Abstract:
A coffee maker contains a siphon tube for discharging hot water from a heated reservoir to a container for coffee grounds. Flow through the siphon tube is initiated by pressurizing the air space in the heated reservoir with an air pump. A siphon flow of hot water through the siphon tube to a coffee grounds container then continues without pressurization. The flow is ended when the desired volume of coffee is brewed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application Ser. No. 60/741,922, Dec. 2, 2005. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to food and beverage devices. More particularly, this invention relates to coffee makers. 
     BACKGROUND OF THE INVENTION 
     Coffee is a drink made by passing hot water and/or steam through the roasted and ground beans of the coffee plant. The process of making coffee is commonly known as brewing. Coffee is the most popular hot drink in the United States and many foreign countries. 
     A variety of coffee makers are used to brew coffee. Home coffee makers typically have a reservoir or tank which is usually empty. When coffee is desired, the reservoir is filled with fresh cold water, the water is heated to the desired temperature (typically about 200° F.), and then all the water is released from the reservoir to flow through the coffee grounds and into a pot. Home coffee makers are relatively slow because of the time it takes for the water to heat in the reservoir. 
     Commercial coffee makers typically have a large reservoir which is partially or completely filled with water at all times. The reservoir is heated so the water in the reservoir is always hot. When a pot of coffee is desired, water from the top of the reservoir is released to flow through the coffee grounds and into the pot. The density of water decreases as its temperature increases so the hottest water in the reservoir rises to the top. Commercial coffee makers are much faster than home coffee makers because there is no wait for the water to heat to the desired temperature. 
     Commercial coffee makers contain various means for starting and stopping the flow of the water from the reservoir to the grounds. One type of coffee maker uses a siphon. A siphon is a flow of water from one level, through an elevated tube, to a lower level. A siphon is illustrated in  FIG. 1 . With the water levels as shown, no flow through the elevated siphon tube occurs. To begin the flow, the elevated siphon tube must be completely filled with liquid. This can be accomplished by: (1) raising the liquid level in the upper tank to the uppermost part of the siphon tube; (2) sealing the upper tank and then pressurizing it to force the liquid up the siphon tube; or (3) sealing the lower tank and applying a vacuum. Once the siphon flow begins, it will continue until the level in the upper tank drops to the inlet or until the siphon is “broken” by opening the tube to the atmosphere. 
     A siphon-type commercial coffee maker is illustrated in  FIG. 2 . When a pot of coffee is desired, a measured volume of water is added to the fill tank, either manually or through a timer-controlled fill valve in the water inlet line. The cold water flows from the fill tank down a tube into the bottom of the heated reservoir. As soon as the water level exceeds the height of a siphon tube, the flow of hot water out of the heated reservoir begins. The flow continues until the fill tank is emptied and the water level in the heated reservoir drops to the intake of the siphon tube. This type of coffee maker immediately dispenses a volume of water from the heated reservoir that is equal to the volume of cold water added to the reservoir. A major disadvantage of this coffee maker is that the brewing of coffee always begins at the time the water is added. In other words, a delay between the time the water is added and the brewing begins is not possible. Another disadvantage is that there is no means for stopping the sipon flow once it begins. Examples of such a coffee maker are the BUNN VPS (manual fill) and BUNN CWT (timer-controlled fill valve) coffee makers, both of which are commercial products of Bunn-O-Matic Corporation of Springfield, Ill. 
     A second type of commercial coffee maker is illustrated in  FIG. 3 . This type of coffee maker contains a water level controller that controls a fill valve in the water inlet to maintain a constant level in the heated reservoir. The coffee maker also contains a timer controller that controls a valve in the outlet line (commonly known as a dump valve) that opens for a period of time and then closes. The coffee maker also contains a vent/overflow line that serves two purposes: (1) it maintains the heated reservoir at atmospheric pressure so water will flow out the outlet line; and (2) it provides an overflow in the event the fill valve malfunctions and fails to close. A major disadvantage of this coffee maker is that the dump valve requires frequent maintenance because lime from the hot water tends to build up at the valve. Lime deposits form from cold water at a much slower rate so maintenance on the fill valve is generally not a problem. Examples of such a coffee maker are the BUNN CDBCF coffee maker, a commercial product of Bunn-O-Matic Corporation of Springfield, Ill., and the GRINDMASTER B3 coffee maker, a commercial product of Grindmaster Corporation of Louisville, Ky. 
     A third type of commercial coffee maker dispenses water from the reservoir only when an air compressor runs. Coffee makers of this type are disclosed in Herrera, U.S. Pat. No. 2,464,862, Mar. 22, 1949; Rosander, U.S. Pat. No. 3,085,494, Apr. 16, 1963; Rosander, U.S. Pat. No. 3,085,495, Apr. 16, 1963; Bixby, U.S. Pat. No. 3,381,604, May 7, 1968; Weber, U.S. Pat. No. 3,423,209, Jan. 21, 1969; Weber, U.S. Pat. No. 4,143,589, Mar. 13, 1979; and Beaulicu, U.S. Pat. No. 6,082,247, Jul. 4, 2000. The disadvantages of this type of coffee maker are that the air compressor is noisy and requires frequent service because it runs the entire time the coffee is being brewed. 
     Accordingly, there is a demand for an improved coffee maker. More particularly, there is a demand for a coffee maker that does not require a dump valve or a continuously running air compressor, that can dispense hot water independently of the time water is added, and that can dispense any desired volume of hot water. 
     SUMMARY OF THE INVENTION 
     The general objects of this invention are to provide an improved coffee maker and an improved method of brewing coffee. More particular objects are to provide a coffee maker that does not require a dump valve or a continuously running air compressor, that can dispense hot water independently of the time water is added, and that can dispense any desired volume of hot water. 
     I have invented an improved coffee maker. The coffee maker comprises: (a) a heated reservoir for holding a volume of hot water such that the hot water forms a level within the heated reservoir with an air space existing above the level of the hot water; (b) an inlet to the heated reservoir for adding water; (c) a siphon tube for discharging hot water from the heated reservoir, the siphon tube having an intake at or below the level of hot water, then rising above the level of hot water, and then descending to an outlet at a level below the intake; (d) a container for coffee grounds located below the siphon tube outlet; (e) a means for temporarily sealing the heated reservoir; and (f) an air pump having a discharge line communicating with the heated reservoir for creating sufficient pressure in the sealed heated reservoir for a period of time sufficient to force hot water into the siphon tube and begin the siphon flow of hot water from the heated reservoir to the coffee grounds container. 
     The coffee maker of this invention does not require a dump valve or a continuously running air compressor, can dispense hot water independently of the time water is added, and can dispense any desired volume of hot water. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustration of a prior art siphon. 
         FIG. 2  is a diagram of a first type of prior art coffee maker. 
         FIG. 3  is a diagram of a second type of prior art coffee maker. 
         FIG. 4  is a diagram of a first embodiment of the coffee maker of this invention. 
         FIG. 5  is a diagram of a second embodiment of the coffee maker of this invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     This invention is best understood by reference to the drawings. A first embodiment  10  of the coffee maker of this invention is shown in  FIG. 4 . This coffee maker is similar in some respects to the prior art coffee maker shown in  FIG. 2 . It has a heated reservoir or tank  15  for holding a volume of hot water  20  that is less than the volume of the tank itself. Accordingly, an air space  25  exists above the level of the hot water. The heated reservoir or tank is generally made of steel, is heated by electrical resistors or the like (not shown), and has a volume of about one to ten gallons. A fill tank  30  is positioned above the heated reservoir and a vertical fill tube  35  provides communication between the two tanks. A water line  40  is connected to the fill tank. A valve  45  in the water line is controlled by an electronic controller  50 . The coffee maker has a container  55  for coffee grounds  60  and a base (not shown) for a coffee pot  65 . 
     This coffee maker differs from the prior art coffee maker shown in  FIG. 2  in two major ways. The first change is that the height of the siphon tube  70  is raised to a level above the fill tank. With this change, the addition of water to the fill tank does not, by itself, begin the flow of water out the siphon tube. The second major change is that an air pump  75  is added which can pressurize the air space in the heated reservoir via a pressurized air line  80 . A suitable air pump is the ELITE 802 air pump, a commercial product of Rolf C. Hagen Inc. of Montreal, Quebec, Canada. This air pump is commonly used to add air to an aquarium. The air pump is controlled by the controller. 
     The operation of the coffee maker can now be considered. The level of hot water is the heated reservoir is generally at the level shown in  FIG. 4 . This level is at the inlet to the siphon tube. To prepare the coffee maker to dispense coffee, the desired volume of water is added to the fill tank. The desired volume can be added manually or by a timer-controlled fill valve, but it is preferably added by a level-controlled fill valve. A major advantage of a level-controlled fill valve is that it adds the same amount of water regardless of the pressure in the water inlet line. The added water flows down the vertical fill tube into the bottom of the heated reservoir and the water level rises above the siphon tube inlet, both inside and outside the siphon tube. The water in the fill tank and vertical fill tube creates a seal from the atmosphere in the heated reservoir. 
     When coffee is desired, the air pump is turned on for a period of time sufficient to pressurize the heated reservoir and force the water all the way up the siphon tube. As soon as the horizontal portion of the siphon tube is filled, water begins to flow by siphon action. Pressure is no longer required so the air pump is turned off. The time needed to initiate siphon flow is very short—less than about five seconds and typically about one-half to two seconds. Once siphon flow begins, it will continue until the level in the heated reservoir drops to the level of the siphon tube inlet as shown in  FIG. 4 . The hot water leaves the outlet of the siphon tube, flows through the ground coffee beans, and into the coffee pot. 
     It can be appreciated that the first embodiment of the coffee maker does not have a dump valve that is prone to malfunction because of lime deposits. Therefore, the coffee maker of this invention never requires maintenance on a dump valve. Nor does the coffee maker have a continuously running air compressor—its air pump runs for no more than a second or two during each brewing cycle. Therefore, the coffee maker is quieter and requires little, if any, maintenance on the air pump. The coffee maker can dispense hot water independently of the time water is added. In other words, it can begin the brewing of coffee simultaneously with the addition of the cold water or it can begin the brewing at a later time because the brewing is not begun until the air pump is turned on. And finally, the coffee maker can dispense any desired volume of hot water because the volume discharged is equal to the volume added to the fill tank. 
     A second embodiment  110  of the coffee maker of this invention is shown in  FIG. 5 . This coffee maker is similar in some respects to the prior art coffee maker shown in  FIG. 3 . It has a heated reservoir or tank  115  for holding a volume of hot water  120  that is less than the volume of the tank itself. Accordingly, an air space  125  exists above the level of the hot water. A water inlet line  140  is connected to the heated reservoir. A fill valve  145  in the water inlet line is controlled by a level controller  150   a  to maintain constant level of water in the heated reservoir. The coffee maker has a container  155  for coffee grounds  160  and a base (not shown) for a coffee pot  165 . 
     This coffee maker differs from the prior art coffee maker shown in  FIG. 3  in several ways. A first change is that the outlet tube is reconfigured from a horizontal tube into a siphon tube  170  that rises above the level of water in the heated reservoir. A stop valve  171  is added to the siphon tube at a point above the water level in the heated reservoir. When the stop valve is open, communication between the atmosphere and the horizontal section of the siphon tube exists. As explained below, the opening of the stop valve is the mechanism for stopping the siphon flow of water. The stop valve is preferably operated by a solenoid (not shown) that is controlled by a timer controller  150   b . If desired, the level controller and the timer controller are within the same housing. 
     A second change is that a vent valve  185  is added to the vent/overflow line  190 . When the vent valve is open, communication between the atmosphere and the heated reservoir exists. A third change is that an air pump  175  is added which can pressurize the air space in the heated reservoir via pressurized air line  180 . The same type of air pump suitable for the first embodiment is suitable for the second embodiment. The pressurized air from the air pump is also used to operate the vent valve. 
     The operation of the second embodiment of the coffee maker can now be considered. The level of hot water in the heated reservoir remains at the level shown in  FIG. 5  at all times due to the action of the water inlet fill valve and the level controller. Both the vent valve and the stop valve are normally in the open position. When coffee is desired, the air pump is turned on for a very short period of time. The air pressure immediately closes the vent valve to seal the heated reservoir from the atmosphere and pressure quickly builds inside the heated reservoir. At the same time, the stop valve is closed. The pressure in the heated reservoir forces hot water all the way up the siphon tube. As soon as the horizontal portion of the siphon tube is filled, water begins to flow by siphon action. Pressure is no longer required so the air pump is turned off and the vent valve reopens. The time needed to initiate siphon flow is generally less than five seconds and is typically about one-half to two seconds. Once siphon flow begins, it will continue until stop valve is opened to break the siphon. If the stop valve were not opened, the siphon flow would continue indefinitely because the water inlet valve would remain open to maintain the water level in the heated reservoir above the level of the siphon tube inlet. 
     It can be appreciated that the second embodiment of the coffee maker does not have a dump valve that is prone to malfunction because of lime deposits. Therefore, the coffee maker of this invention never requires maintenance of a dump valve. Nor does the coffee maker have a continuously running air compressor—its air pump runs for no more than a second or two during each brewing cycle. Therefore, the coffee maker is quieter and requires little, if any, maintenance on the air pump. It can also be appreciated that the coffee maker can dispense hot water at any time—when water is added or at any desired time afterwards. And finally, the coffee maker can dispense any desired volume of hot water because the volume discharged is determined by how long the siphon flow continues before the stop valve in the siphon tube is opened to break the siphon. 
     The coffee maker of this invention can be provided by modifying an existing coffee maker or by new construction. The size, complexity, and cost of the coffee maker is comparable to conventional coffee makers. Unlike any conventional coffee maker, the coffee maker of this invention does not require a dump valve or a continuously running air compressor, can dispense hot water independently of the time water is added, and can dispense any desired volume of hot water.