WO2009153598A1

WO2009153598A1 - Shaving system and razor handle

Info

Publication number: WO2009153598A1
Application number: PCT/GB2009/050696
Authority: WO
Inventors: William Ashley King
Original assignee: The King Of Shaves Company Limited
Priority date: 2008-06-18
Filing date: 2009-06-18
Publication date: 2009-12-23
Also published as: GB2461054A; GB0811171D0

Abstract

A shaving system comprises a range of two or more razor handles (1, 1') and a replaceable blade unit (60) adapted to fit interchangeably on each of the handles. The blade unit is pivotably mounted (i.e. mounted for angular deflection, such as about a living hinge (4)) with respect to the handgrip (2) and biased to a rest position by a bias element (11, 11') on the handle, which provides a "harder" or "softer" shave according to the handle selected. The bias element may comprise a part of an elastomeric body (10, 10') moulded integrally with the handle, the colour and hardness of the elastomer being selected to determine the Spring Index (shave hardness) of each handle and to serve as a corresponding visible indication to the user. Preferably, the pivot axis (P) is arranged just in front of the blade unit so that the maximum shaving force applied in normal use corresponds to the restoring force exerted by the bias element. An apparatus (100) for measuring the Spring Index of the handle is disclosed.

Description

Shaving system and razor handle

This invention relates to shaving systems in which a re-usable razor handle is used together with a disposable shaving cartridge, and in particular to those in which the cartridge is pivotable (which is to say, mounted for angular deflection) with respect to the handgrip.

A disposable shaving cartridge, often referred to as a blade unit, typically comprises a plastics housing containing one, two, three, four or more blades arranged between a guard and a cap, which lie respectively in front of and behind the cutting edges of the blades when considered in the direction of shaving. The cutting edges, the guard and the cap lie substantially in alignment within the shaving plane, which is defined as that plane containing the guard, cap and/or other skin-engaging surfaces in use, with each cutting edge being exposed by a small positive or negative distance above or below the shaving plane.

Alternatively the cartridge may comprise a unitary element having a plurality of cutting edges made for example from a single piece of steel, ceramic or silicon material.

Typically, a shaving system also includes a dispenser for holding new cartridges and for receiving the used cartridges so as to retain them safely prior to disposal.

The pressure exerted against the user's skin by the shaving plane, which is to say, by the cutting edges and by the cap, guard and other skin-engaging surfaces contained in the shaving plane, is an important factor in determining the closeness of the shave, and varies from individual to individual. For example, a user with heavy beard growth may prefer to apply a heavier shaving pressure than one with light beard growth. If too much pressure is exerted, the shave may be overly aggressive so that the blades irritate or cut the user's skin. If too little pressure is exerted, the shave quality may be poor. It is therefore desirable to provide some means for limiting the maximum pressure of the blades against the skin while allowing the user to select the applied pressure so as to suit his/her personal preference. At the same time, the user should be able to exercise precise control over the position of the cartridge.

A pivoting connection between the cartridge and the handle helps the shaving plane to remain in correct relation to the skin as it passes over the changing contours of the user's body, and it is well known to design such mechanisms to provide a limited or variable shaving force.

For example, WO89/10245 discloses a razor having a pivot axis in combination with an elastic bearing that permits the razor head to tilt, rotate and slide relative to the handle. The elastic bearing may comprise one of a variety of colour coded elastomeric components which can be interchanged so as to vary the resilient or directional characteristics of the handle.

In practice, excessive freedom of movement of the razor head may make it difficult for the user to exercise sufficient control over the cutting edges, or to change the cartridge, while small interchangeable parts are inconvenient to use and easily lost. Many other adjustable spring pressure mechanisms have been proposed, but are typically complex, expensive to produce and fiddly to adjust, and tend to accumulate shaving debris in use.

Many razor handles now available in the market provide a pivoting mechanism in which the pivot axis is arranged on the opposite side of the cartridge from the shaving plane and in-between the guard and the cap, allowing the user to apply force to the cutting edges directly in line with the pivot axis. Typically, the cartridge is biased to a rest position by a light spring force which is not adjustable and which has little or no effect on the shaving force applied to the user's skin. Such pivot mechanisms do not effectively limit the force applied to the skin.

GB 2 408 010 A to the present applicant discloses a one-piece razor handle formed as a unitary, two-shot moulding. The handle is bifurcated to form a pair of arms, the cartridge being releasably mounted in fixed relation to the distal ends of the arms by squeezing the arms together and then releasing them so as to engage a hook structure on the end of each arm in a cooperating aperture in the cartridge. Each arm is provided with a living hinge surrounded by an elastomeric material, providing a hinge axis which lies in front of the cartridge and proximate its leading side, which is to say, just in front of the guard in the direction of shaving. Pressure applied to the cartridge during shaving causes the cartridge to pivot about the hinge axis with respect to the handgrip against the restoring force of the elastomer, so that the cartridge follows the contours of the user's skin. The position and structure of the hinge effectively limits the pressure applied to the cutting edges while providing the user with tactile feedback that enables precise control of the shaving operation.

It is the object of the present invention to provide a shaving system that allows the user to select the pressure applied to the skin during shaving, that is simple to use and manufacture, and that preferably also effectively limits the maximum pressure that can be applied to the skin in normal use.

The present invention accordingly provides a shaving system and a razor handle as defined in the claims.

The invention recognises that each individual will tend to shave in a characteristic, individual style in which the pivotal movement of the handle with respect to the shaving plane tends to lie within an angular range typical of that individual. Using this principle, the invention provides a disposable cartridge adapted for use with a range of two or more razor handles. Each handle has a different, predetermined Spring Index (hereafter abbreviated as SI) corresponding to the magnitude of the restoring force exerted by a bias element as the handle is pivoted relative to the cartridge, and is identifiable by the user by colour coding or some other visible indication whereby the user may identify the respective SI of each handle (which is to say, the shave "hardness" or "softness" of the handle) so as to select a handle to give a greater or lesser shaving force as required. The visible indication may be inherently comprehensible (comprising for example an icon suggestive of greater or lesser pressure), and/or may be accompanied by information enabling the user to correlate the SI or "hardness" of the handle with the visible indication.

In use, the "hardness" of the shave is controlled within the range defined by the Spring Index of each respective handle by adjusting the angle of the razor handle relative to the cartridge within the characteristic range of movement corresponding to the user's normal shaving style, so that the Spring Index of the handle selected effectively governs the range of shaving force applied.

The novel system may comprise an integrally moulded, unitary handle which is economical to manufacture and is easy to use and to clean, and which in preferred embodiments also effectively limits the maximum shaving force that can be applied during normal use to a value determined by the Spring Index. The invention thus enables the user to select his or her preferred shaving force, without the disadvantages of cost and complexity inherent in an adjustable mechanism.

Further features and advantages will be evident from the following description of an illustrative embodiment, which is provided purely by way of example and without limitation to the scope of the claims, and by reference to the accompanying drawings, in which:- Figs. IA, IB, 2 A and 2B show a first razor handle with a cartridge in respectively the installed position (Figs. IA and 2A) and in exploded view (Figs. IB and 2B);

Fig. 1C shows a variant handle having a shortened handgrip;

Figs. 3A, 3B, 4A and 4B show a second razor handle, identical in form to the first handle but having a softer elastomer component, with the same cartridge in respectively the installed position (Figs. 3A and 4A) and in exploded view (Figs. 3B and 4B);

Figs. 5 A - 5C show the mounting portion of the first razor handle respectively in the rest position (Fig. 5A) and in use (Figs. 5B and 5C);

Fig. 6A is an exploded view of the first razor handle showing the two components of the unitary moulding together with the cartridge;

Figs. 6B and 6C are enlarged views of the mounting portion of respectively the hard plastics base component (Fig. 6B) and the elastomeric component (Fig. 6C) shown in Fig. 6A;

Figs. 7 and 8 are enlarged views of the mounting portion of the first handle;

Fig. 9 is a graphic representation of the corresponding values of R and A shown in Table A; and

Fig. 10 shows an apparatus for measuring the Spring Index (SI) of a razor handle.

Corresponding elements are indicated by the same reference numerals in each of the figures. Referring to Figs. 1 - 8, a shaving system comprises a first razor handle 1, a second razor handle I¹, and a replaceable, disposable cartridge 60 adapted for selective releasable attachment to corresponding mounting structure on each of the handles.

The first and second handles 1, 1' are structurally identical, having the same size and shape and differing only in the hardness and colour of the respective elastomer component 10, 10' as described in more detail below. Each handle comprises a handgrip portion 2 and a bifurcated portion comprising a pair of arms 3, each with a hinge 4. The arms are arranged between the handgrip portion and a mounting portion 30, which is attached to both hinges so that it may pivot (together with the attached cartridge 60) relative to the handgrip portion 2 about a pivot axis P defined by the two hinges, as illustrated in Figs. 5B and 5C, in response to the rotation of the handgrip portion with respect to the cartridge as the shaving plane S is pressed against the user's skin.

The cartridge 60 is of a known type, comprising a plastics housing 61 containing a plurality of steel blades 62, each blade having a cutting edge 63. The cutting edges lie in a shaving plane S at the top side 64 of the housing and are arranged to exert a cutting action when the shaving plane is moved across a user's skin in a shaving direction S₁.

The top side 64 of the housing has an overall length L₁ extending in a length dimension L₂, and a width W₁ extending in a width dimension W₂, which extends in the shaving direction and transverse to the length dimension. The housing also defines a bottom side 65 opposite the top side 64, and a plurality of side walls 66, 67, 68, the side walls having a height H₁ extending in a height dimension H₂ between the top side and the bottom side. The width W₁ of the cartridge is typically, but not necessarily, smaller than its length L₁, while the height H₁ of the side walls is conveniently, but not necessarily, smaller than the width, so that the cartridge preferably has a compact, flattened shape as shown. This makes the cartridge convenient and economical to manufacture, store and merchandise as well as simplifying the design of the dispenser.

The shaving plane S also contains a plurality of skin engaging surfaces of the plastics housing, including a guard 69 arranged adjacent the leading side (leading side wall 66) of the cartridge, and a cap 70 arranged adjacent its trailing side

(trailing side wall 67), together with the skin-engaging surface 52 of the handle in the installed position of the cartridge as further described below. The guard and the cap encounter the user's skin respectively in advance of and behind the cutting edges of the blades when the cartridge is moved across the user's skin in the shaving direction S ] .

The bottom side 65 of the cartridge defines flat surfaces 71, 72, 73 arranged respectively adjacent its leading side wall 66, trailing side wall 67, and end side walls 68. A curved bar 76 extends in the width dimension W₂ across the centre of a wash-through aperture 74, which has a chamfer 75 at its trailing edge. Each end region of the bottom side of the cartridge also includes a pair of wings 77, the inner wing of each pair defining a recess 78 which opens into the wash-through aperture 74 and extends in the length dimension L₂ of the cartridge.

The respective mounting portion 30 of each of the first and second handles 1, 1' includes mounting structure for mounting the cartridge 60 on the respective handle, the mounting structure comprising a seat and a cartridge engaging structure, the seat comprising abutment surfaces 31, 32, 33. The mounting portion includes a trailing portion 47 which defines a recess 48 between the trailing portion 47 and the flat surface 72 of the cartridge in its installed position. The recess extends along a retraction axis Y and opens towards the trailing side 67 of the cartridge so as to receive a thin, planar retaining structure of a cooperating cartridge dispenser (not shown) when the cartridge is in its retained position in the dispenser. The handle may thus be attached to a new cartridge and then translated along the retraction axis to withdraw the cartridge from the dispenser, the retaining structure being slidingly received in the recess 48. The used cartridge is returned to the dispenser by reversing the procedure, the handle being detached from the cartridge to leave the cartridge retained in the dispenser by the retaining structure.

The cartridge engaging structure comprises a pair of resilient cartridge engaging elements 36, each extending generally in parallel with an engagement axis E, which extends generally in the height dimension H₂ of the cartridge and normal to the shaving plane S in the installed position of the cartridge. An abutment portion 37 extends outwardly from each cartridge engaging element 36 at an angle to the engagement axis. The cartridge engaging elements 36 are received in the wash- through aperture 74 when the mounting portion 30 is moved towards the cartridge along the engagement axis E so that when the user exerts a threshold engaging force against the cartridge, the cartridge engaging elements are deflected by contact of the abutment portions with the wings 77 until each abutment portion snaps into a respective recess 78 to retain the cartridge 60 in the installed position, in which the flat surfaces 71, 72, 73 of the cartridge abut in fixed relation, respectively against the abutment surfaces 31, 32, 33.

The mounting portion also includes guide surfaces 34, 35 which are angled obliquely with respect to the engagement axis E, the guide surfaces being adapted to engage corresponding surfaces arranged respectively on the wings 77 and the chamfer 75 on the bottom side of the cartridge so as to locate the cartridge as it moves towards the installed position. Two digit receiving surfaces 40 are arranged respectively adjacent the distal ends 3' of the arms 3, and comprise generally flat regions adapted to be pressingly engaged by two digits of the user so as to apply an engaging force to the mounting portion 30 so as to urge it into engagement with the cartridge along the engagement axis E.

A moveable cartridge ejection member 41 is also moulded integrally with the mounting portion, and comprises a bar 42 supported by two integral hinge portions 43 and having a digit receiving surface 44 on its upper side and a cartridge engaging surface 45 on its opposite, lower side. The digit receiving surface is adapted to be pressed down by the user's digit, bringing the cartridge engaging surface into abutment with the flat surface 71 of the cartridge so as to apply a threshold disengaging force to the cartridge, which urges the cartridge away from the mounting portion along the engagement axis E and disengages it from the handle. A wash-through aperture 46 is defined between the digit receiving surfaces 40, the bar 42 and the trailing portion 47 of the mounting portion, the aperture 46 communicating with the wash-through aperture 74 of the cartridge so that the blades can be rinsed during use.

Referring in particular to Figs. 6A - 6C, the handgrip portion 2, arms 3 and mounting portion 30 are integral parts of one unitary plastics moulding, which comprises a relatively hard plastics (e.g. polypropylene) base component 5 and a continuous body 10 (10') of elastomeric material, softer than the base component, which is moulded onto the base component 5, e.g. by two-shot moulding. The elastomeric material extends along the arms 3 to provide gripping surfaces 7 on the handgrip portion, and also extends around each digit receiving surface 40 to provide additional grip as well as (since the elastomeric material is preferably a different colour from the base component) indicating to the user the correct position to place the digit. Each hinge 4 comprises a living hinge 6, which is a thin portion of the base component 5, surrounded by a bias element 11 (H') comprising an elastic portion of the body 10 (10') of elastomeric material, the elastic portion providing a restoring force R that urges the mounting portion 30 resiliently towards a rest position as illustrated in Fig. 5A with respect to the handgrip portion. The larger part 11" of the elastic portion 11 is arranged below the living hinge 6 and bonded to the base component 5 during moulding so that it acts in tension to exert the restoring force R against the user's skin, while a smaller part 11'" arranged above the hinge acts simultaneously in compression.

The relatively modest rate of rise of R with respect to A observed in Table A and Fig. 9 in respect of the 20 - 70 Shore "A" range of elastomers (further discussed below) is due in particular to the fact that most of the elastomer works in tension (extension) rather than compression, and this advantageously provides a relatively modest increase in shaving force through a relatively wide range of angular movement of the cartridge, so that handles with different Spring Index values feel significantly different in use.

If the mounting portion is pivoted in the reverse direction N₂ (Fig. 5A), the larger part 11" of the bias element is then placed in compression. This results in a much more rapid rise in force as the mounting portion rotates backwards, making the handle (even with a relatively soft elastomer) very stiff in the reverse direction. This assists in ejecting the cartridge from the mounting portion, and makes it possible to accomplish this even without using the ejection member 41 by engaging the cartridge beneath the retaining structure of the dispenser and then lifting the handgrip portion firmly upwards away from the dispenser with a slight twisting motion so as to lever the mounting structure away from the cartridge. This makes the handle very convenient in use. Those skilled in the art will recognise that the volume of the elastomer within the hinge, the dimensions and geometry of the living hinge, the cross-sectional area of the hinges and many other parameters in addition to the Shore hardness of the elastomer may be varied in order to adjust the spring rate of the bias element and hence obtain the required Spring Index. It is found particularly convenient however to adjust the SI value only by varying the Shore hardness of the elastomeric component 10 (10'), which may be measured by means of a durometer, without otherwise varying the structure or dimensions of the different handles in the range, since this enables the required range of handles to be produced from a standard mould simply by changing the elastomeric raw material used, with the colour being chosen to provide the corresponding visible indication. Preferably, the living hinge 6 is as thin and flexible as possible, so that the spring rate of each hinge 4 is maximally dependent on the hardness of the elastomer.

Suitable elastomeric materials will be readily identified by those skilled in the art, and include for example thermoplastic elastomers such as Santoprene (RTM), manufactured by Advanced Elastomer Systems, LP of Akron, Ohio, USA, an affiliate of Exxon Mobil Chemical Company of Houston, Texas, USA; and Thermolast K (RTM), manufactured by Kraiburg TPE GmbH & Co. KG of Waldkraiburg, Germany.

Referring to Figs. 5A - 5C, the bias element 11 (H') has a spring rate genetically defined as (fd)/a wherein /=force, ^distance from the pivot axis P, and <z=angular deflection, measured as the angular deflection A of the shaving plane S relative to the handgrip portion. The distance d may be measured with respect to a nominal point mid- way between the guard and the cap of the cartridge as indicated by the arrows R in Figs. 5B and 5C. As the user presses the shaving plane S against his/her skin U, the cartridge and mounting portion pivot together about the pivot axis P with respect to the handgrip portion in the direction N₁ (Fig. 5A) against the restoring force R exerted by the bias element 11 (H'). The restoring force R (represented by the arrows R in Figs. 5B and 5C) acts perpendicularly to the shaving plane S as to urge the shaving plane (guard, cap, blades, and skin- engaging surface 52) against the user's skin U in the direction N₂ (Fig. 5A) with a total shaving force substantially equal to the restoring force R.

Line X₀ is a reference line which lies parallel with the shaving plane S in the rest position (Fig. 5A), and which is fixed in position with respect to the handgrip portion and arms 3, passing through the pivot axis P, in each of Figs. 5A - 5C. Lines X₁ and X₂ also pass through the pivot axis P and lie parallel with the shaving plane S in Figs. 5B and 5C respectively, so that the angular deflection A of the shaving plane S relative to the handgrip portion, measured in degrees, is indicated by the angle (X₁ between lines xo and X₁ in Fig. 5B and by the angle α₂ between lines X₀ and X₂ in Fig. 5C. The predetermined Spring Index of each handle 1, T is defined as R/A, wherein R is the restoring force exerted perpendicularly to the shaving plane against the user's skin U. The SI of the handle is thus determined when the handle is manufactured by the spring rate of the bias element 11, 11' and by the distance between the shaving plane S and the pivot axis P. In the example shown, (X₁ is 5° and α₂ is 25°, these values representing a typical but not limiting range of angular deflection of the cartridge in use which may be used as a convenient range of reference values when comparing one handle against another.

The body 10 of elastomeric material of the first handle 1 is harder than that 10' of the second handle 1', and is also a different colour, so that the spring rate of the bias element 11 of the first handle is greater than that of the second handle. The Spring Index of the first handle is also correspondingly higher than the Spring Index of the second handle, with the colour of the whole body 10 or lO' of elastomeric material (desirably extending as shown to form large, prominently visible areas of the handgrip and arms) serving as a visible indication to the user corresponding to the respective Spring Index. In the embodiment illustrated, the elastomeric material of the first handle preferably has a Shore "A" scale hardness of at least 30 and less than 85, producing a soft to very firm shave, with the elastomeric material of the second handle having a Shore "A" scale hardness of at least 20 and less than 70, producing a very soft to firm shave.

More preferably, the elastomeric material of the first handle has a Shore "A" scale hardness of at least 40 and less than 85, producing a moderate to very firm shave, with the elastomeric material of the second handle having a Shore "A" scale hardness of at least 20 and not more than 50, producing a very soft to firm shave.

For example, the elastomer 10 of the first handle 1 might have a Shore "A" scale hardness of 50 and be coloured red, indicating a relatively high SI and firm shave, while the elastomer 10' of the second handle 1' has a Shore "A" scale hardness of 30 and is coloured blue, indicating a relatively low SI and hence a soft shave.

Desirably, the system may comprise three, four or more handles, all structurally identical but having elastomers of various hardnesses and corresponding colours, e.g. white (Shore "A" scale 25 = very soft to soft shave), light blue (Shore "A" scale 40 = moderate shave), mid blue (Shore "A" scale 50 = firm shave), and dark blue (Shore "A" scale 65 = firm to very firm shave).

Of course, it is possible to vary the colour of the base component and/or to provide any other convenient visible indication corresponding to the SI. For example, the visible indication could be indicia on the handle comprising one marking for soft, two for moderate, three for firm, and so forth. Where the visible indication is a colour or marking of the handle, the system may comprise two or more handles differing in the spring rate of the bias element but otherwise identical in structure (i.e. identical in shape or form), which advantageously ensures that the shave characteristics are also identical, except for the shave hardness. This could be achieved for example by substituting a heavy leaf spring or helical spring for a light one.

Alternatively for example, the visible indication could comprise a dimension or dimensions of the handle. For example, the length of the handle could increase as the SI increases (as exemplified by the first handle 1 ' compared with the third handle 1" of Fig. 1C, which is identical to the first except that it has a softer elastomer giving a lower SI and a shorter handgrip portion 2"), and/or the distance between the pivot axis and the shaving plane could decrease as the SI increases; so that the system comprises two or more handles differing in at least one dimension of the handle (and, optionally, in the spring rate of the bias element) but otherwise identical in structure. Information is also provided where necessary to enable the user to identify the visible indication with the spring index or shave "hardness" of the handle. For example, the packaging of each handle might be marked with a scale comprising the words "soft", "moderate", "firm", etc. in their respective colours, so that the user can identify the shave hardness of the respective handle by reference to the scale.

Referring to Fig. 10, an apparatus 100 for measuring the Spring Index of a razor handle comprises a baseplate 101 supporting a vertical backplate 102 with a fixed reference bar 103. A support disc 104 with a pointer 105 is fixed to an axle which is rotatably received in a bore extending through the backplate. A wingnut (not shown) is received on the threaded distal end of the axle and arranged behind the backplate, so that the support disc is free to rotate with respect to the backplate and can be locked in position by tightening the wingnut. A scale disc 106 having an angular scale 107 marked in degrees is mounted on the axle coaxially with the support disc so that it is independently rotatable between the support disc and the backplate, the backplate being provided with a locking screw 108 which can be tightened so as to lock the scale disc in a selected rotational position. A mounting block 109 is fixed to the support disc 104, and the shaving plane (cap, guard and blades) of a cartridge 60 is glued to the downwardly facing surface of the mounting block as shown so that, when the razor handle 1 is attached to the cartridge, the pivot axis P of the handle is co-axial with the rotational axis of the support disc and the scale disc.

Before testing each handle, a hole 110 is drilled through the handgrip portion 2 of the handle at the opposite end from the arms 3, and a wire support 111 is passed through the hole.

The handle 1 (V) is attached to the fixed cartridge as shown, and the apparatus is then laid on its back so that the backplate 102 is horizontal, which effectively relieves the weight of the handle from the bias elements 11 (H') so that the handle adopts the rest position (indicated in Table A as "no load"). The support disc 104 is rotated until the handle is horizontal, just touching the bar 103 as shown, and locked by means of the wingnut. The scale disc is then rotated until its zero mark 113 is aligned with the pointer 105, and locked in position with respect to the backplate by means of the locking screw 108.

The apparatus is then returned to its upright position with the backplate 102 vertical, in which position the weight of the handle and the wire support 111 causes the end of the handle to sag downwards (by an amount depending on the hardness of the elastomer) away from the bar 103. The wingnut is slackened and the support disc is rotated by grasping the mounting block 109 to return the handle to its initial horizontal position, just in contact with the bar 103, and the wingnut is tightened again. The angular deflection A of the cartridge indicated by the pointer 105 in degrees from the zero mark 113 is then read off the scale 107.

The force applied to the handle at the hole 110 (indicated in Table A as "Grams force at end of handle") for this initial reading corresponds to the weight of the wire support 111 plus the effect of the weight of the arms 3 and handgrip portion 2 of the handle 1, which is conveniently calculated based on CAD data generated during the design of the handle and the centre of gravity of the handle. For the embodiment shown, this initial value is 7 grams force (7g_f), and the distance from the hole 110 to the pivot axis P is 1Ox the corresponding distance from the pivot axis P to the centre of the shaving plane (taken to be a point mid- way between the guard and the cap). The corresponding value of the restoring force R at the shaving plane is therefore calculated as 10x the value of the force applied at the hole 110, equating to 70g_f for the initial reading (indicated as "Handle plus wire") as shown in Table A.

The scale disc 106 remains in its locked position while weights 112 are incrementally added to the wire support 111, with the support disc being rotated to bring the handle back into contact with the bar 103 after each successive weight is added, the corresponding angular deflection A then being read off the scale 107 and the restoring force R calculated accordingly.

Those skilled in the art will recognise that many elastomeric materials will typically react slowly to applied force, so that deflection will increase over time under a steady load. This behaviour is of little significance in use since shaving is a dynamic process in which the applied force changes from moment to moment. However, it may become evident during testing if the handle is left under load for an extended period. For this reason, where elastomeric bias elements are employed, the angular deflection of the handle is read off the scale immediately after each weight is added and the support disc rotated, and prolonged loading of the hinges is avoided.

It will be understood that the apparatus 100 is illustrated purely to assist in understanding its component parts, and thus with the scale disc in an arbitrary position and with the handle in a nominal, undeflected position rather than bent at the hinges 4 as would occur during actual testing with the weights shown. Of course, the apparatus may be adapted mutatis mutandis to suit razor handles of other designs.

TABLE A

TABLE B

* SI = R/A (Grams force per degree) averaged for tabulated values of A lying between 5 and 25 degrees.

TABLE C

Referring to Table A, a series of seven handles having elastomeric components of different Shore "A" scale hardnesses from 20 to 95 but otherwise of identical structure to the first and second handles 1, 1' of the illustrated embodiment were tested using the apparatus 100, each weight 112 having a mass of 6.5g, and the results recorded as shown.

In practical shaving tests, the 20 Shore "A" hardness elastomer was found to result in a very soft shave, in which the blades were pressed against the skin in use by a total shaving force just sufficient to produce an acceptable shave. This was also the softest elastomer giving acceptable bonding to the polypropylene base component, which is important when using the elastomer in tension. The 85 and 95 Shore "A" hardness elastomers produced very stiff handles, the 95 Shore "A" elastomer handle being effectively almost rigid in normal use, with the 70 Shore "A" hardness elastomer producing the hardest shave consistent with a normally acceptable range of shaving force when the handle was deflected within a small angular range. The 30, 40 and 50 Shore "A" hardness elastomers produced handles with respectively soft, moderate and firm shaving performance. Those skilled in the art will recognise of course that these shave characteristics reflect the structure and geometry of the embodiment tested as well as the hardness of the elastomer used, and will understand that non-elastomeric bias elements may be used to produce similar values to those shown.

Referring to Table B, the value R/A was calculated in grams force per degree for each tabulated value shown in Table A falling within a range of angular deflection A of the handle from 5 to 25 degrees, with the Spring Index (SI) of each handle being calculated as shown as the average (arithmetic mean) of the calculated results.

It will be recognised of course that some users will prefer to deflect the razor handle in use by an amount typically greater than 25 degrees, and some embodiments may be arranged so that the handle is typically deflected by an amount greater than 25 degrees. In each case however, the shaving technique adopted by the individual is likely to be consistent across a range of structurally similar handles, irrespective of the SI of each handle, so that the range of SI values enables the individual to select the particular handle from any given range of handles that will deliver his or her preferred shave characteristics when used in his or her typical shaving style. The 5 to 25 degree range should therefore be regarded as a convenient range of reference values for comparison of one handle against another, and not as a limitation on the design of any particular embodiment.

Referring to Table C, the Spring Index ratio (the ratio of the SI of the first handle (SI₁) to that of the second handle (SI₂) as shown in Table B) was calculated as shown for each combination of handles from 30 to 70 Shore "A" scale hardness (Handle 1) and from 20 to 50 Shore "A" scale hardness (Handle 2). The resulting values (SI₁ / SI₂) were tabulated as shown to represent the difference in shave "hardness" experienced in practice between different handles in the range.

In shaving systems comprising a range of, say, three or more handles, it is desirable for the SI ratio between adjacent handles in the range to be relatively small, so that the user can select the precise value required. For example, where as many as five handles are provided, the "very soft" shave (20 Shore) and "soft" shave (30 Shore) handles provide a SI ratio of only 1.2, which provides the user with a fine but perceptible distinction in shave hardness. Corresponding values for the 30:40 Shore and 40:50 Shore SI ratios are respectively 1.3 and 1.4, still representing a relatively fine selection of shave hardness values.

For the slightly larger ratio represented by handles having respectively 50 (firm shave) and 70 (very firm shave) Shore "A" hardness bias elements, a SI ratio of 1.5 provides a slightly less fine degree of selection. Shaving systems comprising a range of, say, four handles or fewer, may also provide a rather greater ratio between adjacent handles in the range. For example, the SI ratio between handles of respectively 20 (very soft) and 40 (moderate) Shore "A" hardness is 1.6.

Higher SI ratios still of 1.9 and 2.1 are provided respectively between 30:50 Shore (soft shave : firm shave) and 40:70 (moderate shave : very firm shave) handles, providing a smaller range with a moderately coarse selection of SI values. The 1.9 SI ratio offering a choice of "soft" or "firm" shave might be suitable for example for use in a two-handle range for female users who tend to prefer a generally softer shave, while the 2.1 SI ratio offering a choice of "moderate" or "very firm" shave might be more suitable for a two-handle range aimed primarily at male users.

A still greater SI ratio may represent for example the difference between the first and third handles in a range of more than three handles. For example, a range of 20 Shore (very soft) : 50 Shore (firm) handles provides a SI ratio of 2.3, while a ratio of 30 Shore (soft shave) : 70 Shore (very firm shave) handles provides a SI ratio of 2.1. A SI ratio of 3.4 (between handles having respectively 20 and 70 Shore "A" hardness bias elements) might represent the overall difference between the shaving characteristics of the softest and hardest handles in the range. Of course, SI ratios in excess of 3.4 or below 1.2 may be preferred, depending on the application.

Referring again to Figs. 1 - 8, the pivot axis P is advantageously arranged as shown in parallel with the longitudinal axis of the cartridge, and the mounting portion is not free to pivot about any other, non-parallel axis. This ensures that the cutting edges of the blades remain generally orthogonal to the handgrip (i.e. orthogonal to a plane of symmetry of the handle bisecting the handle along its length) as the cartridge pivots, making it easier to control the position of the blades and to attach and remove the cartridge. Preferably, the pivot axis is arranged in front of the leading side 66 of the cartridge when considered in the shaving direction S₁. This ensures that any pressure applied by the user to the handle will cause rotation of the handle about the pivot axis P in the direction N₁ (Fig. 5A), which loads the bias element 11, 11' of the hinge. The total shaving force (the pressure of the shaving plane S (guard, cap, blades, and skin-engaging surface 52) against the skin) is thus effectively limited within the maximum range of angular movement of the cartridge (which in the embodiment shown is approaching 90 degrees) to the restoring force R, determined in turn by the Spring Index SI of the handle and the angular deflection A of the cartridge relative to the handgrip.

This protects the user's skin by making it very difficult to apply direct pressure to the skin in line with the pivot axis, so that the user can determine the maximum shaving force that he will apply using his normal shaving technique by selecting the handle having the required SI. If he prefers a hard shave then he can select a high SI, which however will still not permit him to apply excessive pressure as long as he shaves using his normal technique.

At the same time, the hinge geometry provides the user with tactile feedback, giving a "feel" for the interaction between the cartridge and the skin via the handle during shaving, and allows the user to exercise precise control over the shaving force within a fine range of adjustment (predetermined by the SI of the handle) by slightly varying the angle of the handgrip relative to the shaving plane within his normal range of movement (typically corresponding to a value of angular deflection A of around 5° - 25°).

Most preferably, the pivot axis is arranged proximate the leading side of the cartridge as shown, which is to say, just in front of it in the shaving direction S₁ or as close to the leading side as possible, as this enables the user to achieve the required shaving pressure with only very light pressure on the handle and maximises the controllability and tactile feedback during the shaving process.

Referring to Fig. 5A, in the illustrated embodiment, the pivot axis P is spaced apart from a line b - b orthogonal to the shaving plane S and lying along the leading side wall 66 of the cartridge by a distance d_\ of approximately one quarter of the width W₁ of the cartridge when measured along the reference line X₀- X₀ parallel with the shaving plane. This distance could be increased to up to the width W₁ of the cartridge with only a relatively small reduction in the controllability of the shave. A distance d_t of several times the width W₁ of the cartridge may make the shave significantly less easy to control, because the increased distance from the handgrip will make the movements of the cartridge less precise as well as requiring the user to apply greater pressure to the handle in order to achieve the required shaving force.

Even if the pivot axis is arranged behind the leading edge of the cartridge when considered in the shaving direction, e.g. between the guard and cap so that the shaving plane is interposed between the pivot axis and the user's skin, the user can still select the range of "hardness" or "softness" of the shave achieved by rotation of the handgrip relative to the cartridge, by selecting a handle having the required SI. However, while such configurations are contemplated as falling within the scope of the claims, they are less preferred insofar as they may allow the user to apply pressure in a direct line via the pivot axis to the shaving plane, so that the total shaving force substantially exceeds the restoring force R. The Spring Index of the handle may then have less influence on the total shaving force applied to the skin, and the pivot mechanism may not effectively limit the maximum total shaving force so that the user may be able to apply excessive pressure to the blades against the skin within the normal range of angular deflection of the handle. Referring again to Figs. 1 - 8, the mounting portion 30 also includes a skin engaging structure comprising a relatively rigid base portion 50 which forms part of the base component 5, and a flexible portion 51 forming part of the body 10 (10') of elastomeric material. The flexible portion defines a textured skin engaging surface 52, which in use lies substantially in alignment with the cutting edges of the blades and is consequently considered as forming part of the shaving plane S. The skin engaging surface lies adjacent the guard 69 and leading side wall 66 of the cartridge in its installed position, so that it stretches the skin and distributes any lubricating fluids in advance of the leading cutting edge, improving the quality of the shave. It also advantageously distributes the force applied to the user's skin under heavier shaving pressure (as shown for example in Fig. 5C) over a wider area than the cartridge, helping to prevent damage to the skin, and improves tactile feedback by helping the user to feel the position of the cartridge on their skin.

Of course, in alternative embodiments, the skin engaging structure may be omitted so that the shaving plane is then confined to the skin-engaging surfaces of the cartridge.

The rigid base portion 50 extends between the two hinges 4 so that it helps to rigidify the mounting portion, preventing differential movement between the hinges. This helps prevent torsional deformation of the mounting portion, ensuring that the two cartridge engaging elements 36 remain in the correct relation and hence ensuring the security of the resilient snap-in cartridge attachment. The base portion 50 also has a flat face 53 which abuts against the leading side wall 66 of the cartridge in the installed position. This helps to locate the cartridge and also shields its leading side wall, ensuring that the cartridge does not become dislodged by heavy transient forces which might result from contact with protuberant body surfaces during shaving. The unitary two-shot moulding incorporating multiple functional elastomeric elements is economical and easily cleaned, avoiding the accumulation of shaving debris which can impair hinges and other intricate assemblies of prior art razors.

It is preferable to form the elastomeric skin engaging surface 52 as part of the mounting portion of the re-usable handle rather than as part of the replaceable cartridge, since the cartridge does not then require the moulding of an elastomeric component and is therefore cheaper and more convenient to manufacture, as well as being more compact, which in turn simplifies the design of the dispenser and reduces the size and cost of the display packaging. The elastomeric material gives the skin-engaging surface advantageous frictional properties which help it to engage and stretch the skin. In yet further embodiments, a skin-engaging surface could alternatively or additionally be arranged on the mounting portion adjacent the trailing side of the cartridge, and need not be elastomeric, so that it may be used for example to provide a source of lubricant.

It is found that elastomers falling between 20 and 85 Shore "A" scale hardness have suitable frictional properties for use in forming the skin engaging surface, although if preferred, the skin-engaging surface could alternatively be formed in a separate moulding step from a different elastomer from that used for the hinges. However, since the coefficient of friction of the elastomer tends to reduce as hardness increases, it is found that by making the skin-engaging surface from the same material as the hinges, the increased frictional engagement of the skin provided by the softer elastomers can tend to compensate for the reduced shaving pressure resulting from the lower restoring force R provided by the softer hinges, so that the skin is still effectively stretched in front of the blades and shaving performance is maintained. Conversely, where a harder elastomer is selected to provide a higher SI (higher restoring force R and higher total shaving force), a lower coefficient of friction is advantageous since it prevents excessive drag resulting from the increased pressure of the skin engaging surface against the skin. In yet further embodiments, the handle may include a body portion made from wood, carbon fibre, injection moulded or die-cast metal, or other material. Conveniently, the mounting portion and hinges are moulded as described above integrally with a bifurcated portion and handgrip portion in a two-shot or equivalent moulding process, after which the bifurcated portion and handgrip portion of the finished moulding (comprising a polypropylene or equivalent base component plus an elastomeric component, which provides the gripping surfaces) are glued into a recess in the body portion, which includes an aperture through which the moulding extends so as to provide gripping surfaces on both the upper and lower faces of the handgrip.

Depending on the. nature and geometry of the cartridge and/or the mounting structure and/or the rigid or flexible structure linking the mounting structure to the handgrip portion, the pivotal movement of the cartridge with respect to the handgrip may include a translation component which moves the pivot axis from its rest position, and the terms "hinge", "pivotable" and "pivot axis" are intended to embrace such arrangements as well as those in which no translation component is present. It is possible for example to articulate the cartridge to the handle using two or more pivot axes, linked by a framework, or alternatively by means of a flexible structure which (like the illustrated embodiment) has no axle. In further alternative embodiments, the handle may provide a unitary stem rather than a forked structure, which stem may comprise a hinge or flexible portion. In each case the "pivot axis" is taken to be that nominal axis, whether static or moving in translation along a straight or curvilinear path, about which the shaving plane is angularly deflected with respect to the handgrip portion.

Preferably the bias element returns the cartridge to a defined rest position when it is not in use. In less preferred embodiments, it is possible for the cartridge to be loose or freely moveable when not in use, in which case the rest position is taken to be the position at which the bias element begins to exert a restoring force that resists further angular deflection of the cartridge resulting from engagement of the shaving plane with the user's skin.

In alternative embodiments the cartridge can be pivotably mounted on the mounting structure and biased to a rest position by contact with an elastomeric bias element mounted on the handle. Instead of an elastomeric bias element, a spring biased cam (having for example a helical steel or plastics spring, a metal or plastics leaf spring, or any alternative bias element as well known in the general field of mechanical engineering), or a resilient cantilever arm, or cooperating magnetic elements, or compressible gas-filled structure, or any other convenient resiliently biased structure as known in the art may be arranged to exert (directly or indirectly) a restoring force against the mounting portion holding the cartridge or against the cartridge mounted on the handle. The pivot axis may then comprise an axle defined by part of the mounting structure which is engaged with the cartridge, and the mounting structure may be either fixed or moveable with respect to the handgrip portion. In each case, as in the illustrated embodiment, the bias element is permanently associated with the handle, which is to say that it is not adapted to be interchangeable or to be removed from the handle in normal use, which makes the handle simple and convenient to use and manufacture and dispenses with the need for complicated adjustment or extraneous components that may be mislaid.

In the embodiment shown, the shaving system comprises at least two handles, the two handles having identical structure and varying only in the hardness and colour of the respective elastomer. Of course, the system might include three or more handles, all having respectively different predetermined Spring Indices.

In less preferred embodiments, the first and second handles may have different structure. In particular, whereas in the illustrated embodiment the Spring Index of the respective handles is differentiated by varying the spring rate of the bias elements, it is also possible to differentiate the Spring Index between handles by providing a bias element or elements having a similar or identical spring rate, and varying the distance from the centre of the shaving plane to the pivot axis, so that for a bias element having a given spring rate, the Spring Index reduces as the distance from the centre of the shaving plane to the pivot axis increases.

For example, in the embodiment illustrated, the elastomeric material of each handle might have the same hardness, with the reduced Spring Index of the softer handle being achieved by positioning the hinges further away from the mounting portion and closer to the handgrip portion.

The restoring force R is taken to be the force exerted by the bias element or elements against the user's skin perpendicularly to the shaving plane. Where the pivot axis is arranged in advance of the leading edge 66 of the cartridge when considered in the shaving direction S₁, it is difficult for the user to apply a significant amount of direct pressure via the pivot axis against the shaving plane within the normal range of angular deflection A, so that the restoring force is preferably substantially equal to the total shaving force, which is the total force exerted against the user's skin perpendicularly to the shaving plane.

In alternative embodiments, the pivot axis may be arranged behind the leading edge of the cartridge when considered in the shaving direction. Configurations of this type still allow the user to select a "soft" or "hard" handle that will supply a greater or lesser range of restoring force according to his/her shaving preferences, but may be arranged so that the user can also apply direct force via the pivot axis against the shaving plane, which is disadvantageous insofar as the razor handle does not effectively limit the maximum total shaving force that can be applied to the skin in use. In such configurations the restoring force may therefore supply only a proportion of the total shaving force, depending on the pressure exerted by the user directly against the shaving plane.

In the embodiment illustrated, the restoring force R increases approximately linearly with increasing angular deflection A of the shaving plane, as shown in the graph of Fig. 9, with the elastomers in the preferred range of 20 to 70 Shore "A" hardness exhibiting a slight S shaped characteristic within the measured range. Relatively little variation in the value of R/A is observed for these preferred elastomers within the range between 5° and 25° of deflection. The 85 Shore "A" hardness elastomer exhibited the most variation across the measured range of deflection. In alternative embodiments, the spring index can be arranged to increase (or even decrease) progressively as the cartridge rotates, e.g. by arranging the bias means as a spring biased cam or resilient cantilever arm extending from the handle and engaging a cam follower surface on the cartridge, the surface being contoured to provide the required non-linear function. The range of pivotal movement may be limited by an end stop. In each case, the predetermined or predefined spring index of each handle is taken to be the measured value of R/A averaged over the range from 5° to 25° of deflection from the normal rest position of the cartridge.

If preferred, the visible indication could be provided on the packaging of the handle instead of on the handle itself, so that the user may select the handle having the required "hardness" of shave at the point of sale. In either case, a user may opt to purchase just one handle from the system so as to obtain his/her preferred "hardness" of shave when shaving in his/her typical shaving style, or more than one handle so as to have a choice of shave "hardness" or "softness" by selecting the appropriate "hard" or "soft" handle for each shave, depending for example on the amount of hair growth since his/her last shave. In summary, a preferred shaving system comprises a range of two or more razor handles and a replaceable blade unit adapted to fit interchangeably on each of the handles. The blade unit is pivotably mounted (i.e. mounted for angular deflection, such as about a living hinge) with respect to the handgrip and biased to a rest position by a bias element on the handle, which provides a "harder" or "softer" shave according to the handle selected. The bias element may comprise a part of an elastomeric body moulded integrally with the handle, the colour and hardness of the elastomer being selected to determine the Spring Index (shave hardness) of each handle and to serve as a corresponding visible indication to the user. Preferably, the pivot axis is arranged just in front of the blade unit so that the maximum shaving force applied in normal use corresponds to the restoring force exerted by the bias element.

Numerous other adaptations will be evident to those skilled in the art on perusing the foregoing description, the scope of the invention being limited solely by the claims.

Claims

1. A shaving system comprising at least a first razor handle, a second razor handle, and a disposable shaving cartridge;

the cartridge comprising at least one cutting edge,

the cutting edge lying in a shaving plane so as to exert a cutting action when the shaving plane is moved across a user's skin in a shaving direction;

each handle comprising a handgrip portion, mounting structure for mounting the cartridge on the handle, and at least one bias element,

the bias element being permanently associated with the handle;

the cartridge being adapted for selective releasable attachment to the respective mounting structure of each of the first and second handles

such that after attachment, the cartridge is pivotable about a pivot axis relative to the respective handgrip against a restoring force exerted by the respective at least one bias element,

the restoring force urging the shaving plane against the user's skin in use;

each handle having a predetermined spring index defined as R/A, wherein R is the restoring force exerted perpendicularly to the shaving plane against the user's skin, and A is the angular deflection of the shaving plane relative to the handgrip;

the spring index of the first handle (R/A)] being different from the spring index of the second handle (R/ A)₂, each handle being provided with a respective visible indication corresponding to its respective spring index.

2. A shaving system according to claim 1, characterised in that (RZA)₁ > 1.2 (R/A)₂.

3. A shaving system according to claim 1, characterised in that (R/ A)₁ > 1.5

(R/A)₂.

4. A shaving system according to claim 1, characterised in that (R/ A)₁ > 1.9 (R/A)₂.

5. A shaving system according to claim 1, characterised in that (RZA)₁ > 2.3 (R/A)₂.

6. A shaving system according to claim 1, characterised in that (RZA)₁ > 2.7 (RZA)₂.

7. A shaving system according to claim 1, characterised in that the at least one bias element of each handle has a predetermined spring rate,

the spring rate of the bias element of the first handle being different from the spring rate of the bias element of the second handle.

8. A shaving system according to claim 1, characterised in that each handle includes a body of elastomeric material,

and the elastomeric material forms the at least one bias element of each respective handle,

the elastomeric material of the first handle being harder than the elastomeric material of the second handle.

9. A shaving system according to claim 8, characterised in that the elastomeric material of the first handle has a Shore A scale hardness of at least 30 and less than 85, and the elastomeric material of the second handle has a Shore A scale hardness of at least 20 and less than 70.

10. A shaving system according to claim 8, characterised in that the elastomeric material of the first handle has a Shore A scale hardness of at least 40 and less than 85, and the elastomeric material of the second handle has a Shore A scale hardness of at least 20 and not more than 50.

11. A shaving system according to claim 1, characterised in that the first and second handles differ in at least one dimension of the respective handle but are otherwise identical in structure.

12. A shaving system according to claim 7, characterised in that the first and second handles differ in the spring rate of the respective bias element but are otherwise identical in structure.

13. A shaving system according to claim 7, characterised in that the first and second handles differ in the spring rate of the respective bias element and in at least one dimension of the respective handle but are otherwise identical in structure.

14. A first razor handle for use in a shaving system,

the shaving system comprising at least the first razor handle, a second razor handle, and a disposable shaving cartridge;

the cartridge comprising at least one cutting edge,

the bias element being permanently associated with the handle;

the cartridge being adapted for selective releasable attachment to the respective mounting structure of each of the first and second handles such that after attachment, the cartridge is pivotable about a pivot axis relative to the respective handgrip against a restoring force exerted by the respective at least one bias element,

the restoring force urging the shaving plane against the user's skin in use;

the spring index of the first handle (RZA)₁ being different from the spring index of the second handle (RfA)₂,

each handle being provided with a respective visible indication corresponding to its respective spring index.

15. A razor handle according to claim 14, characterised in that the pivot axis is arranged such that the cutting edge remains generally orthogonal to the handgrip as the cartridge pivots.

16. A razor handle according to claim 14, characterised in that the pivot axis is arranged in front of the cartridge when considered in the shaving direction.

17. A razor handle according to claim 14, characterised in that the pivot axis is arranged in front of the cartridge and proximate a leading side of the cartridge when considered in the shaving direction.

18. A razor handle according to claim 14, characterised in that the mounting structure is pivotable about the pivot axis relative to the handgrip portion,

and the mounting structure is adapted to releasably retain the cartridge in fixed relation to the mounting structure.

19. A razor handle according to claim 14, characterised in that the handle is bifurcated to define two arms arranged between the handgrip portion and the mounting structure,

and the pivot axis is defined by two hinges, each hinge being arranged on a respective one of the arms.

20. A razor handle according to claim 14, characterised in that the handle includes a body of elastomeric material,

and the elastomeric material forms the at least one bias element.

21. A razor handle according to claim 20, characterised in that the body of elastomeric material is moulded integrally with the handle.

22. A razor handle according to claim 20, characterised in that the elastomeric material extends to provide a gripping surface of the handgrip portion.

23. A razor handle according to claim 20, characterised in that the handle includes a skin engaging surface,

the skin engaging surface comprising a surface of the body of elastomeric material.

24. A razor handle according to claim 20, characterised in that the elastomeric material acts in tension to exert the restoring force.

25. A razor handle according to claim 20, characterised in that the visible indication comprises a colour of the elastomeric material.