The closure in question is of the spring-action type with a combination lock comprising a casing, a bolt and two mechanisms which can be operated separately in order to form the combination.

According to the invention, said closure comprises: at least a first knob mechanism whose axis is fixed with respect to the casing, and a second knob mechanism mounted on the movable bolt unit; forming part of each of said two mechanisms is an annular member which can be operated via the corresponding operating knob and which has a circular profile, a peripheral notch and an inner ring of indentations intended to engage with elastic pin means so as to define a plurality of positions of the operating knob with respect to the annular member and therefore with respect to the peripheral notch; provided on the movable casing and on the movable bolt unit are two projections designed to engage with the corresponding circular profiles and with the corresponding peripheral notches so as to prevent the bolt unit from sliding and so as to allow it to slide only when the operating knobs are positioned in accordance with the correct combination; the combination can be changed only when the bolt unit is in the open position.

Each knob mechanism comprises two elastic pins: one for the click positioning of the knob mechanism and the other for the click movement between the operating knob and the annular member when this annular member is immobilized in the open position of the bolt unit. In practice, these two ball-shaped elastic pins or similar elements are accommodated in a single

incline through-seat such that they engage with a ring of indentations on the corresponding annular member and with an additional ring of indentations f rmed in the casing and in the bolt unit respectively.

The number of knob mechanisms can be increased (in order to increase the combination), preferably providing more than one knob mechanism with a fixed axis.

A better understanding of the invention will be gained by following the description and the appended drawing which shows a practical and non- limiting embodiment of the invention. In the drawing: Fig. 1 shows a view on l-l in Fig. 2, with a number of members removed, in the open position; Fig. 2 shows a section on II-I I in Fig. 1; Figs 3 and 4 are similar to Figs 1 and 2, but show the closed position; Figs 5 and 6 show two enlarged cross sections on V-V and VI-VI in Fig. 1, showing all the members; Fig. 7 shows an exploded perspective view of the main members; and Fig. 8 shows, in isolation, a member of the knob mechanism.

With reference to the illustration in the appended drawing, the numeral 1 is the general reference for a casing which has a slot 1 A into which the element 3 to be immobilized in order to effect closure penetrates, said element 3 being provided with a small bridge 3A designed to penetrate into said aperture 1A; the bridge 3A can be immobilized by the bolt extension piece 5A formed by a movable bolt unit 5 which is able to slide in a recess formed in the casing 1 and having guide surfaces for guiding said bolt unit 5.

The bolt unit 5 is pushed into the closed position (with the bolt extension piece 5A projecting into the opening 1A) by two springs 7 which are designed to press against corresponding shoulders formed by the recess in the casing 1 and by the bolt unit 5 respectively. The bolt unit 5 takes the form of a small plate which can slide within said guide recess formed in the casing 1 and is closed off by a flat cover-plate 9 and by an element 9X which provides an

additional partial thickness. The movable bolt unit 5 has a relatively large and slightly elongated cut-out 5B into which a projection 5C extends axially in the direction of sliding f5 of the bolt unit 5 with respect to the casing. A projection 1 C similar to the one 5C and in alignment with the latter but extending in the opposite direction, is formed in the recess formed by the casing 1. These two projections 5C and 1 C have an immobilizing function which will be described below.

Mounted in correspondence of the cut-out 5B in the casing 1 is a first knob mechanism 13 (see Fig. 5) which has an operating knob 13A on the outside and, fixed inside and coaxially with the knob 13A, a small cylinder element 13B terminating in a flat head 13C designed to engage rotationally with an annular member 13E which is able to rotate around the axis of the knob mechanism assembly 13; this annular member 13E is partially housed within the cut-out 5B of the movable bolt unit 5 in order to allow said unit 5 to slide with respect to the casing 1 and with respect to said first knob mechanism 13. The annular member 13E has a circular profile 13F containing a peripheral notch 13G, while on the inside said annular member 13E has an inner ring of indentations 13H which are able to engage with an elastic pin.

Said first knob mechanism 13 is accommodated in a through-seat 1 H formed in the casing 1 and having a series of indentations designed to engage with an additional elastic pin; this through-seat 1 H is formed within a circular raised part 1 K which-in addition to the through-seat 1 H-also contains a notch 1 L which corresponds to the peripheral notch 13G in the annular member 13 and which is provided for the purposes indicated below; these notches 13G and 1 L are designed to accommodate the projection 5C on the movable bolt unit 5. When assembling the first knob mechanism 13, the operating knob 13A remains outside the casing 1, the cylinder 13B fits inside the through-seat 1 H which is shaped in the form of an inner ring of indentations, and the inner ring of indentations 13H of the annular member 13E fits behind the through-seat 1 H. The cylinder part 13B contains a through-hole 13M whose axis extends along a diametrical plane of said member but is inciined with respect to the axis of the cylinder 13B, of the head 13C and of the threaded shank 13R

which engages in the operating knob 13A; the hole 13M accommodates a spring 13N which presses on two small balls 13P and 13Q designed to form elastic pins which act on the ring of internal indentations 1 H and on the ring of internal indentations 13H respectively; both elastic pins 13P and 13Q engage with a single spring 13N. This arrangement means that two elastic pins are formed: one acting between the operating knob 13A and the casing 1 (the elastic pin formed by the ball 13P), and the other elastic pin-formed by the ball 13Q-engaging in the inner ring of indentations 13H of the annular member 13E (containing the notch 13G formed in the circular profile 13F).

This configuration means that, when the annular member 13E is not prevented from rotating, it is possible to use the operating knob 13A to move the first knob mechanism 13 with the annular member 13E integral with said knob 13A, so that the knob 13A can be indexed around (as a result of the elastic pin 13P acting on the through-seat 13H with the inner ring of indentations) into various positions defined by said ring of indentations 1 H, so that it is possible to position the annular member 13E and its peripheral notch 13G as desired-in accordance with the preselected combination. It is also possible-if the combination for opening the lock is known-to bring the knob 13A into the position corresponding to the number for the combination for the first knob mechanism 13, i. e. to bring the notch 13G in alignment with the projection 5C on the bolt member; under these conditions the bolt member can be moved from the position in which the extension piece 5A is locked in place into one in which it is released so that the lock can be opened and closed; in all the other angular positions of the knob mechanism 13 it is impossible to open the lock because the projection 5C is not in alignment with the peripheral notch 13G but abuts against the circular profile 13F of the annular member 13E, so that the lock cannot be opened. In contrast, when the knob mechanisms are in the correct position, said bolt unit 5 can be moved into the open position because the projection 5C can be accommodated in the notch 13G. Under these conditions the annular member 13E is ;-evented from rotating in any way whatsoever; then, and only then, will it be possible, by exerting a force on the operating knob 13A, to overcome

the retention force of the elastic pin 13P and index the operating knob 13A around relative to the annular member 13E so as to be able to change the combination, i. e. so as to be able to move the operating knob 13A with respect to the annular member 13E into the new position set for the new combination, one different from the previous combination. This means that subsequent opening operation will be effective only if the operating knob 13A has been brought into the new correct position-one in which the notch 13G in the annular member 13E is in alignment with the projection 5C-so that only under these conditions will it be possible to slide the bolt unit 5 back in order to open the lock.

A similar arrangement is provided for the second knob mechanism, which is given the general reference 23 and is equivalent to the knob mechanism 13A but is modified so that it can be mounted on the movable bolt unit 5 rather than on the casing 1. This second knob mechanism 23 is therefore able to move longitudinally, i. e. in the direction of the arrow f5, together with the movable bolt unit 5, and it is this mechanism 23 which allows the lock to be opened since, by acting on the knob 23A of the second knob mechanism 23 in the opposite direction to the force exerted by the springs 7, it is possible to slide the bolt back in order to open the lock, i. e. in order to release the bolt extension piece 5A, thereby also releasing the bridge 3A; this is, of course, possible as long as both the first knob mechanism 13 and the second knob mechanism 23 are in the correct combination position. This second knob mechanism 23 has the operating knob 23A, the small cylinder 23B, the flat head 23C and the annular member 23E with the inner ring of indentations 23H, this second knob mechanism 23 being mounted on the movable bolt unit 5 in a through-seat 5H formed in said movable bolt unit 5 in a manner similar to the through-seat 1 H and, like the latter, having an inner ring of indentations equivalent to the ring 1H. Like the cylinder 13B, the cylinder 23B also has two elastic pins 23P and 23Q which are designed to engage in the indentations in the ring of indentations 5H and 23H formed in the movable unit 5 and in the annular member 23E respectively. In order to allow the knob mechanism 23 to move, together with the bolt unit 5, in the

direction of the arrow f5 with respect to the casing 1, the latter has a slot- shaped hole 1 B whose function is similar to that of the cut-out 5B in the unit 5.

The function of this second knob mechanism 23 is therefore to make the sliding movement that enables the movable bolt unit 5 to open against the force exerted by the antagonistic springs 7, as long as the two operating knobs 13A and 23A have been positioned in accordance with the combination intended to permit opening, this second knob mechanism 23 also allowing the combination to be changed (in a manner similar to that applicable to and as has been described for the first knob mechanism 13) when the bolt unit 5 is held in the open position so that the projection 1 C immobilizes the annular member 23E once it has penetrated into the peripheral notch 23G in the member 23; then, and only then, will it be possible, by rotating the operating knob 23A, to index said knob into place by means of successive angular clicks, in order to set the knob 23A to a new combination for opening the lock, one different from the previous combination. Once the bolt 5,5A is brought back into the closed position under the action of the springs 7, it is then also possible to move the knob 23A, like the knob 13A, freely together with their respective annular members 23E and 13E, in order to conceal the position of the operating knobs and so eliminate the possibility of the lock being opened when the new combination is not known.

The spring-action lock described can be constructed using members readily produced by means of conventional mechanical operations and offers the advantage of being extremely thin.

The example described relates to a configuration whose overall line of symmetry lies along the axis of movement of the bolt member. However, there is nothing to prevent the use of other solutions which are completely equivalent from the functional and kinematic viewpoints but in which the operational members can be laid out in different configurations, for example the knobs may be positioned differently, in a direction transverse to that in the example illustrated and with one of the two operating knobs moving transversely, or the bolt closure may also be placed in a different position to the closure formed by the parts 1 A and 5A illustrated.

It goes without saying that the drawing shows only one example, given solely as a practical demonstration of the invention, and that the latter may vary in terms of form and arrangements without thereby departing from the scope of the concept on which said invention is based.