Coupling systems for conduits, particularly for semi-rigid plastic tubes

A device for coupling semi-rigid plastic tubes of a known type in which two ring members are provided, one within the other. The outer ring member is secured in a bore in a part to which the tube is connected. The outer ring member has a plurality of teeth which engage a tube inserted into the ring members. The inner ring member is movable axially to disengage the teeth for uncoupling the tube and part. The device is improved in one aspect by providing two distinct sealing means, each movable with the inner ring member. A first sealing means comprises a projection on the inner surface of the inner ring member which projection penetrates the wall of a tube to be connected. A second sealing means comprises a sealing member, such as an O-ring, mounted on the inner ring member. In another aspect, the teeth are shaped such that they are easily disengageable, without permanent distortion, so that the device is re-usable.

The invention relates to improvements made to coupling systems of the kind 
specified in the U.S. Pat. No. 4,021,062, meant more specially for 
coupling semi-rigid plastic tubes (although it may be possibly applied to 
metal tubes). It relates in particular to systems of this kind for 
hydraulic or pneumatic installations, for forming connections, either 
between tubes, or between tubes and pneumatic or hydraulic components of 
said installations. 
In U.S. Pat. No. 4,021,062, coupling systems are described characterized by 
the combination, on the one hand, of a lock ring fixed in a bore intended 
to receive it and provided with teeth for hooking on to the tube to be 
fixed and, on the other hand, of an unlocking ring mounted inside the lock 
ring and capable, when axially moved, of spreading out said teeth. 
There was furthermore provided a sealing ring for providing the seal 
between the tube and the lock ring, itself sealingly fixed in its bore. 
It is an object of the present invention to improve the sealing of a device 
of the type shown in U.S. Pat. No. 4,021,062, by simple means and, thus, 
facilitating the operation of the unlocking ring, without risk of 
permanent distortion of the teeth of the lock ring. 
According to one of the embodiments of the invention, the sealing between 
tube and connector, is ensured by two different sealing means, one between 
tube and unlocking ring, the other between the latter and the lock ring. 
The first sealing means involves providing the unlocking ring, towards the 
inside, with an annular swelling having an inner diameter a little less 
than the outer diameter of the tube, so that there is penetration into the 
material of the tube. 
The second sealing means comprises for example an O-ring or similar sealing 
member interposed between the two rings. 
According to another arrangement of the invention, the portion of the teeth 
adjacent their hooking on edges are given a very slightly flared shape. 
The portion of the teeth is separated from the tube by a gap of a value a 
little greater than the thickness of the active end part of the unlocking 
ring, so that, during unlocking, the active end part of the unlocking ring 
may penetrate into said gap while moving aside the hooking on edge by a 
distance sufficient for unlocking, without however exceeding a value 
likely to cause permanent distortion. 
Thus, a connector after use may always be used again. 
The invention comprises, apart from these arrangements, certain other 
arrangements which are preferably used at the same time and which will be 
more explicitly discussed hereafter. 
The invention relates, more particularly, to certain modes of application 
as well as to certain embodiments, of said arrangements; and it relates, 
more particularly still, and this by way of new industrial products, to 
systems of the kind in question comprising application of these same 
arrangements, as well as the special elements for their construction and 
the units or installations comprising similar systems.

In the description which follows, the invention is illustrated as a 
coupling for hydraulic or pneumatic conduits, particularly plastic tubes. 
A part 1 having a bore 7 is provided for coupling to a tube 2. There is 
formed in part 1 two bores 3 and 4. Bore 3 is adapted for receiving a lock 
ring 8 which will be described hereafter. Bore 4 is adapted for receiving 
the end of tube 2, abutting an edge 5, which tube communicates at 6 with 
the bore 7 of part 1. 
For securing tube 2 to part 1, recourse is had essentially to two rings 8 
and 9, viz.: 
(a) a ring 8, for example made from bronze or brass, capable of being 
fixed, by crimping, bonding or other means, to the wall of bore 3, said 
ring comprising, at the base of its full part appearing at the inlet to 
bore 3, a number of teeth 10 separated by slits 11 and finishing in claws 
12, arranged so as to appear along a circular line having a diameter a 
little less than the outer diameter of tube 2; and 
(b) an unlocking ring 9 adapted to be introduced inside lock ring 8 which, 
when pushed towards teeth 10, causes the separation and unlocking of the 
teeth. 
In accordance with one of the arrangements of the present invention, the 
seal between the tube and the connector is provided by two distinct means, 
one between tube 2 and unlocking ring 9, the other between ring 9 and 
outer lock ring 8. 
In so far as the sealing means to be provided between tube 2 and ring 9 are 
concerned, it is advantageously formed (FIGS. 1 and 2) by at least one 
annular projection 30 provided on the inner surface of the ring, the inner 
dimensions of this projection being slightly less than those of the 
external wall of tube 2 so that, during fitting, said projection 
penetrates slightly into the material of the tube, thus providing the 
seal. The outer shapes of the projection has a rounded contour so as not 
to harm the surface of the tube. 
In so far as the second sealing means are concerned, to be provided between 
ring 9 and lock ring 8, it is formed for example by at least one O-ring 
13. This ring may for example be partially engaged in an outer groove 31 
of ring 9 (FIG. 1) or else, according to one of the numerous possible 
variations, it may be housed under a flange 32 (FIG. 2) connecting the 
central part of ring 9 to a thinner part such as sleeve 33 intended to 
cooperate with the teeth 10 of lock ring 8. 
Another arrangement of the invention, relating more especially to the shape 
of teeth 10 and their cooperation with ring 9, 33, is also illustrated in 
FIGS. 1 and 2. 
According to this arrangement, teeth 10 comprise a doubly wavy profile, 
i.e.: 
(a) one part 10.sub.1 whose inner surface comes close, without touching, to 
the outer surface of sleeve 33, while being connected to the body of ring 
8 through a bend 34; and 
(b) one part 10.sub.2, cylindrical or slightly flared, finishing in claw 
12, this part having its inner wall of a diameter slightly less than the 
diameter of the external surface of sleeve 33, and being connected to part 
10.sub.1 through a bend 35. 
The assembly operates in the following way. 
In the fitting and unlocking position (left side of FIG. 1) the two rings 8 
and 9 are one inside the other, and the outer edge 36 of sleeve 33 does 
not penetrate into the gap remaining free, for each tooth 10, between tube 
2 (assumed introduced into part 1) and part 10.sub.2, of said tooth. Thus, 
claw 12 is free penetrate and embed itself in the material of said tube. 
For unlocking, unlocking ring 9 is acted on, for example by means of a tool 
21 (right side of FIG. 1) in order to move it in the direction of arrow F. 
Edge 36 of the sleeve then, by sliding over the bend 35 of each tooth, 
spreads out these latter while penetrating into gap x (FIG. 1) between 
part 10.sub.2 and tube 2. Thus, each of claws 12 (as shown at the right of 
FIG. 1) is lifted up in a very precise way, thus releasing tube 2, but 
without the risk of an exaggerated lifting up causing permanent distortion 
of the teeth. 
The coupling device is thus ready for re-use. 
It is to be noted that, just as in U.S. Pat. No. 4,021,062 is delivered for 
use in the form of a ready-to-use cartridge, in which rings 8 and 9 are 
previously introduced and maintained one in the other, with their seal 13. 
All that is required, to hold the rings in place, is to crimp for example 
at 20, the outer edge of lock ring 8 towards a groove 37 of unlocking ring 
9. Ring 9 will generally be made from a plastic material, but it could 
also be made from metal. 
It is also to be noted that, in the variation of FIG. 2, seal 13 is 
maintained in place by the presence of bends 34 of teeth 10 and that the 
elasticity of said seal thus tends to bring ring 9 backwards, in the 
opposite direction to arrow F, and so to bring it to its normal locking 
position which it must occupy during fitting. 
It will be clear from the foregoing that the present invention provides 
many advantages among which are: 
a particularly simple construction, 
always providing a good seal, 
and, owing to the particular shpae of the teeth and the sleeve cooperating 
therewith, allowing unlocking to be achieved with precision and without 
harming the qualities of the assembly which may then be used again. 
As is evident, and as it follows moreover already from what has gone 
before, the invention is in no wise limited to those of its modes of 
application and embodiments which have been more specially considered; it 
embraces, on the contrary, all variations thereof.