Solenoid winding case and protective overmold and method of making

A solenoid winding and housing for use with an armature actuated fuel poppet valve and the process of applying interior and external annular plastic shields on and in the housing to seal against moisture and fuel and to provide joint and weld protection. A prong housing for the solenoid winding ends is molded along with the exterior molded shields. Noise insulation as well as protection of parts is provided with the molded shields.

FIELD OF INVENTION 
Delivery of fuel to internal combustion engines, in particular, delivery of 
a fuel and air mixture directly to operating pistons using a solenoid 
actuated poppet valve suitably timed for proper combustion. 
BACKGROUND AND FEATURES OF THE INVENTION 
Much development work has been done in connection with delivery fuel to 
internal combustion engines, in particular in recent years, the delivery 
of combustible fuel and gas, especially air, in metered quantities. Much 
of the work has centered around the delivery of a fuel mixture to 
two-cycle, spark ignition engines. U.S. Pat. No. 4,693,224 (Sep. 15, 1987) 
and U.S. Pat. No. 4,825,828 (May 2, 1989) illustrate and describe the 
problems of fuel injection and the advantages of direct in-cylinder 
injection which is effective in operation, economic to manufacture and 
achieves and maintains acceptable atomization of the fuel. 
The present invention is specifically directed to spark ignited, internal 
combustion engines where a premetered quantity of fuel is entrained in a 
gas, conveniently air, and the fuel entrained in the gas is delivered 
directly into the combustion chamber of the engine through a nozzle which 
is intermittently opened. This is achieved by the use of a poppet valve 
which is controlled and moved axially to open and closed positions using 
an electromagnetic coil and an armature closely associated with the poppet 
valve. Each cylinder, in a multi-cylinder engine, is provided with a fuel 
and air nozzle injection assembly. 
The present invention is directed to the construction of the solenoid which 
is used to actuate the poppet valve. The solenoid bobbin assembly is 
housed in a case and cover. It is known to mold plastic simultaneously 
externally and internally of the solenoid assembly and some of the 
problems in connection with this involve the pressure and heat needed. 
This may result in winding bobbin distortion which may cause seal 
failures. Another problem lies in the possibility of plastic resin flowing 
to areas where it cannot be tolerated or allowing fuel leakage past the 
seals to the outside of the injector. 
Other manufacturers of fuel injectors have used injection molding into the 
solenoid assembly by leaving an end of the solenoid open so that when 
inserted into the mold, the mold can be used as a back-up for the bobbin 
to prevent distortion and to prevent mold material from flowing into areas 
where it cannot be tolerated. 
The present invention is directed to a combination of an internal and 
external molding process which is accomplished without any internal mold 
support for the solenoid bobbin assembly. With the proposed process, 
damage to critical areas of the solenoid case and cover is avoided by 
eliminating the use of a support mandrel. 
Other objects and features of the invention will be apparent in the 
following description and claims in which the principles of the invention 
are set forth together with details to enable persons skilled in the art 
to practice the invention, all in connection with the best mode presently 
contemplated for the invention. 
BRIEF DESCRIPTION OF THE INVENTION 
The invention consists of the process of internal and external injection 
molding and the resulting structure in regard to a solenoid bobbin 
assembly and housing to provide external surround walls outside a solenoid 
case and also internal plastic walls which enclose the outside of a bobbin 
assembly while at the same time creating a plug extension housing for 
electrical prongs to conduct energy to the solenoid winding. The external 
walls protect the weld joints between a solenoid case and cover from 
oxidizing. The internal walls outside the bobbin assembly protect the 
winding from water intrusion and provide insulation as well as a sound 
barrier for a poppet valve in the housing.

DETAILED DESCRIPTION OF THE INVENTION AND THE MAKING AND THE MANNER AND 
PROCESS OF USING IT 
In FIGS. 1 and 3, details of the solenoid assembly are illustrated. A 
cup-like case 20 has an upper outer flange 22 and a bottom projecting 
collar 24. This collar fits into the head of the engine. A solenoid 
winding bobbin has an upper land 26 and a lower land 28 connected by a 
cylindrical core 30 having a central passage 32. Each land 26 and 28 has 
an O-ring groove for O-rings 34 and 36. O-ring 36 is in a groove 38 which 
has annular container ridges 40 and 42. O-ring 34 fits in a groove 44 
which has containment ridges 46 and 48. Each land 26 and 28 has three tabs 
projecting outward at circumferentially spaced locations 54 (FIGS. 2 and 
4A). The tabs 54 centrally locate and create an interference fit of the 
solenoid bobbin assembly 84 in case 20. A solenoid cover 50 has an outside 
dropped flange 52 which is stitch welded to the flange 22 of the case at 
circumferentially spaced locations as shown in FIG. 3 at 60. A sectional 
view on line 3A--3A of FIG. 3 shows a weld 60. These spaced welds 60 allow 
the escape of air between the welds when a molding process is proceeding. 
The solenoid cover 50 has also a central neck portion 62 rising from a 
reverse fold 64 in the central cover. Thus, the collar 24, the core 
opening 32 and the neck 62 provide a cylindrical passage 66 through the 
solenoid in which is located a fuel poppet valve (not shown). 
At one side of the bobbin 26,28,30, projecting through a window 69 in the 
side of case 20, is a projection 70 carrying connector pins 72,74. As 
shown in FIGS. 4, 4A and 5, the ends 80,82 of a solenoid wire winding 84 
on the bobbin 26,28,30 are illustrated as wound around lugs 86,88, 
respectively, at the root of the connector pins 72,74. These elements make 
up the solenoid bobbin assembly. 
Now that the various elements of the solenoid assembly are described, we 
turn to the molding process which is called "overmold". It consists of 
placing the assembled solenoid into an outer enclosing mold which has a 
top mold 90 and a bottom mold 92 as shown in FIGS. 6 and 7. The top mold 
90 has a spring-loaded top shut-off plunger 94 backed by a coil spring 96. 
This plunger bears against the outer flange 52 of solenoid cover 50. The 
lower mold 92 has ejector pins 98 and a circumferential bottom shut-off 
fit at 106. The parting line for the molds is at 100. 
On the right side of the combined molds are opposed recesses 102 in the top 
mold 90 and 104 in the bottom mold 92 which together provide a mold recess 
to shape the projection 110 (FIG. 8) on the side of the finished product. 
Into the recess is projected a core insert 112, on a slide mount 114, 
which will be positioned between the mold parts 90 and 92 during the 
molding process. 
In FIGS. 6 and 7, a mold gate opening 120 is provided in mold part 92 which 
has continuity to a window access 122 at window 69 which allows plastic 
resin to flow around the bobbin assembly of the solenoid winding. The 
illustration in FIG. 6 shows the solenoid assembly within the mold parts 
90 and 92, and the core 112 in position for the injection mold process. 
With the parts as shown in FIG. 6, a pressurized injection of a flowable 
plastic resin is introduced through the gate area 120 and the window area 
122. This injection is done very rapidly and the material flows under 
pressure into all accessible spaces inside and outside the solenoid 
assembly. In FIG. 7, the cross-hatching which is angling up and to the 
left indicates the plastic resin in the completed overmold process. 
After the mold injection is completed, the core 112 and the slide mount 114 
are pulled from the right side of the mold, and the molds 90 and 92 
parted. The ejector pins 98 are actuated and the completed part is 
removed. With reference to FIGS. 7 and 8, the completed part shows an 
outer band of plastic 140 molded integrally with the connection socket 
110. Inside the wall of the case 20 is a ring of plastic 142 which may 
extend, in part, up to and down to the O-rings 36 and 34. However, the 
O-rings block any passage of the plastic to the passage 66 inside of the 
solenoid bobbin assembly. The plastic flows around the bobbin assembly and 
is blocked on each side of the interior by the O-rings. The interior 
plastic ring 142 is integrally merged with plug extension 110 at the 
window area 69 and joining portion at 122 (FIG. 6). Thus, the extension 
110 containing the contact prongs 72,74 is rigidly secured and locked to 
the solenoid case 20 by the bottom and side edges of the window 69. 
As previously indicated, air in the assembly will be forced out of the case 
during the plastic injection through gaps between the stitch welds 60 
around the solenoid case 20 and cover 50. The internal plastic 142 serves 
as an insulation and moisture seal as well as a sound barrier. The outer 
annular sheath 140 seals and covers the joint between the solenoid case 20 
and the cover 50 and protects against oxidation, provides a moisture seal, 
and aids in strengthening the extension 110. 
It will be see that this interior and external plastic mold process is 
accomplished without any internal mandrel and thus the surfaces within the 
neck 62, the bobbin passage 30 and the collar 24 are not subject to damage 
in the molding process.