DESC:Field of the invention

The present invention relates to a low voltage current limiting circuit breaker and more particularly, to an integrated multi-gear electrical operating mechanism for a molded case circuit breaker.

Background of the invention

In the prior art it is generally known, 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. Also these are housed inside an enclosure to provide safety to users operating the same.

In the most common type of installation, an operating handle is 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 uses 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.

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, operator shaft, and 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 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, 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.

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 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-OFF and solenoid input from remote location discharges the energized spring through mechanical linkages connected below.

Stored energy operator serves two basic purposes. As a switching device: switching 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 means of operating and achieving the intended function uses larger volume and has higher energy consumption. Prior means of stored energy operating system consists of tension spring for storing and discharging of energy, where the chances of failure in the region of hook are higher. To achieve various functions that needed to perform MCCB operations, require increase energy transmission, increased efficiency, and increased travel accommodation (ON-OFF linear travel).

Accordingly, there is a need for an integrated multi-gear electrical operating mechanism for a molded case circuit breaker that overcomes the above mentioned drawbacks of the prior art.

Objects of the invention

An object of the present invention is to achieve larger reduction from a motor and to achieve higher torque at a molded case circuit breaker end.

Another object of the present invention is to accommodate larger linear travel, with which other case is achieved in higher volume.

Yet another object of the present invention is to provide compact means of arrangement and well utilization of mechanical linkages.

Still another object of the present invention is to provide ability to accommodate a compression spring with proper seating and a 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 with less number of components, fewer backlashes and less friction with higher travel.

Summary of the invention

The present invention provides an integrated multi-gear electrical operating mechanism (herein after ‘the operating mechanism’) for a molded case circuit breaker. The operating mechanism is adapted to operate the molded case circuit breaker 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 and includes a worm gear unit, a spur gear unit, an epicyclic gear train and a pinion and rack assembly.

The worm gear unit is capable of driven by the motor during an automatic switching OFF operation of the molded case circuit breaker for undergoing rotary motion to reduce speed of the motor and increase torque transmission therefrom. The spur gear unit is coupled to the worm gear unit for further reducing the motor speed. The epicyclic gear train is coupled to the spur gear unit to transfer the rotary motion therefrom. The pinion and rack assembly is coupled to the epicyclic gear train for converting rotary motion to larger linear motion. The pinion and rack assembly is a tri-pinion rack assembly that includes a rack for accommodating and charging the spring during the automatic operation of the molded case circuit breaker from ON position to OFF position. The spring is a concentric compression spring coiled on a built-in guide.

Brief description of the 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 an integrated multi-gear electrical operating mechanism for a molded case circuit breaker, in accordance with the present invention;

Figures 2 and 3 show side perspective views of the integrated multi-gear electrical operating mechanism of figure 1;

Figure 4 shows an epicyclic gear train of the integrated multi-gear electrical operating mechanism of figure 1;

Figure 5 shows a tri-pinion and rack assembly of the integrated multi-gear electrical operating mechanism of figure 1; and

Figure 6 shows a spring assembly accommodated in the tri-pinion and rack assembly of figure 4.

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 an integrated multi-gear electrical operating mechanism (herein after ‘the operating mechanism’) for a molded case circuit breaker (herein after ‘the MCCB’). The compact operating mechanism is combined with mechanical elements for achieving intended functions with larger reduction from a motor, accommodation of larger linear travel in small volume and higher torque at the MCCB end. The operating mechanism accommodates concentric compression springs to reduce bounce back effect of the MCCB for achieving final closing position thereof.

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

Referring to figures 1-6, an integrated multi-gear electrical operating mechanism (100) (herein after ‘the operating mechanism (100)’) for a molded case circuit breaker (200) in accordance with the present invention is shown. The operating mechanism (100) is assembled onto the molded case circuit breaker (200) (herein after ‘the MCCB) (200)’) for an automatic/motorized operation thereof even from a remote location. However, the MCCB (200) through a handle (110) thereof is also capable of being operated manually. The operating mechanism (100) operates the MCCB (200) to any one of ON and OFF positions in any of the automatic operation and the manual operation.

The operating mechanism (100) comprises a motor (not shown), a spring (10), a latching system (not numbered), a toggle system (not numbered) and a gear assembly (not numbered).

Specifically, the gear assembly is an integrated multi-gear assembly. The gear assembly (herein after ‘the integrated multi-gear assembly’) includes a worm gear unit (20), a spur gear unit (30), an epicyclic gear train (40) and a pinion and rack assembly (50). In an embodiment, the worm gear unit (20) is made from a phosphor bronze material and the spur gear unit (30) and the epicyclic gear train (40) are made from thermoplastic materials.

The worm gear unit (20) includes a worm shaft (20A) and a worm gear (20B). The worm gear unit (20) is capable of driven by the motor during the automatic switching OFF operation of the MCCB (200). Upon being driven, the worm gear unit (20) undergoes rotary motion for reducing speed of the motor and increasing torque transmission therefrom. The worm gear unit (20) is coupled to the spur gear unit (30) for transferring the rotary motion of the motor thereto.

The spur gear unit (30) includes a smaller gear (30A) and a larger gear (30B). The rotary motion of the worm gear unit (20) drives the spur gear unit (30). More particularly, the worm gear (20B) drives the smaller gear (30A) that in turn drives the larger gear (30B). Thus, the spur gear unit (30) acheives further reduction in speed of the motor. The spur gear unit (30) is coupled to the epicyclic gear train (40) for transferring the rotary motion of the motor thereto.

The epicyclic gear train (40) includes an internal gear (40A), a sun gear (40B) and planet gears (40C). The internal gear (40A) includes a ratchet profile/ serrations (40A1) on an outer periphery (not numbered) thereof. The output of the spur gear unit (30) drives the epicyclic gear train (40). More particularly, the output of the larger gear (30B) drives the sun gear (40B) causing the sun gear (40B) to engage with the planet gears (40C) that in turn drives and transmits the motion to the internal gear (40A) through the ratchet profile (40A1). The epicyclic gear train (40) 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 (40) takes care of unidirectional motor load transmission. During ON-OFF operation when motor loading is required, the sun gear (40B) engages with the planet gears (40C) and transmits the motion. During OFF-ON where spring discharging energy is utilized to switch on the MCCB (200), 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 (40). The epicyclic gear train (40) is coupled to the pinion and rack assembly (50) for transferring the rotary motion of the motor thereto.

Specifically, the pinion and rack assembly (50) is a tri- pinion and rack assembly that includes a primary pinion (50A), at least two secondary pinions (50B) and a rack (50C). The primary pinion (50A) is a pinion shaft that receives the output of the internal gear (40A) to convert rotary motion into linear motion by driving the secondary pinions (50B) at the same time and in same proportion that in turn transfers the motion to the rack (50C). The at least two secondary pinions (50B) (herein after ‘the secondary pinions (50B)’) are placed apart from each other at a particular angle and coupled to the rack (50C). Thus, the rack (50C) moves linearly to and fro between the two secondary pinions (50B) thereby converting rotary motion to larger linear motion in lesser space with less number of components. The gear calculations are done in such a way that the rack (50C) when moved between the secondary pinions (50B) does not lose motion and thus avoids gear head to head collision.

The rack (50C) on a surface (not numbered) accommodates the spring (10) coiled on a built-in guide (12). The built-in guide (12) is a support shaft that supports the spring (10) throughout the operation so as to avoid buckling and provide efficient charging and discharging. In an embodiment, the spring (10) is single or concentric or multiple compression spring placed coaxially or laterally along with the built-in guide (12). Thus, the pinion and rack assembly (50) accommodates and charges the spring (10). The rack (50C) is further connected to the toggle system. The rack (50C) undergoes linear movement by utilizing the motor energy to compress and thus, charge the spring (10) during the operation of the MCCB (200) from ON position to OFF position. The toggle system actuates due to the linear movement of the rack (50C) only after completion of the switching OFF operation and the spring charging to disconnect the supply to the motor circuit.

Referring again to figures 1-6, the automatic and manual switching ON and OFF operations of the MCCB (200) is illustrated.

Automatic switching ON operation: The motor is cut off through the epicyclic gear train (40) by the latching system. Thus, the operating mechanism (100) is actuated by an electrical input (not shown) to utilize the spring energy for rotation of the handle (110) of the MCCB (200) thereby switching ON the MCCB (200).

Automatic switching OFF operation: The motor of the operating mechanism (100) is actuated by an input from the remote location. The motor drives the worm gear unit (20) particularly the worm shaft (20A) that further drives the worm gear (20B). The rotary motion of the worm gear unit (20) reduces the speed of the motor and drives the spur gear unit (30). More particularly, the worm gear (20B) drives the smaller gear (30A) that in turn drives the larger gear (30B) to achieve further reduction in the motor speed. The output of the spur gear unit (30) drives the epicyclic gear train (40). More particularly, the output of the larger gear (30B) through the ratchet profile (40A1) drives the sun gear (40B) causing the sun gear (40B) to engage with the planet gears (40C) that in turn drives and transmits the motion to the internal gear (40).

The output of the internal gear (40) drives the primary pinion (6A) that in turn drives the secondary pinions (50B) at the same time and in same proportion that in turn transfers the motion to the rack (50C) causing the rack (50C) to move linearly to and fro between the two secondary pinions (50B) thereby converting rotary motion into the linear motion. The linear movement of the rack (50C) results in charging of the spring (10) to store energy and at the same time causes switching OFF of the MCCB (200). Thus, the motor energy transferred through the worm gear unit (20), spur gear unit (30) and the epicyclic gear train (40) is used for charging the spring (10) through the pinion and rack assembly (50). Once the switching OFF operation and the spring charging is completed, the movement of the rack (50C) actuates the toggle system to disconnect the input supply to the motor.

Manual switching ON operation: The spring (10) is disengaged from the rack (50C) to utilize the spring energy and thus discharging the spring (10) for operating the handle (110) of the MCCB (200) thereby switching ON the MCCB (200).

Manual switching OFF operation: During manual charging, the motor is disengaged through the epicyclic gear train (40). The handle (110) is attached to the ratchet profile (40A1) of the internal gear (40) to charge the spring (10) and switch OFF the MCCB (200).

Advantages of the invention

1. The operating mechanism (100) includes the multi-gear assembly that allows accommodation of various gear arrangements in the intended volume to improve functionality.
2. The operating mechanism (100) includes the multi-gear assembly having different gear arrangements that function together in allocated volume to achieve the intended functions such as the worm gear unit (20) acheives higher reduction, the epicyclic gear train (40) acheives unidirectional motion transmission as well as torque distribution and the tri-pinion rack assembly (50) acheives larger linear travel.
3. The operating mechanism (100) includes the integrated multi-gear assembly that is arranged in a way to achieve effective space utilization, higher reduction from the available lower torque motor to deliver higher torque.
4. The concentric compression spring (10) of the operating mechanism (100) are placed in such a way to take care of the bounce back of the MCCB (200) that occurs due to physical connection between the spring (10) and moving members that carry the handle (110) of the MCCB (200) thus, the final closing position of the MCCB (200) is easily achieved.
5. The operating mechanism (100) includes the tri-pinion rack assembly (50) designed to accommodate the concentric compression spring (10) between surfaces and with the support shaft to provide built-in support (12) to reduce buckling of the spring (10) thereby increasing the efficiency.
6. Extra energy in the means of bounce back is taken care of by the spring (10) that disengages from the rack (50C) unlike tension springs that remain held onto the rack (50C).
7. The handle (110) for manual operation during charging is made in such a way that the serrations (40A1) on the outer periphery of the internal gear (40A) are utilized and thus reducing one more component usage separately for spring charging.

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. An integrated multi-gear electrical operating mechanism (100) for a
molded case circuit breaker (200), the operating mechanism 100) being adapted to operate the molded case circuit breaker (200) to any one of ON and OFF positions, the operating mechanism comprising a motor, a spring (10), a latching system, a toggle system and a gear assembly,
characterized in that, the gear assembly is an integrated multi-gear assembly having
• a worm gear unit (20) being capable of driven by the motor during
an automatic switching OFF operation of the molded case circuit breaker (200) for undergoing rotary motion to reduce speed of the motor and increase torque transmission therefrom;
• a spur gear unit (30) coupled to the worm gear unit (20) for further
reducing the motor speed;
• an epicyclic gear train (40) coupled to the spur gear unit (30) to
transfer the rotary motion therefrom; and
• a pinion and rack assembly (50) coupled to the epicyclic gear train
(40) for converting rotary motion to larger linear motion, the pinion and rack assembly (50) being capable of accommodating and charging the spring (10) during the automatic operation of the molded case circuit breaker (200) from ON position to OFF position.

2. The integrated multi-gear electrical operating mechanism (100) as claimed
in claim 1, wherein the pinion and rack assembly (50) is a tri-pinion rack assembly having a rack (50C) that accommodates the spring (10).

3. The integrated multi-gear electrical operating mechanism (100) as claimed
in claim 1, wherein the spring (10) is a concentric compression spring.

4. The integrated multi-gear electrical operating mechanism (100) as claimed
in claim 1, wherein the spring (10) is coiled on a built-in guide (12).