Improvement in Core-attracting Solenoids.
Year: 1891

page_text: Date of Application, 16th Oct., 1891
Complete Specification Left, 23rd May, 1892-Accepted, 2nd July, 1892
PROVISIONAL SPECIFICATION.
Improvement in Core-attracting Solenoids.
I, WENZEL ROBERT MICHL, of Wetter on the Ruhr, Kingdom of Prussia,
Electrician, do hereby declare the nature of this invention to be as follows:-
My invention relates to the combination of a solenoid and of a movable iron core
designed to be attracted by and drawn into the solenoid, and the object of the
improvement is to render the action of the solenoid on the core uniform throughout
the course of the latter, or to regulate this action at will.
If the coils of wire constituting a solenoid are arranged uniformly in all portions
thereof, and if all the transverse sections of the core are alike, the said core, when
introduced into the end of the solenoid energized by a current, will be drawn in
with a force which increases until the end of the core has arrived at or near the
centre of the solenoid; thereupon the attracting force will remain constant for a
short distance, and finally it will decrease again.
Now, in order to render the said force uniform, I so construct the solenoid or
combine the same with another part that the action of its individual portions on the
core decreases from both ends towards the middle.
One arrangement answering this condition is obtained by reducing the number of
coils, or the aggregate thickness or density thereof in the succeeding portions of the
solenoid from the ends to the middle. Another arrangement is produced by making
the coils of increasing diameter towards the middle of the solenoid, so that their
distance from the core will be greater at this point than at the ends. A third
arrangement is obtained by placing around an ordinary cylindrical solenoid coils of
wire wound contrarily to the former, or traversed by the current in opposite
direction, the aggregate thickness of the latter coils increasing towards the middle
of the solenoid. A fourth arrangement consists in the combination, with a
cylindrical solenoid, of a tube of non-magnetic metal inserted thereinto and having
upon each half of its length longitudinal slits that taper from the ends to the
middle of the tube.
By suitably regulating the increase and decrease of the aggregate thickness or
the density or the diameter of the coils, or of the form of the said slits, any desired
ratio of increase and decrease in the attracting force of the solenoid may be
obtained.
The invention is applicable to cores of various construction and of uniform or
varying transverse section.
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tabo 1901
J. H. JOHNSON & Co.,
Agents.
COMPLETE SPECIFICATION.
Improvement in Core-attracting Solenoids.
I, WENZEL ROBERT MICHL, of Wetter on the Ruhr, Kingdom of Prussia,
Electrician, 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 the combination of a solenoid and a movable iron core
designed to be attracted by and drawn into the solenoid, and the object of the
improvement is to render the action of the solenoid on the core uniform throughout
the course of the latter, or to regulate this action at will.

page_text: If the coils constituting a solenoid, are arranged uniformly in all portions thereof,
and if all the transverse sections of the core are alike, the said core, when introduced
with one end into the solenoid energised by a current, will be drawn in with a force
which increases until the end of the core has arrived at or near the centre of the
solenoid; thereupon the attracting force remains constant for a short distance, and
finally it will decrease again.
Now, in order to render the said force uniform, I so construct the solenoid, or
combine the same with another part, that the action of its individual portions on the
core decreases from the core introduction end towards the middle and then increases
again towards the other end.
In the annexed drawings
Fig. 1 is a sectional elevation of an ordinary cylindrical solenoid.
Figs. 2 to 7 are sectional elevations of solenoids of uniform core-attracting power
constructed according to my invention.
Fig. 8 is the side view of a tube belonging to the solenoid Fig. 7.
In the solenoid S, Fig. 1, composed of convolutions of wire c that are wound
uniformly in all portions of the same, and which thus form together a hollow
cylindrical body, the force operating to draw in the core K, increases in the
measure as the upper end of the latter rises from the bottom, or introduction end
of the solenoid, to line a. The said force then remains constant up to about the
line and thence decreases again.
In the solenoid S¹, Fig. 2, the number of convolutions is gradually reduced in the
consecutive sectional portions from the bottom to the middle and is then augmented
again in the inverse ratio of the increase and decrease of the force produced by
solenoid S, Fig. 1, the wire being so coiled as to render the aggregate body of wire
in vertical section concave outside and cylindrical inside. The solenoid S³ repre-
sented by Fig. 3, differs from the foregoing one only in this respect that the body
of wire is cylindrical outside and concave in vertical section on the inside.
In the solenoid S³ shown by Fig. 4, the gradual reduction and following increase
in the number of convolutions is attained by coiling the wires in the consecutive
portions at different distances apart, and thus varying the density of the con-
volutions, as indicated in the figure by the difference in closeness of the hatching.
For this purpose the thickness of the insulating covering of the wire may be
varied, or any suitable insulating material is placed in layers of different thickness
between the coils, or wires of different diameter are employed for the succeeding
portions of the coil.
The same effect as by the reduction of the number of convolutions towards the
middle of the solenoid, may be obtained by gradually increasing and then decreasing
the diameter of the coils, so that their distance from the core will be greater, and
consequently their action on the same less, in the middle of the solenoid thau at the
ends. A solenoid S' of this description is represented by Fig. 5.
Another means for producing a solenoid of uniform core-attracting action is
illustrated by Fig. 6. The solenoid S shown by this figure is composed of coils c
forming a common cylindrical solenoid, and coils of wire d placed around the coils c
and wound contrarily to the same, or, in general, so connected to the coils c that
the current flows in the coils c and d in different direction, the aggregate thickness
of the coils d increasing from the ends towards the middle of the solenoid. In this
case the core attracting effect of the cylindrical solenoid is counteracted by the
coils d, the resulting force in each section of the combined solenoid S* corresponding
to the difference of thickness of the bodies of coils c and d.
The non-uniform action of a cylindrical solenoid may, however, also be rendered
uniform by the insertion, between the solenoid and the core, of a metallic tube f,
Figs. 7 and 8, having, upon each half of its length, slits e that taper from the ends
to the middle of the tube. The said tube is preferably made of a non-magnetic
metal.
By suitably regulating the increase and decrease of the aggregate thickness or
density, or the diameter of the coils, or the form of the slits in the tube f, any

page_text: desired ratio of increase or decrease in the attracting force of the solenoid may be
obtained.
The invention is applicable to cores of various construction and of uniform or
varying transverse section.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:
The method of producing in a solenoid uniformity, or any desired ratio of increase
and decrease of core-attracting force, which consists in varying the number of coils
of wire in the different sectional portions of the solenoid, or in making the coils
composing the said portions, of different diameter, or in varying the influence of the
coils on the core either by means of other coils traversed by the current in opposite
direction, or by means of a metal tube inserted into the solenoid and having slits
that increase or decrease in width in proportion to the force required at the different
points, substantially as described.
Dated the 22nd day of May 1909
J. H. JOHNSON & Co.,
Agents.