Patent Publication Number: US-7707725-B2

Title: Electric shaver with extendable longhair cutter unit

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation application of and claims priority to PCT Application Serial No. PCT/EP2007/004437, filed on May 18, 2007, through which priority is claimed under 35 U.S.C. §19(a) from German patent application number 10 2006 028 470.4, filed Jun. 21, 2006. The entire contents of PCT Application Serial No. PCT/EP2007/004437 are incorporated herein by reference. 

   TECHNICAL FIELD 
   This invention relates to an electrically operated shaver with a longhair cutter unit of the type that is movable into an operable position for cutting long hairs. 
   BACKGROUND 
   German patent publication DE 31 11 871 A1 describes an electric shaving apparatus that includes at its top a shorthair cutter unit and on its front a longhair cutter unit. The longhair cutter unit is comprised of an operating switch and a coupled longhair cutter that has at its free end a comb-type lower blade and upper blade which in operation are in sliding relation to each other, thereby shearing off hairs that have entered the combs. In the position of rest, the longhair cutter unit is embedded in a recess formed on the front face of the housing of the shaving apparatus so that the outer contour of the longhair cutter forms a nearly stepless plane with the outside of the housing. To move the longhair cutter unit into its operating position, it is necessary to slide the operating switch upward, whereby the outside of the lower blade slides along a ramp in the housing of the shaving apparatus, swinging obliquely upwardly out of the housing together with the upper blade. As this occurs, a flap closing the longhair cutter exposes the comb-like end to enable it to be moved into contact with an operator&#39;s skin surface. 
   Similarly, Japanese reference JP 58-32767(2) describes an electrically operated shaving apparatus in which a shorthair cutter unit is provided on the upwardly pointing surface and a longhair cutter unit on the front side. Mounted behind a cover plate is a transversely grooved operating switch as well as a barrel-type longhair cutter. On being turned, the longhair cutter is accessible from outside through a square-shaped window. Otherwise, it is turned into the interior of the housing and concealed. Turning of the longhair cutter is effected by an actuator coupled next to the axis of rotation and connected to the operating switch. 
   German document DE 195 21 299 C1 also describes an electrically operated shaving apparatus that has at its top a shorthair cutter unit and on its front a longhair cutter unit. The longhair cutter unit is activated by an operating switch provided in a recess on the front side. An actuator connected to the operating switch is displaced from bottom to top and in reverse direction in the housing, so that due to the eccentric mounting of the actuator on the longhair cutter the latter is swung about its pivot axis forwardly out of the housing and back into the housing. Detent elements are provided in order for the actuator to lend the longhair cutter unit a stable position in the latter&#39;s extended position so that the longhair cutter withstands the shaving forces acting on it during shaving, without folding shut or wobbling. Although in the retracted condition the comb-type cutting plane of the longhair cutter is embedded in the housing recess of the shaver, it is nevertheless visible from outside, and the comb-type sharp edges of the longhair cutter are at least partially exposed. 
   SUMMARY 
   According to one aspect of the invention, an electric shaver has a housing carrying a shorthair cutter unit, a longhair cutter unit and an operating switch. The longhair cutter unit is mounted so as to be pivotable with respect to the housing about a pivot axis, between an open position and a closed position. An electric drive is operable to drive the shorthair cutter unit and is mechanically connected to drive the longhair cutter unit in the open position. The longhair cutter unit has a longhair cutter housing carrying a longhair cutter comprised of a lower blade and an upper blade. The longhair cutter unit is connected to the operating switch via an actuator that both pivots the longhair cutter unit toward its open position, and extends the longhair cutter with respect to the longhair cutter housing, in response to a corresponding actuation of the switch. 
   In some embodiments, the longhair cutter and the actuator are connected via a first rotatable joint, and the actuator is connected to the operating switch via a second rotatable joint. In some configurations, the first joint is disposed outward of the pivot axis with the longhair cutter unit in its closed position. In some arrangements ramps are provided at a free end of the longhair cutter housing as well as at a free end of the actuator, the ramps being configured to slide against one another upon actuation of the actuator, so as to cause a torque that urges the longhair cutter unit toward the open position. In some cases the ramps form an angle with a longitudinal axis of the longhair cutter housing or the actuator which is between 30° and 60°, or about 45°. 
   In some embodiments the longhair cutter is slidably guided in slide rails extending in the form of grooves provided on the longhair cutter housing. 
   In some examples the actuating switch is movably mounted on a guide frame that defines opposing guide grooves in which the operating switch is slidably guided on the guide frame. In some cases, the longhair cutter housing is pivotally mounted on the guide frame. In some designs, the guide frame is flange-mounted on the housing of the shaving apparatus such that outer surfaces of both the longhair cutter housing and the operating switch form part of the outer surface of the housing of the shaving apparatus. The actuator may be, for example, a link that is pivotally connected at one end to the longhair cutter through bearing trunnions and is pivotally connected at another end to the guide frame. In some cases the actuator link has angled fork ends. 
   In some embodiments the operating switch and longhair cutter are guided in straight grooves extending parallel to one another and parallel to a central axis of the longhair cutter unit. 
   In some cases a distal end of the longhair cutter protrudes beyond a distal end of the longhair cutter housing when the longhair cutter unit is in the open position, whereas with the longhair cutter unit in the closed position the distal end of the longhair cutter is retracted into and concealed by the distal end of the longhair cutter housing. In some shavers, a stop is formed on the longhair cutter housing and on the longhair cutter, against which stop the longhair cutter abuts when the longhair cutter unit is in the open position. In some cases, a stop is formed on the longhair cutter housing and on the guide frame in proximity to the pivot axis, said stop limiting a maximum pivot angle of the longhair cutter housing. Such a stop may be formed by lateral boundary surfaces of the longhair cutter housing and the guide frame that extend obliquely to a central axis of the shaver, for example. 
   In some examples the shaver has a spring that applies a force that acts upon the actuator in a transverse direction. 
   In some cases, upon moving the switch to pivot the longhair cutter unit to its open position, the operating switch is acted upon by a force that acts initially in opposition to movement and, after a predetermined length of travel, acts to assist movement of the switch. This force may be provided at least in part, for example, by a leg spring having one end secured directly to the operating switch and another end secured to a lever rotatably mounted on the operating switch, the lever having a distal end that engages a groove extending perpendicularly to a longitudinal axis of the shaver. 
   Various embodiments described herein feature a longhair cutter that can be swung open easily, while also providing that the front of the shaving apparatus can be closed with the longhair cutter in its rest position. 
   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 
       FIG. 1  is a perspective view from top right of an electrically operated shaving apparatus with a longhair cutter unit embedded in the front face. 
       FIG. 2  is a perspective front view of the shorthair cutter unit in closed position, shown enlarged as a single part, with parts of the shorthair cutter housing and the operating switch broken away to expose the interior parts. 
       FIG. 3  is a side view of the shorthair cutter unit, as seen looking from the left in the direction X of  FIG. 2 . 
       FIG. 4  is a view similar to  FIG. 3 , but showing the shorthair cutter housing with its shorthair cutter moved into the maximum open position by actuation of the operating switch. 
       FIG. 5  is a perspective top plan view of the open shorthair cutter unit, as seen looking from top left in the direction of arrow Z of  FIG. 4 . 
       FIG. 6  is a view of the operating switch of the open shorthair cutter unit, as seen looking at right angles to the front in the direction W of  FIG. 4 , with the operating switch partly broken away. 
       FIG. 7  is a perspective view of the longhair cutter extended from the longhair cutter housing, as seen looking from the right in the direction V, with the lower part of the guide frame and the operating switch broken away. 
       FIG. 8  is a perspective front view of the longhair cutter as single part according to  FIG. 7 , as seen looking obliquely from bottom right. 
       FIG. 9  is a rear view of the longhair cutter unit, as seen looking slightly from the left in the direction T of  FIG. 4 , with the lower part of the guide frame broken away. 
       FIG. 10  is a view of the shorthair cutter unit in the direction R of  FIG. 4 , as seen looking from above in the direction of the longhair cutter housing onto its inner side, in contrast to  FIG. 7 . 
       FIG. 11  is a perpendicular view of the broken away outer side of the longhair cutter housing in the direction P of  FIG. 7 , with the lower portion broken away in the area of transition to the guide frame. 
       FIG. 12  is a schematic side view of the closed longhair cutter unit of  FIG. 3 . 
       FIG. 13  is a schematic side view of the open longhair cutter unit of  FIG. 4 . 
   

   Like reference symbols in the various drawings indicate like elements. 
   DETAILED DESCRIPTION 
   In  FIG. 1  an electrically operable shaving apparatus  1  includes a housing  2  having at its upper end a pivotal shaving head  16  that extends in a direction transverse to a central axis  19  and mounts a shorthair cutter unit  3  with a central cutter  17 . The central cutter  17  is arranged between two shaving foils  18  and extends parallel to the foils. The central cutter and the shorthair cutter unit extend perpendicularly to a central axis  46  of the shaving apparatus  1 . The perforations of the shaving foils  18  are not shown in  FIG. 1  in the interest of simplicity of illustration. Provided underneath the shaving foils  18  and the central cutter  17  are undercutters, not shown in the drawing, which are connected to a drive mechanism of the shaving apparatus  1 . 
   Arranged in the lower part of the front face are an on/off switch  20  and below it a charge indicator  21 . A recess  5  provided in the front face  4  of the housing  2  extends from the on/off switch  20  upward to the end of the housing  2 . To avoid duplicate description, reference is made to the Braun “Synchro” type shaver which includes a shaving head of the type herein shown and has on its front face an on/off switch and a longhair cutter. 
   Embedded in recess  5  is a longhair cutter unit  6  that is substantially comprised of a longhair cutter  29  ( FIGS. 2 to 11 ) received in a longhair cutter housing  9 , and an operating switch  22  arranged directly below the longhair cutter. The front sides of the longhair cutter housing  9  and the operating switch  22  form part of the front face  4  of the housing  2 . 
   The longhair cutter unit  6  is illustrated as a single part in  FIGS. 2 to 11  and on an enlarged scale as compared to  FIG. 1 . The size of the shaving apparatus  1  shown in  FIG. 1  is not its real size either but is illustrated on a reduced scale. 
   In  FIGS. 2 to 11  a driving member  8  is shown at the upper end of the longhair cutter unit  6 . The driving member is not part of the longhair cutter unit  6  but is mounted in the housing  2  as a fixed member for establishing the connection to an electrically operated drive mechanism (not shown) of the shaving apparatus  1 . The driving member  8  is shown in  FIGS. 2 to 11  only for the purpose of illustrating how in  FIG. 9  its coupling end  23  engages with a pocket-shaped coupling member  11 . The coupling member  11  is part of a lever  24  mounted in an oscillating manner on a trunnion  14  formed on a rear side  7  of the longhair cutter housing  9 . The lever  24  is connected to the coupling member  11  via a bar  12 , while on the other side of trunnion  14  lever  24  includes an arm  25  ( FIG. 11 ) from which a pin  26  projects and engages in a longitudinal groove  27  provided on a lower blade  13 . Because longhair cutter  29  (comprised of upper and lower blades  13 ,  28 ) slides upward in grooves  31  formed along edges  30  on the rear side  7  of the longhair cutter housing  9  when the longhair cutter housing  9  of  FIGS. 9 and 10  is swung open, pin  26  likewise slides in longitudinal groove  27  from an upper to a lower position due to its fixed mounting on lever  24  and the lever&#39;s mounting on trunnion  14 . 
   According to  FIG. 8 , lower blade  13  is urged against the undersurface of upper blade  28  by a T-shaped spring  32 . Fastened to lower blade  13  between the lower blade  13  and spring  32  is a plastic plate  33  that is configured to reduce sliding friction relative to the spring  32  during the oscillating movement of lower blade  13  to thereby obtain a lasting, non-wearing cutter arrangement. 
   According to  FIGS. 7 to 10 , spring  32  is in positive engagement with upper blade  28  through opposed cross bars  35 . As shown in  FIG. 11 , two support arms  37  extending from a plastic frame  34  rest against an upper side  36  of upper blade  28  and include anchoring pins  38  that are passed through bores  39  defined in cross bars  35  for engagement behind bores  39 . Frame  34  is injection-molded onto both upper blade  28  and spring  32 , thereby providing for positive engagement of both parts. Alternatively, frame  34  may also be mounted on spring  32 , in which case anchoring pins  38  passing through bores  39  are deformed by a subsequent heat treatment in such a way that they rearwardly embrace the upper side  40  of spring  32  of  FIG. 8 , thus firmly connecting the two parts with one another. 
   As shown in  FIG. 8 , spring  32  includes on cross bars  35  upwardly angled portions  41 , so that the central part  42  of spring  32  lies at an elevated level, thereby providing a space  43  for receiving lower blade  13  with its plastic plate  33 . The free end of spring  32  is angled towards lower blade  13 , forming a stop surface  110  to cause lower blade  13  with its plastic plate  33  of  FIGS. 7 and 8  to be bounded in both upward and downward directions by angled portions  41 . Angled portions  41  end short of reaching the lower edge  111  of lower blade  13  and plastic plate  33 , so that lower blade  13  can protrude laterally. The upper blade  28  includes slots  44  that extend in a direction transverse to central part  42  of spring  32  and are engaged by trunnions  45  extending from plastic plate  33 , whereby lower blade  13  is imparted a sliding direction ‘S’ perpendicular to the longitudinal axis  46  of longhair cutter unit  6 . The longitudinal axis  46  extends symmetrically to longhair cutter unit  6  and centrally to the shaving apparatus  1  of  FIG. 1 . 
   As shown in  FIG. 8 , upwardly angled spring elements  47  are provided on the edge of the cross bars  35  of spring  32 . Slide cams or slide rails  48  are formed on the frame  34  beneath spring elements  47 . Also formed on the frame  34  beneath slide cams  48  are opposed bearing blocks  49  defining bores  50  which extend in a direction perpendicular to longitudinal axis  46 . Ramps  51  extending from above toward the outsides of bores  50  serve to elastically expand and subsequently suspend bearing trunnions  54  formed on the actuator  52  at the upper fork ends  53  of  FIG. 7  (illustrated in broken lines). In the assembly process, after fork ends  53  are expanded the bearing, trunnions  54  engage bores  50  and are held captive, but allowed to rotate, inside bores  50  after springback of fork ends  53 . Because the diameters of bores  50  form a sliding fit with the trunnions, there is little excessive bearing play. The spring  32  is a bent blanked part and is made from a very thin, rustproof leaf spring sheet. 
   As shown in  FIGS. 1 to 13 , actuator  52  configured to be in plate shape establishes the connection between longhair cutter  29  and operating switch  22  by being rotatably connected to the longhair cutter via a first joint  57 , and to the operating switch via a second joint  59 . 
   At this point it is mentioned that in  FIGS. 2 ,  5 ,  6  and  11 , lines  61 ,  62  indicate parts of longhair cutter housing  9  and of operating switch  22  that have been broken away to expose the interior parts of shorthair cutter unit  3 . 
   As shown in  FIG. 3 , fork ends  53  are angled obliquely upwardly toward the longhair cutter housing  9  relative to the central region  63 , such that in the maximum swung-open position of the longhair cutter housing  9  these fork ends  53  of actuator  52  extend substantially parallel to the longitudinal extension of longhair cutter housing  9 . 
   As shown in  FIG. 5 , stop surfaces  58  are formed on a guide frame  60  slightly below pivot axis  15 , which stop surfaces extend from the bottom to the top obliquely relative to the central axis  46  and conform with stop surfaces  64  formed on longhair cutter housing  9 . In other words, in the maximum open condition stop surfaces  64  on longhair cutter housing  9  abut stop surfaces  58  on guide frame  60 , thereby maintaining the maximum pivot angle β of 115°. On the other hand, longhair cutter housing  9  is thereby located centrally on pivot axis  15 , avoiding sideways wobbling of longhair cutter housing  9  during shaving. To prevent longhair cutter  29  from extending beyond amount ‘X’ of  FIG. 4 , another stop  65  ( FIG. 13 ) is provided on longhair cutter housing  9 . To make sure that longhair cutter  29  retracts only a predetermined amount into longhair cutter housing  9  when swung in, an inner stop  66  is provided as shown schematically in  FIGS. 12 and 13 . 
   As shown in  FIG. 9 , actuator  52  extends downward along the center and is equally split into two lower fork ends  67  that define at their ends bores  68  (see  FIGS. 12 and 13 ) extending perpendicularly to longitudinal axis  46  and penetrated by a metal shaft  69  ( FIG. 5 ) that in turn is carried in bearing trunnions  70  formed on operating switch  22  on the rear side. In  FIG. 9  part of the upper right edge of the guide frame is broken away to expose the groove  31  into which the slide cams  48  of longhair cutter  29  slidably engage. Similarly, in  FIG. 10  part of the guide frame  60  is broken away in the middle on the left side, which is also the case at  71  in  FIGS. 5 and 6 . 
   Referring to  FIGS. 2 ,  5 ,  6  and  11 , the shaft  69  mounts a leg spring  72  having two ends  73  each fixedly held clamped on a clamping post  75  projecting from a metal frame  74  ( FIG. 5 ). Starting from the ends  73 , spiral-shaped coils  76  are wound around shaft  69 , their ends being connected to each other via a U-shaped loop  77 . The upper end  78  of loop  77  and/or the leg ends  79  ( FIG. 6 ) rest against a contact surface  80  which is recessed relative to the planar section of actuator  52 , and leg spring  72  is biased such that the force exerted on leg ends  79  biases the actuator  52  and hence the longhair cutter  29  of  FIG. 4  in the direction of pivot axis  15 . This is to make sure that in the swung-in condition of  FIG. 3  the longhair cutter housing  9  connected to longhair cutter  29  via slide rail arrangement  31 ,  48  with zero play is flush with housing  2  of the shaving apparatus of  FIG. 1 . As such, longhair cutter housing  9  is in such firm abutting engagement with housing  2  that vibrations acting on the shaving apparatus do not cause rattling of longhair cutter unit  6 . 
   Referring to  FIG. 5 , metal frame  74  is a molded part, preferably injection-molded from metal (aluminum) and having secured to its front face  81  ( FIGS. 2 and 6 ) the operating switch  22  injection-molded from plastic. Here, too, fastening is accomplished by bores (not shown) formed in the metal frame  74 , which are penetrated by trunnions (not shown) formed on operating switch  22 , with the trunnion ends, which project from the front face  81  of metal frame  74 , being deformed by hot deformation so as to lie flush with front face  81 . 
   Referring to  FIG. 6 , a bearing trunnion  82  formed on metal frame  74  rotatably mounts a lever  83  injection-molded from plastic and having formed on its other end a bearing trunnion  84  around which the end  85  of a second leg spring  86  is wound with play, such that this end  85  is rotatable about bearing trunnion  84 . Referring to  FIGS. 2 and 6 , spring end  85  continues in a circular wire section  87  that is made up of about 1½ turns and whose exit end  88  extends tangentially, being fixedly held clamped on a bearing block  89  formed on metal frame  74  as shown in  FIG. 5 . The bearing trunnion  84  formed on lever  83  protrudes also from the other side and engages in a groove  90  formed on guide frame  60  and extending perpendicularly to longitudinal axis  46 , such that on displacement of operating switch  22  in an upward or downward direction the bearing trunnion  84  moves sideways back and forth in groove  90 . 
   The biased second leg spring  86  exerts initially a force F 5  on operating switch  22 , which force acts in opposition to the opening direction but which, as soon as lever  83  adopts a horizontal position, is reversed and urges operating switch  22  upwardly according to  FIG. 6 . The second leg spring  86  thus cooperates with lever  83  to act as a snap-action spring which exerts on operating switch  22  first a force F 5  acting in opposition to the opening direction and, from a certain point on, a force F 5  acting in the opening direction. During closing, this snap-action spring arrangement  91  operates correspondingly, i.e., when the operating switch  22  is pushed down, first the spring force F 5  has to be overcome and, from a certain point on, a force acting in the closing direction is exerted on operating switch  2 . 
   Referring to  FIGS. 2 ,  5  and  6 , slide rails  92  are provided on the edge of operating switch  22  for engagement with grooves  94  that are provided on the edge  93  of guide frame  60  and extend parallel to longitudinal axis  46  of the guide frame. In this manner, operating switch  22  is guided in a straight line and extends parallel to grooves  31  provided on longhair cutter housing  9 . For introducing operating switch  22  into the grooves  94 , superimposed recesses  95 ,  96  are formed on said grooves, as shown in  FIG. 6 . As soon as operating switch  22  is inserted in grooves  94  and connected to actuator  52  via the second joint  59  on the one side and to longhair cutter  29  via the first joint  57  on the other side, operating switch  22  is no longer able to slide out of recesses  95 ,  96  of grooves  94  because these places are out of the reach of slide rails  92 , even on maximum displacement movements of operating switch  22 . 
   In  FIG. 6  part of guide frame  60  is omitted on the top left side to expose a slide rail  92 . These are otherwise concealed in groove  94  according to  FIG. 6  and only shown in broken lines. 
   Referring to  FIG. 3 , ramps  98 ,  99  are formed at the free ends of operating switch  22  and longhair cutter housing  9  lying opposite when in the closed position. In lieu of the second leg spring  86  it is also possible to provide a compression spring  100  on guide frame  60  or on housing  2 , which urges operating switch  22  upwardly according to  FIG. 3  and does not move it until, for example, an inhibiting member  101  inhibiting displacement of operating switch  22  is unlocked. This possible variant is only shown in broken lines in  FIG. 3 . It will be understood, of course, that other spring variants are possible to enable operating switch  22  to be displaced after unlocking. 
   Referring to  FIGS. 1 to 3 , superimposed ribs  103  extending in a direction transverse to central axis  19  are arranged on the upper side of operating switch  22 , which ribs penetrate upwardly through apertures  104  defined in operating switch  22  and are integrally formed on metal frame  74 . Integrally formed on the front face of longhair cutter housing  9  injection-molded from plastic are thin ribs  112  which extend elliptically and are intended to represent a clear separation of the longhair cutter housing from operating switch  22 . 
   The guide frame  60  is provided with fastening devices  105 ,  106  which enable longhair cutter unit  6  to be held in recess  5  of the shaving apparatus with positional accuracy. 
   The mode of operation of shorthair cutter unit  3  is as follows: 
   To activate longhair cutter unit  6 , first the operating switch  22  of  FIGS. 1 to 3  is moved upward in the direction B. Already after a few tenths of a millimeter, the ramp  99  formed in operating switch  22  abuts the ramp  98  formed on longhair cutter housing  9 , and with the sliding motion continuing a torque M 1  is produced from the force F 1  resulting from the actuating force F acting on the ramps and the lever arm ‘b’, which torque enables longhair cutter housing  9  to be swung about pivot axis  15 . After bearing play on the joints  57 ,  59  is overcome, the force of the sliding motion on operating switch  22  causes a force F 2  to act on bearing trunnion  54  that is transmitted via the second joint  59  and from there via actuator  52  to the first joint  57 , so that, due to the resulting lever arm ‘c’ between the center point of first joint  57  and the center point of pivot axis  15 , a torque M 2  is produced that is initially additive to torque M 2 . In this manner, the force required to swing out the longhair cutter housing  9  with its integrated longhair cutter  29  is initially extremely low. 
   While the spring force applied by second leg spring  86  acts in opposition to the displacement force of operating switch  22 , the spring forces are nevertheless designed to keep the energy required to move operating switch  22  at a low level. The more longhair cutter housing  9  is swung open, the longer the lever arm ‘c’ and the higher the torque M 2 . Because of the absence of contact between ramps  98  and  99 , torque M 1  drops to zero after just a few millimeters of displacement travel ‘d’ of operating switch  22 . 
   Although torque M 2  increases as a result of ‘c’ increasing to c 1 , the displacement force F on operating switch  22  does not increase because the force acting in opposition to operating switch  22  increases due to the increasing biasing force of the second leg spring. Advantageously, the mechanism is well balanced such that the displacement force F remains nearly constant in spite of the increase in torque M 2  and the increase in the counteracting force F 3  applied by second leg spring  86 . The longhair cutter  29  is held against stop  66  in longhair cutter housing  9  by the first leg spring  72 . 
   As soon as lever  83  reaches its approximately horizontal position as shown in  FIG. 6 , i.e., it extends perpendicularly to longitudinal axis  46 , the force of the second leg spring acts upwardly according to  FIG. 6 , thereby turning lever  83  about bearing trunnion  82  in a counterclockwise direction. Due to the sliding engagement of bearing trunnion  84  with groove  90  provided on operating switch  22 , the operating switch is swung upwardly without the application of any external force. Because of the fixed coupling of actuator  52 , the longhair cutter  29  is moved outwardly relative to longhair cutter housing  9  in grooves  31  until its abutting engagement with the next stop  65 . This is possible because the force of leg spring  72  is now lower than the force of second leg spring  86 . 
   During the swinging-up movement, the coupling end  23  provided on coupling member  8  engages into the pocket-shaped coupling member  11  of lever  24 , and lever  24  is caused to move in alternating directions by the reciprocating coupling end  23 . Because the lever  24  is rotatably mounted on trunnion  14  through its bore  102 , the other end carrying pin  26  moves in just the opposite direction. As a result of the engagement of pin  26  with longitudinal groove  27 , the lower blade  13  is reciprocated in the direction ‘s’, closing and opening the slots  56  formed on upper blade  28 , so that hairs entering the slots  56  are sheared off between lower blade  13  and upper blade  28 . 
   Closing of the longhair cutter unit  6  takes place precisely in inverted order. To return longhair cutter housing  9  with longhair cutter  29  from its maximum open position back to its closed position, operating switch  22  of  FIG. 1  is moved downwards. This requires a force F 4  to be applied that acts in opposition to the force F 5  of second leg spring  86 . In the initial phase of the return movement, longhair cutter  29  moves in grooves  31  provided on edge  30  in the direction of pivot axis  15 . The angled fork ends cause a displacement force to be produced in the direction of grooves  31  that effects retraction of longhair cutter  29 . At the same time, longhair cutter housing  9  is swung inward about pivot axis  15  by longhair cutter  29 . As soon as lever  83  reaches its horizontal position, which is approximately perpendicular to longitudinal axis  46 , the force of leg spring  86  acts in opposition to the force F 5  ( FIG. 6 ), automatically moving operating switch  22  downward into its home position as shown in  FIG. 2 . As this occurs, actuator  52  pulls longhair cutter  29  inwardly into longhair cutter housing  9  until abutment with stop  66  ( FIG. 13 ). The longhair cutter housing then swings about pivot axis  15  until the closed position shown in  FIGS. 2 and 3  is reached. The closing action of longhair cutter housing  9  is further assisted by the fact that force F 6  acts on actuator  52  and holds it in the closed position when longhair cutter housing  9  is closed. 
   In the example illustrated in  FIGS. 12 and 13 , the length ‘l’ between the first and second joints  57  and  59  is 27 mm, dimension ‘c’ is 1 mm, dimension c 1  is 12.3 mm, dimension ‘d’, which is the maximum actuating travel, is 13.5 mm, distance ‘e’ between the center point of pivot axis  15  and the center point of second joint  59  in the maximum swung-open condition of shorthair cutter housing  9  is 0.3 mm, distance ‘f’ between pivot axis  15  and stop  66  is 3 mm, distance ‘g’ between the center point of first joint  57  and the free end  55  of longhair cutter  29  is 23 mm, the ramp angle α is 45°, distance ‘h’ between the foremost point of longhair cutter housing  9  and the center point of pivot axis  15  is 59 mm, and distance ‘i’ between stop  66  and the upper side of actuator  52  is 0.3 mm. 
   As shown in  FIGS. 12 and 3 , longhair cutter  29  fits snugly within the space  107  formed between fork ends  53  and  67 . The free ends  55  of upper and lower blades  28  and  13  are of a comb-shaped configuration, such that hairs entering the slots are cut off on a sideways movement in the direction ‘s’ of lower blade  13  relative to upper blade  28 . 
   Because the longhair cutter is movably mounted in the longhair cutter housing and the actuator is directly coupled to the longhair cutter, the longhair cutter pops up a small amount out of the longhair cutter housing when the latter swings open, so that the comb-type end of the longhair cutter is easily accessible from outside for cutting hair. When the longhair cutter housing is swung back, the actuator retracts the longhair cutter back into the longhair cutter housing until its comb-type end is concealed by the longhair cutter housing and no longer visible from outside. 
   Because the longhair cutter is completely retracted into the interior of the longhair cutter housing, the shaver is imparted a uniformly closed outer contour which is due to the fact that the longhair cutter housing is able to lie flush with the shaver housing. Dust and other contaminants are thereby prevented from entering the housing interior. Accordingly, the longhair cutter housing serves as a receptacle and mount for the longhair cutter itself on the one hand and, on the other hand, as a protective shield and dust guard in the retracted condition. 
   The longhair cutter unit is configured to swing out of, and back into, the housing of the shaving apparatus with particular ease. The above-described features enable a particularly low-friction flip-up mechanism in which in the open condition of the longhair cutter the actuator is free to pivot outwards at the free end of the operating switch. 
   The longhair cutter unit may be opened solely by actuation of the operating switch. The farther the joint between actuator and longhair cutter housing is disposed outward of the pivot point, the greater the ease with which the longhair cutter unit can be opened. However, increasing this dimension can lead to a broader dimension of the shaving apparatus when the longhair cutter unit is to rest flush with the housing. Preferably, this offset distance is small, allowing the longhair cutter unit to be built to the narrowest possible width. By providing ramps at the free ends of the longhair cutter housing and the operating switch, which rest snugly against each other with the longhair cutter housing closed, the lever force necessary on the operating switch for opening the longhair cutter unit is kept at an extremely low level. The ramps, which extend from the front surface of the operating switch obliquely upwardly towards its rear surface as seen looking at the operating switch from the side and with the longhair cutter unit closed, form a ramp angle preferably of 45°. On axial displacement of the operating switch along the ramp of the longhair cutter housing, a counterclockwise acting torque develops. The initial force results from the force applied by an operator&#39;s hand to the operating switch. Only later does a force act on the bearing trunnion of the longhair cutter housing, because first a defined bearing clearance has to be used up on the joints of the actuator. 
   The longhair cutter is movably guided toward and away from the pivot axis in slide rails formed on the longhair cutter housing. In lieu of slide rails it is also possible to select a dovetail guide or some other linear rail guide, such that the longhair cutter is slidably guided on the longhair cutter housing at right angles away from and towards the pivot axis. 
   The operating switch is also longitudinally guided in slide rails, with the slide rails extending likewise perpendicularly to the pivot axis and lengthwise of the shaver&#39;s central axis. With the longhair cutter unit in closed position, the slide rails extend on the longhair cutter housing and on the guide frame for the operating switch substantially parallel and are superimposed. The axes of the first and second joints as well as the pivot axis extend parallel to each other and perpendicularly to the slide rail arrangements, in order to enable a smooth movement of the operating switch and the longhair cutter. 
   In the open position the comb end of the longhair cutter projects a predetermined amount ‘x’ from the free end of the longhair cutter housing. Given a distance ‘a’ of 0.6 mm between the pivot axis and the first joint, a length ‘l’ of 27 mm between the first and second joint on the actuator, and a pivot angle β of 115° for the longhair cutter housing, a dimension ‘x’ of 0.5 mm, approximately, is obtained. In this case, the operating switch has been moved upwardly by a distance ‘d’ of 6 mm. In the home position of the longhair cutter housing, that is, at an angle β of 0°, the longhair cutter is retracted inside the longhair cutter housing to an extent causing dimension ‘x’ to be smaller than zero, i.e., proceeding in the opposite direction. 
   A first stop is formed on the longhair cutter housing, which stop is configured to conform to a stop on the longhair cutter such that, when the longhair cutter housing has been moved through angle β to the outer extreme of its outward travel, the first stop abuts the longhair cutter so that the latter can no longer be displaced outwardly in its guide groove and is thereby held in this maximum advanced position by the force of a snap-action spring. 
   A second stop for limiting the pivotal movement of the longhair cutter housing is formed in close proximity to the pivot axis, so that the maximum pivot angle β of the longhair cutter housing is accurately maintained. The first and the second stop help to produce a flip-up mechanism which is particularly resistant to bending and wobble-free and ensures that the longhair cutter, in swung-out condition during a shaving operation, always maintains its end position relative to the housing of the shaving apparatus. This enhances the shaving action because the cutters can be guided along the skin surface with great accuracy. 
   Lateral boundary surfaces extending obliquely to the pivot axis are formed on the longhair cutter housing and the guide frame in order to make sure that in the outer extreme of its outward travel the longhair cutter housing is held locked against sideways movement, being centered on the pivot axis with zero play, in order to thereby lend the longhair cutter a stable, zero-play position also at this point during a shaving operation. 
   The illustrated longhair cutter unit is a self-contained unit that only needs to be adapted to the housing of a shaving apparatus. The preassembly of the longhair cutter unit inclusive of the operating switch arranged on the guide frame thus can take place prior to the final assembly on the housing. Accordingly, a function test can also be performed prior to assembly with the housing, so that only properly functioning longhair cutter units are mounted on the housing of the shaving apparatus. 
   The actuator is preferably of a substantially plate-shaped configuration, forming at either end each two fork-shaped arms on which the first and the second joint are provided. As a result of the widely spaced apart fork ends, particularly sturdy joints resisting transverse forces are obtained which are carried in axles or bores of the longhair cutter and actuator. In lieu of bores formed in the joints for engagement by the axles configured as trunnions or as shafts, a possible alternative is to provide trunnions which engage in bores on the longhair cutter and the actuator. If trunnions are provided on the fork ends, during assembly each fork end is expanded until the trunnions resiliently engage the bores provided on the longhair cutter and the actuator, subsequently remaining permanently in the sprung-back position. In the illustrated embodiment, the metallic longhair cutter has plastic arms formed on it which include bores on the sides for engagement with axles provided on the fork ends of the actuator. The fork ends at the other end of the actuator define bores through which a metal axle clipped onto the operating switch extends. A receptacle is formed between the angled fork ends for seating engagement with the longhair cutter when the longhair cutter unit is folded shut. In this manner, the width dimension of the longhair cutter unit can be kept particularly narrow. 
   A restoring force acting on the actuator in the direction of the pivot axis prevents rattling noise in the unit. At the same time, the restoring force acts to move the longhair cutter back into its initial position when the longhair cutter housing is swung in. The spring is preferably a flexed wire spring which is spirally wound about the axle on the second joint and bears with one end against the operating switch and with its other end against the actuator for producing the restoring force. 
   The force of a snap-action spring arrangement acts on the operating switch, as a result of which a spring force acts in opposition to the movement of the operating switch up to about half the actuating travel, the spring force acting in the direction of movement of the operating switch after this half of the actuating travel is overcome. As a result, the actuator is moved, and with it the longhair cutter, to its maximum open position. The illustrated snap-action spring arrangement includes a leg spring having its one end secured directly to the operating switch and its other end to a lever rotatably mounted on the operating switch, with the free end of the lever being pivotally secured to the switch housing. The two legs are connected to each other by a spiral spring coil which, on actuation of the operating switch between its fixed points on the housing and on the lever, experiences a displacement relative to the operating switch. 
   While a number of examples have been described for illustration purposes, the foregoing description is not intended to limit the scope of the invention, which is defined by the scope of the appended claims. There are and will be other examples and modifications within the scope of the following claims.