Patent Publication Number: US-2003235483-A1

Title: Screw with a pointed end

Description:
BACKGROUND OF THE INVENTION  
       [0001] This invention relates to a screw with a pointed end, particularly to one exhausting cut waste bits of wood smoothly, and enhanced effect in securing objects.  
       [0002] At present screws have three problems, namely, swaying, operating twisting force, and securing force. When a tool rotates a screw in a wooden object, the screw should sway with comparatively little degree so as to drive easily the screw accurately straight in the wooden object. The operating twisting force is caused either by squeezing against an object or friction between the screw and the object during rotating the screw. The securing force is a resistant force against separating of the screw from the object caused by exterior force after the screw is driven in the object.  
       [0003] As shown in FIG. 1, a first conventional screw A has two portions of threads, complete threads A 4  of the shank A 2  and incomplete securing threads A 3  of a conical portion A 1 . When the screw A is rotated by a hand tool to move into an object, the threads moves helically in the object by squeezing action. If the screw is wanted to move in an object, it depends on the incomplete threads A 3  of the conical portion, therefore, the threads have to cut a helical groove (track) in the object, and to form a conical shaft hole in the object. This is the main reason that the twisting force happens in driving the screw in the object. As for the complete threads A 4 , they only move along the track made by the incomplete threads A 3 , producing only friction force. The friction force accounts for a small portion of the total operating twisting force. Therefore, if the screw is used for a comparatively hard object, it needs a very large operating twisting force. For a long screw this condition is very serious, possible to cause the screw break off to give a harm to a worker.  
       [0004] Next, as shown in FIG. 2, a second conventional improved screw has a hole drilling thread B 1  provided with a larger angle than those of securing threads B 2 , possible to have drilling effect of a drill by firstly drilling a small hole and then cut a helical groove in an object, lowering operating twisting force needed. But such a screw may easily sway to leave the original secured position, owing to the drilling thread B 1  having only drilling function but no function of securing the screw with the object.  
       [0005] Further, a third conventional screw disclosed in U.S. Pat. No. 4,834,602 has threads C divided into two stages C 1  and C 2  separated by drilling threads C 3 . The drilling threads C 3  are for drilling and carrying out cutting wood bits, and the incomplete securing threads C 1  of a short stage squeezes firstly an object so as to correct the screw into a straight condition so the screw may not sway easily. Then the drilling threads C 3  damages the helical groove already formed in the object, forming a diameter of a hole. After that the complete securing threads C 2  evolves and moves in the object helically. Though this third conventional screw resolves the disadvantage of swaying and partial twisting force (friction), it has to depend on the incomplete securing threads C 1  in squeezing the object, not thoroughly resolve the problem of the operating twisting force. Besides, the diameter of the hole opened by the drilling threads C 3  is a little smaller than the diameter D of the securing threads C 2 , with securing force between the screw and the object being not enough so the screw may easily separate from the object by exterior force.  
       [0006] Furthermore, a fourth conventional screw shown in FIG. 4 is disclosed in a U.S. Pat. No. 4,241,638, having a first screw threads D 1 , a second screw threads D 2  and a third screw threads D 3 . The third screw threads D 3  has a function of cutting a thin iron plate, and the first screw threads D 1  and the second screw threads D 2  have function of securing the screw with an object. The drawback of this screw is the same guiding function that all the three screw threads, D 1 , D 2 , and D 3  have, only producing the same function that the screws shown in FIGS. 1 and 2, that is, the function of squeezing a wooden object, impossible to cut the wooden object. So the fourth conventional screw shown in FIG. 4 cannot be moved without large operating twisting force or without causing split or tear of a wooden object.  
       [0007] Lastly, another U.S. Pat. No. 135,760 obtained by the same applicant of this invention, also has almost the same disadvantages mentioned above.  
       SUMMARY OF THE INVENTION  
       [0008] One purpose of the invention is to offer a screw with a pointed end, which needs a small operating twisting force, and has comparatively small swaying and high securing force.  
       [0009] Another purpose of the invention is to offer a screw with a pointed end, which can perform cutting, exhausting cut waste bits of wood, and moving in an object smoothly, and securing tightly with an object.  
       [0010] The feature of the invention is two kinds of threads formed  10  in a conical end portion for first cutting and drilling, and then rotating by cutting a helical groove in an object, lowering largely twisting force needed in squeezing action. Further, when a first complete securing threads moves in an object, the object is already drilled with a hole by a drill thread. So the screw may be rotated to move in the object smoothly with only a little twisting force. Thus operating twisting force for a screw in driving in an object is largely lowered, and the hole drilled out by the drill thread may not affect the securing force of the screw with the object.  
       [0011] Another feature of the invention is that the pointed end has a function of cutting an object so as to destroy wooden fiber smoothly so that the wooden object may not split or tear off, while a conventional screw has its pointed end squeezes wooden fiber of an object in driving the screw in the object so that the wooden object may split along the grain of the wooden fiber.  
     
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
     [0012] This invention will be better understood by referring to the accompanying drawings, wherein:  
     [0013]FIG. 1 is a front view of a first conventional screw;  
     [0014]FIG. 2 is a front view of a second conventional screw;  
     [0015]FIG. 3 is a front view of a third conventional screw;  
     [0016]FIG. 4 is a partial front view of a fourth conventional screw;  
     [0017]FIG. 5 is a front view of a first embodiment of a screw with a pointed end in the present invention;  
     [0018]FIG. 6 is a partial magnified front view of the first embodiment of a pointed end in the present invention;  
     [0019]FIG. 7 is a front view of a second embodiment of a screw with a pointed end in the present invention;  
     [0020]FIG. 8 is a partial magnified view of the second embodiment of a screw with a pointed end in the present invention; and,  
     [0021]FIG. 9 is a front and partial cross-sectional view of the second embodiment of a screw with a pointed end in the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0022] A first preferred embodiment of a screw with a pointed end in the present invention, as shown in FIGS. 5 and 6, includes a head  1 , a shank  2  and a conical end portion  3 .  
     [0023] The head  1  is of any shape, having a slot in a center for a hand tool to fit therein to rotate the screw.  
     [0024] The shank  2  has complete securing threads  20 , and a non-threaded portion  21  provided  
     [0025] between the complete securing threads  20  and the head  1 .  
     [0026] The conical end portion  3  is formed in a lower portion of the shank  2 , having an incomplete securing thread  30  extending downward below the complete securing threads  20 , functioning to drill and squeeze an object, and its lower end  300  does not connect to two drill threads  31  and  32 . The drill threads  31  and  32  have a comparatively long length, having function of drilling and cutting.  
     [0027] Further, as shown in FIG. 6, the drill threads  31  and  32  extends from a lower tip  33  of the conical end portion  3  or from near the lower tip  33  to a point slightly above an upper end of the conical end portion  3 . Then a waste passageway  301  is formed between the incomplete securing thread and the two drill threads  31  and  32 . Then the incomplete secure thread  30  does not form a hampering force to cut waste bits of wood produced as the securing threads  30  is not connected to the drill threads  31  or  32  so that cutting action may be carried on smoothly as shown in FIG. 9.  
     [0028] When the conical end portion  3  of the screw completely moves in an object, it already drills a small hole in the object  4 . The diameter of the hole is as large as the largest diameter D of the drill thread  31 . So when a first securing thread  200  moves in the object  4 , a small force is enough for squeezing to cut helical groove (track) in the object  4 , and then the securing threads  30  just moves along the cut track, only receiving a twisting force so that the whole operating twisting force is not affected so much. The securing force of the screw does not alter so largely by the cutting action mentioned above, after the screw moves substantially in the object  4 . When the screw begins to move in the object  4  and performs cutting, rotating and moving at the same time into the object, some portion of the securing thread  30  firstly inserts in the object  4 , so that the screw may not sway too largely owing to the function of maintaining the screw in the straight position  
     [0029] Next, a second preferred embodiment of a screw with a pointed end is shown in FIGS. 7 and 8, having a head  5 , a shank  6  under the head  5 , complete securing threads  60  formed on the shank  6 , and a conical end portion  7  formed in a lower portion. The conical end portion  7  has an incomplete securing thread  70  and two drill threads  71 ,  72 , with the end  700  of the incomplete securing thread  70  not connected to the two drill threads  71  and  72  so as to form a waste passageway  701  between the incomplete securing thread and the two drill threads  71  and  72 . Therefore, the second embodiment has the same function as the first embodiment.  
     [0030] The invention has the following advantages, as can be understood from the aforesaid description.  
     [0031] 1. Cut waste wooden bits may not be obstructed by the incomplete securing thread, exhausted out smoothly, and wooden objects may not easily split or tear apart by the screw owing to diminished operating twisting force and enhanced securing force.  
     [0032] 2. In rotating for securing the screw in an object, the pointed end has a function of cutting and lowering resistance in rotating for securing in the object, not having the disadvantage that a conventional screw has to be squeezed largely to cause splitting of a wooden object.  
     [0033] 3. It lessens operating twisting force so as to avoid splitting of a wooden object, and it may not easily break off, with securing force between the screw and the object not diminished.  
     [0034] While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications may be made therein and the appended claims are intended to cover all such modifications that may fall within the spirit and scope of the invention.