Weighing scales – Weigher responsive material control – Feed
Reexamination Certificate
1999-08-04
2001-06-26
Gutierrez, Diego (Department: 2859)
Weighing scales
Weigher responsive material control
Feed
C177S145000
Reexamination Certificate
active
06252181
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for weighing products and, more particularly, for weighing products that are moved using a conveyor by first lifting the product above the conveyor and then measuring the weight of the lifted product.
2. Background Art
Quality control has always been integral to successful operation of an industrial manufacturing and shipping facility. It is, obviously, important to provide the customer with the correct quantity of goods both for the customer's satisfaction and for the highest possible efficiency of the facility. A common method for ensuring that the correct quantity of goods are loaded and shipped to the customer is by weighing the box or container in which the goods are packed.
Many of the packaging lines currently used rely heavily on automation and less on human intervention. However, since there are occasions when the wrong amount of a product is placed into a bag, carton, or other container, or the wrong number of bags, cartons, or other containers are loaded into the final shipping container, a product weigher is a way to ensure that the correct product weight is being shipped to the customer.
There are a number of prior art devices used to weigh the shipping containers on a packaging line. These commercially-available devices often consist of a conveyor belt approximately thirty inches long and twenty inches wide. As the shipping container traverses over load cells below the conveyor at a weighing station, the load cells transmit to a main control board the weight of the conveyor plus any product being conveyed. Digital filters located on the main control board filter out dynamic signals that occur as a result of weighing a moving object.
However, when measurements are taken on a moving conveyor belts, as in the prior art systems, complex digital filtering must be applied to the analog signal to remove dynamic components in the signal. These systems often are very proprietary to the equipment manufacturer and are not easily understood by the end user. Moreover, the prior art systems are difficult to interface with other equipment and supervisory data collection computers. Still another problem is that since the conveyor is part of the load being weighed, the conveyor must be made as light as possible, resulting in a conveyor design that, in many cases, does withstand an industrial environment well.
SUMMARY OF THE INVENTION
The present invention encompasses a method and apparatus for weighing, a product in an industrial environment that overcomes the drawbacks in the prior art. The product is moved by a conveyor to be disposed at a weighing station, which is stationarily positioned relative to the moving conveyor. There, a weighing platform, preferably formed by a plurality of fingers, engages the bottom surface of the product and raises the product upwardly so that the bottom surface of the product is disposed above and spaced apart from the conveyor. After the product is raised above the conveyor, the product is weighed without any interface with the conveyor to obtain a highly accurate measurement.
After the product is weighed, it is then lowered back down onto the conveyor. Concurrently, the measured weight of the product is preferably compared to a predetermined weight range to determine whether the product is acceptable to ship to the customer. If the weight of the product is properly within the predetermined weight range, the product continues down the production line on the conveyor. If, however, the weight of the product is out of tolerance, the unacceptable product is removed from the conveyor, such as by pushing it laterally off to the side.
One difference between the present invention and prior art weighing devices is that the weighing platform is stationary relative to the conveyor and the product is stationary when the actual weight measurements are taken. Since the conveyor is not part of the load being weighed, the conveyor itself can be constructed of standard, heavy duty, industrial components, such as bearings, motors, rollers, and the like, used in most industrial conveyor designs.
In addition, the weighing station of the present invention does not require sophisticated digital filtering techniques used by prior art designs. In fact, the present invention allows the weighing device to utilize the versatility and commercial acceptance of a programmable logic controller (“PLC”). The PLC has been widely used in industrial automation for the past few decades, so the majority of control technicians and engineers in factories are familiar with programming and troubleshooting PLCs. Of course, if desired, the present invention can also be used with digital systems for filtering and weighing the product.
Still another advantage of the present invention over the prior art is that the weighing platform is positioned below the top surface of the conveyor in the lowered position, protecting the load cells from damage in an overload condition. If too much weight is applied to any load cell when the weighing platform raises the product above the conveyor, the PLC generates an alarm, causing the weighing station to shut down. The platform then lowers by the force of gravity to fall below the surface of the conveyor so that the overweight product is again supported by the conveyor, not the weighing platform and load cells.
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Fallas David M.
Fallas Richard J.
Eastman Jacob
Gutierrez Diego
Needle & Rosenberg P.C.
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