Patent Publication Number: US-5291166-A

Title: Electromagnetic relay with resistor and method for manufacturing the same

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an electromagnetic relay used for opening and closing a circuit by operating an armature according to an excitation of a coil, and more particularly to an electromagnetic relay with a built-in resistor for protecting its electromagnetic coil from surge current and a method for manufacturing the electromagnetic relay with the built-in resistor. 
     2. Description of the Prior Art 
     Heretofore, there has been used an electromagnetic relay disclosed in U.S. Pat. No. 5,003,274, for example. 
     The electromagnetic relay is provided with a coil(7), armature(9), connected with a resilient member(10) having a movable contact(11), terminals(5 and 6) having respective fixed contacts(3 and 4), and a resistor R for absorbing surge voltage generated at the time of shutting off the power supply to a coil(7) through terminals(14 and 15), and is so structured as to open a circuit connected between the terminal(5) and a terminal(13) connected with the movable contact(13), and close another circuit connected between the terminal(6) and the terminal(13) according to excitation of the coil(7) by supplying the electric current to the coil(7). 
     However, in the conventional electromagnetic relay described above, the resistor R is disposed on the terminals(14 and 15) and it is necessary to connect lead wires of the resistor R with both ends of a wound wire(7a) of the coil(7), respectively. Therefore, there is a problem since it is troublesome to connect the resistor with the terminals and the both ends of the wound wire of the coil, and it is difficult to rationalize the manufacturing process of the electromagnetic relay of this kind. 
     SUMMARY OF THE INVENTION 
     This invention is made in view of the aforementioned problem of the conventional electromagnetic relay having the resistor, it is an object to provide an electromagnetic relay which is possible to reduce manpower required for connecting its built-in resistor and a method for manufacturing the electromagnetic relay which is possible to rationalize the process for mounting the resistor. 
     The construction of the electromagnetic relay according to this invention for attaining the aforementioned object is characterized in that coil terminals connected with respective ends of a wound wire of a coil is attached on a base in a state of inserting their legs into coil terminal slots provided in the base, and a resistor is disposed between the base and the coil terminals at a state in which lead wires of the resistor are connected to the coil terminal by fitting the lead wires into slits formed in the respective coil terminals so as to open in the protruding direction of the legs of the coil terminals. 
     The construction of the method for manufacturing the electromagnetic relay for attaining the aforementioned object is characterized by comprising the steps of assembling an actuating part of the electromagnetic relay having a coil, an armature, a movable contact connected with the armature through a resilient piece fixed on a frame, a pair of coil terminals and so on, setting a resistor on a base provided with coil terminal slots to receive the coil terminal and a fixed contact, and connecting the resistor with the coil terminals simultaneously with mounting the actuating part of the relay on the base by inserting the coil terminals into the coil terminal slots and fitting lead wires of the resistor on the base into slits formed in the respective coil terminals so as to open in the inserting direction of the coil terminals. 
     Therefore, the lead wires of the resistor are fitted in the slits of the respective coil terminals to be connected with the coil terminals at the same time the coil terminals are inserted into the coil terminal slots of the base and the actuating part of the electromagnetic relay is mounted on the base, so that the process for mounting the resistor in the electromagnetic relay is rationalized. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional front elevation illustrating the electromagnetic relay according to an embodiment of this invention; 
     FIG. 2 is a partially sectional front elevation in the vicinity of the armature of the electromagnetic relay shown in FIG. 1; 
     FIG. 3 is a front elevation illustrating the actuating part of the electromagnetic relay shown in FIG. 1; 
     FIG. 4 is a top view of the actuating part shown in FIG. 3; 
     FIG. 5 is a sectional front elevation illustrating the base of the electromagnetic relay shown in FIG. 1; 
     FIG. 6 is a sectional side elevation of the base shown in FIG. 5; 
     FIG. 7 is a sectional front elevation illustrating the case of the electromagnetic relay shown in FIG. 1; 
     FIG. 8 is a sectional side elevation of the case shown in FIG. 7; 
     FIG. 9 is a left side elevation illustrating the bobbin and the coil terminal of the electromagnetic relay shown in FIG. 1; 
     FIG. 10 is a rear elevation illustrating the bobbin, the coil and the coil terminals of the electromagnetic relay shown in FIG. 1; 
     FIG. 11 is a bottom view of the bobbin and the coil shown in FIG. 10; and 
     FIGS. 12 to 18 are perspective views illustrating the assembling process of the electromagnetic relay shown in FIG. 1. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An embodiment of the electromagnetic relay according to his invention will be described below on basis of FIG. 1 to FIG. 18. 
     An electromagnetic relay 1 shown in the figures is composed mainly of an actuating part 2, a base 3 and a case 4. 
     The actuating part 2 is composed of a iron core 5, a bobbin 6, a frame 7, a coil 8, coil terminals 9 and 10, an armature 11, a resilient piece 12, a movable contact 13 and a movable contact terminal 14. 
     The bobbin 6 is provided with a cylindrical part 6c to be formed with the coil 8 between flanges 6a and 6b, and provided with a core hole 6d to be inserted with the iron core 5 in center points of the flanges 6a and 6b as shown in FIGS. 9-12. The bobbin 6 is formed with the coil 8 by winding a copper wire around the cylindrical part 6c, and inserted with the iron core 5 in the core hole 6d thereof, as shown in FIG. 10. 
     The bobbin 6 is provided with base blocks 6e and 6f on the outsides of the respective flanges 6a and 6b, and the base blocks 6e and 6f are formed with terminal fixative parts 6g and 6h. Furthermore, one of two base blocks 6e and 6f, that is the base block 6f is provided with a restrictive face 6f1 on the upper face thereof so as not to cause the armature 11 to slip from the proper position by restricting the armature 11 between the restrictive face 6f1 and other restrictive faces 4a1 and 4b1 formed on the case 4 (will be described later) even if the relay 1 receives an impact from one cause or another. 
     The terminal fixative parts 6g and 6h is formed with terminal holder grooves 6g3 and 6h3 having L-shaped sections and piercing through the terminal fixative parts 6g and 6h from rear faces 6g1 and 6h1 (upper side in FIG. 11) to front faces 6g2 and 6h2 (lower side in FIG. 11). The terminal holder grooves 6g3 and 6h3 open on the rear faces 6g1 and 6h1, and have small square apertures 6h4 and 6h4 on the front faces 6g2 and 6h2 of the terminal fixative parts 6g and 6h as shown in FIG. 12. Furthermore, the terminal holder grooves 6g3 and 6h3 have cutouts 6g5 and 6h5 on the lower face of the terminal fixative parts 6g and 6h so as to protrude leg parts 9a and 10a of the coil terminals 9 and 10. 
     The bobbin 6 is attached with the coil terminals 9 and 10 in the terminal fixative parts 6g and 6h. 
     The coil terminals 9 and 10 have L-shaped sections, and composed of inset portions 9b and 10b and legs 9a and 10a bending orthogonally and protruding from the inset portions 9b and 10b so as to be connected with an external circuit (not shown) as shown in FIGS. 9-12. The inset portions 9b and 10b are provided with projections 9b2 and 10b2 projecting parallel with the legs 9a and 10a from inset pieces 9b1 and 10b1 having external shapes suitable to be inserted in the terminal holder grooves 6g3 and 6h3 of the bobbin 6. The coil terminals 9 and 10 are provided with slits 9b3 and 10b3 opening in the protruding direction of the legs 9a and 10a for receiving lead wires 30a and 30b of a resistor 30 (will be described later) between the projections 9b2, 10b2 and the legs 9a, 10a, respectively. The slits 9b3 and 10b3 of the coil terminals 9 and 10 have widths slightly smaller than outer diameters of the lead wires 30a and 30b of the resistor 30. 
     The inset portions 9b and 10b of the coil terminals 9 and 10 are also provided with long projections 9b4 and 10b4 extending from the inset pieces 9b1 and 10b1 as shown in FIGS. 9, 11 and 12, the projections 9b4 and 10b4 are so designed as to poke through the base blocks 6e and 6f of the bobbin 6, and stick out from the square apertures 6g4 and 6h4 of the terminal holder grooves 6g3 and 6h3 of the bobbin 6. 
     The coil terminals 9 and 10 are supported by the terminal fixative parts 6g and 6h of the bobbin 6 at the state in which the projections 9b4, 10b4 stick out from the square apertures 6g4, 6h4 and the legs 9a, 10a protrude downwardly from the cutouts 6g5, 6h5 of the lower face of the terminal fixative parts 6g, 6h of the bobbin 6 together with the projection 9b2, 10b2 forming the slits 9b3, 10b3, by inserting the inset portions 9b and 10b of the coil terminals 9 and 10 into the terminal holder grooves 6g3 and 6h3 with the projections 6g4, 6h4 at the head. The long projections 9b4 and 10b4 poking through the base blocks 6e and 6f and sticking out from the square apertures 6g4 and 6h4 are bound with respective end portions 8a and 8b of the wound wire of the coil 8 and connected with solder, whereby the coil 8 is connected with the coil terminals 9 and 10. The soldered joints act so as not to disengage the inset portions 9b and 9a from the terminal holder grooves 6g3 and 6h3, therefore the coil terminals 9 and 10 never fall out from the bobbin 6 so easily. 
     Additionally, as shown in FIG. 9, the long projection 9b4 of the coil terminal 9 (similarly to the projection 10b4 of the coil terminal 10) is so designed that the point to be soldered may be located at a position forward from the line A passing the front edge of the leg 9a of the coil terminal 9 on the side of the projection 9b4 and being in contact with an outer periphery of the flange 6a of the bobbin 6. Accordingly, the coil bobbin 6 and the legs 9a, 10a of the coil terminals 9, 10 are never dipped in a solderbath even when the projections 9b4, 10b4 are dipped into the solder bath in order to solder the projections 9b4, 10b4 of the coil terminals 9, 10 with the respective both ends 8a, 8b of the wound wire of the coil 8. 
     The frame 7 is secured with an end of the iron core 5 pierced through the core hole 6d of the bobbin 6. The frame 7 is made of magnetic substance with electric conductivity, has a L-shaped section as shown in FIGS. 3, 4 and 14, and composed of an armature-side part 7a to be fixed with the resiliend piece 12 attached with the armature 11 and a core-side part 7b to be secured with the iron core 5. 
     The armature-side part 7a and the core-side part 7b of the frame 7 are provided with press-fitting projections 7a1 and 7b1 to be pressed into the press-fitting holes 16d and 16e formed in the base 3 which will be described later. The armature-side part 7a is fixed with a movable contact terminal 14 having a leg 14a protruding downwardly as shown in FIG. 3 so as to be connected with an external circuit at a lower center part thereof. Furthermore, the core-side part 7b of the frame 7 is secured with the iron core 5 in the center part thereof as described above, and the armature-side part 7a is fixed with base end 12a of the resilient piece 12 by caulking in the center part thereof. 
     The resilient piece 12 is formed by bending elastic material with electric conductivity into a L-shape, and so designed as to fix on the armature-side part 7a at the base and 12a thereof and as to move at the moving part 12b extending toward the iron core 5 from the armature-side part 7a of the frame 7. Furthermore, the resilient piece 12 is disposed with the armature 12 formed of magnetic substance in the middle of the moving part 12b by caulking, attached with a movable contact 13 at another end thereof, and energizes the armature 11 and the movable contact 13 in the direction away from the iron core 5 at a state in which the armature 11 is in contact with the edge of the armature-side part 7a of the frame 7. 
     On the other side, the base 3 is composed of a base body 16, fixed contact terminals 19 and 20 provided with fixed contacts 17 and 18, respectively. 
     The base body 16 is provided with a case-fitting part 16b formed in a frame-like shape on a base plate 16a and provided with a connector part 16c having a box-like shape for covering the legs of the respective terminals to be connected with outer circuits on the under side of the base plate 16a as shown in FIGS. 5, 6 and 17. 
     The base body 16 is provided with fixed contact terminal slots 16a1 and 16a2 in the base plate 16a as shown in FIG. 17, and so structured as to fix the fixed contact terminals 19 and 20 by pressing legs 19a and 20a of the terminals 19 and 20 into the fixed contact terminal slots 16a1 and 16a2. The fixed contact terminals 19 and 20 are sited so that contact faces 19b and 20b formed at the top ends of the respective fixed contact terminals 19 and 20 may be erected on the base plate 16a at a predetermined distance, and the fixed contacts 17 and 18 are disposed on the contact faces 19b and 20b so as to facing each other. 
     The base body 16 is provided with press-fitting holes 16d and 16e in the base plate 16a for supporting the frame 7 by fitting the press-fitting projections 7a1 and 7b1 of the frame 7 into them, and further provided with coil terminal slots 16a3, 16a4 and a movable contact terminal slot 16a5 in the base plate 16a for receiving the legs 9a, 10a and 14a of the respective terminals 9, 10 and 14 as shown in FIGS. 17 and 18. 
     Furthermore, the base body 16 is provided with a resistor groove 16a6 crossing orthogonally with the both coil terminal slots 16a3 and 16a4 on the base plate 16a in order to receive the resistor 30 for absorbing surge voltage at the time of stopping the excitation of the coil 8. The resistor 30 is so set in the resistor groove 16a6 as to lay its lead wires 30a and 30b across the coil terminal slots 16a3 and 16a4 as shown in FIG. 18. Additionally, as shown in FIG. 6, the projections 9b2 and 10b2 of the coil terminals 9 and 10 are so designed as to fit into end portions 16a7 and 16a8 on the right sides of the coil terminal slots 16a3 and 16a4 exceeding the resistor groove 16a6 in FIGS. 17 and 18. 
     The resistor 30 placed in the resistor groove 16a6 on the base plate 16a of the base 3 is connected with the coil terminals 9 and 10 by merely inserting the coil terminals 9, 10 and the fixed contact terminal 14 of the actuating part 2 in the base 3 since the lead wires 30a and 30b of the resistor 30 are fitted into the slits 9b3 and 10b3 formed between the legs 9a, 10a and the projections 9b2, 10b2 of the coil terminals 9, 10 simultaneously with inseting the legs 9a, 10a and 14a of the respective terminals 9, 10 and 14 into the coil terminal slots 16a3, 16a4 and the fixed contact terminal slot 19a5 formed in the base plate 16a of the base 3. At this time, the frame 7 of the actuating part 2 is also secured on the base 3 by pressing the press-fitting projections 7a1 and 7b1 of the frame 7 into the press-fitting holes 16d and 16e formed in the base plate 16a of the base 3. 
     The case 4 is formed in a box-like shape having a top wall 4a and side walls 4b as shown in FIGS. 7 and 8, and so formed as to be coupled with the base body 16 of the base 3 by fitting a fitting part 4b2 formed at the lower end of the side walls 4b onto the case-fitting part 16b of the base body 16. 
     The case 4 is provided with the first restricting face 4a1 parallel with the top wall 4a and the second restricting face 4b1 parallel with the side wall 4b on a A lip projecting step-wise from the top wall 4a and the side wall 4b as shown in FIGS. 7 and 8. The restricting faces 4a1, 4b1 including 6f1 of the bobbin 6 are spaced small distances away from the armature 11 at a state in which the case 4 is fitted on the base body 16 of the base 3 as shown in FIGS. 1 and 2, and prevent the armature 11 and the resilient piece 12 having the movable contact 13 from the slippage. Therefore, the electromagnetic relay 1 according to this invention is structured so as not to cause contact fault even if the relay 1 receives a heavy impact by some reason. 
     The electromagnetic relay 1 having the aforementioned structure may be manufactured through process steps as shown in FIGS. 12 to 18. 
     First of all, the actuating part 2 is assembled. Namely, the coil terminals 9 and 10 are attached to the bobbin 6 by inserting the inset portions 9b and 10b of the coil terminals 9 and 10 into the terminal holder grooves 6g3 and 6h3 formed in the terminal fixative parts 6g and 6h of the bobbin 6 as shown in FIG. 12. Whereby, the coil terminals 9 and 10 are secured with the bobbin 6 in the state where the legs 9a, 10a and the long projections 9b4 and 10b4 stick out from the base blocks 6e and 6f of the bobbin 6 as shown in FIG. 13. 
     Secondly, the coil 8 is formed by winding the wire around the cylindrical part 6c of the bobbin 6 secured with the coil terminal 9 and 10, and the ends 8a and 8b of the wire of the coil 8 are bound and soldered to the projections 9b4 and 10b4 of the coil terminals 9 and 10. 
     Next, the bobbin 6 formed with the coil 8 is attached to the frame 7 by caulking the base end of the iron core 5 passing through the bobbin 6 in the coil-side part 7b of the frame 7 as shown in FIG. 14. 
     Subsequently, the resilient piece 12 disposed with the armature 11 and the movable contact 13 and the movable contact terminal 14 are secured on the armature-side part 7a of the frame 7 fixed to the bobbin 6 as shown in FIG. 15. Whereby, the actuating part 2 of the electromagnetic relay 1 is completed as shown in FIG. 16. 
     On the other side, the base 3 is assembled by pressing the legs 19a and 20a of the fixed contact terminals 19 and 20 having the fixed contacts 17 and 18 into the fixed contact terminal slots 16a1 and 16a2 formed in the base plate 16a of the base body 16 as shown in FIG. 17. The base 3 may be also formed in one body by uniting the fixed contacts 17 and 18 with the base body 16 using insert molding process. 
     Next, the resistor 30 is placed in the resistor groove 19a6 formed on the base plate 16a of the base body 16 so as to lay the lead wires 30a and 30b across the coil terminal slots 16a3 and 16a4 formed in the base plate 16a as shown in FIGS. 17 and 18. 
     Subsequently, the actuating part 2 is mounted on the base body 16 of the base 3 by inserting the legs 9a, 10a and 14a of the coil terminals 9, 10 and the movable contact terminal 14 protruding from the bobbin 6 of the actuating part 2 into the coil terminal slots 16a3, 16a4 and the movable contact terminal slot 16a5 formed in the base plate 16a of the base body 16 as shown in FIG. 18. In this time, the resistor 30 is connected with the coil terminals 9 and 10 in the state where the lead wires 30a and 30b of the resistor 30 are fitted in the slits 9b3 and 10b3 formed between the legs 9a, 10a and the projections 9b2, 10b2 of the respective coil terminals 9, 10, since the projections 9b2 and 10b2 are also inserted into the end portions 16a7 and 16a8 of the coil terminal slots 16a3 and 16a4, and the lead wires 30a and 30b are laid across the coil terminal slots 16a3 and 16a4 at the positions to coincide with the slits 9b3 and 10b3 of the coil terminals 9 and 10. 
     Then, the movable contact 13 disposed on the resilient piece 12 of the actuating part 2 is sited between the fixed contacts 17 and 18 disposed on the fixed contact terminals 19 and 20 of the base 3 so as to be in contact with the fixed contact 17 according to elastic force of the resilient piece 12, and the actuating part 2 of the relay 1 is fixed with the base 3 by inserting the press-fitting projections 7a1 and 7b1 of the frame 7 into the press-fitting holes 16d and 16e formed in the base plate 16a of the base 3 by force. 
     Finally, the electromagnetic relay 1 is completed by fitting the fitting part 4b2 of the case 4 onto the case-fitting part 16b provided on the base body 16 of the base 3. 
     Explanation will be given below abount the action of the electromagnetic relay 1 having the aforementioned structure. 
     Namely, the legs 9a and 10a of the coil terminals 9 and 10 are connected with a power circuit having switching means (not shown) for supplying an electric current to the coil 8, a first circuit (not shown) is connected between the leg 14a of the movable contact terminal 14 and the leg 19a of the fixed contact terminal 19, and a second circuit (not shown) is connected between the leg 14a and the leg 20a of another fixed contact terminal 20. 
     In a case the coil 8 is not excited by switching off the switching means of the power circuit, the movable contact 13 is in contact with the fixed contact 17 by the elastic force of the resilient piece 12, therefore the first circuit connected between the movable contact terminal 14 and the fixed contact terminal 19 is closed and the second circuit connected between the movable contact terminal 14 and the fixed contact terminal 20 is opened. 
     By changing the switching means of the power circuit in the on-state, the coil 8 is excited and the iron core 5 attracts the armature 11 according to the magnetic force generated by the excitation of the coil 8. In accordance with the attractive movement of the armature 11, the resilient piece 12 moves toward the iron core 5 together with the armature 11 and the movable contact 13 shifts from the fixed contact 17 to another fixed contact 18, thereby opening the first circuit connected between the movable contact terminal 14 and the fixed contact terminal 19 and closing the second circuit connected between the movable contact terminal 14 and the fixed contact terminal 20. 
     As mentioned above, in the electromagnetic relay and method for manufacturing the electromagnetic relay according to this invention, it is possible to connect the resistor with the coil terminals by fitting the lead wires of the resistor into the slits formed in the respective coil terminals at the same time the actuating part of the relay having the coil, the contacts and so on is mounted on the base. Therefore it is possible to reduce the manpower required for connecting the resistor to the coil terminals, and an excellect effect can be obtained in that the manufacturing process of the electromagnetic relay is remarkably rationalized.