Abstract:
The invention relates to a cutting head ( 1 ), comprising a lower and an upper shears blade ( 2, 3 ), for an electric hair cutting machine ( 4 ). The lower shears blade and the upper shear blade ( 2, 3 ) are connected to each other, whereby a cutting blade ( 5 ), made from a planar material ( 7 ), is driven in oscillation in a slot ( 31 ) between the lower and the upper shears blade ( 2, 3 ) and is provided with cutting teeth ( 6 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the National Stage Entry of PCT/EP04/13846, filed Dec. 6, 2004 and claims priority under 35 U.S.C. 119(a)-(d) to German Patent Application DE 103 56 588.4, filed Dec. 4, 2003. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a cutting head for an electric hair cutting machine. 
     2. Description of Related Art 
     A cutting head for an electric hair cutting machine, forming this generic type, is known for instance from European Patent Disclosure EP0856386B1. In it, in the cutting head, an upper shearing blade is driven oscillatingly by back and forth motions by an electric motor and an eccentric, and cutting of the hair is done between a fixed lower shearing blade and the movable upper shearing blade. For cutting the hair, it is important that the cutting edges between the two blades are sharp, and that as much as possible no gap or play exists between them. Because of the oblique disposition, when hair is being cut between the fixed blade and the movable blade, these blades have a wedging action, which can lead to the gap and thus make the cutting performance substantially worse. To avoid this, the movable upper shearing blade is pressed with strong spring force against the lower shearing blade and is dimensioned correspondingly stably. Because of the stable and thus heavy (massive) embodiment of the movable upper shearing blade and because of the friction resulting from the requisite contact-pressure force, high drive energy is required, which necessitates a relatively heavy drive motor, and in the case of a cordless hair cutting machine a relatively heavy rechargeable battery in addition. Moreover, strong forces of acceleration are transmitted as troublesome vibration to the housing of the hair cutting machine. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the invention is therefore to overcome the above-described disadvantages, in a hair cutting machine of the same generic type. 
     Further advantageous refinements and features of the invention are disclosed in the dependent claims. 
     Because in the cutting head with a lower shearing blade and an upper shearing blade for an electric hair cutting machine, it is provided that the lower and upper shearing blades be joined solidly to one another, and an oscillatingly drivable cutting blade, made from a flat material and having a cutting serration, is located in a slit between the lower and upper shearing blades, the aforementioned disadvantages are overcome. 
     The invention is described in further detail in terms of an exemplary embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1 , in a side view, a cutting head, in a section through a lower shearing blade, an upper shearing blade, and a cutting blade; 
         FIG. 2 , the cutting head of  FIG. 1 , which is connected to a hair cutting machine; 
         FIG. 3 , a sectional view taken along the line III-III in  FIG. 1 ; 
         FIG. 4 , a top view taken along the line IV-IV in  FIG. 1 , but without the cutting blade and slaving device, and without a hair cutting length adjuster; 
         FIG. 5 , a plan view on an underside of the cutting head; 
         FIG. 6 , a side view taken along the line VI-VI of the shearing blade in  FIG. 4 ; 
         FIG. 7 , a side view of the cutting blade with the slaving device; 
         FIG. 8 , a plan view VIII-VIII of the cutting blade and slaving device of  FIG. 7 ; 
         FIG. 9 , a side view IX-IX of the shearing blade of  FIG. 6 ; 
         FIG. 10 , a side view X-X of the shearing blade of  FIG. 6 ; 
         FIG. 11 , a plan view on the cutting head, with a parallel guide of the cutting blade; 
         FIG. 12 , a back view of the cutting head of  FIG. 11 ; and 
         FIG. 13 , in a sectional side view, a cutting head of the prior art, which is joined to a hair cutting machine. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a cutting head  1  with lower and upper shearing blades  2 ,  3  for an electric hair cutting machine  4  ( FIG. 2 ), in which the lower and upper shearing blades  2 ,  3  are solidly joined to one another. Between the lower and upper shearing blades  2 ,  3 , there is a slit  31 , in which a cutting blade  5  is received that is made from a flat material  7  and that can be driven to oscillate by a slaving device  12 . The cutting blade  5  is provided on its end with a cutting serration  6  ( FIG. 8 ), which corresponds with a shearing blade serration  19  of the lower shearing blade  2  and a shearing blade serration  19  of the upper shearing blade  3 . 
     The cutting blade  5  is made from a thin flat material  7 , preferably from a hard metal sheet  7 . 1 , which leads to an extreme reduction in mass and can furthermore be manufactured economically. The cutting blade  5  is preferably provided with a material thickness S of approximately 0.1 to 1.0 mm. Since the low-mass cutting blade  5  is moreover driven without contact-pressure force, substantially less driving energy is necessary, and interfering vibration at the housing  17  of the hair cutting machine  4  is largely suppressed. Because the low-mass cutting blade  5  is moreover driven without contact-pressure force, extremely low friction results, and thus the energy consumption is extremely low. To reduce the weight of the two shearing blades  2 ,  3 , the cutting blade  5  is guided between the two fixed shearing blades  2 ,  3 . The guide width B between the two shearing blades  2 ,  3  can be adapted precisely to the thickness S of the movable cutting blade  5  with extremely minimal play, making an additional contact-pressure force superfluous. 
     The cutting head  1  is selectively provided with an integrated hair cutting length adjuster  9 , making the shearing blades  2 ,  3  capable of being displaced manually relative to the cutting blade  5 , which is disposed in the slit  31 , in the direction of the arrow (arrow  32 ) via a lever  33 . This hair cutting length adjuster  9  is in principle known from the aforementioned EP0856386B1, particularly from FIGS. 1 through 5 thereof along with the corresponding description, but instead of the lower shearing blade, in this case the two shearing blades  2 ,  3  solidly joined to one another are displaceable/adjustable relative to the cutting blade  5 . The cutting head  1  is embodied as a structural unit  34  and is embodied as lockable to the hair cutting machine  4  ( FIG. 2 ). 
       FIG. 2  shows a cutting head  1  that is joined to the hair cutting machine  4 . The hair cutting machine  4  is provided with a drive motor  11  with an eccentric  13 , and an eccentric peg  14  drives the cutting blade  5  via the slaving device  12 . The drive motor  11  is connected to a rechargeable battery  16  via a switch  15 . 
     To prevent soiling in an interstice  10  adjacent the drive motor  11  and in the cutting head  1 , the cutting head  1  can be constructed as fully encapsulated. Moreover, the interstice  10  can be utilized for a lubricant reservoir  8 , thus maximally dispensing with manual refilling. 
     By means of a closed structural form of the cutting head  1 , any kind contact of the movable cutting blade  5  with the scalp of a person is avoided. This makes a further spacing of the cutting blade  5  apart for the housing  17  possible without the risk of injury and makes improved manipulation possible when working with the hair cutting machine  4 . 
       FIG. 3  shows the cutting head  1  along the section line III-III in  FIG. 1 , showing a section through the lower shearing blade  2 , upper shearing blade  3 , and cutting blade  5 . The cutting blade  5  that oscillates back and forth is located between the fixed lower shearing blade  2  and the fixed upper shearing blade  3  and is shown here with its cutting serration  6  in the direction of the arrow (arrow  35 ) just before cutting a plurality of hairs  18  (shown here only symbolically). The lower shearing blade  2  and the upper shearing blade  3  are provided in a line with an identical, diametrically opposed shearing blade serration  19  at equal spacings and having tooth gaps  20  of equal widths, and the cutting serration  6  of the cutting blade  5  is located at lesser spacings, so that the hair  18  will be cut not simultaneously but in staggered fashion. In practice, a serration ratio of 1.5 (shearing blade serration  19 ) to 1.3 (cutting serration  6 ) has proven itself. To prevent the creation of a burr (as would be the case in stamping) in the manufacture of the cutting serration  6 , the cutting serration is produced by erosion. 
       FIG. 4  shows a top view IV-IV on the cutting head  1  of  FIG. 1 , but without the cutting blade  5 , the slaving device, and the hair cutting length adjuster  9 . 
       FIG. 5  shows a plan view on an underside of the complete cutting head  1  with two fastening screws  40 ,  41  for fastening a stationary eccentric part  42  ( FIG. 1 ). 
       FIG. 6  shows a side view taken along the line VI-VI of the two shearing blades  2 ,  3  in  FIG. 4 . 
       FIG. 7  shows a side view of the cutting blade  5  with a slaving device  12  and a connecting rail  43 , which is solidly connected (for instance glued) to the cutting blade  5 . 
       FIG. 8  shows a plan view VIII-VIII on the cutting blade  5  of  FIG. 7 . On both sides of the connecting rail  43 , there is a respective spring leg receptacle  44 ,  45 , each with a respective bore  46 ,  47  for receiving legs  38 ,  39  of a spring  37  ( FIG. 11 ). 
       FIG. 9  shows a side view IX-IX of the shearing blades  2 ,  3  of  FIG. 6 ; here the slit  31  for receiving the cutting blade  5  is clearly visible. In this exemplary embodiment, the slit  31  is located all the way through; however, it is also possible to provide the slit  31  up to just before the ends of the shearing blade serration  19  and to provide it with a common rounding. 
       FIG. 10  shows a side view X-X of the shearing blades  2 ,  3  of  FIG. 6 . 
       FIG. 11  shows a plan view of the cutting head  1  with the lower and upper shearing blades  2 ,  3  and the stationary eccentric part  42  removed, to make a spring  37  more clearly visible. The lever  33  for manually adjusting the shearing blades  2 ,  3  in the direction of the arrow  32  ( FIGS. 1 ,  2 ) with respect to the cutting blade  5  has been shown in dashed lines in  FIG. 11 . The cutting blade  5  is guided by a parallel guide  36  by the one-piece, U-shaped spring  37  with two legs  38 ,  39 , and for this purpose the cutting blade  5  is provided with corresponding receptacles  44 ,  45  for the ends of the legs. The two bores  46 ,  47  serve to receive the angled ends of the legs  38 ,  39 . The spring  37  is embedded in a carriage  48 , so that the cutting blade  5  is capable of moving parallel. For displacing the carriage  48  by the eccentric  13 , the carriage  48  has a sliding face  49 , represented by the dotted features, which corresponds to a plane face  50  ( FIG. 4 ) of the lower shearing blade  2 . 
       FIG. 12  shows a back view of the cutting head  1  of  FIG. 11 , and in this case two detent hooks  51 ,  52  can be seen, which are joined integrally to the carriage  48  of plastic and serve to lock to the hair cutting machine  4 . 
     FIG.  13 —in comparison to FIG.  2 —in a sectional side view shows a cutting head  1 . 1  of the prior art, which is joined to the housing  17  of a hair cutting machine  4 . 1 . It also becomes clear here that a structurally required gap  21  (because of the oscillating upper shearing blade) between the cutting head  1 . 1  and the housing  17  brings about soiling from fine hair particles in the interstice  10 , which is prevented in the exemplary embodiment of  FIG. 2 . 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 List of Reference Numerals: 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                  1 
                 Cutting head 
               
               
                   
                  2 
                 Lower shearing blade 
               
               
                   
                  3 
                 Upper shearing blade 
               
               
                   
                  4 
                 Hair cutting machine 
               
               
                   
                  5 
                 Cutting blade 
               
               
                   
                  6 
                 Cutting serration 
               
               
                   
                  7 
                 Flat material 
               
               
                   
                  7.1 
                 Metal sheet 
               
               
                   
                  8 
                 Lubricant reservoir 
               
               
                   
                  9 
                 Hair cutting length adjuster 
               
               
                   
                 10 
                 Interstice 
               
               
                   
                 11 
                 Drive motor 
               
               
                   
                 12 
                 Slaving device 
               
               
                   
                 13 
                 Eccentric 
               
               
                   
                 14 
                 Eccentric peg 
               
               
                   
                 15 
                 Switch 
               
               
                   
                 16 
                 Rechargeable battery 
               
               
                   
                 17 
                 Housing 
               
               
                   
                 18 
                 Hair 
               
               
                   
                 19 
                 Shearing blade serration 
               
               
                   
                 20 
                 Tooth gap 
               
               
                   
                 21 
                 Gap 
               
               
                   
                 31 
                 Slit 
               
               
                   
                 32 
                 Arrow 
               
               
                   
                 33 
                 Lever 
               
               
                   
                 34 
                 Structural unit 
               
               
                   
                 35 
                 Arrow 
               
               
                   
                 36 
                 Parallel guide 
               
               
                   
                 37 
                 Spring 
               
               
                   
                 38, 39 
                 Leg 
               
               
                   
                 40, 41 
                 Fastening screw 
               
               
                   
                 42 
                 Stationary eccentric part 
               
               
                   
                 43 
                 Connecting rail 
               
               
                   
                 44, 45 
                 Spring leg receptacle 
               
               
                   
                 46, 47 
                 Bore 
               
               
                   
                 48 
                 Carriage 
               
               
                   
                 50 
                 Plane face 
               
               
                   
                 51, 52 
                 Detent hook 
               
               
                   
                 B 
                 Guide width 
               
               
                   
                 S 
                 Thickness of cutting blade 5