DESC:FIELD OF THE INVENTION
The present invention relates generally to the drive mechanism of switchgear. More particularly, the present invention relates to a mechanism that prevents the overcharging of springs used in a spring based drive mechanism for opening and closing a circuit breaker of switchgear.
DESCRIPTION OF THE RELATED ART
Gas insulated switchgear (GIS) is a matured switchgear technology that is dominating the market due to its compactness and lifecycle cost. Circuit breaker is a key component of the Gas Insulated Switchgear. The opening and closing operation of the contacts of a circuit breaker is controlled by an energy storing device. A considerable amount of energy is required to carry the opening and closing operation of the circuit breaker. The conventional energy storing devices make use of either springs or torsion bars for storing energy.
The conventional energy storing devices that use springs as a energy storing elements use a ratchet and pawl based assembly to charge the springs. Generally the ratchet wheel of such an assembly would have a toothless peripheral wheel section. Only during the charging operation a pawl wheel engages with a section of the ratchet wheel that has tooth.
The pawl engages with the tooth of the ratchet wheel thus moving the ratchet wheel and in turn charging the spring. However, when the pawl comes in contact with the toothless portion of the ratchet wheel, it is unable to rotate the ratchet, this action protects the spring from overcharging.
However, in such an arrangement the first teeth of the ratchet wheel that comes into contact with the pawl is prone to failure owing to the fact that there is a single line of contact between the ratchet wheel and the pawl
OBJECTS OF THE INVENTION
An object of the present invention is to develop an improved spur gear based operating mechanism for spring based circuit breaker driving mechanism by means of a charging spur gear with toothless section and gear segment attached to retaining spring, driving spur gear attached to motor and, a spring attached to charging crank via chain. The spring gets compressed during clock wise rotation of the charging spur gear.

Another object of the invention is to develop an improved spur gear based operating mechanism for spring based circuit breaker driving mechanism with the advantage of preventing the overcharging of the spring and hence improving the reliability of the overall drive mechanism by means of mechanism wherein driving spur gear rotates the charging spur gear only for such a duration necessary to completely charge the spring. Once, the spring is completely charged the driving spur gear has a freewheeling rotation operation on the gear segment.
Another object of the invention is to develop a spur gear based operating mechanism for spring based circuit breaker driving mechanism with the advantage of preventing the teeth failure of charging wheel and driving wheel by provision of mechanism wherein the some portion of the teeth on the Driving Spur Gear and charging spur gear are cut on the edges such that orientation of the cut teeth are 180? apart for smooth and proper engagement of Driving spur gear and Charging spur gear.
Yet another object of the invention is to develop compact design of spur gear based operating mechanism for spring based circuit breaker driving mechanism with less number of linkages with the provision of gear chain based charging and discharging mechanism.
BRIEF DESCRIPTION OF DRAWINGS
The features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. Embodiments of the present invention will herein after be described in conjunction with the appended drawings provided to illustrate and not to limit the scope of the claims, wherein like designations denote like elements, and in which:
Fig. 1 is a schematic diagram of an operating mechanism of charging system when the charging spur gear is latched in according to an embodiment of the present invention
Fig. 2 is an isometric view of the operating mechanism in accordance with an embodiment of the present invention.
Fig. 3 is an enlarged view of the driving spur gear in accordance with an embodiment of the present invention.
Fig. 4 is a schematic diagram of an operating mechanism of charging system when the charging spur gear is unlatched in according to an embodiment of the present invention
Fig. 5 is an enlarged view of charging spur gear in accordance with an embodiment of the present invention.
Fig. 6, Fig. 7, Fig. 8 and Fig.9 show the operation of spring charging and discharging in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS
As used in the specification and claims, the singular forms “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. For example, the term “an article” may include a plurality of articles unless the context clearly dictates otherwise.
Those with ordinary skill in the art will appreciate that the elements in the figures are illustrated for simplicity and clarity and are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated, relative to other elements, in order to improve the understanding of the present invention.
There may be additional components described in the foregoing application that are not depicted on one of the described drawings. In the event such a component is described, but not depicted in a drawing, the absence of such a drawing should not be considered as an omission of such design from the specification.
Before describing the present invention in detail, it should be observed that the present invention constitutes a novel mechanism for prevention of the overcharging of spring used for the operation of circuit breakers in switchgear. Such mechanisms generally find applications in gas insulated switchgears (GIS). Accordingly, the components and the method steps have been represented, showing only specific details that are pertinent for an understanding of the present invention so as not to obscure the disclosure with details that will be readily apparent to those with ordinary skill in the art having the benefit of the description herein.
As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting but rather to provide an understandable description of the invention.
Various embodiments of the invention described herein focus primarily on reducing the stresses on the charging and discharging gear of a spring based circuit breaker drive mechanism, and focus on resolving the issues related to overcharging of springs.
Fig.1 is showing the construction of the operating mechanism of charging system. Motor is connected to Driving spur gear 1 through gear train since high torque is required for charging (Motor and Gear train is not shown here). Motor drives Driving spur gear 1 in clockwise direction. Driving spur gear 1 is connected to Charging spur gear 2, So Charging spur gear 2 is rotated in anticlockwise direction. There are two Gear segments 3 which are concentric to the rotation axis of charging spur gear 2 (which are placed at both side of charging spur gear 2 as shown in Fig.2). There is a bearing between spline shaft 4 and Gear segments 3, so both can rotate independently. Gear segments 3 are spring loaded by Retaining spring 5. In normal condition Gear segments 3 are rested on fixed protrusion 6. Retaining spring 5 helps the Gear segment 3 to rest on fixed protrusion 6 as shown in Fig.1.
Construction of Driving Spur Gear 1 is as shown in Fig.3. Teeth on the Driving Spur Gear 1 is cut as shown in Fig.3.(The both side teeth of gear are partially cut such that orientation of the cut teeth are 180? apart from each other). The middle portion of Driving gear 1 teeth (full teeth) are in contact with Charging spur gear 2 and cut portion of Driving gear 1 teeth are in contact with Gear segments 3. This arrangement is used for smooth and proper engagement of Driving spur gear 1 and charging spur gear 2. Charging crank 7 and Charging spur gear 2 both are on the same spline shaft 4 ,so both are rotates simultaneously. Charging crank 7 is connected to the chain 8 and this Chain 8 is connected to the Closing spring 9. So angular rotation of charging crank 7 helps to charge or discharge the closing spring 9.
Fig.4 shows the closing spring 9 in discharged condition. While charging operation (storing energy in spring), motor drives Driving spur gear 1 in clockwise direction through a series of gear pairs. Construction of driving spur gear 1 is as shown in Fig.3. Middle portion of the teeth is having full profile which comes in contact with charging spur gear 2 so it will drive the Charging spur gear 2 in anticlockwise direction. Charging spur gear 2 and charging crank 7 both are on same spline shaft 4 so charging crank 7 also rotates along with Charging spur gear 2 and charge (Compress) the closing spring 9. There is an opposing torque in clockwise direction due to the closing spring 9 until the line of action of chain 8 crosses the centre of spline shaft 4. As shown in Fig.4, once the line of action of chain 8 crosses the centre of spline shaft 4 as shown in Fig.1, there is a reversal in direction of closing spring 9 torque. This helps to rotate the Charging crank 7 and charging spur gear 2 in anticlockwise direction. The charging spur gear 2 is locked by latch 10 (as shown in Fig.1). Since, latch 10 has locked the rotation of charging spur gear 2, energy remains stored in the closing spring 9. As shown in Fig.1and Fig.2, at this position (at the latching condition) Charging spur gear 2 and driving spur gear 1 are not in contact with each other (teeth on this portion of charging spur gear 2 has been removed as shown in Fig.5).
In normal condition, a limit switch (not shown in the figures) stops the motor after latching of charging spur gear 2. But if in case, the limit switch fails or the motor does not stop due to any reason even after latching of Charging spur gear 2 (Spring full charged condition), it will not drive the Charging spur gear 2 due to the removed teeth arrangement (there is no teeth on that portion of Charging spur gear 2 as shown in Fig.2 and Fig.5). So this system avoids overcharging and damage to the system.
During the Charging of Closing spring 9, Gear segments 3 are rotating along with the Charging spur gear 2 due to the protrusion 6 (Gear segments 3 one face is in contact with the protrusion as shown in Fig.4). Arrangement of protrusion 6 is such that, During this position (when Gear segment is in contact with protrusion) profile of Gear segment's 3 last teeth exactly match (coincide) with the profile of Charging spur gear 2 tooth as shown in Fig.2. Protrusion 6 is fixed on the Charging spur gear 2. Those Gear segments 3 are not in contact with the Driving spur gear 1 during Charging of closing spring 9. But at the end of charging (just before latching) the Gear segment 3 gets engaged with the Driving spur gear 1. Side portions of driving spur gear 1 teeth are engaged with the Gear segment 3 as shown in Fig. 1 and Fig.2. This Driving spur gear 1 side portion is having only half teeth portion as shown in Fig.3 and these teeth portion on both sides are exactly opposite to each other. So when one Gear segment 3 is engaged with Driving spur gear 2 another Gear segment 3 is in its resting position (coincide with/resting on protrusion 6) as shown in Fig.6. When Driving spur gear's 1 teeth comes in contact with Gear segment 3, Gear segment 3 will start rotating in anticlockwise direction and it rotates until teeth are in contact as shown in Fig.6. But Gear segment 3 return back (rotates in clockwise direction) to its original resting position (rest on protrusion 6) when portion of the Driving spur gear 1 where teeth are removed comes into the picture as shown in Fig.7. At that time other side of Driving spur gear teeth 1 gets engaged with other side's Gear segment 3. So during latching condition at least one Gear segment 3 will remains in contact with driving spur gear 1. Retaining Springs 5 which is connected to the Gear segments 3 are used to ensure reverse rotation of gear segments 3 (when teeth are not in contact) and to hold Gear segments 3 with protrusion 6.
In normal latched condition, motor will be stopped at position shown in Fig.1. Due to the above arrangement, When latch 10 is triggered, Charging spur gear 2 rotates in anticlockwise direction (due to the closing spring 9 force) and before engaging with Driving spur gear 1, protrusion 6 will get engaged with Gear segment 3 (Gear segment 3 which is already engaged with Charging spur gear 2 as shown in Fig.8). Due to this Gear segment 3 starts rotating along with charging spur gear 2 and it will help to rotates Driving spur gear 1 and ensures proper engagement of both the gears. While engagement of Charging spur gear 2 and driving spur gear 1 as shown in Fig.9, Driving spur gear 1 is already rotating because of Gear segment 3 as mentioned above, so due to this relative rotation we can avoid impact of both the gears. And when the Gear segment 3 is resting on protrusion 6, its last tooth profile coincides with Charging spur gears starting tooth as shown in fig.2 This position ensure proper engagement of teeth profile (engagement of Charging spur gear 2 and Driving spur gear 1).
The present invention has been described herein with reference to a particular embodiment for a particular application. Although selected embodiments have been illustrated and described in detail, it may be understood that various substitutions and alterations are possible. Those having ordinary skill in the art and access to the present teachings may recognize additional various substitutions and alterations are also possible without departing from the spirit and scope of the present invention.
,CLAIMS:1. Spring based circuit breaker drive mechanism, comprising:
a motor and a driving spur gear, wherein the motor is connected to the driving spur gear through a gear train in order to rotate the driving spur gear;
a charging spur gear with gear segments, wherein the charging spur gear is connected to the driving spur gear, said gear segments are concentric to rotation axis of the charging spur gear with the provision of a bearing between a spline shaft and the gear segments;
a charging crank, wherein the charging crank and the charging spur gear are on the same spline shaft;
a spring, wherein the spring is connected to the charging crank through a chain, and an angular rotation of the charging crank provides the charge or discharge of the spring;
a latch, wherein the charging spur gear is locked by the latch to lock the rotation of the charging spur gear;
a stopper and a resetting spring, wherein the arrangement of the stopper and the resting spring ensure alignment of the teeth of the gear segment and the charging spur gear.

2. Spring based circuit breaker drive mechanism of claim1, wherein the teeth of the charging spur gear and the driving spur gear at both ends are partially cut such that orientation of the cut teeth is 180? apart from each other.

3. Spring based circuit breaker drive mechanism of claim 1, wherein the teeth of the gear segments gets engaged with the teeth of the driving spur gear before engagement of the teeth of the charging spur gear.

4. Spring based circuit breaker drive mechanism of claim 1, wherein arrangement of the gear segments on the closing shaft along with the charging spur gear ensures that at least one of the gear segments is engaged with charging spur gear at latched condition of the charging spur gear.