US3526959A

US3526959A - Dry shavers

Info

Publication number: US3526959A
Application number: US681277A
Authority: US
Inventors: George Young
Original assignee: Wilkinson Sword Ltd
Current assignee: Wilkinson Sword Ltd
Priority date: 1967-11-07
Filing date: 1967-11-07
Publication date: 1970-09-08
Anticipated expiration: 1987-09-08

Description

DRY SHAVERS G. YOUNG Sept. 8, '1970 Filed Nov. '7. 1967 IMQM-rvra:

Geo Ree fou a AGNT G. YOUNG 1m SHAVERS Sept. 8, 1970 4 Sheets-Sheet 2 Filed Nov. 7; 1967 f l uvm'ofit GeoM VWMG AGN-F United States Patent 3,526,959 DRY SHAVERS George Young, Alcester, England, assignor, by mesne assignments, to 'Wilkinson Sword Limited, London, England, a British company Filed Nov. 7, 1967, Ser. No. 681,277 Int. Cl. B26b 19/14 US. Cl. 30--43.6 12 Claims ABSTRACT OF THE DISCLOSURE A mains or battery operated dry shaver having a cutter member spring pressed into contact with a guard member (sometimes known as a shear plate). The cutter member comprises a three armed carrierhaving a respective blade carrier pivotally mounted on each arm for angular movement about respective axes extending in a common plane which is itself generally normal to the axis of revolution or oscillation of the carrier member. Each blade carrier supports a radially inner concave blade and is formed to afford a radially outer blade. The guard member is formed with a perforated inner part made of thin tensioned foil with which the inner concave blades co-operate, and an annular outer part formed with genrally radial slots with which the outer blades co-operate and made of thicker metal than the foil. The height of the inner part may be adjustable relative to the outer part.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to dry shavers or cutters (hereinafter referred to for convenience as dry shavers of the kind specified) comprising an apertured guard member having an outer face for placing in facei-to-face relation with the surface to be shaved, and a cutter member disposed at the inner face of the guard member and movable over the inner face thereof to sever hair's projecting through the apertures in the guard member. More specifically, the invention is concerned with guard member assemblies and cutter members for such shavers.

Description of the prior art Various forms of guard member are known. Thus it is known, for example, to have a guard member inrthe form of a ring which is of generally inverted U-shaped cross-section and has formed therein a plurality of slots, the cutter member in this case having a number of rigid blade elements upstanding therefrom which are arranged to co-operate with the inner face of the slotted ring and to sever hairs projecting through the slots. Such rings are normally comparatively thick and they have a thickness, for example, of 0.00 Dry shavers using such guard members give a rapid and comfortable shave but due to the formation of the ring it isnot possible to obtain a very close shave. These rings are usually machined from solid metal and, as mentioned, have a thickness of about 0.005". It might be thought that a closer shave could be obtained by widening the slots, that is to say by increasing the distance between the lands which separate adjacent slots. The problem with so doing is that, if the slots become too wide, when the soft part of the face is being shaved, too much skin will project through the slot and the user will find shaving uncomfortable. Moreover, there will be little projection of skin through the slots at the harder parts of the face so that shaving will not, with wide spacing between the slots, be efiicient.

It is also known to use various foils as guard members which are thinner than the machined rings mentioned above. These foils are provided with apertures by any convenient means, for example, piercing or etching and, while they give a close shave, they are not good gatherers of hair since they will only pick up hair which is sticking up from the surface being shaved and moreover in order to be cut a hair has to enter an aperture which is more diflicult than entering a slot.

In US. Pat. No. 3,279,057 there is described a guard member having a generally planar central apertured portion, a peripheral marginal portion integral with the central portion and extending laterally outwardly thereof and a peripheral skirt portion integral with, and extending from the outer boundary of, the marginal portion, the skirt portion and the marginal portion having slots therein extending transversely of their peripheral extensions and continuing through the junction of the two portions, the assembly including inner and outer supporting rings defining a peripheral skirt-receiving interspace which extends in a direction transverse to the plane of the central apertured portion, the inner ring being slotted transversely of its peripheral extension and the skirt portion bing clamped in a stressed condition in the interspace to tension the central apertured portion against collapse and being arranged so that the slots in the skirt portion are at least partly exposed above the outer ring and are in alignment with the slots in the inner ring.

While guard members made as described in said specification have proved satisfactory in service the gathering power and the comfort of the outer slotted portion is capable of improvement.

It is a first object of the present invention, therefore, to provide an improvement in or modification of the guard member described in the aforementiond US. Pat. No.

'- No. 3,279,057 and also to provide an improvement in or modification of the dry shaver described and claimed in said specification.

Another problem in dry shavers of the kind specified, especially where they are designed for highyelocity movement of the cutter member and for operation by dry batteries, is that a very light spring pressure is required between the blade elements which sever the hairs projecting through the guard member and the inner face of the guard member itself.

A spring bias on the blade elements is desirable to retain these in contact with the inner face of the guard member without the necessity of having to rely upon centrifugal forces generated by movement of the cutter member. However, the force should be kept light in order to reduce the frictional forces between the inner face of the guard member and the blade elements and thus to reduce the heat generated, to reduce wear of the relatively moving parts, and the current (power) required.

The invention is also concerned with distributing the force of a spring over a number of blade elements in a construction in which there are inner blade elements which move over a path nearer to the centre of the guard member and outer blade elements which move over a path further from the centre of the gurad member. Such an arrangement is particularly useful when applied to a dry shaver having a guard member of the type described in detail hereinafter and comprising a central apertured foil for close cutting and a surrounding ringlike comb for rapid and efficient cutting which is not as close as the cut which can be obtained using the central foil, but has the property of being able to receive and cut long hairs.

It is a second object of the invention, therefore, to provide, in a dry shaver, a cutter member having inner and outer blade elements arranged so that a light spring force may be readily applied to the blade elements.

3 SUMMARY OF THE INVENTION In accordance with the first object of the invention we provide a dry shaver of the kind specified wherein the guard member comprises an inner part which comprises a generally planar, apertured, central portion of thin foil having a peripherally disposed skirt portion which is clamped in a stressed condition in a skirt-receiving interspace between inner and outer supporting members to tension the central apertured portion against collapse; and an outer part surrounding the inner part and comprising a ring having a portion which circumscribes, and is generally parallel to, said central portion, the ring having through slots in said circumscribing portion extending outwardly from the inner part, the slotted portion of the ring having a thickness greater than that of the foil and the cutter member having blade elements thereon which cooperate with the central portion and with the slots in the circumscribing portion.

In a preferred construction, the outer ring is of U-shape in cross-section, the slots extending between, and partway along, the depending limbs thereof. Preferably, the ring is manufactured from, say, a solid piece of metal or a heavy pressing subsequently machined. During the formation of the ring, the lands between the slots preferably have their edges in the outer face of the guard member radiused. This radiusing of the edges makes the outer ring comfortable to the face of a user. The slots may have a width of 0.012" and the mean width of the lands between the slots may be 0.023".

In accordance with the second object of the invention we provide a dry shaver of the kind specified wherein the cutter member comprises a carrier member mounted for rotation or oscillation relative to the guard member, at least two blade carriers pivotally mounted on the carrier member about first axes lying in a plane generally normal to a second axis about which said rotation or oscillation of the carrier member takes place, each blade carrier carrying an inner blade element and carrying or providing an outer blade element, the first axis of each blade carrier being disposed between its outer blade element and the attachment point of its inner blade element when viewed along said second axis, and a spring acting on the carrier member to urge it towards, and the blade elements into contact with, inner and outer parts of the guard member, the blade carriers being disposed symmetrically about said second axis and so that the force of the spring acting on the carrier member is equally divided between the blade carriers.

As used herein the terms inner and outer are used to refer to the disposition of parts with respect to the second axis i.e. the axis of rotation or oscillation of the carrier member.

The inner blade element may comprise a concave blade element, by which we mean a concave shell or a ring having a curved cutting edge defined by the meeting at an acute angle of an outer curved convex face of the shell or ring and a contact face for engaging the guard member. The blade element is so mounted on the blade carrier as to be enabled to rotate and rock relative to the blade carrier. Preferably the blade element is in the form of a shallow metal cup secured at its apex or smaller end to the blade carrier and having a wall thickness in the region of the contact face of between 0.003" and 0.005". Where the blade element is in the form of a ring, the ring can be open ended and secured to the blade carrier through a spider. The concave blade elements are more fully described in US. Pat. No. 3,279,057 previously mentioned and to which reference should be made.

Normally, the inner part of the guard member will be formed of perforated foil for close cutting and the outer part will be in the form of a slotted comb so that the comb does the efficient gathering of hairs and takes the first cut while the foil takes a second and closer cut.

4 BRIEF DESCRIPTION OF THE DRAWINGS Various embodiments of the invention will now be described in detail by way of example with reference to the accompanying drawings wherein:

FIG. 1 is a longitudinal cross-section on a medial plane through a dry shaver in accordance with the invention,

FIG. 2 is a view in the direction of arrow A showing an end cap,

FIG. 3 is a section on the line IIIIII of FIG. 1,

FIG. 4 is a fragmentary cross-section on an enlarged scale taken on a diameter through the cutting head showing the guard member and cutter assembly,

FIG. 5 is a fragmentary section through a carrier member and cutter assembly on the line V-V of FIG. 4 with certain parts omitted for clarity,

FIG. 6 is a fragmentary plan view of the part shown in FIG. 5, and

FIGS. 7 and 8 are fragmentary views similar to FIG. 4 showing alternative constructions of guard member in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The first embodiment, which will be described in full, and is shown in FIGS. 1 to 6, has a guard member wherein the two parts are fixed in relation to one another.

The dry shaver illustrated is designed for operation either from one of two different mains voltages or from a dry battery carried in an external casing.

The shaver proper comprises a hollow, generally tubular casing 10 having at one end (hereinafter called the forward end) a cutting head 11 in which is mounted a guard member 12 in accordance with the invention. At the other end (hereinafter called the rear end) electrical connections are made to the mains or battery supply by means of suitable contacts provided on an end cap 13. The axis of symmetry of the casing is not straight but the forward part 14 of the casing is inclined at an angle to the rear part 15 thereof and arranged so that when the rear part is held in the hand the forward part will hold the guard member 12 in a convenient attitude for movement over the face of the user. The casing 10 is made in two parts 10' and 10" which are releasably held together so that access may be obtained to the interior of the shaver.

Mounted within the casing adjacent its mid-point is a transformer 16 which has two tappings (not shown) to accept different mains voltages, for example 240 v. and v. The rear end of the tubular casing is closed by the end cap 13 which is held in position by four screws received in threaded bores in the rear part of the casing. The end cap 13 carries, on its inner surface, a rectifier 17 which is connected in the output circuit of the transformer 16. The end cap 13 also has formed integrally therewith a socket 18 which opens rearwardly. Projecting rearwardly from the end wall of the socket 18 are three terminal pins 19, headed ends 20 of which project into recesses 21 on the forward face of the end wall of the socket, the recesses being separated from one another by upstanding walls 22.

Slidably mounted against the front face of the end cap 13 is a shutter 23. The shutter has an aperture 24 therein which is dimensioned to receive an electrical supply lead plug socket of such a size that it can be engaged with the central terminal pin and one of the outside pins. The central pin is connected to the common input terminal of the transformer and one of the outside pins is connected to one of the transformer input tappings while the other pin is connected to the other transformer input tapplng so that it follows that when the plug socket is engaged with the central and say the left-hand pin it can feed one voltage to the transformer and when the plug socket is connected to the central and say the right-hand pln it can feed the other voltage to the transformer. The

aperture 24 in the shutter is only large enough to accommodate the plug socket with a working clearance and the aperture has to be aligned with the pins 19 to be engaged by the plug socket. The shutter 23 carries markings showing the appropriate position of the shutter for the voltage being fed in. For example if the central and left-hand pin are to be used for 110 v. the aperture will have to be aligned 'with these two pins and a part of the shutter will cover the right-hand pin and will carry a marking indicating 110 v. visible through the mouth of the socket 18. Conversely if the shutter 23 is slid to the .right to expose the central and right-hand pin the part of the shutter covering the left-hand pin will have a marking thereon indicating 240 v.

There is an aperture (not shown) in the end cap 13 which is arranged to take plug which may be inserted into a jack socket 26 within the casing of the shaver. The jack socket 26 is connected directly to the shaver motor terminals. The shutter 23 also controls access to the aperture for the jack plug and a corresponding hole 27 in the shutter 23 will only be in alignment with the hole in the jack plug when the aperture 24 associated with the three terminal pins 19 is in such a position that the mains lead plug socket cannot be engaged with either pair of pins. This is a safety factor ensuring that there can be no feed from the domestic electricity supply to the battery in the event of failure of the insulation between the primary and secondary'windings of the transformer. The battery is contained in a separate casing and has a lead from the casing to the jack plug which latter can be inserted into the shaver when it is-desired to run the shaver directly from the battery supply.

The cutting head 11 includes a cutter member 30 driven by a DC. electric motor 31 which is supplied either directly from the battery as described above or through the transformer and rectifier and is conveniently arranged to operate on 6 v. supply. The stator of the motor-31is located between end plates made of synthetic resinous material. The reard end plate provides the rear bearing 32 for the armature shaft 33 and two contact strips 34 are provided onthe rear surface of the rear plate which engage with spring contacts 29 within the shaver casing.

The forward plate provides a forward bearing 35 for the armature shaft 33 and is provided on its'forward surface with a cup-like depression 36 surrounded by an upstanding wall 37. The armature shaft 33 projects through the forward plate into this depression and carries a sleeve 38 of synthetic resinous material the free end of which is provided with an hexagonal spigot 39 or a' spigot of other non-round formation, such as square. The front plate also carries three radially outwardly directed lugs 40 rearwardly of the cup-shaped depression 36 and these lugs 40 are received behind an inwardly directed circumferential flange 41 at the forward end of the casing by passage through corresponding openings or discontinuities 42 in said flange 41 in the manner of a bayonet coupling. The assembly of motor 31, cutting member 30 and guard member 12 (comprising the cutting head 11) may thus be'secured in the casing 10 merely by inserting the former in the latter to pass the lugs 40 through the appropriate openings in the flange 41 and twisting the former with respect to the latter to engage the lugs behind the fiange. The two spring contacts 29 are engaged by the contact strips 34 on the rear face of the rear plate of the motor housing as the assembly is inserted into the casing. The lugs are preferably arranged to be of different sizes or to have different configurations so that the assembly of motor and cutter member can only be placed into the casing in the correct orientation.

The cutter member 30 is mounted on the hexagonal spigot 39 of the sleeve 38. The cutter member 30 comprises a carrier member 50 which is in the form of a three armed moulding or synthetic resinous material, the arms 51 of which are equiangularly spaced about a central boss 52 which is formed with an hexagonal aperture which fits with a sliding clearance on the hexagonal spigot 39 of the sleeve 38. The clearance is such that the carrier member 50 can also rock to some slight extent about the hexagonal spigot 39 although a driving connection is obtained. The carrier member 50 is located axially on the hexagonal spigot 39 between a shoulder 43 on the sleeve and the head of a plug 45 received in a bore 44 in the hexagonal spigot 39. The carrier member is permitted to slide axially between the stops provided by these parts and is pressed upwardly towards the guard member 12 by a spring 46 which surrounds the sleeve 38 and acts between the underside of the central boss 52 of the carrier member and a flange 47 formed at the lower end of the sleeve 38 adjacent to the forward plate of the motor casing.

Adjacent the end of each arm 51 is mounted a blade carrier 53 made of sheet metal, preferably sheet steel. Each blade carrier 53 has a generally inverted U-shaped bridge portion 54 the upper part 56 of which carries a concave blade element 55. The blade element 55 is in the form of a shallow cup and is provided with a central aperture at its apex or smaller end through which passes a rivet which rivets it to the upper part of the bridge member. The radial and axial clearance between the rivet and the blade element are such that the blade element can rotate about its rivet and relative to the blade carrier and can also rock about the rivet. Such a blade element is described in more detail in the previously mentioned US. patent.

The depending

limbs

57 and 58 of the bridge member 54 are drilled to receive the ends of a pivot pin 59 which passes through the end of the arm 51 in a plane generally normal to the axis of rotation of the motor shaft 33. When the upper part 56 of the bridge member 54 is generally horizontal the depending limbs of the carrier member are inclined slightly from the pivot axis of the blade carrier so that their longitudinal centre lines are not arranged vertically but are directed upwardly towards the axis of rotation of the motor shaft, as seen in FIG. 4.

One of the limbs, i.e. limb 58, of each blade carrier 53 is extended downwardly past the pivot axis of the blade carrier and is retroverted into a planar U-shaped configuration. The free end of this U-shaped limb 58 carries, or preferably as shown, if formed to provide, the outer blade elements 60 and is bent over forwardly with respect to the direction of rotation of the carrier member so that it is at a slight angle to the under surface of the guard member 12, the leading edge 61 of the outer blade element 60 being nearer to the inner surface of the guard member than the remaining portion of the free end.

The leading edge 61 is sharpened and has its upper surface lapped to engage the inner surface of the guard member 12. Moreover, the leading edge 61 is not truly radial with respect to the axis of rotation of the carrier member but is at an angle such that the inner end of the leading edge lags behind a radius drawn to the rotary axis of the carrier member through the outer end of the leading edge as seen in FIG. 6. The blade carriers 53 are stamped and bent from sheet steel and are subsequently hardened. Similarly, the cup-shaped blade elements 55 are stamped and subsequently hardened and are made as described in the previously mentioned US. patent. If desired, the cup-shaped blade elements may also be made as described in US. Pat. No. 3,197,864 which describes the removal of the decarburised zone adjacent the contact face of the blade element.

Pivotal movement of the blade carrier 53 about the pin 59 relative to the carrier member 50 is limited by abutment between the edges of the

limbs

57 and 58 with shoulders 66 afforded by the arms 51 of the carrier member as seen in FIGS. 4 and 6.

The guard member 12 of the shaver is made in two parts 70 and and is fixed within a mounting ring 62 which is a friction fit on the circumscribing wall 37 of the depression 36 in the front plate of the motor. The

inner part 70 of the guard member 12 is made of a thin foil 71. Conveniently, the foil has a thickness of 0.002" but may have any desired thickness within the range of 0.001" and 0.003". The foil is preferably steel and either an alloy steel or plain carbon steel may be employed, both in the form of hard rolled sheet. The foil 71 has an innermost plain portion 72 disposed over the spigot 39 a central portion 73 which is pierced by a plurality of small holes 75 and an unperforated circumferential marginal portion 74. The holes 75, if they are round, have a diameter of approximately 0.020" or within the range 0.015 to 0.025". The lands 76 between adjacent holes typically have a width of approximately 0.006". It will be appreciated, however, that non-circular holes may be provided in which case they will preferably be dimensioned so that, when the foil is pressed against the face of a user, the flesh will not project through the hole more than about 0.003".

The foil 71 is preformed by a stamping operation into a central dished part comprising the

portions

73 and 74 surrounded by a shallow skirt portion 77 and a peripheral flange 78 disposed generally parallel to the plane of the base of the dished portion and formed from the unperforated portion 74. The diameter of the dished part is preferably made slightly less, say 0.002" less, than the outside diameter of an inner supporting member 79 over which the foil 71 is to be stretched as will now be described. The inner supporting member 79 is drawn or may be machined from suitable metal and when the guard member assembly is considered in a horizontal position with the operative face uppermost as shown in FIG. 4, the inner supporting member has a lower generally vertical cylindrical portion 80 which, at its upper edge is of inwardly stepped form, having an upwardly and inwardly inclined portion providing a shoulder 81, a short upper vertical portion 82, and an inturned flange 83.

The outer junction between the upper vertical portion 82 and the inturned flange 83 is rounded to provide an upper shoulder 84. The diameter of the upper shoulder 84 is slightly greater than the diameter of the dished part of the foil 71 as preformed. The foil 71 is placed over the inner supporting member in a position such that the peripheral flange 78 of the foil overlies the lower shoulder 81 of the member 79 and the upper shoulder 84 of the latter is disposed generally in alignment with the dished portion. An outer supporting member 85 also has a lower vertical cylindrical portion 86 which is an interference fit on the lower vertical portion 80 of the inner supporting member and an inturned and upwardly inclined flange 87 at its upper end which is arranged to overlie the lower shoulder 81 of the inner member. The flange 78 of the preformed foil is trapped between the lower shoulder 81 of the inner supporting member 79 and the inturned flange 87 of the outer supporting member 85. During its preforming, the flange 78 of the foil 71 tends to crinkle and upon being stretched over the upper shoulder 84 of the inner ring, the foil is tensioned and the flange 78 is stretched due to the crinkles being deformed in the interspace between the lower shoulder 81 of the inner supporting member 79 and the inturned flange 87 of the outer supporting member 85.

The outer part 90 of the guard member 12 is formed of a ring which is of inverted U-section in radial cross section, the inner depending limb 91 thereof extending downwardly to a greater extent than the outer depending limb 92, which latter has an out turned flange 93 at its lower end. The ring is formed by machining from a solid piece of metal or from a heavy pressing subsequently machined and is thus formed with a geenrally flat upper face 94 merging into the depending limbs 91 and 92 by means of radiused corners. The flat upper face 94 of the ring is then slotted, the slots 95 extending generally radially and through the thickness of metal underlying the face 94 and also extending into the upper parts of the depending limbs. Both the underside and the topside of the portion of the ring which provides the flat face is ground away until the thickness between the underside and the flat face is between 0.007 and 0.008" although any convenient thickness between 0.004 and 0.010" could be used. The upper edges of lands 96 between the slots are radiused, so that the side faces of the lands converge downwardly.

The outer supporting member 85 is a light interference fit within the inner depending limb 91 of the outer part 90. Since the outer supporting member is a drawn component, it tends to be thinner adjacent its upper part than adjacent its lower part so that when the outer supporting member 85 and the outer part 90 of the guard member 12 are fixed together there is a circular space (not shown) of wedge shape between the outer surface of the outer supporting ring and the inner surface of the outer part and this may be filled with a suitable synthetic resin such, for example, as an epoxy resin to cement the two parts of the guard member together. However, other means of securing the parts together may be used, for example, welding or riveting.

The two

parts

70 and 90 of the guard member 12 when secured together are then placed in the mounting ring 62 which has at its upper end an inturned flange 68 against the underside of which the out-turned flange 93 of the outer part of the guard member rests. The mounting ring then has portions of material forced inwardly as indicated at 69 to overlie the out-turned flange 93 of the ring of the guard member to hold the guard member in position. These portions of material will be pressed out by means of a circular tool which is gashed to provide, say, 15 tongues which force small tabs of metal over the out-turned flange. Other methods of holding the guard member in the mounting member are shown in FIGS. 7 and 8.

The mounting ring 62 has an internal shoulder 63 which engages the end of the wall 37 circumscribing the depression 36 in the front motor plate to limit the extent to which the mounting ring 62 may be pushed onto said wall. The mounting ring also has in its internal and lower surface an annular steel spring 64 having 10 to 15 flat facets to provide a friction grip on the outer surface of the circumscribing wall 37.

The parts of the guard member are assembled so that the planar, central portion 73 of the inner part 70 of the guard member stands proud of the slotted surface 94 of the outer ring 90 by a distance of between 0.015 and 0.020". This difference in level has been found to give good results in practice since the outer part 90 comprising the ring cuts the longer hairs and prepare them for a finishing cut by the inner part 70.

The helical compression spring 46 is used to urge the cutter member 30 towards the guard member 12 and as previously mentioned engages between the underside of the carrier member and a shoulder afforded by the flange 47 at the rear end of the sleeve. The axial clearance permitted to the cutter member on the hexagonal spigot is such that it will be approximately centrally located between its axial stops when the guard member is in position.

When the guard member 12 is in position the concave blade elements engage the under surface of the inner part of the guard member and the outer blade elements 60 engage the under surface of the outer slotted ring of the guard member. As the motor shaft 33 rotates, it will rotate the carrier member 30 which in turn will rotate the blade carriers 53. The concave blade elements 55 will sweep out orbital paths on the under surface of the portion of the inner part of the guard member while the outer blade elements 60 will sweep out orbital paths under the slotted outer ring.

The outer blade elements 60 are so formed that they cannot peck, that is to say a blade element has not left the underside of one land 96 between the slots 95 in the outer ring 90 before the leading edge 61 of the blade element 60 has come into contact with the underside of the next succeeding land.

The cutting action of the concave blade elements is as described in the previously mentioned US. patent, to which reference should be had for a fuller description.

The outer blade elements 60, due to the angle of the leading edges 61, have a scissor-like action on hairs projecting through the slots in the outer ring and these are severed. However, a close shave will not be obtained merely by the outer ring due to the thickness of the material thereof but the slots thereof have a good gathering power and will take, as it were, an efiicienct rough cut of the hairs and the hairs will then pass into alignment with the central portion and they will be quite short and will therefore stick up from the skin and will enter the apertures in the central portion and will be cut very close to the skin.

Due to the symmetrical disposition of the blade carriers 53 the spring force will be equally divided between them and. the spring may, for example, be a 24 grm. spring so that each blade carrier 53 will be subjected to a spring force of about 8 grm. The division of this 8 grm. between the inner and

outer blade elements

55 and 60 will depend on the relative dispositions between the point of connection of the inner blade element 55, the pivot axis 59 and the point of action of the outer blade element 60. We have found that a satisfactory division is to arrange that the spring force on the inner blade element will be in the neighbourhood of grm. and the spring force on the outer blade element will be in the neighbourhood of 3 grm. It will be appreciated that, upon rotation of the cutter member, centrifugal forces will be set up in the carrier members and that this centrifugal eifect is taken into account in designing the blade carriers and arranging the, spring force.

Due to the triangular disposition of the blade carriers and the blade elements which they carry, and due to the fact that the carrier member 50 is allowed some slight rocking action on the hexagonal spigot '39, any distortion on the guard member 12 within likely limits can be accepted and the carrier member 50 will be urged to a stable position due to the reactions from the blade elements in their contact with the guard member.

The use of three blade carriers arranged adjacent the apices of an equilateral triangle is preferred for this reason although difierent numbers of blade carriers could'be used. For example, four blade carriers could be used if desired mounted in pairs each pair being mounted on an A-frame. The apex of each A frame would be pivotally mounted to rotate with the motor shaft and so as to be able to pivot about an axis in the frame perpendicular to the motor shaft. The blade carriers will be carried by the outer ends of the A-frame. In this arrangement, the blade carriers could conveniently be mounted at the corners of a square.

As has been mentioned above, the inner and outer parts of the guard member may be arranged to be adjustable relative to one another to vary the relative levels of the planar central portion of the guard member and 'the operative face of the outer ring. One such arrangement is shown in FIG. 7 with parts similar to those previously described bearing the same numbers with the sufiix a. Thelower vertical portion of the outer supporting member 85a is provided with an external thread which may ,be formed by thread rolling, and the inner depending limb 91a of the U-shaped ring forming the outer portion 90a of the guard member is. cut away so as to leave four depending tangs 97, one of which is seen in FIG. 7. These tangs 97 are given a slight inward convergence and also have an internal thread rolled thereon to engage with the external thread on the outer supporting member 85a of the guard member. Due to the convergence of the tangs 97, the threads closely engage one another and a frictional force has to be overcome before the inner part 70a of the guard member can be turned relative to the outer part 90a. This frictional force may be adjusted by adjusting the convergency of the tangs and is preferably arranged so that the adjustment is not sloppy.

The inturned flange 87a of the outer supporting membre a also has four slots 98 cut in its upper surface and these slots 98 may be arranged to be engaged by a key whereby the inner part of the guard member can be turned relative to the outer part. This key may be formed by a number of projections formed on a plastic cover which is conventionally provided for placing over the guard member when the shaver is not in use.

An alternative arrangement is shown in FIG. 8 with parts similar to those previously described bearing the same reference numerals with the suffix b. In this case the inner depending limb 91b of the outer ring b may be provided with a series of inclined slots 99 which are engaged by small balls 100 which are mounted in

apertures

101 and 102 in the inner and outer supporting members 79b and 85b. The balls 100 are forced outwardly into the slots 99 by means of a spring ring 103 which is received within the inner supporting member 7% and which is provided with a number of depressions 104 to mate with the parts of the balls 100 which project inwardly within the inner supporting member.

Adjustment of the levels of the inner and outer parts 70b and 90b of the guard member will be obtained in the same manner as above described by turning the inner part by means of a key which may be formed as described. The balls 100 will ride along the inclined slots 99 and the relative levels of the inner and outer parts of the guard member will be altered.

The adjustment may be such that the inner part of the guard member may be moved up or down within a range of 0.040" relative to the outer ring, typically from a position 0.010" below the outer ring to a position 0.030" above the outer ring. As mentioned above, the normal setting would be from the outer ring 90b to be below the inner part 70b by approximately 0015-0020". It will be appreciated that if the slot portion is too far below the level of the central aperture portion then it will either have no effect or only cut very long hairs. Similarly, if the inner central portion is too far below the slotted outer portion then the central portion will have no effect and the whole of the shaving action will be carried out by the outer ring so that close shaving will not be obtained.

The inner and outer parts would preferably be provided with indicating means to indicate the relative positions of the parts. Such indicating means could be provided on the inturned flange 87b of the outer supporting member and the inner depending limb 91b of the outer ring 90b.

Where adjustment between the parts of the guard member is provided, the undersurface of the slotted outer part is concave and the blade elements which co-operate with this outer part are contoured to have a complementary shape to allow for the slight pivotal movement of the blade carrier.

If the user required a close shave, he would arrange that the central portion was above the outer portion. If, however, the user had a particularly heavy growth of beard or Wished to obtain a rapid but not particularly close shave he could retract the inner part of the guard member below the outer part to obtain the desired shave.

The slots of the slotted outer part 90 of the guard member may, if desired, be radial in which case the leading edges 61 of the outer blade elements 60 must be inclined to radii to the motor axis as explained above to get the required scissor action. The inclination of the leading edge to the radius may be in the neighbourhood of 5". Alternatively, the slots 95 in the outer part of the guard member may themselves be inclined to radii from the motor axis and in such a case the cutting edges of the outer blade members 60 could be truly radial if desired or could be raked to increase the scissor action. It will be seen that the invention provides a dry shaver having both inner and outer blade elements to co-operate with inner and outer parts of a guard member and which are biased into contact with the guard member by light and even spring pressure due to the arrangement of the blades on blade carriers pivoted to the carrier member.

It will be seen that the invention also provides a dry shaver having an improved form of guard member which can provide a comfortable shave for the longer hairs and a close shave for the short hairs also longer hairs after they have previously been cut with the outer part of the guard member.

It will be appreciated that the invention may also be applied to a dry shaver wherein the cutting elements oscillate about an axis through an arc of a circle instead of rotating continuously as in the case of the embodiments described above.

If desired, the foil from which the central portion 70 of the guard member is formed may be treated to increase its effectiveness as described in an application filed concurrently herewith by Norman T. Sanders. For example, the inner face of the foil may be etched with a multiplicity of concentric rings or other regular or random patterns so that each aperture in the foil is intercepted by a plurality of channels or other recessed formations.

What is claimed is:

1. A dry shaver comprising:

(a) a guard member which comprises:

(b) an inner part made of metal having a generally planar, apertured, tensioned, central portion and a peripherally disposed skirt portion,

() an inner supporting member and an outer supporting member assembled together and defining between them a skirt-receiving interspace in which said skirt portion is firmly received to tension said central portion against collapse, and

(d) an annular outer part having a slotted portion which is thicker than said inner part, is generally parallel to said central portion of said inner part and circumscribes the latter, and has through slots extending generally radially outwardly from said central portion,

(e) a cutter member which is disposed beneath said guard member and comprises:

(f) a carrier member having an axis of rotation extending in a direction perpendicular to said central portion of said guard member,

(g) at least one inner blade element engaging said central portion of said guard member, and

(h) at least one outer blade element engaging said slotted portion of said guard member, and

(i) means for moving said cutter member about said axis of rotation relative to said guard member and thereby causing said inner and outer blade elements to cooperate with said inner and outer parts of said guard member respectively to sever hairs projecting through said apertures and slots respectively.

2. A dry shaver comprising:

(a) a guard member which comprises:

(b) an inner part made of metal having a generally planar, apertured, tension central portion and a peripherally disposed skirt portion,

(c) inner and outer supporting members defining between them a skirt-receiving interspace in which said skirt portion is firmly received to tension said central portion against collapse, and

(d) an annular outer part having a slotted portion which is thicker than said inner part, is generally parallel to said central portion of said inner part and circumscribes the latter, and has through slots extending generally radially outwardly from said central portion, said central portion being fixed relative to said slotted portion and disposed between 0.015 and 0.025 inch above the latter,

(e) a cutter member which is disposed beneath said guard member and comprises:

3. A dry shaver comprising:

(a) a guard member which comprises:

(b) an inner part made of metal having a generally planar, apertured, tensioned central portion and a peripherally disposed skirt portion,

(c) inner and outer supporting members defining between them a skirt-receiving interspace in which said skirt portion is firmly received to tension said central portion against collapse,

((1) an annular outer part having a slotted portion which is thicker than said inner part, is generally parallel to said central portion of said inner part and circumscribes the latter, and has through slots extending generally radially outwardly from said central portion, and

(e) means for adjusting said central portion relative to said slotted portion in a direction perpendicular to said central portion,

(f) a cutter member which is disposed beneath said guard member and comprises:

(g) a carrier member having an axis of rotation extending in a direction perpendicular to said central portion of said guard member,

(h) at least one inner blade element engaging said central portion of said guard member, and

(i) at least one outer blade element engaging said slotted portion of said guard member, and

(j) means for moving said cutter member about said axis of rotation relative to said guard member and thereby causing said inner and outer blade elements to cooperate with said inner and outer parts of said guard member respectively to sever hairs projecting through said apertures and slots respectively.

4. A dry shaver according to claim 3 wherein said outer part of said guard member includes a plurality of tangs which are convergent with respect to said axis, said means comprising co-operating screw threads formed respectively on said outer supporting member and on said tangs.

5. A dry shaver according to claim 3 wherein said outer part of said guard member is of inverted U shape in radial section having an inner limb and an outer limb, and said means comprising a series of inclined slots in said inner limb of said outer part, a number of balls mounted in said supporting members, and spring means to urge said balls into said slots.

6. A dry shaver comprising:

(a) a guard member which comprises (b) an inner part having a plurality of apertures formed therein, and

(c) an annular outer part having a plurality of slots formed therein,

(d) a cutter member which is disposed beneath said guard member and comprises:

(e) a carrier member having an axis of rotation,

(f) a plurality of blade carriers mounted on said carrier member, arranged symmetrically about said axis of rotation and having respective mutually co-planar pivotal axes extending transversely with respect to said axis of rotation,

(g) respective inner blade elements on said blade carriers and disposed between said axis of rotation and said pivotal axes of said blade carriers,

(h) respective outer blade elements on said blade cartiers and disposed on the sides of said pivotal axes of said blade carriers remote from said axis of rotation beneath said outer part of said guard member,

(i) spring means for urging said cutter member towards said guard member and thereby press said inner and outer blade elements into contact respectively with said inner and outer parts of said guard member, and

(j) means for moving said cutter member about said axis of rotation relative to said guard member and thereby causing said inner and outer blade elements to co-operate with said inner and outer partsof said guard member respectively to sever hairs projecting through said apertures and slots respectively.

7. A dry shaver according to claim 6 wherein said carrier member has three equiangularly spaced arms and said blade carriers are mounted with their pivotal axes adjacent the outer ends of said arms, there being three such blade carriers arranged at the apices of an equilateral triangle centered on said axes of rotation.

8. A dry shaver according to claim '6 wherein each of said blade carriers comprises a bridge portion which is of invertedU-shape as viewed radially with respect to said axis of rotation and has a cross piece on which said inner blade element is mounted and a pair of limbs supported on a pivot-pin carried on said pivotal axis by said-carrier member.

9. A dry shaver according to claim 8 wherein one of said limbs of said bridge portion of each blade carrier is of U-shaped configuration as viewed in the direction of said pivotal axis, the U-shaped limb having an outer free end of which said outer blade element is formed.

10. A dry shaver according to claim 9 wherein said free end of said U-shaped limb is inclined towards said outer part of said guard member and has a leading edge which is sharpened to form a cutting edge, said cutting edge being disposed at a small angle to said slots in said outer part of said guard member.

11. A dry shaver according to claim 6 wherein:

(a) said inner part of said guard member is made of metal foil and has (b) a generally planar, tensioned, central portion in which said apertures are formed, and

(c) a peripherally disposed skirt portion,

(d) said outer part of said guard member has a portion which is thicker than said foil, is generally parallel to said central portion of said inner part, and circumscribes the latter, said slots being formed in this portion of said outer; part of said guard member, and

(e) said guard membj'er further comprises inner and outer supporting members defining between them a skirt-receiving intersipace in which said skirt portion is firmly received to tension said central portion against collapse. "I

12. A dry shaver according to claim 11 wherein means are provided for adjusting said inner part of said guard member relative to said ojuter part thereof in a direction perpendicular to said central portion of said inner part to vary the height of said inner part relative to said outer part, said slotted portion of said outer part having a slightly concave undersurface and said outer blade elements being contoured to "a complementary convex shape.

References Cited UNITED STATES PATENTS 2,677,885 5/1954 Chaun 30-43.6 3,125,808 3/1964 Starre 3043.6

FOREIGN PATENTS 571,774 9/ 1945 Great Britain. 784,909 10/ 1957 Great Britain.

ROBERT C. RIORDON, Primary Examiner G. F. GRAFEL, Assistant Examiner US. Cl. X.R. 30-50