The Technical Evolution of Flatbed Machines

• The variable stroke optimises the carriage operation, as the stroke is adjusted automatically to the working range determined by the selection of each single feed system (picture 53).

Picture 53 - Optimisation of the variable stroke of the carriage

• The presence of several carriages on the same machine allows different combinations; in fact, the user can choose the best configuration of carriages depending on the pattern to be carried out. In picture 54 for example, each one of the three carriages has its own feed system that can be used either individually, to knit three cloths simultaneously (a); or combining 2 carriages (1 idle) with 1 separate carriage working individually to produce two cloths on two needle-bed sections (b); or combining 3 carriages with 3 feed systems, with the possibility of using the whole width of the needle-bed (c).

Picture 54 - The modular design of a flat-bed knitting machine featuring 3 carriages with 1

feed-system each

Picture 54 - The modular design of a flat-bed knitting machine featuring 3 carriages with 1

feed-system each

• The "open" carriage (i.e. a carriage without linkage with the two needle-beds) incorporates brand new manufacturing technology which has brought a significant improvement: yarns are fed from above and not laterally. In this way, the thread tension is reduced and thread guides are no longer driven by the carriage but are equipped with individual motors and can be therefore adjusted according to the knitting process underway.

Picture 55 - A 4-section flat knitting machine

• The thread feeding system is controlled by quick thread-in knot stop tensioners provided with light signal tower. In addition, an automatic device slows down the carriage speed in the case of small knots and stops the carriage in the case of big knots, breaks or no yarn (picture 56).

Picture 56 - Knot stop tensioners

• The lateral tensioners have small wheels to reduce friction on the yarn (picture 57 and 58).

Picture 57/58 - Lateral tensioners

• The digital control system monitors the stitch density and considers each stitch as a digital value. Before starting the knitting cycle, the operator sets the desired reference value for the stitch length; the systems monitors the set value and tunes the yarn feeding in order to grant a tolerance ratio not exceeding 1% in size and a uniform stitch density for each cloth (picture 59).

Picture 59 - Digital control of the stitch density

The thread guides slide on special double bars allowing the use of special thread guides for weft insertion or the knitting of intarsia or plating patterns; these special thread guides can be used together with standard thread guides. The thread guides stop automatically on the cloth edge and adjust the stroke according to the knitting range. Picture 60 shows the automatic positioning system of the thread guides with backstroke function. Thanks to this system, the thread guides - equipped with a vertical-insertion yarn hook - can be withdrawn from the contact area during the thread guide stroke, using a stepping-motor device.

Picture 60 - Backstroke type thread guide

The integrated cam combination system offers a wide range of possibilities to adjust the stitch density; this allows a full exploitation of the options offered by drown-type needles (picture 61).

Picture 61 - Split l owering cams

Thanks to special split lowering cams it is possible to programme a difference between long and short stitches (picture 62) for each system and on every single course, as well as to vary the density dynamically during the carriage stroke.

Picture 62 - Long and short stitches on the same course

The racking of the needle bed can be carried out selectively on a certain number of needles equalling at least one needle-bed inch; half-racking is also possible. The needle bed can be racked in a single step, or in two steps to reduce the yarn tension.

All the functions of the main take-down motion (picture 63) can be programmed; the motion is controlled by automatic devices which adjust the take-down tension on the stitches according to the quantity of knitting needles, so as to avoid density differences on the cloth length when knitting full-fashioned fabrics.

Picture 63 - Take-down motion with section-type main cylinder and individually adjustable counter-rollers

• An auxiliary take-down motion, placed very close to the needle-bed, only operates on the needles corresponding to the stitch formation line (picture 64).

  • Thanks to a start-up reed provided with hooks, the knitting process can also be started with empty needles.
  • Another important feature guaranteeing the quality of full-fashioned cloths as well as a complete knitting process, is the possibility to retain and/or cut the yarn as desired by means of grippers and cutters, placed on the right and on the left of the needle bed (picture 65).
Picture 65 - Gripper and cutter unit

• Incorporating movable knock-over sinkers in both needle beds, the press-foot allows a gentle knocking over of the fabric for knitting the most complicated patterns with efficient quality control (picture 66).

Picture 66 - Knock-over sinkers

• By means of the hole-repair motion, the stitch can be split to avoid the so-called "hole effect" during the stitch formation on empty needles, without replacing the cams or the thread guides (picture 67).

Picture 67 - Hole-repair motion

• Arranged above the main machine beds, the auxiliary bed incorporates special points which can be selected individually for the lateral transfer of the stitches on the front or on the rear needle bed, transferring and receiving the stitches from one bed to the other (picture 68).

Picture 68 - The auxiliary bed for the lateral transfer of stitches

• The new compound needle without lateral spring for the stitch transfer incorporates a sliding split latch (picture 69). While the needle transfers the stitch, the latch raises and splits into two parts; thereafter, it rises further taking with it the stitch to be transferred. In the meantime, the needle in the opposite bed is lifted and inserted in the space created by split latch, below the stitch. The further lowering of the two needles completes the stitch transfer procedure (picture 70).

Picture 69 - A compound needle of a coarse-gauge flat knitting machine

Picture 70 - Comparison between

  • a) the formation of an asymmetrical loop using standard lateral spring needles and
  • b) the formation of a perfectly symmetrical loop thanks to split latch needles
  • The innovative solution of the four needle beds consists of the addition of two auxiliary beds above the standard ones (picture 71). An upper auxiliary bed equipped with sinkers acting as individual press-foots is placed above the rear needle bed, while the front bed has an upper auxiliary bed equipped with stitch transfer points, thus allowing the transferral and receiving of stitches to/from all the needle beds. The latter auxiliary bed is divided into two sections, each one equipped with a transfer motion allowing different racking positions, as well as e.g. the asymmetrical decreasing of stitches. Some models are equipped with sinkers moving in opposite direction with respect to the needle direction (countersinkers) to reduce the stroke of the compound needle thanks to a combined motion; this limits the stress on the needles, the yarn and the stitches, which is particularly helpful in critical situations.
  • The three-dimensional knitting process allows the creation of multi-layer patterns in a single cycle. For example, on a plain-knit layer, it is possible to add decorative elements such as necks, hoods, pockets, buttonholes, buttons, trimmings, etc. without further sewing work, or manufacture a whole garment by knitting all the parts at the same time or in sequence: body, sleeves or other elements, as a result by-passing the making up stage completely.
  • The possibility of employing needles with three different hook sizes (large, medium and small), and changing the distance between the needle beds, allows the application of a wide range of yarn counts, with the result that the different areas of the same cloth look as they were knitted on machines of different gauge.
Picture 71 - Transfer options with four needle beds

Picture 69 - A compound needle of a coarse-gauge flat knitting machine

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