JP2002089758A - Locking fastening system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exhibit a locking function resistant to an external force such as a vibration by enhancing a screw contact surface pressure while a length of screw and a fastening torque are made constant. SOLUTION: A total area of a screw contact surface is reduced by intermittently disposing a screw thread at a female screw side while a length of screw and fastening torque are made constant. As a result, a unit surface pressure of the screw contact surface is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joint system used for a piping system and a fastening system such as a cap nut.

[0002]

2. Description of the Related Art For example, a screw conventionally used for fastening a coupling nut and a cap nut used in a piping system, whether it is a male screw or a female screw, is continuous on a circumference and is fixed to stabilize a fastening posture. When the screw length is set, a fixed axial stress is generated by the determined tightening torque, and the unit surface pressure of the screw contact surface is uniquely determined.

[0003] That is, there is a disadvantage that the unit surface pressure of the screw contact surface, which is directly related to the important function of the fastening system, namely, the loosening of the screw, cannot be controlled independently of the aforementioned conditions.

The problem to be solved is that the unit surface pressure of the screw contact surface is increased while the screw length and the tightening torque are kept constant, and vibration and the like are utilized by utilizing the elasto-plastic deformation of the screw thread. Is to exert a function of preventing loosening against external force.

[004]

SUMMARY OF THE INVENTION The present invention reduces the total area of the screw contact surface while keeping the screw length and the tightening torque constant by arranging the thread on the female screw side intermittently. The most important feature is that the unit surface pressure has been increased. Further, in order to exert the effect remarkably, the female thread of the nut should be constituted by a group of intermittent threads having a projected area of 50% or less with respect to the projected area of the ordinary continuously existing threads. It is.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As a means for realizing intermittently disposing a screw thread on a female thread side, a technique by plastic working described in Japanese Patent Application No. 8-258898 is adopted. The female thread by this method is not only economically inexpensive to manufacture, but also has a workability near the screw thread well over 50%, and its strength is more than doubled as shown in FIG. In addition to compensating for the decrease, it also induced plastic deformation for a simple machined male screw, and exhibited a more perfect locking function.

[0006]

FIG. 4 is a sectional view showing an embodiment of the present invention. It is used for fittings in piping systems and is one of the fields where the features of this system can be fully demonstrated.

When the male screw and the female screw of the present invention are tightened with a constant torque as shown in FIG. 4, the stress at the screw contact portion increases,
In particular, the elastic deformation caused by the high strength and low stiffness of the female screw and the plastic deformation caused by the low hardness and high stiffness of the male screw side combined, and this system exhibited more than 60% resistance to loosening against external force such as vibration or torsion.

As described above, according to the fastening system of the present invention, the thread contact on the female thread side is intermittently arranged while the conventional male screw side is kept as it is, so that the thread contact and the screw length are kept constant. By reducing the total surface area and increasing the unit surface pressure of the screw contact surface, the elastic deformation caused by the high strength and low stiffness of the internal thread and the plastic deformation caused by the low hardness and high stiffness of the male screw side combined with vibration or Strong loosening resistance against external forces such as torsion was demonstrated.

[Brief description of the drawings]

FIG. 1 shows main components in an embodiment of the present invention.

FIG. 2 is a top view of a nut side.

FIG. 3 is a partially enlarged view of a top view of a nut side.

FIG. 4 is an assembly view of the embodiment of the present invention.

FIG. 5 is a work hardening curve of 18-8 stainless steel.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Male thread 2 Nut 21 Thread of female screw intermittently arranged 31 Hatched part 31 shows projected area of thread part 41 Piping 42 Sealing material

Claims (2)

[Claims] An internal thread of a nut to be fitted is constituted by a group of intermittent threads with respect to a male screw to be fastened, and a loosening prevention effect is exhibited by increasing the contact pressure of a fitting screw portion at the time of fastening. A fastening system characterized by the following. 2. A female thread of a nut to be fitted is constituted by a group of intermittent threads having a projected area of 50% or less of a projected area of an ordinary continuous thread, and A fastening system characterized by exhibiting a loosening prevention effect by increasing the contact pressure of the fitting screw part to at least twice as a result.