Patent Description:
Thus, the invention is particularly designed for use in drinking water dispensing systems, and it will be convenient to describe the invention herein in this exemplary context. It will be appreciated, however, that the invention is not limited to this particular application.

Pumps, such as centrifugal pumps, are well-known mechanical devices for moving or conveying liquids. In a centrifugal pump, a rotating impeller draws the liquid through an inlet of the pump typically arranged on or near its rotational axis and accelerates the liquid radially outwards into the volute chamber or casing of the pump where it then exits through an outlet, thereby transferring rotational kinetic energy of the impeller to hydrodynamic energy.

The pumping of liquids at temperatures close to their boiling point, however, can involve the problem of the liquid undergoing a phase change within the pump due to a reduced pressure to which the liquid is exposed at the inlet- or suction-side of the pump. A phase change of the liquid being pumped to the gas phase inside the pump causes cavitation which, in turn, reduces the efficiency and efficacy of the pump and can also cause damage to the impeller. Thus, if the effects of cavitation become pronounced, this can affect the performance of the pump resulting in reduced volume throughput, an inconsistent flow rate, and potential damage.

It is therefore an object of the invention to provide a new or improved pump assembly for pumping boiling drinking water in a water dispensing system.

A pump assembly for pumping boiling water to a dispenser in a drinking water dispensing system is known from <CIT>. The pump assembly includes a pump housing having an inlet for the boiling water and an outlet arranged in fluid communication with the inlet. The pump assembly also includes an impeller disposed in the pump housing for rotation about a central axis for driving the water from the inlet to the outlet. In this respect, the inlet is arranged on the central axis. The pump assembly further includes an inducer arranged in the inlet to the pump housing and operatively connected to the impeller for rotation therewith about the central axis to induce the water at the inlet towards the impeller. The inducer acts to raise the inlet pressure and, in this way, reduces the chance of a phase change occurring as the water is pumped by the impeller, thereby reducing or avoiding the occurrence of cavitation during operation of the pump.

A pump asssembly according to the present invention is characterised in that the inlet is a conduit having a substantially straight length of at least five times its internal diameter.

In a preferred embodiment, the impeller and the inducer are mounted on a common shaft. The shaft is preferably comprised of a polished engineered ceramic.

In a preferred embodiment, the inducer comprises a generally elongate stem which extends along the central axis away from the impeller into the inlet, and at least one blade or flight that extends in a helical or screw formation on an outer periphery of the stem. The inducer may include a plurality of blades or flights that extends in a helical or screw formation on the outer periphery of the elongate stem; e.g., the inducer may include a pair of helical blades or flights that extend around the outer periphery of the elongate stem. The helical or screw-shaped form of the at least one blade or flight of the inducer acts to drive the water in the inlet towards and into the impeller. An upstream end of the inducer stem typically terminates in a tapered or rounded cap or nose to promote laminar flow through the inlet.

In a preferred embodiment, the inlet comprises a conduit having a substantially straight length of at least six times its internal diameter, and optionally even longer. This length of the inlet conduit acts to promote laminar flow through and along the inlet by providing a sufficient length of straight travel for the water. The internal diameter of the inlet conduit is preferably in the range of about <NUM> to <NUM>, and more preferably about <NUM>.

In a preferred embodiment, the impeller comprises a central hub for mounting on the shaft and a plurality of radially extending vanes for driving the water centrifugally from the inlet to the outlet. A radially innermost edge of each of the vanes is preferably spaced radially outwards of, or away from, the central hub of the impeller. This configuration has been found to produce surprisingly good pumping performance. Preferably, each of the vanes has a height or a depth in the axial direction that reduces or tapers along a length or extent of the vane in a radial direction from a radially innermost edge to a radially outermost edge thereof. This configuration has also been surprisingly found to promote increased flow rate and improved performance.

In a preferred embodiment, the impeller is comprised of heat resistant polymer for thermal stability. The impeller preferably has a diameter in the range of about <NUM> to <NUM>, more preferably about <NUM>.

In a preferred embodiment, the pump assembly includes an electric motor attached to the pump housing for driving rotation of the inducer and the impeller. In this regard, the electric motor is preferably provided as a brushless induction motor. The shaft of the pump assembly is preferably rigidly fixed to the rotor of the electric motor for rotation therewith.

In a preferred embodiment, the pump assembly includes a bearing device for supporting the shaft for rotation on the central axis.

In a preferred embodiment, the impeller is designed to rotate at a speed in the range of about <NUM> to <NUM> revolutions per minute (rpm), preferably in the range of about <NUM> to <NUM> rpm to maintain a suitable flow rate out of the dispenser.

According to yet another aspect, the present invention provides a dispensing system for dispensing boiling drinking water, the system including a pump assembly of any one of the aspects or the embodiments of the invention described above.

For a more complete understanding of the present invention, exemplary embodiments of the invention are explained in more detail in the following description with reference to the accompanying drawing figures, in which like reference signs designate like parts and in which:.

The accompanying drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification. The drawings illustrate particular embodiments of the invention and together with the description serve to explain the principles of the invention. Other embodiments of the invention and many of the attendant advantages of the invention will be readily appreciated as they become better understood with reference to the following detailed description.

It will be appreciated that common and/or well understood elements that may be useful or necessary in a commercially feasible embodiment are not necessarily depicted in order to facilitate a more abstracted view of the embodiments. The elements of the drawings are not necessarily illustrated to scale relative to each other. It will also be understood that certain actions and/or steps in an embodiment of a method may be described or depicted in a particular order of occurrences while those skilled in the art will understand that such specificity with respect to sequence is not actually required.

As it is used in this description, it will be appreciated that "boiling water" generally refers to water at or near its boiling point. In the preferred embodiment, the water is at a temperature in the range of about <NUM>-<NUM>.

Referring to the drawings, a pump assembly <NUM> according to a preferred embodiment of the invention is illustrated. The pump assembly <NUM> is suitable for use with a vented drinking water dispensing system (not shown) for pumping boiling water to a dispenser (not shown) in the drinking water dispensing system. Preferably, the pump assembly <NUM> is configured for pumping water at a temperature of about <NUM>.

With particular reference to <FIG>, the pump assembly <NUM> includes a pump housing <NUM> having an inlet conduit <NUM> for the boiling water and an outlet conduit <NUM> arranged in fluid communication with the inlet conduit <NUM>. Both the inlet conduit <NUM> and the outlet conduit <NUM> have respective longitudinally extending central axes <NUM>, <NUM>. The pump housing <NUM> is comprised of heat resistant polymer for thermal stability during operational pumping of the boiling water.

With reference to <FIG>, silicone tubing in the form of a silicone elbow <NUM> is configured to fit over the inlet conduit <NUM> so that the inlet conduit <NUM> is arranged in fluid communication with a tank (not shown) configured to store the boiling water. The fitted straight section of the silicone elbow <NUM> together with the inlet conduit <NUM> define a substantially straight length L of at least five times the internal diameter of the inlet conduit <NUM>, and preferably six times the internal diameter of the inlet conduit <NUM>, to promote laminar flow through the inlet conduit <NUM>. In a preferred embodiment, the inlet conduit <NUM> has an internal diameter preferably in the range of about <NUM> to <NUM>, more preferably about <NUM>. The inlet conduit <NUM> preferably has an outer diameter in the range of about <NUM> to <NUM>, more preferably about <NUM>. As best depicted in <FIG>, a terminal portion surrounding the open end of the inlet conduit <NUM> forms a lip <NUM> preferably having an axial width of about <NUM> and an outer diameter of about <NUM> over which the straight section of the silicone elbow <NUM> is securely fitted.

With reference again to drawing <FIG>, the outlet conduit <NUM> of the pump housing <NUM> is arranged so that its central axis <NUM> is substantially perpendicular and offset with the central axis <NUM> of the inlet conduit <NUM>. The outlet conduit <NUM> has an internal diameter preferably in the range of about <NUM> to <NUM>, more preferably about <NUM>. Silicone tubing (not shown) is configured to fit over the outlet conduit <NUM> so that the outlet conduit <NUM> is arranged in fluid communication with the dispenser in the drinking water dispensing system. In a preferred embodiment, the outlet conduit <NUM> has a straight length in the range of about <NUM> to <NUM>, more preferably about <NUM>, and an outer diameter in the range of about <NUM> to <NUM>, more preferably about <NUM>. A terminal portion surrounding the open end of the outlet conduit <NUM> forms a lip <NUM> preferably having an axial width of about <NUM> and an outer diameter of about <NUM> over which the silicone tubing is securely fitted.

With particular reference to <FIG>, the pump assembly <NUM> includes an impeller <NUM> disposed in the pump housing <NUM> for rotation about a central axis, that is, the central axis <NUM> of the inlet conduit <NUM>, for driving the water from the inlet conduit <NUM> to the outlet conduit <NUM>. The section of the pump housing <NUM> in which the impeller <NUM> is disposed preferably defines a cylindrical chamber <NUM> having an outer diameter in the range of about <NUM> to <NUM>, more preferably about <NUM>. In this regard, the inlet conduit <NUM> and the outlet conduit <NUM> are preferably integrally formed with the section of the pump housing <NUM> defining the cylindrical chamber <NUM>.

With particular reference to <FIG>, the impeller <NUM> has a central hub <NUM> for mounting on a shaft <NUM> (shown in <FIG>) comprised of a ceramic. The impeller <NUM> includes a plurality of radially extending vanes <NUM> for driving the water centrifugally from the inlet conduit <NUM> to the outlet conduit <NUM>. A radially innermost edge of each of the vanes <NUM> is spaced radially outwards of or away from the central hub <NUM> of the impeller <NUM>, preferably spaced about <NUM> from the central hub <NUM>. Each of the vanes <NUM> has a height or depth in the axial direction that reduces or tapers in the radial direction from the radially innermost edge to a radially outermost edge thereof, that is, the height reduces from about <NUM> to <NUM>. Each of the vanes <NUM> is curved backwardly away from the tangential direction of rotation. Like the pump housing <NUM>, the impeller <NUM> is comprised of heat resistant polymer and has a diameter in the range of about <NUM> to <NUM>, preferably about <NUM>.

With particular reference to <FIG>, the pump assembly <NUM> further includes an inducer <NUM> arranged in the inlet conduit <NUM> to the pump housing <NUM> and mounted on the ceramic shaft <NUM> upstream of the impeller <NUM>. The inducer <NUM> comprises a generally elongate stem which extends along the central axis <NUM> of the inlet conduit <NUM> away from the impeller <NUM> into the inlet conduit <NUM>. In a preferred embodiment, the longitudinal length of the elongate stem is in the range of about <NUM> to <NUM>, preferably about <NUM>. A downstream portion of the elongate stem is rigidly keyed with a portion extending from the central hub <NUM> of the impeller <NUM> so that the inducer <NUM> rotates with the impeller <NUM> about the central axis <NUM> of the inlet conduit <NUM> to induce the water at the inlet conduit <NUM> towards the impeller <NUM> and raise the inlet pressure. The elongate stem has at least one blade or flight <NUM>, preferably two blades or flights, that extends in a helical or screw formation on an outer periphery of the inducer stem. An upstream end of the inducer stem terminates in a tapered or rounded cap or nose <NUM> to promote laminar flow through the inlet conduit <NUM>. As shown in <FIG>, a nose <NUM>' according to another embodiment includes a clip adapter portion <NUM> to enable the nose <NUM>' to be mounted to the shaft <NUM>.

With reference to <FIG>, the pump assembly <NUM> further includes an electric brushless induction motor <NUM> having a housing <NUM> attached to the pump housing <NUM> by way of screws <NUM> (shown in <FIG>) threadably engageable in respective aligned screw holes <NUM> on both the motor housing <NUM> and the pump housing <NUM>. The motor <NUM> drives rotation of the impeller <NUM> and the inducer <NUM>. In this way, the ceramic shaft <NUM>, on which the impeller <NUM> and the inducer <NUM> rotate, is rigidly retained with a clip retainer or other fixing means to the rotor <NUM> of the motor <NUM> for rotation therewith. To facilitate rotation of the ceramic shaft <NUM>, the pump assembly <NUM> includes a bearing <NUM> into which an end of the ceramic shaft <NUM> is inserted for supporting the ceramic shaft <NUM> on the central axis <NUM> of the inlet conduit <NUM>. In this regard, the impeller <NUM> (and the inducer <NUM>) is designed to rotate (without load) at a speed in the range of about <NUM> to <NUM> revolutions per minute (rpm), preferably in the range of about <NUM> to <NUM> rpm, and more preferably <NUM> rpm ± <NUM>%.

According to a preferred embodiment, the motor housing <NUM> has an axial length of about <NUM> and an outer diameter of about <NUM>. By this arrangement, the total weight of the pump assembly <NUM> is in the range of about <NUM> to <NUM>.

Although specific embodiments of the invention are illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternative and/or equivalent implementations exist. It should be appreciated that the exemplary embodiment or exemplary embodiments are examples only and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention, which is defined by the appended claims.

Claim 1:
A pump assembly for pumping boiling water to a dispenser in a drinking water dispensing system, the pump assembly comprising:
a pump housing (<NUM>) having an inlet (<NUM>) for the boiling water and an outlet (<NUM>) arranged in fluid communication with the inlet (<NUM>);
an impeller (<NUM>) disposed in the pump housing (<NUM>) for rotation about a central axis (<NUM>) for driving the water from the inlet (<NUM>) to the outlet (<NUM>), wherein the inlet (<NUM>) is arranged on the central axis (<NUM>); and
an inducer (<NUM>) arranged in the inlet (<NUM>) to the pump housing (<NUM>) and operatively connected to the impeller (<NUM>) for rotation therewith about the central axis (<NUM>) to induce the water at the inlet (<NUM>) towards the impeller (<NUM>) and raise the inlet pressure,
characterized in that the inlet (<NUM>) is a conduit having a substantially straight length of at least five times its internal diameter.