Instead of the worm drive systems discussed here, a bevel gear system could be used to convert rotation to linear movement. This would offer greater efficiency to a machine screw jack because of it making a rolling contact instead of the sliding contact of worm drive parts. It could, however, come at a larger initial cost and will not cover as better 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 defined 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 international screw jacks utilise a trapezoidal lead screw with a 30° flank angle and complies to an ISO metric regular.
Ball screw jacks require the thread of the business lead screw to have a profile that allows for the travel of the balls. To improve load distribution and minimise use, the ball screw track has a gothic arch profile.
Popularity of the trapezoidal screw thread originates from the fact that it’s simpler to machine and is therefore less expensive than sq . and ball screw thread forms. Additionally, because of the large region of contact between your lead screw threads and the worm wheel, there can be a huge load carrying capability. This outcomes in high friction which is certainly harmful to efficiency but also means the system is much more likely to be self-locking. This low efficiency 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 since they usually do not require continual drive. In configuring a screw jack a prediction is made of the frequency of actuation and this will stage to the correct screw jack to become selected.
Translating Design Jacks ‘re normally selected. With this style, a driven insight worm acts on an internal worm gear leading to the lifting screw to increase or retract. Operation requires that rotation of the lifting screw become avoided. This rotation it restrained whenever several jacks are linked with the same load.
Keyed Design 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: An integral, fixed 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 choice. These jacks have a fixed duration lifting screw that rotates. Loads are mounted on a flanged “touring” nut that translates up and down the space of the rotating screw. This type of jack is ideal for applications that cannot accommodate a screw security 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 efficiency between the insight and the useful result compared with a machine screw jack. Furthermore, it allows for better actuation speeds and, because of the low friction, is very durable. However a ball screw jack isn’t inherently self-locking and, as a consequence of its enhanced precision components, the initial outlay is higher. The resulting improved effectiveness however implies this could be offset against smaller sized drive train elements and a significant decrease in the necessary power.