CA1199050A

CA1199050A - Rotary index table with fluid pressure preloaded bearings

Info

Publication number: CA1199050A
Application number: CA000410705A
Authority: CA
Inventors: Daniel J. Pieczulewski
Original assignee: Davis (ag) Gage And Engineering Co
Current assignee: Davis (ag) Gage And Engineering Co
Priority date: 1981-10-26
Filing date: 1982-09-02
Publication date: 1986-01-07
Also published as: IT1152933B; GB2111873B; FR2515086A1; IT8223871A0; DE3239556A1; GB2111873A; JPS58126029A

Abstract

ABSTRACT OF THE DISCLOSURE
Rotary tables for machine tool application are disclosed of the type using "Hirth" couplings to provide precision indexed positions and which are characterized by an hydraulically actuated piston member, one set of mating serrated teeth carried by the rotary tile and a concentric row of teeth fixed to the table base with the rotary table being supported on bearings. In the first version, a series of ball bearings are disposed in corresponding ball grooves, with a built-in predetermined amount of clearance in the bearing to enable the coupling teeth to be seated without interference from the bearing. Fluid pressure is adapted to be applied in the cavity to disengage the piston and to move the table top plate so as to preload the ball bearing, in order to provide a precision rotation of the rotary table for contouring applications. The table top plate also is formed with an outboard bearing surface engaged with a surface on the base when the serrated teeth are locked for maxim support, but are lifted clear when released to reduce wear and friction during indexing rotation of the top plate. In a second embodiment, the rotary table top assembly is mounted on bearings having a fraction characteristic decreasing with increasing pressure until an optimum preload level, and the disengaging air pressure is applied so as to increase the pressure on the bearing during indexing rota-tion of tile table in order to optimize the bearing friction characteristics during indexing as well as to disengage the Hirth coupling teeth.

Description

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This invention concerns rotary tables, and more parti-cularly, rotary tables of the -type employed in the machine tool industry for mountlng of workpieces for precision indexing or rotation of the workpieces during machining or other operations.
~ otary iables have in the past been designed employing the so-called "ilirth" couplings which consist of matinq circular rows of teeth carried by the rotary ,able and by an axially mov-able member mounted within the table base, either hydraulically or pneumatically actuated to move into and out of engagement with the teeth carried by the table. Index positions are achieved in each mating position of the Hirth coupling teeth, while the mem-ber carrying the teeth is moved into engaqement and retracted by hydraulic pressure and counteracting springs.

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SUCh arl arranyemerit is ~isclosed in U.S. Patent ~iFplication Serlal No. lq~,gO6, flled ~lay I~, lq8~ no~: tssued as U.S. Patent No. 4,353,271 to the pres nt lnventor.

Hlrth coupllnys have been found to prov1de great accuracy in each 1ndexed pos1tlon, wh1ch accuracy increases Wit~ ear due to the charac-ter~stlcs of th~ mat~ng engagement. In add~tion, great r1gld~ty 1n each lndexed posltlon ls afforded by the mating teeth, which r191d1ty offers a great advantage 1n the context of maclllnlng ~orkp~eces.

A further refinement of th~s concept involves the provlsion o~
double rows of matlng coupl~ng teeth, w~th the axlally moYable member formed wlth concentr1c c1rculdr rows of teeth, one row mat1ny ~th a correspond1ng clrcle of teeth carr~ed by the rotatable table member or top plate and the other teeth set engagable wlth a corresponding circle or row of ~eeth f1xed to the table base. By hav1ng dlffering numbers of teeth ln the respect1ve 1nner and outer rows, a vernter-like effect can he achleved whlch can achleve enormous numbers of ~ndexed pos1t~ons, each of whlch are hlghly accurately repeatable. In thls 1nstance, the ax1ally movable member ls rotated as well as the rotary table plate.

An eY~amrlP nf such a tahle is shown 1n Canadian Patent Appllca-tion Serial Number 396,444 filed February 17, 1982, aslo by the present i.n-ventor and assigned to the same assignee of the pres~nt application.

As descrlbed ln that applicatton, an ax1ally mcvable p1ston member carry1ng the douhle rcw of H1rth coupl1ng teeth ls engaged by hydraul1c pressure and d1sengaged by a~r pressure7 ~h1ch a1r pressure prov1des a rap1d dlsengagement.

There ls an lnherent problem ln us1ng an ~ndexlng type table utl-tlztng H1rth coupl1ngs as a non1ndex~ng rotary table usable for contour1ng~

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Thls problem is due to the nature of the Hirth coupl1ng and the phys1cal arrangement of the table ln belng supported on rotary bearings. As the p1ston mem~er moves into engagement with the table top plate and flxed gear teeth, the mat~ng teeth should desirably be allowed to freely seat, both radlally and ax1ally~ If the rotary hearing resists full seat~ng of the teeth, accuracy ~s adversely affecte~.

Accord1ngly. ~t is usual to proY1de "play" ln the table bearlng wh~ch enables the H~rth coup~ing te~tl? to fu~ly seat and to not cr~ate an lnterference by the constralnt of the bearing. Contrar1w1~e, wltll the table ~n the unlocked pos1tion, the table rotat~on ls inl~erently not prec1se due to the aforementloned play ln the bearing.

A costly alternative approach ls to mach1ne the bearing raceways to locate the bear1ng p1tch llne to the pitch line of the Hirth coupl1ng teeth ln the locked poslt~on.

In any event, there has not heretofore been prov1ded a precls10n, freely rotatable ta~le comblned ~ith a precls~on index1ng table ut~l1z1ng such H1rth coupllng teeth for provlding the indexed posltlons.

~omet1mes the mach1n1ng forces are relat1vely heavy, such as 1n broach1ng operat10ns, and wlth the workpiece supported on the table th1s tends to create excesstve deflect~on in the table bear1ngs and other parts.
It ~ould thus be hlghly des1rable to provide maxi~um rlg~d1ty to the table top pl~te 1n the locked pos1t~on.

~h1s r191d1ty could be prov1ded by provld1ng mat1ng surfsces at the max1~um rad1al outboard rotation underneath the table and the table base w~th the table top pl~te ~n the locked posit10n. Th1s has heretofore been d1f~1cult to aeh~eve due to the need ~or the H1rth couplln~ teeth to freely se~t caus1ng the table top plate to be axlally shlfted dur1ng se~tlng.

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In ~ddlt10n, 1f such mating surfaces were prov1ded the faces would w1pe dur~ng 1ndex1ng, 1ncreas1ng the power requlred to rotate the table due to frtct10n, and the mating surfaces would be subject to wear wh1ch would lead to 1naccurac1es after extended use~

There ~s also known a lo~/ frictlon resll1ent thrust bear~ng ~ater1al, wh1ch 1s sold under the trade name. "TURCIT~n, wh1ch has been use-ful for bear1ng appl1cat10ns for low~r cost rotary tables~ ln wh1ch the table is s1nlply supported on flat rings of such ~aterlal. There are d1f-ficultles ~nvolved in des1gning the bearing, due to a pecul1ar charac-ter1st1c of the mater1al. Under lightly loaded cond1t10ns, the fr1ct10n of the bear1ng increases rather than decreases unt11 a predeterm1ned load is carr1ed by the bearlng. Th1s predetermined preloadln~ 1s dlfflcult to achleve at the optimum level.

It 1s an object of the Present 1nvent10n to prov1de a rotary ~ork table of the type descr1bed 1n which both a precislon 1ndex1ng funct10n and a prec1s10n non1ndexing rotat10n mode ls posslble.

It 1s a further object of the present invent10n to prov1de such an 1ndex1ng prec1s10n rotst10n table which does not requ1re costly bear~ng construct10ns for support of the table top plate.

It 1s yet another object of the present inventlon to prov1de such a rotary table in wh1ch the table top plate is supported on m~t1ng r~dlally outenmost surfaces ln the 1ndexed locked pos1t10n wh1ch, dur1ng 1ndex1ng rotatlon, are 11fted clear of engage~ent to el1m1nate wear and drag on mat1ng surfaces wh11e enabl1ng full seating of the Hirth coupl1ng teeth 2~ w1thout 1nterference.

It 1s st111 another object of the present 1nvent10n to proY1de a rotary 1ndex1ng table wh1ci~ enables rel1able full seat~ng of the H1rth-coupl1ng teeth ~1thout requ1r1ng prec1s10n bearln~s.

It ts st~ill another object of the present in~ent-on to prov1de a rotary table of the type descr~bed in wh~ch a carefully control1ed preload on the bearings is provided, such as to enat,le proper performance when utl-lizl~g bearing material requirlng ~ predete~m~ined preload, and also to S control the bear~ng load dur~ng rotary indexing to m1nlm~i~e the wear thereof .

SUMMARY OF THE INVENTIO~

These an¢ other ob~ects ~f the pre~nt i~-ventiGn, wh~ch w111 become apparent on a reading of the follow1ng spec~flcdtion and clatms~ are achieved by an arrangement whereby the bear~ngs are preloaded by flu1d pressure supplled to a cav~ty withln the table housing tend~ng to pro duce controlled preload1ng of the bear1ngs support~nq the table top plate.
In each embod~ment, the preload fluici pressure is also exerted ~n the cav1ty whereat the H~rth coupl1ng teeth are located to disengage the Htrth coupling teeth by forcing the mo~a~le p1ston n~mber axially away fram the engaged posltion in whlch preloading fluld pressllre is overcome by the higher actuat1ng pressure appl1ed during locking of the rotary table, In the f1rst embodlment, the fluid pressure 1s appl~ed to a space 1mmed~ately below the table top plate adjacent the H1rth coupling teeth tend~ng to l~ft the rotary table top plate wllich ~s supportecl on a set of bear~ng b~lls d1sposed ~n a correspond~ng groove mach1ned into the per1phery of a c1rcular plate to wh~ch the rotar~ tabl~ top plate is affixed and 1n an outboard fixed gear r~ng sec~red to the table base, such th~t the up~ard flu1d pressure acts to exert an upward or outward flu~d pressure whlch acts to preload the be~r1ng balls The rotary table top plate ltself is aff~xed to a circular coupl~ng gear plate bear~ng the ~,~rth coupl1ng teeth and overlies both the upper surface of the coupl1ng gear plate and the upper surf~ce of the f~xed r~ng. An annular movablo piston member ls mounted round an annular pet~estal member af~ixed to the co~lpling gear plate and which carries two concentr~c circular rows oF teeth movable 1nto respective engagement w1th the ta~lt tcp plate teeth and a second ro~ of teeth rnachlned ~nto the under surface of the fixe~ near r~ng.
The space ~eneath the piston is also defined in part by a flange carrled by a drlve tube connected to the t~ble top assembly such that upon appl~cat~on of hydraulic pressure in the space the table top plate 1s drawn downwArdly to overcome the bearing preload fluid pressure ~h11e the p1ston ~oves upwardly to engage the double row of Hirth coupl~nt) teethO

The ball bear~ng ls deslgned w~th a degree of radial or ax~al play suff~c1ent to enable full and free seating of the Hirth coupltng teeth wlth l;he bear~ng unloaded.

Removal of the hydraulic pressure enables the re-exertion of the air pressure, forc~ng the table top plate upwardly with the bear1ng preloati causing ~lsengagement of tt~e mating untler surface of the table top plate and the upper surface of the f~xed tooth ring. The upper surf~ce of the f1xed tooth r1ng and the under sur~ace of tlle table top plate are manufactured to be in preclse al19nment with the plane produced with the Hirth coupling teeth 1n the locked positlon.

2(~ The p~tch plane is precistly located ~y re~ov1nt~ t~e rotary table top plate and machin~ng across the upper surface of the coupl1ng tooth plate and the tooth f~xed ring with the Hirtil coupling engage-d, prov1d~ng prec1se parallelism between these surfaces and wlth the coupling p~tch plane. The table top plate is then reassembled which Irings the under surface thereof 1nto pos~t10n atop the upper surface of the f~xed tooth r~ng such th~t the table top plate is supported at a rat~ially outermost position on the uppe-surface of the f~xed tooth rint~ in the locked or ~ndexed posltlon, wh1te enabl1ng the creatton of the gap therebetween upon appllcat10n of the pre-loadlng ~lu1d pressure.

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In the second embod1ment 9 the table top plate is supported on a "TURCITE~ bearlng mater1al ~nd the preload1ng pressure acts ln a downward dlrectlon such as to force the table into tight engagement wlth the ~TURCiTE~ bear1ng and with the regulated fluid pressure enabl1ng prec1se control over the preloadihg~ such as tQ prov1de opt~mum preloao for the bear1ng mater1al charac.terist1cs.

~RIEF DESCRIPTION ~F l~lE URAWINGS

F19ure l ls a sectional vie~ of d rotary index;ng taLle aecording to the present 1nvent10n, utll1zing a fluid pressure preloa~ed ball bearing to support the table top plate;

Flgure 2 1s an enlarged fragmentary v1ew of portlons of certa1n components of the r~tary ~ndex tahle as shown 1n Figure l deplcted ln the locked pos~tion, wlth an exag~erated representation of the bear1ng-race clearances;

Figure 3 ls an enlarged fragmentary view of certaln of the table components shown ~n Figure 2 in thc unlocked posttiorl ~/lth an exaggerated representat10n of the bearing race and balls;

Flgure 4 is an enlarged tragmentar~ vi~w of the components shown ~n Flgures 2 and 3 wlth tne table top removed and a diagrammat1c represen-tatlon of the mach1ning of the upper surfaces; and Flgure 5 ls a partlal section~l vlew of another form of rot~ry lndex table employlng the flu1d pressure preloaded bearing arrangement accord1ng to the present 1nventlon.

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ETAILED DESCRIPTION OF rHE PREFER~ED ~MBODIME~T
In the followi:ng detailed description, certain specific terminology will be employed for the sake of clarity and a par-ticular embodiment described in accordance with the requirements of 35. UOS~C~ 112. It is -to be understood -that the same is not intended to be llmiting and should be so cons-trued inasmuch as the invention is capable of taking many forms and variations within the scope of -the appended claims.
According to the drawings and partlcularly Figure 1, this view illustrates an embodiment of the invention applied to a rotary indexing table 10 of the same general arrangement as that described in copending Canadian Application Seria]. Number 396,444. A complete description of all of the details of the table 10 will no-t be herein included, but only those details nec-essary for a complete understanding of the present invention.
The table 10 includes a top plate assembly 12 mounted for rotation on a table base 16. It will be noted that the in-terior of the base 16 is sealed, by -the provision of O-ring gaskets and wiper seals, as shown, thereby sealing each of the mati.ng components assembled together.
This version of the table 10 is usable in either hori-zontal or vertical orientations of the table, and is shown in Figure 1 in the vertical position with the rotary table top plate 14 having its upper or outer surface 15 oriented in the vertical position. The table top plate 14 is mounted for rotation about the centerline "X" on a table base generally indicated as 16, so as to present various aspects of the workpieces which are mounted to the outer surface by way of threaded mounti.ng holes 18 to machine tools, engaging elements, suitable fixturing, etc., (not shown)~
The plate top assembly 12 includes the aforementioned table top plate 14 which in turn is mounted to a rotating serra-ted tooth l~g~S~ I

coupl1ng plate 22 by means of a ser1es of cap scre~s 24 and su1table keys 26 secured by machlne screws 28, providing a preclse angular tndtcatlon therebetween. A cover plate 13 covers a central openlng through the t~ble top plate 14, wlth cap screws 17 secur1ng the same.

The rotating serrate~ tooth coupllng plate 22, in turn~ 1s sup-ported by means of ~ ball bear1ng ass2mbly 30 1ncludtng a serles of bearlng balls 32 d1sposed ln correspond~ng raceways 34 and 36. The raceway 34 1s mach~ned 1nto the outer c1rcumference of the rotat1ng serrated tooth plate 22 and the racew~y 36 ~s mach1ned ~n the tnter10r bore ~ormed ln a f~xed coupl1ng serrated tooth r1n~ 38 and prov1des rad1al and ax1al support for the ~op plate assembly 12 for rotatlon on the table base 16.

The fixed coupl1ng serrated tooth r1n~ 38 ls f1xed to a base c~st1ng 40 by me~ns o~ a ser1es of cap screws 42.

The rotat~ng serrated tooth coupllng plate 22, tn turn, 1s aff1xed to a dr1ve tube 44 by means of cap screws 46 and prec1s10n keys 48 ~nsur1ng r1g1d, prec1sely located angular or1entat10n therebetween. The drive tube 44 1s ad~pted to be turned by means of a worm gear 50 aff1xed to a fldnge 52 of the dr1ve tube 44 and by means of cap screws 54 and a prec~slon key 56 secured by m~ch1ne screws 57. The worm gear 50 ln turn ts ~dapted to be dr~ven by ~ gear 58 ~ounted wlth1n the mach1ne cavltv and dr1ven by an electr1c motor gear dr1ve assemblv (not shown). In stm11ar fash~on to that which is shown and descxibe~ in copen~ing Canadian Application Serial Nu~-ber 396,444, a spur gear series and D.C. drive motor, when ~nergized, causes rotation of the top plate assembly 12.

The worm gear 50 1s p110ted on a closure plug 60 rece~ved w1th1n a bore 62 formed 1n the base cast~ng 40 secured by means of cap sorews 63 h~v1ng a p110t s~ct10n 64 upon wh~ch 1s rot~tabty rece1ved the worm ge~r 50 wlth ~ bore 66 fo~med there~n slldably f1t over the p110t sect10n 64.

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A pos1t1On fee~bark s1gnal rnay be prov1ded electron1cally by me~ns of an encoder decodPr assembly ln~icateb at 6~ ~hich 1ncludes an encoder 70 rotated w1th the rotat1ng serrate~ tooth plate ~2 by ~eans of a flat connec-tlon plate secured by cap screws 7~, the encoder 70 being coupled by a coupl 1 ng shaft 74 to a dec.oder 76.

As described, the top p7ate ass~mbly 12 is indexable to be precl-sely located 1n the lccked dlscret~ rotary poslt10ns by means of a H1rth coupl1ng arr~ngement wh1ch includes an ax~ y mov~ble p1ston member 78 wh1ch 1s sl1dably rece1ven on the outside diameter ~f the dri~e tube 44 as shown. The p1ston member 78 ~s formed wlth two serles of concentrlc c1r-cular rows or r1ngs of serrated teeth on cne ax1al face, an outer r1ng of serrated teeth 80 and an 1nner r1ng of serrated teeth 82. The 1nner r1ng of serrated teeth 82 is adapted to be meshed wlth a corresponditlg r1ng of serrated teeth 8~ mach1ned 1nto the interior or under surface o~ the rotat1ng serrated tooth coupl1ng plate 22, wh11e the outer r1ng o~ serrated teeth ~0 1s adapted t~ be meshed wlth a correspondtng r1ng o~ serrhted t~eth 86 on the un~er surface or 1nterior of the flxed serrated tooth r~ng 38.

As descrlbed 1n ~reater deta11 in the aforementloned copending Can-adian patent application 396,444, this arrangement can pro-vlde an enormous number ot accurate, repeatable, discrete 1ndexed pos1t1Ons by havtng a dlfferent number of teeth in the inner rings of serrated ~eeth 8? and 84 ~s compared to the outer rings of serrated teeth 80 and 86.

For example, the 1nner r1n~s of serrated teeth 82 and 84 may 1nclude 576 mat1ng teeth, whlle the outer rings of serrate~ teeth 8~ and 86 may ~ncl~de 625 teeth which glves a total number of dlscrete posltlons equal to 360,0~.

Thts lndexlng reQu1res n rotatlon of the p1ston mæmber 78, as well as the top plate assembly 12~ To ach1eve th1s potent1ally large number of lndexed poslt1Ons~ the piston member 78 must also be rotatable through 360-.

ln the arrangement shown in Figure 1 a gear r1ng ~8 ls afflxed to the outslde di~neter of a reduced o1ameter pllot sectlon 90 of the plston member 78 secured together by ~eans of a seriPs of cap screw 92 located by means of dowels 940 The gear rlng ~8 includes an outer ser1es of gear teeth 96 ln mesh t~1th 2 drive gear ~X rotatably mounted within the base castlng 40.

The dr;ve gear 98 ls m~unted on a driveshaft 100 tYlth a reduced d~met~r end 102 supported in sll~tablo he~rl~gs 104, th~ opp~stte end of the drlYeshaft ~00 being mounted in bearinqs 10G. The beartngs 106, in turn, are recelved in a closure plug 108 mounted by means of cap scret~S 110 to the base castlng 4Q, and a suitable closure seal 112 i5 provided.

An lnterlor Dpenlng 114 is mach1ned 1nto the base castlng 40 to recelve the drlveshaft 100 and other COmpQnentS. A suitable plug and openlng 116, for lntroduclng sultable lubricant lnto the space is provlded.
A breather vent 118 ls ~lso provlded to enable the addltlon of lubr k ant.
The driveshaft 100 is ad~tpted to be rotated by a suitable gear drive assen~ly 120 in mesh with a worm gear 122 which in turn is driven by a suitable gear train and drive motor (not shown) in similar fashion to the arrangement shown in copending Canadian application Serial ~tber 396 444.
2Q The gear drive assembly 120 is secured by means of a key 124~ with a thrust bearing 126 being provided.
In order to dbsorb the thrusting loads during rotatlon of the p1ston member 78, a sultable thrust roller bearlng 128 1s provlded posl-tioned a~a1nst the end face of the gear ring 8~ as shown w1th a wear pl~te 130 belng poslt10ned ngalnst ~t shoulder 132 nachined ln the base castlng 40.
Sultable openings 13~ and 136 are prov~ded to enable conmunicat10n therethrough of hydr~lIlic fluid~ which are introduced ln order to provlde the actu~tlon of the piston member 78 as will be described.

~Lq~Ç~O

The ~1ston mcm~er 7~ is acIc~Dted to be axially a~vance~ to brlng the r1ngs of serrated teeth 80 and 82 into en~a~ement w1th the rlngs of serrated teeth 86 and 84 by flutd pressure means which includes d hydraul1c c1rcu1t 13&. The hydraulic circuit is prov1ded wlth suitable regulators and valvtng (not shown) such as to control the appllcatlon of a hydraul1c flu1d pressure via a passa~e shown at 140 into the cav~ty 142.
The cav~ty 142 ls defined by the en~I face of the plston me~ber 78. The lnterlor of a ~ore 141 1n the bas~ cast~n~ 4~ r~celves the p1ston ~ember 78 and the 1nter10r face of the flange 5? of thP ~rive tube 44. Su~tab~e seals are prcv1ded lncludlng a seal 144 extend1ng between the per~phery of the gear r1ng 88 an~ the 1nterior cf the bore 141. The p1ston member 78 is rece1ved onto the exter10r of the ,Ir1ve tube 44, w1th a seal 146 being disposed there~etween. A st~al 1~ ~xtends al~out the perlphery of the flange 5~ and seallngly en~ages a bore ld'j formed in the base casting 40.

Upon actuat~on of the cnntrols and the lntroduction of hydraulic pressure ~nto the cav1ty lq2, the top plate a~ser,7~1y 12 is forced to the l~ft as shown ln Flgure l or down~ardly in the horizontal Pcsitlon wh~le the p~ston member 78 1s forced to the ri~ht tendlng to move the rings of serrated teeth 80 and 82 into meshing en~agement ~;1th the rings of serrated teeth 84 and 86, respect1Yely, ~hile in the locked-up or index poslt~on.

The area subiected to hydraultc pressure on the flange 52 is less than the ~rea of the bottom of the piston member 78 lnclud1ng the gear rlng as. There ls thus a net upward force ~enera~ed lnsur1ng that after the rlngs of serrated teeth 8~ and 84 are ~rought into mesh, the r1ng of 2S serrated teeth 80 ls forced upwardly or to the r~ht, as shown ln F1gure 1, lnto engagement with the r1ng of serrated teeth 8~.

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In order to provlde disengagement of the rtngs of serrated teeth 82 and 84 and 80 and 86, there ls prov1ded m~ans for generat1ng a fluld pressure force acting to axially move the plston member 78 to d1sengage the serrated tooth Hirth coupling. Tlle force generat1ng means 1ncludes a pneumat1c circult 150 havinq a sultable regulator, f11ter, etc., to produce 2 controlled air pressure into a passage 152 com~un1catlng w1th a c~vity 154, 1ntermedlate the end face of t~e piston member 78 and the serrated tooth plate 22. A sultable seal 16~ 1s mounted about the outs1de diameter of the p1ston member /~, and a furth~r sedl 1~ is provlded along the per~hery of a oore 15~ fonmed in tl-e piston member 7~. A seal 160 1s mounted intermedlate the rotating scrrate~ tooth coupl~ng plate 22 and the f~xed coupling serrated tooth r1nc 38 to comDlete the sealing of the cav1ty 154.

~-rlng seals lfi2 and 16i are ~rnvided at the interfaces bet~een the fixed coupllng serrated tooth ranq 38, the drive tube 44, and the rotatlng serrated tooth coupling plate 22 to further 1nsure that no leakage of air pressure from the cavity 154 ~ill oecur.

lhe pneumatic circu1t l5n appltes ~ const~nt air pressure 1n the cavlty 154 actlng to separate the rings of serrated teeth S0 and ~6, and 82 and 84, axially moving the p1ston member 7~ to the left as sh~ln tn Figure 1, or downwardly in the vertical hor1zontal mountlng of the table.

The hydraullc pressure intro~,uced tnto the cav1ty 142 is substan-t1ally h1gher, i.e. on the order of 1000 psl, then the pneumatie pressure wh1ch 1s introduced as the negulator pressure, which 1s preferably between 2S 40 and 60 ps1. The hydrau11c pressure ~n the cavity 142 overeomes thepneumatic pressure existing 1n the cavity 154 to produce ~ controlled enga-gement ~nd d1seng~gement of the p1ston member 7~ and the r1ngs of serrated te~th 82, ~4, 80 ~nd 8~.

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Accord~ng to the c.oncept of the presont invention the ball bear1ng assen~bly 30 1s provided ~ith a predeternlined d~gree of play or looseness both rad~all~ and axially such that as the plston member 7~ ts stroked lnto locked posltlon hlth the H~rth coupllng teeth engaged the ball bear1ng assembly 30 does not constrain the posit~on Or the s~rrated tooth coupllng plate Z2 either radially Gr ~xi~lly durlng the full seat1ng of the Hirth coupllrlg teeth. This ~s sho~n in exaggerated fashion 1n F1gure 2, the piston member 78 sl-own ~n d loc~ed ~05ition w~th the r1ngs of serrated teeth 80 and 86 an~ 32 and 84 in full ~nga~ement. ln this posltion clearanee st111 exists bet~een the raceways 36 and 34 and the bearing balls 32 as shown in exaggerated fashi~n i~l Figure 2.

Alo, in this positioll the under surface 166 of the table top plate 14 ~s located against the upper or outer surface 168 such that the f1xed coupltng serrated tooth rinc 38 affords max~mum r~gldlty of the 1~ table top plate 14 ~n the locked position for resisting heavy machlnlng loads such as in broacllin~ operations. This serves to relnforce the rigi-d1ty afforded by the serrated t~eth thelnselv2s.

Upon release of the hy~raulic pressure the air pressure actlng ln the cavlty 154 aga1n ls exerted on ~lle top plate assembly 12 causing llft~ng or ax1al moYement to the right as sho~r ir. Figure 3. Thls has two very s19nlficant effects.

F~rstly, the clearance 1n the bdll hear~ng assembly 30 ls taken up by upward moven~nt of the rotating serrated tooth coupling plate 22 unt11 the ball bearing assembly 30 1s loa~e~ to cause a preloading of the ball bear1ng assembly 30 and el1m~nstion of all the excess clearance as shown 1n exaggerated form 1n F~gure 3 The movement whlch 1s sufflc~ent to take up the play ln the ball bearing assembly 30 also causes the openlng of a gap between the under surface 166 of the table top plate 14 and the upper sur-face 168 o~ the f1xed coupl1ng serrat~d tooth r1ng 38.

1~l99C~5~) Thls enables the indexlng rotatinn of the top plate assembly 12 w1th the r1ngs of serrdted teeth 80 and 8~ and 84 and 86 d~sengaged, as shown, wh11e avoid1ng wear whlch would no~lally result lf the surfaces 166 and 168 were left 1n enga~e~ent dur1ng in~ex~ng rotatlon.

At the same time, the preload~ng of the ball bearlng assembly 30 w1th the table 1n 1ts rotary or unlocked position, enables a relat1vely prec1se rotation of the top plate ~ssembly 12 such as could be Pmployed dur1ng contour1n~ or mach1n~ng operations reqlliring conttnuous rot3t10n of the ta~le top wtthout necess1tat1ng prects10n bearlngs or encounterlng the d1fflcult1es in achieving reliable full seating of the r1ngs of serrated teeth 80, 86, 82 and 84.

The t~ble 1s thus usable for both of these purposes.

It ls important that the surfaces lfi6 ~nd 168 be parallel and 1n engaqement w1th th~ serrated tooth coupl~ng 1n a locked up conditlon~ It 1s also important that the upper surface 15 of the top plate assembly 14 be ~n close parallelism with the plane generated by the coupling teeth ~n the various indexed pos~tions. ~his parallelism is achieved during Inanufacture of the table by the hy~raulic clrcuit 136 actuatlng the p1ston member 78 such ~s to cause en~agement of the rin~s of serrated teeth 82, 84, 80 and B6, in successi~e index pos~t10ns to locate the plane by a su1table engaglng of the upper surface 168 of the serrated tooth coupling plate 22. ~hese - surfaces are ground as by a grinding wheel 170 causlng the surface l66 and surface 168 of the rotating serrated tcoth couplin~ plate 22 to be formed parallel to the coupllng plane, 2nd also flush with each other such as to proY1de ~upport of the under surface 166 of the table top plate 14 1n the locked pos1tions.

3 1~9~,5~

Thus, upon reinstalla-tlon of the tahle top rlate 1~ the upp~?r sur-face 15 of the table top plate 14 is a1so parallel l~ith the surfaces 166 and 168 and wlth the plane g~nf?rated h~ the coupling. It can be seen that the necessary preclslon ls achle~ed relatively slmply without requlrlng a hlgh degree of prec1s1On of the mat~ng components.

Ref~rrlng to F1gure ~, ~ fluid pressure bearing preloadlng arran~ement accord1ng to the concept of the present lnvent~on ls provlded ln a d~f~erent concept for a rotary table 174 ~hl~h Inc7udes a table top assembly 176 1nclud1ng a top plate 17~ ha~lng an t~pper surface 180 adapted to have a part to be rot~ted mounted therE~to.

The top plate 178 of the ro~ary tabl~.? 174 ln the embodiment of F~gure 5 1s capable of hor1~ont~l or~entation only.

The top plate 178 is securf?d to a rotating serrated tooth rlng 18~ by means of a series of cap screws 184 ~n a prec~slon ke~vwaj 186 secured by a machlne screw 188. The serraterl tootk r1n(l 182 1s prov1dcd wlth w1per seals 190 and 194 actinQ on the periphery of the rotattng serrated tooth ring 182 and ~n ~nterlor bore 192 ~f ~ ftxe~ serrated tooth ring 196 located ln allgnment therew1th 2nd concentric to the serrated tooth r1ng 182. The flxed serrated tonth rin~ 1g~ in turn is secured with c~p screws 198 and doweling 20D to a base castlng 202 to prnvide relatiYe fixlng of the serrated tooth ring 19b with respect to tlle rotating serrated tooth ring 182. The wtper seals 190 and 1~4 prEvent the escape of air pressure from an internal caYlty as ~11ll be described. A sll~table gasket 204 is prov1ded betweE!n the top plate 17R an~ t~e rotatlng serrated tooth rlng 182. A
L~ gasket 20h is prov1dE?d ~etween the serrated tooth ring 19fi and a shoulder 208 mounted ~n th~? base castiny 202.

The rotatlng serrated tooth rlng 182 ~s connected to a dr1ve tube 210 by me~ns of cap screws 212 and accurately loc~ted by ~eans of a precl~
~ion key 214 secured by mach1ne screws 21~, wlth a seal 218 se~l1ng the lnterf~ce.

I

S Tha drlve tubQ 210 1s adapted to be rotated to thereby rotate the table top as~embly 17~ by me~ns of a drlve clear 220 secured thereto by me~ns of cap screws 222 ~nd a key Z24 s~cure~ w1th machlne screws 226. The drlve gear 220 1n turn 1s adapted to be rotated by means of a dr~ve asse~bly lncludlng the dr1Ye ~ear 228 and drlve motor (not shown).

A vent passage 230 1s prov1ded to the openlng hcustng th~ dr~ve gear 22B, ~lth ~ vent plug 236 belng prov1ded. A flll pass~ge 234, h~v1ng ~ plug 232~ 1s provtd~d and 1s ln com~un1cfltlon wlth a cross pas~a~a 238, ha~lng ~ ~lu~ 240. ~he cross passage 238 e~pttes lnto tha vent pass~ge 230 to enabla lubr1c~nt to be ~dded. A suttable draln p~ss~ge 242, plu~ 244, cros5 p~ss~ge:~4~ and plug 248 ~re also provtded to en~ble the lubr1cant to be drs1ned thare~rom.

An axlall~ movable plston member 250 ls also provlded h3vlng lnner and--outer rlngs of serrated teeth 252 and 254, respectlvely9 whlch mate ~l~h a correspondlng rlng of serrated teeth 256 formed on the under surface of the rotat1ng s~rrdted tooth r1ng la2 and a r1ng of serrated teeth 25R formed on the under surface of the f1xed serrated tooth r1ng 196. The p1ston member 250 1s adapted to be axlally moved so as to move the serrated teeth lnto and out of engayement.

The serr~ted teeth are moved lnto engagement by the appllcst1On of hydr~ullc prQssure 1nto a c~vtty 260 1nter~7edlate a flange portlon 262 of the drlv~ tub~ 21~ ~nd the under ar back surface of tho pl~ton ffle~er 250.

The piston member 250 is slidably received over an outs1de d1ameter 264 of a huh 266 on the drlve tube 210 belng used for this purpose. The cav1ty 260 1s sealed by means of seals 268 and 270, and an 0-r1ng seal 272 such as to enable rotat10n of the drive tube 2l0 and ax~al movement of the p~ston member 250.

In th~s embodlment, the piston member 250 1s not rotated and thls a~fords fewer 1ndexed positions, which may be adequ~te for the purpose for ~h1ch the table 15 to be employed. Thus, the piston member 250 ls adapted to be ax1ally mov~ble only, but 1s connected to rotate with the dr1ve tube 210 and the rotat1ng serrated tooth ring 182. For this purpose a plug 274 1s provlded dlsposed ln a bore 276 mach1ned ~nto tlle upper face of the p1ston ~ember 250 and hav1ng a flat s~ded portion 278 extend1ng 1nto a correspon~lng ~achlned opentng 28Q formed in the rotatlng serrated taoth ring 182. A plug 284a is provided to close one end of the openlng 280.
Hydraullc pressure ls ~ntroduced in a cross passage 284 and recelved vla ~
sultable hydraulic circ~it 286 lndicated diagrammat1cally. A proxim1ty sen-sor 288 may be prov~ded for deter~ining the zero poslt~on thereof, as d1sclosed ln U.S. Patent No. 4,353,271, lssued on Cctober 12, lg82.

Upon 1ntroduct~on of hydraullc pressure 1nto the cavity 260, the piston member 250 1s axlally stroke~ upwardly, as shown tn Fi~ure 5, to bring the serrated teeth lnto enga~ement and lock the tab~e ln posit~on.
To disengage, air pressure is lntroduced into a cavity 290 intermed1ate the under surface of the rotat~ng serrated tooth rlng 182 and the upper face of the ptston member 25Q ~J1th the gasket 206, wiper seals 190 and 1S4~ and seal 218 sealln~ uff thls cav~ty~ The alr pressure is lntroduced vla a cross o~o passage 292 suppl1ed from a pneumat1c circu1t 2g4 of ~ suit~ble des1gn whlch may include such conventional components as a ~llter~ regulator, safety sw1tchlngg etc. Air pressure is continuously appl1ed in the cav1ty 290, such that upon rel1ef of the relatively h1gher hydraulic pressure 1n the cav1ty 260, the serrated teeth are 1mmediately separated by w1thdrawal of the p1ston member 250 u~der the ~nfluence of the a~r pressure 1n the cavlty 2~0.

The rotary table top assembly 176 is rotatably supported on the base castlng 202 by means of ~TURCITE" (trademark) bearing r1ngs 296 whlch are lnterposed between the under surface 298 of the top plate 178 and the upper surfa~e 300 of the base casting 202 to provide the rotatable support necessary for carry1ng the we~ght of the ta~le top assembly 176 and enablins rotation of the table by drlv1ng of the drive tube 210. In this embodiment9 the table 1s adapted to be urged downwardly, as shown ln F19ure 5, by the appllc~tton of alr pressure 1n the cavlty 2SO. This 15 achleved by the back surface 302 of the p1ston member 250 engaying a front surface 304 of the flanye portion 262, caus1ng a do~:n~ rd forcP to be exerted on the table top asse~bly 17fi upon appltcat10n of fluid pressure 1n the cav1ty 290, to thus preload ~he "TURCITE" bearlnq rlngs 296.

To enable a proper loading to be applled to the ~TURCITE~ bear1ng r1ngs 296, regulation of the air pressure may easlly provide the correct amount of preload pressure.

It can be appreciated th2t the fluid pressure engagement arrange-ment has been employed in these embodiments to ach1eve very s19n1f~cant 1mprovements to both of these embodi~ents ~lithout inYolvir,~ ma~or addltional structure or complexity. ~any varlations of these spec1fics are Gf course poss1ble.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A rotary table of the type including a table base, a table top assembly rotatably mounted on said table base, bearing means rotatably supporting said table top assembly on said table base, and means for rotating said rotary table on said bearings means, the improvement comprising: fluid pressure means acting on said table top assembly to preload said bearing means.

2 The rotary table according to claim 1, further com-prising a first ring of serrated teeth carried by said table top assembly and an axially movable piston member within said table base, said axially movable piston member being formed with a second ring of serrated teeth corresponding to said first ring of serrated teeth and adapted to be brought into meshing engage-ment therewith upon axial movement of said axially movable piston member toward said table top assembly, and means for moving said axially movable piston member to cause engagement and disengage-ment of said serrated teeth.

3. A rotary table comprising: a table base; a table top assembly rotatably mounted on said table base for rotation about a rotation axis and adapted to be urged therealong; bear-inq means rotatably supporting said table top assembly relative to said table base and having a preloaded state in which said bearing means are preloaded to permit a continuous precision rotation of said table top assembly relative to said table base and a non-preloaded state wherein said bearings means are substantially not preloaded to allow an imprecise rotation of said table top assembly relative to said table base;
an axially movable piston member interposed said table top assembly and said table base and adapted to move along said rotation axis in a first axial direction and a second axial direction opposite to said first axial direction;
first fluid pressure means coupled to said table base by a first fluid coupling and adapted to communicate a first pressure fluid therethrough to a first side of said axially movable piston member and said table top assembly, said first fluid pressure means having an actuated state wherein said first pressure fluid applies a preload pressure to said table top assembly and said first side of said axially movable piston member; and controllable rotation means for controllably rotating said table top assembly relative to said table base;
whereby, with said first fluid pressure means in said actuated state, said preload pressure establishes said preloaded state by urging said table top assembly in a preload direction relative to said table base.

4. The rotary table of claim 3, wherein said controllable rotation means comprises indexing means having an indexing mode for allowing an indexed rotation of said table top assembly between successive predetermined indexed positions, said indexing means adapted to effect said indexed rotation during said indexing mode.

5. The rotary table of claim 3, wherein said controllable rotation means comprise contouring means having a non-indexing mode for allowing said continuous precision rotation in accordance with a predetermined contour, said contouring means adapted to effect said continuous precision rotation during said non-indexing mode.

6. The rotary table of claim 3, wherein said preload pressure in said preload direction urges said table top assembly away from said table base.

7. The rotary table of claim 3, wherein said preload pressure in said preload direction urges said table top assembly towards said table base.

8. The rotary table of claim 4, wherein:
said table top assembly carries a first ring of serrated teeth;
said axially movable piston member has a first axial side carrying a second ring of serrated teeth, said axially movable piston member adapted, when moved in said first axial direction, to effect a meshing engagement of said first and said second rings of serrated teeth and further adapted, when moved in said second axial direction, to effect a disengagement of said first and said second rings of serrated teeth; and second fluid pressure means coupled to said table base by a second fluid coupling and adapted to communicate a second pressure fluid to a second side of said axially movable piston member, said second fluid pressure means having an engagement state in which an engagement pressure is applied to said second side of said axially movable piston member to cause said meshing, engagement and further having a disengagement state wherein said engagement pressure is released to allow said disengagement.

9. The rotary table of claim 8, wherein, with said second fluid pressure means in said engagement state, said engagement pressure is greater than said preload pressure to move said axially movable piston member in said first axial direction to cause said meshing engagement while also establishing said rotatable bearing means in said non-preloaded state, and further wherein, with said second fluid pressure means in said disengagement state, said preload pressure moves said axially movable piston member in said second axial direction to effect said disengagement while also establishing said bearing means in said preloaded state.

10. The rotary table of Claim 8, wherein said table top assembly has an outer surface and includes a removable top plate having a top surface and an under surface, said outer surface being adapted to abuttingly engage said under surface of said removable top plate, said outer surface and said top surface being ground at successive assembly with said first and said second rings of serrated teeth in said meshing engagement.

11. The rotary table of Claim 10, wherein both of said top and outer surfaces are ground parallel to a plane generated when said first and second rings of serrated teeth are successively indexed between said successive predetermined indexed positions, said outer surface being ground with said removable top plate removed and said top surface being ground with said removable top plate thereafter mounted on said table top assembly.

12. A rotary index table comprising:
a table base;
a table top assembly rotatably mounted on said table bases rotary bearing means rotatably supporting said table top assembly on said table base;

a first ring of serrated teeth carried by said table top assembly;
an axially movable piston member mounted within said table base, said axially movable piston member being movable towards and away from said first ring of serrated teeth;

a second ring of serrated teeth carried on said axially movable piston member, said second ring of serrated teeth being adapted to be brought into a meshing engagement with said first ring of serrated teeth carried by said table top assembly upon axial movement of said axially movable piston member towards said first ring of serrated teeth;
means for moving said axially movable piston member to selectively cause engagement and disengagement of said first and second rings of serrated teeth such that said first and second rings of serrated teeth cooperate to provide indexed positions of said table top assembly in discrete rotated positions; and first fluid pressure means acting on said table top assembly to preload said rotary bearing means.

13. The rotary table of Claim 12, wherein said rotary bearing means comprises ball bearing means, said ball bearing means further comprising:
a first groove in said table base;
a second groove in said table top assembly overlying said first groove;
a series of bearing balls each disposed partly in each of said first and second grooves, said ball bearing means being provided with a predetermined amount of play, such as to enable full seating of said first and second rings of serrated teeth prior to seating of said series of bearing balls on said first and second grooves; and further wherein said first fluid pressure means preloads said ball bearing means upon activating said first fluid pressure means, so as to cause said preloading of said rotary bearing means only when said first and second rings of serrated teeth are disengaged.

14. The rotary table of Claim 13, wherein said first fluid pressure means acting on said table top assembly to cause said preloading of said ball bearing means further comprises means for causing fluid pressure to be exerted on said axially movable piston member in a first predetermined direction tending to disengage said first and second rings of serrated teeth, such that said first fluid pressure means causes disengagement of said first and second rings of serrated teeth and preloading of said ball bearing means.

15. The rotary table of Claim 14, wherein:
said table top assembly further comprises a top plate with a lower surface formed thereon;
said table base further comprising an upper surface formed thereon, said lower surface overlying said upper surface when said first fluid pressure means is deactivated and when said first and second rings of serrated teeth are in meshing engagement; and said first fluid pressure means raises said lower surface of said table top assembly away from said upper surface of said table base when activated.

16. The rotary table of Claim 14, wherein:
said axially movable piston member has a first side and a second side;
said first fluid pressure means is constantly applied to act on said first side of said axially movable piston member;
said means for moving said axially movable piston member comprises:
second fluid pressure means acting on said second side of said axially movable piston member, said second fluid pressure means being selectively operable to cause said axially movable piston member to move to range said first and second rings of serrated teeth; and means for counteracting the effect of said fluid pressure of said first fluid pressure means acting on said first side of said axially movable piston member which is tending to cause disengagement of said first and second rings of serrated teeth, so that said preloading of said ball bearing means is overcome upon actuation of said second fluid pressure means to cause engaging movement of said axially movable piston member.

17. The rotary table of Claim 16, wherein:
said axially movable piston member comprises a generally annular piston;
said table base includes a drive tube;
said axially movable piston member is slidably mounted on said drive tube;
said drive tube further includes a flange portion located on said second side of said annular piston; and said second fluid pressure means further comprises a fluid pressure cavity defined by a first surface of said flange portion adjacent said annular piston and having a first predetermined surface area, a second surface of said annular piston having a second predetermined surface area, and bore walls formed in said table base, whereby, upon actuation of said second fluid pressure means causing pressurization of said fluid pressure cavity, said table top assembly is biased in the direction opposite said first predetermined direction to cause said preloading by said first fluid pressure means, and said second ring of serrated teeth is urged into engagement with said first ring of serrated teeth.

18. The rotary table of Claim 17 further comprising:
a third ring of serrated teeth carried by said table top assembly and a fourth ring of serrated teeth formed on said annular piston and adapted to be brought into meshing engagement with said third ring of serrated teeth upon axial movement of said annular piston in said first predetermined direction; and wherein said first predetermined surface area of said flange portion subject to said fluid pressure in said fluid pressure cavity is less than said second predetermined surface area of said annular piston subjected to said fluid pressure and further wherein said fourth ring of serrated teeth of said annular piston is urged into engagement with said third ring of serrated teeth after engagement of said second ring of serrated teeth with said first ring of serrated teeth.

19. The rotary table of Claim 12, wherein said table top assembly is supported on low friction resilient thrust bearings and wherein said first fluid pressure means urges said table top assembly downwardly into engagement with said low friction resilient thrust bearings to achieve said bearing preload.

20. The rotary table of Claim 19, wherein said table top assembly includes flange means abutted by said axially movable piston member on said second side thereof; said fluid pressure of said first fluid pressure means being exerted on said flange means, whereby said table top assembly is drawn out of engagement therewith and preloads said low friction resilient thrust bearings.