US2465580A - Fluid-pressure-responsive control circuit for die-casting presses - Google Patents

Description

2 Sheets-Sheet 1 W. ERNST ETAL FOR DIE-CASTING PRESSES March 29, 1949.

l FLUID PRESSURE PFHSPOSIVE CONTROL CIRCUIT Filed sept. ze..1944

ATTORNEYS March 29, 1949. w. ERNST Er Al. 2,465,580

FLUID PRESSURE RESPONSIVE CONTROL CIRCUIT FOR DIE-CASTING PRESSES Filed Sept. 28, 1944 2 Sheets-Sheet 2 INVENTOR WALTER ERNST PHILIP J. LINDN ER ATTORNEYS Patented Mar. 29, 1949 FLUID-PRESSURE-RESPONSIVE CONTROL CIRCUIT FOR DIE-CASTING PRESSES Walter Ernst and Philip J. Lindner, Mount Gilead,

Ohio, assignors to H-P-M Development Corporation, Wilmington, Del., a corporation of Delaware Application September 28, 1944, Serial No. 556,205

(Cl. (S-52) 7 Claims.

This invention relates to uid operable apparatus and, in particular, to fluid operable devices wherein relatively high speeds are desired.

There are many instances in the iield of application of uid actuated devices wherein high speed operation is necessary or desirable in order better to accomplish the work to be done, or in order to reduce the time required for the accomplishr/jent thereof. high speed operation is essential include. die casting, forging. molding and other similar work operations. Most particularly in the die casting of such metals as magnesium and its various alloys, it is necessary to drive the molten casting metal into the die cavity at great speeds in order to produce castings of good and uniform quality.

Heretofore it has been customary to obtain high speed of operation through the use of large capacity uid sources. or to sacrificepower for speed by reducing the size of the driven element or elements.

It has been found, however, that certain jobs such as the die casting of magnesium and its alloys require speeds in excess of those readily obtainable with this type of apparatus.

Accordingly, it is an object of the present invention to provide a fluid operable device, including a fluid source or sources therefor such that high speed operation is obtainable without any substantial reduction in available power.

Also, in the die casting of metals it is necessary, because of the high temperatures thereof, to handle the molten metal with care in order to prevent harmful and possibly serious injury to the machine operator.

Accordingly, it is another object of the present invention to provide an operating system for a uid operable die casting machine including automatic controls for insuring that the molten metal is completely enclosed within the machine before the latter is set into full speed operation.

It is another object to provide in a die casting machine having a high speed injection ram an operating system for the same ram such that the initial portion of the working stroke thereof is accomplished at relatively low speeds.

These and other objects and advantages will become more clearly apparent upon reference to Particular cases in which` 2 the' following description taken in connection with the accompanying drawings, in which:

' Figure 1 is a vertical longitudinal section through a fluid operable device constructed according to this invention;

Figure 2 is a diagrammatic view of the control system which forms a part of this invention; and

Figure 3 is a diagrammatic view showing the wiring diagram for use in connection with the control system of Figure 2.

General arrangermnt This invention comprises, generally, a fluid operable motor to which pressure uid is supplied from two separate iluid sources. The motor, while it may be of any suitable type, is here shown as a reciprocating type plunger motor having a differential piston attached thereto and reciprocably mounted in a pressure cylinder.

A source of pressure fluid, substantially unlimited in comparison with the capacity of the motor is adapted to supply actuating fluid to one area of the differential piston, preferably to the advancing area. This source of fluid pressure comprises a compressible or condensable medium which may be continuously in communication with the area to which it supplies actuating fluid. Any suitable compressible uid medium may be used in this connection, such as nitrogen, hydrogen or similar gases or mixtures thereof which have suitable characteristics.

Retracting means, which may be fluid operable and may comprise a lsecond source of pressure fluid is adapted selectively to drive the motor opposite to the direction to which it is driven by the said first uid source. The second fluid source, according to this invention, may comprise an incompressible huid medium and a pressure generator therefor. The delivery of fluid from the second ud source to the plunger retracting means is preferably controlled by a distributing valve which is also operable to exhaust the said retracting means in order to accomplish the advancing movement of said plunger.

The aforementioned valve means has, in operative association therewith, means for regulating the rate of exhaust of the retracting means during the initial part of the advancing stroke so that the speed of movement of the plunger is thereby retarded. When the plunger has moved a predetermined distance suitable control means such as a limit switch is engaged by the said plunger and the retarding means is thus, automatically, rendered ineffective and the plunger commences the high speed portion of its advancing' stroke.

The means associated with the valve for controlling its operation is preferably a fluid operable pilot system which has choke valves suitable arranged therein so that the speed of movement of the valve member is controlled.

Structural arrangement plunger 3 has an enlarged portion adjacent the piston 2 at 4 which is adapted to be received by the tapered recessed portion at 5 in the end wall 6 of the cylinder I.

The plunger 3 has attached to the free end thereof a coupling 1 to which, in turn, is attached 'a second plunger or work ram 8.. Also attached to the ram 3 adjacent the coupling 1 is a cam member 9 adapted, when the ram has moved a predetermined distance, to engage the roller I0 of the limit switch ii thereby to actuate the latter.

The plunger 8 reciprocates within a cylinder I2 which is suitably attached to, or is integral with, a bolster I3. An aperture at I4 is provided in the cylinder I2 for the purpose of permitting the introduction therein of the plastic material to be molded in the die or mold generally indicated by the dashed outline at I5.

The right end of the cylinder I terminates in a block having a central longitudinal bore I6 therein. Attached to the block is a source of pressure iluid of large capacity relative to the 'size of the motor. cylinder or tank I1 within which is contained a compressible uid medium such as nitrogen, hydrogen or similar gases or mixtures thereof. A passage I8 communicates from the interior of the tank I1 to the bore I6 and permits passage of fluid from the tank to the larger area of the piston 2. A shut-on' valve or similar flow controlling means may be provided in the passage I8, I6 as, for instance, the needle valve indicated at I9. The valve I9 is not only useful to control the rate of uid flow to and from the cylinder I but likewise may be used to close off iiuid communication between the tank I1 and the cylinder I thereby to prevent wasteful leakage of the iiuid medium from the tank I1 when the device is idle. In operation the valve is preferably opened wide.

Referringto the piston 2, this member comprises a shouldered cylindrical member having packing or other suitable sealing means mounted around the periphery thereof in order to inhibit leakage from one side of the said piston to the other. The left end ofthe cylinder I is connected by means of a conduit with a valve 2| which is also adapted, by means of a conduit 22, to communicate with the reservoir 21 and, by means of a conduit 23, with a pump or pressure generator 24. Also connected with the valve is a conduit 25 which connects with the pump control cylinder 25. The valve 2| is preferably located adjacent the cylinder I and within the reservoir 21 so that the fluid flow from the cylinder through the valve and into the reservoir is relatively free and unrestricted. v

The valve 2| includes a reciprocable valve mem- This source may comprise aber 28 which is adapted to be moved into a rst end position to interconnect the conduits 20 and 23 and, into a second end position to interconnect the conduits 23 and 25 and the conduits 20 and 22, The valve member 25 has the reduced diameter projections 29 and 30 on either end thereof Y"and the fluid operable pistons 3| and 32 reciprocably mounted over the projections 29 and 3B respectively. The pistons 3| and 32 are reciprocable within the cylinders 33 and 3d, respectively, and are adapted to engage the valve member and vmove the same to a center position where iiuid communication between the conduits connected therewith is interrupted.

Actuating iluid is conducted to the cylinders 35 and 33 by the` conduits 35 and 36, respectively. which lead to the pilot valve 31. Also connected with the valve 31 is a conduit 38 which conducts iiuid from the conduit23 to the said valve, and the exhaust conduit 33. The valve 31 comprises a valve member 40 movable into a first end position to interconnect the conduits 38 and 36 while connecting the conduit 35 to exhaust and. into a second end position for connecting the conduit 38 with the conduit 35 while simultaneously connecting the conduit 35 to exhaust. The valve member 40 is also movable into an intermediate position where the conduit 38 is connected with both conduits 35 and 36. In this latter position the valve member 28 of the valve 2i is moved to its center or neutral position.

The conduits se and se have therein the choke valves 4| and 42, respectively, which serve to regulate the iiow of pilot uid' to the valve 2| so that the reciprocation of the valve member 28 is accomplished without shock.

The conduit 3B also comprises thel choke valve 43 and the check valve 44. The check valve 44 permits the free flow of pilot iiuid from the Valve 31 to the cylinder 34 while the choke 'valve 43 is adapted to throttle the discharge from the cylinder 34 for a .purpose which will become more apparent hereinafter. Connected withl the conduit 36 between the choke valvey 43 and the cylinder 34 is a. conduit 45 which leads to exhaust and includes a two way valve 46. The two way valve 46 has a reciprocable valve member therein which is normally urg'ed into position to interrupt the flow of uid through the conduit 45 by a spring 41 and is moved into position to permit.

the flow of iiuid through the said conduit solenoid SI.vrvr

The valvel member 40 of the valve 31 is urged into one'of its end positionsby the spring 48 and intov its other end .positionbyl the solenoid by the S2. Th'hand lever 49 is provided for the pur' pose of positioning the valve member manually if it be desired to inch the plunger 3 forward.

'I'he movable portion of the mold I5 is attached to a platen 50 which is actuated by a motor means 5I which is preferably fluid operable. The motor means 5| is supplied with actuating fluid by the conduits 52 and 53 which lead to a distributing valve 54 which receives pressure iluid from the pump 55 through a conduit 56. The pump 55 draws fluid from the reservoir 21 through the conduit 51 which connects with the main exhaust line 58.

The valve 54 is urged into one position by the spring 59 and into its other position by a solenoid S3.

There may be provided, if desired. the check valve 59' in the conduit 55 and the check valve 60 in the conduit 23. Likewise, if desired, the

-alternano 28 is adapted to abut stops at either end of the valve which may comprise the screw threaded members 83 and 34. The adjustable stops 63 and 54 are provided for the purpose of limiting the movement of the valve member 28 thereby to control the rate of duid flow through the valve 2l should it be desirable to do so. Arranged between the stop member 64 and the portion 30 of the valve member 28 is a plunger 65, the right end of which is hydraulically connected by the conduit 63 with the passage I6 in the cylinder i. The purpose of the plunger 65 is to provide for the reversing of the plunger 3 should the pilot iluid from the valve 31 be cut olf for any reason.

Referring to Figure 3, there is shown the electrlcal circuit which actuates the various solenoids. The circuit in Figure 3 comprises the power lines Ll and L2 between which are arranged the solenoids Si and S2 and the contactors A and B. The contactor A is connected from the line L2 through a pair of normally closed blades BI through a stop switch and a start switch'll with the line LI, the switch 1| being by-passed by a hold-in circuit provided by the normally opened contactor blades Al. The solenoid S2 is connected between the lines LI and L2 through the normally open contactor blades A2 and the solneoid Sl is connected between the lines LI and L2 through the normally open contactor blades A3 and the limit switch Il. The contactor B, which actuates the blades BI, is connected between the lines LI and L2 through the time-control switch 12 which may comprise a time delay `element or suitable means for synchronizing the actuation of B with the actuation of lthe mold clamping motor 5|.

Operation Assuming that the device is in the position whereupon the contactor A is energized and closes the blades AI and A2. The blades Al serve to maintain the contactor A energized while the blades A2 affect the energization of the solenoid S2. As previously mentioned, the control 12 may comprise means whereby the blades BI are held open until the mold halves are suitably clamped together thus providing a safety feature.

When the pilot fluid is introduced into the cylinder 33 it acts upon the piston 3| and the rod 29 to move the valve lmember 28 to the right. As the valve member 28 moves to the right fluid is expelled from the cylinder 34 and passes through the conduit 36 and the valves 42 and 43 to the valve 31 whence it is exhausted through the conduit 39 to the exhaust conduit 58. The valve 43 is adjusted so that the movement of the valve member 28 is relatively slow thus throttling the exhaust connection established between the conduits 20 and 22. The valve 43 is so ad .iusted that the throttling eiect is continued until the cam 9 engages the roller I0 of the limit switch Il. At this time the end of the plunger 3 has completely covered the aperture I4 thereby trapping the molten metal within the cylinder l2.

When the limit switch l-I is closed the solenoid SI is energized and shifts the valve 46 into position to connect the conduit 45 with the exhaust conduit 53. The exhaust of fluid from the cylinder 34 is now relatively free and unrestricted and e the valve member 28 moves rightwardly at greater speed and the restriction between the conduit 20 and 22 is substantially eliminated. The plunger 8 now commences the high speed portion of its stroke and moves leftwardly to drive the molten metal into the dies l5.

Following the accomplishment of the molding or casting process, the contactor A may be decnergized manually or by suitable automatic means contained within the time-control switch 12. The deenergization of A deenergizes S2 so that the spring 48 restores the valve member 40 to its Figure 2 position. The valve member 28 is thus also restored to its Figure 2 position and the plungers 3 and 8 move to their retracted position.

The movement of the motor 5I may be controlled by the energization and deenerglzation of the solenoid S3 by theswitch 13 in series therewith.

During the advancing stroke of the plungers 3 and 8 the discharge line 23 of the pump 24 is connected with the conduit 25 which conducts pump pressure to the control cylinder 26 thereby substantially unloading the pump during the said advancing stroke.

It will be apparent that this invention provides for a high speed iluid'operable die casting machine in which the injection ram or plunger moves at a reduced rate of speed until the filling opening is covered thereby preventing any of the molten metal from being splashed out of the injection cylinder.

It will be apparent that various modifications may be made in the structure and arrangement of this device `wifhout in any way departing from the'spirit of the invention.

Having thus fully described our invention,

= what we claim as new and desire to secure by Letters Patent is:

l. A uid operable system for actuating a reciprocable plunger having an advancing and a retracting area comprising a rst fluid source including an expansible fluid medium directly and continuously connected with said advancing area,

a second uid source. valve means connected with said second source and said retracting area and including a movable valve member operable to connect said retracting area with said second source or wih'exhaust. fluid operable means assoclatedA with said valve for moving the same from one position to the other. means for supplying actuating fluid to said fluid operable means.

means for restricting the exhaust from said fluid operable means as said valve is beine.r moved into position +o exhaust said retracting area thereby movable to connect said retracting area with said second source or with exhaust, and means for controlling the reciprocation of said valve member comprising opposed fluid operable plungers associated with said valve member, Yabutment means for limiting the movement of said valve member in either direction, pilot valve means connected with said fluid operable plungers movable to direct pressure fluid to either plunger while exhausting the other to move said valve member in either direction, said pilot valve also being movable to direct pressure fluid to both of said uid operable plungers to center said valve member, a choke valve between said pilot valve and one oi said fluid operable plungers operable to retard the movement of said valve member when the same is being moved into position to exhaust said retracting area, other valve means for by-passing said choke valve, and means including a cam and limit switch adapted in response to a predetermined advancing movement of said plunger to actuate said other valve means thereby permitting the free exhaust of the fluid operable plunger associated with said choke valve so th-at said valve member may be moved ino position freely to exhaust said retraction area.

3. In a fiuid operable system. a reciprocable plunger having fluid operable advancing and retracting areas associated therewith, a first fluid source continuously connected with said advancing area, a fiud source of variable delivery, fluid pressure responsive control means associated with said second source and operable in response to a predetermined pressure to urge the same toward no delivery position, valve means movable into a rst position to interconnect said variable delivery source with said retracting means while simultaneously connecting said :duid operable control means to exhaust and into a second position to interconnect said iiuid operable control means with said variable delivery source while simultaneously connecting said retracting means to exhaust. fluid operable means associated with said valve and selectively operable tomove the same into said first position or into said second position` and other iiuid operable means associated with said valve and hydraulically connected with said first source of uid and operable continuously to urge said valve toward said second position.

4. In a fluid operable system, a, reciprocable Yplunger having advancing and retracting areas,

a first iiuid source comprising an expansible uid m'iiedium continuously connected with said advancing area and operable to drive said plunger at high speed, a second iiuid source, a valve member movable to connect said retracting area with said second source or with exhaust. a first iiuid operable plunger associated with said valve member operable to move the same into position to connect said retracting area with said second source, a second fluid operable plunger associated with said valve member and operable to move the same into position to connect said retracting area with exhaust, means selectivelyoperable for supplying actuating fluid to said iirst iiuid operable plunger or to said second, means to control at least the rst portion of the movement of said valve member when actuated by said second uid operable plunger, and a third fluid operable plunger'associated with said valve member and continuously hydraulically connected with said first fluid source and operable to'move said valve member into position to connect said retracting area with said second source substantially instantaneously upon the loss of pressure uid for actuating at least said second iiuid operable plunger.

5. A fluid operable system for actuating a plunger having an advancing and retracting area and also having means continuously biasing the plunger in itsadvancing direction and operable when said retracting area is exhausted to drive said plunger at high speed, a source of fluid pressure, a valve member movable to connect said retracting area with said source or with exhaust, actuating means for movingA said valve member into position to connect said source with said plunger, fluid operable means for actuating said valve member into position to exhaust said plunger, means for restricting the discharge of fluid from said iiuid operable means as said ,valve is being moved by actuating means to initiate the advancing movement of said plunger at reduced speed, and means operable automatically in response to a predetermined advancing movement of said plunger to render said restricting means ineffective thereby to permit said valve member to be moved into position to exhaust said retracting area freely thus permitting the said advancing movement of said plunger to continue at high speed.

6. In a iiuid operable system for 'actuating a plunger having an advancing and retracting area, and also having means continuously biasing the plunger in its advancing direction and operable when said retracting area is exhausted to drivey said plunger at high speed, a source of fluid pressure, a valve member movable to connect said retracting area with said source or with exhaust, actuating means for moving said valve member into position to connectsaid retracting means with exhaust, uid operable means for actuating said valve member into position to connect said retracting means with said source, means for re,- stricting the discharge of fluid from said fluid operable means as said valve is being moved by actuating means to initiate the advancing Amo`vement of said plunger at reduced speed, means operable automatically in response to a predetermined advancing movement of said plunger to render said restricting means ineffective thereby to permit said valve member to be moved into position to exhaust said retracting area, freely thus permitting the said advancing movement of said plunger to continue at high speed, and means of cushioning the iinal portion of the advancing stroke of lsaid plunger to prevent the same from striking the end of its cylinder at highspeed. l

7. In combination with a recprocable'plunger 'having a, retracting area and which is continuously biased in its advancing direction by a means operable to drive the said plunger at a high rate of speed, a source of fluid pressure, a valve member movable to connect said retracting area with said source or to exhaust, opposed iiuid operable plungers associated with saidv valve member, means of directing pilot iiuid to one or the other -of said plungers for shifting said valve member to `bring about the reciprocation of said plunger, ow restricting means restricting the discharge of uid from one of said fluid operable plungers during the time said member is being moved toward position to exhaust said retracting area, electrically operated valve means for bypassing said flow restricting means and operable auto- .matically in response to a predetermined advancing movement 'of said plunger, means per'- mitting the free flow of fluid toward said plunger around said iiow restricting means; and means continuously acting on one of said piungers to move said valve member into position to connect said retractng area with said source to prevent the accidental advancing movementl of said plunger upon loss of actuating pressure for said uid operable plungers.

WALTER ERNST.

PHILIP J. LINDNER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,870,500 Ernst Aug. 9, 1932 15 Glasner Feb. 10, 1931 Number Number

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