FIELD OF INVENTION
The present invention relates to an improved sweep gauge with a lead screw
to actuate an axial movement of the sweep gauge arm to facilitate core-building
procedure.
BACKGROUND OF THE INVENTION
Hydro generators are large (and usually vertical) machines. A hydro
generator core is made by stacking laminations in the axial direction. This process is
known as core-building. Due to the large size of the cores, the laminations are cut in
segments that are put together to form each circular layer. Consecutive layers are
staggered to improve the integrity of the structure. During core-building, the bore
diameter (J) is checked and rectified at regular intervals. This is a critical step and it
is done using a sweep gauge (s) fixed to the floor (B) at the center of the core.
The sweep gauge (S) consists of a cylindrical pillar (A) that is fixed to the
floor (B) at the center of the core and an arm (C) that is attached to the pillar (A).
The arm (C) can be rotated about the pillar (A) and moved up and down along the
pillar (A). Balance weights are provided to stabilize the arm (C). A stick of adjustable
length (G) with a micrometer (H) mounted on it is attached to the outer end of the

arm (C). After calibration, the micrometer (H), combined with the rotating arm (C),
acts as an inside micrometer that can be used to measure the diameter of the core
(J).
In the existing design (fig.1), the arm (C) is free to slide up and down along
the pillar (A). After the arm is manually moved to the desired position with the help
of a crane, its position is fixed using a clamp (F) placed just below the arm hub (E).
The clamp (F) prevents any downward vertical motion due to the arm's weight.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose an improved sweep
gauge with a lead screw to actuate an axial movement of the sweep gauge arm to
facilitate core-building procedure which is capable of eliminating the hazards of a
tedious process of positioning the sweep gauge arm for checking and rectifying the
bore diameter during core-building.
Another object of the invention is to propose an improved sweep gauge with
a lead screw to actuate an axial movement of the sweep gauge arm to facilitate
core-building procedure which is able to make a significant reduction in the core-
building time.

A further object of the invention is to propose an improved sweep gauge with
a lead screw to actuate an axial movement of the sweep gauge arm to facilitate
core-building procedure which eliminates the requirement of a crane and thus save
valuable production time.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 : Shows the sweep gauge of prior art.
Fig. 2 : Shows the sweep gauge according to the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
As shown in Fig.2 the sweep gauge (17) consists of a cylindrical pillar (1)
fixed to the floor (2) at the center of the core and an sweep gauge arm (3) is
attached to the pillar (1).
Balance weights (5) are provided in the same horizontal axis of the arm (3) to
stabilize the sweep gauge arm (3). A stick of adjustable length (11) having a
micrometer (12) mounted on it is attached to the outer end of the arm (3).
After calibration, the micrometer (12), combined with the rotating arm (3),
acts as an inside micrometer that can be used to measure the diameter (14) of the
core.

In the proposed design (Fig.2), the central pillar (1) of the sweep gauge (17)
houses a lead screw (6) connected to a motor (10) through a gear system. The
direction of rotation of the motor (10) is controlled by two switches (15,16) mounted
on a control panel (8). Threads in the hub (4) of the sweep gauge arm (3) are
connected to the lead screw threads. The arm (3) can thus be moved up or down by
simply turning on a switch (15,16) to rotate the lead screw (6) in the desired
direction. Limit switches (7, 7a) at each end of the lead screw (6) ensure that the
arm's (3) movement is restricted to the portion between two pre-defined points.
ADVANTAGES OF THE INVENTED SWEEP GAUGE OVER THE PRIOR ART
The present invention facilitates the core-building process by eliminating the
hazards involved in the positioning of the sweep gauge arm. It also eliminates the
requirement of a crane. This also results in a significant reduction in the core-
building time.

We Claim:
1. An improved sweep gauge (17) with a lead screw (6) to actuate an axial
movement of the sweep gauge arm (3) to facilitate core-building procedure
comprising;
a cylindrical pillar (1) fixed to the floor (2) at the center of the core;
an sweep gauge arm (3) attached to the pillar (1), rotatable about the pillar
and moveable up and down along the pillar;
balance weights (5) disposed at one end for stabilizing the sweep gauge arm
(3);
a stick of adjustable length (11) having a micrometer (12) mounted on it
attached to the outer end of the arm (3);
a control panel (8) having switches (15, 16);
characterized in that;
a lead screw (6) housed inside the central pillar (1) of the sweep gauge
(17), connected to the threads in the hub (4) of the sweep gauge (17) for moving
the arm (3) up and down by controlling the switches (15,16) disposed on the control
panels (8) wherein limit switches (7, 7a) provided at the end of the lead screw for
ensuring restricted arm's movement to the portion between two pre-defined points
when after calibration the micrometer (12) combined with the rotating arm (3) acts
as an inside micrometer for measuring the diameter (14) of the core.