This invention relates to a drill level attachable to a portable power drill or drill press which will enable a user to readily identify whether the drill has a vertical axis of rotation or a horizontal axis of rotation.

BACKGROUND OF THE INVENTION

Drill levels are old and well known and have been attached to portable drills in various ways, but most drills are made without drill levels even though there is frequently a need for a drill level which will assist an operator to know the orientation of the drill.

Examples of earlier proposals of drill levels exist in the prior art, including:

Australian patent application 58068/80 Breeden which described a curved tube contained within a drill housing near the handle end, and a domed container at the handle end, both incompletely filled with liquid;

Australian petty patent 21402/88 Taylor and O'Reilly, which utilised a disc located in or on the drill housing, hanging as a pendulum, and forming part of an electronic indicator assembly;

Australian patent 243299 Matejicek, which utilised a bracket attached to a drill housing which carried on it a hemispherical level chamber; and

Australian patent 424519 Krebs, which also utilised a hemisperical level chamber attached to a drill housing.

One of the problems previously encountered has been the need to have a sight surface which has a large radius of curvature

in the "bubble" type of drill level so that a reasonable degree of accuracy can be achieved. Another related problem is the need to maintain the drill level to a very small size so that it will not excessively limit the capacity of a drill to enter a confined space. Still further, there is a need for a quickly attachable drill level which can be normally not used but quickly attached to a drill when its use is required, thereby reducing the danger of damage to the level when it is inappropriate for its use.

BRIEF SUMMARY OF THE INVENTION

In this invention a drill level has a resilient clamp portion by which it can be located over and carried by a bearing boss on a drill, and a limb on the clamp portion carrying a transparent sight container containing liquid and a bubble which can be viewed through a side wall of the container when the drill is horizontal or an end wall when vertical.

More specifically, the invention consists of a drill level having a resilient clamp portion of size to be poεitionable over a bearing boss of a portable power drill, a limb on the clamp portion, a sight container carried by the limb and having a curved side wall and a convex end wall both said walls being of transparent material, the container being partially filled with liquid but having a bubble visible through a respective said wall when that wall extends through a horizontal plane.

With this arrangement even though the size can be kept very small, nevertheless the radius of curvature both of the side and end walls of the container can be quite large so that a high degree of accuracy can be readily achieved. Further, since the clamp is only a resilient clamp the level attachment can be readily applied to or removed from the drill bearing boss. In this regard it may be noted that many

drills are made to a standard diameter of drill bearing bosses so that various attachments can be utilised by way of accessories, and therefore one drill level in accordance with this invention is adaptable to a large number of portable drills.

DETAILED DESCRIPTION OF THE DRAWINGS

An embodiment of the invention is described hereunder in some detail with reference to and as illustrated in the accompanying drawings in which

Fig. 1 is a perspective view showing a drill level mounted on the small portable power drill;

Fig. 2 is a front view of the drill level drawn to a larger scale;

Fig. 3 is a side view corresponding to that of Fig. 1; and

Fig. 4 is a top view of Fig. 1.

In this embodiment a portable drill 10 iε provided with a bearing boss 11 having a diameter which may be termed a "standard diameter". Being a "standard diameter", the accessory herein described can be used on other drills.

A drill level 12 comprises a discontinuous resilient clamp portion 13, rendered discontinuous by abutting walls 14, the inner part of clamp portion 13 being curved with a radius R which is a little smaller than the radius of the bearing boss 11 so that the drill level grips the bearing boss when the clamp is engaged around it. Desirably there is sufficient resilience in the clamp portion for it to fit a range of sizes without alteration, or with a minimum of adaptation devices. The abutting walls 14 are at the ends of

outwardly diverging flanges 15 which facilitate positioning of clamp portion 13 on the boss 11, by opening the space between limbs 16.

Resilient clamp 13 has a pair of said limbs 16 which converge outwardly and terminate in a sight container 17 which is generally cylindrical and extends at right angles to limbs 16, and aε shown in Fig 1, extends laterally displaced from but parallel to the axis of rotation of the drill 10. The εight container 17 haε transparent wallε which include a εide wall 19 which iε generally circular in croεε-section and convexly curved in the side view of Fig 3. Container 17 iε partially filled with liquid so that a bubble 20 is readily distinguishable when the side wall 19 is generally horizontal aε in Fig. 3. Grooveε 21 provide datum marks to facilitate reading of the position of bubble 20.

The end of the sight container 17 is a transparent end wall 23 which is outwardly convex, and has a marker ring 24 which assists in reading of the portion of bubble 20 when the drill chuck is oriented vertically.

In both instances, there is a convex outer surface having a very large radius of curvature so that the sensitivity of the level is not impaired by its small εize.

If it is required to check for vertically up and vertically down drilling, the clamp 13 may simply be reversed in direction, or alternatively each transparent end wall 23 can be outwardly convex. In order to facilitate identification of vertical when drilling upwardly, a ball 26 is contained within the sight container, the ball being denser than the liquid, and smaller in diameter than the εight container so that it occupies a central position on the inner surface of the transparent end wall 23 only when the container is inverted and vertical.

Although the invention will be seen to be particularly simple, nevertheless it results in a useful and valuable accesεory for a portable tool. It is of course also usable in a drill press.