Fitting for mounting a winch on the structure of an aircraft such as a helicopter

A fitting for mounting a winch includes an axially sliding ring between an internally splined bearing and a splined shaft. Utilizing internal splines, the ring is constantly engaged with the external splines of the shaft. Axial sliding of the ring, facilitated by a pivoting grip, permits coupling and uncoupling of the interrupted internal splines of the bearing and the interrupted external splines of the ring. This coupling and uncoupling makes it possible to lock and unlock the shaft with respect to rotation.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a fitting for mounting a winch on the 
structure of an aircraft such as a helicopter, this winch being attached 
to one end, distant from the said structure, of a mobile jib whose other 
end is articulated with the said structure about a geometrically 
horizontal axis. 
2. Description of the Prior Art 
A known fitting of this type is shown diagrammatically in FIGS. 1a and 1b 
of the accompanying drawing. 
In these figures the reference 20 indicates a conventional winch, intended 
for example for the rescue of persons in danger in places of difficult 
access. High in the mountains, helicopters with winching installations are 
used for the rescue of climbers trapped in avalanches or on rocky edges. 
In air-sea rescue these same devices are used to rescue shipwrecked 
persons when the state of the sea does not allow an approach by boat. 
This winch is attached to the distal end of a mobile jib 21 whose other end 
is articulated with the structure or cabin 22 of a helicopter about a 
geometrically horizontal axis 23. The jib 21 is also connected to the 
structure 22 of the aircraft by a support rod 24. The reference 25 
indicates an engine cowl, mounted in an articulated manner on the upper 
part of the structure 22. 
In the normal position of use shown in FIG. 1a, the engine cowl 25 is 
closed, the jib 21 is in the raised position and the winch 20 is in the 
normal winching position, separated from the cabin 22. The jib 21 is 
maintained in this practically horizontal position by the support rod 24, 
the bottom end of which is pinned to a fixed mount 26 on the cabin 22. 
In the maintenance position shown in FIG. 1b, the engine cowl 25 is open 
and can be used as gangway allowing the mechanic to walk on the top in 
order to carry out maintenance operations. In the position shown in FIG. 
1a, the opening of the engine cowl 25 would be impeded by the presence of 
the winch 20. That is why it is appropriate to lower the winch, in order 
to bring it into the position shown in FIG. 1b, in which it is no longer 
operational, it being too close to the cabin 22 (that is why it cannot 
remain in this position permanently). In order to pivot the jib 21 
downwards about its axis 23 and to bring the winch 20 into the position 
shown in FIG. 1b, it is convenient to unpin the bottom end of the support 
rod 24, to hold it in the hand and make it continue its support and then 
to re-pin it to the fixed mount by the intermediary of a strut 27 of the 
support rod. These operations require two operators and are difficult 
insofar as there is always a risk of losing the pin (not shown) which 
connects the mount 26 to the bottom end of the support rod 24 or to the 
strut 27. There is also a risk of one of the operators releasing the 
support rod 24, which can damage the aircraft. 
The presence of the support rod 24 also gives rise to the disadvantage that 
it obstructs a portion of the access door 28 of the cabin 22, which makes 
it difficult for people to enter the aircraft. It also presents a jamming 
point for winched persons who can grab this rod in a state of panic and no 
longer wish to release it, thus impeding their rescue. 
BRIEF SUMMARY OF THE INVENTION 
The purpose of the present invention is to overcome all of these 
disadvantages and to propose a new fitting making it possible to eliminate 
the support rod 24. 
For this purpose, a fitting of the type mentioned at the beginning, 
according to the present invention, characterized in that the said other 
end of the jib is provided with horizontal shaft ends which are rigidly 
integral with it and which are respectively mounted in two bearings of the 
structure, one of the bearings receiving the corresponding shaft end in a 
freely rotative manner and the other bearing being provided with an 
unlockable device for locking the other shaft end, with respect to 
rotation, by means of which the said shaft ends and the jib with which 
they are integral can occupy two positions, namely a locked position in 
which the jib is raised and holds the said winch separated from the said 
structure, in the normal winching position, and an unlocked position in 
which the said jib is lowered and brings the winch into a position close 
to the said structure and allowing the maintenance of the said aircraft. 
The invention also relates to the particular embodiment of the unlockable 
locking device which has just been mentioned. 
An additional purpose of the invention is to obtain a simple device which 
can be operated rapidly by hand or mechanically, by a single operator, and 
which also has high reliability and is particularly applicable to 
helicopter winches as will be seen below. 
Such a device is principally characterized, for this purpose, in that it 
comprises two assemblies of mutually cooperating splines, namely a first 
assembly comprising, on the said shaft, a set of first straight external 
splines and, on the said ring, a set of second straight internal splines, 
and a second assembly comprising, on the said bearing, a set of third 
straight internal splines and, on the said ring, a set of fourth straight 
external splines, and in that the said ring is coupled with means of axial 
displacement between two positions: 
a locked position in which the splines of the said first assembly are 
meshed with one another, as are the splines of the said second assembly; 
and 
an unlocked position in which the splines of at least one of the said 
assemblies are mutually disengaged. 
In order to obtain the possibility of unlocking between at least certain of 
the cooperating splines, it will be furthermore possible to provide, in at 
least one of the said assemblies, for at least one of the sets of 
cooperating splines to have a peripheral gap which can allow the passage 
of the other set of splines of the assembly in question. 
It will be seen better below how these gaps make it possible, by an axial 
sliding of the ring, to obtain locking or unlocking between the 
intermediate shaft and its bearing. 
According to a possible variant, the first and second splines of the said 
first assembly are permanently mutually engaged, the splines which can be 
mutually disengaged being the third and fourth splines of the said second 
assembly, namely the internal splines of the said bearing and the external 
splines of the said ring. 
It is understood that it would however be possible to use a reverse device, 
starting from a permanent engagement between the third and fourth splines 
of the second assembly. 
Advantageously, the said peripheral gap is provided in a substantially 
median manner in the sets of splines in question, over a length slightly 
greater than that of the sections of splines extending on either side of 
these gaps. 
Thus, unlocking can be obtained by the axial sliding of the intermediate 
ring in one direction or in the other direction, starting from its median 
locking position. 
As regards the means of axial displacement of the ring, they can comprise a 
pivoting grip mounted on the said ring, locked axially and provided with 
at least one helical slot, each slot being traversed by a pin fixed to the 
said ring.

DETAILED DESCRIPTION OF THE INVENTION 
In FIGS. 2a and 2b, the reference 20 again indicates the winch mounted on 
its mobile jib 21, which is itself mounted in a pivoting and lockable 
manner on the structure 22 of the helicopter by the intermediary of two 
bearings 6 and 6' (FIG. 3), only the bearing 6 being visible in FIGS. 2a 
and 2b. In FIG. 2a it can be seen that the winch 20 is sufficiently 
distant from the cabin 22 for it to be operational in the winching cone C. 
On the other hand it is no longer in the lowered maintenance position of 
FIG. 2b, in which however it is permissible to open the engine cowl 25, 
serving as a gangway for the mechanic. 
In FIG. 3, the raised position of the jib 21 corresponds to the one shown 
in FIG. 2a. The jib 21 carries, along the pivoting axis 21, two shaft 
ends: one of them, 5' is mounted in a freely rotative manner in a bearing 
6' fixed to the structure 22 of the aircraft and the other, referenced 5 
(see FIGS. 4 and the following ones) being mounted in a rotative manner in 
a bearing 6 but which can be manually locked there by means of the 
unlockable locking device which will now be described. 
In FIGS. 4 to 6, the reference 1 indicates a set of first straight external 
splines distributed around the end of shaft 5 for which it is convenient 
to be able to command, manually, locking or unlocking, in rotation, with 
respect to a bearing 6, this being possible by means of an intermediate 
ring 7. For this purpose, this ring internally comprises a set of second 
straight internal splines 2 which between them form grooves suitable for 
receiving the splines 1 of the end 5 after assembly. The splines 1 and 2 
constitute what is referred to above as the "first assembly". 
The bearing 6 comprises a set of third straight internal splines 3, and the 
ring 7 comprises a set of fourth straight external splines 4 constituting 
with the preceding ones what is referred to above as "the second 
assembly". 
All of the splines are angularly equidistributed and their width dimensions 
are such that they together constitute grooves for receiving cooperating 
splines; in order not to clutter the drawing, only the splines have been 
referenced. 
The splines 3 of the bearing 6 have, centrally and substantially over 1/3 
of their length, a peripheral gap 8, thus dividing these splines into 
sections 3a, 3b of equal length. The disposition is the same for the 
external splines 4 of the ring 7: they are divided into sections 4a, 4b by 
a central peripheral gap 9 extending over 1/3 of their total length. In 
this way, the ring 7 can be locked with respect to rotation in the bearing 
6 when the sections of splines 3a and 3b are respectively meshed with the 
sections of splines 4a and 4b, the end 5, constantly locked in rotation 
with respect to the ring 7 by the meshing of the splines 1 and 2, is 
therefore locked in rotation with respect to the bearing 6, this being the 
locked situation of the shaft shown in FIG. 5. 
On the contrary, if the ring 7 is axially slid in one direction or the 
other, sufficiently for its sections of splines 4a and 4b to come into 
alignment with the peripheral gap 8 in the splines 3 of the bearing 6, 
then the ring 7 and therefore the end 5 will be able to rotate in the 
bearing 6; such an unlocked situation is shown in FIG. 6, wherein the 
sections 4a can move in the peripheral gap 8 of the splines 3, whilst the 
sections 3b are in alignment with the gap 9 of the splines 4. 
It will be possible for the axial displacements of the ring 7, in one 
direction or the other, to be controlled by any appropriate means, for 
example by means of a pivoting grip 10 mounted on the ring 7. This grip is 
locked axially on the one hand by bearing against the side of the bearing 
6 and on the other hand by butting with a shoulder 16 against a circlip 15 
engaged in a peripheral groove of a shaft end 17; the end 5 bears with a 
shoulder 18 against the opposite side of the bearing 6. 
Two opposite helical slots 11, 12 in the grip 10 are respectively traversed 
by pins 13, 14 engaged in corresponding radial housings in the ring 7. 
Thus, when the grip 10 is rotated in the clockwise direction, the ring 7 
enters into the bearing 6 (locking of the end 5 in the bearing 6), and it 
moves out of it if the grip 10 is rotated in the opposite direction 
(unlocking of the shaft end 5). This rotation can be carried out by hand 
or by means of a motor. 
The applications of the present invention can be multiplied and can be 
advantageous in cases where it is necessary to be able to lock or unlock a 
shaft with respect to a fixed structure. 
As it follows and already results from the above, the invention can be 
embodied in a large number of variants, and in particular the 1/3 ratio is 
given above only by way of example. The essential operational condition of 
the device is only that the length of the sections of splines 4a is less 
than the distance between the sections of splines 3a and 3b, and that the 
length of the sections of splines 3b is less than the distance between the 
sections of splines 4a and 4b. 
In order to increase the mechanical strength of the device, the bearing 6 
and the ring 7 could each comprise at least two recesses between their 
respective splines according to requirements.