Method of Lubricating Resilient Belt During Web Compaction

This invention was conceived in connection with apparatus for the manufacture of uncreped stretchable paper as disclosed in Cluett U.S. Pat. No. 2,624,245; Welsh et al., U.S. Pat. No. 3,011,545; and Schaefer, U.S. Pat. No. 3,329,562, all owned by a common assignee of those patents and the present invention. Although utility of this invention is not limited to manufacture of uncreped stretchable paper, the invention is shown illustratively and is described herein as applied to that use.

Making an uncreped longitudinally stretchable paper web according to the teachings of these patents is accomplished by shrinking the paper web longitudinally by means of forces parallel to the surfaces of the web while the web is in a suitably moist condition and while the web is maintained under sufficient pressure normal to its surface to prevent creping or crinkling.

An accepted method of providing parallel forces to a web incapable of self support for the purpose of shrinking the web is to feed the web to a segment of travel between a rotating drum and a traveling endless resilient belt. The belt's outside surface is accelerated prior to the point of web feed, and then the belt's outside surface is caused to decelerate after the point of web feed. The deceleration of the belt's outside surface while it is in contact with the web causes the parallel forces on the web which compact or shrink the web.

More specifically, as described in U.S. Pat. Nos. 2,624,245 and 3,011,545, the acceleration and subsequent deceleration of the outside surface of the resilient belt may be effected by feeding the belt along its travel to a restricted nip space formed by and between a loaded compactor bar and a rotating smooth faced drum. As the resilient belt is substantially noncompressible, it accelerates prior to the nip space in order to pass through the restriction of the nip space and it decelerates after it passes through the nip space. The web, which is fed into the nip space and into contact with the outside surface of the traveling belt after the belt has been accelerated, is shrunk by the parallel forces transmitted to it as the outside surface of the belt decelerates and while the web is pressed against the drum. The shrinkage of the web is controlled by varying the restriction of the nip space which causes change in surface velocity of the outside surface of the traveling belt.

In commercial practice, even though the compactor may be a bar rotating type, there tends to be a scuffing effect on the inside surface of the belt if the belt runs dry. The use of a lubricant of water or other liquid eliminates this scuffing and it has been observed that the compactor bar even stops rotating when lubricant is present. With a non-rotating bar, which is more commonly used, the need for a lubricant is essential but presents the following situation. If the amount of lubricating liquid supplied, such as by spraying on the belt, is carefully adjusted so that it equals the loss consumed during lubrication and by evaporation, etc., then the inner belt surface is adequately lubricated in the nip area and there is no surface liquid available to leak out of the nip at the ends of the belt to cause damage to the paper web at those points. It can be readily seen that such a nice adjustment is difficult in practice, however and usually to avoid the nip running dry, an excess of water at the belt approach side of the nip is provided. This further requires that excess water in the puddle be removed, and such removal has been achieved in the past by the fitting of edge pans to the edge of a belt such that the excess water can flow into the pan and be allowed to run away. Because these edge pans have from the very beginning proven to be difficult to design with an effective seal, they have never been very popular. In practice, they leak badly, causing trouble to the edges of the paper web and, from time to time, they damage the rubber belt. To obviate this, many users of equipment have removed these edge pans and have fitted compressed air pipes so that jets of air can be directed at the edges of the belt where the water would normally leak away and this air stream creates an air dam which restricts the leakage of water at this point. However, this is only effective if the pool formed by the excess water at the belt approach side of the compactor bar remains at a constant height. For the reasons given beforehand, this state of affairs cannot usually be kept and, the pool frequently rises to a level whereby it overcomes the air resistance of the air dam and leaks around the belt edges as before. Thus, the main contribution of the new compactor bar of this invention is to maintain a constant but carefully controlled pool height so that, once an air dam or edge pans are adjusted to contain the water at the edges of the belt, the state of equilibrium will not change.

Problems of the prior art are coped with here in a useful, novel, unobvious and particularly facile way. Lubricating liquid is introduced conventionally onto the inside surface of the belt whereby a pool of the liquid is maintained between the compactor bar and the inside surface of the belt as the belt approaches the compactor bar. The compactor bar includes a sidewall portion constituting a liquid dam on the belt approach side of the compactor bar. At least one weir opening is provided in the liquid dam of the compactor bar to enable excess liquid to overflow via the weir to maintain a desired level of the pool of lubricating liquid. Means are provided for removing such excess liquid overflow. The compactor bar is movable for adjusting the weir height. The pool is confined laterally by either air jets or by plates biased into contact with sides of the belt.

Accordingly one object of this invention is to provide more reliable lubrication to the belt.

Another object of this invention is to provide better control of lubrication to the belt.

Still another object of this invention is to reduce wear of the belt.

Still another object of this invention is to avoid outleakage of the lubricant onto the paper or drum with consequent wrinkling or tearing of the web, poor compaction and/or pucker spots on the web.

Still another object of this invention is to improve working conditions in making an uncreped longitudinally stretchable web.

The foregoing and other objects, features and advantages of this invention will appear more fully from a detailed description of a preferred embodiment thereof and from claims, both of which follow, all taken in conjunction with an accompanying drawing wherein like numerals indicate like parts throughout and wherein:

FIG. 1 is a schematic side elevation view of a compacting apparatus according to this invention;

FIG. 2 is an end view showing the compactor bar, the pool of lubricating liquid and confining means therefor;

FIG. 3 is an enlarged detail showing removal of excess lubricating liquid via the weir openings, the interior of the compactor bar and suitable discharge means; and

FIG. 4 is a partly broken away side elevation view to an enlarged scale showing means for adjusting the height of the weir openings in the compactor bar.

A web 11 is shown in FIG. 1 to be supplied from some preceding operation. The compacting apparatus includes a drum 12 (usually heated) of substantial diameter. Drum 12 is of sturdy construction and is mounted on a shaft 13 which preferably is driven rotatably by a suitable means (indicated as an arrow 14). A thick belt 15, made of a resilient elastomeric material (such as rubber), is mounted on three rollers 16, 17 and 18 which are arranged to tension the belt 15. The belt 15 has a run which travels on a segment 19 of the drum 12. The belt 15 is driven by the drum 12. Rotary parts thus far described all are mounted in rigid side frame members (not shown) which are disposed outside lateral bounds of the web 11 and the belt 15.

As shown best in FIG. 2, a compactor bar 21 extends across the machine through the full length of the drum 12 and the compactor bar 21 is supported at its end. The compactor bar 21 preferably is a thick walled but hollow cylinder preferably of a smooth, corrosion resistant steel alloy and is of substantial strength and rigidity. The compactor bar 21 is loaded by well known means and is disposed as shown best in FIG. 4 to engage an inside surface 22 of the belt 15 and to press the belt 15 radially against the drum 12 to form a uniform nip space for the web 11. This is the nip space whereby compacting of the web takes place.

As has been pointed out, improved lubrication of the belt 15 is provided by maintaining a pool 23 of a lubricating liquid between the compactor bar 21 and the inside surface 22 of the belt 15 as shown best in FIG. 4. The lubricating liquid which may be water, a mixture of glycerine and water, or a silicone release agent etc. is introduced from a suitable source (not shown) via some nozzles 24. As shown best in FIG. 3, level of the pool 23 of the lubricating liquid is set by height of weir openings 25 provided in the compactor bar 21, which weir openings 25 communicate in flow series with an interior space 26 in the compactor bar 21, and subsequently via line 27 for convenient discharge of excess of the lubricating liquid. The weir openings 25 may be round as shown in FIGS. 2 and 3, slotted or of any other suitable configuration. The weir openings 25 are provided in a wall surface 21a of the compactor bar 21, which wall 21a constitutes a liquid dam portion of the compactor bar, on the belt approach side of the compactor bar.

Adjustment of height of the weir openings 25 is accomplished in the embodiment illustrated as shown best in FIGS. 2 and 4, by rotating the compactor bar 21 by means of a crank 28 connected to the compactor bar 21 by means of screws 29 and 31. The crank 28 can be rotated using opposed screws 32 and 33 which pass threadably through abutments 34 and 35 respectively both connected on either side rigidly to their housing member 36. The screws 32 and 33 are provided with heads 37 and 38 respectively and have lock nuts 39 and 41 respectively.

Lateral confinements of the pool 23 of lubricating liquid is achieved by plates 42 each depending from the compactor bar 21 and each being maintained in contact with a side 43 of the belt 15 by means of a spring 44. (See FIG. 2).

It will be understood by those familiar with compacting webs that various departures may be made from the foregoing detailed description of a preferred embodiment of the invention, (for example confining means at the end of the nip bar such as air jets could be used) without departing from a main theme of invention set forth in claims which follow.