Printing sheet feed and aligning system for a printer

Claim 2

A printing sheet feed and aligning system for a printer, said system comprising: a printing head movable along a printing line; a plane bearing surface for receiving a sheet to be printed on and having movable stop means aligned in a direction parallel to said printing line; at least one first feed roller rotatable to feed said sheet on said plane surface against said stop means; lateral guide means at the side of said plane surface and perpendicular to said printing line; and a second feed roller rotatable to feed said sheet in a direction of alignment parallel to said printing line against said lateral guide means, said second roller being coupled to said first roller for rotation therewith; said first and second rollers each comprising a pair of substantially diametrically-opposed radial projections, the pair of projections on said first roller being relatively offset with reference to the pair of projections on said second roller by about 90°.

Claim 3

A system as claimed in claim 1, in which said first roller is rotatable on a first shaft parallel to said printing line and said second roller is rotatable on a second shaft perpendicular to said first shaft, said second roller being rotated by said first roller with a transmission ratio of 1:1.

Claim 4

A system as claimed in claim 1, comprising a front sensor located in the proximity of said movable stop means to sense a front edge of said sheet, and a lateral sensor located in the proximity of said lateral guide means for sensing a lateral edge of said sheet.

Claim 5

A system as claimed in claim 3, comprising a control unit, a comparison circuit connected to said control unit and to said sensors, and actuating means for said rollers controlled by said control unit for stopping said first roller on command of said sensors with one of said projections in engagement with said sheet.

Claim 6

A system as claimed in claim 4, in which said comparison circuit detects instants at which said sensors sense said front edge and said lateral edge, respectively, and, when said lateral edge is sensed after said front edge, said comparison circuit enables said actuating means to rotate said rollers by a further predetermined angle, while when said front edge is sensed after said lateral edge, said comparison circuit enables said actuating means to rotate said rollers by an angle less than said predetermined angle.

Claim 7

A system as claimed in claim 5, in which said predetermined angle is 270° and said lesser angle is 180°.

Claim 8

A system as claimed in claim 1, in which said printing head can move vertically to adopt a plurality of positions as a function of the thickness of said printing sheet, and said system comprises a rotatable cam element, a first lever connected to said printing head, a second lever connected to said first lever by means of a spring and moved by said cam element, and sensor means adapted to detect relative rotation of said first and second levers to block rotation of said cam element.

Claim 9

A system as claimed in claim 7, including a rotatable shaft having a lever arm fixed thereto and a slider, said movable stop means being mounted on said rotatable shaft and turned by said first lever by means of said slider and by means of said lever arm cooperating with said slider.

Claim 10

A system as claimed in claim 7, including a control unit responsive to said sensor means, and a stepping motor controlled by said control unit, wherein said cam element is rotated by said motor, whereby vertical movement of said head is stopped when said head rests on said printing sheet.

Claim 11

A system as claimed in claim 8, including a control unit responsive to said sensor means, and a stepping motor controlled by said control unit to rotate said cam element, whereby vertical movement of said head is arrested when said head rests on said printing sheet.

Claim 12

In a printer having a printing head movable along a printing line, a printing sheet feed and alignment system comprising: a plane bearing surface for receiving a sheet to be printed on and having movable stop means aligned in a direction parallel to said printing line; a least one first feed roller rotatable to feed said sheet on said plane surface against said stop means; a front sensor located in the proximity of said stop means to sense a front edge of said sheet; lateral guide means at the side of said plane surface and perpendicular to said printing line; a second feed roller rotatable to feed said sheet in a direction of alignment parallel to said printing line against said lateral guide means; a lateral sensor located in the proximity of said lateral guide means for sensing a lateral edge of said sheet; actuating means for driving said rollers; comparison means coupled to said sensors to detect the instants at which said sensors sense said front edge and said lateral edge respectively, and, when said lateral edge is sensed after said front edge, causing said actuating means to rotate said rollers by a first predetermined amount, and when said front edge is sensed after said lateral edge, causing said actuating means to rotate said rollers by a second amount which is different from said first amount.

Claim 13

In a printer having a printing head movable along a printing line, a printing sheet feed and alignment system comprising: a plane bearing surface for receiving a sheet to be printed on and having movable stop means aligned in a direction parallel to said printing line; a least one first feed roller rotatable to feed said sheet on said plane surface against said stop means; a front sensor located in the proximity of said stop means to sense a front edge of said sheet; lateral guide means at the side of said plane surface and perpendicular to said printing line; a second feed roller rotatable to feed said sheet in a direction of alignment parallel to said printing line against said lateral guide means; a lateral sensor located in the proximity of said lateral guide means for sensing a lateral edge of said sheet; actuating means for driving said rollers; comparison means coupled to said sensors to detect the instants at which said sensors sense said front edge and said lateral edge respectively, and, when said lateral edge is sensed after said front edge, causing said actuating means to rotate said rollers by a first predetermined amount, and when said front edge is sensed after said lateral edge, causing said actuating means to rotate said rollers by a second amount which is different from said first amount.

Claim 14

The invention as claimed in claim 11, in which said second amount is less than said first amount.

Claim 15

The invention as claimed in claim 11 in which said rollers have equally-spaced projections thereon, said second roller is coupled to said first roller for rotation therewith, and said projections on said second roller lie relatively intermediate the projections on said first roller.

Claim 16

A printing head mounting system comprising: a printing head movable along a printing line; a plane bearing surface for receiving a sheet to be printed on and having movable stop means aligned in a direction parallel to said printing line; means for feeding said sheet on said plane surface into engagement with said stop means; and means mounting said printing head for movement towards and away from said plane surface to adopt a plurality of positions as a function of the thickness of said sheet, said mounting means comprising: rotatable cam means; a first lever coupled to said printing head; a second lever; resilient biasing means coupling said second lever to said first lever for movement by said cam means; and sensor means for detecting relative rotation of said first and second levers to block rotation of said cam means.

Claim 17

A printing head mounting system comprising: a printing head movable along a printing line; a plane bearing surface for receiving a sheet to be printed on and having movable stop means aligned in a direction parallel to said printing line; means for feeding said sheet on said plane surface into engagement with said stop means; and means mounting said printing head for movement towards and away from said plane surface to adopt a plurality of positions as a function of the thickness of said sheet, said mounting means comprising: rotatable cam means; a first lever coupled to said printing head; a second lever; resilient biasing means coupling said second lever to said first lever for movement by said cam means; and sensor means for detecting relative rotation of said first and second levers to block rotation of said cam means.

Claim 18

A system as claimed in claim 14, including a rotatable shaft having a lever arm fixed thereto and a slider, said moveable stop means being mounted on said rotatable shaft and turned by said first lever by means of said slider and by means of said lever arm cooperating with said slider.

Claim 19

A systems as claimed in claim 14, including a control unit responsive to said sensor means, and a stepping motor controlled by said control unit, wherein said cam element is rotated by said motor, whereby vertical movement of said head is stopped when said head rests on said printing sheet.

Claim 20

A system as claimed in claim 16, including a control unit responsive to said sensor means, and a stepping motor controlled by said control unit to rotate said cam element, whereby vertical movement of said head is arrested when said head rests on said printing sheet.