Abstract: A vacuum gate valve includes a valve body having an opening therethrough and a valve seat surrounding the opening, and a swing gate assembly rotatable about a pivot axis between an open position and a closed position. The swing gate assembly includes a swing gate body, a resilient seal gasket mounted to the swing gate body so as to sealingly engage the valve seat in the closed position, and a spreader for flattening the resilient seal gasket in a region that engages the valve seat. The gate valve further includes an actuator for rotating the swing gate assembly between the open position and the closed position. In a preferred embodiment, the seal gasket is a resilient tube, and the spreader is located within the tube. The swing gate assembly may include a mechanism for adjusting the spreader to thereby adjust the tension applied to the seal gasket.