(195) The lap being produced is placed upon two rollers, =A A^{ 1}=, as shown in Fig. 114, which is a transverse section through one head of a Heilmann machine, as made by Messrs. John Hetherington and Sons. Enlarged views of portions of the mechanism are shown in Figs. 115 and 116. A combing machine is usually constructed with from six to eight heads, the driving mechanism for all of which is placed at one end of the machine. The lap rollers =A A^{ 1}= are positively rotated at a speed corresponding to that of the passage of the cotton through the machine. The lap as it is unrolled is carried along the trough =B=, made of its full width, the lower end of which terminates a little distance from the feed rollers =C C^{ 1}=. The bottom rollers of each head are suitably carried on brackets fixed to the roller beam, being made of steel, and a little longer than the width of the lap. They are fluted longitudinally, and drive the top rollers by frictional contact. The top rollers are also made of steel, being plainly cylindrical and covered with a sheath of cloth and leather, but a porcupine roller is often used instead of a pair of rollers. This, it is contended, opens the lap and decreases the waste. They are weighted by means of hooks on their axes, to which springs are attached. Immediately in front of the rollers the nipper is placed. This consists of two jaws, the upper one, =D=, being fastened to the lever =E=, which oscillates on the short shaft =F=, receiving its motion from a cam at the driving end of the machine through a shaft, short lever, and the connecting rod =G=. The lower jaw, =H=, is also made of steel, being rounded at its outer edge and covered with smooth leather. As the upper jaw is peculiarly fluted, as shown, the contact of the two establishes a nip of the cotton at the points of the flutes. The lower nipper blade, =H=, is fixed to two levers, =I=, which rock upon the shaft =J=. The spiral springs, =K=, are attached to the tail ends of the levers, =I=, and ordinarily keep the lower jaw in the position shown in Fig. 116, but also permit of it making a slight receding motion when pressed by the upper jaw after the nip is created.
(196) The foregoing portion of the machine constitutes what may be called the feed part, there being three distinct operations in the process—feeding, combing, and detaching. In front of the nipper the top comb, =L=, is fixed, being attached to the lever =M= in such a way that the necessary adjustment can be made. Below the nippers the comb cylinder =N= is placed, being constructed with a barrel or “comb stock,” to which is attached the comb needles. Of these there are seventeen rows, fixed in a metallic bed, or piece, known as the “half lap.” These should be accurately shaped, so as to be readily renewed or replaced when required, and are fastened to the comb stock by screws. The width of each row of combs is a little greater than that of the lap, and each row is parallel to the others. The needles are set at different pitches, beginning with one of 1/30th inch in the first row and terminating with one of 1/90th inch in the last. On the opposite side of the barrel a segment =N^{ 1}= is fixed, which is fluted longitudinally. A circular brush, =O=, is fixed so as to clear the needles as they revolve, and can be easily set up so as always to be in touch with the combs. This brush revolves between the comb stock and the doffing cylinder =P=, and running at a higher velocity than the latter, it removes the waste taken from the cylinder and transfers it to the doffer, which is clothed with a metallic brush surface. An oscillating comb removes the waste from the doffer and beats it into a receptacle formed to receive it.