U.S. patent application number 12/907259 was filed with the patent office on 2011-02-10 for momentum-conserving wind-driven electrical generator.
Invention is credited to Steven J. DeAngeles.
Application Number | 20110031761 12/907259 |
Document ID | / |
Family ID | 40898448 |
Filed Date | 2011-02-10 |
United States Patent
Application |
20110031761 |
Kind Code |
A1 |
DeAngeles; Steven J. |
February 10, 2011 |
Momentum-Conserving Wind-Driven Electrical Generator
Abstract
Wind-driven electrical generators will slow and lose kinetic
energy when the wind slows or stops. When the wind slows or stops,
kinetic energy in the rotating turbine and other rotating
components that would otherwise be lost, is conserved by supplying
a supplemental mechanical energy to the rotating components using a
battery-powered motor. The electrical power for the drive motor is
obtained from solar-charged batteries. In an alternate embodiment,
solar cells provide all of the energy for the drive motor.
Inventors: |
DeAngeles; Steven J.;
(Chicago, IL) |
Correspondence
Address: |
Docket Clerk
1000 JORIE BOULEVARD SUITE 144
OAK BROOK
IL
60523
US
|
Family ID: |
40898448 |
Appl. No.: |
12/907259 |
Filed: |
October 19, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12623670 |
Nov 23, 2009 |
7834473 |
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12907259 |
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|
12019893 |
Jan 25, 2008 |
7635923 |
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12623670 |
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Current U.S.
Class: |
290/55 |
Current CPC
Class: |
F03D 9/11 20160501; F05B
2270/32 20130101; Y02E 70/30 20130101; F05B 2220/60 20130101; H02P
9/04 20130101; H02P 9/06 20130101; H02P 2101/15 20150115; Y02B
10/30 20130101; Y02P 90/50 20151101; F03D 7/0224 20130101; Y02E
10/76 20130101; F05B 2270/304 20130101; Y02B 10/70 20130101; Y02E
10/72 20130101; H02J 7/34 20130101; F03D 7/042 20130101; H02J 7/35
20130101; H02J 7/32 20130101 |
Class at
Publication: |
290/55 |
International
Class: |
F03D 9/00 20060101
F03D009/00; H02P 9/02 20060101 H02P009/02 |
Claims
1. A wind-driven generator comprised of: a wind-driven, rotating
propeller having a plurality of blades, the blades extending from a
rotating hub, and having a length-wise axis, the blades being
configured to be rotatable about the length-wise axis, and wherein
said propeller blades are capable of being rotated about said
length-wise axis by at least one servo motor inside said hub, the
rotation of the propeller by the wind rotating an elongated shaft
coupled to the propeller; an electricity generator coupled to the
elongated shaft such that the generator generates electrical energy
when the elongated shaft is rotating; a wind speed detector
operatively coupled to the computer, and which detects the speed of
wind blowing into the propeller, and which generates a signal that
causes a controller to change a pitch of the propeller blades in
order to minimize wind drag.
2. The wind-driven generator of claim 8, further including a first
clutch, which mechanically couples and mechanically de-couples the
rotating shaft from an electricity generator, responsive to a
signal from said wind speed detector.
3. The wind-driven generator of claim 8 further including a
transfer switch, which decouples the generator from an electrical
load responsive to a decrease in at least one of: wind speed and
elongated shaft speed.
4. A wind-driven generator comprised of: a wind-driven, rotating
propeller having a central hub and a plurality of blades that
extend radially from the central hub, the blades having a
longitudinal axis extending radially from the central hub, at least
one of the blades having a pitch that can be varied by rotating the
at least one propeller blade around the longitudinal axis, the
rotation of the propeller by the wind rotating an elongated shaft
that is coupled to the propeller, the at least one blade being
coupled to a servo motor, the servo motor being configured to be
able to change the pitch of the at least one blade responsive to a
signal; a detector, which generates said signal, the signal causing
the servo motor to change the pitch of the at least one blade, in
order to reduce wind drag on the propeller when at least one of:
wind speed falls below a first predetermined value, and when
propeller rotation speed falls below a second predetermined
value.
5. The wind-driven generator of claim 11 further including a
software controlled transfer switch, which decouples the electric
generator/motor from an electrical load under software control,
when said electric generator/motor changes from said first mode to
the second mode.
Description
RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 12/623,670 filed Nov. 23, 2009, which was a
divisional of U.S. patent application Ser. No. 12/019,893, filed
Jan. 25, 2008. This application therefore claims the benefit of the
filing date of U.S. patent application Ser. No. 12/019,893.
BACKGROUND OF THE INVENTION
[0002] FIG. 1 is a simplified depiction of a wind-driven generator
2. Wind, represented by reference numeral 3, causes a propeller 4
to rotate. The propeller 4 drives a generator 5, which generates
electricity. The electricity generated by the generator 5 flows
through a transmission line 6 to a load, such as an electrical
power grid represented by reference numeral 7 or a consumer's home,
a business or a small factory.
[0003] A problem with wind-driven electric power generation is that
wind is unreliable and its speed is never constant. Excess
propeller speed caused by high winds can be limited by a brake or
by blade pitch, however, propeller speed cannot be downwardly
controlled when wind velocity falls. When the wind speed falls,
electric output power will fall since electric output power is
directly related to propeller rotation speed. When the wind stops,
output power will also stop. Fluctuating wind speed will therefore
cause generator output to fluctuate.
[0004] A closely related problem is that the propeller 4 requires a
certain amount of kinetic energy, i.e., rotational velocity, before
it can even begin to generate usable amounts of output power, as
FIG. 2 shows. Some energy must be imparted to the propeller before
it can generate usable electric output power. When the wind slows
or stops, latent kinetic energy in the rotating propeller and other
rotation machinery connected to the propeller begins to dissipate
through wind loss, bearing loss and electrical loading, if the
generator is not disconnected from its electrical load. The lost
kinetic energy must be restored by the wind before the generator
can resume generating power. Maintaining propeller speed when the
wind slows or stops might improve wind generator efficiency by
shortening the time required to bring the generator on-line after
the wind speed has recovered. A method and apparatus for simply and
economically maintaining propeller speed, during intervals when the
wind slows or has stopped, would be an advantage over the prior
art.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a simplified depiction of a wind-driven generator
2.
[0006] FIG. 2 is a graph of wind generator output power as a
function of wind speed;
[0007] FIG. 3 is a schematic diagram of a momentum-conserving
wind-driven, momentum-conserving electricity generator;
[0008] FIG. 4 is a schematic diagram of an alternate embodiment of
a momentum-conserving wind-driven, momentum-conserving electricity
generator;
[0009] FIG. 5 is a schematic diagram of yet another embodiment of a
momentum-conserving wind-driven, momentum-conserving electricity
generator;
[0010] FIG. 6 depicts a wind driven generator having solar cells on
the tower supporting the wind driven generator;
[0011] FIG. 7A and 7B depict different positions of a propeller
blade rotated about its lengthwise axis;
[0012] FIG. 8 depicts where the views shown in FIG. 7A and 7B are
taken.
DETAILED DESCRIPTION
[0013] FIG. 3 is a schematic diagram of a momentum-conserving
wind-driven electricity generator 10. The generator 10 is comprised
of a wind-driven, rotating propeller 12 that is mounted to a first
elongated drive shaft 16. The propeller 12 is comprised of two or
more propeller blades 14 that are affixed to a central hub 36 that
houses a bi-directional servo motor (not shown) for each blade.
Each servo motor is coupled to the controller 34 and rotates the
blade 14 around its longitudinal axes (extending outwardly, radial
to the hub but not shown for clarity) in order to control the
blade's pitch under software control. The ability to controllably
rotate the propeller blades around their longitudinal axes provides
an ability to control blade speed in response to wind speed
fluctuations.
[0014] When the wind velocity is too low to generate usable power
and/or when the wind has stopped, propeller momentum and the
momentum or other rotating machinery connected to the propeller is
conserved, at least temporarily, using electric energy stored in
rechargeable batteries to drive a motor that keeps the propeller
turning. The rechargeable batteries are kept charged using energy
from photovoltaic cells or from the generator 10 itself during
periods when wind velocity permits the generator 12 to produce
excess power. In an alternate embodiment, the back-up drive motor
is powered directly and exclusively by energy provided by arrays of
photovoltaic cells, i.e., solar cells.
[0015] Still referring to FIG. 3, wind 4 that strike the blades 14
of the propeller 12 will undergo a change in momentum and impart a
force against the propeller blade 14 that causes the propeller 12
to rotate about its axis, which is the geometric center of the
first drive shaft 16. Stated another way, when the wind 4 blows, it
will cause the propeller 12 to rotate the first drive shaft 16, to
which the propeller 12 is attached.
[0016] The first drive shaft 16 is mechanically coupled to a first
drive gear 18, which includes a magnet, which in combination with a
Hall-effect sensor, is used to measure first drive gear 18 rotation
speed. The first drive gear 18 is engaged to a much
smaller-diameter second driven gear 20 so that the relatively slow
propeller 12 speed produces a higher driven gear 20 rotation
speed.
[0017] Driven gear 20, which can also include one or more magnets,
is attached to a second elongated drive shaft 22. The mechanically
rotating armature 23, i.e., the rotating electric field winding 23
of a generator 24, is coupled to the second drive shaft 22 such
that when the wind blows, it causes the propeller 12 to rotate.
Propeller rotation causes the first drive shaft 16 and the first
drive gear 18 to both rotate. Rotation of the first drive gear
causes the second driven gear 20 and the second drive shaft 22 to
rotate, which causes the generator field winding 23 to rotate,
albeit in a direction, opposite the propeller, first drive shaft 16
and first drive gear 18. Since the elongated drive shaft 22 is
directly connected to rotating field winding 23 of the generator
24, propeller rotation causes the generator 24 to generate
electrical energy in the electrical armature 26 of the generator
24.
[0018] Those of ordinary skill in the art are familiar with the use
of so-called Hall-effect sensors to detect the position of a
rotating shaft but also to measure shaft rotation speed. In the
embodiments disclosed herein, a shaft rotation speed detector 32A,
preferably embodied as a Hall effect sensor, is mounted at an
effective distance away from magnets in the first gear 18. The
magnets and their rotation enable the detector 32A, in combination
with the controller 34 to which the detector 32A is coupled, to
detect variations in the shaft rotational speed. Since the detector
32A, in combination with the controller 34, is able to detect and
measure shaft speed, detector 32 is therefore able to indirectly
detect wind speed as well as indirectly detect electrical loading
on the generator 10 because wind speed and loading will both affect
shaft rotation speed.
[0019] Those of ordinary skill in the art know that the rotational
speed of the propeller 12 rarely goes over a few dozen turns per
minute. The generator 24, however, requires a relatively high
rotation speed. The driven gear 20 is therefore usually much
smaller than the drive gear 18 in order to obtain an acceptable
rotation speed from a relatively slo-turning propeller 12. The
faster rotational speed of the driven gear 20 enables a Hall-effect
sensor 32B located proximate to magnets in the driven gear 20 to
detect relatively small changes in the rotational speed of the gear
20, shaft 22 and generator 24. It will therefore usually be
advantageous to detect propeller 12 speed fluctuations using a
second Hall-effect sensor 32B proximate to the driven gear 20,
since a small change in propeller rotation speed will cause a
larger change in driven gear 20 rotation speed.
[0020] As set forth above, generator 24 rotation speed will be
determined by both the wind speed and the electrical load 50 on the
generator 24. Stated another way, shaft speeds will decrease as
electrical loading is increased. In an alternate embodiment, wind
speed is measured by one or more other kinds of wind speed
detectors, such as one or more pitot tubes 52. Shaft speed
decreases, i.e., deceleration, attributable to wind speed can be
more accurately attributed to wind speed decreases by measuring
wind speed using a device such as a pitot tube in combination with
a shaft speed detector since a pitot tube will not be able to
detect minute wind speed changes that might nevertheless affect
shaft speed that is detectable by the sensors 32A and/or 32B.
[0021] In the embodiment shown in FIG. 3, the elongated shaft 22
extends all the way through the generator 24 and is directly
coupled to the rotating armature of a D.C. drive motor 30. Stated
another way, the field of the generator 24 and the armature of the
drive motor 30 are both mechanically coupled to the same elongated
shaft 22 such that they rotate together. Since the armature of the
drive motor 30 rotates with the elongated shaft 22, the mechanical
coupling of the elongated shaft 22 to the armature of the motor 30
effectively couples the drive motor 30 to one or both of the
detectors 32A and 32B. The detector 32A (and/or 32B) can therefore
be used to indirectly measure the speed of the drive motor 30
whenever the drive motor 30 is "powered up" to provide rotational
torque to the elongated shaft 22.
[0022] As was stated above, when wind 4 speed drops, the rotating
machinery in the generator 10 will also drop. When the wind stops,
the rotating machinery in the generator will also stop. When the
wind speed drops or when the wind stops, kinetic energy in the
rotating machinery, i.e., angular momentum, can be maintained or
conserved, by adding rotational torque from an external source,
which in each of FIG. 3, FIG. 4 and FIG. 5, is the D.C. powered
drive motor 30. As shown in the figures and as described above,
drive motor 30 is mechanically connected to the rotating machinery
and powered up, under software control, whenever wind speed falls
or when the wind stops such that usable output power cannot be
generated by the wind.
[0023] Clean and renewable electrical power is supplied to the
drive motor 30 from either a rechargeable battery pack 40 or a
photovoltaic array, i.e., solar cells 42 or both the battery 40 and
the solar cells 42 together. When electrical power is applied to
the drive motor 30 from the battery 40 and/or the solar cells 42,
the drive motor 30 can at least temporarily overcome losses in the
rotating machinery in order to keep the rotating machinery rotating
at either full speed or at a reduced speed until the wind speed
adequately picks up. Clean and renewable electrical energy stored
in the battery 40 can therefore be used to conserve the angular
momentum acquired by rotating machinery of the generator when wind
speed is too low to drive an electrical load or when the wind has
stopped. Maintaining the rotation of speed of at least the
propeller, i.e., conserving its momentum, avoids having to wait
until an otherwise stopped propeller is brought back up to speed by
the wind and thus makes wind-generated power available sooner,
i.e., without having to wait for the wind to adequately spin-up the
propeller 12.
[0024] Electrical energy from the battery pack 40 and the solar
cells 42 is provided to the drive motor 30 through a
software-controlled switch 38, which is activated by and under the
control of a controller 34, such as a microprocessor or
micro-controller. The controller 34 "closes" the switch 38 by
sending an appropriate signal to the coil 39 for the switch 38,
which causes the contacts of the switch to close and complete an
electrical circuit between the drive motor 30 and the rechargeable
battery 40 and solar cells 42. When the switch 38 closes, the
battery 40 and the solar cells 42 are connected to the motor 30.
When the wind speed picks up and becomes sufficient to generate
electrical power, the switch 38 is opened by the controller 34,
which disconnects the motor 30 from the battery 40 and the solar
cells 42. Energy required to at least temporarily maintain
propeller 12 rotation during wind outages is therefore supplied by
solar energy captured by the solar cells 42. The battery is also
kept charged by the solar cells when they're not needed to power
the drive motor 30.
[0025] In one embodiment, the solar cells 42 are attached to the
pole (See FIG. 6) or a tower that the generator 10 is mounted on.
In yet another embodiment, solar cells are applied to surfaces of
the propeller. Since it may be possible to mount numerous cells on
a pole and/or tower, an alternate embodiment of the generators
disclosed herein include a drive motor 30 that is powered
exclusively by energy obtained from solar cells 42, as well as in
addition to power obtained from a battery pack 40.
[0026] The controller 34 that controls operation of the generator
10 is preferably a microcontroller or microprocessor, both of which
are well known to those of ordinary skill. Such devices execute
program instructions that are stored in addressable memory devices,
not shown for clarity and simplicity but well known to those of
ordinary skill.
[0027] In the generator 10 shown in FIG. 3, program instructions
executed by the controller 34 cause the controller 34 to monitor
the output of one or more pitot tubes 52 as well as the Hall-effect
sensor(s) 32A and/or 32B. When the pitot tubes 52 and/or
Hall-effect sensors 32A and/or 32B indicate that the propeller
speed is decreasing due to wind speed, the controller 34 executes
instructions to keep the rotating machinery turning.
[0028] When a wind speed loss is detected, the controller 34 first
disconnects the generator 10 from any electrical load 50 that it
might be driving. Disconnecting the electrical load 50 is readily
accomplished using a software controllable transfer switch or relay
64, well known to those of ordinary skill, the actuation of which
disconnects the generator 24 output from any load that it was
previously driving.
[0029] Simultaneously with or shortly after load disconnection, the
controller 34 changes the pitch of the blades 14 of the propeller
12 in order to minimize wind drag. Reducing wind drag by
"feathering" the propeller blades allows the propeller and other
rotating machinery connected to the propeller to continue to rotate
longer than they would if the propeller blades were "facing" into
the air through which the propeller rotates.
[0030] In the embodiments disclosed herein, the blades 14 of the
propellers 12 extend radially from a central hub 36. FIGS. 7A and
7B are top views of the propeller 12 blade 14 and illustrate how
the blade 14 can be rotated to have different angular orientations
or pitch. At least three different pitches are shown and which are
identified as 14-1, 14-2 and 14-3. The broken line in FIG. 8 shows
the direction from which the views in FIGS. 7A and 7B are
taken.
[0031] In a first position denoted as 14-1, the planar face of the
blade 14 of the propeller 12 forms a first angle denoted as
".alpha." relative to the axis of the shaft 16 and which is
approximately 75 degrees. In a second position 14-2, the blade 14
forms a second angle ".beta." that is approximately 45 degrees. In
a third position 14-3, the blade 14 is "flat." When the propeller
blade 14 is flat as shown in the third position 14-3, wind directed
at the propeller 12 will not cause the propeller 12 to rotate but
wind resistance created by the blades 14 when they are rotated by
the motor 30, will be minimized. In other words, by "feathering"
the blades 14 to the third position 14-3, the power that must be
provided by the drive motor 30 to keep the propeller 12 rotating
will be significantly reduced as compared to the power that would
be required when the blades are at the first position 14-1 or
second position 14-2.
[0032] When the controller 34 detects that the shaft 16 and/or 18
is slowing due to wind speed loss, the controller 34 sends signals
to servo motors within the hub 36, to cause the blades to rotate to
the third position 14-3 (shown in FIG. 7B) so that the wind
resistance created by the rotation of the blades 14, and which must
be overcome by the drive motor 30, can be minimized. By rotating
the blades 14 to minimize wind resistance, the power required from
the drive motor 30 to maintain the speed of the propeller 12 and
other rotating machinery connected to the propeller is
minimized.
[0033] Simultaneously with or shortly after rotating the propeller
blades to minimize wind drag, the controller 34 "closes" switch 38
to connect a power source, either the battery pack 40, the solar
cells 42 or both, to the drive motor 30. Closing switch 38
therefore activates the drive motor 30, which will apply rotational
torque to the rotating machinery for as long as the rechargeable
battery pack 40 and the solar cells 42 are able to keep the motor
turning the rotating components of the generator, i.e., the
generator 24, the drive shafts 22 and 16 and the propeller 12. When
the wind driving the propeller 12 dies down or stops, the momentum
of the rotating propeller and of other rotating components, can be
conserved for as long as the battery 40 and/or the solar cells 42
are able, by having the drive motor 30 supply mechanical energy to
the rotating propeller. Maintaining the propeller's rotation from
the battery pack 40 and solar cells 42 will minimize the energy
that must be restored to the propeller by the wind, before the
generator 10 can start generating power again and hence reduce the
time that the generator is unavailable.
[0034] FIG. 4 depicts another generator embodiment 10B. In FIG. 4,
the generator 24 and the drive motor 30 are separately and
independently connectable to the driven gear 20 through a
combination of separately-operable electrically-controlled clutches
54 and 56 and differential gears 58. The differential gears 58 and
clutches enable the driven gear 20 to be mechanically connected to
either the generator 24 or the drive motor 30. The embodiment of
FIG. 4 differs from the embodiment of FIG. 3 by the mechanical
disconnection of the generator 24 from the shaft 22 and therefore
the shaft 16 and propeller 12 and other rotating machinery. Since
the battery 40 and/or solar cells 42 are not required to supply
power to the motor 30 that would be needed to keep the generator 24
rotating, a battery 40 and solar cells 42 used in the embodiment
depicted in FIG. 4 are able to keep the propeller 12 and drive
shafts 16 and 22 rotating longer than they would the embodiment
shown in FIG. 3.
[0035] As with the embodiment shown in FIG. 3, in FIG. 4, the
controller 34 read signals from wind speed sensors, such as one or
more pitot tubes 52 and/or one or more shaft speed sensors 32A and
32B. When the controller 34 detects that the wind is falling or
that the wind has stopped, the controller 34 is programmed to send
a signal to the generator clutch 54 to mechanically disconnect the
generator 24 from the rotating drive train, i.e., driven gear 20
and shaft 22. Simultaneously or shortly thereafter, the controller
sends a different signal to the motor clutch 56, which mechanically
connects the drive motor 30 to the driven gear 20, through the
differential gears 58.
[0036] After the generator 24 has been mechanically disconnected
from the drive gear 20 and after the drive motor 30 has been
connected in its place, the controller sends a third signal to a
solenoid 38, which in FIG. 4 is configured to connect the drive
motor 30 to the rechargeable battery pack 40 and the solar cells 42
in order to energize the drive motor 30.
[0037] As with the embodiment depicted in FIG. 3, the rechargeable
battery pack 40 is kept in a charged state using current supplied
to it by one or more photovoltaic solar cells 42. As with the
embodiment depicted in FIG. 3, power for the drive motor 30 can
also be provided to it by the solar cells 42, either in parallel
with the battery pack 40 or exclusively, at the same time that the
battery pack 40 provides power to the motor 30.
[0038] The generator clutch 54 and the drive motor clutch 56 are
electrically-actuated clutches that can be separately and
independently controlled by separate and corresponding solenoids,
which are not shown for clarity. In an alternate embodiment, a
single double-pole, double-throw solenoid could be used to control
both clutches by a single signal from the controller 34. The
generator clutch 54 and/or the drive motor clutch 56 can also be
either pneumatic or hydraulic, with the application of the working
fluid, i.e., compressed air or hydraulic fluid, determined by the
actuation of appropriate, software-controlled valves, which are
also not shown for clarity.
[0039] Referring now to FIG. 5 there is shown yet another
embodiment 10C, of a momentum-conserving wind-driven electricity
generator 10. In FIG. 5, a D.C. motor/D.C. generator 60 is used in
place of a separate motor and separate generator.
[0040] In a first mode of operation, the motor/generator 60
armature (not shown) is configured to operate as a D.C. generator.
An external D.C. source generates a magnetic field in that rotates
within field windings that are coupled to an electrical load.
Rotation of the "armature" by the shaft 22 causes the
motor/generator 60 to generate, i.e., output electric power to an
electrical load.
[0041] In a second mode of operation, the electrical connections
the motor/generator 44 are reversed from what they are in the first
mode. In the second mode, the motor/generator operates as a D.C.
motor. In the second mode, the motor/generator 44 is electrically
disconnected from the electrical load using a transfer switch, the
actuation of which connects the stationary "field" windings to the
rechargeable battery pack 40 and/or the solar cells 42. As with the
first and second embodiments, the D.C. motor in the third
embodiment can be powered by the battery or the solar cells or both
the battery and the solar cells in parallel.
[0042] In FIG. 5, electrically re-configuring the motor/generator
60 to function as either a generator or a drive motor eliminates
the need for clutches and gears required by the embodiment shown in
FIG. 4. The embodiment of FIG. 5 also obviates the need to keep two
machines rotating as required by the embodiment shown in FIG. 3. By
simply re-configuring the motor/generator 60 based on wind
conditions, the momentum of the rotating propeller 12 can be
conserved so that the when wind conditions permit electricity
generation to resume, all that needs to be done is to switch the
transfer switch 52 from one position to another.
[0043] Those of ordinary skill in the art will appreciate and
recognize that the true scope of the invention is defined by the
appurtenant claims and not by the foregoing description.
* * * * *