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.
Explanation of Pattern
Fig. 87 shows a fabric made on a double jacquard machine with both card cylinders in operation. Before going any further it should be understood that both the front and back card cylinders can be operated and make a new selection of needles at the end of each course, or when the carriage is at the end of its travel at both ends of the machine. This design is made by operating the card cylinders in this way. Fig. 88 is a layout of the design shown in Fig. 87. It is one complete repeat of the design as shown by the square box in Fig. 87. All the rest of the fabric is simply a repetition of this, but when grouped together on a large piece of fabric they appear entirely different.
As may be seen in Fig. 88, it would take 36 cards to make this design. In cutting the cards for this we would cut out the places shown blank and leave the card whole to push the needles into operation in the places marked by an x or an o. This cutting would of course have to be repeated the width of the fabric, or the length of each card.
The principle as explained is used on all makes of flat jacquard knitting machines, but the method used to put the needles into operation by the cards differs with the different builders. For example, one popular method is shown in Fig. 90, where the card cylinder is placed directly below the under surface of the auxiliary plate as shown at g, and acts on a short nib with the butt turned downward and extending through the plate as shown at f. With this method it is customary to use a long needle with two butts as shown in Fig. 89 at f, instead of the short one with an auxiliary needle. Also with this method the needle plate would be a single wide plate with the tricks or needle slots cut gradually deeper as they reached the lower edge, so that at the point where the lower butts of the needles come the trick is deep enough so that the needle may be depressed to bring the top of the lower butts flush, or just below, the top surface of the needle plate. When operating the machine these butts always remain in this position, therefore will not knit unless raised up and put into operation by the cards.
If we should cut a set of cards just the reverse of the set laid out in Fig. 88, that is, cut out where these are not, and leave uncut where these are cut, and put this set on the front card cylinder and operate them in conjunction with and opposite to the back set, we would have the same design on both sides of the fabric, but the colors would be reversed.