US2923914A

US2923914A - M beck ctal

Info

Publication number: US2923914A
Authority: US
Publication date: 1960-02-02
Anticipated expiration: 1977-02-02

Description

Feb. 2, 1960 F. M. BECK ETAL 2,923,914

PLASTIC-SUPPORTED TERMINAL ASSEMBLY Filed Sept. 9, 1954 16 3 18 31 W fiaJM g, 19

4 Fig. 3. Fig. 5.

PRESSURE INVENTORS,

FRANC'LS M BECK/1ND JAMES R. BURCH BY Wax/Fair THEIR ATTORNEY pensive to embed such metallic manner directly in a which it. is inserted.

United States Patent PLASTIC-SUPPORTED TERMINAL ASSEMBLY Francis M. Beck and James R. Burch, Schenectady, N.Y.,

v assignors to General Electric Company, a corporation of New York Application September 9, 1954, Serial No. 454,976 4 Claims. (Cl. 339-220) are either directly cast or molded within the plastic material or are fastened thereto by auxiliary fastening means such as by rivets or screws. In most applications it has heretofore been either impossible or prohibitively exparts in a self-supporting pre-cast or pre-molded plastic body. Accordingly, one important object of the invention is to provide a new method for economically securing metallic parts in a self-supporting manner within plastic materials and particularly within insulating thermal setting plastic materials; as well as to provide plastic-supported metallic structures made in accord with our new method. In one type of plastic-supported electric terminal block assembly, the metallic terminal member also carries an electrical contact at'an end opposite to its connecting -means. In the construction of such terminal assemblies it normally requires separate operations to fasten the contact to the terminal member and to embed or fasten the terminal member to the supporting plastic body. Another object of the invention, therefore, is to provide a new method both for fastening the contact to the terminal member and for embedding the terminal member within the plastic-supporting body in a single operation.

'A further object is to provide a new terminal assembly structure made in accord with this new method. A still further object of the invention is to provide a terminal member having a configuration which assures rigid and stable support from a plastic body to which it is secured.

In general, in accord with the invention a portion of a metal member having a zone of reduced cross-sectional area is inserted as a close fit within a hole in a plastic body. A strong electric current is then passed through the metal member while a compressive force is applied thereto in order to heat and deform the zone of reduced cross-sectional area so that-this deformed zone presses tightly against the plastic walls of the aperture within In accord with a further feature of the invention a terminal assembly is provided by using the heavy electric current simultaneously to weld a contact to the metal member.

In accord with a still further feature of the invention, the compressive force applied to the terminal member is simultaneously employed slightly to deform the external portion of the terminal member such .that it tightly clamps against the surface of the plastic body thereby aiding the internal clamping action of the deformation of the zone of reduced cross-sectional area. v

The novel aspects of the invention are set forth in the ice appended claims. The invention itself may be easily understood by reference to the following description taken in connection with the accompanying drawings in which:

Figure 1 is a perspective view partly in section of one apparatus which may be used to practice the invention in the construction of a terminal block assembly.

Figures 2 and 3 are side and front elevations, respectively, of a terminal member before it has been subjected to the operation of the apparatus of Figure 1.

Figures 4 and 5 are side and front sectional views, respectively, of a completed terminal member assembly constructed in accord with the invention; for example, after having been subjected to the operation of the apparatus of Figure 1.

Referring to Figure 1, one apparatus for practicing the invention comprises pressure exerting resistance welding equipment including a pair of current delivering and pressure exerting fingers 10 which operate against an electrically conducting, for example-copper, anvil 11 including a pair of upright posts 12 against which the pressure of fingers 10 is exerted. In the example of the invention shown in Figure 1 a pre-molded plastic body 13 has a plurality of rectangular holes or slotted apertures 14 formed therethrough and a terminal member 15 has a shank portion 16 adapted to be inserted as a close fit within each aperture 14. Shank portion 16 has at least one zone of reduced cross-sectional area formed, for example, by the cutting or stamping of holes or cut-outs therethrough. As best seeen in Figure 3, terminal member 15 has two

zones

17 and 18 of reduced cross-sectional area in its shank portion 16 resulting from the presence of two holes or cut-outs 17a and 18a, respectively. Recess or cut-out 18a extends from the lower edge of terminal member 15 in order to increase the local heating to provide effective welding of this lower edge to an associated contact 19 as well as to assist in the fastening and embedding of the terminal member 15 within the plastic base 13, as will be more fully explained hereinafter. As best seen in Figure 2, shank portion 16 is slightly longer than slot or aperture 14 and joins in lateral portion 20 of terminal member 15 which initially extends at a downwardly inclined angle to the shank portion 16. Lateral portion 20, in turn, joins an upturned generally vertical connector portion 21 of member 15 which contains a tapped hole 22 for accommodating a wire holding screw 30 or other connecting means.

In operating the resistance welding apparatus of Figure 1 to form the terminal assembly of the invention, steel backed silver contacts 19 are first placed upon the metal posts 12, and the straight shank portions 16 of terminal member 15 are inserted within slots of apertures 14 of plastic body 13. Electrically conducting pressure-exerting fingers 10 are connected through suitable leads 23 to a source of alternating or direct current (not shown). Fingers 10 are then lowered until the slot 10a of each finger envelops the upstanding portion 21 of a termianl member 15, and the lower edge 10b of each finger 10 comes into contact with the top of shank portion 16 and the upper surface 24 of lateral portion 20 of a terminal member 15. Continued lowering of fingers 10 causes a downward movement of the plastic body 13 until the lower edges 18b of terminal members 15 come into contact with the upper surface of contacts 19 resting on posts 12, whereupon the electrical circuit is completed such that current flows from one finger 10 through the terminal members and posts to the other finger 10.

Considerable compressive force is applied between fingers 10 and the posts 12 of anvil 11 during the time that current is allowed to fiow in the circuit. The

zones

17 and 18 of reduced cross-sectionalarea in shank portion 16 are heated to high temperatures by such current tion being designated as 170 and 18c.

these

zones

17 and 18 of reduced area than in the remaining portions 21 of terminal member having greater cross-sectional areas. As a result of the higher temperatures achieved in the zones of reduced cross-sectional area, these zones exceed the softening temperature of the metal of terminal member 15, and the compressive force exerted longitudinally upon the terminal member 15 between fingers 10 and anvil posts 12 causes these softened zones to deform and expand perimetrically 'so that they tightly engage the plastic walls defining the aperture 14 within which they are located. A typical perimetrical deformation and consequent clamping action within plastic body 13 is illustrated in Figures 4 and 5; the deforma- The term deformed zone is used herein to mean a zone of a metal member (such as zones 17C. and 18C of shank portion 16) having an external configuration that is distorted, and an internal lattice structure that is stressed and strained relative to the non-deformed zones of the metal member; such deformation resulting from metal flow such as under the influence of pressure or heat or a combination of both pressure and heat.

With continued pressure during such deformation, the overall length of shank portion 16 decreases slightly to aid the expansion of the softened

metal zones

17 and 18 within the plastic base 13. In addition, this decrease in length of shank portion 16 causes the undersurface of downwardly bent portion 20 to strike and deflect against the upper surface of the plastic base along a line of contact26 offset from the plane of shank portion 16 and thus firmly seats and further secures the terminal member 15 against lateral movements.

Simultaneously with the deflection of the terminal member 15 and the softening and expansion within plastic body 13 of

zones

17 and 18 a resistance weld is achieved between contact 19 and the lower edge of terminal member 15 as a result of the combined electrical current and mechanical pressure. The resulting terminal assembly may then be used as a stationary contact member cooperating with a movable contact member 31 (Figure 5) in the switching means, for example, of a magnetic motor starter.

It will thus be seen that as a consequence of the single above-described operation the terminal member 15 is securely embedded and fastened to the prefabricated or p-re-cast plastic body 13 both by the bulges of the terminal member within the plastic body and by the clamping action of the terminal member on opposite surfaces of the plastic body 13, and at the 'same time a firm weld is achieved between the electrical connecting portion of the terminal member and a stationary electrical contact It will be appreciated that if it is not desired that terminal member 15 be directly connected to a stationary contact, that contact element 19 may be replaced by any suitable. metal disk or cap capable of being resistance welded to the terminal member 15. It will also be appreciated that the disk or contact 19 is pressed flush against the under surface of the plastic body 13 during the welding operation and aids in clamping the terminal member 15 to the plastic body 13.

After the welding operation is completed the fingers 10 are elevated and the entire terminal assembly block removed from anvil 11. Although one pair of posts 12 and cooperating fingers 10 are illustrated in Figure 1 it will be appreciated that a plurality of such resistance welding sets of fingers and posts may be employed simultaneously to embed and resistance-weld a plurality of such pairs of terminal members within the plastic body 13. An insulating strip 27 is preferably employed under such circumstances to isolate the electrically conducting bases 11 of the anvil.

It is to be noted that the deformities or bulges 17c and 186,; in the zones of reduced cross-sectional area 17 and 1,8 are; generally. of perimetrical configuration and are v g much more effective in securing terminal member 15 to plastic body 13 than if the terminal member were merely embedded within the plastic during a plastic casting or molding operation. This is because the bulges 17c and actually stress and burn their way into the plastic body thereby causing a local deformation of the plastic body as a result of the heat and pressure applied locally during the pressure welding operation. It will also be noted that bulges 17c and 18c bulge perimetrically outwardly in all directions from the longitudinal axis of the shank portion 16. This omnidirectional bulging is desirable because it provides engagement with the plastic walls at more than two points thereon and thus prevents the shank 16 from pivoting around any two given points of engagement. As can be clearly seen in Figs. 4 and 5, bulges 17c and 18c engage the plastic side walls at at least four points, so any tendency of the shank portion 16 to pivot about any two of these points is clearly obviated. The resulting terminal assembly is thus far stronger than conventional molded types. In fact it is virtually impossible to remove terminal member 15 from the plastic body 13 without completely shattering the plastic even if the Welded cap or contact 19 is cutaway. 1

Another important advantage of the invention is that thermosetting as well as thermoplastic materials may be employed since the method of the invention does, not depend upon the thermal flow of the plastic material involved. Thermosetting plastic materials are thermally stable and tend to hold their tolerances and are usually are resistant. Examples of suitable thermosetting materials are phenolic condensation products preferably containing various fillers such as wood flour, talc and mica; mycalex materials; silicone resins; epoxy resins; polyesters, and polyethylene irradiated with high energy electrons. Phenol-formaldehyde and modified phenol-formaldehyde as well as melamine-aldehyde are particularly suitable. Examples of suitable thermoplastic materials are solid polytetrafluoroethylene, known as Teflon, polychlorotrifiuoroethylene, known as KelS, and polystyrene. The invention may also be used with coldmolded insulating compounds such as phenolic cement asbestos materials.

The electrical currents employed are the usual resistancev welding currents and depend, of course, upon, the metal involved and the'cross-sectional area at the weld location.

The pressures involved are also not excessive and need only to be great enough permanently to deform the softened metal in the zones of reduced cross-sectional area. In a typical example of the method of the invention a steel terminal member 15 having a shank portion 16 whose reduced

cross-sectional areas

17 and 18 are approximately .008 square inch. is securely supported within a phenolformaldehyde thermosetting plastic body 13 under a pressure equivalent to a vZOO-pound weight and a current of 11,000 amperes maintained for 0.05 second.

Although we have described above specific embodiments of the invention as well as specific examples of the practice of the method involved in the invention, it will be appreciated that many modifications may be made. It is to be understood, however, that we intend to cover by the appended claimsv all such modifications as fall within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An electrical apparatus comprising a plastic body including walls defining an aperture therein,a metal strip member having a portion inserted as a close fit within said aperture and extending therethrough, said portion having at least one zone of reduced cross-sectional area, said portion bulging perimetrically outwardly in at least four directions from the longitudinal axis of said strip in said zone to press tightly against at least four pf said walls, said plastic walls having a perimetrical deformed zone cooperating with the bulged portion of the metal member, and a metal cap secured to an edge of said inserted member portion and bearing against a surface of said plastic body, whereby the metal memher is firmly secured to and supported within said plastic body by said cap and the cooperation of the perimetrical deformed zone of the plastic walls with the bulged portion of said metal member.

2. The electrical apparatus of claim 1 wherein said inserted portion of said metal member has two spaced deformed zones of reduced cross sectional area and said metal cap is welded to said inserted portion at an edge of one of said deformed zones.

3. Electrical apparatus com rising a plastic bod having an aperture therein with walls of rectangular cross-section, a metal strip terminal member having a shank portion completely embedded within said aperture, said shank portion having at least one deformed zone of reduced cross-sectional area bulging perimetrically outwardly in all directions from the longitudinal axis of said strip in said zone to press tightly against all of the plastic walls defining said aperture, said plastic walls being perimetrically deformed to cooperate with the deformed zone of the metal member to firmly support and secure said member thereto, and a metal cap secured to an edge of said inserted member portion and bearing against a surface of said plastic body, whereby the metal member is firmly secured to and supported Within said plastic body by said cap and the cooperation of the perimetrically deformed zone of the plastic walls with the bulging portion of said metal member.

4. An electrical apparatus comprising a plastic body having an aperture therein with walls of rectangular cross-section, a metal strip member having a portion of substantially rectangular cross-section inserted as a close fit within said aperture and extending therethrough, said portion having two spaced zones of reduced cross-sectional area which have been cut therethrough, said portion bulging perimetrically outwardly in said zones in at least four directions from the longitudinal axis of said strip to press tightly against at least four of said walls, said plastic walls being perimetrically deformed into intimate engagement with said metal member by each of the spaced perimetrically bulged zones of the metal member, and a metal cap secured to the inserted portion at an edge of one of said perimetrically bulged zones, said cap bearing against a surface of said plastic body, whereby the metal member is firmly secured to and supported within said plastic body by said cap and the intimate engagement of the deformed plastic walls with the bulged zones of the metal member.

References Cited in the file of this patent UNITED STATES PATENTS 446,871 Lieb Feb. 24, 1891 1,806,815 Muther May 26, 1931 1,869,162 Miner July 26, 1932 1,982,169 Kollath Nov. 27, 1934 1,984,036 Schwartzmann Dec. 11, 1934 2,023,264 Brucker Dec. 3, 1935 2,056,036 Catron et al Sept. 29, 1936 2,203,099 Osenberg June 4, 1940 2,329,471 King Sept. 14, 1943 2,456,118 Foster Dec. 14, 1948 2,473,570 Chirerstein June 21, 1949 2,569,059 Huff Sept. 25, 1951 2,700,087 Stevens Jan. 18, 1955 FOREIGN PATENTS 556,548 Great Britain Oct. 11, 1943