JPH1151285A - Tube expander - Google Patents

Abstract

PROBLEM TO BE SOLVED: To certainly prevent a tube from being left with no expansion process applied when the tube inserted into a tube sheet of a heat exchanger, etc., is subjected to an expansion process by the use of a tube expander. SOLUTION: A tube expander includes a roller as a tool to expand a tube, and when the roller is inserted into the tube to the specified depth, bearing collars 5 and 7 contact with the tube end or the end face of a tube sheet, wherein the mounting positions of the bearing collars 5 and 7 are made changeable in order to alter the tube inserting depth of the roller 4, and a marking means is installed in the position where the bearing collars 5 and 7 contact with the tube end or the end face of tube sheet. Thereby a marking process is introduced during the tube expansion process, and a mark is applied to the tube end or the end face of tube sheet by the marking means always when the tube expansion process takes place.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tube expander for expanding a portion of a tube of a heat exchanger or a boiler inserted into a tube sheet.

[0002]

2. Description of the Related Art Tubes which are components of various types of heat exchangers and boilers used in a wide range of industries such as nuclear power generation, chemical industry, oil refining, pollution control equipment, ships, cooling and heating equipment, household electric appliances, and automobiles. 2. Description of the Related Art A tube expander is used as a tool for fixing a tube in close contact with a tube sheet to form a bundle.

A large number of holes having a predetermined pitch are formed in a tube sheet of a heat exchanger or the like, and the inner diameter of the hole is slightly larger than the outer diameter of the tube by a predetermined value. A tube expander is a tool for inserting a tube into this hole of a tube sheet, pushing the inserted tube from the inner surface thereof, and bringing the tube into close contact with the tube sheet. The purpose is cooling fluid (or heating fluid) and cooling fluid (or heating fluid)
To prevent contamination of the cooling fluid (or the heating fluid) and the fluid to be cooled (or the fluid to be heated), and to improve the heat exchange rate of the heat exchanger and the like. Since the tube is securely fixed to the tube sheet, it is possible to prevent the device from being broken due to the vibration of the tube caused by the flow of the fluid. In addition, by appropriate pipe expansion, corrosion of the contact portion between the outer peripheral portion of the tube and the inner peripheral portion of the tube sheet can be prevented.

When a wedge is driven into a tree, it breaks. This principle is applied to a tube expander, and a cross section of a conventional tube expander is shown in FIG. Since the tube expander must spread the inner surface of the tube, it is not flat like a wedge but rounded.The inner surface of the tube is not flat but rounded. It is locked in the groove.

A tapered mandrel 3 corresponding to a wedge
2, which penetrates through the hollow portion of the frame 33, and has a roller 34 on its outer periphery. The frame 33 uniformly holds the rollers 34 on the circumference. The roller groove 33A for holding the roller provided in the frame 33 is for allowing the roller 34 to move a predetermined amount in the radial direction in accordance with the insertion and removal of the tapered mandrel 32 in the longitudinal direction. The position is fixed. The tube expander expands the tube by pushing the mandrel 32 into the tube while rotating. Since the mandrel 32 is tapered, the diameter of the imaginary circle passing through the tube contact portion of the roller 34 is expanded by pushing the mandrel 32, so that the inner surface of the tube is gradually expanded.

Although a large force is required to push the mandrel 32, the tube expander has a "feed angle" in which the longitudinal center axis of the mandrel 32 and the longitudinal center axis of the roller 34 are inclined at an angle. Is provided so that when the mandrel 32 is rotated, it is pushed in naturally. This is based on the same principle that when the screw is rotated, the mandrel does not need to be pushed with great force by the action of the feed angle.

[0007]

The conventional tube expander has a structure without a function of automatically marking, and when the expansion of a certain tube is completed, some kind of mark indicating that the expansion of the tube has been completed is provided. Each time, an operator manually marks the tube sheet surface or the like using chalk or magic.

In practice, after an operator expands some tubes, collects some tubes, visually confirms that the expansion has been completed, and then manually marks the tube sheet surface. In some cases, the tube holes in the tube sheet are in a honeycomb shape and a large number of tube holes are arranged at a fixed pitch, resulting in poor work efficiency. In some cases, there was a problem with the quality of the equipment.

[0009]

According to a first aspect of the present invention, in order to solve the above-mentioned problems, the tube expander includes a marking unit. With this marking means, a mark can be automatically added at the time of expansion or at the end of expansion. According to a second aspect of the present invention, in order to solve the above-described problems, a tube expander is provided with a bearing collar that comes into contact with a tube end or a tube sheet end surface when a roller for expanding a tube is inserted into a tube at a predetermined depth. It is possible to change the mounting position of the bearing collar to change the depth,
The bearing collar is provided with marking means. If a marking means is provided on a portion of the bearing collar that comes into contact with the tube end or tube sheet end surface, the contact portion can be marked by performing the pipe expanding work.

According to a third aspect of the present invention, there is provided a tube expander according to the second aspect, wherein the tube expander has a cylindrical shape having a hollow portion with a circular cross section; a tapered portion and a cylindrical portion. And is coaxially disposed with the frame, penetrates the hollow portion of the frame, is movable in the longitudinal direction with respect to the frame, and is rotationally driven at a free end of the columnar portion. An outer peripheral portion of a tapered portion of the mandrel, which is rotatably locked in a groove machined so as to be uniformly arranged in the circumferential direction of the frame and capable of moving a predetermined amount in a radial direction of the frame; , And has a frusto-conical shape having a tapered shape having a half inclination in a direction opposite to the tapered shape portion and having an inclination in a direction opposite to the tapered shape portion. A plurality of the rollers arranged at a central axis inclined at a predetermined angle with respect to a longitudinal central axis of the frame; and a bearing collar is arranged on the outer peripheral portion of the frame via a bearing to adjust the longitudinal position. The marking means is mounted on the tube seat side of the bearing collar.

According to a fourth aspect of the present invention, there is provided a tube expander according to the second aspect or the tube expander according to the third aspect, wherein the marking means includes a marking felt containing ink. It is. Since the marking felt containing the ink comes into contact with the tube end or the tube sheet, it is possible to make a mark with the ink on the contact portion.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A marking means is attached to a tube expander. The marking means can be used to mark the end of the pipe expansion process by marking. The marking means may be attached so as to come into contact with the end of the tube or the end of the tube sheet during the expansion process.

Further, when a roller, which is a tool for expanding the tube, is inserted into the tube to a predetermined depth, the roller comes into contact with the end of the tube or the end surface of the tube sheet to change the insertion depth of the roller inside the tube. For this purpose, the tube expander may have a bearing collar whose mounting position can be changed, and the bearing collar may be provided with marking means. The predetermined depth refers to a depth at which the roller comes to a position where the inside of the tube undergoes the expanding process. By providing a marking means at a contact portion of the bearing collar with the end of the tube or the end of the tube sheet, a mark indicating that the expansion has been completed can be provided on the tube end or the tube sheet by the marking means, and the expansion can be performed. Will always be marked.

The depth of insertion of the roller into the tube is a value that varies depending on the individual tube expanding process, and is determined in accordance with the individual tube expanding process so that the roller is located at the position inside the tube to be expanded. The tube may be expanded over the entire portion inserted into the tube sheet, or the tube may be expanded only part of the portion inserted into the tube sheet.

A mandrel penetrating the hollow portion of a cylindrical frame having a hollow portion with a circular cross section, a tapered portion having a leading end half tapered and a cylindrical portion having a rear end half is coaxial with the frame. Deploy. The diameter of the inner peripheral portion of the hollow portion of the frame is slightly larger than the diameter of the cylindrical portion of the mandrel so that there is a gap, and the mandrel is movable in its longitudinal direction. Further, the mandrel is configured to be driven to rotate at the free end of the cylindrical portion.

The frame is provided with a plurality of long grooves which are uniformly arranged in the circumferential direction at the same position in the longitudinal direction of the frame. A plurality of frustoconical rollers are locked in these long grooves. The number of rollers is, for example, three or five depending on the specification of the tube to be expanded. The roller is partially exposed in the outer circumferential direction and the inner circumferential direction from the long groove of the frame, and its side surface contacts the outer peripheral portion of the tapered portion of the mandrel on the inner circumferential side,
It can rotate around its own longitudinal central axis. On the other hand, on the outer peripheral side, at the time of expanding the tube, the side surface of the roller comes into contact with the inner peripheral portion of the tube to be expanded so as to be rotatable around its own longitudinal central axis. The roller is disposed such that its central axis in the longitudinal direction is inclined at a predetermined angle with respect to the central axis in the longitudinal direction of the frame.

The roller has a frusto-conical shape having a taper shape having a half inclination in a direction opposite to the taper of the tapered portion of the mandrel. When the roller moves, the roller also moves in the radial direction of the mandrel at the same time, so that the diameter of the virtual circle (the tool diameter of the tube expander) passing through the contact portion of the roller with the inner peripheral surface of the tube changes. The rollers are constrained by a roller groove, which is a long groove of the frame, whose longitudinal movement is locked with respect to the frame.

The frame is located near the tip of the mandrel before the pipe expanding process, and the tool diameter of the tube expander is smaller than the diameter of the inner circumference of the tube. In this state, the roller portion of the tube expander can be inserted into the tube for expanding the tube. At this time, a bearing collar described later comes into contact with the tube sheet, and the roller is positioned inside the tube. Thereafter, the mandrel is rotationally driven from the free end of the column. Then, the roller rotates (self-rotates) about its own longitudinal center axis in the rotation direction opposite to that of the mandrel. at the same time,
The frame and the rollers held in the roller grooves of the frame revolve around the mandrel in the same direction as the rotation direction of the mandrel. The length of the roller is preferably determined by the width of the expanded tube sheet.

Further, the movement of the roller relative to the mandrel is primarily due to the fact that the roller's central longitudinal axis is arranged at a predetermined angle to the longitudinal central axis of the frame. This is a helical motion that not only revolves around the mandrel with the frame at the same longitudinal position while rotating in the groove but also moves in the longitudinal direction relative to the mandrel while rotating (FIG. 3). . The predetermined inclination angle is set so that when the mandrel is rotated, the roller moves to the larger diameter side of the taper.

That is, when the mandrel is rotated, the roller rotates in the groove of the frame, and together with the frame,
It moves to the large diameter side on the tapered portion of the mandrel while revolving around the mandrel. Therefore, the tool diameter of the tube expander gradually increases. Accordingly, the inner diameter of the tube increases, and the tube undergoes tube expansion. When the outer diameter of the tube becomes substantially equal to the inner diameter of the tube hole of the tube sheet, a predetermined expanded diameter is reached. Normally, the optimal tube expansion rate is determined by searching for the optimal expansion rate, and torque control is performed by the rotary drive of the mandrel.Therefore, before reaching the maximum diameter of the mandrel, the expansion work is completed and the tube expander is terminated. If the roller reaches the maximum diameter portion of the tapered portion, it is good to provide a stopper for the frame on the mandrel so that the frame and the roller do not further move in the longitudinal direction. .

A disk-shaped bearing collar having a hollow cross section is mounted on the outer peripheral portion of the frame via a bearing. The mounting position of the bearing collar in the longitudinal direction on the frame is adjustable. The longitudinal mounting position of the bearing collar on the frame is such that when the roller is inserted into the tube, the roller is arranged at a position suitable for the pipe expanding process, and the side of the bearing collar on the tube sheet side is in contact with the tube sheet. Is decided. That is, the bearing collar plays a role in positioning the roller inside the tube.

The operator performing the pipe expansion process inserts the tip end of the mandrel of the tube expander and the roller groove of the frame into the tube, and applies a thrust force in the tube inward direction to the tube expander until the bearing collar hits the side of the tube sheet. And push it. At this time, the diameter of the tool of the tube expander is slightly smaller than the inner diameter of the tube because the roller is located at a position near the tip of the tapered portion of the mandrel.

Next, the operator of the tube expander rotates the mandrel. When the mandrel rotates, the roller rotates in the direction opposite to the direction of rotation, and revolves around the mandrel in the direction of rotation of the mandrel. At the same time, the frame holding the roller also rotates about its own longitudinal central axis in the same direction as the revolution of the roller. At this time, since the bearing collar is attached to the outer peripheral portion of the frame via the bearing, the bearing collar stays still in contact with the tube sheet and does not rotate. The bearing collar rests on the frame, while the frame rotates about its longitudinal center axis.
The frame is limited in longitudinal movement by the bearing collar and rotates only about a central longitudinal axis. Therefore, the movement of the roller in the longitudinal direction is also limited, and the roller performs only rotation and revolving around the central axis in the longitudinal direction.

At this time, the rotating mandrel gradually moves toward the tip. Therefore, the roller relatively gradually moves toward the large diameter side of the tapered portion, so that the roller moves radially outward inside the groove of the frame. When the outer diameter of the tube coincides with the inner diameter of the hole diameter of the tube sheet, the tube is further expanded so as to obtain the expansion rate required for fixing. Thereafter, when the mandrel is rotated in the reverse direction to reduce the tool diameter and the tube expander is taken out of the tube, the pipe expanding process is completed. When the marking means is attached to the tube collar side of the bearing collar on the tube sheet side or the tube sheet end surface, the mark is automatically attached to the tube end or tube sheet end surface when the expansion of each tube is performed. can do.

The marking means may be provided with a marking felt containing ink. This makes it possible to mark the end of the tube or the end surface of the tube sheet with ink by performing the pipe expanding process.

[0026]

An embodiment will be described with reference to FIG.
A mandrel 2 having a cap nut 1 at the tip is a tapered portion 2A with a tapered tip and a cylindrical portion 2B at the rear end.
It is composed of A square shank 2C is attached to the rear end. The square shank 2C can be electrically driven torque controlled expansion drive (not shown) or hydraulic torque controlled expansion drive (not shown), pneumatic drive (not shown), and manual ratchet handle (not shown). And is rotationally driven under a predetermined torque.

The mandrel 2 is inserted through a hollow portion of a roughly cylindrical frame 3 having a hollow portion having a circular cross section. The inner diameter of the hollow portion of the frame 3 is slightly larger than the outer diameter of the cylindrical portion 2B of the mandrel 2. A frame stopper 2D is provided at the rear end of the cylindrical portion 2B of the mandrel 2 at the joint with the square shank 2C, and regulates the movement of the frame 3 in the mandrel drive side.

A roller groove 3A, which is a long groove, is uniformly formed in the circumferential direction at intervals of 120 degrees on the front end side of the frame 3. The roller grooves 3A are arranged at the same position in the longitudinal direction of the frame 3. Three frusto-conical rollers 4 are locked in the roller grooves 3A. The roller 4 is partially exposed in the outer circumferential direction and the inner circumferential direction of the frame 3 from the roller groove 3 </ b> A so that the diameter of the head side (small diameter side) is larger than the thickness of the frame 3.

The side surface of the roller 4 contacts the outer peripheral portion of the tapered portion 2A of the mandrel on the inner peripheral side of the frame 3 while rotating around the central axis in the longitudinal direction. On the other hand, the roller 4 rotates on the inner peripheral surface of the tube to be expanded on the outer peripheral side of the frame 3 around the central axis in the longitudinal direction at the time of the expanding process, while being substantially 180 degrees opposite to the contact portion with the mandrel. The sides touch. The roller 4 is disposed so that its central axis in the longitudinal direction is inclined at a predetermined angle θ with respect to the central axis in the longitudinal direction of the frame 3 (FIG. 3).

The roller 4 has a frusto-conical shape having a tapered portion 2A whose direction is opposite to that of the tapered portion 2A of the mandrel 2 and whose inclination is half. Therefore, when θ = 0 degrees, the contact portion of the roller side surface with the inner circumferential portion of the tube is a horizontal line parallel to the longitudinal central axis of the tube. The rear end side of the frame 3 is one step smaller in outer diameter and the outer peripheral portion is threaded. The outer peripheral portion has a first hollow disk portion, and the inner peripheral portion of the hollow portion is screwed. The processed bearing collar rear wheel 5 is screwed. The bearing collar rear wheel 5 further includes a second hollow disk portion having the same outer diameter and a larger hollow inner diameter as the first hollow disk disposed on the left side surface portion of the first hollow disk, and a second hollow disk portion. On the left side surface of the hollow disk portion, a third hollow disk portion having an outer diameter larger than that of the second hollow disk portion and having the same hollow inner diameter is arranged. A ball retainer 6 is attached to the left side surface of the third hollow disk portion.

A bearing collar front wheel 7 is mounted on the left side of the ball retainer 6. The bearing collar front wheel 7 has a two-stage hollow cylindrical shape, and the ball retainer 6 and the bearing collar rear wheel 5 are accommodated and arranged inside the larger hollow cylinder. Further, the ball retainer 6 is arranged to be attached to the right side of the central side wall of the bearing collar front wheel 7. The smaller inner diameter of the hollow portion of the hollow cylindrical portion has a sufficiently large value that does not interfere with the roller 4. A marking felt 8 having an L-shaped cross section is attached to the outer peripheral side of the smaller hollow cylindrical portion. The outer diameter of the maximum outer diameter portion of the marking felt 8 is slightly smaller than the outer diameter of the larger hollow cylinder of the bearing collar front wheel 7.

A hollow cylindrical slide plate 9 having a hollow disk-shaped side wall is mounted on the left side so as to cover a part of the larger hollow cylindrical portion of the marking felt 8 and the bearing collar front wheel 7. The inner peripheral portion of the hollow portion of the side wall slides on the outer peripheral portion of the horizontal portion of the L-shaped cross section of the marking felt 8. A wave washer 10 is housed between the side wall of the slide plate 9 and the vertical portion of the L-shaped cross section of the marking felt 8. When the slide plate 9 is pushed to the right and slid, the wave washer 10 is compressed and the marking felt 8 is exposed. When the force for pushing the slide plate 9 to the right is released, the slide plate 9 slides to the left by the repulsive force of the wave washer 10 that has been compressed, and the marking felt 8 is covered with the slide plate 9. A plug 11 for supplying ink to the marking felt 8 is attached to the slide plate 9.

Further, an O-ring groove is formed near the right end of the inner peripheral portion of the slide plate 9, and the O-ring 12 is fitted therein, thereby preventing ink from leaking to the vicinity of the outer peripheral portion right end of the bearing collar front wheel. A set bolt hole is formed near the center of the outer peripheral portion of the slide plate 9 and a set bolt 13 is attached. The set bolt 13 passes through the slide plate 9, and the tip of the set bolt 13 enters a guide groove formed in the outer peripheral portion of the bearing collar front wheel in the longitudinal direction to guide the slide plate 9 in the longitudinal direction.

Before the pipe expanding process, the roller 4 is located relatively close to the tip end by the tapered portion 2A of the mandrel 2.
The tool diameter of the roller 4 is slightly smaller than the inner diameter of the tube to be expanded. At the time of expanding the pipe, a portion of the mandrel 2 near the distal end of the tapered portion 2A and the distal end of the frame 3 where the roller 4 is locked are inserted into the tube to be expanded. The insertion ends when the left end of the smaller cylindrical portion of the bearing collar front wheel 7 contacts the tube sheet. By this insertion work, the slide plate 9 slides to the right, and the marking felt 8
Are exposed, and when the left end of the smaller cylindrical portion of the bearing collar front wheel 7 contacts the tube sheet, the marking felt 8 also contacts the tube sheet, and the tube sheet is marked.

The rear end of the frame 3 of the rear wheel 5 of the bearing collar so that the roller 4 comes to a predetermined working position inside the tube when the left end of the smaller cylindrical portion of the front collar 7 of the bearing collar contacts the tube sheet. Adjust the mounting position of the part. A set screw 14 is attached to the rear wheel 5 of the bearing collar, and the tip of the set screw 14 is pressed into a groove formed in the longitudinal direction on a threaded portion at the rear end of the frame 3 to position the rear wheel 5 of the bearing collar on the frame 3. Is fixed. The bearing collar front wheel 7 is arranged so as to surround the set screw 14, but a hole is formed in the bearing collar front wheel 7 so that the set screw 14 can be turned from outside the bearing collar front wheel 7. During pipe expansion,
The bearing collar rear wheel 5 rotates integrally with the frame 3, but the bearing collar front wheel 7 is in contact with the tube sheet and does not rotate. The relative rotation of the bearing collar rear wheel 5 and the bearing collar front wheel 7 is the ball retainer 6
Absorbed by. After inserting the ball retainer 6 and the bearing collar rear wheel 5 into the hollow portion of the bearing collar front wheel 7, the snap ring 15 is fitted into the groove formed in the hollow portion of the bearing collar front wheel 7, and the ball retainer 6 and the bearing collar rear wheel 5 are bearing. It is fixed and stored inside the collar front wheel 7.

As described above, during the pipe expanding process, the bearing collar front wheel 7 comes into contact with the tube sheet, and neither rotates nor moves in the longitudinal direction. However, since the mandrel 2 is driven to rotate, the rotation of the mandrel 2 causes the roller 4 to revolve with the frame 3 while rotating on the inner circumferential portion of the tube, but does not move in the longitudinal direction. The frame 3 revolves only around its central axis in the longitudinal direction by the rotation of the roller 4, but does not move in the longitudinal direction. On the other hand, the mandrel 2 moves in the tip direction while rotating. Since the contact position of the roller 4 with the mandrel 2 moves toward the large diameter side by the movement of the mandrel 2, the tool diameter of the roller 4 increases, and the tube undergoes tube expansion. After the end of the tube expanding operation, the operator rotates the mandrel 2 in the reverse direction to release the rollers 4.
Since the tool diameter of the tube expander is reduced, the tube expander can be taken out of the tube subjected to the tube expansion process.

At this time, the tube sheet 19 has an inner diameter D at the position shown in FIG.
1. Mark 17 of outer diameter D2 is attached, tube sheet 19
On the whole, a large number of marks 17 shown in FIG. 5 are provided for each tube 18 for which the pipe expansion work has been completed. When the tube expanding operation of the entire tube bundle is completed or is interrupted for a long time, a cap 16 (shown by a two-dot chain line in FIG. 1) may be attached to a portion where the marking felt 8 is exposed.

[0038]

According to the tube expander of the present invention, since the marking step is incorporated in one step of the tube expanding operation, if a certain tube is expanded, the tube expanding operation is performed. It is possible to make a mark indicating that the tube has been expanded, thereby preventing forgetting to expand the tube. Further, it is not necessary to perform the marking work every time the pipe expanding work is completed, so that work efficiency is improved. In addition, by providing a heat exchanger that does not forget to expand the pipe, it is possible to contribute to the improvement of the quality of the heat exchanger, and it is effective in preventing operation failure during operation of the heat exchanger.

[Brief description of the drawings]

FIG. 1 is a front view, partially in section, of a tube expander according to an embodiment of the present invention.

FIG. 2 is a sectional view of a conventional tube expander.

FIG. 3 is a view for explaining the movement of a roller of a tube expander around a tapered portion of a mandrel.

FIG. 4 is an explanatory diagram showing marking positions on a tube sheet by the tube expander according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a marking state on a tube sheet by the tube expander of the above.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cap nut 2 32 Mandrel 2A Taper part 2B Column part 2C Square shank 2D Frame stopper 3 33 Frame 3A 33A Roller groove 4 34 Roller 5 Bearing collar rear wheel 6 Ball retainer 7 Bearing collar front wheel 8 Marking felt 9 Slide plate 10 Wave washer 11 Plug 12 O-ring 13 Set bolt 14 Set screw 15 Snap ring 16 Cap 17 Mark 18 Tube 19 Tube sheet D1 Inside diameter D2 Outside diameter

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiharu Tanaka 2410 Motoe, Uozu City, Toyama Prefecture

Claims (4)

[Claims] 1. A tube expander comprising a marking means. 2. A bearing collar for contacting a tube end or a tube sheet end surface when a roller for expanding the tube is inserted into the tube to a predetermined depth,
A tube expander, wherein the mounting position of the bearing collar can be changed to change the depth, and the bearing collar has a marking means. 3. A frame having a cylindrical shape with a hollow portion having a circular cross section; a tapered portion and a cylindrical portion;
A mandrel disposed coaxially with the frame, penetrating the hollow portion of the frame, movable in the longitudinal direction with respect to the frame, and driven to rotate at a free end of the columnar portion; The groove, which is arranged and machined uniformly in the circumferential direction of the frame, is rotatably locked to be movable by a predetermined amount in the radial direction of the frame, and is brought into rotational contact with the outer peripheral portion of the tapered portion of the mandrel. Rotating contact with the inner periphery of the tube to be expanded
The tapered portion has a frusto-conical shape having a half tapered shape in the opposite direction to the tapered portion, and a plurality of the truncated cones are arranged with a longitudinal center axis inclined at a predetermined angle with respect to the longitudinal center axis of the frame. The bearing collar is fixedly attached to an outer peripheral portion of the frame via a bearing so as to be adjustable in a longitudinal direction, and the marking means is attached to a tube seat side surface portion of the bearing collar. 3. The tube expander according to claim 2, which is provided. 4. The tube expander according to claim 2, wherein said marking means includes a marking felt containing ink.