Tightening tool

Abstract

 A tightening tool having a sufficient strengh of a T-shaped joint for resisting a strong tightening force to safely transfer required torque to a main shaft. The tightening tool comprises a plastic grip 5, a bonding metal fitting 3 embedded in the plastic grip 5, a transverse pipe 1 having openings at its both ends, a mounting pipe 2 connected to the transverse pipe 1 to provide a T-shaped structure of the bonding metal fitting 3 and a main shaft 4 made from metal for insertion into the mounting pipe 2, having a driver portion protruding from the plastic grip 5. The bonding metal fitting 3 is integrally provided with reinforcing wings 8 between the respective lower portions of the transverse pipe 1 and the respective outside portions of the mounting pipe 2, thereby improving the strength of the bonding metal fitting 3 for resisting torsional force. A mounting hole 11 of the mounting pipe 2 is formed with flat portions having flat opposite surfaces, while one tip of the main shaft 4 is formed with other flat portions 23 having opposite flat surfaces 23A, thereby fitting the latter into the former to improve bonding strength of the mounting pipe 2 and main shaft 4 for resisting torsional force. Stopper recesses 24 are formed in suitable portions of the main shaft 4 to be embedded in the plastic grip 5, thus preventing the main shaft 4 from getting detached therefrom.

Description

[0001] The present invention relates to a tightening tool for mounting and removing screws wherein a large torque is safely and easily obtained by inserting a tightening shaft into a pipe embedded in a grip to form a T-shaped or L-shaped handle.

[0002] Conventionally, a large torque could be obtained from a lateral hole formed in the grip of a screwdriver, with a tightening shaft inserted into this lateral hole to form a T-shaped or L-shaped handle. This technique has been disclosed in Japanese utility model laid-open publication number 61-64967 and Japanese utility model laid-open publication number 61-99473.

[0003] However, in these prior art examples, the bond between the grip and the main shaft, in which the driver portion is disposed at the tip, was based solely on the integral formation of the grip. Since there is no direct bonding between the tightening shaft and the main shaft, there is low bonding strength, and the strength of the lateral hole of the grip itself is inadequate.

[0004] To eliminate the above problems, the inventor of the present invention once proposed a tightening tool in Japanese utility model laid-open publication number 6-83270, in which a hard driver member is formed by bonding a transverse pipe embedded in a plastic grip to a main shaft by welding, soldering, brazing or the like to form a T-shaped structure thereof. The hard driver member is then used as a core member to mould the plastic grip in which is formed a tightening shaft insertion hole for inserting the same thereinto, while the main shaft protrudes from the plastic grip.

[0005] With the conventional tightening tool, the insertion of a suitable length of a tightening shaft into the pipe allows thus obtained T-shaped or L-shaped structure to be used as a rotation handle, thereby transferring a great torque directly to the main shaft across the pipe. Further, in the Japanese utility model laid-open publication number 6-83270, there is also disclosed another tightening tool in which a mounting pipe is provided, perpendicularly to a transverse pipe to form a T-shaped structure, then a main shaft is either pressed-in, inserted into or reveted to the mounting pipe.

[0006] However, according to the above prior art, neither the T-shaped bond between the pipe and the main shaft nor the T-shaped protrusion of the mounting pipe from the transverse pipe with the main shaft being connected to the pipe could attain sufficiently great strength withstanding a large torque. Namely, when a torque is applied to the pipe, it is transferred to the main shaft across a joint located in a point of intersection between the mounting pipe and the main shaft or another joint between the transverse pipe and the mounting pipe. As a result, a large torque applied can cause the break of the joints, which would make it difficult to mount or remove a screw with a large torque. Further, according to the prior art where the mounting pipe is bonded to the transverse pipe, the precise bonding therebetween would be difficult to form a precisely T-shaped structure. In addition, with the prior art where the transverse pipe is bonded to the mounting pipe to which is further connected the main shaft, the main shaft would easily get detached from the mounting pipe or the plastic pipe.

[0007] To eliminate the above problems, it is, therefore, an object of the present invention to provide a tightening tool with which you can safely transfer a sufficiently large torque as required to the main shaft, having the T-shaped joint of sufficient strength for withstanding an applied strong tightening force.

[0008] It is another object of the present invention to enable the mass and precise production of components composed of a mounting pipe and a transverse pipe integrally formed therewith.

[0009] It is further an object to eliminate a fear that the main shaft will get detached from the mounting pipe and the plastic grip.

[0010] According to a major feature of the present invention, a tightening tool of the invention comprises: a plastic grip; a bonding metal fitting embedded in said plastic grip, said bonding metal fitting comprising a transverse pipe having openings at its both ends, a mounting pipe connected to said transverse pipe to provide a T-shaped structure of said bonding metal fitting; a main shaft made from metal, which is to be inserted into said mounting pipe, having a driver portion protruding from said plastic grip; reinforcing wings integrally provided between the respective lower portions of said transverse pipe and the respective outside portions of said mounting pipe.

[0011] Other objects, features and advantages of the invention will be apparent to those skilled in the art from the following description of the preferred embodiments of the invention, wherein reference is made to the accompanying drawings, of which:

Fig.1 is a schematic perspective view showing a tightening tool of the inveniton.

Fig.2 is a cross-sectional view showing a tightening tool of the invention.

Fig.3 is a section taken on III-III line of Fig.2.

Fig.4 is a section taken on IV-IV line of Fig.2.

Fig.5 is a section taken on V-V line of Fig.2.

Fig.6 is an exploded perspective view showing a main part of a tightening tool of the invention.

Fig.7 is a side view showing a bonding metal fitting of a tightening tool of the invention.

Fig.8 (A) is a plane cross section showing a shaft unit related to the invention, while Fig.8 (B) that of a prior shaft.

Fig.9 is a section showing a die-casting die in use for casting the bonding metal fitting of the invention.

Fig.10 is a schematic perspective view showing another embodiment of the invention.

[0012] Hereinafter are described embodiments of the present invention with reference to the drawings.

[0013] In Figs.1 to 9 showing a first embodiment of the ivention, a driver unit A is formed by bonding a main shaft 4 made from steel to a bonding metal fitting 3 formed by T-shaped connection of a transverse pipe 1 with a mounting pipe 2. Around the bonding metal fitting 3 is disposed plastic grip 5, which opens up at the sides of grip 5, thus forming a tightening shaft insertion holes 6, in which a tightening shaft B is inserted. A driver portion 7 is provided at the tip of the main shaft 4, which projects out of plastic grip 1. In this embodiment, the driver portion 7 is taken for example as a ball-pointing driver used for a tightening bolt C with a hexagonal hole.

[0014] Whilst the bonding metal fitting 3 may be T-shaped by welding the transverse pipe 1 to the mounting pipe 2, it may, in a preferred form of the invention, be formed by die-casting method, where melted zinc alloy is cast into a mould under a high pressure, thereby enabling the precise fabrication of the transverse pipe 1 and mounting pipe 2, and the mass production thereof. The bonding metal fitting 3 fabricated by die-casting method is provided with reinforcing wings 8 besides the aforesaid T-shaped connection of the transverse pipe 1 with the mounting pipe 2, each of which wings 8 is integrally formed during the die-casting process, having approximately triangle front faces and thickness less than the respective diameters of the transverse pipe 1 and the mounting pipe 2. Further, the wings 8 are disposed on the same plane relative to a plane including both a shaft core 1A of the transverse pipe 1A and another shaft core 2A of the mounting pipe 2, having an outside upper tip 9 located at the free end of the transverse pipe 1 and an outside lower tip 10 located at the lower end of the mountng pipe 2 respectively. The tightening shaft insertion holes 6, each having a circular cross-section, are formed in the transverse pipe 1, and a mounting hole 11, having flatted cross-section, is formed within the mounting shaft 2, while an insertion hole 12, having a circular cross-section, is formed at the lower end of the mounting shaft 2 respectively.

[0015] Referring to Fig.9, there is illustrated a die 13 for manufacturing the aforesaid bonding metal fitting 3 with zinc alloy through the die-casting process. The die 13 has partial dies 13B and 13C at both sides of a boundary surface 13A, which are capable of moving toward or away from each other. The die 13 further comprises a cavity 14 for moulding a contour of the bonding metal fitting 3 and three slidable pins 15,16 and 17, of which the first and second pins 15,16 are provided for formation of the tightening shaft insertion holes 6, having a small recess 18 and protrusion 19 at the respective tips thereof in alignment to the shaft core 1A. The third pin 17 is provided for formation of the mounting hole 11 and insertion hole 12 where a small protrusion 20 of the third pin 17 is inserted into the small recess 21 of the second pin 16 in order that the shaft core 2A may be precisely disposed perpendicular to the shaft core 1A. Accordingly, the aforesaid cavity 14 with the three pins 15,16 and 17 enables the moulding of the bonding metal fitting 3 by casting the melted zinc alloy. Consequently, there remains a small through-hole 22 formed by the small protrusion 20 in the bonding metal fitting 3, as illustrated in Fig.3.

[0016] An upper end of the main shaft 4 to which is attached the driver portion 7 is formed with a flatted portion 23, which has a cross-section slightly larger than or equal to that of the mounting hole 11. Slightly below the flatted portion 23 are formed stoper recesses 24.

[0017] As above described, the main shaft 4 is inserted into the mounting pipe 2 of the prefabricated bonding metal fitting 3. At this time, the flatted portion 23 is press-fitted into the flatted mounting hole 11. Then, the bonding metal fitting 3 with the main shaft 4 is placed in a mould (not shown), around which is filled and solidified melted plastic to integrally form the plastic grip 5. During the formation, the plastic is filled around the stopper recess 24, thereby allowing the plastic grip 5 to keep the main shaft from being pulled out.

[0018] Now the action and effect of the above-structured tightening tool of the invention are described.

[0019] In cases where a quick rotation with relatively a small torque is needed, the tightening tool of the invention can be used just in the same way as an oridnary driver by directly gripping the plastic grip 5.

[0020] In case where a larger torque is needed, the tightening shaft B of a suitable length is inserted into the tightening shaft insertion holes 6 of the transverse pipe 1, thus forming a T-shaped or L-shaped handle. Then, an appropriate force is applied to the tightening shaft B to directly rotate the main shaft 4 via the bonding metal fitting 3, thereby tightening the bolt C having the hexagonal hole, as illustrated in the embodiment.

[0021] The aforesaid wings 8 serve greatly as reinforcing elements when a larger torque is needed. As illustrated in Fig.6, when some force F₁ in the vertical direction acts on the bonding metal fitting 3, the force F₁ is directly applied to the wings 8 as compressive or tensile force, thus effectively allowing the wings 8 to resist the compressive or tensile force F₁ , which, however, is essentially within a conventional technique. Incidentally, the force F₁ in the vertical direction is relatively small when actually used.

[0022] Whereas, as illustrated in Figs.6 and 7, when a torsion F₂ acts on the transverse pipe 1 of the bonding metal fitting 3, a relative distance between the outside upper end 9 of the transverse pipe 1 and the lower end 10 of the mounting pipe 2 becomes larger. In other words, as illustrated in Fig. 7, the distance L between the outside upper end 9 of the transverse pipe 1 and the lower end 10 of the mounting pipe 2 is extended up to the distance L', which is caused by developing the tensile force F₂ due to the above torsion or twist. In a preferred form of the invention, each wing 8 enables the resisting to the tensile force F₂, whereby any deformation of the bonding metal fitting 3 can be prevented.

[0023] When the aforesaid bonding metal fitting 3 is made from high carbon steel, the tensile force F₃ can be sufficiently resisted even when the aforesaid large torsion F₂ is applied, as the high carbon steel usually has excellently high values of Young's modulus ranging from about 206 to 208 GPa, yield point ranging from about 330 to 430 MPa, tensile strength ranging from about 540 to 740 MPa respectivley.

[0024] On the other hand, when the aforesaid bonding metal fitting 3 is made from zinc alloy, it is noted that the zinc alloy has relatively inferior values such as Youngs' modulus of 12 to 13 GPa, about one-sixteenth of that of the high carbon steel, and yield point of 24 to 26 MPa, about one-fifteenth thereof respectively. Nevertheless, the tensile strengh of zinc alloy ranges from about 280 to 320 MPa, which is as high as one-half of that of high carbon steel. Accordingly, the bonding metal fitting 3 made from zinc alloy can be used to sufficiently resist the tensile force F₃, which provides an effective means for enhancement of the strength of the bonding metal fitting 3 with the use of the wings 8.

[0025] Additionally, when a large torsion is applied to the bonding metal fitting 3, the torsional force is transferred to the main shaft 4 across the bonding metal fitting 3. In that case, some compressive force developed in the main shaft 4 due to the torsional moment acts on both surfaces 11A of the mounting hole 11 from both surfaces 23A of the flatted portion 23 in the main shaft 4, as designated F₄ in Fig.8(A). As compared to a compressive force F₅ developed in a conventional shaft having an ordinally crescent-shaped cross-section as illustrated in Fig.8(B), the aforesaid compressive force is as small as about one half thereof. As a result, the flatted hole 11 and the flatted portion 23 can effect twice as high a strength as the comparative one when resisting the compressive force developed by the above torsion. It should be noted that the bonding metal fitting 3 will have sufficient strength not only when made from steel but also from zinc alloy.

[0026] Further, according to the present invention, the stopper recess 24 can eliminate the fear that the main shaft 4 might get detached from the plastic grip 5. Specifically, when an over-load is applied to both surfaces 11A of the mounting hole 11 in the bonding metal fitting 3 with the main shaft being press-fitted, the surfaces 11A will be subjected to plastic deformation in the order of micron meters due to the compression, so that the main shaft 4 is liable to get detached from the plastic grip 5. In a preferred form of the invention, the main shaft 4 is formed with the stopper recesses 24, around which is filled plastic to form the plastic grip 5, thereby preventing the main shaft 4 from getting detached therefrom. Accordingly, if a slight deformation of the bonding metal fitting 3 occurs during the relatively long-time use of the present tool with the bonding metal fitting 3 being pressed-into the main shaft 4, there is little fear that the main shaft 4 will get detached, so, that a user is capable of using the tool without anxiety.

[0027] Incidentally, the present invention should not be limited to the foregoing embodiment, but may be modified within a scope of the invention. For example, as illustrated in Fig.10, in the case that the tool is used for tightening a screw D with a plus thread, a plus driver portion 25 ordinarily called Phillips head driver can be formed. Alternatively, the stopper recess 24 may be replaced with a stopper projection where necessary.

Claims

1. A tightening tool comprising:

a plastic grip;

a bonding metal fitting embedded in said plastic grip, said bonding metal fitting comprising a transverse pipe having openings at its both ends, a mounting pipe connected to said transverse pipe to provide a T-shaped structure of said bonding metal fitting;

a main shaft made from metal, which is to be inserted into said mounting shaft, having a driver portion protruding from said plastic grip,

reinforcing wings integrally provided between the respective lower portions of said transverse pipe and the respective outside portions of said mounting pipe.

2. A tightening tool according to claim 1, wherein a mounting hole of said mounting pipe is formed with flatted portions each having opposite flat surfaces, while one tip of the main shaft is formed with other flatted portions each having opposite flat surfaces to be fitted into the former flatted portions of said mounting hole.

3. A tightening tool according to claim 1, wherein said main shaft is provided with stopper recesses or protrusions formed in suitable portions to be embedded in said plastic pipe.

4. A tightening tool according to claim 1, wherein said wings have each upper end thereof bonded to each free end of said transverse pipe and each lower end thereof bonded to each lower end of said mounting pipe, being formed like delta-wings at its front.

5. A tightening tool according to claim 4, wherein said wings are formed thinner than the respective diameters of said transverse pipe and the mounting pipe.

6. A tightening tool according to claim 5, wherein said wings are disposed on the same plane relative to a plane including both shaft cores of said transverse pipe and mounting pipe.

7. A tightening tool according to claim 5, wherein said bonding metal fitting is made from zinc alloy.

8. A tightening tool according to claim 6, wherein said bonding metal fitting is formed by die casting.

Drawing