Liquid level gauge with hinged float arm

Details Liquid level gauge with hinged float arm Liquid level gauge with hinged float arm

2000-05-08

2001-07-03

Williams, Hezron (Department: 2856)

Measuring and testing

Liquid level or depth gauge

Float

C073S309000, C073S317000, C073S29000R

Reexamination Certificate

active

06253609

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
This invention relates to liquid level gauges of the type having a float arm which pivots to allow a buoyant float to remain at the surface of the liquid. In one aspect, it relates to a gauge having a float arm that is hinged to allow an outer float arm section to temporarily deflect with respect to an inner float arm section.
BACKGROUND OF THE INVENTION
Liquid level gauges of the type haying a buoyant float mounted on a pivoting float arm which responds to changes in the liquid level being measured are well known. Such pivoting float-type gauges typically utilize mechanical or electrical mechanisms that sense the angular position of the float arm with respect to a stationary support arm or other structure. The mechanism then provides an external indication of the corresponding liquid level. Since the liquid level indication is based on a measurement of the angle between the float arm and another structure, it is important that the float arm have a known configuration in the plane of pivoting motion in order to preserve the accuracy, precision and calibration of the gauge.
The measurement range of a typical pivoting float-type gauge depends (in part) upon the range of vertical positions which can be reached by the float's arc of motion (any liquid level above or below the float's range of travel being unmeasurable). It is therefore often desirable to make the float arm as long as possible consistent with providing sufficient clearance for the float to pivot
In some applications, for example, on pressurized tanks used for storing liquids such as liquefied petroleum gas (often referred to generally as “LPG”), the liquid level gauge is provided with a threaded gauge head for mounting into a threaded pressure fitting on the tank. In such cases, the float, float arm, support arm and other in-tank components of the gauge are inserted through a passage in the threaded fitting on the tank. The entire gauge is then rotated to cause the threaded gauge head to engage the threaded fitting and form a pressure-type seal.
It is known that pivoting float-type gauges can be damaged during installation if the float or float arm strikes the interior walls of the tank or other stationary objects as the gauge is being screwed into the threaded tank fitting. Since the float arm typically hangs downward in an empty tank such damage is unlikely if the gauge is slowly screwed into the fitting by hand or using a manual wrench, as was common industry practice in the past. However, it has now been discovered that power wrenches are increasingly being used for installing screw-in float type gauges into tanks. Power wrenches typically spin the gauge much faster and with more force during installation than a manual wrench. The centrifugal force that results from rapid spinning of a gauge during installation can cause the float and float arm to rapidly swing from a downward, generally vertical position to a laterally extending, generally horizontal position. In many cases, and especially where the storage tank is narrow and/or where the gauge is installed near the sidewall of the tank, the revolution of a horizontally oriented float arm about a vertical axis such as the support arm can result in the float or float arm striking the walls or other interior components of the tank. If the float arm strikes the interior of the storage tank (especially if it is being rotated by a power wrench), this can result in damage to the float, bending of the float arm, damage to the float arm pivot mechanism, twisting of the support arm, or other damage which can adversely affect the calibration, accuracy and/or precision of the gauge. A need therefore exists, for a pivoting float-type liquid level gauge having a float arm that will not be damaged if an obstacle is encountered in the interior of the tank during installation. A need further exists, for a pivoting float-type gauge having a mechanism which retains its accuracy and calibration if the float arm encounters an obstacle during installation.
SUMMARY OF THE INVENTION
In accordance with one aspect of the current invention, a liquid level gauge is provided comprising a gauge head, a support arm, a float arm, and a float. The gauge head is adapted for mounting to a portion of a liquid storing container. The support arm is rigidly connected to the gauge head and depends therefrom. The float arm includes an elongate inner arm section, an elongate outer arm section, and a hinge section. The inner arm section is pivotally connected to the support arm at a pivot point for movement through an arc defining a plane of motion. The hinge section is connected at a first end to the inner arm section and connected at an opposite end to the outer arm section. The hinge section is deflectable to allow movement of the outer arm section between a first configuration in which the outer arm section is in a predetermined position with respect to the inner arm section, and a second configuration in which the outer arm section is not in the predetermined position with respect to the inner arm section. Further, the hinge provides a biasing force for urging the outer arm section into the first configuration. The float is connected to an outer end of the outer arm section and is buoyant so as to remain at the surface of the liquid.
In one embodiment of the current invention, the hinge section of the float arm comprises a close wound cylindrical helical extension spring having an initial tension when in an unflexed condition. In another embodiment of the current invention, the hinge section comprises first and second guide members having an elastic member connected therebetween. Each guide member includes a longitudinally oriented body portion and a terminal portion. Each terminal portion is disposed at one end of the body portion and defines a mating surface facing away from the body portion and generally perpendicular to the longitudinal direction. Each guide member further defines a passage formed through the mating surface and extending into the body portion to an anchor point. The elastic member has a first end secured to the anchor point of the first guide member, extends through the passages in the first and second guide members, and has a second end secured at the anchor point of the second guide member. The elastic member provides a biasing force for urging the mating surfaces into juxtaposition. The elastic member can be a cylindrical helical extension spring held in tension when the mating surfaces are juxtaposed.
In yet another embodiment of the current invention, the hinge section comprises a flat leaf spring. The spring has a rectangular cross-section with a thickness and a width, the thickness being smaller than the width. The spring is connected to the inner arm section such that during use, the width is oriented in a substantially vertical direction. In a further embodiment of the current invention, the hinge section comprises a first hinge member and a second hinge member pivotally connected to one another to allow relative movement along a line of motion. The hinge members are connected to the inner arm section such that during use, the line of motion is oriented in a substantially horizontal direction. The hinge section further includes an elastic member connected between the arm sections and providing a biasing force for urging the outer arm sections into the first configuration. The elastic member of this embodiment may be an elastomer sleeve having a bore and being connected to each arm section with the hinge members being positioned within the bore.
In yet another aspect of the current invention, a float arm for a liquid level gauge having a support member and a float is provided. The float arm comprises an elongate inner arm section, a hinge section, and an elongate outer arm section. The inner arm section has an inner end and an outer end. The inner end is adapted for pivotal connection to the support member and the outer end is connected to a first end of the hinge section. The outer arm section has an inner end and an outer

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