This means that there are two griffes and two cylinders. The same methods are used to operate the moving parts, as are used on the single action machines, but the lever and arms are used in a compound manner. This machine is undoubtedly the best, where large reproduction is aimed at, for it can be run 170 or 180 picks per minute. The illustration, Fig. 24, shows a double action machine.

The shedding motion is obtained by means of a double crank fixed on the end of the pick cam shaft, and to which the long lifting rods are attached. This is shown in Fig. 25. Cams have been used to take the place of the double crank, so as to allow a dwell for the shed while the shuttle is passing through. It is particularly desirable in a broad loom to have the shed full open for a longer period in order to give clearance for the shuttle, but the cam motion was proven to be somewhat detrimental, owing to the quick rise and fall of the harnesses, which causes the lingoes to jump and to be constantly breaking off. The neck cords also were constantly breaking. The cam movement could be used successfully with a jacquard that had not many harness threads attached to the neck cords, and had heavier lingoes fixed to the harnesses, but for general use, the double crank is best, as it gives a more even movement. There is also a short dwell while passing around the extended part of the crank.

The time to set the crank is to have it level, that is, the two extreme points horizontal, when the crank shaft is a little ahead of the bottom center, or to have the reed about 1½ inches from the cloth when the shed is level.

Owing to the general formation of the double action machine, that is, the use of two hooks for one set of harness threads, there is a somewhat uneven movement to the harnesses. When a griffe is descending and some of the hooks that are on the griffe are to be lifted for the next shed, and the hooks are passing each other at the center of movement, the angle of the harness threads is changed, for as one hook is lifted from the top shed, the neck cord attached to the hook that is at the bottom is slack. When this hook is raised for the next pick, at the point when all the slack cord is taken up, the uneven movement is caused, the harnesses swinging over into the line with the lifting hook. The results from this movement are not so harmful if the jacquard is tied up proportionally and run at the right speed; but when the machine is run too fast and the lingoes are too light, also when the neck cord is too short, a large amount of trouble is caused. Instead of connecting the harnesses to the hooks, by means of two neck cords, one is used as shown in Fig. 26. The link answers the purpose for which it is intended, that is, to take away the slack neck cord. It also reduced the uneven movement. However, unless the hooks are kept perfectly straight, the link will not work, and it is common for a hook to be bent a little underneath the grate.

When one neck cord breaks on the ordinary double action machine, the defect is not readily seen, because the harness cord will be lifted by the other hook, unless it is a pattern where that particular hook from which the cord has broken is lifted very often. When the link is used, all the harness threads that are attached to the link will fall, owing to the use of only one neck cord; this also occurs on the single action machine.

Needles. The illustration Fig. 27 shows the arrangement of needles in a double action machine. The first needle at the top marked A, controls the hook B, passing down in regular order until the bottom needle in the right hand needle board, marked C, controls the hook D. The first needle in the left hand or bottom needle board, marked E, controls the hook F, which is the partner to D, that is, F and D control the same harness threads, as will be noticed by the connection at the bottom G. The eighth needle in the bottom needle board, marked H, controls the hook K, which is the partner hook to B. The bottom set of needles is exactly like the top set. They are placed in the same relative position, but work from the opposite direction.

There being two cylinders on this type of machine, one passes in as the other is going out. Both cylinders turn toward the machine as indicated by the arrows, and a glance at the two cards A and B with holes marked 1 and 2, and needles marked the same will show the two hooks F and D control the same harness threads.

It will be noticed that one hook has the top bend bent backward, while the other bends forward in the same direction as the lower bend of the hook. The reason for this latter is that it would require more space in the grate and the needles would have to be longer, which would make a broader machine if the same shape of hook were used; so that by the use of these hooks, considerable space is gained.

When cutting cards for a double action machine, each card is cut from the design singly, just the same as if cutting cards for a single action machine. After the cards are cut, they are divided, the odd numbers from the even numbers, so that when laced they form, as it were, two sets of cards, one set being placed at one side of the machine and the other set at the other side of the machine.

A double action machine is composed of double the number of working parts that are on a single action machine, but they are placed so as to work in different directions, with the exception that with an independent cylinder motion only one eccentric rod is used, and the eccentric is placed on the pick cam shaft. But if the cylinders are operated by a spindle motion, a slotted crank arm is attached to the lifting rod of each griffe and the cylinder is moved out as the griffe to which it is attached is raised, one cylinder moving out from contact with the needle board as the griffe, that comes in contact with the hook controlled by the needles of that board, is raised, at the same time the other cylinder is passing in towards the needle board while the second griffe is descending.

When using the cradle lever on a double action machine, it is necessary to have two different sizes of lifting cranks to allow extra lift for the difference in length of the levers, owing to one of the levers working on the inside of the other. The length of levers used is about 30 inches for the longer end, from fulcrum to connection of lifting rod, and 13 inches for the shortest end on the longer lever. Fulcrum to connection of lifting arm on the shorter lever is 25 inches, and 10 inches on the shorter end. The double crank is made so that the one with the 12-inch stroke is attached to the shorter lever, and the 10-inch stroke operates the longer lever.

The cradle lever lift is used only on machines that have the harnesses attached to them by the cross tie system, because by the straight tie system the machine is turned in the opposite direction; that is, one set of cards would be over the cloth in the loom, and the other set over the warp; and in the cross tie system the cards are over the sides of the loom or over shuttle boxes.

The top lever lift is considered by many to be the best method of operating the griffes, and this method can be used whether the harnesses are attached by the straight tie or the cross tie system. All that is required to be changed is that where as in the straight tie both the levers are on the same stud, and fixed to one support, the levers for the cross tie are placed on separate studs with separate supports. The reason for using separate supports and studs is to meet the different positions of the griffe bar. (See Fig. 28.)

Other lifting methods have been successfully tried on double action machines; one being a rack movement shown in Fig. 29 and another a pulley and belt lift shown in Fig. 30.

The rack movement is as follows: A 1½-inch iron shaft is supported in bearings fixed to the top of the machine. This shaft extends over the end of the machine. The supports are bolted to the cross rail of the griffe, and on these supports the racks are fixed. The shaft passes between the two racks, and the gear is fixed on the shaft in contact with the rack. An arm is set-screwed on the outer end of the shaft, and to this arm a long lifting rod is attached. The bottom of the rod is placed on a stud attached to the face of a round iron plate that is set-screwed on the pick cam shaft.

In Fig. 30 the pulley A is supported on a shaft in the same position as the gear for the rack motion, and to the pulley a strip of belting B is attached, each end being fixed to the cross rail of the griffe at C. The belt motion is a simple arrangement, but the griffe must act freely and perfectly straight or the griffe will not descend low enough to allow the hooks to be pressed off by the cylinder.