Abstract:
There is disclosed an injection mold which may allow for a uniform flow front of the thermo-plastic melt during the injection mold process. Further, a corresponding injection-molded part is disclosed.

Description:
CROSSREFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims priority of the German utility model 20 2012 104 499.4, filed on Nov. 20, 2012 and of German patent application 10 2013 107 468.5, filed on Jul. 15, 2013. Both priority applications are fully incorporated by reference herewith. 
       BACKGROUND OF THE INVENTION 
       [0002]    Injection-molded parts are known in a great variety of shapes. For certain injection-molded parts, in particular in the area of household goods or entertainment electronics, there are high demands regarding the visual appearance of the injection-molded part as perceived by the user. In particular, it is desired that a visible part of the injection-molded part, i.e. that part of the injection-molded part which is visible to the user and which may be touched by the user, is provided homogenously and uniformly. 
         [0003]    If materials with colored particles or pigments are used today, for example colored granulate for obtaining a silver color, the results are not satisfactory today. It is rather required to produce an injection-molded part from raw granulate and paint it with the desired color then. This leads to a complicated and expensive manufacturing process. In addition, the painting typically uncovers tensions in the material which have been locked in the material during the injection mold process. The result is that the painted visible side is visibly inhomogeneous and that the pointed injection-molded part is not suitable for a further use. 
         [0004]    It is an object of the present invention to provide an improved injection mold and an improved injection-molded part which may allow to overcome this disadvantage. 
       SUMMARY OF THE INVENTION 
       [0005]    According to a first aspect there is provided an injection mold for producing an injection-molded part, in particular for producing an operating button of a household device, wherein the injection mold comprises a first cavity for a first section of the injection-molded part, a second cavity for a second section of the injection-molded part and an opening for injecting a plastic material, wherein the first and the second cavity are connected fluidwise along a line-shaped connecting section, wherein the first section is a visible part of the injection-molded part and the second section is a side part of the injection-molded part, wherein the first section extends at least substantially in a first plane, the second section extends at least substantially in a second plane and the first and second planes are at an angle to one another, wherein the opening feeds into the second cavity, wherein the second cavity comprises a deepening which depth extends at least substantially perpendicular to the second plane and wherein the deepening increases in width when considering a central line which points from the opening to a closest point on the connecting section. 
         [0006]    Such injection mold may allow to injection-mold injection-molded parts using a colored granulate. A painting process can thus be avoided. It is believed to be advantageous if the opening or the injection point is placed such that the injection direction is at an angle relative to the subsequently extending flow front of the thermo-plastic melt. The angle between the injection direction and the central line is preferably between 30° and 150°, more preferably between 60° and 120° and in particular between 80° and 100°. An advantageous and in particular simple to realize embodiment is provided when the angle between the injection direction and the central line is at least approximately 90°. 
         [0007]    One of the aspects is to design the geometry of the injection mold such that along the central line or the flow path the flow pressure is steadily reduced in order to ultimately achieve a homogenous flow front across the width of the first section or the surface of the button. In a preferred embodiment this is achieved by providing the area between the opening or the injection point and the beginning of the first section beginning with the connecting section, in particular the beginning of the surface of the button, with a nozzle-like geometry. In other words, initially there is a small cross-section which increases with the advancing flow front to the connecting section, in particular there is a continuous widening, until the flow front has a significant portion of the width of the second section at the connecting section, in particular has the width of the surface of the button. 
         [0008]    Should, nevertheless, very minor inhomogeneities of the surface result or in case a dull finish of the surface is desired, the first cavity of the injection mold is preferably provided with a fine surface structure, i.e. the design surface, in order to hide inhomogeneities and/or to provide the dull finish of the surface. The angle between the first and second planes is preferably between 30° and 150°, more preferably between 60° and 120°, in particular between 90° and 100°. The injection mold can be advantageously realized if the angle is at least approximately 90°. 
         [0009]    The injection mold is suitable for producing small injection-molded parts. It is also suitable for producing a large injection-molded part, wherein the term “large” refers to those injection-molded parts which cannot be considered “small” anymore. 
         [0010]    Each of the previously referenced planes and the planes referenced in the following can be understood as a plane which extends in two directions of a Cartesian coordinate system. The planes can also be understood as planes which are—in reference to a Cartesian coordinate system—curved and which can in particular be described as a plane in an ellipsoid coordinate system, a spherical coordinate system, a spatial polar coordinate system or a cylindrical coordinate system. 
         [0011]    The term line-shaped can be understood as linear along a straight line. The term line-shaped can also be understood as linear along a non-straight line, in particular as curved or swinging. 
         [0012]    According to an refinement, the width of the deepening in the area of the opening is between 5% and 45%, preferably between 8% and 35%, more preferably between 12% and 32% and in particular between 15% and 25% of the width of the second area at the connecting section. 
         [0013]    This refinement may allow for a particularly uniform flow front. 
         [0014]    According to a further refinement the width of the deepening at the connecting area is at least 45%, preferably at least 65%, more preferably at least 85% and in particular at least 95% of the width of the second area at the connecting section. 
         [0015]    This refinement may allow for a particularly uniform flow front. 
         [0016]    According to a further refinement the width of the deepening, considering a view along the central line, increases to a smaller degree in a first area of the deepening closer to the opening than in a second area of the deepening which lies further away from the opening than the first area. 
         [0017]    This refinement may allow for a particularly uniform flow front. 
         [0018]    According to a further refinement the depth of the deepening increases with increasing distance from the central line, in particular at least substantially continuously and at least substantially over the respective width of the deepening. 
         [0019]    This refinement may allow for a particularly uniform flow front, because, among other effects, the increased flow resistance may be compensated for those areas which are located further away from the central line. 
         [0020]    According to a further refinement the deepening is arranged facing the opening when viewed in the injection direction. 
         [0021]    This refinement may allow for a particularly uniform flow front. 
         [0022]    According to a further refinement, there is no direct fluidwise connection between the opening and the first cavity, but only via the second cavity. 
         [0023]    In this refinement, the flow front is obtained starting from the opening in the second cavity and only reaches the first cavity thereafter. This may result in a particularly homogenous flow front through the first cavity. 
         [0024]    According to a further refinement the injection-molded part does not exceed in any dimension a length of 10 cm, preferably 7 cm, more preferably 5 cm and in particular 4 cm. 
         [0025]    For injection-molded parts of this size the flow front becomes very uniform. 
         [0026]    According to a further refinement the injection-molded part does not fall in any dimension below a length of 2 mm, preferably 3 mm, more preferably 5 mm and in particular 10 mm. 
         [0027]    For injected-molded parts of this size the flow front becomes very uniform. 
         [0028]    According to a further refinement the height of the first cavity which extends at least substantially perpendicular to the first plane, increases along a virtual continuation of the central line beyond the connecting section and into the first cavity. 
         [0029]    This refinement may allow for more complex designs of the injection-molded parts. 
         [0030]    According to a further refinement a third cavity for a third section of the injection-molded part, the third cavity spaced apart from and facing the second cavity, wherein the first and third cavity are connected fluidwise, wherein the third section is a further side part of the injection-molded part, the third section extending at least substantially in a third plane and wherein the first and third planes are at an angle relative to one another. 
         [0031]    This refinement may be advantageous for producing control buttons. The further angle is preferably between 30° and 150°, more preferably between 60° and 120° and in particular between 80° and 100°. A particularly advantageous and simple refinement may be obtained if the further angle is at least approximately at 90°. 
         [0032]    According to a second aspect there is provided an injection-molded part which has been produced using the injection mold described above. 
         [0033]    According to a third aspect there is provided an injection-molded part, in particular an operating button of a household device, the injection-molded part comprising a first section, which is a visible part of the injection-molded part, a second section which is a side part of the injection-molded part, and at least a partial imprint of an injection site of an opening of an injection mold, wherein the first and the second section are connected as one integral piece at least along a line-shaped connecting section, wherein the first section extends at least substantially in a first plane, the second section extends at least substantially in a second plane and the first and second planes are at an angle to each other, wherein the imprint is arranged at the second section, wherein the second section comprises a heightening which height extends at least substantially perpendicular to the second plane and wherein the heightening increases in width when considering a central line which points from the imprint to a closest point on the connecting section. 
         [0034]    According to a further refinement the width of the heightening in the area of the imprint is between 5% and 45%, preferably between 8% and 38%, more preferably between 12% and 32% and in particular between 15% and 25% of the width of the second section at the connecting section. 
         [0035]    According to a further refinement the width of the heightening at the connecting section is at least 45%, preferably at least 65%, more preferably at least 85% and in particular at least 95% of the width of the second section at the connecting section. 
         [0036]    According to a further refinement the width of the heightening, considering a view along the central line, increases to a smaller degree in a first area of the heightening closer to the imprint that in a second area of the heightening which lies further away from the imprint than the first area. 
         [0037]    According to a further preferred refinement, the height of the heightening increases with increasing distance from the central line, in particular at least substantially continuously and at least substantially over the respective width of the heightening. 
         [0038]    According to a further refinement the heightening is arranged at a first side of the second section facing the imprint when viewed in the injection direction. 
         [0039]    According to a further refinement the injection-molded part does not exceed in any dimension a length of 10 cm, preferably 7 cm, more preferably 5 cm and in particular 4 cm. 
         [0040]    According to a further refinement the injection-molded part does not fall in any dimension below a length of 2 mm, preferably 3 mm, more preferably 5 mm and in particular 10 mm. 
         [0041]    According to a further refinement the height of the first section which extends at least substantially perpendicular to the first plane, increases along a virtual continuation of the central line beyond the connecting section and into the first section. 
         [0042]    According to a further refinement a third section is spaced apart from and facing the second section, wherein the third section is a further side part of the injection-molded part, the third section extending at least substantially in a third plane and wherein the first and third planes are at an angle relative to one another. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0043]    It is to be understood that the previously mentioned features and the features mentioned in the following may not only be used in a certain combination, but also in other combinations or as isolated features without leaving the spirit and scope of the present invention. 
           [0044]    Preferred embodiments are shown in the drawings and will be explained in more detail in the following. The drawings show: 
           [0045]      FIG. 1  an injection-molded part according to the prior art; 
           [0046]      FIG. 2  a first element of an embodiment of an injection mold according to the present invention; 
           [0047]      FIG. 3  a second element of an embodiment of an injection mold according to the present invention; 
           [0048]      FIG. 4  a first embodiment of an injection-molded part according to the present invention in a first view; 
           [0049]      FIG. 5  the injection-molded part according to  FIG. 4  in a second view; 
           [0050]      FIG. 6  a second embodiment of an injection-molded part according to the present invention; and 
           [0051]      FIG. 7  a third embodiment of an injection-molded part according to the present invention. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0052]      FIG. 1  shows an injection-molded part  10  according to the prior art. The injection-molded part  10  comprises a first section  12  which is a visible part of the injection-molded part  10 . The injection-molded part  10  further comprises a second section  14  which is a side par of the injection-molded part  10 . Further there is shown symbolically an imprint  16  of an injection point of an opening of an injection mold (not shown). 
         [0053]    The first and second sections  12 ,  14  are connected as one integral piece at least along a line-shaped connecting section  18 . 
         [0054]    The first section  12  extends at least substantially in a first plane XY, here, the XY-plane, and the second section  14  extends at least substantially in a second plane XZ, here, the XZ-plane. The first and second planes XY, XZ are at an angle relative to one another which is at least approximately 90°. 
         [0055]    According to a preferred embodiment shown in  FIGS. 2 and 3 , the injection mold  20  for producing a small injection-molded part  10  consists of a first element  22  (see  FIG. 2 ) and a second element  24  (see  FIG. 3 ). The injection mold  20  will now be explained based on these figures. 
         [0056]    The injection mold  20  comprises a first cavity  26  for a first section  12  of the injection-molded part  10 . The cavity  26  is provided by keeping a distance between the termination surface  28  of the first element  22  and the floor  30  of the second element  24 , if the first element  22  is inserted into the second element  24 . Then, when the first element  22  is inserted into the second element  24 , a liquid material is injected and fills the cavities to produce an injection-molded part 
         [0057]    The injection mold  20  further comprises a second cavity  32 , which results from a distance between the side termination surface  34  of the first element  22  and the side wall  36  of the second element  24 . 
         [0058]    Further, an opening  38  for injecting a plastic material or a thermo-plastic melt is shown. The first and second cavities  26 ,  32  are connected at least along a line-shaped connecting section  18  symbolized by a dashed line  40 . 
         [0059]    The first section  12  is a visible part of the injection-molded part  10 , and the second section  14  is a side part of the injection-molded part  10 . The first section  12  or the first cavity  26  extend at least substantially in a first plane XY, here, the XY-plane, and the second section  14  or the second cavity  32  extend at least substantially in a second plane XZ, here, the XZ-plane. The first and second planes XY, XZ are at an angle relative to each other. 
         [0060]    The opening  38  feeds into the second cavity  32 . The second cavity  32  further comprises a deepening  42 , its depth, here in the Y-direction, is at least approximately perpendicular to the second plane XZ. The deepening  42  increases in width, here in the X-direction, when considering moving along the central line  44 . The central line  44  is formed starting from the opening  38  and pointing to a closest point on the connecting section  18 . 
         [0061]    The width of the deepening  42  increases, when considering moving along the central line  44 , in a first area  46  of the deepening  42  close to the opening  38  to a lesser degree than in a second area  48  of the deepening  42  which is located further away from the opening  38  than the first area  46 . 
         [0062]    The depth of the deepening  42  increases with increasing distance from the central line  44 , in particular substantially continuously and substantially across the corresponding width of the deepening  42 . The deepening  42  is arranged facing the opening  38  when viewed in the injection direction  50 , however, as shown, without being limited to this area. 
         [0063]    A third cavity is spaced apart from and facing the second cavity  32  in order to obtain a third section  54  of the injection-molded part  10 . The first and second cavities are connected fluidwise, wherein the third section  54  is a further side part  56  (see  FIG. 4 ) of the injection-molded part  10 . The third section  54  extends at least substantially in a third plane XZ′, here, the XZ-plane, and the first and third planes XY, XZ′ are at an angle relative to one another. 
         [0064]      FIG. 4  shows a first embodiment of an injection-molded part  10 , here an operating button of a household device. The injection-molded part  10  comprises a first section  12 , which is a visible part of the injection-molded part  10 , a second section  14 , which is a side part of the injection-molded part  10 , and at least a partial imprint  16  of an injection point of an opening  38  of an injection mold  20 . 
         [0065]    The first and second sections  12 ,  14  are integrally connected as one piece along at least a line-shaped connecting section  18  which is further shown by dashed line  40 . The first section  12  extends at least substantially in a first plane XY, here, the XY-plane, the second section  14  extends at least substantially in a second plane XZ, here, the XZ-plane, and the first and second planes XY, XZ are at an angle relative to each other. 
         [0066]    The imprint  16  is present on the second section  14 . The second section  14  comprises a heightening  58  (see  FIG. 5 ) which width extends at least approximately perpendicular to the second plane XZ. The heightening  58  increases in width when considering moving along the central line  44 , wherein also for this embodiment the central line  44  starts from the imprint  16  and points to a closest point on the connecting section. 
         [0067]      FIG. 5  shows that the width of the heightening  58  when considering moving along the central line  44  increases to a smaller degree in a first area  60  of the heightening  58  close to the imprint  16  than in a second area  62  of the heightening  58  which is located further away from the imprint  16  than the first area  60 . It is shown that the height of the heightening  58  increases with increasing distance from the central line  44 , in particular substantially continuously and substantially across the whole corresponding width of the heightening  58 . The heightening  58  is located at a first side of the second section  14  facing the imprint  16  in the injection direction  50 . 
         [0068]    The height of the first section  12  which extends at least approximately perpendicular to the first plane XY, increases along a virtual continuation of the central line  44  beyond the connecting section  18  into the first section  12  which is symbolized by the dashed line  64 . 
         [0069]    A third section  56  is spaced apart from and is facing the second section  14 , wherein the third section  56  is a further side part of the injection-molded part  10 , the third section  56  extends at least substantially in a third plane XZ′, here, the XZ-plane, and the first and third planes XY, XZ′ are at angle relative to one another. 
         [0070]      FIG. 6  shows a second embodiment of an injection-molded part  10 , here, again an operating button of a household device. The injection-molded part  10  comprises a first section  12 , which is a visible part of the injection-molded part  10 , and a second section  14 , which is a side part of the injection-molded part  10 . 
         [0071]    The first section  12  extends at least substantially in a first plane XY, The first plane XY may be a plane in a Cartesian coordinate system as well as, as has been explained at the beginning, a plane in an another coordinate system, so it may also be curved. The second section  14  extends at least substantially in a second plane RZ. The second plane RZ is spanned by the Z-axis and a curvature R around the Z-axis. The second plane RZ lies in a barrel plane of a circular cylinder. The first and second planes XY, RZ are at an angle relative to one another. 
         [0072]    For the further explanations reference is made to  FIGS. 4 and 5 . The second embodiment of the injection-molded part  10  discloses directly also a corresponding injection mold  20 , because the mold is the negative of the injection-molded part  10 . Consequently, the deepening  42  of the corresponding injection mold  20  is the negative of the heightening  58  of the injection-molded part  10 . The first section  12  of the corresponding injection mold  20  is the negative of the first cavity  26  of the injection-molded part  10 . The second section  14  of the corresponding injection mold  20  is the negative of the second cavity  32  of the injection-molded part  10 . The imprint of an injection point of an opening of an injection mold  20 , see  FIG. 4 , is hidden. 
         [0073]      FIG. 7  shows a third embodiment of an injection-molded part  10 , which differs from the second embodiment in that the plane RZ lies in the barrel plane of a cylinder having an elliptical base area. The other explanations in the context of  FIG. 6  apply here as well.