GB1559464A - Device for cutting strips having a curved profile from flat sheets - Google Patents

Description

(54) A DEVICE FOR CUTTING STRIPS HAVING A CURVED PROFILE FROM FLAT SHEETS (71) We, ITALSIDER S. p. A., an Italian Company, of Via Corsica 4, Genoa, Italy, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a device for cutting strips having a curved profile from sheets.

Welded beams may be obtained by welding together two or more elements consisting of strips of steel sheet.

The operation of cutting the sheets into strips is an automatic operation performed by using a device hereinafter called a sheet oxycutting travelling carriage.

Such carriages comprise a cross piece supported on wheels moving on two rails, whose track gauge is defined by the maximum width of the sheet to be cut.

The sheet support bed is arranged between the rails, and this arrangement is called a cutting bed.

The carriage moves on the rails, keeping the cross piece always perpendicular to the bed and the direction of motion.

The sheets to be cut are placed on the bed with their larger dimension arranged parallel to the rails. Therefore, the cross piece is arranged perpendicular to the larger dimension of the sheet.

The cross piece is provided with rails along its length. A sliding rod moves on the rails and its movement is thus parallel to the carriage cross piece and perpendicular to the direction of movement of the carriage on its rails.

Carriers carrying blowpipes are fastened to the sliding rod, and move on the same rails as the sliding rod. The carriers may be fastened at any point on the sliding rod. The sliding rod may be also fastened to the cross piece so as to become integral therewith.

The sheet oxycutting carriage of the type heretofore described may move in either direction along the rails of the cutting bed.

The blowpipes, independently of one another, may move up and down with respect to the corresponding carrier.

The controls for moving the carriage and lifting and lowering the blowpipes are arranged in a single control panel.

The sliding rod has no autonomous motion, in operation it may be fixed to the cross piece by hand, or may receive an external movement.

Other possible movements of the blowpipes, i. e. positioning of the blowpipe car riers with respect to the sliding rod, tilting of the blowpipes, with respect to the vertical, in any possible plane, are obtained manually.

The types of beams obtainable from sheet strips cut by such a device may have two orthogonal axes of symmetry, a single axis of symmetry, or no axis of symmetry.

Beams with two axes of symmetry do not have appreciable deformations due to welding shrink. Beams with a single or no axis of symmetry have, after treatment, deformations due to welding shrink so as to require considerable finishing procedures which remarkably increases the cost of the finished product.

Deformation caused in the welded beams by welding shrinkage may be substantially defined as being of two types, i. e. centering and bending.

Centering is the arch deformation of the beam in the plane containing the single symmetry axis of the cross section; e. g. a T iron section warps in the plane formed by the web, independently of whether the latter has a larger or smaller width than the flange.

Bending is the deformation of the beam in the plane orthogonal to the plane in which centering occurs, and occurs in those iron sections whose cross section has no axis of symmetry, e. g. L-shaped iron sections. In this particular case both types of deformation, centering and bending are present.

Another particular example is that of a channel-shaped element having an axis of symmetry passing parallel to the two limbs, in fact it has bending in the plane of the axis.

Generally, in a beam made up from different components, centering is the deformation occurring in the plane of the component of larger size and bending the deformation occurring in the plane of the smaller component, orthogonal to the centering deformation.

A main object of the invention is to obtain straight beams.

With the known devices, after welding and cooling, the beams are curved and thus post-straightening is required.

Various ways may be employed for straightening beams, such as heating followed by strong cooling, the use of a ram with the help of wedges or the like, or recently and for a given range of sections, the use of straightening machine providing straightening with improved results and remarkably higher speed. All these operations increase production costs.

Recently, it was thought that if an asymmetric beam which warps after manufacture is composed of elements having prior to manufacture equal but opposed deformations, the final beam should come out straight.

Thus, it was thought possible to form asymmetric beams by cutting one. component arched and welding it to another component to complete the beam so that during cooling of the weld the arched precut component is straightened.

Various devices were provided for cutting the strips with an arched or curved profile from sheets, after a previous study for defining the most suitable profile.

The profile is a function of: -the length of the beam -the width of the strip -the thickness of the strip The form of the curve is not particularly important. According to theory, the profile should be an arc of a circle; on the contrary, constructive practice gives a curve which is near to an arc of a circle in the central part, but not at the ends of the strip. This does not however compromise the straightness of the beam after cooling.

For cutting strips from sheets along curved lines, it is possible to move the cutting blowpipes along the carriage cross piece, while the latter moves forward together with the carriage along the cutting bed.

The guide for the relative transverse motion of the blowpipes with respect to the cross piece may be obtained through profiled templates arranged near the cutting bed and controlling the transverse motion of the blowpipes while the carriage moves.

The control of blowpipe movement may. be mechanical, this however requires numerous templates near the bed supporting the sheets to be cut.

The present invention has for its object to remove the above inconveniences.

According to the present invention, there is provided a device for cutting strips having a curved profile from sheets, the device comprising a longitudinal bed for supporting the sheets to be cut, at least one travelling carriage which is movable along said bed, a cutting blowpipe controllably movable along said travelling carriage and in a direction perpendicular to the direction of movement thereof, means for controllirig ... e movement of the blowpipe, so that the blowpipe follows the curved profile to be cut, said controlling means including a cam arranged on said travelling carriage, means for rotating the cam and for continuously varying the speed at which the cam is rotated, and a follower device adapted to follow the profile of said cam and to move the blowpipe along the carriage in accordance with variations in the cam profile.

A single motor may be provided to move the carriage along the bed and to rotate the cam. In order to vary the transmission ratio between the speed of the carriage and the angular rotation. speed of the cam, a speed reduction gear with continuously variable transmission ratio may be provided.

The drive shaft of the motor can drive a tyred wheel which drives a tyred disc on a shaft perpendicular to the drive shaft. The tyred wheel can be moved along the drive shaft so as to contact the tyred disc at different points, and therfore to drive the tyred disc at different speeds depending on the relative positions of the wheel and the disc. The shaft on which the disc is keyed is adapted to drive the cam, and a gear reduction unit is provided between the disc and the cam.

The follower device preferably comprises two rollers arranged at ends of a bracket, one of the rollers following a first profile of the cam and the other of the rollers following a second profile of the cam, the first and second profiles being complementary, so that the distance between the two rollers remains constant.

The follower device may be connected to the blowpipe by a connecting rod, one end of which is connected to the follower device and the other end of which is connected to a carrier carrying the cutting blowpipe on the travelling carriage. The connecting rod is hinged to the travelling carriage at an intermediate point which is displaceable along the length of the rod so that the relative movements of the follower device and the carrier can be altered.

The invention will now be described, by way of example, with reference to the accompanying drawings, wherein: Figure 1 is a plan view of a known supporting bed for cutting metal sheets; Figure 1A is an enlarged plan view of a travelling carriage; Figure 2 is a part section on an enlarged scale, along lines II-11 of Figure 1 ; Figure 3A shows in section an I-shaped beam with double symmetry, with respect to two perpendicular axes (X) and (Y) ; Figure 3B shows in section a T-shaped beam with single symmetry with respect to an axis (X); Figures 3C and 3D show in section two L-shaped beams with no symmetry axis ; Figures 3E and 3F show in section two channel-shaped beams with a single sym metry axis (X); Figures 3G, 3H and 3K show three I-shaped beams with a single symmetry axis (X) ; Figure 4 is a diagrammatic perspective view of an example of a T-shaped beam deformed so as to have ; ,. Figure 5 is a diagrammatic perspective view of an example of a chanel-shaped beam deformed so as to have bending; Figure 6 shows half of the curved profile to be cut from a sheet; Figure 7 is derived from Figure 6 by a known geometrical ; Figure 8 is a diagrammatic top view of a portion of a device according to the inven- tion and particularly of the mechanism actuating the cam on which depends the transverse displacement of the blowpipe or blowpipes during the longitudinal motion of the carriage ; Figure 9 is a diagrammatic plan view of mechanism for transmitting transverse mo tion from said cam to the carriage support ing the blowpipe for a preferred embodi- ment of the device according to the present invention; Figure 10 is a diagram showing how the device of Figure 9 may be adjusted; Figure 11 is a more detailed plan view of the mechaism shown in Figure 9; and Figure 12 is a sectional view along line XII-XII of Figure 11.

A sheet supporting bed 1 is shown in Figure 1. Oxycut travelling carriages 2 straddle the bed and move on rails 3 which are parallel to the longitudinal direction of the bed 1 and are arranged on both sides thereof. Each carriage 2 (Figure 1A) con sists of two symmetric uprights 4 and a beam 5 horizontal and perpendicular to the longi- tudinal, direction of the rails 3.

A horizontal guide rail 6 is fixed on the beam 5 and extends parallel thereto. The guide rail 6 supports a sliding rod 7 which may be moved along the beam 5 in a direction parallel thereto.

Carriers 8 are mounted on the sliding rod 7. The carriers 8 support cutting blowpipes 9 which are movable in any suitable manner upwards or downwards, as well as to in clined positions, according to the desired curved profile'required for the edges of the sheet strips.

The sliding rod 7 together with the cutting blowpipe 9 moves parallel to the beam 5, while th , carriage 1 moves longitudinall along rails 3. Thus, the cutting 9 moves transversely out and back, together with the sliding rod 7, to cut the edge of a strip with a curved edge from a sheet on the bed 1.

As shown in Figures 8 to 12, the oxycut carriage. 2 is driven along the rails 3 by a suitable motor, not shown, which drives, through suitable reduction gearing, a secondary shaft 11 which is connected to a cam 10 through a suitable transmission. The transmission comprises a tyred wheel 12 keyed on the shaft 11 which runs on'a. tyred disc 13 provided with a shaft 14 perpendicular to the shaft 11. The wheel 12 can be moved along shaft 12, so that the ratio of the angular speed of the shafts 11 and 14 can be altered by varying the axial position of the wheel 12 on the shaft 11.

On the shaft 14 is keyed an endless worm gear 15 which drives, through a gear wheel 16, a shaft 18 on which a cam 10 is keyed.

By suitably displacing the tyred wheel 12 along the shaft 11, the transmission ratio of the system shown in Figure 8 changes, and thus as the rotation of the shaft 11 is related to the movement of the carrige 2 in a fixed manner, a complet rotation of the cam 10, can be arranged to correspond to any predetermined length of travel of the carriage 2 on the rails 3.

The transmission is arranged so that the transmission ratio can be varied to cater for all the lengths of strips to be cut by a particular device.

The cam 10 keyed on the shaft 18 has two plates, respectivelv having profiles 20 and 21 hereinafter called a positive profile and a negative profile.

The radial distances of individual points of the positive profile 20 from a base circle 22 concentric, to the axis of the shaft 18 carrying the cam, correspond to the length of the arrow (f) of the curved profile required for the sheet strips, as shown in Figures 6 and 7.

Hence, by displacing the blowpipes. 9 through a follower controlled by the profile of cam 10, a curved cut according to the profile shown in Figure 6 is obtained. The cam 10 has a positive profile 20 formed by two symmetric halves such that the curved sheet strip has a symmetry with respect to an intermediate transverse axis.

The follower which is able to follow the positive profile 20 of the cam 10, consists of a roller 30 mounted on one end 31 of a bracket 32 which, by means of a slide 33, is movable along a guide rail 34 integral with the beam 5 of the carriage 2. Hence, by connecting the slide 33 to the cutting blowpipes 9, the latter perform a reciprocating motion along the beam 5 in accordance with the positive profile of the cam 10.

The cam 10, as indicated above, has a positive profile 20 and a negative or complementary profile 21. The plates forming the two profiles are axially offset with respect to each other. The negative profile 21 also has a follower 30 mounted on the other end 31 of the bracket 32. The negative profile 21 is such that both followers are always in contact with their respective profiles.

If the carriers 8 for the blowpipes 9 were directly conncted to the slide 33, so as to follow the same reciprocating motion as the slide 33, it would be necessary to have a different cam 10 for each curved profile which is to be cut. In fact, the shape of the cam 10 just controls the length of arrows f (Figure 6), while the distances between the arrows are controlled by the position of wheel 12 along shaft 11.

In order to overcome this inconvenience, the carriages for the blowpipes 9 are not directly connected to the slide 33, but are conncted to the end of a pivotally mounted connecting rod 40. The other end of the rod 40 is hinged to the bracket 32.

The connecting rod 40 is hinged, at an intermediate point 44, to the beam 5. The ratio between the lengths of the arms (a) and (b) of the connecting rod 40 can be altered to allow a single cam 10 to be used to obtain different curved profiles varying within wide limits, by displacing the intermediate point 44 along the connecting rod 40.

Figure 10 shows two examples relating to practical applications of the invention. wherein the connecting rod 140,140' (corresponding to rod 40 in Figure 9) respective ly, for an equal displacement (b) imposed by the cam on the slide 133 (corresponding to slide 33 in Figure 11), causes different displacement (91) and (92) to the articulation point 145,145' (corresponding to point 45 in Figure 9) respectively, of the other end of the connecting rod with the carrier for the cutting blowpipes, according to the position H, H'respectively, of intermediate point 44 where the connecting rod is hinged.

Therefore, it is clear that with a single cam it is possible to vary, within wide limits, both the length of the sheet strip to be cut and the maximum depth of the desired curved profile (measured from a line joining the ends of the curve).

Claims (7)

WHAT WE CLAIM IS:

1. A device for cutting strips having a curved profile from sheets, the device comprising a longitudinal bed for supporting the sheets to be cut, at least one travelling carriage which is movable along said bed, a cutting blowpipe controllably movable along said travelling carriage and in a direction perpendicular to the direction of movement thereof, means for controlling the movement of the blowpipe, so that the blowpipe follows the curved profile to be cut, said controlling means including a cam arranged on said travelling carriage, means for rotating the cam and for continuously varying the speed at-which the cam-is rotated, and a follower device adapted to follow the profile of said cam and to move the blowpipe along the carriage in accordance with variations in the cam profile.

2. A device as claimed in claim 1, wherein a single motor is provided to move the carriage along the bed and to rotate the cam, the drive being transmitted from the motor to the cam via a speed reduction gear with continuously variable transmission ratio.

3. A device as claimed in claim 2 wherein the speed reduction gear comprises a tyred wheel driven by the drive shaft of said motor, said tyred wheel being arranged to drive a tyred disc keyed on a shaft which is adapted to drive the cam and is perpendicu lar to said drive shaft, said tyred wheel being displaceable along its axis, so as to continuously vary the transmission ratio between the drive shat and the shaft of said tyred disc, and a gear reduction unit downstream of said tyed disc.

4. A device as claimed in any preceding claim, wherein said follower device comprises two rollers arranged at ends of a bracket, a first of said rollers following on a first profile of the cam, while a second of said rollers follows on a second profile of the cam, said first and second profiles being complementary, so that the distance between said two rollers remains constant.

5. A device as claimed in any preceding claim, wherein said follower device is connected to the blowpipe by a connecting rod, one end of which is connected to said follower device and the other to a carrier carrying the cutting blowpipe on the travelling carriage, said connecting rod being hinged to said travelling carriage at an intermediate point which is displaceable along the length of said connecting rod.

6. A device as claimed in any preceding claim, having a plurality of blowpipes displaceable and fixable on a rod connected in an articulated manner to said connecting rod and follower device respectively.

7. A device for cutting strips having a curved profile, from sheets, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.