The invention relates to a protective device for a vehicle cylinder lock. DESCRIPTION OF RELATED ART
Most vehicles employ cylinder locks where a key is inserted in the cylinder lock and turned to unlock the vehicle or for ignition as the case may be. When such vehicles, and particularly two and three wheelers, are parked with the key removed from the cylinder lock the key insertion hole of the said cylinder lock is open to the environment. This has some disadvantages such as miscreants may insert sharp metallic objects such as scissors, wires, nails or even sticky fluids and adhesives into the keyhole causing damage and inconvenience to the vehicle owner. An easily accessible key hole, as in the case of two and three wheelers and also open top four wheelers, provides an opportunity for thieves to tamper with the lock and drive the vehicle away. Moreover, a keyhole open to the environment also allows water, dust, grime and other foreign particles to enter the keyhole and jam the cylinder lock. This ingress of rainwater and dust also results in reduction in the life of the cylinder lock and sometimes failure of the lock at an inappropriate moment.
To overcome these drawbacks, numerous solutions have been proposed where a shutter is positioned over the cylinder lock key hole when the vehicle is not in use. Some protective devices employ a magnet lock that locks the shutter in a closed position over the cylinder lock key hole. A rotor connected to this shutter is operated by a magnet key and rotation of the rotor results in movement of the shutter from a closed position to an open position. The magnet key is inserted into the magnet keyhole in the protective device and rotated by a substantial amount in order to open the shutter covering the ignition keyhole. Some protective devices require the magnet key to rotate up to 90 degrees to rotate the rotor that in turn moves the shutter to open the keyhole of the cylinder lock. Moreover, existing protective devices consist of a large number of parts with a substantial number of moving parts. The large number of parts in turn increases the weight of the device while decreasing its effective life.
It would be useful to reduce the excessive rotation of the magnet key to improve user friendliness of protective devices as also to increase the life of the protective device on account of the reduced number of parts and movement of the components involved.
SUMMARY
The invention relates to a protective device for a vehicle cylinder lock comprising a casing having an insertion hole corresponding to a key hole of the cylinder lock; a shutter placed in the casing and movable between a closed position where the shutter closes the insertion hole and an open position where the shutter opens the insertion hole; a magnet lock placed in the casing for selectively restricting movement of the shutter from the closed position to the open position and a magnet key for operating the magnet lock; and a rotor placed within the casing for receiving the magnet key; wherein the rotor has gear teeth formed on it and the shutter has gear teeth formed on it such that the teeth on the rotor mesh with the teeth on the shutter to form a rack and pinion gear train in that rotation of rotor by the magnet key results in the linear movement of the shutter from the closed position to the open position.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The accompanying drawings illustrate the preferred embodiments of the invention and together with the following detailed description serve to explain the principles of the invention.
Figure 1 illustrates an exploded view of the protective device in accordance with an embodiment of the invention.
Figure 2 illustrates a cross sectional side view of the protective device in accordance with an embodiment of the invention.
Figure 3 illustrates a base of the protective device in accordance with an embodiment of the invention.
Figure 4 illustrates a casing of the protective device in accordance with an embodiment of the invention.
Figures 5(a), 5(b) and 5(c) illustrate bottom, side and top views of the protective device in accordance with an embodiment of the invention.
Figures 6(a) and 6(b) illustrate a top and bottom view of the protective device in accordance with an embodiment of the invention.
Figures 7(a) and 7(b) illustrate a shutter closing knob of the protective device in accordance with an embodiment of the invention.
Figure 8 illustrates a sectional view of the protective device with the shutter in the closed position in accordance with an embodiment of the invention.
Figure 9 illustrates a sectional view of the protective device with the shutter in the open position in accordance with an embodiment of the invention.
Figure 10 illustrates an alternate embodiment of the protective device.
Figure 11 illustrates a base of the protective device in accordance with an embodiment of the invention.
Figure 12 illustrates a casing of the protective device in accordance with an embodiment of the invention.
Figures 13 (a) and 13(b) illustrate the top and bottom view of the rotor gear in accordance with an embodiment of an invention.
Figures 14 (a) and 14 (b) illustrate the cross sectional views of the protective device with the shutter in the open and close position in accordance with an embodiment of the invention.
Figure 15 illustrates an alternate embodiment of the protective device.
Figure 16 illustrates a base of the protective device in accordance with an embodiment of the invention.
Figure 17 illustrates a casing of the protective device in accordance with an embodiment of the invention.
Figures 18 (a) and 18 (b) illustrate a top and bottom view of a rotor in accordance with an embodiment of the invention.


Figures 19 (a), 19(b) and 19(c) illustrate the engagement of the shutter closing knob with the rotor in accordance with an embodiment of the invention.
DETAILED DESCRIPTION
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof. Throughout the patent specification, a convention employed is that in the appended drawings, like numerals denote like components.
A protective device for a vehicle cylinder lock in which a rack and pinion gear train is used to transmit motion from the rotor to the shutter is provided. With reference to figure 1 an exploded view of the protective device in accordance with an embodiment is illustrated. The protective device comprises of a base (1) and a casing (20) that form the outer shell and include a rotor (50) and a shutter (30) in between. The casing has a first insertion hole (22) corresponding to the key hole of the vehicle cylinder lock that is placed below it. The casing has a second insertion hole (23) for receiving a magnet key (120). The key insertion hole of the casing and the key insertion of the base are concentric and are aligned with the key insertion hole of the cylinder lock (130) below it.
The shutter has an insertion hole (31) formed on it such that in the open position of the shutter, the insertion hole of the shutter is aligned with the insertion hole of the casing, base and the cylinder lock.

A magnet lock (85) formed of spring loaded magnets is placed below the rotor such that the magnets tend to position themselves in corresponding cavities formed on the under surface of the rotor, as illustrated in Figure 2.
As illustrated in figure 3, the base (1) has a base key hole (14) that is aligned with the keyhole of the cylinder lock below it. A pivot (10) is provided on which a rotor (50) is mounted. The pivot (10) includes crevices (11) for holding spring loaded magnets that fit in cavities formed on the lower face of the rotor.
The base is provided with at least one rib (5), three in the embodiment illustrated that support the linear movement of the shutter between the closed and open positions. A cavity (12) is also provided in the base to hold a stopper (40) that restricts movement of the shutter in the closed position along with a stopper resting face (13).
To urge the shutter from the open position to the closed position a closed position urging means, a compression spring in the embodiment illustrated, is provided. The compression spring (80) is compressed when the shutter is moved from the closed position to the open position and is pressed against surface (17). A platform (2) is provided on the base to hold the compression spring. The platform (2) is provided with a slot (4) for receiving a corresponding projection (24) from the casing. The slot (4) and the projection (24) are used to accurately fit and align the casing to the base. The platform (2) is also provided with a supporting wall (7) that holds the compression spring in place.
A cavity (8) is formed in the base to hold a spring loaded shutter closing knob (70). The shutter closing knob (70) has been illustrated in figure 7(a) and 7(b) and comprises of a projection (71), a knob (74) and a hollow cavity at the bottom (72) to receive a spring (75) as illustrated in figure 19 (c). The shutter closing knob is movable between a retracted position and an extended position and the spring (75) tends to push the shutter closing knob to the extended position. In the closed position of the shutter and the associated position of the rotor, the bottom face (57) of the rotor is above the face (73) of the shutter closing knob and forces it to remain in the retracted position, as illustrated in figure 19 (a). The projection (71) serves as an open position holding means when the

shutter closing knob is in the extended position, by restricting movement of the rotor as illustrated in figure 19 (b).
With reference to figure 4, a bottom view of the casing is illustrated. The casing comprises of three openings; a magnet key receiving recess (23), a key insertion hole (22) and an opening (28) for the shutter closing knob. The casing is provided with a projection (25) that serves as a stop for the surface (73) of the shutter closing knob, when the shutter closing knob is in the extended position. The casing is also provided with a projection (24) that fits into a slot (4) of the base to align the casing with the base and to ensure a correct fit.
An embodiment of the shutter (30) for the protective device is illustrated in figures 5(a), 5(b) and 5(c) with figure 5(a) illustrating a bottom view of the shutter, figure 5(b) illustrating a side view and figure 5(c) illustrating a top view of the shutter. The shutter has a solid surface with a key insertion hole (31) formed on it. The shutter also has a projection (36) with a mount (37) for engaging the compression spring (80). Gear teeth (32) are formed on one side edge of the shutter. In the embodiment illustrated, the gear teeth are formed on the lower side of the side edge. The teeth on the shutter serve as a rack for a rack and pinion gear train. The key insertion hole (31) is aligned with the key insertion holes of the base and casing when the shutter is in the open position.
An embodiment of the rotor (50) for the protective device is illustrated in figures 6(a) and 6(b) with figure 6(a) illustrating a top view of the rotor and figure 6(b) illustrating a bottom view of the rotor. The rotor is provided with a magnet key receiving recess (51) on its top surface and its bottom surface is provided with recesses for receiving the spring loaded magnets of the magnet lock. Teeth (53) are formed on the rotor along its outer side edges. In the embodiment illustrated, a land (54) is provided for support, in view of the size of the teeth formed. The teeth on the rotor serve as a pinion for a rack and pinion gear train.

The rotor is also provided with a locking face (58) that engages the projection (71) of the shutter closing knob to hold the rotor in place that together serve as open position holding means for the shutter.
The gear teeth (53) formed on the rotor mesh with the gear teeth (32) formed on the shutter to form a rack and pinion gear train. The rack and pinion gear train preferably has a gear ratio such that 55 to 65 mm rack movement is achieved per revolution of the pinion. Preferably the gear ratio allows for a 55 to 60 mm movement of rack per revolution of the pinion. The gear ratio allows the shutter to move from a closed position to an open position with a reduced angle of rotation of the rotor. The protective device also does not require external guide means and has reduced number of parts allowing a lighter and less wear prone device.
With reference to figure 8, a cross sectional top view of the protective device with the shutter in the closed position is illustrated. The shutter is moved from this closed position where the insertion hole (31) is not aligned with the insertion holes of the base, casing and cylinder lock to an open position where the insertion hole (31) is aligned so as to provide access to the keyhole, against the force of a compression spring (80). The compression spring working as a closed position urging means, urges the shutter towards the closed position when the shutter is moved to the open position.
To move the shutter from the closed position to the open position, a magnet key is inserted in to the magnet key insertion hole (23) and is received in the recess (51) of the rotor such that the magnet lock is released and the rotor is capable of rotation. The gear teeth formed on the rotor mesh with the gear teeth formed on the shutter in that rotation of the rotor causes the shutter to move from the closed position to the open position.
With reference to figure 9, a cross sectional top view of the protective device with the shutter in the open position is illustrated. As shown the shutter is held in the open position against the forces exerted by the closed position urging means such that insertion hole (31) of the shutter is aligned with the insertion holes of the casing, base and the cylinder lock, by an open position holding means. The open position holding means in

the embodiment illustrated is a projection (71) at the bottom of a shutter closing knob (70) that restricts the movement of the rotor by blocking the path of the locking face (58) as illustrated in figure 19 (b).
With reference to figure 10 an alternate embodiment of the protective device is illustrated, where the rotor (50) is rotated against the force exerted by a torsion spring (80a). The torsion spring is mounted in the rotor such that rotation of the rotor to move the shutter from the closed position to the open position twists the torsion spring and the torsion spring works as a closed position urging means.
With reference to figure 11 and 12, a base (1) and casing (20) similar to the base described in figure 3 and the casing described in figure 4 are illustrated. A recess (2a) is created around the pivot (10) for holding a torsion spring (80a). A cavity (3a) is also provided in this recess (2a) to retain one end of the torsion spring (80a) with the other end engaged to the rotor. The projection (24) of the casing is used to provide adequate resting support for the casing.
With reference to figure 13(a) and 13(b) a rotor (50) similar to the rotor as described in figure 6 is illustrated. The rotor on its bottom surface has a cavity (59) formed on a surface (56) that serves as a guide for mounting the rotor on the pivot (10). The cavity (59) is used to engage the other end of the torsion spring to the rotor. The land (54) is extended in this embodiment to accommodate the torsion spring, and projection (57) is provided for retaining the shutter closing knob in retracted position.
With reference to figure 14(a) and 14(b) a cross sectional top view of the protective device with the shutter in the closed and open position is illustrated. In the open position of the shutter, the torsion spring (80a) is twisted and tends to urge the rotor back to its home position that corresponds to the closed position of the shutter. The torsion spring serves as a closed position urging means. The force exerted by the closed position urging means is resisted by the open position holding means that is by the projection (71) locked against face (58) of the rotor. In this embodiment, the motion of the rotor is restrained by the open position holding means.

With reference to figure 15, another embodiment of the protective device is illustrated. The protective device as illustrated requires the rotation of the rotor by a key for both the opening and closing of the shutter. As in the earlier embodiments, the magnet key is used to rotate the rotor, by which the shutter is moved from the closed position to the open position. The base (1) in the embodiment illustrated in figure 16, is provided with a cavity (8a) for holding a spring loaded ball (88) and fits with a casing (20) as illustrated in figure 17.
The rotor (50) is provided with two slots (58a) and (58b) for receiving the ball (88), as illustrated in figures 18 (a) and 18 (b). The first slot (58a) receives the ball when the rotor is in a position corresponding to the closed position of the shutter. Rotation of the rotor to move the shutter from the closed position to the open position, causes the ball to enter the second cavity (58b). The ball (88) and the cavities (58a) and (58b) are designed such that the ball only partly enters the cavities and remains partly in the cavity (8a) of the base. The partial positioning of the ball between the cavities of the base and the rotor serves as an open position holding means that prevents rotation of the rotor. The force exerted by the open position holding means can be overcome by turning the rotor by means of a key under ordinary torque.

We claim:
1. A protective device for a vehicle cylinder lock comprising a casing having an insertion hole corresponding to a key hole of the cylinder lock; a shutter placed in the casing and movable between a closed position where the shutter closes the insertion hole and an open position where the shutter opens the insertion hole; a magnet lock placed in the casing for selectively restricting movement of the shutter from the closed position to the open position and a magnet key for operating the magnet lock; and a rotor placed within the casing for receiving the magnet key; wherein the rotor has gear teeth formed on it and the shutter has gear teeth formed on it such that the teeth on the rotor mesh with the teeth on the shutter to form a rack and pinion gear train in that rotation of rotor by the magnet key results in the linear movement of the shutter from the closed position to the open position.
2. A protective device as claimed in claim 1 further comprising a closed position urging means for urging the shutter to the closed position from the open position.
3. A protective device as claimed in claim 2 wherein the closed position urging means comprises a compression spring provided between the shutter and the casing such that movement of the shutter from the closed position to the open position compresses the compression spring.
4. A protective device as claimed in claim 2 wherein the closed position urging means comprises a torsion spring provided between the rotor and the casing such that movement of the shutter from the closed position to the open position twists the torsion spring.
5. A protective device as claimed in claim 1 further comprising an open position holding means for holding the shutter in the open position against the force exerted by the closed position urging means.
6. A protective device as claimed in claim 5 wherein the open position holding means comprises at least one cavity on the lower surface of the rotor to receive a locking element.
7. A protective device as claimed in claim 1 wherein the gear ratio of the rack and pinion gear train is preferably in the range of a 55 to 65 mm movement of the rack for each revolution of the pinion.
8. A protective device as claimed in claim 1 comprising a shutter closing knob operatively connected to the rotor, the shutter closing knob movable between a first position and a second position, such that movement of the shutter from the closed position to the open position pushes the shutter closing knob from the first position to the second position.
9. A protective device as claimed in claim 8 wherein the shutter closing knob includes an open position holding means in the form of a projection at the lower end of the shutter closing knob.
10. A protective device for a vehicle cylinder lock substantially as herein described with reference to and as illustrated by the accompanying drawings.