| What is the delivery time of standard PK Offset Couplings? | Between 3 and 5 weeks from receipt of order depending on the exact specification. |
| How do I indentify an offset coupling? | Couplings comprise 3 discs with 2 sets of connecting links.
The 2 outer discs are connected to the transmission system by hubs or flanges.
The centre disc floats and adopts a position appropriate to the offset.
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| What does the offset coupling order code mean? |
E.g. NA 134.60.160/4 A1-A3
NA indicates the basic design (NAS is the heavy duty version - GL is the very light duty version).
134 indicates the overall length of the coupling measured across the outer faces of the outer discs.
60 is the maximum allowable offset.
160 is the diameter of the discs (these are normally all the same).
/4 is the number of links joining each pair of discs.
A1 and A3 identify the form of interface with the transmission system.
A1 is a simple flange.
A3 is a shrink disc or tension bush fitting. |
| What does PK stand for in offset coupling description? | PK is a German abbreviation for Parallel Kurbelkupplung - translates as parallel crank coupling.
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| What is the maximum offset possible for the PK Offset Coupling? | The nominal offset is twice the length of the coupling links.
The maximum possible adjustment or travel is plus/minus the nominal offset, i.e. 2 x nominal offset. The useable offset should be limited to 1.8 times the nominal offset.
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| What is the efficiency of the PK Offset Coupling? | The losses in the coupling are limited to bearing friction. Hence the efficiency is 98-99%
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| Is the PK Offset Coupling balanced? | There is no imbalance. The link system is always dynamically stable when used within the advised maximum range and speed.
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| What are the reactive forces on related components at maximum offset for the PK Offset Coupling? | The reactive forces for all conditions of offset are zero. All reactions are compensated within the coupling. The coupling transmits pure torque.
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| Does any phase displacement result during offset adjustment? | No, none. The fixed length links ensure true constant velocity of the PK Offset Coupling at any condition of speed or load. Whatever conditions are applied at the input are seen at the output.
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| Can the PK Offset Coupling run in the neutral position i.e. with shafts in line? |
The kinematic conditions are constant regardless of the position of the shafts.
However in practice, when shafts are in line, the friction in the link bearings may cause the centre disk to travel slowly in the direction of rotation leading to instability. At high speeds this would destroy the coupling.
A minimum limiting displacement is advised equal to 25% of the nominal offset.
See catalogue value L3. |
| Does the PK Offset Coupling have any backlash? | The PK Coupling provides a practically rigid connection.
Needle roller bearing tolerances mean there could theoretically be backlash equivalent to bearing clearance.
This normally so small it may be neglected.
If completely backlash freedom must be guaranteed additional links and bearing pre-load will compensate.
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| Does the PK Offset Coupling have limits to transmitted power? | Load capacity is calculated from bearing capacity.
Standard couplings can run at up to 60 r/s. By special design higher speeds can be achieved.
Couplings capable of 250 000 Nm have been produced.
Maximum torque is dependent on the link and pin dimensions and bearing capacity.
No limit has yet been reached.
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| Can the PK Offset Coupling accept angular misalignment? | Needle roller bearings can accept around 0.5 degree but angular displacement will contribute to reduced life and performance. It is therefore essential that good initial alignment is achieved.
The PK Coupling is not a misalignment coupling and angular misalignment if present should be compensated with a good flexible coupling. See Inkoma Inkoflex IFE.
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| How do I connect the PK Offset Coupling to the shaft/s? | A range of options including integral hubs and separable flanged hubs and split collar hubs is available.
Hub options incorporating shrink discs (Tension Bushes) are also available for keyless shaft connection.
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| Can the PK Offset Coupling be tailored to my requirements? | Whilst quantity is clearly a factor in designing a customised coupling, there are many options. Sprockets, pulleys, cams and gears can be incorporated in the fixed outer disc of the coupling.
Couplings having limited offset or offsets greater than the catalogue values are possible.
Please send us a sketch of what you need!
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| What is the life of a PK Offset Coupling? | We provide rated loads for lives of 1000, 5000, 10 000 and 20 000 operating hours.
If you require a longer life please submit your life requirement for us to calculate or select a suitable coupling.
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| Are all PK Offset Couplings fitted with needle roller bearings? | No. Very often, customised couplings utilise plain bearing bushes or ball bearings. |
| Can PK Offset Couplings be supplied in alternative materials? | Corrosion resistance, magnetic characteristics, oil and grease free operation, special fire or explosion risks can dictate materials used. Stainless steel and electroless nickel plating can be offered.
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| Can PK Offset Couplings be fitted to vertical shafts? | Yes. Great care should be taken to avoid the coupling mass placing loads on the coupling bearings. |
| How precisely must the fitted length dimensions be applied for the PK Offset Couplings? |
All bearing have a specified axial float.
Light GL series have + 2 mm.
Standard NA series +/- 2 mm.
Heavy NAS series +/- 4 mm.
Units having greater degrees of float can be manufactured. |
| What are the options for offsets smaller than pernitted by PK Offset Couplings? |
Both Lineflex and Oldham couplings can absorb small radial offsets.
The Inkoflex flexible shaft coupling series can absorb a limited offset too. |
