US3564715A - Dry shaver shear plate - Google Patents

Abstract

A DRY SHAVER SHEAR PLATE HAVING A NON-UNIFORM THICKNESS, AND A CORRESPONDING NON-UNIFORM SURFACE FOR CONTACTING THE SKIN OF THE USER.

Description

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Filed June 21. 1968 INVENTORS HENRICUS J. DRIESSEN JAN VAN VEEN CORNELIS P L. COMMISSARIS United States Patent 3,564,715 DRY SHAVER SHEAR PLATE Henricus Josef Driessen and Jan Van Veen, Drachten, and Cornelis Petrus Lodewijk 'Commissaris, Ri sw1 k, Netherlands, assignors to US. Philips Corporation, New York, N.Y., a corporation of Delaware Filed June 21, 1968, Ser. No. 739,132 Claims priority, application Netherlands, July 5, 1967, 6709297 Int. Cl. B26b 19/06 US. Cl. 30--346.51 Claims ABSTRACT OF THE DISCLOSURE A dry shaver shear plate having a non-uniform thickness, and a corresponding non-uniform surface for contacting the skin of the user.

The invention relates to a shear plate of a shaving head of a dry-shaving apparatus having a running surface for a movable cutting member and having hair passages, the shear plate having in the area of the running surface a variable thickness on the side to be pressed against the skin.

Such shear plates having parts locally reduced in thickness are known.

For the construction of these known shear plates for dry-shaving apparatus use is made of the known phenomenon that, when shaving by means of a dry-shaving apparatus the hairs are cut more rapidly and deeply according as the shear plate of the dry-shaving apparatus is thinner in the area of the running surface for the associated cutting member.

Although on the basis of this recognition shear plates have been constructed whose thickness in the area of the running surface is variable, practice has shown that the presumably expected improved results are not solely obtained by a difference of thickness of the shear plate in the area of the running surface for the cutting member but that other factors such as shaving ability and habit also affect the shaving results.

The shaving ability is determined inter alia by the following factors: the pressure exerted by the shear plate on the skin to be shaved, the direction of movement of the shear plate relative to the skin and even the users manual grip on the shaving apparatus during the shaving operation; moreover, the habit of pressing a larger or smaller surface of the shear plate against the skin and the shape of the housing intended to improve the manageability of the shaving apparatus are found to have a fairly important influence on the shaving results.

It is known that the thickness of the portions of the shear plate to be pressed against the skin must not exceed a given minimum limit in view of reasonable requirements of strength and lifetime.

The invention is based on the recognition that without detracting from the effectiveness and quality of the shaving apparatus very satisfying shaving results can be obtained by preventing completely or at least for the major part an excessively intimate contact between the locally thinner shear plate portions and the skin to be shaved, for example, due to the users manipulation habits of exerting an excessive pressure by the shear plate on the skin, which pressure may give rise to grazing due to locally excessive penetration of the skin through the hair passages of the shear plate and even to premature fracture of the thinner shear plate portions.

The invention based on the aforesaid recognition is characterised in that the running surface portions of dif- 3,564,715 Patented Feb. 23, 1971 ice ferent thicknesses are arranged one after the other in the direction of movement of the cutting member.

When using a dry-shaving apparatus comprising a shear plate according to the invention, the skin to be shaved is, so to say, supported by the thicker portions of the shear plate in the area of the running surface for the cutting member.

During the shaving operation the shear plate pressed against the skin moves along the skin, which is slightly pushed upwards by the exerted pressure in the direction of movement of the shear plate, so that in said direction of movement in front of the shear plate the skin slightly bulges up and the skin beneath the shear plate is slightly stretched.

This effect is increased, though presumably not proportionally, by a larger surface of the shear plate to be pressed against the skin or in other words by a wider path covered by the shear plate on the skin.

A multi-head shaving apparatus can also provide such a wider path.

Stretching of the skin results in that the lower ends of the hair follicles move towards the cuticle.

These hair follicles may be considered to form depressions of the cuticle. When the cuticle is stretched, even to a slight extent, the skin reacts by tending to enlarge its surface so that part of the inner wall of the hair follicles, lying near the inner surface of the cuticle in the unstretched state of the skin, will form part of the outer surface of the stretched skin, as a result of which the hair to be cut projects by a major portion and can be cut nearer the origin during the shaving operation.

The thicker portions of the shear plate then serve for coarse shaving, the hairs being out less deeply, whereas in the areas of the thinner shear plate portions the project hairs can be cut nearer the origin. The skin flattens itself so to say against the thinner shear plate portions so that the risk of an excessive penetration of the skin, which may give rise to the unpleasant grazing, is reduced.

It should be noted, that a stretched skin itself also reduces the risk of excessive penetration into the hair passages of the shear plate, although the extent of this reduction depends inter alia upon the condition of the skin, for example, a natural flexibility and elasticity.

The said step-wise cutting of the hairs need not be troublesome for attaining a satisfactory shaving result, since even with the conventional shear plate of uniform thickness the hairs are neither cut at once to a minimum length, but are also cut stepwise.

The shear plate of a shaving head of a dry-shaving apparatus according to the invention is preferably constructed so that the shear plate portions of different thicknesses are arranged in two groups, in which the individual portions have substantially the same thickness.

Such a construction in which the portions of different thicknesses are arranged in only two groups may be considered to form a compromise between an optimum shaving capacity promoted by the thinner shear plate portions and reasonable requirements of strength and lifetime of the shear plate provided by the thicker shear plate portions.

The invention is furthermore important with a view to manufacturing costs as compared with 'known types of shear plates, which is provided in the area of the running surface with identical hair passages, for example, slots extending transversely of the direction of movement of the cutting member, circular openings and so on.

With these constructions as compared with known types of shear plates the additional work is slight so that the manufacturing costs may be comparatively low.

An appropriate construction of the shearplate of a shaving head of a dry-shaving apparatus according to the invention is obtained by providing the shear plate in the area of the thinner running surface portions with circular hair passages, whereas the thicker portions are provided with slots extending transversely of the direction of movement of the cutting member.

The circular hair passages in the portions of smaller thickness form so to say an additional protection against grazing in the event of excessive penetration of the skin into the hair passages of the thinner portions in spite of the stretching of the skin, since the hair passages of circular form are capable of preventing this excessive penetration of the skin, which is then withheld by the circular inner edge of the hair passage round about the foot of the imminent penetration. This support counteracts the excessive penetration of the skin.

Said construction is particularly important for a shaving head comprising a rotatable cutting member in a niulti-head dry-shaving apparatus.

The multi-head structure of the shaving apparatus provides a greater stress of the skin moving beneath the shaving heads, so that an additional reason is provided, as stated above, for using comparatively thinner shear plates having thinner portions and thicker portions.

The shear plate according to the invention for a shaving head comprising a rotatable cutting member is preferably constructed so that the portions of different thicknesses join each other sector-wise, there being provided 4 to 8 thinner portions among these portions of substantially equal tangential dimensions, each of said thinner portions being adjacent a thicker portion on either side.

A suitable practical embodiment of the shear plate according to the invention for a shaving head comprising a rotatable cutting member is obtained by a thickness of the running surface portions of greater thickness of more than 0.07 m.m., for example, 0.075 mm. or more and by a thickness of the portions of smaller thickness of less than 0.07 mm., for example, 0.065 mm. or less.

The invention will now be described more fully with reference to the accompanying drawing, whilst further advantageous features will be set out.

FIG. 1 is a plan view of an elastically flexible shear plate according to the invention co-operating with a reciprocatory cutting member (not shown), the directions of movement of which are indicated by the arrow AA;

FIG. 2 is a cross sectional view of the shear plate taken on the line II-II in FIG. 1 on an enlarged scale;

FIG. 3 is a plan view of a circular shear plate according to the invention co-operating with a rotatable cutting member (not shown);

FIG. 4 is a cross sectional view of the shear plate taken on the line IV-IV in FIG. 3;

FIG. 5 is a plan view of a circular shear plate according to the invention having identical hair passages and FIG. 6 is a cross sectional view of the shear plate taken on the line IVIV in FIG. 5.

The shear plate 1 according to the invention shown in FIG. 1 comprises three portions 2 of smaller thickness provided with circular hair passages 4 and three portions 3 of greater thickness having slot-shaped hair passages 5.

The thinner portions 2 of the shear plate join the thicker portions 3 in the direction of movement of the cutting member (not shown) co-operating with the shear plate 1 indicated by the arrows AA.

In FIG. 3 each of the thinner portions 2 of the circular 4 shear plate 7 provided with circular passages 4 is marked by parallel cross-hatch lines 6 indicating how the thinner portions 2 are obtained by grinding, it being assumed that the hair passages are made after grinding.

In the circular shear plate 8 according to the invention shown in FIG. 5 first the slot-shaped hair passages 5 are made, after which the portions 2 are ground to the desired smaller thickness. The shear plates shown in FIG. 5 can, of course, be manufactured at lower costs than the shear plates of FIG. 3.

What we claim is:

1. For use in a shaving head of a dry-shaving apparatus, a shear plate having a running surface for cooperation with a movable cutting member and a skin-contact ing, outer surface, the shear plate formed of a plurality of thick and of thin sections, each section having substantially constant thickness and having through it a plurality of spaced-apart hair receiving apertures, and these sections disposed alternately, whereby the skin-contacting surface has non-uniform height corresponding to the variable thickness of said sections.

2. Apparatus according to claim 1 wherein all the thick sections have the same thickness, and all the thin sections have the same thickness.

3. Apparatus according to claim 1 wherein all the hairreceiving apertures in said sections are identical.

4. Apparatus according to claim 3 wherein said cutter is movable along a certain direction relative to the shear plate, and said apertures are slots extending transverse to cutters direction of movement.

5. Apparatus according to claim 3 wherein said apertures are circular holes.

6. Apparatus according to claim 2 wherein the apertures in the thick sections are slots extending transverse to the cutter direction of movement, and the apertures in the thin sections are circular holes.

7. Apparatus according to claim 1 for use in a rotary shaving head wherein each section is a similar-shaped segment of a circle.

8. Apparatus according to claim 6 wherein the thickness of the thick sections is greater than 0.07 mm. and the thickness of the thin sections is less than 0.07 mm.

9. In a dry-shaving apparatus, a shaving head including a rotary cutting member, and a generally round shear plate which comprises a plurality of alternately spaced thick and of thin sections, each section having through it a plurality of spaced-apart hair-receiving apertures, the shear plate having a generally flat running surface for cooperation with the cutting member and a skin-contacting, outer surface which has non-uniform height corresponding to the various thicknesses of said sections.

10. Apparatus according to claim 9 wherein the thin sections are all the same thickness and have round apertures, and the thick sections are all the same thickness and have slit apertures extending transverse to the direction of cutter movement.

References Cited UNITED STATES PATENTS 2,213,872 9/1940 Trachtenberg 30-346.51X 2,494,463 1/1950 Vivie 30346.51X 3,281,937 11/1966 Starre 30346.51

ANDREW R. JUHASZ, Primary Examiner G. F. GRAFEL, Assistant Examiner

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