Machines

The Trailing Arm Gets a Better Supporting Role

A Nebraska farm shop has kept one patent alive for a decade, guarding a closing wheel whose independent evidence is thinner than the marketing.

Clay-diorama editorial illustration of linked support arms and a small wheel.

What changes in this design

Without further detail, a reader might picture two turning pieces being supported separately, or moving without one shared hinge-like point.

This planting-machine support carries the two turning pieces as a pair, and they respond in opposite directions around one shared hinge-like point.

It gives a reader a simple way to picture the device: two turning pieces, one shared hinge-like point, and opposite motion.

Howard Martin's thirty-by-thirty-six-foot shop

Howard Martin patented the first mechanical no-till row cleaner in 1988 and began building them in 1991, in a shop on his Kentucky farm, thirty feet by thirty-six. In 1995 the Martin-Till Planting System carried the first spiked closing wheel with a rear rubber finishing wheel. That shop is a 50,000-square-foot plant now. Martin died in February 2024, at 79.

Everything here descends from that shop. The closing system is the last thing a planter does to a seed, two wheels pushing soil back over the furrow, and farmers have been replacing the ones that came bolted on ever since.

What goes wrong two inches down

The failure modes are specific. Fertilizer equipment ahead of the row disturbs moist soil, which builds up on the gauge wheels, grows their effective diameter and makes the planter run too shallow. Rubber press wheels smear soil instead of crumbling it, and the smeared sidewall cracks in heat and collapses.

How much that costs you depends on the stand. Extension work in Illinois puts a week-and-a-half spread in emergence at 6 to 9 percent of yield. Ohio State, reading older trials, sets a higher bar: unless a quarter of the plants run three weeks late or worse, burying the stragglers changes little.

Five patents, and one filed a day early

Which brings me to a filing published on 13 August 2026 from Schaffert Manufacturing in Nebraska. It covers a trailing arm assembly for a planter row unit: a parallel linkage on the planter frame, a walking arm pivoted to it, and paired implements that respond in opposite directions. Two of the three named inventors are Paul E. and Kris Schaffert.

It is the fifth patent in a chain: three provisionals in 2016, an application in January 2017 granted in October 2020, then continuations granted in 2023, 2024 and on 7 April 2026. This one was filed on 6 April 2026, the day before its own parent issued, and it is still pending.

The root patent claims a four-bar linkage whose upper and lower link pairs share identical pivot spacing, so the links stay parallel through their range, giving about seven inches of vertical travel with the closer held at a fixed angle. The walking arm holds roughly constant pressure on both press wheels and stops trash and rocks bouncing the planter's back end. Staggering them fore and aft lets the front wheel push soil past the furrow centre and the back one push it in.

A walking beam patented in 2007

The walking beam itself is not new. A Canadian seeding-equipment maker filed in December 2008, with priority to December 2007, on a walking beam carrying a gauge wheel forward and a packer wheel aft of a central pivot, so the beam reduces the disc's vertical movement when either wheel rolls over an obstacle or into a hole. Nine years before the Nebraska priority date, and the newer claims turn on combining that beam with the parallel linkage.

The one trial nobody in the industry paid for

Here is what stopped me. The independent test of this whole category is small: three Wisconsin locations, a randomized block, three aftermarket wheels against standard rubber, published in Applied Engineering in Agriculture in 2020 and funded by the state corn checkoff and farmer-led watershed groups. Aftermarket wheels raised final emergence by 2 percent, higher than standard rubber at p=0.069 against an alpha of 0.1, not the usual 0.05. No aftermarket wheel beat another, and yield was not significant by wheel type.

The vendor evidence is larger and much friendlier. A seed company's plot program tested five aftermarket closers and reported roughly 5 bushels an acre of corn and 2.5 of soybeans, Schaffert's own Zipper at 3.1 over factory closers in no-till. The best-funded rival solves the same problem with load cells and a monitor rather than linkage geometry, and reports 3.6 bushels. Nearly all of those numbers come from the people selling the parts.

The open question

I don't think the linkage is a trick. Seven inches of travel with the closer held at a fixed angle is a real mechanical thing, and on rough ground I'd rather have it than not. What I can't get past is that a decade of continuations, each drawing the wall further out around ground already held, sits on top of one independent trial that found 2 percent more emergence at a relaxed threshold and no yield difference.

So who runs the bigger trial? There is no approval regime here, and the closest thing to one is a seed company's plot program. The market is real: no-till and reduced-till wheat acres went from 21 percent in 1998 to 69 percent in 2022. But the honest answer to whether any of this pays is still, mostly, a number the seller generated.

Sources

Reporting for this piece drew on the published filing and the references below.

The record, briefly. US20260231852A1, “Trailing Arm Device and Assembly with Parallel Linkage” The abstract describes a planter trailing-arm assembly in which paired rotatable implements respond in opposite directions around a walking pivot.

More angles on this

The Seed Method's Extremely Serious Fresh StartAnother reading from the same A01C classification family, planting; sowing; fertilising.
Seeds Are Being Asked to Land With IntentionAnother reading from the same A01C classification family, planting; sowing; fertilising.
CPC A01C: Planting; sowing; fertilisingThe official classification family this record was filed into, published in the USPTO Cooperative Patent Classification scheme.
The Leveling Bar Has a Very Firm Opinion About LevelAnother reading from the neighbouring A01B classification family, soil working in agriculture or forestry.
Confectionery, Seen Through the Eyes of a Tiny MuseumAnother reading from the wider A23G classification family, cocoa.

Read around this one:Public patent record USPTO published figure Patent issue-date index