DESCRIPTION

Field of the invention

The present invention relates to the field of small metal hardware and in particular it relates to a bolt snap clasp of the sliding type, especially designed for use in leather goods but more generally usable in other sectors, such as costume jewellery. The invention also relates to a mounting method for assembling the clasp.

Background art

Bolt snap clasps of the type mentioned above are well known and have been used for a long time. More precisely, reference is made herein to a device provided with a tubular body which develops along a longitudinal axis and which serves as a guide for the sliding of a small bolt along the same axis. This bolt has an outer tip which protrudes from a corresponding (first) end of the body and which, together with a hook which extends integrally from the same first end of the body, is adapted to form a loop, openable as a result of the sliding of the bolt and which represents the actual clasp. The sliding can be actuated manually by the operator acting on a tooth which projects from the bolt laterally (i.e. transversely to the longitudinal axis of the body and of sliding of the bolt), being accessible from the outside of the body through a longitudinal slit formed thereon.

The second end of the tubular body is closed by a screw, which acts as an abutment element for a spring housed within the body and compressed between the screw itself and a tail of the bolt. The spring is used to counteract the sliding the bolt from the locked position (that is, where the tip touches the tip of the hook, or comes in the immediate vicinity thereof, resulting in the closure of the clasp), maintaining such a stable position in the absence of a manual actuation that serves to overcome the resistance exerted by the spring.

Finally, the screw serves as a connection element for a rotatable ring, which extends beyond the second end of the body, lying on the bundle of planes passing through the sliding longitudinal axis. For example, according to an embodiment, a head of the screw axially tightens a base collar of the ring rotatably engaged - about the longitudinal axis - on a stem portion formed on the body in the vicinity of the second end. Such a connection between body and ring, which serves as a connection element of the whole device to one of the portions that the device itself is intended to reversibly join (such as body and flap of a purse), allows freely orienting the body around its own axis, making the clasp more functional, in particular during the hooking and unhooking operations.

According to the most widespread constructive solution, the above longitudinal slit extends from the second end, stopping in the vicinity of the first end of the body. With this solution, the assembly of the device takes place by inserting the bolt in the body from the second end, then inserting the spring, and then tightening the screw with its own ring. This solution is however little appreciated in some cases, particularly for the use of the device in high quality products, due to the slit that, by opening on the end adjacent to the ring, is very visible and aesthetically unappealing.

Alternatively, a different solution is therefore adopted in these cases, i.e. with a less evident slit formed starting from the first end and which leaves the body unbroken in the area adjacent to the ring. In this way, however, complications arise with regard to the installation process. In fact, in order to insert the bolt from the first end it is first necessary to deform the hook so as to free the space facing such an end, and then fold it into alignment with the tip of the bolt, after the latter has been inserted. Clearly, it is a challenging task, which not only increases the production costs, but also makes it difficult to regain a perfect alignment between hook and bolt, so there is still a certain aesthetic decay. Moreover, the need to bend the hook prevents the use of certain materials that do not allow such an operation, or whose surface finish would in any case suffer an unacceptable degradation as a result of the bending.

Summary of the invention

The object of the present invention is to overcome this situation by providing a sliding bolt snap of the type mentioned above which has an insertion slit for the bolt formed starting from the first end of the body, that is, that facing the hook, yet simple to assemble and adapted to be used with virtually any metal material, also surface-treated, all while maintaining unchanged the prerogatives of simple and reliable features that are typical of this kind of devices. Such an object is achieved by the bolt snap and corresponding mounting method the essential features whereof are defined by the first and the twelfth of the appended claims.

Brief description of the drawings

The features and the advantages of the bolt snap clasp and the relative mounting method according to the invention shall now be described in more detail with the following description of an embodiment thereof, made by way of a non-limiting example with reference to the accompanying drawings, in which:

- figure 1 is an axonometric view of a clasp according to the invention, in assembled configuration;

- figures 2 and 3 show axonometric views of a bolt and a bushing of the clasp in figure 1 , shown in isolation and enlarged;

- figure 4 shows an exploded view of the clasp in figure 4, seen from a side; and

- figures 5a to 5h show, through side views (figures 5a, 5c, 5e, 5g) and longitudinal sections (figures 5b, 5d, 5f, 5h), respective subsequent steps of the mounting method, according to the invention, of the clasp in the previous figures.

Detailed description of the invention

With reference to said figures, a bolt snap clasp according to the invention generally has the features already mentioned for the similar clasps according to the prior art.

In particular, it is shown a tubular body 1 which extends along a longitudinal axis X and which acts as a guide, within the inner cavity 11 thereof, for the sliding of a bolt. Bolt 2 is an elongated member (according to an axis X' thereof which in the assembled configuration coincides with axis X of the body) which has a cylindrical shaft 21 having an outer diameter nominally equal to that of cavity 11 in which it slides with substantially no crosswise play, culminating with an outer tip 2a which protrudes from a first end 1 a of body 1. A hook 2 integrally extends from such a first end which, together with tip 2a of shaft 21 is adapted to configure, in a closed or maximum advancement position of bolt 2, a loop for engagement with an element complementary to the clasp, not shown, such as an eyelet or the like. The complementary element is provided externally and is configured depending on the specific application in order to achieve, precisely through the coupling through the clasp, a reversible connection between two items or different parts of a same item.

The loop, i.e. the actual clasping part of the device, can be opened as a result of the sliding of bolt 2 to return into body 1 , and to this end bolt 2 comprises an actuating tooth 22, which protrudes laterally (i.e. crosswise with respect to the longitudinal axis X'), through a thin slit 13 formed longitudinally on the body to laterally open cavity 11 along a cylindrical segment of reduced width with respect to the diameter of the cavity itself (and of shaft 21). In order to facilitate the manual actuation of tooth 22, this has, in a known manner, an end portion 22a which is thickened with respect to a root 22b of the tooth, which having to pass through slit 13 has a reduced thickness, smaller than the width of the slit itself and all the more so of the diameter of shaft 21.

The sliding of the bolt in the opening direction is hindered by a spring 3, compressed between a screw 4 which closes body 1 at the second end 1 b, and a tail 2b of the bolt. A ring 5 is then rotatably connected, with a rotation axis coincident with axis X, to the second end 1 b of body 1. To achieve this connection, screw 4 has a head 41 which at the end of the screwing stroke axially tightens a base collar 51 of the ring, rotatably engaged with a pivot portion 14 defined on the outside of the body in the vicinity of the second end 1 b, between the latter and a radial projection 15.

Coming to the characteristic aspects of the invention, the same is applicable in the context of a body the slit 13 whereof extends from the first end, and stops at a point spaced from the second end. As shown particularly clearly in figure 2, bolt 2 downstream of the cylindrical shaft 21 , i.e. towards tail 2b, has a region 23 with a reduced thickness, i.e. the size which is measured orthogonally to a plane defined by X and by the transverse direction Y' along which the tooth protrudes (plane corresponding to that on which hook 12 develops when the bolt is inserted in the body). Such a thickness is in particular not greater than that of root 22b of tooth 22.

The above region 23 of reduced thickness extends longitudinally so as to affect at least partially the junction area in which root 22b branches off laterally, and to reach tail 2b. Preferably, such a region 23 comprises a plate-shaped segment 23a which extends beyond root 22b and which affects the junction area of the same root by at least half the longitudinal development thereof. Even more preferably, root 22b and plate-shaped segment 23a derive from the integral shaping of a single plate of uniform thickness.

Region 23, and specifically the plate-shaped segment 23a, also has a smaller size, with respect to the diameter of shaft 21 , also measured according to the transverse direction Y'. In particular, such a smaller size is achieved by means of a groove 23b which slightly excavates the side of segment 23a opposite to that from which the tooth branches off, thus misaligning this side internally from a corresponding profile line of the shaft (as easily noticeable in figures 2 and 4).

Tail 2b is then affected by engagement means for engagement with a bushing 6 which is adapted to give to the bolt, precisely at the tail, a precise sliding coupling profile with cavity 1 1 , and in particular in this case cylindrical with a diameter substantially corresponding to that of shaft 21 , suitable for preventing the bolt from playing within cavity 1 1 , stopping movements thereof on a plane orthogonal to the longitudinal axis X, and ultimately giving a stable support to the sliding of bolt 11 even in the vicinity of the tail, this being advantageous in particular when the shaft is in the closed position almost completely arranged outside of the cavity. The bushing 6, clearly adapted to be inserted into cavity 11 through the second end 1 b, also determines a safe and reliable abutment for spring 3.

In the depicted example, the engagement means are represented by a pin 24 coaxial with shaft 21 , of diameter equal to or smaller than that of the plate-shaped segment 23a and the free end of which forms tail 2b. In a complementary manner, bushing 6 is provided with a central hole 6a into which the pin fits. Equivalent solutions may be adopted, for example a mirrored configuration which provides a pin on a stopping cylinder similar to the bushing and a small hole at the end of the plate-shaped segment. The bushing may moreover be replaced by elements of shape other than cylindrical, for example spokes, when capable of ensuring the same functionality.

Observing the figures 5a to 5h, one can appreciate the method for assembling the clasp according to the invention. Figure 5a shows in particular a crucial passage, i.e. the insertion of the bolt within the body, with penetration of the slit by the tooth, starting from the first end 1a of the body itself, namely that facing the hook. Such an insertion can occur in spite of the encumbrance and mechanical hindrance determined by the hook itself because region 23 with reduced thickness and width allows in this step to have greater room for manoeuvre, for example and in particular by passing the tail of the bolt in the slit and simultaneously taking advantage of a certain play, which allows, if necessary, slightly angling the bolt with respect to the plane of the hook. Combining these two factors, and obviously assisting the insertion with a suitable rotation and translation of the bolt on the plane just mentioned, one obtains the right alignment of axis X' of the bolt with that X of the body, as shown in figure 5b and actually the positioning of the bolt itself already in the operational position, with shaft 21 which faces the apex of the hook and is stopped thereby in the closed position.

At this point (figures 5c and 5d), bushing 6 first, and then spring 3 are inserted into cavity 1 1 from the second end 1 b of body 1 (and therefore from the corresponding end of the cavity). The bushing can be made simply fall and slide into the cavity by the effect of gravity, and as already mentioned it engages with the tail of the bolt, here in particular with pin 24, causing also the tail to be completely locked within cavity 11 with respect to radial displacements (i.e. transverse the longitudinal ones, functional to the sliding), throughout the whole run of the bolt. The assembly continues at this point as shown in the following figures from 5e to 5h according to steps substantially corresponding to the traditional ones, namely positioning of ring 5 on the pivot portion 14 of body 1 (figure 5f) and tightening of screw 4 to lock the ring and contextually the spring, urging it in compression.

It will be appreciated from the foregoing that, due to the solution proposed herein it is possible to achieve a sliding bolt snap clasp such as the one taken as a reference above, and with the sliding slit of the actuating tooth formed from the hook end of the body, in a manner greatly facilitated compared to the known system with mechanical deformation of the hook. On top of the immediate productive simplification, a qualitatively perfect result is achieved, with always perfect alignment of shaft 21 with the apex of the hook and no whatsoever possibility of surface deterioration.

In addition, the invention allows the use of materials and treatments completely precluded to date, with the aforesaid deformation system of known type. In fact, it is possible to use materials such as "zamak" alloy, preliminarily letting the single parts, and in particular body 1 , undergo protection and surface finish treatments (for example and in particular electrochemical treatments such as galvanic treatments, but also painting etc. obviously unthinkable of, or however practically unfeasible, in a post-assembly phase), and subsequently assembling them precisely without any need for mechanical stress and thus safeguarding the integrity thereof.

Beyond the geometric solutions shown in the example, which correspond to the most typical and common ones, different geometries may be adopted. Shaft 21 may for example not be cylindrical, i.e., be provided with outer profiles other than the circular one, cavity 1 1 being correspondingly made with a couplable profile. Moreover, the screw- ring group may be replaced by closure means of the second end having a different configuration. It should be noted, finally, that the invention can also be applied to so- called double clasps, in the sense that the closure means at the second end may be represented by a further bolt configuration (and relative hook shaping) mirroring that of the first end. Other variants and/or modifications may be brought to the bolt snap clasp and to the relative mounting method, without thereby departing from the scope of protection of the invention itself as defined by the appended claims.