JPS6252529B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an excellent method for tightening connection parts for connecting a plurality of bus ducts by tightening them all at once using bolts and nuts.

Many so-called insulated bus duct plates, in which a plurality of insulated bus bars insulating plate-shaped conductors are closely arranged in a duct, use a one-shot fastening connection method.

Fig. 1 shows an example of this, in which terminals 1, 1 are made by expanding the insulating busbars of each phase in ducts D, D and removing the insulation coating, and connecting duct plates 2,
2 are arranged in parallel, and the terminals of each phase are overlapped individually, and the space between the duct plates 2 and 2 is compressed by screwing and tightening nuts on bolts 3 that pass through between the duct plates 2 and 2. The conductors of each phase are pressed together to make an electrical connection. Insulating spacers 4 are interposed between the stacked conductors of each phase and between the duct plates 2, 2, to link the duct plates 2, 2 and the conductor 1, and to connect the duct plates 2, 2 and the conductor 1 at once. This is what we provide.

Considerable axial force is required to obtain electrical contact between the conductors of each phase. However, if too high a torque is applied, damage such as cracking of the insulating spacer will occur.

For this reason, a tightening method using a torque wrench is adopted in order to provide stable and high tightening force at all times.

That is, the head of the bolt 2 is fixed with a rotation stopper 5, and the nut is tightened with a torque wrench until the required torque is reached.

However, this method requires special tools, and if it is a hydraulic type, the working range is large.
It is unsuitable for bus duct lines that are installed in parallel at intervals of several tens of centimeters, and the workability is poor.

Furthermore, this method has the following drawbacks.

In other words, if a bus duct that is initially tightened and connected with a constant torque is used with electricity applied over time, it will be heated by the resistance caused by contact, and this heating over time will correct uneven contact between the conductors or connect it with insulating spacers and duct plates. It has been experienced that the so-called run-in phenomenon occurs in which the thickness between the duct plates is slightly reduced from the initial thickness as the unevenness in the combination is corrected by long-term compression, and the tightening force decreases due to this reduction. .

The reduction in tightening force due to the decrease in thickness occurs at a value of several hundred kg·cm.

For this reason, the current situation is that in order to recover the initial tightening force, that is, the essentially necessary tightening force between the duct plates, it is necessary to perform additional tightening work again using a torque wrench after a considerable period of time.

In order to eliminate the need for the above-mentioned retightening, it may be possible to retighten the tightening force to compensate for the decrease in the tightening force caused by the break-in phenomenon during initial tightening. The objective is to provide the essentially required axial force by using the tightening force that is reduced due to the break-in phenomenon.

However, by adopting the tightening method using a torque wrench in this method, even if a predetermined torque is applied to the nut, there is a possibility that the tightening force may decrease due to the break-in phenomenon, causing the nut to loosen. Problems remain in maintaining the tightening force.

The present invention has been made in view of the above circumstances, and its purpose is to provide a batch tightening method using a constant torque that has good workability, is reliable, and can maintain stable tightening force over a long period of time. The purpose of this invention is to find an excellent method for tightening bus duct connections.

That is, the present invention brings a plurality of phase conductors into contact with each other separately between the connecting duct plates, and interposes insulating spacers between the contacting conductors and between the duct plates to link the duct plates. In this method, the duct plates are connected by bolts that pass through the duct plates and fastening nuts that are screwed onto the ends of the bolts that protrude from the duct plates. Select arbitrary side surfaces of the upper nut and the lower nut to form identification surfaces. Rotate the upper nut with a wrench and tighten until the narrow neck part is cut, and compress the area between the duct plates with the lower nut. The present invention is further characterized in that the lower nut is locked onto the duct plate by tightening the upper nut at an arbitrary angle from the cutting position of the narrow neck portion, and the deviation of the identification plane between the lower nut and the upper nut is indicated.

A more detailed explanation will be given below with reference to the drawings of the embodiments.

FIG. 2 shows a plan view of a bus duct connection according to the invention, and FIG. 3 shows a section thereof along line A--A. Each phase conductor 12R, 12S, 12T is connected between the duct plates 10, 10 and 11, 11 connected by overlapping.
and 13R, 13S, and 13T are individually stacked, and between these stacked parts and the duct plate 1
1 and 12, an insulating spacer 14 is interposed between them.

Duct plates 10 and 11 and insulating spacer 14
A horizontal through hole 15 is provided in each of the phase conductors 12R-T and 13R-T, and a bolt 16 is passed through this hole.

A nut 17 is screwed onto the portion of the bolt 16 that projects onto the duct plate.

As shown in FIG. 4, the nut 17 has an upper nut 1 on both sides of a narrow neck portion 17a formed by cutting.
7b and the lower nut 17c are set, the lower nut 17c is screwed toward the duct plate side, and the upper nut 1
7b.

FIG. 5 shows the state of tightening, and FIG. 6 shows the state of completion of tightening.

When tightening, first fix the bolt 16 at the head with a stopper (see 5 in Fig. 1), attach the box spanner 18 to the nut 17, engage the upper nut 17b, and tighten the square hole 18a of the spanner 18. Attach the ratchet trench 19 to the
9 to tighten the lower nut 17c onto the duct plate, and further drive the upper nut 17b to break the narrow neck portion 17a and tighten the lower nut to a constant torque.

After the narrow neck portion 17a is broken, the upper nut 17b is rotated by an arbitrary angle with respect to the lower nut 17c using the remaining force of the wrench, and locks the lower nut 17c.
Figure 10 shows a constant torque rupture curve, which shows that when the lower nut is screwed toward a fixed object in the relationship between the rotation angle n of the nut and the torque T, the torque increases rapidly when it is seated. At the point, the narrow neck exceeds the elastic range and breaks, and the specified torque T ₁
is applied to the lower nut.

On the other hand, the torque of the upper nut decreases in the range from T ₁ to T ₂ after the narrow neck is broken, and no change in torque occurs even if a rotation of C is applied to the lower nut. However, as the rotation progresses, the torque tends to increase again.

In order to lock the lower nut, it is desirable to lock the lower nut again at a torque below T ₁ at point a on the increased torque curve.

According to the present invention, it can be confirmed that the lower nut is locked by visually observing the deviation angle between the upper nut and the lower nut.

However, it is difficult to obtain a constant deviation angle due to the irregular fracture engagement of the broken thin neck portion.

For this reason, when using a hexagonal nut, the misalignment between the upper and lower parts causes the corners to be mismatched or coincident with each other, and to check whether or not the upper nut has been tightened to lock it. unclear,
There is a risk of forgetting to tighten the screws.

In view of this, the present invention also takes into consideration the identification of locks.

FIG. 7 is an example of this, where the upper nut 17'b and the lower nut 17'c are provided with a coaxial side corner surface 17d.
The identification surface 17e is set by applying paint, surface processing, etc. to each of the three surfaces in the .degree. direction.

According to this, when the deviation angle θ ₁ in Fig. 8 is 30° or 90°, or when the deviation angle θ ₂ is 60° or 120° as shown in Fig. 9, the side surface 17d coincides. However, it can be replaced with a lock display by displaying the deviation between the identification surfaces _17e1 and _17e2 .

On the other hand, in the present invention, when selecting the breaking torque of the narrow neck part, in order to set the tightening force necessary to obtain stable electrical contact between the conductors after the break-in phenomenon is completed, it is necessary to add a layer to the tightening torque. Something equivalent to torque is desirable.

FIG. 11 shows the tightening torque J that changes due to the heat cycle test.

Although the amount of conformation varies slightly depending on the size and type of material, it has been experienced that similar changes as shown in the figure occur.

The figure shows an example of a three-phase, three-wire Al-Fe insulated bus duct, which was heat cycled twice a day.

Conventionally, the tightening torque required for this bus duct connection was 1000 kg cm from the beginning, but
It started to descend in the beginning, and around the 8th time.
The torque drops to 800Kg・cm and after that the torque remains the same and does not drop.

The above-mentioned drop of 200 kg cm is confirmed by the reduction in size due to fitting in between the duct plates.

When the thickness change Δl between the duct plates was measured by heat cycles, it started to gradually decrease in the initial heat cycles, decreased to 0.2 mm around the 8th heat cycle, and remained unchanged thereafter.

This is the so-called end of familiarity.

The torque that has decreased due to break-in is retightened using a torque wrench after an arbitrary period of time.
Tightened to original 1000Kg/cm.

In this way, it is necessary to tighten twice using a torque wrench.

According to the present invention, the rupture torque of the narrow neck portion is reduced to 200Kg, which is caused by the reduction in size due to the break-in phenomenon.
The one that is set to 1200Kg・cm by increasing the torque of cm is used.

As a result, as shown in the figure, the lower nut receives initial torque from the upper nut by breaking the narrow neck.
The torque is set at 1200Kg・cm, and then after a drop due to break-in, the required torque remains at 1000Kg・cm, and the upper nut does not loosen in the lock, so it can be said to be an extremely reliable torque.

By doing this, the work of retightening can be substantially eliminated, and if necessary, it is only necessary to check with a torque wrench whether or not the specified torque is reached. Therefore, general tools can be used for initial tightening, and if necessary, only one type of small-sized torque wrench is required, so torque management can be greatly simplified.

According to the present invention, the following can be further stated.
That is, since a plurality of bus ducts of this kind are arranged in parallel, the space required for wrench work is small.

According to the present invention, it is possible to apply a general ratchet trunk, etc., so it is effective in places where work space is limited.

Further, the upper nut after the narrow neck is broken is rotated by the remaining force of the wrench, but since the rotation is limited, there is no risk of injury to hands due to excessive rotation.

Conventionally, there is a type in which a rectangular tube for wrench rotation without a thread groove and a threaded nut are integrally connected at a thin neck part.By turning the rectangular tube with a wrench and tightening, the thin neck part of the threaded nut can be broken and tightened to a constant torque. conduct,
There is a device that removes square tubes, but when working at heights, it is dangerous because the square tubes may fall, and the wrench that applies high rotational force rotates rapidly when the narrow neck is broken, causing damage to ducts, etc. You may get hit and get injured. Furthermore, there are problems when applied to this type of electrical contact, such as the possibility of loosening of nuts that have been tightened to a constant torque.

According to the present invention, all of the above-mentioned problems can be solved, and even if a plurality of electrical contact points are present in the tightening method, it is possible to provide a tightening force that can maintain stable conduction at all times.

In the drawings, reference numeral 20 indicates a disc spring (Belleville washer), which is used to spread the tightening force over a wide contact surface.

According to the present invention as explained above, it is possible to use general tools for tightening without requiring special tools such as a torque wrench. Work can be carried out easily even when working on a bus duct, and since falling parts are swept away, work efficiency is greatly improved, contributing to safety.

In addition, according to the present invention, lock tightening can be performed in addition to constant torque tightening, so by setting the breaking torque of the narrow neck part so that the initial tightening torque becomes redundant, the tightening force decreases due to a run-in phenomenon. Even if something happens, it is possible to completely prevent the nut from loosening and maintain the necessary torque over a long period of time, making it possible to achieve the ultimate goal of no maintenance for this type of bus duct connection. This is possible.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing an example of a connection part of a bus duct, FIG. 2 is a plan explanatory view showing a connection mode of a connection part according to the present invention, FIG. FIG. 4 is a partially cutaway side view showing the relationship between the constant torque tightening nut and bolt according to the present invention;
FIGS. 5 and 6 are sectional views of main parts showing when the connection part according to the present invention is tightened and when the tightening is completed, and FIG. 7 is another embodiment of the constant torque tightening nut used in the present invention. , A is a front view, B is a side view, and FIGS. 8 and 9 are two modified examples of the same nut, A is a front view,
B is a side view. FIG. 10 is a graph showing the relationship between the rotation angle and torque of the constant-torque tightening nut according to the present invention, and FIG. 11 is a graph showing changes in tightening torque by heat cycle tests of the present invention and the conventional nut. 10, 11: Duct plate, 12R, 12S, 12
T, 13R, 13S, 13T: Phase conductor, 14: Insulating spacer, 16: Bolt, 17: Nut, 17
a: Narrow neck, 17b, 17b': Upper nut, 17
c, 17c': Lower nut, 17d: Side corner surface, 17
e, 17e ₁ , 17e ₂ : identification surface.

Claims (1)

[Claims] 1 A plurality of phase conductors are brought into contact with each other separately between the connecting duct plates, and an insulating spacer is interposed between the contacting conductors and between the duct plates to connect the duct plates, and these are connected to the duct plates. In a method of collectively tightening and connecting duct plates by means of a bolt passing through the plates and a fastening nut threaded onto the tip of the bolt protruding from the duct plate, a square-shaped upper nut and a lower part are integrally connected by a narrow neck part. Select any side corner surface of each nut to form an identification surface, rotate the upper nut with a wrench, tighten until the narrow neck is cut, compress the space between the duct plates with the lower nut, and then Tightening the bus duct connection part by constant torque tightening, which locks the lower nut on the duct plate by tightening the nut at an arbitrary angle from the cut position of the narrow neck part, and also indicates the deviation of the identification plane between the lower nut and the upper nut. Method.