Improvements in Apparatus for Magnetic Testing.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in Apparatus for Magnetic Testing.
I, JAMES ALFRED EWING of Langdale Lodge, Cambridge, Professor of
Mechanism in the University of Cambridge, do hereby declare the nature of this
invention to be as follows:-
-
My invention relates to apparatus for testing the magnetic quality of iron or
steel by observing the mechanical force required to overcome the magnetic
attraction between the test-piece and another portion of a magnetic circuit of
which the test-piece forms part. The test-piece is in the form of a turned rod, and
is so placed as to constitute the armature of a magnet, generally an electro-
magnet. The magnet is U-shaped and the test-piece lies across the two poles of
the U. By means of a weighted lever or otherwise force is applied at or near
one end of the test-piece, to pull it off one pole of the U, while the other end of
the piece continues to rest on the other pole of the U, with which it may be said
to make a magnetic hinge. I preferably let it rest in a V-shaped notch cut in
that pole of the magnet, and give the other pole, from which the piece is to be
pulled away, a somewhat rounded convex surface. The side of the test-piece
may come into actual contact with the surface of the pole, or it may be held at
a small distance from it by means of a distance-piece or stop. In all cases it is
the cylindrically turned side and not the end face of the test-piece on which the
magnetic attraction which is measured is exerted. I do not infer the magnetic
quality of the test-piece from the absolute value of the magnetic attraction, but
I test the piece by comparing the attraction exerted on it with the
attraction exerted on
whose magnetic
more standard rods
quality is known before-hand.
preferably use a lever with a
sliding weight for measuring the magnetic attraction, and apply the force to
the rod through a linkage which is so arranged as to secure that the side of the
rod may be repeatedly separated from the magnet pole and replaced on the
same spot each time. When an electromagnet is used to form the UI provide
means of adjusting the current to one and the same value in comparing different
rods, and also means of reversing the current to eliminate effects of residual
magnetism in the magnet or in the rods.
one
or
The apparatus is designed in particular to furnish an expeditious means of test-
ing specimens of iron or steel intended for dynamo magnets. For this purpose
it suffices to use one strength of current, namely a strength which will produce
in the test-pieces values of the magnetic induction such as are used in dynamo
magnets. The test is made by observing the differences in the attraction exerted
on the test-pieces and on the standards.
Dated this 24th day of February 1898.

page_text: Improvements in Apparatus for Magnetic Testing.
I, JAMES ALFRED EWING of Langdale Lodge, Cambridge, Professor of
Mechanism in the University of Cambridge, do hereby declare the nature of this
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
My invention relates to apparatus for testing the magnetic quality of iron or
steel by observing the mechanical force required to overcome the magnetic
attraction between the test-piece and another portion of a magnetic circuit of
which the test-piece forms part. The test-piece is in the form of a turned rod, and
is so placed as to constitute the armature of a magnet, generally an electro-
magnet. The magnet is U-shaped and the test-piece lies across the two poles of
the U. By means of a weighted lever or otherwise force is applied at or near
one end of the test-piece to pull it off one pole of the U, while the other end of
the piece continues to rest on the other pole of the U, with which it may be said
to make a magnetic hinge. I preferably let it rest in a V-shaped notch cut in
that pole of the magnet, and give the other pole, from which the piece is to be
pulled away, a somewhat rounded convex surface. In general I allow the side
of the test-piece to come into actual contact with the surface of the pole, but it
may alternatively be held at a small distance from the surface of the pole by
means of a distance-piece or stop. In all cases it is the cylindrically turned
side and not the end face of the test-piece on which the magnetic attraction
which is measured is exerted. I do not infer the magnetic quality of the test-
piece from the absolute value of the magnetic attraction, but I test the piece by
comparing the attraction exerted on it with the attraction exerted on one or more
standard rods whose magnetic quality is known beforehand. I preferably use
a lever with a sliding weight for measuring the magnetic attraction, and apply
the force to the rod in such a manner as to secure that the side of the rod may be
repeatedly separated from the magnet pole and replaced on the same spot each
time. When an electro magnet is used to form the UI provide an adjustable
resistance or other means of adjusting the current to the same value in com-
paring different rods, and also a key for reversing the current in order to eliminate
effects of residual magnetism in the magnet or in the rods.
The apparatus is designed in particular to furnish an expeditious means of
festing specimens of iron or steel intended for dynamo magnets. For this purpose
it suffices to use one strength of current in the electromagnet of the tester, namely
a strength which will produce in the test-pieces values of the magnetic induction
such as are used in dynamo magnets. The test is made by observing the differ-
ences in the attraction exerted on the test-pieces and on the standards. I usually
employ an electromagnet and excite it by a current of such strength that the
average induction produced in the test-piece has approximately the value which
would be produced by a uniform magnetic force of 20 c.g.s. units. The lever
which carries the sliding weight is graduated with a scale which reads directly
the value of the induction produced in each specimen by a force of 20 units. The
scale is determined in the first instance by testing specimens whose magnetic
quality is known beforehand. I generally provide one standard specimen with the
instrument in order that the user may bring the current to its proper value by
adjusting it until the scale reading given by that specimen agrees with the
stated value of its induction under a force of 20 units. The magnetising force
of 20 is selected as a convenient one, but other forces may be used.
Figure 1 shows a form of the apparatus in side elevation, Figure 2 shows
separately in elevation the U-shaped magnet and test-piece and the end of the

page_text: lever in section. Figure 3 shows the magnet with the test-piece lying on its
poles. A is the magnet consisting of a pair of pole pieces B, C, connected by a
core on which an exciting coil is wound. Que of the pole pieces B has a slightly
rounded convex top against which the side of the test-piece F is laid, and from
which it is pulled away by the snout 1 of the lever E. The test-piece rests near
its other end in a groove G, Fig. 3, cut in the top of the pole piece C, and when it
is pulled away from B it moves about G as on a hinge.
The lever rocks about an axis passing across G on the points of two set screws
which rest respectively in a hole H and a slot J (Fig. 3) on brackets fixed at C.
In Fig. 1 the test-piece is shown after being pulled away from B, and the far end
of the lever has dropped against the stop K. The stop K is hinged at L and by
moving it to the left the end of the lever is raised and the specimen again comes
into contact with B. M is a reversing key included in the electric circuit of the
magnet and N is the handle of an adjustable rheostat also included in that
circuit. is the sliding weight, the position of which is varied until it just
suffices to pull away from B after the current has been brought to its proper
value as determined by means of a standard specimen or otherwise.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:
(1.) Apparatus for testing the magnetic quality of iron or steel by observing
the mechanical force exerted between the pole of a magnet and the side of a
cylindrically turned test-piece and comparing that with the force similarly
exerted on a standard rod or rods, substantially as described.
(2.) Apparatus for magnetic testing consisting of a U-shaped magnet across
the poles of which a cylindrically turned test-piece is placed together with a lever
or other device for observing the force required to pull away the side of the
test-piece from one pole of the magnet, substantially as described.
(3.) Apparatus for magnetic testing consisting of a U-shaped magnet, across
the poles of which a cylindrically turned test-piece is placed, together with a
lever and sliding weight for abserving the tractive force, the lever being
graduated as to show the magnetic induction produced by a stated magnetising
force, substantially as described.
SO
(4.) The improved apparatus for testing the magnetic quality of iron or steel,
substantially as described.
Dated this 96th day of October 1808