US 3488993 A
Description (OCR text may contain errors)
United States Patent O 3,488,993 AMBIENT FLUID SAMPLER Gilbert S. Raynor, Manorville, N.Y., assignor to the United States of America as represented by the United States Atomic Energy Commission Filed Feb. 23, 1968, Ser. No. 707,541
Int. Cl. Gflln 1/00 US. Cl. 73--28 2 Claims ABSTRACT OF THE DISCLOSURE An ambient air sampling arrangement which utilizes a container having a slidable hollow portion extending between a pair of end members to trap a fixed volume of air. The slidable portion is moved from a position away from the space between the end members to its position enclosing the fixed volume to trap the sample. A purging system removes the trapped volume and filters out the particulate.
BACKGROUND OF THE INVENTION When atmospheric air is sampled for the purpose of determining its particulate content, a major problem is that of obtaining a sample which contains a representative amount and distribution of particulate. Very often, at the entrance to the sampling apparatus, flow conditions are altered so that the particulate is distributed differently than under true ambient conditions. For example, when an intake tube is employed as the means of sampling the air, alignment difficulties under varying air flow direction may be encountered which place the results in question.
SUMMARY OF THE INVENTION The invention described herein was made in the course of, or under a contract with the US. Atomic Energy Commission.
The present invention overcomes the disadvantages of previous sampling devices by obtaining a sample of a gaseous fluid in a way which avoids the problems and difficulties associated with restricted entrance type sampling devices.
In accordance with this invention, provision is made to trap a fixed volume of a gaseous fluid to be sampled followed by purging to remove one or more constituents which may be particulate or aerosol. Trapping of the gas is done in such a way as to minimize the effect of altered local flow conditions. The apparatus includes a cycling arrangement so that samples of any size may be obtained.
It is thus a principal object of this invention to provide apparatus for sampling a gaseous fluid with improved results.
Other objects and advantages of this invention will be readily apparent from the following description of a preferred embodiment of the invention taken with reference to the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a view, partially in section, of a preferred embodiment of this invention; and
FIG. 2 is a section of the collector of FIG. 1 in a partially open position.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2, there is illustrated a collector incorporating the principles of this invention designed to sample ambient air. Collector 10 consists of a slidable hollow cylindrical body 12, a lower stationary end cover 13 and an upper stationary end cover 14.
Cylindrical body 12 is supported by a member 15 which' is attached to the outside of body 12 by way of a pair of arms 16 and 18. The upper edge of body 12 is provided with an annular lip 12a whose function is described below. Arms 16 and 18 are provided with holes (not shown) through which passes a stationary, vertically disposed rod 22 which is supported at its base and top as shown. It is thus seen that body 12 is slidable vertically as indicated by double arrow A.
Lower cover 13 is frusto-conical in shape with a bottom end surface 24 through which passes an opening 25. Cover 13 is supported by a plurality of legs 28 which may be spring loaded for reasons later explained. Along the upper edge of cover 13 is an annular ledge 29 against which the bottom edge of body 12 rests in its lowermost position as seen in FIG. 1.
Upper cover 14 is similarly frusto-conically shaped as shown with the outer diameter such as to permit collector body 12 to slide snugly though freely over the former as illustrated in FIG. 2. Cover 14 has an annular rim 14a, which, when body 12 is in its lower position shown in FIG. 1, contacts lip 12a and thereby seals collector 10 at this edge. Body 12 is slidable between a lowermost position (shown in FIG. 1) wherein collector 10 is completely enclosed and an uppermost position where the lower edge of body 12 is adjacent to upper cover 14 so that the space between covers 13 and 14 is fully exposed to ambient air. In FIG. 2, body 12 is in an intermediate position, either on the way down or on the way up. When body 12 is lowered, the bottom edge of body 12 contacts lower cover 13 before rim 14a and lip 12a contact each other so that the spring supports in legs 28 are depressed slightly insuring positive sealing with cover 13 when lip 12a is pressed against rim 14a.
Cover 14 is provided with a hollow extension 3-2 interconnected to rod 22 by way of a structural element 39 to insure rigidity of the assembly. It is understood, of course, that any convenient structural arrangement may be utilized.
Mounted in convenient fashion near collector 10 is a pneumatic cylinder 38 from which extends rod 42 to one end of a link 44 whose other end is rigidly attached to member 15. The upper end of rod 42 is connected to a piston (not shown) within cylinder 38, which piston, as is understood in the art is moved upwardly or downwardly in accordance with any unbalance of fluid (in this case air) pressure on opposite sides thereof. Hence movement of the piston within cylinder 38 causes similar movement of collector body 12.
A pair of conduits 46 and 48 extending from a solenoid actuated valve V supplies high pressure fluid to either the upper or lower ends, respectively, of pneumatic cylinder 38. Pressurized air is supplied into either valve V by way of a conduit 52 or cover 14 by way of conduit 36 from a solenoid actuated valve V which is supplied with pressurized air from conduit 56 and air cleaning filter 54.
Fluid pressure for the system is provided by a pump 58 which receives its air from a conduit 62 and supplies the air under pressure to filter 54 by way of conduit 64. Filter 66, for collecting the particulate or aerosol constituents present in the trapped air is located against end surface 24 of cover 14, its entry inlet being in communication with opening 25. A solenoid actuated valve V located at the interconnection of tube 26 from filter 66, conduit 67 open to air, and conduit 62 permits either ambient air to enter the system by way of conduit 67 into conduit 62, thereby by-passing filter 66, or directing air from filter 66 to conduit 62. It is understood that filter 66 may be any collecting device suitable for removing or measuring any of the constituents present in the trapped sample.
in height and six inches in diameter. A typical operating cycle is shown in the following table:
In the operation of the apparatus just described, initially, collector body 12 is in its raised position so that ambient air is flowing freely in the space between covers 13 and 14. Solenoid valve V communicates conduit 67 to conduit 62 to permit ambient air to bypass filter 66 and be supplied to pump '58 which operates throughout the whole cycle. Valve V supplies the compressed air to valve V which passes the air through conduit 48 to the bottom of cylinder 38 holding body 12 in its raised position. Valve V is provided with a pressure relief valve (not shown) which discharges excess air being directed into either conduit 46 or 48.
To start the sampling cycle, valve V is actuated to direct compressed air to the upper portion of pneumatic cylinder 38 (by way of conduit 46) which then causes body 12 to descend. When collector becomes completely closed, thereby entrapping within a substantial body of ambient air, valve V is actuated to direct the compressed air into collector 10 and valve V is actuated to direct the discharge from filter 66 to conduit 62 so that for a period of time there is continuous closed cycle flow of air through collector 10, filter 66, pump 58', and cleaning filter 54. The flow stream of air from conduit 36 to opening 25 through collector 10 entrains air along the walls of the latter and gradually purges collector 10 of all the entrapped sample. The frusto-conical shape of end covers 13 and 14 prevents or reduces the buildup of particulate within collector 10.
After a predetermined period of such closed cycle flow, during which time several volumes of collector 10 may be passed through filter 66 in which the particulate or aerosol is collected, valve V is actuated to direct flow from conduit 67 to conduit 62, valve V is actuated to direct flow to valve V and the latter is actuated to direct flow into the lower entrance to cylinder 38, thereby causing body 12 to rise and exposing the interior of collector 10 to ambient air. The cycle is then repeated, and as many cycles as desired may be utilized to collect the desired sample. In order to obtain time discrimination in the sampling, if desired, filter 66 may employ a collection or sampling tape so that a distribution can be obtained with respect to time.
The purpose of air cleaning filter 54 is to provide clean air to collector 10* at all times so that all collections will have come from the ambient air sample trapped within collector 10.
It is understood that solenoid valves V V and V may be actuated by hand, if desired, or automated through the use of limit switches, timers, and relays as is well understood in the art.
Apparatus which has been constructed in accordance with this invention employed a collector about 12 inches From the description of the preferred embodiment it is seen that the apparatus of this invention is relatively simple in construction and operation and does not require elaborate procedures or testing to ensure representative sampling. It is dependable and any alteration of ambient air flow patterns that does Occur is limited to a much smaller portion of the sample than in previous arrangements known in the art.
It is thus seen that there has been provided an improved arrangement for sampling gaseous fluids for particulates and aerosols. While only a preferred embodiment of this invention has been described it is understood that many variations thereof are possible without departing from the principles of this invention. For example, collector 10 may be used in pairs with staggered cycles so that sampling is continuous.
What I claim is:
1. Gaseous fluid sampling apparatus comprising:
(a) container means for trapping a fixed volume of said gaseous fluid, said means consisting of a pair of spaced end members and a slidable hollow body portion movable between a first position sealing said fixed volume between said end members and a second position wherein substantially all of the space between said end members has unrestricted exposure to said fluid;
(b) means for recycling through a closed circuit said fluid under pressure to purge said container means when in said first position including filter means for removing constituents of said fluid trapped within said fixed volume; and
(0) motor means utilizing said fluid under pressure after a predetermined period of purging to effect the movement of said hollow body from said first to second positions and to reverse said hollow body after a further predetermined period of time to renew the purging of said container means.
2. The apparatus of claim 1 having means to bypass said filter means when said hollow body is in its second position thereby insuring that substantially all constituents collected in said filter means are derived from said container means.
References Cited UNITED STATES PATENTS 2,872,817 2/1959 Pitts 73-421 3,126,730 3/1964 Pfeiffer 732 8 2,982,134 5/1961 Brown 73422 CLEMENT SWISHER, Primary Examiner US. Cl. X.R.