Methods and apparatuses for injection molding walled structures
A process is provided for making a walled structure using an injection molding apparatus. The apparatus has a molding space formed between a mold cavity and an inner core disposed within the mold cavity. The molding space defines a shape of the structure. The process includes injecting molding material into the molding space, moving or retaining a portion of a movable impression member protruding from the inner core within a portion of the molding space so as to create a recess within an inner wall of the structure, and retracting the impression member into the inner core such that the impression member is cleared from the molding space.
1. A process for making a medical barrel using an injection molding apparatus, the apparatus having a molding space formed between a mold cavity and an inner core disposed within the mold cavity, the molding space defining a shape of the medical barrel, the process comprising the steps of:
a. first injecting thermoplastic molding material into the molding space so as to substantially, but not completely, fill the molding space with the thermoplastic molding material;
b. second, during or after injecting thermoplastic molding material into the molding space so as to substantially, but not completely, fill the molding space with the thermoplastic molding material, moving at least a portion of a movable impression member to protrude from the inner core into a portion of the molding space so as to create a bypass groove within an inner wall of the medical barrel; and
c. third, retracting the impression member into the inner core in a direction perpendicular to the central axis of the inner core, such that the impression member is cleared from the molding space and housed entirely within the inner core, the process further comprising providing an actuator disposed within the inner core, wherein the actuator is operatively connected to the impression member and wherein movement of the actuator along the central axis of the inner core operates to retract the impression member.
2. The process of claim 1 further comprising a step of withdrawing the medical barrel from the molding space, after the medical barrel is solidified, in an axial direction.
3. The process of claim 2 , wherein the mold cavity is formed from a solid one-piece mold block.
4. The process of claim 2 , wherein the bypass groove, after the medical barrel is solidified, is located entirely within the inner wall and does not bulge outwardly from an outer wall of the medical barrel.
5. The process of claim 4 , wherein the medical barrel, after it is solidified, does not have a line down its center as an artifact of the process.
6. The process of claim 2 , the inner core comprising therein a longitudinal space, the actuator being disposed within the longitudinal space and being axially movable therein between an extended position of the actuator and a retracted position of the actuator.
7. The process of claim 6 , the inner core comprising a window through which a portion of the impression member protrudes when the actuator is in the extended position of the actuator, wherein the impression member is movable to the retracted position of the impression member when the actuator is in the retracted position of the actuator.
8. The process of claim 6 , the actuator including a slot portion, wherein a portion of the impression member is slidably disposed on:
a. a track within the slot portion, the track running axially along a portion of the actuator at an incline; and/or
b. a ramp on which the impression member is seated, wherein at least a portion of the ramp comprises an incline.
9. The process of claim 8 , wherein the impression member is slidably disposed on both the track and the ramp, wherein the track and the ramp include inclined portions that are substantially parallel to each other.
10. The process of claim 2 , wherein the bypass groove is perpendicular to a central axis of the medical barrel.
11. The process of claim 2 , wherein the bypass groove has a substantially constant cross section.
12. The process of claim 2 , wherein the bypass groove has rounded outer corners.
13. The process of claim 2 , further comprising a step of applying, in a plasma enhanced chemical vapor deposition (PECVD) process, a trilayer coating set to the inner wall of the medical barrel.
14. The process of claim 2 , wherein the step of injecting thermoplastic molding material into the molding space so as to substantially, but not completely, fill the molding space with the thermoplastic molding material, comprises filling 96% to 99.5% of the volume of the molding space with the thermoplastic molding material.
15. The process of claim 14 , wherein the step of moving at least a portion of a movable impression member to protrude from the inner core into a portion of the molding space so as to create a bypass groove within an inner wall of the medical barrel, displaces the thermoplastic molding material sufficiently to completely fill the molding space with the thermoplastic molding material.
16. The process of claim 15 , wherein the bypass groove has rounded outer corners.
17. The process of claim 16 , wherein the bypass groove, after the medical barrel is solidified, is located entirely within the inner wall and does not bulge outwardly from an outer wall of the medical barrel.
18. The process of claim 14 , further comprising, after the step of moving at least a portion of a movable impression member to protrude from the inner core into a portion of the molding space so as to create a bypass groove within an inner wall of the medical barrel, injecting additional thermoplastic molding material into the molding space to as to completely fill the molding space.
19. The process of claim 18 , wherein the bypass groove has rounded outer corners.
20. The process of claim 19 , wherein the bypass groove, after the medical barrel is solidified, is located entirely within the inner wall and does not bulge outwardly from an outer wall of the medical barrel.