Apparatus and method for dynamic weighing of loads in hydraulically operated lifts
First Claim
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1. A lifting device, comprising:
- a frame;
a load bearing member operationally connected to said frame for movement relative thereto;
a hollow cylinder housing a piston and hydraulic fluid, said piston operationally connected to said load bearing member, with said hydraulic fluid disposed between said piston and one end of said housing, said piston imparting a force upon said fluid proportional to a weight associated with said load bearing member;
transducer means, in fluid communication with said hydraulic fluid, for measuring a pressure of said hydraulic fluid for a period of time and creating electrical signals corresponding thereto, defining a sequence of pressure measurements, with said pressure being related to said force;
accelerometer means, in data communication with said transducer means, for identifying from said sequence of pressure measurements, a point in said sequence at which an acceleration of said load bearing member has ceased, with the pressure measurements associated with said sequence and following said point defining a remaining sequence;
processing means, in data communication with said accelerometer means, for determining said weight from said remaining sequence; and
display means, in data communication with said processing means, for producing a visual representation of said weight.
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Abstract
A hydraulic lifting device, such as a forklift, is provided and is capable of dynamically measuring the weight of a load being lifted. A plurality of pressure measurements are taken during the lift for a period of time, which are stored in memory. A computer program is operated on by a microprocessor to process the pressure measurements to filter unwanted signals associated with vibration and other mechanical disturbances. The pressure samples processed by the computer program correspond to a portion of the lift during which acceleration of the forks has ceased, allowing a closer correspondence between the weight lifted and the pressure of the hydraulic fluid sensed.
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Citations
29 Claims
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1. A lifting device, comprising:
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a frame; a load bearing member operationally connected to said frame for movement relative thereto; a hollow cylinder housing a piston and hydraulic fluid, said piston operationally connected to said load bearing member, with said hydraulic fluid disposed between said piston and one end of said housing, said piston imparting a force upon said fluid proportional to a weight associated with said load bearing member; transducer means, in fluid communication with said hydraulic fluid, for measuring a pressure of said hydraulic fluid for a period of time and creating electrical signals corresponding thereto, defining a sequence of pressure measurements, with said pressure being related to said force; accelerometer means, in data communication with said transducer means, for identifying from said sequence of pressure measurements, a point in said sequence at which an acceleration of said load bearing member has ceased, with the pressure measurements associated with said sequence and following said point defining a remaining sequence; processing means, in data communication with said accelerometer means, for determining said weight from said remaining sequence; and display means, in data communication with said processing means, for producing a visual representation of said weight. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A hydraulic lifting device, comprising:
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a frame; load bearing members operationally connected to said frame for movement relative thereto; a hollow cylinder housing a piston and hydraulic fluid, said piston operationally connected to said load bearing members, with said hydraulic fluid disposed between said piston and one end of said housing having an aperture, said piston imparting a force upon said hydraulic fluid related to a weight associated with said load bearing members; transducer means, in fluid communication with said aperture, for measuring a pressure of said hydraulic fluid and creating electrical signals corresponding to a plurality of pressure measurements obtained during a period of time, each of said plurality of measurements being proportional to said force and associated with a unique increment of said period, defining a sequence of pressure measurements, said sequence of pressure measurements being stored in a first memory; accelerometer means, in data communication with said transducer means, for identifying from said sequence of pressure measurements, an increment of time at which an acceleration of said load bearing members has ceased, with the pressure measurements associated with said sequence and following said increment of time defining a remaining sequence; processing means, in data communication with said accelerometer means, for determining said weight from said remaining sequence; and display means, in data communication with said processing means, for producing a visual representation of said weight. - View Dependent Claims (11, 12, 13)
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14. A method for determining the weight of a load placed on a hydraulic lifting device of the type having a frame, a hydraulic lift system operable to move a load carriage, including fork members, with respect to said frame to raise and lower a payload associated with said forks, a control means for regulating the operation of the lifting device, a transducer means for measuring a pressure of fluid associated with said hydraulic system and creating electrical signals corresponding thereto with said pressure being proportional to a weight of said payload, and processing means, electronically coupled to said transducer means, for processing said electrical signals, said method comprising the steps of:
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engaging said payload with said fork members; lifting said payload with said fork members, thereby moving said payload with respect to said frame; measuring a pressure of said fluid for a period of time obtaining a plurality of pressure measurements, each of said plurality of measurements being associated with a unique increment of said period, forming a sequence of pressure measurements; identifying, from said sequence of pressure measurements, an increment of time at which an acceleration of said fork members has ceased, with said sequence of pressure measurements following said increment defining a remaining sequence; determining from said remaining sequence, a weight of said payload; and visually displaying said weight measured. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21)
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22. A lifting device, comprising:
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a frame; load bearing members operationally connected to said frame for movements relative thereto; a hollow cylinder housing a piston and hydraulic fluid, said piston operationally connected to said load bearing members, with said hydraulic fluid disposed between said piston and one end of said housing having an aperture, said piston imparting a force upon said fluid proportional to a weight associated with said load bearing members; control means, in fluid communication with said hydraulic fluid, for regulating ingress and egress of said hydraulic fluid with respect to said aperture; transducer means, in fluid communication with said aperture, for measuring a pressure of said hydraulic fluid and creating electrical signals corresponding to said pressure, said hydraulic fluid being associated with a pressure decay so that said force is represented by a range of pressure levels; processing means, electronically coupled to said transducer means, for processing said electrical signals to produce information corresponding to hydraulic pressure, said information including said weight, said processing means including means for measuring and hulling said pressure decay, thereby reducing a number of pressure levels representing said force; and display means, coupled to receive said information, for producing a visual representation of said weight. - View Dependent Claims (23, 24)
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25. A lifting device, comprising:
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a frame; a load bearing member operationally connected to said frame for movement relative thereto; a hollow cylinder housing a piston and hydraulic fluid, said piston operationally connected to said load bearing member, with said hydraulic fluid disposed between said piston and one end of said housing, said piston imparting a force upon said fluid proportional to a weight associated with said load bearing member; means, in fluid communication with said hydraulic fluid, for measuring a plurality of pressure measurements of said hydraulic fluid, during a period of time, each of which is associated with a unique increment of said period, defining a sequence of pressure measurements; means, in data communication with said measuring means, for identifying, from said plurality of pressure measurements, an increment of time at which an acceleration of said load bearing member has ceased, with pressure measurements of said sequence of pressure measurements following said increment defining a remaining sequence; and means, in data communication with said identifying means, for determining from said remaining sequence, said weight. - View Dependent Claims (26, 27, 28, 29)
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Specification