US3694912A - Method of manufacturing an electrical relay - Google Patents

Abstract

An electrical relay including a plastic header or base and a plastic shell hermetically sealed to the header. Electrical terminals are sealed into said header and extend into a recessed under portion, the periphery or skirt of which is sealed to the plastic shell. The header is also formed with an integral boss providing bearing means for a balanced armature. Accurately positioned plastic core supporting members are cast in fastening relation to the relay''s core, and a plastic coil bobbin is similarly cast around the core.

Description

[ 51 Oct. 3, 1972 United States Patent Sprando et al.

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22 Filed: March 23, 1970 211 App]. No.: 30,369

Primary ExaminerJ0hn F. Campbell Assistant Examiner-Carl E. Hall AtlorneyBuckhorn, Blore, Klarquist and Sparkman Related US. Application Data [62] Division of Ser. No. 611,540, Jan. 23, 1967,

ABSTRACT An electrical relay including a plastic header or base Pat. No. 3,519,966.

and a plastic shell hermetically sealed to the header.

Electrical terminals are sealed into said header and extend into a recessed under portion, the periphery or 335/ 274 skirt of which is sealed to the plastic shell. The header 1101f is also formed with an integral boss providing bearing .29/602, 622; 335/ 128, 202, means for a balanced armature. Accurately positioned 335/125, 151, 153, 270, 274; 200/168 G;

[51] [58] Field of Search plastic core supporting members are cast in fastening relation to the relays core, and a plastic coil bobbin is similarly cast around the core.

5 Claims, 4 Drawing Figures Auer..........................335/125 PA'TENTEnncIa I972 3.694.912

SHEEI10F2 METHOD OF MANUFACTURING AN ELECTRICAL RELAY CROSS-REFERENCE TO RELATED APPLICA- TION This application is a division of our application Ser. No. 611,540, filed Jan. 23, 1967, entitled ELECTRI- CAL RELAY.

BACKGROUND OF THE INVENTION This invention relates to an electrical relay and method of manufacture, and particularly to a miniature, sensitive and low cost relay apparatus which is accurately formed from plastic component parts.

Construction of miniature sensitive relays for mounting on printed circuit boards and the like is difficult and expensive because of the extremely small tolerances encountered. The usual sensitive, miniature relay comprises a plurality of component parts, usually including a core, an armature, movable and fixed contacts, a mounting base or header and also a cover if the relay is to be hermetically sealed. In addition, bearing means are provided which are positioned accurately upon the mounting base or header whereby the armature may move accurately relative to the other elements. Usually positioning of the core, armature and contacts relative to one another for proper operation requires accurate machining and delicate assembly. As a final step in the completion of such a relay, a metal shell or cover may be welded or soldered thereto to complete a hermetic seal.

SUMMARY OF THE INVENTION In accordance with the present invention, a relay is provided having a plurality of plastic component elements which may be easily positioned in place to provide for accurate operation of a miniature relay. The relay includes a plastic header or base carrying an integrally formed bearing boss for supporting a balanced armature or the like. A core is carried upon plastic tabs whichare molded in fastening relation to the core and which are initially slidably received by the plastic header or base. A plurality of electrical terminals extend through the plastic base from the relay side thereof to a recessed under portion which forms a skirt around these terminals. On the relay side, the terminals connect to electrical contacts which are operated by the armature.

In assembly of the relay, a coil is wound on a bobbin, the latter being integrally cast around the core, and such coil is energized to pre-position the armature in operative relation with contacts and with end portions of the core. At this time, the core supporting tabs are heat welded to the plastic base and thus accurately positioned without undue care in manufacture or assembly of the parts. In addition, the integrally formed plastic bearing boss accurately locates the armature for movable operation with respect to the core.

For hermetic sealing, a plastic shell or cover is disposed in enclosing relationship to the relay, and this shell extends downwardly around the skirt portion of the header where it is heat welded to the header at the headers lower periphery. The completed relay according to an embodiment of the present invention was approximately 0.6 inches long by 0.6 inches high, and approximately O.3 inches in width.

It is accordingly an object of the present invention to provide an improved, miniature, sensitive and low cost relay capable of accurate switching of low level signal currents, and which can be conveniently mounted on printed circuit boards or the like.

Another object of the present invention is to provide an improved miniature relay which is economically formed without stringent requirements as to manufacturing tolerances and assembly care.

Another object of the present invention is to provide an improved miniature relay which includes a minimum of metal parts and wherein glass to metal seals are not required.

Another object of the present invention is to provide an improved miniature relay exhibiting reduced capacitance between electrical terminals, and a relay which can be easily sealed hermetically.

The subject matter which we regard as our invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. The invention, however, as to organization and method of operation, together with further advantages and objects thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings wherein like reference characters refer to like elements.

DRAWINGS FIG. 1 is a perspective view, partially broken away and partially in cross section, of a miniature relay in accordance with the present invention;

FIG. 2 is an end cross sectional view of the FIG. 1 relay taken at 2-2;

FIG. 3 is a partial cross sectional view taken at 3-3 in FIG. 2; and

FIG. 4 is a partial cross sectional view taken at 4-4 in FIG. 3.

DETAILED DESCRIPTION Referring to the drawings a miniature relay according to the present invention, which is actually approxi mately 0.6 inches long by 0.6 inches high and 0.3 inches wide, includes a thermoplastic base or header 10 which may be formed of Delrin. This base is recessed underneath as indicated at 12 providing a lower skirt 14 around the lower periphery of the header. The header is generally rectangular with rounded corners and a flat top and further includes an indentation or slot 16 at each end thereof which extends from the top surface of the header part waydown the end side thereof.

The header is molded with a plurality of metal electrical terminals 18 integrally located therein so that they are sealed into the header. These terminals extend from the top surface of the header to the recessed underside thereof where they may be connected by conventional means to an electrical circuit board upon which the header is conveniently mounted. The header is also formed with an integral bearing boss 20 centrally located on the top of the header. This bearing boss is suitably of frustoconical configuration and includes a flat bearing surface 22 at the top thereof upon which a balanced armature 24 is conveniently mounted. The plastic Delrin, for example, forms a good bearing surface. The bearing boss 20 is centrally bored to receive pivot pin 26 which extends through a cylindrical bearing hole in armature 24, the lower end of pin 26 being securely received in the central bore of the bearing boss 20. As thus appears, the balanced armature 24 is free to rotate around pin 26 upon bearing surface 22. Integral formation of the bearing for armature 24 in this manner avoids problems of armature alignment sometimes encountered with a separate metal bearing or the like, Also elimination of a metal bearing and elimination of other unnecessary metal parts in the relay reduces the capacitance between electrical terminals and contacts, which capacitance is troublesome in conventional metal or metal and glass relays. The use of a balanced armature is preferred because of the sensitivity of operation thereof.

Some of the electrical terminals 18 are extended to provide fixed relay contacts and other of these terminals carry reed contacts 28 which make and break with the fixed contacts in a manner well understood by those skilled in the art. A torque actuator arm 30 is carried at each end of balanced armature 24 for operating the reed contacts 30 to make connection thereof with certain fixed contacts. The relay is illustrated in an operated or energized condition in FIG. 1 with the reed contacts so operated. Normally, when the relay is not operated, the spring back pressure provided by such reed contacts restrains such connection. I

A core supporting member or tab 32 is slidably received in the slot 16 at each end of the header such that the tab may initially be moved in a direction longitudinal to pins 34 which extend from either end of each tab 32 and rest on the top of header 10. Thus, slot 16 is somewhat longer than the long dimension of tab 32 where tab 32 is received within the slot. Each tab 32 is formed of thermoplastic material, e.g. Delrin, and is integrally cast in fastening relation with U-shaped core 36. U-shaped core 36, which is conveniently formed of ferromagnetic material molded from iron powder, extends through coil 38 in a horizontal direction and includes a downwardly extending leg at each end thereof fastened to a plastic tab 32. A tongue-and-groove arrangement providing fastening engagement between the core and each tab 32 is illustrated at 40 in FIG. 3.

In construction of the relay according to the present invention, casting of each tab 32 in fastening relation with the core, as illustrated at 40 in FIG. 3, is accomplished prior to the placement of the tabs in slots 16, and at the same time as a plastic bobbin 42 is similarly cast or molded around the upper or horizontal portion of the core. The bobbin includes end pieces 44 carrying pins 46 for providing electrical connection. In one instance, a coil connection 48 extends from coil 38 to one of the terminals 18 molded in header 10. The bobbin 42 also includes an upper ridge 50, illustrated in FIGS. 2, 3 and 4, which assists in rigid positioning of this'molded plastic bobbin.

After the bobbin 42 and tabs 32 are molded in place on core 36, coil 38 is wound around the bobbin and ap propriately connected to the electrical terminals extending through the header 10. The tabs 32 are then positioned in header slots 16.

After positioning of tabs 32 within slots 16, the coil 38 is electrically energized causing the movement of armature 24 into abutting relation against the downwardly extending leg portions of core 36, and

against the restraining force of the reed contacts. At this time, tabs 32 are urged manually, for example, to establish good electrical connection between normally open electrical contacts, e.g., between fixed contact 52 and the adjacent reed contact 28, without causing any interuption of the magnetic circuit between core 36 and armature 24. Then heat is applied at locations 54 on either side of each tab 32 and the adjoining area of header 10 whereby to melt the tab into the header and form a heat weld at these locations. This heating can be applied at each end of the header by a pair of heated arbors. By this means, accurate and permanent positioning of armature, core and contacts is achieved without requiring special manufacturing tolerances with respect to the parts employed, nor special care during the assembly of the relay.

A plastic shell 56 is now desirably fitted over the relay, this shell being provided with an inwardly extending edge 58 flush with the top of the header 10. When in place, the lower edge 60 of shell 56 is also flush with the lower edge of skirt 14. Heat is applied around the periphery of the lower edge of the skirt and the shell in a manner for heat welding and hermetically sealing the header to the shell. The heat may be conveniently provided with a grooved heating element (not shown) having a groove matching the lower periphery of skirt 14 and lower edge 60 of the shell 56, such groove having a rounded lower cross section. This procedure employing this heating element is effective for urging edge 60 and skirt 14 together as the heat is applied so as to melt the shell and header together and provide a closed structure or compartment. To complete hermetic sealing, the shell may be evacuated through an aperture 62. After evacuation of the interior of the shell, a suitable gas may be provided therein if desired, and aperture 62 may be plugged or sealed by heat. The plastic shell also provides a backstop for movement of the armature.

After construction thereof, the miniature relay according to the present invention is conveniently mounted on circuit board or the like, with terminals 18 connected by soldering to such board, and requires no further adjustment for sensitive operation.

While we have shown and described a preferred embodiment of our invention, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from our invention in its broader aspects. We therefore intend the appended claims to cover all such changes and modifications which fall within the true spirit and scope of our invention.

We claim:

1. The method of manufacturing an electrical relay comprising:

casting plastic tabs in integrally connecting relation with a core;

forming a header of thermoplastic material with slots for receiving said tabs and sealing a plurality of electrical terminals into said header so that they extend therethrough from the upper surface to the lower surface of said header;

mounting an armature on the upper surface of said header;

inserting said tabs into said slots to position said core above said upper surface of said header;

3. The method according to claim 1,

'further including magnetically energizing said core to draw said core to said armature for correctly positioning said tabs in said slots before heat welding of said tabs to said header.

4. The method of manufacturing an electrical relay comprising:

mounting an armature on a header for movement relative to said header;

mounting a coil carrying core on said header for movement relative to said header and in operating relation to said armature;

plastic bobbin is cast around said core substantially at the same time as said plastic tabs are integrally cast in connecting relation therewith.

energizing the coil carried on said core to move said armature relative to said core into an energized position;

then moving said core to an adjusted position on said header while said armature is in said energized position and securing said core to said header in said adjusted position.

5. The method of manufacturing an electrical relay comprising:

casting a plastic core supporting tab in integrally fastening relation to a magnetic core;

winding a coil on said magnetic core;

forming a header of plastic material having a slot for receiving said core-supporting tab for movement relative to said header;

inserting said core supporting tab into said slot;

energizing said coil to move an armature carried. by said header relative to said core into an energized position;

and adjusting the position of said tabs in said slots and securing said tabs to said header by heat while said armature is in said energized position.

Claims (5)

1. The method of manufacturing an electrical relay comprising: casting plastic tabs in integrally connecting relation with a core; forming a header of thermoplastic material with slots for receiving said tabs and sealing a plurality of electrical terminals into said header so that they extend therethrough from the upper surface to the lower surface of said header; mounting an armature on the upper surface of said header; inserting said tabs into said slots to position said core above said upper surface of said header; moving said tabs in a direction other than the direction in which they were inserted to move said coil to an adjusted position; heat welding said tabs within said slots to said header to secure said core in said adjusted position; and sealing a thermoplastic shell in enclosing relation to said contacts and said armature by joining said shell to said header at the periphery of said header.

2. The method according to claim 1, wherein a plastic bobbin is cast around said core substantially at the same time as said plastic tabs are integrally cast in connecting relation therewith.

3. The method according to claim 1, further including magnetically energizing said core to draw said core to said armature for correctly positioning said tabs in said slots before heat welding of said tabs to said header.

4. The method of manufacturing an electrical relay comprising: mounting an armature on a header for movement relative to said header; mounting a coil carrying core on said header for movement relative to said header and in operating relation to said armature; energizing the coil carried on said core to move said armature relative to said core into an energized position; then moving said core to an adjusted position on said header while said armature is in said energized position and securing said core to said header in said adjusted position.

5. The method of manufacturing an electrical relay comprising: casting a plastic core supporting tab in integrally fastening relation to a magnetic core; winding a coil on said magnetic core; forming a header of plastic material having a slot for receiving said core-supporting tab for movement relative to said header; inserting said core supporting tab into said slot; energizing said coil to move an armature carried by said header relative to said core intO an energized position; and adjusting the position of said tabs in said slots and securing said tabs to said header by heat while said armature is in said energized position.

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