FIELD OF THE INVENTION:
The present invention relates to an improved device for extraction of pole keys engaging hydrogenerator rotor poles releasably attached to rim punching slots and end plates.
BACKGROUND OF THE INVENTION :
The rotor poles are having 'T ' heads which are engaged in T-shaped slots of the rim punchings and end plates as shown in figure 1(A). Each pole is firmly secured by means of a pair of taper keys. Pole key extractor is put over the pole key and then nut is tightened to pull out the keys.
In prior art the device for pole extraction, consists of one horizontal rectangular plate (5) with a drilled hole and two vertical plates (4). The horizontal plates(5) is welded over the vertical plates (4). A stud (3) is passed through the drilled hole of the horizontal plate (5) and the stud (3) is welded on drive pole key (1). A hydraulic jack (7) is placed over the concrete surface of bottom bracket pit, and is used to generate additional force from below the drive pole key (1). At the same time, a corresponding nut (2) is tightened on the stud (3). The details are shown in figures 1(B) & 1(C).
The twin forces generated from the hydraulic jack (7) and tightening of the nut (2) leads to withdrawl of the key pole from the slot.
The prior art withdrawl arrangement for the pole keys as described hereinabove suffers from the following disadvantages:-

1. Hydraulic jack (7) is used for additional force at the bottom of the drive pole key (1) which increases the cost of the device.
2. The selected stud (3) being smaller in size, the weld joint is unable to sustain high force and breaks number of times during tightening the nut over it. Repeated welding of the stud (3) on pole key makes the surface harder, and due to increase in hardness, welding cannot be done accurately. For accurate welding, the pole key is cut, and then the stud (3) is welded on the key, which make the process complex and time consuming. Further, length of the key is reduced upon repeated welding.
3. Repeated welding process also increases the time of withdrawl process.
OBJECTS OF THE INVENTION :
It is therefore, an object of the invention to propose an improved device for extraction of pole keys engaging hydrogenerator rotor poles releasably attached to rim punching slots and end plates, which eliminates the disadvantages of prior art.
Another object of the invention is to propose an improved device for extraction of pole keys engaging hydrogenerator rotor poles releasably attached to rim punching slots and end plates, which eliminates the hydraulic jack and reduces the cost of the device.
A further object of the invention is to propose an improved device for extraction of pole keys engaging hydrogenerator rotor poles releasably attached to rim punching slots and end plates, which reduces the process time.

SUMMARY OF THE INVENTION
Accordingly, there is provided an improved device for extraction of pole keys engaging hydrogenerator rotor poles releasably attached to rim punching slots and end plates, comprising :
a body plate having a top-threaded portion placed over an extractable pole key; a pair of taper jaws are inserted inside groove of body plate which firmly hold the pole key; a channel assy positionable on an end plate attached to the pole key; a pair of support bar located over the channel assy; and a nut insertable on said top-threaded portion of the body plate, wherein when the nut is rotated causing the body plate to dislodge the pole key from the rotor slot, and wherein the taper jaws is actuated to apply simultaneous force at the bottom of the pole key enabling extraction of the pole key.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS :
The invention can be described in detail with the help of the figures in accompanying drawings.
Figure: - l(A) Shows a filment arrangement of pole keys of hydrogenerator according to prior art.
Figure: - 1(B) Shows an withdrawl arrangement of pole keys according to prior art.
Figure: - 1(C) Shows enlarge details of a pole key extractor device of prior art.

Figure: - 2(A) Shows a device for extraction of pole keys according to the invention.
Figure: - 2(B) Shows a sectional (A-A) view of the device of figure 2(A).
Figure: - 2(C) Shows an enlarged detail (B) view of the device of figure 2A.
Figure: - 2(D) Show sectional views (C-C) and (D-D) of the device of figure 2A.
DETAILED DESCRIPTION OF A PREFERED EMBODIMENT OF THE
INVENTION :
A pole key withdrawl device of prior art as described here in before, comprises a horizontal plate (5), two vertical plates (4), a stud (3), a nut (2), a hydrauiic jack (7), and a plurality of pipes (8) as shown in figure l(B) & l(C), The horizontal plate (5) is welded over the two vertical plates (4), then the vertical plates (4) are placed over the top rim end plate (6), and the stud (3) is welded on a drive pole key (1) which is passing through the horizontal plate (5). The nut (2) is rotated on the stud (3) to force the pole key (1) pull out from the slot and at the same time the hydrauiic jack (7) is forced at the bottom of the drive pole key (1) which adds additional pulling force for withdrawal of the pole key (1).
As shown in figure 2(A), 2(B), 2(C) & 2(D), the device for extraction of pole keys according to the invention. The device comprises a body plate (3) having a top-threaded portion placed over an extractable pole key (1); a pair of taper jaws (6) are insert inside groove of body plate(3) which firmly hold the pole key (1); a channel assy (4) positionable on an end plate

(7) attached to the pole key (3); a pair of support bar (5) located over the channel assy (4); and a nut (2) insertable on said top-threaded portion of the body plate (3), wherein when the nut (2) is rotated causing the body plate (3) to dislodge the pole key (1) from the rotor slot, and wherein the taper jaws is actuated to apply simultaneous force at the bottom of the pole key (1) enabling extraction of the pole key (1)
As regards operation of the inventive device, the body plate (3) over the drive pole key (1), and the taper jaws (6) are mounted so as to drive both sides of the body plate (3) and hold the drive pole key (1) tightly. Then the channel assy (4) is placed on a top rim end plate (7) and support bar (5) are placed on the channel assy (4). After that the nut (2) is inserted and rotated to pull up the body plate (3) along with the drive pole key (1). As the drive pole key is lifted upward, the gripping of the jaw (6) gets further tightened due to its taper shape. A coat of molybdenum disulphide grease is applied between nut (2) and support bar(5) for easy operation. The invented device is easy to use with reduction of time and cost as compared to prior art devices.
ADVANTAGES OF THE INVENTION
1. The invention reduces the operation time due to proper clamping arrangement instead of prior art welding of stud on pole key.
2. Hydraulic jack (7) and pipes (8) are eliminated, and therefore cost of the device decreases.
3. The device is easy to operate.
1.
WE CLAIM :
1. An improved device for extraction of pole keys engaging hydrogenerator rotor poles releasably attached to rim punching slots and end plates; comprising :
a body plate (3) having a top-threaded portion placed over an extractable pole key (1); a pair of taper jaws (6) are inserted inside groove of body plate(3) which firmly hold the pole key (1); a channel assy (4) positionable on an end plate (7) attached to the pole key(1) a pair of support bar (5) located over the channel assy (4); and a nut (2) insertable on said top-threaded portion of the body plate (3), wherein when the nut (2) is rotated causing the body plate (3) to dislodge the pole key (1) from the rotor slot, and wherein the taper jaws is actuated to apply simultaneous force at the bottom of the pole key (1) enabling extraction of the pole key (1).
2. The device as claimed in claim 1, wherein a coat of molybdenum disulphate grease is applied between the nut (2) and the support bars (5).

ABSTRACT

The invention relates to an improved device for extraction of pole keys engaging hydrogenerator "rotor" poles releasably attached to rim punching slots and end plates; comprising : a body plate (3) having a top-threaded portion "placed" over an extractable pole key (1); a pair of taper jaws (6) "are insert inside groove of body plate(3) which" firmly hold the pole key (1); a channel "assy" (4) positionable on an end plate (7) attached to the pole key(1); a pair of support bar (5) located over the channel assy (4); and a nut (2) insertable on said top-threaded portion of the body plate (3), wherein when the nut (2) is rotated causing the body plate (3) to dislodge the pole key (1) from the "rotor" slot, and wherein the taper jaws is actuated to apply simultaneous force at the bottom of the pole key (1) enabling extraction of the pole key (1).