Boiling water dispenser having improved water temperature control system

• US 5,019,690 A
• Filed: 09/15/1989
• Issued: 05/28/1991
• Est. Priority Date: 09/15/1989
• Status: Expired due to Term

• Current Assignee: Bunn-O-Matic Corporation
• Original Assignee: Bunn-O-Matic Corporation
• Inventors: Knepler, John T.
• Primary Examiner(s): Reynolds, Bruce A.
• Assistant Examiner(s): HOANG, TU BA
• Application Number:
  US07/407,811
• Time in Patent Office: 620 Days
• Field of Search: 99/280, 99/281, 99/282, 219/297, 219/306, 219/308, 219/310, 219/312, 219/316, 219/323, 219/337, 219/328, 219/314, 219/437, 219/441, 219/442, 219/333, 219/330, 219/331
• US Class Current: 219/400
• CPC Class Codes: A47J 27/21008 electrically heated
• CPC Class Codes: G05D 23/1912 whose output amplitude can take more than two discrete values
• CPC Class Codes: G05D 23/24 the sensing element having a resistance varying with temperature, e.g. a thermistor

Abstract

A boiling water dispenser includes a hot water reservoir, a user-actuated faucet for drawing boiling water from a discharge zone at the top of the reservoir, and a solenoid-actuated valve for admitting unheated water to an inlet zone at the bottom of the reservoir. An electric resistance heating element within the reservoir is supplied with AC current through a series- connected bilateral switch device which is periodically switched on and off in response to the sensing of steam in a reservoir venting conduit to maintain the dispensing temperature at the boiling point. An indicator lamp conditioned by a sensor in the reservoir confirms to the user that the dispensing temperature is at the boiling point.

Claims

1. A boiling water dispensing apparatus comprising:

a hot water reservoir;

means including a reservoir heating element within said reservoir operable from an applied electric current for heating water in said reservoir;

inlet means for admitting cold water into said reservoir;

outlet means for discharging heated water from said reservoir;

steam detection means responsive to the presence of boiling water in said reservoir for producing a control signal indicative thereof, said steam detection means being generally thermally isolated from said hot water reservoir for preventing the temperature of the reservoir from affecting the steam detection means; and

temperature regulating means responsive to said control signal for controlling the application of electrical current to said resistance means to maintain water in said reservoir substantially at actual boiling temperature.

2. A boiling water dispenser apparatus as defined in claim 1 wherein said reservoir includes a venting port, and said steam detection means detect steam exiting said reservoir through said port.

3. A boiling water dispenser apparatus as defined in claim 2 including a conduit defining a flow path for steam exiting said reservoir and wherein said steam detection means detect steam in said flow path.

4. A boiling water dispenser apparatus as defined in claim 3 wherein said steam detection means comprises a temperature sensing element disposed in said flow path in thermal communication with steam flowing therein, and in relative thermal isolation to the water in said reservoir.

5. A boiling water dispenser apparatus as defined in claim 4 wherein said steam detection means comprise a mounting block formed of a relatively thermally non-conductive material for positioning said sensing element in said flow path.

6. A boiling water dispenser apparatus as defined in claim 4 wherein said temperature sensing means comprises a thermistor.

7. A boiling water dispenser apparatus as defined in claim 1 wherein temperature regulating means apply electrical current continuously in the event said steam detection means fail to detect steam for a predetermined period of time, and upon steam being detected, apply current periodically to said heating element.

8. A boiling water dispensing apparatus comprising:

a hot water reservoir;

means including a resistance heating element within said reservoir operable from an applied electric current for heating water in said reservoir;

inlet means for admitting cold water into said reservoir;

outlet means for discharging heated water from said reservoir;

venting means defining a flow path for transporting steam formed within said reservoir away from said reservoir, said venting means discharging steam to the ambient atmosphere; and

temperature regulating means including a temperature sensing element responsive to the occurrence of steam associated with said venting means for controlling the application of electric current to said resistance heating element to maintain the water in said reservoir at actual boiling temperature, said temperature sensing element being located outside of said vent means generally surrounded by the ambient atmosphere and being thermally isolated from said hot water reservoir for preventing the temperature of the reservoir from affecting the temperature sensing element.

9. A boiling water dispensing apparatus as defined in claim 8 wherein said temperature sensing means comprise a thermistor.

10. A boiling water dispensing apparatus as defined in claim 8 wherein said temperature regulating means apply full excitation to said heating element following a predetermined period of time having elapsed in which steam has not occurred in said venting means, and reduced excitation to said heating element prior to said predetermined period of time having elapsed.

11. A boiling water dispensing apparatus as defined in claim 10 wherein said temperature regulating means apply said reduced excitation to said heating element intermittently prior to said predetermined period of time having elapsed.

12. A dispenser for heated water substantially at a boiling temperature comprising a water reservoir, a heater associated with said reservoir for heating water in the reservoir, means for isolating steam generated when said water is at a boiling temperature and discharging the steam to the ambient atmosphere, and control means including a sensor responsive to the presence or absence of steam at a discharge point of said isolating means for operating said heater means for maintaining the water in said reservoir substantially at said boiling temperature, said sensor being thermally isolated by said isolating means from said reservoir for preventing the temperature of the reservoir from affecting the sensor.

13. A dispenser for providing water at substantially a boiling temperature comprising a water reservoir, electrical heater means associated with said reservoir for heating water in said reservoir, control means for applying electrical current to said heater means at a predetermined high duty cycle when the water is substantially below said boiling temperature and for applying electrical current to said heater means intermittently at a relatively low duty cycle sufficient to maintain the water substantially at said boiling temperature when the water is substantially at said boiling temperature, fluid passageway means for permitting flow of heated fluid from said reservoir to the ambient atmosphere when said water in the reservoir is at least at a boiling temperature, and wherein said control means comprises a sensor positioned outside of said fluid passageway for sensing said fluid flowing through said passageway means to the ambient atmosphere, said sensor being thermally isolated from said reservoir and said fluid passageway means for preventing the temperature of said reservoir or fluid passageway means from affecting the sensor.

14. A dispenser for boiling water comprising a water reservoir, heater means associated with said reservoir for heating water in the reservoir to a boiling temperature, vent means connected with said reservoir and having a discharge opening for venting steam generated by boiling water from the reservoir to the ambient atmosphere, a receptacle disposed in alignment with said discharge opening for accumulating condensate from steam from said discharge opening, said receptacle permitting subsequent evaporation of the condensate into the surrounding atmosphere, said receptacle being thermally connected with said reservoir and heated thereby for promoting evaporation of the condensate, control means comprising a sensor element disposed between said discharge opening and said receptacle in said ambient atmosphere being responsive to the presence and absence of steam flowing from said discharge opening for energizing said heater means intermittently and sufficiently to maintain the water in the reservoir substantially at boiling temperature, said sensor element being thermally isolated from said reservoir, vent means and said receptacle for preventing the temperature of said reservoir, vent means and said receptacle from affecting the sensor element.