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Nov. 25, 1947.v
E. A. STALKER-
‘2,431,592
AIRCRAFT HAVING AXIAL FLOW COMPRESSIOR AND BOUNDARY LAYER INTAKE
Filed Aug. 9, 1945
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2,431,592
Patented Nov. 25, 1947
UNITED STATES PATENT OFFICE
2,431,592
AIRCRAFT HAVING AXIAL FLOW COMPRES
SOR AND BOUNDARY LAYER INTAKE
Edward A. Stalker, Bay City, Mich.
Application August 9, 1945, Serial No. 609,847
11 Claims. (01. 244-15)
2
1
pressure is large is of great importance in an
aircraft, because when the aircraft is stationary
on the ground the in?ow into the compressor
results only from the direct action of the com
pressor in sucking in the air, but when the air
This invention relates to aircraft.
It is the principal object of the invention to
provide a power plant system for an aircraft
incorporating an axial flow compressor which
may be operated at a relatively high compression
ratio while retaining adequate volume range for
plane is ?ying at high speed the inflow to the
compressor is substantially greater because of
the relative wind as well as the inductive action
It is also an object to provide a power plant
of the compressor. It will therefore be clear that
system for an aircraft in which an axial ?ow
compressor is supplied with boundary layer air of 10 the range of volume delivery from the stationary
condition to the high speed condition must be
relatively low velocity and the range of velocities
all normal operating conditions of the aircraft.
very great for best operation.
of which under varying operating conditions of
This invention discloses compressor blades
the aircraft is substantially reduced, making it
which produce relatively high pressure ratios. It
possible and practicable to operate the compres
sor at substantially increased compression ratios. 15 also shows how these blades can be used in a
compressor cooperating with the surfaces of the
aircraft to obtain effective propulsion of the air
craft even at such high values, providing for in
It is also an object to provide such compressor
with a blade shape which is particularly advan
tageous for operation at relatively high pressure
duction of the boundary layer air thus reducing
ratios per stage of the compressor and under
20 the volume range conditions to which the com
reduced volume range conditions.
pressor is subjected in operation.
Other objects and advantages will be appar
For this purpose the compressor inlet is placed
ent from the following description, the accom
in communication with suitable openings in the
panying drawing and the appended claims.
surface of the aircraft so as to induct chie?y the
In the drawing:
Fig. 1 is a typical plot of pressure ratio R 25 boundary layer of air thereon. Since this layer
has an average velocity equal to about one-half
against volume delivery coef?cient C1 for a con
the speed of ?ight, the volume range required of
ventional axial-?ow compressor;
the compressor is reduced by a comparable
Fig. 2 is a similar plot of the characteristics of
amount.
'
a compressor of the type of this invention;
Further it has been found highly desirable to
Fig. 3 is a fragmentary top plan view of an 30
provide such an axial-?ow compressor with blades
aircraft employing a compressor as part of its
of special shape so that the compressor blades
propulsive power plant;
can be run at very high tip peripheral speeds
Fig. 4 is a section of the wing of the aircraft
and at a high pressure rise per stage. Such
along the line 4—4 in Fig. 3;
blades, however, have a limited volumetric range.
Fig 5 is an axial section of a compressor in
That is the blades have relatively sharp leading
edges and unless the flow divides near the edge
turbulence results in the ?ow and the quantity
accordance with this invention;
Fig. 6 is a cross section of a compressor blade
taken along line 6-6 in Fig. ‘5;
delivered declines as Well as the pressure ratio.
Fig. 7 is a diagram illustrating the basic airfoil
secdtion from which the blade of Fig. 6 is derived;
an
Fig. 8 is a fragmentary development of two
rotors and the intervening stator.
40
Referring to the drawings, Fig. 1 shows a plot
of pressure ratios R versus a delivery coe?icient
C1. It is clear from this curve that at a com
pression ratio of 1.23 the available range is zero.
At lower ratios the range of C1 is several hundred
per cent from the left-hand side where stalling
main propulsive system of an aircraft, not only is
of the blades occurs to the right-hand side where
the maximum compression ratio which it can de
choking occurs due to the flow velocity becoming
velop important, but the effect of volume range
sonic. This upper or sonic limit for the available
on that ratio is also highly important. It is
range of compression ratios is given by line I.
known from the characteristics of axial ?ow ‘
blowers that the higher the pressure ratio, the 50 It is apparent that to'obtain a substantial range
in the coef?cient'Cr, it is necessary to operate at
more limited becomes the volume range, volume
a relatively low compression ratio, as shown by
range being de?ned as the range of volume de
livered per revolution (C1) from the condition of
curve a.
stalling to the condition of choking.
Fig. 2 shows a plot of the characteristics of an
The range of volume delivered for which the r
other compressorv having blades designed accord
Where a compressor is utilized as part of the
2,431,592
4
3
‘ing to this invention with relatively sharp lead
ing edges, special camber lines, and special thick
ness distribution so that they can be operated at
high peripheral speeds producing a high pressure
ratio. By operating this compressor with bound
ary layer air the available range is made adequate
to the range of delivery required by the aircraft
power plant. The compressor of the invention
is designed to operate along curve I) much nearer
mean camber line which is straight, as OX, it is
developed with respect to a mean camber line
which has a substantial arching as shown at 3t.
The mean camber line 36 is arched to provide
the maximum ordinate 38 aft of the 0.40 point
and preferably aft the midpoint. Abscissae are
measured off in per cent of the mean camber
line length along the mean camber line. Per~
pendicular'to the mean=camber lineand'at per
to the maximum value m and making possible a 10 centage points corresponding to likepercentage
points along the chord. OX, the half-thickness
much higher compression ratio while still retain—
ordinates of the basic section are laid off above
ing an adequate volume range since by using
and below the mean camber line giving the air
boundary layer air it will not. require as large a
foil'or'blade" section 2| of Fig. 6. Ordinates 3‘!
value of C1,
In Figs. 3 and 4 the airplane is indicated at I, 15 and 3d are typical of those laid off perpendicular
to the mean camber line.
having the wing 2 provided with the slots 4 in
The maximum ordinate 38 of the mean camber
the upper surface and the slots 6 in the lower
line-36 is placed preferably well aft of the mid
surface.
point of the chord. Likewise the maximum
The compressor It] has its inlet 12 in communie
cation with the slots via the compartment M 20 thickness is preferably aft of the midpoint. Since
the greatest acceleration of the external ?ow
in the wing. The compressor delivers air to the
will occur where the upper surface of' an airfoil
combustion chamber It where fuel. is burned
is curved the most, the greatest local velocities
forming products of combustion, suchmixed air
will occur on the aft‘ portion of the blade just
and heated products. of combustion being re
ferredto herein as the gas. Thechamber directs 25
the gas into the turbine. 20 for the generation
of power, the turbine being mechanically con
described.
,
In an axial compressor there is a pressure rise
from the front of therotor tov the'rear which,
according to Bernoulli’s equation, must be ac
companied by a' decrease in velocity between the
to rotate.
The blade for. airfoil section 2| employed to 30 blades. The blade‘ section with‘ its speeding-up
properties near'the rear of‘ the. blade takes ad
produce the large pressure rise is shown in Fig. 6.
vantage of the slowing down in‘ the stage'sov that
It may be developed as followsfrom a basic sec
the velocity/distribution over" the blade, when in
tion, the forward portion of which lies within
the rotor, is‘ substantially‘ uniform. It is also
boundary basic section curves shown in Fig. '7.
The basic airfoil section has the straight line OX 35 found advantageous to provide a substantial in
crease in the maximum ordinates of the mean
asa chord or base line of length C. An ordinate
camber lines of the airfoil sections of axially suc
22 is erected equal to half the thickness of the
cessive blades of‘ a multi-stage compressor in the
airfoil section, such ordinate being located be
downstream direction. This is shown in frag
tween the range of about the 0.4: point and the
0.6 point of the chord. Better results for the 40 mentary developed form in Fig. 8 in which the
blades Q0 of the upstream‘rotor'have substan
present inventionare. secured where such ordi
tially less camber'than the blades 42 of the suc
nate 22 is located well aft of the mid-point of
ceeding or downstream rotor, the stator blades
the chord. In the form shown the’ erection is
being indicated at 43; Other" blades further
made at‘0L6C measured from the nose point 0.
Next, the. elliptic quadrant 24 is constructed @ LA downstream would have even' larger cambers.
Thearrows 185 indicate the direction of rotation
using the 0.6Casthe. major semi—axis_ and ordi“
of the rotors while arrows 46~indicate the direc
nateZZasthe minor, semi-axis. At the 0.30 point
tion of the fluid flow.
the. ordinate 26 is erectedequal to ordinate 22
To achieve this uniform distribution at very
and the elliptic quadrant 28 is constructed with
high peripheral speeds, at the sacri?ce of volu
the ordinate 25 as the. minor semi-axis and‘the
metric range the nose of the‘ section is made,
0.3Cas the major semi-axis. The elliptic quad
quite pointed since it will attack air which has
rant is continued‘ rearward to become tangent
not yet been slowed down‘within'the rotor.
with quadrant 2d, and then with a desirable
It’ is a feature of this‘inventionthat the blade
smooth curve '39 to the trailing point X. Measur~
ing, perpendicular to line OX, ordinates are laid
substantial
has the typevalue
of airfoil
to the
sections
height
described
of the with
mean
off. below quadrant 24 equal tov the distance of
camber
line.
This
value
is
preferably
greater
quadrant 28 thereabove. This gives the lower
than 5 per cent of the chord C and preferably
boundary curve 34.
less than 50 per cent.
The basic airfoil section ahead of its ordinate
Asia result of the use of a compressor with
of‘ maximum thickness will lie in majorv part (30
blades of such construction to obtain a high
within the boundarycurves28 and 34,_ prefer
pressure ratio and relatively low volumetric
ably, below the mean curve 24 to provide a
range, and-operating to cause the induction of
sharper nose contour. By having it lie within
relatively slowly movingair from the surface of
such boundaries the. nose of the basic section
an aircraft, the desirable high pressure ratio is
willhave an appreciable'nose curvature of de
obtained and at the same time the'limiting effects
sirable form; However thenose may besharp
of a low volumetric range are overcome. As
ened further and theiequivalentradius of curva
already described; this is‘ accomplished by'hav
turereduced for services where pressure is al
.ing the blower induct the boundary layer to form
most the only consideration. The remainder of
the propulsive jet. Since the air in this layer
the basic. airfoil section is obtained by laying off
has only about half the velocity’ of ' ?ight, the
below the chord line OK the curve selected above
compressor needs to serve only a fraction of the
the chord line.
volumetric range which would be required by
The compressor blade in Fig. 6 uses the basic
intake of the air having the full relative velocity.
airfoil contour whose upper half is shown inli‘ig.
nected to the compressor 10 to cause the same
7; Instead of being laid off with respect to a
The inventionhasbeen described withrespect
2,431,592
5
to a type of compressor commonly called an
"axial ?ow compressor” to distinguish it from
centrifugal compressors in which the ?ow is ra
dial employing centrifugal action. The invention
however is applicable to any compressor using
airfoil sections for the blades and relying chie?y
on a lift force to impel the ?uid as in my U. S.
Patent No. 2,177,159 of October 24, 1939. Cross
reference is also made to my copending applica
tion, now Patent No. 2,405,768, issued August 13,
1946, which discloses the blades of the type herein
referred to.
While the form of apparatus herein described
6
end of said maximum thickness ordinate, said
auxiliary minor semi-axis being equal to one
half the said maximum thickness of the said air
foil section, means to rotate said blade with a
high peripheral velocity to produce a large pres
sure ratio, means placing the inlet of said com
pressor in communication with said slot to induct
said boundary layer air of low velocity range from
said surface and compress said air thereby re
taining the large pressure ratio and reducing the
need for a large volumetric range, and means to
heat and expel said inducted air rearward with
increased velocity to provide thrust for the air
craft.
constitutes a preferred embodiment of the inven
3. In combination in an aircraft having a slot
tion, it is understood that the invention is not 15
in its external surface for the induction of bound
limited to this precise form of apparatus, and
ary layer air having a substantially lower velocity
that changes may be made therein without de
range relative to the aircraft than the speed of
parting from the scope of the invention which is
?ight, a power plant utilizing compressed air for
de?ned in the appended claims.
What is claimed is:
20 generating power to propel the aircraft, an axial
?ow compressor having a blade across which the
1. In combination in an aircraft having a slot
?ow travels with substantially no increase in ve
in its external surface for the induction of boun
locity from its leading to its trailing edge thereby
dary layer air having a substantially lower veloc
limiting the volumetric range with increasing
ity range relative to the aircraft than the speed
of ?ight, an axial ?ow compressor having a blade 25 pressure ratio, said blade having a section whose
mean camber line has its maximum ordinate
across which the ?ow travels with substantially
above the subtending chord located substantially
no increase in velocity from its leading to its
aft of the midpoint of the chord and whose maxi
trailing edge thereby limiting the volumetric
mum thickness is substantially aft of the 0.40
range with increasing pressure ratio, said blade
having a basic airfoil section whose maximum 30 point, said blade section having a convex upper
aft contour and a concave lower aft contour form
thickness lies aft of about the 0.4 point of the
ing therewith ,a relatively sharp trailing edge,
chord and whose upper contour ahead of the
means to rotate said blade with a high peripheral
maximum thickness ordinate lies in major part
velocity to produce a large pressure ratio, means
within boundary curves whose mean curve is an
elliptic quadrant passing through the nose point 35 placing the inlet of said compressor in communi
cation with said slot to supply said power plant
of the section and the end point of the said maxi
with air at high pressure from the boundary layer
mum thickness ordinate serving as the minor
thereby retaining the large compression ratio of
semi-axis of said quadrant, the outer curve of
the compressor and reducing the need for a large
said boundary curves being an auxiliary elliptic
quadrant passing through said nose point and 40 range of volume delivery.
4. In combination in an aircraft having a slot
the end of an auxiliary minor semi-axis at the
in its external surface for the induction of bound
0.3 point of the chord and extending on to the
ary layer air having a substantially lower velocity
outer end of said maximum thickness ordinate,
range relative to the aircraft than the speed of
said auxiliary minor semi-axis being equal to
?ight, a gas turbine power plant utilizing com
one-half the said maximum thickness of the said
pressed air for generating power to propel the
airfoil section, means to rotate said blade with a
aircraft, an axial flow compressor having a blade
high peripheral velocity to produce a large pres~
across which the flow travels with substantially
sure ratio, and means placing the inlet of said
no increase in velocity from its leading to its
compressor in communication with said slot to
induct said boundary layer air of low velocity 50 trailing edge thereby limiting the volumetric
range with increasing pressure ratio, said blade
range from said surface and compress said air
having a blade section developed from a basic sec
thereby retaining the large pressure ratio and
tion whose maximum thickness ordinate lies aft
reducing the need for a large volumetric range.
of about the 0.4 point of the chord and whose up
2. In combination in an aircraft having a slot
in its external surface for the induction of bound 55 per contour ahead of the maximum thickness
ordinate lies below an elliptic quadrant passing
ary layer air having a substantially lower velocity
through the nose point of the section and the end
range relative to the aircraft than the speed of
point of the said maximum thickness ordinate
?ight, an axial ?ow compressor having a blade
serving as the minor semi-axis of said quadrant,
across which the flow travels with substantially
no increase in velocity from its leading to its 60 said minor semi-axis being equal to one-half the
said maximum thickness of the airfoil section,
trailing edge thereby limiting the volumetric
said blade section being developed with respect to
range with increasing pressure ratio, said blade
an arched mean camber line having its maximum
having a basic airfoil section whose maximum
ordinate
above the subtending chord aft of the
thickness lies aft of about the 0.4 point of the
chord and whose upper contour ahead of the 65 midpoint thereof, means to rotate said blade with
a high peripheral velocity to produce a large presi
maximum thickness ordinate lies in major part
sure ratio, means placing the inlet of said com
within boundary curves whose mean curve is an
pressor in communication with said slot to supply
elliptic quadrant passing through the nose point
said power plant with air from the boundary
of the section and the end point of the said maxi
mum thickness ordinate serving as the minor 70 layer thereby retaining the large compression ra
tio of the compressor and reducing the need for
semi-axis of said quadrant, the outer curve of
a large range of volume delivery.
said boundary curves being an auxiliary elliptic
5. In combination in an axial ?ow compressor,
quadrant passing through said nose point and
a plurality of axial flow compressor blades dis-'
the end of an auxiliary minor semi-axis at the 0.3
posed in tandem along the axis of the compressor,
point of the chord and extending on to the outer
each said blade having a blade section developed
7
8
"with respectto an archedmean camber line from
rant passing. through. said nose, point and the
end of anauxiliary minor semi=axis at the 0.3
point of the chord and extending. on to the outer
end of said maximum thickness ordinate, said
auxiliary minor semi-axis being equal to one,
a; basic airfoil section whose 'maximum thickness
lies aft of'about the’ 0A point of the chord and
whose» upper contour ahead» of‘ the maximum
thicknessordinate lies in major part within bound
ary curves whose ‘mean‘curve is an- elliptic quad—
rant: passing through the nose point of the sec
tion- and the end, point of the said maximum
thickness; ordinate serving as the minor semi
half the said maximum thickness of the said air?
foil section, and means for supplying said-bound.
ary layer into the intake of said- compressor to
provide a. supply of air thereto of relatively low
axis of- said ‘quadrant, the outer curve of'said 10 volume range providing for development by said
boundary curves-beingan auxiliary elliptic ‘quad
rant passing through said nose point and the end
of-‘an auxiliary minor semi-axis at the 0.3point
compressor of substantially increased compres
sion ratios.
8. An aircraft having an airfoil surface on
which a boundary layer is adapted to form in
of said maximum thickness ordinate, said aux 15 ?ight, said boundary layer air having substan
tially half theaverage velocity relative to the air
iliary minor semi-axis 'being'equal to one-half the
craft of the speed of night and a. corresponding
maximum thickness of- said airfoil section, the
reduction in velocity change between the ?ight
maximum ordinates of, the mean camber lines of
and the standstill conditions of. the aircraft, a
the airfoil section of axially successive blades sub
stantiallyincreasing from bladeto blade in the 20 power plant for propelling said aircraft includ
ing a compressor of the axial ?ow type having
downstream direction, and-a casing to-house said
blades and direct a4 ?ow of ?uid through'succes
blades acrosseach of which the flow travels with
of the chord and extending on to the outer end
sivetbladesa
substantially no increase in velocity from the
6, Incombinationin an axial flow compressor,
a plurality of axial flow‘ oompressor‘blades dis
posed in tandem along the-axis of the compressor
leading to the trailing edge-thereof thereby limit
ing the volumetric range with increasing pres
sure ratio, said blades-having a basic airfoil sec~
to. for-ma multistage compressor, each said blade
tion whose maximum thickness lies aft of about
having’ aibladesection developed with respect to
the 0.4 point of the’ chord and whose upper con
an arched mean camber linefrom a‘basic airfoil
tour ahead of the maximum thickness ordinate
sectionwhose maximum thickness-lies aft of the 30 lies in major part within boundary curves whose
station at about the 0.4 point of the-chord and
mean curve is an elliptic quadrant passing
whose upper contour ahead of the maximum
through the nose point of thesection and the‘end
thickness ordinate lies inmajor part within bound
point of said maximum thickness ordinate serv
ary curves-whose mean curve is anelliptic quad
ing as the minor semi-axis of saidrquadrant, the
rantpassing through the nose point of the sec 35 outer curve of said boundary curves being an
tion’ and the end point'of the‘ said maximum
thickness ordinate serving‘asthe minor semi-axis
of said-quadrant, the outer curve ofsaid boundary
curves being an auxiliary elliptic quadrant pass
auxiliary elliptic quadrant passing through said
nose point and the end of- an auxiliary minor
semi-axis at the 0.3 point of the“ chord and ex
tending on to the outer end of said maximum
ing through said nose point and the end of an 40 thickness ordinate, said auxiliary minor semi
auxiliary minor semi~axis at the 0.3 point of the
chord and, extending on to the outer end of said
maximum, thickness ordinate, said auxiliary
minor semi~axis being equal to one-half the max
imum thickness of said airfoil section, the maxi
mum ordinates of the mean camber lines of the
airfoil sections of axially successive blades sub
stantially increasing from blade to blade in the
downstream direction, and a casing: to house said
blades “and direct a ?owtof fluid through succes- .
axis being equal to one-half the said maximum
thickness of the saidairfoil section, and means
for supplying said boundary layer into the intake
of said compressor to provide a supply of air
thereto of relatively low volume range providing
for development by said compressor of substan
tially increased compression ratios.
9. In an aircraft having a slot‘in its external
surface for the induction of- boundary layer air
having a substantially lower velocity range rela
sive blades, the majority of saidblades having
tive to the aircraft‘ than the speed of ?ight, the
a. mean camber line maximum ordinate‘ greater
combination of an axial flow compressor having
a blade across» each of which the ?ow travels with
substantially no increase in velocity from the
thanl5 per cent of the length of the subtending
chord.
‘7. In ‘combination in an aircraft having an
airfoil surface on which a boundary layer is
adapted to form in ?ight, said boundary layer
haying. substantially. less velocity relative to the
aircraft-than-the speed of‘?ight, a power plant for
propelling said aircraft including an axial ?ow
cQmpressor having blades across eachof which
the flow travels with substantially no increase
inrvelocity from the leading to the trailing edge
thereof thereby limiting the volumetric range
with increasing pressure ratio, said blades having
abasic airfoil section whose maximum thickness
ordinate-is located between the range of about
the-0.4 and the 0.16 points of the chord and whose
upper contour ahead of the maximum thickness
ordinate lies in major part within boundary
curves whose'mea-ncurve is an elliptic quadrant
passing through the nose point of the section and
the endpoint of said maximum thickness ordinate
serving as the minor semi-axis of said quadrant,
leading to the trailing edge thereof thereby limit
ing the volumetric range with increasing pres
sure ratio, said blade having a basic‘ airfoil sec
tion whose maximum thickness, lies aft'of about
the 0.4- point of the chord and whose upper con
tour ahead of the maximum thickness ordinate
lies in major part within boundary curves whose
mean curve is an elliptic quadrant passing
through the nose point of the section and the end
point of the said maximum thickness ordinate
serving as the minor semi-axis; of said‘ quadrant,
the outer curve ofl-said boundary curves being an
auxiliary elliptic quadrant passing through said
nose point and the end of an auxiliary minor
semi-axis at the 0.3 point of‘ the chord ‘and ex~
tending on to theroutere end of said maximum
thickness ordinate, said auxiliary minor semi
axis being. equal to one-half the said maximum
thickness. of the said airfoil section, said blade
being rotatable with ahigh peripheral velocity to
the. outer curves being anauxiliary elliptic quad’ 7:; Produce, a large pressure ratio, andmeansfm
2,431,592
10
having a blade across which the ?ow travels with
substantially no increase in velocity from its lead
?ight of the aircraft, an axial flow compressor
having a blade across which the flow travels with
substantially no increase in Velocity from its lead
ing to its trailing edge thereby limiting the vol
umetric range with increasing pressure ratio,
means to rotate said blade with a high peripheral
velocity to produce a large pressure ratio, means
placing the inlet of said compressor in communi
cation with said slot to induct said boundary
10 layer air from said surface and to compress said
air, thereby operating the compressor in the air
ing to its trailing edge thereby limiting the vol
umetric range with increasing pressure ratio,
craft at a range of inlet air velocities substantially
smaller than the range of velocities of ?ight of the
supplying said low velocity boundary layer air
from said slot to said blade to provide for com
pression of said air to a high pressure ratio with
reduced need for a large volumetric range.
10. In combination in an aircraft having a slot
in its external surface for the induction of bound
ary layer air whose range of relative Velocities is
substantially less than the range of velocities of
?ight of the ‘aircraft, an axial ?ow compressor
aircraft with resulting improvement in pressure
velocity to produce a large pressure ratio, and 15 and e?iciency performance, and means to dis
charge said inducted air rearward to propel the
means placing the inlet of said compressor in
‘aircraft throughout said range of ?ight velocities.
communication with said slot to induct said
EDWARD A. STALKER.
boundary layer air from said surface and to com
means to rotate said blade with a high peripheral
press said air at a range of inlet air velocities sub
REFERENCES CITED
stantially smaller than the range of velocities of 20
?ight of the aircraft with resulting improvement
The following references are of record in the
in pressure and efficiency performance.
?le of this patent:
11. In combination in an aircraft having a slot
FOREIGN PATENTS
in its external surface for the induction of bound
Country
Date
ary layer air whose range of relative velocities is 25 Number
Great Britain _____ __ Aug. 29, 1939
substantially less than the range of Velocities of
5 12,064
Certi?cate of Correction
Patent No. 2,431,592.
November 25, 1947.
EDWARD A. STALKER
‘
-
It is hereby certi?ed that errors appear in the printed speci?cation of the above
numbered patent requiring correction as follows: Column 8, line 53, claim 9, strike
out “each of”; lines 54 and 55, each occurrence, for the word “the” read its; line 55,
strike out “thereof”; and that the said Letters Patent should be read with these
ggections therein that the same may conform to the record of the case in the Patent
ce.
Signed and sealed this 24th day of February, A. D. 1948.
[mi
THOMAS F. MURPHY,
Assistant Commissioner of Patents.
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