US3044542A - Papermaking machine - Google Patents

Description

ly 17, 1 6 J. LOYND 3,044,542 PAPERMAKING MACHINE Filed June 11, 1959 3 Sheets-Sheet 1 July 17, 1962 J. LOYND Filed June 11. 1959 PAPERMAKING MACHINE 3 Sheets-Sheet 2 July 17, 1962 J. LOYND PAPERMAKING MACHINE 5 Sheets-Sheet 3 Filed June 11, 1959 w www ,mentioned.

United States Patent ware Filed June 11, 1959, Ser. No. 819,587 4 Claims. (Cl. 162273) My invention relates to paper-making machines of the Fourdrinier type and more particularly to mechanisms for tensiom'ng the moving wires of such machines.

A Fourdrinier type papermaking machine generally comprises a loop of fine mesh wire on which a slurry of paper stock is deposited, the wire being disposed about a plurality of rolls and travelling about the rolls at high speeds. One or more stretch rolls are commonly provided in contact with the lower pass of the wire, and these rolls are manually adjustable so that the wire may be tensioned about the rolls.

It has been found very difficult, using the manually adjustable stretch rolls, to provide the proper tension on the Fourdrinier wire. Should the adjustable rolls be so set that the wire tension is too great, the high tension may cause a stretching of the wire beyond its elastic limit; so that subsequent, undesirable stretching of the wire continues to occur during the life of the wire. On the other hand, wire tension that is too low may be expected to cause slippage of the wire with respect to certain of the rolls, causing premature wearing of the rolls and the wire. Slackness in the F ourdrinier wire can also cause wrinkling of the wire and a jumping or movement up off the wire of globules of slurried stock shortly after its deposit on the wire, and this stock jumping causes poor formation of the paper web.

Fourdrinier wires, particularly when they are new, may

be expected to increase in length during usage. .Such increases in length cause decreases in the wire tension resulting in the premature wearing and other difiiculties just In prior structures, there may be compensation for these increases in wire length by manual adjustment of the stretch rolls; however, the increases in length take place so rapidly that frequent adjustments of the stretch rolls are necessary.

The rolls in prior Fourdrinier machines are all fixed with respect to each other between times of adjustment of the stretch rolls. The Fourdrinier wire as it travels about the rolls tends in effect to contract and expand in length periodically having, for example, a cycle of contraction and expansion for each pass of the wire about the rolls. This may be due to a variable vacuum efiect on the wire by vacuum boxes positioned beneath the wire, as well as by table rolls supporting the upper pass of the wire, to built-in inaccuracies in the machines, such as in the diameters of the rolls, and to unavoidable variations in speed of drive of the wire. The wire may thus be expected to have variations in tension during each pass about the rolls, which are at a frequency due to the high speed at which the wire is driven.

It is therefore an object of the present invention to provide improved mechanism in connection with such papermaking machines for causing the wire to be constantly and properly tensioned so as to thereby increase the life of the equipment and avoid the related inferior quality of web associated with improper wire tension.

More particularly, it is an object of the invention to provide, in such a machine, a wire tensioning roll resting by virtue of its own weight on the lower pass of the Fourdrinier wire holding the wire under constant tension,

and it is a further object to provide mechanism in con- 2 be yieldably mounted so that the roll may move for every period of travel of the wire about the rolls to compensate for the tension changes. that would occur during each pass of the wire as previously mentioned.

In brief, the invention contemplates a wire tensioning roll lying on the lower pass of the wire of a Fourdrinier machine so as to tension the wire. Preferably, air pressure actuated di-aphragrns are mechanically connected with the roll for relieving part of the weight of the roll so as to maintain the tension of the wire at a constant proper value which is not sufficiently great to cause stretching of the wire beyond its elastic limit. In addition, the improved wire tensioning mechanism contemplates an adjustable pressure regulator valve in connection with each of the diaphragrns for adjustment of the wire tension.

The invention consists of the novel constructions, arrangements, and devices to be hereinafter described and claimed for carrying out the above stated objects and such other objects, as will be apparent from the following description of a preferred form of the invention, illustrated with reference to the accompanying drawings, wherein:

FIG. 1 is a diagrammatic elevational view of a papermaking machine including a Fourdrinier wire traveling around a plurality of rolls one of which is a wire tensioning roll;

FIG. 2 is a front elevational view on an enlarged scale of the'wire tensioning roll and mechanism for moving -2; and

FIG. 4 is a side elevational view of the wire tensioning roll and the mechanism for moving the roll.

Like characters of reference design-ate like parts in the several views.

Referring now to FIG. 1, the illustrated paperrnaking machine includes a Fourdrinier wire 10 positioned about a breast roll 11, a couch roll 12, table rolls 13, idler rolls 14, a stretch roll 15, and a wire tensioning roll 16. A head box or pressure feed system 17, which may be of any conventional type, is positioned above the wire, and slurried stock from the headbox or pressure feed system is disposed on the wire by means of a slice 18. Vacuum boxes 19 are positioned beneath the wire 10 and beyond the table rolls 13. 1

The wire tensioning roll 16 is supported on its ends by platforms 20 which are movably attached, as will be presently described, to horizontal members v21 of the Fourdrinier machine frame to permit movement of the wire tensioning roll :16 in a substantially vertical direction. Bell crank levers 22 are pivotally connected with respect to downwardly extending arms 23 of the platforms 2% by means of pivot pins 24 extending through anti-friction bearings 25 set within the levers 22. The lower arms of the levers 22 are in the form of yokes and carry spherical bearings 26, which rotatably mount the wire tensioning roll 16 with respect to the levers 22.

Referring to FIGS. 2 and 3, the paper machine may be seen to have mechanism for vertically moving the wire tensioning roll 16 including an adjustable handwheel 27. The wheel 27 is fitted onto a shafit 28 axially aligned with a second shaft 28 both of which are rotatably supported by housings 29 rigidly aflixed to the horizontal members 21. A bar 30 joins the two shafts 28 by means of couplings 31. Each of the shafts 28 has a worm 32 fixed thereon and positioned within the respective housing 29. Each worm 32 is externally meshed with a revolving nut 33; and vertical screws 34, extending upwardly from the platforms 2%, pass through the nuts 33 and are threadedly engaged therewith. The nuts 33 are held axially stationary within the housings 29 by upper and lower bearings 35 which encompass the vertical screws 34.

Guide bars 36 extend vertically upwardly from the platforms 20 and are received by suitably adapted sockets 37 within the housings 29. v

As shown in FIGS. 3 and 4, a power unit 38 is mounted on one end of each platform 20 for the purpose of I moving the upper ends of the levers 22. The power units 38 each comprise a casing 39 supporting a flexible diaphragm 4G. The closed side of the diaphragm casing 39 is connected by means of an inlet conduit 41 to a source ofair pressure 42, and pressure is maintained at a given level in the conduit 41 by a regulator valve 43.

7 changes in pressure within the inlet conduits 41.

A pressure rod 44 is rigidly attached to each of the Y flexible diaphragms 40 by means including an inner diaphragm plate 45 and an outer diaphragm plate 46. A

'clevis 47 is adjustably attached to the opposite end of each of the pressure rods 44 and receives a pivot pin 48 extending through an anti-friction bearing 49 set Within the lever 22 for pivotally connecting the rod 44 with respect to the upper end of the lever 22.

A threaded stud 50 extends vertically downwardly from each of the platforms 20 and passes slidably through an opening 51 in the associated lever 22. Vertical movement of the lower ends of the levers 22 is restricted by upper and lower nuts 52, adjustable to various limiting positions on the threaded studs 50.

A graduated scale 53 is attached to the lower arm of each of the levers 22 and is aligned with a pointer '54, which extends downwardly from each of the platforms 20, so that theyregister relative vertical movement of the lower end of the lever 22 with respect to the platform 20.

In the operation of the Fourdrinier papermaking machine described above, the Fourdrinier wire 10 passes around the rolls 11, 12, 13, 14, and 16, and one or more of the rolls is rotatably driven by any suitable driving mechanism (not shown) to provide such wire movement. Slurried stock is contained within the headbox 17 and issues out of the slice 18 onto the Fourdrinier wire 10 to form a web on the wire. The vacuum boxes 19 are disposed within the wire 10 and in close contact therewith and draw water from the web. The couch roll 12, from whence the partially dewatered web is trans ferred to a press section (not shown), where more water is expressed from the web, constitutes a direction changing roll permitting the continuous wire 10 to return by means of a lower pass to the breast roll 11.

The idler rolls 14, the stretch roll 15 and the wire tensioning roll 16 are in contact with the lower pass of the wire 10 and maintain the wire in a looped configuration. The wire tensioning roll 16 is suspended between the adjustable platforms 20, so that the roll may be lowered to remove slack from the wire 10 by turning the handwheel 27 manually.

As the handwheel 27 is rotated in a clockwise direction, as seen in FIGURES 3 and 4, the motion is transmitted by means of the shaft 28 on which the handwheel 27' is fixed, the bar 30, and the couplings 29 to the opposite shaft 28, so that each of the worms 32 revolves the respective rotatable nut 33 about its vertical screw 34. The nuts 33 are retained within the housings 29 by the upper and lower bearings 35, and the screws 34, when the nuts are so rotated, move the platforms '20 downwardly. The guide bars 36 are retracted from the sockets 37 on either side of the screws 34 in such an even manner that the platforms remain parallel with respect to the horizontal frames 21 at all positions of travel. At some lower position of the platforms 20, the wire tensioning roll 16 engages the Fourdrinier wire 10. The present invention provides a degree of flexibility to this manual setting by utilizing the levers 22 which permit further limited movement of the wire tensioning roll 16 and thus keep the tension in the wire 10 substantially constant as long as the lower arms of the levers 22 are free to move.

The power units 38 aremounted on the platforms 20 length decreases.

' the wire.

. 4 so as to act upon the movable ends of the levers 22 and by means of the flexible diaphragms 26 respond T e air pressure within each inlet conduit 41 connected to the source of pressure 42 is maintained at a selected level by the respective manually operated regulator valve 43. The air under pressure admitted to the'casings 39 from the inlet conduits 41 tends to force the flexible diaphragms 40 outwardly, as seen in FIGURE 4. The pressure rods 44, which follow. the diaphragms 40 by virtue of their attachment to the inner diaphragm plates 45 and the outer diaphragm plates 46, transmit the forces exerted on the diaphragms through the clevises 47 to the upper end of the levers 22. The levers 22 are pivotally connected to the clevises 47 by the pins 48 and are movable about the downwardly extending arms 23 of the platforms 20. Since the lower arms of the levers 22 support the wire tensioning roll 16, the forces applied to the upper arms of the levers 22 from the power units 38 tend to move the roll 16 arcuately in a generally upward direction and relieve a part of the weight of the roll 16 on the wire 10.

A level of air pressure for actuating the power units 38 is selected in accordance with the amount of tension desired in the wire 10. If a high wire tension is desirable, the air in the power units 38 is maintained at a low pressure by the regulator valves 43, for example, 10 pounds per square inch. A lower wire tension would be maintained by increasing the air pressure in the power units 38 to some higher level and thus relieving a greater portion of the weight of the roll 16 by the action of the mechanical linkages heretofore described.

When the wire is properly tensioned, the lower parts of the levers 22, through which the studs 50 extend, lie between the limiting nuts 52, which are suitably positioned on the studs 50 to prevent undue movement of the roll 16 and the levers 22 with the consequent movement of the pointers 54 beyond the scope of the respective graduated scales 53.

The Weight of the wire tensioning roll 16, when the levers 22 are out of contact with the nuts 52, is par tially supported by the power units 38 acting through the levers 22 and partially-supported by the wire 10 itself. The linkages previously described are made as frictionless as possible by-the anti friction bearings 25 and 49,

and the wire 10 in changing length repositions the wire tensioning roll 16 vertically, lowering the roll when the wire length increases and raising the roll when the wire The roll 16, hearing on the wire 10 with the portion of its weight that is unsupported by the power units 38, maintains the wire at a substantially constant tension regardless of the length of the wire.

Rapid increases in wire length usually occur on the papermaking machine following installation of a new Fourdrinier wire. Using the present invention, the loss of tension in the wire previously associated with such increases is eliminated, since the roll 16 due to its own weight moves downwardly to take up the wire as it stretches and maintains the initial wire tension. In frequent changes in the manual adjustment of the platforms 20 are required from the operator, and the necessity for these changes can be seen by a glance at the pointers 54 which indicate the relative position of the lower ends of the levers 22 with respect to the nuts 52. If, through some inadvertency, the Fourdrinier wire '10 stretches sufliciently so that the wire tensioning roll "16, suspended from the levers 22 connected to the platforms 20, descends beyond the limits of the scales 53 as indicated by the pointers 54, the lower nuts 52 will support the lower ends of the levers in downwardly limiting positions until the platforms 20 are further lowered manually by means of ,the handwheel 27. The pointers 54 are thereby restored to an operable point along the scales 53 as required for correctly tensioning After the run-in phase of the wire 10, the wire tensioning roll 16 is automatically repositioned to sense maintain the desired tension in the wire for extended periods, and manual adjustment is seldom necessary.

During operation of the Fourdrinier machine, there tend to occur, for each pass of the wire 10 about the rolls, small changes in wire tension due to the variable action of the table rolls 13 and the vacuum boxes 19, as well as to unavoidable variations in speed of drive of the wire and other inherent machine characteristics. Since the wire tensioning roll 16 rests on the wire 10, the roll 16 moves downwardly when the wire thus tends to decrease momentarily in tension, and when a momentary increase of wire tension tends to occur, the wire 10 raises the roll 16. Though these tension changes that tend to occur are small, their frequency is on the order of once or more per wire pass, so that an almost continuous upward and downward oscillatory movement of the wire tensioning roll 16 results while maintaining the wire tension substantially constant, and the compressibility of the air from the air pressure source 42 accommodates the resultant rapid movements of the bell cranks 22 and diaphragms 40.

When the wire tensioning roll 16 undergoes a change of position involving movement of the levers 22, the pressure rods 44 act to reposition the diaphragms 40, so that the pressure regulator valves 43 supply air to or exhaust air from the conduits 41 to maintain a constant pressure within the diaphragm casings 39.

The wire tensioning roll 16 may be canted to compensate for unequal wire lengths or unequal rates of stretch, which may occur from side to side across the endless F ourdrinier wire 10, by setting each of the regulator valves 43 to apply a difierent pressure to its respective power unit 38.

In a certain particular example of the present invention, subsequent to the installation of a new wire, an operating pressure of 30 pounds per square inch is admitted to the power units 38 and is maintained therein by the pressure regulator valves 43. The wire tensioning roll 16 is then lowered manually by means of the handwheel 27 until it contacts the wire, and the wire 10 is driven slowly at crawl speed, which may be 100 feet per minute, about the rolls 11, 12, 13, 14, 1S, and the wire tensioning roll 16. Further manual lowering of the roll 16 increases the tension in the Fourdrinier wire 10 until the roll is supported on the wire in such manner that the pointers 54 are free to move along the graduated scales 53. The Fourdrinier machine may then be brought slowly to operational speed, such as, for example, 1400 feet per minute, during which time formation of the web is initiated by admitting the slurried stock to the headboX 17 so that it issues from the slice 18 onto the wire 10.

During the period that initial stretch is being removed from the new wire 10, infrequent manual readjustment downwardly of the platforms 20 by the machine operator is needed to insure that the wire tensioning roll 16 has freedom of movement and that the lower ends of the levers 22 do not rest on the lower limiting nuts 52. After several hours or perhaps a day, substantially all of the initial stretch is out of the wire 10, and further manual readjustment of the platforms 20 is seldom necessary during routine operation.

Imposed upon the above stretch removal action is the motion of the wire tensioning roll 16 reacting to the cyclical changes in length of the wire 10, the roll rising as the wire tension tends to increase and falling as the wire tension tends to decrease. A floating motion is thus imparted to the roll 16, which may have a frequency, for example, of oscillations per minute.

Using my improved wire tension mechanism, the Fourdrinier wire 10 is automatically and constantly tensioned correctly during the preliminary wire stretch phase as well as during subsequent machine operation. A suitable tension thus maintained in the wire 10 increases equipment life, and gives improved operation and product.

In addition, the mechanism herein described is simply constructed, requires little maintenance, and may be an inexpensive addition to existing equipment.

I wish it to be understood that the invention is not to be limited to the specific constructions and arrangements shown and described, except only insofar as the claims may be so limited, as it will be understood to those skilled in the art'that changes may be made without departing from the principles of the invention.

I claim:

1. In a papermaking machine, an endless fabric, a plurality of rolls including a tensioning roll for holding said fabric in the form of a loop,'means for driving one of said rolls so as to drivingly move said fabric, movable mounting means for saidtensioning roll arranged so that the roll rests on said fabric due to the weight of the roll and is supported by the fabric, a fluid pressure operated power mechanism acting on said mounting means in such a direction that it tends to counter-balance the weight of said tensioning roll, and a source of fluid under pressure in continuous connection with said power mechanism while said fabric is being driven, said pressure being at such a predetermined value and said power mechanism having such a purchase on said movable mounting means so as to apply a certain continuous lifting force on said tensioning roll sufficient to counter-balance only a part of the weight of the tensioning roll on said fabric.

2. In a papermaking machine, an endless fabric, a plurality of rolls including a tensioning roll for holding said fabric in the form of a loop, means for driving one of said rolls so as to drivingly move said fabric, movable mounting means for said tensioning roll arranged so that the roll rests on said fabric due to the weight of the roll and is supported by the fabric, air pressure operated power mechanism acting on said mounting means in such a direction that it tends to counterbalance the weight of said tensioning roll, and a source of air under pressure in continuous connection with said power mechanism while said fabric is being driven, said pressure being at such a predetermined value and said power mechanism having such a purchase on said movable mounting means whereby the power mechanism applies a certain continuous lifting force on said tensioning roll sufiicient to counter-balance only a part of the weight of the tensioning roll on said fabric and absorbs and permits small movements of the tensioning roll with movement of the fabric.

3. In a paper-making machine, an endless fabric, a plurality of rolls including a tensioning roll for holding said fabric in the form of a loop, means for driving one of said rolls so as to drivingly move said fabric, movable mounting means for said tensioning roll arranged so that said roll rests on said fabric due to the weight of the roll and is supported by the fabric, a pair of air pressure operated power units acting on said mounting means in such a direction that they tend to counterbalance the weight of said tensioning roll, each of said power units comprising a diaphragm mounted at its periphery within a housing and having the central portion of each dia-, phragm connected with said movable mounting means, and a source of air under pressure in continuous connection with'said power units while said fabric is being driven, said pressure being at such a predetermined value and said power units having such a purchase on said movable mounting means whereby the power units apply a certain continuous lifting force on said tensioning roll sufficient to counter-balance only a part of the weight of the tensioning roll on said fabric and said diaphragms acted on by air pressure absorb and permit small movements of the tensioning roll with movement of the fabric.

4. In a paper-making machine, an endless Fourdrinier wire, a machine frame, a plurality of rolls including a breast roll and a couch roll and -a wire tensioning roll, means for rotatably attaching said rolls to said frame so that they hold said wire in the form of a loop, means for driving one of said rolls so as to drivingly move said a wire, said attaching means including a pair of platforms rests onthe wire due to the weight of the roll and is sup- 7 ported by the wire, means'for adjusting said platforms vertically so as to position said wire tensioning roll on said wire, air pressure operated power units mounted on said tensioning roll sufiicient to counter-balance only a part of 15 2,918,970

the weight of the tensioning roll on said wire and absorb and permit small movements of the tensioning roll with movement of the wire. 3

References Cited in the file of this patent UNITED STATES PATENTS 1,582,322 Warren Apr. 27, 1926 7 1,885,163 Wliite Nov. 1, 1932 2,452,980 Beltz Q Nov. 2, 1948 2,623,630 Erickson Dec. 30, 1952 2,799,209 Wisner et a1. July 16, 1957 2,843,431 Beaufort July 15, 1958 2,907,450 Reid Oct. 6, 1959 Printz Dec. 29, 1959

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