US3523001A

US3523001A - Aerosol sampler arrangement and pump therefor

Info

Publication number: US3523001A
Application number: US757177*A
Authority: US
Inventors: David Sylvester; Barron W Mouring; Henry J Ulrich Jr
Original assignee: AAI Corp
Current assignee: Textron Systems Corp
Priority date: 1968-07-30
Filing date: 1968-07-30
Publication date: 1970-08-04
Anticipated expiration: 1987-08-04

Description

4, 1970 D. SYLVESTER ET AL AEROSOL SAMPLER ARRANGEMENT AND PUMP THEREFOR I 2 Sheets-Sheet 1 Filed July 30, 1968 Dav/'0 Sy/vesfer Barron W. Mour/ng Henry J. Ulric/7 Jr.

Fig. 2

INVENTOR ATTORNEY Aug. 4, 1970 D. SYLVESTER ET AL 3,523,001

AEROSOL SAMPLER ARRANGEMENT AND PUMP THEREFOR Filed July 30, 1968 2 Sheets-Sheet 2 Fig 6 Fig. IO

Dav/'0' Sylvester Barron W. Mour/ng. Henry J. U/nc/v Jr.

| NVENTOR W ATTORNEY United States Patent US. Cl. 417-489 11 Claims ABSTRACT OF THE DISCLOSURE An aerosol sampler arrangement is provided, having a valveless air pump with a removable contaminant-collecting filter connected to its intake side, the air pump having a disc piston which is tilted to make an effective seal with a cylinder bore in the exhaust stroke direction and is tilted to form a bypass about the piston during the return piston stroke, this being effected by a crank arm having its axis of rotation off-center from the piston bore axis. Effective seal and bypass operation of the disc piston is materially enhanced by a flexible piston skirt having gas ports formed therein and which are alternately substan tially blocked and opened by the tilting motion of the piston.

DISCLOSURE This invention relates to an aerosol sampler arrangement and a valveless air pump therefor.

Air sampling generally requires a positive displacement pump which usually must operate with a low pressure air supply to be sampled. For reliable sampling, the sampling arrangement must effect air movement through filter material at a constant known flow rate. In some major applications, such as military use, low noise level operation is also highly desirable.

It is accordingly a major feature of this invention to provide an aerosol sampling arrangement which yields positive air displacement at a known flow rate, and with low noise level in operation.

Still other objects, features and attendant advantages will become apparent from a reading of the following detailed description of a preferred embodiment constructed in accordance with the invention, taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a partial cut-away perspective view of a preferred embodiment constructed according to the invention.

FIG. 2 is a fragmentary view of the pump of FIG. 1, shown partially cut-away for clarity of illustration.

FIGS. 310 are schematic views, showing the sequence of operations of the pump.

Referring now in detail to the features-of the drawings, in the preferred embodiment as illustrated in FIG. 1, an aerosol sampling arrangement is disclosed, including a pump, generally indicated at 11, and a filter, generally indicated at 61, the filter being connected in fluid flow arrangement with the inlet side of the pump 11.

Pump 11 includes a housing 13 having a cover 15 removably secured as by screws 15a, the housing having an inlet port 35 and an exhaust port 37. Within the housing 13 is secured a cylinder block 31 as by screws, cement or the like or any other suitable means (not shown). Cylinder block 31 has a generally rectangular cross-sectional bore 31a having rounded corners, with one end thereof open into the housing 13, and the opposite end thereof closed and connecting with the inlet port 35 of a connecting inlet tube extending through the adjacent wall of the housing 13 and connecting with the interior of filter 61.

Disposed in reciprocating sliding relation within the bore 31a is a disc piston, generally indicated at 21. Piston 21 is reciprocated within the bore 31a through the medium of a motor 41 secured within the housing 13 as by screws (not shown), or by encapsulation in an elastic outer casing 41a of rubber, plastic, or the like, which may be square in cross-sectional outer configuration and retained in position within the housing by light compression between the base of housing 13 and its cover 15 on two sides of the pump encapsulation casing 41a and between the adjacent side wall of housing 13 and the wall of cylinder block 31 on the intermediate other sides of the encapsulation casing 41a. The drive connection includes a pulley 45 fixedly secured on the rotary motor drive shaft 43, pulley 45 in turn driving a pulley 49 through the medium of a drive belt 47, the pulley 49 being mounted on a shaft 49a fixedly secured to the rear wall of the housing 13 and extending at right angles to the motor drive shaft 43 to provide for desired reciprocation directionality for the piston '21 and to provide a suitably large angle tilt of the disc piston during its reciprocation as will be hereinafter described.

Pulley 49 serves a dual purpose of reciprocating the piston 21 within the bore 31a and of tilting the plane of the piston 21 relative to the longitudinal axis of the bore 31a in the course of reciprocating motion of the piston 21 within the bore 31a. To this end, the shaft 49a for the pulley 49 is disposed to one side of the longitudinal axis of the bore 31a, and the piston 21 is pivotally connected in driven relation to pulley 49 through the medium of a piston extension bar 21a and a pivot pin 51 fixed on the pulley 49 at a position radially removed from the central axis thereof to thereby provide a crank arm or eccentric drive connection to the piston 21. To enable the necessary lateral motion of the piston extension bar drive connection within the bore 31a, the piston extension bar 21a is of materially smaller cross-sectional area than the body portion of disc piston 21.

Referring now in more detail to FIG. 2, it is an important feature of the invention to provide a flexible skirt, generally indicated at '27, on the disc piston 21, in which flexible skirt is formed one or more ports 27a. To this end, the disc piston '21 is preferably formed with a rigid rear plate 25, a rigid front plate 23, and an intermediate central flexible sheet 27m from which extends the skirt which is illustrated in the preferred embodiment as formed by a series of overlapping peripheral skirt flaps 27a-27f. In view of the cylinder block and piston as illustrated in FIG. 2 the upper and lower flaps are 27a and 27c, the two vertical side flaps being 27b and the overlapping corner flaps being designated as 2.7 The rigid front and rear plates '23 and 25 are secured in interfacing relation with the central flexible sheet 27m disposed in sandwiched relation therebetween as through the medium of a pair of screws and

nuts

29 and 29a, or by suitably threading a screw through the other plate 27 and into the threaded opening in the plate '25. Flexible skirt 27 may be suitably formed of a resilient somewhat elastic material such as leather, and serves to enable desired sealing between the disc piston 21 and the walls of the cylinder bore 31a during motion of the piston 21 in the direction toward the viewer as illustrated in FIG. 2. The main body portion of disc piston 21, composed of rigid plates 23-25 and flexible skirt, suitably secured in rigid relation to the piston extension bar 21a as through the medium of an end screw 21b extending through the plates 2325 and central flexible sheet 27m into a complementarily threaded opening in the end of piston extension bar 21a, the piston extension bar having its flat end resting in contiguous relation with the rigid rear plate 25.

The upper edges of

plates

23 and 25 are in substantial alignment; however, the lower edge 23a of the front plate 23 is disposed above the lower edge 25a of the rear plate 25, to enable substantially full backup of the central flexibility sheet 27m and its skirt by the rigid rear plate 25, while enabling substantially effective backup by the front plate 23 while preventing undesirable scraping action of the front plate 23 along the bottom wall of the cylinder bore 31a while the piston is sharply tilted during the course of the bypass stroke, and particularly during the midstroke portion thereof, as shown in FIG. 10 and discussed hereinafter.

Filter 61 connects with the interior of the bore 31a formed in cylinder block 31, through the medium of a connecting inlet tube 33 extending in sealed relation through the side wall of housing 13 and being fixedly secured as by press fit in the end wall of cylinder block 31 and having its inlet port 35 opening into the cylinder bore 31a and illustrated embodiment filter 61 includes a base 63 and a. cap 67 between which is removably secured a porous filter disc or sheet 65 on which contaminants are Collected in the course of movement of air through the filter as a function of reciprocating motion of the disc piston 21 within the pump 11. To the end that the filter disc 65 may be easily removable for testing and replacement, the cap '67 is threadedly removably secured to the base 63 as by complementary threads on the base and cap, and the cap 67 has a substantial mouth opening formed therein to enable air or other gas to flow to and through the filter disc or sheet 65 and be pumped back into the atmosphere through the exhaust 37.

The operating sequence of the pump 11 is schematically illustrated in FIGS. 310, in which the pump cylinder block 31, disc piston 21, eccentric or crank arm pulley 49, and filter 61 are schematically illustrated for simplicity and ease of understanding. The removable filter disc 63 is indicated in broken lines within the filter 61. One of the two illustrated bypass air ports 27a is shown at the top of the skirt 27 as illustrated in these figures.

FIG. 3 illustrates the position of the piston 27 immediately prior to the end of the bypass stroke to the left as illustrated in these views. In this position, with the eccentric off-center by the amount illustrated, the disc piston 27 is tilted to the left and is in the process of be coming less tilted in this direction by a motion of the lower portion of the piston to the right at a faster rate than any motion of the upper half of the piston to the right, the upper end being substantially stationary in this position. As will be seen from this view, the bypass parts 27a are open, and also there may still be a slight clearance between the upper edge of the skirt 27 and the upper wall of the cylindrical bore 310. The lower edge of the skirt 27 of piston 21 is in engagement with the bottom wall of the cylinder bore 31a. Thus, at the end of the bypass stroke near the bottom dead center of the piston 21, bypass passage of air past the piston is insured by the open passageways formed by the bypass port 27a in this passage of the piston.

The piston is illustrated in its bottom dead center position, and the bypass ports 27a have now been brought into a closed or almost closed position such that continuing counterclockwise rotation of the crank arm pulley 49 to the position as illustrated in FIG. will now initiate suction of air through the filter disc 65 in the filter 61, the piston 21 being tilted clockwise from the position of FIG. 4 to the position of FIG. 5 to insure closure engagement of the upper flap of the skirt 27 with the bore 31a to a suificient degree to fully restrict the bypass ports 27a, and thereby effect substantially fully effective suction of the air as a function of motion of the piston 21 to the right continued rotation of the pulley 49 through the continued tilting action thereof on the piston as shown in FIG. 6, and the beginning of reverse tilting immediately prior to the end of the suction stroke as shown in FIG. 7, in which latter position the bypass ports 27a are still substantially fully restricted by engagement of the upper fiap 27a of the skirt 27 with the upper wall of the cylinder bore 31a.

In the top dead center position of the piston, as illustrated in FIG. 8, the bypass ports 27a are uncovered to a sufficient degree to enable passage of air therethrough at the commencement of the bypass stroke of the piston 21 to the left as shown in FIG. 9, in which position the piston is further tilted counterclockwise and major motion of the piston is being effected at the upper half thereof to the left. In the bypass midstroke position of the piston, as illustrated in FIG. 10, the upper edge of the piston skirt 27 is now out of engagement with the adjacent wall of the cylinder bore 31a, and air will bypass the piston both around this upper edge and through the open ports 27a. The piston continues its bypass stroke to the left to the position as shown in FIG. 3, and the cycle repeats. It will thus be seen that an effective suction stroke is provided with substantially full insurance against any opposite motion of the air back through the filter 61 during the return stroke of the piston. This is particularly effected by the incorporation of the bypass ports 27a and the skirt 270:, which enable the bypass of gas through the ports both at the critical beginning of the return stroke and immediately prior to the termination of the return stroke in the event that total motion of the piston in these positions is such as to affect decrease of total volume in the zone to the left of the piston during this motion, and is particularly of value in the commencement aspect where this is most likely.

As previously mentioned, it will be noted that the recessing of the lower edge 23a of the front plate 23 of piston 21 prevents any undesired scuffing of the plate 23 against the cylinder bore wall while the piston is in the sharply tilted positions during the bypass return stroke thereof, and the midstroke portion thereof as illustrated in FIG. 10.

It will be apparent that disposition of the axis of the crank arm or pulley 49 to a further or lesser extent of the longitudinal axis of the cylinder bore 31a will affect both the ultimate degree of tilt of the piston in the course of its reciprocating motion and the precise points at which the suction and return bypass strokes are effectively begun and ended. Likewise, the relative length of the crank arm formed by the pulley 49 with respect to the effective width of the piston 21 in this plan will alter the overall stroke operation.

In general, it is desirable that the axis of the pulley 49 located relatively close to the longitudinal axis of the cylinder bore 31a, and be sufficiently far away as to enable sufiicient tilting motion of the piston in the positions thereof at the immediate beginning of the bypass return stroke as illustrated in FIG. 9 and also at the immediate end of the bypass return stroke as illustrated in FIG. 3 to enable the bypass ports 27a to be effectively opened at these locations and thereby prevent any return motion of the air through the filter 61. Thus, only a suction of predetermined quantity and direction will be effected through the filter with this arrangement and the filter disc 65 may be readily changed and tested for pickup of any contaminants after a predetermined time interval and number of strokes with the piston with a concomitant predictable quantity of air having passed therethrough.

While the invention has been illustrated and described with respect to several preferred embodiments, it will be apparent to those skilled in the art that still other embodiments and various modifications and improvements may be made without departing from the scope and spirit of the invention. Accordingly, it is to be understood that the invention is not to be limited by the illustrative embodiments but only by the scope of the appended claims.

That which is claimed is:

1. A pump arrangement comprising:

a disc piston,

a cylinder having a bore within which said piston is disposed for reciprocation therein,

reciprocating motion imparting means for reciprocating said piston with said cylinder bore,

means for tilting said piston relative to the defining wall of said bore during a major portion of its stroke in one direction to enable fluid bypass past said piston, and for substantially reducing the tilt angle of said piston during the opposite stroke of the piston to thereby effect substantial sealing of said piston with the bore wall whereby a fluid pumping stroke may be effected by movement of said piston during said opposite stroke,

said piston comprising a relatively rigid central panel having a flexible sealing skirt having means effecting engagement thereon with said bore wall to aid in sealing said piston with said bore wall during said opposite stroke motion of said piston,

said flexible skirt and means including a fluid passageway port formed said skirt between its opposite faces, said skirt being wedged in port restricting relation against the adjacent bore wall during a major portion of the travel of said piston in said one stroke direction and being freely flexible and in port-open ing relation during a major portion of the piston travel in said opposite stroke direction when said skirt is not wedged against the adjacent bore wall.

2. A pump arrangement according to claim 1, said rotational axis being displaced fromsaid cylinder bore axis on the same transverse side thereof as said fluid passage in said skirt.

3. A pump arrangement according to claim 1, said skirt extending eliectively about the entire periphery of said piston and being normally cup-shaped and being resiliently biased outwardly away from the main central body of said piston.

4. A pump arrangement comprising:

a disc piston,

reciprocating motion imparting means for reciprocating said piston within said cylinder bore,

means for tilting said piston relative to the defining wall of said bore during a major portion of its stroke in one direction to enable fluid bypass past said piston, and for substantially reducing the tilt angle of said piston during the opposite stroke of the piston thereby efl ect substantial sealing of said piston with the bore wall whereby a fluid pumping stroke may be elfected by movement of said piston during said opposite stroke,

said piston comprising a relatively rigid central panel having a flexible sealing skirt thereon and engageable with said bore wall to aid in sealing said piston with said bore wall during said opposite stroke mo tion of said piston,

said skirt extending effectively about the entire periphery of said piston and being normally cup-shaped and being resiliently biased outwardly away from the main central body of said piston,

said piston being polygonal in cross-section, said skirt being split and having mutually overlapping edges at the intersections thereof of the respective corners of said polygonal main piston body to thereby provide a series of overlapping flaps forming said peripheral cup-shaped skirt.

5. A pump arrangement according to claim 4, said skirt having a plurality of fluid passageways formed therein 'in laterally spaced relation, said fluid passageway being ports formed in said one flap and being spaced from the outer edge of said one flap.

'6. A pump arrangement according to claim 5,

said piston being generally quadrilateral in cross-section,

said skirt having -8 flaps, 4 flaps on the respective 4 major sides of said quadrilateral piston and 4 overlapping interjoining flaps at the corners of said piston, said corners being rounded in configuration.

7. A pump arrangement according to claim 5, said reciprocating motion imparting means and said means for tilting said piston comprising a common eccentric having its axis transverse to the longitudinal axis of said bore and disposed to one lateral side of said longitudinal bore axis.

8. An aerosol sampling arrangement comprising a removable filter,

a pump having its intake operatively connected to said filter, said pump comprising a housing having a piston receiving bore formed therein in fluid passage intake communication with said intake, and a disc piston disposed in said bore for tilting reciprocation along and within said bore, and. means for reciprocating said piston and tilting said piston at a substantial angle to the longitudinal axis of said bore during the return stroke of said piston toward the intake end of said bore, and for substantially straightening said piston to a materially lesser angle of tilt during the motion of said piston away from said bore intake end, to thereby seal said piston with said bore and effect a suction stroke to pull gas through said filter during the motion of said piston away from said inlet, said tilting of said piston eifecting a fluid bypass about said piston during the opposite stroke of said piston toward said inlet, said tilting piston having an elastically flexible skirt extending around at least a portion thereof, said skirt having a fluid port formed therein between its forward and rearward surfaces, said skirt being tilted and flexed toward the wall of said piston bore through angular tilting motion of said piston open said fluid port during motion of said piston toward said cylinder inlet and being tilted to a different angle through angular tilting motion of said piston and being thereby restrictively bent toward the main body of said piston to substantially restrict said fluid port by the straightening action of said piston and the confining action on said skirt during the opposite stroke of said piston away from said cylinder bore inlet. 9. An aerosol sampling arrangement comprising a removable filter,

a pump having its intake operatively connected to said filter, said pump comprising a housing having a piston receiving bore formed therein in fluid passage intake communication with said intake, and a disc piston disposed in said bore for tilting reciprocation along and within said bore, and means for reciprocating said piston and tilting said piston at a substantial angle to the longitudinal axis of said bore during the return stroke of said piston toward the intake end of said bore, and for substantially straightening said piston to a materially lesser angle of tilt during the motion of said piston away from said bore intake end, to thereby seal said piston with said bore and elfect a suction stroke to pull gas through said filter during the motion of said piston away from said inlet, said tilting of said piston etfecting a fluid bypass about said piston during the opposite stroke of said piston toward said inlet, said piston having an elastically flexible skirt extending around at least a portion thereof, said skirt having a fluid port formed therein between its forward and rearward surfaces, said skirt being flexed toward the wall of said piston bore to open said fluid port during motion of said piston toward said cylinder inlet and being restrictively bent toward the main body of said piston to substantially restrict said fluid port by the straightening action of said piston and the confining action on said skirt during the opposite stroke of said piston away from said cylinder bore inlet,

said piston being quadrilateral in cross-section and hav- R fer n s Cit d ing a main relatively thin walled main body section UNITED STATES PATENTS with a reduced cross-sectional connecting extenslon 570,528 11/1896 Wyeth 92 177 rigidly extending therefrom and plvotally connected 782 172 2/1905 Penny 103 175 to said eccentric, said elastically flexible skirt having 5 1,264144 4/1918 Bgrg said port formed therein on the same lateral Side 1:338:76 5/1920 Brandt 92 240 of said bore axis as said eccentric axis. 2 0 4 12 1935 Crowley 3 153 10. An aerosol sampling arrangement according to 2 935 353 5 19 1 Lee et 1 23 172 claim 9, said piston having two thin walled relatively 3,078,033 2/1963 Ourutsky 230 17Z rigid main body panels forming a sandwich with a fiexi- 10 3,082,935 3/1963 Arak 230172 ble sheet therebetween and extending laterally therebe- FOREIGN PATENTS yond to form said skirt.

1 1,116,445 2/1956 France. 1011 A fluld sampling arrangement accor mg to c arm 15 123,351 2/1919 Great Bmamsaid connecting extension engaging one of said panels, HENRY RADUAZO Primary Examiner the other of said panels having a lesser width than said one panel to accommodate tilting motion of said piS- US. Cl. X.R. ton without scufling of the wall of said bore. 9278, 177, 240