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the machine over the lower “couch roll” (8). During its passage along the wire the pulp Between the breast roll and the lower couch gradually loses water but not, however, to a roll support is given to the wire by a number sufficient extent to give such a consistency of hollow brass rolls of smaller diameter in | and strength to the web that it can be removed order to ensure a perfectly even surface. from is support without breaking; in order to
The peculiar shaking motion which the make this possible recourse is made to artihand maker imparts to the mould after lifting | ficial drying. For this purpose two or more it from the vat is also imitated on the paper suction boxes (h), constructed either of wood machine ; the whole of the frame carrying the or metal, and divided into compartments, are wire is firmly supported by the lower couch placed immediately below the wire, before it roll whilst the supports under the breast roll reaches the couch rolls ; an outflow pipe of a rest on movable pivots. A rapid to and fro certain length is fitted to the bottom of each motion of the frame, gradually diminishing | box. The box, when filled with water, with in intensity towards the couch roll, is pro. | the outflow pipe closed and with the wire duced by means of a crank shaft.
carrying the wet paper on the top of it, is, This shaking motion, to a certain extent, practically speaking, hermetically sealed. If prevents the fibres from placing themselves in the tap provided on the outflow pipe is now parallel positions on the wire and at the same opened and if the box is just kept full of time promote the intertwining and felting upon water, a partial vacuum is produced underwhich the strength of the paper so largely neath the paper and the atmospheric pressure depends. The width of the paper produced rapidly forces the water out of the web into the may be regulated at will by adjusting the suction box. When suction by means of outtwo “deckle straps,” (e) which are carried and flow pipes proves insufficient, specially deguided by suitable grooved pulleys on the signed vacuum pumps are fitted to the suction deckle frame. On modern machines suitable / boxes. arrangements are provided which enable the Water-marks are not produced in "machine shifting of the deckle straps and the corre made” paper by wires sewn on to the wire sponding alteration of the width of the web to cloth upon which the paper is formed, as in be carried out without necessitating stoppage the case of “hand made,” but by means of of the machine.
the so-called “ dandy roll ;' this is a cylinder, The water which passes through the wire covered with wire gauze, on to which the and which carries along with it a certain design of the water-mark is sewn and which, amount of fibres, loading materials, size, &c., by revolving and pressing upon the surface of is called the “back water."
the soft paper, usually between the suction As already mentioned, to obtain uniformity in boxes, produces the required impression. The certain classes of paper it is necessary to collect first “ dandy roll,” at the time called a “wove the back water and to use it in place of riding roll,'' was made (according to Hofmann) fresh water for diluting the pulp coming from by John Marshall of London and supplied to the stuff chest. It being in many instances Matthew Towgood in the year 1827. Wove impossible to use all the back water for this paper is produced by covering the dandy roll purpose, suitable “save-alls” or “ fibre. with ordinary machine wire. catchers,” such as the “Bertram ” and the The web of paper, still containing a con“ Füllner,” are provided. The use of these siderable amount of water, has next to pass latter is of the utmost importance, not only between the couch rolls. It has already been upon the ground of economy, but also in con pointed out that the wire is conducted back nection with the question of the prevention of over the lower couch roll on the top of which, river pollution ; this problem, with which the but generally slightly behind, revolves the top paper-maker is constantly confronted, may be couch roll (i); this top roll is covered with a solved to a very considerable extent by the tightly-fitting felt tube, called the “jacket,” provision of suitable arrangements for the and is firmly pressed against the lower roll purification of the back water in the mill. by means of screw or lever pressure. A
The speed at which the wire travels varies scraper, called the “doctor,” a spurt pipe according to the kind of paper made and and a revolving brush are usually provided according to the construction of the machine ; | for the purpose of freeing the felt from particles 500 feet per minute is the highest speed ob- | of paper which it may have retained. tained on “news” machines in the author's After the paper has been pressed between experience.
the couch rolls it should possess sufficient
strength to allow of its being parted from the | eliminated by drying. Slow drying, as is supporting wire. It now travels, unsupported customary with hand-made paper, is out of the for the first time, for a short distance to the question on account of the enormous produc“first press felt."
tion of our modern quick running paper Considerable skill is required on the part of machines. The first Fourdrinier machine, the men in conducting the moist web of paper built by Bryan Donkin, had no drying arrangefrom the couch roll to the first endless press ment, the paper being taken from it in a moist felt; along this felt the paper travels to the condition, cut and dried in a drying chamber. first wet press (1), which consists of two bowls J. B. Crompton, of Manchester, may be conmade of cast-iron or of granite, or of cast-iron sidered as the inventor of the drying cylinders covered with hard rubber or bronze. Pressure now attached to the paper machine. The is applied to the top roll and a considerable number of drying cylinders varies very conamount of water is thus pressed out of the 'siderably with the kind of paper made and
paper; small particles of paper which stick to ' with the speed at which the machine runs ; the top roll are removed by a steel “ doctor." these cylinders are made of cast iron, highly
The paper, after leaving the first press rolls, polished, and are heated by steam. As is always slightly marked on the side on which the paper comes from the last wet press it has been in contact with the felt, but a it is conducted to the drying cylinders (), uniform finish on both sides of the paper is against which the paper is pressed by an obtained by passing the web on to another wet endless felt, called the “drying felt” (m). felt and with this through a second wet press Special stretching rollers are provided in (k). This time, however, the paper enters the order to keep the felts tight and in many press from the back so as to bring the other | cases the drying of the felt is facilitated by the side into contact with the upper press roll.
addition of separate drying cylinders (n). The action of the wet presses naturally de. The drying cylinders are generally arranged pends, to a very considerable extent, upon the in batteries and in some machines the paper readiness with which the felts are capable of is passed through a small calender called the absorbing the water. The felts, therefore, “smoother," which is placed in front of the have to be changed frequently and cleaned in last set of cylinders. The “ smoother” conspecial felt washing machines.
sists of a pair of highly polished chilled iron At this stage the paper still contains a con- rollers to which pressure is applied by means siderable amount of moisture which has to be of screws and levers. The paper being in a
damp condition, whilst passing between these machine glazed papers, such as “caps," very rollers, is capable of taking a high class finish. | highly glazed on one side only. It consists of
It is always preferable to perform the drying a wet end (a), similar to that of an ordinary as slowly as possible because rapid drying, as Fourdrinier machine but contains only one also drying at high temperatures, usually results drying cylinder (6), this being of large diameter in a paper of inferior quality, especially in so and having a very highly polished surface. far as its strength and sizing are concerned. The paper is taken from the couch press (0) The first two or three cylinders should be but on to an endless felt (d), by which it is pressed slightly heated, because overheating at this against the surface of the cylinder so that it stage frequently causes cockling of the paper. remains in contact until perfectly dry. After
The surface presented by the paper after it leaving the paper the felt is run through a leaves the last drying cylinder is not sufficiently | washing machine (e), in order to remove even or smooth for many purposes. Printing | absorbed impurities. papers which have been engine-sized are Paper machines with two wet ends have usually finished by a passage through one or been constructed with the object of pressing more sets of calender rolls (0), forming part of both webs together as they come from the couch the paper machine; these are placed imme- , rolls. Differently coloured papers, as well as diately after the drying cylinders.
papers of varying composition, may thus be After having passed over the drying | firmly united. cylinders the fibres constituting the paper In the Imperial Russian paper mills, papers are in a state of absolute dryness and there. bearing peculiar water-marks very difficult to fore incapable of taking a superior finish. counterfeit, are made on a machine which It being impossible to regulate the drying so consists of three wet ends of the “ Fourdrinier" as to leave a definite amount of moisture in the type. Each of the three webs is separately paper before passing it through the calender | water-marked and the machines are so accuthe paper has next to be damped. For this pur rately regulated that in pressing the three pose it may be conducted over revolving copper moist sheets together, the water-marks register cylinders placed in a trough containing water perfectly. or over a cooled cylinder against which a jet The “cylinder paper-machine" (Figs. 25 and of steam is directed. Rotating brushes which 26), in which the paper is formed on a respurt water against the surface of the paper, volving cylinder covered with fine wire gauze, or some other arrangement such as the "spray was invented by George Dickinson, about damping machine " in which water is very | 1820. The cylinder (a), is contained in a finely divided by means of compressed air, are trough (6), to which the paper pulp is conalso used.
ducted. The water which passes through the The bowls, of which there are usually from wire flows out through the hollow journal (c), four to twelve in one calender, are made of whilst the fibres become deposited on the surchilled iron and in some calenders provision face of the cylinder. The paper thus formed is made for heating some of the bowls with is removed from the wire by an endless felt (d), steam; pressure is applied by screws and which is pressed against the cylinder by the levers or in modern arrangements by means couch roll (e). The cylinder itself thereof hydraulic rams. In many instances the fore forms practically the lower couch roll. paper is cut on the machine lengthways, so To obtain a paper of uniform thickness two called “slitter knives” (D), being used for or more cylinder machines are usually comthis purpose.
bined and the wet sheets pressed together. The reeling apparatus (9), forms the final Cylinder machines are mostly used for part of the paper machine. It consists of a the manufacture of various thick papers and number of rollers each of which is inde boards. pendently driven and on which the paper is Although shaking devices have been prowound ; provision being made so as to allow of posed for use with cylinder machines, the the finished reel of paper being replaced by an paper which they yield does not possess the empty core, without causing loss of paper. uniform appearance and is not so thoroughly
Among the other types of paper machines I felted as are papers made on the Fourdrinier will first describe the “single cylinder ma machine. An interesting form of board chine" or “ Yankee machine,” also called the machine, consisting of four paper machines, “ M.G. machine," Fig. 24 (Messrs. James namely, two Fourdrinier and two cylinder Bertram and Son, Ltd.), on which are made machines, one of the latter containing
cylinder machines. For this purpose thin presses the pulp cau: ing it to overflow through strips of rubber or other material are fixed on the tubes on to a frame, covered with wire the wire of the cylinder so as to divide the web gauze, which resembles the hand mould. into single sheets.
The water is extracted by suction whilst the Grahain's patent cylinder or board machine mould is shaken laterally and pressed against (Messrs. J. Marx and Co.), which is shown in a couch roll over which an endless felt travels. Fig. 27, differs from the ordinary cylinder The sheet is transferred from the mould to this machine in that the cylinder (m), does not felt and conducted to a wet press. The empty revolve in a vat; the pulp travels over the mould is then rinsed and moved back to the apron (?), between the deckle straps (k), on to pulp distributor. the cylinder. The preliminary couch roll (f), ! Machine-made papers which have to be tub presses the felt lightly against the stuff and sized are either only slightly sized with rosin the sheet is taken off from the cylinder by the in the beater, or are made without any addition couch roller (8); it then passes between the of size. A solution of glue or gelatine, to which
alum and in some cases soap is added, is used nary calender finish is produced by friction for sizing purposes. The web of paper is run glazing. The “friction calender” used for through the size, contained in a trough, the this purpose consists of one large paper bowl excess being pressed out by rollers. Tub sized on the top of which revolves at a higher speed papers have to be dried very slowly in order ' a smaller, highly-polished steel bowl. The to prevent the size from coming to the surface, paper is pressed and smoothed at the same of the paper and thus making it too hard. For time by means of the friction thus set up, and this purpose the paper is conducted over a a very high finish is obtained by this method large number of skeleton cylinders contained of glazing. in a heated chamber and provided with fans. ! Although sheet finishing is sometimes done Special automatic drying machines, as used in on the ordinary calender, “plate glazing" is drying stained and surface-coated papers, more frequently resorted to. In this operation the are also applied to this purpose. In many single sheets are placed between highly polished cases it is necessary to rewind the paper . zinc or copper plates, and pressed between carefully before sending it to the printer heavy iron bowls. The plates are moved backor before finishing on the calenders. A rewards and forwards several times between the
reeling apparatus, by means of which the bowls, after which the sheets are removed and paper is wound tightly whilst under pressure again placed between plates for a second on a wooden or iron core, is used for this i pressing. purpose.
“Embossing” is another method of calenderThe surface of paper as it comes from the ing by means of which designs are pressed paper machine is for many purposes not suffi- into the surface of the paper. The embossing ciently smooth ; it has to be finished, either in calender consists of two bowls, one of cotton the web or in single sheets, to suit particular or paper and the other of steel, upon which the requirements.
design is engraved. The “ web glazing," as the former operation. The cutting of papers lengthways is accomis called, consists in passing the web of paper plished by slitter knives such as are used in through a calender or calenders in which it is combination with the paper machine. Special strongly pressed between iron bowls and com- sheet cutters are provided for cutting the web pressed paper or cotton bowls. Pressure is into single sheets.' Four or more reels of paper applied to the bowls by screws and levers or are conducted to one of these machines simulby hydraulic rams. The iron bowls are usually taneously and at a uniform speed. A revolyheated by steam.
ing drum, which carries å knife, cuts the paper · A finisn distinctly different from the ordi- once every revolution ; the other cutter is a