US2935909A - Detectors of oil mists and the like - Google Patents

Description

May 10, 1960 A. MATHISEN 2,935,909

DETECTORS OF OIL MISTS AND THE LIKE Filed April 11, 1958 2 Sheets-Sheet 1 ANbEks Mm'wssu A'r'roRNEYy,

May 10, 1960 A. MATHISEN 2,935,909

DETECTORS OF OIL MISTS AND THE LIKE Filed April 11, 1958 2 Sheets-Sheet 2 INVENTOR ANbERs mmmssn ATTORNEY! DETECTORS OF OIL MISTS AND THE LIKE Anders Mathisen, Alvel'stoke, England, assignor t Graviner Manufacturing Company Limited, London, England, a British company This invention relates to detectors of oil mist and the like.

In the specification of U.S. application Serial No.

629,920, filed December 21, 1956, now US. Patent No.-

2,907,993, we have described a detector of this kind in which gas, which may be carrying such mist, is drawn through a space across which a light beam is projected. Transparent windows are provided on opposite sides of this space and an electric lamp is mounted behind one window and a photo-electric cell behind the other window, the passage of mist through the space serving to reduce the amount of light from said lamp which falls on the photo-electric cell. 'The consequent change in output of the photo-electric cell is used to operate appropriate indicating or alarm apparatus.

It has been found that under certain conditions, when using a detector having the construction described in the aforesaid specification, abnormal deposits may occur on the transparent Windows. These deposits may not only be of oil or other vapour but may also consist of particles of combustion products such as soot or carbon dust. Whilst such deposits do not in any Way prevent correct operation of the detector, nevertheless they render clean- I ing of the windows necessary at more frequent intervals fan, this vortex causing the soot or other dust to be projected outwards from the vortex and deposited upon the windows.

In an endeavour to avoid such troubles, the present invention provides a detector of oil mist and the like comprising a chamber having an inlet for gas which may carry such mist, a window in one wall of said chamber, a second window in another wall of said chamber, a duct extending from a position adjacent but spaced from said first Window to a position adjacent but spaced from said second window, a cuff surrounding said first window, said cuff extending through an opening in said duct with the periphery of said cuff spaced from said opening, a second cuff surrounding said second window and extending tates atent 2,935,909 Patented May 10, 1960 first cuff, said duct having a second opening therein into which said second cuff extends, the area of said second opening being greater than the cross-sectional area of said second cuff, an outlet for gas located in said duct at a position between the two openings, and means for mounting a light source behind one window for projecting light through said duct onto a photo-electric cell mounted behind the other window, the arrangement being such that gas passing from said inlet to said outlet passes through the spaces between the cuffs and the respective openings in said duct.

Two constructions of oil mist detectors in accordance with the present invention will now be described, by way of example only, reference being made to the accompanying drawings in which:

Figure l is a side view, partly in section, of the first construction of oil mist detector,

Figure 2 is an end view, partly in section of the detector shown in Figure 1, and

Figure 3 is a side View of the second construction of oil mist detector.

Referring firstly to Figures 1 and 2, it will be seen that this construction of detector is generally similar to that shown in Figures 1 to 3 of the drawings accompanying the aforesaid patent specification. As with the previous construction, there is a monitoring chamber 10 through which gas, which may be carrying oil mist, is drawn by means of a suction fan 11 through a suction pipe 12 the inlet 12a of which is connected to the source which is to be monitored. Windows 13 and 14 are provided on opposite sides of the monitoring chamber 10 and an electric lamp 15 is mounted behind thewindow 14 to project light across the chamber 10 through the window 13 onto a photo-electric cell 16 of the vacuum tube type which is mounted behind the window 13. To compensate for temperature and voltage changes, the output of the cell I into the monitoring chamber 10. In the interior of the through an opening in said duct with the periphery of said cuff spaced from said opening, and an outlet for gas from a position in said duct intermediate its two openings, the arrangement being such that gas entering said inletpasses around the outside of either cuff and thence into said duct and out through said outlet.

The invention further provides a detector of oil mist chamber 10 a rectangular cross-section duct 23 is fitted which overlaps the end of each of the culfs 21, 22 but does not extend to the walls of the monitoring chamber 10. Within the duct 23 and overlapping the upper side of each of the cuffs 21, 22 an arcuate vortex shield 24 is provided, this shield 24 being secured along its centre line to each of the cuffs 21, 22 and having a larger radius of curvature than the radius of the cufis 21, 22. An outlet tube 25 extends from an opening in the top of the duct 23 to the inlet of the fan 11.

To give access to the windows 13, 14, a door 23a is provided in' the side of the duct 23 and, if desired, a window (not shown) can also be provided in the side of the duct 23 to allow observation through a corresponding window 26a provided in a removable closure plate 26 which is removed to give access to the door 23a.

In, operation the gases or vapours from the inlet elbow pipe 12 pass into the duct 23 through its open ends around the sides of the cuffs 21, 22 and this results in a horizontal gas or vapour column in front of the windows 13, l l'which can result in an improved sensitivity to obscuration of the light column. The gases and vapours leave the duct 23 by passing around the edges of the vortex shield 24 and into the outlet tube 25 leading to the fan 11. It is found that where there was previously astendencyto form a .vortexwithin. the. monitoring chamber 10, any vortex will now be formed in the tube 25 above the vortex shield 24. It has also been found that with such anarrangement thetendency; forsolids to. be deposited; on the; windows;l3 and ,i tcis, substantially reduced, suchdepositsaoccurringeitherbefore the gases OI'WVBPOUI'S'CillIfiI the duct 23 -101 after ,theyhave. passed into the tube 25.

-=Ref,erring-now to Figure:3, :thesecond construction of oil mistdetector is arranged to draw: gas-from the -space-tobemonitored, for example, the crankcase of an engine, via Zthe inlet at by .having 3the -outlet 31.0011- nected to a suction source; ;in the case ofanqen'gine the latter may be the induction systemg in. which, case no J opens into aycylindrical, monitoring chamber 32 in which a cylindrical i duct 133,, -of;.-,sm all er diameter than the chamber 32 and of shorter length, is rnounted coaxnially relative to the chamber 32. ,;At eachend of the monitoring chamber 32, windows 34 and 35 are provided,

,andras with thefirst construction a lamp 35 is mounted electric cell 33 is mounted behind the window 35.

in a housing 37 behind the window 34 and a-photo- In this particular construction the cell 38 is a'barrier layer cell,

duct-33 ata position midway alongits length. Thus,

-as'.with the first described construction, gas is drawn ,in through the inlet 30 and passes towards each end of the chamber 32 through the annular space between the ,chamben32 and the duct 33, thence around the ends 33a and- 33b respectively and through the annular spaces between the cuff-39 and mouth 33a on'the onehand, and thecuif 40 and the mouth-33b on theother hand, and

back towardslthe middle of'the duct 33 and out through the outlet31. In this way, it is ensured that the flow ofmiSt-laden gas is always away from the Windows 34,

and 3S and danger of deposit of oil and-dirt on these ,windows is considerably reduced. As with the first described construction, the output of the cell 35 may normally be balanced bythe output, from a similar cell which is located so that, its illumination isnot, affected by the presence. of oil mist.

.I-claim: 1. .In; a detector ofoilumist andthe, like,- a chamber having .an;inlet for gas which may carry such mist, azwindow in one wall of said chamber, asecond window in another. wall or" said chamber, a duct extending from a position adjacentvbut spacedfrom said firstwindow to a position adjacent but spaced from said second window, a:first vcuif surrounding said first window, said duct having an -=opening therein into which saidcuff extends with the periphery of said cuff spaced from said opening, a second cuff surrounding said second window, said-duct having a furtheropening therein into which rsaidsecond cuff extends with the periphery ofsaid second .cuft' spaced-from said further opening, said duct having an outlet for gas located at a position in said duct inter- ..mediate its two .openings, a suctionfan, said suction fan having a suction inlet, said suction inlet being connected to said duct outlet whereby gas entering the gas inlet of said chamber is drawn around the outside of either 5 cult and thence into said duct and out through said gas outlet, and a deflector plate, said deflector plate being mounted in said'duct directly below the gas outlet and havinga greater surface area than the area of said gas outlet, whereby any vortex produced by said suction fan is located on the side of the. deflector plate facing into said gas outlet.

2. A detector according to claim 1, wherein said deflector plate partly overlaps both said first cuff and said second cuif.

3. A detector accordingto claim 1, wherein said plate is of arcuate cross-section with its convex surface facing away from the gas outlet in said duct.

4. A detector of oil mist and the like comprisinga chamber having a plurality of walls, one of said walls having therein an inlet for gas which maycarry such rnist, a first'window, said window being mounted in one ofsaid Walls, a'second window, said second window being mounted' in a different one of said walls from that in which said first window is mounted, a first cuff surroundmg said first window and projecting into said chamber,

-a second cuff surrounding said second window and 'pro- -jecting into said chamber, a duct mounted in said chamber, said duct having an opening therein into which -said first cuifextends, the area of said opening being -greater thanthe cross-sectional area of said-first cuff, =saidduct-ha'ving a second-opening therein into which said second cuif extends, the area of said second opening being greater than the cross-sectional area of said second cuff,

Ysaid'duct having an outlet for gas located in the upper 35. surface of said, duct at a position between the two openings, means fonmounting aphoto-electric cell behind one window, means'for'mounting a light source behind the .other'window for projecting light through said duct onto said photoelectric cell, a suction fan, said suction fan 40 having a suction inlet, said suction inlet being connected to said duct outlet,. and a vortex deflector plate, said vortex deflector. plate being mounted in said duct adjacent. but spaced from the upper surface thereof, said deflectorplate extending across the full extent of said duct. outletwhereby any vortex producedby said suction :fanis located on the side ofthe" deflector plate facing into said gas outlet.

' 5."A. detectoraccording-tor claim 4, wherein said ,deflector platepartly overlaps both said first cod and said secondcutf.

6. -A'; detector according to claim 4, wherein said plate risofi arcuate' cross-section with its convex surface facing away from-the gas outlet in said duct.

-Rei er ences,Cited;in the file of this patent V UNITED STATES PATENTS 2,042,095 Grant May 26, 1936 2,770,162 Fleming Nov. 13, 1956 so "FOREIGN PATENTS 726,484 France, Mar. 7, 1932 704,052 Great Britain Feb. 17, 1954

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