Note: Descriptions are shown in the official language in which they were submitted.
W( /20079 PCT/DE92/00335
2086669
Description:
Coil Former and Method of Producing it
The invention refers to a coil former with ends of terminal pins
suitable for thxough-contact injection-moulded in a lower flange;
these pins can be wound in a section beneath the lower flange with
ends of coil windings. The invention also refers to a process for
the production of a coil former of this kind.
The conventional method of providing contacts for electronic
components on circuit boards has been to pierce holes in the
boards, through which terminal pins projected, and to solder the
pins to the underside of the board on which were contact surfaces
of printed circuits pierced by the holes. It is, however,
becoming increasingly the practice to provide the surface contacts
on such circuit boards by placing the components directly on
contact surfaces of the board and soldering them to these surfaces.
If necessary, the components can also be attached to the board by
gluing. When the contacts are provided by this method the
components must have suitable connectors. As a general rule
lamellate connectors are used for this purpose and these connectors
are anchored in the housing of the component and bent to form an
angle outside the housing. The regular practice is to lead these
connectors out of the housing laterally and downwards, and then
once again to bend them outwards. It has been found that it is not
possible to attach sheet metal strips of this ~ind automatically to
a component made of thermosetting plastic, for example a coil
former made of thermosetting plastic, because the tool cannot be
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sealed and consequently thermosetting plastic material always
escapes and has to be removed again at a subsequent stage of the
processing of the component. In addition, connectors made of sheet
metal strips, when used on a coil former, are liable to suffer
damage while the coil former is being wound and deform easily along
the bends, so that the connectors with their ends bent outwards ro
longer lie flat on the contact surface and therefore do not ensure
proper contact.
It is also ~nown how to make conventional housings with lamellate
connection terminals, which can be plugged into a suitable
receptacle, surface-mountable by bending the terminals back. The
result is an ar~angement comparable to the above-mentioned
lamellate connectors for the surface assembly.
Because of the problems with the known lamellate connectors it has
been proposed to use, as connectors for surface-mountable
components, pins with a relatively large cross-section and a lower
end gradually broadening in the cross-section (so that in vertical
section the shape is that of a T). The cost of this method is high
and uneconomic for most cf the connectors required.
The basic purpose of the invention is to create a coil former which
is free of most of the above-mentioned disadvantages.
The invention achieves this purpose by means of a coil former of
the type described initially, which is characterized in that the
terminal pins are flattened beneath the section in order to give
them a rectangular cross-section and are bent in the region of the
flattened cross-section to form surface-mountable connectors.
The above-mentioned purpose is also achieved by a method of
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producing a coil former in which a conventional pin which can be
used for through connections is anchored in the conventional manner
in the flange of the coil former, the free end of the portion of
the terminal pin projecting from the flange being flattened by
pressing beneath the section of the terminal pin used for winding
and the flattened portion of the terminal pin being bent to form a
surface-mountable connector.
The invention offers the following advantage: a coil former for
providing surface contacts can, in principle, be produced in the
same manner as a coil former for producing through-connections by
the conventional method, and the pins which can be used to produce
through-connections can then be flattened and bent back, thereby
creating a component suitable for surface mounting. It is
therefore possible, in principle, to produce by the same method
coil formers used to make through-contacts in the present manner
and to make surface contacts and to provide the coil formers with
connectors. All that is necessary is to process subsequently the
connectors of the component intended for surface mounting and to
shape them in the manner described above. A coil former will have
the advantage that the connectors can be led downwards out of the
coil former in the form of terminal pins and then bent. As
compared with the method of leading lamellate connectors out
laterally and downwards and then bending them outwards, there will
be a significant saving of space on the board which in the case of
small coil formers can be as much as one third.
The embodiment of a coil former in accordance with the invention is
particularly advantageous, because a rigid section of the connector
is available for winding with the end of the coil wire, so that,
mechanically speaking, the connector is not likely to be bent out
of shape while it is being made. An embodiment in which the
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portion of the connector projecting from the component has a square
cross-section preceding the flattened portion ensures a geometry
which is especially suitable for the winding on of the coil.
The introduction of wire-shaped terminal pins into the injection
mould, for example, when a coil former is being produced, is
effected by the conventional method and does not present any
problems~ The invention therefore requires that no use be made of
expensive new terminal pins with modified cross-sections, which may
have to be straightened and inserted in a specific location,
thereby further increasing the cost.
It is particularly advantageous to have the connectors, which are
located on at least two exterior sides of the component, flattened
by positioning a backrest on the inner side of the connectors and
pressed by means of a die from outside against the firmly fixed
backrest. Because of the flattening, a step is formed on the outer
side of the connector. As a rule the backrest is moved as a piece
between the connectors and the press dies then press the connectors
from outside against the backrest, so that the connectors assume
the desired flattened shape. The invention permits not only the
use of the same kind of production method and the use, if
necessary, of the same kind of housings for the components, but
also the use of identical winding machines for the production of
coil formers. The method to which the invention refers can itself
be applied without exerting greater force to the component, so that
the anchoring of the connectors in the component will not be
subjected to dangerous strain if the terminal`pins are subsequently
deformed.
The connectors to which the invention refers can be made with a
high degree of precision. It is, for example, possible to bend the
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flattened terminal pin in such a way that a small angle is formed
between the contact surface and the supporting surface of the
connector, resulting in an improved flow of solder into the region
of the connector, due to a certain capillary effect, and so in a
firmer solder joint.
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The invention will be explained in detail with reference to the
examples of an embodiment shown in the drawing. The drawing shows
the following:
igure 1 - a terminal pin embedded in a component in four
phases of its production
igure 2 - side elevation of a coil former with anchored
terminal pins
igure 3 - the coil former as in Figure ~ with shortened
terminal pins
igure 4 - the coil former as in Figure 3 after flattening of
the terminal pins by pressing
igure 5 - the coil former with connectors bent outwards
igure 6 - top view of the coil former as in Figure 5.
Figure 1 shows a connector 1 which is anchored in a component 2.
This is usually effected during the production of the plastic
component (e.g. coil former) by placing the connector in an
injection mould for the production of the component 2 and then
partially injection-moulding it. In the present instance the
connector consists of a pin 3 with a round cross-section, as can be
seen from the illustration of the section S2 in Figure 1. At the
upper end the pin 3 is stamped to form a square ~ with a s~uare
cross-section, as can be seen from the illustration of the section
Sl. The connector 1 is anchored in the component with a round
socket 5. In the form illustrated in Figure la the connector 1 is
a pin 3 of the type generally used for the conventional through-
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contacts.
When a connector 1 of this kind is to be used or a surfaceassembly, the terminal pin 3 is first of all shortened by one end
being cut off, as is shown in Figure lb. The shortening is
performed at some distance below the square region 4, in the region
of the round cross-section S2.
In the next step of the method the free end of the connector 1 is
flattened by pressing, so that there is still, beneath a remaining
portion of the square region 4, a piece of the pin 6 whose
rectangular cross-section is illustrated as section S3 in Figure 1.
Figure lc shows that the shaping of a rectangular cross-section as
in S3 is effected on the inner side of connector 1 mainly by
pressure applied from outside inwards against a fixed backrest.
The piece 6 in the connector is then bent outwards at a distance
from the remaining square region 4 to ~orm.essentially a right
angle; here it is advantageous if an acute angle is fonmed with a
level supporting surface. The remaining square region 4 can
advantageously be wound with the ends of a coil winding so as to
produce the electrical connection with the coil. The winding is
performed in the rigid square region 4 so that the bent piece 6 is
not damaged by the winding process.
Figure 2 shows the state in accordance with Figure la of a coil
former 2 as an electronic component. The connectors 1, embodied as
terminal pins, are injection-moulded in attached flanges 2' of the
c~il former 2.
Figure 3 shows the state of the connectors 1 following the
shortening of the terminal pins 3 in accordance with Figure lb.
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Figure 4 shows more clearly the flattening of the connectors 1 in
accordance with Figure lc, so that it can be clearly seen that the
material is forced inwards from outside, that is to say, a press
die is applied from outside inwards against a backrest located
inside.
Fi~ure 5 shows the situation after the connectors 1 have been bent
outwards from the centre of the coil former.
Figure 6 shows more clearly that the flanges 2' of the coil former
2 are disposed laterally and, in this example, that each carries
three connectors 1. Following the shortening in accordance with
Figure 3 a backrest can be inserted from beneath on the inner side
and against the connectors 1; the exterior contour of the backrest
is adapted to the position of the connectors 1. It is then
possible to apply press dies against the connectors 1 from outside
to produce a flattening in accordance with Figure 4.
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