Kusindikiza ukadaulo waukadaulo gawo loyamba

Pakati pa 1926 ndi 1933, woyambitsa ndi wopanga makina wa ku Denmark NielsA Christensen adakulitsanso ndikugwiritsa ntchito bwalo lamtunduwu.Njira yake (O-ring) inasindikizidwa mu 1930, yovomerezeka mu 1933, ndipo inapambana mphoto yaikulu mu 1938.