Title of Invention

A DEVICE USEFUL FOR SIGNAL TRANSFER FROM STATIC TO ROTATING SURFACE

Abstract A device useful for transferring signals from static surface to a rotating surface, said device characterised by a pair of pot cores (9X5; 9mm OD, 1.5mm ID) acting as a primary and secondary core, said pot cores being wound with 6 to 7 turns of SWG 36 copper wire such that each turn of copper wire rests on top of the previous turns thereby increasing in diameter by wire thickness, one of the said pot core is mounted on the rotating surface and the other pot core is fixed to a static surface with minimum air gap between each other so that the coils are always facing each other even if the primary and the secondary cores are rotated through 0 to 360° with respect to each other.
Full Text A DEVICE USEFUL FOR SIGNAL TRANSFER FROM STATIC SURFACE
TO ROTATING SURFACE AND VICEVERSA
FIELD OF THE INVENTION
The present innovation relates to a device useful for signal transfer from static surface
to rotating surface and vice-versa. The device can be used in a variety of applications
wherein signal transfer from static surface to rotating surface and vice-versa is
required for example, for exciting rotating piezoelectric crystals mounted on
mechanical rotating scan head, receiving the echoes picked up by rotating crystal and
transferring to static surface with very high efficiency provided the air gap between
the two surfaces is small. This device of the present invention can also be used for
signal isolation in electronic circuits for ground loop minimization etc.
BACKGROUND OF THE INVENTION
The early method of signal transfer from static surface to rotating surface was through
the use of carbon brushes, spring loaded contractors, gold slip rings or ball bearings.
These methods however, lost ground with time-because of factional wear, noise
generation etc.
The modem method to achieve the above objective is with a rotating transformer
normally used in videocassette recorders (VCR's). It consists of two wire wound discs
of ferrites. One wire wound disc is connected on the stator (primary) and second wire
wound disc is connected on rotor (secondary) with windings facing each other. The
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distance between stator and rotor is very small. Signal transfer from static surface to
rotating surface and vice-versa is via these primary/secondary transformer based on
magnetic flux linkage. It depends upon the current induced in the windings, ferrites
used in the set up, turns ratio, air gap between primary and secondary etc.
Some Japanese companies are believed to be making such VCR rotating transformers.
However, a major limitation is that these companies are only interested in supplying
these items in bulk quantities. In addition VCR cores are not available separately and
ferrftes cannot be trimmed by machining. The companies do not provide their
characteristics and other design details etc. The other sources of supply of these items
are generally not known.
OBJECTS OF THE PRESENT INVENTION
The main object of the present invention is to provide a device useful for signal
transfer from static surface to rotating surface and vice-versa.

Another object of the present invention is to provide a device useful for signal transfer from
static surface to rotating surface and vice-versa with even response throughout 360° rotation of
secondary w.r.t primary wound core.
Yet another object of present innovation is to provide a replacement for the VCR rotating
transformer.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
In the drawings accompanying this specification,
Fig. 1 (A-G) represents the device of the present invention. More specifically,
Fig. 1 (A) represents the Rotor and Stator parts of the device useful for transferring signals from
a static surface to a rotating surface or vice-versa.
Fig. 1 (B) represents the basic block diagram representing the transformer.
Fig. 1 (C) represents the directions of the current in the primary, secondary and the magnetic
flux generated as determined by applying Fleming's Right Hand Rule.
Fig. 1(D) represents the response of the device of the present invention to square
waves.
Fig. 1 (E) represents the assembled view of a scanner probe fitted with the device of the present
invention.
Fig. 1(F) represents the voltage induced in the secondary coils when the primary coil is rotated
by an angle between 0° to 360°.
Fig. 1 (G) represents the novel pot core used In the present invention as the transformer core.
Fig. 2 shows the frequency response obtained using the novel core.
Fig. 3 shows the characteristics due to change in air gap at various frequencies. SUMMARY OF
THE PRESENT INVENTION
Accordingly, the present invention provides a device useful for transferring signals from static
surface to a rotating surface, said device characterised by a pair of pot cores (9X5; 9mm OD,
1.5mm ID) acting as a primary and secondary core, said pot cores being wound with 6 to 7 turns
of SWG 36 copper wire such that each turn of copper wire rests on top of the previous turns
thereby increasing in diameter by wire thickness, one of the said pot core is mounted on the
rotating surface and the other pot core is fixed to a static surface with minimum air gap between
each other so that the coils are always facing each other even if the primary and the secondary
cores are rotated through 0 to 360° with respect to each other.

DETAILED DESCRIPTION OF THE PRESENT INVENTION
The present invention relates to a device useful for signal transfer from static surface to
rotating surface & vice-versa which comprises a small transformer with a special pot core
having 'N1' number of turns- at primary and 'N21 number of turns at secondary wound in a
special way on a readily available pot cores with wire wound faces facing each other with
minimum distance with either primary/secondary on a static/rotating surface or vice-versa
resulting in a very efficient device.
In an embodiment of the present invention, the device provides a wide -3dB
bandwidth (100kHz to 10MHz with 9X5 CEL pot core).
In another embodiment of the present invention, the device provides a wide dynamic
range (1-2 u,v toSOOv pulse of 300ns).
In yet another embodiment of the present invention, no noise is generated during the
operation of the device, as there is no physical contact between the surfaces. So it has
a very long life.
In still another embodiment of the present invention, a set of Pot cores are wound with
V number of turns wherein each turn rests on top of the previous turns thereby
increasing in diameter by wire thickness with each turn. The number of turns, V
depends upon the inside space of pot core. Increase in the number of turns 'V of
secondary compared to primary increases signal strength by ratio of turns and viceversa.
With equal number of turns on primary & secondary, the signal from primary
goes to secondary with 90% efficiency with small air gap and 180° phase shift w.r.t
primary.
In one more embodiment of the present invention, the air space between primary and
secondary, should be as small as possible for maximum efficiency. The minimum air
gap is defined whereby secondary wound core in the device should move freely in
front of primary wound core.
In one another embodiment of the present invention, the effect of rotation of such a
device w.r.t each other throughout 360° angle has no effect on the strength of signal
transferred.
The novelty of the present invention lies in choosing the core of the device. A set of
commonly available pot cores each wound with a particular number of turns of copper
wire constitute the device of the present invention. This set up yields a wide band -3dB
response in ultrasonic range (100KHz to 10MHz with PX5 pot core). The efficiency of
device is around 90% in combined transmit/receive mode. The device has a very wide
dynamic range (from 1-2 uv to 500v pulse) and the response is even throughout 360°
rotation of secondary w.r.t primary wound core.
Accordingly the present innovation provides a device useful for signal transfer from
static surface to rotating surface and vice-versa which comprises a small transformer
with a special core having 'NT number of turns at primary and 'N2' number of turns
of secondary wound in a special way on a readily available pot cores such that the
wire wound faces face each other with minimum distance with either
primary/secondary on a static/rotating surface or vice-versa resulting in a very
efficient device.
The above objective is achieved by using a small pot core (9X5; 9mm OD, 1.5mm ID
as shown in figure 1-G manufactured by M/S CEL, Ghaziabad) as its base material
and keeping 6 turns (N=6) of SWG 36 copper wire each on primary and secondary. If
a bigger pot core is used, the thickness of copper wire has to be increased to
accommodate 6/7 turns each on primary and secondary. The number of turns depends
upon the inside space of pot core and the copper wire is wound in such a way that
each turn rests on top of the previous turns thereby increasing in diameter by wire
thickness. Increase in the number of turns of secondary compared to primary
increases signal strength by ratio of turns and vice-versa.
PRINCIPLE OF OPERATION
When alternating current flows in the circular coil of primary winding, magnetic flux
is generated, the strength of the magnetic flux thus generated depends on magnitude
of current. The direction of the magnetic flux thus generated can be found by applying
Fleming's Right Hand Rule (fig 1-c). The flux strength is enhanced manifolds if the
winding is on a magnetic material such as ferrites. This flux induces an e.m.f. in the
opposite direction in a secondary coil which is 180° out of phase with the primary
(fig. 1-B). Thus, the primary and secondary parts of this device can be connected on
stator / rotor with a little air gap, thus allowing small electrical signals to transfer from
the stator to moving rotor and vice-versa. To keep the voltage gain to unity
approximately, both primary and secondary coils should have the same number of
turns of the coil.
The novelty of the present invention also lies in the fact that the rotation of the
primary and secondary coils with respect to each other through 0° to 360° does not
have any effect on the e.m.f. induced. The Applicants have arrived at this feature by
choosing a core which is circular in shape. As the pot core is circular in shape, the coil
wound on the core is also circular in shape. Thus, the coils are always facing each
other even the primary and the secondary are rotated through 0 to 360° with respect to
each other as shown in fig. 1-F.
Thus, it was observed that the effect of rotary motion of primary or secondary has no
effect on induced e.m.f.
The number of turns depends upon the inside space of pot core and the copper wire is
wound in such a way that each turn rests on top of the previous turns thereby
increasing the inner diameter of the core by a wire thickness each time. This
arrangement results in maximum flux linkage with the secondary winding infront of it
thus resulting in very high efficiency when air gap is small. A readily available pot
core 9X5 from CEL, Ghaziabad constitute the core of such a device. The two sides of
pot core wound with copper wire form primary and secondary of device with wire
wound faces facing each other.
The developed device can be used in a variety of applications such as signal transfer
from static surface to rotating surface and vice-versa e.g. for exciting rotating
piezoelectric crystals mounted on mechanical rotating scan head, receiving the echoes
picked up by rotating crystal and transferring to static surface with very high
efficiency provided the air gap between the two surfaces is small. This device can also
fee used for signal isolation in electronic circuits for ground loop minimization etc.
The present invention is further described with respect to the following examples
which are given by way of illustration and hence, should not be construed to limit the
scope of the present invention in any manner.
EXAMPLE -1
The primary of the device is connected to the transmitter and also to the receiving
amplifier. The secondary of the device is connected to a piezoelectric transducer as
shown in figure IB. There is a narrow air gap between the primary and the secondary
of the device. The device is connected in such a way that the coils are facing each
other. The primary is supported in the static probe frame. The secondary is fixed in
the piezoelectric, transducer housing in such a way that axis of transducer passes
through it so that transducer can move freely as shown in Fig IE. This is applicable
for both rotating type ultrasonic transducer and rocking type ultrasonic transducer
probes.
The transmitter generates narrow pulse (50-300nsec) of high voltage (500v). This
pulse excites the primary winding which converts this electrical impulse to magnetic
flux, which induces a proportional current in the secondary winding. This secondary
current impulse excites the piezoelectric transducer which sends mechanical vibration
in the body. The received echoes are picked up by the transducer inducing
proportional current in the secondary, generating flux proportional to echoes which
gets linked to primary winding from where receiving amplifier picks up the signal for
further processing. This way the device helps to transfer signal from static device
to rotating device and back to static device. The efficiency of device is around 90%
compared to direct wire connector circuit. Signal remains pure as brushes or ball
bearing are not used which is normally the method in such cases which generate noise
and also rubbing is avoided resulting in better output and longer life.
EXAMPLE-2
Ground isolation: This can be effectively used to isolate a signal. Sometimes while
working with high frequencies, ground loops are created which degrade the
performance of the circuit. By isolating the ground the problem can be solved at
higher frequencies also which otherwise has very limited options. The signal however
undergoes a 180° phase shift with slight decrease in amplitude.
CHARACTERISTICS
Fig. 2 shows the frequency; response due to this 9 X 5 CEL core. The gain is between
0.86 to 1 from 100 k to 10 MHz. The diagnostic ultrasound range is 1 MHz to 10
MHz. Thus we have been able to get near ideal response in the diagnostic useful
ultrasound range. This flat response can be effectively used to transfer signal from
static surface to rotating surface for a variety of applications in systems working in
ultrasound range of 100 kHz - 10MHz.
Fig. 3 shows the characteristics due to change in air gap, which shows that the least
gap should be preferred for better results. Response from 200 KHz to MHz is shown.
Response to square-wave is shown in fig. 1-D. Due to poor frequency response at
lower frequencies; the waveform looks differentiated.
ADVANTAGES OF THE PRESENT INVENTION
The main advantages of the present innovation are:
1. A better alternative of rotating transformers.
2. Wide - 3dB bandwidth from 100 KHz to 10 MHz making it ideal even for
wideband multifrequency transducers. Excellent response in ultrasonic
diagnostic range of 1-10 MHz.
3. Wide dynamic range, output of a few micro volts (1-2 uv) to 500 volts pulse
(of 300 nsec pulse width under testing).
4. No noise generating component, pure transmission depending- on magnetic
flux linkage.
5. No wear/tear of parts. No direct contact among surfaces. So very long life.
6. Light Weight, winding/construction is easy.
7. Even response throughout 360° rotation.




We claim:
1. A device useful for transferring signals from static surface to a rotating surface, said device characterised by a pair of pot cores (9X5; 9mm OD, 1.5mm ID) acting as a primary and secondary core, said pot cores being wound with 6 to 7 turns of SWG 36 copper wire such that each turn of copper wire rests on top of the previous turns thereby increasing in diameter by wire thickness, one of the said pot core is mounted on the rotating surface and the other pot core is fixed to a static surface with minimum air gap between each other so that the coils are always facing each other even if the primary and the secondary cores are rotated through 0 to 360° with respect to each other.
2. A device as claimed in claim 1, wherein the conducting wire IS SWG 36 copper wire.
3. A device as claimed in claim 1, wherein the number of turns on the primary and secondary pot cells are equal.
4. A device as claimed in claim 1, wherein the primary and secondary pot cells are wound with 5 to 8 turns of the copper wire.
5. A device as claimed in claim I, wherein the device provides a wide -3dB bandwidth in the range of 100kHz to 10MHz with 9X5 CFL pot core.
6. A device as claimed in claim I, wherein the device provides a dynamic range in the range of21..1.v to 500v pulse of300 ns.
7. A device useful for transferring signals from static surface to a rotating surface substantially as herein describe with reference to examples accompanying this specification.

Documents:

2931-DELNP-2004-Abstract-(03-09-2008).pdf

2931-delnp-2004-abstract.pdf

2931-DELNP-2004-Claims-(03-09-2008).pdf

2931-delnp-2004-claims.pdf

2931-DELNP-2004-Correspondence-Others-(03-09-2008).pdf

2931-delnp-2004-correspondence-others.pdf

2931-DELNP-2004-Description (Complete)-(03-09-2008).pdf

2931-delnp-2004-description (complete).pdf

2931-DELNP-2004-Drawings-(03-09-2008).pdf

2931-delnp-2004-drawings.pdf

2931-DELNP-2004-Form-1-(03-09-2008).pdf

2931-delnp-2004-form-1.pdf

2931-delnp-2004-form-18.pdf

2931-DELNP-2004-Form-2-(03-09-2008).pdf

2931-delnp-2004-form-2.pdf

2931-DELNP-2004-Form-3-(03-09-2008).pdf

2931-delnp-2004-form-3.pdf

2931-delnp-2004-form-5.pdf

2931-DELNP-2004-Petition-137-(03-09-2008).pdf


Patent Number 257621
Indian Patent Application Number 2931/DELNP/2004
PG Journal Number 43/2013
Publication Date 25-Oct-2013
Grant Date 21-Oct-2013
Date of Filing 29-Sep-2004
Name of Patentee COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH
Applicant Address RAFI MARG, NEW DELHI-110001
Inventors:
# Inventor's Name Inventor's Address
1 SURJIT SINGH AHLUWALIA CSIO CHANDIGARH, INDIA
2 SUNIL RATAN TANEJA CS10 CHANDIGARH
3 SANJEEV VERMA CS10 CHANDIGARH
PCT International Classification Number H01L27/20
PCT International Application Number PCT/IB03/00130
PCT International Filing date 2003-03-31
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10/403,547 2003-03-31 U.S.A.