Smooth linear movements in industrial trucks

Profile:

• What was needed: drylin® SHT lead screw-driven actuator
• Requirements: it must be possible to safely swivel wing-shaped sheets up and down by 30 degrees; distance adjustment of the Jet-Pilot multifunction steering wheel should be possible in the longitudinal direction
• Industry: Mechanical engineering, industrial trucks, internal logistics
• Success for the customer: Plain bearing elements made of the high-performance polymer iglide® J ensure smooth and quiet running and are completely dry-running; delivered ready for installation with compact DC motor and end position sensing

Jungheinrich AG from Hamburg is a manufacturer of industrial trucks, such as forklifts and other vehicles for internal material flow. The Lüneburg plant is responsible for special forklifts and small series, and many trucks are developed here from scratch.

This also applied to a special low-lift vehicle for a large Scandinavian dairy. It is striking that there is only a single fork and a single skate wheel. In terms of the chassis, it is a kind of "inverted" three-wheel forklift. The lack of a second fork is compensated for by 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 loading area of an automated washing system. The driver moves the fork between the trolley rollers. When he activates the lifting function, he clamps the trolleys against the upper, fixed load handling attachment and thus secures them.

Jungheinrich has already built special forklift trucks of this type several times for various dairies. For the current project, however, those responsible wanted an additional function. As the washing plant only accommodates ten trolleys, the forklift truck must not be able to transport more than ten trolleys at a time. For this reason, a triangular plate is fitted to the front of the clamping device to limit the number of carriages travelling. However, as there are also other destinations where more than ten trolleys are to be transported, these wings are designed to swivel. In concrete terms, this meant that the designers had to enable the motorised raising and lowering of the limiting triangular plate.

Today, a drylin® SHT actuator with trapezoidal thread and 60 millimeter travel is used. The ball bearing, dry-running spindle-linear system was supplied by igus® ready for installation with a compact DC motor and end position monitoring. A wedge made of wear-resistant plastic translates the linear movement into a pivoting movement and ensures that the wing-shaped plates swivel downwards by 30 degrees.

The operator gives the command at the jet pilot. If the pair of wings is to swivel upwards, the drylin® system moves in the opposite direction, the wedge releases the movement and a spring ensures that the wings return to the "up" position. The ideal sliding pairing of aluminum guidance and plain bearing elements made of the high-performance polymer iglide® J ensures smooth and quiet running; the spindle itself is made of steel. The drive thus translates the rotary 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 machine, which travels very long distances, the drivers wanted a standing platform that they could lean on. For ergonomic reasons, the truck is easier to manoeuvre with the Jet-Pilot multifunction steering wheel than with a tiller. For perfect adjustment of the working position, the Jet-Pilot can be moved 50 millimetres away from the driver. This is made possible by a drylin® SHT-S system with a steep thread, which is moved via a rotary wheel. This axis is also characterized by maintenance-free dry operation. The good sliding properties of the linear system are particularly important: the drylin® unit slides smoothly enough to bring the jet pilot into the desired position without jerking.