Abstract:
The present invention relates to a pilot control valve, especially for use in mining hydraulics. The valve has a valve insert constructed as a valve cartridge, whose single or multipart valve housing has an input entry  17  for pressure fluid P, a connection opening  18  for a load connection A, an output opening  19,  opening into the return flow T and an axial boring  21  to accept a valve closing body  20  provided with a closing surface, which can be lifted from a valve sealing seat  31  arranged between the entry opening  17  and the connection opening  18  by means of an electro-magnetic or piezo-electric switching device which can be fastened onto the valve housing. With the lifting movement of the valve closing body  20  from the valve sealing seat  31  is coupled an at least two part closing mechanism for their separation arranged between the connection opening  18  and the output opening  19.  In accordance with the present invention a single part valve closing body  20  is provided, having the sealing surface in the form of a collar  28  and the moving part of the closing mechanism in the form of a shaft section  22,  whereby the shaft section  22  enters into a boring section  21 C of the axial boring  21  during the lifting movement, closing a radial opening  39.  The valve sealing seat  31  can be exchanged with a valve sleeve  130  and the nominal bore of the pilot control valve can be changed by means of a throttle  47.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a pilot control valve especially for use in mining hydraulics with a valve insert configured as a valve cartridge which can be arranged in the valve accepting boring of a valve block or similar forming a multi-way valve whose valve housing has an inlet for pressure fluid, a connecting opening for a load, an outlet opening into a return feed and an axial boring for the acceptance of a valve closing body provided with a sealing surface, which can be lifted by means of a switching device fixed to the valve housing, against the return force of a spring from a valve sealing seat arranged between the inlet opening and the connecting opening, whereby with the lifting movement of the valve closing body from the valve sealing seat an at least two part closing mechanism arranged between the connecting opening and the outlet opening is coupled for their separation. 
   Previously proposed pilot control valves are employed in underground mining for the switching of main control valves arranged after them with which then hydraulic working cylinders of advancing support frames or other hydraulic equipment can be actuated. Due to the high working pressure and the corrosion promoting underground atmosphere, severe requirements are placed upon valves employed underground in respect of their switching power, switching distance and construction. In mining hydraulics the switching devices in the main comprise electromagnetic actuators which are designed to be intrinsically safe and are connected to corresponding electrical circuits. Using intrinsically safe electro-magnetic switching devices, the switching power which can be applied and the switching distance which is available for actuation is limited. 
   A previously proposed pilot control valve is known from DE 92 11 629 U1. It has a three part valve closing body which comprises two valve closing elements with cone shaped sealing surfaces and a coupling rod, which are accepted axially parallel to each other and with cone surfaces facing each other in a housing part comprising two valve housing parts screwed together to form a cartridge in which they can move too and fro. Each housing part has a valve seat associated with one of the closing surfaces and the distance of the valve seats from each other can be adjusted by the setting of the screw connection between the valve casing parts so as to facilitate an initial and subsequent adjustment of the valve setting. So that dependent upon the valve switching setting in the this pilot control valve a fluid current can take place between the high pressure line and the load or from the load to the return, both the coupling rods and also the valve closing elements are provided on their cylindrical outer surfaces with axially running flats or grooves, which at the same time limit and determine the cross section of flow and consequently the nominal bore of the pilot control valve. The manufacturing effort for the valve sealing elements comprising the valve sealing body and the coupling rod is therefore comparatively high and the functional integrity of this pilot control valve is dependent upon the precise adjustment of the separation of the two valve sealing seats. 
   It is an aim of the invention to produce a pilot control valve which has short switching paths, is simply constructed and has a simply produced valve sealing body in production engineering terms. 
   SUMMARY OF THE INVENTION 
   Accordingly the present invention is directed to a pilot control valve as described in the opening paragraph of the present specification wherein a single part valve closing body has the closing surface and the moving part of the closing mechanism, whereby the moving part comprises a shaft section of the valve closing body which plunges with the lifting movement into a boring section of the axial boring, closing a radial opening. In the pilot control valve according to the invention consequently only the valve seal between the pressure line and the user is made with a completely sealing valve sealing seat and associated closing surface, the valve sealing between the load connection and the return line works in accordance with a different principle and comprises a gap sealing, which from a determined point in the switching separates the connection between the load connector and the return line and requires no adjustment. The use of two different switching and sealing principles not only makes possible the omission of adjustment or re-adjustment, but at the same time simplifies the production engineering effort for the valve closing body, since this can be manufactured from one piece without the expensive matching and coupling surfaces as in a multiple part valve closing body. Owing to the single part valve closing body made as a valve pusher, the switching path and consequently the necessary valve lift is extremely short. 
   In a preferred embodiment the valve closing body has a ring-shaped collar whose rear side facing the valve sealing seat forms the closing surface or the support surface for a sealing body. The ring-shaped collar is simply manufactured and makes for a further simplification of construction of the valve closing body since expensive cone shaped closing surfaces on the valve closing body can be dispensed with. The preferably flat rear side of the ring shaped collar can hereby itself form the closing surface abutting the valve sealing seat or serve as a supporting surface for a sealing body, which can possibly b e exchanged in the event of wear. In order to increase the sealing function of the closing surface and to reduce the liability to wear, the collar can be equipped with an additional seating material on its rear side. The ring shaped collar which is impacted in the closed position of the pilot control valve with the pressure from the pressure line effects an automatic closing of the pilot control valve itself when the return spring fails or the actuator of the switching device blocks the free movement of the valve closing body. 
   Preferably the shaft section, i.e. the moveable part of the closing mechanism, forms one end of the valve closing body and a pin section forms the other end of the valve closing body whereby the pin and the shaft sections have the same diameter and form the guide surfaces of the valve closing body in the boring sections of the axial boring. Both can be provided with a sealing ring groove for the acceptance of an O-ring or a sliding ring. The measures quoted have the advantage that the valve closing body is guided by the shaft and the pin section in the axial boring of the valve housing and owing to the mutually matched diameters a pressure equalised opening position of the valve closing body can be achieved with the collar lifted from the sealing seat. 
   Advantageously the valve closing body has a diameter reducing cut-out with a conical transition section to the shaft section and/or collar between the collar and the shaft section forming the moving part of the closing mechanism. In a preferred embodiment the valve sealing seat is a component an exchangeable valve sleeve which can be inserted, especially pressed, into blind boring extensions of the axial boring. By means of the exchangeable valve sleeves not only is maintenance of the pilot control valve eased but the possibility exists with an otherwise unchanged construction of pilot control valve of matching the material of the valve sealing seat and/or the geometry of the valve sealing seat to the specific application profile of the pilot control valve. Preferably the internal diameter of the valve sleeve at the valve sealing seat is essentially the same diameter as the shaft and the pin sections and forms the inner side of the valve sleeve sections of the axial boring. 
   The arrangement of the exchangeable valve sealing seat depends on the construction of the valve case. In a prefered embodiment the valve case comprises a single case part with a stepped blind hole extension, in which a valve sleeve is inserted the sleeve end of which inserted into the blind hole forms the valve sealing seat with its inside and has the radial opening between two boring sections at a distance from the valve sealing seat, whereby preferably the radial opening opens into a circulating groove on the inner side of the valve sleeve. In a single part valve housing, adjustment of the valve setting is not possible since the distance established between the valve sealing seat and the radial opening by the construction of the valve sleeve determines the switching path the pilot control valve. At the same time however the risk of assembly errors is reduced to a minimum since the exact setting of the switching path is established exclusively by the matching between the switching pin of the switching device, the valve sleeve encompassing the valve sealing seat and the valve closing body inserted and guided therein. The groove on the inner side of the valve sleeve can in a modification of the valve sleeve embodiment also be constructed in that the valve sleeve is made stepped on the inside and the circulating grove is formed by means of an, especially screwed in, valve sleeve insert in the steps of the valve sleeve which is made shorter than the depth of the step, so that between the end of the valve sleeve insert and the bottom of the step a groove is formed. 
   In an alternative embodiment the valve case can comprise a first case part and a second case part joined to it, especially screwed, which is provided with a stepped bind hole extension, in which from the separation plane between the first and second parts a valve sleeve is inserted, whose free end forms the valve sealing seat and between its other end and the stepped section of the blind hole extension, forms the radial opening by means of gap openings at the sleeve end or the extension of the length of the valve sleeve between the abutment surface of a ring shoulder of the sleeve and the base of the sleeve is shorter than the stepped blind hole extension so as to form an annular gap as the radial opening via the shorter sleeve length. With a two-part construction of the valve casing the valve adjustment has a matching chain with four contact positions, whereby as opposed to the form of construction with a single part valve part, the first separation plane forms the additional fourth contact position. 
   In a third alternative embodiment the valve case comprises a first, a second and a third part of the case with a first separation plane between the first and second and a second separation plane between the second and third case parts, whereby the second case part is provided with a stepped blind hole extension, into which a free sleeve end of a valve sleeve forming a valve sealing seat at its free sleeve end is inserted. In this configuration it is especially favourable if the radial opening is formed from an intermediate gap at the second separation plane. In contrast to the form of construction with a single part or two-part valve case in the three part valve case the radial opening is not a component of the valve sealing seat, but it is for instance generated as an intermediate space or annual gap by the separation plane between two parts of the case. It is further expedient in all the forms of construction to provide at least one decentral through boring for driving out the valve sleeve. It is understood that this can be closed by means of a blanking plug, a grub screw or similar. 
   The application possibilities and the range of use of the pilot control valve according to the invention can be further increased as opposed to the known pilot control valves if a flow resistance for the fluid is connected in series with the valve sealing seat and the closing mechanism, since then with a single form of construction of the pilot control valve its effective nominal bore can be changed. In contrast to the known pilot control valves in accordance with the invention the seating geometry of the valve sealing seat between the pressure line and the load is not carried out differently to change the nominal bore but the effective nominal bore is controlled by the selection of the flow resistance. A flow resistance can be especially simply produced using a throttle or a shutter whereby preferably a single throttle or shutter is allocated to the load connector so that this one flow resistance is effective both in the feed flow from the pressure line to the load and also in the return flow from the load into the return line. It is also possible however to arrange a separate throttle or shutter for each connection or only one or two connections are provided with a flow resistor. In the preferred embodiment the throttle or shutter is inserted at a distance from the valve closing body in a cover boring or similar in the valve case which forms the load connection. By this arrangement there results a reduction of the flow forces acting upon the valve closing body. 
   As the switching device preferably an electro-magnetic or piezo-electric actuator is applied as is described in DE 101 34 947, the two which express reference is made, whereby preferably the valve insert is retained in the valve accepting boring by means of the switching device. With the fastening of the switching device to the valve block the valve insert is then immediately accommodated axial and secured in the valve accepting boring. In a multipart valve case the boring sections of the axial boring forming the guide and bearing sections for the shaft and the pin sections can be provided in each outer case part with an accepting groove for a sealing ring on the case side. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Example of pilot control valves made in accordance with the present invention will now be explained with reference to the accompanying drawings, in which; 
       FIG. 1  shows a cross-sectional view of a pilot control valve in accordance with a first embodiment, inserted into a valve block and held in position in the valve accepting boring by the housing of the switching device; 
       FIG. 2  shows a cross-sectional view of a pilot control valve in accordance with the first embodiment with a changed arrangement of seals for the valve closing body; 
       FIG. 3  shows a cross-sectional view of a pilot control valve in accordance with a second embodiment with a two part valve case; 
       FIG. 4A  shows a detailed sectional view of the valve sleeve for the pilot valve shown in  FIG. 3 ; 
       FIG. 4B  shows a view of the left hand sleeve end shown in  FIG. 4A ; 
       FIG. 5A  shows a sectional view of an alternative embodiment of a valve sleeve for use with the pilot control valve made in accordance with the second embodiment; 
       FIG. 5B  shows a view of the left hand sleeve end of the valve sleeve according to  FIG. 5A ; 
       FIG. 6  shows a cross-sectional view of a pilot control valve according to a third embodiment with a single part valve case; and 
       FIG. 7  shows a cross-sectional view of an alternative embodiment for a pilot control valve with a single part valve case. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a vertical section through a valve accepting boring  1  of a valve block  2  possibly having several adjacent and superimposed valve-accepting borings. The valve accepting boring  1  is made as a blind hole into which a pilot control valve  10  made as a cartridge shaped valve insert according to a first embodiment is pushed in from the end  3  of the valve block  2 . The valve insert forming the pilot control valve  10  has a three part valve case with a first valve case part  11 , a second valve case part  12  and a third valve case part  13  which are screwed together individually at their separation planes  38  and  41  and are held together in the valve acceptance boring  1  by means of the case  4  of the switching device  5  indicated only schematically. The case end  4 ′ of the switching device  5  sits in a depression  6  on the end  3  and overlaps the cartridge of the pilot control valve  10  with a fastening flange and is screwed into the walls of the valve block  2  by means of fastening screws  7 . The switching device  5  has a switching pin  8 , which can be impacted electro magnetically or piezo electrically with a switching force F in the direction of the arrow so as to change the closing position of the pilot control valve  10 . The central axis M of the cylindrical switching pin  8  is aligned with the central axis Z of the valve insert  10  and the accepting boring  1  and the free end of the switching pin  8  presses against the end surface  15  of a valve closing body  20  comprising a single piece, which is pre-tensioned against the switching force F by means of a return spring  14 . In the embodiment according to  FIG. 1  the valve closing body  20  sits in a moveable manner in an axial boring  21 , which is formed individually from a boring section  21 A,  21 B,  21 C in the case parts  11 ,  12 ,  13 , whereby all the boring sections  21 A,  21 B,  21 C have the same diameter D as each other. The axial guidance and bearing of the one part valve closing body  20  made as a pusher is effected by means of a shaft section  22  forming the left hand end of the valve closing body  20  with a constant diameter D and a pin section  23  forming its right hand end similarly with the diameter D, which are guided with small play in the boring section  21 A,  21 B or the axial boring  21  in the first case part  11  and the third case part  13 . The end of the switching pin  8  works on the end  15  of the shaft section  22  and on the return spring  14  presses against the end of the pin section  23  via the pressure plate  16 . Both the shaft section  22  and also the pin section  23  have a circumferential groove  24 ,  25  for the acceptance of a sealing ring  26 ,  27  so as to seal the centre boring section  21 C or the actual boring  21  against the outside of the valve case. 
   The pilot control valves shown in the FIGS. are all configured as 3/2 multi way valves and facilitate a connection or separation between the high pressure line P and the load connection A or between this and the return line T. In order to be able to perform the valve function, the first case part  11  has an inlet opening  17 , which opens into the pressure line P. The second case part  12  has a connecting opening  18  which opens into the load connection A in the valve block  2 , and an outlet opening  19 , which leads to the return T in the valve block  2 . The embodiments all show the output or rest position of the valve in which the switching pin  8  is not impacted with the force F and consequently the connection between the entry opening  17  and the connector opening  18  is separated. To achieve the fluid separation the valve closing body  20  is provided a circulating collar  28  as a single part on the pin section  23  and extending radially outwards from this, which abuts against the closing edge of a valve-sealing seat  31 . The closed position of the rear side  28 ′ of the collar  28  with the closing edge of the sealing seat  31  is provided by on the one hand the return force exerted by the return spring  14  and on the other hand by the closing pressure exerted by the pressure of the pressure fluid in the pressure line P on the ring surface  29  of the collar  28 . The shaft of the closing body  21  has a cut out  29  between the rear side  28 ′ or the collar  28  and the shaft section  22 , which for instance can result in a constant reduction of the shaft diameter to the diameter D′. The transitional section  35  to the shaft section  22  and the transitional section  36  to the collar  28  rises conically in each case. In the shown valve position of the closing body  20  the connection opening  18  is joined with the exit opening  19  via the cut out  29  and the freely cut surface of the transitional section  35 . The output opening  19  hereby does not reach up to the associated section of the axial boring  21  in the case section  12  but is open via a cross boring  37  to the separation plane  41  between the second case part  12  and the third case part  13 . Both case parts  12 ,  13  are screwed together in such a manner that at the separation plane  41  a gap  39  is formed out to the height of the cross boring  37 , which in the pilot control valve  10  comprises the static part of a closing mechanism for fluid separation of the connection opening  18  from the exit opening  19 . The second moveable part of the closing mechanism comprises the shaft section  22  since its cylindrical outer side plunges into the section  21 C of the axial boring  21  when the valve closing body  20  is moved to the right, as seen in the FIG., and then seals the access to the gap  39 . The transition edge  40  between the shaft section  22  and the transition section  35  forms a sharp edged control edge for the closing mechanism, which seals the free passage between the connection opening  18  and the outward opening  19  as soon as it is at least at the same position as the end of the second case part  12 . The shaft section  22  plunging into the boring section  21 C in the case part  12  functions as a gap seal with little flow and pressure loss of fluid from the pressure line P, which can overflow due to the movement of the valve closing body  21  in the direction of the arrow F and of the collar  28  being lifted from the valve sealing seat  31  to the connecting opening A. Since both the shaft section  22  as the moveable part of the second closing mechanism and also the collar  28  as the moveable part of the first closing principle formed as a valve seat are formed as one part with the valve closing body  20  the actuating movement of both closing principles are coupled together by force. 
   For reasons of clarity the further description of the pilot control valve according to the first embodiment is now, continued with reference to  FIG. 2 , in which similarly a pilot control valve  10 ′ with three case parts  11 ,  12 ,  13  is shown. The only difference between the pilot control valve  10  is FIG.  1  and the pilot control valve  10 ′ in  FIG. 2  comprises the arrangement of the seals for the shaft section  22  and the shaft section  23  which in the embodiment according to  FIG. 2  are each attached on the housing side. The boring section  21 A in the first case part  11  and the boring section  21 B in the third case part  13  which form the axial guide for the shaft section  22  and the pin section  23  of the valve closing body  20 , are correspondingly provided with accepting grooves  24 ′,  25 ′ into which individually a sealing ring  26 ′,  27 ′ sits. The valve-sealing seat  31  is integrated into an exchangeable valve sleeve  30  which is pressed into a blind hole  42  in the second case part  12  extending from the first separation plane  38  between the first case part  11  and the second case part  12  and sealed in place by means of a sealing ring  43 . The sealing seat  31  is here formed from the free sleeve end  33  of the valve sleeve  30  at the separation plane  38  extending into a ring shaped front space  44  of the valve. The front space  44  comprises a blind hole formed in the first case part  11  and forms the only local extension of the axial boring  21 . The entry opening  17  opens into the front space  44 , so that the through flow of fluid from the pressure line P is assured. The front space  44  also forms the free space for the movement of the collar  28  of the valve closing body  20  whereby the fluid at the collar  28  can freely flow passed the rear side  28 ′ of the collar  28 . The valve sleeve  30  is provided with a ring shoulder  32  extending out over the side walls of the blind hole  42 , which extend radially out to the position of a decentral blind boring  46 , via which the valve sleeve  30  can be driven out from the blind hole  42  when the case parts  11 ,  12  and  13  are disassembled. In the assembled condition the blind boring  46  is closed by means of a blanking plug  45  or a grub screw. The geometry of the sealing seat  31  and the material of the valve sleeve  30  can be varied depending on the pressure to be switched with the pilot control valve and in the embodiments shown the valve-sealing seat  31  on the valve sleeve  30  is made in the form of a cone. When the collar is lifted from the valve sealing seat  31  the fluid flows out of the pressure line P via the entry opening  17  into the advanced area  44 , there passed the collar  28  into the annual space formed by the cut out  29  up to the transitional edge  40  to the shaft section  22  and then via the connecting opening  18  which opens into the boring section  21 C to the load A (not shown). The closing mechanism between the opening connector  18  and the exit opening  19  separate these owing to the shaft section  22  of the closing body  20  which seals the radial opening  39 . 
   A further special feature of the pilot control valves  10  and  10 ′ in  FIGS. 1 and 2  is a throttle  47 , which is inserted or screwed in or directly set into the case  12  in a radial cover boring  18 ′ which has a larger cross section than the connecting opening  18  and forms with this the feed to the load connector A. The throttle  47  forms a stream resistance when flowed through by the fluid both from the open valve sealing seat  31 ,  28  and also from the opened closing mechanism  39 ,  22 . If the throttle  47  has a through flow opening which is smaller than the through flow gap on the valve sealing seat  31 ,  28  or at the closing mechanism  39 ,  22 , it is possible to determine the effective nominal bore of the pilot control valve  10  or  10 ′ by means of the opening cross section of the throttle  47 . By exchanging the throttle  47  for a throttle with a different cross sectional opening the effective nominal bore of the pilot control valve can consequently be varied with otherwise identical construction whereby the distance of the throttle  47  owing to the cover arrangement in the second case part  12  essentially influences the flow in the valve less than would be the case for a changing of the cross section of flow at the valve sealing seat or at the closing mechanism. 
     FIG. 3  shows an embodiment of a pilot control valve  110  according to a second embodiment. The same components are provided with reference numbers raised by  100 . The pilot control valve  110  has a two-part valve case with a first valve case part  111  and a second valve case part  112 . The construction of the valve closing body  120  with collar  128 , transition edge  140  and shaft section  122  is identical as in the first embodiment. Between the first case part and the second case part  112  a single plane of separation  13 B is formed, whereby the two case parts  111 ,  112  are screwed together using threaded sections not shown, on the cover collar  150  of the first case part and on a pin extension  151  of the second case part  112 . A sealing of the shaft section  122  and the pin section  123  can, as in the embodiment according to  FIG. 1 , be effected using sealing rings  126 ,  127  which are fastened to the valve closing body  120  or by sealing rings which are set into the boring sections  121 A and  121 B in the case parts  111 ,  112 . In contrast to the first embodiment in the embodiment according to  FIG. 3 , both the sealing seat  131  and also the fixed part of the closing mechanism formed from the radial opening  139  are integrated into a valve sleeve  130 , which is shown in detail in  FIGS. 4A and 4B , which are now referred to. The valve sealing seat  131  is formed at the free sleeve end  133  whilst the valve sleeve end  134  extending into the base of the blind hole boring  142  in the second case part  112  ( FIG. 3 ) has several radial cut outs  155  distributed around its circumference, which are interrupted by axial corner extensions  156 . With the valve closing body  120  not activated and consequently not moved as shown in  FIG. 3 , fluid from the annular space  129  formed between the reduced diameter closing body shaft  120 ′ of the valve closing body  120  and the surrounding wall of the axial boring  121  can flow into the exit opening  119  to the return flow T, since the transitional edge  140  is moved towards and to the left of the radial opening  139 . The valve-sealing seat  131  is hereby closed by the collar  128 . The sealing seat of the sleeve  130  in the blind hole boring  142  is effected by means of two sealing rings  157 ,  158  (FIG.  3 ), which sit in the sealing ring grooves  161 ,  162  (FIG.  4 A), which are formed on either side of a connecting boring  160  to the load connection  118 . The connecting boring  160  opens into an annular groove  163  on the valve sleeve, so that the connection of the connecting boring  160  to the connecting opening  118  is assured independently of the position of the valve sleeve  130  in the blind hole boring  142 . For the exchange of the valve sleeve  130  pressing into the blind hole boring  142  a decentral blind boring  146  ( FIG. 3 ) is provided which is closed with a blanking plug  145 . 
     FIGS. 5A and 5B  show an alternative embodiment for the valve sleeve  130 ′, which can be inserted in the second case part  112  of a two part valve case shown in FIG.  3 . The valve sleeve  130 ′ is distinguished from the valve sleeve  130  in its extended length between the abutment flange  132 ′ of the ring shoulder  132  and the sleeve base  134 ′ and/or the configuration of the sleeve base  134 ′, which here is formed as a flat surface so that over the shorter length of the valve sleeve  130 ′ relative to the extended length of the stepped blind hole boring  142  between the base of the blind hole boring  142  and the base  134 ′ of the sleeve  130 ′ an annular gap arises which is connected to the outlet opening  119 . The final edge of the valve sleeve  130 ′ on the inner circumference  121 C′ of the valve sleeve  130 ′ marks the control edge of the closing mechanism in the valve sleeve  130 ′ working together with the transitional edge  140  and the shaft section  122  of the valve closing body  120 . The partial section  121 C of the axial boring  121  is formed from the inner circumference of the valve sleeve  130 ,  130 ′ by the use of the valve sleeves  130 ,  130 ′ and a two-part valve case. Since the valve sleeves  130 ,  130 ′ have both the sealing seat  131  and also the fixed part of the second closing mechanism, if wear occurs the sealing function of both major seals of the pilot control valve can again be established by the exchange of a component. 
     FIG. 6  shows an embodiment of a pilot control valve  210  with a single case part  211  forming the cartridge. Here also the valve closing body  220  has an identical construction as in the embodiments in  FIGS. 1 , to  3  so that a description of the valve closing body  220  is not necessary. The valve sealing seat  231  which works together with the collar  228  on the valve closing body  220  from the end face  270  in the pre-space  244  is a component of a valve sleeve  230  which is pushed into a blind stepped boring  242  in the case part  211 , which in the assembled condition abuts the case of the switching device and extends out from the valve accepting boring. The radial opening  239 , which forms the static part of the second closing mechanism, comprises here a radial boring in the cover  280  of the valve sleeve  230  and a circulating groove  281  formed on the inner circumference  221 C of the valve sleeve  230  and aligned with the radial opening  239 . The blind hole boring  242  in the single case part  211  has correspondingly at the same height as the radial boring  239  and the circulating groove  281  a ring groove  282 , which is in connection with the exit opening  219  to the return flow T. For the flow to the user connection A the valve sleeve  230  has at the height of the connection opening  118  a radial boring  260  and a ring groove  263 . Here also as in the previous embodiments a throttle  247  can be inserted in the connecting opening  118  so as to be able to change the effective bore of the pilot control valve. The embodiment shown in  FIG. 6  differs further from the previous embodiments in that the shaft section  222  is guided not in a section of the axial boring within a case part but in the boring section  221 B on the inner surface of the valve sleeve  230 . For this embodiment it therefore offers the advantages of integration of the seals  226 ,  227  in the valve pusher  220 . The boring sections  221 C and  221 B end individually at the radial opening  239  or the groove  281 . Because of the single part valve case  211  assembly errors can hardly arise in the pilot control valve cartridge  210 , which is put together, from very few parts.  FIG. 7  shows an alternative embodiment  210 ′ for a pilot control valve with assembled part valve case part  211 . In contrast to the embodiment in  FIG. 6 , in which a circulating groove  281  on the inner circumference of the valve sleeve  230  has to be turned out, the valve sleeve  230 ′ has a stepped extension  290  in which a valve sleeve insert  291  is screwed or pressed in so as to form the circulating groove  281 ′ between the end  292  of the valve sleeve insert  291  and the base  293 , which again is connected with the outlet opening  219  and the return flow T via the radial boring  239 ′. The boring section  221 E of the axial boring  221  is here consequently formed from the inner side of the sleeve insert  291  and the shaft section  222  is guided on this boring section  221 E. The blind boring for driving out the valve insert  230 ,  230 ′ is not shown. 
   From the foregoing description a range of modifications present themselves to a man skilled in the art, which fall within the range of protection of the attached claims. A throttle blind screwed into the connecting opening of the load connector forms the preferred embodiment for changing the effective nominal cross section of the pilot control valve according to the invention. Alternatively instead of one throttle there also can be one throttle in the inlet opening and the outlet opening or any desired combination of flow resisters can be provided. Instead of a throttle a blind or similar could be used. Further the number and the arrangement of the sealing rings between the individual components and the number of the blind borings can be varied within limits whereby such and other modifications fall in the area of the protection of the claims, insofar as with a single valve closing body, two different closing mechanisms for the multi way valve are realised. Further, the valve according to the present invention cannot only be applied as a pilot control valve but also as a main control valve for low pressures of the fluid to be controlled or switched.