Interlock and surgical instrument including same

1. A surgical instrument, comprising:

an end effector comprising:

a cutting instrument actuable to cut an object;

a longitudinally extending channel, the channel having a proximal end and a distal end;

an anvil pivotally attached to the channel, wherein the object is positionable between the anvil and the channel;

a staple cartridge removably seated in the channel, the staple cartridge having a proximal end and a distal end;

a firing drive slot formed between the cartridge and the channel through which at least a portion of the cutting instrument passes when the cutting instrument is actuated; and

a sled disposed in the staple cartridge, wherein when the cutting instrument is actuated the sled is engaged by the cutting instrument and driven longitudinally through the staple cartridge from an unfired position located at the proximal end of the staple cartridge to a fired position located at the distal end of the staple cartridge;

a motor coupled to the end effector to actuate the cutting instrument; and

an interlock coupled to the end effector and to the motor, the interlock to prevent actuation of the cutting instrument based on a current through the motor, the interlock comprising:

a blocking mechanism to prevent actuation of the cutting instrument when the sled is not present in the unfired position; and

a lockout circuit to sense the current through the motor and to interrupt the current through the motor based on the sensed current.

2. The instrument of claim 1 , wherein the lockout circuit is further to interrupt the current through the motor based on a position of the cutting instrument.

3. The instrument of claim 1 , wherein the current through the motor increases when the blocking mechanism prevents the cutting instrument from advancing longitudinally through the channel.

4. The instrument of claim 1 , wherein the blocking mechanism comprises at least one spring finger disposed in the channel.

5. The instrument of claim 1 , wherein the blocking mechanism comprises at least one ramped hook springedly attached to the channel.

6. The instrument of claim 1 , wherein the blocking mechanism is formed integrally with the staple cartridge and comprises at least one proximally projecting member, wherein the at least one member is movable between the firing drive slot and a recess in the staple cartridge.

7. The instrument of claim 1 , wherein the lockout circuit comprises a current sensor to generate a first signal representative of the sensed current.

8. The instrument of claim 7 , wherein the lockout circuit further comprises a current detection module to compare the first signal to a predetermined threshold signal.

9. The instrument of claim 8 , wherein the current detection module comprises a microprocessor.

10. The instrument of claim 8 , wherein the lockout circuit further comprises a position sensor to determine a position of the cutting instrument.

11. The instrument of claim 10 , wherein the lockout circuit further comprises a switch connected in series with the motor, the switch controllable to interrupt the current through the motor based on the position of the cutting instrument and the comparison of the first signal to the predetermined threshold signal.

12. The instrument of claim 11 , wherein the switch is controllable to interrupt the current through the motor when the position of the cutting instrument is within a predetermined distance of the proximal-most position of the cutting instrument and when the first signal exceeds the predetermined threshold signal.