US3864978A

US3864978A - Automatic rotary sample injection valve

Info

Publication number: US3864978A
Application number: US443873A
Authority: US
Inventors: Thomas M Stephens
Original assignee: Envirotech Corp
Current assignee: Rosemount Inc
Priority date: 1974-02-19
Filing date: 1974-02-19
Publication date: 1975-02-11
Anticipated expiration: 1992-02-11

Abstract

Two disc-shaped body sections are mounted facing one another for rotation about a generally centrally disposed shaft with a flat seal member interposed between the sections. Means are provided to selectively rotate the upper body section through a preselected angle about the shaft. A liquid flow channel is formed through the lower body section in communication with a bore for a sample-taking piston which is located in the upper body section. Drive means are arranged to reciprocate the piston to withdraw a liquid sample from the flow channel. After the sample is drawn, the upper body section is rotated and the sampling piston is driven downward to release the sample into a pyrolysis tube or the like.

Description

AUTOMATIC ROTARY SAMPLE INJECTION VALVE 1 Feb. 11, 1975 Primary Examiner-S. Clement Swisher Attorney, Agent, or FirmRobert E. Krebs; Thomas S. MacDonald [75] Inventor: Thomas M. Stephens, Menlo Park,

Calif. Q [73] Assignee: Envirotech Corporation, Menlo [57] ABSTRACT Park, Calif. Two disc-shaped body sections are mounted facing one another for rotation about a generally centrally [22] 1974 disposed shaft with a-flat seal member interposed be- [211 App]. No.: 443,873 tween the sections. Means are provided to selectively rotate the upper body section through a pre-selected angle about the shaft. A liquid flow channel is formed 2% 'i 73/422 through the lower body section in communication q 1 R with a bore for a sample-taking piston which is located F e .1-.:. in the upper body section. Drive means are arranged to reciprocate the piston to withdraw a liquid sample 56 R f d from the flow channel. After the sample is drawn, the l e erences upper body section is rotated and the sampling piston UNITED STATES PATENTS is driven downward to release the sample into a pyrol- 2,824,859 7/1974 Harris et al. 73/422 GC ysis tube or the like. 3,071,005 l/l963 Skidmore 73/422 GC 0 6 Claims, Drawlng Figures F l 77- I b Z a4 7 a V w v 1 5e AUTOMATIC ROTARY SAMPLE INJECTION VALVE BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates to a device for automatically procuring a liquid sample for subsequent pyrolysis and chemical analysis.

2. State of the Art Accurate sampling is a critical step in virtually all chemical analysis, but particularly so where pyrolytic techniques are used. In such cases both the quantity of substance introduced to the analysis equipment and the manner of introduction should be reproducable to a high degree of precision. Presently, a widely employed method of sample introduction is syringe injection through a rubber septum seal. US. Pat. No. 3,647,385 suggested a device wherein sample boats" are individually loaded to carry carefully measured sample amounts into a pyrolysis oven. In certain cases, however, it is desirable to automatically take samples from a continuously flowing liquid. In those situations, it has been suggested to utilize so-called slide valves or to utilize a four-way valve arrangement wherein two separate flow paths in the valve are established: one for carrier gas and the second a liquid sidestream from the sample source. By rapidly reversing sections of the four-way valve, the carrier gas can be made to carry sample to the analysis equipment. However, slide valves or four-way valves sometimes fail to deliver uniform sized samples. Generally speaking those valves are better suited for gas samples than for liquids because the liquid samples tend to hand up on the walls of the tubing or bores-and thus contaminate the subsequent samples.

OBJECTS OF THE INVENTION A primary object of the present invention is to provide an automatic liquid sampling device for introducing a constant volume sample into chemical analysis equipment; another object of the invention is to pro vide such a device for introducing a liquid sample into a carrier gas stream for subsequent pyrolysis and chemical analysis.

BRIEF DESCRIPTION OF THE DRAWINGS Further objects and advantages of the present invention may be readily ascertained from the following description and appended illustrations which are offered by way of illustration only and not in limitation of the invention, the scope of which is defined by the appended claims and equivalents. In the drawings:

FIG. 1 is an exploded pictorial view of a sampling valve according to the present invention;

FIG. 2 is a pictorial view of the device of FIG. 1 in assembled condition;

FIG. 3 is a side view, partially cut-away, of the device of preceding figures;

FIG. 4 is a top view of the device of the preceding figures showing some of the hidden parts thereof in dashed lines and with optional equipment connected thereto; and FIG. 5 is also a top view similar to FIG. 4 except that a portion of the device is shown in a rotated position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The fluid sampling device or "valve" shown in FIGS. 1-5 includes two discshaped body sections 11 and 13, respectively, which are generally concentrically mounted facing one another for rotation about a centrally disposed shaft 15 which is slideably disposed through the sections. The

opposed faces

16 and 18 of the body sections are flat and are arranged as parallel as possible. The lower end of the shaft 15 is secured by a nut 20 (see FIG. 3) whose contact surface is halfround" so that the nut acts somewhat like a universal joint to allow slight movement of the lower body section relative to the shaft. That is, the nut 20 accomodates a slight lack of parallelism between the

opposed faces

16 and 18 and provides uniform pressure distribution therebetween so that liquid leakage is minimized.

The upper body section 11 of the valve is forced toward the lower section 13 by means of a coil spring 23 which encircles the shaft 15 within a sleeve 25 retained by a nut 27 threaded to the upper end of the shaft. In the illustrated arrangement, a plurality of

washers

29, 30, 32 are disposed on the shaft between the spring and the upper body section; a roller bearing 31 is between

washers

30, 32, so that there is not undue friction between the spring end and the upper body section.

A thin disc-shaped member 35 is concentrically disposed on the shaft 15 between the opposed flat faces of the two valve body sections. This lamina-like member 35, preferably made from Teflon or a similar material, provides a liquid-tight seal between the opposed faces valve sections and, at the same time, allows the sections to freely rotate relative to each other. In the illustrated device, stub posts 37 are fixed to the lower body section 13 and extend into associated holes 38 formed in the disc seal 35 to secure it in place. When salt water samples are taken, thin circular silicon rubber gasket 36 is preferably placed between the disc seal 35 and bottom valve face 16.

Through the lower body section 13 are formed a pair of spaced-apart

liquid flow channels

39 and 40 which open into the flat face 16 of that body member at the same radial distance from the shaft 15.

Standard connectors

41 and 42 are fitted into the valve body 11 in liquid-flow communication with the flow channels '39 and 40, respectively. An arc-shaped slot 43 is formed through the seal member 35 to form a passageway to connect the inlet 39 in fluid-flow communication with the outlet 40 so that liquid can flow between the opposed faces of the valve sections. The

flow channels

39 and 40 can be understood to respectively comprise an inlet and outlet for a liquid side-stream which flows continuously through the valve via the slot 43.

In FIGS. 4 and 5, means are shown for selectively rotating the upper valve body section 11 relative to the lower section 13 through a preselected angle of about The illustrated rotational means comprises a hydraulic or pneumatic piston-and-cylinder set 46 whose one end is pivotably connected to a stationary member and whose other end 47 is connected, by means of a clevis-and-pintle linkage 50, to an arm 52 which fixedly extends from the valves upper body. FIG. 4 shows the upper valve body located at the sample eject position and FIG. 5 shows the upper valve body rotated about ninty degrees to the sample up-take" position. It should be understood that the illustrated linkage arrangement is by way of example only and that skilled workers can readily devise other equally effective means for selectively rotating the upper valve body 11.

Referring again to FIG. 1, a sample-taking means is connected to the upper valve body 11 to withdraw a liquid sample of precise volume from the aforementioned side-stream of liquid which flows continuously through the valve. The illustrated sample-taking means includes a cylindrical sampling" rod 54 which is connected for sliding reciprocation in a bore 56 that extends through the upper body section and that opens into the face 16 at the same radial distance from the shaft as the side stream flow slot 43. Accordingly, the sample up-take position can be defined to be the position at which the valve body sections have been rotated so that the bore 56 is above, and in liquid flow communication with, the slot 43. In the illustrated embodiment, an o-ring 57 is fitted into a circumferential groove adjacent the lower end of the rod 54 to provide a fluid-tight sliding seal between the rod and the bore. As so arranged, the lower or distal end of the rod 54 serves as a piston for withdrawing a liquid sample of selected volume from the liquid in the slot 43. Preferably, a cylindrical tip piece 59 made of a chemically inert material is fixed to the free end of the rod to preclude chemical reaction between the rod and the sampled liquid. Teflon or the like is the preferred material for the tip piece because it is inert.

The upper end of the sampling rod 54 is adjustably connected to a reciprocating drive means 62 which selectively moves the rod along the bore 61. The illustrated drive means includes a generally disc-like piston 64 having annular faces which is slidably disposed within a cylinder housing 66 fixed to the upper valve body. The piston 64 is selectively movable in the housing from a fully upward position to a fully downward position, or vice versa, by selectively applying pressurized gas against the corresponding faces of the piston. Such pressurized gas is supplied into the cylinder through

conventional connectors

68 and 69. in the illustrated arrangement, the upper end wall 71 of the cylinder housing 62 is removably mounted so that the piston 64 can be removed and repaired.

A stem 73 of the piston 64 extends slidably through an aperture 74 formed in the endwall 71. The upper end of the stem 73 is adjustably clamped to the upper end of the sampling rod 54 by a link 76. The illustrated link 76 includes a slot 77 which mates with a groove in the upper end of the rod 54 so that the rod is keyed into the link; such an arrangement permits compensation for lack of parallelism between the associated parts. The adjustable linkage also allows the effective stroke of the sample-taking piston to be selectively varied which, in turn, allows the sample size to be changed. In practice, the sampling piston is usually set so that the sample volume size is about 500 micro-liters of liquid (which corresponds approximately to a 3/16 inch diameter piston having a stroke of 9/8 inches). In some applications, the same size can be accurately set as low as 100 micro-liters.

As shown in FIGS. 3-5, a relatively large aperture 80 is formed through the lower valve body 13 in communication with the face 18 thereof. This aperture is the sample eject port and it is connected in liquid-flow communication with a threaded coupling 82 which, in turn, can be connected to a pyrolysis tube or the like. The sample eject port 80 is located at the same radial distance from the shaft 15 as is sampling rod 54. (In the sample eject position shown in FIG. 4, the sampling rod is located directly above the port 80.) An aperture 8] is formed through the disc-shaped seal member 35 in registry with the eject port so that liquid ejected by the sampling piston can directly enter the eject port. In some applications, it is desirable to maintain the port 80 and coupling 82 at a preselected elevated temperature. in the illustrated device, a heat exchanging tube 85 is fixedly wrapped around the outlet coupling; when the tube carries a heated fluid, the heat will be transferred to the coupling.

As shown in FIG. 1, an aperture 86 is formed through the face 16 of the lower valve body member at a location between the channel 40 and the sample eject port 80. This aperture is optionally provided to drain any liquid leakage from the valve before such leakage can reach the sample eject port where it would cause errors in the subsequent sample analysis. An aperture 87 is formed through the disc-shaped seal member 35 is registry with the drainage outlet 86 in the lower valve body to catch liquid leakage on the upper face of the seal member. To further prevent liquid leakage from reaching the sample eject port, a plurality of radially directed V-shaped groves 90 can be formed in the faces of the seal member 35. Liquid leakage which reaches these grooves will flow to discharge at the side of the valve.

A relatively small channel 94 is formed through the lower valve body 13 in gaseous-flow communication with the sample eject port 80. This channel carrier a continuous flow of carrier gas, such as oxygen, nitrogen, or air, which entrains the sample and carries it to analysis equipment downstream from the outlet. The outlet end of the carrier gas channel is located to direct gas flow away from the sample outlet (see FIG. 3).

In operation, a stream of liquid to be sampled is forced into the inlet connection 41. The liquid then flows upward through channel 39, then between the opposed faces 16 and 18 of the

valve body sections

13 and 18, then down the channel 40 and out the connector 42. Typically, such liquid constitutes a representative side stream from a larger liquid body which is to be analyzed, for example, for its organic carbon content. To procure a single pre-selected volume of sample from the side stream, the sample taking rod 54 is first positioned above the slot 43 through which the side stream flows; then the sample taking rod is driven upward by the piston assembly 62 thereby drawing liquid into the bore 56. The rod is then forced downward to wash the bore with the fresh sample. Then the rod 54 is again driven upward taking the actual preselected volume of liquid sample to be measured. Thereafter, the upper valve body is rotated by the piston-andcylinder set 46 until the bore 56 is directly above the outlet port 80 (see FIG. 4). Then, the sampling rod is driven downward to eject sample into the port where it drops by gravity force into the pyrolysis chamber. Thereafter, the sampling rod is returned to its up position and the upper valve body is rotated back to the sample up-take position (FIG. 5). Before repeating the cycle, the sampling rod is driven down to release, for example a thin film of liquid which may have clung to the end of the rod. Then, the sampling cycle can be repeated.

We claim:

1. A sampling device comprising:

a. a valve body formed of two sections, each of which is constructed and arranged to present a flat face parallel to a corresponding flat face of the other;

b. a lamina-like seal means forming a liquid-tight seal interposed between said faces;

c. means connected to said body assembly to selectively rotate said sections relative to one another from a first position to a second position through a preselected angle while maintaining said faces parallel;

d. a liquid flow inlet and an outlet spaced therefrom,

both of which are formed through one of said sections, said inlet and outlet being arranged in fluidflow communication with said face of that section;

e. passageway means connecting said inlet and outlet in fluid-flow communication with each other across said face of said first section;

. sample-taking piton means arranged in a cylindrical channel formed in the second of said sections in fluid-flow communication with said flow channel in said first section at said first position of said sections;

g. means constructed and arranged to reciprocate said piston to withdraw a liquid sample of selected volume from said flow channel;

h. an outlet port formed through said first section in fluid-flow communication with said face thereof at said-second position for receiving a liquid sample released from said cylinder by said sample-taking piston at said second position of said sections.

1 2. A sampling device according to claim 1 further in'- cluding an aperture formed through the face of said first section at a position between said flow channel and said outlet port for draining liquid which seeps from said flow channel toward said outlet between said sections.

3. A sampling device according to claim 1 wherein said means for reciprocating said sample-taking piston includes a drive piston assembly operable between a first and second position and means adjustable connecting said drive piston assembly to said sampletaking piston.

4. A sampling device according to claim 1 wherein said passageway means comprises a slot formed through said lamina-like seal means.

5. A sampling device according to claim 1 wherein radially extending grooves are formed in said seal means for discharging liquid leakage to the side of th valve.

6. A sampling device according to claim 1 wherein said body sections are generally disc-shaped and are generally concentrically mounted facing one another for rotation about a centrally disposed shaft which is slidably disposed through said sections.

Claims

1. A sampling device comprising: a. a valve body formed of two sections, each of which is constructed and arranged to present a flat face parallel to a corresponding flat face of the other; b. a lamina-like seal means forming a liquid-tight seal interposed between said faces; c. means connected to said body assembly to selectively rotate said sections relative to one another from a first position to a second position through a preselected angle while maintaining said faces parallel; d. a liquid flow inlet and an outlet spaced therefrom, both of which are formed through one of said sections, said inlet and outlet being arranged in fluid-flow communication with said face of that section; e. passageway means connecting said inlet and outlet in fluidflow communication with each other across said face of said first section; f. sample-taking piton means arranged in a cylindrical channel formed in the second of said sections in fluid-flow communication with said flow channel in said first section at said first position of said sections; g. means constructed and arranged to reciprocate said piston to withdraw a liquid sample of selected volume from said flow channel; h. an outlet port formed through said first section in fluidflow communication with said face thereof at said second position for receiving a liquid sample relEased from said cylinder by said sample-taking piston at said second position of said sections.

2. A sampling device according to claim 1 further including an aperture formed through the face of said first section at a position between said flow channel and said outlet port for draining liquid which seeps from said flow channel toward said outlet between said sections.

3. A sampling device according to claim 1 wherein said means for reciprocating said sample-taking piston includes a drive piston assembly operable between a first and second position and means adjustable connecting said drive piston assembly to said sample-taking piston.

5. A sampling device according to claim 1 wherein radially extending grooves are formed in said seal means for discharging liquid leakage to the side of the valve.