FORM 2
THE PATENTS ACT, 1970
(39 Of 1970)
& THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
SITE CONVERTIBLE, DUAL DEAD
CENTRE MECHANISM FOR
CHANGEOVER SWITCH;
LARSEN & TOUBRO LIMITED, A COMPANY INCORPORATED UNDER THE COMPANIES ACT, 1956, WHOSE ADDRESS IS L&T HOUSE, BALLARD ESTATE, MUMBAI - 400 001, MAHARASHTRA, INDIA
THE FOLLOWING SPECIFICATION
PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
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Field of Invention:
The present invention relates to the field of changeover switches and more particularly to the mechanism for changeover s witches.
Background:
Switches are required for activating or deactivating an electrical connection. In certain application an electrical connection needs to be activated based on deactivation of another electrical connection. In these scenarios the deactivation of one switch and activation of the other switch needs to be accomplished simultaneously. The time between the transition needs to be minimal so that the output is not affected.
Changeover or transfer switches are used in such applications. One practical application of changeover switches lies in a backup system for power generation, in such application the load may receive power from either of two available sources, a main power source and a backup power/ generator source which is used when the main power source is discontinued, providing a an uninterrupted power to the load.
The design of the changeover switches requires complete electrical isolation of the two power sources. Also, the mechanism used to operate during transition from one source to the other needs to be agile.
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Crossover switches are provided in prior art WO9824102A11, which discloses switchgear, such as a changeover switch. The switchgear comprises two superposed switching blocks each associated with an actuating block and a control block provided with a control shaft connected to a handle for simultaneously controlling said actuating blocks. This switchgear is characterized in that the actuating blocks are superposed back to back and are arranged between the mutually inverted switching blocks. The actuating blocks comprise a mechanism with modifiable configuration. Likewise, the connection points between this mechanism and the control shaft can also be modified, thus resulting in five switching combinations between the switching blocks. The invention is applicable to electrical installations in general.
The invention comprises two superposed switching blocks arranged one above the other requiring more space. Further, the arrangement allows placement of the shaft to be fixed at one side of the arrangement only, i.e. off-centered.
Therefore, there is a requirement of a dual-dead center mechanism for a changeover switch, which provides for multiple positioning of the shaft, allowing site-convertibility of the mechanism based on installation or working needs.
Summary
A site convertible, dual dead center mechanism for changeover switch is provided. The mechanism allows positioning of shaft of the changeover switch to be at different positions as required by the installation scheme. Shaft slots are provided at two different
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locations, one at the centre of the mechanism and second at an off-centre location. The shaft may be placed at either of the two shaft slots.
The mechanism may be provided with various crossover switches by providing a bridge connector each at the switches for translation of motion from the mechanism to the independent switches respectively. Various bridge assemblies may be used in the switches, which are connected to the mechanism of the invention.
The mechanism provides for the flexibility of installation on site. Further, the provision of a compact design ensures installations in least available spaces. Importantly, the bracket slots are so provided that the transfer of force from the mechanism to the switches is uniform and manually independent operation.
Brief Description of the Drawings
Fig. 1 shows the mechanism as per one embodiment of the present invention.
Fig. 2 shows a part of the mechanism as per one embodiment of the present invention.
Fig. 3 shows the mechanism during OFF position of the bottom and the top switches as
per one embodiment of the present invention.
Fig. 4 shows the mechanism during transition from OFF to ON position of the top switch
as per one embodiment of the present invention.
Fig. 5 shows the mechanism during dead centre position of transition from OFF to ON
position of the top switch as per one embodiment of the present invention.
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Fig. 6 shows the mechanism during transition from OFF to ON position of the top switch as per one embodiment of the present invention.
Fig. 7 shows the mechanism during ON position of the top switch as per one embodiment of the present invention.
Fig.8 shows the mechanism during OFF position of the bottom and the top switches after
transition of the top switch from ON to OFF position as per one embodiment of the present invention.
Fig. 9 shows the mechanism during transition from OFF to ON position of the bottom switch as per one embodiment of the present invention.
Fig. 10 shows the mechanism during dead centre position of transition from OFF to ON
position of the bottom switch as per one embodiment of the present invention.
Fig. 11 shows the mechanism during transition from OFF to ON position of the bottom
switch as per one embodiment of the present invention.
Fig. 12 shows the mechanism during ON position of the bottom switch as per one
embodiment of the present invention.
Fig. 13 shows the mechanism during transition as per one embodiment of the present
invention.
Fig. 14 shows the bottom view of the mechanism as per one embodiment of the present
invention.
Detailed Description of the Invention
The present invention provides a site convertible, dual dead center mechanism for changeover switch. The mechanism allows positioning of shaft of the changeover switch
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to be at different positions as required by the installation scheme. Shaft slots are provided at two different locations, one at the centre of the mechanism and second at an off-centre location. The shaft may be placed at either of the two shaft slots.
Overview
Fig. 1 is a diagram of the site convertible, dual dead center mechanism as per one
embodiment of the invention. A switch each may be placed over and below the
mechanism. A bridge connector each may be provided at the switches for translation of
motion from the mechanism to the independent switches respectively. Various bridge
assemblies may be used in the switches, which are connected to the mechanism of the
invention.
Shaft slots (22, 24), may be provided for placement of a shaft (26). Particularly a centre shaft slot (22) and an off-centre shaft slot (24) are provided. A driver element (3) is provided for translation of motion between the off-centre shaft slot (24) and the centre shaft slot (22) through a driven element (4) as shown in fig.1. The translation of motion takes place through a transfer link (9). A first connecting link (5a) and a second connecting link (5b) are provided for transfer of motion from driven element (4) to a first transfer pin (7a) and a second transfer pin (7b) respectively.
Referring to figure 2, compression means in form of mechanism springs (11a) and (1 lb) are provided for affecting motion of the first transfer pin (7a,) and the second transfer pin (7b). The mechanism springs are provided on spring bases (12a, 12b) fixed to a mechanism bracket (1). Rollers (8a, 8b) are provided to act as a spacer in motion of the
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transfer pins (7a, 7b) in bracket slots (53a, 53b), which are provided on a mechanism
cover (2). A set of bracket slot is also provided on the mechanism bracket (1).
Various positions of the mechanism
The mechanism may operate in various positions. During the position of the mechanism
as shown in fig.3, the switches where the mechanism IS attached are in off position. The pin 7a and 7b are each in a position towards the centre shaft slot (22). The position of pin (7a) is 1A as shown in fig. 3.
In order to change the position of top switch from OFF to ON the driver element (3) or the driven element (4) may be rotated in clockwise direction as shown in fig. (4). If the driver element (3) is rotated the one end of the transfer link (9) transfers the motion through the transfer link (9) through another end of the transfer link (9) to the driven element (4). This causes link (5a) to make pin (7a) slide in a bracket slot (53a). The pin (7b) does not move because a bracket slot (53b) does not allow pin (7b) to move further and the motion transmitted by the driven element to the second connecting link (5b) gets transferred into motion of connecting pin (73b) in link slot (63b) provided on connecting link (5a). As the pin (7a) moves from point 1A to point 2A the motion causes the mechanism spring (1 la) to get compressed. The compression of spring continues till a dead centre position is reached. Fig. 5 indicates dead centre position of the mechanism during transition of position of top switch. The pin movement from point 1A to dead centre is manually dependent operation. While transfer pin (7a) translates from 1A to dead centre position no effect is produced on the top switch to which the mechanism is connected. After reaching dead centre pin movement is manually independent i.e. it is
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fully controlled by potential energy stored in mechanical spring as in Fig. 6, After dead
centre transfer pin (7a) moves with very high velocity and transfers the motion to the bridge of the top switch. When pin reach point 2A top switch becomes ON as shown in figure 7.
In order to change top switch state ON to OFF either of Driver element(3) or Driven element (4) may be rotated in an anticlockwise. This causes the first connecting link (5a) to make the first transfer pin (7a) slide in the mechanism bracket slot (53a). As the pin moves from point 2A to point 1A it causes the mechanism spring (1 la) to get compressed. The compression of spring continues till it reaches a dead centre position. The pin movement from standstill position to dead centre is manually dependent operation i.e. it is affected by a manual external force. This force gets stored in the mechanism spring (11a) after reaching a dead centre position. The mechanism bracket slots are so designed that after reaching the dead centre position the pin (7a) moves towards the point 1A under influence of the energy stored in the mechanism spring (11a). When pin (7a) reaches point 1A top switch becomes OFF.
The switching of the bottom switch is governed by the movement of the second transfer pin 7b. The rotation of either the driver element (3) or the driven element (4) under the influence of an external force applied to the shaft (26) placed at either of the shaft slots (22,24) causes the motion of the second transfer pin (7b). The change in state of the bottom switch from OFF to ON position may be brought about by rotation of the driver element (3) or the driven element (4) in an anticlockwise direction as shown in fig. 9. This causes motion of the pin 7b from a position IB towards 2B. Under the influence of
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the external force the mechanism spring 8b gets compressed until a dead centre position is reached as shown in fig. 10. Further motion of the pin in the bracket slot (53b) is affected by the energy stored in the compressed mechanism spring (lib). The driver element, the connecting links all rotate in anticlockwise direction causing a linear motion of the second transfer pin 7b in the bracket slot 53b as shown in fig. 11. The ON position of the bottom switch is reached when the second transfer pin 7b reaches the position 2B as shown in figure 12.
To bring the bottom switch from the ON position to an OFF position the driver element (3) or the driven element (4) needs to be rotated in clockwise direction. This causes synchronous movement of the driver element and the second connecting link 5b. The mechanism spring 1 lb is compressed till it reaches a dead centre position. The movement of the second transfer pin 7b towards the point IB then continues under the influence of the energy stored in the compressed mechanism spring 11 b. This brings the bottom switch governed by motion of the second transfer pin (7b) to an OFF position.
The mechanism provides for the flexibility of installation on site. Further, the provision of a compact design ensures installations in least available spaces. Importantly, the bracket slots are so provided that the transfer of force from the mechanism to the switches is uniform and manually independent operation.
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WE CLAIM
1. A dual dead center mechanism for changeover switch comprising:
a first transfer pin transferring motion from the mechanism to a top switch;
a second transfer pin transferring motion from the mechanism to a bottom switch;
a shaft;
a centre shaft slot;
an off-centre shaft slot;
a driver element attached to the off-centre shaft slot allowing transfer of motion
between the off-centre shaft slot and the centre shaft slot;
a transfer link one end of which is attached to the driver element;
another end of the transfer link pivotally attached to the off-centre shaft slot
through a driven element;
a first connecting link transferring motion from driven element to the first transfer
pin;
a second connecting link transferring motion from the driven element to the
second transfer pin;
atleast two compression means controlling movement of the transfer pins
independently in bracket slots such that the movement of transfer pin beyond dead
centre position is a manually independent operation.
2. The mechanism of claim 1 wherein the mechanism is placed on a mechanism bracket.
3. The mechanism of claim 2 wherein bracket slots are provided in mechanism bracket for guiding the movement of transfer pins.
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4. The mechanism of claim 3 further comprising a mechanism cover.
5. The mechanism of claim 4 wherein bracket slots are provided for guiding the movement of the transfer pins.
6. The mechanism of claim 1 and 5, wherein a roller is provided on each of the transfer pins.
7. The mechanism of claim 1 and 5, wherein the shaft is placed in the centre shaft slot.
8. The mechanism of claim 1 and 5, wherein the shaft is placed in the off-centre shaft slot.
9. The mechanism of claim 1 and 5,further comprising a link slot in each of the connecting links.
10. The mechanism of claim 9, wherein the link slots are pivoted through a connecting pin each to the driven element at two independent points allowing rotational and linear motion.
Dated this 18th day of December, 2006
For Larsen & Toubro Limited By their Agents
^£&-
(GIRISH VIJAYANAND SHETH) KRISHNA & SAURASTRI
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ABSTRACT
A site convertible, dual dead center mechanism for changeover switch is described. The switch allows positioning of shaft of the changeover switch to be at various positions as required by the installation scheme.
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