Abstract:
A teatcup liner and teatcup assembly are provided with controlled collapse constructions including ribs, notches, sleeves, and thickness variations.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 10/071,332, filed Feb. 8, 2002, now U.S. Pat. No. 6,631,694. This application also claims priority from Provisional U.S. Patent Application Serial. No. 60/355,103, filed Feb. 8, 2002. 
    
    
     BACKGROUND AND SUMMARY 
     Parent Application 
     The parent invention relates to teatcup liners for use in a teatcup assembly for milking a mammal. 
     As known in the prior art, a plurality of teatcups are connected to respective teats suspending from the udder of a mammal such as a cow. Each teatcup assembly has a teatcup liner or inflation around a respective teat and defining a milk flow passage within the liner below the teat, and a pulsation chamber outside the liner between the liner and the teatcup shell, for example U.S. Pat. Nos. 4,269,143, 4,530,307, 5,178,095, 5,218,924, 6,055,931, all incorporated herein by reference. The system has a milking cycle with an on portion and an off portion. Milk flows from the teat towards a milking claw during the on portion, and then to a storage vessel. During the off portion, the liner is collapsed around the teat, to aid in the circulation of body fluids. Vacuum is continuously applied to the milk flow passage within the liner. Vacuum is alternately and cyclically applied to the pulsation chamber between the liner and the teatcup shell, to open and close the liner, all as is known. 
     The parent invention provides a liner series or family enabling the dairyman selectivity in choosing between the trade-off of liner slip versus milk harvest and milking speed. During continuing development efforts, various relationships have been discovered between various liner parameters, and in accordance therewith, a liner series has been developed having at least one and preferably a plurality of parameters which vary liner to liner in optimized manner to afford the noted selectivity. 
     In a further aspect of the parent invention, a particularly cost effective manufacturing method is provided for producing the liner series. 
     Present Invention 
     The present invention arose during continuing development efforts, including related to the noted parent invention. The present invention provides various teatcup liner constructions for desirably controlling collapse of the teatcup liner. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Parent Application 
     FIG. 1 is taken from U.S. Pat. No. 6,055,931 and is a side view partially in section of a teatcup assembly including a teatcup liner for milking a mammal. 
     FIG. 2 is an isometric view of a teatcup liner. 
     FIG. 3 shows a teatcup liner series in accordance with the parent invention. 
     FIG. 4 is a graphical plot of a selected parameter which varies in accordance with the parent invention. 
     FIG. 5 is a graphical plot of the variance of a pair of parameters versus each other in accordance with the parent invention. 
     FIG. 6 is a graphical plot of the variance of another pair of parameters versus each other in accordance with the parent invention. 
     FIG. 7 is a graphical plot of the variance of another pair of parameters versus each other in accordance with the parent invention. 
     FIG. 8 is a graphical plot of the variance of another pair of parameters versus each other in accordance with the parent invention. 
     FIG. 9 is a graphical plot of the variance of another pair of parameters versus each other in accordance with the parent invention. 
     FIG. 10 is a cross-sectional view of a liner. 
     FIG. 11 is like FIG.  10  and shows another embodiment. 
     FIG. 12 is like FIG.  10  and shows another embodiment. 
     FIG. 13 is like FIG.  10  and shows another embodiment. 
     FIG. 14 is like FIG.  10  and shows another embodiment. 
     FIG. 15 is like FIG.  10  and shows another embodiment. 
     FIG. 16 is like FIG.  3  and illustrates a manufacturing method in accordance with the parent invention. 
     Present Application 
     FIG. 17 is like FIG.  1  and shows the present invention. 
     FIG. 18 is like FIG.  2  and shows the present invention. 
     FIG. 19 is a sectional view taken along line  19 — 19  of FIG.  17 . 
     FIG. 20 is a sectional view taken along line  20 — 20  of FIG.  17 . 
     FIG. 21 is a schematic view of a portion of FIG.  17 . 
     FIG. 22 is like FIG.  17  and shows a teatcup assembly in accordance with the invention. 
     FIG. 23 is a sectional view taken along line  23 — 23  of FIG.  22 . 
     FIG. 24 is a sectional view taken along line  24 — 24  of FIG.  22 . 
     FIG. 25 is a side elevation view of one of the components of FIG.  22 . 
     FIG. 26 is a schematic side elevation view of another embodiment of a teatcup liner in accordance with the invention. 
     FIG. 27 is a sectional view taken along line  27 — 27  of FIG.  26 . 
     FIG. 28 is a sectional view taken along line  28 — 28  of FIG.  26 . 
     FIG. 29 is like FIG.  27  and shows another embodiment. 
     FIG. 30 is like FIG.  28  and shows another embodiment. 
     FIG. 31 is like FIG.  21  and shows another embodiment. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Parent Application 
     FIG. 1 shows a teatcup assembly  18  for milking a mammal  20  such as a cow. Teat  22  suspending from udder  24  of the mammal extends into the liner. Teatcup shell  26  is typically a metal, or plastic, member defining an annular pulsation chamber  28  around liner  16  between the liner and the teatcup shell and having a pulsation port  30  for connection to a pulsator valve, as is known. Liner  16  is typically rubber or other flexible material. The lower end of milk tube portion  14  of the liner is connection to a claw, for example U.S. Pat. Nos. 4,537,152 and 5,291,853, incorporated herein by reference, which in turn supplies milk to a storage vessel. As noted above, vacuum is continuously applied to milk passage  32  within the liner through milk tube portion  14 , and vacuum is alternately and cyclically applied to pulsation chamber  28  through port  30 , to open and close liner  16  below teat  22 , all as is known and for which further reference may be had to the above noted incorporated patents. An air vent plug  10  may be inserted through the wall  12  of the milk tube portion  14  of the teat liner, as is known, for example above noted incorporated U.S. Pat. No. 6,055,931. For further background, a teat liner is illustrated in isometric view at  34  in FIG.  2 . 
     FIG. 3 illustrates a teatcup liner series in accordance with the parent invention including in combination a plurality of related teatcup liners comprising n liners L 1  through L n , for example as shown at the nine liners L 1  through L 9 . Each liner such as  40  has an upper mouthpiece  42 , an intermediate barrel  44  defined by a barrel wall  46 , and a lower connecting tube  48 . The barrel extends along an axial direction  50  for receiving teat  22  inserted axially thereinto through mouthpiece  42 . The mouthpiece has an upper lip  52  having an aperture  54  therethrough for receiving teat  22 . Lip  52  has an axial thickness A measured parallel to axial direction  50 . Barrel wall  46  has axially spaced upper and lower portions  56  and  58 . Upper portion  56  of barrel wall  46  has a transverse thickness B measured transversely to axial direction  50 . Lower portion  58  of barrel wall  46  has a transverse thickness C measured transversely to axial direction  50 . Upper portion  56  of barrel wall  46  has inner surfaces  60  defining a hollow interior with an upper transverse span D thereacross taken transversely to axial direction  50 . Lower portion  58  of barrel wall  46  has inner surfaces  62  defining a hollow interior with a lower transverse span E thereacross taken transversely to axial direction  50 . Lip aperture  54  has a transverse dimension taken transversely to axial direction  50  and defining a mouthpiece bore F. Mouthpiece  42  has a cavity  64  between lip  52  and barrel  44 . Cavity  64  has a transverse dimension taken transversely to axial direction  50  and defining a cavity bore G. Cavity  64  has a volume H. 
     In one preferred embodiment, the noted parameters A through H are varied liner to liner from L 1  through L 9  as indicated in the table below, and as set forth in FIG.  3 . The table below gives dimensions for A through G in millimeters (mm). For example, the axial thickness A of lip  52  varies from 2.0 mm for liner L 1  to 3.6 mm for liner L 9 . The table gives dimensions in cubic inches (in 3 ) for H. 
     
       
         
               
             
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 
               
             
             
               
                   
               
               
                 LINER 
               
             
          
           
               
                   
                 L 1   
                 L 2   
                 L 3   
                 L 4   
                 L 5   
                 L 6   
                 L 7   
                 L 8   
                 L 9   
               
               
                   
                   
               
             
          
           
               
                 A (mm) 
                 2.0 
                 2.2 
                 2.4 
                 2.6 
                 2.8 
                 3 
                 3.2 
                 3.4 
                 3.6 
               
               
                 B (mm) 
                 3.2 
                 3.1 
                 3.0 
                 2.9 
                 2.8 
                 2.7 
                 2.6 
                 2.5 
                 2.4 
               
               
                 C (mm) 
                 2.9 
                 2.8 
                 2.7 
                 2.6 
                 2.5 
                 2.4 
                 2.3 
                 2.2 
                 2.1 
               
               
                 D (mm) 
                 20.2 
                 20.4 
                 20.6 
                 20.8 
                 21 
                 21.2 
                 21.4 
                 21.6 
                 21.8 
               
               
                 E (mm) 
                 18.9 
                 19.1 
                 19.3 
                 19.5 
                 19.7 
                 19.9 
                 20.1 
                 20.3 
                 20.5 
               
               
                 F (mm) 
                 20.4 
                 20.3 
                 20.2 
                 20.1 
                 20.0 
                 19.9 
                 19.8 
                 19.7 
                 19.6 
               
               
                 G (mm) 
                 52.95 
                 52.65 
                 52.25 
                 51.85 
                 51.45 
                 51.05 
                 50.65 
                 50.25 
                 49.85 
               
               
                 H (in 3 ) 
                 1.368 
                 1.353 
                 1.336 
                 1.318 
                 1.301 
                 1.283 
                 1.265 
                 1.248 
                 1.230 
               
               
                 A-B (mm) 
                 −1.2 
                 −0.9 
                 −0.6 
                 −0.3 
                 0 
                 0.3 
                 0.6 
                 0.9 
                 1.2 
               
               
                   
               
             
          
         
       
     
     The liner series is characterized by the following relationships, as illustrated in the table and FIG.  3 : axial thickness A of lip  52  continually increases from L 1  through L n , preferably linearly; transverse thickness of barrel wall  46 , including both B and C, continually decreases from L 1  through L n , preferably linearly; the transverse span across the hollow interior, including both D and E, continually increases from L 1  through L n , preferably linearly; mouthpiece bore F continually decreases from L 1  through L n , preferably linearly; cavity bore G continually decreases from L 1  through L n , preferably linearly; cavity volume H continually decreases from L 1  through L n . 
     In the preferred embodiment, B is always greater than C, and D is always greater than E, such that both the barrel wall thickness and the noted transverse span are tapered. In alternate embodiments, the barrel wall thickness and/or the transverse span may be untapered, i.e. straight. 
     Further, in the preferred embodiment, the parameter A−B, i.e. the difference between A and B, varies as illustrated in the table, namely such difference continually increases from L 1  through L 9 , preferably linearly, as further illustrated in FIG.  4 . 
     Further, in the preferred embodiment, in a plot, FIG. 5, of transverse thickness B of barrel wall  46  versus axial thickness A of lip  52  for liners L 1  through L 9 , B decreases as A increases. Further preferably, B decreases linearly with respect to A. 
     Further in the preferred embodiment, in a plot, FIG. 6, of transverse span D versus axial thickness A of lip  52  for L 1  through L 9 , D decreases as A increases. Further preferably, D decreases linearly with respect to A. 
     Further in the preferred embodiment, in a plot, FIG. 7, of axial thickness A of lip  52  versus mouthpiece bore F for L 1  through L 9 , axial thickness A decreases as mouthpiece bore F increases. Further preferably, A decreases linearly with respect to F. 
     Further in the preferred embodiment, in a plot, FIG. 8, of axial thickness A of lip  52  versus cavity bore G for L 1  through L 9 , axial thickness A decreases as cavity bore G increases. Further preferably, A decreases linearly with respect to G. 
     Further in the preferred embodiment, in a plot, FIG. 9, of axial thickness A of lip  52  versus cavity volume H for L 1  through L 9 , axial thickness A decreases as cavity volume H increases. Further preferably, A decreases linearly with respect to H. 
     The disclosed combination enables selection of desired milking characteristics. Liner L 1  provides the highest milk harvest and highest milk speed, but also the greatest liner slip. Liner L 9  provides the lowest liner slip and also the lowest milk harvest and milking speed. The dairyman can choose the right balance and trade-off for his particular needs. As he moves left to right in FIG. 3, liner slip reduces as does milk harvest and milking speed. As he moves right to left in FIG. 3, liner slip increases as does milk harvest and milking speed. 
     The liner is preferably round as shown at  66  in FIG.  10 . The liner may additionally include a plurality of ribs such as  68 , FIGS. 11 and 2, extending axially along the barrel. The ribs may be external as shown, and/or internal. The liner may be triangular as shown at  70  in FIG.  12 . The liner may be square as shown at  72  in FIG.  13 . The liner may be oval as shown at  74  in FIG.  14 . The liner may be fluted as shown at  76  in FIG.  15 . 
     The various combinations of parameters providing the noted selectivity of milking characteristics are set forth in the claims. Deflection of lip  52  is varied by parameter A, and may additionally or alternately be varied by varying the shore hardness of the lip material. Liner barrel tension is varied by varying the noted wall thickness B and C, and may alternately or additionally be varied by the addition of the noted ribs and/or changing the cross-section of individual ribs and/or changing liner material and/or changing barrel length. 
     There is further provided a simple and particularly cost effective and economical manufacturing method for making the teatcup liner series. The method involves: forming a first of the liners L 1  in a mold  80 , FIG. 16, having a first removable core C 1  inserted therein, the mold forming the outer profile surface  82  of liner L 1 , the core C 1  forming the inner profile surface  84  of liner L 1 ; forming a second of the liners L 2  in the same mold  80  having a second removable core C 2  inserted therein, the mold  80  forming the outer profile surface  86  of liner L 2 , the core C 2  forming the inner profile surface  88  of liner L 2 ; forming the remainder of the liners through L n , e.g. L 3  through L 9 , in the same mold  80  having respective removable cores through C n , e.g. C 3  through C 9 , inserted therein, the mold  80  forming the outer profile surface of the liners through L n , the cores through C n  forming the inner profile surfaces of the liners through L n , e.g. cores C 3  through C 9  form the inner profile surfaces for liners L 3  through L 9 , respectively. The same mold  80  is used for each of the liners L 1  through L 9 . The outer profile surface is the same for each of liners L 1  through L 9 . Different cores C 1  through C 9  are used for liners L 1  through L 9 . The inner profile surface is different from liner to liner according to C 1  through C 9 . Any or all or some combination of the noted parameters A-H are varied liner to liner according to C 1  through C 9 . The cores change a selected dimensional parameter or parameters. This is particularly desirable from a manufacturing standpoint because of the savings in tooling cost by using a single mold to produce the liner series, rather than multiple molds, i.e. one for each liner. Instead, different cores are used to provide the variance liner to liner in the series. Cores are significantly less expensive than a mold. 
     Present Invention 
     FIGS. 17 and 18 show a teatcup liner  100  in accordance with the present invention. The liner has an upper mouthpiece  102 , a barrel  104  depending downwardly from the upper mouthpiece and defined by a barrel wall  106 , and a lower connecting tube  108  depending downwardly from the barrel. The barrel extends axially along an axis  110  for receiving teat  22 , FIG. 1, inserted axially thereinto through the mouthpiece at lip aperture  112  of mouthpiece lip  114 . Barrel wall  106  has a wall thickness  116  transverse to axis  110 . A plurality of ribs  118 , for example three such ribs, extend axially along barrel wall  106  and have a rib thickness  120  transverse to axis  110 . At least one of the wall thickness  116  and the rib thickness  120  varies as the barrel and the ribs extend axially, and in preferred form, both such thicknesses  116  and  120  vary. Barrel wall thickness  116  varies from a larger thickness  122  to a smaller thickness  124  as barrel wall  106  extends axially downwardly away from mouthpiece  102 . Reference is made to the cross-sectional views in FIGS. 19 and 20 showing the noted different barrel wall thicknesses  122  and  124 . Rib thickness  120  varies from smaller thicknesses  126  to larger thicknesses  128  as rib  118  extends axially downwardly away from mouthpiece  102 . Reference is made to the cross-sectional views in FIGS. 19 and 20 showing this variance in rib thickness from  126  in FIG. 19 to  128  in FIG.  20 . FIG. 21 is a schematic sectional view further illustrating the reverse tapering of rib  118  relative to barrel wall  106 , showing that rib  118  becomes thicker and barrel wall  106  becomes thinner as they extend axially downwardly away from mouthpiece  102 . 
     FIGS. 22-25 show a further embodiment and use like reference numerals from above where appropriate to facilitate understanding. FIG. 22 shows a teatcup assembly  130  including an outer teatcup shell  132 , like shell  26  in FIG. 1, having a top end  134  and a bottom end  136 . Connecting tube  108  of teatcup liner  100  extends through aperture  138  in bottom end  136  of the shell. FIG. 22 shows a partially assembled position. Assembly is completed by pulling connecting tube  108  rightwardly to seat annular groove  140  in aperture  138 , to the completed assembled condition shown in FIG.  1 . Teatcup liner  100  includes the noted upper mouthpiece  102 , barrel  104  depending downwardly from mouthpiece  102 , and connecting tube  108  depending downwardly from barrel  104 . Mouthpiece  102  is at top end  134  of teatcup shell  132 . Barrel  104  extends axially along axis  110  for receiving teat  22 , FIG. 1, inserted axially thereinto through mouthpiece  102 , namely through lip aperture  112  of mouthpiece lip  114 . Barrel  102  has the noted plurality of ribs  118  extending axially therealong and projecting radially outwardly therefrom. A sleeve  142  is provided in teatcup shell  132  in the annular space  144  between teatcup shell  132  and barrel  104 . Sleeve  142  engages ribs  118  in interference fit, to be described. 
     Sleeve  142  is a tubular member having a plurality of axially extending slots  146 , FIG. 25, receiving ribs  118 , preferably three slots if there are three ribs. Each slot has a first open axial end  148  receiving a respective rib  118  axially slidable thereinto. Each slot has a distally opposite second closed axial end  150  blocking axial sliding of a respective rib  118  therepast. Ribs  118  have enlarged outer ends  152 , FIG. 24, retaining the rib in the respective slot. Open axial end  148  has a beveled entrance  154  receiving and guiding the respective rib  118  therein. Sleeve  142  has a top end  156  at open axial ends  148  of slots  146 , and has a bottom end  158  axially spaced below closed axial ends  150  of slots  146 . Sleeve  142  has a portion  160  between closed axial ends  150  of the slots and bottom end  158  of the sleeve, which portion  160  is a continuous band around the perimeter of the sleeve structurally supporting portions such as  162  of the sleeve extending axially upwardly therefrom between slots  146 , such that sleeve  142  is a one-piece member. 
     Sleeve  142  is mounted to teatcup liner  100  prior to insertion into outer teatcup shell  132 . Sleeve  142  is slid axially upwardly onto and around teatcup liner  100  such that slots  146  slide upwardly along ribs  118 , trapping the ribs therein against radial movement due to outer enlarged portions  152 , FIG.  24 . Sleeve  142  is thus mounted to teatcup liner  100  and circumscribes barrel  104 . This subassembly of sleeve  142  and teatcup liner  100  is then inserted as a unit into teatcup shell  132 , and is removable as a unit from teatcup shell  132 . The assembled subassembly of sleeve  142  and teatcup liner  100  is inserted downwardly into teatcup shell  132 . This is desirable because it enables use of standard teatcup shells  132  without modifying the latter to retain ribs  118  against radial inward collapse. The liner collapses along sections such as  164 , FIG. 24, between the ribs, which, in the case of three ribs, provides triangular collapse. 
     Barrel wall  106 , FIG. 22 has the noted wall thickness  116 , FIG. 17, transverse to axis  110 . Ribs  118  have the noted rib thickness  120 , FIG. 17, transverse to axis  110 . At least one and preferably both of wall thickness  116  and rib thickness  120  in FIG. 22 vary as barrel  104  and ribs  118  extend axially. As shown in the sectional views in FIGS. 23 and 24, barrel wall thickness varies from larger thicknesses  122 , FIG. 23, to smaller thicknesses  124 , FIG. 24, as barrel  104  extends axially downwardly away from mouthpiece  102 . The rib thickness varies from smaller thicknesses  126 , FIG. 23, to larger thicknesses  128 , FIG. 24, as ribs  118  extend axially downwardly away from mouthpiece  102 . 
     FIG. 26 schematically shows another teatcup liner  170  including an upper mouthpiece  172 , a barrel  174  depending downwardly from upper mouthpiece  172 , and a lower connecting tube  176  depending downwardly from barrel  174 . Barrel  174  extends axially along an axis  178  for receiving teat  22 , FIG. 1, inserted axially thereinto through mouthpiece  172 , as above. Barrel  174  has an upper section  180  and a lower section  182 . Upper section  180  is round in lateral cross-section taken transversely to axis  178 , as shown at the sectional view in FIG.  27 . Lower section  182  is triangular in lateral cross-section taken transversely through axis  178 , as shown in the sectional view in FIG.  28 . The shape of barrel  174  transitions from upper round section  180  to lower triangular section  182  at transition zone  184 . In one embodiment, a plurality of ribs extend axially along barrel  174  along at least one of the upper and lower sections, for example ribs  186 ,  188 ,  190  along upper section  180 , and ribs  192 ,  194 ,  196  along lower section  182 , for example three ribs each, though other numbers of ribs may be used. 
     In a further embodiment, FIG. 29, upper section  180  has two ribs  198 ,  200  extending axially therealong, for fostering flat bi-symmetrical liner collapse. Further in FIG. 29, a first pair of diametrically opposite notches  202 ,  204  are provided in the barrel along the outside thereof and extending axially along upper section  180 , and a second pair of diametrically opposite notches  206  and  208  are provided in the barrel along the inside thereof and extending axially along upper section  180  and equally spaced circumferentially from the first pair of notches  202  and  204 . Ribs  198 ,  200  are along the outside of the barrel at notches  206 ,  208 . 
     The noted triangular cross-section of lower section  182 , FIG. 28, has three apexes  210 ,  212 ,  214 , with three respective sides  216 ,  218 ,  220 , extending therebetween. The noted three ribs  192 ,  194 ,  196  extend axially along the respective three sides  216 ,  218 ,  220 . Barrel  174  has a barrel wall  222  with a wall thickness  224  transverse to axis  178 . In a further embodiment, FIG. 30, wall thickness  224  at lower barrel section  182  at the three sides  216 ,  218 ,  220  is less than the wall thickness at the three apexes  210 ,  212 ,  214 , for example as shown at thin tapered wall thickness section  226  as compared to wall thickness section  228 , to foster triangular collapse, as shown in dashed line at  230 . 
     In further embodiments, barrel  174  does not have a lower triangular section  182 , and instead the barrel has the noted shape of upper section  180  along its entire axial length between upper mouthpiece  172  and lower connecting tube  176 , in which embodiment the barrel may have the notch and rib structure described above, for example, FIG.  29 . In another embodiment, barrel  174  has the shape of the noted lower section  182  along the entire axial length thereof, in which embodiment the barrel may have the noted rib structure of FIG. 28 or the noted tapered wall thickness structure of FIG.  30 . In further embodiments, ribs  186 ,  188 ,  190  of FIG.  27  and/or ribs  192 ,  194 ,  196  of FIG.  28  and/or ribs  198 ,  200  of FIG. 29 have the varying radial thickness as they extend axially as shown in FIGS. 17-24, and may also have the remaining features of such ribs as shown in the latter noted figures. 
     FIG. 31 shows a portion of another teatcup liner  240  including an upper mouthpiece  242 , and a barrel  244  depending downwardly from upper mouthpiece  242  and defined by a barrel wall  246 . The barrel extends axially along an axis  248  for receiving a teat  22 , FIG. 1, inserted axially thereinto through mouthpiece  242 . Barrel wall  246  has a wall thickness  250  transverse to axis  248 , which wall thickness varies as barrel  244  extends axially. In the preferred embodiment, the wall thickness becomes thinner as the barrel extends axially downwardly away from mouthpiece  242 . Further, in the preferred embodiment, a circumferential step  252 , preferably an annular step in the case of a round liner, varies the wall thickness of barrel wall  246  as the barrel extends axially downwardly away from mouthpiece  242 . Barrel wall  246  has a first wall thickness  254  above step  252 , and a second wall thickness  256  below step  252 . Wall thickness  256  is less than wall thickness  254 . Barrel wall  246  has an inner surface  258  defining a hollow interior  260  in the barrel, and has an outer surface  262  on the opposite side of the barrel wall. Step  252  is in outer surface  262  of barrel wall  246 . 
     It is recognized that various equivalents, alternatives and modifications are possible within the scope of the appended claims.