A forklift upright has five main components which work together to achieve lift. Most uprights have a number stamped onto the stationary outer-rail assembly or on a tag attached to the outer rail. The number identifies the model and type of upright, which can be referred to for a variety of reasons, including ordering compatible attachments or replacement parts for the upright.
The forklift mast is the set of nested, U-shaped or L-beam steel rails. This telescoping lift assembly uses one fixed set of rails and one, two or three sets of movable rails to gain double, triple or quad stage lift.
The forklift mast consists of the outermost stationary rails and the nested rail sets, called the inner rails. In the case of multiple inner rails, the middle rails are called intermediate rails. Rails are tied together with a series of tie bars. These tie bars make the two rails of each stage rigid and prevent the mast from twisting when put under load.
Each set of rails has a set of rollers attached at two or three points along its length. The rollers allow the rails to move smoothly as the upright assembly is extended and require periodic “shimming” keep the rails properly adjusted.
Chains are connected to the carriage and mast at points called anchors. The chains are looped over pulleys, called sheaves, attached to the lift cylinder or a set of rails. The chain provides a second indirect stage of lift in addition to the direct lift provided by the lift cylinders.
Carriages (Lift Bracket)
The carriage is an assembly that has rollers mounted to it for lift within the inner channel of the inner set of rails. The carriage is held in place and lifted by chains. The carriage also supports the forks.
The forged-steel forks are the lifting arms of the upright. The forks hang from the carriage and can be adjusted for the varying pallet widths.
The load backrest is a grid attached to the carriage which provides backing support for loads. Load backrests come in a variety of shapes and styles matched to the types of loads the truck will be handling.
The lift cylinders use hydraulic power to extend the movable rails of the upright and elevate the load. Tilt cylinders use hydraulic power to move the stationary rails of the upright backward and forward.
Forklift uprights and mast assemblies are heavy, strong components, making it important every operator understands the functionality of the feature and risks to his safety.
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