Patent Publication Number: US-2006007710-A1

Title: Method of manufacturing decorative string light

Description:
FIELD OF THE INVENTION  
      The present invention generally relates to a method of manufacturing decorative string light, and more specifically to an inject molding method to directly form a shielding layer at the bottom of the light bulbs.  
     BACKGROUND OF THE INVENTION  
       FIG. 1  shows an exploded view of a conventional decorative string light structure, including a tungsten filament (generally known as soft filament) bulb  11 , a softhead  12 , a bulb cap  13 , and a pair of metal conductive stripes  14 , assembled in the following manner: plugging bulb  11  into softhead  12  so that the two metal pins  111  of bulb  11  extend beyond softhead  12 , conductive stripe  14  of conductive wire  15  housed inside the bottom of bulb cap  13 , and finally plugging softhead  12  into bulb cap  13  so that metal pins  111  are in contact with conductive strips  14  to form electrical connection. The most difficult part during the assembly is metal pins  111  must be inserted into the small holes (now shown) of bulb cap  12  when bulb  11  is inserted into cap  12  so that metal pins  111  can extend beyond bulb cap  12 . This step is not only difficult but also prone to errors; hence, increases the manufacturing cost In addition, to prevent bulb  11  from turning to cause the break or short circuit of metal pins  111 , some manufacturers would add the adhesive glue between bulb  11  and bulb cap  12  to prevent turning as well as increase the fixture. But this further complicates the manufacture process. It is imperative to devise a new manufacturing method to achieve the goal with less manufacturing cost.  
     SUMMARY OF THE INVENTION  
      The primary goal of the present invention is to provide a decorative string light manufacturing method that is easy to manufacture, safe to use, and low in cost. The method includes forming a monolithic shielding layer at the bottom of the bulb. The shape of the shielding layer resembles the softhead of the conventional structure. Therefore, the finished product can be directly plugged into the conventional bulb cap to form a complete string light. This not only simplifies the assembly process, but also prevents the turning of the bulbs as in the conventional structure; thus the safety of use is improved.  
      To achieve the aforementioned goal, the present invention is to add a step of inject molding to the end of the manufacturing process. That is, after the bulbs are formed, a mold is used to form an inject molding shielding layer at the bottom of the bulbs. The shape of the shielding layer depends on the shape of the bulb cap so that it is more convenient to assemble and safe to use.  
      The foregoing and other objects, features, aspects and advantages of the present invention will become better understood from a careful reading of a detailed description provided herein below with appropriate reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention can be understood in more detail by reading the subsequent detailed description in conjunction with the examples and references made to the accompanying drawings, wherein:  
       FIG. 1  shows an exploded view of a structure of a conventional decorative string light;  
       FIG. 2  shows a flowchart of the manufacturing method of the present invention;  
       FIG. 3  shows a 3-dimensional view of the present invention;  
       FIG. 4  shows a cross-sectional view of the present invention;  
       FIG. 5  shows a second embodiment of the present invention with matched bulb cap and metal conductive stripe;  
       FIG. 6  shows a third embodiment of the present invention with matched bulb cap and metal conductive stripe; and  
       FIG. 7  shows a fourth embodiment of the present invention with matched bulb cap and metal conductive stripe. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       FIG. 2  shows a flowchart of the present invention, including two steps. Step  20  is to manufacture a light bulb. The finished light bulb includes two metal pins at the bottom. Inside the sealed light bulb is a tungsten filament which will illuminate when in use. Step  21  is to form a shielding layer using an inject molding method. The shape of the shielding layer can be manufactured to match the shape of the bulb cap. The entire manufacturing process is complete in sequence; that is, the shielding layer is manufactured directly after the light bulb is manufactured. Therefore, the finished product of the present invention is a light bulb with a monolithic shielding layer at the bottom.  
       FIG. 3  and  FIG. 4  show the three-dimensional and cross-sectional views of a light bulb manufactured in accordance with the method of the present invention. The light bulbs can be used in string lights for Christmas or ceremonial decoration. The main body of a light bulb  3  is made of a glass with low power tungsten filament bulb having a shape of long stripe, as shown in the figures. At the bottom of bulb  3  is a monolithic shielding layer  31 , made of insulation material, such as plastic. The shape of shielding layer  31  is to match the interior shape of the bulb cap. In this embodiment, shielding layer  31  includes a cone  311  at the upper part and a strut  312  at the lower part so that the finished bulb  3  can be directly plugged into a bulb cap of a conventional string light.  FIG. 5  shows another embodiment of the present invention. In this embodiment, a light bulb  3  includes a shielding layer  31  at the bottom. Shielding layer  321  includes two independent struts  312  at the lower part to cover two metal pins  32  of bulb  31 , respectively. In other words, shield layer  31  can be manufactured to match the shape of bulb cap  13 .  
       FIG. 6  and  FIG. 7  show the third and the fourth embodiments of the present invention. The light bulbs of both embodiments are tungsten filament bulbs, but are large in size and may have different shape. The bulb in  FIG. 6  has a shape of a grape, and the bulb in  FIG. 7  has a shape of a screw. Both bulbs have a shielding layer  31  at the bottom. The top of shielding layer  31  includes a large-size shield part  313 , which is made to match the large size of light bulb  3  so that the assembly of the two would be easier. In other words, the shape of the light bulbs of the present invention can be either long stripe, cone, or any other shape, and the shape of the shielding layer cal also be manufactured to match the bulb cap.  
      Although the present invention has been described with reference to the preferred embodiments, it will be understood that the invention is not limited to the details described thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.