Scissor jack
The scissor jack is another type of classic jack . With this design, a distinction is made between the hydraulic and the mechanical scissor car jack. In the mechanical design, it can often be found in the tool kit of vehicles.
Modes of operation
With the mechanical scissor jack, a threaded rod is turned with a crank, which pulls the two lifting arms of the jack together, thus stretching the scissor jack and thereby lifting the vehicle. The disadvantage of the mechanical scissor car jack is that, compared to the hydraulic scissor car jack, considerably more force is required to lift a vehicle. The vehicle is lowered by turning the crank in the opposite direction.
The hydraulic version of the scissor jack is operated by a pump lever and hydraulic cylinder . Operation is much easier because the hydraulic oil is pumped into the working cylinder with the help of a longer lever; this lifts itself and pulls the jack together via two joints and thus raises the vehicle.
There are two construction variants for lowering the vehicle when using the hydraulic jack: either a small lever on the jack has to be flipped and thus pumped out in the opposite direction; or in the second variant, there is a vent valve which, after venting, allows the jack to sink back to the ground due to the weight of the vehicle.
Because of their low weight and their very space-saving design, scissor jacks are suitable as on-board tools for flat tires. A trolley jack is more suitable for regular use .