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)
1. TITLE OF THE INVENTION
A measuring device and method for measuring engagement length between holding catch and closing shaft of switchgear
2. APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company 3.. INVENTOR
(a) Name : Ghosh Baidyanath
(b) Nationality : an Indian National
(c) Address : Crompton Greaves Limited, S2, Switchgear Division, A-3 MIDC, Ambad, Nashik 422010, Maharashtra, India
4.. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed.

BACKGROUND OF THE INVENTION
In case of switchgears generally there are mechanism designed to identify an unfavorable current variation and then trip the mechanism to avoid the excess current to harm the equipments attached thereto. In one of the breaker mechanism for example, the potential energy is stored by compressing / expanding main spring. This energy is subsequently used to close (switch ON) the breaker. The stored energy is latched by holding catch on shaft with engagement of 1.2 ± 0.2 mm. It is technical competency & capability of manufacturing to achieve latching within 1.2 ± 0.1 mm. Else mechanism is reworked which needs precision tools for measurement and controlling.
The length between the holding catch and the closing shaft is of prime importance in designing the switchgears. There are chances of holding catch slipping over the closing shaft by vibration which can lead to faulty trips.
There is required a measuring device which would measure accurately the maximum length between the holding catch and the closing shaft at which the holding catch would slip over the closing shaft.
The right understanding of this length would enable the switchgear designers to design the switchgear keeping in view the chances of vibrations in the system that could lead to faulty trip, and chain of tolerances in the linkage affecting engagement / latching.

There is therefore required a system which provides a safe, efficient and neat means of mixing grinding and similar functions.
SUMMARY
A measuring device and method for measuring engagement length between holding catch and closing shaft of switchgear trippable by movement of closing shaft by pulling of a closing lever attached to said closing shaft by the trip relay is described.
In one embodiment the method comprises the steps of pushing the closing lever and bringing it to tripping position allowing sliding of closing shaft over the holding catch at a first point and measuring the movement of a plunger at a second point on the closing lever. Using the distance between first point and the second point, the distance of second point from the centre of the closing shaft and the movement of plunger at a moment of sliding of closing shaft over holding catch the engagement length between holding catch and the closing shaft is computed that led to sliding of closing shaft over holding catch.
The measuring device and method for measuring engagement length between holding catch and closing shaft of switchgear described herein allows measuring accurately the engagement length thereby enabling the switchgear designers to design, the switchgear taking into account this length. The accidental slipping of holding catch on the closing shaft leading to unfavorable instances of the switchgear are therefore avoided. Also the method and measuring device described herein allows the use on already installed circuit breakers. The mechanism is technically acceptable only if the

engagement of closing & tripping latch is within 1.0 ± 0.2 mm. Else the mechanism is reworked.
BRIEF DESCRIPTION OF THE DRAWINGS
Reference will be made to embodiments of the invention, examples of which may be illustrated in the accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments
Fig. 1 illustrates a method for measuring engagement length between holding catch and closing shaft of a switch gear trippable by movement of closing shaft by pulling of a closing lever attached to said closing shaft by the trip relay as per one embodiment of the present invention.
Fig. 2 illustrates diagrammatically a step in the method described in figure 1.
Fig. 3 illustrates diagrammatically a step in the method described in figure 1.
Fig. 4 illustrates diagrammatical ly a step in the method described in figure 1.
Fig. 5 illustrates a measuring device for measuring engagement length between holding catch and closing shaft of switchgear trippable by movement of closing shaft

by pulling of a closing lever attached to said closing shaft by the trip relay as per one embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A measuring device and method for measuring engagement length between holding catch and closing shaft of switchgear trippable by movement of closing shaft by pulling of a closing lever attached to said closing shaft by the trip relay is described.
In one embodiment the method comprises the steps of pushing the closing lever and bringing it to tripping position allowing sliding of closing shaft over the holding catch at a first point and measuring the movement of a plunger at a second point on the closing lever. Using the distance between first point and the second point, the distance of second point from the centre of the closing shaft and the movement of plunger at a moment of sliding of closing shaft over holding catch the engagement length between holding catch and the closing shaft is computed that led to sliding of closing shaft over holding catch.
In the following description, for purpose of explanation, specific details are set forth in order to provide an understanding of the invention. It will be apparent, however, to one skilled in the art that the invention may be practiced without these details. One skilled in the art will recognize that embodiments of the present invention, some of which are described below, may be incorporated into various assembly line stages. It is understood that one skilled in art may modify or change the data used in the examples described in the specification.

Reference in the specification to "one embodiment" or "an embodiment" means that a particular feature, characteristic, or function described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment,
A method for measuring engagement length between holding catch and closing shaft of a switch gear trippable by movement of closing shaft by pulling of a closing lever attached to said closing shaft by the trip relay is shown with reference to figure 1 as per one embodiment of the present invention. As per one embodiment the method comprises the steps of pushing the closing lever and bringing it to tripping position allowing sliding of closing shaft over the holding catch at a first point. The next step involves, at the instant of sliding of the closing shaft over the holding catch measuring the movement of a plunger at a second point on the closing lever.
Since the point where the closing shaft contacts the holding catch is not contactable directly the above information is to be used to compute the engagement length between the two parts. The further step accordingly comprises of computing the corresponding engagement length between holding catch and the closing shaft based on the distance between first point and the second point, the distance of second point from the centre of the closing shaft and the movement of plunger at a moment of sliding of closing shaft over holding catch, radius of closing shaft.

As per one embodiment the mentioned calculation may be carried out in below
fashion:
If X: is the distance between first point and the second point
Y: Movement of the plunger at the moment of sliding of closing shaft over holding
catch.
0 : angle of rotation corresponding to such movement. This may be diagrammatically
represented as shown in figure 2. The above measured value of the 0 is used further
for measurement as shown with reference to figure 3.
If
r: Radius of closing shaft
B: Movement of the plunger at the moment of sliding of closing shaft over holding
catch.
S: actual engagement length between closing shaft and holding catch of mechanism
S=r Ø
The radial distance of the shaft is thus calculated as above from the known values of r
and Ø
Example that follows is described for illustrating working of the invention during
particular values of the various parameters described above. These examples are
illustrative of the invention but not limitative of the scope thereof.
If X= 15.2 mm and Y= 3.2 mm the 0 is calculated to be 11.888° =.207 radians
Ifr=6 then
S = 6x 0.207= 1.244 mm

Therefore the engagement length between the holding closing shaft and the holding catch is 1.244 mm.
Therefore scale factor: actual distance measured by gauge / actual holding distance of catch to closing shaft.
Therefore scale factor =1.244/3.2 =0.39 mm.
As per one embodiment of the present invention a measuring device for measuring engagement length between holding catch and closing shaft of switchgear trippable by movement of closing shaft by pulling of a closing lever attached to said closing shaft by the trip relay is described with reference to figure 5.
As per one embodiment the measuring device comprises of a knob 503 configured to apply pressure on the closing lever through a sliding shaft 507 at first point 509 on the closing lever. Further, a plunger 511 is positioned at a second point 513 on the closing lever.
A dial gauge 515 is configured to measure the effective contact length between holding catch 13 and closing shaft 15 based on movement of plunger on the closing lever at the moment of tripping of closing shaft from holding catch during pressure application by the knob. The calibration of the dial gauge may be done as per the teachings of this invention so as to show the effective contact length between the holding catch and the closing shaft examples of which are shown with reference to the method for measuring engagement length between holding catch and closing shaft of

a switch gear trippable by movement of closing shaft by pulling of a closing lever attached to said closing shaft by the trip relay described herein.
For supporting the measuring device and for apt placement for measurement a supporting means 525 may be provided.
The measuring device and method for measuring engagement length between holding catch and closing shaft of switchgear described herein allows measuring accurately the engagement length thereby enabling the switchgear designers to design the switchgear taking into account this length. The accidental slipping of holding catch on the closing shaft leading to unfavorable instances of the switchgear are therefore avoided. Also the method and measuring device described herein allows the use on already installed circuit breakers.
The foregoing description of the invention has been described for purposes of clarity and understanding. Although embodiments of the present invention have been described relative to a few standards, and associated attributes therein, one skilled in the art will recognize that the present invention is also very much applicable to other such methods and systems. 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.

We Claim:
1. A measuring device for measuring engagement length between holding catch
and closing shaft of switchgear switched on by movement of closing shaft by pulling
of a closing lever attached to said closing shaft by the trip relay, the measuring device
comprising:
A knob configured to apply pressure on the closing lever through a sliding shaft at
first point on the closing lever;
A plunger positioned at a second point on the closing lever;
A dial gauge configured to measure the effective contact length between holding
catch and closing shaft based on movement of plunger on the closing lever at the
moment of tripping of closing shaft from holding catch during pressure application by
the knob and radius of closing shaft.
2. The measuring device as in claim 1, further comprising a supporting means for
supporting the dial gauge and the measuring device on the switchgear.
3. A method for measuring engagement length between holding catch and closing
shaft of a switch gear switched on by movement of closing shaft by pulling of a
closing lever attached to said closing shaft by the trip relay, the method comprising
the steps of:
pushing the closing lever and bringing it to tripping position allowing sliding of
closing shaft over the holding catch at a first point;
measuring the movement of a plunger at a second point on the closing lever;

computing the corresponding engagement length between holding catch and the closing shaft based on the distance between first point and the second point, the distance of second point from the centre of the closing shaft and the movement of plunger at a moment of sliding of closing shaft over holding catch and radius of closing shaft.