US3595343A - Control system for lift trucks - Google Patents

Control system for lift trucks Download PDF

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Publication number
US3595343A
US3595343A US791354*A US3595343DA US3595343A US 3595343 A US3595343 A US 3595343A US 3595343D A US3595343D A US 3595343DA US 3595343 A US3595343 A US 3595343A
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United States
Prior art keywords
control
engine
lift
truck
speed
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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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US791354*A
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English (en)
Inventor
William A Williamson
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Doosan Bobcat North America Inc
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Clark Equipment Co
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66F—HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD
    • B66F9/00—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes
    • B66F9/06—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes movable, with their loads, on wheels or the like, e.g. fork-lift trucks
    • B66F9/075—Constructional features or details
    • B66F9/20—Means for actuating or controlling masts, platforms, or forks
    • B66F9/22—Hydraulic devices or systems
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66F—HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD
    • B66F9/00—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes
    • B66F9/06—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes movable, with their loads, on wheels or the like, e.g. fork-lift trucks
    • B66F9/075—Constructional features or details
    • B66F9/07572—Propulsion arrangements

Definitions

  • ATTORNEYS In maneuvering a lift truck prior to and during the operation of lifting a load as well as during the placing of the load on the lift fork members, it is quite generally the situation that the forward movement of the vehicle, or rearward as the case may be, is a very slow movement while the rate of the lift of the load-carrying member is desired to be relatively fast. It is necessary in order to accomplish the above outlined results, that special precautions be taken by the operator to cause the truck to move very slowly. This is quite commonly accomplished either by special so-called inching devices or by the well known expedient of slipping the clutch," both of which result in rapid clutch wear. Also, this type of maneuver under the conditions outlined above is often difficult.
  • the conventional type of lift unit is operated by hydraulic means which operates by a pump driven by the vehicle engine. Therefore, increase in rate of lift requires an increase in engine speed which is difficult to obtain while accomplishing at the same time, the slow movement of the truck.
  • the vehicle control could be set to maintain a relatively low forward speed while the engine of the lift truck vehicle could be accelerated at will to a higher speed needed for the most effective lift.
  • SUMMARY Hydraulic system control elements in combination with hydrostatic drive for moving the truck forward as well as providing, by hydraulics, a load lift control and a governor type of vehicle control.
  • the hydrostatic drive makes possible a control over vehicle speed separate from the engine speed, and the accelerator control is made to control the speed of the truck, within limits, independent of engine speed changes, thus making possible a variation in engine speed for the purpose of driving the lift pump fast enough for fast lift while the truck vehicle is operating at a slow speed.
  • FIG. I is a side view of a type of vehicle known as a lift truck on which the present control system may be used.
  • FIG. 2 is a showing ofthe control system with the several elements, both hydraulic and mechanical in diagrammatic form and disclosing their relationship.
  • FIG. 3 is a diagram showing the hydrostatic drive from the engine to the vehicle wheels with the elements thereof in diagrammatic form, together with a showing of the engine and the several pumps driven thereby forming a part of the control system. Certain relief valves and cross check valves being omitted as not pertinent to the description.
  • FIG. 1 shows an industrial lift truck 102 in which the control system shown in FIG. 2 is used.
  • Lift truck 102 is supported on forward drive wheels 106 and rear wheels I08.
  • a lift upright 110 mounted at the forward end of the lift truck is a lift upright 110 which includes a vertically movable carriage 1I2 which carries a pair of forwardly extending fork arms 114 which support the load to be carried.
  • the carriage I12 is connected to a vertically directed fluid motor, so-callcd lift cylinder 116, location of which is designated adjacent the carriage 112 in FIG. I and which is shown in the diagram of FIG. 2.
  • Certain of the elements of the control system shown diagrammatically in FIG. 2 are located in FIG.
  • FIG. 1 by a general designation of location by a lead line from the corresponding reference numeral. It is understood that all of the elements of the control system shown in FIGS. 2 and 3 are present on the lift truck of FIG. 1, with only representation elements being indicated as to their general location in FIG. 1.
  • the engine-driven fixed-displacement pump numeral 1 is connected by line 2 to deliver oil under pressure over a variable orifice 5 formed by a spool 5a, movable in a valve body 4.
  • Spool 5a is movable longitudinally of the valve body 4 by accelerator pedal 15 connected as shown in FIG. 2 so that variation in the position of the spool 5a varies the orifice 5 to control restriction in flow from line 2 as later described.
  • variable orifice spool 5a and a flow regulator spool 3 are both housed in housing 4 and are in alignment with the connection to the accelerator pedal 15.
  • a spring 5b is provided between orifice spool 5a and the top of flow regulator spool 3 and another spring 5c is on the bottom side of regulator spool 3.
  • a spring-loaded hydraulic cylinder 9 is connected to a hydrostatic transmission stem-type servocontrol valve 10 and hydraulically connected to a flow regulator 3 by a line 11, and regulator 3 in turn is connected to line 2 thru line 16. This is a connection to actuate the hydrostatic transmission shown in FIG. 3, with further functions to be described hereinafter.
  • Another hydraulic cylinder 12 is connected by suitable linkage to the carburetor butterfly valve 13. This hydraulic cylinder is hydraulically connected to be actuated from line 2 by line 14.
  • the drive of the vehicle wheels departs from the conventional geared transmission structure most commonly used, by providing a hydrostatic drive shown diagrammatically in FIG. 3.
  • the hook up includes a variable displacement hydrostatic pump 27 driven by vehicle engine 30, which by the hydraulic connections and hydrostatic assembly 113 shown in FIG. 3 drives a hydrostatic motor 118 adjacent the drive wheels to propel the axle which drives the ground wheels 106 of the truck. Between line 17 and motor 118, is a manually operated directional control valve 119.
  • the vehicle engine 30 also drives another pump, a fixed displacement so-called lift pump 26 (FIG. 3). This pump is for the purpose of actuating the lift mechanism of the lift truck and is a apart of the lift truck arrangement.
  • the engine 30 of the truck drives still another fixed displacement pump, the previously mentioned pump 1, which is shown in the diagram of FIG. 2, as well as FIG. 3.
  • a hydrostatic valve servo l0 actuates a so-called swash plate control, known in the art, for the hydro static pump 27 and that this servo mechanism operates the swash plate to change the displacement of the pump and thereby changes the speed of the vehicle wheels. It therefore follows that the total vehicle speed will result from the combination of engine speed and pump displacement.
  • variable speed engine portion of the circuit operates as follows: When it is desired to increase the engine speed, the operator presses down on the accelerator any desired amount.
  • the variable orifice 5 is opened a corresponding amount which allows the pressure in line 2 to decrease. This pressure decrease is reflected in line 14 and in cylinder 12 such that the spring in the base of the cylinder causes the piston to move from right to left. This movement opens the carburetor butterfly valve 13 which causes the engine to increase in speed.
  • the volume of oil delivered by fixed displacement pump 1 also increases. This increased volume is delivered across variable orifice 5 and results in an increasing pressure in line 2, line 14 and cylinder 12. This in turn tends to cause the butterfly valve 13 to close.
  • Line 16 is connected to line 2 and, therefore,, sees any pressure fluctuations that occur in line 2.
  • the best way to explain the reason for this is to assign some values to these pressures. Assuming that cylinder 12 operates over a pressure range of to 50 p.s.i. That is, at 100 p.s.i. the cylinder is collapsed and the engine is idling at 500 r.p.m. At 50 p.s.i the cylinder is extended and the engine is running at 2200 rpm. Now let us assume that cylinder 9 operates over a pressure range of from 20 p.s.i. to 4 p.s.i. Under normal operating conditions cylinder 9 will always see more pressure than is required to fully extend it. Therefore, its movement must be regulated by a volume change.
  • valve spool 8 and control 22 are constructed to control both of these functions.
  • the best way to describe this action is to take an example.
  • the driver wants to move the truck at a very low rate of speed while elevating the load at a very high rate of speed.
  • the driver sets his truck speed by movement of accelerator pedal 15 in a small amount. This causes a small pressure drop in line 2, moves flow regulator spool 3 and causes the operations hereinbefore described to take place, thus setting a low truck speed rate.
  • valve handle 22 To lift the load, the operator moves valve handle 22 (HO. 2) from right to left. This causes pressurized oil from line 23 to communicate with line 24 which is connected to the lift cylinder. This much of the spool 8 is a conventional configuration and permits a certain amount of throttling of the oil. in moving spool 8, the movement of control handle 22 also uncovers the port which is connected to line 7. This allows oil to bleed off to tank and causes the pressure in line 2 to drop. The pressure drop in line 2 is, as described earlier, accompanied by a corresponding increase in carburetor butterfly 13 opening and consequently an increase in engine speed. This increase in engine speed is compensated for in the truck speed by orifice 18 in the return line of the hydrostatic drive (see above discussion).
  • Valve spool 8 was designed to progressively uncover the opening from line 7 thus permitting throttling of the oil and consequently progressive decrease in pressure in line 2. This permits selective increase of engine speed to whatever the operator desires in order to accomplish a satisfactory rate of lift without materially increasing the speed of the truck.
  • Actuation of the lift control lever 22 and spool 8 will cause the engine speed to increase in proportion to the amount of lever 22 movement, thereby providing maximum lift rate capabilities.
  • any change in engine speed will be automatically compensated for by a change in pump displacement, and change in associated drive ratio of the vehicle hydrostatic transmission, thereby leaving the vehicle speed unchanged.
  • lift and lift truck as used herein are considered as applicable to lift truck mechanisms wherein a lift function is accomplished such as dump trucks, tractor scrapers, paving machines, all of which have enginedriven ground-wheel drives and auxiliary power devices which have independently variable control requirements to which the structure disclosed herein could be adapted.
  • a control system for a lift truck said truck having an engine, an acceleration control member, a lift control mechanism, a fuel flow control, and a variable ratio hydrostatic drive for the truck from said engine to propel the truck for ground drive;
  • control members responsive to flow rate in a hydraulic line of said hydrostatic drive
  • connections from said control member constructed and arranged to vary the effective drive ratio thru said hydrostatic drive from said engine to allow said engine to increase in speed as called for by said lift control mechanism while maintaining relatively low ground speed of said truck as called for by said acceleration control member.
  • a carburetor valve controlling fuel flow to said engine
  • connections from said control member constructed and arranged to vary the effective drive ratio thru said hydrostatic drive from said engine to allow said engine to increase in speed as called for by said lift control while maintaining relatively low ground speed of said truck, comprise:
  • a manually actuated control valve spool member for control and actuation of said lift mechanism
  • control valve spool member constructed and arranged to bleed hydraulic fluid from said main delivery line thru auxiliary delivery line on actuation of said control valve spool causing speed up of the engine to actuate said lift and load support member at a relatively fast rate in proportion to movement of said valve spool member.
  • a control system for a lift truck said truck having an engine, an acceleration control member, a fuel control, lift control mechanism, and a variable ratio hydrostatic drive for the truck from said engine to propel the truck for ground drive:
  • control system comprising:
  • hydraulic actuated means controlled by said lift control mechanism and said acceleration control member for varying the hydrostatic drive ratio between the engine and the wheels of said truck to allow said increase in speed of said engine to increase the lift rate of said lift mechanism while continuing to drive said truck at speeds called for by acceleration control member.
  • a manually actuated control valve member for controlling actuation of said fluid pressure operated lift mechanism
  • control valve member including means to bypass fluid from said further hydraulic control mechanism thereby to compensate for variations in at least one of said other components on actuation of said control valve member for control of the lift rate of said lift mechanism;
  • a carburetor valve controlling fuel flow to said engine
  • an auxiliary delivery line connecting said main delivery line with said resiliently biased hydraulic cylinder and piston at a position between said engine-driven pump and said variable orifice thereby supplying fluid under pressure to said piston in a direction to close said carburetor valve against the resilient bias;
  • a manually actuated control valve member for controlling actuation of said fluid pressure operated lift mechanism
  • control valve member including means to bypass fluid from said main delivery line connecting said fluid pump with said outlet orifice on actuation of said lift control valve member whereby said engine output may be increased independently of said acceleration control member for the purpose of actuation of said lift mechanism.
US791354*A 1969-01-15 1969-01-15 Control system for lift trucks Expired - Lifetime US3595343A (en)

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US79135469A 1969-01-15 1969-01-15

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US (1) US3595343A (ja)
JP (1) JPS5014420B1 (ja)
BE (1) BE744407A (ja)
BR (1) BR7015898D0 (ja)
DE (1) DE2001523A1 (ja)
FR (1) FR2028378A1 (ja)
GB (1) GB1240918A (ja)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3834494A (en) * 1973-02-23 1974-09-10 Raymond Corp Manually-controlled hydraulic actuator systems
US3971453A (en) * 1973-01-24 1976-07-27 Clark Equipment Company Hydrostatic control - pivot steering
FR2472490A1 (fr) * 1979-11-23 1981-07-03 Linde Ag Groupe moteur constitue par un moteur a combustion interne et un changement de vitesse de preference hydrostatique, a reglage progressif
US4400935A (en) * 1980-01-28 1983-08-30 Sundstrand Corporation Engine speed control
DE3507963A1 (de) * 1984-03-07 1985-09-12 Kabushiki Kaisha Toyoda Jidoshokki Seisakusho, Kariya, Aichi Drehzahlregler fuer eine einzige antriebsmaschine in gueterumschlagfahrzeugen
US5201629A (en) * 1991-04-09 1993-04-13 Clark Material Handling Company Container transporter
EP0893298A1 (en) * 1997-07-24 1999-01-27 ANTONIO CARRARO S.p.A. Hydrostatic transmission for motor vehicles
US6089353A (en) * 1996-08-16 2000-07-18 Bt Prime Mover, Inc. Material handling vehicle having a stability support
US20040192505A1 (en) * 2003-03-28 2004-09-30 Fritz Leber Method for the operation of a drive train for powering a mobile vehicle
US20060151230A1 (en) * 2002-09-26 2006-07-13 Hitachi Construction Machinery Co., Ltd. Prime mover control device of construction machine
US20070080025A1 (en) * 2005-09-30 2007-04-12 Tadashi Yamada Drive control apparatus for forklift
WO2013082802A1 (zh) * 2011-12-09 2013-06-13 Zhang Yongsheng 液压叉车自动控制系统

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2202026B1 (ja) * 1972-10-11 1976-10-29 Matral Sa
AT400177B (de) * 1993-08-02 1995-10-25 Hoerbiger Ventilwerke Ag Sicherheitseinrichtung mit druckbeaufschlagtem sicherheitsventil
CN110065911B (zh) * 2019-05-13 2023-12-26 安徽维德电源有限公司 一种中大吨位电动叉车集成动力系统及其控制方法
CN114506800B (zh) * 2022-04-20 2022-07-05 杭叉集团股份有限公司 一种电动叉车门架动作控制系统

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3005562A (en) * 1959-10-29 1961-10-24 Towmotor Corp Hydraulic drive for lift truck
US3369360A (en) * 1965-11-18 1968-02-20 Charles P. De Biasi Hydraulic propulsion and braking system for vehicles or the like
US3543508A (en) * 1968-10-16 1970-12-01 Hyster Co Hydrostatic transmission with pressure control

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3005562A (en) * 1959-10-29 1961-10-24 Towmotor Corp Hydraulic drive for lift truck
US3369360A (en) * 1965-11-18 1968-02-20 Charles P. De Biasi Hydraulic propulsion and braking system for vehicles or the like
US3543508A (en) * 1968-10-16 1970-12-01 Hyster Co Hydrostatic transmission with pressure control

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3971453A (en) * 1973-01-24 1976-07-27 Clark Equipment Company Hydrostatic control - pivot steering
US3834494A (en) * 1973-02-23 1974-09-10 Raymond Corp Manually-controlled hydraulic actuator systems
FR2472490A1 (fr) * 1979-11-23 1981-07-03 Linde Ag Groupe moteur constitue par un moteur a combustion interne et un changement de vitesse de preference hydrostatique, a reglage progressif
US4400935A (en) * 1980-01-28 1983-08-30 Sundstrand Corporation Engine speed control
DE3507963A1 (de) * 1984-03-07 1985-09-12 Kabushiki Kaisha Toyoda Jidoshokki Seisakusho, Kariya, Aichi Drehzahlregler fuer eine einzige antriebsmaschine in gueterumschlagfahrzeugen
US4675827A (en) * 1984-03-07 1987-06-23 Kabushiki Kaisha Toyoda Jidoshokki Seisakusho Revolution controller for a single power plant in cargo-handling vehicles
US5201629A (en) * 1991-04-09 1993-04-13 Clark Material Handling Company Container transporter
US6089353A (en) * 1996-08-16 2000-07-18 Bt Prime Mover, Inc. Material handling vehicle having a stability support
EP0893298A1 (en) * 1997-07-24 1999-01-27 ANTONIO CARRARO S.p.A. Hydrostatic transmission for motor vehicles
US20060151230A1 (en) * 2002-09-26 2006-07-13 Hitachi Construction Machinery Co., Ltd. Prime mover control device of construction machine
US7886862B2 (en) * 2002-09-26 2011-02-15 Hitachi Construction Machinery Co., Ltd. Prime mover control device of construction machine
US20040192505A1 (en) * 2003-03-28 2004-09-30 Fritz Leber Method for the operation of a drive train for powering a mobile vehicle
US20070080025A1 (en) * 2005-09-30 2007-04-12 Tadashi Yamada Drive control apparatus for forklift
US7568547B2 (en) * 2005-09-30 2009-08-04 Kabushiki Kaisha Toyota Jidoshokki Drive control apparatus for forklift
WO2013082802A1 (zh) * 2011-12-09 2013-06-13 Zhang Yongsheng 液压叉车自动控制系统

Also Published As

Publication number Publication date
JPS5014420B1 (ja) 1975-05-27
BR7015898D0 (pt) 1973-04-05
GB1240918A (en) 1971-07-28
DE2001523A1 (de) 1970-07-30
BE744407A (fr) 1970-06-15
FR2028378A1 (ja) 1970-10-09

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