AU2002300168A1 - Improvements in Boom Actuators - Google Patents

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "IMPROVEMENTS IN BOOM ACTUATORS" The following statement is a full description of this invention, including the best method of performing it known to me: 2

TITLE

"IMPROVEMENTS IN BOOM ACTUATORS" FIELD OF THE INVENTION This invention is concerned with improvements in boom actuators.

The invention is concerned particularly, although not exclusively, with boom gate actuators of the type employed in tollway plazas.

BACKGROUND OF THE INVENTION Passage through a traffic lane of a toll collection station is usually controlled by a boom moveable between a horizontal barrier position and an upright 'free to pass' position.

The boom is activated by the collection and validation of the correct toll payment whereby a coin receiver and validation apparatus, an electronic smart card or other electronic transmission sends a signal to the boom actuation apparatus to elevate the boom. The presence, or absence, of a vehicle adjacent the boom, and the passage of an authorised vehicle, is determined by optical and/or proximity sensors to close the boom after an authorised vehicle has passed through.

While generally effective for their intended purpose, prior art traffic control booms suffer a number of disadvantages.

Many impatient drivers tend to anticipate the upward movement of a boom within a short period of time after placing the toll coinage in a collection hopper. Either misanticipation or misjudgement of the proximity of a boom leads to contact between the vehicle and the boom resulting in scratched paint on the vehicle, damaged radio aerials and/or damaged windscreens and, frequently, broken booms.

Apart from the cost and inconvenience of frequent boom replacement, tollway operators incur very substantial insurance premiums for vehicle damage caused by lane control booms. In addition, tollway operators can face loss of revenue if a lane has to be closed for repairs during a busy period.

While endeavours have been made to improve vehicle sensing systems to reduce vehicular damage and also to develop breakway boom barriers which reduce boom breakage and vehicle damage, little attention has been paid to boom actuation systems which overcome the above problems while at the same time providing a greater level of comfort and reassurance to patrons that their vehicle will not be damaged by the boom arm.

Known boom actuation systems typically comprise an electrically powered motor coupled to a reduction gearbox having a driveshaft extending transversely of a housing. The driveshaft has a drive crank attached thereto, the drive crank being coupled in turn to a cranked actuator shaft extending parallel to the driveshaft via an arm pivotally connected at tis ends to respective drive and actuator cranks.

The drive motor was coupled to a controller in turn coupled to various sensors including optical and magnetic sensors and to a coin collection device for selective control of a boom arm mounted on one end of the actuator shaft.

The drive motor was controlled to move the boom arm through 90' between a horizontal barrier position and a vertical "free to pass position" by the drive controller operated the drive motor in one rotational direction to elevate the boom arm and then in an opposite direction to return it to its barrier position. This system suffered a number of disadvantages in that the main drive gear attached to the drive shaft of the reduction gearbox was being driven only through an arc of greater than 900 but less than 180', typically 1350, with the result that the reduction gearboxes were prone to early failure and high maintenance requirements. Other problems included excessive wear in bearings and other mechanical components due to high inertial loads and poor response times to sensor or actuator signals. High maintenance downtime and poor response times alone were responsible for reduced traffic throughput. Moreover, with poor response times for a boom arm responding to a mid cycle signal to reverse direction to move away from a detected vehicle, it was difficult to reduce the incidence of vehicle damage.

In order to improve performance of such prior art boom gate actuators and otherwise ease the wear arising from inertial operating loads a substantial tension spring was coupled between a crank on the actuating arm and a frame member to reduce the load on the drive motor during elevation of the boom as the spring contracted from an extended state.

An AC drive motor with a programmable controller was provided with a 20% braking rate on the voltage inverter and otherwise programmed to provide a ramped starting and finishing voltage profile during the actuation cycle to reduce inertial loads on the system. Such a boom actuation system typically has a "boom up" cycle time of 0.7 seconds and a "boom down" cycle also of 0.7 seconds.

While these boom gate actuators offer an improved boom speed they still suffer a number of problems. Mounted on the actuator shaft are a number of cams, each coupled to a respective microswitch to selectively energize or de-energize the drive motor controller. The actuating crank mounted on the actuator shaft is prevented against overrotation by a cushioned mechanical stop which applies an impact load to the boom arm and the actuation system when it is contacted, there is no effective stop means for the actuator shaft as it reaches the horizontal "barrier" position with the result that if poorly calibrated, the momentum of the boom could carry the actuator shaft past its intended rest position to an over centre position. Severe inertial loads cause a degree of "whip" in the actuator shaft to the extent that the microswitches controlling say, mid cycle reverses of direction, can malfunction. In practice it has been shown that these actuators require frequent calibration of the 6 cam/microswitch actuators for accurate operation. These actuators continue to use a reversal of motor direction to operate the boom in up and down cycles.

It is an aim of the present invention to overcome or ameliorate at least some of the problems associated with prior art boom arm controllers of the type employed in tollway plazas.

SUMMARY OF THE INVENTION According to one aspect of the invention there is provided an actuating system for a boom arm, said system including:a drive system having a drive motor coupled to a reduction gearbox having a rotatable drive shaft with at least one drive crank extending therefrom; a boom actuator shaft rotatably journalled in bearing members, said boom actuator shaft including at least one actuator crank extending therefrom, said drive crank and said actuator crank being coupled by an arm pivotally mounted adjacent opposite ends thereof to a respective drive crank and actuator crank, said actuating system characterised in that, in use, said drive motor and reduction gearbox are adapted to rotate unidirectionally to effect movement of a boom arm between an initial barrier position to an upright position and subsequently back to said initial barrier position.

Suitably said drive system includes a variable speed AC drive motor with a programmable drive controller.

Preferably said drive system includes an AC injection brake programmed to provide, in use, a progressive braking reaction to said boom arm as it approaches respective upper and lower limits of an elevation or return cycle.

Preferably said drive controller is programmed, in use, to apply braking rate of from 50% to 200% when a vehicle sensor detects a risk of vehicular engagement with said boom arm in mid cycle.

The drive system, in use is programmed to provide an elevation cycle which is faster than a return cycle.

Suitably, the elevation cycle has a period in the range of from 25% to 75% of the period of the return cycle.

If required the system may include proximity switches to selectively activate or deactivate said drive system at predetermined barrier and elevated positions.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may be more fully understood and put into practical effect, reference will now be made to a preferred embodiment illustrated in the accompanying drawings in which:- FIG. 1 shows schematically a side elevation of the actuating system; and, FIG. 2 shows a rear elevation of the system of FIG. 1.

In FIG. 1, the boom actuation system is enclosed in a housing 1 which includes a support member 2 for a variable speed AC 8 motor 3 having a programmable controller 4. Attached to the output shaft 5 of motor 3 is a reduction gearbox 6 having a drive shaft 7 extending from opposite sides thereof. Crank arms 8 are attached adjacent the opposite ends of shaft 7.

Mounted above drive shaft 7 is an actuator shaft 9 rotatably journalled in bearings (not shown) secured on the inner wall surfaces of housing 1. Actuator shaft 9 includes spaced crank arms 10 aligned with cranks 8 with pivotally coupled connecting arms 11 connected between cranks 8 and On one end of actuator shaft 9 extending through a side wall of housing 1 is a boom arm 12 shown in solid outline in an elevated position and shown in phantom in a horizontal or barrier position. Crank arm 10 is shown in phantom in a position corresponding to the barrier position of boom arm 12 and illustrates the extent of reciprocating movement of actuator shaft 9 through a 90' arc as crank 8 rotates through 180' to move the boom arm 12 to a barrier position and through a further 1800 to return the boom arm to the upright position.

Mounted on actuator shaft 9 are disk like carriers 13 for magnetised buttons 14 which are detectable by proximity detectors 15 at the opposite ends of the 90' boom arc.

FIG. 2 shows a rear elevation of the apparatus of FIG. 1 and for the sake of clarity, like reference numerals are employed for like features.

In use, controller 4 received an initial signal from a coin collection device (not shown) to allow a vehicle to pass. Preprogrammed controller 4 energises AC motor 3 with voltage profile which is initially ramped to provide a "soft" initial acceleration from rest and subsequently an increasing rate of acceleration to a maximum velocity at a point during the 900 boom are arc. As the boom arm approaches the vertical position, the controller applies a braking voltage profile to decelerate the arm to a "soft" stop at the end of the 90' travel arc. The "soft" acceleration from rest and deceleration to rest substantially minimises the inertial loads on the mechanical components of the system.

During the rotation of the actuator shaft and boom arm through 90' from the horizontal rest position to the vertical position, drive shaft 7 has rotated through 180' with the tangential velocity of the free end of arm 8 following a half sine wave pattern through a minimum value at the commencement of the 1800 cycle to a maximum value at and returning back to a minimum value at the end of the 900 arc.

This, combined with the selectively profiled drive motor speed range through the arc substantially minimises inertial shocks on the mechanical components of the system.

As the boom arm 12 approaches a vertical position, proximity detector 15 detects the presence of magnetic button 14 and a signal from detector 15 to controller 4 causes the boom arm to be braked and stopped in the upright position.

When the vehicle clears the field monitored by the optical and/or magnetic detectors (not shown) controller 4 then activates drive motor 3 to return the boom arm 12 back to its horizontal rest position using pre-programmed "soft" acceleration and deceleration voltage profiles and the rest position is determined by a further proximity detector 15 and magnetic button 14. During the upward and downward cycles the drive motor rotates unidirectionally thus ensuring even wear distribution in the main output gear of the reduction gearbox. Respective carriers 13 are adjustably mounted on shaft 9 and as such permit calibration of the precise initial rest position and upright position of the boom arm 12.

In a preferred embodiment of the invention, the controller 4 is programmed to provide an upward boom travel cycle time of 0.4 seconds and a downward cycle time of 1.2 seconds.

In the event that a vehicle is detected in the path of the boom arm as it returns to its horizontal or rest position, the controller upon receiving the sensor signal applies a maximum braking voltage to the variable speed motor to deliver a braking torque of at lest 100% to the motor.

As soon as the controller senses that the drive motor 3 has ceased rotating, it applies an acceleration voltage to the drive motor to rotate it in the opposite direction at a maximum rate of acceleration to avoid engagement between the vehicle and the boom arm. A similar acceleration profile to that employed to accelerate the boom arm from its "normal" rest position has been found to be satisfactory although a different profile may be programmed into controller 4 for this purpose.

It readily will be apparent to a person skilled in the art that many modifications and variations may be made to the invention without departing from the spirit.and scope thereof.

Similarly, it equally will be apparent that the present invention offers substantial advantages over prior art boom gate actuation systems in that while the "up" cycle is much faster, the inertial shock on the mechanical components of the system is less than or no greater than prior art systems. Combined with the unidirectional drive of the drive motor and gearbox, it is expected that maintenance intervals and service life of systems according to the invention will be substantially extended.

Moreover, the effectively instantaneous response to vehicle presence detection as well as the substantially decreased "up" cycle time is expected to permit reduced vehicular damage incidents with consequent reduction in insurance premiums and repair costs.

Claims (9)

1. An actuating system for a boom arm, said system including:- a drive system having a drive motor coupled to a reduction gearbox having a rotatable drive shaft with at least one drive crank extending therefrom; a boom actuator shaft rotatably journalled in bearing members, said boom actuator shaft including at least one actuator crank extending therefrom, said drive crank and said actuator crank being coupled by an arm pivotally mounted adjacent opposite ends thereof to a respective drive crank and actuator crank, said actuating system characterised in that, in use, said drive motor and reduction gearbox are adapted to rotate unidirectionally to effect movement of a boom arm between an initial barrier position to an upright position and subsequently back to said initial barrier position.

2. A system as claimed in Claim 1 including a variable speed AC drive motor with a programmable drive controller.

3. A system as claimed in Claim 1 or Claim 2 including an AC injection brake programmed to provide, in use, a progressive braking reaction to said boom arm as it approaches respective upper and lower limits of an elevation or return cycle.

4. A system as claimed in Claim 3 wherein said drive controller is programmed, in use, to apply braking rate of from 50% to 200% when a vehicle sensor detects a risk of vehicular engagement with said boom arm in mid cycle.

A system as claimed in any one of Claims 2 to 4 wherein the drive system, in use is programmed to provide an elevation cycle which is faster than a return cycle.

6. A system as claimed in Claim 5 wherein the elevation cycle has a period in the range of from 25% to 75% of the period of the return cycle.

7. A system as claimed in any preceding claim including proximity switches to selectively activate or deactivate said drive system at predetermined barrier and elevated positions.

8. An actuating system substantially as hereinbefore described with reference to the accompanying drawings.

9. A boom gate whenever actuated by the actuating system of any one of Claims 1 to 8. 14 A toll barrier having a boom gate actuable by an actuating system of any one of Claims 1 to 8. DATED this Seventeenth day of July 2002. CHRISTOPHER DOUGLAS BROWN by his Patent Attorneys FISHER ADAMS KELLY