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Патент USA US3092741

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June 4, 1963
J. BAUDE
PULSE AMPLITUDE DISCRIMINATOR
Filed Feb. 24, 1959
3,092,731
3,992,731
Patented June 4, 1.963
2
3,092,731
`mitted by means of a slider 16, resistor 17 and parallelly
connected voltage responsive impedance means such as
John Bande, Milwaukee, Wis., assigner to Ailis-Chalmers
Manufacturing Company, Milwaukee, Wis.
Filed Feb. 24, 1959, Ser. No. 794,965
14 Claims. (Cl. 307-885)
Zener diodes 18, 19 and 20 each connected in series with
resistors 21, 22 and 23, respectively, to a terminal 24 of
a primary winding 25 of a transformer 26 and through a
conductor 27 to the other terminal 28 of transformer 26.
This invention relates to circuits responsive to prede
termined pulse amplitude and more particularly to trig
linear voltage limiting breakdown devices.
PULSE AMPLITUDE DÍSCRIMINA'I‘OR
gering circuits wherein pulses of a source are transmitted
as a function of voltage amplitude to a device for con
trolling a load.
The circuits disclosed were provided to detect at least
a two millisecond current pulse and transmit it as a func
tion `of voltage amplitude to a transistor arrangement
which would energize a trip structure for circuit breaker
operation.
ln accordance with the invention claimed a new and
Although three Zener diodes are shown only one or more
may be used. Zener diodes 18, 19 and 20 comprise non
The maximum voltage which appears across resistors
21, 22 and 23 and terminal 28 of transformer 26 is lim
ited by an impedance device such as a varistor 29 which
is connected between resistor 17 and the parallel arrange
ment of resistors 21, 22 and 23 'and conducto-r 27 between
the connection of rheostat 1‘5 and terminal Z8 of trans
former 26. Varistor 29 is a nonlinear voltage regulating
device which limits the maximum voltage to a given
value, i.e., the greater the voltage the more current that is
carried by the varistor resulting eventually in an equilib
improved triggering circuit is provided which is respon
sive to a predetermined pulse amplitude. This circuit is 20 rium condition between the voltage drop and current ñow
connected across a source of electric pulses and comprises
a transformer having a primary winding and a secondary
winding, said primary winding being connected across
the source of pulses, a voltage responsive means con
nected in series with the primary winding for transmitting
to the primary winding pulses of the source as a func
tion of voltage amplitude and a pulse responsive electric
across and through the varistor. lPotentiometer 15 is ad
justed or varied to match the voltage responsive charac
teristics of the Zener diodes 18, 19 and 20.
Upon the application of a voltage pulse to the varistor
greater than the voltage rating of the Zener diodes 18, 19
and 2€), current will pass at that instant through these
Zener diodes, the primary winding 25 of transformer Z6
and back to shunt 12. The pulse applied to primary
device connected across the secondary winding ‘for con
trolling a load.
winding 25 of transformer 26, which in the example being
Itis, therefore, one object of this invention to provide a
new and improved pulse amplitude discriminating circuit.
Another object of this invention is to provide a new and
improved triggering circuit in which pulses of a source
explained is a two millisecond square pulse, is induced
into its secondary winding 30.
The secondary winding 3G of transformer 26 is con
nected across a high speed pulse responsive electric de
are transmitted as a function of voltage amplitude.
A further object of this invention is to provide a new
vice 33 for controlling the tripping mechanism 11 of a
circuit interrupting device. Device 33 comprises a pair
of complementary semiconductor devices such as, for ex
ample, transistors 34 and 35 directly coupled in a cascaded
and improved triggering circuit in which a transistor
switching arrangement is triggered by pulses of only a '
certain amplitude.
>Objects and advantages other than those set forth will
be apparent from the following description when read in
connection with the accompanying drawing, in which:
fFIG. l is a schematic view of an improved pulse ampli
tude discriminating circuit embodying the invention;
FIG. 2 is a modiñcation of the circuit shown in FIG.
system, or an avalanche type semiconductor device such
as the “unijunction” transistor.
Transistors 34 and 35
each comprise bases 36, 37, collectors 313, 39 and emitters
40, 41, respectively. The emitters and collectors of each
transistor are connected in different series circuits 43, 44
across a source of potential such as a direct current source
45, 46.
The terminal 45 of the direct current source is
1 and embodying the invention; and
connected through a conductor 47 and a conductor 4.3 to a
FIG. 3 is a partial view of a modification of the circuit
illustrated in FIGS. l and 2 and embodying the inven
tion.
Referring more particularly to the drawing wherein
like parts are designated by like characters of reference 50
terminal 49 of the secondary winding 3i) of transformer
26, and through conductor 47, a conductor 5€), resistor 51
to the terminal 2S of the primary winding 25 of trans
former 26. Base 36 of PNP transistor 34 is connected
through a conductor 53, a diode 54 and a conductor 55
to a terminal 56 of secondary winding 36 of transformer
26. Base 37 of NPN transistor 35 is connected through
a conductor 57 and resistor 58 to circuit 43 and collector
33 of transistor 34. A diode 59 is connected in circuit
tude discriminator circuit is utilized to detect a two milli 55 43 between conductor 47 and emitter 4i) of transistor 34,
second current pulse taken from a shunt 12 in a klystron
and a diode 6l) is connected in circuit 44 between emitter
throughout the ñgures, FIG. 1 illustates a pulse amplitude i _
discriminating circuit ‘10 which may be, for example, uti
lized for triggering a ‘high speed circuit breaker tripping
mechanism 11. In the circuit illustrated the pulse ampli
radar application. The klystron tube is a transmitting
mechanism which may be triggered thirty times a second
41 of transistor 35 and a conductor 61 connected to ter
minal 46 of the direct current source.
Resistors 62 and 63 are connected between emitters
and is usually capable of carrying thirty ampere square
shaped current pulses. This type of tube is readily de 60 ¿il? and 41 and conductors 61 and 47, respectively. Diodes
stroyed if subjected to current pulses of an amplitude
59, 69 and resistors 62, 63 are utilized to provide tran
greater than its rating and in view of its cost must be ac
sistors 34 and 3S with negative or reverse bias. The volt
curately controlled. Therefore, the claimed invention was
age drop which occurs across these diodes helps keep tran
conceived to ñrst detect a dangerous electrical condition
sistors 34 and 35 at cuto?l’ and render them temperature
and second to trigger a high speed electronic trip mecha 65 stable. A capacitor 64 connected between emitter di) and
nism into conduction and by action of this mechanism
base 36 of transistor 34 is utilized to prevent spurious
trip a high speed circuit breaker controlling the energiza
voltage surges from triggering into conduction transistor
tion of the klystron tube.
34 prematurely. Capacitor 65 connected between con
A voltage signal from shunt 12 connected to the klys
ductors »47 and 61 is used to neutralize any voltage surges
tron tube (not shown) is transmitted by means of a pair 70 that may build up between terminals 45 and 46 of that
of shielded cables 13, 14 across a potentiometer 15. The
direct current source.
voltage pulse appearing across potentiometer 15 is trans'
An adjustable resistor 66 connected across the terminals
3,092,731
3
4
V24», 28 of the primary winding 25 of transformer 26 is
utilized to discharge the primary winding of transformer
tronic trip mechanism 11 connected across terminals 72,
25 rapidly so as to render the tripping circuit responsive
controlling the energization of the klystron tube.
to a plurality of sequential voltage pulses.
The lock in feature of the circuit illustrated in FIG. 1
is omitted in the structure shown in FÍG. 2, however, it
Resistor `51
and capacitor 68 are connected between terminal 2S of
the primary winding 25 of transformer 26 and conductor
47 to bring Vthe potential of the grounded cable 14 close
to the positive terminal 45 of the ungrounded direct cur
rent source. This type of connection avoids the possibili
ty of surge transmittal from the ungrounded direct current
source 45, 46 to the grounded source of pulses from cables
13, 14 by making the potential difference between these
sources as small as possible at the most sensitive point of
the circuit, namely at the point of connection of the posi
46 and triggers mechanism V11 to open a circuit breaker
may be built in another part of -the control circuit such as
the ultra high speed trip mechanism 11.
The circuits illustrated in FIGS. land 2 will respond
to unidirectional positive pulses. If it is desired that the
pulse amplitude discriminator disclosed respond to pulses
of alternating polarity then the circuits illustrated'in FIGS.
1 and 2 should be modified as shown in ¿FIG »3.
FIG. 3 utilizes idouble anode Zener diodes 75, 76 «and
77 in place of Zener diodes 18, 19 and 20 and a varistor
tive terminal 45 of the direct current source to the secon
73 connected in parallel with varistor 29 but connected
dary Winding 30 of the transformer 26.
in opposite polarity thereto.
As noted the
secondary winding 30 is connected through conductor 55,
seconds exceeding the rating of the Zener diodes 18, 19
and 20 is applied to shunt 12 the pulse enters the primary
Although but a few embodiments `of the present inven
tion have been illustrated and described it will be appar
ent to those skilled in the art that various changes and
modifications may be made therein without departing
from the spirit of 4the invention or from the scope of
the appended claims.
Having now particularly described and ascertained the
winding 25 of transformer 26 and is transmitted as a func
nature of my said invention and the manner in which
diode 54, 'conductor 53, base 36 and emitter 4t) of tran
sistor 34, diode 59 and conductor 47 to the positive ter
minal «45 of the direct current source.
When an input voltage signal of, for example, two milli
tion of voltage amplitude to its secondary winding 33. 25 >it is to tbe .per-formed, I declare that what I claim is:
The resultant pulse of the secondary winding 3i) is applied
1. A triggering circuit responsive to a predetermined
through diode 54 to the base 36 of transistor 34. The pulse
-pulse amplitude comprising a sourceof electric oscilla
renders transistor `3d temporarily cöndnctive. As a re
tions, a transformer comprising a primary winding, said
suit current passes from the positive terminal 45 of the
primary winding kbeing connected across said source of
directcurrent source through diode 59, emitter 4t? and 30 oscillations, an adjustable impedance connected in -shunt
collector 3S of the transistor 3ft-,through a resistor 'lil to
across said source of oscillations and said primary wind
the negative terminal 46 of the"direct current source.
ing, a voltage responsive impedance means comprising a
When this happens Voltage builds up »across resistor 7i? and
semiconductor having a very high Voltage characteristic
is applied by means of resistor 58 to the base 37 of tran
in one operating range and a very loW voltage operating
sistor 35. Transistor 3S is then rendered conductive and 35 characteristic in another range, connected in series with
passes current from the positive terminal 45 of the direct
said primary winding for transmitting the oscillations of
current source through a resistor 71, collector 39 and
said source as a function of voltage amplitude, said ad
emitter 41 of transistor 35 and diode 69, conductor 61 to
justable impedance being varied to match the voltage
the negative terminal 46 of the direct current source. The
responsive »impedance means rating.
~ '
voltage build-up across resistor 71 is applied to the input
2. A triggering vcircuit responsive to a predetermined
terminals of an electronic trip device or mechanism -11
pulse amplitude comprising a source of electric pulses, a
connected across a source of electric power such as ter
minals 45, 46. The electronic trip device 11 is triggered
transformer comprising a primary winding, said primary
winding being connected across said source of pulses, an
into conduction and by means of its action the circuit
adjustable impedance connected in shunt across said
breaker is tripped which controls the energization of the 45 source of pulses `and said primary winding, a Zener break
klystron tube.
down diode connected in series with said primary Wind
The above described circuit is so fast acting that if a
ing for transmitting the pulses of said ysource as a func
surge pulse fed to the klystron tube starts at a safe level
-tion of voltage amplitude, said adjustable impedance being
and continues for a while and then increases in ampli
variedrto match the voltage ,responsive characteristics
tude during the last half of the two millisecond pulse to 50 of said Zener diode.
an unsafe value the circuit will respond and trip the cir
3. A triggering circuit responsive to a predetermined
cuit breaker to disconnect the klystron tube from its ener
pulse amplitude comprising a source of electric pulses, a
gizing circuit.
The voltage or current sensing Icircuit disclosed in FIG.
l has a lock in characteristic.
When transistor 34 is ener
transformer comprising a primary winding, said primary
55 winding being connected across said source of pulses,’an
impedance connected in shunt across said source of pulses
gized into conduction the voltage drop across resistor 751
and
said primary winding, said 4impedance vcomprising a
renders transistor 35 conductive `and when transistor 35
nonlinear voltage limiting device, and a voltage respon
conducts its action keeps the base 36 ofY transistor 34 sutîi
sive impedance means connected in series with lsaid pri
ciently negative to insure continuous ‘conduction of both
mary
winding .for transmitting to said primary winding
transistors 34 and 35 until the circuit breaker has inter 60
pulses of said source as a function of voltage amplitude.
rupted the energizing circuit for the klystron tube.
4. A triggering circuit responsive to a predetermined
FIG. 2 illustrates a pulse amplitude discriminating de
pulse
amplitude comprising »a source of electric pulses, a
vice similar to that shown in FIG. l wherein one semi
transformer comprising a primary winding, said primary
conductor device is used to trigger the high speed trip
mechanism 1'1 `for disconnecting by -means of a circuit 65 Winding being connected across said source of'pulses, a
iirst adjustable impedance connected in -shunt across said
breaker Ythe klystron tube from its energizing circuit.
source of pulsesV and said primary winding, a second im
When the primary winding 25 of transformer 26 receives
pedance connected in shunt across said source of pulses
a pulse from shunt 12 in the same »manner as described
and said primary winding, said second impedance >com
in FIG. l the `secondary Winding through the diode 73
renders transistor 35 conductive and current flow occurs 70 prising a nonlinear voltage limiting device, and a Zener
breakdown diode connected -in series with `said primary
from terminal 45 of the direct current source through re
winding for transmitting the pulses of said source Ías a
sistor 71, collector 39 and emitter 41 of transistor 35,
diode `6i) and conductor 6‘1 to the other terminal 46 of
the direct current source. The voltage build-upV across
function of voltage amplitude, said adjustable impedance
being varied to match the voltage responsive character- Y
resistor 71 is applied to the input terminals ofthe elec 75 istics of said Zener diode.
3,092,731
5
6
5. A triggering circuit responsive to a predetermined
pulse amplitude comprising a source of electric pulses,
and said primary winding, a second impedance connected
in shunt across said source of pulses and said primary
across said source of pulses, an impedance connected in
Winding, said second impedance comprising a nonlinear
voltage limiting device, a plurality of Zener breakdown
diodes connected in parallel with each other and in series
shunt across said source of pulses and said primary wind
with said primary winding for transmitting the pulses of
ing, said impedance comprising a nonlinear voltage limit
ing device, a voltage responsive impedance means con
nected in series with said primary -winding for trans
resistor connected in series with each of said diodes be
tween said second impedance and said diodes for limiting
a transformer comprising a primary Winding and a sec
ondary winding, said primary winding being connected
said source as a function of voltage amplitude, a second
mitting the pulses of said source as a function of voltage 10 the voltage drop across said diodes, and a pulse respon
amplitude, and a pulse responsive electric 4device con
sive electric device connected `across said secondary Wind
nected across said secondary winding for controlling a
ing for controlling a load, said first resistor discharging
load.
rapidly said primary winding after each surge applied
6. A triggering circuit responsive to a predetermined
thereto.
pulse amplitude comprising a source of electric pulses, a 15
l0. A triggering circuit responsive to a predetermined
pulse amplitude comprising a source of electric pulses, a
transformer comprising a primary winding and a sec
ondary winding, said primary winding being connected
transformer comprising a primary winding and a sec
lacross said source of pulses, a first adjustable impedance
connected in shunt across said `source of pulses and said
ondary winding, said primary winding being connected
across said source of pulses, an impedance connected in
primary winding, a second impedance connected in shunt 20 shunt across said source »of pulses and said primary wind
across said source of pu-lses and said primary winding,
in-g, -said impedance comprising a nonlinear voltage limit
said second impedance comprising a nonlinear voltage
ing device, a voltage responsive impedance means con
nected in series wit-h said primary winding for trans
4limiting device, `a Zener breakdown diode connected in
series with said primary winding for transmitting the
mitting to said primary winding pulses of said source as
pulses of said source as a function of voltage amplitude, 25 a function of voltage amplitude, and a pulse responsive
a resistor connected in series with said diode between
electric device `comprising a pair of complementary tran
said second impedance and said diode for limiting the
sistors directly coupled in `a cascaded system across said
voltage drop across said diode, and a pulse responsive
secondary winding for controlling a load.
ll. A triggering circuit responsive to a predetermined
electric device connected across said secondary winding
for controlling `a load.
30 pulse amplitude comprising a source of electric pulses,
7. A triggering circuit responsive to a predetermined
a transformer comprising a primary winding and a sec
pulse amplitude comprising a source of electric pulses,
ondary Winding, said primary winding being connected
a transformer comprising a primary winding and a sec
across said source of pulses, a voltage responsive imped
ondary winding, said primary winding being connected
ance means connected in series with said primary winding
across said source `of pulses, a first resistor connected in 35 for transmitting to said primary winding pulses of said
shunt across said primary winding, a first adjustable im
source as a function of voltage amplitude, and a pulse
pedance connected in shunt across said source of pulses
responsive electric device connected across said secondary
and said primary winding, a second impedance connected
winding for controlling a load, said device comprising a
pair of complementary transistors directly `coupled in a
winding, said second impedance comprising `a nonlinear 40 cascaded system, each of said transistors comprising a
in shunt `across said source of pulses and said primary
voltage »limiting device, a Zener breakdown diode con
nected in series with said primary winding for transmitting
the pulses of said source as a function of voltage ampli
tude, a second resistor connected in series with said
diode between said second impedance and said diode for '
limiting the voltage drop across said diode, and a pulse
responsive electric device connected across said secondary
winding for controlling a load, said ñrst resistor dischang
base, collector and emitter, a source of potential, said
emitter Iand collector of each of said transistors being con
nected in a different series circuit across said source of
potential, each of said series circuits being connected at
one end thereof to one terminal of said secondary winding,
said base of one of said transistors being connected to
the other terminal of said secondary Winding, said base of
said other transistor being connected to said collector of
said one of said transistors, said collector of said other
50 of said transistors being connected to said base of said one
thereto.
»
v
S. A triggering circuit responsive to a predetermined
of -said transistors, said one of said transistors upon a
pulse amplitude comprising a source of electric pulses, a
change of base potential upon receiving a pulse from said
transformer comprising a primary winding and a sec
secondary winding energizing said one of said transistors
ing rapidly said primary winding after each surge applied
ondary winding, said primary winding being connected
causing current to pass through its emitter, collector series
across said source of pulses, a lirst adjustable impedance 55 circuit to the load, said current changing the potential of
connected in shunt across said `source of pulses and said
said base of said other transistor causing current to ñow
primary winding, a second impedance connected in shunt
across said source of pulses and said primary winding,
said second impedance comprising a nonlinear voltage
through its emitter, collector series circuit, said latter cur
rent flow retaining transistor conducting potential on said
base of said one of said transistors, and means for dis
limiting device, more than one Zener breakdown diode 60 connecting said source of potential Vfrom said one of said
connected in parallel with each other and in series with
transistors for causing said transistors to become non
said primary winding for transmitting t-he pulses of said
conductive.
source as a ‘function of voltage amplitude, a resistor con
12. A triggering circuit responsive to a predetermined
nected in series with each of said diodes between said
pulse amplitude comprising a source of electric pulses, a
-second impedance and said diodes for limiting the voltage 65 transformer comprising a primary winding and a sec
drop across said diodes, and a pulse responsive electric
ondary winding, said primary winding being connected
device connected across said secondary winding for con
across said source of pulses, an adjustable impedance con
trolling a load.
nected in shunt across said source of pulses and said pri
9. A triggering circuit responsive to a predetermined
mary winding, a voltage responsive impedance means con
pulse amplitude comprising a source of electric pulses, 70 nected in series with said primary winding for transmit
a transformer comprising a primary winding and a sec
ting to said primary winding pulses of said source as a
ondary winding, said primary winding being connected
function of voltage amplitude, and a pulse responsive elec
across said source of pulses, a first resistor connected in
tric device connected across said secondary winding for
shunt across said primary winding, a first adjustable im
controlling a load, said device comprising a pair of com
pedance connected in shunt across said source of pulses
plementary transistors directly coupled in a cascaded sys
3,092,731
8
tem, each of said transistors comprisinga base, collector '
and emitter, a source of potential, said emitter and col
lector of each of said Ytr-ansistors Ábeing connected in a
different series circuit across said source of potential, each
of said series circuits being connected at one end there
of to one terminal of said secondary winding, said base
of one of said transistors being connected to the other ter
minal yof said secondary Winding, said base of said other '
potential on said base of said one of said> transistors, and
means for disconnecting said source of potential .from said
one Vof said transistors for causing said transistors to kbe
come nonconductive.
v
14. A triggering circuit responsive to a predetermined
pulse amplitude comprising a source of electric pulses,
a transformer comprising'. a primary Winding and a sec
ondary Winding, said primary Winding being connected
across said source of pulses, a voltage responsive imped
transistor being connected to said collector of said one
of said transistors, said collector of said other of said l0 ance means connected in series with said primary Winding
for transmitting to said primary winding pulses of said
transistors being connected to said base of said one of said
source as a function of lvoltage amplitude, and a pulse
transistors, said one of said transistors upon a change of
responsive electric device connected across said second
base potential upon receiving a pulse from said second
ary Winding for controlling a> load, said device compris
ary winding energizing said one of said transistors caus
ing a pair of complementary transistors directly coupled '
ing current to pass through its emitter, collector series
in a cascaded system, each of said transistors compris
circuit to the load, said current changing the potential of
ing a base, collector and emitter, a source of potential,
said base of said other transistor causing `cur-rent to flow
said emitter and collector of each of said transistors be
through its emitter, collector »series circuit, saidV latter
ing connected in a series circuit across said source of
current flow retaining transistor conducting potential on
said base of said one of said transistors, and means for 20 potential, each of said series circuits being connected at
one end thereof to the positive terminal Vof said secondary
Vdisconnecting said source of potential from said one of
winding, a pair-of diodes one `being connected adjacent
said transistors `for causing said transistors to become
the emitter in each series circuit lfor driving the potential
nonconductive.
`of the base of the transistor associated Wit-h the emitter
13. A triggering circuit responsive to a predetermined
pulse amplitude comprising a source of electric pulses, a 25 of said circuit beyond cutoff thereby ltemperature stabiliz
ing said transistor, said base of one of said transistors
transformer comprising a primary Winding and a second
being connected to the negative terminal 'of said second
ary Winding, said primary Winding being «connected across
ary Iwinding, said base of said other transistor being con
said source of pulses, an adjustable impedance connected
nected to said collector of said one of said transistors, said
in shunt across said source of pulses and said primary
winding, a Zener breakdown diode connected in series 30 collector of said other or" said transistors being Yconnected
with said primary Winding for transmitting to said pri
to‘said base of said one of said transistors, said one of
said transistors upon a change of base potential upon
mary Winding pulses of lsaid source as a function 'of volt
vage amplitude, -said adjustable impedance being varied to
>receiving a pulse from said secondary Winding energizing
Vsaid ione of said transistors causing current to pass
'Ímatch -the voltage responsive characteristics of said Zener
diode, and a pulse responsive electric device connected 35 through its emitter, collector series circuit to the load,
said current changing the potential of said base of said
across said secondary Winding ‘for controlling a load, said
other transistor causing current to flow through its emit
device comprising a pair of complementary transistors
directly coupled in a cascaded system, each of said tran
ter, collector series circuit, said latter current ñoW retain
ing transistor conducting potential on said base of said
sistors comprising a base, collector and emitter, a source
of potential, said emitter and collector of each of said 40 one of said transistors, and means for disconnecting said
>source of potential from said one of said transistors for
transistors being connected in a different series circuit
causing said transistors to become nonconductive.
across said source of potential, each of said series circuits
being connected -at one end thereof to one termi-nal of
said secondary Winding, said base of one of said transistors
‘being connected to the other terminal of said secondary 45
Winding,V said base of said other transistor being connected
to said collector of said one of said transistors, said co1
lector of said other of said transistors being connected to
»said base of said one of said transistors, said one of said
transistors upon a change of base potential upon receiving 50
a pulse from said secondary Winding energizing said one of
said transistors causing current to pass through its emitter,
collector series `circuit .to the load, said current changing the
potential Vof said base of said other transistor causing cur
rent to ñow through its emitter, collector series circuit, 55
said latter current flow retaining .transistor conducting
References Cited in the tile of this patent
UNITED STATES PATENTS
2,298,657
Smith et al ____________ __ Oct. 13, 1942
2,730,576 '
Car-uthers ____________ __ Jan. 10, -1956
2,832,032
Walker et al. _________ __ Apr. 22, 1958
2,876,411
2,905,885
Cann ________________ __ Mar. 3, 1959
Bunt et al. __,________ __ Sept. 22, «1959
2,912,635
Moore ______________ __ Nov. 10, 1959
2,957,993
Siclrling ________ __,____ __ Oct. 25, 1960
FOREIGN PATENTS
803,07()
Great Britain ____ -..______ Oct. 15p, 1958
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