Field of the Invention The invention relates to a device that indicates to the operator when a drilled hole has reached a pre-determined depth in the drilled material.

Background of the Invention Simple mechanical depth-gauges are commonly supplied with electric hand-drills and can be used to pre-set the depth of a drilled hole. Typically they use an adjustable rod that projects toward the work-piece in the same axis as the drilling- tool and in use the rod is backed-off a set distance from the work-piece surface equivalent to the depth of hole required. They have disadvantages in that the rod's point of contact with the work-piece is off-set from the point of drilling so will only give a true indication of hole-depth if the work-piece is perfectly flat and perpendicular to the drilling-tool, and due to the off-set point of contact they are not suitable for use when drilling angled holes and are difficult to use in tight corners or areas of limited space. Other drilling-depth indicators have been disclosed that use a non-contacting method of distance measurement to determine the distance between the drilling machine body and the work-piece by using ultrasonic, optical or other electronic systems, which can determine any change in distance between the drilling machine body and the work-piece due to the drilled hole depth. These systems require the measurement signal to be bounced from the work-piece surface so will be inaccurate if the work-piece surface is small, curved or un-even or in a corner where adjacent surfaces can interfere.

Another disclosed method is to mark the actual drilling-tool body with annular grooves or coloured rings during manufacture which correspond to pre-determined hole depths. These types of drilling-tools are used when drilling a blind hole in bone or teeth. The depth markings are not able to be changed or adjusted by the operator so have limited use in general industry where hole-depths will vary according to the type and size of fixture or fitting.

In some circumstances it is important that a hole is not drilled too deeply, for example in a concrete floor where a damp-proof-membrane could be holed by the drill. In the construction industry, drilling over-deep holes wastes time and increases wear on the drilling-tool and drilling machine.

It is the object of this invention to provide a visual drilling-depth indicator that indicates the drilling-depth on the actual drilling-tool so is clearly visible to the operator during the drilling operation and can be used on irregular work-pieces and for drilling angled holes, and uses a method that does not require contact with the work-piece surface so can be used in confined areas or anywhere that a hole can be drilled.

Disclosure of the Invention

Accordingly, this invention provides a drilling-depth indicator, that includes a light- emitting device a power-source and control switch attached to the body of a hand- operated drill, that projects a visual reference mark on a drilling-tool at a pre-set distance from a drill-tip equal to the required hole-depth, in use the reference mark advances towards the work-piece surface during the drilling operation and when coinciding with the surface of the work-piece indicates that a pre-determined hole- depth has been achieved.

Preferably the light emitting device is a laser that produces a light-beam in the visible-light spectrum and has a focusing element that shapes the projected laser- beam into a small dot or other shape that produces a clearly visible and defined mark on the drilling-tool, but it may also be a focused bulb or light-emitting-diode (LED) or a semi-conductor device that transmits a light-beam down an optical fibre. The colour of the light-mark may be varied to give optimum visibility according to the operating conditions.

It is also preferable that the light-emitting device is mounted on the actual drilling machine body, but will function equally well if mounted on or in a removable part of a drilling-machine such as a side steadying handle, or a collar or strap that is clamped to the drilling machine body, or attached to the drill body by a temporary method such as a Velcro (RTM) or an adhesive patch or in the case of iron-cased drilling machines by a magnetic clamp, provided it stays in alignment with the drilling-tool during the drilling process. The above summary of the present invention is not intended to represent each embodiment or every aspect of the present invention. The detailed description and Figures will describe many embodiments and aspects of the present invention.

Brief Description of the Drawings

The forgoing and other advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings.

FIGURE 1 shows a side view of a hand drilling machine and drilling-depth indicator.

FIGURE 2 shows a hole drilled to a pre-set depth.

FIGURE 3 shows an alternative arrangement of projecting the laser-beam onto a drilling-tool.

While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

Best Mode for Carrying Out the Invention With reference to Figure 1, a laser pointing module (1) is mounted by a pivot point on the body of a hand drilling machine (2) such that its emitted light-beam (3) is axially aligned to project a moveable visible reference mark on the surface of the drilling-tool (4) at a pre-set position (5). The laser pointing module is powered by the battery (7) via the on-off switch (6). If the distance between the projected light-mark (5) and the drill-tip (8) is set to be equivalent to the depth of the hole required (9), a visual indication that the pre-set hole depth is achieved when the projected light- mark on the drilling-tool coincides with the surface of the drilled work-piece (10) as shown by Figure 2. The rotation of the drilling-tool does not affect the visibility of the light-mark. By rotating the body of the laser pointing device about its pivot point, the included angle between the drill axis and the laser beam (11) is altered, and the visible reference mark (5) is moved along the body of the drilling tool (4) to allow setting for other hole depths.

The rotational movement of the laser pointing module (11) can be coupled to a rotary encoding device (12) and the resultant electrical signal used as an input to a computing device such as a micro-processor (13) which is programmed to convert the angular rotation into a linear measurement. As the distance between the axis of the drilling-tool and the laser pivot point is pre-determined by the design of the laser mounting mechanics it is a known value, by using the measured angle 11 any distance along the drilling-tool can be calculated using a Tangent trigonometric formula as it represents the third side of a right-angled triangle. The resultant value can be shown on an LED or LCD display (14) for direct read-out of the hole setting depth.

In the embodiment previously described the laser light-beam is projected directly at the drilling-tool, and the body of the laser pointing device is moved to vary the position of the light-mark on the tool-body, but for equal effect, the beam of the laser pointing device could be projected towards an inclined mirror or lens (15) which reflects or deflects the light-mark towards the drilling-tool, as depicted in Figure 3. If the mirror or lens is rotated about its mounting point the light-mark is moved along the drilling-tool, and if the mirror or lens is moved linearly closer to, or farther from, the light-emitting device, the light-mark is similarly moved along the body of the drilling-tool body. There is an advantage in a linear movement in that the hole-depth can be read as a direct linear measurement without the need of angular to linear conversion. This linear movement can be sensed and connected to an analogue-to-digital converter for input to the computing device and visual display. A set-zero switch would be beneficial in setting the drilling-depth from the display by using the following procedure;

Firstly, the light-beam is projected to the drill-tip and the display set to zero by the switch; Secondly, the light-mark is backed-off along the drilling-tool to the required distance that can be read-off the display in direct units, for example inches or millimetres. With reference to Figure 3, if the mirror (15) is continuously rotated as the laser beam is pulsed at pre-set timing intervals any number of visual reference marks can be projected onto the drilling-tool, these could be timed to produce a number of visible marks, or graduations on the surface of the drilling-tool and so give a direct indication of drilling-depth as the drilling process proceeds.