US2301992A - Electrical relay - Google Patents

Description

Nov. 17, 1942. N F, AGNEW 2,301,992

ELECTRI CAL RELAY Filed June 5, 19411 1] lNV NTOR F" z. [VOP/HJQiQ/ZQZU.

All? ATTOR N EY Patente tl Nov. 17, 1942 UNITED STATES GFFEQE ELECTRICAL RELAY of Pennsylvania Application June 5, 1941, Serial No. 396,737

1 Claim.

My invention relates to electrical relays, and particularly to electrical relays suitable for use in centralized trafiic controlling systems for railroads.

-One object of my invention is to provide an inexpensive relay of simple, rugged and compact construction having an armature which is moved to an attracted position by operating current of a predetermined polarity only, and which armature is subsequently held in its attracted position until operating current having a polarity opposite to that which moved it to its attracted position is supplied to the relay.

Another object of my invention is to provide inexpensive means for converting a neutral relay of the type described in Letters Patent of the United States No. 1,815,947, granted to Lloyd V. Lewis on July 28, 1931, into the equivalent of a polar stick relay, whereby manufacturing costs, and the number of maintenance parts required by railroads using both types of relays are reduced.

A further object of my invention is to provide a relay of the magnetic stick type which is capable of reliably operating a larger number of contacts than is generally available on polar stick relays, and which is suitable for use as an indica tion relay in a centralized trafiic control system such as that shown and described in Letters Patent of the United States No. 2,197,130, granted to Lloyd V. Lewis on April 16, 1940.

Relays embodying my invention are generally referred to as being of the L type, and in accordance with my invention each relay comprises an L-shaped backstrap of magnetizable material to the short leg of which is secured one pole of a permanent magnet. The other pole of the permanent magnet is spaced from the long leg of the backstrap to provide a magnetic leakage path,

and has secured thereto a magnetizable core which extends parallel to the long leg and is surrounded by the operating winding of the relay. The free end of the magnetizable core cooperates with the relay armature whichis pivoted to the long leg of the backstrap and is operatively connected with contacts mounted on the backstrap. The parts are so proportioned that the armature will be moved toward the magnetizabl cor to an attracted position by operating current of a predetermined polarity only supplied to the operat- The parts are further so proportioned that the magnetic leaka e path which is provided between the said other pole of the permanent magnet and the backstrap will act to provide a return path to the backstrap for fiux from the coil when the flux due to current in the coil is in the direction to tend to demagnetize the permanent magnet, whereby the permanent magnet i caused to maintain its initial strength throughout the useful life of the relay.

Other objects and characteristic features of my invention will become apparent as the description proceeds.

I shall describe one form of relay embodying my invention, and shall then point out th novel features thereof in the claim.

In the accompanying drawing, Fig. 1 is a View showing in side elevation one form of relay em bodying my invention. Fig. 2 is a top plan View of the relay shown in Fig. 1. Fig. 3 is an end View of the permanent magnet 3 forming part of the relay shown in Figs. 1 and 2. Fig. 4 is a detail View of the washer 8 forming part of the relays shown in Figs. 1 and 2.

Similar reference characters refer to similar parts in all three views.

Referring first to Figs. 1 and 2, the relay in the form here illustrated comprises an L-shaped backstrap B of magnetizable material having a short leg I and a long leg 2. A permanent magnet 3 having a high coercive force, preferably of the Alnico type, is cast with a through slot 4 (see Fig. 3) for the reception of the shank of a screw 5 which extends through a hole in the short leg I and is screwed at its free end into a screw threaded hole 6 provided in one end of a magnetizable core I. Interposed between the permanent magnet and the short leg l is a magnetizable washer 8, and interposed between the permanent magnet and the core l is a magnetizable washer As best seen in Fig. 4, the washer 8 is rectangular in form and is provided with a through hole it) and with a flange H which extends at right angles to the lower end of the washer. Th hole 26 receives the screw 5, and the parts are so proportioned that when the screw is in the hole ii the upper edge of the washer will engage the underside of the long leg 2 of the backstrap B, whereby the washer 8 is prevented from turning. The parts are further so proportioned that when the screw 5 is in the bottom of th slot 6, the flange l I will act as a support to hold the magnet in place.

The washer 9 is similar to the washer 8 except for its upper edge i2 which is bent over to provide a magnetic leakage path between the backstrap and the permanent magnet, or the backstrap and the core. under certain conditions which will be described hereinafter. It will be obvious that the washer fl assists the washer 8 in holding the permanent magnet 3 in its proper vertical position.

The core I extends parallel to the long leg 2 of the backstrap B, and is surrounded by an energizing winding l3 held in place by a cotter key M extending through a hole [5 provided in the core adjacent its outer end.

An L-shaped armature A of suitable magnetizable material is pivotally mounted at the free or forward end of the long leg 2 of the backstrap 3 for swinging movement toward or away from the free end of the core I to an attracted or a released position. A plate IE of insulating material is attached to the upper leg of the armature, and this plate extends rearwardly along the backstrap and cooperates with the relay contacts.

The relay contacts are arranged in stacks, and are supported by a metal plate I! which is attached to the long leg 2 of the backstrap by screws 8. The stacks may be readily varied to provide a wide variety of contact combinations, and as here shown are similar to those described in detail in the aforementioned Lewis Patent No. 1,815,947. For purposes of my present invention, it is suflicient to point out that as shown in the drawing the two outer stacks J and L each include a terminal strip 28 or 28a to which the coil leads are attached, while the middle stack K comprises a movable contact finger 2| provided at its free end with a downwardly projecting hook Zia which cooperates with the plate H3. The finger 2i cooperates with fixed front and back contact fingers 22 and 23, and is so adjusted that it exerts a force on the armature which biases the armature toward its released position, and that when the armature occupies its released position, it will engage the fixed back contact fingers to close a back contact 2 l-23, but that, when the armature is moved to its attracted position, the contact finger 2! will be moved out of engagement with the fixed back contact finger and into engagement with the fixed front contact finger to open the back contact 2 L43 and to close a front contact 2l-22.

With the relay constructed in the manner described it will be apparent that when the winding I3 is deenergized, a portion of the flux from the permanent magnet will pass through the leakage path including the magnetizable washer 9, and the remaining portion (excluding unavoidable leakage) will traverse the path including the core 1, the air gap between the core and the armature, and the armature. The parts are so proportioned that when the armature occupies its released position, the force due to that portion of the permanent magnet fiux which traverses the armature will be relatively small and will be insufficient to overcome the biasing force due to the contacts, but that when the armature has once been moved to its attracted position, the increased flux which then traverses the armature due to the decreased air gap between it and the core will be sufficient to retain the armature in its attracted position in opposition to the opposing force of the contact springs.

With the parts proportioned in this manner, if the energizing Widing i3 is supplied with energizing current of such polarity that the resultant fiux traverses the armature in the same direction as the permanent magnet flux, the magiii nitude of the flux traversing the armature will increase sufiiciently to overcome the opposing force of the contact springs, and the armature will move to its attracted position. Once the armature has been moved to its attracted position it will remain in this position until current of a polarity opposite to that which moved it to this position is supplied to the winding. This latter current creates a flux in the core 1 which opposes that due to the permanent magnet, and thereby decreases the flux traversing the armature to such an extent that the resultant tractive force is less than the force due to the relay contact springs. When this happens, the armature returns to its released position.

It should be noted that when the winding [3 is energized in the direction to oppose the permanent magnet flux, the leakage path provided by the washer 9 serves as a part of the return path for the flux set up in the core 1, so that only a relatively small amount of this flux traverses the return path provided by the permanent magnet. This is important because it prevents demagnetization of the permanent magnet due to the en ergization of the operating winding, and insures permanence in the calibration values of the relay.

If the winding i3 is energized in the direction to set up a flux in the core which opposes that due to the permanent magnet when the armature occupies its released position, the effect of this energization will be to decrease the magnetization of the flux traversing the armature from the permanent magnet, and the armature will remain in the position shown unless the winding 13 is energized to an extremely high value much beyond the normal energization level of the relay, in which latter event the armature will pick up. If it does pick up due to excessive energization, it will release as the flux passes through zero when the winding l3 subsequently becomes deenergized, and the permanent magnet cannot therefore hold the armature in its released position under these conditions.

Relays embodying my invention are particularly useful to replace electrical stick relays for in-- dication purposes in centralized traflic control systems. When used for an indication relay 1e magnetic stick provided by the permanent magnet eliminates the stick contact and its wiring as well as saving on battery drain, which makes it more economical than an electrical stick relay.

Another advantage of a relay embodying my invention is that a standard inertia contact such as that shown in my prior Patent No. 2,205,556, granted July 2, 1940, may be used for ringing approach and power-off bells.

Although I have herein shown and described only one form of electrical relay embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claim without depart-- ing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

A relay comprising an L-shaped backstrap having a long leg and a short leg, a bar type permanent magnet provided with a longitudinal slot, a screw extending through the short leg of said backstrap and through said slot and screwed into a core extending parallel to the long leg of said backstrap, an energizing winding on said core, a first magnetizable washer interposed between said magnet and said short leg of said backstrap and engaging the long leg of said backstrap to prevent said washer from turning and provided with means extending underneath said permanent magnet in supporting relation thereto, a second magnetizable washer interposed between said magnet and said core and provided with means extending underneath said magnet in supporting relation thereto and with other means which cooperates with the long leg of said backstrap to provide a leakage path for flux from said permanent magnet and a return path for flux induced in said core to prevent demagnetization of said magnet by energization of said coil in the direction to oppose the permanent magnet flux, an armature pivotally attached to the long leg of said backstrap for swinging movement toward and away from said core to an attracted and a released position, and contacts operated by said armature and biasing said armature toward its released position, the parts being so proportioned that said armature will be moved to its attracted position by operating current of a definite polarity supplied to said winding and will subsequently be held in its attracted position by flux from said permanent magnet until current of opposite polarity is supplied to said winding to release said armature.

NORMAN F. AGNEW.

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