US3369254A

US3369254A - Stylus assembly

Info

Publication number: US3369254A
Application number: US396337A
Authority: US
Inventors: Milton S Cohen
Original assignee: Arthur D Little Inc
Current assignee: Unisys Corp; Arthur D Little Inc
Priority date: 1964-09-14
Filing date: 1964-09-14
Publication date: 1968-02-13
Anticipated expiration: 1985-02-13

Description

M. S. COHEN STYLUS ASSEMBLY Feb, 13, 1968 Filed Sept. 14, 1964 United States Patent Ofiiice 3,369,254 Patented Feb. 13, 1968 3,369,254 STYLUS ASSEMBLY Milton S. Cohen, Arlington, Mass., assignor, by mesne assignments, to Arthur D. Little, Inc., Cambridge, Mass., a corporation of Massachusetts Filed Sept. 14, 1964, Ser. No. 396,337 4 Claims. (Cl. 346-139) ABSTRACT OF THE DISCLOSURE A stylus assembly for writing on electrosensitive paper comprising a wire stylus mounted within an insulation sleeve and inclined in a direction opposite the direction of movement of the paper relative to the stylus, and a weighted member or tension spring detachably secured to the stylus for biasing it against the paper.

This invention relates to dry electrosensitive writing systems and, more particularly, to a new and improved writing stylus assembly for use in such systems.

Dry electrosensitive writing systems, as such, are well known in the art, Such systems generally comprise means for applying electrical energy to an electrosensitive paper to cause the portion of the paper to which the electrical energy is applied to be broken down resulting in a change of color. The electrical energy is usually applied between a metal stylus moving lightly over the coated surface of the electrosensitive paper and a metal platen or drum with which the back of the paper makes good contact. For satisfactory writing, the drum or stylus must be resiliently mounted to provide a substantially uniform stylus-topaper pressure. The optimum pressure required depends somewhat on the relative speed of the stylus and paper. In some systems the stylus is moved relative to the electrosensitive paper; in others the reverse may be true.

The material most generally used in styli is fine drawn tungsten wire approximately 0.010" in diameter. Since an accurate stylus-to-paper pressure can easily be obtained by utilizing relatively fixed stylus mounting, the advantages of using a stylus which has a low rate of wear and erosion are obvious. Tungsten, however, has several characteristics which reduce its desirability. The most serious of these is that drawn tungsten wire has a fibrous crystal structure. As the stylus wears, the end of the wire becomes splintery or broom-like. The worn stylus tends to pick up portions of the insulating coating of the recording paper and becomes loaded with the insulation and/ or develops sharp edges which scratch or gorge the electrosensitive surface of the paper. In either case, the quality of the writing and copy are markedly decreased.

A hard drawn steel wire, e.g., piano or music wire,

wears smoothly and avoids the undesirable effects caused by tungsten splintering. Steel wire has not been widely used in the past because it wears much more rapidly than does tungsten and the stylus must frequently be adjusted and/ or replaced.

An object of the present invention is to provide a stylus mounting assembly which adjusts itself to compensate for wear.

Another object is to provide a stylus assembly of the type mentioned which insures a continuously substantially uniform stylus-to-paper pressure irrespective of the wearing or erosion of the stylus.

Still another object is to provide an assembly of the type mentioned in which a worn stylus may easily be removed and replaced.

The invention accomplishes the above mentioned objects by providing a cylindrical insulating sleeve mounted in a fixed relationship to the electrosensitive paper. The

stylus extends through the sleeve into engagement with the electrosensitive paper, and means are provided for mechanically biasing the stylus towards the paper with a predetermined, continuous pressure.

For a fuller understanding of the natures and objects of the invention, reference is now made to the following detailed disclosure of preferred embodiments thereof taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a sectional view of apparatus comprising one form of the present invention; and

FIG. 2 is a sectional view of an alternative embodiment of the invention.

Reference is now made to drawings which illustrate stylus systems for writing on electrosensitive paper. The paper is shown mounted on a rotating drum for movement relative tothe stylus. As illustrated, each of the systems comprises a steel stylus 10 mounted on a rigid support arm 12 and adapted for Writing on a piece of electrosensitive paper 14 wrapped around a cylindrical drum 15. Electrical energy is applied to the stylus by a connecting wire 16. The stylus is held in a position slightly inclined to the surface of the drum by an insulating cylinder or sleeve 18 surrounding the stylus and extending through support arm 12. The axis of the insulating sleeve is slightly inclined from the perpendicular relative to the surface of drum 15. The inside diameter of sleeve 18 is slightly greater than the diameter of stylus 10 so that there is a slip fit between the stylus and sleeve. The angle at which the point of the stylus engages the surface of the electrosensitive paper wrapped around the drum is not critical. It is only desirable that the stylus be slightly inclined relative to the surface of the drum so that it will be dragged across the electrosensitive paper as the paper is moved relative to the stylus. If the stylus were perpendicular or inclined in the opposite direction, it would have a tendency to dig into the surface of the electrosensitive paper.

In the embodiment illustrated in FIG. 1, stylus 10 is biased towards drum 15 by a helically wound spring mounted coaxially with and surrounding the upper portion of sleeve 18 (the portion of the sleeve on the side of support arm 12 most distant from the drum). A cylindrical insulating ring 20 surrounds sleeve 18 at a point closely adjacent support arm 12 and intermediate spring 22 and the support arm so that the spring and support arm are electrically insulated from each other. Spring 22 extends from adjacent insulating ring 20 axially along the stylus to a point above the upper end of sleeve 18. As illustrated, spring 22 is loosely fitted around sleeve 18 and a retaining collar 24 is provided to secure the lower portion of the spring to the sleeve. A tightly wound helical extension spring 26 is attached to the upper end of spring 22 in position for engaging the adjacent portion of stylus 10 and securing it relative to the upper end of spring 22. Connecting wire 16 is secured to spring 22 and electrical energy conducted from the wire to the stylus through

springs

22 and 26.

As illustrated, spring 22 is axially extended from its relaxed position so that stylus 10 is forced against the electrosensitive paper. Spring 22 is preferably constructed to produce a relatively constant axial force so that, as stylus 10 wears away, the stylus-to-paper pressure will remain substantially constant for a relatively long period of time. When the stylus has worn so much that it must be replaced, it can easily be removed from the mounting by slightly extending or bending spring 26 and manually drawing the stylus upward through sleeve 18. A new stylus may then be dropped into place and spring 26 released to engage it.

Reference is now made to FIG. 2 which illustrates an alternative embodiment of the invention. This embodimen: enters from that illustrated in FIG. 1 in that the stylus is biased towards the drum by a weight 26 secured to an upper portion of the stylus by thumbscrew 28 rather than by a spring. Connecting wire 16 is secured directly to the weight. The stylus-to-paper pressure is a direct function of the size of the weight and will remain constant until so much of the stylus wears away that the weight rests upon the top of sleeve 18. At that time the worn stylus may easily be replaced by merely loosening thumbscrew 28. This alternative embodiment, unlike that illustrated in FIG. 1, is limited to use in systems in which the stylus is above the electrosensitive paper and the speed of the stylus relative to the paper is low enough so that inertial characteristics of the weight are not objectionable.

It should be obvious that the invention herein described is not restricted to the use of steel styli but is adapted for use with any conducting stylus material. Since certain other changes may be made in the above apparatus without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense,

What is claimed is:

1. A writing stylus assembly for writing on electrosensitive paper mounted for movement relative to the stylus assembly comprising, in combination:

a support arm mounted adjacent and extending above the electrosensitive paper;

a cylindrical insulating sleeve secured to the portion of the support arm above the paper with the axis of the sleeve slightly inclined from a direction perpendicular to the paper in a direction opposite the direction of movement of the paper relative to the stylus assembly;

a cylindrical wire stylus having a diameter slightly less than the diameter of the sleeve extending axially through the sleeve;

a weighted member having a weight substantially equal to the desired pressure between the stylus and electrosensitive paper detachably secured to the stylus at a point above the upper axial end of the sleeve for biasing the stylus towards the paper with a predetermined force; and

an electrically conductive wire secured to the weighted member for applying electrical energy to the stylus.

2. A writing stylus assembly for writing on electrosensitive paper mounted for movement relative to the stylus assembly comprising, in combination:

a support arm mounted adjacent the electrosensitive a cylindrical insulating sleeve secured to the support arm with the axis of the sleeve slightly inclined from a direction perpendicular to the paper in a direction opposite the direction of movement of the paper relative to the stylus assembly;

a cylindrical wire stylus having a diameter slightly less than the inside diameter of the sleeve extending axially through the sleeve;

a helical stylus biasing spring mounted coaxially with the insulating sleeve on the side of the support arm most distant from the paper and electrically insulated from the support arm with the portion of the spring nearest the paper secured to the insulating sleeve;

stylus engagement means securedto an upper portion of the spring and detachably secured to the stylus tor applying the force of the stylus biasing spring in tension to the stylus to force the stylus against the paper with a predetermined force; and

an electrically conductive wire electrically connected to the stylus for applying electrical energy thereto, the stylus and insulating spring being electrically insulated from the support arm.

3. The stylus assembly of claim 2 wherein the stylus engagement means includes a tightly Wound helical spring secured to an upper portion of the stylus biasing spring substantially perpendicular to the axis thereof with the coils of the tightly wound spring detachably secured to the stylus.

4. The stylus assembly of claim 3 including an insulating collar surrounding and secured to the sleeve at a point closely adjacent the surface of the support arm and wherein the sleeve extends through the support arm and a portion of the stylus biasing spring is secured to the sleeve at a point closely adjacent the collar.

References Cited UNITED STATES PATENTS 456,668 7/1891 Boyer 346139 2,380,467 7/1945 Ressler 346-139 2,404,975 7/1946 Mathes 346-439 2,442,561 6/1948 Finch 346139 2,850,350 9/1958 Wise 34674 FOREIGN PATENTS.

730,260 1/1943 Germany.

730,844 6/1955 Great Britain.

212,460 2/1941 Switzerland.

RICHARD B. WILKINSON, Primary Examiner.

JOHN W. CALDWELL, Examiner.

J. A. ORSINO, I W. HARTARY, Assistant Examiners,