STO

Technical characteristics

Support rollers are either needle roller or cylin- drical roller bearings with an extra radially thick outer ring.Depending on their series,support ro- llers may be both separable and non -separable

radial bearings.

Support rollers usually run with their outer ring either directly on a guide track or against a ma- chine surface that is for guidance.

Due to their extra-thick outer rings,support ro- llers are able to accept high radial forces as well as shock loads.

Their ability to accommodate axial forces,howe- ver,depends on the particular design of the su- pport roller.

Support rollers are usually exposed to minor mi- salignments during operation.To minimize the negative  effects  of  such   misalignments,(e.g. high edge stresses),support rollers are more fre-

quently used with sphered outer rings.

VEO support  rollers with  parallel  (cylindrical) outer diameters are indicated by the suffix X.

 

Standard design variants

In order to cover as many applications as possi- ble,VEO Support rollers are available in several different design variants as standard.

To provide simple re-lubrication,all support ro- llers have lubrication holes in their inner rings.

 

Support rollers without axial guidance

The most simple design of support rollers is pro-vided by the STO type rollers

For these rollers the outer ring,inner ring and the needle roller and cage assembly may be fit- ted separately.Since  STO type  support  rollers  do not  provide  any  axial guidance

to their needle roller  and  cage  assembly they adequately accept radial loads only.

The axial guidance of outer ring and needle roller and  cage  assembly  must be provided  by  a  suitable design of  adjacent  machine  parts.

STO  type  support  rollers  are  frequently  used  wi- thout  their  inner  rings,namely RSTO rollers.The needle  roller  and  cage  assembly  of  RSTO type su-  pport  rollers  run  

directly onto the shaft surface, which  must  be  designed  in  an  adequate  manner, (e.g.hardened and ground).

STO and  RSTO  type  support  rollers  are  the  only  support  rollers  that  are  satisfactory  for  operating with  oil   lubrication.

Unlike  the  STO type support  rollers,the  outer ring,and  the  needle  rollers  and  cage  assembly  of series NA22..-2RSR  build a  unit,whilst  the  inner ring  may  be  dealt   with individually.

NA22..-2RSR   type   support  rollers  also  accommo- date  radial  loads  only.They  also   require  adequa- te  axial  guidance  of  their  outer  rings  by  adjacent parts.

Due  to  the  contact  seals,which  are  integrated in  their  outer  rings,NA22..-2RSR  type  support rollers  provide  the  possibility  for maintenance-  free  bearing  arrangements.

Sealed  support  rollers,without inner  rings,are also  produced,namely  RNA22..-2RSR.For  these types both the needle rollers and the rubbing seals  run  on  the  contacting  shaft  surface.

 

Support rollers with axial guidance

These types of supporting rollers are able to ac- commodate additional thrust loads as they occur due to aligning errors or if rollers run out of line.

That is why no extra external guiding surfaces are required.

Where high axial loads are anticipated effective axial support of side washers must be achieved by theadjacent machine components.

Support  rollers,type  STO..-2Z

STO..-2Z type support rollers are designed similar to the STO type but have two loose side plates to accept axial forces.

These types of support rollers are separable,this enables simple mounting of the rollers due to the separable parts.

Particular attention must be paid to the adequa- te axial clamping of loose side washers during mounting.The side plates of STO..-2Z type su-  pport rollers must not have any axial play when

they are mounted.

Support  rollers,type  NATR

The side washers of NATR type needle roller su-  pport rollers are pressed into the inner ring to ensure guidance of the outer ring and the needle roller and cage assembly.

Therefore,these roller types are non-separable. NATR type needle roller support rollers are opti- mum for applications where the rollers are expo- sed to high radial loads at high speeds.

The sealed support rollers,namely,NATR..-PP which feature integrated rubbing seals on each side of the outer ring are very suitable foropera- ting in harsh conditions(e.g.heavy dust,dirtand

other contaminates).

Support  rollers,type  NATV

NATV-type rollers  are  identical to the  NATR  type except  they  have  no  fitted  cage  (i.e.full  comple- ment   type).

This enables anincreased numbers of  needle ro- lers  to  be  fitted  in  the  available  space  (i.e.cir- cumferentially  and  radially).Therefore,signifi- cantly higher  basic  load  ratings  are

achieved.

NATV type  full  complement  rollers  are  unsuitable for  high  speed  applications  due  to  the  differing kinematic  operating  condition.Also  they  must  be re-lubricated more  frequently.

For  applications  of  harsh  operating  conditions  the sealed  support  roller,namely,NATV..-PP  is   also available

Support  rollers,type  NUTR

The  base  internal  design  of  NUTR  type  support rollers  is  non-separable and similar  to  that  of  do- uble  row   cylindrical   roller   bearings.

Since the outer ring has  two  shoulders  these  su- pport  rollers are  able  to  accommodate  greater thrust  loads.

The  separate  loose  ribs  of  these  types  are  retai- ned   with    cupped    pressed    steel   washers    press- fitted   into   the   outer   ring.These   washers   also   act as  gap  seals.

Thanks  to  their  full  complement  design,NUTR  type support    roller    feature    a    maximum    load    rating. They   must    be   more   frequently    re-lubrication.

For  extra heavy  duty  applications,particularly where  heavy  shock  loads  occur  NUTR  type   su- pport   rollers  are  available  with   an  extra-radially thick   walled   outer   ring.

VEO's  extra  heavy duty  NUTR  type  support  rollers with  an   increased  outer   ring  wall  thicknessare identified  by  the   fact  that   their  nominal   diame- ters  are  included  in 

their  designation.

Examples :  NUTR 50110

Where: 

Inner ring  d=50mm

Outer ring  d=110mm

All VEO support rollers are produced with crow- ned outer ring as standard they are also available with parallel (cylindrical)outer ring indicated by the suffix X.

Support   rollers,type   PWTR..-2RS

The  internal design of non-separable support rollers PWTR..-2RS is similar to the doublerow cylindrical roller bearings.

The three integral ring of the outer ringsallows it to  accept  high  radial  loads.The  inner  rings are fastened with washers stamped on the outer ring.

These washers incorporate external lip seals that provide efficient lubrication.

Support   rollers,type   NNTR..-2ZL

The internal design of the support rollers NNTR..- 2ZL is non-separable and similar to the double row cylindrical roller bearings.

The inner rings are supported by rings that act as labyrinth seals.

They are therefore effectively sealed and protec- ted against harsh and polluted environments.

 

Material of seals

Several types of VEO support rollers,such as se- ries NA22..-2RSR,NATR..-PP und NATV..-PP are also available in sealed versions.

These  support  rollers  feature   contacting  seals made  from  a  wear  -resistant  synthetic  rubber compound(NBR)that  provides  an  efficient  and effective seal against the  penetration  of

impuri- ties or the escape of grease.

The  synthetic  rubber  used  for  these  contacting seals  is  satisfactory  for  operation  temperatures of  -30℃up  to+120℃(-22°F  up  to  +248°F).

 

Lubrication

All VEO support rollers are already supplied filled with  a  high  quality,lithium-soaped  bearinggrea- se as standard.

This  lubricant  is  adequate  for  operating  tem- peratures  of  -30°C  to  ca.+110℃(-22°F  up  to +230°F).

Although support rollers under normal operating conditions   usually   run   maintenance   -free,they may  require  more  frequent  re-lubrication  under  certain  unfavourable  operating

conditions  such as heavy dust,high speeds,permanent operating temperatures  of  more  than  70℃(+158°F),and  thepresence of increased  humidity  etc.

Therefore a VEO support rollers feature a lubrica- tion hole in the inner ring to provide the possibili-  ty of re-lubricating the rollers,when necessary.    It  must  be  considered

whererelubricationis  ne- cessary,with  a  satisfactory  grease,the  force  of pressure to re-grease must be of a level not to cause permanent damage to either the seals or shields.

VEO also produce rollers with alternative grease fill according to customer's specification upon or- der  request.

 

Cages

VEO support rollers,with cages fitted,are nor- mally have pressed steel cages as standard.Only small support rollers without axial guidance,se- ries STO and RSTO,respectively,are fitted with solid

polyamide cages (suffix TVP),asstandard.

 

Tolerances

VEO support rollers are produced to normal to- lerance class(PN)as standard,according to DIN -standard DIN 620.

The exceptions being the outer ring outer diame- ter tolerance of crowned outer rings and the wi-  dth tolerance of supporting rollers of series STO ..-2Z,NATR,NATV and NUTR.

The tolerance for the outer ring diameter of su- pport rollers with sphered outer ring is uniform at 0/-0,05 mm.

The width tolerance of support rollers of series STO..-2Z,NATR,NATV and NUTR is lateral and lies inthe ISO-tolerance field h12.

The  tolerance  for  the  inside  diameter  of  the needle roller complement,(F),of RSTO and RNA 22..-2RSR type support rollers that are used wi- thout inner rings,is lateral in the ISO tolerance

field F6.

Values of ISO-tolerance fields F6 and h12 are listed in the table below.

 

Tolerance values of ISO-tolerance fields F6 and h12

ISO Tolerance field	Bore diameter(mm)
	>	3	6	10	18	30	50
	≤	6	10	18	30	50	80
F6	min	10	13	16	20	25	30
	max	18	22	27	33	41	49
h12	min	-120	-150	-180	-210	-250	-300
	max	0	0	0	0	0	0

 

Internal radial clearance

VEO  support  rollers  are  produced  to  normal  inter- nal   clearance   group(CN)as   standard   according to  DIN  620.

 

Load  carrying  capability

Unlike   normal   rolling   element   bearings,the   outer ring  of  support  rollers  contacts  the  adjacent  parts with  a  very  small  contacting  surface  only.

This   causes   deformations   of   the   outer   ring.These are    considered    by    the    recommended    maximum values  for  the   permissible   dynamic  and  static   ra- dial  loads  as  given by

the  product  tables.

 

Equivalent dynamic  load

Where   support   rollers   must   be   calculated   as   for rolling    element    bearings:

P=F,

But  P  must  be  ≤F,zul   (for  F,zul  see  product tables)

 

Equivalent static bearing load

For   support    rollers:

P₀=F,

But  P 。must    be<Fozul(for  F 。zul    see  product tables)

 

Design of adjacent machine components

For  support  rollers  of  the  series  STO,RSTO, NA22..-2RSR  and  RNA22..-2RSR,an   effective   axial guidance  of  the  outer  rings  must  be  provided  by satisfactory    designed 

surrounding  parts.

These  guiding  surfaces  must  have  a  clean  and plain  machined  surface,minimum  fine  turned, without  any  burrs.

These guide surfaces which are machined should reach  50%,or  greater,of  the  outer  ring  radial wall section or the equivalent diameter.

Hardened guide surfaces,however,feature a hig- her wear-resistance and may therefore be sma- ller in diameter.

RSTO and RNA22..-2RSR type support rollers that run directly on a shaft require an axial play of 0,2 mm minimum between the lateral guidingsurfa- ces in mounted condition.

The diameter of the supposed shaft raceway should have a diameter tolerance according to k5.

The shaft or pin have to fulfil certain require- ments in terms of hardness,dimensional and geo- metric accuracy.

For support rollers which are exposed to high axial loads,effective lateral support of their side washers is necessary.

Since support rollers usually have point loaded in- ner rings,their shaft fits may be rather loose,(i.e. according to ISO tolerance fields g6,h6 orj6).

 

Abutment and fillet dimensions

The bearing inner ring must contact adjacent surfaces with their side faces only.The radius of inner ring corners must not touch the fillet radius of shaft shoulder.

Therefore,the  largest  fillet   radius(rg)must  be smaller than the minimum fillet dimension of the Support roller inner rings (rs)as listed in the pro- duct tables.