US2943375A - Stretching machine for dryer felts and the like - Google Patents

Description

T. HINDLE 2, STRETCHING MACHINE FOR DRYER FELTS AND THE LIKE July 5, 1960 Filed May 23, 1956 I a. w?

STRETCHING MACHINE FOR DRYER FELTS AND THE LIKE Thomas Hindle, Blackburn, England, assignor to Scapa Dryers Inc., a corporation of Georgia Filed'May'23, 1956, Ser. No. 586,697 8 Claims c1. zs- -ss This invention relates to stretching machines for dryerfelts and the like and is particularly, though not exclusively, applicable to machines for stretching, shrinking and'normalizing papermakers dryer-felts.

In papermaking, dryer-felts in the form of endless woven bands are used to carry the sheet or web of paper in close contact with the drying cylinders of the paper machine. Although such dryer-felts,- being composed of cotton, of asbestos, of the newer synthetic fibres or of any combination of these materials, are not subjected to any form of milling and are therefore not felts in the technical sense of the term, they have, by common usage, become known as dryer-felts.

Dryer-felts are made in a great variety of widths and lengths, and the applicants have found, from the accumulated experience of many years, that great advantages are gained when the final stage of their manufacture consists of a comb ined stretching, shrinking and normalizing treatment. The stretching and shrinkingtreatment serves to make the felt more dimensionally stable for subsequent use on the paper machine, and at the same time the entire substance of the felt is normalized, that is to say, the local tresses set up in the component yarns during the weaving process are gently relaxed. Hereinafter therefore, reference to the stretching process will be understood, where applicable, to include the concurrent shrinking and normalizing processes.

The dryer-felts used in the paper-makingindustry sometimes attain widths of twenty-seven feet and lengths approaching five hundred feet, and the operation of stretching them presents a substantial problem because of their great weight. The only known method of stretching such a dryer-felt is to wet it thoroughly with water after arranging it to run in the form of an endless band over a plurality of rollers, one or more of which is heated and one or more of which is capable of being moved to apply longitudinaltension to the dryer-felt.

The existing machine for stretching papermakers dryer-felts consists of a horizontal frame of sixty feet or more in length, at each end of which is anupstanding frame carrying a bank of rollers. Mounted in bearings adjustably movable along the horizontal frame is one or more stretch rollers over which a bight of the felt is reeved so that tension may be applied to the felt. In order to effect drying of the wetted felt, the lower roller of one bank only is of considerably larger diameter, and is steam-heated. The dryer-felt extends in long horizontal runs between the banks of rollers and over the stretch rollers.

The length of the felt, as received from the weaver, is drawn intothe stretching machine and about the various rollers, and then its ends are stitched or otherwise joined together across the entire width of the felt to form an endless band preparatory to the actual stretching.

Stretching machines as aforesaid present several operational problems. In the first place there is the time factor as the drying time on such machines is commonly in excess of eight hours per dryer-felt. A more difiicult problem, however, is the control of the sag in the aforesaid long horizontal runs of the dryer-felt extending between the two banks of rollers and over the stretch rollers, which sag tends to the formation of longitudinal creases as the dryer-felt runs continuously over the rollers. When it is realised that some of the largest dryer-felts exceed 1,000 in value, and bearing in mind that there is no known method by which such creases can be successfully removed, the serious nature of this problem can be better appreciated.

The present invention is based on the appreciation that the principal cause of the aforesaid longitudinal creasing is the transverse sag in the long unsupported horizontal runs aforesaid of the dryer-felt. In any such unsupported horizontal run, the weight of the dryer-felt, especially when thoroughly wetted, causes notonly a longitudinal (i.e. warpways) sag, but also a transverse (i.e. weftways) sag, both sags approximating to catenary form. Thus, under these conditions, thestraight-line distance between the selvedges of the transversely sagging dryerfelt is markedly less than the width of thedryer-felt as measured without transverse sag. As the dryer-felt runs onto a roller, it attempts to straighten out the transverse sag, but if this is too pronounced, as occurs with long unsupported horizontal, or substantially horizontal, runs, the selvedges do'not move apart to the full width of the dryer-felt, in which case. longitudinal creasing occurs at the on-going rollers, causing irreparable damage to the dryer-felt which is thereby rendered useless for its intended purpose. Intermediate supports to shorten the said unsupported length have been introduced with some measure of success, but damage from longitudinal creasing still occurs though the-risk of such damage has been reduced.

The object of the present invention is an improved machine for stretching papermakers dryer-felts and the like, primarily to eliminate-the damage to the dryer-felts by longitudinal creasing, secondarily to speedup the operation, and thirdly a machine of generally improved construction having its own inherent advantages.

The invention comprises the method of stretching a papermakers dryer-felt wherein the same is run as an endless band over a plurality of rollers whilst being subjected to tension, heat or other necessary condition for its treatment characterized in that the dryer felt is draped or festooned over spaced elevated supports, before its ends are joined to form an endless band, so that sub stantially the entire length of the band is expended in the formation of downwardly depending festoons whose legs are substantially vertical, and which are closed at their lower ends, and restraining the closed lower end of each festoon from upward movement while stretchingforce of such intensity as to increase the length of the felt is being applied to the felt, whereby transverse sagging of the felt and the formation of creases issubstantially prevented.

The invention also comprises a machine for carryingv out the process aforesaid.

According to a preferred embodiment of the invention, a machine for stretching (which, as aforesaid, is to be understood as including the concurrent shrinking and normalizing processes) paper-makers dryer-felts and the like, consists of a plurality of pairs ofrollers in upper and lower staggered arrangement, the felt draping over the upper rolls and forming depending festoons closed at their lower ends, and each lower roller being disposed within the lower .closed end of the corresponding festoon, thus forming two interleaved pleated formations, at least one of the rollers being adjustable for tensioning the felt,

tially vertical, and are also relatively short, whereby all possibility of pronounced sagging of the felt either longitudinally or transversely is obviated, together with the aforesaid objectionable longitudinal creasing of the felt.

In theaccompanying drawing:

Fig. l is a diagrammatic illustration of one example of the machine made in accordance with the invention and for use in the stretching, shrinking, and normalizing of papermakers dryer-felts, the end rollers only of the machine being shown;

Fig. 2 is a front elevation showing mechanism for raising one pair of rollers for the purpose of tensioning the felt.

The drawings are primarily diagrammatic, all framework being omitted with the object of clarity. At the lower part of the machine there are pairs of rollers a with the rollersone above the other, and single endrollers b, whilst at the upper part of the machine there are complementary pairs of rollers c. At one end of the machine is also shown a pair of upper rollers d similar to the rollers but mounted at each end in guide blocks e slidably located in guides f at each side of the machine. An endless dryer-felt g is shown reeved over and under the rollers in two interleaved pleated formations, and motors h are shown coupled to rollers 11 for driving the felt. The rollers d are vertically adjustable by means of a pair of steel wire ropes i (Fig. 2) each attached by one of their ends to a winch i and associated at their other end with a pulley block system k arranged to give mechanical advantage and relatively slow movement, such pulley blocks being connected by links m to the sliding blocks 2. The winch j is adapted to be driven by a reversible electric motor 12 through a suitable reduction gearing 0.

At one end of the machine is also shown a guide roller p supported by its ends through steel wire ropes q and winches r, one set only of which is shown in Fig. 1, for one end of the roller 17. By this means, the roller p may be lowered to have any desired pressure on one end run of the felt and by lowering one end more than the other a guiding effectto the felt may be obtained in known manner. The upper rollers d are shown in their uppermost position whilst their lowermost position is shown in dotted lines at d, together with the complementary run of the felt, when the rollers are in such lower position. Asshown, the horizontal component of inclination of the run of the dryer-felt between the rollers a and c is about /6 of the full length of the run, so that the legs of each festoon make an angle of not more than 10 with the vertical.

The machine above described may be constructed so that the length of a leg of a festoon, that is to say, the substantially vertical run of the dryer felt between consecutive rollers, will not exceed about fifteen feet, and will be so steeply inclined as to be substantially vertical. A machine having eight pairs of upper rollers and seven pairs of lower rollers will accommodate a dryer-felt in excess of five hundred feet in length whilst the stretch adjustment provided by one pair of rollers is of the order of thirty feet. By providing stretch adjustment for two pairs of rollers at each end of the machine, there is ample provision for all the stretch requirements for the largest dryer-felts at present manufactured or contemplated.

It will be evident from inspection of the drawings, that the rollers a, b, c, d, etc. about which the felt passes are cylindrical and devoid of peripheral ribs or grooves, and although the surfaces of these rollers need not be polished, and in fact may, if desired, be such as to exert a frictional effect upon the felt, the rollers are herein referred to as smooth-surfaced to distinguish from rollers having distinct peripheral ribs or grooves.

. The machines also require provision for heating one or more of the rollers during the operation of stretching chines, in which the dryer-felt has long horizontal runs,

the heat applied to the dryer-felt is lost too quickly. With the new arrangement of the rollers, however, ac-

cording to the present invention, heat which may be applied through any number of rollers, for example through some or all of the lower rollers a, is relatively far as such details may be modified without departing and drying the dryer-felts. In the case of existing mafrom the scope of the invention. For instance, a second adjustable guide roller may be provided at the other end of the machine from that shown whilst further intermediate guide rollers may be provided, if found necessary, to ensure correct running of the dryer-felt on the rollers during the stretching operation. It is believed, however, that one such roller at each end will suffice for the purpose. Also, the raising of the stretching rollers could be effected by means other than the steel wire rope and pulley mechanism shown though such mechanism has the advantage of simplicity and there is every reason to believe that it will give complete satisfaction.

A further advantage of the machine constructed in accordance with the invention is that the provision of driving rollers and stretching and guiding equipment at each end of the machine allows for the processing of two dryer-felts at the same time, one at each end of the machine, providing that the sum of the lengths of the two felts does not exceed the total length capacity of the machine. The motors h may be arranged to drive additional rollers a in the lower bank as shown dotted in Fig. 1.

The basic principle of the invention lies in the appreciation that the elimination of the long horizontal runs found in previously known machines, will result in the elimination of damage by longitudinal creasing of the dryer-felts during the stretching and normalizing treatment. The steeply inclined and relatively shorter runs of the dryer-felt between the upper and lower rollers are substantially vertical and consequently transverse sagging of the dryer felt under the action of gravity, which has been the principal cause of the longitudinal creasing of the dryer-felt, is therefore reduced to a negligible quantity. It is also to be appreciated that the improved stretching machine herein described may be operated, with equal safety to the dryer-felt, in either direction, consequently, the motors h may be reversed several times during the stretching and drying operation in order to ensure that the weft in the finished dryer-felt shall be straight and not bowed.

I claim:

1. Method of treating a paper-makers dryer-felt, including the application of longitudinal tension, after the felt has been woven, thereby to make the felt dimensionally stable while avoiding transverse sagging and the consequent formation of longitudinal creases, said method comprising as steps, draping the felt over a series of horizontally spaced elevated supports to form festoons whose legs are substantially vertical, joining the ends of the felt to form an endless band, restraining the closed lower end of each festoon from upward movement, applying stretching force to the felt of such intensity as to increase the length of the felt, and moving the felt in the direction of its length while the stretching force is being applied.

2. Method, according to claim 1, wherein two rows of elevated supports are provided, and the felt is draped over both rows of supports so as to provide pairs of downwardly depending festoons, with one festoon of a pair disposed within the other festoon of the same pair.

3. Apparatus for use in the manufacture of a papermakers dryer-felt, including the application of longitudinal tension thereto, after the felt has been woven and after its ends have been joined to form an endless band, thereby to make the felt dimensionally stable while avoiding transverse sagging and the consequent formation of longitudinal creases, said apparatus comprising supporting means over which the felt may be draped, before its ends have been joined, to form downwardly depending festoons, each festoon being closed at its lower end, and with the legs of each festoon diverging upwardly at an angle not substantially exceeding to the vertical, said apparatus comprising an upper series of horizontally spaced, parallel, horizontal, elongate, smooth-surfaced felt-positioning elements and a lower series of horizontally spaced, parallel, horizontal, smooth-surfaced feltpositioning elements, the elements of the upper series being staggered with relation to those of the lower series, the positioning elements of the lower series constituting restrainers each operative to prevent upward motion of the closed lower end of a corresponding festoon of the festooned material, and each element of the upper series constituting a support over which the felt may be draped, one of the felt-positioning elements of the upper series being bodily movable upwardly, and means for moving said movable element upwardly, relatively to the other elements of the upper series, with force suflicient to increase the length of the felt.

4. Apparatus, according to claim 3, wherein the feltpositioning elements are smooth-surfaced cylindrical rolls whose axes are parallel, and reversible motor means for turning certain, at least, of said rolls thereby to traverse the felt alternately in opposite directions while the longitudinal stretching force is being applied.

5. Apparatus, according to claim 3, wherein the number of said elevated positioning elements is such that when used for stretching a felt of the order of five hundred feet in length, the length of the material constituting each respective leg of a single bight need not exceed fifteen feet.

6. Apparatus for treating paper-makers dryer-felt according to claim 3 characterized in that the means for tensioning the dryer-felt comprises at least one tension roller, journals for the ends of the roller, cables suspending said joumals and a common winch for winding said cables.

7. Apparatus for use in the manufacture of a papermakers dryer-felt to impart dimensional stability thereto, while avoiding the formation of longitudinal creases therein, said apparatus comprising horizontally spaced pairs of rollers forming an upper series, and horizontally spaced pairs of rollers forming a lower series, one roller of each pair being directly above the other, and the lower pairs being staggered with reference to the upper pairs, the rollers providing means about which an endless dryerfelt, of a length as great as five hundred feet, may be compactly reeved in two interleaved, pleated formations, at least one of the rollers benig bodily movable, and means for applying force for so moving said last-named roller as to increase the length of the felt, the arrangement being such that the runs of material, extending between a roller of an upper pair and a corresponding roller of a lower pair, are so steeply inclined as to be substantially vertical, and the number of rollers being such that the maximum length of any run of such a felt, extending from a roller of an upper pair to the corresponding roller of a lower pair, need not exceed fifteen feet, whereby all possibility of sagging of the felt either longitudinally or transversely with consequent creasing is obviated.

8. Apparatus for use in the manufacture of a papermakers dryer-felt, including the application of longitudinal tension thereto after the felt has been woven and after its ends have been joined to form an endless band, thereby to stretch the felt longitudinally and to normalize its structure, said apparatus comprising means operative so to position the material of the felt as to form pairs of downwardly directed festoons, each closed at its lower end and each having upwardly directed legs which are within approximately 10 of the vertical, one festoon of each pair being nested within but spaced from the other festoon of the same pair, the means for so positioning the material of the felt so as to form a series of nested downwardly depending festoons comprising an upper series of horizontally spaced pairs of felt positioning elements and a lower series of horizontally spaced pairs of felt-restraining elements, each lower restraining element of each pair being disposed within the closed lower end of the outer festoon of a nested pair, and the upper restraining element of each pair being disposed within the closed lower end of the inner festoon of a pair of nested festoons.

References Cited in the file of this patent UNITED STATES PATENTS 634,307 Neidhardt Oct. 3, 1899 813,288 Hancock Feb. 20, 1906 1,137,719 Sibson Apr. 27, 1915 FOREIGN PATENTS 560,061 Germany Sept. 28, 1932

Images