MOTORISED BUS DUCT JOINT

FIELD OF THE INVENTION

The present invention relates to electrical bus duct assemblies. More particularly, the present invention relates to means of joining individual bus duct sections.

BACKGROUND ART

Bus ducts axe used to distribute electrical power for higher power systems. Bus duct should contain a suitable j oint along both ends. The function of the joint is to conduct electricity well. Connecting of 3 meter sections making up an entire run connecting from transformer to switchboard or other means of electrical distribution. As the clamp force increases, the joinτ resistance reduces.

If the joint is not tightened, there will be arcing occuring between copper plates due to the electrical current trying to conduct. With the high resistance high heat generated (power loss), the copper will melt and lead to short circuit. This is a very dangerous problem and very often happens. The worst case scenario is when one joint bums - this causes the entire bus duct to be shut down. As bus ducts are usually the main power supply equipment, this can result in costly downtime.

Many other manufacturers have produced indicators, which indicate red or blue color. Red means danger and joint is not tightened, where as blue means safe for use.

However, this solution does not resolve the root cause of the problem which is the human factor on-site. Very often with such a large scale project and managing more than 1000 joints at site always difficult to ensure all bolts are tightened.

SUMMARY OF THE INVENTION

Accordingly the present invention provides a motorised joint assembly for joining two bus ducts, said assembly comprising a plurality of joint conductors to provide electical connectivity between the bars in two bus ducts, a plurality of joint insulators to separate the joint conductors from each other, a bolt inserted through the joint conductors and the joint insulators, a main gear attached to the head of the bolt, a drive gear engaged to the main gear, said drive gear smaller than the main gear, a drive motor powering the drive gear through a shaft connected to the drive gear, a nut secured to the bolt once the bolt is inserted through the joint conductors and the joint insulators to provide an initial tightening, a current limiter to cut-off current supply to the drive motor once the current flow exceeds a pre-determined level.

Additionally, at least one disc spring is provided on each end of the joint assemby to provide an evenly distributed clamping pressure on the joint conductors and joint insulators. A locking means is provided to stop the untightening of the bolt and main gear, said locking means comprising a direction flag pivoting at a point adjacent to the main gear. Power for the drive motor is provided by the bus duct bars once current starts to flow through the bus ducts.

The present invention consists of certain novel features and a combination of parts hereinafter fully described and illustrated in the accompanying drawings and particularly pointed out in the appended claims; it being understood that various changes in the details may be without departing from the scope of the invention or sacrificing any of the advantages of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of facilitating an understanding of the invention, there is illustrated in the accompanying drawings the preferred embodiments from an inspection of which when considered in connection with the following description, the invention, its construction and operation and many of its advantages would be readily understood and appreciated.

FIG 1 shows two bus ducts joined by a motorised bus duct joint.

FIG 2 shows the motorised bus duct joint in detail.

IG 3 shows the gear direction control mechanism of the motorised bus duct joint.

IG 4 shows the lock pin assembly of the motorised bus duct joint.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to electrical bus duct assemblies. More particularly, the present invention relates to means of joining individual bus duct sections. Hereinafter, the motorised bus duct joint shall be described according to the preferred embodiments of the present invention and by referring to the accompanying description and drawings.

However, it is to be understood that limiting the description to the preferred embodiments of the invention and to the drawings is merely to facilitate discussion of the present invention and it is envisioned that those skilled in the art may devise various modifications without departing from the scope of the appended claim.

FIG 1 shows two bus duct sections (20) connected by a joint assembly (10). The example makes use of bus ducts having four runs although the same method and concept can be used for bus ducts with any number of runs.

FIG 2 show individual components of the motorised bus duct joint assembly (10). As seen here, this joint assembly (10) comprises a drive gear (1), a main gear (2) with a bolt (8), four joint conductors (3), five joint insulators (4), a drive motor (5), a nut (6) and two disk springs (7). The individual components and their functions will be described hereon.

The joint insulator is one of the traditional items which all the bus duct joints will have. It has a circular aperture in the centre. These joint insulators are arranged alternately with joint copper. They segregates the phases away so that there will not be any electrical short circuit.

The joint conductors are made of copper, aluminum or other metals with high conductivity and have a circular aperture in the centre. Each joint conductor is disposed in between two joint insulators to connect a phase run from one bus duct section (20) to its corresponding phase run in another bus duct section. Therefore the joint conductor is to conduct the electricity efficiently between the two bus duct runs. The bus runs are laid to have maximum surface overlap with the joint conductors and pressed/tightened to provide

good conductivity. A tightening torque of at least 70 Nm is crucial to lower the contact resistance between the joint conductor and the bus run surfaces. Otherwise, these joints conductors will heat up and melt. This is the part where most of the traditional bus duct system fails.

The function of the disc spring is to ensure an even clamp force is exerted onto the joint assemblies when the bus duct joints are tightened. It also acts like a spring where it will keep a spring loaded action and retains the 70 Nm for a long term. Even if anything should happen where the joint starts to loosen, such as the thinning of the joint insulators, joint conductors or bus runs, this spring will retract back into it's original position and maintain a 70 Nm torque. It should also be noted that the joint conductors and bus runs expand when high current is being supplied and the bus runs heats up.

A nut, preferably a non-metal nut such as a nylon nut is inserted into the main gear bolt which runs through a hole bored in the centre of the joint coppers and joint insulators. The nut must be stationery relative to the joint assembly (10). This is achieved by having a non slipping nut surface or having the nut locked to the disc spring by the use of a groove/ridge mechanism.

The main gear has a bolt directly attached to it. The bolt is preferably milled out in one piece together with the main hear though it can also be a separate component. As the drive gear (1) turns, the main gear, and thus the bolt, will turn accordingly. The threads at the end of the bolt will turn inside the nut and will cause the joint assembly (10) to be tightened.

The drive gear (1) providing the torque to the main gear is attached to the drive motor. Both the drive gear (1) and the main gear make contact with each other at the sharp- pointing gears. The gear ratio between the drive gear (1) and the main gear is such that there is enough torque provided by the drive motor to drive the main gear.

The drive motor is meant to provide torque power to the drive gear (1) which will subsequently rotates the main gear.. The mobility of each is driven by the drive motor in

first instance. The drive motor will get its 24OV power supply from the bus ducts itself.

As soon as the bus ducts are turned on, the drive motor is energized and will start to turn. In situations where the operating voltage not 240V ₅ the drive motor or the current limter will be modified for different requirements.

A current limiter (not shown) is incorporated in the embodiment. Preferably the current limiter is located between the power supply from the bus ducts and the motor. While the preferred method is to use a fuse means of a certain Ampere ratings to reduce cost, it is also possible to use a circuit breaker as a current limiter.

The joint assembly (10) is also provided with a locking means (30) to stop the main gear and bolt assembly (10) from turning in a reverse direction and getting loose as the joint conductors and bus runs expand and shrink due to temperature variations. FIG 3 shows the preferred means, which is to use a direction flag which will let the main gear move in one direction but not the other direction.

A plastic cover is provided that will cover the entire motorized system in order to keep all distorting elements such as dust, water, insects and as a safety measure, to avoid electrocution.

OPERATION:

When the bus duct sections (20) are joined together, the workers will attach the bus duct sections (20) by using the motorised joint assembly (10). The bus runs will be joined by overlapping them on the joint conductors, and the bolt from the main gear is inserted and attached with a nut on its other end. The wires from the motor are attached to the relevant bus runs. The workers need not tighten the joint assembly (10) fully. As such, they can do their job faster and need not bring any heavy-duty tightening tools.

Once the electricity starts flowing through the bus ducts, the drive motor starts and turns the drive gear (1) to begin the tightening of the joint assembly (10). The ampere increases in proportion to the tightness of the joint assembly (10). For certain tightness there is an equivalent increase in ampere. Once the required tightness, such as 70 Nm, is reached the

current will automatically be cut-off by the current limiter.

As such, this method of connecting the bus ducts will eliminate the human factor involved in the tightening of joint bolt.

ALTERNATIVES:

The abovesaid embodiment provides for a joint assembly (10) which enables a specific level of tightness. However, it is also possible for the invention to cater for a situation where a certain number of turns are required by replacing the locking means (30) shown in FIG 3 with the lock pin assembly (40) in FIG 4.

The lock pin assembly (40) comprises a pin sitting on the main gear together with a spring loaded system. The main gear in this case has a spiral slot on the outer surface. It allows the lock pin assembly (40) to sit in. As the drive gear (1) turns, the main gear will turn accordingly and the pin will glide in the slot spiralling outwards. At the end of the spiral there is a hole that allows the spring loaded pin to lock in. The pin sits and runs on top of the turning main gear. The spring tension will always be there pressing the pin on top of the running gear. The purpose of this pin is to lock the gear once the mechanism has made a certain number of turns. As soon as the lock pin meets the hole on the main gear, the spring will push the pin into this hole, stopping the main gear from moving in any direction.

With a current limiter, as soon as the pin in lock position, the current will increase as the motor will still try to turn and draw more current. Henceforth, the current limiter will cut off the power supply and thereby turn off the motor.

Furthermore, a pre-loaded spring can be incorporated into the invention whereby as soon as the bus ducts are installed, there is a spring that will pre-clanip the entire joint assembly (10) onto the conductors even before the motor starts to turn. This pre-loaded spring will eliminate any conductor that is barely touching each other which can cause arcing if the bus ducts are energized suddenly. This pre-loaded spring does not carry a torque up to 70 Nm but nevertheless ensures that there are no air gaps between the

touching conductors.

In another embodiment shown in FIG 5, the main gear is directly connected and powered by the drive motor. This embodiment needs a nut with more threads and have a limitation to the level of tightening since it does not employ a reduction gear to increase torque transmitted to the bolt. Nevertheless such an embodiment is of simpler construction and can be useful for joints needing a medium level of tightening. This embodiment uses a locking means comprising a direction flag. However, if a locking means is not required, the teeth of the main gear shown in the embodiment can be eliminated.

In case of a need for maintenance at a later stage, perhaps in 2 or 3 years, the main gear can be provided with a hexagon headed bolt which allows a worker to turn and release the 70 Nm torque manually. Likewise the lock pin, if used, can also be shifted to an unlock position so that the main gear can be released.

An indicator coloured 'red" and "green" can also be incorporated to allow visual inspection. When using a lock pin assembly (40), this can be implemented by a simple function where as soon as the lock pin is in position, the green color can be seen on the external cover of this assembly (10).

While in the foregoing specification this invention has been described in relation to certain preferred embodiments thereof and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.