Apart from some particular designs (the Pullman of Météore, the Asterope of Aurora and the Capless of Pilot) the cap remains one of the essential components of a fountain pen. The cap basically performs two functions, on the one hand it provides the protection of the nib against accidental bumps to the outside, on the other hand it protects the outside from accidental contact with the nib (and especially with the ink brought by the same) and from any leaks.
From a technical point of view, many inventions have been applied to the cap, almost always related to the way in which it can be opened or closed (interlocking, screw, snap, now also magnetic) and sometimes also to the way in which it can be inserted on the bottom of the pen to balance the weight or size of the same, as in the case of the Pilot Elite (but there are many precursors) in which for the use of the pen it was necessary to put the cap on it because this was a necessary extension of the body.
A second role played by the cap is to keep the environment around the nib well circumscribed, with the pen closed, so that the ink present on it does not dry out (causing a difficulty in restarting) on the one hand but does not even undergo pressure changes that can cause ink to escape. For this reason, there are both ventilated caps (with the presence of ventilation holes) and caps that are completely sealed. In particular, at the beginning of the 1900s, in order to guarantee against the loss of ink, the presence of a second inner cap began to be introduced as a constitutive part of many caps (significant patents nº US-764227 and nº US-1028382), which encloses the part on which the section is bent and isolates it from the rest of the cap, guaranteeing the seal of the ink. Sometimes this same element is also used as a locking component in the assembly of the clip, which can be mounted in a ring on the same, or wedged between the cap and inner cap by means of a lateral slot.
The cap is also often a characteristic element for the design and lines of a pen, and can be the subject of various decorations. Among these, a common element, widely used and still present on most of the caps, are the bands, or the various rings, whose original purpose was also strictly practical in nature. The edge of the cap is in fact one of the most stressed and subject to the risk of breaking a pen, and the original use of rings and metal bands (see patent nº US-662796) was precisely to reinforce the edge, and only later these have assumed the character of a decorative element.
Historically, the first caps were made with a friction closure (those that are generically defined slip caps), with the cap that fits on the body. There are different variants of this type of choice, depending on the way in which the joint is made; the two main classes are the so-called cone cap (conical section cap) in which the interlocking surface is a truncated cone, and the so-called straight cap (cylindrical section cap) in which the interlocking surface is cylindrical, among the latter there are then the so-called tapered cap (conical or tapered cap) in vogue at the end of the 19th century.
The interlocking caps which suffer, especially in the conical version, from problems of wear on the surfaces with loss of tightness, have been followed, with a trend established since the beginning of the '900, by the caps with screw closure (threaded cap), which are still among the most common today. A return of the interlocking caps took place in the '40s with the introduction of metal caps closed with friction on special rings (trend introduced by the Parker 51).
Towards the end of the 1940s, the first snap-action caps began to spread (one of the first companies to use them was the Matador with the Matador-Click model of 1949), which later became very common and still widely used. In this case, the quality of the mechanism is essential to ensure the long-term maintenance of the cap closure.
- Patent n° US-604690, of 1898-05-24, requested on 1895-08-12, of Lewis E. Waterman, Waterman. Fountain-pen.
- Patent n° US-614630, of 1898-11-22, requested on 1898-01-28, of William W. Stewart, Swan. Fountain-pen.
- Patent n° US-634013, of 1899-10-03, requested on 1899-03-13, of Oliver R. Mitchell, Sterling Fountain Pen. Fountain-pen.
- Patent n° US-653818, of 1900-07-17, requested on 1900-04-09, of George S. Parker, The Parker Pen Company. Fountain-pen.
- Patent n° US-655423, of 1900-08-07, requested on 1900-03-23, of Henry J. Upton, Sterling Fountain Pen. Fountain-pen.
- Patent n° US-680117, of 1901-08-06, requested on 1901-05-11, of Claes W. Boman, Eagle. Fountain-pen.
- Patent n° US-692009, of 1902-01-28, requested on 1898-05-16, of Frederick Gilbert, Waterman. Safety fountain-pen.
- Patent n° US-698882, of 1902-04-29, requested on 1898-05-14, of Lewis E. Waterman, Waterman. Safety fountain-pen.
- Patent n° US-711988, of 1902-10-28, requested on 1902-05-18, of George W. Mabie, Swan. Fountain-penholder.
- Patent n° US-716489, of 1902-12-23, requested on 1902-09-15, of John Slater, Swan. Means for attaching caps to fountain or other pens.
- Patent n° US-742036, of 1903-10-20, requested on 1903-07-26, of Edward J. Kastner, Waterman. Fountain-pen.
- Patent n° FR-379615, of 1907-11-13, requested on 1907-06-19, of Eugen Hahn, August Eberstein, Montblanc. Stylographe.
- Patent n° GB-190713900, of 1908-03-12, requested on 1907-06-15, of Eugen Hahn, August Eberstein, Montblanc. Improvements in Fountain Pen Holders.
- Patent n° FR-395110, of 1909-02-11, requested on 1908-10-09, of Paul E. Wirt, Wirt. Plume à réservoir avec capuchon de sureté.
- Patent n° US-950939, of 1910-03-01, requested on 1908-06-04, of Clarence E. Martling, Charles Dunn, Dunn. Fountain-pen.
- Patent n° US-1071538, of 1913-08-26, requested on 1911-07-27, of Francis W. Vaughn Jr., Unbranded. Fountain-pen.
- Patent n° US-1075631, of 1913-10-14, requested on 1912-11-04, of Harry B. Dods, Diamond Point Pen Company. Non-leaking fountain-pen.
- Patent n° US-1283860, of 1918-11-05, requested on 1918-04-19, of Oliver Mitchell, Moore Pen Company. Fountain-pen cap and clip.
- Patent n° US-1326206, of 1919-12-30, requested on 1919-05-21, of Charles A. Luck, Conklin Pen Manufacturing Co.. Fountain-pen cap.
- Patent n° US-1365131, of 1921-01-11, requested on 1920-03-26, of Henry J. Upton, Moore Pen Company. Fountain-pen.
- Patent n° US-1514002, of 1924-11-04, requested on 1923-04-13, of George M. Kracker, Kraker. Fountain pen or the like.
- Patent n° US-1577548, of 1926-03-23, requested on 1925-01-12, of Henry J. Upton, Moore Pen Company. Fountain pen.
- Patent n° US-1586541, of 1926-06-01, requested on 1922-05-27, of John C. Wahl, Wahl Eversharp. Fountain pen.
- Patent n° US-2076796, of 1937-04-13, requested on 1931-08-25, of Gerald L. Bassett et al, Conklin Pen Manufacturing Co.. Process for molding thermoplastic materials and product thereof.
- Patent n° US-2102044, of 1937-12-14, requested on 1934-03-31, of Milford G. Sypher, Chilton. Fountain pen and the like.
- Patent n° GB-517388, of 1940-01-29, requested on 1938-07-26, of Eric Ernest Samuel Wade, Lang - Curzon - Summit. Improvements relating to Fountain Pens.
- Patent n° US-2274470, of 1942-02-24, requested on 1941-02-26, of Farnham F. Boyle, William H. Lindemon, W. A. Sheaffer Pen Company. Fountain pen.
- Patent n° US-2278907, of 1942-04-07, requested on 1940-07-26, of Marlin S. Baker, The Parker Pen Company. Fountain pen.
- Patent n° US-2314551, of 1943-03-23, requested on 1941-06-16, of Wilbur K. Olson, W. A. Sheaffer Pen Company. Fountain pen.
- Patent n° US-2314563, of 1943-03-23, requested on 1942-02-18, of Herman K. Stempel, Robert E. Freeman, W. A. Sheaffer Pen Company. Fountain pen.
- Patent n° US-2392942, of 1946-01-15, requested on 1944-05-20, of Lester W. Ormsby, The Parker Pen Company. Fountain pen cap construction.
- Patent n° FR-907722, of 1946-03-20, requested on 1943-08-02, Kaweco. Couvercle de capuchon pour porte-plume à réservoir.
- Patent n° US-2419483, of 1947-04-22, requested on 1945-06-08, of George D. Cloutier, Wahl Eversharp. Fountain pen.
- Patent n° FR-921485, of 1947-05-08, requested on 1945-11-17, Météore - La Plume d'Or. Système de fermeture d'un capuchon sur une pièce cylindrique, par exemple pour porte-plume à réservoir.
- Patent n° GB-619349, of 1949-03-08, requested on 1946-12-04, of Mark Sydney Finburgh, Wyvern Fountain Pen Company. Improvements in or relating to fountain pens.
- Patent n° US-2509234, of 1950-05-30, requested on 1945-12-28, of David Kahn, Wearever. Fountain pen cap.
- Patent n° US-2533082, of 1950-12-05, requested on 1948-06-18, of Marlin S. Baker, Robert W. Randolph, The Parker Pen Company. Fountain pen cap.
- Patent n° DE-804767, of 1951-04-30, requested on 1949-10-22, of Heinrich Schwarting et al, Montblanc. Verschlusskappe fuer Schreibwerkzeuge.
- Patent n° DE-807778, of 1951-07-05, requested on 1948-10-02, of Christoph Kunkel, Uhu. Fuellfederhalter.
- Patent n° DE-829714, of 1952-01-28, requested on 1950-05-20, of Christoph Kunkel, Uhu. Verschlusskappenverschraubung an Fuellhaltern.
- Patent n° DE-894217, of 1953-10-22, requested on 1952-03-11, Kaweco. Klipp fuer Fuellhalter u. dgl..
- Patent n° DE-1673570U, of 1954-03-18, requested on 1952-11-06, Montblanc. Tintenleiterbuchse mit Verpackungshülse für Füllfederhalter.
- Patent n° DE-933553, of 1955-09-29, requested on 1953-03-26, of Heinrich Schwarting et al, Montblanc. Verschlusskappe mit nachgiebiger Klemmvorrichtung fuer Schreibwerkzeuge.