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The Spring-Opened Tongs: A Hidden Coil by the Pivot
Tongs that spring open by themselves leave one hand free to pick up the next coal, but an exposed spring snags and breaks.
Jacob Kinzer of Pittsburg, Pennsylvania, received US 211,855, dated 4 February 1879 (filed 21 November 1878), for tongs with a coiled spring set in recesses in the facing arms, just below the pivot. "By my improvement the spring is almost wholly covered from view, and protected from displacement or injury".
This rung works out why a spring near the pivot needs only a small squeeze to open the tips wide. You then fit a hidden spring to a pair of tongs and measure the opening and the hand force.
Intermediate
About 3 hours
Instructions
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Spring travel, tip travel and hand force
Spring travel, tip travel and hand force
Loading Jupyter Notebook...
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The oldest tongs
The oldest tongs
The embedded blueprint makes fire tongs from green wood. Kinzer's iron tongs add a pivot, a spring and stops.
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Read US 211,855
Read US 211,855
"My improvement relates to the arrangement of a spring between the arms of a pair of tongs, near the pivot or joint, for the purpose of opening the arms. Springs have heretofore been employed for this purpose; but they have been arranged in such way that the whole or the greater part of such spring was uncovered or exposed, and therefore not only inconvenient and unsightly, but also liable to injury."
"In order to prevent too great a range of motion of the arms, and thereby unseat the spring s, I provide projecting lips or stops c', one on either arm, above the joint a."
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Fit a hidden spring and measure it
Fit a hidden spring and measure it
Take a pair of plain pivoted tongs. Just below the pivot, drill a shallow hole into the inner face of each arm, facing each other. Choose a short compression spring from the assortment that sits in both holes with the tongs part-open.
Above the pivot, file or fit a small stop on each arm so the arms cannot open far enough to drop the spring.
Measure the pivot-to-spring, pivot-to-hand and pivot-to-tip distances. Measure how far the tips open. Hook the force meter to the arms where your hand goes and read the force to close the tips. Compare with the notebook.
Materials for this step:
Compression Spring Assortment1 pieceTools needed:
Tongs
Cordless Drill
Drill Bit Set
Metal File
Bench Vise
Force Meter (Spring Scale)
Steel Ruler5
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Tongs that stay shut, spring out or bind
Tongs that stay shut, spring out or bind
Spring tongs troubleshooting.
Flow
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History and honest limits
History and honest limits
**Jacob Kinzer** of Pittsburg, Allegheny County, Pennsylvania, filed US 211,855 on 21 November 1878; it is dated 4 February 1879. He shows the tongs as "ordinary house or coal tongs".
**Honest limits.** The notebook treats the arms as rigid and the spring as linear, and ignores friction at the pivot. The distances, opening and spring rates are examples. Your force-meter reading is the measurement.
Materials
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Tools Required
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