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US 5,783,755 AGranted
Lifting device employing an equalizer system to reduce weight measurement error
AssigneeGageTek Company
InventorRobert W. Bruns
Life of this patent
Estimating the term…
Abstract
A lifting device that has a carriage supported by a chain which passes over a sprocket-wheel disposed to rotate about an axis and features an equalizer system that reduces variations in the measurement, by a load cell, of a load supported by the carriage. To further enhance the accuracy of the measurement, the load cell is designed to accurately measure the load placed thereon independent of the position of the load on the cell. The equalizer system consists of providing the chain and the sprocket-wheel with the dimensions necessary so that each link of the chain subtends a predetermined portion of the sprocket-wheel's circumference.
Claims15
A device for lifting a load, said device comprising:
- a frame;
- a carriage operationally coupled to said frame for movement relative thereto;
- a linkage member disposed, relative to said frame, to form two spaced-apart opposing sections, one of which is fixedly secured to said frame, defining an anchor portion, with the remaining section attached to said carriage, defining a load portion, said linkage member having a plurality of links, each link including a pair of spaced apart rollers;
- a load bearing member adapted to engage said load, said load bearing member connected to said carriage for movement relative to said frame, exerting a first force on said load portion corresponding to a weight of said load, with said first force producing a second force on said anchor portion;
- a load cell transducer coupled to said carriage to sense said second force and produce signals corresponding thereto;
- and
- a sprocket wheel attached to said frame to rotate about an axis, with said linkage member passing over said sprocket wheel so that the centers of a pair of spaced apart rollers subtend an angle 2.theta. measured between two radii extending from said axis. with e being defined as follows:
- .theta.=180.degree./2n.
5 more elements
A device for lifting a load, said device comprising:
- a frame;
- a carriage operationally coupled to said frame for movement relative thereto;
- a link chain coupled to said frame to form two spaced-apart opposing sections, one of which is fixedly secured to said frame, defining an anchor portion, the remaining section attached to said carriage, defining a load portion, with said load portion being spaced-apart from said axis a first distance and said anchor portion being spaced-apart from said axis a second distance, said link chain having a plurality of links;
- a load bearing member adapted to engage said load, said load bearing member connected to said carriage for movement relative to said frame, said load bearing member exerting a first force on said load portion corresponding to a weight of said load, with said first force producing a second force on said anchor portion, said second force being proportional to a ratio of said first and second distances;
- a load cell transducer coupled to said carriage to sense said second force and produce signals corresponding thereto;
- and
- a sprocket wheel attached to said frame to rotate about an axis;
- said sprocket wheel, said links and the spacing between said links having relative dimensions which satisfy the relation 2.theta.=180.degree./2n. 2.theta. being the angle subtended between two lines extending from said axis to the centers of two adjacent links, n being an integer.
5 more elements
A device for lifting a load, said device comprising:
- a frame;
- a carriage operationally connected to said frame for movement relative thereto;
- a flexible member disposed, relative to said frame, to form two spaced-apart opposing sections, one of which is fixedly secured to said frame, defining an anchor portion, with the remaining section attached to said carriage, defining a load portion;
- a load bearing member adapted to support said load, said load bearing member connected to said carriage, with said load bearing member exerting a first force on said load portion corresponding to a weight of said load, with said first force producing a second force on said anchor portion;
- a spring formed from a helically wound wire, said wire having a neutral axis, with said spring coupled between said frame and said carriage and adapted to compress in response to said force, thereby producing torsion, compression, tension and axial stresses in said wire, defining a group of stresses;
- means, attached to said helical spring, for measuring one of the stresses of said group of stresses while being relatively insensitive to the remaining stresses of said group, said measuring means includes a plurality of strain-gage elements attached to said wire so as to be symmetrically disposed with respect to said neutral axis;
- and
- an equalizer system coupled to said frame and adapted to attenuate variances between said first and second forces, thereby ensuring said signal corresponds to said weight.
5 more elements
Dependencies are inferred from the claim text.