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Title:
SWITCH FOR A POLE HAVING MOVEABLE PORTIONS
Document Type and Number:
WIPO Patent Application WO/2010/085859
Kind Code:
A1
Abstract:
A switch for a pole is disclosed. The pole has a stationary portion and a moveable portion, and an electrical cable passing within. The switch is associated with the electrical cable and selectively allows electricity to pass along the cable. The switch is operatively associated with the moveable portion of the pole such that the position of the moveable portion relative to the stationary portion determines whether the switch is opened or closed.

Inventors:
WALTON MICK (CA)
TAUBER ROB (CA)
BULMER JAMES (CA)
Application Number:
PCT/AU2010/000117
Publication Date:
August 05, 2010
Filing Date:
January 29, 2010
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
SAFE SWIVEL PATENT CO PTY LTD (AU)
WALTON MICK (CA)
TAUBER ROB (CA)
BULMER JAMES (CA)
International Classes:
F21V23/04; F21V25/02; H05B37/02
Foreign References:
US20040156200A12004-08-12
CN2833338Y2006-11-01
CH565305A51975-08-15
FR2647530A31990-11-30
US4381539A1983-04-26
US4731718A1988-03-15
US6585221B12003-07-01
Other References:
PATENT ABSTRACTS OF JAPAN
Attorney, Agent or Firm:
NEWMAN, Barry, Stephen (PO Box 67Burswood, Western Australia 6100, AU)
Download PDF:
Claims:
Claims

1. A switch for a pole, the pole having a stationary portion and a moveable portion, the pole having an electrical cable passing within, the switch being associated with the electrical cable and selectively allowing electricity to pass along the cable, whereby the switch is operatively associated with the moveable portion such that the position of the moveable portion relative to the stationary portion determines whether the switch is opened or closed.

2. A switch for a pole as claimed in claim 1 , wherein the moveable portion is moveable between an operative position and a maintenance position, and the switch acts so as to permit the flow of electricity through the cable when the moveable portion is in the operative position and to prevent the flow of electricity when the moveable portion is in the maintenance position.

3. A switch for a pole as claimed in claim 1 or claim 2, wherein the switch includes a sensor for determining an orientation of the moveable portion.

4. A switch for a pole as claimed in claim 3, wherein the sensor comprises one or more accelerometers coupled to the moveable portion.

5. A switch for a pole as claimed in claim 3 or claim 4, wherein the sensor provides information about the orientation of the moveable portion as one or more electrical signals.

6. A switch for a pole as claimed in any one of claims 3 to 5, wherein the switch includes a controller which can receive information from the sensor and selectively open or close a controllable switch in response to that information.

7. A switch for a pole as claimed in claim 6 wherein the controller is a microcontroller.

8. A switch for a pole as claimed in claim 7 wherein the controllable switch is a relay controlled by output from the microcontroller.

9. A switch for a pole as claimed in any one of claims 3 to 8, wherein the sensor is electrically powered by a battery.

10. A switch for a pole as claimed in any one of claims 3 to 8, wherein the sensor is powered by electrical power sourced from the electrical cable.

11. A switch for a pole as claimed in claim 10, wherein the electrical power for the sensor is sourced from the electrical cable through a transformer circuit.

12. A switch for a pole as claimed in claim 11 , wherein the transformer circuit includes a transformer for transferring an alternating current (AC) input voltage to an AC output voltage, the output voltage being less than the input voltage, a rectifier for rectifying the AC output voltage to a direct current (DC) voltage, and a regulator for regulating the DC voltage to a microcontroller supply voltage.

13. A switch for a pole as claimed in any one of claims 6 to 8, or any one of claims 9 to 11 when dependent on one of claims 6 to 8, wherein the controller has a memory which retains as a reference the signals received from the sensor when the pole is in an initial operative position.

14. A switch for a pole as claimed in claim 13, wherein the controller determines a tilt angle of the moveable pole portion by calculating a difference between a subsequent sensor signal and the reference signal.

15. A switch for a pole as claimed in claim 14, wherein the controller is arranged to compare the tilt angle with a predetermined setpoint, to determine whether or not the moveable pole portion is in a position corresponding to a maintenance position.

16. A switch for a pole as claimed in any one of claims 6 to 8, 12 to 15, or any one of claims 9 to 11 when dependent on one of claims 6 to 8, wherein the controller is arranged to only open or close the controllable switch when the moveable pole portion has been in either an operative or a maintenance position for a predetermined period of time.

17. A switch for a pole as claimed in claim 16, wherein the controller is arranged to open the controllable switch when the moveable pole portion has been in the maintenance position for a first predetermined period of time, and the arranged to close the controllable switch when the moveable pole portion has been in the maintenance position for a second predetermined period of time.

18. A switch for a pole as claimed in claim 17, wherein the first predetermined period of time is shorter than the second predetermined period of time.

19. A pole having a stationary portion and a moveable portion, the pole having an electrical cable passing within, and having a switch as claimed in any preceding claim associated with the electrical cable and selectively allowing electricity to pass along the cable.

20. A pole as claimed in claim 19, wherein the electrical cable provides electricity to an electrical attachment located on the moveable portion of the pole.

21. A pole as claimed in claim 20, wherein the pole is a light pole and the electrical attachment is a light.

Description:
"SWITCH FOR A POLE HAVING MOVEABLE PORTIONS"

Field of the Invention

The present invention relates to poles or similar elongate members having electrical cables or wires passing within. In particular, the invention relates to such poles which include portions moveable between different positions, such as between an operating position and a maintenance position. The invention is of particular utility where the pole includes an attached electrical fixture.

Background to the Invention

It is common to locate electrical fixtures, particularly lights, at elevated locations. This is often done by means of light poles, which extend generally vertically from a base position. In many cases, such as in street lighting, the base position is the ground. In other situations, such as in processing plants or refineries, the base position may be an elevated platform.

When maintenance of the electrical fixture is required, there are several methods used to access the fixture. Where the pole is not too high, and the base is firm and stable, a ladder may be used. Where the pole is higher, it may be necessary to use mechanical lifting equipment, such as a boom lift. Other specialised equipment is also used on occasion.

In order to obviate the need for such equipment, various poles have been proposed which include a moveable portion on which the electrical attachment is located. The moveable portion is generally lowerable from an operating position, in which the electrical attachment is out of reach, to a maintenance position in which the electrical attachment is within reach. The moveable portion may be hinged to a stationary portion, or otherwise connected. One such pole is the Swivelpole™ produced by Safe Swivel Technology Pty Ltd, and patented as US Patent Number 6957832, the contents of which are incorporated herein by reference. This pole includes a joint which allows a moveable portion to swivel relative to a stationary portion between a substantially vertical operating position and a substantially horizontal position. When maintenance is to be performed on an electrical attachment, it is important that electrical power to the attachment be disconnected. Failure to disconnect power can expose a maintenance worker to a risk of electrical shock.

In many situations, for instance in refineries, the power must be disconnected at a substation, which may be some distance from the pole itself. A maintenance worker must be able to identify the correct switch within the substation, in order to turn off power to a particular pole being maintained. This is a time consuming operation. It is common, in fact, for an incorrect switch to be identified in the first instance, thus requiring the maintenance worker to return to the substation in order to identify the correct switch. The time consuming nature of this procedure has led to the situation where some maintenance workers simply don't bother switching off electrical power to a pole being maintained, despite the high degree of risk entailed by such behaviour. In order to mitigate this risk, in some circumstances a manually operable switch is generally provided at or near the electrical attachment, allowing the worker to turn-off electrical power before commencing maintenance work. This arrangement maintains some risk, as it requires the worker to remember to turn off the electrical power before commencing work. In addition, when the switch is provided close to the electrical attachment, a live power source will remain near the worker even when the switch is turned off. This gives rise to a continuing electrical shock hazard.

It is considered desirable to provide a switch for an electrical attachment- carrying, moveable pole which reduces the risk of electrical shock while maintenance is being performed.

Summary of the Invention

In accordance with a first aspect of the present invention there is provided a switch for a pole, the pole having a stationary portion and a moveable portion, the pole having an electrical cable passing within, the switch being associated with the electrical cable and selectively allowing electricity to pass along the cable, whereby the switch is operatively associated with the moveable portion such that the position of the moveable portion relative to the stationary portion determines whether the switch is opened or closed. Advantageously, this allows for electricity to be automatically disconnected from an electrical attachment located on the moveable portion.

The moveable portion may be moveable between an operative position and a maintenance position. In this instance, the switch may act so as to permit the flow of electricity through the cable when the moveable portion is in the operative position and to prevent the flow of electricity when the moveable portion is in the maintenance position. This assists in reducing the risk of electrical shock to a worker performing maintenance. The switch may include a sensor for determining an orientation of the moveable portion. This sensor may comprise one or more accelerometers coupled to the moveable portion, ensuring that the sensing of position is independent. Where more than one accelerometer is used, the accelerometers are preferably oriented along orthogonal axes, in order to provide more quickly determined indications of position. The sensor may provide information about the orientation of the moveable portion as one or more electrical signals, for instance as one or more voltage signals. It is preferred that the switch includes a controller, such as a microcontroller, which can receive information from the sensor and selectively open or close a controllable switch in response to that information. The controllable switch may be a relay controlled by output from the microcontroller.

The sensor may be electrically powered, for instance by a battery. In a preferred embodiment of the invention, the sensor is powered by electrical power sourced from the electrical cable. This may be through a transformer circuit. The transformer circuit may include a transformer for transferring an alternating current (AC) input voltage to an AC output voltage, the output voltage being less than the input voltage, a rectifier for rectifying the AC output voltage to a direct current (DC) voltage, and a regulator for regulating the DC voltage to a microcontroller supply voltage. In a preferred embodiment of the invention, the controller has a memory, which may be employed to retain as a reference the signals received from the sensor when the pole is in an initial operative position. This reference may be considered a tilt angle of 0°. Subsequently, the controller may determine a tilt angle of the moveable pole portion by calculating a difference between a subsequent sensor signal and the reference signal. This may, for instance, be a difference in signal voltage. The controller may also be arranged to compare the tilt angle with a predetermined setpoint, to determine whether or not the moveable pole portion is in a position corresponding to a maintenance position.

The controller may be arranged to only open or close the controllable switch when the moveable pole portion has been in either an operative or a maintenance position for a predetermined period of time. Preferably, the controller is arranged to open the controllable switch when the moveable pole portion has been in the maintenance position for a first predetermined period of time, and the arranged to close the controllable switch when the moveable pole portion has been in the maintenance position for a second predetermined period of time. The first predetermined period of time may be shorter than the second predetermined period of time. In accordance with a second aspect of the present invention there is provided a pole having a stationary portion and a moveable portion, the pole having an electrical cable passing within, and having a switch as previously described associated with the electrical cable and selectively allowing electricity to pass along the cable. Preferably the electrical cable provides electricity to an electrical attachment located on the moveable portion of the pole. In a preferred embodiment, the pole is a light pole and the electrical attachment is a light.

Brief Description of the Drawings It will be convenient to further describe the invention with reference to preferred embodiments of the pole and switch of the present invention. Other embodiments are possible, and consequently the particularity of the following discussion is not to be understood as superseding the generality of the preceding description of the invention. In the drawings: Figure 1 is a perspective of a pole suitable for use in conjunction with the present invention;

Figure 2 is a block diagram showing components of a switch in accordance with the present invention; Figure 3 is a cross sectional view of a central portion of the pole of Figure 1 when in an operative position, including the switch of Figure 2; Figure 4 is a cross sectional view of the central portion of the pole and switch of Figure 3, shown in a maintenance position; Figure 5 is an electrical schematic of an example of the switch of Figure 2; and

Figures 6a, 6b and 6c are an illustrative circuit board layout of the example switch of Figure 5.

Detailed Description of Preferred Embodiments

Figure 1 shows a light pole 10 similar to that described in US Patent Number 6957832, having a base 13, an elongate stationary portion 12, an elongate moveable portion 17 and an electrical fixture, being a light source 11. The base 13 is arranged for attachment to the ground or to another base location, such as on an elevated platform. The stationary portion 12 is fixed to, and extends upwardly from, the base 13. The moveable portion 17 is connected to the stationary portion 12 using a 'Swivelpole'™ joint 16 as produced by Safe Swivel Technology Pty Ltd. The joint 16 permits movement of the moveable portion 17 relative to the stationary portion 12, between an operative position whereby the moveable portion 17 is substantially vertical and parallel to the stationary portion 12, as shown in Figure 1 , and a maintenance position whereby the moveable portion is substantially horizontal and perpendicular to the stationary portion 12. The light source 11 is fixed to the moveable portion 17 at an outer end 19 thereof. An electrical cable passes through the light pole 10 from the base 13 to the light source 11 , in order to provide electrical power to the light source 11.

The light pole 10 includes a switch 200 located internally of the moveable portion 17, near the joint 16. The switch 200 is represented in a block diagram in Figure 2. The switch 200 has three principal components: a sensor 202, a controller being a microcontroller 206, and a controllable switch 210. As shown in Figure 2, information from the sensor 202 is supplied as a sensor output signal 204 to the microcontroller 206, and instructions from the microcontroller 206 are conveyed as a processor output signal 208 to the controllable switch 210.

The switch 200 can be seen in position in Figures 3 and 4, which show a cross section of a portion 300 of the light pole 10 about the joint 16. The electrical cable is shown in two sections, a first section 302 which leads from the base 13 to the controllable switch 210, and a second section 304 which leads from the controllable switch 210 to the light source 11. The sensor 202 of this embodiment is a single accelerometer which is substantially perpendicular to the moveable portion 17 of the light pole 10. In other embodiments, it may be desirable to have more than one accelerometer, preferably arranged to be mutually orthogonal. The sensor 202 provides an output signal 204 in the form of a voltage signal to the microcontroller 206. The accelerometer is acting under the effect of gravity, and is arranged such that changes in its orientation, and hence in the gravitational forces acting on it, cause a change in the output signal 204.

The microcontroller 206 may be an application specific integrated circuit (ASIC), or some other style of circuit. The functions of the microcontroller 206 may be implemented in hardware on in a combination of hardware and software. In the embodiment shown, the microcontroller 206 is implemented in hardware as an ASIC.

The microcontroller 206 is arranged to receive the sensor output signal 204, and to process this signal to determine the orientation of the sensor 202 and thus the moveable portion 17 of the light pole 10. When the microcontroller 206 determines that the moveable portion 17 of the light pole 10 is in the operative position, it provides a signal to close the controllable switch 210, thus allowing power to flow from the first section 302 of electrical cable to the second section 304. When the microcontroller 206 determines that the moveable portion 17 of the light pole 10 is in the maintenance position, it provides a signal to open the controllable switch 210, preventing the flow of electricity from the first section 302 of electrical cable to the second section 304.

The controllable switch 210 may provide switching for one or more wires within the electrical cable. For instance, the controllable switch may only connect/disconnect a hot wire of the cable sections 302, 304, while other wires such as neutral and/or ground remain connected between the base 13 and the light source 11. Alternatively, the controllable switch may switch off all of the wires of the cable sections 302, 304.

The switch 200 may be provided with power from a battery or from some other external power source in order to provide power to its components. In a preferred embodiment of the invention, the switch 200 is provided with a transformer circuit to enable powering of the switch 200 from the electrical cable.

In use, the microcontroller 206 is arranged to detect whether the light pole 10 is in an operative position or a maintenance position, and to open or close the controllable switch 210 accordingly. As the moveable portion 17 is lowered in order for maintenance of the light source to be undertaken, electrical power is thus automatically disconnected from the light source.

Example

Figures 5 and 6a to 6c show an example of a switch 200 as implemented in an ASIC. Figure 5 depicts an electrical schematic of this switch, designated 500. The switch 500 depicted in Figure 5 provides automatic switching of a 347 VAC power line, as is commonly used in North America. The 347 VAC cable from the power source has a hot wire which is connected to the switch 500 at J1. The cable from the power source has a neutral wire which is connected to the switch 500 at J2, and has a ground wire which is connected to the switch 500 at J7. The switch 500 of Figure 5 uses a single pole, single through relay RL1 that provides switching of the hot wire. A neutral wire of the cable connected to the electrical fixture is connected to the neutral wire of the cable connected to the power source at J3 of the switch 500, which is electrically connected to J2. Similarly, a ground wire of the cable connected to the electrical fixture is connected to the ground wire of the cable connected to the power source at J6 of the switch 500, which is electrically connected to J7. A hot wire of the cable connected to the electrical fixture is connected to the switch 500 at J4.

The switch 500 includes a transformer circuit 505 which provides the switch 500 with the required DC power from the AC power of the cable connected to the switch 500 at J1 and J2. The transformer circuit includes a 347V to 12 V transformer T1 , as well as a rectifier D2 for rectifying the AC power from the transformer T1 to DC power, and regulator U5 for providing regulated DC power. The unregulated DC power may be used by components of the switch 500 such as the coil of the relay RL1 , while the regulated DC power may be used by other components of the switch 500 such as the sensor 507 and the microcontroller 509. If it is desirable to use a battery or other power source for operating the components of the switch 500, the transformer circuit, or parts of it, may be omitted. The switch 500 includes a sensor circuit 507 which includes a load switch U3 which provides power to an accelerometer U1. The load switch U3 may be controlled by the microcontroller to selectively provide power to the accelerometer U1. The accelerometer U1 includes outputs for measuring the orientation of the accelerometer in 3 dimensions; however as shown in Figure 5 only 2 of the sensor output signals (AccelZ and AccelX) are coupled to a microcontroller circuit 509.

The microcontroller circuit 509 includes a microcontroller U2 that processes the sensor output signals and provides a microcontroller output signal (RlyCtrl) to a controllable switch circuit 511. The controllable switch circuit 511 connects/disconnects the hot wire between the power source and the electrical fixture based on the microcontroller output signal. The microcontroller circuit 509 may also provide an output signal (AccelEnbl) to the sensor 507 which may control whether or not the load switch U3 provides power to the accelerometer U1. Figures 6a, 6b and 6c show an illustrative circuit board layout of the switch depicted in Figure 5. Figure 6a depicts the location of the individual components on a printed circuit board. Figure 6b depicts the circuit traces on a top side of the printed circuit board, and Figure 6b depicts the circuit traces on a bottom side of the printed circuit board. The connections, J1/J4, J2/J3, and J6/J7, for connecting the wires of the cables to the switch 500 are shown on Figure 6c.

Table 1 describes the circuit components, and their values of the switch 500. The components and their values are for an illustrative switch 500 capable of switching 347 VAC. It is understood that the components, and their values, may be modified based on the requirements of a particular application. Table 1 :Table showing switch components and their values

The accelerometer U1 measures gravitational acceleration on two orthogonal axes perpendicular to the third axis. When the accelerometer U1 is in a perfectly vertical position, the output voltage on each of the two channels, Vx and Vz, is equal to some value VO. When the accelerometer is tilted away from the vertical position, the output voltage on one or both of the channels Vx and Vz changes to a value either greater than or less than VO. The difference between Vx and VO is proportional to the angle of tilt in the X axis as measured from vertical; similarly the difference between Vz and VO is proportional to the angle of tilt in the Z axis as measured from vertical. The tilt signal Vx may be connected to an anti-alias filter comprised of R4 and C7, which provides part of the sensor output signal, then to an analog-to- digital converter that is an integral part of microcontroller U2. Similarly, the tilt signal Vz may be connected to an anti-alias filter comprised of R3 and C5, which provides part of the sensor output signal, then to the analog-to-digital converter of the microcontroller U2. As previously described, the switch 500 does not utilize the third output channel provided by the accelerometer U1 , however one of ordinary skill in the art will recognise that the microcontroller could also process the accelerometer's output signal for the third axis, or alternatively could process only the accelerometer's output from a single axis. The microcontroller U2 is configured to execute instructions stored in a memory of the microcontroller U2. The instructions when executed by the microcontroller, cause the sensor output signal, which may comprise tilt signals Vx and Vz, to be read from the analog-to-digital converter that is integrated with the microcontroller U2, and calculates the resultant tilt angle from the vertical, σ. If the tilt angle σ is greater than some designated setpoint, the microcontroller sets the microcontroller output signal, for example RlyCtrl = OV, to de-energize the relay RL1. This disconnects the power source from the electrical fixture. If the tilt angle σ is less than the setpoint, the microcontroller U2 sets the microcontroller output signal, for example RlyCtrl = 10V, to energize the relay RL1 , which connects the electrical fixture to the power source. Resistor R1 controls the current flow from the microcontroller U2 into the base of transistor Q1. Transistor Q1 amplifies the current to a magnitude sufficient to energize the coil of relay RL1. Diode D1 clamps the inductive current flowing in the coil of RL1 to prevent a voltage spike. If the coil of RL1 is energized, a normally-open contact on RL1 closes. This allows the flow of energy from the power source to the electrical fixture. The instructions stored in memory that are executed by the microcontroller U2 may measure the tilt angle when power is first applied to the switch 500. This angle is designated as the zero angle. The zero angle is subtracted from the tilt angle, σ, when calculating the orientation of the switch 500. This allows the microcontroller to correct errors in the installation of the pole, where the pole is tilted from the vertical when it is in the operative position, or to correct errors in the installation of the switch 500 within the pole. This subtraction also allows the system to correct for deviations of the sensor output signal provided by the accelerometer U1 caused by changes in the ambient temperature. The accelerometer may provide different voltages at different temperatures for the same tilt angle. Temperature effects may be periodically calculated by the microcontroller U2, for example once per minute, and a compensating calculation is made to keep the error due to temperature within acceptable limits. The compensating calculation may modify the value of the zero angle to reflect a temperature corrected value.

The instructions executed by the microcontroller may provide additional processing of the sensor output signal. For example, the processing may provide the microcontroller U2 output signal to energize the relay RL1 , and so connect the electrical fixture to the power source, only after the tilt angle σ has crossed the setpoint threshold for a given period of time, for example 10 seconds. This helps to ensure that possible movement caused by performing maintenance does not cause power to be connected to the electrical fixture while maintenance is being performed. Similarly a delay in providing the microcontroller output signal for de-energizing the relay RL1 may be used to prevent the switch from disconnecting power as a result of possible movement, for example due to wind or vibration. It is noted that it may be desirable to provide a shorter delay for disconnecting power to ensure that the power is disconnected from the electrical fixture by the time the pole is in the maintenance position. As such, the delay may be chosen to be less than the minimum time that is expected to be required to move the pole from an operative position to a maintenance position. Component U3 is a solid state switch that allows the microcontroller U2 to turn the accelerometer U1 under control of the microcontroller. For correct cold temperature operation, the voltage to the accelerometer U1 may be required to rise to the correct operating value within a given time frame, for example 100 microseconds. If the accelerometer U1 is connected directly to the regulated DC power supplied by the transformer circuit 505, this rate of rise cannot be guaranteed. Using U3 to allow the microcontroller U2 to control the power to the accelerometer U1 allows this rise time specification to be met. Capacitor C9 filters the input voltage to U3, and capacitor C10 filters the input voltage to U1. Transformer T1 converts the voltage of the lighting fixture, typically 347 VAC, to approximately 12 VAC for use by a control circuit of the transformer circuit 505. Fuse F1 stops the flow of current to the control circuit, of the transformer circuit 505, in the event of a short circuit. Diode bridge D2 converts the secondary voltage of T1 to a full wave rectified DC voltage. Capacitors C2 and C3 filter the rectified DC voltage. The filtered and rectified DC voltage may be used to energize the coil of relay RL1. Component U5 is a voltage regulator, which converts the rectified and filtered DC voltage to 3.3 VDC for use by the accelerometer U1 , the microcontroller U2 and the load switch U3. Capacitors C4 and C1 filter the 3.3 VDC power supply. The instructions, as well as any data required by the microcontroller, for example the setpoint for the tilt angle may be loaded into the flash memory of the microcontroller U2 via connector J5. Resistors R2 and R5 and capacitor C8 condition the programming signals. This programming interface conforms to the Spy Bi-Wire system specified by Texas Instruments.

It will be appreciated that although a pole is referred to throughout the specification, any elongated member may be used for situating an electrical fixture. The present invention is not to be limited to only poles. Further, although the portions of the poles have been described as rotatable relative to each other, it will be appreciated that the portions may pivot about the interconnecting means in a single plane and need not have full rotation about the joint described with reference to Figure 1. The switch of the present invention may be used in conjunction with poles having a hinge or hinges, or even a flexible connector, to allow movement of a moveable portion relative to a stationary portion. Similarly, although the operative position of the pole described has both the stationary and moveable portions substantially vertical, and the maintenance position has the moveable portion substantially horizontal, it is envisaged that other arrangements may be used in particular applications. Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.