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Патент USA US2404965

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July 30, 1946.
L. A. KILGORE ET AL
‘
2,404,965
OSCILLA'I'ION GENERATING SYSTEM
Filed Jan. 12, 1944
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WITNESSES:
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.INVENTORS
Lee A. ifzlgoi'e and
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July 30, 1946.
2,404,965
L A KILGORE ETAL
OSCILLATION GENERATING SYSTEM
Filed Jan. 12, 1944
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INVENTORS'
Lee A. ifz'lgor-e 072d
Harry
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BY
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‘
_ ATTORNEY
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Patented July 30, 1946
UNITED
2,404,965
STATES
PATENT . OFFICE
2,404,965
OSCILLATION GENERATING SYSTEM
Lee A. Kilgore, Wilkinsburg, and Harry E. Criner,
Forest Hills, Pa, assignors to, Westinghouse
Electric Corporation, East Pittsburgh, Pa., a
corporation of Pennsylvania
Application January 12, 1944, Serial No. 517,922
16 Claims. (Cl. 73-68)
1
2
Our invention relates to oscillation generating
devices for exciting mechanical oscillating sys
tems, for instance, in machines for testing struc
tures as to vibratory strength, fatigue, soundness
of texture or coherence, and the like mechanical
determinants of quality.
mentioned in which rotary generators and motors,
preferably ofstandard design, are used for im
parting forced oscillations to the structure under
The most common methods of exciting a reso
nant‘ mechanical system to oscillations of large
observation.
I
Having these objects in mind and in accordance
with the invention, we provide an oscillation gen
erating device for exciting a mechanical oscilla
tory system bymeans of forced oscillations in
which these oscillations are controlled separately
amplitude are based on the principle of self-ex~
citation. Part of the energy of an oscillation is 10 as to amplitude and frequency. According to an
fed back'through some type of amplifying sys
other feature of our invention, the frequency is
controlled in dependence upon the power factor
temfor producing an exciting force in phase with
of the energy transmission between the separate
the oscillating motion so as to cause the system
oscillation generator and the oscillatory mechan
to continue oscillating at its natural frequency.
It is also known that in a resonant system oscilla 15 ical system excited thereby, this power factor be
ing tantamount to the phase angle between the
tions of large amplitude can be obtained by ap
oscillatory velocity or motion and the oscillator
plying thereto a forcing frequency of a separate
force or torque of the energy transmission. More
oscillator at a frequency very near to the natural
frequency of the system.
a
in particular, the present invention provides
Our invention, more speci?cally, relates to an
means for measuring the oscillatory velocity or a
oscillation generating device of the latter type
and aims at improvements concerning the de
sign, operation, and control of the forcing oscil
magnitude proportional thereto, and separate
measuring means for measuring the force of the
transmitted oscillations or a magnitude propor
tional thereto, in combination with control means
It is an object of the invention to provide a 25 which compare the two measured values with
each other as to phase relation, and regulate the
forced-excited oscillatory system in which the
speed or frequency of the generator in a sense
amplitude of the forcing energy can be regulated
tending to maintain the phase angle at zero or
and varied within wide limits and up to very large
lator.
-
amplitudes while maintaining the frequency of
the exciting force su?iciently close to the natural
more speci?c aspect of the invention, the just
frequency of the excited system to maintain reso
mentioned frequency control is obtained by pro
viding an alternating-current generator (alter
within‘ a range of low values near zero.
In a
nance conditions,
} Another object of the invention is to devise a
nator) acting on a suitable magneto-motoric de
system in which the frequency of the forced os
cillations is automatically adjusted relative tothe
natural frequency of an excited oscillatory speci
vice, such as a synchronous motor, and driving
the alternator by an electric variable speed motor
whose ?eld excitation is controlled by the above
men structure so as to assume a tuned or ap
mentioned phase angle responsive controL.
proximately tuned-vale regardless of differences
in the resonance freqencies of different specimens
to be excited by the same oscillation generator,
These and other objects and features of the
invention will be more fully understood from the
and also for the purpose of requiring, as a rule,
no action or attention by the operator as regards
the proper tuning of the forced oscillations im
posed on the specimens.
following description of the embodiments shown
in the appertaining drawings, in which:
Figure 1 is an explanatory diagram elucidating
the afore mentioned control principle;
Fig, 2 is a schematic showing of a propeller
It is also an object of our invention to achieve 45 testing machine designed in accordance with the
;' the above-mentioned aims by means of an elec
invention;
Fig. 3 represents schematically another pro
trically operated drive of simple design and re
peller testing machine also embodying the in
liable operation and to render such drive readily
applicable to the actuation and excitation of
vention, while
,
mechanical oscillatory systems which are sub 50 Fig. 4 is an explanatory diagram relating to
the operation of the machine shown in Fig. 3.
jected to unidirectional rotation when oscillating,
Referring to Fig. 1, curve A exempli?es sche
‘ as is the case with propellers for aircraft or ships,
for instance.
Another object, allied to the foregoing, is to pro
matically the resonance characteristic of a me
chanical oscillatory system, excited to vibrate at
vide an oscillation generating device of the type 55 its natural ‘frequency, by representing the am
a
'3
2,404,965
4
pli?cation factor versus frequency, the latter be
ing expressed in per cent of the natural fre
quency. The ampli?cation factor is understood
as the amplitude ratio of the excited and exciting
(forced) vibrations. This factor reaches a maxi
mum of about 10 at the natural frequency (100%)
of the chosen example, this maximum value as
well as the rate of change being determined by
the damping of the oscillatory system. Curve B
represents the phase angle between the oscil
latory velocity and the oscillatory ‘force applied
to the resonant system.
Curve C indicates the
8 of the synchronous motor SM is connected
through a rheostat 9 with the mains X and Y.
An alternator AL has its armature ll elec
trically connected with that of the synhcronous
motor SM, while its ?eld winding [2 is energized
from the mains X and Y through an adjustable
rheostat I3. A shaft 14 connects the generator
armature II with the armature IE or a variable
speed motor VM whose armature current is also
10 supplied from the mains X and Y. The ?eld
winding I‘! of motor VM is likewise connected
to the exciter mains X and Y, this connection
phase angle between the oscillatory force and the
being completed by the resistor I8 of a rheostat
oscillatory displacement caused thereby in the
FR whose slider is operated through a suitable
excited system, both curves B and C showing the 15 mechanical transmission I9 by a reversible
angle in degrees versus percentile frequency.
rheostat motor RM whose armature is denoted
According to curve B, the phase angle be
by 2!. Two ?eld windings 22 and 23 are pro
tween oscillatory velocity and exciting force
vided for exciting the armature to run in op
passes through zero and hence changes its direc
posite directions, respectively. The armature
tion at the point (100%) of resonance. In a 20 and ?eld windings of the rheostat motor RM are
simple oscillatory system involving one mass and
also connected to the excited mains X and Y.
one elasticity (spring), the ampli?cation (S) of
A dynamometric relay DR with two control
the impressed force (I) is expressed by the
equation
coils 24 and 25 at right angles to each other,
so as to control a movable relay contact 26 in
25 dependence upon the phase angle between the
excitation of the two coils, serves to control the
connection of the ?eld windings 22 and 23 with
the exciter means. That is, two stationary relay
wherein E represents the oscillatory velocity and
contacts 2'! and 28 cooperating with the movable
6 the phase angle between velocity (E) and force
(I). The magnitude cos 0, in analogy to the 30 contact 26 energize either coil 22 or coil 23 when
S=-IEv cos 0
engaged by contact 26. The control coil 24 of
the dynamometric relay is connected with the
current circuits, is the "power factor” of the
alternator circuit so as to be energized in ac
energy transmission fromlthe oscillation gener
cordance with the electric current fed to the
ator to the oscillating system excited thereby.
While the above equation applies strictly to 35 synchronous motor SM. This current is sub
stantially in phase with the oscillatory torque
simple oscillatory systems, it represents also a
produced by the synchronous motor and super
suf?cient approximation for more complicated
imposed on the rotation of shaft 2 and propeller
resonant systems where the damping is not too
corresponding phenomena in electric alternating
large to suppress a characteristic resonance am
The control coil 25 of the dynamometer DR
pli?cation. Hence, for all intended uses of this 40
is connected with the coil 29 of a torsional
invention, the ampli?cation near resonance is
substantially inverse proportional to the phase
angle and at a maximum when the phase angle
passes through zero.
velocity meter TV whose magnet structure 30
has two poles adjacent to two axially spaced
points of the driving shaft 2 and cooperating
with two armatures (not shown) mounted on the
This being the case, Fig. 1 shows that it is
shaft at these points. Torsiona1 velocity meters
possible to hold the amplitude of the excited
of this type are known as such, and hence not
oscillations within, for instance, 10% of the
further illustrated in detail. Any device for
maximum by holding the phase angle (curve B)
producing a voltage in proportion to a torsional
within about plus and minus 26°, or to hold the
amplitude within 5% of its maximum by main 50 velocity may be used for this purpose. Due to
the just-mentioned connection, the dynamometer
taining the phase angle within the limit of about
coil 25 receives an energizing voltage which
plus and minus 18%. Consequently, a very ac
varies in accordance with the torsional velocity
curate control of ampli?cation can be obtained
of the propeller vibrations excited by the syn
with a relatively broad control of the phase
angle; and this phenomenon is taken advantage 55 chronous motor SM. Hence, the dynamometer
contact 26 is controlled in dependence upon the
of by our invention for achieving an accurate
phase angle between the exciting force or torque
control of the forcing oscillation generator by
and the torsional motion or velocity caused
means of relatively simple operating and control
thereby. Consequently, the control of relay con
devices.
In the propeller testing machine according to 60 tact 26 is governed by the power factor of the
energy transmission from the generator of the
Fig. 2, the propeller structure I, representing the
forced oscillations to the oscillatory mechanical
mechanical oscillatory system to be excited in
system excited by these forced oscillations.
its natural frequency, is mounted on a shaft 2,
When this phase angle is zero or substantially
which is driven by the armature 3 of a direct
zero, the relay contact 26 assumes an inter
current motor DM connected through a speed
regulator 4 with exciter mains X and Y ener
mediate and inoperative position between the
gized from a direct-current source of constant
stationary contacts 2‘! and 28 so that both ?eld
windings 22 and 23 of rheostat motor RM are
voltage. The speed adjustable motor DM per
disconnected. Then the motor RM remains at
mits driving the propeller l at the selected test
ing speed. The shaft 2 carries also the armature 70 rest, and the regulating rheostat FR maintains
6 of a synchronous motor SMwhich serves to
superimpose on the unidirectional rotation of the
shaft a torsional oscillation in order to excite
the propeller structure to rotary oscillations dur
its adjustment.
When the oscillatory motion of the propeller is
out of phase with the excited torque of the
synchronous motor SM and hence the phase angle
ing its continuous rotation. The ?eld winding 75 different from zero, the dynamometer contact 26
Stu-“(M1 liuuwl
2,404, 965
5
engages either contact 2‘! or 28 with the effect of
causing the rheostat motor RM to change the
adjustment of regulator FR in the direction re
circuit of the alternator AL has a secondary 53
tapped in its midpoint for supplying the tubes 54
and 55 with plate current. The voltage of this
quired to return the phase angle to zero. More
current depends on the excitation of the primary
in detail, the change in adjustment of regulator
52, which, in turn, is a measure of the alternator
FR has the e?ect of varying the excitation of
current and hence of the force of the oscillations
imposed on the propeller by the electromagnetic
the motor ?eld winding ll accordingly, thereby
changing the driving speed of motor VM and
device SM’. Another primary 53a also having a
tapped mid-point is connected with the cathodes
hence the frequency of the alternating current
supplied by the generator AL to the motor SM. 10 of the tubes 54 and 55 in order to supply the heat
In this manner, the system has the tendency to
ing current thereto. It will be understood, how
ever, that any other suitable source of heating
maintain the‘ operating frequency of the syn
current may be employed instead. The grids of
chronous motor SM in resonance with‘the natural
frequency of the oscillatory system represented
tubes 54 and 55 are connected with the terminals
15 of the secondary winding of a transformer 56
by the propeller structure I.
Whose primary is connected with the voltage coil
The amplitude of the forced oscillations im
parted to the propeller by the synchronous motor
59 of a measuring device 60, which in coaction
with the armature 36 generates a voltage in pro
SM depends on the direct-current excitation of
portion to the velocity of the oscillatory motion
the generator ?eld winding l2 and also on that
of the motor ?eld winding 8 and hence can be 20 transmitted to the propeller structure. The mid
point of the secondary of transformer 56 is con
adjusted by means of the rheostats l3 and 9.
nected with the mid-point of Winding 53a of
Consequently, these two rheostats permit varying
transformer 5! in order to complete the grid con
the amplitude of the forced oscillations. For
trol circuit of the gas discharge tubes. The con
small phase angles as occurring in a system de
nection contains a potentiometer 51 in combina
signed in accordance with the principles set forth
tion with a voltage source 58 for providing an
above, the control operation of the dynamometric
adjustable grid bias. The output circuit of the
device DR is nearly independent of the amplitude
electronic regulator is connected with the above
of the oscillations. Consequently, the rheostats
mentioned voltage regulator VR. If desired, a
l3 and 9 permit a change in the magnitude of the
excited oscillations within very wide limits with 30 ?lter 49 and a calibrating rheostat 50 may be
interposed in the input circuit of the voltage
out affecting the desired automatic control op
regulator. As will be explained hereinafter, the
eration. It will be understood that one of the
output current of the electronic network FR’ is a
rheostats 9 or l3 may be omitted or need not be
measure of the phase angle or power factor of
varied for obtaining this result.
‘
the oscillatory energy transmission between the
If the inertia of the alternator AL is sufficiently
oscillation generator and the propeller structure.
high, no anti-hunting devices need be employed.
The voltage regulator VR serves to supply the ?eld
However, the system can also be provided with
winding 4‘! of the variable speed motor VM with
such devices in order to increase its accuracy of
excitation in dependence upon the tube ouput
control.
In cases where the inertia of a dynamometer 40
type control instrument is of such magnitude as
current.
,
Different types of voltage regulators suitable
to render the anti-hunting problem difficult, or
for this purpose are known as such. In the illus
where higher accuracy or ease of adjustment is
desired, an electronic control system can be em
ployed for determining the power factor. A sys
trated example, a potentiometer resistor 6| is
tem of the later type is exempli?ed by the
diagram shown in Fig. 3.
According to Fig. 3, a ‘propeller structure to
connected across the mains X and Y and has a
slider 62 which is biased in the upward direction
by a spring and connected with an armature
which is attracted by a control coil 63 to move
in the downward direction, this control coil being
excited by the tube output current. The ?eld
be tested is mounted on a shaft 32 which is driven
by a direct-current motor 33 fed from exciter 50 winding 41 is connected with the slider 62 and
mains X and Y through a speed regulating
with one terminal of the potentiometer resistor
6|. Consequently, the voltage imposed on ?eld
rheostat 34. An electromagnetic device SM’
winding 4‘! depends on the adjustment of the
serves to impart axial oscillations to the propeller
slider 62, which, in turn, is controlled by the
structure 3| during the rotation of the structure.
,
The device has an armature 36 connected with 55 plate current of the tubes. »
Due to the fact that the voltage supplied by
the propeller for cooperation with a stator 31
the transformer secondary 53 to the plate circuit
whose magnetic body is provided with an energiz
of the tubes 54 and 55 maintains a ?xed phase
ing winding 38. This winding is connected with
relation to the alternator output current and
the armature 4| of an alternator AL Whose ?eld
winding 42 is energized from the mains X and Y 60 hence to the axial force of the forced oscilla
tions imparted to the propeller, while the grid
through a control rheostat 43 serving to adjust‘
voltage of the tubes varies in a ?xed relation to
the voltage of the alternating current and hence
the oscillatory axial motion of velocity caused
the amplitude of the forced axial oscillations im
parted to the rotating propeller.
by these forced oscillations, the output current
The alternator armature 4] is mounted on the 65 supplied to the‘ voltage regulator VR can be so
adjusted as to represent a measure of the power
shaft 44 of the armature 46 of a variable speed
factor in accordance with the principle explained
motor VM. The armature circuit of this motor
in the foregoing. By selecting a proper grid bias
is connected with the mains X and Y while the
with the aid of the elements 51 and 58, an output
?eld winding 41 is supplied with variable excita
tion from a voltage regulator VR, which, in turn, 70 current can be obtained whose average value for
small angular differences varies more than pro
is controlled by a regulator‘FR' of the electronic
portionately with the angular displacement.
type. This regulator contains two gaseous dis
Hence, if the frequency of the alternator AL, i. e.
charge tubes 54 and 55 of the type known under
the name “Thyratron.” A transformer 5| whose
the speed of its driving motor VM, is adjusted
primary 52 is series-connected in the armature 75 to give a constant voltage output, a constant
2,404,965
small angular displacement is maintained, thus
tric network connected with said motor for con—
trolling its speed, and phase angle responsive
holding the frequency of the forced oscillations
control apparatus disposed in said network and
close to resonance with the natural frequency
having means for producing a component control
of the propeller structure. If the grid bias is
kept small compared with the amplitude of the Cl magnitude in accordance with the oscillatory
velocity of the imparted oscillations and means
grid voltage, the phase angle is not appreciably
for producing a component control magnitude in
affected by changes in amplitude. Hence, the
accordance with the force effecting said oscilla
control rheostat 43 can be adjusted at will with
tions so as to maintain said motor at a speed
in wide limits, thereby changing the amplitude
corresponding approximately to the zero value of
of the excited oscillations accordingly, without
the phase angle between said two magnitudes.
affecting the desired control function of the
system.
The foregoing explanation will be more fully
understood from a reference to the voltage char
acteristics shown in the diagram of Fig. 4 and
relating to the operation of either electronic tube.
Curve D represents the plate voltage of the tube
supplied by transformer 5|, while curve E exem
2. An oscillation generating device for exciting
a mechanical oscillatory system, comprising elec
tric means for imparting forced oscillations to
said system, an alternating-current generator for
energizing said means, a variable speed motor in
driving connection with said generator, an elec
tric network connected with said motor for con
trolling its speed, and phase angle responsive con
trol apparatus disposed in said network and hav
pli?es the grid voltage supplied by transformer
56. The line F indicates the constant grid bias
applied to the grid circuit by means of the volt
age source 58. The resultant grid voltage repre
senting the sum of voltages E and F at any in
stant is denoted by curve G. The critical grid
voltage of the tube corresponds to curve H.
ing means for producing a component control
magnitude in accordance with the oscillatory ve
locity of the oscillations of said system and means
for producing a component control magnitude in
accordance with the current supplied by said gen
Hence, under the operating conditions represent
ed by Fig. 4, the tube is ignited at the moment
corresponding to the intersection K of curves H
and G. In this moment, the tube is rendered
conductive until the plate voltage D passes
through zero at the instant denoted by point L.
The output current supplied to the voltage regu
lator VB. is in accordance with the area marked
M. It will be seen that any change in the phase
relation of the plate voltage D and the voltage '
breakdown moment K and hence result in a larger
electric control means connected with said motor
40
rent is zero.
It will be understood from the foregoing that
an electronic system of the type described can
also be used for exciting torsional rather than
axial vibrations of the rotating oscillating struc
ture. Furthermore, a torsional excitation of
vibrations can be readily combined with a system
for producing simultaneous axial vibrations. It
should also be understood that the principles of '
our invention as set forth in the foregoing are
applicable for exciting oscillatory mechanical
systems of a type different from the rotating
propeller structures referred to in the above de
scribed examples. In particular, an electronic
control system for regulating a phase angle be
tween two alternating quantities, by comparing
tating system, an alternating-current generator
for energizing said motor, a variable speed motor
in driving connection with said generator, and
component E of the grid voltage will displace the
or smaller output current. By properly adjust
ing the tube circuits, the output current can be
reduced to zero when the voltages D and E have
a phase displacement at which the output cur
erator to said electric means in order to main
tain said motor at a speed corresponding approx
imately to the zero value of the phase angle be
tween said two magnitudes.
3. An oscillation generating device for exciting
a rotatable oscillatory system, comprising a drive
for rotating said system in a given direction, an
alternating-current motor connected with said
drive for superimposing oscillations on said ro
and having means responsive to the phase angle
between the oscillations introduced by said motor
and the oscillations of said system caused by said
introduced oscillations so as to maintain said var
iable speed motor substantially at a speed corre
sponding to the zero value of said phase angle.
4. An oscillation generating device for exciting
a rotatable oscillatory system, comprising a drive
for rotating said system in a given direction, an
alternating-current motor connected with said
drive for superimposing oscillations on said ro
tating system, an alternating-current generator
for energizing said motor, a variable speed motor
in driving connection with said generator, an
electric network connected with said latter motor
for controlling its speed, and phase angle respon
sive control apparatus disposed in said network
and having means for producing a component
control magnitude in accordance with the oscil
latory velocity of the superimposed oscillations
a voltage proportional and in de?nite phase rela
and means for producing a component control
tion to one quantity with a voltage proportional
and in de?nite phase relation to the other can 60 magnitude in accordance with the force effecting
said superimposed oscillations in order to main
be applied in cases other than the testing'of
tain said variable speed motor at a speed corre
oscillatory systems.
sponding substantially to the zero value of the
In view of the possibilities of modifying the
phase angle between said component magnitudes.
systems of the type described without departing
5. An oscillation generating device for exciting
65
from the objects and essential features of the
a rotatable oscillatory system, comprising a drive
invention, we wish this speci?cation to be under
for rotating said system in a given direction, a
stood as illustrative rather than in a limiting
synchronous motor connected with said drive for
sense.
superimposing oscillations on said rotating sys
We claim as our invention:
1. An oscillation generating device for exciting 70 tem, an alternating-current generator for ener
gizing said synchronous motor, a variable speed
a mechanical oscillatory system, comprising elec
motor in driving connection with said generator,
tric means for imparting forced oscillations to
an electric network connected with said latter
said system, an alternating-current generator for
motor for controlling its speed, and phase angle
energizing said means, a variable speed motor in
driving connection with said generator, an elec 75 responsive control apparatus disposed in said net
2,404,965
‘59’
10
work and having means for producing a com
motor, said voltage supply means and said con
ponent control magnitude in accordance with the
trol means being connected with said circuit so
oscillatory velocity of the oscillations of said sys
as to vary the energization of said ?eld winding
in dependence upon the phase angle between said
voltage and said current in order to maintain
said phase angle substantially at the zero value.
10. A device for exciting oscillations in a ro
- tem and means for producing a component con
trol magnitude in accordance with the current
supplied by said generator to said synchronous
motor in order to maintain said variable speed
motor at a speed corresponding substantially to
the zero value of the phase angle between said
tating structure, comprising a drive for driving
said structure in a given direction of rotation,
component magnitudes.
10 a synchronous motor connected with said struc
6. An oscillation generating device for exciting
ture for causing it to oscillate during its rotation,
a mechanical ‘oscillatory system, comprising elec
an alternator for energizing said motor, a varia
ble speed motor having a speed controlling ?eld
tric means for introducing mechanical oscillations
into said system, an alternating-current gener
winding and being connected with said alternator
ator for energizing said means, electric control 15 for driving the latter, an electric energizing cir
means for adjusting the amplitude of the ener
cuit connected with said ?eld winding and con
gization of said means, a variable speed motor
taining a variable circuit member for varying the
in driving connection with said generator,‘ and
energization of said winding, a reversible motor
electric control means connected with said motor
for adjusting said circuit member, a dynamo
and having means responsive to the phase angle 20 metric relay for controlling said reversible motor,
between said introduced oscillations and the os
means for supplying variable voltage in response
cillations of said system caused by said intro
to the oscillatory speed of the transmitted oscil
duced oscillations in order to maintain said motor
lations and control means responsive to the cur
substantially at a speed corresponding to th
rent supplied by said alternator to said syn
zero value of said phase angle.
‘ 25 chronous motor, said voltage supply means and
7. An oscillation generating device for exciting
said control means being connected with said
a mechanical oscillatory system, comprising elec
relay, whereby the energization of said ?eld
tric means for imparting forced oscillations to
winding is controlled in dependence upon the
said system, an alternating-current generator for
phase angle between said voltage and said curenergizing said means, a variable speed motor in 30 rent in order to maintain said phase angle sub
driving connection with said generator, a speed
stantially at the zero value.
control network connected to said motor, a dy
11. An oscillation generating device for excit
namometric control relay forming part of said
ing a mechanical oscillatory system, comprising
network and having two control coils and a con
electric means for introducing oscillations into
tact element movable in response to changes in 35 said system, an alternating-current generator for
phase angle between the energization of said coils
energizing said means, a variable speed motor
respectively, one of said coils being connected to
in driving connection with said generator, and
said generator and electric means so as to be
electric control means responsive to the phase
energized in accordance with the generator cur
angle between said introduced oscillations and
rent. and means responsive to the velocity of the 40 the resulting oscillations of said system, said
oscillations of said system caused by said electric
control means being connected with said motor
means and being connected with said other coil
so as to maintain said motor substantially at a
for energizing it in accordance with said velocity
speed corresponding tothe zero value of said
whereby said motor is maintained at a speed
phase angle.
45
corresponding substantially to the zero value of
12. An oscillation generating device for excit
said phase angle.
-
8. An oscillation generating device for exciting
a mechanical oscillatory system, comprising elec
ing a mechanical oscillatory system, comprising
electric means for imparting forced oscillations
to said system, an alternating-current generator
tric means for introducing mechanical oscilla
for energizing said means, a variable speed motor
tions into said system, an alternating-current 50 in driving connection with said generator, and
generator for energizing said means, a variable
electric control means connected with said motor
speed motor having a speed controlling ?eld
winding and being connected with said generator
and being responsive to the phase angle between
the electric oscillations generated by said ‘gen
for driving the latter, electric control means con
erator and the resulting oscillations of said sys
nected to said ?eld winding for energizing it and 55 tem so as to maintain said motor substantially
containing means responsive to changes in the
at a speed corresponding to the zero Value of
power factor of the energy transmission between
said introduced oscillations and the resulting
said phase angle.
13. An oscillation generating device for exciting
a mechanical oscillatory system, comprising elec
motor substantially at a speed corresponding to 60 tric means for introducing oscillations into said
oscillations of said system so as to maintain said
the unity value of said power factor.
9. A device for exciting oscillations in a ro
system, an alternating-current generator for en
ergizing said means, a variable speed motor in
tating structure, comprising a drive for driving
driving connection with said generator, a speed
said structure in a given direction of rotation,
control network connected to said motor and con
65
a synchronous motor connected with said struc
taining a rheostat for varying the ?eld energiza
ture for causing it to oscillate during its rotation,
tion of said motor, an auxiliary reversible motor
an alternator for energizing said motor, a varia
for adjusting said rheostat, and a dynamometric
lble speed motor having a speed controlling ?eld
control relay for controlling said reversible motor,
winding and being connected with said alternator
said
relay being connected with said electric
70
for driving the latter, an electric energizing cir
means and said oscillatory system so as tore
cuit connected with said ?eld winding, means
spond to changes in the phase angle between said
for supplying variable voltage in response to the
introduced oscillations and the oscillations of said
oscillatory speed of the transmitted oscillations
system caused by said introduced _oscil1ations,‘in
and control means responsive to the current sup
order to control the speed of said variable speed
plied by said alternator to said synchronous
2,404,905 "
11
12
motor so as to maintain said phase angle substan
tially at the zero value.
14. A device for exciting a mechanical oscilla
circuit, means connected with said grid circuit
for controlling said tube in accordance with the
oscillatory velocity of the oscillations caused in
said system by said transmitted oscillations, and
tory system, comprising electromagnetic drive
means for energizing said plate circuit in accord
ance with the torque of said transmitted oscilla
tions in order to vary said speed in dependence
upon the phase angle between said velocity and
said alternator, electronic tube network connected
said torque so as to maintain said phase angle
to said motor for controlling its speed and having
substantially at the zero value.
a plate circuit and a grid circuit, measuring
16. With a machine for testing propellers hav
means responsive to the oscillatory velocity of
ing a shaft for accommodating the propeller to
the oscillations caused in said system by said
be tested and a motor for driving said shaft, in
transmitted oscillations, said measuring means
combination, a synchronous motor connected with
being connected with one of said circuits, and
means for controlling said other circuit in ac 15 said shaft for imposing torsional oscillations
thereon, an alternator for energizing said syn
cordance with the torque of said transmitted
chronous motor, a variable speed motor for driv
oscillations in order to vary said speed in de
ing said alternator, control means responsive to
pendence upon the phase angle between said
the torsional velocity of said shaft, control means
velocity and said torque so as to maintain said
20 responsive to the torsional torque applied by said
phase angle substantially at the zero value,
synchronous motor to said shaft, and electric cir
15. A device for exciting a mechanical oscilla
cuit means connected with said variable speed
tory system, comprising electromagnetic drive
motor and both said control means for controlling
means for transmitting torsional oscillations to
the motor speed in dependence upon the phase
said system, an alternator for energizing said
drive means, a variable speed motor disposed for 25 angle between said velocity and said torque in
order to maintain said phase angle substantially
driving said alternator, a control network con
at the zero value,
nected with said motor for controlling the motor
LEE A. KILGORE.
speed, said network having a gaseous discharge
HARRY E. CRINER.
tube provided with a plate circuit and a grid
means for transmissing torsional oscillations to
said system, an alternator for energizing said
drive means, a variable speed motor for driving
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