Machines for printing different colours on sheets transferred to successive stations including respective impression cylinders must register each sheet with great precision at each station to ensure printing accuracy.

Similarly, punching machines must stationarily register pre-printed sheets with the same precision to ensure punching accuracy. The sheets are often not precisely rectangular, for instance out-of-square or tapered, and front lays carried by each impression cylinder of a printing machine for the precise registration of their leading edges have to be adjusted by before production printing can commence. In one known arrangement, side lays for the registration of their side edges comprise one so- called fixed side-lay secured on a carriage reciprocable out of and into a predetermined registration position, as each sheet travels into printing position, by power- operated means along guides fixed to the machine frame, and another side-lay at the opposite side of the sheet reciprocable in like manner out of and into a predetermined position but in addition acted upon resiliently by spring or pneumatic means so that when in said position it urges the sheet into contact with said one side-lay. The side- lays normally comprise single rollers when so-called body-

plate, which has nominally straight sides, is being printed. However, printing is also regularly effected on so-called scroll-edge sheets which have castellated sides.

The castellations on one side may be offset by half a pitch from the castellations on the other side, and different pitches of castellations may be employed. In order to register the side edges of scroll-edge sheets, side-lays which are elongated strictly in the direction of travel of the sheets, and which typically incorporate a straight line of small ball bearings, have been employed. However, when necessary adjustment of the front lays has resulted in skewing of the side edges of the sheets relative to said direction, these elongated side-lays have the disadvantage that they have not contacted the tips of the castellations along the full length of the side-lays, so that the sheets have been over-constrained by the combined action of the front lays and side-lays and thus misalignment of the sheets has occurred but not been satisfactorily accommodated to the detriment of printing accuracy.

In another known arrangement using elongated side- lays, the angular disposition of these is set by manual adjustment so as to exactly match any skewing of the side edges of a sheet due to necessary adjustment of the front lays, but this arrangement has the disadvantages that misalignment of out-of-square or tapered sheets cannot be avoided, and that extensive time is required to make the manual adjustment.

The object of the present invention is to overcome all of the aforesaid disadvantages.

According to the invention, a side-lay, for a sheet- fed machine, comprises a member incorporating sheet side support means which are elongated generally in the direction of travel of the sheets, said member being so moveably mounted as to enable its support means to make end-to-end contact with skewed sheet sides.

Preferably, the member is pivotally mounted.

Preferably, also, pivotal movement of the member is limited by means of stops.

The stops may be adjustable.

The member may be centred or angularly biased by adjustable spring means.

Alternatively, the member is compliantly mounted.

Alternatively, the member is both pivotally and compliantly mounted.

Movement of the member may be damped.

Preferably, the support means comprise a straight line of bearings.

Preferably, also, the member is mounted on a carriage reciprocable by power-operated means along fixed guides at right angles to the direction of travel of the sheets.

Preferably, where the side-lay has a fixed registration position, the sheets are pulled, pushed or guided into contact therewith.

A preferred embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, of which:- Figure 1 is a diagrammatic plan view of a sheet registered by front lays and side-lays; and Figure 2 is a plan view on a larger scale of one of the side-lays.

Referring now to Figure 1, the leading edge 10 of a scroll-edge sheet 12 travelling through a printing machine in the direction indicated by the arrow 14 is precisely registered at each impression cylinder on the machine by two front lays 16 which are adjustable as shown by the arrows 18. The sheet 12 is urged into contact with the front lays 16 by springs 20 acting on pushers 22 carried by conventional sheet transfer means (not shown) moving continuously along the machine frame. A so-called fixed side-lay indicated generally at 24 comprises a carriage 26 reciprocable by power-operated means (not shown) along guides 28 fixed to the machine frame at right angles to the direction of travel of the sheet 12. An elongated member 30 incorporating sheet side support means (not shown) is pivotally mounted on the carriage 26 about a set-screw 32.

Movement of the fixed side-lay into a predetermined registration position is limited by an adjustable stop 34 secured to the guides 28. Another side-lay indicated generally at 36 comprises a carriage 26 reciprocable by power-operated means (not shown) along guides 28, a member

30 and a set-screw 32 identical to those of the fixed side- lay 24, but instead of a stop 34 the side-lay 36 is provided with a spring 38 acting on its carriage so that it urges the sheet 12 into contact with the fixed side-lay 24.

The elongated members 30 span a plurality of the tips 40 of the castellations 42 along the side edges of the sheet 12, and by virtue of the pivotal connection of said members to the carriages 26 their sheet side support means make end- to-end contact with said tips even though the sheet sides may have been skewed relative to the direction of travel 14 of the sheet 12 by necessary adjustment of the front lays 16. The load is accordingly spread evenly along each side- lay, and the net reaction is always through the axis of its set-screw 32. Thus over-constraint and consequent misalignment due to sheets not being precisely rectangular is avoided.

Referring now to Figure 2, the so-called fixed side- lay 24 is shown in greater detail. The guides 28 comprise a rail which is V-shaped along each edge so as to be engageable between two pairs of rollers 44 with v-shaped peripheral grooves which are rotateably mounted on the carriage 26. The member 30 comprises a body 46 to which there are rigidly secured elongated upper and lower plates 48 with a space between them in which there are rotateably confined a straight line of small ball bearings 50 constituting support means which facilitate sliding of each sheet side through said space as the sheet travels along

the machine. The body 46 is pivotally mounted on the carriage 26 about the set-screw 32 as previously stated, and pivotal movement of the member 30 is limited at each of its ends by means of adjustable stops comprising two set- screws 52 on the carriage 26 which co-act with opposite sides of a tongue 54 formed integrally on the body 46.

Spring means comprising two leaf-springs 56 anchored on the carriage 26 can if required be adjustably moved by respective set-screws 58 on the carriage into contact with the tongue 54 so as to centre or angularly bias the member 30 relative to the body 46. A predetermined registration position of the fixed side-lay 24 is defined by the adjustable stop means indicated generally at 34 which limit movement of the carriage 26 along the guides 28 in the direction towards each sheet.

The construction, arrangement and operation of the other side-lay 36 is identical, except that the adjustable stop means 34 are replaced by spring, pneumatic or other resilient means acting on its carriage 26 to urge each sheet into contact with the fixed side-lay 24 as previously stated.

In a modification, each side-lay is compliantly mounted on its carriage, for example by means of a rubber block or a leaf spring, instead of being pivotally mounted thereon. In another modification, each side-lay is both pivotally and compliantly mounted on its carriage. In a further modification, the adjustable leaf-springs for

centring or angularly biasing each side-lay on its carriage are omitted. In yet another modification, the straight line of small ball bearings is replaced by a linear bearing or by a straight strip of low-friction material. In yet a further modification, the stops which co-act with the tongue are fixed. In still another modification, movement of the member is damped by friction or otherwise. In still a further modification, the member is mounted on means other than a reciprocable carriage, for example on an arcuately-moveable member or on means permanently fixed to the machine frame.

In a still further modification, where the side-lay has a fixed registration position, the sheets are pulled, pushed or guided into contact therewith.

Side-lays according to the invention can also be used with body-plate, with the advantages that the downtime involved in changing over to side-lays of single-roller type is eliminated; and that superior registration is obtained when, as frequently occurs, the side edges of the plates are wavy, in which case said edges are supported at all their high spots.