JP2023183959A - Screw type clamp - Google Patents

Abstract

To improve a fastening check mechanism which indicates that a prescribed fastening force acts on a suspended load in a screw type clamp to achieve visibility and workability.SOLUTION: A screw type clamp includes: a coil spring (19) which biases a pressure nut (16) in a direction such that the pressure nut protrudes toward an opening; a disc spring (20) disposed adjacent to the rear of the coil spring; and a collar (21) having a tip which comes in contact with a rear end of the pressure nut when a fastening bolt (18) is fastened in a state that a suspended load is sandwiched between the fastening bolt and a rotary jaw and the pressure nut moves rearward against the coil spring. When the fastening bolt is further fastened to move the pressure nut rearward against the disc spring through the collar, a fastening check ring (22) is buried into a leg part (14) to become invisible. Thus, it is possible to visually check if a prescribed force acts on the suspended load.SELECTED DRAWING: Figure 4

Description

The present invention relates to a screw-type clamp, and particularly to an improvement in a tightening confirmation mechanism that indicates that a specified tightening force (tightening torque) has been applied to a suspended load in a screw-type clamp.

In Patent Document 1, the present applicants have proposed that in order to safely lift a suspended load held between a rotating jaw of a screw clamp and a tightening bolt, a specified clamping force (for example, 150 kg.cm) is applied to the workpiece. It was proposed to establish a tightening confirmation mechanism to show that the tightening mechanism (or more) has worked.

That is, the rotating jaw is rotatably attached to one leg constituting the U-shaped clamp body, and the rotating jaw is attached so as to be non-rotatable and relatively movable in the axial direction with respect to the attachment hole passing through the other leg. a pressure nut, a tightening bolt that is threaded into the internal thread of the pressure nut and faces the rotating jaw, and a biasing means that biases the tip of the pressure nut in a direction to protrude from the inner open end of the other leg. For screw-type clamps equipped with The pressure nut is equipped with a tightening confirmation ring (tightening confirmation ring) to confirm that the tightening force has been applied to the suspended load.

By adopting such a tightening confirmation mechanism, when the tightening bolt is rotated in the tightening direction with a suspended load being held between the rotating jaw and the tip of the tightening bolt, the biasing means is gradually activated. As the pressure nut contracts, the pressure nut gradually sinks into the mounting hole of the other leg. Therefore, the tightening confirmation ring (28) provided on the outer periphery of a predetermined position at the tip of the pressure nut is exposed in the opening between the pair of legs in the initial stage of tightening, and can be visually confirmed (Patent Document 1: Fig. 2) is completely buried in the other leg and becomes invisible when a specified tightening torque is applied to the suspended load (Patent Document 1: Fig. 3). By visually observing changes in the state of this tightening confirmation ring, the operator can easily confirm that the specified tightening torque has been applied to the suspended load. Work safety can be ensured by avoiding the danger of falling.

Patent No. 3651521

Although the applicant has been manufacturing and selling the screw type clamp having the configuration disclosed in Patent Document 1 for many years and has received high praise for the significance of adopting the tightening confirmation mechanism, there is still room for further improvement. I discovered something. It is described in detail below.

In Patent Document 1, a coil spring is used in an embodiment as a biasing means that plays an important role in a tightening confirmation mechanism. As is well known in the industry, coil springs, which are often used as biasing means in various products, have a large amount of contraction (displacement) when subjected to a load. As mentioned above, in this tightening confirmation mechanism, the biasing means contracts as the tightening bolt rotates in the tightening direction, and as a result, the pressure nut moves backward, causing the tightening confirmation ring to change its state. The premise is that something that was previously visible becomes hidden and becomes invisible. In order for the operator to visually confirm this change in condition reliably and easily, it is necessary to move the pressure nut over a certain distance. Therefore, it is appropriate to use a coil spring that has a characteristic of large displacement. It was considered. In addition, the coil spring can be contracted significantly against the spring pressure even with a relatively light force, making it easier to operate the handle when rotating the tightening bolt in the tightening direction, and maintaining good workability. It was also considered to be preferable in that it allows for

However, in order to give the coil spring a spring pressure equivalent to the specified tightening force, a large coil spring with a thick wire diameter is required. , it must be placed in a limited space between the mounting hole formed in the other leg and the pressure nut. For this reason, in the conventional screw type clamp, it is actually difficult to use a large coil spring having enough spring pressure to apply a specified clamping force to the suspended load. Furthermore, even if it were possible to use a large coil spring with a thick wire diameter that has a spring pressure corresponding to the specified tightening force, changes in the state of the tightening confirmation ring could be reliably and easily visually confirmed. In order to contract the bolt to such a large extent, a large force exceeding the large spring pressure is required, making it difficult to operate the handle when rotating the tightening bolt in the tightening direction, resulting in poor workability.

For the above-mentioned reasons, conventional screw clamps have often been forced to employ relatively small coil springs with a spring pressure smaller than the required clamping force. In this case, it is easy to operate the handle when rotating the tightening bolt in the tightening direction, but when the pressure nut moves backward and the tightening confirmation ring is hidden inside the other leg, the tightening against the suspended load becomes difficult. There will be a lack of power. Therefore, if you finish operating the handle at this point, the load will be lifted without the specified tightening force being generated, and the screw clamp will come off the load, resulting in serious damage caused by the load falling. Accidents may occur.

During actual work, make sure that the worker fully understands the above risks, and then ask the worker to further tighten the tightening bolt by a certain amount by operating the handle after the tightening confirmation ring is hidden. However, the extent to which additional tightening is necessary and sufficient must be determined by empirical rules, and there are large individual differences between workers. If retightening is insufficient, the specified tightening force will not be obtained and the risk of the suspended load falling cannot be completely avoided.On the other hand, excessive retightening in anticipation of safety may impair work efficiency. There were also concerns about deterioration.

Therefore, the problem to be solved by the present invention is to solve the above-mentioned concerns and problems, and to always ensure that the specified tightening force is obtained for the suspended load, regardless of individual differences or empirical rules of workers. Another object of the present invention is to provide a screw type clamp having an improved tightening confirmation mechanism that allows easy visual confirmation and maintains good workability.

In order to solve this problem, the present invention according to claim 1 provides a generally U-shaped clamp body having a pair of legs facing each other with an opening in between, a receiver attached to one leg, A pressure nut that is mounted so that it cannot rotate relative to the mounting hole that passes through the leg of the machine and can move relative to it in the axial direction, and a tightener that is screwed into the female thread of the pressure nut and can move forward and backward in the direction opposite to the receiver. A first urging means for urging the bolt and the pressure nut in a direction to protrude toward the opening, and a first urging means disposed adjacent to the rear of the first urging means in the tightening direction. The pressure nut resists the first biasing means by tightening the clamping bolt with the suspended load sandwiched between the second biasing means having a large spring pressure, the receiver and the clamping bolt. A movement transmitting means provided so as to come into contact with the enlarged diameter portion of the front end of the pressure nut when the pressure nut is moved back to the first position, and a second urging means via the movement transmitting means when the tightening bolt is tightened. and a tightening confirmation means that indicates that a specified tightening force has been applied to the suspended load when the pressure nut is further retreated from the first position to the second position. It is a screw type clamp.

The present invention according to claim 2 is the screw type clamp according to claim 1, in which the first biasing means is a coil spring disposed on the outer periphery of the pressure nut, and the second biasing means is It is characterized in that it is a disc spring disposed between the first locking surface facing inward in the mounting hole and the coil spring.

The present invention according to claim 3 is the screw type clamp according to claim 1 or 2, characterized in that the movement transmission means is a collar provided in the mounting hole so as to surround the first biasing means. do.

The present invention according to claim 4 is the screw type clamp according to any one of claims 1 to 3, when the pressure nut retreats and hits the second locking surface facing inward in the mounting hole. , characterized in that the pressure nut assumes the second position.

The present invention according to claim 5 provides the screw type clamp according to any one of claims 1 to 4, wherein the axial distance between the first position and the second position of the pressure nut is longer than the tightening bolt. It is characterized in that it corresponds to approximately 1/4 of the pitch of .

The present invention according to claim 6 is the screw type clamp according to any one of claims 1 to 5, wherein the tightening confirmation means is provided on the outer periphery of the tip of the pressure nut, and the tightening confirmation means is provided on the outer periphery of the tip of the pressure nut, and the tightening force reaches a specified tightening force. It is characterized in that it is exposed through the opening of the clamp body and can be seen visually, but when a specified tightening force is obtained, it is buried in the other leg and becomes invisible.

The present invention according to claim 7 is the screw type clamp according to any one of claims 1 to 5, in which the tightening confirmation means is provided on the outer periphery of the rear end of the pressure nut, and the clamping force reaches a specified tightening force. It is characterized in that it is buried in the other leg of the clamp body and cannot be seen until the tightening force is reached, but when a specified tightening force is obtained, it becomes exposed outside the other leg and becomes visible.

According to the present invention, in the tightening confirmation mechanism that indicates that a specified tightening force has been applied to the suspended load held between the receiver and the tightening bolt, the spring pressure on the tightening bolt is small, and therefore the load is The first biasing means (coil spring) has a characteristic of having a large displacement or stroke when receiving a load, and the second biasing means has a characteristic of having a large spring pressure and therefore a small displacement or stroke when receiving a load. By tightening the clamping bolt with a suspended load sandwiched between the biasing means (disc spring), the receiver, and the clamping bolt, the pressure nut retreats against the first biasing means and the first The movement transmitting means has a tip that comes into contact with the rear end of the pressure nut when the pressure nut moves to the second position, and when the pressure nut further moves back against the second biasing means and moves to the second position, the pressure nut is suspended. A tightening confirmation means is used to indicate that a specified tightening force has been applied to the load.

As a result, by taking advantage of the characteristic that the first biasing means has a large displacement, the movement of the pressure nut until it reaches the first position where it comes into contact with the movement transmission means when the tightening bolt is tightened is relatively small. The pressure nut can be moved from the first position to the second position via the movement transmission means by making use of the characteristics that the second biasing means has a large spring pressure. It is possible to apply a specified tightening force to the suspended load when the load is moved to the position shown in FIG.

Therefore, according to the present invention, even with a relatively small screw type clamp, a tightening confirmation mechanism can be installed in a limited space, and the workability when tightening the tightening bolt is improved. By visually observing changes in the state of the attachment confirmation means, it is possible to easily and reliably confirm that the specified tightening force has been applied to the suspended load, thereby achieving both safety and safety by enabling safe lifting and transportation. effective.

FIG. 2 is a front view of a screw type clamp (no load state) according to an embodiment of the present invention. This screw type clamp is seen from the bottom side of FIG. 1 (the handle is omitted). This screw-type clamp is seen from the right side of FIG. 1 (handle omitted). FIG. 3A is a sectional view showing the main part of the tightening confirmation mechanism in this screw type clamp. FIG. 5 is a sectional view of a main part similar to FIG. 4 showing a stage in which the tightening bolt is rotated in the tightening direction by operating the handle with a suspended load set in this screw type clamp. At this point, the disc spring is not compressed, only the coil spring is compressed, and the enlarged diameter portion at the front end of the pressure nut comes into contact with the tip of the collar. FIG. 7 is a diagram showing the first position of the pressure nut, in which the tightening confirmation line is not completely buried in the leg and is partially exposed in the opening. FIG. 5 is a sectional view of a main part similar to FIG. 4 , showing a state in which the tightening bolt is further rotated in the tightening direction by operating the handle from the state shown in FIG. 5 to apply a prescribed tightening force to the suspended load; FIG. 7 is a diagram showing the second position of the pressure nut, where the disc spring is compressed by the collar and the tightening confirmation ring is completely buried in the leg and is no longer visible.

The structure and operation of a screw clamp according to an embodiment of the present invention will be explained in detail below with reference to FIGS. 1 to 6.

This screw type clamp 10 has almost the same basic configuration as that according to the prior art disclosed in Patent Document 1, but as will be understood from what will be described later, it includes an improvement in the tightening confirmation mechanism. .

The clamp main body 11 having a substantially U-shape has a pair of legs 13 and 14 facing each other across an opening 12 for receiving a hanging load (not shown). Furthermore, two hanging rings 26 and 27 are provided to enable the clamp body 11 to be lifted in two orthogonal directions.

A rotary jaw 15 is rotatably attached to the leg portion 13 and is constantly biased by a spring in the direction of protruding toward the opening 12 . The mechanism for biasing the rotary jaw 15 with a spring and the mechanism for making it rotatable are not particularly limited and are clearly disclosed in Patent Document 1, so details thereof will be omitted here. Thus, the rotating jaw 15 is rotatable with respect to the clamp body 11, and when a force greater than the spring force is applied, the rotating jaw 15 resists the spring force and moves in the direction of sinking into the inside of the leg portion 13 from the position shown in FIG. retreat to.

A pressure nut 16 is attached to the leg portion 14 so as to be relatively non-rotatable and relatively movable in the axial direction. A mounting hole 17 (numerical symbol omitted in the figure) is formed in the leg 14 and extends through the leg 14 to receive the pressure nut 16. The mounting hole 17 has a tip 17a facing the opening 12; An intermediate portion 17b formed with a slightly smaller diameter adjacent to the inner side of the tip portion 17a, a smaller diameter portion 17c formed with an even smaller diameter further adjacent to the inner side of the intermediate portion 17b, and a smaller diameter portion 17c further back from the small diameter portion 17c. A rear end portion 17d adjacent to the leg portion 17 and having a larger diameter and opening to the outside of the leg portion 14 is continuous and coaxial.

The pressure nut 16 is a substantially cylindrical member having a female thread (not shown) formed at its axis through which a tightening bolt 18 is threaded, and a flange portion 16b is formed at the tip of its main body 16a. The outer diameter of the main body 16a is substantially the same as the small diameter portion 17c of the mounting hole 17, and the outer diameter of the collar portion 16b is substantially the same as the tip portion 17a of the mounting hole 17.

Since the outer diameter of the pressure nut main body 16a is approximately the same as the small diameter part 17c of the mounting hole, a ring-shaped part corresponding to the hole diameter difference between the middle part 17b of the mounting hole and the small diameter part 17c of the mounting hole is provided between the pressure nut main body 16a and the small diameter part 17c of the mounting hole. A space (numerical symbol omitted) is provided, and a coil spring 19, a disc spring 20, and a collar 21, which are the main components of the tightening confirmation mechanism of the present invention, are housed in a predetermined positional relationship in this ring-shaped space. ing.

To explain in more detail with reference to FIGS. 1 to 4, this tightening confirmation mechanism includes two different types of biasing means for biasing the pressure nut 16 from the leg portion 14 in the direction of protruding into the opening 12. A spring member, ie, a combination of a coil spring 19 and a disc spring 20, is used. The coil spring 19 is arranged in front of the ring-shaped space, and its tip is in contact with a stepped surface 16c between the flange 16b of the pressure nut 16 and the main body 16a. The disc spring 20 is disposed adjacent to the rear of the coil spring 19 in the ring-shaped space, and its rear end is in contact with a stepped surface 17e between the intermediate portion 17b and the small diameter portion 17c of the mounting hole 17. .

Further, a collar 21 surrounding the coil spring 19 is accommodated in the mounting hole intermediate portion 17b. The collar 21 is capable of accommodating the coil spring 19, has a diameter size that fits within the mounting hole intermediate portion 17b, and is in an unloaded state (FIGS. 1 to 4) in which no hanging load is set. is formed so that its tip protrudes slightly forward from the mounting hole intermediate portion 17b (that is, into the mounting hole tip portion 17a), and its rear end has an axial length such that it substantially contacts the tip of the disc spring 20. . This protrusion dimension α (FIG. 5) can be set to, for example, approximately 1/4 of the thread pitch (P=2) of the tightening bolt 18 = 0.5 mm. The collar 21 is not fixed relative to the leg 14 and is therefore movable relative to the leg 14 when subjected to an external axial force.

A circumferential groove (number omitted) is formed at a predetermined location on the outer circumferential surface of the tip 16a of the pressure nut 16, and a tightening confirmation ring 22 is fitted into the circumferential groove. In the no-load state shown in FIGS. 1 to 4, the tightening confirmation ring 22 is exposed from the inner surface of the leg portion 14 toward the opening 12, so that its presence can be easily confirmed visually. In addition, it is preferable to provide it conspicuously with respect to peripheral members (pressure nut 16, especially leg portion 14 of clamp body 11, etc.). For example, if the pressure nut 16 is painted black and the clamp body 11 including the legs 14 is painted silver, the tightening confirmation ring 22 painted white or red can be used.

Reference numeral 23 denotes a set screw, which protrudes into the mounting hole small diameter portion 17 through a hole provided in the leg portion 14 (reference numeral omitted), and is inserted into an engagement groove (not shown) having a predetermined axial length carved in the pressure nut body 16b. (omitted). Thereby, the pressure nut 16 is supported non-rotatably with respect to the leg portion 14 (clamp body 11), and is determined by the relationship between the diameter of the set screw 23 and the axial length of the engagement groove. Relative movement in the axial direction is allowed by a predetermined distance.

Reference numeral 24 denotes a snap ring fitted into a circumferential groove (numerical omitted) carved near the rear end of the pressure nut 16, and the snap ring 24 connects the small diameter portion 17c of the mounting hole and the rear end 17d of the mounting hole. The pressure nut 16 is prevented from falling off by engaging with the stepped surface 17f between them.

Reference numeral 25 denotes a handle serving as an operating means for rotating the tightening bolt 18, and is attached to the rear end of the tightening bolt 18 that projects outside of the leg portion 14. Reference numeral 28 denotes a presser pad rotatably and detachably attached to the tip of the tightening bolt 18.

The operation of the screw clamp 10 configured as described above will be explained in detail in chronological order mainly with reference to FIGS. 4 to 6.

From the state shown in FIGS. 1 to 3, the handle 25 is rotated counterclockwise to move the tightening bolt 18 backward, and the suspension to be lifted is placed between the rotating jaw 15 and the holding pad 26 at the tip of the tightening bolt 18. After pinching a predetermined part of the load, the handle 25 is rotated clockwise to move the tightening bolt 18 forward in the tightening direction X, and the rotating jaws 15 and the holding pads 26 are pressed against both sides of the suspended load. When the tightening bolt 18 is further advanced from this state in the tightening direction The rotating jaw 15 retreats in the direction of being buried in the leg portion 13.

When the tightening bolt 18 is further tightened after the rotary jaw 15 reaches the innermost position, the tightening bolt 18 cannot move forward in the tightening direction The pressure nut 16 moves backward in the direction of being buried in the leg 14 against the biasing force of the biasing means (coil spring 19 and disc spring 20) built into the tightening confirmation mechanism, but the disc Coil spring 19, which has a lower spring pressure than spring 20, begins to contract first.

When the pressure nut 16 retreats from the position shown in FIG. 4 while contracting the coil spring 19, the flange 16b of the pressure nut 16 comes into contact with the front end of the collar 21 (FIG. 5). At this time, the disc spring 20 has not yet contracted. Furthermore, most of the tightening confirmation ring 22 provided on the outer periphery of the flange 16b is buried in the leg 14, but it is slightly exposed in the opening 12, so its presence can be seen from the outside. be. At this point, the specified tightening force has not yet been applied to the suspended load.

When the pressure nut 16 is moved backward by further tightening the tightening bolt 18 by operating the handle 25 from the state shown in FIG. 5, the collar 21 is pushed by the flange 16b and moves backward together with the pressure nut 16. 17e begins to contract. Since the disc spring 20 has a large spring pressure, a large force is required to operate the handle 25 at this time. If the disc spring 20 is contracted by 0.5 mm in the example, the pressure nut flange 16b will come into contact with the stepped surface 17g between the mounting hole tip 17a and the intermediate part 17b, and the tightening work will be completed. It can be finished in a short time. According to the example described above, this final tightening operation is completed by turning the handle 25 approximately 1/4 turn.

FIG. 6 shows a state in which the tightening work is completed as described above. At this time, the tightening confirmation ring 22 is completely buried in the leg 14 and cannot be seen from the outside, allowing the operator to reliably and easily confirm that the specified tightening force has been applied to the suspended load. Therefore, lifting and transportation by a crane (not shown) or the like can be carried out safely without the risk of the suspended load falling.

For example, with a 1 ton screw type clamp, a thrust of 500 kg is required to make the tip of the tightening bolt 18 (holding pad 28) bite into the suspended load, and from this thrust, it is necessary to safely lift the suspended load. Calculating the specified tightening force is approximately 150 kg. cm. In one embodiment, when the pressure nut 16 moves to a position where the specified tightening force is obtained (a position where the tightening confirmation ring 22 is completely buried in the leg portion 14 and is no longer visible), the coil spring 19 has a force of 21 kgf. The disk spring 20 contracts by 3.5 mm under a load, and contracts by 0.5 mm under a load of 571 kgf.

In the above embodiment, the tightening confirmation ring 22 fitted in the groove around the tip of the pressure nut 16 is used as a tightening confirmation means to notify the operator that a predetermined tightening force has been applied to the suspended load. Alternatively, the circumferential groove itself may be painted in a conspicuous color, or a line for tightening confirmation may be simply displayed in a conspicuous color on the outer peripheral surface of a predetermined location at the tip of the pressure nut 16.

By providing the tightening confirmation means on the tip side of the pressure nut 16, it is possible to visually observe the change in state (what was visible becomes invisible) due to the backward movement of the pressure nut 16 through the opening 12. By providing the pressure nut 16 at the rear end of the pressure nut 16 instead of or in combination with this, changes in state (what was not visible becoming visible) due to the backward movement of the pressure nut 16 can be prevented from occurring on the outside of the leg portion 14. It may be possible to visually observe from. For example, the pressure nut 16 can be prevented from falling off by providing the snap ring 24 in the illustrated embodiment at a position that causes a state change (an invisible item becomes visible) when a specified tightening force is applied. In addition to this, it can also function as a tightening confirmation means.

Alternatively, a ring, line, or other display means for confirming tightening that appears or disappears when the pressure nut 16 moves backward to a position indicating that a specified tightening force has been applied is placed on the outer circumference of the shaft of the tightening bolt 18. It may also be provided as a tightening confirmation means.

Although the screw type clamp according to the present invention has been described above in detail based on the illustrated embodiments, the present invention is not limited thereto, and can be modified in various ways within the scope of the invention described in the claims. It can be implemented with modifications.

10 Screw type clamp 11 Clamp body 12 Openings 13, 14 Legs 15 Rotating jaw (receiver)
16 Pressure nut 16a Main body 16b Flange part 17 Insertion hole 17a Tip part 17b Middle part 17c Small diameter part 17d Rear end part 17e Step surface between middle part and small diameter part (first locking surface)
17f Snap ring locking surface 17g Step surface between tip and middle part (second locking surface)
18 Tightening bolt 19 Coil spring (first biasing means)
20 Belleville spring (second biasing means)
21 Collar (movement transmission means)
22 Tightening confirmation ring (tightening confirmation means)
23 Set screw 24 Snap ring 25 Handle 26, 27 Hanging ring 28 Holding pad

Claims (7)

A generally U-shaped clamp body having a pair of legs facing each other across an opening, a receiver attached to one leg, and a clamp body that is non-rotatable relative to the mounting hole passing through the other leg and has an axis. A pressure nut that is mounted so as to be relatively movable in this direction, a tightening bolt that is screwed into the internal thread of the pressure nut and that can move forward and backward in the direction opposite to the receiver, and a pressure nut that is biased in the direction of protruding toward the opening. a second biasing means having a spring pressure greater than that of the first biasing means disposed adjacent to the rear of the first biasing means in the tightening direction; When the pressure nut retreats to the first position against the first biasing means by tightening the clamping bolt with a suspended load sandwiched between the clamping bolts, the enlarged diameter portion of the front end of the pressure nut The pressure nut is moved from the first position to the second position through the movement transmission means and the second biasing means when the tightening bolt is further tightened. A screw-type clamp characterized by having a tightening confirmation means that indicates that a specified tightening force has been applied to the suspended load when the suspended load is retracted to a certain extent. The first biasing means is a coil spring arranged on the outer periphery of the pressure nut, and the second biasing means is arranged between the coil spring and the first locking surface facing inward in the mounting hole. 2. The screw clamp according to claim 1, characterized in that it is a disc spring arranged. 3. The screw type clamp according to claim 1, wherein the movement transmission means is a collar provided in the mounting hole so as to surround the first biasing means. Any one of claims 1 to 3, wherein the pressure nut assumes the second position when the pressure nut retreats and abuts a second locking surface facing inward in the mounting hole. Screw clamp as described. Any one of claims 1 to 4, characterized in that the axial distance between the first position and the second position of the pressure nut corresponds to approximately 1/4 of the pitch of the tightening bolt. Screw clamp as described. The tightening confirmation means is provided on the outer periphery of the tip of the pressure nut, and is exposed through the opening of the clamp body and visible until the specified tightening force is reached, but when the specified tightening force is obtained. The screw type clamp according to any one of claims 1 to 5, characterized in that the screw type clamp is buried in the other leg portion and becomes invisible. The tightening confirmation means is provided on the outer periphery of the rear end of the pressure nut, and is buried in the other leg of the clamp body and cannot be seen until the specified tightening force is reached. 6. The screw type clamp according to claim 1, wherein the screw clamp is exposed to the outside of the other leg and becomes visible when the second leg is obtained.