Connection construction for a vacuum exhaust device and a vacuum exhaust system

The invention provides a connection construction for a plurality of vacuum exhaust devices, each vacuum exhaust device having a casing in which at least one pump chamber is formed, and an inlet port and an outlet port provided in the casing to communicate with the pump chamber. The plurality of the vacuum exhaust devices are so arranged that their casings are directly connected to enable the pump chambers to communicate with each other. The connection construction has a connection path which allows at least one inlet port of the first vacuum exhaust device of the above said plurality of the vacuum exhaust devices to communicate with at least one of the first outlet port of the second vacuum exhaust device and allows the gas exhausted from the outlet port of the second vacuum exhaust device to flow into the pump chamber of the first vacuum exhaust device through the inlet chamber of the first vacuum exhaust device. The connection construction is also provided with a connection unit disposed outside of each cas