Barrels and containers made of sheet metal or plastic are still used in sectors of industry for packing, transporting and handling of liquids and powders. This is particularly true of the chemical industry, which transports its raw materials and additives in barrels.
An example of this is a company which produces paint and plastic additives. The amount of chemical products which goes through its factories is correspondingly high, and most of these are transported in 216-litre barrels. This, in turn, means that the company needs large numbers of empty barrels, and these are delivered on trucks and semi-trailers.
Each semi-trailer is loaded with 160 barrels, each weighing 17.8kg, which are stacked in three layers. However, these three layers are possible only if the barrels are stacked without intermediate spacers or pallets. If these were used, only two layers would be possible and the number of semi-trailers, trips and personnel needed to transport the required quantities would be higher. Although dispensing with pallets permits one additional layer to be carried in each vehicle, it also makes unloading of the barrels difficult because each single barrel has to be lifted from the stack, moved out of the semi-trailer, transported to the storage location for the internal material flow and, finally, moved from there to the filling station. Earlier, this was done by three or four persons. The first removed a barrel from the stack and passed it down to the second person, who rolled it down a gangway to the third person. The third person then rolled the barrel to the lading point of a conveyor belt, where the fourth person received it and placed it on the conveyor belts of the internal material-flow system.
When the management decided to erect a new building and reorganise the production in the in-house logistics, the planning work for the future material flow resulted in the idea of unloading barrels from semi-trailers with the aid of an industrial truck equipped with a barrel gripper and BYK looked for a solution which would take various requirements into account. The task was taken up by the application engineers at Schmalz (represented by Millsom Materials Handling in Australia and New Zealand), since the vacuum gripper system had to be designed such that it could safely grip, lift, transport and position between three and seven barrels at once, using only a single gripper system. A further problem was the fact that the three layers of barrels left a space of only 250mm between the top ends of the upper barrels and the roof of the semi-trailer, which meant that the overall height of the gripper could not exceed 180mm.
Using components from their standard range of VacuMaster vacuum lifting devices, the engineers developed a vacuum lifting device for a maximum load of 140kg, which was then mounted on an adapted electrically powered, manually guided lifting truck of the Type Ameise EJB 16. The gripper system comprises two cross-beams, each with seven suction pads, where the suction-pad positions can be adjusted on the cross-beams to required position for gripping the barrels and automating barrel handling with lifting trucks and vacuum lifting devices.
The suction pads are made of the hard-wearing material, NBR (buna N), and adapt themselves to the surface of the barrels. Each pad has a diameter of 160mm. In order to ensure quick and safe gripping of one or two rows of barrels, the suction pads are mounted flexibly, on spring plungers with a length of 40mm and on flexible joints. This combination can compensate for varying barrel heights and also permits tilted barrels to be gripped securely. It also permits suction pads which happen to be placed on the rim of a barrel to be withdrawn in order to prevent them from being damaged. The 2 x 7 = 14 suction pads on the two cross-beams are divided into five vacuum circuits so that the vacuum can be disconnected from pads, which are not in contact with a barrel. This arrangement also ensures that the barrels, which are stacked haphazardly, can be gripped and transported safely. The five separate vacuum circuits permit the following gripping configurations:
- one row of four barrels and one row of three
- one row of three barrels and one row of four
- one (front) of three barrels
- one (front) row of four barrel
The vacuum can be switched off in all five circuits to release all gripped barrels. The vacuum circuits are controlled by the driver of the industrial truck from a multi-function operator panel on the truck. Releasing of the barrels requires a two-hand operation.
An optical display on the truck shows which of the suction pads are actually in contact with barrels. The vacuum is generated by a robust, maintenance-free vacuum pump followed by a large-volume vacuum reservoir to permit rapid evacuation of the gripper system.
The VacuMaster vacuum lifting device is equipped with safety elements to ensure maximum safety under all operating conditions. These include the optical indication of the suction-pad coverage, two manometers for monitoring the vacuum levels, an electronic (audible) warning device which sounds in the case of a low vacuum or a power failure, two-hand operation for releasing the barrels, and a safety inspection in accordance with the applicable regulations before it leaves the factory. The flat design of the cross-beams permits safe gripping of barrels in the top layer. The adjustable limit switches of the lifting truck permit rapid and damage-free insertion of the lifting device into the available space.
The barrels can be stacked with either end at the top, and the operator does not need to worry about the positions of the bungholes. The adjustable proximity switch for stopping the lifting motion ensures that the device automatically detects when the suction pads come into contact with the barrels. This prevents damage to the lifting system and the barrels and means that the operator does not have to press the suction pads hard against the barrels. Once the barrels have been gripped, the truck is moved from the semi-trailer to a conveyor belt.
The barrels are placed on a bench and labels are attached to them, and they move through a roller conveyor to the filling station. According to Schmalz, they only need one person to unload the semi-trailers, rather than the three to four persons previously needed. The time needed for this has been reduced by up to 75%, depending on how far they have to move the barrels. The new ergonomical and safe barrel-handling system has eliminated the risk of injuries caused by incorrect lifting which occurred in the past. With only slight modifications, the vacuum based barrel handling system can also be used to load semi-trailers, permitting further rationalisation effects.