A rubber seal, O shape is a kind of cross section shape is circular sealing element, it is widely used in a variety of machinery and equipment, to a certain temperature, pressure and the different liquid or gas medium sealing effect, compared with other seals, has better performance of the following:
(1), sealing parts, simple structure, compact installation position, and lighter in weight.
(2), since the sealing function, often use only one seal can finish sealing effect.
(3), sealed performance is good, is used as the fixed seal almost no leakage, when used as a sports seal, only some leak when in high speed.
(4), motor friction resistance is very small, for the occasion of alternating pressure can be adaptive.
(5), size and groove has been standardized, low cost, product availability, ease of use and outsourcing.
Compared with other seals, there are the following three questions:
(1), at the time of starting frictional resistance.
(2), used as a pneumatic device sealing, must add lubricant to prevent wear and tear.
(3), the coupled parts, such as sports surface, groove, clearance of machining dimension and accuracy requirement is very strict.
O shaped rubber sealing ring structure design principle
Because O shaped rubber sealing ring is installed in a variety of groove, will now installation groove is listed in table 4-1-3.
Pressure and seal clearance
O shaped rubber sealing ring is usually produced by compression of springback for sealing, but with the increase of pressure, it is turbidity in seal gap and produce shape change, as shown in figure 4-1
In order to make the o-ring rubber sealing ring has good sealing effect and prolong the service life, must make the installation of o-ring rubber sealing ring grooves and the clearance between the sealing parts design properly, when the gap is too large under the action of O shaped rubber seal in hydraulic squeeze gap and damage, causing leakage. When the pressure is less than 9.8 Mpa is generally not collar design, when the pressure is greater than 9.8 Mpa O shaped rubber seal pressure surface being squeezed out easily, should add baffle ring; If the one-way pressure, pressure on a retaining ring, if it is a two-way compression is to set up the two retaining ring, as shown in figure 4-2
Executive standard o-rings
The hardness of o-rings relationship with groove maximum clearance and working pressure
Seal clearance sizes and pressure classes o-type rubber seal, rubber hardness and the diameter of the section related situation, see the table below:
The piston rod sealing groove depth
Cylinder hole sealing groove depth
Radial sealing groove depth
General radial sealing groove width; See table 4-1-5
Different cross section O shaped rubber seal axial groove width and depth
The axial sealing groove width and depth; Axial sealing groove width and depth are shown in table 4-1-8
Type O ring rubber hardness and work pressure
In standard of rubber material, hardness and compression set two performance the most weight. Choose compression deformation smaller rubber material on the sealing performance is good, and the hardness for O shaped rubber seal pressure and collapsing is crucial. According to the national standard and practical experience, the rubber compression permanent deformation under prescribed temperature is more than 50%. The hardness of the rubber and sealing is closely related to the work pressure, the higher the pressure, the hardness is higher; See table 4-1-11
Note: rotary motion working pressure is generally not more than 0.4 Mpa, hardness choose in (70 + 5); Was higher than 0.4 Mpa according to the special sealing device design.
Groove of the finish requirement
Groove of the finish, the groove of the contact surface roughness has a great influence on the sealing effect and durability.
Seal grooves every one with a surface finish
Groove and compression
Fixed sealing o-ring rubber seal compression ratio, usually used 15 ~ 25% (the experience data), motion seal such as reciprocating motion circumstances choose 10 ~ 12% compression ratio, rotation movement usually take 3 ~ 5% under compression ratio, is commonly used O shaped rubber sealing ring compression and groove dimensions are shown in table 4-1-9
