US2574093A - Adjustable trip - Google Patents

Description

W. H. EDMUNDS ADJUSTABLE TRIP NCDV. 6, 31951 2 SHEETSSHEET 1 Filed April 8, 1949 ZNVEN TOR. V104 A //W Harm .0 fww/vovg Nov 11951 H EDMUNDS 2,574fl93 ADJUSTABLE TRIP Filed April 8, 1949 2 SHEETSSHEET 2 @W N M Attmzey Patented Nov. 6, 1951 ADJUSTABLE TRIP William Harold Edmunds, Havertcwn, Pa as= signer to l-T-E Circuit Breaker Ccmpany, Philadelphia, Pa, a corporation of! Pennsylvania Application April 8, 1949, Serial No. 36,135

(Cl. 2ll88) 4 Claims. Z1

My present invention relates to adjustable instantaneous and time delay tripping mechanisms for circuit breakers, and more particularly to an arrangement of a combined thermal magnetic tripping device for a circuit breaker so that the air gap of the instantaneous magnetic tripping portion of the device and the trip point of the thermal element of the device may be readily adjusted from outside the breaker casing without the necessity for opening the breaker casing and without the need for special tools of any kind.

It is, of course, well known that a variation in the air gap between the armature and magnet of a tripping device will result in the variation of the tripping point of the circuit breaker.

Likewise, an adjustment of the position of the thermal member or an adjustment of the mechanical force, such as a spring which the thermal member must overcome in order to trip, will result in variation of the time delay tripping of a thermal magnetic breaker.

Heretofore, however, such adjustments, especially in the small circuit breaker field, were factory made and were not subject to variation in the field, except by opening the casing or housing of the circuit breaker and changing the relative position of the elements therein.

My invention is directed to a simplified means for adjusting the air gap between the armature and the magnet and for adjusting the tripping position of the thermal element of the tripping device from outside the case without the necessity for opening the casing or housing of the circuit breaker and tampering with the interior thereof.

Essentially, my invention contemplates the mounting of the armature of the magnet in such a manner that by rotation of a simple member extending outside the casing, the armature may be moved closer to the magnet to decrease the air gap or further from the magnet to increase the air gap.

In order to accomplish this result, a simple rotatable cam accessible for operation from the outside of the circuit breaker bears against an element connected to the armature. The rotation of the cam moves the element which is connected to the armature and hence the armature itself closer to the magnet; rotation of the cam in an opposite direction permits the armature biasing means which normally maintains the armature away from the magnet to withdraw the armature from the magnet.

Also, my novel device contemplates a rotatable element accessible from outside the circuit break= er and operable either to increase the compression of a spring against which the thermal element must operate in order to trip the circuit breaker or to increase the degree of engagement of the thermal element with the latch within the circuit breaker.

The primary object of my invention, therefore, is the provision of novel means accessible from outside the circuit breaker for adjusting the air gap between the magnet and armature of an instantaneous tripping device.

Another object of my invention is the provision of novel means accessible from outside the casing of the circuit breaker for adjusting the tripping point of a thermal unit of a time delay tripping device in a circuit breaker.

Another object of my invention is, in a combined thermal magnetic tripping device, apparatus operable from outside the casing of the circuit breaker for adjusting the air gap of the magnetic element of the tripping device.

Another object of my invention is, in a thermal magnetic tripping device, the provision of novel means operable from outside the breaker casing for adjusting the tripping point of the thermal device.

Another object of my invention is, in a combined thermal magnetic tripping device, means operable from outside the circuit breaker casing for adjusting the air gap of the magnetic element of the tripping device and the tripping point of the thermal element of the tripping device.

The foregoing and many other objects of my invention will become apparent from the following description and drawings in which Figure 1 is a side elevation partly broken away of a circuit breaker embodying my novel adjustable thermal magnetic tripping device.

Figure 2 is a view partly in cross-section taken on line 2-2 of Figure 1, looking in the direction of the arrows, showing the magnetic element of my novel tripping device.

Figure 3 is a view in persepctive showing the carrying element for the adjustment to my magnetic tripping element.

Figure 4 is an enlarged detail view showing the operation of the adjustable element of the magnetic section of my novel tripping device.

Figure 5 is a fragmentary detail view of one of the embodiments of the thermal tripping device and the adjustment thereof.

Figure 5A is a sectional detail of the thermal 3 adjusting screw taken along line 5A--5A of Figure 5.

Referring now to the figures, the circuit breaker i is enclosed in the casing II and is provided with a lower connecting terminal 12 connected by the pigtail l3 to the thermal trip unit M.

The thermal trip unit 14 is in turn connected to the energizing coil i of the tripping magnet l6. Current then passes through the coil 15 to the terminal l1 and through pigtail E8 to movable contact arm 19 and the movable contact l9a. Current then passes to the stationary contact 20 when the circuit breaker is closed and through the short bus 2i to the upper connectin terminal 22.

The circuit breaker contacts are maintained latched in closed position by the latching element 23 engaging under the latching detent 24, which latching detent 24 is rotatably mounted on the cross-shaft 25.

A crank 26 on the cross-shaft is bifurcated to pass on either side of the rod 21 which passes through the thermal trip sleeve 29 and supports the instantaneous tripping armature 28. When armature 28 is attracted to the magnet 16, the armature supporting rod adjustment nut 3! strikes the right-hand end 29a of the thermal tripping sleeve 29 with respect to Figure 1, and the tripping flange 30 on the thermal trip sleeve 29 strikes the crank 26 and rotates shaft 25 and latching detent 24 clockwise with respect to Figure 1 to disengage latch 23 and permit the circuit breaker 10 to trip.

The circuit breaker I8 may be of any well known standard type similar to that shown in Patent No. 2,421,853.

The invention here relates to the adjusting elements 32 for adjusting the air gap between the armature 28 and magnet l6 and the adjusting elements 33 for adjusting the tripping point of the thermal unit, without removing the cover of the circuit breaker enclosure.

The tripping magnet I5 is mounted in a recess 34 (Figm'e 1) of the casing I], and the armature 28 is slidable in the said recess. The armature 28 is preferably rectangular and is guided by the sides of the recess so that it cannot rotate with respect thereto.

The armature support rod 21 extends through the thermal trip sleeve 29 to the right-hand end 2911. The support member 36 (Figure 3) comprises the parallel legs 31, 31 and the base flanges 38, 38 which are secured in any suitable manner, as by the bolts 39, to an appropriate portion of the interior of the casing. Stationary cross member 48 is carried between the legs 31, 31 of the supporting member 36 and is provided with an opening 4| through which the thermal trip sleeve 29 passes.

The armature support rod 21 terminates at its right-hand end 21a, against the stud 53 of the armature air gap adjusting knob 5|].

Tension springs 45, Figure 2, are connected between stationary lugs 46, 46 extending from the outer section of the support 36 and lugs 41, 41 on the armature 28. The tension springs 45 thus serve to hold the armature 28 away from themagnet 16, the maximum distance being determined by the point at which the outer ends of the lugs 41 bear against the under-side of the flanges 38. This is the maximum air gap which can be provided.

The air gap adjusting knob 50, the top of which is accessible through the opening 5! in casing II and which is provided with a slot 52 or any other appropriate recess so that the same may readily be rotated from the outside of the casing, has an inwardly extending stud 53, the left-hand end of which bears against the rightnanu end 21a of the armature support rod 21. A pin 55 carried by the stud 53 of knob 55 extends into the oetents 63 of the cam surface 51 of the tubular cam section 55.

The compression spring 68 hearing between the outer surface 35 of the support 36 and the under-side of the knob 50 pulls up the stud 53 and the pin 55 into the detents 63 of the cam section 54. The tension springs 45, above described, pull the armature 28 and hence the armature sup port rod 21 against the stud 53 and therefore the pin 55 against the detent 63 in the cam section 53. This serves to maintain the particular setting which must be reached.

In order to operate the element to a new setting, it is necessary to push the knob 50 in with a screw driver in recess 52 to clear the pin 55 from detents 63 in the tubular cam section 54 and then to rotate the stud 53 which will cause the pin 55' to ride out of one detent 63 to the next detent 63. Due to the spiral nature of the cam surface 51 of the tubular cam section 53, each succeeding detent 63 will cause the stud 53 to be nearer or farther away from the magnet 16 in accordance with the direction of rotation of the knob 50. Thus by bearing against the left-hand end 21a of the armature support rod 21, the stud 53 can vary the air gap between the armature 28 and the trip magnet I6.

By this means, therefore, a simple rotation of the knob 50 will result in pushing the rod 21 into the circuit breaker housing when rotation is in one direction and will result in the tension springs 35 pulling the rod 21 out toward the outside of the circuit breaker housing when the rotation is in the opposite direction. This will correspondingly decrease or increase the air gap between armature 28 and magnet l6.

An indicating arrow 18 may be placed on the outer surface of the knob 50 to cooperate with an appropriate scale indicating the condition of the air gap preferably in terms of tripping current values or in the number of times the normal current of the circuit breaker at which it will trip for the particular angular position of the knob 50 and hence for the particular air gap between the armature 28-and the magnet I6;

In appropriate cases, the cam surface 51 may be sloped so that equal increments of rotation of the knob 50 will result in equal increments in the required current flow in the trip magnet for operating the armature. Since magnetic flux across the air gap between the magnet I6 and armature 28 varies inversely as the square of the distance, it will be obvious that progressively smaller movements of the armature toward the magnet will be necessary for equal increments in the flux as the armature approaches the magnet decreasing the air gap.

It will also be obvious that progressively increased movements of the armature 28 from the magnet I6 will be necessary for equal decreases in the magnetic flux asthe armature is adjusted away from the magnet.

The slope of cam 51 may thus be arranged so that equal increments of rotation of knob 50 will result in equal increments in the current response of the magnet. For this purpose, the slope should be relatively fiat at the position where the armature is furthest from the magnet and relatively steep at the position where the armature is closest to the magnet, varying progressively on a logarithmic curve between these two positions.

While I have shown the knob 58 as flush with the casing II so that it may be made accessible simply by using a screw driver in the slot 52, it will be obvious that the knob 58 may be extended out of the casing II to be manually grasped or operated on by a tool embracing the knob; and the knob 58 may be extended sufliciently so that it is accessible from outside a switchboard panel without the necessity for opening the panel to uncover the outer surface of the circuit breaker casing. In the operation of thermal magnetic circuit breakers, it is also necessary, in order to produce a time delay trip, at values below that at which an instantaneous trip is obtained, to provide a thermal unit II.

The thermal unit I8 is provided with a latch 88 at its outer end engaging the latch lever 8| which is. pivoted on a cross shaft 82 mounted between the legs 3101 the trip unit support 88. Latch lever 8| extends out to where it bears at 88 against the adjustable nut 84 on the thermal trip sleeve 28." A compression spring 88 between the platform 48 and the latch lever 8| biases the lever 8| in a counterclockwise direction with respect to Figure 1 so that section 83 of lever 8| will push the thermal trip sleeve 28 to the left with respect to Figure 1 to cause a tripping operation to occur when the latch 88 at the end of the thermal unit 48 releases the end of lever 8| to permit rotation thereof.

In order to provide an adjustment for the thermal unit element 14 and the latch 88, I mount a compression spring 98 on the threaded stud 9|, which stud is received in the tapped opening 92 in wall Ila of casing II.

A lever 94 on the end of the stud 8| will rotate the stud and hence cause it to move back and forth longitudinally in the tapped opening '92, thus causing the compression spring 98 to move inwardly toward the end of the thermal trip unit I4 or away therefrom.

Rotation of lever 98 which is, of course, accessible from outside the casing II thus increases or decreases the distance of the end of compression spring 88 from the end of the thermal element I4. This then permits the thermal element II to deflect a greater or smaller distance before it reaches the spring 88.

Spring 98 will then retard the deflection of the thermal element. Since the torque decreases as the deflection increases, the location of the spring controls the adjustment; the circuit breaker will not trip until the thermal element has deflected sufliciently for the latch 88 thereof to disengage the lever 8|.

In Figure 5 I have shown a modified form of adjustment for the thermal element I4 and its latch 88. This adjustment operates by increasing or decreasing the engagement of latch 88 with lever 8|.

The pin I88 engages with the latching stud 88. Pin I88 has a spiral thread which meshes with the thread of the tapped opening I 8| in the casing. I

Lever [82 which is accessible from the outside of the casing adjusts the longitudinal position of the pin I 88. The rotation of lever I82 thus moves the pin I88 in and out to adjustthe longitudinal position of the latch 88 with respect to the end of the lever 8| and thus to adjust the degree of engagement therebetween. This varies the amount of deflection necessary to obtain a trip.

Lever I82 and the lever 94 may operate over a calibrated scale in order to translate the adjustment into current values to which the thermal unit is responsive for tripping the circuit breaker.

I claim:

1. In a circuit breaker for protecting a circuit, said circuit breaker having a pair of cooperable contacts,-having a contact engaging position and a contact disengaging position; biasing means for biasing said contacts to their disengaging position; a latching mechanism for maintaining said contacts in their engaging position against the action of said biasing means; a trip mechanism for operating said latching mechanism to release said contacts for operation by said biasing means to their disengaged position; an electromagnet having a pole face and an armature spaced from said pole face and operable in response to fault current conditions in the circuit protected by said circuit breaker for operating said trip mechanism; an armature support rod connected to said armature; a sleeve on said rod operable for engaging and operating said trip mechanism, a lever arm for engaging said sleeve, means for biasing said lever arm against said sleeve; a latch device for engaging and maintainin said lever arm out of operating relation with said sleeve; a thermal unit comprising a bimetal operable in response to fault current conditions in said circuit for operating said latch device out of engagement with said lever arm to permit said last-mentioned biasing means to operate said lever arm against said sleeve; an insulation housing for said circuit breaker hav: in a front wall, an operating handle for operating said movable contacts into engagement. said handle protruding through the front of said housing, an adjusting screw engaging said support rod for adjusting the spacing of said armature with respect to said pole face, an opening in the front wall of said insulation housing adjacent said adjusting screw for providing ac cessibility to said adjusting screw from outside and in front of said housing, a spring positioned in the path of movement of said bimetal, and a second adjusting screw accessible outside of and from the front of said housing for adjusting said spring to vary its action on said bimetal.

2. In a circuit breaker for protecting a circuit, said circuit breaker having a pair of cooperable contacts having a contact engaging position and a contact disengaging position; biasing means for biasing said contacts to their disengaging position; a latching mechanism for maintaining said contacts in their engaging position against the action of said biasing means; a trip mechanism for operating said latching mechanism to release said contacts for operation by said biasing means to their disengaged position; an electromagnet having a pole face and an armature spaced from said pole face and operable in response to fault current conditions in the circuit protected by said circuit breaker for operating said trip mechanism; means for releasing said trip mechanism; a latch device for engaging said means; a thermal unit comprising a bimetal operable in response to fault current conditions in said circuit for operating said latch device out of engagement with said means; an insulation housing for said circuit breaker having a front wall; an operating handle for operating said movable contacts into engagement, said handle protruding through the front of said housing; an adjusting mechanism for adjusting the spacing of said armature with respect to said pole face; an opening in the front wall of said insulation housing adjacent said ad justing mechanism for providing accessibility to said adjusting mechanism from outside and in front of said housing; a spring positioned in the path of movement of said bimetal and a second adjusting mechanism accessible outside of and from the front of said housing for adjusting said spring to vary its action on said bimetal.

3. In a circuit breaker for protecting a circuit, said circuit breaker having a pair of cooperable contacts having a contact engaging position and a contact disengaging position; biasing means for biasing said contacts to their disengaging position; a latching mechanism for maintaining said contacts in their engaging position against the action of said biasing means; a trip mechanism for operating said latching mechanism to release said contacts for operation by said biasing means to their disengaged position; an electromagnet having a pole face and an armature spaced from said pole face and operable in response to fault current conditions in the circuit protected by said circuit breaker for operating said trip mechanism; an armature support rod connected to said armature; a sleeve on said rod operable for engaging and operating said trip mechanism, a lever arm for engaging said sleeve, means for biasing said lever arm against said sleeve; a latch device for engaging and maintaining said lever arm out of operating relation with said sleeve; an adjustment screw for adjusting the spacing of said armature with respect to said pole face; a. cam surface having detents, a pin seatable in any one of said detents and operable by said screw from detent to detent, said rod being engaged and operable by said screw as said pin is seatable in different detents for changing the air gap of said armature to said pole face; an insulated housing for said circuit breaker having a front wall; an operating handle for operating said movable contacts into engagement; said handle protruding through the front wall of said housing; and

an opening in the front wall of said housing adjacent to said adjustment screw.

4. In a circuit breaker for protecting a circuit, said circuit breaker having a pair of cooper-able contacts having contact engaging position and contact disengaging position; biasing means for biasing said contacts to their disengaging position; a latching mechanism for maintaining said contacts in their engaging position against the action of said biasing means; a trip mechanism for operating said latching mechanism to release said contacts for operation by said biasing means to their disengaged position; a sleeve for operating said trip mechanism; a lever arm for oper ating said sleeve; biasing means for operating said lever arm; a latch device for restraining said lever arm against the action of said last-mentioned biasing means; a thermal unit comprising a bimetal operable in response to fault current conditions in said circuit for operating said latch device out of engagement with said lever arm to permit said last-mentioned biasing means to operate said lever arm against said sleeve; an insulation housing for said circuit breaker having a, front wall, an operating handle for operating said movable contacts into engagement, said handle protruding through the front of said housing; a movable spring positioned in the path of movement of said bimetal; a mechanism for adjusting said movable spring; an opening in thefront of said insulation housing; and a means for operating said mechanism through said opening.

W. HAROLD EDMUNDS.

REFERENCES @ITED The following references are of record in th file of this patent:

UNITED STATES PATENTS Number Name Date 241,213 Herrmann May 10, 1881 1,646,189 Curtis Oct. 18, 1927 2,265,030 Dorfman Dec. 2, 941 2,459,629 Dorfman et al Jan. 18, 19%

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