Abstract:
A fabric for the forming, press and dryer sections of a paper machine, for use as a reinforcing base for a polymeric-resin-coated paper-processing belt or as a corrugator belt, or in other industrial settings where a material is being dewatered, is formed from a monofilament yarn, which is spirally wound in the form of a closed helix, adjacent turns thereof being abutted against and joined securely to one another. The monofilament yarn has a first side and a second side which are oppositely and correspondingly shaped, so that, when spirally wound in a plurality of turns, the first side fits closely into or against the second side of an adjacent and abutting turn, and adjacent spiral turns are secured to one another at the abutting first and second sides to form the fabric.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the papermaking arts. More specifically, the present invention relates to papermaker&#39;s fabrics, namely the forming, press and dryer fabrics, also known as paper machine clothing, on which paper is manufactured on a paper machine. In addition, the present invention may be applied in other industrial settings where industrial belts are used to dewater a material. 
     2. Description of the Prior Art 
     During the papermaking process, a cellulosic fibrous web is formed by depositing a fibrous slurry, that is, an aqueous dispersion of cellulose fibers, on a moving forming fabric in the forming section of a paper machine. A large amount of water is drained from the slurry through the forming fabric, leaving the cellulosic fibrous web on the surface of the forming fabric. 
     The newly formed cellulosic fibrous web proceeds from the forming section to a press section, which includes a series of press nips. The cellulosic fibrous web passes through the press nips supported by a press fabric, or, as is often the case, between two such press fabrics. In the press nips, the cellulosic fibrous web is subjected to compressive forces which squeeze water therefrom, and which adhere the cellulose fibers in the web to one another to turn the cellulosic fibrous web into a paper sheet. The water is accepted by the press fabric or fabrics and, ideally, does not return to the paper sheet. 
     The paper sheet finally proceeds to a dryer section, which includes at least one series of rotatable dryer drums or cylinders, which are internally heated by steam. The newly formed paper sheet is directed in a serpentine path sequentially around each in the series of drums by a dryer fabric, which holds the paper sheet closely against the surfaces of the drums. The heated drums reduce the water content of the paper sheet to a desirable level through evaporation. 
     It should be appreciated that the forming, press and dryer fabrics all take the form of endless loops on the paper machine and function in the manner of conveyors. It should further be appreciated that paper manufacture is a continuous process which proceeds at considerable speed. That is to say, the fibrous slurry is continuously deposited onto the forming fabric in the forming section, while a newly manufactured paper sheet is continuously wound onto rolls after it exits from the dryer section. 
     It should also be appreciated that the vast majority of forming, press and dryer fabrics are, or at least include as a component, a woven fabric in the form of an endless loop having a specific length, measured longitudinally therearound, and a specific width, measured transversely thereacross. Because paper machine configurations vary widely, paper machine clothing manufacturers are required to produce forming, press and dryer fabrics to the dimensions required to fit particular positions in the forming, press and dryer sections of the paper machines of their customers. Needless to say, this requirement makes it difficult to streamline the manufacturing process, as each fabric must typically be made to order. 
     Moreover, because the surface of a woven fabric is necessarily uneven to some degree, as knuckles formed where yarns lying in one direction of the fabric wrap around those lying in another direction lie on the surface, it is difficult to produce a paper product entirely free of sheet marking. 
     The prior art includes several attempts to solve these problems. For example, U.S. Pat. No. 4,495,680 to Beck shows a method and apparatus for forming a base fabric composed solely of warp yarns to be used in making a papermaker&#39;s felt. Essentially, the warp yarns are helically wound about two parallel rolls. Subsequently, fibrous batting or other nonwoven material is applied and adhered to the helical array of warp yarns to provide a fillingless papermaker&#39;s felt, which is to say that it has no cross-direction yarns. By eliminating cross direction yarns, the drainage characteristics of the felt are said to be improved, and pressure points caused by yarn crossovers are said to be eliminated. 
     U.S. Pat. No. 4,537,658 to Albert shows a papermaker&#39;s fabric made from a plurality of elongated, linked, slotted elements. The elongated elements can be formed by extrusion or by lamination, and are linked one to the next either by an integral tongue or through the use of a pintle connecting means which extends from one elongated element to the adjacent element. The elongated elements extend in the cross-machine direction of the disclosed papermaker&#39;s fabrics, and have flat, parallel top and bottom surfaces. 
     U.S. Pat. No. 4,594,756 to Beck also shows a method and apparatus for forming a base fabric composed solely of warp yarns to be used in making a papermaker&#39;s felt. The method and apparatus shown are improved relative to those disclosed in U.S. Pat. No. 4,495,680, which was discussed above. As in the earlier patent, the endless base fabric, or substrate, produced is composed solely of machine-direction yarns and can subsequently be needled with fibrous batting to produce all or a part of a papermaker&#39;s felt or other fabric. 
     U.S. Pat. No. 4,842,905 to Stech shows a tessellated papermaker&#39;s fabric and elements for making the fabric. The elements are formed so as to have male or projection members which interlock with female or recess members. The papermaker&#39;s fabric comprises a plurality of the tessellated elements which have been interconnected to produce a tessellation of a desired length and width. The fabrics are said to be designed to produce desired air and moisture permeabilities and drainage characteristics while providing an increased control over the paper-carrying surface thereof. 
     The present invention provides an alternative solution to the problems addressed by these prior-art patents. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is a fabric for the forming, press and dryer sections of a paper machine. The fabric may also be used as a reinforcing base for a polymeric-resin-coated paper-processing belt, such as a sheet-transfer, long nip press (LNP) or calender belt, and as part of other industrial process belts, such as corrugator belts. Moreover, the fabric may be used in other industrial settings where industrial belts are used to dewater a material. For example, the present invention may be used as a pulp-forming or pulp-pressing fabric; as a fabric used to dewater recycled paper during the deinking process, such as a dewatering fabric or belt on a double-nip-thickener (DNT) deinking machine; or as a sludge dewatering belt. The fabric is in the form of an endless loop, and has an inner surface and an outer surface. 
     The fabric comprises a monofilament yarn of non-circular cross section, which monofilament yarn has a length, an upper surface and a lower surface. Preferably, the upper and lower surfaces are flat and parallel to one another. Alternatively, the upper and lower surfaces may be convexly or concavely rounded in their widthwise directions. The monofilament yarn also has a first side and a second side, which are oppositely and correspondingly shaped. 
     The monofilament yarn is spirally wound in a plurality of turns wherein the first side of the monofilament yarn fits against the second side of an adjacent abutting spiral turn thereof. Adjacent spiral turns of the monofilament yarn are secured to one another at the abutting first and second sides to form the fabric by a variety of means. 
     The monofilament yarn may have cooperating first and second sides having any one of several different opposite and corresponding shapes. Specifically, the first side may have a cylindrically convex shape while the second side may have a cylindrically concave shape of the same radius of curvature, so that the first and second sides of adjacent turns of the monofilament can fit closely together when abutted against one another. Alternatively, the first and second sides may be planar, and slanted in parallel directions, so that the first and second sides of adjacent turns can fit closely together when abutted against one another. 
     The first and second sides of the monofilament yarn may alternatively form a tongue-in-groove joint, or may have snappingly engagable male and female mutually interlocking members, respectively. The first and second sides may also have portions of reduced thickness which overlap one another when the monofilament yarn is spirally wound to produce the fabric. Attachment of adjacent abutting turns of the monofilament yarn to one another may be made through the use of an adhesive, which may be a heat-activated, room-temperature-cured (RTC) or hot-melt adhesive, where the first and second sides are not provided with interlocking members. 
     The monofilament yarns may be provided with holes passing therethrough from their upper to their lower surfaces for the drainage of water from a cellulosic fibrous web being conveyed by the fabric. The monofilament yarns may also be hollow, providing them with resiliency as well as void volume for the temporary storage of water. Where this is the case, the monofilament yarn may have holes connecting the upper surface of the monofilament yarn to the void volume, and may also have holes connecting the lower surface of the monofilament yarn to the void volume. In any event, the holes may be produced by needling or by laser “punching”, or may be formed during extrusion. 
     One or both of the upper and lower surfaces of the monofilament yarn may be provided with grooves for the temporary storage of water. The grooves may be provided during the extrusion of the monofilament yarns; that is, they may be provided by the die used to extrude the yarns. The grooves may also be provided through the use of a slitter knife or the like while the monofilament yarn is being spirally wound to form the fabric or at any time thereafter. 
     The fabric of the present invention may be included as part of a multi-layered laminated fabric comprising two or more layers produced from the monofilament yarn. Alternatively, the fabric may be laminated with a woven base fabric, or with unwoven systems of longitudinal and/or transverse yarns. 
     The fabric, when used as a press fabric in the press section of a paper machine, may also be provided with a staple fiber batt attached to either one or both of its inner and outer surfaces by needling or by an adhesive, which may be a heat-activated, room-temperature-cured (RTC) or hot-melt adhesive, or by needle punching. Layers of non-woven fibrous material, such as those manufactured by Sharnet, can be used in addition to, or as a substitute for, some portion or all of the staple fiber batt. These can include spun bonds, melt blowns and the like. 
     The present invention will now be described in more complete detail with frequent reference being made to the figures identified below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the fabric of the present invention; 
     FIG. 2 illustrates a method by which the fabric of the present invention may be constructed; 
     FIGS. 3A through 3H are cross-sectional views taken in a widthwise direction of several embodiments of the monofilament yarns used to manufacture the fabric; 
     FIG. 4 is a cross section, taken in a transverse, or cross-machine, direction, of a fabric of the present invention; 
     FIG. 5 is a cross section, taken in a transverse direction, of an alternate embodiment of the fabric; 
     FIG. 6 is a similar view of another embodiment of the fabric; 
     FIG. 7 is a cross section, taken in a transverse direction, of a laminated embodiment of the fabric of the present invention; 
     FIG. 8 is a similar view of another laminated embodiment of the fabric; and 
     FIG. 9 is a similar view of still another laminated embodiment of the fabric. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning now specifically to these figures, FIG. 1 is a perspective view of the fabric  10  of the present invention. The fabric  10  has an inner surface  12  and an outer surface  14 , and is fashioned by spirally winding a monofilament yarn  16  in a plurality of abutting and mutually adjoined turns. The monofilament yarn  16  spirals in a substantially longitudinal direction around the length of the fabric  10  by virtue of the helical fashion in which the fabric  10  is constructed. 
     A method by which the fabric  10  may be manufactured is illustrated in FIG.  2 . Apparatus  20  includes a first process roll  22  and a second process roll  24 , each of which is rotatable around its longitudinal axis. The first process roll  22  and the second process roll  24  are parallel to one another, and are separated by a distance which will determine the overall length of the fabric  10  to be manufactured thereon, as measured longitudinally therearound. 
     To begin the manufacture of the fabric  10 , the beginning of monofilament yarn  16  is extended in taut condition from the first process roll  22  toward the second process roll  24 , around the second process roll  24 , and back to the first process roll  22  forming a first coil of a closed helix  26 . To close the first coil of the closed helix  26 , the beginning of the monofilament yarn  16  is joined to the end of the first coil thereof at point  28 . As will be discussed below, adjacent turns of the spirally wound monofilament yarn  16  are joined to one another by mechanical or adhesive means. 
     Therefore, subsequent coils of closed helix  26  are produced by rotating first process roll  22  and second process roll  24  in a common direction as indicated by the arrows in FIG. 2, while feeding the monofilament yarn  16  onto the first process roll  22 . At the same time, the monofilament yarn  16  being freshly wound onto the first process roll  22  is continuously joined to that already on the first process roll  22  and the second process roll  24  by mechanical or adhesive means to produce additional coils of closed helix  26 . 
     This process continues until the closed helix  26  has a desired width, as measured axially along the first process roll  22  or the second process roll  24 . At that point, the monofilament yarn  16  not yet wound onto the first process roll  22  and the second process roll  24  is cut, and the closed helix  26  produced therefrom is removed from the first process roll  22  and the second process roll  24  to provide the fabric  10  of the present invention. 
     The present method for producing fabric  10  is quite versatile and adaptable to the production of papermaker&#39;s fabrics  10  of a variety of longitudinal and transverse dimensions, since the same apparatus  20  and monofilament yarn  16  are always used. That is to say, the manufacturer, by practicing the present invention, need no longer produce an endless or on-machine-seamable woven fabric of appropriate length and width for a given paper machine. Rather, the manufacturer need only separate the first process roll  22  and the second process roll  24  by the appropriate distance, to determine the length of the fabric  10 , and wind the monofilament yarn  16  onto the first process roll  22  and the second process roll  24  until the closed helix  26  has reached the desired width. 
     Further, because the fabric  10  is produced by spirally winding monofilament yarn  16 , and is not a woven fabric, the outer surface  12  of the fabric  10  is smooth and continuous, and lacks the knuckles which prevent the surfaces of a woven fabric from being perfectly smooth. 
     FIGS. 3A through 3H are cross-sectional views, taken in a widthwise direction, of several embodiments of the monofilament yarn used to produce the present fabric. Each embodiment includes upper and lower surfaces which may be flat (planar) and parallel to one another. 
     Turning to FIG. 3A, monofilament yarn  30  has an upper surface  32 , a lower surface  34 , a cylindrically convex side  36  and a cylindrically concave side  38 . The upper surface  32  and the lower surface  34  are flat (planar) and parallel to one another. The cylindrically convex side  36  and cylindrically concave side  38  have the same radius of curvature, so that the convex side  36  of each spirally wound turn of monofilament yarn  30  fits into the concave side  38  of the immediately preceding turn thereof. Each turn of the monofilament yarn  30  is joined to its adjacent turns by joining their respective convex and concave sides  36 ,  38  to one another by an adhesive, which may be a heat-activated, room-temperature-cured (RTC) or hot-melt adhesive. 
     In FIG. 3B, monofilament yarn  40  has an upper surface  42 , a lower surface  44 , a tongue  46  on one side and a corresponding groove  48  on the other side. The upper surface  42  and the lower surface  44  are flat (planar) and parallel to one another. The tongue  46  has dimensions corresponding to those of the groove  48 , so that the tongue  46  on each spirally wound turn of monofilament yarn  40  fits into the groove  48  of the immediately preceding turn thereof. Each turn of the monofilament yarn  40  is joined to its adjacent turns by securing tongues  46  in the grooves  48  with an adhesive, which may be a heat-activated, room-temperature-cured (RTC) or hot-melt adhesive. 
     In FIG. 3C, monofilament yarn  50  has an upper surface  52 , a lower surface  54 , a male interlocking member  56  on one side and a corresponding female interlocking member  58  on the other side. The upper surface  52  and the lower surface  54  are flat (planar) and parallel to one another. The male interlocking member  56  has rounded dimensions corresponding to those of the female interlocking member  58 , so that the male interlocking member  56  on each spirally wound turn of monofilament yarn  50  snappingly fits into the female interlocking member  58  of the immediately preceding turn thereof. Each turn of the monofilament yarn  50  may be additionally secured to its adjacent turns by joining the male interlocking member  56  to the female interlocking member  58  with an adhesive, which may be a heat-activated, room-temperature-cured (RTC) or hot-melt adhesive. 
     In FIG. 3D, monofilament yarn  60  has an upper surface  62 , a lower surface  64 , a male interlocking member  66  on one side and a corresponding female interlocking member  68  on the other side. The upper surface  62  and the lower surface  64  are flat (planar) and parallel to one another. The male interlocking member  66  has T-shaped dimensions corresponding to those of the female interlocking member  68 , so that the male interlocking member  66  on each spirally wound turn of monofilament yarn  60  snappingly fits into the female interlocking member  68  of the immediately preceding turn thereof. Each turn of the monofilament yarn  60  may be additionally secured to its adjacent turns by joining the male interlocking member  66  to the female interlocking member  68  with an adhesive, which may be a heat-activated, room-temperature-cured (RTC) or hot-melt adhesive. 
     In FIG. 3E, monofilament yarn  70  has an upper surface  72 , a lower surface  74 , a first portion  76  of reduced thickness lying below the upper surface  72  on one side, and a corresponding second portion  78  of reduced thickness lying above the lower surface  74  on the other side. The upper surface  72  and the lower surface  74  are flat (planar) and parallel to one another. The first portion  76  has dimensions corresponding to those of the second portion  78 , so that the first portion  76  on each spirally wound turn of monofilament yarn  70  fits under the second portion  78  of the immediately preceding turn thereof. The first and second portions  76 ,  78  have a combined thickness equal to that of the monofilament yarn  70  as a whole, so that the fabric manufactured therefrom will have a uniform thickness. Each turn of the monofilament yarn  70  is joined to its adjacent turns by securing first portions  76  to second portions  78  with an adhesive, which may be a heat-activated, room-temperature-cured (RTC) or hot-melt adhesive. 
     In FIG. 3F, monofilament yarn  160  has an upper surface  162 , a lower surface  164 , a first planar side  166  and a second planar side  168 . The upper surface  162  and the lower surface  164  are flat (planar) and parallel to one another, and the first planar side  166  and the second planar side  168  are slanted in parallel directions, so that the first planar side  166  of each spirally wound turn of monofilament yarn  160  abuts closely against the second planar side  168  of the immediately preceding turn thereof. Each turn of the monofilament yarn  160  is joined to its adjacent turns by joining their respective first and second planar sides  166 ,  168  to one another by an adhesive, which may be a heat-activated, room-temperature-cured (RTC) or hot-melt adhesive. 
     In FIG. 3G, monofilament yarn  170  has an upper surface  172 , a lower surface  174 , a first planar side  176  and a second planar side  178 . The upper surface  172  and the lower surface  174  are convexly rounded in the widthwise direction thereof. The first planar side  176  and the second planar side  178  are slanted in parallel directions, so that the first planar side  176  of each spirally wound turn of monofilament yarn  170  abuts closely against the second planar side  178  of the immediately preceding turn thereof. Each turn of the monofilament yarn  170  is joined to its adjacent turns by joining their respective first and second planar sides  176 ,  178  to one another by an adhesive, which may be a heat-activated, room-temperature-cured (RTC) or hot-melt adhesive. 
     In FIG. 3H, monofilament yarn  180  has an upper surface  182 , a lower surface  184 , a first planar side  186  and a second planar side  188 . The upper surface  182  and the lower surface  184  are concavely rounded in the widthwise direction thereof. The first planar side  186  and the second planar side  188  are slanted in parallel directions, so that the first planar side  186  of each spirally wound turn of monofilament yarn  180  abuts closely against the second planar side  188  of the immediately preceding turn thereof. Each turn of the monofilament yarn  180  is joined to its adjacent turns by joining their respective first and second planar side  186 ,  188  to one another by an adhesive, which may be a heat-activated, room-temperature-cured (RTC) or hot-melt adhesive. 
     Referring to the embodiments shown in FIGS.  3 G and  3 H, it should be appreciated that only one of the upper surfaces  172 ,  182  or lower surfaces  174 ,  184  may be convexly or concavely rounded in the widthwise direction, while the other surface may be flat (planar). Moreover, the upper surface may be convexly curved, while the lower surface may be concavely curved, or vice versa. Such modifications should be understood to fall within the scope of the present invention. 
     The monofilament yarns described above may be extruded from any of the polymeric resin materials used by those of ordinary skill in the art to manufacture yarns for paper machine clothing, such as polyamide, polyester, polyurethane and polyketone resins. 
     It will be apparent to those of ordinary skill in the art that the monofilament yarns used to manufacture the fabrics of the present invention will ordinarily have to be provided with passages for conveying water away from a cellulosic fibrous web or other material being conveyed thereon. Referring to FIG. 4, which is a cross section, taken in a transverse, or cross-machine, direction, of a fabric  80  of the present invention, monofilament yarns  82  are provided along their entire lengths with a plurality of holes  84  for the passage of water from a cellulosic fibrous web. 
     FIG. 5 is a cross-sectional view, taken in a transverse direction, of an alternate embodiment of the fabric  90  of the present invention. Monofilament yarns  92  are hollow, and include void volume  94  for the storage of water from a cellulosic fibrous web. A plurality of holes  96 , provided along the entire lengths of the monofilament yarns  92 , pass through the monofilament yarn  92  from one of its two surfaces to the void volume. Optionally, a plurality of holes  98 , also provided along the entire lengths of the monofilament yarns  92 , may pass through the monofilament yarn  92  from the other of its two surfaces to the void volume. 
     FIG. 6 is a cross-sectional view, also taken in the transverse direction, of another embodiment of the fabric  100  of the present invention. Monofilament yarns  102  have a plurality of grooves  104  on one side thereof for the storage of water from a cellulosic fibrous web. The grooves  104  run lengthwise along the monofilament yarn  102 . Optionally, a plurality of grooves  106 , also running lengthwise along the monofilament yarn  102  may also be provided on the other of the two sides thereof. 
     The fabrics of the present invention may also be laminated structures having a plurality of layers. For example, FIG. 7 is a cross-sectional view, taken in the transverse direction, of a fabric  110  having two layers  112 ,  114  of spirally wound monofilament yarns  116 . One layer  112  may be assembled in the manner described above, and then the second layer  114  may be assembled by spirally winding monofilament yarns  116  onto layer  112 . The two layers  112 ,  114  may be laminated together with an adhesive, which may be a heat-activated, room-temperature-cured (RTC) or hot-melt adhesive, or with a sheath of low-melt material of the variety manufactured by Sharnet. Monofilament yarns  116  may have holes, void volume or grooves as described above. 
     FIG. 8 is a cross-sectional view, taken in the transverse direction, of another laminated fabric  120 . Fabric  120  has a first layer  122  of longitudinal yarns  130 , a second layer  124  of transverse yarns  132 , and a third layer  126  of monofilament yarns  134 . Longitudinal yarns  130  and transverse yarns  132  are shown to be of circular cross section, but may alternatively have any other cross-sectional shape. Fabric  120  may be manufactured by spirally winding longitudinal yarns  130  around first and second process rolls  22 ,  24  in the same way as described above for monofilament yarns  16 , but leaving space between each spiral turn of longitudinal yarn  130 . Next, transverse yarns  132  are placed at intervals across the longitudinal yarns  130  and secured thereto by an adhesive, which may be a heat-activated, room-temperature-cured (RTC) or hot-melt adhesive. Finally, monofilament yarns  134  are spirally wound onto transverse yarns  132 , and joined thereto by an adhesive, which may be a heat-activated, room-temperature-cured (RTC) or hot-melt adhesive, or with a sheath of low-melt material of the variety manufactured by Sharnet. Monofilament yarns  134  may have holes, void volume or grooves as described above. Alternatively, the order of these manufacturing steps may be reversed by first spirally winding monofilament yarns  134  around first and second process rolls  22 ,  24 , by then placing transverse yarns  132  at intervals across the spirally wound monofilament yarns  134 , and by finally spirally winding monofilament yarns  130  onto transverse yarns  132 . 
     FIG. 9 is a cross-sectional view, taken in the transverse direction, of yet another laminated fabric  140 . Fabric  140  comprises a first layer  142 , which is a base fabric  150  woven from a system of longitudinal yarns  152  and a system of transverse yarns  154 . Base fabric  150  is in the form of an endless loop, which is placed in a taut condition about first and second process rolls  22 ,  24 . Then, a second layer  144  of monofilament yarns  156  is formed by spirally winding monofilament yarns  156  onto base fabric  150  in the manner described above in the discussion of FIG. 2, and by joining monofilament yarns  156  to base fabric  150  with an adhesive, which may be a heat-activated, room-temperature-cured (RTC) or hot-melt adhesive, or by needling. It should be understood that the order of these manufacturing steps may be reversed by first spirally winding monofilament yarns  156  around first and second process rolls  22 ,  24 , and by then placing base fabric  150  in the form of an endless loop of appropriate length about the first and second process rolls  22 ,  24  over layer  144 . Monofilament yarns  156  may have holes, void volume or grooves as described above. Finally, a third layer  146  of staple fiber batt  158  may be attached to the second layer  144  of monofilament yarns  156  by needling or other means, such as an adhesive, which may be a heat-activated, room-temperature-cured (RTC) or hot-melt adhesive. When needled, staple fiber batt  158  may be used to attach the second layer  144  of monofilament yarns  156  to base fabric  150 . Additional staple fiber batt can be added to the opposite side of base fabric  150 . Further, it should also be understood that a layer of staple fiber batt may also be provided between first layer  142  and second layer  144 . These layers may include non-woven fibrous material, such as those manufactured by Sharnet, or may be entirely composed of such material. These can include spun bonds, melt blowns and the like. 
     Modifications to the above would be obvious to those of ordinary skill in the art, but would not bring the invention so modified beyond the scope of the appended claims.