U.S. patent number 3,613,729 [Application Number 05/011,537] was granted by the patent office on 1971-10-19 for valve system.
This patent grant is currently assigned to Packard Instrument Company, Inc.. Invention is credited to Ralph A. Dora.
United States Patent |
3,613,729 |
Dora |
October 19, 1971 |
VALVE SYSTEM
Abstract
A valve system adapted to automatically add solvents and/or
reactants to a sample and a reactor by connecting multiple fluid
inlets or outlets to a main flow path has an upper body with an
open trough formed in the bottom surface thereof, a flexible,
elastically deformable, membrane clamped between the bottom surface
of the body and a lower block to close the open trough and provide
a longitudinal flow path, and a plurality of ports extending into
the body terminating at spaced points on its bottom surface, each
port being separated from the flow path by surrounding partitions.
Reciprocating actuators in the block below each port normally hold
the membrane against the partitions to close the ports, and are
selectively released to perit fluid flow between the flow path and
various of the ports.
Inventors: |
Dora; Ralph A. (Santa Barbara,
CA) |
Assignee: |
Packard Instrument Company,
Inc. (Downers Grove, IL)
|
Family
ID: |
21750824 |
Appl.
No.: |
05/011,537 |
Filed: |
February 16, 1970 |
Current U.S.
Class: |
137/614.18;
251/331 |
Current CPC
Class: |
F16K
31/524 (20130101); F16K 7/16 (20130101); G01N
35/1097 (20130101); Y10T 137/88038 (20150401) |
Current International
Class: |
F16K
31/524 (20060101); F16K 7/12 (20060101); F16K
7/16 (20060101); G01N 1/00 (20060101); F16K
31/52 (20060101); G01n 031/08 (); F16k
019/00 () |
Field of
Search: |
;137/624.18,624.2,624.13,624.15 ;251/331,61.1 ;73/23,23.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Cohan; Alan
Claims
What is claimed is:
1. A valve system comprising a body, open through means formed in
one surface of said body, a membrane positioned against said one
surface of said body and acting as one wall of said trough means to
provide a closed flow path, a plurality of ports extending into
said body and terminating at spaced points on said one surface
adjacent to said flow path, partition means separating each of said
ports from said flow path at said spaced points, said membrane
being elastically deformable in response to fluid pressure to move
away from said partition means and allow fluid communication
between said ports and said flow path, a plurality of movable means
for contacting an opposite surface of said membrane and holding it
in contact with each said partition means to close each said port
from said flow path, actuator means engaging each said movable
means for selectively opening and closing each of said ports to
permit fluid flow between said flow path and any selected ports,
said membrane being clamped between said body and a block, said
block including a series of cylinders located in registration with
each of said partition means, said movable means for closing said
ports constituting plungers which are reciprocatingly mounted in
said cylinders, and said plungers containing separate parts which
are slidably interconnected with resilient spring means for
transferring force to the part which bears against said membrane to
force it in contact with said partition means.
2. A valve system in accordance with claim 1 wherein one end of
said flow path connects to a reactor, and wherein a separate valve
in said valve system which is opened and closed by said membrane
connects to said reactor and to a waste.
3. A valve system in accordance with claim 2 wherein s source of
carrier gas is connected to the end of said flow path opposite to
said one end to supply gas through said flow path to said
reactor.
4. A valve system in accordance with claim 3 wherein means for
introducing a sample is connected to said opposite end of said flow
path through one of said ports.
5. In a valve system for predetermined addition of reactants
selectively to a sample in a reactor, said valve system being
adapted to be connected to a sample source, a plurality of reactant
sources and reactor means, the combination comprising,
a valve body having trough means defining a closed flow path,
a plurality of ports extending into said path and terminating
adjacent to said flow path,
valve means separating each of said ports from the flow path,
means connecting said sample source to one of said ports adjacent
one end of the flow path,
means connecting respective ones of said reactant sources to
intermediate ones of said ports,
means for selectively opening and closing said valve means for each
of said ports to permit flow between the selected port and said
flow path, and
means for establishing a constant purge flow of carrier gas through
the flow path from said sample holder end to the reactor end
thereof so that said sample and reactants when introduced into the
flow path upon opening of their respective valves are moved
completely out of the flow path into said reactor.
6. A valve system as claimed in claim 5 wherein said trough means
is formed in one surface of said body and said valve means
comprises a membrane positioned against said one surface of the
body acting as one wall of said trough means to provide the closed
flow path, partition means separating each of said ports from said
flow path, said membrane being elastically deformable in response
to fluid pressure to move away from said partition means and allow
fluid communication between said ports and said flow path, a
plurality of movable means for contacting an opposite surface of
said membrane and holding it in contact with each of said partition
means to close each said ports from said flow path.
7. A valve system as claimed in claim 6 wherein said membrane is
clamped between said body and a block, said block including a
series of cylinders located in registration with each of said
partition means, said movable means for closing said ports
constituting plungers which are reciprocatingly mounted in said
cylinders, means for biasing said plungers in a direction away from
said partition means, and rotatable cam means for moving said
plungers to open and close said ports in a predetermined selective
manner during rotation of said cam means.
Description
BACKGROUND OF THE INVENTION
The present invention relates to valve systems. More particularly
it is directed to a valve system for connecting multiple passages
to a main flow path, which system is particularly adapted for use
as a part of chemical analysis apparatus.
Chromatographic analysis, for example gas chromatography, is often
used to separate and identify the various components of a sample.
These samples are often originally in liquid or solid form and not
sufficiently volatile to permit direct gas chromatographic
analysis. It is therefore necessary that such samples undergo
various preliminary chemical reactions to prepare them for the
ultimate identification of their components. In such preliminary
reactions, the samples may be treated with several different
reactants in various sequentially performed steps.
For repetitive laboratory analyses of samples, the treatment for
each sample with proper concentrations of reactants in a particular
sequence is desirably automated to facilitate standardized
operation with a minimum of manual intervention. Accordingly, it is
desirable to have an automatic valve system which facilitates the
treatment of a sample with the desired reactants in a predetermined
sequence preparatory to final analysis of the sample.
It is an object of the invention to provide an improved valve
system designed to handle a plurality of fluid components. It is
another object of the present invention to provide a valve system
adapted for the addition of reactants to a sample in predetermined
amounts and in a predetermined sequence. It is a further object of
the present invention to provide a valve system which permits the
automatic addition of several different solvents and/or reactants
to a reactor while maintaining the reagent supplies out of contact
with one another.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects of the present invention should be apparent
from a reading of the following detailed description and in
conjunction with the drawings wherein:
FIG. 1 is a perspective view of a valve system embodying various
features of the present invention;
FIG. 2 is a top view of the valve system shown in FIG. 1,
FIG. 3 is a sectional view of the valve system taken along the line
3--3 of FIG. 2; and
FIG. 4 is a fragmentary sectional view of a valve of the present
invention taken along the line 4--4 of FIG. 3.
DETAILED DESCRIPTION OF THE INVENTION
Briefly, a valve system 10 (FIG. 1) is provided including a head 12
and a block 14, which in the illustrated embodiment are rectangular
in cross section and complementary in size. A deformable membrane
16 is clamped between the head 12 and the block 14. The head 12
contains a series of (inlet or outlet) passageways or ports 18a
through 18i (FIG. 2) which extend into the valve head 12 to several
of which act as inlets for various reagents, and other of which
connect as outlets to collectors. As shown in FIG. 3, each of the
ports 18 is a continuous passageway extending from the front
surface 19 of the head 12 to the bottom surface 20 abutting the
deformable membrane 16 which separates the head and the block.
Individual valves A to I are formed at the end of each passageway
18 at the bottom surface 20 in cooperation with the deformable
membrane 16.
A flow path 22 (FIGS. 2 and 3) in the form of a downwardly open
trough extends longitudinally along the bottom surface 20 of the
head from valves B to G. The deformable membrane 16 closes the
trough to form a generally closed channel serving as the flow path
22. The illustrated flow path 22 is made up of a plurality of
straight sections 23 which interconnect annular sections 24
surrounding each of the ports 18 at the spaced locations at which
they emerge into the bottom surface 20. Each port 18 is separated
by a ring-shaped wall or partition 26 from the annular sections 24
of the flow path. At each end of the flow path 22, (outlet or
inlet) passageways 28 are provided which extend rearward from
annular sections 24 to a rear surface 29 of the head 12.
The membrane 16 is elastically deformable and is unsupported on its
undersurface in the region of the valves as a result of cavities or
cylinders 30 which are provided in the block 14 in underlying
registration with each of the annular sections 24 of the flow path.
Thus, the application of fluid pressure via the respective inlet
passageways 18 to the upper surface of the membrane causes it to
move downward away from the partition 26 to permit fluid flow
between the ports 18 and the annular sections 24 of the flow
path.
To maintain the valves A-I closed until it is desired to open them,
plungers 32 (FIGS. 3 and 4) are provided for reciprocating movement
in the vertical cylinders 30 and extend through the block 14. Each
cylinder 30 has an upper portion 31 of a diameter about the same
size as the annular section 24 of the flow path. The plunger 32 in
each cylinder 30 has a head 34 of a size greater than the
ring-shaped partition 26 and a rod 36 which extends downwardly
therefrom. The lower end of the rod 36 is received in a guide 38
which extends below the bottom surface of the block through a lower
portion 37 of the cylinder 30 of reduced diameter and provides a
bearing surface for the outer surface of the guide 38 which slides
therein. In the illustrated embodiment, each of the nine
independent valves A-I of the system contains such a guide 38, the
bottom surface of which rides along the surface of the rotating cam
40. The shape of the individual cam 40 and the speed of its
revolution determines whether a valve will be open or whether the
plunger head 34 will be held in contact with the deformable
membrane 16 in the latter case forcing it against the partition 26
to close the valve by preventing fluid flow between the port 18 and
the longitudinal flow path 24.
The head 12 made of a block of suitable material, such as
polytrifluoromonochloroethylene (Kel-F), which is not chemically
affected by exposure to the reagents employed and which has a low
wettability with respect to most liquids (so there is a high angle
of liquid contact with respect thereto). The head 12 is suitably
formed by machining or by molding or casting.
Each of the nine ports 18a through 18i (FIG. 3) extends
horizontally into the head from the front surface 19 of the valve
head 12 to approximately its transverse center. At this point, the
horizontal passageway ends at a vertical passageway extending
downward to the bottom surface 20 where the deformable membrane 16
is located. Each of the ports 18 is of identical construction, and
each port contains a tapered entrance section 41a (FIG. 3) of
enlarged diameter which is adapted to receive a tapered plug 41b.
Couplings 42, which may each be provided with a calibrated orifice,
are attached to the outer ends of the plugs 41b.
In the illustrated embodiment, liquid reagents are fed from supply
lines 43 through the orifice-holding couplings 42 into individual
valves A, C, E, E, F, and I. By the employment of the separate
removable orifice-containing couplings 42, careful metering and
regulation of the fluid flow through each of the various ports is
accomplished. The size of the particular orifice is determined by
the properties, e.g. viscosity, surface tension, and/or density of
the liquid which passes therethrough. Generally, a uniform
pressure, for example, 1-2 p.s.i.g., of dry inert gas, upon the
reagent supplies (not shown) is employed to deliver the liquids to
the valves at a constant pressure head.
As stated earlier, the flow path 22 is in the form of a groove or
trough formed in the bottom surface 20 of the head 12. The
deformable membrane 16 is quite thin and may be of any suitable
resilient material that is chemically inert to the various reagents
intended to be employed with the valve system 10, for example
polytetrafluoroethylene or special types of synthetic rubber. The
valve system 10 is designed to operate at relatively low pressures,
i.e., 1 to 2 p.s.i.g., and the thickness of the membrane 16 should
permit deformation at such pressure differentials whenever the
plunger head 34 is withdrawn from the underside of the membrane 16.
A typical membrane 16 of polytetrafluoroethylene which may be used
is of the order of 2 to 5 mils in thickness. When the plunger 32 is
withdrawn from the underside of the membrane 16 (as shown in FIG.
3), it will bow downward as shown to connect the inlet port 18 and
the flow path 12 in fluid communication. Such bowing occurs so long
as the pressure in either the inlet port 18 or the flow path 22 is
above atmospheric (discharge) pressure. The valve construction
permits flow in either direction therethrough, depending upon where
the higher pressure region is located.
The membrane 16 is substantially coextensive with the entire
undersurface 20 of the head 12 and the block 14. The membrane has
no openings except those which permit the passage of fastening
members, such as capscrews 44, (FIG. 3), which are threaded upward
into the head and clamp the membrane 16 between the block 14 and
the undersurface 20 of the head 12. The block 14 may be made of any
suitable material, as all of the fluid flow passageways are in the
head 12 located above the membrane.
Because of its thinness, the membrane 16 does not provide a
reliable seal, and a separate resilient gasket 45 (FIGS. 3 and 4)
is preferably employed, which is substantially thicker than the
membrane 16. The resilient gasket 45 cushions and protects the
membrane 16 and avoids the creation of stresses at locations
adjacent the cylinder openings 30 where it would otherwise be
tightly clamped between two rigid surfaces. The gasket 45 has
circular openings which register with each of the cylinders 30 and
permit the deformation of the membrance thereinto.
As previously indicated, the illustrated block 14 is provided with
nine cylinders 30, wherein plungers 32 are located, below each
partition. The plunger 32 in each cylinder 30 selectively seals the
respective port 18 in a positive manner by forcing the membrane 16
upward against the partition 26. In the illustrated embodiment,
each plunger head 34 is circular, having a flat upper surface upon
which a resilient pad 52 of rubber or other suitable material is
mounted to engage the membrane 16. The resilient pad 52 avoids
damage to the thin membrane 16 which might result from repeated
cycling of the plunger 32 into and out of contact with the
membrane. The guide 38 has a central bore 54 into which the plunger
rod 36 is slidingly accepted. The guide 38 in turn is slidingly
received in the lower portion 37 of the cylinder 30 and is provided
with a circular flange 56 at its upper extremity that prevents its
removal downward from the cylinder.
Near the bottom of the guide 38 (FIGS. 3 and 4) (which carries a
wheel 57 that rides along the peripheral edge of the cam 40), a
groove is provided to receive a retaining or snapring 58. A coil
spring 60 is provided between the retaining ring 58 and the
undersurface of the block 14 to bias the guide 38 downward. When
the location of the cam 40 allows the guide 38 to move downward,
the plunger 32 follows as a result of gravity and the sliding
friction between the outer surface of the rod 36 and the bore 54 of
the guide. To interconnect the plunger 32 and the guide 38, a
second coil spring 62 is located surrounding the rod 36 between the
upper surface of the flange 56 on the guide and the undersurface of
the piston head 34. In order to permit free movement of the rod 36
within the central bore 54 of the guide, a small air vent 64 is
located in the bottom of the guide 38. The provision of the spring
62 cushions the closing of each valve and determines the force with
which each plunger 32 contacts the thin membrane 16.
As mentioned earlier, the plunger assembly of each of the nine
valves is actuated by means of cams 40 which are mounted on a
common shaft 66 positioned therebelow. The radius of each cam 40 is
sufficient at at least one location about its periphery to force
the guide 38 upward a sufficient distance to cause the resilient
pad 52 on the piston head 34 to press the membrane 16 against the
partition and close the respective valve. Each cam 40 is relieved
to provide one or more cutouts 68 which are of varying size and
permit the downward displacement of the guide 38 and plunger 32,
thus establishing the desired sequence of valve openings. For
purpose of illustration, one cutout 68 is shown on the cam 40 in
FIG. 3.
When the guide 38 is forced upward by the cam 40, the coil spring
60 surrounding the guide 38 is compressed, and the flange 56 at the
upper end of the guide moves upward. The coil spring 62 surrounding
the rod 36 in turn elevates the plunger head 34 and the pad 52
until it contacts the membrane 16 and presses it against the
partition 26 and closing the valve. Some compression of the coil
spring 62 occurs which cushions the closing of the valve. Thus, the
strength of the spring 62 determines the force with which the valve
is held closed. The valve remains closed until the cam 40 rotates
to position a cutout 68 below the cylinder 30, to permit the lower
coil spring 60 to withdraw the guide 38 and the plunger 32 which
follows the guide downward. The valve then remains open for the
desired length of time which is determined by the speed of rotation
of the shaft 66 and the cutout area of the cam 40.
EXEMPLARY USE
The operation of the valve system 10 may be better understood in
connection with an illustrative process wherein the valve system
may be utilized. In this respect, reference is made to copending
U.S. Pat. application Ser. No. 750,235, filed Aug. 5, 1968, in the
names of Milton Winitz and Jack Graff, entitled "Amino Acid
Analysis," or to Analytical Chemistry, 34, No. 11, 1414 (Oct.
1962). This copending application describes a process for analyzing
a biological sample to quantitatively determine the amounts of
amino acids therein.
To facilitate treatment of a biological sample according to the
teaching of this copending application, a sample holder 72 (FIG. 1)
is connected between lines 28a and 28b. A reactor 74 wherein the
programmed reaction takes place is connected between lines 28c and
28d. The biological sample, which may for example be human blood
(containing a mixture of nonvolatile amino acids), is first
pretreated using cationic exchange resins and then eluted from the
resins, using a suitable liquid such as acidified n-propanol. The
eluted sample which contains the amino acids is then transferred
manually to the sample holder.
The automatic programming of the device then takes place with the
shaft 66 being driven by a suitable motor (not shown) at the
desired rate of rotation, e.g., 1 revolution an hour, causing the
cams 40 to actuate the individual valves A to I at the desired
sequences. When the process is actuated, a slow constant flow of
dry inert gas, for example nitrogen, is fed to the sample holder 72
through the line 76 and carries the sample through the line 28b to
the valve B. The cams 40 are arranged so that the valves A and B
open generally in unison, and additional solvent for the sample is
supplied to the sample holder 72 through the valve A. The carrier
gas entering through the line 76 moves the sample and solvent to
the valve B. For convenience in making connection, the construction
of the valve B is reserved with respect to the valve A (as seen in
FIG. 2), and the line 28b connects to the center of the valve B
whereas the port 18b connects the annular section 24.
To facilitate movement along the flow path 22 toward the reactor
74, an ancillary flow of dry nitrogen is fed through the port 18b
throughout the operation of the device. This nitrogen flow assists
travel along the flow path into the reactor 74 during the time
allotted.
At the end of the flow path 22, the sample passes out the line 28c
and into the reactor 74 for conversion to volatile amino acid
derivatives preparatory to gas-liquid chromatography. Here, a
liquid gas separation takes place, and the gas flows through the
line 28d and out the valve H, which is open throughout most of the
process, to a line 78 leading to a waste container 80. While the
valves A and B are open, the carrier gas flows through the sample
holder 72 to assure that the sample holder is completely cleared of
sample and solvent.
After the sample has been transferred to the reactor 74, different
reagents are supplied sequentially by systematically opening the
valves C, D, E and F. The reagents sequentially: (1) dry the sample
by azeotropic distillation, (2) esterify the amino acids, (3) again
dry by azeotropic distillation, (4) acetylate to form a volatile
derivative, and (5) again dry. In carrying out the process
described in the copending patent application, a mixture of
n-propanol and benzene (as azeotroping agent) is supplied through
valve c, and anhydrous n-propanol-HC1 (esterification agent) is
supplied through valve D. Acetic anhydride (acetylating agent) is
supplied through valve E, and pyridine (to neutralize the (HC1) is
supplied through valve F. It takes the cams 40 about 60 minutes to
make one complete revolution, and during this time various of the
valves open and close more than once.
As previously indicated, the valve H remains open until the
reaction is complete and then closes. When the valve H closes, the
valves G and I open. The valve I leads to an open top collector 82.
A source of dry nitrogen gas and a suitable solvent, such as ethyl
acetate, is connected to valve I. Accordingly, the ethyl acetate is
carried in a line 28d into the reactor 74, where it dissolves the
sample, and flows out of the bottom of the reactor through line 28c
leading to the flow path 22. Because the valve G is open and
because the supply of carrier gas continues into the port 18b,
preventing flow of the liquid from the reactor along the flow path
22, the liquid leaving the reactor passes out the valve G through
the port 18g to the open top collector 82.
In an operation such as this, it is important that metered amounts
of liquid be fed to the reactor 74 throughout the individual
process steps. Metering of the liquids is carried out by the amount
of time the individual valves are open and by the size of the
individual orifices disposed in the receptive couplings 42
connected between supply of reagent and the port leading to the
valve. A relatively constant gas pressure, for example 1 to 2
p.s.i.g., is maintained on all of the reagent supplies, and it is
this gas pressure which causes the flow of liquid whenever the
valves A, C, D, E or F are opened. Thus, based upon this constant
driving pressure, the desired amount of flow is established by
choosing the proper size orifice relative to the amount of time
that the valve will be open. For a different reaction or when a
liquid of different physical properties is employed, a desired
timed flow can be achieved simply by changing the orifice size,
within certain limits.
Although the invention has been illustrated with respect to a
particular arrangement of a flow path and interconnected valves, it
will be understood that many variances are possible using the basic
valve system to provide automatic, timed, sequential flow of
liquids for use in chemical processes, particularly preliminary to
anaylsis.
The arrangement of the individual valves located generally interior
of the annular sections 24 of a longitudinal flow path provides an
arrangement wherein there is essentially zero dead space at the
valves wherein reagents might accumulate and influence subsequent
steps, as for example by interreacting with another reagent being
supplied for a subsequent step. The constant purge flow of carrier
gas throughout the longitudinal flow path 22 during the operation
assures the transportation of the liquids injected into the system
through the individual valves (particularly when the head 12 is
made of a material having the low wettability of Kel-F). This
serves as a positive prevention of any undesirable accumulation in
the flow path. Likewise, provision of orifices in couplings 42
which can be substituted to change the size thereof affords
flexibility in establishing precise metered amounts of liquid being
fed to the reactor during any single step, and it also affords
adaptation of the overall system to other liquids having different
physical properties.
Other modifications as would be apparent to one skilled in the art
may be made to the illustrated valve system without departing from
the scope of the invention which is defined in the appended claims.
Various of the features of the invention are set forth in the
following claims.
* * * * *