Jacks are used to raise or lower work and heavy loads short distances. Some jacks are used for pushing and pulling operations. Others are used for spreading and clamping operations. In this lesson, you will learn about different types of jacks and their uses. You will also learn how to select the right jack for the job, use various types of jacks, and provide the proper care of jacks to keep them in good working condition.
When you have completed this chapter, you will be able to do the following:
Vertical screw jacks come in several capacities and different lowered and raised heights. The screw moves up or down, depending on the direction the handle is turned. These jacks are used for many different purposes.
Screw jacks can be used to lift vehicles. They can also be used to raise heavy crates, small buildings, or other items too heavy to be raised by prying with wrecking bars.
Vertical bell base screw jack.
The vertical bell base screw jack is operated by hand using a steel bar handle which is inserted in the holes of the top housing or head.
Vertical screw jack with collapsible handle
The vertical screw jack with collapsible handle is operated by hand using the collapsible handle which is inserted into a socket.
Another type of screw jack is called an outrigger jack. The outrigger jack is equipped with end fittings which permit pulling parts together or pushing them apart.
Ratchet Lever Jacks
Vertical ratchet lever jack
A vertical ratchet lever jack has a rack bar that is raised or lowered through a ratchet lever. Some vertical ratchet lever jacks are equipped with a double socket. One of the sockets is used to lower the jack, while the other is used to raise the jack. Other vertical ratchet lever jacks are built with one socket and an automatic lowering feature.
An outrigger ratchet jack is ratchet-operated and has an extra reverse ratchet handle and a base plate.
Hydraulic jacks operate by applying pressure to one side of a hydraulic cylinder which in turn moves the jack head. Hydraulic jacks are lowered automatically by releasing the pressure on the cylinder. Vertical hydraulic jacks come in a variety of types, in capacities from 3 to 100 tons, and have different extended heights.
Porta power jack
A push-pull hydraulic jack, also referred to as a porta power jack, consists of a pump and ram connected by a hydraulic or oil hose. These jacks are rated at 3-, 7-, 20-, 30-, and 100-ton capacities and have many different applications.
The push-pull hydraulic jacks are furnished with an assortment of attachments that enable pushing, pulling, lifting, pressing, bending, spreading, and clamping operations. The pump is hand operated. The control valve on the side of the pump is simply turned clockwise, while the hand lever is stroked up and down to extend the ram. The flexible hydraulic or oil hose allows the user to operate the ram from a safe distance and in any desired position.
The ram retracts automatically by turning the control valve counterclockwise. The attachments can be threaded to the end of the plunger to the ram body or into the ram base.
Airframe (tripod) jack
Airframe jacks are used for lifting an entire aircraft off the ground or deck. Airframe jacks are commonly called tripod jacks. The jacks may also be called wing, nose, fuselage, and tail jacks. These names come from the jack placement on the aircraft.
There are two different types of tripod jacks—fixed height and variable height. Both are mobile, self-contained, hydraulically operated units. They consist of three basic assemblies; the hydraulic cylinder, the tubular steel wheel tripod leg structure, and the hydraulic pump.
Service or shop jack
Service or shop jacks (Figure 8) are used for lifting heavy vehicles for maintenance or repairs. Each jack is rated for different loads ranging from 2 to 20 tons. The long handle is used to pump the hydraulic cylinder to lift the lifting arm and saddle. Wheels and casters allow the jack to move to compensate for the lifting arc.
The following steps describe how to use a vertical screw jack properly:
The following steps describe how to use a hydraulic jack properly:
Use the following guidelines when working with jacks:
Never get under a load that is only supported by a jack. All jacks are subject to failure and personal injury could result.
- To Table of Contents -
1. The screw jack can be used to raise heavy crates, small buildings, or other items too heavy to be raised by what means?
2. Which of the following jacks is another type of screw jack?
3. What type of jack operates through pressure applied to one side of a cylinder?
4. A push-pull hydraulic jack is also referred to as what name?
5. On a push-pull hydraulic jack, the pump is operated by what means?
6. Tripod jacks are used to lift what item off the ground?
7. Before using a jack, what is the first step the operator should accomplish?
8. When selecting the proper jack, what capability should the operator consider?
9. Before using a jack, the operator should perform what action first?
10. Coat all jack surfaces with a thin film of what substance when not in use?
11.At what interval should the hydraulic jack fluid level be checked?
12.When checking the fluid level in a hydraulic jack, the ram should be in what position?
- To Table of Contents -
- To Table of Contents -