US3771564A - Pilot control valve - Google Patents

Pilot control valve Download PDF

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Publication number
US3771564A
US3771564A US00237255A US3771564DA US3771564A US 3771564 A US3771564 A US 3771564A US 00237255 A US00237255 A US 00237255A US 3771564D A US3771564D A US 3771564DA US 3771564 A US3771564 A US 3771564A
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US
United States
Prior art keywords
pilot
spool
control
valve
orifice
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
Application number
US00237255A
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English (en)
Inventor
D Bianchetta
K Lohbauer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Caterpillar Inc
Original Assignee
Caterpillar Tractor Co
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Caterpillar Tractor Co filed Critical Caterpillar Tractor Co
Application granted granted Critical
Publication of US3771564A publication Critical patent/US3771564A/en
Assigned to CATERPILLAR INC., A CORP. OF DE. reassignment CATERPILLAR INC., A CORP. OF DE. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: CATERPILLAR TRACTOR CO., A CORP. OF CALIF.
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/2004—Control mechanisms, e.g. control levers
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2278—Hydraulic circuits
    • E02F9/2285—Pilot-operated systems
    • 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
    • F15B13/00—Details of servomotor systems ; Valves for servomotor systems
    • F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
    • F15B13/04—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor
    • F15B13/042—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by fluid pressure
    • F15B13/0422—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by fluid pressure with manually-operated pilot valves, e.g. joysticks
    • Y—GENERAL 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
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/8593—Systems
    • Y10T137/86493—Multi-way valve unit
    • Y10T137/86574—Supply and exhaust
    • Y10T137/86582—Pilot-actuated
    • Y10T137/86606—Common to plural valve motor chambers
    • Y—GENERAL 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
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/8593—Systems
    • Y10T137/87169—Supply and exhaust
    • Y10T137/87177—With bypass
    • Y10T137/87185—Controlled by supply or exhaust valve

Definitions

  • 31/36 Flk 31/14 throttling means to modulate the control fluid to ef- [581 Md Search 137/6256 feet an accelerated actuation of the main control valve 137/6253, 596.14, 625.61, 625- d to provide an extended modulation range for effective and precise control of the main control valve [56]
  • the present invention relates to valves and pertains more particularly to a modulating pilot valve.
  • pilot valves for the control or operation of main control valves has been known for some time.
  • pilot control permits remote location of operator stations as well as a reduction of operator effort in the actuation of control valves.
  • Remote control can be inexpensively and advantageously accomplished by pilot control because of the low volumes and pressures required of a pilot system.
  • Hydraulic excavators are particularly in need of ef-- fective pilot control of the hydraulic system. This need is especially acute because of the extremely high pressures and high volumes of fluid normally used or required to operate this system. Pilot control is especially desirable in such implements because of the tremedous expense involved in placing control valves in the near vicinity of the operator compartment to permit operation by typical linkage systems. Such a placement of the control valves would require very expensive conduits and fittings and complex arrangements of the conduit systems.
  • Pilot operation is also desirable in such machines because of the numerous and repetitious control motions which the operator must undergo with normal operation of such machines. Pilot operation can considerably reduce the forces which the operator himself must exert in order to actuate or control the system. This tremendously reduces fatigue and permits the operator to remain alert for a reasonable period of operation of the machine.
  • pilot control modulation does have peculiar problems not found in motor control systems.
  • the force required to move a motor will depend on the load imposed thereon, whereas the force required to move the main control valve will normally be dependent upon its position with respect to its center position.
  • the pilot valve is displaced to position the control valve, whereas the control valve functions to obtain movement of a motor as opposed to a positioning'thereof.
  • Another object of the present invention is to provide a pilot valve that is operative to provide precise control of a control valve.
  • a further object of the present invention is to provide a pilot valve having suitable modulating means which is effective to provide precise and accurate control over a main control valve.
  • Still another object of the present invention is to provide modulating means for a pilot valve which is operative to provide precise increments in control pressure for the actuation of a main control valve.
  • a pilot valve for the actuation of a main control valve is provided with suitable throttling means for modulating the control fluid to provide precise increments in control pressure in order to provide complete and accurate control of the positioning of the main control valve.
  • FIG. 1 is a schematic illustration of a pilot control valve incorporating the present invention
  • FIG. 2 is a graphic illustration of implement speed plotted against control movement
  • FIG. 3 is a graphic illustration of pilot pressure plotted against stem travel.
  • FIG. 1 there is illustrated a preferred embodiment of the present invention incorporated in a pilot valve generally designated by the numeral 10.
  • the illustrated embodiment comprises a housing 12 having a pair of generally parallel cylindrical bores 14 and 14' in which is reciprocally mounted identical control spools 16 and 16'.
  • An inlet passage 18 intersects both bores for supplying pressurized fluid from a pump 20 to be directed by the spools to various outlets.
  • a pair of return passages 22 and 24 positioned to either side of the inlet passage intersect the bores 14 for returning fluid to a sump 26.
  • Pilot control passages 28, 30 and 28 and 30 intersect each of the separate bores for communicating pilot control fluid to a main control valve. Since the two spools are identical, only one will be described in detail, with features of the other identified by the same numeral primed.
  • Each of the spools 16 is provided with annular grooves 32, 34, thereby forming a central land 36.
  • Another pair of grooves 38 and 40 are formed outwardly of the previously mentioned grooves to thereby form lands 42, 44.
  • These grooves, together with a plurality of orifices, to be described, operate to control the flow of fluid from the inlet to the pilot passages and the return passages.
  • Modulating means in the form of a plurality of metering slots and orifices are provided for modulating the control fluid to achieve a unique stepped or multi-stage actuation of the control valve.
  • the metering means comprises a first fixed orifice 46 communicating between annular groove 32 and the outer surface or diameter of land 36 and a second fixed metering orifice 48 communicating between the annular groove 34 and with the outer diameter or surface of land 36.
  • Means in the form of cross slots 50 and 52 are provided to render the orifices 46 and 48 instantaneously effective upon movement of the spool to a predetermined position, corresponding with the passage of the edge of the slot into the supply passage.
  • the variable orifices 54 and 56 run parallel to the above described fixed orifices and are in the form of slots extending from the grooves 32; 34 into the central land 36.
  • the grooves or slots 54, 56 are formed such that timing begins immediately after full effectiveness of the fixed orifices 46, 48 so that communications between the inlet 18 and the outlets 28 and 30 become at once a fixed minimum, and from that minimum, a gradual increase to full opening of the pilot valve.
  • Another pair of metering orifices or passages 58 and 60 are placed in series with the aforementioned metering orifices and communicates between the inside grooves 32, 34 and the outside grooves 38 and 40. These passages provide a pilot drain for the control lines 28 and 30 when the valve 16 is in the neutral position and provides a pressure drop during at least a portion of the time that the inlet orifices provide communication between the inlet 18 and the control passages 28 and 30. These passages 58 and 60 are effective when the outer grooves 38 and 40 are in communication with the outlet passages 22 and 24, but become immediately ineffective as soon as either of these grooves is cut off by movement thereof outside the exhaust passage.
  • This means to prevent rotation of the spool comprises a flat 62 formed in the spool 16, against which is positioned a dowel pin 64 retained in a bore 66 such as by plug or screw 68.
  • Suitable centering means 70 is provided for the spool and may be of any conventional form known in the art, but preferably as illustrated.
  • the centering means however, must be properly timed so as to cooperate with other timing functions of the valve to contribute to the achievement of novel results sought herein. For example, in the preferred arrangement, a first spring centers the spool, then a second spring comes into play at a certain point, such as just before the beginning of the modulating function.
  • the above described pilot valve is operatively connected in the illustrated embodiment to control or operate a main control valve 72.
  • the pilot valve is operatively connected by means of pilot lines 74 and 76 to pressure chambers 78 and 80 where pressure is applied to the end of a control spool 82 to move it to selected control positions.
  • the valve 82 may be of any suitable type, such as that illustrated, wherein it has a central neutral position and is operative upon movement to either side of neutral position to supply pressurized fluid for the operation of a double acting motor in its two respective directions.
  • This main control valve typically has the conventional means of modulation of the control fluid.
  • the valve spool will also typically have the usual dead band to provide proper seal of the valve stem. Dead band may be defined as that movement of the stern which must occur before any valving action occurs.
  • FIG. 2 there is illustrated graphically the percentage of hand lever movement generally required with a conventional valve spool (solid line) in which modulation occurs for approximately only the center one third of its travel range, which also corresponds with full percentage range of implement speed.
  • the conventional valve must be moved from zero up to approximately 33 percent (point A) of its total movement before any implement movement begins.
  • the modulation range then, extends from 33 percent where implement speed begins, up to approximately 66 percent (point B) of movement where implement speed reaches 100 percent. Movement from this point to 100 percent (point C) covers dead band movement which is generally necessary to completely clear the passage across the spool for fully unobstructed flow.
  • pilot valve The use of a pilot control valve is illustrated by the dashed line wherein it is indicated that the front end dead band movement extends only up to approximately 15 percent to 18 percent (point D) with modulation beginning at this point and running to the vicinity of 80 percent to 85 percent (point B) of the total movement.
  • point D 15 percent to 18 percent
  • point B 80 percent to 85 percent
  • the use of the pilot valve in accordance with the present invention has the advantage of reducing the dead band movement of the control lever, while at the same time, extending the modulation range to the vicinity of 65 percent of the lever movement.
  • FIG. 3 there is an illustration of the travel for the pilot spool as compared to the travel of the control spool, both plotted against pilot pressure.
  • the cross slots 50 and 52 (FIG. 1) in the stem communicate by way of the fixed orifices 46 and 48 with grooves 32, 34 to supply pilot pump pressure to passages 28, 30 as the stem is moved away from neutral.
  • the cross slot permits an almost instantaneous effec tiveness of the fixed orifices with a very small movement of stem travel such as 0.031 inches in the illustrated embodiment.
  • the restriction created by the second orifice 58 and 60 as related to the instant effective total area of the first orifice establishes the pilot pressure.
  • the two orifices in series makes possible a precise control of the pilot pressure, allowing a high pilot pressure rise rate from the time the cross slot 50 and 52 begins to open (point F) until this orifice is fully open (point D).
  • This primary input restriction raises the pilot pressure along the dotted line point F to point D (FIG. 3), resulting in sufficient pilot pressure to move the main control valve from zero to point L where modulation of the main control fluid begins.
  • Point D of FIG. 3 corresponds to the beginning of the pilot valve hand lever modulation range of FIG. 2 at approximately 16 percent of hand lever movement.
  • the pilot pressure rise rate between point D and G is low with respect to hand lever movement for providing a small increment of main spool movement in the modulation range between points L and M.
  • Point M corresponds to the end of pilot valve hand lever modulation range corresponding to point E of FIG. 2. From point G to point H of the pilot stem movement (FIG. 3) the second orifice 58 or 60 (FIG. 1) is closed off.
  • pilot valve A more complete understanding of the physical characteristics of the pilot valve can be obtained from the following discussion of the sequence of events occuring as the stems are shifted as the pilot spool moves through the total travel of approximately 0.312 inch corresponding to full displacement.
  • Initial displacement of the pilot spool in either direction from zero to 0.031 inch is dead band necessary to provide sealing and minimizes the pilot system flow requirement and tolerances.
  • the fixed orifice area comprising drilled passages 46 and 48 starts to open at approximately 0.031 inch or point F' and is fully effective by approximately the 0.062 inch point D of stem travel at which time pilot line pressure is approximately 40 PSI. Further movement of the pilot stem to 0.07 inch results in a pilot pressure of approximately 50 PSI and the control spool has moved from zero at point J to approximately 0.22 at point L.
  • the effective area of the first orifice increases as the variable orifices in.
  • slot area 54 or 56 adds to the area of the fixed passage 46 such that pilot pressure increases proportional to stem travel to a maximum of approximately PSI at point G.
  • the increase of pilot pressure between points D and G is at a lower rate than that between points F to D, thus providing'an extended and controlled modulation range.
  • the second fixed orifice or passage 58 closes off at approximately 0.250 (point G) of stem travel and pilot pressure then increases at a rapid rate to the maximum system pressure of approximately 325 PSI (point H).
  • the solid line curve of FIG. 3 indicates the main spool travel for the above described ranges of pilot pressures.
  • the main valve spool which makes up the actuating portion of this particular control system, has a low rate centering spring that requires only 20 PSI actuator pressure to initiate control spool travel from point J, and 21 PSI to reach 0.156 inch of main spool travel to point K. At this point, the main spool contacts the second or modulating spring.
  • a pilot pressure of approximately 50 PSI is required to compress this high rate modulating spring in conjunction with the centering spring to approximately 0.219 inches at point L of main stem travel which is the beginning of the modulating range.
  • the pilot valve provides this pressure at approximately 0.07 inch of pilot stem travel point D which is considerably less than one third of its 0.312 inch total travel range.
  • the main control valve spool requires 175 PSI actuating pressure to reach 0.469 inch o fTr avel at point M which is the end of the modulating range and this pressure is provided at approximately 0.250 inch pilot valve stem travel, as indicated at point G. Shifting of the main control valve spool to 0.688 inch full displacement indicated at point N requires 275 PSI actuating pressure. Actuating pressure increases rapidly to 325 PSI at point H between 0.250 and 0.31 inch pilot stem travel, indicated at point I, which again is considerably less than one third of the 0.312 inch total travel of the pilot spool.
  • the relative position of the pilot stern and main control spool, and pilot pressure to move the main spool for a given position can be determined for any position by simply projecting vertical and horizontal lines between the curves and coordinates of the graph of FIG. 3.
  • a vertical line is drawn from 0.10 inch on the horizontal axis upward until it contacts the broken curve of the pilot spool.
  • a horizontal line is then projected rightward until it contacts the solid curve line of the main spool.
  • a vertical line is then projected downward to the trol valve and reducing the dead band range thereof.
  • pilot pressure is rapidly raised to shift the main control valve through ineffective or dead band positions to a point where modulation begins, at which point the pressure rise is extended gradually over a long range of movement of the pilot valve to provide an extended range of modulation control for the main valve spool. Beyond the modulation range, pilot pressure is again rapidly raised to shift the main control valve rapidly to its fully opened position.
  • a valve system comprising in combination: a main control spool for controlling hydraulic fluid for operation of a motor; a source of pressurized pilot control fluid; a pilot control valve operator to direct said pilot fluid for operation of said main control spool; said pilot control valve comprising modulating means operative for modulated control of said pilot fluid for accelerated movement of said main control spool through a dead band range and a substantially proportional movement through a modulation range with respect to movement of said pilot valve; said modulating means comprising an axial slot extending from a circumferential groove into a land; and, a passage extending from said groove to a cross slot in said spool, said slot and said passage being operative to communicate pilot fluid from a pilot inlet to a pilot control passage.
  • modulating means comprises a fixed orifice and means to provide substantially instantaneous communication with said fixed orifice.
  • modulating means comprises a first fixed orifice operative upon initial movement of said pilot spool to communicate said pilot pressure to said pilot control passage;
  • variable orifice operative in parallel with said first orifice to increase the area of communication of said pilot pressure upon further movement of said spool;

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mining & Mineral Resources (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • Servomotors (AREA)
  • Multiple-Way Valves (AREA)
  • Lifting Devices For Agricultural Implements (AREA)
  • Fluid-Driven Valves (AREA)
US00237255A 1972-03-23 1972-03-23 Pilot control valve Expired - Lifetime US3771564A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US23725572A 1972-03-23 1972-03-23

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US3771564A true US3771564A (en) 1973-11-13

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Application Number Title Priority Date Filing Date
US00237255A Expired - Lifetime US3771564A (en) 1972-03-23 1972-03-23 Pilot control valve

Country Status (10)

Country Link
US (1) US3771564A (de)
JP (1) JPS5911794B2 (de)
BE (1) BE796701A (de)
BR (1) BR7302110D0 (de)
CA (1) CA987570A (de)
DE (1) DE2313300A1 (de)
FR (1) FR2176939B1 (de)
GB (1) GB1422273A (de)
IN (1) IN138717B (de)
IT (1) IT979935B (de)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3995532A (en) * 1974-07-15 1976-12-07 Caterpillar Tractor Co. Proportional control valve with preconditioned inlet modulating relief valve
US4011892A (en) * 1975-03-14 1977-03-15 Marotta Scientific Controls, Inc. Three port non-interflow poppet valve
US4066239A (en) * 1976-03-08 1978-01-03 Caterpillar Tractor Co. Metering slot configuration for a valve spool
US4133510A (en) * 1977-02-09 1979-01-09 Caterpillar Tractor Co. Valve spool positioner
US4199293A (en) * 1977-03-07 1980-04-22 Caterpillar Tractor Co. High pressure implement circuit for loader with slow and fast dump position
US4238112A (en) * 1978-12-22 1980-12-09 Rexnord Inc. Spool spin prevention for hydraulic control valves
US4265273A (en) * 1978-12-07 1981-05-05 Caterpillar Tractor Co. High pressure implement circuit for loader with slow and fast dump position
US4506704A (en) * 1981-12-30 1985-03-26 Shell Oil Company Distributing valve
US4890647A (en) * 1987-11-04 1990-01-02 Robert Bosch Gmbh Hydraulic control valve
US20100300552A1 (en) * 2007-11-14 2010-12-02 Rueb Winfried Hydraulic valve device
DE102004048683B4 (de) * 2004-10-06 2012-12-13 Bosch Rexroth Aktiengesellschaft Ventil
US20160201296A1 (en) * 2016-03-24 2016-07-14 Caterpillar Inc. Hydraulic valve

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3200476A1 (de) * 1982-01-09 1983-07-21 Flutec Fluidtechnische Geräte GmbH, 6603 Sulzbach "ventil zum wahlweisen verbinden eines verbrauchers mit einer druckmittelquelle oder einem vorratsbehaelter"
US4709724A (en) * 1986-01-17 1987-12-01 Commercial Shearing, Inc. Fluid valve structures

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3160174A (en) * 1961-03-28 1964-12-08 Parker Hannifin Corp Remote power shift circuits for spool valves and the like
US3447567A (en) * 1968-02-07 1969-06-03 Koehring Co Pilot governed control valve mechanism

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3160174A (en) * 1961-03-28 1964-12-08 Parker Hannifin Corp Remote power shift circuits for spool valves and the like
US3447567A (en) * 1968-02-07 1969-06-03 Koehring Co Pilot governed control valve mechanism

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3995532A (en) * 1974-07-15 1976-12-07 Caterpillar Tractor Co. Proportional control valve with preconditioned inlet modulating relief valve
US4011892A (en) * 1975-03-14 1977-03-15 Marotta Scientific Controls, Inc. Three port non-interflow poppet valve
US4066239A (en) * 1976-03-08 1978-01-03 Caterpillar Tractor Co. Metering slot configuration for a valve spool
US4133510A (en) * 1977-02-09 1979-01-09 Caterpillar Tractor Co. Valve spool positioner
US4199293A (en) * 1977-03-07 1980-04-22 Caterpillar Tractor Co. High pressure implement circuit for loader with slow and fast dump position
US4265273A (en) * 1978-12-07 1981-05-05 Caterpillar Tractor Co. High pressure implement circuit for loader with slow and fast dump position
US4238112A (en) * 1978-12-22 1980-12-09 Rexnord Inc. Spool spin prevention for hydraulic control valves
US4506704A (en) * 1981-12-30 1985-03-26 Shell Oil Company Distributing valve
US4890647A (en) * 1987-11-04 1990-01-02 Robert Bosch Gmbh Hydraulic control valve
DE102004048683B4 (de) * 2004-10-06 2012-12-13 Bosch Rexroth Aktiengesellschaft Ventil
US20100300552A1 (en) * 2007-11-14 2010-12-02 Rueb Winfried Hydraulic valve device
US8464757B2 (en) * 2007-11-14 2013-06-18 Hydac Filtertechnik Gmbh Hydraulic valve device
US20160201296A1 (en) * 2016-03-24 2016-07-14 Caterpillar Inc. Hydraulic valve

Also Published As

Publication number Publication date
IT979935B (it) 1974-09-30
DE2313300A1 (de) 1973-10-04
CA987570A (en) 1976-04-20
IN138717B (de) 1976-03-20
GB1422273A (en) 1976-01-21
JPS5911794B2 (ja) 1984-03-17
FR2176939A1 (de) 1973-11-02
JPS4913726A (de) 1974-02-06
BR7302110D0 (pt) 1974-06-27
FR2176939B1 (de) 1978-07-13
BE796701A (fr) 1973-09-13

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Legal Events

Date Code Title Description
AS Assignment

Owner name: CATERPILLAR INC., A CORP. OF DE.,ILLINOIS

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:CATERPILLAR TRACTOR CO., A CORP. OF CALIF.;REEL/FRAME:004669/0905

Effective date: 19860515

Owner name: CATERPILLAR INC., 100 N.E. ADAMS STREET, PEORIA, I

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:CATERPILLAR TRACTOR CO., A CORP. OF CALIF.;REEL/FRAME:004669/0905

Effective date: 19860515