JPH0343973B2 - - Google Patents

Description

Claim 1: one end of a second thermoplastic plastic flexible tube is inserted into the lumen of the first thermoplastic flexible tube, and a volatile lubricant is present between the first and second tubes. grasping the first tube with a gripper jaw so as to form a contacting interface between the tubes; and axially moving the second tube away from the interface with a shaping jaw. rotating at least one of the tubes with respect to the other to heat and soften the contacting interface; ceasing the rotation and releasing the second tube from the molding jaw; Welding the first tube and the second tube by a method of spin welding a soft flexible plastic tube in a nested relationship.

2. The method of claim 1, wherein the lubricant for lubricating the interface between the tubes is water.

3. The method of claim 1, wherein the lubricant for lubricating the interface between the tubes is a hydroalcoholic solution.

4. The method of item 1 or 2, wherein the polygonal cross-sectional shape of the second tube at the position is a square.

5. The method of item 1 or 2, wherein the polygonal cross-sectional shape of the second tube at the position is triangular.

6. The gripping jaw has a substantially circular cross-sectional shape, and has a diameter of 0.06 to 0.2 inches (0.1524 to 0.508 cm).
The method according to any one of items 1 to 5, for forming an interface having widths in contact with each other.

7. The rotating tube rotates for 0.3 to 0.7 seconds.
4.5 The method according to any one of paragraphs 1 to 6, which is driven by rotation.

8 The ratio of the length of the free tip of the second tube within the lumen of the first tube and axially away from the contact interface to the grasped outer diameter of the first tube is 0.75. The method according to any one of the above items 1 to 7.

9 said first and second tubes are made of substantially the same material and have substantially the same durometer not greater than 30;
Method of paragraphs 4, 5, 6, 7 or 8.

10. The method of clause 9, wherein the first and second tubes are made of polyvinyl chloride.

11 means for inserting one end of a second thermoplastic flexible tube into the lumen of the first thermoplastic flexible tube; said first tube so as to form a contact interface between said tubes; gripping the second tube at a location axially remote from the interface and imparting a polygonal shape to the second tube at the location; a polygon-shaped jaw for imparting a cross-sectional shape; heating and softening the contact interface of the tube; and heating and softening the contact interface of the tube;
means for rotating at least one of the jaws with respect to the other of the jaws to weld the tubes.

12. The apparatus of claim 11, wherein said molded jaw is square and provides said second tube with a square cross-sectional shape at said location.

13. The apparatus of claim 11, wherein said molded jaw is triangular and provides said second tube with a triangular cross-section at said location.

14. The means for rotating at least one of the tubes with respect to the other of the tubes includes a magnetic impulse transducer for counting and controlling the number of revolutions of the one tube rotating with respect to the other of the tubes. The device according to any one of paragraphs 11 to 13, which is

FIELD OF THE INVENTION The present invention relates generally to friction or spin welding methods and apparatus. It particularly relates to a method and apparatus for spin welding soft flexible thermoplastics in a nested relationship. A nested relationship between tubes is commonly found in ports on solution bags for storing and dispensing medical fluids.

BACKGROUND OF THE INVENTION It is known to weld two relatively rotating workpieces at a common interface, where the two workpieces engage axially under pressure at their interface. . The technique of spin welding two pieces of plastic is known and has been successfully used to bond two relatively hard pieces of plastic together. It is also known in the art to weld a piece of rigid plastic to a thin-walled flexible tube. For example, U.S. Pat. No. 3,690,088 to Anderson, entitled "Method of Packaging," discloses a method of welding a relatively rigid plastic member to a flexible tubular plastic member. Another method of spin welding thermoplastic workpieces together is discussed in US Pat. No. 4,090,898 to Tuskos, entitled "Method and Apparatus for Spin Welding Thermoplastic Workpieces." One method involves placing the workpieces in separate fixtures, rotating one fixture, and driving the workpieces in contact to effect the weld. The other method disclosed in Tuskos uses a driven workpiece attached to a stationary workpiece. A rotating drive fixture is used to grip, axially drive, and rotate the driven workpiece to accomplish the weld.

Prior art methods for spin welding known thermoplastic pieces are equally unsuccessful when attempting to weld one soft flexible thermoplastic piece to another soft flexible thermoplastic piece.

The only method available to date for joining two pieces of soft flexible thermoplastic is
They used adhesives or solvent adhesives. Using an adhesive or solvent adhesive to connect two pieces of thermoplastic
Not acceptable if highly reliable connections are required. Solvent adhesives are inconvenient to use and store and are considered undesirable by some.

In certain medical applications, flexible plastic containers, particularly polyvinyl chloride (PVC) bags, have membrane tubes telescopically connected to ports on the container. For example, Baxter, Travenol Laboratories, Inc. manufactures a two-peritoneal dialysis fluid bag that has two ports with membrane access and injection site tubes nested into the ports. Conventional manufacturing uses a solvent adhesive (cyclohexanone) to connect the tube to the port. It would be desirable to obtain a reliable connection to a port while eliminating the use of solvent adhesives.

Spin welding is an alternative, but 2
Spin welding relatively soft flexible plastic tubes (especially PVC) has proven difficult. Relatively soft plastic tubes generally have a durometer of no more than 30. Nevertheless, if a satisfactory spin welding process were to be found, the particulate matter typically inherent in spin welding processes would have to be minimized or eliminated if the plastic pieces were intended for medical use. It will not happen.

The present invention provides a method and apparatus for nesting spin welding of soft, flexible thermoplastic tubes, eliminating the need for the use of solvent adhesives. The generation of particulate plastics is minimized or eliminated by controlling the relative rotational speed of one plastic piece over a given period of time and by controlling the free tip length of the inner tube beyond the welded interface. Ru.

SUMMARY OF THE INVENTION The present invention overcomes the shortcomings of the prior art by providing a method and apparatus for nesting spin welding of soft flexible thermoplastic tubes. The method eliminates the inconveniences encountered in the use and storage of solvent adhesives. A more reliable connection is obtained and generated particulates encountered with spin welding are minimized or eliminated.

In practicing this method, soft flexible thermoplastic tubes are nested one within the lumen of the other. Volatile lubricants, such as water and hydroalcoholic solutions, are added between the tubes. The tubes may or may not be in contact at this stage. A gripper compresses and shapes the outer or first tube, imparting a circular cross-section to the tube and ensuring interfacial contact between the inner and outer tubes. The gripper also compresses both tubes equally and makes them rigid. axially distant from the interface, an inner or second tube is chucked by a molding jaw;
Give the inner tube a polygonal cross-sectional shape. The protruding corners of the polygonal cross-sectional tube are in frictional contact with the lumen of the outer tube. Preferably the inner tube is gripped by a non-rotational molding jaw.
Once the inner tube is gripped by the molding jaw, the molding jaw is rotated. In this manner, the amount of particulate plastic generated is reduced. When the inner tube rotates relative to the outer tube, frictional heat is generated softening the contacting interface. When the molded jaw releases the inner jaw, the two tubes are welded together. The centrifugal force of the rotating inner tube deforms the corners of the inner tube radially, creating closer contact,
Therefore, a larger frictional force is generated at the interface.

The device of the invention includes means for nestingly inserting one soft flexible thermoplastic tube into the lumen of another soft flexible thermoplastic tube. A gripper and a molder are provided. The gripper jaws form a contacting interface between the tubes, and the shaping jaws grip and shape the inner tubes at a portion axially remote from the interface. Means is provided for rotating at least one of the jaws relative to the other in order to generate frictional heat to soften the contacting interface and thereby weld the tubes together.

It is an object of the present invention to provide a method and apparatus for spin welding together soft flexible thermoplastic tubes.

Another object of the present invention is to provide a spin welded connection between nested soft flexible thermoplastic tubes to eliminate the inconvenience of using solvent adhesives.

Another object of the invention is to provide a spin welded connection between nested flexible thermoplastic tubes that is more reliable than an adhesive connection.

Yet another object of the present invention is to provide a method and apparatus for spin welding soft flexible thermoplastic tubes in which generated particulate matter that is commonly a natural result of spin welding is minimized or eliminated. It is to be.

Other objects and advantages of the invention will become apparent upon reading the following detailed description and claims.

[Brief explanation of drawings]

For a fuller understanding of the invention, reference is made to the specific examples illustrated in detail in the accompanying drawings. In the drawings: FIG. 1 is a perspective view of a prototype device of the invention.

FIG. 2 is a partial perspective view of a prototype device of the present invention in which the gripper jaws engage a nesting tube and port combination on a container bag.

FIG. 3 is a partial perspective view of a prototype device of the present invention with a gripper jaw engaging a nesting tube and port combination on a container bag and a rotating molded jaw engaging an inner tube; .

FIG. 4 is a perspective view of the prototype device of the present invention viewed from below to show the molded jaw.

FIG. 5 is an end view of the molded jaw illustrating the chucking surfaces forming a square.

FIG. 6 is an end view of the molded jaw illustrating the chucking surfaces forming a triangle.

7 is a cross-sectional view of the gripper jaw engaging the telescoping tube and port combination taken along line 7--7 of FIG. 2; FIG.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning now to the drawings, FIG. 1 is a perspective view of an apparatus 10 of the present invention. The device 10 includes a frame 12 on which an air motor 14 is mounted. The vertical movement of frame 12 is controlled by hydraulic cylinders 16, 16
controlled by a. A gear-shaped member 20 is connected to the shaft 18 of the air motor 14 . A chuck assembly means 22 is also attached to the motor shaft 18 and includes a spring 24 for biasing the collar 26 of the collet 29 downwardly and terminates in a molded jaw 28. The circular gripping surface 32 of the gripper jaw 30 is axially aligned with the molded jaw 28 . The control unit 34 uses a magnetic impulse counter to count and control the number of drive revolutions of the shaft 18 during a predetermined period of time.

The gripper jaws are shown in their open position prior to inserting a piece of plastic tube therein. Similarly, molded jaws 28 are shown in their open position prior to engagement with the inner tubes of the nesting combination. Spring 24 tends to bias collar 26 of collector 29 downward. A fork means or bar 36 is used to raise the collar 26 or drive the collet 29 over the molding jaw and thereby grip the tube therein.

In the illustrated embodiment, the molding jaw is driven in rotation, thereby driving the tube chucked therein in rotation. The gripper jaw 30 molds and compresses the nested tube chucked therein, but thus remains rotationally secure.

The arrangement of the tube in the embodiment illustrated in FIG.
The intention is to rotate the inner or second tube 40 while rotationally fixing the tube 38 and compressing and stiffening the outer tube 38 and the inner tube 40. Other embodiments of the invention include:
It is intended to rotationally fix the molding jaw and thus the inner or second tube while the gripping jaw rotates the gripping jaw and the outer or first tube as it performs its function of stiffening the outer tube. The first or outer tube is
The molding jaw may be rotated by the gripping jaw in the opposite direction while rotating the second or inner tube.

Still referring to FIG. 2, gripper jaws 30 are shown in their closed gripping position. Outer tube 38 and inner tube 40 are shown nested and held together by gripping jaws 30 to form a contacting interface. Prior to chucking by gripper jaw 30, outer tube 38 and inner tube 40 may or may not be in contacting engagement. Outer tube 38 is actually a port tube on container bag 42.

In FIG. 3, molded jaw 28 is checking the inner tube. To engage the inner tube, the frame 12 and attached structure is lowered so that the molded jaw 28 covers the inner tube. Once the inner tube is covered by the molded jaw 28, the fork means is attached to the collet 29.
Driven up and down to engage the molded jaw onto the inner tube. The fork means remains engaged and the air motor is used to drive the molding jaw. Rotating the inner tube relative to the outer tube generates frictional heat that softens the contacting interface. At the end of the rotation, the fork means 36 is raised. The inner tube is released from the molding jaw and the outer tube and inner tube are welded together at their interface.

Preferably, the inner tube 40 is engaged by a non-rotating molded jaw 28. After the nested combination of inner tube 40 and outer tube 38 has been chucked by gripper jaw 30 to form a contact interface, and when inner tube 40 has been chucked or engaged, molding jaw 2
8 starts rotating. Rather than engaging the inner tube with a rotating molded jaw, by checking and then rotating the molded jaw,
Particulate matter generated is reduced. Both tubes are held together until after the combination is engaged by the gripper jaws.
Preferably, the inner tube remains stationary until after it is engaged by the molded jaw.

Preferably the inner and outer tubes are made of substantially the same material and have substantially the same durometer of no greater than 30. The preferred plastic for the tube is polyvinyl chloride.

In carrying out this method, a volatile lubricant, such as water or a hydroalcoholic solution, is added to the inner tube 4.
0 and the outer tube 30 (FIG. 2). Referring again to FIG. 1, precise control of the drive speed of forming jaw 28 is essential to minimizing or eliminating the amount of generated particulate matter generated during the welding operation. Optimally, 4.5 revolutions within a time period of 0.3 to 0.7 seconds minimizes particulate matter.

The driven revolutions of the forming jaw 28 are counted by a magnetic impulse counter which is part of the control unit 34. The gear-shaped member 20 is used in conjunction with a control unit 34. On the gear-shaped member 20, two teeth 180° apart project further radially outward than the remaining teeth. When these extending teeth pass the magnetic impulse counter, one count is recorded in the control unit 34. After 9 counts (4.5 revolutions), the air motor 14 is disengaged and
The molding jaw 28 is no longer driven. Within a few hundredths of a second, the forming jaw 28 stops rotating, after which the fork means 36 lifts the collar 26, disengaging the collet and moving the inner tube 40 into the forming jaw 2.
Release from engagement with 8.

Referring now to FIG. 4, teeth 44, 46 on gear-shaped member 20 are 180° apart and gear-shaped member 2
It is shown to extend further radially than the other teeth on 0. Grasping jaws 30 are shown in their open position. Typically, the gripping jaws 30 are configured to form a corresponding contact interface between the outer tube 38 and the inner tube 40.
0.060 to 0.200 inch wide. In the practice of the invention, outer tube 38 has an outer diameter of 0.350 inch, which is 0.230 inch by gripper jaw 30.
Reduced to an inch outside diameter. By doing so, the gripper 30 stiffens the soft flexible outer tube. Molded jaws 28 are also shown in their open position. 5 and 6 illustrate two particularly preferred polygonal shapes for the molded jaw 28. FIG. 5 illustrates a molded jaw 28a having a chuck surface that forms a square shape when closed. FIG. 6 illustrates a molded jaw 28b having a chuck surface that forms a triangular shape when closed.

The cross-sectional view of FIG. 7 illustrates the gripping jaws 30 in their closed position, with the circular gripping surface 32 contacting the outer tube 38. Free tip 44
is formed by a free length of the inner tube extending axially beyond the gripped tube contact interface. Particulate matter generated from the action of spin welding can be minimized or eliminated by controlling the ratio of the free tip 44 to the outside diameter of the gripped outer tube. When this ratio is greater than 0.75, minimal to undetectable particulate matter is generated.

The above is provided for illustrative purposes only;
It is not intended to limit the invention as defined in the claims.