US2411716A

US2411716A - Hydraulic press system

Info

Publication number: US2411716A
Application number: US421732A
Authority: US
Inventors: Ernst Walter
Original assignee: Hydraulic Development Corp Inc
Current assignee: Hydraulic Development Corp Inc
Priority date: 1941-12-05
Filing date: 1941-12-05
Publication date: 1946-11-26
Anticipated expiration: 1963-11-26

Description

Nov. 26, 1946. ERNS 2,411,716

HYDRAULIC PRESS SYSTEM Filed Dec. 5, 1941 4 Sheets-Sheet l V IWENT WALTER ERNST Anoauevs Nov. 26, 1946. w. ERNST HYDRAULIC PRESS SYSTEM Filed Deb. 5, 1941 Sheets-Sheet 2 Hoe {NV ENTOR WALTER CRusT STOP 96: 131

Anommva I 7 Nov. 26, 1946. w. EQRNST 2,411,716

HYDRAULIC PRESS SYSTEM Filed Dec. 5, 1941 4 Sheets-Sheet 3 Ira-4 msrmavense PRE5$ RETURN IDLE- WALTER ERNsr 5O Anoma Nov. 26, 1946. WERNST' v 2,411,716

' HYDRAULIC PRESS SYSTEM Filed Dec. 5, 1941 4 Sheets-Sheet 4 49 1 lav 251 I28 130 -7:,/28 .96 I27 .96 I I 'INVENTOR MLTER ERNST ATTORNEY Patented Nov. 26, 1946 I HYDRAULIC mass srs'rslu Walter Ernst, Mount Gilead, Ohio, assignor to The Hydraulic Development Corporation, Inc., Wii I mington, DeL, a corporation of Delaware Application December 5, 1941, Seriai- No. 421,732

9 Claims.

This invention relates to hydraulic machinery and, in particular, to hydraulic presses.

It is an object of the present invention to provide a hydraulic press system in which the press ram may instantaneously be stopped at any position it happens to occupy during the working cycle, and may be held in this position for any desired time. 1 It is another object of the invention to pro vide a hydraulic press system, in which the press ram may be held for any desired time at any posi-'- tion it'may occupy during a working cycle, and may then selectively be advanced or retracted.

A further object of the invention consists in the provision of a press system comprising a fluid operable press ram, in which the supply and withdrawal of fluid to and from said ram respectively may instantaneously be stopped without affect ing the source which supplies fluid to said ram,

It is a still further object to provide a hydraulic press circuit, which comprises a control valve controlling the supply of fluid to and withdrawal of fluid from the press ram, and in which means is provided for by-passing said control valve, when in neutral position, to make up leakage which may occur in the press cylinder while the press ram is in its retracted position.

Still another object consists in the provi'sionoi 1 a hydraulic press circuit, as set forth in the pre ceding paragraph, which comprises an electric control system for automatically controlling the control valve to cause the press ram automatically to perform a complete cycle.

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

-Figure 1 diagrammatically illustrates a press system according-to the invention. I

Figure 2 is a wiring diagram of an electric con-' trol-circuit for use in connectionwith the press system according to the invention. 1. w 'Figure 3 is a graph illustrating'the press ram travel during a cycle, and in idling position due to leakage occurring in the press cylinder.

2 General arrangement The press system according to the present, in

vention substantially comprises a fluid operable press ram, a fluid source, such as an accumulator, for supplying fluid to the press ram, and a main control valve through which the fluid passes from the fluid source to the press ram.

The control valve, which is preferably operable by fluid from the said fluid source, is shiftable into a predetermined position for interrupting fluid connection between the fluid source and the press ram, while simultaneously preventing the escape of fluid from the press ram to an exhaust so as to instantaneously stop the press ram without having to change the condition of the fluid "source. The supply of pilot fluid from the said fluid source to the control valve for actuating the latter is preferably electrically controlled.

The press circuit according to the invention furthermore comprises valve means which automatically establishes a by-pass connection between the fluid source and the retraction side of the press ram when the'latter, while in idling position, drops due to leakage occurring in the press cylinder.

Structural arrangement The press system shown in Figure l'comprises a press cylinder I having reciprocably mountedv therein a press piston 2 with a ram 3 connected thereto.

Mounted in the upper portion of the press cylinder I is a surge valve 4 which may be of any desired type, preferably of the type described in the Ernst Patent No. 2,193,248. The surge valve 4 opens in response to a, suction eiiect in the upper portion of the press cylinder I so as to admit fluid from the fluid reservoir or surge tank:

5, mounted on top of thepress cylinder i, into theupper portion of the presscylinder I. A pilot line 6 .is connectedwith the surge tank 5 and the lower portion of the press cylinder I so as to con- 4s Figured is'a graph illustrating-theclosing and opening of the various control switches during. the-"various phases of travel'of thepress ram, as

illustrated in Figureii.

Figures 5, 6, '7 and 8 show various positions of the main'control valve during a pressing cycle.

Figures 9, 10, l1 and 12 illustrate those portions cf*t he wiring diagram shown in Figure 2 which become-effective at the various phases oi thepress' ram travel.

vey pressure from the lower portion of the press cylinder l', at the initiation of the retraction stroke of the press ram 3, to the surge valve s to open the'latter and to allow fluid to escape therethrough from the upper portion of the press cylinder i into thetank 5.

Also connected with the fluid tank 5 is a suction line 1 leading to the suction side of a variable delivery pump 8, thepressure side offwhich is connected, by means of pressure line 9, with a normally open two-way'valve III. The valve I II,

when in open position, establishes fluid connection between the conduit 9 and the conduit ll' connected to the accumulator |-2 The accumulator l2 has a fluid operable piston or floating member (not shown) therein, which is connected with an arm |3 which latter, when the accumulator is filled up, engages the shaft l4 of a valve member in the valve l8 so as to interrupt fluid connection between the conduits '9 and I.

Branching oil from the conduit 9 is a pilot line |5 leading to a servomotor 6 associated with the pump 8, which servomotor, in response to a pre determined pressure in the conduit 9, shifts the flow-control member of the variable delivery designated l9. This valve is shown in section' in Figures 5 to 8. As will be seen therefrom, the valve |9 comprises a casing 28 with a main bore 2| and two

smaller bores

22 and 23 at one end of the casin and a small bOre 22a at the other end of the casing 28.

Reciprocably mounted in the main bore 2| are two

pistons

24 and 25 interconnected by a shaft 26 of smaller diameter than the

pistons

24 and 25. The piston has a longitudinal bore 21 therethrough which extends into the shaft 26. Passing through the bore 21 is an extension 28 of a piston rod 29 connected to the piston 38. The piston 38, piston rod 29 and extension 28 have a longitudinal bore |32 therethrough so as to admit fluid fro-m the bore 22 into the bore 21 in the shaft 26. ,Similarly, the piston 38a is reciprocably mounted in the bore 22a and has a piston rod 29a with an extension 28a passing through a corresponding bore in the piston 24 into the bore 3| in the shaft 26.

The annular chamber 2|a, confined by the shaft 26, the

pistons

24 and 25 and the casing 20, is in continuous connection with the pressure supply line l1 and is adapted to communicate with fluid connection is established between the conduit I1 and the conduit 33 leading to the lower portion of the press cylinder Connected with the lower end of the main bor'e 2| is 'a conduit 34 which leads to an exhaust line 35 connected with the upper end of the main bore 2|.

Reciprocably mounted in the bore 23 of the casing 28 is a fluid operable stop piston 36 adapted, by means of an abutment 31, to engage and stop the piston 38. Leading to the upper side of the stop piston 36 is a conduit 38 comprising a check valve 39 and leading to a three-way valve 48. The check valve 39 allows fluid to flow freely from the valve 48'into the bore 23 of the four-way valve I9, while preventing the flow of fluid in the opposite direction. The checkyalve 39 is bypassed by a line 4| with a choke valve 42,

Hydraulically connected with the lower side of the stop piston 36 is a conduit 43 with a check valve 44 and a by-pass line 45 comprising a choke valve 46. The check valve 44 allows free flow of fluid into the bore 22, while preventing the flow of fluid in the reverse direction through the check valve 44, The conduit 43 leads to a two-way valve 41, Branching ofi from the conduit 43 is a conduit 48 leading to a three-way valve 49. Connected with the bore 22a is a conline 52 with a choke valve 53. leads to a three-way valve 54.

Branching oil from the pressure supply line H is a conduit 55 comprising a choke valve 56 and leading to the three-way valve 40. The conduit 55 is furthermore connected by lin 51' with the three-way valve 49 and by line 58 with the three-way valve 54. The

valves

48, 49, 54 and 41 have their valve members controlled by

solenoids

62,68, 6| and 59 respectively.

When the solenoid 62 is not energized, fluid connection is established between the

conduits

38 and 55, whereas .energization of the solenoid 62 causes the'valve member pertaining to .the valve 48 to interrupt fluid connection between the

conduits

38 and 55 and to establish fluid connection between the conduit 38 and the conduit 63, which latter is connected to the exhaust line 64 leading to the tank 5. Similarly, deenergization of the solenoid effects fluid connection between the conduits 48 and 51, whereas energization of the solenoid 68 causes interruption of the fluid connection between conduits 48 and 51, while fluid connection is established betWeen the conduit 48 and the conduit 65 connected to the conduit 64. When the solenoid 6| is deenergized, fluid connection is established between the

conduits

58 and 58, whereas energization of the solenoid 6| causes interruption of the fluid connection between

conduits

58 and 58, while establishing fluid connection'between the

conduits

58 and 64.

With regard to the valve 41, this is normally in open position, i. e., fluid connection exists between the conduit 43 and the conduit 66, which latter comprises a choke valve 61 and leads to the conduit 33. However, when the solenoid 59 is energized, hydraulic communication is interrupted between the conduit 43 and the conduit 66.

The electric control circuit governing the

solenoids

59,68, 6| and 62 is illustrated in Figure 2. The diagram of Figure 2 shows the

main supply lines

68 and 69, with a main switch 18 in the latter. Connected with the main supply line 69 is a line 1| comprising a solenoid 12 and leading to one pole ,of the starter switch 13, the other pole of which is connected. with the main supply line 68. Branching off from the line 1| is a line 14 The conduit 58 adapted to be connected with the line 15 by a tion between the line and the line 86', which latter comprises the solenoid 81 and is connected to the main supply line 69. Also connected to the main supply line 69 is a. line 88 comprising the solenoid 89 and being normally connected with line 98 through the limit switch 9|, i. e., when the press ram 3 is not in its uppermost position.

When the limit switch 9| is actuated by the cam 92 (Figure 1) on the press ram 3, the cam 92 moves the lever I33 in clockwise direction about the pivot |34 so that theswitch: 9| interrupts electric connection between the lines '88 and 99 and establishes electric connection between the line 88 and the line 93, which latter comprises the solenoid 94 and is connected with adapted to be connected with the line 98 by a.

switch blade 91 connected to the armature 98,

operation of which is controlled by the solenoid 89. Also connected to the armature 98 is a switch blade 98 adapted to establish electric connection between the line IIiII connected to the main supply line 89 and the line Iiil comprising the solenoid 8! and connected to the main supply line 68. Also connected to the main supply line 68 isa line I02 comprising the solenoid it and adapted to be connected by switch blade Int with the line I02 leading to the main supply line 29. The switch blade We is supported by the ar-'- mature III! controlled by the solenoid 84. Furthermore connected with the main supply line 88 is a line ltd comprising the solenoid 82 and adapted, by means of switch blade Ill'i, to be connected with line "38 leading to the main supply line 69.

The switch blade It? is supported by the ormature ltd, which latter is controlled by the solenoid 8i? and carries asecond switch blade IIii adapted to establish electric connection between the line 85 and the line iii leading to the main supply line 8t. Branching off from the line III is a line it? adapted to be connected with the line H3 leading to the line as when the cam Ht (see Figure 1) on ram it closes the limit switch lit. The limit switch HE is also manually operable when desired by means of an arm 5a.

Furthermore connected with the main supply line 6% is a line HS comprising a solenoid I I1 and adapted to lie-connected with the line H8 .by closure of the position limit switch H9, which latter is adaptcd't'o be closed by the cam 92 on the press ram 3 and is preferably so arranged that it may selectively be moved out of the path of the cam 92, if it is not to be used. The line M6 is also connected with a line I20 adapted to be connected with the line I2I connected to line M8 by closure of the reverse switch button I22 or by closure of the tonnage control switch I23.

The tonnage control switch I23 is a pressure responsive switch connected by conduit I24 with the conduit 32 (Figure 1), and may, for instance, be of the type described in the Ernst Patent No.

2,224,957. The solenoid I I1 controls an armature I25 with two switch blades I28 and I21, of which the switch blade I2'I connects the line I5 with a line I28, leading to line 86 when the solenoid III is not energized. When the solenoid III is in energized condition, the switch blade I21 breaks the connection between the conduits I5 and I28,.while the switch blade I26 connects the .line 90 with a line I29 leading to the main supply line 68. Also connected with the main supply line 68 is a line I30 which is normally connected with the line 9G by the stop button I3I.

Referring now to the energization chart shown in Figure 4, the same comprises a plurality of horizontal columns which, counting from top to bottom and with reference to the press ram travel shown in Figure 3, illustrates in heavy lines the time period of closure of the starter switch I3, the limit switch H5, tonnage control switch I23 and limit switch 9 I and also the period of energization of the

solenoids

12,81, 89, HI and 94.

More specifically, it will be seen from Figures of the fast traverse stroke of the press rain, the starter switch I3 has closed. and that, imme diately after closure of the switch I3, the solenoid I2 is energized and stays energized up to the end of the actual pressing troke. It will furthermore be noted that shortly before the actual pressing stroke begins, the limit switch IE5 is temporarily closed and that soon after the closure of the limit switch Hi, the solenoid 81 is energized and stays energized up to the end of the actual pressing stroke, at which time the tonnage control switch I2! is closed.

I As will furthermore be'seen'from Figure 4, shortly after the closure of the tonnage control switch I23, the solenoid 89 is energized and stays energized until the end of the return stroke, when the limit switch 9| will be closed. I

Figure 4, in connection with Figure 3, also indicates that when during the idling stroke the press ram starts dropping, for instance due to leakage occurring in the press cylinder, the solenoid I I1 is first energized, whereupon the solenoid 94 is energized to return the ram to its retraction stroke position.

Operation Assuming that the press rain 3 is in its uppermost position, i. e.,. slightly higher than shown in Figure 1 while the accumulator I2 is loaded, and that it is now desired to perform a working cycle, the operator closes the main switch iii and the starter switch I3. As a result thereof the circuit shown in heavy lines in Figure 9 is established according to which current flows from the main supply line 69 through line H and now closed starter switch I3 to the main supply line 68. This causes energlzation of the solenoid it so that the armature I1 is moved upwardly with regard to Figurez. 7

As a result thereof, a holding circuit is established for the solenoid 12, which holding circuit comprises main supply line 69, lines It, It and I5, switch blade I2I, lines I28, 96 and I3!) and the main supply line 88. The solenoid 12, therefore, remains energized when the operator takes his hand 01! the starter switch I3, so that the latter again opens.

Energization of the solenoid I2 also causes the switch blades BI and 84 respectively to effect electric connection between the

lines

82 and 83 and between the lines and 86. While closure of the switch blade 84 does not close anew circuit,

closure of the switch blade 8I closes a circuit comprising main supply line 89,

lines

82 and 83 and the main supply line 68. As a result thereof, the solenoid 60 is energized so that the valve member pertaining thereto establishes fluid conmotion between the conduit 42 and the conduit 65, while interrupting fluid connection between the conduits 48 and 51. Consequently, the conduit 43 is connected with the tank 5 and, therefore. also the bore 21 is connected through the bore I32 and bll-pass line 45 with the tank' 5.

Since, on the otherhand, pressure fluid is conthe longitudinal bore I32a in the piston 30a, pis- 3 and 4 for instance that, at the very beginning 76 ton rod 28a and extension 28a into the bore 3!.

Figure 6. In this position hydraulic communication is established between the conduit 33 and the conduit 34, which latter is connected through conduit 35 with the tank 5. Therefore, the lower portion of the press cylinder I is connected with the tank through conduit 33, and the ram 3 now moves downwardly by gravity. The suction nov: exerted in the upper portion of the press cylinder I holds the surge valve 4 open so that, while the press ram 3 moves downwardly, the

upper portion of the press cylinder l is filled by fluid passing fromthe surge tank 5 through the surge valve 4 into the cylinder I.

As soon as the ram 3 has started its down.- ward movement, the cam 92 releases the limit switch 9| so that the latter breaks electric connection between the

lines

80 and 93, while establishing electric connection between the

lines

88 and 90. This however, does not close a new circuit, since the solenoid H1 is not energized and, therefore, the switch blade I26 is in open position.

On the other hand, the circuit shown inFigure 9 is pro-conditioned. This circuit is closed by the limit switch I I5 as soon as the ram, by means of its cam H4, actuates the limit switch H5, and comprises main supply line 69, line 86, solenoid 81, now closed switch blade 84, line 85, line H3, now closed limit switch H5, lines H2, HI and the main supply line 68. As a result thereof, the solenoid 81 is energized.

If, for some reason, it were desired to stop the press ram instantaneously during the fast traverse stroke, i. e., before the switch I I5 is closed by the cam I I4, it is merely necessary to open the stop button I3I, which breaks the holding circuit for the solenoid 12. This immediately breaks the energizing circuit for the solenoid 60 so that the valve 49 reestablishes fluid connection between the conduits 48 and 51, while breaking connection between the

conduits

48 and 65. Consequently, fluid pressure is again conveyed from the pressure supply line I1 through

conduits

55, 51, 48 and 43 into the bore 22 where it acts upon the upper surface or effective area of piston 30. Since this effective area is larger than the efiective area acted upon by pressure fluid in the bore 3|, the pressure acting upon the upper surface of piston 30 moves the latter downwardly, thereby moving

th pistons

24 and 25 likewise downwardly until the piston 24 is stopped by the piston rod 29a. The

pistons

24 and 25 then again occupy the position shown in Figure 5, in which fluid connection is interrupted between the pressure supply line I1 and the press cylinder I. The ram 3, therefore, comes to an instantaneous stop. It will be appreciated that when, during the downward movement of piston 30, the latter dis engages the abutment 31, fluid pressure is also conveyed through bore I32 into the bore 21 where it counteracts the pressure in bore 3|.

The stop button I3I may immediately after its actuation be released and then returns automatically to its closed position. The circuit will then be in the same condition as it was prior to the beginning of th downward stroke of the ram 3, with the exception that the switch 9| does 8 not interconnect the

lines

80 and 93 but connects the

lines

90 and 88. The downward stroke of the ram may then, at any desired time, be continued by closing the starter switch 13 in*the manner previously described.

Assuming new that, as previously mentioned, the press ram had advanced downwardly to such an extent that the switch blade H5 is closed and the solenoid 81 energized as described above, this will cause the switch blades H0 and I01 to move into closing position. Closure of the switch blade H0 establishes a holding circuit for the solenoid 81, which holding circuit comprises main supply line 69,

lines

84 and 85, switch blade H0, line III, and main supply line 68, so that the solenoid 81 remains energized when, during its further advancing movement of the press ram 3, the cam H4 again releases the switch H5.

As will be seen from Figures 3 and 4, closure of the switch I I5 and energization of the solenoid 81 takes place when the actual pressing stroke is about to begin. Closure of the switch blade I01 establishes a new circuit as shown in Figure 10, which circuit comprises main supply line 69, line I08, switch blade I01, line I06 with solenoid 62, and main supply line 68. As a result thereof, the solenoid 62 is energized so that fluid connection is interrupted between the

conduits

55 and 38, whereas fluid connection is established between the conduit 38 and the conduit 63 connected to the exhaust line 64. Therefore, the

upper portion of the bore 23 in the valve casing 20 is connected to the tank 5 so that the pressure prevailing in the bore 3I moves the

pistons

24 and 25 further upwardly int the position shown in Figure '1. In this position, fluidconnection is established between the pressure supply line I1 and the conduit 32 so that the accumulator I2 unloads into the upper portion of the press cylinder I and causes the press ram 3 to carry out its actual pressing stroke.

If, for some reason, it is desired instantaneously to stop the press ram 3 during its actual pressing stroke, it is merely necessary to open the stop button I3I. This will immediately break the holding circuit for the

solenoids

12 and 81, thereby causing deenergization of the

solenoids

60 and 52. Consequently, fluid pressure is again convevd from the pressure supply line I1 .to the upper portion of bore 22 and into the lower portion of bore 23 and furthermore into the bore 21 so that the

pistons

24 and 25 return to their intermediate position shown in Figure 5, thereby interrupting fluid connection between the pressure supply line I1 and the press cylinder I. The press ram 3, therefore, comes to a halt.

When, at the end of the pressing stroke, a predetermined pressure acts upon the piston 2, this pressure is conveyed through conduits 32 and I24 to the tonnage control switch I23, causing the latter to interconnect the lines I20 and I2I. This closes a circuit comprising the main supply line 69, line H6, solenoid I I1, line I20, tonnage control switch I23, lines I2I and H8 and the main supply line 68. If, instead of the tonnage control switch I23, the position limit switch H0 were used, the same circuit just described would be closed by the position limit switch H9; As

- a result of the closure of the above mentioned I tween the lines I and I28breaks the holding the switch blades III) and I01 return to their position shown in Figure 2, with the result that the solenoid 62 is likewise deenergized and fluid connection is again established between the

conduits

55 and 38. Therefore, pressure fluid is now conveyed from pressure supply line H through

conduits

55, 51, 48 and 43 into the bore 22 and from there into the bore 21. Likewise, pressure fluid is conveyed from the pressure supply line I? through

conduits

55 and 38 into the upper portion of the bore 23.

Closure of the switch blade I26, due to the energization o1 solenoid II'I, closes a circuit comprising the main supply line 89, line 88, solenoid 89, limit switch 9|, which latter is now in the upper position, line 90, switch blade I29, line I29 and main supply line 68. In this way, solenoid 38 is energized, moving the

switch blades

91 and 89 into their closing position, as shown in Fig ure 11. p

Closure of the switch blade 9! establishes a holding circuit for the solenoid 89, which circuit comprises the main supply line 59, line 88, solenoid 89, limit switch 9|, lines 99 and 95, switch blade 91, line 96, stop button I3I, line I38 and the main supply line 58. Closure of the switch blade 99 closes a circuit comprising main supply line 89, lines I80 and IIII and main sunply' line 68, thereby energizing the solenoid 6|.

Energization of the solenoid 6| causes valve 54 to interrupt the fluid connection between the

conduits

53 and 58, while establishing fluid connection between the conduit and the exhaust line 54. Therefore, the

bores

22a and 3| are connected with the fluid tank 5 and, since, as previously mentioned, the

bores

22 and 21 receive pressure from the accumulator I2, the

pistons

24 and 25 move downwardly into the position shown in Figure 8. In this position, fluid connection is interrupted between the pressure supply line H and the conduit 32, while the latter now communicates with the exhaust line 35. On the other hand, fluid connection is-now established between the pressure supply line I1 and the conduit 33 so that pressure fluid is conveyed from the accumulator I2 into the lower portion of the press cylinder I and causes the press ram 3 to perform its retraction stroke. Simultaneously, pressure is conveyed from the lower portion of the press cylinder I through conduit 6 to the surge valve 4 so as to open the latter and to allow fluid to escape from the upper portion of the cylinder I directly into the tank 5.

If, for some reason, it is desired instantaneously to stop the ram 3 during its retraction stroke, all that is required is merely momentarily to open the stop button I3I. This immediately breaks the holding circuit for the solenoid 89 so that the latter becomes deenergized and the switch blade 99 breaks the energizing circuit for the solenoid 6|. In this instance, fluid connection between the

conduits

50 and 64 is inter rupted, and fluid connection between the conduits 50 and is established so that pressure fluid from the accumulator I2 is conveyed through conduits I1, 55, 58 and 50 into the bore 22a ill and from there into the bore I32a. Since, at this time, the solenoid I2 \is' deenergized and, therefore, also the solenoid 90 is deenergized, fluid connection prevails between

conduits

51, 48 and 43. Pressure fluid is therefore also conveyed from conduit I'I through

conduits

55, 51, 48 and 43 into the upper portion of bore 22 and through bore I32 into the bore 21. Since at this time the piston 30 abuts the lower end of the bore 22 so that it cannot move further downwardly, and inasmuch as the pressure in bore 21 is substantially balancedby the pressure inbore 3i, it will be clear that the pressure acting upon the lower" surface of piston 3i)v moves the latter upwardly, thereby returning the

pistons

24 and 25 to their Figure 5 position, in which the further upwardmovement of

pistons

24 and 25 is stopped by the piston rod 29. In other words, the pressure acting upon the upper surface of piston 88, plus'the pressure acting upon the closed side of bore 21, is balanced by the pressure acting upon the lower surface of piston 30a plus the pressure acting on the closed side of bore 3|. When the pistons 24 have reached Figure -5 position, the fluid connection between the pressure supply line I1 and' the conduit 33 is interrupted. Since, therefore, no more pressure fluid is supplied to the lower portion of the press cylinder I, the ram 3 immediately comes to a stop.

If new it is desired to return the ram 3 to its full retraction position, it is merely necessary to release the stop button I3I and temporarily to close the reverse switch button I22. Closure of the reverseswitch button I22 will close a circuit comprising the main supply line 89, line II 6, solenoid 1, line I20, reverse switch button I22,

lines I2I and H8 and the main supply line 68.

The energization of the solenoid III will then establish the energizing circuit for the solenoids 39 and BI, as previously mentioned, with the result that the

pistons

24 and 25 again move into Figure 8 position and fluid pressure is again conveyed from the pressure supply line I! to the lower portion of the press cylinder I, moving the latter upwardly.

When the press ram 3, during its upward stroke, temporarily closes the limit switch II5, nothing happens, since the solenoid I2 is deenergized. When the ram 3 reaches the endof its retraction stroke, the cam 92 shifts the arm I33 in anticlockwise direction so as to cause the limit switch 9| to break electric connection between the lines 38 and90, and to establishelectric connection between the lines and'93. Since the'solenoid II'I becomes immediately deenergized again as soon as the reverse switch button I22 is released and, thereby automaticallyreturns to open position or as'soon as, after the initiation of the retraction stroke, the tonnage control switch H9 opens again. the holding circuit for the solenoid 89 is broken and the solenoid 89 becomes deenergized.

Deenergization of the solenoid 89 causes switch blade 99 to break the energizing circuit for the solenoid 9| so that the valve 54 breaks the fluid connection between the

conduits

68 and 54, while establishing fluid connection between the

conduits

55 and 50. Consequently, pressure fluid is again conveyed from the pressure supply line H to the bores 22a and Lil so that the

pistons

24 and 25 are again moved into their intermediate position shown in Figure 5. This instantaneously interrupts the fluid connection between the pressure supply line H and the press cylinder I so that the press ram 3 comes to a halt. -I'h press ram is now in its full retracted position.

On the other hand, due tothe interconnection of

lines

80 and 93 by switch 9|, a.new circuit is established, as shown in'Figure 12. This circuit comprises main supply line 69, line 93, solenoid 94, switch 9|, line 80, switch blade I8, line I9 and main supply line 68. This causes energization of the solenoid 94 which, in its turn, causes the switch blade I03 to establish a new circuit comprising the main supply line 69, line I04, line I02 with solenoid 59 and main supply line 88. Energization of the solenoid 59 causes valve 41 to interrupt communication between the

conduits

68 and 43 and, thereby, prevents any pressure fluid from beingconveyed from line 55 through valve 49,

lines

48, 43 and 66 to the lower part of the press cylinder I, and thereby from by-passing the four way valve I9.

If, due to leakage, the press ram 3 should drop somewhat, the cam 92 will release the arm I33 so that the switch 9| moves to its upper position in which it breaks electric connection between

lines

80 and 93, while establishing electric connection between

lines

88 and 90. While the reestablishment of electric connection between

lines

88 and 90 has no energizing effect on the solenoid 89, because solenoid II! is in deenergized condition, the interruption of electric connection between

lines

80 and 93 causes deenergization oi the solenoid 94. As a result thereof, the switch blade I03 moves to open position, and the solenoid 59 becomes deenergized.

Deenergization of the solenoid 59 causes the valve 41 to reestablish fluid connection between the

conduits

43 and 66, so that pressure fluid is conveyed from pressure supply line I! through

conduits

55, 51, 48, 43 and 66 to conduit 33 and from there into the lower portion of the press cylinder I. The ram 3, therefore, again moves upwardly until it has reached its full retraction position in which the cam 92 causes the switch 9| again to establish connection between

lines

80 and 93, as previously described, so that the

solenoids

94 and 59 are again energized and the valve 41 again interrupts fluid connection between the

conduits

43 and 66. The ram 3 is then again halted.

It should be noted that the automatic filling of the press cylinder I or the automatic returning of the ram 3 to its full retracted position when the ram 3 drops, due to leakage occurring in the press cylinder I, is efiected without shifting the four-way valve I9.

As will be clear from the above, the press ram 3 may selectively be stopped practically instantaneously at any desired point of travel during the advancing as well as during the retraction stroke by the mere temporary opening of the stop button I3I. It will furthermore be obvious that when the press ram 3 has been thus stopped, it can be caused selectively either to return to its full retracted position, or to continue its respective stroke during which it was halted. To return the ram from any halted position to its full retracted position, it is merely necessary to actuate the reverse switch button I22 so as to close the same temporarily, as has been previously explained. When the press ram 3 has been stopped during the fast traverse stroke, it can be made to continue its advancing stroke by merely closing the starter switch I3 again.

When the press ram has been stopped during the actual pressing stroke and it is desired to continue the pressing stroke of the ram, the perator first closes thestarter switch I3 and then manually closes the limit switch II5 by actuating the switch arm I I5a.

As will be clear from the foregoing description, the shifting speed of the valve I9 may be controlled by setting the

choke'valves

42, 53 and 55 accordingly. Similarly, the setting of the choke valve 61 will control the speed of the return movement of the ram 3 to its full retracted position when the ram 3 had dropped, due to leakage in the press cylinder I.

It will be understood that I desire to comprehend within my invention such modifications as come withinthe scope of the claims.

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

1. In a hydraulic system, a reciprocable plunger, fluid operable advancing and retracting means associated with said plunger for reciprocating the same, a fluid source for selectively supplying pressure fluid to said advancing or said retracting means, a valve member movable selectively into a first or second end position, or into a neutral or intermediate'position for controlling the supply of fluid from said fluid source to said advancing and retracting means and'also controlling'the release of fluid therefrom, said valve member being operable selectively .to release fluid from said retracting means, while simultaneously perventing the supply of pressure fluid from said fluid source to said advancing means, other valve means operable to supply fluid to said advancing means when said valve member is in its last mentioned position, means operable in response to a predetermined travel of said plunger for varying the position of said valve means to admit pressure fluid to said advancing means, while allowing escape of fluid from said retracting means, and means operable selectively, irrespective oi the position of said plunger, for moving said valve member into said intermediate or neutral position to cause said valve member to prevent both supply of pressure fluid to and escape of fluid from both said advancing and retracting means to halt said plunger.

2. In a hydraulic system, a substantially vertically reciprocable plunger, fluid operable advancing and retracting means associated with said plunger for reciprocating the same, a fluid source for selectively supplying. pressure fluid to said advancing or retracting means, valve means for controlling the supply of fluid to or withdrawal of fluid from said advancing and retracting means, means for shifting said valve means into position for releasing fluid from said retracting means, while preventing the supply of pressure fluid to said advancing means to eflfect advancing movement of said plunger by gravity, a surge valve connected to supply fluid to said advancing means during its descent by gravity, means responsive to a predetermined advancing movement of said plunger for shifting said valve means into position for admitting pressure fluid from said fluid source to said advancing means, while simultaneously releasing fluid from said retracting means, means for shifting said valve means into position for admitting pressure fluid from said fluid source to said retracting means, while releasing fluid from said advancing means, and means operable irrespective of the position of said plunger for shifting said valve means into an intermediate or neutral position to simultaneously prevent supply of pressure fluid to and release of fluid from either of said advancing and retracting means to halt said plunger.

aurmo 3. In a hydraulic system, a reciprocable plunger, fluid operable advancing and retracting means associated with said plunger for reciprocating the same, a check valve connected to supply fluid to said advancing means in response to a predetermined reduction in pressure therein, a fluid source for selectively supplying pressure fluid to said advancing or said retracting means, valve means operable by pressure fluidirom said fluid source for controlling the supply of pressure fluid to and the release of fluid from said advancing and retracting means, said valve means being movable selectively into position for releasing fluid from said retracting means, while simultaneously pre'- venting the supply of pressure fluid fromsaid fluid source to said advancing means, said valve means also being operable to admit pressure fluid from said fluid source to said advancing means, while simultaneously allowing release of fluid from said retracting means, and vice versa, emergency means, and means responsive to the actuation of said emergency means for causing pressure fluid from said fluid source to move said valve means into position for interrupting fluid connectionbetween said fluid source and either or said advancing and retracting means, while simultaneously preventing release of fluid from either of said advancing and retracting means.-

4. In a hydraulic system, a plunger, fluid operable advancing and retracting means assci ated with said plunger, 9. fluid source for supplying pressure fluid selectively to said advancing or retracting means, a valve member movable selectively into any one of four predetermined positions for controlling the supply of pressure fluid to and the release of fluid from said advancing and retracting means, fluid operable actuating means operable by fluid from said fluid source for first moving said valve member to release fluid from said retracting means, while simultaneously preventing the supply of pressure fluid to said advancing means, a surge valve connected to supply said advancing means when said valve member is in its first mentioned posi tion, and secondly to move said valve member to admit pressure fluid to said advancing means while continuing to release fluid from said re-" tracting means and, thirdly, to move said valve member to admit fluid pressure to said retracting means while releasing fluid from said advancing means, and fourthly to move said valve member. to prevent release of fluid from or supply of pressure fluid to either of said advancing or retracting means, auxiliary valve means for controlling the supply of fluid to and the exhaust oi fluid from said actuating means, means operable selectively for moving said valve member to said fourth position for halting said plunger at any desired point of travel and for any desired time, and means operable selectively to cause said halted plunger to continue its cycle or to return to its retracted position.

5. In a. hydraulic system, a reciprocable plunger, fluid operable advancing and retracting means associated with said plunger, a fluid source for supplying actuating fluid to said advancing or said retracting means, a valve including a movable valve member for controlling the supply oi fluid from said source to said advancing and retracting means and also controlling the release of fluid therefrom, said valve member being movable selectively into position to establish restricted fluid communication between said retracting means and exhaust while simultaneously preventing communication between said source and said advancing means, a surge valve connected to supplying actuating fluid to said plunger, valve means including a reciprocable valve member for controlling the supply of fluid from said source to said plunger and also for controlling the release of fluid therefrom, said valve member having associated therewith fluid operable actuating means adapted to be actuated by pressure fluid from said fluid source, means for controlling the supply or fluid from said fluid source to said valve member actuating means so as selectively to move said valve member into a first position for estab- ,lishing restricted fluid communication between said retracting means and exhaust while simultaneously preventing the supply of fluid from said source to said advancing means, means. operable to supply fluid at substantially no pressure to said advancing means when said valve member is in its first position, and means responsive to a predetermined advancing movement of said plunger for varying the supply of actuating fluid to said valve member and shifting the latter into asecond position for establishing communication between said source and said advancing means while simultaneously reducing the restriction between said retracting means and exhaust.

7. In a hydraulic system, a reciprocable plunger, fluid operable advancing and retracting means associated with said plunger, 2. fluid source for supplying pressure fluid to said advancing or to said retracting means, valve means for controlling the supply of fluid from said source to said advancing and retracting means and also controlling the release of fluid therefrom, means independent of said valve means and. responsive to a predetermined advancing movement of said plunger away from its fully retracted position for bypassing said valve means whereby hydraulically to interconnect said fluid source with said retracting means for returning said plunger to its fully retracted position, and means responsive to the initiation of the forward stroke of said plunger for interrupting said bypass con- 'nection.

" venting the exhaust of fluid from said advancing and retracting means, means responsive to a predetermined advancing movement of said plunger away from its retracted position and when said valve member is in said position for bypassing said valve member thereby interconnecting said fluid source with said retracting means so as to return said plunger to its fully retracted position, and means selectively operable simultaneously to actuate said valve member to permit the exhaust of fluid from said retracting means plunger and to interrupt said bypass connection.

9. In a hydraulic system, a reciprocable plunger, fluid operable advancing and retracting means associated with said plunger, a fluid source for supplying pressure fluid to said advancing or retracting means for reciprocating said plunger, a main control valve means including a movable valve member for controlling the supply of pressure fluid from said fluid source to said advancing and retracting means and also controlling the release 01 fluid therefrom, fluid operable means for actuating said valve member, auxiliary valve means operable to control the supply of fluid to said valve member for moving the latter into position to interrupt the supply of fluid to and the exhaust of fluid from said advancing and retracting means at the end of the retraction stroke of said plunger, means independent of said main control valve means and responsive to a predetermined advancing movement of said plunger away from it retracted position when said valve member is in its last mentioned position for establishing a bypass connection between said fluid source and said retracting means around said main control valve means for returning said plunger to its fully retracted position, means selectively operable tor actuating said auxiliary valve means for moving said valve member into position to bring about an advancing stroke of said plunger, and means operable simultaneously with said last mentioned means for interrupting said bypass connection. WALTER ERNST.