Abstract:
An electromagnetic drive device is proposed comprising an electromagnet ( 21 ) having a magnetizable core ( 22 ) with a plurality of limbs ( 23  and  24 ) and an energizable winding arrangement ( 35 ) surrounding at least one limb ( 23  and  24 ) of the core ( 22 ). Furthermore there is a magnetizable magnet armature ( 15 ) able to be moved in relation to the core (( 22 ) by varying the winding arrangement current. The ( 22 ) core has at least one U arrangement and is formed essentially by a plurality of sheet metal elements ( 30 ) resting against each other and extending athwart the direction of the parallel limbs ( 23  and  24 ), the parallel limbs being respectively surrounded by one winding ( 33  and  34 ) of the winding arrangement ( 35 ).

Description:
FIELD OF THE INVENTION 
     The invention relates to an electromagnetic drive device, more especially for a valve, comprising an electromagnet having a magnetizable core with a plurality of limbs and an energizable winding arrangement surrounding at least one limb of the core, said device further comprising a magnetizable magnet armature able to be moved in relation to the core by varying the winding arrangement current. 
     BACKGROUND OF THE INVENTION 
     Such an electromagnetic drive device is for example disclosed in the British patent publication 2,289,572 A, the core and the magnet armature constituting a so-called EI arrangement and the winding arrangement being constituted by a winding surrounding the middle limb of the E shaped core. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     Starting with such a device one object of the invention is to provide an electromagnetic drive device, which renders possible more rapid switching while having a simple structure. 
     In accordance with the invention this object is to be fulfilled by the core having at least one U arrangement and preferably being formed as a U core or even as an E core and essentially by a plurality of sheet metal elements resting against each other and extending athwart the direction of the parallel limbs, the parallel limbs being respectively surrounded by one winding of the winding arrangement. 
     Owing to this particular arrangement high energy densities are produced in the magnetic field of the electromagnet. Owing to such high energy density there is the possibility of achieving rapid switching movements of the magnet armature, that is to say short switching times. Owing to low losses the drive device of the invention achieves a high efficiency. 
     Advantageous further developments of the invention will appear from the dependent claims. 
     Since the windings of the winding arrangement can be connected in series or in parallel to one another, it is possible for the overall resistance of the winding arrangement to be varied. 
     It is an advantage for the sheet metal elements constituting the core to possess a U or an E configuration. This renders possible simple manufacture of the core by superjacent stacking of the individual sheet metal elements. 
     It is furthermore convenient for the cross section of the core and/or of the magnet armature to have a polygonal and more particularly rectangular outline. For manufacture of a laminated core identical sheet metal elements are employed so that the core may be produced at a low cost. 
     As an alternative to this the cross section of the core and/or of the magnet armature may be oval or circular. More particularly, a circular cross section of the core may allow an adaptation of the form to the frequently circularly cylindrically wound windings. 
     It is also an advantage for the core and/or the magnet armature to consist of low retentivity magnetic material. Owing to this feature an low coercive field strength is ensured. 
     In the case of such low retentivity magnetic material it may be a question of ferrimagnetic or, respectively, ferromagnetic material. A ferrimagnetic material has a high resistivity. As a ferrimagnetic material iron may for example come into question. 
     Moreover it is expedient for the windings respectively to possess a non-magnetizable winding carrier, on which the winding is mounted. It is in this manner that a gap filled with the winding carrier is produced between the windings and the respectively associated limb of the core. 
     In the case of this design the winding carrier may consist of plastic so that extremely economic manufacture is possible. 
     The electromagnetic drive device in accordance with the invention will now be described in detail with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a valve in a partly sectioned lateral elevation, said valve having an electromagnetic drive device. 
     FIG. 2 shows an embodiment of the invention as a laminated U core from the front to show the terminal faces of the two U limbs. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a 3/2 way valve  5 , which possesses an electromagnetic drive device  6  as an example of the invention. 
     The valve has a valve spool  9  able to be reciprocated in a valve spool receiving space  7  in the longitudinal direction  8  between two positions of switching. Three externally accessible fluid ducts  10 ,  11  and  12  open into the valve spool receiving space  7 , the two fluid ducts  10  and  12  or the fluid ducts  10  and  12  being connected fluidwise with each other in a manner dependent on the switching position of the valve spool  9 . 
     For actuation of the valve spool  9  the valve possesses the electromagnetic drive device  6 . By means of the drive device  6  the valve spool can be reciprocated between the two switching positions. 
     The drive device  6  includes a magnet armature  15  of magnetizable material, which is kinematically coupled with the valve spool  9  and in the working example is fixedly joined to same. As shown in FIG. 1 the magnet armature  15  is secured to the terminal region, associated with the interior of the valve  5 , of the valve spool  9 . The magnet armature  15  possesses a rectangular block-like form and so extends athwart the valve spool  9  that its two terminal section  17  and  18  extend away from the valve spool  9  on diametrally opposite sides of the valve spool  9 . The two terminal regions  17  and  18  are essentially of equal length. 
     As a modification of the working embodiment illustrated the cross section of the magnet armature could also be altered in many different ways and it could for example be oval or circular or have a different polygonal cross formation. 
     The electromagnetic drive device  6  comprises furthermore an electromagnet  21 , with whose aid a movement of the magnet armature  15  may be caused so that a switching over of the valve spool from one switching position into the other position can be brought about. 
     The electromagnet  21  possesses a U shaped core  22  of a magnetizable material. In the preferred working example it has a rectangular cross section. Its two mutually parallel U limbs  23  and  24  are associated respectively at their free end  25  and, respectively,  26  with the magnet armature  15 . In the assembled state the two U limbs  23  and  24  extend essentially in the longitudinal direction  8 . By means of a transverse limb  27  the two U limbs  23  and  24  are joined together at their ends opposite to the free ends  25  and  26 . 
     As a modification of the illustrated working example of the drive device  6  the cross section of the core  22  could also be oval or circular or have some other different polygonal configuration. 
     In the example both the core  22  and also the magnet armature  25  are manufactured of low retentivity magnetic material. In this respect basically ferrimagnetic or, respectively, ferromagnetic material could be utilized, a ferromagnetic material, as for instance iron, being employed in the present case of application. 
     The U shaped core  22  is laminated in construction. It accordingly does not consist of solid material but is rather more made up of a plurality of sheet metal elements  30  extending athwart the direction of the two U shaped limbs  23  and  24 , that is to say athwart the longitudinal direction  8 . In the illustrated working embodiment the individual sheet metal elements or laminations  30  also possess a U-like configuration so that their outline is in lateral view the same as that of the core  22 . Owing to the rectangular cross section of the core  22  here same may be built up by stacking a plurality of U-like sheet metal elements  30 . One could also say therefore that the core  22  possesses a layered or laminated structure. 
     The sheet metal elements  30  are insulated from each other so that more particularly in the case of a high frequency of the switching on and off operations of the electromagnet  21  the eddy current losses may be kept extremely low. The insulation of the sheet metal elements  30  may for example be produced by the application of a thin, non-conducting lacquer layer or the like on the sheet metal elements  30 . 
     Furthermore the electromagnet  21  possesses an energizable winding arrangement  35  constituted by two electrical windings  33  and  34 . The winding arrangement  35  is so arranged that the two U limbs  23  and  24  are surrounded by a respective winding  33  and, respectively,  34 . In this respect it is a question of two windings  33  and  34  in the form of cylindrical windings with, for example, a rectangular passage opening for receiving the U limbs  23  and  24  respectively, the axis of the cylinder coinciding with the direction of the respectively associated U limb  23  and, respectively,  24 . 
     The two windings  33  and  34  respectively have a coil  36  and  37 , which is mounted on a respectively associated tubular winding carrier  38  and, respectively,  39 . The internal form of the winding carriers  38  and  39  is adapted to the cross section of the U limbs  23  and  24  so that the winding carriers  38  and  39  can be slipped onto the respectively associated U limb  23  and  24  from the free end  25  and, respectively,  26 . 
     The winding carriers  38  and  39  consist non-magnetizable material, as for example plastic, and consequently there is a peripherally extending intermediate space between the windings  36  and  37  and the respectively associated U limbs  23  and, respectively,  24 . 
     At their two axial end the winding carriers  38  and  39  respectively bear an annular flange  41  and  42  so that the winding carriers  38  and  39  delimit the respectively associated coil  36  ar, respectively,  37  from the two axial sides as well. 
     The two electrical windings  33  and  34  of the winding arrangement  35  of the electromagnets  21  may be connected up either in series or in parallel. The windings  33  and  34  are, in the fitted condition of the drive device  6  in the valve  5 , electrically connected with two externally accessible electrical contacts  43  and  44 , via which the windings  33  and  34  may be energized. 
     In the following the function of the electromagnetic drive device  6  will be explained. 
     In the illustrated working embodiment by means of a spring arrangement, for example, not illustrated in detail, the magnet armature  15  is biased into the switching position in which it is at a greater distance from the electromagnet  21  and, respectively, the two free ends  25  and  26  of the U limbs  23  and. This switching position is illustrated in FIG.  1 . 
     If now starting from this switching position an external winding current is applied to the electrical contacts  43  and  44  and thence to the two windings  33  and  34 , a magnetic field will be produced , which draws the magnet armature  15  toward the two U limbs  23  and  24  of the core  22 . The magnet armature  15  will move until it finds a stable terminal position, which here defines the further switching position. This switching position, wherein the magnet armature  15  is nearer to the core  22 , is maintained as long as DC flows through the two windings  33  and  34 . 
     After switching off the winding current the magnetic field produced by the two windings  33  and  34  will collapse and the magnet armature  15  will be pulled from the core  22  by the biasing means back into the other position of switching. 
     The electromagnetic drive device  6  is in a position to perform the above described switching operations extremely rapidly so that high switching frequencies may be achieved. 
     As a modification of the above described working example it would be feasible as well for the magnet armature  15  to be in the form of a permanent magnet so that the switching motion of the magnet armature  15  could take place in both directions and be performed by the electromagnet  21 . For this purpose the direction of the current of the winding current would be suitably selected so that in the one case the magnet armature  15  by the electromagnet  21  and in the other case on reversing the current there is repulsion of the magnet armature  15  by the electromagnet  21 . It is in this manner that it is possible for the magnet armature  15  and the valve spool  9  connected therewith to be shifted into the two switching positions. When not energized the magnet armature  15  will remain in the attracted position at all times. A bistable design is also possible . 
     It remains to be pointed out that the electromagnetic drive device  6  can be employed for other purposes besides driving a valve  5 , in which an outer drive part is to be reciprocated between the two positions the magnet armature  15 . 
     As a modification of the working example as described and illustrated it is possible for the core  22  to possesses a plurality of adjacently arranged U arrangements instead of a single U arrangement (U core). In the case of second adjacently placed U arrangements there would then be one E core, the middle limb constituting a common limb for both U arrangements. In the case of three or more limbs each limb would be provided with a winding.