A displacement-actuated positive-drive clutch (10, 20) comprising: an input member (11, 21) having a positive engagement structure (11d, 21d) provided thereon; a cam plate (17, 22) connected for rotation with the input member (11, 21); an output member (13, 23); and a clutch plate (16, 25) connected for rotation with and for axial movement relative to the output member (13, 23), the clutch plate (16, 25) having a positive engagement structure (16b, 25b) provided thereon that positively engages the positive engagement structure (11d, 21d) provided on the input member (11, 21) to engage the displacement-actuated positive-drive clutch (10, 20) automatically in response to the occurrence of a predetermined amount of relative rotational movement between the input member (11, 21) and the output member (13, 23), characterized in that: (a) the cam plate includes a cam that cooperates with a cam recess provided on the clutch plate so as to cause the clutch plate to move toward the input member automatically in response to the occurrence of a predetermined amount of relative rotational movement between the input member and the output member; or (b) the cam plate has a surface provided thereon and a cam groove extends throughout at least a portion of the surface, wherein the clutch plate includes a cam follower that is received within the cam groove provided in the surface so as to cause the clutch plate to move toward the input member automatically in response to the occurrence of a predetermined amount of relative rotational movement between the input member and the output member. an input member (11, 21) having a positive engagement structure (11d, 21d) provided thereon; a cam plate (17, 22) connected for rotation with the input member (11, 21); an output member (13, 23); and a clutch plate (16, 25) connected for rotation with and for axial movement relative to the output member (13, 23), the clutch plate (16, 25) having a positive engagement structure (16b, 25b) provided thereon that positively engages the positive engagement structure (11d, 21d) provided on the input member (11, 21) to engage the displacement-actuated positive-drive clutch (10, 20) automatically in response to the occurrence of a predetermined amount of relative rotational movement between the input member (11, 21) and the output member (13, 23), characterized in that: (a) the cam plate includes a cam that cooperates with a cam recess provided on the clutch plate so as to cause the clutch plate to move toward the input member automatically in response to the occurrence of a predetermined amount of relative rotational movement between the input member and the output member; or (b) the cam plate has a surface provided thereon and a cam groove extends throughout at least a portion of the surface, wherein the clutch plate includes a cam follower that is received within the cam groove provided in the surface so as to cause the clutch plate to move toward the input member automatically in response to the occurrence of a predetermined amount of relative rotational movement between the input member and the output member. (a) the cam plate includes a cam that cooperates with a cam recess provided on the clutch plate so as to cause the clutch plate to move toward the input member automatically in response to the occurrence of a predetermined amount of relative rotational movement between the input member and the output member; or (b) the cam plate has a surface provided thereon and a cam groove extends throughout at least a portion of the surface, wherein the clutch plate includes a cam follower that is received within the cam groove provided in the surface so as to cause the clutch plate to move toward the input member automatically in response to the occurrence of a predetermined amount of relative rotational movement between the input member and the output member.