This is a wringer, also known as a mangle. Its job is to squeeze the water out of the clothes you wash, and it does it much more efficiently than wringing them (meaning twisting and squeezing them) by hand. You turn the crank and feed the clothes between the two rollers, being very, very careful not to let your hand get in there as well.
To put someone through the wringer is a common expression meaning to put someone through a lot of trouble until it seems as though everything is squeezed out of him.
Since no one you know uses a wringer anymore, many people have forgotten what a wringer is. We often see the expression written “put him through the ringer.” As far as the Editor is concerned, that use of “ringer” will never be correct no matter how common it becomes, because it will never make sense: there is no meaning of the word “ringer” that describes something you can put someone through to squeeze the life out of him.