Note: Descriptions are shown in the official language in which they were submitted.
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12857/US/CA Dr.v.B/Ri/R10
Applicator Coil for an Electromagnetic
Therapy Apparatus
BACKGROUND OF THE INVENTION
(1) FIELD OF THE INVENTION
The present invention relates to an applicator coil
for an electromagnetic therapy apparatus.
(2) DESCRIPTION OF T~E PRIOR ART
From US Patent Specification 4,066,065 there is known
an ap~licator coil in the form of a multi-layer cylindrical
or solenoid coil with an oval-shaped, especially elliptical
cross-section.
The applicator coils of the kind of interest here serve
for healing treatment by means of low frequency magnetic
alternating fields, whose frequency preferably lies below
20 Hz. The magnetic field can serve directly for the
treatment or be used to induce low frequency alternating
currents in a pick-up coil, which forms part of a device for
promoting the growth of bones or tissue (see e.g. US Patent
Specifications 3,745,995 and 3,890,953, incorporated by
reference).
The known applicator coils with elliptical cross-
section serve first and foremost for treatment of the trunk
region of the human body, especially of the pelvic and
shoulder region.
A disadvantage with the known applicator coils is that
they are felt to be uncomfortable by patients during long
treatment times and/or with sensitive constitutions.
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SUMMARY OF THE INVENTION
The object of the present invention is accordingly so
to form an applicator coil for an electromagnetic therapy
apparatus, that it is not felt to be uncomfortable even by
sensitive patients or with prolonged treatment.
According to an embodiment of the invention, an
applicator coil for an electromagnetic therapy apparatus,
which has an essentially oval-shaped cross-section with a
large and a small diameter, is characterized in that the
cross-section is asymmetrical relative to the large
diameter.
In that the one part of the coil, in use the lower
part, has a smaller curvature - is thus flatter - than the
other part, in use the upper part, the coil is hardly felt
to be disturbing by the patient any more.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is explained in more detail with
reference to the drawings. These show:
Figure 1 an end view of an applicator coil according
to an embodiment of the invention ~nd
Figure 2 a plan view of the applicator coil according
to Figure 1.
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DESCRIPTION OF THE PREFERRED EMBODIMENT
The applicator coil 10 shown in the drawing has the
form of a short, right cylinder and includes a multi-layer
wire winding (not shown), which i5 encased in known manner
with plastics material and provided with terminals, which
are located in a terminal box 12 fitted on the side of the
coil. The applicator coil 10 is devised for producing a low
frequency magnetic field, more specifically a magnetic field
having a frequency below 20 Hz.
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As Figure 1 shows, the coil has an essentially oval-
shaped cross-section with a large diameter or axis a and a
small diameter or axis b. The axial length is smaller than
the small diameter b. The cross-section is symmetrical in
relation to the small diameter b. However, in relation to
the large diameter a the cross-section is asymmetrical. The
part of the coil which is lower in use and in Figure 1 has
the form of a flat shell and a smaller curvature or arching
than the upper part. The lower and the upper part of the
coil can each have a cross-section in the form of a half of
an ellipse divided along its major axis, where the ratio of
the length of the minor axis to the length of the major axis
in the lower half is smaller than in the upper half.
Accordingly the part of the cross-section which is located
below the large diameter a has a smaller area that the part
located above the large diameter a.
Through the flatter curvature the lower part of the
coil fits the part of the trunk of the patient surrounded by
the coil better, especially the pelvic or shoulder region,
so that the coil is not felt to be disturbing. The stronger
curvature and the larger cross-sectional area in the upper
part of the coil leave space for the belly and for the
breast.
