Abstract
A hair cutting appliance includes a linkage unit configured to couple a cutting unit and to a housing of the hair cutting appliance. The linkage unit includes a four-bar linkage mechanism having first and second arms which respectively include first and second bases pivots coupled to a base. The first and second base pivots are arranged at the base at a fixed distance. The first arm and second arms also respectively include first and second top pivots coupled to a connecting bar. The connecting bar is configured to be coupled to the cutting unit such that, during operation, the cutting unit is pivotably supported by the four-bar linkage mechanism.
Claims
1. A cutting unit and a linkage unit for a hair cutting appliance, wherein the cutting unit is arranged to be coupled to a housing of the hair cutting appliance by the linkage unit, the cutting unit comprising a blade set comprising a stationary blade, a movable blade and at least one basically longitudinally extending cutting edge, wherein the stationary blade is arranged to house and to guide the movable blade for longitudinal movement with respect to the stationary blade, the stationary blade comprising a cross-section, viewed in a plane perpendicular to a lateral direction (Y), that is U-shaped at the at least one cutting edge, wherein the U-shaped form comprises a first leg and a second leg, wherein a guiding slot for the movable blade is provided between the first leg and the second leg, and wherein the stationary blade basically encloses the movable blade at a side thereof facing a skin when cutting hair and, at least partially, at a side thereof facing away from the skin when cutting hair, the linkage unit comprising a four-bar linkage mechanism, the four-bar linkage mechanism comprising a first arm and a second arm opposite to the first arm, the first arm comprising a first base pivot coupled to a base, the second arm comprising a second base pivot coupled to the base, the first base pivot and the second base pivot being arranged at the base at a defined distance, the first arm further comprising a first top pivot coupled to a connecting bar, the second arm further comprising a second top pivot coupled to the connecting bar, wherein the connecting bar is arranged to be coupled to the cutting unit, such that, during operation, the cutting unit is pivotably supported by the linkage mechanism, and wherein the cutting unit and the linkage unit further comprise at least one end stop element for preventing undesired motion of the four-bar linkage mechanism, wherein the at least one end stop element comprises at least one protruding contact tab at at least one of the first arm, the second arm and the connecting bar, and at least one corresponding contact surface at the other one of the first arm, the second arm and the connecting bar, such that the at least one protruding contact tab and the at least one corresponding contact surface define a maximal relative rotation between the first and second arms and the connecting bar.
2. The cutting unit and the linkage unit as claimed in claim 1, wherein the four-bar linkage mechanism defines a virtual pivot for the cutting unit, the virtual pivot comprising a virtual pivot axis (p) that is substantially parallel to the cutting edge of the cutting unit.
3. The cutting unit and the linkage unit as claimed in claim 2, wherein the pivot axis is arranged in a vicinity of a top surface of the cutting unit facing away, when mounted, from the housing of the hair cutting appliance, and wherein the pivot axis is offset from the top surface, in a neutral position of the four-bar linkage mechanism, by a pivot offset dimension in a range of between ?2.0 mm and +5.0 mm below and above a level of the top surface.
4. The cutting unit and the linkage unit as claimed in claim 2, wherein the pivot axis is arranged in a vicinity of a top surface of the cutting unit facing away, when mounted, from the housing of the hair cutting appliance, and wherein the pivot axis is offset from the top surface, in a neutral position of the four-bar linkage mechanism, by a pivot offset dimension in a range of between ?1.0 mm and +2.0 mm below and above a level of the top surface.
5. The cutting unit and the linkage unit as claimed in claim 2, wherein the pivot axis is arranged in a vicinity of a top surface of the cutting unit facing away, when mounted, from the housing of the hair cutting appliance, and wherein the pivot axis is offset from the top surface, in a neutral position of the four-bar linkage mechanism, by a pivot offset dimension in a range of between +0.25 mm and +0.75 mm below and above a level of the top surface.
6. The cutting unit and the linkage unit as claimed in claim 1, wherein at least the first arm, the second arm and the connecting bar and their respective base pivots and top pivots are integrally formed as a single piece.
7. The cutting unit and the linkage unit as claimed in claim 6, wherein all pivots of the four-bar linkage mechanism are arranged as living hinges.
8. The cutting unit and the linkage unit as claimed in claim 1, wherein the four-bar linkage mechanism is an integrally formed injection molded plastic part.
9. The cutting unit and the linkage unit as claimed in claim 1, wherein the four-bar linkage mechanism is a three-dimensional near-net shaped molded part, and wherein hinges forming the pivots thereof are basically unbiased when the linkage mechanism is in a neutral position.
10. The cutting unit and the linkage unit as claimed in claim 1, wherein the length of the base, defined by a distance between the first base pivot and the second base pivot, is greater than the length of the connecting bar, defined by a distance between the first top pivot and the second top pivot.
11. The cutting unit and the linkage unit as claimed in claim 1, further comprising at least one biasing element that urges the four-bar linkage mechanism into a defined start position.
12. The cutting unit and the linkage unit as claimed in claim 11, wherein the at least one biasing element is a torsion bar spring arranged at the base, the torsion bar spring comprising a torsion bar pivotably received at the base, the torsion bar being arranged between a first leg and a second leg, wherein the first leg is coupled to the base, and wherein the second leg is coupled to one of the first arm and the second arm.
13. The cutting unit and the linkage unit as claimed in claim 1, wherein the at least one end stop element cooperates with at least one biasing element, wherein a resulting biasing force urges the four-bar linkage mechanism against at least one of the at least one end stop element.
14. The cutting unit and the linkage unit as claimed in claim 1, wherein the at least one end stop element is connected to the base and arranged to limit a motion of the cutting unit.
15. The cutting unit and the linkage unit as claimed in claim 1, wherein the at least one end stop element is arranged at an end stop support comprising at least one end stop beam, the at least one end stop beam comprising at least one end face, wherein the at least one end face abuts a bottom side of the cutting unit for limiting the motion of the cutting unit.
16. The cutting unit and the linkage unit as claimed in claim 1, wherein the at least one end stop element is connected to the base and arranged to limit motion of at least one of the first arm, the second arm and the connecting bar.
17. A hair cutting appliance comprising a housing accommodating a motor, a cutting unit, and a linkage unit for coupling the cutting unit and the housing, wherein the linkage unit comprises a four-bar linkage mechanism, the four-bar linkage mechanism comprising a first arm and a second arm opposite to the first arm, the first arm comprising a first base pivot coupled to a base, the second arm comprising a second base pivot coupled to the base, the first base pivot and the second base pivot being arranged at the base at a defined distance, the first arm further comprising a first top pivot coupled to a connecting bar, the second arm further comprising a second top pivot coupled to the connecting bar, wherein the connecting bar is arranged to be coupled to the cutting unit, such that, during operation, the cutting unit is pivotably supported by the linkage mechanism, and wherein the cutting unit and the linkage unit further comprise at least one end stop element for preventing undesired motion of the four-bar linkage mechanism, wherein the at least one end stop element comprises at least one protruding contact tab at at least one of the first arm, the second arm and the connecting bar, and at least one corresponding contact surface at the other one of the first arm, the second arm and the connecting bar, such that the at least one protruding contact tab and the at least one corresponding contact surface define a maximal relative rotation between the first and second arms and the connecting bar.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. In the following drawings
(2) FIG. 1 shows a schematic perspective view of an exemplary electric hair cutting appliance fitted with an exemplary embodiment of a cutting unit that may be pivotably supported at the hair cutting appliance;
(3) FIG. 1a is a partial perspective bottom view of a blade set of a cutting unit of a hair cutting appliance in accordance with FIG. 1;
(4) FIG. 1b is a further partial perspective bottom view corresponding to the view of FIG. 1a, a wall portion of the blade set being omitted primarily for illustrative purposes;
(5) FIG. 2 is a perspective view of a first embodiment of a four-bar linkage mechanism for pivotably supporting a cutting unit, the mechanism being shown in a neutral position;
(6) FIG. 3 is a simplified partial side view of a four-bar linkage mechanism similar to that one illustrated in FIG. 2 in a first pivoting position, e.g. an end position;
(7) FIG. 4 is a further partial side view corresponding to the view of FIG. 3, the four-bar linkage mechanism shown in another pivoting position, e.g. a start position;
(8) FIG. 5 illustrates a simplified side view of another embodiment of a four-bar linkage mechanism shown in a near-net shaped state;
(9) FIG. 6a illustrates a simplified side view of an injection molded intermediate arrangement from which a four-bar linkage mechanism may be formed;
(10) FIG. 6b is a further simplified schematic side view of a four-bar linkage mechanism that has been formed from a basically flat intermediate arrangement, as shown in FIG. 6a;
(11) FIG. 7 is a simplified perspective view of another embodiment of a linkage unit for pivotably supporting a cutting unit of a hair cutting appliance the linkage unit being shown in a start position;
(12) FIG. 8 is a simplified side view of the embodiment shown in FIG. 7;
(13) FIG. 9 is a simplified side view of yet another embodiment of a linkage unit for pivotably supporting a cutting unit of a hair cutting appliance, the linkage unit being shown in a neutral position;
(14) FIG. 10 is a simplified schematic partial perspective view of the embodiment shown in FIG. 9, wherein a basically hidden biasing element is shown, primarily for illustrative purposes; and
(15) FIG. 11 is a simplified side view of yet another embodiment of a linkage unit for pivotably supporting a cutting unit of a hair cutting appliance, the linkage unit being shown in a neutral position.
DETAILED DESCRIPTION OF THE INVENTION
(16) FIG. 1 schematically illustrates, in a simplified perspective view, an exemplary embodiment of a hair cutting appliance 10, particularly an electric hair cutting appliance 10. The cutting appliance 10 may include a housing 12, a motor indicated by a dashed block 14 in the housing 12, and a drive mechanism indicated by a dashed block 16 in the housing 12. For powering the motor 14, at least in some embodiments of the cutting appliance 10, an electrical battery, indicated by a dashed block 17 in the housing 12, may be provided, such as, for instance, a rechargeable battery, a replaceable battery, etc. However, in some embodiments, the cutting appliance 10 may be provided with a power cable for connecting a power supply. A power supply connector may be provided in addition or in the alternative to the (internal) electric battery 17.
(17) The cutting appliance 10 may further comprise a cutting head or cutting unit 18. At the cutting unit 18, a blade set 20 may be attached to the hair cutting appliance 10. The blade set 20 of the cutting unit 18 may be driven by the motor 14 via the drive mechanism 16 to enable a cutting motion.
(18) The cutting motion may be generally regarded as relative motion between a stationary blade 22 and a movable blade 24 of the blade set 20, see also FIGS. 1a and 1b. Generally, a user may grasp, hold and manually guide the cutting appliance 10 through hair in a moving direction 28 to cut hair. The cutting appliance 10 may be generally regarded as a hand-guided and hand-operated electrically powered device. Furthermore, the blade set 20 can be arranged at the cutting unit 18 in a pivoting manner, refer to the curved double-arrow indicated by reference numeral 26. In some embodiments, the cutting appliance 10, or, more specifically, the cutting unit 18 including the blade set 20, can be passed along skin to cut hair growing at the skin. When cutting hair closely to the skin, basically a shaving operation can be performed aiming at cutting (or chopping) at the level of the skin. However, also clipping (or trimming) operations may be envisaged, wherein the cutting unit 18 comprising a blade set 20 is passed along a path at a desired distance relative to the skin.
(19) When being guided or led through hair, the cutting appliance 10 including the blade set 20 is typically moved along a common moving direction which is indicated by the reference numeral 28 in FIG. 1. It is worth mentioning in this connection that, given that the hair cutting appliance 10 is typically manually guided and moved, the moving direction 28 thus not necessarily has to be construed as a precise geometric reference and having a fixed definition and relation with respect to the orientation of the cutting appliance 10 and its cutting unit 18 fitted with the blade set 20. That is, an overall orientation of the cutting appliance 10 with respect to the to-be-cut hair at the skin may be construed as somewhat unsteady. However, for illustrative purposes, it can be fairly assumed that the (imaginary) moving direction 28 is parallel (or generally parallel) to a main central plane of a coordinate system which may serve in the following as a means for describing structural features of the hair cutting appliance 10.
(20) For ease of reference, coordinate systems are indicated in several of FIGS. 1 to 10. By way of example, a Cartesian coordinate system X-Y-Z is indicated in FIG. 1. An X axis of the respective coordinate system extends in a generally longitudinal direction that is generally associated with length, for the purpose of this disclosure. A Y axis of the coordinate system extends in a lateral (or transverse) direction associated with width, for the purpose of this disclosure. A Z axis of the coordinate system extends in a height (or vertical) direction which may be referred to for illustrative purposes, at least in some embodiments, as a generally vertical direction. It goes without saying that an association of the coordinate system to characteristic features and/or embodiments of the hair cutting appliance 10 is primarily provided for illustrative purposes and shall not be construed in a limiting way. It should be understood that those skilled in the art may readily convert and/or transfer the coordinate system provided herein when being confronted with alternative embodiments, respective Figs. and illustrations including different orientations.
(21) FIGS. 1a and 1b illustrate a partial detailed view of the blade set 20 of the cutting unit 18 exemplarily shown in FIG. 1. The blade set 20 comprises a stationary blade 22 and a movable blade 24. By way of example, the blade set 20 may comprise at least one basically longitudinally extending leading edge or cutting edge 29. It is preferred that the blade set 20 comprises two cutting edges 29a, 29b that are laterally spaced apart from each other. The cutting edges 29a, 29b may be spaced from each other in the moving direction 28 that is basically parallel to the lateral direction Y. The stationary blade 22 and the movable blade 24 may comprise a basically flat shape. It is particularly preferred that the stationary blade 22 is arranged to house and to guide the movable blade 24. In other words, the stationary blade 22 may be regarded as a shell or a cage for the movable blade 24. The stationary blade 22 may comprise a cross-section, viewed in the plane perpendicular to the lateral direction Y, that is basically U-shaped, particularly at the at least one cutting edge. The U shaped form may comprise a first leg and a second leg. Between the first leg and the second leg a guiding slot for the movable blade 24 may be defined. The movable blade 24 can be housed and guided in the stationary blade 22 for longitudinal movement with respect to the stationary blade 22. The movable blade 24 and the stationary blade 22 may comprise respective teeth at their cutting edges that allow cutting of hairs in a scissor-like action. The stationary blade 22 basically encloses the movable blade 24 at the side thereof facing the skin when cutting hair and, at least partially, at the side thereof facing away from the skin when cutting hair.
(22) So as to suitably adapt the blade set 20 to shaving operations, it is preferred that a general height (or thickness) of the blade set 20, at least at the at least one cutting edge, is relatively small. Particularly, it is preferred that a skin-sided portion of the stationary blade 22 has a thickness that is relatively small. Even more preferably, the thickness of the stationary blade portion facing the skin is significantly smaller than the thickness of the stationary blade portion facing away from the skin, at least at the cutting edge. An exemplary blade set 20 for the hair cutting appliance 10 may comprise an overall height or thickness in the range of about 0.3 mm to about 0.75 mm. The height or thickness of the skin-facing portion of the stationary blade 22, at least at the at least one cutting edge, may be in the range of about 0.04 mm to about 0.25 mm. The height or thickness of the stationary blade portion facing away from the skin may be in the range of about 0.08 mm to about 0.4 mm. The height thickness of the movable blade 24, at least at the least one cutting edge, may be in the range of about 0.05 mm to about 0.5 mm. The height of the movable blade 24 may basically correspond to a height of the guiding slot defined by the stationary blade 22 for the movable blade 24.
(23) It is particularly preferred that the cutting unit 18 including the blade set 20 is pivoted or pivotably supported at the housing 12 of the hair cutting appliance 10. To this end, a linkage unit 30 in accordance with the principles of the present disclosure may be utilized. Reference is made in this regard to FIGS. 2, 3 and 4. FIG. 2 illustrates a perspective view of a first embodiment of the linkage unit 30 that is configured to support the cutting unit 18. The linkage unit 30 may comprise a four-bar linkage mechanism 32 that is arranged between the blade set 20 and the housing 12 of the cutting appliance 10, refer to FIG. 1. With further reference to FIG. 2, the linkage unit 30 is further detailed and exemplarily shown as comprising a first linkage section 34 and a second linkage section 36. The first linkage section 34 and the second linkage section 36 may be spaced from each other in the lateral direction Y. However, it may be envisaged that in some embodiments the four-bar linkage mechanism 32 basically comprises a single linkage section. The four-bar linkage mechanism 32 may be configured so as to permit a swiveling or pivoting motion of the cutting unit 18 about a (virtual) axis p that is a basically parallel to the Y-axis and, consequently, basically parallel to the at least one cutting edge 29a, 29b, refer also to FIG. 9 in this connection. A resulting swiveling motion during operation, e.g., when following an actual skin contour, is indicated in FIGS. 3 and 4 by respective double-arrows 26. FIG. 4 may indicate a first position, particularly an end position. FIG. 3 may indicate a second position, particularly a start position.
(24) The four-bar linkage mechanism 32 or, in some embodiments, each linkage section 34, 36 thereof, may comprise a base 38. In accordance with the exemplary embodiment shown in FIGS. 2, 3 and 4, the base 38 may comprise a first base portion 40a and a second base portion 40b. The base portions 40a and 40b may be spaced from each other in the lateral direction Y. Generally, the base 38 may be coupled or connected to the housing 12 of the hair cutting appliance 10 without considerable play during operation, such that basically no relative motion between the base 38 and the housing 12 is permitted. The four-bar linkage mechanism 32 or each respective linkage section 34, 36 thereof may further comprise a first arm 42 and a respective second arm 44. The first arm 42 and the second arm 44 may be spaced from each other in the lateral direction Y. Furthermore, a connecting bar 46 may be provided to which the blade set 20 of the cutting unit 18 is connected or coupled. The respective members of the four-bar linkage mechanism 32 may be movably or pivotably connected by respective pivots 48, 50, 52, 54. A first base pivot 48 may be arranged to connect the first arm 42 and the base 38 for a respective base portion 40a thereof. The second base pivot 50 may be arranged to connect the second arm 44 and the base 38 or a respective base portion 40b thereof. The first top pivot 52 may be configured to connect the first arm 42 and the connecting bar 46. Similarly, the second top pivot 54 may be configured to connect the second arm 44 and the connecting bar 46. Consequently, the top pivots 52, 54 may be spaced from the base pivots 50, 52 in the vertical direction Z.
(25) At least one or, more preferably, each of the pivots 48, 50, 52, 54 may be arranged as a living hinge. Particularly, the pivots 48, 50, 52, 54 may be arranged as film hinges. In other words, the base 38 including the base portions 40a, 40b, the first arm 42, the second arm 44 and the connecting bar 46 including their interposed pivots 48,50, 52, 54 may be integrally manufactured as a single piece, refer also to FIGS. 3 and 4. For instance, the four-bar linkage mechanism 32 may be formed as a single injection-molded part. As can be best seen in FIG. 2, the first linkage section 34 and the second linkage section 36 may be integrally formed as well. However, in the alternative, each of the first linkage section 34 and the second linkage section 36 may be formed as separate integrally-shaped part.
(26) As can be further seen from FIG. 2, the connecting bar 46 may further comprise at least one side arm 56, particularly a first side arm 56a and a second side arm 56b that may be coupled to the blade set 20. Each of the side arms 56a, 56b may extend outwardly from the connecting bar 46. The at least one side arm 56a, 56b may be inclined with respect to the connecting bar 46, and to the blade set 20. It is worth noting in this connection that, as discussed and described herein, structural features and relationships may typically refer to the neutral position (or centered position) of the linkage unit 30 as shown, for instance, in FIGS. 2, 5 and 9, unless otherwise indicated.
(27) FIG. 2 further illustrates an optional limit stop arrangement that may be regarded as relative limit stop arrangement. The limit stop arrangement comprises at least one contact tab 58, 60. As can be seen from FIG. 2, two corresponding contact tabs 58, 60 may be provided. A first contact tab 58 is provided at the first arm 42 and projects therefrom. A second contact tab 60 is provided at the connecting bar 46 or, more specifically, at the first side arm 56a thereof in a laterally protruding manner. Each of the contact tabs 58, 60 may cooperate with a respective contact surface of an opposing component. The contact tabs 58, 60 may cooperate so as to limit a relative pivoting motion between the connecting bar 46 and the first arm 42 about a pivoting axis defined by the hinge defining the first top pivot 52. When the first contact tab 58 and the second contact tab 60 contact or abut each other also general motion of the four-bar linkage mechanism 32 beyond the limit defined by the contact tab 58 and the contact tab 60 is basically prevented. Preventing excessive motion of the four-bar linkage mechanism 32 is beneficial since in this way excessive strain in the pivots 48, 50, 52, 54 can be avoided. Furthermore, the cutting unit 18 can be prevented from assuming undesired orientations, e.g., exaggerated swivel angles, that might increase the risk of skin irritation or even of skin cuts during operation. Preferably, at least two pairs of contact tabs 58, 60 are provided at the linkage mechanism 32 (not explicitly shown in FIG. 2).
(28) With particular reference to FIG. 5, an alternative embodiment of a four-bar linkage mechanism 32a is illustrated and further detailed. Similarly to the four-bar linkage mechanism 32 shown in FIG. 2, the four-bar linkage mechanism 32a illustrated in FIG. 5 comprises a base 38, a first arm 42, a second arm 44 and a connecting bar 46 that are coupled by respective first and second base pivots 48, 50 and first and second top pivots 52, 54. In contrast to the embodiment shown in FIG. 2, the base 38 is shaped as an integral component continuously (or directly) connecting the first base pivot 48 and the second base pivot 50. The four-bar linkage mechanism 32a exemplified in FIG. 5 is arranged as a closed arrangement or closed chain. By contrast, the four-bar linkage mechanism 32 exemplified in FIG. 2 is shaped as an open arrangement or an open chain. With further reference to FIG. 5, the four-bar linkage mechanism 32a is further detailed. An end stop arrangement is provided adding a first pair of contact tabs 58a, 60a at the first arm side of the mechanism 32a. The end stop arrangement further comprises a second pair of contact tabs 58b, 60b arranged at the second arm side of the mechanism 32a. Consequently, the pivoting motion of the four-bar linkage mechanism 32a can be limited both when moving forward and when moving back between a start position and an end position.
(29) It is particularly preferred that, in one embodiment, the four-bar linkage mechanism 32a shown in FIG. 5 is injection-molded, particularly as a three-dimensional near-net shaped molded part. Consequently, the four-bar linkage mechanism 32a and the respective linkage unit may be ready to install after the molding process. Costly finishing steps, alignment steps and effortful assembly steps can be prevented in this way.
(30) However, in some alternative embodiments, another manufacturing approach may be pursued. As best shown in FIG. 6a, a precursor or intermediate part of a four-bar linkage mechanism 32 may be formed, particularly injection-molded as a generally flat intermediate arrangement 62. The intermediate arrangement 62 may comprise at least one thinned recess 64. The at least one thinned 64 recess may define, later on, the respective pivots 48, 50, 52, 54 of the four-bar linkage mechanism 32. The initially basically flat intermediate arrangement 62 of FIG. 6a is shown in FIG. 6b at an advanced manufacturing stage. By deforming, particularly bending, the intermediate arrangement 62, a basically three-dimensional shape of the four-bar linkage mechanism 32 may be achieved. FIG. 6b further illustrates an exemplary open-chain arrangement of the four-bar linkage mechanism 32.
(31) FIG. 7 and FIG. 8 illustrate another alternative embodiment of a linkage unit 30a. The linkage unit 30a may comprise a four-bar linkage mechanism 32b that is basically formed in accordance with at least some of the principles of the embodiments shown in FIGS. 1 to 6b. However, the four-bar linkage mechanism 32b may differ therefrom in that the connecting bar 46, or in other words, the top coupling portion thereof, may be formed by the cutting unit 18 itself. In other words, the four-bar linkage mechanism 32b may comprise a first connecting arm 66a connected to the first arm 42 via the first top pivot 52 and a second connecting arm 66b connected to the second arm 44 via the second top pivot 54. The first connecting arm 66a and the second connecting arm 66b are (mediately) fixedly connected to each other via the cutting unit 18. More particularly, the first connecting arm 66a and the second connecting arm 66b are basically prevented from relative motion. This embodiment may further allow splitting the four-bar linkage mechanism 32b into two laterally spaced-apart parts.
(32) The linkage unit 30a further comprises an absolute end stop arrangement. The end stop arrangement may comprise an end stop support 68. The end stop support 68 may comprise at least one end stop beam 70, 72. Preferably, a first pair of outer end stop beams 70 is provided. Accordingly, a second pair of inner end stop beams 72 may be provided. The end stop beam 70 may be arranged to directly or indirectly corporate with the connecting bar 46 to limit a respective swiveling or pivoting motion thereof. The end stop beam 72 may be configured to corporate with at least one of the first arm 42 and the second arm 44 to limit a respective swiveling or pivoting motion thereof. At least one end face 74a, 74b may be provided at the end beam 70. At least one end face 76a, 76b may be provided at the end beam 72.
(33) The at least one end face 74a, 74b of the end beam 70 may be arranged to contact or abut a respective contact surface that is associated to the connecting bar 46. The at least one end face 76a, 76b of the end beam 72 may be arranged to contact or abut a corresponding contact surface at at least one of the first arm 42 and the second arm 44. The absolute end stop arrangement illustrated in FIGS. 7 and 8 may be beneficial insofar as excessive motion can be limited by external components that are separate from the moving components of the four-bar linkage mechanism 32b. Both FIG. 7 and FIG. 8 illustrate the four-bar linkage mechanism 32 b in a start position.
(34) With particular reference to FIG. 9 and FIG. 10, yet another exemplary embodiment of a linkage unit 30b is exemplified. The linkage unit 30b may comprise a four-bar linkage mechanism 32 that may basically correspond to the embodiment of the four-bar linkage mechanism 32 illustrated in FIG. 2. Apart from that, the linkage unit 30b further comprises at least one biasing element 80a, 80b. Particularly, a first biasing element 80a associated with the first arm 42 may be provided. The first biasing element 80a may be configured to urge the first arm 42 in a first biasing direction 82a. In some embodiments, a second (support) biasing element 80b associated with the second arm 44 may be provided. The second biasing element 80b may be configured to urge the second arm 44 in a second biasing direction 82b. The first biasing direction 82a and the second biasing direction 82b, the biasing elements 80a, 80b may basically bias the first arm 42 and the second arm 44 in opposing directions 82a, 82b. The biasing elements 80a may ensure that the four-bar linkage mechanism 32 returns to the start position illustrated in FIG. 8 after being pivoted when in operation. The biasing element 80a may ensure a basically free-of-play support of the linkage mechanism 32.
(35) As can be schematically seen from FIG. 10, the at least one biasing element 80a, 80b may be configured as a torsion bar spring 80, for example. The torsion bar spring 80 may comprise torsion bar 84 and a first leg 86 and a second leg 88 provided at respective ends of the torsion bar 84. A side view of similar arrangements of the first biasing element 80a and the second biasing element 80b is illustrated in FIG. 9.
(36) Particularly the torsion bar 84 of the torsion bar spring 80 can be mounted at the base 38. Furthermore, the first leg 86 may be fixed in the base 38 against undesired rotation about an excessive find by the torsion bar 84. The torsion bar spring 80 may be designed and shaped such that upon mounting the torsion bar 84 at the base 38 and fixing the first leg 86 at the base 38 the second leg 88 can biased against the first arm 42.
(37) As can be best seen from FIG. 9, the at least one biasing element 80a, 80b can be arranged in the vicinity of or, proximate to the respective first arm 42 and the second arm 44 of the four-bar linkage mechanism 32. Consequently, a central portion of the linkage mechanism 32 can be kept free and unobstructed such that sufficient design space is provided for driving the movable blade of the blade set 20 of the cutting unit 18. It may be further envisaged that each of the linkage sections 34, 36 (refer to FIG. 2) is associated with a respective first biasing element 80a that is configured to urge the linkage mechanism into the start position.
(38) As can be further seen from FIG. 9, the four-bar-linkage mechanism 32, at least in some preferred embodiments, may be designed such that a resulting virtual pivot axis p defined is basically parallel to the at least one toothed cutting edge 29a, 29b, refer also to FIGS. 1a and 1b. Furthermore, the four-bar-linkage mechanism 32 may be configured to include a pivot axis p that is, at least in the neutral position illustrated in FIG. 9, offset from a skin-facing side of the blade set 20 in the vertical direction Z towards the skin. The skin-facing side may be also referred to as top surface 90 for the purpose of this disclosure. A corresponding offset dimension l.sub.o is illustrated in FIG. 9. In other words, the (virtual) pivot axis p of the four-bar-linkage mechanism 32 may be shifted into the skin in some embodiments. This may further improve the shaving performance. Such a configuration cannot be achieved with conventional real structural pivot arrangements. However, in some alternative embodiments, the virtual pivot p may be arranged above the skin level, i.e. below the level of the top surface 90. It is preferred that the pivot offset dimension l.sub.o is, at least in the neutral position, in the range of about ?2.0 mm to about +5.0 mm, preferably in the range of about ?1.0 mm to about +2.0 mm, more preferably in the range of about +0.25 mm to about +0.75 mm. As used herein, + (plus) refers to an arrangement, wherein the pivot axis p is positioned above the level of the top surface 90, i.e. shifted into the skin. By contrast, ? (minus) refers to an arrangement, wherein the pivot axis p is positioned below the level of the top surface 90, i.e. above the skin.
(39) With particular reference to FIG. 11, another alternative embodiment of a linkage unit 30c for pivotably connecting a cutting unit 18 and a housing 12 of a hair cutting appliance 10 (refer also to FIG. 1) is illustrated and further detailed. The linkage unit 30c comprises a four-bar-linkage mechanism 32a that is provided with at least one pivot joint that may comprise a pivot pin that cooperates with two to-be-coupled elements, e.g. via at least one respective distinct pivot seat. The pivot pin can be received at the at least one pivot seat. The pivot pin and the pivot seat may cooperate so as to define a pivot bearing.
(40) The four-bar-linkage mechanism 32a comprises a base 38a, a first arm 42a, a second arm 44a, and a connecting bar 46a. The base 38a is interposed between the first arm 42a and the second arm 44a at a base end thereof. The connecting bar 46a is interposed between the first arm 42a and the second arm 44a at a top end thereof. Between the base 38a and the first arm 42a, a first base pivot or base pivot joint 48a may be provided. Between the base 38a and the second arm 44a, a second base pivot or base pivot joint 50a may be provided. Between the connecting bar 46a and the first arm 42a, a first top pivot or top pivot joint 52a may be provided. Between the connecting bar 46a and the second arm 44a, a second top pivot or top pivot joint 54a may be provided. It goes without saying that at least one of the pivots 48a, 50a, 52a, 54a may be provided as a living hinge. However, it may be preferred in connection with the embodiment shown in FIG. 11 that each of the pivots 48a, 50a, 52a, 54a is an assembled pivot joint comprising at least one distinct part that is not integrally formed with both respective the to-be-coupled elements.
(41) Also the four-bar-linkage mechanism 32a of FIG. 11 may define a virtual pivot axis p that is, in the neutral position (or middle position) illustrated in FIG. 11, offset from a top surface 90 of the blade set 20 by a pivot offset dimension l.sub.o, as discussed above.
(42) Although illustrative embodiments of the present invention have been described above, in part with reference to the accompanying drawings, it is to be understood that the invention is not limited to these embodiments. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the stationary blade, the blade set, etc. according to the present disclosure. Thus, the appearances of the phrases in one embodiment or in an embodiment in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, it is noted that particular features, structures, or characteristics of one or more embodiments may be combined in any suitable manner to form new, not explicitly described embodiments.
(43) In the claims, the word comprising does not exclude other elements or steps, and the indefinite article a or an does not exclude a plurality. A single element or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
(44) Any reference signs in the claims should not be construed as limiting the scope.
