US3038975A - Relay assembly - Google Patents

Description

June 12, 1962 G. w. HUMPHREYS 3,038,975

RELAY ASSEMBLY Filed Sept. 27; 1960 United States Patent 3,038,975 RELAY ASSEMBLY George W. Humphreys, Downers Grove, Ill., assignor to Western Electric Company, Incorporated, a corporation of New York Filed Sept. 27, 1960, Ser. No. 58,667 3 Claims. (Cl. 200-87) This invention relates to electromagnetic relays, and more particularly to a new and improved relay assembly especially adapted for use in an electrical system in which current leakage from the system must be effectively controlled.

In certain electrical systems such as electrical measuring circuits, which depend upon a uniform flow of current for efiicient operation, a substantial problem is presented due to the tendency for current to leak through insulators at relay switch terminals. In this regard, since no known insulating materials will eliminate this current leakage entirely, it becomes necessary to control the same in some manner so that it is reduced to a minimum and so that the approximate value of that which does occur can be determined and taken into consideration.

An object of this invention is to provide a new and improved electromagnetic relay assembly.

Another object of this invention is to provide a new and improved electromagnetic relay assembly which effectively controls and substantially reduces current leakage from an electrical system.

A further object of this invention is to provide a new and improved electromagnetic relay assembly which is simple in construction and highly efiicient in operation.

A still further object of this invention is to provide a new and improved electromagnetic relay assembly including a plurality of independent circuit closing switches, in which current leakage between the switches is sub stantially eliminated.

With these and other objects in view, the present invention contemplates a relay assembly including a base plate having a pair of spaced-apart upstanding switch supports terminating in high resistance insulators, the base plate and supports being of non-magnetic electrically conducting material. Magnetic switch contacts are disposed between the switch supports with their adjacent ends in engageable relationship and their other ends secured to electrical terminals carried by the insulators. Electromagnetic means mounted on the base plate between the supports and extending into closely spaced relationship with respect to the switch contacts, cooperates with the contacts to form a magnetic circuit for moving adjacent end portions of the contacts into circuit closing engagement. The base plate and switch supports, being of electrically conducting material, cooperate with the insulators when the base plate is grounded to form leakage circuits in parallel with the main circuit in which the relay assembly is being utilized. Thus the amount of current leakage which will occur through the insulators, as well as the resistance values which the insulators should have to preclude this current leakage from exceeding permissible limits, readily can be determined by the use of conventional formulas. Further, since the base plate and switch supports are of non-magnetic material, magnetic field generated by the electromagnetic means is concentrated in a path through the electromagnetic means and the switch contacts, thus insuring a positive closing of the switch contacts when the electromagnetic means are energized.

Other objects, advantages and novel aspects of the invention will become apparent upon consideration of the following detailed description in conjunction with the accompanying drawing wherein:

FIG. 1 is a plan view of a relay assembly constructed in accordance with the present invention;

FIG. 2 is a front elevational view of the relay assembly shown in FIG. 1;

FIG. 3 is an end elevational view of the relay assembly shown in FIG. 1; and

FIG. 4 is an electrical circuit illustrating a principle upon which the present invention is based.

Referring to the drawing, a relay assembly according to the present invention is shown which may be used to open or close a pair of circuits simultaneously, and includes a base plate 11 having a pair of spaced upstanding switch supports 12 suitably secured thereto, as by screws. Threaded into the upper ends of the switch supports 12, or other-wise suitably mounted thereon, are a pair of spaced independent insulators 13, preferably of a high resistance material such as Teflon. The insulators may have electrical terminals 14 embedded therein, with the terminals having contacts or reeds 16 of a pair of switches 17 suitably secured thereto as shown, or the contacts 16 may be supported directly on the insulators with the terminals 14 being eliminated.

The base plate 11 and the switch supports 12 are of a suitable non-magnetic electrically conducting material such as brass. When the relay assembly is incorporated into an electrical system and the base plate 11 is grounded, the base plate cooperates with the supports 12 and the insulators 13 to form guard circuits which provide predetermined paths for the current leakage which is bound to occur through the insulators. In this regard, each of the insulators 13 and each of the supports 12., in combination with the grounded base plate 11, form in effect a miniature side circuit which is in parallel with the main circuit of the system in which the relay is being utilized, with the resistance of the insulator being substantially the only resistance in the side circuit. This principle is illustrated in FIG. 4 in which R and R respectively, represent the resistances of a pair of insulators for the terminals 14 of one of the switches 17, R represents the combined value of the remaining resistances in the system, 1 and 1 represent the leakage currents through the insulators, and I represents the main current. The combined value of the leakage currents I and I relative to the value of the main current I will be inversely proportional to the ratio of the combined value of the resistances R and R to the combined value of the other resistances R in the system. Thus, by using conventional formulas the resistance value of the insulators which must be used to keep the leakage currents I and I within permissible limits readily can be determined, or where insulators of a sufiiciently high resistance are not available, the value of these leakage currents can be computed and appropriate allowances made therefor.

The switches 17 are preferably of the sealed reed type, and each may take the form of a cylindrical air-evacuated tube 18 of electrically insulating non-magnetic material such as glass, through the opposite ends of which are extended the contacts or reeds 16. The contacts 16, which are of magnetic material such as soft iron and which may be coated with other material or have precious metal contact surfaces, are positioned to overlap at their inner extremities, which in the absence of magnetic flux are separated by a small distance. In response to the induction of magnetic flux within the contacts, the extremities are engaged whereby an electrical path is completed through the switch between its terminals 14.

Mounted on the base plate 11 between the switch sup ports 12 is a magnetic plate 19. Upstanding from the magnetic plate 19 are a pair of parallel magnetic pole pieces 21 in engagement with the plate and extending upward into close proximity to, but spaced slightly below, the tubes 18. The spacing of the pole pieces slightly below the tubes 18 precludes any current which might pass through the tubes, due to impurities therein, from being diverted from the main circuit through the pole pieces.

The pole pieces 21 are each sunrounded by an electrical coil 22, including a lead 23, the coils 22 being connected in series as shown, or otherwise suitably connected, so that the corresponding ends of the pole pieces will be'of opposed magnetic polarity when the coils are energized. When the coils 22 are energized, since the base plate 11, switch supports 12 and tubes 18 are of non-magnetic material, magnetic field will be concentrated in the pole pieces 21, the magnetic plate 19 and the contacts 16, as indicated by the arrows in FIG. 2, to cause the contacts to move into positive circuit closing engagement.

While a relay assembly utilizing a pair of switches has been shown, it is to be understood that the number of switches in a particular relay assembly will vary according to the number of circuits the relay assembly is intended to control.

From the foregoing description, it is apparent that a new and improved device has been provided which accomplishes the desired objects. For example, the electrically conducting upstanding supports 12 allow wiring to be connected to the terminals 14 out oi contact with adjacent members of the apparatus in which the relay assembly is being utilized, whereby current leakage adjacent the relay assembly is confined to that which occurs through the insulators 13. The supports 12 also provide a shield which prevents current leakage through the insulators 13 between the adjacent switches 17, and they cooperate with the electrically conducting base plate 11 and the high resistance insulators 13 to form guard circuits which are inherent in the relay assembly, whereby the amount of leakage current through the insulators can be determined and readily can be controlled. Further, since the supports 12 and base 11 are of non-magnetic material, magnetic field generated upon energizing of the coils 22 is concentrated in a path through the pole pieces 21, the magnetic plate 19 and the contacts 16, thus insuring quick positive closing of the contacts, whereby arcing across the contacts is minimized and the useful life of the switches is substantially increased.

It is to be understood that the above-described arrangements are simply illustrative of the application of the principles of this invention. Numerous other arrangements may be readily devised by those skilled in the art which will embody the principles of the invention and fall within the spirit and scope thereof.

What is claimed is:

1. A relay assembly, which comprises a base, a pair of spaced substantially parallel supports on said base, spaced independent electrical insulators on each of said supports, said base and said supports being of electrically conducting material and cooperating with said insulators to provide guard circuits for controlling current leakage through said insulators, magnetic electrical contacts supported on said insulators at a substantial distance relative to said base, said contacts extending above said base in pairs and having respective engageable adjacent end portions,

and electromagnetic means supported on said base beneath and in closely spaced relationship with respect to said contacts, said electromagnetic means cooperating with said contacts to form a magnetic circuit for moving the adjacent end portions of said contacts into circuit closing engagement.

2. A relay assembly, .which comprises a base, a pair of spaced substantially parallel supports on said base, spaced independent electrical insulators on each of said supports, said base and said supports being of nonmagnetic electrically conducting material and cooperating with said insulators to provide guard circuits for controlling current leakage through said insulators, magnetic electrical contacts supported on said insulators at a substantial distance relative to said base, said contacts extending above said base in pairs and having respective engageable adjacent end portions, and electromagnetic means supported on said base beneath and in closely spaced relationship with respect to said contacts, said electromagnetic means cooperating with said contacts to form a magnetic circuit for moving the adjacent end portions of said contacts into circuit closing engagement, said base acting to concentrate magnetic field generated by said electromagnetic means within the magnetic circuit formed by said electromagnetic means and said contacts.

3. A relay assembly, which comprises a base, a pair of spaced substantially parallel supports on said base, spaced independent electrical insulators on each of said supports, electrical terminals on said insulators at a substantial distance relative to said base, said base and said supports being of non-magnetic electrically conducting material and cooperating with said insulators to provide guard circuits for controlling current leakage through said insulators, a plurality of switches each including a sealed airevacuated tube of insulating material, pairs of magnetic contacts disposed within the tubes and having engageable adjacent end portions, said contacts extending through opposite extremities of the tubes and being connected to said electrical terminals to support said tubes in substantially superimposed relation with respect to said base, magnetic means on said base having a pair of spaced substantially parallel pole pieces extending therefrom into closely spaced relationship with respect to said tubes, said magnetic means and said pole pieces cooperating with said contacts to form a magnetic circuit, and coils surrounding said pole pieces and connected in series for generating magnetic field in the magnetic circuit formed by said pole pieces, said magnetic means and said contacts, to cause the adjacent end portions of said contacts to move into circuit closing engagement, said base acting to concentrate the magnetic field generated by said coils within the magnetic circuit.

References Cited in the tile of this patent UNITED STATES PATENTS 799,016 Schwarze Sept. 5, 1905 987,192 Turbayne Mar. 21, 1911 2,120,037 OHagan June 7, 1938 2,404,227 Hall July 16, 1946 2,932,773 Matthews Apr. 12, 1960 2,985,733 Kamps May 23, l96l

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