Rod ends and spherical bearings Rod ends and spherical bearings Rod ends and spherical bearings Rod ends and spherical bearings Rod ends and spherical bearings

 

 

ROD ENDS AND SPHERICAL BEARINGS

INTRODUCTION

The rod ends and spherical bearings are mechanical junctions which, because of their internal geometry, are particularly suited for the transmission of static and dynamic forces, together with rotary, oscillatory and tipping movements.

They are standard products which are produced in accordance with ISO 12240-4 Series K and ISO 12240-1 Series K respectively.

The project takes into account the ever more stringent requirements of the market which calls for a reduced clearance, remaining constant with time, and completely maintenance free operation.

Main applications for rod ends and clevises:

  1. farm machinery
  2. construction / earth moving machinery
  3. automation / machinery manufacturers
  4. pneumatic cylinders
  5. automotive, motorcycles
  6. pumps
  7. gearboxes
  8. gates & doors
  9. gas springs
  10. flexible cables / push-pull cables

CHOICE OF ROD ENDS AND SPHERICAL BEARINGS

In order to make the appropriate choice of rod ends or spherical bearings it is important to know what their real application will be.

The type of load applied, static or dynamic, will be decisive for the correct dimensioning of the rod end or the spherical bearing.

Static Load

The static load means he maximum radial or axial load applied to the rod ends or spherical bearings in a static way, without oscillations or rotations, at room temperature, that does not cause permanent deformations or does not endanger its functionality.

The values of the maximum acceptable load were obtained by calculations and then checked on considerable samplings taken from our mass production.

Radial Static Load

The maximum acceptable radial static load for rod ends and spherical bearings is the one indicated on the dimensional table.

Axial Static Load

For the rod ends the maximum axial static load should not exceed the axial holding load of the joint on the head. Furthermore, it should be calculated basing on the length of engagement of the thread for the male type and on the male resistance connected to the female type. For the spherical bearings the maximum acceptable axial static load is the one indicated in the dimensional tables.

Criteria of use

Rod ends and spherical bearings are products, that do not need any kind of maintenance before or during operation.

As precision components they maintain their performances unchanged only if the following criteria are observed:

› keep them in their original packaging and stored them in a suitable place;
› during assembly avoid that foreign bodies might get between the inner and the outer ring;
› do not stress the outer ring during assembly/disassembly and do not put it in contact with any other parts outside the jodint itself during working;
› avoid shocks or damages during assembly.

Use of spherical bearings

It is essential that the assembly is made by following precise rules:

› To make easier the assembly, the end of the shaft and the one of the housing should present a chamfer with an angle between 10° and 20°;
› It is recommended to assemble the joint with a suitable bush (or tube) which sticks to the entire surface of the outer ring. However, direct blows to the spherical bearings should be avoided.
› In assembling the housing and the shaft, it is of primary importance to pay careful attention to the precision of the tolerances and to errors of form.

The chamfers of he shaft and of the housing should be inferior to those ones of the joint indicated on the dimensional tables.

The choice of the coupling should not be made by chance, since a too much high interference may cancel the radial play between the outer and the inner ring, considerably increasing he friction and so compromising the spherical bearing’s life. On the other therefore, the tolerances of he below mentioned table should be strictly followed.

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