GB2236824A - Tightening and loosening apparatus for flange bolts and nuts - Google Patents

Abstract

A tightening and loosening apparatus comprises a bolt tensioner (k) for applying tension to a plurality of bolts (c) (or a single bolt) disposed around a circular flange (b), and rollers (13) (or a roller) each frictionally engaging a cylindrical (or hexagonal) nut (d) to rotate it, and each driven by frictional engagement with a common wheel (17) driven by a motor (15). <IMAGE>

Description

DESCRIPTION TIGHTENING - LOOSENING APPARATUS FOR FLANGE BOLTS AND NUTS This invention relates to an apparatus for tightening and loosening one by one or simultaneously some or all of a plurality of flange bolts and nuts used for fixing bolt-fastened circular flanges or the like of the type employed extensively in general industry.

In such flanges, generally, a plurality of bolts are disposed uniformly around the flange and the operation of tightening or loosening nuts corresponding to these bolts is monotonous manual work, requiring much time and labour. There is also a the problem that the tightening force applied to any particular nut is nonuniform since it depends on the judgement of an operator.

In an attempt to solve these problems, it is known that the tightening force can be made uniform by using a flange bolt pulling apparatus (or tensioning apparatus) (see pages 45 to 47 of the Nuclear Engineering International, Nov., 1987) to which a device for tensioning a bolt (see U.K. Patent No.

2193459A and the Official Gazette on Japanese Patent Laid-Open No. 6076/1980) is applied. This flange bolt pulling apparatus has, like the flange, a generally circular or annular configuration.

According to this known apparatus, however, the operation of tightening the nut while the bolt is being pulled is executed by an operator in a one-byone manner on each bolt by means of a manual tool, and, since the operation of tightening the nut while the bolt is being pulled is repeated several times, the problem that the operation requires considerable time and labour still remains to be solved.

As a method of avoiding the necessity of using a manual tool for tightening the nut, there is also known a mechanism wherein a socket having a gear is placed on the nut and the nut is rotated by rotation of the gear. Using this method, however, it is impossible to rotate all nuts together by one common driving device since the number of rotations of the nuts is not the same, and consequently the problem that the tightening operation requires considerable time and labour is still left unsolved.

Another flange bolt pulling apparatus having an automatic device for rotating bolts and nuts has been developed for large-sized flanges employed for equipment such as the steam generator of a nuclear power plant (see Official Gazette on Japanese Patent Publication No. 15109/1988). However, this apparatus is expensive and, in addition, it is difficult to make it smaller in size, since a separate driving device is provided individually for each bolt and nut therein.

Thus, this apparatus has the shortcoming that it can only be applied to large-sized flanges.

An object of the present invention is to remove the above-described disadvantages, providing an apparatus for tightening/loosening a plurality of bolts and nuts, which can be applied also to smallsized flanges and can tighten and loosen all the bolts and nuts, most preferebly simultaneously by means of one driving device.

In accordance with the present invention, a tightening/loosening apparatus for flange bolts and nuts comprises at least one flange bolt pulling device for engaging over a corresponding bolt and a respective nut applied to said bolt, at least one roller corresponding to said flange bolt pulley device for engaging the nut positioned in the flange bolt pulling device and rotating the nut by frictional engagement there between, a support mechanism enabling free rotation of the roller, a driving wheel in driving contact with said roller for rotating said roller by rotation transmitting engagement therewith, and a driving device for rotating the driving wheel.

The rotation transmitting engagement may be comprised of gears, gear and chain, pulley and belt, or the like.

Preferably, the driving wheel rotates two or more, and most preferably all of, a plurality of rollers simultaneously.

In the case of a tightening operation, the applied rotational torque increases when the nut has been fully tightened and, consequently, slip occurs between the nut and the roller, and/or between the roller and the driving wheel (when the latter engage by friction), whereby to indicate completion of the tightening of said nut. This slip phenomenon occurs sequentially or simultaneously with respect to a plurality of nuts of a flange, and all the nuts (when a plurality of nuts are rotated simultaneously) can be tightened by one operation, i.e. by the rotation of one driving wheel. In the case of a loosening operation, it is only needed, to provide by rotation a linear shift larger than the elongation of each bolt, and by rotating the nuts by the same number of rotations, all of the nuts are loosened in a single operation or repeated operations.

The roller and the driving wheel can be installed radially inwardly of the line occupied by the bolts and nuts in the case where there is such a space available, as is the case with a flat-plate flange of a small-sized reaction vessel. On the other hand, the rollers and driving wheel can be installed radially outwardly of the bolts and nuts in, for example, the case of a protuberant flange or a piping flange.

In regard to the driving wheel, an equivalent operation can be attained by adopting a driving arrangement wherein the rollers are in driving engagement with the inner periphery thereof, not with the outer periphery, as the situation demands.

In regard to the driving device for the driving wheel, an electric motor, an air motor, a hydraulic motor, or the like may be employed.

The invention is described further hereinafter by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a diagrammatic, partial section on line C-C in FIg. 2 of one embodiment of an apparatus in accordance with the present invention; Fig. 2 is a diagrammatic plan view, part of which is in section on the line A-A in Fig. 1 and Fig. 3 is a side view, partly in section, illustrating a typical bolt pulling or tensioner device.

In the illustrated example, the apparatus for tightening and loosening flange bolts and nuts of the present invention has been applied to a situation where a large number (eg 12) of bolts c are disposed at equal intervals around the circumference of circular flanges a and b of a small-sized reactor used in a laboratory or the like. Respective nuts d are to be applied to the bolts c to clamp together the two reactor flanges b and a. The apparatus includes a hydraulically actuated flange bolt pulling device k by which the bolts c can be pulled relative to the flanges a and b in the direction indicated in Fig. 1 by the arrow P.

The apparatus also includes a plurality of rollers 13 made of hard rubber which are supported rotatably within the flange bolt pulling device k by respective shafts and fixing members 12 at positions where they come into contact with the peripheral surfaces of the nuts d. The rollers 13 are arranged to be rotated by frictional engagement with a common driving wheel 17 connected to the driving shaft 16 of a driving device 15, which is itself fixed to fixing members 14. In use, the fixing members 14 are placed on the flange bolt pulling device k, as best seen in Fig. 1.

In the example in Figs. 1 and 2, the bolt-pulling device or tensioner k pulls the bolt c by hydraulically pushing up a puller nut 1 positioned in threaded engagement with bolt c. An annular ram set in a known manner in an annular gutter provided on the top side of the tensioner k is pushed up by the pressure of hydraulic fluid beneath the bottom surface of the ram in the gutter. The puller nut 1 in this example has a stepped shape. The main portion of the tensioner k provided with the ram is supported on the flange b by supporting portions m whose A-A (Fig. 1) cross sections are hatched in Fig. 2 A typical example of a known bolt pulling or tensioner device is shown in Fig. 3. In this example, the puller nut 1 does not have the same stepped shape of the puller nut of Fig. 1. Fig. 3 shows the ram n disposed in the annular gutter p.In this example, the nut d. is arranged to be tightened/loosened by a socket s having holes t for receiving a tommy bar.

First, a description will be made of a tightening operation using the aforegoing apparatus. As a preparatory operation, the nuts d are fitted on the bolts c by a conventional nut fitting means, such as a separately provided general-purpose robot (not shown).

As shown in Fig. 1, the flange b sits on the flange a with the bolts c projecting from the flange a. The flange bolt pulling device k is mounted (over the nuts d) on the flange k by the aforementioned robot, or the like. The driving device 15 is then mounted on the device k by the robot, or the like, so that the driving wheel 17 engages the rollers 13. The nuts d shown in this embodiment are of a type having circular peripheries in consideration of their handling by the general purpose robot and their efficient contact with the circular rollers 13.

When the bolts c are pulled by supplying working fluid to the hydrualically-operated flange bolt pulling device k, gaps are formed between the nuts d and the flange b. Then, when the driving device 15 is energised, the driving wheel 17 rotates to rotate the rollers 13, and the nuts d are rotated with the rotation of the rollers 13 until the gaps between the nuts d and the flange b are closed. When each of the gaps have gone and the torque necessary for rotating the nut d increases, slip occurs between the nut d and the roller 13, and/or between the roller 13 and the driving wheel 17, and the tightening of all of the nuts is complete when slip occurs at each of the nut and roller and/or roller and driving wheel combinations. Since the phenomenon of slip is utilized, the driving wheel 17 can continue to be rotated until all the nuts d have been tightened.In practice, all the nuts can be tightened by making the driving wheel rotate for a certain time. After the rotation of all the nuts is ended, the working fluid in the flange bolt pulling device k is extracted or released from the pressure and thus the first operation of tightening the nuts, in other words, that of bringing the two flanges a and b into close contact with each other, is completed. In using the flange bolt pulling device k, the tensile stress applied to the bolts is weakened a little due to elastic deformation occurring at the threaded parts wherein the bolts and the nuts engage with each other.

Therefore, two additional series of tightening operations are repeated, so that the tightening operation be fully completed. The man-hours required for this operation is one man-fifteen minutes.

The same operation as described in connection with the illustrated embodiment has been executed using ordinary hexagonal nuts in place of the circular nuts d, and it was found that the hexagonal nuts could also be used satisfactorily in the apparatus without further modification.

It is most preferable in practice that the number of the rollers be equal to that of the nuts required to be tightened/loosened followed in preference by the case where a plurality of rollers are disposed at equal intervals on the circumference of the driving wheel and employed repeatedly as required. When flanges are of a very large diameter, for instance, it is also possible to provide just one roller, or several rollers in a less number than the nuts, and to tighten or loosen a larger number of nuts sequentially. If two rollers are disposed preferably on a diagonal line, an even number of nuts can be tightened by half the rotations required in the case when the nuts are tightened or loosened one by one sequentially.

While the driving wheel can be made to rotate for a certain predetermined time in the above-described embodiment, it is also possible to detect an increase in the torque acting on the driving device, to detect completion of the rotation of the nuts therefrom and to stop the rotation of the driving wheel on the basis of this detection.

When for comparison, the above-described operation is executed in the conventional manual manner, it requires at least twenty minutes even by two operators.

In the above-mentioned examples, the number of bolts is twelve.

It is advantageous in the present apparatus that each roller 13 or the surface of the roller 13 and/or the driving wheel 17 or the surface of the driving wheel 17 be constructed of an elastic material having a high frictional coefficient.

By use of the above described apparatuses in accordance with the present invention the operation of tightening and loosening the flange bolts and nuts can be automated, automatic operations of tightening and loosening the bolts and nuts of small-sized flanges, which have so far depended on manual operations, are enabled, the number of operators can be reduced, and operation efficiency is improved. Furthermore, it is possible not only to tighten and loosen the flange bolts and nuts by a remote operation in a place to which men have no access, but also to make the operation unmanned by combining the present apparatus with an automatic transfer-mount apparatus.

Claims (10)

1. A tightening/loosening apparatus for flange bolts and nuts, comprising at least one flange bolt pulling device for engaging over a corresponding bolt and a respective nut applied to said bolt, at least one roller for engaging the nut positioned in the flange bolt pulling device and rotating the nut by frictional engagement therebetween, a support mechanism enabling free rotation of the roller, a driving wheel in driving contact with said roller for rotating said roller by rotation transmitting engagement therewith, and a driving device for rotating the driving wheel.

2. An apparatus as claimed in claim 1 wherein the number of rollers is selected to be equal to that of the nuts.

3. An apparatus as claimed in claim 1 or 2 wherein the surface of the or each roller is made of an elastic material having a high coefficient of friction.

4. An apparatus as claimed in claim 1, 2 or 3 wherein said rotation transmitting engagement is frictional engagement.

5. An apparatus as claimed in claim 4 wherein the driving wheel or the surface of the driving wheel is made of an elastic material having a high coefficient of friction.

6. An apparatus as claimed in claim 1, 2, 3, 4 or 5 wherein the driving device is adapted to be controlled from a remote location.

7. An apparatus as claimed in any of claims 1 to 6, wherein said support mechanism comprises a plurality of shafts carried by said flange bolt pulling device.

8. An apparatus as claimed in any of claims 1 to 7, wherein the driving device is adapted to be supported on the flange bolt pulling device.

9. An apparatus as claimed in claim 7 or 8, wherein the driving wheel rotates all of said rollers simultaneously.

10. A tightening/loosening apparatus for flange nuts and bolts, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.