Hydraulic jacks are extremely useful mechanical devices which are employed to lift heavy loads up. Using hydraulics, these jacks are able to afford greater lift over larger distances. Hydraulic jacks are commonly utilized in the automotive, industrial and construction industries.
There are two types of hydraulic jacks, the bottle jack and the floor jack. As the name implies, the bottle jack is portable and has a vertical piston with a weight bearing pad on top. Bottle jacks are commonly used with vehicles and are very useful for changing wheels. The jack is positioned under the car at the correct point for raising the car, then using a detachable lever, the jack is pumped up, so raising the vehicle to allow the wheel to be changed. A floor jack has horizontal pistons and a long arm which provides the vertical motion for lifting. Floor jacks have wheels or castors and are often found in garages. These jacks are able to lift a heavier load than bottle jacks.
Hydraulic jacks work by compressing hydraulic fluid into the cylinder of the jack by use of a pump plunger. When the plunger is pulled back, the fluid is drawn from the reservoir into the pump chamber so that when the plunger moves forward, the hydraulic fluid is pushed back into the cylinder. This movement of fluid increases pressure in the cylinder which in turn makes the hydraulic jack work.