Shear with Bi-Directional Cutting

FIELD OF INVENTION:

The invention relates to the general field of shearing and in particular to the shearing of metal plates and strips.

BACKGROUND OF THE INVENTION:

The use of hydraulically operated shearing machines to cut sheet metal is well know. For example, GB 2405118 A describes a hydraulically actuated rolling blade shear which achieves a rocking type shearing action by using a curved shear blade and two separately controlled hydraulic cylinders. A simplified cross section is illustrated in Figure 1. The material to be cut 1 is positioned between an upper curved shear blade 2 and a lower straight shear blade 3. The upper curved shear blade 2 is attached to an upper support beam 4 and the lower straight shear blade 3 is attached to a lower support beam 5. Two hydraulic cylinders 6 and 7 of a hydraulic actuating-mechanism are connected between the upper support beam 4 and the lower support beam 5. Each of the hydraulic cylinders 6 and 7 engages the upper support beam 4 in one engaging-area, hydraulic cylinder 6 in the engaging area on the left end of upper support beam 4, and hydraulic cylinder 7 in the engaging area on the right end of upper support beam 4. By controlling the stroke of hydraulic cylinders 6 and 7 separately but in a synchronized manner the upper shear blade 2 can be caused to execute a rocking type shearing action.

Applicants patent application number EP 0725358.8 describes an arrangement which addresses the wide range of demands made by a system which can provide the actuating force necessary to deal with thick and, or wide material but which can also achieve the cutting cycle times and reset-times typically required when cutting thin and, or narrow material.

A hydraulic actuating mechanism is described in which at least one hydraulic cylinder can be switched in and out of operation mode, independently of at least one other hydraulic cylinder of the mechanism. For example, the mechanism may comprise at least one cylinder having a relatively small effective area, and at least one cylinder having a relatively large effective area, the latter being switchable in and out of operation mode.

Such an arrangement is shown in Figure 2, in which the combined effective areas of all hydraulic cylinders 6a, 6b, 7a and 7b is sufficient to generate the overall actuating-force required for the thickest and strongest material that is to be cut. The effective area of the smaller hydraulic cylinders 6a and 7a is chosen such that it is sufficient to generate the overall actuating-force required for cutting products which require the fastest cutting speed and consequently the shortest cutting cycle time, or for resetting the upper blade to a start position in preparation for the next cut.

In either of these arrangements (Figure 1 or 2), during the cutting cycle, the blade moves from a first side to a second side of the apparatus in a rolling motion before resetting to a start position ready to begin the next cutting cycle from the first side. The action of resetting the blade to the start position accounts for a substantial part of the cycle time and, even when small cylinders are used as illustrated in figure 2, a substantial volume of hydraulic fluid is required.

According to the invention, these problems associated with the prior art are addressed by a method of cutting metal having the steps set out in claim 1 attached hereto.

According to a second aspect of the invention, apparatus for shearing metal comprises the features set out in claim 2 attached hereto.

The invention is herein described, by non-limiting example, with reference to the appended figures in which:

Figures 1 and 2 illustrate schematically, rolling shears according to the prior art;

figure 3 illustrates the cutting action of a rolling shear according to the prior art and

figures 4 and 5 illustrate the cutting action of a rolling shear according to the invention.

Referring to figure 3, during a typical cutting cycle, a rolling shear according to the prior art begins a rolling cut from a first side of the apparatus (a) and rolls in a cutting direction 8 to the second side of the apparatus (b) before resetting to a position (c) ready for the next cut. The time that the upper blade 2 and support beam 4 takes to return to position shown at (c) after completing the cut (b) is a significant part of the cutting cycle time.

Referring to figure 4, a shearing apparatus according to the invention has a two- part cutting cycle. In the first part, the upper blade 2 (and in this example the associated support beam 4) moves from a first side (fig 4(a)) to the second side (fig 4(b)) of the apparatus as in the prior art, before assuming a first reset position (fig 4(c)), ready to begin a rolling cut motion from the second side of the apparatus.

Referring to figure 5, in the second part of the cutting cycle, the upper blade moves from the second side (fig5(a)) to the first side (fig 5(b)) before assuming a second reset position (figure 5(c)), ready to begin a rolling cut motion from the first side of the apparatus.

It will be appreciated that prior to each additional cut, and between the two parts of the cutting cycle, the position of the metal is changed (i.e. the slab is typically advanced in a direction perpendicular to the page in figures 4 and 5).

Thus it can be seen that, by performing cuts on the metal in both directions of the blade travel, the throughput of metal can be increased. Moreover, the practice of bi-directional cutting according to the invention allows for more even and widely distributed wear on the blade.

Since the effective cutting angle during a rolling cut is slightly removed from the horizontal (e.g. about two degrees), there is a small horizontal force applied to the metal as the blade rolls through to perform the cut. In prior art systems, conventional practice includes the use of datum rollers against which the metal plate abuts as it passes through the apparatus. The horizontal force simply pushes the plate against the datum without any movement.

Where the present invention is employed, there is a theoretical risk of plate movement during the cut that is performed in a direction away from the datum. However, the inventors calculations have shown that the vertical force applied to the plate during the cutting action is so much greater than the horizontal force that plate movement is prevented.

In the figures, in each reset position the upper blade 2 is shown as removed from the material 1 and lower blade 3 when compared with the position of the

blade as the rolling cut commences (e.g. compare figure 4(c) with figure 5(a)) but in some embodiments there may be physical distinction between the reset position at a given side and the position of the blade as it begins cutting from that side (or completes cutting from the other side).

The motion of upper blade 3 may be conveniently controlled by a processing device (for example a personal computer) arranged and programmed to operate hydraulic valves (note shown) which in turn control the stroke and timing of the hydraulic cylinders.

The realisation of such system (e.g. by upgrading existing systems) is within the abilities of a person skilled in the art.