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Патент USA US2403424

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July 2, 1946-
Filed NOV. 1, 1943
55' >
Pateuled July 2,
Theodore Zusclilag, West Englcwood, N. JL, as
signor to ‘Magnetic Analysis Corporation, Long
Island City, N. ‘iii, a corporation of New York
Apolication November 1, 134:3, Serial No. 508,525
4 Claims. (Gil l‘l'5-—-ill1)
This invention relates to the demagnetization
oi magnetic bodies and is directedespecially to
improvements in demagnctiaing apparatus. The
ages available from a wide range of line voltages,
without the use of additional booster, or step-up,
transformers and without changing any of the
coils in the demagnetizing system itself. Thus,
the demagnetizing apparatus, in accordance with
this invention is useful without structural change
at practically any location, and it also permits
the demagnetization of bodies more heavily mag
invention is an improvement, for example, on the
systems and apparatus disclosed in my United
States Letters Patent No. 2,267,392, granmd July"
0 "3413, and No. $355,940, granted August 15,
it“, this application being ?led as a continua
ticn-in-part of the application which matured
noticed or oi greater retentivity, as well as pro
viding improved e?ciency and more exact and
rapid demagnetization of bodies having low re
sidual. magnetism. The invention thus provides
to o the last-named patent.
Products manufactured of magnetic materials
such as iron and steel are susceptible to roag~
v appar t s at once more simple to operate, more
nctization, and such magnetization in many cases
' universally useful, and more economical in use,
interferes with their satisfactory use. While this
true of articles of any shape it is particularly no L than that heretofore known.
The apparatus of the present invention is il
true of elongated steel and iron products such as
lustrated in the drawing, in which is shown an
rods, bars and tubes“
alternating current supply 5 of, say, 120 volts
‘The unavoidable or inadvertent magnetization
oi”- connnercial frequency, such as 60 cycles, which
oi’ steel or similar products sometimes results as
is couriectilile through a line switch 2 to the de
the natural consequence oi normal manufacture
magnetizing system shown above. This system
includes an
C. (alternating-current) energiz~
the arrangement
which, mechanically
of moleculesaffect
in theorloody
lug coil
the terminals of which are connected
or product, or, again, as a consequence oi‘ the
to the source of A. 53. current which, for con
action of the product to one or more mag“
25 venience, may be considered as the line switch 2.
netic ‘fields at a stage in the process when ‘H
This cell should normally be of suf?cient react»
material, thereof is comparatively fluid and time
once to permit direct connection across the power
susceptible to the in?uence of magnetic ” “‘
line at the prescribed voltage. In the particular
embodiment of: the invention here described this
comprise approximately 860 turns wound
diameter large enough to allow the body ll,
which is to be demagcetized, to be placed within
to be passed through it, depending upon the
Such magnetic fields may, for example, cot.
the normal magnetic ?eld of the
o“ are
tiiiclal ?elds set up ‘lily electrical circuits or a, ‘
in the neighborhood, or a combination
’ products, to on lost them
a '
t sir pnysical or
teristics such, for e:
the existence of strains or flaws,
of; such testing
steel products are
of the body. Preferably connected in
*s with energizing coil
is a condenser ‘Ell
, ed to a capacity value such as to resonate
' ‘ icing coil 3 at the applied line frequem
e assumed case, 60 cycles, By thus tun
, ez'iergizing
to which
the frequency
includes of
likely to leave a certain degree
5 current, a considerable gain in our’
or like products it is usually do
traces of such residual magi
or removed
the material is slug:
is mill. Although such undesired resin
'isiri mayinreadily
my mentioned
lee r'rnoved
in the t'losc
e t,
hence in the strength of the energizing
is simply and economically achieved.
across condenser
is a “bleederw re“
of a resistance suitable to permit the
“ y-rge oi condenser ill.
The secondary,
neutralising, coil 5 is disposed in inductive re
lation to coil ll so as to be also in inductive re
lation. to the body to ‘be demagnetized. To this
have certain inherent limitations which iii? end, soil it should preferably be wound outside of
positioned to be concentric with coil
ourpose oi’ the present invention to over-l.
like. the particular embodiment referred to, sec
ondary coil 5 may be of about 2,000 turns, and
“o oresent invention. makes possible a cone
of much ilitier wire than that with which the
sideralcla enlargement of the range of “oath the
coil 3 is wound. Coils 3 and 5 together
alternating-cui“rent and the direct-current vol‘w
may preferably be constructed as a unitary coil
assembly of the air-core type, of which coil 5
comprises not only the secondary of an alternat
‘mg-current transformer (coil 3 being the pri
lishing the indicated polarities at the respective
terminals of. the resistor. Filter condenser l5
tends to smooth out the pulsations so as to keep
the potential difference of the mentioned termi
mary) , but in addition performs the function of
a D. C. (direct-current) neutralizing coil, as will
nals substantially constant.
Manipulation of the coarse adjustment i5 and
be explained below.
the fine adjustment ll of the potentiometer H
As shown in the drawing, a polarizing or re
permits the very accurate control of the negative
versing switch 6 is connected across the terminals
bias potential applied to grid H with respect to
of coil 5 so that the direct-current polarity of coil 10 the cathode 9 of tube 1, over a wide range. By
5 may be selected as required. The two pairs of
this means, in combination with the selection of
contacts of this reversing switch are connected,
polarity achieved by reversing switch 6, there
respectively, to the anode 8 and cathode 9 of a
may be established a uni-directional current in
triode recti?er tube 1. This tube may be of type
coil 5 of such magnitude and direction as to cre
2A3 or 6A3, for example. Serially connected in 15 ate a uni-directional electromagnetic ?eld exactly
the lead between switch 6 and cathode 8 is a
equal in intensity and opposite in sign to the re
switch I! the purpose of which will be described
sultant ?eld created in the neighborhood of body
I by all extraneous magnetic forces acting on that
A diode recti?er tube I2 is connected to the ter
body. The A. C. ?eld of coil 3 acting in conjunc
minals of the A. C. current source 2 to furnish 20 tion with this D. C. ?eld thus reduces the residual
an adjustable control potential to the control
magnetism in the body to an extremely low value,
grid of half-wave recti?er tube 1. To this end the
or substantially to zero.
cathode“ of diode I2 is connected to one ter
As above explained, coil 5 functions as a sec
minal ot the A. C. voltage source 2 and the anode
ondary of transformer 3, 5 supplying alternating2| of diode I2 is connected in series with a re
current potential to recti?er l, and through this
sistor H to the other terminal of source 2. The
same coil 5 ?ows no appreciable alternating cur
resistance value of resistor l4 may be about 2,000
rent, ‘but only recti?ed current produced by recti
ohms. A ?lter condenser l5, of say 25 micro
?er 1. The alternating-current potential induced
farads, may be shunted across the terminals of
in coil 5, being impressed across the anode and
resistor H, as shown. In the embodiment illus 30 cathode of recti?er 1, produces a flow of current
trated, resistor I4 is used as a potentiometer and
in the circuit including coil 5 when the alternating
has two adjustments, one of which is a switch
potential renders the anode positive with respect
l5 selectively connectible to a plurality of taps
to the cathode but not when it renders the anode
on the resistor for coarse voltage adjustment, and
negative with respect to the cathode. rl'hus the
an adjustable slider I’! on the resistor for ?ne
recti?er “passes” either one half or the other half
voltage adjustment. The resistor I‘ need not
of the cycles, depending upon the position of
comprise a single element as shown in the drawj
switch 6. The recti?ed Zill‘l‘lut ?owing; in coil 5
ing. but may conveniently comprise a rheostat
actually comprises a succession of uni-dint‘, it . type resistor provided with taps cooperating with
current peaks occurring at the frequency of the
a selector switch 16, and connected in series with 40 current in power line I. Although this recti?ed
a potentiometer type resistor having an adjust
current is therefore not actually a continuous
able slider l‘l. I'he ?laments or cathode heaters
direct current the effect of it is to produce a polar~
l0 and I3, respectively, of the tubes should, as is
iZecl or uni-directional ?eld about coil 5; and for
well known in the art, be connected to suitable
the purpose of the present invention such a ?eld
secondary windings of a ?lament-heating trans 45 is equivalent to one produced by a continuous
former, the primary of which should be connected
direct current.
to the current source 2.
From the foregoing it will be evident that since
The operation of this system is as follows: The
the energy source for the recti?er circuit is coil
closing of line switch 2 causes alternating current
3 which is also the source of ‘the alternating de
at the line frequency to flow through energizing 50 magnetizing ?eld, any change or variation in this
coil 3. The value of this current is economically
demagnetizing ?eld, or in the current of the cir
increased by reason of the resonance, or approach
cuit of coil 3, will automatically result in a cor
to resonance, produced by variable condenser 20
responding change or variation in the unidirec
in combination with the inductance of coil 3.
tional neutralizing ?eld, so that the relative
Thus, an A. C. energizing ?eld of considerable
strength of the two ?elds remains the same even
strength is produced by coil 3. It is important
though variations occur in the circuit of coil 3
that the strength of this ?eld be sufficient to ef
which causes variations in the demagnetizing
fect rapid demagnetization, but it is unimportant
if the ?eld is stronger than necessary. Coil 5,
being electromagnetically coupled to coil 3 and
preferably arranged to be symmetrically spaced
in relation thereto, acts as a secondary with re—
spect to coil 3 by reason of which an alternating
potential will be developed across secondary coil
5. Due to the unilateral conducting property of
recti?er ‘I this alternating potential causes a uni
directional pulsating current to ?ow through the
recti?er circuit traced from coil 5 to switch 6,
anode 8 of tube 1, cathode 9 thereof, switch l8,
switch 6, and back again tocoil 5. This coil 5, 70
being disposable in electromagnetic relation to the
body I, also functions as a neutralizing coil. The
connection of resistor M in series with recti?er
l2 across the power line creates uni-directional
current flow through resistor I4, thereby estab
?eld. For example, it frequently happens that,
as the body under treatment moves simultane
ously through the ?elds of coils 3 and 5, struc
tural or metallurgical variations in the body re
act magnetically on coil 3 to produce changes
in the magnitude of current in the coil and hence
in the strength of its ?eld, and if the recti?er
circuit were coupled independently to an energy
source the neutralizing ?eld would remain con
stant while the demagnetizing ?eld varied. This
is a serious disadvantage in clemagnetizing equip
ment for the present purpose, and is here ob
viated by deriving the energy for the recti?er cir
cuit solely from the coil which generates the de
rnagnetizing held (the electron energy from cath
ode Hl being disregarded). Similarly, when the
voltage of the power line I fluctuates, relative
strength of the alternating-current and direct
body movable with respect to said apparatus, the
current?elds with respect to the‘body ‘will re.
combination which includes a demagnetizing coil
main‘substantially constant, ?rst, for the rea--
connectible to a source of alternating current,
. said coil being disposable in inductive relation ‘to
son above described, and ,- second, because the'
control‘ potential applied to grid H of ‘recti?er
tube ‘I is derived directly from recti?er I: which
, in'turii is energized by the ‘same alternating 01.11‘:
l’rent source. The relative strength of the .A, C.
'and D. C. ?elds ‘can, of course, always be adjusted by means of tap switch IS, in conjunction
with ?ner adjustment I1.
The demagnetizingprocess
5 said body, a neutralizing coilinductively related‘
. to said demagnetizing coil and disposable in in-- _
ductive relation to said body, a recti?er tube
having any anode, acontrol‘ grid and a cathode,
/ said coils being positioned to be in inductive rela
10 tion simultaneously to the same portion of said
best be carried ,. - body as said body moves with respect to said
‘out in three stages. _ The ?rst stage requires
' coils. a recti?er circuit for producing unidirec
tional neutralizi'ngcurrent in said neutralizing
merely the placingof a magnetization meter near
-coil,isaid circuit includingsaid neutralizing coil
the body and observing the de?ection of. the “
‘meter to determine whether‘and to what degree _1_5_ and a half-wave recti?er including the anode
and cathode of said tube, said circuit being cou
the body under observation is magnetized. \Meters
pled to; said source only by means of said induc
, suitable for this purpose and'methods for using
tive relation tolsaid demagnetizing coil, where-'
, them are described in more detail in my men-:
tioned patent. If the body is not magnetized, . by changes in the magnitude of alternating cur
rent in said. demagnetizin'g coil resulting from
nothing-further needbeuone to that particular 0 variations
in, the magnetic effect of said bodyv
body .or no on thereof." However, it the mag-l '
netization meter vindicates a de?ection, the body;
is moved slowly through or past the coils 3 and 5,‘
on‘ said demagnetizing coil as said body passes
throughthe ‘?eld thereof automatically produce
corresponding changes in said unidirectional cur-q
at say a speed-of 100 feet per'minute, with only’
‘the energizing coil '3v energized. This may be 5, rent insaid neutralizing'coil, a second recti?er,
accomplished by setting-the switch [8' in its open ; a resistor connected in series with said second
recti?er-f across said source, connections from the
circuit position. The direction of de?ection of
cathode and control grid of said half-wave rec
the magnetization meter at ‘this ‘stage will fur
nish a guide as to the direction ‘in which the re- -' ti?er tubevto said resistor, whereby a bias poten
The 30' tial derived from the second recti?er is impressed,
‘ third stage of operationoomprises passing the\ » on said control grid, and‘, means for adjusting
body again through the apparatus with power - ‘said bias potential.
- versing switch 6 should-then be thrown.
supplied to both the energizing coil 3 and the
' neutralizing coil 5 ‘by closing switch I8 and ad- '
2. In apparatus for demagnetizing a magnetic
body, the combination which includes a demag
justing tap switch l6 and ?ner adjustment I1’ 35 netizing col-l connectible to a source of alternat
ing current,.said coil being disposable in'induc
until the magnetization meter reads zero. Under '
tive relation to said body, a'neutralizing coil in
some circumstances, as for example when the
body 4 is of fairly small size, the grld‘bias avail- 1 ductively related to said‘ demagnetizing coil and
disposable in inductiverelation to said body, said
‘ able through controls l6 and I] may be ‘suf
?cient to block entirely the output current from ‘49 cells being positioned to be in inductive relation
simultaneously to the same portion of said body,
tube 1. In such event the switch It may remain
‘ closed during the entire operation, if desired. _ a recti?er tube'having, an anode, a control grid
Should a neutralizing ?eld of greater strength - and a cathode, a recti?er circuit for producing
unidirectional neutralizing current in said neu-.
i than that provided by a~single triode' recti?er
; tube of the types above mentioned be required, 45 'tralizing coil, said circuit including said rieu~
1 two or more such tubes may be connected in par
allel, or a grid-controlled recti?er tube‘of greater
output may bevsubstituted. The power required
to furnish the bias potential for the control of
the output of tube ‘I being negligible, diode.“ 50
may be of any convenient type, that commonly
designated as type 5Y3 having been found satis
factory. Furthermore, a copper-oxide or‘ other f‘
type‘ of recti?er can be substituted with equal
From the foregoing‘ description of a‘ preferred
I embodiment of the invention and of the opera
tion thereof it will be evident that a precise con
trol of the strength of the neutralizing ?eld can
tralizing coil and a half-wave recti?er includ
ing the anode and cathode of said tube, said '
circuit being coupled to said source only by
means of said inductive relation to said demag»
netizing coil; whereby changes‘ in the-magnitude
of alternating current in said demagnetizing coil
resulting from variations invthe magnetic effect
of said body on said demagnetizing. coil when
said body is in the ?eld thereof automatically
producecorresponding changes in said unidirec»
tional current in said neutralizing coil, a diode
recti?er, a resistor connected in series with. said
diode ‘recti?er across said source, connections
' from the cathode and'control gridpf said hatt
wave recti?er tube to said resistor whereby a
be readily obtained over a large ‘range of ?eld
‘strength, and that the apparatus of the invention
_may without any structural change whatever, be
satisfactorily employed on power supply lines
which diifer'considerably as to voltage or fre
bias potential derived from said diode recti?er
is impressed on said control grid, and variable,
contact means on said resistor included in at
least one of said connections for adjusting said
potential, whereby the strength of said do
quency or both. Furthermore, the apparatus is, 65 bias
magnetizing ?eld may be accurately adiusted' over
without change, adapted to the successful de
a wide range.
magnetization of bodies of a wide variety of types
i 3. In apparatus for demagnetizing a magnetic
and shapes and of any dimensions, so long as the
body, the combination which includes a demag
bodies, or required portions thereof, can be sym
metrically disposed within the magnetic ?elds of _70 netizing coil connectible to a source of alternat
ing current, said coilbeing disposable in induc
coils 3 and 5. Rings, plates, billets and any other
_' shapes and types of magnetizable bodies may
be is
claimed is: ,
tive relation to said body, va condenser connected . _.
in series with said coil, said condenser having a
capacity such as at least approximately to res- -
1. In apparatus for demagnetizing'a'magnetic 75 onate said coil with the frequency of said source,
a bleeder resistor connected in shunt ‘to said
condenser, a neutralizing coil inductively related
to said demasnetizing coil and disposable in in
ductive relation to said body, said coils being posi
tioned to be in inductive relation simultaneously
to the same portion of said body, a recti?er tube
having an anode, a control grid and a cathode,
and a recti?er circuit for producing unidirec
quency or said source, a bleeder resistor con
nected in shunt to said condenser, a neutraliz
ing coil inductively related to said demagnetiz
ing coil and, being 0! the air-core type disposable
in inductive relation to said body, said coils be
ing positioned to be in inductive relation to the
same portion or said body, a recti?er tube hav
ing an anode, a control grid and a cathode, a
tional neutralizing current in said neutralizing
recti?er circuit (or producing unidirectional neu
coil, said circuit including said neutralizing coil 10' tralizing
current in said neutralizing coil, said
and a half-wave recti?er including the anode and
circuit comprising in series connection said neu
cathode of said tube, said circuit being coupled
tralizing coil, va. polarity-reversing switch, and a
to said source only by means of said inductive.
hall-wave recti?er including the anode and cath~
relation to said demagnetizing coil, whereby
ode‘oi said tube, said circuit being coupled to
changes in the magnitude 0! alternating current 15 said
source-only by, means of said inductive rela
in said demagnetizing coil resulting from varia
tion to said demagnetizing coil whereby changes
tions in the magnetic e?ect of said body on said
in magnitude of the alternating current in said
demagnetizing coil when said body isin the ?eld
demagnetizing coil automatically produce corre
thereof automatically produce corresponding
sponding changes in the magnitude of said uni
changes in said unidirectional current in said 20 directional current in said neutralizing coil, a
neutralizing coil, a second recti?er, a resistor,
diode recti?er, a second resistor connected in
connected in series with said second recti?er
serieswith said diode recti?er across said source,
across said source, connections from the oath
coarse resistance-adjusting means and ?ne re
ode and control grid of said hall-wave recti?er
sistance-adjusting means in contact with said
tube to said resistor, whereby a bias potential
second resistor, a ?lter condenser connected in
derived from the second recti?er is impressed
with said second resistor, and connec
on said control grid, and means for accurately
tions from said adjusting means to the control
adjusting said bias potential.
grid and cathode, respectively, of said hall-wave
4. In apparatus for demagnetizing a magnetic
recti?er tube for impressing on said control grid
been‘, the combination which includes a demag
a closely adjustable biasing potential derived from
netlzing coil connectible to a source 01' alternatsaid diode recti?er, whereby the polarity of said
ing current, said coil being of the air-core type
.demagnetizing ?eld may be selected and the
disposable in inductive relation to said body, a
strength or said demasnetizing ?eld may be ac
condenser connected in series with said coil, said
curately adjusted over a wide range.
condenser having a capacity such as at least ap
proximately to resonate said coil with the ire
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