A vented, unitary sealing grommet for establishing a first liquid-tight interface between a ignition coil and a spark plug adapter tube and a second liquid-tight interface between the ignition coil and a valve cover includes a hollow main body portion having a substantially cylindrical shape with a longitudinal axis and including a pair of annular sealing ribs, a planar flange portion which is disposed within a geometric plane which is substantially perpendicular to the longitudinal axis, the main body portion being designed to fit between the ignition coil and the spark plug adapter tube such that the annular sealing ribs are compressed due to the interference fit. The planar flange portion is designed to fit between ignition coil and the valve cover. The vented capability is created in the sealing grommet by means of a pair of oppositely disposed vent channels defined by the inside surface of the main body portion and in cooperation therewith by means of a pair of oppositely disposed second vent channels defined by an upper surface of the planar flange portion, each vent channel defined by the main body portion is in flow communication with a corresponding vent channel defined by the upper surface. The main body portion includes two relief notches which serve to keep the vent channels in the main body portion open.

BACKGROUND OF THE INVENTION 
The present invention relates in general to spark-ignited gaseous fuel 
engine technology and a sealing accessory for the ignition coil and valve 
cover interface. More specifically the present invention relates to the 
use of a grommet to seal the ignition coil-to-valve cover interface as 
well as sealing the area between the ignition coil and a spark plug 
adapter tube. In a related embodiment of the present invention, the 
grommet is designed with a unique vented design to safely release the 
internal air pressure which builds up in the spark plug adapter tube 
during engine operation. 
Current engine technology, such as that associated with large, stationary 
gaseous fuel four-valve engines, may incorporate an ignition system which 
is typically described as a coil-on-plug or COP ignition system. In this 
type of engine and ignition system, as is believed to be well known to 
those of ordinary skill in the art, there is a spark plug, a spark plug 
adapter tube, an ignition coil, and a valve cover. FIG. 1 herein provides 
a cross sectional illustration of this ignition system and the primary 
components, all of which are believed to be known to one of ordinary skill 
in the art. In the interior space beneath the valve cover and around the 
spark plug adapter tube, there is lubricating oil which is jetted and 
splashed around during engine operation due to overhead lubrication. It is 
possible for this lubricating oil to flow or leak through the space 
between the spark plug adapter tube and the valve cover. If this occurs, 
it is possible for the oil to then back flow into the spark plug tube bore 
where it can cause ignition misfire and other service problems. 
It may have been contemplated in the past to wedge an O-ring between the 
valve cover and the spark plug adapter tube in order to block the flow or 
leakage of oil, but this creates its own problems. Another option might 
have been the use of a flat face seal on the coil, but this also generates 
certain problems. For example, once the ignition coil is removed, there is 
nothing on the valve cover to use to pull on or leverage in order to 
remove the cover. With the cover and the tube in effect anchored together 
due to the wedged O-ring, removal of the cover is made quite difficult. 
Removal of the valve cover would be required periodically in order to 
adjust valve lash. Accordingly, this becomes an efficiency and an ease of 
servicing issue as well as a sealing issue. It is desired to prevent the 
flow of oil into critical operating areas and whatever style of O-ring or 
grommet may be used, it needs to be an effective liquid sealer. If there 
is no sealed interface once the coil is removed, then the various 
components are not, in effect, locked together by having a seal or an 
O-ring wedged between them. It would therefore be an improvement to the 
O-ring designs which may have been tried by others to find a way to 
eliminate any O-rings without sacrificing the desired sealing between the 
spark plug adapter tube and the valve cover and, if needed, the sealing 
between the ignition coil and the spark plug adapter tube. 
There is a further concern to be addressed with virtually any type of 
sealing/O-ring arrangement for this engine application, even with the 
present invention, and this concerns the air pressure build up on the 
interior of the spark plug adapter tube due to the fixed volume of air 
which is trapped therein. This fixed volume of air is subjected to an 
elevated temperature during engine operation and accordingly the air is 
heated at a constant volume, generating a higher pressure. The tube 
interior volume is a sealed volume once the seals are installed for the 
prevention of oil leakage. Accordingly, there is initially a fixed mass of 
air inside the tube which is heated as the interior temperature rises. 
This heating of the fixed volume of air causes the interior air pressure 
to increase. Since large, stationary gaseous fuel engines of the type 
being discussed herein are typically serviced while still warm or hot, 
with only a brief cool down period, there is still an elevated interior 
pressure as the service technician begins working on the engine. As engine 
components are disassembled for servicing, specifically the ignition coil, 
there is a risk that the components used for sealing in order to prevent 
oil leakage will act like a cork on a champagne bottle. As the "cork" is 
dislodged, a loud "pop" sound is heard and this can be very unnerving to 
the service technician. 
Engines of the type being discussed herein are relatively large and a step 
ladder or some type of elevated platform is normally used by the service 
technician in order to climb up and get in position. The loud "pop" sound 
comes as a shock to the service technician and there is a concern that 
this individual may be distracted and lose his balance on the step ladder. 
The built-up pressure in the tube may also be large enough to partially 
eject the coil, like the cork on a bottle, and this presents another 
concern. If the interior pressure could be relieved or gradually vented in 
some fashion before any components are disassembled, then the loud "pop" 
sound would be prevented and there would not be the same level of risk of 
components, such as the ignition coil, being partially ejected. 
The present invention provides two improvements to the foregoing design 
problems and concerns. The first improvement relates to a way to eliminate 
any O-ring seals as previously discussed. The second improvement relates 
to a way to provide gradual venting of the interior volume. While each of 
these improvements are novel and unobvious individually, the present 
invention also contemplates the integration of both improvements into a 
single unitary component. 
SUMMARY OF THE INVENTION 
A unitary sealing grommet for establishing a first liquid-tight interface 
between a first component and a second component and a second liquid-tight 
interface between the first component and a third component according to 
one embodiment of the present invention comprises a hollow main body 
portion have a substantially cylindrical shape and a longitudinal axis and 
being constructed and arranged with a pair of annular sealing ribs, a 
substantially planar flange portion lying in a geometric plane which is 
substantially perpendicular to the longitudinal axis and the main body 
portion being constructed and arranged to fit between the first component 
and the second component such that the pair of annular sealing ribs are 
compressed due to an interference fit and the planar flange portion being 
constructed and arranged to fit between the first component and the third 
component. 
One object of the present invention is to provide an improved unitary 
sealing grommet. 
Related objects and advantages of the present invention will be apparent 
from the following description.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
For the purposes of promoting an understanding of the principles of the 
invention, reference will now be made to the embodiment illustrated in the 
drawings and specific language will be used to describe the same. It will 
nevertheless be understood that no limitation of the scope of the 
invention is thereby intended, such alterations and further modifications 
in the illustrated device, and such further applications of the principles 
of the invention as illustrated therein being contemplated as would 
normally occur to one skilled in the art to which the invention relates. 
Referring to FIG. 1 there is illustrated a stationary gas engine 20 which 
includes a valve cover 21, ignition coil 22, and spark plug adapter tube 
23. As illustrated, there is an annular clearance space 34 disposed 
between the outer, cylindrical surface 35 of the ignition coil 22 and the 
inner, cylindrical surface 36 of the adapter tube 23. There is also an 
annular clearance space 37 disposed between valve cover opening 38 and the 
outer cylindrical surface 39 of the adapter tube 23. The upper free end 40 
of the adapter tube 23 is spaced below the upper surface 41 of the valve 
cover 21. The adapter tube 23 is concentric with the cylindrical surface 
35. 
As discussed and explained in the Background, the interior volume 44 is 
subjected to overhead lubrication and there is jetted and splashed oil 
present which can flow through clearance space 37 and from there over end 
40 and into clearance space 34. In order to prevent the leakage of oil 
into clearance space 34, the use of an annular O-ring seal is contemplated 
as illustrated in FIG. 2. Any leakage of oil that does not flow over end 
40 may alternatively leak through the interface 45 between the upper 
surface 41 of the cover 21 and the underside surface 46 of the ignition 
coil head 47 which is securely attached by cap screws 48 to the cover 21. 
In order to prevent oil leakage through interface 45, the use of an 
O-ring, face seal, or gasket in clearance space 37 is contemplated (see 
FIG. 2). 
With reference to FIG. 2, O-ring seal 51 and O-ring seal 52 have been added 
to the FIG. 1 illustration. O-ring seal 51 is positioned in interface 45 
between the ignition coil head 47 and cover 21. A suitable O-ring channel 
51a is machined into the underside surface 46 of head 47 to capture the 
O-ring seal 51. O-ring seal 52 is positioned in clearance space 37. A 
suitable O-ring channel 52a is machined into the outer wall of tube 23 to 
capture the O-ring seal 52. One disadvantage of this possible or 
contemplated solution to the oil leakage concern is the use of two 
separate components and importantly the need to machine some type of 
O-ring channel in one of the two facing surfaces in order to receive and 
capture the corresponding O-ring as would be known in the art as a 
necessary step for preferred O-ring usage. In the event the valve cover 
needs to be removed for the servicing of some portion of the engine, such 
as adjusting valve lash, it is important that the valve cover 21 be easily 
removable. There is nothing present on the valve cover to grasp in order 
to pull on in order to remove it. If the cover 21 is secured to the 
adapter tube 23 by means of a wedged (compressed) O-ring seal, then 
removal of the valve cover 21 is not particularly easy and accordingly 
servicing is not as easy. 
With reference to FIG. 3, a first embodiment of the present invention is 
illustrated where the two O-ring seals 51 and 52 have been replaced by a 
one-piece (unitary) molded rubber grommet 55. There are actually two 
styles for grommet 55, a non-vented style, which is illustrated as grommet 
55a in FIGS. 4-6, and a vented style of grommet, which is illustrated in 
FIGS. 7-12 as grommet 55b. Each grommet, 55a and 55b, includes a radial 
flange portion 56 and 57, respectively, positioned at interface 45 and an 
integral, generally cylindrical body portion 58 and 59, respectively, 
which is positioned in annular clearance space 34. Each grommet is 
constructed out of a suitable material and arranged dimensionally for its 
body portion 58, 59, to be compressed between outer surface 35 and inner 
surface 36 and for its flange 56, 57 to be compressed between underside 
surface 46 and upper surface 41. Compression of the elastomeric material 
used for each grommet 55a and 55b establishes a liquid-tight seal suitable 
to prevent the flow of lubricating oil through interface 45 and through 
annular clearance space 34. The compression of the flange portion 56, 57 
is achieved by the tightening of cap screws 48, which tightening step 
draws ignition coil head 47 toward the upper surface 41 of valve cover 21. 
With reference to FIGS. 4-6, grommet 55a is illustrated in greater detail. 
Grommet 55a includes, in addition to radial flange portion 56 and 
cylindrical body portion 58, a hollow, cylindrical interior 62 and 
optional radiused relief notches 63 and 64 in the flange portion. A pair 
of spaced-apart annular sealing ribs 60 and 61 are molded as part of the 
flange portion 56. A second pair of spaced-apart annular sealing ribs 65 
and 66 are molded as part of the body portion 58. Body portion 58 has a 
centerline axis and flange portion 56 (except for ribs 60 and 61) is 
planar and is in a geometric plane which is perpendicular to the 
centerline axis of the body portion. Annular sealing ribs 60 and 61 (and 
likewise ribs 65 and 66) are spaced apart from one another by 
approximately 4.0-5.0 mm and extend, on a side, approximately 1.0-1.2 mm 
beyond the corresponding base surface. Ribs 65 and 66, which extend beyond 
outer surface 67, are the portions of grommet 55a which are compressed in 
order to establish a liquid-tight seal in clearance space 34 between the 
outer surface 35 of ignition coil 22 and the inner surface 36 of adapter 
tube 23. Compression of ribs 65 and 66 is due to the interference fit 
within clearance space 34. As would be understood, the use of additional 
ribs is contemplated. A minimum of two ribs provides a primary seal as 
well as a back up or secondary seal. 
Flange portion 56 is substantially flat and of substantially uniform 
thickness, except for ribs 60 and 61 which extend beyond lower surface 69. 
It is to be noted that the defining upper and lower surfaces 68 and 69 of 
flange portion 56 are each substantially flat and substantially parallel 
to each other. An annular radiused bend 70 in cooperation with fillet 
radius 71 connects the flange portion 56 and the body portion 58. Ribs 60 
and 61 are sealingly compressed by the tightening of bolts 48 which 
secures the head 47 to the cover 21. 
With reference to FIGS. 7-12, grommet 55b is illustrated in greater detail. 
Grommet 55b is similar in many respects to grommet 55a, the primary 
difference being the addition (incorporation) of a venting feature into 
grommet 55b which is not part of grommet 55a. As such, grommet 55a is a 
non-vented grommet and grommet 55b is a vented grommet. Both grommet 
styles are suitable for use as an improvement and as a replacement to the 
two O-ring possibilities illustrated in FIG. 2. 
Grommet 55b includes, in addition to radial flange portion 57 and 
cylindrical body portion 59, a hollow, cylindrical interior 73, optional 
radiused relief notches 74 and 75, and annular sealing ribs 76 and 77. 
Body portion 59 has a centerline axis and flange portion 57 (with the 
exception of sealing ribs 88 and 89) is planar and in a geometric plane 
which is perpendicular to the centerline axis of the body portion. Annular 
sealing ribs 76 and 77 are spaced apart by approximately 5.0 mm and 
extend, on a side, approximately 1.15 mm beyond the outer surface 78 of 
body portion 59. Ribs 76 and 77 are the portions of grommet 55b which are 
compressed in order to establish a liquid-tight seal in clearance space 34 
between the outer surface 35 of ignition coil 22 and the inner surface 36 
of adapter tube 23. Compression of ribs 76 and 77 is due to the 
interference fit within clearance space 34. As would be understood, the 
use of additional ribs is contemplated. A minimum of two ribs provides a 
primary seal as well as a back up or secondary seal. 
Flange portion 57 is defined by upper and lower surfaces 79 and 80 which 
are substantially flat and parallel to each other with the exception of 
the vent channels and sealing ribs which are disclosed hereinafter. An 
annular radiused bend 81 in cooperation with fillet radius 82 connects the 
flange portion 57 and the body portion 59. In order to incorporate a 
venting feature capability into grommet 55b, a pair of aligned, radial 
vent channels 84 and 85 are formed into the upper surface 79 of flange 
portion 57. Each vent channel 84 and 85 extends from the hollow interior 
73 to the outer peripheral edge of portion 57 which coincides with the 
base or inner edge 86 and 87 of the corresponding optional relief notch, 
74 and 75, respectively. Vent channel 84 extends to edge 86 of relief 
notch 74. Vent channel 85 extends to edge 87 of relief notch 75. In the 
FIG. 10 illustration, material has been added to the top surface of flange 
57 in the form of raised or ramp portions 85a and 85b which are on 
opposite sides of vent channel 85. The same configuration is present with 
regard to vent channel 84. The added material provided by portions 85a and 
85b is adjacent to vent channel 85 and concentrates the sealing load by 
pushing material into the vicinity of vent channel 85. This effectively 
fills in part of the vent channel void and adds to the amount of 
compression which is achieved. This helps to ensure a complete and 
liquid-tight seal. 
The cross sectional (lateral) geometry of vent channel 85 is illustrated in 
FIG. 10. It is to be understood that the shape and geometry of vent 
channel 84 is virtually identical to that of vent channel 85. While two 
vent channels are illustrated, one vent channel as well as more than two 
vent channels could be used. The advantage of two or more is that you at 
least have one vent channel open if one becomes plugged. The channel depth 
below upper surface 79 is approximately 0.7 mm and the channel width is 
approximately 2.0 mm. As part of the present invention of FIG. 7, a pair 
of spaced-apart, annular sealing ribs 88 and 89 are molded into and are 
part of the lower surface 80 of flange portion 57. The details of sealing 
ribs 88 and 89 are illustrated in FIG. 11. Each rib 88 and 89, like ribs 
76 and 77, has a curved or rounded shape in lateral cross section. The two 
ribs 88 and 89 are spaced apart from one another approximately 4.0 mm 
between their corresponding centerlines. The raised height of each rib 88 
and 89 is approximately 1.0 mm. 
In order for the venting capability to be complete, vent channels 92 and 93 
are molded into the inner cylindrical surface 94 of body portion 59. Vent 
channels 92 and 93 are virtually identical in size, shape, and geometry to 
each other and the details of vent channel 93 are illustrated in lateral 
cross section in FIG. 12. Vent channel 93 is recessed (molded) down into 
the inner cylindrical surface 94 a dimension of approximately 0.15 mm and 
has a width dimension of approximately 2.0 mm. Each vent channel 92 and 93 
extends the full length of body portion 59 and each one is in flow 
communication with its corresponding vent channel 84 and 85, respectively. 
This establishes a pair of continuous vent paths from the lower end of the 
body portion to the outer peripheral edge of the flange portion. The two 
vent channels 84 and 85 are positioned opposite to each other 180 degrees 
apart as are vent channels 92 and 93. 
The lowermost edge 96 of body portion 59 includes a pair of relief notches 
97 and 98. Relief notch 97 is aligned with and in flow communication with 
vent channel 92. Relief notch 98, which is 180 degrees apart from relief 
notch 97, is aligned with and in flow communication with vent channel 93. 
Relief notches 97 and 98 ensure that the vent channels 92 and 93 remain 
open. In a typical construction the ignition coil has a retainer ring 
around its cylindrical body. The lowermost edge 96 of body portion 59 
rests against the retainer ring. Without relief notches 97 and 98, the 
vent channels 92 and 93 could be sealed closed by tight contact with the 
retainer ring. 
When grommet 55b is installed where grommet 55 is illustrated in FIG. 3, 
ribs 76 and 77 are compressed slightly so as to establish a liquid-tight 
seal across clearance space 34. The vent channels 92 and 93 remain open as 
it is only ribs 76 and 77 which are sealingly compressed due to the 
interference fit. 
Ribs 88 and 89 rest against the upper surface 41 of cover 21 and as the 
ignition coil is installed and the cap screws 48 tightened, head 47 draws 
down on flange portion 57, clamping flange portion 57 in position. 
Initially the two ribs 88 and 89 are compressed so as to establish a 
liquid-tight seal across interface 45 between the head portion of the 
ignition coil and the valve cover. As the two ribs 88 and 89 begin to be 
compressed, vent channels 84 and 85 are still open and thus venting to the 
atmosphere from the interior of adapter tube 23 is still possible. As the 
cap screws 48 are continued to be tightened, the flange portion is 
compressed to a greater degree and, accordingly, becomes dimensionally 
thinner. In time, and with the continued tightening of the cap screws, the 
flange portion is compressed to a degree that the two radial vent channels 
84 and 85 close in such that the open, flow through interior of each 
channel disappears. The result is a fluid-tight interface between the 
ignition coil head and the cover by means of the flange portion of grommet 
55b. A sealed chamber is created in the adapter tube and pressure build up 
is then possible as previously explained, due to the air trapped within 
this sealed volume and due to the elevated operating temperature which is 
generated. 
When it is time to service the engine, one of the first steps to be 
performed is to gradually loosen the cap screws 48 on the ignition coil 
head. As this occurs, the distance between the head and the cover 
increases and the flange portion 57 is able to resiliently expand from its 
compressed state or gradually recover its original shape due to the 
elastomeric properties of the material used for grommet 55b. As the flange 
portion gradually expands, there will come a time that the two vent 
channels 84 and 85 start to reappear. As soon as a vent opening is created 
by way of channels 84 and 85, the air inside the tube has an escape path 
to the atmosphere. This allows the gradual release of the air pressure 
without the alarming "pop" sound. 
While the invention has been illustrated and described in detail in the 
drawings and foregoing description, the same is to be considered as 
illustrative and not restrictive in character, it being understood that 
only the preferred embodiment has been shown and described and that all 
changes and modifications that come within the spirit of the invention are 
desired to be protected.