Above is the corking and wirehood machine used to produce our sparkling wine. As the small cellars in Europe are usually damp and underground, the machine is pneumatic instead of electric powered. It has a capacity of 10 bottles per minute. The corks and wirehoods are fed into it by hand and that is the limiting factor for the speed of production. Faster machines have automatic feeding of the wirehood and that gives a higher output. As I am also disgorging the sediment and adding the dose, a faster machine is not necessary.
The corks are 30 mm in diameter and 48 mm high before insertion. The corker side pushes it in about half way. The wirehood is then tied over the remainder of the cork that sticks out of the bottle. As the cork conforms to the restrictions of the bottle neck and the wirehood it forms into the mushroom shape you are familiar with when you pull the cork.
Sparkling wines differ from still wines in that they can be stored upright without loosing the carbon dioxide gas that gives the wine its sparkle. The gas pushes the moisture in the headspace between the wine and the cork into the cork keeping it soft and pliable, thus able to contain the approximately 80 pounds of pressure pushing against it. I store and ship the corked wines upright and you can do the same when you receive the wine if you want to age it a bit before opening it. There is one caution to this method of storage: Wines that have been stored on their side for a year or so will have a cork that does not reexpand when opened. The cork will be dark and moist and can be reinserted in the bottle. It also can loose gas when stood upright as the cork is no longer elastic and unable to tightly seal the bottle. The high acid wine against the cork has degraded the elasticity of the cork cells. If you don't know how long a bottle has been on it's side, it is best to continue storing it that way.
There has not been a problem of "corked" sparkling wines. The problem of the corky flavor that has gotten into some still wines is not a threat to sparkling wine. The difference is the way the corks are made. Wine corks are cylinders of cork punched out of cork oak bark parallel to the vertical axis of the tree. Sparkling wine corks are quarter inch thick discs punched perpendicular to the trunk of the tree. The growth rings are a barrier to the gas trying to push its way through the cork. Only high quality cork is used for the discs, so the tainted flavor has so far been avoided. The end of the cork that sticks out of the bottle is made of particles of low quality cork that has been mixed with a thermosetting glue and extruded into a cylinder. Two discs are glued to one end and the cork sanded to shape. If you put the "agglomerated" end into the bottle, you will get a corky flavor.
If you notice some still wines have a disc at each end and the ground up cork agglomerate in between. This is one solution to the cork problem. There is a disc at each end so the cork does not have to be oriented with the disc against the wine. The still wine corkers run at very high speeds compared to sparkling wine so there is no time to orient the cork.