Abstract:
A multi-way valve has a housing with a stepped bore forming two piston guiding regions and a shoulder ring with two sealing shoulders. The housing also has a first, second and central transverse bores which are spaced along the cylindrical bore. A contact piston has a piston rod and sealing members secured thereon. The guide members are pressed fit onto opposite ends of the piston rod.

Description:
REFERENCE TO RELATED APPLICATION 
       [0001]    Applicants claim the priority of German Application, Serial No. 10 2006 011 578.3, filed Mar. 10, 2006. 
       TECHNICAL FIELD 
       [0002]    The field of this invention relates to a multi-way valve, more particularly a 3/2-way valve for controlling compressed air. 
       BACKGROUND OF THE DISCLOSURE 
       [0003]    An example of a directional multi-way valve is known from DE 200 23 376 U1. At its two axial ends, the piston rod is guided in guiding bores in the cover parts of the housing. This construction involves additional machining of the respective guiding bores in the cover parts, and also requires an accurate fit of the cover parts relative to the housing in order to ensure an aligned coaxial position of the guiding bores relative to one another and of the guiding bores relative to the continuous axial housing bore. 
         [0004]    What is needed is a directional multi-way valve which may be expeditiously constructed. 
       SUMMARY OF THE DISCLOSURE 
       [0005]    In accordance with one embodiment of the invention, a multi-way valve has a housing with a stepped bore which forms two piston guiding regions and a shoulder ring with two sealing shoulders. Three transverse bores are spaced along the cylindrical bore and intersect the cylindrical bore. A control piston has a piston rod and sealing members secured thereon; wherein, depending on its position, one sealing member each rests against one of the sealing shoulders for the purpose of sealing off a first outer transverse bore from a central transverse bore and wherein the other sealing member is disengaged from the associated sealing shoulder for fluid communication between the central transverse bore and the second outer transverse bore. The guiding members for guiding the control piston in the bore are pressed by means of a press fit onto the piston rod at both ends of the piston rod. 
         [0006]    It is thus possible with this embodiment to eliminate guiding bores in the cover parts without the need for additional machining operations in other areas. The guiding members can be provided in the form of plastic parts, so that mechanical machining processes do not have to take place on the components. In one embodiment, additional sealing members are mounted by way of a press fit on the piston rod and are directly supported on the shoulders of the piston rod. Alternatively, the guiding members can be produced directly as sealing members which sealingly rest against the sealing shoulders of the shoulder ring. 
         [0007]    In one embodiment, the bores have generally circular cross-sectional shapes and the shoulders are annular. According to a preferred embodiment, the guiding members are each indirectly axially supported on annular shoulders at the piston rod, more particularly via annular-disc-shaped sealing members which, in turn, are directly supported on the annular shoulders of the piston rod. 
         [0008]    In one embodiment, the control piston is provided in the form of a unilaterally acting control piston which operates against a helical pressure spring acting as a return spring. In this case, one of the guiding members is axially supported via helical pressure spring against a housing cover, whereas the other one of the guiding members is sealed by sealing members relative to its piston guiding range while forming a pressure chamber which is positioned opposite the helical pressure spring and which, by use of a pre-control valve, can optionally be loaded with control pressure or ventilated. The control pressure preferably corresponds to the operating pressure which is controlled by the multi-way valve. 
         [0009]    The guiding member preferably is made from plastic. The sealing members which accommodate the axial contact forces preferably are made from metal, so that sufficiently high axial forces can be transmitted via the respective press fits. The sealing members, on their sealing faces, carry preferably annular sealing elements which rest against the annular shoulders in the cylindrical bore. The guiding members and the sealing members can be sealed relative to one another on the piston rod by means of O-rings. The housing with the cylindrical bore and the transverse bores is preferably a light metal pressure die casting, more particularly an aluminum pressure die casting. The cover parts and adapter parts which are held in a largely force-free condition can be made from plastic. 
         [0010]    In accordance with another aspect of the invention, a multi-way valve has an outer annular collar in the region of the shoulder ring on the piston rod. The outer annular collar is positioned axially between the sealing members and which is slideably and sealingly arranged with respect to the shoulder ring. In one embodiment, the shoulder ring has an inner annular collar which, more particularly, is positioned axially between the sealing shoulders and which is slideably and sealingly arranged with respect to the piston rod. In one embodiment, a combination of the above characteristics is provided such that an inner annular collar in the region of the shoulder ring and, in the region of the inner annular collar, there is provided an outer annular collar on the piston rod which, in the operating region of the control piston, is slideably and sealingly arranged with respect to the annular collar. 
         [0011]    The purpose of these described constructions is to prevent the control slide from remaining in a central position between the transverse bores if, a pneumatic short-circuiting occurs as a result of a switching operation that is too slow which would cause a failure at the control of pressure at the central bore. Due to the pressure differential on both sides of the outer annular collar and a resulting additional axial force acting on the control slide, the pneumatic short-circuiting is prevented even if the spring force of the helical pressure spring is inadequate and/or if the pressure in the pressure chamber is inadequate, so that there is provided an increased operational safety in the case of control changes. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    A preferred embodiment of the invention is illustrated in the drawings and will be described below. 
           [0013]      FIG. 1  show an embodiment of a multi-way valve in a plan view from five sides and two isometric illustrations, i.e. 
           [0014]    a) in a first side view 
           [0015]    b) in a plan view 
           [0016]    c) in a second opposite side view 
           [0017]    d) in a first end view 
           [0018]    e) in a second opposite end view 
           [0019]    f) in a perspective view of the upper side 
           [0020]    g) in a perspective view of the underside. 
           [0021]      FIG. 2  shows a cross-sectional view of a multi-way valve along lines  2 A- 2 A shown in  FIG. 1   b    
           [0022]    a) in a first embodiment in an overall view 
           [0023]    b) in a fragmentary view of a second embodiment 
           [0024]      FIG. 3  shows the control piston of the multi-way valve according to  FIG. 2  in an enlarged illustration 
           [0025]    a) in a side elevational view of the longitudinal axis 
           [0026]    b) in a cross-section along line  3 B- 3 B as shown in  3 A 
           [0027]    c) in the enlarged fragmentary detail in area  3 C as shown in  FIG. 3   b    
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0028]    Referring now to  FIGS. 1(   a )- 1 ( g ), a 3/2-way valve  11  has a housing  12  made of a pressure die casting material as well as two parts  13 ,  14  made from a plastic material. A cover  13  closes the housing towards the outside whereas an adapter block  14  forms the connection with an electrically controllable pre-control valve  15 . The upper side is shown to comprise a transverse bore  16  for connecting to a work device (not shown). On the underside, there are two transverse bores  17 ,  18  of which the bore  17  is provided for a supply pressure connection and the bore  18  for a ventilation connection. The underside, furthermore, comprises a connecting bore  19  for an external connection for supplying the pre-control valve  15  via the adapter block  14 . The upper side is shown to comprise a transverse bore  20  for venting the exhaust air of the pre-control valve  15  via the adapter block  14 . The pre-control valve  15  is provided with connector contacts  21  intended for controlling purposes. The pre-control valve  15 , in turn, is a 3/2-way valve. 
         [0029]      FIG. 2  shows the housing  12 , the cover  13 , the adapter block  14  as well as the pre-control valve  15  with its connector contacts  21  along a longitudinal section. The cover  13  is sealed by seal  23  relative to the housing  12  and the adapter block  14  is sealed via seal  24 . The housing  12  is shown to comprise a longitudinally extending cylindrical bore  25  therethrough and which has a shoulder ring  26  with a reduced diameter. The above mentioned transverse bores  16 ,  17  and  18  arranged at axial distances relative to the longitudinal axis end in the cylindrical bore  25 . The cylindrical bore  25  is widened at both ends relative to the shoulder ring  26  in order to form guiding regions  27 ,  28 . In the cylindrical bore  25 , there is positioned a control piston  41  which, on a piston rod  42 , carries two sealing members  47 ,  48  which, as a function of the axial position of the piston, alternately come to rest against two sealing shoulders  29 ,  30  of the shoulder ring  26  at the ends of the guiding regions  27 ,  28 . In the position shown in  FIG. 2(   a ), the sealing member  47  rests against the sealing shoulder  29 , whereas the second sealing member  48  releases the sealing shoulder  30 . In this case, the transverse bore  17  to be connected to the supply pressure connection is disconnected from the transverse bore  16  supplying the work device, whereas the transverse bore  18  to be connected to the ventilation line is connected to the transverse bore  16  leading to the work device. The control piston  41  as illustrated is biased by a pressure spring  32  which moves the piston to the left when a cylindrical chamber  33  positioned on the opposite side to the left of the control piston  41  is not pressurized. 
         [0030]    If the cylindrical chamber  33  is pressurized, the control piston  41  is displaced towards the right and the helical pressure spring  32  is compressed until the control piston abuts the cover part  13  on its right hand side. In this position, the sealing member  48  seals the sealing face  30 , and the sealing face  29  is released by the sealing member  48 . In this position, which is not illustrated, the transverse bore  16  for connecting the work device is connected to the transverse bore  17  for the supply pressure connection, whereas the transverse bore  18  for the ventilation line is disconnected from the transverse bore  16  leading to the work device. 
         [0031]    Whereas in  FIG. 2   a  die piston rod  42  of the control piston  41  between two supporting shoulders  43 ,  44  for the sealing members  47 ,  48  is cylindrical with a constant outer diameter and whereas, equally, the inner diameter of the shoulder ring  26  between the sealing faces  29 ,  30  is constant, in  FIG. 2   b  the piston rod  42 ′, centrally between the supporting shoulders  43 ′,  44 ′ for the sealing members  47 ′,  48 ′, is provided with an outer annular collar  59  which is sealingly displaceable inside an inner annular collar  60  which reduces the inner diameter of the shoulder ring  26 ′. As the transverse bore  16  meets the annular collar  60 , the latter is provided only in the cross-sectional region outside the transverse bore  16  and can thus only be seen in the lower half of  FIG. 2   b . The annular collar  60  ensures that, if the switching process is too slow the control slide  41 ′ does not remain in a central position, due to pneumatic short-circuiting between the transverse bores  17 ,  18 , which would result in a failure of the control of the consumer. Due to the pressure differential on both sides of the outer annular collar  59  and, as a result, due to an additional axial force acting on the control slide  41 ; said pneumatic short circuit is prevented, even if the spring force of the helical pressure spring  31  is inadequate and/or if the pressure in the pressure chamber  33  is inadequate, which means that there is achieved an improvement in operational safety. 
         [0032]    The seal between the outer annular collar  59  and the inner annular collar  60  does not necessarily have to be of the sliding variety; a narrow gap dimension is sufficient. 
         [0033]    Reference is now made to  FIGS. 3   a ,  3   b  and  3   c  which show the control piston  41  according to  FIG. 2   a  in greater detail. The control piston  41  comprises a piston rod  42  which comprises two contact shoulders  43 ,  44  and two cylindrical seat portions  45 ,  46 . The diameter of the contact shoulders is dimensioned in such a way that the piston rod  42  can be passed through the shoulder ring  26  of the cylindrical bore  25  of the housing  12 . Annular disc shaped sealing members  47 ,  48  which, towards their insides, are provided with elastomeric sealing elements  49 ,  50 , have been slid from the outside on to the cylindrical seat regions  45 ,  46 . The sealing elements  49 ,  50  rest against the above mentioned sealing shoulders  29 ,  30 . The sealing members  47 ,  48  are held on the seat regions  45 ,  46  entirely by a press fit and, like the piston rod  42 , are made from metal. Two guiding members  51 ,  52  which are of different designs and which, in turn, are axially supported on the sealing members  47 ,  48  have also been slid by way of a press fit onto the seat regions  45 ,  46 . The guiding member  51  has a disc shaped seal-less guiding portion  53  and a hollow-cylindrical holding portion  31  for guiding the above mentioned helical pressure spring  32  which is not illustrated. The guiding member  52 , in the guiding portion  54 , comprises an annular groove  55  which accommodates a sealing ring  56  which closes the above mentioned cylindrical chamber  33  against the ventilation pressure of the housing. As can be seen in the enlarged detail of  FIG. 3C , O-ring seal  58  between the sealing member  48  and the guiding member  52  has been slid onto the seat portion  46  of the piston rod  42 . Similarly, O-ring seal  57  between the sealing member  47  and the guide member  57  has been slid onto the seat portion  45  of the piston rod  42 . 
         [0034]    Furthermore, the housing has the transverse bore  19  for externally supplying the pre-control valve  15  via the adapter block  14 , as well as the transverse bore  20  for ventilating the pre-control valve  15  via the adapter block  14 . It is also possible for the pre-control valve  15  to be supplied internally via the adapter block  14  with the operating pressure of the main valve. 
         [0035]    A feature of the invention pertains to the construction and the resulting assembly of the control piston  41  which, apart from the seals  57 ,  58 , includes of five functional parts which are mounted axially inside the housing  12  by way of a press fit prior to the cover part  13  and the adapter part  14  being bolted on to the housing  12 . The production and assembly of the inventive 3/2-way valve thus become less expensive. 
         [0036]    Whereas, when the control pressure for the pressure chamber  33  is interrupted, the illustrated embodiment assumes the illustrated position as a result of the effect of the helical pressure spring  32  and thus corresponds to the NC (normally closed) valve type in the case of which the work device is disconnected from the compressed air supply when the control pressure is interrupted. It is also possible to use a modified embodiment which, with the same positioning of the connections at the transverse bores  16 ,  17 ,  18 , by changing the sides of the control slide  41  and of the cover and adapter parts  13 ,  14 ,  15 , becomes a NO (normally open) valve type in the case of which, if the control pressure for a pressure chamber then positioned on the right is interrupted, the effect of the helical pressure spring then positioned on the left would cause the central bore to be permanently connected to the compressed air supply. Internal compressed air channels for supplying the pre-control valve in the housing  12  would not be affected hereby, whereas outer compressed air channels for supplying the pre-control valve would have to be adapted. 
         [0037]    Other variations and modifications are possible without departing from the scope and spirit of the present invention as defined by the appended claims.