1. TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to an anti-theft lock wherein the key plug will engage with the drive member to subsequently unlock the locking mechanism only upon the use of a correct key and not otherwise thereby preventing instances of theft.

2. BACKGROUND OF THE INVENTION

Conventional cylindrical lock comprises a key plug housed in a non- rotatable main lock body which is perpetually engaged or connected to the drive member. With such an arrangement the key plug and drive member becomes one single unit such that when the key plug is turned, the drive member is accordingly turned. Upon the correct key being inserted and turned, the key plug together with the drive member will rotate causing the drive member to subsequently engage with locking mechanisms such as latches, steering locks and other securing devices to unlock them. Locks with such arrangement are frequently violated or overcome by use of sheer brute force which can be easily achieved by inserting an implement other than the correct key such as a screwdriver into the key hole and thereafter applying force to the implement to forcefully rotate the key plug which in turn rotates the drive member that is perpetually engaged to it thereby violating the locking mechanism The fragile key plug plate members protruding from the key plug serving to secure the lock are easily severed and damaged by forced rotation. When the fragile key plug plate members are severed and damaged, the security of the lock is compromised and the key plug together with the drive member that is perpetually engaged to it will rotate to in turn engage with the locking mechanism.

To overcome the above setback, it would be advantageous if the key plug and the drive member are designed not to be perpetually engaged or in contact Such separated arrangement allows the key plug to rotate without the drive member when an implement other than a correct key is used thereby making the lock force-proof and effectively preventing unauthorized activation or unlocking of the locking mechanism.

3. SUMMARY OF THE INVENTION

Accordingly, it is the primary aim of the present invention to provide an anti-theft lock which is force-proof and does not succumb to forced rotation.

It is yet another object of the present invention to provide an anti-theft lock which ensures that the key plug is not perpetually engaged to the drive member.

Yet a further object of the present invention is to provide an anti-theft lock wherein the key plug will only be engaged to the drive member upon the use of a correct key.

It is yet another object of the present invention to provide an anti-theft lock which is capable of preventing unlocking of the locking mechanism by an element other than a correct key.

Yet a further object of the present invention is to provide an anti-theft lock wherein neither the key plug nor the drive member will rotate upon forced rotation thereby preventing any opportunity of advancement to unlock the locking mechanism. It is yet another object of the present invention to provide an anti-theft lock wherein only the rotatable lock body will be caused to freely rotate without the key plug upon forced rotation thereby preventing any opportunity for key plug to engage the drive member.

It is a further object of the present invention to provide an anti-fheft lock wherein there will be no instances of damage to components of the lock upon forced rotation.

It is yet another object of the present invention to provide an anti-theft lock which is simple in construction and low in manufacturing cost.

Other further objects of the invention will become apparent with an understanding of the following detailed description of the invention or upon employment of the invention in practice.

These and other objects of the present invention are achieved by,

An anti-theft lock comprising, at least a main body (10) accommodating at least a key plug (4) with a plurality of key plug plate members (4A) located thereinwithin and at least a drive member (12); at least a resilient member (6); at least a locking mechanism attached to the main body (10); characterized in that said key plug (4) being further located within a rotatable lock body (8) prior to being partially lodged in the said main body (10); said rotatable lock body (8) designed to have its base end (8B), destined to be disposed between the key plug (4) and drive member (12), having a configuration that restricts movemen - said rotatable lock body (8) which is exposed and part of the main body (10) are enveloped by a restraining sheath (2).

4. BRIEF DESCRIPTION OF THE DRAWINGS

Other aspect of the present invention and their advantages will be discerned after studying the Detailed Description in conjunction with the accompanying drawings in which: FIG. 1 is an exploded view of a present invention showing its main components and an enlarged view of the key plug engaging ends.

FIG. 2A shows a vertical cross sectional view of FIG. 1 when fully assembled complete with the > ve member and the locking mechanism but without key inserted.

FIG. 2B is a cross sectional view of FIG. 2A showing the lock in inactive mode with the key plug plate members protruding outwardly to secure the lock.

FIG 3A is a vertical cross sectional view FIG. 1 when fully assembled complete with the drive member and the locking mechanism and having the correct key inserted.

FIG. 3B is a cross sectional view of FIG. 3A showing the lock in active mode with key plug plate members withdrawn into the key plug.

FIG. 4A shows a perspective view of the first embodiment of the rotatable lock body of the present invention.

FIG. 4B shows a perspective external view of the first embodiment of the rotatable lock body as shown in FIG. 4A viewed from its base end. FIG. 4C shows a perspective vertical cross sectional view of the first embodiment of the rotatable lock body revealing the internal surface configuration of its base end, destined to accommodate the key plug.

FIG. 4D is a two dimensional plan view oi u\n internal base end of the first embodiment of the rotatable lock body.

FIG. 4E is a two dimensional plan view of the external base end of the first embodiment of the rotatable lock body.

FIG. 5A shows a perspective view of the second embodiment of the rotatable lock body of the present invention. FIG. 5B shows a perspective external view of the second embodiment of the rotatable lock body as shown in FIG. 5A viewed from its base end.

FIG. 5C shows a perspective vertical cross sectional view of the second embodiment of the rotatable lock body revealing the internal configuration of its base end, destined to accommodate the key plug. FIG. 5D is a two dimensional plan view of the internal base end of the second embodiment of the rotatable lock body.

FIG. 5E is a two dimensional plan view of the external base end of the second embodiment of the rotatable lock body. 5. DETAILED DESCRIPTION OF THE DRAWINGS

In the following detailed description, numerous specific details are set forth in order to provide a understanding of the invention. However, it will be understood by those with ordinary skill in the art that the invention may be practised without these specific details. In other instances, well known methods, procedures and/ or components have not been described in detail so as not to obscure the invention.

The invention will be more clearly understood from the following description of the embodiments thereof, given by way of example only with reference to the accompanying drawings, which are not drawn to scale.

Referring to FIG. 1, 2A, 2B, 3A and 3B, there are shown an exploded view of the preferred embodiment of the present invention showing its main components namely a restraining sheath (2), a key plug (4) provided with key plug plate members (4A) protruding out, a resilient element (6), a rotatable lock body (8) and a main body (10), an enlarged view of the key plug engaging ends (4C), a vertical cross sectional views of FIG. 1 when fully assembled complete with the drive member (12) and the locking mechanism without and with the correct key inserted and cross sectional views of lock in inactive and active mode. The key plug (4) is configured to have a cylindrical block shaped body (4B) combined with a key plug engaging end (4C) complete with a plurality of typical key plug plate members (4A). The key plug engaging end (4C) acts as an activating cum guide member. The key plug engaging end (4C) further comprises at least one but preferably a pair of key plug activating member (4Ci) and at least a guide member (4C ₂ ), said key plug activating members (4Ci) being disposed perpendicularly to each side of the said guide member (4C ₂ ), and preferably has a configuration similar to the lower case letter "t" of the Roman alphabet. The horizontal part of the "t-shaped" key plug engaging end (4C) serves as the key plug activating members (4Ci) to engage the drive member (12) whilst the vertical part of the "t-shaped" key plug engaging end (4C) serves as a guide member (4C ₂ ) for the resilient element (6) to abut and be maintained intact within the rotatable lock body (8). Although the key plug engaging end (4C) has been described and illustrated as being "t-shaped" in configuration, with the perpendicularly disposed guide member (4C ₂ ) serving to allow the resilient element (6) to externally abut, it could also take other configurations such as a "T-junction shaped" configuration to allow the resilient element (6) to internally abut by having an internal channel within the perpendicularly disposed guide member (4C ₂ ), as what is advantageous is that the key plug engaging end (4C) is capable of serving as an activating cum guide member. The key plug activating members (4Ci) are advantageously designed to have weak points (5) to facilitate breakage of the key plug activating members (4Ci) from the perpendicularly disposed guide member (4C ) when stress is applied onto an inactivated or secured key plug (4) that is resting on the rotatable lock body base end platform (this will be described in detail in the following paragraphs). Once broken, the key plug (4) without its key plug activating members (4Ci) becomes a free rod which is not capable of engaging with the drive member (12). This is achieved by having the key plug activating members (4Ci) being provided with at least a cut-out portion (5A) at the side adjacent to the perpendicularly disposed guide member (4C ₂ ). The design of the key plug activating members (4Ci) with lesser thickness around the weak point (5) as compared to the other areas of the key plug activating members (4Ci) not so provided with the said cut-out portion (5A) will facilitate easy breakage at those thinner weak points (5). The weak points (5) of the key plug activating members (4Ci) having its thickness compromised by the cut-out portions (5A), will break with ease under stress and once broken it will not have the necessary configuration enabling it to engage the drive member (12) even if it successfully penetrates into the main body (10) where the drive member (12) is located. Hence the security of the lock is enhanced. The cut-out portions (5A) can take the form of notches, cut-away or the like as what is advantageous is the creation of weak points (5) on key plug activating members (4Ci) to facilitate breakage at the said point under stress. The key plug (4) and the resilient element (6) are contained therewithal the rotatable lock body (8) and the rotatable lock body (8) is in turn partially received by the main body (10) leaving part of the rotatable lock body (8) exposed. By having the key plug (4) contained in the additional rotatable lock body (8), which is not available in prior art, before being accommodated into the main body (10), the key plug (4) will be separated from the drive member (12) by the base end (8B) of the rotatable lock body (8) (as illustrated in more detail in FIG. 2A) when in inactive mode, and will not be perpetually engaged or in contact with the drive member (4) as in the case of conventional models not having the additional rotatable lock body (8). The restraining sheath (2) is an outer covering which encapsulates the exposed portion of the rotatable lock body (8) and part of the main body (10) which has accommodated part of the rotatable lock body (8). The restraining sheath (2) works in tandem with the resilient element (6) to create the necessary tension to at all times maintain the components including the key plug (4) in their respective designated position, whether in active or inactive mode.

The key plug plate members (4A) are caused to protrude from designated key plug slots (not shown) when in its inactive mode so as to be in contact with the rotatable lock body (8). When the correct key is used the key plug plate members (4A) will be withdrawn into the key plug (4) so as to be in active mode in preparation for the next step, that is to locate an opening at the rotatable lock body (8) [this opening is hereinafter called "the rotatable lock body opening" and indicated by reference numeral (8C)] to enable the key plug engaging end (4C) to penetrate therethrough into the main body (10) enabling engagement of the key plug activating members (4Ci) to the drive member (12) disposed in the main body (10) thereby turning the drive member (12) when the key plug (4) is further rotated. At least a retractable locking ball (16) comprising a resilient element (16A) and ball element (16B) is disposed between the rotatable lock body (8) and the said restraining sheath (2) to enable retraction of the ball element (16B) when required. When in a secured position, where the key plug plate members (4A) protrude out to contact the rotatable lock body (8), the said retractable locking ball (16) is caused to contact the restraining sheath (2) to prevent rotation of the rotatable lock body (8). When switched into active mode with the use of a correct key, the said retractable locking ball (16) is also caused to contact the restraining sheath (2) to prevent rotation of the rotatable lock body (8) with the turning of the key to ensure only the key plug (4) turns to locate the rotatable lock body opening (8C) to penetrate into the main body (10).

Referring now to FIGS. 4A to 4C, there are respectively shown a perspective view of a first embodiment of the rotatable lock body (8) of the present invention, a perspective external view of the said first embodiment viewed from its base end (8B) and a perspective vertical cross sectional view of the said first embodiment revealing the internal configuration of its base end, destined to be accommodate the key plug. As illustrated in FIG. 4A, the rotatable lock body (8) is a hollow structure preferably configured to have a two-tier external circumferential dimension; a bigger external circumference at one portion and a smaller external circumference at the other portion. However it is to be understood that the rotatable lock body (8) of this first embodiment is not required to have such two-tiered external circumferential dimensions and can be constructed to have the same external circumferential dimension, the reason for such two-tiered construction is to reduce cost and material utilized. The smaller external circumference of the rotatable lock body (8) is lodged in the hollow main body (10) whilst the bigger external circumference of the rotatable lock body (8) not so lodged and exposed is flush with the external circumference of the main body (10). The end of rotatable lock body (8) from which the resilient element (6) and key plug (4) are inserted is provided with a configuration that complements the configuration of the said key plug (4) and the key plug engaging end (4C) and is hereinafter called the "rotatable lock body inserting end" and indicated by reference numeral (8A). The other end opposing the rotatable lock body inserting end (8A) where the key plug engaging end (4C) is destined to abut is hereinafter called the "rotatable lock body base end" and indicated by reference numeral (8B). The rotatable lock body base end (8B) of this first embodiment comprises different internal and external base end surface configurations namely, an internal rotatable lock body base end (8Bi) as illustrated in FIG. 4C and an external rotatable lock body base end (8B ₂ ) as illustrated in FIG. 4B. As shown in FIG 4C, the internal configuration of the rotatable lock body (8) is flush save for the rotatable lock body inserting end (8A) having a configuration complementing the configuration of the key plug (4) and the key plug engaging end (4C) and the internal rotatable lock body base end (8Bi) being provided with an internal surface configuration that is capable of restricting movement to guide the key plug engaging end (4C) to penetrate the rotatable lock body opening (8C)] into the main body (10) to enable the key plug activating members (4Ci) to engage the drive member (12). FIG. 4B on the other hand illustrates the surface configuration of the external rotatable lock body base end (8B ₂ ) of the first embodiment which is different from the surface configuration of the internal rotatable lock body base end (8Bi).

To better illustrate the differing internal and external rotatable lock body base end FIGS. 4D and 4E are now referred. FIGS. 4D and 4E respectively illustrate two dimensional plan views of the internal rotatable lock body base end (8Bi) and external rotatable lock body base end (8B2) of this first embodiment. The internal rotatable lock body base end (8Bi) of this first embodiment comprises a substantially central rotatable lock body opening (8C) flanked by an internal platform (8D1) on each side with at least one but advantageously both said internal platform (8D1) being provided with at least an internal stop member (8E1). When not in active mode, the key plug activating members (4Ci) rests on the internal platform (8Di) which serves as a separator to separate the key plug activating members (40) from the drive member (12) located in the main body (10). The internal platform (8Di) also serves as a barrier which will cause the key plug activating members (4Ci) to break at their weak points (5) when force is exerted on the key plug (4) against the said internal platform (8Di). As illustrated in FIG. 4C the said internal stop member (8Ei) is raised at a pre-determined position from the comer of the internal platform (8Di). When the key is inserted into the lock and turned, the internal stop member (8Ei) serves to restrict movement of the key plug activating members (4Ci) beyond a predetermined angle, upon the activating members (4Ci) being aligned with the rotatable lock body opening (8C), so that the user will be prompted to stop turning the key. The internal stop member (8Ei) ensures that there is no turning of the key plug activating members (4Ci) beyond a predetermined point so as to overshoot the location of the rotatable lock body opening (8C). The working of the internal platform (8Di) in combination with the internal stop members (8Ei) of the internal rotatable lock body base end (8Bi) guides and assists the key plug activating members (4Ci) in locating the rotatable lock body opening (8C), leading to the main body (10) where the drive member (12) is located, in preparation for the key plug activating members (40) to penetrate into the main body (10) to engage with the drive member (12) and subsequently unlock the locking mechanism upon further turning. The surface configuration of the external rotatable lock body base end (8B ₂ ) of this first embodiment, as illustrated in FIG. 4B and 4E, is provided with similar configuration as the internal rotatable lock body base end (8Bi) save for the stop member. The external rotatable lock body base end (8B ₂ ) comprises a substantially central rotatable lock body opening (8C) flanked by external platform (8D ₂ ) on each side. Once the key plug activating members (4Q) have penetrated into the main body (10) to engage with the drive member (12), the external platform (8D ₂ ) which is in constant contact with the side of the key plug activating member (4Ci) which is not engaged with the drive member (12) serves to maintain the key plug activating members (4Ci) in permanent engagement with the drive member (12) thereby preventing the key plug activating members (4Ci) from being displaced unless desired by turning the key in the reverse direction to re-align the key plug activating members (4Ci) with the rotatable lock body opening (8C) to facilitate disengagement from the drive member (12) and displacement from main body (10) into the rotatable lock body (10) hence securing the lock.

In the second embodiment of the rotatable lock body as illustrated in FIGS 5A to 5E, there are respectively shown a perspective view of the second embodiment of the rotatable lock body (8), a perspective external view of the second embodiment viewed from its base end (8B), a perspective vertical cross sectional view of the second embodiment revealing the internal configuration of its base end (8B) destined to accommodate the key plug (4) and two dimensional plan views of the internal and external rotatable lock body base end (8B) of this second embodiment. This second embodiment has identical configuration with the rotatable lock body (8) of the first embodiment, save for the surface configuration of the external rotatable lock body base end (8B2) which is provided with such surface configuration capable of restricting movement thereby allowing it to have multi-functions. This will be described in detail in the following paragraphs.

The surface configuration of the second embodiment internal rotatable lock body base end (8B1) as illustrated in FIG. 5C and 5D is identical to the surface configuration of the first embodiment internal rotatable lock body base end (8B1) as illustrated in FIGS. 4C and 4D complete with internal platform (8Di), internal stop members (8E;i) and rotatable lock body opening (8C) and both have similar functions. As in the first embodiment, the internal platform (8D1) permits the key plug activating members (4Ci) to rest on it and act as a barrier to prevent permanent engagement with the drive member (12) and to facilitate breaking of the key plug activating members (4Ci) at its weak point (5) when unauthorized force is used. The working of the internal platform (8D1) in combination with the internal stop member (8E1) restricts movement of the key plug activating member (4Ci) assisting it to locate the rotatable lock body opening (8C) for penetration into the main body (10) to engage the drive member (12). Similarly as in the first embodiment, the internal platform (8D1) and the internal stop members (8E ₁ ) of the internal rotatable lock body base end (8B1) of this second embodiment guides and assists the key plug activating members (4Q) in locating the rotatable lock body ope (8C), leading to the main body (10) where the drive member (12) is located, in preparation for the key plug activating members (4Ci) to penetrate into the main body (10) to engage with the drive member (12) and subsequently unlock the locking mechanism upon further turning.

The surface configuration of the second embodiment external rotatable lock body base end (8B ₂ ) as illustrated in FIGS. 5B and 5E, on the other hand, is different from the surface configuration of first embodiment external rotatable lock body base end (8B ₂ ) as illustrated in FIGS. 4B and 4E. In this second embodiment, the external rotatable lock body base end (8B ₂ ) comprises a substantially central rotatable lock body opening (8C) flanked by an external platform (8D ₂ ) on each side with at least one but preferably both said external platform (8D ₂ ) being provided with at least an external stop member (8E ₂ ) raised at a pre-determined position from the corner of the external platform (8D ₂ ). As in the first embodiment once the key plug activating members (4Ci) have penetrated into the main body (10) to engage with the drive member (12), the external platform (8D ₂ ) which is in constant contact with the side of the key plug activating member (4Ci) which is not engaged with the drive member (12) serves to maintain the key plug activating members (4Ci) in permanent engagement with the drive member (12) thereby preventing the key plug activating members (4d) from being displaced unless desired by turning the key in reverse direction to re-align the key plug activating members (4G) with the rotatable lock body opening (8C) to facilitate disengagement from- the drive member (12) and displacement from main body (10) into the rotatable lock body (10) hence securing the lock. The design of this second embodiment external rotatable lock body base end (8B ₂ ) with the external stop member (8E ₂ ) raised from the external platform (8D2) can also be applied to vehicle locks to prevent unintended locking of the steering when switching off the engine for safety reasons. The external stop member (8E ₂ ) raised at a pre-determined position from the corner of the external platform (8D ₂ ) of the second embodiment external rotatable lock body base end (8B2) serves restrict movement of the key plug activating members (4Ci) in reverse beyond a predetermined angle thereby preventing turning of the key plug activating member (40i) beyond the permitted angle to lock the steering after turning off the engine. If desired to lock the steering a further positive act, of pushing the key plug activating members (4Ci) back into the rotatable lock body (8) [assisted by the resilient element (6) abutting the guide member (4C ₂ )] through the rotatable lock body opening (8C) thereby disengaging it from the drive member (12), is required combined with the subsequent turning in reverse to the original start position. As illustrated in FIG. 2B, when the lock of the present invention is in its inactive mode the key plug plate members (4A) is caused to protrude from the key plug slots to contact with the rota table lock body (8). In conventional models where the key plug is housed in the main body which is stationary (and not rotatable in contrast to the rotatable lock body (8) as in the present invention), a thief will be able to unlock the locking mechanism and open the lock by first forcing the key plug with its protruded key plug plates members which is in contact with the stationary main body housing the key plug to turn thus severing off the protruding plate members. Once severed, the restriction to rotate the key plug only with a correct key is overcome. As the key plug is perpetually engaged to the drive member, the drive member accordingly will rotate when the key plug is rotated. This setback is overcome by the present invention designed with the key plug (4) embedded in a rotatable lock body (8) additional to the stationary main body (10). When the lock is violated, by forcibly causing the key plug (4) with its protruding key plate members (4A) to rotate using an implement other than a correct key, the retractable locking ball (16), facilitated by the resilient element (16A), will be retracted to disengage from the restraining sheath (2) thereby allowing the rotatable lock body (8) to freely rotate whilst the key plug (4) is maintained in stationary position thus no damage to the key plug plate members (4A) results. By virtue of the design, that is having the key plug (4) contained in the rotatable lock body (8) additional to the main body (10), thereby separating the key plug (4) from the drive member (12), the drive member (12) being not be perpetually engaged or in contact with the key plug (4) will not be caused to rotate so that when a thief tries to force rotation of the drive member by rotating the key plug (4), only the rotatable lock body (10) but not the key plug (4) is rotated. Without the key plug (4) turning, the key plug activating members (4Ci) will have no opportunity to advance to locate and penetrate the rotatable lock body opening (8C) to engage the drive member (12). As the key plug (4) in particular the key plug activating members (40) is not perpetually engaged or connected to the drive member (12) but separated by the rotatable lock body base end (8B) there is no opportunity for the key plug activating members (4Ci) to engage the drive member (12) to subsequently unlock the locking mechanism.

The present invention will allow only the key plug (4) to rotate and subsequently be engaged with the drive member (12) without rotating the lock body (8) when the correct key is used. In this invention, the key plug (4) in particular the key plug activating members (4Ci) will only become engaged or come into contact with the drive member (12) when in active mode with the use of the correct key. Unless the correct key is used the key plug (4) will not be able to engage with the drive member (12).

While the key plug engaging end (4C) has been described and illustrated as being "t-shaped" it may be designed to have other configurations as what is advantageous is that key plug engaging end (4C) in particular the key plug activating members (4Ci) is not engaged or in contact with the drive member (12) in inactive mode or even if violated by force.

Although the internal and external stop members (8Ei) (8E ₂ ) have been described and illustrated as being provided raised from the corner of the respective internal and external platforms (8DEi) (8D ₂ ) flanking both sides of the rotatable lock body opening (8C), the invention is applicable even if only one of the internal platform (8Di) is provided with an internal stop member (8Ei) whilst the other internal platform (8Di) is not; or one of the external platform (8D ₂ ) is provided with an external stop member (8E ₂ ) whilst the other external platform (8D ₂ ) is not as what is advantageous is that the internal and external rotatable lock body configuration is capable of restricting movement of the key plug (4) in particular the key plug activating members (4Ci).

While the preferred embodiment of the present invention and its advantages has been disclosed in the above Detailed Description, the invention is not limited thereto but only by the scope of the appended claim.