Variable grass-length injection

A yarn injection device for injecting yarn sections into the ground, wherein the yarn injection device comprises:

• a yarn storage comprising a number of spool holders for holding a number of spools with yarn,
• a feeding device configured to feed lengths of yarn via respective supply paths from the storage to an injection unit, the feeding device comprising:
• a number of yarn tubes, each yarn tube defining a yarn channel configured to accommodate a respective yarn, and
• a number of cutting devices located at a side of the number of yarn tubes and being configured to cut a number of yarn sections from the respective yarns extending from the yarn storage into the yarn tubes,
• wherein the feeding device is configured to feed an adjustable length of yarn to the yarn injection device,
• the injection unit comprising:
• an injection needle guide defining a number of first passages extending over a vertical distance and a number of second passages extending over a horizontal distance, wherein each first passage intersects a respective second passage, and wherein each yarn channel is fluidly connected to a respective second passage,
• a number of moveable injection needles moveable between an upper needle position and a lower needle position and configured to pass through the first passages of the injection needle guide, wherein when yarn sections in the yarn tubes are located below the moveable injection needles and the moveable injection needles move downward through the injection needle guide, the yarn sections are injected into the substrate,
• at least one needle actuator configured to move the number of moveable injection needles between the upper needle position and the lower needle position,
• a fluid flow assembly comprising at least one fluid communication channel and a depressurized compartment having an underpressure, wherein the at least one fluid communication channel extends between the injection needle guide and the depressurized compartment,
• wherein the supply paths extend from the respective spool holders via the feeding device to the injection unit, and the feeding device is configured to supply the yarns to the injection unit, and wherein the fluid flow assembly is configured to create a flow of fluid through each fluid communication channel, each injection needle guide and each yarn tube in order to apply a drag force on the yarns and move the yarns through the second passages in the injection needle guide,
• wherein the yarn injection device further comprises a cutting device moving system configured to move the number of cutting devices towards or away from an intersection of the first passages and the second passages.

A method for injecting yarn section into the ground using a yarn injection device comprising:

• a yarn storage comprising a number of spool holders for holding a number of spools with yarn,
• a feeding device comprising:
• a number of yarn tubes configured to accommodate yarn, and
• a number of cutting devices,
• wherein the feeding device is configured to feed an adjustable length of yarn to the yarn injection device, and
• an injection unit comprising:
• an injection needle guide defining a number of first passages extending over a vertical distance and a number of second passages extending over a horizontal distance, wherein each first passage intersects a respective second passage, and wherein each yarn channel is fluidly connected to a respective second passage,
• a number of moveable injection needles,
• at least one needle actuator, and
• a fluid flow assembly comprising at least one fluid communication channel and a depressurized compartment having an underpressure, wherein the at least one fluid communication channel extends between the injection needle guide and the depressurized compartment,
• wherein the yarn injection device further comprises a cutting device moving system configured to move the number of cutting devices towards or away from an intersection of the first passages and the second passages,
• the method defining a cycle comprising the steps:
• a) supplying yarn from the yarn storage along a supply path to the feeding device,
• b) feeding a length of yarn into the number of yarn tubes with the feeding device,
• c) communicating a fluid flow to the number of yarn tubes to apply a drag force on the yarn and feed the yarn through the number of yarn tubes and the number of second passages of the injection needle guide,
• d) cutting the yarn into yarn sections with the number of cutting devices, wherein the yarn sections are at least partially located in the number of yarn tubes and the injection needle guide,
• e) moving the number of moveable injection needles downwards through the number of first passages, wherein the yarn sections are engaged by the number of moveable injection needles and are inserted in a substrate below the injection needle guide,
• the method further comprising:
• adjusting the length of yarn which is fed to the yarn injection injection device, and
• moving the number of cutting devices towards or away from an intersection of the first passages and the second passages by the cutting device moving system.