DESIGN OF SCREW JACK
Y. Mohan S S Ram
Screw jack
A screw jack is a portable device consisting of a screw mechanism used to raise or lower the load
Jack is simple and widely used device
They are 2 types of jacks
1. Hydraulic jack(cylinder and piston mechanism)
2. mechanical (hand operated)
Applications of screw jack
Paper, press, printing industry Gypsum factories Sheet metal forming machinery Mechanical lifting applications Platform lifting applications Food processing machinery Construction sector Bridge jacks for road and bridge lifting Shipyards Opening and closing of penstocks Industrial process Roll form machinery Mining industry Defence industry Lift tables Stage setup applications
In screw jack applications, the hazards are dropping, tipping or slipping of machines or their parts during the operation.
The main reasons
1. Jack is overloaded
2. Load is improperly secured on the jack
3. Jack not placed on hard and level surface
4. Jack is used for a purpose for which it is not designed
Proper size ,strength and stability are essential requirements for the design of the screw jack
Construction of screw jack
Name of component
material
Frame Grey cast iron
Screw Steel 30c8
Nut Phosphor Bronze Grade-1
Handle Steel 30c8
Cup Grey cast iron
Set screw Commercial steel
washer Commercial steel
Inner diameter(D1), Outer diameter(D2) and thickness of the nut collar
Diameter of head D3 = 1.75 do
The cup fitted with a pin of diameter
D4 = D3/4
Buckling