Blind rivet

Details Blind rivet Blind rivet

1996-12-03

2001-02-06

Gorski, Joseph M. (Department: 3726)

Expanded, threaded, driven, headed, tool-deformed, or locked-thr

Having separate expander means

Frangible member

C411S070000

Reexamination Certificate

active

06183179

ABSTRACT:

BACKGROUND AND OBJECTS OF THE INVENTION
The present invention relates to a process for riveting with a blind rivet, and to corresponding blind rivets.
Blind rivets are generally comprised by a tubular sleeve with a longitudinal bore, and a mandrel comprising, for one part, a head of the mandrel having a diameter greater than that of the bore of the sleeve, and for the other part, a shank housed in the bore of the sleeve and extending therefrom at the end of the sleeve opposite to the head of the mandrel. Such rivets are adapted after pulling on the shank of the mandrel to form a head of the blind rivet, by introducing the head of the mandrel into the end adjacent the sleeve, and for maintaining the materials together between a preformed head of the sleeve and the blind head.
The shank of the mandrel is adapted to be broken upon completion of the riveting, in order that it not extend from the sleeve.
These rivets are called “blind” because they are introduced and set it place in the pieces to be assembled, from just one side of the assembly. Such placement is necessary when one of the sides of an assembly is not accessible.
Once set, the blind rivet subjects the assembly of materials to compressive forces of a known type.
However, after stopping application of the forces necessary for setting the rivet, the effect of compression on the assembly has a tendency to be relaxed by a hysteresis effect, such that an axial relaxation leading to a disadvantageous loosening is produced. The sleeve and the assembly then have created between them a certain play, which is harmful to good securing of the assemblage, and creates a poor fastening of the different elements between themselves.
The present invention has as its object to overcome all of these drawbacks by providing a riveting process by means of blind rivets, resulting from a correct fastening, and having no tendency to be relaxed, and not creating disadvantageous play between the different elements being assembled.
The invention provides also for the provision of rivets enabling carrying out such a process.
DESCRIPTION OF THE INVENTION
To this end, the present invention relates to a riveting process for materials by means of a blind rivet comprising a tubular sleeve provided with a longitudinal bore, and a mandrel having, for one part, a head of a diameter greater than the bore of the sleeve, and for the other part, a shank housed in the bore of the sleeve and extending therefrom opposite the head, the process comprising:
a) introducing the rivet into an opening passing through the materials to be assembled, from one side of this assembly of materials,
and being characterized in that it comprises furthermore:
b) exerting on the sleeve an extension force between a stop head situated at one end of the sleeve, and a stop means provided on the interior of the sleeve for placing said sleeve in longitudinal extension over a substantial portion of its length,
c) blocking the sleeve in this position of longitudinal extension from one part to the other of the assembly while shaping a blocking head opposite the stop head in contact with a first support face of the assembly, said blocking head resting against a second rest face of the assembly, and
d) exerting a pulling force on the mandrel for causing a rupture of the shank of the mandrel.
This riveting process, by reason of the extension or the sleeve before being blocked between parts of the assembly, permits obtaining an assembly which is under compression after setting, and which therefor has no tendency, over time, to be relaxed.
In the process according to the invention, the introduction of the blind rivet into a bore passing through the materials to be assembled may be carried out before or after stretching of the sleeve. One thus obtains two types of assembly by blind rivets both having an intimate contact between the pieces to be assembled and the rivets, but differing by the secondary effects, such as the resistance to shear stresses, as well as machining, permitting production of these assemblies.
In a first embodiment, the blind rivet is introduced into a bore formed through the pieces to be assembled from only one of the sides of the assemblage, preliminarily to the extension of the sleeve. In this case, the sleeve of the blind rivet used has a preformed head which is placed into contact with one of the faces of the assemblage. The blind head, also called the abutment head, is then formed by pulling on the shank of the mandrel in a conventional manner. The placing of the sleeve under tension is carried out after a first rupture of the shank of the mandrel. An extension force is applied between the abutment head and a support means arranged on the sleeve. This extension has a tendency to release the preformed head of the sleeve from the assemblage. This preformed head is then reshaped while pushing it against the assembly for blocking the sleeve in the extension position, from one part to the other of this assembly.
Thus, in this process, traction or pulling force exerted on the mandrel is used a first time for forming the stop head before the first rupture of the shank, and a second time for carrying out an extension of the sleeve after the first rupture of this shank.
Such a process permits using conventional setting tools for placing and setting blind rivets and may therefore be carried out without major modification of existing riveting installations.
When extension of the sleeve is carried out preliminarily to the introduction of the rivet into a bore provided through the pieces to be assembled, or (for this same type of rivet) preliminarily to the provision of the blocking head, specific tools are used for carrying out this extension.
The sleeve is then extended between a first tool exerting a tension on the abutment head of the sleeve and a second tool pushing on a stop means secured to this same sleeve.
The stretched sleeve is then introduced into the pieces to be assembled, and blocked in the extension position, by pulling on the shank of the mandrel. This pulling causes the formation of a blocking head, and the sleeve thus squeezes the assembly closely together while being drawn. The continued exertion of the pulling force on the shank of the mandrel causes the rupture of this shank, in a known manner.
According to this process, the second setting tool can be comprised of a single piece and can be withdrawn from the sleeve after the riveting, or may be comprised of two parts. Advantageously, the two piece construction permits leaving the first part of the second tool in place inside the sleeve, after riveting. Only the second part of the second tool is withdrawn.
Advantageously, such a process achieves a riveting providing a good contacting of the materials, but in addition, by reason of the presence of the first part of the second tool in the sleeve, a better shear resistance is achieved, as well as a propitious expansion of the rivet.
Such a process requires, however, carrying it out with specific setting apparatus.
The present invention also relates to a blind rivet comprising a tubular sleeve provided with a longitudinal bore and a mandrel presenting, for one part, a head of a diameter greater than the bore of the sleeve, and for the other part, a mandrel shank housed in the interior of the bore and adapted to extend from this bore on the side opposite the head of the mandrel, said rivet being characterized in that it comprises:
at the level of the sleeve:
a preformed head at the end of the sleeve opposite the head of the mandrel, and
a stop means arranged on the interior of the bore of the sleeve, and
at the level of the mandrel:
a shank having first and second portions, and
first and second rupture grooves provided about the circumference of the shank of the mandrel respectively in the first and second portions of the shank of the mandrel.
Such a rivet is adapted, after double rupture of the shank of the mandrel, to provide a riveting under compression, with a good seating of the materials presence.
Such a rivet may advantageously be put in place with the help

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