US3036388A - Magnetic writing materials set - Google Patents

Description

May 29, 1962 c. R. TATE 3,036,388

MAGNETIC WRITING MATERIALS SET Filed Oct. 27, 1961 INVENTOR: CLARENCE Fl. TATE ATTORNEY Unite States The history of writing materials begins with the stylus and clay tablets. It has progressed through the developments of art to the use of a wide variety of media, instruments and tools. Lithography, in which the artist works directly upon the stone was invented in the last century, as a development branching off from the etching plate upon which early artists worked directly with needles or gravers.

Modern lithography received its great impetus with the invention of the half-tone screen, by means of which areas of colors can be reproduced as composites of three primary colors, each printed as a series of dots of varying sizes. The use of the dots and holes of modern lithography has been necessary to define the resolution with which reproduction can be attained.

I have invented a set of magnetic writing materials, and a method of Writing therewith, which is related to the reproduction of linework by means of dots.

The principal object of my invention is to produce a completely magnetic set of Writing materials. The writing surface is composed of magnetic particles or granules, the writing instrument is composed of a magnetized tool, and the writing eraser is also composed of a magnetized instrument.

A further object of my invention is to produce a dustfree and clean set of writing materials, with none of the many disadvantages inherent in the use of chalk with a blackboard, and the traditional chalk eraser which only serves to smear chalklines into grey smudges, while spreading great amounts of chalkdust in the air.

An additional object of my invention is to produce a set of writing materials which will not dirty or otherwise affect the hands and clothing of the individual writer, such as is common with ink and pencil in combination with the ordinary paper.

A still further object of my invention is to provide a set of writing materials in which no drying fluid will form a part of the combination, in which permanence or stability of the writing is inherent in the materials them selves.

The above and other objects of my invention will be apparent to those skilled in the art from a study of the accompanying drawings forming a part of this specification and illustrating in the different figures several views of the particular embodiment of the invention.

In the drawings:

FIGURE 1 is a cross-section view through the writing surface, together with a portion of the writing instrument involved;

FIGURE 2 is a plan view of a portion of the writing surface as it appears to the writer;

FIGURE 3 is a side view of the magnetic eraser; and

FIGURE 4 is an end view of an alternative eraser.

Referring now particularly to FIG. 1, the numeral 1 is given to the Writing surface or sheet. The surface 1 is seen to consist of a front surface 2 and a rear surface 3, which together form a hollow cavity, which is fluid tight. I prefer to have both the front surface 2 and the rear surface 3 made of a plastic material such as plexiglas, or other acrylics, which are either transparent or translucent, to light in the visible wavelengths.

Front surface 2 is molded on its inner side with a series of pockets or foraminations as shown in FIG. 1. In the embodiment shown the pockets 4, 4 consist of in dentations made in the form of sections of the surface of a sphere, all identical.

Disposed between the front surface 2 and the rear atnt surface 3 are a number of particles. I have chosen to illustrate theseas spheres although they may be granules, pellets, and indeed may be irregular in form. In the preferred form these particles are spheres of a slightly smaller diameter than the diameter of the pockets on the inner side of the front surface 2. The spheres are numbered 5, 5. In the preferred embodiment there are two vertical rows of these spheres, and they are posi tioned in staggered relationship. In fact I prefer to restrain them in a condition such that the distance between the inside of the front surface 2 and the inside of the rear surface 3 is less than two times the diameter of the particles. Thus the particles are not only staggered but crowded.

Also filling the cavity between the front surface 2 and the rear surface is a solution in the form of a liquid 6. In the complete writing surface or sheet, I prefer to have the cavity filled entirely with this solution and to have no air bublbes.

The specific gravity of the solution 6 and the density of the particles 5 is quite close, by choice, so that the particles tend to float without appreciable friction, either from other particles or from the inner walls of the surfaces. As a consequence the particles 5 are free to rotate in their restrained positions, that is they are free to rotate but they cannot move translationally. Each particle is constrained to remain always next to its immediately adjacent neighbors in touching abutment.

The particles are made by mixing an aggregateof equal parts of barium ferrite, a magnetic material of highre tentivity, and plaster of Paris or some other such filler and binder. Another possible combination is barium ferrite together with wood flour and glue. The aggregate is in the former case, mixed thoroughly together and then mixed with water. It is then molded into balls or spheres and allowed to harden, whether by the addition of heat or the passage of time. v I

The purpose of mixing equal parts of the barium ferrite with a filler is to lower the unit volumetric ma netization of the spheres below the point at which they will stick together with magnetization. At this point, I magnetize the spheres so that there is a north pole'at one point on the sphere surface and a south pole situated 180 degrees away from the north pole, that is, on the opposite side of the sphere. I then paint one pole, for instance the north pole a dark color such as a black and the opposite pole a light color or I may leave the latter unpainted in which case it is the color of the mixture of plaster and barium ferrite, which is a chalky mixture and equivalent to white.

The outer surfaces of the spheres may be painted in two equal areas of color, but I prefer to have a dominating" color. For this purpose, in the illustration of FIG; 1, I have used white as the dominating color. This means that the white area is approximately 55% of the total area of a given sphere, whereas the remaining color, black is allowed to cover only 45% of the total area.

For writing on the sheet v1, I use a bar magnet in the shape of a pencil and having a Writing tip between two and three times as wide as the diameter of the spheres 5, 5. The tip is numbered 7 and is magnetized in the illustration of FIG. 1 with a south pole. The tip 7 is covered with a thin film of plastic 8.

Wrapped around the magnet, outside the plastic film is a conical shell 9 made of soft iron which extends past the tip of the magnet 7. The purpose of this shell construction is to restrict the field of the magnet so that while the field extends beyond the tip, horizonally in FIG. 1

to influence the balls, it will not extend sidewise of the soft iron shell 9, that is, vertically in FIG. 1. This means that the field can only affect the positions of two balls at one time.;-

The entire assembly, including the extending soft iron 1 consists of a magnet .12.

As the tip 7 of the writing instrument is brought close to the front surface 2, the two spheres immediately adjacent the tip 7 will rotate in their pockets or sockets 4, 4

so that these two spheres numbered L1, 11 will present their north sides, the black sides to the right of FIG. 1, that is to the front surface. If the magnetized tip 7 has a strong enough field,'a ball or two located behind the first column will also rotate, although I have not illustrated this in FIG. 1. a

Thus in Writing the tip 7 is merely rubbed lightly over the front surface 2 and a re-orientation of the spheres occurs. Whereas at'the beginning all the spheres were aligned so that their white sides, that is, the south poles were at the right in FIG. 1, now those spheres or particles nearest the tip 7 have been rotated so that they are oppcsitely aligned. The result is' shown in FIG. 2, where the numeral seven is shown, written in a two column Wilde stroke in black, as it appears on a background of w ite.

In FIG. 3 I illustrate the eraser of the writing set, which The erasing magnet is a rectangular shape. On one side, the black, 16, it is magnetized north, whereas on the opposite side it is magnetized south, 14. The entire eraser magnet is encased in a covering 15 of thin plastic which is soft and will not mar .or ruin the writing sheet by being rubbed against it.

The eraser is used in the following way. The side which is magnetized north, :13, is laid against the front surface of the sheet 1, and then patted against that sheet. This action causes the south poles of the spheres, to be attracted to the north poles of the eraser. All the spheres are thus aligned with their south sides, the white ones, to the right in FIG. 1. The numeral seven of FIG. 2 has been-erased, and the spheres 11, 11 of FIG 1 have rotated to their original positions.

For a blackboard-sized sheet I prefer to use spheres or particles having a diameter of approximately to 35 mils, that is approximately one-thirt -second of an inch. 7 Thus the tip of the writing instrument is approximately onesixteenth of an inch wide,'and the resulting line drawn by the writing instrument is the same width as that of the writing tip.

For a portable hand toy or ordinary letter-sized writing sheet, I prefer to use particles of a size between 5 and 10 mils though they can of course be made smaller or larger as preferred. Smaller particles have been made by spraying or forcing the aggregate of barium ferrite and plaster through a spray gun so that they dry and harden before they land, in the manner of shot dropped through a layer of heated air. These smaller particles are then laid on a sheet of aluminum and passed through'a magnetizing field, and'painted in any of the customary manner-s for small particles. The S mil particle results in a line 10 mils wide on the Writing sheet. a

In FIG. 4 I show an end view of an alternative eraser magnet which is formed of a sheet of iron. This sheet is magnetized oppositely on its fiat sides and then bent into the form of a cylinder. Thus an inner and outer surface is formed, 16 and 17. This cylinder magnet eraser can then be rolled across the writing surface to erase the writing. The north polar surface 17 attracts the south poles of the spheres and rotates the spheresdl, 11 of FIG. 1 it their original positions. If desired, the cylinder magnet eraser can be provided with a handle, so that it resembles a rolling pin, if the handle is on the end, or it can be made like a paint roller, in which case the handle is set perpendicular to a. wire running down the center of the cylindrical magnet.

It is possible to vary the above proportions between wide margins. I have used a mixture of one-third barium ferrite with two-thirds plaster. In this case it was necessary to change the density of the solution 6 in order to keep the particles buoyant and lower their friction against each other. To vary the density, common table salt, in varying proportions, may be used; it is added simply 'by dissolving in water. Many water-soluble salts can be used alternatively, and even organic salts may be used in connection with an alcohol or other organic solvent. As little as one-tenth barium ferrite may be used, in which case the magnetic forces are very weak. Again the solution may be omitted when a writing tip of relatively stronger magnetization is'employed. The stronger magnetization will provide greater magnetic forces to turn the spheres. In this case the buoyancy forces of the solution are not required, to overcome the friction forces between the particles.

Also it will be obvious to those practicing the invention that more than two vertical columns may be employed and that the dimensions of the tip with respect to the diameter of the particles may 'be greater or lesser. Similarly the back surface may be used as the front surface, so long as it is transparent like the front surface 2. Also another possible modification is to leave out. the pockets and use a writing tip with relatively stronger magnetization, which can itself overcome the friction forces between the particles holding them in position.

Various other modifications and alterations may be made in the combination as will be apparent to those skilled in the art. The scope of the invention therefore should not be considered as limited to these specific details but is to be ascertained from the appended claims.

Iclaim:

1. A set of writing materials consisting of a writing sheet in the form of a front surface and a rear surface, a series of magnetized balls disposed between said front surface and said rear surface in columns, pockets formed on the inside of said front surface and one column of said balls disposed in said pockets, and a friction-lessening solution filling the spaces between said surfaces and said balls, each ball magnetized with a north and a south pole, .said north poles being painted one color and said south poles painted with a contrasting color, a writing instrument consisting of a magnet formed with a pole at one tip and a covering for said pole in the form of a plastic film, a surrounding shell of soft iron which eX- tends beyond the writing tip of said magnet, and a plastic boot covering said writing tip.

2. The combination of claim 1, wherein the writing instrument is provided with a magnetized tip approximately twice as wide as the diameter of the magnetized balls.

References Cited in the file of this patent UNITED STATES PATENTS 1,074,533 Schowalter Sept. 20, 1913 1,549,197 Hanback Aug. 11, 1925 2,530,013 Hanback Nov. 14, 1950 2,589,601 Burnett Mar 18, 1952

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