US3850323A - Overload protection device with differential pressure sensing - Google Patents

Overload protection device with differential pressure sensing Download PDF

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Publication number
US3850323A
US3850323A US00319068A US31906872A US3850323A US 3850323 A US3850323 A US 3850323A US 00319068 A US00319068 A US 00319068A US 31906872 A US31906872 A US 31906872A US 3850323 A US3850323 A US 3850323A
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United States
Prior art keywords
cylinders
pressure
mast
frame
operative
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Expired - Lifetime
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US00319068A
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English (en)
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G Ekstrom
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Yale Materials Handling Corp
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Eaton Corp
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Publication date
Application filed by Eaton Corp filed Critical Eaton Corp
Priority to US00319068A priority Critical patent/US3850323A/en
Priority to GB5922873A priority patent/GB1461914A/en
Priority to JP48142555A priority patent/JPS5911519B2/ja
Priority to IT70836/73A priority patent/IT1000607B/it
Priority to DE2364198A priority patent/DE2364198A1/de
Priority to FR7346560A priority patent/FR2212286B1/fr
Application granted granted Critical
Publication of US3850323A publication Critical patent/US3850323A/en
Assigned to YALE MATERIALS HANDLING CORPORATION ROUTE 523 AND 31 FLEMINGTON NEW JERSEY 08822 reassignment YALE MATERIALS HANDLING CORPORATION ROUTE 523 AND 31 FLEMINGTON NEW JERSEY 08822 ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: EATON CORPORATION
Assigned to CITICORP NORTH AMERICA, INC., AS AGENT reassignment CITICORP NORTH AMERICA, INC., AS AGENT SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: YALE MATERIALS HANDLING CORPORATION
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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
    • B66F17/00—Safety devices, e.g. for limiting or indicating lifting force
    • B66F17/003—Safety devices, e.g. for limiting or indicating lifting force for fork-lift trucks

Definitions

  • An overload protection device for a vehicle such as a lift truck, having a mast pivotally mounted on a frame and moved by a pair of double acting, fluid actuated piston-cylinders.
  • the overload protection device includes a pressure actuated valve operable in response to a difference in pressure between two sources to prevent movement of the mast in one direction when the difference in pressure exceeds a given value.
  • a shuttle check valve interconnects the front chambers within each cylinder and another shuttle check valve interconnects the rear chambers within each cylinder.
  • Each shuttle check valve is operative to transmit only the highest pressure of the fluid existing within the respective front and rear chambers to the pressure actuated valve.
  • the shuttle check valves constantly monitor the pressure of the fluid within the chambers at each end of the two cylinders.
  • the present invention has application to any vehicle of the type including a load carrying member, such as a mast, boom, or arm, that is movable relative to the vehicle frame by at least two motor members interconnecting the load carrying member and the frame.
  • a load carrying member such as a mast, boom, or arm
  • the force exerted on two motors tending to move a load carrying member is sensed and a signal representative of the magnitude of force on each motor is generated.
  • the signals are compared and the one representative of the greatest magnitude of force is transmitted to a device which operates to prevent further movement of the load carrying member when the transmitted signal is representative of a magnitude of force exceeding a predetermined value.
  • a device is provided to sense the pressure of the fluid at the first end of each cylinder and transmit a signal representative of the highest pressure to a valve which also receives a signal representative of the pressure of the fluid at the second end of one cylinder.
  • the valve precludes further movement of the load carrying member relative to the frame when the signals differ in a given manner.
  • the signal from the second end is representative of the highest pressure of the fluids at the second ends of the cylinders.
  • the pressure of the fluid at the first end of each cylinder is constantly monitored and the signal is only representative of the highest existing pressure at any given point in time.
  • FIG. 1 is a perspective view of a lift truck
  • FIG. 2 is a schematic plan view of a portion of the hydraulic circuit used for tilting the mast of the lift truck illustrated in FIG. 1.
  • the industrial lift truck 10 of FIG. 1 comprises a frame 12 supported on a pair of rear steering wheels 14 and a pair of front drive wheels 16.
  • An upright telescoping load carrying member in the form of a mast 18 mounted for pivotal movement about an axle of wheels 16 has a pair of fixed upright channel members 20 interconnected by support members 22.
  • Connected to the side portion of each channel member 20 is a bracket 24 to which is pivotally connected one end of a piston rod 26 of a motor in the form of a double acting, fluid actuated piston-cylinder assembly 28 which is pivotally connected at its base end to a bracket portion 30 of frame 12.
  • the two piston-cylinder assemblies 28 are identical in construction and are adapted to actuate mast 18 in a tilting movement fore and aft of a vertical position.
  • Mounted rearwardly of mast 18 is an operators compartment having a seat 32 mounted on frame 12, a steering wheel 34, and a tilt selector control 36 for controlling the operation of piston-cylinder assemblies 28.
  • Mast 18 includes a fork carriage 38that is adapted to be elevated and lowered in a known manner by a double acting lift piston-cylinder assembly 40 through the use of a lift selector control 42 of a known design.
  • the operation of the circuit illustrated in FIG. 2 is based on the known concept that the moment tending to overturn the truck forwardly about the axle of wheels 16 is proportional to the tensional forces exerted on rods 26.
  • the tensional force on each rod can in turn be shown to be related to the magnitude of the force exerted on the opposite sides of the piston by the pressure of the fluid acting against the sides of the pistons in each piston-cylinder assembly 28.
  • the concept, as well as a portion of the construction and operation of the hydraulic circuit of FIG. 2 is described in US. Pat. No. 3,007,593, Hancock.
  • the circuit of FIG. 2 includes a hydraulic fluid feed line 44 from a pump (not illustrated) leading to tilt selector control 36.
  • a line 46 interconnects the tilt selector control and the full area sides 48 of tilt pistons 50 which are connected to rods 26 and are located within piston-cylinder assemblies 28.
  • the full area side of each piston 50 is further connected via respective lines 54 and 56 to opposite sides of a shuttle check valve 58 of a known design.
  • a line 60 interconnects the center tap of shuttle check valve 58 with a pressure chamber 62 in a tilt limiting valve 64.
  • the annular sides 66 of pistons 50 are connected via lines 68 and 70 with tilt limiting valve 64.
  • each piston 50 is further connected via respective lines 72 and 74 to opposite sides of a shuttle check valve 76 of a known design.
  • the center tap of shuttle check valve 76 is connected with a pressure chamber 78 in tilt limiting valve 64 through a line 80.
  • One type of shuttle check valve which may be used is Model 2456C-l made by Kepner Products Co., Summit, Illinois.
  • Tilt limiting valve 64 includes a piston 82 biased on its full area side 84 by a compressed coil spring 86 located in pressure chamber 62.
  • Full area side 84 of piston 82 communicates with chamber 62.
  • a spool 88 formed with an annular peripheral chamber 90 is connected to piston 82 and is slideable within tilt limiting valve 64.
  • Pressure chamber 78 communicates with side 92 of spool 88.
  • the proportion of the area of side 92 to the area of side 84 is equal to the proportion of the area of side 48 to the area of side 66 of each piston 50.
  • Peripheral chamber 90 when spool 88 is in a normal position as illustrated in FIG. 2, communicates with line 70, and to line 94.
  • Another line 96 interconnects line 94 and tilt selector control 36.
  • An outlet line 98 connects tilt selector control 36 to a reservoir (not illustrated).
  • a bypass line 100 is connected to the annular sides 66 of pistons 50 via line 68 and to lines 94 and 96.
  • Line 100 incorporates a nonretum check valve 102 through which fluid may pass only from the lines 94 and 96 to line 100.
  • stops 104 and 106 are respectively located on annular side 66 and full area side 48 of each piston 50.
  • stops 104 and 106 seal lines 68 and 46, respectively, when piston 50 approaches the respective end of the cylinder. The sealing of the respective line prevents the piston from bottoming, i.e., contacting the end of the cylinder, and maintains a quantity of fluid under pressure between the piston and the end of the cylinder. Lines 54, 56, 72 and 74 are not sealed by stops 104 and 106.
  • tilt selector 36 is moved to a position connecting line 44 with line 46 and line 96 with line 98. Fluid contacting full area sides 48 of pistons 50 forces the pistons to the left in FIG. 2. The fluid at annular sides 66 of pistons 50 flows through line 68, line 70, peripheral chamber 90, assuming spool 88 is located in the normal position, line 94, line 96, tilt selector 36, line 98 and into the reservoir. In tilting mast l8 aft of the vertical position, tilt selector 36 is moved to connect line 44 with line 96 and line 98 with line 46.
  • fluid flowing through line 96 is introduced through line 68 to annular sides 66 of pistons 50 via line 94, peripheral chamber 90, and line 70 assuming spool 88 is located in the normal position, or otherwise via nonretum check valve 102 and line 100. Fluid exits from full area sides 48 of pistons 50 via line 46, tilt selector 36 and line 98 to the reservoir.
  • the pressure of the fluid at annular sides 66 of pistons 50 acts through lines 72 and 74 on shuttle valve 76 forcing ball 108 located therein to seal the line transmitting the lowest fluid pressure and permit the line transmitting the highest fluid pressure to communicate via the center tap, line 80, and chamber 78 of tilt limiting valve 64 with side 92 of spool 88.
  • the pressure of the fluid at full area sides 48 is transmitted via lines 54 and 56 to shuttle valve 58.
  • the line with the highest fluid pressure will force ball 110 in shuttle valve 58 to seal the line having the lowest fluid pressure.
  • the highest fluid pressure existing on the sides 48 will thereby be transmitted, via the center tap, line 60 and chamber 62 to the full area side 84 of piston 82.
  • shuttle check valves 58 and 76 in sensing the fluid pressure at the annular and/or full area sides of tandem operating piston-cylinder assemblies 28 results in the transmittal of the higher of the two fluid pressures from each of the respective sides of pistons 50 to tilt limiting valve 64.
  • This operation allows spool 88 to operate properly in the event of: improper loading of the mast; failure of one of the stops 104 and 106 in each assembly 28, or one 'of the lines 54 and 56 or one of the lines 72 and 74.
  • shuttle valves 58 and 76 are illustrated at each end of piston-cylinder assemblies 28, shuttle valve 58 can be eliminated if forward overturning of truck 10 is the only consideration.
  • relatively high fluid pressures exist at annular sides 66 of pistons 50 and relatively low pressures exist at full area sides 48 of the pistons.
  • the highest fluid pressure existing at annular sides 66 of the pistons must be fed to side 92 of spool 88 along with a low pressure from full area sides 48 of the pistons to side 84 of piston 82 in order to prevent forward overturning. If the pressure of the fluid at side 84 is nonrepresentative of the tensional forces on rods 26 premature movement of spool 88 will occur. Although such premature movement will affect vehicle productivity it will not result in forward overturning of lift truck 10.
  • Both piston-cylinder assemblies 28 are monitored through shuttle check valves 58 and 76.
  • the shuttle check valves always communicate the higher of the fluid pressures being sensed from the given side of the piston to the tilt-limiting.
  • improperly adjusted piston rods 26 are of no consequence to the proper functioning of the valve 64.
  • This is of major importance after the piston-cylinder assemblies 28 have been repaired, removed or disconnected from the mast for any reason.
  • the pressures of the fluids'at the corresponding annular sides and at the corresponding full area sides of the pistons are equalized via the respective lines 68 and 46.
  • An overload protection device for a vehicle having a frame, load carriage mounted for substantially vertical movement on a mast which is pivotally mounted on said frame for tilting motion relative thereto and'two motors operatively connected between said frame and said mast to tilt said mast, the overload protection device comprising:
  • An overload protection device for a vehicle having a frame, a load carriage mounted for movement on a mast pivotally mounted on the frame, first and second piston-cylinder assemblies each having a respective first and second piston, each piston-cylinder assembly having first and second ends connected to the frame and the mast, the assemblies being operative in response to a flow of fluid into the chamber at one end of each cylinder and out of the chamber at the other end of each cylinder to pivotally move the mast relative to the frame, and a fluid circuit for providing a flow of fluid to the chamber at one end of each cylinder and for collecting fluid from the chamber at the other end of each cylinder, the overload protection device comprismg:
  • first means for transmitting a signal representative of the highest pressure of the fluids in the chambers at the first ends of the cylinders to the operative means; and second means for transmitting a signal representative of the pressure of the fluid in the chamber at the second end of at least one of the cylinders to the operative means and means operative in response to'the magnitude of the difference between the two signals for preventing pivotal movement of the mast'in at least one direction by preventing movement of the first and second pistons in the corresponding direction.
  • first means continuously monitors the pressure of the fluids in the chambers at the first ends of the cylinders.
  • An overload protection device according to claim 2 wherein the second means transmits a signal representative of the highest pressure of the fluids in the chambers at the second ends of the cylinders to the operative means.
  • An overload protection device according to claim 4 wherein the first and second means continuously monitor the pressures of the fluids in the chambers respectively at the first and second ends of the cylinders.
  • An overload protection device for a vehicle having a frame, a load carriage mounted on a mast pivotally mounted on the frame, a fluid transmitting circuit having a fluid outlet and a fluid inlet, the overload protection device comprising:
  • a first cylinder having first and second ends and a chamber
  • a first piston located within the chamber in the first cylinder and movable between the first and second ends;
  • a second piston located within the chamber in the second cylinder and movable between the first and second ends;
  • first means to produce a signal representative of highest pressure of the fluids at the first ends of the cylinders and second means to produce a signal from the second ends of the cylinders means operative in response to the magnitude of the difference between the two signals for preventing pivotal movement of the mast in at least one direction by preventing movement of the first and second pistons in the corresponding direction.
  • An overload protection device according to claim 6 wherein the second means transmits the highest pressure of the fluids at the second ends of the cylinders to the operative means.
  • first and second passages each having one end communicating with the first end respectively of the first and second cylinders and another end;
  • third and fourth passages each having one end communicating with the second end respectively of the first and second cylinders and another end;
  • a valve having first and second ends respectively communicating with the other end of the third and fourth passages
  • An overload protection device for a vehicle having a frame, a load carriage mounted on the frame for substantially vertical movement on a mast which is pivotally mounted on the frame a fluid transmitting circuit having a fluid outlet and a fluid inlet, the overload protection device comprising:
  • a first cylinder having first and second ends and a chamber
  • a first piston located within the chamber in the first cylinder and movable between the first and second ends;
  • a second cylinder having first and second ends and a chamber
  • a second piston located within the chamber in the second cylinder and movable between the first and second ends;
  • first means for continuously monitoring the highest pressure of the fluids at the first ends of the cylinders and transmitting it to the operative means including:
  • a first valve having first and second ends respectively communicating with the other end of the first and second passages
  • second means for continuously monitoring the highest pressure of the fluids at the second ends of the cylinders and transmitting it to the operative means including:
  • a second valve having first and second ends respectively communicating with the other end of the third and fourth passages
  • e. means disposed on the first and second pistons preventing movement of the pistons to axial positions effecting the sealing of the third and fourth passages at the second ends of the cylinders.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Geology (AREA)
  • Mechanical Engineering (AREA)
  • Structural Engineering (AREA)
  • Forklifts And Lifting Vehicles (AREA)
US00319068A 1972-12-27 1972-12-27 Overload protection device with differential pressure sensing Expired - Lifetime US3850323A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
US00319068A US3850323A (en) 1972-12-27 1972-12-27 Overload protection device with differential pressure sensing
GB5922873A GB1461914A (en) 1972-12-27 1973-12-20 Vehicle overload proteciton device
IT70836/73A IT1000607B (it) 1972-12-27 1973-12-21 Dispositivo di protezione contro sovraccarico particolarmente per carrelli a forca
JP48142555A JPS5911519B2 (ja) 1972-12-27 1973-12-21 差圧感知方式による過荷重防護装置
DE2364198A DE2364198A1 (de) 1972-12-27 1973-12-22 Ueberlastschutzvorrichtung
FR7346560A FR2212286B1 (enExample) 1972-12-27 1973-12-27

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US00319068A US3850323A (en) 1972-12-27 1972-12-27 Overload protection device with differential pressure sensing

Publications (1)

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US3850323A true US3850323A (en) 1974-11-26

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ID=23240727

Family Applications (1)

Application Number Title Priority Date Filing Date
US00319068A Expired - Lifetime US3850323A (en) 1972-12-27 1972-12-27 Overload protection device with differential pressure sensing

Country Status (6)

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US (1) US3850323A (enExample)
JP (1) JPS5911519B2 (enExample)
DE (1) DE2364198A1 (enExample)
FR (1) FR2212286B1 (enExample)
GB (1) GB1461914A (enExample)
IT (1) IT1000607B (enExample)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3960286A (en) * 1974-12-19 1976-06-01 Allis-Chalmers Corporation Automatic overload control for a counterbalanced lift truck
US3993166A (en) * 1975-04-29 1976-11-23 Bofors America, Inc. Overload signalling system for fork lift trucks and the like
US4003487A (en) * 1975-04-03 1977-01-18 Allis-Chalmers Corporation Truck overload protective system having trip signal sampling means
DE2721755A1 (de) * 1976-06-30 1978-01-05 Towmotor Corp Lastmomentfuehlsystem fuer hubstapler
WO1982002188A1 (en) * 1980-12-19 1982-07-08 Ervin Daniel L Lift mast with offset tilt cylinder mountings
US4340235A (en) * 1979-10-04 1982-07-20 Towmotor Corporation Load responsive damping system
US4352398A (en) * 1980-02-27 1982-10-05 International Harvester Co. Circuit for pitch and tilt of dozer blade
US4433612A (en) 1980-03-04 1984-02-28 Sms Schloemann-Siemag Aktiengesellschaft Safety control device for protecting hydraulically held loads against uncontrolled pressure overloading
WO1991012449A1 (en) * 1990-02-19 1991-08-22 Duotech Innovation Ab A compensation valve
WO2006113363A3 (en) * 2005-04-14 2007-10-11 Nmhg Oregon Llc Hydraulic system for an industrial vehicle
US10017365B2 (en) * 2015-07-10 2018-07-10 Jungheinrich Aktiengesellschaft Standing platform for an industrial truck

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4222491A (en) * 1978-08-02 1980-09-16 Eaton Corporation Crane operating aid and sensor arrangement therefor
DE9103543U1 (de) * 1991-03-22 1992-07-23 J. D. Neuhaus Hebezeuge GmbH & Co, 5810 Witten Ventil zur Begrenzung der anhebbaren Last an einem Hebezeug

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3007593A (en) * 1958-11-21 1961-11-07 Electro Hydraulics Ltd Tilting mask assemblies for fork lift trucks
US3355886A (en) * 1965-10-23 1967-12-05 New York Air Brake Co Hydrostatic transmission

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3007593A (en) * 1958-11-21 1961-11-07 Electro Hydraulics Ltd Tilting mask assemblies for fork lift trucks
US3355886A (en) * 1965-10-23 1967-12-05 New York Air Brake Co Hydrostatic transmission

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3960286A (en) * 1974-12-19 1976-06-01 Allis-Chalmers Corporation Automatic overload control for a counterbalanced lift truck
US4003487A (en) * 1975-04-03 1977-01-18 Allis-Chalmers Corporation Truck overload protective system having trip signal sampling means
US3993166A (en) * 1975-04-29 1976-11-23 Bofors America, Inc. Overload signalling system for fork lift trucks and the like
DE2721755A1 (de) * 1976-06-30 1978-01-05 Towmotor Corp Lastmomentfuehlsystem fuer hubstapler
US4340235A (en) * 1979-10-04 1982-07-20 Towmotor Corporation Load responsive damping system
US4352398A (en) * 1980-02-27 1982-10-05 International Harvester Co. Circuit for pitch and tilt of dozer blade
US4433612A (en) 1980-03-04 1984-02-28 Sms Schloemann-Siemag Aktiengesellschaft Safety control device for protecting hydraulically held loads against uncontrolled pressure overloading
WO1982002188A1 (en) * 1980-12-19 1982-07-08 Ervin Daniel L Lift mast with offset tilt cylinder mountings
WO1991012449A1 (en) * 1990-02-19 1991-08-22 Duotech Innovation Ab A compensation valve
WO2006113363A3 (en) * 2005-04-14 2007-10-11 Nmhg Oregon Llc Hydraulic system for an industrial vehicle
EP1868935A4 (en) * 2005-04-14 2010-06-30 Nacco Materials Handling Group HYDRAULIC SYSTEM FOR A COMMERCIAL VEHICLE
US10017365B2 (en) * 2015-07-10 2018-07-10 Jungheinrich Aktiengesellschaft Standing platform for an industrial truck

Also Published As

Publication number Publication date
DE2364198A1 (de) 1974-07-11
JPS5911519B2 (ja) 1984-03-15
GB1461914A (en) 1977-01-19
JPS49108758A (enExample) 1974-10-16
FR2212286B1 (enExample) 1979-04-06
IT1000607B (it) 1976-04-10
FR2212286A1 (enExample) 1974-07-26

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AS Assignment

Owner name: YALE MATERIALS HANDLING CORPORATION ROUTE 523 AND

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:EATON CORPORATION;REEL/FRAME:004261/0903

Effective date: 19831231

AS Assignment

Owner name: CITICORP NORTH AMERICA, INC., AS AGENT

Free format text: SECURITY INTEREST;ASSIGNOR:YALE MATERIALS HANDLING CORPORATION;REEL/FRAME:005228/0113

Effective date: 19890526