Jack (device)

Jackscrews are integral to the scissor jack, one of the simplest kinds of car jack still used.

A scissor jack use the mechanical advantage of a leadscrew and 4-bar linkage to allow a human to lift a vehicle by manual force alone. They are inexpensive and are common in manufacturer-supplied breakdown kits. The jack shown at the left is made for a modern vehicle and the notch fits into a jack-up point[3] on a unibody. Earlier versions have a platform to lift on a vehicle's frame or axle.

Electrically operated car scissor jacks are powered by 12 volt electricity supplied directly from the car's cigarette lighter receptacle. The electrical energy is used to power these car jacks to raise and lower automatically. Electric jacks require less effort from the motorist for operation.

A 2.5-ton house jack that stands 24 inches from top to bottom fully threaded out

A house jack, also called a screw jack, is a mechanical device primarily used to lift buildings from their foundations for repairs or relocation. A series of jacks is used and then wood cribbing temporarily supports the structure. This process is repeated until the desired height is reached. The house jack can be used for jacking carrying beams that have settled or for installing new structural beams. On the top of the jack is a cast iron circular pad that the jacking post rests on. This pad moves independently of the house jack so that it does not turn as the acme-threaded rod is turned with a metal rod. This piece tilts very slightly, but not enough to render the post dangerously out of plumb.

Car floor jack

In a floor jack (aka 'trolley jack') a horizontal piston pushes on the short end of a bellcrank, with the long arm providing the vertical motion to a lifting pad, kept horizontal with a horizontal linkage. Floor jacks usually include casters and wheels, allowing compensation for the arc taken by the lifting pad. This mechanism provides a low profile when collapsed, for easy maneuvering underneath the vehicle, while allowing considerable extension.

Hydraulic bottle jack

A bottle jack or whiskey jack[6] is a jack which resembles a bottle in shape, having a cylindrical body and a neck. Within is a vertical lifting ram with a support pad of some kind fixed to the top. The jack may be hydraulic or work by screw action. In the hydraulic version, the hydraulic ram emerges from the body vertically by hydraulic pressure provided by a pump either on the baseplate or at a remote location via a pressure hose. With a single action piston the lift range is somewhat limited, so its use for lifting vehicles is limited to those with a relatively high clearance. For lifting structures such as houses the hydraulic interconnection of multiple vertical jacks through valves enables the even distribution of forces while enabling close control of the lift.

The screw version of the bottle jack works by turning a large nut running on the threaded vertical ram at the neck of the body. The nut has gear teeth, and is generally turned by a bevel gear spigotted to the body, the bevel gear being turned manually by a jack handle fitting into a square socket. The ram may have a second screwed ram within it, which doubles the lifting range telescopically.

Bottle jacks have a capacity of up to 50 tons and may be used to lift a variety of objects. Typical uses include the repair of automobiles and house foundations. Larger, heavy-duty models may be known as a barrel jack.[7]

This type of jack is best used for short vertical lifts.[8] Blocks may be used to repeat the operation when a greater amount of elevation is required.[9]

An air hydraulic jack is a hydraulic jack that is actuated by compressed air - for example, air from a compressor - instead of human work. This eliminates the need for the user to actuate the hydraulic mechanism, saving effort and potentially increasing speed. Sometimes, such jacks are also able to be operated by the normal hydraulic actuation method, thereby retaining functionality, even if a source of compressed air is not available.

A demonstration of using two stacked air bags to lift the rear of a car

An inflatable jack, lifting bag, or pneumatic lifting bag is an air bag that is inflated by compressed air (without a hydraulic component) in order to lift objects. The bag can be deflated to be reused later. The objects can be of a smaller load such as an automobile[10] or it can be a larger object such as an airplane.[11]

Air bags are also used by rescuers to lift heavy objects up to help victims who are trapped under those objects. There are three main types of lifting bags for rescue: high pressure, medium pressure and low pressure systems. Low-pressure bags are operated at 7.25 psi for high vertical lift in a large surface area but lower lifting capacities. Medium-pressure bags are operated at 15 psi. High-pressure bags which have higher lifting capacities are operated at pressure between 90 and 145 psi. Two air bags can be stacked together to provide a higher lift. It is recommended that no more than two bags can be used in a stacked configuration, the bigger bag must be the bottom one, and no other objects are inserted between the stacked bags. Incorrect use of stacked bags may result in a bag (or other objects) shooting out to create a dangerous projectile.[12]