1. A document conveying device mounted on a document reading device which sequentially reads a document image moving via an illuminating position with an illuminating section thereof from one edge of said document, and for conveying, when an image of a single document is illuminated by said document reading device a plurality of times, said single document in a reciprocating motion via said illuminating position, said device comprising: a document table located above the illuminating section and for supporting a document laid thereon and guiding said document to an inlet; a turning section for turning over the document inserted into said inlet and guiding said document to the illuminating position; document conveying means located upstream and downstream of the illuminating position with respect to a direction in which the document is inserted, said document conveying means being reversibly driven for conveying said document to a position upstream of said turning section and a position downstream of said illuminating position; an accommodating section positioned between said document table and the illuminating position and capable of accommodating the document conveyed from said turning section when said document conveying means is reversed; a path selector for selectively steering the document being conveyed by said document conveying means either to said inlet or to said accommodating section; document edge sensing means adjoining the illuminating position for sensing a leading edge of the document being conveyed by said document conveying means; and control means for controlling said document conveying means and said path selector in response to a number of times of reciprocation of the document to occur and an output of said document edge sensing means.
1. A document conveying device mounted on a document reading device which sequentially reads a document image moving via an illuminating position with an illuminating section thereof from one edge of said document, and for conveying, when an image of a single document is illuminated by said document reading device a plurality of times, said single document in a reciprocating motion via said illuminating position, said device comprising: a document table located above the illuminating section and for supporting a document laid thereon and guiding said document to an inlet; a turning section for turning over the document inserted into said inlet and guiding said document to the illuminating position; document conveying means located upstream and downstream of the illuminating position with respect to a direction in which the document is inserted, said document conveying means being reversibly driven for conveying said document to a position upstream of said turning section and a position downstream of said illuminating position; an accommodating section positioned between said document table and the illuminating position and capable of accommodating the document conveyed from said turning section when said document conveying means is reversed; a path selector for selectively steering the document being conveyed by said document conveying means either to said inlet or to said accommodating section; document edge sensing means adjoining the illuminating position for sensing a leading edge of the document being conveyed by said document conveying means; and control means for controlling said document conveying means and said path selector in response to a number of times of reciprocation of the document to occur and an output of said document edge sensing means. 2. A device as claimed in claim 1, wherein said document conveying means comprises: reversible drive rollers respectively rotatable in contact with at least opposite side edges of the document; at least two driven rollers constantly biased by respective resilient members having predetermined resiliency, and respectively driven by said drive rollers contacting the opposite side edges of the document with the intermediary of the document; shaft holders each supporting a rotary shaft of said respective driven rollers; said shaft holders each comprising support portions respectively spaced apart from peripheries of opposite ends of said respective rotary shaft by a predetermined gap at least in an intended direction of document conveyance while allowing said rotary shaft to freely move toward said drive rollers, but restricting a movement of said rotary shaft in said intended direction of document conveyance in abutment against said rotary shaft; and gap adjusting means for adjusting at least one of said gaps respectively formed between the outer peripheries of said rotary shaft and said support portions which are respectively positioned at an outer side and an inner side with respect to the document.