BACKGROUND

[0001] In the field of metal packaging, typical containers are sealed by seaming a can end onto a can body using a well-known double seaming process. The double seaming process is typically performed on a seamer machine having a plurality of forming stations or seaming assemblies. Each assembly contains a rotatable seaming chuck that acts as an anvil to support the can end while two rotatable seaming rolls are brought into contact with the can end using a cam motion. The two seaming rolls define specific groove geometries that are configured to form a portion of the can body and a portion of the can end into a commercially acceptable double seam to thereby couple the can end to the can body.

[0002] Before the double seaming process, a can body is raised into engagement with a seaming chuck using a lifter chuck assembly or other positioning mechanism. After the double seam is formed and the positioning mechanism is retracted, the sealed container is ejected from the seaming chuck so that the seam-forming cycle can be repeated on another container.

Ejection of the seamed container may be accomplished by the use of a knockout pad that taps a center panel of the container to knock the container out of engagement with the seaming chuck.

[0003] Today, beverage customers or fillers have options as to the type of can ends that they use to seam onto the can bodies. Most fillers use either a first type of can end 10a such as a SuperEnd can end produced by Crown Holdings Inc. and shown in United States Patent No. 7,591,392 or a second type of can end 10b such as an end developed by Container Development Limited (CDL) and manufactured by Ball Packaging Corporation and shown in United States Patent No. 8,313,004, the entire contents of each of which are hereby incorporated by reference herein.

[0004] As shown in Figs. 1A and IB, each of the first and second types of can ends 10a and 10b requires a specific seaming chuck to be used to seam the can ends 10a and 10b onto the can bodies. In particular, the first type of can end 10a uses a first seaming chuck 14a and the second type of can end 10b uses a second seaming chuck 14b that is different than the first seaming chuck 10a. For example, the first seaming chuck 14a defines a first working profile 15a having a first seaming surface 16a, a substantially flat drive surface 17a and a lower lip 18a, while the second seaming chuck 14b defines a second working profile 15b having a second seaming surface 16b, a drive surface 17b defined by two radii, and a lower lip 18b. Because of the geometries of the first and second types of can ends 10a and 10b and the geometries of the first and second seaming chucks 14a and 14b, the can ends 10a and 10b and seaming chucks 14a and 14b are not interchangeable.

[0005] In that regard a complete seaming chuck change from the first seaming chuck 14a to the second seaming chuck 14b is necessary each time the fillers switch from using the first type of can ends 10a to using the second type of can ends 10b. The line down time for such a changeover is at least 8 hours. For this reason no customer has shown interest in having a dual source of can ends. That is, very few fillers run both the first type of can ends 10a and the second type of can ends 10b, which can be commercially restrictive. Therefore, a seaming chuck that could be used to seam both the first type of can end 10a and the second type of can end 10b would allow fillers to run both types of can ends without having to change the seaming chucks.

SUMMARY

[0006] In an embodiment, a universal seaming chuck is configured to support a can end during a double seaming process. The can end has a center panel, a countersink bead extending radially out from the center panel, a wall extending radially out from the countersink bead, and a curl extending radially out from the wall. The universal seaming chuck includes a cylindrical body that defines a central axis, a distal end, and a proximal end spaced from the distal end along the central axis. The body includes an outer working profile proximate to the distal end that is configured to receive a seaming force. The working profile defines a seaming surface against which the curl of the can end is configured to be pressed, and a chuck wall drive surface that extends distally from the seaming surface and is configured to abut the wall of the can end. The chuck wall drive surface includes a distal radiused portion, a middle radiused portion that merges into the distal radiused portion, and a proximal radiused portion that merges into both the middle radiused portion and the seaming surface. The distal radiused portion has a radius that is between about 0.030 inches and about 0.050 inches, the middle radiused portion has a radius that is between about .020 inches and about 0.050 inches, and the proximal radiused portion has a radius that is between about 0.020 inches and about 0.040 inches.

[0007] In another embodiment, a universal seaming chuck is configured to support both a first type of can end and a second type of can end that is different than the first type of can end during a double seaming process. The universal seaming chuck includes a cylindrical body that defines a central axis, a distal end, and a proximal end spaced from the distal end along the central axis. The body includes an outer working profile proximate to the distal end that is configured to receive a seaming force. The working profile defines a seaming surface and a chuck wall drive surface that extends distally from the seaming surface. The chuck wall drive surface can be defined by a continuous blend of at least three radii such that the chuck wall drive surface is configured to (i) abut a first wall of the first type of can end such that a first curl of the first type of can end can be pressed against the seaming surface to thereby form a double seam, and (ii) abut a second wall of the second type of can end such that a second curl of the second type of can end can be pressed against the seaming surface to thereby form a double seam. The first type of can end includes a center panel having a first diameter and the second type of can end includes a center panel having a second diameter that is greater than the first diameter, and the first wall defines a first profile and the second wall defines a second profile that is different than the first profile.

[0008] In another embodiment, a method of seaming at least a first type of can end and a second type of can end to can bodies with a universal seaming chuck includes the steps of positioning a first type of can end onto a first can body to form a first can combination, the first type of can end having a first center panel that defines a first diameter, a first countersink that extends radially out from the first center panel, a first chuck wall that extends radially out from the first countersink, and a first curl that extends radially out from the first chuck wall, the first chuck wall defining a first profile; moving the first can combination until the first type of can end engages a universal seaming chuck that defines a working profile having a seaming surface that is adjacent the first curl and a chuck wall drive surface that is adjacent the first chuck wall; moving at least one seaming roll toward the first can combination such that the at least one seaming roll presses the second curl against the seaming surface to thereby form a double seam with the second curl and the first can body; positioning a second type of can end onto a second can body to form a second can combination, the second type of can end having a second center panel that defines a second diameter that is greater than the first diameter, a second countersink that extends radially out from the second center panel, a second chuck wall that extends radially out from the second countersink, and a second curl that extends radially out from the second chuck wall, the second chuck wall defining a second profile that is different than the first profile; moving the second can combination until the second type of can end engages the universal seaming chuck such that the seaming surface is adjacent the second curl and the chuck wall drive surface is adjacent the second chuck wall; and moving the at least one seaming roll toward the second can combination such that the at least one seaming roll presses the second curl against the seaming surface to thereby form a double seam with the second curl and the second can body.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The foregoing summary, as well as the following detailed description of the preferred embodiments of the application, will be better understood when read in conjunction with the appended drawings. For the purposes of illustrating the present disclosure, there is shown in the drawings preferred embodiments. It should be understood, however, that the application is not limited to the specific embodiments and methods disclosed, and reference is made to the claims for that purpose. In the drawings:

[0010] Fig. 1 A is a partial cross-sectional view of a first seaming chuck supporting a first type of can end;

[0011] Fig. IB is a partial cross-sectional view of a second seaming chuck supporting a second type of can end;

[0012] Fig. 2A is a schematic showing a seaming assembly seaming a can end onto a can body, the seaming assembly including a seaming chuck that is to be positioned within the can end, and first and second seaming rollers that are configured to press portions of the can body and can end against the seaming chuck to thereby form a double seam and attach the can end to the can body;

[0013] Fig. 2B is a partial cross-sectional view of an example can end attached to a can body by a double seam that is formed by the seaming assembly shown in Fig. 2A;

[0014] Fig. 3 A is a bottom perspective view of a universal seaming chuck in accordance with an embodiment, the universal seaming chuck being configured to seam both a first type of can end, such as the can end shown in Fig. 1A and a second type of can end such as the can end shown in Fig. IB; [0015] Fig. 3B is a cross-sectional view of the universal seaming chuck shown in Fig. 3A, the universal seaming chuck having a working profile that defines a seaming surface and a chuck wall drive surface;

[0016] Fig. 3C is an enhanced cross-sectional view of the working profile shown in Fig.

3B;

[0017] Fig. 4A is a partial cross-sectional view of the first type of can end shown in Fig. 1A;

[0018] Fig. 4B is a partial cross-sectional view of the second type of can end shown in Fig. IB;

[0019] Fig. 5 A is a partial cross-sectional view of the universal seaming chuck shown in Fig. 3B supporting the first type of can end shown in Fig. 4A; and

[0020] Fig. 5B is a partial cross-sectional view of the universal seaming chuck shown in Fig. 3B supporting the second type of can end shown in Fig. 4B.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0021] Certain terminology is used in the following description for convenience only and is not limiting. The words "right", "left", "lower" and "upper" designate directions in the drawings to which reference is made. The terminology includes the above-listed words, derivatives thereof and words of similar import.

[0022] Referring to Figs. 2A and 2B, a seaming assembly 4 is configured to seam a can end 10 onto a can body 18 to form a seamed container 20 ready for consumption by an end user. The seaming assembly 4 includes a frame 22, a chuck-knockout assembly 26 mounted on the frame 22 by a rotating shaft 24, and a lifter assembly 27 mounted on the frame 22 vertically below the chuck-knockout assembly 26. The chuck-knockout assembly 26 includes a seaming chuck, such as a universal seaming chuck 30 shown in Figs. 3A-3C that is configured to be positioned within the can end 10 so as to act as anvil when the can end 10 is being seamed onto the can body 18. The lifter chuck assembly 27 is configured to support the can body 18 and can end 10 combination, and lift the combination until the can end 10 engages the seaming chuck 30 of the chuck-knockout assembly 26. As shown in Fig. 2A, the seaming assembly 4 further includes a pair of seaming rolls 34a and 34b that are configured to form a double seam 38 that seals the can end 10 onto the can body 18 via a double seaming process (e.g., bending a curl portion of the can end 10 and a top edge 18a of the can body 18 as shown in Fig. 2B). This double seaming process occurs while the can end 10 is engaged with the universal seaming chuck 30. [0023] The seaming assembly 4 may be part of a seaming system that includes at least two, such as twelve, fourteen, or eighteen seaming assemblies 4. Each seaming assembly 4 in the seaming system rotates about a center axis of the system from take-up of the can end 10 and can body 18 (i.e. when the can end 10 is placed on top of the can body 18) through to discharge of the seamed container 20 and continues to rotate as it takes another can body and can end through the process. It should be understood, however, that the seaming assembly 4 may be part of a seaming system having other configurations, as desired.

[0024] The seaming assembly 4 and in particular the universal seaming chuck 30 is configured to seam at least two types of can ends to the can bodies 18 while at least maintaining throughput speeds regardless of what type of can end is being seamed. For example, the seaming assembly 4 and in particular the universal seaming chuck 30 may be configured to seam either the first type of can end 10a shown in Fig. 4A or the second type of can end 10b shown in Fig. 4B onto a can body 18 that is filled with a product 40, such as a low carbonated beverage, at speeds of at least about 1250 cans/minute, preferably at least about 1350 cans/minute, and even more preferably at least about 1550 cans/minute. It should be appreciated, however, that the seaming assembly 4 and in particular the universal seaming chuck 30 may be used to seam any one of the first and second types of can ends 10a and 10b onto a can body 18, filled with any product 40, including carbonated beverages (i.e. beer and soda), ready meals, fruits, vegetables, fish, dairy, pet food, or any other product that is desirable of being stored in metal packaging such as the container 20. It should also be appreciated, that the speeds provided are for seaming systems having twelve seaming assemblies 4, and that the speeds may vary depending on the number of seaming assemblies 4 on the machine.

[0025] As shown in Fig. 2B, the container 20, including the can end 10 and the can body 18 that are to be seamed together, may be made from any material, for example, steel, aluminum, or tin plate, and may include a variety of configurations. For example, as shown in Fig. 2B, generally a can end 10 includes an approximately circular center panel 40, a substantially U-shaped countersink bead 44 that extends radially outward from the center panel 40, an angled wall 48 that extends radially outward from the countersink bead 44, and a curl 52 that extends radially outward from the angled wall 48. As shown in Fig. 2B, the curl 52 is configured to be wound tight with the curled top edge 18a of the can body 18 to form the double seam 38. It should be appreciated, however, that while can ends 10 generally include each of a center panel 40, countersink bead 44, wall 48, and curl 52, the shape and dimensioning of these structures can vary between different types of can ends. For example the center panels, countersink beads, walls, and curls of the first and second types of can ends 10a an 10b shown in Figs. 4A and 4B can differ with respect to each other.

[0026] Now in reference to Figs. 3A-3C, the universal seaming chuck 30 can be configured to support at least two types of can ends 10 such as the first type of can end 10a shown in Fig. 4A and the second type of can end 10b shown in Fig. 4B during a double seaming process. As shown in Figs. 3A and 3B, the universal seaming chuck 30 includes a cylindrical body 50 that defines a central axis A, a distal end D, and a proximal end P that is spaced from the distal end D along the central axis A. The cylindrical body 50 includes an outer working profile 60 proximate to the distal end D that is configured to receive a seaming force from for example the seaming rolls 34a and 34b. In the illustrated embodiment, the outer working profile 60 is located at the distal end D of the cylindrical body 50. It should be appreciated, however, that the outer working profile 60 can be located along the body 50 proximal to the distal end D and still be proximate to the distal end D.

[0027] As shown in Figs. 3B and 3C, the outer working profile 60 includes a seaming surface 64 and a chuck wall drive surface 68 that extends distally from the seaming surface 64.

During the seaming process, the chuck wall drive surface 68 is configured to abut the wall 48 of the can end, and the curl 52 of the can end is configured to be pressed against the seaming surface 64 by the seaming rolls 34a and 34b. The outer working profile 60 is configured such that the universal seaming chuck 30 can be used during the seaming of at least two different types of can ends such as the first and second types of can ends 10a and 10b shown in Figs. 4A and 4B. As shown in Fig. 3B, the outer working profile has a height Hi that is measured along the central axis A from a lower most end of the working profile 60 to an upper most end of the working profile 60. As shown, the lower most end of the working profile 60 can be the lower most end of the universal seaming chuck 30. The height Hi of the outer working profile 60 can be less than 0.250 inches, preferably is less than 0.20 inches, and even more preferably is less than 0.175 inches. The working profile height Hi or at least the chuck wall drive surface 68 can be shaped or otherwise configured such that no portion of the chuck wall drive surface 68 or working profile 60 for that matter is disposed within the countersink bead 48 of the can end during the double seaming process. It should be appreciated, however, that the outer working profile can be configured such that the universal seaming chuck 30 can be used during the seaming of any number of types of can ends and any at least two types of can ends. Further, it should be appreciated, that the working profile 60 can have any height Hi as desired and that during the seaming of some types of can ends, portions of the working profile 60 may be disposed within the countersink bead 48 of the can end. [0028] With continued reference to Figs. 3B and 3C, the seaming surface 64 can be flat and can be angled outward with respect to the central axis A by a first angle Q _\ . That is, the seaming surface 64 can extend proximally from the chuck wall drive surface 68 at an angle 0i with respect to the central axis A. The first angle 0i can be about 4 degrees as illustrated. It should be appreciated, however, that the first angle 0i can be any angle as desired. The seaming surface 64 is configured to receive a seaming force from the seaming rolls 34a and 34b such that the seaming rolls 34a and 34b press the curl 52 of the can end against the seaming surface 64 to thereby form the double seam 38

[0029] With continued reference to Figs. 3B and 3C, the chuck wall drive surface 68 extends distally from the seaming surface 64 and is configured to abut the wall 48 of the can end during the seaming process. As shown in Fig. 3C, the chuck wall drive surface 68 is defined by a substantially continuous blend of at least three radii. As shown in Fig. 3C, the chuck wall drive surface 68 includes a distal radiused portion 80, a middle radiused portion 84 that merges into the distal radiused portion 80, and a proximal radiused portion 88 that merges into both the middle radiused portion 84 and the seaming surface 64. As shown, the drive surface 68 can be curved from the distal radiused portion 80 to the middle radiused portion 84 and includes a short flat between the middle radiused portion 84 and the proximal radiused portion 88. The distal radius portion 80 can be convex and can have a radius ri that is between about 0.030 inches and about 0.050 inches, the middle radiused portion 84 can be concave and can have a radius r ₂ that is between about .020 inches and about 0.050 inches, and the proximal radiused portion 88 can be convex and can have a radius ¾ that is between about 0.020 inches and about 0.050 inches. In the illustrated embodiment, the distal radiused portion 80 has a radius ri of about 0.042 inches, the middle radiused portion 84 has a radius r ₂ of about 0.040 inches, and the proximal radiused portion 88 has a radius r ₃ of about 0.035 inches. It should be appreciated, however, that the distal, middle, and proximal radiused portions can have any radii within the specified ranges as desired.

[0030] With continued reference to Fig. 3C, the proximal radiused portion 88 merges with the middle radiused portion 84 at a substantially straight intersection 96 such that the chuck wall drive surface 68 defines an intersection angle 0 ₂ with respect to the central axis A at the intersection 96. The intersection angle 0 ₂ can be between about 45 degrees and about 65 degrees, preferably between about 50 degrees and about 60 degrees, and even more preferably about 60 degrees. The relationship between the distal, middle, and proximal radiused portions 80, 84, and 88 may determine the length of the intersection 96. [0031] Now in reference to Figs. 4A-4B and 5A-5B, the universal seaming chuck 30 is configured to support both the first type of can end 10a shown in Figs. 4A and 5A and the second type of can end 10b as shown in Figs. 4B and 5B. It should be appreciated, however, that the universal seaming chuck 30 is not limited to only supporting the first and second types of can ends 10a and 10b illustrated in Figs. 4A and 4B, and that the universal seaming chuck 30 may be capable of supporting other types of the can ends or variations of the first and second types of can ends 10a and 10b.

[0032] As shown in Fig. 4A, the first type of can end 10a includes a first center panel 40a, a first countersink bead 44a that extends radially out from the first center panel 40a, a first wall 48a that extends radially out from the first countersink bead 44a, and a first curl 52a that extends radially out from the first wall 48a. The first center panel 40a can be substantially flat and defines a diameter di. The first countersink bead 44a can be substantially u-shaped and includes an inner wall 98a, an outer wall 98b, and a bottom portion 98c that joins the inner wall 98a to the outer wall 98b.

[0033] With continued reference to Fig. 4A, the first wall 48a includes a lower wall portion 102a, an upper wall portion 106a, and a juncture 110a between the lower and upper wall portions 102a and 106a. As shown in Fig. 4A, a point A is defined at the transition between the outer wall 98b of the first countersink bead 44a and the lower wall portion 102a, and a point B is defined at the transition between the upper wall portion 106a and the first curl 52a. As shown in Fig. 4A, the lower wall portion 102a is substantially straight and sloped so as to form an angle 03 with respect to a vertical axis X. Similarly, the upper wall portion 106a is substantially straight and sloped so as to form an angle 0 ₄ with respect to the vertical axis X. The magnitude of the angles 0 ₃ and 0 ₄ may be chosen such that a line between point A and point B forms an angle 0 ₅ of between 20 degrees and 60 degrees. Further, the lower wall portion 102a can have a length Li measured from point A to the first juncture 1 10a and the upper wall portion 106a can have a length L2 measured from the first juncture 1 10a to the second point B. In this way, it can be said that the first wall 48a has a first wall profile.

[0034] With continued reference to Fig. 4A, the first type of can end 10a can have an initial countersink depth Di prior to seaming. After the can end 10a has been seamed onto a can body, the countersink depth Di can change. For example, the can end 10a can have an initial countersink depth Di that is about 0.25 inches and a final countersink depth Di that is about 0.268 inches after the can end 10a is seamed onto a can body. It should be appreciated, however, that the first type of can end 10a can be configured such that the countersink depth Di remains unchanged after seaming. [0035] Table 1 below provides the angles and dimensions of the illustrated first type of can end 10a. It should be appreciated, however, that the dimensions are for one example, and that the dimensions can vary.

TABLE 1

[0036] As shown in Fig. 4B, the second type of can end 10b includes a second center panel 40b, a second countersink bead 44b that extends radially out from the second center panel 40b, a second wall 48b that extends radially out from the second countersink bead 44b, and a second curl 52b that extends radially out from the second wall 48b. The second center panel 40b can be substantially flat and defines a diameter d2. As shown, the diameter d2 is greater than the diameter di of the first type of can end 10a. The second countersink bead 44b can be substantially u-shaped and includes an inner wall 124a, an outer wall 124b, and a bottom portion 124c that joins the inner wall 124a to the outer wall 124b.

[0037] With continued reference to Fig. 4B, the second wall 48b includes a lower wall portion 102b, an upper wall portion 106b, and a juncture 110b between the lower and upper wall portions 102b and 106b. As shown in Fig. 4B, a point C is defined at the transition between the outer wall 124b of the second countersink bead 44b and the lower wall portion 102b, and a point D is defined at the transition between the upper wall portion 106b and the second curl 52b. As shown in Fig. 4B, the lower wall portion 102a is sloped so as to form an angle 0 ₆ with respect to a vertical axis X. Similarly, the upper wall portion 106b is substantially straight and sloped so as to form an angle 07 with respect to the vertical axis X. The magnitude of the angles 0 ₆ and 07 may be chosen such that a line between point C and point D forms an angle 0 ₈ of between 20 degrees and 60 degrees. Further, the lower wall portion 102b can have a length L ₃ measured from point C to the second juncture 110b and the upper wall portion 106b can have a length L ₄ measured from the second juncture 110b to the second point D. In this way it can be said that the second wall 48b has a second wall profile that is different than the first wall profile.

[0038] With continued reference to Fig. 4B, the second type of can end 10b can have an initial countersink depth D ₂ prior to seaming. After the can end 10b has been seamed onto a can body, the countersink depth D2 can be unchanged. For example, the can end 10b can have an initial countersink depth D2 that is about 0.25 inches and a final countersink depth D2 that is about 0.25 inches after the can end 10b is seamed onto a can body. It should be appreciated, however, that the second type of can end 10b can be configured such that the countersink depth D2 changes after seaming.

[0039] Table 2 below provides the angles and dimensions of the illustrated second type of can end 10b. It should be appreciated, however, that the dimensions are for one example, and that the dimensions can vary.

TABLE 2

[0040] Now in reference to Figs. 5A and 5B, the universal seaming chuck 30 can be configured to support both the first and second types of can ends 10a and 10b during the seaming process. In particular, the chuck wall drive surface 68 is configured to abut the first wall 48a of the first type of can end 10a such that the first curl 52a of the first type of can end 10a can be pressed against the seaming surface 64 to thereby form a double seam. The chuck wall drive surface 68 can also be configured to abut the second wall 48b of the second type of can end 10b such that the second curl 52b of the second type of can end 10b can be pressed against the seaming surface 64 to thereby form a double seam. Therefore, the universal seaming chuck 30 can be configured to support at least two types of can ends each having a different diameter center panel (i.e. center panels 40a and 40b) and different profiled walls (i.e. walls 48a and 48b).

[0041] With continued reference to Fig. 5A, the universal seaming chuck 30 and in particular the chuck wall drive surface 68 is configured to abut the lower wall portion 102a proximate to the juncture 1 10a and also near a bottom end of the lower wall portion 102a during the seaming process. In particular, the proximal radiused portion 88 abuts the lower wall portion 102a proximate to the juncture 1 10a and the distal radiused portion 80 abuts the lower wall portion 102a proximate to the bottom end of the lower wall portion 102a during the seaming process. It should be appreciated, however, that the chuck wall drive surface 68 can abut any portion of the wall 48a during the seaming process so long as a double seam can be formed.

[0042] Referring back to Fig. 5B, the universal seaming chuck 30 and in particular the chuck wall drive surface 68 is also configured to abut the upper wall portion 106b proximate to the juncture 110b during the seaming process. In particular, the proximal radiused portion 88 abuts the upper wall portion 106b proximate to the juncture 110b during the seaming process. It should be appreciated, however, that the chuck wall drive surface 68 can abut any portion of the wall 48b during the seaming process so long a s a double seam can be formed. Because of the shape of the outer working surface 60, the universal seaming chuck 30 is capable of supporting both the first type and the second type of can ends 10a and 10b during the seaming process such that acceptable double seams are formed.

[0043] While the foregoing description and drawings represent the preferred embodiment of the present invention, it will be understood that various additions, modifications, combinations and/or substitutions may be made therein without departing from the spirit and scope of the invention as defined in the accompanying claims. In particular, it will be clear to those skilled in the art that the invention may be embodied in other specific forms, structures, arrangements, proportions, and with other elements, materials, and components, without departing from the spirit or essential characteristics thereof. One skilled in the art will appreciate that the invention may be used with many modifications of structure, arrangement, proportions, materials, and components, which are particularly adapted to specific environments and operative requirements without departing from the principles of the invention. In addition, features described herein may be used singularly or in combination with other features. For example, features described in connection with one component may be used and/or interchanged with features described in another component. The presently disclosed embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and not limited to the foregoing description.

[0044] It will be appreciated by those skilled in the art that various modifications and alterations of the invention can be made without departing from the broad scope of the appended claims. Some of these have been discussed above and others will be apparent to those skilled in the art.