Screw Jack working Principle

Very typical throughout the world, screw jacks room foundwherever over there is a should lift, position, align and holdload. Your high reliability and also synchronization renders screw jacks perfect for a wide variety of uses that alternativemethods of managing cannot achieve. This spectrum of applications reaches across market sectors and includes SteelWorks Equipment, Water Processing, Pharmaceutical, medical andLaboratory Equipment, Packaging Equipment, Nuclear and also Aerospace and GeneralMechanical Handling. Additionally, screw jacks are increasingly finding uses as alternatives to conventionally pneumatic and hydraulic systems.

You are watching: How does a screw jack work

A Screw Jack (also well-known as a Jack Screw, a Worm Screw Jack, a maker Screw Jack or a lead Screw Jack) is a devise provided to convert rotational motion into linear motion. The utilises the property of a screw thread providing a mechanical advantage i.e. It can be used to amplify force.

Machine Screw Jack and also Ball Screw Jack

A screw jack may incorporate a device cut command screw or a rolling or ground ball screw in bespeak to deliver rotational energy in to straight energy. In both cases, the rotation the the worm screw acting on the command screw via the worm wheel counter rotation in to linear motion.

Machine screw jack: The worm wheel acts straight on the command screw (lifting screw).

Ball screw jack: The worm wheel acts on the ball screw (via the round nut) i m sorry actuates the lead screw. This device offers greater efficiency in between the input and also the useful output compared with a an equipment screw jack. In addition, it allows for greater actuation speed and, due to the short friction, is really durable. But a ball screw jack is not naturally self-locking and, together a consequence of its magnified precision components, the initial outlay is greater. The resulting enhanced efficiency but implies this can be offset against smaller journey train components and a far-ranging reduction in the necessary power.

Many applications carry out not warrant the extra expenditure that a ball screw jack since they do not require consistent drive. In configuring a screw jack a forecast is do of the frequency that actuation and this will point to the proper screw jack to it is in selected.

As opposed to the worm drive systems discussed here, a bevel gear system could be offered to transform rotation to linear motion. This would market greater performance to a an equipment screw jack because of it making a rolling contact as opposed to the sliding call of worm journey components. The could, however, come in ~ a better initial cost and does no cover as greater ratio selection as worm drives.

Lead Screw

Also recognized as strength screws, command screws come with number of different types of thread file which are suitable for various applications. Acme lead screws are characterized by your trapezoidal subject profile and 29° flank angle and also are commonly found in American Imperial device screw jacks. An alternate to the Acme command screw in a an equipment screw jack would be a square command screw.

European or other worldwide screw jacks utilise a trapezoidal command screw v a 30° flank angle and complies come an ISO metric standard.

Ball screw jacks call for the object of the command screw to have a profile that allows for the take trip of the balls. To improve load distribution and minimise wear, the sphere screw track has actually a gothic arch profile.

Popularity the the trapezoidal screw thread originates from the truth that it is simpler to maker and is therefore an ext economical than square and ball screw thread forms. Additionally, due to the huge area that contact between the lead screw threads and the worm wheel, over there is a large load carrying capacity. This results in high friction which is detrimental come efficiency yet also means the device is more likely to be self-locking. This low efficiency implies the such screw jacks are more suited come non-continuous or intermittent operation.

Types of Screw Jack

There are a couple of variations of screw jack obtainable depending top top the specific application. This variations have the right to be accomplished with either a machine screw jack or ball screw jack and also are mainly chosen based top top the system design in come which they room to be fitted:


Translating Screw Jack

The rotation of the worm wheel acts directly on the command screw and also the command screw translates linearly. Uneven the finish of the command screw is resolved (dependent on customer requirements), the command screw will tend to rotate due to friction in between the screw threads.


Translating Keyed Screw Jack

As over but the lead screw is keyed such the it cannot rotate. This is essential if the lead screw finish is not to be addressed to the load. Both the keyed and also un-keyed translating screws are typically used in applications where much more than one screw jack is attached to a typical load.


Rotating Screw Jack

The lead screw is solved to the worm wheel so rotation of the wormwheel causes rotation that the lead screw hence translating the nut alongthe command screw once the nut is attached come the load.

Translating Screw Jack System

6x Screw Jack System. The lead screw ends are to it is in attached to acommon load. Clearance is forced under the bottom mounting airplane ofthe jack human body to accommodate the translating screw cover:

Rotating Screw Jack System

4x Screw Jack System. The lifting nuts translate. Clearance under the bottom mounting aircraft of the jack human body isnot required yet allowance have to be make in the lifting platen design to allowthe platen to pass over or past the lifting screw:


Translation rate of a screw jack is influenced by the variety of starts the the command screw. With single start screw jacks the system is normally self-locking because of the friction angle of the threads being better than the command angle. I.e. An axial force applied to the screw go not result in rotation. This is not the instance with a multi-start screw as the friction angle may be lower than the command angle.

See more: 1999 F250 Super Duty Tire Size On 1999 F, 1999 Ford F

If the device in come which the screw jack is to operate has actually a most vibration the screw jack is much more likely not to me lock due to the fact that there is dynamic loading on the threads which may overcome friction. In this case, and also in the instance of a multi-start screw, the screw jack should have actually a locking mechanism.