US2283368A - Automatically reclosing circuit breaker - Google Patents

Description

May 19, 1942. a. l. HOLMES AUTOMATICALLY REGLOSING CIRCUIT BREAKER Filed Oct. 14, 1938 aqm Patented May 19, 1942 UNITED STATES PATENT OFFICE Gifford 1. Holmes, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn, a corporation of Delaware Application' o'ctober 14,1938, Serial No. 234,991 1's Claims. (Cl. 200-122 I he present invention relates to electric switches and more particularly to the type of switch known as an overload cut-out.

The common form of-overload cut-out is responsive to the amount of current flowing in a circuit, operates to open the circuit on an overload and requires manual resetting to reclose the circuit. Another type of overload cut-out intermittently opens and closes the circuit being protected when the load on the circuit is too great.

Such a device is found to be satisfactory when an attendant is available to correct the difllculty should it be a continuing one,

Still another type of overload cut-out is;designed to intermittently open and-close the chcuit a predeterminednumber of times on excessive current flow, and then, if the condition is not corrected, latch the mechanism in open cir- Figure 2 is a view of the manual reset mechanism oi? the device of Figure 1.

The overload cut-out comprises a casing ill in which the mechanism is mounted. Secured within casing ill at the lower right-hand comer is an insulating block i I. Mounted on this, block are a flexible contact arm- I 2 and an insulating cuit position. This last mentioned type finds special application in protecting various motor circuits in which an excessive current flow on the first or second attempt to start the motor is 7 not necessarily an indication that the overload will be a continuing one. Such aproblem is prey, sented in connection with the starting of a reirigeration compressor motor. The dimculty with .such a device is that while the motor may be given two or three chances to start when the overload cut-out is in its initial or reset position, it may be given a less number or opportunities to start on a subsequent occasion. As an exam le,

- it such a device were designed to give the motor three attempts to start and on one occasion it successfully started on the second attempt then on the next occasion the motor could only at-'- tempt to start twice before the device would positively open the circuit.

The present invention contemplates an overload cut-out which will provide the above function but which will also return to its original conditionautomatically duringintervals or. no overload. 1

' An object of the invention is to provide. an

' overload cut-out which will alternately open and close the circuit being protected a plurality of times when an overload exists before positively opening the circuit, but which will return automatically to its initial condition ii the overload is removed before the circuit is positively opened. 'Another'obiect of the invention is to provide a device which is responsive to the current i'.low-

ing in a circuitto open and clou a switch-"titer nately anumber oi'times before positively opencontact arm l3. Arm i3 is pivotally mounted on block II by a Pin l4 and is biased in a counter-clockwise ection by a spring l5. A'post i8 shown in sure 1 and also in Figure 2 is mounted on a front cover 20, part 01' which is shown in Figure 2, of the mechanism and serves to limit the counter-clockwise movement of contact arm II. A- movable contact 2| is mounted at the upper end of spring contact arm l2 while a normally-stationary contact 22 is mounted on contact arm lliin a position corresponding to the location of contact II on arm l2. Spring.

contact arm I: is 01' such a shape that it will normally hold contactll out of engagement with contact 22.

A heater chamber 24 is secured within casing 14 at theupper right-hand corner thereof. A

heater socket, 25 together with a'similar socket (not shown) serves to support a U-shaped heater 21 and also to form an electrical connection therewith. Mounted within the heater chamber 24 and adjacent the heater 2'! is a bimetallic snap action disc 30, here shown in its cold position. Attached to the center and extending to the left of disc I! is a post. A lever arm 33 is pivoted at 34 to the upper portion of heater chamber 24 and is adapted to be rotated in a clockwise direction by disc 3| through post ll when heater 21 heats disc 3| to a predetermined high temperature. At its lower ext mity lever arm 33 has an extension 31 adapted 0 hold the movable contact 2! in engagement with station- 'ary contact 22 when the disc II is in its cold position, as shown. 1 v

In the illustrated embodiment, the contacts and heater are shown in series with an electrical ing the switch and which is adapted to return load '38. Current supply wire 4| is connected (ii-'- rectly to the spring cont-act arm l2. The circuit then is through movable contact 2|, stationary "contact 22, wire 4|, heater'socket 25, heater 21, wire 43, load 39, and back to a supply wire 44. When a continuing over oad condition exists, heater. 2! will heat disc 6 which will snap to the left rotating lever arm 93 in a clockwise direction and permitting spring contact arm l2 to move the movable contact 21 out of engagement with contact 22. Since the circuit isnow broken, heater 21 and disc 36 will cool down until the inherent diiferential of disc 36 is exceeded and disc 36 will snap back to the posiflon shown. This sequence will be repeated if the overload condition continues.

Mounted within casing ID at the left-hand side is a clockwork mechanism generally indicated at 48. The clock mechanism is of conventional design and comprises the usual balance Wheel 49, hair spring 50, pallet lever arm 5|, escapement wheel 53 and gear train 55 all mounted on a clockwork frame 54. A ratchet wheel 56 is rigidly secured to a shaft 59 iournaled in frame 54 while a gear wheel 59 is free to rotate on shaft 58. A pawl 6| pivoted on gear wheel 59 is biased into engagement with ratchet wheel 56 by a spring 62. turned counter-clockwise with respect to\gear 59 so that the clock may be wound Withputmoving gear train 55. A leaf spring 55 serves as the main spring of the clock mechanism and has its lefthand end secured to shaft 59. Movement of Pawl 6| allows ratchet wheel to be.

shaft 59 in a clockwise direction is limited by pin frame.

The right-hand end of spring 65 normally lies beneath post l9, which was previously described as a stop for contact arm l3, thereby tensioning the spring and tending to rotate shaft 55 in a clockwise direction. It will be seen that when the clock mechanism is wound by rotating ratchet wheel 56 in a counter-clockwise direction the right-hand end of spring. will be moved nearer to the left-hand edge l9 of post I 6. If ratchet wheel 56 is turned counter-clockwise a suflicient amount, the right-hand end of spring 65 will disengage the edge l9 of post l8 and move upward rapidly until it strikes an inclined surface 10 on contact arm ll. This will move contact 22 to the right and out of the rangeoi move- ;nengt of contact 2| to prevent closure of the con- Pivoted at 12 near the-lower end or lever arm 33 i a ratchet arm I5 having a straight portion I6 and a toothed portion 11. A spring 19 biasesratchetarm I5 in a counter-clockwise direction 6 against ratchet wheel 56. It will be seen that when disc so is in its cold position, the straight portion 16 of ratchet arm- I5 lies over ratchet wheel 56 so that wheel is permitted to rotate in a clockwise direction when pin 56 is not in engagement with stop 51.

Thus when heater 2'| become excessively hot,

aiasases permitted to rotate clockwise and permit spring 65 to return the clock mechanism to initial position. In case an overload condition still exists in the circuit, the above operation will be repeated in a short time so that before the clock mechanism has returned the right-hand end of spring 65 to its initial position beneath post l8 ratchet arm I5 will have operated to wind the clock an additional amount and move the right-hand end of spring 65 closer to the edge I9 01' post l8 than it was on the first overload operation of the device, After a predetermined number 01' successive operations spring 65 will disengage the edge l9 of post Hi to positively open the circuit.

Thus it will be seen that the device will positively open the circuit in case a continued overload condition exists. However, if there'is a sufflcient interval between overloads in the circuit, clock mechanism 48 will return spring 65 to its initial position and the predetermined number of openings of the circuit due to overload will again be available before the circuit is positively opened.

In order that the device may be reset after it has operated to positively open the circuit,- a manual reset mechanism shown in Figure 2 is provided. A manual reset lever 9| extends through the front cover 20 .upon which is also mounted post l8 previously described. When successive overload conditions have occurred in the circuit, spring 55will disengage Dost I8, strike the inclined portion 82 of the manual reset lever and slide along inclined portion 82 until it strikes inclined portion ID of contact arm l3 to open the contacts. When spring 65 i in engagement with inclined portion III of contact arm l3, it will also lie within a hooked portion 83 or manual reset lever 9|. As manual reset lever 8| is rotated clockwise from the position shown in Figure 2, it will serve to move the right-hand end of spring 65 to the right and down in such a path as to clear the end of post It and again assume its normal position .under post I8. It should be noted that it will be impossible to reset the spring 55 until the clock mechanism "has had sufficient time to move spring 65 some distance to the right.

While in the illustrated embodiment, contacts 2| and 22 and heater 21 are located in the same circuit, it will be apparent that the same result could be obtained by locating the contacts in a pilot or control circuit. It is alsoapparent that the same device can be used as a time switch in which opening of the contacts depends on the length of time current is applied to the heater.

; Other forms and adaptations of the invention disc 30 will be snapped to the left, lever arm-93 f will be rotated in'a clockwise direction, contact 2| will be .moved out of engagement with contact 22, and the toothed-portion II of ratchet arm I5 will engage ratchet wheel 56 to wind the clock.

mechanism 45- a predetermined amount. The right-handend of spring will then be moved one step nearer the ed e l9 of post but it will not disengage post It. 'Since disc 20 hasnow started to cool, it will soon return to the cold position as shown and move ratchet arm I5 to a position in which the ratchet wheel 56 will be will be apparent to those skilled in the art, and it is to be understood that the scope of the invention is to be determined only by the appended claims.

Y I claim as my invention: 1. In an overload cut-out, in combination, an electric circuit,- a pair ofrm'ating contacts in control of said circuit, thermostatic means operable to open the contacts in response to excessive heating of a'portion of the electric circuit and to reclose the contacts a predetermined time thereafter, supplemental means movableby the thermostatic means from an initial position to a final position in which operation of the thermostatic means to reclose the contacts will be inhibited, and means adapted to' return the supplemental means to initial position if the excesis inhibits the movement of the supplemental means. and

' aaaasos ceases before the supplemental means reaches itsfinalposition. I t

2. In an overload'cut-out, in combination, an electric circuit, contacting means in control of said circuit, thermostatic means for causing the f contacting meansto open in response to excessive heating of a portion of the circuit and to reclose a predetermined time thereafter, and supplemental means movable from an initial position to a final position in which operation of the thermostatic means to 'reclose the contacting means is mental means movable from an initial position to a final position in which operation of thethermostatic means to reclose the contacting means d, said thermostatic means controlling the supplemental means ,being adapted to return to initial position if the excessive heating of the portion of the electric circuit ceases before the supplemental means reaches its final position, and manually operable means to return the suplemental means to initial position.

4. In an electric switch. in combination, a pair of contacts, a thermostatic element operatively connected to the contacts to open the contacts at a predetermined high temperature and to close the contacts at a predetermined lower temperature, a member movable from an initial posi-\ tion in steps by action of the thermostatic element to open the contacts to a finalposition in which it serves to positively open the contacts.

, and a clockwork constantly tending to move said member to its initial position.

5. An overload cut-out comprisingin com-- bination, a spring, a contact adapted to be moved by said spring, thermal timing means for storing energy in said spring in response to an overload cooperable with said member, clockwork mechanism connected to said wheel and adapted to be wound thereby when said wheel is moved by said member, and a main springsecured to said wheel at one end and adapted to be tensioned thereby when said mechanism is wound, the other end of said spring engaging a stop in a manner so that said spring can'move away from said stop when said mechanism is wound beyond apredetermined degree, said last end of said spring being adapted upon disengaging said stop to engage the second inhibited, said thermostatic means controlling of said contacts and move it to a position wherein closure of said contacts will be inhibited.

8. In an electric switch, in combination, a pair of cooperating electrical contacts, a thermostatic element operatively connected to one of said contacts to open the contacts at a first predetermined temperature and to close the contacts at a second predetermined temperature, a ratchet member moved by said element, a ratchet wheel cooperable with said member, time delay means connected to said wheel, and a spring secured at one end to said wheel and having a free end, said free end of said spring being adapted to actuate the second of said contacts and move it to a position wherein closure of said contacts will be inhibited.

9. In an electric switch, in combinatioma pair of cooperating electrical contacts, a thermostatic condition, a second contact cooperable with said first contact, said second contact being moved by said timing means, and means for slowly dissipating stored energy from said spring when said overload condition is absent.

6. An overload cut-out comprising in combination, a resilient means, a contact adapted to be moved by said resilient means, thermal timing means for storing energy in said resilient means in response to an overload condition, a second contact cooperable with said first contact, said second contact being moved by said timing means, and means for slowly dissipating stored energy from said resilient means when said overload condition is absent.

7. In an electric switch, in combination, a pair of cooperating electrical contacts, a thermostatic element operatively connected to one of said contacts to open the contacts at a first predeters mined temperature and to close the contacts at a member moved by said element, a ratchet wheel second predetermined temperature, a ratchet 5o element operatively connected to one of said contacts to open the contacts at a first predetermined temperature and to close the contacts at a second predetermined temperature,-- and spring means tensioned by the movement of said element, iii spring means being adapted to move the sec nd ofsaid contacts to a position wherein closure of said contacts will be inhibited.

10. In an electric switch, in combination. a pair ofcooperating electrical contacts, automatic means including a member, said member operating to open and close said contacts in response to an overload condition, and a spring, said spring being tensioned by said automatic means and operable upon a predetermined number of successive overload conditions to move one of said contacts will be inhibited.

11. In an electric switch, in combination, a

- pair of cooperating electrical contacts, a there mostatic element operatively connected to one of said contacts to open the contacts at a first predetermined temperature and to close the contacts at a second predetermined temperature, spring, means tensii'med by the movement of said element, said spring means being adapted to move the second of said contacts to a position wherein closure of said contacts will be inhibited and time delay means for causing said spring means to return slowly to its initial position.

12. In an electric switch, in combination, a pair of cooperating electrical contacts, automatic means including a member, said member operating to open and close said contacts in response to an overload condition, aspring, said spring being tensioned by said automatic means and operable upon a predetermined number of successive overload conditions to move one ofsaid contacts to a position wherein closure of said contacts will be inhibited, and time delay means for causing said spring to return slowly to its initial position.

. GIFFORD I. HOLMES.

Images