Abstract:
A metal mold forming method for an indoor illuminating lamp lens for a motor vehicle using a metal mold having a cavity having a form of the indoor illuminating lamp lens to be provided with an entire surface as a designed part, the indoor illuminating lamp lens having a prescribed thickness and a rib in a back surface thereof, comprises providing a gate to the rib and the thickness, injecting a molten resin into the cavity of the metal mold from the gate, separating the rib from the gate by inserting a cut pin having a same width as a width of the gate into the rib and the gate at a root of the gate after the step of injecting is completed, and taking out the lens from the metal mold by moving the cut pin backward after the step of separating is completed.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of PCT application No. PCT/JP2011/080562, which was filed on Dec. 22, 2011 based on Japanese Patent Application No. 2010-288102 filed on Dec. 24, 2010, the contents of which are incorporated herein by reference. Also, all the references cited herein are incorporated as a whole. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the invention 
         [0003]    The present invention relates to an indoor illuminating lamp lens for a motor vehicle, and more particularly to a metal mold forming method for an indoor illuminating lamp lens for a motor vehicle and an indoor illuminating lamp lens in which a dimension is easily controlled and there is no fear that scars are left on a ceiling. 
         [0004]    2. Description of the related art 
         [0005]    An indoor illuminating lamp for a motor vehicle including a lens, a housing, a ceiling and a lamp unit is usually known in which the housing having the lamp unit to which the lens is attached is attached to a reinforcement through the ceiling (see JP-A-2005-238966). 
         [0006]      FIGS. 6(A) and 6(B)  are perspective views for explaining an indoor illuminating lamp for a motor vehicle to which the present invention is applied.  FIG. 6(A)  is an exploded view and  FIG. 6(B)  is a view of an assembled state in which an attachment is completed. 
         [0007]    In  FIG. 6(A) , the indoor illuminating lamp is formed by a lens  10 , a housing  20 , a ceiling  30  and a lamp unit in order from an upper part. 
         [0008]    Now, these components will be briefly described below. 
       &lt;Lens  10 &gt; 
       [0009]    The lens  10  is a resin member having a function of a lens for passing lights from a lamp  40 L of the lamp unit  40  fixed to the housing  20 . The lens  10  has a rectangular shape gently curved in one direction in the form of a barrel and ribs  10 B ( FIG. 1(B) ) standing upright over 360° of the periphery of a back side thereof. In the vicinity of the ribs  10 B or between the ribs, lock engaging holes  10 R are provided and the lock engaging holes  10 R are engaged with lock pawls  20 R of the housing  20 . 
       &lt;Housing  20 &gt; 
       [0010]    The housing  20  is a resin member including an upright wall  20 W circulated in a rectangular shape and a bottom plate  20 B that closes about half of a bottom opening surrounded by the upright wall  20 W. The upright wall  20 W is provided with the lock pawls  20 R on side surfaces which are engaged with the lock engaging holes  10 R of the lens  10  and a plurality of lock pawls  20 T in an extending direction of the upright wall  20 W which are engaged with a plurality of lock engaging holes of a reinforcement located in the ceiling side in a vehicle. To the bottom plate  20 B, the lamp unit  40  is fixed. 
       &lt;Ceiling  30 &gt; 
       [0011]    The ceiling  30  is formed with a frame shaped resin member in plan view which forms a ceiling part when an indoor illuminating lamp for a motor vehicle is attached to an upper part of the vehicle, and includes a flat bottom surface part  30 P of an inner side peripheral edge of a central opening  30 L, an inclined surface part  30 S obliquely standing from an end of the bottom surface part  30 P and a top surface part  30 T extending horizontally from a top part of the inclined surface part  30 S. 
       &lt;Lamp Unit  40 &gt; 
       [0012]    The lamp unit  40  has the lamp  40 L and is turned on by a signal from the vehicle. The lamp unit  40  is fixed to the bottom plate  20 B of the housing  20  so that the lamp  40 L protrudes from the bottom plate  20 B. 
         [0000]    &lt;Attachment of Indoor illuminating Lamp&gt; 
         [0013]    In attaching the above-described components to the vehicle, initially, the lock pawls  20 R of the housing  20  are engaged with the lock engaging holes  10 R of the lens  10  ( FIG. 6(A) ) to attach the lens  10  to the housing  20 . Then, the housing  20  is attached to the lamp unit  40  through the ceiling  30 . Thus, the indoor illuminating lamp  1  for the motor vehicle is completed as shown in  FIG. 6(B) . 
         [0014]    Then, the lock pawls  20 T of the housing  20  of the indoor illuminating lamp  1  for the motor vehicle are engaged with the lock engaging holes of the reinforcement of the vehicle to attach the indoor illuminating lamp  1  for the motor vehicle to the vehicle. 
       &lt;Usual Forming Method of Lens&gt; 
       [0015]    FIGS.  7 (A)( 1 ),  7 (A)( 2 ),  7 (B),  7 (C)( 1 ), and  7 (C)( 2 ) are perspective view of a usual forming method of a lens. FIG.  7 (A)( 1 ) is a perspective view of the lens seen from a front side. FIG.  7 (A)( 2 ) is a perspective view of the lens seen from a back side.  FIG. 7(B)  is a perspective view showing a state that a molten resin is injected into a metal mold from a gate. FIG.  7 (C)( 1 ) shows the lens before the gate attached to the molded lens is cut by a nipper.  FIG. 7(C)  ( 2 ) shows the lens after the gate is cut by the nipper. 
         [0016]    The lens  100  formed by the usual forming method is a rectangular resin member curved gently in one direction in the form of a barrel as shown in FIG.  7 (A)( 1 ). When the lens  100  is seen from the back side, such a gate mark as surrounded by a round mark F shown in FIG.  7 (A)( 2 ) is formed. FIG.  7 (C)( 2 ) is an enlarged view of the round mark F of FIG.  7 (A)( 2 ) to show that the gate mark  500 K is formed. A reason why the gate mark  500 K is formed and problems caused from the gate mark will be described below. 
       (Reason Why Gate Mark is Formed) 
       [0017]    In order to injection mold the lens  100  as shown in  FIGS. 7(A) and 7(B) , initially, a metal mold is manufactured which has a cavity with the form of the lens  100  therein. 
         [0018]    Then, an injection passage (a gate)  500  is formed for injecting the molten resin into the cavity of the metal mold to inject the molten resin into the cavity of the metal mold from the gate  500  in a direction shown by a void arrow mark in  FIG. 7(B) . 
         [0019]    When the molten resin is injected into the cavity of the metal mold, the lens  100  and the gate  500  are solidified under a state that the lens  100  is integrally formed with the gate  500 . 
         [0020]    After the molten resin is solidified, when the lens  100  and the gate  500  are taken out from a molding machine, a molded product having the lens  100  formed integrally with the gate  500  is obtained as shown in FIG.  7 (C)( 1 ). 
         [0021]    Thus, when a root part of the gate  500  is cut by a nipper to separate the gate  500  from the lens  100 , the lens  100  with the gate mark  500 K having a remainder of the gate as shown in FIG.  7 (C)( 2 ) is obtained. 
         [0000]    &lt;Problem of Lens  100  with Gate Mark&gt; 
         [0022]    As described above, in the usual lens  100 , since the gate  500  shown in FIG.  7 (C)( 1 ) is cut by the nipper, the gate mark  500 K shown in FIG.  7 (C)( 2 ) has a large gate emerging margin. Accordingly, the large gate emerging out margin of the gate mark  500 K is greatly uneven and hardly dimensionally controlled. 
         [0023]    Further, when the gate  500  is cut by the nipper, there is a fear that a designed surface of the lens  100  may be possibly broken. 
         [0024]    Further, since the gate  500  is cut by the nipper, there is a possibility that a sharp configuration may be formed on a cut surface of the gate mark  500 K. In the case of an entire surface lens, there is possibility that a ceiling may be possibly marred by the sharp cut surface. 
       SUMMARY OF THE INVENTION 
       [0025]    The present invention has been made in view of these situations and possibilities. It is an object of the present invention to provide an indoor illuminating lamp lens for a motor vehicle which can be easily dimensionally controlled and has no possibility of marring a ceiling. 
         [0026]    A first aspect of the present invention relates to a metal mold forming method for an indoor illuminating lamp lens for a motor vehicle using a metal mold having a cavity having a form of the indoor illuminating lamp lens to be provided with an entire surface as a designed part, the indoor illuminating lamp lens having a prescribed thickness and a rib in a back surface thereof, the method comprising steps of providing a gate to the rib and the thickness, injecting a molten resin into the cavity of the metal mold from the gate, separating the rib from the gate by inserting a cut pin having a same width as a width of the gate into the rib and the gate at a root of the gate after the step of injecting is completed, and taking out the lens from the metal mold by moving the cut pin backward after the step of separating is completed. 
         [0027]    In a second aspect of the present invention according to the first aspect, a crepe work is applied to an end of the cut pin in the first invention. 
         [0028]    A third aspect of the present invention relates to an indoor illuminating lamp lens that has a prescribed thickness and an entire surface to be formed as a designed part, wherein a gate setting surface formed by inserting a cut pin to a part of the thickness during a molding has a surface difference applied so as to be lower than a lens control surface as a back surface of the thickness. 
         [0029]    As described above, according to the first aspect of the present invention, since the cut pin having the same width as the width of the gate into the rib and the gate at the root part of the gate after the injection is completed to separate the rib from the gate, the lens can be obtained in which a dimensional control is more easily carried out than a usual method that the gate part is cut by the nipper and there is no fear of marring the ceiling. 
         [0030]    According to the second aspect of the present invention, since the crepe work is applied to the end of the cut pin, the crepe work can be simply applied to the gate setting surface. 
         [0031]    According to the third aspect of the present invention, since the gate setting surface has the surface difference so that the gate setting surface is recessed more than the lens control surface, when the lens is attached to the ceiling, a clearance formed between the lens and the ceiling can be reduced. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0032]      FIG. 1(A)  is a perspective view of an indoor illuminating lamp lens for a motor vehicle according to the present invention which is looked upward from a lower part.  FIG. 1(B)  is an enlarged view of a part surrounded by a circle A in  FIG. 1(A) . 
           [0033]    FIGS.  2 ( 1 ) and  2 ( 2 ) are perspective views of the first half for explaining an overlap forming method. 
           [0034]    FIGS.  3 ( 1 ) and  3 ( 2 ) are perspective views of the latter half for explaining the overlap forming method. 
           [0035]      FIG. 4(A)  is a perspective view of an indoor illuminating lamp for the motor vehicle in which an attachment is completed and shows an illuminating lamp to which a usual lens is attached and an illuminating lamp to which the lens according to the present invention is attached at the same time. FIGS.  4 (B)( 1 ) and (B)( 2 ) show the usual lens. FIG.  4 (B)( 1 ) is a perspective view showing a part in the vicinity of a gate. FIG.  4 (B)( 2 ) is a sectional view taken along a line B-B of the usual lens in  FIG. 4(A) . FIG.  4 (C)( 1 ) and (C)( 2 ) show the lens according to the present invention.  FIG. 4  (C)( 1 ) is a perspective view showing a part in the vicinity of a gate. FIG.  4 (C)( 2 ) is a sectional view taken along a line B-B of the lens according to the present invention shown in  FIG. 4(A) . 
           [0036]    FIG.  5 ( 1 ) is a perspective view of an entire part of a front side of the lens. FIG.  5 ( 2 ) is an enlarged view of a round mark D shown in FIG.  5 ( 1 ). FIG.  5 ( 3 ) shows a specific example of a lens cut C applied to the entire part of the front side of the lens. FIG.  5 ( 4 ) is a perspective view of an entire part of a back side of the lens. FIG.  5 ( 5 ) is an enlarged view of a round mark E shown in FIG.  5 ( 4 ). 
           [0037]      FIGS. 6(A) and 6(B)  are perspective views for explaining an indoor illuminating lamp for a motor vehicle to which the present invention is applied.  FIG. 6(A)  is an exploded view and  FIG. 6(B)  is a view of an assembled state in which an attachment is completed. 
           [0038]    FIGS.  7 (A)( 1 ),  7 (A)( 2 ) and  FIG. 7(B) ,  7 (C)( 1 ) and  7 (C)( 2 ) are perspective views of a usual forming method of a lens. FIG.  7 (A)( 1 ) is a perspective view of the lens seen from a front side. FIG.  7 (A)( 2 ) is a perspective view of the lens seen from a back side.  FIG. 7(B)  is a perspective view showing a state that a molten resin is injected into a metal mold from a gate. FIG.  7 (C)( 1 ) shows the lens before the gate attached to the molded lens is cut by a nipper.  FIG. 7(C)  ( 2 ) shows the lens after the gate is cut by the nipper. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0039]    Now, a metal mold forming method for an indoor illuminating lamp lens for a motor vehicle according to the present invention will be described below which is easily dimensionally controlled and has no fear of marring a ceiling. 
       &lt;Feature of Lens According to the Present Invention&gt; 
       [0040]    A lens  10  shown in  FIG. 1  is manufactured by an injection molding of a molten resin similarly to a usual lens, however, different from the usual lens in view of a point that the lens  10  is formed by an overlap forming method. When the lens  10  is formed by the overlap forming method, the lens  10  is characterized in that a gate setting surface  10 G of the lens  10  is arranged so as to be lower by one step than a lens control surface  10 N. 
         [0041]    Namely, in the enlarged view of a gate part shown in  FIG. 1(B) , it is recognized that the gate setting surface  10 G of the lens  10  is recessed more by one step than the lens control surface  10 N. 
       &lt;Overlap Forming Method Used by the Present Invention&gt; 
       [0042]    FIGS.  2 ( 1 ) and  2 ( 2 ) and FIGS.  3 ( 1 ) and  3 ( 2 ) are views for explaining the overlap forming method, and the overlap forming method is carried out in order of FIGS.  2 ( 1 ), FIG.  2 ( 2 ), FIG.  3 ( 1 ) and FIG.  3 ( 2 ). The overlap forming method itself can be carried out by referring to the invention disclosed in, for instance, JP-A-H9-141708. 
       (1) &lt;Injection of Resin&gt; 
       [0043]    In FIG.  2 ( 1 ), the lens  10  is provided with a rib  10 B over 360° of a periphery of a back side thereof. A metal mold having therein a cavity with such a form of the lens  10  is manufactured. Then, an injection passage (a gate) is formed for injecting a molten resin into the cavity of the metal mold. When the molten resin is injected into the cavity of the metal mold from the gate  50  in a direction shown by a void arrow mark, the lens  10  and the gate  50  are solidified under a state that the lens  10  is integrally formed with the gate  50 , so that the entire part of the lens  10  is formed. A cut pin  60  which can make an access to a root part of the gate in the cavity is located in the metal mold and still stands by. The cut pin  60  has the same width as the width of the gate  50 , so that the cut pin  60  is adequately inserted into the width of the gate  50 . 
       (2) &lt;Press-In of Cut Pin  60 &gt; 
       [0044]    Then, in FIG.  2 ( 2 ), when the injection of the molten resin is completed, the waiting cut pin  60  operates in a direction shown by a black arrow mark so that a resin press-in part  10 P of the molten resin of the gate in the vicinity of the rib  10 B is pressed-in to the rib  10 B of the lens  10 . 
       (3) &lt;Separation of Rib  10 B From Gate  50 &gt; 
       [0045]    Then, in FIG.  3 ( 1 ), when the molten resin is pressed-in to the resin press-in part  10 P by the cut pin  60 , the rib  10 B of the lens  10  is simultaneously separated from the gate  50  by a gate cut part  50 C of the gate  50 . At this time, since the gate cut part  50 C is separated from the lens  10 , a gate cut mark is not left. 
       (4) &lt;Return of Cut Pin  60 &gt; 
       [0046]    Finally, in FIG.  3 ( 2 ), after the gate is completely cut, the cut pin  60  is returned in a direction shown by a black arrow mark, then, the gate is separated and only the lens  10  is taken out from the metal mold. 
         [0047]    In the lens  10  taken out from the metal mold in such a way, an entire form is obtained as shown in  FIG. 1(A) . In a position where the gate is located, the gate setting surface  10 G of the lens  10  is recessed more by one step than the lens control surface  10 N as shown in  FIG. 1(B) . 
         [0000]    &lt;Reason Why Gate Setting Surface  10 G is Preferably Recessed More than Lens Control Surface  10 N&gt; 
         [0048]      FIGS. 4(A) ,  4 (B)( 1 ),  4 (B)( 2 ),  4 (C)( 1 ), and  4 (C)( 2 ) are views for explaining a reason why the gate setting surface  10 G is preferably recessed more than the lens control surface  10 N.  FIG. 4(A)  is a perspective view of an indoor illuminating lamp for the motor vehicle in which an attachment is completed and shows an illuminating lamp to which the usual lens  100  is attached and an illuminating lamp to which the lens  10  according to the present invention is attached at the same time. 
         [0049]    FIGS.  4 (B)( 1 ) and (B)( 2 ) show the usual lens  100 . FIG.  4 (B)( 1 ) is a perspective view showing a part in the vicinity of a gate. FIG.  4 (B)( 2 ) is a sectional view taken along a line B-B of the usual lens in  FIG. 4(A) . FIGS.  4 (C)( 1 ) and (C)( 2 ) show the lens  10  according to the present invention.  FIG. 4  (C)( 1 ) is a perspective view showing a part in the vicinity of a gate. FIG.  4 (C)( 2 ) is a sectional view taken along a line B-B of the lens according to the present invention shown in  FIG. 4(A) . 
         [0050]    In FIG.  4 (B)( 1 ), since a gate setting surface  100 G of the usual lens  100  is the same as a lens control surface  100 N, the gate emerging margin has a width of T 1 . When such a lens  100  is attached to the ceiling  30 , the gate setting surface  100 G of the lens  100  pushes in the ceiling  30  form a large clearance C 1  (a gap) between the lens  100  and the ceiling  30 . 
         [0051]    As compared therewith, in FIG.  4 (C)( 1 ), since the gate setting surface  10 G of the lens  10  according to the present invention is recessed more by one step than the lens control surface  10 N, a gate emerging margin has a width T 2  smaller than the usual width T 1  (T 1 &gt;T 2 ). When such a lens  10  is attached to the ceiling  30 , an amount that the gate setting surface  10 G pushes in the ceiling  30  is reduced, so that only a small clearance C 2  (C 1 &gt;C 2 ) is formed between the lens  10  and the ceiling  30 . 
       &lt;Crepe Work Can Be Applied to End of Cut Pin&gt; 
       [0052]    FIG.  5 ( 1 ) is a perspective view of an entire part of a front side of the lens. FIG.  5 ( 2 ) is an enlarged view of a round mark D shown in FIG.  5 ( 1 ). FIG.  5 ( 3 ) shows a specific example of a lens cut C applied to the entire part of the front side of the lens. FIG.  5 ( 4 ) is a perspective view of an entire part of a back side of the lens. FIG.  5 ( 5 ) is an enlarged view of a round mark E shown in FIG.  5 ( 4 ). 
         [0053]    To a periphery  10 C(FIG.  5 ( 1 )) of the front side of the lens  10  as a designed surface, a work of the lens cut C is applied as shown in FIG.  5 ( 2 ). 
         [0054]    Further, to the entire surface of the back side of the lens  10 , as shown in FIG.  5 ( 4 ) and FIG.  5 ( 5 ), a crepe work S that applies a skin, a pear skin, a grain and a texture thereto or the lens cut work C is applied, so that even when flaws are formed on the back surface of the lens, the flaws are hardly seen to improve an outward appearance. 
         [0055]    Further, a smooth surface having no crepe is slippery, however, when the crepe work S or the lens cut work C is applied to the lens, the lens is easily held to improve a workability. 
         [0056]    Further, since the crepe work S is applied to the periphery of the back side of the lens  10 , an inner side of the lens is prevented from being seen. 
         [0057]    In the lens  10  according to the present invention, since the gate setting surface  10 G is recessed more by one step than the lens control surface  10 N to which the crepe work S is applied, even when the crepe work is not applied to the lens control surface  10 N, the gate setting surface  10 G hardly attracts attention. 
         [0058]    Further, since the crepe work S can be applied to an end  60 P of the cut pin  60  shown in FIG.  5 ( 1 ), when the crepe work S is applied to the end  60 P of the cut pin  60 , the crepe work S can be simply formed in the gate setting surface  10 G as shown in  FIG. 5  ( 5 ), and the lens cut C and the crepe work S can be simply applied to an entire area of a designed back surface. 
       &lt;Summary&gt; 
       [0059]    When the lens  100  is formed by the usual technique, the gate  500  is cut by the nipper. Accordingly, the lens control surface  100 N is flush with the gate setting surface  100 G, so that when the lens is attached to the ceiling, the large clearance is firmed. Further, since a nipping work is hardly uniformly carried out, it is difficult to control the remainder of the gate. As described in  FIGS. 2  ( 1 ) and  2 ( 2 ) and FIGS.  3 ( 1 ) and  3 ( 2 ), since an overlap gate is used, even when the gate is arranged in a mating face of the lens  10  and the ceiling  30 , a ceiling lapping amount is easily dimensionally controlled. Further, as shown in  FIG. 1(B) , since the gate setting surface  10 G has a surface difference from the lens control surface  10 N, an entire surface lens of the indoor illuminating lamp for the motor vehicle can be formed without deteriorating a design property. 
         [0060]    Further, since a cut part of the gate  50  by the nipper is not formed in the lens  10 , the ceiling  30  is not marred. 
         [0061]    Further, since the gate setting surface  10 G is recessed more than the lens control surface  10 N, even when the crepe work is not applied to the lens control surface  10 N, the gate setting surface  10 G does not attract attention. 
         [0062]    Further, since the crepe work can be applied to the end  60 P of the cut pin  60  shown in FIG.  5 ( 1 ), when the crepe work is applied to the end  60 P of the cut pin  60 , the crepe work can be applied to the gate setting surface  10 G ( FIG. 5  ( 4 )). The above-described work is applied respectively to the lens cut C of the designed part of the surface of the lens and the lens cut C and the crepe work S of the back surface of the lens, so that the form of the gate part is not seen and a unification of the deign property can be obtained. 
         [0063]    This application is based upon and claims the benefit of the priority Japanese Patent Application No. 2010-288102 filed on Dec. 24, 2010, the contents of which are incorporated herein by reference. 
         [0064]    As described above, according to the first invention, since the cut pin having the same width as the width of the gate into the rib and the gate at the root part of the gate after the injection is completed to separate the rib from the gate, the lens can be obtained in which a dimensional control is more easily carried out than a usual method that the gate part is cut by the nipper and there is no fear of marring the ceiling.