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Publication numberUS3654801 A
Publication typeGrant
Publication dateApr 11, 1972
Filing dateFeb 14, 1969
Priority dateFeb 14, 1969
Publication numberUS 3654801 A, US 3654801A, US-A-3654801, US3654801 A, US3654801A
InventorsRichard D Keefer, John S Wyman Jr
Original AssigneeBendix Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Gas sampling device
US 3654801 A
Abstract
A gas sampling device having a sampling head with supply and take-up reels mounted on opposite sides of the head to accommodate a filter material in tape form. The sampling head has two blocks which are yieldably urged toward each other to clamp a portion of the filter tape between the blocks. Each block is formed with a gas chamber which is positioned so that a sample of gas can be passed through the filter tape between the blocks. A spool with cam surfaces having serrated teeth is connected to one of the blocks and positioned so that when the spool is rotated the cam surfaces momentarily shift one of the blocks away from the other block and advance the filter tape through the head. The supply reel is connected to a drag clutch and the take-up reel is driven through a friction clutch so that the tape is always under a slight tension.
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United States Patent Keefer et al.

15] 3,654,801 [451 Apr. 11, 1972 [54] GAS SAMPLING DEVICE [72] Inventors: Richard D. Keefer; John S. Wyman, Jr.,

both of Ann Arbor, Mich.

[73] Assignee: The Bendix Corporation [22] Filed: Feb. 14, 1969 [21] Appl. No.: 799,367

[52] US. Cl ..73/28 [51] Int. Cl. ..G01n 21/28 [58] Field ofSearch ..73/421.5, 28; 179/1002;

[56] References Cited UNITED STATES PATENTS 2,019,541 11/1935 Masten ..73/37 3,194,055 7/1965 Knobel .....73/37.5 2,398,958 4/1946 Pellettere ..73/37.5 2,078,357 4/1937 Woodmansee et al ..179/100.2 2,548,573 4/ 1951 Wampole et a1 ..242/75.5 X 2,675,697 4/1954 Quynn et al. 2,722,988 11/1955 Hall ..73/28 X 3,138,015 6/1964 Avery ..73/28 X 3,464,257 9/1969 Schreiber et 3,475,965 1/ 1969 Koblin et al.

Primary Examiner-Louis R. Prince Assistant Examiner-Daniel M. Yasich Att0meyBamess, Kisselle, Raisch & Choate [57] ABSTRACT A gas sampling device having a sampling head with supply and take-up reels mounted on opposite sides of the head to accommodate a filter material in tape form. The sampling head has two blocks which are yieldably urged toward each other to clamp a portion of the filter tape between the blocks. Each block is formed with a gas chamber which is positioned so that a sample of gas can be passed through the filter tape between the blocks. A spool with cam surfaces having serrated teeth is connected to one of the blocks and positioned so that when the spool is rotated the cam surfaces momentarily shift one of the blocks away from the other block and advance the filter tape through the head. The supply reel is connected to a drag clutch and the take-up reel is driven through a friction clutch so that the tape is always under a slight tension.

8 Claims, 9 Drawing Figures POWER CYCLK CALIBRATE SHEET 1 [IF 3 PATENTEDAPR 11 I972 ATTORNEY5 PATENTEDAPR 11 M2 3,654, 8 O1 IN liN'lURS RICHARD D. lQ EEFER QPHN S. WYMAN,JR.

ATTORNEYS GAS SAMPLING DEVICE This invention relates to gas samplers and more particularly to a filter tape sampling head and filter tape drive mechanism.

Gas sampling devices usually have a means of passing a predetermined quantity of the gas to be sampled through a filter membrane. The filter membrane is then examined to determine what the contaminants were in the sample of gas. For example, the number of particles on the filter membrane might be counted or a beam of light and a photoelectric cell might be used to determine the change in translucency ,of the filter and hence the amount of contamination from dust, pollen particles or other debris in the gas. The device might also be used to determined the radioactive fallout from nuclear tests or other sources in a gas sample, or a chemically treated filter tape might be used to identify the various gases of which a sample is composed. In gas samplers in which a filter material is in the form of a tape it is a problem to properly load and align the tape in the sampler and to provide a means for positively and uniformly feeding the filter tape through the samler. p An object of this invention is to provide a sampling device in which the filter tape can be readily and easily inserted in and removed from the sampling device.

Another object of this invention is to provide a sampling device in which the filter tape is positively and uniformly moved through the sampling device.

Other objects, features and advantages of this invention will be apparent from the following description and drawings which disclose the manner of making, using and carrying out the invention in the best mode contemplated by the inventor.

Drawings accompany this disclosure and the various views thereof may be described as:

FIG. 1, a front elevational view of a gas sampling device illustrating the sampling head and filter tape mechanism of this invention.

FIG. 2, a view of a portion of a used filter tape with several samples thereon.

FIG. 3, a front elevational view with broken-out sections of the sampling head of the device of FIG. 1.

FIG. 4, a view on line 4-4 of FIG. 3 showing the arrangement of the light source, sampling chamber, filter tape, and photoelectric cell.

FIG. 5, a sectional view on line 5-5 of FIG. 3 showing the filter tape and the manual disengagement cam mechanism.

FIG. 6, a sectional view on line 6-6 of FIG. 3 illustrating the manual disengagement cam and the filter tape drive spool.

FIG. 7, a view partially in section on line 77 of FIG. 1 il-. lustrating the take-up spool and take-up clutch assembly.

FIG. 8, a plan view of the gas sampling device of FIG. 1.

FIG. 9, a view partially in section on line 99 of FIG. 1 illustrating the supply spool and supply clutch assembly.

Referring in detail to the drawings:

FIG. 1 illustrates an air sampling device, designated generally as 20, with a sampling head 22, a filter tape 24, tape supply reel 26, and tape take-up reel 28 all mounted on a front panel 29. As shown in FIG. 8, a vacuum pump 30 driven by a motor 32 is connected to sampling head 22 to pull the gas sample through a portion of tape 24. A motor 34 acting through a gear train 36, a belt 38 and a clutch assembly 40 takes up tape 24 as it is advanced through sampling head 22, A second clutch 42 provides a frictional drag for supply reel 26. A black box 44 cycles and controls the various components of sampler 20.

In general, sampling head 22 provides a means for mounting a light source and a photoelectric cell to determine the change in translucency of filter tape 24, a chamber enclosing a portion of tape 24 so that a sample of gas can be passed through the tape, and a, means of advancing the tape through head 22 so that a new portion of the tape can be sealed in the chamber. As shown in FIGS. 3 and 4, sampling head 22 is formed with a cover 46, a gas inlet block 48, a gas outlet block 50, and a base 52. A bore 54 with a countersink 56 at one end and a counterbore 58 at the other end cooperate with a passageway 60 to form a gas inlet chamber 66 in block 48. A connector 62 and a hose 74 provide a means of coupling inlet chamber 66 to the supply of gas to be sampled. A bore 68 with counterbore 70 at one end and counterbores 72 and 74 at the other end form a gas outlet chamber 76 in block 50. A passageway 78, connector 80, and tube 82 connect outlet chamber 76 to vacuum pump 30 so that a gas can be urged to pass into inlet chamber 66 through filter tape 24 and out through outlet chamber 76 by the action of vacuum pump 30. A light socket 84 with bulb 86 extending into bore 54 is mounted in a bore 87 and counterbore 89 in cover 46 with an O-ring 88 entrapped between countersink 56 and socket 84 to provide an air-tight seal between the light socket and inlet chamber 66 of block 48. A gasket 90 in counterbore 70 provides a seal between filter tape 24 and chambers 66 and 76. A glass plate 92 is sandwiched between two O-rings 94 in counterbore 72 by a retaining ring 96 to seal ofi the lower end of bore 68. Retaining ring 96 is seated in counterbore 74 and secured therein by screws 98. A bore 100, counterbores 102 and 104, and a plate 106 fastened in counterbore 104 by screws 108 form a pocket 110 in base 52 which captivates a photocell 112 and its socket 114. A spring 115 bearing on socket 114 and plate 106 urges photocell 112 into sliding engagement with bore in the upper portion of pocket so that the photocell bears on retaining ring 96. Ring 96 provides a seal between the exterior of block 50 and photocell 112 so that the light sensitive surface of the photocell is exposed only to light within chamber 76. Spring 115 urges photocell 112 into contact with outlet block 50 so that photocell 104 moves with outlet block 50 when it disengages from filter tape 24. Inlet block 48 and base 52 are rigidly attached to panel 29 by screws 116 and a spring 118 seated in a pocket in base 52 urges outlet block 50 into engagement with tape 24, thereby clamping and sealing the tape between blocks 48 and 50. Two pins 120 provide alignment guides on which outlet block 50 moves when it disengages from tape 24 and inlet block 48.

FIGS. 3, 5 and 6 show the means by which outlet block 50 can be manually disengaged from tape 24 and inlet block 48 so that the tape can be inserted into or removed from sampling head 22 and the means by which block 50 is automatically momentarily disengaged from inlet block 48 and tape 24 is advanced through the head so that another sample of gas can be passed through a new portion of filter tape 24. A shaft 121 with a slotted head 122 on one end extends through and is rotatably mounted in outlet block 50 with a cam 124 connected to the other end so that manual rotation in the clockwise direction (as shown in FIG. 3) forces cam 124 into contact with inlet block 48 and disengages outlet block 50 from tape 24 and inlet block 48 so that the tape can be inserted into and removed from sampling head 22. A spool 128 with serrated teeth 130 on its edges and two flat sides 132 is connected to a shaft 134 which is rotatably mounted in inlet block 48 and connected to gear train 36. Rotation of spool 128 180 counterclockwise (as shown in FIG. 3) by motor 34 causes block 50 to become momentarily disengaged from inlet block 48 while teeth I30 dig into tape 24 and advance or move the tape a short distance through sampling head 22 and then allow outlet block 50 to move toward inlet block 48 and reengage tape 24.

As shown in FIGS. 7 and 8, take-up spool 28 is removably connected to slip clutch assembly 40 and is rotated simultaneously with the tape advancement spool 128 by motor 34 which is coupled to clutch 40 through belt 38. Clutch assembly 40 is formed by a shaft 136 rotatably mounted on 29 by a bushing 138, spacer 140 and a nut 142 threadingly engaging bushing 138. A friction plate 144 is connected to shaft 136 by a set screw 146 and a pulley 148 is mounted on shaft 136 for rotation with respect to the shaft. A clutch disc 150 of a material such as cork, is interposed-between friction plate 144 and pulley 148 to provide a friction clutch. A spring 152 and adjustment nuts 154 threadingly engaging shaft 136 provide a means of adjusting the pressure with which pulley 148 bears on clutch disc 150 and plate 144 so that the torque transmitted from the motor to shaft 136 can be adjusted. Take-up reel 28 is formed with an inner plate 156 formed with an inner plate 156 and spacer 158 secured to shaft 136 by pin 160 and an outer plate 162 fastened to a hub 164. Hub 164 is removably connected to shaft 136 by a spring-loaded detent ball 166 which extends into a groove 167 in shaft 136. A transverse pin 168, captured between hub 164 and plate 162, engages in a slot 170 in the end of shaft 136 so that hub 164 and plate 162 will turn with shaft 136. A wear washer 171 is interposed between reel spacer 158 and bushing 138.

As shown in FIGS. 8 and 9, supply reel 26 is similar to takeup reel 28 and is rotatably mounted on drag clutch assembly 42. Clutch assembly 42 is formed by a shaft 172 rotatably and slidably mounted in a bushing 174 fastened to panel 29 by a spacer 176 and threaded nut 178. A clutch disc 180, of a fraction material such as cork, is interposed between spacer 158 of reel 26 and the end surface of bushing 174 and is urged into engagement with both the bushing and the spacer by a spring 152 entrapped between the other end of bushing 174 and threaded adjusting nuts 154. Adjustment of nuts 154 varies the pressure on clutch disc 180 and hence the amount of drag or resistance to rotary movement of the supply reel 26. The drag of clutch assemblies 40 and 42 is adjusted so that a filter tape inserted in sampling head 22 and coiled on reels 26 and 28 is placed under a slight tension and is taken up by reel 28 when the tape is advanced by rotary movement of spool 128.

In operating the gas sampler, a coil of unused filter tape is placed on supply reel 26, shaft 121 is rotated so that cam 124 disengages outlet block 50 from inlet block 48 and the tape is inserted in the resulting slot and connected to take-up reel 28.

' After the tape is inserted in the sampling head, shaft 121 is released and spring 118 urges outlet block 50 toward the inlet block 48 and into engagement with tape 24 so that the tape is clamped or held in a fixed position in the sampling head between inlet chamber 66 and outlet chamber 76. The gasket 90 assures that there is an airtight seal between the chambers and the tape. Black box 44 starts motor 32 and vacuum pump 30 draws the gas to be sampled through inlet tube 64 and passageway 60 into inlet chamber 66, thence through a portion of the tape and outlet chamber 76, passageway 78 and tube 82. Light source 86 and photoelectric cell 112 are energized and monitored by black box 44 to determine the change in the translucency of the filter tape which is caused by the contaminants in the gas sample being deposited on the filter tape. The photoelectric cell can be monitored either at the end of the sampling period to determine the total change in translucency or it can be monitored throughout the sampling period to provide a continuous sensing of the change in the translucency of the filter tape during the sample period. An adjustable timer in black box 44 provides a predetermined sampling period and at the end of the sampling period black box 44 shuts off motor 32 and hence vacuum pump 30 and then it starts motor 34 which through gear train 36 and shaft 134 turns spool 128 180 counterclockwise (as shown in FIG. 3). A snap-action switch which follows a cam with double flats on shaft 134 shuts off motor 34 after it has turned spool 128 180.As spool 128 is turned 180,teeth 130 simultaneously disengage outlet block 50 from the tape and engage or dig into the tape and advance it through the slot in the sampling head. Near the end of the 180 revolution of spool 128 teeth 130 disengage from both the tape and outlet block 50, thereby allowing springs 115 and 118 to urge outlet block 50 toward inlet block 48 and into engagement with tape 24. When motor 34 is started, it simultaneously acts through gear train 36 and belt 38 to rotate clutch assembly 40 and hence take-up reel 28 so that used filter tape is coiled into a spool on take-up reel 28 as it is advanced through sampling head 22 by spool 128. Spool 128 is constructed so that it advances the tape slightly farther than the width of the inlet chamber 66 as shown in FIG. 2 by .the circular deposits of contaminants from each sampling period. 7

Sampling head 22 and the tape reel mechanism provide a gas sampling device in which the filter tape can be readily and conveniently loaded in the sampling machine and positively advanced through the sampling head by the spool. The use of tape reels provides a means of conveniently and economically dispensing the filter material and also a sampling machine which can run a large number of individual samples or tests without any assistance by either technical or maintenance personnel.

We claim:

1. A sampling device for a filter tape comprising a first block having an inlet chamber opening to the exterior thereof, a second block having an outlet chamber opening to the exterior thereof, said openings being in generally overlying opposed relation to each other, means for guiding the tape along a path between said blocks and across saidopenings of said blocks, means yieldably urging said blocks into firm engagement with opposed surfaces of the tape, means for disengaging said blocks from firm engagement with the tape comprising a cam carried by one of said blocks and adapted to bear on the other of said blocks such that movement of said cam disengages said blocks from firm engagement with the tape, and engagement means carried by one of said blocks and positioned in overlying relation with a portion of the tape between said blocks and adapted to firmly engage and advance the tape across said openings when said blocks are disengaged from firm engagement with the tape by said cam.

2. The sampling device of claim I in which said engagement means comprises a second cam firmly engaging the tape between said second cam and the other of said blocks in advancing the tape across said openings.

3. A sampling device for a filter tape comprising a first block having a tape contact surface and an inlet chamber opening to said surface thereof, a second block having a tape contact surface mating with said contact surface of said first block and an outlet chamber with an opening to said contact surface of said second block, said openings being in generally overlying opposed relation, means for guiding the tape along a path between said contact surfaces of said blocks and across said openings, means yieldably urging said contact surfaces of said blocks into firm engagement with opposed sides of the tape, and a spool mounted for rotation in one of said blocks and positioned in overlying relation with a portion of the tape and the contact surface of the other block, said spool having at least one carn portion engageable with the tape between said contact surfaces such that rotary movement of said spool including said cam portion disengages said contact surfaces from firm engagement with the tape and moves the tape through the blocks between said contact surfaces.

4. The sampling device of claim 3 in which at least said one cam portion of said spool has serrated teeth.

5. The sampling device of claim 3 which also comprises a second cam carried by one of said blocks and adapted to bear on the other of said blocks such that manual manipulation of said cam disengages said contacting surfaces of said blocks to facilitate threading of the tape between said contact surfaces and across said openings of said blocks.

6. A sampling device for a flter tape comprising a first block having a surface for contacting the tape and a gas sample inlet chamber opening to said surface thereof, a second block having a surface for contacting the tape mating with said surface of said first block and having a gas sample outlet opening to said surface of said second block, said openings being in generally overlying opposed relation, means for guiding the filter tape along a path between said surfaces and across said openings of said blocks, means for incrementally advancing the tape between said surfaces and across said openings, a light source carried by one of said blocks, light from said light source passing through one of said chambers and the portion of the tape between said openings and into the other said chambers, a photoelectric cell with its light-sensitive surface exposed to the light in said other chamber which passes through the tape, and means connected to said photoelectric cell and adapted to monitor said portion of the tape between said openings to indicate the amount of contaminants deposited on said portion of the filter tape before said portion of the filter tape is advanced across said openings of said blocks by said means for incrementally advancing the tape.

6. The sampling device of claim 6 which also comprises a cam carried by one of said blocks and adapted to bear on the other of said blocks such that movement of said cam disengages said surfaces of contact from firm engagement with the tape, and engagement means carried by one of said blocks in overlying relation with a portion of the tape between said surfaces and adapted to firmly engage and advance the tape across said openings when said surfaces are disengaged from

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US3736421 *Jul 27, 1971May 29, 1973Mine Safety Appliances CoDetermination of crystalline silica and other material dusts in air
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Classifications
U.S. Classification73/28.4, 96/413, 55/DIG.340, 356/38
International ClassificationG01N21/86, G01T7/04, G01N1/22
Cooperative ClassificationY10S55/34, G01T7/04, G01N2001/2223, G01N21/8483, G01N1/2205
European ClassificationG01N21/84R, G01N1/22B1, G01T7/04
Legal Events
DateCodeEventDescription
Jun 16, 1989ASAssignment
Owner name: ENVIROMENTAL TECHNOLOGIES GROUP, INC., MARYLAND
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:ALLIED-SIGNAL INC.;REEL/FRAME:005115/0035
Effective date: 19890525
Oct 31, 1988AS06Security interest
Owner name: ENVIRONMENTAL ANALYTICAL SYSTEMS, INC.
Effective date: 19880922
Owner name: NATIONAL WESTMINSTER BANK USA, 175 WATER STREET, N
Oct 31, 1988ASAssignment
Owner name: ENVIRONMENTAL ANALYTICAL SYSTEMS, INC., A DE CORP.
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:ALLIED-SIGNAL INC.;REEL/FRAME:005006/0607
Effective date: 19880919
Owner name: NATIONAL WESTMINSTER BANK USA, A NATIONAL BANKING
Free format text: SECURITY INTEREST;ASSIGNOR:ENVIRONMENTAL ANALYTICAL SYSTEMS, INC.;REEL/FRAME:005006/0599
Effective date: 19880922