The invention relates to an apparatus for stacking - sheets- of arr arbitrary mater al , e.g. plain or shaped metal sheet, in one stack or in several consecutive stacks,

The apparatus is of the type comprising a number of suction cups movable in an endless path, which are compressibly engagable with the sheets for gripping same by subat ospheri c pressure in the suction cup and are provided with a valve for breaking the subatmospheric pressure and thus depositing the sheet.

Stackers operating with suction cups exist already but are provided with a vacuum source for effecting the gripping. Such an arrangement results in a complicated connection and control of the suction cups. There are also magnetic stackers wherein magnetic or magnetized wheels grip the sheets but these stackers too are complicated and expensive and cannot be used for sheets consisting of another material than iron, such as glass sheets, aluminium sheets, etc.

For the purpose to make possible that sheets of an arbitrary material are stacked the invention re.lates to an apparatus of the type initially referred to, which has obtained the character stics appearing from claim 1. As a consequence thereof, the construction of the apparatus will be simple in relation to prior art stackers operating with a vacuum source or magnets.

For explanation of the invention an embodiment there- of will be described in more detail below, reference being made to the accompanying drawings, in which Fig. 1 dia¬ grammatical ly discloses the supplying device of the stacker, Fig. 2 is a diagram of the depositing portion of the stacker, Fig. 3 is a vertical cross-sectional view of an endless conveyor supporting the suction cups,

and Fig. 4 is a fragmentary side view of the suction cups and switches with operating arms, included into a device for sensing the length of the sheet and break¬ ing the subatmospheric pressure in the suction cups carrying a sheet, when depositing said sheet in a stack. The stacker shown includes a number of suction cups 10 - see Figs. 1 and 3 - which consist of rubber funnels having a stiffened margin 11. These suction cups are supported by cross .beams 12 spanning the distance between two endless chains 13 running in an endless path in guide bars 14 over end sprockets one ^• of which is shown at 15 in Fig. 1. As will be seen from Fig. 3, two such units can be arranged one beside the other for obtaining a sufficient number of suction cups over the width of the sheet. The drive of the chains is not shown in detail but the chains can be driven in a conventional manner over the end sprockets provided for the chains. ,

The upper portion of each suction cup is connected by a hose 16 to a valve 17 mounted on the cross beam 12, and this valve is normally closed but can be opened by energizing electromagnets 18 fixedly mounted above the valve in part of the moving path thereof, an armature 19 being attracted by the magnets 18, which is connected with the head of the valve to operate same to open posi¬ tion. The control of the energization of the electro¬ magnets 18 will be described below.

In Fig. 1 there is shown a supply conveyor 20 on which the sheets are carried to the stacker. By means of a guide sprocket 22 the chains with the suction cups 10 are guided such that the suction cups are gradually lowered to engage an arriving sheet 21 and are pressed against ^" said sheet, air trapped in the suction cups bein squeezed from the suction cups. Then, when the valves 17 are closed, the suction cups hold the sheet so that

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this will be removed from the supply conveyor 20, hanging from- the- suction cups, as- is shown in Fig. 1 , wherein a gripped sheet 21A hangs from the suction cups. Hanging in this manner, the sheet is then fed over the di stance-«w-here- the electromagnets 18 are- arranged , see Fig. 2, and this distance is assumed to extend over a number of sections distributed along said distance, where the sheets are to be deposited arbitrarily in on.e or the other of a number of stacks. In Fig. 2 it is presupposed that there are four such sections and they are designated 100, 200, 300, and 400, the electro¬ magnets 18 associated with the stacks being designated 118, 218, ^' 318, and 418. Within each section there are four electromagnets to which have been added the suffixes A, B, C, and D.

For the control of the energization of the. electro- magnets a number of switches are provided, designated 123B-D, 223A-D, 323A-D, and 423A-D. Each switch com¬ prises a microswitch 23, Fig. 4, having a pivoted actuating arm 24 which is normally held with a roller 25 rotatably mounted on the arm in such position that the roller 25 is lifted by the leading edge of a passing sheet to roll then on the upper side of the sheet as long as the sheet is passing. When the roller 25 is being lifted the arm 24 is swung counter-clockwise as seen in Fig. 4, to close the normally open switch 23 so that the energization circuit of the associated electromagnet is closed.

Now, the switches and the electromagnets are arranged in such a way that the length of a passing sheet is sensed by means of the switches and the actuating arms thereof and the electromagnets are then activated as required to make all suction cups holding the sheet release simultaneously in a predetermined position in the moving path of the sheet, such position being chosen to

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correspond to one of the four sections. How this contro is performed will be explained with reference to the diagrammatic Fig. 2.

As will be seen from Fig. 2, all electromagnets ar connected at one terminal thereof to a conduit 26 fro a power source, the terminals of which are indicated at 27. As far as the electromagnets are concerned, having the suffixes A, B, and C, the other terminal thereof ca be connected to the other conduit 28 from the power source 27 over a switch gear 29 arranged as section selector, and switches 123, 223, etc. , while the other ^• terminal of electromagnets, having the suffix D, can be connected to the conduit 28 over the switch gear 29 onl The switch gear 29 has four positions designated 1, 2, 3, and 4, which correspond to deposition of the sheets in the associated sections ^' 100, 200, 300, and 400. The switches 23 associated with each section are connected in series with each other and with the switch gear 29, and if the switch gear 29 is set e.g. to position 3, as assumed in Fig. 2, a sheet moving from the right in

Fig. 2 along the row of the actuating arms 24 with the rollers 25, associated with the switches, will close the switches 323A, 323B, and 323C in the order mentione at the arrival at the section 300 without the electro- magnets 318A, 318B, and 318C being energized. The curre circuit through these electromagnets from the conduit 2 to the conduit 28 is interrupted at the switch 323D as long as the sheet has not advanced sufficiently to actuate this switch. However, when this happens during the continued movement of the sheet, all electromagnets the switches of which have been actuated by the sheet, will be activated so that the suction cups holding the sheet will be connected to the atmosphere, via the associated valves 17 to release the sheet as a conseque thereof, said sheet thus dropping into the section 300.

Depending on the position to which the switch gear 29 is set, the sheets will thus be deposited in one of the four sections. The switches 123, 223-, etc. accordingly measure the length of the sheet, and when the last switch in the row of switches, associated with a section, has been actuated, suction cups to the number correspond- ing ^~ to the length of the sheet are caused to release. ^' In order that the sheets shall be stacked in a straight and proper stack a movable abutment designated 130, 230, and 330, respectively, is provided for each of the three first sections 100, 200, and 300. This abut¬ ment is displaced between an inoperative position shown with respect to the abutments 130 and 230, and an operative position shown with respect to the abutment 330, by means of a hydraulic or pneumatic double-acting cylinder 31 to which pressurized fluid is supplied via . a reversing valve 32 from a suitable source of pressurized fluid. The valve 32 is a solenoid valve and is energized over the switch gear 29 through a conduit designated 133, 233, and 333, respectively, for the three abutments. The reversing valves associated with the abutments 130 and 230 are not actuated in order that the abutments shall be maintained in the inoperative position when the switch gear 29 is set to position 3 as shown in the drawing in Fig. 2, while on the contrary the valve of the abutment 330 is energized from the switch 27 and thus is actuated to hold the abutment 330 in the operative position thereof as is also shown in Fig. 2. Accordingly, the abutment 130 is instead in the operative position when the switch gear is in the position 1 , and the abut¬ ment 230 is in the operative position when the switch gear is in the position 2, while all abutments are in the inoperative position when the switch gear is in the posi¬ tion 4 because there can be arranged a stationary abut- ment for the section 400, the last section of the row.

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The sections can comprise areas on the ground- or the floor large enough to receive a stack of the sheets handled, the border between the sections being defined by the abutments. Then, the stacker disclosed . 5 can be used not only for stacking sheets in any one of four separate sections but also for stacking sheets o ^' f different lengths because a sheet which is of such a length that it extends over the total length of two or more sections will be held by the suction cups until

10 the switch 23D for the last one of the sections involved is actuated, all electromagnets along the total length of the .sheet being energized over said switch and the switch gear 29 for the deposition of the sheet. Thus the switch gear is set in dependence on the length of

15 the sheets handled and only the abutment which will be located at the leading edge of the sheets then will be in the operative position, the rest of the abutments being in the inoperative position so a _$ s not to interfere with the deposition of the sheet.

20 In an electronic embodiment the length of the sheet is sensed by a stationary sensor sensing the leading edge of the arriving sheet and starting a pulse generato which controls a shift register. When the sensor senses the trailing edge the pulse generator is stopped. There

25. is now in the shi ft ^' regi ster information indicating the length of the sheet and such information will be shifted in the shift register synchronously with the sheet mov¬ ing to the position where it is to be stacked, by a pre¬ determined number of pulses being counted from the sens-

30 ing of the leading edge. After this number of pulses, the vacuum is broken in suction cups to the number corre sponding to the length of the sheet registered in the shift register. The counting--of the pulses in the shift register is started when the sensor senses the leading

35 edge of the sheet.

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