Measuring and testing – Volume or rate of flow – By measuring thrust or drag forces
Patent
1990-01-23
1991-11-19
Goldstein, Herbert
Measuring and testing
Volume or rate of flow
By measuring thrust or drag forces
G01F 130
Patent
active
050656325
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a weighing device which is suitable for weighing fluent material, including liquids, slurries, powders, metal or the like.
BACKGROUND OF THE INVENTION
At the present time, the most commonly used flow line weighing material comprises an inclined sensing plate carried on the end of a pivoted arm which is coupled to a linear displacement transducer, and which moves in a lateral direction against a spring due to the horizontal component of force of the material impinging upon the sloping face. The linear displacement transducer (load cell) provides a read-out which is a function of the force against the plate.
There are some problems which are encountered however and which not only cause the product to be expensive but also to have accuracy which can be doubted in certain instances.
These difficulties include the lever arm effect, wherein an impingement against a portion of the inclined plate more removed from its support can give a different reading from an impingement on another portion which is closer to the support. Furthermore, the mounting is essentially an expensive arrangement requiring transfer of movement and force from the projecting arm which carries a plate to the inner arm within a cabinet which co-operates with the linear displacement transducer. The moving parts are critical and must be maintained in good condition so that there is no loss due to seized or partly seized parts. Because of the existence of moving parts reliability is not as high as with the arrangement to be described in this specification. The provision of a cabinet to one side of the plate interferes with available space as well as adding to cost.
DESCRIPTION OF THE PRIOR ART
One example of the prior art is shown in U.S. Pat. No. 4,440,029 which is directed to an impact flow meter, there being an inclined impact plate which in one embodiment is pivoted in a housing and connected to a force detector.
In another embodiment a vertical impact plate against which the material impinges at an angle, is supported by a strip spring, there being a piano wire connected to a lever contacting an impact force detector.
U.S. Pat. No. 3,530,714 discloses a target flow meter device, having a target in a fluid pipe, the target being connected to a force bar connected to a force measuring unit.
U.S. Pat. No. 4,063,456 shows a flow measuring unit for bulk material wherein the material impinges on a measuring box supported by springs which positions the box against a force measuring device.
Thus in all of the above there is a mechanism comprising levers, and/or springs or the like, for transmitting the force of reactions on the reaction plate or device to the force measuring unit. These are all subject to wear, and accumulation of material, dust and the like which can affect the ultimate reading of the force measuring device.
Small horizontal force components produce very small deflections and hence very small electrical outputs from transducer. Prior art uses expensive single transducer together with, in some instances, mechanical techniques for amplifying the horizontal force component, to overcome the problem of small forces. This results in high cost, susceptibility to mechanical problems and errors etc.
OBJECTS OF THE INVENTION
The principle object of the invention is to provide an impact flow meter of simple structure for measuring the mass flow rate of free-flowing particulate materials (powders, slurries, grains, metals, etc.) with an accuracy of better than .+-.0.5% of full range.
Other objects of the invention include:
1. To provide an impact flow meter that is free of mechanical errors associated with levers, pivots, etc.
2. To provide an impact flow meter that is unaffected by the location of material impact on the plate.
3. To provide an impact flow meter that incorporates within the framework of the device one or more inexpensive transducers for the measurement of the horizontal component of impact force.
4. To provide an impact flow meter whose accuracy is unaffected by the width of the impact plate
REFERENCES:
patent: 2805574 (1957-09-01), Jackson, Jr. et al.
patent: 3640135 (1972-02-01), Tomiyasu et al.
patent: 4063456 (1977-12-01), Jonkers
patent: 4069709 (1978-01-01), Volk et al.
patent: 4157661 (1979-01-01), Schindel
patent: 4440029 (1984-04-01), Tomiyasu et al.
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