Abstract:
The rigid coupling device includes a closure valve extended by a retractable sliding stop member of general tubular shape made from elastically deformable material, having at least one outward radial projection forming a stop against a corresponding inward radial projection of a movable interior body that contains the valve. The stop member has an open end opposite the opening of the cylindrical cavity of one end connecting to the conduit. Simultaneous withdrawal of the interior body and of the valve into the interior body has the effect of causing this open end to contract, forcibly inserting it into the cylindrical cavity of the connecting end in such a manner as to overcome the stop.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is continuation of copending International Application No. PCT/FR06/002698 filed Dec. 11, 2006, which designated the United States, and which claims priority to French Patent Application No. FR 05/12953, filed Dec. 20, 2005, the disclosures of each of which is expressly incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a rigid coupling for pipes carrying pressurized fluid, allowing these pipes to be connected while pressurized fluid remains in one of them. 
         [0003]    This coupling comprises, in a way known per se, a male element and a female element of which the ends that are to be connected are closed by valves. The male element, connected to a tool actuated by the fluid, contains pressurized fluid, while the female element connected to the fluid source is not under pressure. 
         [0004]    Patent EP 0 847 511, in the name of the applicant, describes a coupling such as this in which the female element has a fixed external sleeve with an end for connection to a pipe supplying hydraulic fluid, and a slideable internal body containing the valve of the female element, a return spring being interposed between the external sleeve and the mobile internal body. 
         [0005]    Each valve comprises a valve shutter that presses against the valve shutter of the other valve upon connection, a return spring pressing this shutter against a seat and a limit stop limiting the opening travel of the shutter. 
         [0006]    The limit stop of the male element containing pressurized fluid is fixed, while the limit stop of the female element is slideably mounted in the female element so that it can occupy a forward fixed position in which the shutter is pressed against the limit stop when the male and female elements are connected, and so as to be able to retreat into the female element so as to allow the shutter associated therewith to retreat further than the aforementioned opening travel, the distance retreated corresponding substantially to the opening travel of the shutter of the male element. 
         [0007]    The coupling also comprises means of locking and of returning the sliding limit stop into/in the forward position, these means allowing the retreating movement of the sliding limit stop upon connection of the male and female elements, and locking the sliding limit stop in the forward position once this connection has been made. 
         [0008]    In a coupling such as this it is necessary to allow the mobile internal body to move in and out with respect to the fixed external sleeve. For this reason, it is common practice for the internal body that can move inside the fixed external sleeve to be “hydraulically balanced”, that is to say to use relationships between pressures and surface areas such that the sum of the forces generated by the pressure effects cancel each other out. 
         [0009]    The return spring acting on the mobile internal body is capable of compensating for the small potential difference in forces that may be due to manufacturing tolerances manifested in the form of different diameters and different levels of friction. 
         [0010]    Here, the technique used is the one known as “differential balancing”. 
         [0011]    The central fluid stream is continuous. Three sealing members are used, two of identical diameter D 1  and a third of a higher diameter D 2  such that D 2 /D 1 =√2. This relationship allows the sealing cross section of small diameter D 1  to be the same as the cross section of the annulus formed between the small diameter D 1  and the large diameter D 2 . 
         [0012]    The supply of pressurized fluid to the annulus between the large and small diameters is achieved via a through-hole passing through the mobile internal body. 
         [0013]    The forces exerted on the two small-diameter sealing members and on the annulus between the large and small diameter are of the same magnitude but of opposite directions, thus balancing the position of the mobile internal body in the fixed external sleeve at a location predefined by the limit stops of the return spring that returns the internal body. 
         [0014]    This technique is economically attractive as to the production of the mechanical parts and displays good hydrodynamic characteristics, but the mechanical relationship between the mobile internal body which notably bears the female shutter and the fixed external sleeve is complicated to achieve. 
         [0015]    To achieve this mechanical relationship, the means for locking and for returning the sliding limit stop in/into the forward position usually comprise mobile sleeve tubes internal and external to the mobile internal body of the female element, and connected to one another via balls or pegs passing through the mobile internal body. 
         [0016]    These elements both balance (in the hydraulic sense) the positions of the shutters of the male and female elements in a position such that the circuit is open to the hydraulic fluid, and allow the shutter to effect an overtravel inside the female element in order mechanically to lock the male and female elements in spite of the approximately 3 to 4 mm protrusion of the shutter of the male element, which protrusion is due to the pressurized fluid contained therein. 
         [0017]    Because the male and female elements are mechanically connected and locked, the opening of the hydraulic circuit, and therefore the balancing of the shutters of the male and female elements, is done by subjecting the female element to the hydraulic line pressure until such point as the pressure therein is enough to counter the pressure in the male element and open the valve thereof. 
         [0018]    This arrangement calls for a great many components and thus entails a great deal of accuracy in producing and assembling these components, to the detriment of the overall cost of the product. 
       SUMMARY OF THE INVENTION 
       [0019]    The present invention aims to avoid these disadvantages by providing a rigid coupling for pipes carrying pressurized fluid, comprising a lower number of components, particularly for selectively locking and returning the sliding limit stop in/into the forward position. 
         [0020]    To this end, the subject of the present invention is a rigid coupling for pipes carrying pressurized fluid, as described in the preamble, and in which the shutter of the female element is extended at the rear by a retractable limit stop member of substantially tubular overall shape made of an elastically deformable material having at least one outward radial projection forming a limit stop against a corresponding inward radial projection of the internal body, and an open end facing the mouth of the cylindrical cavity in the connection end, the simultaneous retreat of the internal body inside the external sleeve and of the shutter inside the internal body having the effect of narrowing this open end by forcibly inserting it into said cylindrical cavity at the connection end, so as to retract said limit stop. 
         [0021]    Thus, the inventive idea is to combine the shutter of the female element with a single member bearing the limit stop for the shutter and capable of deforming elastically upon connection of the male and female elements so as to retract the limit stop and allow the shutter its overtravel. This elastic member prevents the possibility of the shutter of the female element being driven into the female element under the effect of an axial load due to the hydrodynamic forces of the “male-to-female” flow and accidentally shutting off the circuit. This coupling is inexpensive to produce because it comprises just one elastic limit stop member. 
         [0022]    Advantageously, the mouth of the cylindrical cavity at the connection end is chamfered in such a way as to form an annular ramp, and the open end of the retractable limit stop member is of frustoconical shape so that it can slide against this annular ramp, become narrowed, and enter the cavity. 
         [0023]    In an illustrative embodiment, the retractable limit stop member has at least two longitudinal slots creating longitudinal legs which are kept in the normal position by the elasticity of the limit stop member. 
         [0024]    The retractable limit stop member for example comprises an anterior part for attachment to the shutter and a rod-shaped main body provided with at least two guide fins projecting radially outward, which do not disrupt the flow of fluid and position and guide the sliding of the limit stop member inside the internal body. 
         [0025]    These and other advantages will be readily apparent to those skilled in the art based upon the disclosure contained herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings wherein: 
           [0027]      FIG. 1  is a view in longitudinal section of the female element of coupling according to the invention; 
           [0028]      FIG. 2  is a perspective view of one component of the female element of said coupling; 
           [0029]      FIGS. 3-6  are views in longitudinal section, in three successive positions in the connecting with the male and female elements of the coupling; and 
           [0030]      FIG. 7  is a view similar to  FIG. 3  when the male element does not contain any pressurized fluid. 
       
    
    
       [0031]    The drawings will be described further in connection with the following Detailed description of the Invention. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0032]    The coupling according to the invention depicted in the figures comprises a male element  2  and a female element  3  of which the ends that are to be connected are closed by valves. 
         [0033]    In  FIG. 1 , the female element  3  comprises three assembled parts  25 ,  26  and  27  which form a fixed external sleeve  28  and a so-called “adapter” end  29  for connecting to the pipe, and two assembled parts  20  and  21  forming an internal body  22  containing the valve of the female element  3 . 
         [0034]    The internal body  22  is able to slide with respect to the external sleeve  28 , a spring  30  being interposed between the same. The spring  30  normally keeps the internal body  22  and the external sleeve  28  in the relative position shown in  FIG. 1 . 
         [0035]    The valve of the female element  3  comprises a seat formed by an annular projection  31 , a valve shutter  45  extended forward by a cylindrical pin  46 . 
         [0036]    The shutter  45  is extended at the rear via a retractable limit stop member  32  of substantially tubular overall shape made of a highly technical thermoplastic, with a diameter corresponding, give or take the required clearance, to the internal diameter of the part  21  of the internal body  22 , so as to slide in the body  22 . 
         [0037]    As indicated more specifically in  FIG. 2 , the retractable limit stop member  32  comprises an anterior part for attachment to the shutter  45  and a rod-shaped main body provided with four guide fins  47  projecting radially outward. These fins  47  also position and guide the member  32  in the internal body  22  and do not disrupt the flow of fluid and can also leave a sufficiently large fluid passage cross section so that the assembly enjoys good hydrodynamic performance, that is to say presents a projected surface of approximately 100 mm 2 . 
         [0038]    The rear part of the retractable limit stop member  32  is open facing the mouth of the cylindrical cavity in the connection end  29 , and has two longitudinal slots creating opposing and diametrically opposed longitudinal legs  33  which are kept in their normal position by the elasticity of the member  32 . 
         [0039]    The two legs  33  are elastically deformable inward in the radial direction so as to form a kind of tongs arrangement, and emerge from the internal body  22  near the end  29  for connection to the pipe. 
         [0040]    The component  20  behind the component  21  has, in succession, from front to rear, a first internal diameter substantially corresponding to the internal diameter of the component  21 , then a second internal diameter smaller than the first, and finally a third internal diameter that is smaller still, substantially corresponding to the internal diameter of the end  29  for connection to the fluid supply pipe (not depicted). 
         [0041]    The rear wall of the fins  47  of the member  32  presses against a spring  41  which presses against a shoulder which delimits said first and second internal diameters of the component  20  of the internal body  22 . 
         [0042]    The legs  33  are surrounded by the turns of the spring  41 . For this, the two legs  33  are essentially inscribed inside a cylindrical volume of a diameter corresponding, give or take the clearance, to the third internal diameter of the component  20  that forms part of the internal body  22 . 
         [0043]    However, the legs  33  each have an outward radial projection  34  the outside diameter of which corresponds, give or take the clearance, to the second internal diameter of the component  20  of the body  22 . The projection  34  forms a limit stop against an annular shoulder  40  which delimits said second and third internal diameters of the component  20  of the internal body  22 . 
         [0044]    Furthermore, the ends of the legs  33  which emerge from the component  20  of the internal body  22  near the end  29  for connection to the pipe each also form an outward radial shoulder  35  inscribed inside a volume of frustoconical shape, of a shape that complements that of an annular ramp formed at the mouth of the adapter  29  and inclined toward the pipe. 
         [0045]    The legs  33  can enter the adapter  29  by deforming radially inward under the pressure of said annular ramp at the mouth of the adapter  29  against the corresponding ramps formed by the shoulders  35  at the ends of the legs  33 . 
         [0046]    Furthermore the component  21  of the internal body  22  comprises, at its cavity intended to accept the male element  2 , balls  51  engaged in radial bores formed through the wall of the component  21  of the body  22 . These balls  51  can move radially in these bores between an internal position depicted in  FIGS. 1 ,  4  and  5 , and an external position depicted in  FIGS. 3 ,  6  and  7 . 
         [0047]    The external sleeve  28  for its part comprises, level with the balls  51 , an internal annular projection  55  with inclined lateral sides, delimiting two grooves  56  and  57 . 
         [0048]      FIG. 3  illustrates the first step in connecting the coupling that forms the subject of the invention, when the male element  2  is engaged in the cavity of the female element  3 . In a way known per se, the valve of the male element comprises a seat  5 , a shutter  6  extended on the inside by a guide stem  7 , a return spring  8  pressing this shutter  6  against the seat  5  and a fixed limit stop  9  accepting the sliding stem  7  and against which the spring  8  presses. The limit stop  9  limits the opening travel of the shutter  6 . 
         [0049]    On the outside, the shutter  6  comprises a cylindrical pin  15  which presses against the cylindrical pin  46  of the shutter  45  of the female element upon connection of the male and female elements. 
         [0050]    Furthermore, the male element  2  comprises an external annular projection  16  with inclined lateral sides delimiting two grooves  17  and  18 . 
         [0051]    The male element  2 , connected to the tool operated by the fluid, contains pressurized fluid while the female element  3  connected to the fluid source is not under pressure. 
         [0052]    During engagement of the male element  2 , the projection  16  encounters the balls  51  which are held in their furthest-in position by the projection  55  situated facing them. At the same time, the pin  15  of the shutter  6  comes into contact with the corresponding pin  46  belonging to the shutter  45 . 
         [0053]    Continued engagement of the male element  2  causes the internal body  22  to move, to the right in the figure, with respect to the external sleeve  28 . 
         [0054]    This movement leads to compression of the springs  30  and  41 , and engagement of the legs  33  inside the adapter  29  via inward radial deformation (narrowing) under the effect of the annular ramp at the mouth of the adapter  29  pressing against the corresponding ramps formed by the shoulders  35  at the ends of the legs  33 . 
         [0055]    This movement continues until the balls  51  lie facing the groove  57  and are pushed into this groove by the inclined lateral side of the projection  16 . 
         [0056]    Here, retreat against the action of the spring  41 , and therefore radial deformation, of the legs  33  are significant enough that the projections  34  of the legs  33  engage “under” the annular shoulder  40  of the component  20  of the internal body  22  so that the limit stop that limits the travel of the shutter  45  is thus retracted. 
         [0057]    With the male element  2  now completely engaged in the cavity of the female element  3 , the groove  17  faces the balls  51 , and these balls  51  are driven into this groove  17 , thus locking the male  2  and female  3  elements together. 
         [0058]    When the axial force of engagement of the male element  2  in the female element  3  is released as depicted in  FIG. 4 , the spring  30  is released and returns the internal body  22  and the external sleeve  28  to their original relative position, the ends of the legs  33  still being “narrowed” inside the adapter  29 . 
         [0059]    When pressure is established in the female element  3 , the fluid moves the member  32  and the shutter  45  to the left in the figures as far as their position depicted in  FIG. 5 . 
         [0060]    By virtue of the spring  41 , the two valves are therefore opened, with the two shutters  6  and  45  immobilized, the shutter  6  being in abutment against the fixed limit stop  9  and the shutter  45  and its support member  32  pressing against the spring  41 . 
         [0061]    The legs  33  are released from their position inside the adapter  29  and return to the un-narrowed “open” position through their natural elasticity. They therefore come into abutment via their projections  34  against the annular shoulder  40  (of the travel limit stop) of the component  20  of the body  22  so that the limit stop that limits the travel of the shutter  45  is re-established. 
         [0062]    Disconnection (see  FIG. 6 ) of the male  2  and female  3  elements is performed by pulling on the male element, this moving the internal body  22  to the left until the balls  51  enter the groove  56 . The valve of the female element  3  is then closed and sealed. 
         [0063]    The flow of fluid through the member  32  is undisturbed and the guide fins  47  optimize this flow. 
         [0064]    Furthermore, the shutter  45  forms an integral part of the member  32  and is perfectly guided in the body  22 , which gives the valve the ability to withstand high pressures. 
         [0065]    The spring  9  is softer than the spring  41  which means that if there is no pressure in the male element  2 , the valve of the male element  2  opens (see  FIG. 7 ) merely under the return force of the spring  41  which force, in accordance with standard ISO7241-A for ½″ pipe, is greater than 45 N. 
         [0066]    The member  32  in this instance is made of a highly technical thermoplastic that could equally be made of brass, stainless steel or any other material capable of meeting the following specifications:
       a longitudinal elastic modulus that is high in order to withstand the compression loadings resulting from the axial component of the hydrodynamic forces;   a transverse elastic modulus that is high in order to develop sufficient force for returning the legs  33  of the member  32  to the open (un-narrowed) position thus butting against the shoulder  40 ;   a coefficient of elongation A % that is high in order to tolerate significant deflection of the legs  33  without remnant deformation;   the ability to uphold minimum characteristics at temperatures in excess of 110° C.       
 
         [0071]    As goes without saying, the invention is not restricted to the single embodiment described hereinabove by way of indicative example; on the contrary, it encompasses all embodiment and application variants thereof that follow the same principle. Thus, in particular, it would not be a departure from the scope of the invention if the shutter  45  or the member  32  were to be made of several assembled elements made of the same material or different materials. 
         [0072]    It would also be possible to design a similar mechanism with a member again in the form of ridged tongs, but secured to the adapter  29 . 
         [0073]    During the connection phase, upon the retreat movement, this member is made to close by the piston (component  20 ) thus retracting during the double travel retreat of the shutter  45  of the female element. In equilibrium, by virtue of its elasticity, the “tongs” re-open to the open position and provide the shutter  45  with a positive limit stop effect once the shutter has returned to the circuit-open position. 
         [0074]    This alternative, which does not fall within the context of the present invention, is of some benefit in the selection of materials which can then be more conventional than in the present invention because the technical and dimensional characteristics can be divided across two components rather than exhibited by just one. 
         [0075]    By contrast, the characteristics of this version are limited in terms of the maximum authorized return flow rate. This limit is directly linked with the spring force characteristics of the spring  30  that returns the mobile internal body  22 . 
         [0076]    Specifically, all the shutters of the male  2  and female  3  elements are subjected to hydrodynamic forces, in a flow from the male element  2  toward the female element  3 , which will push on the “tongs” of the adapter  29  namely an element of the fixed external sleeve  28 . Further, the force reacting these hydrodynamic loadings is provided by the mechanism that locks the male element  2  which is secured to the mobile internal body  22  of the female element  3  and therefore has a tendency to leave the fixed external sleeve  28 . Only the spring  30  compensates for this phenomenon between the two fixed and mobile frames of reference and when the force due to the hydrodynamic forces becomes greater than the spring force of the spring  30 , the male element  2  becomes uncoupled unintentionally and causes the hydraulic circuit to be suddenly closed. The male element  2  has then to be recoupled in order to make the hydraulic system operational again. 
         [0077]    The limits observed on a test rig demonstrate that accidental disconnection occurs at around about 1501/min for a spring  30  rated at 220 N and ½″ hydraulic coupling with relatively continuous passage cross sections of about 100 mm 2 . 
         [0078]    As it is anticipated that certain changes may be made in the present invention without departing from the precepts herein involved, it is intended that all matter contained in the foregoing description shall be interpreted as illustrative and not in a limiting sense. All references including any priority documents cited herein are expressly incorporated by reference.