Abstract:
An electromagnetic relay has an armature and a number of contact elements disposed in the hollow interior of the spool about which the coil is wound. The contact elements are held in position by respective contact mounts which are inserted in the axial direction from both open end faces of the coil spool. The contact mounts are U-shaped within the coil spool and are aligned therein by the engagement of ribs carried on the contact mounts with corresponding guide grooves in the interior of the coil spool, thereby accurately and fixedly positioning the contact elements.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electromagnetic relay having contact elements disposed substantially axially parallel within the hollow interior of the coil spool, which contact elements are actuated by means of a flat armature, and specifically relates to such a relay having contact element mounts which are inserted into the opposite open end faces of the coil spool. 
     2. Description of the Prior Art 
     A relay having operative elements disposed within the hollow interior of the spool about which the electromagnetic coil is wound is known from German AS 16 39 417 corresponding to U.S. Pat. No. 3,544,930. The relay disclosed therein has two contact mounts which, in one embodiment, are substantially disc shaped and are inserted into a flange of the coil. One contact mount additionally carries the relay yoke as well as the armature, and the other contact mount carries the pole piece. This structure, however, has the disadvantage that because of the short length of fit between the coil spool flanges and the particular contact mount, the danger exists that the pole shoes held in the contact mounts are not in precise alignment with one another, so that the armature does not rest level along its entire length. Moreover, the danger exists that the cooperating contact elements which are inserted into the interior of the coil spool from opposite directions will exhibit large and imprecise tolerances with regard to the spacing between the actual electrical contacts carried on the ends thereof. A subsequent adjustment to correct such imprecision is not possible after the contact mounts have been inserted. 
     In another embodiment disclosed in U.S. Pat. No. 3,544,930, a contact mount is provided which carries all of the contact elements and pole shoes and is inserted into the coil former from one side. In this structure, the contact spacings can be adjusted before insertion, however, the structure has the disadvantage that, at least on one flange side, the terminals of the leaf spring must be subsequently bent over the plastic edge of the carrier. Additionally, the assembly of all parts on a single contact mount is time-consuming and difficult to achieve during automated or manual assembly. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an electromagnetic relay in which the operable components are disposed in the interior of the hollow coil spool permitting all elements of the magnetic circuit and the contact spring set to be assembled in a simple manner with deviations from acceptable tolerances in the spacings between electric contacts being substantially minimized and the position of the contacts being relatively fixed. 
     The above objects are inventively achieved in an electromagnetic relay of the type described above wherein two contact mounts consisting of synthetic material and each having a U-shape such that their lateral arms enclose the contact elements, are each guided in guide grooves of the coil spool by means of correspondingly engaging ribs carried on the contact mounts up to the region of the center of the coil spool. 
     The above structure by the use of the engaging ribs and grooves insures that assembly tolerances between cooperating contact elements and other parts of the magnetic system are kept at a minimum beyond a nominal value. The entire magnetic and contact system which is carried on the two separate contact mounts can be assembled and adjusted by an appropriate device before insertion into the coil spool. This adjustment is then retained during the insertion of the two contact mounts. 
     In order to match the guide grooves of the coil spool laterally protruding guide ribs can be molded onto the contact mounts. The contact mounts may also be constructed in a known manner, in layers or by injection molding in one piece. Depending upon the type of contact mount, the contact elements can then be applied in layers or injected in a manner which is also known. The yoke and pole piece can be connected to the contact mounts in a known manner such as, for example, by insertion in recesses or fastening by means of integral plastic pins. It is preferable if the yoke and pole piece laterally protrude over the width of the contact mounts and similarly lie in guide grooves of the coil spool. 
     In order to retain their adjusted position during insertion of the contact mounts, the pole piece and yoke are preferably provided with assembly shoulders at which slides of the assembly device can engage. The pole piece and the yoke are preferable L-shaped so that the magnetic contact resistance between those parts and a metal cap which serves for flux guidance is as small as possible. 
     The relay may carry a plurality of contact units which are disposed beside one another. Each contact unit preferably consists of a central contact secured to one of the contact mounts and of two counter-contact leaf springs which are secured to the other contact mount and pre-loaded against the central contact associated therewith. In order to facilitate the assembly, it is preferable that the counter-contact springs have unequal lengths. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of one end of an electromagnetic relay constructed in accordance with the principles of the present invention taken along line I--I of FIG. 2. 
     FIG. 2 is a longitudinal sectional view of a relay constructed in accordance with the principles of the present invention. 
     FIG. 3 is a view of the opposite end of a relay constructed in accordance with the principles of the present invention taken along line III--III of FIG. 2. 
     FIG. 4 is a lateral sectional view of the relay shown in FIG. 2. 
     FIG. 5 is a sectional view of a portion of a further embodiment of the electromagnetic relay constructed in accordance with the principles of the present invention having additional positioning and guide means. 
     FIG. 6 is a partial view of the contact mount for the embodiment of FIG. 5 at an end face of the relay. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An electromagnetic relay constructed in accordance with the principles of the present invention is shown in various sectional views in FIGS. 1 through 4. The relay has a coil spool 1 about which the coil is wound and which serves as a carrier for all operative elements of the relay within the hollow interior 2 of the spool 1. Two U-shaped contact mounts 3 and 4 support the various elements in the interior 2 of the spool 1. The mount 3 carries counter-contact springs 5 and 6 in the embodiment shown in the drawings, however, it will be understood that more contact springs may be employed as may be necessary for particular applications. For each contact unit there is provided an upper counter-contact spring, such as the spring 5, and a lower counter-contact spring such as the spring 6. The counter-contact springs 5 and 6 are pre-loaded against one another and against a stationary central contact 7 associated therewith. The stationary central contact 7, and such other central contacts as may be needed, are each connected to the contact mount 4 next to one another and may, for example, be embedded therein. 
     On its upper side the contact mount 3 carries a yoke 8 and an armature 9. The armature 9, together with a pole piece 10, forms the working air gap. The pole piece 10 is secured to the contact mount 4, for example, by riveting. 
     The two contact mounts 3 and 4 are each U-shaped having respective lateral arms 3a and 3b and 4a and 4b which extend on both sides of the contact elements approximately up to the center of the coil spool 1. The lateral arms serve to guide the mounts 3 and 4 in guide grooves 1a and 1b disposed in the interior 2 of the coil spool 1. Guide ribs 3c and 3d, respectively carried on lateral arms 3a and 3b, and guide ribs 4c and 4d, respectively carried on lateral arms 4a and 4b, engage the guide grooves in the interior of the coil spool 1. Additional guide grooves 1c and 1d are present in the coil spool for the yoke 8 and the pole piece 10, which are each connected to the contact mounts 3 and 4 but which laterally protrude over the mounts and are additionally guided in the coil spool 1. In order to insure a defined and fixed insertion of all parts into the coil spool 1 and to prevent a re-alteration of the previously adjusted yoke and pole piece, the yoke 8 and the pole piece 10 are each provided with assembly shoulders 8a and 10a. 
     During assembly one contact mount such as, for example, the mount 3, is first inserted into the coil spool 1. The other contact mount such as, for example, mount 4, is subsequently inserted into the spool 1 from the opposite side to such an extent until the lower counter contact 6 somewhat overlaps the central contact 7. The armature 9 then pulls up, so that the armature 9 pulls up the contact springs 5 by means of the slide 12 and allows the further insertion of the contact mount 4. This manner of assembly is permitted because of the differing lengths of the counter-contact springs 5 and 6. 
     The coil spool 1 carries in a known manner a winding 13 which can be applied before the contact mount assembly process. The inserted contact mounts 3 and 4, together with the bent yoke 8 and the pole piece 10, can be sealed such as, for example, by a foil 15 at the end face of the relay. A metal cap 16 which serves for flux guidance in a known manner is then placed over the entire relay. The metal cap may be filled with a sealing compound in order to hermetically seal the contact chamber therein. 
     A further embodiment for guiding and retaining the contact mounts in place is shown in FIGS. 5 and 6. A longitudinal cross section through the coil spool 1 is shown in FIG. 5 in such a manner that the contact carriers 23 and 24 can be seen from the side in an uncut view. A partial view of the contact carrier 24 at the end face of the relay is shown in FIG. 6. 
     The contact carriers, together with guide ribs 23a and 23b and 24a and 24b are held in guide grooves 1a and 1b of the coil spool 1 as in the preceding embodiment. The preceding embodiment is modified in FIGS. 5 and 6 by the presence of two ribbed projections 23e and 23f carried on the contact 23, and the presence of ribbed projections 24e and 24f carried on the contact mount 24. The projections are on the surfaces of both sides of the respective mounts 23 and 24. The fixing planes 23g and 24g of these ribbed projections are disposed on the same level as the contact surface 23i and 24i for the yoke 8 and the pole piece 10. 
     The ribbed projections 23e, 23f and 24e, 24f of the contact mounts 23 and 24, and both the yoke 8 and the pole piece 10 are held in guide grooves 1c and 1b of the coil spool 1 by press fit. The yoke 8 has a lug 8b and the pole piece 10 has a lug 10b which together with the end wall of the coil spool interior 2 effect a particular penetration so that the yoke 8, the pole piece 10 and the ribbed projections 23e, 23f, 24e and 24f are pressed onto the plane 1e of the guide grooves 1c and 1d of the spool 1 at an upper portion of the wall of the interior 2. 
     The projections extend through recesses 8c and 10c in the yoke 8 and pole piece 10. 
     Because the pole piece 10 extends only to the center of the contact carrier 24, the upper side of the ribbed projection 24f is provided with an additional penetration rib 24h. Additionally, in order to facilitate the assembly a beveled portion 24k is molded onto the contact mount 24. This beveled portion 24k facilitates insertion if the face end 2a of the interior 2 of the coil spool 1 cannot be rounded off for other reasons. 
     Although modifications and changes may be suggested by those skilled in the art it is the intention of the inventor to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of his contribution to the art.