Today, I am going to discuss Screw Jack.
If you are looking to know about the same, then I invite you to come with me and join the journey with Engineers Rail.
Before I start, here is the gift for you, you can take out this whole article as a pdf at the end of the article.
So, let’s begin with the basics…
What is Jack screw?
Basically, a Screw jack is used to lift the weight using rotational motion into push-pull linear motion using screw square thread.
The rotational motion can be provided manually or electrically using motors.
How does the Screw jack works?-
The main working principle behind the jackscrew is the inclined plane. The Screw thread situated on the nut is the heart of the screw jacks.
When the load is placed on the head, it can be lifted up and down by rotating the lever arm or handle in the clockwise direction and vice-versa. This rotation causes to climb up and down the linear pitches or threads and thus load moves up and down with less effort applied.
Screw jack diagram-
Types of screw Jack-
There are simply two types-
- Simple Screw jack
- Differential Screw jack
Simple Screw jack-
A simple screw jack is a simple lifting machine, where a simple mechanism of lifting is used to lift the heavy loads applying marginally less effort. This is also known as a Manual screw jack.
Simple screw jacks consist of–
- Threaded area
Firstly, the cone-shaped base area is given to support the lifting mechanism, and above the base, the bolt is given to regulate the square shape thread and prevent it from slipping, when the load is applied.
The threaded area is consists of the lead screw with square thread. The lead screw counts as the best screw to lift heavyweight. This lead screw is used in various heavyweight machines like lathe machines, drill machines etc.
Lastly, the head where the existing load is applied to lift by applying less effort. The application of the simple screw jack is in car lifting, heavy-vehicle lifting to repair or change the damaged equipment and so on.
Here is some simple jackscrew formula-
The velocity ratio of a simple screw jack,
Where D= diameter of the head and p= pitch gap
The Mechanical advantage of a simple screw jack,
where W= applied load and P= applied effort.
And, the efficiency of a simple jackscrew,
Differential Screw Jack-
A differential screw jack is an upgraded version of a simple screw jack where a differential screw is used to increase the velocity ratio of the differential screw jack.
The same effort is required to lift larger loads than a simple screw jack. It is also known as a compound screw jack or Hunter screw jack. A differential screw jack provides an increased velocity ratio as compared to a simple screw jack.
Now, you may be wondering, why it is called differential jackscrew?
So, the difference between the thread sizes and their pitches is the cause behind the name of differential jack.
Now, Let’s see the diagram of the differential screw jacks.
This mechanism consists of two different screw threads A and B, shown in the figure. The A portion is threaded internally and externally. The outer thread of portion A will rotate with the base nut with a fixed lever arm on the top of the A portion, as you can see in the figure.
The internal threading will give space to rotate Portion B inside. When the lever arm moves clockwise, portion A will go down toward the base nut and this cause to uplift of portion B and vice-versa, hence lifting the load with less amount of effort than a simple jackscrew.
Therefore, the total distance travelled by both of the threads- PA-PB
The velocity ratio of differential screw jack–
And, The mechanical advantage of differential screw jack-
M.A= 2πR/PA-PB (∴η=1)
Uses of Screw Jack-
Screw jacks are modern equipment used in various industries which can be easily seen around you here and there to lift the heavy loads using marginal efforts.
Here are some common jackscrew uses, given below-
1. Assembling- This is used to assemble the vehicle parts while lifting the base of the vehicle up using a screw jack mechanism. This mechanism is also used in fixing errors in a vehicle like cars, trucks, buses etc.
2. Adjusting- This mechanism is also used in adjusting and moving heavyweights such as scaffolding pipes in various industries like civil and mechanical.
3. Holding- This mechanism is used in hold the heavy loads to replace the components inside.
4. Lifting- Lifting loads in the main specification of this mechanism in general such as heavy machinery, heavy-duty vehicles, car, trucks etc. A screw jack is a common mechanism to lift loads around the globe.
5. Stabilization- This mechanism is also used to stabilize the misaligned structures or components in most of the civil, mechanical and aircraft industries.
6. Pushing-Pulling- Pushing and pulling the horizontal stabilizers of the aircraft also comes under the use of a jackscrew.
7. Stage setup- This mechanism is also used in setting up the stage in various stage-related programmes such as music gatherings, political events etc.
8. Opening and closing- The same mechanism is used in opening and closing some types of gates such as shutters in shops or in heavy-weight gates.
9. Weight Measuring- The mechanism of the screw jack is used in weigh scale to lift heavy vehicles and calculate the overall loads in civil plants and mechanical industries.
These were some basic of screw jack is used for, given above.
Now, let’s look at some advantages and disadvantages of a screw jack.
- Can be used to lift a heavy load against gravity
- Loads can be kept in the lifted position
- Due to leverage obtained by the handle, the force required to raise loads is very less & can be applied manually also
- Chances of dropping off the load
- Tipping or slipping the load
- This failure is not SAFE FAIL & can cause serious accidents
- Proper size, strength and stability are the essential requirements for the design of the screw jack from the safety considerations
Application of screw jack-
Here are some major applications of the screw jack-
These jacks are used in aerospace industries to push and pull the aircraft for 1further maintenance. The name, that is used in aerospace industries is known as Joyce jack.
To lift the vehicle, jacks are used. There is various type of jacks that are used in automotive industries like steel body jack, casting body jack, telescopic jack, and classic jack.
The various jacks such as lead screw, ball screw, and roller screw are used in various transmission products.
Jacks are useful in automating the factories nowadays. This causes a huge reduction in human effort and thus increases overall efficiency.
Jacks are used in food industries nowadays to move raw and packed food to the desired destination.
As you know, jacks are used to manage the services of vehicles and in manufacturing plants and also in the maintenance of vehicles.
Military & defence Applications-
jacks are used in a wide range of variety in military & defence applications for positioning and lifting using a hydraulic screw jack.
In machining works, jackscrews are used to position and move the steel items or cast iron materials in CNC machines, drilling machines, planners, shapers etc.
Jacks screws are used in manufacturing tires using tire building machines where stressing jacks are used.
Worm gear jacks are used in paper, press and printing industries, and packaging machinery.
Read Also- 8 Different Types of Screws & Their Uses
Screw jack is very fundamental and important equipment in the mechanical industries which you have learned above in a very fundamental way, from scratch to end.
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Abhishek Tiwary is a blogger by passion and a Quality Engineer by profession. He completed his B.Tech degree in the year 2017. Now working in a reputed firm. He loves to share his knowledge with others.