Gearbox [GB]
One turn of the central gear drives the four compression screws of the cell at once, for a homogeneous mechanical closure.
Mechanical pressure on four screws
BETSA® offers the membrane as the standard pressure maker for its M-DACs. Pressure can also be built up with four compression screws, either by hand or with a gearbox.
The gearboxes are made for users who chose a diamond anvil cell with the clamp screw option. A single rotation on the central gear distributes the movement over the four compression screws of the DAC, so the closure stays homogeneous on all four at the same time — unlike a manual closure, which has to be done crosswise.
To know the closing distance, the upper part of the gearbox is graduated: it controls the degree of central rotation that is transferred to the external gears.
The four compression screws can be supplied with four right-hand threads, four left-hand threads, or two right-hand and two left-hand threads mounted in opposition, depending on the cell.
![BETSA® Gearbox [GB] mounted on a diamond anvil cell](/wp-content/uploads/2026/07/betsa-gear-box-gb-140-2xx-01.webp)
Where it is used
Inside a gas loading system
Loading a diamond anvil cell with helium, argon, nitrogen or hydrogen means closing the cell while it sits inside a vessel filled to several thousand bar. Nobody can reach in. The closure has to be driven from outside, and it has to be measured: too little and the charge escapes when the vessel is vented, too much and the diamonds pay for it.
This is the job this gear box was designed for. It is fitted inside the DAC gas loading systems built by Top Industrie, whose own specification for the machine calls for accurate torque control devices, a gear box or angular adjustment, alongside a compressor reaching 3000 bar and sapphire windows for observing the cell. The graduated dial lets the operator read the rotation degree by degree, and the reduction turns a coarse movement at the feedthrough into the fine, repeatable closure the cell needs.
Four screws are driven at once, the arrangement being chosen at order: four right-hand, four left-hand, or two and two in opposition, plus the central rotation. Reference GB-BHP 140 270. As with everything we build, the ratio, the graduation and the mounting interface are adapted to the loader and to the cell they have to serve.
More than ten different gear boxes have been adapted for gas loading so far, and not only for our own cells: Mao-type cells, cells built to fit a PPMS cryostat, DAC Tool and Merrill-Bassett cells have all been driven this way. If yours is not on that list, send us the drawing. It is usually a question of the screw pattern and of the room available around the cell, not a question of principle.
Top Industrie DAC gas loader →By cell type
Some of our gearboxes
Gas loading
Tozer cells
A central shaft closes the cell, and an offset shaft is added: a particularity, this is the only gearbox that needs one. A gear clamps the Tozer cell.
Gas loading
BETSA cells
For gas loaders, BETSA cells Ø 50 mm, 32 mm high. A central screw drives the four screws at once, in the same direction. A graduated dial can be added to read the orientation.
Gas loading
Merrill-Bassett cells
A central shaft drives the three screws of a Merrill-Bassett cell.
Opposite rotation
BETSA or Mao cells
Two screws turn right-hand and two left-hand, in opposition; the direction is engraved on the top. A central shaft still turns the four screws at once.
External gearbox
BETSA cells
Not dedicated to gas loading: it closes the four screws in the same direction. Screw spacing varies from one cell to another. Option: two right-hand and two left-hand screws in opposite rotation.