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