GB2336877A

GB2336877A - Sealing in a driven-vane flowmeter

Info

Publication number: GB2336877A
Application number: GB9900294A
Authority: GB
Inventors: Thomas Haar
Original assignee: Alfons Haar Maschinenbau GmbH and Co KG
Current assignee: Alfons Haar Maschinenbau GmbH and Co KG
Priority date: 1998-02-20
Filing date: 1999-01-07
Publication date: 1999-11-03
Anticipated expiration: 2019-01-07
Also published as: SE9900509D0; FR2775342A1; SE9900509L; GB2336877B; FR2775342B1; DE29802976U1; GB9900294D0; SE519126C2

Abstract

An impeller 24a,24b for carrying diametrically extending blades (28, Fig 1) of a driven-vane flowmeter is metallically sealed axially and radially in a housing (10) by at least one raised portion 38, in the form of radial web which extends axially on the outer circumference of the impeller 24b and which seals against a wall (22) of the housing (10), and/or by at least one a radially extending portion 32,34 defined between adjacent sectors or segments of sunk surfaces (shaded dark in Fig 2) formed in an end face of the rotor 24a and which seals against an end lid of the housing (10). In use, any impurities carried in the fluid will move from between sealing surfaces of the impeller 24a,24b and the housing (10) and will collect in the gap regions between the sealing surfaces, minimising potential leakage through damaged sealing surfaces and consequential loss in flow measurement accuracy. Bores 32' extend axially through the impeller.

Description

i 2336877 A DRIVEN-VANE FLOWMITER The invention relates to a driven-vane

flowmeter according to the preamble of patent claim 1.

Driven-vane flowmeters are e.g. applied for metering delivered fluid quantities such as petrol, diesel oil or likewise. For this reason drivenvane flowmeters are often used in tank cars.

The basic construction of driven-vane flowmeters is such that an impeller is rotatably mounted in a housing. The impeller in diametrical radial recesses comprises blades which are mounted radially movable in the recesses, wherein diametrically opposite blades are rigidly coupled to one another. Iley are kept at a distance from one another so that in each case with their free end they bear against the facing annular circumferential inner control surface. Since the impeller is mounted eccentrically the blades with each revolution carry out a radial travel. The number of rotations of the impeller is as a result a measure for the volume flowing through, wherein on the jacketshaped housing there is arranged an inlet and outlet for the fluid to be measured. Usually the jacket-shaped housing part is closed by lids at both end faces.

For reasons of calibration technology it must be prevented that erroneous meterings arise. Above all it must be taken care that no medium directly wanders between the entry and exit since this leads to an erTor. Between the end faces of the impeller and the inner sides of the lid as well as between the circumference of the impeller and the part of the control surface in which a sealing between these parts between the entrmce and exit is effected, therefore minimal gaps are to be provided. For reasons of friction these gaps naturally cannot be made to be zero. In practice gaps are applied which are 100 pm or smaller.

With the known driven-vane flowmeters problems may arise due to dirt particles which are carried into the flowmeter. The smallest dirt particles of e.g. 50 gm and larger are rubbed between the described surfaces. Naturally a protective filter may not be kept indefinately fine, since otherwise with the applied vehicles in normal delivery cycles it would block too quickly. In particular steel chippings and particles see to it that the flowmeters block completely. It is known to equip such flowmeters with a very hard housing and with hard lids, e.g. of steel. By way of this however a high weight is obtained. Normally such driven-vane flowmeters are manufactured of an aluminium alloy. There is also the danger of corrosion if steel is used as a material. Corrosion is a further source of danger since rust particles may endanger the metering.

It is therefore the object of the invention to provide a driven-vane flowmeter which is less susceptible to dirt particles and at the same time is lighter than comparable flowmeters.

The object is achieved by the features of claim 1.

With the driven-vane flowmeter according to the invention a few regions which with the housing jacket or with the lids form a sealing gap, are formed by webs, and specifically on the circumference of the impeller andlor at the end faces. By way of this for the impeller in the housing a type of edge sealing is maintained which as has shown provides an adequate sealing without a loss in accuracy of the flowmeter. The remaining surfaces form much larger gaps, for example in the order of 1 mm. Hard dirt particles in these gap regions may no longer embed and accumulate into the material in the surfaces rotating against one another. A total blockage of the flowmeter is avoided in this way. In the remaining edges although hard dirt particles may form rings and over a period of time reduce the tightness to a certain extent they may not however embed and accumulate in the material, but automatically get into the larger fi-ee spaces between the webs. Therefore with the vane-driven flowmeters according to the invention an eating away in the measuring chamber is avoided. In spite of this it is possible to retain the anti- corrosion aluminium alloy for the manufacture of the housing and the impeller.

A ffirther advantage of the driven-vane irnpeller according to the invention lies in the fact that the accuracy may be achieved with much less adjusting work on assembly at the factory. The flowmeter is less sensitive.

One embodiment of the invention sees to it that the radial web in a section of the impeller circumference, which lags with respect to a radial recess, is formed at a certain distance to the recess. With respect to the end-face webs, according to one formation of the invention it is seen to that the webs are arranged on the forward side of the radial recess, preferably directly in front. There may also be provided two webs in each case between two recesses at the end face of the impeller, wherein the second web is arranged at a distance to the lagging side of the respective radial recess.

Preferably on the circumference as well as the end faces of the impeller there are provided webs. It is useful to arrange these such that radial and end-face webs in each case are aligned approximately radially to one another in order to form small flowthrough gaps which e.g. would be 1 mm.

The invention is hereinafter described in more detail by way of embodiment examples shown in the drawings.

Fig. 1 shows partly in a lateral view, partly in section a driven-vane flowmeter of a conventional design.

Fig. 2 shows an impeller for a driven-vane flowmeter according to Fig. L, in a design according to the invention.

Fig. 3 shows a further embodiment form of an impeller according to the invention.

The driven-vane flowmeter shown in Fig. 1 is of a conventional construction and therefore only important parts are dealt with. One recognises a housing part 10, which is partly sectioned. The housing jacket is closed at end faces lying opposite by a lid, wherein the lid facing the observer has been removed. One recognises further an entrance 12 in the housing jacket, through which the medium flows in the direction of the arrow 14. Above this there is located an exit 16 from which the medium flows out in the direction of arrow 18. In the housing jacket 10 there is formed a chamber 20, whose round walling 22 is manufactured according to a predetermined curve.

Eccentrically to the middle of the chamber 20 an impeller 24 is rotatably mounted by the housing lids. The impeller has four radial recesses 26 arranged at a circumferential distance of 90% in which blades are slidingly and sealingly accommodated. Respective diametrically opposite blades 28 are rigidly connected to one another via a rod 30. The distance of the blades 26 to one another and the shape of the walling 22 of the chamber are such that with a revolution of the impeller 24 the blades are sealingly in engagement with the walling 22, at the same time during the rotation of the impeller 24 are selectively driven out of the recess 26 or into this, as this is to be recognised in Fig. 1. The medium flowing in via the entrance 12 therefore sets the impeller 24 in rotation, wherein the number of rotations is a measure for the delivered volume. In order to obtain a precise as possible metering it must be ensured that "short circuits" by way of leakages are avoided. It is therefore known to form the end-face lid and the impeller such that there exists a minimal gap. The same concerns the gap between the impeller 24 and the walling 22 in the region between the entrance 12 and the exit 16. As has already been cited finther above, such narrow gaps however cause considerable problems with unpurified mediums. In the Figs 2 and 3 there are shown examples for impeller disks with which such problems are to be counteracted.

In Fig. 2 there is shown an impeller 24a which is equal to the construction of the impeller 24 according to Fig. 1, wherein however axial bores 32' are provided in each case between the recesses 26. Ile blades which sit in the recesses 26 are neither shown in Fig. 2 nor in Fig. 3.

One recognises that in each case between the recesses there are provided raised or sunk regions. The raised regions are white, whilst the sunk regions are marked dark. One recognises that a raised section (web) 32 extends approximately radially up to the bearing bore, and specifically in the running direction in front of the recess 26. A fin-ther radially running section 34 lies behind the recess 26 and behind a section 36 arranged sunk. Between the radial sections 32, 34 there in each case lies sectors or segments of sunk surfaces. From this it results that a metallic sealing between the nonshown lids and the impeller of the driven- vane flowmeter is only given in narrow or line-like regions. This however has the advantage that hard impurity substances which jam into the gap between the sections 32, 34 and the associated lid by way of rotation subsequently reach into the larger gap regions and by way of this do not do any damage.

The impeller 24b according to Fig. 3 is equal to that according to Fig. 2. It may be provided with raised and sunk sections as has been shown by way of Fig. 2, it may however also in the most surface sections form a narrow gap with the housing lids arranged at the end-face, as this is the case with the embodiment according to Fig. 1. Opposite the impeller, according to Fig. 2, there is the particularity that on the circumference of the runner 24b there are formed radially raised sections 38. They extend in each case at a distance to a radial recess 26 over a certain stretch, seen in the running direction of the impeller 24b. In the sections 38 there is located in each case a slight gap opposite the walling 22 of the housing jacket 10 (Fig. 1), whilst the remaining sections of the circumference of the impeller 24b have a relatively large distance thereto, e.g. 1 mm.

It is to be understood that the particularities of the impeller disks according to Fig. 2 and 3 may also be combined. It is then only essential that the raised sections 38 are arranged in a region on the circumference to which radially there is allocated a raised end-face section in order to prevent a "short circuit".

2

Claims

A driven-vane flowmeter with a housing, which comprises a housing jacket with an annularly closed inner control surface, with an entrance and exit in the housing jacket and with two lids connected to the housing casing at the end-face, and with an impeller which is mounted rotatably in the housing and which comprises diametrically opposite radial recesses for accommodating radially movable blades, wherein diametrically arranged blades are coupled to one another via a rod for the constant engagement of the free ends of the blades on the control surface and wherein the impeller is metallically sealed axially and radially in the housing, characterised in that the mechanical sealing of the impeller (24a, 24b) is only formed by at least one radial web (38) on the circumference of the impeller (24a, 24b) andlor by an approximately radially running raised section (32, 34) lying at the end face of the impeller (24a, 24b) between the radial recesses (26).
2. A driven-vane flowmeter according to claim 1, characterised in that the radial web in a section of the impeller circumference, which lags with respect to a radial recess, is formed at a certain distance to the recess.
3. A driven-vane flowmeter according to claim 1 or 2, characterised in that the webs (32) are arranged at the end face on the forward side of a radial recess (26) preferably directly in front.
4. A driven-vane flowmeter according to claim 3, characterised in that second endface webs (34) are arranged at a distance to the lagging side of the radial recess (26).
5. A driven-vane flowmeter according to one of the claims 1 to 4, characterised in that with radial and end-face webs (38; 32, 34) these in each case are aligned approximately radially to one another.
6. A driven-vane flowmeter according to one of the claims 1 to 5, characterised in that the remaining surface sections opposite the webs lie receded by about 1 mm or more.