Automatic density control system for blending operation
Patent 4779186 Issued on October 18, 1988. Estimated Expiration Date: 
December 24, 2006. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
December 24, 2006. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesInventorsAssigneeApplicationNo. 06/946711 filed on 12/24/1986US Classes:700/67, Plural variables137/101.19, With electrical controller137/88, Mixture condition maintaining or sensing222/52, AUTOMATIC CONTROL366/142, WITH TEST, SIGNAL, OR INDICATOR MEANS366/152.2, By volume or fixed quantity366/153.1, Controlling level of material in mixing chamber366/156.1, Screw conveyor366/160.3, By variable pump366/181.8, Fluid pump366/182.4, Including valve in feed conduit366/192Valve or gateExaminersPrimary: Ruggiero, JosephAttorney, Agent or FirmInternational ClassesG05D 11/13 (20060101)G05D 11/00 (20060101) AbstractA control system is provided which can be retrofit to existing conventional blender devices, such as a blender trailer used for combining a pregelled liquid with a solid particulate additive at a well site. The control is provided either manually or automatically from a remote location where a display unit and a computer unit of the invention are located, such as in a frac van. The display unit and the computer unit are connected together by a multi-conductor cable, and the display unit is connected by a multi-conductor cable to a terminal unit mounted on the blender. Control signals are output from the display unit, under automatic control by the computer unit or under manual control by potentiometers attached to the display unit, to control electrohydraulic valves associated with screw conveyors mounted on the blender. Linear variable differential transformer signals from the electrohydraulic valves, rotational speed signals from the screw conveyors, and flow rate signals from the inlet pregelled liquid are communicated to the display unit for use by it and the computer unit in generating the valve control signals.Other References
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