U.S. patent application number 10/289892 was filed with the patent office on 2004-05-13 for variable injection rate high pressure fuel pump.
Invention is credited to Goetzke, Michael Barry, Gottemoller, Paul, Poola, Ramesh B., Tupek, Richard Wayne.
Application Number | 20040091367 10/289892 |
Document ID | / |
Family ID | 32107644 |
Filed Date | 2004-05-13 |
United States Patent
Application |
20040091367 |
Kind Code |
A1 |
Gottemoller, Paul ; et
al. |
May 13, 2004 |
VARIABLE INJECTION RATE HIGH PRESSURE FUEL PUMP
Abstract
A high pressure fuel pump having a variable fuel injection rate,
including a pump body, a pump cylinder formed in the pump body and
a piston reciprocable within the pump cylinder, which defines a
pressurization chamber. The pump piston has a reduced diameter
portion which provides a primary piston. A piston annulus is
slidably mounted thereon and provides a secondary piston. An
annular actuation chamber adjoins the secondary piston opposite the
pressurization chamber. An actuation passage is provided between a
return fuel drain and the actuation chamber, which is selectively
open or closed passively by pump piston movement and/or dynamically
by operation of an actuation solenoid valve. If the actuation
chamber passage is open, then during the pressurization stroke the
secondary piston will remain stationary relative to the pump body,
but if it is closed then the secondary piston must stroke in unison
with the primary piston.
Inventors: |
Gottemoller, Paul; (Palos
Park, IL) ; Poola, Ramesh B.; (Naperville, IL)
; Tupek, Richard Wayne; (Naperville, IL) ;
Goetzke, Michael Barry; (Orland Park, IL) |
Correspondence
Address: |
CARY W. BROOKS
General Motors Corporation
Legal Staff, Mail Code 482-C23-B21
P.O. Box 300
Detroit
MI
48265-3000
US
|
Family ID: |
32107644 |
Appl. No.: |
10/289892 |
Filed: |
November 7, 2002 |
Current U.S.
Class: |
417/213 |
Current CPC
Class: |
F04B 49/18 20130101;
F02M 45/063 20130101; F02M 59/26 20130101; F02M 59/16 20130101 |
Class at
Publication: |
417/213 |
International
Class: |
F04B 049/00 |
Claims
1. A variable output rate pump, comprising: a pump body having a
pump cylinder formed thereinside; a pump piston reciprocably
mounted in said pump cylinder, a pressurization chamber in said
pump cylinder being defined by said pump piston, said pump piston
comprising: a primary piston; and a secondary piston slidably
mounted to said primary piston; and an actuation assembly for
selectively regulating movement of said secondary piston with
respect to said primary piston as said primary piston
reciprocates.
2. The pump of claim 1, wherein said actuation assembly comprises:
an actuation chamber formed in said pump cylinder adjoining said
secondary piston opposite said pressurization chamber; an actuation
passage formed in said pump body extending between an entry at said
pump cylinder and a source of liquid; and an actuation solenoid
valve interfaced with said actuation passage, said actuation
solenoid valve selectively closing and opening communication of
said actuation chamber with respect to the source of liquid;
wherein when said actuation solenoid valve is in a closed state
liquid in said actuation chamber is trapped, and wherein when said
actuation solenoid valve is in an open state and said entry
communicates with said actuation chamber then liquid is free to
flow from said actuation chamber to the source of liquid.
3. The pump of claim 2, wherein said primary piston comprises a
reduced diameter portion of said pump piston, and wherein said
secondary piston comprises an annulus sealably mounted on said
reduced diameter portion.
4. The pump of claim 3, further comprising an abutment formed in
said pump cylinder which defines a limit of movement of said
secondary piston.
5. The pump of claim 4, wherein a liquid in said pressurization
chamber is at a first pressure, and wherein the source of liquid is
at a second pressure, said first pressure being larger than said
second pressure.
6. The pump of claim 1, wherein said actuation assembly comprises:
an actuation chamber formed in said pump cylinder adjoining said
secondary piston opposite said pressurization chamber; an actuation
passage formed in said pump body extending between an entry at said
pump cylinder and a source of liquid; and said primary piston
comprising: a reduced diameter portion of said pump piston, wherein
said secondary piston comprises an annulus sealably mounted on said
reduced diameter portion; and a main diameter portion having a
diameter larger than said reduced diameter portion, said main
diameter portion being spaced relative to said entry so as to
selectively occlude said entry during reciprocation of said pump
piston; wherein when said main diameter portion occludes said entry
then liquid in said actuation chamber is trapped, and wherein when
said main diameter portion does not occlude said entry then liquid
is free to flow from said actuation chamber to the source of
liquid.
7. The pump of claim 6, further comprising an abutment formed in
said pump cylinder which defines a limit of movement of said
secondary piston; and wherein a liquid in said pressurization
chamber is at a first pressure, and wherein the source of liquid is
at a second pressure, said first pressure being larger than said
second pressure.
8. The pump of claim 6, wherein said actuation assembly further
comprises: an actuation solenoid valve interfaced with said
actuation passage, said actuation solenoid valve selectively
closing and opening communication of said actuation chamber with
respect to the source of liquid; wherein when said actuation
solenoid valve is in a closed state liquid in said actuation
chamber is trapped, and wherein when said actuation solenoid valve
is in an open state and said entry is not occluded by said main
diameter portion then liquid is free to flow from said actuation
chamber to the source of liquid.
9. The pump of claim 8, further comprising an abutment formed in
said pump cylinder which defines a limit of movement of said
secondary piston; and wherein a liquid in said pressurization
chamber is at a first pressure, and wherein the source of liquid is
at a second pressure, said first pressure being larger than said
second pressure.
10. In a high pressure fuel pump comprising a pump body, a fuel
input connected to said pump body, a fuel output connected to said
pump body, a fuel return drain connected with said pump body, and a
main solenoid interfaced with said fuel input and said fuel output
an improvement thereto comprising: said pump body having a pump
cylinder formed thereinside; a pump piston reciprocably mounted in
said pump cylinder, a pressurization chamber in said pump cylinder
being defined by said pump piston, said pressurization chamber
communicating with said main solenoid valve, said pump piston
comprising: a primary piston; and a secondary piston slidably
mounted to said primary piston; and an actuation assembly for
selectively regulating movement of said secondary piston with
respect to said primary piston as said primary piston
reciprocates.
11. The pump of claim 10, wherein said actuation assembly
comprises: an actuation chamber formed in said pump cylinder
adjoining said secondary piston opposite said pressurization
chamber; an actuation passage formed in said pump body extending
between an entry at said pump cylinder and said fuel return drain;
and an actuation solenoid valve interfaced with said actuation
passage, said actuation solenoid valve selectively closing and
opening said actuation chamber with respect to said return fuel
drain; wherein when said actuation solenoid valve is in a closed
state then fuel in said actuation chamber is trapped, and wherein
when said actuation solenoid valve is in an open state and said
entry communicates with said actuation chamber then fuel is free to
flow from said actuation chamber to said return fuel drain.
12. The pump of claim 11, wherein said primary piston comprises a
reduced diameter portion of said pump piston, and wherein said
secondary piston comprises an annulus sealably mounted on said
reduced diameter portion; wherein an abutment formed in said pump
cylinder defines a limit of movement of said secondary piston; and
wherein fuel in said pressurization chamber is at a first pressure,
and wherein fuel in said fuel return drain is at a second pressure,
said first pressure being larger than said second pressure.
13. The pump of claim 10, wherein said actuation assembly
comprises: an actuation chamber formed in said pump cylinder
adjoining said secondary piston opposite said pressurization
chamber; an actuation passage formed in said pump body extending
between an entry at said pump cylinder and said fuel return drain;
and said primary piston comprising: a reduced diameter portion of
said pump piston, wherein said secondary piston comprises an
annulus sealably mounted on said reduced diameter portion; and a
main diameter portion having a diameter larger than said reduced
diameter portion, said main diameter portion being spaced relative
to said entry so as to selectively occlude said entry during
reciprocation of said pump piston; wherein when said main diameter
portion occludes said entry then fuel in said actuation chamber is
trapped, and wherein when said main diameter portion does not
occlude said entry then fuel is free to flow from said actuation
chamber to said return fuel drain.
14. The pump of claim 13, further comprising an abutment formed in
said pump cylinder which defines a limit of movement of said
secondary piston; and wherein fuel in said pressurization chamber
is at a first pressure, and wherein fuel in said return fuel drain
is at a second pressure, said first pressure being larger than said
second pressure.
15. The pump of claim 11, wherein said actuation assembly further
comprises: an actuation solenoid valve interfaced with said
actuation passage, said actuation solenoid valve selectively
closing and opening communication of said actuation chamber with
respect to said return fuel drain; wherein when said actuation
solenoid valve is in a closed state then fuel in said actuation
chamber is trapped, and wherein when said actuation solenoid valve
is in an open state and said entry is not occluded by said main
diameter portion then fuel is free to flow from said actuation
chamber to said return fuel drain.
16. The pump of claim 15, further comprising an abutment formed in
said pump cylinder which defines a limit of movement of said
secondary piston; and wherein fuel in said pressurization chamber
is at a first pressure, and wherein fuel in said return fuel drain
is at a second pressure, said first pressure being larger than said
second pressure.
17. A method for selectively varying the rate of fuel injection of
a fuel pump, comprising the steps of: reciprocating a primary
piston in a cylinder, wherein during a fill stroke of the primary
piston fuel enters the cylinder and during a pressurization stroke
of the primary piston fuel pressurably exits the cylinder; and
selectively moving a secondary piston in unison with said primary
piston, wherein when said secondary piston moves with said primary
piston then the fuel is ejected from the cylinder during said
pressurization stroke at a faster rate than when said secondary
piston does not move with said primary piston during said
pressurization stroke.
18. The method of claim 17, wherein said step selectively moving
the secondary piston is carried out by at least one of: passive
selection, dynamic selection, and a combination of passive and
dynamic selection.
Description
TECHNICAL FIELD
[0001] The present invention relates to fuel pumps for internal
combustion engines, particularly those used for diesel engine fuel
injection. Still more particularly, the present invention relates
to a high pressure fuel pump having a variable piston area which
provides variable fuel injection rates.
BACKGROUND OF THE INVENTION
[0002] Fuel injectors for internal combustion engines require
precisely timed delivery of pressurized fuel in order for the
engine to have maximized performance and minimized harmful
emissions. With respect to diesel engines, it is known that the
rate at which fuel is injected affects the amount of NO.sub.X and
soot emissions. Specifically, a lower rate of fuel injection during
ignition delay provides a lower premixed burnt fraction, which can
lower the initial formation of NO.sub.X and soot, and further lower
the rate of pressure rise which translates to less combustion
noise. Subsequent to the start of combustion, a higher rate of
injection promotes a higher rate of diffusion combustion at lower
flame temperatures. This results in lower NO.sub.X formation and
higher soot oxidation. Contemporary high pressure fuel pumps
provide a predetermined rate of fuel injection based upon the cam
profile. As can be understood by reference to FIGS. 1 through 3, a
prior art high pressure fuel pump 10 has a pump body 12 having a
pump cylinder 14 formed therein. A pump piston 16 reciprocates
within the pump cylinder 14, wherein a spring 18 biases the pump
piston away from the head of the piston cylinder, and an external
agency, such as a cam, drives reciprocation of the pump piston. At
the head 14H of the pump cylinder 14 is a port 20 which
communicates with a passage 22 in the pump body 12 which is
interfaced with a solenoid valve 24. A fuel supply connection 26
provides fuel (at a typical pressure of 100 psig) to the solenoid
valve. A high pressure fuel connection 28 is also connected with
the solenoid valve 24 for supplying high pressure fuel (typically
between 1,000 and 5,000 psig) to a fuel injector (or rail
therefor).
[0003] In operation, a fuel pressurization chamber 30, formed in
the pump cylinder 14 between the pump piston 16 and the head 14H,
is filled selectively via the solenoid valve 24 with fuel from the
fuel supply connection 26 when the pump piston is stroked away from
the head of the pump cylinder, the fill stroke. When the pump
piston is about to begin the pressurization stroke, the solenoid
valve closes off the fuel supply connection and opens the high
pressure fuel connection into communication with the fuel
pressurization chamber. As the pump piston strokes toward the head
of the pump cylinder during the pressurization stroke, the
requisite fuel injection pressure is provided as high pressure fuel
exits the high pressure fuel connection. In that operation of the
high pressure fuel pump inevitably involves internal fuel leakage,
a return fuel drain 32 is provided (filled with fuel with a typical
pressurization of 10 psig), having a return fuel drain connection
34.
[0004] What remains needed in the art is a high pressure fuel pump
having a variable fuel injection rate.
SUMMARY OF THE INVENTION
[0005] The present invention is a high pressure fuel pump having a
variable fuel injection rate.
[0006] The high pressure fuel pump according to the present
invention includes a pump body, a pump cylinder formed in the pump
body and a piston reciprocable within the pump cylinder. The pump
piston has a reduced diameter portion which provides a primary
piston. A piston annulus is slidably and sealingly mounted on the
primary piston, wherein the piston annulus provides a secondary
piston. The secondary piston travel is limited by a cylinder wall
abutment. The secondary piston defines a demarcation between the
fuel pressurization chamber and an oppositely disposed annular
actuation chamber. An actuation passage is provided between the
return fuel drain and the pump cylinder at the actuation chamber
(as it is defined when the primary piston is at the start of the
pressurization stroke), wherein the actuation chamber passage is
selectively open or closed passively by movement of the pump piston
and/or dynamically by operation of an actuation solenoid valve.
[0007] In operation, if the actuation passage is open, then during
the pressurization stroke the secondary piston will remain
stationary relative to the pump body, in that fuel therein is able
to flow out from the actuation chamber to the fuel return drain as
the fuel actuation chamber contracts. On the other hand, if the
actuation passage is closed, then the fuel trapped in the actuation
chamber constitutes an incompressible fluid such that as the
primary piston strokes toward the head of the pump cylinder during
the pressurization stroke, then the secondary piston must stroke
therewith in unison.
[0008] An actuation assembly provides control over movement of the
secondary piston. An example of passive actuation assembly is the
pump piston having a larger diameter portion than that at the
reduced diameter portion of the primary piston, wherein as the pump
piston strokes during the pressurization stroke, the larger
diameter portion eventually occludes the entry of the actuation
passage. An example of a dynamic actuation assembly is by
electronic control of an actuation solenoid valve, wherein as the
primary piston strokes during the pressurization stroke, the
pressurization passage may be closed or open at any time for any
duration by the setting of the actuation solenoid valve. The
actuation assembly may be only passive, only dynamic or a
combination thereof. When the secondary piston is stationary with
respect to the primary piston (in other words, when the secondary
piston is moving in unison with the primary piston) during the
pressurization stroke, a larger amount of fuel is caused to exit
the high pressure fuel connection than would be the case when the
secondary piston is stationary with respect to the pump body.
[0009] Accordingly, it is an object of the present invention to
provide a high pressure fuel pump having selective control over the
fuel injection rate.
[0010] This and additional objects, features and advantages of the
present invention will become clearer from the following
specification of a preferred embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a partly sectional side view of a prior art high
pressure fuel pump.
[0012] FIG. 2 is a side view of the high pressure fuel pump of FIG.
1.
[0013] FIG. 3 is a top elevational view of the high pressure fuel
pump of FIG. 1, seen along lines 3-3 of FIG. 2.
[0014] FIG. 4 is a partly sectional top view of a high pressure
fuel pump according to the present invention, wherein the primary
piston is at the bottom of its stroke.
[0015] FIG. 5A is a broken-away, partly sectional top view of the
high pressure fuel pump of FIG. 4, wherein the primary piston is
shown at a mid-point of its stroke and wherein the actuation
passage has just become occluded by the pump piston and the
actuation solenoid valve is set open.
[0016] FIG. 5B is a partly sectional top view of the high pressure
fuel pump of FIG. 5A, wherein the primary piston is shown at the
top of its stroke.
[0017] FIG. 6 is a partly sectional top view of the high pressure
fuel pump of FIG. 4, wherein the primary piston is shown at the top
of its stroke and wherein the actuation passage has been closed
during the pressurization stroke.
[0018] FIG. 7 is a broken away, sectional view of a high pressure
fuel pump according to the present invention, showing an
alternative actuation passage.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0019] Referring now to the drawings, FIGS. 4 through 7 depict an
example of a high pressure fuel pump 100 according to the present
invention, featuring variability of the rate of fuel injection.
[0020] A pump body 102 has a pump cylinder 104 formed thereinside,
wherein the pump cylinder opens at a lower end portion 102L of the
pump body. The pump cylinder 104 has a cylinder wall 104W and a
cylinder head 104H formed at an upper end portion 102U of the pump
body. A pump piston 106 reciprocates within the pump cylinder 104,
wherein a spring 108 biases the pump piston away from the head
104H, and an external agency, such as a cam, drives reciprocation
of the pump piston via the opening of the pump cylinder at the
lower end of the pump body.
[0021] The pump piston 106 has a main diameter portion 110M and a
reduced diameter portion 110R, wherein the reduced diameter portion
provides a primary piston 112. A piston annulus 114 is slidably
mounted on the primary piston 112 in sealing relation therewith,
wherein the piston annulus provides a secondary piston 116. The
secondary piston 116 travel is limited by a cylinder wall abutment
118. The secondary piston 116 defines a demarcation between the
fuel pressurization chamber 120 (formed between the pump piston 106
and the cylinder head 104H) and an oppositely disposed annular
actuation chamber 122 (formed between the reduced diameter portion
110M and the cylinder wall 104W and extending axially from the
secondary piston 116 to the location whereat the main diameter
portion 110M abuts the cylinder wall 104W). By way of example, the
cylinder wall abutment 118 is in the form of a reduction in the
diameter of the cylinder wall 104W.
[0022] An actuation passage 124 for filling the actuation chamber
122 is provided in the pump body 102 between the return fuel drain
126 and the pump cylinder, having an entry 124E at the actuation
chamber (as it is defined when the pump piston is commencing the
pressurization stroke). An actuation solenoid valve 128 is
interfaced with the actuation passage 124 for selectively opening
and closing fuel flow between the actuation chamber and the fuel
return drain, which is, itself, filled with fuel under relatively
low pressure (ie., about 10 psig). The actuation chamber 122 and
the actuation passage 124 form a part of an actuation assembly
which regulates whether or not the secondary piston 116 moves with
the primary piston 112 during the pressurization stroke.
[0023] An example of a passive actuation assembly includes the pump
piston. In this regard, as the pump piston strokes during the
pressurization stroke, the reduced diameter portion 110R is spaced
from the entry 124E, such that fuel in the actuation chamber freely
flows to the return fuel drain 126 as the main diameter portion
110M approaches and the volume of the actuation chamber gets
smaller (contracts). When the main diameter portion 110M reaches
the entry 124E, it occludes the entry, effectively closing the
actuation passage 124, whereupon the fuel trapped in the actuation
chamber 122 is immediately pressurized (because of its
incompressibility) and this pressurized fuel in the actuation
chamber causes the secondary piston 116 to move in unison with the
primary piston 112.
[0024] An example of a dynamic actuation assembly includes the
actuation solenoid valve 128. Electronic control of operation of
the actuation solenoid valve 128 is provided by an electronic
circuit. For example, an electronic control module (ECM) 130 has
programming which sends a signal to the actuation solenoid valve
which regulates its operation responsive to sensed inputs. Sensed
inputs may include the status of the combustion stroke of a
cylinder subject to fuel injection by the high pressure fuel pump
100. For example, at the sensed beginning of fuel injection, if
initial movement of the pump piston 106 involves only the primary
piston 112, then a lower rate of fuel injection is provided,
resulting in combustion with less noise NO.sub.X and soot
generation. At a sensed later stage of the fuel injection, if the
pump piston involves both the primary and secondary pistons 112,
116, then a higher rate of fuel injection is provided, resulting in
diffusion combustion at lower flame temperatures being
promoted.
[0025] At the cylinder head 104H of the pump cylinder 104 is a port
132 which communicates with a main passage 134 in the upper end
102U of the pump body 102. The main passage 134 is interfaced with
a main solenoid valve 136. A fuel supply connection 138 of the pump
body provides fuel (at a typical pressure of 100 psig) to the main
solenoid valve 136. A high pressure fuel connection 140 of the pump
body is also connected with the main solenoid valve 136 for
supplying high pressure fuel (typically between 1,000 and 5,000
psig) to a fuel injector (or rail therefor) from the fuel
pressurization chamber 120. The return fuel drain 126 has a return
fuel connection 142 of the pump body.
[0026] In operation, the fuel pressurization chamber 120 is under a
pressure greater than that of the actuation chamber 122 such that
the secondary piston retracts to the cylinder wall abutment 118
when the actuation chamber is in open communication with the return
fuel drain 126.
[0027] As the pump piston 106 (more particularly the primary piston
112) moves away from the head 104H during the fill stroke, the fuel
pressurization chamber expands in size. During the fill stroke
(executed by, for example, a cam mechanism), the main solenoid
valve 136 is set to allow exclusive communication between the fuel
supply connection 138 and the main passage 134 such that the fuel
pressurization chamber 120 remains fuel filled all during the fill
stroke. Upon completion of the fill stroke, the pump piston 106
then moves toward the head 104H of the pump cylinder 104, which
movement defines the pressurization stroke.
[0028] However, if only the primary piston 112 is to move during a
selected portion of the pressurization stroke, then the actuation
solenoid valve 128 is set by the ECM 130 to keep the actuation
passage 124 in open communication with the fuel return drain 126.
Accordingly, as the pump piston 106 moves during the pressurization
stroke only the primary piston 112 moves because fuel in the
actuation chamber 122 is free to flow into the return fuel drain as
the actuation chamber contracts, thereby permitting the secondary
piston 116 to remain seated on the cylinder wall abutment 118.
[0029] Dynamically, if movement of the pump piston 106 is to
include movement of the secondary piston 116 along with the primary
piston 112, then the ECM 130 sets the actuation solenoid valve 128
to close communication between the actuation passage 124 and the
fuel return drain 126. Accordingly, as the pump piston 106 moves
during the pressurization stroke fuel inside the actuation chamber
122 is trapped, and being incompressible, forces the secondary
piston 116 to move in unison with the primary piston 112. Because
the secondary piston 116 is moving with the primary piston 112,
fuel is ejected from the fuel pressurization chamber 120 at a
faster rate than would occur if only the primary piston was to move
relative to the pump body.
[0030] An example of operation is depicted by FIGS. 5A and 5B in
combination with FIG. 4. The actuation solenoid valve 128 is either
not present or is always set open. As the pump piston 106 strokes
during the pressurization stroke (beginning at FIG. 4), fuel flows
out of the contracting actuation chamber 122 as the main diameter
portion 110M advances. As a result, the secondary piston 116
remains seated at the cylinder wall abutment 118 (see FIG. 5A).
However, once the main diameter portion 110M occludes the entry
124E, thereby closing the actuation passage 124. Fuel trapped in
the actuation camber 122 is immediately pressurized (because of its
incompressibility) and this pressurized fuel in the actuation
chamber causes the secondary piston 116 to now move in unison with
the primary piston 112 (see FIG. 5B).
[0031] The placement of the entry 124E is operatively selected. If
located as shown at FIG. 4, then the main diameter portion 110M can
never collide with the secondary piston 116, and the movement of
the secondary piston is passively selected. Passive and dynamic
actuation assemblies may in this case cooperate. Otherwise, as
shown at FIG. 7 the entry 124E' of the actuation passage 124 may be
such that the secondary piston 116 will not passively move with the
primary piston 112 during the pressurization stroke, in which case
only a dynamic actuation assembly is used to control the movement
of the secondary piston via the actuation solenoid valve 128.
[0032] By way of illustration, FIG. 6 depicts a situation in which
the actuation solenoid valve 128 has been set closed all during the
pressurization stroke, so that the actuation chamber 122 has not
been in communication with the return fuel drain 126 during the
entire pressurization stroke. As a result, during the
pressurization stroke the secondary piston 116 moved in unison with
the primary piston 112.
[0033] From the foregoing, it is clear that the movement of the
secondary piston with the movement of the primary piston provides
an increased rate of fuel injection as compared to that provided by
the primary piston alone, and that the movement of the secondary
piston with the primary piston may be passively controlled,
dynamically controlled or both passively and dynamically
controlled. For example, the secondary piston could be caused to
move in unison with the primary piston all during the
pressurization stroke, or at any time during, for any part of, or
for multiple parts of, the pressurization stroke.
[0034] To those skilled in the art to which this invention
appertains, the above described preferred embodiment may be subject
to change or modification. For example, while a fuel pump has been
disclosed herein, it is clear that the fuel pump according to the
present invention is a pump capable of pumping a liquid other than
fuel. Further, the volumes and dimensions shown in the attached
drawings are not scalable, the volumes and dimensions shown being
meant to be optimized for specific applications. Such change or
modification can be carried out without departing from the scope of
the invention, which is intended to be limited only by the scope of
the appended claims.
* * * * *