Measuring and testing – Volume or rate of flow – By measuring thrust or drag forces
Patent
1994-10-17
1996-03-05
Chilcot, Richard
Measuring and testing
Volume or rate of flow
By measuring thrust or drag forces
G01F 130
Patent
active
054957737
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an apparatus for weighing a continuous stream of granular or powdery material flowing freely under the influence of gravity.
BACKGROUND ART
An apparatus of the kind referred to above is disclosed in the international patent application WO 89/11082. This known apparatus comprises an inclined plane plate, on which the material passes slidingly, while the weight of the amount of material present on the plate at each instant is registered by the force it exerts against the plate. Thus, the weight of material being present on a known length of plate, in connection with a measured flow velocity, is utilized to determine the mass flow.
In addition to the requirement that this velocity measurement is to be carried out with the sufficient precision independently of the thickness of the layer of the flowing material (and the consequent differences in radius from the axis of the measuring drum), it is a prerequisite for this arrangement to function correctly, that the flow velocity on the whole plate is uniquely determined by the outlet velocity. This is normally not the case, as a coefficient of friction, that is smaller or greater than the tangent to the angle of inclination of the plate relative to the horizontal, will cause an acceleration or a deceleration respectively of the material, so that the mean velocity over the plate will be smaller or greater respectively than the outlet velocity as measured.
DISCLOSURE OF THE INVENTION
It is the object of the present invention to provide an apparatus of the kind initially referred to, with which it is possible to achieve a more accurate measurement of the mass flow independently of the various parameter variations reducing the accuracy of the previously known apparatus discussed above, and this object is achieved with an apparatus, which according to the present invention, the apparatus is attached to perform at least two of said measurements in substantial dependence on the distribution of weight on a basically rectilinear inclined plate, on which the material flows slidingly.
Thus, while the above-mentioned known weighing apparatus does not take into account the variations in the velocity of the material during the sliding movement on the plate, the weighing apparatus according to the present invention thus in fact exploits the variation in velocity from inlet to outlet caused by friction and inclination, as the invention is substantially based on measuring the distribution of the material on the plate in combination with either a measurement of the frictional force on the latter and/or the force required to deflect the stream of flowing material (such a measurement is known per se from several patent publications, such as U.S. Pat. No. 4,637,262, German patent specification No. 3,410,845 and German patent specification No. 3,541,872. Examples of exactly how it is possible to use the results of these measurements to produce an expression for the mass flow, which is independent of the unknown values for flow velocity and frictional resistance, will be explained below with reference to the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following detailed portion of the present specification, the present invention will be explained in more detail with reference to the drawings, in which,
FIG. 1 shows the basic principles of the present invention, and
FIGS. 2-5 show five different exemplary embodiments of an apparatus according to the present invention as envisaged for use in measuring mass flow of grain (cereals).
DESCRIPTION OF THE PREFERRED EMBODIMENT
For a sliding movement with friction on an inclined plate 1 being restricted against longitudinal movement and transversely supported in its "third points", i.e. the two points dividing the length L of the plate into three equally long parts L/3 as shown, it can be shown that the ratio A/B between the forces exerted in the upper and lower points of support 2 and 3 respectively equals the ratio v.sub.2 /v.sub.1 between the inlet and outlet velocities of th
REFERENCES:
patent: 4157661 (1979-06-01), Schindel
patent: 4637262 (1987-01-01), Vesa
patent: 5065632 (1991-11-01), Reuter
Chilcot Richard
Cimbria Unigrain Ltd. A/S
Patel Harshad
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