TECHNICAL FIELD

The present invention relates to printers, typewriters and like office machines and particularly relates to a paper alignment device for such a machine.

BACKGROUND ART

In a printer provided with a paper magazine, the magazine is often arranged above the printer. A sheet of paper from the magazine must be conveyed a ^• * ^■ * ^■' comparatively long distance before it has reached a position where printing starts in the printer. There is utilized for the conveyance a friction drive means arranged between the magazine and the start-of-print position, and said friction drive means may obtain advancing assistanc ^' from a friction drive means arranged in the magazine. Aligning the sheet, i.e. adjusting it so that its side 0 edges run parallel to the advancing direction of the sheet, often takes place in conjunction with the entrance of the sheet into the machine against drive and back-up rolls situated in the ^" upper part of the machine. When the printing start position is considerably further down in the machine, it may occur, inspite of the alignment , that the sheet has come somewhat on the skew due to uneven ^■ advancing when it has arrived at said position. In order to avoid such skewing of the sheet or at least minimize it, alignment should take place as close to the printing position as possible.

The object of the invention is thus to obviate the above-mentioned incon¬ veniences and provide a device of the kind mentioned, which is situated and implemented such that effective alignment of a sheet of paper in a region adjacent the printing position is achieved with the utilization of simple means. The object is achieved in a .paper alignment device having the characterizing features disclosed in the following claims.

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DISCLOSURE OF INVENTION

The invention will now be described in detail in conjunction with two em¬ bodiments and with reference to the appended drawings, on which

BRIEF DESCRIPTION OF DRAWINGS . ^"

Figure 1 schematically illustrates a paper advancing system taken from a printer and with an aligning device in the form of a fixed stop.

Figures 2 and 3 illustrate a modified aligning device in the form of a braking means including a rotatable roll.

The paper advancing system in Figure 1, which is taken from a non-illustrated printer, includes a friction drive means 10 and a paper chute 11 for leading a sheet 12 of paper past a printing head 13. The friction drive means comprises a toothed belt 14 running round a drive roller 15 and a tension roller 16. Four backup rolls 17 urge the sheet towards the smooth side of the belt. The rolls are arranged in a holder 18 pivotably mounted on a shaft 19. The paper chute has a vertical extension in the region of the printing head 13, and via a curved portion 11a continues in a horizontal portion bounded by an upper defining wail 20 and a lower defining wall 21. An aligning means in the form of an edge 22 extends at right angles to the advancing direction of the sheet.

BEST MODE FOR CARRYING OUT THE INVENTION

Aligning a sheet of paper is accomplished in the following manner.

The sheet, assumed to come from an unillustrated paper magazine, is fed by driving means incorporated in said magazine into the space between the timing drive belt 14 and the uppermost backup roll 17. Suitably, the sheet is roughly aligned in this position. The drive roll 15 now begins to rotate and advance the sheet into engagement against the edge 22. The latter is situated such that when the forward end of the sheet has arrived at it, the back end of the sheet has not entirely come out of engagement with the belt 14 and the downmost

backup roll. The result will be that the sheet will be somewhat curved when it has completely left the friction drive means, a force being generated which strives to return the back end of the sheet into the space between the belt and the downmost roll. By mounting the edge 22 with accurate location and direction there is achieved very good fine alignment of the sheet, simulta¬ neously as the returning force assures that the alignment is not lost when the friction drive means begins advancing the sheet in the opposite direction in conjunction with recording information thereon.

The embodiment according to Figure 1 has the disadvantage that the fixed stop only allows alignment of one paper format. If it is desired to utilize the alignment device for different paper formats, it is necessary to arrange several stops as well as guide means, the latter activating the correct stop after detecting the paper format. An alternative solution is illustrated in Figu¬ res 2 and 3, where the fixed stop has been replaced by a braking means 23, allowing the sheet to pass while being retarded until the back edge of the sheet has left the friction drive means. The braking force is used here as the returning force for the sheet. The braking means includes a rotatable body, and in the example this is a roll 24 oriented at right angles to the advancing direction of the sheet. The roll engages against the bottom wall 21 of the paper chute, or runs against a sheet lying between the roll and wall 21, said sheet being denoted by 12, as previously. The roll is disposed in an aperture 25 in the upper defining wall 20, and is retained in the aperture by a flat spring 26 fastened by a screw 27. The spring 26 forms a cuneiform space together with the bottom defining wall 21, said space being formed such that the roll exerts a predetermined braking force on the sheet without stopping it. When the sheet is advanced in the opposite direction, the roll is urged out of the cuneiform space and the braking effect ceases. In Figures 2 and 3 the advancing direction of the sheet 12 is illustrated by arrows at the ends thereof.

• A printer of the illustrated kind suitably has two friction drive means 10, symmetrically placed relative the centre line of the paper as seen in the advancing direction. In this case, the braking means is suitably arranged

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according to Figures 2 and' 3 such that the roll engages with the paper in a region halfway between both friction drive means. Even better alignment can be obtained here if the roll is replaced by a ball, since the latter has point engagement against the sheet.

The paper alignment device in accordance with the invention can also be applied to typewriters with platen feed, where the typing location is situated very close to the contact points between the platen and associated pressure rollers. If such a typewriter is automatically supplied with paper from a magazine, there similarly arises a need of automatically aligning a transferred sheet before writing starts. A braking means according to Figures 2 and 3 may here suitably be placed in the paper magazine, alignment being effected such that a sheet is advanced in the typing direction past a typing start position for it, after which the advance of the sheet is reversed, with simultaneous activation of the braking means, until the paper has come out of engagement with the platen. Alignment then takes place in the same manner as described above.