Device for welding plastic tubes

[0001] Various techniques have been used for welding plastic tubes particularly as used in the medical field. U.S. Pat. No. 7,398,813 describes a device having a first tube holder and a second tube holder. Each of the tube holders has first and second parallel tube holding areas in line with each other. In practice a first tube would be placed in the aligned first tube holding areas across the location where the tube holders are adjacent each other. A second tube would be similarly placed in the aligned second tube holding areas. A tube clamp in each of the first tube holding areas clamps the first tube to create a generally fluid free area of the first tube. A tube clamp is similarly provided in the second tube holding areas to create a generally fluid free area of the second tube. At least one of the clamps is laterally movable while the clamps are maintained in their clamping condition. To increase the length of the fluid free area preferably both clamps of one of the tube holders are laterally movable by having that tube holder moved laterally. Such movement is performed after the tubes are initially loaded in a loading station, then the one tube holder is laterally moved in a stripping station to increase the size of the fluid free area. Thereafter, the tubes are cut. In U.S. Pat. No. 7,398,813 the cutting is done with a non-heated cutting device, such as a cold blade, and the tube holders are then moved to a heating station while the clamps are still maintained in their clamping condition. In the heating station a heating device heats/melts the cut stub ends of the tubes. The cut ends of the tubes are realigned so that a cut stub end of the first tube becomes aligned with a cut stub end of the second tube and these two aligned heated/melted cut stub ends are then shifted into contact with each other to become welded together.

[0002] The specific arrangement for clamping the tubes disclosed in U.S. Pat. No. 7,398,813 includes clamp jaws of different construction in one tube holder as compared with the other tube holder. More particularly the compressed tubing is held tight by square jaws in one tube holder while the jaws in the other tube holder are smooth jaws to allow the tubing to slip through the smooth jaws.

[0003] An object of this invention is to provide a device for welding plastic tubes which facilitates the clamped tubing to slip through the jaws while in the clamped condition.

[0004] A further object of this invention is to modify the structure of the clamping jaws as compared to the structure disclosed in U.S. Pat. No. 7,398,813.

[0005] In accordance with this invention the clamping jaws in both of the tube holders are smooth jaws rather than one set of jaws being square jaws. This permits slippage of the tubing on either or both sides rather than holding one of the tubes tight.

[0008] The present invention is directed to devices for welding plastic tubes, such as disclosed in U.S. Pat. No. 7,398,813 and in the patents referred to in column 1 of U.S. Pat. No. 7,398,813. All of the details of U.S. Pat. No. 7,398,813 and the other patents referred to therein are incorporated herein by reference thereto.

[0009] FIGS. 1-2 illustrate a device 10 for welding plastic tubes. As shown in FIG. 1 device 10 includes a first tube holder 12 and a second tube holder 14. Tube holder 12 includes first tube holding area 16 and a parallel second tube holding area 18. The tube holding areas may be grooves extending across the tube holder. Similarly, second tube holder 14 includes first tube holding area 20 and second tube holding area 22 which is parallel to tube holding area 20. These tube holding areas may also be grooves. The spacing between the tube holder areas 16 and 18 is the same as the spacing between tube holding areas 20 and 22.

[0010] FIG. 1 illustrates the tube holders 12 and 14 in the loading station 24 of the device 10. While in the loading station, a first tube T-1 is inserted in tube holding area 16 of tube holder 12 and in the aligned tube holding area 20 of tube holder 14. Similarly, a second tube T-2 is inserted in the aligned second tube holding areas 18 and 22. While in these tube holding areas the tubes T-1 and T-2 are clamped and held in position in each tube holder. FIG. 2 illustrates the clamping mechanism 26 for tube holder 12 and the clamping mechanism 28 for tube holder 14. The lower half of the first tube holder 12 includes tube holding areas or grooves in which are mounted a lower jaw 30. An upper jaw 32 is pivotally mounted at one end of first tube holder 12. Jaw 32 is pivoted by manipulating handle 34 to move the jaw to and from its clamped condition.

[0011] Similarly, clamp mechanism 28 for the second tube holder 14 includes a lower jaw 36 and an upper jaw 38 pivotally connected to the lower jaw 36. A handle 40 can be used to move the upper jaw into clamping relationship with the lower jaw. The tube holding areas 20,22 are also formed in the lower half of the second tube holder 14.

[0012] After the tubes T-1 and T-2 are clamped in place in the loading station 24, the tube holders 12,14 are jointly moved longitudinally by any suitable structure such as screw 42 away from the loading station 24. Such movement is controlled by cam operation. FIG. 1 illustrates a cam track 50 with two straight portions joined by curved portion 48. Cam 46 rides in track 50. The tube holders 12, 14 carrying the clamped tubes are moved together in a longitudinal direction to a stripping station 44. The cam has a slight outward bend in the track 50 that spreads the tube holders 12,14 apart at the stripping station stripping the fluid from the tubes prior to reaching a cutting blade in the cutting station 52. The carriage carrying the tube holders then reverses direction and the carriage and tube holders move completely up to the outer end of the track 50 to the heating/melting station 54. The cam 46 has a large ramp that separates the tube holders to allow them to clear the infrared heater coil and sets up the proper distance for melting. Once the melting is finished the tube holders 12,14 reverse direction and head back towards the original loading station 24 which is now the welding station. Upon passing the bend 48 the tube holders shift toward each other. One of the tube holders is held in place while the other tube holder is allowed to move longitudinally and realign the tube ends so that the two tube lines will be welded together when the clamps close laterally back together as they move pass the large ramp or bend 48 to the welding station.

[0013] The description indicated above relates to steps which are also performed in the procedures described in U.S. Pat. No. 7,398,813. In that patent, however, the jaws of the tube clamps are of a specific construction wherein the jaws for the second tube holder are specifically designed to be square jaws so that the portions of the tubes T-1 and T-2 in the second tube holder 14 are held tight by the square jaws and the tubing is allowed to slip through smooth jaws in the first tube holder 12.

[0014] FIG. 2 illustrates the tube clamps 26 and 28 to have its jaws of a form which differs from that of U.S. Pat. No. 7,398,813. In that regard, as shown in FIG. 2, the lower jaw 30 for tube holder 12 has its tube contacting wall 58 at the clamping portion to be of smooth continuous curved configuration. Similarly, the upper jaw has its tube contacting wall 60 of smooth continuous curved configuration. The jaws for second tube holder 14 have a similar construction and thus differ from the jaw construction of U.S. Pat. No. 7,398,813 which utilizes square jaws. Accordingly, as shown in FIG. 2 the lower jaw 36 has its tube clamping portion 62 to be of smooth continuous curved configuration and also has its upper jaw tube clamping portion 64 to be of smooth continuous curved configuration.

[0015] By replacing square fixed jaws with smooth radius slip jaws there is no need to hold one side of the tubing fixed. Instead, having smooth slip jaws on both tube holders 12 and 14 results in a number of distinct advantages. For example, the fluid can be stripped back from either or both sides. The tubing will slip through the side with the least resistance. In addition, very small stub ends can be made. In that regard, if hydraulic pressure in the stub end prevents the fluid from being stripped back on one side then the fluid will be stripped back on the opposite side which has less or no back pressure. Further, there is less overall tubing area to be compressed when the clamping is done with a curved radius jaw as compared to a flat jaw.

[0016] Accordingly, the jaw configurations shown in FIG. 2 represent a distinctly different jaw configuration than that previously used when moving the first tube holder laterally away from the second tube holder during a stripping action in a device for welding plastic tubes.

[0017] FIG. 1 illustrates the device 10 to have a cold cutting station 52 which is displaced from the heating station 54. The invention, however, could be practiced where both stations are combined. For example, if the tubes are cut by a heated wafer, the cutting of the tubes also results in melting the cut portions of the tubes to be in a condition for welding once the tubes are realigned and the heated ends are pressed into contact with each other.