claim: 1. In a hydraulic, pres,@ure fluid a-ccumulator, means def-ining a housing including a generall y 35 tubular shaped elongated @main body and closure. means for the termi.nals of said tubular body@ an endless tube of onehor-ring shape having a closed interna-I annular surface and a continuous exterior surfacei said tube received within said hous-. 40 ing with the radial outer periphery thereof adapted to engagq the inner circumference of said tu-. bular main b,ody, valve means extend4ng through. s6id tubular wall for introducing super-atipos- ' I pheric pressure intc) said tub e, means for intrb7. 45 ducing hydraulic fluid under super-a.tmo,spheric pressure intg contact v,7ith the outer peripheryof said toroidal tube w'-thin said@ housing, and a cylindrical perforate wall extending axially through said toroidal tube for liriiting radially 50 inward flexing of the tube, 2. In a hydraulic pressure fluid accuw-ulator, Means defining a geri-erally elongated hous@ng. having a tubular surrounding wall, means defining pisto-nlike end closure members fo,r said tu-, 55 bular wall, means.defining 4 toro-idal shaped flex-, ible tube received within said housing a-djacent the inner periphery c@f sa4d tubular wall, valve means extending through said tubular ivall of. said housing for introducing -uperatmqspheric. 60 pressure into sa@d, toroidal tlibe, means defining aperforated,generally circular wall disposed concentrically within sa-id toroidal tube, for lim-. iti,pg radially, inward flexing of said tube, each of s.aid pistcri-like closure me-Tnbers being fbrmed (;5 with com.plementary shoulder portions receivinq the terminal port-ons of, said perforated wall for;, support thereon, against radial inward mo@vement: when subjected to rres,sure by said tube@ and means for introducing hydraulic fluid under 70 super-atmospheric pre,@sure inluo said ho-using fcr contact with the outer surface of said tgro@dal tube, 3. In a hydraulic flu,d accumulator, means defining a housing having a surrounding. wall gen1?,l pAd the consequent operat@on of sw-itch 6 to: 75 erally eircular@ in, transverse cross, section, a

2,418,667 toroidal shaped flexible tube received within @ttid housi@g, atmospheric air vent means extending ,thr6ugh the wall of said housing for exposing the interi6r of said tube to atrnospheric pressure, means defining an inlet po@rt for the introduction of low pressure return hydraulic fiuid ilitb said housing into 6ontact @vith the exteri6r surface of said tube, whereby to prevent bcclusion of air m the lo,@r pressure hydraulic fluid; and a perforate tubular wall arranged concentrically within said. toro,@dal tube for limiting radially inward flexing of said tube. 4. In a hydraulic pressure fluid accumulator, means defining a housing having a surxounding wall generally circular in transverse crbss sec- 15 tion, an endless toroidal shaped flexible tube received within said housing with the radial outer Pei-iphery thereoi' adjacent the inner surface of said cylindrical housing wall, valve means extending through said hgusing wall for introduc- 2o ing sur@-er-atmospneric pressure into said tube, ihe'an'8 defining a fiuid pressure generator positic>ned axially within said tube and embraced thereby, and means defining an inlet port for introducing fiuid to said generator for delivery into 25 contact with the exterigr surface of said tube at an increased p:ressure. 5. In a iiycirauiie pressure fluid accumulator, means- defining a generally cylindrical housing -having a surrounding tubular wall portion, pis- 30 @tpn6like endclosure members received in sealed -relation to said tubular wall, an endless toroidal filexible@tube-received within said housing, ,'valvo mean-- exter@ding@through the wall of said 5 10. 10 and a perforate wall within soid housing arranged to' lirnit the radialiy inward f.@'exing of said tube. 9. The @hydraulic pressure fluid accumiilator defined in claim 8 in cbmbiiiationwith a. hydraulic pressure fiuid gei-lerator 'arranged d@proxirnately axially within said tube and co m m unicatir. g with the means f 6r i-atroducing 1-iydraulic pressure fliiid into the housing. 10. I_rl a hydraulic Pressure fluid accumulator, means defining a housing having a surrounding wall@ a flexible bag iil said housing@, said bag pri 1 com sing an endl6ss r'ng shaped tube having a continuotis flexible wall; means f6r admitting a@ir ; at atmospheric pressure to the interior of said bag; and means adapted to admit return hydrau'lic T)ressLire fluid intb said housing ex+erior to said bag to be effective upon the exterior slirface of said bag-whereby to prevent occlusion of e@ir in said hydraulic, pressure liquid. J.1. A liydraulic pressiire -.,quid accumulator as 'defined in.claim'10 whereifi means are provided wbich ext&nd axially through the bag for limitihg radi;.illy inward flexirlg of the adjacent wall oi sai-d bag. 12. In a h draulic pressure fluid arcumul dtor, y housing walls defining a high pressure delivery chahiber; 'Pressure generating means if@ said che@m, ber for delivering pressure liquid theret 4 o; a toroidal flexible body bf' hollow cross secti6n e compassing said pressure generziting mearis, said b6dY beirig internally charged with su peratmospl@er@ic pressure 'and being E@@ternall@ '@affected by pressure liquid from-.@tLid geribr@atil@g 'housing for introducing super-atmospheric pres- 35'means; and @; perforate'supporting structure in surl- irito said tube, pressure fluid generating said chambe'r between said generating meaii@ and means suppor-'ed between said piston-like ehd closure rnernbers in axially arranged position with @rbspectto said -toroidal tube and embraced by said tube, means defining an inlet to said gener- 40 ator for i@itroducing low pressure fluid thereto, and rzeans defining a one-way check valve for discharging pressure fluid into contact with the external surface of said tube, said pressure fluid having a higher value than the super-atmos- 4-5 pheric pressure in said tube. 6. In a hydraulic pressure fluid accumulator, walls defining a housing; a 'Llexible endless tube received within said housiiig, said tube having a continuous external annular surface and a 50 closed internal annular surface; valve means extending into said housing for introducir-g superatinospheri c pressure into contact with the internal arnular slrface of said tube; and means for introducir..- hydraulic fluid into said housing 55 urder super-atmospheric pressure into contact with the external annular surface of said tube. 7. The hydraulic pressure fluid accumulator define@@ -in claim 6 in combination with a perforate supporting structure within the housing 60 for limiting expansion of the tube in a radially inward direction, the housing being arranged to limit flexin.- of the tube in a radially outward direction. 8. In a hydraulic press-Lire fluid accumlilator, 65 walls defining a housing of generally tubular shape; ali endless rin.- shaped tube received within said housing, said tub@e having a continuous flexible wall adapted to be affected by internal e,nd external pressures; valve means extending 70 ilito said housing for introducing super-atrnospheric pressidre into contact with the intemal surface of said tube; means for introducing hydraulic fluid pressure into said housing to be, effective upon the exterior surface of said tube; 75 said toroidal body and arranged to limit rbdially irinvard flexir g @ cif , said toroidal body, the radially olitivard @fleking of sa'id ibroidal body being limited' by@@the Vall'of said cha,mber. 13. In a hydraulic pressure fluid accumulator, housing walls defining a high pressure liquid delivery chamber and a low pressure return liquid chamber arranged in side-by-side relationship; perforate annular supportingstructures in said chambers; toroidal flexible bodies of hollow cross section in said chambers between the respective supporting structures and the housing walls, the toroidal body in said low pressure chamber being vented to atmospheric pressure and the toroidal body in said high pressure chamber being charged with super-atmospheric pressure; pressure generating means for delivering pressure liquid into said high pressure chamber to be eff ective upon the flexible toroidal body therein, said pressure generating means being arranged axially within and encompassed by the flexible toroidal body in said high pressure chamber; and means defining an inlet port for introducing low pressure return liquid into said low pressure chamber to be effective upon the flexible toroidal body therein; the radially outward flexing of said toroidal bodies being limited by said housing wall, and the radially inward flexing of said toroidal bodies being liniited by the respective perforate supporting structures. 14. In a hydraulic pressure fluid accumulator, meaiis defining a housing having a tub,ular surrounding wall; a transverse wall dividing the interior of said housing into a first high pressure chamber and a second low pressure fluid return chamber; a perforate cylinder within said high pressure chamber and arranged coaxial to said tubular housing wail; an annulus shaped flexible tube received within said high pressure chamber

between@'said perforate supportirig structure and the housing @ wall, radially'inward and outward movement of said annulus tube being 'limited "respectively by said perforate cylinder and said hoiising wall; valve means extending through said tubular housing wall for introducing superpressure into said annulus tube; means for introducing hydraulic fluid into said high pressure chamber under super-atmospheric pressure to contact with@ the exterior surface of said annulus tube; a perf OTate cylinder within said -low pressure return chamber arranged coaxial t6 said tubular housing wall; a second annulus @shaped flexible tube received within said low pressure return chamber between said housing wall and the adjacent perforate cylinder, radially 'inwa,rd and'outvvard flexing of said second annultis tube being limited respectively by said last-inentioned Perfo-rate cylinder and said h6using wall; venting means for constantly maintaining @said -second annulus tube in communication with @"gUf,i@ounding atmospheric pressure; and inlet means for introducing low pressure return fluid ifito said second low pressure fluid return cham@-6,418, '67 i2 being @o -cbns@tructed @nd arrange'd that @it is adapted to embrace'portions of said E@8sembly and 'to react in all directions upon -hydra@itlic - pressure on the ekterior thereof. 17. In a hydreiulic pre'ssure generator-- and' aeassembly, as defined in clocim- 16 wh6rein the walls of the body are flexible'thbreby,. to, be re@dily aff eoted by iiiternal and @ externa) pressures. 10 i8. In a-hydraulic,pres8ure generatbr'and--accurhulating 'assembly, as defined -in clailh -16, wherein the hollow toroidal bodyis apprbximately V,@holly '8ubmerged iri the hydraulic presstLr6 'fluid. 19. In a hydrauli , c @pressure generator @ arid" ac15 eumujator a.Qsembly, the improvemei-its which ecmprii-,e a holidw toroidal body wholly submerged in the hydraulic 'pressure fluid and coinmunicatiilg With the atmo8phere, -zaid b(idy beirig Adapted -toLnibrac@epdrtioiis'of said-assemblyandto-react 20 -in :@ll direetions upon Etmbient, presgure. EDWARD A. ROCK-WEIJL. IT-VFERENCES- CITED The f6liowing references are of recoid -i I n the ber to be effective upon the annulus shaped 25 flie o@' this patent: 'flexible tube therein. 15..'A hydraulic pressure fluid accu mulator UNITED STATES PA-TENTS "iirangemont as d6fined in claim 14 which includes Num'ber Name Date 'means defining a fluid pressure generator ar- 345 2 53 N o r t h e y - - - - - - - - - - - - J u l y 6 , 1 8 8 6 '-rgn@ed axidlly within and encompassed by said 30 849,777 Adlung ------------- 'Sei)t.@28. i886 fir@t annulus shaped flexible tube for introducing 1,803,685 Pirsch -------------- Jari. 10 1933 -hydi,aiilic pressure fluid. into said first high pres- 2 163,764 Rockwell ---------- I June 27, 1989 sure chamber. .2 9 318,128 T@bb --- ------------ May 41 i 43 16.''In@ a'bydrauiic pressure genetator and Dc2,246,667 Colman ------------ June 2.4, i941 cumulating' as@embly, the imptovements which 35 2,256,8Q@5 Mercier ------- ----- Sebt@23,f941 cor@aprise a holiow body of toroidal shape, - said 2,213 505 Viorian ------------ Feb. 17,- 1942 bbdy being ientirely closed except for relatively 2 320,886 Quiroz -------------- Juiie 1, i943 49mdll,.Port@ means for c6mmunicating with the 2',337-,771 Roberts ------------ Dec.'28, 1943 .'interior 'thereof to supply air thereinto, said body

Patented Apr. 8, 1947 21418,667 UNITED STATES PATENT OFFICE 2,418,667 PACKAGED POWER ACCUMULATOR Edward A. Rockwell, Cleveland, Ohio, assignor, by mesne assignments, to Borg-Warner Corporation, Chicago, Ill., a corporation of Illinois Application April 7, 1944, Serial No. 530,079 19 Claims. (Cl. 103-25) 2 The present invention relates to hydraulic power unit arrangements generally and - particularly to a unitary or package bydraulic power generating and accumulating assembly. It is an object of this invention to provide a 5 unitary assembly functioning to generate and maintain hydra-ulic fluid pressure between selected maximum and minimlim levels of - pressure and wherein the accumulator, the generator and the other necessary equipment are all nested to- 10 gether in a compact efficient manner and are embraceably supported by one housing so tat the unit may be readily located and mounted in the most advantageous pa-sition. . It is an obj-,ct to provide an improved ae- 15 cuinulator arrangement which lends itself particularly to incorporation in a single package asseinbly' It is an important object of this invention to provide a pressure accumulator and low pres- 20 slire reservoir which may be connected up to a system for pressure@utilization of hydraulic fluid, such as a btak6 system wherein the I system is a;dapted to operate as a closed system with all the air excluded from the systein. Also, a more 25 particular object is to provide improved means for effectively bleeding the system, wherein a Pressure bleeder can be used to force fluid through the lines to exclude air. @ A further important object of the invention is 30 to combine a spring accumulator with an aircharged accumulator so in case of failure of the air pressure or puncturing of the fiexibie diaphragm in the air-charged accumulatoi., the spring accumulator will take over and - maintain 35 the system in operation, this being important on brakes so as to increase the safety for brake operation. Another object is the provision of a unit of the said type incorporating in arl improved and 40 novel manner a first primary compact accumulator ond a second rel@tively smaller capacity secondairy accumulator of the plunger type - particularly effect@ ive Dr operating the electrical control switch for stopping and starting the driving elec- 45 tric motor in accordqnce with the level of pressure within the unit. An additional object is the provisi6n of a special snap action switch and cperating connection for actuation by the secondary accumulator. 0 Still another object is the provisicn of an atmospheric'pressure control accumulator - arrangemei-it effective to maintain atmospheric - pressure within the fluid in the lwffl Pressure intake portiori of the accumulator. 55 A still further detailed object is the formation of thesupporting and enclosing housing in a cylindrical shape for the ready reception of piston-like partitions effective to properly divide up' the interior of the housing as wall as to support the several elements of equipment. 'I'he above and other objects, advantages and uses of, my invention will become apparent frbm a reading of the fo-Ilowing specification taken in connection with the accompanying drawings which f orm a part thereof and wherein: Fig. 1 is a schematic layout view indicatingone system arrangement of which my invention, is particularly adapted to form a part; Fig. 2 is an axial sectional view of my special arrangement of unitary cr packaged bydraul-C power generating and accumulating assembly; , Fig. 3 is a transverse crosssectional view taken substantially on the line 3-3 of Fig. 2-1 and Fig. 4 is an elevational view showing the, rear portion of the switch mechanism disclosed in the right-hand portion of Fig. 2. Referring in greater detail to the figures of the drawings and first to Fig. 1, there is illustrated schematically a typical system arrangement of which my invention is particu'a:ly adapted to form a component part. Essentially my special arrangement of unitary or packaged hydraulic power generating and accumulating assembly indicated generally at A functions to maintain a pressure level between selected maximum and minimum values. As will appear from the detal@led description, this unit A includes an electric driving motor fed by a supply of electrical current and contrcl therefor designated generally at B. Electrical supply and control B is effective to automatically start and stop the electric motor driven pressure fluid generator in. accordance with the risa and fall of pressure within the accumulator unit A. As an illustration of one use for the hydraulic pressure, supply maintained in the accumulator A, there is ill@istrated a manually controlled modulating valve assembly C effective to withdraw hydraulic pres-' sure from the accumulator A thus changing the level thereof, which pressure fluid is delivered to a brake shoe operatind @moto @ ed gene ally r indicat r at D. in the more particular aspects of my invention, the same is directed to the construction, the arrangement, and to the mode of edaction of the component parts m@king up accu muiator unit.A. Accumulator A comprises generally an electric motor I driving a hydraulic fluid pressure gen . i erator 2, compactly wid embraceably received,

2,418,667 3 within toroidal or donut-shaped primary air accumulator 3 and axially spaced from smaller capacity secondary switch-actuating hydraulic accumulat6r 4 in turn compactly and embraceably received within a see-ond toroidal or donut- 5 shaped atmospheric pressure accumulator 5, and electric motor, control @ snap actionsivitch, assembly 6 carried I in axial alignment with secondary accumulator 4 for actuation thereby, all of the above elements being supportably carried by a 10 unifying housing assembly 7 including a high pressure cylindrical housing portion 7d and a low pressure cylindrical housing@portion 7b.. Electric motor I is of a readily a-vailabl,@ form including armature I 0 rotatable within field 15 winding I I supported by motor, housing 12 which terminates in radial flange 13. The driving end of motor armature IC has a coupling assembly. 14@ rotatably supported in an anti-friction bearing. Pressure. fil@id, generator- 2 @ comprises a pair 20 of meshing. gears@ IS.'. and @ 17. rotatabl@y, received witwn ai pair of; overiapping- cylindrical, chambers,18@and- 19, these gears meshing-in the areaof @ overlapping of' the chambers.@ Low., pressure fluid from the low'pressure,end of the accumula- 25 tor is @ introduced @ or drawn into the generator proper through passage 21 carried@ around the periphery of the gears aiid' discharged through passage 22. Passage 23 permits th e@recirculation of liquid at low. pressure from di-qcharge @passage 30 2 2 ' back around to inlet 1 passage 2 1 - durihg the initial: starting of the electj:ic motbr I thua eliminating starting the Imotb-r under load. The initial@dO-Iivery of fftiid@by the@gears to passages 22 and@ 2'3'plbces@the same iii contact with piston- 35 liki@ @ valve 241' receivabl@-@ in a complementary shaped cylinder-like pdrt 25 commuliicatirg with outlet passage 26@leading@to check valve 27 d,@'scharging iiito the@,surr-oundiiig aecuniulator 19. A small tolerance is allowed'@ b.-tween piston-like 40 valve 24 and port 23 to,cause a-limited@flow tb2erebetween in the direction of outlet@ passage 2 6 with the@ result- that piston-like valire 24@ begins to move fie6ly in@ response to the generated pres . sure acting thereon, this action being insured by Venturi-like restriction, 28 in passa.ae 23 causing the pres@ure to build' up as the electric motor IC ga'InS sp,,ed. The operation of Piston@like valve 24 raises cylindrical stem 29 sllifting.reduced stem portion 3@l @ transversely of the lower leg portion of 0 passage 23- and@ moving piston@like portion 32 across the, passage 2 3 shutting, off the flow therethrough a-nd loading- the- gears to produce, fiTIl output thtou-,h passage- 2.6 and, check valve 27. 5 The under side of Piston 32.is placed'in ccmmuni- 5 cation with low,pressure inlet 21 through passage 33.' it Will thus appear@ that upon,the electtic motor IO lflrst being started the same o-perates under appreciabiy no load since the fluid pressure L,-e-er- 60 ator 2 is merely recirculating the. output fli-iidback around- thro-ugh. bypa-cs, passage 23. to., the, inle-t Of the-generatbr,. The generator. housing: p-roper is pr6ferably 65 f'orinecl ii@i two. transversely, divided parts 34 and 36 held together by cap screws 37. The out--r section 34@is.shown as including an integral onepiece radial flange 3.8 adapted to function as one end closure for the accumulator 3, and also, si,,p- 70 port,radial,:ffange 13 of the electrie.motor housing, ffange 13 ba-ing,fastened to flange or closure member 38 by means of cap.screws 39. Flange or, el4osure member 38' is formed with, a generally axial orifice 41 in alignment with upper gear 16 75 4 of generator 2 and arranged to support a eGupling ass..,mbly 42 for drivingly coupling electric motor 10 and upper gear 10. Cl-osure flange 38 is formed about its Peripliery with aii annular channel 38a for recep@'uion of a flexible seal ring functioning to prbvide a seal with housing portion47a@ Snap:ring 38b is@ par tially,@received in a complementary annular recess in housing portion 7a and functions to retain closure tange 38 in place. This coupling assembly 42 comprises essentially a bushing insert 43 confined in position by a snap ring 44 and provided with flexible sealing rings as in.dicated. A rotatable bushing 46 has a radial flan.-e 47 engaging 9, bearing washer 48 in turn compressing a flexible seal rirg as indicated. Rotatable bushii-ig 46 is internally splined for coop,,ration with a corqplementary splined terminal portion of upper gear I 6 antq receives in the outer terminal, the non-circular end of @a @second splined gear 52 being fastened by, means @ of a diametrically extending pin 61., Splined gc-ar 52 is received witwn complementarily splined rn(D@tor couplng vssembly 14, Ball check valve 53 places the axial passages through the. gears and the sealed coupling assembly in communication with the low pressure portion of the accumulator with but a slight or few pounds of drop in preqsure across the ball check valve 53. The right-half 36 of the generator housing proper includes a radial flange portion 54 formed in the@ periphery thereof w:th a recessed annular channel 55 for the reception of a sealing riag to provide a seal with the a"@umulator partition as will appear: A passage 56 places the accumulator@ 3 in communicatign with; the@ auxiliary hydraulic, accumulator 4- Still another pasq@age 57 through flange 54. is: threaded to receive and supp@ort check,valve.58 serv.;ng the very important fuiction of facilitating, the air bleeding of the generator and,accumulator unit. Check valve 58 and outlet cheek@valve 27@ e@re of similar co-n@q-truction and hene-e only valve 58 will be@described in its essential.details. Air b,leed checlc- valve 58 comprises essentially a threaded base @ portion for reception within the threaded terminal of passage 57; an outwardly extending tubular body portion receiving a valve proper 59 perforated at 60 to allow the passage of-fluid;therepast when open, this va:ve 59 being normally urgpd toward closed positiol by compresq,,ion springs confined within the valve body, by a; threaded closure 6 1, Toroidal or donut-shaped primary accumulator 3 comprises generally a toroidal shaped flexible tube k62 arranged to be inflalfed by air under presslire which may be:i ntroduced through,valv@e assembly 63. By virtue of this torgidal or automobile inner-tube-like, shape ' this flexible tube is arranged to embracea@bly enclose the centrai-space containing the fluid under Pressure as well as embrace pre,,zsure generator 2. This,results in a compact and effic-ent, us,-, of the spac-e involved. A @,ubular valve stem. 64 passes @ through the *. all . of the housing a-nd. presents.@ a; radial flange, 65-@ w@thin flexible tube 62 for@ clamping the tube@ against a flange insert member. 66 and the@ hous.--@ ing wall by means of nut 67. all very much in a rlanner smila-r to th@,t in which an ial-itomobile inner tu@be is arranged. The difference resides: PrincipaIly in that the flexible tube 62 i@; generally flat. in cross-section ha-ving a Pair-- of, opposed walls extending,generally parailel to the@maior,.. axis, as well@ -as having the air inlet valve mem@ber, extending radial'y outwardly through the housing instead of radially inwardly as in the case of

2'4i8,6d7 5 '@iuf6rii6bil6 @iiiiier ube. A Tadiblly all @-iiiwardly spaced circular cage 68 is formed with a p7urblity 6f radi,@l perfor@ti6ns 69, this 6age functioning'to admit pressure fluid into conta6t@with the flexible tube 62,bi,,,t limiting the ext6nt 6f radial inward movement 6f the tube. Additional cage 70 is located'between the side of tube 62 adjacent the motor ' covering recessed chanriel 71 extending aiound the periphery of closure flange 38 and functioning to prevent flexible tu@be 62 from engaging the inner surface of closure flange 38 which 'would otherwise shut off the exit of high pres.sure fluid from discharge port 72. On the opposite side of flexible tube 62 from ou@let port 72 there is located a partition ring 73 having an inner circular opening 74 complew-entary in size to pumi) flange 54, a sealing ring is carried within annular groove 55 of the pui,-np@ flange serving to provide a seal. Partition rin@ 73 ho.s a, circular outer periphery f.armed with an annular groove 75 for the reception of a flexible se@ling ring cooperating with the inner periphdry of tubular housing wall @Tb to provide a seal therebetween. @ Shoiilder 76 on the partition ring 73 supports one terminal 6f cage 68 against radial inward movement. Recessed annu'ar channel 77 receives the outer periphery of a filter screen 78 confined therein by a snap ring 79. Snap ri-ng 80 is received in a similar recessed annular channei in the inner periphery of housing port;ion 7b e,nd functions to hold partition ring 73 against axial movement when subject to the pressure within primary accumuiat6r S. Secondary switch-actuating aceiimulator 4 com r prises a -fixed tubula piston 8 I threadably ,attached,to pump housing section 30 at o-ne end thereof for.communication with primary accuriulator 3 through p@ssage 58.' Cylinder 82- telescop@@cally embraces p,ston 81 in sealed relation theret6 and is normal'y urged in telegcoping direction by an emb-facing low rate compre.@sion spring 83 acting again,@,t radi@tl flange 84. Fixed piston 81 is provided about the periphery thereof with rel4eving grooves 85 and is given a lapped fit ,@ithin teleccoping cylinder 82. Radial flange 84 is formed with an internal annular channel receiving a flexible sealing ring further providing a se@al with fixed piston 81. Snap ring 87 is supported in a manner, as will appear, such that it functions t( limit the extent of movement of compre,-sion spring 83 while the oploosite terminal of this spring is confined by an additional snap ring 88@ Cyiinder 82 is closed at the outer terminal t,@lereof ond is provided with a niPPl-@7like guide exten.@,ion 89 for cooperation with control switch 6 i--q a sp-eciai manner to be described. It will thus:appear that in operaiion secondary relatively smali capacity accumulator 4 ieceives pressure from primary accumulator 3 through Passage 56 causing reciprocable cy7inder 82 to move in extended direction against the action of low rate co@,npression spring 83 to an e-,,@tent determined by the value 6f the pressure that has been bljlt up by presqure generator 2. By correlating the m6vement of cylinder 82 with the action of control switch 6, as will appear, 9, more effective and efficient operation of electric motor I and pressure generator 2 is accomplished. Atmospheric pressu-re accurqulator 5 comurises a second larger toroidal or donutshaped flexible '@iibe 90 received within housing portion 7b axially spaced from donut tube 62 of primary accumulator 3 on@the opposite side of partition wall 73 and spaced radially in embracing relation to secondary switch-actuatitg accumulator@ 4. 4@-At6 ni6sph6rid viaiit 6, sembly@ 91 f@iietio t admit s ns atrhospheric pressure to the interior of flexible tube 90 dt all times. This vent assembly 91 is siriiilar i'n constructi on to valve assembly 63 of 51 primary accumulator 3 above describedi except that a vent valve 92 is elnployed instead of a connection for the introduction of super-atmbspheric pressure as iia '@he case 6f the former valve assembly. A tdbular cage 93 is interposed between 10 flexible tube 90 and secondary accumulator 4 to li@mit the radial inward movement of tube 90, this tube being preferably supported at One terminal on generator housing secti6n 36 and at the 6ther terminal on'the housing closure as wiU appear. 15 Perforation 94 allows the free flow of low pressure@ fiuid abbut secondary acciimulator 4 and fiexib)e tube 90. It will be noted that atmosl@j-.ier4@c pressure accumi-ilator tube 90 is c6nsiderably larger ir. cr6ss-section than primary 20: accum..ulator tube 62 for a reason that will appear. Atm6,@pneric pressure accumlilator tube 90 is always subject to atmospheric pressure on the' intc-rior tbereof and therefore regardless of variations in tl-ie quantity of low pressure Iiquid con25 tained within contact therewith, this liquid will alwa@,s be rnaintai-ed at atmospheric pressure al'id free froirl any tendency to have air drawn i-nto the liquid and adversely affect the operation. Ti-ibe 90 is iiecessarily larger in cross-section than 30 primalry accuniulator tube 62 since it must perform its flinction in i-esponse to atmospheric pressure which is relatively low. , Accumulatoi--actuated motor control switch assembly 6 comprises adjusting wrencli or plunger 35 97i hc,,vilig a nbn circuiqr terminal portion 97a fur-etioning as a wrer-ch to'adjust internally throade,-l clostire cal) 104, which in turn is engageable by cup 80 of c3r'iinder 82. Sleeve 98 carries trar@sverseiy extending switch-actuating pin 99 40 e'Tcct-lve to cause the snap operation of switch as@erdbly r,,rooer 100 upon movement past the over-center position. SlEeve 98 has radially extending i9-igers IO 1 slid ably cooperatin- with guide, 5? that may be formed either ip- the housing 45 er@,d closure or in a separate part attached thereto. ConipreSS-10n SpTing 103 urges sleeve 98 in the directioli of reciproceble cylinder 82 of secondary accumulator 4. Closure cap 104 is orificed for coo-7.eration with adjusti-og wrench 97 and is interiiaily threaded for attachment to the terminal threaded portion of sleeve 98. This arrangement provides for external adjustment of the cut oiit . pressure as well as the cut in pressure., A radial 'Llange 105 is cariied on the out@.id-- por55 tion of pILinge,r 97 and is held in ergagement with the outside terminal of sleeve 98 bs7 means of a second inter,-iRIly threaded centrally ori@riced cap 10r). It will be seen that this arrangement provides for manual override operation of the switch 60 @ryhen desirecl, nierely by manuaily engaging terminal botinet I PS. Tl-ie switch assembly proper i 00 includes a snap action mechanisip- comprising a walking beam iD7 dri-vingly connected to a switch-oplerating (35 shaft 1 08 contacted by a roller I 0 9 carried on the er, d. of an over-center swinging arw- or yoke I IO @ This arm or yoke roember embraces an arcuate Protub2rance I I I carried by swit,.ch housing 6a, tb.is yoke i7,q,,i-,Dber being urged a-viay from pro70 tuber,,inctl I I I by compression , spring I 1 2 with tl,-ie result that the m(>veipent of actuating pin 99 by plup-ger 97 and sleeve 98 past its center positi-on wit-h re-fe,,ence to the axis of supportin g shaft iBB is effective to caiise a snap action or 7a-@ quick arcllate movement of walking beam 107 @ andi@

7 si@ppq@tin - gsbp@ft @i 00. For. t'he@-pq@po4e. of latching w4w@4g. 40am l@07 in either Position to which thesa iiie: i-@,: mo:ved, there is provided opposite each te,,-,,P-linal of-,the walking beam duplicate latches gachlatchissupportedona 'votil4and Pi is urged in the direction of the walking beam 107 by com ession spring II 56 Shoulders II 6 func. @ p@7 tiaii to lock the associated terminal of walking be@i@i 1-07 subject to the subsequent release thereof @ by ipward-ly-, extending finger II 7 being contacted by arcua@L,ely shiftable arm or yoke II 0. Oscillatable shaft 108 also supports in spaced rel@ktion@to wawng bepm 107 another arcuately swinga,'ole arm II 9 su'opbrted thereon in driving rela@,io-u., Arm i 19 carries contacts 120 cushioned by,,. corii-p@-resqion springs 12 i (on'ly Gne being shoyvi@@, The arm 119 is swung arcuately to bri gcgT-.tact@@120 into engagement with grounded CPP,@act , 12 2, carried b,Y housing Oa or into engagelment with stop 123. S-apporting and enclosing housing assembly 7 com rises in addition to portion 7a and 7b al. P. read d scribed a low pressure chamber closure e member 126,having a circular periphery formed with a recessed annular channel 127 for reception of a. flexible seal riig providing a seal vjith the em4.1@,@ping housing Portion 7b, this closure memb.er, being confined in position by a snap ring 128 fitting@in a complementary channel on the inner p,e@i-ipbery of the 1-iousing Tb. This closure membar is@formed with an inlet port 129 for the return introduction: of low Pressure fluid. A stud bblt 130 or. as many thereof as is desired, may be thre,adably, mounted in end closure 126 for@ attachment to a suitable siipport such, for example, a@@ 4 , bracket I 3@l, a similar supporting arrangeme , @qt - being also provided for the opposite end closure, Air bleed assembly 137 serves to bleed air from the low pressureaccumulator portion 4. A refUl.,Pltig assembly 138 provides for i@e4dily,rel, lenishing hydraulic fluid. Referring@again to n!g. I in somewhat greater detail, the dr-lving Power suPPly assembly B comprises alstelrage battery arranged to deliver electrical current through ccntacts 142d of relay 142 when closed, to electrical motcr 1. Relay 142 is no,rmally energized and deenergi-zed automatically by the operation of corl-trol switch 6 in response to the rise and fall of pressure in the aecumu lator A. Control current passes frrri the ba-ttery through contact 122 e,f switch S. In the eye,nt t,hat the pressure i-,i the accumulator has dropped to a point permitting cylinder 82 t6 move in the telescoping direction suffleiently to allow sp@-ing 103 tb shift plunger 97 and sleeve 93 and thus effect the snap action of walking beam 107 and switch arni II 9 tccontact grgund terminal t;2,, then relay 142 will be energized to clc,se conta@cts, 142a and deliver current to. the electric motor I for operating the same to drive fluid P-ressure generator 2. In addition, signal light 139 will be illuminated to indicate the operating condition of electric motor. Iq@ep@iric mgtor I will co@ntinue to operate until the.- l@ydraulic Pressure acting on shiftable cylinri-ses@ to -a s,uffic4@ent level to cause the cylinO!E@r to again contact plunger 97 and shift the s.ame, . suff-iciently to cause snap -,@ction of walking beam 10 7 and the moving of arm II 9 tc. separate live con'tact 120 from ground contact 122 thus op@pning the moto@r circuit. Lovvering of the presSu Te-I i@iay again be brc,.ught about by o-peration of manualiy@ controlled moduiator valve C to deliypr liressure fluid to the, brake rnotor assembly 2-f4l,S 667- stp@rt th electric-motbr 1, an 44-@4 Rress,7@i@e-g@@l@-!-. e d erator 2. As -a stand-by means,fcr ma ually energi7,ing n reiay 142 a manual push button controlled cire t 5: may be provided as shown. From the above, it will be seen that I haveprovided an improved @and important relationship,,, of elements resulting in compactness and, efflc,.ency in accumulators generally. For example, 10 primary high pressure toroidal tube 62 may be readily substituted f olr the @ present inefficient, cumbersome diaphragm now incorporated in the well-known spherical form of accumulator. The, equivalent of tubular@ surrounding housing por15 tion 7a and associa-ted piston-like end closure members may also be employed and this arrange.. . ment may be used either with or without the;@ incorporation of a pressure fluid generator with-,, in the housing. 20 It will appear further that, when the problem is m-.rely one of maintain:ng atmospheric pres@.. sure within 9, supply of hydraulic fluid, then an arrangement equivalent of that shown in con.!, nection with low pressure to@roidal tube @00 may, 25 be emplc-yed for this purpose. While I have disclosed my invention in connection with certai.n specific embodiments thereo'L, it is Ito b@, urderstood that this is by -way: of examp-le only atid that equivalent arrangements 30 are contemplated as coming within my, inventiori which is defined by the appended claims. I