US2480159A - Power press and fluid control circuit therefor - Google Patents

Description

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nh b W M Aug. 30, 1949. G. JJPETERSON POWER PRESS AND FLUID CONTROL CIRCUIT THEREFOR Filed Aug. 26, 1944 Aug. 30, 1949. G. J. PETERSON POWER PRESS AND FLUID CONTROL CIRCUIT THEREFOR 5 Sheets-Sheet 2 Filed Aug. 26, 1944 I J50 11v 1949. G. J. PETERSON 2,480,159

POWER PRESS AND FLUID CONTROL CIRCUIT THEREFOR Filed Aug. 26, 1944 3 Sheets-Sheet 3 INVENTOR.

Patented Aug. 30, 1949 POWER PRESS AND FLUID CONTROL CIRCUIT THEREFOR Gustaf J. Peterson, Rockford, Ill., assignor to Odin Corporation, Chicago, 111., a corporation of Illinois Application August 26, 1944, Serial No. 551,408

19 Claims.

in a power press structure and fluid control circuit of the type defined, an improved and simplifled control arrangement wherein a single control member may be employed to control both the direction and the efiective actuating pressure of the propelling fluid; and wherein an improved indicating arrangement is provided, in combination with the control means, for indicatthe operating forces transmitted to the actuator.

A still further object of the invention is to rovide an improved fluid control circuit for uid operated power presses, specifically of the hydraulically actuated type, and for like material working apparatus.

Various other objects, advantages and features of the invention will be apparent from the following specification when taken in connection with the accompanying drawings wherein a preferred embodiment is set forth for purposes of illustration.

In the drawings, wherein like reference numerals refer to like parts throughout:

Fig. l is a general assembly view of a hydraulic power press and associated fluid control circuit constructed in accordance with and embodying the principles of the invention; parts of the casing structure being broken away to show the operating elements;

Fig. 2 is a side view of the hydraulic press structure shown in Fig. 1;

Figs. 3 and 4 are detail views, respectively, of two types of valve structures included in the fluid control circuit for the machine;

Fig. 5 is a detail view of the direction and pressure control valve unit, also forming a part of the fluid control circuit, said view being taken as indicated by the line 5--5 of Figs. 1 and 2;

Fig. 6 is a, transverse sectional view through the direction and pressure control valve, taken as indicated by the line 6-6 of Fig. 5;

Fig. 7 is a longitudinal vertical section through the direction and pressure control valve, taken as indicated by the line 1-4 of Fig. 5;

Fig. 8 is a transverse sectional view through the direction and pressure control valve, taken as indicated by the line 8-8 of Fig. 5, and more particularly illustrating the pressure control adjustment mechanism;

Figs. 9 and 10 are enlarged detail views of the pressure control valve shown in Fig. 8, the valve and associated adjustment mechanisms being illustrated respectively in two different positions of operation; and

Fig. 11 is a, diagrammatic layout of the fluid control circuit.

In the drawings the fluid control circuit of the invention has been shown applied to a hydraulic bending or straightening press structure, as the invention in certain of its aspects is particularly adapted to a machine of this character. It is to be understood, however, that the invention in various of its aspects may also be adapted for eflecting the actuation and control of other types 4 of fluid actuated power press machines and structures.

Referring more particularly to the drawings, in Figs. 1 and 2 a power press is illustrated of the type, in the specific embodiment shown, which may be employed for bending or straightening work pieces. As shown, the machine comprises a frame or base ill carrying a work bed II. The bed II is arranged to carry a pair of work support pedestals l2 and I3 upon which may be mounted the work piece M to be bent or straightened. The machine base II) also carries an actuator support bracket or pedestal It in the upper end of which is mounted a hydraulic actuator ll. As best shown in Fig. 11, the actuator comprises a vertically disposed cylinder l8 aflixed to the support pedestal, and within which there is reciprocable a piston I9 having a rod portion 20 the lower end of which carries a pressure tool 2|, adapted upon operation of the piston to be brought into engagement with the work piece l4 whereby to effect the bending or straightening operations.

As best shown in Fig. 1 one end of the machine base structure is adapted to form a housing for the parts comprising a fluid control circuit adapted to effect the actuation of the hydraulic actuator H. The fluid control circuit, and its associated power and pumping mechanisms, comprise an electric motor 25 adapted to be energized from a suitable source of electric current supply, under control of a start button 26 and a stop button 21 disposed on a front portion of the machine base in a position convenient for manipulation by the operator. The motor 25, by means of a transmission mechanism consisting of driving and driven pulleys 3|] and 3|, connected by means of a belt 32, effects the operation of a pumping unit generally indicated by the numeral 33. The pumping unit is disposed within a casing 35 enclosed within the machine base, the pumping unit comprising a gear pump portion 36 and a plunger pump portion 31, Figs. 1 and-11. As will be understood, and as will be hereinafter-more specifically described, the gear and plunger pumps, under suitable control, are adapted to deliver the propelling fluid, preferably oil in the particular machine and control circuit illustrated, to the hydraulic actuator H to effect the operation of the reciprocable piston l9 and the associated tool 2|.

The casing 35 carries a combined direction and pressure control valve 40, the details of which will be later described, for controlling the direction of movement of the piston l9, and alsothe pressureexerted thereon by the propelling fluid delivered from the pumps. The direction and pressure control valve includes an operating arm 4|, fixed to a, pivot shaft 42, and movable either clockwise or counterclockwise from the position illustrated in Fig. 1 between the limits determined by the stops 43 and 44. The valve operating arm is actuated by means of a link 45 pivotally connected at one end to the arm and at its other end to an arm 46 of a bell crank control lever '41 pivotally mounted upon the frame of the machine as indicated at 48. It will be seen that actuation of the manual control lever 41 from the full line position shown, either clockwise to the dotted line position 41a or counterclockwise to the dotted line position 41b, effects corresponding movement of the valve operating arm 4|. While for illustrative purposes the operating lever 41 is shown in mid position or neutral position in Fig. 1, normally when the machine is not in operation it -approach or downward movement. Preferably the gauge is calibrated in terms of the total force inpounds, exerted by the working tool 2| upon the work piece.

The arrangement of the control circuit will be best understood by reference to Fig. 11. "An ofl reservoir 58 is formed within the casing 35 in the bottom portion thereof. The oil or propelling fluid is withdrawn from this reservoir by the gear pump 36 through a supply pipe 59. The outlet side of the gear pump is connected to a conduit 60' through which the oil may be delivered from the pump to any one or all of three conduits 6|. 62, and 63 leading respectively to the plunger pump 31, a relief valve 64, and the direction valve portion 65 of the direction and pressure control valve structure 48. The fluid delivered to the relief valve 64 is returned when the valve is in open position to the reservoir 68 by means of drain lines or conduits 61 and 66. The fluid delivered to the plunger pump 31 through the supply line 6i is propelled by the pump through an outlet conduit 69 connecting with conduits l0 and II leading to the upper end of the hydraulic actuator cylinder l8. The pressure gauge 55 is interconnected with the pipe line H. As will be understood, the gear pump 36 is preferably of the large volume, low pressure type,

whereas the plunger pump 31 is of the low capacassumes its clockwise position as indicated at 41c.

being normally shifted to and held in such position by means of a tension spring 49 connected at one end to the lever arm 46 and at its other end to a suitable anchorage on the machine frame or base. As will presently be described, when the manual operating lever 41 is in its clockwise position 41a, and the pumps 36-31 are in operation, the piston IQ of the hydraulic actuator is caused to be returned or shifted in an upward direction to withdraw the forming tool 2! from the work piece. When the manual control lever is shifted to its counterclockwise position 41b the piston I9 is caused to be propelled downwardly to bring the tool 2i into engagement with the work piece, the pressure exertable by the propelling fluid upon the actuator piston being progressively increased as the control lever is shifted from its mid or neutral position to the counterclockwise position 41b. It will be seen that the single manually operable control lever 41 is thus operable to control the direction of travel of the actuator piston, and also operative to vary and control the pressure exertable by the hydraulic fluid upon the piston during its approach or downward movement, and after the forming tool has been brought into engagement with the work piece. The pressure may be varied between predetermined minimum and maximum limits, the actuating pressure being progressively increased as the control lever is shifted from its full line position, as indicated in Fig. 1, toward the counterclockwise position 411). A pressure gauge 55, Figs. 1, 2 and 11, is arranged in the control circuit so as to indicate the pressure exerted by the hydraulic fluid upon the piston l9, during its ity, high pressure type. Accordingly, only a portion of the fluid delivered by the gear pump passes through the conduits 6| and 69, and through the plunger pump structure when the pumps are in operation. The gear and plunger pumps may be of any suitable construction, the details thereof forming no part of the present invention.

Fluid delivered by the conduit 63 to the revers- 18, depending upon the valve position. The conduits 15 and 11 are pilot pressure conduits for effecting the shifting of the valve member of a by-pass valve structure 80. As will be later described, the by-pass valve is a two-position valve. In one position thereof it is arranged to connect a conduit 8| to a conduit 82 connecting with the return conduit 68 leading tov the fluid reservoir. In the other position of the valve, fluid passage between theconduits 8i and 82 is broken.

When the reverse valve 65 is arranged to transmit fluid from the supply conduit 63 to the interconnected conduits 15 and 16, the oppositely disposed interconnected conduits I1 and 78 are connected through the valve to a drain line 85 leading to the fluid reservoir. Similarly when the valve is positioned to interconnect the supply conduit 63 with the conduits l1 and 18, the opposite 1y disposed conduits l5 and 16 are connected to drain.

When the reverse valve 65 is arranged to dispatch propelling fluid from the conduit 63 to the conduit 16, the fluid is delivered by said conduit 16 top, relief and check valve structure 86 through which the fluid is transmitted to a conduit 83 connecting with the conduits 10 and H leading to the upper end of the actuator cylinder l8. As will be later described, fluid may pass through the relief and check valve 88 in the direction indicatedby the arrow, Fig. 11, but not in an opposite direction. Conversely, when the reverse valve 65 is positioned to direct fluid from the supply conduit 63 t0 the conduit 18, fluid is transmitted thereby to a conduit 90 leading to the lower end oi the actuator cylinder.

A conduit 9| connects with an intermediately disposed port in the actuator cylinder I8. This conduit leads to a relief and check valve structure 92 through which fluid may flow in the direction of the arrow but not in the opposite direction. Fluid passing through the valve 92 is delivered to a conduit 93 connecting with the conduits W and i8.

A conduit 95 connects with the conduit 'iI and leads to the pressure control valve portion 96 of the direction and pressure control valve structure it. As previously indicated, and as will later be more specifically described, this valve is adapted to control pressure conditions within the actuator during the approach or downward movement of the piston is. When the valve 95 is opened, fluid delivered thereto through the conduit 95 is transmitted to a drain line 9'! returning to the reservoir.

Before describing the manner of operation of the control circuit, the structural details of the by-pass valve Bit, of the relief valves 54, 88 and ti, and of the direction and pressure control valve structure ill, will be described. The by-pass valve it is illustrated in Fig. 3. As will be seen, this valve structure comprises a shiftable valve member Wt longitudinally reciprocable within a bore of a valve casing ibi closed by end caps I02 and i ti. When the valve member Iiit is shifted to the right, as shown in Fig. 3, it will be seen that communication between the conduits ti and t2, communicating respectively with valve ports tilt and Hit, is cut oil; whereas when the valve member is shifted to the left from the position shown, communication between the valve ports and conduits is established. The valve member W5 is shifted, as previously brought out, by fluid pressure directed thereto from one or the other of the conduits l5 and 'il communicating with the valve casing bore through the ports iii and It'i.

The relief valves 5t, 8t and 92 may all be of generally similar construction, as indicated for example in Fig. 4. These valves comprise 9. casing i it having a central chamber i I i closed by an end cap M2. A relief valve member H3 is reciprocable within the casing bore lit, said valve member having an axial passage H5 and a connecting transverse passage H6 adapted to communicate with the valve chamber I III when the valve member is shifted to open position or upwardly, as seen in Fig. 4, against the action of a compression spring iii. the valve is opened against the action of the spring by fluid pressure within the bore i I I. The force exerted by the compression spring tendingto close the valve is adjustable by means of an adjustment screw III! threaded into the end cap M2. When the valve is opened communication is established between the conduits 62 and 51 in the case of the valve 66, between the conduits iii and W in the case of the valve 88, and between the conduits 9i and 93 in the case of the valve 92. Reverse flow from conduit 5i to conduit 52, or from conduit 89 to conduit it, or from conduit ti to conduit Qi, is prevented, the valve thus constituting a relief and check valve structure. Adjustrnent of the set screw lit will determine the relief pressure of the valve, in each instance. In the case of the valves 88 and 92 a very light spring and adjustment may be employed, the valves thus being essentially check valves, whereas in the case of valve M a heavier spring and adjustment may As will be understood,

' aeaonca be employed so as to provide a predetermlneddesired relief pressure for the gear pump outlet.

The direction and pressure control valve structure 40 is illustrated in Figs, 5 thru 10. It will be seen that the pivot shaft 42, to which the valve operating arm ll is secured, is formed integrally with a valve member I25 oscillatable within a valve casing I26 formed as a part of the reverse valve portion 65 of the direction and pressure control valve structure. The valve member I25 is provided with a pair of slots I21 and I2! arranged to control communication between the conduits 53, 85, I5, I8, I1 and i8 communicating with the valve. When the valve member is in the position shown in Figs. 5, 6 and 7, corresponding to the full line control position in Fig. 1, the slots oi passages I21 and I28 are inoperative to establish communication between the conduits. When the control lever 41 is in its control position la, the valve member I25 is moved counterclockwise as seen in Figs. 1 and 6 so that the passage i2'i establishes communication between the supply conduit 63 and the conduits ii and It, interconnected within the valve by means of a casing port I30, Fig, 7; while simultaneously the conduits i5 and I6, interconnected by casing port I3i, are placed in communication with the drain line through the valve member slot or passage I28. When the control member 41 is moved to its position til), the valve is moved clockwise, as seen in Figs. 1 and 6, so that passage I25 connectsithe supply conduit 63 with conduits I5 and i5, whereas valve passage i271 connects the conduits TI and ill with the drain line 85. A pin I35, Fig. 5, fixed in the casing operates within an annular groove I35 formed in the valve member, so as to preclude the valve member from longitudinal movement.

An arm Mt, Figs. 5, 7 and 8, is fixed to the reduced end portion itI of the valve member I25, this arm being arranged to effect actuation of the pressure control valve portion 96 of the direction and pressure control valve structure. The pressure control valve 95 comprises a casing M2 within which is reciprocable a plunger member M3, the end portion N4 of which is adapted to be engaged by the end of the arm hill when the reverse valve member I25 is moved to predetermined operating positions. A pin I45 limits the movement of the plunger to the left, as seen in Fig. 8.

The plunger member M3 engages a compression spring I 36, Figs. 8, 9 and 10, the opposite end of which is arranged to engage a relief valve member ill operable within the bore I48 of a bushing member M9. The bushing I49 is connected to the conduit 95 previously described, and is threaded into a sleeve I50 pinned to the casing I42 by means of a pin I5I. The relief valve member Ml is provided with an axial passage I55 and a communicating radial passage I56 which in turn communicates with an angularly disposed annular channel I 51! formed in the valve member. It will be seen that when pressure within the valve bore I 48 builds up to a predetermined value, the relief valve is opened or shifted to the left, as seen in Figs. 8, 9 and 10, against the action of the compression spring I46 whereby to establish communication between conduit 95 and the drain'conduit 91 communicating through the internal valve chamber I58.

The relief pressure, or pressure at which the relief valve Iti will open, is determined by the force exerted on the valve by the compression spring I45, which in turn is dependent upon the v I 7 position of the plunger member I48. When the. direction valve member I25 is in its neutraior mid position as shown in Figs. 1, 6 and 8 the plunger I43 exerts only a predetermined minimum pressure upon the spring, determined by the position of the stop pin I45. As the control lever is moved to its control position 41a the arm I40 is moved clockwise, as seen in Fig. 8, to the position I40a away from the plunger, the position or setting of the plunger thus remaining unchanged. However, when the control lever is swung from its neutral or mid position to the operating position 411), the arm I40 is moved counterclockwise from its Fig. 8 position to the position I48b, shifting the plunger I43 inwardly or to the right and progressively increasing the force exerted by the compression spring upon the relief valve. The plunger is shown in its minimum spring pressure position in Figs. 8 and 9, the relief valve being shown in closed position." In Fig. lo the plunger is shown in position to exert a maximum force upon the spring, as when the control lever is in its position 4117. In Fig. the relief valve H1 is shown in an open position.

Operation Normally the control handle 41 is held in its position 41a by the tension spring 48, and the actuator piston I8 and associated working tool 2| are in their withdrawn or uppermost position. With the pumps 86 and 81 in operation, being driven by the motor 25, fluid-is drawn from the reservoir 58 through the supply conduit 58 by the gear pump 88 and delivered to the pump outlet conduit 60. Part of the fluid from the conduit 60 passes through the supply conduit 6| to the plunger pump 81 and is delivered thereby to the conduits 68 and III. The remainder of the fluid from the conduit 88 passes through 'the conduit 82 and through relief valve 64 to the drain conduits 61 and 68 to the reservoir. Pressure is maintained on the conduit 68 at the setting of the relief valve 64, which in an illustrative embodiment may be on the order of 75#/sq, in. This pressure is transmitted through the reverse valve 65 to the conduits I1 and I8 (the control lever 41 being in its position 41a). The pressure in conduit 11 ensures that the by-pass valve 88 will be maintained in its leftward position as seen in Fig. 3, establishing communicationbetween the conduits BI and 82. The pressure in the conduit I8 is transmitted to the conduit 80 whereby to maintain the actuator piston I8 in its uppermost position. The fluid delivered by the plunger pump through the conduits 88 and III is returned to the reservoir at substantially no pressure through the conduits 8| and 82.

When it is desired to bring the working tool 2| downwardly into engagement with the work, the control handle 4! is swung counterclockwise, as seen in Fig. 1, from the position 41a to and slightly past the full line mid position. As the control handle is moved past its mid or neutral position the relief valve 64 closes and the bulk of the fluid from the conduit 60 is delivered through the conduit 63 and through the reverse valve 65 to the conduits I5 and IS. The pressure fluid delivered to the conduit I5 shifts the by-pass valve 88 to the right or to closed position. The pressure fluid delivered to the conduit 16 passes through the check valve 88 (at a pressure drop or relief spring setting suflicient only to ensure the maintenance. 'of suflicient pressure within. the pilot conduit I5 to efiect proper shifting of the by-P -Ss valve 88) 8. upper end of the hydraulic actuator l8. The

fluid delivered to conduits I8 and II from the conduit 88 is suppiemented by the fluid from the plunger pump, received through conduits 8| and 88.

As the piston I8 moves downwardly the return fluid from the actuator passes through conduits 80 and I8, and through the reverse valve 65 to the drain line 85 and to the reservoir. The valve pilot line 11, being connected to drain, permits the shifting of the valve 80, as stated.

During the downward approach movement or traverse of the piston I8 the maximum pressure which can be exerted on the piston is determined by the setting of the relief valve 86 or the direction and pressure control valve structure, inasmuch as this valve is directly connected to the actuator supply line II by means of the conduit 85. The arm I48 having been moved only slightly counterclockwise from the position shown in Fig. 8, the spring I46 is only slightly compressed and accordingly the relief pressure of the valve 86 at this time is relatively low, suflicient only to ensure downward traverse of the actuator piston. During downward traverse of the actuator piston, the relief setting of the valve 86 may for example be on the order o.10#/sq. in. although, as will be understood, this setting may be varied in accordance with the requirements of the particular installation.

As the forming tool 2I engages the work piece, and movement of the piston I8 is arrested, the relief valve 86 (having a lower pressure setting than the relief valve 84) opens to divert the fluid from the actuator supply line II. As it may now be desired to increase the pressure engagement between the tool and the work, the control handle 41 may be progressively advanced toward its position 4'"), whereby to progressively increase the propelling pressure of the fluid in the actue ator. As the .pressure setting of the valve 88 is increased above the setting of the relief valve 64, the latter opens to divert the bulk delivery of fluid from the gear pump to the drain lines 61 and 68.

45 However, the plunger pump 31 continues to deliver fluid through the conduits 68, I0 and Ii to the actuator, at a pressure controlled by the relief or pressure control valve 88. Reverse flow of the plunger pump fluid through the conduits 88 and I6 is prevented by the check valve 88. The control handle 41 may be progressively shifted toward its position 41b to progressively increase the propelling force of the fluid on the actuator to the maximum limits of the circuit which may be on the order of several thousand pounds per square inch, depending upon the requirements of the I installation; The pressure gauge 55, calibrated in terms of total force exerted by the tool on the work, continuously indicates pressure and working conditions.

To protect the lower end cap I8a of the actuator from the high pressures possible in the system during downward traverse of the piston, means is provided for preventing the high pressure impact of the piston I8 against the end cap l8a in the event the work piece should break or not be present to furnish resistance to the working tool. When the piston I8 reaches its extreme lowered position as indicated in Fig. 11, it uncovers the cylinder port connected to the conduit 8i. Under these conditions fluid delivered to th actuator from the conduit II is by-passed through the conduit 8 I, the relief valve 82 and the conduits 83 and I8 to the reservoir at the pres-l and through the conduits 88, I8 and II to the sure setting of the relief valve 82.

To return the actuator piston to uppermost position the control handle 41 isshlfted to its position "a. As the control lever is shifted the relief valve 64 closes (assuming the actuator piston encounters no unusual resistance) and the bulk of the fluid from the gear pump 3-6 is delivered through conduits G and 63, and through the reverse valve 65. to'conduits l1 and 18. The

pressure fluid in pilot conduit I1 shifts the bya pass valve 80 leftward or to open position. The fluid in conduit 18 is delivered through conduit SI to the lower end of the actuator cylinder to propel the piston l9 upwardly. Reverse flow through conduits 93 and 9| is prevented by the check valve 92. The return fluid from the actuator passes through conduits "H and 8| and through the by-pass valve 80, to drain conduits.

' 82 and =68. The pilot valve conduit is connected by the'reverse valve 65 to the drain line 85, so as to permit the shifting of the by-pass valve 80. During the upward travel of the actuator piston, the fluid delivered by the plunger pump 31 passes through conduits 6i and 69 to, conduit 8!, and thence to drain through the by-pass valve 80 and the drain lines 82 and 68. Accordingly, during upward traverse of the piston the flui from the plunger pump is not used for propelling purposes. However the upward traverserate of the piston, in the particular embodiment shown, is none the less substantially double the downward traverse rate, due to the differential areas. on the opposite faces of the piston because of the piston'rod 20.

When the piston reaches the upper limit of its travel the relief valve 64 opens, the piston being maintained in its uppermost position by the pressure setting of the valve BI, and conditions being established as initially described.

It will thus be seen that a control circuit for the hydraulic actuator is provided wherein the desired movements of and pressure conditions upon the piston at all times are controlled in a desired manner; and wherein the single control lever ll is employed both to control the direction of actuator travel and also accurately and variably to control the pressure engagement between the forming tool and the work piece. The maga third position for variably adjusting the pressure of the propelling fluid, and means for biasing said control member toward and for normally maintaining said control member in said first position. a

2. A power press structure comprising support means for a press tool, support means for a work piece to be operated upon by said tool, and means for shifting said support means relative to each other to selectively engage and disengage the tool and work piece comprising a fluid operated actuator, propelling means for fluid, circuit connections including a direction valve and a pressure control valve for transmitting propelling fluid from the propelling means to the actuator, and a single controlmember associated with said circuit connections to shift said direction valve for controlling the direction of travel of said actuator "and. to shift the pressure control valve for variably controlling the pressure of the-propelling fluid transmitted thereto, said control member being shiftable to a first position to dispatch fluid to the actuator in one direction, to a second position in a given direction to dispatch' fluid to the actuator in the opposite direction'at a predetermined constant minimum pressure, and to a third position in the same direction for progressively increasing the pressure of the propelling fluid. i

3. A powerpress structure comprising support means for a press tool, support means for a work piece to be operated upon by said tool, and means for shifting said support means relative to each other to selectively engage and disengage the tool and work piece comprising a fluid operated ac tuator, propelling means for fluid, circuit connectrol valve for variably controlling the pressure of the propelling fluid transmitted thereto, said control member being shiftable in one direction to a first position to dispatch fluid in one direction to the actuator, said control member being shiftable in the opposite direction to a second pol. A power press structure comprising support meansfor a press tool, support means for a work piece to be operated upon by said tool, and means for shifting said support means relative to each other to selectively engage and disengage the tool and work piece comprising a fluid operated actuator, propelling means for fluid, circuit connections including a reversing valve and an adjustable pressure control valve for transmitting propelling fluid from the propelling means to the actuator, and a single control member associated with said circuit connections operable upon the reversing valve for controlling the direction of travel of said actuator and upon the pressure control valve for variably controlling the pressure of the propelling fluid transmitted thereto, said control member being shiftable to a first position to dispatch fluid to the actuator in one direction, to a second position to dispatch fluid to the actuator in the opposite direction, and to sition to dispatch fluid inthe opposite direction to the actuator at a predetermined minimum pressure, and said control member being further operable in said latter direction to a third position to variably increase the pressure of the propelling fluidwhile maintaining operative connections for the fluid between the propelling means and said actuator in said opposite direction, and means for biasing said control member toward and for normally maintaining said control member in said first position.

4. A' power press structure comprising support means for a press tool, support means for a work piece to be operated upon by said tool, and means for shifting said support means rela- 'tive to each other to selectively engage and disengage the tool and work piece comprising a fluid operated actuator, propelling means for fluid, circuit connections for transmitting propelling fiuid from the propelling means to the actuator, said circuit connections including a direction valve for controlling the direction of fluid flow to the actuator and a pair of pressure control valves respectively operable to control the propelling pressure of the propelling fluid delivered tothe actuator in its opposite directions 11 Y n controlling member for for adjusting the conne of said pressure conof travel, and a co said direction valye' trol pressure of at trol valves.

5. A power press structure comprising support means for a press tool, support meansfor a work piece to be operated upon by said tool, and means for shifting saidsupport means relative to each other to selectively engage and disengage the tool and work piece comprising a fluid operated actuator, propelling means for fluid, circuit connections for transmitting propelling fluid from the propelling means to the actuator, said circuit connections including a rotary direction valve for controlling the direction of fluid flow to 5 the actuator and a pressure adjustable control valve for controlling the propelling pressure of the propelling fluid delivered to the actuator, and a common controlling member for said direction valve and for said pressure control valve, said controlling member being shiftable along a given path of travel between predetermined limits to effect the operative reversal of said direction valve, and being shiftable between additional limits along the same path of travel to effect the variable adjustment of said pressure control valve While maintaining the direction valve in one of its operative positions.

6. A power press structure comprising support means for a press tool, support means for a work piece to be operated upon by said tool, and means for shifting said support means relative to each other to selectively engage and disengage the tool and work piece comprising a fluid operated actuator, propelling means for fluid, circuit conand a spring closed pressure adjustable control valve for controlling the propelling pressure of the propelling fluid delivered to the actuator, and a common controlling member for shifting said direction valve and for adjusting the control pressure of said pressure control valve, said con-,

trolling member being positively connected to the direction valve and having a lost motion connection with said pressure control valve.

7. A power press structure comprising support means for a press tool, support means for a work piece to be operated upon by said tool, and means for shifting said support means relative to each other to selectively engage and disengage the tool and work piece comprising a fluid operated actuator, propelling means for fluid, circuit connections for transmitting propelling fluid from the propelling means to the actuator, said circuit connections including a rotary direction valve for controlling the direction of fluid flow to the actuator, and a spring closed reciprocable pressure adjustable control valve for controlling the propelling pressure of the propelling fluid delivered to the actuator, and a common controlling member reciprocably operable to rotate said direction valve and to control the opening pressure of said pressure control valve against the action of said spring.

8. A power press structure comprising support means for a press tool, support means for a work piece to be operated upon by said tool, and

means for shifting said support means relative to each other to selectively engage and disengage the tool and work piece comprising a fluid operated actuator, propelling means for fluid, circuit connections including a reversing valve and l2 a pressure adjustable control valve for transmitting propelling fluid from the propelling means to the actuator, a single control member associated with said circuit connections operable betweenpredetermined limits to shift the reversing valve for controlling the direction of travel of said actuator and between different limits to adjust the pressure control valve for variably controlling the pressure of the propelling fluid transmitted thereto, pressure gauging means for indicating the pressure of the propelling fluid in the propelling end of the actuator, and means for biasing said control member toward and for maintaining it in a predetermined position.

9. A power press structure comprising support means for a press tool, support means for a work piece to be operated upon by said tool, and means for shifting said support means relative to each other to selectively engage and disengage the tool and work piece comprising a fluid operated actuator, propelling means for fluid, circuit connections for transmitting propelling fluid from the propelling means to the actuator, said circuit connections including a propelling line and a direction valve for controlling the direction of I fluid flow to the actuator, and a pressure control valve for controlling the fluid pressure in the propelling line to the actuator during travel of the actuator in one direction, common controlling means for said direction valve and for said presvsure control valve, and a valve for controlling the pressure in said propelling line upon reversal of 1 said actuator.

10. A power press structure comprising support means for a press tool, support means for a work piece to be operated upon by said tool, and means for shifting said support means relative to each other to selectively engage and disengage the tool and work piece comprising a fluid operated actuator, propelling means for fluid, said propelling means comprising a relatively large volume low pressure pump and a relatively low volume high pressure pump, circuit connections for transmitting propelling fluid from the propelling means to the actuator, said circuit connections including a direction valve for controlling the direction of fluid flow from both pumps to the actuator and a pressure control valve for controlling the propelling pressure of the propelling fluid delivered to the actuator from one of said pumps, and a.common controlling member for said direction valve and for said pressure control valve.

11. A power press structure comprising support means for a press tool, support means for a work piece to be operated upon by said tool, and means for shifting said support means relative to each other to selectively engage and disengage the tool and work piece comprising a fluid operated .actuator, propelling means for fluid, said propelling means comprising a relatively large volume low pressure pump and a relatively low volume high pressure pump, circuit connections for transmitting propelling fluid from the propelling means to the actuator, said circuit connections including a direction valve for controlling the direction of fluid flow to the actuator, and a variable pressure control valve for controlling the maximum propelling pressure of the high pressure pump, control handle operating means for said direction valve and for said variable pressure control valve, and a relief valve for controlling the maximum pressure delivery of said low pressure pump.

12. A power press structure comprising suppelling means to the actuator, said circuit con- I operated actuator, propelling means for fluid, said propelling means comprising a relatively large volume low pressure pump and a relatively low volume high pressure pump, circuit connections for transmitting propelling fluid from the propelling means to the actuator, said circuit connections including a direction valve for controlling the direction of fluid flow to the actuator, and a variable pressure control valve for controlling the maximum propelling pressure of the high pressure pump during travel of the actuator in one direction, control handle operating means for said direction valve and for said variable pressure control valve, and a relief valve for controlling the maximum pressure delivery of said low pressurepump during travel of the actuator in said one direction and for controlling the maximum pressure in the circuit during travel of the actuator in the opposite direction.

13. A power press structure comprising support means for a press tool, support means for a work piece to be operated upon bysaid tool,

'and means for shifting said support means relative to each other to selectively engage and disengage the tool and work piece comprising a fluid operated actuator, propelling means for fluid, circuit connections for transmitting propelling fluid from the propelling means to the actuator, said circuit connections including a direction valve for controlling the direction of fluid flow to the actuator and a pressure control valve for controlling the propelling pressure of the propelling fluid delivered to the actuator during travel thereof in one direction, a common controlling member for said direction valve and for said pressure control valve, and a relief port in said actuator for decreasing the fluid propelling pressure when the actuator reaches a predetermined position during its movement in said one direction.

14. A fluid control circuit for material working nections including a direction valve for controllingthe direction of fluid flow from both pumps to the actuator,- and a variable pressure control valve for controlling the maximum propelling pressure of the high pressure pump, a control handle operable between flrst and second positions for effecting the operation of the direction valve and to a third position for variably actuating the pressure control valve, and arelief valve for-controlling the maximum pressure delivery of said low pressure pump.

16. A power press structure comprising support means for a press tool, support means for a work,

piece to be operated upon by said tool, and means for shifting said suppport' means relative to each other to selectively engage and disengage the tool and work piece comprising a fluid operated actuator, propelling means ,for fluid. said propelling means comprising a relatively large volume of low. pressure pump and a relatively low volume high pressure pump, circuit connections for transmitting propelling fluid from the propelling meansto the actuator, said circuit connections including a direction valve for controlling the direction of fluid flow to the actuator, a by-pass valve for relieving pressure from the high pressure pump during movement of the actuator in one'direction, and a variable pressure control valve for controling the maximum propelling pressure of the high pressure pump during movement of the actuator in the opposite direction,

apparatus comprising a fluid operated actuator;

propelling means for fluid, said propelling means comprising a relatively large volume low pressure pump and a relatively low volume high pressure pump, circuit connections for transmitting propelling fluid from the propelling means to the actuator, said circuit connections including a direction valve for controlling the direction of fluid flow tothe actuator, a variable pressure control valve for controlling the maximum propelling pressure of the high pressure pump during travel of the actuator in one direction, common control means for the direction valve and the pressure control valve, a by-pass valve open upon reversal of the actuator for disabling the pressure control of said pressure control valve, and

a relief valve for controlling the maximum pres- I sure in the circuit during movement of the actuator in the opposite direction.

15. A power press structure comprising support means for a press tool, support means for a work piece to be operated upon by said tool, and means for shifting said support means relative to each other to selectively engage and disengage the tool and work piece comprising a fluid operated actuator, propelling means for fluid, said propelling means comprising a relatively large volume low pressure pump and a relatively low volume, high pressure pump, circuit connections for transmitting propelling fluid from the proand common control means for efiecting the actuation of said direction valve, said by-pass valve, and said variable pressure control valve, and a relief valve for controlling the maximum pressure delivery of said low pressure pump.

17. A power press structure comprising support means for a press tool, support means for a work piece to be operated upon by said tool, and means for shifting said'support means relative to each other to selectively engage and disengage the tool and work piece comprising a fluid circuit having a fluid operated actuator, propelling means for fluid comprising a plurality of pumps, and circuit connections including a reversing valve for transmitting propelling fluid from the propelling means to the actuator, said fluid circuit including means for propelling the actuator from both pumps at a predetermined faster rate of travel so long as the actuator encounters less than a predetermined resistance to movement, a relief valve automatically operable as the actuator encounters a predetermined load resistance for diverting fluid from one pump to propel the actuator at a predetermined slower rate of travel from the other pump, a relief valve for controlling the pressure delivery of said other pump, and common control means for said reversing valve and for said last named relief valve.

18. A power press structure comprising support means for a press tool, support means for a work piece to be operated upon by said tool, and means for shifting said support means relative to each other to selectively engage and disengage the tool and work piece comprising a fluid actuator encounters a predetermined load re- 'sistance for diverting a portion of the fluid from the propelling means to propel the actuator at a predetermined slower rate of travel, means for variably adjusting the maximum propelling pressure of the actuator during its slower travel rate, and a common control device for actuating said last named means and said direction valve.

19. A power press structure comprising support means for a press tool, support means for a work piece to be operated upon by said tool, and means for shifting said support means relative to each other to selectively engage and disengage the tool and work piece comprising a fluid operated actuator, propelling means for fluid, circuit connections for transmitting propelling fluid from the propelling means to the actuator, said circuit connections including a reversing valve, a by-pass valve for by-passing fluid from the propelling means when the actuator is pro- 16 REFERENCES CITED The following references are of record in the file of this patent;

UNITED STATES PATENTS Number s Name Date 634,245 Muncaster Oct. 3, 1899 1,030,234 Elvin June 18, 1912 1,835,976" Ernst Dec. 8, 1931 1,896,052 Ferris Jan. 31, 1933 1,921,955 Vickers J Aug. 8, 1933 1,947,311 Schafer Feb. 13, 1934 1,982,711 Vickers Dec. 4, 1934 I 2,304,793 Montgomery June 11, 1935 2,107,114 Gogan Feb. 1, 1938' 2,202,216 Madsen May 28, 1940 2,218,818 Harrington Oct. 22, 1940 2,243,364 Trautman May 27, 1941 2,316,926 Willett Apr. 20, 1943 2,331,790 Nichols Oct. 12, 1943 2,392,421 Stephens Jan. 8, 1946 2,400,233 Hicks May 14, 1946 2,404,529 Reichelt July 23, 1946

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