US 2622015 A
Description (OCR text may contain errors)
Dec. 16, 1952 J. COOPER ETAL AUTOMATIC GAS RECORDERS 3 Sheets-Sheet l Filed Jan. 25, 1949 INVENTORS Tame; Coo 264 4 BY Hawk/64hr) 7750/7705 g2, r ATTORNEY Dec. 16, 1952 J. COOPER ETAL AUTOMATIC GAS RECORDERS 3 Sheets-Sheet 2 Filed Jan. 25, 1949 J. COOPER ETAL AUTOMATIC GAS RECORDERS' Dec. 16, 1952 3 Sheets-Sheet 5 Filed Jan. 25. 1949 Patented Dec. 16, 1952 UNITED STATES PATENT OFFICE Thomas, Liverpool,
mesne assignments, to Douglas PoleWelman,
Manchester, England Application January 25, 1949, Serial No. 72,702 In Great Britain September 10, 1947 6 Claims.
The present invention relates to improvements in automatic devices for recording the presence of trace constituents in gases.
The device of the present invention is particularly suitable for indicating the existence of traces of hydrogen sulphide in town gas.
According to the present invention a strip of absorbent paper is impregnated with a chemical which is colour reactive to the trace constituent, and is displaced intermittently in the gas stream to expose successive areas to said stream, means being provided if desired to cut on flow of gas during the displacement of the absorbent paper strip.
In one preferred form of construction a continuous strip of paper has a portion thereof temporarily clamped between a pair of surfaced faces on two adjoining portions of a gas chamber provided with gas inlet and outlet passages, one portion of said chamber being displaceable relatively to the other to release the paper strip for periodic displacement in the direction of its length, such means being operated if desired in synchronism with means to cut off gas flow to the chamber during the time when the two portions of the chamber are separated.
In one convenient form of apparatus a detection chamber is formed in two parts, one provided with a gas inlet and the other a gas outlet, these parts being separated by a diaphragm consisting of a continuous strip of porous absorbent paper impregnated for instance with lead acetate solution, the meeting faces of the two parts of the chamber being surfaced to form a gas-tight joint with the paper strip therebetween and preferably formed with guides for the paper strip. One of said portions may be rigidly mounted whilst the other is displaceable relatively thereto in guides against spring pressure, being mounted, for instance, upon a pivoted lever operated by a cam adapted to be rotated at periodic intervals either by clockwork or from an electric motor or other prime mover 3'? or the like, the cam shaft lifting the lever being provided with interrupted serrated wheels engaging with one side of the paper strip supported on the other side by friction rollers, so that the paper strip can be moved forward a predetermined distance each time one section of the gas chamber is lifted away from the other.
It will be preferred that the cam controls the stopping of an electric motor, as for instance by interrupting a motor circuit or a clutch therein by tripping a mercury or other type of electric switch.
Where the device is driven by an electric motor, this may be energized by the operation of a time switch and stopped by a switch operated by the cam shaft.
The ends of the gas chambers may be provided with transparent windows to enable visual examination of the stain obtained on the paper area forming the diaphragm between the sections of the gas chamber or the paper area therein may be disposed within the light field of a photoelectric cell system adapted to operate an indicator or audible alarm whenever the stain forming the reaction between the hydrogen sulphide and the lead acetate impregnation reaches a predetermined density, or again an audible or visual signal may be operated thereby.
The invention will be further described, by way of example, with reference to the accompanying drawings in which:
Fig. 1 shows, in plan, an apparatus in accordance with the invention for detection of hydrogen sulphide,
Fig. 2 is a section taken on the line IIII of Fig. 1,
Fig. 3 is a section taken on the line IIIIII of Fig. 1,
Fig. 4 shows details of actuation of a mercury switch.
Fig. 5 is a fragmentary view showing the photoelectric arrangement for reading the stain, and
Fig. 6 is a fragmentary detail showing the means for cutting off the flow of gas during the displacement of the strip.
A detection or gas chamber comprises an inlet member or first fixed portion l3 (Fig. 2) mounted on a plate H and an outlet member or second movable portion l4 mounted on a smaller plate I2. Adjacent surfaces Ha, Ha of I3, l4 respectively are ground flat and held in gas tight abutment by rods l9 and springs 20. The inlet and outlet members are conveniently one inch in diameter, and the inner surfaces of said members are coated with or formed of a metal which does not react directly with hydrogen sulphide, such as tin. Gas is introduced to the chamber by pipe I30 and leaves said chamber by pipe I40.
A lever arm 24 is pivoted at I8, and fits loosely around the gas outlet member 14 to which a collar 25 is rigidly connected by grub screws 30.
A main shaft carries a cam l6, and rotation of said shaft l5 causes said cam 16 to bear against a roller 26 for part of a revolution of said shaft by which means the lever arm 24 is rotated upwardly about the pivot l8 thus causing the adjacent gas chamber faces to be separated.
A strip of absorbent paper 21 is progressed intermittently through the apparatus by means of wheels I! which are toothed for part of their circumference, and rollers 28 which are grooved; the teeth of wheels I! engaging said grooves and gripping the absorbent paper 21 therebetween. The toothed portion [1a of the circumference of wheels I! moves the paper 2'! a distance such that successive areas of the paper 21 which are exposed to the gas stream do not overlap at any point. The toothed portion Ila of the circumference of wheels I! is so disposed angularly relative to the cam l6 that the gas chamber faces are separated before the paper starts to move, and are not returned to gas tight abutment until movement of the paper has ceased.
A crank 23 is mounted on the driving shaft l5, said crank being adapted to operate a gascock in such manner that the flow of gas is discontinued. during the periods in which the gas chamber faces are not in gas tight abutment.
The apparatus is driven by a small electric motor operated by an adjustable time switch, the interval between successive movements of the paper 21 being such that a suitably dense stain is obtained, which, since the volumetric rate of flow of the gas is known, permits of reasonably accurate measurement of the extent to which the impurity is present.
The rotation of the motor being established by the time switch, it is essential that exactly one revolution of the shaft be completed before the motor is stopped, whereby to ensure that the apparatus is returned to the original condition with the paper held between the abutting faces of the inlet and outlet members. To insure that this essential requirement is fulfilled, a mercury switch 2| is connected in parallel with the time switch, said mercury switch 21 being operated by a cam 22 mounted on the driving shaft l5, the position of said mercury switch 2| being such that the switch is open when the abutting faces of the inlet and outlet members are in contact. In operation the time switch closes for a few seconds and then opens. When the time switch has opened, the shaft l5 has turned sufficiently for the cam 22 to close the mercury switch 2!, which remains closed until the shaft l5 has made one complete revolution.
The ends of members I3, M are formed of transparent material l3b, Mb so that the formation of the stain may be observed.
Referring now to Fig. 5, for reading the stain photoelectrically a photo cell 34 is cemented to the end of the chamber l3. Light from a lamp 35 passes through the stained part of the paper strip and thus to the cell 34. A further photo cell 36 is also provided and light falls on this cell after passing through a movable shutter 29 and an unstained region of the paper strip. Before the gas testing commences the photoelectric apparatus is adjusted to give equal light intensity on the two cells 34, 3B, or alternatively the electrical circuit is trimmed with clean paper before each cell. During the test, the two cells are connected to a recording potentiometer i s ch 4 a manner that the ratio of light intensity on the two cells is measured.
Fig. 6 shows how the gas cut-off is effected. A connecting rod 30 is attached to the crank 23 at 23a. The gas cook having an external handle 3| is open in the position illustrated and on rotation of the shaft I5 is adapted to be closed by movement of the crank transmitted via the rod 30 to the handle 3|. During the remainder of the revolution of the crank 23 after the cock has been firmly closed a lost motion arrangement consisting of a slot in the end of the connecting rod 30 and a tension spring 32 connected between a point on the rod and the handle 3| takes up the rod movement. The dimensions and positions of these elements are such that the gas is shut off before the surfaces [3a, Ma separate and remains shut off until after the surfaces have come together once more in gas tight abutment.
We declare that what we claim is:
1. An apparatus for automatically recording the presence of a trace constituent in a gas of the type wherein the gas is constrained to pass, over a substantial area, through a strip of absorbent paper impregnated with a chemical which is colour reactive to the trace constituent comprising a prime mover, a shaft rotated by the prime mover, a cam rotated by the shaft, a pivoted lever contacted by said cam and adapted to be angularly oscillated in response to the rotation of said cam, a gas chamber, a first fixed portion of the gas chamber, a second portion of the gas chamber movable out of contact with the first portion by angular displacement of the pivoted lever, said portions each having an internal diameter of at least one inch, a surfaced face on each portion, between which surfaced faces a portion of the paper strip may be gripped, guides and resilient means in which guides and against which resilient means said second portion of the gas chamber is movable relative to the first portion, a gas inlet in said first portion, a gas outlet in said second portion, interrupted serrated wheels rotated by the shaft, the teeth on said wheels being so situated as to grip the paper strip and progress it only when the gas chamber portions are separated, a crank rotated by the shaft, said crank being adapted to operate a gas cook in such a manner that the flow of gas is discontinued during the periods in which the gas chamber faces are not in gas tight abutment and means whereby the presence indicated by a colour stain on the paper of said trace constituent may be recorded during formation.
2. An apparatus as set forth in claim 1 in which the ends of the gas chamber are transparent, the apparatus including also photo-electric means for observing the stain by light transmitted through said stain during formation.
3. An apparatus :as set forth in claim 1 in which the inner surfaces of said gas chamber portions are of a metal which does not react directly with hydrogen sulphide.
4. An apparatus as set forth in claim 3 in which the ends of the gas chamber are transparent, the apparatus including also photoelectric means for observing the stain by light transmitted through said stain during formation.
5. An apparatus as set forth in claim 1 in which the inner surfaces of said gas chamber portions are of tin.
6. An apparatus as set forth in claim 5 in which the ends of the gas chamber are trans,- parent, the apparatus including also photo-electrio means for observing the stain by light trans- Number mitted through said stain during formation. 2,113,063 JAMES COOPER. 2,153,568 HAROLD HIRST THOMAS. 2,232,622 2,345,090 REFERENCES CITED 2 371 405 The following references are of record in the 2,551,231 file of this patent: 2,554,414
UNITED STATES PATENTS 0 Number Name Date Number 1,565,109 Rose Dec. 8, 1925 25,953 1,581,847 MacDonald. Apr. 20, 1926 Of 1902 1,711,742 Nordlander May '1, 1929 426, 2,049,947 Cope Aug. 4, 1936 15 Name Date Stryker et a1. Apr. 5, 1938 Johnson Apr. 11, 1939 Moses et a1. Feb. 18, 1941 Brace Mar. 28, 1944 Munn Mar. 13, 1945 Moses et a1. May 1, 1951 McLendon May 22, 1951 FOREIGN PATENTS Country Date Great Britain Sept. 3, 1903 Great Britain Apr. 2, 1935