.NPB stud track roller bearings are available in three basic designs:
The three designs have the same main dimensions. The differences are in their internal design, which make them suitable for various operating conditions. In contrast to ball and roller bearings, where the bearing size refers to the bore diameter d, for cam followers the size refers to their outside diameter D.
KR design track rollers
KR design track rollers are fitted with needle roller and cage assemblies. The bearings are axially guided by the integral flange and an interference fitted washer on the stud.
KR design stud track rollers without a designation suffix have a narrow gap between the outer ring and the two flanges and serves as a gap type seal (fig 1).
Bearings identified with suffix PP are provided with plastic plain washers served as seals on both sides (fig 2).
KR design stud track rollers, size 16 and 19, either with seal suffix or not have one slot in the head of the stud (fig 3) that enables the stud to be held in place by a screwdriver. In the centre of that slot is a lubrication hole to press in a grease fitting. The two sizes are also available with a recessed hexagon in the head of the stud which is suffixed with NK (fig 4), the bearings are supplied with a polyamide 66 axial sliding and sealing ring on both sides and can not be lubricated.
Fig 3 Fig 4
KR design stud track rollers with designation, size 22 and larger, have a recessed hexagon at each side of the stud. However, size 22 and 26 do not have an annular groove and lubrication hole in the middle of the stud (fig 5). In the centre of each hexagon is a lubrication hole to press in a grease fitting, if needed. For stud track rollers from size 30 and larger, the grease can also be supplied via the lubrication hole with an annular groove in the middle (fig 6).
Fig 5 Fig 6
KRV design track rollers
KRV design track rollers are similar to the KR design with a designation suffix PP (fig 7), but the difference is that the KRV design has a full complement of needle rollers. Therefore, stud track rollers with KRV design have higher load capacity than KR design stud track rollers, but the operation speed is lower, and it require more frequent relubrication.
NUKR design track rollers
The NUKR series track rollers (fig 8) are double row full complement cylindrical roller bearings. The stud head and pressed-on flange ring guide the outer ring axially via the roller sets. This enables NUKR design track rollers to accommodate relatively heavy axial loads that are induced when operating in an inclined or tilted position.
The metal angular ring pressed into the outer ring formed an effective labyrinth seal on both sides of the bearings. The recessed hexagons on both sides of the stud enable the track rollers to be held in place with a hexagon key easily during mounting. In the middle of the hexagon is the lubrication hole for a press-in grease fitting.
PWKR..-2RS design track rollers
The PWKR..-2RS design track rollers are designed based on double row, full complement cylindrical roller bearings with three integral flanges on the outer ring (fig 9). The stud head and a pressed-on flange ring axially guided the outer ring via the roller sets. This enables PWKR..2RS design cam followers to accommodate relatively heavy constant axial loads that are induced when operating in an inclined or tilted position.
The PWKR..-2RS design track rollers have contact seals made of NBR on both sides. The seals are protected and integrated with metal angular rings that pressed in the outer ring. The lips of the seals contact with the stud and flange ring, the sheet metal angular ring extend over the stud and flange ring to form a secondary labyrinth seals, making them particularly suitable for operation under arduous conditions.
The large space between the two rows of rollers enables a large quantity of grease to be incorporated. The large grease fill and efficient seal method makes the PWKR..-2RS design bearings possible to operate for long period between maintenance interval even under contaminated conditions.
They also have a recessed hexagon at both ends of the stud that enables the cam follower to be held in place by a hexagonal key during mounting. In the centre of each hexagon is a relubrication hole for a press-in grease fitting or an adapter from a central lubrication system. Lubricant can also be applied via the relubrication hole and the annular groove in the seat.
Stud type track rollers with eccentric collar
The KR design suffixed with PP, NUKR and PWKR design stud track rollers are also available with an eccentric collar ( fig 10, fig 11, fig 12) on the stud. An eccentric collar, which has a shrink-fit onto the stud, enables less stringent manufacturing position tolerances to be specified for associated components. The values for the adjustable eccentricity are listed in the product tables. An eccentric collar is identified by the letter E at the end of the basic designation, KRE, NUKRE and PWKRE for example. Because the eccentric collar covers the duct in the stud, these stud type track rollers can only be lubricated via the stud ends.
Fig 10 Fig 11
Profile of the outer ring running surface
The stud type track rollers with crowned surface are standard type and predominantly used since they are often inclined during operation and edge stress must be avoided. In series KR, the radius of curvature is 500mm. In series KR..PP, KRE..PP, KRV..PP, NUKR, NUKRE, PWKR..2RS and PWKRE..2RS, the outside surface has the optimized profile. The optimized profile provide better load distribution than the stud type track rollers with standard radius.
Bearings with cylindrical outer ring running surface which is suffixed with letter X are also available (fig 13). This kind of bearing is used for applications requiring high stiffness and inclined position can be avoided. These bearings are dimensionally interchangeable with the standard profile stud type track rollers.
.PP KR design track rollers with plastic axial sliding and sealing rings on both sides.
·2RS PWKER design track rollers with protected lip seal on both side of the stud type track roller
·X cylindrical outer ring
·NK KR..PP design track rollers, size 16 and 19 with a hexagon recessed into the head of the stud.