WO2000014491A1

WO2000014491A1 - Flow measuring device

Info

Publication number: WO2000014491A1
Application number: PCT/DK1999/000455
Authority: WO
Inventors: Jørgen Seindal WIWE; Jørgen SEERUP; Arne Markvart; Jan S. Harling
Original assignee: Danfoss A/S
Priority date: 1998-09-02
Filing date: 1999-08-30
Publication date: 2000-03-16
Also published as: AU5279699A; DE19839958C1

Abstract

A flow measuring device has a housing (1), an impeller wheel (19), an orifice (20), a speed measuring device and an evaluating device (31). Further, there is an orifice cleaning device with at least one cleaning element (40), which acts upon the orifice (20) by means of an operating device (37), thus loosening impurities, particularly inside the orifice. Thus, a high measuring accuracy can be maintained for a long period, even with small flows.

Description

Flow measuring device

The invention concerns a flow measuring device with a housing, an impeller wheel, an orifice directing a fluid jet on the impellers, a speed measuring device measuring the speed of the impeller wheel and an evaluating device determining the flow by means of the measuring.

Such flow measuring devices are commonly known as impeller wheel meters, particularly in connection with water consumption measuring, for example for domestic water counters .

The invention is based on the task of providing a flow measuring device of the kind mentioned in the introduction, which also works reliably with a small flow.

According to the invention, this task is solved by an orifice cleaning device with at least one cleaning element, which acts upon the orifice by means of an operating device, thus loosening dirt.

When only a small flow is measured, the dimensions of the impeller wheel and the orifice must be kept correspondingly small. Therefore, the orifice is easily blocked by calcification or other dirt particles. This blocking can be prevented by the orifice cleaning device. Thus, the measuring device maintains its original properties for a long time. A typical example of the need for measuring low flows is the detection of small leakages in a piping, the measuring range being, for example, between 1 and 25 1/h.

It is recommended that the cleaning element is provided with a pin, which is inserted in the orifice opening. Thus, the orifice opening is cleaned. Alternatively or additionally, it can be provided that the orifice is made of a flexible material and is deformed by the cleaning element. This deformation loosens and crushes the dirt particles, so that subsequently they can be flushed out.

In a preferred embodiment it is provided that the cleaning element is arranged on a carrier, which is axially dis- placeable by means of a pin led sealingly to the outside. Thus, the cleaning process can easily be started from the outside.

It is advantageous that the housing carries an element, which has an operating device for displacing the pin. This simplifies the cleaning process. The measuring device can also be placed in less easily accessible places.

Further, it is recommended that a control circuit is provided for time or impurification dependent switching of the operating device. Thus the cleaning process occurs automatically.

A simple construction involves that the operating device displaces a stop and that the carrier is loaded by a spring, by means of which the pin is held against the stop. In this way, the pin, and thus also the carrier of the cleaning element, follow the stop adjustable by operating motor.

Advantageously, it is provided that the speed measuring device scans the impellers optically, that a transparent separating wall is arranged between impeller wheel and speed measuring device, and that the side of the separat- ing wall facing the impeller wheel is provided with a cleaning device having at least one cleaning element, the cleaning element and the separating wall being displace- able in relation to each other by means of the operating device. Thus, an impurification, particularly a calcification, on the inside of the separating wall is removed. Therefore, the optical scanner can be operated with a minimum of energising current. This is particularly advantageous, when only battery supply is available for the optical scanning and the evaluation of the measuring results .

Further, it is advantageous that the impeller wheel is arranged in an auxiliary flow path, which bypasses a blocked main flow path when the flow is low. This construction is recommended for a leakage detector, which is able to detect a small leakage, when the main flow path is closed, and also a large leakage, when the main flow path is open.

An additional advantage is that the main flow path has a lifting valve and the impeller wheel is arranged in the movable valve element of the lifting valve. Complicated channels in the housing can be avoided, when the impeller wheel is arranged in the movable valve element. This gives a very simple construction.

In the following the invention is described on the basis of preferred embodiments on the basis of the drawings, showing:

Fig. 1 a longitudinal section through a flow measuring device equipped according to the invention

Fig. 2. a schematic view of the range of the speed measuring device

The flow measuring device in Fig. 1 serves as leakage detector. It has a housing 1 with an inlet connection 2 and an outlet connection 3 for insertion in a pipe. An insert 6 is mounted in the housing 1 under insertion of two sealing rings 4 and 5, the insert having an upper wall

7 for limiting an inlet chamber 8 and a lower wall 9 for separation an outlet chamber 10 from the inlet chamber 8 and for creating the valve seat 11 of a lifting valve 12.

The valve seat 11 is formed by an annular groove 13, which is connected with the inlet chamber 8 via the bores 14.

The closure element is a movable valve element 15 provided with a sealing ring 16, the valve element 15 being loadable against the flow direction by means of a first, weaker closing spring 17. A main flow path 18 comprising the bores 14, the annular groove 17 and the lifting valve 12 therefore extends between the inlet chamber 8 and the outlet chamber 10. When the sealing ring 16 is lifted off from the valve seat 11, fluid can flow both radially outwards and radially inwards. Therefore, also in connection with large flow quantities, only a small pressure drop occurs.

An impeller wheel 19 is supported in the movable valve element 15. It is supplied with fluid via an orifice 20 arranged on the insert 6, which fluid can flow off via a channel 21 in the movable valve element 15. Between the inlet chamber 8 and the outlet chamber 10 an auxiliary flow path 22 thus occurs, which comprises the orifice 20, the impeller wheel 19 and the channel 21.

The impeller wheel 19 is part of a flowmeter 23, which has an electro-optically working speed measuring device 24. This device comprises an electro-optical transmitter 25, for example a light emission diode, and on the opposite side of the impeller wheel 19 an electro-optical receiver 26, for example a photo cell, a photo transistor or a photo resistor. Transmitter 25 and receiver 26 are separated from the fluid carrying chamber by means of trans- parent separating walls 27 and 28, and thus safely placed.

As shown, the separating walls 27 and 28 can be made in one piece with the insert 6, provided that the whole insert is made of a transparent material. The impellers 29 of the impeller wheel 19, which extend radially maintaining their thickness, temporarily interrupt the light ray transmitted by the transmitter 25, which results in a pulse shaped scanning signal, which is led to the inlet 30 of an evaluating circuit 31. The impeller wheel 19 can have very small dimensions, for example, a diameter of 15 mm and a width of 1 mm.

In the position shown, a carrier 32 projects through openings in the movable valve element 19 by means of a counter flange 33, a second closing spring 34 being made inactive. The carrier 32 bears with an end stop 35 on a pin 36 extending sealingly outwards, which pin again is pressed against an operating device in the form of a motor by the force of the closing spring 34. A displacement of the adjusting element in the outwards direction brings the carrier 32 to a second position, in which not only the first closing spring 17, but also the stronger second closing spring 34 acts upon the movable valve element 15, so that the lifting valve 12 closes.

Further, two cleaning elements 38 and 39 are connected with the carrier 32, which elements bear flexibly with a cleaning edge on the separating walls 27 and 28, respectively, and, on displacement of the carrier 32 cleans the working area of the optic scanning device 24 of impurities, for example calcification.

Additionally, the carrier 32 comprises a cleaning element 40, which, on an upwards movement of the carrier 32, inserts a pin in the orifice opening 41 of the orifice 20, thus cleaning this opening of dirt particles, calcifica- tion etc. The cleaning element 40 also closes the orifice

20, so that the auxiliary flow path 22 is closed. The orifice 20 is made of a resilient material, and is additionally deformed by the cleaning element 40. Also this process will loosen any dirt particles stuck in or on the orifice. To improve the closing and cleaning effect of the cleaning element 40, a third spring 42 is provided, which acts upon the carrier 32, pressing it upwards as far as it is permitted by the operating device 37.

As suggested, the evaluating circuit 31 and the operating device 37 can be arranged in an element 43 placed direct on the housing 1, if required together with a battery and other components .

The following operating conditions are possible.

With a very small flow, the lifting valve is kept closed by the first closing spring 17. The total volume passes through the auxiliary flow path 22. The frequency of the pulses reported by the receiver are converted to the flow in the evaluating circuit 31.

With larger flows, the main flow path 18 is opened, as the pressure difference occurring at the lifting valve 12 exceeds the power of the closing spring 17. The opening lift obtained this way is a measure for the flow quantity flowing through the main flow path 18. The lift and thus also the flow are calculated in the evaluating circuit 31 by means of an evaluation of the pulse-pause relation, and added to the flow in the auxiliary flow path 22.

If an error should occur, the operating motor 37 is controlled so that the pin 36 travels upwards under the influence of the springs 34 and 42, which also causes the carrier 32 to be displaced upwards. Firstly, this causes that the main flow path 18 is closed due to the closing of the lifting valve 12, and that the auxiliary flow path 22 is also closed through a covering of the orifice opening

41 by the cleaning element 40. Further, a cleaning effect occurs at the orifice 20, as the pin of the cleaning element 40 is inserted in the orifice opening 41 and at the same time the cleaning element deforms the resilient material of the orifice. Besides, the cleaning elements 38 and 39 slide across the separating walls 27 and 28, so that also the measuring area is cleaned.

The displacements described above do not necessarily only occur in connection with errors, they can also be effected at random, for example in dependence of impurification or time, meaning that perfect measuring results are obtained for long periods.

The three springs 17, 34 and 42 are supported by a yoke 44, which engages arms 45 carried by the insert 6. The components can be assembled outside the housing and then be introduced in the housing 1 as one unit, and - if required - also be removed again as one unit.

The embodiment shown can be modified in many respects, without abandoning the basic idea of the invention. For example, the operating device can also be operated manually. The auxiliary flow path can extend through the housing. The measuring of the impeller wheel speed can be made differently, for example magnetically. In spite of the fact that the embodiment described concerns the flow of water, it is obvious that equal or similar embodiments can also be used for other fluids or gases.

Claims

Patent Claims

1. Flow measuring device with a housing, an impeller wheel, an orifice directing a fluid jet on the impellers, a speed measuring device measuring the speed of the impeller wheel and an evaluating device determining the flow by means of the measuring, characterised in an orifice cleaning device with at least one clean- ing element (40) , which acts upon the orifice (20) by means of an operating device (37), thus loosening dirt.

2. Flow measuring device according to claim 1, character- ised in that the cleaning element (40) is provided with a pin, which is inserted in the orifice opening (41) .

3. Flow measuring device according to claim 1 or 2, characterised in that the orifice (20) is made of a flexible material and is deformed by the cleaning element (40) .

4. Flow measuring device according to one of the claims 1 to 3, characterised in that the cleaning element (40) is arranged on a carrier (32), which is axially dis- placeable by means of a pin (36) led sealingly to the outside.

5. Flow measuring device according to claim 4, characterised in that the housing (1) carries an element (43), which has an operating device (37) for displacing the pin (36) .

6. Flow measuring device according to claim 5, characterised in that a control circuit (31) is provided for time or impurification dependent switching of the operating device (37) .

7. Flow measuring device according to claim 5 or 6, characterised in that the operating device (37) adjusts a stop and that the carrier (32) is loaded by a spring (42), by means of which the pin (36) is held against the stop.

8. Flow measuring device according to one of the claims 1 to 7, characterised in that the speed measuring device (24) scans the impellers (29) optically, that a trans- parent separating wall (27, 28) is arranged between impeller wheel (19) and speed measuring device (24), and that the side of the separating wall (27,28) facing the impeller wheel (19) is provided with a cleaning device having at least one cleaning element (38, 39) , the cleaning element (38, 39) and the separating wall (27, 28) being displaceable in relation to each other by means of the operating device (37) .

9. Flow measuring device according to one of the claims 1 to 8, characterised in that the impeller wheel (19) is arranged in an auxiliary flow path (22), which bypasses a blocked main flow path (18) when the flow is low.

10. Flow measuring device according to claim 9, characterised in that the main flow path (18) has a lifting valve (12) and the impeller wheel (19) is arranged in the movable valve element (15) of the lifting valve (12) .