Patent Publication Number: US-11642802-B2

Title: Electric beard trimmer

Description:
FIELD OF THE INVENTION 
     The present invention relates to cutting body hair such as beard stubbles of multidays&#39; beard. 
     More particularly, the present invention relates to a cutter system for an electric shaver and/or trimmer, comprising a pair of cooperating cutting elements with two rows of comb-like cutting teeth at opposite edges thereof and at least one field of cutting perforations between said rows of comb-like cutting teeth, wherein said cutting elements are movably supported relative to each other by a support structure with an inner one of the cutting elements being sandwiched between an outer one of the cutting elements and said support structure, wherein said support structure includes a pair of outer frame portions holding said outer cutting element at opposite edge portions thereof and a pair of inner frame portions supporting the inner cutting element with a gap being defined between said inner frame portions and said outer cutting element to movably accommodate said inner cutting element. 
     BACKGROUND OF THE INVENTION 
     Electric shavers and trimmers utilize various mechanisms to provide hair cutting functionality. Some electric shavers include a perforated shear foil cooperating with an undercutter movable relative thereto so as to cut hairs entering the perforations in the shear foil. Such shear foil type shavers are often used on a daily basis to provide for a clean shave wherein short beard stubbles are cut immediately at the skin surface. 
     On the other hand, other cutter systems including a pair of cooperating cutting elements with comb-like edges including one or more rows of comb-like or rake-like cutting teeth reciprocating or rotating relative to each other, are often used for cutting longer beard stubbles or problem hair that is difficult to cut due to, for example, a very small angle to the skin or growing from very resilient skin. The teeth of such comb-like or rake-like cutting elements usually project substantially parallel to each other or substantially radially, depending on the type of driving motion, and may cut hairs entering into the gaps between the cutting teeth, wherein cutting or shearing is achieved in a scissor-like way when the cutting teeth of the cooperating elements close the gap between the finger-like cutting teeth and pass over each other. 
     Such cutter systems for longer hairs may be integrated into electric shavers or trimmers which at the same time may be provided with the aforementioned shear foil cutters. For example, cutting elements may include two rows of comb-like cutting teeth arranged, for example, at opposite sides of the cutting elements and a field of shear foil-like cutting perforations between said rows of comb-like cutting teeth. 
     For example, EP 24 25 938 B1 shows a shaver with a pair of long hair trimmers integrated between shear foil cutters. Furthermore, EP 27 47 958 B1 and CN 206 287 174 U disclose hair trimmers having two rows of cooperating cutting teeth arranged at opposite sides of the shaver head, wherein the cutting teeth of the upper comb-like cutting element are provided with rounded and thickened tooth tips overhanging the tooth tips of the lower cutting element so as to prevent the projecting tooth tips from piercing into the skin and from irritating the skin. A similar cutter system is shown in US 2017/0050326 A1 wherein in such cutter system the lower comb-like cutting element is fixed and the upper comb-like cutting element is movable. 
     Shavers and/or trimmers combining rows of comb-like cutting teeth at opposite edges and shear foil-like cutting perforations between said rows of comb-like teeth sometimes include C-shaped outer cutting elements the edges of which are dog-eared to form limbs bent inwardly like the limbs of a C or a U, wherein such dog-eared limbs are held by a support frame. The transitional edge portion connecting the dog-eared limbs with the central portion of the outer cutting element is contoured or configured to form a row of comb-like teeth for cutting longer stubbles, whereas the central portion of the cutting element is provided with at least one field of perforations for cutting short hair. Said outer cutting element cooperates with an inner cutting element which may be plate-shaped and may include rows of comb-like teeth at opposite edges to cooperate with the comb-like teeth of the outer cutting element, and furthermore at least one field of perforations or other cutouts between the comb-like toothed edges for cooperating with the perforations in the outer cutting element. 
     Thus, shear foil like cutting perforations for cutting short hairs and comb-like cutting teeth for cutting longer hairs or stubbles may be integrated into the same cutting elements, wherein the inner cutting element may be biased against the outer cutting element usually by means of a spring device which may include a pair of flexible spring arms extending from a central base portion of the support structure towards the inner cutting element. Said spring arms may have a sort of V-shaped configuration and may contact the inner cutting element at sections between the central field of perforations and the opposite toothed edges. Due to such biasing of the inner cutting element against the outer cutting element, tugging and pulling hairs to be cut in the perforations can be avoided, but, on the other hand, the friction between the cutting elements is rather high what causes high energy consumption by the drive unit and furthermore heating of the cutting elements what is often felt unpleasing or uncomfortable. Such cutter systems are shown in documents CN 209 478 241 U and US 2018/0257248 A1. 
     A similar cutter system is disclosed by EP 31 31 716 B1, wherein the support structure includes an outer frame holding the outer cutting element at opposite edge portions thereof, wherein such outer frame includes, at its inner surface, a step-like projection forming a shoulder for supporting the inner cutting element at the toothed, comb-like edges. More particularly, said projecting shoulder at the inner surface of the outer support frame defines a gap extending from said shoulder to the outer cutting element, in which gap the inner cutting element is slidably received, wherein such gap provides for a vertical clearance which is adapted to the vertical thickness of the inner cutting element. Depending on the vertical clearance between the projecting shoulder and the outer cutting element, friction may be reduced, whereas the cutter system is prone to pulling and tugging hair to be cut by the cutting perforations since the inner cutting element may not be held close enough to the outer cutting element so hair to be cut may get stuck between the cutting perforations of the outer cutting element and the perforations or cutouts of the inner cutting element cooperating therewith. 
     Such beard stubble trimmers and shavers need to address quite different and diverging functional requirements and performance issues such as closeness, thoroughness, good visibility of the cutting location, efficiency and pleasant skin feel, good ergonomics and handling. Closeness means short or very short remaining stubbles, whereas thoroughness means less missed hairs particularly in problem areas like the neck. Efficiency means less and faster strokes suffice to achieve the desired trimming result. Pleasant skin feel depends on the individual user, but often includes less irritation in form of nicks, cuts or abrasion and better gliding onto the skin. Visibility of the cutting location is particularly important in case of styling or edging contours to accomplish hair removal with local accuracy. 
     Fulfilling such various performance issues at the same time is quite difficult. Meeting such needs becomes even more difficult when different types of cutting contours such as shear foil-like perforations and comb-like rows of teeth are integrated into the same cutting elements such as C-shaped cutting blades reciprocating relative to each other since such multiple-function cutter elements may not be adapted exclusively to one specific cutting function. 
     SUMMARY OF THE INVENTION 
     It is an objective underlying the present invention to provide for an improved cutter system avoiding at least one of the disadvantages of the prior art and/or further developing the existing solutions. A more particular objective underlying the invention is to provide for a close and thorough cutting of hair and longer stubbles including a good control of edging contours and, at the same time, avoiding skin irritations. Another objective underlying the present invention is a reliable and clean cutting action of the cooperating cutting teeth and cutting perforations to avoid pulling and tugging of hair, without sacrificing low friction between the cutting elements, low temperatures of the cutting teeth and low energy consumption and thus long energy storage life. 
     According to an aspect, friction, heat release and reduced battery life can be avoided, but nevertheless a clean and reliable cutting action avoiding pulling and tugging of hair can be achieved by means of a specific support structure holding the cutting elements and the cutting teeth and perforations thereof sufficiently close to each other, but still allowing for low friction movements of the cutting elements relative to each other. More particularly, one of the cutting elements may be sandwiched between the other cutting element and said support structure, wherein said support structure includes a pair of outer frame portions holding said outer cutting element at opposite edge portions thereof and a pair of inner frame portions supporting the inner cutting element with a gap being defined between said inner frame portions and said outer cutting element in which gap said inner cutting element is movably received. So as to keep the cutting elements sufficiently close to each other without generating high friction, said inner frame portions form rigid support ribs extending from a base portion of said support structure at a steeper angle than said outer frame portions and forming rigid support edges supporting the inner cutting element along the outer edge of said field of cutting perforations. Due to the rigidity of said supporting ribs, the position of the support edges is kept and maintained precisely under different load conditions so the inner cutting element does not need to be biased against the outer cutting element, but is nevertheless kept and supported exactly in a desired position at the outer cutting element. The ribs do not flex under operational loads what allows for exact support of the inner cutting element in the desired position. 
     The rather steep inclination of the support ribs originating from a central base portion, gives the support structure rather high stiffness without necessitating heavy, bulky frame structures and allows to hold the inner cutting element sufficiently close to the outer cutting element without necessitating bias of the inner cutting element against the outer cutting element, thereby avoiding pulling and tugging of hair, without sacrificing low friction between the cutting elements, low temperatures of the cutting teeth and low energy consumption and thus long energy storage life. 
     At the same time, as the support edges support the inner cutting element at a section between the comb-like teeth and the cutting perforations, both cutting systems, i.e. the comb-like cutting teeth and the shearfoil-like cutting perforations may operate efficiently, wherein positioning the rigid support edges next to or in close proximity to the cutting perforations along the outer edge of said field of cutting perforations, helps in making the cutting perforations smoothly cut even very short hairs without tugging and pulling. 
     Thus, the sandwiched cutting element may move relative to the outer cutting element without friction or at very low friction, but is nevertheless prevented from deflection even when the thickness of the sandwiched cutting element is very small. To achieve low friction and avoid clamping of hairs between the cutting teeth at the same time, the gap defined between the rigid support edges of the support ribs and the outer cutting element may have a thickness which is larger than the thickness of the sandwiched cutting element only by an amount smaller than the thickness of usual hair such as for example less than 40 μm thicker than the sandwiched cutting element. 
     These and other advantages become more apparent from the following description giving reference to the drawings and possible examples. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1   : perspective views of an electric beard trimmer/shaver including a cutting system with a pair of cooperating comb-like cutting elements reciprocating relative to each other, wherein partial view (a) shows a front side of the electric beard trimmer and partial view (b) shows the beard trimmer working on a chin, 
         FIG.  2   : a cross sectional view of the beard trimmer/shaver showing the cooperating comb-like cutting elements and the drive system for driving said cutting elements, 
         FIG.  3   : a perspective view of the cutter system including the pair of cooperating comb-like cutting elements and the support structure for supporting the cutting elements relative to each other, 
         FIG.  4   : a cross sectional view of the cutter system and the support structure, wherein the C-shaped outer cutting element is shown to be bent or curved around outer frame portions and an inner cutting element is shown to be supported by a V-shaped inner support frame forming rigid support ribs extending from a base portion of the support structure at a steeper angle then said outer frame portions, 
         FIG.  5   : an exploded perspective view of the elements of the cutter system including the outer and inner cutting elements, an outer support frame for holding the outer cutting element, a chute-shaped or trough-shaped inner support frame including rigid support ribs for supporting the inner cutting element, a driving element for reciprocating the inner cutting element and guide blocks for guiding the reciprocating driving element, 
         FIG.  6   : a side view showing the pivoting of the cutter system relative to the handle of the shaver/trimmer as allowed by the support structure, and 
         FIG.  7   : a side view showing the cutter system pivoting about its pivot axis when following the skin contour. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     So as to achieve a smooth, comfortable cutting action, it is helpful to avoid separating the cutting elements and thus, the cooperating comb-like teeth and/or the cooperating cutting perforations from one another so as to avoid that hair is no longer properly cut or even clamped between the teeth moving relative to each other or between the cutting perorations moving relative to each other. Basically, this can be prevented by means of pressing the cooperating cutting elements against each other, for example by means of spring devices urging the teeth of one cutting element against the teeth of the other cutting element. However, large contact pressure between the cooperating teeth and the cooperating perforations increases the friction what in turn causes heat. Such heating of the cutting elements is, however, irritating the skin and makes the user feel uncomfortably at least. Moreover, increasing the contact pressure and thus the friction also increases the energy necessary to drive the cutting elements relative to each other and thus, reduces battery life. 
     In order to combine reliable and comfortable cutting without pulling and tugging hairs on the one hand with efficient movability of the cutting elements with reduced friction, reduced heat generation and thus extended battery life on the other hand, the cutting elements may be supported relative to each other by means of an improved support structure. More particularly, one of the cutting elements may be sandwiched between the other cutting element and support elements or a support structure like a support frame which may include rigid ribs or web-like flanges precisely and rigidly supporting and guiding the inner cutting element at a predetermined position under the outer cutting element and sufficiently close thereto, said rigid support ribs and the outer cutting element defining a gap in which the sandwiched cutting element is slidably and/or movably received, wherein said gap may be slightly thicker than the sandwiched cutting element to provide for some play at least during non-use to reduce friction and heat generation. When the outer cutting element is pressed against the skin or at least contacts the skin during operation of the shaver/trimmer, it may deflect and at least then closely fits onto the inner cutting element. Although the sandwiched cutting element may move relative to the other cutting element without friction or at very low friction, it is nevertheless prevented from deflection even when the thickness of the sandwiched cutting element is very small. 
     The steep inclination of the support ribs and the origin of the ribs at a central base portion of the support structure makes them rather stiff and prevents them from deflection, bending or buckling due to reaction forces caused by skin contact pressure onto the cutting elements as such forces may be taken up straight and do not have much leverage. Such rather high stiffness of the support ribs may hold the inner cutting element sufficiently close to the outer cutting element without necessitating bias of the inner cutting element against the outer cutting element, thereby avoiding pulling and tugging of hair, without sacrificing low friction between the cutting elements, low temperatures of the cutting teeth and low energy consumption and thus long energy storage life. At the same time, as the support edges support the inner cutting element at a section between the comb-like teeth and the cutting perforations, both cutting systems, i.e. the comb-like cutting teeth and the shearfoil-like cutting perforations may operate efficiently, wherein positioning the rigid support edges next to or in close proximity to or immediately adjacent the cutting perforations along the outer edge of said field of cutting perforations, helps in making the cutting perforations smoothly cut even very short hairs without tugging and pulling. 
     To achieve low friction and avoid clamping of hairs between the cutting teeth at the same time, said gap from the tip portions of the supporting ribs to the outer cutting element may have a thickness which is larger than the thickness of the sandwiched cutting element only by an amount smaller than the thickness of hair to be cut. 
     More particularly, the amount by which the width of said gap exceeds the thickness of the sandwiched cutting element may be less than 40 μm. For example, it may range from 20 μm to 40 μm. Such configuration is a good compromise between still easy manufacturing and sufficiently small risk of pulling and tugging hair to be cut. 
     So as to give the support ribs sufficient rigidity, said support ribs may extend from the base portion of the support structure at an angle ranging from 2×20° to 2×40° or 2×25° to 2×30°, wherein said angle may be measured against a plane which is parallel to the axis of reciprocating and perpendicular to the surface of the outer cutting element at a center portion thereof. In other words, the support ribs may extend from the center portion of the support structure at an angle of about 2×30° relative to a center plane perpendicular to the skin contact surface defined by the outer cutting element. 
     The base portion backing the rigid support ribs may be a central portion of the support frame structure extending centrally under the cutting elements and spaced apart therefrom. 
     Said skin contact surface defined by the outer cutting element may be substantially plane or flat. In the alternative, said skin contact surface defined by the outer cutting element may be slightly convex or slightly dome-shaped when viewed in a cross section taken perpendicular to the reciprocating direction. When viewed in a cross sectional plane parallel to said axis of reciprocation, the skin contact surface may be linear. Thus, the skin contact surface may be slightly, smoothly convex in terms of a shallow chute-like or trough-like shape. 
     Both the outer cutting element and the inner cutting element may have such shape corresponding to the skin contact surface. 
     So as to keep the inner and outer cutting elements snugly fitting onto each other in the region where the cutting perforations are formed, it may be helpful when the rigid support ribs, with their support edge, extend directly adjacent to or closely neighboring an outer boundary of the field of perforations. The support ribs, with their support edges, may contact the inner cutting element immediately along the outermost rows of perforations. 
     In the alternative, said support edge of the support ribs may contact the inner cutting element along a line spaced apart from the outermost rows of perforations. Nevertheless, the support edges of the support ribs may be positioned closer to the outermost rows of perforations then to the cutting teeth at the opposite edges of the cutting elements. More particularly, the distance of the support edges of the support ribs from the field of perforations may be less than ⅓ or less than ¼ of the distance of the support edges from the comb-like cutting teeth. 
     So as to take up the skin contact pressure induced in the inner cutting element via the outer cutting element in a balanced way, the support edges of the support ribs facing the inner cutting element may be spaced from each other at a distance ranging from 35% to 70% or 40% to 60% of the distance defined between the rows of comb-like teeth at the opposite edges of the cutting elements. Depending on the user&#39;s preference, different portions of the skin contact surface defined by the outer cutting element may be pressed against the skin with varying forces so that varying skin pressure may arise. So as to balance such varying pressures, it is helpful when the inner cutting element is supported by said rigid support ribs at about ⅓ and about ⅔ of the span width of the inner cutting element when considering a cross sectional view thereof. 
     Said support ribs and/or their supporting edges contacting the inner cutting element may extend parallel to the axis of reciprocation and/or parallel to the rows of comb-like teeth at the opposite edges of the cutting elements. 
     The support ribs may be anchored at the base portion of the support structure in different ways. For example, the support ribs may be welded to said base portion or embedded in the material of said base portion. For example, when there are separate support ribs, each of the ribs may be inserted into a slot-like recess in said base portion to hold the support ribs in the desired orientation and position. 
     In the alternative, the support ribs inclined to each other at an acute angle, may be connected to each other in one piece and/or form integral parts of a support rib element. More particularly, the support ribs may be formed by V-like or dog-eared limbs of a support frame insert that can be inserted into the support structure supporting the cutting elements and/or attached to the base portion of such support structure. Such support rib insert may have a chute-like or trough-like configuration including a strip-like bottom portion from which the two support ribs extend at the described inclination. Such chute-like insert can be inserted into the support structure and fixedly attached to the base portion thereof. For example, the bottom portion of the insert may be seated onto the inner surface of a bottom portion of the outer support frame at a center portion thereof, wherein the central bottom portion of the outer support frame may form a seat for the support rib insert. Seating the support rib insert onto the bottom portion of the outer support frame may take up the support forces and pressure induced into the support ribs, thereby pressing the support rib insert onto the bottom portion of the outer support frame. 
     Said inner support frame insert may be fixedly attached to the outer support frame, e.g. glued and/or welded and/or form-fitted thereto. 
     Said inner support frame forming said rigid support ribs and the outer support frame portions holding the outer cutting element may be formed from different materials. For example, the outer support frame portions may be made from plastic, whereas the inner support frame may be made from metal. 
     In the alternative, both inner and outer support frames may be made from the same material, for example from metal. 
     Irrespective of the materials, the inner support frame, in particular the rigid support ribs, when viewed in cross section, may have a thickness significantly smaller than the thickness of the outer support frame portions holding the outer cutting element. More particularly, the thickness of the rigid support ribs, when viewed in cross section, may range from 20% to 65% or 30% to 50% of the thickness of the outer frame portions holding the outer cutting element. 
     Said outer support frame portions holding the outer cutting element at opposite edge portions thereof, together with the outer cutting element may define a cutter head chamber which may be configured tube-like or barrel-like with open or closed end faces. So as to allow hair dust or cut hair stubbles to be discharged from such cutter head chamber, the axial end sides of said cutter head chamber may be open. 
     More particularly, such cutter head chamber defined by the outer frame portions and the outer cutting element may be divided into a plurality of sub-chambers by the aforementioned support ribs of the inner support frame. More particularly, the cutter head chamber may be divided by the rigid support ribs into an inner sub-chamber for collecting short hair particles from the cutting perforations and a pair of outer sub-chambers for collecting long hair particles cut by the comb-like cutting teeth. 
     Each of said inner and outer sub-chambers may extend from the base portion of the support structure to the inner cutting element, wherein said paid of outer sub-chambers together may define a volume ranging from 50% to 120% or 66% to 100% of the volume of said inner sub-chamber. In other words, the inner subchamber may have a volume larger than the outer subchambers. 
     The hair dust collected in the inner sub-chamber and coming from the perforations as well as the cut hair stubbles collected in the outer sub-chambers may be discharged from the respective subchambers via at least one open end face, wherein each of opposite ends of said subchambers may be open to enhance cleaning of said subchambers and discharging collecting hair dust therefrom. 
     The sandwiched cutting element may be driven by a driver which is connected to the inner cutting element and coupled to a drive train transmitting a driving action of a drive unit, wherein the aforementioned inner support frame including the rigid support ribs and the outer support frame including the outer frame portions holding the outer cutting element and the base portion backing the inner support frame, may include one or more central, elongated or slit-like throughholes in which a portion of said driver and/or said drive train is slidably received. In other words, the driver and/or drive train extends through said throughhole in the inner and outer support frames and is slidably received therein to allow for reciprocating of the driver and thus, the sandwiched cutting element relative to the other cutting element. 
     The driver may include an elongated rod-like portion attached to opposite end portions of the inner cutting element and accommodated in the inner sub-chamber defined between the rigid support ribs and the inner cutting element. 
     The sandwiched cutting element may be the driven cutting element which may reciprocate or rotate, depending of the type of drive. 
     Basically, each of the cooperating cutting elements may be driven. However, to combine an easy drive system with safe and soft cutting action, the upper or outer cutting element having the skin contact surface may be standing and/or may be not reciprocating and not rotating, whereas the lower or inner cutting element which may be the sandwiched cutting element, may reciprocate or rotatorily oscillate. 
     As can be seen from  FIGS.  1  and  2   , the cutter system  3  may be part of a cutter head  2  which may be attached to a handle  100  of a shaver and/or trimmer  1 . More particularly, the shaver and/or trimmer  1  may include an elongated handle  100  accommodating a battery  104 , the electronic and/or electric components such as a control unit  111 , an electric drive motor  103  or a magnetic drive motor and a drive train  109  for transmitting the driving action of the motor to the cutter system at the cutter head  2  which cutter head  2  may be positioned at one end of the elongated handle  100 , cf.  FIGS.  1  and  2   . 
     The cutter system  3  including a pair of cooperating cutting elements  4  and  5  may be the only cutter system of the cutter head  2  as it is the case with the example shown in  FIG.  1   . On the other hand, the cutter system  3  may be incorporated into a shaver head  2  having other cutter systems such as shear foil cutters, wherein, for example, the cutter system  3  having at least one row of cooperating cutting teeth  6 ,  7  may be positioned between a pair of shear foil cutters, or, in the alternative, may be positioned in front of such a shear foil cutter. 
     As shown by  FIG.  1   , the cutter system  3  may include elongated rows of cutting teeth  6  and  7  which may reciprocate relative to each other along a linear path so as to effect the cutting action by closing the gaps between the teeth and passing over each other. On the other hand, the cutter system  3  also may include cutting teeth  6  and  7  which are aligned along a circle and/or are arranged radially. Such rotatory cutting elements  4  and  5  may have cutting teeth  6  and  7  projecting substantially radially, wherein the cutting elements  4  and  5  may be driven to rotate relative to each other and/or to rotatorily oscillate relative to each other. The cutting action is basically similar to reciprocating cutting elements as the radially extending teeth, when rotating and/or rotatorily oscillating, cyclically close and reopen the gap between neighboring teeth and pass over each other like a scissor. 
     As shown by  FIG.  2   , the drive system may include a motor the shaft of which may rotate an eccentric drive pin which is received between the channel-like contours of a driver  18  which is connected to one of the cutting elements  4  which is caused to reciprocate due to the engagement of the rotating eccentric drive pin with the contours of said driver  18 . 
     As shown by  FIGS.  3 ,  4  and  5   , the cooperating cutting elements  4  and  5  basically may have—at least roughly—a plate-shaped configuration, wherein each cutting element  4  and  5  includes two rows of cutting teeth  6  and  7  which may be arranged at opposite longitudinal sides of the plate-like cutting elements  4  and  5 , cf.  FIG.  4    and  FIG.  5   . The cutting elements  4  and  5  are supported and positioned with their flat sides lying onto one another. More particularly, the cutting teeth  6  and  7  of the cutting elements  4  and  5  touch each other back to back like the blades of a scissor. 
     In addition to such comb-like cutting teeth  6  and  7 , the cooperating cutting elements  4  and  5  may be provided with at least one field of cutting perforations arranged between the rows of cutting teeth  6  and  7  in a middle portion of the cutting elements  4  and  5 . More particularly, the outer cutting element  4  defining a skin contact surface of the cutter system  3  may include at least two rows of perforations  8  which may be formed as small sized throughholes having a circular, oval, elliptical or polygonal shape. 
     In particular, such small sized throughholes forming the perforations  8  may have a hexagonal shape, wherein the long axis of such hexagonal throughholes, i.e. the axis going through opposite corners of the hexagonal shape, may be oriented transverse to the reciprocating axis  10  of the cutting elements  4  and  5 . 
     Such perforations  8  in the outer cutter element  4  may cooperate with perforations  9  in the inner cutting element  5  when said cutting elements  4  and  5  reciprocate relative to each other along the axis of reciprocating  10 . Said perforations  9  in the inner cutting element  5  also may be formed as small sized throughholes of a shape corresponding to or differing from the shape of the perforations  8  in the outer cutting element  4 . However, as can be seen from  FIG.  5   , the perforations  9  in the inner cutting element  5  do not need to be small sized throughholes, but may be larger sized cutouts each cooperating with more than one perforations  8  in the other cutting element  4 . More particularly, the perforations  9  in the inner cutting element  5  may be formed as longitudinal, slot-like cutouts extending, with their longitudinal axis, transverse to the axis of reciprocation  10 . Thus, each elongated transverse perforation  9  in the inner cutting element  5  may cooperate with each row of perforations in the outer cutting element  4 . 
     Said cutouts in the inner cutting element  5  overlap with the perforations  8  in the outer cutting element  4  and, depending on the reciprocating action, close said perforations  8  to effect a shearing action and/or cutting-off of hairs introduced into the perforations  8  and  9 . 
     As can be seen from  FIG.  3   , said rows of perforations  8  may substantially extend parallel to the rows of comb-like cutting teeth  6  and  7  in a portion of the cutting elements  4  and  5  between said rows of comb-like cutting teeth  6  and  7 . Said rows of perforations  8  may be spaced apart from said comb-like cutting teeth, wherein unperforated strip-like sections of the outer cutting element  4  may be arranged between the comb-like cutting teeth  6  and  7  and the field of perforations  8 . 
     As can be seen from  FIG.  3   , a central portion of the outer cutting element may define an unperforated skin contact surface and thus, a strip-like center portion dividing the field of perforations  8  into a pair of subgroups of perforations  8  each including a plurality of rows of perforations. 
     So as to support the cutting elements  4  and  5  in the aforementioned position lying and/or seated onto each other back-to-back, but still allowing reciprocating movement of the cutting teeth  6  and  7  and the perforations  8  and  9  relative to each other, the inner cutting element  5  is sandwiched between the outer cutting element  4  and a support structure  14  which includes an inner frame supporting the inner cutting element  5  and an outer frame  12  holding the outer cutting element  4 . 
     More particularly, said support structure  14  defines a gap  16  in which the inner cutting element  5  may move relative to the outer cutting element  4 , wherein the inner cutting element  5  is slidably guided in said gap  16 . 
     More particularly, as can be seen from  FIGS.  4  and  5   , the outer cutting element  4 , when viewed in a cross section, may have a substantially C-shaped configuration with edge portions  4   a  and  4   b  which are bent away or curved away from the skin contact surface and form holding flanges attached to or fixed to said outer frame portions  12  of the support structure  14 . Said edge portions  4   a  and  4   b  may be folded back or bent around the edge portions of said outer frame  12 , as it can be seen from  FIG.  4   . However, in the alternative, it also would be possible to seat said holding flanges  4   a  and  4   b  of the cutting element  4  onto the inner side of said outer frame  12 . 
     The cutting element  4  may be rigidly or fixedly fastened to said outer frame portions  12 . For example, the cutting element  4  may be welded or glued to the outer frame  12 . 
     As can be seen from  FIGS.  4  and  5   , said outer frame portion  12  of the support structure  14  may include a pair of diverging legs forming a shallow chute or trough, wherein the edge portions of said support legs of the outer frame  12  may be provided with slot-like cutouts  13  forming a toothed edge basically corresponding to the cutting teeth  6  and  7  of the cutting elements  4  and  5 . More particularly, said cutouts  13  in the edges of the outer frame  12  allow hair to be cut to enter into the teeth  6  and  7  of the cutting elements  4  and  5 , but at the same time provide for support to the cutting teeth  6  of the outer cutting element  4  to some extent. 
     The cutting teeth  6  of the outer cutting element  4  may be formed in the transitional region between the folded back support flanges  4   a  and  4   b  and the front side of the cutting element  4  defining the skin contact surface of the cutter system  3 . 
     Said outer cutting element  4  may form a C-shaped, plate-like cutting element the edges of which are dog-eared to form limbs bent inwardly like the limbs of a C or a U, wherein such dog-eared limbs  4   a  and  4   b  are held by said outer support frame portions  12 . The transitional edge portion connecting the dog-eared limbs with the central portion of the outer cutting element is contoured or configured to form a row of comb-like teeth  6  for cutting longer stubbles, whereas the central portion  4   c  of the cutting element  4  is provided with said field of perforations  8  for cutting short hair. 
     As can be seen from  FIG.  4   , the outer cutting element  4 , together with the outer frame  12  of the support structure  14 , defines a chamber  17  which is surrounded by the outer cutting element  4  and the outer frame  12 . 
     Within such chamber  17 , the inner frame  11  for supporting the inner cutting element  5  is arranged. Said inner frame  11  includes at least one pair of rigid support ribs  19  which extend from a base section  20  of the support structure  14  towards the inner cutting element  5  lying, back to back, onto the outer cutting element  4 . 
     More particularly, as can be seen from  FIG.  4   , said rigid support ribs  19  originate from a center section of the outer frame  12  where the diverging support legs of the outer frame  12  join each other. Said support ribs  19  of the inner frame  11  extend from said base section  20  towards the inner cutting element  5  at an angle β which is considerably steeper than the angle φ between the outer frame  12 . As can be seen from  FIG.  4   , the support ribs  19  of the inner frame  11  may define an angle β from 2×20° to 2×40° or 2×25° to 2×30° between each other, wherein said rigid support ribs  19  may be arranged symmetrical with regard to a center plane going perpendicular to the skin contact surface and parallel to the axis of reciprocation  10 . 
     So as to give the rigid support ribs  19  sufficient rigidity, said ribs  19  may have a straight longitudinal axis when viewed in a cross sectional view as it is shown in  FIG.  4   . In other words, the inner and outer surfaces of the support ribs  19  may be plane and flat so as to achieve buckling stiffness. These support ribs  19  may define a V-shaped configuration originating from the base portion  20 . 
     As can be seen from  FIG.  5   , the support ribs  19  may be part of a supporting insert and/or formed in one piece with each other. More particularly, the inner frame  11  may have a chute-like or trough-like configuration including a strip-like bottom portion from the edges of which said pair of support ribs  19  extends. For example, said inner frame  11  including the support ribs  19  may be formed from a substantially rectangular metal plate, wherein strip-like edge portions may be bent relative to a middle-section so as to form the inclined support ribs  19 . 
     Said inner frame  11  may form an insert that can be inserted into the chamber  17  defined by the outer frame  12  and the outer cutting element  4 . More particularly, said insert forming the inner frame  11  may be seated onto the base portion  20  of the outer frame  12  which base section  20  takes up the forces and pressure induced into the inner frame  11  when the cutter system  3  is pressed against skin to be shaved. 
     The inner frame  11  is configured such that the aforementioned gap  16  is defined between the support edges of the rigid support ribs  19  on the one hand and the inner side of the outer cutting element  4  on the other hand. More particularly, the height of the support ribs  19  is configured such that said gap  16  between the support edges of the ribs  19  and the outer cutting element  4  substantially corresponds to the thickness of the inner cutting element  5 , wherein the gap  16  may be configured to be slightly wider than the thickness of the plate-like cutting element  5  so as to reduce friction and to provide some play between the inner cutting element  5  and the support ribs  19  and the inner cutting element  5  and the outer cutting element  4 . Such play may be given when the cutter system  3  is unloaded, i.e. not pressed against a skin to be shaved. In the operational state, when the outer cutting element  4  is pressed against the skin to be shaved, such play is eliminated and the cutting elements  4  and  5  are snuggly fitted onto each other to achieve smooth cutting of hair. 
     Despite such possible play provided by the support structure  14 , the support ribs  19  are configured such that the gap  16 , in its width, exceeds the thickness of the inner cutting element  4  by an amount which is smaller than the thickness of hair to be cut. For example, the width of the gap  16  may be larger than the thickness of the sandwiched cutting element  5  by an amount smaller than 40 μm or ranging from 20 μm to 40 μm. 
     As can be seen from  FIG.  4   , the inner and outer cutting elements  4  and  5  may have a slightly convex contour. More particularly, the skin contact surface defined by the outer cutting element  4  may have a slightly convex, substantially chute-like configuration. When viewed in a cross section taken perpendicular to the axis of reciprocation  10 , the outer surface of the outer cutting element  4  may be slightly dome-shaped, cf.  FIG.  4   . 
     The inner cutting element  5  substantially corresponds to the shape of the outer cutting element  4  in terms of said slightly convex chute-like shape. 
     As can be seen from  FIG.  4   , the support edges of the support ribs  19  facing the inner cutting element  5  may be spaced from each other at a distance ranging from about 35% to 70% or 40% to 60% of the distance defined between the rows of comb-like teeth  6  and  7  at the opposite edges of the outer cutting element  4 . Thus, the rigid support ribs  19  may support the inner cutting element  4  at about ⅓ and about ⅔ of its span width, when viewed in a cross section perpendicular to the axis of reciprocation  10 . More particularly, the support edges of the ribs  19  may extend directly adjacent to the outer boundaries of the field of perforations  8 , wherein said support ribs  19  may contact the inner cutting element  5  along the outer longitudinal contour of the cutouts forming the perforations  9  in the inner cutter element  5 . 
     Due to the configuration of the support ribs  19  extending from the base portion  20  of the support structure  14  at an angle steeper than the support legs of the outer frame  12 , the chamber  17  defined by the outer frame  12  and the outer cutting element  4  attached thereto, is divided by said support ribs  19  into an inner subchamber  17   i  and a pair of outer subchambers  17   o , cf.  FIG.  4   , wherein the outer subchambers  17   o  together may have a volume substantially corresponding to the volume of the inner subchamber  17   i.    
     The rigid support ribs  19  of the inner frame  11  may extend substantially parallel to the axis of reciprocation  10 . More particularly, the support edges of the ribs  19  contacting the inner cutting element  5  may extend parallel to the axis of reciprocation  10 . 
     As can be seen from  FIGS.  6  and  7   , the cutter head  2  including the cutter system  3  may be pivotably supported relative to the handle of the shaver/trimmer  1  about a pivot axis  21  which may extend substantially parallel to the axis of reciprocation  10 . Said pivot axis  21  may be positioned close to the cutting elements  4  and  5  and/or within the chamber  17  surrounded by the outer cutting element  4  and the outer frame  12 . As can be seen from  FIGS.  5  and  6   , the outer frame  12  of the support structure  14  holding the outer cutting element  4  may include a pair of pivot bearing sections  12   a  and  12   b  which may be spaced from each other and/or positioned at the opposite end faces of the outer frame  12 . On the other hand, a pair of support flanges  43  may be provided at the cutter head side of the handle  100 , wherein said pivot bearing flanges  43  may be rotatably connected to said pivot bearing sections  12   a  and  12   b  of the outer frame  12  to form the pivot axis  21 . 
     A spring device  22  may be associated with said pivot axis  21  so as to urge the cutter head  2  in a desired, mutual pivot position or orientation which may be a middle orientation allowing pivoting into opposite directions or, in the alternative, an end position or end orientation allowing pivoting into one direction only. 
     Said spring device  22  may be engaged with the support flanges  43  of the handle  100  on the one hand and the outer frame  12  on the other hand. 
     So as to drive the cutting elements  4  and  5  in a reciprocating manner relative to each other, a driver  18  may be connected to the inner cutting element  5 , wherein such driver  18  may include a rod-like driving element attached to opposite end portions of the inner cutting element  5 . On the other hand, said driver  18  may include a coupling section  18   c  to be coupled with a driving element extending from handle  100  to the cutter head  2 . More particularly, the inner frame  11  and the outer frame  12  of the support structure  14  may include an elongated recess  23  or cutout extending through the base section  20  of the support structure  14 , wherein the aforementioned coupling section  18   c  of driver  18  may extend through said elongated cutout  23 , cf.  FIG.  5    and  FIG.  4   , to allow coupling with the driving element of the drive train coming from the motor in the handle  100 . 
     Said driver  18  may be slidably guided at the inner frame  11  and/or outer frame  12 . For example, one or more guiding blocks  24  or bearings  24  may be provided at the outer frame  12 . For example, such guiding blocks  24  may be inserted into the central, elongated recess  23  extending in the base portion of the outer frame  12 , wherein said guiding blocks  24  may include slot-like groves  25 , in which the rod-like driver  18  may be slidably guided. 
     Said driver  18  may be accommodated between said rigid support ribs  19  of the inner frame  11 . In particular, said driver  18  may be accommodated within the inner subchamber  17   i  and thus, may be surrounded by the chute-like insert forming the inner frame  11  including the rigid support ribs  19 , wherein the coupling section  18   c  of the driver  18  may extend through the central, elongated recess  23  in the bottom portion of said insert forming the inner frame  11 . 
     The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.” 
     Every document cited herein, including any cross referenced or related patent or application and any patent application or patent to which this application claims priority or benefit thereof, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern. 
     While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.