Optical scanning device and image forming apparatus including the optical scanning device Number:6,836,633 from the United States Patent and Trademark Office (PTO) owispatent

Title: Optical scanning device and image forming apparatus including the optical scanning device

Abstract: An optical scanning device including a housing, a first carriage carrying a light source and a first mirror, a second carriage carrying second and third mirrors, the second carriage cofigured to move in a sub-scanning direction at one-half of a speed of the first carriage, first and second timing pulleys spaced apart in the sub-scanning direction, a timing belt spanned around the first and second timing pulleys to reciprocate the first carriage in the sub-scanning direction, a drive device to drive the first timing pulley, flat pulleys supported by the second carriage and spaced apart in the sub-scanning direction by a moving distance of the second carriage, a flat belt spanned around the flat pulleys to reciprocate the second carriage in the sub-scanning direction, an engaging member engaging the timing and flat belts to the first carriage, and a fixing member fixing the flat belt to the housing.

Patent Number: 6,836,633 Issued on 12/28/2004 to Bannai,   et al.

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Inventors:	Bannai; Kazunori (Ohta-ku, JP); Fujioka; Tetsuya (Yokohama, JP)
Assignee:	Ricoh Company, Ltd. (Tokyo, JP)
Appl. No.:	133381
Filed:	April 29, 2002

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Foreign Application Priority Data

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Apr 27, 2001 [JP]			2001-132594
Apr 27, 2001 [JP]			2001-132597

Current U.S. Class:	399/211 ; 399/214
Field of Search:	399/177,211,212,206,209,214

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References Cited [Referenced By]

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U.S. Patent Documents

	3586774		June 1971		Brouwer et al.
	5219154		June 1993		Fukube et al.
	5224693		July 1993		Taguchi et al.
	5227842		July 1993		Hayashi et al.
	5255904		October 1993		Taguchi et al.
	5270783		December 1993		Bisaiji et al.
	5297376		March 1994		Taguchi et al.
	5315322		May 1994		Bannai
	5316282		May 1994		Fukube et al.
	5325213		June 1994		Takahashi et al.
	5390033		February 1995		Bannai et al.
	5471277		November 1995		Fujioka et al.
	5583607		December 1996		Fujioka et al.
	5583662		December 1996		Takahashi et al.
	5610720		March 1997		Fujioka et al.
	5682227		October 1997		Taguchi et al.
	5689348		November 1997		Takahashi et al.
	5847845		December 1998		Takahashi et al.
	6075624		June 2000		Bannai et al.

Foreign Patent Documents

	5-274469		Oct., 1993		JP
	6-250292		Sep., 1994		JP
	09-153982		Jun., 1997		JP
	2000-174955		Jun., 2000		JP
	2000-184141		Jun., 2000		JP

Other References

US. Appl. No. 10/133,381, Bannai et al., filed Apr. 29, 2002. . U.S. Appl. No. 10/644,007, Bannai et al., filed Aug. 20, 2003..

Primary Examiner: Tran; Hoan
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt, P.C.

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Claims

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What is claimed as new and is desired to be secured by Letters Patent of the United States is:

1. An optical scanning device, comprising: a housing; a first moving carnage carrying a light source provided to irradiate an image surface of an original document with light and a first mirror provided to reflect the light reflected from the image surface of the original document; a second moving carriage carrying at least one of a second mirror and a third mirror each provided to reflect the light reflected from the first mirror, the second moving carriage being configured to move in a sub-scanning direction at about one-half of a moving speed of the first moving carriage; a plurality of timing pulleys spaced apart in the sub-scanning direction and including at least a first timing pulley and a second timing pulley; a timing belt spanned around the first and second timing pulleys to reciprocate the first moving carriage in the sub-scanning direction; a drive device configured to drive the first timing pulley to rotate; a plurality of flat pulleys rotatably supported by the second moving carriage and spaced apart in the sub-scanning direction by a distance corresponding to a moving amount of the second moving carriage; a flat belt spanned around the plurality of flat pulleys to reciprocate the second moving carriage in the sub-scanning direction; an engaging member detachably engaging the timing belt and the flat belt to the first moving carriage; and a fixing member fixing the flat belt to the housing at a position different from a position where the flat belt is engaged to the first moving carriage by substantially half of a circumference of the flat belt; wherein the plurality of timing pulleys, timing belt, plurality of flat pulleys, flat belt, engaging member, and fixing member are provided at each side of the first and second moving carriages in the main scanning direction.

2. The optical scanning device according to claim 1, wherein the engaging member is engaging the timing belt and the flat belt to the first moving carriage at a substantially equal height.

3. The optical scanning device according to claim 1, further comprising a first rail on which the first moving carriage moves in the sub-scanning direction, wherein the first moving carriage is pressed against the first rail by the timing belt and the flat belt via the engaging member.

4. The optical scanning device according to claim 3, further comprising a second rail on which the second moving carriage moves in the sub-scanning direction, wherein the second moving carriage is pressed against the second rail by the flat belt via the fixing member.

5. The optical scanning device according to claim 4, wherein the optical scanning device has a two-step rail structure in which the first rail is positioned at an upper step and the second rail is positioned at a lower step.

6. The optical scanning device according to claim 1, wherein the flat belt is positioned at an inner side of the timing belt in the main scanning direction in the housing.

7. An optical scanning device, comprising: a moving carriage carrying an exposure optical system; a timing belt positioned along a sub-scanning direction to reciprocate the moving carriage in the sub-scanning direction; and a belt clamp mechanism detachably clamping the timing belt to the moving carriage, the belt clamp mechanism including; a plurality of comb-tooth members provided to a lower surface of the moving carriage spaced apart in the sub-scanning direction by a gap such that the plurality of comb-tooth members protrude from the lower surface of the moving carriage toward the timing belt; and a clamp member having a support surface having a protrusion protruding toward the gap between the plurality of comb-tooth members; wherein the clamp member is secured to the moving carriage such that the clamp member opposes the plurality of comb-tooth members via the timing belt while the protrusion on the support surface pressing the timing belt into the gap between the plurality of comb-tooth members.

8. The optical scanning device according to claim 7, wherein: the plurality of comb-tooth members each have a portion facing the timing belt; and the portion facing the timing belt is longer than a width of the timing belt in a main scanning direction.

9. The optical scanning device according to claim 7, wherein: the plurality of comb-tooth members include inside surfaces and bottom surfaces, respectively, the inside surfaces facing to each other and spaced apart by the gap, the bottom surfaces facing the timing belt; and the inside surfaces are substantially perpendicular to the bottom surfaces, respectively.

10. The optical scanning device according to claim 7, wherein: the moving carriage includes a plurality of clamp member holding members detachably holding the clamp member, the plurality of clamp member holding members protruding from the lower surface of the moving carriage spaced apart in the sub-scanning direction by a distance substantially equal to a length of the clamp member in the sub-scanning direction; the plurality of clamp member holding members have tip ends bent inwardly facing each other and spaced apart by a distance smaller than the length of the clamp member in the sub-scanning direction; and at least one of the plurality of clamp member holding members has a concave portion dented in a direction away from an opposite one of the clamp member holding members.

11. An optical scanning device, comprising: a housing; a first moving carriage carrying a light source provided to irradiate an image surface of an original document with light and a first mirror provided to reflect the light reflected from the image surface of the original document; a second moving carriage carrying at least one of a second mirror and a third mirror each provided to reflect the light reflected from the first mirror, the second moving carriage being configured to move in a sub-scanning direction at about one-half of a moving speed of the first moving carriage; a timing belt positioned along the sub-scanning direction to reciprocate the first moving carriage in the sub-scanning direction; a plurality of flat pulleys rotatably supported by the second moving carriage and spaced apart in the sub-scanning direction by a distance corresponding to a moving amount of the second moving carriage; a flat belt spanned around the plurality of flat pulleys along the sub-scanning direction to reciprocate the second moving carriage in the sub-scanning direction, the flat belt being positioned at a side of the timing belt in a main scanning direction; a fixing member fixing the flat belt to the housing at a position not interfering with reciprocating motions of the second moving carriage; and a belt clamp mechanism detachably clamping the timing belt and the flat belt to the first moving carriage, the belt clamp mechanism including; a first plurality of comb-tooth members provided to a lower surface of the first moving carriage spaced apart in the sub-scanning direction by a gap such that the first plurality of comb-tooth members protrude from the lower surface of the first moving carriage toward the timing belt; a second plurality of comb-tooth members provided to the lower surface of the first moving carriage spaced apart in the sub-scanning direction by a gap such that the second plurality of comb-tooth members protrude from the lower surface of the first moving carriage toward the flat belt; and a clamp member having a first support surface having a first protrusion protruding toward the gap between the first plurality of comb-tooth members, and a second support surface having a second protrusion protruding toward the gap between the second plurality of comb-tooth members; wherein the clamp member is detachably secured to the first moving carriage such that the clamp member opposes the first and second pluralities of comb-tooth members via the timing belt and the flat belt, respectively, while the first protrusion on the first support surface pressing the timing belt into the gap between the first plurality of comb-tooth members and while the second protrusion on the second support surface pressing the flat belt into the gap between the second plurality of comb-tooth members.

12. The optical scanning device according to claim 11, wherein: the first plurality of comb-tooth members each have a portion facing the timing belt; the portion facing the timing belt is longer than a width of the timing belt in the main scanning direction; the second plurality of comb-tooth members each have a portion facing the flat belt; and the portion facing the flat belt is longer than a width of the flat belt in the main scanning direction.

13. The optical scanning device according to claim 11, wherein: the clamp member includes a flat plate member with which the first and second support surfaces are provided in a diagonal relation; and the clamp member is detachably secured to the first moving carriage at a substantially central part of the flat plate member between the first and second support surfaces.

14. The optical scanning device according to claim 11, wherein: the first plurality of comb-tooth members include inside surfaces and bottom surfaces, respectively, the inside surfaces facing to each other and spaced apart by the gap, the bottom surfaces facing the timing belt; the second plurality of comb-tooth members include inside surfaces and bottom surfaces, respectively, the inside surfaces facing to each other and spaced apart by the gap, the bottom surfaces facing the flat belt; the inside surfaces of the first plurality of comb-tooth members are substantially perpendicular to the bottom surfaces of the first plurality of comb-tooth members, respectively; and the inside surfaces of the second plurality of comb-tooth members are substantially perpendicular to the bottom surfaces of the second plurality of comb-tooth members, respectively.

15. The optical scanning device according to claim 11, wherein: the first moving carriage includes a plurality of clamp member holding members detachably holding the clamp member; the plurality of clamp member holding members protruding from the lower surface of the first moving carriage spaced apart in the sub-scanning direction by a distance substantially equal to a length of the clamp member in the sub-scanning direction; the plurality of clamp member holding members have tip ends bent inwardly facing each other and spaced apart by a distance smaller than the length of the clamp member in the sub-scanning direction; and at least one of the plurality of clamp member holding members has a concave portion dented in a direction away from an opposite one of the clamp member holding members.

16. An image forming apparatus, comprising: an optical scanning device configured to scan and read an image on an original document, the optical scanning device including: a housing; a first moving carriage carrying a light source provided to irradiate an image surface of an original document with light and a first mirror provided to reflect the light reflected from the image surface of the original document; a second moving carriage carrying at least one of a second mirror and a third mirror each provided to reflect the light reflected from the first mirror, the second moving carriage configured to move in a sub-scanning direction at about one-half of a moving speed of the first moving carriage; a plurality of timing pulleys spaced apart in the sub-scanning direction and including at least a first timing pulley and a second timing pulley; a timing belt spanned around the first and second timing pulleys to reciprocate the first moving carriage in the sub-scanning direction; a drive device configured to drive the first timing pulley to rotate; a plurality of flat pulleys rotatably supported by the second moving carriage and spaced apart in the sub-scanning direction by a distance corresponding to a moving amount of the second moving carriage; a flat belt spanned around the plurality of flat pulleys to reciprocate the second moving carriage in the sub-scanning direction; an engaging member detachably engaging the timing belt and the flat belt to the first moving carriage; and a fixing member fixing the flat belt to the housing at a position different from a position where the flat belt is engaged to the first moving carriage by substantially half of a circumference of the fiat belt; wherein the plurality of timing pulleys, timing belt, plurality of flat pulleys, flat belt, engaging member, and fixing member are provided at each side of the first and second moving carriages in the main scanning direction; and a printer device configured to print the image of the original document scanned and read by the optical scanning device.

17. The image forming apparatus according to claim 16, wherein the engaging member is engaging the timing belt and the flat belt to the first moving carriage at a substantially equal height.

18. The image forming apparatus according to claim 16, wherein: the optical scanning device further includes a first rail on which the first moving carriage moves in the sub-scanning direction; and the first moving carriage is pressed against the first rail by the timing belt and the flat belt via the engaging member.

19. The image forming apparatus according to claim 18, wherein: the optical scanning device further includes a second rail on which the second moving carriage moves in the sub-scanning direction; and the second moving carriage is pressed against the second rail by the flat belt via the fixing member.

20. The image forming apparatus according to claim 19, wherein the optical scanning device has a two-step rail structure in which the first rail is positioned at an upper step and the second rail is positioned at a lower step.

21. The image forming apparatus according to claim 16, wherein the flat belt is positioned at an inner side of the timing belt in the main scanning direction in the housing.

22. An image forming apparatus, comprising: an optical scanning device configured to scan and read an image on an original document, the optical scanning device including: a moving carriage carrying an exposure optical system; a timing belt positioned along a sub-scanning direction to reciprocate the moving carriage in the sub-scanning direction; and a belt clamp mechanism clamping the timing belt to the moving carriage, the belt clamp mechanism including: a plurality of comb-tooth members provided to a lower surface of the moving carnage spaced apart in the sub-scanning direction by a gap such that the plurality of comb-tooth members protrude from the lower surface of the moving carriage toward the timing belt; and a clamp member having a support surface having a protrusion protruding toward the gap between the plurality of comb-tooth members; wherein the clamp member is detachably secured to the moving carriage such that the clamp member opposes the plurality of comb-tooth members via the timing belt while the protrusion on the support surface pressing the timing belt into the gap between the plurality of comb-tooth members; and a printer device configured to print the image on the original document scanned and read by the optical scanning device.

23. The image forming apparatus according to claim 22, wherein: the plurality of comb-tooth members each have a portion facing the timing belt; and the portion facing the timing belt is longer than a width of the timing belt in a main scanning direction.

24. The image forming apparatus according to claim 22, wherein: the plurality of comb-tooth members include inside surfaces and bottom surfaces, respectively, the inside surfaces facing to each other and spaced apart by the gap, the bottom surfaces facing the timing belt; and the inside surfaces are substantially perpendicular to the bottom surfaces, respectively.

25. The image forming apparatus according to claim 22, wherein: the moving carriage includes a plurality of clamp member holding members detachably holding the clamp member; the plurality of clamp member holding members protruding from the lower surface of the moving carriage spaced apart in the sub-scanning direction by a distance substantially equal to a length of the clamp member in the sub-scanning direction; the plurality of clamp member holding members have tip ends bent inwardly facing each other and spaced apart by a distance smaller than the length of the clamp member in the sub-scanning direction; and at least one of the plurality of clamp member holding members has a concave portion dented in a direction away from an opposite one of the clamp member holding members.

26. An image forming apparatus, comprising: an optical scanning device configured to scan and read an image on an original document, the optical scanning device including: a housing; a first moving carriage carrying a light source provided to irradiate an image surface of an original document with light and a first mirror provided to reflect the light reflected from the image surface of the original document; a second moving carnage carrying at least one of a second mirror and a third mirror each provided to reflect the light reflected from the first mirror, the second moving carriage being configured to move in a sub-scanning direction at about one-half of a moving speed of the first moving carriage; a timing belt positioned along the sub-scanning direction to reciprocate the first moving carriage in the sub-scanning direction; a plurality of flat pulleys rotatably supported by the second moving carriage and spaced apart in the sub-scanning direction by a distance corresponding to a moving amount of the second moving carriage; a flat belt spanned around the plurality of flat pulleys along the sub-scanning direction to reciprocate the second moving carriage in the sub-scanning direction, the flat belt being arranged at a side of the timing belt in a main scanning direction; a fixing member fixing the flat belt to the housing at a position not interfering with reciprocating motions of the second moving carriage; and a belt clamp mechanism detachably clamping the timing belt and the flat belt to the first moving carriage, the belt clamp mechanism including: a first plurality of comb-tooth members provided to a lower surface of the first moving carriage spaced apart in the sub-scanning direction by a gap such that the first plurality of comb-tooth members protrude from the lower surface of the first moving carriage toward the timing belt; a second plurality of comb-tooth members provided to the lower surface of the first moving carriage spaced apart in the sub-scanning direction by a gap such that the second plurality of comb-tooth members protrude from the lower surface of the first moving carriage toward the flat belt; and a clamp member having a first support surface having a first protrusion protruding toward the gap between the first plurality of comb-tooth members, and a second support surface having a second protrusion protruding toward the gap between the second plurality of comb-tooth members; wherein the clamp member is detachably secured to the first moving carriage such that the clamp member opposes the first and second pluralities of comb-tooth members via the timing belt and the flat belt, respectively, while the first protrusion on the first support surface pressing the timing belt into the gap between the first plurality of comb-tooth members and while the second protrusion on the second support surface pressing the flat belt into the gap between the second plurality of comb-tooth members; and a printer device configured to print the image of the original document scanned and read by the optical scanning device.

27. The image forming apparatus according to claim 26, wherein: the first plurality of comb-tooth members each have a portion facing the timing belt; the portion facing the timing belt is longer than a width of the timing belt in the main scanning direction; the second plurality of comb-tooth members each have a portion facing the flat belt; and the portion facing the flat belt is longer than a width of the flat belt in the main scanning direction.

28. The image forming apparatus according to claim 26, wherein: the clamp member includes a flat plate member with which the first and second support surfaces are provided in a diagonal relation; and the clamp member is detachably secured to the first moving carriage at a substantially central part of the flat plate member between the first and second support surfaces.

29. The image forming apparatus according to claim 26, wherein: the first plurality of comb-tooth members include inside surfaces and bottom surfaces, respectively, the inside surfaces facing to each other and spaced apart by the gap, the bottom surfaces facing the timing belt; the second plurality of comb-tooth members include inside surfaces and bottom surfaces, respectively, the inside surfaces facing to each other and spaced apart by the gap, the bottom surfaces facing the flat belt; the inside surfaces of the first plurality of comb-tooth members are substantially perpendicular to the bottom surfaces of the first plurality of comb-tooth members, respectively; and the inside surfaces of the second plurality of comb-tooth members are substantially perpendicular to the bottom surfaces of the second plurality of comb-tooth members, respectively.

30. The image forming apparatus according to claim 26, wherein: the first moving carriage includes a plurality of clamp member holding members detachably holding the clamp member; the plurality of clamp member holding members protruding from the lower surface of the first moving carriage spaced apart in the sub-scanning direction by a distance substantially equal to a length of the clamp member in the sub-scanning direction; the plurality of clamp member holding members have tip ends bent inwardly facing each other and spaced apart by a distance smaller than the length of the clamp member in the sub-scanning direction; and at least one of the plurality of clamp member holding members has a concave portion dented in a direction away from an opposite one of the clamp member holding members.

31. An optical scanning device, comprising: a housing; first carrying means for carrying a light source provided to irradiate an image surface of an original document with light and a first mirror provided to reflect the light reflected from the image surface of the original document; second carrying means for carrying at least one of a second mirror and a third mirror each provided to reflect the light reflected from the first mirror, the second carrying means being capable of moving in a sub-scanning direction at about one-half of a moving speed of the first carrying means; a plurality of timing pulleys spaced apart in the sub-scanning direction and including at least a first timing pulley and a second timing pulley; a timing belt spanned around the first and second timing pulleys to reciprocate the first carrying means in the sub-scanning direction; driving means for driving the first timing pulley to rotate; a plurality of flat pulleys rotatably supported by the second carrying means and spaced apart in the sub-scanning direction by a distance corresponding to a moving amount of the second carrying means; a flat belt spanned around the plurality of flat pulleys to reciprocate the second carrying means in the sub-scanning direction; engaging means for engaging the timing belt and the flat belt to the first carrying means; and fixing means for fixing the flat belt to the housing at a position different from a position where the flat belt is engaged to the first carrying means by substantially half of a circumference of the flat belt; wherein the plurality of timing pulleys, timing belt, plurality of flat pulleys, flat belt, engaging means, and fixing means are provided at each side of the first and second carrying means in the main scanning direction.

32. An optical scanning device, comprising: first carrying means for carrying an exposure optical system; second carrying means for carrying an optical system; a timing belt positioned along a sub-scanning direction to reciprocate the first carrying means in the sub-scanning direction; a flat belt positioned parallel to the timing belt to reciprocate the second carrying means in the sub-scanning direction; and clamping means for clamping the timing belt and flat belt to the first carrying means.

33. An optical scanning device, comprising: a housing; first carrying means for carrying a light source provided to irradiate an image surface of an original document with light and a first mirror provided to reflect the light reflected from the image surface of the original document; second carrying means for carrying at least one of a second mirror and a third mirror each provided to reflect the light reflected from the first mirror, the second carrying means being capable of moving in a sub-scanning direction at about one-half of a moving speed of the first carrying means; a timing belt positioned along the sub-scanning direction to reciprocate the first carrying means in the sub-scanning direction; a plurality of flat pulleys rotatably supported by the second carrying means and spaced apart in the sub-scanning direction by a distance corresponding to a moving amount of the second carrying means; a flat belt spanned around the plurality of flat pulleys along the sub-scanning direction to reciprocate the second carrying means in the sub-scanning direction, the flat belt being positioned at a side of the timing belt in a main scanning direction; fixing means for fixing the flat belt to the housing at a position not interfering with reciprocating motions of the second carrying means; and clamping means for clamping the timing belt and the flat belt to the first carrying means.

34. An optical scanning device comprising: a first moving carriage carrying an exposure optical system; a second carriage carrying an optical system; a timing belt positioned along a sub-scanning direction to reciprocate the first moving carriage in the sub-scanning direction; a flat belt positioned parallel to the timing belt to reciprocate the second carrying means in the sub-scanning direction; and a clamping device detachably clamping the timing belt and flat belt to the first moving carriage.

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Description

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CROSS-REFERENCE TO RELATED APPLICATIONS

This document claims priority to Japanese Patent Application No. 2001-132597 filed in the Japanese Patent Office on Apr. 27, 2001, and Japanese Patent Application No. 2001-132594 filed in the Japanese Patent Office on Apr. 27, 2001. The entire contents of those applications are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical scanning device and an image forming apparatus such as a copying machine, a facsimile machine, a printer, etc., including the optical scanning device.

2. Discussion of the Background

Generally, an optical scanning device of a flatbed scanner type that scans an image of an original document immovably set on a contact glass includes first and second moving carriages that move in a sub-scanning direction at a speed ratio of two to one. The first moving carriage carries a light source that irradiates an image surface of an original document with light and a first mirror that reflects the light reflected from the image surface of the original document. The second moving carriage carries at least one of a second mirror and a third mirror that reflects the light reflected from the first mirror.

The above-described optical scanning device employs a wire driving system in which the first and second moving carriages are driven via driving wires wired at both sides of the first and second moving carriages, respectively.

Alternatively, the above-described optical scanning device may employ a belt driving system in which the first and second moving carriages are individually driven via timing belts. Specifically, stepped pulleys including large-diameter pulleys and small-diameter pulleys are respectively arranged at both sides of the first and second moving carriages. Each diameter of the small-diameter pulleys is one-half that of the large-diameter pulleys.

Two pairs of endless-belt-like long and short timing belts are respectively spanned around the stepped pulleys including the large-diameter pulleys and small-diameter pulleys at both sides of the first and second moving carriages, i.e., four timing belts are provided in total. The both sides of the first moving carriage are respectively fixed to portions of the two long timing belts, and the both sides of the second moving carriage are respectively fixed to portions of the two short timing belts. With the above-described construction, the first and second moving carriages are individually driven via the long and short timing belts, respectively.

The above-described wire driving system has disadvantages as follows:

(1) The wiring of driving wires is so complicated that assembly work may not be easily accomplished. Therefore, auto-assembly of an optical system of a scanning device may be difficult to perform.

(2) In order to prevent driving wires from being tangled, a predetermined tension is necessary to be applied to the driving wires. Because of complicated wiring of the driving wires, many pulleys are required to rotatably support the driving wires. For example, at least two pulleys are required at one side of the moving carriages. Due to the tension applied to the driving wires, the force in the radial direction is exerted on each of the pulleys. In this case, a ball bearing is often used for each of the pulleys to reduce a load on the pulley, driving the cost of the device higher.

Next, an example of a background optical scanning device employing the above-described belt driving system will be described referring to FIG. 15. As illustrated in FIG. 15, long timing belts 116, 117 extending in a sub-scanning direction are respectively arranged at both sides of a first moving carriage 104 in a main scanning direction. Further, short timing belts 118, 119 extending in the sub-scanning direction are respectively arranged at both sides of a second moving carriage 105 in a main scanning direction.

The timing belt 116 is spanned around a set of timing belt pulleys 120, 121, and the timing belt 117 is spanned around another set of timing belt pulleys 122, 123. Further, the timing belt 118 is spanned around a set of timing belt pulleys 124, 125, and the timing belt 119 is spanned around a set of timing belt pulleys 126, 127. The timing belt pulleys, 120 and 124, are intercoupled each other, and the timing belt pulleys, 122 and 126, are intercoupled each other. A drive shaft 128 connects the timing belt pulleys, 120 and 124, and the timing belt pulleys, 122 and 126. One end of the drive shaft 128 is connected to a driven pulley 129. The driven pulley 129 is connected to a drive pulley 132 of a drive motor 131 via a timing belt 130.

End portions 133 of the both sides of the first moving carriage 104 in the main scanning direction are respectively attached to the timing belts, 116 and 117. Further, end portions 134 of the both sides of the second moving carriage 105 in the main scanning direction are respectively attached to the timing belts, 118 and 119, such that the second moving carriage 105 is arranged parallel to the first moving carriage 104 spaced at a predetermined distance. The end portions 133 of the first moving carriage 104 and the end portions 134 of the second moving carriage 105 are moved in the sub-scanning direction along guide rails 113.

A driving force of the drive motor 131 is applied to the timing belt pulleys, 120, 122, 124, and 126, via the drive shaft 128, thereby rotating the timing belts, 116, 117, 118, and 119, and moving the first and second moving carriages 104, 105 in the sub-scanning direction. In this optical scanning device, each diameter of the timing belt pulleys, 124 and 126, is set to be one-half that of the timing belt pulleys, 120 and 122. Thereby, the first and second moving carriages 104, 105 move at a speed ratio of 2 to 1.

The assembly work of the above-described optical scanning device employing the belt driving system may be more easily accomplished than the optical scanning device employing the wire driving system. However, in the above-described background optical scanning device employing the belt driving system, from the theoretical point of view, the first and second moving carriages 104, 105 may not move at a speed ratio of 2 to 1, because the two types of the timing belts, 116, 117, and the timing belts, 118 and 119, undergo speed variations due to engagement errors and decentering of the timing belt pulleys. In this case, the distance between a lens and an original document is minutely changed, causing deterioration of scanned images.

Further, in the above-described background optical scanning device employing the belt driving system, a predetermined tension needs to be applied to each of the timing belts, 116, 117, 118, and 119, to convey the driving force of the drive motor 131 to the first and second moving carriages 104, 105. In the above-described construction of the background optical scanning device, the drive shaft 128 is subject to the tensions of the timing belts, 116, 117, 118, and 119, so that relatively large radial forces are exerted on bearings that rotatably hold the drive shaft 128, and radial forces are also exerted on the four driven timing belt pulleys, 120, 122, 124, and 126, resulting in a high drive load condition.

Moreover, in the above-described background optical scanning device employing the belt driving system, because the first and second moving carriages 104, 105 are coupled to the drive motor 131 via the timing belts, 116, 117, 118, and 119, when the operational condition of the drive motor 131 is switched, for example, between rotation and halt, forward rotation and reverse rotation, etc., the forces in the direction of hindering the movements of the timing belts, 116, 117, 118, and 119, are typically produced due to the inertial forces of the first and second moving carriages 104, 105. As a result, the attachment positions of the first and second moving carriages 104, 105 relative to the timing belts, 116, 117, 118, and 119, may be shifted, causing deformation of scanned images in the sub-scanning direction.

If the first and second moving carriages 104, 105 are attached to the timing belts, 116, 117, 118, and 119, at a plurality positions to avoid the above-described shifts of the attachment positions, assembly work inevitably may become complicated, thereby decreasing productivity.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, an optical scanning device includes a housing, a first moving carriage carrying a light source provided to irradiate an image surface of an original document with light and a first mirror provided to reflect the light reflected from the image surface of the original document, a second moving carriage carrying at least one of a second mirror and a third mirror each provided to reflect the light reflected from the first mirror, the second moving carriage being configured to move in a sub-scanning direction at about one-half of a moving speed of the first moving carriage, a plurality of timing pulleys spaced apart in the sub-scanning direction and including at least a first timing pulley and a second timing pulley, a timing belt spanned around the first and second timing pulleys to reciprocate the first moving carriage in the sub-scanning direction, a drive device configured to drive the first timing pulley to rotate, a plurality of flat pulleys rotatably supported by the second moving carriage and spaced apart in the sub-scanning direction by a distance corresponding to a moving amount of the second moving carriage, a flat belt spanned around the plurality of flat pulleys to reciprocate the second moving carriage in the sub-scanning direction, an engaging member detachably engaging the timing belt and the flat belt to the first moving carriage, and a fixing member fixing the flat belt to the housing at a position different from a position where the flat belt is engaged to the first moving carriage by substantially half of a circumference of the flat belt. The plurality of timing pulleys, timing belt, plurality of flat pulleys, flat belt, engaging member, and fixing member are provided at each side of the first and second moving carriages in the main scanning direction.

According to another aspect of the present invention, an optical scanning device includes a moving carriage carrying an exposure optical system, a timing belt positioned along a sub-scanning direction to reciprocate the moving carriage in the sub-scanning direction, and a belt clamp mechanism detachably clamping the timing belt to the moving carriage, the belt clamp mechanism including, a plurality of comb-tooth members provided to a lower surface of the moving carriage spaced apart in the sub-scanning direction by a gap such that the plurality of comb-tooth members protrude from the lower surface of the moving carriage toward the timing belt, and a clamp member having a support surface having a protrusion protruding toward the gap between the plurality of comb-tooth members. The clamp member is secured to the moving carriage such that the clamp member opposes the plurality of comb-tooth members via the timing belt while the protrusion on the support surface pressing the timing belt into the gap between the pair of comb-tooth members.

Objects, features, and advantages of the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic vertical longitudinal sectional side view of an optical scanning device according to an embodiment of the present invention;

FIG. 2 is a horizontal sectional view of the optical scanning device illustrating an inside construction thereof;

FIG. 3 is a vertical longitudinal sectional side view of the optical scanning device of FIG. 2;

FIG. 4 is a perspective view of elements of the optical scanning device provided in a housing of the optical scanning device;

FIG. 5 is a perspective view of a part of the elements of the optical scanning device of FIG. 4;

FIG. 6 is a schematic view for explaining a state in which a timing belt and a flat belt are engaged to a first moving carriage by a clamp member, and the flat belt is fixed by a fixing member;

FIGS. 7A and 7B are schematic views for explaining moving operations of the first moving carriage and a second moving carriage on the principle of pulley;

FIG. 8A is an exploded view of a belt clamp mechanism according to the embodiment of the present invention;

FIG. 8B is a schematic enlarged view of comb-tooth-like members;

FIG. 8C is a schematic enlarged view of another comb-tooth-like members;

FIG. 9 is a side view of the belt clamp mechanism of FIG. 8;

FIG. 10 is a perspective view of a clamp member;

FIG. 11A is a cross sectional side view of the belt clamp mechanism taken along a main scanning direction;

FIG. 11B is a cross sectional side view of the belt clamp mechanism taken along a sub-scanning direction;

FIGS. 12A and 12B are schematic side views of the first moving carriage and the clamp member for explaining an attachment work of the clamp member to the first moving carriage;

FIG. 13 is a side view of the optical scanning device when a second moving carriage is located at the home position;

FIG. 14 is a schematic vertical longitudinal sectional side view of a copying machine according to another embodiment of the present invention; and

FIG. 15 is a schematic perspective view of an optical scanning device employing a belt driving system according to a background art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention are described in detail referring to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views.

An optical scanning device according to an embodiment of the present invention is a flatbed scanner type that scans an original document immovably set on a contact glass. First, an overall construction of the optical scanning device will be described referring to FIG. 1. FIG. 1 is a schematic vertical longitudinal sectional side view of an optical scanning device 1 according to this embodiment of the present invention. The optical scanning device 1 includes a case-like housing 3 having a contact glass 2 at the upper surface of the housing 3 for setting original documents on the contact glass 2.

In the housing 3, there are provided a first moving carriage 6 and a second moving carriage 9. The first moving carriage 6 carries a xenon lamp 4 (hereinafter referred to as a "Xe lamp") serving as a light source which irradiates an image surface of an original document set on the contacts glass 2 with a light (L), and a first mirror 5 inclined at about 45 degrees to reflect the light (L) reflected from the image surface of the original document. The Xe lamp 4 and the first mirror 5 constitute an exposure optical system. The second moving carriage 9 carries a second mirror 7 and a third mirror 8 respectively inclined at about 45 degrees to reflect the light (L) reflected from the first mirror 5. In the housing 3, the light (L) reflected from the third mirror 8 is imaged on a charge-coupled device 11 (hereinafter referred to as a "CCD 11") serving as an image reading device through a lens block 13. The CCD 11 is mounted on a sensor board unit 12, and the lens block 13 is mounted on a lens block stay 14. As an alternative example, the second moving carriage 9 may carry at least one of the second mirror 7 and the third mirror 8.

The first moving carriage 6 and the second moving carriage 9 are arranged such that each longitudinal direction of the first moving carriage 6 and the second moving carriage 9 corresponds to a main scanning direction, i.e., in a direction perpendicular to the sheet in FIG. 1. The first moving carriage 6 and the second moving carriage 9 reciprocate in a sub-scanning direction, i.e., in a right-and-left direction in FIG. 1, at a speed ratio of two to one. The first moving carriage 6 and the second moving carriage 9 during standby are located at their respective home positions at the left-hand side of the housing 3 in FIG. 1.

The Xe lamp 4 has a slit-like aperture along its axial direction at the position in which the Xe lamp 4 faces the contact glass 2. Further, a light reflecting film is attached to the Xe lamp 4 to cover the portions of the Xe lamp 4 other than the slit-like aperture. By use of the light reflecting film, the light (L) is efficiently emitted from the Xe lamp 4 toward an original document set on the contact glass 2.

In the housing 3, there are further provided a drive motor 10 including a stepping motor and serving as a drive device that drives the first moving carriage 6 and the second moving carriage 9 to reciprocate in the sub-scanning direction, and a sheet width sensor 15 and a sheet length sensor 16 that detect a size of an original document set on the contact glass 2.

Next, a description will be made to elements of the optical scanning device 1 referring to FIGS. 2 through 5. FIG. 2 is a horizontal sectional view of the optical scanning device 1 illustrating an inside construction thereof. FIG. 3 is a vertical longitudinal sectional side view of the optical scanning device 1 of FIG. 2. FIG. 4 is a perspective view of elements of the optical scanning device 1 provided in the housing 3. FIG. 5 is a perspective view of a part of the elements of the optical scanning device 1 of FIG. 4. The optical scanning device 1 according to the present embodiment scans images on sheets of various sizes including an A3 size. Due to limitations of space, the optical scanning device 1 is illustrated in figures in a more elongate rectangular shape than an actual shape by reducing the size of the optical scanning device 1 in the main scanning direction.

The housing 3 is one piece of a sheet metal member in a substantially cross shape including a rectangular shaped bottom plate (3a) and wall plates standing on all sides of the bottom plate (3a). By forming the housing 3 from one piece of a sheet metal member, the size of the housing 3 is obtained with accuracy, and a number of construction parts and assembly processes is reduced.

Referring to FIGS. 2 and 3, the housing 3 includes a pair of side walls (3b) standing on the sides of the bottom plate (3a) along the sub-scanning direction. Substantially U-shaped rail members are respectively provided to the side walls (3b). Specifically, the optical scanning device 1 includes a two-step rail structure including a pair of rails (17a) and a pair of rails (17b) extending along the sub-scanning direction at the inner sides of the housing 3. Hereinafter, a pair of rails for the first moving carriage 6 arranged at upper steps will be referred to as first rails (17a), and a pair of rails for the second moving carriage 9 arranged at lower steps will be referred to as second rails (17b). By providing the sliding surfaces of the first moving carriage 6 and the second moving carriage 9 independently as the first rails (17a) and the second rails (17b), respectively, the first moving carriage 6 and the second moving carriage 9 can be closer to each other at the home positions, thereby allowing the optical scanning device 1 to be compact in size.

The housing 3 further includes a wall (3c) standing on the side of the bottom plate (3a) along the main scanning direction at the side of the home positions of the first moving carriage 6 and the second moving carriage 9. A stopper (17c) that regulates the movement of the second moving carriage 9 located at its home position in a substantially vertical direction is integrally formed with the wall (3c). The stopper (17c) is formed by cutting a part of the wall (3c) and being raised from the plane of the wall (3c). The stopper (17c) is formed at a position corresponding to an arm portion (9c) in L shape formed with a mirror stay (9a) (details of which will be described later) of the second moving carriage 9.

The first moving carriage 6 includes four sliders (not shown) at the four corners of the lower surface of the first moving carriage 6. The first moving carriage 6 reciprocates in the sub-scanning direction by bringing the four sliders into contact with the upper surfaces of the pair of first rails (17a).

The first moving carriage 6 further includes a reflector 18 such that the longitudinal direction of the reflector 18 corresponds to the axial direction of the Xe lamp 4. The reflector 18 includes a reflection surface inclined at about 45 degrees to oppose both the Xe lamp 4 and the contact glass 2. A sheet-like light reflective film (not shown) is attached to the reflection surface of the reflector 18 to reflect the light emitted from the Xe lamp 4 toward the contact glass 2.

At the both sides of the bottom surface of the first moving carriage 6 in the main scanning direction, there are provided through holes (6a) penetrating the bottom surface of the first moving carriage 6 in the substantially vertical direction. The through holes (6a) are used for visually checking positions where the timing belts 21 are engaged to the first moving carriage 6 by use of a clamp member 42 (details of which will be described later).

At both end portions of the lower surface of the first moving carriage 6 in the main scanning direction, endless-belts serving as timing belts 21 extend in the sub-scanning direction across the housing 3.

One end side of each of the timing belts 21 is wound around a drive timing pulley 23. The drive timing pulleys 23 are respectively fixed at both end portions of a drive shaft 22 extending in the main scanning direction. The other end sides of the timing belts 21 are wound around driven timing pulleys 24, respectively, provided to the housing 3. Each of the driven timing pulleys 24 is biased in a direction away from the drive timing pulley 23 by an extension spring (not shown) spanned between the driven timing pulley 24 and the housing 3. Thereby, tension is applied to each of the timing belts 21 in the sub-scanning direction.

A drive transmission timing pulley (25a) is provided at one end of the drive shaft 22. The drive motor 10, which drives the first moving carriage 6 and the second moving carriage 9 to reciprocate in the sub-scanning direction, is arranged at a side of the drive transmission timing pulley (25a). As schematically illustrated in FIG. 3, a helical gear (10b) is fixed on a drive shaft (10a) of the drive motor 10, rotates and is engaging with a reduction gear (25b). A transmission timing pulley (25c) is coaxially provided with the reduction gear (25b). An endless-belt serving as a drive timing belt 26 is spanned around the transmission timing pulley (25c) and the drive transmission timing pulley (25a). With this construction, the drive force of the drive motor 10 is conveyed to the drive timing pulleys 23 via the drive shaft 22.

In order to stabilize the rotation of the drive motor 10, a disk made of iron (not shown) is fixed to the drive shaft 10a at the rear side of the drive motor 10. At the side of the helical gear (10b), a rubber damper (not shown) is provided between the drive motor 10 and a motor bracket (not shown) to prevent vibrations. The motor bracket is slidable so as to adjust the tension of the drive timing belt 26. After a predetermined tension is applied to the motor bracket by a spring, the motor bracket is screwed.

The second moving carriage 9 includes a pair of mirror stays (9a) that support the second mirror 7 and the third mirror 8 at their ends in the main scanning direction, and arms (9b) extending from the mirror stays (9a) toward their outer sides and the first moving carriage 6. The length of the arms (9b) corresponds to a moving amount of the second moving carriage 9 in the sub-scanning direction. Accordingly, the second moving carriage 9 according to this embodiment of the present invention is in a substantially U-shape in a horizontal plane.

On the outer sides of the mirror stays (9a), flat pulleys 27 are rotatably provided, respectively. Further, brackets 28 are respectively provided to the tip end portions of the arms (9b). Flat pulleys 29 are rotatably held by the brackets 28, respectively, such that the flat pulleys 29 are in the plane of the flat pulleys 27. The flat pulley 27 and the flat pulley 29 are used in a pair. Further, endless-belts serving as flat belts 30 are spanned around the flat pulleys 27 and the flat pulleys 29, respectively. The pair of flat belts 30 rotate along the sub-scanning direction at the both end portions of the second moving carriage 9 in the main scanning direction. The flat pulleys 27 and the flat pulleys 29 are arranged so that the flat belts 30 extend in parallel with the timing belts 21 spaced apart.

The brackets 28 holding the flat pulleys 29 are slidable relative to the arms (9b), and are provided with a predetermined tension applied thereto by springs (not shown).

With regard to the flat belts 30, tension need not be applied to each of the flat belts 30 so long as the flat belts 30 do not sag between the flat pulleys 27 and the flat pulleys 29, because the flat belts 30 do not need to convey the drive force of the drive motor 10 as compared to the timing belts 21. However, in order to avoid sag in the flat belts 30 at the time of assembling, a slight tension of about several hundred grams may be applied to the flat belts 30. In this condition, the tension applied to the flat belts 30 is so slight that rotation loads between the flat pulleys 27, 29 and shafts supporting the flat pulleys 27, 29 are very small. Therefore, the flat pulleys 27, 29 do not require ball bearings for reducing the above-described rotation loads.

Further, four sliders (not shown) are provided at the four corners of the lower surface of the second moving carriage 9 corresponding to diagonally opposing positions of the overall configuration of the second moving carriage 9. The second moving carriage 9 reciprocates along the sub-scanning direction by bringing the four sliders into contact with the upper surfaces of the pair of second rails (17b).

The second moving carriage 9 is arranged such that the arms (9b) are positioned inside of respective loops of the timing belts 21. Further, the pair of flat belts 30 are positioned at inner sides of the pair of timing belts 21 in the main scanning direction in the housing 3.

As schematically illustrated in FIG. 6, the timing belts 21 and the flat belts 30 are engaged to the lower surface of the first moving carriage 6 at the both end side portions of the first moving carriage 6 by the clamp member 42 (details of which will be described later). The timing belts 21 and the flat belts 30 are engaged to the first moving carriage 6 in locations at a substantially equal height where the flat belts 30 are engaged to the first moving carriage 6.

When engaging each of the timing belts 21 and flat belts 30 to the lower surface of the first moving carriage 6 by the clamp member 42 in the same plane at the same time, as schematically illustrated in FIG. 6, the first moving carriage 6 engages the timing belts 21 and the flat belts 30 while slightly lifting the timing belts 21 and the flat belts 30 so that a downward force indicated by Arrow (F1) is produced