US 4,100,491 AGranted

Automatic self-cleaning ferromagnetic metal detector

AssigneeSouthwest Research Institute

InventorsFrancis Marion Newman, Jr., H. Stanley Silvus, Jr.

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Abstract

A ferrous metal detecting apparatus is disclosed for detecting metal particles in a flowing fluid, such as engine oil. The detecting apparatus has soft-iron pole pieces with a bridging gap therebetween. The soft-iron pole pieces are electrically insulated from each other and magnetized by direct current through an electromagnetic coil. After a sufficient amount of ferrous metal has accumulated on the bridging gap, a level detector will give a warning signal and cause the electromagnetic coil to degauss the soft-iron pole pieces by applying an alternating current to the electromagnetic coil. After the flowing fluid has washed away the ferrous metal, the direct current will remagnetize the soft-iron pole pieces. If repeated warning signals are within predetermined time intervals, an indication of the amount of ferrous metal contained in the fluid can be interpolated. The recycling for repeated warning signals may be automatically provided through a timing circuit and control logic.

Claims27

Dependent claims

A metal detector adapted for detecting ferromagnetic particles in a flowing fluid having low conductivity comprising:

probe means;
mounting means adapted for attachment to container means for said fluid, said mounting means securing at least one end of said probe means in said flowing fluid;
semipermanent magnetic pole means forming a part of said probe means with at least a portion of said semipermanent magnetic pole means being in contact with said flowing fluid;
coil means adjacent said semipermanent magnetic pole means;
voltage means;
control means connected to said coil means, said control means selectively causing direct current flow from said voltage means through said coil means to magnetize said semipermanent magnetic pole means, said magnetization of said semipermanent magnetic pole means causing said ferromagnetic particles to collect on said portion in contact with said flowing fluid;
said portion of said semipermanent magnetic pole means being constructed and arranged to have a gap therein, said gap being in contact with said flowing fluid;
a conductivity sensor circuit including said voltage means connected to said semipermanent magnetic pole means and measuring current flow therethrough from said voltage means upon said collection of ferromagnetic particles bridging said gap to generate a warning signal when said current flow reaches a predetermined level;
said warning signal being received by and activating said control means to supply alternating current from said voltage means to said coil means to demagnetize said semipermanent magnetic pole means thereby allowing said flowing fluid to carry away said collection of ferromagnetic particles.

6 more elements

A control circuit adapted for use in conjunction with a metal detector to determine amount of ferromagnetic particles in a flowing fluid, said metal detector having semipermanent magnetic pole means with a space therein forming gap means in contact with said flowing fluid, said pole means being of a material that may be magnetized and demagnetized by current flow through a contiguous coil means, said control circuit comprising:

a voltage source for direct current and alternating current, said voltage source being electrically connected to provide a d.c. voltage potential across said gap means;
switch means connected to said voltage source, said switch means having a first position for connecting said direct current to said coil means to magnetize said pole means;
detector means connected in series with said gap means for giving a detector signal upon ferromagnetic particles collecting on said gap means to bridge thereacross, said detector signal operating said switch means for first disconnecting said direct current from said coil means and second connecting said alternating current to said coil means to demagnetize said pole means;
first timer means connected to said switch means, said first timer means being set by said detector signal to begin a first time interval, upon termination of said first time interval said first timer means giving a first timer signal to operate said switch means for second disconnecting of said alternating current from said coil means and restoring said first connection with said direct current to said coil means, and
warning means for giving a warning signal upon receiving said detector signal.

2 more elements

Dependencies are inferred from the claim text.