Abstract:
Electromagnetic actuator having an armature unit which is axially guided in a housing and movable by passing current through a coil device and in particular against a return force of a return spring out of a first stop position defined by means for limiting the stroke, the means for limiting the stroke having a stop element which is mounted terminally in the housing and manufactured by a shaping, stamping, sintering and/or injection molding method, and which is designed to cooperate with a plunger unit which can be actuated outside the housing and is designed for mechanically moving the armature out of the first stop position.

Description:
BACKGROUND OF THE INVENTION 
     The present invention concerns an electromagnetic actuator according to the introductory part of the main claim. A device of this kind is universally known from the state of the art,  FIG. 6  representing the applicant&#39;s internal state of the art but being used as generic and delimiting. 
     Specifically, the sectional view of  FIG. 6  shows an electromagnetic actuator which is typically designed to actuate a hydraulic or pneumatic valve as an actuating partner and which has an armature unit guided in a housing  10  and consisting of an armature body  12  and an armature plunger  14  seated thereon. With its left engaging end, the armature plunger  14  actuates the actuating partner. 
     In a manner not shown, the arrangement (as otherwise known) is surrounded by a coil support together with coil device, and when current is passed through the coil device the armature unit  12 ,  14  is moved (against the force of a return spring, not shown, typically constructed on the side of the actuating partner) into the left position shown in  FIG. 6 . When the current through the coil device is switched off or the polarity of the control signal is reversed, the armature unit then moves back into the right stop position (referred to  FIG. 6 ), then abutting against a plunger element  16  (so-called emergency or manual plunger for manually actuating the armature by e.g. pushing on an engaging end  18 ). As can be seen from  FIG. 6 , the emergency manual plunger (typically made as a rotatable part) is held centrally in a stop element  20  (in a sealing relationship by means of an inner ring seal  22 ), the stop element  22  (which is in turn sealed off from a hollow cylindrical inner wall of the housing  10  by means of an outer ring seal  24  and non-releasably attached to the housing by means of a crimped portion  26  of the end of the housing, which engages in an annular groove  28  in component  20 ) being constructed as a rotatable part as well. In addition the rotatable part  20  has at the end a suitably applied external thread  30  which is provided for cooperation with a sleeve nut (not shown in  FIG. 6 ) with which then e.g. the arrangement shown can be suitably attached or fixed at a point of application. 
     The device shown, which is used as generic, has numerous drawbacks which prove to be unfavourable and in need of improvement particularly with a view to favourable manufacture in large series; thus first of all the design of the manual plunger  16  and of the stroke-limiting stop element  20  as rotatable parts is inherently elaborate and therefore expensive. Also the assembly shown is disadvantageous with respect to internal pressure or fluid equalisation (mainly concerning oil flowing in the assembly): as illustrated for example by the longitudinal bore  32  shown in the sectional view of  FIG. 6  and running axially/eccentrically in the armature body  12  (which bore is then in flow communication with a channel  34  surrounding the solid armature plunger  14  and substantially produced by play and opening towards the outlet end  36 ), fluid conduction for the purpose of equalising pressure between the right end stop and the end  36  is problematic and, for example with respect to precise guiding of the armature, also in need of improvement. 
     SUMMARY OF THE INVENTION 
     It is therefore the object of the present invention to overcome the weak points shown, and in particular to improve the mechanical construction of the stop element provided terminally in the housing, in connection with the manual plunger unit, and in addition to optimise fluid (oil) equalisation in the whole system. 
     The present invention is achieved by the device according to the characteristics of the independent claims; advantageous developments of the invention are described in the subsidiary claims. Here, the invention is not confined to the claims, but instead all characteristics as described in connection with the state of the art selected as generic according to  FIG. 6  are claimed as belonging to the invention, as well as the characteristics which follow from the discussion of  FIGS. 1 to 12  below, individually or in combination in particular with the introductory part of the main claim. 
     Thus first of all the solution for the stop element which is manufactured according to the invention by a shaping, stamping, sintering and/or injection moulding method ensures that it can be manufactured and assembled with full automation, at low cost and with high precision, such production (by primary or other shaping) producing considerable cost advantages. Within the scope of the invention or alternatively it is also possible to design accordingly the plunger unit which can be actuated outside the housing. 
     While preferably the stop element is constructed in two parts, namely with a stop element preferably constructed as a plastic or the like injection moulding and a disc element directly cooperating therewith, so that suitable sealing elements can be held between them—either seated directly on them, e.g. by injection moulding or the like, or by insertion of for example ring seals, alternatively the invention also encompasses constructing the stop element as a one-piece deep-drawn part which can then further preferably be provided with suitable grooves, undercut portions, shoulders or the like for the provision of sealing sections (which are in turn seated integrally or separate). 
     It is also within the scope of the invention (as well as claimed as an independent invention, in particular according to the introductory part of the main claim) to construct the plunger section of the armature unit composed of armature body and plunger section as a sleeve or the like hollow element, so that not only—according to the invention—favourable manufacture is possible by deep drawing or the like, but also this component itself with the central plunger chamber can serve as a fluid-conducting channel for fluid pressure equalisation (e.g. for oil in the system shown), and according to a development additionally in a direction towards the armature body forms a (mounting) flange or collar which can economically simply and elegantly serve as a distance piece (distance section) between armature body and respective stop position in the housing. Advantageously, use of the sleeve-like plunger section for pressure equalisation also makes it possible for an associated pressure-communicating bore in the armature body to be centrally guided advantageously. 
     Advantageously, it is also within the scope of the invention (but also within the scope of independently claimed protection) to design the stop element, which is preferably to be constructed as a deep-drawn part, in such a way terminally in relation to the housing that the latter can there cooperate in snap-fit or latching relationship with a suitable support or undercut portion, so that in this respect beading or the like measure as known from the state of the art can be eliminated; alternatively it is provided within the scope of the invention (and claimed independently of it) that a deep-drawn stop element of this kind can be provided with a connecting section for non-releasable connection to the housing, e.g. gluing or welding. 
     As a result, the present invention in a surprisingly simple and elegant manner provides a way of significantly improving generic electromagnetic actuators which are advantageous, particularly from manufacturing and assembly points of view. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantages, characteristics and details of the invention are apparent from the following description of preferred embodiments and with reference to the drawings; the latter show: 
         FIG. 1 : a side view with partial section to illustrate a first embodiment of the present invention; 
         FIG. 2 : an end view of the embodiment as in  FIG. 1 ; 
         FIG. 3 : a part-sectional view similar to  FIG. 1  to illustrate a second embodiment of the present invention; 
         FIG. 4 : an end view of the embodiment as in  FIG. 3 ; 
         FIG. 5 : a part-sectional view of a third embodiment of the present invention; 
         FIG. 6 : a sectional view to illustrate the (internal) state of the art used as generic; 
         FIG. 7 : a part-sectional view according to a fourth embodiment, for which protection is requested in connection with all the other embodiments, but also independently; 
         FIG. 8 : a part-sectional view of a fifth embodiment of the present invention, for which protection is requested in connection with all the other embodiments, but also independently; 
         FIG. 9 : a part-sectional view of a sixth embodiment of the present invention, for which protection is requested in connection with all the other embodiments, but also independently; 
         FIG. 10 : a part-sectional view of a seventh embodiment of the present invention, for which protection is requested in connection with all the other embodiments, but also independently; 
         FIG. 11 : a part-sectional view according to an eighth embodiment of the present invention, for which protection is requested in connection with all the other embodiments, but also independently; and 
         FIG. 12 : an end view of the embodiment as in  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION 
     The reference numbers and functionality of  FIG. 6 , which is described for the generic state of the art, apply analogously to the description of the practical examples below, unless described otherwise. Furthermore, an actuator body  11 , containing a coil device  13  (schematically shown) may be as disclosed in U.S. Pat. No. 6,848,919 B2 or U.S. patent application Ser. No. 12/061,197, filed Apr. 2, 2008. The disclosures of U.S. Pat. No. 6,848,919 B2 and U.S. patent application Ser. No. 12/061,197 are incorporated by reference in their entireties herein as if set forth at length. 
     Thus the first embodiment of  FIGS. 1 ,  2  shows a plastic stop element  40  as a means for limiting the stroke, which is constructed as an injection moulding and held against a first annular shoulder  42  in the interior of the housing  10  (the armature unit is guided in the housing  10  in other respects as described in connection with  FIG. 6 ). The plastic stop element  40  cooperates with a disc  44  (in the present example made as a sintered element or stamping), ring seals  46  (outer seal) or  48  (inner seal) being inserted and clamped between element  40  and  44  both in the region of the outer edge to the inner wall of the housing, and in the region of the inner edge in a direction towards the plunger  16  (alternatively these seals can also be constructed by e.g. sealing materials which can be placed on top or inserted by injection moulding). 
     The combination of disc  44  and stop element  40  (as can be seen in particular from the end view of  FIG. 2 , a section of the plastic element  40  extends through the disc) abuts against a bead  48  which marks the end of the housing  10 ; in addition the disc  44  abuts against a second inner annular shoulder  50 . Due to the arrangement shown in this way, construction of the (right) armature stop is therefore possible in a particularly elegant and simple manner with respect to manufacture, and in addition receipt and guiding of the grooved plunger  16 , the arrangement shown combining a capacity for easy manufacture and assembly with optimum sealing. 
       FIGS. 3 and 4  show a second embodiment as a variant of the first embodiment shown in  FIGS. 1 and 2 ; in the same way as there, a sleeve nut  52  is seated on an external thread  54  formed by the outer peripheral end of the element  40  protruding through the housing end. 
     Unlike the embodiment of  FIG. 1 , a stop element  56  as a plastic injection moulding is seated in the terminal region, directly adjacent to a (stamped) disc  58  mounted in front in a direction towards the armature; again, inner and outer ring seals  46 ,  48  are provided for sealing off from the inner housing or from a plunger  60  (which is purely cylindrical here). Again unlike the embodiment as in  FIG. 1 , only one annular shoulder  62  is formed in the interior of the housing. 
     The part-sectional view of  FIG. 5  illustrates a further variant of the stop element; in the embodiment shown there, the stop is constructed by a pair of stamped or sintered discs  64 ,  66  which in the embodiment shown are of identical construction (advantageously for serial manufacture). An annular shoulder of the elements  64  and  66  on both sides in cross-section serves to receive inner or outer ring seals  46 ,  48 , or to cooperate with a terminal shoulder of a plunger  68  (protruding terminally here). This arrangement is also held terminally in the housing between a single annular shoulder  62  and a terminal bead  70 . 
     The embodiment of  FIG. 7  brings a further modification of mounting of the sleeve nut  52  shown in  FIG. 1  or in  FIG. 3  (so that the embodiment in  FIG. 7  basically could be combined with any other embodiments of the present invention). Here, the function of the sleeve nut is taken over by a yoke disc  72  which is provided with a suitable internal thread and seated on an external thread  74  of the housing  10  and forms part of the magnetic circuit. 
       FIG. 8  illustrates an alternative design of the plunger, where a plunger  76  manufactured as a deep-drawn part forms a sleeve-like section  78  which forms a peripheral annular collar  80 , as a result of which the plunger assembly is held in the interior region of the stop body  20  (the technology provided as the state of the art is shown here; basically, however, the configuration of the plunger  76  with any other variant of the stop element according to the present application is possible and conceivable). Not only is the plunger easier and cheaper to manufacture and assemble by this procedure, but also the collar  18  produces a distance from the element  20 . 
       FIGS. 9 and 10  show, according to further embodiments, variants in design of the stop element. Here, the latter is constructed as a one-piece deep-drawn part  82  ( FIG. 9 ) or  84  ( FIG. 10 ), has suitable (e.g. annular groove-like or annular shoulder-like) shaped portions  86 ,  88  or  90  for receiving seals relative to the inner surface of the housing or the plunger, and is connected to the housing either by means of a resiliently bent-up latch section  92  ( FIG. 9 ), or alternatively by means of a weld flange  94  which is annularly angled ( FIG. 10 ). In the former case a releasable snap-fit device would thus be formed, and in the latter case the unit  84  would be non-releasably connected to the open end of the housing by gluing or welding. In both cases, as can be seen from the figures, reliable guiding of the respective plungers  96  or  98  is achieved. 
       FIGS. 11 and 12  illustrate a further embodiment of the present invention which designs the armature plunger unit seated on an armature block  102  (corresponding to element  32  in  FIG. 6 , but with centre bore  104 ) as a sleeve (made by deep drawing), such that the open end of the sleeve widens in a direction towards the armature block like an annular collar into a ring flange  108  which is seated on the inner side of the housing  10 ; consequently the flange thus forms a distance piece from the armature block  102  which can effectively prevent sticking, by magnetic action. At the same time in this way a flow channel (for fluid or oil pressure equalisation in the system) is opened centrally towards the centre bore  104 , so that up to the front engaging end of the plunger element  106  (suitable shaped portions or openings  110  for oil escape are formed there) there is a through-connection; unlike the procedure of  FIG. 6 , here it is no longer necessary for fluid equalisation to take place laterally of the plunger, but instead it takes place through its centre.