The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 03, 2000
Filed:
Dec. 27, 1998
Timothy A Boston, Tremont, IL (US);
Bruce E Unger, Peoria, IL (US);
Caterpillar Inc., Peoria, IL (US);
Abstract
An inductive spool displacement sensor for determining the position or displacement of a spool within a particular hydraulic valve including a sensor housing having a cavity formed therein adapted for mounting within the hydraulic valve, the sensor housing being positioned such that at least a portion of the valve spool is disposed to enter the sensor cavity during certain operations of the valve. The sensor further includes a sensing coil wound about the housing cavity and a reference coil wound about the housing and spaced from the sensing coil, the inductance of the sensing coil being responsive to movement of the spool within the cavity and the inductance of the reference coil being responsive to the temperature of the fluid passing through the hydraulic valve. Based upon eddy current principles and because eddy currents are a function of material conductivity, the sensing coil, when energized, generates a signal indicative of that portion of the spool present within the housing cavity. Electronic circuitry, including a microprocessor, are coupled to the coils for receiving signals therefrom, the microprocessor determining the position of the spool relative to the cavity, or some other predetermined reference point, and outputting a signal proportional to the position or displacement of the spool within the hydraulic valve. The reference coil is provided to compensate for changing inductance values due to changing fluid temperature.