GB2031321A

GB2031321A - A shear plate for a dry-shaver

Info

Publication number: GB2031321A
Application number: GB7931881A
Authority: GB
Original assignee: Philips Gloeilampenfabrieken NV
Current assignee: Koninklijke Philips NV
Priority date: 1978-09-18
Filing date: 1979-09-14
Publication date: 1980-04-23
Also published as: NL7809460A; JPS6147551B2; GB2031321B; CH640168A5; ES484174A1; IT1123154B; DE2937201C2; FR2436001B1; JPS5542693A; IT7925723A0; DE2937201A1; FR2436001A1

Abstract

An improved shear plate is provided for a dry-shaver having a movable cutting unit which comprises a plurality of cutters (23) and a corresponding plurality of hair-pulling elements (25) each arranged in front of one of the cutters for movement therewith relative to the shear plate. To enhance the pulling action of each hair-pulling element, the wall (32) of each hair-entry aperture of the shear plate, at the part of the boundary of each aperture where the cutters cooperate with the shear plate to cut off the hairs, is formed with a portion (36) which slopes inwardly of the aperture from the inner side (34) of the shear plate towards the outer side (39). The effect of this sloping portion is to augment that component of the reaction force of the hairs on the hair-pulling elements which gives these elements their pulling action, and also to reduce the frictional resistance of the shear plate to the movement of the hairs by the hair- pulling elements. <IMAGE>

Description

SPECIFICATION Shaving apparatus The invention relates to a shear plate for a dryshaving apparatus of the kind (hereinafter referred to as "the kind described") having a stationary shear plate formed with hair-entry apertures, and a cutting unit which is movable relative to and cooperates with the shear plate and which comprises a plurality of cutters arranged to move over the hair-entry apertures in sliding contact with the inner side of the shear plate and each having a cutting edge for cooperation with the shear plate at the boundaries of the hair-entry apertures to cut off hairs which protrude through these apertures, and a corresponding plurality of hair-pulling elements each located in front of an associated one of the cutters with respect to the direction of the cutting movement thereof and arranged for movement with the cutter relative to the shear plate, each hair-pulling element having a sharp edge which, as the element moves over a hair-entry aperture, penetrates hairs protruding through that aperture and pulls these hairs further through the aperture in front of the associated cutter. This results in the hairs being cut off closer to the skin than they would be without the hairpulling elements.

The term "shear plate" is to be understood herein to include a shear foil. The inner side of the shear plate is the side opposite that which is in contact with the user's face in the operation of the dry-shaving apparatus and which will be referred to herein as the "outer side" of the shear plate.

According to the invention there is provided a shear plate for a dry-shaving apparatus of the kind described, wherein at a part of the boundary of each hair-entry aperture of the shear plate where the cutters of the cutting unit of the apparatus cooperate with the shear plate in the operation of the apparatus, the wall of each aperture comprises a portion which slopes inwardly of the aperture from the inner side of the shear plate towards the outer side thereof.

A shear plate according to the invention is very effective in a dry-shaving apparatus of the kind described having a cutting unit in which each hairpulling element is movable relative to the associated cutter away from and towards the shear plate.

The wall of each hair-entry aperture of the shear plate may comprise a further portion which is substantially perpendicular to the sides of the shear plate and which extends from the outer side of the shear plate to meet the sloping portion of said wall.

The invention also provides a dry-shaving apparatus of the kind described having a shear plate according to the invention.

An embodiment of the invention will now be described with reference to the accompanying drawings, in which Figure 1 is a front elevation of a dry-shaving apparatus of the kind described having three shear plates and associated cutting units, Figure 2 is a side elevation of the shaving apparatus of Figure 1, showing one of the shear plates and cutting units and an associated driving means in cross-section, the section being taken on the line Il-Il in Figure 1, Figure 3 is an enlarged perspective view of one of the cutting units and part of the associated shear plate, and Figures 4 and 5 are diagrammatic side views, drawn to a greatly enlarged scale, of portions of a cutter and associated hair-pulling element and a portion of the associated shear plate iliustrating the operation of the hair-pulling element, the shear plate being constructed in accordance with the invention.

The shaving apparatus shown in Figures 1 and 2 comprises a housing 1 on which is mounted a shear-plate holder 2 for three shear plates 3. The shear plates 3 are of circular form and each have a circular pattern of hair-entry apertures in the form of slots 4.

A rotary cutting unit 5 (Figure 2) is situated on the inner side of each shear plate 3 for cooperation therewith. The cutting units 5, of which one is shown schematically in Figure 2, each comprise a plurality of cutters in the form of hair-cutting blades, and a corrnsppnding'plurnlity of hair-pullingelemTents in the form of hair-pulling blades, as will be described later herein with reference to Figure 3.

The cutting units 5 are rotated relative to the shear plates 3 by an electric motor 10 to which each cutting unit is coupled by an associated hollow spindle 6 and gear wheel 7 and a gear wheel 8 fixed on the shaft 9 of the electric motor 10. Each gear wheel 7 is rotatablyjournalled on an associated spindle 11 which is fixed in a mounting plate 12. The gear wheel 7 is formed with a cavity 13, which is closed by a cover plate 1 4. This cavity accommodates a flange 1 5 formed at the end of the hollow spindle 6.The flange 1 5 has a noncircular, for example, square, shape and by the cavity 13 is shaped accordingly so that a coupling is obtained for the transmission of the rotary movement of the gear wheel 7 to the spindle 6, which coupling allows the spindle to tilt in any direction. A coil spring 16, which for the greater part is situated in the hollow spindle 6 and which is compressed between an end wall of the hollow spindle 6 and an end wall of the cavity 13 in the gear wheel 7, exerts a force on the spindle 6 in the direction of the cutting unit 5. A conical portion 17 of the spindle 6 bears against the cutting unit 5 to transmit this force to the cutting unit and via the cutting unit to the shear plate 3, so that a flange 18 around the periphery of the shear plate is urged against the shear-plate holder 2.During use of the shaving apparatus, the shear plate 33,together with the associated cutting units 5 and spindles 6, can be pressed inwards against the action of the springs 16 underthe pressure with which the shear plates are held against the user's skin.

A coupling for the transmission of the rotary movement of each spindle 6 to the associated cutting unit 5 is formed by an end portion 19 of the spindle 6 of substantially rectangular crosssection engaging in a central coupling aperture 20 of corresponding shape in the cutting unit 5.

All three cutting units of the apparatus shown in Figures 1 and 2 are coupled to the motor 10 in the above manner, the three gear wheels 7 meshing with the one centrally disposed gear wheel 8 on the motor shaft 9.

Each cutting unit 5 (Figure 3) comprises a cutting member 21 having a central body 22 on which is formed a plurality of hair-cutting blades 23 which are evenly distributed around the periphery of the body 22 and which are connected to the body by rigid arms 24. The coupling aperture 20 is formed in the central body 22. As shown in Figures 4 and 5, each hair-cutting blade 23 has at its front (with respect to the direction of movement of the blade) a sloping surface 33 which forms an acute angle with a surface 37 of the blade which is in sliding contact with the inner side 34 of the respective shear plate 3. The edge 26 at which the surfaces 37 and 33 meet is the cutting edge of the haircutting blade.In the operation of the shaving apparatus, which will be described later herein, the sliding surface 37 of each hair-cutting blade travels over the hair-entry slots 4 in the respective shear plate and the cutting edge 26 of the blade, in cooperation with the shear plate at the boundaries of the slots, severs the hairs which protrude through the slots.

Each cutting unit 5 also comprises a plurality of hair-pulling blades 25 which are slidably arranged one on the front surface 33 of each hair-cutting blade 23. The hair-pulling blades 25 are integral with a central annular portion 29 which is secured to the central body 22 of the respective cutting member 21 by, for example, spot-welding organ adhesive. The hair-cutting blades 25 thus travel round with the hair-cutting blades 23 in the operation of the apparatus. The hair-pulling blades 25 are connected to the central annular portion 29 by resilient arms 28 so that the hair-pulling blades are movable relative to the hair-cutting blades 23 in directions away from and towards the respective shear plate 3.Each hair-pulling blade has a surface 38 which is arranged for sliding contact with the inner side 34 of the respective shear plate in front of the sliding surface 37 of the associated hair-cutting blade 23. The edge 27 of each hair-pulling blade at which the sliding surface 38 of the blade meets the front surface thereof is the leading edge of the blade in the movement of the blade over the shear plate, the two surfaces forming an acute angle at this edge.

Figures 4 and 5 illustrate schematically the operation of a combination of hair-pulling blade and hair-cutting blade. A portion of the user's skin is shown at 30, with a hair 31 protruding from it.

When the hair 31 is caught in a hair-entry slot 4, the leading edge 27 of the hair-pulling blade 25, moving in the direction of the arrow P, will come into contact with the hair at location A thereon and will press the hair against the forward wall 32 of the hair-entry slot 4, i.e., the forward wall with respect to the direction of movement of the blade 25 over the shear plate 3. The edge 27 of the blade 25 has a sharpness such that it will slightly penetrate the hair 31 at A without cutting through the hair. A reactive force is exerted on the hairpulling blade 25 by the hair 31 in a direction opposite to the direction of movement P of the blade. This force will be counteracted by the component N1 of the normal force N which is exerted on the hair-pulling blade 25 by the front surface 33 of the associated hair-cutting blade 23 (Figure 4).The component N2 of the normal force N will cause the hair-pulling blade 25 to slide along the surface 33 of the hair-cutting blade 23 away from the shear plate 3, pulling the hair 31 with it, so that the hair now protrudes further through the hair-entry slot 4. The natural elasticity of the user's skin permits this pulling of the hair.

The forward wall 32 of the hair-entry slot 4 comprises a portion 35 which extends substantially perpendicularly to the outer and inner sides of the shear plate 3 from the outer side 39 to a point intermediate the two sides, and a portion 36 which slopes inwardly of the slot 4 from the inner side 34 of the shear plate towards the outer side 39 to join the wall portion 35. The wall portion 36 and the wall portion 35 form between them an obtuse angle a, and the wall portion 36 and the inner side 34 of the shear plate form between them an obtuse angle,3.

As a result of the forces exerted on the hair 31 by the hair-pulling blade 25, the hair assumes an oblique position on the sloping wall portion 36, as shown in Figure 5, and is pressed against this wall portion.

If the frictional forces are neglected, the reactive force R of the wall portion 36 on the hair 31 will be directed perpendicularly to the wall portion 36 and will contain a component R2 which, like the component N2 of the force N, is perpendicular to the inner side 34 of the shear plate. The component R2 thus augments the effect of the component N2, as a result of which the hair 31 is pulled further through the slot 4.

This effect will also occur if slight frictional forces are present between the hair 31 and the wall portion 36.

The hair 31 will slide over the sloping wall portion 36 until the cutting edge 26 of the haircutting blade 23 reaches the hair at location B thereon (Figure 5). The hair is then cut off at this location B by the blade 23 in cooperation with the shear plate 3.

Without the hair-pulling blade the hair would be cut off at the location A. Due to the action of the hair-pulling blade the hair is cut off more closely at the location B, so that a closer shave is obtained.

The sloping wall portion 36 of each hair-entry slot 4 can have a curved or rounded shape in cross-section; for example, it can have the shape of part of a circle.

The invention is not limited to shear plates for dry-shaving apparatuses having rotary cutting units. It can also be applied, for example, to shear foils for dry-shaving apparatuses of the kind described having reciprocatory cutting units.

Claims

1. A shear plate for a dry-shaving apparatus of the kind described, wherein at a part of the boundary of each hair-entry aperture of the shear plate where the cutters of the, cutting unit of the apparatus cooperate with the shear plate in the operation of the apparatus, the wall of each aperture comprises a portion which slopes inwardly of the aperture from the inner side of the shear plate towards the outer side thereof.

2. A shear plate for a dry-shaving apparatus of the kind described having a cutting unit in which each hair-pulling element is movable relative to the associated cutter away from and towards the shear plate, wherein at a part of the boundary of each hair-entry aperture of the shear plate where the cutters of the cutting unit of the apparatus cooperate with the shear plate in the operation of the apparatus, the wall of each aperture comprises a portion which slopes inwardly of the aperture from the inner side of the shear plate towards the outer side thereof.

3. A shear plate as claimed in Claim 1 or 2, wherein said wall of each hair-entry aperture comprises a further portion which is substantially perpendicular to the sides of the shear plate and which extends from the outer side of the shear plate to meet the sloping portion of said wall.

4. A shear plate substantially as herein described with reference to Figures 4 and 5 of the accompanying drawings.

5. A dry-shaving apparatus of the kind described having a shear plate as claimed in Claim 1,2,3 or 4.

6. A dry-shaving apparatus substantially as herein described with reference to the accompanying drawings.