A crank (or Swedish) cavesson lies in the same place as a traditional cavesson. It is typically heavily padded, and instead of buckling normally, it goes up and through a pulley or loop before returning to the buckle (see lower image). Many people believe that due to its abundant padding, it is kinder to the horse than a traditional cavesson.
Unfortunately, that is wrong. A crank noseband is used to force the jaw shut, as the pulley-buckle system allows extreme tightening around the jaw, and a very stable hold.
This noseband has another problem beyond its extreme tightening, however. The padding, which was supposed to make having their mouth clamped shut more comfortable for the horse (oh the irony), instead grates against the teeth. In a traditional cavesson, it is loose enough and typically not padded enough to interfere. But because the crank is so tight and the padding so thick, it grinds the cheek against the molars. I've included a small orange arrow above where that occurs.
In all honesty, if someone wanted to tie their horse's mouth shut (which I don't condone in any way, shape, or form) I would prefer they use a properly fitted flash. If it's the padding you're after, just have a regular cavesson padded. Feel free to ask questions below.