U.S. patent application number 13/857334 was filed with the patent office on 2013-10-24 for method and system for reciprocating compressor starting.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. The applicant listed for this patent is GENERAL ELECTRIC COMPANY. Invention is credited to Richard C. PEOPLES, Jayaprakash Shreeshailappa SABARAD, Jason M. STRODE, Bret Dwayne WORDEN.
Application Number | 20130280095 13/857334 |
Document ID | / |
Family ID | 48326433 |
Filed Date | 2013-10-24 |
United States Patent
Application |
20130280095 |
Kind Code |
A1 |
WORDEN; Bret Dwayne ; et
al. |
October 24, 2013 |
METHOD AND SYSTEM FOR RECIPROCATING COMPRESSOR STARTING
Abstract
Systems and methods of the invention may overcome a higher than
normal starting torque for in a reciprocating, electric motor
driven air compressor for a vehicle. A detection component can be
configured to detect a stall condition for a reciprocating
compressor based on a force from compressed air being compressed
into a reservoir of the reciprocating compressor. Based upon the
detected stall condition, a controller can reverse direction or
increase torque to alleviate the stall condition. In the reverse
direction mode, the controller component can change a direction of
a piston rotation. In the torque increase mode, the controller
increases a number of poles for the motor, a line voltage, or a
volt/hertz.
Inventors: |
WORDEN; Bret Dwayne; (Erie,
PA) ; PEOPLES; Richard C.; (Grove City, PA) ;
SABARAD; Jayaprakash Shreeshailappa; (Bangalore, IN)
; STRODE; Jason M.; (Lawrence Park, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GENERAL ELECTRIC COMPANY |
Schenectady |
NY |
US |
|
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
48326433 |
Appl. No.: |
13/857334 |
Filed: |
April 5, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61636192 |
Apr 20, 2012 |
|
|
|
Current U.S.
Class: |
417/1 |
Current CPC
Class: |
F04B 49/10 20130101;
F04B 23/02 20130101; F04B 25/00 20130101; F04B 2201/0605 20130101;
F15B 19/005 20130101; F04B 49/065 20130101; F04B 2205/063 20130101;
F04B 49/02 20130101; F16K 37/0091 20130101; G01M 3/2876 20130101;
F04B 49/022 20130101; F04B 51/00 20130101; F04B 41/02 20130101 |
Class at
Publication: |
417/1 |
International
Class: |
F04B 49/00 20060101
F04B049/00 |
Claims
1. A method, comprising: removing power from or reducing power to a
motor coupled to a reciprocating compressor; reversing a phase
sequence of the motor to force a recompression of a piston of the
reciprocating compressor; and detecting at least one of a reverse
stall or a start of the reciprocating compressor while in a reverse
direction.
2. The method of claim 1, further comprising reversing a torque
direction of the motor to accelerate the piston past a
Bottom-Dead-Center (BDC) position based on the detected reverse
stall.
3. The method of claim 2, further comprising accelerating the
compressor past the BDC position with at least one of a torque of
the motor or a pneumatic force on the piston to overcome a force
from compressed air being compressed into a reservoir of the
reciprocating compressor.
4. The method of claim 1, further comprising driving the compressor
in the reverse direction for a duration of time based on the
detection of the start of the compressor.
5. The method of claim 1, further comprising reversing a phase
direction of the motor after the start of the compressor for a
duration of time.
6. The method of claim 5, further comprising returning a stuck
loaded control magnet valve (CMV) or an un-loader valve based on
the start of the compressor.
7. The method of claim 5, further comprising returning a stuck
loaded control magnet valve (CMV) or an un-loader valve based on
elevation of a pressure of a reservoir due to the start of the
compressor.
8. The method of claim 1, further comprising detecting a stall
condition to initiate the reversing of the phase sequence, wherein
the stall condition is based on at least one of a control magnet
valve stuck failure, a leakage on a high pressure cylinder
discharge valve of the compressor, a high pressure cylinder
un-loader valve stuck failure, or a low pressure cylinder un-loader
valve stuck failure.
9. The method of claim 1, further comprising increasing a torque to
start the motor of the compressor with at least one of a pole
switching, a line voltage increase, or a volt/hertz increase.
10. The method of claim 9, further comprising increasing the torque
to start the motor in at least one of a forward direction of the
piston or the reverse direction of the piston.
11. The method of claim 9, further comprising increasing the torque
with a selection of a first pole mode to a second pole mode.
12. The method of claim 11, wherein the first pole mode includes a
first number of poles and the second pole mode includes a second
number of poles in which the second number of poles is greater than
the first number of poles, and further comprising detecting a stall
condition based on at least one of a compressor speed, a motor
current, or a measured pressure signal.
13. A system, comprising: a compressor operatively connected to an
electric motor, wherein the compressor includes a reservoir
configured to store compressed air; and a detector component that
is configured to detect a stall condition of the compressor; a
controller that is configured to control the following based on the
detected stall condition: removal of power from the motor of the
compressor; reversal of a phase sequence of the motor to force a
recompression of a piston of the compressor; and detection of at
least one of a reverse stall or a start of the compressor while in
a reverse direction as the piston moves to a Top-Dead-Center (TDC)
position.
14. The system of claim 13, wherein the compressor is a
reciprocating compressor with a bi-directional drive system that
drives the piston in a forward direction and the reverse
direction.
15. The system of claim 13, wherein the controller is further
configured to: control reversal of a phase direction of the motor
to accelerate the piston past a Bottom-Dead-Center (BDC) position
based on the detected reverse stall; and control acceleration of
the compressor past the BDC position with at least one of a torque
of the motor or a pneumatic force on the piston to overcome a force
from compressed air being compressed into a reservoir of the
reciprocating compressor.
16. The system of claim 13, wherein the controller is further
configured to control at least one of the following: a drive of the
compressor in the reverse direction for a first duration of time
based on the detection of the start of the compressor; or a
reversal of a phase direction of the motor after the start of the
compressor for a second duration of time.
17. The system of claim 13, wherein the controller is further
configured to increase a torque to start the motor of the
compressor by selecting a number of poles used by the motor from a
first number to a second number, wherein the second number is
greater than the first number.
18. The system of claim 13, wherein the controller is further
configured to control an increase to at least one of a line voltage
or a volt/hertz to change a torque for an engine start of the
compressor.
19. A system, comprising: means for detecting a stall condition for
a reciprocating bidirectional compressor based on a force from
compressed air being compressed into a reservoir of the
reciprocating bidirectional compressor; means for removing power
from a motor of the reciprocating bidirectional compressor; means
for reversing a phase sequence to the motor to force a
recompression of a piston of the reciprocating bidirectional
compressor; and means for detecting at least one of a reverse stall
or a start of the reciprocating bidirectional compressor while in a
reverse direction as the piston moves to a Top-Dead-Center (TDC)
position.
20. A method to accommodate a failure to start a reciprocating air
compressor due to a high starting torque associated with wear or
failure of a component or system, comprising: detecting a stall
condition for a reciprocating compressor based on at least one of a
compressor speed, a motor current, or a measured pressure signal;
and increasing a torque to start the motor of the compressor with
at least one of a pole switching, a line voltage increase, or a
volt/hertz increase.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 61/636,192, filed Apr. 20, 2012, and entitled
"SYSTEM AND METHOD FOR A COMPRESSOR." The entirety of the
aforementioned application is incorporated herein by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] Embodiments of the subject matter disclosed herein relate to
facilitating starting a reciprocating compressor having a loaded
start condition.
[0004] 2. Discussion of Art
[0005] Compressors compress gas, such as air. An air compressor can
include three cylinders with two stages and can be air cooled and
driven by an electric motor. The compressor can have two low
pressure cylinders which deliver an intermediate pressure air
supply to a single high pressure cylinder for further compression
for final delivery to an air reservoir. Compressors may sometimes
have difficulty in starting.
[0006] It may be desirable to have a system and method that differs
from those systems and methods that are currently available.
BRIEF DESCRIPTION
[0007] In an embodiment, a method is provided that includes
detecting a compressor start failure (e.g., stall) condition for a
reciprocating compressor based on a force from compressed air being
compressed into a reservoir of the reciprocating compressor. Power
may be removed from or reduced to a motor of the reciprocating
compressor. A phase sequence of the motor (e.g., a three (3) phase
AC motor) may be reversed to force a recompression of air against a
piston in the reciprocating compressor. A reverse stall or a start
of the reciprocating compressor may be detected while in a reverse
direction as the piston moves toward a Top-Dead-Center (TDC)
position. In another embodiment, a compressor can be started by
employing a high starting torque due to, for instance, wear or a
failure.
[0008] In an embodiment, a vehicle is provided that includes an
engine, a compressor operatively connected to the engine, wherein
the compressor includes a reservoir configured to store compressed
air, a detector component that is configured to detect a stall
condition of the compressor, and a controller. The controller can
be configured to control at least one of removal power from the
motor of the compressor, reversal a phase sequence of the motor to
force a recompression of a piston of the compressor, and detection
of at least one of a reverse stall or a start of the compressor
while in a reverse direction as the piston moves to a
Top-Dead-Center (TDC) position.
[0009] In an embodiment, a system can be provided that includes
means for detecting a stall-when-starting condition for a
reciprocating bidirectional based on a speed signal, a measured
current signal, or a measured pressure signal. The system further
includes means for removing power from a motor of the reciprocating
bidirectional compressor and means for reversing a phase sequence
to the motor to force a recompression of a piston of the
reciprocating bidirectional compressor. The system includes means
for detecting at least one of a reverse stall or a start of the
reciprocating bidirectional compressor while in a reverse direction
as the piston moves toward a Top-Dead-Center (TDC) position.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Reference is made to the accompanying drawings in which
particular embodiments and further benefits of the invention are
illustrated as described in more detail in the description below,
in which:
[0011] FIG. 1 is an illustration of an embodiment of a vehicle
system with a compressor;
[0012] FIG. 2 is an illustration of an embodiment of system that
includes a compressor;
[0013] FIG. 3 is an illustration of an embodiment of a system that
controls a motor based upon a detection component for a
compressor;
[0014] FIG. 4 is an illustration of an embodiment of a system that
includes a compressor;
[0015] FIG. 5 is an illustration of an embodiment of a system that
includes a compressor;
[0016] FIG. 6 is an illustration of an embodiment of a system that
includes a compressor;
[0017] FIG. 7 is an illustration of an embodiment of a valve that
has a leak to cause a loading sat for a compressor;
[0018] FIG. 8 is an illustration of an embodiment of a system for a
system that includes a compressor;
[0019] FIG. 9 is an illustration of a reverse direction mode in
response to a stall when starting condition of a compressor;
[0020] FIG. 10 illustrates a flow chart of an embodiment of a
method for detecting a stall
[0021] FIG. 11 illustrates a flow chart of an embodiment of a
method for increasing torque for a compressor motor in response to
a detected stall condition and
[0022] FIG. 12 illustrates a flow chart of an embodiment of a
method for increasing torque for a compressor motor and reversing a
phase sequence of the motor in response to a detected stall-when
starting
DETAILED DESCRIPTION
[0023] Embodiments of the subject matter disclosed herein relate to
systems and methods that overcome a higher than normal starting
torque for in a reciprocating, electric motor driven air compressor
for a vehicle. A detection component can be configured to detect a
stall condition for a reciprocating compressor based on a force
from compressed air being compressed into a reservoir of the
reciprocating compressor. Based upon the detected stall condition,
a controller can be configured to control at least one of a reverse
direction mode (also referred to as reverse phase mode) or a torque
increase mode in order to alleviate the stall condition. In the
reverse direction mode, the controller component can be configured
to change a direction of a crankshaft rotation in order to allow a
gain in momentum during a subsequent start attempt to overcome a
high starting torque requirement. In the torque increase mode, the
controller can be configured to increase at least one of a number
of poles for the motor, a line voltage, or a volt/hertz (e.g.,
motor flux). In another embodiment, the controller component can
utilize the reverse direction mode alone, or in combination with
the torque increase mode. In still another embodiment, the
controller component can utilize the torque increase mode alone, or
in combination with the reverse direction mode.
[0024] With reference to the drawings, like reference numerals
designate identical or corresponding parts throughout the several
views. However, the inclusion of like elements in different views
does not mean a given embodiment necessarily includes such elements
or that all embodiments of the invention include such elements.
[0025] The term "component" as used herein can be defined as a
portion of hardware, a portion of software, or a combination
thereof. A portion of hardware can include at least a processor and
a portion of memory, wherein the memory includes an instruction to
execute. The term "vehicle" as used herein can be defined as an
asset that is a mobile machine or a moveable transportation asset
that transports at least one of a person, people, or a cargo. For
instance, a vehicle can be, but is not limited to being, a rail
car, an intermodal container, a locomotive, a marine vessel, mining
equipment, a stationary power generation equipment, industrial
equipment, construction equipment, and the like. The term "loaded"
as used herein can be defined as a compressor system mode where air
is being compressed into the reservoir. The term "loaded start" as
used herein can be defined as a compressor system mode in a loaded
condition during a starting phase of the compressor.
[0026] A compressor compresses gas, such as air. In some
embodiments, the compressed gas is supplied to operate pneumatic or
other equipment powered by compressed gas. A compressor may be used
for mobile applications, such as vehicles. By way of example,
vehicles utilizing compressors include locomotives, on-highway
vehicles, off-highway vehicles, mining equipment, and marine
vessels. In other embodiments, a compressor may be used for
stationary applications, such as in manufacturing or industrial
applications requiring compressed air for pneumatic equipment among
other uses. The compressor depicted in the below figures is one
which utilizes spring return inlet and discharge valves for each
cylinder, wherein the movement of these valves is caused by the
differential pressure across each cylinder as opposed to a
mechanical coupling to the compressor crank shaft. The subject
invention can be applicable to machines with either type of valve
(e.g., spring return valves, mechanical coupled valves, among
others) and the spring return valve is depicted solely for example
and not to be limiting on the subject innovation.
[0027] FIG. 1 illustrates a block diagram of an embodiment of a
vehicle system 100 (e.g., a locomotive system, a system, among
others). The vehicle system 100 is depicted as a rail vehicle 106
configured to run on a rail 102 via a plurality of wheels 108. The
rail vehicle includes a compressor system with a compressor 110. In
an embodiment, the compressor is a reciprocating compressor that
delivers air at high pressure. In another embodiment, the
compressor is a reciprocating compressor with a bi-directional
drive system that drives a piston in a forward direction and the
reverse direction. In an embodiment, the compressor receives air
from an ambient air intake 114. The air is then compressed to a
pressure greater than the ambient pressure and the compressed air
is stored in reservoir 180, which is monitored by a reservoir
pressure sensor 185. In one embodiment, the compressor is a
two-stage compressor (such as illustrated in FIG. 2) in which
ambient air is compressed in a first stage to a first pressure
level and delivered to a second stage, which further compresses the
air to a second pressure level that is higher than the first
pressure level. The compressed air at the second pressure level is
stored in a reservoir. The compressed air may then be provided to
one or more pneumatic devices as needed. In other embodiments, the
compressor 110 may be a single stage or multi-stage compressor.
[0028] The compressor includes a crankcase 160. The crankcase is an
enclosure for a crankshaft (not shown in FIG. 1) connected to
cylinders (not shown in FIG. 1) of the compressor. A motor 104 is
employed to rotate the crankshaft to drive the pistons within the
cylinders. In embodiments, the motor 104 may be an electric or
non-electric motor. In another embodiment, the crankshaft may be
coupled to a drive shaft of an engine or other power source
configured to rotate the crankshaft of the compressor. In each
embodiment, the crankshaft may be lubricated with compressor oil
that is pumped by an oil pump (not shown) and sprayed onto the
crankshaft. The crankshaft is mechanically coupled to a plurality
of pistons via respective connecting rods. The pistons are drawn
and pushed within their respective cylinders as the crankshaft is
rotated to compress a gas in one or more stages.
[0029] The rail vehicle further includes a controller 130 for
controlling various components related to the vehicle system. In an
embodiment, the controller is a computerized control system with a
processor 132 and a memory 134. The memory may be computer readable
storage media, and may include volatile and/or non-volatile memory
storage. In an embodiment, the controller includes multiple control
units and the control system may be distributed among each of the
control units. In yet another embodiment, a plurality of
controllers may cooperate as a single controller interfacing with
multiple compressors distributed across a plurality of vehicles.
Among other features, the controller may include instructions for
enabling on-board monitoring and control of vehicle operation.
Stationary applications may also include a controller for managing
the operation of one or more compressors and related equipment or
machinery.
[0030] In an embodiment, the controller receives signals from one
or more sensors 150 to monitor operating parameters and operating
conditions, and correspondingly adjust actuators 152 to control
operation of the rail vehicle and the compressor. In various
embodiments, the controller receives signals from one or more
sensors corresponding to compressor speed, compressor load, boost
pressure, exhaust pressure, ambient pressure, exhaust temperature,
or other parameters relating to the operation of the compressor or
surrounding system. In another embodiment, the controller receives
a signal from a crankcase pressure sensor 170 that corresponds to
the pressure within the crankcase. In yet another embodiment, the
controller receives a signal from a crankshaft position sensor 172
that indicates a position of the crankshaft. The position of the
crankshaft may be identified by the angular displacement of the
crankshaft relative to a known location such that the controller is
able to determine the position of each piston within its respective
cylinder based upon the position of the crankshaft. In some
embodiments, the controller controls the vehicle system by sending
commands to various components. On a locomotive, for example, such
components may include traction motors, alternators, cylinder
valves, and throttle controls among others. The controller may be
connected to the sensors and actuators through wires that may be
bundled together into one or more wiring harnesses to reduce space
in vehicle system devoted to wiring and to protect the signal wires
from abrasion and vibration. In other embodiments, the controller
communicates over a wired or wireless network that may allow for
the addition of components without dedicated wiring.
[0031] The controller may include onboard electronic diagnostics
for recording operational characteristics of the compressor.
Operational characteristics may include measurements from sensors
associated with the compressor or other components of the system.
These measurements may include motor currents, compressor
rotational speed, air pressure and/or temperature at various
locations. Such operational characteristics may be stored in a
database in memory. In one embodiment, current operational
characteristics may be compared to past operational characteristics
to determine trends of compressor performance.
[0032] The controller may include onboard electronic diagnostics
for identifying and recording potential degradation and failures of
components of vehicle system. For example, when a potentially
degraded component is identified, a diagnostic code may be stored
in memory. In one embodiment, a unique diagnostic code may
correspond to each type of degradation that may be identified by
the controller. For example, a first diagnostic code may indicate a
malfunctioning exhaust valve of a cylinder, a second diagnostic
code may indicate a malfunctioning intake valve of a cylinder, a
third diagnostic code may indicate deterioration of a piston or
cylinder resulting in a blow-by condition. Additional diagnostic
codes may be defined to indicate other deteriorations or failure
modes. In yet other embodiments, diagnostic codes may be generated
dynamically to provide information about a detected problem that
does not correspond to a predetermined diagnostic code. In some
embodiments, the controller modifies the output of charged air from
the compressor, such as by reducing the duty cycle of the
compressor, based on parameters such as the condition or
availability of other compressor systems (such as on adjacent
locomotive engines), environmental conditions, and overall
pneumatic supply demand.
[0033] The controller may be further linked to display 140, such as
a diagnostic interface display, providing a user interface to the
operating crew and/or a maintenance crew. The controller may
control the compressor, in response to operator input via user
input controls 142, by sending a command to correspondingly adjust
various compressor actuators. Non-limiting examples of user input
controls may include a throttle control, a braking control, a
keyboard, and a power switch. Further, operational characteristics
of the compressor, such as diagnostic codes corresponding to
degraded components, may be reported via display to the operator
and/or the maintenance crew.
[0034] The vehicle system may include a communications system 144
linked to the controller. In one embodiment, communications system
may include a radio and an antenna for transmitting and receiving
voice and data messages. For example, data communications may be
between vehicle system and a control center of a railroad, another
locomotive, a satellite, and/or a wayside device, such as a
railroad switch. For example, the controller may estimate
geographic coordinates of a vehicle system using signals from a GPS
receiver. As another example, the controller may transmit
operational characteristics of the compressor to the control center
via a message transmitted from communications system. In one
embodiment, a message may be transmitted to the command center by
communications system when a degraded component of the compressor
is detected and the vehicle system may be scheduled for
maintenance.
[0035] The system can include a detection component 128 that is
configured to detect a stall condition for the compressor. The
detection component can ascertain whether a failure detected
corresponds to a loaded start condition. Based on the stall
condition detected by the detection component, the controller can
be configured to employ at least one of a reverse direction mode or
a torque increase mode. The controller can employ the reverse
direction mode in order to reverse a direction of the compressor
crankshaft temporarily, to be followed by another start attempt in
the forward direction in order to overcome a high starting torque
required to start the compressor. Additionally or alternatively,
the controller can employ the torque increase mode that increases
at least one of a number of poles for the motor, a line voltage, or
a volt/hertz (e.g., motor flux). In an embodiment, the controller
utilizes the reverse direction mode alone, or in combination with
the torque increase mode. In another embodiment, the controller
utilize one of the reverse direction mode or the torque increase
mode for a duration of time and then utilize the both the reverse
direction mode or the torque increase mode in combination. Yet, a
suitable combination of the modes can be employed by the controller
and either mode alone or in combination can be selected with sound
engineering judgment.
[0036] During the reverse direction mode, the controller
communicates to the motor to remove power therefrom. The controller
can communicate with the motor to reverse the phase sequence to the
motor, wherein the reversed direction sequence forces a
recompression. During this reversed direction sequence, the
compressor can either stall again or run in the reverse direction.
If the compressor runs in the reverse direction, the controller can
be configured to run in a reverse direction (if the compressor can
function in such reverse direction). If the compressor is not
capable of reverse direction running, the compressor can change to
the forward directions after a duration of time after a rotation is
detected. A stuck loaded Control Mag Valve (CMV) (not shown but
discussed below) or unloader valves can return to a normal
operation (e.g., not stuck, not loaded condition, and the like)
when the reservoir pressure elevates or the compressor is able to
run again (e.g., in a reverse direction for a duration of time, in
a forward direction after the reverse direction, among others).
[0037] If during the reversed direction sequence, a stall is
detected (e.g., a stall during the reverse direction), the
controller can reverse the motor to the forward direction to
accelerate the compressor. For instance, the stall in the reverse
direction can be detected as pistons move to a Top-Dead-Center
(TDC) and the motor can be reversed to accelerate pistons past
Bottom-Dead-Center (BDC) with a combination of motor torque and
pneumatic force on the piston(s). For instance, the motor torque
and pneumatic forces build enough momentum to overcome the
compressed air forces.
[0038] The recovery of the compressor after rotation at a running
speed is based upon at the following: unloader valve differential
pressure reduces or even changes direction to the unload direction
during high speed piston down-strokes which allows opening of an
unloader valve when the CMV provides compressed control air to
drive the unload mode; or CMV valves transition to an unloaded
state as control air pressure is elevated by the loaded compressor
cycle.
[0039] As discussed above, the term "loaded" refers a compressor
mode where air is being compressed into the reservoir. The
compressor depicted is one which utilizes spring return inlet and
discharge valves for each cylinder in which the movement of these
valves is caused by the differential pressure across them as
opposed to a mechanical coupling to the compressor crank shaft. The
subject disclosure may be applicable to machines with either type
of valve, but the spring return type will be illustrated here for
the sake of brevity. For instance, an unloaded condition or
unloaded compressor mode is illustrated in FIG. 4.
[0040] The detection component can be a stand-alone component (as
depicted), incorporated into the controller component, or a
combination thereof. The controller component can be a stand-alone
component (as depicted), incorporated into the repair component, or
a combination thereof.
[0041] FIG. 2 illustrates a detailed view of the compressor set
forth in FIG. 1 above. The compressor includes three cylinders 210,
220, 230. Each cylinder contains a piston 218, 228, 238 that is
coupled to a crankshaft 250 via connecting rods 240, 242, 244. The
crankshaft is driven by the motor to cyclically pull the respective
pistons to a Bottom-Dead-Center (BDC) and push the pistons to a
Top-Dead-Center (TDC) to output charged air, which is delivered to
the reservoir via air lines 280, 282, 284, 286. In this embodiment,
the compressor is divided into two stages: a low pressure stage and
a high pressure stage to produce charged air in a stepwise
approach. The low pressure stage compresses air to a first pressure
level which is further compressed by the high pressure stage to a
second pressure level. In this example, the low pressure stage
includes cylinders 220, 230 and the high pressure stage includes
cylinder 210.
[0042] In operation, air from the ambient air intake is first drawn
into the low pressure cylinders via intake valves 222, 232, which
open and close within intake ports 223, 233. The ambient air is
drawn in as the low pressure cylinders are pulled towards BDC and
the intake valves 222, 232 separate from intake ports 223, 233 to
allow air to enter each cylinder 220, 230. Once the pistons reach
BDC, the intake valves 222, 232 close the intake ports 223, 233 to
contain air within each cylinder. Subsequently, pistons 228, 238
are pushed toward TDC, thereby compressing the ambient air
initially drawn into the cylinders. Once the cylinders have
compressed the ambient air to a first pressure level, exhaust
valves 224, 234 within exhaust ports 225, 235 are opened to release
the low pressure air into low pressure lines 280, 282.
[0043] The air compressed to a first pressure level is routed to an
intermediate stage reservoir 260. The intermediate stage reservoir
260 received air from one stage of a multistage compressor and
provides the compressed air to a subsequent stage of a multistage
compressor. In an embodiment, the intermediate stage reservoir 260
is a tank or other volume connected between successive stages by
air lines. In other embodiments, the air lines, such as low
pressure lines 280, 282 provide sufficient volume to function as an
intermediate stage reservoir without the need for a tank or other
structure.
[0044] In an embodiment, the compressor system also includes an
intercooler 264 that removes the heat of compression through a
substantially constant pressure cooling process. One or more
intercoolers may be provided along with one or more intercooler
controllers 262. In some embodiments, the intercooler 264 is
integrated with the intermediate stage reservoir 260. A decrease in
the temperature of the compressed air increases the air density
allowing a greater mass to be drawn into the high pressure stage
increasing the efficiency of the compressor. The operation of the
intercooler is controlled by the intercooler controller 262 to
manage the cooling operation. In an embodiment, the intercooler
controller 262 employs a thermostatic control through mechanical
means such as via thermal expansion of metal. In a multistage
compressor system having more than two stages, an intercooler may
be provided at each intermediate stage.
[0045] The air at a first pressure level (e.g., low pressure air)
is exhausted from the intercooler into low pressure air line 284
and subsequently drawn into the high pressure cylinder 210. More
particularly, as piston 218 is pulled toward BDC, the intake valve
212 opens, thereby allowing the low pressure air to be drawn into
the cylinder 210 via intake port 213. Once the piston 218 reaches
BDC, the intake valve 212 closes to seal the low pressure air
within the cylinder 210. The piston is then pushed upward thereby
compressing the low pressure air into high pressure air. High
pressure air is air at a second pressure level greater than the
first pressure level, however the amount of compression will vary
based upon the requirements of the application. As compression
increases, the exhaust valve 214 is opened to allow the high
pressure air to exhaust into high pressure line 286 via exhaust
port 215. An aftercooler 270 cools the high pressure air to
facilitate a greater density to be delivered to the reservoir via
high pressure air line 288.
[0046] The above process is repeated cyclically as the crankshaft
250 rotates to provide high pressure air to the reservoir 180,
which is monitored by the reservoir pressure sensor 185. Once the
reservoir reaches a particular pressure level (e.g., 140 psi), the
compressor operation is discontinued.
[0047] In some embodiments, the compressor includes one or more
valves configured to vent compressed air from intermediate stages
of the compressor system. The unloader valves and/or relief valves
may be operated after compressor operations are discontinued, or
may be operated during compressor operations to relieve pressure in
the compressor system. In an embodiment, an unloader valve 268 is
provided in the intermediate stage reservoir 260 and configured to
vent the low pressure compressed air from the intermediate stage
reservoir, low pressure air lines 280, 282 and intercooler 264.
Venting compressed air reduces stress on system components during
periods when the compressor is not in use and may extend the life
of the system. In another embodiment, the unloader valve 268
operates as a relief valve to limit the buildup of pressure in the
intermediate stage reservoir 260. In yet another embodiment, intake
valves 222, 232 operate as unloader valves for the cylinders 220,
230 allowing compressed air in the cylinders to vent back to the
ambient air intake 114. In another embodiment, the system 200 can
include relief valves such as breather valve 174, a relieve valve
on the intercooler 264 (shown in FIG. 4), a relieve valve for air
line 286, a rapid unloader valve on the intercooler 264 (shown in
FIG. 4)
[0048] A compressor, such as the compressor illustrated in FIG. 2,
operates to charge the reservoir 180 with compressed air or other
gas. Once the compressor charges the reservoir to a determined
pressure value the compressor operation is discontinued. In some
embodiments, when compressor operations are discontinued, one or
more unloader valves are opened to vent intermediate stages of the
compressor to the atmosphere. The intake valves of the cylinders as
well as unloader valves of the intermediate stage reservoirs may
all operate as unloader valves to vent the cylinders of the
compressor to the atmosphere. Once the unloader valves are actuated
and the cylinders and intermediate stages of the compressor have
been vented to the atmosphere the pressure within the reservoir is
expected to remain constant as previously discussed.
[0049] As discussed above, the controller can be configured to
employ at least one of a torque increase mode or a phase reverse
mode or a combination thereof. This mode implementation by the
controller can be based upon, but not limited to, the detection
component identifying at least one of a failure mode, a stall
condition, a loaded start condition, a combination thereof, among
others.
[0050] FIG. 3 illustrates a system 300 that controls a motor based
upon a detection component for a compressor, wherein the control
relates to the increase torque mode. The system 300 can include the
detection component (e.g., detection can be embedded within the
controller) that is configured to identify a stall condition for a
reciprocating compressor based at least one of compressor speed,
compressor motor current, compressor output, and/or reservoir
pressure. The controller can be configured to manage an increase in
torque (e.g., torque increase mode) based upon such detection. For
instance, the increase in torque can be an increase in a pole mode
for the motor, a line voltage increase, or a volt/hertz increase.
The motor can include a number of poles 310 such as pole.sub.1 to
pole.sub.N, where N is a positive integer. For instance, N can be
an even positive integer. The motor can further include a pole mode
that includes use of a set number of poles. In an embodiment, the
motor can include a suitable number of pole modes in which each
pole mode includes a specific amount of poles. For instance, a pole
mode can include a first number of poles and a second pole mode can
include a second number of poles. In such instance, the first
number of poles can be less than the second number of poles. Based
on the detection component, the motor can increase a number of
poles such that the motor updates from the first pole mode to a
second pole mode (e.g., where the second pole mode includes more
poles than the first pole mode). For example, a motor can include a
six (6) pole mode and a twelve (12) pole mode. Based upon detecting
a stall condition, the controller can increase the pole mode from
six (6) to twelve (12) for the motor to increase torque. This can
allow for a degree of freedom for speed which proves useful in
non-inverter applications where auxiliary AC voltage frequency is
supplied by an auxiliary alternator driven by a variable speed
engine. It is to be appreciated that the controller can utilize a
combination of an increase of a number of poles, an increase in
line voltage, and an increase of volt/hertz to increase starting
torque FIG. 4 illustrates a system 400 that depicts a compressor in
an unloaded condition. The system illustrates additional features
and/or components that can be included in FIGS. 1, 2, and 3. The
system includes a Control Mag Valve (CMV) 402, a Thermostatically
Controlled Intercooler System (TCIS) bypass 404, a rapid unloader
valve 406, an unloader valve 408 for cylinder 230, an unloader
valve 410 for cylinder 220, a relief valve 420, a relief valve 430,
and relief valve 440 (e.g., substantially similar to breather valve
174 in FIG. 2).
[0051] Crankshaft can include a first end opposite a second end in
which the first end is coupled to one or more connecting rods for
each respective cylinder. The crankshaft, cylinders, and pistons
are illustrated in BDC position based upon the location of the
first end. BDC position is a location of the first end at
approximately negative ninety degrees (-90 degrees) or 270 degrees.
A TDC position is a location of the first end at approximately
ninety degrees (90 degrees) or -270 degrees.
[0052] As discussed, the controller implements one or more modes
based upon the detection component identifying a stall condition.
For instance, failure modes for the compressor can result in a
fully or partially loaded start condition. In an embodiment, the
detection component can utilize suitable sensor(s) within the
system to identify a loaded start condition. In FIGS. 5-8, examples
of failures for stall conditions are described in which such stall
conditions can be detected by the detection component and, in turn,
utilized by the controller to employ at least one of the torque
increase mode or the reverse direction mode. The below is solely
for exemplary purposes and not to be limiting on the subject
innovation.
[0053] A CMV stuck loaded (e.g., CMV 402 in FIG. 4) failure can
relate to a CMV being stuck in the "loaded" position which closes
all un-loader valves. The effect of the CMV stuck loaded failure is
to strap air within each cylinder which will need to be compressed
on the subsequent "start." This amount of air mass and the pressure
of the trapped air depend on the final position of the pistons and
the reservoir pressure both when the compressor was stopped and
after. The trapped air in the high pressure cylinder results in
increased starting torque and may stall. This is illustrated in
FIG. 5, wherein FIG. 5 illustrates a system 500 that depicts a
compressor in a CMV stuck loaded failure.
[0054] A CMV stuck loaded failure and leakage on a high pressure
cylinder discharge valve can be a failure. For instance, the high
pressure cylinder discharge valve can be exhaust valve 214. This
failure can be related to the CMV stuck in the loaded position
which closes all unloader valves except the main reservoir air
leaks back into the high pressure cylinder via a faulty exhaust
valve. The effect of this failure (e.g., leaking valve) can result
in increased air mass and pressure in the High Pressure Cylinder.
Larger leaks may cause the high pressure piston to move BDC. The
trapped air in the High Pressure Cylinder results in increased
starting torque and may stall. This is illustrated in FIG. 6,
wherein FIG. 6 illustrates a system 600 that depicts a compressor
in a CMV stuck loaded failure and leakage on a high pressure
cylinder discharge valve. Turning to FIG. 7, a valve 700 that is a
high pressure cylinder discharge valve is depicted. The valve 700
can be from a compressor and include a leak source 702 which
relates to the a compressor for a CMV stuck loaded failure and
leakage on a high pressure cylinder discharge valve failure.
[0055] A high pressure cylinder unloader valve stuck loaded failure
can relate to the high pressure cylinder being not able to release
to atmosphere. The effect of this failure is that trapped air in
the high pressure cylinder results in increased starting torque and
may stall. This is illustrated in FIG. 8, wherein FIG. 8
illustrates a system 800 that depicts a compressor in a high
pressure cylinder unloader valve stuck failure in which unloader
valve 268 is unable to release to atmosphere.
[0056] A high pressure cylinder unloader valve stuck loaded and
leakage on the high pressure cylinder discharge valve can be a
failure related to the high pressure cylinder not being able to
release to atmosphere except the main reservoir leaks back into the
main pressure cylinder. The effect of this failure is the discharge
valve leak can result in increased air mass and pressure in the
high pressure cylinder. Larger leaks may cause the high pressure
piston to move to BDC. The trapped air in the high pressure
cylinder results in increased starting torque and may stall.
[0057] A low pressure cylinder unloader valve stuck loaded can be a
failure. This failure relates to a low pressure cylinder not being
able to release to atmosphere. The effect of this failure is the
trapped air in the low pressure cylinder results in increased
starting torque and may stall.
[0058] Another failure can be leakage on the high pressure cylinder
discharge valve. This failure can lead to starting issues if the
CMV is at a point in time put in the loaded state even transiently.
This can be caused by the fact that when the high pressure cylinder
contains pressurized air, the unloader valve actuator may not have
enough force capability to overcome the differential pressure
across the inlet valve. This can lead to a latched unloader state
of closed.
[0059] The controller and the detection component facilitate
overcoming the above stall conditions and/or failures. Moreover,
the above referenced failures are not to be limiting on the subject
disclosure and a suitable combination or amount of failures related
to a stall condition for a loaded start condition can be mitigated
by the controller and the detection component.
[0060] FIG. 9 illustrates a reverse direction mode 900 in response
to a stall condition of a compressor. As discussed above, the
controller can employ a reverse direction mode based upon an
identified stall condition from the detection component. The
reverse direction mode 900 is illustrated in a series of images for
a cylinder of a reciprocating compressor as described above. The
reverse direction mode 900 depicts cylinder 210 but is to be
appreciated that the depiction can apply to each cylinder of the
compressor and the subject innovation is not limited to a single
cylinder. The cylinder 210 includes the unloader valve 268 and is
coupled to the crankshaft via the connecting rod. Once a stall
condition is detected by the detection component, power can be
removed and the cylinder can settle at Bottom-Dead-Center. Once
detection of the cylinder being at BDC, power can be reversed
(e.g., reverse direction of the motor) and compressed air can enter
the cylinder.
[0061] Next, a reverse stall can be detected. As discussed, a
reverse stall can be detected or the compressor can run in reverse.
In FIG. 9, a reverse stall is detected. Upon detection of the
reverse stall, the power is applied in the forward direction (e.g.,
forward power, not reversed power) and forward momentum is built
(e.g., motor torque and/or pneumatic force). In an embodiment, the
torque increase mode can be employed as well to increase torque and
momentum. This forward momentum built and applied increased torque
(e.g., if the increase torque mode is employed) can result in a
start of the compressor.
[0062] The aforementioned systems, components, (e.g., detection
component, controller, among others), and the like have been
described with respect to interaction between several components
and/or elements. It should be appreciated that such devices and
elements can include those elements or sub-elements specified
therein, some of the specified elements or sub-elements, and/or
additional elements. Further yet, one or more elements and/or
sub-elements may be combined into a single component to provide
aggregate functionality. The elements may also interact with one or
more other elements not specifically described herein. These
components or elements may be software, hardware, or a
combination.
[0063] In view of the exemplary devices and elements described
supra, methodologies that may be implemented in accordance with the
disclosed subject matter will be better appreciated with reference
to the flow charts of FIGS. 10-12. The methodologies are shown and
described as a series of blocks, the claimed subject matter is not
limited by the order of the blocks, as some blocks may occur in
different orders and/or concurrently with other blocks from what is
depicted and described herein. Moreover, not all illustrated blocks
may be required to implement the methods described hereinafter. The
methodologies can be implemented by a component or a portion of a
component that includes at least a processor, a memory, and an
instruction stored on the memory for the processor to execute.
[0064] FIG. 10 illustrates a flow chart of a method 1000 for
detecting a stall condition related to a force from compressed air
being compressed into a reservoir of the reciprocating compressor.
At reference numeral 1010, a stall condition can be detected for a
reciprocating compressor based on measured speed, motor current, or
air pressure. For instance, the stall condition can be detected
based on a a force from compressed air being compressed into a
reservoir of the reciprocating compressor, wherein a detection
component can be used to detect such force. At reference numeral
1020, a portion of power from a motor of the reciprocating
compressor can be removed. At reference numeral 1030, a phase
sequence of the motor can be reversed to force a recompression of a
piston of the reciprocating compressor. At reference numeral 1040,
at least one of a reverse stall or a start of the reciprocating
compressor can be detected while in a reverse direction as the
piston moves to a Top-Dead-Center (TDC) position.
[0065] FIG. 11 illustrates a flow chart of a method 1100 for
increasing torque for a compressor motor in response to a detected
stall condition related to a force from compressed air being
compressed into a reservoir of the reciprocating compressor. At
reference numeral 1110, a stall condition can be detected for a
reciprocating compressor based on a force from compressed air being
compressed into a reservoir of the reciprocating compressor. At
reference numeral 1120, a torque to start the motor of the
compressor can be increased with at least one of a pole switching,
a line voltage increase, or a voltz/hertz increase. At reference
numeral 1130, the torque can be increased with a selection from a
first pole mode to a second pole mode, wherein the first pole mode
includes a first number of poles that is less than a second number
of poles for a second pole mode.
[0066] FIG. 12 illustrates a flow chart of a method 1200 for
increasing torque for a compressor motor and reversing a phase
sequence of the motor in response to a detected stall condition
related to a force from compressed air being compressed into a
reservoir of the reciprocating compressor. At reference numeral
1210, a stall condition for a reciprocating compressor can be
detected based on a force from compressed air being compressed into
a reservoir of the reciprocating compressor. At reference numeral
1220, a portion of power can be removed from a motor of the
reciprocating compressor. At reference numeral 1230, a phase
sequence to the motor can be reversed which forces a recompression
of a piston of the reciprocating compressor. At reference numeral
1240, at least one of a reverse stall or a start of the
reciprocating compressor can be detected while in a reverse
direction as the piston moves to a Top-Dead-Center (TDC) position.
At reference numeral 1250, a torque to start the engine of the
reciprocating bidirectional compressor can be increased by
selecting a number of poles used by the motor from a first number
to a second number, wherein the second number is greater than the
first number.
[0067] In an embodiment, the method includes reversing a phase
direction of the motor to accelerate the piston past a
Bottom-Dead-Center (BDC) position based on the detected reverse
stall. In such embodiment, the method further includes accelerating
the compressor past the BDC with at least one of a torque of the
motor or a pneumatic force on the piston to overcome the force. In
an embodiment, the method can include driving the compressor in the
reverse direction for a duration of time based on the detection of
the start of the compressor. In another embodiment, the method can
include reversing a phase direction of the motor after the start of
the compressor for a duration of time.
[0068] In still another embodiment, the method includes returning a
stuck loaded control magnet valve (CMV) or an un-loader valve based
on the start of the compressor. In still another embodiment, the
method includes returning a stuck loaded control magnet valve (CMV)
or an un-loader valve based on elevation of a pressure of the
reservoir due to the start of the compressor.
[0069] In an embodiment of the method, the stall condition can be
based on at least one of a control magnet valve stuck failure, a
leakage on a high pressure cylinder discharge valve of the
compressor, a high pressure cylinder un-loader valve stuck failure,
or a low pressure cylinder un-loader valve stuck failure. In still
another embodiment, the method includes increasing a torque to
start the motor of the compressor with at least one of a pole
switching, a line voltage increase, or a volt/hertz increase.
[0070] In the embodiment of the method, the torque used to start
the motor can be increased in a forward direction of the piston or
the reverse direction of the piston. In the embodiment of the
method, the torque is increased with a selection of a first pole
mode to a second pole mode, wherein the first pole mode includes a
first number of poles and the second pole mode includes a second
number of poles in which the second number of poles is greater than
the first number of poles.
[0071] In an embodiment, a vehicle can be provided with a detector
component and a controller as discussed above. Also, the detector
may be embedded within the controller component. The vehicle can
include an engine in which a compressor can be operatively
connected to the engine, wherein the compressor includes a
reservoir configured to store compressed air. The controller can
provide at least one of a removal power from the motor of the
compressor, a reversal a phase sequence of the motor to force a
recompression of a piston of the compressor, and a detection of at
least one of a reverse stall or a start of the compressor while in
a reverse direction as the piston moves to a Top-Dead-Center (TDC)
position. In the embodiment, the compressor is a reciprocating
compressor with a bi-directional drive system that drives a piston
in a forward direction and the reverse direction.
[0072] In an embodiment, the controller is configured to reverse a
phase direction of the motor to accelerate the piston past a
Bottom-Dead-Center (BDC) position based on the detected reverse
stall and accelerate the compressor past the BDC position with at
least one of a torque of the motor or a pneumatic force on the
piston to overcome the force.
[0073] In an embodiment of the subject disclosure, the controller
can be further configured to control at least one of the following:
a drive of the compressor in the reverse direction for a duration
of time based on the detection of the start of the compressor; or a
reversal of a phase direction of the motor after the start of the
compressor for a duration of time. In an embodiment, the controller
can be further configured to increase a torque to start the engine
of the compressor by selecting a number of poles used by the motor
from a first number to a second number, wherein the second number
is greater than the first number. In the embodiment, the controller
can be configured to control an increase to at least one of a line
voltage or a volt/hertz to change a torque for an engine start of
the compressor.
[0074] In an embodiment, a system can be provided that includes
means for increasing a torque to start the engine of the
reciprocating bidirectional compressor by selecting a number of
poles used by the motor from a first number to a second number,
wherein the second number is greater than the first number.
[0075] In an embodiment, a method is provided to accommodate a
failure to start a reciprocating air compressor due to a high
starting torque associated with wear or failure of a component or
system that includes the steps of: detecting a stall condition for
a reciprocating compressor based on at least one of a compressor
speed, a motor current, or a measured pressure signal; and
increasing a torque to start the motor of the compressor with at
least one of a pole switching, a line voltage increase, or a
volt/hertz increase. In the embodiment, the torque to start the
motor is increased in at least one of a forward direction of a
piston of the motor or a reverse direction of the piston of the
motor. In the embodiment, the torque is increased with a selection
of a first pole mode to a second pole mode.
[0076] In the embodiment, the first pole mode includes a first
number of poles and the second pole mode includes a second number
of poles in which the second number of poles is greater than the
first number of poles. In the embodiment, the method can respond to
a stall during a compressor start sequence by increasing the line
voltage to above-normal levels to facilitate extra starting torque
for the compressor. In the embodiment, the method can respond to a
stall during a compressor start sequence by increasing the motor
flux to above-normal levels to facilitate providing extra starting
torque for the compressor. In the embodiment, after a successful
re-start at increase torque level, the motor control is returned to
normal except the compressor motor run duration is extended in
order to avoid troubled re-starts. In the embodiment, the method
can include regulating reservoir air pressure using a controllable
loading valve to load and unloading the compressor while it
maintains rotation. In the embodiment, the method can include
regulating reservoir air pressure using a hardware relief
valve.
[0077] In an embodiment, a method can be provided to accommodate a
failure to start a reciprocating air compressor due to a high
starting torque associated with wear or failure of a component or
system that includes the steps of: detecting a stall condition for
a compressor based on at least one of a compressor speed, a motor
current, or a measured pressure signal; and reversing the
compressor rotation transiently to accommodate the failure. In the
embodiment, a reverse rotation is driven by reversing a phase
sequence to a three (3) phase induction motor driving the
compressor. In the embodiment, an induction motor is powered by a
variable frequency inverter drive. In the embodiment, a reverse
rotation is limited to a position from which momentum is obtained
on a subsequent forward restart. In the embodiment, if during
reverse rotation, the compressor successfully starts in a reverse
direction, this rotation is maintained if the compressor can pump
air in either direction. In the embodiment, if during reverse
rotation, the compressor successfully starts in a reverse
direction, this rotation is maintained only for a short period of
time after which the compressor is stopped and restarted in a
forward direction.
[0078] In an embodiment, a system can be provided that includes
means for detecting a stall condition for a reciprocating
bidirectional compressor based on a force from compressed air being
compressed into a reservoir of the reciprocating bidirectional
compressor, wherein the means for detecting can be the detection
component, the controller component, a sensor, a component, or a
combination thereof. The system can include means for removing
power from a motor of the reciprocating bidirectional compressor,
wherein the means for removing can be the controller, the motor,
the compressor, a component, among others. The system can include
means for reversing a phase sequence to the motor to force a
recompression of a piston of the reciprocating bidirectional
compressor, wherein the means for reversing can be the controller
component, the compressor, the motor, a component, among others.
The system can include means for detecting at least one of a
reverse stall or a start of the reciprocating bidirectional
compressor while in a reverse direction as the piston moves to a
Top-Dead-Center (TDC) position, wherein the means for detecting is
the detector component, a sensor, a compressor, a controller
component, a component, among others.
[0079] In the specification and claims, reference will be made to a
number of terms that have the following meanings. The singular
forms "a", "an" and "the" include plural referents unless the
context clearly dictates otherwise. Approximating language, as used
herein throughout the specification and claims, may be applied to
modify a quantitative representation that could permissibly vary
without resulting in a change in the basic function to which it is
related. Accordingly, a value modified by a term such as "about" is
not to be limited to the precise value specified. In some
instances, the approximating language may correspond to the
precision of an instrument for measuring the value. Moreover,
unless specifically stated otherwise, a use of the terms "first,"
"second," etc., do not denote an order or importance, but rather
the terms "first," "second," etc., are used to distinguish one
element from another.
[0080] As used herein, the terms "may" and "may be" indicate a
possibility of an occurrence within a set of circumstances; a
possession of a specified property, characteristic or function;
and/or qualify another verb by expressing one or more of an
ability, capability, or possibility associated with the qualified
verb. Accordingly, usage of "may" and "may be" indicates that a
modified term is apparently appropriate, capable, or suitable for
an indicated capacity, function, or usage, while taking into
account that in some circumstances the modified term may sometimes
not be appropriate, capable, or suitable. For example, in some
circumstances an event or capacity can be expected, while in other
circumstances the event or capacity cannot occur--this distinction
is captured by the terms "may" and "may be."
[0081] This written description uses examples to disclose the
invention, including the best mode, and also to enable one of
ordinary skill in the art to practice the invention, including
making and using a devices or systems and performing incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to one of
ordinary skill in the art. Such other examples are intended to be
within the scope of the claims if they have structural elements
that do not differentiate from the literal language of the claims,
or if they include equivalent structural elements with
insubstantial differences from the literal language of the
claims.
* * * * *