U.S. patent number 3,601,103 [Application Number 04/868,973] was granted by the patent office on 1971-08-24 for engine-condition-responsive cutoff apparatus.
Invention is credited to LaDell Ray Swiden.
United States Patent |
3,601,103 |
Swiden |
August 24, 1971 |
**Please see images for:
( Certificate of Correction ) ** |
ENGINE-CONDITION-RESPONSIVE CUTOFF APPARATUS
Abstract
Apparatus for inhibiting the operation of an engine in response
to engine speeds which exceed a preset number of revolutions per
minute employs a cutoff circuit for detecting and shaping firing
signals and a switch interposed in either the ignition powering
circuit, or the fuel circuit of a diesel, which is operable upon a
detected predetermined overlap of a shaped signal and the previous
signal delayed a predetermined interval. The apparatus also
utilizes temperature and pressure-sensing devices which are
effective to operate the cutoff circuit in response to the
detection of adverse temperature or pressure conditions within the
engine. An engine cutoff device, i.e. a relay, is operated in
response to a true output from an OR gate which has as its inputs
the overlap detection circuit and the individual sensing devices.
The cutoff device and the OR gate are also provided as a separate
package for applications which require engine conditions detection
other than overspeed detection.
Inventors: |
Swiden; LaDell Ray (N/A,
SD) |
Family
ID: |
25352680 |
Appl.
No.: |
04/868,973 |
Filed: |
October 13, 1969 |
Current U.S.
Class: |
123/335;
123/198DB; 123/198DC; 123/198D; 123/352 |
Current CPC
Class: |
F02P
9/005 (20130101); G01P 1/106 (20130101); F02B
2075/027 (20130101) |
Current International
Class: |
G01P
1/10 (20060101); G01P 1/00 (20060101); F02P
9/00 (20060101); F02B 75/02 (20060101); F02P
011/00 () |
Field of
Search: |
;123/102,148E,140.3,198D,198DB,198DC ;317/5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Goodridge; Laurence M.
Parent Case Text
CROSS-REFERENCES TO RELATED APPLICATION
This application is a continuation-in-part of my prior application
of the same title, Ser. No. 780,441, filed Dec. 2, 1968, now
abandoned.
Claims
I claim:
1. Apparatus for cutting off ignition power to an engine having a
spark-generating ignition system in response to adverse
engine-operating conditions, comprising:
an ignition-powering circuit including a source of power connected
to the ignition system;
means connected to the ignition system for detecting successively
occurring spark signals;
means for delaying said signals;
means connected to said detecting means and said delaying means for
timing the overlap between a signal and the delayed previous
signal;
means connected to said engine for detecting temperature conditions
of said engine; and
means connected to said timing means and to said
temperature-detecting means and interposed in said powering circuit
between said source of power and the ignition system for opening
said powering circuit in response to a predetermined overlap of a
signal and the delayed previous signal and in response to detection
of engine temperature in excess of a predetermined temperature,
said means for opening said ignition-powering circuit including
switch means in said powering circuit, and an OR gate having a
first input connection to said timing means, a second input
connected to said means for detecting temperature conditions, and
an output connected to said switch means for operating same upon
detection of predetermined pulse overlap or an excessive
temperature condition.
2. Apparatus for cutting off ignition power to an engine having a
spark-generating ignition system in response to adverse
engine-operating conditions, comprising:
an ignition-powering circuit including a source of power connected
to the ignition system;
means connected to said ignition system for detecting successively
occurring spark signals;
means for delaying said signals;
means connected to said detecting means and said delaying means for
timing the overlap between a signal and the delayed previous
signal;
means connected to said engine for detecting pressure conditions
within said engine; and
means connected to said timing means and to said pressure-detecting
means and interposed in said powering circuit between said source
of power and the ignition system for opening said powering circuit
in response to the detection of a predetermined overlap of a signal
and the delayed previous signal and in response to the detection of
a pressure within said engine below a predetermined pressure, said
means for opening said powering circuit including
switch means connected in said powering circuit and operable to
open said powering circuit, and an OR gate having a first input
connected to said timing means, a second input connected to said
pressure-detecting means, and an output connected to said switch
means for operating said switch means upon detection of a
predetermined pulse overlap or an insufficient pressure
condition.
3. Apparatus for cutting off an engine in response to
adverse-operating conditions of an engine which includes a
fuel-firing system which produces successively occurring fuel
firings, comprising:
means connected to said engine for detecting successively occurring
fuel firings and generating corresponding firing signals indicative
of speed;
means for delaying said signals;
timing means connected to said delaying means for timing the
overlap between a signal and the delayed previous signal to detect
excess engine speed;
means connected to said engine for detecting at least one
adverse-engine-operating condition other than excess speed; and cut
off means connected to both said timing means and said
adverse-condition-detecting means and interposed in the fuel firing
system for rendering the engine inoperative, said cutoff means
including
switch means in the fuel-firing system and operable to render the
fuel-firing system inoperative, and an OR gate including a first
input connected to said timing means, a second input connected to
said adverse-condition-detecting means and an output connected to
said switch means for operating said switch means in response to
the detection of excess pulse overlap or an adverse
engine-operating condition.
4. Apparatus according to claim 3, wherein said delay means
comprises a monostable multivibrator for effecting said delay, said
fuel firing-detecting means includes means operable to generate
bipolar signals, and a clipping amplifier and a differentiator
circuit for converting said bipolar signals into pulse signals for
said multivibrator.
5. Apparatus according to claim 4, wherein said monostable
multivibrator includes an adjustable circuit for determining signal
width of the delayed signal.
6. Apparatus according to claim 3, wherein said timing means
includes an AND circuit for detecting pulse overlap and means for
detecting the duration of pulse overlap.
7. Apparatus according to claim 6, wherein said means for detecting
pulse overlap comprises a unijunction transistor circuit including
an input electrode and an output electrode, said means for
detecting the duration of pulse overlap connected between said
input electrode and said AND circuit for firing said unijunction
transistor circuit, and said switch means includes a solid-state
switching device and a solenoid cutoff device connected in the
fuel-firing system and operated by said solid-state switching
device, said solid-state switching device including a gate
electrode connected to said unijunction transistor circuit whereby
firing of said unijunction transistor circuit effects operation of
said solid-state switching device.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to apparatus for detecting adverse engine
conditions and is particularly concerned with apparatus for
inhibiting the operation of an engine in response to the detection
of engine speeds which are in excess of a preset number of
revolutions per minute, or the detection of abnormal temperature or
pressure conditions.
2. Description of the Prior Art
Heretofore, control of engine speed has been primarily limited to
speed-governing-type apparatus wherein the engine, say an internal
combustion engine, has the effects of loading of the engine
compensated for by apparatus which adjusts fuel flow to the
carburetor of the engine. Such governing techniques may be employed
to control engine overspeed; however, engine overspeed in either a
continuously loaded or unloaded condition indicates a recurring
malfunction which should be repaired. Also, abnormal temperatures
of coolant and lubricant and abnormal lubricant pressure are
indications that should provide some type of an alarm to indicate
that corrective action should be taken. Speed-dependent clutches
may also be employed to correct overspeed; however, these require a
certain amount of maintenance attention and are not particularly
adaptable to accurately provide engine cutoff speeds. An operator
could detect any of the above conditions and manually shut down the
engine; however, this would require his constant attention, either
visual or audible, to determine the occurrence of such a condition.
Thus, it is highly desirable that apparatus be provided which
automatically shuts down an engine in response to the detection of
an adverse engine condition. Inasmuch as an automotive type engine
may be operated as a prime mover in a variety of systems which are
manned by operators of an undetermined background with respect to
automotive equipment, apparatus for cutting off an engine should be
easily installed and easily preset to a variety of predetermined
numbers of required revolutions per minute, or pressure or
temperature settings so that no special training would be necessary
for an operator.
It is also highly desirable to provide apparatus for automatically
curtailing the operation of an engine in response to the detection
of an adverse condition externally of the engine. For example, it
is desireable and advantageous to shut down an engine which is
driving a generator in response to adverse conditions occurring
within the generator, i.e. generator temperature conditions.
SUMMARY OF THE INVENTION
According to the invention, apparatus is provided for opening the
powering circuit of an ignition system or blocking the fuel circuit
of a diesel system in response to an engine speed in excess of a
preset number of revolutions per minute. The preferred embodiment
of the invention is realized by the provision of circuit means for
detecting the firing of the cylinders and providing electrical
signals as indications of cylinder firing and means for converting
the signals thus detected into pulse signals. The pulse signal and
the previous signal delayed are fed into a circuit for comparing
the duration of overlap between these two pulses. A switching
circuit which comprises contacts included in the ignition-powering
circuit (or a valve in a fuel line) is operated in response to
pulse overlap in excess of a predetermined or preset interval which
corresponds to the desired engine cutoff speed. Engine cutoff is
positive in that, in a preferred embodiment of the invention, the
switching circuit includes a controlled rectifier in a relay
driving circuit. As is well known in the art, a controlled
rectifier, once conductive, remains conductive with little
sustaining input and can only be deactivated by opening its
anode-cathode circuit. Advantageously, contacts of the ignition
switch are employed for this purpose in the case of engines which
have an ignition system.
According to the invention, apparatus is provided for opening the
powering circuit of an ignition system or blocking the fuel circuit
of a diesel system in response to the detection of adverse
conditions, which conditions may be indication of engine operation
or may be indirectly related to engine operation. A switching
device is operated from any of a plurality of condition detection
devices through the medium of an OR gate to inhibit engine
operation by opening the engine-firing system. In the preferred
embodiment, the switching device includes a relay and the OR gate
includes a plurality of diodes. The relay is operatively connected
to a solenoid valve in the case of diesel systems, and to the
powering circuit in the case of ignition systems.
Apparatus constructed in accordance with the principles of the
present invention may be packaged as a complete
engine-condition-responsive system, with or without the speed
detection feature, as a hermetically sealed unit for mounting on or
adjacent the engine.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features and advantages of the invention, its
organization, construction and operation will be readily apparent
from the following description of certain embodiments thereof which
are illustrated in the drawings, although modifications thereof may
be made without departing from the spirit and scope of the novel
concepts thereof, and
FIG. 1 is a block diagram of engine overspeed cutoff apparatus
according to the present invention;
FIG. 2 is a combination block diagram and symbolic representation
of an embodiment of the invention;
FIG. 3 is a schematic circuit diagram showing the embodiment of
FIG. 2 in greater detail;
FIG. 4 is a schematic diagram showing the temperature and pressure
responsive apparatus which may be included in the circuit of FIG.
3;
FIG. 5 is a plan view of a packaged engine overspeed cutoff device
according to the invention;
FIG. 6 is a partial block, partial schematic diagram of the circuit
of FIG. 3 as it would appear modified to control a diesel
system;
FIG. 7 is a schematic circuit diagram of a modification of the
apparatus of FIG. 2 for sensing the output of a magnetic sender for
diesel engine applications;
FIG. 8 is a schematic circuit diagram showing another modification
of the apparatus of FIG. 2 having a magnetic pickup as source of
engine speed information;
FIG. 9 is a graphical illustration of the input signal to the
apparatus as modified in FIG. 8;
FIG. 10 is a schematic circuit diagram of apparatus according to
the present invention for controlling engine cutoff in response to
any one of several control conditions; and
FIGS. 11, 12 and 13 illustrate various circuit connections to the
apparatus of FIG. 9.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 illustrates the invention as it pertains to an engine having
an ignition system as comprising a pulse shaper 1, as the input
circuit which detects ignition spark signals and transforms these
signals into shaped pulse signals. The apparatus further includes a
delay circuit connected to the pulse shaper 1 and having its output
connected to a comparator 3. A second input to comparator 3 is
extended directly from the output of the pulse shaper 1, so that
the inputs to the comparator 3 are a shaped pulse and the previous
pulse delayed. Connected to the output of the comparator 3 is a
switch 4 which has a portion thereof interposed in the
ignition-powering circuit and which is operable upon detection of a
preset amount of pulse overlap to open the ignition-powering
circuit.
The above is brought out more clearly in FIG. 2 which shows an
embodiment of the invention wherein the pulse shaper 1 comprises an
input-shaping circuit 10 which has its output connected to a
monostable multivibrator 20. The input shaping circuit 10 detects
the spark signals from the ignition system and forms a trigger
therefrom for the monostable multivibrator 20. Monostable
multivibrator 20 upon receipt of the trigger operates in a well
known fashion to provide an output pulse having a pulse width which
is determined by the timing portion (e.g. capacitor 26, FIG. 3) of
the monostable circuit.
The delay circuit above-referred to includes in this instance a NOR
gate or inverter circuit 30 which operates on the trailing edge of
the output pulse of the monostable multivibrator 20 to provide a
triggering signal for monostable multivibrator 40. Multivibrator 40
operates in a manner similar to that of monostable circuit 20 to
provide an output pulse which is essentially the same as the output
pulse of monostable multivibrator 20, except it is delayed a
predetermined interval due to the reformation of the signal through
circuits 30 and 40. The shaped pulse and the previous pulse delayed
are applied to an AND gate 50, as a means of determining overlap
between the two signals. The signal overlap at the output of an AND
circuit 50 is employed as a pulse input to a unijunction transistor
circuit 60. The unijunction transistor circuit 60 has an input
which detects the duration of the overlap signal and which fires
its unijunction transistor in response to an overlap signal in
excess of a predetermined duration. The unijunction transistor
circuit 60, is, in turn, employed to operate a controlled rectifier
circuit (65, FIG. 3) which has a relay 66 connected in series
therewith and which is also interposed in the powering circuit of
the ignition system. Therefore, upon receipt of an overlap signal
at the input to the unijunction circuit 60, the relay is operated
to open the powering circuit of the ignition system.
The above embodiment is shown in greater detail and in connection
to the ignition system of an automotive engine in FIG. 3. In the
circuit shown, the input circuit 10 comprises a resistor 11, a
capacitor 12, a resistor 13, and an output resistor 14. The input
to circuit 10 is connected to an adequate source of spark signal,
preferably at the points or the ignition coil of the ignition
system. The spark signal is developed as an input to monostable
multivibrator 20 over resistances 11, 13 and 14, capacitor 12 being
effective as a high frequency ground to the complex spark signal.
The monostable multivibrator 20 includes a transistor 21 having its
collector connected to a source of positive potential through
resistor 22 and its emitter connected to ground through resistor
25. The circuit also includes a second transistor 23 which has it
collector connected to a positive potential through resistor 24 and
its emitter connected to ground through resistor 25. The base of
transistor 23 is also connected to the positive potential through
resistor 27 and a timing capacitor 26 is connected between the base
of transistor 23 and the collector transistor 21. It can easily be
seen from the drawing that, with the bias potentials thus applied,
transistor 23 is the normally conducting transistor and transistor
21 if the normally nonconducting transistor of the monostable
multivibrator 20.
An inverter circuit 30, (or single input NOR gate) receives its
input through resistor 31 from the output 29 of the monostable
multivibrator 20. The inverter circuit 30 includes a transistor 32
having its base connected to resistor 31, its collector connected
to a source of positive potential through resistor 33 and its
emitter connected to ground. The collector of transistor 32 is also
coupled to the anode of diode 36 through a capacitor 34. The anode
of diode 36 is also connected to ground through a resistor 35. A
positive-going input signal to this circuit, due to the turning off
of transistor 23, causes transistor 32 to conduct for the duration
of the output pulse of monostable multivibrator 20 and the
negative-going trailing edge of such output turns off transistor
32. This causes the output pulse of transistor 32 to be an
inversion of the output of the monostable multivibrator 20. This
inverted pulse is coupled by capacitors 34 to the anode of diode 36
where the positive-going trailing edge thereof causes conduction of
diode 36 and provides a trigger for monostable multivibrator
40.
The monostable multivibrator 40 is essentially the same as
monostable multivibrator 20. This circuit comprises transistor 41
having its base connected to the cathode of diode 36 for receiving
the input triggering signal, its collector connected to a positive
potential through resistor 42 and its emitter connected to ground
through resistor 45. Further, a transistor 43 has its collector
connected to positive potential through resistor 44 and its emitter
connected to ground by way of resistor 45. The monostable
multivibrator 40 also includes a timing capacitor 46 connected
between the base transistor 43 and the collector of transistor 41
and a resistor 48 connected between the base of transistor 41 and
the collector of transistor 43. The primary difference between the
monostable multivibrator 40 and the monostable multivibrator 20
resides in the resistance connected between the base of transistor
43 and the positive potential. In monostable multivibrator 20 this
was a single resistor 27: in monostable multivibrator 40 it is a
resistance which includes a fixed resistor 47a and a variable
resistor 47b. This variable portion of the circuit is effective to
adjust the apparatus for different engine operating speeds. In
operation, the engine speed would be increased to the desired
cutoff speed and the variable resistance 47b would be adjusted
until the cutoff is attained. The variance of resistance 47b
operates to vary the quasistable state of the monostable
multivibrator 40 and thus provide a variation of output pulse
width. A single fixed resistance would provide a fixed
predetermined shutdown point.
The output 29 of monostable multivibrator 20 and the output 49 of
monostable multivibrator 40 are connected to diodes 51 and 52
respectively, of AND gate 50. A resistor 53 is connected between
the anodes of diodes 51, 52 and the source of positive potential.
Also connected to the anodes of diodes 51, 52 is a capacitor 54
which serves to develop an input signal for firing the unijunction
transistor of circuit 60. The unijunction circuit 60 comprises a
unijunction transistor 61 having a first base connected to ground
through resistor 62 and a second base connected to the source of
positive potential through resistor 63 and a firing electrode
connected in common with the anodes of diodes 51, 52, resistor 53
and capacitor 54. Upon an overlap of a delay pulse from the
monostable multivibrator 40 and the next shaped pulse from
monostable multivibrator 20, the diodes 51, 52 are reversed biased
and permit the capacitor 54 to be charged over resistor 53 from the
source of positive potential. When the charging of capacitor 54
reaches a firing level for unijunction circuit 60, unijunction
transistor 61 fires and current flows from the source of positive
potential through the resistor 63, unijunction transistor 61, and
resistor 62 to ground. A resistor 64 which is connected to the
first base of the unijunction transistor couples the potential
developed by the voltage divider so formed to the gate electrode of
a controlled rectifier 65. The diode 65 conducts to establish a
current flow from a second source of positive potential through
relay winding 66 and the diode 65 to ground. Relay winding 66 has a
set of normally closed contacts 67 operatively coupled thereto and
electrically connected between the battery of the ignition system
and the spark-generating apparatus of the ignition system.
Therefore, the power for the spark-generating apparatus is
disconnected from such apparatus and the engine is cutoff.
Inasmuch as a controlled rectifier will sustain its conductive
condition after the removal of a triggering input to its gate, some
means must be provided for resetting this circuit to its
nonconductive condition. Advantageously, the engine is inoperative
at this point and must be restarted; therefore, a set of contacts
80 of the ignition switch are interposed between the battery input
terminal B and the direct current supply 70 of the overspeed cutoff
apparatus. The circuit 70 comprises a first output VI for
connection to the relay winding 66, a resistor 71, a breakdown
diode 72 and a capacitor 73 for providing a second and lower stable
source of potential V for the components of the remainder of the
cutoff apparatus.
FIG. 4 illustrates the switch portion of FIG. 3 as it may appear
modified to operate in response to adverse temperature or pressure
conditions. An OR gate 90 is formed by a plurality of diodes 91-93
connected through relay winding 66, each of these diodes having an
input which is connectable to ground via a respective condition
sensing device 94-96. These devices sense internal engine
conditions on an analog basis. For example, sensor 94 is associated
with the temperature of the engine system coolant; sensor 95 is
associated with the temperature of the engine lubricant; and sensor
96 is concerned with the pressure of the lubricant. The sensors
continuously detect conditions of the engine and each may provide
an enabling ground potential to its corresponding diode upon
detection of an adverse condition to complete an operating circuit
for relay winding 66. The sensors may be of a variable setting type
or may be of a quick-change type for easy conversion of permissable
temperature or pressure conditions. Generally though, fixed
components will suffice for a number of different engines having
substantially the same normal pressure and temperature
conditions.
FIG. 5 illustrates an engine overspeed cutoff device as it may
appear as a sealed package. This unit comprises a cover 100 having
a pair of mounting flanges 101 with mounting holes 102 therein. A
terminal strip 103 provides for the necessary connection between
the ignition system and the working components interior of the
cover 100. As indicated in the drawing for a negative ground
ignition system, terminal A+ is for connection to the ignition
switch (or it may be connected to COIL (+) if no ballast is used);
terminal GND is to be connected to the frame; terminal PTS is for
connection to the points (may also be connected to the ignition
coil); terminal COIL PWR is for connection to the ignition switch;
and terminal COIL (+) is for connection to the positive terminal of
the ignition coil.
In a particular design for a 12-volt negative ground system, an
overspeed device provided the following tabulated speed control
ranges.
---------------------------------------------------------------------------
ENGINE R.P.M. RANGE
__________________________________________________________________________
4 Cycle, 8 Cylinder 1,300-7,000 4 Cycle, 6 Cylinder 1,500-10,000 4
Cycle, 4 Cylinder 2,200-14,000
__________________________________________________________________________
FIG. 6 illustrates the application of the circuit of FIG. 3 to a
diesel engine wherein a pickup transducer 107, either photoelectric
or magnetic, feeds the ignition representative signals to an input
shaper 10a for processing as hereinbefore described. A
predetermined amount of overlap turns on the controlled rectifier
65 and provides an operating path for solenoid winding 104 for
shutting off its associated valve 105 in a fuel line between the
fuel tank 106 and the remainder of the fuel system. A switch 80a
corresponds to the ignition switch 80 of FIG. 3 for restoring the
controlled rectifier 65 to its nonconductive condition.
FIG. 7 illustrates the apparatus of FIG. 3 having a modified input
circuit 110 to receive an input signal indicative of engine speed
from a magnetic pickup at input terminal 111. The circuit of FIG. 7
is referenced to that of FIG. 3 by the point a and the monostable
circuit 20. The input circuit 110 therefore replaces the input
shaper 10 (elements 11, 12 and 13) of FIG. 3 and comprises a
clipping amplifier and differentiator circuit. A representative
input signal to terminal 111 would be a 50-volt peak to peak sine
wave of a frequency that is proportional to engine speed. One
proportion employed for the frequency was three time engine speed.
The input signal is fed to the speed-determining circuit in
response to the positive portions of the cycle by way of transistor
117, the triggering signal for the monostable circuit 20 being
developed across resistor 120; diode 114 provides negative
clipping. A diode 121 provides a definite trigger level for the
monostable circuit 20 to initiate speed determination as set forth
above in the discussion of FIG. 3.
FIG. 8 illustrates another modification of the speed sensing input
circuit which is designed to operate in response to a more
generalized magnetic sender, generally referenced 131. This circuit
is referenced to FIG. 3 by point b and the monostable circuit 20.
FIG. 9 illustrates input signals c and d which are generated by the
magnetic sender 131 and fed via capacitor 132 to the base of
transistor 136 which is biased normally conductive. The negative
peaks of signals c and d pulse off the transistor 136 and the
voltage rise at the collector thereof is employed to operate the
monostable circuit 20.
FIG. 10 illustrates a condition-responsive cutoff unit 140
hermetically sealed in a housing 141 (illustrated in phantom) and
comprising a plurality of circuit terminals 142-150. Terminals 143,
145 and 146 form signal input terminals for receiving ground
signals from pressure, temperature, etc. senders, as illustrated in
FIGS. 4 and 12. A plurality of diodes 151-153 have their anodes
connected in common and their cathodes connected to respective ones
of terminals 143, 145 and 146 to form an OR gate. The anodes of the
diodes 151-153 are also connected to a relay winding 155 and an arc
suppression diode which elements are in turn connected to a
terminal 147 which carries the A+ potential.
An external warning lamp 159 may be connected across relay winding
155 by connecting such a lamp to terminals 142 and 144 as
illustrated in FIG. 11.
The circuit illustrated in FIG. 10 is universal for both ignition
and diesel systems as shown in FIG. 13. With A+ applied at terminal
148 operation of relay winding 155 and transfer of contact 156 may
be employed, for example, to complete an operating circuit to a
normally open solenoid fuel flow valve 162 via contact 158 and
terminal 150. By the same token contacts 156 and 157 may open an
ignition system, or contacts 156 and 158 may complete an operating
path for a slave relay to open an ignition circuit. Also the relay
may be employed to operate auxiliary devices, such as clutches,
gears, etc., as well as ignition circuits and fuel valves.
One unit constructed in accordance with FIG. 10 employed four 1N914
diodes for elements 151-154 and a Price Electric relay, No. 28 E111
AE to great advantage.
* * * * *