The present invention refers to an unscrewing- preventing system for bolts.

The invention finds its application in the field of mechanics.

In mechanics, a bolt is a component composed of a screw (head with threaded stem) and a nut with a corresponding thread.

The nut, usually with an hexagonal shape, is screwed on the stem of the screw to mutually connect parts to be assembled. When there are vibrations, stresses or impacts, the nut tends to be loosened, so that several solutions are used, among which the addition of a lock nut.

The current system provides that, on the screw, the nut is assembled, followed, for a higher safety, by a lock nut (Figure 1) . Cases however can happen in which loosening of the lock nut occurs with the consequent loosening of the nut.

Object of the present invention, therefore, is solving the above prior art problems, by providing an unscrewing-preventing system for bolts which is efficient, unmovable and easily made. The above and other objects and advantages of the invention, as will appear from the following description, are obtained with an unscrewing-preventing system for bolts as claimed in Claim 1. Preferred embodiments and non-trivial variations of the present invention are the subject matter of the dependent claims .

It is intended that all enclosed claims are an integral part of the present description.

The present invention will be better described by some preferred embodiments thereof, provided as a non- limiting example, with reference to the enclosed drawings, in which:

Figure 1.1 shows the prior art situation with nut and lock nut; Figures 2.1 to 4.1 show embodiments with a high nut with tightening action on the screw reductions .

Figures 1.2 to 4.2 show embodiments with nut and lock nut with tightening action on the screw reductions; Figure 5.2 shows an embodiment with special nut and lock nut with tightening action on the screw reduction .

Figures 1.3 and 2.3 show embodiments with a nut with tightening action on the reductions of a screw with biting catch; Figure 3.3 shows an embodiment with a high nut with tightening action on the reductions of a screw with biting catch; Figure 4.3 shows an embodiment with a nut with tightening action on the reduction of a screw with biting catch (and tightening action on the stem of the under-head); Figure 5.3 shows an embodiment with special nut and lock nut with tightening action on the reduction of a screw with biting catch.

Figure 1.4 shows an embodiment with special nut and lock nut with tightening action between the reduction of the former and the chamber of the latter; Figure 2.4 shows an embodiment with special nut and lock nut with tightening action on the screw reduction and on a deformable insert with pliers effect on the screw stem; Figure 3.4 shows an embodiment with a nut with tightening action on a deformable flanged insert with pliers effect on the screw stem and a lock nut; Figure 4.4 shows an embodiment with special nut and lock nut with tightening action on the screw reduction; Figure 5.4 shows an embodiment with a high nut with tightening action on the screw and lock nut reductions.

With reference to the Figures, a preferred embodiment of the unscrewing-preventing system for bolts of the present invention is shown and described. It will be immediately obvious that numerous variations and modifications (for example related to shape, sizes, arrangements and parts with equivalent functionality) can be made to what is described, without departing from the scope of the invention, as claimed in the enclosed claims.

The invention deals with unscrewing-preventing systems for bolts (of the simple use or biting catch types) in which the male has a single or double threading; has deformable inserts and reductions with tightening functions and, in the mentioned cases, uses special nuts.

The material to be used for each of the embodiments shown in the above Figures will clearly have to be in compliance with the corresponding needs for every single case. Therefore, the invention covers any material which is used for its realisation.

Figure 1.1 shows the prior art situation with a screw (1) , a nut (2) and a lock nut (3) .

Figure 2.1 shows a screw (1) with a cylindrical reduction chamfered at its end; an oriented nut (2) with its threaded part biting and equipped with a through-hole which is coupled with the screw reduction. The unscrewing-preventing action is obtained by the friction existing in this cylindrical coupling (3) , where male and female comply with the working tolerances suitable for an adequate driving.

Figure 3.1 shows a screw (1) and a high oriented nut (2) with the threaded part preceded by a cylindrical chamber whose diameter is bigger than the thread crests, but such as to obtain a locking condition on the screw stem. The unscrewing-preventing action is obtained by the friction existing in this cylindrical coupling (3), where male and female comply with the working tolerances suitable for an adequate driving .

Figure 4.1 shows a screw (1) with a cylindrical reduction chamfered at its end ; a high and oriented nut (2) with its central part preceded by a cylindrical chamber, whose diameter is bigger than the thread crests, but such as to obtain a locking condition on the screw stem and followed by a cylindrical through- reduction which is coupled with the male reduction. The unscrewing-preventing action is obtained by the friction existing in this double cylindrical coupling (3), where male and female comply with the working tolerances suitable for an adequate driving.

Figure 1.2 shows a screw (1) with a cylindrical reduction chamfered at its end; a nut (2) ; a high and oriented lock nut (3) with its threaded part having a cylindrical through-reduction which is coupled with the screw reduction. The unscrewing-preventing action is obtained by the friction existing in this cylindrical coupling (4) , where male and female comply with the working tolerances suitable for an adequate driving.

Figure 2.2 shows a screw (1) with a cylindrical reduction whose diameter is not bigger than the screw core and a further threaded reduction; a nut (2); an oriented lock nut (3) with its threaded part preceded by a cylindrical chamber which is coupled with the intermediate cylindrical section of the screw. The unscrewing-preventing action is obtained by the friction existing in this cylindrical coupling (4), where male and female comply with the working tolerances suitable for an adequate driving.

Figure 3.2 shows a screw (1) with a cylindrical reduction chamfered at its end; an oriented nut (2) with its threaded part preceded by a cylindrical chamber whose diameter is bigger than the thread crests, but such as to obtain a locking condition on the screw stem; an oriented lock nut (3) with its threaded part having a cylindrical through-reduction which is coupled with the cylindrical screw reduction. The unscrewing-preventing action is obtained by the friction existing in this double cylindrical coupling (4) (5) , where male and female comply with the working tolerances suitable for an adequate driving.

Figure 4.2 4 shows a screw (1) with a cylindrical reduction whose diameter is not bigger than the screw core and a further threaded reduction; an oriented nut (2) with non-threaded section (collar) which is coupled with the intermediate cylindrical section of the screw in order to obtain a blocking condition; an oriented lock nut (3) with its threaded part preceded by a cylindrical chamber which is coupled with the intermediate cylindrical section of the screw in order to obtain a blocking condition. The unscrewing- preventing action is obtained by the friction existing in this double cylindrical coupling (4) (5), where male and female comply with the working tolerances suitable for an adequate driving.

Figure 5.2 shows a screw (1) with a cylindrical reduction chamfered at its end; an oriented nut (2) with an externally threaded reduction; a lock nut (3) with threaded chamber which engages the external thread of the nut and which goes in with a cylindrical through-hole coupled with the screw reduction. The unscrewing-preventing action is obtained by the friction existing in this cylindrical coupling (4) , where male and female comply with the working tolerances suitable for an adequate driving.

Figure 1.3 shows a screw with biting catch (1) with a cylindrical reduction chamfered at its end; an oriented nut (2) with its threaded part and a cylindrical through-reduction which is coupled with the screw reduction. The unscrewing-preventing action is obtained by the friction existing in this cylindrical coupling (3) , where male and female comply with the working tolerances suitable for an adequate driving. Section a shows an alternative solution in which the same unscrewing-preventing action is directly performed on the part to be assembled. Figure 2.3 shows a screw with biting catch (1) with a cylindrical reduction whose diameter is not bigger than the screw core and a further threaded reduction; an oriented nut (2) with its threaded part preceded by a cylindrical chamber which is coupled with the intermediate cylindrical section of the screw. The unscrewing-preventing action is obtained by the friction existing in this cylindrical coupling (3) , where male and female comply with the working tolerances suitable for an adequate driving.

Figure 3.3 shows a screw with biting catch (1) with an intermediate cylindrical reduction whose diameter is not bigger than the screw core, a further threaded reduction and a last cylindrical reduction chamfered at its end; a high oriented nut (2) with its threaded part preceded by a cylindrical chamber which is coupled with the intermediate cylindrical section of the screw and a second cylindrical section which is coupled with the last screw reduction. The unscrewing- preventing action is obtained by the friction existing in this double cylindrical coupling (3) (4), where male and female comply with the working tolerances suitable for an adequate driving.

Figure 4.3 shows a screw with biting catch (1) with a section under the head with forced assembling tolerances and with a cylindrical reduction chamfered at its end; an oriented nut (2) with its threaded part and a cylindrical through-reduction which is coupled with the cylindrical screw reduction. The unscrewing- preventing action is obtained by the friction existing in this double cylindrical coupling (3) (4), where male and female comply with the working tolerances suitable for an adequate driving.

Figure 5.3 shows a screw with biting catch (1) with a cylindrical reduction chamfered at its end; an oriented nut (2) with an externally threaded reduction; a lock nut (3) with threaded chamber which engages the external thread of the nut and which goes on with a cylindrical through-hole coupled with the screw reduction. The unscrewing-preventing action is obtained by the friction existing in this cylindrical coupling (4) , where male and female comply with the working tolerances suitable for an adequate driving.

Figure 1.4 shows a screw (1); an oriented nut (2) with a cylindrical reduction on its hexagonal section; a lock nut (3) with a cylindrical chamber which is coupled with the cylindrical reduction of the nut. The unscrewing-preventing action is obtained by the friction existing in this cylindrical coupling (4), where male and female comply with the working tolerances suitable for an adequate driving.

Figure 2.4 shows a screw (1) with a cylindrical reduction chamfered at its end; an oriented nut (2) which has an externally threaded reduction and an internal chamber below; a deformable bush (4) constrained between screw reduction and nut chamber under the screwing thrust of the lock nut (3) , whose threaded chamber gets engaged with the external thread of the nut and goes on with a through-hole being coupled with the screw reduction. The unscrewing- preventing action is obtained by the friction (6) following the driving of the bush and the friction (5) existing in the cylindrical coupling (5) between screw and lock nut, where male and female comply with the working tolerances suitable for an adequate driving. Section a is an alternative solution in which the deformable insert is composed of a flanged bush.

Figure 3.4 shows a screw (1), an oriented nut (2) with its threaded part, and a cylindrical chamber on its opposite side; a deformable flanged insert (4) constrained between cylindrical screw reduction, nut and lock nut (3) . The unscrewing-preventing action is obtained by tightening the insert between the faces (6) of nut and lock nut, and by the friction (5) created in compressing the insert between screw reduction and nut chamber, since the working tolerances are suitable for an adequate driving.

Figure 4.4 shows the screw (1) with a cylindrical reduction chamfered at its end; a high oriented nut (2) with a read threaded chamber; a screw-type plug (3) with cylindrical recess adapted to be forced on the screw reduction. The unscrewing-preventing action is obtained by the friction existing in this coupling (4), where male and female comply with the working tolerances for an adequate driving.

Figure 5.4 shows a screw (1); a high and symmetrical nut which has two chamber with forced couplings; a counter-screw (3) with a cylindrical section under the head. The unscrewing-preventing action is obtained by frictions existing in this double coupling (5) , where males and females comply with the working tolerances suitable for an adequate driving.