Parker O-Ring Handbook.pdf

Dynamic O-Ring Sealing
5-20
5.30 Drive Belts
O-rings can be used as low power transmission elements.
They are not only an economic solution but also offer many
advantages:
• Simple installation
• Constant tension
• Flexible fi tting
• Because of their elastic properties, O-ring compounds
require no adjustment,
• Freely available in standard compounds and sizes
• Greatest possible tolerances in positioning of pulleys.
An O-ring compound is selected for minimum stretch relaxation
(tensile set) and maximum dynamic properties. The
choice of elastomer is made to the environment:
• Contact medium, e.g. ozone, oil grease,
• Extreme temperatures
The general requirements are:
• Good aging resistance
• Wear resistance
• Relatively low tendency to return to original shape
under tension and temperature caused by friction; this
means a higher resistance to the Joule effect;
• Good bending fl exibility
Open Design Crossed Design
Compound Selection
Please see Section III, paragraph 3.17 for information about
drive belt compound selection
Design Information
• Direct contact with fl uids should be avoided. For
contact medium see medium Compatibility Table.
• The smaller pulley minimum diameter
is D2 mm = 6 x d2 (cross section).
• The elongation of the O-ring inner diameter d1 is a maximum
of 15% (average elongation between 8% and 12%).
• Tension when fi tted approximately 0.6 to 1.0 N/mm2 .
• Cross section d2 should be greater or equal to 2,62mm.
Ordering Detail
All O-rings which are used as drive belts are subject to additional
quality inspection procedures and inspection for surface
defects under elongation. O-rings ordered for this application
are to be coded as follows: “E0540 DBA2-250”.
Parker O-Ring Handbook
D 1
C
Abbreviations:
C Center line distance of pulleys (mm)
D1 Diameter of driven pulley (mm)
D2 Diameter of drive pulley (mm)
S Elongation as a decimal (e.g. 10% = 0.1)
d1 O-ring inner diameter (mm)
d2 O-ring cross-section (mm)
L Length of drive belt (mm)
B Calculation factor
5.30.1 Calculation of Drive Belt Open Design
1. Calculation of O-Ring size d1:
Known – D1 and D2, diameter of pulley
C center line distance of pulleys
S elongation as a decimal (e.g. 10% = 0.1)
a) Calculation of drive belt L:
L = 2 x C + 1.57 x (D1 + D2) + (D1 + D2) 2
4 xC
b) Calculation of O-ring inside diameter d1:
d1 = L
3.14 x (1.0 + S)
c) O-ringis selected according to the O-ring size
list. If a size is required between the sizes then
the smaller size should be taken.
2. Calculation of elongation S:
Known – d1 inside diameter of O-ring
C center line distance of pulleys
D1 and D2, diameter of pulleys
a) Calculation of drive belt L: (see above, 1a)
b) Calculation of elongation S as a decimal:
S = L - 1
3.14 x d1
3. Calculation of center line distance C of pulley:
Known – d1 inside diameter of O-ring
S elongation as a decimal (e.g. 10% = 0.10)
D1 and D2, diameters of pulleys
a) Calculation of factor B:
B = 3.14 x d1 x (S + 1) – 1.57 x (D1 + D2)
b) Thereafter calculation of center line distance C:
C = B+√B2 – (D1 – D2) 2
4
D 2
Parker Hannifi n Corporation • O-Ring Division
2360 Palumbo Drive, Lexington, KY 40509
Phone: (859) 269-2351 Fax: (859) 335-5128
www.parkerorings.com