Patent Publication Number: US-2013240224-A1

Title: Process for Making a One-Piece Garden Tool

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
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     INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
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     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to the field of garden tools, and more particularly to a one-piece plastic shovel manufactured by coupling two plastic pieces together and melting them into a single unit. 
     2. Background Art 
     Garden tools are typically made in two pieces. They consist of an implement such as a shovel or rake head to which a rod is attached by a joint. The head is typically stamped metal, and the rod is either wood or some type of fiberglass resin material. 
     Tools with wooden handles are inexpensive to make, but are heavy and not very durable, particularly for shovels. The wood often breaks in two when substantial force is exerted against the shovel, and sometimes the joint where the wood and metal are secured fails. Tools with fiberglass rods are lighter, but more expensive, and may lack sufficient durability in the joint, such that it breaks when sufficient force is exerted on the shovel. 
     One design by Remco (www.remcoproducts.com) attempts to solve this problem by creating a one-piece plastic shovel. While this provides for a strong one-piece light-weight shovel with sufficient durability, it is very expensive to make because a large mold is required to make the entire shovel, or other garden tool. 
     It would be advantageous to make a one-piece garden tool that does not require a large single mold, thereby substantially reducing the cost of manufacturing and in turn the retail sales price of the garden tool. 
     An additional problem with shovel designs is that the user&#39;s foot sometimes slips off the top of the shovel head when the user applies significant force against the shovel when pushing it into the ground. This frustrates the user and sometimes results in injury if the person&#39;s leg hits the shovel top with substantial force. It would be advantageous to create means to prevent or substantially limit one&#39;s foot from sliding off the shovel head when significant force is applied. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention solves these problems by creating a smaller plastic mold for the garden tool head with a male joint in line with the tip of the shovel blade or the center of the garden tool on the operative edge. A plastic rod of the same plastic material may be manufactured using a standard extrusion machine, into which the male joint of the plastic head of the shovel or garden tool is inserted. Axial and rotational force is then applied to the rod or shovel head such that the friction causes the plastic in the joint region to melt, thereby bonding the rod and joint of the garden tool into a single plastic unit as it cools. This solves the problems of conventional two-piece designs by creating a durable light-weight garden tool made of strong plastic, without the excessive cost of a large one-piece mold. 
     Alternately, an ultrasonic method may be employed to melt the plastic in the joint region instead of applying axial and rotational force to the rod and joint. Ultrasonic waves of sufficient amplitude, frequency and duration are directed toward the joint region to heat the plastic to melt such that it may later cool into a single integral unit. 
     It is another object of the present invention to create a shovel head that yields a shovel having ridges on the top side of the shovel where the user&#39;s foot is applied when pushing the shovel into the ground. The outer sides of the shovel head also has extensions that prevent the user&#39;s foot from sliding off the side of the shovel head. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The accompanying drawings illustrate the invention, where like reference numerals indicate the same feature throughout the drawings: 
         FIG. 1  shows a 3-dimensional view of a finished shovel in accordance with the preferred embodiment of the present invention; 
         FIG. 2(   a ) shows a 3-dimensional view of a mold for forming the shovel head shown in  FIG. 1 ; 
         FIG. 2(   b ) shows a 3-dimensional view of an extrusion machine ejecting the rod of the shovel in the preferred embodiment of the present invention; 
         FIG. 2(   c ) shows a 3-dimensional view of the shovel head about to be inserted onto the rod shown in the preferred embodiment of the present invention; 
         FIG. 2(   d ) shows an alternate embodiment of the present invention in which ultrasonic waves are used to melt the joint between the shovel head and rod; 
         FIG. 3(   a ) shows an enlarged cross-sectional view of the joint between the rod and shovel head onto which the rod is inserted and rotated in the preferred embodiment of the present invention; 
         FIG. 3(   b ) is a cross-sectional view enlargement of the joint between the rod and shovel shown in  FIG. 3(   a ) with a thin layer of plastic on each melted when axial force and rotational speed have been applied between the two portions; 
         FIG. 4(   a ) shows a plane view the shovel head of  FIG. 1  having ridges and side extensions; and 
         FIG. 4(   b ) shows an enlargement of the plane view of  FIG. 4(   a ), showing the geometry and relative heights of the ridges and side extension of the preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The drawings are for illustrative purposes of the preferred embodiment of the present invention, shown for a shovel. The same design characteristics apply to other garden tools and similar implements, as would be obvious to one ordinarily skilled in the art. 
       FIG. 1  shows the completed one-piece shovel, including rod  10  which is attached to shovel head  100  via joint  20 . It is preferably comprised of a hard, rigid thermoplastic that is capable of melting at high temperatures and reforming when cooled. Many such thermoplastics may be used, although the preferred embodiment employs nylon or polypropylene material. 
     In the completed one-piece shovel, joint  20  and rod  10  become a single unit after a layer of thermoplastic on the adjacent surfaces melt and reform upon cooling. This process shall be explained in further detail below. 
       FIG. 2(   a ) shows mold  200  in which shovel head  100  is fabricated. Note that shovel head  100  includes joint  20 . Those skilled in the art will appreciate that any standard mold and process for using the mold may be used. 
       FIG. 2(   b ) shows extraction machine  300  that produces rod  10 , which is cylindrical and of the desired diameter and length. Rod  10  preferably comprises a hollow tube, as shown in  FIG. 3(   a ). The crux of the present invention is inserting joint  20  into rod  10 —as shown in  FIG. 2(   c ) and  FIG. 3(   a )—and applying sufficient axial force and rotational speed to produce friction that melts a layer of plastic on the internal periphery of rod  10  and the external periphery of joint  20 , as shown in  FIG. 3(   b ). When the axial and rotational force is terminated after a sufficient time period, the plastic cools, forming a solid connection between rod  10  and joint  20  such that the plastic becomes one uniform piece from the tip of shovel head  100  to the end of rod  10  opposite shovel head  100 , as shown in  FIG. 1 . This yields a one-piece construction that is durable, light weight and relatively inexpensive to manufacture. 
     A customized machine—not shown in the drawings—is employed to produce the axial force and rotational speed required to produce the necessary friction to melt the layer of plastic on rod  10  and joint  20 . Such a machine would be obvious to those skilled in the art.  FIG. 3(   b ) shows an enlargement of  FIG. 3(   a ) after joint  20  is inserted into rod  10  and axial force and rotational speed employed. Either shovel head  100  or rod  10  may be rotated, or both, an axial force may also be applied to either or both shovel head  100  and rod  10 . 
     The rotational speed and axial force causes rod layer  11  and joint layer  21  of rod  10  and joint  20 , respectively, to melt during this process, and the melted plastic of rod layer  11  and joint layer  21  mix such that when cooled, they form a continuous integral piece of plastic. 
     An alternate embodiment of the present invention is shown in  FIG. 2(   d ), in which ultrasonic waves are directed towards the area in which rod  10  touches joint  20 . An ultrasonic device (not shown) directs ultrasonic waves  410  towards rod  10  and joint  20  after joint  20  is inserted into rod  10 . Ultrasonic waves  410  should be of sufficient amplitude, frequency and duration to melt the layers of rod  10  and joint  20  to allow them to cool into a single integral piece just as shown in  FIGS. 3(   a ) and  3 ( b ) and as described above. 
     Another feature of the present invention, shown in  FIG. 4 , is a construction of shovel head  100  that has ridges  120  on the top portion, opposite the tip of shovel head  100 . Ridges  120  are designed to provide better traction between a user&#39;s shoe or boot and shovel head  100  to substantially reduce slippage during use. Extensions  110  extend upwards from shovel head  100  to form a barrier to prevent the user&#39;s show or boot from slipping sideways off ridge  120 . As shown in  FIG. 4 , extensions  110  extend outward from the top edge of shovel head  100  in a generally parallel direction relative to rod  10 . 
     While the various drawings depict a shovel, those skilled in the art will appreciate that many different garden tool heads (and other implements) may be inserted into rod  10  with different designs than shovel head  100 . For example, shovel head  100  may be replaced by a rake, or a snow shovel. Additionally, other shovel head geometries may replace the shape shown in the various drawings for shovels having different primary functions. And if an ultrasonic method is used to melt and meld rod  10  to joint  20  into a single integral piece, other geometries of the rod and joint other than cylindrical may be employed. 
     In the preferred embodiment, the periphery of rod  10  and joint  20  are smooth; however, those skilled in the art will understand that each may contain slight ridges or grooves. 
     Various other modifications may be made to that depicted in the various drawings of the preferred embodiment of the present invention without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited by the preferred embodiment shown in the various drawings and described herein, but by the scope of the claims.