Hermetic Terminal

Abstract

A hermetic terminal comprising a metallic wall having at least one opening therein through which a conductor pin extends, said pin being secured in said opening by means of a glass-to-metal seal, said pin comprising three distinct sections, namely, a first section of any suitable electrically conductive material, such as cold rolled steel, a second intermediate section of a sealing alloy, such as stainless steel or a nickel-iron alloy, and a third section of a highly conductive, corrosion-resistant metal, such as copper. The intermediate section of the pin, i.e., the sealing alloy, contacts the glass in the aforesaid glass-to-metal seal with the copper section of the pin extending in one direction from the metallic wall and the cold rolled steel section of the pin extending in the opposite direction therefrom. The present invention relates to hermetic terminals, and more particularly to hermetic compressor terminals of the type used in air conditioners, refrigerators, and the like. This type of terminal is used to carry electrical current into a hermetically enclosed compressor to run the motor in any type of electrical cooling system. Terminals of this general type are well known in the art, and examples of same are illustrated in Wyzenbeek U.S. Pat. No. 3,160,460 dated Dec. 8, 1964, and Elbling et al. U.S. Pat. No. 3,551,191 dated Dec. 29, 1970. Terminals of this type traditionally comprise a generally cup-shaped metallic body having a plurality of openings in the end wall of the body, through each of which a conductor pin extends, the pin being hermetically sealed to the body by means of a glass-to-metal seal. The aforesaid conductor pins have traditionally been constructed of No. 446 stainless steel for a number of reasons. First of all, in order to provide an effective glass-to-metal seal, it is necessary that the coefficient of thermal expansion of the pin relate properly with the coefficient of thermal expansion of the glass, since if the coefficients do not properly relate, then proper sealing between the pin and the glass cannot be achieved. The coefficient of thermal expansion of No. 446 stainless steel is such that an effective glass-to-metal seal can be achieved, although it will be understood that there are other materials, such as a nickel-iron alloy, which also permit effective sealing to glass. Another desirable feature of stainless steel is that it is corrosion resistant, it being understood that in hermetic compressor terminals of the type with which the present invention is concerned, one end of the conductor pins will be extending outside of the enclosure housing the compressor, and in many cases will be exposed to the outside, whereby corrosion of the exposed ends becomes a possibility if the conductor pins are not constructed of a corrosion-resistant material. It will be understood that it is the usual practice to weld tabs or spades to the exposed outer ends of the conductor pins, which tabs or spades are adapted to receive terminals clips carried by the wiring which extends from the source of electrical power. Thus, the electrical current is transmitted from the wiring to the conductor pins by means of the mechanical interconnection which exists between the terminal clips and the conductabs or spades. The current then passes throuugh the conductor pins into the enclosure, said pins being connected at their inner ends to the terminals of the compressor by any suitable means, such as the means shown in the aforesaid Wyzenbeek patent. It will be understood that stainless steel is a sufficiently good conductor of electricity so as to make its use desirable for that reason as well. The problem with the aforesaid stainless steel conductor pins is primarily the high material cost of stainless steel, plus its limited current-carrying capacity for higher power applications. In such high-power applications, copper-core stainless steel may be effectively used, but is extremely expensive. In addition, the assembly of the conductor tabs or spades to the exposed outer ends of the conductor pins is costly; and it has been further found that the securement of the aforesaid conductor tabs or spades to the conductor pins may reuslt in some reduction of electrical conductivity of the overall assembly. The present invention is directed to the provision of a novel and unique conductor pin for hermetic compressor terminals and the like wherein the pin comprises three distinct sections secured to each other in tandem. More specifically, the conductor pin of the present invention comprises a first section of any suitable electriclly conductive material, such as cold rolled steel, a second intermediate section constructed of a material having a coefficient of thermal expansion such as to permit effective sealing with glass, and a third section constructed of a highly conductive, corrosion-resistant material, such as copper. The intermediate section, which may be stainless steel or a nickel-iron alloy, constitutes the portion of the pin that is sealed to the glass. The cold rolled steel section of the pin extends inwardly into the compressor housing, while the copper section of the pin extends outwardly of the terminal for receiving the wiring from the outside source of electricity. As a further feature of the present invention, the exposed copper sections of the pins are cold formed so as to assume a flattened configuration adjacent their outer ends, which flattened portions are adapted to receive a conventional terminal clip. It will be understood that where the entire conductor pin is constructed of stainless steel it is not economically feasible to flatten the ends, whereas it is feasible to do so with the softer copper material. It will be seen that by flattening the exposed copper ends of the pins, said flattened portions function as the conductor tab or spade, hence eliminating the necessity of welding separate tabs or spades to the ends of the pins, as must be done where the pins are conducted of stainless steel. It has been found that the cost of providing the three-section conductor pin of the present invention, including the cost of flattening the copper ends thereof, approximately equals the cost of making the entire conductor pin of stainless steel and then welding thereof a separate cold rolled steel tab or spade. In other words, the lower overall material costs of the conductor pin of the present invention, and the omission of a separate conductor tab or spade and securement of same to the pin, cancels out the costs involved in fabricating the three-section pin and flattening the end thereof, whereby the end result, from a cost standpoint, is a conductor pin comparable to that used in the prior art, i.e., a sold stainless steel pin with a separate cold rolled steel tab or spade welded to the outer end thereof. On the other hand, it has been found that the conductor pin of the present invention results in better electrical conductivity than the prior art, since the cold rolled steel tabs or spades conventionally welded to the exposed outer ends of the conventional stainless steel pins are subject to corrosion, which, of course, results in a reduction of electrical conductivity. Even without such corrosion, it has been found that the electrical conductiveity of the conductor pin of the present invention, wherein separate conductor tabs and spades are eliminated, and wherein a portion of the pin is of highly conductive copper, is appreciably better than the electrical conductivity of the solid stainless steel conductor pin having the separate tab or spade welded thereto. Other objects, features and advantages of the present invention will become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.

Patent Drawings (1 sheets)

Sheet 1