Method and apparatus for shaping cylindrical electrical parts

A process for transforming a cylindrical electrical part into a component having at least one flat surface, suitable for use as a surface mounted device.

The invention relates to a process for shaping electric parts that are 
cylindrical or circular cylindrical into electric components whose 
peripheral surface exhibits at least one flat surface area or section. 
Cylindrical electric parts are known in the most varied embodiments (as 
diodes, resistors, capacitors, etc) and are often also designated as 
"MELF." These parts belong to the group of so-called SMD parts (surface 
mounted devices) and are, among other things, processed for the production 
of electric circuits using printed boards so that these parts, to equip 
the printed boards in question, are placed on the latter and are 
preliminarily fastened there (for example with an adhesive coating). The 
electrical connection of these parts to the circuit board conductors of 
the printed circuit board then occurs in another process step by soldering 
so that the parts, with contact surfaces provided on their two ends in 
each case, are soldered directly to the circuit board conductors of the 
printed circuit board. The drawback here is, among other things, that the 
cylindrical parts, because of their shape, easily slip or curl up without 
preliminary fastening to the mother board, thus the fastening (for example 
with the help of an adhesive) is absolutely necessary for an orderly 
assembly of a printed circuit board; however, because of the cylindrical 
shape of the parts, such a fastening in the necessary way is not always 
guaranteed. 
The object of the invention is to indicate a process or a device with which 
it is possible in a relatively simple way to transform these kinds of 
electrical parts into electrical components whose peripheral surface 
exhibits at least one flat surface area, to simplify in this way the 
assembly of an electrical circuit. 
To achieve this object, a process is designed according to the 
characterizing part of claim 1 or a device according to the characterizing 
part of claim 23. 
In that after the shaping or transformation, electrical components are 
obtained which, on their peripheral surface, exhibit at least one flat 
surface area, these components, which are also SMD parts, can be processed 
considerably more simply during assembly of an electrical circuit, i.e., 
the transformed components with at least the one flat surface area can be 
placed on the printed circuit board so that even, without a preliminary 
fastening before soldering, an orderly positioning of the components and 
thus an orderly assembly of the printed circuit board is possible. But the 
one flat surface area at least also provides the possibility of a 
considerably improved fastening in those cases in which a fastening before 
soldering is necessary or sought. 
The metal plates attached on both ends of the electrical parts to be 
transformed constitute, in the reshaped component, the exposed contact 
surfaces of this component. 
In one embodiment of the invention, the metal plates and the parts to be 
transformed are pushed into a mold or forming space into which, for 
example, the compound of electrically insulating material is next inserted 
which, after it hardens or sets, at least partially encloses not only the 
part after shaping but also constitutes at least the one flat surface area 
of the reshaped component. In this forming space, blanks consisting of 
parts and plates to be reshaped can also be constructed, blanks which, 
after removal from the forming space are inserted or put into a separate 
mold for applying the compound of electrically insulating material. 
In another embodiment, the plates are fed to at least one support strip of 
a work position and connected there to the ends of the parts to be 
reshaped, and then the blanks thus obtained from at least one part and two 
plates in each case are inserted or put into a mold for applying the 
compound of electrically insulating material. 
The electrical part to be reshaped can be a MELF or another part exhibiting 
a cylindrical body, e.g., a coil wound on a ferrite body, etc., so that it 
is also possible with the device according to the invention, for example, 
to produce inductors economically. 
Further developments of the invention are the object of the subclaims.

In the figures, 1 is a MELF part that exhibits a component body 2 with a 
circular cylindrical shape which, on its two ends or faces, is in each 
case provided with a contact surface 3 constructed, for example, of a 
metal cap or produced in another suitable way. Such MELF parts, which can 
be active electrical parts (e.g., diodes) or also passive electrical parts 
(e.g., resistors or capacitors) are used especially for the production of 
electrical circuits with high part density, and it is usual to connect, by 
soldering, respective MELF part 1 on its contact surfaces 3 directly, for 
example, to the circuit board conductors of a printed circuit board that 
forms the basis of the circuit. Because of the circular cylindrical-shaped 
design of MELF parts 1, the latter must be fastened, with their peripheral 
surface lying on the printed circuit board, to the printed circuit board, 
for example by an application of adhesive, at least until soldering, which 
is complicated and, especially also because of the circular cylindrical 
shape, often not possible or only possible with difficulty in the 
necessary, reliable way. 
In FIGS. 1 to 5, 4 designates a component which is produced according to 
the process according to the invention or with the device according to the 
invention in the simplest case from a MELF part 1 and which, in the 
embodiment represented, is produced square-shaped with an essentially 
square cross section, i.e., with a peripheral surface that exhibits four 
surface areas 5 that join each other in each case in the peripheral 
direction at a right angle. On its two ends, component 4 has in each case 
an essentially square plate 6 that is produced from a sheet metal and 
constitutes an exposed contact surface, a plate whose cross section 
dimensions or whose side lengths are somewhat larger than the cross 
section of MELF part 1. Each plate 6 is fastened to a front contact 
surface 3 of MELF part 1 so that the center of plate 6, which lies with 
its surface sides perpendicular to the axis of MELF part 1, lies in the 
axis of MELF part 1 and an electrical connection also exists between plate 
6 and respective contact surface 3. To keep plates 6 on contact surfaces 
3, for example a so-called "conductive adhesive" can be used, i.e., an 
adhesive that also produces, after hardening or setting, a galvanically 
conducting connection between respective contact surface 3 and plate 6 
fastened to it. Of course, to connect plates 6 to contact surfaces 3 of 
MELF part 1, other techniques are conceivable. Both plates 6 are further 
fastened to both faces of MELF part 1 so that these plates each exhibit 
the same orientation, i.e., each side edge of a plate 6 lies parallel to 
one side edge of other plate 6. The space remaining between the two plates 
6 is filled with a compound of electrically insulating material (plastic) 
that constitutes, outside plates 6, the body of component 4 that encloses 
MELF part 1 and is shaped so that component 4 has, between two plates 6, 
the square cross section that remains the same over the entire length of 
this component, exhibits surface areas 5, and is the same in its shape and 
size as the cross section of plates 6. In the same way as MELF part 1 for 
production of a circuit, component 4 is positioned on the printed circuit 
board used and, with the help of plates 6 that constitute the contact 
surfaces of component 4, is soldered directly to the circuit board 
conductors of the printed circuit board. 
Component 4 is thus also a SMD, but due to flat surface areas 5, the 
positioning of component 4 on the printed circuit board and, above all, 
maintaining the respective position until establishment of the solder 
connection are considerably simpler than with MELF part 1. With a suitable 
handling of the assembled printed circuit board, sometimes when using 
components 4 their preliminary fastening to the printed circuit board can 
be completely dispensed with. 
As shown especially in FIG. 5, each plate 6 exhibits 4 recesses 7, one each 
is provided in the middle of each peripheral side of plate 6 in question 
and is open toward this peripheral side. The recesses which, in the 
embodiment represented, are constructed essentially rectangular and are 
placed distributed at even angular distances around the axis of MELF part 
1 have in each case a depth such that each recess ends at the peripheral 
surface of MELF part 1. As explained further below recesses 7, necessary 
auxiliary means for the production of component 4, constitute in each case 
the front, open end of a longitudinal groove 8 provided on surface areas 5 
and also open toward the periphery of component 4. Corresponding to the 
number of recesses 7, such a longitudinal groove 8 is provided on each 
surface area 5. 
FIGS. 1 to 3 reflect, in diagrammatic representation, a device that makes 
possible in an especially simple way the transformation of MELF parts 1 
into components 4. 
This device first exhibits a transport element 9, which moves in cycles 
past a work position 10 and feeds MELF parts 1 from a stock, which is not 
shown in more detail and which exhibits a multiplicity of such parts, 
individually, i.e., one after another, to work position 10. For this 
purpose, transport element 9 has several groove-shaped recesses 11 which 
constitute in each case a support for a MELF part 1 and which, with their 
longitudinal extension, are oriented perpendicular to movement direction A 
of transport element 9 and are open on both sides 9' and 9" of transport 
element 9 that run in movement direction A and in the embodiment 
represented also on the top side of transport element 9. Each recess 11 
has a cross section that is matched to the cross section of plates 6, 
i.e., essentially square in the embodiment represented, with two surfaces 
12 and 13 that border respective recess 11 laterally in each case and lie 
perpendicular to movement direction A and with a surface 14 lying 
perpendicular to surface 12 and 13 and constituting the floor of 
respective recess 11. On each of surfaces 12 to 14, a striplike projection 
15 projecting into recess 11 and perpendicular to movement direction A is 
provided so that the arrangement exhibited by projections 15 relative to 
each other on the surfaces mentioned is the same as the arrangement of 
recesses 7 on three consecutive peripheral sides of plates 6. By 
projections 15, each MELF part 1 conveyed to work position 10 is kept in 
suitable recess 11 so that this component, with its axis perpendicular to 
movement direction A, exhibits in each case the same distance from 
surfaces 12 to 14. Perpendicular to the movement direction and in the 
direction of the longitudinal extension of recesses 11, transport element 
9 has, at least in the area of these recesses, a width that is 
approximately the same as the length of MELF parts 1. 
A stationary core 16 ends at work position 10 on the one side of transport 
element 9, specifically in the representation selected for FIG. 2 on rear 
side 9', a core that constitutes a mold and forming space, lies with its 
longitudinal extension perpendicular to movement direction A and, for 
example, is constructed inside a pipelike element 17. Core 16 has a square 
cross section that is matched to the cross section of plates 6, a cross 
section that is constructed of four inner surfaces 18 to 21 that join each 
other in each case at right angles. On each inner surface 18 there is 
provided a flangelike projection 22 that projects into core 16 and extends 
in the longitudinal direction of this core, and these projections 
correspond in their cross section and their arrangement to the size and 
arrangement of recesses 7 on plates 6, i.e., each projection 22 is 
provided in each case in the middle of respective inner surface 18 to 21 
and is constructed in cross section perpendicular to the longitudinal 
extension of core 16 so that it completely or almost completely fills up a 
recess 7 in each case. 
The arrangement of transport element 9 relative to core 16 and the drive 
for transport element 9 are selected so that in every stoppage phase of 
cycle-driven transport element 9 a recess 11 coincident with core 16 so 
that not only does this recess with its surfaces 12 to 14 continue without 
transition in inner surfaces 18 to 20 of core 16, but also every 
projection 15 continues in a projection 22 of core 16. 
Two metal material strips 23 and 24 are fed in the direction f arrow B to 
work position 10 on side 9" lying opposite core 16 with the aid of a 
conveying device, not shown in more detail, so that these material strips, 
resting with one surface side in each case flat against each other, are 
oriented with their surface sides perpendicular to the longitudinal 
extension of recesses 11. Material strips 23 and 24, from which plates 6 
are generated by separation, are already precut with recesses 7 on their 
longitudinal sides running in conveying direction B. In the middle, each 
material strip exhibits a multiplicity of rectangular recesses 7', which 
form a row of holes or perforation extending in the longitudinal direction 
of the material strip in question, and each recess 7' is provided in the 
longitudinal direction of the material strip in question between two 
recesses 7 provided on the longitudinal sides of this material strip 23 or 
24 and further has, in the longitudinal direction of the material strip, a 
cross section dimension that is twice as large as the depth of recesses 7. 
Both material strips 23 and 24 are fed further to work position 10 so that 
they are placed to coincide on recesses 7 and 7'. 
At work position 10, where material strips 23 and 24 are fed, a punching or 
cutting device is further provided which essentially consists of a ram 25 
that can be moved back and forth in a direction perpendicular to movement 
direction A and of a stationary pressure pad 26, constructed for example 
of a matrix. 
The method of operation of the device according to FIGS. 1 to 3 can be 
described as follows: 
Each MELF part 1 placed in a recess 11 of transport element 9 is provided, 
before reaching work position 10, with a conductive adhesive coating on 
both front contact surfaces 3. Whenever a recess 11 exhibiting a MELF part 
1 has reached work position 10, by moving ram 25 in the direction of arrow 
C, a front section each that forms a plate 6 is separated from each 
material strip 23 and 24, and the separation occurs in the middle of 
recesses 7'. Two plates 6, thus produced from material strips 23 and 24 
and lying on each other like a stack, are then brought to lie against 
contact surface 3 adjacent to side 9" of transport element 9, and plate 6 
obtained from material strip 24 rests directly against contact surface 3 
in question of MELF part 1 and can enter into an adhesive bond with this 
contact surface 3, while plate 6 obtained from material strip 23 rests 
only by flat contact against plate 6 obtained from material strip 24. By 
further movement of ram 25 in the direction of arrow C, MELF part 1 is 
then pushed, together with two plates 6 obtained from material strips 23 
and 24, into core 16, and plates 6, by projections 15 or 22 engaging in 
recesses 7, are guided precisely and are secured against tipping or 
tilting during movement along recess 11 and during movement inside core 
16. 
In the next work cycle, i.e., when a recess 11 of transport element 9 has 
again reached work position 10, two plates 6 are again separated from two 
material strips 23 and 24 and, together with MELF part 1 in question, they 
are pushed through recess 11 into core 16, and MELF part 1, with its face 
that is in front during this insertion and that is provided with the 
conductive adhesive, comes to rest against that plate 6 which was obtained 
from material strip 23 during the preceding work cycle. It is understood 
that after every insertion of a MELF part 1 and both plates 6, ram 25 in 
each case is moved back into its starting position opposite arrow C. 
In the way described, core 16 is thus filled with MELF parts 1 and in each 
case two plates 6 lying between each part, and at every work cycle MELF 
parts 1 and plates 6 located in core 16 are pushed farther. A feed core 27 
empties at a distance from transport element 9 into core 16, a feed core 
by which the plastic compound that constitutes the component bodies of 
component 4 is fed, so that after going through this feed core 27, MELF 
parts 1 provided between plates 6 are covered by the plastic compound, 
also resulting in the desired cross section shape for components 4 by the 
cross section of core 16. At a distance from feed core 27, core 16 
exhibits an outlet, at which components 4 then leave core 16 after 
hardening of the plastic compound and can be conveyed away, for example 
with the aid of a transport element. 
Transport element 9 is, for example, a conveyor band or a conveyor belt, 
preferably a wheel rotating in the direction of arrow A that exhibits, on 
its peripheral surface, recesses 11 distributed at even angular distances. 
The process or device described above can also be used like the processes 
and devices described below for producing inductors, and then instead of a 
MELF part, a body is used that corresponds to component body 2, consists 
at least partially of ferromagnetic material and is provided with a 
winding. 
FIG. 6 shows a component 4a which is obtained by shaping using plates 6 and 
MELF part 1 and which differs from component 4 in that component 4a does 
not have longitudinal grooves 8, i.e., part 4a is constructed, on its 
surface areas 5, completely flat, without interruption by longitudinal 
groove 8 in each case, and the plastic compound that envelops MELF part 1 
and constitutes surface areas 5 also extends into recesses 7 of both 
plates 6 or fills these recesses. Component 4a which, because of surface 
areas 5 that are uninterrupted by longitudinal grooves 8, is especially 
suitable also for processing with suction grippers, is produced in the 
same way as component 4 with the help of the device according to FIGS. 1 
to 3, thus in the way described above by shaping, but with the difference 
that the holding tool that forms the peripheral surface, i.e., surface 
areas 5 of component 4a does not exhibit flangelike projections 22. 
To produce component 4a, plates 6 punched out of material strips 23 and 24 
and the MELF components fed by transport element 9 are pushed in the same 
way as was described for the embodiment according to FIGS. 1 to 5, in each 
case consecutively into core 16 of pipelike element 17a which, with 
respect to its function and arrangement relative to the remaining parts of 
the device, corresponds to pipelike element 17 of FIGS. 1 to 3. MELF 
components 1 here are again provided, on their front contact surfaces 3 
that rest against plates 6, with the conductive adhesive, so that a 
connection is established between each contact surface 3 and plate 6 
directly adjacent to it. Core 16 exhibits (starting from its end lying 
adjacent to transport element 9), over a certain length, flangelike 
projections 22, so that over this length and by flangelike projections 22, 
plates 6 and MELF parts 1 are kept in the correct orientation also with 
respect to each other, as this was described above in connection with 
FIGS. 1 to 3. The length of part 16' of core 16 provided with flanges 22 
is (also when considering the setting or hardening time of the conductive 
adhesive used and considering the maximum possible output of the device, 
i.e., considering the maximum processed measuring components 1 per unit of 
time) selected so that whenever a MELF component 1 with its respective 
plates 6 has reached this core by further pushing the end of part 16' in 
core 16, MELF part 1 is already fastened sufficiently solidly to 
respective plates 6 by sticking. A part 16" of core 16 joins part 16' in 
the movement direction of MELF parts 1 and of plates 6 connected to the 
latter, and in part 16", with otherwise the same cross section as core 16, 
projections 22 are missing. Into this part 16" there then empties feed 
core 27, by which the plastic compound that constitutes the component body 
of component 4a is fed. After passing through this feed core 27, MELF 
parts 1 then provided between plates 6 are covered with the plastic 
compound, and by the cross section that core 16 exhibits in part 16", and 
especially by the lack there of projections 22, the desired cross section 
shape of components 4a is obtained without longitudinal grooves 8. 
But components 4a can also be produced with the device according to FIGS. 1 
to 3 in that the covering of MELF components 1 with the plastic compound 
occurs not inside core 16, but with set or hardened conductive adhesive 
and thus with MELF parts 1 connected to plates 6 outside core 16 and 
preferably by molding under pressure in a separate mold that exhibits the 
flat mold surfaces that mold surface areas 5. 
According to FIG. 8, here it is preferable to proceed so that, using the 
device according to FIGS. 1 to 3, a rodlike blank 29 is produced in which 
two plates 6 follow each MELF component 1 in each case and which 
terminates at both ends with one plate 6 in each case. Each plate 6 is 
again connected, with the aid of the conductive adhesive, to front contact 
surface 3 on an end of a MELF component 1. Further, in rodlike blank 29, 
plates 6 that follow each other directly are connected to each other on 
their surface sides facing each other by a fastener, as this is indicated 
in FIG. 8 by the certainly exaggerated and thick layers 30 represented 
there of this fastener. Blank 28 is then inserted as a whole into a mold 
in which the plastic covering that constitutes the component body of 
components 4a is applied, and specifically preferably again by molding 
under pressure. After this, rodlike blank 29 is split into individual 
components 4a, specifically at the joint spots between plates 6 (layers 
30). Here the fastener is one which, for example, with heating easily 
allows a splitting of blank 29 into individual components 4a. As a 
fastener, for example wax or a plastic or adhesive that becomes soft under 
the effect of heat is used. But preferred as a fastener is a solder with a 
low melting point so that, with this fastener, a solder coating of plates 
6 on their exposed surfaces is simultaneously achieved. In this 
embodiment, metal or material strips 23 and 24 are already preferably 
connected to each other with this fastener on their surfaces facing each 
other. 
FIG. 9 shows, in perspective representation, a component 4b obtained by 
shaping using a MELF component 1, a component 4b which, in the same way as 
component 4a, on surface areas 5 of its component body, does not exhibit 
longitudinal grooves 8 but in which plates 6 do not have recesses 7 
either. 
To produce this component 4b, MELF components 1 are fed by a transport 
element 31 to a work station 32. Transport element 31 has supports 31' for 
MELF components 1 in the form such that each MELF component 1 lies with 
its longitudinal axis perpendicular to conveyance direction E of transport 
element 31 and adjacent MELF components 1 on transport element 31 in 
transport direction E exhibit, in each case, an equal, set distance from 
each other. Transport element 31 which, in the embodiment represented in 
FIGS. 10 to 12 is a conveyor band or conveyor belt, is further constructed 
so that MELF components 1, with their ends exhibiting front contact 
surfaces 3, project beyond the longitudinal sides of this transport 
element 31. 
Whenever a certain number of MELF components 1 has reached work station 32, 
the movement of transport element 31 is stopped. At work station 32 a 
number of plates 6 is also ready then that corresponds to the number of 
MELF components 1, specifically there is, on each end exhibiting front 
contact surface 3 of each MELF component 1, a plate that lies with its 
plane perpendicular to the longitudinal extension of respective MELF 
component 1. Here plates 6 are provided on support strips 33 that are fed 
to work station 32 so that there is, at this work station, in each case, 
such a support strip 33 on which plates 6 are provided in the longitudinal 
direction of the support strip at the same distance that is exhibited by 
MELF components 1 on transport element 31. In the embodiment represented, 
plates 6 are fastened by bars 34 to a longitudinal side of support strip 
33 in each case so that plates 6 project beyond this longitudinal side of 
support strip 33 and plates 6, support strip 33 and bars 34 are produced 
as one piece from the same material (sheet metal). In respective support 
strip 33, openings 35 are provided that constitute a perforation and that 
make it possible to feed support strips 33 to work station 32 so that with 
a transport element 31 stopped in its movement each plate 6 lies exactly 
adjacent to a face end of a MELF component 1 and specifically, especially 
also so that the longitudinal axis of each MELF component 1 intersect the 
center of both plates 6 adjacent to the ends of this MELF part 1. 
The individual MELF components 1 located in work station 32 are then 
connected on their two front contact surfaces 3 to respective plate 6, 
which occurs also in this embodiment preferably again with the aid of a 
contact adhesive that is applied either on front contact surfaces 3 of 
MELF components 1, and specifically preferably before these MELF 
components 1 reach work station 32, or are also applied on plates 6, and 
specifically preferably before the latter reach work station 32. The 
conductive adhesive here can be an adhesive that can harden by UV light. 
In this case, plates 6 have in their middle an opening 36 into which, by 
pressing plates 6 against contact surface 3 in each case [word or words 
missing]flows, so that in the area of each opening 36, but also on the 
periphery of front contact surfaces 3, adhesive areas 37 and 38 result 
between each plate 6 and MELF component 1 and the adhesive areas are 
exposed and can be hardened by the UV light. 
As soon as MELF components 1 located in work station 32 are connected to 
plates 6 of both support strips 33, i.e., by using a conductive adhesive 
after hardening of this adhesive, the suitable length is separated from 
each support strip 33. The blank thus obtained, which consists of two 
parallel lengths of support strips 33 with plates 6 provided on them and 
with MELF components 1 fastened on them, is then inserted into a mold in 
which MELF components 1 are embedded in the plastic compound or 
preferably, under pressure, the component bodies of individual components 
4b are molded. After this molding process, individual components 4b are 
separated from the two support strip lengths, and specifically in the 
embodiment represented by splitting bars 34. In the embodiment described 
above, in each work operation a multiplicity of components 4b are thus 
obtained simultaneously. Basically it is of course also possible that in 
each work operation in each case only one MELF component 1, is provided on 
both its front contact surfaces 3 with a plate 6 in each case and next the 
mold to incorporate MELF component 1 in the plastic compound and for 
formation of the component body of component 4b is fed. 
The invention was described above based on embodiments. Of course, other 
changes and modifications are possible without leaving the basic concept 
of the invention.