Method of assembling a relay
BACKGROUND OF THE INVENTION 
     In U.S. Pat. No. 4,195,275 of Mar. 25, 1980 entitled &#34;A multiple electromagnetic relay&#34;, there is described a multiple electromagnetic relay which includes a plurality of individual relays disposed on a base. Each individual relay mainly comprises a stand, a magnetic circuit constituted by a pole piece and a winding, and a moving spring-carrying armature which co-operates with the pole piece. 
     Proper operation of the individual relay depends in particular on the value of the air gap between the pole piece and the armature. 
     Up till now, said air gap is obtained as a result of stacking the component parts such as the stand, the pole piece, the armature, the armature stop and the spring carrier. 
     The air gap tolerance is a function of the sum of the tolerances allowed for the dimensions of the abovementioned parts. To obtain an air gap of acceptable size, care must be taken when adjusting the size of said parts. This increases the cost of the relay. If, in contrast, relatively large variations in the value of the air gap are tolerated, allowance must be made for an increase in the value of the relay control current. 
     One aim of the invention is to define a method of assembling a relay in such a way as to guarantee a particular size of air gap of the relay without requiring an increase in production accuracy of its component parts. 
     SUMMARY OF THE INVENTION 
     The invention provides a method of assembling a multiple electromagnetic relay formed by a plurality of individual relays each of which comprises a magnetic circuit equipped with a winding, a magnetic armature, and a moving spring which includes a contact, said method comprising the following operations: 
     the moving springs of the individual relays are assembled together with their respective magnetic armatures by moulding so as to constitute a single spring-carrier part; 
     said part is laid on a base and is held stationary with resepect thereto; 
     by means of a first moving tool, the springs of said part are moved so as to bring the armature up to a first surface of a limit plane in the position which they occupy when the windings of the individual relays are in energized condition; 
     the magnetic circuits of the individual relays are placed on the base and, by means of a second moving tool, they are brought up to the other surface of the limit plane; and 
     a settable resin is cast into the base so as to trap the foot of the spring-carrier part and the bases of the magnetic circuits. 
     Preferably, a third moving tool is used to hold the tops of the magnetic circuits stationary when the resin is cast. 
    
    
     The method of the invention will be made clearer by the following description, given by way of example with reference to the accompanying drawing. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 and 2 are sectional views which illustrate the various phases of the method. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates a transverse cross-section through one of the individual relays of a multiple electromagnetic relay. 
     In FIG. 1, reference 1 designates the base of a multiple electromagnetic relay. Said base is a hollow parallelepiped reinforced by a central rib 2. 
     The various moving parts of the individual relays include a spring blade 3 having a contact 3a, and a magnetic armature 4 made fast with the spring by an insulating component 5. These components are assembled together by moulding so as to constitute a single spring support part which is placed in the base and is stationary with respect thereto. This is easily achieved by plugging the springs in holes in the base from which they protrude in the form of pins. 
     A moving tool 10 moves the plate support part so as to bring the armature up to a first surface 14a of a limit plane 14 which corresponds to the positions of the armatures when the relays are in the operated position. Said plane may either be provided in physical form, as shown, in the form of a rigid but thin plane sheet, or alternatively the limit plane may be no more than a geometrical indication which is implemented indirectly, see below. 
     The magnetic circuits 12 equipped with their windings 13 are placed in the base. 
     Advantageously, they press against a reference plane 15 constituted by the top of the rib 2. 
     A moving tool 16 moves them so as to bring them against the surface 14b of the limit plane 14. 
     A moving tool 17 with a cavity for accommodating the ends of the springs then presses against the tops of the magnetic circuits so as to block the assembly in position. 
     A resin is then cast within base 1 and when it hardens it fixes the various components of the relay. 
     The tools and the limit plane (if provided in physical form) are then removed. 
     If the limit plane is not provided in physical form the tools must be made to move over precise distances, e.g. using a micrometer screw, but otherwise the method is identical. 
     The method of the invention provides relays with constant and repetitive characteristics. Tolerances and the value of the control currents can therefore be reduced. The size of the air gap is thus automatically adjusted during assembly without it being necessary to proceed with any subsequent air-gap adjusting steps.