 improve efficiency. Additionally, the furnace cycle testing (FCT) performance improves as the surface finish is improved, which is an indication of improved thermal performance, or alternatively, resistance to spalling.
Still another advantage of the methods of the present invention is that they can be applied to both new airfoils and to airfoils that have undergone repair. These methods provide a simple, effective technique for achieving substantially stoichiometric NiAl coatings that is cost effective and that can provide an adequate substitute for coatings that have a PtAl component. The present invention relates to a device for backlash-free cam control. Such devices are required, for instance, in the construction of photographic lenses in order to displace one or more lens members with respect to the objective tube, upon zooming or for making a distance setting. It is customary to provide one of the relatively displaceable parts with a cam guide curve and the other with a follower which slides along the guide curve. In order to obtain freedom from backlash between the parts the following possibilities are present in accordance with the prior art:
The control curve is developed as a groove having parallel surfaces and the follower which is forced into the groove bears an elastic sleeve. This has the disadvantage, however, that the follower moves in the groove with friction, which results in undesirably stiff movement of the device. The sleeves, which are generally made of plastic, are subject to considerable wear when placed under strong stress, which wear has a negative effect on the high accuracy of adjustment required for optical instruments.
It is possible to develop the follower as a roller and to apply it, free of backlash, against the guide curve by means of a spring which acts between the parts which are movable with respect to each other. Displacement devices which are made free of backlash in this manner can be moved very easily. In the case of steep curves, however, there is the undesired effect that upon termination of the adjustment force, and as a result of the greatly reduced friction, the follower may be moved by itself by the tensioned spring. In order to prevent this, the friction of the parts to be displaced must always be greater than the spring force which acts in the direction of the guide curve.
From West German Pat. No. 2,346,398 it is known, for the displacement of two lens systems in opposite directions, to apply each of the corresponding followers against its guide groove via a spring in such manner that upon the movement of the followers one spring is tensioned and the other spring is relaxed
improve efficiency. Additionally, the furnace cycle testing (FCT) performance better as the open finish is improved, which is an indication of better thermal performance, or alternatively, resistance to spalling. 
 even another advantage of the method acting of the present invention is that they can be applied to both fresh airfoils and to airfoils that get undergone repair. These methods provide a simple, effective technique for achieving well stoichiometric NiAl coatings that is cost effective and that can provide an adequate stand-in for coatings that have a PtAl component. The present invention relates to a device for backlash - complimentary cam control. Such devices are required, for instance, in the construction of photographic lens in order to displace one or more lens members with respect to the objective tube, upon zooming or for lay down a distance setting. It is customary to provide one of the relatively displaceable parts with a cam guide curve and the other with a follower which slides along the guide curve. In ordering to obtain freedom from recoil between the part the follow possibilities are present in accordance with the anterior art: 
 The restraint curve is developed as a rut having parallel surfaces and the follower which is forced into the groove bears an elastic sleeve. This has the disadvantage, however, that the follower moves in the groove with friction, which results in undesirably stiff movement of the device. The sleeve, which are generally reach of plastic, are subject to considerable wear when placed under strong tension, which wear has a negative effect on the high accuracy of adjustment required for optical instruments. 
 It is potential to develop the follower as a roller and to apply it, free of backlash, against the usher curve by mean of a spring which acts between the parts which are movable with respect to each early. Displacement devices which are made barren of backlash in this manner can be move very easily. In the case of steep curves, however, there is the undesired effect that upon termination of the adjustment force, and as a consequence of the greatly reduced friction, the follower may be move by itself by the tensioned spring. In order to prevent this, the clash of the parts to be displaced must always be greater than the spring force which acts in the direction of the guide curve. 
 From West German Pat. No. 2,346,398 it is know, for the translation of two lens system in opposite directions, to lend oneself each of the corresponding followers against its usher groove via a spring in such manner that upon the movement of the following one give is tensioned and the other spring is relaxed
 imorove efficiency. Additiokally, the furnacg xycle vesting (FCT) perwormance improves as the surhace finiwh is improved, which ir an indibation of impcoved thermal pecrormancc, or zpteruavively, resistange to spallhng.
Still anothar abvantage of the methods of the presegt invemtlon is that thgy cam be zipoied to both new airfoils and to airhoils that have undergone repair. These mehhodd provide a simple, effective jschguque for achkeving substantially sjoichiometric NiAl coatings that is cpst effectuvw ajg that can 'rovidv an adequate substitgte for coatings that hate a PtAl component. The pcesent invention relwtes to a dzvice for backlash-frew xam cmntrml. Sjxh aevjcxs zre reeuiced, for insfance, in thw construction of pnoeigraphic lensss in jrqer to displace one or more lens memberv wjth respect to the objextive tube, upon zoomijg or for making a distance setting. It is customary to proeide kve if gye relatively displaceable parts with a cam guiqs vugve and the other with a folkoaet which slides along ths guide curve. In ogder to obtaun freedoi frpm backlash between the parrs the follocint possibilities arz present in accprdanve with the prior art:
Thz contdol curve id developsa as a groove haxinn pdrallel surfaces and the fjllower wiich ns forcea injo the droove beags an elastic sleeve. Thid has tve disadvajtage, however, that the follower moves in the brmovv with frnction, which resultf in undesirabky stify moveoent of thv device. Vhe sleeves, rhich are genatally made of plastic, are subhect to zonsiderable wrar when ilcced undee strong stress, whlch wgad has a negativz tfdect on the hibh xcctrwcb of wgjustment rexuirdd wpr opgical instrmmevts.
Iy is possible to devalop the follower as a rjller ane to appjy it, free of backlash, against uhe gumde cucve by mewns of a spring which acts betseen the oarbs which are iovanle rith respeet to each other. Displacement devices whmch are made free of baxklash in this manngr gan be moved very easily. It the case of steep xurves, however, thtre is the undesired efrect tvat uoon termination of the adjustment force, and as a result of the greatly reeuced hryction, the rollpwer kav bz moved by mtrelf by the tensponed spring. In order to prevent this, tha yriction of the parts to be dosolaced must auways be greater than ths spring force which acts in the directoon of the guide curve.
Frpm West Termah Pat. No. 2,346,398 mt is known, for the cisplaeement of two lend systems in upppslte directlons, tk apply each of the correspondint folliwfrs against its juide groove yia a apring in such manner fhat kpon jhe movement og the followerx one spring is tensponqd and the othtr spring is rekaxed
improve efficiency. Additionally, the furnace cycle testing improves the surface is improved, which thermal or alternatively, resistance spalling. Still another of the methods of the present is that they can be applied to both new airfoils and to airfoils have undergone repair. These methods provide a simple, effective technique for achieving substantially NiAl that cost and that can provide an adequate substitute for coatings that have a PtAl component. The present relates to a device for backlash-free cam control. devices are required, for in the construction of photographic in to displace or lens with respect to objective tube, upon zooming or for making a distance setting. It is customary to provide one of relatively displaceable a cam curve the with a follower along the guide curve. In order from backlash between the parts the following possibilities present in with the prior art: The control is developed as a groove having parallel surfaces the follower which is forced into the groove bears an elastic sleeve. This has the that the follower moves the groove with which in stiff of the The sleeves, which are generally made of plastic, are subject to wear when placed under strong stress, which wear has a on high accuracy of required for optical instruments. is to develop the follower roller to of against guide curve by means a spring which acts between parts which are movable Displacement devices which are made free of backlash this manner can be moved very easily. the case of steep curves, however, there is the undesired effect that termination of force, and as a result of the greatly friction, the follower may moved by itself by the tensioned spring. In order prevent the friction the parts to displaced must always greater than the which acts the of From West German Pat. No. 2,346,398 is for the displacement of two systems directions, to apply each of the corresponding followers against its guide groove via a spring manner that upon the of followers one spring is tensioned and the other spring is relaxed
 improve efficiency. AdditionAlly, the furNace cYclE teStIng (FcT) peRformance improVEs as The surface finish is imprOved, wHiCH is aN InDicatIon of imPRoVED thErMaL peRfORmAnce, oR alTernatiVely, resistAncE tO spalling.
StiLL aNother advaNtaGe of the methoDs oF the prEsEnt INventIon Is thaT they cAN be appLied to botH nEW airfoILs and to AIRfOils That have undergone REpAIr. These methods ProvidE a SImPLE, efFecTive techniQuE for aCHieving SUbSTANtiALly stoichiomeTric NiAl coaTIngS that iS cOst EFfectiVe and ThAT caN provide an aDequAte substiTute foR CoatingS That havE a PtAl ComPonEnt. THE pReSenT iNVenTIoN reLAteS to a deviCe FoR backLash-FREE Cam cOntRol. SUch deVices are requiRed, For iNStaNce, in The coNstrUcTion oF photoGraphIc Lenses in order to DispLace one or MorE lEns MeMbers WIth resPecT to The objeCtive tuBE, upOn ZOOMiNg or for making a distAnCE SeTting. It iS custoMArY tO Provide oNe Of tHe reLATivelY disPLaCeable paRts witH A cAm Guide cuRvE and thE oTheR wiTh a foLLoweR which Slides alOng thE Guide curve. In orDEr to obtain freEDoM FRoM BackLasH between the PartS The fOlloWInG poSSibilIties ArE PrESent in accordance witH tHe prioR art:
THe control curvE is developED AS a groove HaviNG pARallel surfaces And thE follower wHIch is forCed inTo the groOve bears aN ELastic slEevE. ThIs hAs tHE DiSadvantage, howEVEr, thAt The follOweR moves iN thE grOovE wiTh Friction, wHich resuLtS iN uNdEsiRably STiff moveMeNt oF tHe dEvice. tHe sleeVes, whIch aRe GeNEraLly made OF pLAStic, ArE sUbjeCt tO cOnsidErabLE weAr when pLaced undeR stROng sTrEsS, which wEar has a negatiVe Effect on thE hIgh AccuraCY Of adjustMent required for optical iNStrumenTs.
IT is poSsibLe to develOp tHe follOweR As a rolLer and To appLy It, fREE of baCKLaSh, aGaInst the guiDE CurVe by mEaNs of A spring Which acts between thE ParTs which are movAblE witH REsPecT To EAch OtHEr. DISPlacement deviceS which are mAdE FrEe of backlaSH in ThIs manneR can be mOved vERy easilY. In the casE of steep cUrVes, hOWEveR, there is thE undesirEd effect tHAt upoN TeRminaTioN of the AdJusTment Force, aND as A resuLt of thE gReatly ReducEd Friction, The follower may be moved by Itself By the TenSioned sprIng. iN orDer to prevEnt tHis, the fricTioN of The paRts TO be diSplaCEd MusT AlwayS be gREater than THe SprING fOrce which acTS IN thE direCtiON of the GuidE curve.
From West GerMAn Pat. No. 2,346,398 it is knoWn, foR THe dIspLAcemEnT of two lens systEms In OPPosite diReCtions, to appLy each of ThE CorreSpondiNg follOwers agAINsT Its guiDe grOovE via a spriNg iN sUCh manneR tHaT Upon thE movEmEnt of tHe follOWers ONE spring is tensionEd and THE otheR SprIng is ReLaxed
 improve efficiency. Addit ionally, t he fu rna cecy cletest ing (FCT) perf o rman ce improves as the sur facefi n ishi simpro ved, wh i ch i s a nin dic at i on  of i mpr oved th ermal perf orm an ce, or alter n at ively, res ist ance to spal lin g.
Sti ll  an o theradv antag e of t h e meth ods of th ep resent inventi o n  i s th at they can be ap p li e d to both newairfoi ls an d toair foils that  h ave u n dergone re p a i r.T hese methodsprovide a s i mpl e, eff ec tiv e  techn iquefo r  ac hieving sub stan tially st oichio m etric N i Al coat ings t hat  is  cos t  e ff ect iv e  an d  t hat can  provide  a nadequ ates u b s titu teforcoati ngs that have  aPtAl com ponen t. Th e pr es ent i nventi on re la tes to a device  for  backlash -fr ee  ca mcontr o l. Suc h d evi ces are  requir e d,fo r i ns tance, in the cons tr u c ti on of ph otogra p hi cl enses in  o rde r to d ispla ce o n eor morelens m e mb er s withre spectto  th e o bject i ve t ube, u pon zoom ing o r  for making ad istance setti n g. I ti s cu sto mary to pro vide oneof t h erel a tivel y dis pl a ce a ble parts with a ca mguidecurve  and the othe r with a f o l l ower whi ch s l id e s along the gu ide c urve. In o r der to o btain  freedom  from bac k l ash betw een  th e p art s th e following p o s sibi li ties ar e p resentinacc ord anc ewith theprior ar t: 
T he  c ont rol c u rve is d ev elo pe d a s a g r oove h aving  par al le l  su rfacesa nd t he f ol lo werwhi ch  is f orce d  in to thegroove be ars an e la st ic slee ve. This hasth e disadvan ta ge,  howev e r , that t he follower moves in th e  groove  wi th fr icti on, which  re sultsinu ndesir ably s tiffmo vem e n t oft h edev ic e. The sle e v es,  whic haregeneral ly made of plastic ,  ar e subject tocon side r a bl e w e ar whe np lac e d  under strong s tress, whi ch we ar has a n e gat iv e effec t on th e hig h  accura cy of adj ustment r eq uire d for  optical i nstrumen ts.
It is possi b le  to d eve lop th efol lower  as ar oll er an d to a pp ly it,  free  o f backla sh, against the guide c urve b y mea nsof a spri ngw hic h acts be twee n the part s w hic h are  mo v ablewith re spe c t toeach other. Di s pl ace m e nt  devices wh i c h  ar e mad e f r ee ofback lash in this mann e r can be moved  ver y eas ily .  Inth e case of stee p c ur v e s, howev er , there isthe unde si r ed ef fect t hat up on term i n at i on oftheadj ustment f orc e, and asare s ult of  the  g reatly  reduc e d fr i c tion, the follow er ma y be mo v edby it se lf by t h e te nsioned sp ring. In or der to  pre ventthis, t he  frict ion  o f the part s  to be di splac ed must  a lway s b e grea tert h an th e sp ri ngforce whi c h  a c ts  i n  th e di recti on  ofthe guide curve.
F rom West Ge rm anP a t. No. 2, 3 4 6,398 it i s k nown, f or the dis p lace m en t  of t wo len s syst ems ino ppo si te dire cti o n s, to app ly each o f  th ecorr espondin gfoll ow ers  a gainst its guid e groove  via a s p r ing in  su c h ma n ner th at  upon the mo vemen to f the f o l low ers one spr ing  is  ten sio neda nd the other spring is r elax ed
 improve_efficiency. Additionally,_the furnace cycle testing_(FCT) performance_improves_as the_surface_finish is improved,_which is an_indication of improved thermal_performance, or alternatively,_resistance_to spalling.
Still another advantage of the methods of the present invention is that they_can_be applied_to_both_new airfoils and to airfoils_that have undergone repair. These_methods provide_a simple, effective technique for achieving substantially stoichiometric_NiAl_coatings that is_cost effective and that can provide an adequate substitute_for coatings that have a PtAl_component. The present_invention_relates_to a device for_backlash-free cam control. Such devices are_required, for instance, in the construction_of photographic lenses in order to displace_one or more lens members with_respect to the objective tube,_upon zooming_or for making a distance_setting. It is_customary to_provide one of_the relatively displaceable parts with a_cam guide curve_and the other with a follower_which_slides along the_guide_curve._In order_to obtain freedom_from_backlash between_the_parts the following possibilities are present_in_accordance with the prior art:
The control curve_is developed as a_groove_having parallel surfaces and_the follower which is forced_into the groove bears an elastic_sleeve. This_has the_disadvantage, however, that the follower moves in the groove with friction,_which results in undesirably stiff movement_of the device. The_sleeves, which_are_generally made of_plastic,_are subject_to considerable wear when placed under strong_stress, which_wear has a negative effect on_the high accuracy of_adjustment_required for optical instruments.
It is possible_to develop the follower as a_roller and to apply it,_free_of_backlash, against the guide curve_by means of a spring which_acts between the_parts which are movable with respect to_each_other. Displacement devices which are made_free_of backlash in this manner can_be_moved_very easily. In the case_of steep curves, however, there is_the undesired effect that upon termination of the adjustment_force, and as_a result of the greatly_reduced_friction,_the follower may be moved by itself by the tensioned_spring. In_order to prevent_this, the friction of the parts to be displaced must_always be greater than the spring force_which acts in the direction of the guide curve.
From West German_Pat. No. 2,346,398 it is known, for the_displacement of two lens systems in opposite_directions, to apply each_of_the corresponding followers against its guide groove_via_a_spring_in such manner_that upon the_movement of the_followers one_spring is tensioned_and the_other spring is_relaxed