DESC:Stored Energy Operating Mechanism for Molded Case Circuit Breaker

Field of the invention

The present invention relates to a low voltage current limiting circuit breaker and more particularly, to a stored energy operating mechanism for a molded case circuit breaker that includes a scotch yoke assembly.

Background of the invention

Circuit breakers are designed for use in switchboards, control panels, and combination starters in separate enclosures for effective single location distribution and control and safe operation by operators. Typically, a circuit breaker such as a molded case circuit breaker (herein after ‘the MCCB’) serves as a switching device for switching ON/OFF during normal operating conditions for the purpose of operation and maintenance and also, serves as a protecting device during abnormal conditions such as short-circuit, overload and under voltage for tripping/ isolating an electrical circuit by breaking the contacts to interrupt the fault current.

In most common type of installation, the circuit breaker is switched ON and OFF by rotating an operating handle mounted on a panel door of an enclosure. For remote operations as well as high end operations that require an electric supply to be reinstated in a very short span of time ranging in micro seconds or while swapping ends between two supplies, an add-on accessory such as a stored energy electrical operating mechanism (hereinafter referred as “the SE-EOM”) mounted on the MCCB is used.

The SE-EOM consists of a combination of mechanical linkages to operate automatically using a motor or manually to generate energy for switching OFF or closing operation of the MCCB which in turn stores energy in a system which is released for use in switching ON or opening operation of the MCCB to reinstate the supply. The energy is stored by charging a spring and the spring is discharged to release energy.

In manual operation of the SE-EOM, a charging unit, a handle attached to it and a cranking system provided onto the handle allow the operator to drive the MCCB from ON to OFF positions and a manual OFF button allows discharging the energized spring through various linkages mechanically connected. In automatic operation of the SE-EOM, the motor charges the spring and drives the MCCB from ON to OFF positions and a solenoid input from remote location discharges the energized spring through mechanical linkages connected below. Some of the patent publications disclosing the SE-EOM are described below.

In U.S. Patent 6130392, disclosed is a stored energy circuit breaker operator for association with an operating handle of a circuit breaker contains springs that store energy when charged and that release energy when discharged. Energy is stored when a movement translation assembly is moved in a charging direction by an operator gear and stored energy is released when a release apparatus releases the operator gear causing the movement translation assembly to move in a discharging direction. The circuit breaker operating handle is moved to ON position by the charging movement of the movement translation assembly, and as stored energy is released, the discharging movement of the translation assembly moves the operating handle to OFF position. The operator gear is operated via an operator handle, an operator shaft and a pinion gear assembly. The pinion gear assembly has a carrier pivotally associated with the operator shaft and a pinion gear that rotates the operator gear. The operator gear may also be turned by an electric motor and a series of gears to accomplish electric operation of the circuit breaker.

Similarly, U.S. Patent 6166343 discloses a unidirectional clutch assembly for use with an operator handle, a pinion shaft assembly, a worm gear assembly and a pinion gear assembly of a stored energy assembly for use with a circuit breaker assembly, the operator handle and pinion shaft assembly including an operator handle having an outer handle hub having a first recess for receiving a first end of the pinion shaft assembly, the worm gear assembly fitting over the pinion shaft assembly and the pinion shaft assembly having a second end for receiving a pinion gear assembly, the unidirectional clutch assembly comprising a first unidirectional clutch structure, wherein the first unidirectional clutch structure fits over the first end of the pinion shaft and the unidirectional clutch structure is fitted into the first recess of the outer handle hub and a second unidirectional clutch structure, wherein the second unidirectional clutch structure fits within the worm gear assembly and over the pinion shaft assembly between the first and second ends of the pinion shaft assembly, wherein the first unidirectional clutch structure and said second unidirectional clutch structure are oriented in the same direction so that they slip unidirectionally in the same direction.

Also, in another U.S. Patent 6192718, it is disclosed that a key lock and locking hasp assembly is used for a stored energy circuit breaker operator assembly. It is provided with an electrical control module for use with a stored energy circuit breaker assembly having a motor for use with a circuit breaker assembly, the circuit breaker assembly providing an electrical signal through electrical contacts for actuating the circuit breaker assembly, the electrical control module comprising: a rectifying circuit, which receives and rectifies said electrical signal so as to provide a rectified electrical signal; a motor switch circuit connected to the motor; and an electrical signal flow maintenance circuit, which is operatively connected to said rectifying circuit, said motor switch circuit and the motor, wherein said electrical signal flow circuit maintenance maintains at least a threshold rectified electrical when the electrical contacts are closed so that said motor switch circuit is on and the motor operates.

Another U.S. Patent 4042896 discloses a manual and motor operated circuit breaker. It is provided with a circuit function which is adapted for either manual or motor driven operation, as desired. Motor driven operation is achieved by the incorporation of a power unit comprising a motor selectively drivingly coupled to the circuit breaker operating mechanism and operating to charge the mechanism spring incident to closing the breaker contacts. Upon completion of a charging function, a closing solenoid is energized to effect release of the stored energy, which powers the breaker contacts to their closed position. Control elements sensitive to the condition of the operating mechanism and the position of the breaker movable contacts function to appropriately condition switching logic in the motor and closing solenoid circuit for sequencing the charging and closing functions in a reliable manner. The control elements further function to selectively position indicator means effective to visually identify the various breaker conditions.

In the existing SE-EOM, a portion of stored energy is used to close the circuit breaker. Thus, energy is wasted in overcoming resistance introduced by components used in charging systems. Further, if the charging system is manually operated, it can be interrupted or overrun when the charging system is engaged during manual operation of the charging system. Further, the use of two springs of different stiffness for charging and discharging mechanism in motor operating system for circuit breaker switching operation adds to the complexity and cost of operation. With domain driving towards compact and cost effective modules, volume allocated for constructing SE-EOM module was limited. The prior means of operating and achieving the intended function uses larger volume and has higher energy consumption.

Moreover, prior SE-EOM consists of a tension spring for storing and discharging of energy, where the chances of failure in the region of hook are higher. As the tension spring is held physically between pins, the restitution energy stored in the springs during discharging or closing of the circuit breaker causes a knob to wobble and not attain its final closed position as it is physically held to the member which transmits the knob thereby resulting in no continuity and thus preventing the circuit breaker from switching ON. The spring is held tight between two members and a cam link provided to transfer the required rotary motion has bouncing effect. To absorb the bouncing effect, a separate system was introduced on the rotating elements which again acquires more space and increases the cost.

Accordingly, there exists a need of a compact and cost effective stored energy operating mechanism for a molded case circuit breaker that overcomes the above mentioned drawbacks of the prior art.

Object of the invention

An object of the present invention is to provide a multi-link scotch yoke assembly that uses less number of components to achieve desired functions with effective space utilization and without raising issues of backlashes, continuity and bouncing back.

Another object of the present invention is to use an integrated gear arrangement to achieve less friction, larger speed reduction and higher torque from a smaller motor.

Yet another object of the present invention is to accommodate a compression spring between floating members with proper seating and support throughout an operation that takes care of buckling effect.

Still another object of the present invention is to provide compact means of arrangement with well utilization of mechanical linkages for achieving intended functions with increased energy transmission, increased efficiency and increased travel accommodation (ON-OFF linear travel) for a molded case circuit breaker.

Summary of the invention

Accordingly, the present invention provides a stored energy operating mechanism (hereinafter ‘operating mechanism’) for a molded case circuit breaker. The operating mechanism comprises a motor, a gear assembly such as an integrated gear assembly being driven by the motor, a shaft being driven by the gear assembly, a scotch-yoke assembly allowing the shaft to pass there through for being driven by the gear assembly and a spring assembly held in the scotch-yoke assembly. The scotch-yoke assembly is a multi-link scotch-yoke assembly that includes a moving member, a fixed member and a pin.

The moving member includes a first slot and a second slot configured on either side thereof. The first slot adaptably allows the shaft to pass there through for being driven by the gear assembly. The fixed member includes the spring assembly resting on a side plate thereof for charging or discharging during any of a manual operation and an automatic operation of the molded case circuit breaker. The spring assembly includes a support member and a spring coiled thereon for compressing and charging against the side plate of the fixed member of the multi-link scotch-yoke assembly. The support member is a pin that supports and guides the spring therefrom towards the side plate. The spring is a floating concentric compression spring.

The fixed member includes a plurality of third slots and a fourth slot configured on either side thereof. The plurality of third slots is adapted for fixing the moving member therein. The pin is adapted for passing through the second slot of the moving member and the fourth slot of the fixed member for converting rotary motion transmitted from the motor to the gear assembly and then to the shaft into a linear motion.

The multi-link scotch-yoke assembly charges the spring assembly that undergoes compression against the side plate to store energy therein during ON-OFF travel of the molded case circuit breaker and the multi-link scotch-yoke assembly discharges the spring assembly during OFF-ON travel of the molded case circuit breaker.

Brief description of drawings

Other features as well as the advantages of the invention will be clear from the following description.

In the appended drawings:
Figure 1 shows a front view of a stored energy operating mechanism for a molded case circuit breaker, in accordance with the present invention;

Figure 2 shows a side perspective view of the stored energy operating mechanism of figure 1;

Figure 3 is a sectional view of the stored energy operating mechanism of figure 1 showing an integrated gear assembly;

Figure 4 is a sectional view of the stored energy operating mechanism of figure 1 showing a multi-link scotch-yoke assembly along with a spring assembly;

Figure 5 shows a side perspective view of a fixed component of the multi-link scotch-yoke assembly of figure 4; and

Figure 6 shows a side perspective view of an engagement of a moving component with the fixed component of the multi-link scotch-yoke assembly, in accordance with the present invention.

Detailed description of the invention

The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiment.

The present invention provides a stored energy operating mechanism (hereinafter ‘operating mechanism’) for a molded case circuit breaker. The operating mechanism includes a multi-link scotch yoke assembly, an integrated gear arrangement that use less number of components with effective space utilization to achieve desired functions with less friction, larger speed reduction and higher torque from a smaller motor without raising issues of backlashes, continuity and bouncing back. The operating mechanism accommodates a compression spring between floating members with proper seating and support throughout an operation that takes care of buckling effect. The operating mechanism achieves intended functions with increased energy transmission, increased efficiency and increased travel accommodation (ON-OFF linear travel) for a molded case circuit breaker with well utilization of mechanical linkages.

The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures.

Referring now to figures 1-6, a stored energy operating mechanism (100) for a molded case circuit breaker (200) in accordance with the present invention is shown. The stored energy operating mechanism (100) (herein after ‘the operating mechanism (100)’) is assembled onto the molded case circuit breaker (200) (herein after ‘the MCCB (200)’). The operating mechanism (100) switches ON or OFF the MCCB (200) even from a remote place in any of an automatic operation or a manual operation. The MCCB (200) includes a handle (110) for the manual operation thereof. The operating mechanism (100) comprises a motor (10), a gear assembly (20), a shaft (30), a scotch-yoke assembly (60) and a spring assembly (not numbered).

The motor (10) is operably coupled to the gear assembly (20). Specifically, the gear assembly (20) is an integrated gear assembly that includes a compound gear (11), an outer gear (12), a sun gear/ epicyclic gear train (14), a planet gear (15) and an internal gear (18) as shown in figures 2 and 3. However, it is understood that the gear assembly (20) can include any other suitable types of gears known in the art. The compound gear (11) is coupled to the outer gear (12). The outer gear (12) is coupled to the epicyclic gear train (14). The epicyclic gear train (14) is capable of engaging the planet gear (16) that in turn engages with the internal gear (18). The internal gear (18) includes a ratchet profile or ratchet type serrations (not numbered) on an outer surface (not numbered) thereof. Entire gear assembly (20) is analytically calculated and strategically arranged so as to achieve the required torque transmission and reduced velocity. The gear assembly (20) is capable of being driven by the motor (10). More particularly, the motor (10) undergoes rotary motion to drive the compound gear (11) of the gear assembly (20). The compound gear (11) in turn transfers the rotary motion from the motor (10) to the internal gear (18) through the gears (12, 14 and 16).

The gear assembly (20) drives the shaft (30) through the motor (10). The shaft (30) is adapted to pass through the scotch yoke assembly (60) for being driven by the gear assembly (20) such that output from any of the epicyclic gear train (16) and the internal gear (18) is coupled to the scotch yoke assembly (60). Specifically, the scotch yoke assembly (60) is a multi-link scotch yoke assembly that converts rotary motion transmitted from the motor (10) to the gear assembly (20) into larger linear motion in less space. The scotch yoke assembly (60) (herein after ‘the multi-link scotch yoke assembly (60)’) includes a moving member (45), a fixed member (55) and a pin (58). In an embodiment, the moving member (45) and the fixed member (55) are made by a simple metal forming or a plastic forming process.

The moving member (45) (refer figure 5) includes a first slot (42) and a second slot (not shown) configured on either side thereof. Specifically, the first slot (42) is configured on each side of a top surface (not numbered) thereof and the second slot is configured on each side of a bottom surface (not numbered) thereof. The first slot (42) is adapted for allowing the shaft (30) to pass there through to be driven the gear assembly (20). The moving member (45) is fitted on a top open side (not numbered) of the fixed member (55).

The fixed member (55) includes a plurality of third slots (52) and a fourth slot (54) configured on either side thereof. The plurality of third slots (52) is configured on the fixed member (55) for adaptably fixing the moving member (45) therein. The position on the fixed member (55) where the fourth slot (54) is configured depends on the travel.

The pin (58) is adapted for passing through the second slot of the moving member (45) and the fourth slot (54) of the fixed member (55) for converting rotary motion transmitted from the motor (10) to the gear assembly (20) and then to the shaft (30) into a linear motion to enable intended operations of the MCCB (200).

The fixed member (55) includes a side plate (51) (refer figures 5 and 6) to take care of the placement and charging of the spring assembly. In other words, the spring assembly rests on the side plate (51) for compression/expansion and charging/ discharging there against during any of a manual operation and an automatic operation of the MCCB (200). The spring assembly is held in the multi-link scotch-yoke assembly (60). The multi-link scotch-yoke assembly (60) charges the spring assembly when the MCCB (200) travels from ON position to OFF position and discharges the spring assembly during the OFF-ON travel of the MCCB (200) in any of the manual operation and the automatic operation.

The spring assembly includes a support member (80) and a spring (75). The support member (80) is fixed between a support plate (90) and the side plate (51) of the fixed member (55) of the multi-link scotch-yoke assembly (60) as shown in figure 4. The spring (75) is coiled on the support member (80) that supports and guides the spring (75) therefrom towards the side plate (51) without any buckling effect. The spring assembly is placed as a floating member without any physical connection so as to inherently take care of the bounce effect. In an embodiment, the support member (80) is a pin and the spring (75) is a floating concentric compression spring. The spring (75) is capable of compressing and charging against the side plate (51) of the fixed member (55) of the multi-link scotch-yoke assembly (60). The charged spring (75) has energy stored therein for use in any one of the manual operation and the automatic operation of the MCCB (200).

During the automatic operation, the motor (10) drives the compound gear (11) that in turn drives other gears (12, 14, 16 and 18) of the gear assembly (20). The gear assembly (20) further drives the shaft (30) such that the epicyclic gear train (16) of the gear assembly (20) transmits the rotary motion (20) from the shaft (30) to the pin (58) of the multi-link scotch-yoke assembly (60) through the second slots and the fourth slots (54) for conversion to the linear motion. Thus, multi-link scotch-yoke assembly (60) uses the motor energy during ON-OFF travel of the MCCB (200) and at the same time causes compression and thus charging of the spring assembly. The spring energy is utilized during OFF-ON travel of the MCCB (200).

During the manual operation, the motor (10) is disengaged through the gear assembly (20). The handle (110) of the MCCB (200) interacts with the ratchet profile on the internal gear (18) to drive the gear assembly (20) that further drives the shaft (30) such that the internal gear (18) of the gear assembly (20) transmits the rotary motion (20) to cause the multi-link scotch-yoke assembly (60) to compress and charge the spring assembly ON-OFF travel of the MCCB (200) and discharge the spring assembly OFF-ON travel of the MCCB (200).

Advantages of the invention

1. The multi-link scotch yoke assembly (60) of the operating mechanism (100) forms as a separate modular unit that is easy to assemble in less volume, helps in achieving intended function at lesser cost and in lesser time requiring less energy consumption thereby improving functionality and efficiency.
2. A single component made of press part operation is used as a scotch and the same is used for supporting the floating concentric compression spring (4).
3. The multi-link scotch yoke assembly (60) and the spring assembly are placed in a way to take care of the bounce back effect. Bouncing here is addressed in a way that the spring (75) used for storing the energy is disengaged when the multi-link scotch yoke assembly (60) attains final position.
4. From the point where the spring (75) becomes floating member, the restitution energy stored in the system is left in such a way that the spring (75) becomes independent and doesn’t affect final close position of the MCCB (200) and thus, avoids complaints relating to no final stop, no continuity or the MCCB (200) not switching ON.
5. The spring (75) of the operating mechanism (100) is assembled in such a way to remain supported at the time of operation when there is a requirement for higher force.
6. The gear assembly (20) of the operating mechanism (100) achieves unidirectional motor load transmission and reduces surface contact and friction between the gears (10, 12, 14, 16 and 18) and thus avoids backlash involved.
7. During use of the motor (10) for remote operation, the input is reduced through the gear assembly (20) to achieve required torque and in turn translates them to the MCCB motion.
8. The epicyclic gear train (14) gives the advantage of higher reduction, force distribution in all gear teeth engaged at a time leading to less failure and less stress concentration on single tooth. Additionally, the epicyclic gear train (14) takes care of unidirectional motor load transmission, which means, during ON-OFF operation when motor loading is required; the epicyclic gear train (14) engages with the planet gear (16) and transmits the motion. During OFF-ON where spring discharging energy is utilized to switch on the MCCB (200), the reverse loading and thus, heating up of the motor (10) is prevented by the epicyclic gear train (14).

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.

,CLAIMS:We claim:

1. A stored energy operating mechanism (100) for a molded case circuit breaker
(200), the stored energy operating mechanism (100) comprising a motor (10), a gear assembly (20) being driven by the motor (10), a shaft (30), a scotch-yoke assembly (60) allowing the shaft (30) to pass there through for being driven by the gear assembly (20) and a spring assembly held in the scotch-yoke assembly (60),
characterized in that the scotch-yoke assembly (60) is a multi-link scotch-yoke assembly (60) having
a moving member (45) having a first slot (42) and a second slot configured on either side thereof, the first slots (42) being adapted for allowing the shaft (30) to pass there through for being driven by the gear assembly (20);
a fixed member (55) having the spring assembly resting against a side plate
(51) thereof for charging or discharging during any of a manual operation and an automatic operation of the molded case circuit breaker (200), the fixed member (55) having a plurality of third slot (52) and a fourth slot (54) configured on either side thereof, the plurality of third slot (52) being adapted for fixing the moving member (45) therein; and
a pin (58) adapted for passing through the second slot of the moving member
(45) and the fourth slot (54) of the fixed member (55) for converting rotary motion transmitted from the motor (10) to the gear assembly (20) and then to the shaft (30) into a linear motion,
wherein, the multi-link scotch-yoke assembly (60) charges the spring assembly that undergoes compression against the side plate (51) to store energy therein during ON-OFF travel of the molded case circuit breaker (200) and the multi-link scotch-yoke assembly (60) discharges the spring assembly during OFF-ON travel of the molded case circuit breaker (200).

2. The stored energy operating mechanism (100), wherein the gear assembly
(20) is an integrated gear assembly.

3. The stored energy operating mechanism (100), wherein the spring assembly
includes a support member (80) and a spring (75) coiled thereon for compressing and charging against the side plate (51) of the fixed member (55) of the multi-link scotch-yoke assembly (60).

4. The stored energy operating mechanism (100), wherein the support member
(80) is a pin that supports and guides the spring (75) therefrom towards the side plate (51).

5. The stored energy operating mechanism (100), wherein the spring (75) is a
floating concentric compression spring.