FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION
A portable apparatus for calibration of the chest displacement sensor
of a crash test dummy


APPLICANTS
TATA MOTORS LIMITED, an Indian company
having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India

INVENTORS
Rajesh Chaugule and Ashishkumar both Indian nationals
of TATA MOTORS LIMITED an Indian company
having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner
in which it is to be performed.


FIELD OF INVENTION
This invention relates to calibration of displacement sensor and more particularly it relates to an apparatus for calibration of chest displacement sensor of a crash test dummy.
BACKGROUND OF INVENTION
Crash test dummies are used for assessing the crashworthiness of a vehicle through crash test. These dummies have been instrumented at various parts in order to acquire the body response in the event of a crash. The instrumentations provided at the various locations require periodic calibrations to ensure correctness of the data produced.
A displacement transducer has been provided at the chest of a crash test dummy to measure the rib cage or sternum displacement with respect to the spine in a crash test. It consists of a stem connected to a rotary potentiometer. One end of the stem is connected to the sternum & another one is connected to a rotary potentiometer. When sternum end of the stem displaces, it rotates the potentiometer resulting into change in the electric resistance of the rotary potentiometer. The change in the electric resistance of the rotary potentiometer is proportional to the displacement of the sternum.
In a conventional calibration method, the sternum of end of the stem is made to displace through a predetermined distance using calibrated slip gauges positioned on the sternum surface. The associated change in the electrical resistance of the potentiometer is recorded. This sequence is repeated with slip gauges of different thicknesses. However this method has several disadvantages as follows ;
- The calibration is carried out with the chest displacement potentiometer installed in a crash test dummy. Therefore availability of the crash test dummy
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is a prerequisite for the calibration which limits the freedom for calibration schedules. For the same reason the calibration set up is not portable.
- checking of chest displacement transducer alone is not possible posing limitations for fault finding & repairs,
- due to use of slip gauges for calibration, the calibration is carried out in steps and a continuous calibration over the range of the sensor is not possible,
- also due to insertion & removal of slip gauges, the calibration is time consuming,
- since the reference surface for the slip gauges is the sternum, local damages to the sternum affects & limits the calibration,
OBJECTS OF THE INVENTION
The main object of the present invention is to provide a portable apparatus for calibrating chest displacement sensor of a crash test dummy.
Another object of the present invention is to provide a portable apparatus for calibrating chest displacement sensor of a crash test dummy which facilitates a continuous calibration over the range of the sensor.
Another object of the present invention is to provide a portable apparatus for calibrating chest displacement sensor of a crash test dummy which takes less time for calibration.
Another object of the present invention is to provide a portable apparatus for calibrating chest displacement sensor of a crash test dummy which simple in construction.
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STATEMENT OF THE INVENTION
Accordingly the present invention discloses, a portable apparatus for calibration of chest displacement sensor of crash test dummy comprising
a base plate;
a top plate configured to mount the rotary potentiometer and to support sliding head through screw mechanism adapted for actuating said sliding head;
a vertical support plate connected perpendicular to the said top plate and base plate;
at least one support block mounted on said top plate to restrict rotation of rotary sensor;
at least two guide rods provided on sliding head to ensure proper movement of the sliding head;
at least one reference displacement transducer to be mounted on one of the said guide rods for sensing displacement of the sliding head;
a chest displacement sensor mounted on said top plate comprising
a stem configured to rest its free end having spherical ball adapted as follower on said sliding head;
at least one display unit to show the displacements of said chest displacement sensor and said reference displacement transducer;
BRIEF DESCRIPTION OF INVENTION
In accordance with the present invention, a portable apparatus for calibration of a chest displacement sensor of a crash test dummy comprises;
a base plate; a vertical support plate ; a top plate having sliding head supported on it; a lead screw mechanism for actuating said sliding head; chest displacement sensor is mounted on said top plate facing downwards; the stem of the said chest displacement
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sensor is kept in contact with said sliding head supported on the said top plate; said sliding head is moved gradually by turning said lead screw mechanism which makes said stem of said chest displacement sensor to move; said chest displacement sensor is positioned on said top plate in such a way that moving end of said sensor maintains contact with said sliding head by gravity.
BRIEF DESCRIPTION OF DRAWINGS
In accordance to the present invention,
Figure-01 shows the chest displacement sensor used in a crash test dummy,
Figure-02 shows the portable apparatus prepared for calibration of the chest
displacement sensor of a crash test dummy
Figure-03 shows installation of the chest displacement sensor on the portable
calibration apparatus.
DETAILED DESCRIPTION OF INVENTION
Referring now to the drawings wherein the showings are for the purpose of
illustrating a preferred embodiment of the invention only, and not for the purpose of
limiting the same.
In accordance with the present invention, a portable apparatus for calibration of a
chest displacement sensor of a crash test dummy comprises;
a base plate (2.1); a vertical support plate(2.2);
a top plate (2.3) having sliding head (2.4) supported on it;
a lead screw mechanism (2.5) for actuating said sliding head;
chest displacement sensor is mounted on said top plate facing downwards; stem of
said chest displacement sensor is in contact with said sliding head supported on the
said top plate; said sliding head is moved gradually by turning said lead screw
mechanism which makes said stem of said chest displacement sensor to move; said
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chest displacement sensor is positioned on said top plate in such a way that moving end of said sensor maintains contact with said sliding head by gravity.
Now referring to figure-01 which shows the chest displacement sensor of a crash test dummy (1). Said chest displacement sensor (1) comprises; an electrical rotary potentiometer (1.1) installed in a housing (1.2). The said rotary potentiometer (1.1) is attached at one end of a stem (1.3). The other end of the said stem is connected to the sternum of a crash test dummy and its follows the displacement of the sternum. The other end of the said stem (1.3) comprises a spherical ball (1.4) to be used as follower. When the sternum displaces, the said stem rotates about the centre of the said rotary potentiometer (1.1). The rotation of the said rotary potentiometer results into change in its electrical resistance. Thus the change in the position of sternum is translated into change in electrical resistance which makes it simple for reading and recording through appropriate circuitry.
Referring to figure 02 which show the portable apparatus (2) for calibration of the chest displacement sensor of a crash test dummy in accordance with this invention. Said apparatus comprises; a base plate (2.1), a vertical support plate (2.2) and top plate (2.3). The said base plate and the top plate are connected perpendicular to the said vertical support plate (2.2). The said top plate (2.3) has appropriate provisions for mounting of the chest displacement sensor. Said top plate (2.3) has also been provided with a support block (2.7) to prevent rotation of the chest displacement sensor during calibration. The said top plate (2.3) has further been provided with a sliding head (2.4) connected to a lead screw arrangement (2.5). With the rotation of the said lead screw mechanism, the said sliding head (2.4) moves up and down. The said sliding head is also been provided with guide rods (2.8) to ensure appropriateness of its movement. One of the said guide rods also houses a reference displacement transducer (not shown) to sense the movement of the moving head. The said apparatus has also been
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provided with display unit (2.6) to show the displacements of the said chest displacement sensor and the said displacement transducer attached to the moving head. Both these measurements are used for verifying calibration of the said displacement sensor. The said display unit (2.6) also houses electrical circuitry for signal conditioning of the electrical feedback available from the said rotary potentiometer.
Referring to figure 03 which shows assembly of the said chest displacement sensor on the said portable calibration apparatus. Said chest displacement sensor is adapted to be mounted vertically facing downwards to ensure the contact between the said stem and sliding head with gravity. The figure-03 also shows intermediate positions of the stem of the chest displacement sensor & the moving head for illustrating the functionality of the said apparatus.
The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.
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WE CLAIM
1. A portable apparatus for calibration of chest displacement sensor of crash test
dummy comprising
a base plate;
a top plate configured to mount the rotary potentiometer and to support sliding
head through lead screw mechanism adapted for actuating said sliding head;
a vertical support plate connected perpendicular to the said top plate and base
plate;
at least one support block mounted on said top plate to restrict rotation of
rotary sensor;
at least two guide rods provided on sliding head to ensure proper movement of
the sliding head;
at least one reference displacement transducer to be mounted on one of the said
guide rods for sensing displacement of the sliding head;
a chest displacement sensor mounted on said top plate comprising
a stem configured to rest its free end having spherical ball adapted as follower
on said sliding head;
at least one display unit to show the displacements of said chest displacement
sensor and said reference displacement transducer.
2. The portable apparatus for calibration as claimed in claim 1, wherein said display unit houses an electrical circuitry for signal conditioning of electrical feedback from said rotary potentiometer.
3. The portable apparatus for calibration as claimed in claim 1, wherein said chest displacement sensor is mounted vertically facing downwards to ensure contact between the said stem and sliding head with gravity.
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4; The portable apparatus for calibration as claimed in claim 1, wherein upward and downward movement of the said sliding head is facilitated by rotation of said lead screw mechanism.


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5. A portable apparatus for calibration of chest displacement sensor of crash test dummy substantially as herein above described and as illustrated in accompanying drawings.