FIELD OF THE INVENTION This invention relates to an impeller for a water meter and more particularly to impeller blades.

BACKGROUND OF THE INVENTION Multi-jet water meters are used to measure fluid flow e.g. water, includes a meter body having a cavity or opening interconnecting an inlet chamber and an outlet chamber. A flow measuring arrangement or system to measure and, optionally, record the fluid flow, e.g., water moving through the meter body, is mounted in the opening connecting the inlet chamber to the outlet chamber. The flow measuring arrangement includes, an impeller and a meter register. The impeller and the meter register each includes a magnet which interacts with one another to power the meter register. Essentially, during operation, water flows into the flow distribution chamber from the inlet end of the water meter. The impeller is rotatably mounted in the flow distribution chamber, and the water flowing into and through the flow distribution chamber rotates the impeller to power the meter register in order to record the fluid flow. The water moves from the flow distribution chamber into the outlet chamber and, thereafter, out of the water meter. A calibration screw arranged at the outlet chamber is used to control the amount of water passby to get calibration range. Existing impellers are not able to provide accurate readings, especially, when the fluid flow is low in the meter body. Further, applying unbalanced transverse loads on the impeller can result in premature side wear of the shaft on which the impeller rotates. Eventually, the side of the shaft has uneven wear resulting in random variations in the rotation of the impeller resulting in inaccurate readings.

Existing calibration screws do not provide desired calibrations range due to its shape. Minimal screw turn causes change in the calibration range. It is the intention of the present invention to provide the impeller with parabolic curved shaped blades at a tilted angle and the calibration screw that allows minimal fluid bypass for accurate readings.

SUMMARY OF THE INVENTION

The present invention provides a meter to measure fluid flow comprises: a meter body, having an inlet end, an outlet end and a chamber associated to the inlet end and outlet end; and, an impeller, located within the chamber having a body with a plurality of spaced blades extending from the body; the each blade of the impeller is curved in parabolic shape and the blades extends from the body of the impeller at a tilted angle, regulates the fluid flow in such a way that when the fluid hits at least one of the blade, the impeller rotates and the blades reduces friction to enable smooth flow of the fluid.

According to preferred embodiment, the impeller regulates the fluid flow in such a way that when the fluid hits at least one of the blade, the impeller rotates and the fluid flows in parabolic profile in a direction to form effortless flow of the fluid. According to further embodiment, the each blade comprises a high pressure surface which is in contact with the fluid entering into the flow distributing chamber and low pressure surface creates a cavity for the fluid to fill in.

According to preferred embodiment, the tilted angle of the blades is greater at tip than at root.

According to preferred embodiment, the blades require minimal torque to rotate the impeller. According to further embodiment, meter further includes a calibration screw to adjust opening at the outlet end and to control volume of the fluid flowing towards the outlet end. According to preferred embodiment, the tip of the calibration screw is in cone shape.

According to further embodiment, meter further includes a flow straightening strainer which straightens the fluid flow inside the meter body.

According to preferred embodiment, impeller is able to rotate at minimal flow rate of the fluid flow. According to further embodiment, edges of the blades are sharp edged. BRIEF DESCRIPTION OF DRAWINGS

These and other features, aspects, and advantages of the present invention will become better understood, when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

Fig. 1 illustrates a water meter, in accordance to an embodiment of the present invention;

Fig. 2 illustrates an impeller (a) side view of the impeller; (b) top view of the impeller; (c) bottom view of the impeller; (d) isometric view of the impeller; and, (e) internal view of the impeller; in accordance to an embodiment of the present invention;

Fig. 3 illustrates the fluid flow directions in the water meter (a) inlet and (b) outlet, in accordance to an embodiment of the present invention; and, Fig. 4 illustrates a graph plotted for intrinsic error (of Indication) of DN15 water meter using the proposed impeller and conventional impeller. DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1 with respect is a water meter (100) having a body, an inlet end (110), an outlet end (120), a flow distributing chamber (130), an impeller (140), a calibration screw (150) and a meter register assembly (160). The flow distributing chamber (130) is in between the inlet end (110) and the outlet end (120). The impeller (140) is positioned within the flow distributing chamber (130). The fluid flow measuring system or arrangement is mounted on top of the flow distributing chamber (130) between the inlet end (110) and outlet end (120). The fluid, flows through the inlet end (110), into the flow distributing chamber (130) and hits at least one of the blades (142) of the impeller (140). When the fluid comes in contact with the blades (142) of the impeller (140) or hits the blades (142), rotates the impeller (140). The impeller (140) rotates according to the speed of the fluid passing through. The blades (142) of the impeller (140) are curved in a parabolic shape comprises a high pressure surface (146) which is in contact with the fluid entering into the flow distributing chamber (130) and low pressure surface (145) creates a cavity for the fluid to fill in. Further, the design of the blades (142) reduces friction to enable smooth flow of the fluid. The movement of the fluid around the impeller (140) and through the flow distributing chamber (130) rotates the impeller (140). The impeller (140) further includes a magnet (143) and is magnetically coupled with a meter register (180). During the rotation of the impeller (140) magnetically drives the meter register (180) in the meter register assembly (160). The fluid moves out of the flow distributing chamber (130) and out of the outlet end (120) of the water meter (100). Essentially, in operation, fluid flows into the flow distributing chamber (130) from the inlet end (110) of the water meter (100). The impeller (140) is rotatably mounted in the flow distributing chamber (130), and the fluid flowing into and through the flow distributing chamber (130) rotates the impeller (140) to drive the meter register (180) in the meter registry assembly (160) to record fluid volume flowing through the flow distributing chamber (130). The fluid flows from the flow distributing chamber (130) into the outlet (120) end and, thereafter, out of the water meter (100). In an embodiment, the flow distributing chamber (130) includes a base having a plurality of spaced flow directional columns having one end, e.g., the lower end, secured to peripheral surface of the base and opposite other end secured to platform (131) to space the platform (131) from the base. In a non-limiting embodiment, to secure the flow directional columns in a fixed, spaced relationship to one another from the base. The flow directional members are mounted on upper surface of the platform (131) to form a plurality of flow directional exit passageways (133) for directing the fluid out of the flow distributing chamber (130) towards the outlet end (120) of the fluid meter (100) in a predetermined direction (shown in fig 3(a) and (b)). In further non-limiting embodiment of the invention, the exit passageways (133) directs the fluid out of the flow distributing chamber (130) in a counter clockwise direction. In this manner, the flow of fluid as it enters the flow distributing chamber (130) through the entry passageways (132) between the flow directional columns is in a counter clockwise direction, and the flow of fluid as it exits the flow distributing chamber (130) through the flow directional exit passageways (133) is in a counter clockwise direction. Referring to figs (3(a) and 3(b)) the passageways (132 and 133) are constructed on body of the flow distributing chamber (130) by spacing four generally a port or opening in slanted flow directional members on upper surface of the platform to form the exit passageways (133). While the entry passageways (132) is located on the bottom surface of the flow distributing chamber (130).

In another embodiment, the water meter (100) further includes a flow straightening strainer (170) arranged in the inlet end (110). The fluid entering into the flow distributing chamber (130) enters through the flow straightening strainer (170) causes the fluid to flow in multiple jets into the flow distributing chamber (130).

In yet another embodiment, the water meter (100) includes the calibration screw (150) which is positioned near the outlet end (120) of the water meter (100). The calibration screw (150) has a two ends (shown clearly in fig 3a). While one end of the calibration screw (150) is tail end which is in cone shape and other end is head portion. The head portion includes a hole plug (151). Further, the calibration screw (150) includes a cylindrical body with spiral threading's on it. By adjusting the calibration screw (150), enables to adjust opening hole at the outlet end (120). Thereby, controls the amount of the fluid flow to bypass through the outlet end (120). Thus, makes the water meter (100) performance within maximum permissible error. Further, allows minimal flow to bypass and thus can makes easy to get desired calibration range.

With reference to FIGS. 2 (a) to (e), illustrates the various views of the impeller (140). The impeller (140), comprises an elongated shaft (141) having plurality of spaced blades (142) extending from body of the shaft (141) at the tilted angle (as shown in figures 2(a) and 2(d)) and the blades (142) are curved in parabolic shape. The shaft (141) is a hollow cylindrical body having a closed end and the plurality of the equally spaced blades (142) extending therefrom. In the non-limiting embodiment, there are seven blades (142). The magnet (143) is mounted in upper end of the shaft (141) for driving the magnetic driver of the meter register (180). A pin shaft (144) is centrally mounted in the shaft (141) and is magnetically coupled to the meter register assembly (160) (as shown in figures 2 (a) to 2 (e)). The shaft (141) further, includes passageway (147) extending along the length of the shaft (141) for the fluid to bypass through it.

The blade (142) profile of the impeller (140) is stepped (lamella) with single step, in the non-limiting embodiment of the impeller (140) can be double step (as shown in 2(d)). The design of the blade (142) is in parabolic curve with tilted angle is attached to the body of the shaft (141) and the edges of the blades (142) are stepped with sharp edges. The blades (142) comprises of high pressure surface (146) which is in contact with the fluid entering into the flow distributing chamber (130) and low pressure surface (145) creates a cavity for the fluid to fill in. When the fluid hits the high pressure surface (146) of the blade (142), the fluid is drawn in causing the fluid to flow in parabolic profile and in circular upward motion to exit out of the flow distributing chamber (130) due to design of the blades (142). The low pressure surface (145) has the titled angle surface helps to reduce the friction during the rotation especially at low flow rate and enables smooth flow of the fluid. Thus, the blades (142) of the impeller (140) possess minimal friction rotation towards the fluid resistance and is able to measure the fluid flow accurately during low flow rate. The impeller (140) regulates the fluid flow in parabolic profile in a direction to form effortless flow of the fluid. The blades (142) attached at the tilted angle ensures that the fluid flow enters the flow distribution chamber (130) with a uniform axial velocity and reduced friction. The shaft (141) has a sleeve having a jewel bearing (148) at bottom of the impeller (140). One end of the shaft (141) is provided with the magnet (143) is magnetically coupled to meter register assembly (160) and another end having the jewel bearing (148) is mounted on the top of metal shaft of the flow distributing chamber (130), rotates the impeller (140) about a centrally disposed axis with minimal, if any, wobble (as shown in figure 2 (e)). The distance of bottom of the impeller (140) from the base of the flow distributing chamber (130) is not limited to the invention; however, the distance should be sufficient to allow for movement of the fluid there between and free rotation of the impeller (140). The impeller (140) with the blades (142) in parabolic curved is provided with improved sensitivity during the low flow rate of the fluid which is able to rotate and trigger the meter registry (180) to record the readings.

The impeller (140) can be made of any material, in the non-limiting embodiment of the impeller (140), the impeller (140) is a one-piece moulded plastic of light weight. The shaft (141) of the impeller (140) is a one piece structure to form the body of the impeller (140) and the blades (142) extending from it. Preferably, the plastic material used for the impeller (140) has a density less than or equal to the fluid it is to measure, i.e., less than fluid for the water meter application. Any addition or reduction in the weights or the selection of materials to obtain this relationship can be determined by one skilled in the art.

Referring to figure 4, illustrates graph (200) shows the Intrinsic Error (of indication) of DN15 water meter for the proposed impeller (140) and conventional impeller. Intrinsic error is referring to the difference of amount of the water measured by the water meter and the amount of the water has passed, i.e., if the amount of the water measured by the water meter is equal to the amount of water that has passed, the water meter measurement error is 0%. The water meters (100) using the proposed impeller (140) has capability of measuring at low flow rate and achieves better accuracy water meter class represented by R160. While, the R80 represents the curve for the conventional impellers, which are not able to measure the volume of the fluid flow with accuracy during low flow rate.