Fairbanks, Inc.

Fairbanks Scales Inc.

Harry J Keen

Alec T Douglas

Walter W Sevigny

Mike Dunne

Leon E Saucier

Frank J Rusk

A pressure transducer module includes a plurality of cavities, each cavity in fluid communication with a hydraulic load cell. Each cavity deforms with variations in the pressure of the hydraulic fluid in the cavity. Sensors generate output signals representative of the deformation of the cavities. The sensor output signals are digitized and multiplexed, whereby the transducer module generates a digital output data stream. The pressure transducer module is pre-calibrated for creep, hysteresis, non-linearity and temperature related errors. A computer controller stores the calibration data for the module. The pressure transducer module also includes a temperature sensor. A weighing system includes a weighing platform or structure; at least one pressure transducer module; and hydraulic transducers for measuring the load applied to the weighing platform or structure. A controller receives the outputs of the sensors and applies the calibration data to calculate the weight of the load on the platform. The transducer module may be used in weighing systems having different load ranges. Also provided is a method and apparatus for pre-calibrating the pressure transducer module, a method and apparatus for pre-calibrating the hydraulic transducers, and a method of performing cornering correction in a weighing system. In an alternative embodiment, the pressure transducer module may include a microprocessor and calibration data memory so as to perform error compensation on the pressure transducer module within the module itself.

Digitally compensated hydraulic scale system

An apparatus for measuring the dimensions or volume of an object on a conveyor is disclosed. A light source on one side of the conveyor is focused onto a spinning scanning drum having a pattern of holes therethrough. The holes are arrayed in a spiral pattern. The rotating drum is positioned parallel to the dimension to be measured between the source of light and a light detector on the other side of the conveyor from the light source. The pattern of holes is arranged so that when the scanning drum rotates a scanning pattern is generated across the conveyor. The light detector on the other side of the conveyor generates an output signal each time a beam of light passes through the rotating scanning drum and across the conveyor. A controller receives the output signal and correlates the output signal with the scanning pattern using a look-up table. Using this information, the controller determines from the scanning pattern and the detected output signals, the dimension of the object. If more than one dimension is to be measured, a height measuring unit and a width measuring unit may be positioned around the conveyor. From the measured height, width and length, the controller determines the volume of the object. A method and apparatus are provided for determining the volume of boxes passing on the conveyor with are positioned at an angle relative to the conveyor.

Dimension-measuring apparatus

A modular checkweigher/grader system is disclosed. A feed conveyor is provided for directing items to be weighed to a weighing conveyor. The entire system is modularly designed using lightweight durable materials, such as plastics and stainless steel. Each conveyor includes a conveyor belt in contact with upper and lower surfaces of a platform. The belts are tightened and loosened with quick release tension clamps and driven by air powered motors. The feed conveyor is attached to a frame by toggle clamps. The weighing conveyor is attached to a load cell which is connected to the frame by toggle clamps. These toggle clamps permit the entire feed and weighing conveyors to be easily removed. All of the air and electrical connector to the conveyors are by quick release connectors. The entire weighing conveyor is used as the weighing platform. A tachometer may be used to regulate the conveyor speed. A modular grading conveyor is disclosed for categorizing objects from the weighing conveyor. A tensioner is provided for allowing the grader belt to be slackened for easy cleaning. Grader paddle control modules are hinged for easy cleaning. The hinges are secured by butterfly nuts for easy removal of broken modules. All air and electrical connections to the paddle control modules are by quick release connectors.

Modular checkweigher and grading system

A microprocessor (8) controlled power-saving electronic measuring system is disclosed. A load cell (1) generates an output signal indicative of the magnitude of the load applied to the cell (1). A DC power supply (2) is switched to supply the load cell (1) with power pulses (10) at varying frequencies and duty cycles determinable by the microprocessor (8) to optimize battery life. The microprocessor (8) determines the optimal duty cycle and frequency for the power pulses responsive to desired parameters. The circuitry of the present invention is located in close proximity to a temperature sensor (34) which accurately reads the temperatures of all of the components and compensates for all heat related inaccuracies simultaneously. The microprocessor (8) determines a temperature corrected value for the load cell (1) output via a previously programmed table containing the temperature response characteristics for the load cell (1) and the circuitry. In an over/under indicator mode, segments of the display (36) LED's are configured to graphically indicate whether the current weight on the scale is within a desired tolerance. A power saving sleep mode in described in which the system voltage level is reduced, and most of the circuitry is disabled.

Low power electronic measuring system

An electronic weighing system is disclosed which, employs spaced cylindrical dielectric rings as the load measuring transducer. A support structure is provided to linearly vary the spacing between the rings responsive to applied load which will linearly vary the resonant frequency of the rings. In an active mode, each microwave load cell is excited by an unstable oscillator, the dielectric rings stabilizing the oscillator at a resonant frequency which is proportional to their spacing. The oscillation frequency of the load cell is measured and used to compute the magnitude of the load applied to the cell based upon a predetermined relationship between output frequency and load. A plurality of multiplexed load cells may be employed. In a passive mode, a voltage controlled oscillator generates a microwave signal which linearly sweeps a preset frequency band. The sweeping signal is applied across the dielectric rings which generate a detectable pulse at their primary resonant frequency. The pulse is detected and the resonant frequency at which the pulse was generated is determined. The applied load is calculated from the resonant frequency and routed to a display panel. In a temperature compensation embodiment, a temperature sensor generates a voltage output which is converted to an RF signal and modulated onto the microwave oscillator output.

Microwave electronic load measuring system

A load indicator conversion system is disclosed for converting a scale having a mechanical measuring system, such as a conventional portable beam scale, into a scale having an electronic measuring system for providing an electronic display, such as an LCD display, corresponding to the load applied to the mechanical load receiver of the scale, such as the scale platform [104], which is mechanically linked via the beam load rod assembly [110] and an s-hook arrangement [150] to a load cell transducer [1]. A single common temperature sensor is employed adjacent the load cell and the associated electronics to provide information on the variations in temperature to the microprocessor for enabling temperature compensation to take place. The mechanical linkable between the transducer and the existing mechanical load receiving member is accomplished by removing the balance beam [106] and connecting the load cell [1] to the beam load rod [110] which normally mechanically transfers the applied load from the scale platform to [104] the balance beam [106 ].

Growing community of inventors

St. Johnsbury, VT, United States of America

Harry J Keen