Process for manufacturing an air flow valve

A process for manufacturing an air flow throttle valve assembly in which the valve disc or blade is precisely sized and centered after assembly to the shaft and throttle body by heating and squeezing of the disc, preferably while the shaft is held at a shallow angle to extrude the perimeter slightly out to the bore wall. After cooling, the shaft angle is reset to a slightly greater angle.

BACKGROUND OF THE INVENTION 
This invention concerns techniques for manufacturing assemblies of molded 
parts. 
Recent trends particularly in the auto industry have been to manufacture 
many parts from molded plastics in order to reduce weight and costs. The 
engine air intake system is one example in which the intake manifold and 
air induction ducts and air flow throttle valve are now commonly 
constructed of molded parts, whereas formerly those parts were constructed 
of cast and machined metal. 
This trend is continuing and as a further development, efforts are being 
made to mold complete assemblies as of the air flow throttle body and the 
intake manifold as one molded part. 
Air flow valves include a flow control blade or disc fit into a bore in the 
throttle housing body defining the air flow passage. The disc is pivoted 
on a shaft to open and close the flow passage, and must fit accurately to 
be able to rotate between a closed position allowing a low flow of air and 
open positions. With machined or stamped metal parts, a sufficiently 
accurate fit has been obtained by a technique of centering the disc at 
assembly. 
The centering of the disc within the bore has in the past been accomplished 
during assembly by rotating the disc to a closed position to center the 
disc in the bore, and then fixedly attaching it to the mounting shaft as 
with screws or by a staking operation. 
However, where the valve body and the valve disc are both molded, a 
difficult manufacturing problem is encountered due to the close tolerances 
required for a proper fit. 
Precision molding techniques have been developed for this purpose, but are 
only marginally economic. 
Advances in plastic molding technology have included techniques for molding 
assemblies including moving parts. In U.S. Pat. Nos. 5,421,718 and 
5,304,336 there is described a process for molding the movable valve disc 
inside the valve body, using the throttle body bore to size the disc. 
A complex mold configuration is required involving movable inserts, etc., 
as well as multistaged molding steps. 
The efforts to achieve an integrated molded manifold and air flow throttle 
body have involved quite complex mold configurations, such that it does 
not appear feasible to also mold the disc into the air flow valve body at 
the same time that the manifold and throttle body are molded. 
It is the object of the present invention to provide a manufacturing 
process for molding an accurately fitted valve disc of an air flow valve 
which can be carried out without a complex mold configuration such as to 
be able to be applied to the manufacture of integrated manifold and 
throttle body components. 
SUMMARY OF THE INVENTION 
This object is achieved by a process in which the valve disc is separately 
made as by molding to a size less than the final size such that it can be 
fit into the throttle body bore with a clearance space. 
The disc is then assembled onto the mounting shaft and within the throttle 
body bore. The shaft is then positioned so that the disc is at a small 
angle from the fully closed position within the bore. 
The disc is of a deformable material so as to able to be resized by being 
subjected to a secondary reshaping operation in which a tool is inserted 
into each end of the air flow valve from each end to engage the opposite 
faces of the disc to squeeze the disc and cause outward flow of material. 
Heat energy is applied to cause the disc perimeter to be heated while 
pressure is exerted on opposite radial faces of the disc by the tools, 
extruding the disc material out into contact with the surrounding bore 
walls. 
After cooling and removal of the tools, the shaft angle is adjusted to set 
a fully closed position inclined a few degrees greater than the thermoform 
press fitting position of the disc. 
The disc is accurately sized and centered with respect to the bore with a 
slight chamfer about its peripheral edge for accommodating its slightly 
angled closed position. 
No increased complexity of the mold is required to mold the air flow valve 
throttle body and/or an integrated manifold-throttle body.

DETAILED DESCRIPTION 
In the following detailed description, certain specific terminology will be 
employed for the sake of clarity and a particular embodiment described in 
accordance with the requirements of 35 USC 112, but it is to be understood 
that the same is not intended to be limiting and should not be so 
construed inasmuch as the invention is capable of taking many forms and 
variations within the scope of the appended claims. 
FIG. 1 sets out the steps of the process according to the invention. 
According to this concept, the parts including the housing throttle body 
10 (FIG. 2), the support shaft 12, and disc or blade 14 are molded 
separately using conventional techniques, the disc being molded to be 
substantially undersized from the size of the bore 16 in the 25 throttle 
body 10. 
The shaft 12 is then assembled to the throttle body housing 10 (with 
bearings 18) and the disc 14 is then assembled to the shaft 12 with the 
shaft 12 at a low angle, i.e., 60 after being centered by touching the 
bore 16 at an outermost point. The disc is preferably fixedly attached at 
this time by heat staking plug bosses 15 (FIGS. 6 and 7). The details of a 
preferred heat staked connection are set forth in copending allowed 
application U.S. Ser. No. 08/596,017, filed Feb. 6, 1997, now U.S. Pat. 
No. 5,666,988 issued Sep. 16, 1997, assigned to the same assignee as the 
present application. 
As seen in FIGS. 6 and 7, the bosses 15 extend through respective chamfered 
holes 21 when the disc 12 is laid onto a flat surface 13 formed into the 
shaft 12. 
Prior to staking, there is a clearance between the bosses 1 5 and the walls 
of the holes 21 to allow shifting of the disc to be centered. After 
staking, as with an ultrasonic tool, the staked bosses 15A fixedly attach 
the disc 14 to the shaft 12. 
Next, the blade or disc 14 is finally sized by being thermoformed while in 
this position, causing the disc material to be forced outwardly or 
extruded into contact with the bore wall to be precisely sized and 
centered within the bore 16. 
Alternatively, the disc 14 can be left loosely assembled to the shaft 12 
during the final sizing operation by leaving the bosses 15 unstaked. The 
shaft 12 is thereafter rotated in the closing direction to center the disc 
15 in the bore 16, the plugs 15 thereafter heat staked to fixedly attach 
the disc 14 to the shaft 12. 
The disc material can be of a lower melting point material than that of the 
throttle body housing 10 so as to prevent sticking. For example, Nylon 6 
could be used for the disc, Nylon 66 for the body 10. 
After cooling, the shaft closed angle is set at a slightly greater angle to 
allow idle air allow, the slight perimeter chamfer formed during the 
thermoforming operation allowing a slight open angle. 
FIG. 3 shows in simplified form an apparatus for carrying out the 
thermoforming of the disc 14. 
The apparatus includes a fixed support 20 inserted into the bore 16 from 
below the disc 14, and a movable piston 22 inserted from above, after 
lowering the throttle body 10 so as to position the underside. 
The support 20 and piston 22 are adapted to be heated as by the flow of 
heated fluid from a source 24, 26 into cavities 28, 30 (or by an 
electrical heater coil disposed therein). 
The piston 22 is able to be advanced as by an actuator 32 during operation. 
The support 20 has an inclined upper surface 34 relieved at 36 to 
accommodate the shaft 12, and initially the underside of the disc 14 rests 
on the surface 34 as the throttle body housing 10 is lowered onto the 
support 20. 
The piston 22 has a corresponding inclined surface 38 relieved at 40 to 
accommodate the shaft 12. The piston 22 is advanced to engage the disc 14 
and exert a squeezing pressure on the upper surface of the disc 14. 
Heat conducted from the piston 22 and support 20 causes the material of the 
disc 114 to be slightly extruded radially outwardly as shown in FIG. 4 
until it engages the wall of the bore 16. This may create a slight annular 
bulge at the perimeter of the disc 14. 
Detection of the slightly increased resistance to movement of the piston 22 
can be used as a control signal to discontinue the piston advance at this 
stage. 
The support 20 and piston 22 are then allowed to cool, which may be speeded 
by active cooling prior to withdrawal of the piston 22 and removal of the 
assembly from the support 20. 
Finally, the shaft stop is adjusted to establish a closed position slightly 
more inclined to have a slight opening about its perimeter, as indicated 
in FIG. 5. 
FIGS. 8 and 9 show details of a refined version of the support 20A, which 
has narrow curving segments 42A, 42, either semi-circular or 
semi-elliptical in shape, corresponding to the disc shape. The segments 
42A, 42B are affixed on either side of a relieved area 36A to create a 
raised area recessed in from the outer perimeter of the support 20A. The 
ring segments 42A, 42B concentrate the extruding pressure in a narrow 
annular area adjacent the outer perimeter of the disc 14. 
An outer heat insulating jacket 44 may also be provided. 
A suitably configured inner cavity 46 may also be provided to provide a 
proper rate of cool down after each forming cycle. 
Alternate ways of heating the disc 14 can be employed, such as by using one 
or more laser sources 48 shown in FIG. 10, which generate laser beams 
passing through piston 22B and support 20B, which are made of a material 
transparent to the particular laser beam frequency for this purpose to 
impinge and heat the outer perimeter of the disc 114. This causes 
appropriate heating of the disc 14 to cause softening sufficient to carry 
out the extruding process described. 
Ultrasonic energy may alternatively be utilized for carrying out the 
heating process.