Abstract:
An insertion endpiece for connecting a part carrying the endpiece with another part provided with a bore for receiving the endpiece. The endpiece is provided with an outer groove in which there is received a cylindrical ring, that is free to turn and to slide. The ring has teeth projecting from its outside surface, the ends of the teeth being contained, in the free state, in a substantially cylindrical envelope of diameter that is greater than the diameter of the bore. The ring is received in the groove while being free to turn and to slide. The axial width (L) of the groove is greater than the axial width (L 1 ) of the ring. When the ring is in abutment against a flank of the groove, the teeth are in register with a secondary groove formed in the bottom of the groove receiving the ring, and into which secondary groove the teeth are capable of penetrating elastically.

Description:
The present invention relates to means for making a cylindrical housing or connection well suitable for receiving and retaining in leaktight manner the end of a tube having its inside volume put into communication with a channel that opens out into the bottom of the well. 
     BACKGROUND OF THE INVENTION 
     In the pneumatic or hydraulic fields, functional equipment is fed with control or power fluid that is delivered thereto via a tube that needs to be connected in leaktight manner to an internal channel of the equipment. To do this, the body of the equipment is provided with a bore or well that opens out into one of its outside surfaces, and that has the fluid-feed channel terminating in its bottom. The connection means of the tube are for placing in the bore in leaktight manner. The connection means may be embodied in numerous ways on the tube end. On the equipment, there is either a tapped well for making a screw connection with a sleeve that carries the connection members of the tube, or else there is a well in which a sleeve becomes anchored. Anchoring is provided by teeth that are machined on the outside surface of the sleeve and that co-operate with the well after the sleeve has been engaged under force in the well. This engagement requires special tooling for it to be performed, and it gives rise in the engaged parts to permanent stresses and tensions that harm their lifetimes and that can give rise to microcracks leading to a coupling that leaks or indeed to the coupling spontaneously disconnecting. 
     Attempts have therefore been made to eliminate stresses from this type of connection and to reduce assembly forces. The known solution makes use of an intermediate structure (washer) between the sleeve and the well, which intermediate structure is elastically retractable on being engaged and, under a pull-out force, grips either to the sleeve or to the well by biting into the corresponding surface or by placing the sleeve or the well behind a shoulder that was passed during engagement. That type of connection presents the drawbacks of possessing a radial size that is not negligible, thereby penalizing either the working section for passing fluid through the connection, or else increasing the overall size of the coupling that is to be inserted in the well, which requires wells to be made of greater diameter and thus impeding the provision of a set of couplings arranged side by side on a baseplate of the equipment that is to be fed with fluid. 
     The beginning of a solution to this problem can be found in document FR 2 102 518. That document discloses an intermediate structure that is not in the form of a toothed washer, but rather in the form of a toothed cylindrical ring, the ring being received in an outer groove of the sleeve that is inserted in the well and biting into the inside surface of the well. The flexibility of the teeth is small and their fastening power is relatively weak. 
     In addition, that connection cannot be disassembled without destroying at least the toothed ring. In order to enable a gripped-together connection to be disassembled by applying rotation, it is known that the active portions of the teeth need to be given a slope such that the bite mark made by each tooth in the surface that it grips is tangential to a helix lying in the surface, as contrasted to being tangential to a circle lying therein. The major drawback of such gripping and unscrewable connections lies in the fact that they can become unscrewed spontaneously under the effect of axial forces between the two connected-together elements. 
     The invention provides a solution to each of these presently poorly-solved problems. 
     SUBJECT MATTER OF THE INVENTION 
     The invention thus provides an insertion endpiece for connecting a part carrying said endpiece with another part provided with a bore for receiving the endpiece, the endpiece being provided with an outer groove in which there is received a cylindrical ring possessing teeth projecting from its outside surface, the ends of the teeth being contained, in the free state, in a substantially cylindrical envelope of diameter that is greater than the diameter of the bore, the endpiece being characterized in that the ring is received in the groove while being free to turn and to slide, in that the axial width of the groove is greater than the axial width of the ring, and in that when the ring is in abutment against an edge of the groove, the teeth are in register with a secondary groove formed in the bottom of the groove receiving the ring, into which secondary groove the teeth are capable of penetrating elastically. 
     The edge in question of the groove is the edge against which the ring bears while the two parts are being mutually engaged. It constitutes the flank of the groove that is at the rear in the engagement direction. 
     The teeth are preferably made as axial tongues cut out in the wall of the ring and having free ends remote from the roots of the teeth that are curved outwards to form spikes enabling the ring to bite into the surface of the bore. The spike is thus carried by a flexible blade, i.e. the tongue, and during engagement it dips resiliently into the secondary groove. The force needed for engagement is then much smaller than it would be if such elastic flexing were not possible. 
     If an attempt is made to extract the endpiece (either using an external pull-out force, or as a result of pressure becoming established inside the assembly, assuming that the assembly involves tubular parts forming a passage for pressurized fluid), the ring remains attached in the bore and the endpiece slides rearwards. The spring blades of the teeth are then pushed back out from the secondary groove and serves to anchor the teeth in the bore. The radial stiffness of the teeth is then considerably greater than when the teeth were in register with the secondary groove. Anchoring is then extremely firm. The ring is in contact with the front flank of the groove and holds the endpiece anchored in the bore. 
     According to another characteristic of the invention, one of the flanks of the groove (the rear flank) and the facing end of the ring possess means for putting the ring into rotary abutment in the groove in such a manner that, when the ring is in abutment against said flank, the ring is free to turn relative to the endpiece over an angle of less than 360 degrees. 
     Naturally, the difference between the axial dimensions of the groove and of the ring are sufficient to enable the abutment means to escape and to enable the ring to rotate completely freely relative to the groove. This applies in particular when the ring bears against the other flank of the groove. The first flank is the flank that is situated at the rear end of the groove in the engagement direction, and the second flank is the front flank. 
     This set of characteristics enables the assembly to be disassembled by unscrewing providing, in known manner, the ends of the teeth are cut skew so as to bite into the bore at an angle of inclination relative to a generator line of its surface. Thus, rotation between the endpiece and the bore causes each tooth to follow a helix on the inside surface of the bore. It also makes it possible to protect the assembly from accidental disassembly, since when the assembly is in operation, in particular if it is a coupling for pipework carrying fluid, the abutment means are decoupled by being axially moved apart from one each other, because of the freedom of the ring to slide axially in the groove. By way of example, these means may be in the form of a tooth projecting axially from the flank of the groove and a similar tooth projecting from an axial edge of the ring, or else a notch formed in said edge. When designing these angular abutments or indexes, it is necessary to take account of the fact that the engagement force is transmitted from the endpiece to the ring via this flank, in order to ensure that this force does not have the consequence of destroying the above-mentioned abutment means, since such destruction or damage would make it impossible to disassemble the connection by unscrewing it. 
     Other characteristics and advantages of the invention appear from the description given below of an embodiment of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference is made to the accompanying drawings, in which: 
         FIG. 1  is a diagram of two parts comprising a bore and an endpiece, the parts being assembled in accordance with the invention; 
         FIG. 2  is an axial half-section showing an assembly ring for the two parts of  FIG. 1 ; 
         FIGS. 3A ,  3 B, and  3 C show a sequence of mounting the endpiece of the invention in the bore; 
         FIG. 4  is an axial half-section showing another assembly ring for the two parts of  FIG. 1 ; 
         FIGS. 5A to 5D  show an assembly-disassembly sequence for the endpiece of the invention fitted with the ring of  FIG. 4 ; 
         FIG. 6  is a fragmentary diagram of the abutment for enabling the endpiece to apply rotary drive to the ring; and 
         FIGS. 7A and 7B  show a variant of the embodiment of  FIGS. 5A to 5D . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows an assembly of two parts  1  and  2 , the part  1  having a bore  3  and the part  2  having an endpiece  4 . In this configuration, the part  1  forms part of equipment that consumes fluid under pressure (valve, manifold, actuator, . . . ), and the part  2  is a coupling for a tube (not shown). The coupling is shown in this example as having a bend, but it could have any known configuration. 
     In  FIG. 1 , means given overall reference  5  represent the connection of the endpiece  4  in the bore  3 , these means together with the endpiece and the bore constituting the subject matter of the invention. 
       FIGS. 2 and 3A  to  3 C show an embodiment of the invention in detail.  FIG. 2  is an axial section view of a ring  6  that possesses a cylindrical portion  6   a  and a toothed axial end  6   b . Each tooth  7  is formed by the outwardly-curved end of a tongue or blade  8  that is cut out in the wall of the ring  6 . Each tooth  7  alternates with a prong  8   a  that is not curved at its end. The ring  6  is made from cut-out sheet metal that is then rolled up with its ends being fastened together to make a cylinder. In this example, the fastening is performed by a cutout in one end of the sheet-metal segment that co-operates with a cutout of complementary shape in the other end. In the example shown in the figures, the cutout is a male dovetail  6   c  that is received in a female dovetail  6   d , thereby providing great axial and circumferential stiffness to the resulting ring or loop. 
     The ends are connected together when the sheet is received in an outer groove  9  of the endpiece  4 . In this configuration, the ring  6  presents its teeth  7  in a configuration in which their envelope constitutes a cylindrical surface of diameter that is slightly greater than that of the bore  3 . Thus, in order to enable the endpiece fitted with its ring  6  to penetrate into the bore, it is necessary to constrain the teeth  7  to move inwards. The invention makes this possible while exerting a force that is moderate, because the bottom of the groove  9  includes a secondary groove  10  into which the tongues  8  can easily flex, since they behave like spring blades, providing the groove  10  is situated under the tongues or blades  8  when they are inserted into the bore  3 . This position arises necessarily since, according to the invention, the axial length L of the groove is greater than the axial length L 1  of the ring  6 , and the secondary groove  10  is situated beside the flank  9   a  of the groove that constitutes the flank that is at the rear in the direction F in which the endpiece  4  is engaged in the bore  3 . Thus, while the endpiece is being engaged in the bore, the ring  6  is entrained towards the flank  9   a . The axial length L 2  of the secondary groove is sufficient to ensure that, when the straight tongues  8   a  come into contact with the flank  9   a , the tongues  8  carrying the teeth  7  can flex into the groove  10  (see  FIG. 3B ). There is an abutment to stop movement in the engagement direction, which abutment is not shown. 
     When the assembly is assembled, as shown in  FIG. 3B , pressure can be established in the circuit, and that causes the endpiece to reverse in direction P in  FIG. 3C . It should be recalled that in conventional manner the endpiece  4  is provided with a sealing gasket  11  that acts as a piston that is sensitive to the pressure that exists in the circuit. During this movement, the ring  6  is stationary and the flexed tongues  8  are expelled from the secondary groove  10  (which possesses a sloping flank in order to facilitate the sliding of the tongues  8  out from the groove  10 ), so the teeth  7  bite still more firmly into the wall of the bore  3 . The stiffness of each tooth  7  and the associated blade  8  is then considerably increased and the ability of the endpiece to oppose extraction is correspondingly increased. 
     This configuration enables the endpiece to be engaged in the bore using a force that is small compared with the force that would otherwise need to be developed in the absence of any possibility of the tongues  8  flexing. 
       FIG. 4  shows a second embodiment of the ring. In this figure it is given reference  20  with teeth  21  formed by the outwardly-curved ends of tongues  22  obtained by being cut out from the wall of the ring  20  in the middle portion thereof. Unlike  FIG. 2 , the ring carries central teeth that lie between cylindrical portions  20   a  and  20   b . As before, the ring is formed by rolling up a precut piece of sheet metal that is fastened together via dovetail-shaped ends  20   c  and  20   d.    
     The ring is thus rolled up in a groove  23  of the endpiece  4  that differs from the groove  9  described above by the presence on the rear flanks  23   a  of said groove of an abutment  24  that is suitable for entraining one of two abutments  20   e  and  20   f  forming parts of one of the axial ends of the ring  20 .  FIG. 6  shows this characteristic. Another difference between the grooves  9  and  23  lies in the position of the secondary groove, here referenced  25 . In  FIGS. 3A-3C  the secondary groove is adjacent to the flank  9   a , whereas in  FIGS. 5A-5D  it is more towards the central portion of the groove  23  so as to accommodate the position of the teeth  21  in the ring  20 , and so as to give them the possibility of flexing inwards during engagement. 
     It should also be observed that the free end  21   a  of each tooth  21  is skew relative to the general axis X of the assembly. This shape, itself known, serves to obtain a screwing/unscrewing effect for the ring in the bore in which it is engaged. If the ring is turned in the bore, the ends of the teeth of the ring describe respective helixes, thereby enabling relative movement to be obtained between the bore and the ring, and thus the endpiece that it carries, which relative movement includes a component that is axial. In this context, the end edge  21   a  of each tooth, it should be observed that the corner  21   b  that is at the front of the tooth in the unscrewing direction is blunted or rounded in order to prevent it from digging into the wall of the bore  3 . In contrast, the other corner  21   d  is much sharper so as to oppose a large force against the ring being screwed into the bore. It is important to ensure that the ring does not screw either spontaneously or accidentally into abutment against the front flank of the groove  23  while the body of the part  1  is at its engagement limit as defined by an abutment on the outside of the part  2  and bearing against the part  1 . Under such circumstances, the abutments or dogs  20   e  and  20   f  for transferring rotary drive could no longer co-operate with the dog  24  carried by the endpiece  4 . During engagement, this situation of the ring  20  being too far away from the flank  23   a  could result in a most peculiar situation in the event of the top of the drive dog  24  coming to bear against the top of one or other of the abutments  20   e  or  20   f , since the ring would then be permanently out of reach of engaging the endpiece in rotary manner. This risk is practically eliminated by the triangular shape of the dogs  20   e ,  20   f , and  24  visible in  FIG. 6 , leading to one dog sliding relative to another when axial thrust is applied. It should also be mentioned that the faces of these dogs that co-operate during rotation are axially undercut, thereby ensuring the ring “catches” on the endpiece during rotary drive. 
     As in the preceding figures, it should also be observed that the axial length of the ring  20  is less than that of the groove  23 , such that when the ring is in contact with the flank  23   a  of the groove, the abutment  20   e ,  20   f  lies on the path of the abutment  24  of the endpiece, and can be driven thereby, which makes it possible to unscrew the connection. In contrast, when the ring is remote from the flank  23   a , the ring can no longer be made to turn about its axis, so any unscrewing is impossible. However this is a position that is taken up when a pressure P exists in the pipe (see preceding  FIGS. 3A-3C ). It is thus not possible for the connection to be unscrewed accidentally. Disconnection can be achieved only by applying a manual force FM ( FIG. 5C ) on the endpiece in the engagement direction and also manual rotation RM ( FIG. 5D ) so as to cause the ring to be driven by the endpiece via the abutments  20   e ,  20   f , and  24 . The abutment means  6   a  and  24  may be single, or there may be two, three, . . . of them in an angular distribution such that these means can be brought into mutual engagement after turning the endpiece through no more than one free turn (360°) if there is only one lug between the ring and the endpiece. 
     In the variant embodiment shown in  FIGS. 7A and 7B , there can be seen all of the elements described above with reference to  FIGS. 5A-5D , with the same references. These figures show the presence of an abutment for engaging the endpiece in the bore, which abutment is constituted by an O-ring  30 . In  FIG. 7A , it can be seen that the O-ring is squeezed at the end of engagement, with the ring  20  coming to bear against the flank  23   a  of the groove  23 . When the engagement force F ceases, the O-ring  30  returns to its initial shape causing the endpiece to move outwards relative to the bore, thereby moving the flank  23   a  away from the ring  20  and ensuring that the two abutments  24  and  20   e ,  20   f  cannot interfere. This provides security against accidental unscrewing even where there is no pressure in the circuit. Furthermore, since the resilient abutment for engagement ( 30 ) is preferably constituted by an O-ring, it is very inexpensive to provide and also provides the connection with protection against external pollution. 
     It should be observed that the embodiment of  FIGS. 2 and 3  also lends itself to being unscrewed if the tips of the teeth are skew. The flank  9   a  of the groove may include a projection suitable for being received between two tongues  8   a  that are not curved to form teeth.