US 4,045,971 AGranted

Frost detector

AssigneeEmerson Electric Co.

InventorGeorge John Brenner, Jr.

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Abstract

A frost sensor for detecting the presence of frost in a refrigeration device includes a light impervious enclosure having an air passage through it. Means preferably are provided for directing ambient air through the air passage. The air passage has thermal conducting means mounted in it, the thermal conducting means having a first surface forming a portion of the air passage. A connection device also is provided for attaching the conducting means to the refrigeration device. A photocell and a light source are mounted so that the photocell senses reflectivity of the conductive means. The volume of ambient air passing through the air passage and the thermal resistance between the conducting means and the refrigeration device may be varied so that the formation of frost on the conducting means can be made to agree with the formation of frost on the refrigeration device.

Claims14

Dependent claims

A frost detector for a refrigeration device having an evaporating coil, comprising:

a housing, said housing having a light impervious passageway through it, said housing including at least one side wall partially defining said passageway, said side wall having an opening in it;
a thermal conductive means mounted in said opening, said conducting means having a first surface area closing the opening in said passageway, and a second surface area;
an energy source operatively mounted to said housing, said energy source being adapted to illuminate the first surface area of said thermal conducting means;
an energy sensitive device operatively mounted to said housing to sense the level of energy reflected from said thermal conductive means;
means for mounting said housing to a refrigerant carrying portion of said refrigeration device along the second surface of said thermal conducting means, the thermal resistance between the second surface of said thermal conducting means and the refrigerant carrying portion of said refrigeration device being adjustable to vary the heat transfer characteristic of said thermal conducting means;
and
means for operatively connecting said light impervious passageway to a source of air, said connecting means being positioned so that the air pressure drop across said evaporating coil forces air through said light impervious passageway.

4 more elements

In a refrigeration device having an evaporating coil, said coil having a refrigerant carrying part including an inlet, an outlet and a main body portion, the improvement which comprises detector means for initiating a defrost cycle by sensing frost formation and for terminating the defrost cycle upon removal of frost, said detector means comprising a housing, said housing including an enclosure having an inlet, an outlet, and an air passageway between said inlet and said outlet, thermal conductive means having a first surface area exposed in said air passageway and a second surface area, a light source operatively mounted to said housing, said light source adapted to illuminate said first surface area, a light sensitive device operatively mounted to said housing, said light sensitive device being adapted to sense the level of light reflected from said thermal conductive means, means for mounting said sensor to a refrigerant carrying portion of said refrigeration device along the second surface of said thermal conductive means, means for directing an air flow through the air passageway of said housing, means responsive to said light sensitive device for initiating a defrost cycle upon the formation of a predetermined amount of frost on the first surface area of said thermal conductive means, and for terminating the defrost cycle upon removal of a predetermined amount of frost from the first surface area of said thermal conductive means, and means for adjusting the frosting conditions of said thermal conductive means independently of said refrigeration device.

Dependencies are inferred from the claim text.