US3881614A - Receivers in public works machines - Google Patents

Receivers in public works machines Download PDF

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Publication number
US3881614A
US3881614A US432880A US43288074A US3881614A US 3881614 A US3881614 A US 3881614A US 432880 A US432880 A US 432880A US 43288074 A US43288074 A US 43288074A US 3881614 A US3881614 A US 3881614A
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United States
Prior art keywords
boom
receiver
fluid
conduit
adjustment
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US432880A
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English (en)
Inventor
Rene F Jacob
Pierre C Fillion
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Sony Corp
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Sony Corp
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Filing date
Publication date
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Publication of US3881614A publication Critical patent/US3881614A/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
    • F15B11/17—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors using two or more pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
    • F16K17/00—Safety valves; Equalising valves, e.g. pressure relief valves
    • F16K17/02—Safety valves; Equalising valves, e.g. pressure relief valves opening on surplus pressure on one side; closing on insufficient pressure on one side
    • F16K17/04—Safety valves; Equalising valves, e.g. pressure relief valves opening on surplus pressure on one side; closing on insufficient pressure on one side spring-loaded
    • F16K17/06—Safety valves; Equalising valves, e.g. pressure relief valves opening on surplus pressure on one side; closing on insufficient pressure on one side spring-loaded with special arrangements for adjusting the opening pressure
    • F16K17/065—Safety valves; Equalising valves, e.g. pressure relief valves opening on surplus pressure on one side; closing on insufficient pressure on one side spring-loaded with special arrangements for adjusting the opening pressure with differential piston
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/20576—Systems with pumps with multiple pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30505—Non-return valves, i.e. check valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/31—Directional control characterised by the positions of the valve element
    • F15B2211/3105—Neutral or centre positions
    • F15B2211/3116—Neutral or centre positions the pump port being open in the centre position, e.g. so-called open centre
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/32—Directional control characterised by the type of actuation
    • F15B2211/321—Directional control characterised by the type of actuation mechanically
    • F15B2211/324—Directional control characterised by the type of actuation mechanically manually, e.g. by using a lever or pedal
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/405—Flow control characterised by the type of flow control means or valve
    • F15B2211/40515—Flow control characterised by the type of flow control means or valve with variable throttles or orifices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/42—Flow control characterised by the type of actuation
    • F15B2211/428—Flow control characterised by the type of actuation actuated by fluid pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/45—Control of bleed-off flow, e.g. control of bypass flow to the return line
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/50—Pressure control
    • F15B2211/505—Pressure control characterised by the type of pressure control means
    • F15B2211/50509—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means
    • F15B2211/50518—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means using pressure relief valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/50—Pressure control
    • F15B2211/52—Pressure control characterised by the type of actuation
    • F15B2211/528—Pressure control characterised by the type of actuation actuated by fluid pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7051—Linear output members
    • F15B2211/7053—Double-acting output members
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/76—Control of force or torque of the output member

Definitions

  • ABSTRACT A public works machine includes a boom articulated Foreign Appncafion i i Data to a frame and means for adjusting the relative posi- Jan 25 973 France 73 02665 tion of the boom with respect to the frame.
  • the adjusting means includes fluid supply means operatively [52] Us Cl 214/138, /486, 91/6 connected between a source of fluid and a receiver or [51] [m 3128 jack; said fluid supply means has a selectively position- [58] Field 762 77!
  • the invention therefore has firstly as an object a device for supplying a receiver with pressurised fluid constituted by:
  • a selection device having at least two positions, which is interposed between at least one of the sources of fluid and the receiver and by means of which this receiver is connected, in a first position of the selection device, only to one of said fluid sources and, in a second position to at least two of these fluid sources,
  • This discharge valve is provided with a device for regulating its adjustment in the course of operation having at least two pre-adjustments.
  • the selection device and the adjustment regulating device are coupled to a common control device, with two positions, one of which corresponds to the communication of the receiver with only one of said fluid sources and to the selection of a determined pressure adjustment and the other of which corresponds to the communication of the receiver with at least two fluid sources and to the selection of another pressure of adjustment of value lower than that of the determined adjustment pressure.
  • the invention also has for an object a public works machine constituted by a boom articulated to the frame and by a member for adjusting the relative position of this boom on this frame, applying the above-mentioned supply device.
  • the receiver of the supply device is then constituted by said adjusting member, whilst the first position of the selection device corresponds to the precise handling ofa load by the boom and to a slow pivoting of said boom, and the second position of this selection device corresponds to a rapid pivoting of said boom.
  • FIG. 1 shows a supply circuit according to the invention
  • FIG. 2 is an axial section through the valve used in the circuit of FIG. I,
  • FIG. 3 is a view ofa hydraulic shovel using the supply device of FIG. I.
  • FIG. 1 shows a receiver, constituted in the present case of a doubleacting jack 1, which comprises two chambers 2 and 3 connected to a distributor valve 4 with manual control 5 by two conduits 6 and 7 respectively.
  • a conduit 8 is connected in shunt to conduit 6 and is connected to a fluid tank 9.
  • an adjusted discharge valve 10 which comprises an elastic return member II and the opening of which is controlled by the pressurised fluid contained in the part of the conduit 8 between the conduit 6 and said valve 10, and regulated by the pressurised fluid contained in the inlet chamber 12.
  • the three positions of the distributor 4 correspond as follows:
  • the second position corresponds again to the obturation, at the level of the distributor 4, of conduits l7 and 24, and to the communication on the one hand of conduit 26 with conduit 7 and on the other hand, of conduit 25 with conduit 6',
  • the third position which is intermediate between the first and second positions, corresponds to the communication of conduit 17 with conduit 24 and to the obturation, at the level of distributor 4, of conduits 6, 7, 25 and 26. It will be noted that a spring 36 is connected to the mobile member of the distributor 4 to ensure that it is maintained in its third position.
  • the two positions of distributor 30 correspond as follows:
  • the second position corresponds to the communication of conduit 34 with conduit 29 and to the obturation at the level of distributor 30, of conduit 35.
  • the two positions of the distributor I9 correspond as follows:
  • the second position corresponds to the second position of the distributor 30, the action of the fluid contained in chamber 21 being preponderant, this time, on that of the elastic return member 20, since said chamher is placed in communication with the delivery of the auxiliary pump 32 by conduits 34, 29 and 28.
  • the distributor I9 communicates the conduit 18 with conduit 22, and obturates at its level conduit 23.
  • the auxiliary source of pressurised fluid constituted by the auxiliary pump 32 has of course various equivalents, such as for example a general conduit for the return of the fluid from the tank in which an adjusted discharge valve has been interposed in order to maintain a low but not a zero pressure, which is sufficient to actuate the control jacks coupled to the distrib utor l9 and to the element for obturating the valve 10.
  • Another equivalent is constituted by an accumulator of pressurised fluid.
  • the use of such equivalents which are, moreover, well known per se, would not cause the device provided therewith to exceed the domain of the present invention.
  • FIG. 2 shows the details of the adjusted valve 10.
  • the body of the valve is constituted of three parts 37a, 37b, 37c screwed on one another in order to allow assembly of the elements disposed in said body.
  • the conduit 8 is shown in the section of part 37a.
  • a valve seating 38 has been screwed into the conduit 8 and possesses a bearing 38a on which the element 39 obturating the valve is in abutment.
  • the obturation element 39 comprises a guide rod 39a on which elastic washers 40 constituting the elastic return member 1 l have been fitted.
  • wash' ers abut on one another and, for one of the end washers, on the obturation element 39, whilst the other end washer is in abutment on a stop 40 screwed in the part 37! of the valve body by means of an intermediate stop 4].
  • a counterscrew 420 blocks the stop 40 correctly screwed in part 37b.
  • the guide rod 39a is mounted to slide in a bore 45 of the intermediate stop 41.
  • a piston 42 is mounted to slide in abore 43 made in the part 37c of the valve body, and may abut on the end 3917 of the rod 390 by means of a pusher 44 mounted to slide in a bore 47.
  • gaskets 46 have been interposed between the parts 37a and 37b of the valve body, between the intermediate stop 41 and the body 32b and between the pusher member 44 and said intermediate stop 41, so that the fluid contained in the cylinder defined by the bore 45 is isolated from piston 42.
  • This piston defines, with the bore 43, the inlet chamber 12, to which conduit 28 is connected.
  • a hydraulic shovel on endless tracks comprises a chassis 48 on which a turret 49 is pivotally mounted.
  • a working equipment 50 equips the shovel and is constituted by a boom articulated on the turret 49 about an axis 52, then an arm 53 articulated on the boom 5] about an axis 54 and by a bucket 55 articulated on the arm 53 about an axis 56.
  • Jacks are coupled between these various elements: jack 57 between bucket 55 and arm 53, jack 58 between arm 53 and boom 51, and jack 1 of FIG. 1, which is coupled between boom SI and turret 49.
  • a first adjust ment of the valve 10 is obtained which is such that the obturator element 39 is repelled out of abutment of the bearing 380, when the effect of the pressure of the fluid contained in the part of the conduit 8 connected to conduit 6 becomes greater than the return stress of the washers 1].
  • the valve communicates the two parts of conduit 8, so that the pressure in the conduit 6 drops to become again lower than the pressure corresponding to the return stress of the washers 11, known as first adjustment pressure.
  • the stress exerted on the piston 42 is also not zero and equal to the product of the pressure given by the section of said piston.
  • the piston 42 then pushes pusher 44 and diposes the end thereof in abutment on the end 39b of the guide rod 39a.
  • a supplementary stress equal to the stress exerted on the piston 42 is thus added to that already exerted by the elastic washers 11 to maintain the obturator element 39 in abutment on the bearing 38a.
  • the pressure of the fluid contained in the part of the conduit 8 connected to the conduit 6 necessary for removing the obturator element 39 from abutment on the bearing 380 will be greater than the first adjustment pressure mentioned hereinabove, and will have to be at least equal to a given threshold, which constitutes a second adjustment pressure.
  • the maximum pressure in the conduit 6 will be greater than the maximum pressure in the same conduit, corresponding to the absence of pressure in conduit 28.
  • An adjusted valve has therefore been made which comprises two adjustments. According to the uses provided, it will either be considered that the normal adjustment is that which corresponds to the lowest ad justment pressure and it will be said that the other adjustment constitutes an over adjustment" of the valve 10, or that on the contrary the normal adjustment is that corresponding to the highest adjustment pressure, and it will then be said that the other adjustment constitutes an under adjustment" of said valve 10.
  • valve 10 has been shown in FIG. l. [t is assumed that distributor 4 is placed in its first position and the functioning obtained by placing the distributor 30 in its first, then in its second position is successively studied.
  • the distributor 30 being in its first position, the distributor 19 is also disposed in its first position, as has been seen previously.
  • the fluid delivered in conduits l7 and 23 by pumps 13 and 14 is conveyed, through conduits 26 and 6, into chamber 2 of jack 1.
  • the fluid contained in chamber 3 is delivered out of said chamber and returns to tank 9 via conduits 7, 25 and 22. If it happens that the external stress acting between the axes of articulation of the cylinder and the piston rod of the jack 1 becomes greater than a given limiting value, the pressure in the chamber 2 will increase until it reaches the value of the adjustment pressure of the valve 10 and will have for its effect momentarily to open said valve to allow the return of the fluid contained in chamber 2 to tank 9.
  • the pressure of the fluid is zero in conduit 28, and consequently likewise in chamber 12, so that the adjustment pressure of the valve 10 is equal to the first ad justment pressure mentioned above.
  • the supply of the chamber 2 of the jack 1 has been effected by placing the outputs of the two pumps l3 and 14 in parallel.
  • the maximum pressure of the fluid contained in the chamber 2 will be greater than what it was when the distributor 30 was in its first position. It will be noted that it has been possible to tolerate an increase in the maximum pressure in the chamber 2 only when the supply output is limited to the value of the delivery output of one of the two pumps 13 and 14, that of pump 14 in the present case. Consequently, the possibility of developping a stress between the axes of articulation of the jack is therefore obtained when the supply output is limited to a given value, which is greater than the maximum stress admissible relative to a supply under an output greater than said given value.
  • the second position of the distributor 4 corresponds to a telescoping movement of the jack 1, which is the reverse of that relative to the first position of said distributor. This movement is known per se and does not necessitate any particular explanation.
  • the supply device of PK]. 1 may therefore also be applied to a crane, instead of the bucket of FIG. 3.
  • the same search for precision and safety of functioning could find the solution in the above-described disposition.
  • a device for supplying a receiver with pressurised fluid constituted by: a fluid receiver, at least two sources of pressurised fluid, a selector device having at least two positions, which is interposed between at least one of the fluid sources and the receiver and by means of which this receiver is connected, in a first position of the selection device, only to one of said fluid sources, and in a second position, to at least two of these fluid sources, and an adjusted discharge valve connected in shunt to the supply conduit of the receiver, wherein this discharge valve is provided with a device for regulating its adjustment in the course of operation having at least two pre-adjustments, and the se lection device and adjustment regulating device are coupled to a common control device with two positions one of which corresponds to the communication of the receiver with only one of said fluid sources and to the selection of a determined adjustment pressure. and the other to the communication of the receiver with at least two fluid sources and to the selection of another adjustment pressure of value lower than that of the determined adjustment pressure.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Operation Control Of Excavators (AREA)
  • Forklifts And Lifting Vehicles (AREA)
US432880A 1973-01-25 1974-01-14 Receivers in public works machines Expired - Lifetime US3881614A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR7302665A FR2215563B1 (enrdf_load_stackoverflow) 1973-01-25 1973-01-25

Publications (1)

Publication Number Publication Date
US3881614A true US3881614A (en) 1975-05-06

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ID=9113846

Family Applications (1)

Application Number Title Priority Date Filing Date
US432880A Expired - Lifetime US3881614A (en) 1973-01-25 1974-01-14 Receivers in public works machines

Country Status (10)

Country Link
US (1) US3881614A (enrdf_load_stackoverflow)
JP (1) JPS578961B2 (enrdf_load_stackoverflow)
AR (1) AR204088A1 (enrdf_load_stackoverflow)
BE (1) BE809845A (enrdf_load_stackoverflow)
BR (1) BR7400396D0 (enrdf_load_stackoverflow)
DE (1) DE2403241A1 (enrdf_load_stackoverflow)
ES (1) ES422602A1 (enrdf_load_stackoverflow)
FR (1) FR2215563B1 (enrdf_load_stackoverflow)
GB (1) GB1427864A (enrdf_load_stackoverflow)
IT (1) IT1004762B (enrdf_load_stackoverflow)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2215700A (en) * 1988-03-16 1989-09-27 Massey Ferguson Mfg Hydraulic circuits

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3037354A (en) * 1961-05-02 1962-06-05 Hydraulic Unit Specialities Co Hydraulic apparatus for variable load systems
US3095990A (en) * 1961-03-30 1963-07-02 Hough Co Frank Transmission controlled loader hydraulic circuit
US3181430A (en) * 1962-07-30 1965-05-04 Caterpillar Tractor Co Relief valve for bucket loader circuits
US3478646A (en) * 1967-12-20 1969-11-18 Tractor Co Relief valve for hydraulic circuits
US3614273A (en) * 1970-01-26 1971-10-19 Clark Equipment Co Mechanism for controlling the boom arms and bucket of a front end loader

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3095990A (en) * 1961-03-30 1963-07-02 Hough Co Frank Transmission controlled loader hydraulic circuit
US3037354A (en) * 1961-05-02 1962-06-05 Hydraulic Unit Specialities Co Hydraulic apparatus for variable load systems
US3181430A (en) * 1962-07-30 1965-05-04 Caterpillar Tractor Co Relief valve for bucket loader circuits
US3478646A (en) * 1967-12-20 1969-11-18 Tractor Co Relief valve for hydraulic circuits
US3614273A (en) * 1970-01-26 1971-10-19 Clark Equipment Co Mechanism for controlling the boom arms and bucket of a front end loader

Also Published As

Publication number Publication date
AR204088A1 (es) 1975-11-20
FR2215563A1 (enrdf_load_stackoverflow) 1974-08-23
GB1427864A (en) 1976-03-10
BR7400396D0 (pt) 1974-12-03
JPS49104080A (enrdf_load_stackoverflow) 1974-10-02
DE2403241A1 (de) 1974-08-01
IT1004762B (it) 1976-07-20
ES422602A1 (es) 1976-04-01
BE809845A (fr) 1974-05-16
FR2215563B1 (enrdf_load_stackoverflow) 1976-09-10
JPS578961B2 (enrdf_load_stackoverflow) 1982-02-19

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