Method and machine for manufacturing paper products using fourdrinier forming

Abstract

An improved method for producing paper from pulp includes a plurality of subassemblies arranged in the forming or wet section of a Fourdrinier. The Fourdrinier includes a dewatering table having a plurality of blades that are static and on-the run adjustable in height and/or angle to control orientation of paper fibers in the stock to create a superior quality of paper and improved paper strength characteristics. Gravity and vacuum assisted drainage elements are equipped with on-the-run adjustable angle and height dewatering foil blades starting from a paper dryness of 0.1% and extending all the way to 5% dryness. The result of this process and machine is to improve the paper quality, save fibers and chemicals and fulfill the required paper properties.

Claims

1. A wet end for a Fourdrinier machine, the wet end comprising: I. a forming board section comprising: A. a lead blade and B. a plurality of trailing blades each including: II. a hydrofoil section having: A. natural gravity drainage; B. a plurality of height adjustable blades including a control subassembly that controls a height of a respective blade relative to an underside of a forming fabric: and C. a plurality of angle adjustable blades alternatively arranged with the plurality of height adjustable blades, each and wherein the plurality of angle adjustable blades each have a control subassembly that controls an angle of a respective blade relative to the underside of the forming fabric; and, III. a low-vacuum section comprising: A. at least one external vacuum source, B. a plurality of height adjustable blades each including a control subassembly that controls height relative to the underside of the forming fabric, and wherein the at least one external vacuum source comprises a plurality of angle adjustable blades each including a control subassembly that controls an angle of a respective blade relative to the underside of the forming fabric.

2. The wet end of claim 1, wherein each of the height adjustable blades comprise: a height adjustment control mechanism and an adjustable T-bar which extends across a frame of the Fourdrinier machine and having a drive that raises and lowers the adjustable T-bar to adjust the height of the blade in relation to the underside of the forming fabric.

3. The wet end of claim 2, wherein the wet end includes a high vacuum section being free of automatically adjustable height adjustable blades or automatically angle adjustable blades.

4. The wet end of claim 1, wherein each of the angle adjustable blades comprise: an angle adjustment mechanism, wherein an underside of the angle adjustment mechanism is secured to a frame of the Fourdrinier machine and said angle adjustment mechanism includes an adjustable T-bar that extends across the frame of the Fourdrinier machine, the angle adjustment mechanism including a drive that rotates a leading edge of the angle adjustable blade over a range of angles.

5. The wet end claim 1, wherein the lead blade of the forming board section is a fixed ceramic lead blade.

6. The wet end of claim 1, wherein the forming board section includes a plurality of angle adjustable blades.

7. The wet end of claim 1, wherein the wet end includes a high vacuum section being free of automatically adjustable height adjustable blades or automatically angle adjustable blades.

8. A wet end for a Fourdrinier comprising: I. a forming board section; II. a gravity assisted section comprising: A. a plurality of height adjustable blades and B. a plurality of fixed blades; and III. a low-vacuum section comprising: A. vacuum assisted drainage elements; and B. a plurality of height adjustable blades; IV. a high vacuum section being free of automatically adjustable height adjustable blades or automatically angle adjustable blades.

9. The wet end claim 8 wherein the plurality of height adjustable blades are three height adjustable blades and the plurality of angle adjustable blades are three angle adjustable blades, and the three height adjustable blades and the three angle adjustable blades being alternatively arranged, wherein the three height adjustable blades each include a control subassembly that controls a height of a respective blade relative to an underside of a forming fabric, the three angle adjustable blades each including a control subassembly that controls an angle of a respective blade relative to the underside of the forming fabric.

10. The wet end of claim 8, wherein the plurality of height adjustable blades in a first section of the low-vacuum section are six height adjustable blades, the six height adjustable blades each including a control subassembly that controls height relative to an underside of a forming fabric, and wherein the first section comprises one fixed blade, and wherein a second section of the low-vacuum section comprises seven angle adjustable blades sandwiched by two fixed blades, said seven adjustable angle blades each including a control subassembly that controls an angle of a respective blade relative to the underside of the forming fabric.

11. The wet end of claim 8, wherein the forming board section includes a plurality of angle adjustable blades.

12. The wet end of claim 11, wherein the gravity assisted section is located upstream of the low-vacuum section, wherein the low-vacuum section includes a plurality of angle adjustable blades and each of the plurality of angle adjustable blades includes an angle adjusting mechanism that is secured with the C-channel via a clamping bar, and wherein each of the plurality of angle adjustable blades include a blade and a protective shield is provided on the blade to prevent items from being caught when the angle adjusting mechanism is actuated.

13. The wet end of claim 12, wherein the low-vacuum section is downstream of the gravity assisted section.

14. The wet end of claim 8, wherein the forming board section is located upstream of the gravity assisted section, and wherein the low-vacuum section includes a plurality of angle adjustable blades and each of the plurality of angle adjustable blades includes an angle adjusting mechanism that is secured with the C-channel via a clamping bar, and wherein each of the plurality of angle adjustable blades include a blade and a protective shield is provided on the blade to prevent items from being caught when the angle adjusting mechanism is actuated.

15. The wet end of claim 14, wherein the low-vacuum section is downstream of the gravity assisted section.

16. A wet end for a Fourdrinier machine comprising: I. a forming board section having a fixed ceramic lead blade that is arranged substantially near a breast roll; II. a hydrofoil section comprising: a. natural gravity drainage; b. a plurality of height adjustable blades; and c. a plurality of angle adjustable blades; III a low-vacuum section comprising: a dynamic and an external vacuum source that creates a vacuum, a plurality of height adjustable blades, and a plurality of angle adjustable blades.

17. The wet end of claim 16, wherein the forming board section includes a plurality of height adjustable blades.

18. The wet end of claim 17, wherein the forming board section and the hydrofoil section are located upstream of the low-vacuum section, wherein each of the plurality of angle adjustable blades includes an angle adjusting mechanism that is secured with a C-channel via a clamping bar, and wherein each of the plurality of angle adjustable blades include a blade and a protective shield that is provided on the blade to prevent items from being caught when the angle adjusting mechanism is actuated.

19. The wet end of claim 18, wherein the low-vacuum section is downstream of the hydrofoil section.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) Other objects and purposes of this invention will be apparent to person acquainted with apparatus of this general type upon reading the following specification and inspecting the accompanying drawings, in which:

(2) FIG. 1 illustrates a Fourdrinier papermaking machine incorporating the present invention therein.

(3) FIG. 2 is an enlarged view showing a formline element with stationary and adjustable height foil blades and which forms part of the forming board section of the Fourdrinier.

(4) FIG. 3 shows a Hydroline element with adjustable angle and height foil blades and which forms part of the hydrofoil section of the Fourdrinier.

(5) FIG. 4 shows a Varioline element with stationary and adjustable height foil units and being part of the low-vacuum section.

(6) FIG. 5 shows a Vaculine element with stationary and angle adjustable foil blades and being part of the low-vacuum section.

(7) FIG. 6A shows a detailed view of an adjustable angle foil blade mounted on a C-channel and with the leading edge of the angle adjustable blade raised to +1. FIG. 6B shows the blade of FIG. 6A having a 3 separation from an underside of the forming fabric. FIG. 6C shows a detailed view of an adjustable height foil blade mounted on a T-bar and with the leading edge of the angle adjustable blade raised to +1. FIG. 6D shows the blade of FIG. 6C having a 3 separation from an underside of the forming fabric.

(8) FIG. 7A shows a detailed view of an adjustable height activity blade mounted on a C-channel and with the height being at 0 mm where it is in contact with the underside of the forming fabric. FIG. 7B shows the blade of FIG. 7A at a 5 mm height below the forming fabric. FIG. 7C shows a detailed view of an adjustable height blade mounted on a T-bar and with the height being at 0 mm where it is in contact with the underside of the forming fabric. FIG. 7D shows the blade of FIG. 7C at a 5 mm height below the forming fabric.

(9) FIG. 8A shows a control subassembly for an angle adjustable blade taken from an end of the Fourdrinier. FIG. 8B shows a cutaway view of the drive that is actuated to adjust the angle of a respective blade.

(10) FIG. 9A shows a control subassembly for the height adjustable blade taken from an end of the Fourdrinier. FIG. 9B shows a cutaway view of the drive that is actuated to adjust the height of a respective blade.

DETAILED DESCRIPTION OF THE INVENTION

(11) The embodiments of the invention and the various features and advantageous details thereof are more fully explained with reference to the non-limiting embodiments and examples that are described and/or illustrated in the accompanying drawings and set forth in the following description. It should be noted that the features illustrated in the drawings are not necessarily drawn to scale, and the features of one embodiment may be employed with the other embodiments as the skilled artisan recognizes, even if not explicitly stated herein. Descriptions of well-known components and techniques may be omitted to avoid obscuring the invention. The examples used herein are intended merely to facilitate an understanding of ways in which the invention may be practiced and to further enable those skilled in the art to practice the invention. Accordingly, the examples and embodiments set forth herein should not be construed as limiting the scope of the invention, which is defined by the appended claims. Moreover, it is noted that like reference numerals represent similar parts throughout the several views of the drawings.

(12) For illustrative purposes only, the invention will be described in conjunction with a Fourdrinier papermaking machine although the invention and concept could also be applied to hybrid and gap formers. The invention is implemented in the wet section of the Fourdrinier and includes a forming board section 10, a hydrofoil section 20, and a low-vacuum section 30. High-vacuum section 40 does not include automatically adjustable height blades or automatically angle adjustable blades. It should be noted that a headbox is known and is therefore not shown in FIG. 1. Referring now to FIG. 1, a Fourdrinier comprises a forming fabric 105, a breast roll 106 and couch roll 107. The forming fabric is continuous and travels between the breast and couch rolls 106, 107. The stock which comprises pulp fibers is deposited from the headbox to the top surface of the forming fabric 105 at a paper dryness ranging from 0.1% to 1%. Immediately following the headbox, the forming fabric passes over a forming board section 10 which comprises a formline element 11.

(13) As shown in FIGS. 1 and 2, the forming board section 10 includes formline element 11 which includes a fixed ceramic lead blade 12 and a plurality of trailing blades 13, 14. The blades 13, 14 are arranged beneath the forming fabric or wire and are fixed atop either stationary or adjustable C-bar or T-bar which extend from one side of the Fourdrinier to the other. The support bars preferably comprise fiber reinforced composite. The stationary bars are fixed. In the preferred embodiment, the formline element 11 includes three adjustable trailing blades 13 which may be raised and lowered or the angle adjusted as shown in the respective figures with the use of respective drive 17A. The drives are arranged at opposite ends of a support bar and fixed. The drives arranged at opposite ends of the support bar operate in concert to lower or raise a respective blade. It should be noted that the air, hydraulic and electrical lines for actuating the drives are not shown for ease in understanding the drawings. It should be understood that it is contemplated that various other drives, pistons or motors including electric and hydraulic ones and their associated supply lines may be employed to practice the invention. The adjustable blades 13 are raised or lowered to cause them to intersect the underside of the forming fabric 105 at a predetermined height to influence the alignment of the fibers within the paper web. Two fixed trailing blades 14 are arranged between the height adjustable blades 13, as shown. In a preferred embodiment, the height of the adjustable blades may be changed to ensure that the paper fibers are aligned in a desired direction. The forming board lead blade 12 is arranged near the breast roll and is stationary. A plurality of forming board trailing blades is arranged in an alternating sequence of adjustable height blades 13 and stationary blades 14. The forming board trailing blades preferably comprise ceramic.

(14) During this stage, some water is drained from the stock and a very thin wet sheet is carried over to various other dewatering devices such as foil blades in hydrofoil section 20, until a sheet paper dryness of around 1% to 1.5% is achieved. Following this, the paper dryness is increased by the foil blades in the Varioline and Vaculine in the low vacuum section 20 to a dryness level of 5%. Next, a paper dryness of 8% to 10% is achieved in the elements of the low-vacuum section 30 and the sheet is transferred to the high-vacuum section 40 to achieve a paper dryness of 18% or greater. Finally, the sheet is transferred over the couch roll where additional dryness level is achieved.

(15) A Fourdrinier composed of the previously described equipment is fitted with a plurality of adjustable angle and height foil blades starting from the forming board section 10 and partially through the low-vacuum section 30. As the stock travels with the forming fabric 105, it encounters the adjustable angle and height foil blades at various points along the dewatering table to manipulate the paper web and orient more fibers in a desired direction. On the forming board section 10 and the hydrofoil or gravity section 20, the adjustable angle foil blades generate a vacuum pulse that dewaters the stock slurry. The amount of drainage produced along each adjustable angle foil blade is determined by the angle setting of the foil blade which can be typically varied between +2 and 4 degrees. A higher angle will produce more drainage.

(16) Also within the forming board section and hydrofoil or gravity section of the papermaking process, the stock encounters adjustable height foil blades. These blades also drain water from the stock slurry. The amount of water drained by the adjustable height foil blades is determined by their height setting in relation to the forming fabric. At a setting of 5 mm, they do not touch the fabric and do not drain any water. At a setting of 0 mm, they are in the same plane as the forming fabric and will drain water. As the adjustable height foil blades are lowered from the fabric, the amount of drainage increases up until a point at which the static and dynamic vacuum forces generated by the adjustable height foil blade are overcome by the tension forces of the forming fabric. When this occurs, the fabric breaks its seal with the adjustable height foil blade and no dewatering, occurs. The setting at which this occurs will vary based on the drainage characteristics of the stock, the stock consistency, and the speed of the forming fabric. As can be understood, changing the height settings will directly influence the fiber orientation.

(17) The wet slurry will leave the hydrofoil section 20 at a consistency of around 1.5% depending on the paper grade and speed. From here, it travels to the initial vacuum assisted foil units in the low-vacuum section 30 which are referred to as the Varioline elements. In addition to natural gravity drainage, these Varioline elements also use a dynamic and an external vacuum source to create a vacuum which is drawn onto the lower side of the forming fabric 105. This further increases drainage within these units. The Varioline elements are equipped with a plurality of stationary and adjustable height foil blades. Similar to the previous section, as the foil blades are lowered from the forming fabric, the drainage rate increases as discussed above.

(18) Following the Varioline table elements, another set of vacuum assisted units is encountered by the underside of the forming fabric 105. These table elements are the Vaculine elements which are equipped with adjustable angle foil blades. Again, as the angle of the foil blades is increased, the drainage rate will increase until a consistency of 5% is achieved.

(19) In addition to controlling drainage, the adjustable angle and height foil blades in the previously described drainage units also control turbulence within the wet slurry. This is accomplished through deflection of the forming fabric from its original plane as it travels along the top surface of the adjustable angle foil blades and adjustable height foil blades. This deflection creates a series of accelerations within the stock slurry that results in turbulence and shear within the stock slurry. This turbulence keeps the fibers fluidized and mobile within the wet slurry so that they can be orientated in the cross-machine or machine direction, depending on what the finish paper property strength requirements are.

(20) For example, if machine direction fiber orientation is desired, the headbox jet speed is operated in a rush or drag mode to promote an initial strong machine direction alignment of the paper fibers. From here, the foil blade angles and height, along with the vacuum levels on the vacuum assisted dewatering units are adjusted to produce a high early drainage rate in the initial sheet dewatering zone (0.1% to 2% paper dryness) to immediately freeze the machine direction fiber orientation produced by the headbox.

(21) In addition to this, the foil blade angles, heights and vacuum levels are adjusted to produce a high amount of turbulence in this paper dryness zone (0.1% to 2%). This keeps the fibers from entangling with each other and allows the headbox shear to become more effective in orientating fibers in the machine direction. After 2% paper dryness, the angle and height and vacuum levels are adjusted to gradually achieve a paper dryness of 5%. However, the foil angle and height are adjusted to achieve only moderate turbulence levels to prevent disruption of the machine direction fiber orientation achieved earlier in the sheet dewatering and forming process.

(22) For cross-machine direction fiber alignment, the process is completely reversed. The headbox stock jet is adjusted to produce a speed difference close to zero (square mode) to promote the highest possible cross-machine direction fiber orientation. However, due to friction created within the headbox nozzle, a certain unavoidable degree of machine direction fiber alignment is still always present in the fiber slurry when it lands on the dewatering fabric that cannot be reversed through normal fourdrinier dewatering equipment.

(23) To break this natural machine direction fiber orientation up and produce the most random fiber orientation and highest amount of cross-machine direction fiber orientation, the claimed invention is operated as follows. First, the foil blade angles and heights along with the vacuum levels of the vacuum assisted dewatering elements are adjusted to significantly retard drainage in the early sheet forming zone (0.1% to 2% dryness). This is completely opposite of the previously described process. In addition to this, the angle height of the foil blades are adjusted to produce a very high degree of turbulence to prevent fiber entanglement and generate the most random fiber orientation possible for the highest level of cross-machine direction fiber alignment. After a dryness of 2% is achieved, the foil angle and height is adjusted to maintain this high level of turbulence all the way until a paper dryness of 5% is achieved. A very gentle early drainage along with high turbulence all the way until a dryness of 5% is achieved will create the most random fiber network resulting in the highest amount of cross-machine direction fiber alignment.

(24) After passing through the forming board section, the paper stock is moved along to pass through a hydrofoil or gravity section 20 equipped with Hydroline elements 21. Each Hydroline element 21 comprises height adjustable blades 13 and angle adjustable blades 22 which are alternately arranged as shown in FIG. 3. Depending on the paper grade, Hydrolines may also be fixed with all height or angle adjustable blades. The angle adjustable blades are controlled through an angle adjustment mechanism 25, 27 as shown in FIG. 8A. Height adjustable blades are controlled through a height adjustment mechanism 18, 21 as shown in FIG. 9B.

(25) FIG. 4 depicts a vacuum assisted unit or Varioline table element 51 with stationary or angle adjustable foil blades and adjustable height blades and being part of the low-vacuum section. The Varioline element 51 comprises a dewatering blade 32 followed by height adjustable blades 13. A deckle is arranged blades and may comprise a poly material. A drop leg 34 extends down from the Varioline for draining purposes.

(26) FIG. 5 shows a Vaculine element 41 that is part of the low-vacuum section 30. Vaculine elements 41 are arranged downstream from the last Varioline element 51. Each Vaculine element includes a fixed blade 14 arranged on stationary T-bar 55 at the front and back ends as shown. Adjustable angle blades 22 are arranged in the Vaculine element. Adjustable deckles are interposed between the fixed blades 14 and the adjustable angle blades 22 as shown. A drop leg 34 extends downward for draining purposes.

(27) FIGS. 6A, 6B show a detailed view of an adjustable angle blade mounted on a C-channel. Blade 22 comprises a ceramic top 22A having a yoke 22B formed of fiberglass reinforced composite and having an offset front side as shown. The yoke 22B is fitted atop an adjusting mechanism 25. An underside of the angle adjusting mechanism 25 is secured within C-channel 76 via clamping bar 77. Protective shield 79 is provided on the blade 22 to prevent items from being caught when the adjustment mechanism 25 is actuated. The C-channel is preferably formed from stainless steel and rests atop the frame of the Fourdrinier.

(28) FIGS. 6C, 6D show a detailed view of an adjustable angle blade mounted on a T-bar. In this instance, the mounting means is a T-bar 55 instead of the C-channel and clamping bar of FIGS. 6A, 6B. The Adjustment Mechanism and remaining parts are the same and operate in similar fashion. The respective angles and their range are also the same.

(29) FIGS. 7A, 7B show a detailed view of an adjustable height blade mounted on a C-channel. Height adjustable blade 13 includes an upper end having a leading and trailing edge of ceramic 13A which is fixed in a yoke 13B preferably formed of fiberglass reinforced composite. A height adjustment mechanism 18 is arranged within the yoke 13B. An underside of the height adjusting mechanism 18 is secured within C-channel 76 via clamping bar 77. Protective shield 79 is provided on the blade 13 to prevent items from being caught when the height adjustment mechanism 18 is actuated. The C-channel is preferably formed from stainless steel and rests atop the frame of the Fourdrinier. The height adjustment mechanism 18 includes an adjustable T-bar 21 which extends across the Fourdrinier frame and onto which the blade 13 is attached as shown FIG. 9A. In this manner, the drive 17A raises and lowers the T-bar 21 to adjust the height of the blade 13 in relation to an underside of the forming fabric 105.

(30) FIGS. 7C, 7D shows a detailed view of an adjustable height foil blade mounted on a T-bar, in this instance, the mounting means is a T-bar instead of the C-channel and clamping bar of FIGS. 7A, 7B. The adjustment mechanism is the same and operates in similar fashion. The respective heights and their range are also the same.

(31) FIGS. 8A, 8B shows an angle adjustment mechanism 25 which is a control subassembly for an angle adjustable blade 22. A rotating T-bar 27 is formed from fiber reinforced composite and is the same length as a substructure upon which it is mounted. The angle adjustment mechanism 25 is secured atop a C-channel. The drive 17B is indexed to rotate blade 22 over the range of angles shown in FIGS. 6A-D. The blade 22 is attached to the top side of T-bar 27 which is arranged to rotate in a clockwise or counter clockwise direction. In this manner, the angle of the blade 22 relative to the underside of the forming fabric is controlled.

(32) FIGS. 9A, 9B shows a height adjustment mechanism 78 which is a control subassembly for the height adjustable blade 13. Blade 13 rests atop a T-bar having a drive 17A that automatically raises and lowers the blade 13 to a desired height.

(33) Tables 1 and 2 show blade angle and height settings for a paper grade with machine direction fiber alignment and a grade with cross-machine direction fiber alignment. The tables show a variety of angle adjustable and height adjustable blades which may be utilized in the respective regions of the wet end of the Fourdrinier to achieve synergistic results. It should be noted that in this instance seven blades are shown in each section with the abbreviations H or A indicating that the blade is either height or angle adjustable respectively. Moreover, the gravity units 1-3 correspond to the hydrofoil sections and are three Hydroline elements. Low vacuum units 1-3 correspond to Varioline elements. Low vacuum units 4, 5 correspond to Vaculine elements.

(34) TABLE-US-00001 TABLE 1 Machine Direction Fiber Alignment Low Vac- Low Low Low Low uum Forming Gravity Gravity Gravity Vacuum Vacuum Vacuum Vacuum Unit Blade Board Unit 1 Unit 2 Unit 3 Unit 1 Unit 2 Unit 3 Unit 4 5 1 H 0.25 mm A 1.5 H 0.5 mm A 1.5 H 0.5 mm H 0.5 mm H 0.5 mm A 0.75 A 0.0 2 A 0.25 H 0.5 mm A 1.5 H 0.5 mm H 0.5 mm H 0.5 mm H 0.5 mm A 0.75 A 0.0 3 H 0.25 mm A 1.5 H 0.5 mm A 1.5 H 0.5 mm H 0.5 mm H 0.5 mm A 0.75 A 0.0 4 A 0.25 H 0.5 mm A 1.5 H 0.5 mm H 0.5 mm H 0.5 mm H 0.5 mm A 0.75 A 0.0 5 H 0.25 mm A 1.5 H 0.5 mm A 1.5 H 0.5 mm H 0.5 mm H 0.5 mm A 0.75 A 0.0 6 A 0.25 H 0.5 mm A 1.5 H 0.5 mm H 0.5 mm H 0.5 mm H 0.5 mm A 0.75 A 0.0 7 H 0.25 mm A 1.5 H 0.5 mm A 1.5 H 0.5 mm H 0.5 mm H 0.5 mm A 0.75 A 0.0

(35) TABLE-US-00002 TABLE 2 Cross-machine Direction Fiber Alignment Low Vac- Low Low Low Low uum Forming Gravity Gravity Gravity Vacuum Vacuum Vacuum Vacuum Unit Blade Board Unit 1 Unit 2 Unit 3 Unit 1 Unit 2 Unit 3 Unit 4 5 1 H 0.0 mm A 0.0 H 0.0 mm A 0.5 H 1.0 mm H 1.25 mm H 1.5 mm A 1.5 A 2.0 2 A 0.0 H 0.0 mm A 0.25 H 0.0 mm H 1.0 mm H 1.25 mm H 1.5 mm A 1.5 A 2.0 3 H 0.0 mm A 0.0 H 0.0 mm A 0.5 H 1.0 mm H 1.25 mm H 1.5 mm A 1.5 A 2.0 4 A 0.0 H 0.0 mm A 0.25 H 0.0 mm H 1.0 mm H 1.25 mm H 1.5 mm A 1.5 A 2.0 5 H 0.0 mm A 0.0 H 0.0 mm A 0.5 H 1.0 mm H 1.25 mm H 1.5 mm A 1.5 A 2.0 6 A 0.0 H 0.0 mm A 0.25 H 0.0 mm H 1.0 mm H 1.25 mm H 1.5 mm A 1.5 A 2.0 7 H 0.0 mm A 0.0 H 0.0 mm A 0.5 H 1.0 mm H 1.25 mm H 1.5 mm A 1.5 A 2.0

(36) It is to be understood that the invention is not limited to the exact construction illustrated and described above, but that various changes and modifications may be made without departing from the spirit and the scope of the invention as defined in the following claims. While the invention has been described with respect to preferred embodiments, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in limiting sense. From the above disclosure of the general principles of the present invention and the preceding detailed description, those skilled in the art will readily comprehend the various modifications to which the present invention is susceptible. Therefore, the scope of the invention should be limited only by the following claims and equivalents thereof.