A coupling device that requires no manual actuation to achieve coupling features a locking bolt movable along a hole extending into a mouth of a hook body to secure a coupling pin therein. A control lever pivotally connected to the locking bolt opposite the mouth end is biased toward a locked position in which motion of the locking bolt is blocked. To engage the coupling pin and the hook mouth, the coupling pin and an operable pin extending through the hollow locking bolt are brought into contact. This causes an end of the operable pin opposite the mouth to push against the control lever to unlock it from the latching position. The coupling pin pushes the locking bolt out of the mouth so that it can pass by further into it, at which point the lever and bolt return to the locked positions to secure the coupling pin inside.