Flat Machine Knitting and Fabrics

by H. D. Buck

Three Units May Be Racked

In this type of jacquard machine there are three separate and distinct units which may be racked or moved at right angles to the movement of the needles. They are, first, the needle plate proper which racks the same as the ordinary flat machine; second, the auxiliary needle plate; and third, the card cylinder together with the cards. The racking of the needle plate proper is necessary to make those designs in which a rack in the fabric is required, but the other two are chiefly a matter of convenience to save making up cards. There are many designs that may be made with one or four cards, or even without any cards, by manipulation of these racking movements, where otherwise quite a string of cards would be required.

Fig. 89.
Needles Proper and Auxiliary Needles
Used in Jacquard Machine.

We will take for example any design consisting of a small block or check within the limits of the needles the auxiliary plate will rack over. Such a design may be made without cards in this way. Say we wish to make a black and white check four needles wide and four courses high. We would put up into operating position four auxiliary needles and draw four down, alternating in this way with four up and four down for the width of the fabric. Then, referring to Fig. 86, we would draw up out of operating position as shown the rise cams c, d and e, also the wing cams f and g. This would permit the alternating four auxiliary needles we have left in operating position to always stay in this position. Now, after putting on one round or two courses of, let us say, white we would rack the auxiliary plate over four needles and then put on a round of black; rack back the four needles and put on a round of white, rack the other way four needles and put on a round of black. If we could see the fabric made thus far we would find that we had a row of blocks or checks four needles wide and four courses high. For although we have put on four courses each of the black and white, which makes eight courses in all, each color has been put on its own group of four needles; therefore the whole will build up the fabric but four courses. If we continued to operate the machine in the same manner we would get alternate black and white stripes, each four needles wide.

To break them up into checks or squares we would at this point have to either skip racking once while continuing the change of carriers each round, or miss changing carriers once while continuing the rack of four needles each round. This change must of course be made every four rounds throughout the length of the fabric, or as long as it is desired to make the check. It should be remembered that it is the auxiliary plate that is racked in this case, and not the needles proper; therefore the rack does not show in the fabric. But the shifting of these alternate sets of four auxiliary needles each round causes alternate groups of four of the needles proper to knit, the set which knits depending on which way the auxiliary plate is racked.

This same check design may be made with one card properly cut by preventing the card cylinder from turning and racking, or moving the card cylinder back and forth four needles in the same manner as the auxiliary plate was moved. Or it may be made with four cards without moving either the plate or card cylinder. In this case it would be necessary to use all the auxiliary needles and lower the wing cams f and g, Fig. 86, into action.

Fig. 90.
Cross Section of Needle Plates and Card Cylinder.

In making a fabric on a double jacquard machine which shows the design on one side only, it is good practice to put four cards on the front cylinder properly cut to put alternate needles into operation on alternate courses, in order to prevent putting more courses on the front plate than on the back. Or to explain it in another way, the needle in the back plate that makes the white part of the design knit only on the rounds on which the white thread carrier is used, and the needles that make the black parts operate only when the carrier with the black yarn is in use.

Now it is plain that if all the needles in the front plate are permitted to knit each round we would have approximately twice as many courses on the front as on the back. This is obviated, as stated before, by using cards on the front card cylinder to push up into operation every alternate needle when moving the carriage say from left to right, and permitting these to remain idle and pushing those not operated on this course into operation on the return course from right to left. While this is desirable it is not essential, for it cannot be done on a single jacquard, though there are many nice designs and fabrics made on this machine.