Instead of the worm drive systems discussed here, a bevel gear system could be used to convert rotation to linear motion. This might offer greater efficiency to a machine screw jack due to it making a rolling contact instead of the sliding contact of worm drive elements. It could, however, come at a larger initial cost and will not cover as higher ratio range as worm drives.
Also referred to as power screws, lead screws come with several different types of thread profile which are ideal for different applications. Acme business lead screws are described by their trapezoidal thread profile and 29° flank angle and are commonly found in American Imperial machine screw jacks. An alternative solution to the Acme business lead screw in a machine screw jack would 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 standard.
Ball screw jacks require the thread of the business lead screw to possess a profile which allows for the travel of the balls. To improve load distribution and minimise put on, the ball screw monitor has a gothic arch profile.
Popularity of the trapezoidal screw thread comes from the fact that it’s easier to machine and is therefore more economical than sq . and ball screw thread forms. Additionally, because of the large region of contact between the business lead screw threads and the worm wheel, there is usually a large load carrying capability. This results in high friction which is definitely harmful to efficiency but also means the system is much more likely to end up being self-locking. This low performance implies that this kind of screw jacks are more suited to non-continuous or intermittent operation.
Many applications do not warrant the extra expenditure of a ball screw jack since they usually do not require continual drive. In configuring a screw jack a prediction is constructed of the frequency of actuation which will stage to the appropriate screw jack to become selected.
Translating Design Jacks ‘re normally selected. With this design, a driven input worm functions on an internal worm gear leading to the lifting screw to extend or retract. Operation requires 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 moment rotation of the lifting screw isn’t restrained. For example, when you must lift the jack to meet a load. This is one way they work: A key, set to the jack casing and inserted into a keyway milled in to the amount of the lifting screw forces the lifting screw to translate without rotating.
Keyed For Travelign Nut Design Jacks (KFTN) are another choice. These jacks have a fixed length lifting screw that rotates. Loads are attached to a flanged “vacationing” nut that translates up and down the space of the rotating screw. This kind of jack is ideal for applications that cannot accommodate a screw safety tube or that require a flush mount
The worm wheel acts on the ball screw (via the ball nut) which actuates the lead screw. This system offers greater effectiveness between the insight and the useful output weighed against a machine screw jack. In addition, it allows for better actuation speeds and, due to the low friction, is very durable. However a ball screw jack is not inherently self-locking and, as a consequence of its enhanced precision components, the initial outlay is higher. The resulting improved performance however implies this can be offset against smaller drive train parts and a significant decrease in the necessary power.