Pivot joint for a movable contact arm in a molded case circuit breaker

A molded case circuit breaker comprising:

• a molded housing including a breaker cover;
• a first terminal and a second terminal mounted in the housing;
• a contact electrically coupled to the first terminal;
• an operating mechanism having a pivoting member moveable between an “ON” position, an “OFF” position and a “TRIPPED” position;
• an intermediate latching mechanism mounted in the housing and coupled to the operating mechanism;
• a trip mechanism selectively coupled to the operating mechanism and electrically connected to the second terminal;
• a moving contact arm and assembly including a pivot mounting member coupled to the second terminal and the pivoting member of the operating mechanism;
• and,
• a pivot joint for the moving contact arm, the pivot joint comprising:
• a recess in a first sidewall of the contact arm, with the recess co-axial with a mounting hole in the contact arm;
• a second recess in a second sidewall of the contact arm, with the second recess co-axial with a second mounting hole in the contact arm, wherein the first and second recesses are co-axial with each other;
• a shaped washer, configured to fit in each of the first and second recesses;
• a mounting axle configured to engage each shaped washer, mounting hole and the pivot mounting member, wherein the contact arm is free to pivot about the mounting axle;
• and,
• a spring, with the spring configured to engage both ends of the mounting axle and urge the contact arm against each shaped washer.

A circuit breaker comprising:

• a housing including a base;
• a means for connecting a load to the breaker, mounted in the housing;
• a means for connecting an electrical line to the breaker, mounted in the housing;
• a stationary contact electrically coupled to the means for connecting an electrical line;
• a means for moving a contact arm coupled to a means for operating mounted in the housing and having a pivoting member moveable between an “ON” position and “OFF” position, and a “TRIPPED” position, with the pivoting member coupled to the means for moving a contact arm and with the means for operating coupled to an intermediate means for latching the means for operating;
• a means for tripping coupled to the means for moving a contact arm and the means for connecting a load with the means for tripping in selective operative contact with the intermediate means for latching and the means for connecting a load coupled to a means for mounting the contact arm;
• and,
• a means for pivoting the contact arm, the means for pivoting the contact arm comprising:
• a means for recessing in a first sidewall of the contact arm, with the means for recessing co-axial with a mounting hole in the contact arm;
• a second means for recessing in a second sidewall of the contact arm, with the second means for recessing co-axial with a second mounting hole in the contact arm, wherein the first and second means for recessing are co-axial with each other;
• a means for reducing binding configured to fit in each of the first and second means for recessing;
• a mounting axle configured to engage each means for reducing binding, each mounting hole and the means for mounting the contact arm, wherein the contact arm is free to pivot about the mounting axle;
• and,
• a means for biasing, with the means for biasing configured to engage both ends of the mounting axle and urge the contact arm against each means for reducing binding.

A method for improving the current carrying capacity of a pivot joint for a movable contact arm in a molded case circuit breaker, with the circuit breaker having an operating mechanism coupled to a line terminal, a trip mechanism and a load terminal, with the load terminal coupled to a pivot mounting member, the method comprising the steps of:

• providing a recess in a first sidewall of the contact arm, with the recess co-axial with a mounting hole in the contact arm;
• providing a second recess in a second sidewall of the contact arm, with the second recess co-axial with a second mounting hole in the contact arm, wherein the first and second recesses are co-axial with each other;
• providing a pair of shaped washers;
• placing one of the shaped washers in each recess;
• providing a mounting axle;
• inserting the mounting axle into each mounting hole and engaging each shaped washer and the pivot mounting member;
• and,
• positioning a spring to engage both ends of the mounting axle and urging the contact arm against each shaped washer.