Title:
Syringe locking structures
Kind Code:
A1


Abstract:
Locking structures and syringe systems provide increased locking force and/or sealing between a syringe and another syringe or applicator tip coupled thereto. One locking structure includes a tubular member having an interior surface, an exterior surface, and a longitudinal axis extending therethrough, one or more first tabs projecting from the exterior surface of the tubular member so as to at least partially encircle the tubular member, and means for increasing resistance between the one or more first tabs and corresponding structure (e.g., grooves) of a device (e.g., a syringe or applicator tip) that is selectively coupleable to the tubular member.



Inventors:
Fischer, Dan E. (Sandy, UT, US)
Mclean, Bruce S. (Sandy, UT, US)
Application Number:
11/235461
Publication Date:
03/29/2007
Filing Date:
09/26/2005
Primary Class:
Other Classes:
604/416
International Classes:
B65B1/04
View Patent Images:



Primary Examiner:
MAUST, TIMOTHY LEWIS
Attorney, Agent or Firm:
Rick D. Nydegger (Salt Lake City, UT, US)
Claims:
What is claimed is:

1. A locking structure of a syringe system for use in reliably coupling a syringe to corresponding structure of another syringe or an applicator tip, comprising: a tubular member having an interior surface, an exterior surface, and a longitudinal axis extending therethrough; one or more first tabs projecting from the exterior surface of the tubular member so as to at least partially encircle the tubular member; and means for increasing resistance between the one or more first tabs and corresponding structure on a device that is selectively coupleable to the tubular member as the tubular member and the corresponding structure on the device are rotatably joined together.

2. A locking structure as recited in claim 1, wherein the means for increasing resistance comprises one or more second tabs projecting from the exterior surface of the tubular member so as to at least partially encircle the tubular member, the one or more second tabs being spaced longitudinally apart from the one or more first tabs.

3. A locking structure as recited in claim 2, wherein at least one of the first or second tabs is formed so as to be of a greater diameter with respect to a corresponding depth of corresponding receiving structure of the device that is selectively coupleable to the tubular member.

4. A locking structure as recited in claim 2, wherein at least one of the first or second tabs is formed so as to be of a greater height with respect to a corresponding width of corresponding receiving structure of the device that is selectively coupleable to the tubular member.

5. A locking structure as recited in claim 2, wherein at least one of the first or second tabs is formed so as to have an arc length that is out of sync with respect to a pitch of the corresponding receiving structure of the device that is selectively coupleable to the tubular member.

6. A locking structure as recited in claim 2, wherein the one or more second tabs comprises a pair of second tabs.

7. A locking structure as recited in claim 1, wherein the means for increasing resistance comprises a ridge projecting from the exterior surface of the tubular member so as to at least partially encircle the tubular member, the ridge being spaced longitudinally apart from the one or more first tabs.

8. A locking structure as recited in claim 1, wherein the one or more first tabs only partially encircle the tubular member.

9. A locking structure as recited in claim 1, wherein the one or more first tabs comprise a pair of first tabs.

10. A locking structure as recited in claim 1, wherein the tubular member comprises a portion of a syringe barrel.

11. A locking structure of a syringe system for use in reliably coupling a syringe to corresponding structure of another syringe or an applicator tip, comprising: a tubular member having an interior surface, an exterior surface, and a longitudinal axis extending therethrough; a projection projecting from the exterior surface of the tubular member so as to at least partially encircle the tubular member; and means for increasing resistance between the projection and corresponding structure on a device that is selectively coupleable to the tubular member.

12. A locking structure as recited in claim 11, wherein the projection comprises at least one of a thread, a tab, or a ridge.

13. A locking structure as recited in claim 11, wherein the projection comprises a pair of threads or a pair of tabs.

14. A locking structure as recited in claim 11, wherein the tubular member comprises a portion of a syringe barrel.

15. A locking structure as recited in claim 11, wherein the means for increasing resistance comprises one or more teeth formed on the projection configured for increasing resistance between the teeth and the corresponding receiving structure of a device that is selectively coupleable to the tubular member.

16. A locking structure as recited in claim 11, wherein the means for increasing resistance comprises an interference structure that selectively applies pressure to an exterior surface of the device that is selectively coupleable to the tubular member.

17. A locking structure as recited in claim 16, wherein the interference structure comprises a loop that grips and applies pressure to an exterior surface of a collar of the selectively coupleable device, the loop having an inside diameter that is less than the outer diameter of the collar of the selectively coupleable device.

18. A syringe system comprising: a first syringe; a second syringe and/or an applicator tip; locking structure on at least one of the first syringe, the second syringe and/or the applicator tip for coupling the syringe or applicator tip having the locking structure to another syringe or applicator tip, the locking structure comprising: a tubular member having an interior surface, an exterior surface, and a longitudinal axis extending therethrough; a projection projecting from the exterior surface of the tubular member so as to at least partially encircle the tubular member; and means for increasing resistance between the projection and corresponding structure of the other syringe or applicator tip that is selectively coupleable to the tubular member.

19. A syringe system as recited in claim 18, wherein the means for increasing resistance comprises one or more teeth formed on the projection configured for increasing resistance between the teeth and the corresponding receiving structure of the other syringe or applicator tip that is selectively coupleable to the tubular member.

20. A syringe system as recited in claim 19, further comprising additional teeth formed on the corresponding receiving structure configured to irreversibly engage the one or more teeth formed on the at least a first projection.

Description:

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates to structures for coupling syringes and other dispensing or mixing apparatuses together in a secure liquid tight engagement.

2. The Relevant Technology

Occasionally it is necessary to mix two components together before dispensing the resulting composition. For example, various adhesives and dental compositions comprise two discrete components which are independently stable but when combined interact to set in a cementitious manner. One approach to combining the discrete components is simply to dispense each of the discrete components into a third compartment where they are mixed and subsequently dispensed. In an alternative approach, the individual components are each retained in a respective syringe. The dispensing ends of the syringes are coupled together and the discrete components are passed back and forth between the syringes by advancing and retracting the corresponding plunger. The components are passed back and forth until the components are fully mixed. The mixed composition is then loaded into one of the syringes for subsequent dispensing while the later syringe is typically discarded.

A similar approach is also used in transferring material between syringes. That is, bulk quantities of materials, such as many dental compositions, are often stored in relatively large syringes. In order to mix measured amounts of the stored materials or to more easily apply the materials to a tooth or other oral tissue, a large bulk syringe is coupled with a smaller syringe such that a measured amount of the stored material can be transferred to the smaller syringe.

One approach to coupling two syringes together has been the use of discrete connectors which either press fit or threadedly engage with the nozzles of the syringes. Although such connectors are useful in many situations, such connectors often fail when it is necessary to transfer highly viscous materials between syringes. In such situations, the syringes will often separate from the connectors under the force applied to the material by the plunger. This problem is further exacerbated where the material being transferred is highly lubricious, thereby making the coupling between the syringe and the connector slippery.

It is further noted that the use of a discrete connector to couple two syringes together is undesirable in that the connector is an added expense to the system. Furthermore, such connectors are time consuming to use in that they require a separate connection to each of the syringes.

SUMMARY OF THE INVENTION

The present invention is directed to locking structures and syringe systems for use in reliably coupling a syringe to corresponding structure of another syringe or an applicator tip. One locking structure includes a tubular member having an interior surface, an exterior surface, and a longitudinal axis extending therethrough, one or more first tabs projecting from the exterior surface of the tubular member so as to at least partially encircle the tubular member, and means for increasing resistance between the one or more first tabs and corresponding structure on a device (e.g. a syringe or applicator tip) that is selectively coupleable to the tubular member as the tubular member and the corresponding structure on the coupleable device are rotatably joined together.

In one example, the means for increasing resistance between the one or more first tabs and corresponding structure of the selectively coupleable device may comprise one or more second tabs projecting from the exterior surface of the tubular member so as to at least partially encircle the tubular member, the one or more second tab being spaced longitudinally apart from the first tab. In order to further increase resistance, the first and/or second tabs may be formed so as to have an arc length (i.e., the length of the tab around the tip) that causes the tab to be out of sync with respect to the pitch of the corresponding receiving structure of the device that is selectively coupleable to the tubular member. Another way to further increase resistance is to form the first and/or second tabs so as to be of different sizes (e.g. greater diameter and/or greater height) with respect to corresponding receiving structure of the device that is selectively coupleable to the tubular member.

Alternatively, the means for increasing resistance between the one or more first tabs and corresponding structure of the selectively coupleable device may comprise a ridge projecting from the exterior surface of the tubular member so as to at least partially encircle the tubular member, the ridge being spaced longitudinally apart from the one or more first tabs.

In another example, the locking structure may include a tubular member having an interior surface, an exterior surface, and a longitudinal axis extending therethrough, at least a first projection (e.g. a thread, a tab, or a ridge) projecting from the exterior surface of the tubular member so as to at least partially encircle the tubular member, and means for increasing resistance between the projection and corresponding structure on a device that is selectively coupleable to the tubular member as the tubular member and the corresponding structure on the coupleable device are rotatably joined together.

The means for increasing resistance may comprise one or more teeth formed on the at least one projection. The teeth may be configured to engage opposing teeth formed on corresponding structure on the coupleable device. Alternatively, the means for increasing resistance may comprise an interference structure that selectively bites into the outside of the device that is selectively coupleable to the tubular member.

These and other advantages and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

To further clarify the above and other advantages and features of the present invention, a more particular description of the invention will be rendered by references to specific embodiments thereof, which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which:

FIG. 1 is a perspective view of a first syringe and a second syringe configured for selective coupling together;

FIG. 2 is a cross sectional side view of the first syringe of FIG. 1;

FIG. 3 is a cross sectional side view of the second syringe of FIG. 1;

FIG. 4 is a cross sectional side view of an alternative second syringe;

FIG. 5 is a cross sectional side view of the first syringe and the second syringe of FIG. 1 coupled together;

FIG. 6A is a side view of the tip of a modified version of the first syringe shown in FIG. 1, wherein the second tabs have a maximum outer diameter greater than the maximum outer diameter of the first tabs;

FIG. 6B is a side view of the tip of a modified version of the first syringe shown in FIG. 1, wherein the second tabs have a maximum height greater than the maximum height of the first tabs;

FIG. 7A is a side view of an alternative embodiment of the first syringe shown in FIG. 1, wherein the second tabs are replaced by an annular ridge;

FIG. 7B is a side view of an alternative embodiment of the first syringe shown in FIG. 7A, wherein a plurality of smaller ridges are provided in place of the annular ridge;

FIG. 8 is a perspective view of the tip of an alternative embodiment of a first syringe including a pair of first threads, and a pair of second threads, wherein the second threads include one or more teeth;

FIGS. 9A illustrates a side view of an alternative embodiment of a first syringe and a second syringe coupled together wherein the first syringe includes an interference structure that selectively bites into the outside of the second syringe; and

FIG. 9B illustrates a perspective view of the coupled first and second syringes of FIG. 9A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

I. Introduction and Definitions

A detailed description of the invention will now be provided with specific reference to figures illustrating preferred embodiments of the invention. It will be appreciated that like structures will be provided with like reference designations. To help clarify the scope of the invention, certain terms will now be defined.

As used herein, the term “thread” generally refers to a helical projection extending from an exterior surface of a tubular member. A thread may partially or completely encircle the tubular member.

As used herein, the term “tab” refers to a projection extending from an exterior surface of a tubular member in a plane that is substantially perpendicular to the longitudinal axis of the tubular member. A tab may also partially or completely encircle the tubular member. For example, a tab that completely encircles the tubular member may include portions of relatively greater projecting diameter.

II. Exemplary Locking Structures Including One or More Tabs

FIG. 1 illustrates an embodiment of a syringe system 10 incorporating a locking structure including one or more tabs. Syringe system 10 includes a first syringe 12 and a second syringe 14 which are designed to be coupled together so as to pass one or more components therebetween. First syringe 12 includes a barrel 16 having a first end 18 and an a opposing second end 20. First syringe 12 also includes a tubular tip 22 projecting from first end 18, and a plunger 24 slidably disposed within second end 20 of barrel 16.

As depicted in FIG. 2, barrel 16 has an interior surface 26 bounding a chamber 28. Chamber 28 is configured to slidably receive plunger 24 and to hold a component (not shown) for mixing and or dispensing.

Tip 22 of first syringe 12 is shown having an exterior surface 30 and an opposing interior surface 26. Interior surface 26 bounds a channel 34 in fluid communication with chamber 28 as discussed below in greater detail. Interior surface 26 may be tapered into a frustoconical configuration, while a central longitudinal axis A extends through channel 34 and chamber 28. In the depicted embodiment, tubular tip 22 has a smaller outer diameter than barrel 16. In alternative embodiments, however, tip 22 may have the same or a larger diameter relative to barrel 16.

As depicted in FIGS. 1 and 2, outwardly projecting from exterior surface 30 at the end of tip 22 are a pair of first tabs 36 and a pair of second tabs 38. Second tabs 38 are longitudinally spaced art from first tabs 36. In the embodiment depicted, each of tabs 36 and 38 only partially encircle tip 22.

Second syringe 14 includes a barrel 42 having a first end 44 and an opposing second end 46. Slidably disposed within the second end 46 of barrel 42 is a plunger 50. As seen in FIG. 3, barrel 42 has an interior surface 52 bounding a chamber 54. Chamber 54 is configured to slidably receive plunger 50 (FIG. 1) and to hold a component (not shown) for mixing and/or dispensing. A tubular collar 48 projects from first end 44 of barrel 42. Collar 48 has an interior surface 56. Inwardly projecting from interior surface 56 are engagement grooves 58. Projecting from first end 44 of barrel 42 centrally within collar 48 is a tubular luer cone 60. Luer cone 60 has a tapered configuration complementary to channel 34 of tip 22. An annular recess 62 is formed between the exterior of luer cone 60 and the interior of collar 48.

FIG. 4 illustrates an alternative second syringe 64 that can also be used for coupling with first syringe 12. Second syringe 64 is substantially identical to second syringe 14 except that luer cone 60 has been removed. Like elements between syringes 14 and 64 are identified by like reference characters.

As shown in FIG. 5, first syringe 12 and second syringe 14 (of FIG. 3) are configured such that tubular tip 22 can be selectively received within recess 62 and secured therein by engagement of tabs 36 and 38 within engagement grooves 58. In this configuration, luer cone 60 is received in frictional engagement within channel 34 of tubular tip 22. In this coupled arrangement, chambers 28 and 54 are in fluid communication. By selectively advancing one of plungers 24 or 50, the component within the syringe of the advancing plunger is passed into the chamber of the opposing syringe. Furthermore, by selectively advancing and retracting each of plungers 24 and 50, discrete components within each of syringes 12 and 14 can be passed back and forth between the two syringes, thereby mixing the two components.

Syringes 12 and 14 can be of any desired size or configuration and can be used with any desired types of components in any desired environment (e.g., medical, dental, or industrial). In one embodiment, syringes 12 and 14 are injection molded from a suitable plastic material. The syringes may alternatively be manufactured by other milling or molding processes and can be formed from other materials. One example of how luer cone 60 and chamber 54 can be configured for complementary mating is disclosed in International Standard ISO 549/1-1986(E), which is incorporated herein by reference. Similarly, one example of how engagement grooves 58 can be configured for engagement is disclosed in International Standard ISO 594-2:1991(E), which is also incorporated herein by reference. Further disclosure with regard to the configuration and coupling of the syringes and mixing of components between two syringes is disclosed in U.S. Pat. Nos. 6,610,034 and 6,234,196 each of which is herein incorporated by reference.

The locking structures of the present invention include means for increasing resistance between first tabs 36 and corresponding structure (e.g., engagement grooves 58) formed on the device (e.g., second syringe 14) that is selectively coupleable to the tubular member. One example of suitable means for increasing resistance is one or more second tabs 38 that also project from the exterior surface of tubular member 22. Second tabs 38 are spaced apart longitudinally from first tabs 36. The pair of second tabs 38 are illustrated as partially encircling tubular member 22. At least one of first or second tabs 36 and 38 may be formed so as to be of a sufficient arc length so as to be out of sync with respect to the pitch of the corresponding receiving structure (e.g., engagement grooves 58) of the selectively coupleable device. In other words, when one or more of the tabs are formed so as to more completely encircle (longer arc length) tubular member 22, the path of the longer tab no longer easily fits within engagement groove 58. The longer tab (particularly its ends) experience increased resistance as the tab is introduced further into groove 58.

In another example, one or more of the tabs may be formed so as to be of a larger diameter and/or height with respect to corresponding receiving structure (e.g., engagement grooves 58) of the selectively coupleable device. Forming one or more of the pairs of tabs in such a way even further increases the resistance between the enlarged tab or tabs and the corresponding receiving structure, which results in an even tighter coupling between the coupled structures (e.g., first and second syringes)

For example, where one or more of the tabs are formed so as to be of a sufficient arc length so as to out of sync with respect to engagement grooves 58, the lengthened tab(s) experiences increased resistance as it engages grooves 58. First tabs 36 and second tabs 38 are configured and sufficiently aligned such that when first syringe 12 is coupled to second syringe 14, first tab 36 and second tab 38 are received within engagement grooves 58 of second syringe 14. However, because at least one set of tabs is longer than the other, there is increased resistance as the tabs engage grooves 58. This increased resistance results in a tighter seal, which better prevents leaking or accidental uncoupling as components are passed between the syringes.

In another example, where one or more of tabs 36 or 38 are formed so as to have a larger diameter or height with respect to engagement grooves 58, the oversized tab or tabs experience increased resistance as the tabs engage grooves 58. First tabs 36 and second tabs 38 are configured and aligned such that when first syringe 12 is coupled to second syringe 14, first tab 36 and second tab 38 are received within engagement grooves 58 of second syringe 14. The increased diameter or height causes increased resistance between the oversized tab or tabs 36, 38 and engagement grooves 58, thereby preventing leaking or accidental uncoupling as components are passed between the syringes.

FIG. 6A illustrates an embodiment of a locking structure including a pair of second tabs 38, where second tabs 38 include an larger diameter relative to the diameter of first tabs 36. As illustrated, first tabs 36 have a maximum outer diameter D1, while second tabs 38 have a maximum outer diameter D2. Diameter D2 is greater than D1, such that as tip 22 is received within collar 48 (FIGS. 3 and 4), second tabs 38 bias in greater frictional engagement against interior surface 56 of collar 48. Second tabs 38 include an exposed outer surface that may be flat (as depicted), or may alternatively be sloped or pointed so as to wedge or cut against the interior surface 56 of collar 48 within engagement groove 58.

In an alternative example, the maximum outer diameter D1 of first tabs 36 may be the same as the maximum outer diameter D2 of second tabs 38, such that both pairs of tabs are enlarged relative to the diameter (i.e., depth) of engagement groove 58. In such an embodiment (not shown), as tip 22 is received within collar 48 (FIGS. 3 and 4), both first tabs 36 and second tabs 38 bias in greater frictional engagement against interior surface 56 of collar 48 because they are formed so as to have a diameter greater than the depth of engagement groove 58.

FIG. 6B illustrates another embodiment of a locking structure including a pair of second tabs 38′, where second tabs 38′ include an increased height relative to the height of first tabs 36′ (and relative to engagement groove 58′ of second syringe 14). As illustrated, first tabs 36′ have a maximum height H1, while second tabs 38′ have a maximum outer height H2. Height H2 is greater than H1, such that as tip 22′ is received within collar 48 (FIGS. 3 and 4), second tabs 38′ bias in greater frictional engagement against interior surface 56 of collar 48.

In an alternative example, the maximum height H1 of first tabs 36′ may be the same as the maximum height H2 of second tab 38′, such that both pairs of tabs are enlarged relative to the thickness (i.e., width) of engagement groove 58. In such an embodiment, as tip 22′ is received within collar 48 (FIGS. 3 and 4), both first tabs 36′ and second tabs 38′ bias in greater frictional engagement against interior surface 56 of collar 48 because they are formed so as to have a height greater than the width of engagement groove 58. In each of the above described embodiments, the increased resistance between the oversized tab or tabs and engagement groove 58 helps prevent leaking or accidental uncoupling as components are passed between the syringes.

FIG. 7A illustrates an alternative embodiment of a locking structure including a pair of first tabs 36 formed on tip 22, and a ridge 66 projecting outwardly from tip 22 so as to encircle tip 22. Ridge 66 is configured such that engagement grooves 58 of syringe 14 are first engaged by first tabs 36, and then the male thread bounded by engagement groove 58 is biased into direct contact with ridge 66. As a result, the male thread adjacent to engagement groove 58 either rides over and/or gouges into ridge 66 so as to create a tight frictional engagement between engagement grooves 58 and first tabs 36.

FIG. 7B illustrates an alternative ridge 66′ comprising a plurality of smaller ridges 68 or teeth formed on a top surface thereof. Smaller ridges 68 act to bite against the male thread bounded by engagement groove 58 so as to further retain syringes 12 and 14 in locked frictional engagement.

III. Exemplary Alternative Embodiments

FIG. 8 illustrates an alternative locking structure including threads instead of tabs. Outwardly projecting from an exterior surface of tip 22 is a first thread 136 and a second thread 138. Second thread 138 is longitudinally spaced art from first thread 136. Thread 138 includes at least one engagement tooth 70 formed thereon. In use, the syringe locking structure of FIG. 8 may be coupled to a second syringe (e.g., syringe 14) having engagement grooves 58. As coupling begins, engagement grooves 58 of second syringe 14 couple normally with first thread 136, and then second thread 138 begins to engage grooves 58, such that the engagement tooth 70 cuts into the wall of engagement groove 58. This increased frictional engagement increases the seal and coupling strength between the first and second syringes.

Alternatively, engagement grooves 58 may also include corresponding engagement teeth formed thereon. Such an embodiment allows a first syringe to be coupled to a second syringe, which coupling may be so tightly sealed so as to be irreversible (e.g., ratcheting engagement teeth formed on threads 136 and/or 138 irreversibly engage opposing teeth formed in engagement groove 58). Such an irreversible coupling may be useful when coupling a syringe to a dispensing or applicator tip, for example. Although illustrated as including first and second threads 136 and 138 with one or more teeth 70 formed on second thread 138, it will be apparent to one skilled in the art that teeth may be formed on either or both of threads 136 and/or 138. Additionally, one or more of threads 136 or 138 may be replaced with tabs and/or a ridge, which may also include one or more engagement teeth.

FIG. 9A illustrates a cross sectional side view of coupled first and second syringes including an alternative locking structure, while FIG. 9B illustrates a perspective view of the coupled syringes of FIG. 9A. First syringe 212 includes a tip 222. Outwardly projecting from an exterior surface of tip 222 is a first pair of tabs 236 and a second pair of tabs 238. Second tabs 238 are longitudinally spaced art from first tabs 236. An interference structure 272 includes a base 274 attached to the barrel of first syringe 212. An arm 276 extends from base 274 to a partial loop 278.

In use, first syringe 212 may be coupled to a second syringe (e.g., second syringe 14). As coupling begins, engagement grooves of second syringe 214 couple normally with first tabs 236 and second tabs 238, similar to the coupling illustrated in FIG. 5. In an alternative embodiment, tabs 236 and/or tabs 238 may be replaced with threads and/or a ridge, or the system may only include one pair of tabs (e.g., tabs 236). Arm 276 may be flexible so as to allow the user to lock partial loop 278 into place over the collar 248 of second syringe 214, applying pressure, gripping, and/or cutting into the exterior surface of collar 248. Partial loop 278 may be resiliently flexible, and may have an inside diameter that is smaller than the outer diameter of collar 248 such that the loop tightly grips collar 248. A resiliently flexible loop may be flexed so as to fit over collar 248, and upon release, the loop snaps back, tightly gripping collar 248. The inside surface of loop 278 that grips collar 248 may include teeth or other structure so as to more tightly grip and apply pressure to collar 248. Loop 278 grips the exterior surface of the collar opposite to where tabs 236 and 238 engage the engagement grooves of the second syringe. This increased frictional engagement increases the seal and coupling strength between first syringe 212 and second syringe 214.

It is to be appreciated that the above embodiments and alternatives thereof can be grouped in different combinations to achieve the desired effect. Furthermore, the inventive locking structures as disclosed herein can be used on other structures besides syringes. For example, the locking structures may be used on discrete connectors for coupling syringes, dispensing tips to be coupled to a syringe, cartridges, and other types of containers which are to be coupled together.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.