US2367241A

US2367241A - Control for fluid operated motors

Info

Publication number: US2367241A
Application number: US262709A
Authority: US
Inventors: Thomas F Stacy
Original assignee: French Oil Mill Machinery Co
Current assignee: French Oil Mill Machinery Co
Priority date: 1939-03-18
Filing date: 1939-03-18
Publication date: 1945-01-16
Anticipated expiration: 1962-01-16

Description

Jan. 16; 1945. 1', STACY 2,367,241

' CONTROL FOR-FLUID OPERATED MOTORS Filed March 18,- 1959 5 Sheets-Sheet 1 RESERVO/E Jan. 16, 1945. F, STACY O. I 2,367,241

CONTROL FOR FLUID OPERATED MOTORS 'Filed March 18, 195 3 Sheets-Sheet s 35 .35

, C ii 11 .J

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' ATTORNEYS Patented Jan. 16, 1945 UNITED STATE CONTROL FOR FLUID OPERATED MOTORS Thomas F. Stain? Piqua, Ohio, assignor to The chinery Company, Piqua,

French Oil Mill Ma Ohio Application March 18, 1939, Serial No. 262,709

9 Claims. (01. 60-52) This invention relates to fluid operated motors such as hydraulic presses, and more particularly to a hydraulic circuit and control means therefor. It, is in the nature of an improvement upon the subject matter disclosed and claimed in my copending application. Serial No. 204,375 filed April 26,1938, now Patent No. 2,335,809, dated November 30, 1943. 4 One object of the invention is to provide an improved hydraulic system and control means In the embodiment of the invention illustrated in Fig. 1 the fluid actuated motorincludes a ram or fluid actuated motors, which may be successfully applied to various types of fluid operated motors in'cluding the standard, high speed, selfcontained, hydraulic press, with automatic reversing means either when a predetermined pressure on the work has been reached or the working member vof the motor has reached a predetermined position in its travel, and which will be relatively smooth, efiicient. and dependable in operation, and relatively simple, compact and inexpensive.

' Another object of the invention is to provide an improved operating system and control for hydraulic presses and the like, with which rapid operation of the press in both directions will be possible/with which the' advance travel of the working member or ram may be terminated by manual control or automatically, with which objectionable shocks in the system will be prevented, and which will be exceptionally free from operating troubles. I

Other objects and advantages will appear from the following description of some embodimentsof the invention, and the novel features will be particularly pointed out hereinafter in connection with the appended claims.

In the accompanying drawings:

Fig. 1 is a schematic diagram of portions of a fluid actuated motor having thecontrol of the; hydraulic system therefor constructed and arranged in accordance with this invention;

element or working member I having a piston 2 reciprocating in a ram casing 3, with a mam cylinder 4 at one side of the piston to force the ram element forwardly in a working stroke anda pullback cylinder 5 at the opposite side of the piston 2 for retracting the ram element I from the work. These parts are typical of fluid actuated motors such as are employed in hydraulic presses, for example. In many cases the pullback cylinder is in a separate housing from the main cylinder 3. but connected to the ram element or working member I, and it will be understood that the'ram elementor working member is actuated vin one direction by pressure in the main cylinder and in the opposite or retracting direction by gravity or a pullback cylinder, whether the main and pullback cylinders operate'on the same or different pistons connected to the working member].

Anysource of operating fluid underpressure may be employed, but the source is, preferably a pump 6 which draws liquid from a suitable reservoir 1 through a passage-8 and delivers it under pressure through a pipe 9. Any suitable type of pump may be employed, the oneillustrated being cf the variable displacement or variable delivery Fig. 2 is a schematic diagram of a portion of the same system and controls shown in Fig; 1,

but illustrating a slight modification thereof;

Fig. 3 is a schematic diagram of a portion of the system of Fig. 1 and showing another slight type, in which any slippage of liquid vis'returned by pipe I0 .to the reservoir 1. A light pressure the pump 6 and the main controlling br operating valve l2. This valve II is set to open on a predetermined light pressure, and thus it operates as a choke valve to provide a sufiicient back pressure for a purpose which will appear presently. The valve l2 includes a casing for a valve chamber l3, in which reciprocates a valve element M. The valve element M is provided with a pair of spaced lands I 5 and I6 which are of a size to fit closely with the wall of the chamber I3 and cooperate with ports in the wallet chamber l 3 in a manner which will be described presently.

A helical compression spring I1 is compressed between one of the lands-,such as l6, and an end wall It of thel'lousing l2, and'urges the valve element It in a downward direction (Fig. 1). The pipe 9 opens into the valve chamber l3 through a port l9 which is located between the lands l5 and I6 when the valve element It is in an intermediate position, which is the position shown by full lines in Fig. 1. A pipe 20 opens into the valve chamber l 3 through a port aligned with the land 16 when the valve element is in said intermediate position, and also is connected to the main cylinder 4. Another pipe 22 opens into the chamber [3 through a port 23 which is aligned with the land l when the valve element I4 is in its said intermediate position. The land I5 is of a width which normally closes this port 23, so as to close communication to that end of the pipe 22. It will be understood that the ports l9, 2| and 23 may be annular grooves in the wall of the chamber l3, into which grooves the pipes open.

The land I5 is bevelled on opposite faces at theperiphery thereof, as shown in Fig. 1, so that when it is aligned with the port 2| there will beclearance between the land and the sidesof the port 2|, and fluid in the chamber [3 received through the port l9 and pipe 9 may pass through port 2| around the land l5 tothe upper end of the chamber l3, as. well as pass to the pipe 20.

An exhaust pipe 24 opens into the upper end of the chamber l3 through a port 25,. and in turn is connected to the pipe [0 leading back to the reservoir 1. The lower end of thechamber l3 also has a port 25 opening into the pipe 24.

The pipe 22' is connected to the pullback cylinder v 5. A pipe 21 leads from the reservoir 1 to the cylinder 4 and it contains in series thereina pilot operated, free check valve 25. This check valve opens freely to pass liquid from the reservoir 1 to the main cylinder 4 but normally closes automatically to prevent all reverse flow.

The reservoir I should preferably be elevated abovethecylinder 4 to facilitate free flowof oil or liquid from the reservoir into the cylinder during the prefill portion of the movement of the ram or working member I, or else the liquid in the reservoir 1 may be under air or other .similar pressure. When fluid pressure supplied to'the pilot cylinder 29, however, it forces the pilot piston upwardly or outwardly against the action of the pilot spring 3|, so as to engage and force open the 'movable free valve. element 32 of the check valve 28, and thus allow fluid to flow from the cylinder .4 through the pipe 21 back to the reservoir I. The pilot cylinder 23 is connected by a pipe 33 to-the pipe 22 which leads to the pullback cylinder 5.

The valve element |4 extends outwardly through one end of the valve housing I2, and this projecting end has two

annular flanges

34 and 35 spaced apart. Between these flanges is disposed a forked end35 of a lever 31, which is and lower the piston 44 in the chamber 42, or in other words to withdraw it from contact with an end of the valve element l4.

The press is also provided with an auxiliary valve casing 5| having a chamber 52 therein in which' reciprocates a valve element 53. The valve element 53 extends through both ends of the casing 5|, suitable packing glands bein Provided in the end walls through which the valve element extends. The portion of the valve element within the chamber 52 is provided with two lands-54 and 55 which are arranged in spaced relation to one another along the chamber 52. A helical spring 51 is compressed between the upper part of the chamber 52 and the land 54, so as to normally urge the valve element 53 downwardly. The lower end of the valve element 53 depends through a slot or aperture 58 provided in a laterally extending arm of the platen 59 which is carried by the working member or ram This element 53 carries an adjustable collar 50 at a point above the platen 59,'so that as the platen 59 is elevated during a retraction, it will pick up the collar 55 and shift the valve element 53 ,upwardly against the action of spring 51'. It is shown in its upper position in Fig. 1. A pipe 5| connects the pipe 25, leading to the main the lands 54-and 55 when the valve element 53 is in its elevated position shown in Fig. 1. An-

pivoted at 38 and urged into a neutral or intermediate position by two oppositely disposed springs 39. The free end of the lever 31 has a handle 4|) by which it may be operated in either or both directions.

The lower end of the valve element l4 passes through a packing 4| and into a chamber 42.

. ilange or head 45. A rod 41 extends from the head 45 outwardly through the bottom of the chamber 45, through a packing 48 in said bottom wall, and exteriorly of the chamber 45 carries an adjustable abutment 49 which may be a pair of nuts threaded onto the rod, and one acting as a lock nut for the other. A helical compression spring 50 compressed between the nuts 45 other'pipe 55 leads from the chamber 52 between the lands 54 and 55, but close to the land 55, when the-valve element 53 is in its elevated position and at its other-end is connected to the chamber 45 in the lower part of the housing of the valve 2. 1

The port 54 is at apoint substantially above the opening into pipe 55 so that when the valve element 53 is released by the platen 59 and moved downwardly by the spring 51, the land 54 will cover-or pass port 54 and interrupt communication between pipes 53 and 55. It will be noted that when the valve element 53 is in 'the position shown in Fig. 1, which is its elevated position, the chamber 45 of the main control valve ber 52 and

pipes

53 and 22 with the pullback chamber 5. when the valve element 53 is released and is moved downwardly by its spring 51, this communication of the chamber 45 with the pullback chamber of the ram will be broken by land 54 covering port 54, and since the land 55 will then be below the port 52, the pipe 55 from the chamber 45 will then be in communication with the pipe 5| leading to the pipe 20 and the main chamber 4.

An auxiliary or activities control valve 55 is provided with a reciprocating valve element 5'! which has portions of the same diameter extending through opposite ends of its housing, so as to be a balanced valve. Within the chamber 58 of this valve, the valve element 51 is pro vided with spaced lands 5!! and 10 of equal diameters or face areas. A pipe 1| opens at one end into the chamber 42 and at its other end through a port 12 into the chamber 58 of this activities control valve 55. Another pipe 13 opensinto the chamber 68 of the same valve through the When the valve element 61 is in the position shown by full lines in Fig. 1, the land will be between the

ports

12 and 14, so that the fluid delivered by thepump through the pipes 9 and I3 and entering the chamber 68 will be confined in the chamber 88 by the lands 69 and "hand by reason of the fact that the

lands

69 and 10 are the same size, such pressure between those lands will-be balanced and will not urge the valve element 81 in either direction. Since the port 12 will-be in free communication, through the chamber as, with the port 15, the chamber 42 will be in communicationwith the reservoir; and there will be no fluid under pressure in chamber 42.' When the valve element 61 .is in its dotted line position shown in Fig. 1, the land 10 will be disposed between the ports Y72 and I5,

' and the land 69 will stay between the

ports

14 and 16.

In that situation, the communication between is in the dotted line position of Fig. 1, the fluid under pressure from the pump 9 and passing through valve 66 not only serves to shift the valve element i4 upwardly into the position in which the land I6 is between the ports 21' and to initiate a forward or working movement of the ram l, but it also holds the valve element l4 hydraulically in that active position with the spring I! compressed. It now the valve element 81 is returned to the full line position of Fig. 1, the land 10 will cut oil the flow of fluid under pressure from the pump to the chamber 42, and will vent the chamber 42 to the pipe 11, whereupon the spring I will urge the valve element l4 downwardly or inwardly, and tend to carry the :land l6 into a position between the ports l9 and 2| and the land I5 between the

ports

23 and 26.

It will be understood, however, that even when the valve element I4 was inits elevated position, during which it caused an advance or working movement of the ram or member i, the chamber 45 was at first in communication with the pullback chamber 5 through the valve chamber 52,

the pipes II and 11 will be broken and the pipes H and 13 will be placed in communication with one another through the chamber 68 in the space between the lands 69 and iii. The fluid under pressure from the pump will then be free to pass through the

pipes

9 and 13, through the-chamber 68, thence through pipe H to chamber 42 where it exerts a pressure on the inner end of the valve element l4 tending to shift it upwardly against the action' of the spring I1 and carry the land l6 into a position between the ports 2| and 25 and the land l5 between the ports 23 and I9. It will be understood that the piston 44 cannot go up at this time because the head 46 in the chamber 45 limits such upward movement.

-When the valve element I4 is moved upwardly inFlg. 1, the land It is carried into aposition in communication with .the chamber l3, and thus the fluid under pressure from the pump 9 passes through the chamber l3and pipe 20 to the main cylinder 4. At the same time, the upward movement of the land l5 uncovers th port 23, and-this places ports 23 and 26-in communication with one another through the lower part of chamber", l3.

This places the pullback chamber 5 in =commuhication, through, the pipe 22 and the lower part of chamber l3, withthe pipe 24 leading back to the reservoir, so that the fluid trapped in the pullback cylinder previously is now released'and is free to pass back to the reservoir. The working member then is free to descend because of gravity and such descent creates a suction in the main chamber 4 and draws fluid from thereservoir through pipe 21 and check valve 28. When the working member or ram l encounters resistance, however,

oi! the valve element l4, however. moved the land l5 above the port 23, whereupon the chamber 5 was placed in communication, throughv the-

pipes

22 and 24, with the reservoir, whereupon'the pressure in the pullback chamber fell and immediately also the pressure in chamber 45. The spring '50 then forced the flange 46 downwardly and moved thepiston 44 downwardly and away from the full line position shown in Fig. 1. The platen 59 in moving downwardly, however, released the rod 53 stop piston 44 in its downward position clear of the valve element l4.. The element 14, however,

remains in its elevated position by reason of the hydraulic pressure thereon in the'chamber'42.

As soon as pressure in the main chamber 4 be- 7 gins to build up, a corresponding pressure will also build up in the chamber 45 and when sufflcient to overcome the action of spring 50 will force the piston 44 upwardly into the full line position shown in Fig. 1, but it will still be outof contact with the element l4 because the latter is it stops further rapid descent, whereupon the valve element 32in check valve 28 closes, but continued delivery of fluid from the pump through

pipes

9 and 20 to the main chamber 4 builds-pp pressure in the main chamber and forces oq'ntinued descent of the member I.

It will be noted that when the valve element 61 then still held-hydraulically in its elevated position.

At the end of the forward or working movement of the platen 59, the valve element 61 is I to be returned to the position shown in full lines in Fig. 1, whereupon the release of pressure in the chamber 42 allows the spring ll to shift the valve element downwardly until it engages the rull lineor intermediate position shown in Fig. 1,

the pipe 20 leading to the main chamber. 4 is connected .to the pipe 24 and the reservoir, and con ment I4 will continue downwardly until the-land I8 is disposed between the ports I8 and 2| and the land I5v is disposed between the

ports

23 and 26. This places the pipe 8 from themump in communication with the pullback chamber 5 and connects the pipe 28 from the main chamber 4 to the return to the reservoir.

The pump then delivers operating fluid to the pullback chamber to return the working member or ram I and the platen to the elevated or retracted position, and as the pressure'in the pullback chamber builds up, the same pressure will be communicated through the pipe 33 to the pilot chamber 28 of the pilot valve 28 and forcibly open the check valve 32, so that liquid may not only escape from chamber 4 through the pipe 28 and valve chamber I3 back to the reservoir, but also may directly pass through pipe 21 and valve 28 back to the reservoir, which expedites the return of the platen.

The valve element 81 may of course be operated manually in both directions if desired, and inasmuch as it is a balanced valve it will remain in either position in which it is placed. A convenient means for operating the valve 81 in one direction to start a downward movement of the platen, which would be to operate the valve element 81 from the full to the dotted line position in Fig. 1 includes a bellcrank lever 18 pivoted at 88 to a suitable support adjacent the one side of the'element 81, one arm of the bell crank lever being connected by a link 8| to an armature 82 of a solenoid 83, The solenoid 83 is connected to line wires L and L with a switch 84 included in series-therein. The switch 84 is a normally open switch, and by closing it momentarily, the solenoid 83 will be energized, drawing the armature 82 upwardly; Through the bell crank lever 18, the armature will shift the valve element 81 to the left in Fig. 1 from the full to the dotted line position. The valve element 81 is operated in the opposite direction, either automatically through the activity or operation of the platen or manually, as may be desired, and mechanism suitable for accomplishing this result will now be described;

A bell crank lever 85, similar to the lever 18, is disposed at the opposite end of the valve ele ment 81 for operating the latter inthe other direction. The lever 85 is pivoted at 88 to a suitable part of the frame, and is connected through a link 81 to an armature 88 of a soleducting bar 95 carried by a small piston 88 which reciprocates in a chamber 81.

The piston 98 has a reduced extension 88 extending through the closed end of the casing 88 which provides the chamber 81, and carrying anadjustable abutment I88. A helical compres sion spring I8I is compressed between the abutment I88 and the casing 88 so as to yieldingly The chamber 91 at its inner or closed end is connected by a pipe I82 tothe pipe 28 leading to the main chamber 4,so that the chamber 8? will at all times be subject to the pressure in the main cylinder 4 of the hydraulic motor or ram. During the working stroke, when the fluid pressure in the chamber 4 becomes 'suflicientiy great or exceeds a predetermined pressure, such pressure in the chamber 81 will be sufficient to 1 overcome the sprin I8I and force the piston 88 noid 88. The solenoid 89 is also connected to the line wires L and L, but included in the connection to one of theseline wires is a suitable controlling switch mechanism. The line wire L is connected by awire 88 to a normally open outwardly or downwardly and cause the contact bar 85 to bridge contacts 83 and 84.

Thus the circuit through the solenoid 88 will be closed automatically whenever the pressure in the main chamber of the ram or hydraulic motor exceeds a predetermined pressure depending upon the resistance of the spring I8I, and as soon as the pressure in the main chamber 8 falls, the spring I8I will return the piston 98 to its elevated or retracted position and open the circuit through the solenoid 88. This arrangement provides for the automatic shifting of the valve element 81 into the full line position of Fig. 1=to release the hydraulic holding pressure on the valve element I4 automatically after the pressure on the main ram has exceeded the predetermined pressure.

The circuit through the solenoid 88 may also be closed automatically by disposing an electric switch I 83in a position to be operated by the platen at a selected point. in the latters travel, and this switch I83 is connected in parallel across the

wires

88 and 82 to the contacts of switch 8|. The switch I83 may have an operating arm I84 disposed in the path of travel of a cam I85 on the platen 58, and the switch I83 may be mounted on the press frame in a position to be shifted in a direction along the path of travel of the platen so that the point in the travel of the platen 58 at which the switch I83 will be operated to reverse the direction of travel of the platen may be varied.

In order that the action of the switch I83, and the pressure operated switch formed by contacts 83 "and 84 and 85, may be selectively rendered inoperative at will, a switch I 88 may be 'confrom the dotted to the full line position of Fig. l.

Connected in parallel across the switch 9| is another switch including a pair of contacts 83 and 84 which are arranged to be bridged .by-a connected in series in the-wires I81 and I88 connecting the switch. I83 to the

wires

88 and 82 respectively, and a switch I88 maybe connected in the wire II8 which connects the wire 88 to the contact 84. The contact 93 is connected to one side of the switch 8| by a wire III. The valve element 81 may be, returned to its normal position shown in Fig. l by operation of the button 8|, which is a selective manual control, or by the pressure responsive device which bridges contacts 83 and 84 by the bar 85, or by the operation of the position responsive switch I83.

The button at also functions its a may button :of dies. As soon as the handle '49 is released it is returned to the neutral position and the valve element l4 in then under the control or the auxilia y valve 68. h

In the operation of the press with this system, when one, desires to start a forward or-downward movement of the platen 59, one merely presses the button 84 which causes a movement of the valve element 61 from the full to the dotted line position in. Fig. 1. This causes a hydraulic actuation of the valve element [4 into its upper .position where it initiates -a forward movement of the main ram I. This forward movement is stopped either by a manual operation of the button 9|, by the position responsive switch I03 when the cam I engages and operates the switch arm I04, or by 'the pressure on the main ram or work which, when it reaches a predetermined pressure, forces the piston 96 outwardly and closes the circuit between the

contacts

93 and 94. The operation, of the solenoid 89 through any of these three switches causes a return movement of the valve element Ii! to the full'line position of Fig. 1 and the parts return to their normal retracted positions.

It should be noted that when the platen 59 has nearly reached its upper limit'of movement, as

determined by its engagement with the collar 60,

it shifts the valve element 53 upwardly and breaks the connection between the chamber 45 and the main'ramchamber 4, and establishes communication between the chamber 45 and the pullback chamber 5. At this time th pressure in the pullbackchamber 5 is communicated to the chamber 45 which forces the piston 44 upwardly, and thus forcibly holds the valve element l4 in the intermediate position shown in full lines in Fig. 1 and this establishes the normal idle condition of the press, which remains until a new operation is started by a closing of the switch 84. When in this position the pump is by-passing at no pressure through pipe 9, port l9, around land IGthrough port 2|, and through the port to pipes 24 and ill to reservoir 1.

Referring now to Fig. 2, a slight modification of the system shown in Fig. 1 has been illustrated. The system is substantially the same as in Fig. 1

except that the spring I1 is omitted and in place thereof the valve element l4 extends through a.

cha er l|2 which is preferably smaller than andseparate from thechamber [3. Within the chamber H2 the valveelement l4 carries'a piston flange or collar I I3 fitting the side walls of chamber 2. A pipe Il4 is connected to the upper end of the chamber H2 and also to a port 'I I5 in-the valve chamber 68 of the valve 68. The port H5 is disposed between the ports 16 and I4 and between the lands 69 and I8 when the valve element 61 is in the full line position shown in Fig. 1. Thus when the valve element 61 is'in its normal or idle position shown in full lines in Figs. 1 and 2, the pipe 13 from thepump will deliver fluid under pressure through the pipe I I4 to the chamber H2 and hydraulically urge the piston flange H3 downwardly and through it urge the valve element I4 downwardlyv in the same manner as the spring II. The chamber 2 and the head or flange 3 are sufficiently small,

. however, so that the pressure thereof can be overcome by the pressure in the chamber 45.

Thus the only difference between the embodi-' -ment shown in Fig. 2 and that shown in Fig. l

is the replacement of the spring I! with the hydraulib pressure through the chamber ll2',- and the control of that pressure by the auxiliary or activities valve 66. The operation otherwise the same as in Fig. 1.

It will be noted that the pump a, in both Figs.

., 1 and 2, may be of the type which automatically sets itself to neutral delivery position to. maintain' a predetermined pressure in the pipe 9, a pipe I 16 being connected for this purpose between the pipe 9 and the small piston chamber III of pressure, as is well known in the art.

In the embodiment of th invention shown in Fig. 3, the system is the same as in Figs. 1 and 2, except that instead of havingv electrical 'circuits controlling the solenoid 89 which operates the valve element 61 back into its normal full line position of Fig. 1, a pressure responsive piston 96a is disposed in alignment with and adiacent one end of the valve element 61 so as to force the latter to theright in Fig. 1, into its normal return and idle position. The piston 98a corresponds to the piston 98 of Fig. l, and its chamber is connected to the pipe 2|! leading to -the main cylinder 4 through the pipe I02, as in 'to pass fluid from the chamber 91 and. which closes automaticallyto prevent reverse flow.

Connected in parallel across the check valve H8 is a pressure relief valve H9 which maybe of any well known type, and which is pressure closed but which opens to pass fluid from the pipe 12- towards the piston chamber 91. Thus fluid will flow from the pipes 20 and I02 to the. pressure responsive piston chamberv 91. only after the pressure built up in the pipe 20 is suflicient to unseat the spring or'pressure' closed valve element of valve 9. In such a case the spring or resistance pressurein the valve H9 will beset for an amount greater than that for which the spring I0! is setso that as soon as the valve 9 opens, the pressure then created'in chamber 91 will immediately cause a relatively rapid movement of the piston 96a and a prompt movement of the .valve element 61, so as to prevent wire drawing in the activities valve 86. The check valve 8 permits free escape of the actuating fluid from the chamber. 91 as soon as the pressure in the pipe 20 and chamber 4 falls.

In the embodiment of the" vention shown in Figs. 1 to 3, it will be noted that the main controlling element is the valve element of'the main reversing valve. It is hydraulically operated into and held in'one position, and yieldingly urged into the other position by spring or hydraulie means, so that the controlling element may be said to be hydraulically operated and controlled.

It will also be noted that this hydraulic holding of the reversing valve element maybe discontinned or interrupted to change the direction of movement of the working member, by means responsive switch or device which is responsive to the pressure of the working member on the work, or the resistance encountered by the working member. Another of such means is the position responsive switch which is disposed in a position to be operated by the platen when the platen reaches a predetermined point in its movement,

and which position may be adjusted by shiftingof the position operated switch along the path of travel of the platen. Either or both of these means may be rendered effective or ineffective as desired, and I have also provided the safety switch which may be operated at any point in the travel of the platen to cause an immediate reversal of the motor. In some instances it may be desirable to stop the press ram on its return stroke at some intermediate position, and to make this possible the collar 60 is made adjustable into diiferent positions along the rod 53. Thus the point at which the ram is brought to rest and the. pump set for idle delivery at substantially no pressure, may be varied by shifting collar 60 along rod 53.

In the modifications of the invention shown in Figs. 4 to 6, those parts which correspond to similar parts in Figs. 1 to 3 are given similar reference characters and will not be again specifically described. These modifications are similar to the system shown in Fig. 1, except that the reversal of the press at the end of the working stroke is responsive to a time interval after the forward working stroke is started, instead of being responsive to the working pressure or platen position. In the system as modified in the manner shown in Fig. 4, the pressure responsive switch, the switch operated by the platen, and the solenoid 89 and bell crank lever 85 are omitted. Instead, a helical compression spring I is disposed in the chamber 68, under compression between one end of the chamber and the land I0. This spring I20 yieldingly urges the valve element 01 to the right whenever the valve element is released.

The solenoid 83 is supplied with current from line wires L and L as in Figs. 1 and 2, but the circuit of the solenoid 83 iscontrolled by a normally closed switch I2I and a time switch I22. This time switch I22 is in series with the switch IN and when idle opens 'the circuit to the solenoid 83. When the operating or control button I23 of the time switch I22 is operated, the time switch closes the circuit to the solenoid 83 and keeps its closed for a predetermined interval of time and then automatically opens it. The switch I2I is merely a safety switch which may be operated to open the circuit and deenergize solenoid 83 when one desires to reverse the travel of the press before the time interval for which the time switch is set, has been completed. Thus, to start the press the attendant operates the button I23 to set the time switch into operation and close the circuit to the solenoid 83.

The solenoid 83 when energized, operates the valve element 61 to the left into the dotted line position of Fig. 4 against the action of spring I20. This causes an advance of the press in the. same manner as explained in connection with Fig. 1, except that the solenoid 83 remains energized to hold the valve element 61 in the dotted line until the end of a predetermined interval of time, whereupon the circuit is opened automatically; The spring I20 then shift the valve element 61 to the right to cause a return of the platen to the normal, retracted position. The

travel of the'platen is thus automatically reversed after the lapse of a predetermined interval of time, regardless, of the position of the platen or the pressure developed on the working member, but if the pump 6 is of the type which automatically sets itself to neutral or non-delivery position when a predetermined pressure has been reached, the press could move into pressing position, build up a selected pressure, and maintain I it until the lapse of the predetermined interval of time, whereupon the platen would be automatically retracted. 4

The time switches of the types which will. per- .form such a function are common articles of commerce, and per se form no part of the present invention. One type of switch which may be adapted ctor thi purpose is known as a Microfiex" timer switch manufactured under U. S. Patents Nos. 1,383,533, 1,460,707 and 1,794,762, to which reference may be had for further information. Similar time switches which may be used to perform the same function are, for example, those which have also been employed as circuit controlling timers for vehicle direction signals. Examples of these are found in U. S. Patents Nos. 1,672,791 and 2,001,266.

In Fig. 5, the valve 66 is substantially the same as in Fig. 1, and its element 61 is shifted in opposite directions by the

solenoids

83 and 88 operating through the bell cranks 19 and 85. The solenoid 83 is supplied with current from the line wires L and L and this circuit is controlled by a normally open switch I24. The operating part of the switch I24 also preferably operates the stem I25 of a time switch I26 which may be similar to the switch I22 of Fig. 4, except that the circuit through switch I26 is normally closed, but when the switch I26 is operated, it opens the circuit therethrough and holds it open for a selected time intervaL-then recloses it automatically; The time switch I26 is included in series with the solenoid 89 which operates the valve element 67 to the right of Fig. 5, and the solenoid 89 is supplied with current from line wires L and L The time switch I26 is connected by a wire I2'I to the line wire L and the other side of switch I26 is connect-ed by a wire I28 to one side of the solenoid 89. The other side of solenoid 89 is connected by a wire I20 to a contact I30 of a suitable switch, the other contact I3I of which is connected by a wire I32 to the other line wire L.

A wiper blade I33 is arranged to bridge the contacts I30 and I3I and complete a circuit therethrough under conditions which will be explained presently. The wiper blade I33 is carried by a lever I34 which is pivoted at I35, and which has a forked end thatloosely straddles a collar I36 provided on the valve element 61 exteriorly of the valve casing 68. When the solenoid 83 is energized and the valve element 6'! is shifted to the left in Fig. 5, the collar I36 will engage one arm of the forked end of lever I35 and rock the lever in a manner to shift the wiper I33 across the contacts I30 and I 3I as' the valve element 61 reaches its dotted line position in Fig. 5. This completes a circuit through the solenoid 89 except as controlled by the time switch I26. The valve element 61, being balanced, will remain in that position and will hold the wiper blade I33 across the contacts I30 and I3I.

To start an operation of the press with this modification, the attendant closes switch I24 'to energize solenoid 83, and this causes a shifting of the valve element 61 from the full line to the dotted line position of Fig. 5. At the same time that the switch I24 is closed, the stem I25 is operated to start an operation of the time switch I26 which immediately opens the circuit between the wires I21 and- I28 leading to the solenoid 89. Since the time witch I26 is set in operation before or simultaneously with the movement of the valve element 61 into the .dotted line position, the circuit through the solenoid 89 will be opened at the time switch I26 before or simultaneously with the closing of the circuit across the contacts I30 and IN, so. that the solenoid 89 will remain deenergized. The switch I24 may be immediately reopened or it may remain closed until the time switch completes its period of time, but after the lapse of a predetermined interval of time, which of course may be adjustable the same as that for the time switch I22, the time switch I26 will complete a circuit'between the wires I21 and I28 and thus complete an energization of the solenoid 89. This solenoid 88 then operates the valve eleswitch I24 can cause a movement of the valve element 61 to the left to start a new advance of the platen. Connected across the wires I21 and I28 is a normally open switch I31 which operates as a safety switch. The time switch I26 should preferably have some optional or selective provision by which it .may be returned quickly to starting position 'without'waiting for the lapse of time, so that after the platen has been started on an advancing movement it could be reversed as a safety measure.

Unless the switch I26 is provided with such a selective release and return, the switch I31 should be used, and since it is a normally open switch, its closing causes energization of .the

solenoid 89 and a reversal of the platen. In 81.11011 a case the solenoid 89 shouldv be more powerful than the solenoid 83, so that it may force the valve element 61 to the right against the action of the solenoid 83. The switch I31, if used,.is preferably of the reset type so that when closed it will remain closed and keep the valve element 61 in the full line position until the switch I24 is opened, after which the switch I31 is manually reset to open position. If the switch I24 is of the type which immediately opens without waiting for the control stem I25 of the time switch to return to normal position and open I into three positions,in one end position of which the circuit of' solenoid 83, then theswitch'l31' may be merly a normally open switch without the reset feature, because then a momentary closing of the solenoid 89 would be all that would be necessary to cause 'areturn of the platen.

In Fig. 6, the arrangement is the same as explained for Fig. 5, except that the circuit of solenoid 89, instead of be ngbontrolled by the lever I34 and contacts I30, I3I v.andi I33, is controlled-:by a switch I38 which is included in series with the solenoid 89. The switch I38 is a normally closed type but is opened when the switch arm I39 thereof is operated by a cam I40 provided on the platen as the platen approaches or reaches its upper limit of movement.

Thus the solenoid 89 could remain energized to hold the valve element 61 to the* right'or'full platen.

line position until the. platen completed any ar-t or all of its return stroke, at which time the cam I40 would engage and operates'witch arm I39 and open the circuit at the switch I38, and keep it open, and thus dee'nergize the solenoid 89.-

ciently long so that the'switch arm I30 may be engaged and operated to open the switclf- I38 soon after the platen starts its return stroke,

and to keep it open until the platen has again advanced approximately to its full extent. The

operation is otherwise the same as in Fig. 5.

It will be understood that various changes in the details and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention,

may be made by those skilled in the art within the principle and scope of the invention, asexcylinder connected to said member for operating it toward and from work, and pipes connecting the pump and cylinders to form ahydraulic circuit, a controlling valve connected to said fluid actuated means in said pipes for causing an adv member and having a valve element operable it causes delivery of actuating fluid to the main cylinder and opens the pull-back cylinder for escape of actuating fluid, and in another end position of which it connects the actuating fluid to the pull back cylinder and opens the main connections to said pump to create a desirable J minimum back pressure on the pump, hydraulic means supplied directly from said pump before said choke for urging said valve element into one ofsaid end positions and holding it there, hydraulic means also connected to said pump before saidchoke and also operable on said valve element for forcibly actuating said valve element, into the other of said end positions, and holding it there, an auxiliary valve for rendering both of said hydraulic means alternately effective on said element to determine the direction of 7 travel of ,said working member, a fluid operated device for overcoming the pressure of one of said hydraulic meansand forcing said element into said intermedate position to stop the actuation pull-back cylinder and while out of said zone for connecting saiddevice to said main cylinder.

2. In a hydraulic motor, a working member,

fluid actuated means including a continuously vance, a return or a, stopping of said member and having a valve element operable intothree The cam surface I40 may be made sufllce, 9, return or a stopping of said delivery of actuating fluid to the main cylinder and opens the pull-back cylinder for escape of actuating fluid, and in another end position of which it connects the actuating fluid to the pullback cylinder and opens the main cylinder for both cylinders, a choke in said pipe connections to said pump to create a desirable minimum back pressure on the pump, hydraulic means supplied directly from said pump before said choke for urging said valve element into one of said" end positions, and holding it there, hydraulic means also connected to said pump before said choke and also operable on. said valve element for forcibly actuating said valve element into the other of said end postions and holding it there, an auxiliary valve for rendering both of said hydraulic means alternately effective on said element to'determine the direction of travel of said working member, a hydraulic device operable on said valve element to shift it from said other position into said intermediate position against the action of said urging means, and means controlled by said working member at a desired point in its return movement for connecting said pull-back cylinder to said hydraulic device and by the pressure of fluid from the pull-back cylinder operating said valve element into said intermediate position .and holding it in that position after the valve element reaches said intermediate position.

3. An improved operating system for a hydraulic motor of the type having a working member, hydraulic means for advancing said member, hydraulic means for retracting said member, and a source of operating fluid under pressure, which comprises the combination therewith of a main valve having a chamber, and a valve element movable back and forth in said chamber along a selected path, said element having lands spaced apart in a direction along said path, said casing having ports connected in groups by the spaces between said lands and covered and uncovered by the lands as they pass, one of said ports being connected to said advancing means, another to,

said retracting means, another disposed between these two and connected to said source, others beyond both of said first two ports and connected to exhaust, means operable on said element and urging it yieldingly into one end position in which 3,867,941 positions, in one end position of which it causes,

meansior moving said element into the opposite end position in which it connects said source to said advancing means and said retracting-means to exhaust and holds saidelement releasably in that end position solely by a continuance of the fluid moving pressure on said element until release of said element is desired, a valve controlling the activity of said fluid actuated means, and unbiased into any'of its positions, means for moving said last mentioned valve in a manner to admit fluid to said fluid actuated means to cause movement of said element into said opposite end position, and additional and separate means responsive' to a selected operation of said motor for operating said last mentioned valve in a manner to cause release of actuating fluid from said element through said fluid actuated means.

4. An improved operating system for a hydraulic motor of the type having a working member, hydraulic means for advancing said member, hydraulic means for retracting said member, and a source oi operating fluid under pressure, which comprises the combination therewith of a main valve having a chamber, and a valve element movable back and forth in said chamber along a selected path, said element having lands spaced apart in a direction along said path, said casing having ports connected in groups by thespaces between said lands and covered and uncovered by the lands as they pass, one of said ports being connected to said advancing means, another to said retracting means, another disposed between these two and connected to said source, others beyond both of said first two ports and connected to exhaust, means operable on said element and urging it yieldingly into one end position in which it connects said retracting means to said source and said advancing means to exhaust, and holding it yieldingly in that position, a hydraulic device having a piston normally inoperative to opposemovement of said element into said one end position, but movable under hydraulic pressure into a position in which it releasably limits movementof said element under the action of said it connects said retracting means tOsald source and said advancing means to exhaust,,and'holding it yieldingly in that position, a hydraulic device having a piston normally inoperative to oppose movement of said element into said one end position, but movable under hydraulic pressure into a position in whichit releasably limits movement of said element under the action of said urging means to an intennediate position in urging means to an intermediate position in which a land closes said port connected to said retracting means and said source port and said port connected to said advancing means are connected to exhaust, means including a valve controlled by said member and operable to connect said retracting means to said hydraulic device and cause said movement of said piston when said member is "retracted within a selected extent and to connect said element releasably in that end position solely by'a continuance of fluid pressure on said element nected to exhaust, means including a valve controlled by said member and operable to connect said retracting means to said hydraulic device and cause said movement or said piston when said member is retracted within a selected extent and to disconnect said retracting means from said hydraulic device when said member is away from said selected extent of retraction, fluid actuated moving means until release of said element is desired, whereby said element cannot be moved sure, a main valve connected to said source and ent successive positions in one of which positions it connects said source to said advancing means and said retracting means to exhaust to. cause an advance of said working member, in another of which positions it connects said source to said retracting means and said advancing means to exhaust to cause a retraction of said member, and in a third, intermediate position in which it closes said retracting means against escape of operating fluid and connects said source and said advancing means to exhaust to cause said member to remain stationary, means for yieldingly urging said element into said anotherposition, a hydraulic device operable into' one position in which it directly prevents movement of said element by said urging means beyond said intermediate position and into another position in which it permits movefree of bias into either position, means controlled by the position of said member for connecting said hydraulic device to said retracting means for operation of said device into its said one position automatically when said retracting means is under fluid pressure, and for also connecting said device to said advancing means when said working member is being advanced, for operation into its said one position when fluid pressure on said ment of said element by said urging means into said urging means into said oneposition to cause an advance of said element, wpereby said element may be manually moved and held momentarily in said one position selectively, and means controlled by said working member for causing operation oi said hydraulic device into said one position -when said member is retracted to a selected extent, and into its other position when said member is away from its said retracted extent. a

6. In a hydraulic motor system, a working member, hydraulic means for advancing said member, hydraulic means for retracting said member, a source of operating fluid under presboth of said means to form therewith a hydraulic circuit for operating said member, said valve having a control element operable into three difierent successivepositions, in one of which positions it connects said source to said advancing means and said retracting means to exhaust to cause an advance of said working member, in another of which positions" it connects said source to said ,retracting means and said advancing means to exhaust to cause a retraction of said member, and

. in a third, intermediate position in which it closes said retracting meansagainst escape of operating fluid and connects said source and said advanc-v 'said element into said another position, a hyadvancing means is abov a predetermined pressure, means for operating said balanced valve in a manner to cause admission of operating fluid to said element operating means, and additional means responsive to a selected operating condition of said system for moving said balanced valve in a.' manner to release operating fluid from said element operating means.

'i. In a hydraulic motor system, a working member, hydraulic means for advancing said member, hydraulic means for retracting said member, a source of operating fluid under pres sure, a'main valve connected to said source and both oi said meansto form therewith a hydraulic circuit for operating said member, said valve having a control element operable into three difierent successive positions, in one of which positions it connects said source to said advancing means and said retracting means to exhaust to-cause an advance of said working member, in another of retracting means and said advancing means to exhaust to cause-a retraction of said member, and a third, intermediate position in which it closes saidretracting means against escape of operating fluid and connects said source and said advancing means to exhaust to "cause said member to remain stationary, means for yieldingly urging said element into said another position, a hydraulic devi'ce operable into one position in which it pre- 40}v entsmovement of said element by said urging 'nieans-beyond said intermediate position and into an' other position in'which it permits movement not, said element by said urging means into said sure, a main valve connected to said source and .jorcing it into-said one position to cause an adg other position for that element, fluid operated means selectively operable on said element for operating pressure thereon after movement of said element has occurred, releasing it from that I one position by a release of fluid pressure thereon,

draulic device operable into one position in which it prevents movement of said elementby said urging means beyond said-intermediate position and into another position in which it permits movement of said element by said urging means into saidanother position for that element, fluid operated means operable on said element for forcing it into, said one position to cause an advance of to said element operating means and its release therefrom, said balanced valve being normally and means including a valve operated by said member to place said device automatically under the fluid pressure on said' retracting means when said member is within a predetermined zone of retraction, and under the fluid pressure on said advancing means when said outside of said zone. V r

I 8. In a hydraulic -motor system, a working member, fluid actuated means for advancing said member, fluid actuated means 'for retracting said member, a source of actuating fluid under pressure, a circuit having a controllingvalve for causing actuation of said member both advance and retraction, said valve havi a controlelement movable into any of thy e positions, in one of which it causes actuating fluid pressure on said member'advancingmeans, in another of which it causes actuating fluid pressure on said member retracting means, and in a third of which it is intermediate its other mentioned positions and closes said member retracting means'against e'scape of actuating fluid,means for yieldingly urging said element into its said another position and holding it there, fluid operated means for overwhich positions it connects said source to said member is disposed which it causes actuating fluid pressure. on said member advancing means, in another of which it .causes actuating fluid pressure on said member retracting means, and in a third of which it is intermediate its other mentioned position and closes said member retracting means against escape of actuating fluid, means for yieldingly urging said element into, its said another position and holding it there, means operated by fluid presmember during its travel for connecting said fluid operated device to the fluid pressure on said re-' tracting means when said member is in one zone of retraction, and breaking that connection and releasing said device from the fluid pressure obtained from said retracting means when said member is outside said zone.

9. In a hydraulic motor system, a' working member, fluid actuated means for advancing said member, fluid actuated means for retracting said member, a source of actuating'fluid under pressure, a circuit having a controlling valve for causing actuation of said member in both advance and retraction, said valve having a control element 'movable into any 01' three positions, in one of sure for operating said element into its said one position and holding it there by continuance of fluid pressure. a pressure balancedvalve for controlling vthe admission of fluid under pressure is and its release from said element operating means, a fluid operated device efl'ective when operated by fluid pressure to mm said element from its said another position into said intermediate position or limit movement of said element from its said one position past said intermediate position, means including a valve operated automatically by said member during its travel for connecting said fluid operated device alternately to the fluid pressures on said retracting means and said ad'- vancing means, depending upon the zone 01 movement in'which said member happens to be.

moms F. STACY.