GB2462636A

GB2462636A - Separating non-ferrous metal sheets from a stack

Info

Publication number: GB2462636A
Application number: GB0814885A
Authority: GB
Inventors: John Charles Cooke
Original assignee: COCATALYST Ltd
Current assignee: COCATALYST Ltd
Priority date: 2008-08-15
Filing date: 2008-08-15
Publication date: 2010-02-17
Also published as: GB2462499A; GB0904019D0; GB0814885D0

Abstract

In an automatic sheet or part transportation system for feeding individual nonferrous metallic sheets or parts from a stack of sheets or parts to a subsequent processing stage, the separation of the uppermost sheet or part 1 from subsequent sheets or parts 2 is facilitated by the application of electromagnetic fields. The applied electromagnetic field, created by current passed between electrodes 10, 11, may either be alternating, to create periodic and ultrasonic vibration within the upper sheet or part in the stack, facilitating separation by reducing the viscosity of the oil coating on the sheet or part and/or it may be configured to interact with a current applied to or induced in the uppermost sheet or part 1, such that the sheet or part is forced away from any subsequent sheet or part 2. There may be permanent magnets 8, 9 to interact with the induced fields. Manipulation devices 4, 5 for removing the sheet 1 may be vacuum suckers.

Description

Field

The present invention relates to automatic transport systems for substantially planar sheets, such as are used in the processing of metal sheets to produce formed metal panels, i.e. automotive body panels. More specifically, this invention relates to automatic transport systems for de-stacking and feeding metal sheets into panel forming presses.

Background

Steel in sheet form has been used for many years as raw material for pressed steel automotive body panels. The systems for de-stacking and feeding steel sheets into panel forming pressing have been well known and optimised so that commonly used sheet steel feeding systems can operate at feed rates of up to 30 sheets per minute. This high feed rate has been achieved largely through use of the magneto-ferrous properties of the steel sheets. The steel sheets are often manipulated by electromagnetic handling devices, such as the Goudsmit "Magvacu combigripper", and the steel sheets can be pre-separated while still stored in stack form by means of permanent magnet systems such as the Goudsmit TB SPO2 series magnetic sheet separator system. Such pre-separation of the steel sheets can completely obviate the effect of sticky oil coatings on the steel sheets, which would otherwise severely limit feed rate by causing two or more steel sheets to stick together when fed.

Due to the need to reduce the fuel consumption and C02 emissions associated with road vehicles, there is an emerging trend within the automotive industry to reduce vehicle weight through replacement of steel components by parts made from aluminium. Steel sheet feeding and de-stacking systems, adapted to work with aluminium, have been implemented in many automotive factories to manufacture cars with aluminium body panels (for example the Jaguar XJ6 and Audi A8).

The feed rate for these systems is severely limited, however, because aluminium is non-ferrous and cannot be manipulated in the same way as steel. In particular, when aluminium sheets are supplied with an oil coating, it can be difficult to separate the first sheet to be fed from the second sheet in the stack. This problem is especially severe when the sheet to be moved is thin, of a large surface area and the viscosity of the oil coating on the sheets is relatively high.

Brief Summary of the invention

Against this background, the object of the present invention is to improve the current sheet metal de-stacking and feeding system to overcome the issue of poor sheet separation and to enable significant increases in feed rate to be achieved for non-ferrous metallic sheets. The inventive sheet de-stacking and feeding system described in this document achieves greatly improved separation effectiveness than previous designs through the application of electromechanical fields to interact advantageously with both the first sheet of the stack of non-ferrous sheets and its associated oil coating contacting the second sheet in the stack.

The first inventive configuration improves sheet separation effectiveness through application of periodic vibration or oscillations to the first sheet to be separated from the stack of sheets. This vibration may be generated through direct contact with a vibrational transducer such as a piezoelectric or magneto-strictive device or more preferably through excitation of the aluminium sheet by application of a directed electro-magnetic field or fields generated by an inductive coil or coils positioned directly above the first sheet to be moved. Preferably, at least one of the frequencies of the induced vibration will match either the resonant frequency or harmonic of the resonant frequency of the first sheet. More preferably, at least one of the induced frequencies will interact with the oil coating between the first sheet and second sheet to reduce the viscosity of the oil. More preferably, at least one of the frequencies induced in the first sheet will be ultrasonic (at least 20 KHz) such that the oil viscosity is subject to the ultrasound induced viscosity reduction effect, which patent number W02008024532 teaches can result in a 7 to 15 times viscosity reduction. Most preferably, vibration can effectively be limited to the first sheet in the stack through use of the skin effect wherein a higher applied frequency results in a smaller depth in which currents are induced.

The skin depth can be calculated using this equation: 6 503 Where: Skinth'pth p = resistiiity of coductcr p riti:i perrnabiUtv if condicttn f = frequ4ncy For example, to achieve a skin depth of less than 0.5mm, the applied frequency for an aluminium sheet should be more than 28,300 Hz.

The second inventive configuration improves sheet separation effectiveness through the interaction of an electric current flowing through the first sheet to be moved in the stack and an applied magnetic field. Preferably, the electric current is caused to flow in the first sheet by direct contact with positive and negative electrodes positioned to create a current flow at right angles to the applied magnetic field such that a resultant motion is induced in the first sheet away from the second. The resultant motion in the first sheet causes the partial vacuum between the first and second sheet to be broken and can be induced as part of the lifting cycle itself or, preferably, during the waiting time between lifting cycles or. Additionally a second current may be caused to flow in the second sheet, flowing in the opposite direction to that in the first sheet, further increasing the force separating the two sheets. The magnetic field may be static such as results from the use of a suitably positioned permanent magnet or magnets adjacent to the stack of sheets or, preferably, may be adjustable and/or dynamic such that the magnetic field or fields interact most strongly with the first sheet in the stack More preferably, the adjustable or dynamic magnetic field or fields are generated by one or more electro-magnets. Most preferably the electro-magnets will be constructed on a laminated iron or steel core in order to generate sufficient magnetic field strength. The electric current may also be unidirectional or alternating in synchronisation with the applied magnetic field, creating a separation action between the first and second sheets.

It will be appreciated that the features mentioned above and those yet to be explained below may be used not only in the combination specified in each case, but also in other combinations or alone, without departing from the scope of the present invention as will be clear to a person skilled in the art.

Brief description of the drawings within the patent document Figure 1 shows a diagrammatic side view of the first configuration of the inventive non-ferrous sheet de-stack feeder where the top-most sheet is caused to vibrate by electromagnetic induction.

Figure 2 shows a diagrammatic plan view of the first configuration of the inventive non-ferrous sheet de-stack feeder showing the arrangement of induction coil and vacuum manipulators.

Figure 3 shows a diagrammatic plan view of the second configuration of the inventive non-ferrous sheet de-stack feeder showing one arrangement of the magnets and electrodes Figure 4 shows a diagrammatic side view of the second configuration of the inventive non-ferrous sheet de-stack feeder where the top-most sheet is cause to move away from the second sheet by the interaction of a current flowing though the top sheet and an applied magnetic field Figure 5 shows a diagrammatic side view of the third configuration of the inventive non-ferrous sheet de-stack feeder where the top-most sheet is cause to move away from the second sheet by the interaction of a current flowing though the top sheet and an applied magnetic field from an electromagnet Figure 6 shows a diagrammatic side view of the forth configuration of the inventive non-ferrous sheet de-stack feeder where the top-most sheet is cause to move away from the second sheet by the interaction of induced eddy currents flowing though the top sheet and an applied magnetic field from an intermediate inductor and an electromagnet

Detailed description of the invention

A first embodiment of the novel de-stack feeder for non-ferrous conductive sheets according to the invention is shown in Figures 1 and 2. The system consists of the stack of sheets, 7, supported by base plate 3, manipulation devices, for example vacuum suckers, 4 and 5 and electromagnetic coil 6 positioned above the stack and optionally mounted to the manipulation assembly. In this first embodiment, the manipulation devices, 4 and 5, are brought into contact with the uppermost sheet, 1, of non-ferrous material and an alternating current is fed from frequency generator and amplifier through the electromagnetic coil 6. The frequency in the current through the coil is tuned to create ultrasonic vibration through the entire surface of the non-ferrous sheet 1 without exciting vibration in sheet 2. For example, in aluminium, an applied frequency of 20 KHz will act to a skin depth of approximately 0.6mm. With an applied power level of less than 500W, the viscosity of the oil coating between the two sheets will be reduced by at least 7 times, causing any obstructive oil to flow easily and in such a way that it allows air to pass rapidly between sheets 1 and 2, greatly reducing the time needed for sheet 1 to separate from sheet 2. Additionally, the vibration in sheet 1 will help to accelerate separation of sheet 1 from 2.

A second embodiment of the novel de-stack feeder for non-ferrous conductive sheets according to the invention is shown in Figures 3 and 4. The system is shown at a point in the operating cycle when the manipulation devices, 4and 5, are not yet contacting sheet 1 so that in this view the system consists of a stack of sheets, 7, supported by base plate 3, with adjacent permanent magnets, 8 and 9, with negative electrode 10 and positive electrode 11, being brought into contact with the upper sheet in the stack 1. When a current is passed through sheet 1, between electrodes 10 and 11, the interaction of the induced magnetic field in sheet 1 and the magnetic field from the permanent magnets 8 and 9, creates an upward movement of sheet 1 away from sheet 2. This action can be generated before the manipulators, 4 and 5, are brought into contact with sheet 1 so that sheet 1 is effectively pre-separated from second sheet, 2.

A third embodiment of the novel de-stack feeder for non-ferrous conductive sheets according to the invention is shown in Figure 5. The system is shown at a point in the operating cycle when the manipulation devices, 4and 5, are not yet contacting sheet 1 so that in this view the system consists of a stack of sheets, 7, supported by base plate 3, with adjacent electro-magnet, 13, with negative electrode 12 and positive electrode 14, being brought into contact with the upper sheet in the stack 1. When a current is passed through sheet 1, between electrodes 10 and 11, and a current is passed through the electro-magnet 13, the interaction of the induced magnetic field in sheet 1 and the magnetic field from the electro-magnet 13 creates an upward movement of sheet 1 away from sheet 2. This action can be generated before the manipulators, 4 and 5, are brought into contact with sheet 1 so that sheet 1 is effectively pre-separated from second sheet, 2. The field in the electro-magnet, 13 is varied to interact favourably with the first sheet in the stack, 1, in preference to the second sheet in the stack, 2. The electro-magnet, 13, can optionally be mounted onto or separated from the manipulation device support structure (not shown).

A forth embodiment of the novel de-stack feeder for non-ferrous conductive sheets according to the invention is shown in Figure 6 The system is shown at a point in the operating cycle when the manipulation devices, 4and 5, are not yet contacting sheet 1 so that in this view the system consists of a stack of sheets, 7, supported by base plate 3, with adjacent electro-magnet, 13, and intermediary non-ferrous inductor, 16. When an alternating current is passed through the electromagnet, 13, eddy currents are induced in the intermediary non-ferrous inductor, 16, which in turn induces eddy currents in the uppermost sheet which create an attraction of the uppermost sheet to the electromagnet. The attraction may be limited to one sheet thickness through application of the skin effect as previously described.