JP3954323B2 - screwdriver - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a screwdriver having an engagement projection that can be engaged with an engagement recess formed in a screw head at the tip of a shank portion.
[0002]
[Prior art]
For example, the cross screwdriver is defined in Japanese Industrial Standard (JIS) B4633 and the like shown in FIGS. In the case of a cross screwdriver, it has an engagement part made of a cross-shaped unevenness provided at the tip of the shank part 5, and the direction of the center line of the engagement convex part 6, commonly referred to as a blade, is the axis 7 of the shank part. It coincides with the direction (FIG. 3B). The cross hole 8 of the cross hole screw naturally corresponds to the cross screw driver (FIG. 3E), and is defined in B1012 and the like in JIS.
[0003]
When a screw is tightened using such a screwdriver, the screwing engagement convex portion is fitted into the screw engagement concave portion to transmit torque, and in this case, the way of fitting affects the torque transmission efficiency. For example, the screw-in engagement projection has a tapered shape toward the tip, and the front surface 9 in the screw tightening direction is inclined to the front of the shank portion axis 7, so that when screwing, from the screw hole Although it receives a component force in the direction of pulling out, this is not preferable from the viewpoint of torque transmission. Further, the opening angle θ between the engagement protrusions, commonly referred to as a valley, is defined as an obtuse angle of 92 degrees according to JISB4633 (FIG. 3D), and between the engagement protrusions, the planes s, t, u, and v The angle β formed by the surfaces t and u of the processed formation line shown is defined as four types from No. 1 138 degrees to No. 4 153 degrees. Such a point is considered to cause a cam-out phenomenon when the screwdriver and the screw are fitted.
[0004]
[Problems to be solved by the invention]
In the case of a conventional screwdriver, the shape of the engagement protrusion, the inclination of the front surface of the engagement engagement portion, and the process forming lines indicated by the surfaces s, t, u, v between the engagement protrusions are substantially parallel to each other in the same direction. It was thought that there was a cause of the come-out phenomenon due to the structure.
[0005]
The present invention has been made paying attention to the above-mentioned points and knowledge, and its object is to provide a screwdriver that is unlikely to cause a cam-out phenomenon under any circumstances during rotation in the screw tightening direction.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention relates to a screwdriver in which the shaft center of the shank portion and the shaft center of the screw coincide with each other, the engagement convex portion engages with the engagement concave portion, and is rotated in the screw tightening direction. In the state, a rake angle having a relationship of inclining forward on the distal end side and backward on the proximal end side with respect to the axial center of the shank portion is given to the engagement convex portion , and the valley space between the engagement convex portions is also provided. A means for giving a rake angle having the same relationship as described above to the angle formed by the center line and the axis of the shank portion is taken.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The screwdriver which concerns on this invention has the engagement convex part commonly called a blade | wing which can be engaged with the engagement recessed part formed in the screw head at the front-end | tip of a shank part. Therefore, what is called a screwdriver for manual operation and a driver bit for power are included. Here, the shaft center of the shank coincides with the shaft center of the screw, the engagement convex portion engages with the engagement recess, and the tip of the shank rotates with respect to the screw tightening direction. A rake angle having a relationship in which the side is inclined forward and the base end side is inclined rearward is given to the engagement convex portion. In the present invention, the rake angle is defined as an angle formed by the axis of the shank portion and the center line of the engagement convex portion. Here, the center line of the engagement protrusion is a line located at the center when the engagement protrusion has a substantially symmetric side surface shape, and refers to, for example, reference numeral 19 in FIG. Therefore, the rake angle can be applied not only to a cross screwdriver but also to a Y-shaped (triangular) screwdriver or a minus (-) screwdriver.
[0008]
Since the engagement convex portion constituting the screwdriver has a shape tapered from the proximal end side to the distal end side or a parallel shape, when the rake angle is 0 degree, the front surface in the screw tightening direction is a shank on the proximal end side. When the rake angle is increased, the angle becomes parallel to the axis of the shank part, and when the rake angle is further increased, the part is inclined after the axis of the shank part. Therefore, the smaller the rake angle is, the closer it is to a conventional screwdriver, so it is easier for the cam-out phenomenon to occur.The larger the rake angle is, the less likely it is to cause the cam-out phenomenon. Will not enter. According to the experiment leading to the present invention, when the rake angle is set within the range of 0.5 degrees or more and 5 degrees or less, a suitable result is obtained, and 3 degrees is more preferable. The rake angle condition that has been made.
[0009]
Further, when the screwdriver is a cross screwdriver, the opening angle θ between the valleys constituting the screwdriver, that is, the engagement convex portion, can be set to a range of less than 92 degrees and 80 degrees or more. Furthermore, by forming deeper valleys (bottoms) of the adjacent engagement convex portions with curved surfaces instead of flat surfaces, a structure that does not cause unnecessary contact during screw tightening is created.
[0010]
【Example】
Hereinafter, the present invention will be described in more detail with reference to the illustrated embodiments. FIG. 1 shows a screwdriver 10 according to the present invention. The screw driver 10 is shown as a cross screw driver used for the cross screw 15, and is formed at the tip of the shank portion 11 and has a cross-shaped engagement convex portion 12 commonly called a blade, and a valley between the engagement convex portions. And a space 13 commonly referred to as The cross screw 15 has an engagement recess 16 commonly referred to as a cross hole in the head portion 17, and a screw portion in a portion of the shaft portion 18 outside the figure.
[0011]
As shown in FIGS. 1 and 2, each engagement convex portion 12 crosses the axis line (same as the axial center) 14 of the shank portion 11 so that the distal end side is inclined forward and the proximal end side is inclined rearward. It has an angle A. The front and rear are the directions before and after the screwdriver is rotated in the tightening direction, and the reference for the inclination of the engagement convex portion 12 is the center line 19 related to the engagement convex portion 12. The above-described rake angle A of the engagement convex portion 12 is similarly applied to the angle formed by the center line 20 of the valley space 13 between the engagement convex portions of the screwdriver and the shank portion axis line 14 (see the lower half of FIG. 2). .
[0012]
In the case of the illustrated screwdriver 10, the center line 19 of the engagement protrusion 12 is given a rake angle of 3 degrees with respect to the axis 14 of the shank portion 11 so that the base end side is inclined backward in the screw tightening direction. Yes. In addition, the shape of the engagement convex part 12 is made into the substantially left-right symmetry about the centerline as mentioned above.
[0013]
In the screwdriver 10 of FIGS. 1 and 2, which is a cross screwdriver, the opening angle θ between the engagement convex portions is set to 90 degrees, and a rake angle B of 3 degrees is given to the center line of the valley. ing. The centerline 20 at the upper part (base end side) of the valley is also 46 degrees in the screw tightening direction and 44 degrees in the rear direction. Furthermore, the bottom 21 of the space between the adjacent engagement projections is not a flat surface but a curved surface, and the radius of curvature enters inwardly from the surfaces t and u of the process forming lines indicated by the surfaces s, t, u, and v. It is composed of small curved surfaces.
[0014]
When the cross screw 15 is tightened by using the screwdriver 10 of the present invention configured as described above, each engagement projection 12 is given a rake angle of 3 degrees with respect to the axis 14 of the shank 11 in the longitudinal direction. In addition, since the same angle B is given as the rake angle in the transverse direction, each engagement projection 12 acts to bite into the engagement recess 16 which is a cross hole in the operation in the screw tightening direction. Further, since there is no possibility that each engagement recess 16 hits the bottom portion 21 particularly between the engagement protrusions, the screwdriver 10 bites into the screw hole (16) and is pulled in the screw tightening operation. According to the screwdriver of the present invention, the floating phenomenon is suppressed to the minimum by such an action. Further, each engagement projection 12 has a cross-sectional shape of 44 + 46 ° = 90 ° as shown in the lower half of FIG. 2, and as a result, the durability of the screwdriver 10 is improved. To do.
[0015]
【The invention's effect】
Since the present invention is configured and operates as described above, the rake angle with respect to the axis of the shank portion given to the engagement convex portion and the rake angle similarly given to the center line of the valley space in the cross-sectional direction. Since a situation occurs in which the screwdriver bites into the screw hole, there is an effect that there is almost no room for the cam-out phenomenon.
[Brief description of the drawings]
FIG. 1 is a partially broken side view showing an embodiment of a screwdriver according to the present invention.
FIG. 2 is an enlarged side view and an end front view of the main part of the same.
3A is an end view of a conventional cross screwdriver shown in JIS B4633. FIG.
(B) Similarly side view.
(C) Similarly CC sectional drawing of Fig.3 (a).
(D) Similarly DD sectional drawing of FIG.3 (c).
(E) The longitudinal cross-sectional view of the cross screw hole shown by JISB1012.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Screwdriver 11 Shank part 12 Engagement convex part 14 Axis 15 Cross screw 16 Engagement recessed part 17 Head 18 Center line

Claims (3)

A screwdriver having an engagement convex portion at the tip of the shank portion that can be engaged with an engagement concave portion formed on the screw head, the shaft center of the shank portion and the axis of the screw coincide, and the engagement convex portion in the engagement concave portion a state but which has been engaged, and is rotated in the screwing direction, to impart rake angle with relation to the inclined rearwardly at the front and base end side at the distal end side with respect to the axis of the shank portion to engage the convex portion In addition, a screwdriver characterized in that a rake angle having a relation similar to the above is also given to the angle formed by the center line of the valley space between the engagement convex portions and the axis of the shank portion .  The screwdriver according to claim 1, wherein the rake angle is certified in a range of 0.5 degrees or more and 5 degrees or less with respect to the axial center of the shank portion. The bottom of the space between the adjacent engagement projections is not a plane indicated by the planes s, t, u, v of the machining formation line defined in JIS B4633, and is a constituent plane of the machining formation line. The screwdriver according to claim 1, wherein the screwdriver is configured by a curved surface having a smaller radius of curvature that enters inward than t and u.

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