Problem
To imitate the natural arm movement when running, the baby carriage is equipped with two arm levers like a cross trainer. To generate the pivoting motion, the JogAlong engineers originally connected the two levers at the rotary axis with shafts and a differential gearbox. The latter had to be made of metal to cope with the high torque and to keep the diameter of the gears as small as possible. This solution was too complicated, too heavy and too expensive. The challenge was to find another way to manage the many degrees of freedom between the levers and the connecting link, to simplify the connection and to realise it as easily and cost-effectively as possible.
Solution
After numerous further attempts, igus finally found the solution: spherical igubal spherical bearings from the EGLM series, mounted between the levers and a second connecting piece. The bearings permit three degrees of freedom simultaneously: the spherical outer diameter allows the connecting piece to pivote in relation to each lever; the cylindrical inner hole of the ball is used for an axial sliding degree of freedom in addition to a rotational degree of freedom. This significantly reduced the complexity of the assembly and therefore also the costs and weight. An additional plus: the bearings do not require lubrication or maintenance.