The present invention relates to apparatus for holding test piece, and more
particularly to Fixtures and Jigs used in conjunction with apparatus generating sub
zero level cooling.
BACKGROUND OF THE INVENTION
The existing facility of sub-zero level temperature cooling is mainly by high pressure
dry Nitrogen blowing through Micro-Heat Exchanger. For example, better thermal
detection of IR photo detector, the relative temperature with respect to its
surrounding should be as low as possible. Normally high pressure dry Nitrogen
blowing cooling process through Micro-Heat Exchanger is used for such type of
temperature cooling which requires approx 1 to 2 hours set-up time and it is also not
healthy for human. During IR channel tuning the very thin capillary type pipeline
arrangement get chocked due to moisture or impurity problem in Nitrogen Station.
This stop continuity of the IR channel Tuning (Focusing-Linearity- Centering), which
cause repetition of tuning stage and results in delay. At the same time, blowing of
Nitrogen gas is also health hazardous for operator who is performing optical tuning.
The cooling procedure of IR DETECTION SYSTEM via Micro-cryogenic (MCG) is
implemented using innovative fixture arrangement.
SUMMARY OF PRESENT INVENTION
The existing process of cooling in IR DETECTION SYSTEM is via Microcryogenic
(MCG). The MCG is high speed compressor which blow the Special gas
( Original Equipment Manufacturer supplied cooling gas) through very fine capillary
pipeline assembly & distributed throughout 64- channel Infra-red Photo Detector strip
by Micro-Heat Exchanger. This system provides high speed (77°K within 3 min.)
cooling to Photo-detector channel without any humidity.
As per assembly stage of IR DETECTION SYSTEM, after IR Optical
Channel tuning, assembly of MCG for final level test of the system is performed. In
this stage, a MCG mounting with pipeline assembly and fill the Special Cooling gas.
The inventor reorganizes the assembly stage and prepone the MCG assembly ( ie
Annexure‐II
before the optical tuning) and to avoid the vibration problem during tuning the fixture
is designed to hold the MCG without touching the main IR DETECTION SYSTEM
body & transfer the whole vibration in fixture itself.
New adopted Methodology by designed fixture for Cooling (by Micro Cryogenic
Cooling System) of Infra-red Photo Detector strip provide following aspect-
Reducing set uptime (previous set-up time 1 to 2 hours, new set-up time
approx.15 to 30min.).
Minimizing the hazardous condition for operator
Eliminate chocking of Micro-Heat Exchanger
Re-sequencing of assembly operation in IR DETECTION SYSTEM also
reduce cycle time.
The said fixture of MCG is simple & handy and can be use for the same
application on any other check apparatus.
The height adjustment facility in designed fixture makes it compatible for all
height check apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a Fixture Arrangement with MCG at IR Optical Channel Tuning
Fig. 2 is a Bench MCG Fixture for holding with mechanical dimension
Fig. 3 is a Fixture Mechanical Dimension for Manufacturing
DETAILED DESCRIPTION
The invented fixture adds value in process & improves the quality of optical
tuning. One such application of said invention is in assembly of IR DETECTION
SYSTEM. During tuning of optical channel, operator has to test the Photo receiving
device should be cooled at 77° K. During testing, it is achieved by high pressure dry
Nitrogen blowing causing chocking of Micro-Heat Exchanger. The inventors make
the feasibility study to make alternate arrangement to cool Photo-detector channel as
available in IR DETECTION SYSTEM (MCG) for testing also. But MCG generate
vibration which does not allow IR Optics Channel tuning. During study inventor
observed that mounting of IR DETECTION SYSTEM in its called up platform, the
MCG assembly along with clamp mounted on the upper side frame & IR
DETECTION SYSTEM mounted on the lower frame.. Inventors studied the feasibility
Annexure‐II
for its design to implement in production shop with same arrangement so that during
optical tuning shop operator able to perform the operation without any obstruction.
The said fixture is simulating the same arrangement which is available in
called up platform. The length of the fixture is adjustable which provide flexibility to
use it at different test station as well as some adjustment for pipeline length w.r.t.
tuning bench. The clamping diameter of fixture is same as the diameter of MCG and
the weight of the fixture made up to the limit which make it easy to transfer the all
vibration of MCG to fixture itself.
The Figure 3 is divided in three regions-
Region a : This is the section where MCG is mounted. The position no. 5 & 6 is the
height adjustment for the MCG assembly, this provide sufficient gap between IR
DETECTION SYSTEM & MCG assembly which is represented in figure 3 in section
a.1
Region b: This is base section of fixture which provide stability for the fixture during
running of MCG , as it generates substantial amount of vibration.
Region c : This is article IR DETECTION SYSTEM side with tuning bench, on which
operator make IR Channel optical tuning.
Figure 1 & 2 is basic mechanical design drawing for manufacturing of fixture.
During optical alignment of IR DETECTION SYSTEM, the Infra-red Photo
Detector strip should be at 77°K for optimum performance otherwise the signal to
noise ratio degraded below the threshold which result variation of optical parameter.
With above arrangement, the capillary pipeline assembly
(combination of three pipeline) with MCG & Infra-red Photo Detector strip made
before the IR optical channel alignment. During alignment of optics the Special
Cooling gas circulate with high pressure by MCG which results as cooling effect on
IR Photo Detector Strip & operator able to tune the optics.

WE CLAIMS:-
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. The said system, comprising, mechanical fixture capable of holding a sub zero level cooling device
2. The system according to claim 1, capable of dampening vibration generated by sub zero level cooling device.
3. The system according to claim 1, capable of mounting sub zero level cooling device without harming it.
4. The system according to claim 1, a methodology for cooling of IR Photo Detector Strip by re-sequencing of operation is claimed
5. The system according to claim 1, minimization hazardous condition due to circulation of cooling gas in closed loop without contamination in both inside and outside.
6. The system according to claim 1, the said invention imparts obstruction free IR Optical Channel Tuning.
7. The system according to claim 1, the height adjustment facility of holding fixture makes it compatible for other tuning test benches. ,TagSPECI:As per Annexure-II