Tolerance sleeve

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Tolerance sleeves , also called tolerance rings, can be used in a variety of ways as force-fit connecting elements - for example in pumps and drive technology , in compressors or in electric motors . Above all, users save costs, and connections that have been created once can be released again in contrast to pressing or gluing . Form-fitting connections such as feather keys or toothing are more complex and expensive to produce. Compared to other shaft-hub connections , tolerance sleeves are usually easier to handle.

Tolerance sleeves are an inexpensive shaft-hub connection. They are available in numerous designs.
The corrugation peaks, which are distributed over the entire circumference of the tolerance sleeve and act like many small compression springs, ensure a tight fit.
Application in the electric motor: The tolerance sleeve centers a stator in the housing and also fixes it against the torque forces of the rotor.
Use in a centrifugal pump: Tolerance sleeves are used as connecting elements in order to compensate for different thermal expansions of stainless steel and silicon carbide in the area of ​​the pump's slide bearings.

Basic structure

Tolerance sleeves are slotted sheet metal sleeves in which beads are embossed like wave crests. The tolerance sleeve sits in the gap between the bearing bore and the shaft. The wave crests, which are distributed over its entire circumference and act like many small compression springs , ensure a tight fit. The wave crests are elastically deformed by a certain oversize of the tolerance sleeve. This creates a frictional connection between the bearing and the shaft . The tolerance rings can compensate center misalignments or different temperature expansions and prevent vibrations or fretting corrosion. If precise concentricity is required, the components to be connected are centered.

Compared to other connection types

Connections cannot be loosened again when gluing and pressing - with tolerance sleeves they can. And in contrast to the wedge and press fit , torque can be transmitted with tolerance sleeves. In addition, tolerance sleeves can be used to connect different materials without pre-treating them as with gluing. The user saves time and money during assembly. They take up little space and when installed they reduce vibrations and noise.

Areas of application

There are numerous areas of application for tolerance sleeves in shaft-hub connections . Challenges can be solved that arise in connection with offset, centering, vibrations, temperature expansion, excessive tolerances of the connection components or torque limitation.

With tolerance sleeves:

  • transmit indefinite forces as well as certain minimum and maximum forces
  • Implement simple applications without defined power transmission such as fastening of operating handles, armrests and spring tubes in seating furniture
  • Attach fan or rotary encoder to electric motors
  • Transferring low torques to pump wheels at low cost
  • Center the stator in the housing of an electric motor and fix it against the torque forces of the rotor
  • Transferring defined forces in drive technology - for example with belt pulleys, flywheels or gearwheels
  • Connect materials with different expansion coefficients - for example steel bearings in aluminum housings or ceramic bearings in pump technology
  • transmit certain torques or torque ranges.

For this purpose, the spring force of the tolerance sleeve can be designed in such a way that the seating force is ensured for a permissible range and the tolerance sleeve slips through when the force is greater. Damage to the components is therefore excluded in the event of an overload situation. In the case of applications as a slip clutch or overload protection, the tolerances of the add-on parts must be known precisely and not too large, and the tolerance sleeve must also be adapted accordingly, which is why the manufacturer must always be consulted.

Cost comparison: tolerance sleeve - feather keys

How the cost savings can actually have an impact is shown by a calculation example from the provider Dr. Tretter: Three toothed belt pulleys are to be attached to a shaft with a diameter of eight millimeters. A spring twelve millimeters long and three millimeters wide was selected as the key . This can transmit 5.8 Newton meters. A comparable tolerance sleeve is the BN08-515 for up to 5.7 Newton meters. Specifically, the cost of the three toothed belt pulleys for the feather key connection would be around 96 euros, and for the solution with tolerance sleeves, 75 euros. The same applies to the shaft: while the machining costs for the feather key connection are 71 euros, with the tolerance sleeves it is only around 28 euros, because they allow easier machining and better compensate for inaccuracies in the components. Only the tolerance sleeves themselves are more expensive at 1.20 euros - while the costs for the three parallel keys together are only 0.72 euros. For that accounts required for the key connection retaining rings worth 0.24 euros. In total, the cost of the key connection is 168 euros, and the solution with the tolerance sleeve is 104 euros. This saves around 64 euros per module, which is a cost saving of 38 percent.

Material selection

The material used for the tolerance sleeves is spring band steel , which in the stainless steel version can withstand temperatures of up to 250 degrees Celsius with constant spring properties. These rust-free, clean tolerance sleeves can be reliably manufactured. There are also many special materials available. This also includes the spring band material Hastelloy . The material is resistant to both oxidizing and reducing media and operating temperatures from −70 to 450 degrees Celsius.

Tolerance sleeves are available in various designs:

  • System unit shaft (AN type): The wave profile protrudes inwards. The ends of the tolerance sleeve are open. It is fixed in a groove in the bore and pressed onto a standard shaft (h9). The gap narrows when pressed with the shaft.
  • System unit bore (BN type): the wave profile protrudes outwards. The ends of the tolerance sleeve overlap. It is fixed in a groove on the shaft and pressed into a standard bore (H9). Since the tolerance sleeve is slotted, it can be fitted very easily.
  • Shape AL: A variant of the AN shape that was specially developed for smaller rolling bearings . It has a lower shaft height and is made of a thinner material so as not to affect the internal clearance. This tolerance sleeve is only designed as a slightly curved strip.

Installation

The tolerance sleeve is installed “freely” or “centered”.

The free installation

  • does not require any processing of the connecting parts
  • is recommended if the radial load does not exceed the permissible radial load of the sleeve used, even in the event of additional load surges
  • usually requires an assembly tool to support the tolerance sleeve when it is pressed in

The centered installation

  • is suitable for inserting the AN sleeve into a groove in the bore and the BN sleeve in a groove in the shaft. The groove width must be selected so that sufficiently wide shoulders remain on the bore or the shaft on both sides. These shoulders allow centering.
  • is more advantageous during assembly because the ring inserted into the groove can be supported on its side surfaces. Deformation due to tilting can thus be avoided.

There is also the third type of installation, “supported”: This is a compromise between free and centered installation.

Web links

Individual evidence

  1. ↑ https://www.tretter.de/toleranzhuelsen/ (as of November 28, 2017)
  2. ↑ Roloff / Matek machine elements, standardization, calculation, design - textbook and book of tables, Springer, 2011, page 401
  3. ↑ https : //www. Konstruktionsatlas.de/antriebstechnik/welle-nabe-verbindungen-kraftschluss.shtml (as of November 24, 2017)
  4. ↑ http://www.hreiter.at/userfiles/file/1680a465-3283-44dc-a5a2-7ced964f202aToleranzringe.pdf (as of November 24, 2017)
  5. ↑ http://www.hreiter.at/userfiles/file/1680a465-3283-44dc-a5a2-7ced964f202aToleranzringe.pdf (as of November 24, 2017)
  6. ↑ Machine and construction elements 2: connecting elements, Springer, W. Steinhilper, R. Röper, page 65
  7. ↑ http://www.beham.com/fileadmin/beham/Downloads/5L-04-18T_Uebersicht_Niro.pdf (as of November 24, 2017)
  8. ↑ http://www.hreiter.at/userfiles/file/1680a465-3283-44dc-a5a2-7ced964f202aToleranzringe.pdf (as of November 24, 2017)
  9. ↑ http://www.inggo.com/teachnet/452-Toleranzringe.html?pageID=2295&ID=472&linkOrdner=1 (as of November 24, 2017)
  10. ↑ http://www.inggo.com/teachnet/452-Toleranzringe.html?pageID=2295&ID=472&linkOrdner=1 (as of November 24, 2017)
  11. ↑ http://www.inggo.com/teachnet/452-Toleranzringe.html?pageID=2295&ID=472&linkOrdner=1 (as of November 24, 2017)