Patent Publication Number: US-2016228675-A1

Title: Apparatus and Method to Form Tip Profiles

Description:
PRIORITY CLAIM 
     In accordance with 37 C.F.R. 1.76, a claim of priority is included in an Application Data Sheet filed concurrently herewith. Accordingly, this present invention claims priority to U.S. Provisional Patent Application No. 62/113,870 entitled “APPARATUS AND METHOD TO FORM TIP PROFILES”, filed Feb. 9, 2015. The contents of the above referenced application is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The field of the invention is related to the apparatus used to manufacture medical devices and, in particular, to an apparatus and method to thermally form a smooth profile tip on a polymer tube such as a catheter. 
     BACKGROUND OF THE INVENTION 
     Prior art device control was typically limited to manually adjusted air pressure and digitally controlled temperature and time. By adding software controlled insertion force, distance, and speed a user can now control the process and determine if the resulting product is the same from cycle to cycle. 
     SUMMARY OF THE INVENTION 
     An apparatus and method to thermally form a smooth profile tip on a polymer tube such as a catheter. The process typically uses a metal mold that contains the desired form. The tube is inserted partially into the cool mold which is then heated sufficiently to soften the plastic. The tube is then forced further into the mold until the form is completed. The mold and part are cooled to solidify the form and the completed part is removed from the mold. Typically the tube is gripped with a clamp and inserted into the mold using an air cylinder and manually controlled air pressure. Automatic process control is limited to temperature and time. 
     The apparatus provides process flexibility by allowing a user to manipulate more parameters and achieve output repeatability by controlling more parameters. By adding software controlled insertion force, distance, and speed the user has many more options for both controlling the process and determining if the resulting product is the same from cycle to cycle. The cooling cycle is terminated based on temperature assuring each part starts at the same temperature. The force to withdraw a part from the mold is also monitored and can provide feedback for corrective action before sticking in the mold becomes a problem. Each parameter can be individually manipulated in a user defined multi-step process sequence to produce the desired results. Namely, (1) the part can be inserted into the cooled mold until a user defined force is reached to ensure a consistent starting position, (2) mold/part preheat can be initiated for a user programmable time period, and (3) additional insertion(s) at distance and/or force can be programmed. The final insertion distance and force can be registered by the control computer and deviations used to detect process anomalies. Finally, the optional vision inspection module can measure the part for proper profile dimensions and detect defects such as flash and incomplete form. 
     An objective of the invention is to control an RF tipping and bonding process using an apparatus that is flexible and output repeatable. 
     Another objective of the invention is to provide a temperature control using a temperature feedback device. 
     Still another objective of the invention is to provide a dwell time control using digital timer in controller. 
     Another objective of the invention is to provide part insertion speed control using motor driven linear stage. 
     Still another objective of the invention is to provide part insertion force control using strain gage feedback device. 
     Yet still another objective of the invention is to provide part insertion depth control using encoder feedback. 
     Another objective of the invention is to provide a cooling temperature control temperature feedback device. 
     Still another objective of the invention is to provide part retraction speed control using motor driven linear stage. 
     Yet still another objective of the invention is to provide part retract force detection using strain gage feedback device. 
     Another objective of the invention is to provide an optional machine vision inspection of dimensions and quality. 
     Other objectives and further advantages and benefits associated with this invention will be apparent to those skilled in the art from the description, examples and claims which follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a right front perspective view of the tip forming apparatus; 
         FIG. 2  is a left front perspective view of the tip forming apparatus with a cover plate removed; 
         FIG. 3  illustrates the clamp axis encoder, lead screw and linear slide; 
         FIG. 4  illustrates the clamp is a perspective view of the clamp axis drive motor and limit sensors; 
         FIG. 5A  illustrates a perspective view of the primary part clamp carriage assembly; 
         FIG. 5B  is a cross sectional view of the clamp carriage of  FIG. 5A ; 
         FIG. 5C  is a side view of the clamp carriage of  FIG. 5A ; 
         FIG. 5D  is a front view of the clamp carriage of  FIG. 5A ; 
         FIG. 6A  illustrates a perspective view of the auxiliary part clamp carriage assembly; 
         FIG. 6B  is a cross sectional view of the clamp carriage of  FIG. 6A ; 
         FIG. 6C  is a side view of the clamp carriage of  FIG. 6A ; and 
         FIG. 6D  is a front view of the clamp carriage of  FIG. 6A . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Detailed embodiments of the instant invention are disclosed herein, however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific functional and structural details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representation basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. 
     Disclosed is an apparatus and method to thermally form a smooth profile tip on a polymer tube such as a catheter. The process employs a metal mold that contains the desired form. The tube is inserted partially into the cool mold which is then heated sufficiently to soften the plastic. The tube is then forced further into the mold until the form is completed. The mold and part are cooled to solidify the form and the completed part is removed from the mold. Traditionally the tube is gripped with a clamp and inserted into the mold using an air cylinder and manually controlled air pressure. Automatic process control is limited to temperature and time. In addition to time and temperature control, the instant apparatus and method adds load cell based force feedback and a motorized linear stage with speed control and encoder based position feedback. This additional feedback and control presents flexible options for multiple modes of operation. The control software provides a multi-step process flow where each step includes user programmable force, distance, speed, temperature, and time. Users can define each parameter in each step to produce a desired result. 
     Referring to Figures in general, set forth are illustrations of the tip forming apparatus  10  of the instant invention. The apparatus has a base  12  with a tip mold and thermocouple  14  positioned along a frontal surface  16 . A primary clamp  18  can be used on either side of the mold for left to right, or right to left operation. An auxiliary clamp  20  with pneumatic actuation positioned opposite the primary clamp  18 . An RF heater position adjuster  22  is accessible for operating of a temperature controller  24  through a programmable logic controller  26 . Operation modes of the apparatus include a run button  28 , an emergency stop button  30  and a human-machine interface (HMI)  32 . 
     The clamp axis encoder  34  which operates the clamp axis lead screw  36  and clamp axis linear slide  38  for displacement of the primary clamp. An RF heater  40  provides the part softening temperature. 
     The primary clamp is positioned by use of a clamp axis drive motor  42  coupled to the axis by a drive belt  43 . Limit sensors  44  provide right to left operation control. Limit sensors  46  provide left to right operation control. The RF heater position adjuster  22  provides adjustment through a belt coupler  48  to an RF position adjustment lead screw  50  for control through an RF control head  52 . 
       FIGS. 5A-5D  discloses the primary part clamp assembly  60 . The primary part  60  has a clamp mounting surface  62  and a car  64  linear slide, constructed and arranged to attach to the main rail. The assembly is further defined by a rail  66  linear slide and a preloaded nut  65  lead screw. A bracket encoder cable  68  is positioned along an upper surface. A load cell plunger  70  engages the button load cell  72  with preload springs  74  providing a biasing force. 
       FIGS. 6A-6D  discloses the auxiliary part clamp assembly  80 . The auxiliary part  80  has a car  82 , further defined by the rail linear slide  84  and car linear slide  86 . The assembly employs a pneumatic actuator  88  having a return spring  90 . 
     The control software provides a multi-step process flow where each step includes user programmable force, distance, speed, temperature, and time. Users can define each parameter in each step to produce a desired result. The following examples illustrate some of the options available. 
     Insert with constant force:
     1. The operator loads a tube into the gripper and presses start   2. The tube is gripped and inserted into the mold by the motor driven linear stage at the user defined speed until the user defined force is reached as indicated by the load cell. This provides a known and repeatable starting position for each cycle.   3. The RF generator heats the mold by induction until the user defined temperature is reached as indicated by the thermocouple   4. The mold is held at the defined temperature for a user defined time which is controlled by the computer   5. The tube is inserted into the mold at the user defined speed until the user defined force is reached and continues to insert further if the force drops below the set-point. The force is maintained until the user defined time expires   6. The insertion depth provided by the encoder on the linear stage is recorded for comparison to a known good depth. Should a deviation from expected depth be detected a warning message can be displayed.   7. The cooling operation starts and continues until the user defined temperature is reached   8. The linear stage withdraws the tube from the mold while monitoring the force. Should the force exceed acceptable limits a warning message can be displayed.   

     Insertion to distance:
     1. The operator loads a tube into the gripper and presses start   2. The tube is gripped and inserted into the mold by the motor driven linear stage at the user defined speed until the user defined force is reached as indicated by the load cell. This provides a known and repeatable starting position for each cycle.   3. The RF generator heats the mold by induction until the user defined temperature is reached as indicated by the thermocouple   4. The mold is held at the defined temperature for a user defined time which is controlled by the computer   5. The tube is inserted into the mold at the user defined speed until the user defined depth is reached   6. The tube is held in position for a user defined time   7. Steps 5 &amp; 6 can be repeated multiple times with different speed and depth as defined by the user   8. The force provided by the load cell is monitored during tube insertion and compared with user defined maximum force. Should a deviation from expected force be detected a warning message can be displayed.   9. The cooling operation starts and continues until the user defined temperature is reached   10. The linear stage withdraws the tube from the mold while monitoring the force. Should the force exceed acceptable limits a warning message can be displayed.   

     Users can define many unique cycles by defining force, insertion depth, speed, temperature, and time. Once the process steps are defined the operator need only choose the process from a list (or using a bar code reader) and load the tube and start the process. 
     It is to be understood that while a certain form of the invention is illustrated, it is not to be limited to the specific form or arrangement herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown and described in the specification and any drawings/figures included herein. 
     One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objectives and obtain the ends and advantages mentioned, as well as those inherent therein. The embodiments, methods, procedures and techniques described herein are presently representative of the preferred embodiments, are intended to be exemplary and are not intended as limitations on the scope. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention and are defined by the scope of the appended claims. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in the art are intended to be within the scope of the following claims.