FIELD OF THE INVENTION This invention relates to electronic padlocks, and specifically to padlocks with solenoid servomechanism.

BACKGROUND OF THE INVENTION Electronic locks are known in many varieties. All kinds of them use some electrical servomechanism to block the locking-unlocking function such as moving a latch or a bolt or to perform the locking-unlocking itself. Most often, the servomechanism is an electric motor or solenoid. The advantages of solenoids versus electric motors are lower cost, simplicity of application, reliability and durability of the mechanism. In a solenoid mechanism, the armature performs a simple linear or swinging motion under the action of electromagnetic forces and elastic elements.

The simplicity of the motion is however accompanied by a major problem, which is that the armature may be moved also by an inertial force. Such force may be created by a shock applied on the lock, especially on a pendant padlock. In this way, a solenoid mechanism may be switched into unblocked or open state without any key or coded input. Many complicated ways have been developed to overcome this problem. They require complex additional parts, space in the padlock and are not reliable in all positions of the padlock.

SUMMARY OF THE INVENTION A solenoid blocking device of a lock or padlock includes an electromagnetic coil, a stator, and an armature adapted to perform a first motion relative to the stator

under magnetic action of the coil. According to the present invention, there is provided in that device an anti-shock arrangement comprising a first element mounted to the armature and a second element fixed to the stator. The first element is engaged to the second element so as to be forced to perform a second motion when the armature performs the first motion. The second motion is associated with friction preventing the second motion, and thereby the first motion, under shock applied on the whole device in direction of the first motion but allowing the second motion under the magnetic action.

The second motion of the first element is preferably a sliding motion, in particular a helical motion, along a path defined by the second element, the path constituting an inclined plane of angle a with respect to the direction of the first motion.

In a specific embodiment of the anti-shock arrangement, the first element is a pin mounted to the armature and protruding transversely to the direction of the first motion. The path is an inclined channel in the second element, the pin being slidingly received in the channel. The second element is preferably a plate fixed to the stator, while the inclined channel is a slit in the plate, disposed in a plane parallel to the direction of the first motion.

The first and the second elements may be made of steel. The angle a is preferably between 60° and 70° but it depends on the friction properties of the materials used for making the two elements and on the geometrical range of the two motions.

The anti-shock arrangement of the present invention has a very simple and reliable structure ; it operates irrespective of the current spatial position of the lock and may be employed in an electronic lock of any construction. It is especially advantageous in portable (pendent) locks and padlocks for preventing easy opening by a shock that would otherwise cause the armature to retract and unblock the lock.

BRIEF DESCRIPTION OF THE DRAWINGS In order to understand the invention and to see how it may be carried out in practice, a preferred embodiment will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of an electronic padlock with vibration code.

Fig. 2 is an exploded sectional view of the padlock of Fig. 1, in open state.

Fig. 3 is a sectional view of the padlock of Fig. 1, in closed state.

Fig. 4A is an elevation of an anti-shock solenoid drive of the present invention in extended state.

Fig. 4B is an elevation of the anti-shock solenoid drive of Fig. 4A in contracted state.

Fig. 4C is an axial view of the anti-shock solenoid drive of Fig. 4A.

DETAILED DESCRIPTION OF THE INVENTION With reference to Figs. 1, 2 and 3, a padlock 10 of the present invention comprises a housing 12 with a base plate 14, a lock bolt 16, a lock pin 18, a blocking drive 20, and an electronic blocking device (EBD) 22 with battery 24.

The housing 12 is a sturdy hollow U-shaped body with a through cylindrical bore 26 extending into a blind bore 28, a cavity 30, and another cylindrical bore 32 perpendicular to and crossing the bore 28. The base plate 14 is adapted to close the housing 12 flush with its edge, and is formed with a cavity 34 accommodating the blocking drive 20. The base 14 is mounted to the housing 12 by means of two screws 36. The housing further accommodates a dummy plug 40 in the bottom of the blind bore 28 urged by a cylindrical compression spring 42 towards the opening of the bore 28, and the lock pin 18 in the bore 32 urged towards the bore 28 by a second compression spring 44.

The lock bolt 16 has a notch 46 sized to receive the lock pin 18, and a handle 48 attached by two screws 50. The lock bolt 16 is slidingly and rotatably disposed in the bores 26-28.

The blocking drive 20 is a bi-stable solenoid. It is fixed in the cavity 34 of the base 14 by means of a bracket 52 and screws or rivets (not shown in Fig. 3).

With reference to Figs. 4A and 4B, the solenoid comprises a housing 54 with an electromagnetic coil 56 and a permanent magnet 58 formed with a cylindrical bore 60. The blocking drive 20 further comprises an armature 62 movable in the bore 60, with a head 64. A compression spring 66 urges the armature 62 away from the magnet 58. The armature 62 has two stable states: an extended state with the head 64 urged away from the magnet (as shown in Fig. 4A), and a contracted state with the head 64 close to the magnet 58 and the spring 66 compressed (as shown in Fig. 4B).

The electronic blocking device 22 is accommodated in the cavity 30 and includes an impact sensitive microphone 72, and a programmable controller with memory. The controller is adapted to decode signals received by the microphone and to compare them to a lock access code stored in the memory.

The padlock 10 with the EBD 22 is completed by an impact generating electronic key 76, which is a hand-held programmable data-transmitting device.

The key includes an impact head 78 using, for example, electromagnetic, piezoelectric or magnetostriction effect. The key 76 further comprises a programmable controller with memory, and a battery. The key 76 is designed to produce a coded series of pulse-like, high-energy impacts of the impact head 78, in accordance with a key access code stored in the memory. The key may have a numeric keypad for programming the key access code or, alternatively, the access code may be programmed in a special device.

With reference to Fig. 3, in a locked state of the padlock 10, the bolt 16 is inserted in the bore 26-28 until the handle 48 abuts the housing 12, with the notch 46 facing the lock pin 18. In this position of the lock bolt 16, the pin 18 enters the notch 46 under the action of the spring 44, thereby preventing an axial extraction of the lock bolt 16. The head 64 of the blocking drive moves under the edge of the lock pin 18 urged by the spring 66 (see below), thereby preventing any return of the

lock pin 18. The U-shape of the padlock is now closed and the lock bolt 16 is blocked.

In order to unblock the lock bolt and to open the padlock 10, the key 76 is urged by hand to any point of the padlock 10. A key access code (a number) is input via the keypad and a corresponding coded series of impacts is delivered by the impact head 78 to the surface of the housing 12. Alternatively, the key access code may be pre-programmed in the memory or pre-dialed, in which case a coded series of impacts may be initiated by pressing a single button on the key. The microphone 72 picks up vibrations inside the padlock resulting from the impacts. The vibrations are suitably processed and decoded by the controller of the EBD 22, and are then compared to the lock access code programmed in the memory of the EBD 22.

Upon successful match, the EBD 22 energizes the coil 56 for a moment to create electromagnetic force complementary to the force of the permanent magnet 58.

Thereby, the armature 62 is attracted towards the coil 56, overcoming the action of the spring 66. When the head 64 comes closer to the magnet 58, the latter holds the blocking drive in contracted state where the lock pin 18 is free to move in the bore 32. Now the lock bolt 16 can be turned by hand using the handle 48. In the process of turning, the bottom of the notch 46 presses the lock pin 18 against the action of the spring 44, to sink in the bore 32. At about 1/4 turn and more from the blocked state, the lock bolt 16 pushes the lock pin 18 entirely into the bore 32, whereby the lock bolt can be extracted axially (see also Fig. 3). During the axial motion, the lock bolt 16 is followed by the dummy plug 40, under the action of the spring 42.

The dummy plug 40 takes the place of the lock bolt 16 over the end of the lock pin 18, thereby preventing an irreversible entry of the latter into the bore 26. In a predetermined time, the EBD automatically energizes the coil 56 for a moment to create electromagnetic force opposite to the force of the permanent magnet 58.

Thereby the spring 66 overcomes the attractive force of the magnet 58, and pushes the armature 62 towards its extended state. The head 64 abuts the side surface of the lock pin 18. In this state, the padlock is unlocked and unblocked, and is ready for locking.

In order to lock the padlock, the lock bolt 16 is manually inserted back into the bore 28-26 and turned with the notch 46 towards the lock pin 18, pushing back the dummy plug 40. The lock pin 18 then jumps into the notch 46, blocking the lock bolt, while the head 64 jumps under the lock pin 18, blocking the lock pin, as explained above.

With reference to Figs. 4A, B and C, the bi-stable solenoid 20 is provided with an anti-shock arrangement comprising an elongated guiding slit 82 and a radial pin 84 attached to the head 64 and slidingly received in the slit 82. The guiding slit 82 is made in an extension of the bracket 52 and is disposed in a plane parallel to the axis 86 of the bore 60, at a predetermined angle of inclination a to that axis. The length of the pin 84 and the configuration of the slit 82 are selected so that when the head 64 is in the extended state of the blocking drive 20, the pin 84 is in one end of the slit 82 (Fig. 4A) and when the head 64 is in the contracted state of the blocking drive, the pin 84 is in the other end of the slit 82 (Fig. 4B).

Thereby, the axial force of the magnet 58, the coil 56 and the spring 66 exerted upon the armature 62 results both in linear motion and in rotary motion of the head 64 (Fig. 4C), whereby the pin 84 performs a helical motion.

It should be understood that during the above described motion of the head 64, the radial pin 84 slides in the slit 82 with some measure of friction depending on the angle a, on the material of the pin 84 and the bracket 52 and on the quality of their contacting surfaces. This measure of friction should not prevent the normal operation of the solenoid as blocking device, as described with reference to Figs. 2 and 3. The inventor has found, however, that this arrangement, at some angle a, will prevent the movement of the head 64 and the armature 62 under impulsive or shock force of short duration. Since the padlock is typically used in more or less freely pendant state, an impulsive force may be easily applied by knocking on the padlock or, alternatively, by slamming the padlock into a nearby hard object.

Thereby, an unauthorized person would be able to shift the solenoid 20 without an anti-shock arrangement into contracted state where the magnet 58 holds the head 64 and the padlock is unblocked, without any key.

The inventor has further found that there exists a range of angles a where the movement under shock force is prevented while the solenoid 20 is able to operate normally. For a steel pin 84 and a steel bracket 52, the angle a is about 65°, preferably between 60° and 70°. This can be explained by the relatively prolonged application of the magnetic force in the solenoid coil as opposed to the instant character of the shock effect.

The anti-shock arrangement shown above is only an example of a very simple way to prevent the linear motion of the armature under impulsive force (shock force) by engaging the armature in a second motion associated with friction along an inclined plane. This principle may be embodied in a variety of specific constructions. For example, a helical channel may be machined in the armature itself, engaging a cam fixed to the solenoid structure. The armature may not necessarily perform the second motion but has to be engaged so that the first (linear) motion would be impossible without the second motion. For example, in the above embodiment, the armature 62 rotates together with the pin 84. However, the head 64 with the pin 84 may be mounted for free rotation to the armature 62 so that the armature will not rotate together with the head. Nevertheless, the armature would not slide in the bore 60 without the pin 84 sliding in the slit 82.

Although a description of specific embodiments has been presented, it is contemplated that various changes could be made without deviating from the scope of the present invention. For example, the second motion may be linear or rotational or more complex, the inclined plane may have variable angle of inclination, pairs of materials with lower or higher friction coefficient than steel may be used, the sliding surfaces may be specially treated, etc.