US2484907A - Fluid operable system - Google Patents

Description

Oct. 18, 1949. H. M. PURCELL 2,484,907

FLUID OPERABLE SYSTEM Filed oct. 7, 194e 4 sheets-sheet 1 I rl INVENTOR HOWARD MPURCELLH d l I I 4 S l" l @L mm SI,

Q NI BY ,f TJ@ 5TM" ATTORNEY Oct. 18, 1949. H, M. PURCELL.

FLUID OPERABLE SYSTEM 4 Sheets-Shea?I 2 Filed 00?.. '7, 1946 NOK INVENTOR HOWARD M. PURCELL,

ATTORNEYS Oct. 18, 1949. H. M. PURCELL 2,484,907

FLUID OPERABLE SYSTEM Filed Oct. 7, 1946 v 4 Sheets-Sheet 3 FlG. 3

INVENTOR HOWARD M. PURCELL BY gounwr.

ATTORNEYS Oct. 18, 1949. H. M. PURCELL 2,484,907

FLUID OPERABLE SYSTEM Filed oct. 7, 194e 4 sheets-sheet 4 iNvENToR HOWARD M. PURCELL,

ATTORNEYS Patented @et i3; E949 Howard M. lburceii, Mount Giiead, @hisy assigner to H-Y-'MI ilieveiopment Corporation, Wiimington, Dei., a corporation ci' Delaware Application @amber L MG16, Selriai No. 701,713

(Ci. .6d-97) it Claims. i

This invention relates to uid operable systems and to methods of operation thereof, and more particularly relates to such systems wherein there are a plurality of :duid motors.

l'n many instances in hydraulic circuits there are a plurality of iiuid motors to be operated according to a predetermined sequence. in some instances it is required to hold pressure on one of 'the motors while another thereof is moving under substantially no load. Usually this is accomplished by employing separate fluid sources for the motors, or by arranging a valve in circuit with the motor operating under no load which only opensat a predetermined pressure.

When separate uid sources are used there is the additional expense of duplicate units as well as a considerable waste of power during the time thai/'the fluid sources are not being used. When a valve is placed in series with one of the motors to be opened in response to a predetermined pressure, there is often a loss ofpressure in the circuit which can only be made up after a predetermined time delay.

A particular instance of the -foregoing is a molding machine wherein there is a clamping ram for clamping together a multipart mold, and in injection ram for driving an extrusion plunger to extrude molding material into the clamped molds. A typical work cycle on a machine of this nature involves the preliminary clamping together of the mold and the subsequent extrusion of the plastic therein.

The mold must be retained tightly clamped together at all times or else the molding material will flash between the parts thereof and cause a loss of plastic material and improper or ruined workpieces. Furthermore, the clamping ram is usually of such a size that it takes a considerable period of time to develop the necessary pressure therein so that any loss of pressure in the fluid circuit would be accompanied by a delay in the building up of the necessary clamping pressure. If this loss in pressure occurred during the time that the injection ram was being actuated, then there Wouldbe greater likelihood of the mold hashing.

Accordingly, the principal object of this invention is to provide a fluid operable circuit wherein there are a plurality of motors to be operated from a single iiuid source and in which the pressure can be maintained in the circuit at all times.

Another object is to provide a hydraulic circuit including a single source of pressure which is operable sequentially to actuate a plurality o! fluid motors and to maintain the pressure on the actuated motors.

Still another object of this invention is the provision of an improved fluid circuit including a single pump and several motors so that the motors can be actuated independently and sequentially without any loss of pressure in the circuit.

A particular object of this invention is to provide an improved actuating circuit for a uid operated molding machine having a plurality of iluid Figure 4 is a modified arrangement applied to a vertical molding machine; and

Figure 5 is a wiring diagram for controlling the valves in the circuit of Figure 4.'

General arrangement According to this invention, there are a plurality of uid motors and a single iluid source for actuating the said motors. The motors are arranged to be actuated sequentially so that one thereof is moved into working position and dwells therein under pressure while the other thereof goes through its working cycle. The second actuated motor is provided with means whereby there is a predetermined minimum pressure acting thereon even when the motor is not externally loaded, so that there is no loss of pressure at the inlet of the rst actuated motor.

According to this invention, the predetermined pressure is maintained on the second actuated motor by throttling the discharge therefrom during at least its initial movement. Optionally, the aforementioned restriction can be removed from the discharge line of the second actuated motor in response to a predetermined pressure acting on the inlet side thereof.

According to one modification of this invention, a single operating valve controls an entire operating cycle for a pair of reciprocable plungers so that one thereof advanced to working position and dwells therein, thereafter the other thereof advances into working position and retracts, and iinally the said one retracts to its original position.

According to another modification, the actuation of the Iiuid motors is interlocked by a suitable electric circuit and the ilow of iluid to and from the motors is controlled by solenoid operated valves.

Still another modification of this invention provides for independent pressures to be held 3 on each of the several motors up to the maximum supplied by the pumping means in the system, and irrespective of the pressure standing in any other part of the circuit.

Arrangement of the modification illustrated in Figure 1 Referring to the drawings, Figure 1 illustrates a molding machine having a stationary mold part I8 and a movable mold part I2 which is carried on a movable platen I4. The platen |4 is mounted on the ram |8 having the piston i8 reciprocable in the cylind'er 28 thereby defining the ram advancing means 22 and the ram retracting means 24. f

The mold half |8 is carried on a stationary bolster member 28 which has a passage 28 therethrough and through which molding material is 48 whichis connected to draw uid from a reservoir 48 through a, conduit 58. The pump 46 discharges uid into a conduit 52 which is connected with the inlet side of a check valve 54, the discharge side of which opens into a conduit 58. The conduit 56 leads to the inlet port of a four-way valve 58 having the movable valve member 88 which can be actuated by the hand lever 62. The valve 58 includes a first service port connected by a conduit 84 with the clamping ram retracting means 24, and a second service port which is connected by the conduit 88 with the clamping ram advancing means 22.

The conduit 52 is also connected by a conduit 68 with one port of a valve 18 which has a valve member 12 therein continuously urged in one direction by a spring 14. A pilot piston 18 is also connected with the conduit 68 for moving the valve member 12 against the thrust of the spring 14 in response to a predetermined pressure. The valve 18 also has a port connected by a conduit 18 with a port in another valve 88. When the valve member is under the influence of the spring 14, the conduits 68 and 18 are connected together, and when the valve member is under the influence of the pilot piston 16 the conduit 18 is disconnected from the conduit 68 and is connected instead with the exhaust conduit 82 leading to the reservoir 48.

The valve 88 is similar to the valve 18 and includes a port which is connected by a conduit 84 through a restricting valve means 88 with the reservoir, and another port which is connected by a conduit 88 with the advancing means 42 of the extrusion ram.

A spring 98 in the valve v88 normally urges the valve member 92 thereof into position to connect the conduits 84 and 88, and a pilot plunger 94 is connected to be responsive to the pressure acting in the conduit 18 for moving the valve member 92 against the thrust of the spring to disconnect the conduit 88 from the conduit 84 and to connect it instead to the conduit 18. The retracting means of the extrusion ram is connected by a conduit 98 with one port of a, valve 4 98 which also includes a port connected with the conduit 82 and another port connected with the conduit 58.

The valve member |88 of the valve 98 is continuously urged by a spring |82 to connect the conduits 58 and 98, and there is a pilot plunger |84 which is connected to be responsive to the pressure in the conduit 88 for moving the valve member |88 to disconnect the conduit 98 from the conduit 58 and to connect it instead with the conduit 82. For a purpose which will become more apparent hereinafter. the check valve 54 is bypassed by a flow controlling or flow restricting valve means as indicated at |86.

Operation of the embodiment of Figure 1l 88 to interconnect the conduits 58 and 66, and to connect the conduit 64 with-the exhaust conduit 81 of the valve 58. With the valve 58 so Set, uid from the pump 46 passes through the conduit 52. the check valve 54, the conduit 56, the valve 58 and the conduit 66 to the clamping ram advancing means 22. This moves'. the clamping ram rightwardly and brings the mold halves together in clamping relationship. The meeting of the mold .halves causes a pressure rise in the conduit 52 which extends through the conduit 68 and the valve 18.to the conduit 18. When this pressure reaches a predetermined value the pilot plunger 94 of the valve 88 is actuated to move the valve member thereof leftwardly to interconnect the valve conduits 18 andA 88, thus extending the supply of pressure iiuid to the extrusion ram advancing means 42.

The supply of iluid to the extrusion ram advancing means 42 moves the said ram leftwardly to expel iiuid from the retracting means 44 thereof through the conduit 98 and the valve 98. The fluid so expelled through the valve 98 enters the conduit 56 where it is connected with the said valve and then passes through the restricting means |88 to the conduit 52 where it joins with the pump discharge passing to the advancing means 42.

It will be noted that the pressure in the conduit 56 is necessarily higher than the pressure in the conduit 52 because of the flow restricting means |86. Thus, the clamping pressure standing in the clamping ram advancing means 22 is also higher than the pressure in the conduit 52. This positively insures that the pressure on the clamping ram advancing means 22 will be maintained during the initial advancing movement of the extrusion ram 38.

When the extrusion ram 36 has advanced to the point where it engages the molding material in the chamber 32 and develops a pressure thereon, this brings about an increase in pressure in the advancing means 42 which is conveyed through the conduit 88 to the' pilot plunger |84 of the valve 98. When the pressure reaches a predetermined value, the valve member |88 moves leftwardly to connect the conduit 96 directly with the exhaust conduit 82. At this time, the full thrust on the piston 38 from the advancing means 42 is exerted on the extrusion ram 38. At the same time, the speed of movement of the extrusion ram slows down so that this circuit provides for a rapid advance of the clamping ram to working position.I

assess? 8 Whenthemoldcavityhasbeeniilledwith molding material, the extrusion ram comes to a halt, and the discharge pressure increases. This increased pressure extends through the conduits 82 and 88 to the pilot plunger 18 oi the g valve 10. When the pressure reaches a predetermined amount, the valve member 12 moves leitwardly and connects the conduit 18 with the conduit 82 while simultaneously interrupting the communication between the conduits 18 and 88. lo

When the conduit 18 is connected with exhaust. the pressure acting on the plunger 84 drops to exhaust pressure and the spring 80 returns the .valve member 82 to the position shown in the drawings. The valve member 82 now interconnects the conduits 84 and 88 so that the advanclng means 42 of the extrusion ram is connected with the reservoir through the ilow restricting means 88.

The connecting of the advancing means 42 ,o

. s workingareasoiaboosterram |44. 'l'hereisallo connected with the valve |84 an exhaust conduit means |88, and reciprocable in the 'valve is"a valve member |48 movable to interconnect the pressure conduit |82 with either of the service ports while connecting the other o! the service ports with the exhaust conduit. The solenoids Bl and B2 at the opposite ends of the valve are selectively energizable ior shifting the valve member therein.

The conduit |82 also connects directly with the retracting means |80 of the extrusion ram |82. From between the check valves |28 and |88 there is a branch conduit |84 which leads to one port of a valve |88 which also comprises a port connected by the conduit |58 with the extrusion ram advancing means |80, and a port which is connected by a conduit |02 through the iiow restricting means |84 with the reservoir |24. The valve member |08 of the valve |58 is normally urged by a spring |88 to interconnect the conduits |88 and |82, and by the energizatioxr of the solenoid B8 to interconnect the conduits |84 and |08.

For supplying intensified iluid pressure to the gs rams, there may be included in the circuit a iiuid intensifier as indicated at |10 which has its discharge port connected with the conduit |84' and its inlet .port connected with the discharge port ci' a normally closed pilot operated valve |12. The

the advancing means 42 thereof passes through .o lmet port of the valve m is connected with the the restricting means 88 so that a high pressure is maintained in the retracting means 44 and the conduits 86 and 56. This insures that the pressure in the clamping ram advancing means 22 will remain high enough to maintain the mold 3g cure, the lever 62 may be actuated to return the 45v valve member 60 to the position shown in the drawings. This retracts the clamping ram I8 to the position shown in the drawings and the machine is ready for anew cycle of operations.

It will be noted that the clamping ram I8 is 50 directly under the control of the valve 80, while the extrusion ram goes through a complete cycle of operations for one position of the clamp ram.

In the event that it is desired for the extru- 65 sion plunger to dwell against the material to hold a pressure within the cavity oi.' the clamp mold halves, the actuation of the valve 10 may be somewhat delayed, as by the choke valve ||8 which is connected in series with the pilot plunger 00 Arrangement of the modification illustrated in Figure 2 In Figure 2 there is shown an arrangement similar to that shown in Figure .1 wherein there is a a pump |20 which draws iiuid through a conduit |22 from a reservoir |24, and discharges the said fluid through a conduit |28 and the serially arranged check valves |28 and |30 to the conduit |32. The

conduit |82 connects with the inlet port of a iour- 70 way valve |34 which includes a first service port connected by a conduit |38 with the retracting means |88 oi the clamping ram |4'0.

The valve |84 also has a second service port discharge side of the pump |20 and the valve is adapted for being piloted into open position by iluid conducted thereto from between the check valves |28 and |80 by a conduit |14.

As in the case of the modiilcation shown in Figure 1, there is provided the ilow restricting means as at |18 for passing the discharge from the extrusion ram retracting means during the advancing stroke of the said ram. This valve |18 by- 4o passes the check valve |80.

For supplying` uid to the advancing means |18 of the clamping ram during its rapid approach toward clamping position, there is provided a check valve |80 opening from the reservoir |24 into the said advancing means. A pilot operated unloading valve as at |82 is actuated by pressure iluid conducted thereto from the retracting means |88 by a conduit |84 for bypassing the check valve during the retracting stroke of the clamping ram.

In order to commence the actuation of the extruslon ram at the proper instant. there may be provided the limit switch LSI which is positioned to be engaged by the cam |88 carried by the clamping ram which is prior to the clamping together of the mold halves. This serves the purpose of checking the speed of the clamping ram by diverting a portion of .the pump discharge to the extrusion plunger, and also shortens the cycling time of the machine.

Operation of the embodiment of Figure 2 In the operation of the circuit shown in Figure 2. the clamping ram |40 is moved in its clamping direction by energizing the solenoid Si which shifts the valve member |48 to direct pressure fluid from the conduit |82 through the conduit |42 to the booster ram |44. `When the clamping ram has moved to a point where the cam |88 engages and closes the limit switch LSI the solenoid S8 is energized and shifts the valve member |88 to connect the conduits |84 and |58. This last mentioned connection directs a portion of the pump discharge to the extrusion ram advancing means |80. As the extrusion ram advances the which is connected by a conduit |42 with the 75 iluid expelled from the retracting means |88 7 thereof is passed through the flow restricting means |16 so as to maintain at least as high a pressure in the clamping ram advancing means as there is at the discharge side of the pump |20.

Following the extrusion of material into the clamped mold halves, the extrusion plunger may be retracted by de-energizing the solenoid S3 whereupon the pressure standing in the retracting means |50 drives the said ram in its retracting direction. The iluid expelled from the advancing means |60 at this time is passed through the re-4 stricting means |64 so that a substantial pressure is maintained in the iiuid circuit to maintain the mold halves clamped together.

After a predetermined dwell of the mold halves together, the solenoid SI is de-energized and the solenoid S2 is energized to return the clamping ram |40 to the position shown in the drawings.

It will be apparent that any time the discharge pressure to the pump reaches the value necessary to open the valve |12, the intensifier will commence operating to supply fluid at increased pressure to the fluid circuit.

Arrangement of the modification illustrated in Figure 3 In Figure 3 there is shown a fluid circuit wherein a pump |90 draws uid from a reservoir |92 through a conduit` |94, and discharges the said fluid through a conduit |96 to the ports |90 and 200 and a valve 202. The valve 202 also comprises a port 204 connected by a conduit 206 with one port of a fluid pressure converter 206, and a port 2|0 which is connected by a conduit 2| 2 with the other port of the said converter. The converter 208 is adapted for passing uid from the conduit 2|2 to the conduit 206 and to increase the pressure thereof while reducing the volume, or to pass fluid from the conduit 206 to the conduit 2|2 reducing the preure thereon l while increasing the volume.

A converter of this type forms no part of the present invention except the particular use to which it is being put and is illustrated and described in the co-pending application Serial No. 594,413, iled May 18,` 1945, in the name of Warren R. Tucker and assigned to the same assignee as the instant application.

The valve 202 also includes a discharge port 2|4 which is connected with a conduit 2|6. The conduit 2|6 is connected through a check valve 2|8 with a conduit 220 which leads to the inlet of a four-way reversing valve 222 which has one service port connected by a conduit 224 with a retracting means 226 of the clamping ram 228, and a second service port connected by a conduit 230 with the advancing means 232 of the said clamping ram. Preferably, there is inserted in the conduit 230 a pressure reducing valve 234 of a type to be described hereinafter which is by-passed by a check valve 236 opening away from the said advancing means. The conduit 220 has a branch 238 which is connected directly with the retracting means 240 of the extrusion ram 242.

Branching oif from the conduit 2|6 is a conduit 244 that leads to one port of a valve 246 which includes another port connected with the reservoir |92 by a conduit 246, and another port connected by a conduit 250 through the pressure reducing valve 252 with the advancing means 254 of the extrusion ram. Preferably, the valve 262 is bypassed by a check valve 256 opening away from the said retracting means.

which is normally positioned to interrupt coni munication between the conduit 244 and 250 while providing a restricted communication between the conduits 250 and 248, andmovable by fluid pressure on the pilot plunger -260 to interconnect the conduits 244 and 250.

The valves 234 and 252, as best seen in connection with the latter. each comprise an inlet port 262, an outlet port 264, and` an exhaust port 266. A valve member 260 isnormally urged by a spring 210 to connect the ports 262 and 264.

charge pressure substantially constant withinV very close limits up to the pressure supplied at the inlet port thereof. As in the case of the modification shown in Figure 2, there may be a limit switch LS2 adaptedvfor being engaged by a cam 216 shortly prior to the meeting of the mold halves so that the valve 246 can be actuated to commence the extrusion stroke' as soon aspossible.

Operation of the embodiment of- Figure 3 In the operation of the circuit of Figure 3, the movable valve number 218 of the valve 202 is positioned in its left-hand position .asshown by the spring 260 when the discharge pressure of the pump |90 is low. This connects the pump through the conduit |96, the ports |90 and 204 and the conduit 206 with the converter 200 so that fluid at reduced pressure and increased volume is discharged through the conduit 2|2 and ports 2|0 and 2|4 to the conduit 2|6. The clamping ram may be moved in its clamping direction by shifting the movable valve member of the valve 222 to connectthe conduit 220 with the conduit 230. When the clamping ram moves far enough to bring the em 21s against the switch Lsz the valve member 256 of the valve 246 is actuated leftwardl'y to interconnect the conduits 244 and 250. This brings about a supply of fluid from the conduit 2|6 through the valve 252 to the extrusion ram advancing means 254. As the extrusion ram advances, the fluid displaced from the retracting means 240 thereof is passed through the ow restricting means 262 which bypasses the check valve 2|0. As in the case of the other modifications of this invention, this maintains a relatively high pressure in the portion of the fluid circuit leading to the clamping ram.

After the extrusion cycle is completed, the extrusion ram 242 is retracted by again shifting the valve member 250 to the position shown in the drawings. This permits the throttled discharge from the advancing means 254 and the retracting movement of the extrusion ram takes place by the supply of fluid to the retracting means 240 from the conduit 230.

The clamping ram may be returned by the shifting of the valve 222 to supply actuating fluid to the retracting means 226.

It will be apparent that whenever the discharge pressure of the pump rises to a predetermined value, the pilot plunger 263, which is connected The valve 246 has therein a valve member 258 with the discharge side of the pump, will move 9 the valve member 218 rightwardly against the spring 260 in order to reverse the ilow of duid through the converter 208 whereby a reduced supply of duid at intensified pressures is passed to the conduit m.

cycles.'

Arrangement of the modification illustrated in Figure 4 In Figure 4 there is a pump 300 which draws fluid from a reservoir 302 through a conduit 304 and dischargesthe iluid at increased pressure into a conduit 306. The conduit 306 leads to the inlet port of a valve 308 lwhich includes a flrst service port connected by a conduit 3|0 with the advancing means 3I2 of the mold clamping ram 3|4, and a second service port which is connected by a conduit 3i8 with the retracting means 3I8 of the said clamping ram. The valve,also includes an exhaust connection represented by the conduit 320 and a valve member 322 movable to con nect the pressure port with either of the service ports while connecting the other with exhaust.

'I'he valve member is normally centered by the springs 324 and when centered provides a bypass directly to exhaust for the pump discharge. Energization of the solenoid Si moves the valve member to direct actuating fluid to the retracting means 3|8 and energization of the solenoid S2 moves'the valve member to direct actuating fluid to the advancing means 3I2.

The conduit 306 has a branch 326 extending therefrom which leads to one port of a valve 328 having a valve member 330 movable into a rst position by a spring 332 to interconnect the conduit 336 with an exhaust conduit 334, and by the energization of a solenoid S3 to move into position to connect the conduit 326 with the conduit 336. The conduit 336 extends to the advancing means 338 of the extrusion ram 340 and includes a check valve 342 opening toward the said advancing means and a choke valve 344 which bypasses the said check valve.

The retracting means 346 of the extrusion ram is connected by a conduit 348 with vone port of a valve 350 which includes a valve member 352 which is normally positioned Iby a spring 354 to connect the conduit 348 with a conduit 356. A pilotpiston 358 is responsive to pressure from the advancing means 338 for moving the valve member into position to connect the conduit 348 with the exhaust conduit 360 which leads directly to the reservoir 3ll2.r The conduit 356 is connected with the conduit 326 through a choke valve 362 and a check valve 364 which bypasses the said choke valve and opens toward the valve 350.

Figure 5 illustrates an electrical circuit adapted for controlling the solenoids Si, S2 and S3 of Figure 4. In Figure 5 there are the power lines LI and L2 and connected therebetween is a contactor coil A which is in series with the normally closed blades T3 of avtimer motor T and a normally open push button indicated at 366. Closure of the push button 366 energizes A which brings about the closure of the blades AI to provide a holding circuit for A, and the closure of the bladesv A2 to energize the timer motor T. Energization of the timermotor T immediately closes the blades Tl thereof which are connected in l series with the solenoid S2. Energization of S2 brings about the clamping together of the mold halves of the press for a molding cycle.

After a predetermined time, the blades T2 of the timer close and energize the solenoid S3. En-

ergization of the solenoid S3 brings about the advancing movement of the extrusion plunger 343. After a predetermined greater time, the blades T4 open to de-energize the solenoid S3 to bring 'about the retractingmovement o! the extrusion plunger. Thereafter, after the material has set within the mold, the blades TI open and the blades T5 close to energize Si to bring about a retracting movement of the clamping ram. After the ram has fully retracted, the cam 368 on the platen may strike the limit switch L83 which brings about the deenergization of A. and therethrough the de-energization of T which clears the entire circuit and de-energizes all of the solenoids. Optionally, the cycle may be halted by the timing out of the timer T whereupon the blltcles T3 and T6 open in order to clear the circ For actuating the ram 3i4 independently of the extrusion ram, there may be provided the push buttons 310 and 312, as shown. These may be selectively closed for shifting the valve to reciprocate the ram 3|4. When the injection ram is to be reciprocated independently of the clamping ram, there is provided the push button 314 and in addition thereto the selector switch 316 which bypasses the push button 310 so that the valve 308 can be shifted away from its bypassing center position in order to provide a supply of pressure iluid for actuating the extrusion ram.

Operation of the embodiment o! Figure 4 In operation, the embodiment illustrated in Figure 4 is similar to that of the modication in Figures 1, 2 and 3. The valve member'322 is first shifted to the right to supply pressure iluid to the clamping ram advancing means 3|2 to move the molds into clamped position. Thereafter, the valve member 330 is moved leftwardly to connect 45 the discharge side of the pump directly with the extrusion ram advancing means 338. This brings about an extrusion stroke and the fluid expelled from the extrusion ram retracting means is passed through the choke valve 362 to augment the sup- 50 ply of actuating iluid for the advancing means 333. When the extrusion ram 340 encounters resistance, the pressure in the advancing means 338 increases and actuates-the valve member 352 to connect the retracting means 346 directly with 55 exhaust. This provides for the full thrust of the advancing means to be employed in the extrusion of the molding material.

The extrusion ram is retracted by returning the valve member 330 to its Figure 4 position 60 whereupon the valve member 352 also returns to its Figure 4 position and the retracting means 346 is supplied lwith pressure while the advancing means is exhausted.

During the retraction of the extrusion ram, the 65 choke valve 344 maintains pressure in the circuit for holding the molds clamped together. After a predetermined dwell, the clamping ram is retracted by shifting the valve member 322 into its left end position, and fofiowing the retraction 70 of the clamping ram, the valve member 322 is again moved to its center position.

' It will be apparent from the foregoing that the iluid circuits constructed according to this invention provide a means whereby a. plurality of rams 76 can be operated according to a predetermined It will be understood that this invention issusceptible to modification in order to adapt it to dierent usages and conditions and, accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

I claim':

1. In a fluid operable system; a plurality of independently operable iiuid motors at least one of which is double acting; a single iluid source; a `valve movable to direct fluid from said source to one of said motors other than said double acting motor; another valve movable for thereafter directing fluid said source to one side of saidv double acting motor; andvmeans for restricting the discharge from the other side of said double acting motor whereby a predetermined minimum pressure is maintained by said source.

2. In a fluid operable system; a plurality of fluid motors having inlets and outlets: a single fluid source for supplying actuating uid to said motor means; meansfof connecting said source with the inlet oi one of said motor means for actuating the same; means of thereafter connecting said source with the inlet of another motor means: and means operable to maintain a predetermined pressure at the outlet port of the last mentioned motor for maintaining a predetermined minimum .pressure in the system for maintaining the first mentioned motor energized.

3. In a fluid operable system; rst and second iluid motors having inlets and outlets; a single fluid source for supplying said motors; means to connect said source with the inlet'of one of said motors for energizing the same: means of thereafter connecting said source with the inlet of the other of said motors; and means of restricting the discharge from the said other motor for maintaining a predetermined minimum pressure in the system for maintaining both of said motors energized.

4. In a uid operable system; first and second motor means; a fluid source; means of connecting said source with the iirst of said motor means: means responsive to a predetermined pressure acting on said rst motor means for connecting said source with said second motor means; means operable automatically for maintaining a predetermined minimum pressure in said system; and means responsive to a predetermined pressure acting on said second motor means for disconnesting it from said source while maintaining the connection between said source and said first motor means.

5. In a iiuid operable system;rst and second motor means having inlets and outlets; a fluid source: means to connect said source with the inlet of the rst of said motors; means responsive to a predetermined pressure thereon for thereafter connecting said source with the inlet of said second motor; means resisting the discharge of fluid from the outlet of said second motor for -...vmaintaining a predetermined minimum actuating 12 pressure in said system; and means responsive to a predetermined pressure at the inlet of said second motor for making the said means for resisting ineffective whereby said second motor develops its full operating thrust.

6. In a iiuid operable system; first and second motor means having inlets and outlets; a fluid source: valve means m'ovable to connect said source with the inlet of said rst motor; means responsive to a predetermined pressure at the inlet of said first motor for connecting said source with the inlet of said second motor; means restricting the discharge of iiuid from the outlet of said second motor to maintain a predetermined minimum actuating pressure in the system; and means responsive to a predetermined pressure at the inlet ofsaid second motor for disconnecting the said inlet from said source and for connecting said source instead with the outlet of said second motor.

'7. In a uid operable System; first and second motor means having inlets and outlets; a. uid

source; valve means movable to connect said source with the inlet of said rst motor; means responsive to a predetermined pressure at the inlet of said rst motor for connecting said source ywith the inlet of said second motor; means restricting the discharge of iluid from the outlet of said second motor to maintain a. predetermined' minimumuactuating pressure in the system; means responsive to a predetermined pressure at the inlet of said second motor for dislconnecting the said inlet from said source and for connecting said source instead with the outlet of said second motor; and means restricting the subsequent discharge of fluid from the inlet of said second motor to maintain the actuating pressure in said system.

8.. In a fluid operable system; iirst and second motors having advancing and retracting means; a fluid source continuously connected with the retracting means of said second motor; means to connect said source with the advancing means of said rst motor; means responsive to a predetermined pressure acting on the said advancing means for connecting said source with the advancing means of said second motor; means responsive to a predetermined pressure acting on theadvancing means of said second motor for disconnecting the retracting means thereof from said source and for connecting it instead with the exhaust; and means responsive to a still higher pressure acting on the advancing means of said second motor `for again connecting the retracting means thereof with said source While connecting the said advancing means with exhaust.

9. In a fluid operable system; a uid motor having advancing means and a smaller retracting means; a iiuid source connected with said retracting means; rst means responsive to a predetermined discharge pressure of said source for connecting said advancing means with said source; means responsive to a higher pressure acting on said advancing means for disconnecting said retracting means from said source and connecting it with exhaust; and means responsive to a still higher pressure at said source for disconnecting said advancing means therefrom` and for connecting the advancing means with exhaust. said means also being operable at the same time to again connect said retracting means with said source.

13 nect said source with the advancing or the retracting side of said clamping ram; m'eans normally connecting said source with the retracting side of said extrusion ram; means to connect said source with the advancing side of the said extrusion ram; and means responsive to a predetermined pressure developed by said source for disconnecting said extrusion ram retracting means therefrom and for connecting the said means with exhaust whereby the said extrusion ram advances rapidly to working position and thereafter develops full thrust. y

11. In a molding machine having a mold clamping ram and a material extruding ram; a single fluid source for actuating said rams; means to connect said source with the advancing or the retracting means of said clamping lram; means normally connecting said source with the retracting means of said ex ion ram for free flow toward the said retracting means and restricted flow therefrom; meahs responsive to a predetermined pressure developed by said source for connecting the same with the advancing means of said extrusion ram; and means responsive to a predetermined higher pressure developed by said source for disconnecting said retracting means therefrom and for connecting the said means instead with exhaust.

12. In a molding machine having a mold clamping ram and a material extruding ram; a single iiuid source for actuating said rams; means to connect said source with the advancing or the retracting means of said clamping ram; means normally connecting said source with the retracting means of said extrusion ram for free flow toward the said retracting means and restricted flow therefrom; means responsive to a predetermined pressure developed by said source for connecting the same with the advancing means of said extrusion ram; means responsive to a predetermined higher pressure developed by said source for disconnecting said retracting means therefrom and for connecting the said means instead with exhaust; and means responsive to a still higher pressure for again connecting said source with said retracting means of said extrusion plunger while connecting the advancing means thereof with exhaust.

13. In a molding machine having a clamping ram and an extrusion ram; a single fluid source for supplying actuating fluid to said rams; means to direct the delivery of said source to the advancing or retracting side of said clamping ram; means normally connecting said source with the retracting side of said extrusion ram; means responsive to a predetermined movement of said clamping ram in the advancing direction for connecting said source with the advancing side of said extrusion ram; and means restricting the discharge of iluid from the retracting side of said extrusion ram for maintaining a predetermined minimum actuating pressure on the advancing sides of both of said rams.

14. In a molding machine; clamping and extrusion rams each having larger advancing areas and smaller retracting areas; a single iiuid source for supplying said areas and normally connected with the retracting area of said extrusion ram; valve means selectively operable to connect said source with the advancing or retracting area of said clamping ram; means responsive to a predetermined movement of said clamping ram in the advancing direction for connecting said source with the advancing area of said extrusion ram; means controlling the discharge of fluid from the retracting area of said extrusion ram to maintain a predetermined ram; valve means selectively operable to connect said source with the advancing or retracting area of said clamping ram; means responsive to a predetermined movement of said clamping ram in the advancing direction for connecting said source with the advancing area of said extrusion ram;y means cntrollingthe discharge of iluid from the retracting area of said extrusion ram to maintain a predetermined minimum actuating pressure in the circuit; means responsive to a predetermined pressure acting on the advancing area of said extrusion ram for disconnecting the retracting area thereof from said source and for connecting it instead with exhaust; and means of again connecting said source with the retracting area of said extrusion ram while controllably exhausting the advancing side thereof to retract said extrusion ram while maintaining said clamping ram energized. y

16. In a molding machine having a clamping ram and a double acting extrusion ram; a single fluid source for supplying said rams; means of connecting said source with said clamping ram for clamping a mold; means of thereafter connecting said source with the advancing side of said extrusion ram for bringing about an extrusion of material into said mold; a. valve between the retracting side of said extrusion ram and exhaust for restricting the discharge of fluid therefrom to maintain a, predetermined minimum pressure in the actuating circuit during the advancing movement of said extrusion ram; and a valve between said source and each of said rams operable to maintain independent pressures on said clamping ram and the advancing side of said extrusion ram for controlling the thrusts thereof.

HOWARD M. PURCELL.

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

UNITED STATES PATENTS Date Tucker Jan. 1,

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