1. In a beverage infusion appliance having means for holding coffee or other material to be infused, and means including a pump for introducing liquid into the material to be infused, the improvement wherein said pump has a unitary housing provided with an upper portion, a midportion and a lower portion
2. The appliance of claim 1 wherein the inlet portion of the fountain tube is flared to provide an enlarged area for entry of liquid into the fountain tube.
3. The appliance of claim 1 having a well element for receiving the pump housing to form therewith a pressure generating chamber, said pressure generating chamber adapted to receive fluid, means for heating the well element to generate fluid pressure in the pressure generating chamber, said pump housing being formed of a material which has a lower coefficient of thermal conductivity than the well element to reduce the deposition of minerals in the well element.
4. The appliance of claim 3 wherein the inlet portion of the fountain tube is flared to provide an enlarged area for entry of liquid into the fountain tube.
5. A coffee maker, comprising
6. The coffee maker of claim 5 wherein the lower inlet of the fountain tube is flared to provide an enlarged area for entry of liquid into the fountain tube.
BACKGROUND OF THE INVENTION
This invention relates to improvements in the type of coffee maker wherein a jet pump is used to impel water up a fountain tube into an infusion basket which holds ground coffee or other material to be infused. A previous coffee maker of this type is shown by the Graham U.S. Pat. No. 2,784,678 which is incorporated into this disclosure by reference, wherein the jet pump nozzle orifice is located centrally within a valve member which admits liquid into the steam or pressure-generating chamber.
In the normal course of development, there have been a number of modifications to the specific arrangement shown in the above-mentioned Graham U.S. Pat. No. 2,784,678. Immediately prior to the improvement of the present invention, it was the practice to make the pump housing of two separate, threadedly engaged members, the lower member supporting the valve/nozzle member and providing the upper half of a pressure generating chamber. The upper element of the housing carried the fountain tube and was provided with openings which admitted liquid into the area surrounding the nozzle.
SUMMARY OF THE INVENTION
This invention is devoted to improvements in and relating to the construction of the pump assembly used in beverage infusion devices of this type. In order to simplify the construction of such pump housings, this improvement provides for a pump housing made of a unitary piece of material provided with a longitudinal bore at the lower end thereof to form the upper portion of the pressure generating chamber for the jet pump. A transverse bore is located in an upper portion of the pump housing and has positioned therein the nozzle outlet from the pressure generating chamber and the lower inlet end of the fountain tube which carries liquid upwardly into the infusion basket. The longitudinal bore intersects only partially with the transverse bore, and at this point of intersection a combination valve/nozzle member is positioned. The valve/nozzle member when in its lower or open position admits liquid into the pressure generating chamber. It has an upwardly-facing valve seat for engaging the downwardly-facing upper end of the longitudinal bore to prevent the escape of pressure around the valve/nozzle member when in its upper or closed position. An orifice centrally located in the valve/nozzle member creates a high velocity release of pressurized fluid from the pressure generating chamber when the valve is in its upper and closed position. When in this position, fluid under pressure is released by the orifice of the nozzle into the fountain tube, thereby aspirating liquid from the transverse bore into the fountain tube and upwardly into the infusion basket.
The invention also involves the concept of flaring the lower or inlet end of the fountain tube in order to improve the pumping capacity of the jet pump. It is believed that such improvement is attributable, at least in part, to the streamlines of flow which are permitted by the flared end which enlarges the area through which liquid may be aspirated into the fountain tube.
Still another concept utilized in the present invention is the minimization of mineral deposition in the heated well of the apparatus, this effect being achieved by making the pump housing of a material which has a lower coefficient of thermal conductivity than the well itself. This is a highly desirable feature since it reduces the buildup of minerals on the heat transfer surfaces of the well cavity, it avoids or reduces the loss of thermal efficiency of the well in heating the water and it permits the operation of appliances of this type in locales where high mineral content of the water has precluded their use heretofore. This improved performance is due, at least in part to the relative thermal conductivity of the pump elements, and it is possibly also enhanced by providing maximum area liquid passage leading to the vicinity where the jet nozzle is directed at the fountain tube, and also by providing an enlarged fountain tube inlet.
In accordance with usual practice, only a preferred embodiment of the invention is disclosed hereinbelow, it being understood that many modifications and variations thereto will fall within the spirit of the invention.
For a complete understanding of the invention, reference is made to the following description and to the accompanying drawings which disclose the following:
FIG. 1 is a sectional view of an apparatus constructed according to the invention in a coffee maker;
FIG. 2 is a perspective view of a pump and fountain tube assembly made according to the preferred embodiment of the invention; and
FIG. 3 is an enlarged view illustrating the details of the pump assembly.
Referring to FIG. 1, it will be seen that the apparatus includes a vessel 2 for holding a liquid which in most instances will initially be water and then be coffee after completion of the infusion process. Located centrally within the vessel 2 is a fountain tube 4 which supports the perforated infusion basket 6 at its upper end. The infusion basket is held downwardly in the illustrated position by the cover 8 which is coupled to the vessel 2, thereby compressing the spring 10 to bias the fountain tube 4 downwardly. The infusion basket 6 has a cylindrical central tube 12 which has an outlet 14 at its upper end for releasing liquid from the fountain tube into coffee or other material in the infusion basket 6.
This invention is concerned with the means for impelling liquid upwardly through the fountain tube 4. Generally speaking, this is a jet pump which has a nozzle orifice 16 directed into the lower end of the fountain tube 4 to aspirate liquid from vessel 2 into the transverse bore 31 of the pump housing and upwardly into the fountain tube 4. Pressure for operating the jet pump is created by heating a small amount of water to create steam pressure which drives fluid at a high velocity through the nozzle orifice 16 and into the fountain tube 4.
The jet pump housing 18 serves several functions. At its upper end, it supports the fountain tube 4. In its midsection, it supports the valve/nozzle member 20 which includes the previously-mentioned nozzle orifice 16. At its lower end, it has a longitudinal bore 22 which forms the upper portion of the pressure generating chamber 24. The lower portion of the pressure generating chamber is the cavity 26 formed in the upper wall of the well member 28. An electrical heating element 30 of conventional construction surrounds the well member 28 to boil water in the pressure generating chamber 24, thereby providing the pressure which operates the jet pump.
The valve/nozzle member 20 has a dual function. At the outset of operation, before pressure is generated in the chamber 24, the valve/nozzle member 20 admits liquid into the pressure generating chamber. At this point, it is in its lower position which is illustrated in FIG. 1 where its downward movement is limited by the spring pin 32. An annular gap around the upper portion of the valve/nozzle member 20 admits liquid into the chamber 24. Thereafter, the electrical heating element 30 creates steam pressure in the pressure generating chamber 24, creating enough pressure to drive the valve/nozzle member 20 upwardly until the frusto-conical valve disc surface 34 on member 20 engages and seals against the complementary valve seat surface 36 which is the upper face of the longitudinal bore 22. When in this position, fluid cannot pass through the annular opening around the member 20, and must be released through the nozzle orifice 16 into the fountain tube 4. Of course, this will aspirate liquid inwardly through the transverse bore 31 and upwardly into the fountain tube 4. During infusion, the valve/nozzle operates cyclically at frequencies of a few seconds so that the apparatus goes back and forth from a pumping phase to a chamber-refill phase.
The flow of liquid from the vessel 2 toward the fountain tube 4 is enhanced by virtue of the enlarged transverse bore 31 and the enlarged, flared lower end 38 of the fountain tube 4. These features have been found to increase the capacity of the pump.
Experimentation has shown that advantages accrue from making the pump housing 18 of a material which has a lower coefficient of thermal conductivity than the well member 28. For example, the well member 28 may be bronze and the pump housing 18 may be 303 stainless steel. For reasons which are not completely understood, this relationship between these materials avoids a very substantial problem in that it reduces the amount of minerals which are built up on the wall of the cavity 26 in the well member 28. Mineral depositions of this type are undesirable since they interfere with the transfer of heat from the well member 28 to the water in the pressure generating chamber 24, and they require frequent cleaning. In some geographical locations, the mineral content of the water is so great that prior art apparatus of this type cannot be used.
The construction of the pump housing 18 is of ultimate simplicity since it includes only a unitary member with a transverse bore 31, a small upper longitudinal bore for receiving the fountain tube 4 which is upset and flared to hold it in place, and a larger lower longitudinal bore 22 which partially intersects the transverse bore 31, forms the valve seat for the valve/nozzle member 20 and forms the upper portion of the pressure generating chamber 24. This construction avoids the previous practice of making a pump housing of two separable, threadedly engaged parts which have necessitated many machine operations.
Persons skilled in the art will appreciate that there are many ways in which the disclosed apparatus may be modified without departing from the spirit of the invention and its general objectives which are to simplify construction, increase pumping capacity and reduce mineral deposition. Therefore, it is emphasized that the invention is not limited only to the disclosed preferred embodiment, but is encompassing of all modifications and improvements hereto which fall within the spirit of the claims which follow.