Geometrical instruments – Indicator of direction of force traversing natural media – Level or plumb – terrestrial gravitation responsive
Patent
1997-06-09
1999-03-16
Bennett, G. Bradley
Geometrical instruments
Indicator of direction of force traversing natural media
Level or plumb, terrestrial gravitation responsive
33451, G01C 928
Patent
active
058814680
DESCRIPTION:
BRIEF SUMMARY
This invention relates generally to a spirit level and, more specifically, to a dual-armed spirit level for determining two-dimensional inclination with respect to a plane.
Such a spirit level of the general kind set forth is known from DE 35 26 018 A1. Spirit levels have a wide area of use, for example in structural engineering and in mechanical engineering, and serve to check the position of vertical and horizontal components.
A conventional spirit level comprises a wood or metal strip of substantially rectangular cross-section, which is provided with at least one level. Hereinafter the term level is used to denote a slightly curved glass tube (tube level) or a glass capsule with slightly spherical top (circular spirit level) which are filled except for a gas bubble with alcohol, ether or another liquid. When the level is in a horizontal position that gas bubble is disposed precisely at the centre thereof.
Such spirit levels which only comprise one strip can only be used to determine inclination in one direction (that is to say one-dimensionally), whereby problems can be involved in aligning planes or surfaces, for example a table top. In such a case the above-described conventional spirit levels can provide a remedy by virtue of adopting a procedure whereby firstly the inclination of the plane is checked and set in a first direction and thereupon the inclination of the plane is checked and set in a second direction, with the first and second directions generally being perpendicular to each other. However such a procedure is made difficult not least by virtue of the fact that usually adaptation of the inclination of the plane in respect of the first direction inevitably also involves a change in the inclination of the plane in the second direction so that an alignment process becomes a recursive and lengthy procedure which, besides the amount of time involved, achieves a correspondingly low level of accuracy.
Now, spirit levels are known from the state of the art, which permit two-dimensional determination of inclination, that is to say with respect to a plane.
Thus DE 35 26 018 A1 disclosing the general kind of apparatus involved has an elongate main body of rectangular cross-section on which a smaller arm is centrally pivotably arranged. When the arm is in the outwardly pivoted condition it is therefore possible to provide for two-dimensional determination of inclination.
However that spirit level in accordance with the state of the art is not only structurally expensive and disadvantageous--the arm must be designed to be precisely aligned to be received in a suitable recess in the main body and production of the pivot or hinge axis is as a result inevitably complicated or imperfect--but also that known spirit level is disadvantageous in regard to accuracy and further measurement properties: the fact that the pivotable arm is completely received in the associated recess in the main body necessarily means that the spirit level, along the main body, is of a greater length than the arm. As however the degree of measuring accuracy of a spirit level is influenced by the spacing of a level provided at the end of an arm relative to the central point, the spirit level which is known in accordance with the general kind set forth with levels disposed at each of its respective ends and thus arranged at different spacings relative to the axial centre, is inaccurate in regard to its measuring accuracy between the arms and is thus inevitably disadvantageous.
Furthermore the spirit level of the general kind set forth evidently permits it to be put only on to a continuous plane for the fact that the recess for the arm, which is formed almost entirely along the underside of the main body, means that the spirit level must be put on to the subjacent plane or surface, at both end portions of the main body, in order to be able to perform any measurement procedure at all. If however for example the situation involves ascertaining the slope of a plane or a surface which in terms of its dimensions is smaller than the spacing
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Baumann Urs
Bennett G. Bradley
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