Distributor cap

A distributor cap for an internal combustion engine ignition distributor. The distributor cap is comprised of a cap member formed of insulating material that has terminals located at the outer periphery of the cap member that are adapted to be connected to ignition cables. The cap member has a laterally extending wall. A plurality of electrodes are carried by the wall and extend through the wall. End portions of the electrodes are located inside the wall and are adapted to cooperate with a distributor rotor. A respective terminal is electrically connected to a respective electrode by a conductive ink trace that is bonded to an outer surface of the wall.

This invention relates to a distributor cap for internal combustion engine 
ignition distributors. 
Distributor caps for ignition distributors that have terminals that extend 
radially of the cap are known, examples being the distributor caps shown 
in the United States patents to Morgan et al. U.S. Pat. No. 3,591,736 and 
to Arima et al. U.S. Pat. No. 4,897,514. 
The distributor cap of this invention, like the above-referenced patents, 
has terminals that have portions that extend radially of the cap. However, 
unlike the distributor cap of the above-referenced patents, the 
distributor cap of this invention utilizes conductive ink traces to 
electrically connect terminals, that are adapted to be connected to 
ignition cables, with the inserts or electrodes of the distributor cap 
that cooperate with a distributor rotor. 
It, accordingly, is one of the objects of this invention to provide an 
ignition distributor cap that utilizes conductive ink traces to 
electrically connect terminals, that are adapted to be connected with 
ignition cables, with the inserts or electrodes of the cap that cooperate 
with the distributor rotor. 
Another object of this invention is to provide a distributor cap that has a 
laterally extending wall and wherein the ink traces are bonded to an outer 
surface of the wall. The inserts or electrodes are carried by the wall and 
extend through the wall. The terminals are carried by the cap and have end 
surfaces located adjacent the outer surface of the wall. Portions of the 
ink traces are bonded to the end surfaces of the terminals and to end 
surfaces of the inserts or electrodes. The ink traces may be covered by a 
potting compound or by a cover formed of insulating material.

Referring now to the drawings, and more particularly to FIGS. 1 and 2, the 
distributor cap 10 of this invention has a cap member 12. Cap member 12 is 
a molded plastic part and it has nine tubular housing parts 14-30. Cap 
member 12 can be formed of a 30-35% glass filled moldable thermoplastic 
polyester material such as a material sold under the trade name "RYNITE 
935" by E. I. DuPont de Nemours & Co. The cap member 12 further has a 
laterally extending wall 32 that has opposed flat surfaces 32A and 32B. 
The cap member 12 also has an axially extending outer peripheral wall 34. 
Tubular portions 14-30 extend radially, and as will be more fully 
described hereinafter, are adapted to accommodate ignition cables. 
The wall 32 carries a plurality of metallic electrodes or inserts each 
designated as 36. The electrodes 36 may be formed of aluminum. Since the 
distributor cap is for an eight cylinder engine, there are eight 
electrodes 36 located on an imaginary circle, as shown in FIG. 1. These 
electrodes are all molded into wall 32 and extend through wall 32. The 
electrodes 36 have a circular cross section and have opposed flat end 
surfaces 36A and 36B. End surface 36A is substantially flush with surface 
32A of wall 32. End surfaces 36B are located inside of cap member 12. The 
conductive insert of a distributor rotor (not illustrated) swings past end 
surfaces 36B when the distributor cap is in use on a distributor. 
The cap member 12 further carries nine L-shaped metallic terminals each 
designated as 38 which are molded into the plastic material of cap member 
12. Terminals 38 may be formed of zinc. Only one terminal 38 has been 
illustrated, since the other eight terminals are the same as the one 
illustrated. The terminal 38 that has been illustrated is shown associated 
with tubular housing portion 16. Thus, as shown in FIGS. 2 and 3, the 
terminal 38 has a male terminal portion 38A that projects into tubular 
housing portion 16. Terminal 38 further has a surface 38B that is bonded 
to and therefore electrically connected to a conductive ink trace 40 in a 
manner that will be more fully described hereinafer. Surface 38B of 
terminal 38 is substantially flush with surface 32A of wall 32. Tubular 
housing portion 14 and portions 18-30 each have an L-shaped connector 38. 
Wall 32 of cap member 12 carries a center contact assembly comprised of 
metallic insert 42 and a spherical carbon ball 45 that is carried by 
insert 42. Insert 42 can be formed of aluminum and it has a flat surface 
42A that is substantially flush with surface 32A of wall 32. The ball 45 
is adapted to engage the conductive metallic spring portion of a 
distributor rotor. The flat surface 42A is connected to a conductive ink 
trace as is described more fully hereinafter. 
The various terminals and electrodes that have been described are 
electrically connected by conductive ink traces in a manner that will now 
be described. As an example of the ink trace connections, it can be seen 
that ink trace 40 electrically connects a terminal 38 associated with 
tubular housing portion 16 to an electrode or insert 36. The ink trace 40 
is bonded to surface 32A of wall 32 and the ends of ink trace 40 are 
bonded respectively to surface 38B of terminal 38 and surface 36A of an 
electrode or insert 36 to thereby electrically connect the ends of trace 
40 to terminal 38 and an insert 36. As previously pointed out, surfaces 
38B and 36A are substantially flush with surface 32A of wall 32. 
Ink trace 44 electrically connects the terminal 38 associated with housing 
portion 14 to insert 42. Ink traces 46-58 respectively connect a terminal 
38 to an insert 36. The ink traces 44-58 are all bonded to surface 32A and 
they all are bonded to ends of the respective terminals 38 and electrode 
36 in the same manner that has been described in regard to the connection 
of ink trace 40 to surfaces 38B and 36A. It is noted that surface 42A of 
center insert 42 is substantially flush with surface 32A and surface 42A 
is bonded to an end portion of trace 44. 
In the manufacture of the distributor cap that has been described, the 
electrodes 36 and terminals 38 and insert 42 are molded to the plastic 
material of the cap member 12. The ink traces are then applied to surface 
32A and over the end surfaces of electrodes 36 and terminals 38 and over 
the end surface of insert 42 to make electrical connections to these 
parts. 
After the ink traces have been applied, a plastic potting compound 60, 
formed of electrical insulating material is applied over the conductive 
traces. The potting compound 60 completely fills the cavity defined by 
marginal wall 62 and surface 32A. The potting compound engages and is 
bonded to surface 32A and engages and covers the ink traces. The potting 
compound 60 serves to electrically insulate the traces from each other and 
forms an end wall for the cap. Potting compound 60 further operates as a 
high voltage insulator and as a hermetic seal to prevent moisture 
intrusion into the high voltage conducting parts. The potting compound 60 
can be comprised of an epoxy resin and a curing agent with an inert 
filler. 
The cap that has been described is adapted to be secured to a distributor. 
The distributor shaft drives a rotor (not illustrated) which has a spring 
contact that engages ball 45. The conductive insert of the rotor swings 
past the ends 36B of the inserts 36. 
In use, the terminals 38 associated with tubular housing portions 16-30 are 
connected respectively to spark plugs on the engine. The terminal 38 
associated with tubular housing portion 14 is connected to the secondary 
winding of an ignition coil. 
FIGS. 5 and 6 illustrate a modified distributor cap made in accordance with 
this invention. The same reference numerals have been used in FIGS. 5 and 
6 as were used in FIGS. 1-4 to identify corresponding parts. 
The pattern of the conductive ink traces in FIGS. 5 and 6 is somewhat 
different than the pattern of ink traces shown in FIG. 1. The primary 
difference, however, between the cap of FIGS. 5 and 6 and the cap of FIGS. 
1-4 is that in the cap of FIGS. 5 and 6 a lid or cover 66 that is formed 
of a molded plastic insulating material is used instead of the potting 
compound 60. Further in the cap of FIGS. 5 and 6, the conductive ink 
traces are insulated from each other by divider ribs that extend axially 
from surface 32A. Some of the divider ribs have been designated by 
reference numerals, namely ribs 68, 70 and 72. It can be seen that the 
pattern of ribs together with wall 62 serve to insulate each conductive 
trace from an adjacent conductive trace. 
The upper surfaces of the ribs and the upper surface of wall 62 are welded 
to plastic lid or cover 66. The lid or cover 62 prevents the high voltage 
on the traces from arcing to ground and also provides a hermetic seal to 
prevent moisture intrusion into the high voltage conducting parts. 
The conductive ink that is used for the traces can take various forms as 
long as it can be applied in a liquid form and which after being applied 
cures to a solid form that is bonded to surface 32A and to connector 
surfaces of the various terminals and inserts. The conductive ink can take 
the form of an ink composition containing a finely divided metal powder 
such as particles of silver, a curable polymer and a solvent or thinner. 
One material that may be utilized is a thick film material type 4922N 
available from the Electronics Department of E. I. DuPont de Nemours & Co. 
This material is about 60% by weight silver metallic particles and uses an 
acrylic resin as a binder. After this material is applied to form the 
traces, the material can be cured at a temperature of about 200.degree. F. 
The metallic particles are carried by the resin binder and the binder is 
bonded to the surface 32A. 
As has been described, the ink traces are applied directly to flat surface 
32A in a predetermined pattern. This is accomplished by use of a suitable 
applicator like a hypodermic needle which can be moved by a robot to apply 
a predetermined trace pattern to flat surface 32A. The ink traces may be 
about 1 mm. wide.