IE47411B1 - Cutting foil for an electrically driven dry shaver - Google Patents

Abstract

In a process for electroforming a cutting foil 16 for an electrically driven dry shaver, a sheet 11, on which the foil 16 is to be deposited, has a pattern corresponding to that of the cutting aperture distribution formed thereon with the parts 13 corresponding to the apertures formed electrically non-conductive and the parts corresponding to the lands formed electrically conductive. However, the portions of the parts 14 corresponding to the lands where convolutions are required are also formed electrically non-conductive. The foil 16 may be directly deposited on the sheet. Alternatively, an intermediate foil 15 e.g. of nickel may be deposited on the sheet and the cutting foil 16 deposited on the intermediate foil.

Description

This invention relates to a process for the manufacture of a cutting foil for an electrically driven dry shaver with lands between the cutting apertures thereof having elevated and recessed portions.

On shaving the skin is tensioned by the elevated portions of the lands, thus facilitating the threading of the hairs to be sheared into the cutting apertures and improv ing the cutting performance.

Such cutting foils are known from U.S. Patent Specification No. 2,297,915, wherein the shaping of the lands is effected mechanically.

A disadvantage is that, with known processes, mass production of large quantities cannot be achieved in an accurate and economic manner.

An object of the invention is to overcome this disadvantage and make available a process which enables the manufacture of a cutting foil with lands having elevated and recessed portions by mass production in large quantities and in an accurate and economic manner.

According to the invention, there is provided a process for the manufacture of a cutting foil for an electrically driven dry shaver, which foil has a plurality of cutting apertures and lands comprising elevated portions and recessed portions between the elevated portions on the side of the foil which is to face the user's skin, the process comprising 411 - 3 rendering a surface of a base electrically non-conductive in parts corresponc ing to the pattern of the cutting aperture distribution and also in parts corresponding to the pattern of the recessed portions of the lands and electrically conductive in parts corresponding to the pattern of the elevated portions of the lands, and electro-depositing material on the base in such a manner that the material bridges the electrically non-conductive parts corresponding to the recessed portions of the lands to form said recessed portions.

Preferentially, an intermediate metal foil, in paeticular nickel foil, is electro-deposited as a frame-work before deposition of the cutting foil.

The electrically non-conductive parts of said corresponding to the recessed portions of the lands may comprise at least one unbroken line. Alternatively, tha electrically non-conductive parts corresponding to the recessed portions of the lands m.iy comprise at least one broken line. In either case the line* may be arranged either symmetrically or asymmetrically.

Preferably the electrically conductive parts of said surface surround the electrically non-conductive parts corresponding to the cutting apertures, and the electrically non-conductive parts corresponding to the recessed portions of the lands are disposed b> tween adjacent electrically conductive parts. Furthermore it is advantageous if the electrically non-conductive parts of said surface corresponding to the recessed portions of the lands cover about a third of the width of the parts corresponding to the lands between adjacent parts corresponding to the apertures.

The base may be either a metal sheet or a sheet of - 4 electrically insulating material with a conductive surface.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which :Figure 1 is a cross-sectional view showing the first stage of a manufacturing process in accordance with the invention.

Figures 2 and 3 are plan views of alternative forms of transparency for use in the process to be described with reference to Figure 1, Figures 4 and 5 are cross-sectional views illustrating further stages in die process to be described with reference to Figure 1, and Figure 6 is a cross-sectional view of a completed cutting foil formed by the process to be described with reference to Figures 1 to 5.

Referring to Figure 1, an electrically conductive bright metal sheet 11 has one surface coated in a manner known per se with a layer of photo-sensitive varnish 12 which is then exposed through a negative transparency. In this transparency both the parts 13 corresponding to the cutting apertures and the parts 14 corresponding to the recessed portions of the lands are permeable to light.

This can be achieved by copying the geometrical shape of the elevated portions of the lands onto a negative transparency of the cutting foil. Figure 2 shows a transparency for use when the cecessed portions are to be in the form of unbroken lines 14b, the width 2 of tbe lines being 1/3 of the width of the lands. Figure 3 shows a transparency for use when the recessed portions are to be in the form of 7 411 broken lines 14a.

If the layer of photo-sensitive varnish 12 on the metal sheet 11 is now exposed through this negative transparency, the varnish is hardened at the exposed parts. During subsequent development, the varnish is removed at the unexposed parts.

Next, as shown in Figure 4, a metallic intermediate foil 15, preferably a nickel foil, is deposited in a manner known per se as a skeletal base. The metallic intermediate foil 15 is deposited between the parts 13 covered by varaiih which correspond to the cutting apertures, but grows over the parts 14 covered by varnish corresponding to the h:·..·.... ' portions of the lands, to form bridges 14c which are, hcwrrrr, recessed. Accordingly, each land of the metallic intermediate foil 15 features two parts 15a and 15b which are elevated relative to the bridge 14c, If not, as shown in Figure 5, a cutting foil 16, preferably a nickel foil, is deposited in a manner known per se on the metallic intermediate foil 15, then these elevated parts are reproduced on the lands of the cutting foil. After separating the foils 15 and 16, as shown at the right hand side of Figure 5, there is obtained a cutting foil having elevated and recessed portions on the side of the foil which is to face the user's skin (Figure 6).

The recessed portions can be arranged symmetrically or alternatively asymmetrically.

It is known that electro-deposition depends strongly on the composition of the bath and operational conditions.

The respective optimum shape of the additional parts to be rendered electrically non-conductive can be determined by those skilled in the art merely on the basis of simple trials.

Alternatively, the metal sheet can be masked and etched at the parts corresponding to the lands of the cutting foil, with the exception of the parts corresponding to the recessed portions in the lands, in a known manner for example by printing the desired pattern on an electrically conductive metal sheet with a varnish and then etching the sheet. Subsequently, the islands of varnish are removed in a known manner and the recesses produced by the etching are coated with an electrically non-conductive varnish. Next the cut10 ting foil is electro-deposited on the sheet. Whilst the parts corresponding to the cutting apertures remain free, the parts forming the lands grow together in such a manner that recesses form at the parts which are non-conductively formed and in this way the cutting foil deposited on the parts of the meta sheet which are formed conductive, has the required prof le.

If a plastics sheet with a conductive surface is used instead of a metal sheet, the non-conductive parts can be formed by stamping.

Claims (1)

1. A process for the manufacture of a cutting foil for an electrically driven dry shaver, which foil has a plurality of cutting apertures and lands comprising elevated 5 portions and recessed portions between the elevated portions on the side of the foil which is to face the user's skin, the process comprising rendering a surface of a base electrically non-conductive in parts corresponding to the patter: of the cutting aperture distribution and also in parts co:-·· 10 ponding to the pattern of the recessed portions cf the isr