Cuffs - MA

Cuffs are axial sealing elements for translational movement. The development of cuffs is the response
to the demand for sealing elements for dynamic sealing, which do not cause a too high friction while operating, the consequence of which would be a high wear of the seal and a shorter lifetime.

The profile of the cuff is made from a sealing lip -
the edge and a powerfull base part which leans on in the installation canal and which, during the installation of the seal, makes possible a harder fit, necessary for sealing on a stative sealing surface. The basic part of the cuff acts, at the same time, as a support for the seal in the groove, so that the additional supporting rings are not neccessary in most cases. The forms of the sealing lips - edges and base part of the seal have been made in line with the tasks of the seal during operation and taking into account the demanding sealing conditions (inside / outside sealing, the hight of the pressure of the media, speed of movement). A cuff is an independent sealing element with elastic edges, primarily intended for dynamic sealing of translational movements to wide ranges of pressure from the pressure media (different forms oz. realisations) and used in operating conditions (a large choice of materials). Cuff sealing is reached with its installation in the canal which is a little wider than the cuff (app 10 %), when the sealing lips deform elastically achieving the neccessary contact pressure of the sealing edge on the surface (pretension). As the pressure of the medium gets higher, the pressure of the sealing edge on the surface gets proportionally higher and provides quality sealing (the principle of loading pressure - force). During very high pressures of the medium the intersection of the cuff widens also radially enlarging the contact surface and the sealing effect, but, at the same time, friction and consequently wear of the seal follow. Thus, the right choice of the seal is very important (form - production, material) in the relation sealing / friction / wear.

Materials:

The most frequently used materials for cuffs are:
- rubber based on NBR rubber
- NBR + cloth
- Polyurethane (PU, AU / EU)

Adding cloth to rubber makes it harder – resistance to higher media pressure and makes possible the occurrence of smaller »pockets« on the surface of the seal between single fibers of the cloth, with which a lubricating film merges during operation, which can not be torn apart in either high pressures. In this way, by hightening the contact pressure of the cuff and the sealing surface, excessive friction and wear are stopped. For special demands EPDM, VMQ, FPM, HNBR, PTFE are also used.

Advantages of cuffs:
- linear dependence of the sealing effect with the hightening pressure of the media
- very good sealing effect in a wide range of pressures
- a low friction coefficient
- simple construction of installation canals
- simple installation
- a large choice of given intersection forms and materials
- a wide range of uses (pressures, temperatures, media)

Areas of use:
- for the sealing of pistons and rods in hydraulic and pneumatic cylinders
- for underwater pistons (plungers) liquid pumps


User instructions:

Before the installation it is neccessary to check – ensure:
- if the prescribed chamfes have been made on the cylinder oz. rod (15 - 20º ),
  which stop mechanical wear of the seal during installation
- surfaces without sharp edges
- the system cleaned of foreign particles and dirt
- threads protected – covered
- it is neccessary to oil the seals and sealing elements oz. grease them. The use of the sole
  medium or a compatible mean is recommended
- during installation do not use lubricants which contain solid parts - additives
- during installation use tools with no sharp edges