DISC BRAKE LOCKS

The invention relates to disc brake locks.

A known disc brake lock comprises a U-shaped body having first and second interconnected limbs defining a slot for receipt of an edge of a brake disc. The first limb includes a chamber containing an alarm system and a locking pin is provided that is movable between a locked position in which the pin extends across the slot and, in use, through a hole in the brake disc and in an inoperative position to allow the lock to released from the disc. The alarm system sounds an alarm if there is an attempt to tamper with the lock. In some embodiments the chamber includes an aperture closed by a removable cover through which the alarm system is inserted into the chamber. Since the first link contains the alarm system, it is deeper than the second limb. In use, therefore, the first limb is arranged between the disc and an associated wheel and the first limb is exposed on the outer surface of the disc. This means that the cover is exposed and is vulnerable to attack to disable the alarm system.

According to a first aspect of the invention, there is provided a disc brake lock comprising a U-shaped body having first and second interconnected limbs defining a slot for receipt of an edge of a brake disc, the first limb containing an

alarm system and the second limb including an aperture closed by a removable cover through which the alarm system is inserted into the first limb, a locking pin being provided that is movable between a locked position in which the pin extends across the slot and, in use, through a hole in a brake disc, and an inoperative position to allow the lock to be released from the disc.

By inserting the alarm system through the second limb, greater security can be achieved.

According to a second aspect of the invention, there is provided a disc brake lock comprising a U-shaped body having first and second interconnected limbs defining a slot for receipt of an edge of a brake disc, the first limb including a chamber containing an alarm system, a locking pin being provided that is held by one limb to engage with the other limb to resist movement of the pin away from a locked position the pin being movable between the locked position in which the pin extends across the slot and, in use, through a hole in a brake disc into said engagement with said other limb, and an inoperative position to allow the lock to be released from the disc.

In other embodiments of the known disc brake lock, the pin is formed in multiple parts. This makes the pin weak to attach.

According to a third aspect of the invention, there is provided a disc brake lock comprising a U-shaped body having first and second interconnected limbs defining a slot for receipt of an edge of a brake disc, the first limb containing an alarm system, a locking pin being provided that is movable between a locked position in which the pin extends across the slot and, in use, through a hole in a brake disc, and an inoperative position to allow the lock to be released from the disc, the locking pin being held by one limb and being held against removal from said limb by engagement between the pin and the limb.

According to a fourth aspect in the invention, there is provided a wheellock combination in which the wheel carries a brake disc for rotation therewith and lying in a plane parallel to the plane of the wheel and to one side of said wheel plane, and a lock according to any one of the first, second and third aspects of the invention with the disc in the slot and the second limb located between the disc and the wheel, so preventing access to the cover.

The following is a more detailed description of an embodiment of the invention, by way of example, reference being made to the accompanying drawings in which:-

Figure 1 is a cross section through a disc brake lock,

Figure 2 is an exploded view of the disc brake lock of Figure 1 from above, and

Figure 3 is an exploded view of the disc brake lock of Figures 1 and 2 from beneath, and

Figure 4 is a sectional view through a cylinder lock and a co-operating hole of a second limb of the disc brake lock of Figures 1 to 3, a retracted position of a locking pin of the cylinder lock being shown in full line and an extended position being shown in broken line.

Referring to the Figures, the lock comprises a U-shaped body having first and second limbs 11, 12 defining a slot 13 therebetween. The first limb 11 contains an alarm system 14 and also carries a cylinder lock 15 and a locking pin 16. The second limb 12 has an aperture 17 closed by a removable cover 18. The second limb 12 also includes a hole 19 for receiving an end of the locking pin 16.

The body 10 may, for example, be formed of stainless steel. The body 10 is a single casting to provide the first and second limbs 11, 12. The body 10 has first and second U-shaped side walls 20, 21 that meet at one end at a rounded end 22 of the first limb 11 and a rounded end 23 of the second limb 12. A

generally U-shaped top cover 24 extends between the outer edges of the first and second side walls 20, 21. The inner edges of the first and second side walls 20, 21 are connected by respective first and second parallel spaced surfaces 25a, 25b that define the slot 13.

The end of the first limb 11 is formed with a circular cross section tube 26 having an axis lying in a plane normal to the plane of the slot 13. The cylinder lock 15, which will be described in more detail below, is held in the tube 26. The locking pin 16 is co-axial with the cylinder lock 15 and in the operative position shown in Figure 2, extends into the hole 19 that is co-axial with the tube 26.

The first limb 11 is thus formed with a first chamber 28 that is defined between the first and second sidewalls 20, 21, the top cover 24, the inner wall 25 and the tube 26. The first chamber 28 is open around the base of the body 10 between the first and second limbs 11, 12 and leads into a second chamber 29 provided in the second limb 12. The second chamber is also defined between the first and second sidewalls 20, 21 the top cover 24 and the inner wall 25. The aperture 30 is formed in the top cover 24 over the second chamber 29, (see Figure 3). The aperture 30 has a narrower end wall adjacent the hole 24 and a longer end wall 32 adjacent the base of the body 10. The narrower end wall 31

is provided with a passage 33 extending into the hole 19 in a direction normal to the axis of the hole 19. The purpose of this passage 33 will be described below.

The longer end wall 32 is provided with two spaced peg holes (not shown). The purpose of the peg holes will also be described below.

The removable cover 18 is generally rectangular and is sized to fit the aperture 17. The cover 18 has a shorter end edge 35 and a longer end edge 36. The shorter end edge 35 carries a pin 37 that projects from the shorter end edge 35 and can be retracted against the action of a spring 39 into a housing 38 provided on the cover 18. The longer end edge 36 carries a pair of projecting pegs 40 (see Figure 3). The pegs 40 fit into the peg holes (not shown) and the cover 34 can then be swung into a position where the pin 37 is retracted by contact against the narrower end wall 31 of the aperture 30 before being urged by the spring 39 into the passage 33, as seen in Figure 1. In this position, there is nothing on the first and second side walls 21 or the top cover 24 that allows the cover 18 to be removed. The importance of this will be described below.

The alarm system 14 comprises a mounting plate 41 that carries an electronics module 42 with a power supply 43. The electronics module 42 includes a

contact plate that extends through a hole in the inner wall 25 (see Figure 1). The alarm system 14 is of the type that provides an audible alarm when the alarm is set and the lock is moved. The details of the alarm system 14 are known and will not be described in any further detail.

The alarm system 14 is inserted into the body 10 through the aperture 30 with the cover 34 removed. It passes around the base of the body 10 until the alarm system 14 is received within the first chamber 28, as seen in Figure 1. It is held in position by a screw 45 that extends through the mounting plate 41 and engages into a threaded aperture 46 in the top cover 34. After the alarm system 14 has been located and fixed, the cover 34 is replaced as described above.

The tube 26 that holds the cylinder lock 15 terminates at its inner end in an inwardly directed flange 50 defining a hole through which the locking pin 16 projects. A cylinder lock 15 has a barrel 51 that holds the locking pin 16 and has a key operated locking mechanism 52. The barrel 51 is urged partially out of the body 10 (to the position shown in Figure 2) by a spring 48 (see Figure 1) acting between the flange 50 and an annular rib 53 on the locking pin 16.

When the barrel 51 is in the position shown in Figure 2, the locking pin 16 is retracted into the tube 26 in the first limb 11. When the barrel 51 is depressed

against the action of the spring 48, the locking pin 16 is moved across the gap 13 and into the hole 19 in the second limb 12. The locking pin 16 is formed with a T-shaped head 55 (Figure 4) that passes two diametrically opposed lugs 56 projecting inwardly of the hole 19. Once past the lugs 56, rotation of the key 47 rotates the locking pin 16 until the arms of the T-shaped head 55 of the locking pin 16 engage behind the lugs 56, against which the head is held by the spring 48. In this way, the locking pin resists the lock being broken by forced separation of the first and second limbs 11, 12.

In addition, the locking pin 16 is shaped so that it cannot be pulled from the limb 11. This is an added security feature. Further, the locking pin 16 is made in one piece from machined steel so that it cannot be disassembled. This is a further security feature.

Moving the cylinder lock 15 to the operative position shown in Figure 1 sets the alarm system 14. The reverse movement of the cylinder lock 15 back to the inoperative position seen in Figure 3, disables the alarm system 14.

The lock described above with reference to the drawings is for use on the disc of a disc brake, usually the disc brake of a motorcycle. Such a brake comprises a disc that is carried by a wheel and is co-axial with the wheel and to one side

of the wheel. The disc lies in a plane parallel to the plane of the wheel. The disc rotates with the wheel and cooperates with a calliper device that, on operation, clamps brake pads against the disc to slow or stop rotation of the wheel. The disc is provided with a number of angularly spaced holes inwardly of the outer edge of the disc.

The edge of the disc is inserted into the slot 13 until the tube 26 and hole 27 are lined with a hole in the disc. The second limb 12 is between the wheel and the disc with the first limb 11, because of its size, on the outer side of the disc. It is not possible to orientate the lock in any other way, because the first limb 11 will not fit between the wheel and the disc.

The cylinder lock 16 is then pressed inwardly to extend the locking pin 16 through the hole in the disc and into the hole 19 in the second limb 12. This locks the lock to the disc. In addition, it activates the alarm system 14.

In this disposition, there is no access to the alarm system 14. The first limb 11 presents an uninterrupted outer surface formed by the first and second side walls 20, 21 and the top cover 24. The only access is through the cover 18 which is located between the wheel and the disc and thus is not accessible.

Even, however, were the second limb 12 accessible, the cover 18 is not easily removed. The end of the pin 37 is not accessible in the passage 33 because the end of the passage 33 is covered by the end of the locking pin 16 as seen in Figure 1. Only with the locking pin 16 retracted out of the hole 27, can the end of the pin 37 be accessed to depress the pin 37 against the action of the spring 39 so moving the pin 37 out of the passage 33 and allowing the cover 18 to be removed. This, therefore, provides a second level of protection.

If an attempt is made to interfere with the lock, the disc contacts the contact plate 44 to operate the alarm. Separation of the limbs 11, 12 is resisted by engagement of the head of the locking pin 16 with the hole 27 in the second limb 12, as described above. As also described above, the locking pin 16 cannot be pulled through the top of the lock and the locking pin 16 is formed in one piece. These features both increase significantly the security of the lock.

It will be appreciated that there are a number of changes that can be made to the arrangement described above with reference to the drawings. The use of the spring loaded pin 37 accessible only from the end of the passage 33 is optional. The cover 18 could be screwed to the body 10. This would not be as secure as the arrangement described above but would still provide the major benefit of having the alarm system 14 in a chamber 28 that is inaccessible when

the lock is fitted to a disc. The pin 37 could, for example, be replaced by a ball or any suitable spring- loaded latch. The cylinder lock 15 could be replaced by an electronic lock. The body 10 need not be shaped as shown; it could have any suitable shape.