US2918878A

US2918878A - Double-acting diaphragm pump

Info

Publication number: US2918878A
Authority: US
Inventors: Clifford V Zieg; John C Lee; Robert D Lambert
Original assignee: Symington Wayne Corp
Current assignee: Symington Wayne Corp
Priority date: 1957-12-05
Filing date: 1957-12-05
Publication date: 1959-12-29
Anticipated expiration: 1976-12-29

Description

Dec. 29, 1959 c. v. ZlEG ETAL 2,918,878

DOUBLE-ACTING DIAPHRAGM PUMP Filed Dec. 5, 1957 4 Sheets-Sheet l 1Z4 INVENTOR 140 Wk 4.0a;

ATTORNEY Dec. 29, 1959 c, v, z ET AL 2,918,878

DOUBLE-ACTING DIAPHRAGM PUMP Filed Dec. 5, 1957 4 sheets-sheet z ATTORNEY EAZTOR I w. 7

Dec. 29, 1959 c. v. ZIEG ETAL 2,918,878

- DOUBLE-ACTING DIAPHRAGM PUMP Filed Dec. 5, 1957 4 Sheets-Sheet 3 BY i/aqa ATTORNEY Dec. 29, 1959 c, v, z ETAL DOUBLE-ACTING DIAPHRAGM PUMP 4 Sheets-Sheet 4 Filed Dec. 5, 1957 United States Patent 7 2,918,878 D U L -AC NG DIA HRAGM U Clifford V. Zieg, Fort Wayne, Ind.,=John C.'-Lee, Mount Prospect, 111., and Robert -'D. Lambert, Fort Wayne, .Ind., .assignors, by,mesne assignments, to Syrnington- Wayne Corporation, Salisbury, ;Md ..-a corporation of Maryland I Application December, 195."lyserialfNok700,841 1;3-.Cl.aims. .l(Cl-::10.3-1.5.

"Th D lfi .elatcs t r c proca ing ouhl ract n pump including a pair of flexible diaphragms, -,and more particularly relates to a purnp.ofthis type which can be operated by manual power.

Since pumps of most types include a connection from a prime mover to a. movable pumping-element, .a pr ob- 1cm usually exists of sealing the. space between ,a moving motion-transmitting element and the aperture ,through which it passes into the pumping chamber. ,Doubleacting pumps utilizing flexible diaphragms are subject to this sealing problem especially when the chambers are placed side-by-side to conservespace and to simplify the structure.

An object of this invention istoprovide a simple, .com

pact and economical structure for ,a double-acting diaphragm pump that doesmot requi e the use .of a fluid seal about amoving element.

In accordance with this inventiona pair ofdiaphragms are secured to .both sides ,of a partitioning structure. These diaphragms are tightly secured at a-predetermined longitudinal spacing upon a shaft which reciprocates along a portion of its length disposed between these diaphragms within a bearing in a wall of the partitioning structure. An actuating means, for example a lever mechanism, is connectedto a portionof the shaft disposed outside of the diaphragms for reciprocating the shaft along its longitudinalaxis to impart a pumping action to the diaphragrns. A.cleara nce is permitted to exist .between the shaft and this bearing which permits a slight flow of fluid between the chambers, which flow-is not sufficiently great to interferewith adequate pumping efiiciency. Since this leakage occurs entirely within elements of the pump sealed within the diaphragms, partitioning structure, and shaft, there is no necessity for fluid seals to be used about any moving part.

Novel features and advantages of the present-invention will becomeapparent toone skilledin the art from a reading of the following description in conjunction with the accompanying drawings wherein similar reference characters refer to similar parts and in which:

Fig. 1 is a front view in elevation, partially incross section of one embodiment of this invention;

Fig. 2 is a cross-sectional view taken throughFig. 1 along the line '2 2 and lookingin the direction of the arrows;

Fig. 3 is a cross-sectional view taken through .Fig. .1 along the line 3-3 and looking in the direction offthe arrows;

Fig. 4 is an enlarged .view of a portion of Fig. .2;

Figs. 5, 6 and 7 are cross-sectional views respectively taken through Fig. 1 along 'the lines 5-5, .6.6, and 7-7, looking in the direction of the arrows;

Fig. 8 is a view in elevation partially in cross section of another embodiment of this invention;

Fig. 9- is a plan view of a portion of the embodiment shown in Fig.8;

Fig. 10 is a side view in elevation of the portion shown inxFig. 9;

of the. driving *bearing hub 50 in coverplate Fig. .1 1 is' an enlarged plan \view of a portion .of .the embodimentshown in Figs. .8 and 9;

Fig. 12 is .a cross-sectional' view taken through Fig.

11 along the line 12:12.an.d lookingin the.direction.of

14. A, pair. of.fiexible.diaphragms 20, :for; example, made of relatively strong'rubber including suitable reinforce.

ments (later described inz 'detail) .aresealed :to :both sides ofypartitioningtstructure 12 by means of ring 1incorporatingelements 22 and .23. ,Ring incorporating elements.

22. and23are, ifor, example, -a;pair of. dishedicovertplates 22 ;and. 23 .whichare clamped, for example, :to flanges or rim. elements24 .which, for example, extend from :the ends of wall'14.at obtuse angles relative to-the substantially flat .central I portion 7 of 1 wall -1-4 As shown :in. 'Figs.

land 2, wall .14 is substantially circular and, rims .or

flanges ,24 extend :from its gperiphery to ,form substantially .circular flanges extending therefrom with .a .U- shaped or A l-shaped space 26 formed between iflanges 24. The peripheral edges 28 of diaphragms :20 are enlarged .to .lock. them within corresponding recesses 330 in the 'peripheral edges-of covers 22 and .123 :to securely seal .peripheral .edges 28 of diaphragms20 sides of the central partitioning structure 12.

Covers

22 and 23-.are maintained -in engagement with the central partitioning structure 12, for exan1ple,,by means of screwandboltfasteners 32.

Diaphragms 20 incorporate, for example, circular Jinserts 34 made, forexample, of plate steel for-stiffening their central portionsto facilitate transmission'of .a reciprocatingmotion thereto. The outer .regions 10f diaphragms20which are subject to considerable flexing are strengthened by incorporating, for example, a .web .of fabric 36 made, for example, of woven nylon.

The central portions of diaphragms 20 are'secured in a fluid tight .manner at ,a predeterminedlongitudinal spacing upon a shaft 38 which reciprocates through. a portion of its lengthdisposed' means of a screw and washer 42; and the diaphragm .20

and insert 34 .atthe intermediate position alongshaft 38 are fastened within groove 40 by, for example, the threaded engagement of spacershaft portion .44 disposed between diaphragms .20 with a threaded projection -46 portion 48 of theshaft 38, which driving portion 48 is disposed outside-of the space between diaphragm'20.

Thediameter of shaft 38 and the aperture in bearing 16 are manufactured to standard tolerances to provide, a for example, between 0.001 and 0.003 inch. The slight leakage of fluidthrough this clearance is insufiicient to interfere with adequaute pumping. action.

The driving portion 48 of .shaft 38 extends through a 23 to providea means for connecting an actuating mechanism, for example, ahand operated lever 52 thereto. The frictionalresistance between shaft 38 and bearing hub 50 is minimized, for

example, bymeans of a nylon bearing insert 54 mounted withinhub 50. Lever mechanism 52 includes, for exagainst *both' ample, a hand operated lever 56 connected to react against partitioning structure 12 through cover 23, for example, by means of connecting linkage 58 rotatably connected at one end thereof by means of pin 60 to cover 23. The other end of connecting linkage 58 is rotatably connected to a lower extension of handle 56 by means of a pin 62. An intermediate portion of handle 64, for example, disposed at short distance above pivot 62 is rotatably connected to driving portion 48 of shaft 38 by means of a pin 66. Handle 52 is conveniently fabricated in a channel form with the various enumerated connections disposed within the arms of the channel.

Apertured extensions

68 and 70 are respectively provided upon handle 56 and casing 23 to permit handle 56 to be attached to casing 23 by means of a pin inserted therethrough when the pump is inoperative. This, for example, provides a convenient means for carrying the disconnected pump or for locking it to prevent unauthorized use.

A convenient material for fabricating the partitioning structure 12 and

cover plates

22 and 23 is, for example, an aluminum alloy suitable for die casting. This facilitates provision of the various functional shapes in their proper relationship by an inexpensive manufacturing method. All non-moving parts including a cover plate 72 upon a discharge chamber 74 and an inlet conduit unit 76, connected to dual inlet chambers 78, may also be conveniently fabricated of this same aluminum alloy. However, shaft 38, connecting link 58 and handle 52 are, for example, made of forms of steel to provide adequate strength. Shaft 38 is, for example, made of stainless steel to resist corrosion by the fluids being pumped, and connecting link 58 and handle 52 are, for example, made of carbon steel suitably hardened at parts subject to wear, and coated to resist atmospheric corrosion, for example, by cadmium plating.

As shown in Fig. 1, pairs of separating

walls

80 and 82 are respectively disposed between rim flanges 24 extending from central wall 14 or partitioning structure 12, to segregate respective discharge chamber 74 and dual inlet chamber 78. An intermediate separating wall 84 is disposed between separating walls 82 to provide a dual inlet chamber 78. These separating walls are, for example, conveniently formed during the die-casting operation which forms partitioning structure 12.

Discharge chamber 74 is, for example, connected to pumping chambers 86 and 88 formed between diaphragms 20 and opposite sides of partitioning structure 12, by means of aligned passageways 90 extending through flanges 24. A strip of resilient valve material 92 is disposed within the angular space between flanges 24 and within discharge chamber 74 with its central portion 94 anchored to the end of central wall 14, for example, by a forced fit engagement of projections 96 of central wall 14 which extend into discharge chamber 74. The outer portions 98 of resilient valve element 92 are thereby maintained in firm resilient engagement with the inner surface of flanges 24 in position to cover passageway 90. The outer portions 98, therefore, act as discharge check valves which permit a flow of fluid from pumping chambers 86 and 88 and prevent a backflow from discharge chamber 74 thereto. Outer portions 28 are stiffened, for example, by reinforcing ribs 100 molded, for example, in its non-sealing upper surface. Discharge chamber 74 also includes an open end or discharge connection 75 which is internally threaded, for example, for connection to discharge piping (not shown).

Cover plate 72 includes, for example, a bleeder valve means 102 which permits air to enter discharge chamber 74 when the pressure therein drops below atmospheric pressure. Bleeder valve 102 includes, for example, an elongated aperture 104 within which a resilient closure element 106, made of rubber for example, is inserted. Resilient closure element 106 incorporates, for example, a stem 108 inserted through aperture 104 and a flexible head 110 which is large enough to completely cover aperture 104. Head 110 is disposed substantially perpendicularly to stem 108 and lies within discharge chamber 74. Stem 108 is recessed at 112 adjacent head 110 to provide a shoulder 114 for locking closure element 106 within aperture 104 between head 110 and itself. The outer portion or skirt 116 of head 110 is inclined at an angle towards plate 72 to lock element 106 in resilient contact with plate 72. Resilient closure element 106 is constructed and arranged to permit the head to be flexed away from the wall to facilitate flow of air through aperture 104 into discharge chamber 74 when the pressure within chamber 74 falls a slight predetermined amount below atmospheric pressure. This flexing is facilitated by a cutout 118 extending axially through the closure element from head 110 a distance into stem 108 along its axis.

Inlet conduit unit 76 is connected to dual inlet chamber 78 by means of

respective flanges

120 and 122 connected together, for example, by cap screws 124. A specially shaped and formed strip of resilient material 126 is disposed between

flanges

120 and 122 to simultaneously provide a sealing gasket and for providing inlet check valve elements. This gasket is formed by the frame portion 128 of strip 126, and the inlet check valve elements are formed by a pair of valve flaps 130 which extend from a central web 132 which connects the sides of frame 128. Flaps 130 are stiffened by ribs 133 formed upon their upper surfaces as shown in Fig. 6. Strip 126 is, for example, made of rubber of adequate stiflness to act as valve elements.

Inlet conduit 76 includes a pair of sloped rims or extensions 134 extending a short distance into inlet chambers 78 as shown in Figs. 1 and 5. These sloped rims 134 are constructed and arranged to extend within the inside edge of frame 128 of strip 126 and lie under flaps 130. When frame 128 is securely squeezed between

flanges

120 and 122, flaps 130 are maintained in firm resilient contact with the upper surfaces 136 of sloped rims 134 to provide separate check valve elements for dual inlet chambers 78.

The lower portion of inlet conduit 76 includes a tubular extension 138 which is internally threaded at 140 and externally threaded at 142 for respective connection, for example, to a suction standpipe and supply tank (not shown). Slot 141 and small hole 143 in flange 120 admit air into the tank, for example, through annular space 145 between

threads

140 and 142 to permit withdrawal of fluid through threaded hole 140. A strainer 144, for example, made of wire screen is inserted within the central flow passage of conduit 76 to prevent large particles from entering the pump.

As shown in Figs. 1, 2 and 7, flow passageways from dual inlet chamber 78 into pumping chambers 86 and 88 are, for example, provided by a passageway 146 extending from one inlet chamber 78 to pumping chamber 88 and a second inlet passageway 148 extending through flange rim 24 into pumping chamber 86.

Passageways

146 and 148 are staggered from each other to provide separate access means to chambers 86 and 88.

Cover plates

22 and 23 are herein represented as substantially continuous plates with the exception of apertures 150 therein which permit air to enter into the space between diaphragms 20 and

plates

22 and 23. This flow of air prevents a vacuum from being formed between the diaphragms and the cover plates when the pump is actuated.

Cover plates

22 and 23, however, might be formed of ribbed or perforated elements so long as their outer peripheries are substantially unbroken to seal the peripheries of diaphragms 20 against partitioning structure 12. Cover plate 22 also includes a recessed protuberance formed at 152 to receive the head of screw 42 to permit full flexure of the diaphragm up to the limit provided by the cover plate. This limit of travel for the diaphragms provided by

cover plates

22 and 23 prevents them LfIOIIl abeing .overstressed during .the pumping operation.

In-Figs. 8-10..is shown'a-discharge chamber;cover assembly -154 which is constructed and arranged to include elements and featureswhich supplementthe featuresof cover plate 72 shown in Figs. 2 and 4. Discharge cover assembly 154 includes a superimposed outer shell 160 which forms a horizontallydisposed pocket or housing 162 for receiving a discharge nozzle 164 which,.for example, is attached to a hose 166 connected to discharge connection 75a-of pump 10a. The lower flange 168 of assembly 154 extends past discharge chamber 74a at 170. An aperture 172'is providedrin-extension170 for receiving a lug 174 formed in the lower surface of nozzle 164. Aperture 172 is, for example, rectangular. This permitsa nozzle 164 v to be conveniently housed within pocket 162 when the'pump is not in use. Assembly 154 is also constructed and arranged to receive a controllable bleeder-valve 103 (later described in detail).

Discharge chamber 74a-continues upwardly a short distance 'above walls 24a into a space provided between the lowerwall .178 of pocket 162 and the vertically dis- POSCdzWflll .180 which contains controllable bleeder valve 103. This makes valve 103 accessible for convenient manipulation (later described in detail) and places it in a substantially vertically disposed wall with a projecting ridge .182 extending outwardly from wall 180 to shield aperture200 in wall 180, for-example, from rain. A small projection 186 extends from wall 180 a short vdistance below and to the side of valve 103 to help locate its on and off positions.

.Details of valve 103 are shown in Figs. 11 and 12. Valve 103 is made of a resilient material, for example, 30-40 durometer-rubberof the Buna N variety. Valve 103-includes a flexible head 188, a stern 190, and a'knob or enlargedend 192. Stem 190 isinsertedthrough aperture 200in wall 180 in substantially the samemannerdescribed in conjunction with valve 102 shown in Fig. 4. Skirt 188 includes, for example, a relatively thick section 194 disposed opposite nose 196 of control knob 192. This thicker section 194 helps maintain a seal between the lowersurface 198 of nose 19.6 and the ,bleederslot laterdescribed in conjunction withlFig. 10.

In Fig. 10 are shown details of the aperture 200 formed in .wall 180 of assembly 72a. Aperture 200includes a single. slot 202 similarto dual slots 104 shown in Fig. 3. Extension or nose 196 of bleeder valve 103 is constructed and arranged to cover slot extension 202 when it is rotated in a position to directly overlie it. .However, when knob 192 is turned at the position shown in Fig. .8, extension 196 extends downward leaving slot 202 unobstructed. This permits the zbleeder valve to be optionally turned on or off to permit optional admission to or exclusion from a flow of air into discharge chamber 74a between each discharge stroke.

Bleeder valve 103 in the on position allows air to enter discharge chamber 74a through slot 202 to prevent siphoning whenever'the pump outlet is situated below the level of the pump. This vacuum-breaking feature is required, for example, if hose nozzle 164 attached toflexible hose 166 were dropped on the floor while pumping liquidfrom a barrel or overhead tank (not shown). However, the siphoning-preventing or vacuum-breaking feature is not required, for example, when pumping from an underground tank or when a discharge spout is directly connected to the pump outlet. In such instances the bleeder .valve is turned to the off position by turning knob 192 to place its nose or extension 196 directly over slot 202. Furthermore, the off position is advantageous for the purpose of excluding air from the chamber 74a when more volatile fluids are being pumped.

In Fig. 13 a modified cover assembly 156 is shown which includesa controllable bleeder valve 105 disposed in the horizontal lower flange 168b in a manner similar tothat. shown in Fig. 4. Assembly 156 includes an upper roof .or shell .6 Q r tain ng e t. -p 20 ahnzzle .(-not shown) in a manner similar to that indicated'in Fig. -18 with-the lower projection 174 of the;nozzle1(not;shown disposed within aperture or slot 172k. Shell 160b, accordingly, performs the dual functions of shielding thebleeder valve and aperture fromrain and ofproviding ahousing for the nozzle. Roof 16% is supported by side walls 1561b, mounted upon flange 168b. Projections 182b ;an d 186b which are similar to projections ;182; and 18.6 in Fig. 10 extend from flange168b adjacenttheknob192b of valve 105. The structure of cover assembly 156, shown in Fig. 13 is slightly .simpler than thatzofcover assembly 154, shown in Figs. 8-10; .t;the:positioning of the control valve ,105 ofcover assembly ,156 ,under roof 16% makes it slightly less convliifint 10.-operate than the moreexposed control .valve 103.

Operation When lever 156-is ractuated back :and forth, it reciprocates diaphragms 20 with'it:to alternately'compress and expand -pumping-chambers86 and 88 against partitioning structure 12. .In the position shown in Fig. 2,;pumping chamber 86 has been expanded to substantially its full capacity which opens the check :valve flap element to. permit a flow of fluidtobedrawnthrough-inlet chamber 78 and passageway 1'485into pumping chamber '86.

At the same time, pumping chamber88 has been com pressedto its minimum volume which discharges a 'flow of fluid through discharge check-valveelement 98 to discharge chamber'74. From discharge chamber 74, the fluid is carried away through -a discharge conduit not shown, connectedto the open end75 of discharge'74.

[At the same time, a slight flow of fluid leaks through the clearance between shaft 38 and bearing 16 into expanded pump chamber 86. However, this does not interfere materially with the adequate pumping operation because this clearance-or leakage is insignificant in comparison to the relatively 'large flow of fluid through discharge passageway 90. This leakage is'maintained within sealed portions of the pump and it mingles -with the fluid being drawn into:pumping chamber 86 through inletpassageway 148. This leakage is also insignificant in comparison with the relatively large amount of fluid drawn into the inlet chamber and, therefore, does not materially decrease theamount of fluid :drawn into the pump.

.Since this leakageis contained entirely-within portions of the pump sealed .betweendiaphragms '20, partitioning structure 12 and shaft 38, there is no-necessity'to provide afluid-tight seal about anymoving portions of thepump. This'permits an embodiment of this invention to be-constructed in an unusuallyeconomical manner.

When handleJ56 is moved to the limit oftravel indicated in broken outline, :the diaphragms 20-move'to the positions shown in broken outline to reverse the conditionslof pump chambers 86 and 88. Fluid is then'discharged from pumping chamber 86 into discharge chamber 74 and drawn from respective inletchamber 78 into pumping chamber 88 through an inlet passageway 146. A steady stream of fluidis, therefore, 'drawn into and discharged from the pump with each stroke of handle '56.

,If many time,'the:pressure withindischarge chamber 74 falls below atmospheric pressure, bleeder valve 102 permits an to enter chamber 74 Which'prevents a reduced pressure from existing in chamber 74 which might interfere with proper operation of. discharge checkvalve flapsor outer portions 98.

The

controllable bleeder valves

103 and 1 05'shown-in Figs. 813 can be optionally turned -off or on! When these valves are turned .on,- noses or extensions 196 and 19617 are positioned-remote'from keyhole slots 202 and 20212 which freestheseslotsfor the passage of airewhen the pressure in the discharge chamberjdrops below atmospheric pressure. These bleeder valves "are, accordingly,

, placed .on the "on,position when the pumps .1 are "com a nected to fixed piping to prevent any siphoning from the discharge lines when the pressure in the discharge chamber falls below atmospheric pressure between discharge strokes.

However, when the pump discharges to the atmosphere through a hose 166 and nozzle 164 this siphoning problem does not exist, and the

bleeder valve

103 or 105 is turned off by positioning nose 196 or 19Gb respectively over keyhole slots 202 or 2112b. This prevents any air from entering the discharge chamber which sealing is advantageous for handling certain type of liquids, for example, light and volatile liquids.

What is claimed is:

l. A double-acting diaphragm pump for fluids comprising a partitioning structure including a substantially fiat central plate and a pair of flanges extending away from each other about its periphery at obtuse angles relative to said central plate, a bearing means disposed in said central plate, a pair of diaphragms disposed on both sides of said partitioning structure, cover elements including ring means sealing the peripheries of said diaphragms to outer surface of said flanges to form a pumping chamber of variable volume on both sides of said partitioning structure, said flanges being cut out to provide inlet and outlet passageways into said chambers, said inlet passageways being provided with inlet check valves, a reciprocating shaft means, said diaphragms being secured in a fluid-tight manner at a predetermined longitudinal spacing upon said shaft means, said shaft means being inserted to reciprocate within said bearing means along a portion of said shaft disposed between said diaphragms, a clearance existing between said shaft and said bearing means which permits a slight flow of fluid between said chambers which is not sufliciently great to interfere with adequate pumping efliciency, a lever means mounted upon the outside of one of said cover means and operatively connected to a portion of said shaft disposed outside of said cover means for reciprocating said shaft along its longitudinal axis whereby a pumping action relative to said chambers is imparted to said diaphragms, separating walls being disposed within the substantially angular space formed between adjacent portions of said flanges on both sides of said inlet and outlet passageways to provide inlet and outlet chambers connected thereto, and the end of said substantially flat central plate being disposed substantially midway between a pair of said passageways through said flanges, a strip of resilient valve material being disposed within the angular space formed between said flanges within one of said chambers with the central portion of said strip disposed at the junction of said flanges and its outer portions disposed in resilient contact with one pair of said cutouts in said flanges, and securing means attached to said end of said central plate and extending through said central portion of said strip for anchoring said strip within said chamber with its outer portions maintained in firm resilient contact with said flanges to act as discharge check valves relative to said cutouts whereby said one chamber is constituted as a discharge chamber.

2. A pump as set forth in claim 1 wherein said securing means includes projections extending from said end of said central wall into said angular space between said flanges.

3. A pump as set forth in claim 1 wherein an additional separating wall is positioned between a pair of said separating walls to provide dual inlet chambers therebetween, and one of said cutouts is disposed Within each of said duel chambers to provide separate passageways into each of said pumping chambers.

4. A pump as set forth in claim 3 wherein an inlet conduit means is connected to said dual inlet chambers by means of a pair of flanges connected respectively thereto, said conduit means including a pair of inlet passageways aligned with said dual inlet chambers, a pair of sloped rims extend from said conduit into said dual chambers, a strip of resilient material including a frame and a pair of flaps is disposed between said conduit means and said dual inlet chambers with said frame held between said flanges to simultaneously act as a sealing gasket and to maintain said flaps in resilient contact with said sloped rims to provide inlet check valve elements for said dual inlet chambers.

5. A pump as set forth in claim 1 wherein a bleeder valve means is incorporated in a wall of said discharge chamber for allowing air to enter said chamber when the pressure therein drops below atmospheric pressure, said wall being secured to the outer edges of said flanges and said separating walls of said outlet chamber, said wall of said discharge chamber cut out in the form of an elongated aperture, a resilient closure element being mounted within said elongated aperture, said resilient closure element including a stem inserted within said aperture and a flexible head constructed and arranged to cover said aperture and disposed substantially perpendicularly to said shaft within said discharge chamber, said stem being recessed adjacent said head to form an enlarged end which provides a shoulder for locking said element within said aperture between said head and said shoulder, the outer portion of said head adjacent said wall being inclined at an angle towards said wall to maintain the outer edge of said head locked in resilient contact with said wall, an external portion of said elongated aperture extending past said enlarged end of said stem, and said resilient closure element being constructed and arranged to permit said head to be flexed away from said wall to facilitate a flow of air through said portion of said aperture into said discharge chamber when the pressure in said discharge chamber falls a slight predeter-- mined amount below atmospheric pressure.

6. A pump as set forth in claim 5 wherein an axial portion of said closure element extending through said head into said stem is cut out to facilitate said flexing of said head, and the end of said stem remote from said head is conically shaped to facilitate insertion of said stem into said aperture.

7. A pump as set forth in claim 5 wherein the larger portion of said stem adjacent said shoulder is constructed and arranged to provide a nose for optionally covering and sealing said external portion of said elongated aperture, and said stem and main portion of said aperture are constructed and arranged to permit said bleeder valve to be manually rotated to optionally cover and uncover said external portion of said aperture.

8. A pump as set forth in claim 7 wherein a portion of the upper wall of said outlet chamber is inclined upwardly away from said outlet chamber to provide a continuation of said outlet chamber, and said bleeder valve means is positioned within said inclined wall of said continuation to provide convenient access to said bleeder valve means.

9. A pump as set forth in claim 8 wherein projections extend from said inclined wall of said continuation of said outlet chamber above and below said nose to provide a shield over said aperture and indexing projections for locating the on and ofl positions of said nose.

10. A pump as set forth in claim 7 wherein the portion of said skirt adjacent said nose is thickened to help seal said external portion of said aperture between said nose and said skirt.

11. A pump as set forth in claim 1 wherein a cover assembly is disposed upon said outlet chamber, a hose and nozzle are attached to said outlet chamber, said cover assembly including extending walls which are constructed and arranged to form a pocket for receiving the tip of said nozzle, said cover assembly including an extending flange, and said nozzle and said flange including interlocking projection and recess means for engaging said nozzle with said flange when the tip of said nozzle is disposed within said pocket.

12. A pump as set forth in claim 11 wherein a portion 10 of the wall between said cover assembly and said outlet References Cited in the file of this patent chamber is extended upwardly to provide a continuation of said outlet chamber, and a controllable bleeder valve UNITED STATES PATENTS means is disposed within said inclined wall of said con- 677,474 Russell July 2, 1901 tinuation. 5 1,087,671 Loud Feb. 17, 1914 13. A pump as set forth in claim 11 wherein said cover 1,920,014 Horton et a1. July 25, 1933 assembly includes a lower flange sealing a side of said 2,307,566 Brown Jan. 5, 1943 outlet chamber, a controllable bleeder valve is disposed in said lower flange, and said extending walls of said FOREIGN PATENTS pocket adjacent said bleeder valve are cut out to provide 10 34,296 Austria Sept. 10, 1908 access to said controllable bleeder valve. 214,210 Germany Oct. 12, 1909