Traffic access control system

[0002] This application is based upon Provisional Patent Application Ser. No. 60/144,997 filed Jul. 22, 1999, incorporated herein by reference.

[0003] This invention relates to access control systems and more particularly to electrically controlled systems for opening and closing one or more obstructions to traverse of a vehicle or an individual through a passage.

[0004] It is well known to apply barriers of one sort or another to passage of a vehicle. These barriers may require payment of a fee for temporary removal such as on a toll road. They may require entry of a secret or identifier code, application of a code card, display of a pass, or the like, such as in gated communities. There may be a complete secondary barrier, such as a door, and a primary gate, such as a bar that rotates about a horizontal axis through an angle of 90 degrees. It is useful to delay opening the secondary gate until the barrier is fully open. Gates of the prior art are often subject to damage when the gate is forced open. Their use may be lost while repairs are awaited. These are not the sort of items whose loss of use, even temporarily, is tolerated. Some provision should also be provided for opening the gate in case of power failure. These gates require a non-uniform motion for best operation. They often use a non-circular rotary actuator for this purpose, but this results in undesirable variable forces on the gear system as well as more costly structure. It also wears the gears irregularly because only a fraction of the gear teeth are ever used. In the case of a fire, and/or power loss it is especially important that the access barrier remain open or be openable or by fire fighters from outside, or by people trapped inside, even with loss of power.

[0005] It is accordingly an object of the invention to provide a traffic access control system that overcomes some of the deficiencies of the prior art. The system of the invention may be applied to a variety of access barriers, including, but not limited to, vertically or horizontally swinging bars and gates, vertically and horizontally rolling doors and grilles and the like. It may be applied to traffic by vehicles or individuals. It is another object that the control system of the invention anticipate many of the maintenance problems of the prior art, and provide means for rapid and simple repair that reduce the time that the apparatus is out of operation and the cost of many repairs. The system of the invention includes a high ratio gearmotor whose output may turn an output gear through only about 90°, when moving a barrier between open and closed positions. The gear drives an output shaft through a slip clutch. The output shaft is directly attached to a barrier connecting member that holds the barrier bar and to shaft position sensors. When the motor drives the output gear in normal operation between open and closed positions, the system automatically senses whether the bar is up or down. If the bar is down, and someone lifts the bar to gain access, the shaft will rotate with the bar and the system will sense the bar position. An optional output trigger may be generated to notify the system of such an event. However, the clutch will slip so that there will be no turning of the output gear, and no damage to the apparatus. Once a close signal is received, the barrier automatically realigns the barrier to the horizontal position. Another advantage is that a different quadrant of the gear is now in use. For routine maintenance, one need only lift the bar periodically to ensure uniform wear of the gear. It is necessary to provide some means of allowing access in case of power failure. The system provides a backup battery on continuous charge. The system senses when power fails. It provides a signal to open the gate if the power has been off for more than a preset time. It may include means requiring a trigger before the backup opens the gate. The system may also be provided with battery charge sensing means and means to elevate the gate when power fails and the battery charge falls below a pre-selected value.

[0006] The motor drive is a reversing DC gearmotor. It is driven by a series of DC pulses of variable width so that the output rotary motion can be non-uniform. This results in the same motion as provided by non-circular drive components such as the sinusoidal drives well known in this art, but with numerous cost and function advantages enjoyed by uniform circular components.

[0007] Alternatively, the motor drive may be an AC motor with variable frequency power to achieve non-uniform motion.

[0008] A principal application of the invention will be to operate vehicular barriers that pivot through about 90° about a horizontal axis from a horizontal closed position to vertical open position. Other applications operate barriers such as doors that slide, raise, or pivot about a vertical axis.

[0009] These and other objects, features and advantages of the invention will become more apparent when the detailed description is studied in conjunction with the drawings, in which like reference characters indicate like elements in the various drawing figures.

[0010] FIG. 1 is an exploded view of a reduction gear with clutch of the invention.

[0011] FIG. 2 is a rear elevation view of the device of FIG. 1.

[0012] FIG. 3 is a perspective view, partially exploded and broken away, of a gate control system of the invention.

[0013] FIG. 4 is a diagrammatic, partially exploded, perspective view of an access control system of the invention.

[0014] FIG. 5 is a schematic diagrammatic representation of the invention with pulse width DC speed control.

[0015] FIG. 6 is a schematic diagrammatic representation of another embodiment of the invention using variable frequency AC speed control.

[0016] FIG. 7 is a schematic diagrammatic representation of another embodiment in which a control system operates two separate traffic lane barriers.

[0017] Referring now to the drawing FIGS. 1-5, an exemplary access control system of the invention is shown in the form of a rotary bar that swings about a horizontal axis through an angle of 90 degrees between a horizontal closed position and a vertical open position. The actuation of the mechanism may be initiated by a manual switch in a gatehouse, a card reader, a keypad, or another device well known in the art. The reversible motor is powered by a low voltage direct current from an AC line through a DC power supply 25. A solar panel or trickle charger (not shown) keeps a standby battery 26 fully charged. When a sensor detects a failure of power, the battery power automatically cuts in. The system may be programmed to automatically open the barrier at that time, or when a trigger signal is applied. As best seen in FIG. 4, the bar 1 is held securely in a three sided member 2 such that the member takes the weight of the bar distributed over its lower flange 3. Bolts 4 through apertures 31 in the web of member 2 hold the bar to member 2 with frangible plastic nuts 5. When a vehicle strikes the bar, the nuts will yield before any other damage is done. A supply of inexpensive nuts is kept on hand. The damage is then readily repaired with negligible time or labor cost. The member 2 is secured to rotary drive shaft 6 by shear pin 7 that will not yield before nuts 5. Shaft 6 passes through housing or gearcase 8 and out the other side to end 9, which is fixed to magnet carrier 10. Circuit board 11 carries all of the control circuitry including: a microprocessor or microcontroller 18; semiconductor switch means 19 to drive the motor in forward or reverse; and two Hall effect sensors 12, 13 to cooperate with magnet 14 on carrier 10 to detect the up and down positions respectively of the bar 1. Optionally other position sensors such as mechanical switches may be used. A reduction gear assembly 24 includes worm 23 that drives the output worm gear 15 (FIG. 1) that is rotatably mounted on shaft 6. The friction-clutch or slip clutch assembly 20 causes the gear to move with the shaft until a certain resistance to shaft motion is encountered. The slip point is adjusted by nut 16, which forces the friction discs 17 against the sides of the gear 15. In normal operation, only one quarter of the gear is in use. When the bar is forced up while the motor is stopped, the shaft will rotate, but the gear will not. An optional output pulse may be sent to the system to notify it of the occurrence of that event. The system will then automatically level the arm at the horizontal position after receiving a close signal. The position sensor mechanism will remain functional, and no damage is done. Furthermore, a new quadrant of the gear is now in use. This mechanism may be used to ensure uniform wear of the gear. The semiconductor switch mechanism 19 that drives the motor 21 applies power in the form of a series of DC pulses 22. It drives the motor in either forward or reverse direction as required to permit or deny access. It is desirable to move the barrier more slowly at the beginning and end of the travel for safety. The mechanism for achieving this is provided by pulse width modulation. That is, the pulses are narrower at the beginning and end of travel, which results in slower motion at these times. Since this is under control of microprocessor 18, any particular motion can be achieved by simply changing the program. This has many advantages over a hardware mechanism. When the system includes a movable first gate and a more complete second barrier such as a door, a signal to open the first gate will be stored while the system interrogates the second barrier until it senses that it is open before it will open the first gate. The system may lock out opening of the more complete second barrier when the first barrier is forced open to prevent tampering with the access control.

[0018] This mechanism of monitoring two access control devices may also be used to regulate two gates in adjacent lanes, such as a resident lane and a visitor lane as illustrated schematically in FIG. 7. Each may lock out the other while the first is operating, but the order to open the second one will be stored by the system in memories 34 and begin opening the second gate when the first gate has finished operation by action of the first-in-first-out (FIFO) program well known in the art of microprocessor 18.

[0019] The microcontroller or electronic control means 18 may be programmed to perform other useful functions, such as shutting off the motor after a preset time of operation so as to prevent the continuing running when the barrier encounters an obstacle before completion of the motion. In gated communities there are frequent complaints when a following vehicle tries to pass before the gate comes down. The system may be programmed to open the barrier when it encounters an obstacle during closing to overcome this problem.

[0020] Referring now to FIG. 6, non-uniform motion of the output shaft may be alternatively achieved by use of an AC motor 28 powered by an alternating current power supply 27 whose frequency is controlled by the microcontroller 18, generating an alternating current of variable frequency 29. The motor is reversed by reversing switch 30.

[0021] The above disclosed invention has a number of particular features which should preferably be employed in combination, although each is useful separately without departure from the scope of the invention.

[0022] While I have shown and described the preferred embodiments of my invention, it will be understood that the invention may be embodied otherwise than herein specifically illustrated or described, and that certain changes in form and arrangement of parts and the specific manner of practicing the invention may be made within the underlying idea or principles of the invention.