As a responsible owner, you the dog to the vet. They say it sounds like the dog is regurgitating his food, rather than vomiting. After some blood tests and x-rays, it transpires the dog has a condition called megaoesophagus.
This condition means your dog's gullet (the tube down which food passes from the mouth to the stomach) doesn't push food down into the stomach. The end result is when he puts his head down, the food literally tumbles out again under gravity.
The answer is for your dog to sit upright for 20 - 30 minutes after eating. That's all very well but it's mighty time-consuming to sit with the dog for over an hour a day, just holding him upright. In this scenario, a Bailey chair could be just the piece of equipment you need.
However, man-handling a dog, especially a large one, into the chair is a task and a half. Better by far is to have the dog reverse himself in willingly, in the happy anticipation of a full stomach.