A coupling device includes a tubular body defining a channel having along an axis a first segment for receiving an endpiece and a second segment including an axially movable valve member which is spring-thrustable from the endpiece from a closed position, towards a disengaged position. The first segment includes a latch movably mounted to the housing and transversely movable via spring relative to the channel-between unlocked and locked positions. The latch includes a transverse bore enabling the endpiece to pass through the latch to push against the valve member, and first and second steps projecting into the bore in axially offset positions such that, when the latch is locked, the first step retains the endpiece in a pushed-in position holding the valve member disengaged and when the latch is unlocked, the second step retains the endpiece in an intermediate position leaving the valve member closed to enable endpiece purging.