Patent Application
20160346742
It should be noted that throughout the disclosure, where a definition or use of a term in any incorporated document(s) is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the incorporated document(s) does not apply.
Field of the Invention
One or more embodiments of the present invention relate to shaft assemblies used in dissolution instruments and in particular, to two-piece dissolution instrument agitator shaft assemblies.
Description of Related Art
Drugs are commonly manufactured in the form of pills, which are disseminated into the body over a period as the pill dissolves. Manufacturers of pills are required by law to determine the precise dissolving characteristics of a pill before it is placed on the market.
In the pharmaceutical industry, the stirring or agitation of sample drugs or other substances in test vessels is an important step in mimicking the dissolution rate or dissolution characteristics of a drug within the stomach. Examples of such test procedures include those performed for the purpose of testing and analyzing the rate at which doses of a drug is released from pharmaceutical products, such as tablets or capsules, under controlled conditions.
The procedural steps, test duration, dissolution medium, and apparatus employed in dissolution tests typically must comply with established, well-recognized guidelines, such as those promulgated by United States Pharmacopeia (USP) in order for the test to be accepted as valid for the specific substance tested. The apparatus utilized for carrying out dissolution testing typically includes a vessel plate having an array of apertures into which test vessels are mounted.
Each test vessel includes a liquid called media, which is a dissolution bath that essentially duplicates the liquid solution that is contained within the stomach, with a precise quantity of the solution placed within the test vessel. The pill or capsule to be tested is then inserted within the test vessel with a dissolution instrument agitator shaft assembly (e.g., a mixing paddle) inserted therein the test vessel to mix the solution at a precise rate, which duplicates the natural turbulence (churning) that is created within the stomach. Aliquots are then removed from the solution at precise time intervals, which are then analyzed to determine the amount of drug that has been dissolved within the solution in relation to the time that the pill or capsule has been in the solution.
Accordingly, dissolution instruments are highly precision multiple spindle instruments that are used to test the dissolution rate of pharmaceutical drugs. As best illustrated in the related art
An important USP specification related to two-piece shaft assemblies 102 used by dissolution instruments is wobbling, which should not exceed a maximum of 1.0 mm. It is commonly known that excessive wobble (unsteady movement from side to side) of rotating shaft assemblies 102 contributes to dissolution test error, which is the result of an unaccounted change in hydrodynamics within the dissolution vessel when a paddle or basket portion (detailed below) of a shaft assembly exhibits excessive wobble due to the wobbling of the rotating shaft assembly.
Accordingly, in light of the current state of the art and the drawbacks to current shaft assemblies mentioned above, a need exists for a dissolution instrument shaft assembly with substantially reduced wobbling.
A non-limiting, exemplary aspect of an embodiment of the present invention provides a two-piece dissolution instrument agitator shaft assembly of a dissolution instrument, comprising:
tapered connection with no diametrical clearance between first and second mating sections;
wherein an inner diameter of the first mating section is equal to or less than an outer diameter of the second mating section.
Another non-limiting, exemplary aspect of an embodiment of the present invention provides a a two-piece dissolution instrument agitator shaft assembly of a dissolution instrument, comprising:
an upper shaft that is associated with a drive spindle of the dissolution instrument;
a lower shaft that is immersed into a vessel filled with solution, with upper and lower shafts detachably coupled together by a complementary female and male connecting structures of respective upper and lower shafts to form the two-piece dissolution instrument agitator shaft assembly;
wherein an inner diameter of the female connecting structure is equal to or less than an outer diameter of the male connecting structure.
These and other features and aspects of the invention will be apparent to those skilled in the art from the following detailed description of preferred non-limiting exemplary embodiments, taken together with the drawings and the claims that follow.
It is to be understood that the drawings are to be used for the purposes of exemplary illustration only and not as a definition of the limits of the invention. Throughout the disclosure, the word “exemplary” may be used to mean “serving as an example, instance, or illustration,” but the absence of the term “exemplary” does not denote a limiting embodiment. Any embodiment described as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. In the drawings, like reference character(s) present corresponding part(s) throughout.
The detailed description set forth below in connection with the appended drawings is intended as a description of presently preferred embodiments of the invention and is not intended to represent the only forms in which the present invention may be constructed and or utilized.
It is to be appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention that are, for brevity, described in the context of a single embodiment may also be provided separately or in any suitable sub-combination or as suitable in any other described embodiment of the invention. Stated otherwise, although the invention is described below in terms of various exemplary embodiments and implementations, it should be understood that the various features and aspects described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied, alone or in various combinations, to one or more of the other embodiments of the invention.
Throughout the disclosure, references to a paddle shaft assembly or basket shaft assembly are meant as illustrative, convenience of example, and for discussion purposes only. That is, the present invention should not be limited to use of a “paddle” or “basket” shafts or assemblies thereof but may also be used (without much modifications, if any) for other types of dissolution instruments shaft assemblies that may or may not be used for agitation or mixing in the pharmaceutical industry.
In the description given below and or the corresponding set of drawing figures, when it is necessary to distinguish the various members, elements, sections/portions, components, parts, or any other aspects (functional or otherwise) or features or concepts or operations of a device(s) or method(s) from each other, the description and or the corresponding drawing figures may follow reference numbers with a small alphabet character such as (for example) “paddle shaft assembly 102a, basket shaft assembly 102b, and etc.” If the description is common to all of the various members, elements, sections/portions, components, parts, or any other aspects (functional or otherwise) or features or concepts or operations of a device(s) or method(s) such as (for example) to all shaft assemblies, then they may simply be referred to with reference number only and with no alphabet character such as (for example) “shaft assembly 102.”
In general, if lower shaft 106 has a paddle 108 (
As best illustrated in
In general, excessive wobble is generally a function of straightness of shaft assembly 102 along its longitudinal axis 120. In particular, an important aspect of the present invention is the discovery that straightness of conventional two-piece shaft assembly 102 along its longitudinal axis 120 is impacted by geometric tolerances of the mating parts. In other words, geometric tolerances and variations cause critical diametrical clearance 122 (
It should be noted that it is not just geometric tolerances (that allows for some error), but actual intentional design of mating sections 112 and 114 that allows for undesirable diametric clearance 122. In particular, inner diameter 132 of mating section 114 is designed to be larger than an outer diameter 134 of mating section 112 to enable upper shaft 104 to receive and mate with lower shaft 106. Accordingly, diametric clearance is in fact the very slight or small delta (or difference) between inner and outer diameters 132 and 134. Therefore, mating sections 114 and 116 have two contact points or surfaces—threading between outer threaded male 116 and inner threaded female 118 threading points, and periphery or edge mating surfaces 124 and 126. Although mating sections 114 and 116 have two contact points or surfaces, they only have the threading that connects them together and hence, wobbling may also occur if for any reason that threaded connection is loosened.
Another important aspect of the present invention is the discovery that perpendicularity of mating surfaces 124 and 126 (
Accordingly, one or more embodiments of the present invention provide a dissolution instrument shaft assembly that obviates the problems with the conventional shafts, resulting in a substantially reduced wobbling.
As detailed below, one or more embodiments of the present invention eliminate design requirement for diametric clearance 122 between mating structures and further, eliminate the need for contact between mating surfaces 124 and 126, which simply eliminate potential contributions to wobbling from these sources. Further, one or more embodiments of the present invention provide frictional as well as threaded connectivity, which further reduce the potential of dissolution instrument shaft assembly being loosened at the treading.
As illustrated in
In general, if lower shaft 246 has a paddle 108, two-piece dissolution instrument agitator shaft assembly 242 is referred to as a dissolution instrument paddle shaft assembly 242a whereas if lower shaft 246 has a basket 110, two-piece dissolution instrument agitator shaft assembly 242 is referred to as a dissolution instrument basket shaft assembly 242b. Accordingly, lower shaft 246 may be a paddle shaft 246a or a basket shaft 246b that assemble with upper shaft 244 to form either a dissolution instrument paddle agitator shaft assembly 242a or a dissolution instrument agitator basket shaft assembly 242b, with both using identical upper shaft 244. In general, basket 110 is detachably coupled with the basket shaft 246b.
As best illustrated in
Cavity 240 further includes a secondary frustum of a short right circular cone (second chamber 206) that has a diameter 250 that decreases along a central longitudinal axis of second (or intermediate) chamber 206 from a first distal end (which is the same as distal end 250) to distal end 252, with the first distal end diameter having a span that is longer than second distal end diameter. It should be noted that intermediate chamber 206 is a result of manufacturing process using tooling to bore and create the next chamber (blind-hole chamber 208 detailed below) in relation to first chamber 204.
As further illustrated, cavity 240 further includes a cylindrically configured blind-hole (third chamber 208) that has internal threading 210, with chamber 208 having a constant diameter 224. The very tip 256 of chamber 208 having a cone structure is the result of tooling that bored blind-hole chamber 208.
Accordingly, overall, cavity 240 includes a diameter that decreases along central longitudinal axis 220 of cavity 240 from opening 202 to blind-hole chamber 208, with diameter 222 of chamber 204 at opening 202 larger than a next, subsequent diameter 226 of chamber 206, with a final diameter 224 of blind-hole chamber 208 of cavity 240 being generally constant and smallest.
First chamber 204, the intermediate chamber 206, and blind-hole chamber 208 have a common axial center (which is the same as central longitudinal axis 220), with first chamber 204 associated with blind-hole chamber 208 by intermediate chamber 206 in a cascading series of sequentially decreasing dimension. The first chamber 204, the intermediate chamber 206, and blind-hole chamber 208 are therefore concentric chambers.
As best illustrated in
As further illustrated, male connecting structure 230 also includes second section 234, which is composed of a first cylindrical portion 270 that forms a relief (or recess), and a second cylindrical portion 258 with outer threading. First cylindrical portion 270 is positioned between second distal end 238 of first section 232, forming a bottom or base of second cylindrical portion 258. First cylindrical portion has a first cylindrical diameter 272 that is shorter than a diameter of the second distal end 238, forming a periphery upper edge 274 of first section 232, with a second cylindrical diameter 276 being longer than first cylindrical diameter 272.
As best illustrated in
As further illustrated, locations where the size of outer diameter 262 is equal to the size of inner diameter 222 are near respective first distal ends 236 and at opening 202 so that periphery upper edge 268 of lower shaft 246 never come into contact with lower periphery edge 254 of upper shaft 244. In other words, outer diameter 262 of first section 232 is sized such that it equals the inner diameter 222 at opening 202 where lower periphery edge 254 and periphery upper edge 268 are separated by distance 278 and hence, never contact one another when two-piece dissolution instrument agitator shaft assembly 242 is fully assembled. Accordingly, one or more embodiments of the present invention eliminate design requirement for diametric clearance between mating structures and further, eliminate the need for contact between mating surfaces, eliminating potential contributions to wobbling from these sources. Further, due to equality between inner and outer diameters as described, a frictional hold is generated at the contacting surfaces, which reduce potential of loosening of lower and upper shaft connections.
Although the invention has been described in considerable detail in language specific to structural features and or method acts, it is to be understood that the invention defined in the appended claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as exemplary preferred forms of implementing the claimed invention. Stated otherwise, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. Further, the specification is not confined to the disclosed embodiments. Therefore, while exemplary illustrative embodiments of the invention have been described, numerous variations and alternative embodiments will occur to those skilled in the art. Such variations and alternate embodiments are contemplated, and can be made without departing from the spirit and scope of the invention.
It should further be noted that throughout the entire disclosure, the labels such as left, right, front, back, top, inside, outside, bottom, forward, reverse, clockwise, counter clockwise, up, down, or other similar terms such as upper, lower, aft, fore, vertical, horizontal, oblique, proximal, distal, parallel, perpendicular, transverse, longitudinal, etc. have been used for convenience purposes only and are not intended to imply any particular fixed direction, orientation, or position. Instead, they are used to reflect relative locations/positions and/or directions/orientations between various portions of an object.
In addition, reference to “first,” “second,” “third,” and etc. members throughout the disclosure (and in particular, claims) is not used to show a serial or numerical limitation but instead is used to distinguish or identify the various members of the group.
In addition, any element in a claim that does not explicitly state “means for” performing a specified function, or “step for” performing a specific function, is not to be interpreted as a “means” or “step” clause as specified in 35 U.S.C. Section 112, Paragraph 6. In particular, the use of “step of,” “act of,” “operation of,” or “operational act of in the claims herein is not intended to invoke the provisions of 35 U.S.C. 112, Paragraph 6.
This Application claims the benefit of priority of co-pending U.S. Utility Provisional Patent Application 62/168,779, filed 30 MAY 2015, the entire disclosure of which is expressly incorporated by reference in its entirety herein.
| Number | Date | Country | |
|---|---|---|---|
| 62168779 | May 2015 | US |
