As opposed to the worm drive systems discussed here, a bevel gear system could be used to convert rotation to linear movement. 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 called power screws, lead screws come with a number of 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 position and are commonly within American Imperial machine screw jacks. An alternative 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 angle and complies to an ISO metric regular.
Ball screw jacks require the thread of the business lead screw to get a profile which allows for the travel of the balls. To enhance load distribution and minimise use, the ball screw track has a gothic arch profile.
Reputation of the trapezoidal screw thread originates from the fact that it is simpler to machine and is therefore less expensive than square and ball screw thread forms. Additionally, due to the large region of contact between your business lead screw threads and the worm wheel, there is usually a sizable load carrying capacity. This outcomes in high friction which is certainly detrimental to efficiency but does mean the system is much more likely to become self-locking. This low efficiency means that this kind of screw jacks are more suitable for non-continuous or intermittent operation.
Many applications 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 made of the frequency of actuation which will stage to the correct screw jack to become selected.
Translating Design Jacks ‘re normally selected. With this design, a driven input worm functions on an interior worm gear leading to the lifting screw to extend or retract. Operation needs that rotation of the lifting screw become prevented. This rotation it restrained whenever several jacks are linked with the same load.
Keyed Design Jacks are utilized any moment rotation of the lifting screw isn’t restrained. For example, when you need to lift the jack to meet up a load. This is one way they work: A key, fixed to the jack casing and inserted into a keyway milled into 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 size lifting screw that rotates. Loads are mounted on a flanged “journeying” nut that translates along the space of the rotating screw. This kind of jack is well suited 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 input and the useful result compared with a machine screw jack. In addition, it allows for higher actuation speeds and, because of the low friction, is very 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 efficiency however implies this could be offset against smaller sized drive train elements and a significant decrease in the necessary power.