Abstract:
A compound screwdriver head, which comprises a first working portion and a second working portion of the same size, the first, second working portion of the bigger size is used for screwing and unscrewing a bolt of bigger, smaller size respectively, so that different sizes of bolts can be locked and unloaded by one screwdriver. Thereby this invention is not only can save the structure of the bolt, but also can prolong the life of the bolt.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a screwdriver head, and more particularly to a compound screwdriver head. 
   DESCRIPTION OF THE PRIOR ART 
     FIG. 1  is a perspective view of a conventional cross-shaped screwdriver head, which comprises a body  10  having a working section  11 . The working section  11  includes four working surfaces  12 , four working grooves  14  are formed in the working section  11 , and the top end  13  of the working section  11  is cross-shaped so as to screw and unscrew the bolt of the same size as the screwdriver head. 
   However, the conventional screwdriver head is only suitable for a size of bolt, when using for screwing and unscrewing the bolts of other sizes, it is needed to use other sizes of screwdriver head, so it is very inconvenient. 
   It is feasible to screwing and unscrewing every size of bolts of a single screwdriver head, however, since the material of the bolt is softer than that of the bolt, when using a screwdriver of bigger size for screwing and unscrewing a bolt of small size, the screw groove of the bolt will be damaged and the life of the bolt will be reduced. 
   The present invention has arisen to mitigate and/or obviate the afore-described disadvantages. 
   SUMMARY OF THE INVENTION 
   The primary objective of the present invention is to provide a compound screwdriver head, which is integrally formed and can screw and unscrew every size of screws. 
   Another objective of the present invention is to provide a compound screwdriver head, which is integrally formed and not only can screw and unscrew every kind of screws, but also cannot damage the bolt groove of the bolt so as to prolong the life of the bolt. 
   The present invention will become more obvious from the following description when taken in connection with the accompanying drawings, which show, for purpose of illustrations only, the preferred embodiments in accordance with the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a conventional cross-shaped screwdriver head; 
       FIG. 2  is a lateral view of a compound cross-shaped screwdriver head in accordance with the present invention; 
       FIG. 3  is a perspective view of the compound cross-shaped screwdriver head in accordance with the present invention; 
       FIG. 4  is a perspective view of showing the compound cross-shaped screwdriver head locking and unlocking a small bolt; 
       FIG. 5  is a perspective view of showing the compound cross-shaped screwdriver head screwing and unscrewing a bigger bolt; 
       FIG. 6  is a lateral view of a compound *-shaped screwdriver head in accordance with the present invention; and 
       FIG. 7  is a perspective view of the compound *-shaped screwdriver head in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 2 , a compound screwdriver head in accordance with the present invention comprises a body  20 , a first working portion  21 , a connecting surface  22 , a second working surface  23 , an awl portion  24  and a plurality of working grooves  25 . One end of the first working portion  21  is connected with the body  20 , and the other end is connected with an outer ring  221  of a plurality of connecting surfaces  22 . An inner ring  222  of the connecting surface  22  is connected with the second working portion  23 . The size of the outer ring  221  is larger than that of the inner ring  222 , and the awl portion  24  is formed on the end of the connecting surface  22 , the working grooves  25  are extended from the awl portion  24  to the first working portion  21  via the second working portion  23 . 
   The said compound screwdriver head, wherein the size of the working grooves of the first and the second working portions  21 ,  23  are different, since the first and second working portions  21 ,  23  are integrally formed, the bolts of different sizes can be screwed and unscrewed. 
   Furthermore, the compound screwdriver head in accordance with the present invention, wherein the angle of the awl portion  24  is suitable for the groove of the bolt of small size. When screwing and unscrewing the bolt of small size, the screw lines of the bolt will not be damaged so as to prolong the life of the bolt. 
   Referring to  FIGS. 2 and 3 ,  FIG. 2  is a side view of a compound cross-shaped screwdriver head in accordance with the present invention, and  FIG. 3  is a perspective view of the compound cross-shaped screwdriver head in accordance with the present invention. 
   A compound cross-shaped screwdriver head is integrally formed, comprising the cylindrical body  20 , the first working portion  21 , the connecting surface  22 , the second working portion  23 , the awl portion  24  and the working groove  25 . 
   The first working portion  21  is formed on the cylindrical body  20 , including four abutting surfaces  211  that formed an angle of 28 degree relative to the center line Z of the body  20  respectively. Each two abutting surfaces  211  are equidistantly separated, which are relative to each other. The end of each first abutting surface  211  is connected with the connecting surface  22  that vertical to the center line Z of the body  20  respectively, the connecting surface  22  includes the outer ring  221  and the inner ring  222 . The outer ring  221  is connected with the first abutting surface  211  of the first working portion  21 , and the radius of the outer ring  221  is bigger than that of the inner ring  222 . 
   The inner ring  222  of the connecting surface  22  is connected with a second abutting surface  231  of the second working portion  23 . Similarly, the second working portion  23  includes four second abutting surfaces  231  that are equidistantly separated from one another and arranged oppositely in pairs. 
   An awl portion  24 , defined in the second working portion  23 , is a square shaped pyramid. On each awl surface is formed a working groove  25 , which is extended from the awl portion  24  to the first working portion  21  and then to the body  20  via the second working portion  23 , the awl portion  24  is cross-shaped by overlooking from the upper side. 
   The included angles a 1  between the first abutting surface  211  and the center line Z of the body  20  is 26 to 30 degree preferably, and 28 degree optimally; the angle a 1  formed between the second abutting surface  231  and the center line Z of the body  20  is 26 to 30 degree preferably, and 28 degree optimally. The height G 1  and H 1  of the first and second working portions  21 ,  23  are 1.85 to 2.15 mm and 1.95 to 2.35 preferably, and 1.9 to 2.1 mm and 2.0 to 2.3 mm optimally. The width A 1  of the connecting portion of the first working portion  21  and the body  20  that connected with the groove surface of the working groove  25  is 3.0 to 4.1 mm preferably, and 3.5 to 3.6 mm optimally. The biggest width B 1  of the outer ring  221  of the adjacent connecting surfaces  22  is 3.8 mm to 5.0 mm preferably, and 4.3 to 4.5 mm optimally. The angle β 1  of the awl portion  24  is 5 to 15 degree preferably, and the optimal is 10 degree. The size C 1  of the top end of the awl portion  24  is 1.1 to 1.2 mm preferably. 
   The screwing and unscrewing of the small bolt as shown in  FIG. 4 , the second abutting surface  231  of the second working portion  23  is engaged with the screw groove of a small bolt  30  for screwing and unscrewing. 
   Similarly, the screwing and unscrewing of the bigger bolt as shown in  FIG. 5 , the first abutting surface  211  of the first working portion  21  is engaged with the screw groove of a bigger bolt  40  for screwing and unscrewing. 
   A compound *-shaped (also called Pozidriv) screwdriver head in accordance with another embodiment of the present invention as shown in  FIGS. 6 and 7 , comprising four first abutting surfaces  511 , four second abutting surfaces  531 , four third working portions  55  that includes eight third abutting surfaces  551  and eight working grooves  56 , the structure of the compound *-shaped screwdriver head is similar to that of the cross-shaped screwdriver head of the first embodiment, and the differences are described as follows: 
   The compound *-shaped screwdriver head is integrally formed, on the basis of the structure of the compound cross-shaped screwdriver head, at the time the working groove is formed, two working grooves  56  are formed by groove lines  552  of 1.5 to 1.7 mm, the groove lines  552  of the working grooves  56  are approached from the direction of the body  50  to the awl portion  54 . A third working portion  55  is protruded out of the two working grooves  56 , the adjacent surface of the two working grooves  56  is defined as a third abutting surface  551 . The *-shaped screw can be screwed and unscrewed by cooperating the third abutting surface  551  of the third working portion  55  with the first abutting surface  511  of the first working portion  53 , similarly, small screw can be screwed and unscrewed by cooperating the third abutting surface  551  of the third working portion  55  with the second abutting surface  531  of the second working portion  53 . 
   The included angles a 2  formed between the first abutting surfaces  511  and the center line Z of the body  50  is 26 to 28 degree preferably; the angle a 2  formed between the second abutting surface  531  and the center line Z of the body  50  is 26 to 28 degree preferably. The height G 2  of the first abutting surface  511  is 1.9 to 2.1 mm preferably, and the height H 2  of the second abutting surface  531  is 1.95 to 2.35 mm preferably, and 2.0 to 2.3 mm optimally. The width of the first and the second abutting surfaces  511 ,  531  are 0.4 to 0.7 mm. The included angle γ between a groove edge  561  located between the groove  56  and the first abutting surface  511  and the axis of symmetry L of the first abutting surface  511  is 4 to 8 degree. The biggest width A 2  of the ends of the adjacent first abutting surfaces  511  is 3.0 to 4.1 mm preferably, and 3.5 to 3.6 mm optimally. The biggest width B 2  of the outer rings  521  the adjacent connecting surfaces  52  is 3.8 to 5.0 mm preferably, and 4.3 to 4.5 mm optimally. The angle β 2  of the awl portion  54  is 5 to 15 degree preferably, and 10 degree optimally. The size C 2  of the tip portion of the awl portion  54  is 1.1 to 1.2 mm preferably. 
   A compound *-shaped (also called star-shaped) screwdriver head in accordance with a further embodiment of the present invention, the awl portion of this screwdriver head is *-shaped from a top view, comprises six first abutting surfaces, six second abutting surfaces and six working grooves. 
   The present invention is characterized in that the screwdriver head is designed to have a first working portion and a second working portion that are different in diameter, the first working portion is designed for small size screws, and the second working portion is particularly designed for large size screws. Therefore, the screwdriver head is applicable to different sized skewers. 
   While we have shown and described various embodiments in accordance with the present invention, it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.