JPH0723724B2 - Fastener and fastening assembly using the fastener - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fastener for fixing an object to be fastened and a fastening assembly using the fastener.

[Prior Art] When tightening an object to be fastened with a bolt and the coefficients of thermal expansion of the object to be fastened and the bolt are different from each other, a difference in thermal expansion occurs due to a temperature change after tightening, and the bolt moves in the axial direction. The axial force changes due to plastic deformation and the axial force changes due to the tightening seat surface of a soft object such as synthetic resin being depressed, and the bolt loosens.

A spring washer as shown in FIG. 6 is known as a well-known means for preventing such loosening of the bolt.
In this conventional example, bolts a, nuts b, and spring washers c are used to fasten the objects to be fastened d, e.

[Problems to be Solved by the Invention] Since the spring washer c absorbs the difference in thermal expansion by bending in the thickness direction, the amount of bending is small. Therefore, when the objects to be fastened d, e are made of a material having a large coefficient of thermal expansion such as a synthetic resin or an aluminum alloy, the spring washer alone may not be able to prevent loosening due to the difference in thermal expansion.

As seen in Japanese Utility Model Laid-Open No. 2-101114, a first screw part having a screw head, a second screw part separated from the first screw part, and a space between these screw parts. A spring-loaded screw having a coil spring provided in the above has been proposed.
In this known example, the coil spring and the second screw portion are rotatably engaged with each other, and the first screw portion is relatively rotated with respect to the second screw portion, so that the distance between the both screw portions is reduced. It is changed so as to change the flexure of the coil spring to generate a desired tensile load. Therefore, in this known example, since the second screw portion cannot be rotated even if the screw head is rotated, it cannot be used like a normal bolt and the fastening force is weak. Moreover, since the first screw portion, the second screw portion, and the coil spring are required as the constituent parts, there is a problem that the number of parts is large, and it is not possible to exhibit the fastening function comparable to the bolt.

Therefore, an object of the present invention is to provide a fastener which can exhibit a fastening function equivalent to a bolt, has a small number of constituent parts, and has a high anti-loosening effect, and a fastening assembly using the fastener.

[Means for Solving the Problems] The fastener of the present invention developed to achieve the above object is
For example, a cylindrical spring shaft portion obtained by coiling a wire made of an elastic material such as spring steel in one direction, and the element in the same direction as the spring shaft portion continuously to at least one end of the spring shaft portion. A terminal threaded portion around which the wire is wound, and a thread opposite to the winding direction of the wire is provided on the outer peripheral surface of the wire of the terminal threaded portion.

[Operation] In the spring shaft portion of the fastener of the present invention, since the winding direction of the wire is opposite to the direction of the thread of the terminal screw portion, the nut is screwed onto the terminal screw portion to tighten in the tightening direction. When rotated, the torque acts in the winding direction of the wire. That is, since torque acts in a direction in which the diameter of the spring shaft portion decreases when tightened, the nut can be easily tightened like a normal bolt. On the contrary, since the force in the slack direction acts in the direction in which the diameter of the spring shaft portion increases, the effect of preventing the slack is extremely large. Further, with respect to the load in the direction in which the spring shaft portion is extended, the spring shaft portion is bent in the axial direction, and a reaction force corresponding to the amount of the bending is generated to fasten the object to be fastened.

When a difference in thermal expansion occurs after tightening, the difference in thermal expansion is absorbed within a range in which the spring shaft portion can bend in the axial direction, and the occurrence of slack is avoided. Since a spiral element wire made of an elastic material is used for the spring shaft portion, a large bending can be obtained in the axial direction.

[Embodiment] An embodiment of the present invention will be described below with reference to Figs.
It will be described with reference to the drawings.

The fastener 1 shown in FIG. 1 includes a spring shaft portion 2. The spring shaft portion 2 is formed by coiling a wire 3 made of an elastic material having a rectangular cross section in one direction (in this embodiment, the left-handed direction) as shown in FIG. In the case of this embodiment, the wires 3 are in close contact with each other in a free state. That is, the coil spring is a close-wound coil spring, but the invention is not limited to this, and a normal pitch coil spring having a space between the wires may be used.

For the purpose of adjusting the load-deflection characteristic of the spring shaft portion 2, the wire 3 may be given an initial tension by appropriately selecting a pitch angle and a twist rate during coiling.
An example of the material of the wire 3 is an iron-based metal such as spring steel, but other metals or an appropriate inorganic material or organic material may be used. The cross-sectional shape of the wire 3 is not limited to a quadrangle, and may be a circle or a similar shape, a polygon, or any other suitable cross-sectional shape.

Terminal screw portions 5 and 6 are formed at both ends of the spring shaft portion 2, respectively. The terminal screw portions 5 and 6 are provided on their outer peripheral portions with screw threads 7 and 8 which are provided in the direction opposite to the winding direction of the wire 3, that is, in the present embodiment, in the clockwise direction. The terminal screw portions 5 and 6 are obtained by threading both ends of the spring shaft portion 2.

The fastening assembly 10 illustrated in FIG. 3 includes the fastener 1 and
Objects to be fastened 13 and 14 are fastened by nuts 11 and 12. In this case, the nuts 11 and 12 are screwed into the terminal screw portions 5 and 6, respectively, and the nuts 11 and 12 are respectively rotated in the clockwise direction for tightening. The torque in the direction of tightening the nuts 11 and 12 is the direction in which the terminal screw portions 5 and 6 and the wire 3 of the spring shaft portion 2 are wound and tightened, that is, the direction in which the wire wires 3 adhere closely to each other (the diameter of the spring shaft portion 2 decreases. Direction). Therefore, the tightening work can be performed without any problem.

When the tightening force of the nuts 11 and 12 is increased, the nut 1
The nuts 11 and 12 are screwed in the direction in which the distance between the nuts 1 and 12 decreases.
Since the objects 13 and 14 to be fastened, which are substantially rigid bodies, have a predetermined thickness t, when the screw advance amount of the nuts 11 and 12 exceeds a predetermined value, the spring shaft portion 2 is The wires are bent in a direction in which they are separated from each other, a reaction force corresponding to the amount of the bending is generated in the axial direction, and the objects to be tightened 13 and 14 are tightened.

When the material of the objects to be fastened 13, 14 has a coefficient of thermal expansion larger than that of the fastener 1, such as an appropriate synthetic resin or aluminum alloy, this fastening is performed after fastening the nuts 11, 12. When the assembly 10 becomes hot, the thickness increases relatively by Δt, as shown in FIG. The thermal expansion difference generated at this time is absorbed by the spring shaft portion 2 bending by Δt in the axial direction. The spring shaft portion 2 formed of the spiral wire 3 has a significantly greater flexure than the shaft portion of the conventional bolt. That is, since the spring shaft portion 2 is not deformed to the plastic region, the spring shaft portion 2 is not plastically deformed due to the thermal expansion of the tightened objects 13 and 14.
After that, when the temperature lowers and contracts, the original shape (state of FIG. 3) can be restored. In this way, the anti-loosening effect is exerted and the predetermined tightening force is maintained.

Contrary to the above, when the temperature of the objects to be tightened 13 and 14 is lower than that during tightening and a difference in thermal expansion occurs on the contracted side, the range in which the spring shaft portion 2 can flex in the axial direction as in the case of expansion Can absorb the difference in thermal expansion.

Since the tightening tool 1 of the present embodiment can be kept in a state in which an appropriate axial force is always applied to the spring shaft portion 2 as described above,
An appropriate frictional force can always be generated at the contact surface between the screw threads 7,8 of the terminal screw parts 5,6 and the nuts 11,12.
The 11 and 12 anti-loosening effects are more effectively exhibited.

Moreover, the torque to loosen the nuts 11 and 12 is
When acting on 12, the terminal screw parts 5, 6 and the spring shaft part 2
The torque in the slack direction is absorbed by bending the terminal screw parts 5 and 6 and the spring shaft part 2 in the direction in which the diameter of the wire expands, that is, in the direction in which the winding of the strand 3 returns, so that the nuts 11 and 12 are not loosened. It is effective in preventing. Since the spring shaft portion 2 is composed of the coiled wire 3,
It can be used even when the spring shaft portion 2 is bent. Also, conventional spring washers can be omitted.

The strand 3 may be wound in the opposite direction to the illustrated example. In that case, the threads 7 and 8 are both left-hand threads.

FIG. 5 shows another embodiment of the present invention. In this case, a non-circular (eg hexagonal) head 20 corresponding to the head of a bolt is provided at one end of the spring shaft portion 2. At the same time, a terminal screw portion 6 is formed on the other end side of the spring shaft portion 2, and the nut 12 is screwed into the terminal screw portion 6. The other structure is the same as that of the above embodiment. Also in this embodiment, the excellent anti-loosening effect is exhibited.

[Advantages of the Invention] According to the present invention, it is possible to fasten an object to be fastened with an appropriate axial force, the tightening work can be easily performed like an ordinary bolt, and an excellent anti-loosening effect is provided. It is possible to effectively prevent the occurrence of slack due to the difference in thermal expansion. The fastener of the present invention can use a single strand of wire wound in the same direction from the spring shaft portion to the terminal screw portion, and forms a screw thread on the outer peripheral surface of the strand itself in the direction opposite to the winding direction. Therefore, the number of components is small and it is durable. In addition, since it is possible to take a large amount of bending in the axial direction, it is effective even for large displacements.

[Brief description of drawings]

1 is a side view of a fastener showing an embodiment of the present invention, FIG.
1 is a cross-sectional view of the fastener shown in FIG. 1, FIG. 3 is a side view partially showing a fastening assembly using the fastener shown in FIG. 1, and FIG. Fig. 5 is a side view showing a partial cross-section of the operation of the fastening assembly shown in Fig. 5, Fig. 5 is a side view of a fastener showing another embodiment of the present invention, and Fig. 6 shows a conventional bolt and loosening prevention means. It is a side view shown in a partial section. 1 ... Fastener, 2 ... Spring shaft part, 3 ... Strand, 5,6 ...
Terminal screw part, 7,8 …… Screw thread, 10 …… Fastening assembly, 13,14
…… The object to be fastened.

Claims (4)

[Claims] 1. A cylindrical spring shaft formed by coiling a wire made of an elastic material in one direction and at least one end of the spring shaft continuously extending in the same direction as the spring shaft. And a threaded end that is wound around the terminal threaded portion, and a thread opposite to the winding direction of the wire is provided on the outer peripheral surface of the wire of the terminal threaded portion. 2. The fastener according to claim 1, wherein the spring shaft portion is a coil spring formed by closely winding the wire. 3. The fastener according to claim 1, wherein the terminal screw portion is provided at each end of the spring shaft portion. 4. A cylindrical spring shaft formed by coiling a wire made of an elastic material in one direction, and the wire extending continuously from the end of the spring shaft in the same direction as the spring shaft. And a threaded thread opposite to the winding direction of the element wire is provided on the outer peripheral surface of the elemental wire of the terminal threaded portion, and the threaded portion is screwed to the terminal threaded portion. Tighten the nut and the nut by screwing it into the above-mentioned terminal screw part.
A fastening assembly to be fastened.