Surveying Tripod with Bevel-Gear Micro-Leveling and Circular Bubble Scale

The problem

Setting up a conventional surveying tripod over a ground mark involves loosening leg clamps, sliding sections by hand, retightening, checking the bubble, and repeating until the instrument is roughly level. On uneven terrain this cycle takes time, and coarse sliding makes it easy to overshoot the mark. Standard tubular bubble levels also give limited directional feedback, forcing the operator to guess which leg to move. According to the patent, the goal is a tripod that is quick to operate, easy to adjust, and efficient for measurement work.

The solution

1. The instrument fixed seat (1) has a circular fixing groove (4) at its center. Three lock-screws (5) thread in from the sides, each ending in an arc spacer (6) that presses against the instrument base.
2. A bubble and scale assembly (36) is embedded beside the groove. It uses a round glass panel (31) printed with three principal mark lines (32) radiating from the center—each corresponding to one leg—and several concentric secondary graticules (33).
3. An adjusting rod (7) hangs vertically from the seat’s underside and slides coaxially into the adjustment seat (2). A fastening bolt (8) locks it at the desired height.
4. A hook (9) at the bottom of the adjustment seat suspends a plummet or a load-carrying disk (35) via a bracing wire (34).
5. Three supporting legs (3) hinge to the adjustment seat through hinges (10). Each leg ends in a retractive leg section (11) containing a telescopic cavity (23) with an expansion link (24) secured by a clamping screw (25).
6. A micro-adjusting mechanism (12) sits near the bottom of each supporting leg. It houses a transmission case (13) containing an adjusting screw rod (14) that rides in a guide groove (15). A bushing (16) threaded onto the rod is supported by two thrust bearings (17) and carries a first bevel gear (18) keyed to it. A horizontal rotating shaft (20) on a mounting seat (19) holds a second bevel gear (22) meshing with the first, and ends in a regulation handle (21) outside the leg.
7. The expansion link terminates in a support foot: a bulb (29) fixed to the expansion link by studs (28) and hinged on a support base (26), with a replaceable fixed pin (27)—either a cone nail for soft ground or a rubber cushion block for hard surfaces—attached by a mounting screw (30).

Who it is for

• Surveying instrument brands looking for a tripod to bundle with total stations and optical levels, where fast setup reduces crew downtime.
• Construction layout contractors who set up and break down tripods dozens of times per day on job sites and need repeatable leveling without fighting leg clamps.
• Photogrammetry and laser-scanning service providers whose accuracy depends on a level base and who benefit from fine-threaded adjustment rather than manual sliding.
• Equipment rental companies supplying tripods to field crews; the geared mechanism reduces wear from operators overtightening friction clamps.

How it works

The main parts

Setup and leveling steps

1. Spread the legs and place the tripod over the ground mark. Hang the plummet from the hook (9) so it aligns with the crosshair on the ground.
2. Select the foot pin: attach the cone nail for soft soil or the rubber cushion block for pavement using the mounting screw (30). For extra stability, hang the load-carrying disk (35) and add stones or weights.
3. Coarse level: loosen the clamping screws (25) on the retractive legs (11), slide the expansion links (24) until the bubble (37) falls within the smallest secondary graticule (33), then retighten.
4. Set height: loosen the fastening bolt (8), slide the adjusting rod (7) to raise or lower the instrument seat (1), and retighten.
5. Mount the instrument: place it in the fixing groove (4) and turn the three lock-screws (5) so the arc spacers (6) grip the base.
6. Fine level: read the bubble position relative to the three principal mark lines (32). Turn the regulation handle (21) on the corresponding leg. The handle spins the rotating shaft (20) and second bevel gear (22), which meshes with the first bevel gear (18) on the bushing (16). Because the bushing is threaded onto the adjusting screw rod (14) and held by thrust bearings (17), its rotation drives the rod up or down along the guide groove (15), changing that leg’s effective length by small increments until the bubble centers.

Applications

Topographic land surveying

Crews working across hillsides and ditches constantly change tripod positions. The geared micro-adjustment lets them dial in a level base without repeatedly loosening friction clamps, saving time at every station.

Construction site layout

Staking out foundations requires frequent setups on compacted dirt or concrete slabs. Swapping between cone nails and rubber pads keeps the feet secure, while the plummet hook ensures the instrument stays centered over the stake.

Monitoring and deformation measurement

Long-term monitoring prisms demand repeatability. Fine-threaded screw adjustments provide more controlled movements than sliding tubes, helping technicians return the bubble to the exact same center position during repeated visits.

Photogrammetry and drone base-station setup

Ground control points for aerial mapping often sit in open fields exposed to wind. Hanging a weight disk from the bottom hook lowers the center of gravity, reducing vibration transmitted to the GPS receiver mounted above.

Where it is less suitable

• Lightweight hiking or backpacking surveys - the transmission cases, gears and thrust bearings add mass compared to simple clamp tripods.
• High-vibration environments such as pile driving - continuous heavy shock loads could accelerate wear on the bevel gears and bushings.
• Budget consumer-grade instruments - the added machining and assembly cost exceeds what entry-level rotary lasers or basic levels require.