US2379668A - Hydraulic circuit for presses - Google Patents

Description

July 3, 1945.

G. w. WACKER 2,379,668

HYDRAULIC CIRCUIT FOR PRESSES Original Filed March 5, 1941 2 Sheets-Sheet l h 10 J05 go July 3, 1945. G; WJWACKER I 2,379,668

HYDRAULIQ CIRCUIT FOR PRESSES Original Filed March 5,1941 2 Sheets-Sheet 2 ll? 11 @M/ ii/ll Jaye/Z257 Patented July 3, 1945 HYDRAULIC omomr Fon. raEssEs GeorgeW. Waeker, Chicago, Ill., asslgnor to rporation, Chicago, Ill., in.

Clearing Machine Co corporation of Illinoi March 5, 1941, Serial No. and this application October Original application 381,841. Divided 10, 1941, Serial No. 414,491

This application is a division of original application, Serial No. 381,841, filed March 5, 1941.

The present invention relates more specifically to an improved hydraulic circuit for operating the parts of a press, and one of the objects of the same is to provide an improved, safe, and economical hydraulic circuit whereby a fluid pressure line common to a plurality of driven elements and supplied by a plurality of constant delivery pumps maybe operated:

(a) With the normally used volume of fluid at operating pressure.

(b) With the maximum fluid at operating pressure.

(c) With a greatly reduced volume of fluid at operating pressure.

(01) With either maximum volume, normal .volume, or reduced volume of fluid at negligible pressure. v

Another object is to maintain, in a supplemental or pilot circuit supplied by a pump which is also adapted to supply the main circuit, sumcient pressure, at all times, to assure the positive operation of controldevices supplied by the pilot Y ircuit, regardless of the pressure existing in the ain circuit.

Another object is to provide a fluid pressure circuit supplied by a large and a small constant delivery pump, the larger of which is by-passed at negligible pressure after it has supplied the circuit for a predetermined period of time, the

smaller pump continuously supplying pressure fluid to the circuit.

Another object is to direct the normally bypassed flow from the larger of two pumps to a fluid pressure circuit, to supplement the continuous flow of the smaller pump, automatically and simultaneously with the operation of controls,

the functioning of which latter brings about the necessity for a greatly increased fluid supply from said circuit.

Another object is to provide a circuit supplied by constant delivery pumps, whereby a fluid driven clamping'mechanism will be economically operated to obtain three successive stages of mold closing and clamping pressure, the last stage requiring an intensifier.

To the attainment of these ends and the accomplishment of other new and useful objects as will appear, the invention consists of the features of novelty in substantially the construction, combination and arrangement of the several parts hereinafter more fully described and claimed and shown in the accompanying drawings, illustrative of this invention.

14 Claims.

available volume of i part which is moved by the pistons 21 against a: mold, or abutment when the piston is lowered, cushioning means are provided in ,means of the use In the drawings, I Figure 1 is a diagrannnatic illustration oi. the

system with parts of the mechanisms operatedpartly in trolled.

Figure 3 is a detail sectional view, on an enlarged scale, of the unloading valve for the circuit. The fluid for the system is supplied from any suitable source through a pipe ill, which pipe is.

connected with a ated bya motor is a pipe it which it, the of branches through the medium of pipes l5 and it, with a four-way valve H, which latter controls the direction of flow of the fluid with respect to the piston It connected, by means of a piston rod l 9, to a movably operated part 20 of the press and embodying the injection mechanism.

This pipe it isconnected, by means of a pipe 25, with one side of a 22, and connected also to the valve 22 is an exhaust or outlet pipe 23. A pipe 24 leads from the casing of the valve 22, and communicates with a pipe 25 having communication with the cylinders 28 in which pistons Z'ljoperate, and constitute a platen-operating mechanism, and these pistons 21 are connected, by means of piston rods 28, to the long stroke platen of the press, for raising and loweringlsuch platen.

The valve also has communication with a pipe 29, which in turn has communication with a pipe at leading to the cylinders Won the other side of the pistons 21, and in the arranged a globe or suitable valve 3t. i

The valve 22 is manuallyoperated in any suitable manner, such as by means of an operating lever or handle 32. e

Both of the pipes 2t and 29 serve as fluid inlet and fluid outlet pipes for the cylinders 26 :1 that is, when the valve 22 is set so as to direct the fluid into the cylinders 26 on one side of the pistons 27, the fluid on the will flow through the pipe 30, pipe 29, through pump it that, in turn, is oper- 112. Leading from the pump l i the valve 22, into the exhaust pipe 23, When the valve 22 is reversed, the direction of the flow of the material will also be reversed.

As a means for preventing a sudden blow to the the cylinders of which the circuit is 'conhas communication with a pipe 7 latter in turn being connected by means manually controlled valve pipe 28 may be other side of the pistons .26, and comprise a pipe 33 of a verysmalldiameter, which leads from the ends of the cylinders below the pistons 21, and has communication with the pipe 23, by means of a valve 34.

This valve 34 may be of any desired or suitable construction, such as an ordinary open and shut valve, and is adapted to be opened to any degree or extent so 'as to control the size of the passage through which the fluid, being forced out oithe cylinders 26, will flow back into the pipe 29. It will therefore be manifest that, inasmuch as the pipe 33 trapped between the piston and the end of the cylinder, will flow slowly through the pipe 33, and thereby iornia cushion.

The pipe 30 has communication with the cylinders 26 at a higher elevation than the point at which the pipe 33 has communication with the cylinder, and it will be seen that during the first part of the descent of the piston Tl in the cylinis of a'smaller diameter. the fluid, when aaraeea I v by means of a pump 6a, which receives its supply through a pipe $6. This pump discharges into a 1 pipe 6|, and this pipe with the branches which der 26, fluid will be forced out through the pipe 30, but whenthe piston -assumes a position to close the pipe 30 and the corresponding opening in the cylinder 26, the only escape for the fluid will be through the pipe 33.

The pipe |4 also has communication with another pipe 35 that leads to a valve 33, which latter may be of any desired or suitable construction, but is preferably of the four-way type, and is the valve which controls the flow of fluid through the pipes 31 and 38 that control the operation of the short stroke or supplemental ram 39, which ram embodies the mold clamping mechanism of the press. To the casing of the valve 36 is also connected an exhaust pipe 46.

Similarly, the pipe I4 is connected, by means of a branch 4|, with a valve casing 42, and the easing in turn is connected, by means of a pipe Ma,

to a cylinder 43. This valve controls the admission of the fluid pressure to the cylinder 43 to actuate a plunger or intensifier mechanism 44, through the mediumof a piston 35, to move the plunger into an opening 46 of a cylinder El, in

which the ram 39 operates, to intensify the pressure of the fluid in the cylinder 41, and within the pipe 4| may be arranged a check valve 58. Leading from the casing of the valve 42 is an exhaust pipe 49. V i

Leading from the pipe I4 is another pipe 5|! which has communication with a valve mechanism 5| the latter operating to control the direction of flow of the fluid through the pipes 52 and 53 for moving the piston 54 in a cylinder 55, and which piston 54 is connected, by means of a plunger rod 56, to a thrust transmission mechanism that is positioned between the platen and a supplemental or short stroke ram 39 of the press, and leading from the casing of the valve 5| is a discharge outlet pipe 51.

Thus it will be seen that the pump ii, receiving itssupply of fluid from the pipe- 6, will direct the same through the pipe i3, to be distributed to the various mechanisms, a check valve 68 being provided between the pipes l3 and i4.

The pump H is a continuously operating pump, and will establish and maintain a pressure in the line through the pipe l4, and by means of controlling the respective valves 36, 5|, 42, and I7, the directionof the flow of the fluid will be controlled to move the respective parts accordingly. The raising and lowering movement of the part to which the pistons 21 are connected is controlled by the valve 22.

The valves 36, 5|, 42, and H are fluid actuated valves, and pressure is supplied to actuate them are attached thereto is of a smaller diameter-than the diameter of the pipe 94 with the various pipes attached to the latter.

In the description of the pipe 6| and its communicating pipes which convey the fluid pressure to the valves to operate them, they will hereinafter be designated as the pilot pipes or pilot system.

This pilot pipe 6! has communication with a pipe 62 controlled by a manually operated valve 63, and leading from the casing of this valve is a pipe 64, which connects with an exhaust'pipe 65. Leading also from the casing of .the valve as is a pilot pipe 66, which has communication with the casing of the valve 16, and a second pilot pipe 61 also has communication with the casing of the valve 36 and the valve 63, so that by manipulating the valve 63, the direction of flow of the fluid through the pilot line to the valve 36 will be controlled, as will also the raising and lowering movement of the piston 68 in the cylinder 4'! that is connected to the ram 39.

. Similarly, leading from the pipe 6| is another pipe 69, which has communication with the easing of a valve 10, and leading from the casing of the valve 10 is another pipe 1| which communicates with the exhaust pipe 65. The valve I0 is manually controllable, and leading from the casing of this valve is apipe 12 which has communication with the valve 42, and another pipe 13 also has communication with the valve casing it and the valve casing 42, so that by positioning the cylinder 43, so that the fluid in the cylinder 43 behind the piston 45 will flow through the valve 42, thence through the pipe 49 back to the exhaust or tank.

Still another ipe 74 forms communication between the pipe 6| and a valve casing 15, the latter having a valve therein which is preferably manually operated, and alpipe 16 forms communication between the casing of the valve I51and the exhaust pipe 65.

.Leading also from the valve casing 15 is a pipe 17, which has communication with the casing of the valve 5|, and another pipe 18 forms communication between the casing of the valve 5! and the casing of the valve 15, with the result that when thevalve 15 is set to direct the fluid pressure from the pilot system through the pipe ll, and the valve 5| is moved in one direction, the piston 54-will be correspondingly moved by the advance of fluid pressure from the pipe 50, 52, and at the same time the fluid on the other side of the piston 54 will flow out of the cylinder through the pipe 53 to the exhaust through the pipe 51. The exhaust from the pilot system will flow from the valve casing 5|, pipe 18, through the valve 15, pipe 16, to the exhaust pipe 65.

The action of the movable part or plunger 20 is controlled by a. valve 19, which is also preferably a manually operated valve, the casing of which has communication, by means of a pipe 80,

able part 28, the fluid pressure to operate the valve I! will be from the pilot pipe 6|, through sure to the cylinder 84 will then be through the pipe 85 leading from the valvecasing ll, beneath the piston l8. At the same time, fluid on the other side of the piston l8 will be exhausted from the cylinder 89, through the pipe 86, to theexhaust pipe l6.

Thus it will be seen that by manipulating the various valves 63, I8, and 15, as well as the valve 32, the operation of the various parts of the press will be controlled. i

The pipe l4 also has communication with a discharge or outlet pipe 81, and in the operation of the pump I I to build up the necessary pressure in the system, such pressure is controlled by means of the necessary pressure-regulating valve 88 in the pipe I4, and this pressure-regulating valve 88 will also operate as a relief valve.

When the part of the mechanism to which the pressure is applied (such as the slide),reaches the limit of its movementior meets with sufficient resistance, then no more fluid in volume can be supplied to the operating parts, but the pump I I will still be operating, and by attempting to force more fluid into the system, the adjustable relief valve 88 will open to handle the surplus fluid, and the pump it will then operate to discharge the fluid, at full pressure, back to the tank or source of supply through the pipe i8, past the valve 58, out through the pipe 87, back to the tank or source of supply. However, such a condition would result in the loss of power, and in order to obviate such loss, .an unloading valve 89 is provided in the pipe 88, and connected also to the casing of this valve is an exhaust pipe 98. This valve 89 is operated at a predetermined time in the operation of the mechanism, and the means for controlling the operation of this valve itself operates to automatically open the valve, with the result that the fluid, at low pressure, will be discharged from the pump ii, through the pipe it, past the valve 89, into the pipe 99, back to the tank or source of supply. However, at this time, and although the fluid is being discharged back to the tank or source of supply by the pump i i, it is necessary tomaintain the operating fluid pressure within the system and against the actuated parts, that is, such as against the slides, etc. This may be accomplished by the use of the pump 99, which is preferably of a smaller capacity and connected with the system so as to supply the necessary fluid to maintain such pressure, such connection being made by means of a pipe 90, which has communication With the pipe 8!, and

in which pipe 9i is arranged a sequence valve 92.

The output of the pump 59 is prevented from discharging through the valve 89 when open, by means of the check valve 58. This pump 59 directs fluid through the pilot system 6|, and the direction of flow in this pilot system is controlled by the manually operated valves i8, 83, 15, and 19, so as to direct the fluid to one side or the other of the respective four-way valves. 36, 5!, 42, and I? to cause a change in the direction of flow of operating pistons.

The-valve 92, hereafter designated as a "sequence valve, is provided to insure that the pump 5 59 first supplies fluid to thepilot system 6| up to a predetermined minimum pressure, after which the valve 92 is open to the pipe 9 I, permitting fluid flow from the pilot system to the main circuit. In this way, a'positive supply of pressure fluid is al- 10 ways available to operate the controls, regardless "the pipe 88, pipe 82, to valve IT. The fluid presof the pressure existing elsewhere in the circuit.

Another valve 93 controls the operation of a dump valve 94 in the pipe .I4, and which valve 94 controls, the discharge of fluid pressure into an exhaust pipe 95, and which valve 94 is opened to permit a. sudden discharge of the fluid pressure from the system back intothe tank or source of supply through the pipe 95. This is sometimes necessary or desirable to temporarily render the machine inoperative.

through the pipe 96, thereby unbalancing the controlling pressure in the valve and causing it to open to the exhaust pipe 95, Reversing the valve 93 to block the vent line 96, will cause the valve 94 to close the opening to pipe 95, thereby resuming pressure in the circuit.

A Vent line 91 normally maintains the valve 89 in a position that the, pump It will cause the fluid to flow therethrough into the exhaust line 98, and is operated so as to be positioned to direct the supply of fluid from the pump I I to the fluid system, through the pipes l3 and I4.

The unloading or by-pass valve 89 is normally open to the exhaust pipe 90, and is provided to prevent the loss of power and the heating of fluid due to the unnecessary flow of pressure fluid from the pump H during non-flow periods of pressure operation, during which times the flow must discharge at high pressure through the pressure relief valve 88. This purpose is accomplished by limiting the duration of pressure operation of the pump H to the time necessary for the completion of any operative function of thepress requiring pressure-fluid, and then by-passing the fluid supply from the pump to the source through the pipe 99 at substantially zero pressure.

\ .Fluid flow from the pump i I into the operative circuit of the press is established simultaneously with the necessity for such flow, by causing the valve 89 to direct the fluid flow into the pipe i3 each time any one of the four-way valves is reversed, thereby creating a fluid demand. By'providing an automatically operated apparatus, such as described, or any other suitable electrically operated mechanism, the same control which operates the valve 89 to by-pass the pump I i may be employed to resume the fiowfrom the pump into the operative circuit when required, and for a timed duration.

There may be times when it is desired to maintain the valve 89 open for a prolonged period,

and to that end there is provided a by-pass 99, preferably manually controlled by a valve mechanism I89, lay-passing the fluid around the valve mechanism 98, and the valve I88 may be any ordinary valve to open and close the by-pass.

A manually adjustable pressure regulator i8! is provided for remote control of the circuit pressure through the valve 88, one side of the latter being connected with the valve Hll by a pipe 7 I82, and the other side oi the valve MI is connected with an exhaust pipe I03, so that by opening the valve I I the pressure in the system which it is necessary to maintain may be increased or decreased; that is, the circuit pressure necessary to open the valve 88 may be varied at will.

An auxiliary pump I04 is provided to meet operating conditions which require exceptionally high injection plunger speeds, and operates to supplement the flow from pump II. Pump I04 is substantially a duplicate of pump II, and is normally by -passed through the valve I01 to the exhaust ipe I06 at substantially zero pressure. When the injection plunger 20 starts its working stroke, it carries collar I09 out of contact with a spring returnedvalve I08, thu closing the normally open vent line IIO. This action causes the valve I01 to close the passage to pipe I06, thus directing the flow from pump I04 into the operating line under pressure and where it is added to the flow from pump II to increase the speed of the injection plunger.

As the injection plunger resumes its retracted position, the vent line I I0 is againblocked by the valve I08, and this causes the valve I01 to open the passage. to the exhaust pipe I06. Escape of pressure fluid from the other pumps through the valve I07 into the pipe I06 is prevented by check valve III.

The check valve II I is provided in the pipe it between the pump I 04 and the line I4, and a check valve H2 may also be provided in the line 35. Pressure gauges II3 may also be provided in the line 35 on both sides of the line'! I2, so as to in-' dicate different pressures, while a pressure gauge I I4 may also be provided in the pilot line. 6!.

Obviously, check and relief valves may be provided at any desired or necessary points in either the main line or the pilot line.

When this system is employed with the injection method and apparatus as described in my aforesaid application, a chamber H5, in which a piston H6 operates, is connected to the supply line gtlfi and the exhaust line I6, through the medium of a valve mechanism I H, one-side of the valve casing I ll being connected to the chamber I I5 by means of a pipe I I8, and to the supply line ,Ili5 by means of a pipe H9, and is also connected to theexhaust line I0 by means of a pipe I20. This valve II! is of any ordinary and suitable type, and is adapted to be positioned so as to form communication between the pipe H9 and the chamber I I 5, to permit the fluid pressure from the line I4-I5 to enter the chamber M5 to actuate the piston i It.

The valve H1 is also adapted to be positioned so'as to close the pipe I I9 with respect to the pipe H8, and open communication between the pipe I I8 and a pipe I20, to permit the fluid pressure to escape.

Electrical control of the valve 09 is preferred, and may be accomplished in any of a number of difierent ways, one of which is illustrated in Fig. 2

' In describing the control, it is assumed that the four- way valves 32, 63, 10-, I5 and I8 are equipped with normally closed contacts, and that as the lever is shifted to reverse the fluid flow of the pilot controls governed by the valve, the lever I25 is tripped, thus momentarily opening the contact I26. Opening this contact de-energizes the coil in the magnet clutch I 21, which latter is mounted to revolve with the slow-turning spindle of the self -starting synchronous motor I29.

Adjoining the clutch I21 and rotatably mounted on the spindle I28, is a tripping member I30, normally held against a stop by a spring and adapted tobe rotated in a clockwise direction when the clutch is. energized. When the hand lever of the valve I8 momentarily opens the con tact I26, the tripping mechanism is snapped into as a result, the'pressure in the valve 89 becomes equalized, closing the'valve to the exhaust line 30, and causing the pump I I to discharge its flow into pipe I 3, thence to the common line. I4. A

In the meantime, the member I30 has rotated through an are determined by the setting of the control, so that at the end of a predetermined intervaL'the member I30 will engage the contact arm I32. and open the contact I3I. This stops the motor I29 and de-energizes the spring returned solenoid valve 98, permitting the fluid flow from the valve 89 to be resumed to the exhaust pipe 65 through the pipe 91. The valve 89 will now open, because the internal pressure becomes unbalanced, and the fluid flow from the pump II will be by-passed at practically zero pressureto the exhaustpipe 90;.

The pump 5 i will continue to run under no load until another control valve lever is turned to initiate movement of another press element, when the aforesaid cycle of operation will be repeated.

The electrical control, therefore, provides automatic means to operate the main supply pump under pressure for a definite and limited period of a construction as-shown in and close the passage 90.

A relatively restricted passage I43 is provided,

connecting the chamber I44 with .th main pas-.

sage through the valve. Another passage I45 is provided entirely through the piston valve, to connect the spring chamber I42 with the passage 90, to prevent the accumulation of any pressure in the chamber.

It will be seen that if the passage 911s closed, pressure will be builtup in chamber I44, equal to the pressure in the through passage I45, and the piston valve will be in approximately hydraulic balance. Therefore, the pressure ofthe spring predominates, and will keep the valve on its seat, closing the passage to 90, but when passage 91 is opened by the control valve 98, it will discharge fluid faster than the passage I43, which latter,"- being restricted, can supply it, thereby dissipating the pressure in the chamber I44, and creating an unbalanced hydraulic condition with refer ence to the piston valve.

The pressure irom the pump I I will now be able to move the valve against the pressure of the spring, opening the passage to 90, and reducing the pressure of the fluid flow from the pump II to the negligible amount needed to overcome the pressure of the spring. Blocking or closing of the passage 97 will resume the hydraulic balance in the valve, and the spring will again return the valve to its seat.

It is thought that the operation of this circuit will be clearly understood from-the foregoing description; but. briefly stated, it will be seen I that the main pressure for operating the parts of With this improved systemit willalso be mani -IL' fest that there is provided a pump of relatively large capacity operating to feed the liquid into the pressure circuit, and a pump of a smaller capacity which also feeds into the sam circuit. The valve mechanism operates to divert the output 01 the larger pump away from the circuit at a negligible pressure, and the pump of smaller capacity operates, during such diversion by the pump of larger capacit to supply thecircuit and maintain full pressure therein.

There is also provided a supplemental fluid or pilot circuit which is supplied by the pump of smaller capacity ,for controlling the valve mechanism, andthe pressure in the pilot circuit will be always maintained at a predetermined minimum pressure, regardless of the pressure of the main circuit.

With this improved circuit, the maximum power input to the pressure sources is maintained at a predetermined andlimited. power input is substantially reduced while the full pressure on the hydraulic circuit will be maintained.

While the preferred ating the various herein diagrammaticall shown and described, it is to be understood made in the system, within the scope of the claims, without departing from the spirit of this invention.

What is claimed as new is:

1. An hydraulic circuit providing variable volume of fluid at constant pressure for operating the fluid driven elements of apress, comprising a constant delivery high pump adapted to intermittently supply said circuit through an unloading valve and a check valve, a small volume pump continuously supplying said circuit, and electrically operated control means responsive to the expiration of a predetermined tooperate the duration, and the form and manner of operparts of this system have been that various changes/may be pressure large volume and operating to resume the taneously with the initiation or said reversal.

period of circuit supply by said large pump, to

by-pass the supply from the large pump through said unloading valve, said check valve operating to'maintain the small pump from discharging through said unloading valve, said electrically'operated control meansbeing also responsive to the initiation of fluid flow to said driven elements, and also operating to resume the supply from the large pump to the circuit simultaneously with the initiation of said fluid flow.

2. In an hydraulic circuit for operating the fluid driven elements of a press, comprising a plurality of pilot operated four-way valves, and including a main supply line, a pilot supply line, a constant delivery high pressure large volume pump adapted to intermittently supply said main line through an unloading valve and a check valve, a small volume pump continuously supply-' ing said pilot line, a sequence valve connecting said pilot line and said main line, and open only while a predetermined minimum. pressure is maintained in said pilot supply line, and electrically operated control means responsive to the expiraply by said large P reversal of the pilot asraooe I tion of a predetermined period of mainline supfrom the large pump through the said unloading valve, said check valve ope ating to maintain the small pump from discharging through the said unloadingvalve, said electrically operated control means being also responsive to the ,initiation of reversal of the pilot operated four-wa valves,

pumpl to the main line automatically and simul- 3. An hydraulic circuit for operating the fluid driven elements of a press, said circuit comprising a ,main supply line, and including a plurality of pilot operated tour-way valves, a pilot supply line, a dump valve in said main supply line, a constant delivery high pressure large volume pump adapted to supply the main suppl line through an unloading valve and a check valve, 2. small volume pump continuously supp 8 said pilot line, a sequence valve connecting said pilot line and said main line, and open only while a predetermined minimum pressureis the pilot line, electrically operated control means responsive to the expiration of a predetermined period of main line supply by said large pump, to by-pass said large pump through said unloading valve, said check valve operating to maintain the small pump from discharging through said unloading valve, said electrically operated control means being also responsive to the initiation of operated four-way valves, said control means operating to resume the flow from the large pump to the main line automatically and simultaneously with the initiation or said reversal, of fluid from the main line through the said dump valve in emergencies, therebyreducing the pressure in said main line to a. degree suflicient to arrest, movement of the driven elements.

4. An' hydraulic circuit for operating the elements of a press, embodying a main supply line, a constant delivery pump of relatively large capacity adapted to supply pressure fluid intermittently to said line, a constant delivery pump of small capacity continuously delivering pressure fluid to'said line, and electrically operated control means for controlling the how from said large pump, to by-pass the large pump at negligible pressure after a predetermined period of supply from said large pump to said line, and to resume the pressure supply from said large pump to said line upon the initiation of fluid demand to operate the press elements at maximum speed.

5. Means for controlling the hydraulic system of a molding press, embodying a small and a relatively large pressure supply pump, and a plurality of elements driven by the pressure fluid from said .pump, a main supply line, and a pilot supply line, automatic tive control means responsiveto both the continuity of operation of said large pump and the fluid requirements, of the press, the said control means operating to obtain either a full or reduced high pressure fluid supply in said main line, means to reduce the fluid pressure in said main line to substantially zero, and means to maintain a constant fluid supply of a predepumps for supplying fluid to said circuit foroperating said mechanisms, one of which operates as a main, and the to-b -p ss the sup flow from the large maintained in and means to cause the discharge electrically operated selecother as an auxiliary, pump,

both of which are of relatively large capacity,

and adapted to supply the circuit intermittently, and a pilot pump of small capacity which sup-- plies the circuit continuously, a source of fluid supply; and a plurality of means tor controlling the supply of fluid from said main and auxiliary pumps to said circuit, one of said control means operating automatically, under predetermined working conditions with respect to the complete cycle of said mechanisms, to direct the fluid flow from the auxiliary pump into the circuit for a portion of said cycle, and lay-passing said auxil iary pump to the fluid source at negligible pressure for the remainder of the cycle, the other control means :being electrically operated and responsive to the expiration of a predetermined time and the like, which embodies an injection plunger adapted to move throughout its stroke at substantially constant speed, said circuit embodying. a source of supply of fluid, a main constant delivery high pressure pump for advancing and retracting said plunger, anauxiliary and substantially similar pump for augmenting the supply of fluid from said main pump, means to by-pass the flow from; said auxiliary pump to the source or supply at negligible pressure while the injection plunger is in its retractedposition, said means also operating to direct the flow from said auxiliary pump to supplement the flow from the main pump while the plunger is not in its retracted position, means to prevent the flow from the main pump being by-passed with the flow from the auxiliary pump, and an electrically operated control means responsive to a predetermined period of pressure operation of said main pump to by-pass said main pump to said source of fluid at negligible pressure, said electrically operated means being also responsive to the initiation of movement of said injection plunger,

and operating to resume the flow from the said main pump to operate said plunger simultaneously with the initiation of plunger movement.

8. In an hydraulic circuit for operating the fluid driven elements of a press, comprising a source of fluid, a constant delivery high pressure large volume pump normally by-passed to the source of fluid supply at substantially zero pressure, a small volume pump continuously supplying pressure fluid to said pressure circuit, an electrically operated control means to direct the fluid flow from the large pump into the circuit upon the initiation o1 fluid flow to any of the driven elements, the duration of said diversion of flow to the circuit-being timed and terminated by the said electrical control, and valve means to maintain fluid pressurein said circuit while the large pump is by-passed.

9. In an hydraulic circuit arrangement for operating the fluid driven elements of a press,

comprising a source of fluid supply, a main fluidv circuit, a pilot fluid circuit, a constant delivery high pressure large volume pump normally bypassed to the source of supply at substantially zero pressure, a small volume pump continusaid electrically operated means being also 7 der the aforesaid electrical means inoperative and to keep the large pump,by-passe'd to the source of supply, Valve means to provide free fluid flow from the. pilot circuit to the main circuit while pressure equaling or exceeding a predetermined minimumexists in said pilot circuit, and valve means to maintain fluid pressure in the main line delivered by the small pump, while the large pump is being by-passed, to render possible the operation of the driven elements at greatly reduced speed.

10. In an hydraulic circuit arrangement for operating the fluid driven elements of a press, comprising a source of fluid, a main fluid circult, a pilot fluid circuit, a constant delivery high pressure large volume main pump normally by-passed to the source of supply at negligible pressure, a small volume pilot'pump continuously supplying pressure fluid to thepilot circult, ari electrically operated control means for .directing the fluid supply from the main pump into the main circuit upon the initiation of fluid flow to any of the driven elements, the duration of said diversion of flow into the main circult being timed and terminated by said electrical means, valve means to provide free fluid flow from the pilot circuit into the main circuit while pressure equaling or exceeding a predeter- I mined minimum exists in said pilot circuit, and

valve means to maintain fluid pressure in the main circuit while the main pump is by-passed.

11. In an hydraulic circuit for supplying fluid pressure to a plurality of fluid driven elements, including an injection cylinder and plunger, and embodying a source of fluid supply, a main constant delivery large volume pump normally bypassed to the source of fluid at substantially zero pressure, an auxiliary constant delivery large volume pump also normally by-passed to said source of fluid at substantially zero pressure, a small volume pump continuously supplying fluid pressure to said circuit, control means for directing the fluid flow from said auxiliary pump to the circuit only during such time as the injection plunger is not in its retracted position, electrically operated control means to direct the fluid flow from the main pump to the circuit upon the initiation of fluid flow therefrom to any of the driven elements, the durationof said diversion of flow to the circuit bein'g timed and terminated by said electrical control, and valve means' to maintain pressure in said circuit during the icy-passing of either or both of the large 12. An hydraulic circuit for operating the parts of a press and normally maintained at operative pressure, said circuit comprising a constant delivery pump of relatively large capacity adapted to supply fluid under operating pressure to a main circuit and normally by-passed at non-operative pressure regardless of the circuit pressure, a constant delivery pump of. relatively small capacity continuously supplying pressure fluid to the same circuit and selectively adapted to operate parts of the press at slow speed, a plurality of pilot operated valves in the said circuit, a' plurality of controls manually operated at will for controlling the pilot operated valves and thus the functioning of the parts of the press and simultaneously momentarily 2,379,668 initiating the flow of fluid from saidlarge pump into the main circuit, said-controls also operating to automatically first maintain said fluid flow for a predetermined timeandthen divert said flow from the main circuit at non-operative pressure, means independent of other control means, operable at will and adapted to reduce the pressure in the main circuit to a non-operative condition and to resume the normal operat ing pressure at will while maintaining the press parts against operation, and a pilot fluid circuit for operating said pilot operated valves, and

pressure regardless of said circuit pressure, the

which. pilot fluid circuit is continually maintained at a predetermined minimum pressure regardless of pressure fluctuations in the. main circuit.

13. An hydraulic circuit for operating the elements of a press, sai circuit being continually maintained at operative pressure and embody ing a main hydraulic line, a secondary hydraulic line, a constant delivery pump of relatively large capacity adapted to supply fluid intermittently to said main line, a primemover for said pump, a constant delivery pump of relatively small capacity continuously supplying fluid to said secondary line and adapted to operate certain of said elements independently of the large pump,

means embodying control" mechanism operable at will during the cycle of operation of the press fordirecting the fluid flow of the large pump into the main line, said means being also operable to normally divert the fluid flow from the large pump away from the line at non-operative said means being further and automatically operable to divert said flow away from the main line to prevent a continuous overload upon the prime mover, means whereby the secondary line will continually supply the main line and maintain operating pressure therein,and means to automatically maintain a minimum pressure in the secondary line regardless of the pressure fluctuations in the main line.

14. An hydraulic main circuit for operating -a press, said press embodying a plurality of movable members, a source of fluid supply, a pump of relatively large capacity adapted to supply fluid under pressure to said circuit to motion to said members, and normally by-passed to said source at negligible pressure regardless of said circuit pressure, a pump of relatively small capacity, a pilot circuit in which the last said pump is included, said pilot circuit continuously supplying fluid under pressure to the main circuit to impart steady pressure upon said members andto selectively operate said members', means embodying mechanism manually controlled and operable at will to direct the fluid supplied by the large pump into the main circuit, and timing mechanism automatically 'controlled and operable in conjunction with said means to again divert said fluid flow fromthe main circuit to the source, the said means being also operable to simultaneously control the supply of fluid to said movable members.

. GEORGE W. WACKER.

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