GB2244665A

GB2244665A - Drill shaft and bit with compressed gas swarf clearance

Info

Publication number: GB2244665A
Application number: GB9019735A
Authority: GB
Inventors: Colin Edward Lawrence
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-02-23
Filing date: 1990-09-10
Publication date: 1991-12-11
Anticipated expiration: 2010-09-10
Also published as: GB9019735D0; GB2244665B; GB9004151D0

Abstract

The bit 11 of larger diameter is either releasably secured to the hollow shaft 10 by screwthreading, to allow worn bits to be replaced, or formed as part of the hollow shaft. The shaft is rotated by means of a drilling mechanism, ie electric drill. A sealed bearing 13 is connected to a compressed gas source. A releasably detachable clip or bracket 15, connects the sealed bearing on the drill shaft to the drill in order to prevent movement of the bearing when the drill shaft rotates during drilling. Gas is passed through the drill shaft and expelled at the bit during drilling, forcing swarf from the bore hole; the gas may be pulsed. <IMAGE>

Description

DRILL SHAFT AND BIT WITH COMPRESSED GAS SWARF CLEARANCE.

This invention relates to a drilling tool where swarf is cleared from the cutting head by means of compressed gas.

Conventional twist Drill bits are well known mechanical tools incorporating a cutting tip that cuts the face of the material to be drilled and a double spiral groove that transports swarf away from the cutting head and eventually out of the hole being cut or bored. Removal of swarf reduces friction between the bit and the walls of the bore hole, allowing drilling to continue.

This type of Drill bit is very limited in the length of the hole that it can drill. This is because the spiral which extends the full cutting length of the shaft, exerts friction on the bore hole wall and where long narrow diameter holes are being bored the friction will eventually exceed the mechanical strength of the shaft, causing it to snap.

Gun drills have largely overcome this problem by using a hollow shaft through which compressed gas or coollant fluid is passed. A "V" shaped slot is provided along the cutting length of the drill down which the cut swarf and compressed gas or cutting fluid is passed and eventually expelled from the hole. However Gun drills require heavy floor standing equipment to operate.

The present invention is capable of attachment to a portable hand held drilling mechanism as shown in figure 2 or an industrial drilling machine without direct modification to either.

According to the present invention there is provided a rotatable hollow shaft of a smaller diameter than the bit or cutting head. The cutting head may be releasably detachable or fixed and formed as part of the hollow shaft.

A sealed bearing is provided which is held stationary by a clip or bracket through which compressed gas can be transferred into the rotating shaft. The shaft is clamped in a drill chuck or similar and caused to turn. Compressed gas is allowed to escape from the end of the shaft at the cutting head. This creates turbulence to break up the swarf and expell it from the cutting head and down the outside of the shaft and out of the bore hole. Gas is supplied under pressure from a compressor or pressure vessel. A regulator may be provided in order to control the rate of air flow.

A pressure switch or valve allows the gas to be released into, or prevented from entering, the drill shaft.

In order to facilitate drilling the shaft is inserted into a drill chuck or similar, Figure 2, the sealed bearing is prevented from rotating with the shaft by means of a clip or bracket.

A pressure vessel or compressor (not shown) is attached by means of a pressure hose or tube to the sealed bearing via a valve, regulator and pressure switch (not shown).

The shaft is caused to turn and the compressed gas released by means of operating the valve and pressure switch.

Drilling occurs, Figure 3, when the bit is placed against the material to be cut and slight pressure exerted. The tip cuts the face of the material and compressed gas is released into the shaft. Gas is expelled at the bit, blowing cut material back down the bore hole on the outside of the shaft and out of the drilled hole. In order to drill long narrow holes it may be necessary to increase the shaft lengths in consecutive order as drilling progresses, in order that the shaft is adequately supported during drilling.

This maintains the accuracy of the hole being drilled and damps out oscillations in the shaft. A collett (not shown) may also be included to centralise the shaft in the hole being drilled, to increase accuracy. Various profiles of cutting tips are required to best suit the material being drilled.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which : Figure 1 - shows in plan the drill shaft with sealed bearing and bit in position.

Figure 2 - shows in perspective the drill shaft and bit inserted into an electric drill, with pressure tube attached, also bearing clip or bracket attached to drill and sealed bearing.

Figure 3 - Shows in cross section the bit drilling into a substance, the gas being caused to swirl around the drill bit flutes and expelling the swarf from the bore hole by means of compressed gas, passed through the drill shaft.

Referring to the drawing Figure 1, the drill shaft 10 comprises a hollow shaft of slightly smaller diameter than the bit 11. The bit is attached to the end of the shaft and secured for example by a male thread ground into the flutes and a female thread cut into the end of the shaft (not shown). The cutting head may also be welded, brazed to or forged from, the end of the shaft, with apertures formed for the gas to escape. The opposite end of the shaft is reinforced and stopped off 12. A sealed bearing is provided towards the rear end of the drill shaft, allowing sufficient shaft to lock into the drill chuck or similar and clear the bearing. The sealed bearing 13 is prevented from turning by means of a clip or bracket 15. A hole 16 is made in the shaft to allow compressed gas to enter through the bearing by means of a pressure tube 14. A pressure vessel or compressor (not shown) supplies compressed gas to the shaft and bit, via a valve and pressure switch (not shown) a regulator may be attached to control gas flow rates.

The gas may also be caused to pulse to further aid removal of swarf.

Claims

1. A drill shaft and bit with compressed gas swarf clearance comprising a rotatable hollow shaft and a fixed or detachable cutting head of larger diameter than the shaft. The detachable bit has means of releasably securing the drill bit to the shaft. There is a sealed bearing through which compressed gas can be passed into the hollow shaft and expelled at the drill bit or cutting head.

2. A drill shaft and bit with compressed gas swarf clearance, as claimed in claim 1, wherein gas passed through the hollow shaft and ejected at the drill bit causes swarf to be cleared away, simultaneously cooling the drill bit or cutting head.

3. A drill shaft and bit with compressed gas, swarf clearance, as claimed in claim 1 or claim 2, wherein the drill shaft is of a smaller diameter than the drill bit or cutting tip, reducing friction and allowing a deeper hole to be bored.

4. A drill shaft and bit with compressed gas swarf clearance, as claimed in claim 1, claim 2 or claim 3, wherein the differing diameter of the drill bit and shaft provide clearance for the expulsion of swarf from the bore hole.

5. A drill shaft and bit, as claimed in claim 1, capable of attachment to a portable drilling mechanism or industrial drilling machine, without direct modification to either.

6. A drill shaft and bit with compressed gas swarf clearance, as claimed in Claim 1, wherein the sealed bearing is held in a static position on the rotating shaft by means of a releasable clip or bracket.

7. A drill shaft and bit with compressed gas swarf clearance, as claimed in claim 1, where the bit can be detached from the hollow shaft, allowing worn bits to be replaced.

8. A drill shaft and bit with compressed gas swarf clearance, as claimed in claim 1 and claim 2, wherein the compressed gas expelled at the cutting head is caused to pulse to further aid swarf removal.

9. A drill shaft and bit with compressed gas swarf clearance substantially as described herein, with reference to figures 1-3 of the accompanying drawing.