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Патент USA US2404664

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19%“
R. L. SKINNER
PR ESSURE SEALING —MEANS
Filed May 2'7, 1944
2 Sheets-Sheetv l
R. L. SKENNEE
PRESSURE SEALIBIG-MEANS
Filed May 27, 1944
,
'2 Sheets-Shem’; 2
Patented July 23, “19,46
' 2,404,664
UNITED STATES PATENT OFFICE
Ralph L. Skinner, Detroit, Mich, assignor tonsil
niks Company, Detroit, ‘Mich, ‘a copartnership
ApplicationMay '27, 1944, Se?'al‘No. 537,757
‘1 Claim. (Cl. 1286-26)
‘
2
‘1
The current invention pertains to certain valu
and important ‘functions during the landing of
able betterments and re?nements in ?uid-pres
the airplane .as follows: .(a) the'absorptio‘n of the
sure sealing-means for packing-glands of special
impact-energy cf the landing airplane is ac
‘advantage when employed in connection with
complished by the compression of the air in the
the struts of the landing-gears .of airplanes, al :5 upper chamber during the compression stroke
though the invention is not limited or restricted
of the wheel-carrying piston .or plunger; ‘(11) the
to such particular service, in that the structural
loads developed in the appliance while the air
_ and functional features of superiority of suitable
plane is taxiing are carried mainly by the com
embodiments .of the invention may be availed
pressed-air in the upper chamber; and (c) the
of in shock-absorbers for automobiles, sealing 10 snubbing effect, which is necessary to prevent
means for pump-shafts, globe-valves, etc., and
quick rebound, is produced by forcing the liquid
in other relations.
to pass through restrictions on the expansion
As is well known, aircraft landing-gears .in
stroke of the plunger or piston.
clude a, plurality of rubber-tired wheels, each of
Bearing in mind these essential duties which
which
mounted on the lower portion of a so
called strut which may be swung down into oper
15
the strut must perform, remembering that the
airplanes are subject to great ranges of atmos
pheric temperature, and that they encounter
water... :ice, dust, dirt, mud, Ietc., it is obvious that
to render proper, e?‘icient and effective perform
ative position or retracted upwardly into inoper
at'ive elevated relation, each such strut, when
down in working position comprising a vertically
disposed cylinder within which is slidingly ?tted 20 ance over reasonable periods of time without re
a hollow piston .or plunger which extends down
out of the end of .the cylinder and carries at its
lower end the rotatable landing-wheel de
ing ?uid-pressure sealing-gland must be used be
signed to descend with the airplane into contact
with the ground and to roll thereon.
The interior of the hollow, reciprocable piston
vent leaking of either contained ?uid, liquid .or
air, and without undue friction.
The provision of such an adequate pressure
may be considered as a lower chamber, and the
interior of the cylinder in which the piston slides
sealing means remained an aggravating‘, per
uni-ring ‘servicing, a simple, suitable, long-wear?
tween the cylinder and plunger to positively .pre4
sistent, expensive, unsolved problem over a long
may be regarded as an upper chamber, such
period of years until its answer was compara
lower chamber accommodating a suitable liquid,
tively recently discovered and that ,dii?oulty
such as a mineral-oil, and the upper chamber
being charged with air under substantial pres
sure, the wall of such cylinder having a valve
ment in this portion of the structure described ‘
assembly by which the two ?uids may be origi
nally admitted into the combined communicat
ing chambers.
overcome by ‘the invention of the novel improve
hereinafter.
The employment of a present desirable em
35 bodiment of the current invention in such a
landing-gear strut has been illustrated in detail
in the accompanying drawings, forming a part of
bly are slidable longitudinally relatively to one
this speci?cation, and to which reference should
another and these two telescopic tubes are main
be had in connection with ‘the following descrip
tained in line by the links of a torque-arm as 4.0 ti0n,'like reference numerals being vemployed in
sembly which prevents the piston from turning
the several views of the drawings to designate
angularly in the cylinder, the upper end of the.
the same parts of the structure.
latter having suitable means for attachment to
In these drawings:
the airplane with which the strut is employed».
Figure 1 is a perspective veiw of ‘one such strut;
The lower chamber of these two telescoping 45 Figure 2 is a longitudinal section through the
members, piston and cylinder, of the shock-ab
same on line 2-2 of Figure 1;
sorbing unit, when in operative position, is i
Figure 3 is ‘an enlarged, fragmentary, longi
always filled with the liquid and the upper cham
tudinalsection on line 3-3 of Figure 1;
ber has the compressed-air in its top portion and
Figure 4 is a detailed section on a still larger
some of the liquid in its lower parts, although 50 scale through the new and improved packing
when the strut is swung up in its substantially
gland;
'
horizontal inactive position both hollow elements
Figure -5 is a somewhat modi?ed‘corrstruction
may be occupied by both liquid and air.
on a smaller scale; and
An oleo-pneumatic shock-absorbing strut of
Figure 6 shows in perspective the group of ‘the
The piston-assembly and the cylinder-assem
this kind is designed to perform three necessary 55
thin, ?exible, metallic reeds,
'
a
'
2,404,664
3
"
4
.
cient compression stroke has been made to ab
sorb the impact-energy of the lending airplane,
Referring to these drawings, it will be seen
that the airplane strut cylinder II is closed at
and, as such load decreases, the air, which has ‘
- its upper end and open at its lower end, the ex
been compressed above the liquid-level, expands
causing the strut to elongate, the recoil-valve be
ing closed instantly by the returning liquid, the
latter in the outer chamber 36 passing through
terior of the cylinder-assembly having bearings
l2, l3, and It for attachment, by means not
shown, to the airplane for which the strut was
designed.
Internally this cylinder has an upper cylin
drical space l5 and near the lower endofthe
small. holes in the piston-head before it can enter
the upper chamber duringthe extension stroke,
cylinder it has an aligned, cylindrical chamber 10 the expansion of the strut being slowed due to
I6 of slightly greater‘diameter, all as is clearly a the restriction of the flow created, this resistance
resulting in an e?ect known as snubbing and re
presented in Figure 2, an annular shoulder l1
bound isreduced in two ways, ?rst by absorbing
being present at the junction of such two spaces. ‘
metal, cylindrical piston or plunger‘; ‘i3, whose
energy and second by changing the natural period ~
15 offluctuation in such a way that it dampens out
round, outer surface is preferably chromium
plated, ground and highly polishedf'to present an.
‘ 1 .The elongation of the strut increases the avail
Cylinder ll internally accommodates a hollow,
tire oscillation.
unusually smooth, external, cylindrical‘ surface, ~ able volume of the lower chamber 34 in the pis
' ton below the ori?ce-plate and this forces the liq
the piston having a sliding or reciprocatory fit
uid above the ori?ce-plate to return through such
in an appropriate metal ‘bearing 19 mounted in
plate into the‘ chamber below the plate, this ?uid
the lower end portion N5, of the cylinder, 'such
movement continuing until'the a'ir-pressureiri
piston or plunger at its upper end having an ex
the top of the cylinder equalizes the'weight of the
ternal, round head 2l'with a sliding ?t in the
smaller chamber l5'of the cylinder. ' 4
plane and the ground forces thrusting upwardly,
7
Intermediate 'its internal length piston I8 has 25 the piston then coming to rest in what is‘ known
as the static position, it being understood, of
an imperforate partitionewall 22 (Fig/2) divid
course, that when an airplane lands, oscillation
ing its interior into‘two non-communicating
consisting of compression and expansion strokes
chambers, and at its lower end the piston has a
re-occur with diminishing intensity until the air
member 23 (equipped with a landing-wheel axle
f
'
‘ " '
29) mounted thereon to which is hinged at 21 the 30 plane comes to rest.
Inasmuch as struts of this kind or-cornparable
corresponding end of'the torque-arm assembly 25,
ones must successfully withstand varying pres
the upper end of which’is hinged at 25 to the
lower portion of cylinder ll.
~
-
I
sures sometimes in excess of- 3,000'pounds per
u
square inch and must ef?ciently undergo temper
The upper part of the interior of cylinder l l is
closed by a' member 28 on which is mounted a de 35 ature ranges from minus 70° F.- to plus 180° F., it
is obvious that a packing-gland of unusual func
pending; stationary plunger-tube 29 apertured at
tional properties is required to meet‘ the speci?ed
3!,‘3! and supporting at its lower end an ori?ce
conditions in that such gland must prevent leak
plate 32 closing the bottom end‘of the tube, ex
age of both oil and air in the static‘ condition of
cept for its central aperture 33, and’?tting snugly
40 the strut and as well as while undergoing recip
inside of cylindrical chamber of the piston l8.
rocation, both for inde?nite periods of time; '
' vAs will be noted, this ori?ce-plate separates the
,
Loss of hydraulic oil from a'strut causesfre
quent servicing and additional expense,‘besides
the possibility of severe‘ damage to the plane or
through which liquid passes upwardly'into the
upper chamber during compression of ‘the strut 45 occupants in'the event of a large loss of oil in
?ight; and loss of air will eliminate in most cases
and through which’it returns during extension of
lower chamber 34 in the‘piston' and the ‘upper
chamber 35 in the cylinder I I, it 'being' this ori?ce
the
strut.
‘
'
~-
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v
the cushioning effect of the strut and ' hence
‘
cause possible damage to the aircraft during land
The initial,‘ upward compression-stroke of the
piston occurs when the impact-load of the lend
ing airplane‘is applied to the landing-gear and 50
In addition, a gland which will perform satis}
factorily should have long wearing qualities, it
under these circumstances‘, the hollow piston as
should be relatively simple in ‘structure, it should
cends further into the encasing chamber, thus
be substantially inexpensive to produce, it should
reducing the volume of the lower chamber 34 and
be of such form as to be comparatively; easily
forcing liquid to leave such‘ chamber through the
ori?ce-plate, and the liquid, in overcoming the 55 placed into position and removed, and: it should
resistance to its flow through such ori?ce-plate,
he non-corrosive and not subject todetrimental
effects when subjected to radical 1 temperature
absorbs the greater portion of the impact-energy
ing
of the landing airplane, such energy vbeing con
operations,
changes.
'
V
-
"
>
‘
_‘ '
"
V
i
‘
'
Before the discovery and inventionof the new
As the compression-stroke continues, the liqui
level rises above the ori?ce-plate in- chamber 35
and valuable style of packing-gland constituting
the present invention, no available pressure-scab
having issued through one or more of the ports
ing means was able to meet all the required con
3|, 3i and a portion ?ows downwardly through
ditions with reasonable satisfaction; particularly
verted into heat and'dissipated.
1
the essential non-leaking properties over a pro‘
holes in the piston-head 2i and passes a recoil
'
_
valve not shown in detail, which remains open 65 tracting period of time.
during the compression-stroke, into the outer
‘As shown most clearly in detail in Fig.‘ 4,. one
form of such improved 'pressureesealing. packing
annular chamber 36 between the piston and’ cyl
inder, and'the rise of'the liquid in chamber35
compresses the air from its nominal value, thus
creating further resistance to the telescopic ac
tion, compression of the strut stoppingwhen the
entire‘ impact-load of the landing _aircraft has
been absorbed by the liquid and by thecompres
siohoftheair."
"
__
'
Expansion of the strut takes place after a‘suf?
76
gland comprises a group, four in'the present case,‘
of nested'or inter?tted, face-to-‘face contacting,
resilient, metal, conical reeds 4|,‘ 4| ‘resting
against, and held'?xedly pressed together against,
a sloping or oblique, circular-shoulder 42 con-_
stituting, inthis'particular case, part of an an-‘
nular sleeve or collar-40> of the shape.'in'cross.-._ _
section'shown' in Fig. 4, and ‘internally screw
2,404,564
6
threaded at 43, such screw-thread cooperating
gree of flexibility and‘ the angle to ‘properly care
with a screw-thread 44 on a reduced-diameter
for all pressures which may be present.
end portion of bearing 19, the companion or cor
responding terminal portion of the bearing hav
ing an annular chamber 45 with a sloping shoul
der 45, opposite and ‘parallel to shoulder G2,
pressing against the outer portion only of the
‘
As to the metal to be used in‘the reeds, this
is a substantial factor in that it vmust ‘be (a)
G!
tough,‘ (b) of appropriate tensile-strength, (c)
of suitable bearingand wearing properties, and
(d) possess high resistance to corrosion and rust.
uppermost or terminal reed 4! of the group, so
Up to the present time, apparently the best metals
that the uncon?ned, inwardly-directed parts of
for this purpose have been beryllium copper alloy
the reeds whose edges are in direct functional 10 and Wm. Chase Co. Alloy No. ‘720, the latter com
engagement with the cylindrical surface of the
posed of 20% nickel, 20% manganese and 66%
piston are free to yield or ?ex slightly by reason
copper, the second alloy being preferable. In
of the shortness of the surface 46 and ‘the size
order to have a good material with constant ten
of the bearing chamber 45.
sile-strength and physical properties, it is neces
As ‘will be appreciated, this mounting of the 15 sary to control closely and accurately the per
reeds leaves their terminal portions projecting
centage of beryllium in the berryllium cop-per
inwardly with their inner edges pressing on the
alloy, and, since the percentage thereof is quite
highly-polished, cylindrical surface of the re
small, and has to be precise, any variation in
ciprocatory, hollow piston E8, the angular inclin
the alloying of the metal will result in various
ation of the reeds to the axis of the piston, in this 20 finished products which in some cases might ‘be
particular instance, being about 30“.
As will be readily understood, the liquid under
unsatisfactory.
‘Whereas, the relatively large
percentages of the three ingredients of ‘the nickel
pressure in the annular chamber 36 keeps the
manganese-copper alloy is such that any small
bearing 19 adequately supplied with lubricant
variation in the percentage of the different metals
and its pressure is applied to the exposed inner 25 which go to make up the alloy do not affect
portion of the reeds which project inwardly
the ?nished properties materially.
lengthwise of the piston toward the source of
The speci?ed reeds, as to thickness would
pressure, .so that such applied'pressure tends to
flex the inner ends of the reeds into ?rm pres
sure-sealing engagement with the piston regard
less of whether the latter is stationary or sliding.
To facilitate the performance of this advanta
geous function, the foot of the oblique shoulder
G2 does not reach quite the end of the super
ordinarily individually be somewhere between
.005 up to .020 inch, but ‘such dimension is sub»
30 ject to modi?cation.
Now as to the sizes of the parts, assuming that
the internal-diameter of the cylinder-chamber
is from 5.374 to 5.376 inches and that the ex ternal~
diameter of the piston is from 4.4919 to 4.501
posed reeds.
35 inches, that is to say a tolerance of .002 inch
The inter?tted, outwardly-directed portions
in each case, and assuming that the plurality
l4! of the reeds may have their external edges
ground to the same diameter so that they ac
curately contact the adjacent inner surface of
the element 40, although this feature of construc
tion is not always necessary or availed of.
Inwardly longitudinally of the bearing 10 be
yond the reeds 1H the bearing, which in part con
stitutes the mounting for the reeds, is provided
of the reeds have been secured in their mounting,
in this case including the bearing, outside of the
cylinder and with their outer edges desirably,
but not necessarily,,in contact with the inner
cylindrical surface of the collar 40 and with such
collar ?rmly screwed in place against the reeds,
the inner edges of the reeds are ground down
to a diameter of 4.496 plus or minus .001 inch
with a circular peripheral groove 41 around the
diameter so the stepped-edge feature of such reeds
45
bearing accommodating a neoprene or other suit
is eliminated.
able arti?cial-rubber ring-gasket 138 of normal,
After this these inner edges of the reeds are
substantially-round shape in cross-section slightly
lapped on a piston, or its equivalent, of the same
larger in diameter than the depth of the groove,
diameter as the piston to be used in the strut,
so that any of the indicated fluid-pressure which
such lapping being done ‘with a ?ne optical dust.
50
might reach the groove tends to ?atten the gas
This lapping operation increases the free diameter
ket against both the bottom surface of the groove
of the reeds only about .001 inch and careful
and also against the inner face of the cylinder,
measurements will disclose that the diameter of
as presented in Figs. 3 and 4, such means con
the toe of the reeds is slightly smaller than the
stituting an adequate pressure-seal between such
55 diameter of their heel when measured in their
static or stationary surfaces.
free position. Thus the surface of the reeds bear
The reed pressure-con?ning means is not so
ing on the piston in the strut in the slightly
simple of production for any particular strut
?exed normal relation of the reeds is parallel to
service as might at ?rst appear, as will now be
the axis of the piston so that the full width of the
set forth more in detail.
reeds contacts with the surface of the piston.
In the ?rst place, the number of reeds to be 60
It will be understood that after the reeds have
employed in the gland, whether one or more, is
been placed in the cylinder and the piston forced
a matter which depends upon the particular con
through them, there is an interference fit between
ditions of service which the gland must suc
the two parts owing to their slightly different
cessfully meet.
diameters, the male part being of minor larger
Then again, the angular slope or inclination of 65 diameter than that of the female part.
the reeds is of importance since it depends in
It will be appreciated that to preserve this
substantial measure on the ?exibility of the reeds.
?neness and nicety of ?t of parts, it is necessary
In order to obtain an efficient seal, the gland
to prevent foreign matter from entering between
pressure happens to be low, then the reeds will 70 the reeds and their cooperating highly-?nished
piston surface.
seal as well as if the ?uid pressure were high.
should be as ?exible as possible, so that if the
Where, if the angle were greater, say up to 60°
or more, the cantilever action would be less and
It will also be understood that the part of the
reciprocatory piston exposed to the weather out
side of the cylinder is likely to become coated
require high pressures to seal. In other words,
it is a real problem to determine the correct de 75 with moisture, ice, dirt, dust and deposit from
2,404,664
8
exhaust-gases and these must not be allowed
to remain thereon.
>
Accordingly, improved and effective means have
been provided to accomplish this result and to
protect the piston and its complementary or com
panion gland-reeds.
‘
'
The opposite outer or lower end of the threaded
collar or sleeve 40 is in somewhat similar manner
provided with one or more downwardly, in
lapped in a different cylinder of the same di
ameter as that in which they are to be employed,
so that when introduced into their cylinder, the
reeds will be ?exed slightly inwardly, and their
cylinder-engaged edges will be parallel to the
axis of the cylinder, their flexure combined with
the ?uid-pressure acting on the reeds maintain
ing them in proper and adequate pressure-seal
ing relation with the cylinder.
'
wardly-converging, conical, metal reeds 50, in 10
Whereas, in both instances, the reeds have been
described as a group of nested or inter?tted in
the present instance one, similar to those previ
ously referred to, bearing on an annular, conical
dividual, thin, conical reeds or units, it is to be
borne in mind that to take their place a suitable
surface 5| of part 48, comparable to the opposite
surface 42 of the collar, and also on a second,
or proper ?exible metal-ribbon may be wound
outstanding surface 52 at a right-angle to the 15 helically to provide the required coacting plurality
axis of the collar.
of overlying registered layers in face-to-face con
-
This reed, or plurality of nested reeds, if more
than one is employed, is held ?rmly in the speci
?ed relation by another annular, externally
screw-threaded collar 53, screwed into the
tact with one another provided means are used to
prevent leakage of pressure at their ends.
It will be appreciated that'the length of the
operative life of the new/packing-gland depends
threaded mouth of the lower end of the cylinder
l I, such second collar having a surface 54 pressing
the outstanding part of the reed against the
shoulder 52 and an adjacent inclined surface 55
upon the number of reeds employed and these
should have suf?cient thickness to preclude col
lapse of the reed or reeds due to overstressing of
the metal by reason of excessive pressure imposed
contacting the reed outwardly beyond the shoulder 25
thereon.
.
The number of reeds used also has a relation
If preferred, the extreme outer portion of the
reed may have a circular part 56 occupying a
to the degree of smoothness of the surface on
which they bear, in that if the surface is some
groove 51 in the surface of the collar 40.
what irregular the plurality of reeds is needed
This one or more reeds or scraper-blades 50 are
desirably ground and lapped as in the other case.
As will be readily understood from what pre
cedes the collar 49 is screwed on to the bearing H!
by means of a spaner-wrench occupying holes not
to conform to such surface contour.
In the normal airplane, it is very desirable or
essential to have proper weight distribution, and,
in order to correctly allocate or apportion the
weight, a series of scales have heretofore been
shown and holds the reeds 4| in proper place, the
second collar 53 being screwed into the threaded
mouth of the cylinder by a spaner-wrench tem
used to weigh .the loads on the various scales or
supporting means so that the weight can be prop
porarily ?tted in holes not illustrated and holding
With the pressure-sealing g‘lands previously
erly located in the structure of the ship.
the one or more reeds 53 in place ?rmly by de
used in the struts the friction has been very high
mountably maintaining the bearing is against 40 so that it has been impossible to ascertain the
the cylinder shoulder ll, any suitable means being
weights without the use of scales.
’
’
employed to prevent unintentional loosening of
In the new design incorporating the present
invention, it is possible to employ a pressure
the two threaded collars.
By having the packing-gland near the lower
gauge at the top of each strut cylinder and from
‘ them instantly determine the amount of load in
end
always
of supplied
the cylinder,
with clean
the bearing
lubricant
is from
aboveabove,
it
the various portions of the airplane and to enable
the load to be shifted if necessary.
7 ~
and, of course, the scraper or wiper 53] keeps the
reciprocatory piston clean and free from objec~
Suitable scales for this purpose are frequently
not available at landing-?elds and this advantage
tionable foreign matter.
If preferred, the novel and improved packing 50 in the use of the new pressure-sealing means
gland may be mounted on the piston, and the
constitutes a materially desirable feature, and, at
piston or the cylinder may reciprocate and the
the same time, may well eliminate crash landings
other remain stationary, or both such members
of airplanes due to improper weight distribution.
may slide back and forth relatively to one an
In addition to this speci?ed reduction of fric
other, such a construction being presented in 55 tion in the pressure-sealing means, it is also to be
Fig. 5.
noted that change in temperature has practically
In such exempli?cation, the collar or mounting
no influence on the operation of the novel gland,
I46 in which the face-to-face, contacting layers
since the coe?icients of expansion of the piston,
of the flexible, metal laminations are secured, is
cylinder and sealing-means are substantially the
separate from the bearing in which the piston ! i8 60 same, and a temperature range from minus ‘70°
reciprocates, and such annular sleeve I40 and its
F. to 130° F. can occur without detrimental effect.
cooperating member l9! surrounding the piston
By reason of the positioning of this improved
I I8 are mounted on the latter in any approved or
gland and its cooperating piston scraper a good
Well-known manner and reciprocate therewith,
clean lubricant is furnished to the cylinder bear
although not so shown in detail.
ing at all times.
The reed construction and its mounting is sim
This invention, as de?ned by the appended
ilar to that already described, except that it is
claim, is not necessarily limited and restricted
' reversed, outwardly for inwardly, and the reeds
to the details of structure illustrated and de
4H3 project outwardly and longitudinally in
scribed since these may be varied within reason
wardly of the cylinder Ill toward the pressure 70 able limits without departure from the heart and
essence ofthe invention and without the lossor
.In this case, of course, the outside diameter
sacrifice of any of its material bene?ts and ad-v
vantages.
,
.
of the reeds is slightly greater than the inside
Whereas above this invention has been set forth
diameter of the cylinder, the reeds are ground to
therein.
.
I
free them from their stepped edges, and they are 15 in .connection with one particular. form of strut
2,404,664
it will, of course, be understood that struts vary
10
means including thin, truncated-cone shape, ?ex
somewhat in construction but no di?iculty will
ible reed-means, the novel improvement of a ?rst
be encountered in applying the present invention
element having a truncated-cone surface against
to the other styles of constructions, or to ap
which the acute-angle face of said reed-means
pliances of di?erent character.
bears for at least the major portion of its length
I claim:
and terminating short of the active edge of said
In a pressure-sealing construction of the type
reed-means, and a second element having a trun
incorporating a ?rst member having a cylindrical
cated-cone surface of the same inclination as and
chamber subjected to ?uid-pressure, a companion
bearing against the obtuse-angle surface of said
cylindrical member coaxially occupying said 10 reed-means and located at such a distance from
chamber, said members having movement rela
the active edge of said reed-means that the ?uid
tive to one another, and ?uid-pressure sealing
pressure acting on the exposed portion of the
means mounted on one of said members and hear
obtuse-angle face of said reed-means prevents the
ing edgewise at an oblique-angle on the cylin
reed-means from buckling.
drical surface of the other member, said sea1ing~ 15
RALPH L. SKINNER.
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