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Патент USA US2407654

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Sept. 17,1946. 1
P. J. cos'rA '
Original Filed June 6, 1942
2 Sheets-Sheet 1‘
gum" 2 a 4
HQ. 2
uc' nauas‘rog FIGS
Sept. 17, 1946.‘
P. J. cosTA
Original‘ Filed June 6, 1942
2 Sheets-Sheet 2
FIG. 4
Patented Sept. 17, 1946
Philip J. ‘Costa, Franklin Square, N. Y., assignor
to Sperry Gyroscope Company, Inc., Brooklyn,
N. Y., a corporation of New York
Continuation of application Serial No. 446,070,
This application February 28,
1944, Serial No. 524,170
20 Claims. (Cl. 123-119)
June 6, 1942.
‘ This invention relates to detonation responsive
means for controlling an internal combustion en
More particularly the invention is con
cerned with a‘ detonation responsive system
which includes a device for transmitting cyclic
movements of variable duration to known in
strumentalities for controlling the operation of
an internal combustion engine. While the im
proved system is useful in the elimination of the
occurrence of detonation in the cylinders of any 10
internal combustion engine, it “is particularly
adapted to be employed with aircraft engines in
which the relatively thin cylinder walls are sub
ject to severe damage or complete destruction
under such conditions. This application is a con
tinuation of my copending application S. N. 446,
070, ?led June 6, 1942.
The principal object of the present invention is
to provide an automatically operative system by
detonation responsive system illustrated in Fig.
1, and.
Fig. 5 is an elevation view of the control unit
illustrated in Fig. 4 showing the ?xed type of
control ‘unit employed in‘ Figs. 2 and 3.
_ With reference particularly to Fig. 1, the det
onation responsive system is shown to include an
internal combustion engine of the radial cylinder
type employed in aircraft which is‘outlined sche
matically and indicated at N. The carburetor
and the air intake tube for the same are desige
nated at II and I2, respectively. These parts
being of conventional construction are also
shown schematically. The means for controlling
the working conditions of the engine may co
operate to regulate any portion of the engine op
erable to suppress detonation, typically as out
lined in Van Dijck Patent 2,220,558. The regu
lator is herein illustrated, by way of example, as
which the time interval between recurrences of 20 the usual fuel mixture control on carburetor H
having the usual throttle arm l3 which may con
detonating or “knocking” engine conditions is
trol a throttle valve (not shown) of the butter?y
effectively and controllably delayed.
type. This valve provides a means of controlling
One of the important features of the invention
engine speed or power output by regulating the
resides in “the'provision of a combined manual
air-?ow toythe cylinders. The throttle control
and automatic system for controlling the ratio
determines the speed at which the crank shaft
of ‘the fuel to air mixture being utilized by the
of the engine is revolved, and by a direct link
internal combustion engine.
age .(not shown) to the arm the same is posi
Another feature of the invention is provided in
, tioned manually in a desired manner by the pilot
the combination of elements included in the sys
of the craft. A fuel mixture valve (not shown)
tem which cooperate to obtain the desired result
which controls ‘the flow of fuel through the main
and consist of an internal combustion engine,
metering system of the carburetor and into the
a means for controlling ‘the working conditions of
air-?ow of tube I2 is also directly controlled by
the engine such as the carburetor or ignition
the‘pilot by way of pivotal arm l4, connecting
timing control device, a detonation pick-up
' links-45 and I5’, and adjustable lever l6 located
transmitter or means for detecting detonation in
in the cockpit of the craft.
the cylinders of the engine and the means or
‘ On most high-powered engines the mixture of
device included in the system which is operable
fuel to air supplied the engine is regulated by
in response to the detonation detecting means.
limiting‘ the amount of fuel vaporized in the air
Other objects, features and structural ‘details
intake tube. [2. By a suitable detent and stop
of the invention will be apparent from ‘the fol
construction usually provided within the carbu
lowing description when read in connection with
retor, the arm l4 may be positioned in any one
the accompanying drawings, wherein;
of four operating positions, shown at‘ the dial
Fig. 1 is a schematic view and wiring diagram
indications in the’ cockpit of the craft, with ref
inwh'ich the preferred form of the invention is 4.5 erence to the settable lever Iii,v as “full rich,”
Fig. 2 is a detail view showing the system em
ployed to control the engine by means of an
ignition timing device.
Fig. 3 is a further detail view showing the sys
tem employed to control the engine by means of
an additional or auxiliary fuel supply valve.
Fig. 4 is an enlarged vertical section showing in
detail the internal construction of the rocker
“auto-rich,” “auto-lean” and “idle cut-off,” by
manual manipulation of the pilot. Provisions
of this nature may or may not be incorporated
in the‘ improved detonation responsive control‘
system.‘ Such an arrangement, having proven
satisfactory, is provided for in the instant case
by a relatively ?xed holding piece I’! having four
notches in the under-surface of the same and a
spring urged detent 18 that engages the notches.
type of control unit'included in the improved 55 Deten-t I8 is situated on a vertical arm l9 which‘
extends from the casing of the control device or
unit 23 which itself, in this instance, is mounted
to rock about a ?xed pivot point 2!. Link I5 is
ventional construction may also be energized by'
the output of the ampli?er 23 by way of leads 28.
The automatic detonation contro1 unit 20 is ,in
pivotally connected to the end of the rod of a
Qluded in. the circuit completed by the relay 21, in
this instance, vthe circuit : being energized by a
piston element contained within the unit 20, and
hereinafter more particularly described. Also,
link I5’ is pivotally connected to the casing of
suitable source of'energy such as battery 29.' If
desired, the control unit 20, hereinafter more par
the unit 25] so that the unit is included as an
ticularly described could be actuated directly by
the output of the schematically shown detonation
the valve positioning arm 14 is controlled. Arm 10 pick-up transmitter 22 thereby obviating the use
It may be termed the gas to air mixture control
of the relay 2‘! and the independent circuit which
in this embodiment of the invention.
the same closes upon occurrence of detonation in
With respect to the various positions in which
any of the cylinders of the ,prime mover. As
integral portion of the linkage system by which
the linkage system may be manually set by the ' - shown in’ Fig. l, the single ?exible cable so in
pliot, it may be considered that when the craft _‘
takes off the throttle of the carburetor is fully
open and the mixture control is set at “full rich”
cludes separate leads for completing the circuit
containing the relay 21, source 29 and control de
vice or unitv 29. It will be understood from the
foregoing description that operation of the sys
surrounding obstacles. If the craft is still climb
tem is effected by the detonation pick-up trans
ing, the pilot can then set lever it to the “auto 20 mitter 22 which transforms the high frequency
rich?’ position which moves arm M to open the
vibrations in the cylinder in which detonation is
position until the craft is at a safe height above
valve slightly. The valve, in turn, permits less
occurringinto, electrical impulses. These
pulses are ampli?ed in the instant caseby means
creasing the richness of thefuel toair mixture
of amplifier 23 and the output of the ampli?er
entering the cylinders. Throttle arm‘ [3 is moved 25 is utilized to. both effect illumination of the indi
independently of the lever lt'and is adjusted as
cator 25; and close the relay ‘2'! controlled circuit.
fuel to be vaporized in theair tube l2, thus de
desired by the pilot. When the craft reaches a
which includes the, in this instance, pivotally
desired altitude and is traveling under normal
mounted control unit, 29. By- suitably controlling
straight ?ight conditions, the engine may be ad
justed to obtain maximum economy of operation
by-setting the mixture lever to. the “auto-lean”
position. As the economy of operation of the
prime mover is increased, the frequency of occur
the sensitivity of the ampli?er 23, the pick-up
transmitter may be rendered as sensitive as; de
sired. Both the control unit and indicatorof
the system are preferably rendered, operable upon
that approach of detonating conditions in-the
rence of detonation in the cylinders of'the same
also increases so that due to engine failures and
the inability to determine a safe operating point
above that providing most economical operation,
the pilots have been warned by engine and car
buretor manufacturers against the danger in
using- the “auto-lean” position. With the present
' cylinders of the engine known as incipient dot-,7
onation, characterized by’ several occurrences per
minute and not apparently harmful to engines;
even for prolonged periods.
With particular reference to Figs. 4, and 5, the
illustrated control unit or device 20 is shown in
the form of a cylinder element having- a casing
3i and end walls 32 and 33. In Fig; 4, the cyl
system, the mixture control lever can be safely
set in the “auto-lean” position and an indicator
observed to ascertain the frequency of occurrence
inder element is divided into two ?uid containing
compartments 3.4. and 35 by» a ?xed central wall
of; detonation in the engine. If such occurrences
36 and a solenoid or coil 31 having a side de?ning
appear too frequently or are heavier in nature, 45 plate 3,8. The solenoid 3'! is included in the relay '
than desired, the position of the relative ?xed
controlled circuit whose cable 30 is ?xed, to the
holding piece ll may be changed slightly by a
casing 3| by a suitahleg connection, A piston
suitable’ adjustment- and the mixture arm reset
member for the cylinder element is indicated at
to slightly enrich the ratio, of fuel to air being
40., the same de?ning one wall of the compart
supplied the engine to maintain detonation below 50 ment 35. This piston performs the function of
a predetermined maximum level of severity. In
an actuating member for the control unit to auto
this manner, the prime mover may be controlled
matically position the instrumentalities employed
to, obtain the greatest operating economy con
in controlling the working conditions of operation
sistent with engine safety, When‘ in the “idle.
cut-off” position the mixture valve, by special
internal design, actually closes again to. richen
up the, mixture, even though the-lever is put into
a diiferent position.
Further, with reference to Fig. 1, each of the
of the internal combustion engine. , In the rocker
type control unit in Fig. 4, such controlling move
mentisimparted to lever I5 byway of the piston
rod 4,], for piston Ml.v A. Spring 42" or other suit.-.
able means is effective to restore the piston ac,
tuatingmember to, a normal or vinitial position
cylinders of the internal combustion engine is 60 against stops d3 situated on the face of ‘?xed
provided with a means for detecting detonation,
dividing wall 36‘. In the form of the control unit
one of such detonation'pickeup transmitters be
shown‘ in Fig. 5, the casing 3| is suitably mounted
ingv indicated at 22. This transmitter which is
in a ?xed position on a bracket piece 46.
illustrated schematically in the drawing may be
In both of' the types of' control units 20 shown
of the type particularly described in U. S. Letters
in the drawings, the solenoid 31 provides a part
Patent No. 2,275,675, issued March 10, 1942, to
of the electromagnetic means employed for- ef
C. S; Draper et al. The output of the transmit
fecting unidirectional movement of the ?uid to
ter may be fed to a suitable ampli?er indicated
the piston member wall de?ning‘ compartment.
schematically at 23 by way» of leads Z4. The am
35 to cause movement of the piston actuating
pli?er is energized from a suitable source of elec 70 member. It will be understood that this result
trical energy (not shown) and the output of the
occurs in response to energization of the solenoid
same may be employed to illuminate a neon tube
when the relay controlled circuit is closed by
indicator 25 situated in the cockpit of the craft,
the detection of detonation at the. pick-up. trans
the circuit leads for this purpose being shown at
mitter. A hollow electromagnetic core piece 48
2,6,. A separate circuit-closing relay 21 of con
of cylindrical form cooperates with the solenoid
and is mounted for axial movement within a‘
cylindrical wall de?ning element 43 whose longi
tudinal axis is arranged in coaxial relation to
the central axis of the solenoid. The core piece
48 has a valve-controlled passageway 50 therein,
the valve being represented in the form of a ball
5| which is normally pressed against its seat. by
transmitter 22 ‘for each, of the cylinders of the
engine and generally causes a number of pulsat
ing movements of the core 48, each movement
e?ectingdisplacement of the piston member over
a predetermined ‘minor portion of the full oper
ating range of the piston. When thesolenoid
is no, longer energized, the return movement of?
the control device‘ occurs underin?uence of the
spring 42, the fluid being forced to return to the‘
aspring 52 situated within the hollow core 48.
The electromagnetic plunger or‘ core 43' is posi
tioned within the cylindrical wall de?ning ele 10 compartment 34, under normal‘ circumstances,
by way of passageway 59 which contains the ad
ment 49 by means of a spacing spring 53, which
justable valve 60, operating as an escapement to
the plunger 48 compresses when it moves through
delay the return‘ movement. On each return
in?uence of the energized solenoid, and an op
movement of the core 48, ?uid from the compart-'
posing spring 53’. The extent of axial move
ment permitted the core is de?ned by a stop, as. 15 ment 34 is admitted to the chamber‘de?ned by
the cylindrical wall member 49 and the interior
indicated. at 54, situated at the end of a hub
piece on the central wall 36.
‘VA valve-controlled passageway is included in
the structural provisions shown in the drawing
for connecting the interior of the fluid. contain
ing ‘chamber de?ned by the cylindrical wall 43
and the chamber 35. In this instance, this con
struction is provided by valve plate 55, valve ball
56 and the open ended, screw-threaded plug 51.
of the hollow core 48 by way of the unidirection
ally acting valve controlled by spring-loaded ball
5!. The adjustable valve 53 provides a means
for regulating the duration of the return move
ment affected by the control unit which functions
as a cyclic actuating means having initiating
and returning movements. In the combined
manual and automatic control system illustrated
A spring 58 normally holds the valve ball 56 25 in Fig. 1, .the automatic mixture control‘unit
functions when necessary upon occurrence of
against its seat in the valve plate 55. Compart
detonation in the cylinders of the engine at
ments 35 and 34 are connected by a passageway
either manual position 2 or 3, it being presumed
59 situated in the wall of the casing 3!. An
that no detonation will occur at either of ‘the.
adjustable valve element 5!] is located in a posi
tion in the casing 3| to restrict the flow of ?uid 30 other manual settings for the system. When
operative, the device functions to enrich the fuel
passing from compartment 35 to compartment
to air mixture supplied the engine u'ntil detona
34. ‘In addition to passageway 59, a further pas
tion ‘ceases, after which it slowly restores the
sageway‘is provided in the wall of‘ the casing
system to the original conditions of operation
3|, as indicated at 6|, the same connecting the
at which the same was manually set by the pilot.
area 34' ‘of the cylindrical casing to the rear of It is apparent that by setting valve ‘60, as desired,
the piston member 40 to compartment 34. There
the duration of the restorative portion of the
is no valve situated in passageway 6! so in effect
cyclic actuating means may be extended to ap- '
the connected compartments 34 and 34’ form a
proximately control cyclic recurrence of detona
single compartment. The ‘end of the passageway
6| in the wall of the cylinder element 3| adja 4-0 tion in the engine atsuch spaced intervals as
to provide safe operation of the craft at the
cent compartment 34' is of su?icient longitudinal
“auto-lean” mixture setting. Incipient detona
dimensions, the same being formed of greater
tion of the order of several occurrences per min
length than the thickness of the piston member
ute may be maintained steadily when the return
40, to provide an operative position‘limit for the
movement of the piston member within the cyl 45 movement of the piston requires somewhat over
10 seconds. Normal operation of the automatic
inder element. This position is indicated by the
system thus is indicated by several flashesv
dotted line position of the piston member 40 in
perminute on the signal device or indicator 25.
Fig. 4, in which the passageway BI is shown as
directly connecting both compartments 35 and
34. The entire cylinder element 3i is preferably
?lled with a ?uid such as oil and a pressure
responsive means such as bellows unit 62 is pro
vided for the structure, the same compressing
Rapidly recurring ?ashes de?nitely indicate
trouble in the automatic control, and warn the
operator to shift the manual control lever l6 as
an emergency measure in a direction to suppress
detonation, e. g. byenriching the fuel mixture.
It will be apparent that while the manual control
upon expansion of the fluid due-to temperature
changes and expanding upon shrinkage in the 55 lever always is operable to enrich the fuel mix
ture and eliminate detonation, its effectiveness
volume of fluid when the temperature condition
in the reverse direction is limited by the effect
affecting the device causes such to occur.
on engine operation, since the automatic control
In operation, the energized solenoid 31 of this
becomes operative when detonation conditions
unit effects movement of the magnetic core 48
arise‘; to preclude manually setting the engine
to the left, as viewed in Fig. 4, against the action 60 regulator beyond a position corresponding to a
of spring 53. A portion of the fluid within the
maximum allowable detonation severity.
chamber de?ned by the cylinder wall 49 and the
The ?xed type of control unit, as shown in Figs.
interior of the hollow core 48 is consequently
2 and 5, is mounted on a bracket 46 situated in
forced-past the valve ball 56 into the compart
?xed position‘ with respect to the body of the
ment 35. Valve ball 55 permits unidirectional
engine. In the instance shown in Fig. 2, the unit
movement of the ?uid into the compartment 35
is employed to initially retard the timed occur
only, such movement resulting in displacement
rence of ignition in the operation of the internal
of the piston member 40 and consequent sup
combustion engine. In this fully automatic ar
pression of detonation, e. g. by movement of the
rangement, a pair of linked magnetos of conven
mixture control arm of the carburetor. This, in
construction illustrated schematically at
turn, causes enrichment of the fuel mixture sup
63 are controlled from the unit 20 by the con
plied the engine by the carburetor to automati
necting link arm 64. The cyclic movement trans
cally change the operating conditions of the
mitting device or unit 20 operates in themanner
engine so that detonation is overcome. The
solenoid 3'1 is energized by the detonationpick-up 75 previously described in response to the means for
detecting detonation in the cylinders of the en
In Fig. 3, a further modi?cation of the‘ inven
tion is shown in which a ?xed type of control
unit 20 is operative to control the mixture valve
for-the carburetor by which ‘the ratio of pre
heated and‘ cold air admitted thereto is regulated
in a desired manner. In this instance, the car
buretor includes a conventional air temperature
controlling valve (not shown) which is automati
cally regulated by a unit 20‘ through means of
thepivotally mounted arm 65 and link 66. This
form of utilization of’ the control device is slower
in. response in overcoming detonation but is
equally eifective.
Since many changes could be made in the above
construction and many apparently widely differ
ent. embodiments of this invention could be made
without ‘departing from the scope thereof, it is
intended that all matter contained in the above ,
description or shown in the accompanying draw‘
ings shall be interpreted as illustrative and not
in. a limiting sense.
What is claimed is:
1. The combination of an internal combustion
engine ‘having means for controlling its working
conditions of operation, a linkage system. by
which said controlling means is positioned, means
in which said‘ unidirectionally operable" means is
provided by a solenoid, energized by the detonation pick-up transmitter, and a movable, ?uid
receiving, hollow core piece, cooperating with said
. solenoid, having a valve controlledv passageway
8. A device responsive to a detonation pick-up
transmitter for controlling internal combustion
engines comprising a cylinder element‘ having
two ?uid containing compartments, a piston‘ ac
tuating member for the device de?ning a wall
for'one of said compartments, electromagnetic
means, responsive to the detonation pick-up
transmitter, operable unidirectionally to supply
: ?uid to the piston member wall de?ned compart
ment and thereby effect movement of the piston
member, means for restoring the piston member
to an. initial position, a passageway for said cyl
inder‘ element through which the ?uid moves
from said piston member wall de?ned compart
ment to said other compartment, and means situ
ated in said passageway for controlling the: rate
of movement of the ?uid.
9. A device of the character claimed in claim 8,
in which the electromagnetic means is provided
by a solenoid, energized by the detonation pick
up transmitter, and a movable ?uid receiving,
hollowing core piece, cooperating with said sole
for detecting detonation in the cylinders of said
noid, which receives ?uid from the other of said
engine, and cyclic actuating means included in
compartments and supplies ?uid to the piston
said linkage system for‘ automatically operating 30 member
wall de?ned ‘compartment.
the controlling means for‘ the engine responsive
combination of elements claimed in.
to‘ said detonation detecting means.
claim 1, in which the means for controlling the
2.. The combination of elements claimed in’
working conditions of operation of the. internal
claim 1, which includes means for controlling the
35 combustion engine is provided by an ignition tim—
time interval in which the return portion of the.
ing control device, and the cyclic actuating means
cycle of operation of said actuating means is
operates to initially retard the timed occurrence.
of ignition in the operation of the engine.
3. The combination of elements claimed in
11. A device for regulating internal combustion
claim 1, in which the means for controlling the
engine is a carburetor having a valve positioned 40 engines comprising means for controlling the
by said‘ linkage system by which the ratio of fuel
to air supplied the engine is regulated.
4. The combination of an internal combustion
engine having a carburetor with a fuel regulating
valve therein, a linkage system by which said
regulating valve is manually positioned, means
for detecting detonation in the cylinders of said
engine, and a device, included in said linkage sys
tem, responsive to said detonation detecting
means and operative to automatically change the‘
engine, a linkage system bylwhich said control
ling means is positioned, means for detecting det~
onation in the cylinders of the engine, and actu
ating‘ means included in said linkage system for
automatically operating the controlling means ‘for
the engine responsive to said detonation detect-r
ing means in a manner tending to reduce the'
occurrence of detonation.
12. A device for automaticallyoperating a posi
tionable fuel~air mixture determining means as
sociated with the carburetor of an internal com
position of said valve to control the engine.
5... A. device responsive to a detonation pick-up
bustion engine comprising‘ a linkage system by
transmitter for controlling internal. combustion
engines, comprising a cylinder element having
two ?uid containing. compartments, a piston ac-~
ally'positioned, means for detecting detonation. in
tuating member for the device situated in said
cylinder element, means responsive to the deto
nation pick-up transmitter, operable unidirec
tionally to supply fluid to one of said compart
-ments- and eifect movement of the piston actuat
ing member, means for restoring the piston mem
ber‘to an. initial position, and means for resisting
the action of said restoring means, comprising a.
which the mixture determining means is manu
a cylinder of the engine, and means operatively
connected in said linkage system, responsive to
saiddetecting means for automatically changing
the position of the mixture determining means
in a manner tending to reduce‘ the occurrence of
13. A device for regulating an internal com
bustion engine, comprising means adapted‘. to
control detonation occurring in said engine, man
ual means for setting said detonation control
fluid restricting valve contair-iingv passageway
which connects the ?uid supplied compartment 65 means in a desired operating position, and auto
matic means for modifying the: setting of said‘
with the other compartment.
detonation control means in response to engine
6. A device of thecharacter claimed-in claim.5,.
in which the compartments of the cylinder ele
14. A device for regulating an internal com
ment are ?lled with; fluid, which. includes: pres--v ‘ bustion
engine, comprising means adapted to
sure responsive means for compensating for
regulate detonation occurring in said engine,
changes: in volume of thelfl-ui'd due. to. variances in
manual control means for setting said detonation
temperature conditions in which the‘. device
regulating means in a desired operating position,
and. automatic control means for modifying sucl'r
7. A device of the character claimed in claim 5, 75
setting in response to engine detonation, said
responsive to a predetermined maximum level of
detonation severity to operate said regulator so
as to suppress detonation, emergency manual
control means operative on said regulator to
eliminate detonation, and signal means for indi
cating when said automatic control means is in
actuating said engine regulator, manual control
means for also actuating said engine regulator,
and a warning indicator for showing when opera
tion of said manual control means is required.
16. Automatic detonation suppression appa
ratus for an internal combustion engine of the
type having an engine regulator operative to vary
the detonation tendencies of said engine, said
apparatus comprising a manual ‘controller for
said regulator, and automatic control means re
sponsive to engine detonation for rendering said
manual controller ineffectual to adjust said regu
lator in a manner to aggravate engine detonation
when said detonation reaches a predetermined
maximum level of severity.
17. Automatic detonation suppression appa
ratus for controlling a fuel-air mixture regulator
of an internal combustion engine, comprising
manually operable means for setting said regu
lator at a desired operating position, and auto
matic control means responsive to a predeter
mined intensity of detonation in said engine for
regulator operative to vary the detonation tend
encies of said engine, automatic control means
automatic control means including means for
urging said detonation regulating means toward
its original manual setting.
15. Detonation suppression apparatus for an
internal combustion engine, comprising an engine
regulator adapted when actuated to suppress det
onation occurring in said engine, automatic con
trol means responsive to engine detonation for
19. An automatic detonation suppression appa
ratus for an internal combustion engine, compris
ing an engine regulator operative through a pre
determined range to vary detonation tendencies
in said engine, and an automatic controller re
15 sponsive to each engine detonation of predeter
mined intensity for effectively adjusting said reg
ulator by an amount corresponding to only a
minor fraction of its effective range, in a direc
tion to suppress detonation.
20. An automatic detonation suppression appa
ratus for an internal combustion engine compris
ing a fuel mixture regulator operative over a pre
determined range to vary the detonation tend
encies of said engine, and an automatic controller
25 responsive to each engine detonation of at least
a predetermined intensity for shifting said regu
lator a distance corresponding to a portion of its
entire range in a direction to suppress detonation,
limiting the minimum fuel-air ratio position of
said regulator.
18. Detonation suppression apparatus for an
internal combustion engine, comprising an engine 35
said controller including escapement means for
restoring said regulator to its original. position
during a time interval substantially equal to the
reciprocal of the desired incipient detonation,
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