Abstract:
A housing cover for a solenoid housing operable for accommodating solenoids for switching hydraulic directional valves is disclosed. A housing cover box has a plurality of side walls, a top side, and an open bottom side, with first and second actuating guides for guiding first and second solenoid control push rods being located on the top side. A plug connector is located between the actuating guides. At least one screw clearance hole is located at each corner of the housing cover box for locating a screw for joining the housing cover box to the solenoid housing. A sealing plate is located between the housing cover box and the solenoid housing, and at least one mounting foot is located at a corner and on a bottom surface of the housing cover box. A tubular spigot is aligned with and extends each screw clearance hole.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority from German patent application No. 20 2005 016 473.9, filed on Oct. 19, 2005. 
   BACKGROUND OF THE INVENTION 
   The invention relates to a housing cover for a switching solenoid housing, which accommodates solenoids for switching electrohydraulic valves, in particular as used in underground mining, with a housing cover box, which is open at a bottom side and is made from a plastic injection molded part with closed sidewalls and a top side that is integrally connected to these, in the interior of which a printed circuit board can be or is arranged, with two actuating guides on the top side for a manual operation of solenoid control push rods, with a plug connector arranged centrally between the two actuating guides, and with screw clearance holes in the corners of the housing cover box for fixing screws for joining the housing cover to the switching solenoid housing while interposing a sealing plate. 
   A double multi-way solenoid valve intended for use in underground mining with a switching solenoid housing with two solenoids arranged in the housing and a housing cover that can be releasably fixed to the switching solenoid housing while interposing a sealing plate is known from DE 196 46 611C1 and has been successfully marketed by the applicant for years. The housing cover used with the switching solenoid housing constitutes a special fabrication for the double 3/2-way solenoid pilot valves that are overridingly used in underground mining. Particularly when using a solenoid valve fitted with a releasable housing cover in underground mining, the environmental influences such as moisture, fine carbon dust etc. must be reliably prevented from entering the interior of the switching solenoid housing or the housing cover, as this could lead to malfunctions. 
   DE 201 04 677 discloses the assignment to the solenoid control push rod of an adjustment disk, which is arranged in the switching solenoid housing underneath the sealing plate and enables the solenoid switching stroke to be adjusted. For the purposes of adjusting the control push rod switching stroke, the control push rod is connected to an armature arranged within the windings by means of a screw connection, the adjustment of which enables the relative position between control push rod and armature, and therefore the switching stroke, to be changed. 
   BRIEF SUMMARY OF THE INVENTION 
   The object of the invention is to create a housing cover, which is easy to manufacture, which enables reliable sealing of the separating joint with the switching solenoid housing, and which, furthermore, by design can be easily fitted with different sockets or plug connectors. 
   According to the invention, this and other problems are solved in that the bottom side is provided in the corners with mounting feet formed integrally on the housing cover box, which are each provided with a tubular spigot, which extends the screw clearance hole, and between which are arranged set-back boundary edges of the sidewalls, which form clamping edges for the sealing plate. With the housing cover according to the invention, the tubular spigots located before the mounting feet cause the housing cover to be centered and accurately positioned on the switching solenoid housing before the fixing screws are tightened. At the same time, the mounting feet and the set-back boundary edges of the sidewalls enable the sealing plate to be accurately fitted and in no case be compressed too strongly in one edge zone, as the size of the set-back section of the boundary edges relative to the bottomsides of the mounting feet produces a minimum gap in each case, which remains as a free space for the interposing of the sealing plate even at maximum tightening torque of the fixing screws. 
   According to a preferred embodiment, the sealing effect of the sealing plate can be increased in that the boundary edges, which are set back compared with the mounting feet and which form the bottomside of the housing cover box in the area of the sidewalls, are provided with a peripheral sealing rib, which effects an additional compression of the sealing plate at the peripheral edge and, at the same time, serves as an additional barrier against a penetration of moisture. Here, the height of the sealing rib is preferably chosen to be somewhat less than the thickness of the mounting feet in order to prevent excessive compressions of the sealing plate at its edge. 
   According to a particularly preferred embodiment, a double-walled mounting with an annular gap for anchoring an anchoring section of a threaded bush is cast onto the top side, wherein more preferably a ring-shaped collar is connected to the rear of the mounting base of the mounting. This embodiment has the further advantages that different threaded bushes can be anchored to the housing cover for different connecting threads of connecting plugs or the like, and also that, at the same time, the ring-shaped collar enables an appropriate plug section to press against the printed circuit board at the rear and thus inside the housing cover with a suitable seal, such as for example a sealing ring sealing against the inner circumference of the ring-shaped collar. Different threaded bushes and/or different plug sections on the printed circuit board can then be fixed to a switching solenoid housing with one and the same housing cover enabling a standard housing cover to be fitted with almost all plug systems available on the market for underground mining. The threaded bush can be glued in the annular gap or anchored in another way. In a preferred embodiment, the anchoring section of the threaded bush is already cast into the top side when the housing cover is injection molded. The anchoring of the anchoring section of a threaded bush in an annular gap of a mounting, which is preferably double-walled and designed in the form of a depression, is of independent inventive significance. 
   According to a further advantageous embodiment, likewise of independent inventive significance, an adjustment disk for adjusting a control push rod switching stroke, which is accessible from the top side, consequently from the outside and thus when the housing cover is fitted, is arranged in or by each control push rod actuating guide. It is particularly advantageous if, for each adjustment disk, at least one projection, which engages in a locking recess in the adjustment disk, is formed on the top side, which enables the set adjustment of the control push rod switching stroke to be fixed. In order to then securely anchor the adjustment disk in the selected adjustment, it is particularly advantageous if the projection is initially longer than the thickness of the adjustment disk. This enables a positive and/or bonded fixing of the adjustment disk to be achieved by reshaping the projection with the action of heat, for example with a soldering iron or similar, after adjusting the control push rod switching stroke. 
   More preferably, each control push rod actuating guide can have a ring-shaped extension on the top side with a peripheral indentation for fixing an elastic hood. By means of the elastic hood, each solenoid can also be operated manually in emergency situations. At the same time, the elastic hoods can be easily anchored or released by positively engaging with the indentation from behind without additional measures or additional fixing means being required for this. More preferably, a tapped hole for a locking screw for the adjustment disk can be formed in the bottom of each control push rod actuating guide within the ring-shaped extension. The locking screw need only be used if readjustment after a repair or the like was necessary and all the projections previously melted by the effect of heat have become unusable. The tapped holes, which are formed right at the injection molding process stage, can of course also be used if no projections are provided. 
   It is more advantageous if both control push rod actuating guides are provided with cast-on tubular pieces extending from the top side to the bottom side, which each form sealed casings for the control push rods. The abovementioned tapped holes can then advantageously be cast in the sides of the tubular pieces at the same time. The tubular pieces, which form a casing for the control push rods, enable the interior of the housing cover to be filled with potting compound in order to form an additional seal and encapsulation of the printed circuit board. In order to be able to carry out the potting, it is particularly advantageous if the top side is provided with filling openings for potting compound. When at least two filling openings are provided, one of the openings can be used for pouring in the potting compound and the other as a ventilation opening. 
   In underground mining, it is desirable that the switching state of each solenoid be indicated directly at the solenoid. In order to simplify the indication, it is more advantageous if at least one fiber-optic rod is cast on in the top side, one end of which passes through and is anchored in the top side, and the other end of which extends down to the position of the printed circuit board. As two solenoids are usually arranged in the switching solenoid housing, it is particularly expedient if two fiber-optic rods, which work together with LEDs on the printed circuit board, are cast in in order to be able to indicate the switching state of the two solenoids independently from one another. The fiber-optic rods have the particular advantage that even filling the interior with potting compound does not prevent the switching state from being indicated, as the length of the fiber-optic rods and the positioning of the LEDs on the printed circuit board can be exactly matched to one another so that it can be ensured that the indication of the LEDs is guided into the fiber-optic rods before the potting compound is poured in. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     Further advantages and embodiments of a multi-way solenoid valve with housing cover according to the invention can be seen from the following description of an exemplary embodiment shown schematically in the drawing. In the drawing: 
       FIG. 1  shows a switching solenoid housing with fitted housing cover in perspective; 
       FIG. 2  shows a housing cover according to the invention in side view; 
       FIG. 3  shows a plan view on the housing cover of  FIG. 2 ; 
       FIG. 4  shows a sectional view along IV-IV in  FIG. 3 ; 
       FIG. 5  shows the fixing and centering of the housing cover on the switching solenoid housing in sectional view through one corner; 
       FIG. 6  shows a vertical section through housing cover and solenoid housing in the area of one solenoid; 
       FIG. 7  shows a detailed view of the control push rod actuating guide in the top side of the housing cover box; and 
       FIG. 8  shows a locked adjustment disk in plan view on the control push rod actuating guide with the hood removed. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A double 3/2-way solenoid pilot valve is shown in  FIG. 1  with the overall reference  1 , which comprises a switching solenoid housing  2 , accommodating the solenoid inserts and the pilot valve inserts for hydraulic directional valves that can in particular be used in underground mining, and a housing cover  10  that is releasable and screwed in a fixed manner to the end face of the switching solenoid housing  2 . Here, two solenoids with two pilot valve inserts are arranged in the solenoid housing  2  of the valve  1 , from which the term double multi-way solenoid pilot valve is derived. The construction of the housing cover  10  is explained below with reference also to  FIGS. 2 to 8 . 
   The housing cover  10  consists of an injection molded part made from a suitable plastic with sidewalls  11  at right angles to one another and a top side  12  integrally connected to these. The housing cover  10 , which is designed as a housing cover box, is only open at the bottom side  13 . The releasable screw fixing of the housing cover  10  to the switching solenoid housing  2  is achieved by means of four fixing screws  3  arranged in its four corners  14  and with their heads lying in depressions  15  in the top side  12 . The screw shaft of each fixing screw  3  passes through in each case one hollow screw clearance hole  16  arranged in the relatively solidly constructed corner  14 . On the bottom side  13 , cast on in each corner  14  of the housing cover  10 , is a mounting foot  17  with an essentially square base area, to which is connected a likewise cast-on tubular spigot  18  as an extension of each screw clearance hole  16 . The mounting feet  17  with the square base area and cross section have the effect that a set-back boundary edge  19  on each sidewall  11  is formed between two mounting feet  17 . 
   In the assembled state of the housing cover  10  on the switching solenoid housing  2 , as  FIGS. 4 to 6  particularly show, a sealing plate  4  can then be arranged between the housing cover  10  and the switching solenoid housing  2  in such a way that the sealing plate  4  is compressed by a pre-determined amount on each edge. Here, the amount of compression depends on the initial thickness of the sealing plate  4  and the depth of the mounting foot  17  relative to the set-back boundary edge  19 . The sealing clamping of the sealing plate  4  at its edges to the respective boundary edges  19  which form clamping edges for these, is improved according to the invention in that all set-back boundary edges  19  are provided with a peripheral sealing rib  20  already formed during the manufacturing process of the housing cover  10 . At the same time, the clamping of the sealing plate  4  and its positioning are improved by the tubular spigots  18 , because as  FIG. 5  especially shows, these are engaged and centered in appropriately arranged and preferably precisely fitting stepped depressions  5  in the corners  6  of the peripheral wall of the metal switching solenoid housing  2 . Due to the interaction between the tubular spigots  18 , which are designed in line with the screw clearance holes  16  in the housing cover  10 , and the stepped depressions  5 , which are designed in line with the threaded holes  7  into which the fixing screws  3  are screwed, an exact centering and positioning of the housing cover  10  relative to the switching solenoid housing  2  can consequently be achieved. 
   In the exemplary embodiment shown, a printed circuit board  8  shown in  FIGS. 4 and 6 , to which an electrical contact plug  9  is soldered, which meets the requirements and wishes of the respective mine operator, is arranged in the interior  21  of the housing cover box consisting of an injection molded part and forming the housing cover  10 . A double-walled mounting  22 , the mounting base  23  of which is set back in the interior  21 , is formed centrally on the top side  12  of the housing cover  10  for connecting a connecting cable (not shown) to the contact plug  9  connected to the printed circuit board  8 . Between the two protruding wall sections of the mounting  22 , an anchoring section  51  holds a brass threaded bush  50 , which is glued in the annular gap of the mounting, or preferably is already cast in at this point during the manufacturing process of the housing cover  10 . The annular gap and the anchoring section can each have a conical cross section opening outwards towards the top side  12 . On the rear of the base  23  of the mounting  22  is connected a ring-shaped plastic collar  24 , against the inner circumference of which a section of shaft of the contact plug  9  is sealed by interposing an O-ring  53 . Here, the electrical contacts of the contact plug  9  protrude through a hole in the center of the mounting base  23  of the mounting  22 . The threaded bush  50  can be designed in accordance with the specifications required by the customer, and different threaded bushes  50  can be fixed to or mounted on the housing cover  10 . 
   As already explained above, two solenoids  60 , of which only one is shown in  FIG. 6 , are arranged in the switching solenoid housing  2  of the double solenoid valve  1 . Each solenoid  60  has a cylindrical coil body  61  to which current can be applied and which is connected to the printed circuit board  8  by means of a connecting piece  62 , and is arranged in a magnetizable iron core  63 . Arranged in the iron core  63  so that it can slide while being guided longitudinally, is an armature  64  into which a control push rod  65  is screwed, which can be adjusted by means of a screw connector  66  as is disclosed in detail in DE 201 04 677 U1 to which reference is made in this regard. The control push rod  65 , the position of which can be changed by energizing the coil body  61 , protrudes with its top control push rod end through the housing cover  10  as far as the top side  12 . For this purpose, the housing cover  10  is provided with two control push rod actuating guides  25  for each control push rod  65 , which on the one hand have tubular pieces  26  extending integrally from the top side  12  to the bottom side, and, on the other, incorporate ring-shaped extensions  27  formed on the top side  12  with a peripheral indentation  28  to which an elastic hood  70  can be fixed by snapping into place. The elastic hoods  70  enable each control push rod  65  to be operated manually. At the same time, they seal each control push rod actuating guide  25  against the ingress of moisture. 
   An adjustment disk  80 , which sits rotationally fixed on a multi-sided section  67  at the end of the control push rod  65 , is arranged within the ring-shaped extension  27  of the control push rod actuating guide  25 , and is accessible from the top side  12  with the hood  70  removed. The switching stroke of each solenoid  60  can be adjusted and fixed in the factory by means of the adjustment disk  80 . To adjust the switching stroke, the position of the control push rod  65  is changed relative to the armature  64  by means of the screw-in thread  66 . As  FIG. 8  particularly shows, the adjustment disk  80  can have a multiplicity of tooth-shaped indentations  81  on the external circumference, the factory-set position of the adjustment disk  80  being fixed by means of projections  29  integrally formed on the top side  12  within the collar-shaped extensions  27 . As  FIGS. 7 and 8  show, the adjustment disk  80  in the exemplary embodiment shown is fixed by means of three projections  29 , wherein the three projections  29  not only fix the adjustment disk  80  in the direction of rotation of the control push rod  65 , but also positively fix this in the axial direction of the control push rod in that the individual projections  29  are reshaped from their initial state by the effect of heat, as shown by means of the dotted line in  FIG. 7 , so that they partially engage over the adjustment disk  80 . After adjusting the switching stroke and reshaping the projections  29 , the positioning of the adjustment disk  80  cannot normally change. However, notwithstanding this, in order to enable a readjustment to be carried out under certain circumstances, a screw-in projection  30  with an integral tapped hole  31  for a locking screw  82  is molded in each case onto the side of each tubular piece  26  as an additional embodiment. The adjustment disk  80  can then be adjusted by means of the locking screw  82  even when the protruding part of the projections  29  has been removed. 
   As  FIG. 3  particularly shows, the top side  12  of the housing cover  10  is also provided with two filling openings  32  for potting compound, wherein, if necessary when filling with potting compound, one of the two filling openings  32  only forms a ventilation opening. Furthermore, two fiber-optic rods  35  are anchored in the top side  12  in such a way that they lie free at the top side  12  with their one, preferably lenticular end, and extend down to the printed circuit board  8  with their other ends. The signals from LEDs (not shown), which are arranged on the printed circuit board  8  for this purpose, can be passed on by means of the fiber-optic rods to the top side  12  and be displayed there so that during operation it can be seen from the outside on the top side  12  of the housing cover  10  which operating state the individual solenoids are in. 
   For the person skilled in the art, numerous modifications arise from the above description, which are intended to fall within the area of protection of the attached claims. It is understood that the size of the set-back section of the boundary edges relative to the bottomsides of the sidewalls as well as the geometry of the mounting feet and the geometry of the tubular spigots can be varied within limits in order to continue to achieve a pre-determined clamping of a sealing plate without causing excessive compression. Neither is the invention restricted to the threaded bush and the contact plug shown in the figures, but different threaded bushes and contact plugs can be associated with a housing cover with identical construction.