A sheet conveying device comprising: an endless belt for conveying sheets wherein the endless belt has an inner surface, an outer surface and a thickness therebetween and allows passage of air through the thickness and wherein the endless belt extends lengthwise along a forward portion and back along a return portion and is movable lengthwise so as to convey a sheet along the forward portion; a fan for generating a negative pressure on the inner surface of the endless belt at the forward portion so as to pull a sheet onto the outer surface of the endless belt at the forward portion; wherein the inner surface of the endless belt at the forward portion is in fluid communication with the inner surface of the endless belt at the return portion; and the fan is arranged to provide a negative pressure to the outer surface of the endless belt at the return portion so as to create the negative pressure at the inner surface of the endless belt at the forward portion; and a case having side surfaces extending from the inner surface of the endless belt at the return portion to the inner surface of the endless belt at the forward portion so as to duct the negative pressure at the outer surface of the endless belt at the return portion to the inner surface of the endless belt at the return portion; wherein the case includes side surfaces extending away from the outer surface of the endless belt at the return portion such that the case, in conjunction with the endless belt at the forward portion, defines a chamber accommodating the endless belt at the return portion characterised in that: the endless belt extends from one side surface of the case to the other, so that the chamber is divided by the endless belt at the return portion into a first chamber and a second chamber, the first chamber being formed between the forward portion and return portion of the endless belt, and wherein the fan is disposed in the second chamber. an endless belt for conveying sheets wherein the endless belt has an inner surface, an outer surface and a thickness therebetween and allows passage of air through the thickness and wherein the endless belt extends lengthwise along a forward portion and back along a return portion and is movable lengthwise so as to convey a sheet along the forward portion; a fan for generating a negative pressure on the inner surface of the endless belt at the forward portion so as to pull a sheet onto the outer surface of the endless belt at the forward portion; wherein the inner surface of the endless belt at the forward portion is in fluid communication with the inner surface of the endless belt at the return portion; and the fan is arranged to provide a negative pressure to the outer surface of the endless belt at the return portion so as to create the negative pressure at the inner surface of the endless belt at the forward portion; and a case having side surfaces extending from the inner surface of the endless belt at the return portion to the inner surface of the endless belt at the forward portion so as to duct the negative pressure at the outer surface of the endless belt at the return portion to the inner surface of the endless belt at the return portion; wherein the case includes side surfaces extending away from the outer surface of the endless belt at the return portion such that the case, in conjunction with the endless belt at the forward portion, defines a chamber accommodating the endless belt at the return portion characterised in that: the endless belt extends from one side surface of the case to the other, so that the chamber is divided by the endless belt at the return portion into a first chamber and a second chamber, the first chamber being formed between the forward portion and return portion of the endless belt, and wherein the fan is disposed in the second chamber. the endless belt extends from one side surface of the case to the other, so that the chamber is divided by the endless belt at the return portion into a first chamber and a second chamber, the first chamber being formed between the forward portion and return portion of the endless belt, and wherein the fan is disposed in the second chamber.