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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. ‘ ' ~- - 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.