Double feed sensing device, double feed determining method and image forming apparatus

• US 20070018383A1
• Filed: 07/10/2006
• Published: 01/25/2007
• Est. Priority Date: 07/08/2005
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Printing Systems Limited (Ricoh Company Limited)
• Inventors: Furutono, Masuo, Satou, Kunio, Ohara, Shunichi
• Granted Patent: US 7,817,957 B2
• Time in Patent Office: Days
• US Class Current: 271/262
• CPC Class Codes: B65H 2220/01 indicating an entity as a function of which control, adjustment or change is performed, i.e. input
• CPC Class Codes: B65H 2220/03 indicating an entity which is measured, estimated, evaluated, calculated or determined but which does not constitute an entity which is adjusted or changed by the control process per se
• CPC Class Codes: B65H 2220/11 indicating that the input or output entities exclusively relate to machine elements
• CPC Class Codes: B65H 2301/512125 by abutting against a stop
• CPC Class Codes: B65H 2511/13 Thickness
• CPC Class Codes: B65H 2511/212 Rotary position
• CPC Class Codes: B65H 2511/524 Multiple articles, e.g. double feed
• CPC Class Codes: B65H 2515/81 Rigidity; Stiffness; Elasticity
• CPC Class Codes: B65H 2553/61 Mechanical means, e.g. contact arms
• CPC Class Codes: B65H 7/12 responsive to double feed or separation
• CPC Class Codes: B65H 9/006 the stop being formed by forwarding means in stand-by

Abstract

The invention provides a double feed sensing device capable of sensing double feed of paper sent out for the first time. The double feed sensing device includes a thickness sensing unit for sensing thickness of cut paper conveyed, a rigidity sensing unit for sensing bending rigidity of the conveyed paper, and a double feed determining unit for comparing a value of the thickness of the paper sensed by the thickness sensing unit and a value of the bending rigidity of the paper sensed by the rigidity sensing unit with threshold values of thickness and rigidity of the paper set based on values of thickness and bending rigidity of one sheet of the paper and values of thickness and bending rigidity of stacked sheets of the paper, so as to determine whether the paper is double-fed or not.

Claims

1. A double feed sensing device comprising:

a thickness sensing unit for sensing thickness of cut paper conveyed;

a rigidity sensing unit for sensing bending rigidity of the conveyed paper; and

a double feed determining unit for comparing a value of the thickness of the paper sensed by the thickness sensing unit and a value of the bending rigidity of the paper sensed by the rigidity sensing unit with threshold values of thickness and rigidity of the paper set based on values of thickness and bending rigidity of one sheet of the paper and values of thickness and bending rigidity of stacked sheets of the paper, so as to determine whether the paper is double-fed or not.

2. A double feed sensing device according to claim 1, wherein the thickness sensing unit includes a driving roller capable of rotating, a driven roller in press contact with the driving roller, and a displacement sensing unit for sensing a displacement of a shaft of the driven roller with respect to a shaft of the driving roller when the paper is held between the driven roller and the driving roller.

3. A double feed sensing device according to claim 2, wherein the displacement sensing unit includes a lever capable of pivoting while supporting the driven roller at one end thereof, and the displacement sensing unit senses the displacement of the shaft of the driven roller with respect to the shaft of the driving roller based on a displacement of the other end of the lever.

4. A double feed sensing device according to claim 3, wherein a distance L1 between a pivoting fulcrum of the lever and a point where the driven roller is supported is shorter than a distance L2 between the pivoting fulcrum of the lever and a sensing portion where the displacement of the other end of the lever is sensed.

5. A double feed sensing device according to claim 2, wherein the rigidity sensing unit is attached to a rotating shaft of the driving roller.

6. A double feed sensing device according to claim 1, wherein the rigidity sensing unit includes a sensing member supported so that the sensing member pivots when a front end of the paper abuts against the sensing member, an elastic member for elastically urging a part of the sensing member to appear on a conveyance path of the paper, and a displacement sensing unit for sensing a pivotal displacement of the sensing member when the paper abuts against the part of the sensing member so as to be bent.

7. A double feed sensing device according to claim 6, wherein:

the sensing member has a first arm portion and a second arm portion integrally, the front end of the paper abutting against the first arm portion, the second arm portion having a sensing portion for sensing the pivotal displacement by means of the displacement sensing unit; and

a distance L3 between a position where the front end of the paper abuts against the first arm portion and the pivoting fulcrum is shorter than a distance L4 between the sensing portion and the pivoting fulcrum.

9. An image forming apparatus comprising:

a photoconductor;

an exposure unit for forming an electrostatic latent image on the photoconductor;

a development unit for forming a toner image on the photoconductor;

a paper stacking portion where cut sheets of paper are stacked;

a conveyance mechanism for sending out the paper from the paper stacking portion toward the photoconductor;

a transfer unit for transferring the toner image on the photoconductor to the paper;

a fixation unit for fixing the transferred toner image to the paper; and

a double feed sensing device according to claim 1, provided on a paper-conveyance-direction upstream side of the transfer unit.

10. An image forming apparatus according to claim 9, further comprising a double-fed paper retracting portion for retracting the paper regarded as double-fed by the double feed sensing device.

11. A double feed sensing device according to claim 5, wherein the rigidity sensing unit includes a sensing member supported so that the sensing member pivots when a front end of the paper abuts against the sensing member, an elastic member for elastically urging a part of the sensing member to appear on a conveyance path of the paper, and a displacement sensing unit for sensing a pivotal displacement of the sensing member when the paper abuts against the part of the sensing member so as to be bent.

12. A double feed sensing device according to claim 11, wherein:

the sensing member has a first arm portion and a second arm portion integrally, the front end of the paper abutting against the first arm portion, the second arm portion having a sensing portion for sensing the pivotal displacement by means of the displacement sensing unit; and

a distance L3 between a position where the front end of the paper abuts against the first arm portion and the pivoting fulcrum is shorter than a distance L4 between the sensing portion and the pivoting fulcrum.

13. An image forming apparatus comprising:

a photoconductor;

an exposure unit for forming an electrostatic latent image on the photoconductor;

a development unit for forming a toner image on the photoconductor;

a paper stacking portion where cut sheets of paper are stacked;

a conveyance mechanism for sending out the paper from the paper stacking portion toward the photoconductor;

a transfer unit for transferring the toner image on the photoconductor to the paper;

a fixation unit for fixing the transferred toner image to the paper; and

a double feed sensing device according to claim 2, provided on a paper-conveyance-direction upstream side of the transfer unit.

14. An image forming apparatus comprising:

a photoconductor;

an exposure unit for forming an electrostatic latent image on the photoconductor;

a development unit for forming a toner image on the photoconductor;

a paper stacking portion where cut sheets of paper are stacked;

a conveyance mechanism for sending out the paper from the paper stacking portion toward the photoconductor;

a transfer unit for transferring the toner image on the photoconductor to the paper;

a fixation unit for fixing the transferred toner image to the paper; and

a double feed sensing device according to claim 3, provided on a paper-conveyance-direction upstream side of the transfer unit.

15. An image forming apparatus comprising:

a photoconductor;

an exposure unit for forming an electrostatic latent image on the photoconductor;

a development unit for forming a toner image on the photoconductor;

a paper stacking portion where cut sheets of paper are stacked;

a conveyance mechanism for sending out the paper from the paper stacking portion toward the photoconductor;

a transfer unit for transferring the toner image on the photoconductor to the paper;

a fixation unit for fixing the transferred toner image to the paper; and

a double feed sensing device according to claim 4, provided on a paper-conveyance-direction upstream side of the transfer unit.

16. An image forming apparatus comprising:

a photoconductor;

an exposure unit for forming an electrostatic latent image on the photoconductor;

a development unit for forming a toner image on the photoconductor;

a paper stacking portion where cut sheets of paper are stacked;

a conveyance mechanism for sending out the paper from the paper stacking portion toward the photoconductor;

a transfer unit for transferring the toner image on the photoconductor to the paper;

a fixation unit for fixing the transferred toner image to the paper; and

a double feed sensing device according to claim 5, provided on a paper-conveyance-direction upstream side of the transfer unit.

17. An image forming apparatus comprising:

a photoconductor;

an exposure unit for forming an electrostatic latent image on the photoconductor;

a development unit for forming a toner image on the photoconductor;

a paper stacking portion where cut sheets of paper are stacked;

a conveyance mechanism for sending out the paper from the paper stacking portion toward the photoconductor;

a transfer unit for transferring the toner image on the photoconductor to the paper;

a fixation unit for fixing the transferred toner image to the paper; and

a double feed sensing device according to claim 6, provided on a paper-conveyance-direction upstream side of the transfer unit.

18. An image forming apparatus comprising:

a photoconductor;

an exposure unit for forming an electrostatic latent image on the photoconductor;

a development unit for forming a toner image on the photoconductor;

a paper stacking portion where cut sheets of paper are stacked;

a conveyance mechanism for sending out the paper from the paper stacking portion toward the photoconductor;

a transfer unit for transferring the toner image on the photoconductor to the paper;

a fixation unit for fixing the transferred toner image to the paper; and

a double feed sensing device according to claim 7, provided on a paper-conveyance-direction upstream side of the transfer unit.

8. A double feed determining method comprising the steps of:

using a thickness sensing unit to sense thickness of cut paper which is being conveyed;

using a rigidity sensing unit to sense bending rigidity of the paper which is being conveyed; and

using a double feed determining unit to determine double feed of the paper;

wherein;

threshold values of the thickness and the bending rigidity of the paper are set based on values of thickness and bending rigidity of one sheet of the paper and values of thickness and bending rigidity of stacked sheets of the paper, and stored in a storage portion of the double feed determining unit; and

a value of the thickness of the paper sensed by the thickness sensing unit and a value of the bending rigidity of the paper sensed by the rigidity sensing unit are input to the double feed determining unit and compared with the threshold values respectively so as to determine existence of double feed of the paper.