US2335809A

US2335809A - Fluid operated motor

Info

Publication number: US2335809A
Application number: US204375A
Authority: US
Inventors: Thomas F Stacy
Original assignee: French Oil Mill Machinery Co
Current assignee: French Oil Mill Machinery Co
Priority date: 1938-04-26
Filing date: 1938-04-26
Publication date: 1943-11-30
Anticipated expiration: 1960-11-30

Description

Nov. 30, 1943.

T F. sTA cY FLUID OPERATED MOTOR Filed April 26, 1938 3 Sheets-Sheet l Eh l Nav. 30, 1943. T. F. STACY 2,335,809

FLUID OPERATED MOTOR Filed April 26, 1938 5 Sheets-Sheet 2 INVENTOR ATTORNEYS Nov. 30, 1943. T. F. STACY 2,335,809

I FLUID OPERATED MOTOR Filed April 26, 1938 3 Sheets- Sheet s easxvam? ATTORNEYS 1 inexpensive.

Patented Nov. 30, N43

I 2,335,809 mm orsaa'rsn Moron 'Ifhomas F. Stacy, Piqua, Ohio, asslgnor to "Elie French Gil Mill Machinery Company, Pique,

14 Claims.

This invention relates to fluid operated motors such as hydraulic presses, and more particularly to the mechanism for controlling the reciprocations of a ram element.

One object of the invention is to provide improved controlling means for a fluid operated mtor, with which objectionable shock to the motor and system through high pressures will be eliminated, particularly when the system is operated to reverse the direction of travel of the ram element after it reaches a desired forward position; with which jumping of the ram element during a working stroke and upon a sudden decrease in resistance to its forward-movement is reduced until it is unobjectionable; with which speedy Preliminary advance movement of the ram element will not be materially restricted; and which will be relatively simple, practical, dependable, rapid in operation, and inexpensive.

Another object of the invention is to provide an improved method of operation of ram elements in a fluid actuated motor, with which objectionable shocks to the system upon reversals in the direction of travel of the platen will be eliminated; with which rapid advance of the ram element will be possible until substantial resistance is encountered; with which objectionable jumping of the ram element during a working stroke, upon a sudden decrease in resistance to its forward movement, will be prevented; with which the direction of travel of the ram element may be changed at any point in either forward or retracting movements; and which will be relatively simple; practical, and require a minimum of expensive equipment and a minimum of Other objects and advantages will be appar ent from the following description of some embodiments or examples of 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 oi portions of a fluid actuated motor having a controlling system therefor constructed in accordance with this invention;

Fig. 2 is a somewhat similar schematic diagram, but illustrating slight modifications in the systerm, and

Fig. 3 is a. diagram similar to Fig, 1 further modification thereof.

In the embodiment of the invention illustrated in Fig. i, the fiuid actuated motor includes a ram element 5 having a piston 2 reciprocating in a ram casing 3, with a main cylinder 5 at one side of the piston to force the ram element forwardbut with I 'ly in a working stroke and a pull-back cylinder h improved means for controlling the activity of the movable ram element of a fluid act ated motor, with which objectionable shocks o thetflui'd system and apparatus will be prevented at the stoppage of the forward movement or the ram element at any points in its working and retraction strokes; with which rapid closing of the ram element may be obtained, but with resistance to jumping of the ram element if the resistance to its working stroke is suddenly decreased; and with which the controlling valve may be either power or manually operated, or both.

Another object of the'invention is to provide improved means for controlling a fluid actuated motor, with. which smoothness and rapidity of operationbf the motor may be obtained, and

which will berelatively simple, dependable, and

at the opposite side of the piston 2 for retracting the ram element i. These parts are typical of a fluid acuated'motor, and in many cases the pullback cylinder is in a separate housing from the main cylinder 3 but connected to the ram element 6, and it will be understood that the invention relates to the actuation of the ram element in one direction by pressure in a main cylinder and in the opposite or retracting direction by a pull-back cylinder, whether the main cylinder and pull-back cylinders operate on the same or different pistons connected to the ram element.

Any source of operating fluid under pressure may be'employed, but for convenience I have i1-' iustratedthe source to be a pump 6 which draws liquid from a suitable reservoir 1 through a pipe .8, and delivers it under pressure through a pipe 9. Any suitable type of pump may be employed, the one illustrated being of the variable displacement or variable delivery type, in whichany slippage of liquid is returned by pipe it to the reser- A light pressure opened check valve ii of any suitable construction is connected in series in the pipe 9 between the pump 6 and the controlling or operating valve l2. The valve l2 includes a casing with a valve chamber lit in which reciprocates a valve element It. The valve element It is provided with a pair of spaced lands l5 and I6 which are of a size to fit closely with the wall of the chamber l3 and cooperate with ports in the wall of chamber iii in a manner which willbe described presently.

A helical compression spring I! is compressed operated, free check valve 3|.

between one of the lands. such as I8, and an end wall I8 of the housing I2, and urges the valve element I4 in a downward direction in Fig. 1. The pipe 9 opens into the valve chamber I3 through a port I9 which is between the lands I5 and I8 when the valve element I4 is in an intermediate position, which is the position shown by full lines in Fig. 1. A pipe 28 opens into the valve chamber I3 through a port 2I'aligned with the land I8 when the valve element I4 is in said intermediate position, and also is connected to the main cylinder 4. 'Another pipe 22 opens into the chamber I3 through a port 23 which is aligned with the land I5 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.

pilot cylinder 32 is connected by a pipe 36 to the pipe 22 which leads to the pull-back cylinder 5 at a point between the three branch circuits 22a, 22b and 22c and the valve I2.

The valve element I4 extends outwardly through, one end of the valve housing I2, and this projecting end has a peripheral notch 31 which 4| of a housing 42, and a piston 43 is mounted for The land I6 is bevelled on opposite sides, as

shown in Fig. 1, so that when it is aligned with the port 2| there will be'clearance between the land and the port 2|, and.fluid in the chamber I3 received through the port I9 and pipe 9 may -pass around the land I6 to the upper end of the chamber I3 as well as pass to the pipe 28. An exhaust pipe 24 opens into the upper end of the chamber I3 through a port 25, and in turn is connected to the pipe I8 leading back to the reservoir I. The lower end of the chamber I3 also has a port 25 opening into the pipe 24. The pipe 22 is connected to the pull-back cylinder 5, but one zone of it is sub-divided into three branch pipes 22a, 22b and 220 which,are all in parallel to one another. The branch 22a contains a free check valve 21 which opens freely to pass fluid through the pipe 22 toward the pull-back cylinder 5 and automatically closes to prevent reverse flow.

In the branch pipe 22b I have included a meter valve or adjustable valve 28 which may be adjusted to pass a, selected and regulatable amount of operating fluid in both directions therethrough, which would be both toward and from the pull back cylinder 5. In the branch 220 I have'ineluded a heavy pressure release valve 29 which opens to pass fluid leaving the pull-back cylinder 5 when the pressure on the escaping fluid exceeds a predetermined pressure, and closes automatically to prevent flow of the operating fluid therethrough towards the cylinder 5. This pressure release valve 29.ma'y be adjusted by varying the spring pressure on its valve element so as to vary the pressure that must be created in the cylinder 5 before it will lift the ,valve element and pass operating fluid therethrough from the cylinder 5. This valve 29 is in a sense a safety valve, and ordinarily becomes efl'ective only when the fluid pressure in the cylinder 5 becomes excessive, such as might happen, for example, if someone should inadvertently close 011? the valve 28 entirely or largely so. I

A pipe 38 leads from the reservoir 1 to the cylinder 4, and it contains in series therein a pilot 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 1 should preferably be elevated above' the cylinder 4 to. facilitate free flow of oil from the reciprocation on the valve element I4 and in the chamber 4|. In fact, the piston 43 extends through. opposite walls of the housing 42, with suitable gaskets or packing where it passes through the opposite walls of the housing. The end which passes through the upper wall, in Fig. 1, of the housing 42 is of lesser diameter than the portion which passes through the opposite or lower wall of housing 42. A helical compression spring 44 is compressed between a flange 45 on the outer reduced end of the piston 43' and the housing 42, so as to normally urge the piston 43 upwardly in Fig. 1, that is, to retract the larger end of piston 43 into the chamber 4|. The lower end of the piston 43 is bevelled as at 46, so as to act as a cam surface which engages with the latch or detent 39 and cams it into a position to carry its nose 38 out of the notch 31 and release the valve element I 4, whenever the piston 43 is forced downwardly sufficiently in Fig. 1.

A pipe 41 leads from the pipe 28 to the chamber 4| and it may include therein a freely operating check valve 48 of the type which opens freely to pass fluid through the pipe 41 from reservoir into the cylinder during the preflll stroke able valve element 35 of the check valve 3|, and

thus allow fluid to flow from the cylinder -4 the chamber 4| to the pipe 28, and closes automatically to prevent reverse flow. Connected to the pipe 41 at opposite sides of the valve 48, so

' as tube in parallel with the latter, is 'a branch pipe 49 having in series therein a pressure relief valve 58 of the typewhich opens to pass fluid from the pipe 28 to the chamber 4| whenever the pressure in the pipe 28 exceeds a. predetermined pressure for which the pressure relief valve 58 is set. This valve 58 closes automatically to prevent reverse flow. The valve element 5| of the pressure relief valye 58 is urged into closed position, for example, by a spring, and the compression of the spring may be varied by the adjustable screw 52 as usual in pressure relief valves. Therefore when the pressure in the cylinder 4 reaches or exceeds a predetermined pressure corresponding to that for which the relief valve 58 is set, this pressure which also exists in the supply pipe 28 will be transmitted to the pipe 41 and will be sufllcient to lift the valve element 5| and flow through the branch 49 and then again through the pipe 41 to the chamber 4|." The fluid under pressure thus delivered to .the chamber 4| will force the piston 43 downwardly against the action of spring 44, and the bevelled nose 48 of piston 43 will engage the latch or detent 39 and cam it into a position to re- /lease the valve element I4, whereupon the spring I1 will force the valve element downwardly into and, if or when possible, beyond the intermediate position shown by full lines in Fig. 1.

h A hand control lever 53 is pivoted at 54 to any I through the pipe 38 back to the reservoir 1. The suitable support, and an arm of this lever'en.

. to the reservoir.

-is not then in alignment with either of these ports, it will close communication between those ports, and operating fluid will therefore no longer be able to pass around the periphery or past the edge of the land l6. At the same time'the land l5 was carried out of alignment with the port 23 and into a position between the ports 19 and 25.

'Ihereupon the fluid under pressure which is delivered by the pipe 9 to the chamber 65 is free to pass directly from the port I9 across chamber l3 to the port 2 i, but it will be. cut ofi from reaching the port 25. This fluid reaching the port 26 will pass through the pipe 25 to the cylinder a and thus tend to exert a fluid pressure on the piston 2 and cause it.to descend and carry the ram element i downwardly.

When the land i 5 moved between the ports i9 and 23 it uncovered the port 23, and thereupon.

of the chamber 3; The pipe 22 is thus placed directly in communication with the pipe 25 leading back to the reservoir 11, and any fluid in the pipe 22 may thus pass freely back to the'reservoir l. Fluid from the pull-back cylinder 5 may therefore escape through the pipe 22, meter valve 25, pipe 22, lower part of chamber it and pipes 25 and [El back to the'reservoir i, so that the ram element I may descent at a rate depending upon the rate of escape of the operating fluid from cylinder 5 through the valve 25. As the piston 2 descends, the pressure chamber in cylinder 5 will increase in volume more rapidly than the pump can supply operating liquid thereto,' and therefore until resistance is encountered by. the descendingram element 9, a suction may be created in cylinder 4 which. through the pipe 35, will draw liquid from the reservoir l to fill the space vacated by the descending piston 2. It will be understood that the valve element of pilot check valve 30 will open freely to pass this fluid into the cylinder 1.

When the descending piston encounters resistance, the suction in cylinder 5 will stop because the liquid passing through pipe 28 will be sufiicient to fill the space vacated by the descending piston, whereupon the valve 55 will close automatically, and continued delivery of operating fluid through theapipe 20 to the cylinder 4 will valve is set,- it will escape past the valve element 5! of valve 50'a nd reach the chamber 4|,

and then by forcing the piston 4.3 downwardly 1 will disengage the latch 39 from the valve element l4 and allow the latter to be shifted back into the intermediate position shbwnsin full lines in Fig. 1. Wlren this occurs the pipe'2ii will again be connected throughthe' port 2! with the port 25, and the operating fluid may then escape from cylinder 4 through pipe 20, port 2i, upperpart of chamber l3, port 25 and pipes 24 and in back At the same time the land l5. again closes the port 23 so that operating fluid cannot escape from the cylinder '5. Pressure will. therefore, drop in cylinder 6 and the liquid delivered by the pump will be by-passed at no pressure around land i6 through pipes 25 and I9 back to the reservoir.

If the valve element l4 passes the position shown in full lines; in Fig. 1, it will carry the land l5 between the

ports

23 and 26 so as to cut off communication between the same and to uncover the port 23. The land I6 will similarly be carried into a position between the ports i9 and M so as to shut off communication between the same and thereupon the pipes 9 and 22 will be directly connected. When that happens, the pipe 20 will still be connected to thepipe 24 to allow escape of operating'fluid from cylinder 4 back to the reservoir 5, and the operating fluid delivered by the pump through the pipe 9 will be conducted across the chamber E3 to the pipe 22 and then will pass partly through the check valve 2? which opens freely to permit this 'passageand partly through the valve 28 to the pull-back cylinder 5 so as to create a fluid pressure in the latter tending to force the piston 2 upwardly and retract the ram -element l.

Since the effective volume of the cylinder 5 increased by the upwardly moving piston 2 is very greatly less than the rate of decrease in the effective volume of cylinder 2 by the same movement of piston 2, it follows that if the fluid pressure from the pump is delivered to the pull-back cylinder '5 before the pressure in cylinder 5 has fallen sufliciently, unnecessarily high pressures may be created in the pull-back cylinder 5 with the resulting shock to the press or fluid motor and the system- The pressure in the pipe 22 is until the pressure in the main cylinder 4 has fallen to such an extent that the valve element 35 may be immediately opened.

For'this purpose an end 63 of valve' element it extends into a closed chamber where it functions as a piston. Extending into the same chamber 55 is a stop piston 51 which passes in the opposite direction out of the chamber 55' and into another chamber 58 where it carries a outwardly of the chamber 58. A spring 6| is compressed between the hopusinlg for chamber 58, and adjustable nuts 62 on the outer end of the stem 60, so as to normally urge the stem downwardly or outwardly and thus tend to retract the stop piston 51 out of the chamber 56 or in a direction away from the end 63 of the valve element M which is within the chamber 55. The flange or head 59 of this stop piston 57 which is within the chamber 58, by engagement with the wall of the chamber. 58, limits the upward movement of the stop piston to a position suchthat it'engages with the end 63 of the valve element l4 and opposes or block further movement thereof under the urge of the spring it beyond the intermediate position shown in full to the chamber 58 the stop piston 51 may be held in a position to limit the movement of the valve element under the action of its spring H to the intermediate position shown, .until it is desired to allow further movement of the valve element, and then the lowering of the pressure in chamber 58 will permit the spring 6| to retract the stop piston 51 and allow continued movement-of the valve element |4 into the second position in which it connects the pipe 9 to the pipe 22 and starts the retraction of the ram element I.

The pressure in the chamber 58 is established at the proper time by means of a pipe 64 which leads from the pipe 20 to a valve 65 having three lands 66, 61, and 68 on a movable valve element 69 thereof.v A pipe 10 connects the valve 65 to the chamber 58. A pipe -1| connectsthe chamber of valve 65 to the pipe 22. A spring 12 in the housing of valve 65 acts on the valve element 69 to force it downwardly in Fig. 1 from the position shown in full lines, to the position shown in dotted lines. The valve element 69, however, is connected to a trip rod 13 and it carries a collar 14-which may be in a position to be engaged by the arm 15 on'the ram element I, when the latter reaches a selected position in its retraction or return stroke. The collar 14 is adjustable, such as by means of a set screw in the collar, to diiferent positions along the rod 13 so as to determine, and enable variation in, the position in the return movement of the element at whichthe arm 15 will engage collar 14 and force it and the valve element 69 up into the position shown in full lines in Fig. l.

When the valve element 69 is held in its upper position, as shown in Fig. 1, the pipe 1| will be connected by the space between the lands 66 and 61 to the pipe 18, and thus the chamber 58 will be subjected to the pressure in the pipes 1| and 22 and the cylinder 5. Since the pipe 22 is closed at, the port 23 by the land l5, the weight of the piston 2 and the ram element I will placethe fluid confined in cylinder under pressure whichwill be transmitted through the pipes 22, 1| and to the chamber 58, and will hold the stop piston 51 in the elevated position where it prevents downward movement of the valve element I4 ,check valve H and the pump 6.

thence back to the reservoir, and to another pipe 19 leading to the pipe 9 at a point between the- A spring 80 acting on the valve element 8| of the valve 11 normally urges the valve element 8| upwardly into the position shown in full lines in Fig. 1, at which time the pipe 16 is connected to the pipe 18, which relieves th chamber 56 of all fluid pressure. A land 82 on the valve element 8| obstructs communication between the pipes 16 and 19. A solenoid 83 is connected to the valve element 8| so as to operate the same against the action of the spring 88, and this solenoid is energized at will from line wires L and L under the control of a switch 84. Thus, when the solenoic' 83 is energized following closing the switch 84, the valve element 8| will be pulled downwardly so as to place the land 82 between the openings to pipes 16 and, 18 and obstruct communication between them, and by moving beyond the opening to passage 16, it will connect pipes 16 and 19. Thereupon fluid from the pipe 9, between the pump 6 and the check valve II, will pass through pipes 19 and 16 to the chamber 56, and by exerting pressure on the end 63 of the 'valve element M, will force the latter upwardly to a position in.

' may tend to force thestop piston 51 downwardly,

under the action of spring l1. During this time yond the opening to pipe 64 so that communication will then be established between the

pip

54 and 10 by the space between the lands 66 and 61. At such time, since the pipe 64 is connected to the pipe 28 leading to the cylinder 4, the fluid pressure in-the cylinder I will pass through the P pes 28, 66 and 18 to the chamber 58 and the stop 51 will 'be held in its obstructing position shown .in Fig. 1. When this pressure lessens sufllciently the piston 51 can descend, allowin valve element M to descend and connect pipe 9 from the pump to the pipe 22 running'to the return ram chamber 5. When the valve element II is moved upwardly, however, so as to uncover port 23, the pipe 22 will be relieved of fluid pressure because the operating fluid is then but this does no harm and it is only momentary.

The pressure-opened check valve ll serves a dual purpose. It creates enough back pressure in the portion of pipe 9 leading to the pump to provide a continuous source of fluid under pressure to supply pipe 19 with operating fluid, and

it also prevents the feeding of oil from the press back to the pump. Y

If the press is open and idl and if the pump and motor should be stopped, then the press ram will gradually drop down, due to leakage, and

- as soon as it has dropped down far enough, valve 65 will operate, which will allow the rod 13 to drop and will connect chamber 58 through the

pipes

64 and 20 to the main cylinder. This will allow the valve stem 51 to drop, and pipe 22 will then be-connected through the ports 23 and I9 to pipe 9. The weight of the press will then feed th oil back through th pipe 9, and without the check valve in.this pipe 9, the pump would act as a motor and run backward, and the press ram would drop rapidly.

When the valve element I4 is latched in the above manner, it initiates a downward movement ,of the ram element l as previously explained. As

soon as the element starts downwardly it releases collar 14, and rod 13. then falls under the action of spring 12, and the valve element 69 is shifted into the dotted line position so as to connect the pipe 84- to the pipe 10 and thusto the chamber 58. During the initial downward movement of thepiston 2, a suction will be created in the cylinder 4 which is filled by liquid from the reservoir through pipe 38, and thus there will be little or no pressure created in the chamber 58. As soon as the element .1 encounters subassasoe stantial resistance, however, the valve 3! closes and fluid pressure begins to build up in cylinder 3. This pressure is then communicated throughin its upper or latched position.

When the valve element IQ is released by the pressure in chamber ii of the unlatching device, the valve element it will be shifted endwise by spring it until it engages the stop piston 5'! and 'is stopped in the intermediate-position shown by full lines in Fig. 1. This closes off the pipe 22 at port 23, so that no fluid can escape from cylinder 5, and the pipe 2t is then connected around land it to the pipe 2 1, so that by the escape of fluid from cylinder l through pipes 28 and 2t element it, or by closing the switch 84 to' cause a hydraulic operation of ,the valve element i4 back into latched position.

If, at any time while the valve element M is latched and the piston 2 is descending, one desires to stop the further forward movement of the piston 2 and return it, it is merely necessary to operate the hand-controlled lever 53 in the opposite direction so that the end beneath the flange 55 will engage with the flange B5 on the unlatching piston t3, and force the same along the valve element it to disengage the detent or latch 39 and release valve element I4, whereupon the spring ll will operate the valve element M to cause a return movement of the piston, as above explained.

After a tripping of latch 33 by pressure in chamber ti, it is advisable to reduce the pressure back to the reservoir, the pressure in cylinder 4 I will fall. Since the arm i5 is still in a lower position where it is free of collar it, the valve 65 will still keep the pipe (it connected through the pipe ill to the chamber 58 and thus maintain the same fluid pressure in chamber 58 as exists in cylinder 4. When the pressure in cylinder 3 has fallen, however, to a relatively low pressure, the pressure in chamber 58 will also have fallen correspondingly and spring 6|, aided by the spring ll, will then retract stop 51 and allow the valve element G4 to follow under the pressure of spring it until it moves into the reversing position in which the land I5 is between ports 23 and 28 and the land I6 is between ports 19 and 2!.

When this happens the pipe 9 will be connected to pipe 22, so as to deliver ,fluid under pressure to the cylinder 5 to start a. retraction of the piston 2, and pipe 20 will be connected to the return pipe 24, so that the fluid displaced from the cylinder 4 by the piston 2 may flow freely back to the reservoir 1. Since more liquid is displaced'from cylinder 4 than is delivered to the cylinder 5, and work must be done to retract the ramelement l and piston 2, pressure will build up in pipe 22 and this pressure entering pipe 38 will force open the valve element 35 and permit flow of the iiuid from cylinder 4 also through pipe til and valve 3! back to the reservoir l, thus making two paths for escape of fluid from cylinder 4i and making possible a more rapid return movement of the piston 2. As the piston 2 approaches its upper limit of movement, the arm it will reengage the collar 14 and shift the valve element 69 backinto the position shown in full lines in Fig. l and thus break the connection in chamber at quickly so that the valve element 84 can again be relatched, and immediately if desired. The valve it will quickly release this pressure after the pressure in the main cylinder has fallen s'uficiently, but since the fall of pressure in cylinder t is not instantaneous, a bleeder he may he provided between the chamber iii and pipe 3t leading to the reservoir 7, so that fluid may escape from chamber it either by valve at or bleeder 85, or by both. Only one of these paths of escape from chamber ti is necessary, but both may be used if desired." The bleeder 35 must be suiflciently small so that flow of fluid through the valve 50 will be greater than'the rate of escape through the bleeder and create a pressure in chamber 4| sufficient to operate piston 43.

While, as explained above, the pump 6 may be of any suitable type, even a fixed stroke type,

I have illustrated it as of the pressure'holding, variable displacement type which is particularly advantageous in this type of system. As usual in this type of pump, a pipe 86 connects the, pipe 9 to the usual cylinder. 81 in which reciprocates piston 88 that acts upon a shifting lever that varies the rate of delivery of-the pump 6. A spring 90 is confined on a rod 90a between a-collar 90b on the rod and a. U-shaped arm 90c hinged The spring 90, acting on the arm 90c, urges the lever 89 in a direction to throw the pump I on to full stroke or maximum delivery, and forces the piston 88 inwardly into the chamber 81.

Since the chamber 31 through the pipe 86 is re-' sponsive to the pressure in the pipe 9, it follows between pipes 64 and I0 and reestablish the connection between pipes H and HL'thus returning the chamber 58 to the pressure existing in the pull-back cylinder 5.

This pressure of the pull-back cylinder 5 which is received directly from the pipe 9 and the pump, and which is transmitted to the chamber 58, will force the stop piston 51 back into its obstructing position and will forcibly shift the valve element l4 back into the intermediate position shown in full lines in Fig. 1, stop the further upward movement of the piston 2, and'allow the fluid under pressure from the pipe 9 and pump 6 to circulate past the land i6 to pipe 24 and then back to the reservoir 1. The parts remain in these positions until another forward movement of the ram element I is initiated, either by operating the hand lever 53 to release the valve that when the working pressure in the main cylinder 4 increases suillciently to overcome the pressure of the spring 90, the piston 88 will be forced outwardly and will shift the lever 89 and 60 set the pump 6 to a very small delivery, or to valve element I4 is shifted into the intermediate inder 4, and through the pipe 64, valve 65, pipe-- neutral or no delivery to hold that pressure. The

pump will then continue to operate until the valve element I4 is released to cause a. reversal of the ram. When the latch 39 is operated, the

chamber 58 andpipe 86, the chamber 81 at the pump will also remain subject to the pressure in cylinder 4.

In the foregoing description, reference has.

been made to vertical movements for various parts, but this has been done for convenience of reference and to indicate directions of movement, but it will be understood that the parts will perform these relative functions just the same whether arranged in the position shown or disposed in horizontal or other positions, and such positions or movements as are described as either horizontal or vertical, are to be understood as not limiting details of the invention.

Referring now to Fig. 2, a slight modification of the system shown in Fig. 1 is illustrated. Parts in Fig. 2 which correspond to similar parts in Fig. 1 are designated by the same reference characters and will not be further specifically described, but the differences from Fig. 1 will be expressly set forth. Referring now particu-- larly to Fig. 2, a pressure closed valve 9I is included in series in the branch pipe 22b. This valve 9| has a valve element 92 which is urged into open positionby a spring 93 so that normally the valve 9| is fully open and the valve 29 then represents the only restriction to fluid flow through the branch pipe 22b. The valve element 92 extends into a closed chamber 94, and the latter is connected by a pipe 95 to the pipe 20. Thus when the pressure in the pipe 20, as communicated through the pipe 95 to the chamber 94, becomes high enough to overcome the pressure ofspring 93 it will force the valve element 92 into closed position and thus keep valve 9I closed and shut off all fluid flow through the branch pipe 22?). Hence the valve 9I is pilot closed immediately so that substantial back pres sure in cylinder 5 will be built up. Then, the operating fluid can escape from cylinder 5 only when its pressureis suflicient to pass the pressure opened relief valve .29. With valve 9| closed, if the resistance to movement of the ram element I should be suddenly lessened, the piston 2 and ram element I cannot jump ahead material ly because of the back pressure in the pull-back cylinder 5. press stroke makes the press or motor particularly applicable for use in blanking operations, such as in the drawing or blanking of metal sheets. Heretofore hydraulic presses have been used very little for blanking operations, because the press ram will come down against the metal to be blanked, the required blanking pressure will be built up, and then as the metal is blanked, this energy must be suddenly released which tends to cause the press ram to jump forward with considerable shock toall the equipment. With this arrangement, however, ,oi creating substantial back pressure in the pullback cylinder only during the actual drawing or blanking operation, the tendency of the ram to jump forward when the metal is blanked is substantially prevented or reduced to such an extent that it is unobjectionable, yet since the valve 9| is opened whilh the press is closing, there is no material decrease in the speed of operation of the press as a whole.

In order to prevent overrunning or oversitroke This jumping restriction during aof the ram element, I may also provide a limit device for reversing the motor which will now be described. A valve device 96 is disposed in position for operation by the arm I5 or other suitable part of the ram element I when the desired maximum limit of movement of element I isreac'hed. For example, the valve element 91 of valve 96 extends out of the valve housing 99 and terminates in a rod 99 'along which the arm 15 moves. A collar I00 is secured on the rod 99 for adjustment into diiierent positions therealong where it may be engaged-by the arm I5. A spring I! acts on the valve element 96 to hold it normally in its upper position, and when the arm I5 engages collar I00, continued descent of the element I will'force the rod 99 downwardly againstthe action of spring I M The chamber of valve 98 is connected by a pipe I02 to' the pipe 19 which communicates with the pipe 9, so that fluid under pressure normally delivered by the pump 5 will be transmitted to the chamber of the valve 98 at a point between the lands I03 and I04 on the valve element 91.

A pipe I05 extends from the pipe 41 to the chamber of valve 98 at a point below the land I03 when the valve element is in its upper position shown in full lines in Fig. 2. The land I03 thus normally interrupts communication between the pipes I02 and I05. When the arm I5 engages collar I00 and depresses the valve element 91, the land I03 moves beyond the opening topipe I05 before the land I04 reaches the opening to pipe I02 and thus communication will be immediately established from the pipe I02 to the pipe I05, and thence through pipe 41 to chamber H of the housing 42. This transmits fluid under pressure directly to the chamber M where it actuates the latch-tripping piston v I3 to disengage latch 39, the same as described in connection with Fig. 1 when the fluid under pressure was delivered to the chamber 4| directly from pipe 20. Thus the valve is a position responsive reversing control which acts in addition to the pressure responsive control device 50, and if the pressure responsive device does not cause reversal automatically when a desired pressure has been built. up, the device will be reversed by thisposltion responsive device, provided that the element I travels the necessary further distance. The purpose ofthis combination of position and pressure reversing control is a perfectly logical one from an operating point of view as well as from a safety point of view. If the press is used for blanking operations the positioning-control may be used, and

, the ram is desired before reversal. By adjusting the collar I00 along the rod 99, the-point in the travel of the ram element I at which the reversal takes place may be varied. The operation is otherwise the same as described in connection with Fig. 1 and need not be repeated.

In the embodiment of the invention shown in Fig. 3, the construction is the same as in Fig. 1, except that I have illustrated a diflerent means for holding the valve element M in the position it occupies in causing an advance of the ram element i, and for releasing it in response to pressure in the main cylinder 4. Those parts of Fig. 3 which are the same as in Fig. 1 are given the same reference characters. In Fig. 3 the pipe d! is removed from the'pipe 2B and the valves d3, 50, blee'der $5, the latch 39 and the latch l which is disposed in flexed condition between two abutm'ents ltd so as to snap between the positions shown'hy full and dotted lines. The plate ltd may carry a contact lit which engages a contact ii i on a leaf springi i2, and the movement of spring M2 toward plate ltd is limited by a stop M3.

When the plate itt'is in the position shown in dotted lines, its contact lit engages the contact iii crfispring lit and forces the latter slightly away from stop H3. A piston lid operating in cylinder H5 is disposed in a position to engage the plate 508 and push it, through dead center position and cause it to snap into the full line position. The piston H4 is normally retracted by a. spring H6, and compressionof the spring H6 may be adjustable in anysuitable manner so as to vary the pressure at which it.

may be overcome and allow-the operation of piston ill. When the pressure on the pipe 20 exceeds a predetermined pressure for which the spring H6 is set, this pressure which is transmitted through. pipe llll to chamber H5, will the plate mt from the full line position to thedotted line position, when it is desired to set the pressure operated switch for operation. The

spring H2 is connected by a wire i it to one end of the solenoid 8.3 and=the other end of solenoid 83 is connected by wire 4 i9 to line wire L The plate Mill is connected by wire iii! to a manually operated switch i2i, which remains in either open or closed position into which it is moved,

and the latter is connected to the line wire L In operation, one starts the press by first closing the switch i2l, which remains closed. One then pushes button H1, which forces'plate I08 into dotted line position where it closes the circuit through solenoid 83. Solenoid 83 operates valve TI to shift valve element M from the position shown in full lines in Fig. 1, against the action of spring ll into the position in which-it starts an advance movement of piston 2. The plate l08- remains in circuit-closing position and thus thesolenoid 83 willrmaintain the valve 11 force the piston H4 in va direction to cam the in a position to keep the valve M in the position in which it causes an advance of the piston 2, when the pressure in pipe 20 has reached a predetermined pressure, ior which the pressureresponsive switch is set, the piston H4 of the switch i136 will become active .and cam the plate 908 to' open the circuit through solenoid 83.. This tie-energizes solenoid t3 and the valve ll is then operated to release the valve element it, whereupon the spring ill shifts it into the full line position of Fig.1, momentarily until the pressure in the main cylinder falls, and then shifts the element i l to cause the retraction of piston 2.. histon 2 isv then returned automatically to retracted position and stopped in the manner explained in connection with Figs. 1 and 2.

To start the press for another advance movement, it is merely necessary to again press the button ill and cam the plate tilt back into circuit-closing position where it remains until operated, by pressure in pipe 28, back into open circuit position. If one desires to stop the advance of the piston 2 before the pressure in the pipe 29 has reached that for which the pressureresponsive switch is set, it is merely necessary to open the switch iii, which will "do-energize solenoid83 and stop the advance, and cause the return of the piston 2 in the same manner as with the opening of the circuit of the solenoid '83 by the pressure-responsive switch. To start another advanc of piston 2; one then merely closes switch itl and the piston 2 will again advance because the circuit'is closed at the pressure-responsive switch and then when the pressure again reaches that for which switch I06 is set, the latter will reverse the press,. as above explained.

It will be understood the details 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, as expressed in the appended claims.

I claim as my invention:

1. In a fluid operated motor, a main cylinder,

a pull-back cylinder, a ram element operated in opposite directions by fluid pressures in said cylinders, means for supplying operating fluid under pressure to each cylinder and releasing fluid from the other cylinder, alternately, to cause reciprocation of said element, means responsive to pressurein said main'cylinder for automatically I restricting the escape of fluid from the pull-back cylinder whenever thepressure in the main cyltractsaid element whenever said element reaches a predetermined position in its travel under the action of, the main cylinder.

2. In a fluid operated motor, a gnain cylinder,

that various changes in said cylinders by which said valve connects said source to the main cylinder and the pull-back cylinder to exhaust whenever said valve element is in one position, by which the valve element connects said source to the pull-back cylinder and said main cylinder to exhaust when said valve element is inanother of its positions, and by which it cuts off escape of operating fluid from said pull-back cylinder, prevents delivery of fluid under pressure from said source to said main cylinder and relieves the pressure .on the fluid in the main cylinder when said valve element is in an intermediate position, and means responsive to the pressure in said main cylinder for preventing movement of said valve element beyond said intermediate position into said another position while the pressure in said main cylinder exceeds a predetermined pressure, and for automatically releasing said valve element for movement into said another position as soon as the pressure in said main cylinder falls belo said predetermined pressure.

3. In a fluid operated motor, a main cylinder, a pull-back cylinder, a ram element operated in opposite directions by fluid pressures in said cylinders, a source of operating fluid under pressure, an operating valve having its movable valve= element shiftable into three different positions, connectionsbetween said source, said valve and said cylinders by which said valve connects said source to the main cylinder and the pull-back cylinder to exhaust whenever said valve element is in one position, by which the valve element connects said source to the pull-back cylinder and said main cylinder to exhaust when said valve element is in another of its positions, and by which it cuts off escape of operating fluid from said pull-back cylinder and prevents delivery of fluid under pressure from said source to said main cylinder when said valve element is in intermediate position, and means responsive to the pressure in' said main'cylinder and rendered eifective by said pressure operated element when the latter is away from a selected retracted position, for preventing movement of said valve element from said intermediate position into said another position where it would cause delivery of fluid under pressure to said pull back cylinder, until the pressure in said main cylinder has fallen below a predetermined pressure.

4. In a fluid operated motor, a main cylinder, 'a pull-back cylinder, a ram element operated in opposite directions by fluid pressures in said cylinders, a source of operat' fluid under pressure, a reciprocating operating valve having its movable valve element 'shiftable endwise into three difierent positions, connections between said source, said valve and said cylinders by which said valve connects said source to the main cylinder and the pull-back cylinder to exhaust whenever said valve element is in one position, by which the valve element connects said source to the pull-back cylinder and said main cylinder to exhaust while said valve element is in another of its positions, and by which the valve element cuts off escape of operating fluid from said pullback cylinder, prevents delivery of fluid under pressure from said source to said main cylinder and relieves the pressure on the fluidu'n the main cylinder while said valve element is in an intermediate position, means urging said valve element continuously and yieldingly in a direction from said first to said another position, means for holding said valve element in said first position, means responsive to the pressure in said main cylinder and operable solely when the pressure in said main cylinder exceeds a predetermined pressure for operating said holding means to release said valve element, and means also responsive to the pressure in said main cylinder for preventing movement of said valve element past said intermediate position when released by said holding means until the pressure in said main cylinder has dropped below a predetermined pressure, and then to release said valve element for continued movement into said another position to cause retraction of said ram element.

5. In a fluid operated motor, a main cylinder, a pull-back cylinder, a ram element operated in opposite directions by fluid pressures in said cylinders, a source oioperating fluid under pressure, a reciprocating operating valve'having its movable valve element shiftable into three different positions, connections between said source, said valve and said cylinder by which said valve connects said source to the main cylinder and the pull-back cylinder to exhaust whenever said valve element is in one position, by which the valve element connects said source to the pull-back cylinder and said main cylinder to exhaust while said valve element is in another of its positions, and by which the valve element cuts oif escape of operating fluidfrom said pull-back cylinder and prevents delivery of fluid under pressure from said source to said main cylinder while said valve element is in an intermediate position, means urging said valve element yieldingly in a direction from said first to said another position, latch means for latching said valve element in said first position, means responsive to the pressure in said main cylinder and operable solely when the pressure in said main cylinder exceeds a predetermined pressure for operating said latch to release said valve element, and means also responsive to the pressure in said main cylinder but controlled by said ram element and effective only when the latter is away from a predetermined retracted position, for preventing movement of 'said valve element past said intermediate position when released by said latch until the pressure in said main cylinder has dropped below a predetermined pressure, and then to release I, said valve element for continued movement into said another position to cause retraction of said ram element. I

6. In a fluid operated motor, a mainlcylinder, a pull-back cylinder, a ram element operated in opposite directions by fluid pressures in said cylinders, a source of operating fluid under pressure, a reciprocating operating valve having its' movable valve element shiftable into three different positions, connections between said source, said valve and said cylinders bywvihich said valve connects said-source to the main cylinder and meansfor latching said valve element in saidfirst position, means responsive to the pressure in said main cylinder andoperable solely when the pressure in said main cylinder exceeds a predetermined pressure for operating said latch to release said valve element, means also responsive to the pressure in said main cylinder for preventing movement of said valve elementpast said intermediate position when released by said latch until the pressure in said main cylinder has dropped below a predetermined pressure, and then for releasing said valve element automatically for continued movement into said another position to cause retraction of said ram, element, and manually controlled means operable in one direction to shift said valve element into said one position which is the latched position, and in another direction to release said latch.

7. In a'fluid operated motor, a main cylinder, a pull-back cylinder, a ram element operatedin opposite directions by fluid pressures in said cylinders, a source of operating fluid under pressure, a reciprocating operating valve having its I movable valve element shiftable endwise into three different positions, connections between said source, said valve and said cylinder by which said valve connects said source to themain cylinder and the pull-back cylinder to exhaust when- ,ever said valve element is in one position, by

ment in said first position, means responsive to the pressure in said main cylinder and operable solely when the pressure in said main cylinder exceeds a predetermined ,pressure for operating said latch to release said valve element, means also responsive to the pressure in said main.

cylinder for preventing movement of said valve element past said intermediate position when released by said latch until the pressure in said main cylinder has dropped below a predeterminedpressure, and then to release said valve element for continued movement into said another position to cause retraction of said ram element, a connection from said source to said latch releasing means and having a valve therein to control flow of fluid from said source to said latch releasing means, means operable by said ram element at a selected position in its forward travel under pressure from said main cylinder for operating said valve to direct fluid under pressure from said source directly to said 'latch releasing means and thus cause a retraction of said ram element, and means operabl automatically to release'the operating fluid under pressure delivered to said latch releasing means,

when the flow of operating fluid under pressure -to said latch releasing means is discontinued.

8. In a fluid actuated motor, a main cylinder, a pull-back cylinder, a ram element operated in opposite directions by fluidpressure applied alternately to said cylinders, a source of operating fluid under pressure, a controlling valvehaving a shiftable valve element, connections between said source and said cylindersand including said valve and eflective' when said valve element is in one position for directing operating fluid under pressure to said main cylinder and cylinder, effective for directing operating fluid under. pressure to the pull-back cylinder and releasing fluid from the main cylinder when said valve element is in another position into which it may be moved, and effective to interrupt the delivery of operating fluid under pressure to the main cylinder when the valv element is in an intermediate position, a latch for releasably holding saidvalve element in said first position, means acting on said valve element for urging it from the first position into said another posi-' tion, releasing means operable on said latch to release said valve element and controlled in parallel by the pressure in said main cylinder and the position of said ram element during a forward movement under pressure in said main cylinder, and operable to release said latch whenever the pressure on said main cylinder exceeds a predetermined pressure or the ram element reaches a predetermined and selected position in its movement under pressure fromysaid main cylinder, whichever occurs first, and means also responsive to the pressure in said main cylinder during a forward movement of said ram element for blocking movement of said valve element, when the latter is released, beyond said intermediate position until the pressure on said main cylinder has fallen below a predeterminedlow pressure. I

9. In a fluid actuated motor, a main cylinder, a pull-back cylinder, a ram,element operated in opposite directions by fluid pressure applied alternately to said cylinders, a source of operating fluid under pressure, a controlling valve having a shiftable valve element, connections between said source and said cylinders and including said valve and eflective when said valve element is in one position for directing operating fluid under-pressure to said main cylinder and releasing the operating fluid from the pull back cylinder, eflective for directing operating fluid under pressure to the pull-back cylinder and releasing fluid from the main cylinder when said tion, releasing means operable on said latch to release said valve element and controlled in parallel by the pressure in said main cylinder and the position of said ram element during a, forward movement under'pressure in said main cylinder, and operable, to release said latch whenever the pressure on saidmain cylinder exceeds a predetermined pressure or the ram element reaches a predetermined and selected position in its movement under pressure from said main cylinder, whichever occurs first, means also responsive to the pressure in said main cylinder \during a forward movement of said ram element for forcibly blockingmovement of said valve element, when the latter is released, beyond said intermediate position until the pressure on said main'cylinder has fallen-below a predetermlned manually operated means also operable, when v moved in one direction, on said valve elementto shift it into latched position and when moved inmeans acting on said valve element for urging it another direction for moving said latch to release said valve element.

10. In a fluid actuated motor, means including a hydraulic circuit for actuating said motor and having in said circuit a main controlling valve for controlling the operation of said motor, said valve having a valve element operable into diflerent positions to regulate the activity of said motor, means for moving said element into one position into which it may be moved to cause movement of said motor in one direction, and including a controlling electric circuit, and a snap switch therefor having a switch member operable between oif and on positions, in one of which it causes movement of said element into said one position and in the other of which it causes release of said element, said switch member being resiliently urged into off when moved one side of an intermediate position and into on" position when moved in the other direction past said intermediate position, means yieldingly urging said element out of said one position and into a second position in which it stops further movement of said motor in the same direction, a hydraulic plunger directly responsive to the fluid pressure actuating said motor in said one direction and operable directly and mechanically upon said switch member to forcibly move it past said intermediate position towards said open position and cause release of said element when said pressure so actuating the motor exceeds a. selected, predetermined pressure. I

11. In a fluid operated motor, a main cylinde a pull-back cylinder, a ram element operated in connects said source to the pull-back cylinder and said main cylinder to exhaust when said valve element is in another of its positions, and by which it cuts of! escape of operating fluid from said pull-back cylinder and prevents delivery oi! fluid under pressure from said source to said main cylinderwhen said valve element is in an intermediate position, means yieldingly urging said valve element from said one position through said intermediate position into said another of its positions, means releasably holding said valve element in said one position, and a fluid actuated piston disposed in the path of movement of said valve element and'operable when under pressure to prevent movement of said valve element under the action of said urging means beyond said intermediate position towards said another position, means including a cylinder for said piston and a connection from said piston cylinder to said main cylinder for applying to said piston the pressure of said main cylinder, whereby said valve element will be momentarily held in saidv intermediate position after release, until the pressure in the main cylinder has fallen below a predetermined pressure, and valve wns in said last named ccimection and operable by said ram element to disconnect said piston cylinder from said main. cylinder and connect it to the pullback cylinder when the ram element reaches a predetermined retracted position.

' 12. In a fluid operated motor, a main cylinder, a pull-back cylinder, a ram element operated in opposite directions by fluid pressures in said cylinders, a source of operating fluid under pressure, a main controlling valve having a casing and a movable valve element therein shiftable into three different positions, connections between said source, said valve casing and said cylinders by which said valve element in its movements connects the source to the main cylinder and the pull-back cylinder to exhaust when in one position, connects said source to the pull-back cylinder and-said main cylinder to exhaust when in position, said valve casing having two separate chambers arranged in tandem at one end thereof, and said valve. element extending piston-like into the first one of said chambers, a second piston disposed for endwise sliding movement in the wall between said chambers in th directions oi movement of said valve element, opposing movement of said valve element, and having means limiting its movement in such opposing direction, a connection between'the other of said chambers and said main cylinder by which the pressure on said main cylinder will betransmitted to said other of said chambers and will urge said piston in said opposing direction to limit the movement of said valve element beyond said intermediate position when the pressure on said main cylinder is above a predetermined pressure, a connection from said source to said one chamber for supplying thereto a fluid under pressure to shift said valve element into said one position, a valv in said last named connection for connecting said source to said one chamber or the latter to ex: haust selectively.

13. In a hydraulic motor, a working member, a continuously operating pump, -fluid actuated meansincluding a main cylinder and a pull-back cylinder operable on said member to operate said member toward and from work, a reversing and controlling valve, a connection from said pump to said valve, connections from said valve to each of said cylinders, said valve having therein a valve element operable selectively into three positions, in one end position of whichit connects said pump to the main cylinder and. opens the connection to said pull-back cylinder to allow escape of operating fluid from that cylinder, and in another end position of which it connects said pump to said pull-back cylinder and opens the connectidn to said main cylinder to allow escape of operating fluid from that cylinder, and in an intermediate position of which it-[prevents escape of actuating fluid from said pull-back cylinder,

releases the actuating fluid from said main cylinder and bypasses the fluid received in the valve from the pump, a choke the connection from the pump to the valve for maintaining a predetermined, minimum back pressure on said pump, an auxiliary valve having a, connection therefrom to said pump before said choke, so as to receive fluid under a minimum desired pressure continuously, hydraulic means controlled by said auxiliary valve and operable on said valve element to operate it into said one end position, means for urging said valve element -into said another end position when said elementis released by said hydraulic means, hydraulic means for forcibly moving said valve element'into said intermediate position to stop the actuation of said member,

and means including a controlling valve connecting Said last hydraulic means to said pull-back cylinder for operation by the fluid pressure in that cylinder, said valve being positioned for op -o nected to said fluid actuated means for causing an advance, a return or a stopping of said memher and having a valve element operable into three positions, in one end position of which it causes delivery of actuating fluid to the main cylinder and opens the pull-back cylinderfor escape of actuating fluid, and in another end I position of which it connects the operating fluid to the pull-back cylinder and opens the main cylworking member at pump away from both said valve element into said-other end position,

inder for escape of operating fluid, and in an intermediate position or which it closes the pullback cylinder against escape of actuating fluid, opens said main cylinder for the escape of actuating fluid and bypasses the fluid from said cylinders, means for urging power means connected to said valve element for forcibly actuating the latter into said one position, 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 a desired movement for connecting said pull-back cylinder to said hydraulic device and by the pressure of fluid from the pull-back cylinder operate said valve element into said'intermediate position and hold it in that position after the valve element reaches said intermediate position.

. THOMAS F. STACY.

point in its return