Herder J.L., Tuijthof G.J.M., Balancing mechanism to hold object in required vertical position involves use of parallelogram or hinged arms and two tensioned springs, NL1009886 C
Herder J.L., Tuijthof G.J.M., Balancing mechanism to hold object in required vertical position involves use of parallelogram or hinged arms and two tensioned springs, NL1009886 C