GB2024082A - Safety razors - Google Patents

Abstract

A shaving unit which comprises at least one blade 6, 7, and a blade support of moulded polymeric material which provides skin-engaging cap and guard surfaces 3, 4, in which the portion of the blade support that provides the guard surface and/or the cap surface being formed wholly in part of a moulded mixture of at least one hydrophobic material and at least one water- leachable hydrophilic polymeric material such that, during shaving the water present on the area to be shaved leaches out the hydrophilic material which consequently serves as a lubricant in place of a conventional shaving soap or cream. <IMAGE>

Description

SPECIFICATION Safety razors This invention is concerned with safety razors of the kind comprising at least one blade and a blade support of moulded polymeric material which together form a unit which is discarded as a whole when the cutting edge of the or each blade becomes dulled. The support is designed to form skin-engaging guard and cap surfaces for engaging the skin respectively ahead and rearwardly of the blade edge or edges.

The support may be of the disposable cartridge type adapted for coupling to and uncoupling from a razor handle or may be integral with the handle so that the complete razor is discarded as a unit when the blade or blades become dulled.

We have found that if the portion of the support that provides the guard surface and/or the cap surface is formed wholly or in part of a moulded mixture of at least one hydrophobic polymeric material and at least one hydrophilic polymeric material, the hydrophilic material being such that it can be leached out of the mixture on contact with water, comfortable and effective shaving can be obtained by simply wetting the shaving area with water prior to shaving, that is without using conventional shaving soap or cream. The water present on the shaving area leaches out of a proportion of the hydrophilic material which serves as a lubricant in place of shaving soap or cream.

The present invention accordingly comprises a shaving unit comprising at least one blade and a blade support of moulded polymeric material which provides skin-engaging guard and cap surfaces, the portion of the blade support that provides the guard surface and/or the cap surface being formed wholly or in part of a moulded mixture of at least one hydrophilic polymeric material and at least one water-leachable hydrophilic polymeric material.

The blade support of the shaving unit may be formed wholly of the polymer mixture.

Alternatively, where the support is formed of separate guard and cap portions which are secured together, for example by rivetting, either or both of the guard and cap portions may be formed wholly of the polymer mixture. Further alternatively, a part of either or both of the guard and cap portions of the support may be formed of the polymer mixture. In the latter case, the polymer mixture suitably takes the form of a moulded insert in the guard or cap portion as the case may be, the remainder of the guard or cap portion being formed of a polymer as conventionally used in shaving units, such as polystyrene.

The nature and relative proportions of the hydrophilic and hydrophobic polymeric materials in the polymer mixture should be such that (i) the unit has adequate mechanical strength both as initially produced and when the hydrophilic material has been leached out (it will be understood that this requirement does not arise when the part of the shaving unit formed of the polymer mixture makes little or no contribution to the structural strength of the unit-as in the case of an insert of the polymer mixture), and (ii) there is sufficient hydrophilic material to provide lubrication for substantially the whole of the expected life of the blade or blades.

The mixture should, of course, be mouldable to form the blade support or part thereof and is preferably such that it can be injection moulded.

Suitable hydrophilic materials include, for example, polyethylene oxide, polyvinyl pyrrolidone, polyacrylamides, hydroxypropyl cellulose, polyvinyl imidazoline and polyhydroxyethylmethacrylate.

Suitable hydrophobic materials include, for example, polyethylene, polypropylene, polystyrene and polyacetal.

Suitable proportions of the materials are, for example, 85 to 5% by weight of the hydrophobic material and 1 5 to 95% by weight of the hydrophilic material, preferably from 50 to 60% by weight of the hydrophobic material and from 50 to 40% by weight of the hydrophilic material.

The shaving unit may be assembled from a number of parts in substantially the same way as the shaving units described and illustrated in Specification 1 362443. In this case, the base member (reference 30 in Figs. 4 and 4A of Specification 1362443) and/or the cap member (reference 38 in Figs. 4 and 4A of the said specification) is/are formed of the polymer mixture.

Alternatively, the blade support may be moulded as a single article from the polymer mixture and the or each blade is pushed into the support and retained in position mechanically. This enables the manufacturing and assembly costs of the unit to be kept very low.

The edge of the or each blade opposite the cutting edge thereof is preferably formed with spaced projections to assist penetration of the moulded blade support and may also have barbs to assist secure retention of the blade(s).

The moulded blade support may be formed with a slot to receive the or each blade, the latter having a hole or holes through it and the blade is secured in the slot by punching or "coining" the polymeric material locally to upset material into the hole or holes.

In other embodiments, the or each blade is pushed into a planar gap defined by two opposed rows of spaced projections integral with the moulded support, which bear against the inserted blade from above and below, each projection being positioned opposite a gap between adjacent projections in the opposite row. This arrangement permits accurate sizing of the gap and also has the advantage of weight saving compared with a simple slit being formed in the support.

In preferred embodiments of this last kind, tandem blades are provided, at least some of the projections acting to set the spacing between the blades and preferably to define soap slots between the blades for the passage of shaving debris away from the cutting edges.

Alternatively the cap and/or the guard portion of the blade support of a shaving unit formed of a conventional polymer, such as polystyrene, can be modified to provide a recess for the location of a moulded insert therein, the insert being formed of the polymer mixture. In this case the blade support can be moulded as a single article or in two or more parts which are secured together, for example for rivetting.

Some forms of razor in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figures 1 and 2 are scrap cross-sections of a first embodiment of razor; Figure 3 is a scrap perspective view of the tandem blades employed in the razor of Figs. 1 and 2; Figure 4 is an exploded perspective view of a second embodiment of razor; Figure 5 is a scrap view on arrow 'B' of Fig. 4; Figure 6 is a scrap perspective view showing a detail of the razor shown in Fig. 4; Figure 7 is an enlarged cross-section showing a modification to the razor of Fig. 4; and Figure 8 is a cross-section of a disposable cartidge type shaving unit adapted for coupling to and uncoupling from a razor handle.

In each of the embodiments illustrated in Figs. 1 to 7, the razor comprises a moulded support in the form of a head 1 integral with a handle 2 (see Fig. 4) and having skin engaging cap and guard portions 3, 4. The moulded support is formed of a mixture of hydrophilic and hydrophobic polymers as described above. Tandem blades 6 and 7 are set in the head 1, having their parallel cutting edges exposed between the cap and guard portions and arranged to act in tandem upon the skin of the user. It will be readily appreciated by those skilled in the art that the heads 1 could in each case alternatively be detachably mounted on the handle 2.

Figs. 1, 2 and 3 illustrate a razor in which the head is moulded with slots 1 3 to receive the blades 6, 7. Each blade has, say, four holes, two holes 14 being of larger diameter than the other two holes 1 6 in each blade, and the larger holes 14 of each blade are aligned with smaller holes 1 6 of the other when the blades are positioned in their slots.

The head is formed with two holes to receive lower coining punches 17, these holes being aligned with the larger holes 14 of the leading blade 6 and extending upwardly to the level of the slot which receives the trailing blade 7. Correspondingly, two holes for upper coining punches 18 extend downwardly through the .head to the level of the slot which receives the leading blade 6. Additionally, blind bores are aligned with the latter holes to receive punches 19.

In assembly, the blades are inserted in their slots with slight frictional restraint and the coining punches 1 7 and 18 are advanced to their illustrated positions. The punches 1 9 and a corresponding pair of punches 21 are then operated to deform the plastics material into the smaller holes 1 6 and thus secure the blades. The punches are then withdrawn and the finished assembly removed from the punch fixture.

In the razor shown in Figs. 4 to 6, the head 1 is moulded to have a comb-form spacer constituted by a series of forwardly projecting fingers 24 disposed between the cap portion 3 and an underlying blade platform porton 26. The lower surface of the cap portion 3 and the upper surface of the blade platform portion both consist of a series of spaced parallel projections 3A and 26A, the projections above and below the spacer fingers 24 being in line with each other and vertically opposite a gap between adjacent spacer fingers 24. There is thus defined a planar gap 27 between the spacer and the cap to receive the trailing blade 7, and another planar gap 28 between the spacer and the blade platform portion 26 to receive the leading blade 6. Each gap has a depth of, say, 0.1 mm to suit the thickness of the blades.

The formation of the two narrow gaps by offset staggered projection is more readily achieved in an injection moulding process than is the formation of gaps having continuous upper and lower walls, for which a very thin insert is required in the mould, and there is also a weight saving benefit which reduces the cost of material per unit.

By very careful dimensioning and control of manufacture, it may be possible to obtain adequate retention of the blades within their slots by friction alone, but we prefer to provide for positive retention of the blades. Thus, the blades are formed at their end edges with rectangular notches 30 and the head is formed with ramp projections 31 to provide snap-fitting engagement in the notches when the blades are pushed home. In a possible modification of this technique, illustrated in Fig. 7, the blades have resilient barbs 32 struck-up out of them, which bite into the plastics material of the head 1 to resist withdrawal of the inserted blades.

A further detailed modification is illustrated in the ringed portion of Fig. 4, which shows the gaps between the cap projections 3A carried through to the upper skin engaging surface of the cap 3.

The spaces between the various blade engaging projections may be connected to soap drainage holes (not shown) extending upwardly from the underside of the head 1, to permit ready clearance from the blade edge regions of soap and shaving debris.

The disposable cartridge type shaving unit shown in Fig. 8 is adapted for coupling to and uncoupling from a razor handle (not shown). The shaving unit, generally indicated at 33, comprises a moulded support made up of a guard portion 34 and a cap portion 35, both formed of a conventional polymeric material, such as polystyrene. Located between the guard portion 34 and the cap portion 35 are tandem blades 36 and 37 and a spacer 38 therebetween. The portions 34 and 35 are secured together, and the blades 36, 37 and spacer 38 are secured therebetween, by polymeric material rivets (not shown) in a generally conventional manner.

The cap portion 35 is provided with a recess 39 which extends longitudinally parallel to the cutting edges of the blades and which is terminated at each end by an end wall provided by the cap portion. Making a snap fit within the recess 39 is a moulded insert 40 of a polymer mixture as described above, the insert 40 being provided with a forwardly projecting lug 41 and a rearwardly projecting lug 42 which engage corresponding undercut channels 43 and 44 in the recess 39.

In order that the invention may be more fully understood, the following examples are given by way of illustration only: Examples 1-9 A series of razors having the construction shown in Figs. 1, 2 and 3 of the drawings were produced, the moulded head 1 being formed of the polymer mixtures described below and the handle 2 being moulded from polystyrene. The polymer mixture used were as follows (all percentages being by weight).

Hydrophobic material Hydrophilic material 1. 50% polystyrene 50% polyethylene oxide (coagulant) 2. 50% polystyrene 30% polyethylene oxide (coagulant) 20% polyethylene oxide (WSRN-750) 3. 50% polystyrene 49% polyethylene oxide (coagulant) 1 % polyvinyl imidazoline 4. 50% polyacetal 50% polyethylene oxide (coagulant) 5. 50% polyacetal 50% polyethylene oxide (WSR 301) 6. 50% polyacetal 30% polyethylene oxide (coagulant) 20% polyethylene oxide (WSRN-750) 7. 50% polyacetal 49% polyethylene oxide (coagulant) 1 % polyvinyl imidazoline 8. 50% HD polyethylene 30% polyethylene oxide (coagulant) 20% polyethylene oxide (WSRN-750) 9. 50% HD polyethylene 49% polyethylene oxide (coagulant) 1 % polyvinyl imidazoline Further details of the polymers used are as follows: : polystyrene - general purpose grade sold as Erinoid 1B001 KLP 35 by B.P.

Plastics polyacetal - homopolymer sold as Delrin 500 by Du Pont de Nemours (UK) HD polyethylene - high density polyethylene sold as Rigidex 500 BL 9742 by B.P. Plastics polyethylene grades Coagulant, WSRN-750 and oxides - WSR 341 obtained from Union Carbide Corporation polyvinyl made by Rohm 8 Hass Co. Ltd.

imidazoline - (Belgium Patent 637380) In using these razors, the face vFas wetted with warm water and the back of the razor, that is the rear part of the cap portion 3, was rubbed over the face to release a film of the hydrophilic material and shaving was then carried out normally. Entirely acceptable shaves in terms of closeness and drag were obtained with all the razors.

Claims (14)

1. A shaving unit which comprises at least one blade and a blade support of moulded polymeric material which provides skin-engaging guard and cap-surfaces, the portion of the blade support that provides the guard surface and/or the cap surface being formed wholly or in part of a moulded mixture of at least one hydrophobic polymeric material and at least one waterleachable hydrophilic polymeric material.

2. A shaving unit according to claim 1, in which the mixture of polymeric materials comprises 85 to 5% by weight of the hydrophobic material(s) and 1 5 to 95% by weight of the hydrophilic material(s).

3. A shaving unit according to claim 1 or 2, in which the mixture of polymeric materials comprises from 50 to 60% by weight of the hydrophobic material(s) and 50 to 40% by weight of hydrophilic material(s).

4. A shaving unit according to any of claims 1 to 3, in which the hydrophobic polymeric material is polystyrene, polyethylene, polypropylene or polyacetal.

5. A shaving unit according to any of claims 1 to 4, in which the hydrophilic polymeric material is polyethylene oxide, polyvinyl pyrrolidone, polyacrylamide, hydroxypropyl cellulose, polyvinyl imidazoline or polyhydroxyethyl methacrylate.

6. A shaving unit according to any of claim 1 to 5, in which the blade support is moulded as a single article from the polymer mixture and the or each blade is pushed into the support and retained in position mechanically.

7. A shaving unit according to claim 6, in which the edge of the or each blade opposite the cutting edge thereof, is formed with spaced projections to assist penetration of the blade support.

8. A shaving unit according to claim 6 or 7, in which the or each blade is provided with barbs which assist in securing retention of the blade in the blade support.

9. A shaving unit according to any of claims 1 to 5, in which the blade support is formed with a slot to receive the or each blade, the latter having a hole or holes through it, and the blade is secured in the slot by punching the polymeric material locally to upset material into the hole or holes.

10. A shaving unit according to any of claims 1 to 5, in which the or each blade is pushed into a planar gap defined by two opposed rows of spaced projections integral with the blade support, which projections bear against the inserted blade from above and below, each projection being positioned opposite a gap between adjacent projections in the opposite row.

11. A shaving unit according to claim 10, which comprises two tandem blades, at least some of the projections acting to set the spacing between the blades.

12. A shaving unit according to claim 11, in which said projections which set the blade spacing also define soap slots between the blades for the passage of shaving debris away from the cutting edges.

1 3. A shaving unit according to any of claims 1 to 5, in which the cap and/or the guard portion of the blade support is/are provided with a recess in which is located a moulded insert formed of the polymer mixture.

14. A shaving unit substantially as herein described with reference to Figs. 1 to 3, Figs. 4 to 6, Fig. 7 or Fig. 8 of the accompanying drawings.

1 5. A shaving unit substantially as herein described in any of the Examples.