Dock plate
Encyclopedia
In a loading dock
, one problem to overcome is the problem of bridging the gap between a truck
and the dock or warehouse
floor. Not all trucks are the same height, and the height of the trailer floor within a truck can vary according to how heavily the truck is laden. Thus there is not only a gap to bridge but a height difference to overcome. Various devices are employed in order to achieve this: dock plates, dock levellers, dock boards, and various forms of lift
. These devices vary in construction, suitability to dock conditions, cost of installation, and loading capacity.
Dock levellers and lifts are generally permanent fixtures at each door of a dock. Dock plates and dock boards are generally, by contrast, portable, and not fixed either to dock or truck.
Dock plates and dock boards are simply metal ramps, bridging the gaps between dock and truck. Dock plates are generally made out of aluminium
whilst dock boards are generally made out of steel
. Aluminium dock plates are thus more suitable for lighter loads, such as handcarts and dollies
, whereas steel dock boards are more suitable for heavier motorized equipment such as fork lift trucks and electric pallet trucks. Another difference between dock plates and dock boards, in addition to their load-bearing capabilities, is their construction. Dock plates are simple flat plates, whereas dock boards have curbs, bolted or welded to the edge of the board. Run-off is prevented by a simple painted yellow strip along the edge of a dock plate, whereas it is the curbs (also generally painted yellow) that prevent run-off on dock boards. Run-off is thus a significant risk on dock plates, since the yellow strip is not a particularly effective mechanism for preventing it.
Both dock plates and dock boards have a diamond pattern embossed onto their upper surfaces, to prevent wheel slip as carts and vehicles travel up and down the incline. Similarly, they both have locking T-bar legs that extend down into the gap between truck and dock, to secure them. They are both portable. But dock boards are heavier than dock plates. The latter may be carried by hand, and are generally fitted with handles for doing so. The former usually require a fork lift in order to place and remove them, and are generally fitted with either loops or chains, used for attaching the dock board to the forks of the fork lift.
Dock levellers are, as mentioned, fixed to the dock. They comprise a simple metal plate, called a lip, that is raised from a stowed position and then lowered onto the back of the truck. They are operated either manually, via a simple pull chain, or hydraulically, with an electric pump driving a piston
to lift the plate.
Dock levellers are more expensive devices than the comparatively light-weight dock plates and dock boards. The most common form of dock leveller is the recessed, or pit, dock leveller. As the name suggests, this type of leveller is contained in a recess, or pit, beneath the dock door and floor surface. Dock levellers are stronger than dock plates and dock boards, making them suitable not only for motorized fork lift trucks but also for master conveyors (for which neither dock plates or dock boards are suitable).
Because they carry heavy motorized equipment, the grade of the incline has to be shallow. The greater the height differential between truck and dock that a dock leveller can compensate for, the longer the leveller itself has to be. Moreover, the grade of the incline must not be so great that the vehicles cannot climb it. A height differential of between 7 and 8 inches generally requires a 6 feet (1.8 m) leveller for an electric palette carrier. A height differential of between 17 and 18 inches generally requires a 12 feet (3.7 m) leveller for a petrol-engined fork lift truck.
Dock levellers (and indeed dock plates and dock boards) are used where a building has a truck-level door, i.e. a door with a floor level roughly at the same height as the floor of the truck's trailer. Some buildings only have drive-in doors, i.e. doors at the same level as the ground outside of the building, suitable for driving directly into the building.
For loading docks with drive-in doors, and also (albeit rarely) for loading docks with truck-level doors, a lift is sometimes employed.
Other, less common, devices employed when bridging the gap between truck and dock are truck levellers. These are hydraulic lifts positioned beneath the rear wheels of the truck, that are used to raise and lower the truck so that it is level with the loading dock edge. The problems with truck levellers, that make them rarely employed, are twofold. First: They cause the truck interior to be at an incline, which causes loading and unloading difficulties. Second: They are expensive to maintain, since they require (being below ground level and open to the air) proper drainage and protection against the weather.
Recessed dock levellers also have problems of exposure to the weather. However, because they are recessed into the dock, which is above ground level, they do not have as great a problem with drainage. Equally, because they are recessed into the dock, they extend partially back from the dock edge. A dock leveller can be installed so that it extends inside the loading dock door, and thus inside the building, protecting it from the weather.
Loading dock
A loading dock is a recessed bay in a building or facility where trucks are loaded and unloaded. They are commonly found on commercial and industrial buildings, and warehouses in particular....
, one problem to overcome is the problem of bridging the gap between a truck
Truck
A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration, with the smallest being mechanically similar to an automobile...
and the dock or warehouse
Warehouse
A warehouse is a commercial building for storage of goods. Warehouses are used by manufacturers, importers, exporters, wholesalers, transport businesses, customs, etc. They are usually large plain buildings in industrial areas of cities and towns. They usually have loading docks to load and unload...
floor. Not all trucks are the same height, and the height of the trailer floor within a truck can vary according to how heavily the truck is laden. Thus there is not only a gap to bridge but a height difference to overcome. Various devices are employed in order to achieve this: dock plates, dock levellers, dock boards, and various forms of lift
Elevator
An elevator is a type of vertical transport equipment that efficiently moves people or goods between floors of a building, vessel or other structures...
. These devices vary in construction, suitability to dock conditions, cost of installation, and loading capacity.
Dock levellers and lifts are generally permanent fixtures at each door of a dock. Dock plates and dock boards are generally, by contrast, portable, and not fixed either to dock or truck.
Dock plates and dock boards are simply metal ramps, bridging the gaps between dock and truck. Dock plates are generally made out of aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
whilst dock boards are generally made out of steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
. Aluminium dock plates are thus more suitable for lighter loads, such as handcarts and dollies
Dolly
Dolly may refer to one of the following:*Camera dolly, platform that enables a movie or video camera to move during shots*Dolly , a portable anvil*Dolly , for towing behind a vehicle...
, whereas steel dock boards are more suitable for heavier motorized equipment such as fork lift trucks and electric pallet trucks. Another difference between dock plates and dock boards, in addition to their load-bearing capabilities, is their construction. Dock plates are simple flat plates, whereas dock boards have curbs, bolted or welded to the edge of the board. Run-off is prevented by a simple painted yellow strip along the edge of a dock plate, whereas it is the curbs (also generally painted yellow) that prevent run-off on dock boards. Run-off is thus a significant risk on dock plates, since the yellow strip is not a particularly effective mechanism for preventing it.
Both dock plates and dock boards have a diamond pattern embossed onto their upper surfaces, to prevent wheel slip as carts and vehicles travel up and down the incline. Similarly, they both have locking T-bar legs that extend down into the gap between truck and dock, to secure them. They are both portable. But dock boards are heavier than dock plates. The latter may be carried by hand, and are generally fitted with handles for doing so. The former usually require a fork lift in order to place and remove them, and are generally fitted with either loops or chains, used for attaching the dock board to the forks of the fork lift.
Dock levellers are, as mentioned, fixed to the dock. They comprise a simple metal plate, called a lip, that is raised from a stowed position and then lowered onto the back of the truck. They are operated either manually, via a simple pull chain, or hydraulically, with an electric pump driving a piston
Piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...
to lift the plate.
Dock levellers are more expensive devices than the comparatively light-weight dock plates and dock boards. The most common form of dock leveller is the recessed, or pit, dock leveller. As the name suggests, this type of leveller is contained in a recess, or pit, beneath the dock door and floor surface. Dock levellers are stronger than dock plates and dock boards, making them suitable not only for motorized fork lift trucks but also for master conveyors (for which neither dock plates or dock boards are suitable).
Because they carry heavy motorized equipment, the grade of the incline has to be shallow. The greater the height differential between truck and dock that a dock leveller can compensate for, the longer the leveller itself has to be. Moreover, the grade of the incline must not be so great that the vehicles cannot climb it. A height differential of between 7 and 8 inches generally requires a 6 feet (1.8 m) leveller for an electric palette carrier. A height differential of between 17 and 18 inches generally requires a 12 feet (3.7 m) leveller for a petrol-engined fork lift truck.
Dock levellers (and indeed dock plates and dock boards) are used where a building has a truck-level door, i.e. a door with a floor level roughly at the same height as the floor of the truck's trailer. Some buildings only have drive-in doors, i.e. doors at the same level as the ground outside of the building, suitable for driving directly into the building.
For loading docks with drive-in doors, and also (albeit rarely) for loading docks with truck-level doors, a lift is sometimes employed.
Other, less common, devices employed when bridging the gap between truck and dock are truck levellers. These are hydraulic lifts positioned beneath the rear wheels of the truck, that are used to raise and lower the truck so that it is level with the loading dock edge. The problems with truck levellers, that make them rarely employed, are twofold. First: They cause the truck interior to be at an incline, which causes loading and unloading difficulties. Second: They are expensive to maintain, since they require (being below ground level and open to the air) proper drainage and protection against the weather.
Recessed dock levellers also have problems of exposure to the weather. However, because they are recessed into the dock, which is above ground level, they do not have as great a problem with drainage. Equally, because they are recessed into the dock, they extend partially back from the dock edge. A dock leveller can be installed so that it extends inside the loading dock door, and thus inside the building, protecting it from the weather.
Major manufacturers & Distributors
- Dynamic Loading http://www.dynamicloading.com
- Butt http://www.butt.de
- Rite Hite Ramps http://www.ritehite.com
- Beacon Technology http://www.beacontechnology.com