JPH0235167B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is formed on the head of a screw used in an automatic screw tightening machine, etc., and engages with the tip of the screwdriver, that is, the driver bit, when tightening or removing the screw, thereby transmitting the rotational torque of the driver to the screw. The invention relates to a screw having a cross recess for Conventionally, the Phillips cross recess as shown in Figures 1 to 3 has been established as a national standard in each country as a cross recess for such screws, and is the most widely used around the world. This is because it has the following advantages over holes. (A) Good fit with driver bit. (B) Good adhesion with driver bits. (C) Fewer types of driver bits are needed when using screws with various nominal dimensions. (D) Productivity is excellent because the cross recess can be formed at the same time as the screw head. By the way, in the commonly used Phillips cross recess, as shown in FIGS. Angle γ _D formed by both side surfaces 107, 107 of each wing portion 106
Therefore, when the driver bit 102 and the cross recess 101 are engaged, as shown in FIG.
09 and the valley 11 near the bottom 112 of the cross recess 101
When the screwdriver bit 102 comes into close contact with the screwdriver bit 102, causing a so-called sticking, and when the driver is driven to rotate, the driver bit 102 will only tighten at its tip, as shown from the driving start state in FIG. 2 to the driving state in FIG. cross hole 1
01, the contact pressure between the driver bit 102 and the cross recess 101 increases in a quadratic curve toward the tip of the driver bit 102, as shown in FIG. 3a. For this reason, with the recent advances in mass production assembly methods, various drawbacks have appeared in the Phillips cross recess.
They are as follows. (a) As is often the case with automatic screw tightening machines that have become widely used in recent years, the good grip of the Phillips cross recess has the opposite effect, and when removing the screwdriver bit from the screw cross recess after tightening, The driver bit may become stuck in the cross recess and the bit may be pulled out of the driver socket, or the product may be lifted together with the driver bit. (b) The tip of the driver bit touches the cross recess of the screw, so when tightening the screw,
The tightening torque of the screwdriver concentrates on the tip of the bit, generating an extremely large surface pressure there. This surface pressure causes severe deformation and damage to the tip of the driver bit and the bottom of the cross recess, which causes the screwdriver bit to deteriorate. life span becomes shorter. This is the biggest reason why driver bits wear out quickly. (c) Since the angle formed by both sides of each wing of the Phillips cross recess is larger than the angle of each side of each wing of the cross shape of the driver bit,
Even if the tip of the driver bit and the bottom of the cross recess of the screw are deformed, the side surfaces of the wing parts of both will come into contact near the tip of the driver bit, as shown in Figure 3c, and the entrance of the cross recess will remain in contact. There is almost no contact at the top surface of the screw head. For this reason, stress concentrates on the side surface of the blade at the tip of the driver bit, causing this portion to be twisted and deformed. (d) As wear and torsional deformation near the tip of the driver bit progresses, the so-called cam-out phenomenon occurs, in which the driver bit gradually lifts up and slips out of the cross recess due to vibrations when the driver is driven. The tip of the bit scrapes the valley of the cross recess, causing a so-called reaming phenomenon, making it difficult to remove or retighten the screw. Furthermore, once the driver bit has come out, it becomes unusable. (e) When tightening a screw, a large thrust must be applied to the driver bit to prevent it from coming out, which increases worker fatigue. Therefore, the present invention makes it possible to increase the contact area between the driver bit and the cross recess by simply inserting and rotating a general-purpose screwdriver bit, which improves the transmission of tightening torque and increases the transmission of tightening torque to the tip of the screwdriver bit. The object of the present invention is to provide a cross-recessed screw that can simultaneously avoid stress concentration. According to the present invention, the above object is to, in a screw having a conical cross recess that engages with a driver bit having a cross cross section, adjust the angle formed by both sides of each wing part of the cross recess to the cross shape of the driver bit. smaller than the angle formed by both sides of each wing, preferably from 4°
By setting the screwdriver bit between 7° and 30', when the driver bit is engaged with the cross recess, the outer circumferential surface and both sides of each cross-shaped wing of the driver bit are aligned with the outer periphery of each wing of the cross recess. This is achieved by configuring the surface and both side surfaces to contact each other near the top surface of the head of the screw. Embodiments of the present invention will be described below with reference to the drawings. First, FIGS. 4 to 6 show a first embodiment of the present invention in which the cross recess is designed to prevent the screwdriver bit from getting stuck. . Figures 4a and 4b are longitudinal sectional views of the screw head, and in these figures, 1 is a cross recess provided in the head of the screw so that it can engage with the driver bit 2, which has a cross-shaped cross section;
The cross recesses 1 are spaced approximately 90 degrees apart in the circumferential direction 4
It has a leaf wing part 3, and these wing parts 3 have both tapered side surfaces 4, 4 extending in the axial direction, and these both side surfaces 4,
4, and the angle γ formed by both side surfaces 4, 4 is A--A in FIGS. 4a and 4b.
As shown in FIG. 4e, which is a cross-sectional view taken along line A, the angle γ _D formed by both side surfaces 7, 7 of the cross-shaped wing portion 6 of the driver bit 2 is set to be smaller than the angle γ D, and the center of the conical outer circumferential surface 5 is The angle is set to be approximately equal to or slightly smaller than the central angle of the conical outer peripheral surface 8 of the wing portion 6 of the driver bit 2. When the driver bit 2 is engaged with the cross recess 1, the conical outer circumferential surface 8 of the wing section 6 of the driver bit 2 comes into close contact with the corresponding conical outer circumferential surface 5 of the wing section 3 of the cross recess 1, and their In this case, M in FIG. 4b is prevented.
The fourth figure is a cross-sectional view in the plane and the G _G plane.
As shown in FIG. Like the conventional Phillips cross recess shown in FIGS. 1 to 3, the valleys 9 and 10 of the driver bit 2 and the cross recess 1 come into close contact with each other to prevent so-called sticking. Next, the operation of this embodiment will be explained.
First, when no rotational torque is applied to the screwdriver, as shown in FIGS. , 4. When the driver is rotated, as shown in FIG. 5, immediately after the driver starts rotating, the driving side side surface 7 (the right side surface in FIG. 5) of the wing section 6 of the driver bit 2 is in contact with the wing section 3 of the cross recess 1. It comes into contact with one side surface 4 at the entrance of the cross recess 1, that is, near the top surface 11 of the screw head, and the rotational torque is transmitted satisfactorily. While this driver is rotating, the contact area between the wing section 6 of the driver bit 2 and the wing section 3 of the cross recess 1 is as follows.
As shown in Fig. 6b, surface contact occurs at the entrance 11 of the cross recess 1 (the top surface of the screw head), but as shown in Fig. 6c, the bottom 12 of the cross recess 1 or the screwdriver bit 2 There is no contact near the tip.
Therefore, as shown in FIG. 6a, the surface pressure of these contact parts decreases in a quadratic curve from the entrance 11 of the cross recess 1 toward the bottom 12, and the contact pressure decreases in a substantially conical cross shape. A large surface pressure is applied near the entrance of the hole 1 at its maximum diameter. For this reason, the cross recess 1 and the driver bit 2 come into surface contact over a relatively wide area near the large diameter entrance 11 of the cross recess 1, so as shown in FIGS. The contact area is significantly larger than that of the conventional Phillips cross recess, in which the tip of the cross recess 1 contacts in a relatively small area near the small diameter bottom 12 of the cross recess 1.
Therefore, the surface pressure of the contact portion is relatively small, and deformation and damage of the driver bit 2 and the cross recess 1 are effectively prevented. FIG. 7 shows a second embodiment of the present invention in which the cross recess is designed to fit into the driver bit. In this embodiment, when the driver bit 2 is fitted into the cross recess 1, each of the driver bits 2 Both side surfaces 7, 7 of the wing section 6 are closely fitted to both side surfaces 4, 4 of each wing section 3 of the cross recess 1 near the entrance 11 of the cross recess 1, so that a tight contact occurs between the two sides.
Also in this embodiment, the angle γ formed by both side surfaces 4, 4 of each wing portion 3 of the cross recess 1 is smaller than the angle γ _D formed by both side surfaces 7, 7 of each wing portion of the driver bit 2. It is set. The structure and effects of this embodiment other than those described above are substantially the same as those of the first embodiment. In addition, the angle α' [Fig. 1a] formed by the valley part 109 between the wings 106, 106 of the conventional Phillips cross recess according to the JIS standard with respect to the vertical central axis 0, and both sides of each wing part 106. 107, 107 (FIG. 1 a) and the corresponding angles α, γ of the cross recess 1 of the present invention [FIG.
The ranges shown in Figures b and 7a] are shown in the table below.

[Table] As described above, according to the present invention, when a driver bit having a cross-shaped cross section is engaged with a cross recess having a conical outer peripheral surface, the outer peripheral surface of each cross-shaped wing portion of the driver bit Since both side surfaces are in contact with the outer peripheral surface of each wing of the cross recess and both side surfaces near the top surface of the screw head, the contact area between the driver bit and the cross recess is a conical cross recess. The contact area between the driver bit and the cross recess is larger than that of a conventional Phillips cross recessed screw, which contacts at the bottom of the screwdriver bit, that is, near the tip of the driver bit. Therefore, not only is it possible to effectively transmit the rotational torque from the driver bit to the screw, but also the surface pressure of the contact portion is reduced, and stress concentration on the tip of the driver bit can be avoided. Therefore, when the driver is driven to rotate, the tip of the driver bit is less likely to be twisted, deformed or worn out, and the cam-out phenomenon of the driver bit caused by these factors can be effectively prevented, and the driver bit can be In addition to significantly improving the lifespan of the screwdriver, there is no need to apply excessive thrust to the screwdriver bit to prevent the cam-out phenomenon when driving the screwdriver, as was the case with conventional screwdrivers, which reduces worker fatigue. Efficiency can be significantly increased. In addition, since the sticking phenomenon caused by the deformation of the screw hole and driver bit is effectively suppressed, the screwdriver bit can be easily removed from the screw hole when the screw has been tightened. Ideal for Furthermore, since the screw hole is less likely to deform or collapse, the screw can be used repeatedly, making it very economical. In addition, since the bottom of the screw hole according to the present invention is larger than the bottom of a conventional Phillips cross recess with the same top size, the punch for forming the screw hole has a wider cutting edge than the conventional one, which reduces its lifespan. This is a significant increase. Moreover, since the plating etc. will not peel off due to deformation of the cross recess during tightening, it is possible to prevent the occurrence of rust caused by this. Since a general-purpose screwdriver bit can be directly inserted into the cross recess to transmit rotational torque, its range of applications is wide.

[Brief explanation of drawings]

Figures 1 to 3 show conventional screws with Phillips cross recesses; Figure 1a is a vertical sectional view of the cross recess with the driver bit (shown in chain lines) engaged; Figures 1b and 3; Fig. 1c is a cross-sectional view taken along the M plane and G _G plane of Fig. 1a, Fig. 1d is a sectional view taken along the line A-A of Fig. 1a, and Figs. 2a to 2c are driver bits. 3a to 3c are cross-sectional views showing the relationship between the driver bit and the cross recess at the start of the rotational drive (shown by the chain line). FIGS. 4 to 6 are cross-sectional views showing the relationship between the two screws, and FIGS. 1 to 3, FIG. 7 shows a screw with a cross recess for screwing into a screwdriver bit according to a second embodiment of the invention, and FIGS. 7a to 7d respectively Figure 1 a~
This corresponds to FIG. 1d. 1...Cross recess, 2...Driver bit, 3...
...Wings of the cross recess, 4, 4...Both sides of the wing of the cross recess, 6...Wings of the driver bit, 7, 7...
Both sides of the wing of the driver bit, γ...Angle formed by both sides of each wing of the cross recess, _γD ...Angle formed by both sides of each wing of the driver bit.

Claims (1)

[Scope of Claims] 1. In a screw having a conical cross recess that engages with a driver bit having a cross-shaped cross section, the angle formed by both sides of each wing of the cross recess is the angle formed by each cross-shaped wing of the driver bit. By setting the angle smaller than the angle formed by both sides of the screwdriver bit, preferably between 4° and 7°30′, when the driver bit is engaged in the cross recess, the outer periphery of each cross-shaped wing of the driver bit A cross-recessed screw configured such that the surface and both side surfaces contact the outer circumferential surface and both side surfaces of each wing portion of the cross-recessed portion near the top surface of the head of the screw.