Abstract:
A filter is provided within a transparent drinking straw. The filter has a dense core region and a less dense outer peripherial region. The filter is retained in place within the straw by frictional forces under static conditions. The frictional forces which maintain the filter in place under static conditions may be overcome by fluid flowing through the straw causing the filter to move within the conduit. The filter may support particulate matter which may be a medication or drug. Accordingly, the device may be used as delivery device for drugs administered by oral ingestion. Movement of the filter from a first to a second position provides a visual indication that a predetemined volume of fluid has passed through the conduit.

Description:
The present invention relates to a filter and its use in conjunction with a tubular conduit. The filter is specifically constructed to fit within a conduit in such a manner that enables it to move in response to flow of liquid under certain conditions. According to the invention, the filter is constructed to have at least two distinct regions, a central core region having a more dense construction and an outer peripheral region having a less dense construction. A filter constructed in such a manner and to predetermined dimensions which compliment the dimensions of a conduit, may be seated within the conduit under relatively static conditions but may travel within the conduit in response to flow of liquid through the conduit. The filter is constructed so that frictional forces maintain the filter in place when it is under static conditions and when it is subject to forces from the flow of air necessary to draw liquid up through the conduit. In the preferred embodiment of the invention, these forces are analogous to the conditions created by an individual drawing air through a filter seated within a conventional drinking straw. The filter is constructed to allow for the passage of air through the conduit with an insignificant pressure drop across the filter. When liquid traveling through the conduit comes in contact with the filter, the force of the liquid on the filter overcomes the frictional forces holding the filter in place within the conduit and causes the filter to move. 
     In a preferred and contemplated embodiment, the device as described above is used in conjunction with a medication delivery system for oral ingestion. 
     BACKGROUND OF THE INVENTION 
     Filters are routinely used within conduits for filtration and their use in such applications is both well known and widespread. In most applications filters are designed to be securely seated against the forces of fluid flow. In connection with prior art directed to the provision of oral medications, it is known to use filters as a substrate to support medication within a conduit such as a drinking straw. Such devices typically contain a single dose of medication which, in some circumstances, is supported by either a screen or a porous material which is wedged between the sidewalls of the straw. Some devices may provide a separate support structure to maintain the screen or filter in place. The prior art also discloses the use of solid impediments which will move within a conduit in response to fluid flow in connection with other applications. Such solid impediments typically have a diameter less than the diameter of the conduit and thus are not designed to frictionally engage the conduit or to be retained in a stationary position. One application where such solid impediments are used is in connection with the regulation and or metering of fluid flow. 
     In connection with the provision of oral medications, straws are frequently used to administer a single dose of a drug. In such devices, fluid enters the straw, passes through the filter, then puts the drug into suspension or solution, and next exits the opposite end of the straw. It is desirable to provide a substrate which would support the drug and allow the patient to draw liquid through the straw and, enable the substrate to move a predetermined distance depending on the volume of fluid which passed through the straw. The movement of the substrate in the device in response to fluid flow would provide a visual indication as to whether a predetermined amount of fluid had passed through the straw and consequently was ingested by a patient. Accordingly, it is one object of the invention to provide a substrate which will both support medication within a straw, allow for the administration of the medication and further allow the substrate to move in response to the flow of fluid. It is a further object of the present invention to provide a material within a conduit which will remain seated within the conduit in response to fluctuations in air pressure, however move in response to fluid flow under conditions analogous to those created and typically encountered using a drinking straw. A further object of the invention is to provide a substrate which allows air to freely travel through an impediment and thus exhibit no response to air flow however, when liquid is allowed to contact the impediment, the impediment may move in response to the flow. A further object of the present invention is to provide a device which provides an indication of whether a predetermined amount of fluid has passed through a conduit. Yet a further object of the invention is to provide a device to assist in the oral delivery of solid medication which provides an indication of whether or not a predetermined amount of fluid has passed through the liquid and thereby provide an indication as to whether or not medication has been ingested. A further object of the invention is to provide a device which is appealing and which provides encouragement to children by providing a positive indication that a medication has passed through a conduit. 
     SUMMARY OF THE INVENTION 
     According to the invention, a filter is constructed from synthetic fibers and provided within a conduit. Both the filter and conduit are manufactured to precise specifications in order to meet certain performance criteria relating to the movement of the filter under preselected operating conditions. In order to construct the filter which will meet the desired performance criteria in a reproducible manner, the various operating parameters are first identified including the dimensions of the conduit and expected forces acting upon the filter. For example, the expected pressure differentials applied to conduits in order to initiate and maintain flow of fluid through the conduit are determined. 
     In the preferred embodiment, a filter is provided which will remain stationary within the conduit until it is subjected to forces from the flow of liquid. In this embodiment, the filter remains stationary within the conduit as air is drawn through the conduit to cause fluid to rise up into and flow through an opening of the conduit. When the flow of fluid comes into contact with the filter, the force imposed by the fluid will dislodge the filter and allow it to move along the tubular passage. The filter impediment is designed to travel from the upstream end of the conduit, along the distance of the conduit until it is impeded by a constriction provided within the conduit at the downstream end. Upon the interruption of fluid flow, the filter impediment is retained in a stationary position at the opposite, downstream end of the conduit. 
     In a preferred embodiment the conduit is similar to a conventional drinking straw having a uniform inner diameter oriented in a substantially vertical position however the ends are modified to prevent the filter from passing out of the straw. The flow of fluid through the straw is accomplished by a person sucking on the downstream end of the straw, located at the upright end. It is contemplated that flow through a conduit could be effected in alternative manners which subject the filter contained therein to analogous forces and, both the movement of the filter and the performance of the device would be substantially similar. For example, in a further contemplated embodiment, flow through the conduit is initiated by drawing back a plunger creating a vacuum in the conduit, such as accomplished using a conventional syringe. In another contemplated embodiment, the conduit is an overflow channel and flow is initiated by gravity. In yet a further contemplated embodiment, a conduit is in communication with a flexible reservoir and flow of the fluid is initiated by compression of the reservoir. 
     In the preferred embodiment, upon application of suction by an individual to the top of the straw, the filter impediment will rapidly travel up the straw until further upward movement is physically impeded by a constriction in the straw. The desired performance characteristics are achieved and optimized by creating a filter having variable densities, wherein a central core region is more dense than an outer peripheral region. While the inner core region provides an increased resistance to flow, the less dense outer peripheral section enables the filter to provide a light frictional force against the sidewalls of the conduit. In the preferred embodiment, the filter is comprised of oriented fibers and the density of the filter is altered by changing the distribution of the fibers. Because the density of the filter is lower along the peripheral region of the filter, fluid traveling through the conduit may flow at a faster rate through the peripheral region. It is contemplated that the increased rate of flow through this region also reduces the frictional forces holding the filter in place against the sidewalls of the conduit. Under normal laminar flow conditions, the flow rate through a conduit would be expected to be at its maximum rate at the innermost region of the conduit due to the frictional forces imposed by the sidewalls of the conduit on the fluid. However, when the filter as described herein is positioned within the conduit, the flow of liquid past the filter will be fastest along the outside or periphery of the conduit and correspondingly is slower through the interior core region having the highest density of fibers. The faster fluid flow around the edges of the filter creates a region having less pressure directly behind or downstream of the filter which may serve to further facilitate movement of the filter through the conduit. It is believed that the flow dynamics associated with the flow through the conduit past a filter having the variable density as described above significantly contributes to the desired movement and performance characteristics of the filter within the conduit. 
     In the preferred embodiment, the oriented fiber filter is placed in a transparent drinking straw and the flow is created by the creation of a vacuum on the top of the straw applied by a person. A powdered medication is provided within the straw and is supported by the filter. In addition to serving as a support medium for the medication, the filter prevents the medication from being dispensed out of the lower end of the straw. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of a conduit containing a filter. 
     FIG. 2 is a plan view of a first embodiment of a filter used in connection with the device. 
     FIG. 3 is an alternative embodiment of a conduit and filter according to the invention. 
     FIG. 4 is an alternative embodiment of the filter used in connection with the invention. 
     FIG. 5 is a schematic representation of an apparatus used to test the filter and conduit combination made in accordance with the invention. 
     FIG. 6 a  is a schematic representation of a filter within a transparent conduit in the initial position prior to subjecting it to predetemined conditions by the apparatus depicted in FIG.  5 . 
     FIG. 6 b  is a schematic representation of the filter shown in FIG. 6 a  after exhibiting the desired performance characteristics in response to predetermined test criteria. 
     FIG. 6 c  is a schematic representation of the filter of FIG. 6 a  which does not exhibit desired performance characteristics in response to the predetermined test criteria. 
     FIG. 6 d  is a further schematic representation of the filter depicted in FIG. 6 a  which does not exhibit the desired performance characteristics in response to the predetermined test criteria. 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 1 a first contemplated embodiment of the invention is shown where the invention is used in connection with a transparent conduit such as a drinking straw. Filter  10  is provided within a transparent cylindrically shaped conduit  12  on top of which is provided a powdered medication  14 . The filter provides support for the solid medication  14  and prevents the release of medication out of the bottom of the conduit. Filter  10  is generally formed in the shape of a cylinder and is comprised of a bundle of synthetic fibers, the majority of which are generally oriented in a direction parallel with conduit  12 . As best seen in FIG. 2, filter  10  has an inner more dense core region  16  and a second less dense annular region  18  which surrounds the core. The less dense annular region  18  located at the outer periphery of filter  10  enables the filter to engage the interior sidewalls of the conduit by a light frictional engagement. In the absence of significant forces acting upon filter  10 , the filter  10  will remain fixed in its position. The filter is constructed so that a number of fibers in the peripheral region extend in a radial direction with respect to the orientation of the fiber bundle within the conduit. The fibers or portions of the fibers which extend in a radial direction function like springs which frictionally engage the sidewalls of the conduit. Since the filter has a less dense fiber distribution in this peripherial region  18 , the forces acting on sidewall of the conduit are less than what would be expected to be encountered by a filter having a uniform density. The filter is constructed so that its maximum diameter is somewhat larger than the inner diameter of the conduit and, when inserted within the conduit will slightly compress to conform to the diameter of the conduit. The inner dense core region  16  of the filter functions to increase the resistance to fluid flow of the filter in the central region. 
     In the embodiment depicted in FIG. 1, conduit  10  is constricted on its opposite ends  20  and  21  whereby the inner diameter of the ends are less than the maximal interior dimension of the conduit located in the median section. The constrictions of the ends of the conduit serve to prevent the filter from passing out of the conduit in response to fluid flow through the conduit. FIG. 4 shows a another contemplated embodiment of the invention where an annular insert  23  and  24  are provided within the conduit to decrease the inner diameter of the conduit  25  at opposite ends and thus prevent movement of the filter element  28  within the conduit beyond a predetermined distance. An alternative embodiment of a filter which may be used in accordance with the invention is depicted in FIG.  4 . In this embodiment the region  27  of lower density is also formed at the peripheral region however the radial dimension of the annular section is significantly less than the radius of the more dense core region  29 . In the second embodiment, the central core region  29  is manufactured to equal approximately the same diameter as the diameter of the conduit of which it is designed to compliment. Like the first embodiment, the filter is retained in place by frictional forces imposed by the fibers located in the outer low density region  27 . The total frictional forces between the filter and the conduit may be increased by providing a filter having a greater axial length or causing more of the fibers to extend in the radial direction thereby increasing the density of the outer peripheral region. Although the embodiments show herein depicted filters having two distinct regions, in other contemplated embodiments the density of the filter gradually decreases from the central axis of the filter towards the outer peripheral region, or may contain multiple distinct regions having different densities. 
     In an example a conduit was provided with a minimum inner diameter of 0.278 inches and a maximum inner diameter of 0.282 inches and a length of about eight inches. A filter made of a bundle of synthetic fibers was created using an annular die having an inner diameter between 0.306-0.310 inches. In this example fibers comprised of a polyester core and a polyolefin sheath and having a weight of 60 grains per yard were heated to a temperature of approximately 450 degrees F and then drawn through the die at a rate of 1.5 feet per minute. The die was maintained at a temperature of approximately 85 degrees F. The heat causes the resin to slightly melt and the fibers will adhere to one another. Because of the temperature of the die is less than the operating temperature, those fibers located on the periphery begin to cool faster than those fibers located at the core. The process also causes some of the fibers located at and near the periphery to extend in a radial direction giving the filter a hairy appearance as illustrated in FIG.  4 . The filters were then cut to an axial length of approximately 0.31 inches. The filters made according to this process have a cylindrical shape and have a diameter slightly greater than the die used in the manufacturing process. The filters are resilient and can be compressed to fit within the conduit and thus conform to the dimensions of the conduit set forth above. The filter expands in a radial direction to create a frictional engagement with the sidewalls of the conduit. 
     Filters made in accordance with the manufacturing parameters set forth above were tested in a device which is schematically depicted in FIG.  5 . FIG. 5 shows a vacuum generator  33  connected to a conduit  31  in communication with a flow control valve  34 . A flow meter  36  measures the flow of air through the device and vacuum gage  38  measures the vacuum on the system. An air filter  40  serves as a trap for water drawn into the system and protects the vacuum source and other downstream instrumentation. Upstream from the air filter  40  is a pinch valve  42  activated by a solenoid and controlled by electric timer  44 . The tubing  46  is flexible and engages the top of conduit  31  which contains filter  55  which was made according to the process described above. The testing is conducted by first priming the system by drawing water into the tubing  46  and then connecting the tubing to the conduit  31 . Conduit  31  has a substantially smooth interior and has an inner diameter of between 0.278-0.282 inches and a length of approximately eight inches. The vacuum  33  is set at 3 in/Hg@5LPM flow rate and applied to the conduit for a time interval of one second. Energizing the vacuum causes liquid  50  to be drawn from reservoir  52  into the lower end of conduit  31 . The fluid flows through filter  55  and continues to flow upwards through conduit  31  and into tubing  46 . As the liquid flows through filter  55  it pushes the filter upward within the confines of conduit  31 . After one second, the timer sends a signal to activate the solenoid which closes valve  42 . Closing valve  42  isolates vacuum generator  33  from acting on the conduit and flow is arrested. At this time the conduit is removed from the fluid reservoir and separated from the tubing  46 . Any residual fluid is allowed to flow out of the bottom of conduit  31 . The foregoing procedure closely simulates the forces imposed by a person on a conventional drinking straw and was designed as a performance test to determine the precise dimensions and manufacturing parameters necessary to construct a device which will consistently exhibit the desired properties of allowing a filter to move up the conduit and having the filter retained at the top of the conduit after the vacuum is released. 
     Using the apparatus depicted in FIG. 5, twenty filters made in accordance with the manufacturing specifications described above were tested and the position of the filter was noted at the end of each test iteration. FIG. 6 a  depicts the filter  55  at the initial position within a conduit before the test as described above was performed. FIG. 6 b  depicts the filter  55  which has exhibited the desired performance characteristics after being subject to the test procedures as set forth above. In FIG. 8 b  filter  55  is shown after it has traveled from the initial position at the bottom of the conduit as depicted in FIG. 8 a  to a position at the top of the conduit and, has retained its position at the top of the conduit after the liquid was withdrawn from the reservoir. The arrow  56  represents the vector of travel of the filter within the conduit. Filters considered to have failed the requisite performance test are illustrated in FIGS. 6 c  and  6   d.  In FIG. 6 c  a filter  60  is depicted at an intermediate position within the conduit and accordingly, did not travel to the top of the conduit after application of the vacuum for a time period of one second. Another failure mode is shown in FIG. 6 d  where a filter  62  did not retain its position at the top of the conduit. In FIG. 6 d  the arrow represents the where the filter traveled to the top of the conduit and then traveled back to an intermediate location within the conduit. The twenty filters constructed in accordance with the manufacturing specifications described in the preferred or first embodiment were tested and each satisfactorily traveled to the top of the conduit and remained in place after removal of the conduit from the liquid as depicted in FIG. 6 b  reflecting a 100 percent pass rate. 
     In the embodiment described above, the filter will consistently move up to the conduit in response to the fluid flow created by suction applied by an individual directly on top of the conduit. Providing a filter having a variable density assists in achieving the desired results because the outer annular region is provides less total pressure against the walls of the conduit than a filter having an uniform distribution of fibers. At the same time, the region of increased density located at the center of the filter serves to increase the filter&#39;s resistance to fluid flow. 
     The construction and concomitant characteristics of oriented fiber filters may be altered by changing various parameters governing the manufacturing process used to make the filters including (1) the fibrous materials used for the construction of the filter, (2) the temperature conditions at various steps and of various components in the manufacturing process, (3) the rate of which the filter fibers pass through the die, (4) and the cutting procedure. Alteration of the various manufacturing parameters can effect the density, the size and radial resilience of the filter and accordingly, the performance characteristics of the filter can be effected. For example, by altering the length of the filter, the total circumferential surface area available for the engagement to the conduit sidewalls is altered and, the resulting forces necessary to overcome the frictional engagement are correspondingly increased. Although a single conduit having the precise dimension and a corresponding filter for the conduit is described herein, the invention is applicable to a wide range of combinations of conduits and filters. Other combinations may be made by determining the proper relationship between the conduit, the filter and the range of expected pressure differentials expected through the device in the contemplated application. 
     It is accordingly contemplated that filters constructed of other materials and from alternative structural matrixes could be satisfactorily engineered to meet the desired performance specifications. To be effective the filters should demonstrate adequate resilient properties in the radial direction which enables the frictional engagement of the the sidewalls of the conduit in the manner described herein. For example, it is contemplated that the performance objectives of the invention could be met using filters having differing structural matrixes and filters made from other materials including polyethylene, polyproplyene, Teflon, or nylon. It is further contemplated that substantially solid impediments having sufficient radial resiliency and channels provided for the facilitation of flow of liquid past the impediment may satisfactory be engineered to perform as required. Thus, it should be understood that various modifications within the scope of this invention can be made without departing from the spirt thereof. 
     In use, a patient is provided a straw containing a filter which supports a single dose of a medication in powder form or in small particles. Providing medication in powdered form is often advantageous because it enables the drug to be rapidly be absorbed in the alimentary canal. The patient immerses the lower end of the straw into an ingestible fluid such as water, and the patient draws the fluid through the filter and into his or her mouth. As the fluid contacts the medication it is suspended or dissolved into the fluid. As the fluid moves through the filter it also moves the filter up to the top of the straw and, the filter is retained at this position when the patient stops application of suction. The high flow rate into the alimentary canal using a straw allows the administration of medication with minimal perception by the patent and takes advantage of the natural swallowing reflex. The foregoing application provides particular advantage for the oral administration of medication to both pediatric and geriatric patients, especially when the medication is unpalatable. 
     The foregoing specific embodiments and applications are illustrative only and are not intended to limit the scope of the invention. It is contemplated that the invention will be functional and effective in other diverse applications where it is desirable to allow for the movement and subsequent retention of an impediment in response to predetermined pressure differentials and rates of fluid flow within a conduit.