Geometrical instruments – Indicator of direction of force traversing natural media – Level or plumb – terrestrial gravitation responsive
Utility Patent
1999-05-28
2001-01-02
Bennett, G. Bradley (Department: 2859)
Geometrical instruments
Indicator of direction of force traversing natural media
Level or plumb, terrestrial gravitation responsive
C033S374000
Utility Patent
active
06167631
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a plummet level, and more particularly to a plummet level having a balance beam and a weight-loaded swing link provided in a front and a rear compartment, respectively, of the level. The balance beam and the swing link both have a reference line marked on their front surface. By visually overlapping one of several spaced check lines provided at front and rear surfaces of the plummet level and one of the reference lines, a working surface may be easily tested for its horizontal or vertical state.
A plummet level has been widely used in construction works and interior decorative works to find an accurate horizontal and/or vertical surface, and is particularly useful in wood working. The conventional plummet level normally includes a liquid container mounted on a main body of the level and having a bubble contained therein. There are many improved levels developed in recent years and being equipped with auxiliary laser means. Taiwanese New Utility Model Patent Application No. 87204670 published under Pub. No. 342936 entitled “A Level”; No. 87202762 published under Pub. No. 344456 entitled “Structure for a Laser Level”; and No. 87207229 published under Pub. No. 344457 entitled “A Laser Level” all disclose levels with laser. The provision of laser means on the levels is only to enable locating of a certain distant point. To determine a horizontal or vertical surface, such laser levels still rely on conventional bubble levels.
The conventional bubble level mainly includes a see-through container in which a liquid and a small amount of gas are contained so that a bubble of suitable size is formed in the container. Two laterally spaced locating lines are very precisely marked on the wall of the clear container to define a center mark area on the container. When the bubble is centered in the center mark area, it indicates the surface under checking is a horizontal or vertical surface. Since the bubble has a width usually smaller than that of the center mark area, a user must visually determine whether the bubble is just centered in the center mark area. Due to the very small distances existing between two ends of the bubble and the two marking lines, as well as the observation of the bubble from different visual angles, it is very possible to make inaccurate and incorrect determination of the location of the bubble in the center mark area. Such inaccurate determination will inevitably affect precise connections in wood works, such as in the condition of mortise and tenon joints.
Moreover, when using the auxiliary laser means on the level to conveniently locate a remote point by projecting a laser beam simply based on a visually determined reference point, the possibility of producing a big error is high. On the other hand, the auxiliary laser means is not necessarily useful or practical for woodworks in an interior decorative project that usually involves only very small space and short distances. This is because a worker can easily and directly locate a horizontally or vertically distant point by means of a plummet level. In the event a laser beam is to be projected from a plummet level for measuring another distant target, the plummet level itself must be first adjusted and controlled to serve as a reference point by, for example, mounting the level on a tripod and adjusting the latter to a desired position. This is, of course, very troublesome for a wood work that does not include so many distant points to be measured or located.
However, it is indeed a common situation that only one single level is not long enough for locating and marking a somewhat distant point that is located by using the plummet level. For example, when a wooden mullion is to be vertically mounted between two horizontal wooden transoms, it is necessary to use a plummet level to locate two vertically corresponding points separately on the two horizontal transoms. It is very possible a vertical distance between the two transoms is larger than an overall length of the plummet level and an operator fails to easily and directly mark the point on the distant transom by aligning a distal end angle of the plummet level with the point. At this time, an auxiliary laser beam surely would be helpful to locate the vertically corresponding point on the distant transom. However, it would be easier and more convenient if the plummet level is provided with extensible end portions that can be pulled out to increase the overall length of the plummet level and serve as means to contact and align with the corresponding point located at the distant transom to permit accurate marking it on the transom.
FIGS. 1 and 2
illustrate a conventional plummet level
10
on which two bubble levels
11
are provided. One of the bubble levels
11
extends in a horizontal direction for checking the horizontal state of a working surface and the other in a vertical direction for checking the vertical state of a working surface. The bubble level
11
includes a clear container
111
for containing a liquid and a small amount of gas, so that a suitably sized bubble
112
is formed in the container
111
. Two laterally spaced marking lines
113
are very precisely provided on the clear wall of the container
111
to define a center mark area between them. When the plummet level
10
is in a horizontal position on a working surface, and the bubble
112
in the liquid container
111
of the horizontal bubble level
11
is centered between the two marking lines
113
, the working surface is determined as a horizontal surface. Similarly, when the plummet level
10
is in an upright position for checking a vertical working surface or locating two vertically spaced points, and the bubble
112
in the liquid container
111
of the vertical bubble level
11
that is now in a horizontal position is centered between the two marking lines
113
, the working surface are determined as a vertical surface or the two spaced points are determined as on a vertical line.
It is very uneasy to determine whether the bubble
112
is just centered between the two marking lines
113
. An operator can visually determine a centered bubble
112
only by distances
114
between two ends of the bubble
112
and the two marking lines
113
. When the distances
114
at either end of the bubble
112
are visually determined as equal, the working surface is determined as horizontal or vertical.
It is known that the distances
114
are so small that they can not be easily and accurately determined as longer or shorter compared to one another. They are also other factors, such as different visual angles relative to the liquid container
111
that would affect correct determination of a centered bubble
112
.
Although the plummet level
10
has simple structure based on a self-explaining principle and been widely used for a long time, it does not ensure an accurate and precise determination of a horizontal and vertical surface.
It is therefore tried by the inventor to develop a plummet level that does not employ liquid container and bubble to determine a horizontal or vertical surface, but employs nowadays precision machining technique to achieve easy but absolutely accurate determination of a horizontal or vertical surface.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a plummet level that includes a main body in which a balance beam and a weight-loaded swing link are separately mounted on a central pivot shaft to provide a reference level line and a reference vertical line, respectively. A plurality of spaced and parallel check lines extend a full length of long clear windows separately provided on two walls of the main body facing the balance beam and the swing link. By visually overlapping one of the check lines with the level or vertical reference line depending on actual need, a working surface under checking can be easily decided to be horizontal/vertical or not.
Another object of the present invention is to provide the above-mentioned plummet level that further includes two extensi
Bennett G. Bradley
Dougherty & Troxell
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