The stitch formation cycle on double-bed machines is similar to single-bed machines. The difference is that these machines incorporate two needle beds with their hook turned outwards, two grooved plates supporting the fabric and a single group of bars working alternatively with both the needle-beds, forming the stitch first with the needles of one bed and then with the needles of the other.
Double-bed machines can incorporate spring beard needles (picture 135), in this case they
Crochet machines can incorporate spring beard needles, latch needles or compound needles.
The most recent electronic models include up to 16 weft bars to create elaborated patterns; the pins that in the past were used for driving the bars of conventional machines have been first replaced with glider chains, and then with electronic control systems.
The operating speed of these machines can reach 2,000 rpm.
The single warp threads always feed the same needles with a bar motion that generates separated pillars of chain stitches.
At each revolution of the machine, a inlay weft thread is inserted between the loop sides and the interloops, as a result tying the pillars and creating the fabric (picture 139).
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