BACKGROUND OF THE INVENTION
There has been a requirement to provide frictionless bearing assembly in
gyroscope in order to achieve a higher operating life. Moreover, since the gyro is
hermetically sealed, this process should be in-built and shouldn’t require periodic
lubrication through conventional methods. Hence, a self-lubrication method by
way of impregnation of oil in ball cages has been developed.
SUMMARY OF PRESENT INVENTION
In accordance with one aspect of present invention, the ball cages were cleaned
extensively, baked at high temperature and degassed to remove trapped air
bubbles so as to increase overall porosity.
In accordance with second aspect of present invention, based upon the various
iterations of cleaning with various cleaning agents, an optimum cleaning was
achieved, before these cages were made ready for impregnation.
Soline 10 : It is used for cleaning thick layer of oil & grease (visible from
microscope). It dissolves the molecules of thick layer of oil & grease. It is a rough
cleaning agent.
Cloroform: It removes the dissolved molecules of Soline 10, oil & grease from the
surface of ball cages.
Vetrel: It is a type of white petrol. It is a fine cleaning agent. It removes the final
layer of oil & grease from the porous holes of ball cages.
Essence C: It is a fine cleaning agent. It removes the final layer of oil &
grease from the porous holes of ball cages.
Acetone: It is a degreasing agent. It completely degreases the fine holes of
ball cages and makes it suitable for oil soaking.
In accordance with another aspect of present invention, according to the system
applications requirements, selection of oil SRG 160 (synthetic oil) was done. The
cages were soaked in oil, to ensure absorption level between 12% to 16% of
their dry weight and subsequently centrifuged to remove excess oil on its
surfaces.
In accordance with yet another aspect of present invention, unique feature of
lubricating oil is that when gyro motor rotates at a high rpm greater than
Annexure‐II
10000rpm at a temperature of 80°C, this impregnated oil comes out and
lubricates the metallic balls, which provides low frictional torque, thus increasing
the overall operating life of Gyro.
BRIEF DESCRIPTION OF THE DRAWINGS
The features and advantages of the present invention will become more apparent
and descriptive in the description when considered together with figures/flow
charts presented:
Fig. 1 is a test set-up for measuring LST of gyro motor after impregnation of ball
cage
Fig. 2 is an instrument used for measuring LST of gyro motor
Fig. 3 is an oven used for storage of gyro motor after impregnation of ball cage
Fig 4. Is impregnation process
DETAILED DESCRIPTION
Motor assembly
The motor assembly consists of following three types of coil, and bearing
assembly:
Stator coil: One number of Stator coil is used in each Gyro motor. This is a
three phase delta winding coil, which provides the Rotor a changing magnetic
field and hence the required torque for running the motor at synchronised high
rpm of greater than 10,000.
Pick-off coil: Four numbers of inductive pick-off (Detector) coils are used in
each Gyro motor. These coils detect the angular deviation of Gyro wheel w.r.t
the casing and gives the output to the electronic circuitry for processing, giving
feedback to the torquer coil for correction.
Torquer coil: One number of Torquer coil assembly is used in each Gyro
motor. Torquer coil assembly consists of four coils mounted on support, and is
responsible for aligning the Gyro wheel to its stabilised position.
Bearing Assembly: Bearing assembly consists of two sets of bearing. Each
bearing set consists of a ball cage, inner race, outer race and seven numbers
of metallic balls.
Annexure‐II
Ball cage: It is made of non-metallic polymide porous material. Ball cage looks
like a hollow cylindrical ring, having seven holes at its periphery, equidistant
from each other.
The major Dimensions are: Ball diameter 1.58 mm, Outer diameter of cage:
7.21 mm (with tolerance of 20 microns), Inner diameter of cage=5.35 mm (with
tolerance of 20 microns), tip angle of seven conical slots/holes= 30 degrees.
The bearing assembly is required to perform at temperature of 80 deg C and
run at synchronous rpm of greater than 10,000. Since the Gyroscope is
hermetically sealed and filled with pure Helium gas, the bearings are required
to perform with very low frictional torque.
Bearing performance:
‐ Rotational speed : greater than 10,000 rpm
‐ Working temperature range : 20 deg C to 80 deg C
‐ Stabilisation time for reaching synchronous speed: 12 sec
‐ suitable for long storage
‐ frictional low-speed torque (at 2rpm) of less than 1100 dyne-cm
Impregnation: The ball cages were cleaned extensively, baked at high
temperature and degassed to remove trapped air bubbles so as to increase
overall porosity. Based upon the various iterations of cleaning with various
cleaning agents, an optimum cleaning was achieved, before these cages were
made ready for impregnation. According to the system applications
requirements, selection of oil SRG 160 (synthetic oil) was done. The cages
were soaked in oil, to ensure absorption level between 12 to 16 % of their dry
weight, and subsequently centrifuged to remove excess oil on its surfaces.
The unique feature of this lubricating oil is that when gyro motor rotates at a
high rpm of greater than 10000 at a temperature of 80°C, this impregnated oil
comes out and lubricates the metallic balls, which provides low frictional
torque, thus increasing the overall operating life of Gyro.
Annexure‐II
Characteristics of cleaning consumables used
Soline 10 : It is used for cleaning thick layer of oil & grease (visible from
microscope). It dissolves the molecules of thick layer of oil & grease. It is a
rough cleaning agent.
Cloroform: It removes the dissolved molecules of Soline 10, oil & grease from
the surface of ball cages.
Vetrel: It is a type of white petrol. It is a fine cleaning agent. It removes the
final layer of oil & grease from the porous holes of ball cages.
Essence C: It is a fine cleaning agent. It removes the final layer of oil & grease
from the porous holes of ball cages.
Acetone: It is a degreasing agent. It completely degreases the fine holes of
ball cages and makes it suitable for oil soaking.
Friction Torque characteristics:
The weight of ball cages were accurately determined using precise weighing
balance with a least count of 10 micrograms (controlling any air draft). After
carrying out centrifugation, the Torque characteristics were tested using Modia
torque test set-up. The test set-up consists of a low speed motor (2 rpm) for
rotating the Gyroscope motor and a torque pick-up which can be connected to
the bearings through a flexible coupling. The pre-loaded bearing assembly
was mounted in the test set-up and the frictional torque was accurately
determined. This test was repeated after carrying out a run-in of approximate
140 hours at a high temperature of 80 deg C and in inert Helium atmosphere.

WE CLIAMS:-
Accordingly, the description of the present invention is to be considered as illustrative only and is for the purpose of teaching those skilled in the art of the best mode of carrying out the invention. The details may be varied substantially without departing from the spirit of the invention, and exclusive use of all modifications which are within the scope of the appended claims is reserved. We Claim

1. Atleast one of the applications of ball cage is in Dynamically Tuned Gyroscope. It is made of non-metallic polymide porous material (MELDIN 9000). Ball cage looks like a hollow cylindrical ring, having seven holes at its periphery, equidistant from each other.

2. The major Dimensions of ball cage are: Ball diameter 1.58 mm, Outer diameter of cage: 7.21 mm (with tolerance of 20 microns), Inner diameter of cage=5.35 mm (with tolerance of 20 microns), tip angle of seven conical slots/holes= 30 degrees. The proportion of length is also claimed.

3. The bearing assembly is required to perform at temperature range of 20 deg C to 80 deg C and run at synchronous rpm greater than 10000. The stabilisation time for reaching synchronous speed is 12 sec and it is suitable for long storage. The bearings are required to perform with very low frictional torque (Low speed torque should be less than 1100 dyne-cm at 2 rpm).

4. There has been a requirement to provide frictionless bearing assembly in gyroscope in order to achieve a higher operating life. Moreover since the Gyroscope is hermetically sealed and filled with pure Helium gas, this process should be in-built and shouldn’t require periodic lubrication through conventional methods. Hence a self-lubrication method by way of impregnation of oil in ball cages.

5. The ball cages were cleaned extensively, baked at high temperature and degassed to remove trapped air bubbles so as to increase overall porosity. Based upon the various iterations of cleaning with various cleaning agents (Soline 10, Cloroform, Vetrel, Essence C & Acetone) an optimum cleaning was achieved, before these cages were made ready for impregnation. The process details are as per fig.4.

6. According to the system applications requirements, selection of oil SRG 160 (synthetic oil) was done. The cages were soaked in oil, to ensure absorption level between 12 to 16 % of their dry weight, and subsequently centrifuged to remove excess oil on its surfaces. The unique feature of this lubricating oil is that when gyro motor rotates at a high rpm of 10667 at a temperature of 80°C, this impregnated oil comes out and lubricates the metallic balls, which provides low frictional torque, thus increasing the overall operating life of Gyro. ,TagSPECI:As per Annexure-II