BACKGROUND OF THE INVENTION
This invention is directed to cylindrical locks, and more particularly to a system for providing a motor-driven latch.
A cylindrical lock is installed through an opening drilled through the door. To applicant's knowledge, an electrically powered latch for a cylindrical lock has not been available. This invention addresses this need, in a reliable and cost-effective manner.
BRIEF DESCRIPTION OF DRAWINGS
Features and advantages of the disclosure will readily be appreciated by persons skilled in the art from the following detailed description when read in conjunction with the drawings wherein:
FIG. 1A is an exploded isometric view of an exemplary embodiment of a cylindrical lock system with an electrified latch bolt retraction system. FIGS. 1B and 1C are isometric views of the cylindrical lock system as in FIG. 1A, in assembled form.
FIG. 2A is an isometric view of the cylindrical lock mechanism of FIG. 1A, showing details of the linkage to the latch bolt pin interface. FIG. 2B is a front plan view of the mechanism of FIG. 2A, in front plan view.
FIG. 3 is a simplified schematic diagram of the control for actuating the cylindrical lock mechanism of FIG. 1A, and illustrating a logic flow of operation.
FIGS. 4A, 4B, 4C, 4D, 4E, 4F, 4H and 4I are plan cross-sectional views, similar to FIG. 2B, but with the cross-section taken to show internal features of the latch bolt and the linkage to the motor drive system, showing different states of the latch bolt and motor drive assembly as the cylindrical lock moves from a locking state to an unlocked state and returning to the locking state.
FIG. 5 depicts a portion of a door in which the lock is installed and depicting a hollow pocket in which the control module is located.
DETAILED DESCRIPTION OF THE INVENTION
In the following detailed description and in the several figures of the drawing, like elements are identified with like reference numerals.
FIGS. 1A-4I illustrate an exemplary embodiment of a cylindrical lock 50 with a motor-driven latch bolt in accordance with an aspect of the invention. The lock includes an electro-mechanical mechanism enabling the pull-back of the latch bolt to a retracted position. The internal parts of the lock are mounted to/within an inner hub 12 and outer hub 12-A, which are secured in assembled configuration by threaded fasteners 21. A flange 24 is fitted to the inner hub 12. The internal parts include a DC brushed gear motor 9, which is fitted in spindle 10, which in turn fits within hub sleeve 11. A motor mounting bracket 8 is secured to the hub sleeve (11), which is in turn keyed to the inside hub 12.
The latch bolt assembly includes latch bolt 17, fitted within outer cylindrical housing 17A. A latch bolt link 17B is connected to the latch bolt, and a distal end is connected to a latch end of latch moving bracket 16 by dowel pin 18. End plate 17C is connected to the housing 17A.
A magnet holder crank 14 is mounted to the shaft 9A of motor 9, and holds magnet 15. A motor end of the latch moving bracket 16 is attached to the periphery of the magnet holder crank by threaded fastener 19.
A slide structure 20 is fitted within slide holder 2, which in turn is fitted into slide cover 3. Compression springs 22 are positioned between the slide structure and the slide holder, biasing the slide structure 20 towards the end plate 17C so the latch bolt 17 is in the locked position.
A PCB holder 1 is attached to the slide holder 2, holding PCB 4 and a Hall effect position sensor 5, positioned to sense the magnet 15 mounted to the periphery of the magnet holder 14 when the latch bolt 17 has been moved to the retracted position.
In operation, the brushed DC motor 9 drives magnet holder crank 14 connected to the latch moving bracket 16, to retract the latch bolt 17 of the cylindrical lock.
Referring to FIG. 3, an exemplary embodiment of a control scheme includes a control module 38, which in this embodiment includes a microcontroller 34 with a built-in motor driver, and position sensor 5 for sensing magnet 15.
The exemplary embodiment of the mechanism described herein involves a brushed DC motor 9 that drives a crank (i.e. the magnet holder crank 14) and latch moving bracket 16 to retract the latch bolt 17 of the cylindrical lock. The mechanism includes two main aspects:
- 1. Cylindrical lock with latch bolt pull-back functionality. The electro-mechanical mechanism is a cylindrical lock that includes an electrical mechanism enabling the pull back of the latch bolt. This feature distinguishes it from conventional cylindrical locks, which do not have any electrically-operated latch retraction features of any kind.
- 2. Utilization of the crank link mechanism: The mechanism achieves the retraction of the latch bolt through the implementation of a crank (magnet holder crank 14) and the latch moving bracket 16. The specific design and operation of this crank link mechanism form a unique aspect of this invention.
The control scheme of the lock system involves a control module and a magnet position sensor 5. FIG. 3 is a simplified schematic and logic flow diagram of features of the system 50. The control module 38 includes microcontroller 34 and return capacitors 36. Control of the lock is by an access control system 30, including, by way of example only, a card key, or manual switch. When actuated by the access control system, an access control power supply 32 provides 24 VDC via wiring 32A to control module 34 which in turn provides low voltage DC drive signals to the motor 9. Electrical power to the lock system 50 can be through wire conductors 44 fed through a door hinge and then through passageways 44 formed in the door to the cylindrical lock 50. Return capacitors 36 (in this exemplary embodiment, two capacitors in series) are connected between the microcontroller 34 and the motor 9. The control module and capacitors will typically be mounted in a hollowed-out pocket 42 in the door beside the lock 50. FIG. 5 illustrates a cut-away portion of a door 40 in which the lock 50 is installed, showing the hollow pocket 42 in which the control module 38 is located. In other embodiments, the control module and capacitors may be mounted at other locations, e.g. at or near the access control system.
When the control module 38 is powered up, low voltage DC is applied to the motor 9, and the motor shaft 9A rotates until the sensor 5 indicates that the retracted position is reached. The magnet sensor (hall effect sensor) 5 will spike in voltage when the magnet 15 is in range. The control module 38 is tuned so a specific voltage limit corresponds with a fully retracted latch position. Once the motor reaches its fully retracted position, the microcontroller 34 is programmed to cut the power to the motor gearbox. The mechanism will keep that position due to the motor and gear friction from the motor gearbox and the angle of the springs 22 and linkage 16 making minimal torque.
Thus, when the access control system through its power supply (32) sends a 24VDC signal to the control module, the control module 38 is powered up, and in turn will power the motor 9 until the motor position reaches full retraction. The retracted position is determined by magnet 15 on the motor spindle and the magnetic hall effect sensor 5, which act as a limit switch. Once the magnet 15 is within range, indicated by the control module detecting a predetermined voltage limit from the hall effect sensor 5, the limit switch will trip, and the control module will cut power to the motor 9. The motor will stop and hold its position due to the friction in the motor assembly and gearbox assembly. Furthermore, in the fully retracted position, the spring and link mechanism are configured to impart a neutral force to the motor assembly. No torque is being applied due to the motor position and linkage angle. For this reason, motor and gearbox friction are sufficient to hold the mechanism in place. It will remain in place as long as the access control system continues to send a 24VDC open signal to the control module. Once the 24VDC open signal to the control module is cut, the control module will initiate a return sequence powered by the reserve energy bank in the capacitors 36. The motor will spin in the reverse direction for a predetermined duration under power from the capacitor charge, and with assistance from the springs and linkage mechanism, it will return the lock to the extended and latching position.
In an exemplary embodiment, the operation of the cylindrical lock system follows the steps outlined below, and as illustrated in the schematic diagram of FIG. 3:
- 1. Starting position: The latch bolt 17 is in the locking state initially, as illustrated in FIGS. 1C, 2A, 2B and 4G.
- 2. The access control system 30 sends a 24 VDC signal to activate the cylindrical lock system, initiating its operation (FIG. 4A). In an exemplary embodiment, the control module is only powered when the access control system 30 sends an activation voltage of 24 VDC.
- 3. While the system 50 is powered, the return capacitors 36 begin to charge, storing electrical energy.
- 4. While under power, the motor 9 spins, which in turn drives the crank 14 and latch moving bracket 16 to retract the latch bolt 17 by acting on latch bolt link 17B, as shown in FIG. 4B.
- 5. The motor and linkage continue to rotate, retracting the latch bolt further (FIG. 4C).
- 6. The motor 9 is stopped when the magnet 15 enters the sensor 5 range, triggering the position limit (FIG. 4D), and the control module removes power to the motor. The fully retracted position is also shown in FIG. 4H.
- 7. The sensor detects the magnet 15, indicating that the latch bolt 17 is in the fully retracted position.
- 8. The motor 9 maintains The position of the latch bolt in the retracted position is maintained until power (fixed 24 VDC) is cut to the controller 34 by the access control system 30. With power applied to the control module, the motor will remain in the latch-bolt-retracted position. When power is removed from the control module, the latch bolt returns to the extended, locked position.
- 9. When power to the control module is cut, i.e. reduced to zero voltage, the motor shaft spins in reverse, returning to the starting position (FIGS. 4E, 4F, 4G and 4I). This reverse motion is powered by the stored energy in the capacitors and the force of the latch bolt springs.
Although the foregoing has been a description and illustration of specific embodiments of the subject matter, various modifications and changes thereto can be made by persons skilled in the art without departing from the scope and spirit of the invention.
Patent Application
20240410208
