Assembly of a tube and a part and apparatus and method of manufacture

• US 5,280,130 A
• Filed: 05/22/1992
• Issued: 01/18/1994
• Est. Priority Date: 05/22/1992
• Status: Expired due to Fees

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Biomedical Sensors Limited (Allegro Biodiesel Corp.)
• Inventors: Markle, David R., Paterson, William
• Primary Examiner(s): Picard, Leo P.
• Assistant Examiner(s): TONE, DAVID
• Application Number:
  US07/887,993
• Time in Patent Office: 606 Days
• Field of Search: 174/1, 174/DIG. 8, 128/634, 403/273
• US Class Current: 174/1
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/1473 invasive, e.g. introduced into the body by a catheter A61B5/1482 takes precedence
• CPC Class Codes: B29C 61/04 Thermal expansion
• CPC Class Codes: B29C 65/66 by liberation of internal stresses, e.g. shrinking of one of the parts to be joined
• CPC Class Codes: B29C 66/1122 Single lap to lap joints, i.e. overlap joints B29C66/45, B29C66/472, B29C66/52272 take precedence
• CPC Class Codes: B29C 66/52 Joining tubular articles, bars or profiled elements
• CPC Class Codes: B29C 66/91411 of the parts to be joined, e.g. the joining process taking the temperature of the parts to be joined into account
• CPC Class Codes: B29L 2031/7542 Catheters
• CPC Class Codes: Y10S 174/08 Shrinkable tubes
• CPC Class Codes: Y10T 403/48 Shrunk fit

Abstract

An apparatus for assembling a tube and a part has a polymeric tube with an axis along the longitude thereof. The part has a cross sectional shape and size to be near an inside surface of the tube when the part is at least partially therewithin. The part or tube is supported so that relative movement along the axis places the part at least partially within the tube located between the ends or in the tube near the distal or proximal end thereof. The part and/or the tube is a thermoplastic polymer made by a process that develops within the polymer a memory of the polymer prior to forming so that residual stresses remaining in the part can be relaxed by changing temperature causing expansion. A form of a relatively nonconductive material is positioned for relative movement along the axis and for placement about the tube. The form is shaped and sized to fit and contain the outside surface of the tube. A heater has an electrically resistive element wrapped about the form for changing the temperature of the tube and the part. A method of assembly of the tube has the steps of supporting it and/or the part for relative movement along the axis placing the part at least partially within the tube, positioning the form for relative movement along the axis for placement about the tube whereinside the part is located to thereby contain the outside surface, changing the temperature of the tube and the part sufficiently to relax residual stresses of the manufacturing processes used to make the tube and/or the part for causing engagement of the inside surface of the tube and the part.

Claims

1. An apparatus for assembling a tube and a part inserted at least partially therwithin comprising:

a tube having a longitudinal axis, inside and outside surfaces, proximal and distal ends, an internal cross sectional shape identical to the part and defined by a bore therethrough and a cross sectional size larger than the part prior to changing temperature;

a part with a cross sectional shape and size to be near the inside surface of the tube when the part is at least partially within the tube and having an external cross sectional size identical to the internal cross-sectional size of the tube after change in temperature and initially a circular cross sectional shape of a diameter that allows some axial movement within the tube when there is substantially no contact with the inside surface, the part or the tube being supported so that relative movement along the axis places the part at least partially within the tube, and wherein the part is made of a thermoplastic polymer by a process that develops within the polymer thereof a memory of the unshaped thermoplastic polymer prior to forming into the cross sectional shape of the part so that residual stresses remaining in the part are relaxed by changing temperature causing expansion of the cross sectional size of the part;

a form positioned for relative movement along the axis for placement about the tube whereinside the part is located, the form shaped and sized to fit the tube outside surface and contain it, and

a heater associated with the form for changing the temperature of the tube and the part sufficiently to relax residual stresses of the manufacturing processes respectively used to make the tube and the part and thereby permit engagement between the inside surface and the part.

2. An apparatus according to claim 1 wherein the process for making the theremoplastic polymer part is an extrusion process.

3. An apparatus according to claim 1, wherein the part and the tube are formed of a polymer and the heater changes the temperature beyond the glass transition point of the polymer allowing the part to expand to the external cross-sectional size identical to the internal cross sectional size of the tube and to remain expanded thereafter and engaged together.

4. An apparatus according to claim 3 wherein the form, the tube and the part are generally circular.

5. An apparatus according to claim 4 wherein the form is made of a relatively nonconductive material.

6. An apparatus according to claim 5 wherein the heater is made of an electrically resistive element wrapped about the form.

7. An apparatus according to claim 4 wherein the part is located in the tube between the ends thereof.

8. An apparatus according to claim 4 wherein the part is located in the tube near the distal of proximal end thereof.

9. An apparatus according to claim 4 wherein the part engages the tube to seal with a fluid tight juncture therebetween.

10. An apparatus for assembling a tube and a part inserted at least partially therewithin comprising:

a polymeric circular tube with a bore therethrough along a longitudinal axis, inside and outside surfaces and proximal and distal ends;

a part with a circular cross sectional shape and size to fit within the inside surface of the tube when the part is at least partially within the tube, the part or the tube supported so that relative movement along the axis places the part at least partially within the tube, the cross sectional size of the part having a diameter that allows axial movement of the part into the tube, the part being made of a thermoplastic polymer by a process that develops within the polymer thereof a memory of the unshaped thermoplastic polymer prior to forming into the cross sectional shape of the part;

a form of a relatively nonconductive material shaped to circumscribe the outside surface, the form supported for relative movement along the axis for placement about the tube whereinside the part is located, the form being shaped and sized to fit the tube outside surface and contain it, and

a heater including an electrically resistive element wrapped about the form for changing the temperature of the tube and the part sufficiently and beyond the glass transition point of their polymers to relax residual stresses of their respective manufacturing processes used to make the tube and the part and thereby cause expansion and engagement of the part and the inside surface as the tube has across sectional size larger than the part prior to changing temperature and the part has an external cross sectional size identical to the internal cross sectional size of the tube after change in temperature because the form restricts radial expansion of the outside surface.

11. A method of assembly of a tube with a longitudinal axis, inside and outside surfaces and proximal and distal ends and a part with a cross sectional shape and size to be near the inside surface of the tube when the part is at least partially within the tube using a form shaped and sized to fit about the tube outside surface and a heater associated with the form;

which method comprises;

supporting the tube or the part so that relative movement therebetween and along the tube axis places the part at least partially within the tube;

positioning the form for relative movement along the axis for placement about the tube whereinside the part is located to thereby contain the outside surface;

clearing displaced fluid about the junction between the part and the tube before heating;

changing the temperature of the tube and the part sufficiently to relax residual stresses of the manufacturing process respectively used to make the tube and the part for causing engagement of the inside surface of the tube and the part; and

conducting sufficient heat through the form into the part to relax residual stresses therein to cause engagement between the part and the tube.

12. A method according to claim 11 wherein the clearing of displaced fluid is performed by moving a gas about the space.

13. A method according to claim 12 wherein the gas is moved by applying a vacuum near the space.

14. An assembly of a tube and a part inserted at least partially therewithin comprising:

a circular tube with a bore therethrough a longitudinal axis, inside and outside surfaces, proximal and distal ends, and an internal circular cross sectional shape;

a part with a circular cross sectional shape and size to fit within the inside surface of the tube when the part is at least partially within the tube, the part made of a thermoplastic polymer by a process that develops within the polymer thereof a memory of the unshaped thermoplastic polymer prior to forming into the cross sectional shape of the part so that residual stresses remaining in the part are relaxed by changing temperature causing expansion of the cross sectional size of the part by exceeding the glass transition point of the polymer to relax residual stresses of the manufacturing extrusion process used to make the part and thereby cause the part to engage the inside surface of the tube so the internal cross sectional size of the part remains expanded and engaged against the tube after the change in temperature, the part being between the ends of the tube or at an end of the tube, wherein the tube is extruded thermoplastic polymer so that relaxation of residual stresses by change in temperature causes the inside surface thereof to move toward the part for engagement.

15. An assembly according to claim 14 wherein the tube has conductors passing therewithin so that relaxation of residual stresses by change in temperature coupled with urging the tube toward where it is heated causes the inside surface thereof to become a radially inwardly expanded section that engages the conductors for supporting them in passages created thereby and holds in space apart relation.