Prezentace na téma: "Conveyors and jacks Scissor Jack (Nůžkový zvedák)."— Transkript prezentace:
Conveyors and jacks Scissor Jack (Nůžkový zvedák)
Nůžkový zvedák před zvednutím Nůžkový zvedák ve zvednuté pozici
Scissor jack (also called scissor lift or scissor mechanism) is a type of a screw jack. Description The main difference from other screw jacks is that the leadscrew of a scissor jack is in horizontal position (typical screw jack has the leadscrew positioned vertically). The leadscrew operates two metal arms, which are usually of equal length. The term “scissor“ is derived from its shape, because the two arms resemble the letter X. Operation When turning the screw, the arms can move nearer or farther from each other, and thus the crossing pattern is elongated and the load is lifted. The force that is necessary to apply to the leadscrew can be calculated from the following scissor jack equation: Where: F is the force provided by the leadscrew W are combined weights of the load and the load platform W a is the combined weight of the two scissor arms φ is the angle between the scissor arms and the horizontal If the lift consists of several pairs of scissors combined in a series, then the force (F) has to be multiplied by the number of scissor mechanisms. The equation can be applied only to the scissor jacks with equally long arms.
Vocabulary Scissor jack, scissor lift, scissor mechanism – nůžkový zvedák Screw jack – šroubový zvedák Screw – šroub Leadscrew – vodící šroub Metal – kovový Arm – rameno Equal – stejný Shape – tvar Resemble – podobat se Pattern – vzor Elongate – prodloužit Lift – zvednout; zvedák Force – síla Apply – použít Calculate – vypočítat Equation – rovnice Weight – hmotnost Load – náklad, zatížení Platform – plošina Angle – úhel Horizontal – horizontála Multiply – násobit