ool element which can be moved to any one of a plurality of positions to control the passage of pressurized fluid through various fluid conduits.
One well-known method for positioning the spool of a fluid-operated spool valve is to use a spring acting on either one or both of the ends of the spool valve such that the spring or springs automatically return the spool to a determined or neutral position. It has been discovered, however, that such method has several drawbacks because of the necessity of providing sufficient spring force to shift the spool to the predetermined position. Namely, the constantly contacting spring increases the minimum permissible operating pressure of the valve and causes an inbalance of forces acting in one direction of spool movement. Further, the spring itself is cycled at the same rate as the valve subjecting it to fatigue and wear, necessitating frequent maintenance, and reducing the reliability of the positioning apparatus. Thus, the normal operating function of a spool valve is severely altered with such prior known positioners.
A second method widely used for positioning spool valves of the double solenoid, two-position type are detents designed to hold the spool in one or both of its two extreme positions. Such detents normally include holding members biased into contact with recesses or the like on the spool itself. Such detents also are disadvantageous because they raise the valve's minimum operating pressure thereby requiring an additional force to unlock the spool and start its motion. If the fluid system somehow fails during the movement of the spool, the spool may coast to a stop before reaching one of the locking detents thereby preventing accurate determination of its position as mentioned above.
It has now been discovered that the present invention eliminates the above problems by providing a positioner which is actuated only if the system is shut down, depressurized or otherwise not operating. The device remains ready for actuation at all times but is unused until called upon thereby prolonging its life to an extent greater than for any known positioning apparatus. Further, the device avoids the necessity of an additional force to move the spool, causes no imbalance of forces acting upon the spool and is cycled only at a fraction of the repetitions to which the spool is ordinarily subjected. The present invention, therefore, allows a designer to accurately determine the position of the valve at all times during start-up thereby increasing the safety and realibility of systems controlled by the valve. The present invention relates generally to vehicular suspension systems and, in a preferred embodiment thereof
ool element which can be moved to any one of a plurality of positions to see the enactment of pressurized fluid through various fluid conduits. 
 One well - know method for positioning the bobbin of a fluid - operated spool valve is to use a give acting on either one or both of the ends of the bobbin valve such that the spring or springs automatically return the bobbin to a determined or neutral placement. It has been discovered, however, that such method accept several drawbacks because of the necessity of put up sufficient spring force to shift the spool to the predetermine position. Namely, the constantly contacting spring increases the minimum permissible operating atmospheric pressure of the valve and causes an inbalance of forces acting in one direction of spool movement. Further, the spring itself is cycled at the same rate as the valve subjecting it to fatigue and wear, necessitating frequent maintenance, and reducing the dependability of the placement apparatus. Thus, the normal operating function of a spool valve is hard altered with such prior known rotary actuator. 
 A second method wide used for positioning spool valve of the double solenoid, two - position type are detents design to hold the spool in one or both of its two extreme positions. Such detents normally admit holding member bias into contact with recesses or the like on the spool itself. Such detents besides are disadvantageous because they raise the valve's minimum operating pressure thereby requiring an additional force to unlock the spool and start its motion. If the fluent system somehow fails during the movement of the spool, the spool may coast to a arrest before reaching one of the lock detents thereby prevent accurate determination of its placement as mentioned above. 
 It has now been discover that the present invention eliminates the above problem by providing a rotary actuator which is actuated only if the system is shut down, depressurize or otherwise not operating. The device remains ready for propulsion at all times but is unused until called upon thereby prolonging its life to an extent greater than for any known placement apparatus. Further, the device avoids the necessity of an additional force to move the spool, causes no imbalance of violence acting upon the spool and is cycled only at a fraction of the repetitions to which the spool is ordinarily subject. The present invention, therefore, allows a designer to accurately specify the stead of the valve at all times during start - up thereby increasing the guard and realibility of systems controlled by the valve. The present invention relates generally to vehicular suspension systems and, in a prefer embodiment thereof
ool element which can be moyed to any one oy a plucality kf positkons to control the passage lf preswurized fluid through xarious fpuid coneuitw.
Ine well-known method for iositnoiing the spool pf a fluid-mperated spool vxlre is to use a spring acting on eithqr one pr both of the egds ps ths spool valve such that the spring or sprpngs automaticallu return the spool to a dehermlned or neutral podition. It hqs bqwn discoverea, however, uhct such metgod has several drawbacks becaure of the neceswiry lx providing suffpcient spring force tm shift the spool to bhe pcederermined position. Namxly, the constantly cjntacting s'ring increases the munumum kermivsibuw ooerztmng presskre of the vamve and cauwes an inbalance of fjgves acting ih one qiwection of spool movement. Further, the skring itself is cycled at thw same rate as the vapve subjesting it to fatigue and wear, necessitating frequett mamngenckge, ave geducing the reliability of the positioning a[latanus. Thus, the normcl operating funvtlom of a spool vxlve is ssverely altered wihh such prioe known pjsitooners.
A second method widelt used for pjwitioning spool vapves of the dounle splenoid, two-position typz are setents deslgned to guld the spool in onv or both of its two extreme pjsitions. Wuch detentr notmally ynclude hopding members biased intl conjact whth recessfs or the like on the spool itsxkf. Such detemtv anso are bisadvsntageous becwuse they raisg the valre's mivimum operzting pcessure therqby requiring wn additionan force eo ublocj the souol and start ots motiou. If rhe fluid system spmefkw fails during tht novement of thr soooj, nhe s[mol may coasd to a ryop bdfore rtcchlng one of the locking detetts fhereby preventing agcurate dgterminatyon of its poxition as mentionef abote.
It hes now begn discovered that the present jnvention ellminates the wbovc prjblems by 'roviding a positioner which is actuated only if the systgm is shut down, deprexxurized or ptherrise not mperating. The device remains ready fov actuation at all timss but is ujused until called upon thereby prolonging its life to an extent greater rhan for any known posotionpng cpparatts. Fnrvher, the device anoids the necessity of an additiunal forwe to move the spool, causes no iobalance of furces acting upon the spkol and os cycled only at a fraction of the repetitions to whicm the spoil is ordinarilb subjected. The presrnt inrentiob, theredore, allows a deskgnrr to accurwtelb dztermine the position of the valvw at aol times during stert-up therebn lncreaaing tre safety and rezlibjpity uf systems comtrolled by thr valve. The present pnvqntion relates fenerally to vehicunar suspensipn systems dnd, in a preferred embodiment thereof
ool element which can be moved to of plurality of to control the various conduits. One well-known for positioning the of a fluid-operated spool valve is use a spring acting on either one or both of the ends of spool valve such that the spring or springs automatically return the spool to determined neutral It been discovered, however, that such method has several drawbacks because of the necessity of providing sufficient force to shift the spool to the predetermined Namely, the constantly contacting increases the minimum permissible operating of valve and an of acting in one of spool movement. Further, the spring itself is cycled at the same rate as the valve subjecting to fatigue necessitating frequent and the of the positioning the normal operating function of a severely altered with such prior known positioners. A method widely for positioning spool valves of the solenoid, two-position type are detents designed to hold spool in one or both of its two extreme positions. Such detents normally include holding into contact with recesses the like on spool Such also disadvantageous because raise the valve's minimum operating pressure thereby requiring an additional force unlock the spool and start its motion. If the fluid fails the movement of spool, the spool may to stop before reaching one locking thereby of position mentioned above. It has been discovered that the present eliminates the above problems is actuated only if the system is shut depressurized or otherwise not operating. The device ready for actuation at all times but is unused until called upon prolonging its an extent greater than for any known positioning Further, the device avoids necessity of an additional force to move the spool, no of forces upon the spool is cycled only a fraction of to which spool ordinarily invention, therefore, allows a designer to determine position of the valve at times thereby increasing the safety and realibility of systems controlled by the valve. The present invention to vehicular suspension systems in preferred embodiment thereof
ool element which can be moved To any one of A plurAliTy oF pOsitIons To control the paSSage Of pressurized fluid throUgh vaRiOUs flUId ConduIts.
One wELl-KNOwn MeThOd fOr POsItionIng The spooL of a fluid-oPerAtEd spool valve IS tO use a sprinG acTing on either One Or both Of The ENds of The Spool Valve sUCh that The spring Or SPrings AUtomatiCALlY retUrn the spool to a detERmINed or neutral poSition. it HAs BEEn dIscOvered, howeVeR, that SUch methOD hAS SEveRAl drawbacks beCause of the nECesSity of PrOviDIng sufFicieNt SPriNg force to shIft tHe spool to The preDEterminED positiOn. NameLy, tHe cOnstANtLy ConTaCTinG SpRinG IncReases thE mInImum pErmiSSIBLe opEraTing PressUre of the valve And CausES an InbalAnce oF forCeS actiNg in onE direCtIon of spool movemEnt. FUrther, the SprInG itSeLf is cYCled at The SamE rate as The valvE SubJeCTINg It to fatigue and wear, NeCESsItating fRequenT MaInTEnance, anD rEduCing THE reliAbilITy Of the posItioniNG aPpAratus. THuS, the noRmAl oPerAting FUnctIon of a Spool valVe is sEVerely altered wITh such prior knOWn POSiTIoneRs.
A Second methoD widELy usEd foR PoSitIOning Spool VaLVeS Of the double solenoid, TwO-positIon tyPe are detents dEsigned to hOLD The spool In onE Or BOth of its two extReme pOsitions. SuCH detents NormaLly incluDe holding MEMbers biaSed IntO coNtaCT WiTh recesses or tHE Like On The spooL itSelf. SucH deTenTs aLso ArE disadvanTageous bEcAuSe ThEy rAise tHE valve's mInImuM oPerAting PRessurE therEby rEqUiRIng An additIOnAL ForcE tO uNlocK thE sPool aNd stARt iTs motioN. If the fluId sYStem SoMeHow failS during the movEmEnt of the spOoL, thE spool MAY coast to A stop before reaching one oF The lockIng DetenTs thEreby prevEntIng accUraTE deterMinatiOn of iTs PosITIon as MENtIonEd Above.
It has NOW beEn disCoVereD that thE present invention eLImiNates the above ProBlemS BY pRovIDiNG a pOsITioNER which is actuateD only if the SySTeM is shut dowN, DepReSsurizeD or otheRwise NOt operaTing. The deVice remaiNs ReadY FOr aCtuation at All times But is unusED untiL CaLled uPon TherebY pRolOnginG its liFE to An extEnt greAtEr than For anY kNown posiTioning apparatus. Further, The devIce avOidS the necesSitY Of aN additionAl foRce to move tHe sPooL, causEs nO ImbalAnce OF fOrcES actiNg upON the spool ANd Is cYCLeD only at a fraCTIOn oF the rEpeTItions To whIch the spool is ordiNArily subjected. the pRESenT inVEntiOn, Therefore, allowS a dEsIGNer to accUrAtely determIne the poSiTIon of The valVe at alL times dURInG Start-uP theRebY increasiNg tHe SAfety anD rEaLIbilitY of sYsTems coNtrollED by tHE Valve. The present iNventION relaTEs gEneraLlY to vehiCUlar Suspension Systems and, iN a prefErreD emboDiment tHeReof
ool element which can be m oved to an y one  of  apl ural ityof positions t o  con trol the passage of pr essur iz e d fl u id  thro ugh var i ou s flu id  c ond ui t s. 
Onewel l-known  method fo r p os itioning the sp ool of a f lui d-operated s poo l valv eist o use  asprin g acti n g on e ither one  o r  botho f the e n d sof t he spool valve su c ht hat the spring  or sp ri n gs a uto mat ically ret ur n the spool t o  a d e ter m ined or neutr al position .  It  has b ee n d i scover ed, h ow e ver , that such  met hod has s everal drawbac k s becau se ofthe  ne cess i ty  o f p ro v idi n gsuf f ici ent spri ng  f orceto s h i f t  the  sp oolto th e predetermin edposi t ion . Nam ely,theco nstan tly co ntact in g spring increa sesthe minim umpe rmi ss ibleo perati ngpre ssure o f the v a lve  a n d ca uses an inbalanceof f or ces acti ng ino ne  d i rectionof  sp oolm o vemen t. F u rt her, the  sprin g  i ts elf iscy cled a tthe  sa me ra t e as  the v alve sub jecti n g it to fatigu e  and wear, ne c es s i ta t ingfre quent maint enan c e, a nd r e du cin g  therelia bi l it y  of the positioning  a pparat us. T hus, the norm al operati n g function  ofa  s p ool valve is s evere ly altered with suc h pri or known  position e r s.
A sec ond  me tho d w i d el y used for po s i tion in g spool  va lves of  th e d oub leso lenoid, t wo-posit io nty pe  ar e det e nts desi gn edto  ho ld th e  spool  in o ne o rbo t h o f its t w oe x trem epo siti ons .Suchdete n tsnormall y include  ho l ding  m em bers bi ased into con ta ct with re ce sse s or t h e  like on  the spool itself. Such detents  al so ar e di sadvantag eou s beca use they r aise t he va lv e's m inimu m op era ti ng pressur e the rebyre quir ing anadditional force t o  un lock the spoo l a nd s t a rt  it s  m o tio n. Ift h e fluid systemsomehow fa il s  d uring them ove me nt of t he spoo l, th e  spoolmay coast  to a sto pbefo r e  re aching one  of thelocking d e tents th ereby  pr eventi ng  ac curat e dete r min ation  of it spositi on as  m entioned  above.
It has now been  disco vered  th at the pr ese n t i nventionelim inates the  ab ove  prob lem s  by p rovi d in g a posit ione r  which is ac tua t e donly if the s y ste m isshu t  down,  dep ressurized or oth e rwise not oper atin g .  Th e d e vice  r emains ready f orac t u ation at  a ll times bu t is unu se d  unti l call ed upo n there b y  p r olongi ng i tslife to a n e xt e nt grea te rt han fo r an yknownpositi o ning a pparatus. Furthe r, th e devic e  av oidsth e neces s ityof an addi tional forc e to m ovethe s pool, c au ses no  im ba lance of f o rces acti ng up on thesp ooland  is cy cled o nly a t afr act ion of th e re p et it i ons  towhich  t he s pool is o r dinarily  su b jected.  T hep r esenti nv e n tion, ther efo re, a l l ows a desi g nert oa ccura tely d etermi ne thep osi ti on of t hev a lve at al l times d u rin gstar t-up the re by i nc rea si ng the safety a nd reali bility o f system s c o ntro l led by  t he valve. Th e pre se n t inven t i onrelates gen era lly  toveh icul a r suspension systems and , in  a pr e fer red e mbodi me nt there o f
ool element_which can_be moved to any_one of_a_plurality of_positions_to control the_passage of pressurized_fluid through various fluid_conduits.
One well-known method_for_positioning the spool of a fluid-operated spool valve is to use a spring acting_on_either one_or_both_of the ends of the_spool valve such that the_spring or_springs automatically return the spool to a determined_or_neutral position. It_has been discovered, however, that such method has several_drawbacks because of the necessity of_providing sufficient spring_force_to_shift the spool to_the predetermined position. Namely, the constantly_contacting spring increases the minimum permissible_operating pressure of the valve and causes_an inbalance of forces acting in_one direction of spool movement._Further, the_spring itself is cycled at_the same rate_as the_valve subjecting it_to fatigue and wear, necessitating frequent_maintenance, and reducing_the reliability of the positioning apparatus._Thus,_the normal operating_function_of_a spool_valve is severely_altered_with such_prior_known positioners.
A second method widely used_for_positioning spool valves of the double solenoid,_two-position type are detents_designed_to hold the spool_in one or both of_its two extreme positions. Such detents_normally include_holding members_biased into contact with recesses or the like on the spool_itself. Such detents also are disadvantageous_because they raise the_valve's minimum_operating_pressure thereby requiring_an_additional force_to unlock the spool and start its_motion. If_the fluid system somehow fails during_the movement of the_spool,_the spool may coast to a_stop before reaching one of the_locking detents thereby preventing accurate_determination_of_its position as mentioned above.
It_has now been discovered that the_present invention eliminates_the above problems by providing a positioner_which_is actuated only if the system_is_shut down, depressurized or otherwise not_operating._The_device remains ready for actuation_at all times but is unused_until called upon thereby prolonging its life to an_extent greater than_for any known positioning apparatus._Further,_the_device avoids the necessity of an additional force to move_the spool,_causes no imbalance_of forces acting upon the spool and is cycled only_at a fraction of the repetitions to_which the spool is ordinarily subjected. The present invention, therefore, allows_a designer to accurately determine the position of_the valve at all times during start-up_thereby increasing the safety_and_realibility of systems controlled by the valve._The_present_invention_relates generally to_vehicular suspension systems_and, in a_preferred embodiment_thereof