U.S. patent application number 10/782264 was filed with the patent office on 2004-10-07 for fuel injector control module with unidirectional dampening.
This patent application is currently assigned to Robert Bosch Fuel Systems Corporation. Invention is credited to Foote, Tedd R., Harkema, Randall C., Seelbach, Klaus.
Application Number | 20040195349 10/782264 |
Document ID | / |
Family ID | 30115114 |
Filed Date | 2004-10-07 |
United States Patent
Application |
20040195349 |
Kind Code |
A1 |
Seelbach, Klaus ; et
al. |
October 7, 2004 |
Fuel injector control module with unidirectional dampening
Abstract
Fluid in a chamber, through which a fuel control armature is
moving, is used to dampen armature vibrations. This dampening
effect is achieved by forming a passage through which the fluid
flows as the actuator moves to a steady state position. This
passage may be implemented in a control module for controlling fuel
delivery in a fuel injector. The control module includes a control
module housing defining the cavity. The armature is disposed at
least partially within the cavity. The armature affects the flow of
fuel in the injector by changing the area of a fuel port through
which fuel passes. The fluid passage is formed as the armature
moves towards a contact wall defining the cavity.
Inventors: |
Seelbach, Klaus; (Grand
Rapids, MI) ; Foote, Tedd R.; (Wayland, MI) ;
Harkema, Randall C.; (Caledonia, MI) |
Correspondence
Address: |
BROOKS KUSHMAN P.C.
1000 TOWN CENTER
TWENTY-SECOND FLOOR
SOUTHFIELD
MI
48075
US
|
Assignee: |
Robert Bosch Fuel Systems
Corporation
Kentwood
MI
|
Family ID: |
30115114 |
Appl. No.: |
10/782264 |
Filed: |
February 19, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10782264 |
Feb 19, 2004 |
|
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|
10196894 |
Jul 16, 2002 |
|
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6702207 |
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Current U.S.
Class: |
239/88 |
Current CPC
Class: |
F02M 47/027 20130101;
F02M 2200/304 20130101; F02M 63/0021 20130101; F16K 31/0693
20130101; F02M 59/466 20130101; F02M 63/0064 20130101; F02M 59/366
20130101; F02M 57/022 20130101; F02M 63/0017 20130101; F16K 47/10
20130101; F02M 57/023 20130101; F02M 2200/44 20130101 |
Class at
Publication: |
239/088 |
International
Class: |
F02M 047/02 |
Claims
1-24. (canceled)
25. A method of controlling a flow of fuel in a fuel injector
comprising: moving at least a portion of an armature in a cavity
containing fluid; changing an opening area of a fuel port through
the movement of the armature, thereby affecting the flow of fuel;
forming a fluid passage for passing fluid between the armature and
a wall defining the cavity as the armature moves towards the wall,
the fluid passage formed by moving a dampener sleeve extending from
the armature in a direction of armature motion, the dampener sleeve
defining at least one notch; contacting the wall with the dampener
sleeve; increasing fluid pressure as the fluid passage forms; and
dampening armature vibration through the increasing fluid
pressure.
26. A method of controlling a flow of fuel in a fuel injector
comprising: moving at least a portion of an armature in a cavity
containing fluid; changing an opening area of a fuel port through
the movement of the armature, thereby affecting the flow of fuel;
forming a fluid passage for passing fluid between the armature and
a wall defining the cavity as the armature moves towards the wall,
the fluid passage formed by capping a portion of a channel formed
in the wall; increasing fluid pressure as the fluid passage forms;
and dampening armature vibration through the increasing fluid
pressure.
27. A method of controlling a flow of fuel in a fuel injector as in
claim 26 wherein capping a portion of the channel comprises
contacting the wall with a sleeve extending from the armature.
28. A method of controlling a flow of fuel in a fuel injector
comprising: moving at least a portion of an armature in a cavity
containing fluid; changing an opening area of a fuel port through
the movement of the armature, thereby affecting the flow of fuel;
forming a fluid passage for passing fluid between the armature and
a wall defining the cavity as the armature moves towards the wall,
the fluid passage formed by narrowing a gap between the armature
and a dampener shim extending from the wall; increasing fluid
pressure as the fluid passage forms; and dampening armature
vibration through the increasing fluid pressure.
29. A method of controlling a flow of fuel in a fuel injector as in
claim 28 wherein the armature has a compression side facing the
wall and wherein the dampener shim defines an opening facing the
compression side, the opening smaller than the compression
side.
30. A method of controlling a flow of fuel in a fuel injector as in
claim 29 further comprising contacting a valve stop between the
armature and the wall to prevent the gap from closing.
31. A method of controlling a flow of fuel in a fuel injector
comprising: moving at least a portion of an armature in a cavity
containing fluid; changing an opening area of a fuel port through
the movement of the armature, thereby affecting the flow of fuel;
forming a fluid passage for passing fluid between the armature and
a wall defining the cavity as the armature moves towards the wall,
the fluid passage formed by narrowing a gap between a shoulder on
the armature and a dampener sleeve fixed within the cavity;
increasing fluid pressure as the fluid passage forms; and dampening
armature vibration through the increasing fluid pressure.
32. A method of controlling a flow of fuel in a fuel injector as in
claim 31 further comprising contacting a valve stop to prevent the
gap from closing.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 10/196,894 filed Jul. 16, 2002.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to controlling the flow of
fuel through an injector.
[0004] 2. Background Art
[0005] Fuel injectors provide controlled pulses of fuel for
combustion in internal combustion engines. The flow of fuel through
a fuel injector may be controlled by one or more solenoids that
open ports, close ports, or otherwise affect the flow of fuel
within the fuel injector through movement of an armature.
Typically, each solenoid armature is biased in a first position by
a mechanical spring and activated to a second position by a motive
force provided by a solenoid electromagnet. When the motive force
is removed, the spring returns the solenoid armature to its
deactivated position. This deactivation results in ringing of the
armature or other mechanical vibrations due to contact with a
mechanical stop. Such vibrations interfere with or otherwise
complicate the control of fuel flowing through the injector and may
shorten the effective injector life.
[0006] What is needed is to minimize ringing and other vibrations
caused by deactivation of a control solenoid within a fuel
injector.
SUMMARY OF THE INVENTION
[0007] The present invention utilizes a fluid in a chamber, through
which a fuel control armature is moving, to dampen armature
vibrations. This dampening effect is achieved by forming a passage
through which the fluid flows as the actuator moves to a
deactivated or steady state position.
[0008] A control module for controlling fuel delivery in a fuel
injector is provided. The control module includes a control module
housing defining a cavity. An armature is disposed at least
partially within the cavity. The armature affects the flow of fuel
by changing the area of a fuel port through which fuel passes. The
control module includes a drive for moving the armature towards a
contact wall of the cavity. The drive may include mechanical
elements, such as a spring, electromagnetic elements, hydraulic
elements, and the like. A fluid passage is formed as the armature
moves towards the contact wall. The fluid passage remains open to
pass a minimum volume of fluid when the armature contacts the
contact wall. Vibrations in the armature are dampened by the fluid
as fluid moves through the passage.
[0009] In an embodiment of the present invention, the fluid passage
is formed by a dampener sleeve extending from the armature towards
the contact wall. A stop may extend from the armature towards the
contact wall farther than the dampener sleeve such that, when the
stop contacts the wall, the fluid passage forms a minimum passage
gap between the dampener sleeve and the contact wall.
Alternatively, or in addition to the gap provided by the stop, the
fluid passage may be formed by at least one notch or hole in the
dampener sleeve.
[0010] In another embodiment of the present invention, the fluid
passage is formed by a channel in the contact wall.
[0011] In yet another embodiment of the present invention, the
fluid passage is formed between a dampener shim on the contact wall
and a compression side of the armature. The compression side may be
circular and the dampener shim may define a circular opening having
an opening radius smaller than the compression side radius. A stop
may extend from the compression side towards the contact wall a
distance greater than the thickness of the dampener shim.
[0012] In still another embodiment of the present invention, the
armature defines a shoulder at least partially around the armature.
The fluid passage is formed between a dampener sleeve extending
from the contact wall and the shoulder.
[0013] In a further embodiment of the present invention, the
control module may define a second cavity within which is at least
partially disposed a second armature. The second armature forms a
second fluid passage. Fluid exiting the second armature cavity
through the second fluid passage provides dampening of the second
armature.
[0014] A method of controlling a flow of fuel in a fuel injector is
also provided. At least a portion of an armature in a cavity
containing fluid is moved. An opening area of a fuel port changes
through the movement of the armature to affect the flow of fuel. A
fluid passage for passing fluid between the armature and a wall
defining the cavity is formed as the armature moves into contact
with the wall. Fluid pressure increases as the fluid passage forms
to dampen armature vibration.
[0015] A fuel injector is also provided. The fuel injector includes
an injector body defining a fuel outlet. A fuel delivery path
delivers pressurized fuel to the outlet. A control module connected
to the fuel delivery path has at least one solenoid for controlling
fuel delivery. Each solenoid has an armature biased by a spring to
contact a wall defining a cavity when the solenoid is not
energized. The armature and the wall form a passage as the armature
approaches the wall. This passage passes fluid from between the
armature and the wall into the remaining cavity to dampen
vibrations caused by the armature contacting the wall.
[0016] A method of injecting fuel into an engine is also provided.
The fuel is compressed. The compressed fuel is supplied to an
opening in an injector through a controlled path. A solenoid in the
injector is activated to control the flow of fuel along the path.
The solenoid has an armature traveling through a fluid containing
cavity. The solenoid, when deactivated, allows the armature to
contact a wall defining the cavity. A passage is formed as the
armature contacts the wall. Fluid is passed from between the
armature and the wall resulting in dampened vibrations.
[0017] The above objects and other objects, features, and
advantages of the present invention are readily apparent from the
following detailed description of the best mode for carrying out
the invention when taken in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a conceptualized cut view drawing of a fuel
injector which may incorporate the present invention;
[0019] FIG. 2 is a schematic diagram illustrating the operation of
a fuel injector which may incorporate the present invention;
[0020] FIG. 3 is a cut view drawing of a control module having a
dampener sleeve according to an embodiment of the present
invention;
[0021] FIG. 4 is a cut view drawing of a control module having a
notched dampener sleeve according to an embodiment of the present
invention;
[0022] FIG. 5 is a perspective view drawing of a notched dampener
sleeve according to an embodiment of the present invention;
[0023] FIG. 6 is a cut view drawing of a control module defining a
fluid passage channel according to an embodiment of the present
invention;
[0024] FIG. 7 is a cut view drawing of a control module with a
dampener shim according to an embodiment of the present
invention;
[0025] FIG. 8 is a cut view drawing of a control module with a
dampener sleeve according to an embodiment of the present
invention;
[0026] FIG. 9 is a plot of graphs illustrating control valve
bouncing; and
[0027] FIG. 10 is a plot of graphs illustrating vibration reduction
due to an embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0028] Referring to FIG. 1, a conceptualized cut view drawing of a
fuel injector which may incorporate the present invention is shown.
A fuel injector, shown generally by 20, includes injector body 22
defining a fuel outlet shown generally by 24. Plunger 26 disposed
within injector body 22 pressurizes fuel 28 due to an external
force applied to cam cup 30 overcoming bias force supplied by
plunger spring 32. Fuel 28 in reservoir 34 is routed to fuel outlet
24 through fuel delivery path 36.
[0029] Nozzle needle 38 is biased by needle spring 40 around load
pin 42 to seal off fuel outlet 24. Pressurized fuel 28 from
reservoir 34 is routed through fuel delivery path 36 to fuel outlet
24. Pressurized fuel 28 pushes nozzle needle 38 back, opening fuel
outlet 24 to permit the escape of fuel 28 from fuel injector 20.
The flow of fuel along fuel delivery path 36 to fuel outlet 24 is
controlled by control module 44 having at least one solenoid for
controlling fuel delivery. As will be described in greater detail
below, each solenoid has an armature biased by a spring to contact
a wall defining a cavity when the solenoid is not energized by a
signal from electrical connector 46. The armature and the wall form
a passage as the armature approaches the wall. The passage passes
fluid from between the armature and the wall into the remaining
cavity to dampen armature vibrations.
[0030] Referring now to FIG. 2, a schematic diagram illustrating
the operation of a fuel injector which may incorporate the present
invention is shown. As cam 60 rotates, plunger 26 pressurizes fuel
28 in reservoir 34. Main control valve 62 in control module 44 is
normally open, allowing fuel from reservoir 34 to dump through main
control valve 62 into low pressure circuit 64. Control module 44
also includes normally closed needle control valve 66. Load pin 42
includes piston 68 in chamber 70. Chamber 70 fills from fuel
delivery path 36 and empties through needle control valve 66 into
low pressure circuit 64. When needle control valve 66 is not
energized, pressurized fuel 28 within chamber 70 prevents nozzle
needle 38 from opening fuel outlet 24. Thus, by controlling main
control valve 62 and needle control valve 66, the shape of a fuel
pulse exiting fuel outlet 24 may be controlled.
[0031] FIGS. 3, 4, and 6-8 illustrate various embodiments of the
present invention with cross-sectional views of control modules
having a main control valve and a needle control valve. Various
techniques for dampening vibrations may be applied to either or
both of the main control valve and the needle control valve.
Further, as will be recognized by one of ordinary skill in the art,
the present invention applies to a wide variety of valves for
controlling the flow of fuel within a fuel injector.
[0032] Referring now to FIG. 3, a cut view drawing of a control
module having a dampener sleeve according to an embodiment of the
present invention is shown. Control module 44 includes normally
open main control valve 62 and normally closed needle control valve
66. The operation of both valves 62, 66 is similar. Each valve 62,
66 is implemented as an electromagnetic solenoid with an armature
that moves to open or close a fuel flow port. As will be recognized
by one skilled in the art, the present invention applies to valves
or ports driven by any means.
[0033] Main control valve 62 is defined within control module
housing 80. Stator block 82 is fixed within control module housing
80. Stator block 82 includes stator coil 84 which, when carrying
sufficient current, activates main control valve 62. Main control
valve 62 also includes an armature, shown generally by 86. Armature
86 is biased away from stator coil 84 by spring 88 pushing against
flange 90. Thus, when main control valve 62 is deactivated, flange
90 is pushed by spring 88 towards contact wall 92 of control module
housing 80. In the embodiment shown, contact wall 92 of housing 80
is formed by an interior portion of injector body 22.
[0034] Flange 90 is constructed of a magnetically attractable
material such that, when stator coil 84 is energized, flange 90 is
pulled against the force of spring 88 onto stator block 82. Shaft
94 is attached to flange 90. Shaft 94 passes through chamber 96
which is connected to high pressure fuel delivery path 36 via a
port not shown. When main control valve 62 is energized, shaft 94
is hard against seat 98, sealing chamber 96 from fuel outlet 100.
When main control valve 62 is not energized, spring 88 pulls shaft
94 away from seat 98 allowing fuel to pass from chamber 96 out
through fuel outlet 100 to low pressure circuit 64.
[0035] Control module housing 80 defines cavity 102 through which
passes flange 90 of armature 86. Cavity 102 is filled with fluid
104. Fluid 104 in cavity 102 in the embodiment shown is low
pressure fuel. However, fluid 104 may be any fluid capable of
dampening vibrations. Port 106 allows fluid 104 to escape cavity
102.
[0036] Prior to the present invention, de-energizing main control
valve 62 caused spring 88 to force compression side 108 of flange
90 against contact wall 92. Flange 90 would bounce off contact wall
92 creating ringing and other vibrations. One problem with such
ringing is a rapid opening and closing of chamber 96 to fuel outlet
100, decreasing the ability for main control valve 62 to precisely
control the flow of fuel 28. In addition, vibrations decrease the
effective life of fuel injector 20.
[0037] The present invention utilizes fluid 104 exiting through a
passage formed as armature 86 moves towards contact wall 92 to
dampen vibrations in armature 86. In the embodiment shown in FIG.
3, dampener sleeve 110 extends from flange 90 towards contact wall
92. Stop 112 also extends from armature 86. Stop 112 extends
farther towards contact wall 92 than dampener sleeve 110 such that,
when stop 112 contacts contact wall 92, fluid passage 114 is formed
between dampener sleeve 110 and contact wall 92. As will be
recognized by one skilled in the art, stop 112 may also extend from
contact wall 92 towards contact flange 90 or shaft 94.
[0038] Dampener sleeve 110 may be formed from any suitable material
such as, for example, steel. Dampener sleeve 110 may be press fit
over flange 90, may be spot welded to flange 90, or may be attached
by any other suitable means. Dampener sleeve 110 may also be formed
as part of flange 90. Stop 112 is also preferably steel and may be
formed as part of shaft 94, may be attached to shaft 94, may be
attached to flange 90, may be formed as part of flange 90, or the
like. A typical throw for armature 86 is about 180 microns with
resulting gap distance for fluid passage 114 between dampener
sleeve 110 and contact wall 92 of about 20 microns.
[0039] Control module housing 80 also contains normally closed
needle control valve 66. Stator block 120 is fixed within control
module housing 80. Stator block 120 includes stator coil 122 for
carrying electrical current. A needle control valve armature, shown
generally by 124, is biased away from stator coil 122 by spring
126. Armature 124 includes flange 128 made of a magnetically
attractable material. When stator coil 122 carries sufficient
current, flange 128 is pulled back against stator block 120,
compressing spring 126. When stator coil 122 is de-energized,
spring 126 forces flange 128 towards contact wall 130. Shaft 132 is
fixed to flange 128. Shaft 132 passes through chamber 134 and
contacts seat 136 to seal fuel inlet 138 from fuel outlet 140.
Energizing stator coil 122 pulls shaft 132 away from seat 136
allowing pressurized fuel 28 to flow through fuel inlet 138 into
chamber 134 through fuel outlet 140 and into low pressure circuit
64.
[0040] Control module housing 44 defines cavity 142 through which
moves flange 128. Cavity 142 contains fluid 104 which may be, for
example, low pressure fuel. Flange 128 has compression side 144
facing contact wall 130. Dampener sleeve 146 extends from
compression side 144 towards contact wall 130 a distance such that
fluid passage 114 between dampener sleeve 146 and contact wall 130
remains open when shaft 132 is against seat 136. Fluid 104 is
forced through fluid passage 114 formed as flange 128 moves towards
contact wall 130. Fluid 104 serves to dampen vibrations of armature
124 when needle control valve port 66 is de-activated.
[0041] Referring now to FIG. 4, a cut view drawing of a control
module having a notched dampener sleeve according to an embodiment
of the present invention is shown. Dampener sleeve 160 extends from
flange 90 towards contact wall 92. When stator coil 84 is
de-energized, spring 88 forces flange 90 towards contact wall 92
until dampener sleeve 160 strikes contact wall 92. Dampener sleeve
160 contains one or more notch 162 or similar opening. As dampener
sleeve 160 approaches contact wall 92, notch 162 forms fluid
passage 114 through which fluid 104 passes. Fluid 104, including
fluid 104 escaping through fluid passage 114, dampens vibrations of
armature 86.
[0042] Referring now to FIG. 5, a perspective view drawing of a
notched dampener sleeve according to an embodiment of the present
invention is shown. Dampener sleeve 160 is shown having two notches
162. As will be recognized by one of ordinary skill in the art, the
number and size of notches 162 will depend on a variety of factors
including the characteristics of fluid 104, the amount of dampening
required for armature 86, the design of armature 86, the force
applied to flange 90 by spring 88, and the like. Dampener sleeve
160 may be constructed of a variety of engineering materials such
as, for example, steel. Dampener sleeve 160 may be press fit onto
flange 90, may be spot welded, may be formed as part of flange 90,
and the like.
[0043] Referring now to FIG. 6, a cut view drawing of a control
module defining a fluid passage channel according to an embodiment
of the present invention is shown. Dampener sleeve 170, similar in
construction to dampener sleeve 160, extends from flange 90 towards
contact wall 92. In this embodiment, dampener sleeve 170 may or may
not include notches 162. Channel 172 is formed in contact wall 92
in a portion of contact wall 92 where dampener sleeve 170 contacts
contact wall 92. As spring 88 forces flange 90 towards contact wall
92, channel 172 forms fluid passage 114 through which fluid 104
passes. Fluid 104 around flange 90 provides dampening of vibrations
such as those caused when dampener sleeve 170 strikes contact wall
92.
[0044] Referring now to FIG. 7, a cut view drawing of a control
module with a dampener shim according to an embodiment of the
present invention as shown. Control module 44 includes dampener
shim 180 extending from contact wall 92. Fluid passage 114 is
formed between dampener shim 180 and compression side 108 of flange
90 as flange 90 moves towards contact wall 92.
[0045] In an embodiment, compression side 108 is circular. Dampener
shim 180 defines a circular opening with a radius smaller than the
radius of compression side 108. Stop 112 extends from shaft 94
towards contact wall 92. When stator coil 84 is de-energized,
spring 88 forces armature 86 towards contact wall 92. Stop 112
strikes contact wall 92 leaving fluid passage 114 open between
flange 90 and dampener shim 180.
[0046] Dampener shim 182 in needle control valve 66 defines fluid
passage 114 between flange 128 and dampener shim 182. The height of
dampener shim 182 is adjusted such that passage 114 remains open
when shaft 32 is against seat 136.
[0047] Referring now to FIG. 8, a cut view drawing of a control
module with a dampener sleeve according to an embodiment of the
present invention is shown. Dampener sleeve 190 extends from
contact wall 92 towards flange 90. Fluid passage 114 is formed
between shoulder 192 on flange 90 and dampener sleeve 190. Dampener
sleeve 190 and flange 90 are designed such that stop 112 on shaft
94 contacts contact surface 92 leaving fluid passage 114
opened.
[0048] Dampener sleeve 194 extends from contact wall 130. Fluid
passage 114 is formed between shoulder 196 on flange 128 and
dampener sleeve 194 as flange 128 moves towards contact wall 130.
Fluid passage 114 remains open when shaft 132 is seated on seat
136.
[0049] Referring now to FIG. 9, a plot of graphs illustrating
control valve bouncing is shown. These graphs illustrate operation
of fuel injector 20, such as described with regards to FIGS. 1 and
2, prior to the present invention. Plot 210 shows current applied
to stator coil 84 of main control valve 62. Similarly, plot 212
shows stator current applied to coil 122 of needle control valve
66. Plot 214 shows the movement of armature 86 in main control
valve 62 to close main control valve 62. Plot 216 shows the motion
of armature 124 in needle control valve 66 to open needle control
valve 66. Closing main control valve 62 and opening needle control
valve 66 allows nozzle needle 38 to move so that fuel 28 escapes
from fuel outlet 24 in fuel injector 20. The motion of nozzle
needle 38 is shown in plot 218.
[0050] After approximately 1.8 milliseconds, current to stator 122
is switched off to close nozzle needle 38. Deactivating nozzle
needle control valve 66 prior to the present invention causes
compression side 144 of flange 128 to bounce off contact wall 130
causing ringing 222 in plot 216. Ringing 222 causes needle control
valve 66 to bounce between an opened state and a closed state,
creating extensive delay 224 between control signal 212 and the
close of nozzle needle 38 as shown in plot 218. Turning off stator
current 210 to stator coil 84 causes main control valve 62 to
de-energize. Prior to the present invention, compression side 108
of flange 90 would bounce off contact wall 92 causing ringing 226
seen plot 214.
[0051] Referring now to FIG. 10, a plot of graphs illustrating
vibration reduction according to an embodiment of the present
invention are shown. These graphs illustrate fuel injector 20
implementing dampening as described with regards to FIGS. 1-3. Plot
240 illustrates stator current for main control valve 62 and plot
242 illustrates stator current for needle control valve 66
substantially the same as the control currents 210 and 212,
respectively, in FIG. 9. The movement of armature 86 in main
control valve 62, shown by plot 244, exhibits greatly reduced
ringing. The motion of armature 124 in needle control valve 66,
illustrated by plot 246, shows no ringing whatsoever. The reduced
vibrations in valves 62, 66 results in less delay, indicated by
time 252, between control signal 242 to close nozzle needle 38 and
the time which nozzle needle 38 actually closes. In addition, the
greatly reduced ringing and vibration decreases the wear on
elements within fuel injector 20.
[0052] While embodiments of the invention have been illustrated and
described, it is not intended that these embodiments illustrate and
describe all possible forms of the invention. Rather, the words
used in the specification are words of description rather than
limitation, and it is understood that various changes may be made
without departing from the spirit and scope of the invention.
* * * * *