Cylindrical lock with motor-driven latch

1 . A cylindrical lock with a latch bolt for locking an access door, comprising:

a latch bolt assembly comprising a latch bolt and an outer housing, the latch bolt arranged for linear movement between an extended position in which the lock is in a locked state and a retracted position in which the lock is in an unlocked state;

an electro-mechanical mechanism enabling pull-back of the latch bolt from the extended position to the retracted position, the electro-mechanical mechanism comprising an electrically powered motor with a motor shaft and a drive linkage system coupling the motor to the latch bolt to convert rotary motion of the motor shaft to linear motion to electrically power linear movement of the latch bolt, the electro-mechanical mechanism configured to fit within a cylindrical hole or opening formed in a door;

the drive linkage comprising a crank driven by the motor and a latch moving bracket configured to retract the latch bolt of the cylindrical lock from the extended position to the retracted position;

an inner hub and an outer hub;

a hollow spindle coupled to the inner hub and configured to fit within the cylindrical hole or opening; and

wherein the motor is fitted within the hollow spindle.

2 . The cylindrical lock of claim 1 , further comprising:

a control module and one or more return capacitors.

3 . The cylindrical lock of claim 2 , wherein the electro-mechanical mechanism is configured so that when electrical power to the control module is cut, the motor shaft of the motor spins in reverse, returning the latch bolt to the extended position.

4 . The cylindrical lock of claim 3 , wherein the reverse motion is powered by the stored energy in said one or more return capacitors and force of one or more latch bolt springs configured to bias the latch bolt to the extended position.

5 . The cylindrical lock of claim 2 , further including an access control system, and wherein the control module is responsive to a latch retract signal from the access control system and configured to supply drive signals to the motor to retract the latch bolt.

6 . The cylindrical lock of claim 2 , further comprising:

a position sensor;

a magnet secured to the crank, the crank secured to a shaft of the motor;

wherein said position sensor is responsive to the magnet secured to the crank, and the control module is responsive to the position sensor to sense when the latch is fully retracted from the extended position.

7 . The cylindrical lock of claim 6 , further comprising a latch bolt link structure extending from the latch bolt, and wherein the latch bolt bracket is coupled to the latch bolt link structure, wherein the crank, latch bolt bracket and latch bolt link structure cooperate to convert rotary motion of the motor shaft into linear motion of the latch bolt.

8 . A cylindrical lock with a latch bolt configured for locking an access door, comprising:

a latch bolt assembly comprising a latch bolt and an outer housing, the latch bolt arranged for linear movement between an extended position in which the lock is in a locked state and a retracted position in which the lock is in an unlocked state;

an electro-mechanical mechanism enabling pull-back of the latch bolt to a retracted position, the electro-mechanical mechanism configured to fit within a cylindrical hole or opening formed in the access door, the electro-mechanical mechanism comprising:

an electrically powered motor having a motor shaft;

an inner hub and an outer hub;

a hollow spindle coupled to the inner hub and configured to fit within the cylindrical hole or opening;

wherein the motor is fitted within the hollow spindle;

a drive linkage system coupling the motor shaft to the latch bolt, the drive linkage system including a crank affixed to the motor shaft and carrying a magnet, a latch moving bracket coupled to the crank and to the latch bolt; and

a position sensor arranged to sense the presence of the magnet when the latch bolt is at the retracted position; and

the lock further comprising a control module including a microcomputer responsive to access control signals to activate and provide drive signals to the motor, the microcomputer responsive to the position sensor to stop motor drive signals when the latch bolt is at the retracted position.

9 . The cylindrical lock of claim 8 , further comprising a latch bolt link structure extending from the latch bolt, and wherein the latch bolt bracket is coupled to the latch bolt link structure, wherein the crank, latch bolt bracket and latch bolt link structure cooperate to convert rotary motion of the motor shaft into linear motion of the latch bolt.

10 . A cylindrical lock with a latch bolt configured for an access door, comprising:

an electro-mechanical mechanism enabling pull-back of the latch bolt to a retracted position, the electro-mechanical mechanism configured to fit within a cylindrical hole or opening formed in the access door, the electro-mechanical mechanism comprising:

an electrically powered motor having a motor shaft;

a drive linkage system coupling the motor shaft to the latch bolt, the drive linkage system including a crank affixed to the motor shaft and carrying a magnet, a latch moving bracket coupled to the crank and to the latch bolt; and

a position sensor arranged to sense the presence of the magnet when the latch bolt is at the retracted position; and

the cylindrical lock further comprising a control module including a microcomputer responsive to access control signals to activate and provide drive signals to the motor, the microcomputer responsive to the position sensor to stop motor drive signals when the latch bolt is at the retracted position,

wherein the control module further comprises one or more return capacitors connected between the microcomputer and the motor, such that the return capacitors are charged when the microcomputer is activated by the access control signals, and wherein once the access control signals to the control module are cut, the control module is configured to initiate a return sequence powered by charge stored in the return capacitors, the motor turning in a reverse direction for a predetermined duration under power from the capacitor charge, and with assistance from the springs and linkage mechanism, return the latch bolt to the extended position.

11 . The cylindrical lock of claim 10 , wherein the access control signals are DC signals.

12 . The cylindrical lock of claim 11 , wherein the access control signals are 24 V DC signals.