FIELD OF APPLICATION
The present invention relates to an apparatus and method for automatic
electronic measurement of taper value on bore of ball bearing inner races in real
time. In particular, the invention relates to automatic measurement of internal
diameter and taper of deep groove ball bearings as post inspection gauge in
grinding line.
BACKGROUND OF THE INVENTION
Ball bearings are the most important components in a product with a rotating
shaft. The uninterrupted performance of the production depends greatly on the
ball bearings. Precise surface finish, material properties, cleanliness, accurate
dimensioning and tolerances used will decide the performance of the ball
bearings.

Thus the performance of the ball bearing depends heavily on the manufacturing
technique developed and the measurement process used for the bearing
components.
Gauging is a method of measurement of geometric tolerances of a part while
manufacturing. There can be in process or post process gauging. Gauging can
be performed by air gauging or electronic gauging.
Air gauging - using air flow volumes and pressures to measure part dimensions
- is a reliable, repeatable technology that's well-suited for measuring dimensions
with tolerances smaller than 0.13 mm. Air gauging systems can achieve
submicron resolution, and their non-contact nature makes them useful for
measuring soft, thin walled, or other delicate workpieces.
To achieve its precise dimensional measurement, air gauging relies on the laws
of physics, which state that flow and pressure are directly proportionate to
clearance and they react inversely to each other.

The regulated air flows through the restriction a needle valve, jeweled orifice etc.
and then through the nozzle. When the nozzle is open to the atmosphere, there
is maximum flow through it and there is a minimum of pressure called "Back-
Pressure" between the restriction and the nozzle. As an obstruction is brought
increasingly close to the front of the nozzle, airflow from the nozzle diminishes
and backpressure builds. When the nozzle is completely obstructed, airflow is
zero, and back-pressure reaches the pressure of the regulated air supply. During
this example, air flow moved from maximum to minimum, while back-pressure
moved in the opposite direction: minimum to maximum.
Of course, air gauging has some drawbacks. The short measurement range of
air gauging systems makes them impractical for use on rough machined parts or
components with surface finish greater than about, 50 [mu]in R˄sub a˄. Systems
have a relatively high initial cost, and require clean, dry compressed air to
operate. It also require double master for zero setting after every tenth part
which itself costlier.

Traditionally a taper measurement is done using an air gauge and the bearing
race is placed in the air plug manually. Such manual measurements may lead to
under size or over size races not suitable for bearing assembly.
Electronic gauging is performed by causing a mechanical contact to touch the
surface to be measured, the contact is connected to a transducer that transforms
the mechanical shift into an analog electric signal. The latter is then processed
by an expressly-designed electronic processing unit, which amplifies, digitalizes
and processes the signals coming from all the transducers, combines them
suitably and supplies the desired measurements, together with the statistical
analyses, if required, and the compensation data to be supplied to the machine
tools, as needed in certain cases.
Electronic gauging cells use three basic transduction systems.

An air gap is an inductive-type system that transforms the mechanical shift of a
mobile ferromagnetic part with respect to a fixed coil into an inductance
variation.
A linear variable differential transformer (LVDT) is a transformer that supplies an
output voltage that depends on the variation in the mutual induction between
the primary circuit and the secondary one, due to the shift of a ferromagnetic
core within the primary and secondary coils.
A half bridge transducer (HBT) is a Wheatstone half bridge in which the shift of a
core causes an unbalance between two inductive impedances.
Because of the accuracy of the mechanical transmission system, only one master
is needed for zero setting in a shift.

There was thus a need for a fully automated electronic gauging machine tool to
measure the ovality or taper of bore of deep groove ball bearing inner race in
real time.
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SUMMARY OF THE INVENTION
One of the main object of the present invention is to electronically obtain the
taper value on bore of ball bearing inner race in real time.
Another object of the present invention is to provide an automatic process
measurement device to measure automatically in real time the bore and taper of
bearing races.
Yet another object of the present invention is to use a programmable logic
controller (PLC) to calculate automatically the taper value, the difference
between two diameter, of bore based on the measurement and set points.

In the present invention the device comprises an automatic bore gauge that is
used to determine the taper value on bore of ball bearing inner race after the
internal diameter of the race is ground to close dimensions. The apparatus
comprises a measuring head, an input conveyor with work position unit and an
output conveyor with NG gates, a microprocessor display column and an
electrical control unit.
Based on the measurement and the set points, the race falling within the range
is allowed to the next operation. Any under sized or over sized races are sorted
out from the production line. The gauge is used as post inspection gauge in the
grinding line.
The taper values are obtained using a self-centered linear voltage differential
transformer (LVDT) Ml plug and microprocessor based control unit. The Ml
Plug is mounted on a dual stroke sliding head comprising two slides and
pneumatic actuators. The work piece is positioned accurately below the Ml plug
using combination of pneumatic actuators and mechanical system.

The electrical control unit comprise of a microprocessor based control unit,
operator panel and sensors to command the equipment against given situation
during measuring operation, operational logic and PLC programming.
Thus the present invention provides an apparatus for automatic measurement of
taper value on bore of ball bearing inner races in real time, comprising: an input
conveyor for transferring bearing inner races from a grinding machine to a
measuring position of said apparatus; a measurement head provided at the
measuring position for measuring the bore and taper of said bearing inner races;
and an electrical control unit for commanding the equipment against a given
situation during measuring operation.
BREIF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention can now be described in detail with the help of the figures of the
accompanying drawings in which

Figure 1 shows an arrangement of the device of the present invention.
Figure 2 shows a side view of the system shown in Figure 1.
Figure 3 shows a schematic arrangement of the automatic
bore gauge of the present invention.
Figure 4 shows in diagrammatic form the process of measuring the taper.
Figure 5 shows the control flow diagram of the operational
sequence of the present invention.
DETAILED DESCRIPTION
The general arrangement of the system of the present invention is shown in
Figure 1. Figure 2 shows the diagrammatic side view of Figure 1. As shown,
the system comprises an input conveyor, a measuring head with LVDT Ml Plug,
a pusher, an out conveyor, NG gates and an operator panel-cum-microprocessor
control unit.

Figure 3 shows the automatic bore gauge in more details. The bearing races are
brought out from manufacturing machine by a transfer conveyor 10 and fed to
the measuring position C with the help of two pneumatic cylinders 5 and 6. The
conveyor 10 is moved left to right (position A to G) with the help of motor and
gear box 11. The cylinder 5 stops the incoming race at the position A and
transfers it to position B. The cylinder 6 transfers it from position B to position C
where the measurement is done. This work position unit comprising of two
antifriction slides tandem mounted, positions the work piece accurately below
the measuring head 3 at the time of measurement. After the measurement is
done the cylinder 4 pushes the races back to the conveyor. While in retarded
position the link of cylinder 5 is so designed that races are stopped at position A
until the measurement is over and the race is put back to the conveyor at D
position. v
As shown in Figure 4 the taper is measured as follows:
Taper Value (T) = Dl - D2 at different height.

The measuring head consists of a self-centered linear voltage differential
transformer (LVDT) Ml plug, a nose-piece and slides 3. There are two cylinders
7 and 8 to move the probe in two-step for measuring the bore and taper
microprocessor display column 12 designed to display dimensional and
geometrical measurements, in either static or dynamic elaboration. The
measurement value is displayed in an analog way on the three colors LED bar
graph scale, showing the measurement status (green = good; red = scrap;
- yellow = pre scrap).
If the measurement is out of range the races are sorted out using NG (No Go)
gates by cylinders 8 and 9 at E and F position respectively. There are two NG
gates, one for under size and other for over size. Therefore only correct size is
allowed to go to G (output) 'position.

The operational sequence of the present invention is shown in the control flow
diagram of Figure 5. The entire sequence of operation is done by pneumatic
actuators 2, 4, 5, 6, 7, 8 and 9 (Figure 3). Sensors, microprocessor controller
and operator panel 12 command these actuators. Various binary sensors like
magnetic reed switches, inductive proximity switches and infrared through beam
and retro reflective type of sensors are used to track the material flow and detect
position of the actuators.
Before putting the equipment in use the gauge head needs to be calibrated to its
nominal size using single setting masters. Setting masters are the physical
standards by which a gauging system is calibrated. Usually carbide or steel disks
or rings, masters generally have their actual size verified by mechanical
comparison to certified gauge blocks. Once the reference contact of Ml plug is
set to the desired size with master, the locking screw should be made snug, and
the gauge should be tested again for zero and repeatability. If nothing has
changed, keep snugging down the locking screw until it is locked into position.
Then check repeatability again until the gauge is performing accurately.

While setting automatic bore gauge its nominal size, care needs to be taken and
setup of the master is key. This means they must be clean and free of dirt.
After mastering the part feed automatically from conveyor to the measuring
station and positioned below the measuring head, where a proximity switch
senses the work piece and triggers measuring head.
Programmable logic controllers (PLCs) control all of the gauge's logic functions.
The systems have proven to be extremely reliable, and can operate round the
clock for months between downtime for preventive maintenance. Fully
automated electronic gauging eliminates the operator and can be used by
companies that require 100 % checking on quality. Labor-saving advantages
over manual gauging are enormous.
An air-driven actuator traverses the measuring head and measures the work
piece at two positions. When the measurement is complete, the part is pushed
to out put conveyor. Out-of-range readings trigger NG gate, which diverts bad
parts into a reject bin, while good parts pass straight through to the next
production process.

An operator panel 12 is located in front of the machine with appropriate controls
and indicators operation of the machine. Operator can select various machine
preset parameters and runs the machine in auto using controls of this panel also
suitable diagnostic features and visual indicators have been provided for
parameter tracking and locating operational faults. Manual controls have been
provided to operate the components and set the machine during sequence
failures. The operator gets fault condition indications and group indications as
well as audio alarm in case of any sequence fault. A signal tower with green,
yellow and red lamps are used to indicate working, ready and fault status of the
machine.
Various binary sensors like magnetic reed switches, inductive proximity switches
and infrared through beam and retro reflective type of sensors are used to track
the material flow and detect position of the actuators.

The entire sequence of operation of the machine is controlled by ladder logic and
PLC. Ladder logic - a programming technique using a ladder-like structure. It
was originally adopted because of its similarity to relay logic diagrams to ease its
acceptance in manufacturing facilities. The ladder approach is somewhat limited
by the lack of loops, etc. (although this is changing).
The PLC continuously scans the inputs and changes the outputs into memory.
After this, the ladder logic program is run once and it creates a temporary table
of all outputs in memory. This table is then written to the outputs after the
ladder logic program is done. This continues indefinitely while the PLC is
running.
In this also included the safety interlocks, fault diagnostic and visual indications
to run the machine at low maintenance cost. The details of logic control are
given in the control flow chart of Figure 5 which is self-explanatory.

The apparatus of the present invention will be extremely useful to bearing
manufacturers to obtain consistency in quality by 100 % in-line inspection,
increase in throughput and tool adjustment of grinding machine. It is also a very
low cost equipment for gauging the bore taper of deep-groove ball bearings.
Some of the benefits to be derived are:
• Increased plant throughput, consistency in quality and reduced
manufacturing cost.
• Due to a combination of microprocessor electronics provided with
dedicated algorithms, repeatability and accuracy are guaranteed
comparable to those obtained in metrological Laboratory.
• Capable of maintaining reduced cycle times and quality control of an
entire production run.
• New, highly advanced measuring plugs provide durable, flexible and
economical solution to the inspection of bore diameters.

WE CLAIM
1. An apparatus for measurement of taper value on bore of ball bearing
inner races in real time comprising and characterized in that;
- an input conveyor (10) for transferring bearing inner races from a
grinding machine to a measuring position (C) of said apparatus;
- a measurement head (3) provided at the measuring position (C)
for measuring the bore and taper of said bearing inner races; and
- an electrical control unit (12) for commanding the equipment
against a given situation during measuring operation.
2. The apparatus as claimed in claim 1, wherein said input conveyor is for
feeding the bearing races at the measuring position (C) with the help of
two pneumatic cylinders (5, 6).

3. The apparatus as claimed in claim 1, wherein said measurement head
(3) comprises a self-centered linear voltage differential transformer
(LVDT) Ml plug, a nose piece and slides.
4. The apparatus as claimed in claim 1, wherein said electrical control unit
(12) comprises a microprocessor based control unit.
5. The apparatus as claimed in claim 4, wherein said control unit (12) is
provided with programmable logic controllers (PLC) for controlling the
logic functions of said apparatus.
6. The apparatus as claimed in claim 5, wherein said PLC is configured to
operate with ladder logic for controlling the entire sequence of the
measurement operation.

7. The apparatus as claimed in claim 4, wherein the control unit (12) is
provided with sensors and an operator panel for commanding the
equipment in a given situation using a set of pneumatic actuators (2, 4,
5, 6, 7, 8, 9) and controls of said operator panel.
8. The apparatus as claimed in the preceding claims, wherein said operator
. panel is provided with manual controls to operate during sequence
failures.
9. The apparatus as claimed in claim 5, wherein said sensors are binary
sensors like magnetic reed switches inductive proximity switches and
infrared through beam and retro reflective type sensors.
10.A method for automatic measurement of taper value on bore of ball
bearing inner races in real time in a taper measuring apparatus as
claimed in claims 1 to 9, said method comprising the steps of:

- placing the bearing inner races from a grinding machine to a
measuring position (C) of the apparatus with the help of an input
conveyor (10);
- measuring bore diameters Dl and D2 with the help of a measuring
head (3) and an electrical control unit (12); and
- sorting out under / over sized races from the production line
while allowing races falling within permissible range.

ABSTRACT

APPARATUS FOR AUTOMATIC MEASUREMENT OF TAPER VALUE ON
BORE OF BALL BEARING INNER RACES
An apparatus for automatic measurement of taper value on bore of ball bearing
inner races comprises of an input conveyor for transferring bearing inner races
from a grinding machine to a measuring position (C) of said apparatus where a
measuring head (3) is disposed at the measuring position (C) for measuring the
bore and taper of said bearing inner races when an electrical control unit (12)
is disposed for commanding the equipment against a given situation during
measuring operation. The control unit (12) is provided with sensors and an
operator panel for commanding the equipment in a given situation using a set
of Pneumatic actuators (2, 4, 5, 6, 7, 8, 9) and controls of the operator Panel.