Method of making a plastic article having a plurality of tiny, through openings

The method of making a plastic article having a plurality of small openings which utilizes a plurality of thin plastic tubular members combined together in a side-by-side relationship forming an assemblage. Each tubular member has an exterior layer of a first plastic and a core of a second plastic. The second plastic is to be dissolvable by a solvent. This assemblage is passed through a furnace with the result that the assemblage is drawn into a thin filament. Once cooled, the thin filament is cut into segments of a desired length and these segments are placed within a solvent bath for a sufficient period of time in order to affect complete removal of the second type of plastic resulting in producing of a plurality of small, through openings within each section.

BACKGROUND OF THE INVENTION 
The field of this invention relates to the locating of one or more tiny 
holes within a block of material and principally to the locating of the 
holes within a block of plastic. 
The subject matter of the present invention is to be discussed in 
conjunction with the field of medicine. However, it is to be understood 
that the subject matter of this invention could be utilized in numerous 
other fields, many of which may even be unknown to the inventor. The 
contemplated field of utility of this invention is directed to obtaining 
of an orifice member which provides for a restricted flow of a liquid 
through this orifice member. This restriction of flow can be of particular 
advantage within the medical field or within any other field where a 
restricted flow would be desirable. 
In the constructing of any liquid conducting orifice, the side wall of the 
orifice would frictionally resist the flow of the liquid through the 
orifice. Normally, it is the intention to decrease this restriction so 
that the liquid can flow through the orifice with the minimum amount of 
resistance, therefore, a minimal amount of energy loss. However, this 
restriction to the flow of a liquid through an orifice can be utilized to 
advantage in certain environments. 
The smaller the orifice, the greater the restriction. Also, the longer the 
orifice, the greater the restriction. If the orifice size is a thousandth 
of an inch or less, and the orifice separates a pair of fluid mediums with 
one fluid medium being at a pressure differential greater than the other, 
then that restriction could be utilized to maintain a certain pressure 
differential relationship between the two fluid mediums. There is a 
problem with a single orifice in that not much flow is permitted. 
Therefore, it is common to utilize a mass of orifices, all of which have 
the same size and which have the same amount of restriction. It is this 
mass of orifices that more effectively control and maintain the 
established pressure differential. 
Within the field of medicine, a common disease in conjunction with eyes is 
glaucoma. Within the eyeball is located a liquid. This liquid is under 
pressure with a common pressure being approximately twenty millimeters of 
mercury. In glaucoma, this pressure increases and if the pressure gets too 
severe, the patient can actually go blind. 
In the past, there have been different techniques in order to relieve this 
excessive pressure. A vast amount of money is spent each year on drops 
that are to be placed onto the eye that are minimally effective. 
Additionally, there have been numerous surgical techniques in order to 
relieve this pressure. One of the most common surgical techniques is 
merely to cut a hole into the eyeball which provides an outlet for some of 
the liquid contained in the eyeball thereby relieving the pressure. This 
hole is then sutured. The disadvantage of this technique is that initially 
the pressure of the liquid in the eyeball is decreased below the desired 
level to atmospheric pressure. As time goes on, the pressure will again 
build up back to its original level which will require a duplicating of 
the surgical technique. 
To overcome the disadvantage of this technique, there has been manufactured 
a valve assembly which is to be mounted in conjunction with the eyeball 
and located within the hole cut into the eyeball. It is the function of 
the valve to be activated if a certain pressure level is exceeded and 
provide an escape route for some of the liquid contained within the 
eyeball thereby releasing the pressure. The disadvantage to this valve is 
that it frequently malfunctions thereby requiring replacement or complete 
removal of this valve unit. 
Another known device has to do with utilizing a balloon operating pump as 
opposed to a valve. This balloon operated pump is to release liquid when 
the pressure is applied to the balloon. This pressure is to be applied by 
the natural blinking process of a human being or is to be applied by 
manual rubbing of one's eye. However, the patient is not sensitive to 
increased eye pressure, therefore, is not able to determine when it is 
desirable to operate the pump. Again, this type of unit is not free from 
malfunction although, prior to the present invention, is probably the best 
device available to relieve accumulated liquid pressure from the interior 
of an eyeball. 
The present inventor discovered that if a tiny block of plastic could be 
manufactured with a mass of tiny, through openings, and this block of 
material was installed in conjunction with a hole extending into the 
interior of an eyeball, that depending on the size of these openings, a 
pressure differential can be established between the interior of the 
eyeball and the ambient which could be maintained without utilizing any 
moving parts. By varying the size of these holes, this pressure 
differential could also be varied. As the pressure increases, the amount 
of flow through the orifices increases, thereby decreasing the pressure. 
This is a desirable feature since not all people have the same liquid 
pressure within the interior of the eyeball. Therefore, if the size of the 
orifices could be precisely controlled, a custom designed liquid relief 
passage arrangement could be manufactured for that particular individual. 
The liquid that is conducted from the interior of the eyeball to the 
exterior of the eyeball is discharged naturally through the waste disposal 
system of the human being. 
It has been impossible in the past to manufacture a block of material which 
had a mass of precisely sized, tiny openings. Small openings can be formed 
within a block of material, such as plastic, by the utilizing of a laser. 
However, lasers cannot, at present, make the openings that are required by 
the present invention as the minimal size of opening that can be formed by 
the laser is still too large or not of sufficient length. Therefore, 
another method had to be arrived at to manufacture such small openings of 
adequate length. 
It is to be reiterated that the method of the present invention can be used 
to manufacture articles which are usable in other fields of endeavor. One 
example would be in the making of contact lenses for the eye. One of the 
inherent problems of a contact lens is that liquid and oxygen is normally 
blocked by the lens so there is no way for fluid from the exterior surface 
of the eyeball to penetrate to the interior surface of the lens. If a lens 
was manufactured in accordance with the method of the present invention, 
there would be a mass of tiny holes, or through openings, formed within 
the lens which would permit this liquid and oxygen to be conducted to the 
interior surface of the lens. This mass of tiny holes would not interfere 
with the normal vision of the lens. 
SUMMARY OF THE INVENTION 
The method of making a plastic article which has a plurality of small, 
through openings. This method has to do with the forming of an enlarged, 
elongated, tubular bar which is substantially hollow with this bar being 
constructed of a first type of plastic that is not dissolvable by a 
solvent. Within the hollow is located a second type of plastic that is 
dissolvable by a solvent. This bar is conducted vertically from an 
elevated position to a lowered position through a furnace which causes the 
lower end of the bar to melt and be drawn into a thin, elongated tubular 
member having a cross-sectional area less than the cross-sectional area of 
the bar while maintaining substantially the same proportion of first 
plastic to the second plastic as was contained within the bar. Sections of 
this tubular member are produced to a given length. A quantity of these 
tubular members are located in juxtaposition and bound together forming an 
assemblage. This assemblage is then conducted through the furnace in the 
manner previously described resulting in producing of a thin filament 
having a plurality of internally located threads of the second type of 
plastic. This filament is then to be cut into desired lengths and placed 
within a solvent bath for a period of time, sufficient to dissolve the 
second type of plastic producing a plurality of spaced apart small, 
through openings within this filament. 
The primary objective of the present invention is to provide a method which 
permits the forming of tiny, through openings within a block of plastic 
material with the size of these openings being so small that they are not 
capable of being manufactured by any known prior art technique. 
Another objective of the present invention is to utilize a method which 
provides for obtaining of a precise size of opening and capable of 
precisely varying the size of opening within a block of plastic material. 
Another objective of the present invention is to provide for a method which 
permits relatively inexpensive manufacture of products with precisely 
sized, tiny openings within a plastic block of material.

DETAILED DESCRIPTION OF THE INVENTION 
Within the drawing, there is generally depicted the method of the present 
invention. It is to be understood that the drawing only gives a 
generalized representation of the procedure of the method of this 
invention and that in actual practice the structure that is to effect the 
method of this invention may be different than what is actually shown. 
There are two different plastics, generally, that will be utilized. Common 
types of plastics that have been found to preferable would be a polymethyl 
methacrylate and polystyrene. Polymethyl methacrylate would probably be 
the preferable material for the reason that this material has been found 
to be an acceptable material within the medical field and would not 
require any material approval by any federal agency. However, it is 
considered to be within the scope of this invention that other material 
could be utilized without departing from the scope of this invention. 
Of the two different plastics that are utilized, both could comprise 
polymethyl methacrylate. One of the polymethyl methacrylates would not be 
dissolvable by a solvent, with the other polymethyl methacrylate being 
dissolvable by a solvent. For the purpose of this invention, the plastic 
not dissolvable will be referred to as the first plastic and the plastic 
that is dissolvable by a solvent will be referred to as a second plastic. 
Both the first and second plastics will have substantially identical 
melting points somewhere in the range of three hundred thirty degrees 
Fahrenheit to three hundred ninety degrees Fahrenheit. It is important 
that the second plastic have a melting point no greater than the first 
plastic. Actually, it would probably be preferable that the second plastic 
have a slightly less melting point than the first plastic for a reason 
which will become apparent further on in this specification. 
The first plastic will normally come in the initial form of a mass of 
pellets (not shown). These pellets will be melted within a vessel 10 
forming a liquid plastic 12. This liquid plastic 12 is poured into an 
internal chamber 14 of a mold 16. The mold 16 includes a center tube 18 
which will result into the forming of a hollow cylindrical shaped hole 20 
of the resultingly formed plastic bar 22 when it is removed from the mold 
16. It is to be understood that, normally, the mold 16 will be placed 
within an injection molding machine (not shown). It is preferable that the 
transverse cross-sectional configuration of the bar 22 be square with the 
hollow 20 being circular. However, it is considered to be within the scope 
of this invention that the bar 22 could be another polygonal 
configuration, or could be a non-polygonal configuration, such as 
cylindrical. Generally, the length of the bar 22 is one and one-half to 
two feet long and being one and one-half to three inches square. The 
diameter of the hole 20 will normally be between one inch to one and 
one-half inches. 
When the bar 22 has been removed from mold 16 it is permitted to cool to 
room temperature. It is desirable to insure that any gas and moisture that 
has become impregnated in the bar 22 be released. The reason for this is 
that gas and/or moisture will cause producing of a rejectable product. 
Also, at times, in the molding procedure, there may be produced a certain 
amount of stress within the bar 22 and it is desirable to remove this 
stress. In order to remove the gas, moisture and stress, the bar 22 is 
placed within a vacuum chamber (not shown) with a slight vacuum, such as 
twenty-nine inches of mercury being pulled on the bar 22. This bar 22 is 
stored within this chamber, which is heated to approximately two hundred 
fifty degrees Fahrenheit, for a certain length of time such as twenty-four 
hours. This procedure is to be described as THERMOVAC throughout the 
specification of this invention. 
After the twenty-four hour period, the bar 22 is removed from the THERMOVAC 
chamber and permitted to again cool to room temperature. At this 
particular time, a quantity of the second plastic is heated within heating 
vessel 24 and liquefied into a liquid plastic 26. This liquid plastic is 
then poured into the hollow 20. Normally, this pouring into hollow 20 will 
be completed within an injection molding machine in order to insure the 
side walls of the bar 22 do not bow in an outward direction because of the 
application of the heat from the second plastic 26. Once the liquid second 
plastic 26 is cooled into a solid plastic 28, the bar 22 is then placed 
again within the THERMOVAC chamber for a twenty-four hour period. 
After the bar 22 has been removed from the THERMOVAC chamber and cooled, it 
is suspended in a vertically oriented manner by an appropriate overhead 
suspension mechanism (not shown). The bar 22 is to be located in an 
elevated position. Vertically oriented means one end of the bar 22 is 
located directly above and in alignment with the opposite end of the bar 
22 and the longitudinal center axis of the bar 22 is in alignment with the 
direction of the gravity force on the bar 22. 
The bar 22 is then to be moved into the through opening 30 of a furnace 32. 
The lower portion of this furnace 32 includes a heating coil assembly 34. 
When the lower end of the bar 22 become located directly adjacent the coil 
34, the heat will be sufficient to cause expansion of the bar 22 forming 
an expanded section 36. Melting of the entire cross-sectional area of the 
bar 22 is to occur. Bar 22 is then drawn into a substantially decreased 
cross-sectional size tubular member 38. Centrally disposed within this 
tubular member 38 is a core 40. In cross-section, the proportional size of 
the core 40 to the overall cross-section of the tubular member 38 is 
maintained the same as the relationship of hollow 20 to bar 22. It is to 
be understood that the core 40 is actually hollow 20 but in a small 
diameter. Each core 40 is filled with second plastic 28. The tubular 
member 38 is then to be cut into prescribed lengths such as two foot 
lengths 42. 
The lengths 42 are again cooled and then placed within the THERMOVAC 
chamber for a period of time, such as four hours. A quantity of the 
lengths 42 are to be assembled together in juxtaposition, secured at the 
ends by means of a tape-like band 44 forming an assemblage 46. The 
assemblage 46 is basically the same size and of a square configuration as 
bar 22. This assemblage 46 is then again placed within the THERMOVAC 
chamber. The temperature at this time within the THERMOVAC chamber is 
increased to be just below the melting point of the plastics which will 
result in the tubular members 42 slightly melting together thereby bonding 
the assemblage 46 into a single unit. The assemblage 46 is then removed 
from the THERMOVAC chamber and permitted to cool. At this particular time, 
the bands 44 could be removed if such is deemed to be desired. 
The assemblage 46 is mounted in the same manner as bar 22 was mounted in 
conjunction with the furnace 32. Assemblage 46 is moved through the 
chamber 30 of the furnace 32 with the lower end of the assemblage 46 being 
melted by being located directly adjacent the heating coil 34. The 
assemblage 46 will assume an expanded section 48 prior to being drawn into 
a thin filament 50. The thin filament 50 will be cut into desired lengths 
52, such as a two foot length. The length 52 is to be cut by means of a 
cutting blade 54 into a mass of small blocks 56. Prior to being cut into 
the blocks 56, the filaments 52 will normally be placed in the THERMOVAC 
chamber again for a short period of time such as four hours. Prior to 
being cut into the blocks 56, the filaments 52 are to be cooled to room 
temperature. 
The size of the blocks 56 can be any desired length. A preferable size is 
one-sixteenth to one-eighth inch long when used in conjunction with a 
device that will ultimately be mounted to treat glaucoma. Blocks 56 will 
actually be polished in bulk to eliminate any burrs and sharp corners 
prior to being deposited within reservoir 58 which contains a solvent 60. 
A desirable solvent 60 could be any liquid which would remove the now 
formed mass of threads of second plastic that extend through each block 
56. Each thread is actually a smaller diametered section of second plastic 
28 which is contained within the smaller diametered cores 40. A typical 
solvent would be within the group of xylene, trichloroethylene, acetone, 
methyl ethyl ketone, and methylene chloride. However, it is considered to 
be within the scope of this invention that other solvents could possibly 
be utilized. Generally, the length of time within the solvent reservoir 58 
would be between five minutes to two hours. 
After the submersion of the blocks 56 within the reservoir 58 which 
contains the solvent 60, the blocks 56 are removed and permitted to dry. 
The resultingly formed block 56 includes a plurality of evenly spaced 
apart, through openings 64, small in cross-section, which were actually 
cores 40. In essence, these openings 64 resemble a mass of threads formed 
within the blocks 62. The cross-sectional size of each of the openings 64 
will generally be one-thousandth of an inch or less. The actual size of 
the opening 64 can be controlled by the cross-sectional thinness of the 
filament 52 that is produced. It is to be kept in mind that the 
proportional size of each of the cores 40 of each tubular member 42 is 
maintained in conjunction with the filament 52. So, therefore, the thinner 
the filament 52 that is produced, the smaller the block 62 and, hence, 
smaller the opening 64. It is not at all uncommon to produce two hundred 
twenty-five openings 64 within an eighth inch square block 62. 
It is envisioned that different techniques could be utilized to eliminate 
the core plastic 40. Possibly, by utilizing a slightly different melting 
temperature for the core plastic 40 relative to the first plastic, and by 
carefully raising of the temperature of each of the blocks 56 that the 
core plastic can be eliminated by melting leaving intact the remaining 
portion of the block 56 thereby producing the block 62. At the present 
time, there is no known method to produce such small, through openings 64 
by physically cutting either by drilling or by a laser.