U.S. patent number 3,834,241 [Application Number 05/355,714] was granted by the patent office on 1974-09-10 for pipette.
Invention is credited to Ralph F. Garren, Marvin B. Sarver.
United States Patent |
3,834,241 |
Garren , et al. |
September 10, 1974 |
PIPETTE
Abstract
A pipette which is formed within a mold in which a raw material
of a given tubing thickness is employed, the tubing to be of a
plastic material, the tubing placed within the mold and caused to
be raised in temperature until pliable, the plastic tube caused to
be expanded against the surface of the mold, the drawing tube and
the container section of the pipette being formed of a thickness to
make such substantially rigid, an enlarged bulbous section
connected to the container section, the thickness of the bulbous
section to be substantially thinner than the container section and
the drawing tube section whereby the bulbous portion may be readily
manually compressed and then permitted to retract back to its at
rest state causing a drawing of liquid through the drawing tube
section into the container section.
Inventors: |
Garren; Ralph F. (Canoga Park,
CA), Sarver; Marvin B. (Burbank, CA) |
Family
ID: |
23398531 |
Appl.
No.: |
05/355,714 |
Filed: |
April 30, 1973 |
Current U.S.
Class: |
73/864.11;
422/922; 222/209 |
Current CPC
Class: |
B01L
3/021 (20130101) |
Current International
Class: |
B01L
3/02 (20060101); B01l 003/02 () |
Field of
Search: |
;73/425.4Q,425.6
;128/233 ;141/24 ;222/209 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
|
602,363 |
|
Feb 1960 |
|
IT |
|
1,169,255 |
|
Nov 1969 |
|
GB |
|
Primary Examiner: Swisher; S. Clement
Attorney, Agent or Firm: Munro; Jack C.
Claims
What is claimed:
1. A single piece pipette formed in an intergral manner of plastic
material, said pipette comprising:
a drawing tube section adapted to draw fluid from a vessel;
a container portion connected to said drawing tube, said drawing
tube having an opening therethrough communicating with an enlarged
interior chamber located within said container portion, both said
container portion and said drawing tube being formed substantially
rigid;
a bulbous portion connected to the free end of said container
portion, said bulbous portion being readily felxible so that it is
capable of being squeezed to apply an air pressure force or a
vacuum within said chamber of said container portion;
the wall thickness of said container portion being approximately
one-half the wall thickness of said drawing tube, the wall
thickness of said bulbous portion being approximately one-half the
wall thickness of said container portion; and
means interconnecting said bulbous portion and said container
portion for preventing local collapse of said container portion
during squeezing of said bulbous portion.
2. The pipette as defined in claim 1 wherein:
said means comprises a rigid wall disposed at an angle to both the
wall of said container portion and the wall of said bulbous
portion.
Description
BACKGROUND OF THE INVENTION
A pipette is usually defined as a small piece of apparatus into
which liquids are taken and which principally consist of a narrow
tube into which the liquid is drawn by suction and retained therein
by closing the upper end of the tube. Pipettes are usually made of
glass and are used almost exclusively to deliver accurately known
volumes of liquids or solutions. In the use of pipettes it is
common to place an elastomeric bulb over one end of the glass tube
pipette to facilitate the drawing of a vacuum so that liquid can be
drawn into the pipette.
There are two general categories of pipettes: volumetric or
transfer pipettes and the graduated measuring type of pipette.
Volumetric pipettes, which includes transfer pipettes, are used by
sucking liquid up into the container portion of the pipette, with
this liquid being retained therein, and the pipette then moved to a
receiving container wherein the liquid is discharged from the
pipette. Liquid clinging to the tip of the pipette is removed and
the pipette is allowed to empty freely into the receiving vessel.
After a few seconds or a time specified on the pipette for
drainage, the pipette is then removed. Volumetric pipettes, when
handled in the described manner, will deliver reproducibly a
definite amount of liquid or solution.
In performing certain laboratory tests, as for example blood tests,
transfer pipettes are in extremely common use. From a given sample
of a patient's blood, a precise volume of blood will be placed
within the transfer pipette with that blood within the pipette
being removed to a separate receiving vessel wherein a particular
laboratory test is to be performed. Within a given sample of blood,
there may be a multitude of different tests performed. A transfer
pipette is used to deposit a given volumetric amount of the blood
within this particular receiving container. Frequently, a separate
transfer pipette is employed to make each deposit so that in
performing the tests on a given sample of blood of blood there can
be five, ten or more in number of pipettes used. It is readily
apparent, considering only blood tests and the number of blood
tests performed each year, that a substantial number of pipettes
are employed each year with this number being in the
multimillions.
Because of the quantity of pipettes employed, such have to be
manufactured as inexpensively as possible. Previously, the only
known way in which a pipette could be made inexpensively enough was
to make the pipettes from glass. Glass is inert and does not
contaminate any fluid which the pipette is being used to transfer.
However, there is one main disadvantage to glass and that is
because glass is so brittle that frequently glass pipettes are
broken during transporting from the manufacturer to the
consumer.
It has been known that certain types of plastic are inert to most
fluids. However, to previously manufacture a plastic pipette in
large quantities was not economically feasible because the cost
could not be maintained at a low enough level to successfully
compete with the cost of glass pipettes.
SUMMARY OF THE INVENTION
The primary objective of the apparatus of this invention is to
design a plastic pipette which can be made of an inert material,
made sterile, and be manufactured inexpensively enough to be
substantially equal in cost to a conventional glass pipette. The
primary objective of the method of manufacturing of this invention
is to employ a method of making a pipette wherein the resultant
overall cost of the pipette is at a level to successfully compete
with the cost of conventional glass pipettes.
According to the present invention, the transfer pipette is to be
molded as a complete one piece unit including the drawing tube,
container portion and bulbous portion so that the overall pipette
functions basically as a syringe. Therefore, costs are greatly
reduced compared to currently manufactured glass pipettes. In
addition, assembly time in the laboratory is eliminated since there
is no need to place a syringe upon the pipette.
The pipette of this invention is to be formed from a single plastic
tube of a constant diameter. The plastic tube is to be located
within a mold cavity and then the mold cavity is to be closed. The
tube is to be heated either prior to or after insertion in the mold
cavity so that the tube will become soft and pliable. Fluid under
pressure is to be forced within the tube to force the tube tightly
against the mold cavity surfaces. The drawing tube and the
container portion of the pipette are formed substantially rigid.
The upper end of the pipette is formed into an enlarged bulbous
section, with the thickness of the bulbous section being less than
the container portion from the drawing tube portion. The bulbous
section can be readily manually squeezed so as to apply either a
vacuum or a pressure within the drawing tube section and the
container section.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is an overall isometric view of a mold cavity showing the
placement of the tube within the mold cavity prior to the forming
of the pipette of this invention;
FIG. 2 is a cross-sectional view through the mold cavity basically
showing the forming of the pipette of this invention; and
FIG. 3 is an isometric view of the formed pipette of this
invention.
DETAILED DESCRIPTION OF THE SHOWN EMBODIMENT
Referring particularly to the drawing, there is shown in FIG. 1, a
molding apparatus 10 which is basically composed of a lower molding
section 12 and an upper molding section 14. Within the lower
molding section 12 there is included a lower mold cavity 16. Within
the upper molding section 14 is included an upper mold cavity 18.
When the molding sections 12 and 14 are located in the together
position, the mold cavities 16 and 18 cooperate together to form an
overall mold cavity for the pipette of this invention.
The fore edge of each of the molding sections 12 and 14 is formed
quite sharp so as to facilitate cutting of the raw material tube 22
when the molding sections 12 and 14 are closed. Fixedly mounted
within the upper molding section 14 is a needle 26 which includes
an elongated opening 28 formed therein. A connector 30 is connected
to the needle 26 with the connector 30 also being attached to air
supply tube 32. The length of the needle 28 is selected so that it
extends within the upper mold cavity 18. The tube 32 is to be
connected to the source of pressurized air (or other fluid) not
shown.
The material of construction of the tube 22 can be any suitable
thermoplastic material. However, the selection of materials is
considered to be a matter of choice. It is envisioned that the
material 22 will be a purchased commodity from a manufacturer with
a substantial length of the tube 22 being wound upon a reel.
The pipette 34 of this invention includes bassically a drawing tube
section 36, a container section 38 and a bulbous portion 40. The
drawing tube section 36 is adapted to be inserted within a vessel
as to draw liquid up into the drawing tube and into the container
section 38. A graduated scale may be located upon the outer surface
of the container section 38 so as to indicate to a person the
quantity of liquid being drawn into the container portion 38. The
bulbous portion 40 is to be of suitable flexibility to prevent
failure when squeezed and is to be used to create a vacuum for
drawing within and a pressure for expelling the liquid from the
container portion 38. A ring 42 is to interconnnect the bulbous
portion 40 with the container portion 38. The function of the ring
is to prevent local collapse of the container portion 38 when the
bulbous portion 40 is squeezed.
As was previously stated, the thickness of the raw material tube 22
was constant. When the molding elements 12 and 14 are in the closed
position shown in FIG. 2 of the drawing, the pressurized air is to
be conducted through the tube 32 into the opening 28 within the
needle 26 and then interiorly of the tube 22 located within the
mold cavity. This pressurized air is to force the surfaces of the
tube 22 against the mold cavity surfaces. The tube 22 at this point
will be pliable. The size of the drawing tube 36 is basically the
same size of the outer diameter of the tube 22 so therefore the
thickness of the drawing tube will be substantially equal to the
original thickness of the tube 22. The size of the container
portion 38 is larger than the drawing tube 36 therefore the
thickness of the container portion 38 will be less than the
thickness of the drawing tube 36 because the material is forced to
stretch to accommodate the larger area of the container portion 38.
The stretching of the material within the container portion 38 is
not to be accomplished to such an extent so that the container
portion 38 loses its rigidity.
The same stretching is accomplished within the bulbous portion 40
with the area of the bulbous portion cavity being substantially
greater than the area of the container portion 38. As a result, the
thickness of the material within the bulbous portion 40 is
substantially less than that of the container portion 38. As a
result, the bulbous portion 40 loses its rigidity and can be
readily manually squeezed. However, once the manually squeezing
force is no longer applied to the bulbous portion 40, the bulbous
portion 40 will return to its initially established shape. However,
this squeezing action will cause a vacuum to be drawn within the
container portion 38 and the drawing tube 36 in order to suck fluid
into the container portion 38. The bulbous portion 40 will also be
used to expel fluid from the container portion 38.
A annular ring 40 interconnects the bulbous portion 40 to the
container portion 38. This ring is to prevent collapse of the aft
end of the container portion 38 during the squeezing action of the
bulbous portion 40.
The manufacturing process for the making of the pipette 34 of this
invention is designed so that the pipette can be made in one stage.
The various components of the maufacturing equipment are designed
to work automatically. The various manufacturing steps will be
accomplished sequentially on a predetermined time cycle. The raw
material tubing 22 will be fed into the molding apparatus 10 from
reels. The finished pipettes 34 will be placed onto a conveyor belt
and to a gravimetric station where such will be packaged and
distributed.
The process of this invention is as follows:
1. The extruded plastic tube 22 is drawn through the open molding
sections 12 and 14 of the molding apparatus 10 as shown in FIG. 1
of the drawing.
2. The tubing 22 will then be heated to its softening point by a
heat source such as by quartz heaters, infared heaters or some
other type of energy source.
3. The molding sections 12 and 14 will then be closed when the
plastic tube 22 has reached the softening point. The heaters will
then be removed. By closing of the molding sections 14 and 16 the
tube 22 is pinched shut at each end of the cavity which describes
the longitudinal ends of the pipette 34. It is considered to be
within the scope of this invention to heat the tube after the
molding sections 12 and 14 are closed rather than prior to closing
of these sections.
4. When the molding sections 12 and 14 are closed, the heat
softened plastic tube 22 is expanded against the walls of the
molding cavities 16 and 18 by means of air pressure supplied
through the passage 28 of the needle 26. Also, it is considered to
be within the scope of this invention that instead of using a
needle 26, that a vacuum could be applied to the surfaces of the
molding cavity 16 and 18. This vacuum would cause the tube 22 to
expand against the cavity surfaces. It is also considered to be
within the scope of this invention to use both of the needle and
vacuum simultaneously.
5. Once the pipette 34 has been formed within the molding sections
12 and 14, the tube is to be cooled. This cooling can be
accomplished by circulating a cooling liquid through cooling
circulating passages located within the molding sections 12 and 14.
This cooling is to be accomplished until the plastic is cooled
below the softening point. If a vacuum is used to form the pipette,
then the air inside the softened tube will expand rapidly and
subsequently cool the plastic below the softening point during the
following process. It is considered within the scope of this
invention that both of these methods could be accomplished
simultaneously or other cooling methods could be employed.
6. The molding sections 12 and 14 will now be opened to the spaced
apart position shown in FIG. 1 and the finished pipette 34
ejected.
After the pipette 34 is formed and removed from the mold cavity, a
small aperture may be formed through the sidewall of the container
portion 38 which would be produced due to the needle 26. It is
envisioned that this aperture will be closed by the placing of a
plastic or paper patch over this hole prior to distributing of the
pipette 34 to the consumer. It is also to be considered within the
scope of this invention that the pipette 34 can be removed from the
mold cavity prior to complete hardening and the aperture formed
within the container portion 38 can then be closed during final
hardening.
No cutting or trimming will be necessary of the pipette 34. The
process described above relates to a method for making a single
pipette 34 at a time It is envisioned that the pipettes will be
formed in multiples through the use of multicavity molds. It is
envisioned that the thickness of the raw material tube 22 will be
30 thousandths of an inch. After the forming of the pipette 34, the
drawing tube 36 will be 30 thousandths of an inch in thickness, the
container portion 38 will be 15 thousandths of an inch in thickness
and the bulbous portion 40 will be 7 thousandths of an inch in
thickness. It is to be considered that these dimensions are merely
illustrative and this invention is in no way to strictly adhere to
these dimensions.
* * * * *