Abstract:
The invention relates to a fluid distributor for a heavy-construction machine, comprising a body and a pressure-reducing means which is mounted in said body and comprises a pushrod arranged in a cavity of the body, a plunger being mounted in an oscillating manner. At least one guide in which the pushrod is displaced is immobilised in the cavity, a first seal and a second seal respectively ensuring the hydraulic sealing inside and outside the guide. Said guide comprises at least part of the upper guide and part of the lower guide which are nested inside each other and mutually define a recess facing the pushrod, the first seal being trapped in the recess.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The subject of the present invention is a pressurized fluid distributor, particularly a manipulator for a construction machine. These distributors are mainly used for controlling various hydraulic functions such as the movement of various receiving members installed on board these construction machines.  
       DESCRIPTION OF THE PRIOR ART  
       [0002]     Such hydraulic distribution devices are well known to those skilled in the art and are described for example in documents FR-2 507 732, or FR-2 376 978.  
         [0003]     The pressurized fluid distributors of the type described in the aforementioned documents comprise: 
        a body that comprises at least one cavity of which one end is open onto at least one upper face of the body,     at least one pressure reducer which is mounted in the body, and which comprises a pushrod which is housed with to-and-fro movement in said at least one cavity of the body in an axial direction, and a plunger which is mounted so as to oscillate substantially in the same axial direction to perform the function of pressure reducer, and a regulating spring interposed between the plunger and the pushrod, the balance of the plunger depending on the compression of the spring imposed by the downward movement of the pushrod and the output regulating pressure to be delivered to a receiving member downstream,     a handle that is mounted so as to tilt relative to the body, opposite the upper face of said body to control the to-and-fro movement of said at least one pushrod,     at least one guide in which the pushrod moves and which is immobilized in the cavity, at the open end, and     at least one first seal and one second seal which respectively provide the hydraulic seal inside and outside the guide.        
 
         [0009]     For a good quality seal to be obtained, it is necessary to take great care with the mounting of the first and second seals on the guide. Specifically, the guides currently encountered have grooves that are machined on their outer surface and on their inner surface, and in which the seals are intended to be inserted. These grooves must be capable of not harming the seals during mounting. This therefore requires a good control of the machining and of the dimensions obtained, which generates high costs.  
       SUMMARY OF THE INVENTION  
       [0010]     The object of the present invention is to remedy the aforementioned disadvantages by providing a fluid distributor whose guide is obtained at low cost, and in which the mounting of the seals is simplified. As a result, according to the invention, a fluid distributor of the aforementioned type is essentially characterized in that the guide comprises at least one upper guide portion and one lower guide portion which are nested one on the other,  
         [0000]     in that said upper guide portion and lower guide portion mutually delimit a housing turned toward the pushrod,  
         [0000]     and in that the first seal is captive in the housing.  
         [0011]     Thus, thanks to these arrangements, the fluid distributor has a guide made in two portions so that the guide portions and the seals are mounted by successive stacking. Thus, the risks of damaging the seals during mounting are much reduced.  
         [0012]     Preferably, the distributor comprises immobilization means which are fitted onto the body, at the upper face of said body, for locking at least the upper guide portion in position.  
         [0013]     Again preferably, the immobilization means comprise a retention flange attached to the upper face of the body.  
         [0014]     Advantageously, the upper guide portion and lower guide portion also mutually delimit a housing turned toward the body and in which the second seal is captive.  
         [0015]     Again advantageously, the upper guide portion is made of the same material as the retention flange.  
         [0016]     As a variant, the body is formed in two superposed sections along a parting line: an upper section in which the pushrod is movably mounted and a lower section in which the major portion of the plunger is mounted so as to oscillate, the upper guide portion being made of the same material as the upper section of the body.  
         [0017]     Advantageously, the retention flange and the upper portion of the body are made together of the same material.  
         [0018]     Preferably, the second seal is interposed between the upper section and lower section of the body at their parting line.  
         [0019]     Preferably, at least the lower guide portion is made of one of the materials chosen from plastic, an injected alloy, a sintered material, and a machined material. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]     Other features and advantages of the invention will become apparent during the following description of three of its embodiments, given as nonlimiting examples, with reference to the appended drawings in which:  
         [0021]      FIG. 1  is a view in longitudinal section of a fluid distributor according to the prior art.  
         [0022]      FIG. 2  is a view in longitudinal section of a fluid distributor according to a first embodiment of the present invention.  
         [0023]      FIG. 3  is a view in longitudinal section of the guide fitted to the distributor of  FIG. 2 .  
         [0024]      FIGS. 4 and 5  are respectively views, similar to those of  FIG. 2 , of a second embodiment and of a third embodiment of a distributor according to the present invention.  
         [0025]      FIG. 6  is a view in longitudinal section of the upper section of the body of the distributor represented in  FIG. 5 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]     The pressurized fluid distributor  1  represented in  FIG. 1  is a distributor belonging to the prior art. The fluid delivered by this distributor is intended to supply a downstream receiving member not shown, at a pressure that is appropriate to the use of that member.  
         [0027]     As is well understood by those skilled in the art, the fluid distributor  1  comprises a body  2  in which are mounted at least one and preferably several pressure reducers  3 . Even though only two reducers are shown in  FIG. 1 , these distributors are usually fitted with four pressure reducers that are identical to one another. These reducers are usually parallel with one another and are oriented along the longitudinal axis X-X of the distributor  1 .  
         [0028]     Each pressure reducer  3  comprises a plunger  5  that is mounted so as to oscillate substantially in an axial direction parallel to the axis X-X, and which moves in a cavity  6  arranged in the body  2  of the distributor  1 . This cavity  6  has one end  8  open at an upper face  7  of the body  2 .  
         [0029]     The adjustment of the pressure reducer  3  is controlled by an operator by means of a handle  10  (partially shown in  FIG. 1 ). This handle  10  is mounted so as to tilt on the body  2 , opposite the upper face  7  of this body. An articulation  11 , for example of the universal joint type, is used to fixedly attach the handle  10  to the body  2 . As a variant, this articulation is for example a spherical articulation or else a pivoting connection.  
         [0030]     The pressure reducer  3  comprises, again in a manner known per se, a pushrod  15  and a regulating spring  16 . The regulating spring is interposed between the plunger  5  and the pushrod  15  so that the balance of the plunger  5  depends on the compression of the spring  16  imposed by the downward movement of the pushrod  16  and the output regulating pressure to be delivered to the receiving member (not shown).  
         [0031]     The downward movement of the pushrod  15  is controlled by the handle  10  so that it has a to-and-fro movement inside the upper end  8  of the cavity  9 .  
         [0032]     The operation of such a fluid distributor is well known to those skilled in the art and is for example described in the aforementioned documents.  
         [0033]     As is again well known, the guidance in translation of the pushrod  15  is provided by means of a guide  20  which takes the form of a single-piece sleeve immobilized at the open end  8  of the cavity  6  by means of a blanking plate  21 . Two peripheral grooves  22  and  23  have been machined in the guide  20 , respectively at the outer surface and the inner surface of this guide.  
         [0034]     In the outer peripheral groove  22 , an O-ring  24  has been immobilized to provide the seal between the guide  20  and the body  2  while a lip seal  25  is immobilized in the groove  23  to provide the seal between the pushrod  15  and the guide  20 .  
         [0035]     Such a distributor has the disadvantage of requiring very good machining of the outer and inner peripheral grooves of the guide  20  so that the O-ring  24  and the lip seal  25  are not damaged when they are mounted on the guide. This requires good control of the dimensions and the quality of the surface obtained, generating a high cost.  
         [0036]     By contrast, according to the present invention, the seal of the pushrod guide is obtained more simply and hence at lower cost. The distributor according to the present invention shown in FIGS.  2  to  6  comprises the same constituent parts as those previously described with relation to the pressure regulating function. The identical constituent parts bear the same reference numbers. Hereinafter, all that will be described will be the constituent parts of the pressure distributor according to the present invention that are used to guide the pushrod  15 .  
         [0037]     According to an essential feature of the present invention, the pushrod  15  moves in a to-and-fro movement inside a guide  30  that is immobilized at the open end  8  of the cavity  6  of the body  2  and that is made in two portions distinct from one another.  
         [0038]     The guide  30  thus comprises an upper guide portion  31  and a lower guide portion  32  which are nested in one another. More particularly, the two portions  31  and  32  are nested along the axis X-X so that one of the portions penetrates into the other while mutually delimiting internally a first housing  33  which opens internally, in the direction of the pushrod  15 . Likewise, the interpenetration of the upper portion  31  with the lower portion  32  of the guide  30  delimits externally a second housing  34 , which is turned in the opposite direction to the first housing  33 , opening in the direction of the body  2 .  
         [0039]     As is shown more particularly in  FIG. 3 , the upper portion  31  has a head  40  and a body  41 , the internal diameter of the head  40  being smaller than that of the body  41 . The lower portion  32  of the guide  30  has a foot  42  and a core  43 , the outer diameter of the foot  42  being greater than that of the core  43 . The shape of the core  43  and the shape of the body  41  are complementary so that the core  43  can be sleeve-coupled inside the body  41 , their respective length being suitable for delimiting the inner housing  33  and the outer housing  34 .  
         [0040]     The lower portion  31  and the upper portion  32  of the guide  30  are of generally cylindrical shape whose internal diameter is substantially equal to the diameter of the pushrod  15 .  
         [0041]     Thus it is understood that the lower and upper portions of the guide have simple shoulders formed by a change of diameter, so that no groove is machined for inserting the first seal  36  and the second seal  37  which respectively provide the inner and outer seal of the guide  30  against the pushrod  15  and the body  2 .  
         [0042]     The fluid distributor  1  also comprises immobilization means  45  that are fitted onto the body  2 , at the upper face  7  of this body to lock the lower guide portion  32  in position while resting against a collar  46  belonging to the upper guide portion  31 .  
         [0043]     The immobilization means  45  take for example the form of a retention flange screwed onto the upper face  7  of this body  2 .  
         [0044]     Prior to the immobilization of the guide  30  in the cavity  6  of the body  2 , the lower portion  32  of the guide  30 , the second seal  37 , and the upper portion  31  of the guide  30  are simply stacked, the first seal  36  having been previously positioned inside the shoulder of this upper portion. The assembly is then immobilized by means of the flange  45  inside the cavity  6 .  
         [0045]     The guide according to the present invention is thus obtained without risking damaging the two seals, and while minimizing the machining costs.  
         [0046]     In the second embodiment of the guide  30  shown in  FIG. 4 , the upper portion  31  of the guide  30  is made of the same material as the flange  45 . This minimizes the number of constituent parts providing the guidance of the pushrod  15  because, during the assembly, the upper portion of the guide is fixedly attached to the flange  45 . As previously, the outer seal  37  is placed against the shoulder of the lower portion  32  of the guide  30  while the inner seal  36  is placed inside the shoulder supported by the retention flange  45 , the lower portion  32  then being nested into the flange  45 .  
         [0047]     In a third embodiment of the guide shown in  FIGS. 5 and 6 , the guide  30  consists of a single portion  50  of generally cylindrical shape. The retention flange  51  is much thicker than the flange  45  of the previous embodiments, so that the lower portion  50  of the guide  30  is entirely housed inside the retention flange  51 . The guide portion  50  is housed inside a bore  52  which has a diameter reduction in order to house the inner seal  36  between the diameter reduction of the bore  52  and the end of the guide portion  50 .  
         [0048]     In addition, in order to make it easier to machine the inner portions of the body  2 , this body  2  is formed of two superposed sections  55  and  56  that are in contact along a parting line  60 . The pushrod  15  is mounted movably inside the upper portion  56  while the major portion of the plunger  5  is mounted so as to oscillate inside the lower section  55 . The retention flange  51  is in the present case made of the same material as the upper portion  56  of the body  2 . The number of constituent parts necessary for the guidance is thereby further reduced.  
         [0049]     It goes without saying that the invention is not limited to the embodiments described hereinabove as nonlimiting examples; on the contrary, it embraces all the variant embodiments in the context of the following claims.