Tumbler locks according to the present invention are used for instance as se- curity locks in doors. While the security requirements are getting more strin- gent, a great number of additional key alternatives of various kinds are needed. In principle this can be achieved e. g. by adding the number of tum- bler discs or stepping alternatives for combination surface milling, i. e. the number of combination values. Both the size of the key and the lock must, however, be kept reasonable and the decreased stepping of milling might, for its part, cause malfunctions and erroneous openings.

The picking of locks should also be as difficult as possible. The locking chan- nel of the tumbler discs utilized in these locks conventionally includes a straight branch interconnecting the locking branches and extending in the di- rection of the transfer movements of the lock bolt. Thus it is sufficient for picking the lock to arrange the tumbler discs so that the connecting branches for their respective locking channels coincide with the position of the locking pin. After this the lock bolt can be pressed to its opening position while the locking pin moves directly through the locking channel branch in question. In order to prevent picking it is known to provide the locking branches of the locking channel with various recesses, in which the locking pin can get stuck while searching for the correct position of the tumbler discs. Thereby the probing of the position of the tumbler discs is at least impeded.

One type of a tumbler lock is shown in EP 1 035 278 A2. In the disclosed solution the key blade comprises a guide member, which affects the lock bolt at the final stage of the selecting movement of the tumbler disc so that it guides the locking pin into the branch interconnecting the locking branches of the locking channel. In addition, the third branch of the locking channel com-

prises at least one guiding member to guide the locking pin at the same time with the transfer movement of the lock bolt and the selecting movement of the tumbler disc.

The object of the present invention is to provide a tumbler lock, the picking of which can be prevented more reliably than before.

The aims of the invention can be achieved principally as is described in more detail in claim 1 and in the other claims. A tumbler lock according to the pre- sent invention comprises a lock casing or similar including a plurality of tum- bler discs provided with locking channels, a lock bolt and a locking pin or similar, arranged in force transmitting connection with the lock bolt and in interaction with the locking channels of the tumbler discs. The tumbler lock also comprises a separate force transmitting member for providing force transmitting connection between the lock bolt and the locking pin or similar.

The force transmitting member is movably mounted in the lock bolt so that it has a determined freedom of movement and the locking pin is arranged in the force transmitting member. The force transmitting member is preferably ar- ranged in operative communication with the lock bolt so that their lateral sur- faces face each other and a mechanical guide system is provided for guiding their reciprocal movement. This guide system determines the limits for and/or the direction of the movement between the lock bolt and said force transmit- ting member. The mechanical guide system comprises at least one pin and guide groove combination or similar arranged to guide the force transmitting member in a direction deviating from the direction of movement of the lock bolt.

Blocking members are arranged in the lock casing, in the vicinity of the lock bolt, and the force transmitting member comprises a detent or similar mem- bers arranged by means of the movement between the force transmitting member and the lock bolt to interact with the blocking members so that the

force exerted on the lock bolt and parallel with its direction of movement can be transmitted to the lock casing by means of said members.

A tumbler lock according to the invention comprises members on the other side of the lock bolt for transforming the turning movement of the key to a linear movement of the lock bolt, whereby the detent or similar members of the force transmitting member are preferably arranged on the opposite side of the lock bolt with respect to said members of the lock bolt.

In the following the invention is described by way of example with reference to the attached drawings, in which Fig. 1 shows schematically a tumbler lock according to the inven- tion in locked position; Fig. 2 shows schematically a tumbler lock according to the inven- tion during a picking attempt at the first stage; and Fig. 3 shows schematically a tumbler lock according to the inven- tion during a picking attempt at the second stage.

In the drawings the reference number 1 indicates a tumbler lock comprising a lock casing 2 or similar, where several tumbler discs 3 equipped with locking channels 4 are provided. In addition, the lock comprises a lock bolt 5 mova- bly mounted in the direction of its longitudinal axis in the lock casing 2. The tumbler lock comprises further a locking pin 6 or similar arranged in force transmitting connection with the lock bolt 5 so that the force exerted on the lock bolt and parallel with its direction of movement can be transmitted to the tumbler discs 3 via the locking pin 6. Further, the locking pin 6 is ar- ranged to interact with the locking channels 4 of the tumbler discs. The tum- bler discs are arranged in the lock casing 2 in a way known per se by means of elongated guide openings 3'to be moved in a transversal direction with respect to the lock bolt's direction of movement and against the pressure of spring means.

Fig. 1 depicts the initial position of the tumbler lock 1 according to the inven- tion in locked position. The lock comprises a separate force transmitting member 7 for providing force transmitting connection between the lock bolt 5 and the locking pin 6. In this connection the force transmitting member is called a detent plate. The detent plate 7 is arranged in force transmitting connection with the lock bolt 5 allowing a specific reciprocal movement be- tween them. The elements are located so that their lateral surfaces face each other. In addition, a mechanical guide system 8 is provided for guiding their reciprocal movement comprising pairs of pins and guide grooves or similar and determining the limits for and/or the direction of movement between the lock bolt 5 and the detent plate 7. In the embodiment according to the drawings two pins 8'are arranged in the lock bolt 5 and correspondingly, two grooves or elongated holes 8"in the detent plate 7. The direction of the grooves 8"is such that the movement between the lock bolt 5 and the de- tent plate 7 deviates from the direction of movement of the lock bolt.

In the lock casing 2, in the vicinity of lock bolt 5, are arranged blocking members 9, and correspondingly the detent plate 7 comprises a detent 10 or similar members, which can be arranged by means of the movement between the detent plate 7 and the lock bolt 5 to interact in a picking situation. The lower edge of the lock bolt 5 is provided with a guide surface 11 for a key for transforming the turning movement of the key to a linear movement of the lock bolt, and the detent 10 of the detent plate 7 is arranged on the op- posite side of the lock bolt with respect to the guide surface 11 for the key.

The locking pin 6 is arranged on the detent plate 7, whereby the pressing force exerted on the lock bolt 5 from outside makes the detent plate 7 actu- ated by the guide system 8 to move in such a way that the detent 10 hits the blocking members 9 and the movement of the lock bolt is prevented (cf.

Fig. 2). Thus the force exerted on the lock bolt by the interaction of the de- tent 10 and the blocking members 9 and being parallel with the lock bolt's direction of movement can be transmitted to the lock casing and the force exerted on the tumbler discs 3 via the dead-locking pin 6 will cease. In this

case there are two blocking members 9. Thus the arrangement according to the invention is applicable in all necessary opening phases of the lock. Gener- ally, the number of blocking members is preferably one less than the number of locking channel branches parallel with the direction of movement of the tumbler discs.

By means of the arrangement according to the invention the picking of the lock, especially by the so-called Hobbs'method and its derivates, can be im- peded efficiently. In this method the lock bolt is exposed to a load that presses the lock bolt inwards, whereby the locking pin is pressed against the edge of the locking channel of the tumbler disc that prevents the movement of the lock bolt. Thus, by lifting the tumbler disc through the keyhole it is possible to probe the position of the branch being parallel with the movement of the lock bolt in the locking channel. This measure is repeated for each tumbler disc until the correct opening combination is found. Even the more advanced versions of the picking method are based on this principle.

Fig. 2 depicts the situation while a picking attempt is in progress. The essen- tial element in the present solution is the detent plate 7 attached to the lock bolt 5 or in association therewith, which plate is loaded by a spring 12 against the lock bolt in such a way that the spring urges the detent plate 7 away from the end of the lock bolt 5 protruding from the lock. Since the locking pin 6 is arranged in the detent plate 7, the external pressing force ex- erted on the lock bolt is transmitted at the first stage to the tumbler discs 3 via the detent plate 7. When the lock bolt is exposed to a load for instance through the keyhole pushing the lock bolt backwards, the locking pin 6 is pressed against one or more tumbler discs 3. This is also the case if a wrong key inserted through the keyhole causes the load. If the right key had been used, the tumbler discs would have risen even before the movement of the lock bolt to a position allowing free movement of the lock bolt. In addition, the detent plate 7 always remains immobile with respect to the lock bolt, when the right key is used.

In Fig. 2 the lock bolt 5 is, however, loaded in a way different from the key matching the lock, whereby it is sufficient that even one tumbler disc 3 is in a position deviating from the correct combination. This makes the locking pin 6 to be pressed against the tumbling disc 3. Thus, the detent plate 7 is ex- posed to an opposite force with respect to the load on the lock bolt, which force under the influence of the pins 8'and grooves 8"moves the detent plate 7 upwards in the figure, whereby the detent 10 of the detent plate is pressed against the blocking members 9. Now the force exerted on the lock bolt is transmitted through the pins 8'and grooves 8"over to the detent plate 7 and further through the blocking members 9 to the lock casing 1, and not to the tumbler discs 3. This situation is shown in Fig. 3.

Fig. 3 also depicts a picklock or similar 13, by which the probing of the tum- bler discs is attempted. However, the present invention makes it impossible to determine by probing the position of the branch 4 parallel with the move- ment of the lock bolt in the locking channel of the tumbler discs 3, since the tumbler disc is at this stage moving without any load by the lock pin 6. This can be made even more efficient by designing locking channels 4 in the tum- bler discs and the locking pin 6 so that the contact of the locking pin 6 with the tumbler disc 3 is easily released, when the tumbler disc is probed, i. e. lifted.

It is obvious that the technical solutions described above are only exemplary.

The invention is thus not limited to the above-described embodiment, but several modifications thereof are feasible within the scope of the appended claims.