FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A turn-and-twist type isolator with two insulator bushings, per phase
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTORS
Kamble Deepak Gajanan and More Sachin Vasant-both of Crompton Greaves Limited, engineering Department, Global R&D center, Kanjurmarg (east), Mumbai - 400042; all Indian Nationals.
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed.

FIELD OF THE INVENTION:
This invention relates to the field of electrical engineering.
Particularly, this invention relates to the field of isolators or disconnectors.
More particularly, this invention relates to turn and twist type isolators.
Specifically, this invention relates to a turn-and-twist type isolator with two insulator bushings, per phase.
BACKGROUND OF THE INVENTION:
Isolator switch is used to make sure that an electrical circuit can be completely de-energized for service or maintenance. Such switches are often found in electrical distribution and industrial applications where machinery must have its source of driving power removed for adjustment or repair. High-voltage isolation switches are used in electrical substations to allow isolation of apparatus such as circuit breakers and transformers, and transmission lines, for maintenance.
In order to ground all the residual voltage, an earth switch with finger contacts is provided. This isolator finger contacts receive an operating rod, connected to ground (earth), which grounds the charge. Typically, there are provided a pair of finger contacts with face opposite to each other, and the operating rod is adapted to slide in between said two finger contacts. The contacts include a stopper element, in between its faces, in a position placed posterior to said contacts, in order to stop the operating rod motion from its operative resting position to its operative active position in between said faces of contacts so as to mate with the contact faces, for transfer of charge from said contact faces to operating rod.
According to the prior art, turn-and-twist type isolators are known. The prior art turn-and-twist isolator is lever based. The operating rod of the isolator is basically a copper pipe which enters inside the span of a 'C'-shaped OR 'M'-shaped opening with a 'turn' action and after this with a 'twist' action, it makes contact with fixed 'C'-shaped OR 'M'-shaped contact by pushing the contact outwards, thereby pressing the spring. The isolator of the prior are requires a centre

insulaot pole bushing for holding the operating mechanism. Each isolator, hence, required 9 numbers of insulator bushings (i.e. 3 per phase).
This results in high cost of material, difficulty in alignment at site, high accuracy, and the like.
OBJECTS OF THE INVENTION:
An object of the invention is to provide a reduced insulator bushing isolator.
Another object of the invention is to reduce the time for manufacturing an isolator.
Yet another object of the invention is to reduce the weight of an isolator.
Still another object of the invention is to reduce the alignment required, on site, for an isolator.
An additional object of the invention is to provide a compact design for an isolator.
SUMMARY OF THE INVENTION:
According to this invention, there is provided a turn-and-twist type isolator with two insulator bushings, per phase, said isolator comprises:
a. a first insulator bushing and a second insulator bushing, per phase, said first insulator
bushing being spaced apart from said second insulator bushing, said first insulator bushing
being a fixed bushing, and said second insulator bushing being a rotatable bushing;
b. fixed contact mounted on said first insulator bushing; and
c. moving contact mounted on said second insulator bushing, said moving contact adapted to
mate with said fixed contact for disconnection or isolation.
Typically, said fixed contact comprises a female contact.
Typically, said moving contact comprises a male contact.

Typically, said moving contact comprises an operating rod with an end section, said operating rod adapted to be angularly displaced about its pivoting point on said second insulator bushing.
Typically, a first drive mechanism drives said moving contact to 'turn' about a pivot point in an operative horizontal plane, so that said moving contact enters fixed contact area.
Typically, a second drive mechanism drives said moving contact to 'twist' about its longitudinal axis so that there is appropriate contact of said moving contact with said fixed contact.
Typically, said fixed contact comprises a C-shaped or M-shaped finger contact with bushings.
Preferably, said fixed contact comprises a C-shaped or M-shaped finger contact with bushings, said bushings being brass bushings.
Typically, said fixed contact comprises a terminal and a terminal connector.
Preferably, said fixed contact comprises a terminal and a terminal connector, said terminal being a Copper terminal.
Typically, said isolator comprises three pairs of said first insulator bushings and said second insulator bushings.
Typically, said isolator comprises three pairs of said first insulator bushings and said second insulator bushings, each of said pairs corresponding to a single phase.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates a front view of a three-phase turn-and-twist type isolator of the prior art;
Figure 2 illustrates atop view of the isolator of Figure 1; Figure 3 illustrates a side view of the isolator of Figure 1;

Figure 4 illustrates an auxiliary view of the isolator of Figure 1, in its closed condition;
Figure 5 illustrates an auxiliary view of the isolator of Figure 1, in its opened condition;
Figure 6 illustrates an auxiliary view of an isolator, in part, of the prior art, in its closed condition, the part being a detailed view of the encircled portion 'A' of Figure 5;
Figure 7 illustrates a close-up auxiliary view of the contact assembly of the isolator, in part, of the prior art, in its closed condition, the part being a detailed view of the encircled portion 'B' of Figure 6;
Figure 8 illustrates a sectional side view of the isolator of Figure 1; and
Figure 9 illustrates a close-up view of the rotating assembly of the isolator, in part, of the prior art, the part being a detailed view of the encircled portion 'C of Figure 8.
The invention will now be described in relation to the accompanying drawings, in which:
Figure 10 illustrates a schematic auxiliary view of the entire isolator in its closed condition;
Figure 11 illustrates a schematic auxiliary view of the entire isolator in its opened condition;
Figure 12 illustrates a side view of the isolator of Figure 10;
Figure 13 illustrates a front view of the isolator of Figure 10;
Figure 14 illustrates a top view of the isolator of Figure 10;
Figure 15 illustrates a close-up auxiliary view of the isolator, in part, in its closed condition, the part being a detailed view of the encircled portion 'D' of Figure 10;

Figure 16 illustrates a close-up view auxiliary view of the contact assembly of the isolator, in part, in its closed condition, the part being a detailed view of the encircled portion 'E' of Figure
15;
Figure 17 illustrates a sectional side view of the isolator; and
Figure 18 illustrates a close-up front auxiliary view of the contact assembly of the isolator, in part, in its closed condition, the part being a detailed view of the encircled portion 'F' of Figure 17.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates a front view of a three-phase turn-and-twist type isolator of the prior art.
Figure 2 illustrates a top view of the isolator of Figure 1.
Figure 3 illustrates a side view of the isolator of Figure 1.
Figure 4 illustrates an auxiliary view of the isolator of Figure 1, in its closed condition.
Figure 5 illustrates an auxiliary view of the isolator of Figure 1, in its opened condition.
Figure 6 illustrates an auxiliary view of an isolator, in part, of the prior art, in its closed condition, the part being a detailed view of the encircled portion 'A' of Figure 5.
Figure 7 illustrates a close-up auxiliary view of the contact assembly of the isolator, in part, of the prior art, in its closed condition, the part being a detailed view of the encircled portion 'B' of Figure 6.
Figure 8 illustrates a sectional side view of the isolator of Figure 1.
Figure 9 illustrates a close-up view of the rotating assembly of the isolator, in part, of the prior art, the part being a detailed view of the encircled portion 'C of Figure 8.

An isolator comprises bushings (10a, 10b), a turn-and-twist mechanism with an operating rod (12), and a turn-and-twist mechanism stopper (14). Reference numeral 10a refers to laterally located insulator bushings. Reference numeral 10b refers to centrally located rotating insulator bushing. The bushings include an isolator first phase input pole (10a), an isolator first phase centre pole (10b), and an isolator first phase output pole (10a) linearly aligned one beside another. Similarly, there are corresponding isolator second phase input pole, isolator second phase centre pole, and isolator second phase output pole. Similarly, there are corresponding isolator third phase input pole, isolator third phase centre pole, and isolator third phase output pole.
At the extreme ends of the isolator i.e. on the isolator first phase input pole (10a) and on the isolator first phase output pole (10a), a contact assembly is installed. It comprises isolator fixed finger contact assembly (16) and a terminal pad (18) for isolator contacts. The sixed contact assembly is a female contact assembly. The isolator finger contacts are adapted to receive, in the spaced apart region between its fingers, the ends of the operating rod (12) such that it mates with the spaced apart contacts. Typically, the spaced apart measurement is equal to the major axis dimensions of the end section (17) of the operating rod (12). This end section of the operating rod (12) is the male contact
The operating rod (12) swivels ('turn' action), about the isolator centre pole (15), said swiveling is in an operative horizontal plane with an axis which is collinear with respect to the isolator centre pole (15).
Typically, this is a triple pole isolator. Only the first phase poles are shown in Figure 6 of the accompanying drawings. The second pole and the third pole components are parallely lined to the component shown in Figure 6 of the accompanying drawings and are shown in Figures 1 to 5 of the accompanying drawings.
Isolator fixed contact assembly (16) include finger contacts (21) which are made, typically, of copper with either a 'C or an 'M' shaped cross-section and with spring back-up. These finger contacts (21) are compression spring-loaded 'C'-shape or 'M'-shape fork type contact, typically

made of copper with silver plating on inner mating faces. Operating rod (12) of isolator is basically a Copper pipe which enters inside the span of 'C OR 'M' opening with a turn action and after this, with a 'twist' action, it makes contact with fixed 'C OR 'M' profiled contact pushing contact outward, thus depressing the spring. The moving contact i.e. operating rod is made from hard drawn copper pipe with pressed end in elliptical shape and may be tin or silver plated.
Thus, this type of rod and fixed contact engagement relies on parameters such as contact cross-section, bend and thickness based spring back action for ensuring positive contact make.
To achieve high contact pressure combined with easy operation and self cleaning of contacts, a turn and twist mechanism is provided on the centre rotating insulator. Spring loaded linkages retain the end section of operating rod in one position where it can centre freely as it twists to the close condition. As the operating rod is restricted by fix contact, it starts to 'twist' around its own axis. The spring loaded linkages causes the operating rod and its end sections to rotate on its axis so that the contact gets pressurized. Similarly when isolator has to be open contact, pressure restricts the operating rod end section to swing around central bushing (10b) axis. The spring loaded linkages causes the operating rod end section to turn in reverse direction around operating rod turning axis and resulting the release of contact pressure.
In its operative configuration, the operating rod (12), with elliptical end cross-sections (17) at the two extreme ends of the operating rod (12) which is parallel to an operative horizontal plane, 'turns' in the operative horizontal plane with a motor gear box arrangement around a central operative vertical axis of central bushing (10b). This angular displacement is by about 45 degrees. Due to this motion, the operating rod, particularly, its elliptical end sections (17) enter inside the fixed 'C OR 'M' cross section contact on two extreme bushings (10a) out of 3 bushings (10a, 10b, 10c) per phase.
Further, 'twisting' action takes place which twists the rod by about 90 degrees around the rod axial axis without allowing any rotation of rod around central bushing vertical axis making elliptical section of operating rod at two ends to push the fixed 'C OR "M' cross section contact

forks to deflect outward and allowing accommodation of rod end elliptical section inside the fixed contact forks.
This completes contact-make operation. For contact-break operation, the operation is reversed with the 'twist' operation first followed by the 'turn' operation. The deflected forks of'C or 'M' cross section contacts falls inward and operating rod comes back to its original position.
The centre pole insulator bushing (10b) is mounted on a rotatable bearing (31) located in a bearing housing (32).
According to this invention, there is provided a turn-and-twist type isolator with two insulator bushings, per phase.
Figure 10 illustrates a schematic auxiliary view of the entire isolator in its closed condition.
Figure 11 illustrates a schematic auxiliary view of the entire isolator in its opened condition.
Figure 12 illustrates a side view of the isolator of Figure 10.
Figure 13 illustrates a front view of the isolator of Figure 10.
Figure 14 illustrates a top view of the isolator of Figure 10.
Figure 15 illustrates a close-up auxiliary view of the isolator, in part, in its closed condition, the part being a detailed view of the encircled portion 'D' of Figure 10.
Figure 16 illustrates a close-up view auxiliary view of the contact assembly of the isolator, in part, in its closed condition, the part being a detailed view of the encircled portion 'E' of Figure 15.
Figure 17 illustrates a sectional side view of the isolator.

Figure 18 illustrates a close-up front auxiliary view of the contact assembly of the isolator, in part, in its closed condition, the part being a detailed view of the encircled portion 'F' of Figure .17.
In accordance with an embodiment of this invention, there is provided a first insulator bushing (101) and a second insulator bushing (102), per phase. The first insulator bushing (101) is a fixed bushing. The second insulator bushing (102) is a rotatable bushing. There are three such pairs of first insulator bushings and second insulator bushings. A single pair of first insulator bushing and second insulator bushing corresponds to a single phase. Hence, there are only six numbers of insulator bushings required. Typically, this first insulator bushing (101) is spaced apart from the second insulator bushing (103).
Typically, the first insulator bushing (101) includes a fixed contact (105). This fixed contact (105) is a female contact as it receives a male contact for the purposes of disconnection or isolation of the phase. The fixed contact (105) or the female contact (105) is depicted in detail in Figure 18 of the accompanying drawings.
Typically, the second insulator bushing (103) includes a moving contact (107). This second contact (107) is a male contact as it mates with the female contact (105) of the first insulator bushing. The male contact is operating rod (109) mounted. The operating rod (109) angularly displaces about its pivoting point (111) on the second insulator bushing (103). A first drive mechanism drives the operating rod to 'turn' about the pivot point so that the end section (male contact) (107) of the operating rod enters the fixed contact area (105) mounted on the first insulator bushing (101). Further, a second drive mechanism drives the operating rod to 'twist' about its longitudinal axis so that there is appropriate contact of the male contact (107) with the female contact (105).
The fixed contact (105) typically comprises a C-shaped or M-shaped finger contact (113) with bushings (115). These bushing, preferably, are brass bushings. The fixed contact further comprises a terminal (117) and a terminal connector (119). Preferably, the terminal is a Copper terminal.

The technical advancement of this invention lies in provisioning an isolator with reduced number of insulator bushings. Particularly, there are two bushings per phase. The isolator of this invention also reduces alignment problems as there is only one moving arm and one fixed contact.
While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim,
1. A turn-and-twist type isolator with two insulator bushings, per phase, said isolator
comprising:
a. a first insulator bushing and a second insulator bushing, per phase, said first
insulator bushing being spaced apart from said second insulator bushing, said first
insulator bushing being a fixed bushing, and said second insulator bushing being a
rotatable bushing;
b. fixed contact mounted on said first insulator bushing; and
c. moving contact mounted on said second insulator bushing, said moving contact
adapted to mate with said fixed contact for disconnection or isolation.
2. The isolator as claimed in claim 1, wherein said fixed contact comprising a female contact.
3. The isolator as claimed in claim 1, wherein said moving contact comprising a male contact.
4. The isolator as claimed in claim 1, wherein said moving contact comprising an operating rod with an end section, said operating rod adapted to be angularly displaced about its pivoting point on said second insulator bushing.
5. The isolator as claimed in claim 1, wherein a first drive mechanism drives said moving contact to 'turn' about a pivot point in an operative horizontal plane, so that said moving contact enters fixed contact area.
6. The isolator as claimed in claim 1, wherein a second drive mechanism drives said moving contact to 'twist' about its longitudinal axis so that there is appropriate contact of said moving contact with said fixed contact.

7. The isolator as claimed in claim 1, wheirein said fixed contact comprising a C-shaped or M-shaped finger contact with bushings.
8. The isolator as claimed in claim 1, wheirein said fixed contact comprising a C-shaped or M-shaped finger contact with bushings, said bushings being brass bushings.
9. The isolator as claimed in claim 1, wherein said fixed contact comprising a terminal and a terminal connector.
a terminal connector, said terminal being a Copper terminal.
11. The isolator as claimed in claim 1, wherein said isolator comprising three pairs of said first insulator bushings and said second insulator bushings.
12. The isolator as claimed in claim 1, wherein said isolator comprising three pairs of said first insulator bushings and said second insulator bushings, each of said pairs corresponding to a single phase.