FLEXIBLE RAZOR HEAD

Abstract: According to this invention a flexible razor head is provided which features a flexible cap (10) and blade support (20) with the blade support (20) featuring a segmented guard bar (21) with the spaces separating the segment correlating to the space or areas of reduced thickness in the cap (10). Corrugations (24) present in the blade support (20) enable the blade support (20) to lengthen in response to shaving forces.

Description: This invention relates to a razor head, and particularly relates to a razor head which is movable in response to shaving forces. Recently several razors have featured shaving heads designed to be dynamically movable in response to various forces exerted during shaving. An example of such a razor head is the pivotting cartridge sold under the trademark ULTREX by the Schick Safety Razor Group of the Warner-Lambert Company. Such a cartridge pivots about fixed pivot points provided by a handle in response to razor movement during shaving. A razor head is defined herein and throughout the specification as the combination of a razor blade cover, a razor blade support having a guard bar depending outward therefrom and either one or two razor blades; when more than one blade is provided, the blades can be separated by a spacer means, with the bottom blade extending farther outward toward the user during shaving than the top blade. The razor head as used herein includes both disposable razors wherein the razor head and handle are integral, and also includes cartridges which are used with a permanent handle. US-A-4,446,619 disclosed a razor head having individual spring mounting of blades and, additionally, in some instances, a guard bar to provide vertical movement in response to shaving forces. The blades and guard bar are designed to move up and down within the razor cartridge as shaving force is exerted against them. The cap disclosed in this patent provides a limiting feature for travel of the uppermost blade in the two blade system and is fixed to the remaining non-movable parts of the cartridge. This patent, however, does not take into account the configuration of the face which tends to be made up of a flexible series of arcs and angles rather than separate distinct planes. Other examples of dynamic shaving razors are found, for example, in US-A-4,443,939. This patent discloses a razor cap having corrugated segments disposed on either side of the cap centre as well as a guard bar which is individually segmented and a seat portion of the blade support structure from which the guard bar depends having a convoluted, cage-like structure. The spacer in this blade system has cut out areas to increase flexibility and the blades feature extended longitudinal slots. This patent describes suspending the cartridge by keyholes provided in the blade support portion and matching key-like projections extending from a handle. There is also described pin means depending downward from the cap which is designed to maintain the individual elements of the razor head in a predetermined configuration. To this end a snap fit configuration for the pin means is provided in which a necked-in portion of the pin means is positioned between an enlarged lower portion and an enlarged upper portion. The lower portion cross sectional diameter is somewhat larger than the receiving holes in the blade support portion. The holes are, however, chamfered to provide sufficient flexibility for the pins to be "snap fit" with the bulbous bottom end of the pins passing through the chamfered hole and providing an anchoring site. The tapering necked-in portion allows the blade assembly comprising the upper blade, spacer and lower blade to ride upward in response to downward forces exerted against the razor head. The amount of the upper movement is limited by the length of the necked-in portion. Another approach for the design of a flexible razor head is found in US-A-4,069,580, US-A-4,409,735 and US reissue Patent 30,913 (hereinafter referred to as the Cartwright patents). This dynamically flexible razor head features a pinless assembly in which the head components are held together either by adhesive strips contacting each of the elements or (in the embodiment depicted at Figure 7 of the US-A-4,409,735 patent) the blades are inserted into a premoulded razor head with slots. The embodiment depicted in Figure 7 shows a fingered cap with the fingers being separated by spaces coinciding with spaces separating ribs of blade support portions for the bottom-most blade in a two-blade system. The blades are inset into mating slots in this particular embodiment. The razor head is also suspended by pins in much the same way as the razor head described in US-A-4,443,939. Another example of a razor having dynamically movable elements is described in US-A-4,516,320 in which the razor blade assembly is supported only at each end, and therefore deflects in response to shaving forces while the guard bar moves backward and upward due to certain constructional features. Each of the razor systems wherein the razor head is movable suffers from some disadvantages. The arrangements shown in US-A-4,443,939 and the Cartwright patents use cantilevered attachment means which are extremely difficult to assemble, and the pins utilized for attachment to the handle tend to snap off in response to conventional shaving forces. Moreover, in the case of US-A-4,443,939, flexibility is inhibited because the blade support portion including the guard bar and the cap flex at different flex points. This tends to inhibit the overall flexibility of the razor head. In the case of the embodiment in Figure 7 referred to above, both the cap and blade support portion have open areas which are aligned with each other, but the blades are inhibited from free movement by the clamping associated with the slots formed for them in the one piece cap and support structure. The use of relatively thick support ribs also tends to inhibit flexibility. According to the invention there is provided a flexible razor head comprising: a) a blade cover having spaced areas of reduced thickness positioned across its length; b) pin means extending downward from a position near each longitudinal underside and centre of said blade cover; c) a blade support positioned beneath said blade cover providing a planar blade support having: i) a segmented guard bar extending outwardly therefrom; ii) pin receiving means positioned below said pin means; said blade support being corrugated between said pin receiving means to provide an expanded length when subjected to downward force; and d) a blade assembly including at least one blade with pin receiving holes greater in area than the cross-sectional area of said pin means when said head is in its unstressed condition, the blade assembly being positioned between said blade cover and said blade support, characterised in that the spaced areas of reduced thickness are positioned across the entire length of the blade cover and the spacing between the segments of the guard bar is aligned with the spaced areas of reduced thickness of the blade cover. The blade assembly may consist of two blades separated by a spacer. The blades and/or said spacer preferably have cutout portions positioned between said pin receiving holes. Handle attachment means can be provided on the lower surface at each end of said blade support. The handle attachment means can be designed for inside out attachment. The pin means preferably makes a snap fit with the pin receiving means. Desirably at least one of the blade cover and blade support are made of segmented thermoplastic copolyester elastomers containing recurring polymeric long chain ester units derived from dicarboxylic acids and long chain diols, and short chain ester units derived from dicarboxylic acids and low molecular weight diols. Preferably the blade assembly has at least 15% to 30% open area. Preferably also, the blade, or one of the blades, is adjacent the blade support and has an open area of about 25 to 30%. The flexibility is preferably defined by a force between 45 and 75 gms. (0.442 N and 0.736 N) to obtain a deflection of 0.050 inches (0.127 cm). Between about 15 and 30% of the force needed to define the flexibility is preferably contributed by the blade assembly. Reference is now made to the accompanying drawings, in which:- Figure 1 is a perspective view of a razor head according to the invention; Figure 2 is a cross-sectional view taken along the lines 2-2 of Figure 1; Figure 3 is an exploded perspective view of a razor head according to the invention; Figure 4 is an exploded front elevational view shown partially in cross-section of a razor head according to the invention; Figure 5 is a partial rear section taken along lines 5-5 of Figure 4; Figures 6 and 7 are cross-sectional views corresponding to the views shown in Figure 2; Figure 8 is a partial cross-section of a blade seat taken along lines 8-8 of Figure 3; Figure 9 is a top view of a portion of the seat; and Figure 10 shows a tensile tester base for use in the example described hereinafter. In the drawings a razor head includes a blade cover in the form of a cap 10, a blade support in the form of a seat 20, blades 30 and 30', and a spacer 36. While the configuration shown in Figure 3 includes the two blades 30 and 30' and the spacer 36, increased flexibility will result if the razor head features only one blade. A certain trade off occurs between the closeness of the shave encountered with two blades and the increased flexibility associated with one blade and, as a result, the choice between these configurations is one based upon economics and design properties. The cap 10 features raised areas 12 and recessed areas 13. The recessed areas may in fact be open areas such as shown in US-A-4,409,735 mentioned above. Open areas will decrease strength but will increase flexibility and a balance can be struck in limiting the depth of the open areas or under cutting the thickness in the "open areas". Throughout the specification "open area" is used generically for these variations. Open areas are provided by design in the embodiment depicted in Figure 7 of US-A-4,409,735. The cap 10 is provided with raised end areas 14 and end sides 7. An inside surface 6 of the cap 10 is designed to mate with raised ends 27 and 28 of the blade seat 20. Upon assembly, the sides 7 of cap 10 and sides 23 of blade seat 20 form a continuous side surface which acts not only to protect the user from gouging of the blade sides but also forms a barrier to help limit shifting of blades 30 and 30' in a lateral direction. As can best be seen by reference to Figures 3 and 4, blades 30 and 30' are identical in configuration although the seat blade 30' is larger in area. The seat blade 30' is provided with three pin receiving holes 31A', 31B' and 31C'; the cap blade 30 is provided with three pin receiving holes 31A, 31B and 31C; and the spacer 36 is provided with three pin receiving holes 37A, 37B and 37C. A slot 32A is positioned between holes 31A and 31B; a slot 32B is positioned between holes 31B and 31C; a slot 32A' is positioned between holes 31A' and 31B'; and a slot 32B' is positioned between holes 31B' and 31C'. Also a slot 38A is provided between holes 37A and 37B, and a slot 38B is provided between holes 37B and 37C. As shown in Figure 3, the blade seat 20 includes flat surface 22 upon which bottom blade 30' rests; a segmented guard bar 21 is attached to the flat surface 22 by ribs 29. Chamfered receiving holes 25A, 25B and 25C are provided in the seat 20 for receiving pins 5; the pins 5 each have a bulbous end 11, a necked in portion 9 and a conventional diameter pin portion 8. As can best be seen by reference to Figures 2, 6 and 7, the pins 5 extend downward through the blades 30 and 30' and the spacer 36 (see also Figures 3 and 4), while allowing the blades 30 and 30' to flex freely up on surface 8 of pin 5. As shown in Figure 3, the pins 5 pass through the chamfered holes 25A, 25B and 25C to anchor the cap 10, the blades 30 and 30', and the spacer 36 to the blade seat 20. The holes 31A, 31B , 31C, 31A', 31B' and 31C' are greater in size than the diameter of pin portion 8 and therefore the blades 30 and 30' are capable of moving laterally in response to bending forces. The use of a centre pin 5 (i.e. pin 5 disposed substantially centrally along the razor head between the two outer pins 5) provides the assembly with stability and controlled movement. The slots 32A, 32B, 32A' and 32B' in the blades 30 and 30', and the slots 38A and 38B in the spacer 36, increase the flexibility of the blades 30 and 30' and the spacer 36 without structurally weakening either. The blades 30 and 30' each have rear ends 35 and 35' respectively and forward projecting shaving edges 34 and 34' respectively (Figure 3). The shaving edges 34 and 34' are positioned parallel to one another, as can best be seen by reference to Figure 1. As can be seen, the upper or cap blade 30 is positioned with its shaving edge 34 behind the shaving edge 34' of the lower or seat blade 30'. This particular arrangement is well known in the art. As shown in Figures 3, 4 and 5, the blade seat 20 is provided with a plurality of corrugations 24 extending along the length of the seat 20. The corrugations flatten out and deform downwardly when downward pressure is exerted during shaving; this results in an expansion of the overall length of the seat. Figure 6 shows the position when the razor head is not being used for shaving, whilst Figure 7 shows the position during shaving. As can be seen from Figure 7, during shaving the pins 5 move laterally withy respect to the holes 31A, 31A', 37A, 31B, 31B', 37B, 31C, 31C' and 37C. Attachment of the razor head is by "inside-out" connection as can best be seen by reference to Figures 8 and 9. The handle arms (which are shown in phantom lines in Figures 8 and 9) are biased to be deflected inward in response to downwardly directing shaving forces. The biased outwardly directed forces maintain the shaving arms in an at rest position. The arms themselves may be resiliently flexible or may be inwardly and/or outwardly biased as desired. The biasing and/or arm flexing serves to provide a limiting means for downward deflection of the central portion of the razor head. The limiting of the downward deflection can be dependent upon the amount of elastic deformation possible with the handle arms. It is preferred that the maximum amount of downward deflection of the razor head at its centre point is between about 0.090 in. (0.229 cm) and 0.140 in. (0.356 cm) and most preferably between about 0.120 in. (0.301 cm) and about 0.140 in. (0.356 cm). As a measure of total resilience for the razor head from 45 to 75 gm of force (0.442 to 0.736 N) should be applied to achieve a deflection of 0.050 in. (0.127 cm). It is also preferred that the blade assembly (i.e. the single blade or the two blade and spacer combination) should contribute from 15 to 30% of the gram force needed to obtain the 0.050 in. (0.127 cm) deflection. Preferably the blade assembly should contribute from 20 to 25% of the 45 to 75 gram force (0.442 to 0.736 N). This is obtained by creating a blade assembly which flexes in the same locations as the seat 20 and the cap 10 and which has an open area covering between about 15 and about 30% of the surface of the assembly. As can be seen particularly by reference to Figure 2 the seat blade 30' is actually larger than the cap blade 30. It is particularly preferred that the seat blade 30' have an open area of about 25 to about 30%. The cap blade 30 should preferably have about 20 to 25% open area. Deflection values are determined as discussed below in the following example. Example The purpose of the tests in this example was to compare the stiffness characteristics of the razor head according to the present invention and the razor heads described in US-A-4,443,939 and the Cartwright patents. Referring to Figure 10, the razor head is held in a fixture which is rigidly attached to an Instron tensile tester base. A ram fixture, as its name depicts, is kinematically mounted to the movable ram of the Instron and is hung from a calibrated load cell. At the bottom of the ram fixture is a pin which applies a load to the razor head in the razor head fixture as the ram fixture moves upward. The purpose of this system is to apply a known deflection to the razor head and simultaneously measure the force. Tabulated below are the results of such testing of the razor head as well as a blade assembly made up of two blades and a spacer. The comparative data can be summarized as follows: 1. The razor head according to this invention is 68% more stiff than the razor head according to the Cartwright patents. 2. The stiffness of the razor head according to this invention is 115% less stiff than the original R&D version. 3. The razor head according to US-A-4,443,939 is much more stiff than either the razor head according to the present invention or the razor head according to the Cartwright patents. 4. The plastic modulus of the plastic used in the Cartwright patents was less than 5000 psi (34.5 MPa) in order to achieve the desired stiffness characteristics. The proposed design, however, was tested with a modulus of 400,000 psi (2758 MPa). There is, therefore, a great deal of room to modify the stiffness by either reducing the elastic modulus, the moment of inertia, or a combination of the two. It is particularly preferred to utilize highly flexible thermoplastic material having high levels of structural integrity. A particularly suitable material is one which is made out of the segmented copolyester elastomer which contains recurring polymeric long chained ester units derived from dicarboxylic acids and long chain diols and short chain ester units derived from dicarboxylic acids and low molecular weight diols. Suitable materials particularly favoured for construction of plastic cap and blade support portions are described in US-A-3,766,146 and US-A-3,651,014 (by Witsiepe assigned to E.I. du Pont de Nemours, and sold under the tradenames Hytrel 5556 and Hytrell 4056 respectively). It is even possible to make a plastic resilient spacer member out of these particular polymers which will add to the overall resilience of the razor head. When these compounds are used as part or all of the razor head plastic components the elastic modulus of the head can be minimized and, bearing in mind the resistance programmed from the blade assembly, a wide range of modulus values can be attained.

Claims: A flexible razor head comprising: a) a blade cover (10) having spaced areas (13) of reduced thickness positioned across its length; b) pin means (5) extending downward from a position near each longitudinal underside and centre of said blade cover (10); c) a blade support (20) positioned beneath said blade cover (10) providing a planar blade support having: i) a segmented guard bar (21) extending outwardly therefrom; ii) pin receiving means (25A,25B,25C) positioned below said pin means (5); said blade support (20) being corrugated (24) between said pin receiving means (25A,25B,25C) to provide an expanded length when subjected to downward force; and d) a blade assembly including at least one blade (30) with pin receiving holes (31A,31B,31C) greater in area than the cross-sectional area of said pin means (5) when said head is in its unstressed condition, the blade assembly being positioned between said blade cover (10) and said blade support (20), characterised in that the spaced areas (13) of reduced thickness are positioned across the entire length of the blade cover (10) and the spacing between the segments of the guard bar (21) is aligned with the spaced areas (13) of reduced thickness of the blade cover (10). A razor head according to Claim 1 characterised in that the blade assembly consists of 2 blades (30,30') separated by a spacer (36). A razor head according to Claim 1 or 2 characterised in that said blades (30,30') and/or said spacer (36) have cutout portions (32A,32B,32A',32B',38A,38B) positioned between said pin receiving holes (31A,31B,31C,31A',31B', 31C',37A,37B,37C). A razor head according to Claim 1 characterized in that handle attachment means are provided on the lower surface at each end of said blade support (20). A razor head according to Claim 4 characterised in that said handle attachment means are designed for inside out attachment. A razor head according to any preceding claim, characterised in that the pin means (5) makes a snap fit with said pin receiving means (25A,25B,25C). A razor head according to any preceding claim, characterised in that at least one of the blade cover (10) and blade support (20) are made of segmented thermoplastic copolyester elastomers containing recurring polymeric long chain ester units derived from dicarboxylic acids and long chain diols, and short chain ester units derived from dicarboxylic acids and low molecular weight diols. A razor head according to any preceding claim, characterised in that the blade assembly has at least 15% to 30% open area. A razor head according to any preceding claim, characterised in that the blade (30), or one of the blades (30,30'), is adjacent the blade support and has an open area of about 25 to about 30%. A razor head according to any preceding claim, characterised in that the flexibility is defined by a force between 45 and 75 gms. (0.442 N and 0.736 N) to obtain a deflection of 0.050 inches (0.127 cm). A razor head according to any preceding claim, characterised in that between about 15 and 30% of the force needed to define the flexibility is contributed by the blade assembly.

Inventors: CHEN, EVAN NAI-KEUNG
Applicants: WARNER-LAMBERT COMPANY
Application year: 1988
Main classification: B26B21
IPC codes: B26B21