BURR

Abstract

The present invention provides a burr in the form of a generally cylindrical rod, the burr having a proximal end for mounting in a tool for rotating the burr and a distal cutting end, the burr having a cutting portion defined by a portion of a surface of the burr which comprises a plurality of teeth, the cutting portion including and extending from the distal end back towards the proximal end, wherein the cutting portion comprises a cylindrical portion of a first diameter and a distal end portion of a second diameter that is greater than the first diameter. The burr is particularly suited to the drilling of cylinder locks.

Claims

1. A burr in the form of a generally cylindrical rod, the burr comprising: a proximal end for mounting in a tool for rotating the burr; a distal cutting end; and a cutting portion defined by a portion of a surface of the burr which comprises a plurality of teeth, the cutting portion including the distal cutting end and extending from the distal cutting end back towards the proximal end; wherein the cutting portion comprises a cylindrical portion of a first diameter and comprises a distal end portion having a second diameter that is greater than the first diameter.

2. The burr as claimed in claim 1, wherein the cutting portion extends from the distal end to a shaft portion that is devoid of teeth, and the shaft portion extends to the proximal end.

3. The burr as claimed in claim 2, wherein the shaft portion has a diameter that is equal to the first diameter.

4. The burr as claimed in claim 2, wherein the shaft portion has a diameter that is greater than the first diameter.

5. The burr as claimed in claim 1, wherein the distal end portion of the cutting portion is teardrop shaped.

6. The burr as claimed in claim 1, wherein the distal end portion of the cutting portion has a length that is less than 0.2 times a length of the cylindrical portion of the cutting portion

7. The burr as claimed in claim 1, wherein the burr is formed solely from a single tungsten carbide rod.

8. The burr as claimed in claim 1, wherein the distal end portion of the cutting portion has a ball end having a hemispherical profile.

9. The burr as claimed in claim 1, wherein the cutting portion extends more than 25 mm from the distal end.

10. The burr as claimed in claim 1, wherein the second diameter is between 1.08 and 1.12 times greater than the first diameter.

11. The burr as claimed in claim 1, wherein the first diameter is between 2.8 mm and 3.2 mm.

12. The burr as claimed in claim 1, wherein the first diameter is between 5.7 mm and 6.3 mm.

13. The burr as claimed in claim 1, wherein the burr is between 55 mm and 65 mm in length.

14. The burr as claimed in claim 1, wherein the burr is formed from tungsten carbide.

15. A method for fabricating a burr according to claim 1, the method comprising: grinding a single tungsten carbide rod, to form a blank having a cylindrical portion of the first diameter from which the cylindrical cutting portion is formed; and grinding the single tungsten carbide rod to form a distal end portion having a second diameter that is greater than the first diameter, from which the distal end cutting portion is formed.

16. The method of claim 15, further comprising cutting a plurality of teeth into the single cylindrical portion to form the cylindrical cutting portion and cutting a plurality of teeth into the distal end portion to form the distal end cutting portion.

17. A method of drilling a pin cylinder lock using a burr as claimed in claim 1.

18. The method of claim 17, comprising drilling into the pin cylinder lock in an axial direction along a line parallel to a line of pins of the pin cylinder lock and subsequently moving the burr laterally to form a slot in a region of the pins and aligned with the pins.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Three embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, of which:

[0041] FIG. 1 illustrates the principle components of a cylinder lock;

[0042] FIG. 2 is a perspective view of a 3 mm burr in accordance with a first embodiment of the present invention;

[0043] FIG. 3 is a side elevation of a blank from which the burr of FIG. 2 is to be formed;

[0044] FIG. 4 is a side elevation of the burr of FIG. 2;

[0045] FIG. 5 is a view of the distal end of the burr of FIGS. 2 and 4;

[0046] FIG. 6 is a perspective view of a 6 mm burr in accordance with a second embodiment of the present invention;

[0047] FIG. 7 is a side elevation of a blank from which the burr of FIG. 6 is to be formed;

[0048] FIG. 8 is a side elevation of the burr of FIG. 6;

[0049] FIG. 9 is a view of the distal end of the burr of FIGS. 6 and 8;

[0050] FIG. 10 is a perspective view of a 3 mm burr in accordance with a third embodiment of the present invention;

[0051] FIG. 11 is a side elevation of a blank from which the burr of FIG. 10 is to be formed;

[0052] FIG. 12 is a side elevation of the burr of FIG. 10;

[0053] FIG. 13 is a view of the distal end of the burr of FIGS. 10 and 12; and

[0054] FIGS. 14A to 14D illustrate one way in which a burr in accordance with any of FIG. 2, 6 or 10 may be used to drill the cylinder lock of FIG. 1.

[0055] All dimensions shown in the figures are in millimeters.

DETAILED DESCRIPTION

[0056] The known cylinder lock of FIG. 1 and the working thereof, has previously been described in the introduction of the present specification.

[0057] Referring now to FIG. 2, a burr 13 in accordance with the present invention is illustrated which may be used to drill the cylinder lock of FIG. 1, as described later with reference to FIGS. 14A to 14D. The burr 13 is formed of tungsten carbide and is in the form of a rod having a proximal end 14 and a distal end 15. A plurality of cutting teeth 16 extend from the distal end 15 to approximately half way along the burr and these define a cutting portion 17a, 17b of the burr 13. The remaining portion of the burr 13 does not have teeth formed on it and this forms an engagement portion 18, to engage with a chuck, or similar, of a tool such as a DREMEL rotary machine, a similar rotary tool or die grinder, which typically will rotate the burr at speeds in the range of 25,000 to 30,000 rpm.

[0058] The burr 13 of FIG. 2 can be formed by grinding a 3.3 mm diameter rod of tungsten carbide into a blank 19, as illustrated in FIG. 3.

[0059] The blank 19 comprises a cylindrical portion of 3 mm diameter which forms a first portion 17b of the cutting portion 17a, 17b and the engaging portion 18. Towards the distal end 15 the rod is machined to form an outwardly tapered portion 20 and a hemispherical distal end 21 of the blank 19, the tapered portion 20 and hemispherical distal end 21 forming a generally tear drop shape having a maximum diameter of 3.3 mm. Once the blank 19 of FIG. 3 has been formed, the cutting teeth 16 are then cut into this, as illustrated in FIGS. 4 and 5, to produce the burr as illustrated in FIG. 2.

[0060] Referring now to FIGS. 6 to 9, these figures correspond to the views shown and described previously with reference to FIGS. 2 to 5, but in FIGS. 6 to 9 a burr 22 having a maximum diameter of 6.6 mm is illustrated. Except for the dimensions, the burr 22 is identical to the burr 13 of FIG. 2 and is formed in exactly the same manner, here the blank 23, illustrated FIG. 7 being ground from a tungsten carbide rod having a diameter of 6.6 mm.

[0061] FIGS. 10 to 13 are views which again correspond to the views of FIGS. 2 to 5, but these illustrate a burr 24 formed from a blank 25 having the dimensions illustrated in FIG. 11, to form the burr 24 with a cutting portion 26 having the same dimensions as the cutting portion 17a, 17b of the burr 13 of FIG. 2. However the burr 24, illustrated here with reference to FIGS. 10 to 13, has an engaging portion 27 of 6 mm diameter, to enable it to engage with a standard chuck, or similar, of a die grinder or similar device. Apart from this, the burr 24 and the manner of forming it is the same as that previously described with reference to FIGS. 2 to 5 and FIGS. 6 to 9.

[0062] Referring now to FIGS. 14A to 14D, there is illustrated a method by which the burr 13 of FIG. 2, (or any of the burrs 22 or 24 illustrated in FIGS. 6 and 10 respectively), may be used to drill the cylinder lock of FIG. 1.

[0063] Referring to FIG. 14A, the burr 13, rotated at between approximately 25,000 and 30,000 rpm, is inserted axially in the direction of arrow 28 until it passes below the first of the bottom pins 9. It is then raised vertically in the direction of arrow 29 and this movement is continued, as represented by arrow 30 in FIG. 14B, until a large enough slot is created for both the first bottom pin 9 and the first top 5 to be released by the burr 13 and ejected from the lock 1.

[0064] A significant point to note here is that, unlike with previous methods, the manoeuvrability provided by the burr 13 having a larger diameter distal end, enables significant sideward pressure on the burr 13 to be applied without fear of the burr 13 snapping by becoming misaligned. Thus a locksmith may be relatively aggressive in using the burr 13, enabling large amounts of material to be cutaway relatively swiftly. This in turn provides a larger space which will often result in the bottom pin 9 and top 5 being ejected from the lock 1, rather than having to be drilled through, although the burr 13 will drill through these pins if they should remain lodged in position or if it is desired to drill along the shear line in the conventional manner.

[0065] With reference now to FIGS. 14C and 14D, the burr 13 may now be advanced stepwise in a manner represented by the arrows 31 to 34, until the shear line is drilled and/or all the bottom pins 9 and top pins 5 have been removed, allowing the plug 7 to rotate in the cylinder 6.

[0066] How the burr 13 is used to attack the lock 1 may depend on the preference of the locksmith and also the features of the lock, for example anti-drill devices fitted in a lock may be encountered and may tend to deflect the burr 13.

[0067] Thus although the burr 13 may be used in the manner previously described with reference to FIGS. 14A to 14D, alternatively the burr could be used in the manner of a conventional device to drill straight along the shear line, the clearance provided behind the distal head of the burr making it far easier to use the burr to drill a single hole, requiring far less pressure than with known devices.

[0068] As a further alternative example, the burr may be used to drill all the way in through the path of least resistance, following a line a key would follow beneath the bottom pins 9. This may be particularly easy for the burr 13 will automatically centre itself on the recess (not shown) which is normally provided on the first end 10 of the plug 7, to in normal use guide the key into the slot in the plug 7. Once fully inserted the burr may then be moved laterally (vertically as shown in FIGS. 14A to 14D), to then free or destroy all of the pins 9, 5. The burr may also find applications other than for the drilling of cylinder locks.

[0069] Three embodiments of a burr in accordance with the present invention have been described above. However, it will be realised that many additional embodiments are possible within the scope of the following claims.