US2298359A

US2298359A - Press control

Info

Publication number: US2298359A
Application number: US375030A
Authority: US
Inventors: Ernst Walter; Philip J Lindner
Original assignee: Hydraulic Development Corp Inc
Current assignee: Hydraulic Development Corp Inc
Priority date: 1941-01-18
Filing date: 1941-01-18
Publication date: 1942-10-13
Anticipated expiration: 1959-10-13

Description

Oct. 13, 1-942. w. ERNST ETAL PRESS CONTROL 2 Sheets-Sheet 1 Filed Jan. 18, 1941 WALTER ERNST: E

Patented Oct. 13, 1942 mass CONTROL Walter Ernst and Philip J. Lindner, Mount Gilcad, Ohio, assignors to The Hydraulic Development Corporation Inc., Wilmington, Del, a

corporation of Delaware A plication January is, 1941, Serial No. 375,030

13 Claims.

This invention relates to hydraulic machinery, and in particular to hydraulic pumps having a flow-control member and servomotor means for controlling the position of said flow-control member. Although not limited to the use in con- 'nection with presses, the present invention is of particular advantage in connection with hydraulic presses in which provision is made for slowing down the movement of the press platen shortly before the work piece is engaged by the die connected with said platen.

Presses of this type, as heretofore known, havethe drawback that if for some reason it has been omitted to'insert a work piece in the press, so

that no resistanceis encountered by the press platen, the press will immediately speed up again to full speed. This may result in injuries to the operator and also completely ruin the dies.

In our copending application 357,444 filed Sen tember 19, 1940, there is described a press which overcomes the abovedrawback by allowing the platen to advance in its pressing direction only at a reduced speed if the platen, after having passed its normal work piece engaging position,

does not encounter a resistance of a predeter-' mined magnitude. In such instances the platen may very slowly move downwardly until it engages the press bed and automatically return to itsinitial position, or the driving connection for the pump which supplies fluid pressure to the press ram may be interrupted, thereby stopping the pump delivery and the movement of the platen. However, even in the last mentioned case, it might be that the period of time for stopping the press may exceed a minimum time for I meeting an emergency.

Accordingly, it is an object of the present invention to provide means which, when used in connection with a press of the above character, may cause the platen, at any time during its ing means may be made efiective for shifting said pump instantaneously to neutral or no-delivery position, while latching means will maintain said pump in said neutral position.

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings, in which:

Figure 1 diagrammatically illustrates a first embodiment of the invention.

Figure 2 is a simplified wiring diagram for the electric system controlling the device of Figure 1. Figure 3 is a second embodiment of the invention, and

Figure 4 illustrates, ina. manner similar to that of Figure 2, the electric control circuit for the embodiment of Figure 3.

General arrangement Accordingto the presentinvention the flowcontrol member of a variable delivery pump supplying pressure fluid to the press platen is operatively connected with a cylinder-piston-as- I sembly which, at a desired time during the workworking stroke, to, stop virtually instantaneously.

It is a further object of the invention to provide servomotor meansfor a variable delivery pump which at any desired time during the work ing stroke of the pump, ,may cause the latter instantaneously to shift to neutral pr no-delivery position. v

A still further object of the invention consists in the provision of servomotor means of the type set forth in the preceding paragraph, in which the shifting of the variable delivery pump to neutral position is efiected by fluidmeans.

It'is still another object of the invention to provide a variable delivery pump comprising servomotor means in which, at a desired time, yieldj Referring now to shown thereincomprisesa press head I including stroke of the press platen, may be controlled so that itmoves the flow-control member of said variable delivery pump to no-delivery position and maintains the same in said position for a desired length of time.

According to a first embodiment of the invention, a variable delivery pump is shiftable into forward'delivery position by a fluid operable cylinder-piston-assembly which is operatively connected with a second cylinder-piston-assembly adapted to counteract said first mentioned cylinder-piston-assembly for movingthe pump to neutral or no-delivery position. According to asecond embodiment of the invention, a reversible variable delivery pump is provided for supplying pressure fluid to the press platen to-advance or retract the latter. Yielding means associated with the pump and constantly urging the same to retraction stroke position may, whenever desired, be counteracted by a fluid operable cylinder-piston-assembly for moving the pump into forward stroke position,-while a fluid operable latching member may be made operable to stop the flow-control member of the pump in neutral or no-delivery position when said yielding means is made effective for shifting the pump to its retraction stroke position.

Structural arrangement of first embodiment (Figures 1 and 2) Figure 1 in detail, the press ing a press cylinder bore 2 which has reciprocably 22 is, in its construction, similar to that of the mounted therein a double-acting press piston 2 control valve 28 and slow-down valve 18 and comsupportmg the press platen 4. prises a cylinder 22 having reciprocably mount- The upper portion of the press cylinder bore 2 communicates, by means of a conduit 8, with one 5 side of a reversible variable delivery pump 8. The other side of the reversible variable delivery pump 8 communicates, by means of conduit I, with the lower portion of the press cylinder bore 2.

Connected with the conduit 8 is a low pressure 10 responsive or tonnage control valve 8 adapted to communicate with a fluid reservoiror surge tank 8 arranged on top of the press head I, and adapted to supply pressure fluid to the upper portion n; the cylinder bore 2 by means of a surge valve The surge valve I8 is adapted to communicate through a conduit II with the conduit l2 communicating on one hand with a check valve l2 and on the other hand with a main cylinder relief and pump by-pass valve I4. The surge valve l8 and main cylinder relief and pump bypass valve N do not form a part of the present invention and for a more detailed description thereof reference may be had to U. 8. Patent No. 2,193,248 to Ernst and U. S. patent application Serial No. 286,063, flied July 24, 1939, like- Wis to Ernst. I i

The purpose of the surge valve |8 merely consists in pre-filling the proper portion of the cylinder bore 2 when the press piston is moved downwardly by gravity, whereas the main cylinder relief and pump by-pass valve l4 facilitates the reversal of the movement of the press platen at the end of its working stroke. .Also communicating with the conduit 8 is a high pressure tonnage control valve l8 which, when actuated, effects the reversal of the movement of the press platen of the variable delivery pump 8, thereby causing the platen to effect its retraction stroke.. v

The pressing platen 4 is adapted to actuate a switch |8 which is electrically connected with a solenoid |1 adapted to actuate a slow-down valve,

generally designated I8. 4 The slow-down valve l8 comprises a cylinder I8 having reciprocably mounted therein a piston 28 and communicating, by means of a conduit 2|, with a conduit 22 leading to a. fluid pressure Any .kind of ,fluid pressure source may be used in'this connection, for instance a tank' filled with compressed air or a fluid pressure creating pump. Arranged in the cylinder I8 is a strong spring 24 which continuously urges the piston 28 to its lowermost position andis adapted to co teract fluid pressure confeyed from the fluid pressure source 28 through conduits 22 and 2| to the lower surface 'of the piston 28.

The condui 2| also communicateswith a con- ,duit 28 leading to a control valve, generally des- The control valve 28 comprises a having reciprocably mounted therein a piston 28, the movement of which is controlled by a solenoid 28. 1 I I Also provided in the ,cylinder 21 is a spring 24 of valve M. The

28-similar to the spring urges the piston 28 to its is adapted to counteract fluid pressure conveyed from the fluid source 22 through

conduits

22 and 28 to the lower surface of the piston 28.

Communicating with conduits and 28 and the conduit :2 is a conduit :1 which leads to an emergency valve 22. The emergency valve upper portion, a bleeder opening 21, 38 V respectively.

- a piston 8| having a bore inder 22 of the emergency inder bore 88 and the trapped between ed therein a piston 24, the movement of which is controlled by a solenoid 85. A strong spring 28 acts upon the upper surface of the piston 24 and is adapted to move the piston-24 to its lowermost position against the action of fluid pressure conveyed from the fluid source conduits 22 and 2| through the lower surface of the piston 24.

Each of the valves I8, 20 and a: has, at its The cylinder IQ of the slow-down valve l8 furthermore communicates through a conduit 48 with the port 4| at one end of a cylinder-pistonassembly generally designated 42. Theopposite end of the cylinder-piston-assembly 42 comprises a port communicating through a check valve 44 and a conduit 48 with the cylinder 21 of the control valve 28. in a closure member connected in any convenient manner, for instance by screws 41, with a cylinder 48 having a-bore opening 88 therein.

Reciprocably mounted in the cylinder bore 48 is a piston 8| mounted on the smaller portion 82 of, ashaft or push rod 82. The bottom of the cylinder 48 has a bore ,84 through which passes the shaft 82 and in order to prevent leakage along the shaft 82 a sealing member 58 is provided in the bore 84 and is enclosed in said opening by a disc 88. The bottom of the cylinder 48 is connected'in any convenient manner, for instance by screws 81, with a cylinder 88 having a larger bore 89 and a smaller bore 88.

Reciprocably mounted in-the larger bore 59 is 82 through which the shaft 83 siidably passes. When the piston 8| is in its extreme right-hand position with regard to Figure 1, it abuts the-shoulder 82 of the cylinder 48, whereas in its left-hand position it abuts a shoulder 84. Adjacent the shoulder is provided. a bleeder opening 88. The space 88 between the piston 8| and the disc 88 communicates with a passage 81 which in its turn communicates through the conduit 88 with the cylvalve 22. I

The piston 8| has a U- haped recess 89 adapted to be engaged by a correspondingly shaped portion of a piston 18 reciprocably mounted in the bore 88 of the'cylinder 88.

The piston 18 which is movable independently of the pistons 8| and 8| is provided with one or more L-shaped bores 1| adapted to allow fluid entrapped between the pistons 8| and 18 to escape into the bore 88.

The'piston 18 has threadedly connected there to a shaft 12 passing through-the closed end of the bore 88. To prevent leakage between the cylshaft 12, a sealing member 12 is pjrovided which is enclosed bya nut .14. The end of the cylinder bore 88 adjacent the port 42 is provided with an exhaust bore 18 which is spaced a short distance from the extreme end of the bore 88 so that the piston 18 covers the exhaustbore 18 before the piston 18 abuts the bottom portion 18 of the bore 88.

To prevent fluid from being completely en- I the cylinder bottom portion 18 and the piston 18 when the latter in its movement toward the left with regard to Figure 1 has and 18 are provided which 23 through the and' 28 I The port 4| is provided 48 with a bleeder the outside but communicatewith each other accents andwith the exhaust bore .18 which in its turn comvmunicates through conduit ll with'the conduit 48. In this way thefiuid entrapped. between the cylinder-bottom portion 18 and piston I8, when the latter has covered the exhaust bore "(can escape into the, conduit 48 only through the choke bores I1 and I8, thereby cushioning and slowing,

down the last 'p'ortion'of the movement of the piston 18 toward the cylinder bottom. II; A direct escape of said entrapped fluid vthrough the port 48 into the conduit 48 is prevented by the check valve 84 which opens only toward the port 48 and is arranged between the latter and the point where the conduit I8 leads into the conduit 48. V,

Threadedly' connected to the shaft "and se cured in its position by a nut 88 is a yoke II tactor blade Ill-bridgesits'adjadent of which the terminal III is connected through line II8 with the main supply line I84, while the terminal II8'-'is connected-to a terminal III of the normally closed high pressure tonnage. con- 'trol valve I8. The other terminal I I8 of the high pressure tonnage control valve I8 is connected.

bymeans of-line II8, with theline II8. 'l'he'con tactor blade 8 is adapted to effect communicanested in its turn I ply. line J88.

' .Ajlso'connected with the main supply line I84 tion between the line I28 and the line I2l, which latter leads to the control valve solenoid 28 conis a line I28 leading to a terminal of a platen operable switch I8, the other terminal of which is connected-by line I24 with one end of a solenoid m. The other-end or the solenoid m, communicates, by means of line I28, with the main supply line I85. The solenoid I28 controls the operation of the contactor blades I21 and I18. The blade-I21 is adapted to erect communicationrbetween the line no connected with the main supply line I84 and the line I38 leading to one terminal of the normally closed low pressu're tonnage control valve 8, the other terminal (not shown) of the variable delivery pump 8- so g as to move the pump selectively into forward stroke, retraction stroke, or no-delivery position. A spring 92 abuts a collar 98 on the shift rod 9! and continuously urges the shift rod 8| toward the left with regard'to Figure 1, so that the pump 8 is moved to its retraction stroke position. .It

will be clear from the drawings that when the spring 92 moves the shift rod 9i toward the left,

the aim 9 4of the bellcrank lever '88 will, by

means of the shaft '52,,shift the piston I8 toward the left. Reversible variable delivery pumps of the above character are well known to those skiied in the art, and an assembly of the said type of pumps is disclosed, for instance, inv the U. S.

Patent No. 2,039,893 to The free arm 95 has a rounded portion 98 engaging a collar 91 provided in the uppermost portion of the push rod 98. The push rod 98 has adjustably mounted thereon a collar 98 engag- I88, the other end of which abuts a stationary lug I8I, which guides the push rod 98 in its re-.

mg with its upper portion one end of a spring ciprocating movement. The spring I88 urges the I push rod 98 downwardly. Also adjustably mounted on the push rod 98 is a collar I82 adapted to be engaged by the arm I88 connected to the platen d. Lifting movement of the platen 4 will, therefore, lift the push rod 98 as soon as the arm I83 engages the collar I82. g

The electric control system pertaining to the solenoids I1, 29 and 35 of the slow-down valve, control valve and emergency valve respectively, and also comprising the tonnage control valves 8 and I5, is shown in a simpliiied diagram in Figure 2. In this diagram the numerals I88 and I85 designate the main supply lines.

The main supp y line I84 is connected with a line I88 leading to a terminal I81 which isadapted to be connected with the terminal I88 by operation of the normally open push button switch I89. The terminal I88 is connected to the line II8 leading to one end of the solenoid III controlling the contactor blades M2 and H3. The other endof the solenoid H I is connected with the line II4 leading to the main supply line I85.

When the solenoid III is energized, its conof which is connected through line I8I to the line I24. Closure of contactor blade I28 efiects communication of line I32 connected to the main supply. line I84 with line I88 leading to one end of the slow-down valve solenoid II, the other end of which communicates through line I84 with the main supply line I85.

Further communicating with the main supply line I88 is a line as leading to a terminal' I88 which is adapted to be. connected with the terminal I81 by closure of the normally open emergency switch I38. Connected with the terminal I31 is a line I88 which is normally connected with the line I39 by means of the normally closed reset switch I48. The line I39 leads 1 to one end of a solenoid I, the other end of which communicates through line I42-with the main supply line I85. 'Connectedwith the line I88 is a line I43 which, by closure of the contactor blade I48 pertaining to solenoid I, is adapted to be connected with the line I45 leading to the main supply line I 84. A second contactor blade I 48 pertaining to the solenoid I4I effects, when closed, communication between the A, line I4! connected to the main supply line I84 with the line I48 leading to one end of the emergency valve solenoid 85, the other end of which is connected to a line I49 leading to the main supply line I85.

Operation of first embodiment Supposing that the press ram 3 is in the posi -tion shown in Figure 1, while the pistons 18, 8|

and 5| are in their extreme left-hand position, and assuming further that the. pump 6 is rotated by a driving motor, to start a working cycle, the operator actuates the push button switch I89 so as temporarily to bridge the terminals I81 and Current will then flow from'the main supply line I84 through line I88, switch I89, line H8, solenoid III and line II4 to the main supply line I85. Energization of the solenoid II I causes switch blade 2 to bridge the terminals 5 and H5, thereby establishing a holding circuit for the solenoid III, which holding circuit comprises the main supply line I84, line 8, contactor' blade II2, high pressure tonnage control valve prises main supply line I04,

port H.

" a result thereof, pressure fluid from the pressure fluid source 23 passes "through conduits 22, 25 and 45 through the check valve 44 into the port 43. From here the fluid flows into the cylinder bore 50 where it acts upon the piston 10 so as to move the latter toward the right. As soon as the piston 10 engages the piston 6|, it carries the latter along in its rightward movement.

when the piston 10 during its rightward movement engages the shaft 53, al'sothe latter is moved toward the right, thereby shifting thepiston 5| likewise toward the right. When the pistons 10, SI and 5| have reached the position shown in Figure 1 they come to a standstill.

Since rightward movement of .the piston 10 pulls the shaft 12 toward the right, bell-crank lever 33 will be shifted so that the shift rod 3| likewise moves toward the right, thereby compressing the spring 32. Consequently, when the piston 10 has reached its extreme right-hand po, sition, the

shift rod 9| has shifted the pump 6 to full stroke forward delivery position. The pump 5 now delivers fluid through conduit. 5 into the upper portion of the cylinder bore 2, while the ram 3 moves downwardly by gravity furthermore, fluid from the fluid tank 9 passes through the now open surge valve I into the upper portion of the cylinder bore 2.

As soon as the press platen] approaches th position where it normally engages a work piece, the platen 4 actuates the switch I so as to close the latter. As a result thereof, current flows from the main supply line I04 through. the now closed switch I6, the line I24, solenoid I25 and line I26 to the main supply line I05. The solenoid I25 is therefore energized, thereby causing the contactor blade I21 to' close the holding circuit for solenoid I25, which holding circuit comline I29, contactor blade I21, line I30, low pressure tonnage control valve 3, line I3I, solenoid I25, line I25 and main supply line I05. Energization of the solenoid contactor blade I23 to close the circuit comprising the main supply line I04, line I32, blade I28, line I33, slow-down valve solenoid I1, line I34 and main supp y line I05.

Energization of the slow-down valve solenoid I1 causes upward movement of the piston 23 against the thrust of the spring 24 so that pressure fluid from thepressure fluid source 23 is conveyed through conduits 2|, 22 and 40 to the From here the fluid flows past the piston 5| and inasmuch as the effective piston area of-the piston 5| is larger than the effective piston area of the piston upon which the pressure to the main supply line cylinder bore 2. The downward movement of and,

the press piston'l is, therefore, slowed down in accordance with the rate at which the pump withdraws fluid from the retraction side of the press piston 3. Although the platen 4, after a very short time, disengages the switch I0 so that the latter is open again, this will not affect the slow-down movement due to the fact that the solenoid I25 remains energized, in view of the holding circuit established by, the closure of the blade I21, as mentioned above.

The downward movement ofthe press piston 3 therefore continues with reduced speed until the platen 4 comes to a standstill by engaging a die onthe press bed, unless a work piece was placed on the press bed and engaged by the die connected to the platen. If, during the downward movement of the press piston 3 the die connected to the platen engages a work piece, pressure starts to build up in the upper portion of the press cylinder' 2, and as soon as a minimum pressure is attained the surge valv I0 closes, whereas the low pressure tonnage control valve 8 opens. Opening of the low pressure tonnage control valve 3 breaks the holding circuit for the solenoid I25 so that the blade I28 interrupts the energizing circuit for the slow-down valve solenoid I1.

. As a result of the deenergization of the solenoid I1, the spring 24 returns the piston 20 to its lowermost position, thereby interruptin'g' communi- I25 also causes the cation between th fluid pressure source 23 and the conduit 40, while enabling communication between the conduit 43 and the bleeder opening 31 so that the fluid past the piston 5| may escape through the bleeder opening 31 to an exhaust. Since, on the other hand, the cylinder bore 33 through conduit 45, the control valve 26 and conduits 25 and 22 still communicates with the pressure fluid source", the piston 10 is again moved toward its extreme right-hand position, thereby retuming'the pump, 3 to full stroke forward position. As a result thereof, the downward movement of the press piston 3 is speeded up and the eggs! pressing operation is effected with high s As soon as the pressing operation is finished and a predetermined high pressure built up in the upper portion of the cylinder bore 2, the high pressure tonnage control valve I5 is actuated by the'said high pressure so as to break the holding circuit for the solenoid III. Consequently, the

' a the conduit 45 now communicates with the bleedfluid admitted through the port '43 acts, the piston 5| moves toward the left, thereby ing the shaft .53 toward the left which moves the piston 10 toward the left.

also movin its turn The piston.

5| in its leftward movement-comes to a standshifts the shaft 12 and the piston 10 connected The leftward movement of the piston II and,

er opening 33. The spring 32 in the servomotor cylinder 31 is, therefore, not opposed by pressure acting upon the piston 10 so that the spring 32 will now actuate the shift rod 3| so as to move the pump 3 to full stroke retraction position. When carrying out this movement, the lever 33 thereto toward the left. 5

Due to the provision of the small choke-bores 11 and 1a, a throttling action isproducedat the point of reversal of the variable deliverypump so that a smooth initiation of- .the retraction rod 98 which in its turn engages the arm 35 of the bellcrank lever 83 at the end of the retraction stroke of the platen and shifts the lever 35- so that the shift rod 9i moves the pump kto neutral position. Thepump is then ready fora new cycle.

Supposing now ,that during the downward structure illustrated in Figure 3 ;with the press stroke of the press'platen 4 an emergency occurs,

' for instance that a work piece while being pressed starts cracking, and that it is desired instantaneously to stop the press, As mentioned above,

' duringthe downward stroke of the press platen 4 and engagement'of a work piece by said platen, the solenoid .I II and, consequently, also the solenoid 29 of the control valve 26 is energized so that pressure fluid from the fluid source 23 has moved the piston III to its extreme right-hand position and has placed the pump 6 on full stroke forward delivery position against the thrust of the spring 92.

. In order to'stop the press platen. when an emergency occurs during the downward stroke of said platen, the operator actuates the emergency switch I 38, thereby closing the circuit comprising the main supply line I04, line I 35, line I60, reset switch I40, line I33, solenoid I4I, line I42 and main supply line I05.

Energization of the solenoid I4I causes contactor switch blade I44 to close, thereby establishing a holding circuit for the solenoid I. This holding circuit comprises the main supply line I94, line I45, contactor blade I44, line I43,

reset switch I40, line I39, solenoid I4I, line I42 and main supply line I05. Energization of the solenoid I4I also causes the blade I46 to eflect communication between the line I41 and'the line I48, thereby closing the circuit through the emergency valve solenoid 35.

Energization of the solenoid 35=causes lifting movement of the emergency valve piston 34 against the thrust of spring 36, thereby establishing communication between conduits 3I and 63. As a result thereof, pressure fluid is conveyed from the fluid source 23 through conduit 58 into the passage 61 and the space 66. Here the pressure fluid acts upon the piston GI and, inasmuch as the effective piston area of the piston GI is greater than the effective piston area of the piston 13 acted upon by pressurefluid admitted-through. conduit 45, the piston 6| moves toward the left, thereby also shifting the piston I0 and the shaft'72 toward the left.

When the piston GI abuts the shoulder 64, the pistons 6| and I0 come to a standstill and, at this time, the piston shaft, and thereby the shift rod SI, has been shifted to such an extent that the pump 6 is in neutral or no-delivery position. Since, in this position, no fluid is withdrawn from below the press piston 3, no further downward movement of the platen 4 can occur. In other words, the press platen has come to. a standstill.

If desired, the shoulder 64 may be located so that the pump 6 is moved slightly beyond neutral position-so that, if the emergency switch I38 is actuated, a very slow retraction stroke of the platen 4 is started.

Second embodiment Figures 3 and 4 assembly is'the same as that illustrated in Fig ure 1. Inasmuch as the variable delivery pump of Figure 3 and-the structure of the control valve, emergency valve and slow-down'valve fully corresponds to that described in connection with Figure 1, these members have been provided with the same reference numerals as the corresponding members in Figure 1, however, with. the additional letter a. As will be seen from. Figure 3, the control cylinder-piston-assembly I50 shown therein has omitted the cylinder 48 of Figure 1 and has the closure member 46a connected directly to the cylinder 5811. Furthermore, the piston 5| and shaft 53 of the embodiment of Figure 1 have been omitted.

The cylinder 58a is provided with -a boss' l5l comprising a cylinder bore I 52 in which is reciprocabiy mounted a piston I53 carrying a latch I54. Arranged between the top of the cylinder bore I52 and the upper surface of the piston I53 ton' I53 to its lowermost position.

The upper end of the cylinder bore I52 commu'nicates through a conduit I56 with the conduit'19a which in its turn communicates with the conduit 45a. The lower end of the cylinder bore I52 communicates through a conduit 68a. with the upper portion of the emergency valve cylinder 33a. v

The electrical control system pertaining to Figure -3 is shown in Figure 4 and substantially corresponds to that of Figure 2. The corresponding parts'have, therefore, been designated with thesame reference numerals, however, with the'additional letter, a. The electricaleircuit of Figure 4 differs from that in Figure 2 substantially inthearrangement of the holding circuit for the solenoid controlling the energization of the control valve.

As will be seen from Figure 4, the solenoid -I4Ia controls a contactor with three blades 144a, 5a and I51. While the normally open blades I441; and I46a correspond to the blades I44 and I46 of Figure 2, the third blade I51 is normally in closed position, in which it connects the line II9a with a line I58 which in its tum is connected to line IIfla.

Operation of second embodiment actuates the starting switch I 09a. Actuation of the switch IIiQa closes a circuit comprising the main supply line I04a, line I 06a, line IIIIa, solenoid Illa, line II4a and main supply line I05a. Energization of the solenoidl IIa causes contactor blade IIZa to establish a holding circuit for the solenoid III-a, which holding circuit comprises the main supply line I'II4a,-line "5a, blade 2a, high pressure tonnage control valve I511,

only the pumpcation between the lowermost position,

- extreme right-hand position, the pump byestablishing a supply line Illa,

line Illa, contactor blade I51, line I58, solenoid 1 Illa, line Illa and main supply line ll5a.

Energization of the solenoid Illa also causes blade Illa to connect the lines Illa and Illa, thereby energizing the control valve solenoid 29a. As a result thereof, thecontrol valve piston 28a is lifted against the thereby establishing communication between the conduits 25a and l5 a so that pressure fluid from the fluid source 23a is conveyed through conduits 22a, 25a and l5a into the cylinder bore Ola past the piston Ila. This pressure fluid moves the piston Ila toward the piston 5la toward the right. when piston 5Ia abuts the closure member lla, both pistons 5Ia and'lla come to a standstill. The rightward movement of the piston Ila causes the shift rod lila, in the same manner as described in connection with Figure 2, to move the pump 6a to full stroke forward delivery position.

when the press platen approaches its normal work-piece engagi position, it closesthe switch Ila, thereby connecting the lines l23a and Illa and energizes the solenoid l25 a in themanner described above.

Energization of the solenoid l25a causes the blades Illa and Illa to bridge the adjacent terminals pertaining thereto so that a-holding circuit for solenoid l25a is established and the slowdown valve solenoid Ila is energized. .Con-

the right, thereby also moving thrust of the spring lla,

sequently, slow-down valve piston 20a is lifted I so that pressure fluid from the pressure fluid source 23a is conveyed through lines 22a, 2la and lla past the piston 5la. Inasmuch as the eflfective area of piston 5la is greater than the effective area of piston Ila, the piston 5la moves toward the left untilit abuts the left-hand bottom surface lla of the cylinder bore 59a. Leftward movement of the piston 5la also causes leftward movement of the piston 10a. which latter movement causes the shift rod lla to move the pump 6a to a restricted forward delivery position. The press platen, therefore, advances now only slowly. 7

If a work piece has been inserted previously, pressure will build up in the press as soon as the work piece is engaged so that the low pressure tonnage control valve la will interrupt communies Illa and Illa, thereby breaking the holding As a result, the blade Illa opens and the slowdown valve solenoid lla is deenergized'so that the slow-down valve piston Zla is returned to its while communication between the conduit lla and the bleeder opening 31a is established. Fluid pressure acting upon piston Ila therefore returns piston Ila to. its previous to is restored to full stroke forward The further operation of the delivery position. a

described in connection with press is the same as Figures 1 and 2.

Supposing now stroke of the press platen the same instantaneously. To this end, the operator closes the emergency switch Illa, thereholding circuit comprising the main supply line Illa, line I35a. the switch Illa, reset switch Illa, line Illa, solenoid Illa, line Ilia and main supplyfline Il5a.

Energization of the solenoid Illa causes the blades Illa and Illa to close and the blade I51 to open. Consequent a holding circuit for solenoid Illa is established comprising main line. Illa, blade Illa, line Illa,

that during the advancing it is desired to stop circuit for solenoid 5a.-

as a result of which sequently,

line Illa, reset switch Illa, line Illa, solenoid Illa, line Illa and main supply line Ilia. The energizing circuit for the solenoid 35a is closed, which circuitcomprises main supply line Illa,

line Illa, blade Illa, line Illa, solenoid 35a, line Illa and main supply line ll5a.

Energization of the emergency valve solenoid 35a lifts the emergency valve piston lla to its uppermost position, thereby effecting communication between the conduits lla and 68a. Pressifre fluid'from the fluid source 23a is, therefore, conveyed through conduits 22a, lla and 68a past the stop piston I53 which is pushed forward against the action of the spring I55 so that the latch I5l entersthe cylinder bore 50a.

Opening of the blade l5'l interrupts communication between the lines Illa and I58, thereby breaking the energizing circuit for the solenoid Illa. As a result thereof, the control valve solenoid 29a is deenergized so that the control valve piston 28a is returned to its lowermost position and the connection between the lines 25a and l5a is interrupted, while communication between the line l5a and bleeder opening lla is established. Inasmuch as the spring 92a urging the pump 5a to full stroke retraction position is now no more opposed by fluid pressure acting upon piston Ila, it will shift the bellcrank lever 83a so as to move the piston 'lla toward the left; lligzvezer, as soon as the piston Ila abuts the latch i is in no-delivery position so that the press platen comes to a standstill.

To reset the device, the reset switch Illa is momentarily opened, thereby breaking the energizing circuit for the solenoid Illa and, conalso deenergizes 'the emergency valve solenoid 35a so that the emergency valve piston Ila is returned to its lowermost position by'the spring 35a in the emergency valve 32a. Consequently, communication between the conduits Ila and 58a is interrupted, while communication between the conduit 68a and the bleeder opening 39a is established. The fluid past the stop piston I53 therefore escapes through the bleeder opening Ila, and the spring I55 returns the piston I53 to its lowermost position so that the piston Ila is unlocked. The spring 92a pertaining to the servomotor cylinder lla may then shift the pump to retraction stroke position for retracting the press platen.

It will be understood that we desire to comprehend within our invention such modifications as come within the scope of the claims and the invention.

Having thus fully described our invention what we claim as-new and desire to secure by Letters Patent, is: I

1. In combination with the flow-control member of a reversible variable delivery pump, yielding means continuously urging said flow-control .member into retraction strokeposition, a flrst fluid pressure acting on fluid operable plunger operatively connected with said flow-control member and responsive to fluid pressure acting thereupon to move said flowcontrol member into full forward stroke position against the thrust of said yielding means, a fluid source for supplyin fluid pressure to said flrst plunger, a second plunger operable by fluid pressure from said fluid source, to move 'said flowcontrol member to a restricted forward delivery position, pressure from said fluid source independently-of the position of said second plunger and against said flrs't plunger for is stopped. In this position the pump la and a third plimger 'operableby fluid areas shifting said flow-control member to neutral or no delivery position. 1

2. In combination with the flow-control member of a reversible variable delivery pump, yielding means continuously urging said flow-control member into full stroke position in one direction,

a first fluid operable plunger operable to countermember into full stroke position in the opposite direction, and a second plunger adapted to stop said flow-control member in said last mentioned position and operable by fluid pressure to counteract said first plunger for positively moving said flow-control member to position.

3. In combination with the flow-control member of a reversible variable delivery pump, yielding means'tor continuously urging said flow control-member into full stroke position in one direcneutral or no-delivery tion, a first plunger operable by pressure fluid to counteract said yielding means to move said pump into full stroke position in the opposite direction,

a second fluid operable plunger for selectively stopping said flow-control member in said last mentioned full stroke position, said second plunger having an efiective area opposed to and act said yielding means to move said flow-control 4 ate position, thereby shitting said flow-control member into neutral or no-delivery position.

. 6. In combination with the flow-control member of a reversible variable delivery pump, servomotor means constantly urging said flow-control member to full retraction stroke position, a first plunger operatively connected with 'said flowcontrol member and movable by pressure fluid in one directionto move said flow-control member to full advancing stroke position against said servomotor means, a second plunger operable by-pressure fluid to engage and move said first plunger in theopposite direction against the fluid pressure acting upon said first plunger for shifting said flow-control member into a restricted forward delivery position, and fluid operable emergency I means operable independently of the position 'of said second plunger and responsive to the simultaneous admission of fluid pressure to said first plunger and said emergency means for moving said first plunger into an intermediate position substantially corresponding to no-delivery position of said flow-control member.

'7. In combination with the flow-control member ofa reversible variable delivery pump, means .i'or continuously urging said flow-control member larger than the efiective area of said first plunger,

and means for simultaneously subjecting said two efiective areas to fluid pressure for positively moving said flow-control member'into an intermediate or neutral position.

into full retraction stroke position, a first fluid operable plunger operatively connected with said flow-control member and movable to shift the same into full forward stroke position, a second 7 plunger responsive to the admission of pressure 4. In combination with the flow-control member of a reversible variable delivery pump, yielding means for continuously urging said fiowcontrol member in one direction into a first full stroke position, a control plunger operatively connected with said flow-control member and open able by pressure fluid to counteract said yielding I means for moving said flow-control member into a second full stroke position in the opposite direction, a fluid operable emergency plunger adapted to engage and stop said control plunger when said flow-control member has reached said second full stroke position, said emergency plunger having its efiective area opposed to and greater than the efiective area of said control plunger, means for admitting pressure fluid simultaneously to said opposed efiective areas of said plungers so asto cause said emergency plunger to move said control plunger toward an intermediate position corfluid'thereto for shifting said flow-control mem- :ber to a restricted forward position against fluid said flow-control member to an intermediate .or

substantially no-delivery position- 8. In combination with the flow-control member of a reversible variable delivery pump, resilient means constantly urging said flow-control member into a first full stroke position in one direction, a first plunger operatively connected responding to the neutral or no delivery position a of said flow-control member, and means for stopping the movement of said control plunger by said emergency plunger when said control plunger has reached said intermediate position.

5. In combination with the flow-control member of a reversible variable delivery'pump, yield ing means for continuously urging said flow-control member" in one direction into a first full stroke position, a, first plunger operativelycofinected with said flow-control member and operable by fluid pressure for moving said flow-control member in the opposite direction through an intermediate position into a second iullstroke position against the influence of said yielding means, a second plunger arranged in alignment with said first plunger and movable by pressure fluid from one end position into another end position to move'said first plunger into a position between said intermediate position and said second tull stroke position, and a third. plunger betweensaid first and second plungers and operable by fluid pressure independently of the position of said second plunger to engage said first plunger' ior moving the same into said intermediwith said flow-control member and operable by pressure fluid to move said flow-control member in the opposite direction into a second full stroke position through an intermediate or neutral position, a second plunger having a larger diameter than said first plunger but a stroke less than half the stroke of said first plunger, and being operable by pressure fluid to move said flow-control member into a position between said intermediate and said second full stroke position, said second plunger being mounted for engagement with said first plunger, a third fluid operable plunger having a diameter larger than said first plunger and a stroke substantially equalling half the stroke of said first plunger, means associated with said third plunger and arranged for engagement with said first plunger, valve means for selectively admitting pressure fluid to one or more of said plungers for actuating the same, and emergency means operable irrespective of the pressure acting Y upon said second plunger for subjecting both said first and said third plunger to fluid pressure, to cause movement of said first plunger by said third plunger to said intermediate position, thereby causing said flow-control member to move to and stop at substantially no-delivery position.-

9. In combination with the flow-control member of a reversible variable delivery pump, a first position in another fluid operable piston operatively connected with said flow-control member for moving said flowcontrol member in one direction into a first iull 'operable to make said yielding means ,eflective,

and stop means to stop said first piston in a position corresponding to no-delivery position of said flow-control member when said yielding means has been made effective.

10. In combination with a reciprocable member, servomotor means comprising yielding means continuously urging said reciprocable member into full stroke position in one direction, a reciprocable first plunger operable by fluid pressure to move said reciprocable member into full stroke direction against the thrust of said yielding means, a reciprocable second plunger operable by fluid pressure to move said reciprocable member to a restricted stroke position against the fluid pressure acting upon said first plunger, and a third reciprocable plunger operable by fluid pressure to move said reciprocable member into an intermediate or neutral position against fluid pressure acting upon said acting upon said second plunger.

11. In combination with a reciprocable member, yielding means continuously urging said reciprocable member in one direction into a first full stroke position, a. plunger operatively connected with said reciprocable member and operable by pressure fluidfor moving said reciprocable member against the thrust of said yielding means into a second full able stop means movable selectively into stopping positionior stopping said plunger in a predetermined position between said two full stroke positions, means normally holding said stop means in ineflective position, and emergency means operable to control the supply of pressure fluid to said flrst plunger and irrespective of .fluid pressure stroke position, fluid pressure oper- 2,aos,sso

plunger and said stop means to cause said yieldto move said reciprocable member stroke position while ing means away from said second full simultaneously causing said stop means to move into said stopping position to prevent said yielding means from moving said reciprocable member beyond said predetermined position.

Y 12. In combination with a reciprocable member, yielding means continuously urging said reciprocable member in one direction into a first full stroke position, a first plunger operatively connected with said reciprocable member and operable by pressure fluid for moving said reciprocable member against the thrust of said yielding means into a secondiull stroke position, stop means for stopping said reciprocable member in an intermediate or neutral position against the thrust of said yielding means, a second plunger operable by fluid pressure to move said reciprocable member into a position between said intermediate and said second full stroke positions, valve means movable selectively into closed position for admitting pressure fluid to said first plunger tor actuating the same or into open position for exhausting fluid from said first plunger, and means responsive to movement of said valve means to open position for making said stop means efiective.

13. In combination with a reciprocablemember, yielding means continuously urging said reciprocable member in one direction into a first full stroke position, a plunger operatively connected with said reciprocable member and operable by pressure fluid for moving said reciprocable member against the thrust of said yielding means into a second full stroke position, valve means movable selectively into closed position for admitting pressure fluid to said plunger for actuating the same or into openposition tor exhausting fluid from said plunger, and fluid operable stop means operable selectively to stop said reciprocable member in a position intermediate said two full stroke positions in response to movement of said valve means into open position.

WALTER ERNST.

PHILIP J. LINDNER.