Multiple Air Chamber Foam Pump

• US 20150209811A1
• Filed: 01/28/2015
• Published: 07/30/2015
• Est. Priority Date: 01/29/2014
• Status: Active Grant

• Current Assignee: OP hygiene IP Gmbh
• Original Assignee: OP hygiene IP Gmbh
• Inventors: Ophardt, Heiner, Jones, Andrew
• Granted Patent: US 9,573,152 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A47K 5/14 Foam or lather making devices for shaving A45D27/02
• CPC Class Codes: B05B 11/1001 Piston pumps B05B11/1087, B05B11/1088, B05B11/109 take precedence
• CPC Class Codes: B05B 11/1069 the valve being made of a resiliently deformable material or being urged in a closed position by a spring
• CPC Class Codes: B05B 11/1074 located outside pump chambers
• CPC Class Codes: B05B 11/1087 Combination of liquid and air pumps
• CPC Class Codes: B05B 7/0037 including sieves, porous members or the like
• CPC Class Codes: B05B 7/0491 the liquid and the gas being mixed at least twice along the flow path of the liquid

Abstract

An improved foam piston pump in which a multiple of air pumps are disposed coaxially about a piston member and spaced axially along the piston member, preferably coaxially with a liquid pump for discharging air and liquid as foam. Each air pump is preferably provided by a modular piston within a modular casing assembly such that arrangements with one, two or more identical air pumps can be assembled from a plurality of the same modular components.

Claims

1. A piston pump comprising:

a piston chamber-forming member 20 extending longitudinally about an axis 23 from an inner end 24 to an outer end 25;

the piston chamber-forming member 20 defining a central chamber 26 therein coaxially about the axis within an annular chamber wall 27;

the piston chamber-forming member having a liquid inlet 28 at the inner end in communication with a liquid 14 in a reservoir 13;

a piston-forming element 22 coaxially slidably received within the chamber 26 in the piston chamber-forming member 20;

the piston-forming element 22 comprising an elongate tubular stem 90 with a central passageway 63 longitudinally therethrough, the passageway 63 extending from an inner end 134 to an outer end;

the piston-forming element 22 coaxially slidable within the piston chamber-forming member 20 between an extended position and a retracted position in a cycle of operation comprising a withdrawal stroke and a retraction stroke to draw the liquid 14 from the reservoir 13 via the liquid inlet 28 and discharge the liquid mixed with air through the outer end of the passageway 63;

a liquid pump 70 formed between the piston chamber-forming member 20 and the piston-forming element 22 proximate the inner end 134 of the piston chamber-forming member 22, the liquid pump 70 operative in the cycle of operation to draw the liquid from the reservoir 13 via the liquid inlet 28 and discharge the liquid into the passageway 63 proximate the inner end 134 of the passageway 63;

an inner air pump 170 formed between the piston chamber-forming member 20 and the piston-forming element 22 axially outwardly of the liquid pump 70 operative in the cycle of operation in a withdrawal stroke to draw air from the atmosphere and in a retraction stroke to discharge air into the passageway 63 through an inner air port 142 which extends radially inwardly through the stem 90 into the passageway 63;

a first outer air pump 270 formed between the piston chamber-forming member 20 and the piston-forming element 22 axially outwardly of the inner air pump 170, the first outer air pump 270 operative in the cycle of operation in the withdrawal stroke to draw air from the atmosphere and in the retraction stroke to discharge air into the passageway 63 through a first outer air port 162 which extends radially inwardly through the stem 90 into the passageway 91 at an axial location on the stem 90 spaced axially outwardly of the inner air port 142;

a first outer air sealing annular flange 203 on the piston chamber-forming member 20 axially outwardly of the inner air pump 170, the first outer air sealing annular flange 203 extending from the chamber wall 47 radially inwardly to an annular distal edge 232 in engagement with a radially outwardly directed first outer cylindrical wall 152 on the stem 91 axially inwardly of the first outer air port 162;

the annular distal edge 232 of the first outer air sealing annular flange 203 engaging the first outer cylindrical wall 152 of the stem 91 to prevent fluid flow axially inwardly therepast,

a first outer air sealing disc 256 on the stem 91 axially outwardly of the first outer air port 162 and axially outwardly of the first outer air sealing annular flange 203 on the piston chamber-forming member 20;

the first outer air sealing disc 256 extending radially outwardly from the stem 91 to an annular distal edge 257 in engagement with a first cylindrical outer portion 210 of the chamber wall 47 on the piston chamber-forming member 22 axially outwardly of the first outer air sealing annular flange 203;

the annular distal edge 257 of the first outer air sealing disc 256 engaging the first cylindrical outer portion 210 of the chamber wall 47 on the piston chamber-forming member 20 to prevent fluid flow axially upwardly therepast;

the first outer air pump 270 having a first outer air compartment 271 open to the first outer air port 162 and defined (a) annularly between the stem 90 of the piston-forming element 22 and the first cylindrical outer portion 210 of the chamber wall 47 of the piston chamber-forming member 20, and (b) axially between the first outer air sealing annular flange 203 and the first outer air sealing disc 256;

in a cycle of operation in the withdrawal stroke, an axial distance between the first outer air sealing annular flange 203 and the first outer air sealing disc 256 increases thereby increasing a volume of the first outer air compartment 271 and drawing air into the first outer air compartment 271 and, in the refraction stroke, the axial distance between the first outer air sealing annular flange 203 and the first outer air sealing disc 256 decreases thereby decreasing the volume of the first outer air compartment 271 and discharging air from the first outer air compartment 271 through the first outer air port 162 into the passageway 63.

2. A piston pump as claimed in claim 1 wherein:

the liquid pump 70 operative in a cycle of operation in the withdrawal stroke to draw liquid from the reservoir 13 via the liquid inlet 28 and, in the retraction stroke, to discharge liquid into the passageway 63 proximate the inner end 134 of the passageway 63.

3. A piston pump as claimed in claim 1 including:

a second outer air pump 370 formed between the piston chamber-forming member 20 and the piston-forming element 22 axially outwardly of the first outer air pump 270,

the second outer air pump 370 operative in the cycle of operation in the withdrawal stroke to draw air from the atmosphere and, in the retraction stroke, to discharge air into the passageway 63 through a second outer air port 262 which extends radially inwardly through the stem 90 into the passageway 63 at an axial location on the stem 90 spaced axially outwardly of the first outer air port 162;

a second outer air sealing annular flange 303 on the piston chamber-forming member 20 above the first outer air pump 270, the second outer air sealing annular flange 203 extending from the chamber wall 47 radially inwardly to an annular distal edge 332 in engagement with a radially outwardly directed second outer cylindrical wall 252 on the stem 90 axially outwardly of the second outer air port 262;

the annular distal edge 332 of the second outer air sealing annular flange 303 engaging the second outer cylindrical wall 252 of the stem 90 to prevent fluid flow axially inwardly therepast,

a second outer air sealing disc 356 on the stem 90 axially outwardly of the second outer air sealing annular flange 303 on the piston chamber-forming member 20;

the second outer air sealing disc 356 extending radially outwardly from the stem 90 to an annular distal edge 357 in engagement with a second cylindrical outer portion 310 of the chamber wall 47 on the piston chamber-forming member 20 axially outwardly of the second outer air sealing annular flange 303;

the annular distal edge 357 of the second outer air sealing disc 256 engaging the second cylindrical outer portion 310 of the chamber wall 47 on the piston chamber-forming member 20 to prevent fluid flow axially outwardly therepast;

the second outer air pump 370 having a second outer air compartment 371 open to the second outer air port 262 and defined (a) annularly between the stem 90 of the piston-forming element 22 and the second cylindrical outer portion 310 of the chamber wall 47 of the piston chamber-forming member 20, and (b) axially between the second outer air sealing annular flange 303 and the second outer air sealing disc 356;

in a cycle of operation in the withdrawal stroke, an axial distance between the second outer air sealing annular flange 303 and the second outer air sealing disc 356 increases thereby increasing a volume of the second outer air compartment 371 and drawing air into the second outer air compartment 371 and, in the retraction stroke, the axial distance between the second outer air sealing annular flange 303 and the second outer air sealing disc 356 decreases thereby decreasing the volume of the second outer air compartment 371 and discharging air from the second outer air compartment 371 through the second outer air port 262 into the passageway 63.

4. A piston pump as claimed in claim 3 wherein:

the first cylindrical outer portion 210 of the chamber wall 47 on the piston chamber-forming member 20 extends axially between the first outer air sealing annular flange 203 and the second outer air sealing annular flange 303; and

the second cylindrical outer portion 310 of the chamber wall 47 on the piston chamber-forming member 20 extends axially outwardly from the second outer air sealing annular flange 303.

5. A piston pump as claimed in claim 4 wherein:

the first outer air sealing annular flange 203 engages the second cylindrical outer portion 210 of the chamber wall 47 on the piston chamber-forming member 20 axially outwardly of the first outer air sealing disc 256 on the stem 90 and axially inwardly of the second outer air sealing disc 356 on the stem 90.

6. A piston pump as claimed in claim 1 wherein:

a cylindrical first inner portion 110 of the chamber wall 47 on the piston chamber-forming member 20 extends axially inwardly from the first outer air sealing annular flange 203;

a first inner air sealing disc 156 on the stem 90 axially inwardly of the first outwardly air sealing annular flange 203 on the piston chamber-forming member 20;

the first inner air sealing disc 156 extending radially outwardly from the stem 90 to an annular distal edge 157 in engagement with the cylindrical first inner portion 110 of the chamber wall 47 on the piston chamber-forming member 20 axially inwardly of the first outer air sealing annular flange 203;

the annular distal edge 157 of the first inner air sealing disc 156 engaging the first cylindrical inner portion 110 of the chamber wall 47 on the piston chamber-forming member 20 to prevent fluid flow axially outwardly therepast;

the inner air pump 170 having an inner air compartment 171 open to the inner air port 142 and defined (a) annularly between the stem 90 of the piston-forming element 22 and the first cylindrical inner portion 110 of the chamber wall 47 of the piston chamber-forming member 22, and (b) axially inwardly of the first inner air sealing disc 156;

in a cycle of operation in the withdrawal stroke, a volume of the inner air compartment 171 increases drawing air into the inner air compartment 171 and, in the retraction stroke, the volume of the inner air compartment 171 decreases discharging air from the inner air compartment 171 through the inner air port 142 into the passageway 63.

7. A piston pump as claimed in claim 6 wherein:

a cylindrical second inner portion 109 of the chamber wall 47 on the piston chamber-forming member 20 extends axially inwardly from the cylindrical first inner portion 110 of the chamber wall 47, the cylindrical second inner portion 109 of the chamber wall 47 having a diameter less than a diameter of the cylindrical first inner portion 110 of the chamber wall 47;

a second inner air sealing disc 140 on the stem 90 axially inwardly of the first outer air sealing annular flange 156 on the stem 90,

the second inner air sealing disc 140 extending radially outwardly from the stem 90 to an annular distal edge 144 in engagement with the cylindrical second inner portion 109 of the chamber wall 47 on the piston chamber-forming member 20;

the annular distal edge 144 of the second inner air sealing disc 140 engaging the second cylindrical inner portion 109 of the chamber wall 47 on the piston chamber-forming member 20 to prevent fluid flow axially inwardly therepast;

an inner air compartment 142 defined (a) annularly between the stem 90 of the piston-forming element 22 and the first cylindrical inner portion 110 and the second cylindrical inner portion 109 of the chamber wall 47 of the piston chamber-forming member 20, and (b) axially between the first inner air sealing annular flange 156 and the second inner air sealing disc 140.

8. A piston pump as claimed in claim 7 wherein:

a liquid sealing disc 139 on the stem 90 axially inwardly of the first inner air sealing disc 140;

the liquid sealing disc 139 extending radially outwardly from the stem 90 to an annular distal edge 145 in engagement with the cylindrical second inner portion 109 of the chamber wall 47 on the piston chamber-forming member 20 axially inwardly of the second inner air sealing disc 140;

the annular distal edge 145 of the liquid sealing disc 139 engaging the second inner portion 109 of the chamber wall 47 on the piston chamber-forming member 20 to prevent fluid flow axially inwardly therepast;

the liquid sealing disc 139 being resilient and having an inherent bias biasing the annular distal edge 145 into engagement with the second inner portion 109 of the chamber wall 47 and deflectable against the bias from engagement with the second inner portion 109 of the chamber wall 47 to permit liquid fluid flow axially outwardly therepast when a pressure differential between a pressure on an inner axial side of the liquid sealing disc 139 is sufficiently greater than a pressure on an inner axial side of the liquid sealing disc 139;

a one-way valve 102 across the liquid inlet 28 permitting fluid flow therepast from the reservoir 13 into the chamber 26 and preventing fluid flow therepast from the chamber 26 into the reservoir 13,

a liquid port 141 on the stem 90 axially between the liquid sealing disc 139 and the second inner air sealing disc 140;

the liquid port 141 extending radially inwardly through the stem 90 into the passageway 63;

the liquid pump 70 having a liquid compartment 106 open to the liquid port 141 and defined (a) annularly between the stem 90 of the piston-forming element 22 and the second inner portion 109 of the chamber wall 47 of the piston chamber-forming member 20, and (b) axially inwardly of the liquid sealing disc 139 between the liquid sealing disc 139 and the one-way valve 102;

in the cycle of operation in the withdrawal stroke, a volume of the liquid compartment 106 increases drawing liquid past the one-way valve 102 from the reservoir 13 into the liquid compartment 106 and, in the retraction stroke, the volume of the liquid compartment 106 decreases discharging liquid from the liquid compartment 106 past the liquid sealing disc 139 to between the liquid sealing disc 139 and the second inner air sealing disc 140 and through the liquid port 141 into the passageway 63.

9. A piston pump as claimed in claim 1 wherein:

the inner air pump 170 having a cylindrical inner air pump wall 110 provided by the piston chamber-forming member 20,

a first inner air sealing disc 156 extending radially outwardly on the stem 90 axially outwardly of the inner air port 142 for sealing engagement with the inner air pump wall 110;

the first outer air sealing disc 256 extending radially outwardly on the stem 90 axially outwardly of the first inner air sealing disc 156 of the inner air pump 170;

the first outer air sealing annular flange 203 on the piston chamber-forming member 20 being axially outwardly of the first inner air sealing disc 156 of the inner air pump 170,

the first outer air sealing annular flange 203 extending radially inwardly for sealing engagement with the radially outwardly directed stem wall 152 of the stem 90 axially outwardly of the first inner air sealing disc 156 of the inner air pump 170;

the first inner air sealing disc 156 extending radially outwardly on the stem 90 axially outwardly of the second inner air sealing disc 140 of the inner air pump 170 into sealing engagement with the cylindrical outer air pump wall 110 provided by the piston chamber-forming member 20 axially inwardly of the outer air sealing annular flange 203.

10. A piston pump as claimed in claim 1 wherein:

the piston-forming element 22 comprises;

a liquid piston 130 having a hollow tubular stem 131 with the inner end 134 and an outer end 135 and a central passage 133 longitudinally therethrough about the axis 23,

an inner air piston 150 having a hollow tubular stem 151 with an inner end 154 and an outer end 155 and a central passage 153 longitudinally therethrough about the axis 23, and

a first outer air piston 250 having a hollow tubular stem 251 with an inner end 254 and the outer end 255 and a central passage 253 longitudinally therethrough about the axis 23,

the liquid piston 130, the inner air piston 150 and the first outer air piston 250 coaxially disposed about the axis 23 with;

(a) the outer end 135 of the liquid piston 130 coupled to the inner end 154 of the inner air piston 150 and the outer end 155 of the inner air piston 150 coupled to the inner end 254 of the first outer air piston 250, and

(b) the central passage 133 of the liquid piston 130 opening axially into the central passage 153 of the inner air piston 150 and the central passage 153 of the inner air piston 150 opening axially into the central passage 253 of the first outer air piston 250 forming the central passageway 63 through the liquid piston 130, the inner air piston 150 and the first outer air piston 250,

the first outer air sealing disc 256 carried on the inner end 254 of the first outer air piston 250 extending radially outwardly from the stem 251;

the first outer air port 162 on the inner air piston 150 proximate but axially inwardly of the first outer air sealing disc 256,

the piston chamber-forming member 20 comprising;

a hollow tubular inner casing 101 having the end 24 and an outer end 105, and

a hollow tubular first outer casing 201 having an inner end 204 and the outer end 205;

the inner casing 101 defining a liquid chamber 106 and an inner air chamber 107 therein, the liquid chamber 106 axially open to the inner end 24 of the inner casing 101 and opening axially inwardly into the inner air chamber 107 which is open to the outer end 105 of the inner casing 101;

the first outer casing 201 defining a first outer air chamber 207 therein,

the inner casing 101 and the first outer casing 210 coaxially disposed about the axis 23 with;

(a) the outer end 105 of the inner casing 101 coupled to the inner end 204 of the first outer casing 201, and

(b) the inner air chamber 107 opening axially into the first outer air chamber 207,

the first annular air sealing flange 203 coaxially carried by the first outer casing 201 fixed to the first outer casing 201 at the inner end 204 of the first outer casing 201,

the stem 151 of the inner air piston 150 passing coaxially through the first annular air sealing flange 203 axially inwardly of the first outer air sealing disc 256,

the first annular air sealing flange 203 extending radially inwardly from sealed engagement with the first outer casing 201 into engagement with the stem 151 of the inner air piston 150 axially inwardly of the first outer air port 162,

the first outer air chamber 207 defined in an annular space radially inside the first outer casing 201 between the first outer casing 201 and the stem 151 of the inner air piston 150 and axially between first annular air sealing flange 203 and the first outer air sealing disc 256,

the first outer air chamber 207 open via the first outer air port 162 into the passageway 153.

11. A piston pump as claimed in claim 4 wherein:

the piston-forming element 22 comprises;

a liquid piston 130 having a hollow tubular stem 131 with the inner end 134 and an outer end 135 and a central passage 133 longitudinally therethrough about the axis 23,

an inner air piston 150 having a hollow tubular stem 151 with an inner end 154 and an outer end 155 and a central passage 153 longitudinally therethrough about the axis 23, and

a first outer air piston 250 having a hollow tubular stem 251 with an inner end 254 and the outer end 255 and a central passage 253 longitudinally therethrough about the axis 23,

a second outer air piston 350 having a hollow tubular stem 351 with an inner end 354 and an outer end 355 and a central passage 353 longitudinally therethrough about the axis 23,

the liquid piston 130, the inner air piston 150, the first outer air piston 250 and the second outer air piston 350 coaxially disposed about the axis 23 with;

(a) the outer end 135 of the liquid piston 130 coupled to the inner end 154 of the inner air piston 150, the outer end 155 of the inner air piston 150 coupled to the inner end 254 of the first outer air piston 250, and the outer end of the first outer air piston 250 coupled to the inner end of the second outer air piston 350, and

(b) the central passage 133 of the liquid piston 130 opening axially into the central passage 153 of the inner air piston 150, the central passage 153 of the inner air piston 150 opening axially into the central passage 253 of the first outer air piston 250 and the central passage of the first outer air piston opening axially into the central passage of the second outer air piston forming the central passageway 63 through the liquid piston 130, the inner air piston 150, the first outer air piston 250 and the second outer air piston 350,

the first outer air sealing disc 256 carried on the inner end 254 of the first outer air piston 250 extending radially outwardly from the stem 251, the second outer air sealing disc 356 carried on the inner end 354 of the second outer air piston 350 extending radially outwardly from the stem 351,

the first outer air port 162 on the inner air piston 150 proximate but axially inwardly of the first outer air sealing disc 256, the second outer air port 262 on the first outer air piston 250 proximate but axially inwardly of the second outer air sealing disc 356,

the piston chamber-forming member 20 comprising;

a hollow tubular inner casing 101 having the inner end 24 and an outer end 105,

a hollow tubular first outer casing 201 having an inner end 204 and the outer end 205; and

a hollow tubular second outer casing 301 having an inner end 304 and an outer end 305;

the inner casing 101 defining a liquid chamber 106 and an inner air chamber 107 therein, the liquid chamber 106 axially open to the inner end 24 of the inner casing 101 and opening axially inwardly into the inner air chamber 107 which is open to the outer end 105 of the inner casing 101;

the first outer casing 201 defining a first outer air chamber 207 therein, the second outer casing 301 defining a second outer air chamber 307 therein;

the inner casing 101, the first outer casing 201 and the second outer casing 301 coaxially disposed about the axis 23 with;

(a) the outer end 105 of the inner casing 101 coupled to the inner end 204 of the first outer casing 201,

(b) the inner air chamber 107 opening axially into the first outer air chamber 207, and

(c) the first outer air chamber 207 opening axially into the second outer air chamber 307;

the first annular air sealing flange 203 coaxially carried by the first outer casing 201 fixed to the first outer casing 201 at the inner end 204 of the first outer casing 201,

the stem 151 of the inner air piston 150 passing coaxially through the first annular air sealing flange 203 axially inwardly of the first outer air sealing disc 256,

the first annular air sealing flange 203 extending radially inwardly from sealed engagement with the first outer casing 201 into engagement with the stem 151 of the inner air piston 150 axially inwardly of the first outer air port 162,

the first outer air chamber 207 defined in an annular space radially inside the first outer casing 201 between the first outer casing 201 and the stem 151 of the inner air piston 150 and axially between first annular air sealing flange 203 and the first outer air sealing disc 256,

the first outer air chamber 207 open via the first outer air port 162 into the passageway 153,

the second annular air sealing flange 303 coaxially carried by the second outer casing 301 fixed to the second outer casing 301 at the inner end 304 of the second first outer casing 301,

the stem 251 of the first outer air piston 250 passing coaxially through the second annular air sealing flange 303 axially inwardly of the second outer air sealing disc 356,

the second annular air sealing flange 303 extending radially inwardly from sealed engagement with the second outer casing 301 into engagement with the stem 251 of the first outer air piston 250 axially inwardly of the second outer air port 262,

the second outer air chamber 307 defined in an annular space radially inside the second outer casing 301 between the second first outer casing 301 and the stem 251 of the first outer air piston 250 and axially between the second annular air sealing flange 303 and the second outer air sealing disc 356,

the second outer air chamber 307 open via the second outer air port 262 into the passageway 253.

12. A piston pump as claimed in claim 11 wherein the inner air piston 150 and the first outer air piston 250 are identical modular elements.

13. A piston pump as claimed in claim 11 wherein the first outer casing 201 and the second outer casing 301 are identical modular elements.

14. A piston pump as claimed in claim 10 wherein a cross-sectional area of the passageway 63 normal the axis varies along the axis.

15. A piston pump as claimed in claim 1 including a foam generator in the passageway 63 to mix the air and the liquid passing outwardly therethrough to produce foam.

16. A piston pump as claimed in claim 5 wherein:

a cylindrical first inner portion 110 of the chamber wall 47 on the piston chamber-forming member 20 extends axially inwardly from the first outer air sealing annular flange 203;

a first inner air sealing disc 156 on the stem 90 axially inwardly of the first outwardly air sealing annular flange 203 on the piston chamber-forming member 20;

the first inner air sealing disc 156 extending radially outwardly from the stem 90 to an annular distal edge 157 in engagement with the cylindrical first inner portion 110 of the chamber wall 47 on the piston chamber-forming member 20 axially inwardly of the first outer air sealing annular flange 203;

the annular distal edge 157 of the first inner air sealing disc 156 engaging the first cylindrical inner portion 110 of the chamber wall 47 on the piston chamber-forming member 20 to prevent fluid flow axially upwardly therepast;

the inner air pump 170 having an inner air compartment 171 open to the inner air port 142 and defined (a) annularly between the stem 90 of the piston-forming element 22 and the first cylindrical inner portion 110 of the chamber wall 47 of the piston chamber-forming member 22, and (b) axially inwardly of the first inner air sealing disc 156;

in a cycle of operation in the withdrawal stroke, a volume of the inner air compartment 171 increases drawing air into the inner air compartment 171 and, in the retraction stroke, the volume of the inner air compartment 171 decreases discharging air from the inner air compartment 171 through the inner air port 142 into the passageway 63.

17. A piston pump as claimed in claim 16 wherein:

a cylindrical second inner portion 109 of the chamber wall 47 on the piston chamber-forming member 20 extends axially inwardly from the cylindrical first inner portion 110 of the chamber wall 47, the cylindrical second inner portion 109 of the chamber wall 47 having a diameter less than a diameter of the cylindrical first inner portion 110 of the chamber wall 47;

a second inner air sealing disc 140 on the stem 90 axially inwardly of the first outer air sealing annular flange 156 on the stem 90,

the second inner air sealing disc 140 extending radially outwardly from the stem 90 to an annular distal edge 144 in engagement with the cylindrical second inner portion 109 of the chamber wall 47 on the piston chamber-forming member 20;

the annular distal edge 144 of the second inner air sealing disc 140 engaging the second cylindrical inner portion 109 of the chamber wall 47 on the piston chamber-forming member 20 to prevent fluid flow axially inwardly therepast;

an inner air compartment 142 defined (a) annularly between the stem 90 of the piston-forming element 22 and the first cylindrical inner portion 110 and the second cylindrical inner portion 109 of the chamber wall 47 of the piston chamber-forming member 20, and (b) axially between the first inner air sealing annular flange 156 and the second inner air sealing disc 140.

18. A piston pump as claimed in claim 17 wherein:

a liquid sealing disc 139 on the stem 90 axially inwardly of the first inner air sealing disc 140;

the liquid sealing disc 139 extending radially outwardly from the stem 90 to an annular distal edge 145 in engagement with the cylindrical second inner portion 109 of the chamber wall 47 on the piston chamber-forming member 20 axially inwardly of the second inner air sealing disc 140;

the annular distal edge 145 of the liquid sealing disc 139 engaging the second inner portion 109 of the chamber wall 47 on the piston chamber-forming member 20 to prevent fluid flow axially inwardly therepast;

the liquid sealing disc 139 being resilient and having an inherent bias biasing the annular distal edge 145 into engagement with the second inner portion 109 of the chamber wall 47 and deflectable against the bias from engagement with the second inner portion 109 of the chamber wall 47 to permit liquid fluid flow axially outwardly therepast when a pressure differential between a pressure on an inner axial side of the liquid sealing disc 139 is sufficiently greater than a pressure on an inner axial side of the liquid sealing disc 139;

a one-way valve 102 across the liquid inlet 28 permitting fluid flow therepast from the reservoir 13 into the chamber 26 and preventing fluid flow therepast from the chamber 26 into the reservoir 13,

a liquid port 141 on the stem 90 axially between the liquid sealing disc 139 and the second inner air sealing disc 140;

the liquid port 141 extending radially inwardly through the stem 90 into the passageway 63;

the liquid pump 70 having a liquid compartment 106 open to the liquid port 141 and defined (a) annularly between the stem 90 of the piston-forming element 22 and the second inner portion 109 of the chamber wall 47 of the piston chamber-forming member 20, and (b) axially inwardly of the liquid sealing disc 139 between the liquid sealing disc 139 and the one-way valve 102;

in the cycle of operation in the withdrawal stroke, a volume of the liquid compartment 106 increases drawing liquid past the one-way valve 102 from the reservoir 13 into the liquid compartment 106 and, in the retraction stroke, the volume of the liquid compartment 106 decreases discharging liquid from the liquid compartment 106 past the liquid sealing disc 139 to between the liquid sealing disc 139 and the second inner air sealing disc 140 and through the liquid port 141 into the passageway 63.

19. A piston pump as claimed in claim 18 wherein:

the inner air pump 170 having a cylindrical inner air pump wall 110 provided by the piston chamber-forming member 20,

a first inner air sealing disc 156 extending radially outwardly on the stem 90 axially outwardly of the inner air port 142 for sealing engagement with the inner air pump wall 110;

the first outer air sealing disc 256 extending radially outwardly on the stem 90 axially outwardly of the first inner air sealing disc 156 of the inner air pump 170;

the first outer air sealing annular flange 203 on the piston chamber-forming member 20 being axially outwardly of the first inner air sealing disc 156 of the inner air pump 170,

the first outer air sealing annular flange 203 extending radially inwardly for sealing engagement with the radially outwardly directed stem wall 152 of the stem 90 axially outwardly of the first inner air sealing disc 156 of the inner air pump 170;

the first inner air sealing disc 156 extending radially outwardly on the stem 90 above the second inner air sealing disc 140 of the inner air pump 170 into sealing engagement with the cylindrical outer air pump wall 110 provided by the piston chamber-forming member 20 axially inwardly of the outer air sealing annular flange 203.

20. A piston pump as claimed in claim 19 wherein:

the piston-forming element 22 comprises;

a liquid piston 130 having a hollow tubular stem 131 with the inner end 134 and an outer end 135 and a central passage 133 longitudinally therethrough about the axis 23,

an inner air piston 150 having a hollow tubular stem 151 with an inner end 154 and an outer end 155 and a central passage 153 longitudinally therethrough about the axis 23, and

a first outer air piston 250 having a hollow tubular stem 251 with an inner end 254 and the outer end 255 and a central passage 253 longitudinally therethrough about the axis 23,

the liquid piston 130, the inner air piston 150 and the first outer air piston 250 coaxially disposed about the axis 23 with;

(a) the outer end 135 of the liquid piston 130 coupled to the inner end 154 of the inner air piston 150 and the outer end 155 of the inner air piston 150 coupled to the inner end 254 of the first outer air piston 250, and

(b) the central passage 133 of the liquid piston 130 opening axially into the central passage 153 of the inner air piston 150 and the central passage 153 of the inner air piston 150 opening axially into the central passage 253 of the first outer air piston 250 forming the central passageway 63 through the liquid piston 130, the inner air piston 150 and the first outer air piston 250,

the first outer air sealing disc 256 carried on the inner end 254 of the first outer air piston 250 extending radially outwardly from the stem 251;

the first outer air port 162 on the inner air piston 150 proximate but axially inwardly of the first outer air sealing disc 256,

the piston chamber-forming member 20 comprising;

a hollow tubular inner casing 101 having the end 24 and an outer end 105, and

a hollow tubular first outer casing 201 having an inner end 204 and the outer end 205;

the inner casing 101 defining a liquid chamber 106 and an inner air chamber 107 therein, the liquid chamber 106 axially open to the inner end 24 of the inner casing 101 and opening axially inwardly into the inner air chamber 107 which is open to the outer end 105 of the inner casing 101;

the first outer casing 201 defining a first outer air chamber 207 therein,

the inner casing 101 and the first outer casing 210 coaxially disposed about the axis 23 with;

(a) the outer end 105 of the inner casing 101 coupled to the inner end 204 of the first outer casing 201, and

(b) the inner air chamber 107 opening axially into the first outer air chamber 207;

the first annular air sealing flange 203 coaxially carried by the first outer casing 201 fixed to the first outer casing 201 at the inner end 204 of the first outer casing 201,

the stem 151 of the inner air piston 150 passing coaxially through the first annular air sealing flange 203 axially inwardly of the first outer air sealing disc 256,

the first annular air sealing flange 203 extending radially inwardly from sealed engagement with the first outer casing 201 into engagement with the stem 151 of the inner air piston 150 axially inwardly of the first outer air port 162,

the first outer air chamber 207 defined in an annular space radially inside the first outer casing 201 between the first outer casing 201 and the stem 151 of the inner air piston 150 and axially between first annular air sealing flange 203 and the first outer air sealing disc 256,

the first outer air chamber 207 open via the first outer air port 162 into the passageway 153.