Instead of a normal container roof, an open top container is fitted with a removable tarpaulin, supported by a series of roof bows. Major challenges for container operators are how to easily open and close the roof, and how to avoid losing the removable parts, (the tarpaulin and roof bows) once the cargo has been discharged from the container.
BoxJoin’s concept is for the roof bows and tarpaulin to stay with the container. Instead of the roof bows being secured by pins in the top rail (as on a standard open top), the roof bows on the new Sliding Open Top have rollers at each end, which sit in a track on the inside of the container’s top rail, running the whole length of the unit.
After the rope securing the tarpaulin to the container has been untied, the roof bows and the tarpaulin together can now be pulled along the track either to the front or back of the container, giving access for quick and easy loading and discharging of the cargo. Alternatively, the roof bows can be pulled along the track after the tarpaulin has been pulled back in the same way as on a normal open top
The roof bows are held an equal distance apart from each other by a simple cord. To pull the roof bows backwards and forwards, a hand rope is attached at both sides of the first and last roof bow ends. When the roof is closed, the hand ropes can be tied to the four corner posts’ inner lashing bars, to prevent the roof bows moving in transit. If the roof bows have to be removed, they can easily be taken out of the track on the top rail through a slot at each end of track and then stowed on the front wall of the container, behind a simple securing bar that is installed in both inside front corner posts.
One of the main benefits of the system is that it avoids the need to remove the roof bows and the tarpaulin during loading and discharge, so there is much less chance of them being lost or damaged. In addition, there is no need for people to climb up onto the top rail to remove the roof bows. Operations are therefore much safer, because the roof bows and tarpaulin together can be pulled up and down the track either from inside the container or from alongside the container with a rope. Trials have also shown that cargo loading and discharge is much quicker than with a normal open top.
Compared to a normal open top design, the only real differences in the construction of the Sliding Open Top are the roof bow ends and the track on the inside of the top rail. According to the company the cost of a Sliding Open Top is about US$200 more than for a standard open top container but this will easily be covered by the equipment’s reduced M&R costs and faster turnround time and will pay for itself within the first year of operation.