GB2341384A - Stacking or destacking sheets from a pile - Google Patents

Abstract

Sheets, eg for the production of printed circuit boards, are removed from a pile 11 by lifting the front edge of the top sheet 10 so that a train 20 of rollers 21 can be inserted thereunder. The train is then reversed, so feeding the sheet to a pair of pinch rollers 30. Lilting is effected pneumatically or by grippers. To form a stack, sheets are advanced by the train, held above the stack by suction grippers while the train withdraws, and then lowered onto the stack.

Description

2341384 HANDUNG SYSTEMS The present invention relates to handling systems,

particularly handling systems for rigid or semi-rigid sheet materials such as those in the production of printed circuit boards.

In the production of printed circuit boards, panels are subjected to various sequential treatments, such as coating treatments, by various different machines. The processes are semi-continuous and the panels are generally supported upon a conveyor through each machine. The panels must be transferred from one machine to another without damaging the panel or any coating which may have been applied thereto. Often the panels are stored or collected in vertical or angled stacks in face to face relationship often with a slip sheet material between the faces.

These stacks of panels have to be created following a particular process in what is known 1 as an unloader and stacks are introduced into a process by what is known as a loader.

Typically stacks of panels are either placed by hand on (or removed) from to a table or would be placed on to a cart (or removed) from which they are automatically placed on the table of the loader or taken from the table of the unloader.

Current loadin methods of such a stack involve either a large space requirement, 9 0 typically of almost or more than double the length of the longest panel being handled. These processes also carry the risk of sliding the surface of one panel over the surface of another. Current loading methods employing large areas of suction cups also increase the risk of picking up more than one panel at a time as panels frequently have multiple holes in them.

Current methods also require a large amount of vertical space to allow panels to be transported over the top of the stack onto where they can be lowered to avoid surfaces sliding together. The most common unloaders, in fact, make little attempt to avoid the surface sliding by simply allowing panels to pass through a pair of drive rollers and slide 0 2 across the top of the stack being collected.

Particularly in the context of 'clean room' operation, the large space occupation of existing panel handling apparatus can have significant cost implications. The present 1 invention seeks to address these disadvantages and provide a reduced size panel handling apparatus.

In its broadest sense, the present invention provides an improvement to the system described above avoiding the requirement to have approximately double the length ofthe longest panel by re-directing the "table" supporting the panel from a horizontal to vertical C trajectory shortly after panels have been transported from the table.

According to the present invention there is provided a sheet material handling apparatus wherein sheet materials are transferred between a substantially vertical stack of such materials in a face-to-face relationship sequentially and an, optionally spaced, end-to-end train of said sheet materials at an outlet or inlet of the apparatus; the apparatus comprising means for elevating an uppermost sheet material from the stack whilst a table advances between the elevated sheet material and the sheet below; the table being a flexible reciprocating table and being adapted to output a sheet deposited thereon through the outlet of the apparatus; wherein the reciprocating table comprises a series of rollers each mounted for free rotation in at least one direction, the series of rollers being adapted to travel between an engaged position in which at least a portion of the table is horizontal at a point where the table is intermediate the elevated sheet and the sheet below, and a disengaged position in which the table is substantially vertical at a point intermediate the means for elevating the sheet materials and the outlet of the apparatus.

11) Preferably, the table is adapted to travel along an at least partially arcuate path between the engaged and disengaged positions.

Preferably, each roller is mounted for ftee rotation between two blocks, all such blocks being flexibly coupled to form a chain, which chain is driven by a motor.

3 The means for elevating the sheet material typically comprises a plurality of suction cups mounted longitudinally with respect to the direction of motion of the table. Preferably, the suction caps are adapted to operate within a range of separations from the uppermost 5 panel.

Preferably, some or all of the rollers include clutch mechanisms to allow free rotation in one direction only.

The above and other aspects of the present invention will now be illustrated, by way of example only, with reference to the accompanying figures in which:

Figure I illustrates, schematically, in four side views, the operation of an embodiment of a handling system in accordance with the present invention; "D Figure 2 is a more detailed schematic side representation of a handling system in accordance with the present Invention; Figure 3) is a schematic end view of the system of Figure 2; and Figure 4 illustrates, in four side views, the operation of the table of the apparatus of I Figures 2 and 3.

With reference to Figure 1, the leading edge of a top panel (10) on a vertical stack (11) of panels in a face-to face configuration is picked up by a row of suction heads or cups (12) and the panel is tilted with the leading edge raised and back edge remaining on the stack in a conventional manner. The conventional systems then have a solid planar table of approximately the length of the panel cycled back against the eventual direction of travel of the panel and below the level of the suction cups. When fully cycled back, the back end of the panel (10) raises and rests on the table. The suction cups then release the panel which drops onto the table leaving , a short length projecting over the front of the 4 table. The table then cycles forward until the short projecting length enters nip rollers (3)0) driving the panel at the entrance to a processing machine (not shown) for further processing, such as the application of a coating to the panel. As soon as the table is far enough forward the suction head lowers picks up the next panel and waits for the table to cycle back again. As a result of this sequence of operations, a train of panels (10) in an end-to-end arrangement is formed and output from the apparatus. The panels will usually be well spaced apart in this configuration, but the timing of the apparatus can be adjusted to provide that each panel contacts the previous panel.

The present invention allows for this action to be accomplished without the need for the added space by making the reciprocating table flexible. Thi s can be achieved by forming a flexible table (20) from a set of rollers (2 1), typically formed of or coated with a rubber compound. The rollers are free to rotate within support blocks (25) provided at each end of each roller (some omitted in Figure 2 for clarity). The support blocks (25) are coupled together with a chain (22), belt or other flexible drive to form the flexible table, driven by an electric motor (23). The drive can either be a complete chain driven in a loop as illustrated or a short length held in a slide and reciprocated. In this embodiment, shortly after exiting the suction cup position, the chain (22) and with it the table (20), follows a path which carries it vertically downwards. This allows the pinch rollers (330) at the extremity of the processing machine (not shown) to be brought closer to the suckers considerably reducing the machine length.

The operation of the table is most clearly illustrated in Figure 4, which shows, in side view, a section of the table, comprising just six rollers (2 1) with respective blocks (25). A panel (10) is supported upon four rollers (2 1) each being held in respective blocks (25) of a chain of such blocks. The chain passes over a cog (26) and is directed downwardly towards a further, motor driven, cog (27). As the chain advances, the panel (10) is ejected from the apparatus or into another part of the apparatus through pinch rollers,0).

To prevent the free running rollers (2 1) rolling backwards due to inertia when the flexible table (20) is travelling forwards, clutches may be fitted to some rolls so they can run freely only in one direction.

As each panel (10) is removed ftorn the stack (11), the stack is raised by being mounted upon a table (40) which is raised or lifted along rams (4 1) by an actuating mechanism 1 1 (43) including a further electric motor (42), actuated in response to output signals from a sensor placed to sense the position of the uppermost panel at any particular time.

In some fields, the raising mechanism for the table (40) will be omitted, preference being given to a higher, fixed height, table and smaller stacks of panels on a tray, the tray being placed, in use, upon the fixed table. In such a case, the suction cup assembly will include means for enabling operation of the suction cups across an extended range of separations above the stack of panels.

The same invention can be applied equally to unloading and again allows the pinch (nip) rollers to be placed very close to the table or stack, thereby reducing machine length. In this case a single row of suction cups need not be on the machine but may instead be an array of suction cups covering most of the panel area would be positioned above the level of the table movement and over the top of the stack. In this case, as a panel exists through the pinch roller the table (20) cycles from vertical to horizontal until the panel is resting on the reciprocating table (20) and over the stack (11). At this point the suction cups (12) grip the panel, the table returns to the vertical position and the suction cups lower the panel onto the top of the stack.

Instead of suction cups, a gripper system can be used and this can be configured to allow panels to be positioned before being lowered on to the stack to create a neat stack.

In the case of both loading and unloading, the use of interleaves can be facilitated by-- I. Loading - The interleave (which must not be fed forward into the process) is placed on the table in the way described but before the table can index forward it 6 is identified as an interleaf and removed by a suction head alongside the machine. The table then makes a dummy run (without a panel) and picks up a panel on its return.

2. Unloading - In this case following the lowering of a panel on top of the stack a 0 0 suction head alongside the machine lowers an interleaf on the top of the stack while the indexing table is in a vertical position.

The reduced size advantages of the handling system of the present invention are achieved equally whether the system is used as an integral component within a larger assembly or as a stand-alone transfer station. Additional features will, of course be required, to enable the system to interoperate with other components, but these features will be immediately apparent to those skilled in the art and will not be described in any further detail.

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Claims (5)

Claims.

1 A sheet material handling apparatus wherein sheet materials are transferred between a substantially vertical stack of such materials in a face-to- face relationship sequentially and an, optionally spaced, end-to-end train of said sheet materials at an outlet or inlet of the apparatus; the apparatus comprising means for elevating an uppermost sheet material from the stack whilst a table 0 advances between the elevated sheet material and the sheet below; the table being a flexible reciprocating table and being adapted to output a sheet deposited thereon through the outlet of the apparatus; wherein the reciprocating table comprises a series of rollers each mounted for free rotation in at least one direction, the series of rollers being adapted to travel between an engaged position in which at least a portion of the table is horizontal at a point where the table is intermediate the elevated sheet and the sheet below, and a disengaged position in which the table is substantially vertical at a point intermediate the means for elevating the sheet materials and the outlet of the apparatus.

2. A sheet material handling apparatus as claimed in Claim 1 wherein the table is adapted to travel along an at least partially arcuate path between the engaged and disengaged positions.

0 A sheet material handling apparatus as claimed in Claim 1 or Claim 2 wherein each roller is mounted at each end thereof within a support block, all such support blocks being coupled together with a flexible drive mechanism.

4. A sheet material handling apparatus as claimed in any one of claims 1 to 3 wherein the means for elevating the sheet material comprises a plurality of suction cups mounted longitudinally with respect to the direction of motion of the table.

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5. A sheet material handling apparatus substantially as herein described with reference to the accompanying drawings.

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