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Feeds: Whatever Happened to the Lucky Curve?

(This page revised July 25, 2014)

Reference Info Index | Glossopedia  ]

In 1893 the United States Patent and Trademark Office granted to George S. Parker a patent for an improved feed design. The next year, on January 9, 1894, Parker patented a further advancement, the overfeed version of the famed Lucky Curve feed (U.S. Patent No 512,319). The underfeed version (U.S. Patent No 606,231) came later. Ordinary feeds of the time had no buffering capacity, or ability to absorb excess ink flow and hold the ink, releasing it slowly as conditions warranted. The Lucky Curve solved the problem of excess ink left in the feed when the pen was capped and put in the user’s pocket. The expansion of air within the pen when the pen was brought into use again could drive that ink out, making a blot on the paper and, inevitably, on the user’s hands as well. Parker’s enhancement was ingenious. He extended the feed farther into the barrel of the pen and curved the extension so that it touched the wall, providing a way for capillary action to drain the excess ink out of the feed.

The Lucky Curve feed proved so successful that the Parker company continued producing it for decades. Better than other feeds it may have been, but the Lucky Curve was still not capable of buffering enough ink to prevent all occurrences of blotting. Further refinement of the feed to increase its buffering capacity, culminating in another patent issued in 1905 (U.S. Patent No 778,997), resulted in the eye-catching notched shape that has come to be known as the Christmas Tree feed. (The feed shown below is a later version, with the back end stepped to accommodate the pressure bar in a button-filling pen.)


In 1929, Parker replaced the Lucky Curve feed in the top-line Duofold with a flat comb feed, but the simple Christmas Tree feed, with the Lucky Curve extension cut off, remained in use into the early 1930s, probably to use up existing stock of the parts. The principle of the Lucky Curve was doomed at Parker by the comb feed, which had sufficient buffering capacity that draining the ink out of the feed was no longer necessary.

The last trace of Parker’s Lucky Curve passed into history in about 1934, with the introduction of the Parkette, whose design included a comb feed like that in the Duofold and the Vacumatic.

Or did it? Did the Lucky Curve remain in use after Parker discontinued it? The quick answer is no, of course, because other manufacturers couldn’t simply steal the patented design. But they could design their own feeds to do what the Lucky Curve did, and at least two of Parker’s competitors did just that.

Forty years after Parker patented his feed, in 1934, the W. A. Sheaffer Pen Company began producing pens with the Vacuum-Fil plunger-style filling system. To move the plunger aside, Sheaffer added a small extension to the feed by boring a hole in the back end of the feed and inserting a U-shaped channel of hard rubber into the hole to form a “center feed.” A saw-cut slit in the feed provides a path between the center hole and the upper surface, where the nib sits. The Vacuum-Fil system’s plunger serves as the “Lucky Curve” feature, but there’s no equivalent capillary path in a lever-filling pen. Sheaffer solved the problem by bending the center feed sideways so that it contacts the section wall to provide the necessary capillary path to drain ink out of the feed and back into the sac. This feed design, touted on Sheaffer’s flight-safe Skyboy pen models but actually implemented across the company’s product line, received the name Flo-Rite:


At about the same time as Sheaffer began producing center-feed pens, Wahl introduced its own design for accomplishing the function of the Lucky Curve. In the Wahl version, a sliver of celluloid is inserted into a hole bored into the back of the feed. The celluloid sliver is curved at the back end so that it contacts the sac wall a small fraction of an inch past the end of the section. A small transverse hole provides a path between the ink fissures and the center hole in the feed, allowing ink to drain down the length of the celluloid and into the sac:


The feed shown here is from a Wahl Oxford pen, which the company marketed as a second-line “student” model.

But the feed design shown above was not appropriate for pens, such as the top-line Doric, that were fitted with Wahl’s Personal-Point interchangeable nibs. To provide the same feature for these pens, Wahl’s designers modified the celluloid sliver so that the end closest to the feed is split, making a Y shape that can be glued into the back end of the section so that it will extend into the sac. This provides a continuous path from the bore of the section to the wall of the sac, and again the “Lucky Curve” does its job.

Toward the end of the 1930s, Wahl developed a new feed design, called the “Magic Feed.” The Magic feed was fitted to the Eversharp Skyline beginning in 1941, but before that it appeared on the Doric. Constructed generally like the feed illustrated above, the Magic Feed version replaces the celluloid sliver with a short length of hard rubber tubing that has been formed to contact the sac wall. To ensure good access between the sac and the tube, the curved part of the tube is open, forming a channel or gutter:


And there you have it, photographic proof that the Lucky Curve didn’t die when Janesville put it out to pasture. It just packed up and relocated!

The information in this article is as accurate as possible, but you should not take it as absolutely authoritative or complete. If you have additions or corrections to this page, please consider sharing them with us to improve the accuracy of our information. The photographs have been retouched to show detail more clearly.

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