DESC:“INTEGRATED LATCHING SYSTEM IN ELECTRICAL OPERATING MECHANISM FORCIRCUIT BREAKER”
Field of the invention
The present invention generally relates to molded case circuit breakers, more particularly it relates to the stored energy electrical operating contact mechanism of molded case circuit breaker, still more particularly it relates to an integrated latching system for stored energy electrical operating contact mechanism of molded case circuit breaker
Background of the invention
A circuit breaker typically serves two basic purposes: first as a switching device for switching On/Off during normal operating conditions for the purpose of operation and maintenance; and second as a protecting device for tripping or isolating by breaking the contacts interrupting the fault current during abnormal conditions such as short-circuit, overload and under voltage. Circuit breaker consists of one or more electric poles, whose number determined by the application as single pole circuit breaker, two-pole circuit breaker, three-pole circuit breaker and four-pole circuit breaker and so on. They are designed for use in switchboards, control panels, and combination starters in separate enclosures for effective single location distribution and control. Circuit breakers are housed inside an enclosure to provide safety to users operating the same.
In the most common type of installation, an operating handle mounted on the panel door has to be rotated to switch the circuit breaker ON and OFF. For high end operations wherein the electric supply needs to be reinstated in a very short span of time ranging in micro seconds, or while swapping ends between two supplies, a stored energy operating mechanism is mounted on the molded case circuit breaker (hereinafter referred as “MCCB”) and used to release energy required to close the contacts of the circuit breaker and reinstate the supply. The stored energy operating mechanism is one such device which is a combination of mechanisms for accumulating and storing mechanical energy, wherein the energy is used to close the primary contacts of the circuit breaker. The energy can be input to the mechanism manually or by means of a motor. The mechanism includes a series of linkages which function to utilize the energy to close the primary contacts. These linkages also function to maintain the closing force upon the primary contacts, while also functioning to allow rapid contact opening when desired.
Use of electrical devices is well known for making, breaking and to provide safety in a typical electrical distribution system. These devices get mounted inside a board or panel board for added safety to the operator. Most often these devices are required to be operated either from outside or by opening the enclosure/ panel. In view of operator’s safety, remote operation is an alternative way to operate the switching devices. Usually to achieve this, an add-on accessory is mounted over the switching device, which may operate the device when called for.
Also in today’s scenario response time for an electrical switching system to switchover from one desired source to the other is gaining importance. Thus with a view of lesser operational time and remote operation of a switching device, stored energy type of motor mechanism are used.
In current scenario, inventions in the art use portion of stored energy 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 manual charging system. Yet in another scenario, some of inventions use two springs of different stiffness for charging and discharging mechanism in motor operating system for circuit breaker switching operation.
Electrical operating mechanism (hereinafter referred as “EOM”), is mainly used to drive MCCB from a remote location through electrical input. EOM can be of two main types, motor operator and stored energy operator. In case of Motor operator, motor energy is used in both ways of closing and opening the MCCB. In case of stored energy operator, the motor energy is used in the direction of ON-OFF movement, which means opening of MCCB, in which the spring assembled in the system is charged and allowed to store energy through various mechanical means. The stored energy is discharged, during the OFF-ON motion, which means closing of MCCB contacts.
Stored energy operator has two modes of operation: Manual and Auto. Manual mode consists of a charging unit and the handle attached to it, so that cranking system provided onto the handle allows customer to drive the MCCB from ON-OFF and a manual OFF button allowing the unit to discharge the energized spring through various linkages mechanically connected. Auto mode consists of motor charging the spring and driving the unit from ON to OFF which is an input from remote location charging the spring through mechanical linkages connected below.
Stored energy operator serves two basic purposes. As a switching device: On/Off during normal operating conditions for the purpose of operation and maintenance. As a protecting device: Tripping or isolating by breaking the contacts interrupting the fault current during abnormal conditions such as short-circuit, overload and under voltage. Stored energy electrical operating mechanism (hereinafter referred as “SE-EOM”) is also supposed to meet the standard and Foot print requirements of basic breaker.
MCCB being the governing element, with preset boundary conditions and constraints, SE-EOM has to perform primary, secondary and tertiary functions in a determined manner.
With domain driving towards compact and cost effective modules, volume allocated for constructing SE-EOM module was limited.
The prior art patent US 6130392 discloses a stored energy circuit breaker operator for association with an operating handle of a circuit breaker, containing 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. Another prior art patent US6192718 discloses a key lock and locking assembly 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. US4042896 discloses a manual and motor operated circuit breaker. In the disclosure, 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.
The prior means of operating and achieving the intended function uses larger volume and has higher energy consumption. Prior means of stored energy operating system consist of tension spring for storing and discharging of energy, where the chances of failure in the region of hook are higher. Separate mechanism with latch is used to keep spring in charged condition, which increases the number of components and reduces the reliability of mechanism. Also, different latching components are used to discharge the spring, which increases the operating force of the mechanism. Prior means of stored energy operating system consist of cam latch for latching during handle charging and ratchet based latching during motor charging. Various functions that are needed to perform MCCB operations are achieved by increased energy transmission, increased efficiency, and increased travel accommodation (ON-OFF linear travel) with increased number of components and reducing reliability.
Accordingly, there exists a need for an integrated latching arrangement reducing number of components, improving reliability of electrical operating mechanism for molded case circuit breaker that overcomes the above mentioned drawbacks of the prior art.
Objects of the invention
The primary object of the present invention is to provide an integrated latching system for stored energy electrical operating mechanism in a molded case circuit breaker
Another object of the present invention is to provide a simple operating mechanism to keep spring in charged condition without any additional arrangements.
Still another object of the present invention is to provide a compact means of arrangement and well utilization of mechanical linkages improving reliability.
Still another object of the present invention is to provide ability to accommodate compression spring with proper seating and built-in spring guide throughout an operation.
Further object of the present invention is to take care of buckling effect which will be predominant if there is no support.
Furthermore object of the present invention is to achieve the desired function in less number of components, fewer backlashes and less friction with higher travel.
Summary of the invention
The present invention provides an integrated latching system for a stored energy electrical operating mechanism, adapted to operate a molded case circuit breaker to any of the ON or OFF position. The electrical operating system mainly comprises of a motor, a spring, a multi gear assembly, a toggle system and a latching system. During automatic switching OFF operation of the MCCB, the motor of the operating mechanism is actuated by an input from the remote location. The multi-gear assembly driven by the motor reduces the speed of the motor and charges the spring. The integrated latching assembly comprising the solenoid assisted main latch and the supportive latch. The latching arrangement is such that once charging is initiated and on the way of achieving completion, load is shifted from supportive latch to the main latch. This way the sudden impact faced by the main latch during motor charging and latching on the ratchet. This sudden impact in turn is faced by the solenoid during discharging. Due to increased delatching load faced by solenoid, sometimes it may lead to delayed opening and heating up of solenoid coil and non-delatching. Supportive latch being spring loaded has a tendency to fall back to original position all times. To avoid intermittent falling and latch engagement before complete discharge is being ensured by providing compact solenoid. This solenoid will always ensure the completion of operation when the circuit is powered. To avoid this issue of non-delatching and improving reliability the supportive latch and innovative method of load shifting to main epicyclic latch and assisted supportive latch is utilized. The solution is achieved with the utilization of minimum number of components with minimal changes in existing components. Hence improving functionality with increased reliability.
Brief description of the drawings
Figure 1 shows a perspective view of full assembly of stored energy electrical operating mechanism of a molded case circuit breaker in accordance with the present invention;
Figure 2 shows a perspective view of mechanism assembly without base, for stored energy electrical operating mechanism in accordance with the present invention;
Figure 3 shows the epicyclic gear train assembly in accordance with the present invention;
Figure 4 shows the exploded view of the stored energy electrical operating mechanism in accordance with the present invention;
Figure 5 shows the back side view of the sun gear of epicyclic gear train assembly in accordance with the present invention;
Figure 6 shows the detailed view of the planet gears of the epicyclic gear train assembly in accordance with the present invention;
Figure 7 shows the internal gear of the epicyclic gear train assembly in accordance with the present invention;
Figure 8 shows the compound gear assembly of worm gear unit in accordance with the present invention;
Figure 9 shows worm gear in accordance with the present invention;
Figure 10 shows the unidirectional bearing of the worm gear unit in accordance with the present invention;
Figures 11 and 12 respectively show the rack and pinion arrangement in accordance with the present invention;
Figure 13 shows the spring of the stored energy electrical operating mechanism in accordance with the present invention;
Figure 14 and 15 respectively show the motor and motor gear in accordance with the present invention;
Figure 16 shows the main shaft in accordance with the present invention;
Figures 17 and 18 respectively show the right side plate and left side plate in accordance with the present invention; and
Figure 19 shows the perspective view of integrated latching arrangement in accordance with the present invention.
Figure 20 shows the perspective view of toggle system mounted on Rack, in accordance with the present invention.
Detailed description of the invention
The foregoing objects of the 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 an integrated latching system for a stored energy electrical operating mechanism (hereinafter referred as “SE-EOM”) for a molded case circuit breaker (hereinafter referred as “MCCB”). The SE-EOM is adapted to operate the MCCB to any one of ON and OFF positions. The operating mechanism comprises a motor, a spring, a latching system, a toggle system and a gear assembly. The gear assembly is an integrated multi-gear assembly including a worm gear unit, an epicyclic gear train and a pinion and rack assembly. The pinion and rack assembly has a rack for accommodating and charging a spring during the automatic ON to OFF operation of the MCCB. The internal gear driven by the planet gears of epicyclic gear train consists of a projection on the start point of charging or ON position of MCCB. This enables the load being transferred to the supportive latch at the initial point. Once charging is initiated and on the way of achieving completion, load is shifted from supportive latch to the main epicyclic latch. This way the sudden impact faced by the main epicyclic latch during motor charging and latching on the ratchet is eliminated. This sudden impact in turn is faced by the solenoid during discharging. Due to increased delatching load faced by solenoid, sometimes it may lead to delayed opening and heating up of solenoid coil and non-delatching. Supportive latch being spring loaded has a tendency to fall back to original position all times. To avoid intermittent falling and latch engagement before complete discharge is being ensured by providing compact solenoid. This solenoid will always ensure the completion of operation when the circuit is powered.
The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description. The components of the invention and the reference numbers are also listed in the Table 1 below:
Table 1:
Ref No Name of the component / system Ref No. Name of the component / system
100 Operating mechanism 10 Motor plate
50 Epicyclic gear train 11 Pinion
60 Integrated latching assembly 12 Spring support plate 2
1 Sun gear 13 Rack
2 Planet gears 14 Internal Gear
3 Main latch 14A Projection on internal gear (14)
4 Worm gear unit 15 Side plate (left)
4a Spur gear 16 Motor
4b Worm wheel 17 Motor sleeve
4c Unidirectional bearing 18 Supportive latch
4d Worm gear 19 Ratchet
5 Spring support plate 1 20 Solenoid
6 Spring shaft 21 Compact solenoid
7 Compression spring 22 Toggle switch
8 Side plate (right) 23 Toggle plate
9 Main shaft mechanism

The stored energy electrical operating mechanism (100) (hereinafter “SE-EOM (100)”) comprises a motor (16), a spring (7), an integrated latching assembly (60), a toggle system (not numbered) and a gear assembly.
Specifically, the gear assembly is an integrated multi-gear assembly. The gear assembly includes a worm gear unit (4), an epicyclic gear train (50) and a rack and pinion (13, 11). In an embodiment, the worm gear unit (4) is made from a phosphor bronze material except 4C and the sun gear (1) and planet gears (2) of the epicyclic gear train (50) are made from thermoplastic materials.
The worm gear unit (4) includes a worm wheel (4B), an unidirectional bearing (4C), a spur gear (4A) and a worm gear (4D). The worm gear unit (4) is capable of driven by the motor during the automatic switching OFF operation of the MCCB. The motor (16) drives the worm gear (4D), which in turn drives the worm wheel (4B). The worm wheel (4B) drives the spur gear (4A) that in turn drives the sun gear (1). The unifdirectional bearing (4C) allows the worm gear unit (4) to rotate only in one direction, i.e. in clockwise direction. Upon being driven, the worm gear unit (4) undergoes rotary motion for reducing speed of the motor and increasing torque transmission therefrom.
The worm gear unit (4) is coupled to the sun gear (1) of the epicyclic gear train (50) through the spur gear (A) for transferring the rotary motion of the motor thereto. The rotary motion of the worm gear unit (4) drives the spur gear (4A). More particularly, the worm wheel (4B) drives the spur gear (4A) that in turn drives the sun gear (1). Thus, here achieves further reduction in speed of the motor.
The epicyclic gear train (50) further transfers the rotational motion to an internal gear (14). The internal gear (14) has a ratchet profile/ serrations and a projection (14A) on the outer periphery thereof. The output of the spur gear (4A) drives the sun gear (1) causing the sun gear (1) to engage with the planet gears (2) that in turn drives and transmits the motion to the internal gear (14) through the ratchet profile (19). The epicyclic gear train (50) gives the advantage of higher reduction, force distribution in all the gear teeth engaged at a time leading to less failure and less stress concentration on single tooth. Additionally the epicyclic gear train (50) takes care of unidirectional motor load transmission. During ON-OFF operation when motor loading is required, the sun gear (1) engages with the planet gears (2) and transmits the motion. During OFF-ON where spring discharging energy is utilized to switch on the MCCB, the reverse loading of the motor is to be prevented to avoid heating up of the motor. This is taken care of with the help of epicyclic gear train (50) and Worm gear unit (4). The epicyclic gear train (50) is coupled to the pinion (11) and rack assembly (13) for transferring the rotary motion of the motor thereto.
The pinion and rack assembly is that includes a rack (13) for accommodating and charging the spring (7) during the automatic ON to OFF operation of the MCCB. The spring (7) is a concentric compression spring (7) coiled on a built-in guide.
An integrated latching assembly (60) is having a main latch (3), a solenoid (20) engaging the main latch (3), a supportive latch (18) and a compact solenoid (21) engaging the supportive latch (18); the main latch (3) and the supportive latch (18) restrict the rotation of the ratchet (19) in unidirectional way.
The main feature to keep spring (7) in charged condition is explained as follows:
During charging of the spring (7), pinion (11) rotates in anticlockwise direction which rotates the internal gear (14) in same direction as it is coupled with the same shaft (9) which tries to rotate the sun gear (1) in clockwise direction which in turn tries to rotate the worm gear unit (4) in anticlockwise but due to unidirectional bearing (4C) it will not rotate in anticlockwise direction. An epicyclic latch (3) and the planet gear (2) keep the spring (7) in charged condition unless and until it is manually discharged.
During charging, main epicyclic latch (3) is in open position due to projection (14a) on internal gear (14). Supportive latch (18) is in engaged position holding the ratchet (19) thus assisting in charging action. Once the projection (14a) rotates along with the charging motion and reaches the supportive latch (18), the same is disengaged and the latching is shifted to main epicyclic latch (3). At this point, when shifting happens, spring is in charged position and the MCCB is in OFF position, Load faced by the motor is high at this point, in correlation to it speed of the motor reduces to meet the torque requirements. In relation, impact faced by the latch (3) will also be less during shifting and latching in turn reducing the delatching load faced by the solenoid (20).
During ON (discharging) operation, solenoid (20) disengages the main latch and compact solenoid (21) disengages the supportive latch (18) to ensure positive disengagement till the completion.
Figure 21 shows the perspective view of toggle system mounted on Rack, enabling to take the feedback of Rack position in turn the MCCB position
Entire charging and discharging operation happens in fool proof manner with a toggle system feedback is designed to provide one pulse at a time. Toggle system as shown in Fig.20 takes the MCCB position as the Toggle plate (23) is coupled to Rack which in turn coupled to MCCB knob, thus ensuring a positive interlocking. Toggle (22) being a DPDT switch provides an input to the motor (16) during charging or when the rack (13) is in ON position and the same provides input to the solenoid (20) during discharging or when rack (13) is in OFF position.

Advantages of the present invention
• Need for this invention arise when there is limited space and market depends for operation of unit under larger voltage bandwidths.
• At lower voltages when power supplied to motor is not sufficient, motor may have burnt out. To avoid such cases and to avoid fuse getting blown out, Motor has to be disengaged from the load
• This invention is an embodiment of present assembly which enhances the functional need to meet latch load shifting and low voltage disengagement.
• The current invention defines a way to keep spring in charged condition using integrated latching arrangement on single latch eliminating multiple latch arrangements. It also has integrated latch arranged with compact solenoid which only senses input voltage and magnetizes or demagnetizes based on the input.
• When voltage is above particular level, solenoid is magnetized and latch is closed to enable the unit to charging during motor operation. When voltage drops, solenoid is unable to magnetize and latching does not happen.
• Single latch in optimized location along with compact solenoid so as to ensure load shifting during operation
• Optimized location load shifting so as to reduce the force faced by solenoid is reduced
• In this way Single main solenoid which is connected to the Remote circuit will be able to discharge the latch without much effort.
• As compared to prior art and previous product where the load shifting does not happen, main solenoid energy required during delatching is higher.
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment. Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure, or matter. The embodiments of the invention as described above and the methods disclosed herein will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the spirit and scope of the invention.
,CLAIMS:We Claim:
1. An electrical operating mechanism (100) for a molded case circuit breaker, the electrical operating mechanism (100) being adapted to operate the molded case circuit breaker to any one of ON and OFF positions, the electrical operating mechanism (100) comprising:
a motor (16),
a spring (7), being adapted for storing energy when the circuit breaker is in OFF position and releasing energy to make the circuit breaker ON;
a gear assembly driven by the motor (16) and being adapted to transfer the motor load in unidirectional way comprising:
a worm gear unit (4) including a worm gear (4D) capable of being driven by the motor (16), a unidirectional bearing (4C) coupled to the worm gear (4D), a worm wheel (4B) coupled to the unidirectional bearing (4C), and a spur gear (4A) coupled to the worm wheel (4B); the unidirectional bearing (4C) allowing the worm gear unit (4) to rotate in one direction only; and the worm gear unit reducing the speed of motor (16);
an epicyclic gear train unit (50) coupled to the spur gear (4A) and comprising a sun gear (1) coupled to a planet gear (2) having a ratchet profile (19) on outer periphery; the epicyclic gear train (50) further reducing the speed of motor (16);
an internal gear (14) having a ratchet profile and a projection (14A) on the outer periphery and capable of being driven by the planet gear (2) through the ratchet profile (19); and
a rack and pinion assembly including a pinion (11) coupled to the internal gear (14) through the main shaft (9); and a rack (13) accommodating the spring (7), wherein, during automatic ON to OFF operation of the molded case circuit breaker, the motor (16) drives the gear assembly unidirectionally to charge the spring (7);
an integrated latching assembly (60) having a main latch (3), a solenoid (20) engaging the main latch (3), a supportive latch (18) and a compact solenoid (21) engaging the supportive latch (18); the main latch (3) and the supportive latch (18) restricting the rotation of the ratchet (19) in unidirectional way; and
a toggle system comprising a toggle switch (22) having a toggle plate (23) coupled to the rack (13), the toggle switch (22) providing input to the motor (16) during ON position and providing input to the solenoid (22) during OFF position; wherein,
during charging of the spring (7), the main latch (3) is in open position due to the projection (14a) while the supportive latch (18) holds the ratchet (19) assisting the charging action till the projection (14a) reaches the supportive latch (18);
at completion of charging of the spring (7), the latching is shifted to main epicyclic latch (3) reducing the delatching load faced by the solenoid (20); and
during discharging of the spring (7), solenoid (20) disengages the main latch and compact solenoid (21) disengages the supportive latch (18) to ensure positive disengagement till the completion
2. The electrical operating mechanism (100) as claimed in claim 1, wherein the spring (7) is a concentric compression spring coiled on a built-in guide.
3. The electrical operating mechanism (100) as claimed in claim 1, wherein the projection projection (14A) is on the start point of charging of the spring (7) which is ON position of molded case circuit breaker, enabling the load being transferred to the supportive latch (18) at the initial point of charging.
4. The electrical operating mechanism (100) as claimed in claim 1, wherein the toggle switch (22) is a double pole double throw switch.
Dated this 9th day of October 2017

Ashwini Kelkar
(Agent for Applicant)
IN-PA/2461