Geometrical instruments – Indicator of direction of force traversing natural media – Level or plumb – terrestrial gravitation responsive
Reexamination Certificate
2001-05-02
2002-12-10
Gutierrez, Diego (Department: 2859)
Geometrical instruments
Indicator of direction of force traversing natural media
Level or plumb, terrestrial gravitation responsive
C033S366170
Reexamination Certificate
active
06490802
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is an apparatus for determining orientation with respect to acceleration, and more particularly the invention is an apparatus for determining orientation with respect to gravity, and where the orientation can be determined statically or dynamically.
Orientation devices, sometimes referred to as levels, tilt devices or inclinometers, are similar, in that all measure at least one component of an angle of deflection from a true vertical, where the true vertical is defined as a direction that is coextensive with gravity. The angle of deflection is conventionally termed tilt, or angle of tilt. A simple device for determining the direction of gravity is a plumb line. A plumb line is a string or line having a weight attached to one end and the other end attached to a stationary point, such that the hanging weight is free to move. After being positioned, once the weight becomes stationary, the plumb line indicates the true vertical.
If an object is not level then this is another manifestation of being tilted. Unlevelness is how much a plane is deflected from a true horizontal, where the true horizontal is a plane that is perpendicular to true vertical. Many orientation devices measure tilt by measuring levelness. A bubble tube is a means of using a gravitational force to determine true vertical by measuring levelness. The bubble tube is based on the observation that an air bubble in a liquid will seek to escape that liquid, and that under the pull of gravity, the action route will take the air bubble to a position in the liquid of lowest gravitational influence, that is lowest pressure. This action occurs because the pressure drops as the bubble moves upward, enabling the bubble to expand. The expanded bubble continues to proportionately increase in buoyancy, and the process continues until the bubble is either restrained or it reaches the surface. When the bubble is in a horizontal liquid filled tube, where the tube is slightly arced upward, then the position of lowest gravitational influence is at the apex of the arc, and this coincides with true vertical for one planar component. If the bubble is displaced from the apex, then this indicates that the tube is tilted, because the highest point in the tube is displaced. An example of a commonly utilized tool that employs the bubble tube technique is a level. One bubble tube can measure only one axis component at a time, so to determine the tilt on the other axes the level either has two or more bubble tubes offset 90 degrees, or the user has to rotate the level through 90 degrees, taking measurements at each angle. Even then, unless the user knows exactly how to line up the level, the level could be actually rotated slightly, and thereby produce an erroneous level reading in the bubble tube. More recent inventions employing bubble tubes, often called electronic bubble tubes, have a domed chamber instead of a tube and the chamber has a shallow convex curvature. The convex curvature enables the air bubble to move in either the x or the y direction or any combination thereof, as it seeks the point of lowest pressure. However, the additional degree of freedom comes at a substantial price. The forces acting on the air bubble producing movement, are now spread over a much larger angle, instead along just one axis. Therefore, domed chambered bubble tubes are substantially less sensitive to small changes in tilt compared to tubes.
There are several considerations the user must be aware of when using orientation devices that use the bubble tube technique. Firstly, bubble tubes are subject to error because if either the tube or the apparatus seating the tube is rotated, a false orientation reading will be generated. Also, competing interfacial interactions can be substantial. By way of example, the reader is encouraged to recall the way small bubbles cling to the walls of a glass of water, or a glass of champagne. As previously implied, omni-directional bubble tubes offer the advantage of determining the direction of tilt with one measurement, but omni-directional bubble tubes are less sensitive than single axis bubble tubes. An improved technology would be an orientation sensor that had the convenience of measuring tilt through 360 degrees, but without the loss of sensitivity. Another limitation of the prior art is that to amplify small changes in tilt requires using a tube that is has very little arch. However, with a substantially straight tube the operative gravitational forces and the competing interfacial forces are approaching each other in magnitude, and the net result is that the bubble tends to stick and then jump, in an all or none fashion. An improved technique would be one that utilized the heretofore described action of the bubble to move to the point of lower pressure, while at the same time minimizing the interfacial interactions.
Kikuo Shimura U.S. Pat. No. 5,101,570 discloses an Inclination Angle Detector that is a bubble tube that casts a shadow on a circular detector, where the detector is divided into quadrants. The resulting electronic signal is converted/calculated into an angle of tilt or incline, where not only the degree or magnitude of tilt is determined, but also the direction.
Fumio Ohtomo U.S. Pat. No. 5,953,116 discloses a Tilt Detecting Device that is comprised of a bubble tube, light, detector and electronics . His invention is geared for survey equipment, i.e. transit theodolite. Page 11, FIG. 18 shows a light profile of the photo detector of the prior art. By using plates (slits) the overall light is reduced but the background noise light is greatly reduced, permitting accurate determinations.
Franklin U.S. Pat. No. 4,800,542 discloses an orientation device that uses moving mercury to change the capacitance in response to a change in orientation.
Augutin U.S. Pat. No. 5,704,130 discloses an invention developed for Bayer that uses a chamber containing two immiscible media, where one of the media is either a gas, liquid or solid. The preferred invention uses a gas.
SUMMARY OF THE INVENTION
The invention is an apparatus for measuring tilt, where tilt can generally be described as an angular component of a vector, where the vector is equal and opposite the force exerted by gravity and, on occasion, one or more additional forces. The angular component or tilt is three dimensional. The three angular dimensions can be measured and described in a two dimensional format. Two of the dimensions are described in terms of direction and the third dimension in terms of magnitude. The format can use purely scalar units, purely angular-units or a blend of units, such as polar notation. The reader is encouraged to preview
FIG. 4
for a pictorial explanation of tilt. In the current discussion, for purposes of clarity, the direction of tilt will refer to the orientation of a substantially horizontal plane where the tilt is steepest. The magnitude will refer to the grade of that horizontal plane.
The invention is set up to adhere to this format, which has a visual representation that is easily understood, and is grounded with an historical basis
Mechanistically, the invention uses the observed action of a buoyant element immersed in a liquid to seek a position of minimum pressure to determine orientation. Under static conditions, that position is as close to the surface as permitted by the constraints of the invention. The action is not dissimilar to the bubble tube, but with several significant departures that all but eliminate some of the more onerous limitations associated with the prior art.
The invention is an apparatus for determining the orientation with respect to gravity, wherein the apparatus comprises:
a lower chamber that is filled with a liquid, and an upper chamber that is superimposed over the lower chamber, where the lower chamber and the upper chamber share a light communicating wall, where said light communicating wall is a window;
a light transmitting cable that is transmitting light through the cable, wherein said cable has a source end which is an entrance point for t
Brockington F. Rhett
Cohen Amy R
Gutierrez Diego
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