GB2143214A - Sheet feeder for printing machine - Google Patents

Abstract

A sheet feeder comprises a pair of guide rails (4) one at either side of the feeder and a pair of feed boards (1,2) each having at either side thereof a pair of vertically aligned rollers (7 and 8) and a third roller (9) retractable by means of a lever (10) to allow the roller (9) to pass through a notch (4b) in a flange (4a) of the feed board guide rail (4). The feed board (1) is lifted by means of studs (12) mounted at spaced intervals along respective drive chains (5) at either side of the sheet feeder. During feeding from an upper feed board (1) a lower feed board can be loaded with paper so that upon depletion of the stack of sheets on the upper feed board that depleted board can be removed and the next successive, already loaded feed board, indexed to the sheet feeding position. <IMAGE>

Description

SPECIFICATION Sheet feeder for printing machine The present invention relates to a sheet feeder for a printing machine. Such a printing machine will normally be of a type expected to handle high throughput rates of printing, but the invention can be used with any kind of sheet fed printer which may, for example, be an offset printer, a relief plate printer, a photocopier, or a stencil printer.

The present invention provides a sheet feeder for a printing machine, the sheet feeder including at least two feed boards each adapted to support a stack of sheets to be fed, a feed board moving mechanism to carry the feed boards and operable to bring an appropriate one of the feed boards into a common sheet feeding position and to support at least one other of the feed boards in a waiting position, and common means for feeding sheets from a stack supported by the said feed board which is in the sheet feeding position, the arrangement being such that upon depletion of the stack of the feed board in the sheet feeding position that feed board can be cleared from the sheet feeding position and the feed board then in the waiting position can be brought into the common feeding position.

Preferably the feed board in the sheet feeding position is manually released from the feed board moving mechanism and the moving mechanism is then operated mechanically to move the feed board from the waiting position to the sheet feeding position.

In order that the present invention may more readily understood the following description is given, merely by way of example, with reference to the accompanying drawings in which: Figure 1 is a perspective view of an offset printer incorporating the sheet feeder in accordance with the present invention; and Figure 2 is a detail of the sheet feeder shown in perspective and looking from the righthand side of Fig. 1.

The sheet feeder shown in Fig. 1 is a Gestetner Model 211 feeder and is shown with both of the feed boards in position.

Conventionally the Model 211 only has one feed board which is lifted to and lowered from the sheet feeding position occupied by the sole feed board 1 shown in Fig. 1, and has a loading position occupied by an empty feed board 2 of Fig. 1.

With the conventional single feed board printer, despite the fact that the feed board 1 is capable of carrying a considerable number of sheets once it has been fully loaded, there is a considerable down time involved at the end of feeding of a stack of sheets from the feed board 1 because the feed board 1 then needs to be mechanically lowered to position 2 of Fig. 1 and then loaded with a fresh stack which may comprise several reams of paper each ream being packed in a separate container which needs to be opened and the sheets carefully arranged on the feed board.

Printing cannot resume until the feed board has then been raised to bring the top of the newly formed stack of sheets into engagement with sheet feed members of the sheet feed means generally designated 3.

The sheet feeder in accordance with the present invention offers the improvement of having a second feed board which is identical to feed board 1, and is such that upon depletion of the stack on the feed board 1 in the sheet feeding position that feed board can be cleared from the sheet feeding position to allow the already loaded second feed board 2 in the waiting position to be lifted by the small distance necessary to bring the top of the stack of sheets on that second feed board into engagement with the sheet feed members 3.The down time of the machine is thus considerably reduced because the careful stacking of the sheets on the feed board in the waiting position can take place while the feed board 1 is in the sheet feeding position and there is furthermore no need for the feed board moving mechanism to be caused to execute its time-consuming cycle to lower the feed board 1 to the waiting position 2.

In this embodiment of the present invention the two feed boards are each releasably attachable to the feed board raising and lowering machanism which includes a guide rail 4 and an endless chain 5, therebeing one such guide rail 4 and one such chain on each side of the printer to ensure that both sides of the feed board 1 are adequately supported.

Mere removal of the top feed board 1 from the feed board moving mechanism 4 and 5 aliows immediate operation of the feed board moving mechanism 4, 5, to lift the other feed board 2 from the waiting position to the sheet feeding position shown at 1 in Fig. 1.

Fig. 2 is a detail of the feed boards 1, 2, the guide rail 4, and the endless chain 5, and is intended to illustrate the way in which the feed board 1 can readily be removed from the guide rail 4 once the stack of sheets on that feeder has been depleted.

Referring now to Fig. 2, it will be seen that the sidewall 6 of the feed board carries a pair of vertically aligned upper and lower rollers 7 and 8, respectively, and a further roller 9 which is spaced from the vertical plane passing through the axes of rotation of the upper and lower rollers 7 and 8 in such a way that when the feed board is mounted on the guide rail 4 the two rollers 7 and 8 are positioned to one side of a flange 4a of the guide rail and the other roller 9 is positioned to the other side of that flange 4a.

As also shown in Fig. 2, the top end of the guide rail 4 has a notch 4b formed in the flange 4a, for a purpose to be described below.

At each side of the feed board, and partially concealed beneath and behind the sidewall 6, is a manually operable lever 10 which can be puiled outwardly to retract the respective roller 9 inwardly along the direction of arrow 11 through a small distance sufficient to ensure that the feed board can be removed from the guide rail 4 by movement of the partially retracted roller 9 leftwardiy as viewed in Fig.

2 through the notch 4b.

The arrangement must be such that until the retractable rollers 9 have been partially retracted those rollers cannot pass through even the notch 4b, and that even when fully retracted they cannot pass the flange 4a at any other point away from the notch 4b or a similar notch provided lower down the guide rail 4. Thus, inadvertent removal of the feed board 1 from the guide rail 4 is prevented.

It will of course be understood that there will be a movement stop to prevent the feed board 1 from being lifted vertically clean off the guide plate 4 because this would interfere with the sheet feed elements 3 which, as shown in Fig. 1, are cantilevered out from the front of the printing machine to overlie the feed board 1.

Although not shown in Fig. 1, there is a similar notch 4b lower down the guide rail 4 at a position such that while the upper feed board 1 is in the feeding position shown in Fig. 1 a second feed board 2 can be mounted releasably on the guide rail 4 below that feed board in the feeding position.

Fig. 2 shows that the feed board is raised towards the loading position by engagement of a stud 12 carried by the chain 5 and abutting the underside of a block 1 3 secured to the sidewall of the feed board 1. In practice the chain 5 carries at least two of these studs so that there is no need for the chain to be reversed in order to entrain the feed board 2 in the waiting position of Fig. 1, it is simply sufficient to actuate the chain for forward movement until the next stud 1 2 lifts into engagement with the block 1 3 of the feed board in the waiting position.

From the above it will be understood that the operation of mounting the second feed board lower down the guide rail 4 while the upper feed board 1 is being indexed upwardly for sheet feeding action positions that second feed board 2 either with its block 1 3 sitting on the next successive stud 12, or on a stop at the bottom of its permissible path of movement to await the arrival of the next stud 12.

Of these two possibilities, the second is preferable so that the next stud 1 2 will just about be in contact with the lower feed board by the time the stack of sheets on the upper feed board has been depleted to a level which requires substitution of the other feed board.

It is possible to provide more than two feed boards and correspondingly more than two studs, if desired.

At various points throughout the above description we have referred to the existence of similar elements to either side of the printing machine and of the feed board, and it will be understood that these duplicated elements comprise the chains 5, the rollers 7, 8 and 9, the studs 12, and the guide plates 4 with identical notches 4b.

The operating lever 10 shown in Fig. 2 as being movable in the direction of the arrow 14 to effect retracting movement of the roller 9 along the direction of the arrow 11 is in the preferred embodiment duplicated so that it is necessary for both of the levers 10 to be operated simultaneously before the feed board can be removed. However, it may be possible for only one such operating means to be provided in order to effect release of both sides of the feed board.

For rapid raising of the lower feed board 2, the handwheel 1 5 (Fig. 1) may be rotated with the release lever 1 6 (Fig. 1) depressed in order to disengage the normal incrementally indexing feed board raising drive and enable the chains to be circulated rapidly by the wheel 15.

The suction feed means of the Model 211 machine allows the very last sheet to be fed from the upper feed board 1. Then the operator must remove the feed board 1 and raise the lower feed board 2. If desired a warning may automatically be given when only a few sheets are remaining on the upper feed board 1 to make sure the operator is ready to change boards.

The preferred embodiment of the present invention uses releasable feed boards carried by the feed board moving mechanism 4, 5.

However, where space permits, it may be possible for a complete feed board recycling system to be provided so that instead of the need for manual removement of the upper feed board from the sheet feeding position, all that is required is for the feed board moving chains 5 or any mechanical equivalent thereof to be operated so as to clear the upper feed board from the sheet feeding position and simultaneously to index the waiting feed board towards the sheet feeding position.

Such an alternative will be readily apparent to the expert.

Claims (8)

1. A sheet feeder for a printing machine, the sheet feeder including at least two feed boards each adapted to support a stack of sheets to be fed, a feed board moving mechanism to carry the feed boards and operable to bring an appropriate one of the feed boards into a common sheet feeding position and to support at least one other of the feed boards in a waiting position, and common means for- feeding sheets from a stack supported by the said feed board which is in the sheet feeding position, the arrangement being such that upon depletion of the stack of the feed board in the sheet feeding position that feed board can be cleared from the sheet feeding position and the feed board then in the waiting position can be brought into the common feeding position.

2. A sheet feeder according to claim 1, wherein the feed boards are releasably securable to the feed board moving mechanism.

3. A sheet feeder according to claim 2, wherein the feed board moving mechanism comprises guide means and separate drive means to engage a said feed board when carried by the guide means.

4. A sheet feeder according to claim 3, wherein said guide means comprises parallel guide rails to either side of the sheet feederand rollers at either side of the feed boards for attaching the respective feed board to the guide rails for movement along the guide rails.

5. A sheet feeder according to claim 4, wherein there are three such rollers, arranged such that two of the rollers will be positioned at one side of a flange of the guide rail and the other roller will be positioned at the opposite side of the flange of the guide rail, and the feed board includes means for retracting the or each roller at one side of said flange.

6. A sheet feeder according to claim 5, wherein it is the single roller at one side of said flange which is retracted and the retracting mechanism comprises a manually-operable member underneath the feed board.

7. A sheet feeder according to claim 6, wherein there are two said manually-operable members, each comprising a lever under the respective side of the feed board.

8. A sheet feeder constructed and adapted to be operated substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

8. A sheet feeder according to any one of claims 3 to 7, wherein the feed board drive means comprises a chain carrying studs which drivingly abut the respective feed board to move that feed board towards the common sheet feeding position.

9. A sheet feeder according to claim 8 when appendant to claim 7, wherein the flange of the guide rail has at least two notches each arranged such that the retractable roller of the feed board can pass through that notch when it has been retracted to its maximum extent, but that the retracted roller cannot pass the flange at any other point away from the notch, and that it will not even pass through the notch until it has been retracted.

10. A sheet feeder constructed and adapted to be operated substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

CLAIMS (20th Sep 1984)

1. A sheet feeder for a printing machine, the sheet feeder including at least two feed boards each adapted to support a stack of sheets to be fed; feed board guide rails to guide the feed boards for movement towards and away from a common sheet feeding position and to support at least one other of the feed boards in a waiting position; common means for feeding sheets from a stack supported by the said feed board which is in the sheet feeding position; a feed board moving mechanism to drive the feed boards along the guide rails towards said common sheet feeding position; and rollers carried by the feed boards for supporting each feed board on the guide rails, one of said rollers carried by each feed board for engagement with a respective one of said guide rails being movable between a normal rail-engaging position and an alternative position in which that roller can pass through a slot at one position along that guide rail, the arrangement being such that said one roller can pass through said slot in the respective rail only when in said alternative position but that the retracted roller cannot pass the flange at any other point away from the notch, and that it will not even pass through the notch until it has been retracted. 2.A sheet feeder according to claim 1, wherein each said guide rail has a flange with at least two of said notches each arranged such that the movable roller of the feed board can pass through that notch when in said alternative position.

3. A sheet feeder according to claim 2, wherein, for each said guide rail, one of said notches corresponds to arrival of the feed board at said common feeding position and the other notch corresponds to positioning of the feed board at the opposite end of its travel along the guide rail.

4. A sheet feeder according to claim 1, 2 or 3, wherein there are three such rollers only one of which is a said movable roller, the rollers being arranged such that the movable roller will be positioned at one side of the or a flange of the guide rail and the other rollers will be positioned at the opposite side of the flange of the guide rail, and the feed board includes a manually operable control for retracting the movable roller.

5. A sheet feeder according to claim 4, wherein the manually-operable control is carried underneath the feed board.

6. A sheet feeder according to claim 5, wherein there are two said manually-operable controls, each comprising a lever under the respective side of the feed board.

7. A sheet feeder according to any one of the preceding claims, wherein the feed board drive means comprises a chain carrying studs which drivingly abut the respective feed board to move that feed board towards the common sheet feeding position.