Measuring and testing – Liquid level or depth gauge – Float
Utility Patent
1998-03-02
2001-01-02
Williams, Hezron (Department: 2856)
Measuring and testing
Liquid level or depth gauge
Float
C073S315000, C073S305000, C073S322500, C137S206000, C137S207000
Utility Patent
active
06167756
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, in general, to liquid level detection apparatus and, more specifically, to magnetostrictive position transducers.
2. Description of the Art
The phenomenon of magnetostriction has been widely employed in linear distance and position measuring devices. A magnet located near or around a magnetostrictive wire marks the location to be measured. Such devices can operate with either mechanical or electrical excitation. When an acoustical/mechanical strain propagating along the wire reaches the area of influence of the magnet, an electrical signal is generated in the wire. Conversely, when an electrical signal propagating along the wire reaches the area of influence of the magnet, a torsional strain is generated in the wire.
Such linear position detectors using a magnet mounted in a float have been utilized as liquid level detectors to provide an indication of a level of liquid within a tank, such as an underground tank. The position of the magnet, and hence, the liquid level, is determined as a function of the time required for a torsional disturbance to propagate from one end of the wire through the area of influence of the magnet, in the case of mechanical excitation, or from the position of the magnet to a sensing apparatus located at one end of the wire in the case of electrical excitation.
Other types of magnetostrictive position measuring devices utilize a reflective termination at the foot end of the magnetostrictive wire. Such devices measure the difference between the propagation times of a pulse from the magnet position to the foot of the wire and reflected back to the head of the device and a pulse traveling on the wire directly from the magnet to the head.
As shown in U.S. Pat. Nos. 4,839,590; 5,017,867; 5,050,430; and 5,253,521, all of which are assigned to the assignee of the present invention, such magnetostrictive devices include an elongated, small diameter tube, typically made of stainless steel, on which a movable magnet is mounted for providing an indication of a liquid level. An enlarged head and cap are mounted on one end of the tube, typically above the liquid level and enclose electronic components, such as terminal connections and a signal conditioning circuit used to supply or output signals to and from the magnetostrictive wire in the tube. As shown in these prior art patents, the head has a considerably larger diameter than the diameter of the elongated tube extending through the tank.
Fluid tanks, such as underground gasoline or fuel tanks, are typically provided with one or more risers or hollow conduits mounted on a top surface of the tank and extending upward to an upper end which is located at ground level. One riser is usually employed for filling the tank and typically will have a diameter of approximately four inches. A second smaller riser, such as a two inch diameter riser, may also be provided as a vent.
Existing tanks which are buried underground and which were not provided with the expectation of using liquid level detection within the tank, typically will not have a large riser or a riser dedicated to liquid level detection. Thus, where it is desirable to provide liquid level detection to such existing underground tanks, previously devised magnetostrictive positioning measuring devices having an enlarged head cannot fit within the fill nozzle of the existing riser on such tanks or will completely fill the interior of the riser thereby preventing the insertion of a fuel nozzle into the riser. The only recourse in such situations is to dig up the existing tank and add a riser specifically for a liquid level detection apparatus.
One attempt to overcome these problems is disclosed in U.S. patent application Ser. No. 08/848,891, entitled “Self-Contained Liquid Level Detection Apparatus”, and assigned to the same assignee as the present invention. The liquid level detection apparatus disclosed in this application has all of the liquid level detection components contained completely within a small diameter outer tube. This enables the small diameter tube to be mounted through a small diameter riser of a liquid tank, including risers or even apertures of relatively small diameter, such as a two inch diameter riser.
However, a problem still exists with respect to the float carrying the magnet which interacts with the magnetostrictive wire contained within the outer tube. It is known that the greater the amount of surface area of a float in contact with a liquid surface creates greater buoyancy due to the larger surface area displaced by the float. When a smaller amount of surface area of a float in contact with a liquid surface creates bobbing and erratic movements which, in a liquid level detector, can cause erroneous level measurements.
With tanks having risers with an inner diameter of approximately 4 inches a float with a diameter of slightly less than 4 inches can be inserted along the tube into the interior of the tank. This diameter float has proved to be sufficient in terms of having adequate buoyancy to minimize bobbing or erratic movements on the liquid surface.
However, with smaller diameter risers or apertures in older tanks, such as risers or apertures having a 2 inches inner diameter, only a float having a diameter of slightly less than 2 inches can be inserted through the riser or aperture. This size float displaces less surface area and thereby has less buoyancy which causes it to bob and introduce undesirable error into liquid level measurement.
Thus, it would be desirable to provide a float for a liquid level detection apparatus and, more specifically, a magnetostrictive waveguide liquid level detection apparatus which is capable of being inserted along the liquid level detection pipe through any size riser or aperture in a tank while still having sufficient buoyancy when in contact with the liquid surface to minimize bobbing or erratic movements on the liquid surface. It would also be desirable to provide a float for a liquid level detection apparatus which can easily fit into small diameter pipes of approximately two inch diameter. It would also be desirable to provide a float for a liquid level detection apparatus which presents an overall small diameter when slid along the pipe through a riser or aperture in the tank and then is capable of expanding or moving to a position creating large surface area displacement on the liquid surface.
SUMMARY OF THE INVENTION
The present invention is a pivotal float for a liquid level detection apparatus, such as a magnetostrictive wave guide liquid level detection apparatus.
The float is used with a liquid level detection apparatus including elongated tube containing liquid level detection means, the tube extending through a liquid surface and liquid in a tank, the float comprises:
a buoyant body slidable along the tube.
means, carried on the body, for supporting the body in a first axial position substantially in line with the tube and slidable along the tube, and for allowing the body to pivot to a second position about the tube buoyantly supported on a liquid surface.
Preferably, the second position of the float is substantially perpendicular to the first position. The buoyant body of the float is preferably formed, of first and second, spaced, buoyant body members. The pivot means, preferably includes first spacer means mounted along and connecting one side edge of the first and second body member, second spacer means mounted along and connecting opposed side edges of the first and second body member, and the first and second spacer means spaced longitudinally apart from each other to allow the first and second body members to move to the first position axially concentric with the tube.
The spacer means preferably comprises the first spacer means in the form of a first pair of separate, spaced pins extending between and joined to the first and second body members; and the second spacer means includes a second pair of separate, spaced pins extending between and joined to the first and second body member. On
Everson, Jr. Harold William
Jenkins Anthony L.
Loo Dennis
Patriot Sensors & Controls, Inc.
Williams Hezron
Young & Basile P.C.
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