US2659204A

US2659204A - Hydraulic power system

Info

Publication number: US2659204A
Application number: US196474A
Authority: US
Inventors: Conway Hugh Graham; Fairclough Roy
Original assignee: Societe dInventions Aeronautiques et Mechaniques SIAM SA
Current assignee: Societe dInventions Aeronautiques et Mechaniques SIAM SA
Priority date: 1950-11-18
Filing date: 1950-11-18
Publication date: 1953-11-17
Anticipated expiration: 1970-11-17

Description

NOV. 17, 1953 H, Q CONWAY ETAL v l 2,659,204

HYDRAULIC POWER SYSTEM Filed Nov. 18, 1950 2 SheelZs-Shee'lI 1 F' ,j /21314 Wij/01620015 JACK ARGE VOL ME l Mf'a//v pz/Mp u VALVE msm/euros j] 40 /22 Z) 20 M0702 35 gb-s Nov. 17, 1953 H. G. coNwAY ET Al. 2,659,204

HYDRAULIC POWER SYSTEM Filed Nov. 18, 1950 2 Sheets-Sheet 2 l y V155 75d. 30 [L l NM f f77 L L@ j@ Z [if mi' O .them to prevent trouble.

Patented Nov. 17, 1953 Hugh Graham Conway,

Fairclough, Gloucester,

Societe dInventions ques S. I. A. M., Genev ration of Switzerland George Orloff, and Roy England, assignors to Aeronautiques et Mecania, Switzerland, a corpo- Application November 18, 1950, Serial No. 196.474

This invention comprises-improvements in or relating to hydraulic power systems. It is lan object of the invention to provide means Where- -by excessively low temperature of the system is prevented Whether freezing up, vor such` thickening of the hydraulic liquid interferes with proper operation of the system. While the system herein described is particularly applicable to aircraft, where low temperature presents an especial problem, the system is also capable of being applied inother connections.

According to the present invention, an hydraulic system is provided with controlled leakage in an operated element or elements of the system, the leakage being adequate to provide such heat as is necessary under normal working conditions to preventl such excessively low temperature of the system; Wherever leakage occurs in an hydraulic system, heat is necessarily generated due to the waste of energy. It is the operated elements of the system which are normally liable to become frozen or put out of practical operation by thickening of the hydraulic medium, and by providing controlled leakage in these elements sufficient energy is set free in comme. (c1. lso- 52) The resultant 'ow of hydraulic fluid from the Vpump and on return to l the reservoir clear.

In'order to prevent Waste of energy when the operated elements of the system are-being used, the leakage is preferably effected through. a leakage channel or channels which are vonly open When vthe operated element or elements .are in a normal position of rest. For example, there may be an operated element in the form of ajack of the system also keeps theppes 'and the'leakage channel may comprise-a leak-V age port opened automatically by the jack-piston on .reaching the end of its stroke.` Preferably the leakage channel is located in the piston itself and -closed by :a lift-valve, in` the piston, which valve isL opened yautomaticallyby.tappet1action when the pistonreaches one end lof itsstroke.,

In one `form of the-system according tothe present invention, an auxiliary pump is provided of `capacity adequateto s upply the leakage,v in

addition to the main supplypumpjvofvthesystem.

. The auxiliary pumprcanbe kept runninghfwhen Vthe parts are in theirV normal ,positionsgof rest 'and win supply the energy-necessary tn .prevent 'freezing'upvwhile Atlriemain pump Will be set in operation .whenV the parts, Vare' tobev actuated. i This obviates using the-large pump continuously, which Ywould' be disadvanta'geous. rbecause either excess-j energy. would Y have. lto be'k hWasted orflth Pump Wpuldheveiwbekspt #tewater Quand off load for the whole time, and notonly when parts are to be actuated. l r

In an alternative form of the system according to the present invention, the by-pass to the main pump delivery is provided with throttling means under thermostatic control with the object of ensuring that. sufcient heat is developed to keep the liquid in the main supply tank at a suitable temperature. I f

Preferably, in a jack constructed fas above described, in addition to the said valve there is a fixed leakage aperture of 'restricted bore provided' in series with the valve so that Whenthe valve is opened a substantial proportion of the pressuredrop through the leak takes place at this aperture. The pressure drop across the restricted aperture is proportional to the square of the velocity of flow therethrough..V If therefore the aperture itself should become. partly `frozen up and so restricted further, the eifect will be to raise very substantially (morethan in direct pro- Y portion ,to the degree of restriction) the pressure lon thereceiving side of the aperture,'assuming the normal type of.pump is employed for producing'the pressure, which has a substantially constant rate of delivery, .irrespective of pressure, at a given speedof operation. The result is1increased power applied at the aperture, and increased evolution of heat,;.so thatthe'aperture spill-valve-and acts to ensure maximum energy l dissipation Therspill-valve 'also automatically jack is operatedjinthe-'reverse direction.

prevents return flow through 'the leak Iwhenthe The Afollowing is'v adescriptiony by W'ayf'o'f-'example j' of specic v"constructions 'in' accordance l Wtlfr theinvention'.` .v Y

In the acc'ompnying'drawmss Figurefl tiene?)Y Y l Figure A1a isja uetaiivtoianeniarged scale o fa Apart of said diagram;

Figure 2 miami section-ihatgiia end of ajack construted, .go jmurat@ nacco'rr Y.

ance with the present invention y yFigure Sis afsimilar'lview-,of anotherfjack; .Y Y Figures lLand uare similaryiews of; alternative Figures isfalceieidielnietig-an eiiar showing' such a Y i on the by-pass from the auxiliary pump30 if desired instead of or in addition to operating on the by-pass from the main pump Il.

Figures 2 to 6 show various forms of jack for use as the jack I6 shown in Figure 1. Referring to Figure 2 this shows a jack cylinder I 5 containing a piston 24 which is`connected to a hollow jackl rod 25. They tappetsystem which corresponds to the valve 21 and tappet 28 of Figure 1 is arranged to operate in this case when the jack is extended, that is to say when it reaches the end corresponding to the pipe I9 of Figure 1. In the piston 24 is an axial bore 50 which is divided bya bushing 5I from a second axial bore 52. Through the bushing there is a passage 53 which constitutes a leakage aperture and in which is loosely fitted a valve 54 corresponding.

to the valve 21 of Figure 1. The valve 54 is closed by a light spring 55 beyond which is a screwed plug 55 containing a narrow leakage aperture 51.

On the other side of the bushing 5I there is a v valve-lifting member 53 which engages'the stem of the lift valve 54 and which is backed up by a spring 59 which is stronger than the spring 55. Beyond the valve-lifting member 58 there is a tappet member 60 which backs up the spring 59, slides to and fro in the bore 50 and is connected by a cross pin 6I to a tappet sleeve 52 which surrounds the piston rod 25 and is capable of sliding thereon due to a slot 63 in the piston rod 25 through which slot the pin 5I passes.

The valve lifting member 58 is conical at its end portion as shown at 64 and the conical end portion of the lifting member can seat upon the material of the valve 24 surrounding the bushing 5I to block the leakage aperture 53 on the side remote from that upon which the head of the lift valve 54 seats. From the space around the conical end of the valve lifting member 58 there extends a passage 65 to the side of the piston 24 which is open to the-pipe I9.

If the jack, with its piston so constructed, has a normal position of rest in which it is extended, that is to say with the piston rod 25 fully pushed out of the jack as shown in Figure 2 of the drawing, the tappet sleeve 62 .engages the end of the jack cylinder IB where it surrounds the hollow piston rod 25 and pushes the tappet member 59 to the left as viewed in the drawing, compressing the spring 59 and causing the Valvelifting member 58 to push the lift Valvel 54 olf its seat as shown. The valve 54 at first resists being pushed ofi" its seat but the tappetl 50 can engage the end of the valve-lifting member 58 when the spring 59 is compressed and will so force the valve off its seatV after which the spring V59 expands again and pushes ther valve 54 fully open. l

The conical end 54 of the valve lifting member'4 58 tends to seat on the bushing 5I but pressure fluid coming through the aperture 51 forces the conical end a little way olf itsseat and leakage takes place in succession through the aperture 51, the

leakage aperture 53, past the conical end 6,4 and through the passage V to the pipe I9. The

valve-lifting member 58 acts as a spill-valve in series with the leakage apertures 51, 53 and increases the total pressure loss when there is a considerable pressure drop through the aperture 51, that is to say if the viscosity of the liquid is high due to low temperature. Y

Referring to Figure 3, this shows a similary construction for the case when the leakage through the piston is to be controlledr from the other end of the jack, that is1to say the-end vremote from that at which the piston rod v25 Vend pressure exerted by plug 12 containing a narrow leakage aperture 13,-, and corresponding in function to the plug 550i.' Figure 2, is provided inthe end of the passage 65.A

The operation is the same as Figure 2.

Referring to Figure 4, partof this corresponds1 to Figure 2 and as far as possible similar parts: are similarly numbered in thedrawing and will. However,` ball valveaccordingly not be further described. instead of the lift valve 54 there is a 15 which floats between the two

springs

55, 59= and the valve lifting member 58 is done awayl with.- The .ball Valve 15 floats in an enlarged'. portion 16 of the bore 50 between seatings 11, 18.. When pressure in the jack cylinder I5 is urging the piston to move from the left hand end of the jack towards the position shown in the draw ing the tappet sleeve 62 will be pressed towards; the right hand end of the slot 63, the compression of the spring 55 will be relaxed and the pressure in the cylinder I5, acting through the bore -51 will press the valve 15 on to the seating 11 and prevent leakage of hydraulic liquid through the piston. When the tappetv sleeve 62 engages' the end of the cylinder and the valve lifting member 5@ is held from movement with the piston, the end of the valve lifting member'. S0 engages the ball i5 and also compresses the spring 59 and pushes the ball 15 off-the seat l11. After this the ball 15 acts as a spill-Valve against the seat-` ing 18.

Precisely the same action takes place in Figure 5 where, however, the tappet member y(il) directly engages the end of the cylinder I6 and the parts are modified as compared with Figure 4 in the'- same way that the p-arts of Figure 3 are modified as compared with Figure 2. y

:Referring-howto Figure 6 this shows al con-V described inthe aforesaidpatent specificationl No. 527,225, and that these engage a locking sleeve 8i held in the end of the Vcylinder I6 by an end cap isecured on the cylinder I5. The end cap contains a bore 83 for a locking piston 84 which is urgedforward into locking position by a strong spring 85. The locking piston 84 is provided with a cylindrical bolt portion 85 which, as shown in the drawing, when the crown of the locking teeth or claws 85 are pushed fully home through the locking sleeve 8|, is able the space within the crown vof locking claws and to prevent them from withdrawing. The springpressed bolt 86 constitues in effectl the end of thel jack cylinder and 'it is against the end of this bolt that the tappet member engages. The valvemembjer instead of being constituted to shoot forward into hir .9.- buil l! is acnettuied lav e deubleeeoned eigener .8l whien plays, hetneenseetinea 11, 1,18 and a eten; 88. te engage an intermediate niemeer QS which pressed sin direetlv by the Serine. 59. .and is: Qpereted.. bv the tappen memberlll- The pesseee. Si represented. in Eiern@ ti 9v fletes 9.0 cui. the @inside 0i the tapnetixneni, ber 6 and. the resirieted anemie .i1 ie farmed l. ee 5.6 on the. mesme VSide vf the' valve merel? 81 insteasi er reime@ a, eine. Slick as. l2 011 the eige marient@ Paseages Si! in fille Wells Qi the @New pieton red .25 'Peimit M0855. Qi the hld. lic mi@ t9 the: various Paaess. end; velvee Thev Qeeiatiqnthe .seme *Q6/follia Reiellfirie te Een@ il., @his .snows e nel: me having. e Pieten il operates e hollen leek. mi... .we leakage is nr d. ier by means @fr eeerieree H95: ihelale. 'W lead t0 e S12-eee. Sheieel .lied Wlhieliis in eornmunif @eilen 1w e..peseee @0i with.' the: leakage aner-y tnre it... 'Elie pie-estre@ i104 is; @entrai-lee by naive and. the4 valve: le bn a. valve red. lill" te the; @oxe- LQS oiaseleneie me... The salenoidis @exalted by eleetiiieai .naect 4mi., .H1-which sees: Gemeen the .ieee rod; and. ,are .cpnneeted to ein! Suitable centrali. .The ieakeee. passage me s desee., te the action of a spring. IJ .3 wliihf @losee thevalne. m6 until the vselezioni. |593 ,ie enenginagi.A een. befarranged te be ai. ieetel einer autpmatieallvwhen the. nistnn lai reaches ille-.enel oi itsstmleor: under the central .et endeten thermstatiallvbmatemneratmzeqenimllee switch: ar.- lzy; e; -enibinatipn of; s uch mainbedesired.

.In lira inet-in omeaincnatvit may bedesirable to. prev-irl@ additinnal means for heating; variaus; vente furthe; eineuitiwheratne. pines. pass. throne-li. particularly cold parts of the aircraft. This. may be dene; electriiallx Iim'.willemise, as .desi-red.

.1r-.In a hldlaui. imiterl system including: a.y Hillman intermittently v`operative cirm:u't.iory nunk medium. lla-ving. a. main circulating pump and.' drive motor therefor.` innluded;` theueinf, `a sec-- Onify; CiIZQuit the medium having an auxiliary: 911.11ml Aand drive: motor therefor invcludeliliherein;.Selectiuelyfoperableimanual:means; rendering said .seennidanvr` circuiti inoneratiivrei when, Said` primary .circuiti is operative andi Rendering-...said secondary circuit. operative. when seickprmarxgeincuit -isinoperative and a jaeny having; a. dvlinden `eQnneeted-ctu said means .andl a. piston; alicia-ble.A in. .the cylinder, the .provision of' means .011 .maintaining the uid medium; insaid.y

secqndary cireuit` when. uperative:- at a desired:

werking temperature, saidl last, meanseornpris ing aleakage channel@ in'. the piston, aV lift valve in the pieten .constructed and arranged te close the channel at; all pesitions of' the .piston other than a predetermined end position. in the eylinfn der, means. fm: said valve when the. piston at. said predetermined end position, and a, xed leakage aperture in the cylinder of re.- stristed bore in series with said lift valve.

2. In ahydraulic power' system including a primaity intermittently operative circuit` for fluid medium having a circulating ypumpy and drive motor tnerefmv included therein, a. sec: ondany circuit for the fluid medimn having an auxiliary' pum-p and drive motor therefor in-v cluded. i;lieizezrn,` selectively operable manual means rendering saidi secdndary .circuit inoperative `\v,hen said primary' is operative andv rendering said seeolzrdary circuit operative when said primary .circuiti is inoperative, andv a. jack. a cylinder connected tu said means and ay piston `slida'blej in. the. evlinder, the provision .of ineens forA maintaining the fluid medium in said; secondary circuit when operative at a desired working temperature', said last means comprising a. leakauge` channel in the piston, a lift valve in the. piston construeted and. arranged to close the channel at all nesitions @i the piston .other than a predetermined end. position in the cylinder, a stern projecting from said, lift valve. beyond said. piston toward the end` of said. cylinder corre..- Snoilding. to; said end. position of the piston, a xed leakagepaperture in. .the cylinder .of restricted herein. series with saidf. lift valve,v .a .spill valve in series with. .sa-id. aperture.l :and spring-y means urgina said spil-l valve to. ,closed position..

GRAHAM QGNWAY.

GEQRGE' ORLOFF.

FARGLQUGH- Beierenees Cited in the file .of this. patent.

UNIfIaFlD. STATES PATENTS.

Number' Name Date 1,520,035 stones Aug. 25, 193i 13904.-,345 Anthony et al Apr. '18, 1933 alize-,aessmith Jan. '1, i936 213713505"- Anthonyr et al. Feb; 23, 1937 2,;146366 v Anthony et al. Feb. 'A 1939 2,166,940 Gon'rad'sene r July 25, 1-989 aesinet Wylie sept. 29, 1942 l2;,-9ia3'r5` Herma-n T -e Mar. '1, 194e -2',? 55',669 Moser V Y Aug. 15; 1944' 2&' 43,989A Rockwell Mar; 6, 1951l 25m-333 zwael: Y June 193 19e-1 1 2,55l;334f Zweck' June 19-,-1'951 FOeElGN PATENTS Number.. A Countryf Date BfOABs Geteat Britain Nov. v2, 1931