Patent Application
20080202669
This application claims the benefit of French patent application Ser. No. 07/01014, filed Feb. 13, 2007.
The present invention relates to a new method and a new device for connecting plastic tubes end to end. It is used above all in the medical field for the sterile connection of plastic tubes and for instance, but not exclusively, for the sterile connection of blood bags.
In the medical field, patient treatment sometimes requires the carrying out of blood transfusions. For this, a large quantity of human blood platelets may be necessary to treat the patient. In general, the quantity of blood necessary to treat a patient is much greater than the quantity of blood contained in a bag from a single donor. In this case, it is necessary and usual to extract the blood (the platelets) from several bags of compatible donors and to transfer it into a single bag of a greater size.
Each blood bag carries a tube made of thermoplastic, generally PVC, the extremity of which is closed by squeezing the tube and high frequency welding of the tube walls. To carry out the transfer of the blood of the bags of compatible donors into a single bag of a greater size, the extremities of the tubes of the blood bags must be opened and the open extremities of these tubes must be connected to a collector, which will distribute the blood towards the bag of the greater size. In order to avoid contamination of the blood and in order not to decrease the storage life of the blood contained in the bag of the greater size, it is important that the connection of the extremities of the tube be carried out in a sterile manner. A sterile connection means that no foreign body is introduced into the tubes during the connection, that the properties of the materials used for the tubes remain unchanged (absence of burnt areas) and in particular that air does not penetrate inside the tubes. If all these conditions are met, asepsis is maintained throughout the entire length of the procedure and there can be no contamination of blood connected to the procedure.
In the past, various solutions have been suggested to connect plastic tubes in a sterile manner.
For instance, document U.S. Pat. No. 4,369,779 describes a method and a device for connecting plastic tubes in a sterile manner by using a hot cutting blade. Said hot cutting blade is introduced simultaneously and transversally across each tube so that the closed extremities of the tubes are cut. The tubes are then axially aligned by sliding along the hot blade. Then, said hot blade is retracted and the tubes are joined end to end in order to be connected. Finally, it is necessary to carry out longitudinal traction on each tube to open the tubes and allow the passage of a fluid. The main disadvantage of this type of device is the use of a consumable object, i.e. the blade, which necessarily must be changed for each connection operation. In addition, sterility is not guaranteed throughout the entire length of time of the procedure. In fact, at the moment when the blade is retracted, air or even plastic chips can penetrate the inside of the tubes and thus contaminate the inside of these tubes.
Document U.S. Pat. No. 4,737,214 describes a method for connecting plastic tubes in a sterile manner by using means of heating the tubes via radiation and/or convection. To this effect, two tubes, the extremities of which are welded, are axially aligned in such a manner that said extremities are situated at a distance from one another. The tubes are then crimped perpendicularly to the welding line, and then heating means without contact are used in the space situated between the two tube extremities. The combined action of the heating means and the crimping allows the welding lines of the tubes to be opened and to confer an essentially circular shape to the tube extremities. Finally, the heating means are retracted and the open extremities of the tubes are placed in contact to carry out the connection of the two tubes. The advantage of this method in comparison with that described in the previous document lies in the fact that no foreign body can penetrate into the inside of the tubes, since there is no cut or contact between the tube extremities and the heating means. Nevertheless, in this other example of the connection of plastic tubes, sterility is still not guaranteed. In fact, the tubes are open before being welded and even if said tubes are crimped upstream, air can penetrate through the produced opening and contaminate the inside of the tubes.
Document WO 03/063940 describes a laser for welding tubes used for medical purposes. The laser is in particular used for connecting plastic tubes. The tubes are initially spaced apart from one another and their extremities are submitted to the action of the laser in order to be heated. Once heated, the extremities are moved closer and connected end to end. A disadvantage of the system described in this document is that the laser beam must be divided into two secondary beams, which are deviated in the direction of the two extremities of the two tubes spaced apart. In addition, as in the previous documents, sterility is not guaranteed since the tube extremities are open before being joined end to end, and air can thus penetrate into the inside of the tubes and contaminate the latter.
Document WO 2005/102671 describes a method for connecting tubes in a sterile manner by the use of a laser. According to the method described, the laser can weld together the extremities of the two tubes by joining said extremities end to end on an absorbent film. To this effect, two tube extremities are arranged opposite one another, their section extending essentially parallel, and then a film absorbing the energy of the laser is placed between the two extremities, so that the tube extremities are thus in contact with the film. Finally, the laser is directed towards the film and the extremities that are to be connected. The main disadvantage of this method is that the absorbent film takes part in the welding of the two extremities. In fact, a film residue, which is ripped at the moment that the tubes are opened, is caught inside the tubes. This method is complicated and delicate to implement, and the contact between the film and the tubes prior to the welding, as well as the film residue caught inside the tube, compromise the sterility of the tubes.
The main object of the invention is to provide a new technical solution for the end-to-end connection of two plastic tubes, the extremities of which are initially closed, without air and/or foreign bodies being able to penetrate inside the tubes.
The invention thus has as a first object a method for connecting two plastic tubes end to end, the extremities of which are closed by compression and welding or gluing of the tube wall.
According to this method, the two closed extremities of the tubes are axially aligned and placed in abutment, the two closed and abutting extremities of the tubes are heated from a distance and without contact and the two extremities of the tubes are axially brought together, so as to splay and weld together the extremities of the tubes end to end, while constantly maintaining said extremities in abutment.
Preferably, but optionally according to the invention, the method according to the invention comprises the following additional technical features, used individually or in combination:
A further object of the invention is a device for the connection of the tubes that allows the implementation of the method referred to above and comprises abutment means enabling the two tubes to be axially aligned and brought into abutment, and means of heating without contact; the abutment means are designed to automatically displace the two extremities of the two tubes in abutment in a translation movement one towards the other during the implementation of the heating means.
Preferably, but optionally according to the invention, the device according to the invention comprises the following additional technical features, used individually or in combination:
A further object of the invention is the use of the method or the device referred to above to connect in a sterile manner the closed tubes of two bags, one of which contains blood platelets or another fluid requiring the same asepsis conditions.
The invention and its advantages will appear more clearly upon reading the following description of a non-limiting and non-exhaustive example and with reference to the accompanying drawings, in which:
One of the preferred, but non-exclusive and non-limiting applications of the invention can be found in the medical field of blood transfusion, and consists in the sterile connection of bags containing concentrates of blood platelets. The degree and requirement of sterility varies according to the applications (medical, food processing, . . . ). It is in the medical field of blood transfusion, however, that the degree and requirements are the highest. It is thus imperative that asepsis be preserved.
To treat a patient it is sometimes necessary to carry out blood transfusions. For this, a large quantity of human blood platelets may be necessary to treat the patient. In general, the quantity of platelets necessary to treat a patient is much greater than the quantity of platelets contained in a bag from a single donor. In this case, it is necessary and usual to extract the platelets from several bags of compatible donors and to transfer them into a single bag of a greater size.
By way of example,
Each intermediate bag P1 to P4 includes a flexible tube 11 of a thermoplastic material, the extremity 111 of which is closed in an airtight manner by compression and high-frequency welding of the wall of the tube 11. The collector P5 includes four flexible tubes 12 enabling it to be filled. The extremity 121 of each tube 12 is closed in an airtight manner by compression and high-frequency welding of the wall of the tube 12.
The compressed and welded extremities 111, 121 of the tubes 11, 12 are shown in more detail in
To carry out the transfer of the concentrates of platelets from the intermediate bags P1 to P4 to the bag P6 with the greater capacity, the intermediate bags P1 to P4 must be connected to the collector P5. To connect one intermediate bag P1, P2, P3 or P4 to the collector P5, the closed extremity 111 of the tube 11 of this intermediate bag must be opened, as well as the closed extremity 121 of one of the tubes 12 of the collector P5, and the open extremities of these two tubes 11 and 12 must be connected end to end. In
In order to avoid contamination of the blood platelets transferred to the bag with the greater capacity P6 and in order not to decrease their storage life, it is important that the connection of the extremities of the tubes 11, 12 be carried out in a sterile manner. A sterile connection means that no foreign body is introduced into the tubes 11, 12 during the connection, that the properties of the material of the tubes 11, 12 remain unchanged (absence of burnt areas) and in particular that air does not penetrate inside the tubes 11, 12. If all these conditions are met, asepsis is maintained throughout the entire length of the procedure and there can be no contamination of the blood platelets.
This device 1 is advantageously used in the medical field of blood transfusion for the connection of tubes 11, 12 of bags during a previously mentioned transfer operation of blood platelets.
More generally, the device of the invention can be used in any application where it is necessary to connect two plastic, and more particularly thermoplastic, tubes end to end, the respective extremities 111 and 121 of which are initially closed by compression and welding or gluing of the wall of the tube. The invention is not limited to tubes closed by HF welding, but can also be applied to any plastic tube with an extremity closed by compression and welding or gluing of the wall of the tube, and able to be opened by heating.
With reference to
The diameter of the laser beam FL is preferably inferior or equal to the width (I) of the welds (for instance 1 mm), but generally inferior to the length (L) of the welds 112, 122. In this case, it is preferable that the laser beam FL scans the welds 112, 122 of the tubes 11, 12 according to their length (L), namely with reference to
The two carriages 6 and 7 are mounted on an endless screw 13 and are translationally movable along this endless screw. This endless screw 13 is driven to rotate on itself by a motor. The rotation of the endless screw 13 in one sense triggers the coming together of the two carriages 6, 7 and the rotation of the endless screw in the other sense triggers the spacing apart of the two carriages 6, 7 at a speed depending in particular on the speed of rotation of the endless screw 13. The carriages 6, 7 are equipped with clamping means 61, 71, which enable the extremities of the tubes 11, 12 to be temporarily fastened onto the carriages and, if necessary, liquid contained inside the extremities 111, 121 of the tubes 11, 12 to be removed prior to the connection operations. The two carriages 6, 7 and their clamping means 61, 71 are aligned so as to enable the tubes 11 and 12, which are to be connected, to be axially aligned.
The hot air heating means 3 include two blowing nozzles 30, which are supplied with hot air. These nozzles 30 open in the proximity of the connection zone of the tubes 11, 12. This stream of hot air enables the heating of the extremities 111, 121 of the tubes 11, 12 to be accelerated and thus the time of the tube connection cycle to be reduced.
The pyrometer 2 is a captor enabling the temperature of the tubes to be detected without contact and in an optical manner (generally via infrared detection). Preferably, the pyrometer 2 used in the device 1 is compact and mounted in proximity to the connection zone of the tubes 11, 12. The temperature detected by this pyrometer is an average temperature taken in the field of vision of the pyrometer, the walls of the extremities 111, 121 of the tubes 11, 12 being comprised in the field of vision.
With reference to
A particular example of the implementation and functioning of the above connection device 1 for connecting two tubes 11, 12 end to end will be detailed with reference to
To connect two closed tubes 11, 12 end to end, by means of the device 1, the following steps are carried out:
Each tube 11, 12 is positioned on a carriage 6, 7 and temporarily fastened to the carriage via clamping means 61, 71. As shown on
The laser and the hot air heating means 3 are started (hot air supply from the blowing nozzles 30), enabling the triggering of a heating without contact of the closed and abutting extremities 111, 121 of the two tubes 11, 12 with, if necessary, a scanning by the laser of the extremity welds 112, 122 of the two tubes 11, 12.
This first heating step is continued until the temperature measured by the pyrometer 2 reaches a first predefined temperature threshold (T1).
When the temperature measured by the pyrometer 2 reaches the first temperature threshold T1, the control means 8 command the motor (M) driving the endless screw 13 so as to bring the two carriages 6, 7 closer to one another at a predefined speed V1.
This heating step is continued until the temperature measured by the pyrometer 2 reaches a second predefined temperature threshold T2 (T2>T1).
When the temperature measured by the pyrometer 2 reaches the second temperature threshold T2, the control means 8 command the motor (M) driving the endless screw 13 so as to bring the two carriages 6, 7 closer to one another at a predefined speed V2, superior to the above speed V1.
This heating step is continued until the temperature measured by the pyrometer 2 reaches a third predefined temperature threshold T3 (T3>T2).
When the temperature measured by the pyrometer 2 reaches the third temperature threshold T3, the control means 8 stop the motor (M) (immobilisation of the carriages 6 and 7), stop the laser and cut the hot air supply from the blowing nozzles 30.
During the above heating steps, the closed and abutting extremities 111, 121 of the two tubes 11, 12 are heated until the glass transition temperature of the material is reached, for instance between 130° C. and 150° C. for PVC. The glass transition temperature corresponds to an augmentation in viscosity of the tube, which nevertheless enables the shape of the tube to be maintained.
The localised heating by laser and hot air stream of the abutting extremities 111, 121 of the two tubes 11, 12 alters the two extremity welds 112, 122 and triggers the softening of the material at the level of the extremities of the tubes 11, 12.
The bringing together of the carriages 6 and 7 during the course of the above 3rd and 4th steps enables in a first instance the shrinkage of the material ensuing from the softening of the material to be compensated for, and the tubes 11, 12 to remain constantly abutting (
Generally, upon completion of the above 5th step, the two tubes 11, 12 connected end to end communicate together, enabling the passage of a fluid inside the tubes 11, 12. Nevertheless, in certain cases, owing to the initial compression of the extremities 111, 121 of the tubes 11 and 12, it can happen that a fine film is created at the level of the connection 9 during the opening of the tubes 11, 12, thus blocking said tubes 11, 12. To remedy this problem, the procedure can include an additional step subsequent to the welding of the two tubes in which the abutment means are in action, via actuating means on the carriages 6, 7 so that the carriages 6, 7 are slightly moved apart. This moving apart has the effect of exercising traction on the two tubes 11, 12 connected end to end, said traction being sufficient to tear said film and thus freeing up the passage for a fluid, without disconnecting the two tubes.
Upon completion of the procedure, the two tubes 11 and 12 are connected end to end, as illustrated in
The temperature thresholds T1, T2, T3 and the speeds of movement of the carriages V1 and V2 are determined on a case-by-case basis by the person skilled in the art, such as to obtain the end-to-end connection of the tubes 11, 12 by maintaining the two extremities 111, 121 of the tubes 11, 12 in constant abutment. This maintaining of the abutment is important, since it enables a contamination of the inside of the tubes 11, 12 to be avoided, in particular with air from outside the bags, and contributes to maintaining the sterility and asepsis of the tubes 11 and 12.
By way of a non-limiting example of the invention, in a specific embodiment, the connection device 1 has been used to connect end to end tubes 11, 12, identical to those shown in
The laser fitted to the device 1 was designed to emit the range of wavelengths between 1.5 and 2.1 μm, with a power of 2 W to 3 W. The hot air blown by the nozzles 30 was brought up to a temperature comprised between 400° C. and 650° C.
The pyrometer 2 used was the infrared captor without contact marketed by the company CALEX with the reference EL21 and was suitable for detecting temperatures superior to 15° C. with a precision of +/−1° C. and with a rapid response time at the rate of 200 ms. The pyrometer 2 was situated at approximately 5 cm from the connection zone of the tubes 11, 12, between the two carriages 6, 7 and the diameter of the temperature measurement zone measured 35.5 mm.
The temperature thresholds T1, T2 and T3 measured 31° C., 40° C. and 43° C., respectively. The set speeds V1 and V2 measured 150 μm/s and 200 μm/s, respectively.
The implementation of a heating by laser advantageously enables a localised heating of the extremity welds 112, 122 of the tubes to be obtained, acting directly on the centre of the material, enabling a more efficient and more rapid destruction through heating of the welds 112, 122. The injection of a hot air stream in combination with the laser enables the procedure to be accelerated, in particular to obtain the end-to-end welding of the tubes.
Nevertheless, the invention is not limited to the implementation of a laser combined with a hot air stream. It can be envisaged to use for instance a laser only or hot air only. More generally, any known means of heating can be used (by radiation, in particular microwave or infrared radiation and/or convection), enabling the extremities of the tubes to be heated at a distance and without contact.
In an advantageous manner according to the invention, the inside volume of the enclosure can be preheated by the injection of a hot air stream by means of nozzles 30a, 30b and before the introduction into the enclosure E of the two tubes 11, 12 to be connected. This preheating ensures not only the elimination of all the bacteria that may be found inside the enclosure E, but also the reduction in length of time of a connection cycle of the two tubes 11, 12.
In the embodiments that have just been described, the actuating of the carriages 6, 7 is controlled in function of a temperature measured by means of a pyrometer 2. On the one hand, this pyrometer 2 can be replaced by any other known equivalent temperature measuring device, for instance by a thermal camera connected to the control means 8.
In addition, the implementation of a temperature control by means of a thermal captor 2 is preferable but nevertheless not indispensable. In a further embodiment, the control means 8 can for instance be programmed to control the movement of the carriages with predefined cycle times. For instance, the length of time of the 2nd, 3rd and 4th steps can be predefined. In this case, the use of a temperature captor 2 is not necessary.
The abutment means of the two tubes do not necessarily include two carriages 6, 7 that are movable in translation, said carriages 6, 7 being able to be replaced by any equivalent means enabling two tubes to be abutting and these two tubes to be moved in translation, one towards the other, while maintaining the two tubes in abutment.
The means of translationally moving the carriages (endless screw 13, motor M) can be replaced by any other means enabling the two carriages 6, 7 to be brought together or moved apart.
In particular, the movement of the carriages 6, 7 can be commanded by the control means 8 by means of any linear two-way actuator. For instance, with reference to
In a further, simpler embodiment, the device does not necessarily include electronic control means 8 and the movement of the carriages 6, 7 is controlled in a purely mechanical manner. For instance, the two carriages 6, 7 can be guided in translation by being mounted on a non-rising spindle or equivalent, and the actuating means of the carriages include elastic means (for instance restoring springs) exerting constant spring forces on the carriages 6, 7, pushing them towards one another. In this case, during the softening of the material resulting from the heating of the abutting extremities 111, 121 of the two tubes 11, 12, the springs mechanically push the two tubes 11, 12 towards one another, while maintaining them constantly abutting.
In certain cases, the welds 112, 122 at the extremity of the tubes 11, 12 can be carried out in too strong a manner (too great a welding depth and/or too great a welding surface (I×L)), which in a prejudicial manner can slow down the connection procedure, with the length of duration of heating of the welds needing to be increased.
To offset this problem, in one embodiment of the invention, prior to the above 1st step, the following additional operations can be carried out, which will be described with reference to
Firstly, two secondary HF welds 112′, 122′ (
Once the secondary welds 112′, 122′ have been carried out, the extremities of each tube 11, 12 are cut, for instance by means of a cutting blade or a laser, at the level of the secondary welds 112′ and 122′, and the extremity portions 113 and 123 of the two tubes 11, 12 including the original welds 112, 122 are removed.
Then the above steps of the method of the invention can be implemented as described above (1st step, 2nd step, . . . ) on the tubes 11 and 12 closed by extremity welds 112′, 122′.
If necessary, prior to carrying out the secondary welds 112′, 122′, it may be necessary to clamp the tubes 11 and 12 with the aim of removing liquid contained in the extremities of the tubes 11 and 12.
| Number | Date | Country | Kind |
|---|---|---|---|
| 07/01014 | Feb 2007 | FR | national |
