METHOD FOR MANUFACTURING A URINARY CATHETER BY INJECTION MOLDING A THERMOPLASTIC MATERIAL INTO A MOULD

Description

[0001] The present invention relates to a method of manufacturing a urinary catheter, by injection molding a thermoplastic material into a mold. Document WO2014 / 052770A1 represents a representative state of the art.

[0002] The production of thin, elongated hollow bodies, such as urinary catheters, in an injection molding process is difficult for several reasons. Several injection points distributed along the length of the mold are required to reliably and evenly inject material into a thin, elongated mold. As a result, a multitude of injection points are created, which must be carefully smoothed. Especially with injection molded parts such as urinary catheters, there is a considerable risk of injury if the injection points have not been carefully deburred.

[0003] The situation is even more difficult with molds for manufacturing a hollow body by injection molding. The cavity is produced by a core, further compromising the circulation of material inside the mold and requiring even more injection points.

[0004] Demolding poses another problem. Injection molding molds are therefore usually made in two parts with a division in a plane that encloses the longitudinal axis of the mold to open it after cooling of the injected material and to be able to extract the injection molded part. Two-part molds, however, produce seams on the molded part. These seams must be carefully trimmed, especially for urinary catheters manufactured in this way to avoid any injury.

[0005] In addition to the risks associated with insufficient deburring, additional costs can result from deburring and extensive inspection, resulting in significant additional costs, particularly for disposable products such as urinary catheters. Elongated, cylindrical injection-molded parts are difficult to release from molds without a longitudinal parting plane. If they are hollowed by a pin inserted into the mold, it is also difficult to demold the part from the pin. To facilitate demolding, such parts are usually slightly tapered. With fairly long catheters, the result is that the diameter is noticeably increased along the length of the catheter.

[0006] The aim of the present invention is to provide a method for manufacturing a urinary catheter, in an injection molding process allowing good distribution of the material inside the mold, making deburring of the mold body unnecessary and facilitating demolding of the mold body.

[0007] According to the invention, this aim is achieved by a method of manufacturing a urinary catheter according to claim 1.

[0008] For the method according to the invention, a mold with an elongated cavity having the shape of the part to be manufactured is used. For example, to manufacture a urinary catheter, a mold with a cylindrical cavity of approximately 3 mm in diameter and a length of up to more than 40 cm is used. The mold can be cylindrical or slightly conical to facilitate demolding of the molded part.

[0009] The mold has a distal end that is closed. For the production of a urinary catheter, the closed distal end can, for example, be shaped like a rounded cup. The mold has an opening at the proximal end. Material can be injected into this area. In addition, the resulting injection-molded part can be removed from the mold there.

[0010] In addition, a pin is used that is movable along the longitudinal axis of the mold. The pin is used to obtain the cavity in the hollow body to be produced and is provided near the proximal end of the mold. The pin can be located completely outside the mold near its proximal end, or it can be introduced into the mold in the area of ​​the proximal end. The pin is preferably cylindrical and can have, for example, a diameter of about 1 mm for the production of a urinary catheter. The pin can also be slightly conical.

[0011] To carry out the method according to the invention, thermoplastic material in a plastic state is injected into the region of the proximal end of the mold. In addition, the pin is moved in the direction of the distal end of the mold.

[0012] The injection of the thermoplastic material and the movement of the pin may be successive. Preferably, the injection of the thermoplastic material and the movement of the pin are at least temporarily simultaneous. The material injected at the proximal end of the mold is advantageously driven by the pin pushes into the mold so that the mold is filled with material evenly. The cavity is formed simultaneously in the body to be manufactured. In particular, a certain quantity of material may be injected first into the mold and then the pin moved while further material is injected.

[0013] According to the invention, the spindle rotates at least temporarily around its axis, particularly during its movement, in order to distribute the material evenly. This also reduces the risk of lateral deviation of the spindle relative to the mold axis. If a viscous thermoplastic material is injected at the proximal end on one side of the spindle, there is a risk that the injected material will shift the thin, long spindle to the other side and that the cavity in the hollow body will no longer be formed in its central part. This is particularly problematic when manufacturing urinary catheters, since the cavity to be molded is very long and has a small diameter. Lateral displacement of the spindle must be avoided at all costs because the very thin wall of the catheter could be damaged by the spindle and the cavity will no longer be sealed laterally.As the spindle rotates during its movement, the injected material is distributed around the spindle in a helical manner. The material is distributed evenly without the mandrel deviating from its predetermined path.

[0014] The movement of the spindle is advantageously controlled according to a control value. A control value can, for example, be the pressure prevailing in the mold. A pressure sensor can be provided at a suitable location in the mold, for example in the area of ​​the distal end.

[0015] Fill pressure occurs during material injection. This pressure will increase as the mold is filled with material. During material injection, the pressure around the pin, which drives the material as it moves toward the distal end of the mold, should remain approximately constant. Pressure will increase when more material is injected than the pin's travel can handle. The pin's movement and / or the amount of material injected can be controlled as appropriate to keep the pressure constant.

[0016] If a pressure sensor is placed at the distal end of the mold, the pressure curve can indicate that the injected material has reached the distal end of the mold. The pressure will then increase.

[0017] The movement of the pin can also be controlled based on the volume of material injected so that the pin is always in the desired location relative to the volume of injected material expanding in the mold.

[0018] The spindle movement can also be time dependent so that the amount of material injected and the spindle position can be coordinated without the two parameters directly influencing each other.

[0019] A control value can also be the temperature of the injected material. The higher the material temperature, the more plastic the material. The spindle movement, especially the travel speed, can be controlled based on the temperature. The spindle retraction can be triggered after sufficient cooling so as not to deform the injected part.

[0020] All of the above spindle control variants can be used alone or in any combination.

[0021] In one embodiment of the method according to the invention, the mold has one or more closable openings at its distal end. The opening(s) can be opened at the beginning of the injection operation to expel air from the mold. The openings are closed again towards the end of the injection operation so that the mold body to be produced can take the desired shape at the distal end. The closing operation can be controlled in a manner similar to the movement of the spindle, for example by sensing the pressure in the mold, as a function of the volume of material injected or as a function of time.

[0022] According to another embodiment of the invention, the mold has a movable insert that can move from a proximal position to a distal position during the injection operation. The insert can be designed to move inside the mold cavity, in the form of a movable bottom, in particular if the cavity is cylindrical. The insert can adopt a proximal position in the vicinity of the proximal end of the mold at the start of the injection operation. The volume of air inside the mold to be discharged during the injection operation can be minimized. During the injection of the material, the insert moves in the distal direction with the arrival of material and successively releases the elongated cavity of the mold.

[0023] The movement of the insert can be controlled according to pressure, time and / or volume of injected material or without external control, simply by the pressure that the injected material exerts on the insert.

[0024] The invention is explained more precisely below with the aid of the attached figures: Les Figures 1a à 1e schematically show different phases of the method according to the invention for manufacturing a urinary catheter in cross-section of a suitable injection molding device; La Figure 2 shows an example of carrying out the method according to the invention using a mold with a closable opening at its distal end; Les Figures 3a à 3c show an example of carrying out the method according to the invention using a mold with a movable insert;

[0025] Those skilled in the art will readily understand that the drawings shown here are intended solely to illustrate the principle of the invention and only convey the invention schematically. They are not to scale and do not encompass all the necessary components of a device for carrying out the method according to the invention. The actual dimensions and dimensional ratios as well as all necessary dimensions can be defined by those skilled in the art on the basis of their experience.

[0026] There figure 1a represents a mold 1 in longitudinal section showing a cylindrical cavity 2, elongated along an axis A with the external contours of a urinary catheter. The mold 1 consists of a probe shape 1a, which has an open proximal end 3 and a closed distal end 4. The mold part 1a can be closed by the mold part1b .

[0027] The canals 5 are integrated into the mold part 1b for the injection of a thermoplastic material. The cavity 2 of the mold part 1a is pressurized with a thermoplastic material in plastic phase through the two channels 5.

[0028] Additionally, the device contains an elongated cylindrical pin 6, mobile along the axis A. The brooch 6 is sized so that it defines the internal cavity of the catheter to be obtained. The free end of the pin 6 is located at the beginning of the manufacturing process in the proximal end area 3 of the mold part 1a and a short length of it is inserted into the cavity 2 of the mold.

[0029] There figure 1b represents a process stage in which a first volume of the thermoplastic material 7is injected under pressure into the cavity 2 of the mold part 1a . During injection, the pin 6 moves simultaneously in the direction of the arrow D towards the distal end 4 of the mold. This allows the pin 6 drives the injected material 7 at the proximal end 3 of the mold part 1a. The material is fed from the spindle into the elongated cavity 2 of the mold 1. The brooch 6 further rotates around its axis, as shown by the arrow R, to allow for even distribution of the material 7.

[0030] There figure 1c represents the process stage in which the urinary catheter 8 is fully formed. Compared to the stage represents on the figure 1b , the amount of material needed to make the catheter is now injected The pin6 is displaced in the direction of the distal end 5 of the mold 1 so that the cavity of the urinary catheter 8 has formed. The thermoplastic material can then cool and loses its plastic properties.

[0031] There figure 1d shows the demolding stage in which the pin is removed 6 of the mold 1 after cooling of the thermoplastic material. The rotary movement of the spindle 6 facilitates pin extraction 6 compared to the injected material. The raw catheter 8 then remains in the mold part 1b.

[0032] There figure 1e shows the raw catheter 8 released from the mold, The casting 12 must still be removed. In addition, side eyelets must be placed appropriately in the tip of the catheter 13 to provide access to the internal canal 14.

[0033] There figure 2 shows a part 1a of a mold, presenting at its distal end 4 an opening 10 can be closed using a push button 9. Any other suitable closing mechanism may also be used. The opening 10 opens at the start of the injection process so that the air contained in the cavity 2 mold can escape through the opening 10 during the injection of the material into the mold.

[0034] If the mold is completely filled with material, the opening 10 is closed using the push button 9. The moment of closing can be determined in several ways. The pressure build-up in the mold can be measured using a sensor. The pressure builds up as soon as the mold is completely filled and the material flows through the opening. 10. The more the opening 10The smaller the selected size, the higher the pressure rise.

[0035] The time of closing of the opening can also be determined 10 depending on the volume of material injected. A sensor can also detect when the material exits the opening 10, and can then close the opening.

[0036] The demolding process can also be facilitated by opening the closure 10 since a vacuum is not created in the mold and the exit of the shaped catheter will be compromised. In addition, demolding can be facilitated by the application of compressed air or by mechanical means, such as a mandrel inserted into the opening to expel the catheter from the mold.

[0037] There figure 3a schematically shows a mold 1 with a mobile insert 11 at the distal end 4 of the mold. The insert 11takes the shape of a cylinder with the diameter of the cavity 2 of the mold so that it is movable along the cavity.

[0038] As shown in the Figure 3b , the insert 11 of the mold can be moved at the beginning of the injection operation in the direction of the proximal end 3 of the mold, to find itself near the spindle 6.

[0039] During the injection operation, the insert 11 and the pin 6 are moved together in the direction of the distal end 4 of the mold while continuing to inject material into the mold as shown in figure 3c . The volume of air in the mold at the beginning of the molding process is very minimal and is completely expelled at the beginning of the injection operation. The introduction of the thermoplastic material 7 in the mold is supported by the movement of the movable insert11 and the pin 6, also mobile, and is distributed evenly in the mold.

Claims

1. Method for manufacturing a urinary catheter, by injection moulding a thermoplastic material in a mould (1), comprising the following steps: - providing a mould (1) with an elongated cavity (2), oriented along a longitudinal axis (A), which has an open proximal end (3) and a closed distal end (4); - providing a pin (6), in the vicinity of the proximal end (3) of the mould (1), that can move along the longitudinal axis (A) of the mould; - injecting a thermoplastic material in a plastic state into the region of the proximal end (3) of the mould (1); - moving the pin (6) towards the distal end (4) of the mould (1); wherein the pin (6) rotates at least temporarily about its axis.

2. Method according to claim 1, characterised in that injecting the thermoplastic material and moving the pin (6) are at least temporarily simultaneous.

3. Method according to any one of claims 1 to 2, characterised in that moving the pin (6) is controlled according to a control value, in particular according to the pressure in the mould and / or to the volume of injected material and / or to time and / or to the temperature of the injected material.

4. Method according to any one of claims 1 to 3, characterised in that the mould (1) has, at its distal end (4), at least one closable opening (10), which opens at the start of the injection operation and closes towards the end of the injection operation.

5. Method according to any one of claims 1 to 4, characterised in that the mould (1) has a movable insert (11) which can move from a proximal position to a distal position during the injection operation.

6. Method according to claim 5, characterised in that the movable insert (11) of the mould moves according to the position of the pin (6).

7. Method according to any one of claims 1 to 6, characterised in that the cavity (2) of the mould (1) and / or the pin (6) are cylindrical or slightly conical with the reduced diameter at the respective distal end.