GB2100165A - Shaping the cutting edge of the upper blade of pivoting blade sheet metal shears by way of rigid blade clamping. - Google Patents

Abstract

The blade 5 is rigidly clamped to a holder 1 with two identical bolster plates (3,4) flat on one side and curved (3b, 4a) on the other interposed. The curved faces are convexly and concavely part-conical and confront each with their respective directrices (V1, V2) reversed so that the flat face 4b, when the blade and its mounting are assembled, assumes a part conical shape which it imposes on the blade. A double cam arrangement provides for relative vertical movement of the plates to vary the curve of the blade and the cutting clearance. <IMAGE>

Description

SPECIFICATION Shaping the upper blade-edge of tipping blade sheet metal shears by way of rigid blade clamping The invention relates to the shaping by elastic deformation of bent upper blade-edge of tipping blade sheet metal shears by way of rigid blade clamping with the aid of bolster plates having suitably machined surface.

The tipping blade sheet metal shears are widely used in the industry. Their characteristic feature against other sheet metal shears is that the moving upper blade is fixed to a blade-bar rotating (swivelling around a theoretical axis of revolution. The theoretical axis of revolution is parallel with the blade-edge. In order to avoid excessive cutting force, the upper blade is arranged at an angle to the lower blade. The result of the oblique arrangement of the upper blade and the swivelling motion is that the cutting edge of the upper blade cannot be straight but the upper blade has to be bent. In this way the gap between the blades is constant along the full length of the cut.

Such solution is also known where the bending of the blade is realized by pressing the blade against adjusting screws arranged in the blade-bar, and the shape of the upper blade is set by movement of these screws in such a way that the constant gap between the blades is measured with a feeler stock. This solution is used by the West German Weinbrenner firm.

Furthermore, the solution of the Austrian Voest Alpine firm is also known, where the upper blade is supported by packing plates in such a way that moving from the end of the blade towards the centre, thicker and thicker packing plates or pack of packing plates are placed under the blade, thereby producing suitable bending of the blade-edge.

In these solutions the blade is not rigidly fixed in the blade-bar because in the first case the upper blade has nearly a pointed seat on the adjusting screwends, while in the second case the packing plates are parallel giving a stepped supporting surface for the blade.

In view of above, high surface pressure arises on the adjusting screw-ends causing plastic deformation and therefore the set blade gap cannot be kept, on the other hand the blade bends as a result of the cutting force between the adjusting screws and stepped supporting surfaces, whereby stresses arise in the blade and the quality of the cutting surface will deteriorate.

In the solution of the Voest Alpine firm, setting of the necessary blade shape represents additional difficulty, since due to the machining inaccuracies of the upper and lower blades, thickness of the necessary packing plates cannot be accurately determined in advance.

The invention is aimed at the realization of rigid blade clamping which allows the shaping of the required bent blade-edge in such a way that the shape deviations arising from the machining inaccuracies of the upper and lower blade can be compensated, whereby the gap between the blades will be constant along the cutting length.

The invention is based on the recognition that in case of rigid blade clamping with conoidal bolster plates the shape of the upper blade can be varied to have the upper blade seated on continuous cylindrical surface.

Above objective is realized by insertion of two identical bolster plates - flat on one side and convex conoidal on the other side - between the blade-bar and upper blade, the convex surfaces of the bolster plates are turned to face each other in such a way that the directrices of the conoids are on the opposite side, furthermore, the so-assembled bolster plates are pressed against the flat surface of the blade nest formed in the bladebar, whereby the uppermost surface assumes the required cylindrical shape and the blade is fitted to this cylindrical surface by fixing the blade to the blade-bar through the bolster plate with releasable joint, suitably with screwed joint.

The shape of the blade-edge can be varied by displacement of the bolster plates parallel with each other, or at an angle. A suitable method of realizing the parallel displacement is the movement with a double cam.

The invention is described in detail by way of example with the aid of drawings, in which Figure 1 is a schematic arrangement of the bolster plates between the blade-bar and upper blade, Figure 2 is a schematic diagram of the compressed bolster plates, Figure 3 is a front view of fastening the bolster plates to the blade-bar, Figure 4 is the section A-A of the previous diagram (Fig. 3), Figure 5 is a cross-section of fastening the upper blade on the blade-bar, Figure 6 is a schematic diagram showing the mirror image of the 4 identical bolster plates, and Figure 7 is an outline drawing showing a side view of the tipping blade sheet metal shears.

Bolster plates 3 and 4 are arranged between a blade nest 2 formed in a blade-bar 1 and an upper blade 5. Surfaces 3b and 4a are identical straight conoidal surfaces. Directirces V1 and V2 on the conoidal surfaces 3b and 4a divide the surfaces into convex and concave parts. The conoidal surfaces 3b and 4a of the bolster plates 3 and 4 are turned to face each other as to have the directrix V, on the top and directrix V2 at the bottom. The so-arranged bolster plates 3 and 4 with the prisma tic (parallelepipedic) upper blade 5 are pressed against the flat surface 2a of the blade nest 2 with the aid of clamping screws 6. At the place of the blade clamping screws 6 the bolster plates 3 and 4 are perforated by oval cut-outs 7 and 8, allowing y-directional movement of the bolster plates 3 and 4.

After assembly, the conoidal surface 4a of the bolster plate 4 fits closely to the conoidal surface 3b of the bloster plate 3, it will become its negative counterpart and thus the bolster plate 4 and the upper blade 5 become bent, i.e. the conoidal surface 4b and the flat surfaces 5a, 5b assume cylindrical shape.

The perpendicular section of the cylindrical surface 5n of the deformed upper blade 5 gives the-edge-curve E - being identical with the directrices of the conoidal surfaces 3b and 4a - which is an elliptic section. This elliptic section can be determined by known methods according to the geometrical dimensions of the blade-bar 1 and the upper blade 5.

The bolster plates 3 and 4 have to be secured in the blade-bar 1 against falling out when the upper blade 5 is replaced -, suitably with a screwed joint. This is done with a stepped socket head bolt and with oviform through-bolts 10 and 11 stepped in the bolster plates 3 and 4, in such a way that the threaded part 9a of the stepped socket head bolt 9 is fixed in the blade-bar 1, while the cylindrical part 9b is in the stepped oviform through-bolts, where the diameter of the cylindrical part 9b is identical with the transverse dimension of the oviform hole-parts 10 and 11, whereby there is no cross movement, while the bolster plates 3 and 4 are movable on each other in y-direction, furthermore the cylindrical part 9c bears on the surface 1 1 b of the oviform through-bolt 11.

The length of the bolster plates 3 and 4 with regard to the manufacturing aspects -can be divided into two or several pieces, similarly to the division of the length of the blades by known method. When the length of the bolster plates 3 and 4 is divided, the shape of the bolster plates on the right and left-hand side is the same, production of pieces according to the mirror image is not necessary for the right and left-hand side provided that the division takes place along a bisecting plane perpendicular to the longitudinal direction of the pair of bolster plates and each further division is carried out along a plane symmetrical and parallel to this perpendicular bisecting plane, as well as the pair of bolster plates on the right-hand side are arranged at 1 80' to the pair of bolster plates on the left-hand side.

The principle of a solution is represented by way of example in Fig. 6, where each bolster plate 3 and 4 is divided into two bolster plates 12, 13 and 14, 15 respectively.

For movement of bolster plates 3 and 4 in the y-direction and conodial surfaces 3b and 4a parallel to each other a double cam 16 is used.

The formation of the double cam 16 is such that it can be turned only within the 0 and 180 angle interval ensured by suitable selection of the eccentricity value. This suitable eccentricity value is always greater than the maximum displacement in the y-direction of the bolster plates 3 and 4 in relation to each other, which displacement is perpendicular to the plane of directrices V1 and V2. Two double cams 16 are required for each pair of bolster plates, i.e. two double cams 16 in case of bolster plates 3 and 4, and four pieces in case of bolster plates 12, 13, 14 and 1 5 for the movement in the y-direction.

In the case of rigid blade clamping according to the invention the fine adjustment of the blade gap is as follows: On assembly of the apparatus, the bolster plates 3 and 4 are placed in their normal positions in the blade-bar 1, i.e. the bolster plates 3 and 4 cover each other.

The constant gap between the blades 5 and 17, i.e. the blade gap s, is set first at the two ends of the upper blade 5 with the eccentric bearings 18 of the blade-bar 1, then the gap between the upper blade 5 and lower blade 17 is checked in the middle part and in case of deviation it is corrected.

The theoretically determined edge-curve E of the upper blade 5 - which is an elliptic section - slightly deviates from the actually necessary edge-curve, because of the dimension variations occuring as a result of the machining faults (faulty position and shape of the surfaces of the blade nest on the blade-bar 1 and table 19), as well as because of the regrinding of the upper blade 5, whereby it becomes more or less convex. The theoretically determined and realized edge-curve E of the upper blade 5 can be corrected by moving the bolster plates 3 and 4 on each other in the y-direction. This movement is carried out with two double cams 16.By turning the two double cams 16 in the same direction, the bolster plates 3 and 4 move parallel on each other and thus the surface 4b of the bolster plate 4 varies together with the upper blade 5, which means the variation of edge-curve E as well as the same time. The sense of the variation - i.e. surface 5/b of upper blade 5 is more or less convex than the initial state depends on the relative position of directrices V1 and V2, or cams of the two conoidal surfaces 3b and 4a. Namely, when the directrix V, or the cam of the conoidal surface 3b moves away from the directrix V2 or from the cam of conoidal surface 4a, the variation results in more convex cylindrical surface 4b and blade 5 than the original condition, while in case of opposite movement a less convex cylindrical surface 4b or blade 5 than the original condition is obtained. An extreme position of the latter case - when the directrices V1 and V2 coincide - results in a flat surface 4b. In this case the straight edge of the bolster plates 3 and 4 is used for supporting the blades of the shears.

The end points of blade-edge of the upper blade 5 do not move on fine adjustment.

When the bolster plates 3 and 4 are divided and arranged according to Fig. 6, the incorporation of four double cams 16 is necessary for each two bolster plates 12, 13 and 14, 15 which is suitably realized by making the variation of the blade gap s identical along the full edge-curve E when turning in the same direction. This is realized by arranging the double cams 16 on the right and left-hand side according to mirror image.

The solution according to the invention eliminates the attributive stresses arising in the upper blade in case of other solutions, and the gap between the upper and lower blades is always constant along the full cutting length. Production of these bolster plates is simple, since they can be made in divided construction (shorter apparatus is necessary), and even in this case, a single type of bolster plate has to be produced.

In the appended claims reference numbers have been used purely by way of aiding understanding but not by way of limitation of scope.

Claims (4)

1. Shaping by elastic deformation of the upper blade-edge of tipping blade sheet metal shears by way of rigid blade clamping, characterized in that two identical bolster plates (3,4) flat on one side (3a, 4b) having a covex conoidal surface (3b, 4a) on the other side are arranged between the blade-bar (1) and the upper blade (5), the length of which is identical with that of the upper blade (5), the conoidal convex surfaces of the bolster plates (3,4) are turned to face each other as to have the directrices (V1, V2) of the conoids on the opposite side, furthermore, the assembled bolster plates (3,4) are pressed against the flat surface (2a) of the blade nest (2) formed in the blade-bar (1), whereby the uppermost surface (4b) will become cylindrical, and the blade (5) fits closely to the cylindrical surface (4b) by fixing the blade (5) to the blade-bar (1) with a releasable joint, suitably with screwed joints (6), through the bolster plates (3,4), furthermore characterized in that it is provided with a bolster plate (3,4)-actuating mechanism, preferably with two double cams (16), for moving the bolster plates (3,4) on each other in an optional, suitably in the ydirection.

2. Bolster plates as claimed in claim 1, wherein the bolster plates (3, 4) are longtiduinally divided preferably at each 1500 mm.

3. Blades for metal shears, or bolster plates therefor, substantially as herein described with reference to and as shown in the accompanying drawings.

4. Metal shears including blade(s) and/or bolster plate(s) according to any preceding claim.