Patent Application
20070125482
This invention relates generally to an improved apparatus for manufacturing a toroidal carcass ply for a tire and, more specifically, to an applicator head for applying a single end cord to an annular tire building surface.
Historically, the pneumatic tire has been fabricated as a laminate structure of generally toroidal shape having beads, a tread, belt reinforcement, and a carcass. The tire is made of rubber, fabric, and steel. The manufacturing technologies employed for the most part involved assembling the many tire components from flat strips or sheets of material. Each component is placed on a building drum and cut to length such that the ends of the component meet or overlap creating a splice.
In the first stage of assembly the prior art carcass will normally include one or more plies, and a pair of sidewalls, a pair of apexes, an innerliner (for a tubeless tire), a pair of chafers and perhaps a pair of gum shoulder strips. Annular bead cores can be added during this first stage of tire building and the plies can be turned around the bead cores to form the ply turnups. Additional components may be used or even replace some of those mentioned above.
This intermediate article of manufacture would be cylindrically formed at this point in the first stage of assembly. The cylindrical carcass is then expanded into a toroidal shape after completion of the first stage of tire building. Reinforcing belts and the tread are added to this intermediate article during a second stage of tire manufacture, which can occur using the same building drum or work station.
This form of manufacturing a tire from flat components that are then formed toroidially limits the ability of the tire to be produced in a most uniform fashion. As a result, an improved method and apparatus has been proposed, the method involving applying an elastomeric layer on a toroidal surface and placing and stitching one or more cords in continuous lengths onto the elastomeric layer in predetermined cord paths. The method further includes dispensing the one or more cords from spools and guiding the cord in a predetermined path as the cord is being dispensed. Preferably, each cord, pre-coated with rubber or not so coated, is held against the elastomeric layer after the cord is placed and stitched and then indexing the cord path to a next circumferential location forming a loop end by reversing the direction of the cord and releasing the held cord after the loop end is formed and the cord path direction is reversed. Preferably, the indexing of the toroidal surface establishes the cord pitch uniformly in discrete angular spacing at specific diameters.
The above method is performed using an apparatus for forming an annular toroidially shaped cord reinforced ply which has a toroidal mandrel, a cord dispenser, a device to guide the dispensed cords along predetermined paths, a device to place an elastomeric layer on the toroidal mandrel, a device to stitch the cords onto the elastomeric layer, and a device to hold the cords while loop ends are formed. The device to stitch the cords onto the elastomeric layer can include a bi-directional tooling head mounted to a tooling arm. A pair of roller members is mounted side by side at a remote end of the tooling head and defining a cord exiting opening therebetween. The arm moves the head across the curvature of a tire carcass built on a drum or core while the cord is fed through the exit opening between the rollers. The rollers stitch the cord against the annular surface as the cord is laid back and forth across the surface, the first roller engaging the cord along a first directional path and the second roller engaging the cord in a reversed opposite second directional path.
The toroidal mandrel is preferably rotatable about its axis and a means for rotating is provided which permits the mandrel to index circumferentially as the cord is placed in a predetermined cord path. The guide device preferably includes a multi axis robotic computer controlled system and a ply mechanism to permit the cord path to follow the contour of the mandrel including the concave and convex profiles.
While working well, certain challenges exist in the aforementioned proposed apparatus and method. First, the tooling head rollers are configured and mounted to maintain continuous contact with the annular surface while each roller alternatively engages the cord along a respective application path. Such a configuration results in greater than preferred surface contact between the applicator head and the annular surface because both rollers are in constant contact with the surface. Constant contact between each roller and the annular surface requires that relatively more force is needed to move the roller head over the surface. Moreover, the mechanism required to move the applicator head along the curvature of a tire carcass and to form the loop ends of the cord at each terminal end of a carcass traverse is complicated because of the fixed angular relationship of both rollers to the annular carcass surface, resulting in increased tooling manufacturing and maintenance costs.
A need, accordingly, remains for an applicator head that is simple to construct, operationally reliable and efficient, and effective in bi-directional application of a single end cord to a tire carcass. Furthermore, a need exists for an applicator head that can effectively apply a tire cord without the need for equipment to form loop ends, and equipment necessary to press and release the cord.
Generally, one aspect of the invention contemplates a tooling head for applying tire cored to an annular surface of a tire component in a bi-directional manner. The head may include a cord engagement element configured to reciprocate in a forward and reverse direction across the annular surface while applying the tire cord to the annular surface. The cord engagement element includes at least a first and second cord engaging components. A re-orientation element is configured to reposition the cord engagement element such that the first cord engaging component engages the annular surface in the forward direction and the second cord engaging component engages the annular surface in the reverse direction. The annular surface may, for example, comprise an elastomeric layer of a tire.
In another aspect, the invention provides a method for applying tire cord to an annular surface of a tire component in a bi-directional manner. The method may include applying one or more cords on the annular surface by engaging at least a first cord engaging component with the annular surface as the first cord engaging component moves in a forward direction. The method further includes disengaging the first cord engaging component from the annular surface and applying one or more cords on the annular surface by engaging at least a second cord engaging component with the annular surface as the second cord engaging component moves in a reverse direction. The second cord engaging component is then disengaged from the annular surface.
Pursuant to one aspect of the invention a bi-directional tooling head is mounted to reciprocally move in a forward and a reverse direction across an annular surface, preferably but not necessarily as the annular surface is rotated. The tooling head includes a plurality of rollers for impressing one or more cords on an elastomeric layer on the annular surface in the forward and reverse directions and a tilt mechanism for angularly repositioning the rollers into alternative engagement with the annular surface in the forward and reverse directions. According to another aspect of the invention, at least one roller engages against the annular surface in the forward direction and at least a second roller engages against the annular surface in the reverse direction while the first roller is disengaged.
Yet a further aspect of the invention utilizes the tilt mechanism to simultaneously engage and disengage the first and second rollers from the annular surface. Pursuant to another aspect of the invention, the first and second rollers are mounted to a terminal end of the tooling head in-line and define a cord exiting passageway therebetween.
A method for bi-directional tire cord application to an annular surface constitutes an additional aspect of the invention, the method comprising the steps: mounting a tooling head for reciprocal movement in a forward and a reverse direction across the annular surface, the tooling head having a plurality of roller components; impressing one or more cords on an elastomeric layer on the annular surface by at least a first roller component of the tooling head in the forward direction; disengaging the first roller component of the tooling head from the annular surface at the conclusion of tooling head movement in the forward direction; impressing one or more cords on the elastomeric layer on the annular surface by at least a second roller component of the tooling head in a reverse direction; and disengaging the second roller component of the tooling head from the annular surface at the conclusion of tooling head movement in the reverse direction.
According to a further aspect of the invention, the method may include the steps of pivotally reorienting the tooling head from an initial orientation into a secondary orientation at the conclusion of tooling head movement in the forward direction to disengage the first roller component of the tooling head from the annular surface and engage the second roller component of the tooling head with the annular surface; and pivotally reorienting the tooling head from the secondary orientation into the initial orientation at the conclusion of tooling head movement in the reverse direction to disengage the second roller component of the tooling head from the annular surface and engage the first roller component of the tooling head with the annular surface.
In another aspect of the invention, a roller component may be structured to at least partially capture a cord into a cord receiving channel as the first cord engaging component moves and, using the channel to align the at least one cord relative to the annular surface, accurately position and apply the cord.
Definitions
“Aspect Ratio” means the ratio of a tire's section height to its section width.
“Axial” and “axially” means the lines or directions that are parallel to the axis of rotation of the tire.
“Bead” or “Bead Core” means generally that part of the tire comprising an annular tensile member, the radially inner beads are associated with holding the tire to the rim being wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes or fillers, toe guards and chaffers.
“Belt Structure” or “Reinforcing Belts” means at least two annular layers or plies of parallel cords, woven or unwoven, underlying the tread, unanchored to the bead, and having both left and right cord angles in the range from 17° to 27° with respect to the equatorial plane of the tire.
“Circumferential” means lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction.
“Carcass” means the tire structure apart from the belt structure, tread, undertread, over the plies, but including beads, if used, on any alternative rim attachment.
“Casing” means the carcass, belt structure, beads, sidewalls and all other components of the tire excepting the tread and undertread.
“Chaffers” refers to narrow strips of material placed around the outside of the bead to protect cord plies from the rim, distribute flexing above the rim.
“Cord” means one of the reinforcement strands of which the plies in the tire are comprised.
“Equatorial Plane (EP)” means the plane perpendicular to the tire's axis of rotation and passing through the center of its tread.
“Footprint” means the contact patch or area of contact of the tire tread with a flat surface at zero speed and under normal load and pressure.
“Innerliner” means the layer or layers of elastomer or other material that form the inside surface of a tubeless tire and that contain the inflating fluid within the tire.
“Normal Inflation Pressure” means the specific design inflation pressure and load assigned by the appropriate standards organization for the service condition for the tire.
“Normal Load” means the specific design inflation pressure and load assigned by the appropriate standards organization for the service condition for the tire.
“Placement” means positioning a cord on a surface by means of applying pressure to adhere the cord at the location of placement along the desired ply path.
“Ply” means a layer of rubber-coated parallel cords.
“Radial” and “radially” mean directions radially toward or away from the axis of rotation of the tire.
“Radial Ply Tire” means a belted or circumferentially-restricted pneumatic tire in which at least one ply has cords which extend from bead to bead are laid at cord angles between 65° and 90° with respect to the equatorial plane of the tire.
“Section Height” means the radial distance from the nominal rim diameter to the outer diameter of the tire at its equatorial plane.
“Section Width” means the maximum linear distance parallel to the axis of the tire and between the exterior of its sidewalls when and after it has been inflated at normal pressure for 24 hours, but unloaded, excluding elevations of the sidewalls due to labeling, decoration or protective bands.
“Shoulder” means the upper portion of sidewall just below the tread edge.
“Sidewall” means that portion of a tire between the tread and the bead.
“Tread Width” means the arc length of the tread surface in the axial direction, that is, in a plane parallel to the axis of rotation of the tire.
“Winding” means a wrapping of a cord under tension onto a convex surface along a linear path.
The invention will be described by way of example and with reference to the accompanying drawings in which:
FIGS. 18A-D are sequential views of the tire forming mandrel showing the build of a ply layer by means of single cord application pursuant to the invention.
Referring initially to
The referenced drawings depict four arm assemblies 16 A-D surrounding the core assembly in a preferred arrangement. While four assemblies are incorporated in the system embodiment 10, the invention is not to be so limited. A single arm assembly may be used if desired. Alternatively, more or fewer than four assemblies may constitute the system if desired. The four arm assemblies 16 A-D are disposed to surround the core assembly 10 at a preferred spacing that allows the arm assemblies to simultaneously construct a cord ply to respective regions of the toroidal core. Dividing the surface area of the toroidal core into four quadrants, each assigned to a respective one of the four arm assemblies, allows the cord ply layer to be formed simultaneously to all four quadrants, whereby expediting the process and saving time and manufacturing cost.
A core removal assembly 18 is shown disposed to remove the core assembly 11 from between the arm assemblies 16 A-D once tire construction on the core is complete. An appropriate computer control system conventional to the industry may be employed to control the operation of the system 10 including arm assemblies 16 A-D. A control system of the type shown will typically include a housing 22 enclosing the computer and system control hardware. Electrical control signals will be transmitted to the system 10 by means one or more suitable cable conduit such as that show at numeral 23.
A cage or peripheral guard structure 24 may enclose the system 10 as shown in
In FIGS. 3A-C and 4, operation of one arm assembly 16D is sequentially depicted and will be readily understood. The arm assembly 16D is configured to provide end of arm tooling assembly 34 carried by C-frame arm 36, electrically serviced by suitable cabling extending through cable tray 38. As explained previously, the core assembly 11 is configured having a rotational axial shaft 40 and a segmented toroidal core body 42 providing an annular outer toroidal surface 43. A main mounting bracket 44 supports the end of arm tooling assembly 34 as well as a drive motor 46 and clutch assembly 48. As best seen from joint consideration of
An end of arm tooling motor 52 is further mounted on arm assembly 36 and rotatably drives end of arm tooling shaft 54. The end of arm tooling 34 consists of a bi-directional cord laying head assembly 56, an intermediate housing assembly 57, and an upper housing assembly 59. The end of arm tooling 34 further includes a cord tensioning sub-assembly 58 as shown in detail in
Referring next to
The intermediate assembly 57 includes a pre-loaded coil spring 82 that seats within a spring housing 84 residing within an outer housing block 85. The bi-directional cord laying head assembly 56 is placed in a downward bias against the surface 43 by the pre-loaded coil spring 82. O-rings 86 A-F are suitably located between adjacent housing block elements. The intermediate assembly 57 further includes a lower housing 88 receiving a housing block 89 therein. A terminal end of the block 89 is closed by an end cap 90 with the intersection sealed by means of O-rings 91. The block 89 represents a plunger, or piston, slideably contained within the outer housing 88 that moves axially relative to the end of arm tooling for a purpose explained below. The end of arm tooling 34 is pivotally mounted to the bracket 62 and reciprocally rotated by means of drive shaft 54 in the direction 69 as will be appreciated from
From
It will further be appreciated from
The final guide tube 80 extends along the center axis of the end-of-arm tooling 34 and, as will be understood from
With reference to
The housing block 85 includes an axial passageway 128. A recessed peripheral ledge 122 circumscribes a forward end of the passageway 128 and a through bore 124 extends into and through the housing ledge 122. A slide pin 126 projects through the bore 124 of housing 85, the bore 116 of cap 112, and into the housing 89 as shown. Piston 89 is thus slideably coupled to the block 85 and moves reciprocally in an axial direction relative thereto as described above.
A transverse bore 130 extends through housing 85 from side to side in communication with passageway 128. Mounting flanges 132, 134 extend laterally from the housing 85 and mounting screws 134 project through the flanges and into housing 88 to secure housing 85 to housing 88. The cord cutting assembly 98 includes a tubular member 136 rotatably residing within the transverse bore 130 and projecting from opposite sides of the housing 85. An attachment lug 138 projects outward from an end of the tubular member 136 and carries an inward facing attachment stud 139. The tubular member 136 has locking flanges 140 at an opposite end and a centrally disposed axial through bore 142. A transverse bore 144 having a funnel shaped guide entry 145 is positioned to extend through the tubular member 136.
A connector block 146 is attached to an end of the tubular member 136 and includes a locking socket 148 engaging the locking flanges 140 of member 136. An attachment stud 150 extends inwardly from the block 146. Piston 89 is configured having a cylindrical rearwardly disposed socket 152 stepping inward to a forward smaller diametered cylindrical portion 154. Outwardly projecting pin members 156 extending from opposite sides of the cylindrical portion 154 of the piston 89. As will be appreciated, forward ends 158 of pivot arms 102, 104 fixedly attach to the pins 156 and rearward ends of the arm 102, 104 fixedly attach through the studs 150, 139, respectively, to flanges 146, 138 of the tubular component 136.
Tubular member 136 resides within the transverse bore 130 of the block 85 and rotates freely therein. The ends of member 136 are journalled to the piston 89 through lever arms 102, 104. The funnel shaped entry 145 is positioned facing axially rearward of assembly 34. The cord 32 is dispensed and routed downward through entry 145 of member 136 and exits from the transverse bore 144 along the longitudinal center axis of the end of arm tooling assembly 34. As described previously, spring 82 is in a pre-loaded, state of compression between housing 85 and piston 89 while the cord 32 is applied in a predesigned pattern to the annular outer core surface 43. At the completion of the cord laying sequence or at required interim points in the application process, the cord 32 may be severed through the operation of shear assembly 98. An axial movement of the piston is initiated by a reduction of air pressure at intake 94. Spring 82 thereupon is uncoils and influences the piston 89 axially away from the housing 85. As the piston 89 moves away from the housing 85, the lever arms 102, 104 pull against the ends of the tubular member 136 and impart rotation thereto within housing block 85. As the member 136 rotates, edges defining the funnel shaped entry 145 are rotated into severing engagement against the cord 32 extending through the member 136. The cord 32 is thereby severed. The free end of cord 32, subsequent to the severing procedure, is generally in an axial alignment with the tooling assembly 34.
To re-route the cord 32 down the assembly 34 in order to resume laying cord, air pressure is re-applied through intake 94 and piston 97 is forced into the higher, retracted position of
Rollers 74, 76 are shown in
Assembly of the end of arm tooling 34 will be readily apparent from FIGS. 13 A,B; 16, and 17. The nose block 97 is fixedly coupled to the housing 88 by the pin 67. The motor shaft 54 rotates reciprocally and causes the end of arm tooling to resultantly reciprocally rotate through an angular travel of plus or minus three to eight degrees. A greater or lesser range of pivotal movement may be used if desired. Pivotal movement of commensurate angular travel of in-line rollers 72, 74 is thus effected as best seen from
As seen from FIGS. 3A-C; 5; and 7, end of arm tooling 34 mounts to the C-frame arm 36 and is carried thereby toward and away from the surface 43 of core 42. The C-frame arm 36 is slideably mounted to the Z-axis slide 50 and reciprocally moves end of arm tooling 34 laterally across the surface 43 in a predefined pattern. Adjustment in the Z axis along slide 50 is computer controlled to coordinate with the other axis of adjustment of end of arm tooling 34 to allow for the application of cord to cores of varying sizes. The cord 32 is dispensed from cord let-off spool 28, through a conventional balancer mechanism 34 and to the arm assembly. The end of cord 32 is routed at the end of arm cord tensioning assembly 58 (
Referring to
The reciprocal pivotal movement of the end of arm tooling 34 is carefully coordinated with rotational indexing of the core 42 and lateral movement of the tooling assembly 34. Referring to
The arm assembly 16 A, carrying end of arm tooling 34, is further adjustable along a linear path representing a z-axis as shown in
As will be appreciated, a reciprocal pivoting movement of the end of arm tooling head that alternately places one of the rollers 74, 76 into engagement with cord 32 while disengaging the opposite roller results in several significant advantages. First, in disengaging one of the rollers from the carcass layer, the frictional drag of the disengaged roller is eliminated. As a result, the associated drive motor that drives the end of arm tooling may operate with greater speed and efficiency. Additionally, redundant and unnecessary engagement of the disengaged roller from the cord 32 with the underlying elastomeric layer and the cord is eliminated, reducing the potential for damage to both the cord 32 and the underlying carcass layer. Moreover, in utilizing dual rollers mounted in-line, the speed of cord application is at which the cord 32 is applied to the carcass may be improved and the drive mechanism simplified.
It will be appreciated that the application head portion of the tooling 34 is air spring biased against the surface 43 of core 42 during the application of cord 32 through pressurized intake 94. The air spring created by intake 94 exerts a substantially constant force through nose housing 97 to rollers 74, 76. The biasing force upon rollers 74, 76 is applied to cord 32 as described above, and serves to pressure the cord 32 against a carcass layer previously applied to the core surface 43. The tackiness of the pre-applied layer retains the cord 32 at its intended placement. A more secure placement of the cord 32 results, and the potential for any unwanted, inadvertent post-application movement of the cord 32 from the underlying carcass layer is minimized. At the appropriate time for severing the cord 32 by means of the shearing assembly 98, separation of housings 89 and 85 is effected as shown in
As described previously, to reposition the severed end of the cord 32 for another application cycle, pressurized air is introduced through intake portal 92 and pneumatically forces the free cord end down the axial passageway 80 to the cord outlet 78 between rollers 74, 76. Application of the cord to the carcass layer on the core 42 may then recommence.
With reference to
Referring to FIGS. 18A-D, 19-27. to advance the cords 32 on a specified path 190, the end of arm tooling mechanism 34 which contains the two rollers 74, 76 forms the cord outlet 78 which enables the cord path 190 to be maintained in this center. As illustrated, the cords 32 are held in place by a combination of embedding the cord into an elastomeric compound 192 previously placed onto the toroidal surface 43 and the surface tackiness of the uncured compound. Once the cords 32 are properly applied around the entire circumference of the toroidal surface 43 a subsequent lamination of elastomeric topcoat compound (not shown) can be used to complete the construction of the ply 194. It will be appreciated that more than one cord layer may be applied to the core 42, if desired or required. Additional elastomeric layers may be added to the core and additional cord layers applied as described above. Optionally, if desired, the top or bottom coat of elastomeric material may be eliminated and the cord applied in successive layers to form multiple plies on the core 42.
As illustrated and explained previously, the first roller 76 will embed the cord 32 on a forward traverse across the toroidal surface 43 as illustrated in
The process is repeated to form a series of cords 32 that are continuous and which have the intended preselected optimal pattern. For example, without intent to limit the patterns achievable from the practice of the invention, the toroidal core 42 with the toroidal surface 43 with an elastomeric compound 192 laminated onto it may be indexed or advanced uniformly about its axis with each traverse of the pair of rollers 74,76 to create a linearly parallel path 190 uniformly distributed about the toroidal surface 43. By varying the advance of the cord 32 as the mechanism 34 traverses, it is possible to create non-linear parallel cord paths 190 to tune tire stiffness and to vary flexure with the load.
Preferably the cord 32 is wrapped around the tensioner assembly 58 to adjust and maintain the required tension in the cord 32 (
With reference to FIGS. 18A-D, depicted is a three dimensional view of a cylinder representing how the ply path 190 is initiated along what would generally be considered the bead region 198 of the carcass 194 along the tire sidewall 200 toward the shoulder region 202 of the toroidal surface 43 and then traverses across the toroidal surface 43 in an area commonly referred to as the crown 204 as illustrated in
Other cord patterns may be devised and implemented using the end of arm tooling 34 of the present invention. The speed at which core 42 is rotated and or the speed of the traverse travel of the tooling head 56 across surface 43 may be varied in order to generate patterns of preferred configuration. By way of example, cord laying patterns are depicted in
From the foregoing, it will be appreciated that one aspect of the present invention is to achieve a bi-directional tooling head that may be mounted to reciprocally move in a forward and a reverse direction across an annular surface (such as, but not limited to a tire surface), preferably but not necessarily as the annular surface is rotated. The tooling head includes a plurality of rollers, described above as comprising the dual rollers 74, 76. However, more rollers may be deployed if desired. The rollers act to impress one or more cords on an elastomeric layer on the annular surface in the forward and reverse directions and a tilt mechanism for angular repositioning the rollers into alternative engagement with the annular surface in the forward and reverse directions. At least one roller engages against the annular surface in the forward direction and at least a second roller engages against the annular surface in the reverse direction while the first roller is disengaged.
Yet a further aspect of the invention utilizes the tilt mechanism to simultaneously engage and disengage the first and second rollers from the annular surface. Pursuant to another aspect of the invention, the first and second rollers are mounted to a terminal end of the tooling head in side by side adjacent relationship and define a cord exiting passageway therebetween.
A method for bi-directional tire cord application to an annular surface utilizing the described embodiment and other embodiments apparent to those skilled in the art may be practiced comprising: mounting a tooling head for reciprocal movement in a forward and a reverse direction across the annular surface, the tooling head having a plurality of roller components; impressing one or more cords on an elastomeric layer on the annular surface by at least a first roller component of the tooling head in the forward direction; disengaging the first roller component of the tooling head from the annular surface at the conclusion of tooling head movement in the forward direction; impressing one or more cords on the elastomeric layer on the annular surface by at least a second roller component of the tooling head in a reverse direction; and disengaging the second roller component of the tooling head from the annular surface at the conclusion of tooling head movement in the reverse direction.
The method of the invention may further include pivotally reorienting the tooling head from an initial orientation into a secondary orientation at the conclusion of tooling head movement in the forward direction to disengage the first roller component of the tooling head from the annular surface and engage the second roller component of the tooling head with the annular surface; and
pivotally reorienting the tooling head from the secondary orientation into the initial orientation at the conclusion of tooling head movement in the reverse direction to disengage the second roller component of the tooling head from the annular surface and engage the first roller component of the tooling head with the annular surface.
The apparatus and method of the invention thus efficiently and expeditiously applies a cord layer to an underlying elastomeric layer in the process of building a tire to a final finished dimension, layer by layer, on a core. The cord layer may be configured in varied patterns pursuant to the design and performance requirements of the tire. The tooling head rollers are configured and mounted for alternating contact with the annular surface while each roller alternatively engages the cord along a respective application path. Such a configuration results in no more than necessary surface contact between the applicator head and the annular surface because both rollers are not in constant contact with the surface. The force required to move the applicator end of arm tooling is minimized. Moreover, the mechanism required to move the applicator head along the curvature of a tire carcass is simplified compared to fixed side by side rollers because a change of direction at the conclusion of a cord path traverse is achieved by angular repositionment of the head rollers. Tooling, manufacturing, and maintenance costs are thus minimized as well.
Variations in the present invention are possible in light of the description of it provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the full intended scope of the invention as defined by the following appended claims.
