GB2195567A

GB2195567A - Straightening machine roll

Info

Publication number: GB2195567A
Application number: GB8623604A
Authority: GB
Original assignee: URAL NII TRUBNOI PROMY URALNIT
Current assignee: URAL NII TRUBNOI PROMY URALNIT
Priority date: 1986-10-01
Filing date: 1986-10-01
Publication date: 1988-04-13
Anticipated expiration: 2006-10-01
Also published as: FR2604930B1; GB8623604D0; FR2604930A1; GB2195567B; DE3633610A1

Abstract

The roll comprises a rigid shaft (1) and an elastic sleeve (3) positioned concentrlcally on it. On the shaft (1) at both ends (10) of the sleeve (3) rigid supports (14) are provided, made in the shape of truncated cones, facing each other with their smaller faces. The rigid supports (14) are pressed with their conical surfaces (15) to the sleeve (3). This roll features a high wear resistance of the external working surface (11) of the sleeve (3) and ensures straightening of thin-walled precision tubes of a high quality. A gap may be provided between the sleeve (3) and shaft (1) with liquid supply to it via the shaft. Alternatively, a resilient bushing may be located between the sleeve and shaft. <IMAGE>

Description

SPECIFICATION Straightening machine roll The present invention relates to rolls for tube or rod working machines, especially straightening machines.

Most advantageously the present invention may be used in concave roll tube straighteners for straightening thin-walled precision tubes.

A roll of the straightening machine, made according to the present invention, may be used also as a bending roll in bending machines, as well as a transporting roller in charging-discharging devices of straighteners and other machines.

Known in the art is a roll of the straightening machine (see, for example, the book of Semenenko U.L. "Finishing shapes and tubes by pressure". Moscow, "Metallurgia" publishing House, 1972, p.163, Fig.78-e).

The known roll of the straightening machine comprises a metal rigid shaft and an elastic sleeve arranged concentrically on the shaft.

The elastic sleeve has end surfaces, which are perpendicular to the geometrical axis of the rigid shaft, an external working surfacs designed for interacting with the tube to be worked, and an internal surface. The external surface of the sleeve is curvilinear to provide a contact with the tube during the straightening process.

Between the shaft and the internal surface of the sleeve there is a metal bushing engaged with the rigid shaft through a key. The elastic sleeve is in interference fit with the metal bushing.

The external working surface of the elastic sleeve of the prior-art roll has an insufficient wear resistance.

This can be explained by the fact that when the elastic sleeve is in contact with the tube being straightened, high tension stresses arise in the external working surface, resulting in increasing surface microcracks and cuts and finally in failure of the external working surface of the elastic sleeve. Microcracks and cuts usually appear on the external working surface of the elastic sleeve due to contact of the elastic sleeve with the end face of the tube being worked, when it enters the machine and goes out.

Besides, the elastic sleeve is under high cyclic loads during straightening, and this results in high stresses and heating of the most loaded portion of the sleeve and in subsequent failure of the structure, i.e. a failure, which is associated with changes in the mechanical characteristics of the elastic material upon heating.

Besides, the prior art roll of the straightening machine does not provide high quality of straightening of thin-walled tubes of a wide curvature range, because the external working surface of the elastic sleeve is made in the shape corresponding to a definite size and length of the longitudinal curvature of the tube. When going over to straightening a different size of tubes this definite profile of the external working surface of the elastic sleeve does not provide the full contact of the elastic sleeve with the tube, this resulting in the origination of creases, folds and other defects on the external surface of thin-walled tubes. To change the profile of the external working surface of the elastic sleeve, it is necessary to stop and dismount the straightening machine, to change the roll or turn it down on a lathe and adjust.

The object of the present invention is to provide such a roll for straightening machines, whose design would permit to increase the wear resistance of the roll and improve the quality of straightening of tubes of different sizes and curvatures.

This object is accomplished by that in a roll of the straightening machine, comprising a rigid shaft and a sleeve, arranged concentrically on it, according to the invention, rigid supports are provided on the rigid shaft at both sides of the elastic sleeve, said support being made in the form of truncated cones with their smaller sides facing each other and with their conical surfaces pressed to the elastic sleeve.

The provision of the above-described rigid supports with conical surfaces permits the creation of a zone of all-round compressive stresses in the external working surface of the elastic sleeve during assembling the straightening machine roll, this ensuring an increase in the wear resistance of the roll of the straightening machine.

These compressive stresses decrease the microcrack and cut formation on the external working surface of the elastic sleeve, when it is in contact with the tube ends at the moment of tube entering the straightening machine and going out, and thus increse the wear resistance of the roll of the straightening machine in general.

It is expedient that the surface of the both ends of the elastic sleeve should be made in the form of truncated cones pressed to the conical surfaces of the rigid supports.

The truncated cone shape of the both end surfaces of the elastic sleeve permits, during the axial movement of the rigid supports in assembling, to create sufficient forces of friction between the conical surfaces of the rigid supports and the elastic sleeve, which rules out the necessity to use fixing means for transferring the torque from the rigid shaft to the elastic sleeve.

It is advisable to have a gap between the inner surface of the elastic sleeve and the rigid shaft, to make axial and radial channels in the rigid shaft for the supply of a liquid medium into this gap, and to make through radial holes in the elastic sleeve, which are commu nicated with this gap.

The provision of the channels in the rigid shaft and the radial holes in the elastic sleeve, which are communicated with the gap between the inner surface of the elastic sleeve and the rigid shaft, facilitates intensive cooling of the inner and. external surfaces of the elastic sleeve, which are most exposed to the destructive wear and failure, especially when the roll of the straightening machine is used for straightening tubes.

An intensive cooling of the elastic sleeve reduces the heating of the roll during straightening, thus increasing its wear resistance.

Besides, the provision of the gap between the inner surface of the elastic sleeve and the rigid shaft increasing the contact surface area between the roll of the straightening machine and the tube and reduces the specific contact loads (stresses) on the external working surface of the elastic sleeve, what also increases the durability and wear resistance of the roll of the straightening machine.

It is also advisable to have a resilient bushing located on the rigid shaft between the elastic sleeve and the rigid shaft and pressed to the rigid supports with their ends and to the inner surface of the elastic sleeve with their external surfaces.

The resilient bushing positioned between the elastic sleeve and the rigid shaft and squeezed with the rigid supports creates compressive stresses on the inner surface of the elastic sleeve, which preclude the expanding and spreading of microcracks on the inner surface of the elastic sleeve, and, therefore, increase the wear resistance of the roll of the straightening machine as a whole.

Besides, the provision of the resilient bushing, positioned between the sleeve and the rigid shaft, permits to making the roll of the straightening machine with a variable rigidity, that is with a smaller rigidity in the middle portion and with a higher rigidity in the end portions thereof.

Straightening thin-walled tubes with the rolls of variable rigidity provides a more uniform distribution of pressure rendered by the roll of the straightening machine to the tube being straightened; this minimizes the danger of surface defects (folds, creases, etc.) on the thinwalled tubes being straightened.

It is preferable that the axial length of the resilient bushing in free state should be 0.250.55 of the full axial length of the elastic sleeve, and the thickness of the elastic sleeve wall should be 0.67--0.89 of the axial length of the resilient bushing in free state.

The above-stated size ratio of the resilient bushing and the elastic sleeve makes it possible to create a zone of all-round compression in the middle portion of the elastic sleeve during roll assembling, this, in its turn, resulting in increasing the cyclic strength of the elastic sleeve.

It has been experimentally found,that if the length of the resilient bushing "1" is less than 0.25 of the full axial length "L" of the elastic sleeve, the compressive stresses are not spread throughout the full thickness "t" of the elastic sleeve. This decreases the cyclic strength of the elastic sleeve.

When the length "1" of the bushing is more than 0.55 of the total length "L" of the elastic sleeve, the lengths of the conical surfaces of the rigid supports are not enough to originate the force of friction providing the transfer of the torque from the rigid shaft to the elastic sleeve.

It was also corfirmed by experiments, that if the ratio of the thickness "t" of the wall of the elastic sleeve and the length "1" of the resilient bushing in free state is less than 0.67, the elastic sleeve due to its low rigidity broadens (expands) along the full length of the elastic sleeve without bending under the action of the rigid supports; this results in the origination of tension stresses along the full length of the elastic sleeve and in a great decrease of the wear resistance of the roll of the straightening machine.

With an increase of the width "t" of the elastic sleeve wall over 0.89 of the length "1" of the resilient bushing in free state the elastic sleeve bending resistance greatly increases, whereby big axial compressive pressure is required when assembling the roll of the straightener and this, in its turn, results in greater deformation of the end portions of the elastic sleeve and cracking of its ends.

Therefore, the roll of the straightening machine, made according to the present invention has the external working surface of the elastic sleeve of a rather high wear resistance and provides a high quality of straightening of thin-walled and very thin-walled precision tubes.

The above-said and other advantages of the present invention will be more apparent from the following description of an embodiment of the invention taken with reference to the accompanying drawings, in which: Fig. 1 is a schematic diagram of a straightener roll made according to the present invention, a sectional view with a cutout in the rigid shaft; Fig.2 is the same for an embodiment with a resilient bushing positioned between the elastic sleeve and the rigid shaft and set on the rigid shaft between rigid supports.

A roll of the straightening machine referred to hereinbelow as a "roll" made according to the present invention comprises a rigid shaft 1 (Fig.1) with a geometrical longitudinal axis 2 and an elastic sleeve 3 installed concentrically on it.

The rigid shaft 1 is of a stepped shape with a central portion 4 of the shaft 1 having a surface 4a curvilinear and concave to the axis 2 the generatrix of the surface 4a being an arc of a circumference.

End portions 5 of the central portion 4 have cylindrical surfaces, and to the end portions 5 there are adjoined threaded portions 6, to which there are adjoined cylindrical portions 7.

The cylindrical portions 7 are designed for interaction with bearings (not shown) of conventional design, which are parts of the straightener.

The diameter of the threaded portion 6 is less than the diameter of the end portions 5 of the central portion 4, and the diameter of the cylindrical portions 7 is less than the diameter of the threaded portions 6.

The cylindrical parts 7 pass into end portions 8 and 8a of the shaft 1, one end portion 8 of which (left in Fig.1) has a key slot 9 designed for positioning a key (not shown) therein and used for connecting the shaft 1 with a drive (not shown) of any conventional design.

The roll shown in Fig. 1 may be used as an idle roll. In this case there is no key slot 9 in the cylindrical portion.

The elastic sleeve 3 has ends 10, an external surface 11 and an inner surface 12, between which and the curvilinear surface 4a of the central portion 4 of the shaft 1 there is a gap 13.

At both sides 10 of the sleeve 3 there are rigid supports 14 installed on the shaft 1, which are made in the form of truncated cones with their smaller sides directed to each other and with their bigger sides pressed to the sleeve 3.

The surfaces of both ends 10 of the sleeve 3 are made in the form of the truncated cones conjugated with the conical surfaces 15 of the rigid supports 14 and pressed to them.

Between the bigger sides of the truncated cones of the sleeve 5 there is its external working surface 11, and between the smaller sides there is its inner surface 12.

Each support 14 has an external surface 15a of rounded shape most remote from the axis 2 and slightly protruding over the working surface 11 of the sleeve 3.

This is done to avoid contact between the tube ends and the bigger sides of the truncated cones of the elastic sleeve 3 and therefore to preclude its failure when straightening tubes of a big curvature. The end surfaces 16 of the rigid supports 14 are perpendicular to the geometrical axis of the shaft 1.

Each support 14 has an axial hole 17 of a steeped shape. The portion 17a of smaller diameter of the hole 17 of each support 14 has a thread for contact with the threaded portion 6 of the shaft 1. The portion 17b of the bigger diameter is of cylindrical shape for holding the support 14 in the end portions 5 of the central portion 4 of the shaft 1.

An axial channel 18 and a radial channel 19 are made in the shaft for feeding a cooling medium from a source (not shown) into the gap 13 between the rigid supports 14, the inner surface 12 of the elastic sleeve 3 and the rigid shaft 1.

The channel 18 is made along the geometrical axis 2 of the shaft 1 up to the middle of the central portion of the shaft 1; the channel 19 is made perpendicular to the axis 2 and communicated with the channel 18 and the gap 13.

There is a plurality of through radial holes 20 in the sleeve 3, which are communicated with the gap 13.

It is most advisable to use the roll of such a design as an idle roll or a driving roll in the bending case (not shown) of the straightener.

In other embodiment shown in Fig. 2 the roll comprises a rigid shaft 21 with a geometrical longitudinal axis 22 and an elastic sleeve 23 positioned concentrically on the rigid shaft 21.

The rigid shaft 21 is of a stepped shape.

The central portion 24 of the shaft 21 is of cylindrical shape and to its both sides there are adjoined threaded portions 25, to which cylindrical portions 26 are adjoined. The cylindrical portions 26 are designed for contact with bearings (not shown) of a conventional design.

The threaded portions 25 are of a smaller diameter than the central portion 24 and the cylindlical portions 26 are of a smaller diameter than the threaded portions 25.

The cylindrical portions 26 go on to the end portions 27 and 27a of the shaft 21, one end portion 27 of which (the left one in Fig.2) has a key slot 28 designed for positioning therein a key (not shown) used for engaging the shaft 21 with a drive (not shown) of the known design.

The elastic sleeve 23 comprises ends 29 positioned perpendicular to the axis 22, an external working surface 30 and an inner surface 31, between which and the central portion 24 of the shaft 21 there is a space wherein a resilient bushing 32 is positioned.

In both ends 29 of the elastic sleeve 23 there are installed on the rigid shaft 21 rigid supports 33, which have the shape of truncated cones facing each other with their smaller sides and pressed with their conical surfaces 34 to the inner surfaces 31 of the sleeve 23.

The inner ends 35 of the supports 33 are the smaller sides of the truncated cones and the external ends 36 of the support 33 are the bigger sides of the truncated cones. The ends 35 and 36 are perpendicular to the axis 22.

On the threaded portions 25 of the shaft 21 nuts 37 are screwed, which are pressed to the external ends 36 of the rigid supports 33 and designed for holding down the supports 33 to the inner surface of the elastic sleeve 23.

The resilient bushing 32 is set on the shaft 21 between the supports 33 and pressed to its ends, while its external surface is pressed to the inner surface 31 of the sleeve 23.

The resilient bushing 32 is designed for creating a pressure on the inner surface 31 of the elastic sleeve 23 and transferring the torque from the shaft 21 to the elastic sleeve 23.

The axial length "1" of the resilient bushing in free state before roll assembling, measured along the axis 22, is 0.25-0.55 and in the given case 0.45 of the full axial length "L" of the elastic sleeve 23.

The wall thickness "t" of the elastic sleeve 23 is 0.67-0.89 and in this example 0.7 of the axial length "1" of the resilient bushing 32 in free state, i.e. before roll assembling.

The above-said ratio of the wall thickness "t" of the elastic sleeve, the length "L" of the elastic sleeve and the length "1" of the resilient bushing in free state has been determined experimentally and provides a zone of all-round compression in the elastic sleeve during the roll assembling, thus increasing the wear resistance of the elastic material.

It is advisable to use the roll of such a design in entry-and exit stands (not shown) of the straightener.

The roll of the straightener accomplished in the embodiment shown in Fig. 1 operates as follows.

Before installing into a straightener, in this case, in a tube straightener, and before its use the roll is assembled. The elastic sleeve 3 is installed on the central portion 4 of the rigid shaft 1. On the threaded portions 6 of the shaft 1 the rigid supports 14 are screwed, which with their truncated conical surfaces 15 are pressed to the conical ends of the elastic sleeve 3. Due to axial compression of the ends of the elastic sleeve 3 with the rigid supports 14 its initial cylindrical external surface 11 acquires a slightly concave shape, which is necessary for providing stable holding of a tube when it enters the straightener.

Such an assembly of the straightener roll provides sufficient forces of friction between the conical surfaces 15 of the rigid supports 14 and the ends of the elastic sleeve 3, which eliminate the necessity to use additional fixing means for transferring the torque from the shaft 1 to the elastic sleeve 3 during tube straightening. The assembled roll is installed in the bearings of the straightener.

During straightener operation the rotation from the drive is transferred via a key to the shaft 1 and further through the rigid supports 14 to the elastic sleeve 3.

In the process of tube straightening the elastic sleeve 3 interacting with the tube is first bent down, filling the gap 13 and then is compressed (deformed) along the concave surface 4a of the central portion 4 of the shaft 1.

Due to the initial bending deformation of the elastic sleeve 3 the contact surface area between the roll and the tube (not shown) increases and correspondingly the contact loads on the external working surface 11 of the elastic sleeve 3 diminish, this resulting in an increase of its longevity and wear resistance.

During the straightening process while the roll is rotating, into the gap 13 between the inner surface 12 of the elastic sleeve 3 and the rigid shaft 1 through the channels 18 and 19 a cooling liquid medium, in this case an emulsion, is fed, which cools the inner surface of the elastic sleeve and then goes through the radial holes 20 to the external working surface 11 of the elastic sleeve 3. The intensive cooling of the inner and external surface of the elastic sleeve excludes heating and failure of the structure of the elastic sleeve during the tube straightening process.

The roll of the straightener accomplished in the embodiment shown in Fig. 2 is assembled as follows.

On the central portion 24 of the rigid shaft 21 the resilient bushing 32 is installed, and then, on it, the elastic sleeve 23 is mounted on it. At the initial moment of roll assembling there is a fit-up gap between the inner surface 31 of the elastic sleeve 23 and the external surface of the resilient bushing 32.

The rigid supports 33 are placed to the ends 29 of the elastic sleeve 23. The nuts 37 while being screwed down on the threaded portions 25 of the shaft 21 press with their ends the external ends 36 of the rigid supports 33. Under the action of the nuts 37 the rigid supports 33 move along the shaft 21 pressing with the conical surfaces 34 the inner surface 31 of the elastic sleeve 23 and bending it in the plane passing through the axis 22 of the shaft 21.

Due to this the cylindrical elastic sleeve 23 acquires a slightly concave shape, as shown in Fig. 2. Further screwing down of the nuts 37 and axial movement of the rigid supports 33 to the bushing 32 cause the interaction between their inner ends 35 and the ends of the resilient bushing 32; the latter becomes compressed and its diameter increases.

An increase in the diameter of the resilient bushing 32 results in filling up the gap between the inner surface 31 of the elastic sleeve 23 and the external surface of the resilient bushing 32. This creates an additional pressure rendered to the inner surface 31 in the central portion of the elastic sleeve 23 and provides a reliable engagement of the elastic sleeve 23 with the central portion 24 of the rigid shaft 21.

With such an assembly of the straightener roll, in the elastic sleeve middle portion 23a adjoined to the resilient bushing 32 it is created a zone of all-round compression is created, which increases the wear resistance of the elastic sleeve during its interaction with the tube being straightened. The assembled roll is installed in the bearings of the straightener.

During the straightener operation the rotation from the drive is transferred through the key positioned in the key slot 28 of the end portion 27 of the shaft 21. From the shaft 21 the torque is transferred to the rigid supports 33 and the resilient bushing 32 and through them to the elastic sleeve 23.

During the straightening process the elastic sleeve 23 interacting with the tube is elastically deformed, thus increasing the contact surface area between the roll and the tube being straightened.

The provision of the resilient bushing 32 reduces the rigidity of the middle portion 23a of the elastic sleeve and provides a possibility for additionally increasing the contact surface and for a more uniform distribution of the roll pressure onto the tube being straightened, this, in its turn, diminishing the danger of defects (folds, etc.) being formed on the thinwalled tubes during the straightening process.

Pilot straightener rolls made according to the present invention have successfully passed comprehensive tests.

The results of the tests have confirmed an increase in the durability of the roll with the elastic sleeve and the rigid supports as well as an improvement in the quality of the straightened thin-walled precision tubes.

Straightening thin-walled tube by the rolls of the invention provides: ~high quality of the external surface (no dents, ovality, screw-marks) of the tubes of improved elasticity; ~reduction of residual stresses in tubes; -no strain hardening or changes in the mechanical properties of tubes after straightening; ~enlarging the range of thin-walled and very thin-walled tubes to be straightened.

Moreover, straightening of the tube length curvature is done per one pass, which enables installing the straightener with the rolls of the invention in a continuous tube production line.

Claims

1. A roll for a tubs or rod working machine, comprising a rigid shaft and an elsastic sleeve arranged concentrically on it, with rigid supports on the rigid shaft at both ends of the elastic sleeve, which are made in the form of truncated cones, facing each other with their smaller sides and pressed with their conical surfaces to the elastic sleeve.

2. A roll as claimed in claim 1, wherein both elastic sleeve end surfaces are made in the shape of truncated cones pressed to the conical surfaces of the rigid supports.

3. A roll as claimed in Claims 1, 2, wherein a gap is provided between the inner surface of the elastic sleeve and the rigid shaft, the rigid shaft has axial and radial channels for the supply of a liquid medium into said gap, and the elastic sleeve has through radial holes, communicated with said gap.

4. A roll as claimed in Claim 1, wherein a resilient bushing is provided on the rigid shaft between the elastic sleeve and the rigid shaft and pressed with its ends to the rigid supports and with its external surface to the inner surface of the elastic sleeve.

5. A roll as claimed in Claim 4, wherein the axial length of the resilient bushing in free state is 0.25-0.55 of the full axial length of the elastic sleeve, and the wall thickness of the elastic sleeve is 0.67-0.89 of the axial length of the resilient bushing in free state.

6. A roll according to claim 1, substantially as described with reference to Figure 1 or Figure 2 of the accompanying drawings.

7. A tube straightening machine having a roll according to any one of the preceding claims.