EP0663860A1

EP0663860A1 - Plate bending machine

Info

Publication number: EP0663860A1
Application number: EP93922129A
Authority: EP
Inventors: Lars-Olof Ragnmark
Original assignee: BJOERK REIDAR; Bjork Reidar
Current assignee: Nya Nossebro Mekaniska Verkstad AB
Priority date: 1992-10-05
Filing date: 1993-10-05
Publication date: 1995-07-26
Anticipated expiration: 2013-10-05
Also published as: DE69323089D1; SE9202912L; AU5124293A; ATE175597T1; DE69323089T2; SE9202912D0; WO1994007622A1; EP0663860B1; SE505964C2

Abstract

A plate bending machine (1) for bending sheet metal into completely or partly circular profile members, such as pipes or profile members bent into a U-shape, of a kind wherein the bending is effected with the aid of one stationary roll (2) and a plurality of ointerconnected rolls (3-5) supported in a signal, common bearing unit (6), such as a roll cradle (6), which bearing unit (6) consists of a first cradle part (7) and of a second cradle part (8) each one of which supports the associated rolls (3-5) by the roll ends, and wherein the bearing parts are supported in the machine frame in such a manner that each cradle roll is supported at both its ends, and wherein the bearing parts (7, 8) and the cradle rolls are interconnected so as to form an integrated installation unit (9) which may be removed from the machine as one single piece. The detachment of the installation unit is facilitated in that its attachment means in the associated side of the machine is arranged for sliding movement, normally in the vertical direction, and that this slidability is extended at one end wall (12) of the machine to the end of the machine side and out of the latter.

Description

PLATE BENDING MACHINE

TECHNICAL FIELD

The subject invention concerns a machine for bending sheet metal into completely or partly circular profile members, such as pipes or profile members bent into a U- shape, of a kind wherein the bending is effected with the aid of one stationary roller and a plurality of inter¬ connected"rolls mounted in a single, common bearing unit.

BACKGROUND OF THE INVENTION

For circular bending of sheet metal into completely or partly circular profile members machines known as plate beinding machines are used. The plate or sheet metal is bent into a fully circular piece whereupon it is removed from the machine and welded. By welding together the edges of the originally open profile member a closed tube is obtained. Also profile members configured as a simple U or in the shape of two combined U-shapes may be produced in this manner. The plate bending machines normally used include three or four rolls, which normally assume fixed positions during the rolling. One consequence of this is that a flat area is produced adjacent each free edge.

Obviously this is awkward, particularly in tube-bending operations. It is in the light of these facts that an Italian machine has been developed, wherein the three subjacent rolls are kept together by means of one mounting unit or roll cradle. An air-cylinder turns the cradle clockwise to one end position and anti-clockwise to another end position. Owing to this arrangement it becomes possible to bend the entire plate, including the free edge, allowing a tube having the desired bent shape to be produced. A feature common to all prior-art types of plate bending machines is that it is very complicated to replace the rolls in the machine. The rolls must be removed one by one in connection with dismantling of the machine. Removal of the rolls and replacement thereof by fresh rolls there¬ fore is a time-consuming task. This is a serious problem, since causes to exchange rolls arise frequently. The reasons therefor are that different materials require rolls having different surface structures and that some materials, such as galvanized sheet, tend to form deposits on the rolls with consequential cleaning of the rolls becoming necessary. In addition, different materials have different bending resistance and it is also considerably more difficult to bend thick sheets than thin ones. For instance, bending of igslvanized sheet having a thickness of 1 mm could be performed by means of roll having a diameter of 70 mm but the same roll cannot be used to bend stainless steel sheet metal having a thickness of 1.5 mm. One reason therefor is that impurities that the galvanized sheet may deposit on the 70 mm diameter roll could adhere to the surface of the stainless steel sheet and damage it and another that a 70 mm diameter roll is not sufficiently rigid to correctly bend the thicker stainless steel sheet because of the flexing of the rolls during the bending operation. For instance, if a tube were then to be bent there would be no even-width spacing between the free edges that are to be welded together. In addition, the roll diameter imposes limits as to the minimum bending diameter that may be achieved. In all, this means that the rolls must be replaced often, which leads to lengthy standstills and a low rate of productivity.

The prior-art machine including the turnable roll cradle has some other limitations in addition to the draw¬ backs outlined above. Its roll cradle is positioned at the centre of the rolls. The consequence of this position is a lack of proper support of the roll ends. For this reason, the rolling operation must be performed close to the middle in order to give a correct result. When the rolling operation is effected across the entire width of a stiff sheet metal material the roll ends flex more heavily outwards and the bending result will be unsatisfactory. In addition, the roll cradle can be turned by the air cylinder only to the set end positions. One such end position is e.g. bending to the smallest possible diameter. This arrangement allows the use of the largest possible roll diameters for a predetermined curvature, which is advantageous considering the limited roll stability of the machine. Bending of the material to a larger diameter size would require resetting of the limit position and the end-position stop means of the cylinder, which is time consuming. Thus, it is not possible to alter the bending diameter quickly by rapidly altering the angle of the cradle.

PURPOSE OF THE INVENTION

The purpose of the subject invention is primarily to provide a plate bending machine the rolls of which may be replaced considerably quicker than has hitherto been possible. Another purpose of the invention is to provide a plate bending machine having a tiltable roll cradle wherein the rolls achieve a high degree of stability. Yet another purpose is to allow the roll cradle to be turned to varying tilting angles and allowing shifting between them rapidly. ^~ t±s allows roll exchanges to be performed quickly and efficiently and high-quality bending opera- tionsto be performed rapidly and efficiently and with a high degree of flexibility of resetting.

SUMMARY OF THE INVENTION

The above purpose is achieved in a machine possessing the characterizing features defined in the appended claims. Thus, the machine in accordance with the invention is characterized essentially in that the bearing unit in which the interconnected rolls are supported consists of a first bearing part, such as a first cradle part, and of a second bearing part, such as a second cradle part, each one of which supports the associated rolls by the roll ends, in that both bearing parts are supported in the machine frame in such a manner that each cradle roll is supported at both its ends, and in that the bearing parts and the cradle rolls are interconnected so as to form an integrated .installation or assembly unit which may be removed from the machine as a single piece. This means that the cradle rolls are connected with both parts of the bearing unit, at both ends of each individual roll, so that one single integral mounting unit is formed. This unit may be removed from the machine as a whole and another mounting unit, for instance one comprising rolls having a larger diameter size, be installed in the machine as one integral unit. In this case, the mounting unit also includes drive members interconnecting the various rolls so that the latter, when installed in position in the machine, are driven at the same speed and in the same direction. In this manner it becomes possible to replace the mutually interconnected rolls, usually two or three in number, in a very simple and rapid manner. The bearing unit or roll cradle thus consists of a first part and a second part each, one of which supports the individual rolls by the roll ends. In this way all the rolls of the machine are supported at each one of their two ends and this provides for excellent stability, which is an essential feature in obtaining correct rolling results. In addition, the two bearing parts are turned in a fully syn¬ chronized manner, so that the two bearing parts move as a single unit or roll cradle clockwise or anti-clockwise. Furthermore, the bearing unit or roll cradle may be turned in a continuous manner clockwise or anti-clockwise. As a result, resetting from one bending diameter to another can be done extremely quickly, and data control may be used to alter the bending diameter during the very bending operation, allowing e.g. bending a piece into a super-ellipse configuration. The machine thus is extremely versatile in these respects.

The new mounting unit including rolls, which may be exchanged for a new complete mounting unit including different rolls, creates possibilities for rapid exchanges of rolls in the machine. It has likewise become possible to remove the very mounting unit in a convenient manner from the machine. This is due to the support of the mounting unit in bearing housings in each machine end frame. The bearing housings are not stationary but are arranged for sliding movement in grooves formed in the associated machine frame end. Normally, these grooves extend vertically as a consequence of the stationary roll being positioned vertically above the mounting unit incorporating the rest of the rolls. Obviously, the rolls may be directed differently in the machine, whenever such different direction is judged to be suitable. However, normally the bearing housings are displaceable in vertical grooves formed in the associated machine frame ends. Each bearing housing is supported by a device allowing rapid raising and lowering of the mounting unit together with its associated rolls in a direction towards or away from the stationary or fixed roll. At one side of the machine the bearing associated with the top roll may be withdrawn, allowing the top roll to be pulled out laterally. At this machine side the usually vertical bearing groove extends all the way up to the edge of the machine frame end. Owing to this arrangement, the bearing may be pulled to the edge and out of the machine frame end. It then becomes possible to pull the mounting unit axially away from the second bearing by simply pulling its shaft mounted in the bearing housing out of the bearing. The bearing housing is shaped as a square block which thus travels in usually vertical grooves in each machine end. It thus becomes possible to exchange all rolls in the machine in a rapid and convenient manner, thus minimizing the duration of standstills of the plate bending machine.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in closer detail in the following with reference to the accompanying drawings wherein identical numeral references have been used in the respective drawing figures to identify corresponding components. Some parts of the machine have a symmetrical construction and consequently identical detail components are used on both sides. In these cases the components positioned on the right-hand side of the machine are identified by the addition of the sign ' . For example, sprockets 27 on the left-hand side are referenced on the right-hand side by 27' .

Fig. 1 is a perspective view of the plate bending machine in accordance with the invention as seen from the front, and includes one left and one right side. Fig. 2 shows the same machine in a view from the rear.

Figs. 3a-3d show the operational sequence of the rolls as seen from the side in the machine in accordance with the invention. Fig. 4 illustrates bending of a sheet to a larger diameter curvature than in accordance with Figs. 3a-3d.

Fig. 5 is a sectional view through the machine rolls as seen in the direction towards the left frame end of the machine. Fig. 6 is a sectional view corresponding to that of Fig. 5 but with the section taken through one of the bearing units or cradle parts and showing the mutual cradle roll driving arrangement.

Fig. 7 is a vertical cross-sectional view through the top and bottom rolls at the left frame end of the machine. Fig. 8 is a lateral view of the arrangement of drive transmission from the top roll to the bottom roll in the left frame end of the machine.

Fig. 9a is an alternative to the intermediate wheel unit shown in Fig. 8.

Fig. 9b shows the intermediate wheel unit of Fig. 9a in a lateral cross-sectional view.

Fig. 10a illustrates the manner of disengaging the top roll attachment means at the right frame end of the machine.

Fig. 10b shows a detail of the means of Fig. 10a.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

In Fig. 1, numeral reference 1 designates a plate bending machine intended to form sheet metal into round or U-shaped members. One such round member may later be welded together into a tube. The plate bending machine has a sturdy frame 10 including two projecting end walls, one left-hand end wall 11 and one right-hand end wall 12. A number of rolls are mounted intermediate the end walls 11 and 12. The uppermost roll is a stationary roll or top roll 2. A number mutually interconnected rolls 3 - 5 are positioned underneath the top roll. These rolls are inter¬ connected by means of a bearing unit 6 comprising a first bearing part 7 at the left-hand end wall 11 and a second bearing part 8 at the right-hand end wall 12. The bearing unit is often mounted for turning movement about an axis which is parallel to the roll shafts. In this case it is called roll cradle 6 and includes a first cradle part 7 and a second cradle part 8. The rolls 3 - 5 are then often known as cradle rolls. The bearing unit or roll cradle 6 including its rolls are assembled into a single mounting unit 9 which may be taken out of or be installed in the machine as one single piece. In accordance with the shown embodiment the bearing unit or roll cradle 6 comprises three rolls, viz. a lower roll 3 which normally is positioned straight underneath the top roll 2. In addition, there is a front bending roll 4 and a rear bending roll 5, the latter being concealed in Fig. 1 but visible in Fig. 2. Normally, the three rolls are aligned and usually the bearing unit 6 may be turned, i.e. tilted. However, the bearing unit 6 could also comprise two rolls and in that case it need not be tilt- able The sheet metal to be bent thus is introduced into the nip between the top roll 2 and the cradle rolls 3 - 5. As already mentioned, the machine may also be used to roll tubular sections. Each such section is removed from the plate bending machine by detaching the right-hand attachment of the top roll 2 and pushing it aside. The top roll 2 is sufficiently sturdidly mounted in the left end wall 11 to prevent the right-hand side of the roll to sag. The tubular section may then be pulled to the right above the free end of the top roll. The right-hand bearing of the top roll 2 is housed in a sleeve 15 which is secured in a pivotable arm or suspension means 16. The suspension means is pivoted outwards with the aid of a positioning device 17. Similar solutions are already known.

The right and left end walls of the machine are interconnected by means of a front stay 13 and a rear stay 14. Normally, the machine is provided with a control panel 18 and very often with one pedal 19 for actuating the rolls and one pedal 20 for turning the cradle. In accord¬ ance with one embodiment the machine may be controlled entirely manually with the aid of the pedals but in other versions it may be more or less computer-controlled.

Fig. 2 illustrates the plate bending machine in a view from the rear. The rolls 2-5 of the machine are driven with the aid of a driving motor 21. By means of a chain the motor drives the top roll 2 which in turn drives the lower roll 3. The latter in turn drives the front bending roll 4 and the rear bending roll 5 with the aid of a front interconnection chain travelling around chain wheels on the lower roll 3 and chain wheels on the front bending roll 4. A rear interconnection chain .travels around chain wheels of the lower roll 3 and the rear bending roll 5. In this manner, all cradle rolls are driven in the same rotaional direction and at the same speed. The drive connection between the cradle rolls 3 - £ could also be effected with the aid of toothed wheels positioned on the opposite side of the rolls. Thiε- situation is shown in Fig. 6. In this manner all drive arrangements are located in the left-hand side of the machine, which is an advantage. The first bearing part of cradle part 7, like the second bearing part of cradle part 8, are tilted with the aid of their individual one of setting screws 26 and 26', respectively. The left setting screw, when viewing the machine from the front, is designated by 26 and the right one with 26'. These threaded screws thus actuate one cradle part each. It is important that such actuation is effected in perfect synchrony at the left and right side. For this reason the actuation is effected with the aid of a chain 23 driving the left chain wheel 27 as well as the right chain wheel 27' . The chain wheels have an equal number of teeth and are secured to their asociated one of setting screws 26, 26'. The chain 23 is driven by a driving chain wheel 25. The latter is positioned on a sh,._ ; mounted in a drive carriage 24 and by means of e.g. an angular gear it may be driven by a driving motor 22 arranged to drive the cradle.

Figs. 3a - 3d thus show an operational sequence relating to the machine in accordance with the invention. The operational cycle starts by introduction of the sheet 39 to be rolled into the iru. line to the position illus¬ trated in Fig. 3a. Normally, the pivot arm or suspension means 16 assumes its outer position at this point. This means that the sheet may be introduced either in the longitudinal direction of the machine or in the transverse direction thereof. The sheet thus is introduced in such a manner that its front edge will be positioned between the top roll 2 and the bottom roll 3. The roll cradle 6, which consists of a first roll part 7 and a second roll part 8, is then raised. This is illustrated in Fig. 3b. The above operational step was effected while the rolls were stationary. The roll cradle is then tilted clockwise, the rolls still being stationary in accordance with Fig. 3c. This means that the sheet will be bent from its very front edge and rearwards. The rolls are then driven forwards, whereby the sheet front edge will be positioned approxi¬ mately as illustrated in Fig. 3c. On account of the spring back properties of the sheet the latter will not follow the roll contour entirely. The roll cradle is then turned counter-clockwise as illustrated in Fig. 3d, while the rolls are stationary, whereupon the rolls are driven forwards until a finished cylinder is produced. Fig. 3d illustrates a position, wherein the rolls have been driven somewhat forwards compared with the position in Fig. 3c. The rolling in accordance with Fig. 3d thus is continued until a round cylinder is obtained. At this point the roll cradle is lowered and tilted back to its horizontal position. In addition, the suspension means 16 is pivoted laterally outwards to expose the end of the top roll. The machine is now again in its starting position or dwell position illustrated in Fig. 3a and the bent cylinder profile member thus produced wraps the top roll 2. It may be pulled out of the machine in the axial direction of the roll.

Fig. 4 illustrates bending of a sheet to a larger- diameter curvature than in Figs. 3a-3d. The bending operation is carried out exactly as described before with the exception that the angle of the cradle tilting in the clockwise and counter-clockwise directions is smaller.

Fig. 5 illustrates the manner in which the operation of the roll cradle 6 including its two parts 7 and 8 is effected. As mentioned, the first cradle part 7 supports the left-hand side of the cradle rolls 3 - 5. The top roll 2 is stationarily mounted in the left end wall 11 of the machine. The first cradle part 7 is rotatably mounted in the left bearing housing 29. Normally the position of this rotary bearing means coincides with the position of the rotary bearing means of the lower roll. The left bearing housing 29 is arranged for sliding movement in a usually vertical groove 40 in the left end wall 11 of the machine. For reasons of clarity, the groove 40 is shown in this drawing figure to be a great deal wider than the bearing housing 29 but in actual fact the bearing housing of course has a perfect sliding fit in the groove 40. The extension of the groove 40 is such that the rolls 2 and 3 may be moved close together and such that the cradle rolls may be lowered to the desired degree. Raising and lowering of the roll cradle is effected in the same manner in the left and the right part of the cradle. The bearing housing 29 thus is supported on the left height adjustment means 34. In the manner of a stretching screw, the latter may be lengthened or shortened for precision setting of the vertical position. The lower end of the height adjustment means 34 rests on the left cam member 35. The cam member is attached to a shaft which may be turned clockwise or anti-clockwise with the aid of the left lever 36. The latter is actuated for instance by an air cylinder, not illustrated in the drawing figures, but the action of which is shown by arrows directed upwards and downwards, respectively. In an exactly corresponding manner the right-hand bearing housing 29' is supported on the right- hand height adjustment means which is supported on the right-hand cam member 35' and is operated by the right- hand lever 36'. On the other hand, the corresponding groove 41 in the right end wall 12 of the machine is prolonged vertically upwards so as to stretch out to the side of the machine and even externally thereof. In other words, the roll cradle 6 may be turned in bearings positioned in bearing housings 29, 29' in the left and right side walls, respectively, of the machine. The first cradle part 7 in the left side of the machine is connected with the opposite cradle part 8 in the right side of the machine by means of a connection plate 31. The latter is screwed into the first and second cradle parts by means of fastening screws 32 and 32', respectively. The left end of the connection plate supports the left pivotal attachment means 30 and the right end the right attachment means 30' . Both pivotal attachment means are of identical appearance and are operated in the same manner. The pivotal attach¬ ment 30 is fork-shaped, having its two leges enclosing a positioning nut 28. The latter is provided with two pivot pins 33 each one of which travels in an associated groove formed in the corresponding leg of the pivotal attachment means 30. The positioning nut 28 travels on and cooperates with the left positioning screw 26. The latter is driven by the left chain wheel in the manner described previously. This means that when the left chain wheel is turned by the chain 23 the positioning nut 28 will be dis¬ placed in the longitudinal direction of the positioning screw and thus turn the pivot attachment means 30 which will tilt the first cradle part 7 about its bearing in the left bearing housing 29. In the same manner the second cradle part 8 will be tilted when the right chain wheel 27' is turned by the chain 23. The chain 23 ensures that the chain wheels will be turned in an exactly uniform manner. This means that the first cradle part 7 and the second cradle part 8 will tilt in perfect synchrony, turning as one single part. The driving motor 22 driving the chain 23 may be arranged to effect its driving motion in essentially continuously variable time intervals. With the aid of computer control the drive could also be correlated with the drive of the rolls, which means that also elliptically curved configurations could be formed. The roll cradle 6 incorporating the first cradle part 7 and the second cradle part 8, together with the cradle rolls 3 - 5, form an integral mounting unit 9. The latter also includes the interconnecting drive relating to the rolls 3 - 5. This may be effected either by means of interconnecting chains 37, 38 or interconnecting chain wheels 42, 43. To detach the mounting unit, one preferably starts by separating the connection plate 31 from the first cradle part 7 and from the second cradle part 8, which is effected by untightening the fastening screws 32, 32' .

Fig. 6 is a cross-sectional view corresponding that in Fig. 5 but taken closer to the left machine end wall 11. This drawing figure shows the drive connection relationship between the cradle rolls 3 - 5. The bottom roll is driven by the top roll 2 in a manner to be described in closer detail in the following. A front interconnecting cog wheel 42 is mounted in the first cradle part 7 in driving engagement with cog wheels supported on the associated trunnions of respectively the bottom roll 3 and the front bending roll 4. In the same manner a rear connecting cog wheel 43 is mounted in the first cradle part 7 in driving engagement with a cog wheel which is attached to the bottom roll 3 and a cog wheel attached to the rear bending roll 5. Owing to this arrangement all three rolls 33 - 5 will rotate in the same direction and at the same speed, and this is due to the equal number of teeth and the equal size of the cog wheels on the rolls 3 - 5. Also the cog wheels 42 and 43 are of equal size and their teeth equal in number. This drive arrangement is an alternative to the solution shown previously including a front connection chain 37 and a rear connection chain 38. The solution including the connecting cog wheels is less bulky and may be placed on the left side of the machine, which means that all drive arrangements are positioned on this side. This is an obvious advantage.

Figs. 7 -9b illustrates the arrangement of the drive of the top and bottom rolls. A driving chain 44 extends from a sprocket which is driven by the driving motor 21. The driving chain 44 rotates a sprocket 45 which is secured to the trunnion of the top roll by means of a key. Fig. 7 shows the stationary mounting of the top roll 2 in the left end wall 11 of the machine. The bearings are able to absorb axially as well as radially directed forces. The bottom roll 3 is supported in bearings in the left bearing housing 29. It should be noted that the left bearing housing could be raised and lowered in the groove 40 and also swing somewhat vertically inside that groove.

The transmission of drive from the top roll 2 is effected by means of an upper driving cog wheel 46. The latter drives a lower driven cog wheel 47. The drive is not effected by direct engagement between the two cog wheels 46, .47, an arrangement that would have been possible as such, had the two cog wheels been of equal size, and this because the diameters of the rolls 2 and 3 normally are equal. But since the cradle rolls 3 - 5 are arranged to be raised and lowered in relation to the top roll it is desirable that the drive transmission does not to any large extent limit the extent of raising and lower¬ ing the rolls. In order also to provide for an increased versatility of replacement of the rolls in the machine two intermediate cog wheels are used instead, one upper 48 and one lower 49. Normally, the machine is operated with rolls of a diameter size of 70, 80 or 90 mm. All rolls 2 - 5 have the same diameter. This means that when 90 mm diameter rolls are used the spacing between the top roll and the bottom roll by 20 mm exceeds the spacing between these rolls when 70 mm diameter rolls are used. In order to accommodate these variations an upper bearing unit 50 and a lower bearing unit 51 are used to support the cog wheels 48, 49. The bearing units 50, 51 are designed to allow them to be screwed to the machine end wall 11 in several different ways. When rolls of diameter size 70 mm are exchanged for rolls of diameter size 80 mm, for instance, it may be possible to turn the bearing units 50, 51 in such a manner that they transfer the drive from cog wheel 46 to wheel 47. This could be effected for instance by shifting both wheel 48 and wheel 49 somewhat downwards by turning the associated bearing unit 50, 51. However, also the intermediate cog wheels may need exchanging as also the driving cog wheel 46 and the lower driven cog wheel 47. Fig. 9a illustrates a situation when the upper bearing unit 50 has been provided with a larger intermediate cog wheel. Fig. 9b shows the bearing unit in a cross-sectional view with the cog wheel seen from the side.

Figs. 10a and 10b illustrate in closer detail the manner in which the right-hand support of the top roll 2 may be detached. A pivotable arm or suspension means 16 is pivotally attached in the left end wall 11 of the machine. The pivotal movement is controlled by a positioning device 17 which is also pivotally mounted in the left end wall 11. The positioning device could be an electrically operated positioning screw. The upper end of the sus¬ pension means 16 comprises a sleeve 15. The latter is pivotally mounted in the suspension means 16 and comprises bearings for support of the top roll trunnion. The support of the suspension means 16 in the left end wall 11 and the support of the sleeve 15 both have parallel pivot axes. When the positioning device contracts from the position shown the suspension means consequently will tilt outwards, away from the left end wall 11. This will free the right-hand end of the upper roll. The tilting of the suspension means 16 continues until its upper end is out of the path of movement of the bent sections being pulled out in the axial direction of the upper roll.

Claims

1. A plate bending machine (1 ) for bending sheet metal into completely or partly circular profile members, such as pipes or profile members bent into a U-shape, of the kind wherein the bending is effected with the aid of one stationary roll (2), such as a top roll (2), and a plurality of interconnected rolls (3 - 5), such as cradle rolls (3 - 5) which are supported in a single, common bearing unit (6), such as a roll cradle (6), c h a r ¬ a c t e r i z e d in that said bearing unit (6) consists of a first bearing part (7) , such as a first cradle part ( ), and of a second bearing part (8), such as a second cradle part (8), each one of which supports the associated rolls (3 -5) by the roll ends, in that both bearing parts (7, 8) are supported in the machine frame (10) in such a manner that each cradle roll (3 - 5) is supported at both its ends, and in that the bearing parts (7, 8) and the cradle rolls (3 - 5) are interconnected so as to form an integrated installation unit (9 ) which may be removed from the machine as one single piece.

2. A plate bending machine as claimed in claim 1, c h a r a c t e r i z e d in that each bearing part (7, 8) or cradle part (7, 8) is supported in the associated machine side by means of an attachment means which is arranged for sliding movement, normally in a vertical direction, in a manner to allow said cradle rolls (3 - 5) to be moved closer to or further away from the stationary roll (2).

3. A plate bending machine as claimed in claim 2, c h a r a c t e r i z e d in that the attachment means of at least one of the cradle parts (7, 8) in the machine end wall (11, 12) is arranged for sliding movement, normally in a vertical direction, all the way out to the end of the machine side and out of the latter so as to allow the entire installation unit (9) including the roll cradle (6) and the cradle rolls (3 -5) to be removed, provided the stationary roll (2) or other part does not obstruct the removal.

4. A plate bending machine as claimed in claim 2 or 3, c h a r a c t e r i z e d in that the attachment means of each cradle part (7, 8) in the associated machine end wall (11, 12) consists of a bearing housing (29 and 29', respectively) having two parallel external faces, said external faces sliding against the side faces of a groove (40, 41) formed in the corresponding machine end wall (11, 12), and in that in at least one of the end walls, for instance the right-hand end wall (12), said groove extends all the way out to the end of the machine end wall (12) and out of the latter.

5. A plate bending machine as claimed in any one of the preceding claims, c h a r a c t e r i z e d in that each bearing part (7, 8) is arranged to turn about an axis which is parallel to the longitudinal extension of the rolls (2 -5), and in that the turning movement of each bearing part is effected in a completely synchronized manner with the aid of turning means (26-28, 30-33, 26'- 28', 30' -33' ) in such a manner that the bearing parts (7, 8) or cradle parts (7, 8) move in the form of a unit (6) or roll cradle (6) clockwise or anti-clockwise.

6. A plate bending machine as claimed in claim 5, c h a r a c t e r i z e d in that the turning means (26-28, 30-33, 26'-28', 30'-33') are arranged to tilt the roll cradle (6) for variable angular displacement, for instance continuously variably, to allow rapid re-setting of the bending diameter.

7. A plate bending machine as claimed in any one of the preceding claims, c h a r a c t e r i z e d in that the stationary roll (2) has an attachment means in one (12) of the machine end walls which is arranged to be pushed aside laterally to allow the roll (2) to be pulled out laterally at the opposite machine end wall (11), whereby the roll (2) is disengaged from its attachment means also at this machine end wall (11) and thus may be removed.

8. A plate bending machine as claimed in claim 7, c h a r a c t e r i z e d in that the attachment means in one machine end wall (12) that is arranged to be pushed aside lateraly, consists of a sleeve (15) comprising a bearing supporting the roll (2), and in that said sleeve is pivotally mounted in an arm (16) or suspension means (16) which in turn is pivotally mounted in the machine end wall, and in that the pivot axes of respectively the sleeve (15) and the suspension means (16) are mutually parallel so that the suspension means may be tilted outwards, for instance with the aid of a positioning means (17), thus exposing the stationary roll (2) to allow the latter to be pulled out axially.