GB2311028A - Drilling Machine - Google Patents

Abstract

A portable drilling machine comprises an electromagnetic base 12 from which a column 14 extends perpendicularly. An electric power drill 16 is slidably disposed on the column 14 by means of a slide 18 . An electrical cable 30 extends between a terminal block 32 on the column to a terminal box 34 on the drill 16. An intermediate portion of the cable is formed into a loop located between the power drill 16 and the column 14 and is protected with an articulated plastics cable carrier 50 which restricts the minimum radius into which the looped portion can be bent, thereby reducing the likelihood of damage to the cable as the power drill 16 is moved and removing the necessity for the power cable to extend externally from the column 14 to the power drill 16 which could otherwise be incorrectly used to handle the machine.

Description

DESCRIPTION DRILLING MACHINE The present invention relates to drilling machines and in particular, but not exclusively, to portable drilling machines for use, for example, in the in situ drilling of a hole in the flange faces or webs of steel beams or-railway tracks.

Portable drilling machines are well known and one type of such machines takes the form of a base having means for attaching it to the item to be drilled, a column extending generally perpendicularly from the base, a power drill slidably disposed on the column longitudinally thereof and means for advancing and retracting the power drill along the column.

The power drill is commonly either a petrol-driven drill or an electric power drill. Electric power drills are preferred in many circumstances because of their lighter weight which allows easier manipulation of the drilling machine and requires less support, if any, to keep the drilling machine in position.

In the case of electric power drills, it is necessary to connect a power cable from a control box (which usually forms part of the column) to the electric power drill. Since the power drill is movable along the column the electrical cable must be capable of taking into account such movement. This is usually achieved by looping a cable externally of the machine between the control box and the terminal contacts on the power drill.

Such drills suffer from a practical disadvantage in that, although a handle is usually provided to assist in the manipulation and handling of the drilling machine, the loop of cable formed externally of the drilling machine is often used to carry the drilling machine instead of the correct handle. Even if the external cable loop is protected by, for example, a protective sheathing, the sheer weight of the machine often causes one or both ends of the cable to become disconnected when the loop is used to carry the machine, thus requiring the drilling machine to be repaired.

One attempt to overcome the aforementioned disadvantage is disclosed in US 5415503, which discloses an enclosed power cable between the column and the power tool. Opposite ends of the cable are secured to a control box and to a power tool respectively and movement of the power tool is permitted by disposing a looped intermediate portion in a space between the housing and the electric motor. As the power tool is advanced and retracted along the column the cable is drawn out of, or pushed back into, its space, thereby supplying electrical power to the drill whilst permitting movement of the drill with respect to the base, without the need for an extemally-looped power cable.

Although the arrangement of US 5415503 avoids the need for an external cable loop which might be used to handle the machine, the location of an intermediate portion of the cable in an intermediate chamber between the column and the drilling machine can in itself cause problems. It will be noted from Fig. 1 of US 5415503 that the cable is formed into two tight loops in a very short space. As the electric power drill is advanced and retracted along the column such tight loops of the cable will cause damage to the cable very quickly, thus requiring repair and rewiring of the equipment.

It is an object of the present invention to provide a drilling apparatus which overcomes the problems associated with the prior art.

According to the present invention, a portable drilling machine comprises a base, means for attaching the base to an article to be drilled, a column extending from the base, an electric power drill slidably mounted on the column and means for adjusting the position of the power drill with respect to the column, the drilling machine further comprising a cable extending between a terrninal block on the column and the drill motor, and comprising an intermediate portion enclosed between the column and the power drill and formed into a loop sheathed by a cable protector which restricts the bending of the looped portion By providing an intermediate portion of the cable with a flexible sheath the curvature of the portion of the cable between the fixed terminal block and the movable power drill can be controlled to a minimum value at which flexing of the cable does not result in damage to the cable.

Preferably, the looped intermediate portion of the cable lies in a recess formed between the column and a portion of the power drill, e.g. a slide by means of which the power drill is mounted on the column.

In one embodiment, the flexible cable carrier comprises an articulated cable carrier comprising a plurality of hinged, interconnected cable carrier portions. Alternatively, the cable carrier may comprise, for example, a flexible plastics tube having a wall which is undulating in cross-section to increase its flexibility.

In one embodiment, the base comprises an electromagnet for securing the machine to the article to be drilled.

By way of example, a specific embodiment of the present invention will now be described, with reference to the accompanying drawings, in which: Fig. 1 is a side elevation, partly in cross-section, of an embodiment in drilling machine in accordance with the present invention; and Fig. 2 is a view, partly cut away, looking in the direction of arrows II - II of Fig. 1.

The drawings show a drilling machine in accordance with the present invention which comprises a base 10 in the form of a rectangular electromagnet with a planar lower face 12 and a column 14 extending generally perpendicularly to the base 12. An electric power drill 16 is slidably mounted on the column 14 by means of a slide 18 on the column 14 and has a drill spindle 20 for supporting at its free end a drill bit (not shown). The spindle is guided for linear movement by means of a support bracket 22 secured to the base 12. The electric power drill 16 is movable along the column by means of a conventional rack and pinion arrangement which is operated by means of a handwheel 24 (illustrated in chain dot). The column 14 is also provided with a carrying handle 26.

The column 14 incorporates a control box 28 having on/off buttons on its side and an electrical cable 30 for powering the electric drill 16 leads from a terminal block 32 within the control box 26 to a motor terminal box 34 on the power drill. One end of the cable adjacent the terminal block is secured in position by means of a cable clamp 36 secured to the column 14 and the cable then passes through a plastics bush 38 in an aperture 40 in the column wall.

As best illustrated in Fig. 2, an intermediate portion of the cable, enclosed in a recess formed between the column 14 and the slide 18 of the power drill 16, is formed into a loop. The loop passes through an articulated plastic cable carrier 50 which has one end secured to the slide 18 by means of a bracket 48, the other end is secured to the column 14, a suitable cable carrier being that manufactured by IGUS. The cable carrier has a first straight leg 42 extending downwardly from where it is attached to the column, a looped portion 44 and a second straight portion 46 extending upwardly from the loop 44. The cable carrier is essentially in the form of a hollow chain having plurality of hollow hinged links 52 which, when joined together form a continuous passage for the cable but which, as best seen in Fig. 2, ensure that the looped intermediate portion of the cable is always folded into a looped portion having a certain defined minimum radius of curvature, the radius of curvature being chosen to ensure that damage to the cable will not occur when the cable flexes.

In use, the base 10 is placed on a metallic article to be drilled and is secured thereto by actuating the electromagnetic base. A suitable drill bit (for example an annular hole cutter such as that described in GB-A1403041) is secured to the drill spindle 20 and the position of the power drill 16 on the column 14 is adjusted to form the desired aperture in the article. As the position of the drill is adjusted with respect to the column, the looped intermediate portion of the cable is moved up and down with the power drill but the articulated plastics casing 50 ensures that the looped portion of the cable cannot assume a radius below a certain minimum. As the power drill is moved upwardly from the lowermost position as illustrated in Fig. 1, the arcuate portion of the articulated carrier 50 and the cable therein moves upwardly with substantially the same radius of curvature. In this way, wearing of the cable, even after repeated flexing due to the longitudinal displacement of the drill in both directions, can be effectively prevented.

More importantly, it will be noted that, in contrast to the prior art, the cable does not extend externally between the terminal block and the electric power drill in the form of a loop. Thus, there is no loop of cable which can be (incorrectly) used as a carrying handle and the users of the machine will be forced to use the handle 24 extending from the column, thereby greatly reducing the requirement for repair or replacement of the cable.

Although the cable protector has been illustrated and described with reference to an articulated flexible, plastics cable carrier, other cable protectors can be used, so long as they ensure that the cable cannot be bent to a radius small enough which would result in damage to the cable upon repeated flexing. For example, the cable protector may be in the form of a flexible plastics tube whose wall has a corrugated cross-section which will allow the cable to be bent into a loop, but only of a certain minimum radius.

The invention is not restricted to the details of the foregoing embodiment.

Claims (8)

1. A portable drilling machine comprising a base, means for attaching the base to an article to be drilled, a column extending from the base, an electric power drill slidably mounted on the column and means for adjusting the position of the power drill with respect to the column, the drilling machine further comprising a cable extending between a terminal block on the column and the drill motor and comprising an intermediate portion enclosed between the column and the power drill and formed into a loop sheathed by a cable protector which restricts the bending of the looped portion.

2. A drilling machine as claimed in claim 1, wherein the looped intermediate portion of the cable lies in a recess formed between the column and the power drill.

3. A drilling machine as claimed in claim 2, wherein the power drill is provided with a slide member for mounting the power drill on the column, the recess being formed between the slide portion and the column.

4. A drilling machine as claimed in any of claims 1 to 3, wherein the cable protector restricts the minimum radius into which the looped portion of the cable can be bent.

5. A drilling machine as claimed in any of claims 1 to 4, in which the cable protector comprises an articulated plastics cable carrier.

6. A drilling machine as claimed in claim 5, wherein the cable carrier comprises a plurality of hollow, hinged links.

7. A drilling machine as claimed in any of claims 1 to 6, wherein the means for securing the base portion to the article to be drilled comprises an electromagnet.

8. A drilling machine substantially as herein described, with reference to and as illustrated in, the accompanying drawings.