Abstract:
A heating plate for a hair styling appliance, the heating plate having a length, a depth and a width. The heating plate includes a first continuous hair facing surface and a second surface opposite the first surface. The heating plate includes at least one groove which run across the width of the heating plate, each groove extends from the second surface towards the first surface and allows the heating plate to flex.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of United Kingdom Application No. 1521716.9, filed Dec. 9, 2015, the entire contents of which are incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to a hair styling appliance. Heated hair styling appliances are designed to use the action of heat and, optionally mechanical means to form hair into a desired shape or style. 
       BACKGROUND OF THE INVENTION 
       [0003]    In particular the present invention relates to a heating plate for a hair straightener, otherwise known as a hair styling iron. Hair straighteners conventionally include two articulated arms which are pivotally attached to each other at one end and to which one or more heating plates are attached at the other end. Where both arms have a heating plate they are generally positioned on inner opposed surfaces of the arms. The heating plates generally have hair contacting surfaces which are designed to come into contact with hair to be styled during use of the hair straighteners. Such a straightener can be seen in WO2014/056957. 
         [0004]    Heating plates for hair straighteners are conventionally made from a solid metal, ceramic or a combination of the two. They are also often resiliently mounted to the arm of the hair straightener such that they can move up and down or rock slightly as hair is pressed between the two arms. These resilient mounts help to ensure that hair pressed between the heating plates isn&#39;t subjected to too much pressure. They can also help to ensure that the plates remain flat and parallel during use. An example of such a resilient mounting can be seen in EP2745728. 
         [0005]    In order to reduce the damage to hair caused by over compression, hair straighteners have been described where the heating plate, or an opposed surface which contacts the heating plate is segmented to help it conform to the hair which is pressed between the arms of the straightener. Examples of such schemes are shown in EP2745728 and US2011/0083695. A problem does exist with such schemes however in that strands of hair can get trapped between the segments during use of the hair straightener. 
         [0006]    It is therefore desirable to provide an improved heating plate and hair straightener. 
       SUMMARY OF THE INVENTION 
       [0007]    A first aspect of the present invention therefore provides a heating plate for a hair styling appliance, the heating plate having a length a depth and a width, the heating plate comprising a first continuous hair facing surface and a second surface opposite the first surface, the heating plate comprising at least one groove which run across the width of the heating plate, each groove extends from the second surface towards the first surface and allows the heating plate to flex. 
         [0008]    This invention is advantageous because the at least one groove allows the heating plate to flex but the first continuous hair facing surface ensures that hair does not get trapped. The word “continuous” means that the first surface has no joints and is unbroken. The first surface is preferably formed from a single piece. In a preferred embodiment there may be a plurality of grooves. 
         [0009]    In a preferred embodiment the first surface is smooth. In a preferred embodiment the first surface may be flat. It is possible that the first surface could be slightly curved or have an undulating surface as long as it is continuous. In a particular embodiment the heating plate may be rectangular in shape. 
         [0010]    In a particularly preferred embodiment the whole heating plate may be monolithic. 
         [0011]    A layer is preferably formed between the first surface and the top of each of the grooves. The layer may have a depth (D 2 ) of from 0.001 mm to 1 mm. In a preferred embodiment the depth (D 2 ) may be from 0.01 mm to 0.1 mm Most preferably the depth (D 2 ) of the layer is 0.05 mm. This layer is preferably thin enough to be able to flex. 
         [0012]    The depth (D 1 ) of the heating plate may be from 0.01, or 0.06, or 0.5, or 1, or 3 to 5, or 7, or 10 mm. In a particular embodiment the depth (D 1 ) of the heating plate may be from 0.06 mm to 2 cm. In a most preferred embodiment the depth (D 1 ) of the heating plate is 3 mm Preferably the ratio between the depth (D 2 ) of the layer and the depth (D 1 ) of the heating plate is 1:60. 
         [0013]    In a particular embodiment there are from 20, or 30, or 40, or 50 to 60, or 70, or 80, or 90 to 100 grooves. In a preferred embodiment there are 80 grooves. Each groove  16  may be from 0.01, 02 0.1, or 0.2, or 0.3, or 0.4 to 0.5, or 0.6, or 0.7, or 0.8, or 0.9 mm wide. Ideally each groove is 0.4 mm wide. The heating plate is preferably from 20, or 40, or 60, to 80, or 100, or 125, or 150 to 200 mm in length. Ideally the heating plate is 90 mm in length. 
         [0014]    Walls are preferably present on each side of each groove and the walls define the grooves. The walls are preferably from 0.01, or 0.2, or 0.4, or 0.6, or 1 to 1.2, or 1.4, or 1.6, or 2 mm wide. Preferably the walls are 0.6 mm wide. In a particularly preferred embodiment the walls are wider than the grooves as this helps to increase the thermal mass of the heating plate. 
         [0015]    The heating plate may be formed from any suitable material, for example Aluminium, Copper, Steel, Titanium or Beryllium Copper. The heating plate can be manufactured using any suitable method. The layer may be formed in one piece and the walls may then be added to the layer to form the heating plate. Alternatively the whole heating plate may be formed in one piece and may therefore be monolithic. 
         [0016]    The heating plate may be formed using any suitable technique, for example by the use of extrusion, casting, wire cutting, computer numerical control machining (CNC), laser cutting, water jets, electro discharge machining (EDM), precision electro chemical machining (PECM) or additive manufacture. 
         [0017]    The heating plate may further comprise a first channel which runs along the length of a side of the heating plate. Preferably a first channel is arranged on both sides of the heating plate. The first channel(s) ideally house a first strip of material which is softer than the remainder of the heating plate. It may have a shore value which is lower than the shore value of the heating plate. The first strip of material may be arranged to protrude slightly from the first channel such that the top of the first strip of material is level with the first surface of the heating plate. This first strip of material can therefore act as a protective smooth edge. 
         [0018]    The heating plate may also further comprise a second channel which runs along the length of a side of the heating plate. Ideally a second channel will be arranged on both sides of the heating plate. The second channel(s) preferably house a resilient member. The resilient member may be a strip of resilient material which runs the length of the second channel(s). Alternatively the resilient member may be one or more springs located within the second channel(s). The resilient member is also preferably less conductive than the heating plate. The resilient member advantageously may help to allow the heating plate to flex when pressure is applied to the first surface of the heating plate. The resilient member may help to allow local flexing of an area of the heating plate. 
         [0019]    In a particular embodiment the heating plate may further comprise an elongate recess formed in the second surface. The elongate recess may extend the full length (L) of the heating plate. 
         [0020]    A second aspect of the present invention provides a hair straightener comprising a heating plate as described above. In a preferred embodiment the hair straighteners comprise first and second arms which are connected such that they can move between an open position and a closed position for the purpose of gripping hair. 
         [0021]    Such hair straighteners are advantageous over prior hair straighteners because whilst the heating plate is flexible and therefore hair being straightened is subjected to controlled pressure, the first continuous hair facing surface is formed in one piece and therefore hairs cannot become trapped. This may advantageously reduce hair breakage and may improve the final style of the straightened hair. 
         [0022]    Ideally each arm has a heating plate arranged such that the first continuous hair facing surfaces are opposed and are brought together when the arms are moved into the closed position. In a particular embodiment only one of the heating plates may have the structure described above. The additional plate may be a rigid plate or a rigid plate which is resiliently mounted. However in a preferred embodiment both of the heating plates may have the structure described above and they may both therefore be capable of flexing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    In order that the present invention may be more readily understood, an embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
           [0024]      FIG. 1  is a side view of a hair straightener according to the present invention; 
           [0025]      FIG. 2  is a top view of the hair straightener shown in  FIG. 1 ; 
           [0026]      FIG. 3  is a section through line G-G shown in  FIG. 2 ; 
           [0027]      FIG. 4 a    is a close up of the area H shown in  FIG. 3 ; 
           [0028]      FIG. 4 b    is a perspective view of the hair straighteners shown in  FIG. 1  with the arms in the closed position; 
           [0029]      FIG. 4 c    is a perspective view of the hair straighteners shown in  FIG. 1  with the arms in the open position; 
           [0030]      FIG. 5  is a top view of a heating plate according to a first embodiment, showing the hair contacting surface; 
           [0031]      FIG. 6 a    is a side view of the heating plate shown in  FIG. 5 ; 
           [0032]      FIG. 6 b    is an enlarge view of a portion of the heating plate shown in  FIG. 6   a;    
           [0033]      FIG. 6 c    shows the heating plate shown in  FIGS. 5 and 6   a - 6   b  flexing under pressure; 
           [0034]      FIG. 7  is a view of the underside of the heating plate shown in  FIGS. 5 and 6   a - 6   c;    
           [0035]      FIG. 8  is a top view of a heating plate according to a second embodiment, showing the hair contacting surface; 
           [0036]      FIG. 9  is a side view of the heating plate shown in  FIG. 8 ; 
           [0037]      FIG. 10  is a view of the underside of the heating plate shown in  FIGS. 8 and 7 ; 
           [0038]      FIG. 11  is a plan view of a plate carrier having a heating plate as shown in  FIGS. 8 to 10 ; 
           [0039]      FIG. 12  is a side view of the plate carrier shown in  FIG. 11 ; 
           [0040]      FIG. 13  is a section through the plate carrier shown in  FIG. 12  taken along line E-E; 
           [0041]      FIG. 14  is an end view of the plate carrier shown in  FIGS. 11 to 13 ; 
           [0042]      FIG. 15  is a perspective view of the plate carrier shown in  FIGS. 11 to 14 ; 
           [0043]      FIG. 16  is a section through the plate carrier shown in  FIG. 11  taken along the line D-D; 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0044]    The hair straightener  1  shown in  FIGS. 1 to 4   c  can be seen to comprise a first arm  2  and a second arm  4  which are joined together at one end by a hinge  6 . A power supply cable  8  is located at the hinge end of the hair straightener. 
         [0045]    Each arm  2 ,  4  further comprises a heating plate  10  located at the end of the arm furthest from the hinge  6 . Wiring  9  from the power supply cable  8  connects to a printed circuit board (PCB)  11  which controls the hair straighteners  1 . Each heating plate  10  has a hair contacting surface  12  and an opposed outer surface  14 . The hair contacting surfaces  12  on each plate  10  are arranged such that they face each other. The arms  2 ,  4  are hinged such that they can move between an open position, as shown in  FIG. 4 c   , where the hair contacting surfaces  12  are spaced apart and a closed position, as shown in  FIG. 4 b   , where the hair contacting surfaces  12  are brought together such that hair to be straightened can be held between the hair contacting surfaces  12 . 
         [0046]      FIGS. 5 to 7  show a first embodiment of the heating plate  10  which may be located on each arm  2 ,  4  of the hair straightener  1 . 
         [0047]    It can be seen that the heating plate  10  has a smooth hair contacting surface  12  which is formed in a single piece and in the embodiment shown is flat. The hair contacting surface  12  is rectangular in shape. The heating plate  10  may be formed from any suitable material which can transfer heat from the heating plate  10  to the hair to be straightened. Examples of suitable materials are metals and alloys of metals such as Aluminium, Copper, Steel, Titanium and Beryllium Copper. 
         [0048]    The heating plate  10  has an opposed surface  14  which is opposite the hair contacting surface. The whole heating plate  10  is ideally formed in one piece or from one piece of material. The heating plate  10  can be seen to have a length (L) a depth (D 1 ) and a width (W). The heating plate  10  can be seen to have a plurality of grooves  16  each of which runs across the full width (W) of the heating plate  10 . Each groove  16  extends from the opposed surface  14  towards the hair contacting surface  12 . The grooves  16  stop short of the hair contacting surface  12 . The grooves  16  allow the heating plate  10  to flex. This flexing can be seen in  FIG. 6 c   . It can be seen that when a downward force (F) is applied to the hair contacting surface  12 , for example when a tress of hair  19  is sandwiched between the first arm  2  and the second arm  4  and the arms  2 ,  4  are pressed together, the heating plate  10  flexes. 
         [0049]    A layer  20 , shown best in  FIG. 6 b   , of the heating plate  10 , is formed between the top 18 of the grooves  16  and the hair contacting surface  12 . This layer has a depth (D 2 ) of from 0.001 mm to 1 mm, ideally the depth (D 2 ) is 0.05 mm. The depth (D 1 ) of the heating plate  10  is from 0.01 mm to 10 cm. Ideally the depth (D 1 ) of the heating plate  10  is 3 mm Preferably the ratio between the depth (D 2 ) of the layer  20  and the depth (D 1 ) of the heating plate  10  is 1:60. 
         [0050]    Preferably there are from 20 to 100 grooves  16 . In a preferred embodiment there are 80 grooves. Each groove  16  may be from 0.01 to 10 mm wide. Ideally each groove is 0.4 mm wide. Walls  22  are present on each side of each groove  16 . The walls  22  help to define the grooves  16 . The walls  22  are preferably from 0.01 mm to 10 mm wide. Preferably the walls  22  are 0.6 mm wide. In a particularly preferred embodiment the walls  22  are wider than the grooves  16  as this helps to increase the thermal mass of the heating plate  10 . 
         [0051]    The heating plate  10  is preferably from 20 mm to 200 mm in length. Ideally the heating plate  10  is 90 mm in length. 
         [0052]    The heating plate  10  can be manufactured using any suitable method. The layer  20  may be formed in one piece and the walls may then be added to the layer  20  to form the heating plate  10 . Alternatively the whole heating plate  10  may be formed in one piece and may therefore be monolithic. 
         [0053]    Suitable methods of manufacture include the use of extrusion, casting, wire cutting, computer numerical control machining (CNC), laser cutting, water jets, electro discharge machining (EDM), precision electro chemical machining (PECM) and additive manufacture. 
         [0054]    A second embodiment of the heating plate  10  can be seen in  FIGS. 8 to 10 . The heating plate  10  in these figures has the same basic structure as in the first embodiment but it has a few additional features. 
         [0055]    In  FIG. 9  it can be seen that a first channel  24  runs along the length of the side of the heating plate  10 . A first channel  24  is preferably arranged on both sides of the heating plate  10 . The first channel  24  is bounded by a first protruding wall  26  which runs parallel to the hair contacting surface  12  and a second protruding wall  28  which runs parallel to the first protruding wall. The first protruding wall  26  on each side can be seen in the plan view shown in  FIG. 8 . The first channel  24  on each side of the heating plate  10  is arranged to house a first strip of material  30 . The first strip of material  30  preferably has a lower shore value than the remainder of the heating plate  10 . The first strip of material  30  can be seen in  FIG. 13 . It can be seen in  FIG. 13  that the first strip of material  30  protrudes slightly from the first channel  24  such that the top of the first strip of material  30  is level with the hair contacting surface  12  of the heating plate  10 . This first strip of material  30  can therefore act as a smooth, soft edge to the hair contacting surface  12 . This may help to protect a user during use of the hair straightener  1  as the edge will be softer than the remainder of the hair contacting surface  12 . 
         [0056]    In  FIG. 9  it can be seen that a second channel  32  runs along the length of the side of the heating plate  10 . A second channel  32  is preferably arranged on both sides of the heating plate  10 . The second channel  32  is bounded by the second protruding wall  28  and a third protruding wall  34  which runs parallel to the first  26  and second  28  protruding walls. The second channel  32  on each side of the heating plate  10  is arranged to house a resilient member  36 . The resilient member  36  is also preferably less conductive than the heating plate  10 . Ideally the resilient member  36  is formed from silicone rubber. The resilient member  36  is preferably in the form of a strip of material which runs the length of the second channel  32 . The resilient member  36  may alternatively may be formed from one or more springs arranged along the length of the second channel  32 . The resilient member  36  acts to allow the heating plate  10  to flex when pressure is applied to the hair contacting surface  12 , for example when hair to be straightened is clamped between the first and second arms  2 ,  4  of the hair straightener  1 . The resilient member  36  in the form of a strip of material can be seen in  FIG. 13 . 
         [0057]    From  FIGS. 10 and 13 to 15  it can be seen that an elongate recess  38  is formed in the opposed surface  14  of the heating plate  10 . This elongate recess  38  extends the full length (L) of the heating plate  10  and is bordered on its two long sides by a fourth  42  and a fifth  44  protruding wall. 
         [0058]    In  FIGS. 13 to 16  it can be seen that a heater  46  is located in the elongate recess  38  such that it is pressed against the opposed surface  14  of the heating plate  10 . The heating plate  10  and heater  46  are mounted on a plate carrier  48 . A resilient member, for example one or more springs  50  are mounted inside the plate carrier  48 . The spring(s)  50  act to push the heater  46  against the opposed surface  14  of the heating plate  10 . A first end  52  of the spring(s)  50  contacts the inner surface  54  of the plate carrier  48  and a second end  56  of the spring(s)  50  contact the heater  46 . The aim is to maximise the amount of contact between the heater  46  and the opposed surface  14  of the heating plate  10 . 
         [0059]    The plate carrier  48  can be seen in more detail in  FIGS. 11 to 17 . The plate carrier  48  has an elongate lower wall  58  and a pair of elongate side walls  60  which extend upwardly from each side of the elongate lower wall  58 . The elongate side walls  60  then turn towards the centre of the plate carrier  48  running parallel to the elongate lower wall  58  to provide first runners  62 . These first runners  62  can engage with corresponding second runners  64  which are located on the free ends of the fourth and fifth protruding walls  42 ,  44 . These first and second runners  62 ,  64  run the length (L) of the heating plate  10  and the plate carrier  48  and allow the heating plate  10  to be slid into position on the plate carrier  48  during construction. It can be seen that the second runners  64  are located underneath the first runners  62 . This means that the heating plate  10 , or a portion of it, can be moved toward the lower wall  58  against the action of the spring(s)  50  and the resilient members  36 , if pressure is applied to the hair contacting surface  12  of the heating plate  10 . 
         [0060]    It can be seen in  FIGS. 11, 12, 14 and 16  that the plate carrier  48  further comprises a pair of tabs  66  which are protrude outwardly from the lower wall  58  of the plate carrier  48 . These tabs  66  are designed to engage with the arms  2 ,  4  of the hair straightener.  FIGS. 3 and 4  show a pair of plate carriers  48  engaged in position on the hair straightener  1 . One plate carrier  48  is engaged on the first arm  2  and one plate carrier  48  is engaged on the second arm  4 . The tabs  66  engage on the arms  2 ,  4  behind forward retaining means  68  and rearward retaining means  70  located on the arms  2 ,  4  of the hair straightener  1 . Each arm  2 ,  4  also has a plurality of resilient supports  72  which are located between the lower walls  58  of the plate carriers  48  and the inner wall  74  of the arms  2 , 4 . These resilient supports  72  may be made of a resilient material for example silicone rubber or they may be in the form of springs. The resilient supports  72  allow the plate carriers  48  to move slightly if subjected to pressure. This means that in addition to the heating plates  10  being able to flex under pressure, they may also move as one piece towards the inner wall  74  of the arms  2 ,  4 .