US3259839A

US3259839A - Electric circuit breakers

Info

Publication number: US3259839A
Application number: US83563A
Authority: US
Inventors: Coleman Edward; Thompson Walter Henry
Original assignee: JA Crabtree and Co Ltd
Current assignee: JA Crabtree and Co Ltd
Priority date: 1960-01-27
Filing date: 1961-01-18
Publication date: 1966-07-05
Anticipated expiration: 1983-07-05

Description

July 5, 1966 COLEMAN ET AL 3,259,839

ELECTRIC CIRCUIT BREAKERS Filed Jan. 18, 1961 4 Sheets-Sheet l July 5, 1966 COLEMAN ET AL 3,259,839

ELECTRIC CIRCUIT BREAKERS Filed Jan 18, 1961 4 Sheets-Sheet 2 2 z i ngenors 121. 72:3,;

Attorney July 5, 1966 E. COLEMAN ET AL ELECTRIC CIRCUIT BREAKERS 4 Sheets-Sheet 5 Filed Jan 18, 1961 w m 0/ Atn um n 1 m? i fl Us fi a W rt H: M I M I a n 5 5 n. II N 5 "III IIIIIL :2. I /V/ w "r m R r July 5, 1966 COLEMAN ET AL 3,259,839

ELECTRI C G IRCUI T BREAKERS Filed Jan. 18, 1961 4 Sheets-Sheet 4 A ftorney United States Patent 3,259,839 ELECTRIC CIRCUIT BREAKERS Edward Coleman, Walsall, and Walter Henry Thompson, Solihull, England, assignors to J. A. Crabtree & Co. Limited, Walsall, England, a British company Filed Jan. 18, 1961, Ser. No. 83,563 Claims priority, application Great Britain, Jan. 27, 1960, 2,903/ 60 7 Claims. (Cl. 324-28) This invention relates to the setting of the current value for. the tripping of electric circuit breakers having electromagnetically-operated trip mechanism, the object of the invention being to provide an improved arrangement for automatically performing the requisite operations in a simple and efiicient manner.

Prior to introduction of the circuit breakers to the pertinent method and apparatus for setting their current rating or value, the breakers are pre-set by a screwdriver with a positive stop to ensure that they are overset. Thus all of the breakers require setting adjustment in one direction only.

According to this invention the electromagnet of the circuit breaker is actuated by a heavy excess current while obstructive means are introduced to prevent operation of the trip mechanism, after which the current is reduced, the obstructive means are withdrawn, and adjustment means are set to produce tripping. The obstructive means, in the form of a pin or peg, may be introduced through an aperture or opening in the casing of an assembled circuit breaker so as to be located in the path of a catch plate or trip lever of the trip mechanism. This invention is applicable to circuit breakers as described and claimed in our United States Patent No. 3,105,131, dated September 24, 1963.

The assembled breakers may be fed to a setting position during which they actuate a switch to commence operation of a timing mechanism which controls sequential operation of means comprising contactors for controlling the current to the circuit breakers, the introduction and withdrawal of the obstructive means, and the advance and retraction of a motor-driven screwdriver for setting an adjusting screw in the circuit breaker. This screw may adjust the compression of a helical spring so that the force applied by the electromagnet for disengaging the latching engagement between parts of the tripping mechanism is varied. Once adjusted, the screw is set as by wax and unauthorized access thereto is prevented by a rivet extending between the casing members of the otherwise fully assembled circuit breaker.

In order to enable the invention to be readily understood reference will now be made to the accompanying drawings illustrating an arrangement, by way of example, for carrying the invention into effect, in which drawings:

FIGURE 1 is a perspective view of a panel and table to and from which the circuit breaker are fed by a band.

FIGURE 2 is a circuit diagram.

FIGURE 3 is a cross-section to an enlarged scale of operating means shown in FIGURE 1.

FIGURE 4 is a view of the circuit breaker forming the subject of our Patent No. 3,105,131 hereinbefore referred to and shown in the on position.

Referring to the drawings the assembled circuit breakers 1, each mounted on a jig plate 2, are carried by means such as a rod or endless belt 3 to the testing table 4. On arrival at the position shown in the centre of the table, FIGURE 1, the circuit breaker actuates an arm 5, pivotally mounted at 5 to the position shown in FIGURE 2, so as to close a switch 6, which operates a timing mechanism 8 for starting the motor of a main timer 9. This preliminary timer 8 acts for only a short period as a holding means for the main rotary timer 9 until the sequence of operations is commenced. The main timer comprises a number of arcuate cams operating on switches, the period for which each switch is closed being denoted by the thick concentric circumferential lines in FIGURE 2. The main switch 9 having been closed, and a circuit breaker having closed the switch 6, the timer 9 produces the following sequence of operations:

(1) The timer closes a switch 10 which causes a solenoid-operated valve 11 to be opened for the supply of pneumatic pressure from a pipe A to a cylinder 12 the ram 12a of which is moved forward in order to clamp the jig plate 2 in position and also to cause engagement of contacts 14, carried by the ram, with circuit breaker terminals 13 protruding from the ends of the circuit breaker, see FIG. 3.

(2) Projection of a peg or pin 15 through aligning openings 16 in the jig 2 and the circuit breaker easing into obstructive engagement with a trip lever or catch plate 16* therein in order to prevent operation of the trip mechanism. Introduction of this peg or pin into the circuit breaker is produced by the timer 9 closing a switch 17 for the supply of current to a solenoid operated air valve 18 to permit pneumatic pressure from the supply A to a cylinder 15 containing the peg or pin.

(3) Closure of the timer switch 19 which causes a first contactor, 20 to be actuated to permit the passage of a heavy current from a transformer 20a, which is controlled by a variable resistance, .to a coil 16d. This current, which may for example be six times or 600% full load rating, is passed through the coil of the circuit breaker so as to cause the plunger 16 of its electromagnet trip to be operated to its full extent against the action of a spring 16. This heavy excess current enables the plunger to be raised rapidly without time delay. Despite this operation of the plunger, which would otherwise cause the breaker to be tripped, the trip mechanism is prevented from operating due to the obstructive engagement of the peg 15 with the plate 16 (4) Actuation of a second contactor-operated switch, not shown, to bring into the circuit of the transformer 20a a resistance which reduces the current passing to the circuit breaker to a value of 1.2 times or of the rated current. This second contactor is operated by closure of the timer switch 21. At the same time, the peg or pin 15 is withdrawn from obstructive engagement with the trip lever or catch plate 16. In this instance, the plunger 16 of the circuit breaker is still in the raised position.

(5) At this stage it is necessary to ensure that the circuit breaker is in the on position with the dolly 1 up, as seen in FIGURES 2 and 4. This is ensured by passing a first test pulse, due to the closure of the timer switch 22, to the lower of a pair of

switches

23, 24, between which the dolly 1 is disposed. Thus if the dolly should be down, denoting that the circuit breaker is off, this lower switch 23 is closed and the test pulse thereby op crates a contactor 25 to cause operation of a bell 26 and illumination of a light 27. In addition the contactor-operated switch 25 is opened in order to stop the conveyor 3.

(6) The operation of a screwdriver 27 which is first projected forwardly into engagement with an adjustment screw 16e bearing upon a compression spring 16f of the circuit breaker by a ram operated in a cylinder 30 which is controlled by pneumatic pressure admitted from the supply A upon the opening of a solenoid controlled valve 31 which in turn is operated upon closing of the timer switch 29. The screwdriver 27 is then rotated by an electric motor 28 which is started by the closing of a timer-controlled switch 32 to cause adjustment of the.

setting of the adjustment screw 16:: to vary the tension of spring 16 until it permits the circuit breaker to trip,

the pin 15 having been withdrawn as previously described. The tripping of the circuit breaker causes its dolly 1 to fall so that the switch 24 moves by spring pressure from the position shown in full lines in FIG. 2, to that shown in dotted lines, in order to break the circuit of the screwdriver motor 28. The possibility of further movement of the screwdriver is excluded due to the inertia of the gearing.

(7) Retraction of the screwdriver from the circuit breaker is eifected towards the end of the cycle.

(8) A second pulse is passed by actuation of the timer switch 33 through the switch 23 which, if open with the dolly in the now correct off position results in no action. On the other hand if the dolly should be incorrectly up the switch 23 is closed to cause the alarm to be operated.

(9) 'Finally, the first timer switch 34 is actuated at the completion of the cycle in order to operate a solenoid controlled pneumatic valve 35 for the supply of air pressure to a cylinder 36 for operating transferring means for feeding the next jig and circuit breaker into position through the means 37. The screwdriver 27 the peg 15 and the clamping ram 12a are withdrawn by spring action when the pneumatic pressure from the supply A is withdrawn to their

cylinders

12 and 30. The cylinder 36 is provided with air supply pipes at each end for operating it in respective directions.

As described in our above referred to patent, after adjustment to the proper rating, the set of screw 16c is sealed as by wax in its tapped opening. The wax is then maintained in sealing position by a rivet introduced through aligned holes 16g which connects the two parts of the casing.

The forms of the invention here described and illustrated are presented merely as examples of how the invention may be embodied and applied. Other forms, embodiments and applications of the invention, coming within the proper scope of the appended claims, will, of course suggest themselves to those skilled in the art.

What is claimed is:

1. The method of setting a predetermined current value for an assembled circuit breaker :having a casing with an aperture therein, a dolly, fixed and moving contacts, an adjustment screw, a tension means, an electromagnetically operated trip mechanism including a plunger, said method consisting in first ramming a pin through said aperture into said mechanism to prevent tripping thereof, then passing a heavy current of approximately six times said value through said mechanism to raise said plunger, thereafter lowering said plunger by reducing said current to approximately 1.2 times said value and simultaneously withdrawing said pin, then turning said screw and adjusting said tension means to trip said mechanism at said value.

2. The method of setting a predetermined current value for an assembled circuit breaker according to claim 1 consisting in rapidly actuating said plunger into said raised position, checking the position of said dolly which eifects the engagement of said contacts after withdrawing said pin, maintaining said plunger in said raised position while adjusting said screw and then checking the position of said dolly which effects the disengagement of said contacts after tripping said mechanism at said predetermined value.

3. An apparatus for automatically testing and regulating the current value setting of assembled circuit breakers having a casing with an aperture therein, a tripping element, a coil for energizing an electromagnetic operated mechanism provided with a plunger, fixed and moving contacts, a manually operated dolly for operating said mechanism, a tension means and a screw for adjusting said setting bearing upon said tension means, said apparatus being connected to a pneumatic pressure supply and an electric power source and comprising a rotary timer, a plurality of electric switches disposed on said timer, a

first means operated by a first of said switches to feed said breaker into testing position, pivotal means actuated by said breaker to switch on said timer, a first pneumatic means operated by a second of said switches to clamp and secure said breaker in said position and connect said coil with said power source, a second pneumatic means operated by a third of said switches to project an obstruction through said aperture to prevent tripping of said element, a first contactor operated by a fourth of said switches to permit passage of a heavy current to said coil up to six times said current value to raise said plunger without time delay, a resistance and a second contactor operated by a fifth of said switches to reduce said heavy current to slightly over said current value setting, screwdriver means, a third of said pneumatic means operated by a sixth of said switches to project said screwdriver means into engagement with said screw, rotating means to turn said screwdriver means until said element trips at a predetermined current value for said breaker, conduit means disposed between said supply and said pneumatic means, a valve disposed in said conduit means leading to each of said pneumatic means, said switches sequentially opening and closing upon rotation of said timer to control the operation of each said valve.

4. An apparatus for automatically testing and setting the current value of an assembled circuit breaker having a first pair of contacts, an electromagnetically operated mechanism provided with a tripping element, adjustment means therefor and a dolly, said apparatus comprising an electric timer, a starter for said timer, a series of switches disposed in rotational sequence on said timer, a plurality of cylinders connected to a pneumatic pressure supply, a first of said cylinders being connected to an electric power source, said first cylinder provided with a clamping ram and a second pair of contacts in alignment with said first pair of contacts, a second of said cylinders provided with a projectible peg, a third of said cylinders provided with an advancing and retracting screwdriver, a plurality of solenoid valves, each of said valves being disposed between said supply and one of said cylinders, said timer being actuated by feeding said breaker into engagement with said starter to open and close said switches at selectively spaced intervals and turn each of said valves on and off consecutively, a first means to pass a heavy current of approximately 600% of said current value through said mechanism after projection of said peg, and a second means to thereafter reduce said current to approximately 115% said current value, whereby said first cylinder sequentially clamps said breaker and connects it to said power source in an adjustment setting position, said second cylinder projects said peg into engagement with said element, and said third cylinder advances said screwdriver into engagement with said adjustment means.

5. An apparatus according to claim 4, including an electric motor connected to said screwdriver, said motor turning said screwdriver after the latter has been advanced to rotate said adjustment means until it trips said element, and resilient means to retract said peg, screwdriver and ram from projected positions thereof, when each respective switch sequentially cuts said pressure supply from its respective cylinder.

6. An apparatus for automatically testing and setting the current value of an assembled circuit breaker according to claim 5, wherein said breaker is provided with fixed and moving contacts, and said apparatus includes a pair of separate switches connected to said dolly, one of said series of switches passing a first test pulse to said separate switches to determine the respective position of said dolly which results in the engagement of said fixed and moving contacts before projecting said screwdriver to and from said adjustment means, and another of said series of switches passing a second test pulse to said separate switches after rotation of said screwdriver to determine the respective posit-ion of said dolly which. results in the disengagement of said fixed and moving contacts before retraction of said screwdriver.

7.- An apparatus for automatically testing and setting the current value of an assembled circuit breaker according to claim 4, wherein said timer is rotational, said switches being arranged in concentric circles on said timer, each said switch being disposed in consecutive order and turned on and ofi by the rotation of said timer.

References Cited hy the Examiner UNITED STATES PATENTS WALTER L. CARLSON, Primary Examiner.

SAMUEL BERNS'FEIN, Examiner.

G. L. LETI, Assistant Examiner.

Claims

1. THE METHOD OF SETTING A PREDETERMINED CURRENT VALUE FOR AN ASSEMBLED CIRCUIT BREAKER HAVING A CASING WITH AN APERTURE THEREIN, A DOLLY, FIXED AND MOVING CONTACTS, AN ADJUSTMENT SCREW, A TENSION MEANS, AN ELECTROMAGNETICALLY OPERATED TRIP MECHANISM INCLUDING A PLUNGER, SAID METHOD CONSISTING IN FIRST RAMMING A PIN THROUGH SAID APERTURE INTO SAID MECHANISM TO PREVENT TRIPPING THEREOF, THEN PASSING A HEAVY CURRENT OF APPROXIMATELY SIX TIMES SAID VALUE THROUGH SAID MECHANISM TO RAISE SAID PLUNGER, THEREAFTER LOWERING SAID PLUNGER BY REDUCING SAID CURRENT TO APPROXIMATELY 1.2 TIMES SAID VALUE AND SIMULTANEOUSLY WITHDRAWING SAID PIN, THEN TURNING SAID SCREW AND ADJUSTING SAID TENSION MEANS TO TRIP SAID MECHANISM AT SAID VALUE