Pin with breakneck groove, fastener comprising such a pin, related assembly and installation method

1. A pin extends along a main axis and comprising a head and a threaded portion, an end of the head opposite to the threaded portion forming an end surface in a first plane perpendicular to the main axis,

the pin further comprises a handling component which is an integral part of the head opposite the threaded portion, a junction between that head and the handling component comprising a breakneck groove configured to break under a torsional stress greater than a predetermined threshold, said breakneck groove having substantially a shape of revolution around the main axis,

characterized in that, in a second plane comprising the main axis, a section of the breakneck groove has an arc of circle portion, a center of said circle being substantially set in the first plane, so that a plane containing a breakneck groove surface substantially coincides with the first plane.

2. Pin according to claim 1 , wherein the arc of circle portion of the breakneck groove comprises a first part and a second part arranged on the first plane on either side of the head and handling component respectively,

said first part forming a cavity in the head in relation to the first end surface.

3. Pin according to claim 1 , wherein the breakneck groove has a first lip and a second lip tangential to the arc of circle portion and substantially tapered, said first and second lips being respectively arranged on the head and on the handling component.

4. Pin according to claim 3 , in which:

the first lip forms a first angle (α) with the end surface of the head, and a second angle (β) with the second lip,

the first angle (α) is between 5° and 25° and preferably between 10° and 15°; and

the second angle (β) is between 15° and 60°, preferably between 25° and 35° and more preferably close to 30°.

5. Pin according to claim 1 , wherein the head is a countersunk head.

6. A fastener comprising:

a pin as claimed in claim 1 ; and

a sleeve comprising a collar and a cylindrical body, adjacent to the main axis;

the sleeve body comprising: a deformation zone capable of forming an outer bulb; and a threaded portion able to cooperate with the threaded portion of the pin.

7. Fastener according to claim 6 wherein the head is a countersunk head, wherein the sleeve collar is tapered and able to house the countersunk pin head,

an end of that collar, opposite the sleeve body, being substantially set in a third plane perpendicular to the main axis.

8. An assembly comprising:

at least one structure comprising a first surface and a second surface opposite, a hole opening on each of those surfaces; and

a fastener according to claim 6 ,

in which:

the collar of the sleeve is in contact with the head of the pin and butts up the end of the hole in the structure,

the deformation zone of the sleeve body is in an installed configuration, in the form of an outer bulb in contact with the second surface of the structure; and

the head and the handling component of the pin are separated, said head having a fracture surface that is substantially coplanar with the end surface of the pin and end of the sleeve collar.

9. Assembly according to claim 8 , wherein the arc of circle portion of the breakneck groove comprises a first part and a second part arranged on the first plane on either side of the head and handling component respectively, said first part forming a cavity in the head in relation to the first end surface, and wherein the fracture surface is bordered by the first portion of the arc of circle portion of the breakneck groove.

10. A method for fitting a fastener according to claim 6 in a structure comprising a first surface and a second surface opposite and a hole opening on each of those surfaces, said method comprising the following successive steps:

assembly of the threaded portion of the pin with the threaded portion of the sleeve, the deformation zone of the body of that sleeve being in an initial cylindrical configuration;

inserting the sleeve in the hole of the structure, on the first surface;

maintaining the collar in contact with the first surface;

pulling or torquing the pin into the sleeve until an outer bulb is formed in contact with the second surface; and

torquing the handling component in relation to the head of the pin around the main axis until fracture of the breakneck groove and formation of the fracture surface on the head.

11. A pin extends along a main axis and comprising a head and a threaded portion, an end of the head opposite to the threaded portion forming an end surface in a first plane perpendicular to the main axis,

the pin further comprises a handling component which is an integral part of the head opposite the threaded portion, a junction between that head and the handling component comprising a breakneck groove configured to break under a torsional stress greater than a predetermined threshold, said breakneck groove having substantially a shape of revolution around the main axis,

characterized in that, in a second plane comprising the main axis, a section of the breakneck groove has an arc of circle portion, a center of said circle being substantially set in the first plane, wherein the arc of circle portion comprises a first part and a second part arranged on the first plane on either side of the head and handling component respectively, said first part forming a cavity in the head in relation to the first end surface.

12. A pin extends along a main axis and comprising a head and a threaded portion, an end of the head opposite to the threaded portion forming an end surface in a first plane perpendicular to the main axis,

the pin further comprises a handling component which is an integral part of the head opposite the threaded portion, a junction between that head and the handling component comprising a breakneck groove configured to break under a torsional stress greater than a predetermined threshold, said breakneck groove having substantially a shape of revolution around the main axis,

characterized in that, in a second plane comprising the main axis, a section of the breakneck groove has an arc of circle portion, wherein the breakneck groove has a first lip and a second lip tangential to the arc of circle portion and substantially tapered, said first and second lips being respectively arranged on the head and on the handling component whereby the first lip has at least a portion on a side of the first plane opposite the second lip.