US 3574956 A
Description (OCR text may contain errors)
United States Patent Inventor Robert Hamelin 17 Boulevard Bentrand, Caen,Ca1vados, France Appl. No. 777,552 Filed Nov. 18, 1968 Patented Apr. 13, 1971 Priority Nov. 17, 1967 France 128640 WRITING SUPPORT 5 Claims, 2 Drawing Figs.
11.8. CI 35/66 Int. Cl B431 1/10 Field of Search 35/61, 66,
Primary ExaminerHarland S. Skogquist Attorney-Karl F. Ross ABSTRACT: An erasable writing pad is formed from a transparent or translucent plastic sheet, e.g. of
polyvinylchloride, whose front surface is embossed with rows of hemispherical bulges of about 0.1 mm diameter and a mutual separation equal to or less than that diameter, the rear surface of the sheet carrying a grating overlain by a distinctive color layer.
Patented 'April 13, 1971 3,574,956
Robert HAMELIN INVEN'IOR (KM 6R0 Attorney WRITING SUPPORT My present invention relates to an improved support on which one can write by using an instrument such as pencil, chalk, crayon or the like depositing solid particles on the surface thereof.
Conventional supports of this type consist essentially of a plate of natural slate or black cardboard.
It is the principal object of the present invention to provide an improved support of this general character.
The support according to this invention comprises a transparent or translucent sheet of plastic material whose front side, to be engaged by the writing instrument, has a grained surface.
According to a specific feature of this invention, this sheet further has a backside printed or coated with a backgroundforming color layer on which there is printed, before the background impression is applied a guiding cross-ruling pattern or grating which will on the one hand remain visible by transparency when the user looks from the front and on the other hand stand out in clear contrast against said background.
According to a further feature of my invention, this writing support or pad may comprise a stack of several sheets including a rear sheet acting as a backing layer, an intermediate stiffening sheet, and a plastic front sheetas described above constituting the writing surface, these various sheets being assembled by high frequency welding along their marginal portions.
Other features and advantages of this invention will appear as the following description proceeds with reference to the accompanying drawing illustrating diagrammatically by way of example the manner in which the present invention may be carried out in practice. In the drawing:
FIG. 1 illustrates a writing support according to this invention; and
FIG. 2 is a considerably magnified view of the grained plastic sheet. 7
As already explained hereinabove, a writing support designed to replace conventional slates" consists of a transparent or translucent plastic sheet A grained by calendering and having printed on its backside on the one hand a guiding cross-ruling pattern B and on the other hand a background-forming layer C.
Thus, the cross-ruled pattern visible by transparency from t the front side will stand out clearly against said background.
I have found that the characteristics of the graining are of primary importance when it'i's desired on the one hand to make the reading as easy as possible, i.e. with the formation of visually unbroken lines, and on the other hand to facilitate the erasing as the deposited particles constituting the writing or other symbols remain on the lines of the grained pattern or structure.
-After exhaustive tests, I finally adopted a grained surface' consisting of fine hemispherical projections having for example the following dimensions: diameter d=0.l mm, height h=0.05 mm.
Moreover, the distance e between adjacent rows of grains shall not exceed the value of the grain diameter d.
The improved writing support embodying this invention may be made from heat-weldable material, notably highfrequency-fusible synthetic resin such as PVC. It is also recommended to reinforce this supporting sheet with other layers or sheets to form the aforedescribed stack.
This support may be folded along a median line XX so that the writing surface is protected during transportation.
Of course, the backside of the sheet A may be grained to register with the front side graining. However, it is preferred to leave this backside plain or smooth, in order to facilitate the printing of the cross ruling B and background C.
1. A support on which one can write by using an instrument of the type depositing solid particles when rubbed thereagainst, such as pencil, chalk, crayon, comprising a transparent or translucent plastic sheet having a front side, which is to be engaged by the instrument, substantially covered by rows of bulged hemispherical grains of a diameter of about 0.l mm, said sheet having its backside printed or coated with a color layer acting as a background after guiding cross-ruling has been printed thereon.
2. A support as defined in claim 1 wherein the height of said grains is about 0.05 millimeter.
3. A support as defined in claim 1 wherein the distance between two adjacent rows of grains is less than 0.1 millimeter.
4. A support as defined in claim 1 wherein said sheet consists of thermally fusible synthetic resin.
5. A support as defined in claim 4 wherein said resin is PVC.