Design and History of Screw Jack

Kumar Sourav (514ME1016)Department of Mechanical Engineering

National Institute of Technology, Rourkela, Orissa, India

AbstractOver the years, Screw Jack has played a significant role in everyday life. This work briefly describes the screw jack mechanism along with its

different types. Self-locking feature of the Screw Jack enables it to retain its position regardless of whatever weight it supports. Different types of

Screw Jacks can nowadays be found ranging from C series to E,M,S,A series which nowadays perform better power transmission which was

earlier not possible and gave an efficiency of approximately 30%. The work also discusses about the mechanical advantage of screw jack.

Introduction Screw Jack is basically utilized to lift heavy objects like

automobiles, house foundations etc.

Screw Jacks are used where linear motion is required. Pushing of mechanical equipments as well as pulling

can be performed

Fig.1. A basic screw jack

Gears can either be operated manually or by using electric motors

History It was the creative thinking of Frank L. Gormley Sr.

who invented the first jack in 1905 He named it the lifting jack and got the same

patented in 1905 . Subsequently, he invented the first Screw Jack in 1908.

Fig.2. The first patented Lifting Jack

Basic PartsA screw Jack basically comprises of the following parts:

Frame Handle Nut Screw Washer Cup Set Screw

Fig.3. A screw Jack with basic components

Design of Screw Jack

Fig.4. CAD modelling of Basic Parts

Important Equations:Effort force of a screw jack without friction,F= (Qp) / 2*3.14*RF= effort force at the end of armQ=weight or loadP=pitch distancer=pitch radius of screwR=lever arm radius

Fig.5. Side view of Screw Jack assembly

Self-locking is the property which enables it to retain its position irrespective of the weight. A screw will be self locking if its efficiency will be less than 50%

n= Fin / Fout * (l / 2*3.14*r) < 0.5

Self-Locking