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Патент USA US2110759

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March 8,1938.
‘
‘A, v, DE FoREs-r'_
_
_2,110;759
TESTING APPARATUS '
Filed July 19, less
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INVENTOR
Wild?re/l’
2,110,159
Patented Mar. 8,- _1 938
"um'rso STATES PATENT OFFICE
Alfred V. dc Forest, Southport, Conn., assignorv ~
toMagnaiiux Corporation.
corporation ‘of Pennsylvania Pittsburgh, Pa... a‘
‘Application July 19, 1935. Serial No. 32,165"
9 Claims.
(m. 175-183) '
The present invention relates to testing appa
ratus, and moreespecially to apparatus for the
which consists of two toothed wheels i0 insulated
from the pole pieces having cam surfaces Ii and
magnetic testing~of objects of paramagnetic
‘
material.
operated by means of a handle l2. ‘ When the '
‘
object is to betested .by means of the electro
In my prior patent, No.;1,960,898,v I have ex
plained the testing of objects of paramagnetic , magnet 5, the electric contacts 1 and 8 are
lowered to allow the objects to come in direct
material, such, for example, as iron and steel ‘contact
with the pole ,pieces 3 and 4. When the
articles, to detect cracks‘, ?aws, etc. in the metal. object is to be tested by passing the electric cur
Brie?y stated, the method comprises magnetizing
10 the article and applying to the surface of the
article finely divided magnetic materiaL' There
is a tendency for the ?nely divided particles to
v
rent through it,‘the electric contact pieces ‘i and
8 are raised to lift the test piece off of the pole
pieces 3 and I.
'
.'
'
The test piece may be tested by means of ap
cluster on the surface at places wherev there is '
plied magnetism, from the ' electromagnet 5.
a crack or flaw. In this way cracks or flaws may
be detected, although'not visible to the eye.
The present invention relates to improved ap
paratus for carrying out testing of this character.
In this apparatus the test‘ piece maybe sub
jected to magnetization by means of an electro
20 magnet, and also magnetization by means of an
When this is done the lines of electromagnetic
flux tend to run longitudinally of the test bar 2,
creating a testing condition most favorable for
‘detecting laterally extending cracks which are at
right angles to the major axis of the test piece 2.
The test piece can also be subjected to mag
netization so that the magnetic lines of flux lie IO
As hereinafter explained, the piece can thus be circumferentially of the test piece 2 and at right
angles to the length of the test piece. This may
' subjected‘to magnetic lines of force in different
directions so as to better detect both longitudinal be done by passing the electric current through
the test piece. v'I'his causes a magnetic condi
Ni and transverse cracks. The apparatus is also
most favorable for the detection of cracks 25
provided ‘with means for demagnetizing the _tion
which run longitudinally of the test piece and
article.
-
electric current passed through the test piece.
In the drawing-
30
7
-
parallel of its major axis. Also, the current test-. .
ing does not produce polar ‘effects at the end of '
Figure 1 is a diagrammatic view showing one
form of apparatus embodying the invention:
the test piece and inspectionmay be carried close
Figure 2 is adetail view showing the preferred
The current for the electromagnet 5 is supplied
form of switch for breaking the alternating cur
to the ends.
,
307
_from;-a,suitable source‘, such as a generator 28,‘ .
rent when used for magnetizing;
Figure ,3 is a detail view of the current contact which may be either a direct current generator
or alternating current generator, When an ob
" elevating mechanism;‘ and
Figure 4 is a diagrammatic view of a‘ modified
‘ form of apparatus.
Referring to the embodiment illustrated in
Figure l, the test piece‘ 2 is supported‘ on pole
pieces 3 and 4 of the electromagnet 6; For sim
plicity the test piece is shown as a shaft, although
other objects may be tested. preferably objects
of greater length than width with the‘type of
apparatus illustrated in Figure 1. ‘The pole
pieces 3 and l are adjustable along the core bar 6
of the electromagnet 5 in order to accommodate
objects of di?erent length. The core and pole
pieces of the electromagnet are preferably made
‘of laminated soft steel sheets to cut down eddy
50 currents when alternating current is employed.
Carried by the; pole pieces 3 and l are electric
contact pieces 1 and 8 insulated from the pole
pieces by means'pf insulation 9. These electric
contact pieces may be raised or lowered by means
55 of the elevating mechanism ‘shown in Figure 3
ject of soft iron or steel‘is to be tested, the cur
rent is allowed to remain on during testing.
When a hard steel object is to be tested, the cur-_
rent can be applied‘ and the object permanently
magnetized. When alternating current is used
for, magnetizing a hardened steel article, the
switch 2i should be such as‘ to break the current
at the end of a half current cycle. When this is
done the vobject is left permanently magnetized.
The magnetism imparted by the previous half‘
cycle is left in the article. For this purpose the
preferred form of switch is a mercury switch, as
shown .in Figure 2, which consists of a' tube 22
having two contacts 28 and 24 extending through
it and into a pool of mercury 25. When the tube
is tilted to the right aboout its axis 26 the mercury
flows to the other end of the tube and the circuit
is broken. It is one of the characteristics of such
a mercury switch that the current-is broken at
the end of a half cycle when the current reaches"
zero value. While I prefer to use the mercury 55
2,110,759
2
III and ii are provided for the pole pieces 48 and
41 respectively, and are insulated therefrom by
insulation 52.
The piece to be tested is clamped between the
pole pieces 46 and 41 which carry the contacts 50
and BI when testing is to be carried out by passing
the electric current through the test piece. When
the testing is to be carried out by the applied
magnetism from the electromagnet 42, the con
break switch in order to insure the breaking of
the current at substantially the end of a half cur
rent cycle, other forms of switches may be used.
For example, a switch having contacts made of
some relatively fusible metal, such as brass or
copper, and which has a not too fast separation
of the contacts, will break the current at substan
tially the end of a half current cycle. The readily
fusible metal forms a metallic arc and if the con
10 tacts are separated relatively slowly, such are per
’ tact pieces 50 and iii are removed so as to bring
sists until the end of the half current cycle.
the iron pole pieces into direct contact with the
In case it is desired to demagnetize the article
after the testing, as, for example, a hardened steel
article.
The object to be tested may be clamped in
article, the article can be demagnetized by means
15 of the electromagnet 5 by passing an alternating
electric current through it and gradually reducing
the value of the current to substantially zero by
means of a variable resistance 21.
The electric contacts ‘I and I may be supplied
with either direct or alternating current. For
this purpose the leads II and II to the contact
pieces ‘I and i are connected with a double pole
double throw switch 32.
when the switch 32
‘is thrown to the left as shown in Figure 1, the
different positions between the pole pieces 46 and
41, to thereby produce magnetic ?uxes in different 15
directions in the object to be tested. In this way
effective testing for cracks running in different
directions may be had. The differences in direc
tion of the magnetic ?uxes may also be secured
byv testing with the electromagnet which produces 20
flux in a vertical direction, and by passing the
electric current through the object which pro
duces a circumferential flux in the horizontal
direction.
'
The current connections for the electromagnet
current from the battery I! is passed through the
test piece 2. The passage of the current through l2 and the contacts 5! and SI are similar to those
the test piece induces magnetism therein, the shown in Figure l and corresponding reference
magnetic lines of force running circumferentially characters are used therefor.
While I have illustrated and described the pre
around the test piece.
30
when the switch 32 is thrown to the right, the , ferred embodiment of my invention, it is to be
understood
that
the
invention
may
be
otherwise
test piece is connected to alternating current. For
embodied and practiced within the scope of the
this purpose there is provided a step-down trans
following claims.
former ll whose primary is connected with an al
I claim:
ternating current generator 35. A switch It is
1. Apparatus for the magnetic testing of ob
provided preferably of the same character as
the switch 2!, whereby alternatingcurrent may jects of paramagnetic material. comprising an
be used, if desired, for permanently magnetizing electromagnet having adjustable pole pieces for
engaging the object, and contact pieces carried
a hardened steel article.
‘
The article may be demagnetized by passing the . by the pole pieces for also engaging the object
to pass an electric current directly through the 40
40 alternating current through it and gradually re
.
'
ducing the current to substantially zero by means object.
of a variable resistance 81.
.
I
1
As will appear from the above description, the
test piece may be subjected in one testing appara45 tus to both longitudinally and transversely directed lines of magnetic ?ux. Not only the di
rection, but also the distribution of the magnetic
flux can be controlled by the apparatus.‘ A mag
netic flux which is distributed substantially uni
formly through the body of the test piece can be
secured by magnetizing it by means of the elec
tromagnet 5, particularly when direct current is
used for this purpose.
On the other hand, a
concentration of the magnetic flux at the surface
of the article can be secured by magnetizing it
by passing an alternating current through the
‘article. In this case the magnetic flux is concen
trated at the surface due to the “skin effect” pro
duced by the current alternations. This distribu
tion of ?ux is particularly desirable for detecting
surface ?aws.
After the test piece has been tested by apply
ing the finely divided magnetic material as de
' scribed in my Patent 1,960,898, it can be de
magnetized in the same apparatus as above ex
Dlained.
-
In Figure 4 is illustrated a modification intend
ed for the testing of shorter more chunky pieces
of‘ material. This form of apparatus comprises
70 a base “having an upright ll carrying an elec
tromagneticcdlll. Anarm?isadiustableon
the upright ll by means‘of a gear ll meshing with
rackteethllintheum‘llhti Thebasellhasa
magnetic pole piece 48 and the arm 43 carries a
complementary pole piece ‘1. Conducting ‘plates
Apparatus for the magnetic testing of ob- »
fleets of paramagnetic material, comprising an
electromagnet having adjustable pole pieces for
engaging the object to be tested, electrical con 45
tacts carried by the pole pieces, and means. for
moving the contacts against the object to be
tested and raising it away from the pole pieces,
and means for supplying electric current to the
contact pieces.
3. Apparatus for the magnetic testing of ob
iects of paramagnetic material, comprising an
electromagnet having adjustable pole pieces for
engaging the object to be tested, contact plates
50
arranged to be interposed between the pole pieces .
and the piece to be tested, and means for sup
plying current to the contact plates.
4. Apparatus for the magnetic testing of ob
jects of paramagnetic material, comprising an
electromagnet having pole pieces for engaging 00
the object, means for supplying electricvcurrent
to the electromagnet, electric contacts on said
pole. pieces for engaging the object, and means
for supplying electric current to said contacts.
5. Apparatus for the magnetic testing of ob-' 63
jects of paramagnetic material, comprising means
including contact pieces for producing magnetic
?ux in one direction in the object and means on
said contact pieces for producing a magnetic ?ux
in the object at an angle to the first flux.
6. Apparatus for the magnetic testing of ob
Jects of paramagnetic material, comprising an
electromagnet having pole pieces engaging the
object, electric contact pieces mounted-on said
pole pieces adapted to be brought into contact
,
\
~ 9,110,769
3 l
with the object to be tested for passing electric ' v for passing either a direct or an=alternating cur
current directly through said object to magnetize rent. through the electromagnet, electrical con—
said object, and means for passing an alternating 'tacts movably mounted on the poles of said elec
current of ‘decreasing intensity through said cb-Y
5 ject to demagnetize the same.
‘
'1. Apparatus for the magnetic testing of ob
jects of paramagnetic material, comprising an
tromagnet for engaging the object, and means '
for passing either a direct or an alternating cur
rent to thevobject through such contacts, and
means including a, variable resistance for gradu
electromagnet for magnetizing the object, means i ally cutting down an alternating current to de
magnetize the object.
for supplying a magnetizing current to the elec
10 tromagnet, electric contacts mounted on the pole
9. Apparatus for the magnetic testing of ob
of said electromagnet for engaging the object, jects of paramagnetic material, comprising an
\means for supplying an alternating current to ‘electromagnet for producing a ?ux through the
‘
said contacts, and means for gradually reducing object in one direction, and means on the poles
'the alternating current to .demagnetize the ob
of said electromagnet for passing current di
15 ject.
'
'
rectly through the‘ object to produce a magnetic 1
,8. Apparatus for the vmagnetic testing of ob flux in another direction in the object.
jects of paramagnetic material, comprising an
eiectromagnet for magnetizing the object, means
i V. BE FOREST.
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