US20040158380A1 - Hydraulic stabilizer system and process for monitoring load conditions - Google Patents

Abstract

A process for monitoring load conditions on a lifting machine having a rated load moment includes determining an actual load moment of the lifting machine due a weighted load. The actual load moment may be determined by measuring a tilt pressure within a hydraulic tilt cylinder of the lifting machine, and then calculating the actual load moment from the tilt pressure within the hydraulic tilt cylinder. The location of a center of gravity of the weighted load is also determined by measuring a lift pressure within a hydraulic lift cylinder of the lifting machine, and then calculating the weight of the weighted load from the lift pressure. Once the weight is determined, the location of the center of gravity of the weighted load may be found using the actual load moment and the calculated weight. Information about the weight and the location of the center of gravity of the weighted load may be also provided to a user as well as warnings if the operating parameters of the lifting machine are in danger of being exceeded or actually exceeded. If a load pressure switch of the lifting machine is activated, at the very least, the lifting function of the machine will be disabled.

Description

BACKGROUND OF THE INVENTION
• The present invention relates to a lifting device. More particularly, the present invention relates to a lifting device capable of calculating the center of gravity of a load and determining if the center of gravity exceeds safety parameters.[0001]
• In fork lifts, the tipping moment is critical to machine safety. In fork-lift trucks, the center of gravity of the lifted load is naturally outside the wheel contact surface. The amount of counterweight is sized based on factors such as wheel base, lifting capacity, and distance from the center of the front axle to the center of the load.[0002]
• In some applications, the operator has a limited knowledge of either the weight of the lifted load, the center of gravity of the load, or both. If an operator lifts a load that has a weight within the lifting capacity of the machine, but the center of gravity is too far out front, the machine risks tipping forward. If the center of gravity of the load is within the machine rating, but the weight lifted is too great, the machine risks tipping forward. The product of the load weight times the distance to the load center is known as the load moment. The operator needs to know if the load moment is within the safe limits of the machine.[0003]
• In other lifting systems, such as cranes, there are many techniques used to provide an operator information on the safe lifting of various loads. In most fork lift applications, if the load weight varies or is not known, a scale is added to the machine such that the load weight can be measured and displayed. The shape of the load is typically of a sort that an operator can easily measure or evaluate the load center of gravity location. Thus, in most fork lift applications, the operator can determine the safety of lifting various loads.[0004]
• Prior attempts have been made to address the issue of tilt and center of gravity. For example, Rickers et al., U.S. Pat. No. 6,385,518, discloses an industrial truck, such as a fork-lift, that detects a tilt of the industrial truck based on wheel load. Wheel load sensors are used to detect a load moment of the fork-lift and then signal an alarm if tilt is detected. However, the condition of the wheels themselves may affect the ability of the wheel load sensors to properly detect load moment. In another example, Goto, U.S. Pat. No. 6,425,728, discloses a tilt speed control system that controls the tilt speed of a fork-lift mast, based on the weight of a load and lift height of the load as the load is being lifted. However, this system fails to assist the user in determining if the load is causing the lift to exceed safety limits. In a further example, Bruns, U.S. Pat. No. 5,666,295, discloses dynamic weighing of loads in hydraulically operated lifts. However, Bruns only discloses determining the weight of a load and fails to assist the user in determining if the load is causing the lift to exceed safety limits.[0005]
• In a few applications, even if the operator knew the weight of the load, there still might be considerable difficulty in determining the location of the center of gravity. An example is that of lifting boats. Engine location, amount and location of ballast, amount of fluid in the water and fuel tanks, all can be extremely difficult for the operator to determine or evaluate. There is a need to know what the load moment is as the forks engage the boat hull.[0006]
• While methods such as those described above may provide a means for tilt caused by a load on a lift, such methods can always be improved.[0007]
• Accordingly, there is a need for a means to measure both load weight and load moment as the load is engaged on the lifting machine. Further, there is a need to provide information to the operator about the weight and location of the center of gravity, provide a warning if the load is near the rated capacity of the machine, and disable the lifting capability if there is a danger of tipping. The present invention fulfills these needs and provides other related advantages.[0008]
SUMMARY OF THE INVENTION
• The present invention resides in a process and system for a lifting determining an actual load moment, weight, and location of the center of gravity of a weighted load on a lifting machine and determining if the safety parameters of the machine are exceeded.[0009]
• The invention provides a means to measure both load weight and load moment as the load is engaged on the lifting machine, provide information to the operator about the weight and location of the center of gravity, provide a warning if the load is near the rated capacity of the machine, and disable the lifting capability if there is a danger of tipping.[0010]
• In accordance with a preferred embodiment of the present invention, a process for monitoring load conditions on a lifting machine having a rated load moment includes determining an actual load moment of the lifting machine due a weighted load. The actual load moment may be determined by measuring a tilt pressure within a hydraulic tilt cylinder of the lifting machine, and then calculating the actual load moment from the tilt pressure within the hydraulic tilt cylinder.[0011]
• The process also includes determining a location of a center of gravity of the weighted load. This is determined by measuring a lift pressure within a hydraulic lift cylinder of the lifting machine, and then calculating the weight of the weighted load from the lift pressure. Once the weight is determined, the location of the center of gravity of the weighted load may be found using the actual load moment and the calculated weight.[0012]
• Information about the weight and the location of the center of gravity of the weighted load may be also provided to a user. Warnings may be provided to the user if the weighted load is near the rated load moment of the lifting machine. A first warning may be activated if the actual load moment is below a first predetermined load moment. Second and third warnings may be activated, respectively if the actual load moment is above the first predetermined load moment and below a second predetermined load moment, or if the actual load moment is above the second predetermined load moment.[0013]
• The first, second, and third warnings may be in the form of colored lights. The first and second predetermined load moments may be, respectively, between 80% to 100% of the rated load moment and 100% to 120% of the rated load moment. Additionally, an audio alarm may be engaged, respectively, if the actual load moment is above the first predetermined load moment and below the second predetermined load moment or if the actual load moment is above the second predetermined load moment.[0014]
• If a load pressure switch of the lifting machine is activated, the hydraulic lift will be disabled.[0015]
• Further in accordance with the present invention, a hydraulic stabilizer system may be configured as a hydraulic lift having a rated load moment. The system includes a means for measuring pressure within the hydraulic lift and a processor for determining an actual load moment of the hydraulic lift and for determining a weight of a load on the hydraulic lift based on pressure within the hydraulic lift.[0016]
• The system also includes an illuminated display for warning an operator of the hydraulic lift if at least one predetermined operating parameter is exceeded; and a load pressure switch for disabling the hydraulic lift if another predetermined operating parameter is exceeded.[0017]
• The hydraulic lift includes a frame, at least one load bearing member operationally connected to the frame for movement relative thereto. The lift also includes a hollow lift cylinder housing a lift piston and hydraulic fluid and a hollow tilt cylinder housing a tilt piston and hydraulic fluid. Each cylinder piston is operationally connected to the load bearing member, with the hydraulic fluid disposed between the piston and one end of the frame. The lift piston imparts a lift force upon the hydraulic fluid within the lift cylinder proportional to a weight associated with the load bearing member and the tilt piston imparts a tilt force upon the fluid proportional to a load moment associated with the load bearing member.[0018]
• The means for measuring pressure within the hydraulic lift may be a number of pressure sensors with at least one pressure sensor in fluid communication with the hydraulic fluid within the lift cylinder and at least one pressure sensor in fluid communication with the hydraulic fluid within the tilt cylinder. The lift pressure sensor measures pressure of the hydraulic fluid within the lift cylinder for a period of time and creates electrical signals corresponding thereto, defining at least one pressure measurement within the lift cylinder, with the pressure within the lift cylinder being related to the lift force associated with the load bearing member. The tilt pressure sensor measures pressure of the hydraulic fluid within the tilt cylinder for a period of time and creates electrical signals corresponding thereto, defining at least one pressure measurement within the tilt cylinder, with the pressure being related to the tilt force associated with the load bearing member.[0019]
• The processor includes a first sub-routine of a program stored in a memory to be operated on by the processor, determining, from a plurality of pressure measurements within the lift cylinder, the weight of the load on the hydraulic lift. The processor also includes a second sub-routine of the program stored in the memory to be operated on by the processor, determining, from another plurality of pressure measurements within the tilt cylinder, an actual load moment of the load on the hydraulic lift. The processor may then use another sub-routine of the program that uses the actual load moment and the weight of the load to determine a location of a center of gravity of the load on the hydraulic lift.[0020]
• The illuminated display is in data communication with the processor and produces a visual representation of the weight on the hydraulic lift. The illuminated display activates a first warning if the actual load moment is below a first predetermined load moment, activates a second warning if the actual load moment is above the first predetermined load moment and below a second predetermined load moment, and activates a third warning if the actual load moment is above the second predetermined load moment.[0021]
• As stated above, the first predetermined load moment may be 80% to 100% of the rated load moment, and the second predetermined load moment may be 100% to 120% of the rated load moment. Also, the first, second, and third warnings may be colored lights. Again, the illuminated display may engage a first audio alarm if the actual load moment is above a first predetermined load moment and below a second predetermined load moment, and/or engage a second audio alarm if the actual load moment is above the second predetermined load moment.[0022]
• Other features and advantages of the invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.[0023]
BRIEF DESCRIPTION OF THE DRAWINGS
• The accompanying drawings illustrate the invention. In such drawings:[0024]
• FIG. 1 is an orthogonal view of a hi-lift marina bull in accordance with an embodiment of the present invention;[0025]
• FIG. 2. is a simplified schematic view of a hydraulic system of hi-lift marina bull of FIG. 1;[0026]
• FIG. 3. is a simplified schematic view of the electrical/hydraulic system of the hi-lift marina bull of FIG. 1;[0027]
• FIG. 4. is a flowchart illustrating a process for determining the actual load moment, actual load weight, and load center of gravity of a load lifted by the marina bull of FIG. 1; and[0028]
• FIG. 5. is a flowchart illustrating an alternative process for determining the load moment of a load lifted by the marina bull of FIG. 1.[0029]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
• The present invention is useful in a variety of applications involving lifting machines, in particular, forklifts that lift loads, such as watercraft. It provides a means to measure operating conditions of the lifting machine, such as both the weight and longitudinal load moment of a load as the load is engaged on the lifting machine. When combined with the geometry of the lifting machine, the load moment and load weight are used to calculate the load center of gravity location. Continuous information may also be provided to a user operating the lifting machine; information relating to the weight and location of the center of gravity during the lifting, transporting, and lowering of the load. The present invention also provides a warning if the load is near a rated capacity of the lifting machine, and disables the lifting capability of the lifting machine if there is a danger of the lifting machine tipping. The lifting machine has a rated load moment determined by adding the rated load center (i.e., distance from the face of the forks to the center of the rated load) to the lost load (i.e., distance from the face of the lifting machine to the center of a front drive axle of the lifting machine). The result is then multiplied by the load weight to reach the rated load moment.[0030]
• A process and system are designed for continuously monitoring the operating conditions of the lifting machine by monitoring pressure in the tilt and lift cylinders of the lifting machine. This tilt pressure is proportional to the tilt moment of the fork lift. Use of this tilt pressure combined with lift hydraulic pressure through a mathematical algorithm, executed by an on-board processor, yields values for both load weight and load center of gravity. This provides for a system with continuous, real-time monitoring of an operator's usage of the machine and provides warnings and function disabling in order to improve safety.[0031]
• In accordance with the invention, a hydraulic stabilizer system may be configured on a number of different hydraulic lifting machines, such as a fork-lift, marina bull, yard bull, etc. However, for the purposes of discussion, as illustrated in FIGS.[0032]1-3, the present invention will be described with reference to a high-lift marina bull10 having a rated load moment. Themarina bull10 has a main body orframe12 supported by a plurality ofwheels14. Themain body12 further includes aoperator seat16 having acontrol console18 to control the operation of themarina bull10. Attached to themain body12 is a vertically extendingmast20. A load bearing member, in the form of acarriage22, is movably attached to themast20 and includes a plurality offorks24, extending perpendicular from themast20 away from themain body12. Lift-chains26 are attached to thecarriage22 and extend oversprockets28 which are positioned proximate to one end of themast20, opposite to the plurality ofwheels14. At least onehollow lift cylinder30 housing alift piston32 andhydraulic fluid34 is attached to themast20, with one end of the lift-chains26 being attached to thecylinder30. Thepiston32 is connected to thesprockets28 by a rod and movement of thecylinder30 causes thecarriage22 to move along themast20. One or morehollow tilt cylinders36, preferably two tilt-cylinders, are also attached to themain body12. Eachtilt cylinder36 houses atilt piston38 andhydraulic fluid34, with one end of eachtilt cylinder36 attached to the mast20 (by the rod connected to the tilt piston38) and the other end of thetilt cylinder36 is connected to theframe12. Movement of thetilt cylinders36 causes themast20 to tilt so as to prevent tipping of the high-lift marina bull10.
• [0033]Hydraulic fluid34 in thelift cylinder30 is disposed between thelift piston32 and one end of thecylinder30 having anaperture40, with thepiston32 imparting a force upon thehydraulic fluid34 proportional to a weight associated with the load bearing member (i.e.,carriage22,forks24, and load).Hydraulic fluid34 in eachtilt cylinder36 is disposed between thepiston38 and one end of thecylinder36 having anaperture42, with thepiston38 imparting a force upon thehydraulic fluid34 proportional to a load moment associated with the load bearing member (i.e.,carriage22,forks24, and load).
• A conventional[0034]hydraulic control system44 is connected to thecontrol console18. Thehydraulic control system44 is in fluid communication with eachcylinder30,36, and regulates the ingress and egress of thehydraulic fluid34 through therespective apertures40,42 of eachcylinder30,36. A means for measuringpressure46 is located between thecontrol system44 and eachcylinder30,36. Thecontrol system44 includes adirectional control valve48 that routeshydraulic fluid34 into the top or bottom of a given hydraulic cylinder (i.e., above or below the piston)30,36 in order to cause thecylinder30,36 to expand or contract by moving the piston within eachcylinder32,38.
• In order to measure the pressure of the[0035]hydraulic fluid34 in thecylinders30,36, the means for measuringpressure46, such as a pressure sensor which may be in the form of a pressure transducer, is placed in fluid communication withhydraulic fluid34 within eachcylinder30,36. The pressure sensor converts pressure readings into electrical signals. Acontrol unit50 is in electrical communication with the means for measuring pressure and receives the electrical signals from the pressure sensors to determine, from the pressure of the fluid34 within thelift cylinder30, the weight of a load on theforks24, and from the pressure of the fluid34 within thetilt cylinder36, the load moment of the load on the forks.
• The[0036]pressure sensor46 connected to thelift cylinder30 continuously measures the pressure of thehydraulic fluid34 within thelift cylinder30 and creates electrical signals corresponding thereto, defining at least one pressure measurement within thelift cylinder30. The pressure within thelift cylinder30 is related to the lift force associated with the load bearing member (i.e., the force required to lift thecarriage22,forks24, and load on the load bearing member). Thepressure sensor46 connected to thetilt cylinder36 continuously measures the pressure of thehydraulic fluid34 within thetilt cylinder36 and creates electrical signals corresponding thereto, defining a at least one pressure measurement within thetilt cylinder36. The pressure within thetilt cylinder36 is related to the tilt force associated with the load bearing member (i.e., the force required to tilt thecarriage22,forks24, and load on the load bearing member).
• The[0037]pressure sensors46 are connected to counter-balancevalves52 which acts as check valves to hold thecylinders30,36 in position when the operator is not directing the expansion or contraction of thecylinders30,36. Thecounter-balance valves52 are located between, and in fluid communication with, theirrespective cylinders30,36 and thedirectional control valve48. Thedirectional control valve48 is in fluid communication with ahydraulic fluid tank54. When activated, apump56 moves the hydraulic fluid34 from thetank54 to thedirectional control valve48 which then directs thehydraulic fluid34 to, for example, below thelift piston32 of thelift cylinder30 if a user desires to raise a load. When a user desires to lower a load, thedirectional control valve48 directshydraulic fluid34 into thelift cylinder30 above thelift piston32 in order to lower the load.
• The[0038]control unit50 is electrically connected to aload pressure switch58, in the form of a solenoid valve. Theload pressure switch58 is activated by electrical signals from thecontrol unit50 and disables the lift function by closing a valve that either divertshydraulic fluid34 back to thetank54, or otherwise prevents the hydraulic fluid34 from reaching thelift cylinder30. When there is an overload condition that could cause the liftingmachine10 to tip over (e.g., weight of the load exceeds the capacity of the lifting machine; the actual load moment exceeds the rated load moment, etc.), thecontrol unit50 sends an electrical impulse to thepressure switch58, opening the valve thereby disabling the lifting function of the liftingmachine10 by diverting the hydraulic fluid34 from thedirectional control unit48 to thetank54.
• The[0039]control unit50 is also electrically connected to an illuminateddisplay60 andaudio alarm62 on or near thecontrol console18. Thecontrol unit50 includes a digital computer that has a processor and a memory. In the alternative, an analog computer may be used. A computer program stored within the memory includes a mathematical″algorithm, executed by the processor which yields load weight, load moment, and load center of gravity when the processor receives electrical signals corresponding to pressure measurements within the hydraulic lift andtilt cylinders30,36 from the means for measuringpressure46.
• A software program is stored in a memory to be operated on by the processor within the[0040]control unit50. This program includes a first sub-routine for determining, from at least one pressure measurement within thelift cylinder30, the weight of the load on the liftingmachine10. In the alternative, a plurality of lift cylinder pressure measurements may be taken, preferably ten pressure measurements. The program also includes a second sub-routine for determining, from at least one pressure measurement within thetilt cylinder36, an actual load moment of the load on the liftingmachine10. In the alternative, a plurality of tilt cylinder pressure measurements may be taken, preferably ten pressure measurements. Yet another sub-routine within the program may then use the actual load moment and the weight of the load to determine a location of a center of gravity of the load on the liftingmachine10.
• The illuminated[0041]display60 warns an operator of the liftingmachine10 if a predetermined operating parameter of the liftingmachine10 is being exceeded. The illuminateddisplay60 is in data communication with the processor and produces a visual representation of the weight, actual load moment, and center of gravity. The visual representation may be produced by a Liquid Crystal Display (LCD) monitor, Cathode Ray Tube (CRT) monitor, dials, gauges, etc. If operating parameters are exceeded, warnings may be provided in the form of colored lights and/or audible alarms. For example, when the pressure on the rod side of the tilt cylinder(s)36 is below a set pressure, the actual load moment is below a specified rated load moment (e.g., 90% of the rated load moment), a first warning, in the form of agreen light64 located on thedisplay60 will be illuminated. If the actual load moment is above the specified rated load moment and below a specified overload rated load moment (e.g., 110% of the rated load moment), a second warning, in the form of ayellow light66 and alow frequency alarm68 will be activated (the green light is not illuminated). If the actual load moment is above the specified overload rated load moment, a third warning, in the form of ared light70 will be illuminated (green andyellow lights64,66 are not illuminated) and ahigh frequency alarm72 will be activated, in addition to the lift function being disabled. Additionally, if aload pressure switch58 is activated, the lift function is disabled, and lights64,66 are off while light70 remains on.
• The predetermined operating parameters may vary, depending on individual application and operating environment. The operator may change settings on the[0042]control console18 for the proper application and operating environment. As stated above, the first predetermined load moment may be 90% of the rated load moment although the first predetermined load moment may be anywhere in the range of 80% to 90% of the rated load moment. Likewise, the second predetermined load moment may be 110% of the rated load moment although the second predetermined load moment may be anywhere in the range of 100% to 120% of the rated load moment. Also, the first, second, and third warnings may be colored lights. Again, the illuminated display may engage a first audio alarm if the actual load moment is above a first predetermined load moment and below a second predetermined load moment, and/or engage a second audio alarm if the actual load moment is above the second predetermined load moment. The first predetermined load moment may be in the range of 80% to 100% of the rated load moment, and the second predetermined load moment may be in the range of 100% to 120% of the rated load moment.
• As stated above, the[0043]display60 may produce a visual representation of the weight, actual load moment, and center of gravity. The illuminateddisplay60 may also include a visual representation of a graduated scale that illuminates and displays the actual load moment. This graduated scale may include indicia that runs from 0% to 150% of the rated load moment. The scale may included colored zones. For example, an actual load moment that is less than 50% of the rated load moment may be in a blue zone, an actual load moment that is more than 50% of the rated load moment but less than a first predetermined load moment may be in a green zone; an actual load moment that is in the between the first predetermined load moment and a second predetermined load moment may be in a yellow zone, and an actual load moment that is above the second predetermined load moment may be in a red zone. As stated above, the first predetermined load moment may be in the range of 80% to 100% of the rated load moment, and the second predetermined load moment may be in the range of 100% to 120% of the rated load moment.
• In the alternative,[0044]pressure sensors46 may be in the form of pressure switches that may be placed in direct fluid communication withhydraulic fluid34 within eachcylinder30,36. The pressure switches sense pressure and create electrical signals that may be sent to one or more of thelights64,66,70. These pressure switches are connected directly to a warning system that includes audio and visual alarms. For example, the pressure switch may be pre-set to be tripped if the pressure within thetilt cylinder36 reaches a first predetermined load moment that is in the range of 80% to 100% of the rated load moment, and the second predetermined load moment is in the range of 100% to 120% of the rated load moment. In another example, the pressure valve connected to the lift cylinder may be pre-set to be tripped if the pressure within thelift cylinder36 is at least, near or about the lifting capacity of the lifting machine.
• In use, one particular embodiment of a[0045]process74 for monitoring load conditions on a lifting machine having a rated load moment is illustrated in FIG. 4. Theprocess74 determines an actual load moment of the liftingmachine10 due the weight of the load by a computer program using input signals frompressure sensors46. The actual load moment may be determined by measuring tilt pressure within thehydraulic tilt cylinder36 of the liftingmachine10, and then calculating the actual load moment from the tilt pressure.
• The process begins with an initialization period,[0046]76 during which the lifting machine is activated and thecontrol unit50 begins a start-up process that activates the program stored in memory. Electrical signals from thepressure sensors46 arrive at the processor, when then converts the signals into numerical values which the processor uses as input values for the program.
• After initialization, the processor implements a[0047]first subroutine78 of the program to calculate the actual load moment of the liftingmachine10 using a plurality of pressure measurements (e.g., ten pressure measurements) sent to the processor from thepressure sensors46 connected to thetilt cylinder36. The program then calculates the average value of the ten tilt pressure measurements and, temporarily, stores the value.
• The processor then implements a[0048]second subroutine80 of the program to calculate the actual weight of the load using ten lift pressure measurements sent to the processor from thepressure sensors46 connected to thelift cylinder30. The program then calculates the average value of the ten pressure measurements and, temporarily, stores the value.
• The program then takes the stored values of the average tilt and lift pressures and converts[0049]82 them, respectively, to load moment and load weight. The center of gravity of the load is then determined84 by dividing the load moment by the load weight.
• Once the load weight, actual load moment, and load center of gravity are determined, information and warnings about the preceding may be provided to the operator of the lifting[0050]machine10 when the program determines if the actual load moment is greater than a pre-determined load moment somewhere in the range of 80% to 100% of the rated load moment of the liftingmachine10. If the load moment is not greater88 than that pre-determined load moment (e.g., 90% of the rated load moment of the lifting machine10), the processor will then display a first warning, by illuminating thegreen light64 located on thedisplay60. The processor will also output the calculated load weight, actual load moment, and center of gravity of the load to thedisplay60 in order to provide this information to the operator. The processor will also then repeat the process with another ten pressure measurements from the tilt and liftcylinders36,30 and repeat steps78-88.
• If the load moment is greater than 90% of the rated load moment of the lifting[0051]machine10, the program will then determine90 if the load moment is greater a second pre-determined load moment someone in the range of 100% to 120% (e.g., 110%) of the rated load moment. If the load moment is not greater92 than 90% of the rated load moment of the liftingmachine10, the processor will then display a second warning, by illuminating theyellow light66 located on thedisplay60. The processor will also output the calculated load weight, actual load moment, and center of gravity of the load to thedisplay60 in order to provide this information to the operator. The processor will also activate thelow frequency alarm68. The processor will then repeat the process with another ten pressure measurements from the tilt and liftcylinders36,30 and repeat steps78-92.
• If the load moment is greater than 110% of the rated load moment of the lifting[0052]machine10, the program will then display94 a third warning, by illuminating thered light70 located on thedisplay60. The processor will also output the calculated load weight, actual load moment, and center of gravity of the load to thedisplay60 in order to provide this information to the operator. The processor will also activate thehigh frequency alarm72 and disable lift function. The processor will also activate theload pressure switch58 to disable the lift function. The processor will then repeat the process with another plurality of pressure measurements (e.g., ten pressure measurements) from the tilt and liftcylinders36,30 and repeat steps78-94. Lift function will remain disabled if actual load moment remains greater than 110% of the rated load moment. Alternatively, lift function will be disabled if thepressure sensor46 within thelift cylinder30 measures pressure that correlates to the weight associated with the maximum lifting capacity of the liftingmachine10.
• An alternative embodiment of a[0053]process96 for monitoring load conditions on a lifting machine having a rated load moment is illustrated in FIG. 5. Theprocess96 is similar to theprocess74 of FIG. 4 except that pressure switches are used instead of pressure transducers and no program is used to calculate values into load moments, weight, and load center of gravity. Instead, the pressure switches directly activate warnings if pressure measurements exceed operating parameters. The process begins with aninitialization period98, during which the liftingmachine10 is activated and agreen light66 located on thedisplay60 is illuminated if the pressure switches are not open. For example, at least two pressure switches are pre-set to open at certain pressures which have been respectively correlated to, for example, 90% and 110% of the rated load moment of the liftingmachine10 and are in fluid communication with thetilt cylinder36 to measurepressure100 within thecylinder36. A pressure valve in fluid communication with thelift cylinder30 is pre-set to open at a certain pressure which has been correlated to the maximum weight the lifting machine is able to lift.
• The pre-set pressure switches ‘measure’[0054]pressure100 within theirrespective cylinders30,36, and set to determine if pressure within the tilt cylinder is greater than the pressure correlated to 90% of the ratedload moment102. If the pressure within thetilt cylinder36 is not greater104 than 90% of the rated load moment of the liftingmachine10, a first warning, in the form of the illuminatedgreen light64, will continue to be illuminated. The process continuously repeats as the pressure switch continues to ‘measure’ pressure within thetilt cylinder36, and repeats steps100-104.
• If pressure within the[0055]tilt cylinder36 is greater than the pressure correlated to 90% of the ratedload moment102, then the pressure switch pre-set to 90% of the rated load moment will open while the pressure switch pre-set to 110% of the rated load moment remains closed106. If the actual load moment is not greater108 than 110% of the rated load moment of the liftingmachine10, a second warning will be displayed by illuminating theyellow light66 located on thedisplay60, and illuminating thelow frequency alarm68. Thedisplay60 may also illuminate a warning indicator showing the approximate load moment which the pre-set pressure switch indicates has been exceeded. The process continuously repeats as the pressure switches continue to ‘measure’ pressure within thetilt cylinder36, and repeats steps100-108.
• If the load moment is greater than 110% of the rated load moment of the lifting[0056]machine10, a third warning will then be displayed110, by illuminating thered light70 located on thedisplay60, activating thehigh frequency alarm72, and disabling the lift function. The process continuously repeats as the pressure switches continue to ‘measure’ pressure within thetilt cylinder36, and repeats steps100-110. Lift function will remain disabled if actual load moment remains greater than 110% of the rated load moment. If the actual weight of the load exceeds the lifting capacity of the liftingmachine10, the pre-set pressure switch in thelift cylinder30, set to open when hydraulic fluid pressure within thelift cylinder30 meets or exceeds the pressure correlated to the maximum lifting capacity of the lifting machine, will open and the lift function will be disabled.
• In an alternative embodiment, a single pre-set pressure switch may be used to determine if pressure within the[0057]tilt cylinder36 is greater than a pre-determined load moment. This pre-determined load moment can be set anywhere in the range of 100% to 150% of the rated load moment. If the single pre-set pressure switch is activated, electrical signals will be sent to illuminate thered light70, sound an audio alarm, and/or activate theload pressure switch58 to disable the lifting function of the lifting machine.
• The above-described embodiments of the present invention are illustrative only and not limiting. It will thus be apparent to those skilled in the art that various changes and modifications may be made without departing from this invention in its broader aspects. Therefore, the appended claims encompass all such changes and modifications as falling within the true spirit and scope of this invention.[0058]

Claims (42)

What is claimed is:

1. A process for monitoring load conditions on a lifting machine having a rated load moment, comprising the steps of:

determining an actual load moment of the lifting machine due a weighted load;

activating a first warning if the actual load moment is below a first predetermined load moment;

activating a second warning if the actual load moment is above the first predetermined load moment and below a second predetermined load moment; and

activating a third warning if the actual load moment is above the second predetermined load moment.

2. The system ofclaim 1, wherein the first, second, and third warnings are colored lights.

3. The process ofclaim 1, wherein the determining step further includes the steps of measuring a tilt pressure within a hydraulic tilt cylinder of the lifting machine, and calculating the actual load moment from the tilt pressure within the hydraulic tilt cylinder.

4. The process ofclaim 3, further including the steps of measuring a lift pressure within a hydraulic lift cylinder of the lifting machine, calculating the weight of the weighted load from the lift pressure, and calculating a location of the center of gravity of the weighted load using the actual load moment and the calculated weight.

5. The process ofclaim 1, wherein the first predetermined load moment is 80% to 100% of the rated load moment.

6. The process ofclaim 1, wherein the second predetermined load moment is 100% to 120% of the rated load moment.

7. The process ofclaim 1, including the step of engaging an audio alarm if the actual load moment is above the first predetermined load moment and below the second predetermined load moment.

8. The process ofclaim 1, including the step of engaging an audio alarm if the actual load moment is above the second predetermined load moment.

9. The process ofclaim 1, including the step of disabling the lifting machine if a load pressure switch of the lifting machine is activated.

10. The process ofclaim 1, wherein the determining step includes the steps of weighing the weighted load and calculating a location of a center of gravity of the weighted load.

11. The process ofclaim 10, further including the step of providing information to a user about the weight and the location of the center of gravity of the weighted load, whereby a warning is provided to the user if the load is near the rated load moment of the lifting machine.

12. A process for monitoring load conditions on a lifting machine having a rated load moment, comprising the steps of:

measuring a tilt pressure within a hydraulic tilt cylinder of the lifting machine, and calculating an actual load moment of the lifting machine from the tilt pressure due to a weighted load on the lifting machine;

measuring a lift pressure within a hydraulic lift cylinder of the lifting machine, calculating the weight of the weighted load from the lift pressure and calculating a location of a center of gravity of the weighted load using the actual load moment and the calculated weight;

activating a first warning if the actual load moment is below a first predetermined load moment;

activating a second warning if the actual load moment is above the first predetermined load moment and below a second predetermined load moment;

and activating a third warning if the actual load moment is above the second predetermined load moment.

13. The system ofclaim 12 engaging a first audio alarm if the actual load moment is above the first predetermined load moment and below the second predetermined load moment, and engaging a second audio alarm if the actual load moment is above the second predetermined load moment.

14. The system ofclaim 13, wherein the first, second, and third warnings are colored lights.

15. The process ofclaim 12, wherein the first predetermined load moment is 80% to 100% of the rated load moment.

16. The process ofclaim 12, wherein the second predetermined load moment is 100% to 120% of the rated load moment.

17. The process ofclaim 12, including the step of disabling the lifting machine if a load pressure switch of the lifting machine is activated.

18. The process ofclaim 12, further including the step of providing information to a user about the weight and the location of the center of gravity of the weighted load, whereby a warning is provided to the user if the load is at least 90% of the rated load moment of the lifting machine.

19. A hydraulic stabilizer system, comprising:

a hydraulic lift having a rated load moment;

a means for measuring pressure within the hydraulic lift;

a processor for determining an actual load moment of the hydraulic lift and for determining a weight of a load on the hydraulic lift based on pressure within the hydraulic lift;

an illuminated display for warning an operator of the hydraulic lift if at least one predetermined operating parameter is exceeded; and

a load pressure switch for disabling the hydraulic lift if another predetermined operating parameter is exceeded.

20. The system ofclaim 19, wherein the hydraulic lift includes a frame, at least one load bearing member operationally connected to the frame for movement relative thereto, a hollow lift cylinder housing a lift piston and hydraulic fluid, the lift cylinder piston operationally connected to the load bearing member, with the hydraulic fluid disposed between the lift piston and one end of the frame, the lift piston imparting a lift force upon the hydraulic fluid within the lift cylinder proportional to a weight associated with the load bearing member, and a hollow tilt cylinder housing a tilt piston and hydraulic fluid, the tilt piston operationally connected to the load bearing member, with the hydraulic fluid within the tilt cylinder disposed between the tilt piston and one end of the frame, the tilt piston imparting a tilt force upon the fluid proportional to an actual load moment associated with the load bearing member.

21. The system ofclaim 20, wherein the means for measuring pressure within the hydraulic lift is a lift pressure sensor in fluid communication with the hydraulic fluid within the lift cylinder, for measuring pressure of the hydraulic fluid within the lift cylinder for a period of time and creating electrical signals corresponding thereto, defining at least one pressure measurement within the lift cylinder, with the pressure within the lift cylinder being related to the lift force associated with the load bearing member, and a tilt pressure sensor in fluid communication with the hydraulic fluid within the tilt cylinder, for measuring pressure of the hydraulic fluid within the tilt cylinder for a period of time and creating electrical signals corresponding thereto, defining at least one pressure measurement within the tilt cylinder, with the pressure being related to the tilt force associated with the load bearing member.

22. The system ofclaim 19, wherein the illuminated display is in data communication with the processor and produces a visual representation of the weight on the hydraulic lift.

23. The system ofclaim 19, wherein the processor includes a first sub-routine of a program stored in a memory to be operated on by the processor, determining, from at least one pressure measurement within the lift cylinder, the weight of the load on the hydraulic lift.

24. The system ofclaim 23, wherein the processor includes a second sub-routine of the program stored in the memory to be operated on by the processor, determining, from at least one pressure measurement within the tilt cylinder, the actual load moment of the load on the hydraulic lift.

25. The system ofclaim 19, the processor includes at least one sub-routine of a program stored in a memory to be operated on by the processor, determining, from at least one pressure measurement within the lift cylinder, the weight of the load on the hydraulic lift, and determining, from at least one pressure measurement within the tilt cylinder, the actual load moment of the load on the hydraulic lift, wherein another sub-routine of the program stored in the memory to be operated on by the processor uses the actual load moment and the weight of the load to determine a location of a center of gravity of the load on the hydraulic lift.

26. The system ofclaim 19, wherein the illuminated display30 activates a first warning if the actual load moment is below a first predetermined load moment, activates a second warning if the actual load moment is above the first predetermined load moment and below a second predetermined load moment, and activates a third warning if the actual load moment is above the second predetermined load moment.

27. The process ofclaim 26, wherein the first predetermined load moment is 80% to 100% of the rated load moment, and the second predetermined load moment is 100% to 120% of the rated load moment.

28. The system ofclaim 26, wherein the first, second, and third warnings are colored lights.

29. The system ofclaim 19, wherein the illuminated display engages a first audio alarm if the actual load moment is above a first predetermined load moment and below a second predetermined load moment, and engages a second audio alarm if the actual load moment is above the second predetermined load moment.

30. The process ofclaim 29, wherein the first predetermined load moment is 80% to 100% of the rated load moment, and the second predetermined load moment is 100% to 120% of the rated load moment.

31. The process ofclaim 19, wherein the hydraulic lift is disabled if the load pressure switch is activated.

32. A hydraulic stabilizer system, comprising:

a hydraulic lift having a rated load moment and maximum lifting capacity, wherein the hydraulic lift includes a frame, at least one load bearing member operationally connected to the frame for movement relative thereto, a hollow lift cylinder housing a lift piston and hydraulic fluid, the lift cylinder piston operationally connected to the load bearing member, with the hydraulic fluid disposed between the lift piston and one end of the frame, the lift piston imparting a lift force upon the hydraulic fluid within the lift cylinder proportional to a weight associated with the load bearing member, and a hollow tilt cylinder housing a tilt piston and hydraulic fluid, the tilt piston operationally connected to the load bearing member, with the hydraulic fluid within the tilt cylinder disposed between the tilt piston and one end of the frame, the tilt piston imparting a tilt force upon the fluid proportional to an actual load moment associated with the load bearing member;

at least one lift pressure switch in fluid communication with the hydraulic fluid within the lift cylinder, for measuring pressure of the hydraulic fluid within the lift cylinder, with the pressure within the lift cylinder being related to the lift force associated with the load bearing member, and at least one tilt pressure switch in fluid communication with the hydraulic fluid within the tilt cylinder, for measuring pressure of the hydraulic fluid within the tilt cylinder, with the pressure being related to the tilt force associated with the load bearing member.

an illuminated display for warning an operator of the hydraulic lift if at least one predetermined operating parameter is exceeded, wherein the illuminated display is in communication with the at least one lift pressure switch and the at least one tilt pressure switch; and

a load pressure switch for disabling the hydraulic lift if another predetermined operating parameter is exceeded, wherein the lift pressure switch measures the lift force and the tilt pressure switch measures the tilt force, whereby the illuminated display activates a first warning if the actual load moment is below a first predetermined load moment, activates a second warning if the actual load moment is above the first predetermined load moment and below a second predetermined load moment, activates a third warning if the actual load moment is above the second predetermined load moment, and disables the hydraulic lift if the weight is above the maximum lifting capacity.

33. The process ofclaim 32, wherein the first predetermined load moment is 80% to 100% of the rated load moment, and the second predetermined load moment is 100% to 120% of the rated load moment.

34. The system ofclaim 32, wherein the first, second, and third warnings are colored lights.

35. The system ofclaim 32, wherein the illuminated display engages a first audio alarm if the actual load moment is above a first predetermined load moment and below a second predetermined load moment, and engages a second audio alarm if the actual load moment is above the second predetermined load moment.

36. The process ofclaim 32, wherein the first predetermined load moment is 80% to 100% of the rated load moment, and the second predetermined load moment is 100% to 120% of the rated load moment.

37. The process ofclaim 32, wherein the hydraulic lift is disabled if the load pressure switch is activated.

38. A hydraulic stabilizer system, comprising:

a hydraulic lift having a rated load moment and maximum lifting capacity, wherein the hydraulic lift includes a frame, at least one load bearing member operationally connected to the frame for movement relative thereto, a hollow lift cylinder housing a lift piston and hydraulic fluid, the lift cylinder piston operationally connected to the load bearing member, with the hydraulic fluid disposed between the lift piston and one end of the frame, the lift piston imparting a lift force upon the hydraulic fluid within the lift cylinder proportional to a weight associated with the load bearing member, and a hollow tilt cylinder housing a tilt piston and hydraulic fluid, the tilt piston operationally connected to the load bearing member, with the hydraulic fluid within the tilt cylinder disposed between the tilt piston and one end of the frame, the tilt piston imparting a tilt force upon the fluid proportional to an actual load moment associated with the load bearing member;

at least one tilt pressure switch in fluid communication with the hydraulic fluid within the tilt cylinder, for measuring pressure of the hydraulic fluid within the tilt cylinder, with the pressure being related to the tilt force associated with the load bearing member.

an illuminated display for warning an operator of the hydraulic lift if at least one predetermined operating parameter is exceeded, wherein the illuminated display is in communication with the at least one tilt pressure switch; and

a load pressure switch for disabling the hydraulic lift if the predetermined operating parameter is exceeded, wherein the tilt pressure switch measures the tilt force, whereby the illuminated display activates a warning if the actual load moment is above a predetermined load moment.

39. The process ofclaim 38, wherein the predetermined load moment ranges from 100% to 150% of the rated load moment.

40. The system ofclaim 38, wherein the warning is a colored light.

41. The system ofclaim 38, wherein the illuminated display engages an audio alarm if the actual load moment is above the predetermined load moment.

42. The process ofclaim 38, wherein the hydraulic lift is disabled if the load pressure switch is activated.

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