US1716808A - Electromagnetic device - Google Patents

Description

June 11, 1929. H. A. WALLACE ELECTROMAGNETIC DEVICE Filed April 50, 1926 w 9 Q 5 W m i Q I n1 n D.-

INVENTOR Patented June 11, 1929.

UNITED STATES PATENT OFFICE.

HERBERT A. WALLACE, OF EDGEWOOD BOROUGH, PENNSYLVANIA, ASSIGNOR TO THE UNION SWITCH 8a SIGNAL COMPANY, OF SWISSVALE, PENNSYLVANIA, A CORPO- RATION OF PENNSYLVANIA.

ELECTROMAGNETIC DEVICE.

Application filed April 30, 1926.

My invention relates to electromagnetic devices, and particularly to means for ren dering the rate of operation of such devices inde pendent of temperature changes.

I will describe two forms of electromagnetic devices embodying my invention. and will. then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a view of a retarded relay embodying my invention, the top plate, the base and a portion of the magnet being shown in section, Fig. 2 is a similar view of a modification also embodying my invention.

Similar reference characters refer to similar parts in both views.

Referring first to Fig. 1, the relay comprises a top plate 1, supported upon a base designated generally by the reference character 2.. Mounted upon the top plate 1 is an electromagnet 3, comprising an iron core 4, a winding 5, a back strap 22 and a metallic sleeve 6. The sleeve 6 forms a short eircuited conducting path about the core 4, to cause a slow release of the armature, after de-energization of the relay, in the usual manner.

Secured to the lower end of the core 4 1s a pole piece 7 from which the armature 8 is pivotally suspended at pivot 9. The movement of the armature 8 is limited by a stop member 10, this member being secured to a compensating rod 11 which is rigidly fastened to back strap 22. The rod 11 passes loosely through an aperture in plate 1 and is of material having a smaller temperature coefficient of expansion than the material of which the core 4. is made, for a purpose which will appear hereinafter. The stop member 10 carries a contact 12 which is secured thereto by an insulating member 13. The armature 8 carries the usual contact bar 14 on which the movable contact 15 is mounted. The bar 14 is secured to armature 8 by insulating studs 19. The contact 12 is electrically connected to a binding post 16,.and movable contact 15 is electrically connected to a binding post 18 by means of contact bar 14: and flexible lead 17.

Energization of electromagnet 3 will cause armature 8 to be lifted until it strikes the upper portion of stop member 10 and contacts 15 and 12 will engage. When the electromagnet 3 is de-energized, the electromotive force induced in sleeve 6 will tend to keep the flux Serial No. 105,764.

in core 4.- constant so that the armature will not be released until the flux in core 4 falls below its critical value.

The time required for the relay to pick up may be made constant; by over-energizing it but the time required for the armature 8 to release after de-energization of winding 5 depends mainly upon the resistance of the short-circuited sleeve 6, the percentage change in the winding 5 being relatively small. It has been found that changes iii ambient temperature affect the resistance of slcct e 6 so as to materially alter the time required for the relay to release its armature under different temperature conditions. If a relay of this type is to be used where a con stant rate of release is necessary, some thermally responsive means must be provided for compensation.

If the sleeve 6 is made of copper, since copper has a positive temperature coeflicient of resistance, a rise in temperature increases the resistance of the sleeve so that for a given current in the winding 5 the current induced in sleeve 6 is materially lessened. A smaller induced current in sleeve 6 produces a smaller flux so that the armature 8 is released quicker at high temperatures than at low temperatures. If uniform retardation is to be secured at all temperatures, means must be provided for varying the position of the armature so as to compensate for temperature changes. The armature 8 must be moved closer to the core 4: upon rise in temperature and moved away from the core upon fall in temperature.

One means of rendering the rate of operation of the relay independent of temperature changes is shown in Fig. 1, wherein the stop member 10 for limiting the extent of movement of armature 8 is secured to the compensating rod 11. Rod 11 is made of a material which has a lower temperature coeflicient of expansion than the iron core 4, for example, hard wood may be used. lVhen the temperature of sleeve 6 is increased, the core 4 expandsmore rapidly than rod 11 so that the air gap between pole piece 7 and armature 8 is decreased. A decrease in flux due to increase in ambient temperature will be compensated for, by the shortening of the air gap, hence the length of time required for armature 8 to be released, will be substan tially constant throughout the range for which the relay is calibrated.

sion so that an increase in temperature will move the free end upward and a decrease in temperature will -move it downward. One end of the thermostat 20 is secured to the top plate 1 by means of a bolt 21, and the free end carries the stop member 10. Any movement of the thermostat will move the stop 10 and thus vary the air gap between pole piece 7 and armature 8. As previously explained with reference to Fig. 1, the compensating means has such characteristics that variations in the temperature of sleeve 6 will not vary the time required for the relay to drop its armature, within the temperature range over which the relay is calibrated.

lVhile I have shown and described but two forms of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is: Y

1. An electromagnetic device comprising an armature, an electromagnet for operating said armature, a short-circuited conductor on said electromagnet subject to temperature variations, a stop 'for said armature, and thermal responsive means for moving said stop to compensate for temperature variations in the short circuited conductor.

2. An electromagnetic device comprising an electromagnet including a short-circuited metallic sleeve mounted thereon, an armature controlled by said electromagnet, and temper ature controlled means to compensate for changes in the retardation effect of the metallic sleeve during temperature variations in said sleeve.

3. A relay comprising a supporting plate, an electromagnet carried by said plate and having a short-circuited conductor in inductive relation therewith, an armature, a stop for said armature, a contact on said stop, a contact on the armature adapted to engage the contact on the stop, and thermal responsive means for changing the position of said stop to compensate for the efiect of temperature variations in the short-circuited conductor.

- 4. A relay comprising an armature having a contact thereon, an electromagnet for moving said armature, a short-circuited conductor on said electromagnet, a stop for said armature, a contact mounted on said stop and adapted for engagement with said first contact. and thermal responsive means for moving the stop and the contact associated therewith.

5. An electromagnetic device comprising an armature, an electromagnet including an secured thereto, said member having a lower 7 temperature co-eiiicient of expansion than said iron core and being constructed and arranged to co-operate with the iron core of the electromagnet to compensate for temperature variations in the conducting sleeve.

6. An electromagnetic device comprising an armature, an electromagnet for operating the armature, a conducting sleeve on the electromagnet and temperature controlled means for adjusting the rate of operation of said armature to compensate for changes in temperature in the sleeve.

7. An electromagnetic device comprising an armature, a stop for said armature, an electromagnet having an iron core, a short circuited sleeve on said core, a back strap secured to said core and a temperature compensating rod secured to said back strap and carrying said stop.

8. An electromagnetic device comprising an armature, an electromagnet including an iron core and a back strap, a temperature compensating rod secured to said back strap and mounted approximately parallel to the iron core of the electromagnet, and a stop for said armature secured to said rod.

In testimony whereof I affix my signature.

HERBERT A. WALLACE.

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