Patent Publication Number: US-6709254-B2

Title: Tiltable web former support

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 60,243,996, filed Oct. 27, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a support for a web forming machine. More particularly, this invention relates to a support for a web forming machine which allows for vertical adjustment of a web forming belt with respect to at least one die head positioned above the web forming belt, and allows for tilting of the web forming belt. 
     2. Description of Prior Art 
     Conventional supports or guide posts for supporting a web forming machine prevent any lateral or vertical movement of the web forming machine. Further, because the conventional guide posts also prevent any rotational movement or tilting of the web forming machine, the web forming belt is not allowed to tilt or slope with respect to a base of the web forming machine. 
     In order to provide for tilting of the conventional web forming machines, as is often desired during polymer extrusion applications, the conventional guide posts must be mechanically bent. Thus, these guide posts are generally constructed of an easily bendable material. As a result of using easily bendable materials for the construction of the guide posts, the guide posts do not provide proper lateral restraint for the web forming machine. Additionally, mechanical binding and/or bending of the web forming belt occurs as it moves across the conventional guide posts. Further, the web forming belt cannot be vertically positioned and/or adjusted with respect to the die heads using conventional guide posts. 
     It is apparent that there is a need for a support for a web forming machine which allows the vertical positioning and/or adjustment of the web forming belt with respect to the die heads positioned above the web forming belt. 
     It is also apparent that there is a need for a support for a web forming machine which allows for rotational or axial positioning and/or adjustment of the support to prevent mechanical binding and/or bending of the web forming belt as it moves across the supports. 
     SUMMARY OF THE INVENTION 
     In response to the discussed difficulties and problems encountered in the prior art, a support for a web forming machine which provides linear motion along a y-axis and rotational motion about a x-axis perpendicular to the y-axis, has been discovered. The support for the web forming machine allows a web forming belt to be vertically positioned with respect to die heads positioned along the length of the web forming belt. Further, the support can be axially or rotationally positioned to maintain an outer surface of the web forming belt in a generally flat or planar orientation and to prevent mechanical binding and/or bending of the web forming belt as the web forming belt moves across the support. 
     During polymer extrusion applications, it is often desirable to increase or decrease the vertical distance between the web forming belt and the successive die heads. For example, a first vertical distance between a first die head and the web forming belt may be about 12 inches, a second vertical distance between a second die head, downstream from the first die head, and the web forming belt may be about 13 inches, and a third vertical distance between a third die head, downstream from the second die head, and the web forming belt may be about 14 inches. As the vertical distances between successive die heads and the web forming belt increase or decrease, the web forming belt will have either a positive or negative slope, respectively, with respect to a base of the web forming machine. 
     The support according to this invention allows linear motion along the y-axis defined by the length of the guide shaft while preventing linear motion along the x-axis and a z-axis, e.g. the two axes perpendicular to the y-axis. Further, the support allows rotational or axial motion about the x-axis perpendicular to the y-axis but prevents rotational motion about the y-axis and the z-axis. 
     With the foregoing in mind, it is a feature and advantage of this invention to provide a support for a web forming machine which allows for the vertical adjustment of a web forming belt with respect to a die head of the web forming machine while preventing either lateral or longitudinal movement of the web forming machine. 
     It is also a feature and advantage of this invention to provide a support for a web forming machine which allows for tilting or sloping of a web forming belt to vary a distance between the web forming belt and successive die heads and prevent subsequent mechanical binding and/or bending of the web forming belt. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and features of this invention will be better understood from the following detailed description taken in conjunction with the drawings wherein: 
     FIG. 1 is a side view of a web forming machine, in accordance with one embodiment of this invention; 
     FIG. 2 is a top view of a web forming machine, in accordance with one embodiment of this invention; 
     FIG. 3 is a front view of a support for a web forming machine, in accordance with one embodiment of this invention; 
     FIG. 4 is a side view of a support for a web forming machine, in accordance with one embodiment of this invention; 
     FIG. 5 is a cross-sectional top view through line A—A of a support for a web forming machine, in accordance with one embodiment of this invention; 
     FIG. 6 is a top view of a guide shaft clamp block for mounting a guide shaft to a guide post, in accordance with one embodiment of this invention; 
     FIG. 7 is a top view of a bushing housing, in accordance with one embodiment of this invention; 
     FIG. 8 is a cross-sectional view of a bushing housing, in accordance with one embodiment of this invention; 
     FIG. 9 is a front view of a bushing housing cover plate, in accordance with one embodiment of this invention; 
     FIG. 10 is a top view of a guide bushing, in accordance with one embodiment of this invention; 
     FIG. 11 is a front view of a guide bushing, in accordance with one embodiment of this invention; 
     FIG. 12 is a front view of a guide mounting plate, in accordance with one embodiment of this invention; 
     FIG. 13 is a partial front view of a support for a web forming machine, in accordance with one embodiment of this invention; 
     FIG. 14 is a partial side view of a support for a web forming machine, in accordance with one embodiment of this invention; and 
     FIG. 15 is a partial front view of a support for a web forming machine showing rotation of the web forming machine about a x-axis with respect to the support, in accordance with one embodiment of this invention. 
    
    
     DEFINITIONS 
     As used herein, the term “web” is related, for example to a nonwoven web, but it is understood by one having ordinary skill in the art that the term includes, but is not limited to, other materials in sheet and film form. 
     As used herein, “longitudinal”, “transverse” and “lateral” have their customary meaning. The longitudinal axis lies in the plane of the web forming machine and is generally parallel to a machine direction. The term “x-axis” refers to an axis which lies in the plane of the support and is generally perpendicular to the longitudinal axis. The term “y-axis” refers to an axis which lies in the plane of the support and is generally perpendicular to the x-axis. 
     As used herein, the term “major axis” refers to the axis of an ellipse that passes through the two foci. 
     As used herein, the term “minor axis” refers to the axis of an ellipse that is perpendicular to the major axis at a point equidistant from the foci. 
     As used herein, the term “polymer” generally includes, but is not limited to, homopolymers, copolymers, such as for example, block, graft, random and alternating copolymers, terpolymers, etc., and blends and modifications thereof. In addition, unless otherwise specifically limited, the term “polymer” also includes all possible geometric configurations of the molecule. These configurations include, but are not limited to, isotactic, atactic, syndiotactic and random symmetries. 
     As used herein, the term “nonwoven” or “nonwoven web” means a structure of individual fibers or threads which are interlaid, but not in an identifiable repeating manner. Nonwoven webs have been, in the past, formed by a variety of processes such as, for example, meltblowing processes, spunbonding processes, coforming processes, hydroentangling, air-laid and bonded carded web processes. 
     As used herein, the term “spunbond fibers” refers to small diameter fibers which are formed by extruding molten thermoplastic material as filaments from a plurality of fine, usually circular capillaries of a spinneret, with the diameter of the extruded filaments then being rapidly reduced as by, for example, in U.S. Pat. No. 4,340,563 to Appel et al., U.S. Pat. No. 3,692,618 to Dorschner et al., U.S. Pat. No. 3,802,817 to Matsuki et al., U.S. Pat. Nos. 3,338,992 and 3,341,394 to Kinney, U.S. Pat. No. 3,502,763 to Hartmann, and U.S. Pat. No. 3,542,615 to Dobo et al. Spunbond fibers are generally not tacky when they are deposited onto a collecting surface. Spunbond fibers are generally continuous and have average diameters (from a sample of at least 10 fibers) larger than 7 microns, more particularly, between about 10 and 30 microns. The fibers may also have shapes such as those described in U.S. Pat. No. 5,277,976 to Hogle et al., U.S. Pat. No. 5,466,410 to Hills, and U.S. Pat. No. 5,069,970 and U.S. Pat. No. 5,057,368 to Largman et al., which describe hybrids with unconventional shapes. A nonwoven web of spunbond fibers produced by melt spinning is referred to as a “spunbond web”. 
     As used herein, the term “meltblown fibers” means fibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into converging high velocity, usually hot, gas (for example, air) streams which attenuate the filaments of molten thermoplastic material to reduce their diameter, which may be to microfiber diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. Such a process is disclosed, for example, by U.S. Pat. No. 3,849,241 to Butin et al. Meltblown fibers are microfibers which may be continuous or discontinuous, are generally smaller than 10 microns in average diameter. A nonwoven web of meltblown fibers is referred to as a “meltblown web”. 
     As used herein, the term “bonded carded web” refers to webs made from staple fibers which are sent through a combing or carding unit, which breaks apart and aligns the staple fibers in the machine direction to form a generally machine direction-oriented fibrous nonwoven web. Such fibers are usually purchased in bales which are placed in a picker or fiberizer which separates the fibers prior to the carding unit. Once the web is formed, it is then bonded by one or more of several known bonding methods. 
     These terms may be defined with additional language in the remaining portions of the specification. 
     DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 and 2, a web forming machine  20  has a web forming belt  22  which rotates or moves in a machine direction, as indicated by the arrow and may have a length of about 80 feet or greater for certain applications. The web forming machine  20  may produce or form nonwoven webs or fabrics using a variety of conventional polymer extrusion processes such as, for example, meltblowing processes, spunbonding processes, coforming processes, hydroentangling, air-laid and bonded carded web processes. At least one die head  25 , as shown in FIG. 1, is positioned vertically with respect to an outer surface of the web forming belt  22  and traverse to the machine direction, e.g. in a cross-machine direction. In accordance with one embodiment of this invention, a plurality of die heads  25 , for example eight (8) die heads  25  are fixedly positioned above the web forming belt  22  along the length of the web forming belt  22 . Each die head  25  may be different than the other die heads  25  and/or extrude different polymeric material than the other die heads  25 . As the web forming belt  22  moves in the machine direction, fibers or filaments are extruded from each die head  25  and are deposited onto the web forming belt  22  to form a nonwoven web or fabric. 
     During polymer extrusion applications, it is often desirable to vary a vertical distance between the web forming belt  22  and each die head  25  positioned along the length of the web forming belt  22  in order to deposit fibers or filaments onto the web forming belt  22  to form layers of extruded material. In accordance with one embodiment of this invention, a support  30  for the web forming machine  20 , as shown in FIGS. 3-5, provides support to the web forming machine  20  and allows the web forming belt  22  to be vertically positioned and/or adjusted with respect to the die heads  25  positioned along the length of the web forming belt  22 . Further, the support  30  can be axially or rotationally positioned and/or adjusted to maintain the outer surface of the web forming belt  22  in a generally flat or planar orientation and to prevent mechanical binding and/or bending of the web forming belt  22  as the web forming belt  22  moves across the support  30 . 
     In accordance with one embodiment of this invention, the support  30  for the web forming machine  20  has at least one guide post  32  rigidly mounted to a base  33 , for example a floor of a production plant. Desirably, the guide post  32  has a conventional I-beam cross-sectional shape and is constructed or fabricated of hot rolled steel. The guide post  32  may have any suitable cross-sectional shape and other suitable materials may be used to construct or fabricate the guide post  32  which exhibit the necessary strength. The guide post  32  may be rigidly mounted to the floor using conventional fastening means suitable for mounting heavy equipment, for example suitably-sized bolts. Further, a guide post base plate  34  may be positioned between the guide post  32  and the floor for added structural support. The guide post base plate  34  may be made of hot rolled steel or other suitable material capable of providing the required support. 
     Desirably, a plurality of corresponding guide posts  32  are positioned along a length of the web forming machine  20  with one guide post  32  on a first side portion  24  of the web forming machine  20  and a corresponding guide post  32  positioned on a second laterally opposing side portion  26  of the web forming machine  20 , as shown in FIG.  2 . 
     In accordance with one embodiment of this invention, a guide shaft  36  is fixedly mounted or connected to the guide post  32 . Desirably, the guide shaft  36  is mounted to the guide post  32  with at least one guide shaft clamp block  38 . As shown in FIG. 6, the guide shaft clamp block  38  has two components which when fitted together form a bore  39 , which is positionable about the guide shaft  36 . The guide shaft clamp block  38  is fastened to the guide post  32  using conventional fastening means, for example a plurality of suitably-sized bolts and corresponding nuts. As shown in FIGS. 3 and 4, a first guide shaft clamp block  38  is positioned at a first end portion of the guide shaft  36  and a second guide shaft clamp block  38  is positioned at an opposite second end portion of the guide shaft  36  to fixedly mount the guide shaft  36  to the guide post  32 . The guide shaft  36  has a length which defines a y-axis generally perpendicular to a base of the web forming machine  20 . The guide shaft  36  desirably has a solid cross-section and is made of steel or another suitably strong material. In accordance with one embodiment of this invention, the guide shaft  36  is produced by Thompson, Inc. and has a length of about 5 feet and an outer diameter of about 4.0 inches. The guide shaft may have any suitable length and/or outer diameter. 
     In accordance with one embodiment of this invention, the support  30  has a bushing housing  40  positionable about the guide shaft  36 . Desirably, the bushing housing  40  is made of stainless steel and forms a bore  42  slightly larger than a circumference of the guide shaft  36 . In accordance with one embodiment of this invention, the bushing housing  40  forms the bore  42  having a generally elliptical or oval cross-section with a major axis greater than the outer diameter of the guide shaft  36  and a minor axis about equal to but slightly larger than the outer diameter of the guide shaft  36 . The bore  42  may have any suitable cross-sectional shape. As shown in FIG. 8, the bushing housing  40  forms a cylindrical cavity  44  which intersects with the bore  42 . Desirably, a bushing housing cover plate  56 , as shown in FIG. 9, having an aperture  57  coaxially aligned with the cavity  44  is fastened to an end surface  41  of the bushing housing  40  using conventional fastening means, for example screws. 
     At least a portion of a cylindrical guide bushing  50  is positioned within the cylindrical cavity  44  formed by the bushing housing  40 . The guide bushing  50  is desirably, but not necessarily, made of bronze. The guide bushing  50  has an outer diameter slightly smaller than the diameter of the cavity  44  to allow the guide bushing  50  to fit tightly within the cavity  44  while allowing the bushing housing  40  to rotate with respect to the guide bushing  50 . The outer surface of the guide bushing  50  may have at least one oil groove  51 . Application of a suitable oil or other lubricant ensures proper rotation of the bushing housing  40  with respect to the guide bushing  50  without undesired friction and/or binding. As shown in FIGS. 10 and 11, the cylindrical guide bushing  50  forms a bore  52  having a cross-sectional area about equal to but slightly larger than the cross-sectional area of the guide shaft  36 . With the guide bushing  50  positioned within the cavity  44  of the bushing housing  40  and the bore  52  coaxially aligned with the bore  42 , the bushing housing  40  and the guide bushing  50  are positioned about the circumference of the guide shaft  36 , as shown in FIGS. 3-5. The bushing housing  40  and the guide bushing  50  are slidably movable along the y-axis defined by the length of the guide shaft  36  between the guide shaft clamp blocks  38  mounting the guide shaft  36  to the guide post  32 . A bumper  60  may be positioned around the guide shaft  36  and against an inner surface  61  of at least one of the guide shaft clamp blocks  38  to prevent damage to the bushing housing and/or the guide shaft clamp block  38  when the bushing housing  40  contacts the inner surface  61 . Desirably, the bumper  60  is made of an elastic rubber material, for example 95 durometer neoprene. Other suitable materials may be used to make the bumper  60 . 
     As shown in FIGS. 3-5 and  12 , the bushing housing  40  is securely attached or fastened to a guide mounting plate  46  for mounting a portion of the web forming machine  20  to the support  30 , for example at a side portion  24  and  26 . The guide mounting plate  46  desirably has a plurality of apertures  47  for fastening the web forming machine  20  to the support  30  using conventional fastening means, for example bolts and screws. 
     In one embodiment of this invention, the web forming machine  20  is mounted at the first side portion  24  to the bushing housing  40  attached to a first guide shaft  36  and at the second laterally opposing side portion  26  to the bushing housing  40  attached to a corresponding second guide shaft  36  positioned on an opposing side of the web forming machine  20 . Any suitable number of corresponding supports  30  may be positioned along the length of the web forming machine  20 , for example five pairs of supports  30 , equaling ten supports  30 , as shown in FIG.  2 . 
     Referring to FIGS. 13-15, the bushing housing  40  and the guide bushing  50  are slidably movable along the length of the guide shaft  36  to position the web forming belt  22  vertically with respect to the die head  25  positioned above the web forming belt  22 . During polymer extrusion applications, it is often desirable to increase or decrease the vertical distance between the web forming belt  22  and the successive die heads  25 . For example, a first vertical distance between a first die head  25  and the web forming belt  22  may be about 12 inches, a second vertical distance between a second die head  25 , downstream from the first die head  25 , and the web forming belt  22  may be about 13 inches, and a third vertical distance between a third die head  25 , downstream from the second die head  25 , and the web forming belt  22  may be about 14 inches. As the vertical distances between successive die heads  25  and the web forming belt  22  increase or decrease, the web forming belt  22  will have either a positive or negative slope, respectively, with respect to a base of the web forming machine  20 . In accordance with one embodiment of this invention, the web forming belt  22  may slope, from a first end portion to a second end portion, as much as about 12 inches to about 13 inches. In other embodiments of this invention, the slope may be greater. Further, as a result of the slope of the web forming belt  22 , a distance between a front side of each die head  25  and the web forming belt  22  may be shorter than a distance between a back side of each die head  25  and the web forming belt  22 . 
     In order to prevent the web forming belt  22  from mechanically binding as a result of the vertical positioning of the web forming belt  22  with respect to the die heads  25 , the bushing housing  40  is rotatable about the x-axis, traverse to the machine direction and perpendicular to the y-axis. 
     The vertical positioning of the web forming belt  22  with respect to the die heads  25  is accomplished by slidably moving the bushing housing  40  along the length of the guide shaft  36 . Once the web forming belt  22  is positioned at a desired vertical distance from the die head  25 , the bushing housing  40  is fixedly mounted to the guide shaft  36  to prevent undesired linear displacement of the bushing housing  40  along the y-axis defined by the length of the guide shaft  36 . The length of the guide shaft  36  between the guide shaft clamp blocks  38  limits the linear motion of the bushing housing  40 . 
     As shown in FIG. 15, the bushing housing  40  is rotatable about the x-axis with respect to the guide bushing  50  to provide a generally flat outer surface of the web forming belt  22  and prevent mechanical binding and/or bending of the web forming belt  22  as it moves across the support  30 . The axial or rotational positioning and/or adjustment of each support  30  may be simultaneous with or subsequent to the vertical positioning and/or adjustment of each support  30 . In accordance with one embodiment of this invention, the rotational or axial motion of the bushing housing  40  with respect to the guide bushing  50  is limited within a range of about 0° to about 45°. The rotational or axial motion of the bushing housing  40  is limited by the length of the major axis of the bore  42 . In accordance with other embodiments of this invention, the rotational or axial motion of the bushing housing  40  with respect to the guide bushing  50  may be limited to about 0° to about 360° depending on the mounting arrangement of the web forming machine  20  to the support  30 . 
     Thus, the support  30  allows linear motion along the y-axis defined by the length of the guide shaft  36  while preventing linear motion along the x-axis and a z-axis, e.g. the two axes perpendicular to the y-axis. Further, the support  30  allows rotational or axial motion about the x-axis perpendicular to the y-axis but prevents rotational motion about the y-axis and the z-axis. 
     While in the foregoing specification this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.