Kaco DILAG© components are maintenance-free sealing elements which fulfill three different tasks at the same time:
Sealing Scraping • Bearing
Formerly, U-rings were mostly used to seal rods, and, to fulfill the purpose of bearing, special elements were provided in the machine housing or in the bearing cover. In this case, expensive bearing bushes were normally necessary as the materials of the housing or cover were not suitable to fulfill a bearing function. In
addition, scrapers were also necessary to prevent the penetration of dirt into the sliding bearing. These expensive individual elements have been placed together in a sealing combination as a DILAG component and have been expanded to form a standard series (refer to the dimension list on page 47). Figure 50 shows a DILAG component of the standard series and figure 51 shows a special version developed on the basis of a client’s specification.
DILAG components consist of a metallic support body to which the elastic sealing lip, the bearing component, and the scraper are permanently connected by means of vulcanization. The bearing component begins directly after the sealing lip and its whole bearing length is provided with slots that run like a multiple-start thread. Immediately after this is a chamber which is closed off by the dust or scraper lip. The grooves and chamber accommodate the grease for lubrication. Due to the threadlike course of the grooves, intensive lubrication is achieved which is particularly advantageous in the case of short strokes and high vibrations. Extensive tests and practical experience have shown that, in comparison with metallic sliding bearings, the service life is extended by a multiple due to the bearing of the piston rod in the rubber of the DILAG component. At the same time, there is no noticeable formation of marks on the piston rod.
For design reasons, the internal diameter in the bearing area of the DILAG component is up to 0.2 mm greater than the rod diameter. This clearance is necessary in order to compensate, in the case of elastomer materials, for the possible swelling of the medium and in order to compensate for the expansion of the elastomer due to the effects of temperature during operation, which expands by approximately 10 times more than in the case of steel.
Especially in the case of multiple or parallel guided rods, for example, in the case of tandem cylinders and in the case of pneumatic-hydraulic feed units, the bearing clearance and the elastic guidance of the seal have proven advantageous. In comparison with rigid metallic bearings, a greater off-center displacement is possible in the case of DILAG components with the same degree of reliability.
hydraulics ≤ 200 bar
pneumatics ≤ 16 bar
Permissible sliding speed
hydraulics ≤ 0.3 m/s
pneumatics ≤ 1 m/s
dynamic (rod) H9
static (housing) H8
Nowadays, because of their numerous advantages, large numbers of DILAG components are used for rod sealing in hydraulic and pneumatic cylinders. The use of aluminum or plastic components is a further advantage which is often possible with the use of DILAG elements.
The following contains a short description of some possible applications:
In a standard installed automatic door closer, a lateral force of 300 N is present with a piston rod of 10 mm diameter and a stroke of 80 mm. The seal is flooded with oil. The door closer is alternately operated with 10 bar overpressure and approximately 0.5 bar under pressure. A comparison of figures 52 and 53 show the considerable simplification of the sealing and bearing point, which has been achieved by using a DILAG component. It was possible to replace the four individual parts previously used with one component. The results were more rational production and a considerable increase in service life.
Figure 54 shows an air cylinder in which the piston is equipped with a double U-ring PDA (refer to page 42) and the piston rod is mounted in a DILAG component. The fact that there is no metallic contact between the moving parts is particularly worth mention. For this reason, it was possible to manufacture the cylinder from light metal.
DILAG components can be put to use not only in the field of pneumatics (up to16 bar) but also in the field of hydraulics (up to 200 bar). Taking into consideration the smallest possible installation dimensions, a standard series was created for DILAG components in order to comply with the practical demands for standardization (page 47). Whilst in hydraulic equipment with operating pressures up to 200 bar, these are installed to come into contact with a stop component (page 48), a continuous whole with a surrounding squeeze groove (page 49) is sufficient in the case of flooding up to a maximum value of 16 bar. In the case of installation from the outside of the device, in addition to the press fit, the DILAG component is additionally held by the elastic material of the outer jacket of the sealing ring which is pressed into the squeezed groove. The pressing out force achieved in this way amounts to at least 14 times the force acting upon the DILAG component as a result of the operating pressure. Figure 55 shows a standard DILAG component in a pneumatic working cylinder.
For all DILAG sizes, the diameter of the location hole must be in accordance with the ISO tolerance field H 8. The surface of the hole should not be machined too finely. Finishing with a peak-to-valley height Rt =10 to 16 pm has proven favorable.
The outer surface of the DILAG component should be lightly oiled or greased before pressing in. This should be pressed in rapidly. Driving home is inadmissible! Page 48 and page 49 contain dimensions for arbors to be used during installation and removal.
Before installation of the piston rod, make absolutely sure that grooves and chambers of the DILAG component are filled with grease.
Greases on a mineral oil basis should be given preference. If other greases are used, we request that you enquire with us as to the possibility of their use.
Dimensions List QFN (This item is used for Hydraulics and Pneumatics)
QFNH= Hydraulics (up to 200bar)
QFNP= Pneumatics (up to 16 bar)
Please note: it is the same seal, used for 2 applications.
|QFN 8 x 15 VG 02
QFN 10 x 17 VG 02
|QFN 11 x 19 VG 02||11||19||13,5||14,5||4||2,5|
|QFN 12 x 19 VG 02||12||19||16||15,5||4||2,5|
|QFN 14 x 21 VG 02||14||21||17||17,5||4||2,5|
|QFN 15 x 23 VG 02||15||23||18||18,5||3,5||3|
|QFN 16 x 25 VG 02||16||25||17,5||20,5||5||3|
|QFN 18 x 27 VG 02||18||27||19,5||22,5||4,5||3,5|
|QFN 20 x 29 VG 02||20||29||22||24,5||5||3,5|
|QFN 22 x 31 VG 02||22||31||22||26,5||5||3,5|
|QFN 25 x 35 VG 02||25||35||27||30||5||3,5|
|QFN 26 x 36 VG 02||26||36||27||30||5||3,5|
|QFN 30 x 41 VG 02||30||41||32||35||5,5||3,5|
|QFN 32 x 43 VG 02||32||43||32||37||5,5||3,5|
|QFN 35 x 46 VG 02||35||46||34||40||5,5||3,5|
|QFN 36 x 49 VGU 01||36||49||43,5||41||5||3,5|
|QFN 40 x 51 VG 02||40||51||34||45||5,5||3,5|
|QFN 45 x 56 VG 02||45||56||37||50||5,5||3,5|
QFNH (Hydraulics) installation information only, up to 200 Bar
|QFN 8 x 15VG 02||15||12,5||14,7||11||12,2||12,2||10,4||5||0,5|
|QFN 10 x 17VG 02||17||14,5||16,7||13||14,2||12,4||5||4||0,5|
|QFN 11 x 19VG 02||19||15,5||18,7||14,7||15,2||13,4||5,5||4,5||0,5|
|QFN 12 x 19VG 02||19||16,5||18,7||15,7||16,2||14,4||5,5||4,5||0,5|
|QFN 14 x 21VG 02||21||18,5||20,7||17,7||18,2||16,4||5,5||4,5||0,8|
|QFN 15 x 23VG 02||23||19,5||22,7||19,1||19,2||17,4||5,5||4,5||0,8|
|QFN 16 x 25VG 02||25||21,5||24,7||20,5||21,2||19,4||6,5||5||0,8|
|QFN 18 x 27VG 02||27||23,5||26,7||22,5||23,2||21,2||6,5||5||0,8|
|QFN 20 x 29VG 02||29||25,5||28,7||24,5||25,2||23,2||6,5||5,5||0,8|
|QFN 22 x 31VG 02||31||27,5||30,7||26,5||27,2||25,2||6,5||5,5||0,8|
|QFN 25 x 35VG 02||35||31||34,7||29,5||30,7||28,7||6,5||5,5||0,8|
|QFN 26 x 36VG 02||36||32||35,7||30,6||31,7||29,7||6,5||5,5||0,8|
|QFN 30 x 41VG 02||41||36,5||40,7||34,7||36,2||33,7||7||5,5||0,8|
|QFN 32 x 43VG 02||43||38,5||42,7||36,7||38,2||35,7||7||5,5||0,8|
|QFN 35 x 46VG 02||46||41,5||45,7||40||41,2||38,7||7||5,5||0,8|
|QFN 36 x 49VGU 01||49||50,5||48,7||39,5||50,3||39,7||7||5,5||0,8|
|QFN 40 x 51VG 02||51||46,5||50,7||45||46,2||43,7||7||5,5||0,8|
|QFN 45 x 56VG 02||56||51,5||55,7||50||51,2||48,7||7||5,5||0,8|
QFNP (Pneumatics) installation information only, up to 16bar
|QFN 8 x 15 VG 02||15||0,3||5,5||14,7||1 1,8||14,7||1 1||2,5||5||0,5|
|QFN 10 x 17 VG 02||17||0,3||7||16,7||13,8||16,7||13||2,5||5||0,5|
|QFN 11 x 19 VG 02||19||0,3||6||18,7||14,7||18,7||14,7||3||5,5||0,5|
|QFN 12 x 19 VG 02||19||0,3||7||18,7||15,7||18,7||15,7||3||5,5||0,5|
|QFN 14 x 21 VG 02||21||0,3||7,5||20,7||17,9||20,7||17,7||3||5,5||0,5|
|QFN 15 x 23 VG 02||23||0,3||8||22,7||18,8||22,7||19,1||3||5,5||0,5|
|QFN 16 x 25 VG 02||25||0,3||8||24,7||20,9||24,7||20,5||3,5||6,5||0,5|
|QFN 18 x 27 VG 02||27||0,3||9||26,7||22,8||26,7||22,5||3,5||6,5||0,5|
|QFN 20 x 29 VG 02||29||0,4||10||28,7||24,8||28,7||24,5||4||6,5||0,5|
|QFN 22 x 31 VG 02||31||0,4||10||30,7||26,8||30,7||26,5||4||6,5||0,5|
|QFN 25 x 35 VG 02||35||0,4||12,5||34,7||30,3||34,7||29,5||4||6,5||0,5|
|QFN 26 x 36 VG 02||36||0,4||12,5||35,7||31,3||35,7||30,6||4||6,5||0,5|
|QFN 30 x 41 VG 02||41||0,4||15||40,7||35,3||40,7||34,7||4||7||0,5|
|QFN 32 x 43 VG 02||43||0,4||15||42,7||37,3||42,7||36,7||4||7||0,5|
|QFN 35 x 46 VG 02||46||0,4||16||45,7||40,3||45,7||40||4||7||0,5|
|QFN 36 x 49 VGU 01||49||0,4||16||48,7||41,3||48,7||39,5||4||7||0,5|
|QFN 40 x 51 VG 02||51||0,4||16||50,7||45,3||50,7||45||4||7||0,5|
|QFN 45 x 56 VG 02||56||0,4||16,5||55,7||50,3||55,7||50||4||7||0,5|