US2343862A - Thermal relay unit - Google Patents

Description

March 14, 194 P. M. CHRISTENSEN ,3

THERMAL RELAY UNIT Filed Jan. 4, 1941 Z m F- 5 /0 wry/10000017004111 1 70 MISULATION PEMZM 57:12:52: 275527 .5 J. W. J mist :02??

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Patented Mar. 14, 1944 THERMAL RELAY UNIT Paul M. Christensen, Newington, Conn., assignor to Colts Patent Fire Arms Manufacturing Company, Hartford, Conn., a corporation of Connecticut Application January 4, 1941, Serial No. 373,189

20 Claims. (01. zoo- 122) The invention relates to thermal relays, and the general object of the invention is to provide a thermal relay for electromagnetic motor starters, and including a quick acting switch actuated by deflection of a thermostatic element to interrupt a circuit under abnormal current conditions; and means to make the relay either automatically or manually resettable to re-establish the interrupted circuit when normal current conditions again prevail in the circuit controlled by the motor starter; the construction and arrangement being such as to provide a complete and compact thermal relay embodying the above features conveniently connectible electrically and mechanically with the motor starter and its support to provide a unitary structure.

An important feature of the invention is the provision of means for making the relay operable either automatically or manually to reset it, that is, to, re-establish an electric circuit which has been interrupted by the relay because of abnormal conditions in the circuit. The invention accomplishes this by a simple and easily operated construction and arrangement of parts on the relay casing and accessible for manipulation without in any way altering the electrical connections or disturbing the original arrangement of the parts of the relay in their assembled relation. More specifically this is accomplished by the provision of a device, simple in construction and easily assembled on the housing, which is positionable either in operative relation with respect to the movable electric contact arm of the relay, or in inoperative position in the relay casing with respect to the movable contact arm, in which positions, respectively, the relay is manually and automatically resettable as hereinafter explained in detail.

Another. important feature of the invention resides in the provision of a relatively light but extremely quick acting switch, the parts of which may be manufactured and assembled in operative relation with respect to their operating and operated mechanism cheaply and with facility.

Still another feature of the invention resides in the construction of the body or casing of the relay itself in regard to its adaptability as a unitary part of an electric motor starter, as well as from the structural standpoint. With regard to the latter, the details of the construction and arrangement of the casing and the manner of- In the accompanying drawing I have shown thenow preferred embodiment of the invention, but it will be understood that the drawing is intended for illustrative purposes only and is not to be.

construed as defining or limiting the scope of the invention, the claims forming a part of this specification being relied upon for that purpose.

In the drawing:

Fig. 1 is a front elevational view of an electromagnetic motor starter showing two thermal relays embodying the present invention mounted on the base supporting the motor starter, the casing cover being broken away; and one of the thermal relays being shown in section taken on the line l--l of Fig. 2;

Fig. 2 is a sectional view taken on the line 2-2 of Fig. 1;

Fig. 3 is a sectionalview taken on the line 3-3 of Fig. 1;

Fig. 4 isv a sectional view taken on the line 4--4 of Fig. '7; showing the switch in open circuit position, and the relay operable as automatically resettable.

Fig. 5 is a sectional view similar to Fig. 4, showing the switch in closed circuit position, and the relay operable as manually resettable;

Fig. 6 is a'sectional view similar to Fig. 5 showing the switch in open circuit position and held against closing the circuit by the manually operable reset means;

Fig. '7 is a view taken on the line 11 of Fig. 1 and showing the relay as being arranged to'operate as automatically resettable;

Fig. 8 is a sectional view taken on the line 8-8 of Fig. 5;

Fig. 9 is a sectional view similar to Fig. 8 showing the parts in their relative positions of Fig. 6; and

Fig. 10 is a detail view showing the switch operating link in plan and the switch lever in section on an enlarged scale.

Referring to the drawing and particularly to Figs. 1 and 2 thereof, the numeral l0 designates a casing in which a unitary electro-magnetic motor starter and thermal relays embodying the present invention is housed. The electro-magnetic motor starter and thermal relays are mounted on a base II, and the base is secured to the bottom of the casing III by suitable means such as screws i2, only one of which is shown in the drawing. The motor starter includes a stationary insulating contact base it which is shown fastened to the base II by screws l4 which extend therethrough and engage in screw threaded openings in the base II.

A frame II is statlonarily mounted on the base H by suitable means, not shown, in spaced relation to the stationary insulating contact base (I, and houses the electro-magnet of the motor starter. The coil ll of the electro-magnet is shown held against accidental movement in its housing I! by a removable yoke member H, which is not shown nor described in detail in this application since it is not a part of the present invention. The electro-magnet is adapted to reciprocate an armature It. To afford easy guided movement to the armature, it is suitably attached to a carrier frame H, which is not shown nor described in detail in this application, but which is slidably supported in the frame IS. A movable insulating contact carrier is attached to the movable frame I! for reciprocating movement in the space between the stationary contact base I! and the fixed frame or electro-magnet housing II to bring contacts 2| into bridging relation with respect to contacts 22 on the stationary insulating base II, when the armature J! is attracted by the electro-magnet and causes frame I! and carrier 28 to move. Obviously when the armature is released it drops and causes carrier 20 and contacts 2| to move away from contacts 22.

A push button control station 23 is convenlently mounted on the top 01' the electro-magnet housing I5 with the "start" and "stop push buttons exposed through the cover of the casing for manual operation; and suitable connection bindin! P sts 24 are provided for making desired circuit connections.

Figs. 1 and 2 of the drawing show two thermal relays, designated generally by the numeral 25, and embodying the present invention, mounted on the base II at opposite sides of the frame It. The relays are identical in construction but reversed as to position. Only one of the relays will be described, the reason for showing two relays being to illustrate a complete actual magnetic motor starter unit adapted to control different circuits. Each relay body or casing is shown as comprising a relatively thick part or block 28 of molded insulating material, and a. plate 21 of molded insulating material. The parts 26 and 21 of the casing are separableaipon removal of a screw, not shown, which extends through the plate 21 and engages in a screw threaded opening 28 (Fig. 7) in the block. The opening 28 is located at the bottom of a recess 29 which receives a correspondingly shaped projection on the plate 21 and through which the screw extends. Each casing 25, with the mechanism of the thermal relay switch assembled thereon is positioned on the base II with the plate 21 against frame l5 of the magnetic motor starter and with openings 30 in alignment with screw threaded openings in the sides of theframe l8. Screws 3| are then inserted through the openings 30 and threaded into the openings in the frame I5 to hold the relays in their established places as part of the unitary structure of the magnetic motor starter.

The relay casing part 26 is substantially rectangular in form, and has an outwardly extending projection I3 on its top. Two of the top corners one at each side of the projection 31, are cut away to provide shoulders 34 for reception of stationary electrical terminal members or contact plates 35 and 38 which receive the terminal binding posts 35' and 34' to electrically connect the relay switch, hereinafter described, to the electro-magnet of the motor starter. The arm of the contact plate 35 which receives the binding post 35 overlies one of the shoulders 34, and the other arm of the contact plate is flatly disposed against the face of the casing part 28 at one end thereof. The plate 38 is similarly mounted on the other shoulder 34, and will be hereinafter described more in detail in connection with the switch mechanism. When the plate 21 is attached to the part 28 the structure of the casing then provides recesses at the cut away corv ners and shoulders 34 in which the binding posts 35', 36' are located (Fig. 1). The relay casing part 26 is open at its front, and a removable closure plate 31 forms, in conjunction with a transverse partition plate 38 and walls of the casing, a chamber to receive and house an electric resistance unit and a bimetallic thermostatic element.

The construction of the electric resistance unit does not form part of the present invention, and the description of the one illustrated will be general, since various types of electric resistance units can be employed. In the drawing (Figs. 2 and 8), the resistance unit comprises a plate 39 of insulating material supporting a grid 40, the terminals of which are looped around eyelets 4| on the insulating plate 39. The plate 3!! partially overlies and thus covers a portion of a notch in the top of the casing part 26 through which the grid is insertible into and removable from the casing 25. The eyelets 4| engage or rest on the tops of stationary electric contact plates 42 which are secured to the top of the casing by any suitable means. Screws or terminals 43 engage threaded openings in the contact plates 42 and the heads of the screws engage the tops of the eyelets 4| through which the screws extend to detachably mount the electric resistance unit in operating position-in the relay casing. Binding posts 44 on the stationary contact plates 42 are provided for electrically connecting the resistance unit in electric circuits which the thermal relay and motor starter are to control.

The thermostatic element which operates the switch hereinafter described, comprises a bimetallic plate 45, one end of which is rigidly secured to a bracket 46 in any suitable manner. The bracket 46 is substantially Ushaped, and a screw 41 is threaded through openings in the arms of the bracket for calibrating purposes in properly locating the bimetallic plate 45 relative to the grid 40 in its operative P sition in casing 25. The bracket has an extension 48 (Fig. 2) which receives screws 49 extending through the casing part 26 to firmly but detachably secure the bracket to the casing and maintain the bimetallic plate, in its normal condition, in properly adjusted relation with respect to the grid 40, so that the bimetallic plate will be deflected to operate the switch, about to be described, to interrupt the circuit when abnormal conditions therein cause the resistance unit to be overheated.

Although the grid 40 is shown in the drawing as being positioned in front of the bimetallic plate 45 in the said casing chamber, this arrangement can be reversed, that is, the bimetalaasaaea lic plate can be positioned in front of the grid because the grid is removable from the top oi the casing independently of the bimetallic plate. Of course, under such reversed arrangement the bimetallic plate would be secured to its supporting bracket with its other face confronting the grid to obtain deflection of the plate in the same direction as illustrated in the drawing to properly operate the switch without changing or altering the structure presently described.

The bimetallic plate 45 has a tongue 56 on its free end, and the tongue extends through a slot in the reduced portion 52 of a slide or link in the nature of a strip of insulating material,

' to detachably connect the bimetallic plate and slide. Obviously, movement of the bimetallic plate during deflections under thermal conditions to which it is subjected in the relay casing will impart movements to the slide or link. The casing part 26 is provided with channels 58 (Fig. 7) which receive the longitudinal edges of the enlarged portion 54 of the slide or link to support it and guide it during its movements. The reduced portion 52 of the slide or link extends through a slot 55 (Fig. 2) in the partition plate 38 in casing part 26, and this arrangement also assists in supporting and guiding the slide or link.

It will be noted, (Figs. 4-9) that a chamber 56 is provided in the rear of casing 25 longitudinally thereacross being formed by walls of the part 26, the partition plate 38, and the casing plate 21, to house the switch mechanism; and the enlarged portion 54 of the slide is located transversely across the chamber 56 to actuate the lever 51 of the quick action switch. The switch lever 51 is preferably formed from a thin strip of metal the central area of which is struck-up to impart rigidity to the strip, the struck-up area or hump being designated by the numeral 58. The provision of the struck-up area 58also stabilizes the lever during its working movements. The area 58 is located, as shown best in Fig. 10, through a slot 59 in the portion 54 of the slide, and the slot 58 has a straight side and a convex side. The hump or struck-up area 58 engages the convex side of the slot while the straight portions of the lever 51 at the sides and base of the struck-up portion 58 engage the straight side of the slot, thus providing a threepoint mechanical contact between the slide and lever 51, which rocks relative to the slide during actuation thereof. The lever 51 has a tongue 60 extending from one of its ends into an opening in the bottom of the trough of a substantially V-shaped saddle 6|, which is seated in a recess provided therefor in the wall of the casing part 26 at one end of the chamber, 56, serving to fulcrum said end of the lever. The other end of the lever 51 is notched for reception of one end of a substantially U-shaped over-center spring 64, the other end of which is similarly arranged in the notched end of a movable electrical contact arm 65 to mechanically connect the switch and movable electric contact arm for operation in a manner hereinafter described in detail.

The movable electric contact arm comprises a resilient strip of conducting material having one the casing 25 has an arm 61 arranged along a portion of chamber 56 in front of the switch, and an electric contact point 68 is secured to the inner face of the arm 61 adjacent its end. The movable contact arm has a similar contact point 68 secured to its outer face adjacent its end which is connected to the overcenter spring 64 and in alignment with contact point 66. The movable contact arm 65 is biased to closed circuit position, that is, to normally maintain the contact points 68 and 69 in engagement so that the relay will not interrupt the circuit in which it is connected so long as normal conditions exist in the circuit, but upon creation of abnormal conditions the thermostatic plate 45 will be deflected by the grid 46 and move slide 54 which in turn moves lever 51 from the position of Fig. 1 to the position shown in Fig. 4. This causes shifting movement of the overcenter spring 64 to move contact arm 65 and the contact point 66 thereon away from contact point 68, breaking the circuit. If there is nothing, other than the abnormal current-conditions which heat the grid and cause deflection of the bimetallic plate which causes opening of the circuit by operation of the switch as described, to prevent closing movement of biased arm 65 the movable contact will automatically be returned to closed circuit position when normal condition in the circuit again prevails and permits cooling of the bimetallic element and return to its original position, aashould be obvious. However, there are conditions under which it is desirable to maintain the switch and movable electric contact arm from re-establishing or closing the circuit automatically, and making it necessary to effect reclosing of the circuit by hand operation, and the present invention provides means for making the relay either automatically or hand resettable as desired, which feature will now be described.

The casing parts 26 and 21 have complemental faces which interfit .to form a housing for the stationary contact plates 35 and 36, movable contact arm 65, and reset control plunger 10 and its associated parts.

The movable contact arm 65, a thin resilient strip of metal, previously described in part, has a curved substantially U-shaped portion 1| intermediate its ends arranged in alignment with the plunger 16, the said U-shaped portion 1i to accommodate and cooperate with the plunger as will be pointed out in detail hereinafter. The complemental faces of the casing parts 26 and 21 each have corresponding grooves 12 formed therein adjacent their tops to form a chamber 13 when assembled. A coil spring 14 is mounted on the plunger stem 10 and partly compressed between a fixed collar 15 on the plunger stem and the. bottom of chamber 13 to press against the collar and urge the plunger outwardly. A head 16 is provided on the outer end of the plunger stem for engagement by a finger of the hand when turning the plunger to establish it in operative and inoperative positions when making the relay either manually or automatically resettable. A reset button 11 is conveniently provided on the cover ill on the casing l0 adjacent the push button control station 23. A spring plate 11* is rigidly connected at or near its bottom edge to the inner face of the front cover Ill". The plate extends upward from its points of attachment to the cover and its front face is in position to be engaged by the rear end of the button 11 as clearly shown in Figs. 2 and 3. The spring plate I'! has two arms, one of which designated as II is shown in Fig. l. The other arm is broken away but is similar as to shape and position except that it is left-handed instead of righthanded The upper end of the arm ll is directly in front of the corresponding head 16 at the right and the other arm is directly in front of the similar head at the left. When the plungers are in their forward positions to bring each head 16 into the position shown by dot-anddash lines in Fig. 3, the corresponding arms on the plate ll' are positioned to engage the heads to move the plungers inward or rearward. It will be apparent that with the plungers in their forward positions, they can be moved simultane ously rearward by pressing on the button ll to flex the spring plate 11 rearward, the said spring plate through its respective arms engaging and moving the respective plungers.

Each of the relay casing parts 25 and 2'! also has a groove 18 between the chambers "l3 and 55 which afford, in conjunction with opening '18 at the top of the casing, stabilized guided movement to the plunger 10, as best shown in Figs. 8 and 9. Below the chamber 56 of the casing, and the U- shaped port-ion ll of the contact arm 65, the cas ing parts 26 and 21 have grooves which provide a socket or chamber 80 in which the lower end of the plunger is located. Lugs 8| at the topof chamber 80 and at one side thereof are situated to be engaged by the top edge or shoulasr of a lug 82 radially projecting from the lower end of the plunger stem to hold the plunger in the inoperative position shown in Fig. 7, at which time the movable contact arm 65 is freely movable to open and closed circuit positions relative to the fixed contact 68 in accordance with movements of the bimetallic plate 45, as previously explained.

As shown best in Fig. 8, the bottom of U-shaped portion ll 01' the movable contact arm when in closed circuit position is in a plane substantially parallel to but spaced from a plane in which the front wall of socket B is located and along which the lug 82 of the plunger moves when the relay is used as manually resettable. lhe top edge or shoulder of lug 82 is in engagement withqthe confronting edge of the contact arm when in closed position, as shown in Figs. and 8. At this time the plunger spring is exerting force against the collar 15, which is sufllcient to maintain the locking engagement between the movable contact arm and shoulder of lug 82, as shown in Fig. 8, so long as the electric circuit remains closed. As soon as the circuit is interrupted; however, the snap-action switch moves the movable contact arm back and clear of the shoulder of the lug 82, at which moment the spring H expands and forces the plunger up in the casing to the position of Fig. 9, where the lug 82 sufficiently overlaps the bottom of U-shaped portion H to block circuit closing movement of the movable contact arm. Under the then prevailing conditions, whether normal or abnormal in the circult, closing of the circuit cannot be accomplished until the plunger is suiliciently depressed manually by pressure on its head 16 to move the lug 8! beyond and clear of U-shaped portion ll of the movable contact arm 55, to permit the arm 65 being moved by the thermal relay switch mechanism to the position of Fig. 8. Obviously, when downward pressure on the plunger is released the spring I4 urges it upward and it is arrested in its upward movement by engagement of the shoulder of lug 82 against the confronting edge of the movable contact arm portion 1|.

Opening or rearward movement of the movable contact arm 85 is limited by stops or lugs 88 located in the chamber 58 of the casing 25 behind said arm, and by similar lugs 84 in the chamber behind the switch lever 51 for abutment thereby. Closing or forward movement of the same parts is limited by engagement of contact points 88 and 69.

It should be apparent from the foregoing that in order to make the relay automatically resettable the plunger 70 is depressed as far as it can move downwardly against spring I l and given a quarter turn to place the lug 82 in locked relation with the lugs 81 in chamber so that only the stem of the plunger extends across the U-shaped portion H of movable contact arm 65 and spring 14 is inactive. The stem of plunger 10 is then disposed across U-shaped portion ll but sufllcien'tly clear or spaced therefrom to not interfere with operation of the contact arm 65 in either direction of its circuit making and breaking movements. To make the relay manually resettable the plunger is given a quarter turn in reverse direction to establish the lug 82 in operative relation "with the movable contact arm 65 as previously explained. -The head 16 of the plunger is pointed at one end to conveniently serve as an indicator as to which of its selective positions, operative or inoperative, the plunger occupies, so that the operator will readily know whether the relay is manually or automatically resettable.

What I claim is:

l. A thermal relay for use in an electric circult and adapted to break the circuit upon the occurrence of abnormal current conditions in the circuit, said relay comprising in combination, a base, terminal members thereon by which the relay is adapted to be connected in an electric circuit, relatively movable electric contacts re spectively electrically connected to one of said terminals, a thermally responsive member, means operatively connecting said thermally responsive member to one of said electric contacts and said thermally responsive member normally serving upon the occurrence of variations in current in the circuit to automatically actuate said connecting means and said one electric contact to make and break said circuit, and control means movably mounted with respect to said base and having a portion free from said means connecting said one contact and thermally responsive member and adapted to be selectively set in one position to permit automatic functioning of said thermally responsive member to relatively move the electric contacts to make and break the circuit and to be set in another position to engage said means connecting said one contact and thermally responsive member and prevent automatic engagement of said electric contacts to make the circuit following a breaking of the same.

2. A thermal relay for use in an electric circuit and adapted to break the circuit upon the occurrence of abnormal current conditions in the circuit, said relay comprising in combination, a base, terminal members thereon by which the relay is adapted to be connected in an electric circuit, an arm movably mounted on the base, relatively movable electric contacts respectively electrically connected to one of said terminals, one 01 said contacts being carried by said movable arm, a thermally responsive member operatively connected to said movable arm and normally serving upon the occurrence of variations in current in the circuit to automatically actuate said electric contact carried by said movable arm.

responsive member to actuate said movable arm and contact thereon to make and break the circuit and to be set in another position to engage said movable arm to prevent automatic movement of the contact thereon into circuit making position following a breaking of the same.

3. A thermal relay for use in an electric circuit and adapted to break the circuit upon the occurrence of abnormal current conditions in the circuit, said relay comprising in combination, a base, terminal members thereon by which the relay is adapted to be connected in an electric circuit, an arm movably mounted on the base, relatively movable electric contacts respectively electrically connected to one of said terminals, one of said contacts being carried'by said movable arm, a thermally responsive member operatively connected to said movable arm and normally serving upon the occurrence of variations in current in the circuit to automatically actuate said electric contact carried by said movable arm to make and break said circuit, and control means movably mounted with respect to said base and comprising a member having a projection thereon adapted to be selectively set in one position to permit automatic functioning of said thermally responsive member to actuate said movable arm and contact thereon to make and break the circuit and to be set in another position to permit said projection on said member to engage said movable arm to prevent automatic movement of the contact thereon into circuit making position following a breaking of the same.

4. A thermal relay for use in an electric circuit and adapted to break the circuit upon the occurrence of abnormal current conditions in the circuit, said relay comprising in combination, a base, terminal members thereon by which the relay is adapted to be connected in an electric circuit, an arm movably mounted on the base, relatively movable electric contacts respectively electrically connected to one of said terminals, one 01 said contacts being carried by said movable arm, a thermally responsive member operatively connected to said movable arm and normally serving upon the occurrence of variations in current in the circuit to automatically actuate said electric contact carried by said movable arm to make and break said circuit, and control meansmovably mounted with respect to said base and comprising a member having a projection thereonadapted to be selectively set in one position to permit automatic functioning of said thermally responsive member to actuate said movable arm and contact thereon to make and break the circuit and to be set in another position to permit said projection on said member to engage said movable armto prevent automatic movement of the contact thereon into circuit making position following a breaking of the same, said control member also being movable to disconnect the projection thereon from engagement with said arm and permit automatic movement of the contact thereon to circuit closing position following said disconnection.

5. A thermal relay for use in an electric circuit and adapted to break the circuit upon the occurrence of abnormal current conditions in the circuit, said relay comprising in combination, a base, terminal members thereon by which the relay is adapted to be connected in an electric circuit, an arm movably mounted on the base, relatively movable electric contacts respectively electrically connected to one of said terminals, one of said contacts being carried by said movable arm, a thermally responsive member operatively connected to said movable arm and normally serving upon the occurrence of variations in current in the circuit to automatically actuate said electric contact carried by said movable arm to make and break said circuit, a control member movably mounted with respect to said base and having a projection thereon adapted to be selectively set in one position to permit automatic functioning of said thermally responsive member to actuate said movable arm and contact thereon to make and break the circuit and to be set in another position to permit said projection on said member to engage said movable arm to prevent automatic movement of the contact thereon into circuit making position following a breaking of the same, and a spring normally engaging said control member and biasing the projection thereon in a direction to engage said movable arm following a breaking of the circuit.

6. A thermal relay for use in an electric circuit and adapted to break the circuit upon the occurrence of abnormal current conditions in the circuit, said relay comprising in combination, a base, terminal members thereon by which the relay is adapted to be connected in an electric circuit, an arm movably mounted on the base,

relatively movable electric contacts respectively electrically connected to one of said terminals, one of said contacts being carried by said movable arm, a thermally responsive member operatively connected to said movable arm and normally serving upon the occurrence of variations in current in the circuit to automatically actuate said electric contact carried by said movable arm to make and break said circuit, a control member movably mounted with respect to said casing and having a projection thereon adapted to be selectively set in one position to permit automatic functioning of said thermally responsive member to actuate said movable arm and contact thereon to make and brake the circuit and to be set in another position to permit said projection on said member to engage said movable arm to prevent automatic movement of the contact thereon into circuit making position following a breaking or the same, and a spring normally engaging said control member and biasing the projection thereon in a direction to engage said movable arm following abreaking of the circuit, said control member being movable against the force of said spring to remove the projection from engagement with said movable arm and permit automatic movement of the contact thereon to circuit closing position following said disconnection.

7. A thermal relay for use in an electric circuit and adapted to break the circuit upon the occurence of abnormal current conditions in the circuit, said relay comprising in combination, a base, terminal members thereon by which the relay is adapted to be connected in an electric circuit, a snap-acting toggle operatively mounted in said base and including a plurality of links and resilient means operatively connected thereto, relatively movable electric contacts respectively electrically connected to one oi.said terminals, one of said electric contacts bein mounted on one of the component parts of and movable by said toggle, a thermally responsive member operatively connected to one of the component parts of said toggle and normally serving upon the occurrence of variations in current in the circuit to automatically actuate said toggle to move the contact carried thereby to make and break said circuit, and control means movably mounted with respect to said base and adapted to be selectively set in one position to permit automatic functioning of said thermally responsive member to relatively move the electric contacts to make and break the circuit and to be set in another position to engage one component part of the toggle to prevent automatic engagement of said electric contacts to make the circuit following a breaking of the same.

8. A thermal relay ior use in an electric circuit and adapted to break the circuit upon the occurrence of abnormal current conditions in the circuit, said relay comprising in combination, a base, terminal members thereon by which the relay is adapted to be connected in an electric circuit, a snap-acting toggle operatively mounted on said base and including a plurality of links and resilient means operatively connected thereto, one 01' said links being resilient, relatively movable electric contacts respectively electrically connected to one of said terminals, one of said electric contacts being mounted on one of the component parts of and movable by said toggle, a thermally responsive member operatively connected to one of the component parts of said toggle and normally serving upon the occurrence of variations in current in the circuitto automatically actuate said toggle to move the contact carried thereby to make and break said circuit, and control means movably mounted with respect to said base and adapted to be selectively set in one position to permit automatic functioning of said thermally responsive member to relatively move the electric contacts to make and break the circuit and to be set in another position to engage one component part of the toggle to prevent automatic engagement of said electric contacts to make the circuit following a breaking of the same.

9. A thermal relay for use in an electric circuit and adapted to break the circuit upon the occurrence of abnormal current conditions in the circuit, said relay comprising in combination, a base, terminal members thereon by which the relay is adapted to be connected in an electric circuit, a snap-acting toggle operatively mounted on said base and including a plurality of links and resilient means operatively connected thereto, relatively movable electric contacts respectively electrically connected to one of said terminals, one of said electric contacts being mounted on one of the component parts of and, movable by said toggle, a thermally responsive member operatively connected to one of the component parts of said toggle and normally serving upon the occurrence of variations in current in the circuit to automatically actuate said toggle to move the contact carried thereby to make and break said circuit, and a control aember movably mounted with respect to said base and having a projection thereon adapted to be selectively set in one position to permit automatic functioning of said thermally responsive member to make and break the circuit and to be set in another position to permit said proiection on said member to engage one component part of the toggle to prevent automatic engagei ment of said electric contacts to make the circult following a breaking of the same.

10. A thermal relay for use in an electric circuit and adapted to break the circuit upon the occurrence of abnormal current conditions in the circuit, said relay comprising in combination, a base, terminal members thereon by which the relay is adapted to be connected in an electric circuit, a snap-acting toggle operatively mounted on said base and including a plurality of resilient means operatively connected thereto, relatively movable electric contacts respectively electrically connected to one of said terminals, one of said electric contacts being mounted on one of the component parts of and movable by said toggle, a thermally responsive member operatively connected to one of the component parts of said toggle and normally serving upon the occurrence of variations in current in the circuit to automatically actuate said toggle to move the contact carried thereby to make and break said circuit, a control member movably mounted with respect to the base and having a projection thereon adapted to be selectively set in one position to permit automatic functioning of said thermally responsive member to make and break the circuit and to be set in another position to permit said projection on said member to engage one component part of the toggle to prevent automatic engagement of said electric contacts to make the circuit following a breaking of the same, and a spring normally engaging said control member and biasing the projection thereof in a direction to engage said one component part of the toggle following a breaking of the circuit.

11. A thermal relay for use in an electric circuit and adapted to break the circuit upon the occurrence of abnormal current conditions in the circuit, said relay comprising in combination, a base, terminal members thereon by which the relay is adapted to be connected in an electric circuit, a snap-acting toggle operatively mounted on said base and including a plurality of resilient means operatively connected thereto, relatively movable electric contacts respectively electrically connected to one of said terminals, one of said electric contacts being mounted on one oi the component parts of and movable by said toggle, a thermally responsive member operatively connected to one of the component parts of said toggle and normally serving upon the occurrence of variations in current in the circuit to automatically actuate said toggle to move the contact carried thereby to make and break said circuit, a control member movably mounted with respect to the base and having a projection thereon adapted to be selectively set in one position to permit automatic functioning of said thermally responsive member to make and break the circuit and to be set in another position to permit said projection on said member to engage one component part of the toggle to prevent automatic engagement of said electric contacts to make the circuit following a breaking of the same, and a spring normally engaging said control member and biasing the projection thereof in a direction to engage said one component part of the toggle following a breaking of the circuit, said control member being movable against the force of said spring to remove the projection from engagement with said one component part of the toggle and permit automatic engagement of said electric contacts to make the circuit following said disconnection.

12. A thermal relay for use with electro-magnetic electric motor starters comprising a body or housing of insulating material, said body including complemental parts forming a housing, an electrical resistance unit housed in one part, electric terminals on said part by means of which said resistance unit is adapted to be connected in an electric circuit including the motor starter and devices controlled thereby, a thermostatic element housed in said part and responsive to changes in temperatures occurring in the resistance unit, electric terminal members on said one part by means of which said relay is adapted to be connected in circuit with the electro-magnet of the motor starter, a movable electric contact normally bridging and electrically connecting said terminal members, a switch in said one part mechanically operable by movement of said thermostatic element to move said movable contact out of co'htacting relation with one of said terminal members and interrupt the circuit, the second of said complemental parts of the body inter- ,-;'-'=fitting with the first part to complete the housing at the side of the body where the movable contact is located, and manually operable means located between said parts and selectively positionable to control the movable contact whereby the relay must be manually reset in one position of said means and is automatically reset in another position of said means.

13. A thermal relay including a casing having two chambers therein, a thermostatic element mounted in one of the chambers, an electric resistance unit adapted to be connected in a circuit, said electric resistance unit being mounted in said chamber to cause deflection of the thermostatic element due to variations in current conditions in said circuit, electric terminal members on the casing, a movable electric contact member in the other chamber of the casing, a switch in said other chamber operable to position said movable contact in closed and open circuit positions relative to the terminal members, means mechanically connecting the thermostatic element and switch to operate the switch and effect movements of the movable contact member relative to one terminal member to open and close said circuit in accordance with conditions aiiecting the thermostatic element, and means on the casing selectively positionable in operative and inoperative positions with relation to the movable contact whereby the relay may operate as manually or automatically resettable as desired.

14. A thermal relay including a casing having two chambers therein, a thermostatic element mounted in one of the chambers, an electric resistance unit adapted to be connected in a circuit, said electric resistance unit being mounted in said chamber to cause deflection of the ther- 4 mostatic element due to variations in current conditions in said circuit, electric terminal members on the casing, a movable electric contact member in the other chamber of the casing, a switch in said other chamber operable to position said movable contact in closed and open circuit positions relative to the terminal members, a link extending from one chamber into the other having guided reciprocating movement in the casing and mechanically connecting the thermostatic element and switch to operate the switch and effect movements of the movable contact member relative to one terminal member to open mostatic element due to variations in current conditions in said circuit, electric terminal members on the casing, a movable electric contact member in the other chamber of the casing, a switch in said other chamber operable to position said movable contact in closed and open circuit positions relative to the terminal members, means mechanically connecting the thermostatic element and switch to operate the switch and effect movements of the movable contact member relative to one terminal member to open and close said circuit in accordance with conditions affecting the thermostatic element, a manually operable spring pressed plunger in the casing adapted to automaticall block circuit closing movement of the movable contact by said switch except upon manual operation of the plungenand means to position said plunger in the casing relative to the movable contact whereby the switch can be automatically operable by th thermostatic element to close and open the circuit.

16. A thermal relay comprising a casing composed of inter-fitting parts having opposed complemental portions forming a guideway, terminal members mounted on one of said parts and adapted to be connected in an electric circuit, a movable electric contact electrically connected to one of said terminal members, a thermally responsive mechanism operably connected to said movable electric contact and serving upon the occurrence of variations in current condition to actuate said movable electric contact to make and break said electric circuit, and a manually operable control member for the movable contact mounted between said opposed complemental portions of said casing for guided movement with respect to said movable electric contact.

17. A thermal relay comprising a casing composed of interfitting parts having opposed complemental portion forming a, chamber and a guideway, terminal members mounted on one or said parts and adapted to be connected in an electric circuit, a movable electric contact electrically connected to one of said terminal members, a thermally responsive mechanism operably connected to said movable electric contact and serving upon the occurrence of variations in current conditions to actuate said movable electric contact to make and break said electric circuit, a manually operable plunger mounted between said opposed complemental portions of said casing for guided movementwith respect to said movable electric contact, and a spring mounted in said housing and engaging said plunger to urge it in one direction.

18. A thermal relay comprising terminal members adapted to be connected in an electric circuit, a movable electric contact electricall connected to one of said terminal members, a thermally responsive mechanism operably connected to said movable electric contact and serving upon the occurrence of variations in current conditions to actuate said movable electric contact to make and break said electric circuit, a manually operable plunger having an engageable element Iorcontrolling the. movable contact, a spring coacting with said manually operable plungerto normally urge it in one direction} and a casing composed of lnterfltting parts and having opposed complemental portions forming a housing for said spring and a guideway for said manually operable plunger and also having an engageable element with which said engaseable element on said plunger is adapted to co-engage to hold said manually operable plunger in a selective predetermined position against the force of said spring. 19. In combination with an encased thermal relay including terminals by which it may be connected in an electric circuit and also including relatively movable electric contacts and thermally responsive means operatively connected to one of said electric contacts to move the same relatively to the other electric contact in response to variations in current in the circuit, a control member partially extending outward of the thermal rela case and selectively movable to a plurality of positions, means connected to said control member and operative in one position of said control member to render the thermally responsive means automatically operative upon the recurrence oi normal conditions in the circuit to close said contacts and said means also being operative in another position or said control member to prevent the closing or said contacts upon recurrence or normal conditions in the circuit until said control member i manual- 1y moved to a reset position, and means on said outward extending portion oi said control member to readily indicate exterior]? or said case in which position the means on said control member is disposed.

20. In combination with an encased thermal relay including terminals by which it may be connected in an electric circuit and also including relatively movable electric contacts and thermally responsive means operatively connected to one or said electric contacts to move the same relatively to the other electric contact in response to variations in current in the circuit, an elongated control member partially extending outward of the thermal relay case and mounted for longitudinal movement and also being axially rotatable and selectively disposable in a plurality of positions, means connected to said control member and operative in one position of said control member to render the thermally responsive means automatically operative upon the recurrence of normal conditions in the circuit to close said contacts and said means also being operative in another position or said control member to prevent the closing of said contacts upon recurrence of normal conditions in th circuit until said control member is manually moved longitudinally thereof to a reset position, a manually engageable member carried by the outward extendin portion of said control member and by which it is longitudinally movable to said reset position and also axially rotatable to said plurality of positions, and indicating means carried by said manually engageable member to readily indicate exteriorly of said case in which position the means on said control member is disposed.

PAUL M. CHRISTENSEN.

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