4
Introduction
Since the introduction of the first timing belt at the end of the 40’s,
this type of drive element has gained in importance for the
synchronous transmission of torque and power. The non-slip timing
belt has been successfully employed in many standard drives and
has provided economical design solutions in every sector of
mechanical engineering.
The position that the timing belt occupies today is due to the
development of tooth profiles and belt design. The Optibelt ZRM/
ZRP/ZRL single and double-section polyurethane timing belts are a
result of this progress. The properties specific to the polyurethane,
offer the following advantages:
●High resistance to abrasion
●Good to very good resistance to oil, grease and a
number of aggressive chemicals
●Colour fast
●Simple to weld, for attaching cleats and joining
endless to make belts of any length
●High resistance to tooth shear
●Good thermal tolerance (–30 °C to +80 °C)
●Good electrical insulation properties using poly-
urethane with Aramid tension cord
●Ageing resistant
●Ozone and UV resistant
Apart from the higher noise level at high belt speeds when
compared to V-belt drives, the timing belt has all of the advantages
of other drive mechanisms.
●Synchronous speed transmission, high angle and
positional accuracy due to the low-stretch tension
member and to the positive pulley/belt interlock.
●Double section belts permit multi-pulley arrange-
ments and contra-rotating pulleys.
●Belt flexibility allows high drive ratios requiring
minimum space.
●Low belt specific mass enables high belt speeds.
●Low-stretch tension cord means zero maintenance.
●High drive efficiency due to belt flexibility and lack
of slip.
●The low drive tension allows the use of smaller drive
bearings.
●No drive lubricant necessary, thus the drive is envi-
ronmentally friendly.
●Durable belt components ensure longer belt life.
1 Product Description
1.1 Construction
In addition to the features of the standard synchronised drive, the
Optibelt ZRM/ZRP/ZRL timing belts offer the additional advan-
tages of polyurethane, as shown above, as a contribution to the
economical solution of design problems.
Top surface
Tension cord
Tooth
Base
Construction: Timing belts
Fig.1.1: Timing belts
a) Top surface
The top surface of the belt is polyurethane. Its function is to hold and
support the tension cord. This abrasion-proof, thin and extremely
flexible layer also protects the tension cord against wear and the
effects of ambient conditions.
b) Tension cord
The tension cord of the endless Optibelt ZRM/ZRP timing belt is
spirally wound steel cord. The teeth, base and top surface form a
unit so that the tension cord is enclosed in polyurethane.
The extremely strong, low stretch tension cord has a very small
cross section.
The open-ended Optibelt ZRL-M belting has parallel steel or
Aramid tension cords. This is also the case with the joined endless
Optibelt ZRL-V timing belt.
c) Teeth and base
The polyurethane teeth transfer power between the pulley teeth and
the belt tension cord, whilst the polyurethane base cushions the
tension cord against the abrasion from the top of the pulley teeth
(see Fig. 1.3).
The durable, shear resistant belt teeth are so formed and arranged
as to engage with the matching pulley with minimum friction and
maximum precision. When six teeth on the belt type ZRL-V, and
twelve teeth or more on the ZRM, ZRP and ZRL-M belts are in mesh
with the small pulley at any one time, their shear resistance exceeds
the maximum permitted circumferential force of the timing belt.
