GB2405117A

GB2405117A - Shear blade gap compensator

Info

Publication number: GB2405117A
Application number: GB0319373A
Authority: GB
Inventors: Shaun Tyas; David Stonecliffe
Original assignee: VAI Industries UK Ltd
Current assignee: Primetals Asset Management UK Ltd
Priority date: 2003-08-18
Filing date: 2003-08-18
Publication date: 2005-02-23
Anticipated expiration: 2023-08-18
Also published as: GB2405117B; GB0319373D0

Abstract

A shearing machine for cutting sheet material in which a pair of opposed planar blades are arranged with a predetermined gap (Fig 4, G) between the planes of the blades B and D, and including actuators G arranged to counteract the deformation produced by the shearing force F, to maintain the gap at the predetermined size. Preferably, the actuators are controlled by an open or closed feedback loop, in response to stress or deformation produced by the shearing force. The actual deflection of the shear beams C and E or the back up beams H and J, may be detected by strain gauges or other transducers and the control system then causes the actuators G to expand until the deflection is suitably adjusted. The mechanism dynamically applies forces to maintain the shear gap close to its optimum value.

Description

24051 1 7 "Shear Blade Gap Compensator" This invention relates to shearing

equipment for cutting flat material stock such as metal in the form of strip or plate.

In order to cut metals or other materials by the action of shearing a shearing force is normally applied by a pair of opposed shear blades to the material to be sheared. Some examples of conventional systems are shown in Figures 1 to 10.

Referring firstly to figures 1 and 2: A shearing force F. is applied to the material A being sheared, by the shear blade B mounted on the movable upper beam C. An opposing lower shear blade D is mounted on the lower beam E. It is known to arrange the shear blades in such away that there is a horizontal displacement between their vertical planes as illustrated at "G" in Figure 4. The magnitude of this gap "G" is critical to the shearing operation and the quality of the cut edges of the sheared material.

During the shearing process a horizontal force, f, is generated on the vertical faces of the shearing blades, as illustrated in Figure 5.

Because of the inevitably elastic nature of the shearing machine structure, the force f, causes the gap G to increase during the cutting, thereby opening the gap away from its optimum value. This is illustrated in Figure 3.

In order to reduce the tendency of the gap to open during shearing, shearing machines are generally built with large rigid beams. Consequently they are both large and expensive.

One method of controlling the opening of the gap is illustrated in Figures 6, 7 and 8. This arrangement incorporates a pair of fixed back up beams, R and S. with adjustable packers between them and the moving shear beams. Whilst this reduces the tendency of the gap to open, in order for them to be significantly effective the secondary beams need to be large and consequently expensive.

As shown in Figure 9 it is also known for shearing machines to be constructed so that the one of the shear blades B is curved and is caused to roll across the plate which is being cut during the shearing action U. The centre of the region being sheared W. thus traverses across the shear blade in the direction X. Similarly and referring to figure 10, it is known for shearing machines to be constructed so that one of the shear blades B. is inclined while the direction of shearing action is vertical, V. Again, during the shearing operation, the contra of the region being sheared W. traverses across the shear blade in the direction, X. Because the blades are supported on beams, the maximum deflection will occur when the centre of the shearing force W is midway across the span of the beam. Therefore the degree to which the gap opens up during shearing will vary throughout the shearing action.

Thus, it will be apparent that the known methods of reducing the opening of the shear blade gap cannot respond to any variation in separating forces, either due to differences in shearing resistance or the position of the centre of the shearing force along the blade.

The present invention seeks to provide a mechanism for dynamically applying forces to oppose those generated by the horizontal separating force of the shear.

Accordingly the present invention provides a shearing machine for cutting sheet material in which a pair of opposed planar blades are arranged with a predetermined gap between the planes of the blades, and including actuators arranged to counteract the deformation produced by the shearing force, to maintain the gap at the predetermined size.

Preferably the actuators are controlled by a feedback loop in response to the stress or deformation produced by the shearing force.

Some embodiments of the invention will now be described with reference to the accompanying drawings.

Referring firstly to Figure 11:

J

In this embodiment the horizontal separating force, f, between the shearing blades B and D, is opposed by one or more hydraulic actuators G. that apply forces P. between the back up beams H and J. and the shear blade beams C and E. This reduces the deflection of the shear blades and consequently reduces or eliminates the opening of the shear blade gap.

The extension of the actuators may be controlled by an open loop control system whereby the anticipated deflection of the shear beams throughout the shearing action is eliminated by the operation of the actuators.

An alternative is closed loop control of the actuators. For example the force F. generated by the shearing actuator may be measured and the force P. of the actuators G. then controlled relatively to the shearing force F. As another alternative the actual deflection of the shear beams C and E or the back up beams H and J. may be detected by strain gauges or other transducers and the control system then causes the actuators G to expand until the deflection is suitably 1 5 adjusted.

In this way, using one or a combination of the above means, the shear gap can be maintained close to its optimum value Referring to Figure 12, this illustrates an alternative method of counteracting the separating force f, and thereby preventing the opening of the shear blade gap away from the optimum value.

Most of the deflection of the shear beams is caused by bending produced by the application of the bending moment, M, which is generated by the separating force "f" and the reactions "e" at the beam's fixing points. The deflection can thus be counteracted by applying an equal but opposite bending moment. In this example the moment is generated by a force, W. produced by the hydraulic actuators G and H. through links J and K, and lever arms L, N. P and Q. - 4 The force W. produced by the hydraulic actuators may be controlled by an open loop control system whereby the anticipated deflection of the shear beams throughout the shearing action is countered by the operation of the actuators.

Again as an alternative, a closed loop control of the actuators may be utilised whereby the force F. generated by the shearing actuator or the horizontal reaction force e, is measured, and the force W. applied by the actuators G and H. is controlled relatively to the shearing force F. As another alternative the actual deflection of the shear beams C and E, can be detected by strain gauges or other transducer and the control system then causes the actuators, G and H to apply a force W such that the deflection is adjusted to the desired value.

A further alternative is illustrated in Figure 13. In this arrangement, static backup beams, R and S are used to support the shear beams C and E, via pads T. The deflection of the combined backup and shear beam is counteracted by applying an equal but opposite bending moment to the backup beams. In this example the moment is generated by a force W. produced by the hydraulic actuators G and H. through links J and K, and lever arms L, N. P and Q. The control philosophies in this alternative arrangement are similar to those described for the example of Figure 12.

Using one or a combination of the above arrangements, the shear gap can be maintained close to its optimum value Although the above examples refer to hydraulic actuators, any other suitable type of actuator may be used, for example, mechanical, pneumatic, or electrical. - 5

Claims

1. A shearing machine for cutting sheet material in which a pair of opposed planar blades are arranged with a predetermined gap between the planes of the blades, and including actuators arranged to counteract the deformation produced by the shearing force, to maintain the gap at the predetermined size.

2. A shearing machine according to claim 1 in which the actuators are controlled by a feedback loop, in response to the stress or deformation produced by the shearing force.

3. A shearing machine according to claim 1 or claim 2 in which each blade is mounted on a support beam with a backup beam arranged on the opposite side of the support beam, the actuators being arranged between each support beam an its respective backup beam.

4. A shearing machine according to claim 1 or claim 2 in which each blade is mounted on an elongate support beam with a corresponding elongate backup beam arranged on the opposite side of the support beam, a pair of outwardly projecting mounting points being spaced apart on the outside of each backup beam and having an actuator connected between them, whereby a compensating bending movement can be applied to each backup beam.

5. A shearing machine according to claim 1 or claim 2 in which each blade is mounted on an elongate support beam having a pair of outwardly projecting mounting points on the opposite side, an actuator being connected between the mounting points so as to apply a compensating bending movement directly to the support beam.

6. A shearing machine substantially as herein described with reference to any of Figures 11 to 13 of the accompanying drawings.