Catheter tip mold and cut process

In a first process described a tapered catheter tip is molded by placing a tubular catheter over a mandrel and inserting the mandrel and catheter assembly into a mold having an inner mold surface. The molded catheter with flash is thereafter removed from the mold and the mandrel removed from the catheter. The catheter and flash are inserted into a jig which defines an opening through which the flash extends. The opening is defined by a cutting surface and the flash extends above such cutting surface. A cutter is then moved along the cutting surface in order to severe the flash at precisely the appropriate point along the catheter length to leave a formed trimmed catheter. The catheter is thereafter removed from the jig for further processing.

FIELD OF THE INVENTION 
The invention relates to a process for forming medical devices and in 
particular a process for forming tapered tipped catheters. 
BACKGROUND OF THE INVENTION 
It has long been known to taper the tip of a catheter, in particular, a 
peripherally inserted intravenous catheter in order to ease the insertion 
process. It has further been found and many products today have a dual 
bevel formed at the catheter tip. The first bevel is a taper of 
approximately 3.degree. and the second bevel is a taper of approximately 
27.degree.. 
These tips may be formed for example by laser cutting as shown in U.S. Pat. 
No. 5,425,903 or by molding as shown in U.S. Pat. No. 4,661,300 to 
Daugherty. 
The Daugherty patent shows a molding process in which a single step 
operation is used to form and clip the catheter. That is, the catheter is 
placed on a mandrel with the catheter material extending beyond the 
mandrel and this assembly is then inserted into a heated mold to form the 
outer surface of the catheter. The mandrel is advanced to a point where it 
engages the mold surface to clip the flash from the catheter in a single 
step. 
The single step process, however, has significant disadvantages as it 
provides short tool life in that both the mold and the mandrel are used as 
cutting devices and therefore must engage and wear upon each other. This 
means that during usage the outer surface formed on the catheter varies as 
the contact between the mandrel and the die wears upon the inner surface 
of the die. Furthermore, tooling must be replaced in order to maintain a 
sharp edge on the mandrel to provide appropriate cutting action. 
SUMMARY OF THE INVENTION 
The present invention calls for a process of forming a tip on an 
intravenous catheter including the steps of mounting a tubular catheter on 
a mandrel which mandrel extends beyond the catheter end or proposed tip 
area. A mold having a tapered inner mold surface that compliments the 
desired outer surface of the finished catheter is heated and the 
catheter-carrying mandrel is inserted into the mold to engage the catheter 
material with the inner mold surface. The engagement of the catheter 
material with the inner mold surface causes the catheter material to 
soften and conform to the inner mold surface and forms flash which extends 
beyond the desired catheter tip. The catheter and mandrel are removed from 
the mold after the material has had an opportunity to cool and thereafter 
the mandrel is removed from the catheter. Alternatively, this may be done 
as a single step removing the mandrel from the catheter and thereafter 
removing the catheter from the mold. 
In a second operation, the catheter with flash attached is inserted into a 
jig having a cutting surface which defines an opening. The insertion of 
the catheter into the jig permits the flash to extend through the opening 
beyond the cutting surface. A cutter is moved along the cutting surface 
and severs the flash which extends above the surface and separates that 
flash from the remainder of the catheter. This forms a trimmed catheter 
which is thereafter removed from the jig for further processing. 
The jig may be formed to define a passage that terminates in the desired 
opening. The passage may be complimentary to the outer surface of the 
catheter to ease in positioning of the catheter with the flash extending 
an appropriate distance. The cutter may be a single or double blade such 
as a razor blade in a hand-held operation. The blade may preferably be 
from about 0.003" to about 0.010" thick and the catheter may be formed of 
a material such as polytetrafluoroethylene (PTFE) or polyurethane.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention relates to a simplified and accurate method for 
forming tips of catheters. In particular, in forming tapered catheter tips 
it is necessary to both form the taper and remove any flash that may be 
formed. 
In the present process a tubular catheter 1 made of, for example, either 
polytetrafluoroethylene or polyurethane is placed over a concentric 
mandrel 2. The mandrel 2 is received within the inner bore 3 of the 
catheter cannula and extends beyond the end 5 of the catheter. A mold 6 is 
provided having a tapered inner surface 7 which is complimentary to the 
outer surface desired on the ultimate catheter. For example, it may be 
preferred that a shallow taper of approximately 3.degree. is provided 
along some length of the catheter and a sharper bevel at the very tip of 
the catheter of for example 27.degree. is provided to draw the catheter 
surface down to where it would meet a needle cannula passing through the 
inner bore of the catheter. The mold is heated to a temperature 
appropriate for softening the catheter material. For example, for a 
polytetrafluoroethylene catheter of 20 gauge (i.e. 0.045" diameter) this 
temperature is from about 650.degree. F. to about 750.degree. F. The 
catheter 1 and mandrel 2 are inserted into the mold 6 in a known manner in 
order to engage the catheter material with the heated mold surface. The 
catheter material heats and softens and begins to flow into the space 
within the mold surrounding the mandrel. A portion of the catheter 
material flows out of the desired mold area to form a flash tip 8. 
It should be noted that the mandrel 2 of the present process passes beyond 
the flash tip in order to support it such that on cooling a cylindrical 
piece of flash 8 extends beyond the desired tip of the catheter. This 
flash 8 will later be removed and extends in such a way as to provide a 
consistent filling of the mold as well as a consistent portion to be 
removed by the secondary cutting process. 
The mold 6 and catheter 1 are permitted to cool whereupon the catheter 1 
and mandrel 2 are withdrawn from the inner mold passage. The mandrel is 
then withdrawn from within the catheter and the catheter inserted into a 
female jig 9 (FIG. 2). The female jig 9 has an opening 10 defined 
therethrough which compliments the desired outer surface of the ultimate 
catheter. This opening 10 terminates at an upper cutting surface 11 which 
is positioned with respect to the opening precisely where it is desired 
that the catheter be cut. 
Upon insertion of the catheter 1 within this opening, the flash 8 extends 
beyond the cutting surface 11 and is exposed outside of the jig. A cutting 
blade is thereafter run along the cutting surface 11 in order to severe 
the flash 8 and remove it from the end of the catheter tube. This cutting 
blade 12 should be as thin as consistent with sufficient strength to cut 
the catheter material in order to prevent collapsing of the catheter upon 
itself during the cutting process. It will be easily seen that a dull or 
thick cutting edge upon passage along the cutting surface would tend to 
crush the initial side contacted by the blade towards the opposite side 
thus deforming the catheter and the ultimate cut. 
The flash is thereby removed from the tip of the catheter 1 and the 
catheter removed from the jig 9 for further processing. 
The invention has been described in connection with the attached drawings 
and its preferred embodiments. Minor changes may be made to the invention 
without exceeding the scope of the contemplated invention.