GB1589931A

GB1589931A - Solvent-bonded joint and method of making the same

Info

Publication number: GB1589931A
Application number: GB45455/77A
Authority: GB
Original assignee: American Hospital Supply Corp
Current assignee: American Hospital Supply Corp
Priority date: 1977-03-10
Filing date: 1977-11-01
Publication date: 1981-05-20
Also published as: DE2810559A1; FR2382998A1; AU3025777A; NL7712337A

Description

(54) SOLVENT-BONDED JOINT AND METHOD OF MAKING THE SAME (71) We, AMERICAN HOSPITAL SUPPLY CORPORATION organized and existing under the laws of the State of Illinois, United States of America, of 1740 Ridge Avenue, Evanston, Illinois 60201, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement:- Various methods have been used in the past for permanently joining plastics parts in fluidtight sealing relation, including heat sealing and solvent-bonding techniques. Heat sealing, although widely used, ordinarily requires elaborate supports and operating mechanisms to achieve reliability and production volume in the assembly or relatively small plastics parts such as, for example, filter housing, couplings, port assemblies, and other elements and assemblies commonly used in medical equipment.

Solvent sealing, which ordinarily involves coating one of the parts with solvent before the two parts are fitted together, is suitable for some operations but has severe limitations for volume production. Parts once coated must be immediately assembled; it is not feasible, for example, to coat successively a multiplicity of parts and then assemble them in a batch-type operation. Also, in those cases where one of the parts contains (or communicates with) a liquid, the usual solvent coating and fitting operations are not only awkward and unwieldly, but present risks of liquid interrfering with proper solvent bonding and, even more important, of small amounts of solvent invading the liquid-containing compartment. It is apparent that any contact between the liquid or solvent is undesirable and, especially if it might result in contamination of the liquid (such as parenteral fluid), must be strictly avoided.

An important aspect of this invention lies in the discovery that the shortcomings of conventional solvent-bonding techniques might be overcome by pre-assembling the parts to form a temporary liquid-tight seal, and then introducing any appropriate solvent for the plastics materials involved into a graduallytapered crevice leading to the seal, the solvent flowing into and being retained within the crevice by a capillary action. The temporary seal serves as a barrier to block the extent of capillary flow of the solvent and, in those cases where a liquid, such as a parenteral solution, is disposed on the other side of that barrier, the interference fit prevents contact between such a liquid and the solvent. Furthermore, because of the capillary action, solvent introduced into the crevice will remain in that crevice even though the parts are handled and oriented at random. Unlike prior solvent-welding techniques, the method of this invention permits pre-assembly of a multiplicity of parts and, after all have been assembled, solvent may then be applied to each assembled pair to complete the solventwelding process.

Accordingly, from one aspect, the invention consists in the method of joining two plastics members, comprising forming said members for frictional engagement therebetween in a fluid-tight zone of interference with a crevice leading to the zone of interference, fitting said members together in frictional engagement with said zone of interference serving as a fluid-tight barrier, simultaneously spacing said members apart by means of spaced points of contact disposed in a series along the entrance to said crevice, and thereafter introducing a solvent into said tapered crevice and between said points of contact to form a solvent bond between said members, with said zone of interference serving as a barrier against contact between said solvent and any flowable material on the opposite side of said zone.

The series of uniformly-and circumferentially-spaced nubs or projections, formed integrally with at least one of the members, which extends about the mouth of the crevice at the time of solvent introduction, serves to maintain the parts in concentric relation, with the mouth of the crevice at uniform width, throughout solvent sealing, thereby ensuring the formation of a circumferentially-uniform solvent bond between the parts. The nubs may also contribute in retaining solvent immediately following its introduction and pro viding a visual indication when the preferred amount of solvent has been introduced. When solvent has been added to the optimum level or extent, evaporation of such solvent is accompanied by concurrent dissolving of the nubs so that upon completion of the solvent bonding step the nubs are substantially if not entirely dissolved and the plastics material thereof is reformed as part of the joint.

The invention also consists in a joint allowing liquid flow comprising a pair of plastics members frictionally engageable in a liquidtight zone of interference, a crevice between said plastics members leading to said zone of interference with said zone of interference serving as a barrier against flowable material entering said crevice from the opposite side of said barrier, and a solvent bond between said plastics members in said crevice.

The invention further comprises, in combination, a pair of plastics members frictionally joined together along a fluid-tight zone of interference with a tapered crevice between said members leading to said zone, said members being tubular and including an outer member having an end portion telescopingly receiving an end portion of an inner member, said zone of interference being disposed adjacent the end portion of said inner member, said outer tubular member having a tubular insert portion disposed within said inner member, said insert portion frictionally engaging the inner surface of said inner member to form a second fluid-tight zone of interference, and a solvent bond between said plastics members within said crevice.

The method of the present invention includes forming two plastics members for frictional engagement in a fluid-tight zone of interference with a tapered crevice leading to that zone of interference, fitting the members together in preliminary sealing engagement with the zone of interference serving as a barrier against fluid flow, and introducing a solvent into the tapered crevice to form a permanent solvent bond between the parts.

Where one of the parts is associated with a body of liquid or other flowable material (as, for example, where such part constitutes the neck of a liquid-containing plastics bag), the frictional seal blocks such material from flowing into the crevice through its apical end and from interfering with the subsequent formation of a solvent bond, and later, after solvent is introduced, prevents such solvent from entering the material-containing chamber and possibly contaminating that material.

The joint is therefore suitable for carrying a flowable material such as a sterile medical liquid suitable for use in surgery or for administration to a patient.

In order that the invention may be more clearly understood, reference will now be made to the accompanying drawings in which Figure 1 is a front elevational view of a bag adapted for use in the administration of medi cal liquid, the bag utilizing the solventbonded joint and method embodying this invention.

Figure 2 is a longitudinal sectional view showing the assembled parts just prior to solvent introduction and fusion.

Figure 3 is a side elevational view showing the parts in exploded condition.

Figure 4 is a greatly enlarged longitudinal sectional view of a portion indicated by a circle in Figure 2.

Figure 5 is an enlarged transverse cross sectional view taken along line 5-5 of Figure 2.

Figure 6 is an enlarged longitudinal sectional view showing the joint of the present invention during introduction of a solvent to form the solvent bond.

Figure 7 is a fragmentary sectional view similar to Figure 6 but showing the parts following solvent fusion.

With reference to Figure 1, the numeral 101 generally designates a parenteral fluid administration bag having an outlet port assembly 111.

The part assembly includes a solvent joint 121 (Figure 7) formed in accordance with one embodiment of this invention. The solvent joint is particularly well suited for use in such medical liquid administration equipment for operatively connecting the components together even where one of the components (such as the bag of this illustration) contains such liquid at the time the solvent joint is formed.

The outlet portion assembly 111 includes a tear cap 131, a port closure 141, and an outlet tube or neck 151. The tube has one end attached to a corner of the bag 101 and communicates with the interior of that bag. Port closure 141 includes a tubular insert portion 161 which is received within the end of neck or tube 151 and which terminates in a diaphragm 171. The port closure also has a concentric outer skirt portion 181 which extends about the insert portion and is joined thereto by integral connecting portion 191.

The solvent joint 121 is formed between a pair of plastics members or parts which, in the illustration given, constitue the outlet tube or neck 151 and the outer portion or skirt 181 of port closure 141. It is to be understood, however, that the joint is shown as being operatively associated with an outlet port assembly primarily for purposes of illustrating one of the many advantageous applications of this invention. Accordingly, the solvent joint in the following description is equally well suited for joining plastics members of many different configurations within the contemplation of the present invention.

Referring to Figures 4 and 5, in which the parts are shown just prior to solvent introduction and fusion, members 151 and 181 arse in fluid-tight frictional contact along an annular zone of interference 201. That zone of interference takes the form of direct sealing contact between the inner surface of skirt member 181 near the base thereof and the outer surface of tube member 151 adjacent its free end. A tapered crevice 211 extends from the free end of skirt member 181 to the zone of interference 201.

In the embodiment shown, member 18 is provided with a plurality of uniformly-and circumferentially-spaced enlargements or nubs 231 which bear against the outer surface of member 151 and which extend in a series substantially parallel with, but spaced from, the zone of interference 201. Figure 4 reveals that the nubs or projections are disposed near the free end of skirt portion 181, that is, adjacent the mouth or entrance to the crevice and at a substantial axial distance from interference zone 201.

A second zone of interference 241 is located between the inner surface of port tube 151 (adjacent the end of that tube) and the outer surface of the base of insert 161. Therefore, insertion of the port tube 151 into the annular recess of the port closure 141 results in the formation of two fluid-tight sealing zones 20 and 241 with the enlargements or projections 231 of member 181 bearing forceably against the outer surface of member 151. The projections control the configuration of the tapered crevice 211, maintaining its dimensions substantially uniform throughout the entire circumference of the assembly and ensuring that solvent introduced after the parts have been so pre-assembled will be distributed uniformly by a capillary action regardless of the circumferential location of solvent introduction.

It is believed apparent that the invention is of particular importance where the cooperating members 151 and 181, or at least the latter of these members, are formed of flexible plastics material. Any flexible plastics material capable of being solvent bonded may be used. Examples are plasticised polyvinyl chloride and styrene butadiene; however, other solvent-bondable plastics materials having similar properties are well known and may be used.

The circumscribing skirt portion 181, which may be regarded as an overlapping or receiving member, has an inner surface which forms an angle of from 1 to 20 degrees, and preferably 2 to 6 degrees, with respect to the outer surface of member 151. Stated differently, in the preferred form of the invention the taper of crevice 21 is 2 to 6 degrees. Such a relationship ensures that solvent will wick into the crevice to the zone of interference 201 and will remain in the crevice even if the parts are inverted immediately following introduction of the solvent.

The method of joining the parts is as follows: The parts are first fitted together in frictional engagement as shown in Figures 2, 4, and 5. Precise relative positioning of the parts is easily achieved because no solvent is yet present and fusion has therefore not commenced. When the parts are properly interfitted, zone of interference 241 is formed and serves primarily as a liquid-tight barrier to block the flow of liquid (or other flowable material) from bag 10' to the tapered crevice 211 where it might otherwise wet the surfaces of that crevice and prevent the formation of an effective solvent bond.

The solvent bond 121 is formed by introducing solvent 221 into the mouth of the crevice as indicated in Figure 6. The liquid solvent spreads uniformly about member 15 within the crevice, exposing the opposing surfaces of the parts to uniform solvent action.

While the amount of solvent might be varied according to preference, in the best mode presently known for practicing the invention a sufficient volume of solvent is added to surround the nubs or projections 231. Under such circumstances, the nubs serve as a gauge to indicate whether a sufficient solvent volume has been introduced. If the solvent bridges the space between adjacent nubs, then the volume of added solvent is at or near its optimum level.

Following addition of liquid solvent 221, the solvent begins to evaporate and also commences to dissolve the strata of plastics material in direct contact therwith. The final solvent-formed bond 121 results when evaporation is completed. At that time the parts assume the relationship somewhat schematically depicted in Figure 7. It is to be understood that the material illustrated in the crevice and designated by a stippled shading, is resolidified plastics from members 141 and 151. Hence, the joint is a fusion joint and in actual practice the material in the previouslyexisting crevice is visually indistinguishable from the plastics members themselves. Furthermore, where the joint is formed by adding solvent to a level at or above projections 231, such projections no longer exist in their original form, at least to any appreciable extent in the final joint. After functioning as spacers to insure uniform distribution of solvent within the crevice, such projections themselves dissolve, at least partly because of their relatively great surface area, and become part of the resolidified mass of material which fuses the parts together.

As the solvent is evaporating, interference zone 201 performs the function of blocking the escape of solvent through the apex of the crevice. Therefore, the two zones of inter ference, zones 201 and 241, together prevent contact between the liquid (or other flowable material) within the bag and the solvent introduced to form the permanent joint, eliminating the risk of contaminating the contents of the bag by solvent, and also reduce the danger that the flowable contents of the bag might impair the formation of an effective solvent bond. The result, following introduction of the solvent and evaporation thereafter, is a permanent solvent bond 121 which provides a contamination-proof and leadk-proof joint between the parts.

The solvent 221 may be formulated from any of a variety of well-known plastics solvents such as, for example, cyclohexanone or tetrahydrofuran. As used herein, the term "solvent" means any liquid bonding agent which has some capability of dissolving or softening the plastics material or materials from which the parts are formed, even though such agent may also contain fillers or other ingredients which have no such properties.

Thus, a bodied solvent, or a cement having a liquid medium which is also a solvent for the plastics materials, is regarded as a solvent within the meaning of this application.

WHAT WE CLAIM IS: 1. The method of joining two plastics members comprising forming said members for frictional engagement therebetween in a fluid-tight zone of interference with a crevice leading to the zone of interference, fitting said members together in frictional engagement with said zone of interference serving as a fluid-tight barrier, simultaneously spacing said members apart by means of spaced points of contact disposed in a series along the entrance to said crevice, and thereafter introducing a solvent into said tapered crevice and between said points of contact to form a solvent bond between said members, with said zone of interference serving as a barrier against contact between said solvent and any flowable material on the opposite side of said zone.

2. The method of Claim 1, in which said members are tubular and in which an end of one of said members telescopically receives an end of the outer of said members in overlapping relationship.

3. The method of Claim 2, in which said crevice is tapered.

4. The method of Claim 3, in which the overlapping portions of said members define said tapered crevice and said end of said telescoping member frictionally engages said end of said receiving member at said zone of interference.

5. The method of Claim 4, in which the overlapping portion of said receiving member forms an angle of 1 to 20 degrees with respect to the overlapped portion of said telescoping member.

6. The method of Claim 5, in which said angle falls within the range of 2 to 6 degrees.

7. The method of Claim 5, in which said receiving member includes a tubular insert portion disposed within said other of said members, said insert portion engaging said other of said members to form a second zone of interference.

8. The method of Claim 4, in which said tapered crevice is an annular recess for receiving said solvent to form said solvent bond adjacent said zone of interference.

9. The method of Claim 8, in which the overlapping portion of said receiving member forms an angle of 1 to 3 degrees with respect to its axis and the overlapped portion of said telescoping member forms an angle of 1 to 3 degrees with respect to its axis whereby the overlapping portion of said receiving members form an angle of 2 to 6 degrees with respect to the overlapping portion of said telescoping member.

10. The method of Claim 8, in which the overlapping portion of said receiving member is provided with an annular shoulder and said telescoping member is inserted into said receiving member in abutting relationship with said shoulder.

11. The method of Claim 8, in which said solvent flows through said annular recess to said zone of interference to form said solvent bond by capillary action.

12. The method of Claim 8, in which said members are formed of rigid plastics material.

13. The method of Claim 1 in which said plastics members are formed of flexible plastics material.

14. A joint allowing a liquid flow comprising a pair of plastics members firctionally engageable in a liquid-tight zone of interference, a crevice between said plastics members leading to said zone of interference with said zone of interference serving as a barrier against flowable material entering said crevice from the opposite side of said barrier, and a solvent bond between said plastic members in said crevice.

15. The joint of Claim 14, in which said members are tubular and in which an end of one of said members telescopically receives an end of the other of said members in overlapping relationship.

16. The joint of Claim 15, in which said crevice is tapered.

17. The joint of Claim 16, in which the overlapping portions of said members define said tapered crevice and said end of said telescoping member frictionally engages said end of said receiving member at said zone of interference.

18. The joint of Claim 17, in which said tapered crevice is an annular recess for receiving said solvent to form said solvent bond adjacent said zone of interference.

19. The joint of Claim 17, in which the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. ference, zones 201 and 241, together prevent contact between the liquid (or other flowable material) within the bag and the solvent introduced to form the permanent joint, eliminating the risk of contaminating the contents of the bag by solvent, and also reduce the danger that the flowable contents of the bag might impair the formation of an effective solvent bond. The result, following introduction of the solvent and evaporation thereafter, is a permanent solvent bond 121 which provides a contamination-proof and leadk-proof joint between the parts. The solvent 221 may be formulated from any of a variety of well-known plastics solvents such as, for example, cyclohexanone or tetrahydrofuran. As used herein, the term "solvent" means any liquid bonding agent which has some capability of dissolving or softening the plastics material or materials from which the parts are formed, even though such agent may also contain fillers or other ingredients which have no such properties. Thus, a bodied solvent, or a cement having a liquid medium which is also a solvent for the plastics materials, is regarded as a solvent within the meaning of this application. WHAT WE CLAIM IS:

1. The method of joining two plastics members comprising forming said members for frictional engagement therebetween in a fluid-tight zone of interference with a crevice leading to the zone of interference, fitting said members together in frictional engagement with said zone of interference serving as a fluid-tight barrier, simultaneously spacing said members apart by means of spaced points of contact disposed in a series along the entrance to said crevice, and thereafter introducing a solvent into said tapered crevice and between said points of contact to form a solvent bond between said members, with said zone of interference serving as a barrier against contact between said solvent and any flowable material on the opposite side of said zone.

3. The method of Claim 2, in which said crevice is tapered.

16. The joint of Claim 15, in which said crevice is tapered.

19. The joint of Claim 17, in which the

overlapping portion of said receiving members forms an angle of 1 to 20 degrees with respect to the overlapped portion of said telescoping member.

20. The joint of Claim 19, in which said angle falls within the range of 2 to 6 degrees.

21. The joint of Claim 20, in which the overlapping portion of said receiving member forms an angle of 1 to 3 degrees with respect to its axis and the overlapped portion of said telescoping members forms an angle of 1 to 3 degrees with respect to its axis whereby the overlapping portion of said receiving member forms an angle of 2 to 6 degrees with respect to the overlapped portion of said telescoping member.

22. The joint of Claim 17, in which the overlapping portion of said receiving member is provided with an annular shoulder and said telescoping member is inserted into said receiving member in abutting relationship with said shoulder.

23. The joint of Claim 20, in which at least one of said members is formed of rigid plastics material.

24. The method of Claim 1, in which said spaced points of contact are defined by integral projections from one of said members engaging the other of said members adjacent the mouth of said crevice, said solvent being introduced in a quantity sufficient to substantially dissolve said projections in the formation of said solvent bond.

25. The method of Claim 1, in which at least one of said members communicates with a body of flowable material at the commencement and throughout the performance of said method.

26. The method of Claim 25, in which said flowable material is a liquid.

27. In combination, a pair of plastics members frictionally joined together along a fluid-tight zone of interference with a tapered crevice between said members leading to said zone, said members being tubular and including an outer member having an end portion telescopingly receiving an end portion of an inner member, said zone of interference being disposed adjacent the end portion of said inner member, said outer tubular member having a tubular insert portion disposed within said inner member, said insert portion frictionally engaging the inner surface of said inner member to form a second fluidtight zone of interference, and a solvent bond between said plastics members within said crevice.

28. The combination of Claim 27, in which said tubular members are formed of flexible plastics material.

29. The methods of joining plastics members substantially as hereinbefore described with reference to the accompanying drawings.

30. An assembly of plastics members joined by the method claimed in any of claims 1 to 13, 24 to 26 and 29.

31. Assemblies of plastics members substantially as hereinbefore described with reference to the accompanying drawings.