US3235699A

US3235699A - Circuit breaker contact pressure adjusting means

Info

Publication number: US3235699A
Application number: US329689A
Authority: US
Inventors: John C Brumfield
Original assignee: ITE Circuit Breaker Co
Current assignee: Siemens Energy and Automation Inc; ITE Circuit Breaker Co
Priority date: 1963-12-11
Filing date: 1963-12-11
Publication date: 1966-02-15
Anticipated expiration: 1983-02-15

Description

Feb. 15, 1966 J. c. BRUMFIELD CIRCUIT BREAKER CONTACT PRESSURE ADJUSTING MEANS 3 Sheets-Shea?l 1 Filed Dec. 11, 1963 A 4/ 4/ //vf -NIE Feb. 15, 1966 J. c. BRUMFIELD 3,235,699

CIRCUIT BREAKER CONTACT PRESSURE ADJUSTING MEANS Filed Dec. ll, 1963 5 Sheets-Sheet 2 l-I E115- Feb. 15, 1966 J. c. BRUMFIELD CIRCUIT BREAKER CONTACT PRESSURE ADJUSTING MEANS Filed DSC. ll, 1963 5 Sheets-Sheet 5 INVENTOR, Ja//A/ C www-na United States Patent O 3,235,699 CIRCUIT BREAKER CGNTACT PRESSURE ADJUSTING MEANS John C. Brumiield, Philadelphia, Pa., 'assigner to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Dec. 11, 1963, Ser. No. 329,689 9 Claims. (Cl. 200-170) This invention relates to means for adjusting circuit breaker contact pressure without disturbing the spacing between the contacts in the open position thereof. More particularly, this invention is an improvement over the contact pressure adjusting means disclosed in the copending application U.S. Serial No. 174, 767 tiled February 21, 1962, entitled Means for Adjusting Contact Pressure, with I. C Brumtield et al. `as inventors and .assigned to the assignee of the instant invention.

In circuit breakers having quick make and quick break features the movable contact moves at a very high rate of speed into engagement with the stationary contact upon closing of the circuit breaker. Thus, it is necessary to provide means for absorbing the energy released by the closing mechanism in a very short travel of the movable contact.

In the circuit breaker art this has traditionally been accomplished by mounting the stationary Contact on a spring or providing a spring which is interposed between the movable Contact and the closing mechanism. Such springs must be of considerable strength to maintain high pressure between the contacts when they are in engagement so that good electrical contact is maintained in spite of magnetic blow-oil:` forces which accompany current flow. Because of manufacturing tolerances it is necessary to adjust the contact pressure after the Contact operating mechanism and stationary contacts are mounted to the circuit breaker base.

In recent years circuit breaker constructions have become so compact that nding room for adjusting the movable contact in the open position of the circuit breaker has presented a problem. That is, in order to achieve etlicient circuit interruption and prevent restriking of an arc, there is a minimum distance required for contact separation in the open position of the circuit breaker.

Prior to the invention described in the aforesaid copending application, Serial No. 174,767, prior art means for adjusting contact pressure was limited for the most part to the tedious process of shimming up the stationary contact and the lengthening or shortening of the Contact pressure springs. The invention set forth in the aforesaid copending appli-cation Serial No. 174,767 has proven entirely satisfactory from the adjusting and operating viewpoints whereas the other prior art methods have proved unsatisfactory since adjustments of contact pressure resulted in the changing of the gap between the contacts in the open position of the circuit breaker.

The instant invention retains the advantages of the invention set forth in aforementioned copending application Serial No. 174,767 without any of the disadvantages of prior art construction. In addition, the instant invention sets forth a construction which is more compact than that of the prior art and is especially economical to produce.

More particularly, the device of the instant invention provides an adjusting nut threada'bly mounted to a short screw. Contact spring pressure and the fact that the screw head is captured in a recess of the contact carrier mounts the screw to the carrier. The contact pressure spring bears against the movable contact arm and the adjusting nut urging the arm away from the nut. The adjusting nut is provided with a plurality of circularly arranged axially extending tabs which form an open ended cage to conline the end of the spring seated against the nut against transverse movement.

By rotating the nut relative to the screw, spring pressure is adjusted as required. After the nut is rotated to position such that the required contact pressure is obtained, the nut is maintained in this position by bending two of the circularly arranged tabs outwardly to radial positions. The radially extending tabs are so positioned that one or the other thereof will engage the contact carrier should the adjusting nut attempt to rotate and in this way rotation of the adjusting nut is prevented.

Accordingly, a primary object of this invention is to provide a circuit breaker having novel means for adjusting pressure between cooperating contacts.

Another object is to provide novel contact pressure adjusting means which, during the adjusting process, will not affect the gap setting between contacts in the open position of the circuit breaker.

Still another object is to provide a contact pressure adjusting nut having a plurality -of bendable tabs movable to positions for cooperating with the contact carrier to prevent rotation of the adjusting nut after the desired contact pressure is obtained.

These as well as other objects of the instant invention shall become readily apparent after reading the following description of the accompanying drawings, in which:

FIGURE 1 is a longitudinal cross-section taken through the center phase of a multi-phase molded case -circuit breaker constructed in accordance with the teachings of the instant invention.

FIGURE 2 is a side elevation of the Contact operating mechanism with certain elements removed to better reveal the structure of other elements.

FIGURE 3 is a plan View showing the contact carrier and elements mounted directly thereto when disconnected from the operating mechanism.

FIGURE 4 is a cross-section `taken through line 4-4 of FIGURE 3 looking in the direction of arrow 4-4.

FIGURE 5 is a `front elevat-ion of the elements of FIG- URE 3 looking in the direction of arrows 5-5 of FIG- URE 4.

FIGURE 6 is an exploded perspective illustrating the construction of the contact pressure adjusting means.

Now referring to the gures. Circuit breaker 10` includes a molded housing comprising base 11 and Iremovable cover 12 joined together along line 13. Suitable barriers in base 11 and cover 12 divide the housing into three longitudinally extending compartments, each housing `the elements of an individual phase of circuit breaker 10. Since the current carrying ele-ments of all three phases are substantially identical, for the sake `of brevity, only the current carrying elements of the center phase will be described. 'Ihe current path between line termin-a1 15 and load terminal strip 16 proceeds from stationary contacts 17 and 24 on line terminal strip 15, to

movable contacts

18 and 25 carried by

contact arms

19 and 26, through tr-ifurcated laminated dexible conductor 2li and clamp 21 to bimetal heater 22, and then to load terminal str-ip 16.

Since circuit breaker is of relatively high current,

carrying capacity, contacts 17, 1S function as arcing contacts which are paralleled by .two sets of main contacts, each comprising a stationary ycontact 24 and a cooperating movable contact 25. Movable contacts 25 are each mounted to individual contact arms 26 with each of the arms 26 being connected by an individual section of conductor to clamp 21 while stationary contacts 24 are mounted to line terminal strip 15.

Circuit breaker 1G also includes an automatic tripping mechanism 28 and a toggle operating mechanism 29, each Well known to the art. The details of mechanisms 28 and 29 form no part of this invention. For details of these mechanisms reference is made to copending application Serial No. 108,812 Itiled May 9, 1961, in the name of E. Wortman, now U.S. Patent No. 3,155,802, entitled U-Shaped Cradle for Circuit Breaker and assigned to the assignee of the instant invention.

Operating mechanism 29 is connected to the contacts of all three phases by means of transverse insulating tie bar 30. Individual V-shaped straps 31 connect all three contact carriers 32 to tie bar 30, so that the Contact pairs corresponding to one another in the different phases are operated into and out of engagement simultaneously.

Contact carrier 32 of the center phase is connected at pin 36 to the lower end of the operating mechanism toggle 34, 35. As is well known to the art, cooperating main contacts 2'4, 25 separate prior to the separation of the cooperating arcing contacts 17, 18 when the circuit breaker 10 is being opened and upon closing of the circuit breaker 1@ arcing contacts 17, 18 engage prior to the engagement of

main contacts

24, 25. Movable contact arm 19 is pi-votally mounted to carrier 3-2 at pin 43. Spring means 44, constituted by a plurali-ty of leaf springs arranged in stack, is anchored at one end to carrier 32 by means of screws 45. The other end of spring means 44 engages roller 46 pivotally mounted at the free end of contact arm 19 to bias arm 19 in a counterclockwise direction (with rsepect to FIGURE 2) about pin 43', with this motion being limited through the engagement of the right end of arm 19 with the bottommost of the springs in stack 44.

Each of the contact arms 26 is pivotally mounted to carrier 32 on an individual pin 43.

Contact pressure springs

51, 52 bias contact arm 26 in a counterclockwise direction (with respect .to FIGURE 4) about pin 43, with this motion being limited in the open circuit position of circuit breaker 10 through the engagement of the right end of arm 26 with carrier surface 53. Springs 51, 52 are concentrically wound coil units with spring 52 being mounted within spring 51. The lower end of

springs

51, 52 abut the upper surface of contact arm 26 at the end thereof to the left of pivot 43. The upper ends of

springs

51, 52 abut adjusting nut 55 and are aligned with the central threaded aperture 56 of nut S5. The threads of aperture 56 are in engagement with the` threads of screw 57.

Nut 55 is a flat circular member having a plurality of bendable tabs positioned around the periphery thereof. As will become more readily apparent, prior to making the final adjustment of contact pressure all of the tabs 60 extend in a downward or axial direction so as to form an open-ended cage which contines the upper end of

springs

51, 52 against transverse movement. Boss 59, projecting upwardly from contact arm` 26, prevents transverse movement of the lower end of

springs

51, 52. The underside of the upper wall of carrier 32 is undercut to form a recess which houses head 61 of screw 57. A portion of head 61 is deformed to form radial projection 61a which fits into carrier notch 63 thereby preventing rotation of screw 61 relative to carrier 32.

In order to adjust the degree of pressure exerted by

springs

51, 52 upon contact arm 26, nut 55 is rotated while screw 57 remains tixed. Thus, nut 55 moves in an axial direction with respect to

springs

51, 52 thereby lengthening or shortening springs 51, 52 as desired, and -by so doing controlling the pressure exerted thereby. When lthe desired pressure is obtained, `the exposed tabs 60 nearest vertical walls 32a, 321; of carrier 32 are bent outwardly so that they extend radially outward. With tabs 66a and 60h extending radially, rotation of nut 55 in one direction is prevented through the engagement of tab 60a with wall 32a and rotation of nut 55 in the opposite direction is prevented through the engagement of tab 6017 with wall 3217 so that the adjusted pressure setting for

springs

51, 52 is maintained.

Thus, this invention provides a means, of especially simplified construction, for adjusting circuit breaker contact pressure without altering or in any way affecting the open circuit position of the cooperating contacts.

Although this invention has been described with respect to preferred embodiment thereof, it should be understood that many variations and modifications will now be obvious to those skilled in the art, and it is preferred therefore that the scope of the invention be limited not by the specific disclosure herein but only by the appended claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are deiined as follows:

1. A circuit breaker including a pair of cooperating contacts; an arm carrying one of said contacts; a carrier to which said arm is mounted; an operating mechanism connected to said carrier for moving said arm between a first and a second position wherein said contacts are disengaged and engaged respectively; first means for establishing the gap separation between said pair of contacts when in said first position; spring means acting between said arm and said carrier to exert pressure between said contacts when said arm is in said second position; and second means for adjusting the degree of pressure exerted lby said spring means when said arm is in said second position Without alecting the gap separation established by said tirst means; said second means including a threaded member carried by said carrier and a nut threadably mounted to said member; means maintaining said member against rotation; said nut in operative engagement with said spring means whereby movement of said nut relative to said member results in changing the pressure exerted by said spring means when said arm is in said second position.

2. A circuit breaker as set forth in claim 1 in which the threaded member is a screw having a bead disposed Within a recess of said carrier defined by boundary means integrally formed with said carrier.

3. A circuit breaker including a pair of cooperating contacts; an arm carrying one of said contacts; a carrier to which said arm is mounted; an operating mechanism connected to said carrier for moving said arm between a first and a second position wherein said contacts are disengaged and engaged respectively; spring means acting between said arm and said carrier to exert pressure between said contacts when said arm is in said second position; and means for adjusting the degree of pressure exerted by said spring means when said arm is in said second position; said means including a threaded member carried by said carrier and a nut threadably mounted to said member; means maintaining said member against rotation; said nut in operative engagement with said spring means whereby movement of said nut relative to said member results in changing the pressure exerted by said spring means when said arm is in said second position; said nut is provided with bendable means positionable for cooperation with portions of said carrier to prevent movement of said nut relative to said threaded member.

4. A circuit breaker as set forth in claim 3 in which the bendable means includes a plurality of tabs arranged along the periphery edge of said nut,

5. A circuit breaker as set forth in claim 4 in which the spring means is a coiled member; at least some of said plurality of tabs extending parallel to the axis of said coiled member and constituting means for confining one end of said coiled member against transverse movement.

6. A circuit breaker as set forth in claim 5 in which a rst of said plurality of tabs is radially extending.

7. lA circuit breaker as set forth in claim 6 in which a second of said plurality of tabs is radially extending.

S. A circuit breaker as set forth in claim 6 in which the threaded member is a screw having a bead disposed within a recess of said carrier defined by boundary means integrally formed with said carrier.

9. A circuit breaker as set forth in claim 8 in which References Cited by the Examiner UNITED STATES PATENTS 12/1949 Sandin et al. .ZOO-166 X 5/1964 Murphy 20G-170 KATHLEEN H. CLAFF Y, Primary Examiner.

BERNARD A. GILHEANY, Examiner.

Claims

1. A CIRCUIT BREAKER INCLUDING A PAIR OF COOPERATING CONTACTS; AN ARM CARRYING ONE OF SAID CONTACTS; A CARRIER TO WHICH SAID ARM IS MOUNTED; AN OPERATING MECHANISM CONNECTED TO SAID CARRIER FOR MOVING SAID ARM BETWEEN A FIRST AND A SECOND POSITION WHEREIN SAID CONTACTS ARE DISENGAGED AND ENGAGED RESPECTIVELY; FIRST MEANS FOR ESTABLISHING THE GAP SEPARATION BETWEEN SAID PAIR OF CONTACTS WHEN IN SAID FIRST POSITION; SPRING MEANS ACTING BETWEEN SAID ARM AND SAID CARRIER TO EXERT PRESSURE BETWEEN SAID CONTACTS WHEN SAID ARM IS IN SAID SECOND POSITIONS; AND SECOND MEANS FOR ADJUSTING THE DEGREE OF PRESSURE EXERTED BY SAID SPRING MEANS WHEN SAID ARM IS IN SAID SECOND POSITION WITHOUT AFFECTING THE GAP SEPARATION ESTABLISHED BY SAID FIRST MEANS; SAID SECOND MEANS INCLUDING A THREADED MEMBER CARRIED BY SAID CARRIER AND A NUT THREADABLY MOUTEED TO SAID MEMBER; MEANS MAINTAINING SAID MEMBER AGAINST ROTATION; SAID NUT IN OPERATIVE ENGAGEMENT WITH SAID SPRING MEANS WHEREBY MOVEMENT OF SAID NUT RELATIVE TO SAID MEMBER RESULTS IN CHANGING THE PRESSURE EXERTED BY SAID SPRING MEANS WHEN SAID ARM IS IN SAID SECOND POSITION.