Title of Invention

"A NOVEL APPARATUS FOR SLIP GAUGE CALIBRATION AND A METHOD FOR CALIBRATION OF SLIP GAUGES"

Abstract A novel apparatus for slip gauge calibration which comprises: a flat bottom non corrosive tank (1) filled with a transparent non corrosive liquid of known refractive index, the said tank (1) having placed at the inside bottom a platen (2), characterized in that the said platen (2) having placed on its top a reference slip gauge (3) having standard value ranges from 2.50009 to 50.00014 mm and a slip gauge (4) under test, the said test gauge (4) wrung adjacent to the said standard gauge (1) and on the same platen (2), the said tank (1) being provided with a liquid level adjuster essentially consisting of a solid cylinder (5) for sliding vertically in the said tank (1), the said solid cylinder being guided for vertical motion by a vertical support (6) fixed to the side wall of the tank (1) by known means, the top of the said solid cylinder being attached to a threaded screw (7) passing through a threaded hole in a horizontal plate (8) attached to the rim of the said tank (1), the said tank and accessories being placed on a standard platform with three dimensional movement, the said standard platform having a conventional optical microscope (9), the said microscope having attached to it, at the objective lens portion, a probe by known means, the said probe being connected to a digital position measuring instrument (10).
Full Text The present invention relates to a novel apparatus for slip gauge calibration and a method for calibration of slip gauges.
More particularly the present invention relates to an apparatus and a simple method for the calibration of slip gauges using the known value of refractive index of a liquid .
Slip gauges are precision mechanical devices used in any machine shop, manufacturing mechanical components used in automobiles, aircrafts, locomotives and other sophisticated mechanical instruments. In all these situations quality assurance is of critical importance. It is due to this there is a need to have standards of measurements of dimensional metrology parameters like length. These standards of measurements need to be calibrated frequently as environmental conditions tend to alter the parametric values. Hence, ;here is a need to have a simple system which can be used easily to do a routine but accurate calibration routine. In the area of slip gauges there are basically two types of most frequently used slip gauges namely; Inspection grade and workshop grade slip gauges and both having the need for repeated calibration.
In a conventional interferometric method, use is made of sets of "00" slip gauges and interferometers, for the calibration of slip gauges. .Further, this method needs accurate temperature control, of the ambient, in the calibration laboratory, to the extent of ±0.02° C. Due to this, the method can be used only in a calibration laboratory and proves to be very costly and tedious in regular calibration routines.
In another conventional method, called the electronic gauge block comparator method at least 100 sets of 00" or "0" grade slip gauges are used along with an electronic comparator. In this method, the standard reference slip gauge and the test gauge must necessarily be of the same material, to account for identical effects due to any temperature variation in the ambient. Besides this method needs the length of the standard slip gauges to be 100 mm. Further, this method also needs accurate control of ambient temperature to at least within ±2.0° C. Both the above mentioned methods have the limitations of higher cost with regard to interferometers and electronic comparator and use of 00-grade slip gauges. Both the methods also need maintenance of precise temperature.
In National Physical Laboratory, a constituent laboratory of Council of Scientific and Industrial Research, precision interferometric technique to calibrate slip gauges, has been developed. In this method the accuracy obtained is very high but has the limitation of use only in the calibration laboratory and not in the field.
The apparatus of the present invention obviates the above mentioned drawbacks. The main object of the present invention is to provide a novel apparatus for slip gauge
calibration and a method for calibration of slip gauges. Another objective of the present invention is to provide use of maximum of 50
numbers of 00-grade slip gauges enabling the dispensation of the costly electronic
comparator and interferometer and full set of slip gauges. Still another objective of the present invention is to enable calibration of slip gauges in
a field location.
Yet another object of the present invention is to eliminate the use of precise temperature control of the ambient in a calibration laboratory.
In the drawing accompanying this specification, Figure 1 represents a device for the calibration of slip gauges other than 00-grade and 0 grade, using liquid medium refractive index, wherein (1) is a metal tank, (2) is a platen, (3) and (4) are slip gauges, (5) is sliding cubic cylinder, (6) is a support for the sliding cubic cylinder, (7) is a threaded screw for effecting liquid level fine adjustment, (8) is plate with a threaded hole for the threaded screw (7) for liquid level adjustment, with parts (5), (6), (7) and (8) together forming the liquid level adjustment system, (9) is an optical microscope and (10) is a digital position measuring instrument.
Accordingly, the present invention provides a novel apparatus for slip gauge calibration which comprises: a flat bottom non corrosive tank (1) filled with a transparent non corrosive liquid of known refractive index, the said tank (1) having placed at the inside bottom a platen (2), characterized in that the said platen (2) having placed on its top a reference slip gauge (3) having standard value ranges from 2.50009 to 50.00014 mm and a slip gauge (4) under test, the said test gauge (4) wrung adjacent to the said standard gauge (1) and on the same platen (2), the said tank (1) being provided with a liquid level adjuster essentially consisting of a solid cylinder (5) for sliding vertically in the said tank (1), the said solid cylinder being guided for vertical motion by a vertical support (6) fixed to the side wall of the tank (1) by known means, the top of the said solid cylinder being attached to a threaded screw (7) passing through a threaded hole in a horizontal plate (8) attached to the rim of the said tank (1), the said tank and accessories being placed on a standard platform with three dimensional movement, the said standard platform having a conventional optical microscope (9), the said microscope having attached to it, at the objective lens portion, a probe by known means, the said probe being connected to a digital position measuring instrument (10).
In an embodiment of the present invention the tank may be filled with a transparent non corrosive liquid of known refractive index such as water, glycerin.
In another embodiment of the present invention, the platen used may be of a material such as steel, stainless steel, tungsten carbide.
In still another embodiment of the present invention the platen chosen may be highly polished to enable slip gauges to be wrung on it.
In yet another embodiment of the present invention the threaded screw may have a pitch in the range of 1 to 2 mm.
In still another embodiment of the present invention the solid cylinder may be of any light material such as brass, aluminium.
In yet another embodiment of the present invention the solid cylinder may be of any suitable cross section such as circle, square, rectangular.
In an embodiment of the present invention the digital position indicator may be any known electronic indicator.
In a further embodiment of the present invention, the standard slip gauge (3) may be of a grade such as '00'.
Accordingly the present invention provides a method for calibration of slip gauges, using the novel apparatus of the invention disclosed herein, which comprises: placing
by wrunging a standard slip gauge (3) and the slip gauge (4) under check, on platen (2) placed in the flat bottom tank (1), focusing the microscope (9) onto the top surface of the slip gauge (4) under check , filling the tank (1) with a non corrosive transparent liquid of known refractive index n, adjusting the liquid level adjuster to obtain a focussed bright image of the surface of the platen in the field of view of the microscope without refocusing the microscope , focusing the top surface of the liquid by shifting vertically the position of the microscope from the platen focused position, recording the focussed position x1 of the microscope with the digital position indicator, shifting the microscope to focus the top surface of the standard slip gauge (3), recording the focussed position x2 of the microscope, incorporating the refractive index n of liquid , the length of the standard slip gauge (3) and the positions x1 and x2 in the known equation n (refractive index) = real depth / apparent depth to determine precisely the calibration length of slip gauge (4) under check.
The apparatus of the present invention has been constructed with a tank (1) of stainless steel even though any other non corrosive material can also be used. The tank is preferably cubical in geometry having dimensions of 120 mm3 with the top surface being open. The tank has a base platen (2) having a highly polished surface so that slip gauges can be wrung on it. On this are wrung the standard slip gauge (3) and the slip gauge under test (4). These gauges preferably have lengths having nominally a ratio of 3 to 4.5 depending on the liquid medium used. The liquid level adjustment system is a combination of a few mechanical parts fabricated for the purpose. Essentially the
system is made up of a fine threaded screw (7) made specifically for the apparatus . The screw has a pitch in a range between 1 to 2 mm.
This screw passes through a plate (8) having a hole to accept the threaded screw. The plate is attached to the rim of the tank (1). To the bottom of the screw is attached a solid cylinder (5) of preferably a circular cross section and of a light material. The solid cylinder is allowed to move vertically only by getting a guiding action from a support (6) fixed to the side of the tank (1). This restricted guiding action is achieved by letting the cylinder and the support just touch each other without any friction. The purpose of the arrangement is to make fine adjustment of the liquid surface . The optical focusing of various surfaces is done by a conventional optical microscope (9) attached on a standard platform with three dimensional movement,. The distances traversed by the microscope and the geometrical positions are determined by an electronic digital position indicator. (10) with its probe being attached to the objective lens portion of the microscope.
In a typical measurement sequence with the apparatus of the present invention, standard reference slip gauge (3) of length L2 and slip gauge (4) under test of nominal length L1 , are wrung on the platen. Microscope is focused on the top surface of (4) and the same is then shifted sideways without changing the focussed condition corresponding to top surface of slip gauge (4) . Now a liquid, say water of known refractive index 'n' is poured in the tank to such height that the image level of the common platen is seen raised in the field of view of the microscope. The liquid is poured till a near clear image of the raised platen surface is seen in the field of view. At
this point, the liquid level is seen to approximately coincide with the top surface of the slip gauge (4) under test. To bring the image to full focussed condition, liquid height adjustment is necessary which is achieved by using the liquid level adjustment arrangement by moving the solid cylinder (5) attached to the threaded screw (7). This motion of the cylinder pushes the liquid surface either up or down leading to a brighter image of the platen, in the field of view of the microscope. After attaining the brighter image of the raised base platen, the microscope is raised upward and is then refocused on the top surface of the liquid and the measurement corresponding to this position is determined, say as Xi. Next the microscope is shifted to focus the top surface of the other slip gauge (3), the standard, of known length L2. This focused image gives another reading x2.
Now the principle underlying this invention is covered by the general expression given below in Eq.1, n (refractive index)= real depth/apparent depth
(Equation Removed) (1)
where ,L2- (x2-x1) is the real depth and [(L2-L1)- (x2-X1] is the apparent depth. From the known values of, length L2 the distances x1 and x2 and of the refractive index n, the unknown length L1 can be determined by using the formula given in Eq 2,
(Equation Removed) (2)
For the slip gauges of lengths larger than L2, respective positions of the slip gauges need to be reversed in this invention so that smaller number of standard slip gauges can also be used and also to overcome the non-availability of the standard slip gauges
having size of > 100 mm..
In this situation, the formula for determination of L1 would become:
(Equation Removed) (3)
The novelty of the present invention rests in: eliminating the need for precise temperature control. This novelty of the invention is realized due to the inventive step of measurement of small lengths thereby allowing substitution of larger lengths by very small lengths minimizing the temperature affected length measurement error. This inventive step is achieved by the use of a simple liquid level adjustment device incorporated in the apparatus of the present invention.
The following examples are given by way of illustration only and should not be construed to limit the scope of the present invention.
Example 1
To calibrate 1.00000 mm. (nominal value, 1.0 mm.) test slip gauge , first the slip gauge was wrung on the common platen. Then a reference standard slip gauge of the value 4.49992 mm. was wrung adjacent to the test slip gauge, on the same common platen. Next microscope was focused on the top surface of test slip gauge followed by an horizontal shift away from this slip gauge.. At this position of microscope the common platen gets defocused in the field of view. Water was then poured slowly in the tank to such a height that the image of the platen surface gets raised to the level of top surface of test piece. This brings about the re-appearance of the brightness in the microscope . To sharpen the brightness in the microscope, the height of the liquid level was slightly adjusted by the use of liquid level adjustment arrangement. Next, the microscope was lifted upwards, to focus the top level of the liquid surface. Measurement corresponding
to this position, X1 was 0.805 mm.. Microscope was lifted a bit above and shifted horizontally to bring above the surface of the standard reference slip gauge and the top surface was now focused. Measurement corresponding to this position , x2 was 1.304 mm Now these values of L2, x1 and x2 were fed to a computer software, employing the formula L1= [L2-(x2-x1)] * (n-1)/n and corrected value of test slip gauge was obtained at the output which is 1.00001 mm. Giving an error of +0.01 micrometer.
Example 2
To calibrate 4.50000 mm. (nominal value, 4.5 mm.) test slip gauge , first the slip gauge was wrung on the common platen. Then a reference standard slip gauge of the value 18.5004 mm. was wrung adjacent to the test slip gauge, on the same common platen. Next microscope was focused on the top surface of test slip gauge followed by an horizontal shift away from this slip gauge. At this position of microscope the common platen gets defocused in the field of view. Water was then poured slowly in the tank to such a height that the image of the platen surface gets raised to the level of top surface of test piece. This brings about the re-appearance of the brightness in the microscope . To sharpen the brightness in the microscope, the height of the liquid level was slightly adjusted by the use of liquid level adjustment arrangement. Next, the microscope was lifted upwards, to focus the top level of the liquid surface. Measurement corresponding to this position, X1 was 0.6155 mm.. Microscope was lifted a bit above and shifted horizontally to bring above the surface of the standard reference slip gauge and the top surface was now focused. Measurement corresponding to this position , x2 was 1.114mm Now these values of L2, x1 and x2 were fed to a computer software
employing the formula L1= [L2-(X2-X1)] * (n-1)/n and corrected value of test slip gauge was obtained at the output which is 4.49992 mm. giving an error of -0.08 micrometer.
Example 3
To calibrate 10.5000 mm. (nominal value, 10. mm.) test slip gauge , first the slip gauge
was wrung on the common platen. Then a reference standard slip gauge of the value
50.00014 mm. was wrung adjacent to the test slip gauge, on the same common platen.
Next microscope was focused on the top surface of test slip gauge followed by an
horizontal shift away from this slip gauge. At this position of microscope the common
platen gets defocused in the field of view. Water was then poured slowly in the tank to
such a height that the image of the platen surface gets raised to the level of top surface
of test piece. This brings about the re-appearance of the brightness in the microscope .
To sharpen the brightness in the microscope, the height of the liquid level was slightly
adjusted by the use of liquid level adjustment arrangement. Next, the microscope was
lifted upwards, to focus the top level of the liquid surface. Measurement corresponding
to this position, x1 was 0.710 mm.. Microscope was lifted a bit above and shifted
horizontally to bring above the surface of the standard reference slip gauge and the top
surface was now focused. Measurement corresponding to this position , x2 was 1.215
mm. Now these values of L2, X1 and x2 were fed to a computer software employing the
formula L1= [L2-(x2-x1)] * (n-1)/n but the software did not result in any output. Instead,
the software prompted for interchanging of the position of the two slip gauges.
Example 4
To calibrate 10.0000 mm. (nominal value, 1.0 mm.) test slip gauge , first the slip gauge was wrung on the common platen. Then a reference standard slip gauge of the value 2.50009 mm. was wrung adjacent to the test slip gauge, on the same common platen. Next microscope was focused on the top surface of the reference standard slip gauge followed by an horizontal shift away from this slip gauge.. At this position of microscope the common platen gets defocused in the field of view. Water was then poured slowly in the tank to such a height that the image of the platen surface gets raised to the level of top surface of reference standard slip gauge piece. This brings about the re¬appearance of the brightness in the microscope . To sharpen the brightness in the microscope, the height of the liquid level was slightly adjusted by the use of liquid level adjustment arrangement. Next, the microscope was lifted upwards, to focus the top level of the liquid surface. Measurement corresponding to this position, x1 was 0.635 mm.. Microscope was lifted a bit above and shifted horizontally to bring above the surface of the test slip gauge and the top surface was now focused. Measurement corresponding to this position, X2 was 1.304 mm Now these values of L2, x1 and X2 were fed to a computer software employing the formula L1 = {L2 * [n/(n-1)]} + (x2-x1) and corrected value of test slip gauge was obtained at the output which is 10.50011 mm. giving an error of +0.01 micrometer.
Example 5
To calibrate 40.0000 mm. (nominal value, 1.0 mm.) test slip gauge , first the slip gauge was wrung on the common platen. Then a reference standard slip gauge of the value
9.90002 mm. was wrung adjacent to the test slip gauge, on the same common platen. Next microscope was focused on the top surface of the reference standard slip gauge followed by an horizontal shift away from this slip gauge.. At this position of microscope the common platen gets defocused in the field of view. Water was then poured slowly in the tank to such a height that the image of the platen surface gets raised to the level of top surface of reference standard slip gauge piece. This brings about the re¬appearance of the brightness in the microscope . To sharpen the brightness in the microscope, the height of the liquid level was slightly adjusted by the use of liquid level adjustment arrangement. Next, the microscope was lifted upwards, to focus the top level of the liquid surface. Measurement corresponding to this position, xi was 0.640 mm.. Microscope was lifted a bit above and shifted horizontally to bring above the surface of the test slip gauge and the top surface was now focused. Measurement corresponding to this position , X2 was 1.307 mm
Now these values of L2, X1 and X2 were fed to a computer software employing the formula L1 = {L2 * [n/(n-1)]} + (x2-X1) and corrected value of test slip gauge was obtained at the output which was 40.00005 rnm. showing an error of +0.05 micrometer.
Example 6
To calibrate 2.00000 mm. (nominal value, 2.0 mm.) test slip gauge , first the slip gauge was wrung on the common platen. Then a reference standard slip gauge of the value 5.50003. mm. was wrung adjacent to the test slip gauge, on the same common platen. Next microscope was focused on the top surface of test slip gauge followed by an
horizontal shift away from this slip gauge.. At this position of microscope the common platen gets defocused in the field of view. Glycerine was then poured slowly in the tank to such a height that the image of the platen surface gets raised to the level of top surface of test piece. This brings about the re-appearance of the brightness in the microscope . To sharpen the brightness in the microscope, the height of the liquid level was slightly adjusted by the use of liquid level adjustment arrangement. Next, the microscope was lifted upwards, to focus the top level of the liquid surface. Measurement corresponding to this position, Xi was 0.610 mm.. Microscope was lifted a bit above and shifted horizontally to bring above the surface of the standard reference slip gauge and the top surface was now focused. Measurement corresponding to this position , X2 was 0.0877 mm Now these values of L2, X1 and X2 were fed to a computer software employing the formula L1= [L2-(x2-x1)] * (n-1)/n and corrected value of test slip gauge was obtained at the output which is 2.00007 mm. Giving an error of +0.07 micrometer.
Example 7
To calibrate 5.00000 mm. (nominal value, 2.0 rnm.) test slip gauge , first the slip gauge was wrung on the common platen. Then a reference standard slip gauge of the value 16.00011. mm. was wrung adjacent to the test slip gauge, on the same common platen. Next microscope was focused on the top surface of test slip gauge followed by an horizontal shift away from this slip gauge.. At this position of microscope the common platen gets defocused in the field of view. Glycerine was then poured slowly in the tank to such a height that the image of the platen surface gets raised to the level of top surface of test piece. This brings about the re-appearance of the brightness in the
microscope . To sharpen the brightness in the microscope, the height of the liquid level was slightly adjusted by the use of liquid level adjustment arrangement. Next, the microscope was lifted upwards, to focus the top level of the liquid surface. Measurement corresponding to this position, x1 was 0.7500 mm.. Microscope was lifted a bit above and shifted horizontally to bring above the surface of the standard reference slip gauge and the top surface was now focused. Measurement corresponding to this position , x2 was 1.168 mm Now these values of L2, X1 and x2 were fed to a computer software employing the formula L1= [L2-(x2-x1)] * (n-1)/n and corrected value of test slip gauge was obtained at the output which is 5.00003 mm. Giving an error of +0.03 micrometer.
Example 8
To calibrate 13.00000 mm. (nominal value, 13.0 mm.) test slip gauge , first the slip gauge was wrung on the common platen. Then a reference standard slip gauge of the value 40.00000 mm. was wrung adjacent to the test slip gauge, on the same common platen. Next microscope was focused on the top surface of test slip gauge followed by an horizontal shift away from this slip gauge.. At this position of microscope the common platen gets defocused in the field of view. Glycerine was then poured slowly in the tank to such a height that the image of the platen surface gets raised to the level of top surface of test piece. This brings about the re-appearance of the brightness in the microscope . To sharpen the brightness in the microscope, the height of the liquid level was slightly adjusted by the use of liquid level adjustment arrangement. Next, the microscope was lifted upwards, to focus the top level of the liquid surface. Measurement corresponding to this position, x1 was 0.505 mm.. Microscope was lifted a bit above
and shifted horizontally to bring above the surface of the standard reference slip gauge and the top surface was now focused. Measurement corresponding to this position , x2 was 0.956 mm Now these values of L2, X1 and x2 were fed to a computer software employing the formula l1= [L2-(x2-x-1)] * (n-1)/n but the software did not result in any output. Instead, the software prompted for interchanging of the position of the two slip gauges.
Example 9
To calibrate 13.0000 mm. (nominal value, 1.0 mm.) test slip gauge , first the slip gauge was wrung on the common platen. Then a reference standard slip gauge of the value 4.00002 mm. was wrung adjacent to the test slip gauge, on the same common platen. Next microscope was focused on the top surface of the reference standard slip gauge followed by an horizontal shift away from this slip gauge.. At this position of microscope the common platen gets defocused in the field of view. Glycerine was then poured slowly in the tank to such a height that the image of the platen surface gets raised to the level of top surface of reference standard slip gauge piece. This brings about the re¬appearance of the brightness in the microscope . To sharpen the brightness in the microscope, the height of the liquid level was slightly adjusted by the use of liquid level adjustment arrangement. Next, the microscope was lifted upwards, to focus the top level of the liquid surface. Measurement corresponding to this position, x1 was 0.605 mm.. Microscope was lifted a bit above and shifted horizontally to bring above the surface of the test slip gauge and the top surface was now focused. Measurement corresponding to this position , x2 was 1.139 mm Now these values of L2, X1 and x2
were fed to a computer software employing the formula L1 = {L2 * [n/(n-1)]} + (x2-x1) and corrected value of test slip gauge is obtained at the output which is 12.99967 mm. showing an error of -0.33 micrometer.
Example 10
To calibrate 40.00000 mm. (nominal value, 40.0 mm.) test slip gauge , first the slip gauge was wrung on the common platen. Then a reference standard slip gauge of the value 12.49997 was wrung adjacent to the test slip gauge, on the same common platen. Next microscope was focused on the top surface of the reference standard slip gauge followed by an horizontal shift away from this slip gauge.. At this position of microscope the common platen gets defocused in the field of view. Glycerine was then poured slowly in the tank to such a height that the image of the platen surface gets raised to the level of top surface of reference standard slip gauge piece. To sharpen the brightness in the microscope, the height of the liquid level was slightly adjusted by the use of liquid level adjustment arrangement. Next, the microscope was lifted upwards, to focus the top level of the liquid surface. Measurement corresponding to this position, xi was 0.610 mm.. Microscope was lifted a bit above and shifted horizontally to bring above the surface of the test slip gauge and the top surface was now focused. Measurement corresponding to this position , x2 was 1.655 mm Now these value of length L2 of standard reference gauge, x1 and x2 were fed to a computer software employing the formula LI = {L2 * [n/(n-1)]} + (x2-x1) and corrected value of test slip gauge was obtained at the output which is 39.99994 mm. showing an
error of -0.06 micrometer.
Main advantages of the present invention are:
1. Use of lesser number of slip gauges e.g 50 as compared to larger number say at
least 100 of slip gauges needed in electronic gauge block comparator method.
2. It is less error prone to temperature effect thereby avoiding the need for precise
ambient temperature control.
3. The maximum size of the standard slip gauge needed in the apparatus of the
present invention is 40 mm.




We Claim:
1. A novel apparatus for slip gauge calibration which comprises: a flat bottom non corrosive tank (1) filled with a transparent non corrosive liquid of known refractive index, the said tank (1) having placed at the inside bottom a platen (2), characterized in that the said platen (2) having placed on its top a reference slip gauge (3) having standard value ranges from 2.50009 to 50.00014 mm and a slip gauge (4) under test, the said test gauge (4) wrung adjacent to the said standard gauge (1) and on the same platen (2), the said tank (1) being provided with a liquid level adjuster essentially consisting of a solid cylinder (5) for sliding vertically in the said tank (1), the said solid cylinder being guided for vertical motion by a vertical support (6) fixed to the side wall of the tank (1) by known means, the top of the said solid cylinder being attached to a threaded screw (7) passing through a threaded hole in a horizontal plate (8) attached to the rim of the said tank (1), the said tank and accessories being placed on a standard platform with three dimensional movement, the said standard platform having a conventional optical microscope (9), the said microscope having attached to it, at the objective lens portion, a probe by known means, the said probe being connected to a digital position measuring instrument (10),
2. A novel apparatus as claimed in claim 1, wherein the non corrosive tank used is such
as steel, stainless steel, aluminium and non corrosive liquid used is selected from
water or glycerine.
3. A novel apparatus as claimed in claims 1-2, wherein the platen used is of a material
such as steel, stainless steel, tungsten carbide.
4. A novel apparatus as claimed in claims 1-3, wherein the platen is highly polished to
enable slip gauges to be wrung on it.
5. A novel apparatus as claimed in claims 1-4, wherein the threaded screw has a pitch
in the range of 1 to 2 mm.
6. A novel apparatus as claimed in claims 1-5, wherein the solid cylinder is of any light
material such as brass, aluminium.
7. A novel apparatus as claimed in claims 1-6, wherein the solid cylinder is of any
suitable cross section such as circle, square, rectangular.
8. A novel apparatus as claimed in claims 1-7, the digital position indicator is any known
electronic indicator.
9. A novel apparatus as claimed in claims 1 - 8, wherein the standard slip gauge (3) is
of a grade such as '00'.
10. A method for calibration of slip gauges, using the novel apparatus of the invention as
claimed in claims 1-9, disclosed herein, which comprises: placing by wrunging a
standard slip gauge (3) and the slip gauge (4) under check, on platen (2) placed in
the flat bottom tank (1), focusing the microscope (9) onto the top surface of the slip
gauge (4) under check, filling the tank (1) with a non corrosive transparent liquid of
known refractive index n, adjusting the liquid level adjuster to obtain a focused
bright image of the surface of the platen in the field of view of the microscope
without refocusing the microscope, focusing the top surface of the liquid by shifting
vertically the position of the microscope from the platen focused position, recording
the focused position (xi)of the microscope of the microscope with the digital position
indicator, shifting the microscope to focus the top surface of the standard slip gauge
(3), recording the focused position (x2) of the microscope to determine precisely the
calibration length of slip gauge (4) under check.
11. A novel apparatus for slip gauge calibration substantially as herein described with
reference to the examples and drawing accompanying this specification.

Documents:

402-del-2001-abstract.pdf

402-del-2001-claims.pdf

402-del-2001-correspondence-others.pdf

402-del-2001-correspondence-po.pdf

402-del-2001-description (complete).pdf

402-del-2001-drawings.pdf

402-del-2001-form-1.pdf

402-del-2001-form-18.pdf

402-del-2001-form-2.pdf

402-del-2001-form-3.pdf


Patent Number 230766
Indian Patent Application Number 402/DEL/2001
PG Journal Number 11/2009
Publication Date 13-Mar-2009
Grant Date 27-Feb-2009
Date of Filing 29-Mar-2001
Name of Patentee COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
Applicant Address RAFI MARG, NEW DELHI-110 001, INDIA.
Inventors:
# Inventor's Name Inventor's Address
1 MRITYUNJAY KARFA NATIONAL PHYSICAL LABORATORY K S KRISHNAN MARG, NEW DELHI.
PCT International Classification Number A01B 063/12
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA