Geometrical instruments – Indicator of direction of force traversing natural media – Level or plumb – terrestrial gravitation responsive
Patent
1989-11-28
1991-03-26
Will, Thomas B.
Geometrical instruments
Indicator of direction of force traversing natural media
Level or plumb, terrestrial gravitation responsive
33384, G01C 928
Patent
active
050018388
DESCRIPTION:
BRIEF SUMMARY
The present invention is concerned with spirit levels suitable for use by carpenters, bricklayers or the like, which levels can be used not only to provide an indication of whether a surface is vertical or horizontal, but also to provide a measure of the angle of such a surface relative to the vertical or horizontal.
Conventional spirit levels commonly used in the home and workshops by bricklayers, carpenters or the like incorporate at least one transparent tube containing a coloured liquid with a gas bubble incorporated therein. The bubble tube is housed in the spirit level such that when the level is placed on a flat horizontal or vertical surface (depending on the orientation of the bubble tube with respect to the level) the gas bubble comes to rest in the centre of the bubble tube between two lines or gradations marked on the tube. This type of spirit level is convenient for checking whether surfaces are level, for example, when finishing a workpiece with a plane or other such tool; however, such a spirit level is of little or no use in measuring the angles of surfaces relative to the horizontal or vertical.
Spirit levels are known, however, which can be used to measure angles of surfaces relative to the horizontal or vertical; such a known type of spirit level comprises a bubble tube housed in a rotatable member. The rotatable member has an angular scale at its periphery and is calibrated such that when the reading on the angular scale is 0.degree., the bubble tube is parallel to the longitudinal axis of the spirit level, and when the spirit level is placed on a level horizontal surface in this configuration, the gas bubble comes to rest substantially in the middle of the bubble tube between the two marking lines or gradations.
In use, the spirit level is placed on a surface and the rotatable member is rotated until the gas bubble comes to rest in the middle of the bubble tube between the marking lines or gradations. The bubble tube is then parallel to the horizontal, and the angle between the bubble tube and the longitudinal axis of the spirit level (that is, the angle of the surface with respect to the horizontal) is read from the scale. However, the accuracy of the angular scale is limited to approximately two degress, which may well not be accurate enough in certain applications.
It is an object of the present invention to provide a spirit level capable of measuring the angle of a surface relative to the horizontal or vertical in which the above disadvantages are at least alleviated. A spirit level according to the invention comprises: lateral edge thereof, said body having a transverse circular aperture therethrough; outer rotatable member having a transverse circular aperture therethrough coaxial with the aperture in said elongate body; outer rotatable member; and respect thereto; whereby rotation of said inner rotatable member effects coarse adjustment of the orientation of said bubble tube relative to said lateral edge, and rotation of said outer rotatable member with said bubble tube in fixed orientation with respect thereto effects fine adjustment of the orientation of said bubble tube relative to said lateral edge.
The inner rotatable member preferably carries a pointer which indicates the longitudinal axis of the bubble tube. Typically, the outer rotatable member has a coarse angular scale thereon, around the aperture in which the inner rotatable member is mounted, so as to indicate the relative angle between the longitudinal axis of the bubble tube and the supporting lateral edge of the spirit level.
The inner rotatable member is preferably rotatable through a series of predetermined positions, typically at 10.degree. spacings and defined by complementary stop formations on inner and outer rotatable members. The inner rotatable member is typically rotatable through a full 360.degree..
The outer rotatable member is typically provided with an elongate pointer arranged to extend, in one position, parallel to the lateral supporting edge of the spirit level body. A fine angular scale is prefer
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patent: 1830009 (1931-11-01), Walters
patent: 2277071 (1942-03-01), Cassell
patent: 2692440 (1954-10-01), Walters
patent: 3159926 (1964-12-01), Holderer
Huxley, deceased Terrence
Huxley, heir by Mary E.
Lewis Garry I.
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