F O R M 2

THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)

1. Title of the invention: AN IMPROVED MECHANISM FOR CHANGEOVER SWITCH-DISCONNECTOR

2. Applicant(s):

(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY : An Indian Company
(c) ADDRESS : L & T House, Ballard Estate, Mumbai 400 001, State of Maharashtra, India

3. PREAMBLE TO THE DESCRIPTION

The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF THE INVENTION

The present invention relates to site convertible dual shaft position, mechanical interlock mechanism of electrical switches. More particularly the invention relates to an improved mechanism specifically in transfer switch or changeover switch-disconnector adapted at places where isolation of two or more switches is necessary.

BACKGROUND OF THE INVENTION

Many critical applications need backup system, which is used when the main power source is discontinued, the critical operations will continue on backup supply, like generator. Thus there is need to have a switch which will have two main power supply and backup power supply at input side of the switch and one output for the load, further these input power supplies must have complete electrical isolation from each other, and only one power supply should get connected to a load at a time.

These requirements are fulfilled by changeover or transfer switch, this type of switch is able to obtain perfect isolation between two input power supplies and only one power supply gets connected to a load at a time.

During customer interaction it was observed that one segment of customer wanted to operate transfer switch from center position. And other segment of customer wants a switch which can be operated from side position. So it was a need to have a transfer switch which can be operated from both center as well as side position.

The prior art 2069/MUM/2006 involves transfer of motion from driver located at the side to the driven link located at the centre using a floating transfer link with pin joints established with the driver and the driven links. The motion transfer efficiency defined as the ratio of torque provided at the center to the torque applied at the side is largely determined by the angle of transmission of the transfer link with that of the driven and driver links. This creates multiple torque reduction transmission resulting in a higher torque requirement from the side for a particular center operation torque.

WO9824102A11 relates to switchgear, comprises double-decker switch-disconnectors, which sandwiches two mechanism modules connected with an interlock module. Mechanism comprises of shaft connected to interlocking component. One connecting link is connected between interlocking component and a one end of a pivoted link. This pivoted link is pivoted at center; the other end is connected to bridge (which houses moving contacts). A torsion spring is connected to free end of the pivoted link. Thus connecting link, pivoted link and spring forms an actuating mechanism which will operate one switch disconnector. When a shaft rotates the connecting link make the pivot link to rotate about pivoted point. Because of rotation of pivoted link the torsion spring connected to free end of the pivoted link will get charge. After dead center the spring will get discharge and the bridge connected to pivoted link will rotate. At the end of rotation of bridge the moving contacts will close the circuit. There is another actuating mechanism to operate second switch disconnector. These two mechanisms are interlocked by means of interlock mechanism.

GB492979 discloses a change-over electric switch, in which the movable contact elements are arranged to be carried in two or more rows on two or more substantially parallel rocking members coupled together by a connecting link adapted to be moved substantially longitudinally in one direction or the other by the automatically or manually operated mechanism of the device so as to oscillate the rocking members in one direction or the other from on operative position of the contact elements to the other operative position of these elements. The movable contact elements may be mercury switch which when inclined in one direction complete one set of circuits and when inclined in the opposite direction complete another set of circuits, or the movable contact elements may each be arranged to co-operate with one or the other of a pair of fixed contacts in accordance with the direction in which the rocking members are oscillated.

2069/MUM/2006 discloses a site convertible dual dead center mechanism involves transfer of motion from driver located at the side to the driven link located at the centre using a floating transfer link with pin joints established with the driver and the driven links.

The disadvantages of the above mentioned prior art is that the switches cannot be operated from both side and center position thus higher mechanism efficiency. Further in the prior art for plurality of switches, plurality of actuating mechanism is required to operate different switch disconnector which is a cumbersome procedure. Two mechanisms are arranged one above the other that requires depth wise more space.

Further in the prior art transfer link is used to transfer motion from side to center. The motion transfer efficiency depends on angle between transfer link and driver/driven link hence torque from side is higher than particular torque at center. The Motion transfer is not that much efficient in case where transfer link is used. The interlocking in this invention is achieved through link lever mechanism which does not show fluent mechanism.

The present invention involves a linear motion transfer methodology using a rack and pinion philosophy to transfer motion largely at the same torque. The rack involves linear travel in forward and backward directions transferring rotary motion from the side operator to central gear and thus consuming space in the mechanism for its motion. The construction of the switch does not offer much space for the rack in one direction creating a constraint for the usage of a single rack to operate for the complete 100 degrees from Top switch ON to Bottom switch ON. To compensate for the space, multiple racks have been employed for the purpose of motion transfer.

OBJECTS OF THE INVENTION

A basic object of the present invention is to overcome the drawbacks/disadvantages of the prior art.

One of the main objects of the invention is to an improved mechanism for electric changeover switch-disconnector that has Site convertible dual shaft position and Single mechanism having two dead centers.

Another object of the present invention is to provide an improved mechanism for electric changeover switch-disconnector that has higher mechanism efficiency causing same operating torque from side operation and center operation.

Yet another object of the present invention is to provide an improved mechanism for electric changeover switch-disconnector interlocking of two switches, Depth wise compactness and Widthwise compactness

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided an improved mechanism for changeover switch–disconnector, said mechanism comprising :

plurality of switch ;
an operating means adapted to initiate ON-OFF operation on said switch; wherein location/position of said operating means is changeable;
a mechanism assembly located in-between the said switches adapted to perform the ON-OFF operation in switches comprising :
a central gear means having teeth arrangements in two different planes comprising first gear teeth and second gear teeth;
a side gear means substantially located on one of the side of said mechanism assembly having gear teeth;
plurality of rack means having horizontal profile with gear teeth on its horizontal side , said plurality of rack means comprising first and second rack means;
plurality of slotted gear having its one arm with slots , said gear comprising first and second slotted gear , first slotted gear is placed opposite to the second slotted gear , both first and second gears operatively connected with said central gear means adapted to engage or disengage with said central gear means;
plurality of pin means operatively connected with said plurality of said slotted gears adapted to translate motion from said slotted gears to plurality of switches to performing ON-OFF operations;
plurality of arms fixed with said plurality of slotted gear at its one end and a cylindrical joint on its another end; and
plurality of energy storing element laid on said arms adapted to store and release energy to switches.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

Fig. 1 illustrates the changeover switch as per one embodiment of the present invention.
Fig. 2 illustrates Mechanism cassette in assembled condition.
Fig. 3 illustrates the Mechanism of changeover switch in different orientation as per one embodiment of the present invention.
Fig. 4 illustrates the engagement of Central gear with Rack 1 and Rack 2.
Fig.4a illustrates central gear and Rack orientation
Fig 4b illustrates how central gear teeth disengages from Rack 1 and completely engages with Rack 2 when rotated in clockwise direction.
Fig 4c illustrates how central gear teeth disengages from Rack 2 and completely engages with Rack 1 when rotated in anticlockwise direction.
Fig. 5 illustrates the engagement of Side operator with Rack 1 and Rack 2
Fig.5a illustrates Side operator teeth and Rack teeth orientation
Fig 5b illustrates how side operator gear teeth disengages from Rack 2 and completely engages with Rack 1 when rotated in anticlockwise direction.
Fig 5c illustrates how side operator gear teeth disengages from Rack 1 and completely engages with Rack 2 when rotated in clockwise direction.
Fig. 6 illustrates top view of mechanism when both switch are in OFF condition.
Fig.7 illustrates top view of mechanism with dead center position while making bottom switch OFF to ON condition.
Fig.8 illustrates top view of mechanism with bottom switch ON & top switch OFF.
Fig. 9 illustrates top view of mechanism with dead center position while making bottom switch ON to OFF condition.
Fig. 10 illustrates top view of mechanism when both switch are in OFF condition.
Fig.11 illustrates top view of mechanism with dead center position while making top switch OFF to ON condition.
Fig.12 illustrates top view of mechanism with top switch ON & bottom switch in OFF state.
Fig.13 illustrates top view of mechanism with dead center position while making bottom switch ON to OFF condition
Fig.14 illustrates Top view of mechanism when both the switch are in OFF condition.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWING

Elements and Construction:
Operating Handle (1): Handle is used to actuate mechanism which makes switch ON and OFF
Shaft (2): it acts as a positive connecting link between operating handle and Central gear/Side operator to actuate mechanism.
Bottom switch (Switch Disconnector II) (3): Bottom switch is an assembly of terminals, bridge, housing & cover mounted on bottom side of the mechanism.
Mechanism (4): Heart of the switch which makes Top and Bottom switch ON and OFF.
Top switch (Switch Disconnector I) (5): Top switch is an assembly of terminals, bridge, housing & cover mounted on top of the mechanism.
Mechanism Plate (6): It’s a Mild steel component on which all mechanism components gets assembled.
Central gear (7): It is a cast component having two set of gear teeth on two different plane. One teeth set engages and disengages with slotted gears teeth to make switch ON and OFF. Other teeth set engages and disengages with Rack 1 and Rack 2 teeth to transfer force from side operator to slotted gear. The shaft can be mounted on central gear.
Side operator (8): It is a cast component on which shaft can be mounted. The teeth of side operator engages and disengages with Rack teeth to transfer force from Operating handle to central gear and hence make switch ON and OFF.
Bridge pin1 (9a): Bridge pin1 is metallic component in mechanism which translates motion from slotted gears to bridge of top switch and makes bridges to translate in switch. Hence making switch ON/OFF.
Bridge pin2 (9b): Bridge pin2 is metallic component in mechanism which translates motion from slotted gears to bridge of Bottom switch and makes bridges to translate in switch. Hence making switch ON/OFF.
Mechanism spring1 (10a): It is a helical spring of spring steel material which stores and releases energy to make Top switch ON and OFF.
Mechanism spring2 (10b): It is a helical spring of spring steel material which stores and releases energy to make Bottom switch ON and OFF.
Slotted gear1 (11a): Slotted gear is cast component having gear teeth that engaged or disengaged with central gear & has one arm with slot. Bridge pin1 translate in this slotted arm.
Slotted gear2 (11b): Slotted gear is cast component having gear teeth that engaged or disengaged with central gear & has one arm with slot. Bridge pin2 translate in this slotted arm.
Spring arm1 (12a): It’s a steel component whose one end is connected to slotted gear by pin joint and other end is connected to spring rest by cylindrical joint. It holds Mechanism Spring1.
Spring arm2 (12b): It’s a steel component whose one end is connected to slotted gear by pin joint and other end is connected to spring rest by cylindrical joint. It holds Mechanism Spring2.
Rack1 (13a): It transfers force from side operator to central gear when side operator is rotated in anticlockwise direction.
Rack2 (13b): It transfers force from side operator to central gear when side operator is rotated in clockwise direction.

The different states of the switch and the related parts there of are further explained below in detail referring to figures 1-14:

Top switch & Bottom switch in OFF condition: When both the Bridge pins are towards the center of mechanism ( Closer to central gear), both the switches are in OFF condition as shown in Fig. 6.
Bottom switch OFF to ON: To make bottom switch ON, We have to put shaft and operating handle on side operator and operating handle is to be rotated in anticlockwise direction. As shown in fig.5 small cut is provided on teeth of Rack1 and Rack2 for required engagement and disengagement of side operator with Rack1 and Rack 2. When side operator rotates in anticlockwise direction, side operator teeth completely disengages from Rack 2 and engages with Rack 1. Same engagement of Rack is done with Central gear teeth as shown in Fig.4. So side operator translates motion to central gear through Rack1. Hence central gear rotates in anticlockwise direction. Central gear tooth engages with slotted gear2 causing it to move in clockwise direction. The clockwise rotation of slotted gear2 causes bridge pin2 to move linearly in slot of mechanism plate and Mechanism spring2 to compress. The springs get charged i.e. energy gets stored in the springs. Till the dead center position as shown in fig.7, the spring continue to get charge. Once springs cross the dead center, it starts releasing the energy. Released force tend to move the slotted gear in clockwise direction and hence causing the bridge pin to move towards right side as shown by arrow. As the force is provided by mechanism spring the speed and movement of Bridge pin 2 does not depend on operator speed. Thus from dead center position bridge pin2 move to its right most position (i.e. Bottom switch ON condition) with a greater velocity by virtue of the spring releasing force. And makes Bottom switch ON as shown in fig. 8. From OFF to dead center the motion of Bridge pin 2 don’t affect bridge movement. Bridge start moving along with the bridge pin only after crossing the dead center. This ensures velocity / motion of bridge & contacts housed in bridge to be manually independent.

Bottom switch ON to OFF: To make bottom switch OFF, we have to rotate operating handle in clockwise direction. This causes all components viz. side driver , rack1 , slotted gear2, & bridge pin2 to move exactly in opposite direction as that while turning Bottom switch from OFF to ON. And thus bridge pin2 move from right most position as shown in fig. 8 to left. Till dead center position Mechanism spring compresses and stores the energy as shown in Fig.9. After dead center position spring releases the energy hence bridge pin moves with high velocity causing bottom switch to become OFF as shown in fig.10. This is manually independent operation.

Top switch OFF to ON: To make Top switch ON, operating handle is to be rotated in clockwise direction. When side operator rotates in clockwise direction, side operator teeth completely disengages from Rack 1 and engages with Rack 2. Same engagement of Rack is done with Central gear teeth as shown in Fig.4. So side operator translates motion to central gear through Rack2. Hence central gear rotates in a clockwise direction. Central gear tooth engages with slotted gear1 causing it to move in anticlockwise direction. The anticlockwise rotation of slotted gear1 causes bridge pin1 to move linearly in slot of mechanism plate and Mechanism spring1 to compress. The springs get charged i.e. energy gets stored in the spring. Till the dead center position as shown in fig.11, the spring continue to get charge. Once springs cross the dead center, it starts releasing the energy. Released force tend to move the slotted gear in clockwise direction and hence causing the bridge pin to move towards left side as shown by arrow. As the force is provided by mechanism spring the speed and movement of Bridge pin1 does not depend on operator speed. Thus from dead center position bridge pin1 move to its left most position (i.e. Top switch ON condition) with a greater velocity by virtue of the spring releasing force. And makes Bottom switch ON as shown in fig. 12. From OFF to dead center the motion of Bridge pin 1 don’t affect bridge movement. Bridge start moving along with the bridge pin only after crossing the dead center. This ensures velocity / motion of bridge & contacts housed in bridge to be manually independent.
Top switch ON to OFF: To make top switch OFF, we have to rotate operating handle in anticlockwise direction. This causes all components viz. side driver , rack2 , slotted gear1, & bridge pin1 to move exactly in opposite direction as that while turning Top switch from OFF to ON. And thus bridge pin1 move from left most position as shown in fig. 12 to left. Till dead center position Mechanism spring1 compresses and stores the energy as shown in Fig.13. After dead center position spring releases the energy hence bridge pin moves with high velocity causing bottom switch to become OFF as shown in fig.14.

Definitions of the technical terms
Bridge - Bridge is an assembly of plastic component which supports 8 moving contacts of copper. Bridge reciprocates in housing due to force exerted by bridge pin causing closing or opening of contact i.e. making switch OFF or ON.
Switch Interlocking - it is imperative that not more than one switch should be in ON condition at any time. I.e. either both switches should be OFF or only one of the two switches should be ON at any time.
Dead center - Dead center is a position of a mechanism at which spring has maximum potential energy stored in it & it is ready to release the same.
Manual dependent - when Output speed i.e. velocity of pin depends on the speed at which the Operator rotates the operating handle the operation is known as manual dependent.
Manual independent - when Output speed i.e. velocity of pin is not depends on the speed at which the Operator rotates the operating handle the operation is known as manual independent.

Key Features of the invention:
 Positive interlocking of two switches. i.e. both switches should not on at the same time.
 Very high torque efficiency.
 Depth & width wise compactness – Two racks are used instead of one in order to make mechanism compact.
 Single mechanism having two dead centers.
 Site convertible dual shaft position

The invention has been described in a preferred form only and many variations may be made in the invention which will still be comprised within its spirit. The invention is not limited to the details cited above. The structure thus conceived is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit.

WE CLAIM

1. An improved mechanism for changeover switch–disconnector, said mechanism comprising :

plurality of switch;
an operating means adapted to initiate ON-OFF operation on said switch; wherein location/position of said operating means is changeable;
a mechanism assembly located in-between the said switches adapted to perform the ON-OFF operation in switches comprising :
a central gear means having teeth arrangements in two different planes comprising first gear teeth and second gear teeth;
a side gear means substantially located on one of the side of said mechanism assembly having gear teeth;
plurality of rack means having horizontal profile with gear teeth on its horizontal side , said plurality of rack means comprising first and second rack means;
plurality of slotted gear having its one arm with slots , said gear comprising first and second slotted gear , first slotted gear is placed opposite to the second slotted gear , both first and second gears operatively connected with said central gear means adapted to engage or disengage with said central gear means;
plurality of pin means operatively connected with said plurality of said slotted gears adapted to translate motion from said slotted gears to plurality of switches to performing ON-OFF operations;
plurality of arms fixed with said plurality of slotted gear at its one end and a cylindrical joint on its another end; and
plurality of energy storing element laid on said arms adapted to store and release energy to switches.

2. Mechanism as claimed in claim 1 wherein said plurality of switch comprising top switch substantially placed in-between said mechanism assembly.

3. Mechanism as claimed in claim 1 wherein said plurality of switch comprising bottom switch substantially placed in-between said mechanism assembly.

4. Mechanism as claimed in claim 2 wherein said top switch is placed on top of said mechanism assembly.

5. Mechanism as claimed in claim 3 wherein said bottom switch is placed at bottom of said mechanism assembly.

6. Mechanism as claimed in claim 1 wherein said mechanism assembly comprising plate means.

7. Mechanism as claimed in claim 1 wherein said operating means is located substantially at the centre of said plate means.

8. Mechanism as claimed in claim 1 wherein said operating means is optionally located on one side of said plate means.

9. Mechanism as claimed in claim 1 wherein said operating means is operatively connected with said central gear means or side gear means.

10. Mechanism as claimed in claim 1 wherein said central gear means being located substantially at the center of said plate means.

11. Mechanism as claimed in claim 1 wherein said first gear teeth of the central gear engages and disengages with said first and second slotted gear teeth to make switch ON and OFF.

12. Mechanism as claimed in claim 1 wherein second gear teeth of the central gear engages and disengages with said gear teeth of first and second rack means to transfer force from operator means to slotted gear.

13. Mechanism as claimed in claim 1 wherein said plurality of energy storing element comprising plurality of helical spring.

14. Mechanism as claimed in claim 13 wherein said plurality of spring comprises of first and second springs.

15. Mechanism as claimed in claim 13 wherein said first spring is adapted to make top switch on and off.

16. Mechanism as claimed in claim 13 wherein said second spring is adapted to make bottom switch on and off.

17. Mechanism as claimed in claim 1 wherein said plurality of pin comprises of first and second pin.

18. Mechanism as claimed in claim 16 wherein said first pin adapted to perform on-off operation of top switch.

19. Mechanism as claimed in claim 16 wherein said second pin being adapted to perform on-off operation of bottom switch.

20. Mechanism as claimed in claim 1 wherein said first rack adapted to transfer force to central gear means when rotated in clockwise direction.

21. Mechanism as claimed in claim 1 wherein said second rack adapted to transfer force from to central gear means when rotated in anticlockwise direction.

22. An improved mechanism for changeover switch –disconnector as herein substantially described and illustrated with the accompanying drawings.