A linear jack includes a first outer sleeve, an inner sleeve disposed at least partially within the first outer sleeve, a second outer sleeve disposed at least partially within the inner sleeve, a translating screw disposed at least partially within the second outer sleeve, and a cover sleeve coupled to the translating screw. The first outer sleeve is threadedly coupled to the inner sleeve. The second outer sleeve is threadedly coupled to the translating screw. The translating screw is disposed at least partially within the cover sleeve. The cover sleeve is configured to translate with the translating screw.

A linear jack includes a first outer sleeve, an inner sleeve disposed at least partially within the first outer sleeve, a second outer sleeve disposed at least partially within the inner sleeve, a translating screw disposed at least partially within the second outer sleeve, and a cover sleeve coupled to the translating screw. The first outer sleeve is threadedly coupled to the inner sleeve. The second outer sleeve is threadedly coupled to the translating screw. The translating screw is disposed at least partially within the cover sleeve. The cover sleeve is configured to translate with the translating screw.

An up-and-down driving device allows an up-and-down driving unit to move while supporting an object's load, in a support module in which the up-and-down driving unit is movably inserted into an inner space of a fixed housing. The up-and-down driving device includes: a driving means for moving the up-and-down driving unit in an up-and-down direction; a fixed-position compression spring main module including a fixed-position compression spring having one side fixed to a lower end of the housing and the other side supporting the up-and-down driving unit and mounted in a motion direction of the up-and-down driving unit; and a variable-position compression spring supplemental module including a variable-position compression spring having one side mounted rotatably to a side of the housing and the other side fastened rotatably to the up-and-down driving unit and configured to rotate while making a predetermined angle with the motion direction of the up-and-down driving unit.

A linear jack includes an outer sleeve, an inner sleeve disposed at least partially within the outer sleeve, and an inner screw disposed at least partially within the inner sleeve. The outer sleeve is threadedly coupled to an outer diameter surface of the inner sleeve. The inner screw is threadedly coupled to an inner diameter surface of the inner sleeve. A thread pitch of the outer sleeve is greater than a thread pitch of the inner screw.

A linear jack includes an outer sleeve, an inner sleeve disposed at least partially within the outer sleeve, and an inner screw disposed at least partially within the inner sleeve. The outer sleeve is threadedly coupled to an outer diameter surface of the inner sleeve. The inner screw is threadedly coupled to an inner diameter surface of the inner sleeve. A thread pitch of the outer sleeve is greater than a thread pitch of the inner screw.

In one example, a platform lift includes a rotationally stationary leadscrew to support a platform, a rotatable nut to drive the leadscrew up and down through a range of motion, a first spring to apply a continuous downward force to the leadscrew throughout the range of motion, and a second spring to apply a continuous upward force to the leadscrew throughout the range of motion.

Adjustable fixtures for buried tubulars, forming tools for defining a hole in the adjustable fixtures, and/or methods of manufacturing the adjustable fixtures. The adjustable fixtures include a fixture body and a plurality of spaced-apart holes extending between an upper surface of the fixture body and a lower surface of the fixture body. The adjustable fixtures also include a plurality of jack-screw-accepting threaded regions that at least partially defines the plurality of spaced-apart holes. The forming tools include a forming tool engagement structure, a threaded tool end region, and a hole-defining body. The methods include positioning a plurality of jack-screw-accepting threaded regions and a plurality of forming tools within a mold, filling a fixture-defining cavity of the mold with a composite material, curing the composite material, disengaging the plurality of forming tools from the plurality of jack-screw-accepting threaded regions, and removing the fixture body from the mold.

A linear jack includes a first outer sleeve, an inner sleeve disposed at least partially within the first outer sleeve, a second outer sleeve disposed at least partially within the inner sleeve, a translating screw disposed at least partially within the second outer sleeve, and a cover sleeve coupled to the translating screw. The first outer sleeve is threadedly coupled to the inner sleeve. The second outer sleeve is threadedly coupled to the translating screw. The translating screw is disposed at least partially within the cover sleeve. The cover sleeve is configured to translate with the translating screw.

A linear jack includes a first outer sleeve, an inner sleeve disposed at least partially within the first outer sleeve, a second outer sleeve disposed at least partially within the inner sleeve, a translating screw disposed at least partially within the second outer sleeve, and a cover sleeve coupled to the translating screw. The first outer sleeve is threadedly coupled to the inner sleeve. The second outer sleeve is threadedly coupled to the translating screw. The translating screw is disposed at least partially within the cover sleeve. The cover sleeve is configured to translate with the translating screw.

An improved bearing or bushing body extraction from a stuffing box using jack screws is provided. The bearing or bushing seal body includes at least one jack screw on each half of a split body. The jack screw passes axially through the sidewall of the body to the inner flange of the stuffing box and turning the jack screw against the inner flange to lift the body from the stuffing box. A single inner threaded or double threaded insert with a reverse outer thread and standard inner thread is inserted into the bottom wall of the body so that the body may be installed flush against the inner flange. By turning the jack screw through the insert and against the flange, the seal body is pushed out rather than pulled.