GB2063752A

GB2063752A - Dry-shaving apparatus

Info

Publication number: GB2063752A
Application number: GB8037428A
Authority: GB
Original assignee: Philips Gloeilampenfabrieken NV
Current assignee: Koninklijke Philips NV
Priority date: 1979-11-26
Filing date: 1980-11-21
Publication date: 1981-06-10
Also published as: FR2469987A1; FR2469987B1; DE2947587C2; JPS5685384A; GB2063752B; DE2947587A1

Abstract

The movable cutting unit of a dry-shaver comprises a plurality of cutters (24) and a corresponding plurality of hair-pulling blades (26) each arranged in front of one of the cutters for movement therewith relative to the shear plate (3) of the shaver, and each slidable on the cutter so as to be movable relative thereto for its hair-pulling action. In order to increase the distance through which the hairs are pulled up from the skin, the leading edge 39 of each hair-pulling blade which contacts the hairs is formed on a projection (35) on the front of the blade and the blade has a surface (55) at the front which, when the leading edge of the blade penetrates a hair, abuts the hair to limit the penetration of the depth of the projection. In order to reduce the mass of the blade, the abutment surface (55) and the projection (35) are formed on a locally thickened portion (54) of the blade. <IMAGE>

Description

SPECIFICATION Dry-shaving apparatus The invention relates to a dry-shaving apparatus of the kind (hereinafter referred to as "the kind described") having a shear plate 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 each having a surface which is in sliding contact with the shear plate and which is bounded at one side by a cutting edge, and a corresponding plurality of hairpulling blades each disposed in front of an associated one of the cutters with respect to the direction of the cutting movement thereof, the hair-pulling blades being arranged for movement with the cutters relative to the shear plate when the apparatus is in operation, and each hair-pulling blade being arranged in sliding contact with a surface of the associated cutter for movement relative to the cutter in directions away from and towards the shear plate, and each hair-pulling blade having a leading edge which, as the blade moves over a hair-entry aperture of the shear plate in front of the associated cutter when the apparatus is in operation, penetrates hairs protruding through that aperture and, by movement of the hair-pulling blade away from the shear plate as a result of the reaction force from said hairs, pulls these hairs further through the aperture.

Such a shaving apparatus is known from the Applicants' prior United Kingdom Patent Specification No. 1,467,557.

It has been found that the depth of penetration of the leading edge of a hair-pulling blade into a hair is not uniform and depends, for example on the hardness of the hair. This hardness differs from person to person. The depth of penetration of the hair-pulling blade into the hair in turn determines how far the hair is pulled up by the hair-pulling blade before being severed by the associated cutter.

As the hair-pulling blade penetrates deeper, the path length available for lifting the hair decreases, because the distance through which the hair-pulling blade moves relative to the cutter depends on the depth of penetration of the hair-puiling blade into the hair. A further parameter for the lifting height of the hair by the hair-pulling blade is the angle between the surface of the cutter on which the hair-pulling blade slides and the surface of the cutter which is in sliding contact with the shear plate. This angle may be, for example, 50".

In the specification of the Applicants' earlier application no. 7941736, published under serial no. 2036629A, there is described and claimed a dry-shaving apparatus of the kind described, in which the leading edge of each hair-pulling blade is formed on a projection on the front of the blade, and in which each hair pulling blade has a surface at the front which, when the leading edge of the blade penetrates a hair, abuts the hair to limit the penetration to the depth of the projection. By thus limiting the depth of penetration of the hair-pulling blade into the hair, the displacement of the blade on the cutter can be effectively in creased, because for the penetration depth and the displacement only a specific maxi mum overall distance is available for the given dimensions of the cutters and hair-pulling blades.

In the construction described in the afore said specification no. 2036629A, the abut ment surface on each hair-pulling blade is formed by the front surface of the blade, and to bring this surface forward to a position which will produce the desired limitation on the depth of penetration of the blade into the hair, the blade has simply been made thicker.

This has a drawback, however, in that it increases the mass of the blade, and for a satisfactory operation of the blade it is impor tant that its mass is minimised.

It is an object of the invention to mitigate this drawback.

According to the present invention there is provided a dry-shaving apparatus of the kind described and in which the leading edge of each hair-pulling blade is formed on a projec tion on the front of the blade, and in which each hair-pulling blade has a surface at the front which, when the leading edge of the blade penetrates a hair, abuts the hair to limit the penetration to the depth of the projection, wherein the projection and said abutment surface of each hair-pulling blade are formed on a locally thickened portion of the blade.

As in the construction described in the earlier specification no. 2036629A, in the construction according to the present inven tion also the depth of penetration of each hair pulling blade into a hair is limited in a particu larly effective manner if the orientation of the abutment surface of each hair-pulling blade relative to that surface of the associated cutter which is in sliding contact with the shear plate approximates as closely as possible to the average angle of entry of the hairs into the hair-entry apertures in the shear plate.

In one embodiment of the invention the abutment surface of each hair-pulling blade has a dimension measured from the base of the projection on the blade in a direction perpendicular to the leading edge of the blade which is equal to at least twice the dimension of the base of the projection measured in the same direction.

An embodiment of the invention will now be described in more detail with reference to the accompanying drawings, in which Figure 1 is a front elevation of a dry shaving appartus of the kind described having three shear plates and associated cutting units, Figure 2 is a side elevation of the shaving apparatus of Fig. 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 ll-ll in Fig. 1, Figure 3 is an exploded perspective view drawn to an enlarged scale, of a cutting unit for the apparatus shown in Figs. 1 and 2, Figure 4 is a plan view of the cutting unit of Fig. 3 in the assembled condition, Figure 5 is a sectional view taken on the line V-V in Fig. 4 but showing only three of the cutters and associated hair-pulling blades, and Figure 6 is a diagrammatic side view, drawn to a greatly enlarged scale, of portions of a cutter and associated hair-pulling blade constructed in accordance with the invention, and a portion of the associated shear plate, illustrating the operation of the hair-pulling blade.

The shaving apparatus of Figs. 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 have hair-entry apertures in the form of slots 4.

A rotary cutting unit 5 (Fig. 2) is disposed on the inner side of each shear plate 3 for cooperation therewith. The cutting units 5, of which one is shown schematically in Fig. 2, comprises a plurality of cutters and a corresponding plurality of hair-pulling blades, as will be described later herein with reference to Figs. 3 to 5.

The cutting units 5 are rotated relative to the shear plates by an electric motor 10 to which each cutting unit is coupled by an associated hollow spindle 6 (Fig. 2) and gear wheel 7 and a gear wheel 8 fixed on the shaft 9 of the motor 10. The gear wheels 7 are each rotatably journalled on an associated spindle 11 which is fixed in a mounting plate 1 2. Each gear wheel 7 is formed with a recess 13, which is closed by a cover plate 14. This recess accommodates a flange 1 5 formed at the end of the respective hollow spindle 6. The flange has a non-circular, for example, square, shape and the recess 1 3 is shaped accordingly so that a coupling is obtained for transmitting the rotary movement of the gear wheel 7 to the spindle 6.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 recess 1 3 in the gear wheel 7, exerts a force on the spindle 6 in the direction of the cutting unit 5. A conical portion 1 7 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 1 8 around the periphery of the shear plate is urged against the shear plate holder 2.During use of the shaving apparatus, the shear plates 3, together with the associated cutting units 5 and spindles 6, can be pressed inwards against the action of the spring 1 6 under the pressure with which the shear plates are held against the user's skin.

A coupling for transmitting 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 rectangular cross-section engaging in a central coupling aperture 20 of corresponding shape in the cutting unit 5.

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

Each cutting unit 5 (Figs. 3 to 5) comprises a cutting member 21 formed with cutters 24, and a hair-pulling member 22 formed with hair-pulling blades 26.

The cutting member 21 is constituted by a disc-shaped central body 23, around the circumference of which the cutters 24 are evenly distributed and in which the coupling aperture 20 is formed.

The hair-pulling member 22 is made from resilient sheet material and comprises an annular central portion 25, around the periphery of which the hair-pulling blades 26 are evenly distributed. These blades, which are equal in number and spacing to the cutters 24, are connected to the central portion 25 by bent resilient connecting arms 27. The central portion 25 has a central opening 28.

As shown in Figs. 5 and 6, each cutter 24 has at its front (with respect to the directive of movement X of the cutter) a sloping surface 29 which forms an acute angle with a surface 37 of the cutter which is in sliding contact with the inner side of the respective shear plate 3. The edge 30 at which the surfaces 29 and 37 meet is the cutting edge of the cutter. In the operation of the shaving apparatus the sliding surface 37 of each cutter 24 travels over the hair-entry slots 4 in the respective shear plate and the cutting edge 30 of the cutter, in cooperation with the shear plate at the boundaries of the slots, severs the hairs which protrude through the slots.

The cutting member 21 and the hair-pulling member 22 are assembled to form a cutting unit 5 by securing the central portion 25 of the hair-pulling member to the central body 23 of the cutting member, for example, by adhesive, by spot-welding or by screws, in relative positions such that each hair-pulling blade 26 is in sliding contact with the front surface 38 of an associated one of the cutters 24. Owing to the resilience of the connecting arms 27, the hair-pulling blades 26 are movable relative to the cutters 24 in directions away from and towards the respective shear plate 3, the resilience of the arms urging the blades towards the shear plate.The resilient sheet material from which the hair-pulling member 22 is made has a thinness such that the bends 51 in the connecting arms 27 will allow the hair-pulling blades 26 to recede elastically, sliding up the front surfaces of the cutters 24. The hair-pulling blades travel round with the cutters relative to the shear plate in the operation of the apparatus. The hair-pulling blades have an elongate shape, and as its free end 32 each blade has a surface 38 which is in sliding contact with the inner side of the shear plate ir' front of the sliding surface 37 of the associated cutter 24.

Each hair-pulling blade 25 is formed on its front side at the free end of the blade with a sharp leading edge 39 (Fig. 6) which forms a boundary of the sliding surface 38 of the blade. This edge is formed on a projection 35 on the hair-pulling blade, which projection extends across the front side of the blade at the free end thereof.

The hair-pulling blades operate in known manner to pull hairs which are caught in the hair-entry apertures 4 slightly out of the hair follicles just before the hairs are severed by the cutters 24. As can be seen in Fig. 6, when the leading edge 39 of a hair-pulling blade 26 contacts a hair 34 caught in a hairentry aperture, the edge 39 of the blade penetrates the hair, and as a result of the reaction force from the hair and the counteracting force from the associated cutter 24, the hair-pulling blade slides up the front surface 29 of the cutter away from the shear plate 3.

The point on the hair 34 at which the edge 39 of the hair-pulling blade penetrates the hair is designated A in Fig. 6, and the direction of movement of the hair-pulling blade away from the shear plate is designated y.

The hair-pulling blade pulls the hair 34 up with it until the cutting edge 30 of the cutter 24 reaches the hair at point B thereon and severs the hair at this point.

When examining these movements it is found that specific distances and movements are coordinated within specific displacement parameters. The hair 34 is severed inside the hair-entry aperture 4 when the cutting edge 30 of the cutter 24 contacts the hair which bears at its front side 31 against the front wall 36 of the aperture 4.Since the cutter 24 is preceded by the hair-pulling blade 26 which holds the hair, the path length remaining for pulling-up the hair in the y-direction follows from the equation: yr = (d,, - x,,)tan ss In this equation: y, is the length over which the hair is pulled up by the hair-pulling blade between points A and B, dr, is the dimension of the sliding surfacw 38 of the hair-pulling blade 26 from front to rear thereof, xrs is the depth of penetration of the hairpulling blade 26 into the hair 34, and ss is the angle between the sliding surface 37 of the cutter 24 and the front surface 29 of the cutter.

It follows from the equation that the pull-up length y, is a maximum if the penetration depth of the hair-pulling blade 26 into the hair 34 is zero. Obviously, this situation cannot be achieved, because in that case the hairpulling blade would have no effect at all on the hair. Therefore, steps mast be taken to limit the penetration depth of the hair-pulling blade 26 to a extent necessary for an optimum hair-pulling function. Furthermore, it follows from the equation that the thickness of the hair-pulling blade 26 as well as the angle ss should be as large as possible.

A further parameter which influences the hair-pulling process is the friction of the hair 34 on the front wall 36 of the hair-entry aperture 4. This coefficient yhl is suitably < 0.5.

Fig. 6 represents an embodiment which conforms to the above equation. In this embodiment, when the hair-pulling blade 26 contacts the hair 34, only the projection 35 on the blade can penetrate the hair, because a surface 55 at the front of the hair-pulling blade 26 adjoining the base of the projection 35 comes up against the hair and the blade consequently cannot penetrate further into the hair. Thus, the depth of penetration of the hair-pulling blade into the hair is limited to the depth of the projection 35, i.e., the distance from the base of the projection to edge 39 at the tip of the projection.

The orientation of the surface 55 relative to the sliding surface 37 of the cutter 24 approximates as closely as possible to the average angle of entry of the hairs into the hair-entry apertures in the shear plate. It may be assumed that this angle does not differ substantially from the normal to the shear plate.

The angle has a value between 55 and 75 . If the angle is too large the friction between the front surface 29 of the cutter 24 and the part of the hair-pulling blade 26 at the rear side 53 thereof which slides on the surface 29 may become too high.

The dimension d,x of the hair-pulling blade is made as large as possible. but is limited for reasons of elasticity and mass.

The sheet material from which the hairpulling member 22 is made should have a resilience such that the hair-pulling blades 26 can readily resile down the front surface 29 of the cutters 24. This means that in order to obtain a low mass and a high elasticity the material should be as thin as possible. A preferred thickness a is in the range 50 to 100 ym. In order to meet the requirements of a dimension drx which is as large as possible and a well-defined projection 35, the hairpulling blade 26 is thickened at the location of the projection 35. The thickened portion designated 54, is such that the values d, and x,, are within the desired orders of magnitude.

The surface 55 at the front of the hair-pulling blade which abuts the hair 34 is located on the thickened portion 54 of the blade and extends at an angle a relative to the front surface 29 of the associated cutter, substantially in a direction perpendicular to the shear plate 3. The sum of the angles ss and a is 90 . The dimension of the abutment surface 55 of the hair-pulling blade measured from the base of the projection 35 in a direction perpendicular to the leading edge 39 of the blade, i.e., the vertical direction in Fig. 6, is selected in accordance with the engagement requirements and is preferably equal to at least twice the dimension of the base of the projection 35 measured in the same direction.

From the upper end 57 of the surface 55 the front of the hair-pulling blade recedes along a surface 59 until the main thickness a of the hair-pulling blade 26 is reached. The shape of the surface 59 may be adapted to suit production requirements.

By forming the projection 35 and the abutment surface 55 on a thickened portion of the hair-pulling blade 26, the blade can be made from a sheet material which has the desired resilience and gives the blade a minimal mass, whilst the blade is still capable of pulling-up the hair 34 over a length y, from point A to point B, before the cutting edge 30 of the cutter 24 reaches the hair 34 and severs it.

Claims

1. A dry-shaving apparatus of the kind described and in which the leading edge of each hair-pulling blade is formed on a projection on the front of the blade, and in which each hair-pulling blade has a surface at the front which, when the leading edge of the blade penetrates a hair, abuts the hair to limit the penetration to the depth of the projection, wherein the projection and said abutment surface of each hair-pulling blade are formed on a locally thickened portion of the blade.

2. A dry-shaving apparatus as claimed in Claim 1, wherein the orientation of said abutment surface of each hair-pulling blade relative to that surface of the associated cutter which is in sliding contact with the shear plate approximates as closely as possible to the average angle of entry of the hairs into the hair-entry apertures in the shear plate.

3. A dry-shaving apparatus as claimed in Claim 1 or 2, wherein said abutment surface of each hair-pulling blade has a dimension measured from the base of the projection on the blade in a direction perpendicular to the lead edge of the blade which is equal to at least twice the dimension of the base of said projection measured in the same direction.

4. A dry-shaving apparatus substantially as herein described with reference to Figs. 1 to 6 of the accompanying drawings.