The present invention relates to a break-in resistant double-bit lock and a related key.

The use is known of several approaches to breaking in, in order to fraudulently open double-bit locks.

Among the different types of breaking-in tools, the so-called "Bulgarian lockpick" is increasingly widespread.

It is a tool adapted to fraudulently open only double-bit locks, which is one of the most widespread types in Italy.

It is a series of lockpicks and "keys" which can modify the shape of a contoured end, until it is rendered perfectly compatible with the coding pattern of the lock on which the burglar is working.

An acute problem generated by this type of break-in is linked to the fact that the opening does not cause any damage to the lock (which in fact is opened as if the burglar had the respective key), which for example can even be completely locked again. This also leads to serious difficulties with obtaining approval of payment of a claim by the insurance company with which specific insurance policies are taken out for burglaries.

The most correct definition of the so-called Bulgarian lockpick is a decoder for double-bit locks.

Once inserted in the lock, it progressively assumes the toothing profile of the key, eventually opening it: such action is controlled by its user by way of at least one respective handle which makes it possible to act directly on the length of its end teeth. It should moreover be noted that, with the imprint obtained on the decoder, duplicates of the original key can subsequently be made (thus making repeated break-ins possible, and simpler, for the burglar).

The aim of the present invention is to solve the above mentioned drawbacks, by providing a break-in resistant double-bit lock and a related key which prevent break-ins using specific decoders for double-bit locks, of the type normally known as Bulgarian lockpicks and the like.

Within this aim, an object of the invention is to provide a break-in resistant double-bit lock and a related key, which are complex to pick with any type of utensil.

Another object of the present invention is to provide a break-in resistant double-bit lock and related key which is low cost, easily and practically implemented and safely applied.

This aim and these and other objects which will become better apparent hereinafter are achieved by a break-in resistant double-bit and a related key, characterized in that the access opening to the accommodation cavity of said key is contoured so as to define a central portion from which branch two mutually opposite slots, at least one of said slots comprising a portion, with a curved progression, with the lower edge arranged at a height that is substantially not lower than the midpoint plane of the respective slot, the head of said key comprising a central body from which branch two mutually opposite tongues, of which at least one is provided with at least one respective codifiable edge, at least one of said tongues comprising a region, with a curved progression, with the lower edge arranged at a height that is substantially not lower than the midpoint plane of the respective tongue of said head of said key.

Further characteristics and advantages of the invention will become better apparent from the description of a preferred, but not exclusive, embodiment of the break-in resistant double-bit lock and related key according to the invention, which is illustrated by way of non-limiting example in the accompanying drawings wherein:

Figure 1 is a perspective view of a break-in resistant double-bit lock and the related key, according to the invention;

Figure 2 is a perspective view of a key according to the invention; Figure 3 is a perspective view from a different viewpoint of the key of Figure 2; Figure 4 is a view from above of the key of Figure 2;

Figure 5 is a front elevation view of the key of Figure 2;

Figure 6 is a sectional front elevation view, taken along a transverse line, of the key of Figure 2;

Figure 7 is a sectional front elevation view, taken along a transverse line, of the lock of Figure 1 ;

Figure 8 is a sectional front elevation view, taken along a transverse line, of a different embodiment of a key according to the invention;

Figure 9 is a sectional front elevation view, taken along a transverse line, of a further embodiment of a key according to the invention.

With reference to the figures, the reference numeral 1 generally designates a break-in resistant double-bit lock and the reference numeral 2 a related key.

The access opening 3 to the accommodation cavity of the key 2, in the lock according to the invention, is contoured so as to define a central portion 4 from which branch two mutually opposite slots 5 and 6.

At least one of the slots 5 and 6 comprises a portion, respectively 7 and 8, with a curved progression.

The portion 7, 8 will have a partial protrusion with respect to the plane containing the remaining part of the access opening 3 (as well as the remaining part of the slots 5 and 6). More specifically the portion 7, 8 will have the lower edge arranged at a height that is substantially not lower than the midpoint plane of the respective slot 5, 6, thus presenting an obstacle to the insertion in the access opening 3 of any flat component.

Each curved portion 7 and 8 will thus define a deviation from the plane containing the central portion 4 and the ends of the slots 5 and 6: it is thus evident that the access opening 3 will not lie on a single plane but will comprise deviations with respect to it (which are constituted by the portions 7 and 8). It can thus be seen that it is not possible to accommodate a double- bit key of the conventional type in the opening 3 according to the invention if the coded head has elements that are mutually coplanar: there would in fact be interference between the head of the key and the portions 7 and 8 of the opening 3 if one attempted to insert a traditional key.

The head 9 of the key 2 according to the invention comprises a central body 10 from which branch two mutually opposite tongues 11 and 12.

At least one of the tongues 11 and 12 is provided with at least one respective codifiable edge, respectively 13 and 14.

Each tongue 11 and 12 can moreover be provided with a region, respectively 15 and 16, with a curved progression.

The region 15, 16 has a partial protrusion with respect to the plane containing the remaining part of the head 9 of the key 2. More specifically, each region 15, 16 will have the lower edge arranged at a height that is substantially not lower than the midpoint plane of the respective tongue 11 , 12 of the head 9 of the key 2, in order to present a shape complementary to that of the access opening 3 described previously.

According to a particular embodiment, the portion 7 with curved progression has a shape structure that is substantially of the type of an arc of circumference (or in any case a curve that is comparable thereto, even if it is at least partially irregular) which constitutes the connection between a first part 7a associated with the central portion 4 and a second part 7b associated with the respective slot 5.

Also with reference to the cited embodiment, the region 15 with curved progression of the head 9 of the key 2 has a shape structure that is substantially of the type of an arc of circumference which constitutes the connection between a first portion 15a associated with the central body 10 and a second portion 15b associated with the respective tongue 11.

According to a further embodiment (which can in any case be paired with the one described previously), the portion 8 with curved progression will have a shape structure that is substantially of the type of a corner angle formed by a first slit 8a associated with the central portion 4 and a second slit 8b associated with the respective slot 6.

With reference to such embodiment, the region 16 with curved progression of the head 9 of the key 2 has a shape structure that is substantially of the type of a corner angle which constitutes the connection between a first strip 16a associated with the central body 10 and a second strip 16b associated with the respective tongue 12.

The possibility is not ruled out of the curved portions 7 and 8 and the curved regions 15 and 16 having a shape structure of the polygonal type in which the angles are mutually connected.

Moreover it should be noted that the protrusions with respect to the plane containing the central portion 4 and the ends of the slots 5 and 6, as well as the central body 10 and the ends of the tongues 1 1 and 12, can also be facing in mutually opposite directions.

It should be noted moreover that the central portion 4 can have a cross-section that is preferably selected from among circular, polygonal and combinations thereof.

In the same way, the central body 10 can also have a cross-section that is preferably selected from among circular, polygonal and combinations thereof.

Obviously, both of the slots 5 and 6 can comprise a portion 7 and 8, with a curved pattern, with the lower edge arranged at a height that is substantially not lower than the midpoint plane of the respective slot 5, 6: this will make it possible to increase security, by preventing the (forced) insertion of a key of the conventional type and/or of a utensil having such shape.

In such case both of the tongues 1 1 and 12 comprise a respective region 15 and 16, with curved progression, with the lower edge arranged at a height that is substantially not lower than the midpoint plane of the respective tongue 11 , 12 of the head 9 of the key 2: this is in order to be able to be correctly inserted into the access opening 3 described previously. According to a particular embodiment of undoubted practical and applicative interest, the access opening 3 and the head 4 of the key 2 have a shape that is at least partially contoured substantially like a letter "M".

It should be noted that the portion 7, 8 with curved progression profitably will have at least one protruding tooth 17 or 18 which constitutes an obstacle upon the insertion of components of the type of keys 2 with substantially flat tongues 11 , 12 and tools with substantially flat lateral appendages.

Advantageously the break-in resistant double-bit lock 1 and the related key 2 prevent break-ins perpetrated using specific decoders for double-bit locks, of the type normally called Bulgarian lockpicks and the like.

In fact such decoders necessitate a seat into which the movable pins, which provide the codified contoured edge, can slide: the presence of the curved portions 7 and 8 and of the curved regions 15 and 16 prevents the provision of a seat into which the rigid pins can perform a translational motion, if it is decided to make a Bulgarian lockpick shaped like the key 2.

The constructional difficulties and the extremely high costs associated therewith will make it particularly complex to provide a decoder for double- bit locks that can function on the lock 1 according to the invention.

At the same time conventional decoders cannot be inserted in the opening 3 owing to the presence of the two curved portions 7 and 8.

It is thus evident that the lock 1 will effectively be protected against break-in attempts perpetrated using a decoder for double-bit locks, of the type usually called a Bulgarian lockpick.

Positively, the break-in resistant double-bit lock 1 is also particularly effective against other types of break-in with any type of utensil, which is due to the fact that the contoured opening 3 does not permit the insertion of utensils having flat portions (which are very efficient for actuating the internal lever mechanisms adapted to the movement of sliding latches). Advantageously the break-in resistant double-bit lock 1 and the related key 2 are low cost and are easily and practically implemented, and are safely applied.

It should be noted that the regions 15 and 16 of the key 2 can be obtained by subjecting a traditional key to the action of a press provided with correctly shaped molds and/or by way of mechanical processing to remove material from a block of greater dimensions than those of a traditional key.

The contoured opening 3 can be provided by punching or die cutting with a specific automatic machine.

The invention, thus conceived, is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. Moreover, all the details may be substituted by other, technically equivalent elements.

In the embodiments illustrated, individual characteristics shown in relation to specific examples may in reality be interchanged with other, different characteristics, existing in other embodiments.

In practice, the materials employed, as well as the dimensions, may be any according to requirements and to the state of the art.

Where the technical features mentioned in any claim are followed by reference numerals and/or signs, those reference numerals and/or signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference numerals and/or signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference numerals and/or signs.