Automatic weighing machines

An automatic weighing machine for weighing out a predetermined quantity of fluid material into a container, including a fluid material valve of the downward delivery type comprising a closure member having a plurality of selectable positions corresponding to different flow rates through the valve, the fluid material valve including an annular valve body and a circular sectioned closure member which are relatively displaceable for opening and closing of the valve, the closure member comprising a cylindrical body which is closed at its upper end and which is adapted to be slidably received in a cylindrical bore in the valve body in at least the positions of the closure member corresponding to the intermediate and low flow rate positions, the body of the closure member having at least one vertically extending slot in its peripheral surface for the restricted passage of fluid material in the intermediate and low flow rate positions when said closure member is partially inserted into said bore, the closure member having a lowermost rim of acute angled section and the valve body also having a lowermost rim of acute angled section which forms an annular valve seat, said lowermost rims on the valve seat and closure member being arranged to mate together, when the valve seat and closure member are in their closed position, to define a downwardly directed, sharp, circular composite edge, and a weighing control system which is adapted to control the valve so as to dispense an appropriate weight of fluid material into the container in accordance with a predetermined programme, the control system comprising load cell means arranged to provide an electrical output dependent upon the weight of the container plus its contents, and a comparator for comparing the signal from the load cell means with a predetermined target weight to be achieved in accordance with the programme to provide an electrical error signal instantaneously representative of the additional weight of fluid material to be dispensed, and dynamic detector means responsive to both the magnitude of the instantaneous error and the rate of change of error for initiating a change in the valve from a positive flow position to OFF in advance of the error reducing to zero.

An automatic weighing machine for weighing out a predetermined quantity of fluid material into a container, including a fluid material valve of the downward delivery type comprising a closure member having a plurality of selectable discreet positions corresponding to different predetermined flow rates through the valve, and a weighing control system which is adapted to control the valve so as to dispense an appropriate weight of fluid material into the container in accordance with a predetermined program, the control system comprising load cell means arranged to provide an electrical output dependent upon the weight of the container plus its contents, and a comparator for comparing the signal from said load cell means with a predetermined target weight to be achieved in accordance with said program to thereby provide an electrical air signal instantaneously representative of the additional weight of fluid material to be dispensed, dynamic detector means responsive to both the magnitude of the instantaneous error and the rate of change of the error for initiating a change in the valve from a positive flow position to OFF in advance of the error reducing to zero, said dynamic detector means including a plurality of dynamic detectors which are sensitive to the error falling to different predetermined levels respectively the detectors providing signals for initiating changes to different flow rates in accordance with the reduced air, a plurality of level detectors which detect the initial error at the commencement of a weighing operation, and select a high initial flow rate when the initial error is high but inhibits said high flow rate and selects a lower initial flow rate when the initial error is low, and at least one double level detector which provides a control signal when the error has fallen to lie within acceptable tolerance limits, means being provided which inhibit a subsequent weighing operation until such a control signal has been generated.