US 4,593,533 A · Method and apparatus for detecting and controlling the formation of ice or frost

Abstract

In one exemplar embodiment, a method and apparatus are disclosed for detecting the accumulation of frost on the evaporator coils of refrigerating equipment. An emitter or source of electromagnetic radiation having a selected narrow band of wavelengths and a selected intensity directs the electromagnetic radiation at the frost. A detector, spaced from the frost and emitter, receives the narrow band of electromagnetic radiation and detects changes in the intensity of the radiation due to absorption or scattering of the radiation by the frost in a relation proportional to the thickness of the frost. Control means responding to the detected change in intensity of the radiation is provided to initiate a defrost cycle and control the accumulation of the frost on the evaporator coil surfaces. Other embodiments of the invention include a liquid level detector and a physical state phase change detector.

Claims18

Dependent claims

An improved apparatus for more consistent and sensitive detection of ice or frost accumulation on a refrigerator evaporator coil chracterized by passing electromagnetic radiation through ice or frost accumulated on the evaporator coil, detecting changes in the intensity of the electromagnetic radiation passing through the frost and initiating a defrost cycle in response to the detected changes in the electromagnetic radiation intensity, the improvement comprising:

(a) a radiation means for reducing ambient radiation variation effects and increasing thermal and voltage stability by directing at said frost, electromagnetic radiation of a narrow band of wavelengths selected from the absorption and scattering spectrum of said frost and having a bandwidth substantially equivalent to the bandwidth of the electromagnetic radiation emitted by electrons traversing the energy gap of a semiconductor device;
(b) a detection means for detecting the change in intensity of said electromagnetic radiation due to scattering and absorption from the frost;
(c) a body member supporting said radiation means and said detection means in a spaced-apart relationship;
(d) a mounting means adapted for mounting said body member adjacent to said evaporator coil for detecting decreases in intensity of said electromagnetic radiation in response to increases in frost accumulation thereon;
and
(e) a frost forming member interposed between said radiation means and said detection means for accumulating frost thereon directly proportional to the frost accumulation on the evaporator coil and permitting substantially unhindered transmission of said electromagetic radiation when no frost is present thereon.

3 more elements

An improved apparatus for more consistent and sensitive detection of ice or frost accumulation on a refrigerator evaporator coil characterized by passing electromagnetic radiation through ice or frost accumulated on the evaporator coil, detecting changes in the intensity of the electromagnetic radiation passing through the frost and initiating a defrost cycle in response to the detected changes in the electromagnetic radiation intensity, the improvement comprising:

(a) a radiation means for reducing ambient radiation variation effects and increasing thermal and voltage stability by directing said frost electromagnetic radiation of a narrow band of wavelengths selected from the absorption and scattering spectrum of said frost and having a bandwidth substantially equivalent to the bandwidth of the electromagnetic radiation emitted by electrons traversing the energy gap of a semiconductor device;
(b) a detection means for detecting the change and intensity of said electromagnetic radiation due to scattering and absorption from the frost;
and
(c) a circuit means cooperating with said detection means for initiating and terminating operation of refrigerator defrost equipment for removing the accumulation of frost on said evaporator coil, said detection means comprising a photodetector selected to receive and detect changes in be intensity of said electromagnetic energy and for generating a control signal in response to a preselected change in said intensity level, said circuit means including,
(i) a defrost power switch means for applying electrical power to said refrigerator equipment when said power switch means is energized,
(ii) a defrost coupling switch means interconnected between said detector and said defrost power switch means and responsive to said control signal generated by said detector to energize said defrost coupling switch means and said defrost power switch means, and
(iii) a time delay circuit interconnected between said detector and said defrost coupling switch means and cooperating with said coupling switch means for holding said coupling switch means in an energized state for a preselected time period after initiation of the defrost cycle by said defrost equipment.

4 more elements

An improved apparatus for more consistent and sensitive detection of ice or frost accmulation on a refrigerator evaporator coil characterized by passing electromagnetic radiation through ice or frost accumulated on the evaporator coil, detecting changes in the intensity of the electromagnetic radiation passing through the frost and initiating a defrost cycle in response to the detected changes in the electromagnetic radiation intensity, the improvement comprising:

(a) a radiation means for reducing ambient radiation variation effects and increasing thermal and voltage stability by directing said frost electromagnetic radiation of a narrow band of wavelengths selected from the absorption and scattering spectrum of said frost and having bandwidth substantially equivalent to the bandwidth of the electromagnetic radiation emitted by electrons traversing the energy gap of a semiconductor device;
(b) a detection means for detecting the change and intensity of said electromagnetic radiation due to scattering and absorption from the frost;
(c) a body member supporting said radiation means and said detection means in a spaced-apart relationship;
(d) a mounting means adapted for mounting said body member adjacent to said evaporator coil for detecting decreases in intensity of said electromagnetic radiation in response to increases in frost accumulation thereon;
and
(e) a frost forming member interposed between said radiation means and said detection means for accumulating frost thereon directly proportional to the frost accumulation on the evaporator coil and permitting substantially unhindered transmission of said electromagnetic radiation when no forst is present thereon, said frost-forming member comprising a generally L-shaped metal strip metal strip, one leg of said L-shaped metal strip adapted for heat transfer contact with said evaporator coil sufface, said other leg projecting from said evaporator coil surface and having an aperture therethrough for passing said electromagnetic radiation therethrough.

3 more elements

(a) a radiation means for reducing ambient radiation variation effects and increasing thermal and voltage stability by directing said frost electromagnetic radiation of a narrow band of wavelengths selected from the absorption and scattering spectrum of said frost and having a bandwidth substantially equivalent to the bandwidth of the electromagnetic radiation emitted by electrons traversing the energy gap of a semiconductor device;
(b) detection means for detecting the change and intensity of said electromagnetic radiation due to scattering and absorption from the frost, said detection means comprising a photodetector selected to receive and detect changes in the intensity of said electromagnetic energy and for generating a control signal in response to a preselected change in said intensity level;
(c) a body member supporting said radiation means and said detection means in a spaced-apart relationship;
(d) a mounting means adapted for mounting said body member adjacent to said evaporator coil for detecting decreases in intensity of said electromagnetic radiation in response to increases in frost accumulation thereon;
and
(e) a circuit means cooperating with said detection means for initiating and terminating operation of refrigerator defrost equipment for removing the accumulation of frost on said evaporator coil, said circuit means including,
(i) a defrost power switch means for applying electrical power to said refrigerator system defrost equipment when said power switch means is energized,
(ii) defrost coupling switch means interconnected between said detector and said defrost power switch means and responsive to said control signal generated by said detector to energize said defrost coupling switch means and said defrost power switch means, and
(iii) a time delay circuit interconnected between said detector and said defrost coupling switch means and cooperating with said coupling switch means for holding said coupling switch means in an energized state for a preselected time period after initiation of the defrost cycle by said defrost equipment.

6 more elements

Dependencies are inferred from the claim text.

Method and apparatus for detecting and controlling the formation of ice or frost

Life of this patent

Method and apparatus for detecting and controlling the formation of ice or frost

Life of this patent

Abstract

Claims18