Abstract:
An enteral feeding adapter is disclosed for use with a medical feeding device to deliver substances into a patient, the enteral feeding adapter being suitable for use with a plurality of infusion sets having distal connectors of differing dimensions. The enteral feeding adapter includes an adapter body containing at least a first port configured for receiving a distal connector of an infusion set, the first port having at least one arcuate sidewall for frictionally engaging the distal connector to sealingly secure the distal connector to the adapter body. The enteral feeding adapter also includes a tube extending between the first port and the medical device for transmitting substances that pass through the first port to the medical device. Related methods are also disclosed.

Description:
This application claims the benefit of Provisional application Ser. No. 60/166,202, filed Nov. 18, 1999. 
     This application claims priority under 35 U.S.C. § 119(e) to prior co-pending Provisional Application Ser. No. 60/166,202, filed Nov. 18, 1999, and such prior application is incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to enteral feeding devices, and more particularly to an enteral feeding adapter which may be used with infusion sets of various sizes. 
     It is a known medical procedure to catheterize a body in order to provide nutritional solutions directly into the stomach or intestines of a patient. A stoma is formed in the stomach or intestinal wall and a catheter is placed through the stoma. Feeding solutions can be injected through a catheter inserted in the stoma to provide nutrients directly to the stomach or intestines (known as enteral feeding). 
     To ensure that the catheter is maintained in the proper position, it is common to use a balloon disposed near the distal (patient) end of the catheter shaft. Inflating the balloon causes the balloon to contact the anatomical structure (i.e., a duct or stomach wall) and thereby prevent the catheter from moving out of the proper position. Such balloon catheter devices may include a “low-profile” head at the proximal end of the catheter shaft. The head, which also helps hold the balloon catheter in place, includes an opening for receiving the feeding solution and a one-way valve for preventing fluids from passing out of the patient via the catheter. U.S. Pat. No. 5,997,503 and 5,997,546, both owned by Applicants&#39; Assignee and incorporated by reference herein for all purposes, disclose examples of low-profile balloon catheters suitable for enteral feeding. 
     The balloon catheters of the cited patents are configured to have a low profile above the user&#39;s skin so that the catheters do not significantly interfere with the patient&#39;s other activities. Because feeding solutions must be fed through the relatively small head of the balloon catheter located atop the patient&#39;s skin, an enteral feeding adapter is often used to transfer the solutions from a source to the catheter. 
     Such adapters often include an elongate feeding tube having connecting elements on each end of the tube. On the distal end of the tube, one of the connecting elements engages the head of the balloon catheter to place the tube in communication with the catheter. The proximal end of the tube typically includes another connecting element in the form of an adapter body for receiving the distal end of an infusion set and also possibly a syringe. The infusion set, in turn, may be connected to an enteral feeding pump, a drip chamber, or any other mechanism for providing a feeding solution. 
     One problem with available enteral feeding adapters is that the adapter bodies are typically configured specifically for use with a particular infusion set of a given diameter and configuration. Most of the commercially available infusion sets, however, are not of a standardized size or configuration. For example, infusion sets marketed by various companies have widely different distal end configurations. Some have substantially cylindrical surfaces at the infusion set distal end, and some have substantially frustoconical surfaces at this location. Additionally, although infusion sets and mating enteral feeding adapters are made in varying sizes, only a very limited range exists where infusion sets and adapters of differing sizes might work together. For example, if a portion of the distal end of an infusion set is configured to be received in an adapter having a cross-sectional diameter of 0.22 inches, the distal end will likely not work in an adapter with a cross-sectional diameter of 0.24 inches. While the infusion set distal end would be received by the adapter body, the engagement would be so loose that the distal end could easily be pulled from the adapter. 
     Thus, infusion sets and the adapters are generally not interchangeable. To provide an enteral feeding adapter for a patient, the infusion set and the enteral feeding adapter typically must be matched. This situation can lead to inventory and supply problems, added cost and complexity, etc. The situation can be compounded greatly where the enteral feeding adapter distal end does not work with all balloon catheters. 
     Frustoconically shaped feeding ports, although they may allow infusion sets of differing sizes to be inserted, inherently may provide only limited contact between the exterior of the distal end of the infusion set and the frustoconical port&#39;s wall. Thus, the distal end of the infusion set may be easily pulled from the feeding port. 
     Thus, there is a need for an improved enteral feeding adapter which can be used with a wide variety of infusion sets while inhibiting inadvertent removal of the distal end of the infusion set from the feeding port of the adapter body. 
     SUMMARY OF THE INVENTION 
     Objects and advantages of the invention will be set forth in part in the following description, or may be apparent from the description, or may be learned through practice of the invention. 
     It should be noted that any given range presented herein is intended to include any and all lesser included ranges. For example, a range of from 45-90 would also include 50-90, 45-80, 46-89, and the like. 
     According to the invention, an adapter is provided for use with an enteral feeding device for delivering substances into a patient. The enteral feeding adapter is suitable for use with a plurality of infusion sets having distal connectors of differing dimensions. The enteral feeding adapter includes an adapter body containing at least a first port configured for receiving a distal connector of an infusion set, the first port having at least one arcuate sidewall for frictionally engaging the distal connector to sealingly secure the distal connector to the adapter body. The arcuate sidewall may have various radii of curvatures, for example between about 0.18 inches to about 0.55 inches. The enteral feeding adapter also includes a tube extending between the first port and the medical device for transmitting substances that pass through the first port to the medical device. 
     A second port may also be defined in the adapter for delivering medicine to the patient, for example by a syringe. 
     The at least one arcuate sidewall may define a proximal portion of the first port, and the first port may further include a second arcuate sidewall, which may be located distally the first arcuate sidewall. If so, the first arcuate sidewall may have a radius of curvature greater than that of the second arcuate sidewall. For example, the first arcuate sidewall may have a radius of curvature of between 0.45 and 0.55 inches and the second arcuate sidewall may have a radius of curvature between 0.22 and 0.24 inches. 
     The first port may also include a third arcuate sidewall distal of the second arcuate sidewall. If so, the first arcuate sidewall may have a radius of curvature of between 0.45 and 0.55 inches, the second arcuate sidewall may have a radius of curvature of between 0.22 and 0.24 inches, and the third arcuate sidewall may have a radius of curvature of between 0.18 and 0.22 inches. 
     The first arcuate sidewall may have a varying diameter between 0.330 and 0.220 inches, the second arcuate sidewall may have a varying diameter between 0.220 and 0.153 inches, and the third arcuate sidewall may have a varying diameter between 0.153 and 0.127 inches. 
     In accordance with another aspect of the invention, an enteral feeding adapter is provided and configured for receiving the distal end of an infusion set for delivering substances into a patient. The enteral feeding adapter includes an adapter body having a first port, the first port having at least a cylindrical first section and a second section defined by a first arcuate sidewall disposed distally of the first section, the first arcuate sidewall being configured to frictionally engage the distal end of the infusion set. The adapter also includes a tube extending between the adapter body and the medical device for transmitting the substances from the infusion set to the medical device and thereafter into the patient. 
     The present invention also includes the methods of utilizing the enteral feeding adapter described herein. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a cross-sectional view of an enteral feeding adapter made in accordance with the present invention; 
     FIG. 2 shows a cross-sectional view of the enteral feeding adapter body of FIG. 1 with the distal end of an infusion set disposed therein; 
     FIG. 3 shows a cross-sectional view of the enteral feeding adapter body of FIG. 1 with the distal end of an infusion set having a different outer diameter than that shown in FIG. 2; 
     FIG. 4 shows a cross-sectional view of another embodiment of an enteral feeding adapter body made in accordance with the present invention; 
     FIG. 5 shows a cross-sectional view of the enteral feeding adapter body of FIG. 4 with the distal end of an infusion set disposed therein; 
     FIG. 6 shows a cross-sectional view of the enteral feeding adapter body of FIG. 4 with the distal end of an infusion set having a different outer diameter than that of FIG. 5; 
     FIG. 7 shows a cross-sectional view of yet another embodiment of an enteral feeding adapter body made in accordance with the present invention; 
     FIG. 8 shows a cross-sectional view of the enteral feeding adapter body of FIG. 7 with the distal end of an infusion set disposed therein; 
     FIG. 9 shows a cross-sectional view of the enteral feeding adapter body of FIG. 7 with the distal end of an infusion set having a different outer diameter than that of FIG. 8; and 
     FIG. 10 shows a cross-sectional view of the enteral feeding adapter body of FIG. 7 with the distal end of an infusion set having a different outer diameter than those of FIGS.  8  and  9 . 
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention will now be described in detail with reference to examples shown in the figures. Each example is provided by way of explaining the invention, and not as a limitation of the invention. Various modifications and variations can be made in the invention without departing from the scope and spirit of the invention. For example, features illustrated or described with respect to one embodiment may be used in another embodiment to yield still a further embodiment. 
     Turning now to FIG. 1, an enteral feeding adapter  100  according to the invention is shown. The adapter  100  includes a proximal adapter body  102 , a distal end connector  106 , and an adapter tube  162  extending therebetween. The adapter body  102  has a first port  104  and a second port  108  is a feed port configured for receipt of the distal end of an infusion set and is discussed in detail below. The port  108  is a medication port configured for the injection of medication therethrough and is sized to receive the distal end of a syringe. One or more grooves  112  are formed in the second port  108  to receive the nub  116  of a cap  120  so as to securely close the medication port  108  when it is not in use. 
     The feed port  104  may also include a groove  124  to receive the nub  128  of a cap  132 . The groove  124  is most often disposed adjacent the proximal end  104   a  of the feed port  104 . A tapered entry  136  can also be provided at the proximal end  104   a  of the port  104 . 
     As shown in FIG. 1, the first port  104  has a channel formed therein which has three general sections. A first proximal section  140  is generally cylindrical with a constant diameter, for example a diameter of approximately 0.330 inches. The first proximal section  140  is designed to receive the distal end of an infusion set (not shown in FIG.  1 ). Typically, the first proximal section  140  will have a diameter slightly larger than that of the infusion set so that the distal end of the infusion set can be advanced through the first proximal section. However, an infusion set which has a portion which is substantially the same outer diameter as the inner diameter of the first proximal section  140  can be nested in the first proximal section  140  if desired. 
     Disposed adjacent the first proximal section  140  is a second proximal section  144  having an arcuate (convex) sidewall  148  which tapers inwardly and distally. (As used herein, an “arcuate sidewall” refers to the sidewall being arcuate from a proximal end to a distal end and not to an annular sidewall defining a cylinder.) 
     It should be appreciated that the adapter  100  according to the invention is not limited to particular dimension or size. By way of example, the arcuate sidewall  148  may have a radius of curvature of about 0.5 inches. For the presently available infusion sets, a radius of curvature of about 0.45 to about 0.55 inches, about 0.22 to about 0.24 inches, or about 0.18 to about 0.22 inches is preferred depending on the diameter of the second proximal section  144 . 
     Disposed distally from the second proximal section  144  is a third proximal section  152  defining a generally straight channel which extends distally until it joins the channel  156  extending through the second port  108 . From that point, a single distal channel  160  is formed for directing enteral feeding solutions and medication to the patient through the adapter tube  162  and the distal end  106  of the adapter  100 . 
     In FIG. 2, a distal end  164  and tube  166  of an infusion set  168  is shown mated with the adapter body  102 . The distal end of the infusion set would be carefully sized to nest in the feed port  104 . However, the arcuate sidewall  148  of feed port  104  accommodates a relatively wide range of outer diameters which can be held in the feed port  104 . 
     The arcuate sidewall  148  forms a channel having a varying diameter. The largest diameter occurs at the top or proximal end  144   a  of the second proximal section  144  and may be, for example, approximately 0.330 inches. At an opposing distal end  144   b  of the second proximal section  144 , the diameter may be, for example, only about 0.220 inches. 
     Thus, the distal end  164  of virtually any infusion set having an outer diameter of any size between 0.330 inches and 0.220 inches will engage the arcuate sidewall  148  and secure the infusion set. The exact point of engagement will depend upon the size of the outer diameter of the infusion set  164 ; the larger the outer the diameter, the closer to the proximal end  144   a  the engagement occurs. Thus, as shown in FIG. 2, the distal end  164  of an infusion set  168  has stepped (and ringed) segments, one outer ring  164   a  of which has an outer diameter of approximately 0.300 inches. The ring  164   a  is held secure adjacent the proximal end  144   a  of the arcuate section  144  defined by sidewall  148 . 
     To further facilitate engagement, the adapter body  102  is preferably formed of flexible pvc or some other slightly deformable substance to maximize the area of the sidewall  148  which engages the distal end  164  of the infusion set  168 . In addition to the above, depending on the configuration of the steps of the distal end  164 , the arcuate sidewall  148  can actually engage an additional step, such as ring  164   b  to provide an even more secure hold of the distal end. 
     In contrast, FIG. 3 shows an alternate infusion set  172  which has a distal end  170  with a frustoconical step  170   a . The distal end  170  of the infusion set is advanced until the proximal end  170   b  of the step  170   a  is only a short distance from the distal end  148   b  of the arcuate sidewall  148 . The step  170   a  then engages the arcuate sidewall  148  as shown in FIG.  3 . An infusion set having a step or ring with an outer diameter between that of the proximal and distal ends  148   a  and  148   b  of arcuate wall  148  would advance to a position between the proximal and distal ends of the arcuate wall. Thus, those skilled in the art will appreciate that a wider range of infusion sets can be used with the feed port  104  of the adapter  100  than with prior art configurations. Further, one significant advantage which the arcuate sidewall  148  provides is that the diameter at the point at which the infusion set distal end engages the sidewall changes gradually. This provides a greater surface area for forming the friction fit necessary to securely hold the distal end, especially for distal end configurations such as that shown in FIG.  3 . 
     FIG. 4 illustrates an embodiment having two arcuate sidewall portions with different diameters. This configuration provides even further improved compatibility with variously sized infusion sets. An enteral feeding adapter  200  includes an adapter body  202  made of flexible pvc or some other similar medical grade material. For simplicity&#39;s sake, no adapter tube or distal end are shown in FIG. 4., but it should be understood that the elements shown in FIGS. 1-3 could be suitably utilized with the adapter body  202  of FIG.  4 . 
     The adapter body  202  includes a first feed port  204  configured for receipt of the distal end of an infusion set and a second medication port  208  provided for the injection of medication. The second port  208  will typically have structures similar to the second port of FIG.  1  and therefore will not be discussed in detail. 
     The first port  204  may include a groove  224  to receive the nub  228  of a cap  232 . 
     The groove  224  is typically disposed adjacent the proximal end  204   a  of the port  204 . A tapered entry  236  can also be provided at the proximal end  204   a  of the port  204 . 
     As shown in FIG. 4, the first port  204  has four general sections. A first proximal section  240  is sized to receive the distal end of an infusion set and may be, for example, approximately 0.330 inches in diameter. Typically, the first proximal section  240  will be slightly larger than the distal end of the feeding set. However, an infusion set could have substantially the same outer diameter as the diameter of the first proximal section  240  and thereby nest snugly in the first proximal section  240 . 
     The adapter body  202  also forms a second proximal section  244  disposed distally from the first proximal section  240 . The second proximal section  244  is defined by an arcuate sidewall  248  so that a proximal end  244   a  of the second proximal section  244  has a larger diameter than a distal end  244   b  of the second proximal section. Optionally, the second proximal section  244  may have a linear portion at either end. For example, a linear portion  250  having a cylindrical shape is disposed at the distal end  244   b  of the second proximal section  244  for spacing purposes. 
     As with the previous embodiment, a preferred radius of curvature for the arcuate sidewall  248  is approximately 0.500 inches. This gradual curve provides sufficient surface area to securely, frictionally engage the distal end of an infusion set. 
     A third proximal section  252  of the feed port  204  is disposed adjacent to and distally from the second proximal section  244 . The third proximal section  252  preferably includes a second arcuate sidewall  256 . As with the sidewall  248  of the second proximal section  244 , the sidewall  256  is arcuate extending from a proximal end  256   a  to a distal end  256   b , but may include a linear portion (not shown) adjacent the distal end  256   b . The proximal end  256   a  may have an inner diameter of approximately 0.220 inches and the distal end  256   b  may have an inner diameter of approximately 0.153 inches. 
     The radius of curvature of the second arcuate sidewall  256  is less than that of the first arcuate sidewall  248 , for example between about 0.22 inches and 0.24 inches. More particularly, the radius of curvature may be about 0.231 inches. 
     The second arcuate sidewall  256  is advantageous in that it enables the adapter body  202  to receive and secure the distal end of an infusion set which has an outer diameter which would not be secured by the first arcuate sidewall  248 . For example, with the diameters stated above, the first arcuate sidewall  248  will receive and secure the distal end of an infusion set having an outer diameter between 0.330 inches and 0.220 inches, and the second arcuate sidewall will receive and secure a distal end having a diameter between 0.22 inches and 0.153 inches. Thus, the adapter body  202  provides a range between about 0.153 inches to 0.330 inches. 
     Disposed distally of the third proximal section  252  is a fourth proximal section  260  defining a generally linear channel which extends distally until it joins the distal channel  264  extending through the second port  208 . From that point, a single distal channel  268  is formed for directing enteral feeding solutions and medication to the patient. 
     FIG. 5 shows the adapter body  202  shown in FIG. 4 mated with the distal portions of end  270  of an infusion set  272 . The distal end  270  is advanced through the first and second proximal sections  240  and  244 , and into engagement with the second arcuate sidewall  256  which forms the third proximal section  252  of the feed port  204 . The distal end  270  of the infusion set has a step  270   a  with an outer diameter of approximately 0.16 inches. Thus, the step  270   a  of the distal end  270  engages the arcuate sidewall  256  near the distal end  256   b . If the step  270   a  of the distal end  270  were larger (i.e. 0.20 inches) it would engage the arcuate sidewall  256  adjacent the proximal end  256   a.    
     Also shown in FIG. 5 is a more proximal step  270   b  of the distal end  270  having a diameter between 0.220 inches and 0.330 inches. The proximal step  270   b  engages the first arcuate sidewall  248  to provide an enhanced engagement between the distal end  270  and the adapter body  202 . 
     FIG. 6 shows the adapter body  202  of FIGS. 4 and 5 with an alternate distal end  274  of an infusion set  276 . The distal end  274  has two steps  274   a  and  274   b  which respectively engage the first and second arcuate sidewalls  248  and  256 . (Step  274   a  comprises a ring as shown). Thus, the adapter body  202 , having two arcuate surfaces can provide two (substantially circular) points of sealing engagement with a distal end of certain infusion sets. However, while a double engagement is desirable, it is not necessary to ensure a secure hold of the distal end of an infusion set. Having a single step firmly engage one of the arcuate sidewalls  248  or  256  is adequate. 
     Thus, the dual arcuate sidewall configuration of the adapter body  202  shown in FIGS. 4 through 6 provides a marked improvement over the prior art because of the broad range of infusion sets with which it can be used. Those skilled in the art will appreciate that modifications can be made so that the adapter body  202  could receive other sizes if desired. 
     FIG. 7 shows a cross-sectional view of another embodiment of an adapter body  302 . The adapter body  302  defines a first feed port  304  and a second medication port  308 . 
     The medication port  308  has one or more grooves  312  formed therein to receive the nub  316  of a cap  320  which is attached to the adapter body  302 . The cap  320  enables the user to securely close the medication port  308  when it is not in use. 
     The feed port  304  is also provided with a groove  324  to receive the nub  328  of a cap  332 . A tapered entry  336  can also be provided in the port  304 . 
     The feed port  304  includes five proximal sections which facilitate the retention of the distal end of an infusion set. The first proximal section  340  is disposed adjacent the proximal end  304   a  of feed port  304  and forms a generally cylindrical void having a diameter of, for example, approximately 0.330 inches. 
     Disposed distally from but adjacent to the first proximal section  340  is a second proximal section  344 . The sidewall  348  which defines the second proximal section  344  tapers inwardly between the proximal end  344   a  and the distal end  344   b  of the second proximal section. The arcuate taper of the sidewall  348  has a radius of curvature, for example between about 0.450 and 0.550 inches, and particularly 0.500 inches. Thus, while the proximal end  344   a  of the second proximal section  344  has an inner diameter of 0.330 inches, the inner diameter decreases to approximately 0.220 by the distal end  344   b . Such a configuration allows the second proximal section  344  to secure infusion sets having outer diameters from between about 0.220 to 0.330 inches. A cylindrical portion  350  may be disposed distally to second proximal section  344 . 
     Disposed distally from the second proximal section  344  is a third proximal section  352 . At a proximal end  352   a , the third proximal section  352  as a diameter of about 0.220 inches. At an opposing distal end  352   b , the diameter of the third proximal section  352  is reduced to 0.153 inches. The reduction is preferably accomplished by a second arcuate sidewall  356  having a radius of curvature between about 0.220 inches and 0.240 inches, and more particularly 0.231. Thus, the distal end of an infusion set with an outer diameter between about 0.220 inches and 0.153 inches will be securely held in the third proximal section  352 . 
     The feed port  304  also includes a fourth proximal section  360 . The proximal end  360   a  of the fourth proximal section  360  is disposed adjacent the distal end  352   b  of the third proximal section  352  and has a diameter of approximately 0.153 inches. The fourth proximal section  360  has an arcuate sidewall  364  so that the section tapers inwardly toward the distal end  360   b . At the distal end  360   b , the sidewall  364  has a diameter which is approximately 0.127 inches. The radius of curvature of the sidewall  364  may be between about 0.18 and 0.22 inches, and more particularly 0.200 inches. 
     Disposed distally from the fourth proximal section  360  is a fifth proximal section  368 . The fifth proximal section  368  forms a generally cylindrical channel which extends distally until it joins a channel  370  extending through the second port  308 . From that point, a single distal channel  374  is formed for directing enteral feeding solutions and medication to the patient. 
     As with the two previous embodiments, the configuration shown in FIG. 7 provides a significant advantage over the prior art in that an infusion set having an outer diameter of between 0.127 inches and 0.330 inches may be snugly nested in the feed port  304 . This is in contrast to the prior art embodiments which typically provide a range of only a few hundredths of an inch. 
     FIG. 8 shows the adapter body  302  of FIG. 7 mated with the distal end  380  of an infusion set  382 . Because the outer diameter of the middle conical step  380   b  of the distal end  380  is varied, the distal end is advanced through the first proximal section  340  and the middle step frictionally engages a significant portion of the arcuate sidewall  348  of the second proximal section  344 . The engagement of the middle step  380   b  with the first arcuate sidewall  348  prevents the upper cylindrical step  308   a  from engaging the same sidewall, and prevents the lower cylindrical step  380   c  from engaging the third arcuate sidewall  364 . 
     In contrast, FIG. 9 shows a similar view of the adapter body  302  of FIGS. 7 and 8. However, the outer diameter of distal most step  384   a  of the distal end  384  of the infusion set  386  shown in FIG. 9 is only about 0.24 inches. Thus, the distal end  384  passes through the first proximal section  340  and frictionally engages the arcuate sidewall  356  of the third proximal section  352 . The remaining steps of the distal end  384  do not engage the adapter body  302 . 
     FIG. 10 shows a similar view of the adapter body  302  to that in FIGS. 7 through 9, but includes a distal end  388  of an infusion set  390  which has a step  388   a  with an outer diameter of about 0.28 inches. Because of the size of the step  388   a , of the distal end  388  and the configuration of the more distal steps, the step  388   a  is the only one which sealingly engages the adapter body  302 . 
     The adapter body  302  shown in FIGS. 7 through 10 provides a marked improvement over the prior art. Rather than receiving the infusion set of a single manufacturer, the adapter body  302  has been demonstrated to securely hold the infusion sets of at least six different manufacturers. Despite the differences in sizes in infusion sets, the adapter body  302  forms an almost universal adapter for connecting infusion sets to gastric balloon catheters. This enables producers of the adapter of the present invention not only to use the adapter with the infusion sets of other manufacturers, it also facilitates the use of gastric balloon catheters and adapters from the same manufacturer. Additionally, clinicians and patients who must change out infusion sets and adapters no longer need to worry about matching the infusion set with the adapter. If the adapter of the present invention is used, the majority of the infusion sets on the market may be used without also requiring changing of the adapter and the gastric balloon catheter. 
     While industry standards require that a distal end/adapter engagement withstand a pull force of about 4 pounds, use of the adapter shown in FIGS. 7 through 10 has consistently provided a pull resistance of 16 to 20 pounds. Thus, not only does the adapter body  302  enable the use of numerous different infusion sets, it provides a secure engagement of the same which is many times that required in the industry. 
     Thus, there is disclosed an improved enteral feeding adapter. Those skilled in the art will appreciate numerous modifications which can be made without departing from the scope and spirit of the present invention. The appended claims are intended to cover such modifications.