US2051380A - Thermal relay - Google Patents

Description

Aug. 18, 1936. B. W. JONES THERMAL RELAY Filed D60. 29, 1934 inve mtor: Benjam im V\/. Jones,

n ifm/1765,

Ld His Attorney Patented Aug. 1h87, v1936 THERMAL RELAY Benjamin W. Jones, Schenectady, N. Y., assigner to General Electric Company, a corporation of New York Application December 29, 1934, Serial No. 759,719 22 Claims. (C1200-122) paratus to dangerous temperatures. In applying thermal overload protection to such apparatus, it is often desirable or necessary that the entire control including the Ythermal relay, be immersed in a body of oil, as for'instance, when the appaplace which is subject to explosive or corrosive atmospheres, and consequently considerable need has arisen for a thermal overload relay which will operate satisfactorily when immersed in a body of oil.

The operation of thermal overload relays is to a large extent dependent upon the thermal propertics of the medium surrounding the thermal working parts of the relay, and serious operating difficulties are encountered, therefore, in the design of thermal relays for oil immersed operation. For example, the required Watt input to operate a thermal relay in air is increased by approximately 400% when the relay is immersed in a large body of oil.

This large watt input is of course unsatisfactory, and may be offset by thermally isolating the working parts of the relay from the large bcdy of oil. Resort may be had, for this purpose,

to the practice of enclosing the thermal working parts of the relay in an oil-lled sealed container of thermal insulating material, so that the relay parts are thermally associated with only a small body of oil which is thermally isolated from the main body of immersing oil.

Operating diiculties are again encountered, however, due to the susceptibility of the sealed container to leakage. relay requires that the thermal parts of theyrelay be subjected at all times to the same ambient medium, and it will be apparent that if the sealed container develops a leak before the relay is immersed, or if the relay is removed from its oil bath after the leak occurs, the oil within the container will drain out and the operation of the relay will be considerably affected by the air which enters the container. When the relay container is immersed in oil after the oil originally sealed therein has escaped it willpbe found that ratus to be protected is located in a hazardous-y Uniform operation vof the the air whichl is trapped within the container will substantially prevent the container from refilling with oil, that is, a diving-bell eiect exists. 'I'he construction of a tightly sealed container may also involve considerable expense.

Much is yet to be desired, therefore, in a ther- 5 mal relay suitable for oil immersed operation in which provision is made forensuring that the Working parts of the/relay are subjected at all times to the proper immersing medium, the relay being designed for low watt input when subjected 10 to that medium. Accordingly, it is a further object of my invention to provide a simple and inexpensive thermal relay the operation of which is reliable and uniform when immersed in oil.

In carrying out my invention in one form, I l5v provide a container for the thermal operating parts of the relay comprising walls of thermal insulating material, at least one of the Walls having an aperture therein for the admission of oil when the device is immersed in a body of oil. Such a 20 device is described and broadly claimed in a copendlng application of Charles H. Chapman, Serial No. 43,741 led October 5, 1935, entitled Temperature overload relay, which application i is assigned to the same assignee as the present invention. The present invention is an improvement of the invention disclosed in the above ap'- -plication, which invention was madeby the said Charles H. Chapman prior to my invention and I, therefore, do not herein claim anything shown 30 or described in that application, which is to be regarded as prior art. When the relay is immersed in a body of oil, sufllcient oil ilows through the aperture in the container wall substantially toA fill the container, the walls being arranged in 3`5 a non-airtight manner so as to prevent the entrapping of air therewithin. The restricted character of the aperture is such as substantially to isolate the thermal operating parts of the relay and the oil within the container from the main 40 body of oil so as to minimizethe transfer of heat therebetween.

More specifically I provide a thermal insulat-` ing container within which is supported a. `core having an axially extending slot therein, a'heat- 45 ing winding surrounding the core and a bimetallic element disposed in the slot with an end thereof adjacent a movable member which extends through an aperture in the container wall to control the external contactsg- In order 4elec 50 trically to insulate the working parts of the relay from the circuit to be protected, the core is formed of magnetizable material and the heat-A ing winding comprises a closed circuited second.- `iuy inductively. related to a primary Winding,

Same.

Referring now to the drawing,thepreferred embodiment of my invention shown comprises a base I0 of thermal insulating material having a pair of intersecting recesses II and I2 respectively formed therein. Disposed in the recess II is a core member I3 secured to the base Ill as by the screw I4 and provided with an axially extending slot I5 in which a bimetallic element I6 is disposed, with one end thereof secured to a heating member comprising a cylindrical conductor I1 closely surrounding the portion of the core I3 which extends outwardly from the base I0. The outermost end of the core I3 is threaded as shown at I8 and is engaged by a cap I9 of thermal insulating material one face of which is provided with a groove 20 to form shoulders for positioning a cylindrical member 2l of thermal insulating material which surrounds the cylindrical conductor I1, with its opposite end abutting against a face of the base I0 which is provided with a positioning shoulder 22.

It will be apparent that the cap I9, the cylinder '2l and the base I0 comprise the walls of a nonairtight 4container for the thermal working parts of the relay, no sealing means being provided between the walls, the intersecting recesses II and I2 forming an aperture in one of the walls. It is highly important that the walls of the container be arranged in a non-airtight manner so as to allow the escape of air therefrom when the relay is `immersed in oil, and in some cases it may be desirable to provide a second aperture inthe container.

the bimetallic element I6 and the core I3 which are arranged to occupy a minimum of space, with a substantial portion of the bimetallic element enclosed on three sides by the core which is formed of heat storage material and on the fourth side by the heating member I1 to provide a high degree of heat transfer to the bimetallic element. The free end of the bimetallic element I6 is adjacent the intersection of the recesses II and I2 and engages one end of a movable member comprising a floating plunger 23 of insulating material arranged in the recess I2, sufficient clearance being provided between the plunger and the walls of the recess to permit oil to iiow ltherethrough into the container. -I'n Fig. 1 a' portion ofv the plunger. 23 is broken away more clearly to show the arrangement of the circuit controlling contacts.

Supported externally of the container on a face of the base I0 adjacentthe recess II, I provide a pair of movable contacts 24 and 25, respectively carried by a pair, of spring arms 26 and 21 which are supported respectively on the terminal-members 28 and 29 fastened to the base I0 as by the screws 30. The spring arms 26 and 21 are arranged normally to bias the contacts 24 and 25 into engagement with each other, the spring arm 26 which exerts a relatively greater biasing The thermal working parts of-the relay comprise the heating memberv II,I

aosiso force than the spring arm 21 being provided with an adjustable stop 3l for adjusting the normal position of the contacts relative to the movable member 23 which is disposed as shown to engage thel spring arm 21 and move the contact 25 away from the contact 24 when the bimetallic element I6 ilexes to operate the movable member. It will be apparent that by adjusting the stop member 3|, the initial position of the contacts 24 and 25 may be adjusted to predetermine the amount of flexure of the bimetallic element I6 which will be necessary to disengage the contacts 24 and 25. Supported on the terminal member 29 and extending along the spring arm 21, I provide a guard piece 32 which serves as a stop for the spring arm 21 and also protects the contact arrangement from injury due to accidental blows.

Although any-'suitable means may be employed for producing a flow of current through the heating member I1 to heat the thermal Working parts of the relay in accordance with the heating conditions in the circuit to be protected, I prefer, in order electrically to insulate the thermal working parts of the relay from the circuit to be protected, to form the core member I3 of magnetizable material and to arrange the heating member I1 as a closed circuited secondary winding which is inductively related to a primary winding 33 supported on an insulating spool 34 surrounding the insulating cylinder 2l. Surrounding the primary winding 33, I provide an insulating cylinder 35 arranged concentrically with the insulating cylinder 2| and having its respective opposite ends abutting the base I0 and the end cap, I9 which are respectively provided with suitable positioning shoulders 36 and 31. The cylinder 35, which maybe omitted Without greatly aecting the operation of the relay, is provided with a pair of apertures 38 and 39 through which suitable connecting leads may extend from the primary Winding 33 to the circuit to be protected. Itwill be apparent that the apertures 38 and 39 also permit the escape of air from the cylinders 2D and 35, and the dow of oil thereinto.

It will be observed that this embodiment of my invention is in eilect, a combination of a current transformer and a thermal relay. Accordingly, the relay is very flexible in its application and may bc applied to the protectionof apparatus designed to operate at any value of voltage within practi- 'cal limits simply by employing a properly wound primary winding.

When the relayV is immersed in a body of oil9 sumcient oil seeps into the container substantially to fill the slot I5 in the core member I3 and when the primary winding 35 is connected in circuit with the apparatus to be protected, a. magnetic flux will be produced in the magnetizable core 'I3 which will induce a current in the closed circuited secondary winding comprising the heating member I1, the heating effect of which will be proportional to the heating effect of the current flowing in the apparatus to be protected. The heat generated in the heating member I'I is conducted therefrom to the bimetallic element, to the core member I3 and to the oil contained in the slot I5, and upon the occurrence of an overload of sunlcient magnitude and duration to endanger the apparatus to be protected, there will be suiiicient heat transferred to the bimetalllc element I6 to cause the bimetallic element to flex. When the free end of the bimetallic element I8 moves upwardly as viewed in the drawing, the plunger 23 is moved upwardly in the recess I2 to engage the spring'arm 21 and open the contacts 24 and 25.

It will be apparent now that I have provided an improved thermal relay in which the control contacts and the thermal working parts of the relay are electrically insulated from each other and from the circuit to be protected, all of the elements being immersed in oil, and in which the working parts of the relay are substantially thermally isolated from the main body of immersing oil.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto 'since many modifications may bemade and I, therefore, contempla-te by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

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

1. A thermal relay comprising a core having a slot extending axially thereof, a heating member adapted to be heated'by current ow therein comprising a conductor body closely surrounding said core and a thermo-responsive device disposed in said slot to be inuenced by said heating member. l

2. A thermal relay comprising a core having an axially extending slot therein, a heating winding closely surrounding said core, a bimetallic element disposed in said slot to be inuenced by said heating winding, and relatively movable contacts controlled by said bimetallic element.

3. A thermal relay comprising a magnetizable core having an axially extending slot therein, a closed circuited winding surrounding said core,

mea-ns for producing a magnetic flux in said core to induce a heating current in said closed circuited winding, and a thermo-responsive device disposed in said slot to be thermally iniluenced by said closed circuited Winding.

i. A thermal relay comprising a magnetizable core having` an axially extending slot therein, n single-turn closed circuited winding comprising a conductor body surrounding said core, means for producing a magnetic iiux in said core to induce a heating current in said conductor body, a bimetallic element disposed in said slot to be thermally influenced by said conductor body, and relatively movable contacts controlled by said bimetallic element. Y

5. A thermal relay comprising a primary winding, a magnetiaable core disposed within and spaced from said winding, said core having a slot extending axially thereof, a closed circulted heating winding surrounding said core in inductive relation with said primary Winding and a thermorwponsive device disposed. in solo: slot to be thermolly lnuenceol by said closed clrcuited Winsl-v 6. A thermal relay comprising e. primary Windable contacts controlled by said bimetallic ele-- ment.

t. A. thermal relay comprising walls oi thermal insulating material arranged to form a container, one of said walls having an aperture therein, relatively movable contacts supported externally of said container, means including a movable member extending through said aperture for controlling said contacts, a movable. thermo-responsive element within said container having a portion ,engaging said movable member, and means within said container for heating said thermo-responsive element tol operate said movable member.

8. A thermal relay comprising walls of thermal insulating material arranged to form a container, one of said walls having Aan aperture therein, relatively movable contacts supported externally of said container, means including a e movable member extending through said aperture for controlling said contacts, a heating member adapted to be heated by current ow therein comprising a cylindrical conductor within said container and a bimetallic element having a portion extending within said cylindrical conductor to be thermally inuenced thereby and another portion arranged to operate said movable member.

9. A thermal relay comprising walls of thermal insulating material arranged to form a container,

one of Said walls having an aperture therein, relatively movable contacts supported externally of said container, means including a movable member extending through said aperture for controlling said contacts, a bimetallic element within said container arranged to operate said ymovable member, a closed circuited heating winding within said container thermally associated with said bimetalllc element, and means disposed externally oi said container for inducing aheating current in said closed circuited winding to influence i said bimetallic element.

i0. A thermal relay comprising walls of thermal insulating material arranged to form a container, one oi said `tvalls having an aperture therein' a core within said container having a slot extending axially thereof, a heating winding surrounding said core, a movable thermo-responsive element disposed in said slot to be influenced by said heating,` winding, a movable member extending through said aperture arranged to be operated by said thermo-responsive element and relatively movable contacts supported externally ot; said container controlled by said movable member.

lli. A thermal relay comprising walls of thermal insulating material arranged to form a connosed in said slot to be thermally inuenced by --said winding, e, movable lmember extending through said aperture arranged to be operated by said bimetallic element and relatively movable contacts supported externally of said container controlled by said movable member.

l2. A thermal relay comprising walls oi thermal insulating material arranged toform a container, one of said `Walls having an aperture therein, a magnetizalole core within said container having a slot extending axially thereof, a single-turn secondary winding comprising a cons doctor body closely surrounding said core, means including a primary winding surrounding said container for producing a iiux in said core to induce a heating current in said conductor body,

a bimetallic element disposed in said slot to loe thermally influenced by said conductor body, va movable member extending through said aperture arranged to be operated by said bimetallic element and relatively movable contacts supported externally of said container controlled by said movable member.

13. A thermal relay comprising walls of thermal insulating material arranged to form a container, one of said Walls having an aperture therein, a magnetizable core Within said container having a slot extending axially thereof, a heating member comprising a cylindrical conductor surrounding said core, means'including a primary winding surrounding said container for producing a ux in said core to induce a heating current in said cylindrical conductor, a bimetallic element disposed in said slot having one end secured to said cylindrical conductor, a movable member extending through said aperture arranged to be operated by said bimetallic element and relatively movable contacts supported externally of said container controlled by said movable member.

' 14. A thermal relay comprising a base of insulatingv material having a pair of intersecting recesses therein, Walls of thermal insulating material cooperating with said base to form a container enclosing one of said recesses, a bimetallic element supported in said container with a movable portion thereof extending into said one recess, a movable member disposed in said other recess to be operated by said bimetallic element,

relatively movable contacts supported on said base adjacent said other recess to be controlled by said movable member, and means for heating said bimetallic element. f

15. A thermal relay comprising a base of thermal insulating material having a pair of intersecting recesses therein, a core supported in one of said recesses and extending outwardly from said base, said core having a slot extending axially thereof, a movable thermo-responsive element arranged in said slot with a portion thereof adjacent the intersection or' said recesses, a movable member disposed in said other recess to be operated by said thermo-responsive element, relatively movable contacts supported on said base to be controlled by said movable member, Walls of thermal insulating material cooperating with said base to enclose said core and said therino-responsive element, and means Within said enclosing walls for heating said thermo-responsive element to operate said movable member.

- 16. A thermal relay comprising a base or" insulatingl material having a pair of intersecting recesses therein, a magnetizable core supported in one of said recesses and extending outwardly from said base, said core having a slot extending axially thereof, a, bimetallic element disposed in said slot with a movable portion thereof vadjacent the intersection of said recesses, a movable inember disposed in said other recess to be operated by said bimetallic element,- relatively movable contacts supported on said base to be controlled by said movable member, Walls of insulating material cooperating with said base to enclose saidcoreand said bimetallic element, agclosed circuited winding surrounding said core'vvithin said enclosing walls, and means disposed externally of said enclosing Walls for producinga nur: in .said magnetizable 'core to induce a heating current in said closed circuited Winding whereby saidbimetallic element is heated to able member. f

operate said moving end of said accingo Vmovable member disposed in said other recess to be operated by said bimetallic element, relatively movable contacts supported on said base to be controlled by said movable member, Walls of thermal insulating material cooperating vwith said base to enclose said core and said heating member, and means including a primary Winding surrounding said enclsing Walls for producing a flux in said magnetizable core to induce a heating current in said heating member whereby said bimetallic element is heated to operate said movable member. f

i8. A thermal relay comprising a base of thermal insulating material having a pair of interseating recesses therein, a magnetizable core supported in one of said recesses and extending out- Wardly from said base, a pair of spaced concentric cylinders of insulating material surrounding v said core and having their adjacent ends abutting said base, a cap member of thermal insulating material threadedly supported on the extendcore abutting the opposite adjacent ends of said spaced cylinders, said cap and l said base being provided with concentric shoulders for positioning said spaced cylinders to form a container having inner and outer spaced Walls, a primary winding disposedybetween said spaced walls surrounding said inner Wall, a heating member comprising a cylindrical conductor disposed Within said inner wall in inductive relation with said primary winding surrounding said magnetizable core, a bimetallic element disposed in said slot having one end directly secured to said heat- `ing member, said bimetallic element having its free end adjacentv the intersection of said recesses, a movable member disposed in said other recess to be operated by said bimetallic element and relatively movable contacts supported on said base to be controlled by said movable member.

19. ln a relay having a movable member, a movable contact biased toward said member, a second movable contact engaging said rst contact and biased in the opposite direction, the biasing force on said second contact predominatihg whereby the resultant biasing force urges said engaging contacts away from said movable member, and means including an adjustable stop member associated with said second contact for positioning said engaging contacts relative to said movable member, said movable member being arranged when operated to move said first contact tacts.

205. A thermal relay comprising a member. movable in accordance with the thermal condition of .arm predominating whereby said engaging con-y 'tacts' are biased away from said movable memy ber, and means including an adjustable stop eni against `the bias thereon to disengage said cona heating current in said closed circuited windgaging said second spring arm for positioning said engaging contacts relative to said movable member, said movable member being arranged to engage said rst spring arm to open said contacts upon the occurrence of a thermal condition predetermined by the adjustment of said stop.

21. A thermal relay adapted for oil immersed operation comprising walls of thermal insulating material arranged to form a perforate container, the degree of perforation being such as to permit said container substantially to fill with oil when said container is immersed in a body of oil, the relatively small body of oil within said container being thermally insulated from the main body of oil, a thermo-responsive device disposed within said container, a closed circuited heating winding within said container thermally related to said thermo-responsive device, and means arranged externally of said container for inducing ing to iniluence said thermo-responsive device.

22. A thermal relay adapted for oil immersed operation comprising walls of thermal insulating,

material arranged toform a perforate container, the degree of perforation being such as to permit said container substantially to ll with oil when said container is immersed in a body of oil, the relatively small body of oil within said container being thermally insulated from the main. body of oil, a bimetallic element disposed within said container, a closed circuited winding thermally related to said bimetallic element within said container, and means including a primary winding surrounding said container for inducing a heating current in said closed circuited winding thermally to influence said bimetallic element.

BENJAMIN W. JONES.

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