As opposed to the worm drive systems discussed here, a bevel gear system could possibly be used to convert rotation to linear movement. This would offer greater effectiveness to a machine screw jack because of it making a rolling contact instead of the sliding contact of worm drive elements. It could, however, come at a larger initial cost and does not cover as higher ratio range as worm drives.
Also known as power screws, lead screws include several different types of thread profile which are ideal for different applications. Acme lead screws are described by their trapezoidal thread profile and 29° flank position and are commonly within American Imperial machine screw jacks. An alternative solution to the Acme lead screw in a machine screw jack will be a square lead screw.
European or other worldwide screw jacks utilise a trapezoidal lead screw with a 30° flank position and complies to an ISO metric regular.
Ball screw jacks require the thread of the lead screw to have a profile which allows for the travel of the balls. To improve load distribution and minimise put on, the ball screw monitor includes a gothic arch profile.
Popularity of the trapezoidal screw thread originates from the fact that it’s easier to machine and is therefore more economical than square and ball screw thread forms. Additionally, because of the large area of contact between the business lead screw threads and the worm wheel, there is certainly a big load carrying capacity. This outcomes in high friction which is definitely detrimental to efficiency but also means the system is much more likely to become self-locking. This low performance means that this kind of screw jacks are more suited to noncontinuous or intermittent operation.
Many applications usually do not warrant the excess expenditure of a ball screw jack given that they usually do not require continual drive. In configuring a screw jack a prediction is constructed of the frequency of actuation and this will stage to the correct screw jack to be selected.
Translating Design Jacks are most often selected. With this design, a driven insight worm works on an internal worm gear causing the lifting screw to increase or retract. Operation needs that rotation of the lifting screw be prevented. This rotation it restrained whenever several jacks are linked with the same load.
Keyed Style Jacks are used any time rotation of the lifting screw is not restrained. For instance, when you must lift the jack to meet a load. This is how they work: A key, set to the jack housing and inserted into a keyway milled into the length of the lifting screw forces the lifting screw to translate without rotating.
Keyed For Travelign Nut Design Jacks (KFTN) are another option. These jacks possess a fixed length lifting screw that rotates. Loads are mounted on a flanged “journeying” nut that translates up and down the length of the rotating screw. This kind of jack is perfect for applications that cannot accommodate a screw safety tube or that want a flush mount
The worm wheel acts on the ball screw (via the ball nut) which actuates the lead screw. This system offers greater efficiency between the input and the useful result weighed against a machine screw jack. In addition, it allows for higher actuation speeds and, because of the low friction, is quite durable. Nevertheless a ball screw jack is not inherently self-locking and, because of its enhanced precision components, the initial outlay is greater. The resulting improved effectiveness however implies this is often offset against smaller sized drive train parts and a significant decrease in the necessary power.