Patent Publication Number: US-2007113434-A1

Title: Display sheet and method of manufacturing the same

Description:
BACKGROUND OF THE INVENTION  
      This invention relates to a display sheet used by applying it to such a surface that is formed so as to extend along an outer circumferential surface of a cone; and a method of manufacturing the same.  
      For example, on an air-conditioning control panel for automobiles, a temperature display is provided on a circumferential portion of a temperature-setting operating knob. Such temperature displays include a plastic display formed by applying a plastic display sheet, on which, for example, numerals are printed, to a flat sheet-applying surface. In a display sheet of such a structure, a sheet-applying surface is formed flat, so that a display surface of the display sheet is also flat. Although the display surface is easily seen front ways, it is difficult that the display surface be seen sideways and diagonally.  
      Therefore, it is conceivable that, in order to have a display surface of a display sheet seen easily, a sheet-applying surface be formed to such an inclined surface that extends along an outer circumferential surface of a cone, and that the display sheet be applied to this sheet-applying surface. However, when such a structure is employed, the display sheet becomes readily peeled off since a force for returning the display sheet to an original flat shape works on the display sheet.  
      A display sheet of the following construction is being discussed as a display sheet which solves such problems. This display sheet is obtained by punching a flat plastic sheet into a doughnut-shaped sheet having a circular hole in the central portion thereof, vacuum molding the resultant sheet into such a three-dimensional shape that is in conformity with that of an outer circumferential surface of a cone, and finishing this molded product as a display sheet. A display sheet of such a construction is molded into a sheet of such a three-dimensional shape that is in conformity with that of an outer circumferential surface of a cone, so that, even when this sheet is applied to a sheet-applying surface constituting an inclined surface extending along an outer circumferential surface of a cone, the sheet is rarely peeled off. However, in the display sheet thus formed, the shape thereof is limited to that of a doughnut (shape of a ring), i.e., the shape of the display sheet is greatly restricted. Moreover, the mold cost for the vacuum molding of the plastic sheet and equipment cost are high, so that the display sheet manufacturing cost necessarily becomes high.  
      JP-A-2002-123197 discloses technique for obtaining a display panel by forming a display portion (indicator portion) thereof positioned around an operating knob into a member having an inclined surface extending along an outer circumferential surface of a cone, by an in-mold molding method. However, the in-mold molding of a display sheet of this construction causes the cost of a mold for forming a display sheet and that of equipment needed therefor to become high, so that the display sheet manufacturing cost also becomes high.  
     SUMMARY OF THE INVENTION  
      The present invention has been made in view of these circumstances. One of the objects of the present invention is to provide a display sheet formed so that what is displayed thereon can be seen easily, rarely peeled off from a sheet-applying surface, and little restricted with respect to the shape thereof. Another object of the invention is to provide a method of manufacturing the same display sheet at a low cost.  
      In order to solve the aforesaid object, the invention is characterized by having the following arrangement. 
      Aspect 1. A display sheet applied to a sheet-applying surface formed so as to extend along an outer circumferential surface of a cone comprising:    

      a dual-ended, annular plastic sheet body having a three-dimensional shape in conformity with that of the sheet-applying surface in a natural state. 
      Aspect 2. A method of manufacturing a display sheet to be applied to a sheet-applying surface formed so as to extend along an outer circumferential surface of a cone, the method comprising:    

      providing a flat, dual-ended, annular plastic display sheet; and  
      subjecting the display sheet to an annealing process in a state that the display sheet is retained in a three-dimensional shape in conformity with that of the sheet-applying surface, whereby the display sheet has the three-dimensional shape in conformity with that of the sheet-applying surface in a natural state. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIGS. 1A and 1B  is a drawing showing a first embodiment of the present invention, wherein  FIG. 1A  is a plan view of a display sheet in a punched state; and  FIG. 1B  a perspective view of a display sheet which has just been annealed.  
       FIG. 2  is a front view of an air-conditioning control panel.  
       FIG. 3  is a perspective view of this control panel.  
       FIG. 4  is an enlarged sectional view of a principal portion of the control panel, taken along the line X-X in  FIG. 2 .  
       FIG. 5  is a sectional view of a jig.  
       FIG. 6  is a sectional view showing a second example of a jig used in the present invention.  
       FIG. 7  is a plan view of this jig. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
      A first embodiment of the present invention will now be described with reference to  FIG. 1  to  FIG. 5 .  
      First,  FIG. 2  and  FIG. 3  show an air-conditioning control panel  1  used for an automobile. On a front surface of the air-conditioning control panel  1 , a front plastic panel  2  is provided. Looking at the front panel  2  front ways, a temperature-setting operating knob  3  and an air quantity-setting operating knob  4  for a blower are provided on a left portion and a right portion thereof respectively such that these knobs  3 ,  4  can be turned. Referring to  FIG. 3 , the air quantity-setting operating knob  4  is removed.  
      In the portion of the front panel  2  which corresponds to the operating knob  3 , a circular opening  5  is formed as shown in  FIG. 4 . On a circumferential portion of this opening  5 , such an inclined sheet-applying surface  6  that extends along an outer circumferential surface of a cone is formed, and a dual-ended, annular (substantially C-shaped) temperature display sheet  7  is applied to the sheet-applying surface  6 . On the display sheet  7 , temperature display portions  7   a  are shown.  
      In the portion as well of the front panel  2  which corresponds to the operating knob  4 , a circular opening  5  is formed in the same manner as that on the side of the operating knob  3 . On a circumferential portion of the opening  5 , such an inclined sheet-applying surface  8  that extends along an outer circumferential surface of a cone is formed. To this sheet-applying surface  8 , a dual-ended, annular (substantially C-shaped) air quantity display sheet  9  is applied. An air quantity display portion  9   a  is shown on the display sheet  9 .  
      The temperature-setting operating knob  3  is mounted on an operating shaft  10  (refer to  FIG. 4 ) for a temperature setting knob (not shown) provided in a rear portion of the front panel  2 . The air quantity-setting operating knob  4  is also mounted on an operating shaft  11  (refer to  FIG. 3 ) for an air quantity-setting switch (not shown) provided in a rear portion of the front panel  2 .  
      Although the display sheets  7 ,  9  differ from each other in that the display sheets  7 ,  9  have different display portions, i.e., the temperature display portion  7   a  and air quantity display portion  9   a  respectively, the remaining portions thereof are identical with each other. Therefore, the temperature display sheet  7  will be representatively described. A body  12  of the display sheet  7  is made of a plastic, which is, in this embodiment, polycarbonate, and has a thickness of about 0.3 mm. A bonding agent-protecting paper (not shown) is applied to a rear surface of the sheet body  12  not yet applied to a sheet-applying portion  6 .  
      The display sheet  7  is manufactured in the following manner. First, as shown in  FIG. 1A , a flat, substantially dual-ended, annular sheet body  12  is punched with the protective paper. The sheet body  12  is thereafter subjected to an annealing process by using a jig  14  shown in  FIG. 5 , to obtain a structure in which in the natural state thereof such a three-dimensional shape is maintained that is in conformity with that of the sheet-applying surface  6  as shown in  FIG. 1B .  
      To be concrete, the jig  14  includes a first jig member  15 , and a second jig member  16 . Both the first and second jigs  15 ,  16  are made of aluminum. The first jig member  15  has a substantially cylindrical shape, and includes a first cylindrical bore  17  in a lower portion of the interior thereof, a second cylindrical bore  18 , the diameter of which is larger than that of the first bore  17 , in an upper portion thereof, and a tapering surface  19  connecting these first and second bores  17 ,  18  together in the intermediate portion thereof which is between the first and second bores. An angle α of inclination of the tapering surface  19  is set to about 28 degrees.  
      The second jig  16  includes at a lower part thereof a first columnar insert portion  20  to be inserted into the first bore  17 , at an upper part thereof a second columnar insert portion  21  to be inserted into the second bore  18 , and at the intermediate part thereof which is between the upper and lower insert portions a tapering surface  22  connecting these first insert portion  20  and second insert portion  21  together. An angle of inclination of this tapering surface  22  is also set equal to that α of the tapering surface  19 . The second insert portion  21  is provided in an outer circumferential surface thereof with an annular groove  23  extending at right angles to the axial direction thereof, and a vertical groove  24  extending in the same axial direction. The vertical groove  24  is provided solely between the annular groove  23  and tapering surface  22 , and opened at an upper end portion thereof on the side of the annular groove  23  and at a lower end portion thereof on the side of the tapering surface  22 .  
      The annealing process for the sheet body  12  is carried out as follows. First, a plurality of punched sheet bodies  12  are laminated, and the laminated sheet bodies are placed on the tapering surface  19  of the first jig member  15 . The first insert portion  20  of the second jig member  16  is then inserted into the first bore  17  of the first jig member  15 , and the second tapering surface  22  of the second jig member  16  is applied to the laminated sheet bodies  12  from the upper side thereof. As a result, the plural laminated sheet bodies  12  are held between the tapering surface  19  of the first jig member  15  and the tapering surface  22  of the second jig member  16 , and kept in such a three-dimensional shape that is in conformity with that of an outer circumferential surface of a cone. During this operation, the vertical groove  24  of the second jig member  16  works as an air vent when the second jig member  16  is inserted into the first jig member  15 , and enables the insertion of the second jig member  16  thereinto to be carried out smoothly.  
      The sheet bodies inclusive of the jig  14  in this condition are inserted into a heating furnace (not shown) and subjected to a heat treatment at about 130° C. for 1 to 2 hours. As a result, the temperature of each sheet body  12  exceeds a thermal deformation temperature, and the sheet body  12  is permanently deformed to such a dimensional shape that is in conformity with that of an outer circumferential surface of a cone. The sheet bodies inclusive of the jig  14  are thereafter taken out from the heating furnace, and the first jig member  15  and second jig member  16  are separated from each other to take out each sheet body  12  therefrom. Consequently, each sheet body  12  is retained in a natural state thereof such a three-dimensional shape that is in conformity with that of an outer circumferential surface of a cone as shown in  FIG. 1B , thereby manufacturing a display sheet  7 .  
      The protective paper on the rear surface of the display sheet  7  thus manufactured is peeled off, and the resultant display sheet  7  is applied to the sheet-applying surface  6 . The display sheet  9  manufactured in the same manner is also applied to the sheet-applying surface  8  in the same manner as the display sheet  7 .  
      Referring to  FIGS. 2 and 3 , on the air-conditioning control panel  1 , a plurality of air blow-out port selecting switches  25   a  to  25   d,  a front defroster switch  26 , an automatic control AUTO switch  27  and an inside-outside air change-over switch  28  are provided between the operating knob  3 ,  4 , and an air-conditioner switch  29 , a rear defogger switch  30  and a hazard lamp switch  31  and the like are provided at an upper portion of the panel  1 .  
      In the above-described embodiment, the following effects are obtained. First, since the display sheets  7 ,  9  are formed so that these display sheets are applied to such sheet-applying surfaces  6 ,  8  that extend along an outer circumferential surface of a cone, the display surfaces thereof become inclined, so that the display surfaces become easily seen not only front ways but also sideways and diagonally. The sheet bodies  12  of the display sheets  6 ,  7  are formed as shown in  FIG. 1B , to such a structure in which a three-dimensional shape extending in the natural state thereof in conformity with that of the sheet-applying surfaces  6 ,  8  is retained. Accordingly, even when the sheet bodies  12  are applied to such sheet-applying surfaces  6 ,  8  that extend along an outer circumferential surface of a cone, a force in the sheet body-peeling direction does not substantially occur, so that the sheet bodies are rarely peeled off and easily applied to the sheet-applying surfaces  6 ,  8 . Since the sheet bodies  12  of the display sheets  7 ,  9  have a dual-ended, annular shape, the sheet bodies are less restricted with respected to the shape than the sheet bodies the shape of which is limited to a doughnut shape (endless annular shape).  
      When the display sheets  7 ,  9  are subjected to an annealing process, the residual strain thereon is removed therefrom, and the three-dimensional shape of these display sheets is retained. Therefore, the display sheets can be applied excellently to such sheet-applying surfaces  6 ,  8  that extend along an outer circumferential surface of a cone. Since the annealing process can be carried out by heating the sheet bodies  12 , which are retained in a three-dimensional shape by the jig  14 , at a temperature in excess of a thermal deformation temperature of the sheet bodies  12 , a jig and equipment in use may be simpler than those used when a sheet body is obtained by carrying out a vacuum molding process or an in-mold molding process, so that the display sheets  7 ,  9  can be manufactured at a low cost.  
       FIG. 6  and  FIG. 7  show a second embodiment of the present invention. The second embodiment is different from the above-described first embodiment in the following point. Namely, a jig  35  used when display sheets  7 ,  9  are subjected to an annealing process is different from the jig  14  used in the first embodiment.  
      The jig  35  is formed like a circular shallow vessel, and provided with a circular opening  36  in a bottom portion  35   a  thereof. A radius of curvature of an inner surface of a circumferential wall  35   b  of the jig  35  is set slightly smaller than that of an outer surface of sheet bodies  12  of display sheets  7 ,  9 .  
      The annealing of the display sheets  7 ,  9  is carried out as follows. First, one punched sheet body  12  is inserted into the jig  35 , or a plurality of punched sheet bodies  12  are laminated on each other and inserted thereinto. Since the radius of curvature of the inner surface of the circumferential wall  35   b  of the jig  35  is set slightly smaller than that of the outer surface of the sheet body  12 , the sheet body  12  retains such a three-dimensional shape that is in conformity with that of an outer circumferential surface of a cone with an outer circumferential edge portion  12   a  of the sheet body  12  partially contacting an inner circumferential surface of the circumferential wall  35   b  as shown in  FIG. 7 . In this condition, the sheet body  12  is higher at an inner circumferential edge portion  12   b  thereof than at the outer circumferential edge portion  12   a  thereof.  
      The sheet body inclusive of the jig  35  are then placed as they are in a heating furnace (not shown), and thermally treated at about 130° C. for 1 to 2 hours in the same manner as in the first embodiment. As a result, the temperature of each sheet body  12  exceeds a thermal deformation temperature thereof, and the sheet body  12  is permanently deformed to such a three-dimensional shape that is in conformity with that of an outer circumferential surface of a cone. The sheet body  12  is then taken out with the jig  35  from the heating furnace, and the finished sheet body is obtained. Owing to these operations, the sheet body  12  retains in the natural state thereof such a three-dimensional shape that is in conformity with that of an outer circumferential surface of a cone as shown in  FIG. 1B . The display sheets  7 ,  9  are thus manufactured.  
      In such a second embodiment, the jig  35  used, especially, when the sheet body is annealed may be made of only one kind of jig of a simple construction, so that the cost of the jig  35  can further be held down. In the jig  35 , the opening  36  in the bottom portion  35   a  thereof may not be formed.  
      The present invention is not limited to the above-described embodiments only. The invention can be modified or extended as follows.  
      The object for which the display sheets  7 ,  9  are used is not limited to a control panel for an air-conditioner provided in an automobile. The display sheets can also be utilized for household electric appliances.  
      As is clear from the above description, the display sheet of the invention is advantageous in that what is shown on the display sheet is easily seen; the display sheet is rarely peeled off; and, moreover, the shape of the display sheet is little restricted. According to the display sheet manufacturing method of the invention, the display sheet of the invention can be manufactured at a low cost.