Note: Descriptions are shown in the official language in which they were submitted.
~8312~
1 The present invention relates in general to coil forms
and in particular to coil forms of the type having a tubular body
for supporting coil windings and being provided a-t each end
thereof with a flange or collar for confining coil windings.
Coil forms of this kind find application in large
quantities in many fields of technology. In particular, such
coil forms are employed in electromagnetically actuated switching
devices, such as for example circuit breakers. Hitherto, the
manufacture of coil forms was relatively expensive, even if they
are produced in large quantities. For example, to produce such a
form from a synthetic material, a very complicated injection
split mold is necessary. Such a split mold is composed of two
disconnectable mold blocks which define the contour of the outer
surface of the tubular body of the form as well as the opposite
inner surfaces of the end flanges. Moreover, two additional mold
parts must be provided for shaping the outer surfaces of the end
flanges, and also a core or pin is used for delimiting the central
hollow space of the tubular body. Such ccmplex component parts
of the injection split mold must fit together with extreme accuracy,
and also it is necessary in opening or closing the mold to move the
mold parts along exactly predetermined paths. In spite of the
most accurate manufacture and guidance of the component parts of
the injection mold, the formation of seams or fins on completed
forms frequently cannot be avoided, inasmuch as plastic material
injected under pressure into the mold penetrates into the joints
of the mold parts. The formation of such seams on the periphery
of the hollow form bodies is particularly detrimental inasmuch as
sharp seams or fins can damage the applied coil windings. Additional
machining of the completed coil forms, for example by grinding off
the seam, is cumbersome and, due to the projecting end flanges on
~LZ~33~Z
1 which the fins may also occur/ is very difficult to accomplish.
The two opposite, radially outwardly projecting end flanges cannot
be dispensed with, as -they are necessary for laterally bounding
and protecting the coil applied on the supporting tubular body.
It is therefore a general object of the present invention
to avoid the aforementioned disadvantages.
In particular, it is an object of the invention to
provide a coil body of the aforedescribed kind which is easy to
manufacture.
Another object of this invention is to provide such an
improved coil form which is free of surface defects resulting from
processing in the injection mold.
In keeping with these objects and others which will become
apparent hereafter, one feature of the invention resides in the
provision of the tubular body with radially projecting end flanges,
which is composed of two parts adjoining each other in a separation
plane extending at right angles to the end flanges, and at least one
flexible hinge band connects the two parts along a separation line.
In this manner, a substantial advantage is achieved in
that for manufacturing the entire coil form by an injection molding
process, only two mold parts are needed, and the movements for
openiny and closing the mold are very simple and fast. In addition,
there are no seams or fins on the surface of the tubular form body
on which the coil windings are to be applied.
The novel features which are considered characteristic for
the invention are set forth in particular in the appended claims.
The invention itself, however, both as to its construction and
its method of operation, together with additional objects and
advantages thereof, will be best understood from thefollowing
description of specific embodiments when read in connection with
the accompanying drawing.
3~;~
l FIG. l is a perspective view of a coil form of this
invention shown in its unfolded position in which it is manufactured
by an injection molding process;
FIG. 2 is a perspective view of the form of FIG. l in
its folded condition;
FIG. 3 is a side view of the form of FIG. 2 in direction
of arrow III;
FIG. 4 shows a perspective view of a modification of the
coil form, shown in its unfolded position, in which two forms of
FIG. 1 are combined in a single unit;
FIG. 5 is a plan view of the form of FIG. 4 shown in the
direction V;
FIG. 6 is a side view of the form of FIG. 5, shown in
direction ox arrow VI;
FIG. 7 is a front view of the form of FIG. 5, shown in
the direction of VII;
FIG. 8 is a view similar to FIG. 7, showing the form in
its folded position;
FIG. 9 is a side view of the form of FIG. 8 in the
direction of arrow IV;
FIG. lO is a perspective view of the coil form of FIG. 9;
FIG lL is a view similar to FIG. 10, showing the form
with applied coil windings;
FIG. 12 is a perspective view of a completed coil; and
FIG. 13 is a perspective view of the coil of FIG. 12 coated
with an outer layer of plastic material.
FIGS. 1-3 show an embodiment of a single coil form for
supporting a single winding. The form consists of two halves l and 2,
manufactured simu]taneously by an injection molding process and, as
will be explained below, the resulting completed coil form is divided
~8.~Z2
1 lengthwise along a plane extending pexpendicularly to the end flanges
of the coil form. The separation plane is indicated in FIG. 3 by
reference numeral 13. According to this invention, the two parts 1
and 2 of the form are interconnected by two flexible hinge bands 16
and 17 which are also produced simultaneously with the injection
molding of the form halvesO In this embodiment, the form in its folded
condition has the shape of a hollow or tubular body of a substantially
rectangular cross section. It will be seen from FIGS. 1 and 2 that
the rectangular full size surfaces 3 and 4 in folded condition of the
form are placed opposite each other, and the half surfaces 5, 6 and 7,
adjoin one another along the separation plane 13 to form lateral walls
of the central channel of the coil form. It will be seen from FIG. 2
that the outer surfaces of the rectangular sides have rounded edges.
In this preferred embodiment, the separation plane 13 bisects the coil
form into two symmetrical halves 1 and 2. accordingly, the end flanges
9, 10 and 11, 12 are also composed of symmetrical halves projecting
radially from the ends of the tubular body 1 and 2. The outer faces
of the flanges are provided with reinforcing ribs 14 and 15. By virtue
of the two flexible hinge bands 16 and 17, which in this embodiment
20 connect the opposite corners of divided flanges 11, 12 and 9 and 10, the
both halves of the coil form can be readily rotated by 180 from their
unfolded position shown in FIG. 1 into their folded, final position
shown in FIG. 2.
In its unfolded position, in which the coil form is produced
in the injection mold, the form has no undercuts, and consequently the
manufacture of the form proceeds in a very simple manner in only two
mold parts by an injection molding process. One of the mold parts
defines the upper contour of the form, and the other mold part corresponds
to the lower contour. Both form halves 1 and 2 and the interconnecting
flexible hinge bands 16 and 17 form together a single piece of tough
~Z~33~
1 and hard plastic material. The flexible hinge bands 16 and 17 are
so thin that the plastic material in this range still maintains the
desired flexibility or bendability, while maintaining a strong
connection between the two form halves 1 and 2. Preferably, the
two flexible hinge bands 16 and 17 are formed with advantage between
the outermost separation lines, which in this example are at the plane
of separation between the narrow sides of the end flanges 9, 10 and
11, 12. After the coil form is removed in its unfolded condition from
the injection mold, the two form halves 1 and 2 are folded together
by rotation by 180 as indicated by dashed arrows 22 and 23. In order
to obtain a fixed contact in the folded position, the facing surfaces
of the form halves are provided in the separation plane 13 with project-
ing pins 20 on one half and with corresponding retaining holes 21 on
the opposite half for snugly engaging the pins 20. Preferably, there
are provided four holding pins 20 with corresponding holes 21 in the
end regions of the dividing surfaces 18 and 19, that is in the range
of the end flanges 9-12, so as to ensure a reliable connection of the
two mold halves. In its folded or assembled condition, the coil form
is provided with coil windings in conventional fashion.
A preferred embodiment of this invention which is particularly
important in practice is illustrated in FIGS. 4-12. In this preferred
embodiment, the two form halves 24, 25 and 26, 27 are arranged end-
to-end and axe interconnected by a flexible hinge band 36 (FIG. 5) to
a single unit. The individual single winding coil forms or form halves
24, 25 and 26, 27 correspond in all details to the form halves 1 and 2
of FIGS. 1-3. In other words, the form halves 24 and 25 are again
interconnected by flexible hinge bands 28 and 29 and the adjoining
form halves 26 and 27 are provided with flexible hinge bands 30 and 31.
Similarly, the xetaining pins 32 and 34 and corresponding snugly fitting
holds 33 and 35 are equal to those of FIG. 1. The manufacture of the
.3~2
1 unfolded double form is also made in the manner described in
connection with FIG. 1. Since the double coil form is held together
by the flexible hinge band 36, it can be remcved fro~l the injection
molding device as a single unit.
Thereafter, the form halves 24, 25 and 26, 27 are bent along
the flexible hinge bands 28 31 about 18Q and snapped together into
the completed coil form illustrated in FIG. 8. The provision of the
flexible hinge band 36 between the outer rims of facing end flanges
of series-arranged coil worms does no-t obstruct the folding of the two
coil forms along the aligned hinge bands 28-31. In the folded condition
shwon in FIGS. 8-10 the end flanges of the axially aligned, series-
connected tubular forms are arranged parallel to each other. The outer
surfaces of respective flanges, similarly as in the preceding example,
are provided with reinforcing ribs. These ribs in the range between
the consecutive coil forms, serve simultaneously as spacers. In the
folded condition of this double coil form, the coil windings 40 and 41
(FIG. 11) can be wound simultaneously on both supporting tubular bodies.
This possibility, in comparison with the prior art technology, has the
essential advantage that the winding time is cut by half, inasmuch as
it is possible without any additional measures to clamp both coil forms
on a single winding machine. After the first mentioned folding of the
form halves in the direction of arrow 39 (FIG. 8) about the flexible
hinge bands 28-31, and after the application of windings 40 and 41 on
the tubular body, a further folding of the form is made, namely about
the flexible hinge band 36 in the direction of arrow 42 (FIG. 11). It
will be seen from FIGS. 5 and 9 that the flexible hinge band 36 extends
at right angles to the flexible hinge bands 28-31, and consequently
the two consecutively arranged coil forms with their windings 40 and 41
can be folded into a new position illustrated in FIG. 12, in which the
windings are arranged parallel to one another. In this final position,
332~
1 the corresponding narrow sides of the end faces abut against each
other, and the center axis of respective tubular bodies of the form
extend in parallel. In order to secure the coil form in this final
position, there is provided a projecting pin 37 and a corresponding
retaining hole 38 on the narrow sides of the end flanges which are
remote from the flexible hinge band 36~
The end portions of the wires 43 of windings 40 and 41
can be now simply twisted together and soldered, whereas the free
~Jires are comlected each Jo a conductive yoke 4. The yokes are clamped
to opposite outer edges of adjoining end flanges, as depicted in FIG. 12.
Preferably, each yoke is shaped so as to define an outwardly projecting
knee with a conductive contact surface 45. The knee projects outwardly
to such an extent that, after the insertion of the completed coil body
in an electromagnetic device, for example a circuit breaker or magnetic
switch, a conductive contact with non-illustrated terminals, such as
conductive rails on the device, is established.
In order to protect the two windings ~0 and 41 and to hold
the contact yoke 44 in position, both windings are coated by an in-
sulating adhesive band. The protective insulating band is provided with
small cut-outs to uncover the conductive areas 45 on the yokes 44.
Instead of adhesive bands, it is also possible to coat the
entire outer surface of the coil with a closed layer of a plastic
material through which the contact surfaces 45 project (FIG. 13). In
the completed coil according to FIGS. 12 or 13 the hollow channels 47
and 48 in the centers of respective coil forms remain open, so that the
coils can be inserted in conventional manner on the arms of a U-shaped
electromagnetic core.
The embodiment according to FIGS. 4-13 has the following
substantial advantages.
As mentioned before, the manufacturing process is consider-
ably simplified, whereby the halves of the split injection mold can
~2l)8~,~2
l be constructed in such a manner that no detrimental seams and
separation edges will result in the range of the form where the
coil windings are to be applied. The separation gaps in the coil
form if desired can serve also as a very simple intake pocket for the
terminal wires of respective windings. The two windings can be
simultaneously produced during a single winding process. The con-
ventional tubing for protection of the soldered sections on the ends
of the wires can be dispensed with, and it is also no longer necessary
to solder additional flexible conductors to the ends of the winding.
lQ The halves of the coil form are rigidly connected one to the other by
means of the aforedescribed flexible hinge bands as well as by the pin
and hole connections, and consequently thin wires interconnecting the
two separate windings on the composite coll form are not subject to
any load. Inasmuch as the two consecutive coil forms, together with
their windings, are united in a single unit, the storage of the coils
is simplified and also is increased safety margin against damage during
transportation and during insertion into the electromagnetic cores
The construction of electrical contacts in the electromagnetic devices
is also simplified.
It will be pointed out that the aforedescribed flexible
hinge bands 28-31 and 36, during the injection of a plastic mass of
a synthetic plastic material, permit the through-flow of the material
in the injection mold. Accordingly, it is sufficient to provide for
a single injection channel at a suitable point of the split mold for
injection the material in both form halves. In this mannert the
manufacture and design of injection molds is in practice substantially
facilitated.
It will be understood that each of the elements described
above, or two or more together, may also find a useful application
in other types of constructions differing from the types described
above.
_g _
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1 While the invention has been illustrated and described
as embodied in speclfic examples of a coil mold for use with
electromagnetie devices, it i5 not intended to be limited to the
details shown, since various modi*icat:i.ons and structural ehanges
may be made without departing in any way from the spirit of the
present invention.
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