CN103128184A

CN103128184A - Device and method for expanding tubes

Info

Publication number: CN103128184A
Application number: CN2012104952777A
Authority: CN
Inventors: 维尼乔·马焦洛; 洛里斯·萨尔托里
Original assignee: Cms Costruzione Macchine Speciali Srl
Current assignee: C M S 工程机械专业有限公司; Cms Costruzione Macchine Speciali Srl
Priority date: 2011-11-28
Filing date: 2012-11-28
Publication date: 2013-06-05
Also published as: ITVR20110212A1; EP2596879A1

Abstract

Device for expanding tubes (2;102;202), inserted in a finned pack (3;103) of a heat exchanger (1;101), comprising, support means (5;105) of the finned pack (3;103), a tool (6;106) for enlarging the ends (7,8;107,108;207) of each one of the tubes (2;102;202), a mandrel (9; 109) for the radial expansion of each one of the tubes (2;102;202). The device also comprises axial abutment means (10;110;210) for both enlarged ends (7,8;107,108;207) of each one of the tubes (2;102;202) in the contraction direction of each one of the tubes (2;102;202) during the radial expansion operation. A method for expanding tubes carried out with such a device is also proposed.

Description

The equipment and the method that are used for convergent divergent channel

Technical field

The present invention relates to a kind of equipment for convergent divergent channel and method.

More specifically, the present invention relates to for equipment and the method for expansion for the manufacture of the pipe of heat exchanger.

Background technology

As is known, most of common heat exchanger in the market, no matter have little size or large size, all comprise pipe in a row, that usually have circular cross-section, pipe is inserted in the band wing assembly that disposes suitable hole, represents the outer surface of the expansion on a secondary fluid that generally includes air with the wing assembly.

For the side at pipe forms the loop, pipe in series or in parallel connects together in their end, is best suited for the channel cross-section that carries out heat exchange and the load loss of length and acceptable first fluid to have.

For the aspect of different product, for example the application with cost and service time and the other side of manufactured type, product, can use rectilinear tubes or be known as pipe hairpin tube, that bend to " U " shape.

Pipe in a row and usually being undertaken by the radial dilatation of the pipe mechanically carried out, be known as expansion with the permanent connection between the wing assembly.Due to expansion, pipe in a row with being connected fully firm and having rigidity between the wing assembly, and make it possible to obtain good efficiencies aspect optimal heat exchange between pipe and wing.

The technical problem underlying relevant to carrying out this operation is to expansion their the reducing of length afterwards at caliber.

Therefore, in the art traditionally, axially the amplifying of the pipe of the default approximately 2%-4% of final lengths that often need to obtain with respect to hope.

can't guarantee the abundant precision of the final lengths of the pipe expanded due to this increasing of usually calculating based on experience the size of estimating, therefore designed the scheme that obtains a kind of machinery, this machinery comprises the clamping device of the axial locking of carrying out pipe or hairpin tube, make at each pipe and stand in the process of mechanical expansion, the predetermined length of managing self is maintained and can change significantly, perhaps only has under any circumstance acceptable variation on the whole within the specific limits, be apparent that: as the result of this axial locking, to there be certain reducing aspect the thickness of each pipe, it must be foreseen in the step of sizing.

Observe, particularly but be not exclusively, in the application of the pipe with minor diameter and low thickness, the use of this clamping device---clamping device is by end of claw or other similar member locking pipe---causes the surperficial cutting-up that material is in certainly in the end, namely, permanent deformation or strain hardening, it makes the loop necessary machined subsequently of connection of carrying out pipe be difficult to carry out or require great effort.

In some cases, in the process of the mechanical expansion step of pipe, must carry out the processing of the first distortion of the pipe that causes by the effect because of fixture to offset the contraction of pipe, pipe is out of shape again so that manage and recover original size, allow in this way to expand axle from the pipe taking-up.Connect in order to carry out the loop, the machined of the end of pipe subsequently is called as socket, that is, a kind of enlarging, it for example allows the insertion subsequently of elbow, nipple or other the necessary elements fixed by soldering or by other equivalent technologies.If socket is carried out after the end of pipe as above has been narrowed down and be extended subsequently, people must be by causing further distortion (expansion) generation effect on the material of strain hardening, that can cause irreversible lesion, particularly in case of emergency even cause fracture, thereby cause the high ratio of defects of technique.

Summary of the invention

Therefore, technical assignment of the present invention a kind ofly can be eliminated defects by designing, the equipment and the method that are used for convergent divergent channel improve prior art.

In this technical assignment, the objective of the invention is to design a kind of equipment and method, it can be in the situation that do not utilize fixture, claw or other similar members of the end itself that can damage potentially pipe to lock the end of pipe self, carry out the expansion of pipe in the mode of controlling, and keep predetermined length.

This task and this purpose are by according to the equipment that is used for convergent divergent channel of claims 1 and realize by the method that is used for convergent divergent channel according to claims 8.

According to aspects of the present invention, in the process of the dilation procedure of the diameter of pipe, the end that enlarges in advance to form cupule of managing self is kept by the end portion supports element of the axial shrinkage that prevents from managing self.

In this way, the end that formerly enlarges be not out of shape by any way or situation about damaging under, accurately judge the length of the pipe of expansion.

Further favorable characteristics is described in the dependent claims.

Description of drawings

To those skilled in the art, from the following description and from the accompanying drawing that provides as non-limiting example, it is clearer that feature of the present invention will become, in the accompanying drawings:

Fig. 1-7 are the partial side view in cross section according to the continuous expansion step of the straight tube of heat exchanger of the present invention;

Fig. 8-14 are the partial side view in cross section according to the continuous expansion step of the pipe that bends to hairpin of the heat exchanger of another embodiment of the present invention;

Figure 15 is the detailed sectional view in expansion step according to another embodiment of equipment of the present invention;

Figure 16 is the partial side view in cross section of the expansion step of particularly expanding under thrust of straight tube;

Figure 17 is the pipe that bends to hairpin, the partial side view in cross section of the expansion step of particularly expanding under thrust.

The specific embodiment

With reference to accompanying drawing 1, the heat exchanger by 1 expression comprises insertion with the pipe in a row 2 in wing assembly 3 on the whole, and described pipe in a row 2 will stand dilation procedure by apparatus and method according to the invention.

In known manner, band wing assembly 3 comprises hole 4, and pipe 2 is inserted in hole 4.

At first should be noted that, comprise according to the expansion device of pipe of the present invention the known parts that appear in the such all machines that belong to prior art, supporting construction, actuating device, therefore,, will not carry out any further description except the significant feature of description of this invention purpose.

In a manner known way, this equipment comprises the bracing or strutting arrangement 5 with wing assembly 3.

Bracing or strutting arrangement 5 with wing assembly 3 is illustrated by the broken lines in Fig. 1, and bracing or strutting arrangement 5 comprises for example metal framework.

Metal framework is for example at place, both sides at least support belt wing assembly 3.

Alternatively, can there be the bracing or strutting arrangement with other structures or other configurations 5 with wing assembly 3, the present invention do not carried out any restriction.

Also comprise the end 7 of each pipe in

pipe

2,8 expansion instrument 6 according to equipment of the present invention.

Expansion instrument 6 can be type as known in the art, is preferably on the

end

7,8 that is suitable for each pipe in pipe 2 and applies the rotary-type of appropriate load.

Alternatively, can use the expansion instrument of any other types, for example, the mechanical type, air-driven type or the power type that have the mechanical type of radial effect or have axial action.

Expansion instrument 6 is associated with the corresponding actuating device of for example power type of prediction in the device in accordance with the invention, and because actuating device is original known type and no longer representing in this area.Should be pointed out that according to expansion device of the present invention can according to use and the specific requirement of product comprise can be for example concurrently, a plurality of expansion instruments 6 of namely synchronously working.

According to equipment of the present invention also comprise on the whole axles by 9 expressions, this axle 9 be used for pull and promote under carry out radial dilatation to managing each pipe of 2, the feature of axle 9 will more clearly be described hereinafter.

As the description that expansion instrument 6 is carried out, can also comprise a plurality of axles 9 of working concurrently according to the specific requirement of application and product according to equipment of the present invention.

According to aspects of the present invention, expansion device comprises axial meeting device 10, is used in radial dilatation or radially enlarges the process of operation, two

ends

7,8 on the shrinkage direction of each Guan Zaiguan in pipe 22 self, that extended instrument 6 enlarges.The contraction of the pipe 2 that the end 7 that be used for to enlarge, 8 axial meeting device 10 prevent from expanding, but axially meeting device 10 does not prevent in opposite direction motion will be as will be clearer hereinafter.

Due to this characteristic, in expansion process, in the situation that do not utilize the member such as fixture, claw etc. of strain hardening potentially, distortion or infringement end self to come clamping or

clamp end

7,8, each pipe 2 is carried out axial constraint to prevent its contraction.

Above-mentioned axial meeting device 10 comprises for the end 7 of each expansion of each pipe of

pipe

2,8 end formed element 11.

End formed element 11 is opposite each other along the axis of pipe to be expanded 2, and end formed element 11 is provided with the flared surfaces 12 that separately the end 7 that is suitable for enlarges, 8 corresponding outer surface are complementary.Can be according to specific requirement, have any amount according to pipe 2 size etc., for example one, two or more, end formed element 11, with the best butt of the end 7 that to enlarge, 8 outer surface, contact does not cause local deformation thereby this butt suitably distributes.

In further details, each end formed element 11 can both move to the open position of not expressing in the drawings from the closing position of the axial restraint of the corresponding pipe 2 expressed Fig. 3-6.

End formed element 11 for example hingedly or otherwise with do not express in the accompanying drawings but in the art known type itself for example electronic, oil pressure or similarly actuating device be associated.

In the present embodiment, and as can see in Fig. 3-6, end formed element 11 general arrangement become to be similar to the end 7 that holds expansion, 8 the outside but do not apply the nipper of any clamping force.

Thus, the end 7 of expansion, 8 flared surfaces 12 of mating in closing position.

Yet in other embodiments, end formed element 11 can have different configurations, for example, ring-type or similar configuration, it is any fixed the present invention not to be carried out.

As described, the type of axle 9 for operating under pulling force.

Yet, in other embodiments of the present invention, utilize the constructive scheme that is suitable for for this reason retrofiting, axle 9 can be the type that operates under thrust.

As shown in Fig. 4-6, axle 9 comprises that claw keeps bar 13, the turnover panel expander 15 of the end claw 14 that is integrated with bar 13 and the hollow that can slide along bar 13.

Claw keeps bar 13 to be associated to the relevant actuating device of not expressing in the accompanying drawings, actuating device allows claw to keep bar 13 in insertion and the taking-up of pipe 2 inside, or in the situation that bending to " U " shape, pipe allow claw to keep bar 13 in insertion and the taking-up of the straight line portion inside of pipe, as clearer hereinafter.

Claw keeps the actuating device of bar 13 can be power type, oil pressure type or similar type.

End claw 14 comprises the frusto-conically shaped portion 17 that the head 16 that is used as stop part and the turnover panel that allows expander 15 are opened.

Expander 15 can keep bar 13 resting position as can be seen from Fig. 4 visible expanded position in Fig. 5,6 to slide along claw, in resting position, expander 15 regain with respect to head 16 and the external diameter of expander 15 less than the external diameter of end claw 14, in expanded position, the head 16 of claw 14 is against expander 15, thereby determines opening of turnover panel by this way: expander 15 presents greater than the external diameter of claw 14 and greater than the external diameter of the internal diameter of pipe to be expanded 2.

Hereinafter the method that is used for convergent divergent channel 2 of carrying out by equipment according to the present invention is described.

In the initial step of the method, carry out the expansion of the first end 7 of pipe 2 by expansion instrument 6, for example, directly carrying out with the output of the machinery of this pipe of cutting from being used for straightening.

Then, according to Fig. 1, will manage 2 and be inserted in band wing assembly 3.

In step subsequently, again utilize expansion instrument 6 to carry out the expansion that is inserted into the second end 8 of the pipe 2 in wing assembly 3, as shown in Figure 2.

The end 7 of pipe, 8 expansion make it possible to produce the part that is called cupule in this area, namely, the end that for example is connected with other loop elements that consist of heat exchanger by soldering, and this connection end must be not to be subjected to be out of shape or to rupture, with execution operation subsequently, thereby complete the heat exchanger with best in quality.

In step subsequently, axially retrain the

end

7,8 of extended instrument 6 expansions along the direction of the rear natural shrinking of expansion.

This axial constraint step makes the flared surfaces 12 of end formed element 11 and the end 7 of the expansion of

pipe

2,8 outer surface be complementary to carry out by clamping end forming element 11, as shown in Figure 3.

In this case, pipe 2 can not stand any axial shrinkage, thereby has kept the necessary predetermined length that forms in finished product; Simultaneously,

end

7,8 is only put and is leaned against on flared surfaces 12, can not stand any locking by fixture, claw or analog, therefore can not bear the risk of any distortion or fracture.

Afterwards, the step of the method prediction each pipe 2 of expansion under pulling force.

In this step, in the situation that expander 15 is in resting position, and therefore in the situation that the external diameter of expander 15 less than the internal diameter of pipe 2, a plurality of axles of axle 9 or operation concurrently are inserted in each pipe 2.

Axle 9 is inserted in each pipe 2, at least until axle 9 process metal frameworks appear at the end opposite with inserting end 8 with the wing assembly, as shown in Figure 5.

Afterwards, expansion has predicted that the claw that resets keeps bar 13 until the head 16 of claw 14 makes turnover panel open and expander 15 self is rendered as the step of expanded position against expander 15.

As described, in this case, the external diameter of expander 15 is greater than pipe 2 internal diameter, therefore as shown in Figure 6, make axle 9 backward translation until axle 9 itself take out from managing 2, thereby in the situation that do not have the radial expansion that axial shrinkage is determined the expectation of pipe 2.

At this moment, end formed element 11 is opened, and has the heat exchanger 1 of the pipe 2 of expansion with taking-up, as shown in Figure 7.

As described, described method also can be expanded to carry out under thrust by prediction and realize.

This situation is shown in Figure 16.

In a rear situation, the contact surface of axle 9, namely the head 16 of axle 9 has the large external diameter of internal diameter than pipe 2; Axle 9 causes the expansion of pipe 2 in the insertion of the arrival end of pipe 2, it is proceeded in the whole translation process of axle 9, until arrive the opposite ends with the wing assembly.

In following step, by bar 13, pipe the resetting of 2 internal actuating axles 9, until surpass the resting position of end 8 of the expansion of pipe 2.

The present invention of design can obtain important technical advantage thus.

As described, the expansion length of pipe 2 can be in the situation that do not have axial shrinkage and therefore have predetermined carrying out with the accurate final lengths of controlling, thereby end 7, any distortion of 8 or the risk of fracture of 2 expansion have been avoided managing in pipe 2 process of expansion, and therefore provide the heat exchanger with best in quality characteristic, then to stand machined in succession.

This process also makes it possible to carry out the end 7 of

pipe

2,8 expansion operation before with quicker and easier mode and the initial expansion step of being undertaken by the expansion instrument 6 that produces very appropriate axial load,, makes so-called cupule that is.In fact, apparatus and method according to the invention has guaranteed that the

end

7,8 that enlarges will can not be out of shape or rupture in production stage in succession, as implied above.In addition, realize the axial constraint of the pipe 2 in process of expansion by the simple flared surfaces 12 that is provided at prediction in end formed element 11, therefore need not predict the clamping component of clip-like complicated and that cost is high, claw etc.In described embodiment, expansion is advantageously carried out under pulling force, and it makes it possible to more accurately control from the side that pulling force produces the phenomenon of the distortion that each pipe 2 stands self process of expansion.

Yet as described, expansion also can be carried out under thrust.

Another embodiment of apparatus and method according to the invention is shown in Fig. 8-14.

In Fig. 8-14,100 the Reference numeral that used the increase identical with aforementioned embodiments represents corresponding element.

This embodiment relates to heat exchanger 101, and this heat exchanger 101 comprises the pipe 102 that is inserted into 180 ° of in the hole 104 in wing assembly 103, bendings that be known in the industry as hairpin tube.As previously described, according to the equipment of present embodiment comprise bracing or strutting arrangement with wing assembly 105, be used for each pipe of convergent divergent channel 102 end 107,108 instrument 106, be used in the axle 109 of each pipe of radial dilatation pipe 102 under pulling force and the end 107 of two expansions of each pipe in being used for pipe 102 on self shrinkage direction at each pipe of radial dilatation operating process in pipe, 108 axial meeting device 110.

In this embodiment, as shown in Figure 10,13, axially the end formed element 111 of meeting device 110 is arranged to adjacent one another are and is not toward each other, on the adjacent end 107,108 that locks onto the pipe 102 of crooked 180 ° or hairpin tube.

Identical with described in aforementioned embodiments of axle 109 or a plurality of axle.

In this embodiment, expansion device also comprises the middle locking member 118 for each pipe ancon of 102 section, as described in shown in accompanying drawing 10-13.This expansion method in embodiment comprises the identical step of describing in aforementioned embodiments, except following situation: in the situation that pipe 102 has inserted with utilizing expansion instrument 106 actuation end 107,108 expansion in wing assembly 103, for example utilize single expansion instrument 106 or utilize a plurality of expansion instruments 106 to carry out.

In addition, provide at least two axles 109 of operation concurrently in the radial dilatation step of pipe 102, as shown in Figure 11-13.

Alternatively, can once carry out by same axle 109 expansion of two straight line portioies of each pipe in pipe 102.

Particularly, by carry out two expansions under pulling force and thrust, due to this process in the situation that the length of the single arm of hairpin tube 102 does not change occurs, therefore be single arm expanded or two arms to be expanded simultaneously be exactly what it doesn't matter, it means: in band wing assembly, hairpin tube 102 can cover the same line, the operative axis of supposing device is level, but hairpin tube 102 also can vertically cover two lines, that is, in the situation that the pipe of alignment, or cover diagonally two lines, that is, in the situation that the pipe biasing.

In addition, except described according to aforementioned embodiments, the actuation step of locking member 118 in the middle of the method is also predicted, this centre locking member 118 be operated with end formed element 11 open and close side by side.

Therefore, in this embodiment, pipe 102 or the hairpin tube of crooked 180 ° are expanded, thereby obtain the same advantage described in aforementioned embodiments.

Figure 17 has represented to bend to the expansion step that the pipe 102 of hairpin is particularly expanded under thrust.

In this case, the expansion with in the situation that the mode of the mode all fours described in the situation of straight tube Figure 16 occur.

There is shown another embodiment according to equipment of the present invention in the detail section of Figure 15.

In this embodiment, axial meeting device 20 also comprises the end formed element 211 with corresponding flared surfaces 212 of the type described in aforementioned embodiments and the complementary forming element 220 that comprises flared surfaces 222, this flared surfaces 222 is built-inly against the corresponding flared surfaces of the end 207 of the expansion of pipe to be expanded 202, but do not apply end 207 distortion or the strain hardenings that any pressure does not make described expansion.

The existence of this complementation forming element 220 has for example particularly in case of emergency consisted of the further locking constraint to the end that enlarges in the process of dilation procedure.

Learnt thus how the present invention realizes the target that proposes.

Invention has been described according to preferred embodiment, but in the situation that the protection domain that is provided by appended claim is not provided, can conceive equivalent modifications.

Claims

1. one kind is used for convergent divergent channel (2; 102; 202) equipment, described pipe (2; 102; 202) be inserted into heat exchanger (1; 101) band wing assembly (3; 103) in, described equipment comprises:

Described band wing assembly (3; 103) bracing or strutting arrangement (5; 105),

Instrument (6; 106), described instrument (6; 106) be used for enlarging described pipe (2; 102; The end of each pipe 202) (7,8; 107,108; 207),

Axle (9; 109), described axle (9; 109) be used for radially expanding described pipe (2; 102; 202) each pipe in,

It is characterized in that,

Described equipment comprises axial meeting device (10; 110; 210), described axial meeting device (10; 110; 210) be used for described pipe (2; 102; 202) each pipe in the radial dilatation operating process along described pipe (2; 102; The end (7,8 of two expansions of the shrinkage direction of each pipe 202); 107,108; 207).

2. equipment according to claim 1, wherein, described axial meeting device (10; 110; 210) comprising: be used for described pipe (2; 102; The end of each expansion of each pipe 202) (7,8; 107,108; 207) end formed element (11; 111; 211), described end formed element (11; 111; 211) be provided with separately flared surfaces (12; 112; 212), described flared surfaces (12; 112; 212) with the end (7,8 of described expansion; 107,108; 207) corresponding outer surface is complementary.

3. equipment according to claim 2 is especially for rectilinear tubes (2; 102) wherein, described end formed element (11; 211) along described pipe (2 to be expanded; 102) axis is arranged relative to one another.

4. equipment according to claim 2, especially for crooked 180 ° to form the pipes (102) of hairpin tube, wherein, described end formed element (111) is arranged adjacent to each other.

5. the described equipment of any one according to claim 2 to 4, wherein, described end formed element (11; 111; 211) can be from corresponding described pipe (2; 102; The axial butt position of closure 202) moves to open position.

6. equipment according to claim 1, especially for crooked 180 ° forming the pipes (102) of hairpin tube, described equipment comprises the middle locking member (118) for the ancon section of each described pipe (102).

7. equipment according to claim 1, wherein, described axle (9; 109) comprise that claw keeps bar (13; 113), with described bar (13; 113) all-in-one-piece end claw (14; 114) and can be along described bar (13; 113) the hollow turnover panel expander (15 that slides; 115), described expander (15; 115) can be along described bar (13; 113) slide into expanded position from resting position, in described resting position, described expander (15; 115) withdrawal and described expander (15; 115) external diameter is less than described pipe (2; 102; 202) internal diameter, in described expanded position, described expander (15; 115) against described end claw (14; 114) and described expander (15; 115) have than the described pipe (2 of waiting to be expanded; 102; 202) external diameter that internal diameter is large.

8. equipment according to claim 2, wherein, described axial meeting device (210) comprises for the complementary forming element (220) in the end of the end (207) of each expansion of each pipe of described pipe (202), the complementary forming element in described end (220) is provided with flared surfaces (222) separately, and described flared surfaces (222) is complementary with the corresponding inner surface of the end (207) of described expansion.

9. a utilization described expansion device of according to claim 1 to 8 is carried out is used for convergent divergent channel (2; 102; 202) method, described pipe (2; 102; 202) be inserted into heat exchanger (1; 101) band wing assembly (3; 103) in, it is characterized in that, described method comprises the steps:

Expand described pipe (2; 102; The end of each pipe 202) (7,8; 107,108; 207);

Axially retrain described pipe (2 on shrinkage direction; 102; The end of the described expansion of each pipe 202) (7,8; 107,108; 207);

Expand each described pipe (2; 102; 202) or expand each straight line portion of each described pipe (102).

10. method according to claim 9 wherein, describedly axially retrains described pipe (2 on shrinkage direction; 102; The end of the described expansion of each pipe 202) (7,8; 107,108; 207) step comprises: closure is resisted against the end (7,8 of described expansion; 107,108; 207) the described end formed element (11 on corresponding outer surface; 111; 211).

11. method according to claim 9, wherein, each described pipe (2 of described expansion; 102; 202) or the step of expanding each straight line portion of each described pipe (102) carry out under pulling force and comprise: utilize the described expander (15 that is in resting position; 115) and at described expander (15; 115) external diameter is less than described pipe (2; 102; In the situation of internal diameter 202) with described axle (9; 109) insert each described pipe (2; 102) in or insert step in each straight line portion of each described pipe (102).

12. method according to claim 10, wherein, described under pulling force the expansion described pipe (2; 202) or the step of each straight line portion of described pipe (102) comprise the steps: to reset described claw keep bar (13; 113), cause thus described expander (15; 115) be expanded in expanded position and present than described pipe (2; 102; 202) external diameter that internal diameter is large is until from described pipe (2; 102; 202) take out described axle (9; 109).

13. the described method of any one according to claim 9 to 12 comprises: open described end formed element (11; 111; 211) to take out the pipe (2 with expansion; 102; 202) heat exchanger (1; 101) step.

14. the described method of any one according to claim 9 to 13, especially for crooked 180 ° forming the pipes (102) of hairpin tube, the step that described method comprises locking and again opens subsequently locking member (118) in the middle of described in the ancon section of each described pipe (102).

15. the described method of any one according to claim 9 to 14 is especially for rectilinear tubes (2; 202), wherein, the described pipe (2 of described expansion; 202) described end (7,8; 207) step comprises: enlarge described pipe (2 after the operation of cutting and the described pipe of straightening; 202) first end (7; 207), and at described pipe (2; 202) enlarge described pipe (2 in the situation of the described band wing assembly of insertion (3); 202) the second end (8).

16. the described method of any one according to claim 9 to 14, especially for crooked 180 ° of pipes (102) with the formation hairpin tube, wherein, when inserting in described band wing assembly (103), carries out described pipe (102) step of the described end (107,108) of the described pipe of described expansion (102).