KNURLED CALENDER ROLL, METHOD AND APPARATUS FOR FORMING THE KNURLED CALENDER ROLL AND GEOMEMBRANE PRODUCED BY THE KNURLED CALENDER ROLL

Abstract

An apparatus is provided for forming recesses in a calender roll. The apparatus includes a rotational drive for rotating the calender roll around a rotational axis. The apparatus further includes a knurling wheel with knurling spikes projecting there from. The knurling wheel is rotatable about an axis that is aligned an acute angle to a plane that contains the rotational axis of the calender roll so that the knurling spikes produce a helical array of recesses in the outer surface of the calender roll. The calender roll then can be used to form a landfill liner with projections that are offset from one another to avoid having the projections form grooves and thereby preventing slippage of the landfill liner.

Claims

1. An apparatus for forming recesses in a calender roll, the calender roll having a longitudinal axis and an outer circumferential surface concentric with the longitudinal axis, the apparatus comprising: a rotating mechanism configured for rotating the calender roll around the longitudinal axis of the calender roll; and a knurling apparatus having at least one knurling tool with a rotatable knurling wheel that has an outer circumferential surface with a plurality of knurling spikes projecting radially outward thereon, the rotatable knurling wheel being rotatable about a knurling wheel rotational axis that is aligned at an acute angle to a plane that contains the rotational axis of the calender roll, the knurling apparatus being configured for moving the outer circumferential surface of the knurling wheel into contact with the outer circumferential surface of the calender roll so that the knurling spikes form recesses in the outer circumferential surface of the calender roll with the recesses defining a helical array along the outer circumferential surface of the calender roll.

2. The apparatus of claim 1, wherein the knurling wheel is mounted rotatably on a support arm that is movable toward and away from the outer circumferential surface of the calender roll along a moving direction that passes through the rotational axis of the calender roll.

3. The apparatus of claim 2, wherein the moving direction of the support arm toward and away from the calender roll is carried out with the support arm being aligned along a radius of the calender roll, the support arm and the rotational axis of the calender roll defining a plane, the knurling wheel rotational axis intersecting the plane defined by the support arm and the rotational axis of the calender roll at an acute angle.

4. The apparatus of claim 1, wherein the outer circumferential surface of the knurling wheel is formed from a material that is harder than the outer circumferential surface of the calender roll.

5. A calender roll having a rotational axis and an outer circumferential surface concentric with the rotational axis, the outer circumferential surface having a plurality of recesses arranged in a helical array on the outer circumferential surface of the calender roll.

6. The calender roll of claim 5, wherein the recesses are conical recesses.

7. A method for forming a calendering surface on a calender roll, the method comprising: providing a calender roll having a rotational axis and an outer circumferential surface concentric with the rotational axis; providing a knurling wheel mounted for rotation about an axis that is aligned at an acute angle to the rotational axis of the calender roll, the knurling wheel having an outer circumferential surface formed with knurling spikes projecting outward thereon; rotating the calender roll about the rotational axis; moving the knurling wheel toward the outer circumferential surface of the calender roll along a radius of the calender roller while the calender roll is being rotated about the rotational axis; and moving the knurling wheel parallel to the rotational axis so that the knurling spikes form a helical array of knurling recesses in the outer circumferential surface of the calender roll.

8. A landfill liner formed from a sheet of resin and having a first surface for facing a ground surface of a landfill site and a second surface opposite the first surface, the landfill liner having opposite first and second side edges spaced apart in a lateral direction and opposite first and second end edges intersecting the side edges, the first surface of the landfill liner being formed with a plurality of projections arranged so that the projections form rows angularly aligned to the first and second side edges at an acute angle.

9. The landfill liner of claim 8, wherein the acute angle is in a range of 1-5.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 is perspective view of a calender roll and a knurling tool in accordance with an embodiment of the invention.

[0020] FIG. 2A is an enlarged perspective view showing the knurling tool and FIG. 2B is a cross-sectional view taken through the support arm of the knurling tool and showing the angular alignment of the rotational axis of the knurling tool relative to the longitudinal axis of the calender roll.

[0021] FIG. 3 is an elevational view of the calender roll and showing the alignment of the knurling tool with a radius of the calender roll.

[0022] FIG. 4 is an end in view of the calender roll showing the alignment of the knurling tools to a radial plane of the calender roll.

[0023] FIG. 5 is a side elevational view of the calender roll.

[0024] FIG. 6 is a schematic illustration showing the calender roll of the invention producing a liner.

[0025] FIG. 7 is a top plan view of a liner produced by the calender roll of the invention.

DETAILED DESCRIPTION

[0026] A calender roll in accordance with an embodiment of the invention is identified generally by 10 in FIGS. 1-5. The calender roll 10 is a cylindrical structure with a longitudinal axis X and a cylindrical outer surface 12 substantially concentric with the axis X. Areas of the calender roll 10 adjacent the cylindrical outer surface 12 are formed from mild low carbon steel with a hardness typically less than 135 BHN (Brinell Hardness). However, aluminum, brass or other soft metal or certain nonmetals can be used. The outer cylindrical surface 12 of the calender roll 10 is provided with knurling recesses 14 arranged in a specific pattern, as explained further herein. Opposite ends of the calender roll 10 can be mounted in an apparatus 16 (FIG. 3) that is operative to rotate the calender roll 10 about the longitudinal axis X. Rotating devices for calender rolls can be large lathe machines and are very well known in the art.

[0027] The calender roll 10 is used with a knurling apparatus 20 that is configured to form the knurling recesses 14 in the outer cylindrical surface 12 of the calender roll 10. The knurling apparatus 20 includes at least one knurling tool 22 that has a rigid support arm 24 extending coincident with a radial direction from the rotational axis X of the calender roll 10. Thus, the extending direction of the support arm 24 and the rotational axis X of the calender roll 10 define a plane. The leading end 26 of the support arm 24 of the illustrated embodiment is forked to define two parallel spaced apart fingers 28. A knurling wheel 30 is mounted rotationally between the fingers 28 of the support arm 24 for rotation about a rotational axis 32 that passes through the fingers 28 and is aligned perpendicular to the extending direction of the support arm 24. The support arm 24 can be rotated about its longitudinal axis (longitudinal direction), and hence about a radius of the calender roll 10. Accordingly, the rotational axis 32 of the knurling wheel 30 will intersect the plane that contains both the rotational axis X of the calender roll 10 and the extending direction of the support arm 24. The angle of intersection of the rotational axis 32 of the knurling wheel 30 and the plane that contains bother the rotational axis X of the calender roll 10 and the longitudinal direction of the support arm 24 typically will be in a range of 1-5.

[0028] The knurling wheel 30 includes an outer circumferential surface 34 that is concentric with the rotational axis 32 of the knurling wheel 30. Knurling spikes 36 project radially out from the outer circumferential surface 34 of the knurling wheel 30 to define a radial projecting dimension from the circumferential surface of the knurling wheel 30 in the range of 0.5-2.0 mm. Each knurling spike 36 in the illustrated embodiment is substantially conical to terminate at a well-defined point. However, other spike configurations are possible including pyramidal spikes or rounded spikes. The knurling spikes 36 are spaced at equal circumferential distances from one another on the outer circumferential surface 34 of the knurling wheel 30. The circumferential distance between adjacent knurling spikes 36 in some embodiments is about 2.5-7 mm, with a spacing of about 4.5 mm in one exemplary embodiment. Outer circumferential regions of the knurling wheel 30, including the knurling spikes 36 are formed from a metal material, such as a carbide steel, cemented carbide, tungsten carbide or other carbide materials or tool steel with diamond or other precious stone tips so that the spikes 36 are significantly harder than the metal material that forms the outer cylindrical surface 12 of the calender roll 10.

[0029] The support arm 24 of the knurling tool 22 lies in a plane that extends through the axis X of the calender roll 10 and coincides with a radius r of the calender roll 10. However, the support arm 24 is rotated about its own longitudinal axis so that the rotational axis 32 of the knurling wheel 30 is aligned at an acute angle to the plane that contains both the axis X of the calender roll 10 and the extending direction of the support arm 24. The angle typically will be in a range of 1-5, and is 2.5 in one exemplary embodiment. The particular angle may be determined in accordance with the radius r of the calender roll 10, characteristics of the liner produced by the calender roll 10, as well as characteristics of the landfill site at which the liner will be used.

[0030] Some embodiments may have a knurling apparatus 20 with a single knurling tool 22, as shown in FIGS. 1 and 2. However, other embodiments of the knurling apparatus 20 may have two or more knurling tools 22, such as the two knurling tools 22 shown schematically in FIG. 3 or the three knurling tools 22 illustrated schematically in FIG. 4. Embodiments of the knurling apparatus 20 with plural knurling tools 22 will generally have the knurling tools 22 at substantially equal circumferential spacings about the axis X of the calender roll 10. Additionally, the axial direction x of each support arm 24 will all be aligned along radii r of the calender roll 10.

[0031] The knurling wheel 30 of each knurling tool 22 is rotatable between the fingers 28 of the support arm 24, but need not be driven rotatably by any part of the knurling apparatus 20. Rather, the knurling wheel 30 is rotated by forces exerted by the rotating calender roll 10. On the other hand, the knurling apparatus 20 is operative to move the knurling tool 22 toward and away from the calender roll 10 along the axial direction of the support arm 24. Additionally, the knurling apparatus 20 is operative to move the knurling tool 22 or the knurling tools 22 parallel to the axis X of the calender roll 10.

[0032] The knurling apparatus 20 forms the calender roll 10 by initially positioning the calender roll 20 in a rotatable drive device, such as a lathe machine, that is in proximity to the knurling apparatus 10. The calender roll 10 then is rotated about the longitudinal axis X, and the knurling apparatus 20 advances the knurling tool 22 toward the outer circumferential surface 12 of the calender roll 10 with the longitudinal direction of the support arm 24 aligned along a radius r of the calender roll 10. As noted above, the outer circumferential surface of the knurling wheel 30, and specifically the knurling spikes 36 thereof, are formed from a metal material that is significantly harder than the outer peripheral surface 12 of the calender roll 10. As result, the knurling spikes 36 will displace the softer material of the calender roll 10 thereby forming knurling recesses 14 in the outer peripheral surface 12 of the calender roll 10. In the illustrated embodiment, the knurling spikes 26 are conical, and accordingly the knurling recesses 14 will be conical. The knurling wheel 34 rotates in response to forces generated by the rotation of the calender roll 10 while in engagement with the knurling spikes 26 on the outer periphery of the rotatable knurling wheel 24. The angular alignment of the rotational axis of the knurling wheel 30 to the plane that contains both the rotational axis X of the calender roll 10 and the longitudinal direction of the support arm 24 will cause the knurling recesses 14 to be arranged in a helical array with the knurling apparatus 20 moving parallel to the axis X of the calender roll 10 to define the pitch of the helical array. The knurling recesses 14 are spaced at equal circumferential distances of about 2.5-7 mm from one another on the outer circumferential surface 12 of the calender roll 10 with a circumferential spacing of about 4.5 mm in one exemplary embodiment. Dimensions between knurling recesses measured parallel to the axis X of the calender roll 10 typically will be in a range of 2-6 mm with an axial spacing of about 4 mm in some embodiments. The outer surface 12 of the calender roll 10 may have other surface discontinuities between the knurling recesses 14 to perform a general roughening. However, the predominant surface discontinuities 15 in the outer circumferential surface 12 of the calender roll 10 will be the knurling recesses 14.

[0033] The calender roll 10 with the knurling recesses 14 formed therein is used in the manner illustrated schematically in FIG. 6. In particular, an extrusion apparatus 50 extrudes a resin sheet 52 having a length L extending in the extruding direction 54 and a width extending parallel to the longitudinal axis X of the calender roll 10. Forces generated at the nips between the calender roll 10 and the adjacent rollers 56, 58 will urge the resin of the extruded sheet 52 of liner material into the knurling recesses 14, thereby forming conical projections 54 projecting from the surface of the sheet 52. However, the knurling recesses 14 are arranged in a helical pattern on the outer surface 12 of the calender roll 10. As a result, the conical projections 54 on the surface of the sheet 52 will not extend parallel to the length L direction of the sheet 52 but rather will be arranged so that each subsequent conical projection 54 is offset laterally with respect to the previously or subsequently formed conical projections 54, as illustrated most clearly in FIG. 7. The conical projections that are adjacent in the length direction L are offset from one another by an angle to the longitudinal direction of about 1-5, and is about 2.5 in one exemplary embodiment. The spacing b between the projections 54 in the width direction W of the sheet 52 typically is in a range of 2-6 mm, and is about 4 mm in one exemplary embodiment. The spacing c between the projections 54 in the length direction of the sheet 52 typically is in a range of 2.5-7.0 mm, and is about 4.5 mm in one exemplary embodiment. The random lines 60 on the sheet in 52 in FIG. 7 represent random roughening caused by surface discontinuities 15 in the calender roll 10 other than the knurling recesses 14

[0034] The sheet 52 shown in FIG. 7 is rolled and transported to an installation site, such as a landfill. Each sheet 52 is unrolled so that adjacent sheets 52 are in substantially edge-to-edge or slightly overlapping relationship with one another and are fused or welded to one another at their respective edges. The conical projections 54 described above face toward the ground surface over which the liner sheets 52 are installed. The conical projections 54 do not align with one another in the length direction of the sheet 52. As a result, any sliding movement of the liner sheets 52 in response to gravitational or other forces will not cause any projection 54 to form a groove that will be followed by subsequent projections 54. As result, the liner 52 will exhibit very secure retention capabilities even on steep slopes.

[0035] While the invention has been described with respect to certain preferred embodiments, it is understood that the scope of the invention is not limited to these embodiments.