Rotating frame animal traps have long been used in the humane trapping of fur-bearing and other animals. As is well known in the art, a rotating frame trap typically comprises a pair of similar frames, which frames can be of a generally square, rectangular, or part trapezoidal shape. The frames are pivotally connected at adjacent ends for relative rotation about a common axis. Two pairs of coacting jaws are thereby formed by the sides of the frames. At least one actuator, consisting of a coil spring having arms terminated in closed rings slidable along and encircling one set of the adjacent ends of the frames, is used to urge the jaws toward a closed position and, when the trap is sprung, to maintain said jaws in a closed position. A rotating frame trap of this type is described and illustrated in U.S. Pat. No. 3,426,471 (Lehn), the disclosure from which is incorporated herein by reference. In such a trap, the ends which cooperate with the rings are shaped so that, in the set position of the trap, these ends lie substantially parallel to one another. The central portions of the ends, near the common axis of the frames, form a cross within the rings on the arms of the coil springs. Trigger mechanisms useful with rotating frame traps maintain the frames of the traps in an open position when the traps are set. The frames are released when the traps are sprung in order to permit, as a result of the action of the spring and the rings on the end of the actuator, rapid rotation of the frame through an angle of approximately 90.degree.. The jaws of the trap thus quickly strike and kill an animal in the trap.
Commonly used trigger mechanisms, such as that described in the aforementioned Lehn patent, comprise a pair of prongs adapted to project inwardly towards the center of an open, set trap. The prongs are fixedly connected to a sleeve rotatably connected to one of the sides of one of the frames of the trap. A bar is rotatably mounted on the adjacent side of the other trap frame opposite the sleeve and has one or more notches formed therein which are adapted to releasably engage the sleeve and thereby releasably hold the trap frames in open set position against the bias of the actuator. When the prongs are moved forward or backward in a plane essentially perpendicular to the plane of the trap (for example, by an animal passing through the open trap) the prongs rotate the sleeve and thereby dislodge the bar to permit the trap to close.
The two-pronged trigger arm described and illustrated in the Lehn patent is formed from a bent wire which is fixed at its bend to a flat portion of one of two members of the trigger sleeve. The trigger sleeve is formed of two similar members, each having a generally semi-cylindrical portion and a flat portion. The two members are joined together by the rivets which hold the bent wire to the flat portion of one of the members, the two members being joined about the side of one of the trap frames. The overall trigger mechanism, therefore, includes three parts, namely, the two sleeve members and the bent wire trigger arm.
We have found that during manufacture of the trap, particularly during the assembly of the trigger device onto the frame, the Lehn-type trigger mechanism described above is quite disadvantageous. Specifically, it becomes relatively time-consuming to join the two sleeve members together with rivets while making sure that the bent wire is also being secured by those rivets to the flat portion of one of the sleeve members. In addition, we have found that replacement of the bent wire trigger arm, should it break, by a trapper or other user of the trap, is extremely difficult in view of the use of rivets to hold the entire trigger mechanism together. Specifically, in order to replace the bent wire, the trapper would have to disengage the rivets which hold the bent wire and the two sleeve members together. This disengagement is of itself difficult; of greater difficulty is reassembly of the three elements by means of the rivets.