Note: Descriptions are shown in the official language in which they were submitted.
The present invention relates to a method and
a device for treating ferromagnetic materials, which method
and device can be used in engineering industries.
A known method for the treatment o~ ferroma-
S gnetic materials consists in produclng unipolar magneticfield pulses of specified repeti-tion frequency, amplitude
ar~d width. The ferromagnetic material is introduced in the
magnetic field, and it is then subjected to complete dema-
gnetization.
A known device for carrying out into practice
this prior art method comprises a current source, a genera-
tor of unipolar electric pulses adjustable in terms of ampli-
tude and frequency, a magnetic field generator which includes
a coil for producing the magnetic field in which the ferro-
magnetic material is introduced, all connected in series,
and a control unit connected to the current source.
A disadvantage of the above described prior
art method and device is the low wear resistance of the
treated ferromagnetic materials.
An object of the present invention is therefore
to provide a method and a device which treat Eerromagnetic
materials so as to improve their wear xesistance.
According to the invention, there is provided
a method for treating ferromagnetic materials with magnetic
field pulses having preset repetition frequency, amplitude
and width, said materials being demagnetized at the end of
the treatment, wherein the magnetic field pulses include
positive pulses and negative pulses, the amplitude ratio of
the positive to the negative pulses is 1,8; 0,2,and the
magnetic field pulses of one polarity repeat with an equal
or lower frequency compared with the repetition frequency
of the pulses of the other polarity.
Preferably, at the end of the treatment, the
amplitude of the magnetic field pulses is gradually reduced
3;3~
to zero.
~ lso in accordance with -the invention, there
is provided a device for treating ferromagnetic materials
. with magnetic Eield pulses having preset repetition fre-
quency, amplitude and width, said ma-terials being demagne-
tized at the end of the -treatment, said treating device
comprising:
a magnetic field pulse generator comprising
a first and a second generating units each including a
cpacitor and a coil interconnected i.n series, and a thyris-
tor connected in parallel with the serially interconnected
capacitor and coil, each thyris-tor being provided with an
anode, a control electrode and a cathode connected to a
reEerence voltage, said magnetic field pulses being generated
through said coils and the coil of said first unit being
connected to generate positive magnetic field pulses while
the coil of said second unit is connected to generate nega-
tive magnetic field pulses;
a controllable rectifier for applying a first
vol-tage to the anode of the thyristor of said first generating
unit, and for applying a second voltage to the anode of the
thyristor of said second generating uni-t, the amplitude of
said first and second voltages being adjusted so that the
amplitude ratio of the positive to the negative magnetic
field pulses is 1,8; 0,2;
control pulse generating means including a
first output for delivering control pulses to the control
electrode of the thyristor of said first generating unit, and
a second output for delivering control pulses to the control
electrode of the thyristor of said second generating unit,
said control pulses controlling operation of said thyristors
to cause production thro.ugh said coils of magnetic field
pulses of one polarity which repeat with an equal or lower
frequency compared with the repetition frequency of the
magnetic field pulses of the other polari-ty; and
control means for controlling operation of
said rectifier and said con-trol pulse generating means.
- As already mentioned hereinabove, the method
and device of the present invention have the advantage of
lmproving the wear resistance of the treated ferromagnetic
materials.
The objects, advantages and other features of
the present invention will become more apparent upon reading
of the following non restrictive description thereof, made
with reference to the accompanying drawing which represents,
under the form of block diagram, a preferred embodimen-t
of the device according to the present invention.
Referring now to the attached drawing , the
device according to the present invention comprises a magne-
tic field pulse generator 5. This generator comprises two
similar, separate generating units. The first generating
unit comprises a capacitor 6 connected in series with a
coil 7, as well as a thyristor 8 connected in parallel with
the serially interconnected capacitor 6 and coil 7O As can
be seen, the cathode 82 of the thyristor 8 is grounded.
Accordingly, the second generating unit of the magnetic field
pulse generator 5 includes a capacitor 6' connected in series
with a coil 7'~ and a thyristor 8' connected in parallel
with the serially interconnected capacitor 6' and coil 7'.
The cathode 85 of the thyristor 8' is also grounded.
The magnetic field pulses produced through the
coils 7 and 7' are applied to a ferromagnetic material 9
positioned in the proximity of these two coils. As can be
seen on the attached drawing, the two coils of the generator
5 are so connected that the coil 7 produces positive magnetic
field pulses while the coil 7' generates negative magnetic
field pulses. Each coil 7, 7' may be provided with a magnetic
core, not shown in the attached drawing.
-- 3
The device in accordance with the present
invention further comprises a controllable, adjustable
recti.Eier 2 which is supplied through its input 21 by a
supply alternating voltage 0~ The rectifier 2 applies through
its output terminal 22 a first direct curren-t voltage to the
anode 81 of the -thyristor 8, and also applies through its
output 23 a second di.rect current voltage to the anode 84
of the thyristor 8'.
A control pulse generator 3 supplies through
its output 31 control pulses on the control electrode 83
of the thyris-tor 8. The generator 3 also supplies through
its output 32 control pulses to the controi electrode 86 of
the thyristor 8'. The control pulses from the generator 3
therefo:re control production of the positive and negative
magnetic field pulses through the coils 7 and 7' by controlling
operation of the thyristors 8 and 8', as will be seen in
more details herei..nafter.
A trigger coil 10 surrounding the material 9
is responsive to the magnetic field pulses applied to this
ferromagnetic material to produce a signal on an input 41 of
a control unit 4. This unit 4 supplies in accordance with
the signal on its input 41 control pulses to the rectifier 2
and the generator 3 through its outputs 43 and 42, respec-
tively, so as to control operation of these rectifier 2 and
generator 3.
A current source 1 receiving on its input 11
the alternating voltage 0 supplies through its outputs
12, 13 and 14 a direct current to the rectifier 2, the gene
rator 3 and the control unit 4, so as to supply these rectifier
2, generator 3 and unit 4 with electric energy required for
operation thereof.
In operatlon, the direct current voltage on
the rectifier output 22 charges the capacitor 6 when the
thyristor 8 is in the off state. Accordingly, the direct
33~33
current voltage on the rectifier output 23 charges the capa-
citor 6' when the thyristor 8 7 iS in -the off state. As soon
as a con-trol pulse is applied on the control electrode 83
- th:rough the output 31 of the generator 3, the thyristor 8
becomes .in the on state and a current i flows in the loop
Eormed by the thyristor 8, the coil 7 and the capacitor 6
to produce a positive magnetic field pulse through the coil
7. In the same manner, as soon as a control pulse is trans-
mitted to the control electrode 86 through the output 32 of
the generator 3, the thyristor 8' becomes in -the on state
and the capacitor 6' discharges into the coil 7' through the
thyristor 8' in order to produce a current i' into this coil
7' so as to generate a negative magnetic field pulse. As
soon as the voltage between the anode and the cathode of
each thyristor 8, 8' becomes negative, this thyristor is
switched back into the off state.
It can therefore be easily appreciated that
by controlling supplying of the control pulses through the
outputs 31 and 32 of the generator 3, positive and negative
magnetic field pulses can be consecutively produced through
the coils 7 and 7'.
In order to improve the wear resistance of the
treated ferromagnetic materials, the amplitude of the voltages
on the outputs 22 and 23 of the rectifier 2 are adjusted
2S through conkrol of the unit 4 so that the ratio amplitude of
the positive pulses produced through the coil 7 to the nega-
tive pulses produced through the coil 7' is 1,8; 0,2. Indeed
the amplitude of the positive and negative magnetic field pulses
can be varied through the amplitude of the voltages from the
outputs 22 and 23 of the adjustable rectifier 2. Of course,
the width of the positive and the negative magnetic field
pulses can be adjusted through adjustment of the capacitive
and inductive values of the capacitors 6 and 6' and of the
coils 7 and 7'.
3~3
Also in order to improve the wear resistance
of the treated ferromagnetic materials, the control pulse
generator 3 is controlled -through the unit 4 -to produce on
its outputs 31 and 32 control pulses which causes magnetic
field pulses oE one polarity to repeat with an equal or
lower frequency compared to the repetition frequency of the
magnetic field pulses of the other polarity.
At the end of the treatment, the control unit
delivers through its output 43 to the rectifier 2 pulses
which control the rectifier 2 so that the voltages on its
outputs 22 and 23 gradually reduced to zero so as to gradually
reduce to zero the amplitude of the positive and negative
magnetic field pulses generated by the coils 7 and 7'. For
-that purpose, the control unit 4 may comprise a program
stored therein and which causes production of the latter
pulses on its output ~3 at the end of a certain preset
period of -time. Of course, the prograrn of -the control unit 4
can be modified at will depending on the type of ferromagne-
tic materials to be treated.
Another important advantage of the device in
accordance with the present invention is that after the
treatment the ferromagnetic materials are completely dema-
gnetized.
Although the present invention has been described
hereinabove by way of a preferred embodiment thereof, it
should be pointed out that any modification to this embodi-
ment within the scope of the appended claims is not deemed
to alter or change the nature and scope of the present inven-
tion.
