Patent Publication Number: US-7895753-B2

Title: Shaving system

Description:
RELATED APPLICATIONS 
     This application is a continuation of, and claims priority under 35 U.S.C. 120 from, International Application No. PCT/EP2006/001345, filed Feb. 15, 2006, which claimed priority under 35 U.S.C. 119(a) from German Patent Application DE 10 2005 010244.1, filed Mar. 5, 2005. Both priority applications are incorporated herein in their entirety. 
    
    
     TECHNICAL FIELD 
     This invention relates to a cutter assembly for an electric hair cutting appliance, an electric hair cutting appliance equipped with such a shaving cutter assembly and a method of manufacturing such a shaving cutter assembly. 
     BACKGROUND 
     In general, as a rule, an electric shaving appliance has a shaving cutter or undercutter and an overcutter or foil which lie close together and move relative to each other to cut beard hairs entering the region between the overcutter and the undercutter. 
     Such a shaving apparatus is discussed in EP 1 182 014 A2, in which an electric shaving apparatus has two undercutters and one overcutter that is constructed as a shaving foil. The undercutters are made to perform an oscillatory linear motion, severing in the process the beard hairs in cooperating relationship with the overcutter. 
     WO 2004/076135 A1 also discusses an electric shaving apparatus with two undercutters which oscillate relative to an overcutter constructed as a shaving foil. The undercutters are each connected to a drive element via a coupling element. For this purpose the respective undercutter is arranged on the coupling element such that projections formed on the coupling element engage in recesses of the undercutter. 
     The shaving results achievable with a shaving apparatus of such construction depend, among other factors, on the accuracy of the cooperating relationship between the undercutters and the overcutter. 
     SUMMARY 
     One aspect of the invention features a shaving cutter of an electric hair cutting appliance that is permanently fixed to a carrier. The carrier is acted upon by a drive mechanism of the electric cutting appliance to cause the carrier and shaving cutter to oscillate. 
     In some embodiments, the shaving cutter assembly has a shaving cutter including multiple connected cutting blades for severing hairs and a carrier to which the shaving cutter is fixedly connected. More particularly, the shaving cutter and the carrier are connected to each other via at least one metallic weld. The carrier serves to transfer oscillation or other movement from the drive mechanism of the appliance to the shaving cutter. 
     The shaving cutter is precisely and permanently fixed to the carrier. The metallic weld is very durable, has low space requirements and can be produced quickly and cost-effectively. 
     In a preferred embodiment of the invention, at least one mounting structure is provided on the shaving cutter and the weld is arranged in the region of the mounting structure. In this arrangement, the mounting structure is configured to be more readily deformable than the shaving cutter. For example, the mounting structure may be connected to the shaving cutter by a web or region of reduced material cross-section. Stresses and deformation created during production of the weld are isolated by the region of the reduced material cross-section, eliminating or reducing the transfer of stress to the shaving cutter. Consequently, it is possible to avoid undesirable deformation of the shaving cutter and to achieve good dimensional stability. This is an important factor in achieving good shaving results. 
     Several welds may be formed per mounting structure. In such cases, the welds are preferably arranged to at least partially balance stresses caused by the welds. For example, the welds may be formed at mutually symmetrical locations on the mounting structure. These arrangements lead in turn to any distortions in the shaving cutter being maintained within tolerance. 
     The mounting structure and the shaving cutter are preferably integrally made of one piece. In addition it is advantageous for the mounting structure to be connected to the shaving cutter via a neck region or web of reduced cross-section. The web serves to isolate the weld or several welds from the shaving cutter and to minimize any weld-induced distortions in the shaving cutter. 
     The mounting structure may embrace the carrier on multiple sides. This makes it easier to fixedly locate the shaving cutter on the carrier and results in a reliable hold. In this arrangement, according to one variation, the mounting structure is adapted to continuously conform with the shape of the carrier. According to another variant, the mounting structure deviates from the shape of the carrier in a region adjoining the weld, to provide a gap between the mounting structure and the carrier. In this region, the mounting structure includes a reduced material cross-section so that any stresses, or deformations are further isolated from the shaving cutter. 
     The shaving cutter assembly may be constructed such that the mounting structure has at least one holding arm. It is further advantageous for the mounting structure to have two symmetrically constructed holding arms between which the carrier is fixed. With this embodiment, it is possible to achieve a particularly effective suppression, or isolation of stresses. 
     The shaving cutter may be constructed as an undercutter having multiple connected blades adapted to be driven in an oscillating motion by the carrier. In particular the multiple blades of the shaving cutter may be bent such that the shaving cutter has a U-shaped cross-section. The blades of the shaving cutter may have a material thickness of less than 1 mm, preferably less than 0.5 mm and in particular around 0.3 mm. Preferably, provision is made for another shaving cutter, such as an overcutter foil, for cooperation with the shaving cutter. 
     The invention relates furthermore to an electric hair cutting appliance with at least one shaving cutter assembly constructed as discussed above. 
     Another aspect of the invention features a method of manufacturing a shaving cutter assembly for an electric hair cutting appliance, in which a shaving cutter for severing hairs is fixedly connected to at least one carrier. The method is characterized in that the shaving cutter and the carrier are connected to each other by at least one metallic weld. 
     It is particularly advantageous for several welds to be formed simultaneously. In this way, it is possible to restrict the development of stresses during formation of the welds. A similar effect is achievable if the energy for producing several welds is supplied successively over time, with the respective time difference being selected to be so small that molten material exists simultaneously in the region of several welds. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
       The present invention will be explained in greater detail in the following with reference to the embodiments illustrated in the accompanying drawings. Like reference symbols in the various drawings indicate like elements. 
         FIG. 1  is a side view of an embodiment of an electric shaving appliance; 
         FIG. 2  is a side view of an embodiment of a shaving cutter constructed in accordance with the invention; 
         FIG. 3  is a sectional view of the shaving cutter of  FIG. 2 ; 
         FIG. 4  is an enlarged detail view of  FIG. 2  in the region of one of the mounting structures; 
         FIGS. 5 and 6  are views of further embodiments of the shaving cutter in a representation corresponding to  FIG. 4 , showing the respective mounting structures fixedly located on the carrier with two weld points each; and 
         FIGS. 7 to 10  are views of embodiments of the shaving cutter in a representation corresponding to  FIG. 4 , showing the respective mounting structures fixedly located on the carrier with single weld points. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a side view of an embodiment of an electric shaving appliance  1 . The shaving appliance  1  includes a housing  2 , which can be held in the hand, and a shaving head  3  attached thereto. Arranged on the housing  2  is a switch  4  for switching the shaving appliance  1  on and off. The shaving head  3  includes a shaving cutter assembly  5  and shaving foil  7  arranged in a mounting frame  6  to cooperate with the shaving cutter assembly  5 . 
       FIG. 2  is a side view of an example of a shaving cutter or undercutter  8 . A related sectional view is shown in  FIG. 3 . The shaving cutter  8  represents another component of the shaving cutter assembly  5  and, in the mounted state, lies close to the inner side of the shaving foil  7  shown in  FIG. 1 . During operation of the shaving appliance  1 , the shaving cutter  8  is set in an oscillatory linear motion relative to the shaving foil  7 . Hairs passing through the shaving foil  7  up to the shaving cutter  8 , are caught between the shaving cutter  8  and the shaving foil  7  and are severed. Alternatively, the overcutter may include blade sections like the undercutter. 
     With reference to  FIGS. 2-3 , in its cross-section, the shaving cutter  8  is of a U-shaped configuration and is made up of a first base  9 , a second base  10  and an arcuate section  11  arranged between the bases  9  and  10 . Disposed at regular relative distances in the longitudinal direction of the shaving cutter  8  are multiple individual blades  12  forming arcuate section  11 . The individual blades  12  are constructed to be sharp-edged. Formed on each base  9  and  10  of the shaving cutter  8  are two mounting structures  13  with which the shaving cutter  8  is fastened to two carrier shafts  14  that are oriented in a direction transverse to the longitudinal extension of the shaving cutter  8 . The carrier shafts  14  are engaged by a drive system  21  of the shaving appliance  1  operable to set the shaving cutter  8  in an oscillatory linear motion. The construction of the mounting structures  13  will be described in detail with reference to  FIG. 4 . 
       FIG. 4  shows an enlarged detail from  FIG. 2  in the region of one of the mounting structures  13 . In the embodiment shown, the mounting structure  13  is symmetrically and integrally formed with the first base  9  of the shaving cutter  8 . In this arrangement, the mounting structure  13  has two holding arms  15  in the form of a fork partially embracing the illustrated carrier  14 . The two holding arms  15  unite in a neck region or web  16  via which the mounting structure  13  is connected to the first base  9  of the shaving cutter  8 . The web  16  extends laterally parallel to the outer contour of the first base  9  of the shaving cutter  8  to a distance smaller than the lateral extension of the two holding arms  15 . The holding arms  15  rest with inner surfaces  17  against the carrier  14 . The interface between the holding arms  15  and carrier  14  is shown here to be circular or arc-shaped but may be of any other suitable shape. 
     The carrier shafts  14  are made of metal, preferably steel. The shaving cutter  8  is made of metal at least in the region of the mounting structures  13 . Preferably the shaving cutter  8  is made entirely of metal, with steel being again particularly well suited as a material. The material thickness of the shaving cutter  8  is less than 1 mm. Preferably a material thickness of less than 0.5 mm is selected. In the embodiment shown, the material thickness is around 0.3 mm. For example, the shaving cutter  8  and holding arms  15  may be formed by stamping or die cutting a steel sheet that is then bent into a U-shaped elongated form and fixed in this shape by attachment of carrier shafts  14  at holding arms  15 . 
     To fixedly locate the mounting structure  13  on the carrier shafts  14 , the mounting structure  13  and each carrier shaft  14  are welded together. In the embodiment shown, two weld points  18  are produced near the free ends of the holding arms  15  in mutually symmetrical positions. Between the weld points  18  and the web  16  the holding arms  15  each have a locally reduced material cross-section. 
     The weld points  18  may be produced by any suitable means such as by laser welding. During laser welding, the selected boundary regions between the holding arms  15  and the carrier shaft  14  are exposed briefly to a high-energy laser beam. This leads to local melting of the material in the region of the laser beam. During cooling, the molten material of the holding arm  15  fuses with the molten material of the carrier shaft  14 . The melting takes place within a period of around 1 ms to 10 ms and is performed for both weld points  18  either simultaneously or in quick succession. The time offset for melting the two weld points  18  is a maximum of around 1 ms, which means that the material in the region of the second weld point  18  has already been melted before the material in the first weld point  18  has solidified. Simultaneous melting in the region of the two weld points  18  is achievable, for example, with the aid of a bifocal laser beam which is adjusted such that one focus point is produced in the region of each of the two weld points  18 . When the molten regions solidify, stresses develop due to the reduction in volume and contraction during cooling. In particular, tensile stresses develop normal to the enveloping surface of the melt volume, which corresponds to the weld points  18  illustrated. The stresses can be reduced to a certain degree using a small melt volume and a small weld gap. 
     Within the scope of the invention several provisions are made enabling the stresses to be limited to very small values. One of these provisions entails forming several weld points  18  at least approximately simultaneously in the manner described so that the stresses partially cancel out each other during contraction of the melt volume. For example, the four weld points  18 , by means of which a single carrier shaft  14  is joined to both a mounting structure  13  of the first base  9  and to a mounting structure  13  of the second base  10  of the shaving cutter  8 , can be produced simultaneously or approximately simultaneously. 
     The individual weld points  18  may be arranged such that the stresses are cancelled, after cooling of the melts in the weld gap normal to the enveloping surface of the melt volume. In the example of  FIG. 4 , the weld points  18  are arranged symmetrically opposite each other for this purpose. 
     If stresses develop nevertheless, their impact on the shape of the shaving cutter  8  may be limited by arranging for the mounting structures  13  to deform more easily than the shaving cutter  8 . This may be achieved by the forked shape of the mounting structures  13  and by the locally reduced material cross-section of the holding arms  15 . 
     The stresses acting on the shaving cutter  8  can be limited particularly effectively by the described steps being applied in combination. However, it is also possible for the described characteristics to be employed individually or in sub-combinations. The described arrangement of the weld points  18  and the simultaneous or approximately simultaneous welding are preferably used in combination. Further alternative examples are illustrated in  FIGS. 5 and 6 . As a single provision, it is possible to use the easy deformability of the mounting structures  13 . Examples of this are shown in  FIGS. 7 to 10 . 
       FIGS. 5 and 6  show further examples of the shaving cutter  8  in a representation corresponding to  FIG. 4 , in which the mounting structures  13  are fixedly located on the carrier shaft  14  with two weld points  18  each. In both examples, the carrier shaft  14  is embraced nearly completely by the holding arms  15  of the mounting structure  13 , in each case but for a small gap  19 . The gap  19  is formed in each case between the free ends of the holding arms on a side of the mounting structure  13  opposite the web  16 . One weld point  18  each is produced on both sides adjacent to the gap  19 . In the example shown in  FIG. 5 , the respective inner surface  17  of the two holding arms  15  is entirely shaped in the manner of a circular arc. In the example shown in  FIG. 6 , by contrast, only a sub-region of the respective inner surface  17  of the two holding arms  15  is constructed in the shape of a circular arc. In this example the inner surface  17  deviates in each case in a region of the holding arm  15  adjoining the weld point  18  from the shape of a circular arc such that initially the radii increase progressively and then are reduced again to the point where the circular arc is regained. Each holding arm  15  thus has, adjoining its weld point  18 , a gap  20  in the region of which the inner surface  17  of the holding arm  15  is spaced from the carrier shaft  14 , thereby reducing the material cross-section of the holding arm  15 . In this way it is possible to further improve the reduction of stresses. 
       FIGS. 7 through 10  show examples of the shaving cutter  8  in a representation corresponding to  FIG. 4 , in which the mounting structures  13  are fixedly located on the carrier shaft  14  with one weld point  18  each. In these examples the mounting structure  13  has in each case only one holding arm  15  and is constructed on the whole in the shape of a hook. Near its free end the holding arm  15  is connected by a weld point  18  to the carrier shaft  14 . 
     In the examples of  FIGS. 7 and 8 , the respective holding arm  15  embraces approximately half the circumferential area of the carrier shaft  14 . In the embodiment of  FIG. 7  the inner surface  17  of the holding arm  15  is constructed fully in the shape of a circular arc. The example of  FIG. 8  has, adjacent to the weld point  18 , a gap  20  such that the inner surface  17  of the holding arm  15  is constructed only locally in the shape of a circular arc. 
     In the examples of  FIGS. 9 and 10 , the respective holding arm  15  embraces the carrier shaft  14  nearly completely such that the free end of the holding arm  15  nearly reaches in each case to the web  16 . In these examples, too, the weld point  18  is again produced in each case near the free end of the holding arm  15 . In the example of  FIG. 9  the holding arm  15  has a circular-arc-shaped inner surface  17 . In the example of  FIG. 10 , a gap  20  is formed adjacent to the weld point  18 . Outside the gap  20 , the inner surface  17  of the holding arm  15  is of a circular-arc-shaped configuration. 
     The weld points  18  can be produced not only by the previously described laser welding method but also by other welding methods, such as micro-plasma welding or electron beam welding, for example. 
     A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, multiple carriers may be used to transfer motion from the appliance drive mechanism to the shaving cutter and any number of other reinforcing structures, such as cross-members, may be use with the shaving cutter. Accordingly, other embodiments are within the scope of the following claims.