Measuring and testing – Liquid level or depth gauge
Patent
1982-06-21
1984-11-06
Swisher, S. Clement
Measuring and testing
Liquid level or depth gauge
G01F 2328
Patent
active
044804687
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an apparatus for measuring and indicating the fluid level in vessels.
The liquid level in non-transparent vessels heretofore has been indicated by means of stand pipes (for example at boilers) or floating bodies (for example at oil or gasoline tanks). At other vessels or containers, such as LP-gas tubes or bottles for household purposes or the like, level indication was not provided at all. In order to find out the filling degree, one had to weigh the vessel with contents, which obviously can be a complicated and troublesome procedure especially when the vessels are large and heavy.
The present invention offers a solution of the indication problem without any encroachment in the vessel. The invention is characterized by a mechanically operating arrangement or a pulse device for causing the vessel wall to vibrate, a transducer for sensing the vibration progress varying with the filling degree of the vessel, and a processing unit for evaluating the output signal of the transducer and transmitting the result to an indicator.
The invention is described in greater detail in the following where it is applied to an LP-gas tube and reference is made to the accompanying drawings, in which
FIG. 1 is a schematic front view of a LP-gas tube for household purposes, equipped with a stationary apparatus according to the invention, shown partially in block form,
FIG. 2 is a view of an apparatus designed as a separate accessory to be held in the hand and formed as a pistol, part of its casing cut-off,
FIGS. 3a,b are typical curves of the output signal from the transducer of the apparatus at full and, respectively, empty tube,
FIGS. 4,5 and 6 are block diagrams for the electric arrangement with digital indication by using only the frequency of the tube wall (FIG. 4), a combination of the frequency of the tube wall and its vibration amplitude (FIG. 5), and the reverberation time of the wall vibration (FIG. 6), and
FIG. 7 is the block diagram for an arrangement with analogous indication.
The LP-gas tube 1 in FIG. 1 rests on a support 2 indicated by dash-dotted lines. In the support a stationary pulse device 3 with striking pin 4, and to the side of the device a transducer generally designated by 5 are carried. The transducer comprises a piezoelectric crystal 6, which is movable in vertical direction and carries upwardly a mass weight 7, which is influenced by an upward directed force, which here is represented by a compression spring 8. The pulse device and the transducer are so located in the support 2, that the bottom wall 1a of the applied tube 1 will be located within the stroke length of the device and compresses the spring 8 so that an intimate contact with the crystal 6 is ensured.
The output signal from the transducer 5 is passed to a processing unit 9 and therefrom to an indicator 10.
The mode of operation substantially is as follows:
The striking pin 4 of the pulse device is released, for example by pressing a button (not shown), which releases a prestress, which acts on the pin--and possibly is generated at the beginning of said pressing--so that the bottom of the tube is subjected to a forceful thrust. Thereby the entire tube wall 1 is caused to perform decaying vibration. The LP-gas amount in the tube exercises a damping effect on this vibration which decreases with decreasing amount. This implies increased vibration frequency and decreasing amplitude.
The vibrations of the wall (bottom) are transferred by the piezoelectric transducer 5 in the form of a correspondingly varying voltage to the processing unit 9, which processes the signal and emits a signal to the indicator 10 which is related to the frequency (or amplitude) and thereby to the filling degree of the tube. The indicator 10 then indicates the LP-gas level, for example in the form of a pointer deflection or in digital manner (as in the Figure).
The mechanical releasable prestress of the striking pin 4 can be replaced by electro-dynamic switching-on or application of a strong voltage pulse on a fixed piezoelectric crystal, whic
Roskos Joseph W.
Swisher S. Clement
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