Lubrication-free linear plain bearings for smooth linear motion in industrial vehicles

Profile

• What was needed: drylin linear axes from the SHT product range
• Requirements: Wing-shaped panels must be able to be safely pivoted 30 degrees downwards and upwards; distance adjustment of the multifunction steering wheel jet pilot should be possible in longitudinal direction
• Industry: Mechanical engineering industrial vehicles, internal logistics
• Success for the customer: Plain bearing elements made of the high-performance polymer iglidur J ensure smooth and quiet operation and are completely lubrication-free at the same time; Supplied ready for installation with compact DC motor and end position sensing

The special forklift is used to gather trolleys in a large dairy facility and feed them into the washing system.

Problem

Jungheinrich AG from Hamburg is a manufacturer of industrial vehicles, such as forklifts and other vehicles for the internal flow of materials. The Lüneburg factory is responsible for special forklifts and small volume production, and many trucks are developed here from scratch.
This also applied to a special low-lift vehicle for a major Scandinavian dairy. It is noticeable that there is only one fork and one skate wheel here. Considered from the chassis perspective this is sort of a "turned around" three-wheel forklift. The missing second fork is compensated through an additional boom-like load-handling device in the third dimension. The purpose of the vehicle: It collects trolleys in the dairy that can be pushed into each other and transports them to the intake point of an automated washing plant. With the fork, the driver moves between the rollers of the trolley. When it actuates the lifting function, it clamps the trolleys against the upper, fixed load handling device and thus fixes them in place.
Jungheinrich has already built these types of machines several times for various dairies. However, for the current project the responsible parties desired an additional function. As the washing facility only accommodates ten trolleys, the forklift must also not be able to transport more than ten trolleys at a time. Therefore, a triangular plate is mounted at the front of the clamping device, which limits the amount of trolleys that can be carried. However, as there are also other destinations where more than ten trolleys are to be transported, these wings are designed to pivot. In concrete terms, this meant that the designers had to enable the motor-driven upward and downward movement of the limiting triangular plate.

Solution

Today, an igus linear axis from the drylin SHT product range with trapezoidal thread and 60 millimetre travel is used. The ball bearing supported, lubrication-free lead screw unit was delivered by igus ready to install with a compact DC motor and end position scan. A wedge made of wear-resistant plastic translates the linear motion into a pivoting movement and ensures that the wing-shaped sheet metal elements pivot downward 30°. The command is given by the operator at the jet pilot. If the pair of wings should be pivoted upward, the drylin system moves in the opposite direction, the wedge enables the motion and a spring ensures retraction of the wings to the "Up" position. The ideal slide pairing of aluminium guidance and plain bearing elements made of the high-performance polymer iglidur J ensures a quiet run, the lead screw itself is made of steel. The drive thus translates the rotational movement of the motor into the linear movement of the linear system and then into the pivoting movement of the wing.
But an igus linear axis is also used in the design of the driver's workplace. For the special equipment, which travels very long distances, the drivers wanted an operator platform against which they could lean. For ergonomic reasons, this makes the forklift easier to move with the jet pilot multifunction steering wheel than with a drawbar. For perfect adjustment of the working position, the jet pilot's distance to the driver can be shifted by 50 millimetres. This is made possible by a drylin SHT-S system with high helix thread, which is moved via a hand wheel. This axis is also characterised by maintenance-free dry operation. The good sliding properties of the linear system are particularly important: the drylin unit is capable of sliding well to bring the jet pilot into the desired position without jerking.

The linear system in installed condition.

The motion of the drylin SHT linear axis causes the pivoting of the wing-shaped sheet metal elements on the end of the boom.

The position of the jet pilot can be adapted to the operator's body size via an additional drylin linear unit.

The drylin SHT linear axis works wear-free and lubrication-free. A DC motor and an end position scan ensure optimal integration in the movement sequences of the forklift when taking up and setting down the trolleys.