2. Description of the Prior Art Most bicycles are equipped with some type of unidirectional clutch, known as a freewheel, to permit the rider to coast such that the peddles do not rotate while the tires do. These devices allow the rear wheel, which is connected to one or a series of sprockets and a chain, which in turn is connected to a front sprocket, to overrun, or rotate faster than, the front and rear

tension on the chain so that a gear change may be ma Heretofore, bicycles which provide this *back pedalling" fiβat have done so through the use of a ratchet and pawl arrangeme which includes a series of pivotable spring-loaded teeth connec to a fixed member in the hub engageable by corresponding ratc members connected to a rotatable member. Such an arrangem requires the ratchet member to be moved into a positibn engagement relative to the pawl when beginning to pedal, wh often requires the rider to pedal forward before the chain engag the sprockets. Further, the ratchet and pawl arrangement occupi a substantial amount of space due to size requirements and th limits the number of ratchet members that can be used. A sti further disadvantage is that the ratchet and pawl arrangement noisy. It would therefore be desirable to provide a freewhe for use with a bicycle that is compact, lightweight, and provid instantaneous engagement when changing from the freewheeling, back peddling, state to the torque transmitting, or pedallin state. SUMMARY OF THE INVENTION It is a principle object of the instant invention provide a bicycle hub which incorporates a novel freewheel h^fc i lightweight, compact, quiet, and can be readily adapted to 'mos bicycles as presently manufactured. It is also an object of the instant invention to pr vid a freewheel for use with a bicycle which provides instantaneou

provides instantaneous lock-up when changing from the coasting or back pedalling to the pedalling state. It is a further object of the present invention to provide a bicycle freewheel of the hyperboloidal type. It is a still further object of the instant invention to provide a bicycle freewheel of the hyperboloidal type where the inner and outer race members are permanently biased into an optimal position for torque transmission. To accomplish these and other objectives, I have invented a novel bicycle hub which incorporates at least one unidirectional clutch/bearing/freewheel of the hyperboloidal type as an integral component. The invention is comprised generally of an ordinary hub member adapted to rotate about an axle or shaft, the hub member having a pair of opposed parallel flanges defining a plurality of apertures through which are disposed a series of spokes for connecting the hub member to a rim. In one embodiment, the hub is located relative to the axle by a pair of ball bearing arrangements and retaining nuts in a manner to be set forth hereinbelow. In a first embodiment, the hub member receives a correspondingly threaded shoulder portion connected to the outer race member of the hyperboloidal type freewheel. The inner race member of the freewheel is sandwiched between one of the aforementioned ball bearing arrangements, and the sprocket or sprockets connected to

In a second embodiment, the inner race member of the hyperboloidal clutch is threadingly engaged by the threaded portion of the hub member, and the outer race member connected to the sprocket or sprockets. In a third embodiment, a pair of unidirectional clutches of the hyperboloidal type are employed, the first of which performs the freewheeling function, the second of which acts to maintain the inner and outer race surfaces of the first clutch in position with respect to one another so that torque is immediately transferred therebetween when the rider begins to pedal after coasting or back pedalling without backlash. In a fourth embodiment, the inner and outer race members are recessed partially within the hub, resulting in a reduced size hub/freewheel arrangement. In a fifth embodiment, the hub member defines, or receives a press-fit collar which defines, a superderivative hyperboloidal outer race surface of revolution about the axis of rotation of the hub. An inner race member, which defines a subderivative hyperboloidal inner race surface of revolution about the axis, is unidirectionally rotatably disposed concentrically about an axle, which supports and connects the hub to the bicycle fork. The inner race member is rigidly connected to the rear sprocket or sprockets, and is sandwiched between a plurality of cylindrical, thrust transmitting, rollers disposed between the inner and

supports the second end of the bicycle hub with respect to the axle. The inner and outer race surfaces of the freewheel are located generally wholly between the parallel flanges within the hub. As such, the hub occupies an absolute minimum of space, allowing the rear sprocket to be comprised of as few as eight teeth. Prior art rear sprockets have been required to be comprised of 14 or more teeth. In a sixth embodiment, the hub member is constructed of a phenolic plastic, and the outer race member stamped or otherwise formed out of a thin sheet material and shaped to define a superderivative hyperboloidal outer race surface of revolution. The inner race member, which is rigidly connected to the rear sprocket or sprockets, may likewise be formed of a phenolic material, and be integrally connected to a thin- walled sheet material member defining a subderivative hyperboloidal inner race surface of revolution. The orientation of the inner and outer ball bearing races is selected such that the inner and outer race surfaces of the hyperboloidal freewheel are normally biased into positive engagement with the cylindrical thrust transmitting rollers used with the freewheel. By "positive" engagement is meant that the rollers are all disposed at a similar angle with respect to radial planes, each making line contact with the subderivative hyperboloidal inner race surface of revolution along a

hyperboloidal outer race surface of revolution along a generator of the outer race surface. In accordance with these and other objects which will become apparent hereinafter, the instant invention will now be described with particular reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view of the first embodiment of the instant invention. Figure 2 is an exploded view of the first embodiment of the instant invention. Figure 3 is a cross-sectional view taken along lines 3-3 of Figure 1. Figure 4 is a schematic representation of the embodiment shown in Figures 1 through 3 illustrating the force relationships involved in keeping the hyperboloidal clutch self-aligned. Figure 4A is an enlargement of the area of detail indicated as 4a shown in Figure 4. Figure 5 is a partial cross-sectional view of a second embodiment of the instant invention. Figure 6 is a cross-sectional view of a third embodiment of the instant invention. Figure 7 is a schematic view of the rollers utilized in the third embodiment of my invention. Figure 8 is a cross-sectional view of a fourth embodiment of the instant invention.

Figure 10 is an exploded view of the fifth embodiment of the instant invention. Figure 11 is a cross-sectional view of the fifth embodiment of the instant invention taken along lines 11-11 of Figure 9. Figure 12 is a schematic representation of the embodiment shown in Figures 9 through 11 illustrating the force relationships involved in keeping the hyperboloidal clutch self-aligned. Figure 12A is an enlarged view of the area of detail indicated as 12A in Figure 12. Figure 13 is a cross-sectional view of the sixth embodiment of the instant invention. Figure 14 is a cross-section of the sixth embodiment of the instant invention taken along lines 14- 14 of Figure 13. Figure 15 is a schematic representation of the embodiment shown in Figures 13 and 14 illustrating the force relationships involved in keeping the hyperboloidal clutch self-aligned. Figure 15A is an enlarged view of the area of detail indicated by 15A in Figure 15. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, Figures 1 through 3 show a first embodiment of the novel bicycle hub 10 which is comprised of a central hub member 12 defining a pair of parallel, opposed, spoke flanges 14,

apertures 18 adapted to receive spokes (not shown) to attach hub member 12 to a bicycle rim (not shown) . Hub member 12 is rotatably disposed about axle 20. Axle 20 is provided with first and second threaded end segments 21, 22, respectively adapted to receive corresponding threaded elements (not shown) so as to connect hub assembly 10 to a bicycle frame (not shown) .

Hub member 12 is located on axle 20 by nuts 24, 25, and inner ball bearing race members 28, 29. Spherical balls 30 isolate hub member 12 from axle 20. The first end of hub member 12, shown to the left in Figure 1, is provided with an extended shoulder 34 defining internal threads thereon. Freewheel 35 is provided having an outer race member 38 having external threads corresponding to the internal threads on shoulder 34. In this manner, outer race member 38 of freewheel 35 can be attached to hub member 12. An inner race member 48 is sandwiched between outer race member 38 and balls 30. Inner race member 48 defines an outer ball bearing race 53' and is permitted to rotate freely in both the clockwise and counter- clockwise directions with respect to axle 20. Inner race member 48 is likewise permitted to rotate freely with respect to outer race member 38 and thus hub member 12 with respect to one direction of relative rotation thereof, but is not permitted to rotate with respect to

member 48. Additional sprockets of varying diameters may be added to sprocket 55 to permit the rider to vary the gear ratio of the bicycle. Freewheel 35 functions as a unidirectional clutch and bearing and is comprised of outer race member 38, which defines a super-derivative hyperboloidal outer race surface of revolution 40 about the axis of rotation 23 of freewheel 35 and axle 20, an inner race member 48 defining a sub-derivative hyperboloidal surface of revolution 50 about axis 23, and a plurality of thrust transmitting rollers 52 disposed in the annular volume created by the confronting outer and inner race surfaces 40, 50. Rollers 52 are all similarly inclined with respect to radial planes and each makes line contact with both the outer and inner race surfaces 40, 50, respectively, along generators of those surfaces. Outer race member 38 has associated therewith at the smaller end of the freewheel 35 an annular shoulder member 42 adapted to support the rollers axially thereof. Inner race member 48 has associated therewith a shoulder 51 adapted to support rollers 52 axially thereof opposite shoulder 42. Preferably, annular thrust washer 54 is slidably disposed on shoulder 51 and sandwiched between first ends of rollers 52 and shoulder 51 to facilitate sliding movement of the rollers with respect to shoulder 51 in the freewheeling mode. Likewise, in the preferred embodiment, a second thrust

facilitate sliding movement of rollers 52 with respect to shoulder 42 in the freewheeling mode. The hyperboloidal type clutch/bearing/freewheel disclosed herein for all embodiments is constructed and arranged in accordance with the disclosure set forth in my co-pending U.S. patent application Serial No. 07/418,795, filed October 3, 1989, which is incorporated herein by reference as though fully set forth herein. Because friction forces duringthe freewheeling mode between the rollers and the race surfaces tend to cause the race members 38, 48 to separate and thereby increase the distance between outer and inner race surfaces 40, 50 respectively, it is desired to provide means for maintaining the inner and outer race surfaces at the appropriate distance from one another at all times. Failure to do so may result in the failure of the freewheel 35 to lock up instantaneously when torque is applied to sprocket 55 after freewheeling. To accomplish this, ball bearing assembly A acts to maintain inner race member 48 in a biased condition so that even if wear occurs to the rollers 52 or the outer or inner race surfaces 40, 50, respectively, outer and inner race members 38, 48 will be properly aligned to avoid backlash. Inner race member 48 must be permitted to move axially at least slightly relative to outer race member 38. Any other suitable apparatus for maintaining such alignment may be employed.

to urge inner and outer hyperboloidal race surfaces 50, 40 in operative engagement with rollers 52. In this way, when hyperboloidal clutch 35 is freewheeling, the natural tendency of the inner and outer race members 28, 38 to move apart from each other is counteracted by forces F _χ . Because the radius of curvature of inner and outer ball bearing races 53, 53' is greater than the radius of curvature of the spherical balls 30, a force represented by the vector F _R is imposed on outer ball bearing race 53' by said balls 30 resulting from the weight force F ₁ which is approximately one-half the weight of the rider and bicycle and the counteracting forces F ₂ of the bicycle frame acting upon axle 20. Resolving the force F _R into its x and y components F _χ and F _r , respectively, it is well settled that

F _χ = F _R cos θ

so long as F _χ is greater than the separation force F _A tending to cause inner race member 48 to separate from outer race member 38, no backlash will occur when freewheel/bearing 35 is switched from the freewheeling to the torque transmitting state. In the alternative, hub member 12 may be supported for rotation about axle 20 by the use of an appropriate tapered roller bearing arrangement. By selecting such a roller bearing which exerts a net axial

race members 48, 38 remain biased into optimal, positive, alignment. A second embodiment of the invention is shown in Figure 5 and is comprised of hub member 12 having connected thereto a modified freewheel 65 connected to hub member 12 via threaded shoulders 34 and 68. Freewheel 65 is comprised of an inner race member 70 defining a sub-derivative hyperboloidal inner race surface of revolution 72 about axis 23, an outer race member 80 connected to sprocket 85 and defining a super- derivative hyperboloidal outer race surface of revolution 82 about axis 23. Inner and outer race surfaces 72, 82 are positioned in confronting relationship and establish an annular volume therebetween in which are disposed a plurality of cylindrical thrust transmitting rollers 78, all said rollers 78 being similarly inclined with respect to radial planes and making line contact with both the inner and outer race surfaces 72, 82 along generators of those surfaces, respectively. An annular thrust washer 76 is preferably employed between shoulder 72 of inner race member 70 and first ends of rollers 78 nearest the large diameter end of the clutch. Washer 76 facilitates sliding movement of the rollers with respect to shoulder 74 during the freewheeling mode. Also in the preferred embodiment, a second annular thrust washer 82 is provided between second ends of rollers 78 and retaining ring 84 to

ring 84 supports the rollers axially thereof and is preferably removably but rigidly connected to shoulder 75 of inner race member 70, as by threads as shown in Figure 4. Ring 84 may also be a snap on circling or other connector. Figure 6 shows a third embodiment of the instant invention wherein freewheel 95 is comprised of a pair of unidirectional clutches of the hyperboloidal type, both having rollers oriented at such an angle that torque is transmitted with respect to rotation of the inner race member relative to the outer race member in a first direction, and freewheeling permitted therebetween with respect to rotation in the opposite direction. Freewheel 95 is comprised of an inner race member 96 connected to shoulder 34 of hub member 12 by internally threaded shoulder 97. Inner race member 96 defines a first stage subderivative hyperboloidal inner race surface of revolution 98 about axis 23. Inner race member 96 also defines a subderivative second stage hyperboloidal inner race surface of revolution 106 about axis 23. Outer race member 99 defines a first stage superderivative hyperboloidal outer race surface of revolution 100 situated in confronting relationship with inner race surface 98 to form an annular volume therebetween in which are located a plurality of cylindrical thrust transmitting rollers 102. All said rollers are similarly inclined with respect to radial

surfaces, respectively. Outer race member 99 also defines a second stage hyperboloidal superderivative outer race surface of revolution 108 about axis 23, which is likewise disposed in confronting relationship with inner race surface 106, forming an annular volume therebetween. A plurality of cylindrical thrust transmitting rollers 110 are disposed in said volume, all being similarly inclined with respect to radial planes and making line contact with each of inner and outer race surfaces 106, 108, respectively along generators thereof. Retaining ring 103 is connected to inner race member 96 and forms an annular shoulder adapted to support rollers 102 axially thereof. In the preferred embodiment, an annular thrust washer 104 is sandwiched between first ends of said rollers 102 and said retaining ring 103 to facilitate siding movement of said rollers 102 with respect to ring 103 in the freewheeling mode. A second thrust washer 105 may be used to support the ends of rollers 102 opposite washer 104, and may be disposed in sliding relationship with shoulder 116, which may have integrally connected therewith a bearing arrangement such as ball bearings. Second stage hyperboloidal freewheel/bearing/clutch II has associated therewith an annular shoulder member 107 adapted to support rollers 110 axially thereof. Thrust washer 112 is preferably sandwiched between first ends of rollers 110 and shoulder member 107 to facilitate sliding movement of rollers 110

sliding movement of second ends of rollers 110 with respect to shoulder 116. Both thrust washers 105 and 114 will be associated with said ball bearings 119. Sprocket 115 is connected to outer race member 99 as by threading, welding, etc. Figure 7 shows the force relationships imposed on rollers 102 and 110 to cause the second stage clutch/bearing/freewheel to exert a net axial force F _A in the direction of the first stage clutch/bearing/freewheel to cause said first stage clutch I to be maintained in proper alignment during the freewheeling mode so that race surfaces 98, 100 are in operative engagement with rollers 102 and the point in time when both clutches are switched from the freewheeling to the torque transmitting mode. Forces F _A2 and F _A1 are derived by resolving the components of normal forces F _N2 and F _N1 , respectively, into their axial components. These normal forces F _N2 , F _N1 arise due to the force F ₁₇ and counteracting forces F ₂ , caused by the weight of the rider and bicycle. Figure 8 shows a fourth embodiment of the bicycle hub of the instant invention wherein clutch/bearing/freewheel 125 is recessed within hub member 12 to form a modified hub member of substantially reduced size. Freewheel 125 functions in accordance with the disclosure set forth for freewheel 35 shown in Figures 1 through 3. Figures 9 through 12 show a fifth embodiment of

opposed, spoke flanges 14, 16 which define a plurality of spoke-end receiving apertures 18 adapted to receive spokes (not shown) to attach hub member 212 to a bicycle rim (not shown) . Hub member 212 is rotatably disposed about axle 220. Axle 220 is provided with first and second threaded end segments 221, 222, respectively, adapted to receive corresponding threaded elements (not shown) so as to connect hub assembly 210 to a bicycle frame (not shown) , as well known in the field Hub member 212 is located on axle 220 by connecting means such as nuts 224, 225, and inner ball bearing race members 228, 229. Spherical balls 230 isolate hub member 212 from axle 220. The first end .of hub member 212, shown to the left in Figure 1, is provided with an internal recess 234 adapted to receive outer freewheel race member 238 press- fit or otherwise connected to hub member 212. An inner race member 248 is sandwiched between outer race member 238 and balls 230. Inner race member 248 defines an outer ball bearing race 253 and is permitted to rotate freely in both the clockwise and counter-clockwise directions with respect to axle 220. Inner race member 248 is likewise permitted to rotate freely with respect to outer race member 238, and thus hub member 212, with respect to one direction of relative rotation thereof, but is not permitted to rotate with

255 may be formed integrally with inner race member 248. Additional sprockets 255 of varying diameters may be added to sprocket 255 to permit the rider to vary the gear ratio of the bicycle. It is to be particularly noted, however, that an eight-tooth sprocket 255 may be used, reducing the size and weight thereof by 30% to 40%. Freewheel 235 functions as a unidirectional clutch and bearing and is comprised of outer race member 238, which defines a super-derivative hyperboloidal outer race surface of revolution 240 about the axis of rotation 223 of freewheel 235 and axle 220, an inner race member 248 defining a sub-derivative hyperboloidal inner race surface of revolution 250 about axis 223, and a plurality of thrust transmitting cylindrical rollers 252 disposed in the annular volume created by the confronting outer and inner race surfaces 240, 250. Rollers 252 are all similarly inclined with respect to radial planes and each makes line contact with both the outer and inner race surfaces 240, 250, respectively, along generators of those surfaces. Inner race member 248 has associated therewith at the large diameter end A of the freewheel 235 a first annular shoulder member 242 adapted to support the rollers axially thereof. Outer race member 238 has associated therewith a second annular shoulder 251 adapted to support rollers 252 axially thereof opposite shoulder 242. Preferably, a first annular thrust washer

facilitate sliding movement of the rollers with respect to shoulder 242 in the freewheeling mode. Likewise, in the preferred embodiment, a second thrust washer 256 is slidably associated with shoulder 251 at the second, or smaller diameter end B of clutch/bearing freewheel 235 to facilitate sliding movement of rollers 252 with respect to shoulder 251 in the freewheeling mode. Because friction forces generated during the freewheeling mode between the rollers 252 and the race surfaces 240, 250 tend to cause the race members 238, 248 to separate and thereby increase the distance between outer and inner race surfaces 240, 250 respectively, it is desired to provide means for maintaining the inner and outer race surfaces in line contact with each of rollers 252 at all times. Failure to do so may result in the failure of the freewheel 235 to lock up instantaneously when torque is applied to sprocket 255 after freewheeling. To accomplish this, ball bearing assembly C acts to maintain inner race member 248 in a biased condition so that even if wear occurs to the rollers 252 or the outer or inner race surfaces 240, 250, respectively, outer and inner race members 238, 248 will be properly aligned to avoid backlash. Inner race member 248 should be permitted to move axially at least slightly relative to outer race member 238. Any other suitable apparatus for maintaining the inner and outer race surfaces 240, 250 in line contact with each other may be

Figure 12 shows in schematic representation the forces acting on the outer ball bearing races which tend to urge inner and outer hyperboloidal race surfaces 250, 240 into positive engagement with rollers 252. In this way, when hyperboloidal clutch 235 is freewheeling, the natural tendency of the inner and outer race members 228, 238 to move apart from each other is counteracted by forces F _χ . Because the radius of curvature of inner and outer ball bearing races 253, 253' is greater than the radius of curvature of the spherical balls 230, a force represented by the vector F _R is imposed on outer ball bearing race 253 by balls 230 resulting from the weight force F ₁ which is approximately one-half the weight of the rider and bicycle, and the counteracting forces F ₂ of the bicycle frame acting upon axle 220. Resolving the force F _R into its x and y components, it is well settled that

F _χ = F _R cos θ

So long as F _χ is greater than the separation force F _A tending to cause inner race member 248 to separate from outer race member 238, no backlash will occur when freewheel/bearing 235 is switched from the freewheeling to the torque transmitting state. In the alternative, hub member 212 may be supported for rotation about axle 220 by the use of

F which exceeds the axial force F. exerted on inner race member 248 during freewheeling, inner and outer race members 248, 238 remain biased into positive engagement with rollers 252. In the sixth embodiment of the instant invention, shown in Figures 13 and 14, the inner and outer freewheel race surfaces 350, 340 are defined by inner and outer shell race members 348, 338, which are stamped or otherwise formed out of a thin-walled hardened material such as steel. Preferably, hub member 312 is fabricated of a lightweight, durable material, such as phenolic plastic, and outer shell race member 338 connected thereto so that no movement can occur between outer shell race member 338 and hub member 12. To accomplish this, the outer facing surface of outer shell race member 338 should be treated so as to mate firmly with the corresponding inner facing portion of hub member 312. Inner shell race member 348, which defines a subderivative hyperboloidal inner race surface of revolution 350 about axis of rotation 323 of shaft 320. Inner shell race member 348 is rigidly connected to sprocket member 335, which in turn is connected to outer ball bearing race surface 353'. Like outer shell race member 338, inner shell race member 348 may have its inwardly facing surface treated so as to firmly mate with sprocket member 335 so that there is no slip

be a phenolic plastic. The use of such a lightweight material results in the reduction of weight of the bicycle hub member between 30 to 40%. Inner and outer race surfaces 350, 340 are positioned in confronting relationship and establish an annular volume therebetween in which are disposed a plurality of cylindrical thrust transmitting rollers 352, all said rollers 352 being similarly inclined with respect to radial planes and making line contact with both the inner and outer race surfaces 350, 340 along generators of those surfaces, respectively. An annular thrust washer 354 is preferably employed between shoulder 351 of inner shell race member 348. and first ends of rollers 352 nearest the large diameter end of the clutch shown to the left in Figure 13. Thrust washer 354 facilitates sliding movement of the rollers with respect to shoulder 351 during the freewheeling mode. Also in the preferred embodiment, a second annular thrust washer 356 is provided between second ends of rollers 352 and second annular shoulder 342 formed in outer shell race member 338. Second thrust washer 356 facilitates sliding movement of rollers 352 with respect to shoulder 342 during freewheeling. Both shoulders 351 and 342 support rollers 352 axially. Because friction forces generated during the freewheeling mode between the rollers 352 and the race surfaces 340, 350 tend to cause the race members 338, 348

is desired to provide means for maintaining the inner and outer race surfaces in positive, line, contact with each of rollers 352 at all times. Failure to do so may result in the failure of the freewheel 335 to lock up instantaneously when torque is applied to sprocket 355 after freewheeling. To accomplish this, ball bearing assembly E acts to maintain inner race member 348 in a biased condition so that even if wear occurs to rollers 352 or the outer or inner race surfaces 340, 350, respectively, outer and inner race members 338, 348 will be properly aligned to avoid backlash. Inner race member 348 must be permitted to move axially at least slightly relative to outer race member 338. Any other suitable apparatus for maintaining the inner and outer race surfaces 340, 350 in line contact with each other may be employed. Figure 15 shows in schematic representation the forces acting on the outer ball bearing races 353 ' which tend to urge inner and outer hyperboloidal race surfaces 350, 340 into positive engagement with rollers 352. In this way, the hyperboloidal clutch 335 is freewheeling, the natural tendency of the inner and outer shell race members to move apart from each other as counteracted from each other by forces at F _χ . Because the radius of curvature of inner and outer races 353, 353' is greater than the radius of curvature of the spherical balls 330 used, a force represented by the vector F _R is imposed on

weight of the rider and bicycle, and the counteracting forces F ₂ of the bicycle frame acting upon axle 320. Resolving the force F _R into its x and y components, it is well settled that:

F _χ = F _R cos θ

So long as F _χ is greater than the separation force F _A tending to cause inner race member 348 to separate from outer race member 338, no backlash will occur when freewheel/bearing 335 is switched from the freewheeling to the torque transmitting state. In the alternative, hub member 312 may be supported for rotation about axle 320 by the use of appropriate tapered roller bearing arrangements. By selecting roller bearings which exert a net axial force F _v X which exceeds the axial force FA. exerted on inner shell race member 348 during freewheeling, inner and outer race members 348, 338 remain biased into positive engagement with rollers 352. The instant invention has been shown and described herein in what is considered to be the most practical and preferred embodiment. It is recognized, however, that departures may be made therefrom within the scope of the invention and that obvious modifications will occur to a person skilled in the art.