Abstract:
A locking device ( 1 ) is fixed to a nut ( 4 ) and includes a coupling unit ( 42 ) insertable into a hexagonal configuration ( 11 ) of a spigot end ( 2 ) at a reduced axial distance being coupled by mutually interpenetrable gears ( 49, 51 ) with a stop unit ( 38 ) which axially slides in a body ( 18 ) opposite to a compression spring ( 36 ). The gears ( 49, 51 ) are symmetric and are insertable into each other with a predetermined elastic resistance by the action of compression or loosing torque. The device is embodied in one piece which is mounted by assembling with the nut without affecting the spigot ends ( 2, 3 ).

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a locking device for two components which are in a mutual screw connection. 
     This invention also relates to a pipe coupling provided with such a device. 
     The function of the locking device is to prevent undesirable unscrewing of the two components from each other, in particular in applications where the two components are subject to vibrations or shaking during use. 
     The invention is more particularly but not limitatively aimed at standardized couplings comprising a nipple at the end of one of the pipes, intended to be pressed into a flaring of the end of the other pipe, by tightening a nut captively mounted on one of the pipes and engaging a thread formed on the other pipe. 
     2. Description of Related Art 
     U.S. Pat. No. 6,293,595 B1 describes such a locking device capable of simultaneously engaging, by an axial movement under pressure from a spring, the hexagonal formation of the nut and a stop component integral with the male end-portion of the pipe. In order to be able to separate the two pipe end-portions, the coupling component must be pushed back against the return spring to the position where it is disconnected from the hexagonal formation provided on the nut and/or from the stop component attached to the male end-portion of the pipe. 
     During screwing or unscrewing, the presence of the tool on the nut prevents the coupling component from returning to the locking position. As soon as the tool is withdrawn when the screwing operation is completed, the coupling component is free to move to the locking position through the action of the spring. 
     This known device has the considerable advantage of being able to be adapted to a standard pipe coupling without modifications other than merely securing a bearing element on the male end-portion of the coupling. 
     In certain applications, where accessibility is difficult, in particular in aeronautics, it is desirable to minimize the interference caused by the locking device. With the known device, if the nut resists the unscrewing force exerted by the operator, the operator, who cannot see the nut, does not know whether the resistance is due to the screwing connection itself or to an incorrect disengagement of the coupling component. Moreover, and in any case, he must remember the structure of the locking device in order to displace his tool axially along the hexagonal formation thereby to push the coupling component back before being able to perform the unscrewing operation strictly speaking. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of this invention is to improve the known locking device in terms of ease of use. 
     According to the invention, the locking device for a screw coupling comprising a first and a second component which are rotatable in relation to one another during the screwing, a first of the components comprising a first thread and a rotating engagement formation distant from this first thread, the locking device being mounted on the second component and comprising:
         a coupling component for coupling with the engagement formation,   a stop component firmly connected for common rotation with a body carried by the second component,   disconnectable coupling means between the coupling component and the stop component,
 
is characterized in that the coupling means are of the type with a ratchet allowing relative rotation in the direction of unscrewing when a predetermined spring resistance is overcome.
       

     According to the invention it has been found that a reversible ratchet system is very effective for preventing any unscrewing as a result of vibrations. The ratchet only disconnects the two components from one another when a spring resistance has been overcome over a sufficient angular distance to reach the point passing over the apex of a ratchet tooth. However the vibratory excitation in one direction or in the other is of too short a duration for this process of passing over the tooth apex to be possible. The process can certainly begin, but it is followed by a springing back to the most stable locking situation. 
     By contrast, when an intentional unscrewing is carried out, the operator is not subjected to any feeling of malfunction or disturbance. 
     The unscrewing is therefore possible without the operator having to undertake special precautions or actions. He need only engage his tool with the hexagonal or other engagement formation provided on the first component of the screw coupling, and actuate his tool as usual. 
     The locking device according to the invention can be designed to be entirely compatible with standard pipe couplings without these requiring modifications other than fixing the device body onto the second component. Preferably, it is the nut which constitutes the second component. It is in fact easier to produce a special nut, in particular in the case of subsequent fitting. Moreover if the nut is equipped with the device, the two end-portions can be completely cleared when they are in the uncoupled state, simply by sliding the nut far enough back along the pipe which carries it, and the locking device no longer forms any obstruction to moving a pipe laterally in relation to the other. 
     According to a second aspect of the invention, the pipe coupling comprising a pipe end-portion provided with an external thread and a nut which can be screwed onto the external thread and rotatably mounted on another pipe end-portion, is characterized in that it also comprises a locking device according to the first aspect, for selectively locking the relative rotation of the two components constituted by the nut and the end-portion provided with an external thread. 
     Other features and advantages of the invention will also become apparent in the following description, which relates to non-limitative examples. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the attached drawings: 
         FIG. 1  is an axial sectional half-view of a pipe coupling according to the invention in the locking position, a first variant being illustrated for the means of securing the locking device onto the nut; 
         FIG. 1A  is a view similar to  FIG. 1 , but showing the other half of the pipe coupling according to the invention, and in the unlocking position at the start of unscrewing or at the end of screwing, a second variant being illustrated for the means of securing the locking device onto the nut; 
         FIG. 2  is a perspective half-view of the locking device and of a part of the nut before mounting the device on the nut, the first variant for the means of securing the locking device onto the nut being illustrated; 
         FIG. 2A  is another perspective half-view of the locking device and of a part of the nut before mounting the device on the nut, the second variant for the means of securing the locking device onto the nut being illustrated; 
         FIG. 3  is a partial sectional view along line III-III of  FIG. 1 ; 
         FIG. 4  is a perspective view of the coupling and stop components, as well as of a part of the spring; and 
         FIG. 5  is a view similar to the upper half-view of  FIG. 1 , but in the case of a worn pipe coupling. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in  FIGS. 1 and 1A , the locking device  1  according to the invention can be adapted to a first pipe coupling comprising a male end-portion  2 - or nipple-, firmly attached to a first one of the pipes to be coupled, and a female end-portion  3 , which is firmly attached to the second one of the pipes to be coupled, as well as a nut  4 . 
     The end-portions  2  and  3  comprise at their free end a male seal formation, with an ovoid shape  6  and respectively a female seal formation  7 , with a frusto-conical shape, intended to leak-tightly bear on one another. Starting from the ovoid seal formation  6 , the nipple  2  comprises an external thread  8  then a flange  9  provided on its periphery with a rotational engagement formation such as a hexagonal formation  11 . The formation is distant or separated from the thread  8  of the component  2  in the sense that this formation  11  which will be used for the locking is not constituted by an alteration of the thread such as a flat section or a groove eliminating part of the threads. 
     The nut  4  comprises at its rear end, remote from the end-coupling  2 , an internal flange  12  and an external rotational engagement formation  13  such as a hexagonal formation. The internal flange  12  is behind and engages a shoulder  14  of the end-portion  3 . The shoulder  14  faces away from the end-portion  2  in order to retain the nut  4  in a captive condition and in order to receive from the nut  4  a force which causes the seal formation  7  to leak-tightly engage the seal formation  6  of the end-portion  2 . 
     The nut  4  is extended forwardly by a tube  32  which comprises starting from its front end turned towards the end-portion  2  an internal thread  16  capable of cooperating with the thread  8  of the end-portion  2  in order to produce the above-mentioned tightening pressure. 
     The locking device  1  according to the invention comprises a support body  18 —or cup—comprising at its rear end a sleeve  19  which is fitted around the hexagonal formation  13  of the nut  4 . To this effect, the sleeve  19  comprises an internal surface  21  having a prismatic shape with a hexagonal contour which allows the sleeve  19  to be fitted, with practically no play, onto the hexagonal formation  13  (see also  FIG. 2 ). Once this fitting has been carried out, the nut  4  and the body  18  are connected for common rotation. Moreover, the sleeve  19  is equipped with retaining means for axially attaching the sleeve  19  and therefore the body  18  to the nut  4 . These means comprise at the annular inner end of the surface  21  an internal flange  22  ( FIG. 1 ) intended to abut a front shoulder  23  of the nut  4 , said shoulder adjacent to the front edge of the formation  13 . In the version represented in  FIGS. 1 and 2 , the retaining means also comprise locking lugs  24  cut out in the wall of the sleeve  19  with essentially axial slits  26  opening though the rear edge of the sleeve  19 . The locking lugs  24  end in locking jaws  27  which, once assembling is completed, grasp the rear face  28  of the nut  4 , adjacent the rear annular edge of the hexagonal formation  13 . 
     In the embodiment shown in  FIGS. 1A and 2A , the retaining means comprise crimping tabs  29  which are initially in the extension of at least some of the faces of the inner surface  21  of the sleeve  19  ( FIG. 2A ). Once assembling is completed, the tabs  29  are plastically bent back against the rear surface  28  of the nut  4 , as shown at the bottom of  FIG. 1 . 
     The sleeve  19  has on its external surface its own hexagonal formation  25  intended to substitute for the hexagonal formation  13  of the nut in order to allow the nut to be rotated using a tool such as a wrench (not represented) when the device  1  is in place. 
     At its front end, the sleeve  19  is rigidly connected to and forms a single piece with the rear end of a generally cylindrical skirt  31  which extends around the tube  32  while forming an annular chamber  34  between the skirt  31  and the tube  32 . 
     Inside the chamber  34  there is, starting from the rear end thereof, a helical compression spring  36  having the same axis  37  as the pipe, an annular stop component  38  around the axis  37  and comprising blocks  39  slidingly mounted in axial grooves  41  of the internal wall of the skirt  31 , and finally a coupling component  42  comprising on its external periphery a boss  43  which prevents the coupling component  42  from disengaging from the skirt  31 . To this effect, the boss  43  abuts a terminal rim  44  of the skirt  31 , formed by plastic deformation, projecting radially towards the axis  37 . 
     As particularly shown in  FIG. 4 , the coupling component  42  protrudes outside the skirt  31  beyond the terminal rim  44  and has in its front portion, which protrudes from the skirt  31  at least when the spring  36  is in the state of relatively low compression, a hexagonal female recess  46  with a size corresponding to that of the male hexagonal formation  11  of the first component  2 . The axial width of this recess is much smaller than that of the hexagonal formation  11  and it is delimited, at its rear end, by stops  47  intended to engage a shoulder  48  adjacent the hexagonal formation  11 . This engagement limits the axial extent by which the recess  46  covers the formation  11 . 
     The axial dimensioning of the assembly is such that when the two end-portions  2 ,  3  in a new condition ( FIG. 1 ) are leak-tightly pressed axially against one another by the clamping exerted by the nut  4 , the coupling component  42  engages the hexagonal formation  11 , the stops  47  engage the shoulder  48  while the stop  43  is almost bearing against the rim  44 . 
     As illustrated in  FIG. 5 , the generic type pipe couplings addressed by the invention tend to become worn by radial contraction of the male part  6 , and widening or flaring out of the frusto-conical part  7 . This results in an increase in the travel of the nut  4  along the first component  2  which is necessary in order for the desirable axial clamping to be achieved. This is allowed for according to the invention by means of a sufficient compression displacement of the spring  36 , and sufficient initial axial mobility distances d ( FIG. 1 ) between the coupling component  42  and the free end of the nut  4 , and D between the rear end of the blocks  39  and the bottom of the chamber  34 . 
     The stop component  38  and the coupling component  42  have on their annular edges turned towards one another teeth  49 ,  51  pointing axially and having a symmetrical profile. In other words, in relation to a circumferential direction, the teeth, which have a triangular configuration, each have a front face and a rear face which have the same oblique slope. Moreover, the teeth  49  of the stop component  38  and the teeth  51  of the coupling component  42  have complementary profiles so that they can interpenetrate as represented in  FIG. 1  and in  FIGS. 4 and 5 . By contrast, in  FIG. 1A , the teeth are tip to tip. 
     It is very easy to provide a pipe coupling with the locking device according to the invention. The nut being completely separate from the first component  2 , and the latter being separate from the second component  3 , the device  1  is fitted onto the nut  4  from the front end of the nut  4  until the flange  22  abuts against the shoulder  23 . In the self-locking embodiment, the lugs  24  are forced radially outwards in order to pass the shoulder  23  then resiliently spring back inwardly when the jaws  27  can snap behind the face  28  of the nut  4 . In the version with crimping tabs  29 , the fitting is carried out without resistance until the flange  22  abuts the shoulder  23 . At this stage, the crimping tabs  29  are bent back radially inwardly as represented at the bottom of  FIG. 1 . It is noteworthy that the device  1  forms an assembly all in one piece being entirely mounted on only one of the components to be locked together, without requiring any arrangement on the other component. 
     In order to couple the pipe coupling, the nut  4  is screwed around the thread  8  of the end-portion  2  using a wrench which engages the hexagonal formation  11  of the end-portion  2  and another wrench which engages the hexagonal formation  25  of the device  1 . The coupling component  42  abuts the edge  44  through the action of the compression spring  36 . As the end of screwing approaches, the coupling component  42  abuts the shoulder  48  of the end-portion  2 , the spring  36  starts to compress and then, as the component  42  is driven in rotation by the interpenetration of the teeth  49  and  51 , its recess  46  ends up matching with the formation  11  of the end-portion  2  and the spring  36  springs back while causing the recess  46  to fit onto the formation  11 . The coupling component  42  is consequently prevented from turning with the nut  4  and the teeth  49  and  51  click one on another, each time with a brief compression of the spring  36  when the teeth  49  and  51  are tip to tip as illustrated in  FIG. 1A . Finally the situation represented in  FIG. 1  is reached, where the pipe is locked and leak-tight, and the nut  4  is prevented from turning under the effect of vibrations or other parasitic loads thanks to the locking of the nut  4  and the end-portion  2  via the body  18 , the stop component prevented from turning in relation to the body  18  thanks to the blocks  39  engaged in the grooves  41 , and the coupling component  42  prevented from turning in relation to the stop component  38  because of the interpenetration of the teeth  49  and  51 . If the rotation of the nut at the end of locking ends at a position where the teeth  49  and  51  are tip to tip as represented in  FIG. 1A , any stress, vibratory or otherwise, can then only result in a slight turn of the nut until the situation of interpenetration of the teeth is achieved. 
     In order to unscrew the nut, it is sufficient to again position the two tools on the hexagonal formations  25  and  11 , and to make the device  1  and the nut  4  turn together in the direction of the unscrewing. The teeth and  51  jump one above the other with brief compressions of the spring  36  until, as a result of the axial backward movement of the nut  4  associated with the unscrewing movement, the coupling component  42  ends up being disengaged from the hexagonal formation  11  of the end-portion  2 . The coupling component  42  now turns with the nut  4  in the unscrewing direction. Once unscrewing is completed, the nut  4  and the device  1  can move together as far as desired rearwardly (therefore towards the left side of  FIGS. 1 and 1A ) in order to allow the desired technical operation to be carried out on the coupling without any interference. 
     When the coupling is worn, the residual spring compression travel of the spring  36  and the distance D′ ( FIG. 5 ) still allowed for the blocks  39  in the locked state are sufficient to allow the teeth  49  and  51  to pass each other by a ratchet movement. 
     Of course, the invention is not limited to the examples described and represented. 
     The device could also be attached to the male end-portion  2  and be caused to cooperate, for locking, with the hexagonal formation  13  of the nut. This solution is less preferred because the device may then prevent good access to the components of the coupling such as the male and female end-portions even after unscrewing is completed. 
     If it is sought to have a different resistance of the teeth  49  and  51  when screwing and unscrewing, they can be made asymmetrical but they must always have a sufficiently small slope to be able to pass each other simply by the action of a turning torque exerted on the locking device  1  in relation to the other component which is not equipped with the device. 
     It is also possible to produce pipe coupling components, and in particular nuts which are directly equipped with a device according to the invention, in which case the body  18  and the nut  4  can simply constitute one and the same part, or for example two parts assembled together in a permanent fashion, by welding or bonding, etc.