraulic motor which is provided with a piston which is movable in a cylinder, a piston rod being connected to the said piston. Hydraulic pressing liquid can'be supplied to the spaces on both sides of this piston by means of a servo valve. The piston rod is provided with a force detector and a displacement detector. The signals supplied by these detectors are compared with adjusted values. As long as the pressing force remains below the adjusted value, the control unit controls the servo valve such that the piston moves at an adjusted speed. When the adjusted pressing force is reached, the control unit controls the servo valve such that the piston rod does not exceed the adjusted pressing force.

2 Claims, 1 Drawing Figure l I l "'22 20 l I I m 2, ll 1. 14* 15 l I l I 1 i i: W I 12-. l. I 10 I 11 l I 16 L 13 9 fl Iv,4 4/ 2 /1, KY

PATENTED JUL 2 3 I974 W H'HY rlllll WWNNWWNNNNWWxQ A PRESSING CONTROL DEVICE The invention relates to a pressing device, in particular for the pressing of synthetic resin materials in a mould, provided with an hydraulic motor which comprises a piston which is movable in a cylinder, a piston rod being connected to said piston, it being possible to supply or withdraw hydraulic pressure liquid to or from the spaces on both sides of said piston by means of a servo valve.

The products which are pressed of synthetic resin materials by means of suitable known pressing devices often have defects. These defects can be inter alia excessive burrs, air-inclusions, poor surface condition, poor material distribution, premature hardening etc. All these defects are an indication of insufficient control of the pressing process which in known pressing devices is controlled mainly by adjustment of the pressure difference across the piston.

The invention has for its object to provide an improved pressing device of the kind set forth. So as to achieve this object, the pressing device according to the invention is characterized in that the piston rod is provided with a force detector and a displacement detector, the signals supplied by these detectors being applied to a control unit in which these signals are compared with adjusted values, the control unit controlling the servo valve such that the piston moves at an adjusted speed as long as the pressing force remains below the adjusted value, the control unit controlling the servo valve, when the, adjusted pressing force is reached such that the piston rod does not exceed the adjusted pressing force.

Because the force detector measures on the piston rod, always the pressing force which is actually exerted on the synthetic resin material is measured as well'as possible. The effect of, for example, the piston friction in the cylinder is then completely eliminated. I

By effecting the control in reaction to the displacement detector and by imparting to the piston a speed which corresponds to an adjusted value during the time that the pressing force is lower than the adjusted force, the plunger will introduce the material to be pressed in the mould at such a speed that the risk of air-inclusions, premature hardening and poor surface conditions is very small.

If the pressing force increases, a change-over will be made, when the adjusted pressing force is reached, from control of the piston speed to control of the pressing force which now will not exceed the adjusted value, so that burrs are prevented.

By selective feedback of a displacement and a pressing force signal to the servo valve, the signals corresponding as well as possible to the speed and pressing force experienced by the synthetic resin material, a pressing device is thus obtained in which the drawbacks of the known pressing devices are eliminated.

So as to eliminate the adverse effect of any misalignment of the hydraulic piston with respect to the mould, a further preferred embodiment of the pressing device according to the invention is characterized in that the piston rod is connected to a pressing plunger via a thrust bearing, the said thrust bearing allowing the pressing plunger some play in the transverse direction with respect to the piston rod.

The invention willbe described in detail with reference to the drawing which is a diagrammatic representation of an embodiment of a pressing device.

The reference numeral 1 in the drawing denotes a cylinder. Accommodated in this cylinder is a piston 2 which is provided with a piston rod 3.

The cylinder 1 is supported by a plate 4, which is connected to the frame 6 of the pressing device via a number of columns 5.

Arranged on the frame 6 is a mould 7 in which one or more cavities are present in which synthetic resin material can be pressed. Pressing is effected by means of a plunger 8, the upper side of which is provided with a structural part 9 which grips about a plate 10 which is connected to the piston rod 3.

Part 9 and plate 10 together constitute a hydrostatic thrust bearing. To this end, the plate 10 is provided with a number of pressure chambers 11 which receive liquid from the space 14in cylinder 1 via a duct 12 incorporating restrictions 13. The space 14 communicates, via a duct 15, with a liquid supply duct 16 which communicates with the outlet side of a liquid pump 17. The liquid pump is driven by an electric motor 18 and derives its liquid from liquid reservoir 19.

The space 21 cancommunicate, via duct 22 and servo valve 20, with the liquid supply duct l6'or with the liquid outlet duct 25. Liquid from the bearing chambers 11 of the hydrostatic bearing can reach outlet duct 25 via duct 24. I

The plunger 8 is provided with a force detector 30 which supplies its signal to control unit 31. Also provided is a displacement detector 32 which detects the displacement of the piston rod 2 and which applies a corresponding signal to the control unit 31. The control unit 31 controls the control unit 33 of the servo valve 20. The operation of the device set forth is as follows. When the matrix is filled, an hydraulic force is exerted on the piston 2 such that the piston with the plunger starts to move in the downward direction. This is achieved by supplying liquid to space 21 by means of servo valve 20.

The displacement of piston 2 is detected by displacement detector 32, whilst the delivered pressing force is measured by the pressure detector 30. The measured values are compared in the control unit 31 with adjusted values, the control unit 31 comparing the value measured by the displacement detector 32 with the adjusted desired piston speed when the force measured by the pressure detector 30 is below the adjusted value. Any difference between adjusted and measured value produces a signal which is applied to the control unit 33 which adjusts the control valve 20 so that the supply of liquid to the space 21 is changed such that'the desired piston speed is obtained.

As soon as the pressure detector 30 measures a pressing force which corresponds to the adjusted value, the control unit 31 switches over from speed control to force control, the signal of pressure detector 30 then being compared with the adjusted pressing force, and any difference producing a signal by means of which the control unit of the servo valve 20 is controlled such that the liquid flow applied to the space 21 is so large that the adjusted value of the pressing force is exactly maintained. If the speed increases beyond a given value again, a change-over takes place to speed control.

Instead of the measuring of the force on thepiston rod, the pressure in the mould can also be used as an control quantity in given circumstances.

A pressing device is thus obtained in which the pressing process can be very well controlled. Control is effected in reaction to signals which are measured very near to the synthetic resin mass on which the process is performed. This means that very few secondary effects such as, for example, friction of piston 2 in cylinder 1 etc. can adversely influence the measurement.

Due to the use of an axial bearing 9, 10, ll, 12, 13 between piston rod 3 and plunger 8, any misalignment will not give rise to excessive friction of the plunger 8 in mould 7.

It will be obvious that instead of an hydrostatic bearing, another axial bearing can be used for this purpose.

The force and displacement detectors, the control unit and the servo valve are only diagrammatically shown, but a variety of types which are known to those skilled in the art can be used for these purposes. Of importance is only that the piston displacement can be controlled both as regards speed and force.

What is claimed is:

l. Apressing device, in particular for the pressing of synthetic resin materials in a mould, provided with an hydraulic motor which comprises a piston which is movable in a cylinder, a piston rod being connected to said piston, it being possible to supply or withdrawn pressure liquid to or from the spaces on both sides of said piston by means of a servo valve, characterized in that the piston rod is provided with a force detector and a displacement detector, the signals supplied by these detectors being applied to a control unit in which these signals are compared with adjusted values, the control unit controlling the servo valve such that the piston moves at an adjusted speed as long as the pressing force remains below the adjusted value, the control unit controlling the servo valve, when the said pressing force is reached, such that the piston rod does not exceed the adjusted pressing force.

2. A pressing device as claimed in claim 1, characterized in that the piston rod is connected, via a thrust bearing, to a pressing plunger, the said thrust bearing allowing the pressing plunger some play in the transverse direction with respect to the piston rod.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,825,386 Dated Julv 23, 1974 Inventor(s) WOLFERT BELLO ET AL It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 2. The pressing device as claimed in Claim 1, further comprising a pressing plunger and a thrust bearing connecting said pressing plunger to said piston rod, said thrust bearing allowing the pressing plunger some play in the transverse direction with respect to the piston rod.

Signed and sealed this 29th day of April 1975.

(SEAL) Attest:

. C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks

Patent Citations
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US2983956 *Mar 13, 1958May 16, 1961Essex Wire CorpInjection molding machine
US3509595 *Apr 22, 1968May 5, 1970Phillips Petroleum CoTension control of running thermoplastic filaments
US3749535 *Oct 14, 1971Jul 31, 1973Conwed CorpApparatus for extrusion of plastic net
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3885899 *Aug 5, 1974May 27, 1975Ford Motor CoApparatus for expanding a laminating interlayer
US4038004 *Jul 28, 1975Jul 26, 1977Bucher-Guyer Ag MaschinenfabrikMeasurement apparatus for determining the degree of filling of a casting mold
US4049762 *Sep 15, 1975Sep 20, 1977Harsco CorporationBlow molding thermoplastic resin
US4060362 *May 12, 1975Nov 29, 1977International Business Machines CorporationInjection molding same cycle control
US4317649 *May 12, 1980Mar 2, 1982Per-Fil IndustriesPellet molding apparatus
US4335063 *Jun 11, 1979Jun 15, 1982Werner & PfleidererMethod and apparatus for pressure control in a press
US4457684 *Jun 17, 1983Jul 3, 1984Mts Systems CorporationHydraulic press
US4458189 *Aug 6, 1982Jul 3, 1984Mts Systems CorporationControl mode switching circuit
US4470787 *May 11, 1983Sep 11, 1984Mts Systems CorporationHydraulic press
US4594065 *Aug 29, 1984Jun 10, 1986U.S. Philips CorporationDrive control apparatus for an injection-molding machine
US4942004 *Nov 1, 1988Jul 17, 1990Cincinnati Milacron Inc.Method and apparatus for regulating mold clamping force in an injection molding machine
US4943400 *Feb 2, 1989Jul 24, 1990Data Card Japan Ltd.Method of manufacturing printing and embossing type elements
US4954067 *Jan 30, 1989Sep 4, 1990Fried. Krupp Gesellschaft Mit Beschrankter HaftungHydraulic press
US4954068 *Jan 30, 1989Sep 4, 1990Fried. Krupp Gesellschaft Mit Beschrankter HaftungHydraulic press
US4966538 *Jun 1, 1988Oct 30, 1990Buehler, Ltd.Mounting press
US5002475 *Nov 9, 1989Mar 26, 1991Intellex CorporationReaction injection molding apparatus
US5039294 *May 26, 1989Aug 13, 1991L'orealApparatus for compacting powder
US5071603 *Dec 13, 1988Dec 10, 1991Kabushiki Kaisha Kobe Seiko ShoMethod of controlling hydraulic press
US5141682 *Jan 11, 1991Aug 25, 1992Engel Maschinebau Gesellschaft M.B.H.Injection molding process with pressure increasing mechanism
US20120227825 *Feb 29, 2012Sep 13, 2012Krones AgMethod and device for recycling compressed gas
DE3207242A1 *Feb 24, 1982Sep 23, 1982Mts System Corp"hydraulische presse"
DE3802761A1 *Jan 30, 1988Aug 10, 1989Krupp GmbhHydraulische presse
Classifications
U.S. Classification425/150, 425/406, 425/135
International ClassificationB29C43/58, B30B15/06, B30B15/20, B30B15/16, B30B15/26
Cooperative ClassificationB29C43/58, B30B15/16, B30B15/068
European ClassificationB30B15/16, B29C43/58, B30B15/06E