EP0058671B1 - Force-moment compensating apparatus - Google Patents
Force-moment compensating apparatus Download PDFInfo
- Publication number
- EP0058671B1 EP0058671B1 EP81901391A EP81901391A EP0058671B1 EP 0058671 B1 EP0058671 B1 EP 0058671B1 EP 81901391 A EP81901391 A EP 81901391A EP 81901391 A EP81901391 A EP 81901391A EP 0058671 B1 EP0058671 B1 EP 0058671B1
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- EP
- European Patent Office
- Prior art keywords
- load
- frame
- mast
- signal
- angular
- 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
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Classifications
-
- 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
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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
- B66F9/07554—Counterweights
Definitions
- This invention relates to a force-moment compensating apparatus, and more particularly to a load compensating apparatus.
- US-A-3 497 495 there is disclosed a forklift truck having a frame subjected to changes in moments of force.
- the truck is provided with force-moment compensating apparatus comprising motive means for moving said frame and speed-change means for varying the speed of said motive means in response to an electrical output signal.
- a translatory sensor senses the translatory position of the load and an angular sensor senses its angular position, the outputs of the two sensors energizing a control apparatus either independently or in combination to shift the counterweight or to change the speed of the vehicle.
- the weight of the load may be sensed by a pressure transducer sensor, the position of the load may be sensed by position sensors.
- the signals developed by these respective sensors are processed by the electrical control apparatus for shifting the counterweight on the vehicle by a commensurate amount to change the center of gravity of the vehicle and/or to vary the speed of the vehicle, so that the vehicle operates under a safe speed for the value or position of the load it is handling or carrying.
- FIG. 1 discloses, as an example of a load handling apparatus or vehicle, a forklift truck 10 including a frame 11 supported by front wheels 12 and rear wheels 13.
- the forklift mechanism 15 Pivotally mounted upon the front end of the frame 11 by a journal pin 14 is the forklift mechanism 15.
- the forklift mechanism 15 includes a mast 16 supporting hydraulic cylinder 17 telescopically receiving a piston rod 18 for vertical reciprocal movement. Fixed to the top of the piston rod 18 is a transverse yoke 19 supporting sprockets 20, over which are trained the lift chains 21.
- the rear ends of the lift chains 21 are fixed to the transverse beam 22 of the mast 16, while the opposite ends of the chains 21 are fixed to the fork frame 23 from which project forwardly the lift forks 24.
- the forks 24 are adapted to support and carry a load 25.
- the mast 16 may be pivoted or tilted about the journal pin 14 by a hydraulic tilt cylinder 27 journalled by pin 28 to the frame 11, and reciprocally supporting the piston rod 29 journalled by pin 30 to mast 16.
- the forklift truck 10 is preferably driven by a prime mover, such as the electrical motor 32 (FIG. 2), which drives a pump shaft 33 for operating the variable-volume pump 34 and the fixed rate pump 35.
- a prime mover such as the electrical motor 32 (FIG. 2), which drives a pump shaft 33 for operating the variable-volume pump 34 and the fixed rate pump 35.
- Variable-volume pump 34 circulates hydraulic fluid in either direction through the hydraulic line 36, relief valve 37 and back through the return line 38 to the variable pump 34. Such flow occurs when relief valve 37 is in static position.
- hydraulic fluid flows in the direction of the arrows disclosed in FIG. 2 through the forward input lines 39, 40, 41, respectively, to the left and right front wheel hydraulic motors 43 and 44. Fluid from the wheel motors 43 and 44 returns through the lines 45, 46 and 47 to the relief valve 37.
- flow through the lines 39, 40, 41, 45, 46 and 47 is reversed, to reverse the direction of the vehicle or forklift truck 10.
- the wheel motors 43 and 44 may be driven at the same speed forward, the same speed rearward, or at different speeds in order to turn the vehicle to the left or right.
- the speed of the vehicle may be controlled by varying the speed of the variable-volume pump 34, such as by the speed control positioning device 50, which is adapted to be electrically energized.
- the variable-pump 34 may be any of several conventional types, such as a swash-plate pump.
- the fixed rate pump 35 pumps hydraulic fluid from the reservoir 52 through lines 53 and 54 to the mast-controlled 4-way valve 55.
- the mast control valve 55 When the mast control valve 55 is in its "raise” position, hydraulic fluid flows through the hydraulic line 56 to the mast cylinder 17.
- Hydraulic fluid also flows from line 54 through the mast control valve 55 and through line 57 to the tilt control valve 58, also a manually controlled 4-way valve.
- the tilt control valve 58 When the tilt control valve 58 is in its forward position, hydraulic fluid flows through the tilt feed line 59 to one end of the tilt cylinder 27, while the return fluid from the other end of the tilt cylinder 27 passes through the return line 60, tilt control valve 58, and return line 61 to the reservoir 52.
- the load 25 may be raised and lowered by the forks 24 in response to the manual operation of the mast control valve 55, while the mast 16 may be tilted by operation of the tilt control valve 58.
- the force-moment compensator apparatus made in accordance with this invention includes a counterweight 64 mounted for movement on the frame 11 of the forklift truck 10, such as in the longitudinal, front-to-rear direction along a slide bar or track 65.
- the counterweight 64 may be moved along the slide bar or track 65 by means of a piston rod 66 reciprocally movable within a hydraulic cylinder 67.
- Flow of the hydraulic fluid into the actuator cylinder 67 is controlled by a spool valve 68, disclosed in its neutral position in FIG. 3.
- the spool valve 68 is shifted to the right (FIG. 3) to cause hydraulic fluid from the line 61 to pass through the line 71 into the rear end of the cylinder 67 thereby projecting the piston rod 66 forward, to extend the counterweight 64 along the slide rod 65.
- -Fluid from the cylinder 67 passed through the forward line 72 back through the spool valve 68 to the return line 62 into the reservoir 52.
- the extension solenoid 69 and the return solenoid 70 are energized through their respective electrical lines 73 and 74 from the electronic control circuit device 75 (FIG. 2).
- the extent of travel of the counterweight 64 along the track 65, or the position to which the counterweight 64 is moved, is controlled by a sensing device, in the form of the pressure transducer 77, mounted in fluid communication with the base of the hydraulic lift cylinder 17, or other lift-type device.
- a sensing device in the form of the pressure transducer 77, mounted in fluid communication with the base of the hydraulic lift cylinder 17, or other lift-type device.
- the pressure of the hydraulic fluid within the cylinder 17, which in turn is determined by the weight of the load 25 upon the forks 24, determines the value of the electrical signal transmitted from the pressure transducer 77 through the input line 78 to the electrical control circuit 75.
- the signal from the input line 78 is processed in the control circuit 75 to arm or condition one of the spaced limit switches 80, 81, or 82, or a variable transducer, for engagement by the actuator 83 to sense the position of the counterweight 64.
- the counterweight 64 when the counterweight 64 arrives at the desired position to counterbalance the sensed weight of the load 25, it will actuate the particular limit switch, such as limit switch 81, or variable transducer, which in turn will energize the control circuit 75 to de-energize the extension solenoid 69 and stop the counterweight in the desired safe position.
- limit switch such as limit switch 81, or variable transducer
- the counterweight circuit 85 within the control circuit 75 for controlling the position of the counterweight 64 is disclosed in the upper portion of FIG. 4.
- the pressure transducer 77 includes a plurality of graduated pressure threshold settings, P1, P2 and P3, or it may be a variable sensing transducer (FIG. 4). For example, a low-pressure signal from the transducer 77 (FIG. 4) will be admitted through the input lead 88 for P1 (FIG. 4), whereas no signals will be transmitted through leads 89 and 90.
- the input signal passing through the input lead 88 will be processed in the comparator circuit 91 to produce an amplified output signal transmitted through output line 92 to the integrated amplifier 93.
- the input signal passing through the input line 92 will be compared, or integrated, in the integrated amplifier 93 with a feedback signal transmitted from the line 94.
- the resultant output signal in the line 95 energizes the counterweight positioning control 96, which transmits a signal through the line 73 to the extension solenoid 69.
- the feedback signal transmitted to the integrated amplifier 93 through the line 94 originates in one of the limit switches 80, 81 or 82 (or variable transducer).
- the generated feedback signals are transmitted through the feedback line 97 to a relay circuit 98 in order to provide a reference signal to indicate in the circuit 85 the actual position of the counterweight 64 at any particular moment.
- the extension solenoid 69 will be de-energized and the spool valve 68 returned to its neutral position to stop the counterweight 64 at the desired position corresponding to the pressure signal generated by the transducer 77.
- the magnetic relay circuit 100 in lieu of the electronic counterweight circuit 85, the magnetic relay circuit 100, disclosed in FIG. 5, could be employed.
- PS1, PS2 and PS3 indicate the respective pressure switches which are actuated respectively at increasing intervals of pressure sensed by transducer 77.
- the three relay coils are designated R1, R2 and R3.
- the relay coil R1 when energized, closes the respective relay switches RS1, in each of the pressure sensing circuit 101, the overload circuit 102 and the counterweight circuit 103.
- the relay coil R2 when the relay coil R2 is energized, the normally closed relay switches RS2 are opened, while the normally open relay switches RS2 are closed.
- the relay coil R3 controls the relay switches RS3 in the same manner.
- the relay coil R1 is energized, while the relay coils R2 and R3 are de-energized.
- the relay switch RS1 across the pressure switch PS1 is closed to hold the circuit 101, controlled by the relay coil R1, energized.
- the overload safety circuit 102 controlled by the switch RS1 is closed, and the counterweight circuit 103 including the relay switch RS1 is also closed to energize the extension relay coil 69 causing the counterweight 64 to travel toward the left in FIG. 2.
- the limit switch is opened to de-energize the counterweight coil 69 and stop the counterweight 64 in its first position.
- the switch 104 may be opened, simultaneously closing the switch 105 to energize the return counterweight coil 70 and restore the counterweight 64 to its original position.
- the counterweight 64 returns to its original position, it engages and opens limit switch 106 to de-energize the return solenoid 70.
- a translatory sensor 108 preferably in the form of a rotary potentiometer, is mounted in a fixed position relative to the mast 16. Fixed to the piston rod 18 is an elongated bracket arm or track against which the rotary member of the rotary potentiometer 108 is adapted to travel. Thus, as the piston rod 18 rises relative to the hydraulic lift cylinder 17, the rotary potentiometer or translatory sensor 108 produces an electrical signal of a value or voltage proportionate or commensurate with the vertical distance traveled by the arm 109, and therefore the piston rod 18 and the load 25. The translatory signal is transmitted from the translatory sensor 108 through lead 110 to the control circuit 75.
- an angular sensor 112 also preferably in the form of a rotary potentiometer having its rotary member adapted to roll on the elongated bracket or track 113 fixed to the tilt piston rod 29, produces a signal commensurate with, or proportional to, the tilt angle of the mast 16, which is transmitted through the lead 114 to the control circuit 75.
- the translatory signal transmitted through the input line 110, and the angular signal transmitted through the line 114, are amplified by the respective amplifier circuits 115 and 116.
- the resultant output signals are integrated in the amplifier 118 and compared with the feedback signal received through the line 120.
- the resultant signal from the integrated amplifier 118 is transmitted through the output lead 122 to energize the speed-control device 50, thereby actuating the variable pump 34 to adjust the flow of hydraulic fluid, and consequently the speed of the vehicle 10 commensurate with the signals generated by the translatory sensor 108 and the angular sensor 112.
- an overload safety device 123 including three solenoid valves 124,125, and 126, all connected in parallel, and each adapted to be energized at the same time that a corresponding limit switch 80, 81 or 82 is actuated.
- the solenoid valve 124 is opened to activate the overload switch 127 (FIG. 6).
- the solenoid valve 124 While the counterweight 64 is in its first position and the hydraulic circuitry, particularly in the mast feed line 56 has its pressure suddenly rise, the excess pressure will be dumped through the solenoid valve 124 (FIG. 6) and overload valve 127 back to the reservoir.
- the valves 125, 128 and 126, 129 function in the same manner for overload safety when the counterweight 64 is located in its second and third positions, respectively.
- the circuit 102 in FIG. 5 has the same function as the circuit 123 in FIG. 6.
- the counterweight control circuit 85 disclosed in FIG. 4 is connected to the overload safety circuit 123 by the lead 130.
- forks 24 are lowered to their load-engaging position by manipulation of the handle on the mast control valve 55.
- the vehicle 10 is then propelled forward to insert the forks 24 beneath the load 25, and the mast control valve 55 is manipulated to lift the forks 24, and therefore the load 25, to the desired elevation, such as the elevation disclosed in phantom in FIG. 1.
- the load 25 may be tilted rearward by manipulating the tilt control valve 58.
- the pressure sensor 77 then senses the pressure within the mast cylinder 17, which is commensurate with the weight of the load 25, and sends a corresponding signal to the control circuit 75 for processing, such as by the counterweight control circuit 85 of FIG. 4. If the sensed load is within its limits, that is, less than its predetermined threshold value, the counterweight 64 does not move. If the threshold value is exceeded, the extension solenoid 69 is energized to actuate the spool valve 68. Spool valve 68 is then manipulated to actuate the counterweight cylinder 67 to extend the counterweight 64 to a predetermined position, such as the position disclosed in FIG. 2 in which the actuator 83 engages and actuates the limit switch 80.
- the feedback signal generated by the limit switch 80 is then fed to the control circuit 85 in order to stop the movement of the counterweight 64 in its desired position, properly counterbalancing the weight and position of the load 25 resting upon the forks 24 to provide a predetermined safe center of gravity for the forklift truck 15 which will adequately stabilize the vehicle during its movement.
- signals from the translatory sensor 108 and the tilt sensor 112 will be transmitted to the speed control circuit 111 where the desired output signal will be produced and transmitted through the line 122 to the speed control device 50 to actuate the variable-volume pump 34 in order to reduce the speed of the vehicle 10 to a safe speed for movement of the vehicle 10 with the load 25 in its particular elevated and angular position.
- overload safety circuits 123 or 102 will effectively dump hydraulic fluid back to the reservoir 52 should the mast feed line 56 encounter any sudden or excessively high fluid pressures.
- Loads 25 having weights of different values will develop corresponding signals of different values in the pressure transducer 77 for varying the position of the counterweight 64 to properly counterbalance the load 25 in the vehicle 10 to appropriately maintain the center of gravity of the vehicle 10 between the wheels 12 and 13 for safety.
- the same circuits and components can be adapted and applied to other types of vehicles and other types of load handling apparatus in which the center of gravity or other forces or force-moments are apt to change by virtue of the weights and positions of the loads handled by load handling apparatus, or by virtue of changes in movement of vehicles, such as changes in turning or directional movements creating centrifugal forces.
Abstract
Description
- This invention relates to a force-moment compensating apparatus, and more particularly to a load compensating apparatus.
- Heretofore, in load handling apparatus and vehicles, such a forklike trucks, cranes, lifts, hoists and other types of load handling apparatus in which the force-moments, including the weight and/or position of the load, change, fixed centers of gravity and counterweights are designed into the original vehicles. Accordingly, the weight or position of loads handled by such vehicles are limited by the original design of the vehicle.
- In US-A-3 497 495 there is disclosed a forklift truck having a frame subjected to changes in moments of force. The truck is provided with force-moment compensating apparatus comprising motive means for moving said frame and speed-change means for varying the speed of said motive means in response to an electrical output signal.
- It is an object of this invention to provide in an apparatus subjected to changes in force-moment, such as a vehicle or load handling apparatus, means for sensing the position of the load relative to the vehicle to change the speed of the vehicle in response to the position of the load.
- The above object is achieved by the features of the characterizing part of
claim 1. In a preferred embodiment, a translatory sensor senses the translatory position of the load and an angular sensor senses its angular position, the outputs of the two sensors energizing a control apparatus either independently or in combination to shift the counterweight or to change the speed of the vehicle. - For example, in a forklift truck having a tiltable mast supporting a hoist mechanism for raising and lowering load-supporting forks, the weight of the load may be sensed by a pressure transducer sensor, the position of the load may be sensed by position sensors. The signals developed by these respective sensors are processed by the electrical control apparatus for shifting the counterweight on the vehicle by a commensurate amount to change the center of gravity of the vehicle and/or to vary the speed of the vehicle, so that the vehicle operates under a safe speed for the value or position of the load it is handling or carrying.
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- FIG. 1 is a side elevation of a forklift truck incorporating the force-moment compensating apparatus made in accordance with this invention;
- FIG. 2 is a schematic hydraulic-electric circuit diagram of the force-moment compensating apparatus incorporated in the forklift truck of FIG. 1;
- FIG. 3 is an enlarged schematic diagram of the hydraulic circuit for controlling the counterweight;
- FIG. 4 is an electrical circuit diagram of the electrical control circuit disclosed in FIG. 2;
- FIG. 5 is an electrical circuit diagram of a modified form of electrical control circuit for the counterweight; and
- FIG. 6 is a hydraulic-electric diagram of the overload safety system disclosed in FIG. 2.
- Referring now to the invention in more detail, FIG. 1 discloses, as an example of a load handling apparatus or vehicle, a forklift truck 10 including a
frame 11 supported byfront wheels 12 andrear wheels 13. - Pivotally mounted upon the front end of the
frame 11 by ajournal pin 14 is theforklift mechanism 15. Theforklift mechanism 15 includes amast 16 supportinghydraulic cylinder 17 telescopically receiving apiston rod 18 for vertical reciprocal movement. Fixed to the top of thepiston rod 18 is atransverse yoke 19 supportingsprockets 20, over which are trained thelift chains 21. The rear ends of thelift chains 21 are fixed to thetransverse beam 22 of themast 16, while the opposite ends of thechains 21 are fixed to thefork frame 23 from which project forwardly thelift forks 24. Theforks 24 are adapted to support and carry aload 25. - The
mast 16 may be pivoted or tilted about thejournal pin 14 by ahydraulic tilt cylinder 27 journalled bypin 28 to theframe 11, and reciprocally supporting thepiston rod 29 journalled by pin 30 to mast 16. - The forklift truck 10 is preferably driven by a prime mover, such as the electrical motor 32 (FIG. 2), which drives a
pump shaft 33 for operating the variable-volume pump 34 and the fixed rate pump 35. - Variable-volume pump 34 circulates hydraulic fluid in either direction through the hydraulic line 36,
relief valve 37 and back through thereturn line 38 to the variable pump 34. Such flow occurs whenrelief valve 37 is in static position. When the pump 34 is shifted to forward position, hydraulic fluid flows in the direction of the arrows disclosed in FIG. 2 through theforward input lines hydraulic motors wheel motors lines relief valve 37. By reversing the direction of the pump 34, flow through thelines wheel motors - The fixed rate pump 35 pumps hydraulic fluid from the
reservoir 52 throughlines hydraulic line 56 to themast cylinder 17. - Hydraulic fluid also flows from
line 54 through the mast control valve 55 and through line 57 to thetilt control valve 58, also a manually controlled 4-way valve. When thetilt control valve 58 is in its forward position, hydraulic fluid flows through thetilt feed line 59 to one end of thetilt cylinder 27, while the return fluid from the other end of thetilt cylinder 27 passes through thereturn line 60,tilt control valve 58, andreturn line 61 to thereservoir 52. - Thus, the
load 25 may be raised and lowered by theforks 24 in response to the manual operation of the mast control valve 55, while themast 16 may be tilted by operation of thetilt control valve 58. - The force-moment compensator apparatus made in accordance with this invention includes a
counterweight 64 mounted for movement on theframe 11 of the forklift truck 10, such as in the longitudinal, front-to-rear direction along a slide bar ortrack 65. - The
counterweight 64 may be moved along the slide bar ortrack 65 by means of apiston rod 66 reciprocally movable within ahydraulic cylinder 67. Flow of the hydraulic fluid into theactuator cylinder 67 is controlled by aspool valve 68, disclosed in its neutral position in FIG. 3. By energization of theextension solenoid 69, thespool valve 68 is shifted to the right (FIG. 3) to cause hydraulic fluid from theline 61 to pass through theline 71 into the rear end of thecylinder 67 thereby projecting thepiston rod 66 forward, to extend thecounterweight 64 along the slide rod 65.-Fluid from thecylinder 67 passed through theforward line 72 back through thespool valve 68 to thereturn line 62 into thereservoir 52. - The
extension solenoid 69 and thereturn solenoid 70 are energized through their respectiveelectrical lines - When the
return solenoid 70 is energized, thespool valve 68 is shifted to the left of FIG. 3, to reverse the direction of the flow of hydraulic fluid from theline 61 to theline 72 in order to retract thepiston rod 66 andcounterweight 64. - The extent of travel of the
counterweight 64 along thetrack 65, or the position to which thecounterweight 64 is moved, is controlled by a sensing device, in the form of the pressure transducer 77, mounted in fluid communication with the base of thehydraulic lift cylinder 17, or other lift-type device. Thus, the pressure of the hydraulic fluid within thecylinder 17, which in turn is determined by the weight of theload 25 upon theforks 24, determines the value of the electrical signal transmitted from the pressure transducer 77 through theinput line 78 to theelectrical control circuit 75. The signal from theinput line 78 is processed in thecontrol circuit 75 to arm or condition one of the spacedlimit switches counterweight 64. Thus, when thecounterweight 64 arrives at the desired position to counterbalance the sensed weight of theload 25, it will actuate the particular limit switch, such aslimit switch 81, or variable transducer, which in turn will energize thecontrol circuit 75 to de-energize theextension solenoid 69 and stop the counterweight in the desired safe position. - The
counterweight circuit 85 within thecontrol circuit 75 for controlling the position of thecounterweight 64 is disclosed in the upper portion of FIG. 4. - The pressure transducer 77 includes a plurality of graduated pressure threshold settings, P1, P2 and P3, or it may be a variable sensing transducer (FIG. 4). For example, a low-pressure signal from the transducer 77 (FIG. 4) will be admitted through the
input lead 88 for P1 (FIG. 4), whereas no signals will be transmitted throughleads input lead 88 will be processed in thecomparator circuit 91 to produce an amplified output signal transmitted throughoutput line 92 to the integratedamplifier 93. The input signal passing through theinput line 92 will be compared, or integrated, in the integratedamplifier 93 with a feedback signal transmitted from theline 94. The resultant output signal in theline 95 energizes thecounterweight positioning control 96, which transmits a signal through theline 73 to theextension solenoid 69. - The feedback signal transmitted to the integrated
amplifier 93 through theline 94 originates in one of thelimit switches feedback line 97 to arelay circuit 98 in order to provide a reference signal to indicate in thecircuit 85 the actual position of thecounterweight 64 at any particular moment. Thus, when the summation of the feedback signal and the input signal fromline 92 in the integratedamplifier 93 produces a resultant null or zero signal in theoutput circuit 95, then theextension solenoid 69 will be de-energized and thespool valve 68 returned to its neutral position to stop thecounterweight 64 at the desired position corresponding to the pressure signal generated by the transducer 77. - In lieu of the
electronic counterweight circuit 85, themagnetic relay circuit 100, disclosed in FIG. 5, could be employed. The terms PS1, PS2 and PS3 indicate the respective pressure switches which are actuated respectively at increasing intervals of pressure sensed by transducer 77. The three relay coils are designated R1, R2 and R3. The relay coil R1, when energized, closes the respective relay switches RS1, in each of thepressure sensing circuit 101, theoverload circuit 102 and thecounterweight circuit 103. - In like manner, when the relay coil R2 is energized, the normally closed relay switches RS2 are opened, while the normally open relay switches RS2 are closed. The relay coil R3 controls the relay switches RS3 in the same manner.
- Therefore, if a low-pressure signal is detected to close the pressure switch PS1, the relay coil R1 is energized, while the relay coils R2 and R3 are de-energized. The relay switch RS1 across the pressure switch PS1 is closed to hold the
circuit 101, controlled by the relay coil R1, energized. Theoverload safety circuit 102 controlled by the switch RS1 is closed, and thecounterweight circuit 103 including the relay switch RS1 is also closed to energize theextension relay coil 69 causing thecounterweight 64 to travel toward the left in FIG. 2. When the actuator arm 83 engages thelimit switch 80, the limit switch is opened to de-energize thecounterweight coil 69 and stop thecounterweight 64 in its first position. - The same operation is effected for successively higher pressures to successively energize relay coils R2 and then R3.
- When the
load 25 is removed from the forklift, or when it is no longer desired to operate the forklift truck 10, or for any reason, theswitch 104 may be opened, simultaneously closing theswitch 105 to energize thereturn counterweight coil 70 and restore thecounterweight 64 to its original position. When thecounterweight 64 returns to its original position, it engages and openslimit switch 106 to de-energize thereturn solenoid 70. - A
translatory sensor 108, preferably in the form of a rotary potentiometer, is mounted in a fixed position relative to themast 16. Fixed to thepiston rod 18 is an elongated bracket arm or track against which the rotary member of therotary potentiometer 108 is adapted to travel. Thus, as thepiston rod 18 rises relative to thehydraulic lift cylinder 17, the rotary potentiometer ortranslatory sensor 108 produces an electrical signal of a value or voltage proportionate or commensurate with the vertical distance traveled by thearm 109, and therefore thepiston rod 18 and theload 25. The translatory signal is transmitted from thetranslatory sensor 108 throughlead 110 to thecontrol circuit 75. - In like manner, an
angular sensor 112, also preferably in the form of a rotary potentiometer having its rotary member adapted to roll on the elongated bracket or track 113 fixed to thetilt piston rod 29, produces a signal commensurate with, or proportional to, the tilt angle of themast 16, which is transmitted through thelead 114 to thecontrol circuit 75. - As best disclosed in the lower portion of the circuit diagram of FIG. 4, the translatory signal transmitted through the
input line 110, and the angular signal transmitted through theline 114, are amplified by therespective amplifier circuits amplifier 118 and compared with the feedback signal received through theline 120. The resultant signal from theintegrated amplifier 118 is transmitted through theoutput lead 122 to energize the speed-control device 50, thereby actuating the variable pump 34 to adjust the flow of hydraulic fluid, and consequently the speed of the vehicle 10 commensurate with the signals generated by thetranslatory sensor 108 and theangular sensor 112. - Connected in the
mast feed circuit 56 is anoverload safety device 123 including three solenoid valves 124,125, and 126, all connected in parallel, and each adapted to be energized at the same time that acorresponding limit switch counterweight 64 is atposition 1, as disclosed in FIG. 2, that is when the actuator 83 is actuating thefirst limit switch 80, then thesolenoid valve 124 is opened to activate the overload switch 127 (FIG. 6). While thecounterweight 64 is in its first position and the hydraulic circuitry, particularly in themast feed line 56 has its pressure suddenly rise, the excess pressure will be dumped through the solenoid valve 124 (FIG. 6) andoverload valve 127 back to the reservoir. Thevalves counterweight 64 is located in its second and third positions, respectively. - The
circuit 102 in FIG. 5 has the same function as thecircuit 123 in FIG. 6. - The
counterweight control circuit 85, disclosed in FIG. 4 is connected to theoverload safety circuit 123 by thelead 130. - The operation of the force-moment compensator apparatus when specifically applied to a load-handling apparatus or vehicle, such as forklift truck 10, is as follows:
- The operator of the forklift truck 10 starts the
prime mover 32 to commence the circulation of hydraulic fluid via the variable-volume pump 34 through thehydraulic fluid lines 36 and 38 to drive therespective wheel motors lines 54 and 57 to the mast control valve 55 and thetilt control valve 58. - In order to lift a
load 25,forks 24 are lowered to their load-engaging position by manipulation of the handle on the mast control valve 55. The vehicle 10 is then propelled forward to insert theforks 24 beneath theload 25, and the mast control valve 55 is manipulated to lift theforks 24, and therefore theload 25, to the desired elevation, such as the elevation disclosed in phantom in FIG. 1. Theload 25 may be tilted rearward by manipulating thetilt control valve 58. - The pressure sensor 77 then senses the pressure within the
mast cylinder 17, which is commensurate with the weight of theload 25, and sends a corresponding signal to thecontrol circuit 75 for processing, such as by thecounterweight control circuit 85 of FIG. 4. If the sensed load is within its limits, that is, less than its predetermined threshold value, thecounterweight 64 does not move. If the threshold value is exceeded, theextension solenoid 69 is energized to actuate thespool valve 68.Spool valve 68 is then manipulated to actuate thecounterweight cylinder 67 to extend thecounterweight 64 to a predetermined position, such as the position disclosed in FIG. 2 in which the actuator 83 engages and actuates thelimit switch 80. The feedback signal generated by thelimit switch 80 is then fed to thecontrol circuit 85 in order to stop the movement of thecounterweight 64 in its desired position, properly counterbalancing the weight and position of theload 25 resting upon theforks 24 to provide a predetermined safe center of gravity for theforklift truck 15 which will adequately stabilize the vehicle during its movement. - If the
load 25 is raised to an excessive elevation, signals from thetranslatory sensor 108 and thetilt sensor 112 will be transmitted to thespeed control circuit 111 where the desired output signal will be produced and transmitted through theline 122 to the speed control device 50 to actuate the variable-volume pump 34 in order to reduce the speed of the vehicle 10 to a safe speed for movement of the vehicle 10 with theload 25 in its particular elevated and angular position. - The
overload safety circuits reservoir 52 should themast feed line 56 encounter any sudden or excessively high fluid pressures. - When the angle of tilt of the
load 25 is changed by the actuation of thetilt cylinder 27 through thetilt control valve 58, or theload 25 is lowered by lowering theforks 24, then the signals generated by thetranslatory sensor 108 and thetilt sensor 112 will be processed in thespeed control circuit 111 to produce a corresponding resultant signal in theline 122 for ultimately increasing, or otherwise changing the maximum or travel speed of the vehicle 10. -
Loads 25 having weights of different values will develop corresponding signals of different values in the pressure transducer 77 for varying the position of thecounterweight 64 to properly counterbalance theload 25 in the vehicle 10 to appropriately maintain the center of gravity of the vehicle 10 between thewheels - Thus, the stability of the vehicle 10 will always be maintained regardless of the value or position of the
load 25 handled by theforks 24. - The same circuits and components can be adapted and applied to other types of vehicles and other types of load handling apparatus in which the center of gravity or other forces or force-moments are apt to change by virtue of the weights and positions of the loads handled by load handling apparatus, or by virtue of changes in movement of vehicles, such as changes in turning or directional movements creating centrifugal forces.
Claims (8)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AT81901391T ATE20458T1 (en) | 1980-09-02 | 1980-09-02 | FORCE-TORQUE COMPENSATION DEVICE. |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/US1980/001131 WO1982000815A1 (en) | 1980-09-02 | 1980-09-02 | Force-moment compensating apparatus |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0058671A1 EP0058671A1 (en) | 1982-09-01 |
EP0058671A4 EP0058671A4 (en) | 1983-04-29 |
EP0058671B1 true EP0058671B1 (en) | 1986-06-18 |
Family
ID=22154519
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP81901391A Expired EP0058671B1 (en) | 1980-09-02 | 1980-09-02 | Force-moment compensating apparatus |
Country Status (6)
Country | Link |
---|---|
EP (1) | EP0058671B1 (en) |
JP (1) | JPS57501424A (en) |
AT (1) | ATE20458T1 (en) |
AU (1) | AU7223581A (en) |
DE (1) | DE3071653D1 (en) |
WO (1) | WO1982000815A1 (en) |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2160167B (en) * | 1984-06-04 | 1987-12-02 | Trevor Frederick Spencer | Improvements in or relating to tractors |
AU623485B2 (en) * | 1989-01-31 | 1992-05-14 | Phillip Jules Arnold | Fork lift truck |
DE29922311U1 (en) * | 1998-12-23 | 2000-04-06 | Palfinger Crayler Staplertechn | Forklift |
GB2347132A (en) * | 1999-02-27 | 2000-08-30 | Translift Engineering Limited | Lift truck |
GB2355244A (en) * | 1999-08-05 | 2001-04-18 | Terence Harley | Fork-lift truck auto-balancing system |
ITTO20070365A1 (en) * | 2007-05-23 | 2008-11-24 | Cnh Italia Spa | METHOD AND DEVICE FOR THE LONGITUDINAL BALANCE OF AN AGRICULTURAL VEHICLE |
US8131433B2 (en) | 2007-05-23 | 2012-03-06 | Cnh America Llc | Device for longitudinally balancing an agricultural vehicle |
Family Cites Families (15)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2759563A (en) * | 1952-09-13 | 1956-08-21 | Marnon | Adjustable counterweight for lift vehicles |
DE1057534B (en) * | 1957-02-01 | 1959-05-14 | Hans Still Ag | Counterweight for truck |
US2935161A (en) * | 1957-11-07 | 1960-05-03 | Allis Chalmers Mfg Co | Safety system for load elevating vehicles |
US2916172A (en) * | 1958-06-13 | 1959-12-08 | Burton H Locke | Fork lift truck with shiftable ballast |
FR1330879A (en) * | 1962-05-17 | 1963-06-28 | Device for distributing the weight of a vehicle carrying cantilever loads over the axles | |
US3497095A (en) * | 1966-01-12 | 1970-02-24 | Benjamin L Couberly | Counterbalance apparatus for a lift truck |
US3713129A (en) * | 1970-03-30 | 1973-01-23 | R Buchholz | Crane overloading protective system |
US3680714A (en) * | 1970-07-22 | 1972-08-01 | Case Co J I | Safety device for mobile cranes |
PL76664B1 (en) * | 1971-05-13 | 1975-02-28 | ||
US3734326A (en) * | 1971-07-15 | 1973-05-22 | Eaton Corp | Variable capacity lift truck |
GB1526047A (en) * | 1974-11-22 | 1978-09-27 | Pye Ltd | Calibration of crane load indicating arrangement |
US4068773A (en) * | 1975-04-03 | 1978-01-17 | Allis-Chalmers Corporation | Lift vehicle with fail-safe overload protective system |
US3993166A (en) * | 1975-04-29 | 1976-11-23 | Bofors America, Inc. | Overload signalling system for fork lift trucks and the like |
FR2415599A1 (en) * | 1978-01-26 | 1979-08-24 | B & A Eng Co | LOAD WEIGHING DEVICE FOR CRANES |
US4221530A (en) * | 1978-06-08 | 1980-09-09 | Williams Iv James M | Force-moment compensating apparatus |
-
1980
- 1980-09-02 AU AU72235/81A patent/AU7223581A/en not_active Abandoned
- 1980-09-02 DE DE8181901391T patent/DE3071653D1/en not_active Expired
- 1980-09-02 AT AT81901391T patent/ATE20458T1/en not_active IP Right Cessation
- 1980-09-02 JP JP56501877A patent/JPS57501424A/ja active Pending
- 1980-09-02 WO PCT/US1980/001131 patent/WO1982000815A1/en active IP Right Grant
- 1980-09-02 EP EP81901391A patent/EP0058671B1/en not_active Expired
Also Published As
Publication number | Publication date |
---|---|
JPS57501424A (en) | 1982-08-12 |
EP0058671A1 (en) | 1982-09-01 |
AU7223581A (en) | 1982-04-05 |
WO1982000815A1 (en) | 1982-03-18 |
DE3071653D1 (en) | 1986-07-24 |
ATE20458T1 (en) | 1986-07-15 |
EP0058671A4 (en) | 1983-04-29 |
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