This assembly comprises a collar (3) having splines cooperating with splines on the bolt (1) and lateral tabs (4) in contact with flat sides of the nut (2). This assembly further comprises at least one bent elastically yieldable locking element (5, 5') having a first branch (6, 6') trapped between a tab (4) of the collar (3) and a flat side of the nut, a second branch (8, 8') having an aperture (9, 9') through which extends the bolt and which has an edge engaged between screw threads of the bolt. By exerting a lateral pressure on the locking elements (5, 5'), the screw threads of the bolt are elastically disengaged.

BACKGROUND OF THE INVENTION 
The present invention relates to a nut-locking device. 
Many assemblies of nuts and lock-washers are known for preventing the nut 
from untightening after it has been placed in position and tightened on a 
bolt. 
Document FR-A-2,025,676 in particular describes such an assembly in which a 
cylindrical collar having internal splines and teeth which axially project 
is forcefully pressed on the bolt on top of the nut after the latter has 
been tightened. 
The nut has axial apertures adapted to receive the teeth of the collar when 
it is pressed on the bolt, the latter also having if desired splines 
corresponding to those of the collar with which they cooperate. 
An assembly of this type is relativey effective, but however does not 
afford complete safety. Indeed, the collar must not move up the bolt away 
from the nut. 
For this purpose, the apertures of the bolt are drilled obliquely and 
diverge outwardly so as to deform the teeth of the collar which is of a 
relatively malleable metal and, owing to this malleability, there is a 
danger that the teeth leave the apertures of the bolt, for example under 
the action of large vibrations. 
In other known devices, described for example document U.S. Pat. No. 
3,022,809, a collar is mounted on the bolt with which it cooperates 
through splines and is then clipped onto the nut. 
In all these arrangements, the behavior of the collar depends on the 
resistance of the latter to deformation, this resistance being however 
required to permit the initial deformation. Such a compromise is not 
absolutely reliable and the collar cannot be recovered in the event of 
disassembly. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide a nut-locking assembly of the 
aforementioned type in which the collar is positively locked on the bolt, 
but in a detachable manner, thus permitting a disassembly and re-use of 
the assembly. 
The invention therefore provides a re-usable assembly for locking a nut on 
a bolt, of the type comprising a collar whose opening has inner splines 
adapted to cooperate with complementary splines provided on the bolt, and 
two axially extending lateral tabs for straddling the nut in contact with 
the flat sides of the latter, said assembly comprising at least one bent 
elastically yieldable locking element having a first branch bearing 
against one of the tabs of the collar and a second branch having a portion 
which is engaged between two of the screw threads of the bolt above the 
collar and in contact with the collar. 
Preferably, a locking element is provided associated with each of the tabs 
of the collar. 
According to another feature of the invention, each elastically yieldable 
locking element is made from a spring steel strip, its first branch being 
parallel to the axis of the bolt and trapped between said tab of the 
collar and a flat side of the nut and connected to the second branch by an 
intermediate portion ensuring the elasticity of the element. 
According to a further feature of the invention, the second branch of each 
locking element has an elongated aperture through which the bolt extends 
in a direction roughly perpendicular to said branch. 
According to one embodiment, the length of said aperture is a little 
greater than the diameter of the bolt. 
Advantageously, in the unstressed condition of the locking element, said 
portion of the second branch engaged between the threads of the bolt 
partly extends across the opening of the collar. 
The following description, with reference to the accompanying drawings 
given by way of a non-limiting example, will explain how the invention can 
be put into practice.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 represents a bolt 1 on which is screwed a nut 2 locked or braked by 
an assembly according to the invention. 
In the known manner, the stem of the bolt has axial splines in the crests 
of its screw threads and a collar 3, defining an opening with 
corresponding splines and including two axially extending opposed lateral 
tabs 4, is mounted on the bolt 1 in such manner that the tabs 4 straddle 
the nut 2 and extend along two opposed flat sides of the latter and thus 
lock it against rotation. 
According to the invention, the collar 3 is positively locked against any 
axial sliding along the splines of the bolt 1 by two elastically yieldable 
locking elements 5, 5' according to the represented embodiment. 
Each element 5, 5' is formed by the punching and folding of a spring steel 
strip and comprises a first short branch 6, 6' connected by a bent portion 
to an oblique intermediate portion 7, 7' to which is connected a longer 
second branch 8, 8' by a second bent portion, these bent portions being 
such that the branches 6, 6' and 8, 8' make therebetween an angle slightly 
less then 90.degree. in the unstressed state of the element 5, 5' (FIG. 
2). 
Each locking element 5, 5' defines an aperture 9, 9' of elongated shape 
(FIG. 4) having a rounded end 10, 10', its opposite end 11, 11' in the 
vicinity of the end of the branch 8, 8' being curved in the opposite 
direction with a radius substantially equal to the radius of the bolt 1, 
and the length of the aperture between the ends 10, 11 and 10', 11' and 
its width being distinctly greater than the diameter of the bolt 1. 
Each element 5, 5' further comprises two lateral ears 12, 12' located at 
the end of the first branch 6, 6' and folded toward the intermediate 
portion 7, 7'. 
In the illustrated embodiment, the assembly comprises two locking elements 
5, 5' and, in this case, the second element 5' advantageously includes on 
its longer second branch 8' two other lateral ears 13 substantially in the 
middle of the length of the aperture 9' and bent in such manner as to 
extend toward the interior of the aperture and above the plane of the 
branch in the manner of a hook, for a purpose which will be specified 
hereinafter. 
The positioning and the operation of the assembly according to the 
invention will now be described with reference to FIGS. 2 and 4. 
The two locking elements 5, 5' are presented in opposite directions with 
the first branches 6, 6' parallel to the lateral tabs 4 of the collar 3 so 
as to engage the lateral tabs between the ears 12, 12' and consequently 
between the branches 6, 6' and the lateral portions 7, 7' respectively, 
the branches 8, 8' partly overlapping and the branch 8 of the first 
element 5 being introduced between the ears 13 of the element 5' by 
slightly elastically deforming the two elements. The dimensions of the 
branches and of the apertures are such that, in this position represented 
in FIG. 3, the edges 11, 11' of the corresponding ends of the apertures 9, 
9' define therebetween a gap whose diameter is less than the diameter of 
the bolt 1. 
It is then sufficient to exert a pressure on the intermediate portions 7, 
7' of the two elements 5, 5' toward the bolt, as represented by the arrows 
in FIG. 1. 
Owing to their elasticity, the two elements 5, 5' are deformed, the 
branches 8, 8' sliding on each other in opposite directions and spreading 
apart the edges 11, 11' of the apertures and thus increasing the size of 
the gap therebetween. 
After a precise tightening of the nut 2 at the exact torque required by the 
assembly, it is then sufficient to mount the assembly represented in FIG. 
3, partly in dot-dash lines, on the bolt 1 by making the splines of the 
bolt coincide with those of th collar 3. 
The branches 6, 6' are then trapped between the tabs 4 of the collar (the 
spacing of which tabs takes, as manufactured, into account the thickness 
of these branches) and the corresponding flat side of the nut 2. 
When the locking elements 5, 5' are released, they elastically resume their 
shape and the edges 11, 11' of the apertures come to be locked between the 
screw threads of the bolt and oppose, by bearing against the upper surface 
of the collar 3 and jamming, any displacement of the collar, even if large 
forces are applied. Note that a slight clearance between the collar 3 and 
the top of the nut 2 may result from a correct locking of the edges 11, 
11' of the locking elements between the screw threads of the bolt, without 
altering the quality of the previously-defined retaining effect. 
It will be observed that reversing the procedure enables the assembly to be 
easily removed, thereby permitting the untightening and removal of the 
nut. 
As no component part has been permanently deformed, the assembly can be 
used again. 
The ears 12 retain the locking elements on the collar and the ears 13 of 
the second element maintain the two elements 5, 5' against any risk of 
displacement.