US2545246A - Main cylinder release and pump bypass valve - Google Patents

Main cylinder release and pump bypass valve Download PDF

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Publication number
US2545246A
US2545246A US62228245A US2545246A US 2545246 A US2545246 A US 2545246A US 62228245 A US62228245 A US 62228245A US 2545246 A US2545246 A US 2545246A
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fluid
valve
pressure
advancing
conduit
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Warren R Tucker
Howard F Macmillin
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HPM DEV CORP
H-P-M DEVELOPMENT Corp
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HPM DEV CORP
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Priority to US62228245 priority patent/US2545246A/en
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B30PRESSES
    • B30BPRESSES IN GENERAL
    • B30B15/00Details of, or accessories for, presses; Auxiliary measures in connection with pressing
    • B30B15/16Control arrangements for fluid-driven presses
    • B30B15/18Control arrangements for fluid-driven presses controlling the reciprocating motion of the ram
    • B30B15/186Controlling the return movement of the ram, e.g. decompression valves
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00Fluid handling
    • Y10T137/2496Self-proportioning or correlating systems
    • Y10T137/2703Flow rate responsive
    • Y10T137/2705Pressure differential

Description

March 1951 w. R. TUCKER ET AL 2,545,246
' MAIN CYLINDER RELEASE AND PUMP BYPASS VALVE Original Filed March 6, 1944 lf'gl.
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: 224s ll 4/2- 42@-- 35s- 56 48 R (live/w m 3 own/4m ,Jml'w, mfwwmzm Patented Mar. 13, 1951 p Warren E. Iucirer, Dayton, Ohio, and, Howard- F. ltlacMillin,Gambridge, Mass assignors to H-P-M Development Corporation, Wilmington, BeL, a corporatiomof Delaware Original application March- -6, 1944, Serial No, 525,140. Divided and this application. October 1.5,lfi45, SeriallNo'. 622,282
'9" Claims. (Cl. 137-153) V This invention relates by hydraulic systems and, in particular, to control systems i -or hydraulic presses. I
Many classes of work such: as sheet metal drawing, metal forging and other allied pressing operations are best performed by a reciprocatinghydraulic ram. 111 this type of press a. ram is advanced into the work under hydraulic pressure suiilciently-great adequately toperformthe work to be accomplished. Since much of this work requires high forces, the working pressuresencountered are likewise relatively high. The operation of such apress involves reciprocating the ram under both high and low pressures and it is with the. problemof changing from high to low pressures that thepresent-Iinvention is concerned.
It is a ,primary object of the present invention toiprovide a zvalve structure for an operating -sys tem fora hydraulic press wherein the changeover from :high. pressure operation "to low pressure operation is accomplished smoothly, and without shock, and in a minimum of time.
It is another object to accomplish the aforementionedchangeover of, pressures in a minimum .of time-by means-of'controls on the valve.
:Thisapplicationis a division of our co-pending application Serial No. 525,140, .filed -March it, .1944; now abandoned.
These andzother objects will become more apparent from :the following description taken in connection with the attached-drawingsi-n which: Figure 1 is a diagrammatic viewof a hydraulic press having an operating circuit according to this invention, and
Figure 2 isa'portion oijthe circuit of Figure 1 showing a modified structure capable of. accomplishing the objects of this invention.
General arrangement According to this invention, a fluid operable motor which may -'be a downward acting plunger type of motor, has actuating fluid supplied therefto'froln any suitable source of pressure fluid.
The ram is caused to move into engagement with the work and thereafter to perform the work by introducing pressure fluid into the advancing area of the said ram. Upon the accomplishment of the work the ram isreversed by 5 exhausting the advancing area and supplying pressure fluid to the retraction area.
If; during the working stroke of the ram,. a
ture.- A sudden release of the pressure on th advancing area would result in a severe shock to the hydraulic. circuit. and the press. Therefore, it is desirable that the fluid on the advancing area be drawn off at a controlled rate in order to eliminate the aforementioned shock.
According to this invention a valve meansis provided which initially permits the release of pressure fluid from the advancing area at a controlled rate and, subsequently, when'the pressure hasreached a predetermined lower value permits the complete and free evacuation of the remainder of the fluidf'r'om the advancing area.
According to the principaI 'formofthis invention pressure fluid is supplied to theram by a reversible variable delivery pump. During the aforementioned period, that 'is, during the time that the pressureis being released from the advancing area, the discharge of the pump is bypassed by a valve structure operatively associated with the valve structure which is accomplishing the relief of pressure from the advancing area. When the i aforementioned shift-over from controlled. relief of the pressure on the advancing area to the free evacuation thereof takes place the valve which is by-pa'ssing the pump shifts automatically to direct "the delivery from the pump to the retraction area o'f'the ram so asto initiate the retraction stroke of the said. ram.
Structural arrangement -motor structure H which is operable to control the 1 direction and rate-of. delivery of thepump-in accordance with the operationof the-linkage i8 interconnecting theservomotor. with the threearmed lever 19. The three-armed lever .19 is pivoted at- .2B; and inclules addition to. the
arm which en ages. the linkag an arm-21 which is operatively -.conneetecl with the-solenoid '22. by thevcol-lar 2s ofithe rod- 25. rod-;2:5 fur ther comprises the adjustable collar 26-Whichis third armrzs :15; adapted.- to be engaged adapted to be engaged by the arm 21 of the plunger I when the latter is in its fully retracted position.
A surge valve 30 is mounted in the top of the cylinder IE1 and is operable to permit fluid from the surge tank 3| to fill the advancing chamber of the cylinder ||l during the initial advancing stroke of the plunger and, freely to evacuate the said advancing chamber during the retraction stroke of the said plunger. A conduit 32 interconnects the operating cylinder of the surge valve 3|] with the conduit l6 so that the said surge valve is responsive to a predetermined pressure created within the conduit l6 or the retraction chamber of the cylinder l0. Normally, the weight of the plunger maintains a pressure within the retraction chamber of the cylinder ill sufiicient to hold the surge valve 30 in an open position so as to cause the same to permit fluid communication between the tank 3| and the advancing chamber of the cylinder H]. A check valve 33 is arranged within the tank 3| and is connected with the conduit 32 and permits free flow from the tank 3| into the conduit 32 but not vice-versa. This valve is for the purpose of supplying fluid to the pump |4 during the working stroke of the plunger H in a manner which will become more apparent hereinafter.
Connected to the retraction area by the conduit 32 and, to the advancing area by the conduit 34 is a valve generally indicated at 35. The valve 35 comprises a casing 36 having a pair of bores 31 and 38 therein. Reciprocably mounted within the bore 31 is a valve member 39 which is continuously urged to the right by a spring 46 and reciprocably mounted within the bore 38 is a valve member 4| which is continuously urged to the right by a spring member 42. Each of the reciprocable members 39 and 4| comprises a spool shaped element adapted to effect fluid communication between various conduits and ports in the valve. The member 39 is adapted to be moved to the left against the thrust of the spring 40 by pressure fluid delivered to the right hand end of the member 39 by the conduit 32. When the valve member 39 moves to the left under the in- 'fluence of pressure delivered thereto from the retraction area by the conduit 32, fluid communi-- cation is established between the conduits 45 and 46, the former of these conduits being connected with the advancing area. of the member 39 is also efiective to establish fluidcommunication between the conduit 32 and the passage 4! within the casing 36. The passage 41 terminates within the bore 38 at a point midway between the enlarged end portions of the member 4|. Pressure fluid from the advancing area is conducted through the conduit 44 to the right hand end of the member 4| and, when sufflciently great, urges the said member leftwardly against the thrust of the spring 42 so as to establish fluid communication between the passage 41 and the outlet passage 48, which latter opens into the reservoir or tank 3|.
The conduit 46 communicates with the reservoir 3| through an adjustable throttling valve 41 and is also connected with a two-way valve generally indicated at by means of the conduit 49.
The valve 50 comprises a casing 5| within which is reciprocable avalve member 52 which has atached thereto, or in abutting relationship therewith, a pair of operating plungers. The plunger at the right end serves continuously to urge the member 52 to the left by means of the spring 53 and, the plunger at the left of the valve Movement to the left 4 is effective to urge the member 52 to the right against the thrust of the spring 53 in response to pressure conveyed to the said plunger from the advancing area by the conduits 44, 45 and 54. The arrangement of the valve 56 is such that the Spring 53 normally moves the member 52 into position to establish fluid communication between the conduit 49 and 55, the latter of which communicates with the reservoir 3|. In response to 'a predetermined pressure within the advancing chamber of the cylinder |ll, higher than that required to shift the valve member 4|, the valve member 52 is urged to the right against the thrust of the sprin 53 thereby to interrupt the communication between the conduits 49 and 55.
Referring now to Figure 2, there is shown an alternative structure for obtaining the result accomplished by the structure of Figure 1. In Figure 2 the valve generally indicated 35a is substantially identical with the valve generally indicated at 35 in Figure 1 and similar parts are similarly numbered with the addition of an a. The valve 35a is connected into a press circuit in a manner identical with the manner in which valve 35 is connected in Figure 1, with the exception that the valve 56 is eliminated. Instead, the conduit 46a communicates directly with the reservoir.
In Figure 2 the valve includes, in addition to the structure described in connection with valve 35 in Figure 1, an additional piston-cylinder construction generally-indicated at 6B. The pistoncylinder 60 is attached to the casing 36a of the valve in alignment with the reciprocable member 39a. The cylinder of the unit 66 comprises a shouldered bore 6| within which is reciprocable a piston 62. The piston 62 is urged leftwardly by a spring 63 and is adapted to be urged to the right by pressure fluid conducted thereto by a conduit 64 which is in continuous hydraulic communication with the conduit 45a and, hence, with the advancing chamber of the associated hydraulic motor. The piston 62 is centrally bored and threaded to receive a screw 65 which is locked in any desired position of adjustment by a lock nut 66. The screw 65 extends completely through the" piston 62 and extends rightwardly therefrom through an aperture in the bottom of the unit 60 so as to be in position to abut the tail rod 61 of the member 39a when the latter is in a predetermined position.
The arrangement is such that, when pressure fluid from the retraction chamber of the hydraulic motor is conducted by conduit 32a to the right hand end of the member 390. and moves the latter to the left, the screw 65 abuts the rod 61 before the said movement is completed. Specifically, the member 39:; is stopped at a point which will provide a predetermined restriction between the conduits 45a and 46a while permitting free fluid communication between the conduit 32a and the passage 4101.. It will be apparent that the amount of restriction created by the member 39a may be varied by adjusting the screw 65 so as to vary the position at which the member 3911 is stopped.
With the valve in the position indicated in Figure 2, the delivery from the pump is by-passed through conduit 32a, the passage 41a and the conduit 48a to the reservoir. At the same time the pressure within the advancing area of the associated motor is decreased at a controlled rate through the conduit 45a and the conduit 46a to the reservoir. So long as the pressure within the advancing chamber and the conduit 45a is above theipiiedeter'minedlevel, th'e'fplston 62 maintained .its rightward; position by thepressure conducted thereto through-the conduit 64' from the conduit 45a. When the pressurewithin the advancing chamber decreased to a' predetermined level," the thrust "of the "spring '63 and the thrust of th'e 'right hand end of'the member 33a, becomes 'efiective to move "them'emb'er 39a "and the piston "62 to the left. "The"further movement tothe left of the member 3911' is 'effectiveto eliminate the restriction between the conduits 45a and 46a and the: flow o'fjpressure' fluid from the advancing chamber of theihydrauliomotor is, therefore, unrestricted "and, the "pressure therein is reduced to substantially that of thertmcspheric pressure Tof thesesenmi r.
"simultaneouslyiwiththe finalniovementtothe 1 left of the "member "39d; andc'ompleteTelease' of pressure Within the advancing "chamber ftl'ie pressure standing on 'the"right'-hand end of the meinbei' 41a is released and the "spring-fla becomes effective to move the said memberto the right thereby interrupting .fiui'dpommunicati'on between theypassage 47a and the conduit "48a. The delivery o'f'the pump which has been bypassed through the a'forementionedfiuid passage is now directed to the retraction'a'rea 'of'the-r'e- 'ciprocable plunger fiand "the latter commences its retraction stroke.
The operation of the circuitbi Fi u f 3 identical with that of Figure "2 except that "the 'final release of pressure from "the advancing chamber is accomplished by theactuation of the conduit 32 thereby tofper'mit thefree evacuation of the fluid within the advancing chamberduring the retraction stroke of theplungerl i.
Operation In operation, an advancing stroke of the plunger may be instituted by energizing the solenoid 22 wherebythe'lever 4-9 is rotated in a clock -wise -direction and, through -.-the --linkage l8 and the servomotorllplaces thepump inypo- .sition to deliver fluid tout-he advancing chamber through the-conduit i5. During the-advancing movement of the plunger the pump withdraws &
fluid from theretraction -ohamber through-the conduit It so as to. permit the, plunger-ii-to move rapidly downwardly by its own weight .towork engaging position. During this initial portion of the advancing stroke, the surge valve-3i! is held open bythe pressure in-the retraction chamber or by the suction within thesadvancing chamber thereby permitting fluid to flow into the advancing chamber from the reservoirs-I.
When the plunger engagesthe wcrkethe surge valve closes andpressure is built-up within the advancing chamber During the workingportion of the advancing stroke the .pump draws fluid from the reservoir through the'check valve 33 in order to compensate forthe differencefin displacement between the advancing and .-retrac tion chambers.
Following the accomplishment of the work to be done, the retraction stroke of the plunger is instituted by de-energizing the solenoid 122 in thetank or reservoir.
surge valve 30 to thereservoir. "stroke or theplunger continues until the arm '21 "attached "therewith engages the collar 26 and lifts the latter together with the rod 25 and the anyponvenientmanner such-"asbya switch op-= "erated" manually, by the pressure "within the adtion counter-clockwise from'its 'Figure 1 position.
It will be noted that the working pressure established within the advancing chamber during the working stroke of'theplunger was elfective to""shift-'thevalvemember llto the left-and the valve member 52 to the right but that thish'ad no efiecton' the operation or the'circuit since the fluid connections established by the valve members areeffective only in cooperation with fluid connections established by thevalve member 39.
However, whe'n'the pump is shiftedto 'deliver into conduit t6, the pressure developed within the retraction chamber and also in conduits iii and 32 will'shift the'valve member 39 "to theleft. in the advancing ehamber remains relatively 'A-t' the same'ti-me the pressure withhigh because-the fluid therein is highly pressurized-and --themechanical parts of the press are stressed andghence, the valve members fil and 52- are maintained in their left and right 'hand positions respectively.
' With the v-alve members 39: and 4! in their left hand position-andithe valve member '52 in its right han'd pes'itien, I the pump 4 is bypassed through-conduits it and 32 passage stand :con- -du-it-48 to the reservoir. Optionally, the conduit 48 may comprise a ch'oke.valvei forithe.: purpose o'f =maintaining :a ii -predetermined pressure -'wi-thin the aforementioned channel. Simultaneous with thebypassingof the pump the pressure-within the advancing chamber is released through conduits [-5, 14, 15, Afi and valves? to The valve t? is preferably adJuste'd to permit fluid to flow therethrough as rapidly as-ispossible without releasing the pressure from theadvancing chamber solsuddenlyas to createa shock within thelhydraulic circuit.
When .the pressure within the advancing chamber has been :reduced to a predetermined valuathe spring .53 becomes effective to move the valvememberEZ to the leftthereby to permit the sudden releaseiof the remaining .pressure withinathe advancing chamber. .However, the
pressure in theadvancing chamber being relaber4l to move to the right thereby directing the delivery of the pump'to the retraction chamber and creating a pressure therein which is conducted through the conduit 32 to the surge valve to 'open the latter.
The retraction stroke of the plungernowcommences with the pump delivering into the re- "traction chamber of the cylinder fllwhile the advancing chamber is exhausted through the The retraction co1lar24 so as to rotate the three-armed lever the"lin'kage 18, to ac'tuatethe servomotor "1'1 of the pump to move the latter into substantially no delivery position thereby to halt the retraction stroke of the plunger.
It will be apparent that the time required for the relief of pressure within the advancing chamber and the institution oi the retraction stroke is materially reduced through the use of this inventi-on and, accordingly, the hydraulic press associated withthe circuit is capable of preforming work at an increased rate.
It will be understood that the particular structure shown and described in connection with our invention is merely exemplary and does not represent the only use to which thi invention may be put.
Accordingly, we do not wish to be limited by the specific structure shown in the drawings and described in the specification but desire to comprehend such modifications in structure and arrangement as may be considered to come within the spirit of the appended claims.
We claim:
1. In a valve for releasing the pressure from a first body of fluid while simultaneously by-passing a second body of fluid the combination of; a first valve member movable in response to a predetermined pressure of said second body for establishing fluid communication between said first body and exhaust; a second valve member movable in response to a predetermined pressure on said first body to establish fluid communication between said second body and exhaust; and fluidpressure-responsive means communicating with said first body and responsive to a predetermined pressure thereon for restricting the flow of fluid from said first body to exhaust.
2. A valve comprising a casing having a first bore and a second bore therein; a fluid inlet and a fluid outlet in each of said bores; a control member reciprocable in each of said bores for controlling communication between the inlet and outlet of each of said bores; fluid pressure responsive means associated with each of said control members and operable in response to a predetermined pressure to move the associated control member into position to establish fluid connection. between the associated inlet and outlet; means hydraulically connecting the fluid inlet of each bore with the fluid pressure responsive means associated with the other of said bores; and other fluid-pressure-responsive means hydraulically connected with one of said inlets and operable in response to a predetermined pressure therein to control the rate of discharge from one of said outlets.
3. In a valve for releasing the pressure from a first body of fluid while simultaneousl by-passin a second body of fluid the combination of; a first valve member movable in response to a predetermined pressure of said second body for establishing fluid communication between said first body and exhaust; a second valve member movable in response to a predetermined pressure on said first body to establish fluid communication between said second body and exhaust; stop means engageable with said first valve member to limit movement thereof to a position providing for restricted flow of fluid from said first body to exhaust; and fluid pressure responsive means associated with said stop means for maintaining said stop means in engagementwith said first valve member in response to a predetermined pressure within said first body.
4. A valve comprising a casing having a bore with an inlet port and outlet port therein; a con- 8 tro1 member reciprocable in said bore. between .afirst end position for disconnecting said ports and a second end position for connecting said ports; yielding means for continuously urging said member toward said first position; fluid operable means for urging said member toward said .second position; stop means adapted to engage and stop said member between said first and second end positions; yielding means for urging said stop means into ineffective position; fluid operable means for rendering said stop means effective and hydraulically connected with said in- I let port; and means for icy-passing at least a portion of the fluid supplied to said first mentioned fluid operable means.
5. In a valve comprising a casing having a bore .with-an inlet and an outlet port therein; a control member-reciprocable within said bore between a first end position for disconnectin said ports and a second end position for connecting said ports; fluid pressure responsive means operable in response to a predetermined pressure for moving said member from said first end position into said second end position; stop means associated with said member for halting the same intermediate said first and second positions; fluid pressure responsive means hydraulically connected with said inlet port and associated with said stop means and operable to render the latter effective in response to a predetermined pressure; and means for by-passing at least a portion of the fluid supply to said first mentioned fluid pressure responsive means.
6. A valve comprising a casing having a bore with an inlet and an outlet port therein; a control member reciprocable within said bore between a first position for interrupting fiuid communication between said ports into a second position for establishing fluid communication between said ports; fluid pressure responsive means for moving said member from said first position into said second position; stop means for halting said member intermediate said first and second positions; means responsive to a predetermined pressure at said inlet port for rendering efiective said stop means; and means automatically operable for by-passing at least a portion of the fluid supplied to said fluid pressure responsive means.
7. A valve comprising a casing having a bore with an inlet and an outlet port therein; a control member movable in said bore between a first position for interrupting fluid communication between said ports and a second position for establishing fluid communication between said ports; means for moving said control member from said first position into said second position; stop means for halting said member intermediate said first and second positions; and means responsive to a predetermined pressure at said inlet port for rendering effective said stop means.
8. A valve comprising a casing having a bore with an inlet and an outlet port therein; a control member reciprocable within said bore between a first position for interrupting fluid communication between said ports and a second position for establishing substantially free fluid communcation between said ports; fluid pressure responsive means for moving said member from said first position into said second position; stop means for halting said member intermediate said first and second positions for establishing a restricted fluid communication between said ports; and means responsive to a predetermined pressure at said inlet port for rendering effective said stop means.
9. A valve comprising a casing having a bore with an inlet port and outlet port therein; a control member reciprocable in said bore between a first end position for disconnecting said ports and a second end position for connecting said ports; yielding means for continuously urging said member toward said first position; fluid operable means for urgin said member toward said second position; adjustable stop means movable into a first position for halting said control member between said first and second end positions and into a second position for permittin said control member to move into said second end position; fluid operable means associated with said stop means and hydraulically connected with said inlet port for moving said stop means into said first position; yielding means associated with said stop means for urging the same into said second position; and fluid pressure responsive means hydraulically connected with said inlet port and operable to by-pass at least a portion of the fluid supplied to said fluid operable means associated with said control member.
W'ARREN R. TUCKER. HOWARD F. MACMILLIN.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS
US62228245 1944-03-06 1945-10-15 Main cylinder release and pump bypass valve Expired - Lifetime US2545246A (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2687739A (en) * 1950-10-05 1954-08-31 Shelburne Augustine Control mechanism for spraying apparatus
US2803266A (en) * 1951-02-06 1957-08-20 Electraulic Presses Ltd Fluid motor valve with exhaust surge prevention control
US2993393A (en) * 1957-05-29 1961-07-25 Kendall Edgar Homer Edge roll control for wheel rolling mills
EP1279488A1 (en) * 2000-03-06 2003-01-29 Amada Company, Ltd. Device and method for controlling stop of hydraulic press and device and method for detecting trouble of speed selector valve

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US853693A (en) * 1906-06-22 1907-05-14 Frank F Healey Pressure-regulating valve.
US894102A (en) * 1907-03-25 1908-07-21 John G Banjock Automatic valve.
US1956758A (en) * 1931-10-19 1934-05-01 Hydraulic Press Mfg Co Hydraulic press operating circuits
US2268205A (en) * 1939-07-24 1941-12-30 Hydraulic Dev Corp Inc Main cylinder release and pump bypass valve
US2316944A (en) * 1941-12-22 1943-04-20 Hydraulic Dev Corp Inc Valve
US2335809A (en) * 1938-04-26 1943-11-30 French Oil Mill Machinery Fluid operated motor
US2362864A (en) * 1941-03-07 1944-11-14 Towler John Maurice Control valve for hydraulic presses
US2366382A (en) * 1939-03-28 1945-01-02 Douglas Aircraft Co Inc Control surface boost device and gust dampener

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US853693A (en) * 1906-06-22 1907-05-14 Frank F Healey Pressure-regulating valve.
US894102A (en) * 1907-03-25 1908-07-21 John G Banjock Automatic valve.
US1956758A (en) * 1931-10-19 1934-05-01 Hydraulic Press Mfg Co Hydraulic press operating circuits
US2335809A (en) * 1938-04-26 1943-11-30 French Oil Mill Machinery Fluid operated motor
US2366382A (en) * 1939-03-28 1945-01-02 Douglas Aircraft Co Inc Control surface boost device and gust dampener
US2268205A (en) * 1939-07-24 1941-12-30 Hydraulic Dev Corp Inc Main cylinder release and pump bypass valve
US2362864A (en) * 1941-03-07 1944-11-14 Towler John Maurice Control valve for hydraulic presses
US2316944A (en) * 1941-12-22 1943-04-20 Hydraulic Dev Corp Inc Valve

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2687739A (en) * 1950-10-05 1954-08-31 Shelburne Augustine Control mechanism for spraying apparatus
US2803266A (en) * 1951-02-06 1957-08-20 Electraulic Presses Ltd Fluid motor valve with exhaust surge prevention control
US2993393A (en) * 1957-05-29 1961-07-25 Kendall Edgar Homer Edge roll control for wheel rolling mills
EP1279488A1 (en) * 2000-03-06 2003-01-29 Amada Company, Ltd. Device and method for controlling stop of hydraulic press and device and method for detecting trouble of speed selector valve
EP1279488A4 (en) * 2000-03-06 2005-03-30 Amada Co Ltd Device and method for controlling stop of hydraulic press and device and method for detecting trouble of speed selector valve
US6920821B2 (en) 2000-03-06 2005-07-26 Amada Company, Limited Device and method for controlling stop of hydraulic press and device and method for detecting trouble of speed selector valve

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