Endless flexible belt for a printing system
A flexible belt is disclosed for use in a printing system. The belt comprises an endless strip which, in use, travels along a continuous path. Formations are provided along the sides of the strip which are capable of engaging with lateral tracks to place the belt under lateral tension, the lateral tracks further serving to constrain the belt to follow the continuous path.
1. A flexible belt for use in a printing system, comprising an elongate strip having parallel straight sides of which the ends are releasably or permanently securable to one another to form an endless loop, which belt, when in use, travels along a continuous path and serves to transport ink images from an image forming station to an impression station of the printing system, wherein the belt has a degree of elasticity in a width ways direction that is greater than the elasticity of the belt in a longitudinal direction such that, under lateral tension, the strip is maintained flat in a width-wise direction as the belt is pulled through the image forming station and wherein formations are provided along the sides of the belt which are capable of engaging with lateral tracks in such a manner as to place the belt under width ways tension and to constrain the belt to follow a continuous path defined by the lateral tracks.
2. A flexible belt as claimed in claim 1 , wherein the strip from which the belt is made comprises an elastically anisotropic reinforcement layer and a release layer.
3. A flexible belt as claimed in claim 2 , wherein the strip from which the belt is made additionally includes a compressible layer.
4. A flexible belt as claimed in claim 1 , wherein at least one side of the strip from which the belt is made is provided with a plurality of formations that are spaced from one another along the length of the strip.
5. A flexible belt as claimed in claim 4 , wherein the spaced formations are teeth of one half of a zip fastener that is secured to the belt along the side of the strip.
6. A flexible belt as claimed in claim 1 , wherein the formations comprises two flexible beads of greater thickness than the strip, arranged one on each side of the strip.
7. A flexible belt as claimed in claim 1 , wherein the formations are made of a material having a low friction coefficient to ensure smooth running of the formations within the lateral tracks.
8. A flexible belt as claimed in claim 1 , wherein the formations are made of a material, or comprise an agent, having lubricating properties.
9. A flexible belt as claimed in claim 1 , wherein the formations are made of a polyamide polymer supplemented with molybdenum disulfide or of a polyacetal filled with PFTE.
10. A flexible belt as claimed in claim 1 , wherein the formations have an anti-friction coating of PTFE.
11. A flexible belt as claimed in claim 1 , wherein the belt includes one or more markings detectable by a sensor of the printing system.
12. A method of printing comprising:
a. at an image forming station, directing droplets of an ink onto the surface of the flexible belt of claim 1 to form ink images on the belt surface as the belt is pulled through the image forming station;
b. guiding the belt so as to transport the ink images from the image-forming station to an impression station; and
c. transferring the ink images from the belt surface to substrate, wherein: (i) as the belt is guided, first and second lateral tracks disposed on opposite lateral sides of the belt are engaged to the belt-side-disposed formations to maintain the belt under lateral tension and (ii) the belt is both substantially inextensible lengthwise and has a sufficient degree of elasticity in a width ways direction so that the lateral tension applied by the first and second lateral tracks maintains the strip flat in a widthwise direction as the belt is pulled through the image forming station.