WO2008038049A2

WO2008038049A2 - Level

Info

Publication number: WO2008038049A2
Application number: PCT/GB2007/050589
Authority: WO
Inventors: Leslie Adrian Alfred Woolard
Original assignee: Leslie Adrian Alfred Woolard
Priority date: 2006-09-29
Filing date: 2007-09-28
Publication date: 2008-04-03
Also published as: WO2008038049A3; GB2442243A; GB0619177D0

Abstract

The present invention provides a level (20) comprising a housing (21) that is set on a surface to determine its inclination. An oblate spheroid vial (22) is disposed within the housing and contains a liquid and inclination indicating means (23) to indicate the inclination of the surface. The indicating means may comprise an air bubble formed in the liquid or a float. The vial may have opposed raised hemispheroid surfaces (30, 31) and a curved equatorial periphery and positional markings may be provided on the vial. The housing may be located on a surface in at least two orientations, and can provide differing levels of accuracy in each.

Description

LEVEL

The present invention relates to levels, and in particular to levels (often known as spirit levels) where a highly mobile liquid is contained within a vial mounted in a housing or frame.

Levels are used to indicate the inclination of a surface relative to the direction of gravity. Spirit levels generally comprise a housing with at least one flat surface for setting on a surface whose angle is to be measured, and a vial generally partially filled with a liquid, so that an air bubble forms therein. The air bubble will always find the highest point of the vial, so the positioning of the air bubble, for instance within a certain indicated area on the vial, indicates the inclination relative to gravity, and usually the horizontal plane. In most instances, the vial will be in the form of a cylinder with closed ends. When the vial (or the housing within which the vial is disposed) is placed on a level, horizontal surface, with the cylinder generally parallel with the surface the air bubble will float on the upper surface of the liquid towards the centre of the vial. If the surface is not level, then the air bubble will float towards one of the ends of the vial. These levels find utility only if a measurement is to be taken along one axis, as they will not show a slope in more than one axis without rotation of the housing to be coincident with that other axis.

Levels may also be used to measure various angles between the horizontal and the vertical. However to check whether a surface is at the desired angle the vial must be horizontal at that angle. Therefore, for each angle to be measured, a different spirit level is required, each with vials disposed at different angles within the housing. Alternatively a number of vials can be provided set at different angles within a single housing. In a yet further alternative it has been suggested to provide a vial whose position within the housing is adjustable, but this is still undesirable as the position must be altered which makes the procedure fiddly. Further designs of level have been proposed that are capable of providing an indication of inclination in two axes on a flat surface, however these are expensive and/or cumbersome. More importantly these have been of no use in dealing with the indication of inclination in a single axis that other prior art levels have dealt with.

The present invention aims to address these problems and to provide an improved level that avoids the problems of known levels, and can provide an indication of inclination in only one axis or in two perpendicular axes by simple rotation of the level.

According to the present invention there is provided a level comprising: a housing adapted to be set on a surface whose inclination is to be determined, an oblate spheroid vial disposed within the housing and containing a liquid, and inclination indicating means located within the vial to indicate the inclination of the surface.

An oblate spheroid is a rotationally symmetric ellipsoid having a polar axis shorter than the diameter of the equatorial circle whose plane bisects it. It is formed by rotating an ellipse about its minor axis, forming an equator with the end points of the major axis. As with all ellipsoids, it can also be described by the lengths of three mutually perpendicular principal axes, which are in this case two arbitrary equatorial semi-major axes and one semi-minor axis.

The aspect ratio b:a is the ratio of the polar to equatorial lengths (a = radius of equatorial circle, and b = half of the polar axis), while the flattening, f, is the ratio of the equatorial-polar length difference to the equatorial length defined by the equation:

'- ^•- ^■

As used herein the term oblate spheroid as referring to the vial generally means that the vial has such a shape but with a fair degree of flattening as the advantages of the present invention do not accrue if the shape is too spherical. In general it is preferred that f > 0.5 and preferably > 0.75 such that it is some way from approaching a regular sphere.

The inclination indicating means may comprise an air bubble formed in the liquid, which liquid is usually highly mobile i.e. with a low viscosity. However a bubble can change shape in different positions in the vial so it is highly desirable that the inclination indicating means instead comprises a float that is buoyant within the liquid. Preferably but independently this float is: spherical in shape, hollow to give buoyancy, of a bright or contrasting colour for easy visual tracking, and formed from a plastic material.

The oblate spheroid vial has two opposed hemispheroid surfaces with polar regions and a curved equatorial periphery. At least one of the hemispheroid surfaces and possibly at least part of the curved equatorial perimeter may be visible when mounted in the housing. Preferably, both hemispheroid surfaces are visible so that the level may be used in any orientation. The curved equatorial periphery may be visible from one side of the housing, and the hemispheroid surfaces may be visible from a side of the housing perpendicular to that side.

Positional markings may be provided on the vial, and the position of the inclination indicating means relative to these markings gives an indication of inclination. These positional markings may be printed, etched or otherwise formed upon the inner or outer surface of the material from which the vial is formed. The positional markings may include central marks at the apex of one or both hemispheroid surfaces ie at the poles of the spheroid. They may also include edge marks disposed on the edge region of at least one hemispheroid surface adjacent, or even extending over the equator. If both hemispheroid surfaces are to be visible there may be matching markings on both sides. The edge marks may be arranged in any suitable pattern but it has been found convenient to place them at intervals of 15°, 30°, 45° or 90° around the equatorial periphery.

The housing may be located on a surface in at least two orientations. In a first orientation the equatorial plane of the oblate spheroid vial is generally parallel to the surface, and in a second orientation the equatorial plane of the oblate spheroid vial is generally normal to the surface. The housing may take a variety of forms, but preferably it is elongate and generally cubic. The housing may have two pairs of opposed elongate side faces and it may be possible to locate the housing on the surface by resting on any one or more of these faces. The vial is positioned in the housing such that the orientation of the housing on either of one pair of side faces arranges the equatorial plane of the oblate spheroid vial generally normal to the surface (second orientation). This allows a single axial inclination measurement. The orientation of the housing on either of - A -

the other pair of side faces arranges the equatorial plane of the oblate spheroid vial generally parallel to the surface (first orientation). This allows a simultaneous dual axial inclination measurement.

The advantages of the present invention are provided in a large part by the shape of the vial. The radius of the curve of the hemispheroid surfaces and the curved equator differ, and this gives a different level of accuracy. The equatorial periphery can be used to provide an accurate measurement in one plane, but an even greater accuracy can be achieved using the level rotated such that the float floats in one of the hemispheroid surfaces. The length of the polar axis relative to the equatorial diameter is important, because it affects the sensitivity of the level. If the shape of the curve of the curved surface is too steep (at the most extreme where the vial is cylindrical), then the spirit level will not be sensitive to small variations in level and no alteration will be achieved by rotation of the level. The exact shape of the oblate spheroid is therefore dependent on the sensitivity of spirit level required in the two orientations for different applications.

In order that it may be better understood, one embodiment of the present invention will now be described in detail, by way of example only, with reference to the following figures wherein: Figure 1 shows a side view of a prior art level;

Figure 2 shows the prior art level of Figure 1 in use;

Figure 3 shows a perspective view of a level according to the present invention;

Figure 4a shows a cross section along a polar plane through the vial of the invention;

Figure 4b shows a similar cross section with the vial rotated by 90°;

Figure 5a, 5b and 5c show the present invention in use on a number of surfaces set at different angles;

Figure 6 is a perspective view of the embodiment of the present invention on a flat surface; and

Figures 7a, 7b, 7c and 7d show plan views of the vial of the level shown in Figure 6, each showing an exemplary selection of different float positions. Turning to Figures 1 and 2 there is an embodiment of prior art spirit level generally indicated 9. The level 9 comprises a housing 10, and disposed within a circular hole 11 therein is a vial 12. The vial 12 is cylindrical and partially filled with a liquid so that an air bubble 13 is formed within. Markings 14 in the form of two thin bands extend around the vial 12, and when the vial is perpendicular to the direction of gravity (ie horizontal) the air bubble 13 floats between the markings 14. The housing 10 has a rectangular cross section, and two straight side faces 15 suitable for placing on the surface. In Figure 1 the level indicates whether a surface 16 is horizontal. As shown, the air bubble 13 is floating between the two markings 14 to indicate that this surface 16 is horizontal. Alternative orientations of the vial in the housing 10 allow surfaces at different angles (e.g. 45° or 90°) to be checked. The disadvantage of these spirit levels is clear in that a separate spirit level is required for each angle to be measured. Levels can be purchased with two or more vials set at different angles, but these are more expensive than providing a single vial, and still the user is limited to the exact angle that the vial is adapted to check.

Figure 2 shows the prior art level of Figure 1 in use to determine whether a surface 20 is horizontal in one axial plane. The level 9 is laid on the surface, and the vial is visible from above. In this position the level indicates that the plane of AC to BD is horizontal, but gives no indication of the inclination of the plane AB to CD. The level must be rotated by 90° to measure the plane of AB to CD. Once necessary adjustments have been made to the angle of the surface 19 to ensure it is horizontal, the user must recheck that plane AC-BD has not altered. Alternatively, or additionally, measurements may be taken across the diagonal A to D and B to C. The disadvantage of using the prior art level 9 to measure across two planes is that many measurements have to be taken, and it is therefore time consuming to ensure the surface is indeed level.

The present invention overcomes these problems. Figure 3 shows a level according to the present invention generally indicated 20. This level comprises a generally elongate rectangular housing 21 with a front face 28, an opposed rear face (not visible) and a pair of mutually opposed side faces 29 (only one of which is visible). A vial 22 is mounted in the housing 21 to be visible when viewed from the front and rear sides at least. The vial 22 is formed from translucent material such as glass or plastics and is an oblate spheroid, with an elliptical cross section (normal to and bisecting the equatorial plane) as shown in Figures 4a and 4b, whose minor axis to major axis ratio is approximately 1 :4. The vial 22 is filled with liquid of appropriate viscosity and floating within the liquid is a small plastic spherical float 23 that is visually distinct from the liquid. As shown in Figures 3, 4a and 4b, the float always rises to the top of the vial 22 because it is buoyant within the liquid.

As shown in Figure 4a, when the housing is laid horizontally on a rear face the float rises to the highest part of the vial which is the pole (or apex) 30 of the upper hemispheroid surface. As shown in Figure 4b if the housing is standing on a side edge 29 the float will rise to the highest part of the equatorial periphery in which it will fit. Ideally the float is of a size to fit neatly against the inside of the vial at the equator thereof.

Printed or otherwise marked onto the surface (inner or outer) of the vial are circular markings, which have a diameter approximately the same as that of the float 23. There is a central marking 25 to indicate when the float 23 is at the pole 30. Radially extending around and from the central marking 25 are spokes 26 at 45° intervals. At the end of each spoke 26 is a circular peripheral marking 27a to 27g. When the housing is placed on a side edge, as shown in Figure 3, the float floats at the top and aligns with the uppermost peripheral marking 27a, which indicates that the surface is horizontal in an axis parallel to the length of the housing.

Figure 5a to 5c shows the present invention in use on a range of surfaces at different angles. Figure 5a shows the level 20 in use on a generally horizontal surface. The float 23 has risen to the top of the vial 22 and when it aligns with the uppermost marking 27a it indicates that the surface is horizontal in that plane. Figure 5b shows the level 20 in use on a surface which is at approximately 45° from the horizontal. The float has risen to the top of the vial, and lines up with marking 27b to indicate that the surface is at 45° from the horizontal. Figure 5c shows the level 20 on a vertical surface. The level 20 is held against the surface, and the float again sits at the highest point in the vial. If the float lines up with the marking 27c it shows that the surface is vertical. When the housing is placed on a side face 29 the level 20 can be used, as described above, to measure the inclination in only one plane. However the present invention offers a significant advantage in that it can simultaneously measure the angle in more than one plane, by placing the housing on the rear or front face and observing the position of the float relative to the pole 30. Figure 6 shows the level 20 resting on its rear face on a surface 35. In this arrangement the equatorial plane of the vial is generally parallel to the surface 35 (as shown in Figure 4a).

Figures 7a to 7d show an enlarged schematic plan representation of the vial 22 as it would appear on level 20 when the surface 35 is in 4 different inclinations. The surface may be non-horizontal in the X-X plane and/or the Y-Y plane. As shown in Figure 7a, surface 35 is horizontal in both the X and Y planes so the float 23 is within the central marking 25. In Figure 7b the position of the float within the vial 22 indicates that the surface is not level with respect to either plane. To make the surface level, the user will have to raise the edge CD and AC slightly until the float 23 lines up with circular central marking 25.

In Figure 7c the float indicates that the surface is not level with respect to the X axis but is level in the Y axis. To make the surface level, the user will have to slightly lower edge BD (or raise edge AC) until the float 23 lines up with central marker 25. In Figure 7d the vial 22 indicates that the surface is not level with respect to either the X or Y plane. To make the surface level, the user will have to slightly raise corner B (or lower corner C) until the float 23 lines up with central marker 25.

In use a person can choose to use the level on a side face or front/rear face (ie the first or second orientations) depending on their requirements. Also, as the shape of curvature as compared between the equator and the polar regions is different, each can have varying degrees of accuracy. For example an inclination in a single plane can be measured with the housing on a side face, and then the housing rotated 90° to the rear face and re-measured to a slightly greater degree of accuracy relative to the central marking 25 - or a line running along the spokes 26 between markings 27a and 27e through marking 25. The present invention also permits the monitoring of the inclination of the surface of a moving object - even if the degree of variation is large. For example in the second orientation, with the float at or adjacent the equator, the angle of inclination in that plane may be measured regardless of the extent of rotation because the float simple repositions within the vial, and the angle may be determined from the position of the float relative to the markings 27a to 27h.

Claims

1. A level comprising: a housing to be set on a surface whose inclination is to be determined, an oblate spheroid vial disposed within the housing and containing a liquid, and inclination indicating means located within the vial to indicate the inclination of the surface.

2. A level as claimed in claim 1 , wherein the inclination indicating means comprises an air bubble formed in the liquid.

3. A level as claimed in claim 1 , wherein the inclination indicating means comprises a float that is buoyant within the liquid.

4. A level as claimed in claim 3, wherein the float comprise a sphere.

5. A level as claimed in any of the preceding claims, wherein the vial has two opposed raised hemispheroid surfaces and a curved equatorial periphery, and at least one of the hemispheroid surfaces and optionally at least part of the curved equatorial perimeter are visible when mounted in the housing.

6. A level as claimed in any of the preceding claims wherein positional markings are provided on the vial, and the position of the inclination indicating means relative to these markings gives an indication of inclination.

7. A level as claimed in claim 6, wherein the positional markings are printed or etched upon the inner or outer surface of the vial.

8. A level as claimed in claims 6 or 7 wherein the positional markings include a central mark at the pole of one or both hemispheroid surfaces.

9. A level as claimed in claim 6 to claim 8, wherein positional marking include edge marks disposed on the edge region of at least one hemispheroid surface in a region adjacent the equatorial perimeter.

10. A level as claimed in claim 9, wherein the edge marks are arranged at intervals of 15°, 30°, 45° or 90° around the equatorial perimeter.

11. A level as claimed in any of the preceding claims, wherein the housing may be located on the surface in at least two orientations, in a first orientation the equatorial plane of the oblate spheroid vial being generally parallel to the surface, and in a second orientation the equatorial plane of the oblate spheroid vial is generally normal to the surface.

12. A level as claimed in any of the preceding claims, wherein the housing is elongate and generally cubic in shape.

13. A level as claimed in claim 12, wherein the housing has elongate pairs of side faces and the housing may be located in different orientations on the surface by resting the housing on one or more of these faces.

14. A level as claimed in claim any of the preceding claims, wherein the degree of flattening in the oblate spheroid vial is at least 0.5.