Weighing scales – Plural distinct load holders with common evaluator – Load comparing type
Patent
1989-07-10
1991-09-24
Miller, Jr., George H.
Weighing scales
Plural distinct load holders with common evaluator
Load comparing type
177 2514, 177185, G01G 1900, G01G 1940, G01G 2310
Patent
active
050506935
DESCRIPTION:
BRIEF SUMMARY
The present invention refers to a balance for measurement of true mass, in which the weight of the material being weighed is compared with the weight of a reference mass. The balance must be calibrated only by the manufacturer and without recalibration correctly determines the mass of the material being weighed both in inclined position as well as with gravitational acceleration, g, deviating from the normal value and in the presence of vertical accelerations. Depending on the conditions, both the angular deviation and vertical acceleration can represent large fractions of the gravitational acceleration g.
The combined influence of the three mentioned values henceforth will be called effective local acceleration.
A dynamometer primarily measures the mass of the material being weighed. With given mass, this is dependent on the local gravitational acceleration g: therefore
Additional dynamic forces occur if the dynamometer is mounted on an unsteady, however horizontal, base. The force determined is then: stable base and with normal value of g, consequently under calibrated conditions for determination of the mass of the material being weighed. When both angular deviation and unsteadiness of the base must be compensated, the mass determination has to be accomplished by comparison with a reference mass. This procedure in the past was accomplished with the old--purely mechanical--Kramer balance, for example of the Beranger type. Modern loading balances and automatic scales in packaging lines are basically calibrated at the use site provided that they are based on a single force measurement. Thus, the local gravitational acceleration is taken into account and random errors in the leveling element are also considered in the calibration. In balances with reference mass--such as those described for example in Swiss Patent 492,961--allowances can be made for angular deviations of more than 5% slope without error. Balances with reference mass, such as those described for example in the cited patent, theoretically are completely insensitive to leveling errors, however in practice are insensitive only up to a designated, small limit angle. Both the weight forces of the working load and that of the reference mass are proportional to the effective local acceleration. However, this applies strictly only when elastic initial loads do not occur as will be shown below in further detail.
In contrast to this, the known measures fail when an on-site recalibration and correct leveling absolutely must be foregone. This is particularly the case when, for example, the packaging lines must be installed on a ship where a frozen fish catch will be packaged during ocean transport or for permanently located industrial packaging lines which create a dynamically unstable environment for the balance. The additional dynamic loads occurring in this case easily can amount to and exceed 10% of the local gravitational acceleration.
The goal to be achieved by the present invention is the creation of a balance which will be calibrated only one time by the manufacturer and without needing to be recalibrated will determine the correct mass of the material being weighed during operation under relatively high, additional dynamic load and with unknown angular deviations.
The achievement of the stated goal has the characteristics cited in patent claim 12 with respect to the process and the characteristics of patent claim 1 with respect to the apparatus. The process according to the invention and the apparatus according to the invention are explained in more detail by means of the attached drawing.
There are shown:
FIG. 1: a schematic representation of the construction of the balance according to the invention,
FIG. 2: a side view of a balance according to the invention,
FIG. 3: the model example of FIG. 2 from the opposite side,
FIG. 4A,B: a second model example of a part of the balance according to the invention,
FIG. 5A,B: a third model example of a part of the balance according to the invention,
FIG. 6A: a schematic representation of the computer.
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REFERENCES:
patent: 3494437 (1970-02-01), Fathauer
patent: 4212361 (1980-07-01), Stocker
patent: 4258811 (1981-03-01), Franzon et al.
patent: 4396080 (1983-08-01), Dee
patent: 4624331 (1986-11-01), Naito
Gallo Mario
Wirth Johannes
Miller Jr. George H.
Wirth Gallo Messtechnik AG
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