EP1088605B1

EP1088605B1 - Process and apparatus for continuous production of corrugated metal pipe with parallel ridges

Info

Publication number: EP1088605B1
Application number: EP00120973A
Authority: EP
Inventors: Giuseppe Brega; Vittorio Travini
Original assignee: Olimpia 80 SRL
Current assignee: Olimpia 80 SRL
Priority date: 1999-10-01
Filing date: 2000-09-27
Publication date: 2006-05-03
Anticipated expiration: 2020-09-27
Also published as: ITMI992053A0; EP1088605A3; IT1313765B1; ITMI992053A1; DE60027658D1; ATE324950T1; EP1088605A2; ES2264412T3; DE60027658T2

Abstract

A metal pipe (T) is fed at a first speed into a space between delimited successive contiguous mechanical corrugators (34, 38), each of which turns around an axis coinciding with the axis of the pipe (a) and is disposed eccentrically with respect thereto and has a spiral inner corrugating surface with its axis (b, c) offset with respect to the axis of the pipe and a diameter greater than the diameter of the pipe. The corrugated pipe (TC) is extracted at a second speed lower than the first speed. An appropriate coordination between the input speed, the output speed and the pitch of the spirals of the corrugating fixtures allows corrugated metal pipes with parallel annular ridges to be produced continuously. <IMAGE>

Description

The invention relates to the field of production of corrugated metal pipes.
There is a wide demand for corrugated metal pipes on the market for gas installations, for sanitary fixtures and heating systems or also for marine systems, to replace the flexible plastic or rubber pipes used until now which no longer comply with standards or in any case are deemed not sufficiently reliable.
A large proportion of the corrugated metal pipes on the market at present has a spiral corrugation obtained continuously by means of corrugating fixtures also having a spiral shape. However, there is currently a greater demand for metal pipes, particularly in stainless or tempered steel, provided with a ring-type or parallel ridge-type corrugation, in that it has been found that they have greater flexibility and are therefore more desirable.
The corrugated pipes with parallel-ridge corrugation on the market at present are generally obtained by means of a discontinuous process which uses dies on a press, or by means of a process of hydroforming, again discontinuous, which provides for introduction of water into sections of pipe wherein the water, under pressure, presses the pipe against an outer die.
Production with a discontinuous process is necessarily slow and therefore costly.
Continuous processes and apparatuses for forming annular corrugations in metal pipes through at least one corrugator tool are known, for example, from documents US-A-4 435 968, US-A-3 788 113 and US-A-3 572 074.
The object of the present invention is to simplify and speed up the production of metal corrugated pipes with parallel ridges.
Another object is to form corrugated metal pipes with parallel ridges that have constant properties along their entire length.
A further object is to make an apparatus for production of corrugated metal tubes with parallel ridges that can operate completely automatically.
These objects have been achieved with a procedure as stated in claim 1 and an apparatus as stated in claim 3.
In other words, according to the new process a pipe to be corrugated (fed inside a corrugating assembly at a first speed or input speed and extracted from the corrugating assembly at a second speed, or output speed, lower than the input speed) is subjected to the combined action of at least three idle, offset, spiral corrugating toothings, with a greater diameter than the pipe, rotationally driven around the axis of the pipe; the pitch of the thread of the corrugating toothings and the feed speed of the pipe being correlated with each other.
The new process includes the further step of adjusting the distance of the rotation axes of the corrugating toothings from the axis of the pipe.
The corrugating apparatus comprises at least three corrugating fixtures with an inner corrugating thread, having an inner diameter greater than the diameter of the pipe on which they must operate, and disposed one after the other along the axis of travel of the pipe, offset with respect to said axis and preferably adjustable in position at right angles to said axis. It further comprises a mandrel containing said fixtures and rotatable around an axis coinciding with the axis of the pipe, means for rotating said mandrel around the tube axis and means for adjusting the distance of the rotation axes of said fixtures from the mandrel axis. It then comprises an upstream draft device and a downstream draft device to determine an input pipe speed and an output pipe speed.
The new procedure and the new apparatus make it possible to obtain corrugated metal pipes with parallel ridges in a continuous process and with substantially constant characteristics along the length of the pipe. Furthermore, they allow the height of the corrugation ridge to be regulated.
An apparatus and the relative process will be explained below with reference to the appended figures in which:

Figure 1 is a side elevational view on a reduced scale of a portion of the apparatus;
Figure 2 is a top plan view of the apparatus shown in Figure 1;
Figure 3 shows the corrugation assembly of Figure 1, in an enlarged, part-sectional view taken in a vertical plane along the axis thereof;
Figure 4 is a vertical axial sectional view of a detail of the assembly in Figure 3; the illustration is enlarged with respect to Figure 3;
Figure 5 is a front elevational view of the assembly, from the left with respect to Figure 3;
Figure 6 is a part-sectional side view of a portion of corrugated pipe obtained with the apparatus and process.

The above mentioned apparatus and process do not fall within the scope of the invention only in that they provided two corrugating fixtures means instead of the claimed three corrugating fixtures; a preferred embodiment of the means for adjusting the distance of the rotation axes of said fixtures from the mandrel axis is disclosed with reference to appended figure 4.
With reference firstly to Figure 1, a production line for corrugated pipes comprises a first upstream drive or draft device, referenced 2, a second downstream drive or draft device, referenced 4, and a corrugating assembly referenced 10. The upstream and downstream drive devices 2, 4 are of a per se known type and generally comprise two collaborating tracks, 2a, 2b and 4a, 4b, respectively, of rubber or similar material; the facing portions of the tracks of each device move at the same speed to convey a pipe in the direction of the arrow F.
A smooth incoming pipe T generally comes from an upstream forming device, not shown, which can be, for example, a longitudinal welder, per se known. The smooth pipe T is gripped between the tracks 2a, 2b of the drive device 2 and fed at a first speed, or input speed, through a guide bushing 9 to the corrugating assembly 10.
The corrugating assembly will now be described, with reference particularly to Figures 3 and 4.
A fixed annular seat 14 that houses two conical bearings, 15 and 16 respectively, is mounted on a base 12. Integral with the inner rings of the bearings 15 and 16 is a sleeve 20, which is therefore rotatable around the longitudinal axis a. A tubular member 22 having its axis coincident with a is mounted within sleeve 20. The member 22 is carried on the sleeve 20 by means of bearings 23, and is thus free in rotation with respect to the sleeve. The seat 14 carries integrally a mandrel denoted as a whole by 24, which will be further described below, which carries two corrugating devices denoted respectively by 26 and 28. The corrugating devices are carried by the mandrel on respective slides 30, 32 and precisely the device 26 is fixed on the slide 30 and 28 on the slide 32.
The device 26 carries a corrugating fixture 34 by means of a bearing 36; the corrugating fixture has an inner spiral shaped corrugating surface 37 with its axis b parallel and at a distance with respect to the axis a.
The corrugating device 28 carries a corrugating fixture 38 by means of a bearing 40 and the corrugating fixture 38 is similar to 34, that is to say it has a spiral-shaped inner surface 39, and it has a longitudinal axis c spaced from axis a and axis b; in particular in this case it is coplanar with said two axes and on the opposite side of a with respect to b.
Each corrugating fixture 34 and 38 is thus idle around its own axis a or c and is rotationally driven around axis a.
The mandrel further carries a guide bushing 42, generally made of bronze or a low-friction material, to guide an outgoing corrugated pipe.
The smooth incoming pipe T has its own axis aligned and coinciding with the axis a.
Rotation around the axis a is imparted to the sleeve 20, the mandrel 24 and the connected parts from a motor 44, through a shaft 46, a double pulley 48, belts 50 and a further pulley 52 integral with the sleeve.
The slides 30, 32 are preferably radially adjustable in position on the mandrel 24, that is to say, it is possible to adjust the distance between the axes b, c and the axis a by a certain amount, according to the diameter of the pipe T to be corrugated.
A position adjustment device is shown in Figure 4 and comprises a sleeve 54, applied to one end of the tubular member 22 by means of a threaded coupling 55. The sleeve 54 has a conical tongue 56 that is received in a corresponding groove, respectively 57 in the slide 30 and 58 in the slide 32. The grooves 57 and 58 extend only for an arc of the conical surface. A rotation imparted to the member 22 in any way (for example through adjustment means 60 at the end thereof on the right in the figures) causes extension or retraction respectively of the sleeve 54.
Extension (towards the left in Figure 3) of the sleeve 54 reduces the distance between the axes b and c (which remain symmetrical with respect to the axis a); movement of the sleeve 54 towards the right in Figure 3 increases the distance between the axes b and c (symmetrically with respect to the axis a).
Operation of the apparatus will now be described.
The fixtures 34 and 38 (axes b and c) are adjusted according to the diameter of the pipe T to be corrugated. The speeds of the upstream draft device and the downstream draft device are then adjusted according to the pitch of the spirals of the fixtures 34 and 38, generally on an tentative basis. The sleeve and the connected parts are then rotated around axis a from the motor 44. The smooth pipe T is introduced continuously, at the end on the left in the figures, advances in the direction of the arrow F and exits as a corrugated pipe TC. The spirals of the corrugating fixtures 34 and 38 cause a deformation of the side wall of the pipe turning all around it. It is seen that in practice each fixture provides a force contrasting the force exerted by the other fixture at all times.
The correlation between the feeding speed of the pipe, the rotational speed of the spirals of the fixtures and the pitch of the spirals thereof determines the corrugation with parallel ridges of the pipe TC. The pitch of the parallel ridges of the pipe TC can be increased or decreased by increasing or decreasing the speed of the downstream draft device 4.
It should be noted that, although the embodiment shows an apparatus equipped with two corrugating fixtures 34 and 38, three or more corrugating fixtures could nevertheless be mounted on the mandrel, disposed with the respective axes offset in a uniform manner around the axis a.
It should also be noted that the apparatus described makes it possible to work on pipes with different diameters by changing the corrugating devices on the slides 30, 32; in Figure 4 references 31 are the axes of fixing means for fixing the device 26 on the slide 30 and references 33 are the axes of fixing means for fixing the corrugating device 28 on the slide 32.

Claims

A process for producing a corrugated metal pipe (TC) with parallel ridges, where a first speed (or input speed) of the pipe (T) to be corrugated and a second speed (or output speed) of the corrugated pipe (TC), lower than the input speed, are determined;
characterized in that the surface of the pipe is subjected to the contrasting actions of at least three spiral profiles - or work surfaces - positioned inside a mandrel (24) driven in rotation around the axis (a) of the pipe (T) but idle around respective axes different each other and offset with respect to the axis (a) of the pipe (T),
and in that the distance of the axes of said spiral profiles from the rotational axis (a) of the mandrel (24) is adjusted through adjusting means comprising:
- a slide for each corrugating fixture, each slide having an inclined groove;

- an adjustment member (54) translatable axially along the rotational axis (a) of the mandrel (24) and provided with inclined tongues (56) in sliding engagement with said inclined grooves.
A procedure according to claim 1, characterized in that the output speed of the corrugated pipe (TC) is adjusted to adjust the pitch of the corrugations with parallel ridges of the pipe produced (TC).
An apparatus for continuous production of corrugated metal pipes (TC) with parallel ridges, comprising:
- a mandrel (24) rotatable around an axis (a) of rotation, said mandrel (24) receiving idle corrugating fixtures with respective axes different each other, parallel and at an equal distance from the axis of rotation (a) of the mandrel (24);

- means for rotationally moving said mandrel (24) around said axis of rotation (a), and

- drive means (2, 4) upstream and downstream of the mandrel (24) to produce feeding of the pipe (T, TC);
characterized in that it further comprises:
- at least three corrugating fixtures, each equipped with an inner spiral corrugating surface, with a larger diameter than the diameter of the pipe (T) to be processed, each of said corrugating fixtures being mounted idle around its own axis; and

- means for adjusting the distance of the axes of the corrugating fixtures from the rotational axis (a) of the mandrel, said adjusting means comprising:

- a slide for each corrugating fixture, each slide having an inclined groove;

- an adjustment member (54) translatable axially along the rotational axis (a) of the mandrel (24) and provided with inclined tongues (56) in sliding engagement with said inclined grooves.
An apparatus according to claim 3, characterized in that said driving means (2, 4) for the pipe (T, TC) comprise an upstream drive or draft device (2) and a downstream drive or draft device (4), which are adjustable to different feeding speeds.
An apparatus according to claim 3, characterized in that said corrugating fixtures are mounted in adjacent positions along a direction of travel of the pipe (T).
An apparatus according to claim 3, characterized in that said corrugating fixtures are interchangeable on the mandrel (24).
An apparatus according to claim 1, characterized in that it comprises a tubular element (22) disposed with its axis coinciding or parallel to the axis (a) of the mandrel (24) and engaged with said adjustment member (54) to determine feeding thereof.
An apparatus according to claim 3, characterized in that said at least three corrugating fixtures are disposed with their axes offset with respect to the rotational axis (a) of the mandrel (24) and angularly equidistant around said axis (a).
An apparatus according to claim 3, characterized in that it comprises a guide bushing (9) to guide the pipe (T) upstream of the corrugating fixtures and a guide bushing (42) to guide the pipe (TC) downstream of the corrugating fixtures.
An apparatus according to claim 9, characterized in that the downstream guide bushing (42) rotates with the mandrel (20).