FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
TRIPPABLE SWITCH DEVICE;
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:
This invention relates to a switching device and more particularly to remote operable switching device.
BACKGROUND OF THE INVENTION:
Switch is a device that makes, breaks, or changes the course of an electric circuit. Usually switch are used to denote only those devices intended to function when the circuit is energized or deenergized under normal manual operating conditions; as contrasted with circuit breakers, which have as one of their primary functions the interruption of short-circuit currents.
In power applications, switches function to energize or de energize an electric load. On the low end of the power scale, wall switches are used in homes and offices for turning lights on and off; dial and push-button switches control power to electric ranges, washing machines, and dishwashers. On the high end of the scale are load-break switches and disconnecting switches (switch disconnector) in power systems at the highest voltages (several hundred thousand volts).
Switch disconnector are utilized in many electrical installations to form a safe clearance between an electric circuit to be disconnected and other electric circuits, or it is used to de-energize a part of the electric circuit in order to assure the safety of the work. They must be capable of withstanding the high currents and electrodynamic loads that occur during short circuit without suffering damage. This requirement imposes use of high contact pressure.
Switches generally have two state mechanisms (contacts open or contacts closed) that can be operated by hand. These mechanisms are generally simple and economic. These switches unlike the circuit breakers cannot be operated by means of remote controlled electromagnets, thus there is need for operating switch disconnector by means of remote-controlled electromagnets.
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US patent document US 6,603,087 discloses a switch-disconnector control unit comprising an electromagnet as an actuator including a moving control arm, and a spring actuator including a control shaft. The control arm is controlled by an armature of the actuator and connected to the control shaft. Said control shaft is arranged to control the contacts of the switch-disconnector using the spring actuator. The control arm comprises a connection element, which is jointedly connected through a control element to the control shaft and the actuator. An articulated joint at the end of said connection element is formed of an oval opening and a pin. Said opening is shaped as an ellipse in the longitudinal direction of the connection element, and is dimensioned to form a clearance in the joint between the connection element and the control arm of the actuator.
In the above cited US patent US 6,603,087 the opening and closing of the contacts can be done manually as well by means of remote control. For manual operation it is required to connect the crank to the control shaft, wherein the armature controls the motion of the control shaft through the actuator. Further the switch disconnector of the cited document presents one earthed position, wherein switching between the open position and the earthed position can be done only manually.
In the US document US 6,603,087 there is no separate trip position in the switch-disconnector control unit. Further there is presence of earthed position that may make the above invention sophisticated.
The patent application EP 1443534A1 provides a switch disconnector comprising a supporting structure that contains a contact-carrier shaft pivotable between an opening position and a closing position of the contacts and means for operating the contact-carrier shaft, a control shaft operated by the handle, coupling means between the control shaft, contact-carrier shaft and a snap organ to apply an elastic force both opening and closing.
In the aforesaid EP patent application in tripping operation trip spring directly gives energy for the bridge to operate, charging trip spring involves
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handle motion that is transferred to the cam and horizontal motion that is given to the trip spring that is again converted into rotating motion through cam. Further more than one arrester means are used to hold the trip spring against the force thus increasing the use of the elements and resetting operation involves resetting of the trip spring.
The EP document EP 1443534A1 may provide the charging and locking of trip spring that may be more complicated and uses more elements thereby making it more expensive. Further resetting operation involves resetting of the trip spring thereby requiring greater effort than is needed for resetting.
Thus it is the aim of the present invention to provide a trippable switch device that uses less elements, whose working and operation is simple, that does not require much greater effort and is cost effective.
SUMMARY OF THE INVENTION:
According to the present invention a trippable switch device comprises: a control shaft having a pawl and a ratchet to provide rotating motion for compressing and decompressing the springs, a trip spring arrangement coaxially linked to the control shaft by a clamp, a main spring arrangement coaxially coupled to the control shaft by a coupling means, holding and restricting the motion of the spring arrangement, and a bridge pivotally connected to the coupling means providing opening and closing of contacts.
Wherein the main spring arrangement provides energy to the bridge for opening and closing the contacts and the trip spring arrangement that supports the main spring arrangement for opening the contacts.
According to the present invention, the trip spring arrangement comprises of a trip spring mounted on a link of the trip spring arrangement that is pin joint to the clamp at one end and slides in a vertical slot at other end that supports the link, and the main spring arrangement comprises of a main spring mounted on a link of the main spring arrangement. One end of the link of the main spring
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arrangement is connected to the coupling means by a pin incorporated in a kidney slot of the coupling means and the other end of the link is connected to the wedge shaped structure that holds the main spring arrangement. The said coupling means comprises of one coupling means attached to the control shaft and second coupling means attached to the bridge.
Further, according to the present invention the stopper restricts the motion of the trip spring arrangement and holds the trip spring arrangement against its force when the control shaft is rotated in anticlockwise direction by a certain angle.
One embodiment of the present invention provides a trippable switch device that further comprises an electromagnet for remote controlled operation of the trippable switch device. The electromagnet is placed beside the stopper for remote controlled operation of the trippable switch device.
Other object, feature and advantage of the invention will be apparent from the drawings, and from the detailed description of the invention that follows below.
BRIEF DESCRIPTION OF THE DRAWINGS:
To complement the description that is being given and in order to promote
a better understanding of the characteristics of the invention in accordance with a
practical embodiment of the same and as an integral part of the said description
a set of drawing accompany it in which, in an illustrative and non restrictive way,
the following are represented:
Figure 1 shows a trippable switch device as per one embodiment of the present
invention.
Figure 2 shows a trippable device as per one embodiment of the present
invention,
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Figure 3 shows the isometric view of the trippable switch device as per one
embodiment of the present invention.
Figure 4 shows the position of linkages when the contacts are open i.e. normal
OFF condition.
Figure 5 shows the compressed position of trip spring (4).
Figure 6 shows the compressed position of the main spring (5).
Figure 7 shows the position of the linkages when the contacts are closed i.e.
normal ON condition.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
The present invention provides a trippable switch device that withstands high contact pressure and high currents.
According to one of the embodiment, the arrangement of the trippable switch device is shown in the figures.
Referring to figure 1 the trippable switch device of the present invention comprises of atleast two spring arrangements a trip spring arrangement and a main spring arrangement, wherein the main spring arrangement provides energy to a bridge for opening and closing the contacts and the trip spring arrangement supports the main spring arrangement for opening the contacts.
The trip spring arrangement comprises of a trip spring (4) mounted on a link (9) of the trip spring arrangement. One end of the link (9) is pin joint to a clamp (12) on which is mounted a pawl (11) of a ratchet (10) and other end of the link (9) slides in a vertical slot (16) that supports the link (9). The pawl (11) is mounted on the clamp (12) that moves freely on a control shaft (3). The main spring arrangement comprises of a main spring (5) mounted on a link (6) of the main spring arrangement, one end of the link (6) is connected to a pin (7) that couples a coupling means (8, 13) and other end of the link (6) is connected to a wedge shaped structure (21) that holds the main spring arrangement when the control shaft (3) is rotated in an anticlockwise direction a certain angle. In one of the embodiment the angle may be 12 to 15 degrees. The trippable switch device also
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comprises a stopper (2) that restricts the motion of the trip spring arrangement and holds the trip spring arrangement when the control shaft (3) is rotated in an anticlockwise direction. The elements of the trippable switch device can be supported by a supporting structure (1) and the control shaft (3) can be rotated by an handle in clockwise and an anticlockwise direction. The supporting structure (1) can be supported with the help of supporting pillars (17, 18, 19, and 20).
In one embodiment of the present invention the trippable switch device provided enables remote controlled operation. The trippable switch device may be further provided with an electromagnet (22) placed to control the trip spring arrangement. The electromagnet (22) may be placed beside the stopper (2). The invention also allows for manual operation in another embodiment by means of a handle.
Figure 2 shows the trippable device as per one embodiment of the present invention. As shown in the figure, a pawl stopper (15) disengages the pawl (11) from the ratchet (10) after rotation i.e. when the trip spring (4) just crosses the dead centre and rests against the stopper (2).
Figure 3 shows the isometric view of the trippable switch device as per one embodiment of the present invention. As shown in this figure, the pin (7) is coupled to the coupling means (8, 13) having a kidney slot. The coupling means comprises of one coupling means (8) fixed on the control shaft (3) and the second coupling means (13) fixed on a bridge (14) pivotable between opening and closing of the contacts
Figure 4 shows the position of linkages when the contacts are open, according to one embodiment of the present invention. This position of the trippable switch device refers to the normal OFF condition. When the control shaft (3) is rotated in an anticlockwise direction as shown in figure 4, the ratchet
(10) and one coupling means (8> also rotates. The ratchet (10) drives the pawl
(11) and thus the clamp (12) thereby compressing the trip spring (4). When the trip spring (4) just crosses the dead centre and rests against the stopper (2) the pawl (11) gets disengaged from the ratchet (10).
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As per the present invention for normal OFF condition i.e. to open the contacts, the control shaft (3) is need to be rotated using handle in an clockwise direction, wherein one coupling means (8) drives the pin (7) thereby decompressing the main spring (5) and applying torque to the bridge (14)
Further as per the present invention remote controlled operation of the trippable switch device can be performed to open the contacts independently of the handle by using the electromagnet (22) placed just beside the stopper (2). The electromagnet (22) pushes the clamp (12) in downward direction thereby decompressing the trip spring (4) and thus applying torque to the clamp (12). During this operation the motion given by the electromagnet (22) engages the pawl (11) into the ratchet (10) and thus the torque given by the trip spring (4) gets transferred to the control shaft (3). In this operation the trip spring (4) performs the same work as the handle does at the time of opening the contacts.
Figure 5 shows compressed position of the trip spring (4) i.e. dead center for trip spring. As shown in this figure, at the dead center of the trip spring the stopper (2) restricts the motion of the clamp (12) in an anticlockwise direction and provides the force to the clamp (12) in clockwise direction. After compressing the trip spring (4) the pin (7) disengages the pawl (11) from the ratchet (10). This compressed trip spring (4) does not interfere in the normal ON and normal OFF condition of the trippable switch until it gets signal manually or by an electromagnet.
Figure 6 shows the compressed position of the main spring (5), i.e. dead center for main spring (5). As shown in this figure, after disengagement of the pawl (11) and further rotation of the control shaft (3) in an anticlockwise direction rotates the one coupling means (8) that drives the pin (7) fixed on the link (6)., Thus the main spring (5) gets compressed. During this rotation, pin (7) moves in the predetermined kidney slot of the second coupling means (13).
Figure 7 shows the position of the linkages when the contacts are closed according to one embodiment of the present invention. This position of the trippable switch device refers to the normal ON condition. As shown in this figure the wedge shaped structure (21) holds the main spring (5) thereby locking the
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main spring (5) on further rotation of the control shaft (3) in the anticlockwise direction that suddenly decompresses the main spring (5) thereby applying torque to the second coupling means (13) due to which second coupling means (13) undergoes sudden acceleration and drags the bridge (14) into rotation. During this rotation pin (7) do not drive the control shaft as it is in the kidney slot of the one coupling means (8).
As used herein "kidney slot" refers to a slot that has a kidney shape and is used to maintain the coupling between the two shafts.
Thus the present invention provides a trippable switch device comprising atleast two spring arrangements i.e. trip spring arrangement and main spring arrangement, wherein compressing of the springs is required one after another. The main spring provides energy to the bridge for opening and closing the contacts and the trip spring supports the main spring for opening the contacts. Trip spring remains in energized condition and does not interfere in the operation until it gets the signal manually or by the electromagnet. Decompressing of the trip spring energizes the main spring, wherein the energy is liberated by the main spring white decompressing thereby opening the contacts.
The foregoing description of the invention has been described for purposes of clarity and understanding. It is not intended to limit the invention to the precise form disclosed. Various modifications may be possible within the scope and equivalence of the appended claims.
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WE CLAIM
1. A trippable switch device comprising:
a control shaft having a pawl and a ratchet to provide rotating motion for compressing and decompressing springs;
a trip spring arrangement coaxially linked to the control shaft by a clamp; a main spring arrangement coaxially coupled to the control shaft by a coupling means;
a stopper for holding and restricting the motion of the spring arrangement; and
a bridge pivotally connected to the coupling means providing opening and closing of contacts.
Wherein the main spring arrangement provides energy to the bridge for opening and closing the contacts and the trip spring arrangement supports the main spring arrangement for opening the contacts.
2. A trippable switch device as claimed in claim 1, wherein said pawl is mounted on the clamp of the trip spring arrangement.
3. A trippable switch device as claimed in claim 1, wherein said ratchet is attached to the control shaft for providing movement of trip spring arrangement when the control shaft is rotated.
4. A trippable switch device as claimed in claim 1, wherein said control shaft is rotatable by an handle.
5. A trippable switch device as claimed in claim 1, wherein said trip spring arrangement comprises of a trip spring mounted on a link of the trip spring arrangement that is pin joint to the clamp at one end.
6. A trippable switch device as claimed in claim 5, wherein said link of the trip spring arrangement at the other end slides in a vertical slot that supports the link.
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7. A trippable switch device as claimed in claim 1, wherein said stopper restricts the motion of the said trip spring arrangement and holds the trip spring arrangement when the control shaft is rotated in an anticlockwise direction.
8. A trippable switch device as claimed in claim 1, wherein said main spring arrangement comprises of a main spring mounted on a link of the main spring arrangement connected to the coupling means by a pin incorporated in an kidney slot of the coupling means at one end.
9. A trippable switch device as claimed in claim 8, wherein said link of the main spring arrangement at the other end is connected to a wedge shaped structure that holds the main spring arrangement and thereby locks the main spring arrangement when the control shaft is rotated in an anticlockwise direction.
10. A trippable switch device as claimed in claim 1, wherein said coupling means comprises of one coupling means attached to the control shaft and second coupling means attached to the bridge.
11. A trippable switch device as claimed in claim 1, further comprising an electromagnet for remote control operation of the trippable switch device.
12. A trippable switch device as claimed in claim 11, wherein the electromagnet is placed beside the said stopper that supports the trip spring arrangement.
13. A trippable switch device as claimed in claim 5 and claim 11, wherein said electromagnet gets charged during voltage variation that gives downward push to the clamp thereby decompressing the trip spring that applies torque to the control shaft and opens the contact.
14. A trippable switch device as claimed in claim 1, wherein the rotation of the
control shaft in an clockwise direction opens the contacts.
Dated this 30th day of March, 2007

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ABSTRACT
The present invention provides a trippable switch device comprising: a control shaft (3) having a pawl (11) and a ratchet (10), a trip spring (4) arrangement coaxially linked to the control shaft (3) by a clamp (12), a main spring (5) arrangement coaxially coupled to the control shaft (3) by a coupling means (8, 13), a stopper (2) for holding and restricting the motion of the spring arrangement and a bridge (14) pivotally connected to the coupling means for providing opening and closing of contacts.
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