US3044127A - Electrical element and method of insulating same - Google Patents

Description

July 17, 1962 J. M. ALDEN 3,044,127

ELECTRICAL ELEMENT AND METHOD OF INSULATING SAME Filed Jan. 21, 1959 4 Sheets-Sheet 1 H fl I! H ii 52% W H Q AM 1/ \\mu 1/ 24 a 1/ '9 A46 2 31 2 4W j [an ry/107' Ja/wM 02% 2% 9 1 f @172;

July 17, 1962 J. M. ALDEN 3,044,127

ELECTRICAL ELEMENT AND METHOD OF INSULATING SAME Filed Jan. 21, 1959 4 Sheets-Sheet 2 July 17, 1962 J. M. ALDEN 3, 4

ELECTRICAL ELEMENT AND METHOD OF INSULATING SAME Filed Jan. 21, 1959 4 Sheets-Sheet 3 July 17, 1962 J. M. ALDEN 3,044,127

ELECTRICAL ELEMENT AND METHOD OF INSULATING SAME Filed Jan. 21, 1959 4SheetsSheet 4 ar 1 l an r gay .2;

States 3,044,127 ELECTRICAL ELEMENT AND WTHGD F INSULATING SAL m John M. Alden, 380 Grove St., Needham, Mass. Filed Jan. 21, 1959, Ser. No. 788,101 1 Claim. (Cl. 1854) UIIII of the finished product. Potting is inherently a low pressure process and. does not form a strong seal around the elements. Since no closed mold is involved it results in a poorly formed external and bulky appearance. Furthermore, the process requires careful attention of the operator and is slow as a result of the time required for potting and curing.

Injection molding with plastic insulation appears highly preferable because of the better sealing action, much faster injection and curing speed and the smooth, compact appearance of the product. However, high pressures are needed to force the fluid plastic into a mold and around the components, and such high pressures disarrange the elements with respect to each other and the walls of the mold cavity. The result has been that the components are not properly located in the cavity, and an insuflicient thickness of insulation is formed around them.

According to the present invention a method of encasing an electrical element in insulation comprises, fitting a separate support in a mold, placing an electrical element on the support to securely position the element in the mold, closing the mold, injecting insulation into the mold at least partially to encase the element, and subsequently separating the encased element and support from the mold.

Preferably the support is formed of a primary covering of a fusible material compatible with a secondary encasing material. The support may be molded on a part of the element prior to secondary encasement, or the primary covering may be formed separately and applied to the element prior to putting it in the mold for secondary encasement.

For the purpose of illustration typical methods are illustrated in the accompanying drawings in which:

FIG. 1 is an end elevation of a mold;

FIG. 2 is a side elevation of one-half the mold;

FIG. 3 is an enlarged fragmentary side elevation of the mold showing a resistor and connector supported therein;

FIG. 4 is a section on line 44 of FIG. 3;

FIG. 5 is an elevation like FIG. 3, showing the encased resistor and connector;

FIG. 6 is a section on line 6-6of FIG. 5;

FIG. 7 is a section on line 7-7 of FIG. 6;

FIG. 8 is a side view of the encased element;

FIG. 9 is a bottom view of the encased element;

FIG. 10 is a side elevation of a primary mold half showing an assembly of resistors, a connector and an insulated wire therein;

FIG. 11 is a side elevation of the assembly partially encased in a support;

FIG. 12 is a side elevation of a secondary mold half with the supported assembly therein;

FIG. 13 is a side view of the assembly insulated by the steps of FIGS. 1( to 12;

FIG. 14 is a section on line 14-14 of FIG. 13;

atent G FIG. 15 is a section online 15--15 of FIG. 12;

FIG. -16 is a left end elevation of a preformed support;

FIG. 17 is a right end elevation of the preformed support;

FIG. 18 is a side elevation of the preformed support shown partly in section, and with an assembly resistor, a terminal and insulated wires'connected thereto;

FIG. 19 is a side elevation of a mold half with the preformed support and assembly therein;

FIG. 20 is a section on line 2020 of FIG. 19;

FIG. 21 is a side elevation of the encased preformed support and assembly;

FIG. 22 is an end elevation of a two part support;

FIG. 23 is a section on line 23-23 of FIG. 22;

FIG. 24 is a plan view of the two part support;

FIG. 25 is a section of a mold half with the two part support holding a connector and lead therein;

FIG. 26 is a side elevation showing the encased two part support and connector; and

FIG. 27 is an isometric view of the connector and lead I ing two halves 11a and 11b, each of which comprises a cavity with a semicylindricalhorizontal chamber 12,vertical chamber 13, andwire passage 14 andentrance 16. Thevertical chamber 13 is adapted to receive acylindrical support plug 17 having an upwardly extending tubular wall 18' within which is located a stub 19. The stub 19 is generally cylindrical, as best shown in FIG; 6, and spaced inwardly of thewall 18, except for two "ears 21 which abut the wall, thereby defining two arcuate spaces between the wall and stub.

Theplug 17 is adapted to support the tube cap connector 1 with its jaws 2 fitting in the arcuate spaces of the plug and with its connector portion 3 resting-on top of the stub 19. In addition to supporting the connector, the stub covers the lower end of its jaws and the underside of the connector portion.

When the connector is fitted on the plug the connector and plug are placed in one mold half with theresistor 6 in thehorizontalchamber 12 and the insulated Wire extending from thepassage 14 into thehorizontal chamber 12.

When the mold halves are clamped together in a conven-- tional manner, the insulation is gripped in thepassage 14, and the resistor is gripped between two pairs ofstuds 15 whose ends are shaped to extend slightly around the sides and ends of theresistor 6. The insulated wire, resistor and connector are then positively located in the cavity with thetubular walls 18 of theplug 17 sealing off the connector jaws 2.

I A hot, fluid, insulating plastic, such as polyethylene, vinyl resins or nylon, is injected through the opening 16 at a high pressure, for example 1200 psi. so as to flow around all exposed parts of the connector assembly and form thejacket 26 of FIGS. 8 and 9. An insulating material compatible with the insulation on thewire 8 will form a homogeneous bond therewith and permanently embed the wire end in the jacket and seal the assembly against moisture, contamination and leakage. The jacketed assembly is removed from the mold together with the plug and are thereafter separated.

The jacket and connector assembly are thereby molded as a unit with a single injection shot. .Since the connector assembly is also embedded in the jacket, excellent strain relief is provided for the leads, minimizing wire and solder joint fratigue under vibration and shock. The connector is seated in the jacket, but its jaws are free from accidental coating owing to the sealing otf effect of theplug walls 18.

Another way of insulating a connector assembly is shown in FIGS. to 16, whereinthe assembly comprises aconnector pin 31havinga contact portion 32 andconnector portion 33 connectedto a series ofresistors 6 withleads 4 and aninsulated wire 8. The assembly is located in a first mold of which one half 34a is shown in 51G. 10.

V therectangular recess 88. Between eachchannel 39 and The first mold comprises a horizontal chamber 36 withopposite end openings 37 and 38, three semi-cylindrical vertical recesses, two horizontalcylindrical recesses 41, and three studs 4-2 having concave upper surfaces complementary to theresistors 6. When the mold halvesare clamped together the resistors are seated on the studs 42.

A first onprimary jacket 46 isformed by injecting hot plastic under high pressure as described above. The first jacket has vertical bosses formed by therecesses 39, andhorizontal bosses 48 formed byrecesses 41.Recesses 49 exposing theresistors 6 are'formed by the studs 42 as shown in FIGS. 11, 12 and 15. An annular bossStl is formed at the enlarged right end of chamber 36.

Thefirst jacket 46 forms a support-for the connectorresistor assembly in a second mold of whosehalves 51a and 51b are shown in FIG. 12. The second mold has ahorizontal chamber 52 withend passages 53 and 54. Thecontact portion 32 of thepin 31 is held in oneend opening 53 with itsconnector portion 33 extending into "thechamber 52. In the second mold 51a'51b thebosses 56 fuses with theinner jacket 46 and completes the ena casing of the connector assembly. Thepin 31 is em: bedded in the matrix, and the'openings '49 to theresistors 6 areclosed. Thebosses 47, 48 and 50 having served their purpose of holding the jacketed assembly in position.

are merged with the outer jacket.

' As shown in FIGS. 17 to 21 the first orprimary jacket 61 may be preformed prior to the assembly of elements therein. In FIGS. 16 to the primary jacket is a generally cylindrical body of plastic insulating material formed with lengthwisecylindrical chambers 62, connectingpassages 63 between the chambers, and upper andlower bosses 64. One or-more resistors 6-andinsulated wires 66 are inserted in thechambers 62, and solder connected to apin jack 67 after theirlead wires 68 are passed through a wall 71 at the right end of the primary jacket; Thejack 67 is positioned against an axial boss 72. g

The primary jacket supports the assembly of "wires, resistors and jack in a mold 73 shown'in FIGS. 19 and 20, comprising halves 73a and 73b. Thehalves form a main chamber 74 having upper and lower recesses 76 receiving thebosses 64 of the jacket. A separable mold member is held in aribbed chamber 78 by attachment to the mold; The inner end of the member has a tip (not Thus when a matrix molten plastic is forced shown) over which the jack 67 V fits. The boss 72 prevents preformed support as indicated in FIG. 17 thereby forming an integral unit.

In FIGS. 22 to 26 is shown a method of supporting anelectrical jack 81, elements in a two-part preformedbody gular base 83 extends at one end, and at the other end a lug -84 to which the conductor of aninsulated wire 85 is 7 86a, 86b. As shown in FIG. 27, eachjack 81 is formed by punch-press techniques from resilientsheet metal and has a triangular socket portionBZ from which arectanwire entrance 87 the two-part body forms a'wall 91 having asmall passage 92 communicating with therecess 39 and a larger passage communicating with thewire entrance 87.

As shown in FIG-25 thejacks 81 and wires are supported in a two-part mold 96a-96b by'clamping the two-part support86a-86b therein having first fitted the jacks and wires in the two part body. The wires and jacks may be joined prior to placing them in the support. When in the support the insulation ofwire 85 fills theenlarged passage 93 closing oif therecess 88 andchannel 89 from thewire entrance 87 as shown in MG. 25.

The mold 96a--96b has amain chamber 97 and asmaller chamber 98 which is filled by the two-part support 86a86b. Thewall 91 of the supportcloses oft" the smaller chamber .98 from themain chamber 97. Thus when amatrix 99 of hot plastic, under high pressure, is injected in the mold, the support not only holds the clip and wire firmly positioned, but also restricts the matrix to covering the wire 35 and the part of the support to the right of thewall 91, so that the matrix does not reach thejack 81. e

From the foregoing description it can be seen that the present method insuresthat the various circuit elements will be positioned properly in their insulating casing despite the high pressure faces tending to dislocate them in the mold. The injected matrix or casing not only afiords rigid support, resistance against breakage from shock and vibration and complete sealing against moisture, dust and electrical leakage, but also it is a far more speedy, inexpensive and convenient operation. 1

While I have shown several specific methods by which the advantages of injection molding can be fully realized, it should be understood the steps illustrated may be com bined in other and equivalent ways within the scope of the appended claim.

I claim: The methodof encasing in insulation an electrical element of relatively large Width having a lead of relatively smaller width connected thereto which comprises locating the element in an insulating support having two parts forming a chamber of a size to receive said element and a Wall at one end of said chamber having a smaller opening therefrom for said lead, said well facing toward said element and away from said lead so as to engage the element against movement axially of the lead, placing the insulating support, element and lead in a mold 'so that the support is engaged by the mold thereby positively to locate the element in the mold, simultaneously clamping in the mold a portion of the lead spaced from the element so that the element and said lead portion are mechanically engaged without further preparation such that the intermediate portion of the lead is positively held against dislocation by pressure of insulation injected in the mold, and injecting an insulating coating over said support.

ReferencesCited in the file of this patent UNITED STATES PATENTS 2,713,700Fisher Ju1y 26, 1955 2,747,230 Magnus May 29, '1956 2,856,639 Forrest et al Oct. 21, 1958 FOREIGN PATENTS 211,774v Australia Janfll, 1957 657,821

Great Britain Sept. 26, 1951

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