GB2234824A

GB2234824A - "Turbine of flowmeter"

Info

Publication number: GB2234824A
Application number: GB8917805A
Authority: GB
Inventors: Hajime Onoda; Yoshiji Matsuda
Original assignee: Kimmon Manufacturing Co Ltd
Current assignee: Kimmon Manufacturing Co Ltd
Priority date: 1989-08-03
Filing date: 1989-08-03
Publication date: 1991-02-13
Anticipated expiration: 2009-08-03
Also published as: GB2234824B; GB8917805D0

Abstract

The turbine (10) of a flowmeter comprises a hub (11) and blades (12) made of a mixture of magnetic powder and resin. The particles of the magnetic powder contained in the blades (12) are magnetized in the radial directions. <IMAGE>

Description

"TURBINE OF FLOWMETER" This invention relates to a turbine of a flowmeter, and particularly to a turbine having a permanent magnet in each of the blades, Among the various types of flowmeters widely known is a turbine flowmeter. Most turbine flowmeters comprise a turbine, a magnetic sensor, and a signal processing means. The turbine is located in a fluid passage and rotates at a speed corresponding to the rate at which fluid flows through the passage. It has blades and permanent magnets, each embedded in one blade. The magnetic sensor is arranged close to, not in contact, with the turbine. The output of the sensor changes every time each permanent magnet passes by the sensor due to the magnetic flux generated from the magnet. The signal processing means calculates the flow rate of the fluid or the total amount of the fluid from the output of the magnetic sensor.

The turbine described above is made of plastics such as ABS resin by means of injection molding. During or after the injection molding, a permanent magnet is buried in the top portion of each of the blades.

The turbine thus formed has the following drawbacks. Since it is difficult to obtain a plurality of permanent magnets of equal weight, and to bury the permanent magnets in the same position on all of the blades, the turbine must be put to a rotation balance test and a troublesome imbalance correction. If the turbine is operated before it is modified and made sufficiently balanced, it will generate a moment of inertia, inevitably reducing the accuracy of the flowmeter, particularly when too little fluid or too much fluid flows though the fluid passage. Moreover, the shaft and the bearing of the turbine wear locally, and their lives are extremely short. In addition, when the blades are increased in number in order to improve the accuracy of the flowmeter, more time is required to bury the magnets in the blades, and the turbine is likely to be more imbalanced.

Accordingly, an object of the present invention is to provide a flowmeter turbine which is easy to manufacture and accurately measures volume of a fluid, not requiring a rotation balance test or an imbalance correcting process.

To achieve this object, the flowmeter turbine according to this invention rotates at a speed corresponding to the speed at which fluid flows though the passage in which the turbine is located, and have a hub and blades are integrally formed of a mixture of magnetic powder and resin, the particles of the magnetic powder being magnetized in radial directions.

This invention will be explained in the following description, taken in connection with the accsmpanying drawings, in which: Fig. 1 is a sectional view of a flowmeter in which a turbine according to an embodiment of the present invention is incorporated; and Fig. 2 is a sectional view in the axial direction of the turbine shown in Fig. 1.

In Fig. 1, numeral 1 denotes a fluid passage through which a fluid to be measured in the direction shown by thick arrows. In passage 1, auxiliary cylinder 2 made of non-magnetic material such as stainless steel is connected tightly between flanges 3a and 3b. Within auxiliary cylinder 2, supporting members 4a and 4b, which are formed so as not to interfere with flow of the fluid, are fixed to the junctions between auxiliary cylinder 2 and each of flanges 3a and 3b by means of the faucet junction and the like. Supporting members 4a and 4b rotatably support shaft 6 via bearings 5a and 5b, on the center of the axis of auxiliary cylinder 2. Turbine 10 is fixed to shaft 6.

Turbine 10 consists of cylindrical hub 11 and six blades 12 protruding therefrom with an angle of 60 between each blade. Each of blades 12 has a three dimensional configuration so that it can receive a constant circumferential force by the fluid flowing through auxiliary cylinder 2. The diameter of a circle including the tips of blades 12 on its circumference is slightly smaller than that of auxiliary cylinder 2.

Hub 11 has through hole 13 formed in its center in the axial direction, through which the above-mentioned shaft 6 is inserted. Turbine 10 is fixed to shaft 6 by nut 14a and 14b.

Turbine 10 will now be further described in detail.

Turbine 10 is formed of hub 11 and blades 12 integrally by means of injection molding, which are made of a mixture of resin and magnetic powder. In this embodiment, the mixture contains polyamide resin of 50wt.% and barium ferrite (BaO 6F203) powder of 50wt.%.

After the injection molding has been completed, magnetic fields are formed in blades 12 so that the lines of magnetic force extend radially from through hole 13.

Each of blades 12 is magnetized by the magnetic field, thereby functioning as a permanent magnet, the root thereof, for example, being the S pole, and the top thereof being the N pole, as shown in Fig. 2.

On the outside of auxiliary cylinder 2, recess 15 having a predetermined depth is formed at the position where each of the tips of blade 12 approaches closest to cylinder 2. In recess 15 provided magnetic sensor 16, in which magnetic resistance element is incorporated.

The resistance of the magnetic resistance element changes in response to the magnetic flux generated from the N poles of blades 12, every time each of blades 12 passes by magnetic sensor 16. An output of magnetic sensor 16 is supplied to signal processing device 18 via output terminals 17a and 17b.

In signal processing device 18, whenever the output supplied from magnetic sensor 16 changes, a signal processing circuit converts a change into a pulse signal, which is counted by means of the counter. The total volume of the fluid is calculated from the count, and displayed on display 19. In this embodiment, the amount A (m3) of the fluid which flows through the passage while turbine 10 rotates by 60 , i.e., a flow per pulse, is given beforehand, and a total flow is calculated by multiplying amount A by count N. Thus, the total flow can be measured based on the pulse rate, which changes in accordance with the speed of the fluid flowing through passage 1.

As has been described above, the turbine of the flowmeter according to the present invention is formed integrally hub 11 and blades 12, made of magnetic powder and resin, and the magnetic powder is magnetized in radial directions of the turbine. Because of this structure, it is unnecessary to bury permanent magnets in the blades during the molding process. In addition, the rotation balance is not adversely affected through the magnetizing process. Hence, if the mold, which is used in the molding process, is made accurately, a good-balanced turbine can be produced. To sum up, the turbine of the present invention can be manufactured with easy, not requiring a rotation balance test or a imbalance correcting process.

The present invention is not limited to the embodiment described above. In the above-described embodiment, the turbine is made of a mixture of polyamide resin of 50wt.% and barium ferrite (BaO 6F203) powder of 50wt.% by means of injection molding. However, it may be made of a mixture of polyamide resin of 50wt.% and rare earth cobalt (e.g., samarium cobalt) of 50wt.% by means of injection molding. In the magnetic sensor, an induction coil can be used as a magnetic detecting element. Further, the turbine can be variously modified within a range of the gist of the present invention.

Claims

Claims:

1. A turbine of a flowmeter rotatably provided in the passage of a fluid, rotating at a speed corresponding to the flow speed of the fluid and having permanent magnets in blades, wherein a hub and the blades are formed integrally of a mixture of magnetic powder and resin, and the particles of the magnetic powder in the blades is magnetized in the radial directions.

2. The turbine of a flowmeter according to claim 1, wherein the mixture consists of polyamide and one of ferrite magnetic powder and rare earth cobalt magnetic powder in the ratio of 1:1 by weight.

3. The turbine of a flowmeter according to claim 1, wherein said hub is cylindrical.

4. A turbine of flowmeter, substantially as hereinbefore described with reference to the accompanying drawings.