TECHNICAL FIELD

[0001] The present invention relates generally to water pumps and, in particular, to portable multistage centrifugal water pumps.

BACKGROUND

[0002] Portable water pumps are used in fighting forest fires or otherfires in remote locations where a water supply from a fire hydrant or firetruck is unavailable. These portable water pumps are typically gas-powered and designed to draw water from a local water source like a lake, pond, river, stream, etc. Atypical portable gas-powered water pump has an internal combustion engine having one or more cylinders, e.g. a two-cycle or four-cycle internal combustion engine. The engine may be mounted to a frame that may be a hand-carrying tube frame or a channel base frame for mounting to a vehicle such as an all-terrain vehicle. Each cylinder of the engine has a spark plug that may be sparked by a battery-powered push-button electric starter and/or a manual recoil pull-cord. The engine may include an oil filter and an air intake filter. The engine has an exhaust outlet. The engine has a crankshaft that is mechanically coupled to a pump shaft of the pump. Specifically, the crankshaft is mechanically coupled to a rotating shaft of the pump to rotate an impeller of the pump unit. The impeller of the pump unit displaces the water inside the pump unit such that the water is forced to exit through an outlet of the pump unit. The swirling action of the impeller causes the water to move centrifugally toward the exit. Accordingly, this type of pump unit is known as a centrifugal pump unit. If the pump has a single impeller, it is known as a single-stage pump. If the pump has two or more serially disposed (cascaded) impellers, the pump is known as a multistage pump. In a multistage pump, the water is pressurized in the first stage and then conveyed to the second stage where it is further pressurized. A multistage centrifugal pump is generally able to generate greater pressure and is thus useful in applications such as firefighting.

[0003] In a multistage centrifugal water pump, there is an inter-stage component placed between the first stage and the second stage known as a distributor whose function is to distribute the water from the first stage to the second stage. This distributor is conventionally secured against water-induced rotation by threaded fasteners such as screws. In order to prolong the service life of the pump, it is beneficial to occasionally dismantle the pump for maintenance. However, over time, the screws may become very difficult to unfasten due to corrosion and/or general wear and tear, thereby preventing the pump from being dismantled for maintenance.

[0004] Other multistage centrifugal water pumps rely on clamping pressure to secure the distributor. Typically, the distributor is clamped axially outside the diameter of the impeller where vane passages are provided to allow the water to pass from the first to the second stage. This design has two shortcomings: a larger housing diameter is required to provide for these vanes around the impeller which adds cost and weight. Secondly, typically the distributor is clamped by a flange or cover that bears up against the distributor. The cover is, in turn, clamped by screws (or studs) which are tightened into tapped holes in the housing. This adds weights and increases cost for drilling and tapping holes.

[0005] A technical solution to the problems noted above is highly desirable.

SUMMARY

[0006] In general, the present specification discloses a multistage centrifugal water pump that includes a housing, a first impeller defining a first stage and a second impeller defining a second stage. The pump includes a distributor having an interstage wall between the first impeller and the second impeller. The distributor has first and second cutwaters. The housing has first and second slots into which the first and second cutwaters are fitted in order to secure the distributor against water-induced rotation. This novel design eliminates the need for screws and thus facilitates dismantling of the pump for maintenance.

[0007] An aspect of the disclosure is a multistage centrifugal water pump that includes a housing having a water inlet for receiving water into the housing and a water outlet for expelling the water from the housing. A first impeller rotates within the housing about an axis of rotation to impel the water centrifugally to define a first stage in which the water is pressurized. A second impeller also rotates within the housing about the axis of rotation to impel the water centrifugally to define a second stage in which the water is further pressurized. A distributor defines an inter-stage wall between the first impeller of the first stage and the second impeller at the second stage, the distributor having first and second cutwaters. The housing has a first slot into which the first cutwater is inserted. The housing has a second slot, opposite from the first slot, into which the second cutwater is inserted.

[0008] Another aspect of the disclosure is a multistage centrifugal water pump that includes a housing having a water inlet for receiving water into the housing and a water outlet for expelling the water from the housing. The pump includes a shaft that rotates within the housing about an axis of rotation. The pump includes first and second impellers mounted to the shaft to rotate with the shaft to impel the water centrifugally in first and second stages, respectively. The pump further includes a distributor disposed between the first stage and the second stage, the distributor having first and second cutwaters, wherein the first cutwater is arranged opposite from the second cutwater for rotational balance. The housing has a first slot into which the first cutwater is fitted. The housing also has a second slot, opposite from the first slot, into which the second cutwater is fitted.

[0009] The foregoing presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an exhaustive overview of the invention. It is not intended to identify essential, key or critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later. Other aspects of the invention are described below in relation to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Further features and advantages of the present technology will become apparent from the following detailed description, taken in combination with the appended drawings, in which:

[0011] FIG. 1 depicts a multistage centrifugal water pump in accordance with an embodiment of the present invention.

[0012] FIG. 2 is a cross-sectional view of the multistage centrifugal water pump of FIG. 1. [0013] FIG. 3 depicts the two cutwaters inserted into respective slots in the housing.

[0014] FIG. 4 depicts a prior-art pump design that requires clamping pressure and threaded fasteners to secure the distributor.

[0015] It will be noted that throughout the appended drawings, like features are identified by like reference numerals.

DETAILED DESCRIPTION

[0016] FIG. 1 depicts a multistage centrifugal water pump in accordance with an embodiment of the present invention. The multistage centrifugal water pump (also referred to simply as the pump in this specification) is designated generally by reference numeral 10. The pump 10 has a housing 12. The housing 12 has a water inlet for receiving water into the housing and a water outlet 16 for expelling the water from the housing. The multistage centrifugal water pump may be driven by a gas engine, i.e. a two-cycle or four-cycle internal combustion engine having one or more cylinders. The engine may be started using any suitable ignition system, e.g. by pulling a manual recoil pull-cord or by a battery-powered electric starter. The pump and engine may be packaged together to constitute a portable water pump unit. This portable water pump unit is particularly useful for firefighting, especially fighting forest fires or brush fires in remote places where there are no fire hydrants and which are inaccessible to firetrucks. The pump may be used to draw water from a local water source such as a lake, pond, river or stream and to discharge the water from a hose to extinguish the fire. The pump may also be used in other water-pumping applications outside of the field of firefighting.

[0017] FIG. 2 is a cross-sectional view of the pump 10. In the embodiment depicted by way of example in FIG. 2, the pump includes a first impeller 18 that rotates within the housing 12 about an axis of rotation 20 to impel the water centrifugally to define a first stage 22 in which the water is pressurized. The pump depicted in FIG. 2 also includes a second impeller 24 that also rotates within the housing 12 about the axis of rotation 20 to impel the water centrifugally to define a second stage 26 in which the water is further pressurized. The pump 10 further includes a distributor 30 defining an inter-stage wall between the first impeller 18 of the first stage 22 and the second impeller 24 of the second stage 26. The distributor 30 has a first cutwater 32 and a second cutwater 34. As depicted by way of example in FIG. 2, the housing 12 of the pump 10 has a first slot 40 into which the first cutwater 32 is inserted. The housing 12 also has a second slot 42, opposite from the first slot 40, into which the second cutwater 34 is inserted. The cutwaters extend through the slots in the housing 12 to engage pockets or recesses in a rear flange 50, thereby securing the distributor from rotation. A clip 39 holds the flange 50 on axis in the housing.

[0018] In the embodiment of FIG. 2, the first and second cutwaters 32, 34 fit into the respective first and second slots 40, 42 to secure the distributor 30 against rotation that would be otherwise induced by the swirling water. The use of slots to receive the cutwaters eliminates the need for threaded fasteners to retain the distributor. Fasteners can become very difficult to unfasten, for example if corroded or damaged. Also, if the fasteners are unfastened and re-fastened repeatedly the heads of the fasteners may become stripped, making them very difficult to remove. This design also eliminates the need to axially clamp the distributor.

[0019] In one specific embodiment, as depicted in FIG. 3, the first cutwater 32 is angled 180 degrees opposite from the second cutwater 34 for rotational balance. The two cutwaters 32, 34 are offset by approximately 180° relative to each other. The two cutwaters balances the impeller in the radial direction by reducing the radial thrust on the shaft carrying the impellers.

[0020] In one embodiment, as depicted in FIG. 2, each of the first and second cutwaters 32, 34 has a cutwater leg 36. The cutwater leg 36, as depicted in FIG. 2, extends in a direction parallel to the axis of rotation of the first and second impellers. A forward end of the cutwater leg 36 fits into the housing. A rearward end 37 of the cutwater leg fits into the flange. The distributor is thus locked in place between the housing and the flange and thus cannot rotate relative to the housing.

[0021] As depicted in FIG. 3, the cutwaters 32, 34 fit respectively into the first and second slots 40, 42 in the housing 12.

[0022] As depicted in FIG. 3, the rearward portion 37 of the first and second cutwater legs also engages respectively first and second portions of a rear flange 50 that is secured to, or integral with, the housing 12 to inhibit rotation of the distributor 30 relative to the housing.

[0023] The first impeller impels the water into a first volute 60 that has a return path 62 to direct the water to the second impeller. The second impeller impels the water into a second volute 70. In one embodiment, the volutes are spiral-shaped portions of the housing that have an increasing cross-sectional area that has the effect of increasing the static pressure of the water.

[0024] In the specific embodiment shown in FIG. 2, the first and second cutwater legs are disposed radially outwardly of the second impeller. However, in other embodiments, the legs may be disposed elsewhere.

[0025] In the specific embodiment shown in FIG. 2, the first and second cutwater legs are disposed radially inwardly of the second volute.

[0026] In the specific embodiment shown in FIG. 2, the first and second cutwater legs are disposed radially inwardly of the second volute.

[0027] In the specific embodiment depicted in FIG. 1 , the water outlet 16 is orthogonal to the axis of rotation 20.

[0028] FIG. 3 shows that the novel design of this pump is still able to provide a very small gap G between the impeller and the housing. Maintaining this small gap G is important to preserve the efficiency of the pump. If this gap G becomes too large, the efficiency of the pump diminishes due to escape and recirculation.

[0029] In the particular exemplary embodiment of FIG. 2, the second impeller has a greater radius than the first impeller. In other variants, the impellers may have the same radius or the first impeller may have a radius greater than the second impeller.

[0030] In comparison with the prior-art pump design of FIG. 4, which is presented to contrast with, and elucidate, the present invention, the embodiments of the present invention do not need to forcefully clamp the distributor to preclude the distributor from rotating. In FIG. 4, threaded fasteners 80 are used to secure the distributor. As described above with respect to FIGS. 1-3, machined slots (or grooves) in the housing 12 are provided to receive the cutwaters. Clips may be used to retain the cutwaters in their respective slots (grooves). This novel design is less expensive than the prior art design shown in FIG. 4. Furthermore, the clips that retain the cutwaters are lighter than the studs/nuts that they replace. Providing cutwaters that fit into the slots/grooves in the housing enables this novel design. This avoids the need to provide the pump with vanes, which makes the housing much larger. Also, this avoids having to provide a large housing to impeller gap, which would render the pump very inefficient. FIG. 4 shows the distributor 30 with vanes 90 around the impeller 18. This makes the housing 12 more than 1” larger in diameter for this particular design but may increase the housing diameter by more than that amount for other pump designs.

[0031] As noted above, the water pump may be used for firefighting but also for any other water-pumping applications.

[0032] For the purposes of interpreting this specification, when referring to elements of various embodiments of the present invention, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including”, “having”, “entailing” and “involving”, and verb tense variants thereof, are intended to be inclusive and open-ended by which it is meant that there may be additional elements other than the listed elements.

[0033] This new technology has been described in terms of specific implementations and configurations which are intended to be exemplary only. Persons of ordinary skill in the art will appreciate that many obvious variations, refinements and modifications may be made without departing from the inventive concepts presented in this application. The scope of the exclusive right sought by the Applicant(s) is therefore intended to be limited solely by the appended claims.