Fluid meter.

p0001The invention relates to fluid meter, in particular water meters for vertical installation for the single beam and multibeam principle according to the preamble of claim 1.

p0002Fluid meter, in particular water meter, according to the single-jet or multi-jet principle, in which an impeller rotates in a generally cylindrical measuring chamber, are in millions of units in use worldwide. They are calibrated and certified. The calibration and certification is valid for a certain period, with water meters for example in Germany 6 years. During the calibration period of the liquid counter must show the actual consumption within certain limits of error.

p0003The approval, verification or certification according to specific metrological classes. While at high flow rates have the metrological classes A, B and C the same error limits, the metrological class A at low flow rates between Q_release and Q_min the lowest requirements, the metrological class C, however, the highest standards of accuracy and measurement sensitivity. It is understood that the utilities, such as drinking water supplying waterworks, the use of liquid counters the metrological class C aspire to even the smallest flows, such as dripping faucets, to be able to detect yet.

p0004The impellers of single beam and multibeam counters have a shaft which is supported by each of a bearing at both ends in the so-called measuring cup. These bearings consist of a conical bearing tip, for example of steel, and a likewise conical bearing shell, for example, of sapphire. The shaft is seated with an albeit small clearance between the fixed bearing points.

p0005In liquid counters a distinction between dry running, part dry runners and wet rotor. When dry rotor is directly mounted on the impeller shaft, a permanent magnet, which transmits the rotation of the impeller by a pressure-resistant wall through to a second magnet, which in turn is coupled to the counter. By the magnetic field caused both axial and radial friction moments. Glanded can therefore generally in a horizontal installation position, ie with a vertical shaft of the impeller, the only class B and in vertical position, ie with a horizontal shaft of the impeller, only the Class A meet.

p0006When Teiltrocken- and wet rotor, however, the load of the impeller bearing is considerably lower. Depending on whether the impeller specifically heavier or lighter than the liquid to be measured, it undergoes an output or boost. If the fluid meter installed horizontally, is charged either the lower or the upper bearing at low flow rates. Due to the conical shape of the bearing elements, the bearings, bearing friction and friction centered minimal and the impeller rotates even at low flow rates. Impeller with horizontal mounting therefore meet in many cases, the metrological class C.

p0007The DE-U 81 03 132 shows a particular of heating oil and fuels liquid counter with a flat-cylindrical Meßrotor vertical shaft. Rotation of Meßrotors contactless sensing by a light barrier. To operate the Meßrotor without shaft and shaft bearings, it is made from a material whose Artgewicht which the liquid to be measured as close as possible. Any differences are compensated by buoyancy chambers or additional weights.

p0008A disadvantage of this construction is that additional electrical energy is required for operation of the light barrier and the evaluation of the signals. A transfer of the known from DE-U 81 03 132 principle on commercial domestic water meter, in which the speed of the impeller is reduced via a gear train and stored in a mechanical roller counter is not possible.

p0009Considering liquid counter with vertical installation, ie, it is moved with a horizontally positioned impeller through the resulting lift or downward drift of the impeller in the measuring liquid, the central axis of the impeller with respect to the central axis of the fixed bearing members. It arises as to both camps friction torque which not only curbs the rotation of the impeller at low flow rates, but also to an increased radial wear specially leads the pivot points, which in turn results in an increase of friction.

p0010A first consequence of the described is that a liquid counter with horizontal installation meets the metrological class C and vertical mounting at best meets the metrological class B. A second consequence is a reduction in function of time.

p0011Although in the previously mentioned DE-U 81 03 132 these problems are not addressed, it will be understood that there proposed for other purposes approximation of the specific gravities of measuring liquid and impeller triggered by lift or downward drift of the impeller in the measuring liquid additional friction moments disappear , A liquid counter with such impeller would have to start up even at very low flow rates in accordance with the metrological class C. Surprisingly, however, this is not so in most cases.

p0012The present invention is therefore the object of developing fluid meter of the aforementioned kind such that it specially easy to start at low flow rates and view the fuel with the highest accuracy, according to the metrological class C, regardless of whether the installation horizontal, vertical or done otherwise.

p0013This object is achieved by a generic impeller having the features according to the characterizing of claim 1.

p0014The present invention is based on the knowledge that, in spite of a balance between the specific gravities of the impeller and the measuring liquid, the increased friction moments so do not disappear in the camps of the impeller, because especially due to the structural conditions the center of engaging the impeller lift forces usually not with the center of all acting on the impeller driving forces coincide. This suffers the one end of the impeller a lift, the other end of a drive, so that the movable bearing elements are restored relative to the fixed bearing elements and caused by buoyancy and driven frictional torque preventing the slight tarnishing of the impeller. However, this is prevented by the invention.

p0015For an explanation should here be noted that the focusing point of the impeller is defined at which coincide the centers of mutually canceling buoyancy forces and downforce.

p0016In a wet rotor or a part Glanded the wheels of the counter not only run the impeller but also the wheels of the reduction gear, optionally in the measuring liquid and will be led by two bearings. Approximation of the specific gravities of the specific gravity of measuring liquid and transfer the center of gravity in the middle between the two camps - - According to a preferred embodiment of the invention that are applied to the impeller measures to further reduce the friction moments in the camps also applied. Thanks to these measures the sum of all Lagerreibmomente is minimal and the measurement sensitivity and accuracy are maximized as the function of time.

p0017The inventive principle can be realized with various technical measures that are generally known in part for a long time without its importance had been recognized for the solution of the problem as long known.

p0018According to a first aspect of the invention are impeller, reducing gear or counter of materials whose specific weights correspond to the measuring liquid.

p0019Alternatively or in combination therewith can also at least one lift-increasing cavity be provided. This allows the weight of the bearing elements, the z. B. made of metal, hard plastics or semi-precious stones are made, can be compensated. Furthermore, these measures are intended to compensate for asymmetrical distributions of material that can be caused by external circumstances such that the focus comes to rest exactly in the middle between the two camps.

p0020According to a further embodiment of the invention the at least one output or the lift raising additive body is provided. Type and size of the additional body is determined by first, the resulting lift or downward drift of the impeller, the wheels of the reduction gear and the counter are determined. After the thus-determined additional body is mounted, it must be positioned such that the resulting center of gravity comes to lie exactly in the middle between the bearings. For this purpose, the additional body is displaced in accordance with an advantageous development of the invention to the longitudinal axis of the shaft.

p0021It is understood that in order to avoid imbalances of the impeller any voids and auxiliary members must be designed rotationally symmetrical.

p0022Reference to the drawing, the invention will be explained in the form of an embodiment. Show it<dl id="dl0001"><dt>Fig. 1</dt><dd>schematically and in a partial section an impeller in a liquid counter with vertical installation and</dd><dt>FIG. 2</dt><dd>a longitudinal section through a fluid meter of wet rotor-type.</dd></dl>

p0023In Fig. 1 shows an impeller 10 with an example cylindrical impeller 11, are evenly distributed on the wing pallets 12th The wings pallets 12 are acted upon tangentially from the measured flow of liquid, whereby the impeller 10 is rotated.

p0024At one end of the shaft 11 can be seen a journal 13 'with a conical tip which is guided in a fixed bearing bushing 13 with a conical recess. The other end of the impeller shaft 11 has an inner bore in which a bearing bushing 14 'is positioned with conical depressions. As fixed bearing element is a journal 14 is provided with a conical tip.

p0025Because of the structural conditions of a part of the impeller shaft 11 is considerably longer than the other part. He also carries a pinion 31, which meshes with the reduction gear. Such impeller thus represents a completely unbalanced structure.

p0026In the drawings of 10 it was assumed that the left end of the impeller 10 easily, the right end of the same on the other hand is heavier than the liquid to be measured, so that the left end a lift, the right end undergoes a stripping and the central axis 8 of the impeller obliquely to the central axis 9 of the stationary bearing elements 13, 14 provides. As a result, the pivot pins 13 ', 14 and the associated bearing sockets 13, 14 respectively contact eccentrically. It caused friction forces corresponding to the respective buoyancy or output power, multiplied by the coefficient of friction of the respective material pairing, and as a result of axis displacement and a corresponding braking torque.

p0027Fig. Figure 1 also shows constructive ways to remove the brake torque.

p0028The first, in the drawing, however, can not be displayed option is to select a plastic material with appropriate specific gravity. For water meters, the use of polypropylene is recommended, whose specific court is slightly smaller than that of water, so that for example the weight of the bearing elements 13 ', 14' offset.

p0029The second possibility is the installation of a closed cavity 41, which increases lift.

p0030A third possibility is the use of an additional member 42, which may consist of a lift or the output-increasing material, depending on requirements. In connection with larger cavities 41 normally propose the use of additional bodies that support the output.

p0031Fourth option is to use an additional weight 40, here for example in a closed cavity 41st

p0032In order to eliminate now the inclined position shown in the drawing of the impeller 11, additional weight 40 or additional body 42 along the impeller shaft 11 are shifted so far to the center of lift and downforce coincident gravity and the axis 8 of the impeller 11 exactly with the axis 9 of the fixed bearing members 13, 14 coincide. This disappearing all the forces caused by lift or downforce on the bearings 13, 13 '; 14, 14 'and the corresponding friction torques.

p0033It is understood that the same principles can be applied to the wheels of the reduction gear and the counter itself, so that even when these friction torques generated by lift or downward drift disappear.

p0034FIG. 2 shows a section through a single-jet domestic water meters with vertical installation, ie with a horizontally positioned impeller shaft 11. The extended part of the impeller shaft 11 projects into a Zählwerkskammer 30 and the pinion 31 meshes with the gears 32, 33, 34 of the reduction, the turn a roller-35 drive. Also the shafts of the gear wheels 32, 33, 34 and the counter 35 are each guided in bearings. Are their specific weights made equal to that of the liquid to be measured and also adjusted their priorities to the center between the two camps, disappearing even there the braking torques.

p0035Such measures are impeller liquid counters in any position, whether standardized or not standardized, respond at minimal flow rates and meet the highest accuracy of flow measurement according to the metrological class C, whereby in the medium and large flow rates no differences or even disadvantages compared with conventional solutions result.