The previous model with sealed swivel head served as the basis for the new swivel castor, which was upgraded with a directional latch. The unique aspect is that the latch locks the swivel head by default. When travelling straight, as is the case in the washing line, the swivel castors are fixed in position. To make it easier to operate the trolley at other times, however, the swivel head is released with even a relatively slight sideways application of force: The latching torque is overcome already at 2.5 to 3 newton-metres. This makes it easy for the staff to steer the trolley while also satisfying the safety requirements of the washing line.
Technically, the latching torque requested by the customer was implemented with a “slot and key principle”. A slot was set into the upper swivel head ring. A ball situated beneath a spring serves as counterpart to the slot. The spring presses the ball into the slot, blocking the swivel head of the castor. If a torque of 2.5 to 3 newton-metres is applied to the swivel head, the ball is pushed up and out of the swivel head ring, compressing the spring. This disables the latching function.