JPS605806B2 - screw - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in screws.

Conventionally, screws have been known that have a bit locking hole such as a cross recess or a regular hexagonal hole formed on the upper surface of the head.

However, these screws have common drawbacks in that the bit retaining hole is easily damaged and it is difficult to obtain strong competitive torque. As a result of various studies conducted by the applicant and others regarding this point, it has been found that the reason for the above-mentioned drawback is related to the shape of the bit retaining hole, as described below. That is, to illustrate and explain a screw 1 having a cross-shaped bit locking hole and a screw 1' having a regular hexagonal bit locking hole, respectively, in FIGS. 1A and 1B, a normal vertical screw attachment x
The shape and dimensions of the cotton fittings are made somewhat smaller than the shape and dimensions of the bit locking holes so that the iron fitting to the bit locking holes 2 and 2' can be carried out smoothly, as shown in the same figure. like,
The inner wall surface of the bit locking hole 2, 2' comes into contact with the surface of the attachment, and the point where the rotational torque T of the attachment is transmitted to the screws 1, 1' becomes a point contact. In P),
The rotational torque T of the fastener x is applied to the screws 1, 1' as a force (hereinafter referred to as a force perpendicular to the plane) N acting in a direction perpendicular to the inner wall surfaces of the bit locking holes 2, 2'.

This plane normal force N acts in the tangential direction of the circumference of the screws 1, 1' and generates a force (hereinafter referred to as driving force) F that rotates the screws 1, 1'. If the direction of the force N perpendicular to the plane and the direction of the driving force F do not match,
A component force that is a component of the surface normal force N in the direction of the driving force F acts as the driving force F. That is, the tangent line 1 of the contact surface of the cotton fitting × to the bit locking hole 2, 2' at the force application point P is between the radius line 12 passing from the center point 0 of the screw 1, 1' to the force application point P. When there is an angle (hereinafter referred to as drive angle) 8, the driving force F is F=N·COS. Therefore, in the case of cross recess 2 in screw 1 of FIG. 1A, 8
Since D is 200, F=0. In the case of the regular hexagonal hole 2' in Fig. 1B, it is a3600, so F=0. Becomes a state. As described above, as the driving angle a increases, the driving force F decreases, and the torque T applied to the vertical attachment x is not effectively transmitted as the rotational torque of the screws 1 and 1'. In this way, as the driving angle 8 increases, the driving force F against the surface normal force N' decreases. In other words, in order to apply a predetermined driving force F to the screw, the surface normal force N'
must be made larger than necessary, but from another perspective, this force N perpendicular to the plane also becomes a force that presses against the inner wall of the bit retaining hole at the force point P, so the broken line of the screw can be In order to prevent this, it is preferable that the force N perpendicular to the plane is as small as possible. Further, the radial component force R of the surface normal force N acts as a compressive destructive force on the fastener x. On the other hand, with conventional screw threads, the fastener can fit smoothly into the bit locking hole, so as mentioned above, the cotton fitting is somewhat smaller than the bit locking hole. In addition to making it, for example, the upper part of the bit locking hole is made into a large diameter hole, and the lower part is made into a small diameter.
It is also possible to form a structure as shown in FIG. 2A, which is formed as a paper.

The cross-shaped recess 2'' shown in the figure has a cross-shaped groove whose middle dimension gradually narrows from the upper part to the lower part.However, if the taper is simply provided in this way, the bit locking hole 2'' at the force application point P becomes narrower. As shown in Figure 2 B', the inner wall surface 2''a of the screw is inclined with respect to the plane S passing through the axis of the screw. A force Q is generated, and a force is generated that tries to push the vertical fixture It is necessary to hold down the bit, which causes fatigue for the operator.Also, if the bit locking hole 2'' is tapered as described above, the tightening tool x
A sliding force corresponding to this taper angle is generated as one of the various acting forces that occur between the fastener When the coefficient of friction is smaller than the coefficient of friction, the adhesion between the fastener x and the inner wall surface 2''a is good, but conventionally the taper angle is about 10 to 20
o is relatively large, the sliding force becomes larger than the coefficient of static friction, and the adhesion between the attachment tool x and the inner wall surface 2''a is poor, making it particularly difficult to install screws in narrow spaces where your fingertips cannot fit. The present invention was developed in view of the above circumstances, and it is possible to improve the torque transmission efficiency by reducing the drive angle 8 of the bit locking hole to zero degrees, and to prevent damage to the screw. In addition, it provides a screw that does not have cam-out and has good adhesion.Hereinafter, the present invention will be explained in detail based on the embodiments shown in FIGS. 3 to 7. , 10 is a screw portion 11 and a head 12
The head 12 is formed in the shape of a flat plate with a diameter larger than the ridge of the threaded part 11 centered on the axis of the threaded part 11. Reference numeral 13 denotes a bit alignment hole formed on the upper surface of the head 12 in a planar circular shape with the screw portion 11 as the center, and can be fitted horizontally with a bit which is the tip of a screwdriver or the like.

The peripheral wall portion 13a of the bit ironing hole 13 is formed to be substantially vertical, or to have a large diameter at the top and a small diameter at the bottom, and to be inclined inward at a slight angle.
A has a plurality of (4 to 6) semicircular locking bars 14.
are equally distributed in the circumferential direction and extend from the upper surface of the head 12 to the lower surface of the bit formation hole 13.
To explain the details using FIG. 4, the tangent line of the semicircular locking bar 14 to both side walls 14a, 14b in the circumferential direction, that is, the tangent line 1 of the wall surface 14a, which is the force application point P, is the threaded part 11. It is formed so that the center point ○' of the arc is located on the circumferential circle of the bit fitting hole 13 so as to coincide with the radius line 12 passing through the center 0 of the circle. This locking bar 14 is such that no matter which plane in the rut direction the head 12 is cut, the position of the center point ○' is located at the reinforcing hole 13 in each cut plane.
In other words, the locking bars 14 are formed in the same direction in the axial direction and are provided along the tapered peripheral wall surface 13a of the steel hole 13. . Therefore, as shown in FIG. 3C, the side wall surface 14a of the locking bar 14 in the direction perpendicular to the radius of the reinforcing hole 13 substantially coincides with the plane S passing through the radius, that is, the axis O. Further, it is preferable for strength to make the middle dimension L of the locking bar 14 equal to or larger than the middle length L of the other parts. Since the present invention has a configuration with more than one screw, Fig. 5A
, B, by fitting the bit 18 of the screwdriver 17, which has a head 15 and a locking groove 16 corresponding to the locking hole 13 and the locking bar 14, into the locking hole 13, the screw 1
It is possible to perform zero tightening and tightening.

At this time, as shown in FIG. 4, the force application point P of the screw 10 and screwdriver 17 is on the side wall 14a of the locking bar 14, and the tangent line 12 at this force application point P coincides with the radius line 1 of the screw 10. Therefore, the driving angle 8' becomes almost zero, and the surface normal force N generated at the force application point P almost coincides with the direction perpendicular to the radial lines 1, 12, that is, the direction of the driving force F. Therefore, since the force N perpendicular to the plane directly becomes the driving force F to rotate the screw 10, the torque transmission efficiency is extremely good, and the force N perpendicular to the plane is the minimum force necessary to rotate the screw 10. This can reduce the damaging force exerted on the screw 10' and prevent the screw 10 from being damaged. This also means that a radial component of the force N perpendicular to the plane is not generated, and no destructive force is generated in the cotton attachment. In addition, since the locking bars 14 are the same, one side 14a of the locking bar 14 almost coincides with the plane passing through the center of the screw 10, as shown in FIG. In this case, the force application point P occurs on a line along the axial direction), so there is no axial component force of the screw, especially an upward component force, and therefore the screwdriver 17 acts to be pushed out from the steel plate 13. No cam-out force is generated, making screw tightening extremely easy.

In other words, most of the wall surfaces of the steel fitting hole 13 and the locking bar 14 (
The aforementioned portions of the locking bar 14 (excluding the side walls 14a, 14b) are formed vertically or with a slight inclination, so that the sliding force generated in the axial direction of the screw between the locking bar 17 and the screwdriver 17 is absorbed by its rest. This makes it easier to make the friction coefficient smaller than the friction coefficient, and it is possible to improve the adhesion between the screwdriver 17 and the screw 10. Further, since the drum hole 13 is perpendicular to the screw axis direction or is only slightly inclined, the torque transmitted by the vertical tool can be applied almost evenly to the side wall surface 14a without changing in the direction of the bag. Therefore, torque transmission is good, stress concentration does not occur, and the iron joint hole 13
It won't get complicated. Furthermore, since the bit hole is inclined at only a small angle, the cutting force, which is difficult to achieve with vertical torque, is almost constant from the top to the bottom of the bit hole, and the inside of the locking bar is constant in the screw axis direction. Therefore, the sea bream shear stress that occurs in the locking bar is almost constant from the top to the bottom, and it is vertically attached.There is no stress concentration during tightening, and the locking bar in the bit hole is not damaged. In the embodiment, the case where the screw head is formed into a flat dish shape has been described, but it may be formed into a round dish shape as shown in FIGS.
, B, the head diameter may be the same as the screw diameter, and it goes without saying that various other shapes can be adopted.

[Brief explanation of the drawing]

Figures 1A and B are plan views of a conventional screw, Figure 2A is a detailed plan view of a conventional screw, B is a sectional view taken along line B-B of Figure A, and Figure 3A is a plane view of a screw according to the present invention. Figure 4 is a partially enlarged view of Figure 3A; A plan view of the screwdriver, B is a side view, and FIGS. 6A, B and 7 A, B are plan views and partially cutaway side views of other embodiments, respectively. 10... Screw, 11... Thread portion, 12... Head, 13... Bit formation hole, 14... Locking bar, 17... Screwdriver. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 5 Division (2) Change of applicant's name (published on June 12, 1960) Patent Classification
Identification Application number Old applicant
Publication number for new application Symbol: 1984 General 06 F16B 23/00 1984-125
457 Yamamoto Kushiro Co., Ltd. Yamamoto Kushiro Co., Ltd. 4-2-2 Arakawa, Arakawa-ku, Tokyo 4-2-2 Arakawa, Arakawa-ku, Tokyo OSG Sales Co., Ltd. 240 Honnogahara, Toyokawa-cho, Toyokawa-shi The above application has been filed. It was inherited before the public announcement.

Claims (1)

[Claims] 1 Consisting of a screw part and a head, a bit fitting hole concentric with the screw part is formed on the upper surface of the head, and four to six halves are formed in the peripheral wall along the rotation axis of the screw. A circular locking rod is provided protrudingly, and its fitting hole is almost vertical or has a large diameter at the top and a small diameter at the bottom, and the circumferential wall is inclined inward at a slight angle. The radius of the semicircular shape is formed to be constant in the screw axial direction along the surface of the peripheral wall portion, and the center point of the semicircular shape is approximately fitted as described above so that the tangent at the point of contact with the fastener coincides with the radius line of the screw. A screw characterized in that it is formed so as to be located on the circumscribed circle of the periphery of the hole.