Where steel chains are used, chain wheels are needed. If only the direction
in which the chain moves is changed, non-geared chain
wheels serve as deflection pulley. If tangential forces must be transmitted,
only geared chain wheels serve the purpose. Chain
wheels are cast or manufactured of steel. Which material should be used, depends
on the intended use of the chain wheel. The
most common materials are gray cast iron, gray cast iron with additions, nodular
graphite iron or cast steel, possibly with alloying
constituents. Low-alloy to high-alloy stainless steels can be: heat resistant,
non-magnetic and/or corrosion resistant. The teeth can
be hardened. the chain wheel can serve its purpose only together with the matching
chain. Basically, the chain should be matched
to the chain wheel. Thus, chain wheel and chain will only make a good match
if the chain wheel producer also has the chain to
calibrate it to fit the chain wheel. In some cases, however, it cannot be avoided
that in extreme cases the tolerance groups clash
in such a way that the chain must be recalibrated. If the chain wheels in a
machine system are to be changed without at the same
time also changing the chain, the chain wheel producer must be informed of this
to enable him, by making a sample wheel, to find
out if the machine system will operate properly with the new replacement wheels.
To check the proper interaction between the
chain wheel and the chain, the chain under load must run over a chain wheel,
and a condition is that the chain wheel is powered.
It is not enough just to mount the chain on the wheel and run a test.
If cast chain wheels are to be used in the machine, the general tolerances
for castings according to DIN norm be observed for the
materials of which the wheels are made. Some of these are:
- for unmachined gray cast iron castings DIN 1686
- for unmachined nodular cast iron castings DIN 1685
- for unmachined steel castings DIN 1683
As the castings are not machined, there may be some deviation from the nominal
pitch. For this reason, it is good practice to produce
a sample wheel before pouring a larger number of chain wheels to make sure that
the pitch matches the chain. Only when
the pitch is found to be in order should be other wheels be poured. Whenever
a sample wheel must be made, this is at the buyer`s
cost. Once the sample wheel is accepted by the buyer, no complaints based on
pattern defects can be raised. If a new pattern
must be made, the cost will be prorated but the pattern remains our property.
An overview of available patterns is appended
hereto.
The above terms apply likewise to steel wheels which are commonly manufactured
from solid metal. If small series are produced
and no casting pattern is available, steel wheels should be preferred for cost
reasons. Any design can be made. |
