Patent US3768820A successfully refreshed from Google Patents.
Patent US3846615A successfully refreshed from Google Patents.
US3846615A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Liquid temperature control and low liquid level detector
Assignee: Hobart Manfacturing Co
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Filing: 1973-04-05
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Granted: 1974-11-05
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Expires: 1993-04-05
Abstract
Abstract A dishwasher includes a wash tank having means for heating a washing liquid in the tank, a temperature sensor arranged in the tank for controlling the heating means, and means for sensing that the liquid is above a predetermined level. The temperature sensor is a thermistor connected to a circuit for controlling the operation of the heating means. The control circuit will also disable the heating means should the thermistor become either open or shorted. The liquid level detector is a reed switch actuated by a magnet in a float. The reed switch is connected to the control circuit and will cause the heating means to be disabled should the liquid level fall below the temperature sensor. A time delay circuit is provided to prevent intermittent operation of the heating means due to turbulence of the surface of the liquid which causes the reed switch to open and close rapidly. The reed switch and thermistor are contained in a single housing within the wash tank. A light emitting diode is connected in the circuit to the heater means to indicate when it is operative.
Inventors
- 👤 S Athey
- 👤 W Thornburg
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 18:49
CPC Classifications
A; A47; A47L; A47L15/00; A47L15/42; A47L15/4244; G; G05; G05D; G05D23/00; G05D23/19; G05D23/1906; G05D23/1909; G05D23/20; G05D23/24; A47L2401/00; A47L2401/09; A47L2501/00; A47L2501/06
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
138 words
Apparatus for maintaining an elevated temperature of a liquid comprising a reservoir adapted to contain the liquid to be heated, heating means in said reservoir, means positioned in said reservoir at a level above the level of said heating means including means for sensing the temperature of said liquid including a thermistor whose electrical characteristics vary in accordance with temperature and means for sensing that the liquid is above a predetermined level, and circuit means responsive to said temperature sensing means for controlling the operation of said heating means whereby to maintain the liquid within a predetermined temperature range, said circuit means being responsive to said liquid level sensing means and said temperature sensing means for disabling said heating means if the liquid level falls below said predetermined level or if said thermistor becomes either open or shorted.
Claim 2
Dependent Claim
138 words
Apparatus for maintaining an elevated temperature of a liquid comprising a reservoir adapted to contain the liquid to be heated, heating means in said reservoir, means positioned in said reservoir at a level above the level of said heating means including means for sensing the temperature of said liquid including a thermistor whose electrical characteristics vary in accordance with temperature and means for sensing that the liquid is above a predetermined level, and circuit means responsive to said temperature sensing means for controlling the operation of said heating means whereby to maintain the liquid within a predetermined temperature range, said circuit means being responsive to said liquid level sensing means and said temperature sensing means for disabling said heating means if the liquid level falls below said predetermined level or if said thermistor becomes either open or shorted.
Claim 3
Dependent Claim
28 words
The apparatus of claim 1 wherein said temperature sensing means and said level sensing means are contained within a single housing and are located above said heating means.
Claim 4
Dependent Claim
21 words
The apparatus of claim 3 wherein said circuit means further includes means for visually indicating when said heating means is operative.
Claim 5
Dependent Claim
33 words
The circuit means of claim 4 further including time delay means whereby momentary indications of low water level of less than a predetermined duration will not be operative to disable said heating means.
Claim 6
Dependent Claim
56 words
The apparatus of claim 1 wherein said liquid level detecting means includes a reed switch and a float mounted beneath said reed switch and containing a magnet to cause the contacts within said reed switch to close when said liquid level is sufficient to raise said float and said magnet into proximity to said reed switch.
Claim 7
Dependent Claim
159 words
In a dishwasher including a washing chamber with a tank at its bottom for containing a quantity of washing solution, means for heating the solution in said tank, a temperature sensor arranged to respond to the temperature of the solution in said tank, means for spraying the solution over articles supported in said washing chamber, a pump connected to circulate solution from said tank through said spray means, and means for spraying rinsing water over the articles after they have been sprayed with the washing solution, the improvement comprising means positioned in said tank for sensing that the quantity of washing solution is above a predetermined level, said means including said temperature sensor, and circuit means responsive to said temperature sensor and said level sensing means for controlling the operation of said heating means to maintain the solution within a predetermined temperature range and to disable said heating means if the quantity of solution falls below said predetermined level.
Claim 8
Dependent Claim
159 words
In a dishwasher including a washing chamber with a tank at its bottom for containing a quantity of washing solution, means for heating the solution in said tank, a temperature sensor arranged to respond to the temperature of the solution in said tank, means for spraying the solution over articles supported in said washing chamber, a pump connected to circulate solution from said tank through said spray means, and means for spraying rinsing water over the articles after they have been sprayed with the washing solution, the improvement comprising means positioned in said tank for sensing that the quantity of washing solution is above a predetermined level, said means including said temperature sensor, and circuit means responsive to said temperature sensor and said level sensing means for controlling the operation of said heating means to maintain the solution within a predetermined temperature range and to disable said heating means if the quantity of solution falls below said predetermined level.
Claim 9
Dependent Claim
144 words
In a dishwasher including a washing chamber, a tank for containing a quantity of washing liquid, means for heating the liquid in said tank, temperature sensing means arranged to respond to the temperature of the liquid in said tank for controlling operation of said heating means, means for spraying the liquid over articles supported in said washing chamber, and a pump connected to circulate liquid from said tank through said spray means, the improvement comprising a float member supported from said tank by a flexure member, said float member responding to the level of liquid in said tank, electrical means external to said float member and responsive to the presence of said float member in a predetermined upper position, and means responsive to said electrical means for limiting operation of said heating means when said float member is absent from said predetermined upper position.
Claim 10
Dependent Claim
144 words
In a dishwasher including a washing chamber, a tank for containing a quantity of washing liquid, means for heating the liquid in said tank, temperature sensing means arranged to respond to the temperature of the liquid in said tank for controlling operation of said heating means, means for spraying the liquid over articles supported in said washing chamber, and a pump connected to circulate liquid from said tank through said spray means, the improvement comprising a float member supported from said tank by a flexure member, said float member responding to the level of liquid in said tank, electrical means external to said float member and responsive to the presence of said float member in a predetermined upper position, and means responsive to said electrical means for limiting operation of said heating means when said float member is absent from said predetermined upper position.
Claim 11
Dependent Claim
23 words
The dishwasher of claim 7 wherein said flexure member supporting said float members include a bendable central region of reduced cross sectional area.
Claim 12
Dependent Claim
16 words
The dishwasHer of claim 8 wherein said flexure member is formed from a flexible plastic material.
Claim 13
Dependent Claim
33 words
The dishwasher of claim 7 wherein said float member contains a magnet and wherein said electrical means external to said float member includes reed switch means responsive to the proximity of said magnet.
Claim 14
Dependent Claim
28 words
The dishwasher of claim 10 wherein said reed switch means is located immediately above the predetermined upper portion of said float member and is responsive to said magnet.
Claim 15
Dependent Claim
41 words
The dishwasher of claim 7 wherein said means for limiting the operation of said heating means includes means for terminating operation of said heating means upon departure of said float member from said predetermined upper position for a predetermined time interval.
Claim 16
Dependent Claim
28 words
The dishwasher of claim 7 wherein said electrical means responsive to the presence of said float member and said temperature responsive element are mounted in a common enclosure.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-11-04 | 1978-05-06 | 1978-11-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-11-04 | 1982-05-06 | 1982-11-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-11-04 | 1986-05-06 | 1986-11-05 | $7700.00 | Window Closed / Lapsed |