JPH0430976A - Method and device for tightening threaded connector - Google Patents

Abstract

PURPOSE: To stop rotation of a nut by surely grasping the time when a threaded connector reaches a specified elongation at and below a yielding point through the turning action of the nut by an additional angle distance enough to reach a specified elongation of a bolt at and below a yielding point. CONSTITUTION: During fastening operation of a threaded connector including a bolt 2 and a nut 1, the time when the nut 1 starts its elongation is determined at first. Thereafter, the nut 1 is rotated by a wrench 4 by an angle distance to allow the bolt 2 to reach a required elongation at and below its yielding poing, and at that time, a valve 10 is closed to stop the operation of the wrench 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method and apparatus for tightening a threaded connector using a tightening tool.

[Conventional technology]

It is known to tighten and loosen threaded connectors, such as bolts, with respective bolting tools. The main purpose of tightening bolts with a bolt tightening tool is to
When turning the nut of the flange to be assembled, the bolt is stretched. Stretching the bolts provides a clamping force that holds the flanges together. There are various methods for applying that tightening force. One method is to use a hydraulic torque tool, the other is to use a tension tool to extend the bolt using water pressure, and there is also a method to tighten the nut. The most common method is to use a controlled torque to stretch the bolt. Due to the effects of friction between the screw and the nut and bolt surfaces, this method provides pure clamping load accuracy but not bolt elongation. In the case of tensioning tools that extend the bolt by pulling, bolt extension is achieved, but inaccuracies remain because the bolt tends to loosen when the tensioning mechanism is removed.

The nut-rotating method is ideal if the correct starting point for the bolt to extend is precisely set.

"Nut rotation" here refers to the method of rotating a nut on a bolt to clamp the flanges together. With the known method of tightening a threaded connector based on the principle of nut rotation, it has been impossible to ensure the desired elongation of the bolt in order to reliably obtain the desired tightening force. Thus, although this method has important advantages, it has not been possible to utilize it efficiently for the reasons mentioned above.

[Problem to be solved by the invention]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method and a device for tightening screw connectors which avoids the above-mentioned drawbacks.

[Means to solve the problem]

In view of these objects and others that will become apparent later, one feature of the present invention is, briefly, that while rotating the nut on the bolt, the time at which the bolt begins to extend is determined; After determining the tightening of the threaded connector, the nut is rotated below its yield point so that the bolt reaches the target elongation.

Another feature of the invention includes a tool for rotating a nut on the bolt and means for determining when the bolt begins to stretch, and after determining said time, the tool causes the bolt to reach the target below its yield point. The tightening of the threaded connector consists of a device that rotates the nut to achieve the desired elongation.

[For production]

Tightening of threaded connectors including bolts and nuts is performed during operation.
The point at which nut elongation begins is first determined, and then
Rotate the nut an angular distance until the bolt reaches the desired elongation below its yield point.

〔Example〕

New matters considered to be characteristic of the present invention are particularly described in the claims. However, the structure and operation of the present invention, as well as further separate objects and advantages, can be fully understood by reading the following description of the embodiments in conjunction with the accompanying drawings.

In the present invention, the threaded connector is tightened by rotating the nut l on the bolt 2. The nut l and the bolt 2 are, for example, composed of two flange parts and a washer inserted between them. It is used to connect the flanges 3.

A tool, such as a wrench 4, is engaged with the nut 1, and the nut 1 is rotated relative to the bolt 2. As the tool, any known tool that is actually used can be used. For example, the tool receives a working fluid through a supply line 5 which displaces a piston with a piston rod that engages a ratchet 8 mounted in a central opening that engages the nut 1. It is possible to adopt a method in which the claws are rotated in sequence.

As can be seen from Figure 1, the characteristic line representing the relationship between the torque pressure applied to the nut and the degree of rotation of the nut while rotating the nut on the bolt is the curved part at the beginning of the end. The first curved part at the end, starting from point A and ending at point B, reflects the setting process of the flange, its bolts, gaskets, etc. Once these parts are set, Then the bolt begins to actually stretch.

Such a relationship was confirmed in a study described in ``Design and Performance of Automatic Control Devices for Fastening Fasteners,'' published in the 1977 edition of the Bulletin of the Japan Society of Mechanical Engineers, Vol. 191, 38/77. . In the above publications it is proposed to tighten the threaded connector beyond the yield point of the bolt.

According to the present invention, the relationship between the torque/pressure applied to the nut and the degree of rotation of the nut is continuously monitored. The first parameter is monitored, for example, by a pressure sensor 6 connected to the supply line 5 that supplies the working fluid to the tool 4.

The rotation degree of the nut is monitored, for example, by monitoring the position of a mark (marked with an X in the figure) provided on the ratchet 8 of the tool 4 with, for example, the motion detector 7.

The signals from the components 6 and 4 are sent to a processing device 11 which processes the received actual values and also e.g.
It is also possible to display a characteristic line corresponding to the characteristic line in the figure on the display device 9 that displays the characteristic line on the screen. When the characteristic line reaches point B, the operator rotates the nut a predetermined angular distance or a predetermined number of rotations, and stops rotating the nut when the bolt reaches the desired elongation. The elongation can be set by knowing the number of threads per inch of the bolt. Most bolts used in the industry have eight threads per inch, so each full turn of the nut corresponds to an elongation of the bolt by 125 thousandths of an inch.

Therefore, the degree of rotation required for the nut to achieve the desired elongation can be determined in advance.

On the other hand, the rotation of the nut can be stopped automatically the moment the bolt reaches the desired elongation. In this case, a valve is connected to the process device 11 and placed in the supply line 5 that supplies the working fluid to the tool 4 when the relationship between the torque/pressure and the rotation degree of the nut reaches point l-B. 10 can be programmed to close the supply line.

It is an important and inventive feature that the nut stops rotating when the bolt reaches the desired elongation, where the elongation of the bolt is always below the yield point of the bolt.

When the yield point of the bolt is exceeded, it results in irreversible elongation, which is extremely rare in this field. If this method is implemented and the device is designed according to this invention,
Due to the reliable tightening of the threaded connector, the desired bolt elongation is reliably achieved and the risk of exceeding the bolt yield point is avoided.

It should be emphasized that the process device 11 is adjustable for a variety of bolts with different threads per inch so that it can be used with a large number of threaded connectors.

It will also be appreciated that each of the components described above, or combinations of two or more, may be usefully applied to different types of configurations than those described above.

Although the present invention has been illustrated and described as being embodied as a method and two positions for tightening a screw connector, various modifications and structural changes can be made without departing from the spirit of the invention. The invention is not limited to what has been described in detail above.

Without further analysis, the foregoing sufficiently expresses the gist of the invention and, with the present knowledge,
It can be easily applied to various applications without lacking what others would consider to be the general or characteristic essential features of the invention in view of the prior art.

〔Effect of the invention〕

The present invention is as described above, and includes reliably grasping when the screw connector reaches a desired elongation below the yield point,
The method and device for tightening a screw connector that can stop the rotation of the nut and provide reliable rotation are effective.

[Brief explanation of drawings]

Figure 1 is a diagram showing the rotation process of the nut on the bolt and the characteristic line of the correlation between torque/pressure and the rotation degree of the nut.
FIG. 2 is a diagram showing an embodiment of a device for tightening a screw connector according to the present invention. Explanation of symbols 1-nut, 3-flange, 5-supply line, 7-motion detector, 9-display device, 11-process equipment Bordeaux wrench single pressure gas sensor ratchet valve

Claims (11)

[Claims] (1) The process of turning the nut on the bolt, the process of continuously monitoring the correlation between the pressure applied to turn the nut and the angular distance of rotation of the nut, and the position of the nut when the bolt starts to extend. and then turning said nut an additional angular distance sufficient to achieve the desired elongation of the bolt below its yield point. 2. The method for tightening a threaded connector according to claim 1, wherein the monitor includes monitoring the pressure by detecting the pressure of a working fluid supplied to a tool for turning a nut on a bolt. 3. The method of tightening a threaded connector according to claim 1, wherein the monitor includes detecting movement of the nut while the nut is rotated on the bolt. (4) The method for tightening a threaded connector according to claim 3, wherein detecting the movement of the nut includes detecting movement of a nut support portion of a tool that turns the nut. 5. Displaying the relationship between pressure and angular distance on the display to enable the operator to determine the point at which the bolt begins to extend and then begins to turn the nut an additional angular distance. How to tighten a screw connector. 6. The method of tightening a threaded connector according to claim 1, further comprising the step of: automatically stopping a tool for turning a nut on the bolt when the bolt reaches a desired elongation. (7) The method for tightening a threaded connector according to claim 6, wherein the automatic stop is performed by cutting off the supply of a working medium to a tool for turning a nut on a bolt. (8) determine the correlation between the pressure applied to turn the nut and the angular distance of rotation of the nut so that the tool for turning the nut on the bolt and the starting point of bolt extension can be determined;
means for enabling said tool to turn said nut an additional angular distance so as to obtain the desired elongation of the bolt below the yield point of the bolt. (9) further comprising means for displaying the relationship between the pressure applied to the nut and the angular distance of rotation of the nut, such that bolt extension begins on the display of said display means and then a predetermined additional angular distance; 9. The screw connector tightening device according to claim 8, wherein the operator can decide when to start turning the nut. (10) The device for tightening a threaded connector according to claim 8, further comprising means for automatically stopping the rotational movement of the nut when the bolt reaches a desired elongation. (11) The automatic stop means includes a pressure sensor disposed in a working fluid supply line to the tool and that sets the pressure of the working fluid supplied to the tool that turns the nut, and detects the rotational angular position of the nut. a motion detector in the supply line upon receiving signals from said pressure sensor and motion detector and determining the relationship between pressure and angular distance at which the bolt reaches the target elongation below the yield point. 11. The device for tightening a threaded connector according to claim 10, further comprising means for stopping the supply of working fluid.