US3640433A

US3640433A - Beverage dispenser for metering a plurality of liquids

Info

Publication number: US3640433A
Application number: US842793A
Authority: US
Inventors: Joseph J Rodth
Original assignee: Coca Cola Co
Current assignee: Coca Cola Co
Priority date: 1969-07-11
Filing date: 1969-07-11
Publication date: 1972-02-08
Anticipated expiration: 1989-02-08
Also published as: FR2055371A5; NL7010319A; NL160784C; DE2033445A1; BE754736Q; NO136184C; CH529063A; BE753206A; GB1320017A; NO136184B; ES381714A1; AT309258B; NL160784B

Abstract

Apparatus including a plurality of coaxial pistons reciprocable in unison in a chamber of a pump body for simultaneously admitting different fluids to and discharging them from the chamber, the pistons defining fluid-metering compartments and an operating compartment in the chamber, means for supplying fluids to the chamber including a tank for one of the fluids, and supply and return means including a conduit in permanently open communication with the operating compartment for alternatively supplying said one fluid in raw condition thereto for operating the pistons and for returning said one fluid when spent to the tank to be conditioned for subsequent discharge.

Description

I United States Patent [151 3,640,433

Rodth Feb. 8, 1972 [54] BEVERAGE DISPENSER FOR 2,566,436 9/l95l Waite ..222/l29.2 X METERING A PLURALITY OF LIQUIDS 3,162,336 12/1964 Erickson.. ..222/386.5 X

, 16,890 10 I940 Ph'll' [72] Inventor: Joseph J. Rodth, Swansea, Mass. 2 2 I I lpps 222,133

[73] Assignee: The Coca-Cola Company, Atlanta, Ga. Primary Examiner R0be" Reeves Assistant ExaminerDavid A. Scherbel [22] Wed: July 1969 Attorney-Prutzman, Hayes, Kalb&Chilton [2]] Appl. No.: 842,793

ABSTRACT Related U.S. Application Data Apparatus Including a plurality of coaxial pistons reclprocable [63] commuatlon'm'pan of 631,219, 7, in unison in a chamber of a pump body for simultaneously ad- 1967' abandonedmitting difierent fluids to and discharging them from the chamber, the pistons defining fluid-metering compartments [52] [1.5. CI ..222/ 129.2, 222/129.4, 222/ l 37, and an operating compartment in the chamber means for mt Cl plying fluids to the chamber including a tank for one of the a u I I I s I s s 1 I s I s I t t t t t Q t t a [58] Field of 5 manently open communication with the operating compartment for alternatively supplying said one fluid in raw condition thereto for operating the pistons and for returning said [56] References cued one fluid when spent to the tank to be conditioned for sub- UNITED STATES PATENTS sequent discharge- 2,427,429 9/1947 Waite et al ..222/ I 29.2 X 39 Claims, 9 Drawing Figures Milt UlltHI'l'I'lhhH'. ill'li'l'l l l i l l PATENTED FEE 8 I372 3.640.433 SHiE-E if]? 6 llllllll l INVENTOR. JOSEPH J RODTH WW 7 ATTORNEYS PATENTED FEB 81872 saw 2* av 6 PATENTED FEB 8 m2 am? 3 BF 6 PATHEQ FEB @1972 BEVERAGE DISPENSER FOR METERING A PLURALITY F LIQUIDS This application is a continuation-in-part of applicant's prior copending application Ser. No. 681,219, filed Nov. 7, 1967, now abandoned and assigned to the assignee of this invention.

This invention generally relates to beverage dispensers and particularly concerns a dispenser for discharging two or more different liquids in a blended mixture of preselected proportions.

A principal object of this invention is to provide an improved beverage dispenser particularly suited for mixing precisely measured proportions of two or more different fluids at the moment of serving.

Another object of this invention is to provide an improved dispenser of the above-described type capable of trouble-free dependable operation in dispensing blended beverages in high speed operating cycles.

Still another object of this invention is to provide such a dispenser which discharges a mixture of liquids, one of which may be heated almost to its boiling point, and which is particularly suited to discharge such liquids in precisely metered amounts without danger of vaporizing the heated liquid.

A further object of this invention is to provide an improved beverage dispenser having minimal energy requirements and wherein one of the fluids to be conditioned and dispensed is actually used in a raw condition as an actuating fluid for effecting an operating cycle and is then recycled to be conditioned and subsequently dispensed in a beverage.

A still further object of this invention is to provide a metering pump which not only meters and dispenses fluids in measured proportions but also serves to assist in maintaining a desired fluid level in a tank which receives spent actuating fluid to be conditioned for subsequent discharge in a beverage.

Another object of this invention is to provide a dispenser capable of simultaneously dispensing hot water and a cold concentrate and wherein the arrangement of parts is particu larly suited to separately maintain each of the liquids at selected uniform temperatures under widely varying conditions until they are mixed and discharged.

A still further object of this invention is to provide an improved metering pump of rugged compact construction having a minimum number of moving parts and which exhibits significantly improved operating characteristics in positively dispensing different fluids.

Still another object of this invention is to provide a metering pump of the above-described type which is quick and easy to assembly and service.

Other objects will be in part obvious and in part pointed out more in detail hereinafter.

A better understanding of the invention will be obtained from the following detailed description and the accompanying drawings of illustrative applications of the invention.

In the drawings:

FIG. 1 is a schematic view, partly in section and partly broken away, showing one embodiment of a dispenser constructed in accordance with this invention and wherein the dispenser is shown in a loaded condition;

FIG. 2 is a view similar to FIG. 1 showing the dispenser in a discharged condition;

FIG. 3 is an enlarged section view, partly broken away, showing details of a metering pump embodied in this invention;

FIG. 4 is an enlarged section view, partly broken away, showing details of a discharge nozzle embodied in this invention;

FIG. 5 is an enlarged view, partly in section and partly broken away, showing another embodiment of a dispenser incorporating this invention;

FIG. 6 is an enlarged section view showing a pump housing extension arrangement;

FIG. 7 is an enlarged section view showing a piston seal construction of the metering pump;

FIG. 8 is a reduced side view of a liquid level control incorporated in this invention; and

FIG. 9 is a top view ofthe liquid level control of FIG. 8.

Referring to the drawings in detail wherein one embodiment of a dispenser incorporating this invention is shown in FIGS. 1-4, it will be understood that a housing, not shown, may be provided for supporting and enclosing various operating components (schematically illustrated in FIGS. 1 and 2) in operative assembled relation. While the dispenser is capable of quickly and positively discharging fluids of various types in different applications, it is particularly suited for dispensing both hot and cold liquid beverages. The term beverage will be understood to include a variety of consumable liquids such as coffee, soup, beer, fruitjuices, vegetable juices, milk, tea and similar liquid foods and drinks. Separate metered quantities of either hot or cold liquids may be dispensed from each metering compartment of the dispenser, but for purposes of illustration, the embodiment shown in FIGS. 1-4 will be described in connection with the metering and dispensing of separate slugs of hot water and cold concentrate, or syrup, to provide a blended hot beverage.

To effect precision metering and simultaneous discharge of water and beverage concentrate in precisely proportioned quantities for a single serving, a two-stroke cycle-metering pump 10 is provided in accordance with this invention as best seen in FIG. 3. The pump 10 has a tubular body 12 and an attached coaxial housing portion 14 jointly defining a longitudinally extending chamber 16 wherein a piston subassembly is received for reciprocating movement.

The piston subassembly includes a water piston 18 of U- shaped half-section opening toward the housing portion 14 and a concentrate piston 20 which is of reduced size and is reciprocable within a cylindrical liner 22 preferably formed of stainless steel for increased abrasion resistance while minimizing any resistance to piston movement. The liner 22 projects beyond housing portion 14 and into a concentrate plug 24 suitably fixed to the housing portion 14 by a nut 26 tightly drawn up against a snapring 28 fixed around the concentrate plug 24.

Concentrate inlet and outlet fittings 30, 32 are provided in the concentrate plug 24, and in the preferred embodiment, the inlet fitting 30 is shown having a check valve 34 exclusively providing one-way flow of concentrate into the plug 24 through a supply line 35 connected to an insulated concentrate tank 36 (FIGS. 1 and 2) shown having a conventional heat-absorbing unit 37 for maintaining the concentrate in a refrigerated condition until discharged in a drink. Other arrangements, of course, could be provided, e.g., wherein a container is simply positioned within a refrigerated compartment of the dispenser so that the container may be readily removed and replaced for purposes of repair, cleaning or refilling with any one of a number of different beverage concentrates. If desired, the tank 36 could also be adapted to serve as a source of concentrate to be dispensed at room temperature or even at elevated temperatures depending on the uses to which the dispenser is to be applied.

A throw adjustment screw 38 is threadably secured in a sleeve 40 pinned within an end of the plug 24. The screw 38 may be set to project a preselected distance beyond an inner end of the sleeve 40 and then locked in position by a hex nut 42 to provide a left-hand stop for the concentrate piston 20 defining a discharged position for the piston subassembly.

The piston 20 is secured by a pin 44 to an axially extending connecting rod 46 integrally fixed to a circular end plate 48 of a cylindrical hub 50 of the water piston 18 which is reciprocable within chamber 16 to an extent limited by the throw adjustment screw 38 and a spacer plug 52 coaxially mounted inside the water piston hub 50 to provide a right-hand stop defining a loaded position for the piston subassembly. The spacer plug 52 is secured to an end plate 54 fixed to body 12 by a retaining ring 56 secured within an annular end cap 58 suitably retained on the right-hand end of the body 12.

To provide a radially self-centering piston subassembly virtually free of frictional resistance to piston movement, the water piston 18 in the preferred embodiment is supported by a rolling diaphragm comprising an outer diaphragm sac 60 and an inner diaphragm sac 62, each of which are clamped at one of their ends against end cap 58 and the spacer plug 52, respectively, by outer and inner peripheral portions of a disk 64 fixed in position between end plate 54 and a shoulder on the end cap 58. The diaphragm sacs 60, 62 have meeting ends secured to an end wall portion of the water piston 18 by a clamping flange 66 retained by a screw stud and locking hex nut arrangement 68.

While the diaphragm sacs 60, 62 can be formed of any suitable strong, tough flexible material, polymers and copolymers of polypropylene are preferred and have been found to work satisfactorily to effectively maintain the piston subassembly in frictionless self-centering alignment relative to the longitudinal axis of the chamber 16.

To assist self-centering reciprocating movement of the pump 10, a perforated guide tube 70 is coaxially received within the chamber 16 and has a flared end 71 abutting housing portion 14 for seating one end of a return compression spring 72 coiled about the guide tube 70 and the water piston hub 50. It is to be noted that the guide tube 70 additionally serves to maintain the return spring 72 in proper position. To continuously urge the water piston 18 toward its loaded position (FIGS. 1 and 3), an opposite end of the return spring 72 seats against an annular thrust plate 74 in abutment with a ball bearing assembly 76. The latter is mounted on the end wall portion of the diaphragm supported water piston 18, permitting it to seek a properly oriented angular position independently of the continuously applied biasing force of the return spring 72 to minimize undesired twisting of the rolling diaphragm.

To maintain the ball bearing assembly 76 in assembled relation when the pump is stripped for servicing, the thrust plate 74 is preferably maintained against excessive axial movement by a bearing retaining ring 78 secured to a peripheral wall portion of the water piston 18.

The piston and the diaphragm-supported water piston 18 thus divide chamber 16 into separate concentrate and

watermeasuring chamber portions

80, 82 and a rear operating chamber portion 84, the pistons 18, 20 and their respective chamber portions or compartments being of predetermined sizes for precisely metering measured quantities of concentrate and water in a fixed preselected ratio which may be controlled in volume by setting the throw adjustment screw 38. The forward concentrate compartment 80 is provided with separate concentrate inlet and outlet fittings 30 and 32 as described above, and the intennediate water compartment 82 is also provided with separate inlet and outlet fittings 86 and 88 secured to the body 12 and the housing portion 14 respectively.

While not described in detail, suitable fluidtight seals and packing rings are provided as shown in the drawings to ensure against undesired fluid leakage between component body parts as well as between the different compartments of the chamber 16 and their respective fittings in accordance with well-known conventional techniques.

Radial mounting flanges 89 are shown in the specific illustrated embodiment integrally formed on the housing portion 14 in abutting engagement with the body 12 for quick and easy mounting of the pump 10 to a wall of a second tank 90.

For illustrative purposes, the tank 90 is shown having a suitable heating unit 91, although it is to be understood that the dispenser could be easily modified to permit tank 90 to serve in a diflerent capacity, e.g., wherein another cold liquid is desired to be mixed with the refrigerated concentrate to provide a blended, cold beverage.

In this specifically illustrated first embodiment, water will be understood to be contained in tank 90, and the water, like the concentrate, is desirably maintained at a uniformly controlled preselected temperature with minimal heat transfer between the water and the concentrate. For this purpose, the water tank is arranged in spaced isolated relation to the concentrate tank 36. The body 12 and its inlet fitting 86 are received within the confines of the water tank 90 with the body 12 being in good heat-conducting relation to the heated water contained within the tank 90.

To operate the pump 10 at high-speed dispensing cycles with minimal energy requirements, as well as to provide for minimum water consumption, a common supply and tank return conduit 92 is connected in permanently open communication with the operating compartment 84 for supplying tap water under pressure to drive the piston subassembly from its loaded position (FIGS. 1 and 3) to its discharged position (FIG. 2). Thereafter, the spent tap water returns from the operating compartment 84 via conduit 92 to the water tank 90 to be heated such that it is conditioned to be dispensed in a subsequent cycle. Moreover, the fluid circuit of the preferred embodiment is particularly suited for operation wherein ordinary city water is supplied at approximately 35 p.s.i. to 15 p.s.i. gage pressure.

More specifically, the supply and tank return conduit 92 is connected to an open service port 94 in a solenoid-operated main flow control valve 96. The main control valve 96 has a normally closed inlet port 98 communicating with an ordinary water supply line 100, preferably provided with a pressureregulating valve 102, and a normally open outlet port 104 of the main control valve 96 is connected with the water tank 90. Immediately downstream of the pressure-regulating valve 102 is a branch inlet line 105 for supplying water to the tank 90, excessive flow being accommodated by an overflow line 103 connected to a suitable drain, not shown. The inlet water is controlled by a float-operated valve 106 in the line 105 to assist in maintaining a substantially constant volume within the tank 90.

The main control valve 96 is provided with suitable electrical connections to be energized in response to a demand signal in a well-known manner. Energization of the main valve 96 causes a valve member 107 to shift from an OFF position shown in FIG. 1 to an ON position shown in FIG. 2, closing outlet port 104 to the water tank 90 and simultaneously opening inlet port 98 to direct water under full line pressure through service port 94 and conduit 92 into the operating compartment 84 of the pump 10. Pistons 18 and 20 are immediately thrust forward against the spring force into discharged position to simultaneously dispense cold concentrate and hot water from the pump 10 through their respective outlets 32 and 88.

During this power stroke, the fluid circuit inlets to the concentrate and

water compartments

80, 82 of the pump 10 are closed. While the check valve 34 effectively prevents reverse flow of concentrate into tank 36, the inlet 86 to the water compartment 82 is closed off to the water tank 90 by a valve member 108 of a solenoid-operated auxiliary control valve 110 seating against a normally open working port 112 between a pump inlet line 114 and a hot water conduit 116 extending upwardly in the tank 90 for conducting hot water from the top of the tank 90 into the water compartment 82 of the pump 10. Although the auxiliary control valve 110 is normally open, it is energized in phase with the main control valve 96 to close off the inlet 86 between the pump 10 and the tank 90 during the power stroke of the pump.

Upon deenergizing the control valves 96 and 110, auxiliary valve 110 opens working port 112 connecting water compartment 82 to the tank 90, and the main valve 96 returns to its normal position shown in FIG. 1, closing inlet port 98 against the full line supply pressure. Thus, it will be seen that piston 18 is returned under the force of the return spring 72 after the working port 112 of the auxiliary control valve 110 shifts back to its normally opened position and the main control valve 96 shifts to close off the supply water and open the outlet port 104, whereby the spent raw water in operating compartment 84 immediately discharges into the water tank 90 via the permanently open supply and return tank conduit 92 upon return of the water piston 18 into loaded position. Accordingly, a normally open passageway under normal atmospheric pressure is established between the water compartment 82 and the water in the tank 90 before piston 18 returns under the action of the return spring 72.

While the water in the tank 90 may be heated to a temperature near boiling, any tendency of the water in the conduit 114 to flash or vaporize within a partially evacuated water compartment 82 during a return stroke of the pistons is completely eliminated, thereby to overcome a problem normally associated with the use of conventional pressure-responsive check valves in conduits such as at 116. Such problems are particularly troublesome at high elevations when even a slight suction in the water compartment 82 tends to cause vaporization of hot water past a conventional check valve. The abovedescribed construction utilizing the disclosed solenoidoperated auxiliary control valve 110 thus serves to ensure a uniform volume discharge of water in metered quantities from the pump and avoids even slight variations in the volume of water being discharged during a succession of servings.

During this return stroke, the pressure in the concentrate and

water compartments

80 and 82 drops and the resultant differential pressure causes new charges of concentrate and water to be automatically injected into the pump 10 through their respective inlets 30 and 86, thereby conditioning the pump 10 for the next dispensing cycle. Due to the abovedescribed diaphragm mounting of the water piston 18, the return stroke of the pump 10 is accomplished in about 2 seconds. A bleed passage 117 is formed in spacer plug 52 to provide pressure relief behind the water piston (FIG. 2). By virtue of the common supply and return conduit 92, the need for complex valving normally associated with apparatus of this type is eliminated while additionally minimizing the number of moving parts.

The return discharge of the spent raw water materially assists in maintaining a water supply of constant volume and of a closely controlled uniform temperature in tank 90. To ensure that the dispenser can be operated under dry stand" conditions even when a drain such as at 103 is unavailable to pipe off overflow water, a predetermined differential in the volume of cold and hot water on opposite sides of the water piston 18 is provided by spacer plug 52. That is, the volume of relatively cold raw water required to fill the operating compartment 84 to drive the piston 18 is less than the volume of hot water which fills the water compartment 32. Accordingly, less cold water will be discharged into tank 90 during a return stroke of the piston 18 than the volume of hot water removed from tank 90 to fill the water compartment 82 for subsequent discharge. The volume differential between the operating compartment compensates for 84 and the water compartment 82 thus compensates volume expansion of the raw water discharged into tank 90 as the temperature of the raw water is increased to be conditioned to be drawn into the water-metering compartment 82. Such construction also serves to maintain a substantially constant liquid level in the tank 90 even when a number of servings are being made in relatively quick succession. However, it will be appreciated that steady, prolonged operation of a pump having the disclosed differential in its water and operating compartments would gradually empty the tank 90, and the provision of the previously described valve 106 serves to maintain the desired liquid level in the tank 90.

Referring now to FIG. 4 in conjunction with FIGS. 1 and 2, the outlet fittings 32 and 88 from the concentrate and

water compartments

80 and 82 are connected by

outlet lines

118 and 120 to a serving nozzle 122, a suitable check valve 124 being provided in the water outlet line 120 downstream of the pump 10 to prevent water flowing back into water compartment 82 during the return stroke of the pump 10.

Specifically, the serving nozzle 122 is provided with an adapter 126 connected to the outlet line 118. The adapter 126 is fitted within a tubular housing 128 and secured in position by a nut 130 threadably connected to the housing 128. At the lower axial end of the adapter 126, a sleeve 132 is fitted within the housing 128 for receiving a ball 134 serving as a check valve with the ball 134 being continuously urged toward sealing engagement with the lower axial end of the adapter 126 under a biasing force of a coil compression spring 136 seated on a reduced collar portion ofa perforated seal holder 138.

Thus, the outlet line 118 is normally closed off from a mixing chamber 140 formed within the serving nozzle 122, while yet permitting one-way flow of concentrate into the mixing chamber 140 during a power stroke of the pump 10, whereby measured quantities of concentrate and water are turbulently mixed before being dispensed as a blended beverage through a discharge orifice 141 at a downstream end of the nozzle 122. Fluidtight connections between the above-described cooperating parts are ensured by the provision of suitable elastomeric O-ring seals such as at 139.

As will be recognized by those skilled in the art, a longstanding difficulty in utilizing a concentrate such as a coffee or tea concentrate, soup syrups, beer and other liquid beverage concentrates is that the concentrate or syrup solidifies or is chemically changed upon being exposed to air and essentially forms a high-grade protein glue. To overcome this objectionable difficulty, a lipped seal 142, formed of a tough resilient material, is mounted inside the lower axial end of the housing 128 and maintained in place by the seal holder 138, and an expandable tip 144 is provided for the seal 142 to project into the mixing chamber 140 such that the tip 144 is disposed in the water path downstream of the water inlet to the mixing chamber 140.

By virtue of this construction, the seal 142 directs concentrate flow into the nozzle 122 during a power stroke of the pump 10 while otherwise effectively preventing air passing upstream of the seal 142 from the mixing chamber 140 as well as minimizing undesired concentrate leakage into the mixing chamber. The seal 142 is relieved from the pressure head of the concentrate in the outlet line 118 by the above-described ball check arrangement 134, and with the tip 144 being disposed in the water path, it will be seen that the seal tip 144 is provided a water wash to prevent excessive accumulation of concentrate and ensure a dependable controlled delivery of the beverage concentrate at the serving nozzle 122.

Referring now to another embodiment of the dispenser pump as shown in FIGS. 5-9, by virtue of the above-described construction and arrangement of parts, an additional, third metering compartment 200 is readily formed in the pump 202 for dispensing three different fluids with minimal structural changes to the body of the pump 202.

The third metering compartment 200 is shown defined in part by an imperforate sleeve 204 coaxially fixed within the chamber 206 between the rear fluid compartment 208 and the forward fluid compartment 210, and a piston 212 is received within the sleeve 204 and secured on a forward end of hub 214 of rear piston 216 for simultaneous reciprocable movement therewith. As in the previous embodiment, piston 216 separates the rear fluid compartment 208 from the rear operating compartment 218.

To ensure that any undesired heat transfer among the fluids to be dispensed is minimized, the forward piston 220 is secured by a pin 221 to a rearwardly extending body 222, and an intermediate metering pump housing portion 224, also of extended length and preferably formed of a material such as plastic having low thermal conductivity, is suitably secured between the

end housing portions

226 and 228 surrounding

compartments

208 and 210. In the illustrated preferred embodiment, the forward piston 220 includes an elongated body 222 having a length greater than its stroke. A piston cup seal 230 at an end of the piston 220 prevents fluid flow between

compartments

200 and 210 past the piston 220.

A check valve housing 232 is threadably secured to the intermediate housing portion 224, and intake and discharge check valves 234i, 236 are fitted within the check valve housing 232 for communicating with a passage 238 connecting to the third metering compartment 200 of the pump.

To provide lubrication for the piston 220 in an essentially self-lubricating manner while yet minimizing any unintended heat transfer between highand low-temperature portions of the pump, a minimal clearance of predetermined dimension, say, not greater than 0.005 inch may be intentionally introduced at 240 between the forward piston body 222 and its guide sleeve 242 for maintaining therebetween a thin annular lubricating film of fluid from compartment 200. The essentially negligible mass of the fluid film not only eliminates any turbulence but also prevents unacceptable heat transfer through the film.

Thus, when the piston subassembly moves forwardly toward a discharged position, proportionally metered fluid will simultaneously flow through the discharge check valve 236 at the time the rear and

forward compartments

208 and 210 are being discharged, to make a blended three part mixture. When the piston subassembly returns, the intake check valve 234 permits compartment 200 to be filled. Intake and discharge from the

other metering compartments

208, 210 and the operating compartment 218 is effected as described in the previous embodiment.

If the dispenser pump is to be used for dispensing a variety of cold drink mixtures in blended proportions, a relatively high rate of heat exchange may be desired between the pumphousing portions, and in this regard still another modification of the metering pump housing is shown in FIG. 6 wherein a metal extension sleeve 244 of high thermal conductivity is threadably secured to the body of an' intermediate housing portion 246 which, if desired, also may be formed of metal or a similar material having a low resistance to heat transfer to promote such heat transfer between the housing components of the metering pump.

The body of the forward housing portion 228 may also be extended in length to readily permit the housing portion to be positioned in its entirety within a heated or refrigerated part of the dispenser in spaced isolated relation to the intermediate housing portion 224 of the pump.

When it is also desired to locate the concentrate discharge check valve (such as that shown at 134 in the previous embodiment) in a remote position from the discharge outlet of the dispenser, an open capillary line such as at 248 is preferably connected to the dispenser outlet (not shown in FIG. Capillary action is relied upon to hold concentrate in the line, and the concentrate compartment, e.g., the forward compartment 210 of the illustrated pump, is provided with a suitably modified outlet incorporating a pressure-responsive mechanical check valve 250 at the forward extremity of the chamber 210.

To reduce any tendency of a portion of the concentrate remaining in the forward compartment 210 for any prolonged period of time, the throw adjustment device 252 disclosed in FIG. 5 provides an additional advantage ensuring that the forward piston 220 will always travel to the forward extremity of the chamber 206 during each power stroke of the pump regardless of the adjusted position of the tubular throw adjusting screw 254. For this reason, the screw 254 is adjustably mounted in fixed relation to the end wall 255 of the pump 202 to provide a variable stop limiting the return of the piston subassembly from discharged to loaded positions when piston shaft 256 engages end 257 of screw 254. The latter is releasably locked by a clamp nut 258 which upon being loosened from a fixed nut 259 permits longitudinal adjustment of the screw 254 coaxially within a tubular stem 260 of a fluid displacement member or piston 262 fixed within the movable piston hub 214. Forward movement of the piston subassembly terminates when piston 212 engages an internal boss 264 within the intermediate housing portion 224. It will also be noted that both sides of the piston 262 may be desirably wetted by virtue of the tubular screw 254 which is suited to extend beyond the end wall 255 for immersion in a fluid tank such as tank 90 in the first embodiment.

Such construction ensures that only a minimal amount of concentrate remains in the pump 202 after each power stroke thereby providing for self-purging and further minimizing any possibility of a chemical change in the concentrate which might affect the nature of the beverage being served, particularly those beverages which have only a narrow latitude of taste tolerance.

As in the previously described embodiment, the diameter of the displacement piston 262 is of a predetermined size, much like that of the spacer plug 52, to provide a desired differential in the volumetric quantities of the fluids which are to be passed through the pump 202 on opposite sides of rear piston 216. The displacement piston stem 260 is shown threadably secured to the nut 259 to fix the displacement piston 262 in position within the chamber 206. Adjustment of the effective maximum volume of the operating compartment 218 may be effected by providing a displacement piston of a different diameter, and adjusting the inside diameter of the piston hub 214 correspondingly.

Additional modifications which will be noted in the second embodiment of the pump 202 include a variety of different piston seal constructions. A piston cup arrangement is shown provided on the relatively large rear piston 216 which incorporates back-to-back cup seals 266, 268 of C-shaped half-section, preferably of plastic, secured between a pair of

plates

270, 272 clamped in position against a shoulder 274 of the piston hub 214 by means of a nut 276 threaded onto the rear end of the piston hub 214. The diameter of the

plates

270, 272 are dimensioned to provide a preselected clearance relative to the inside wall of the rear housing portion 226 whereby the perimeter of each

piston cup seal

266, 268 readily expands under pressure radially outwardly against the cylinder wall to provide a reliable seal of increased integrity, while readily providing sliding contact within the rear housing portion 226.

Another modification of a piston seal arrangement is shown wherein a slipper ring 278 (FIGS. 5 and 7) is fitted about the piston 212 received in the third metering compartment 200. It will be noted that a prestressed O-ring 280 is fitted within a circumferentially extending groove 282 in the piston 212, and a plastic slipper ring 278 of U-shaped half section is fitted over the O-ring 280 to extend about the piston 212, providing a dry, self lubricating bearing surface for sliding contact with the inside wall of the sleeve 204.

Still another modified piston cup seal construction is shown formed on the displacement piston 262 and on the forward piston 220. In both constructions, cup seals such as at 230 and 284 are fixed coaxially of their respective pistons in contact engagement with their cylinder walls to efiectively prevent fluid leakage past the pistons regardless of whether the piston is intended to be fixed or slidably mounted within the chamber 206 of the pump 202.

Each of the above-described piston seal constructions are preferably formed of a suitable, commercially available, dry bearing plastic material exhibiting low-abrasive characteristics and minimal deformation under load while possessing high wear resistance and high compressive strength over a wide range of temperatures to provide a suitable low-friction piston seal.

An alternate valve control system for automatically introducing controlled quantities of fluid on a demand basis into a tank is also shown in FIGS. 8 and 9 in conjunction with this second embodiment. A support bracket 286 is secured to a sidewall of a tank 288 (which could be a tank similar to that of tank in the first embodiment) to provide a fulcrum for a generally L-shaped pivot arm 290 of a float 292 which causes the arm 290 to move toward and away from the sidewall of the tank 288 respectively in response to the float 292 being lowered and raised by the fluid level (such as indicated by broken line 294) within the tank 288.

To automatically control the fluid level within the tank 288, a solenoid operated control valve 296 is provided in a supply line 298 leading to a feed tube 300 for introducing supply fluid to the tank 288 from an outside source. To selectively open and close the control valve 296, a magnetically actuated reed switch 302 is connected in series with a suitable source of electrical power (not shown) and with the solenoid winding of the control valve 296 whereby the latter will be operated in response to movement of the float assembly. Specifically, a magnet 304 carried on the float arm 290 causes the reed switch 302 to close and open when the magnet 304 is moved toward and away from the sidewall of the tank 288 by the action of the float 292, thereby to automatically open the supply line 298 when the float 292 is lowered to a predetermined level and shut off the flow of supply fluid when the increased height of the fluid within the tank 288 raises the float 292 to a preselected level.

In view of the abovedescribed embodiments it will be seen that a dispenser can be readily constructed in accordance with this invention for dispensing metered quantities of a plurality of different fluids each of which can be either hot or cold, depending on the requirements of the beverage desired to be dispensed. The beverage dispenser of this invention will be seen to be of rugged, compact construction which is quick and easy to assembly in addition to being capable of providing high speed, dependable operation over extended periods of time with minimal maintenance and service requirements.

As will be apparent to persons skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure can be made without departing from the teachings of the present invention.

lclaim:

1. An apparatus for simultaneously dispensing different fluids in a blended beverage of measured proportions and comprising a body having a chamber, a pumping member reciprocable in the chamber between loaded and discharged positions and dividing the chamber into a plurality of fluid measuring chamber portions and an operating chamber portion, fluid circuit means in communication with the measuring chamber portions for admitting different fluids to and discharging them simultaneously from the measuring chamber portions respectively, the fluid circuit means including a pres surized source of supply for one of the fluids, means for holding said one fluid for discharge, and a common inlet and outlet passage connected to the operating chamber portion and serving to communicate the operating chamber portion alternately to the source of supply, for driving the pumping member to discharged position, and to the holding means for conveying said one fluid thereto from the operating chamber portion for subsequent discharge.

2. The apparatus of claim 1 wherein said chamber portions are in coaxial alignment, and wherein the pumping members comprises a pair of coaxially spaced pistons and a connecting rodjoining the pistons to form a one-piece operating unit.

3. The apparatus of claim 1 wherein the pressurized source of supply includes a water tank, and wherein the apparatus further includes a concentrate tank in separated relation to the water tank, the fluid circuit means further including separate inlet passages and outlet passages connected to each of the measuring chamber portions for simultaneously admitting concentrate and water thereto when the pumping member moves to loaded position and simultaneously conducting discharged concentrate and water away from the measuring chamber portions when the pumping member moves to discharged position.

4. The apparatus of claim 3 further including a serving nozzle having a mixing chamber and a discharge orifice downstream thereof, the outlet passages of the measuring chamber portions respectively opening into the mixing chamber for independent delivery of accurately measured quantities of concentrate and water to be mixed and discharged in a blended beverage of measured proportions.

5. The apparatus of claim 3 wherein the fluid circuit means further includes valve means between the pressurized source of supply and the operating chamber portion for controlling longitudinal movement of the pumping member, and an additional valve means for closing the inlet passages to each of the measuring chamber portions during movement of the pumping member from loaded to discharged position.

ill

6. The apparatus of claim 1 wherein a metal extension sleeve of high thermal conductivity is secured to the body between the plurality of fluid measuring chamber portions so as to provide a high rate of heat exchange between said chamber portions.

7. An apparatus for simultaneously dispensing different fluids in a blended beverage of measured proportions and comprising a metering pump including a body having a longitudinally extending chamber, coaxially aligned pistons joined together for simultaneous reciprocating movement in the chamber between loaded and discharged positions and dividing the chamber into a plurality of fluid measuring chamber portions and an operating chamber portion, a plurality of isolated tanks respectively containing different fluids, inlet and outlet means for each of said chamber portions including separate inlet connections between the tanks and the fluid measuring chamber portions, respectively, and supply and return passage means connected with the operating chamber portion, a fluid supply line for supplying one of the fluids in a raw state under pressure, and a fluid valve in the supply and return passage means for alternatively connecting the operating chamber portion to the fluid supply line and one of the tanks to respectively drive the pistons into discharged position and, upon their return to loaded position, to exhaust spent raw fluid to said one tank for discharge in a subsequent dispensing operation:

3. The apparatus of claim 7 wherein said tanks include a water tank and a concentrate tank in isolated relation to the water tank, wherein heating means is provided for the water tank and heat absorbing means is provided for the concentrate tank, and wherein heated water and refrigerated concentrate are independently conducted to the measuring chamber portions of the pump, respectively, through the separate inlet connections thereto responsive to piston movement from discharged to loaded position.

9. The apparatus of claim 8 wherein a part of the body surrounding at least a portion of the water-measuring chamber portion of the pump is received within the water tank in good heat-conducting relation to its heated contents, the concentrate-measuring chamber portion being positioned in its entirety outside the confines of the water tank.

10. The apparatus of claim 8 wherein the fluid valve in the supply and return passage means is normally closed to the fluid supply line and normally open to the water tank, and wherein a second fluid valve is provided in the inlet connection to the water measuring chamber portion of the pump, the second fluid valve normally being open to permit communication between the water tank and the water-measuring chamber portion for charging the same with a supply of heated water to be discharged, said fluid valves being simultaneously operable to effect reversal of their operative positions for supplying raw water to the operating chamber portion while closing the water tank to both the operating and water measuring chamber portions during piston movement from loaded to discharge position,

11. The apparatus of claim 8 wherein the supply and return passage means is connected for exhausting spent raw water into a bottom portion of the water tank, and wherein the inlet connection for the water measuring chamber portion of the pump is connected to open into an upper portion of the water tank.

12. The apparatus of claim 7 further including a return spring received in the chamber and seated against the body and one of the pistons for continuously urging them toward loaded position.

13. An apparatus for simultaneously dispensing two different fluids in a blended beverage of measured proportions and comprising a metering pump including a body having a longitudinally extending chamber, a pair of coaxially spaced pistons and a connecting rod joining the pistons to form a onepiece operating unit longitudinally reciprocable in the chamber in unison between a loaded limit position and a discharged limit position, the pistons dividing the chamber into coaxial chamber portions including a pair of fluid-measuring chamber portions and an operating chamber portion, a return compression spring in the chamber continuously urging the pistons toward said loaded limit position, one of the pistons being of U-shaped half-section opening toward the spring and receiving the same in concentric relation thereto, fluid circuit means in communication with the measuring chamber portions for simultaneously admitting two different fluids to and discharging them from the measuring chamber portions respectively, the fluid circuit means including a fluid valve and a common supply and return passage connecting the fluid valve with the operating chamber portion for controlling longitudinal movement of the pistons, the common supply and return passage being in permanently open communication with the operating chamber portion and providing a highly responsive pumping action with minimal time delay.

14. The apparatus of claim 13 wherein said one piston has an annular end wall, and wherein a rolling diaphragm is secured to the body and to one side of the end wall of said one piston opposite the spring for supporting said one piston for frictionless, self-centering movement relative to the longitudinal axis of the chamber.

15. The apparatus of claim 14 wherein a ball bearing assembly is mounted on an opposite side of the end wall of said one piston with a thrust plate interposed between the spring and the ball bearing assembly, whereby said one piston is free to rotate relative to the spring for ensuring minimal twisting of the diaphragm.

16. An apparatus for simultaneously dispensing two different fluids in a blended beverage of measured proportions and comprising a metering pump including a body having a longitudinally extending chamber, a pair of coaxially spaced pistons and a connecting rod joining the pistons to form a onepiece operating unit longitudinally reciprocable in the chamber in unison between loaded and discharged positions, the pistons dividing the chamber into coaxial chamber portions including a pair of fluid-measuring chamber portions and an operating chamber portion, a guide tube coaxially mounted in the chamber between the pistons, one of the pistons being of U-shaped half-section having an elongated hub portion slidably received in the guide tube for maintaining the pistons in radially self-centering alignment in the chamber, and fluid circuit means in communication with the measuring chamber portions for simultaneously admitting two difi'erent fluids to and discharging them from the measuring chamber portions respectively, the fluid circuit means including a fluid valve and a common supply and return passage connecting the fluid valve with the operating chamber portion for controlling longitudinal movement of the pistons, the common supply and return passage being in permanently open communication with the operating chamber portion and providing a highly responsive pumping action with minimal time delay.

17. An apparatus for simultaneously dispensing two different fluids in a blended beverage of measured proportions and comprising a body having a chamber, a pair of pumping members movable in unison in the chamber between loaded and discharged positions and dividing the chamber into a pair of fluid-measuring chamber portions and an operating chamber portion, a water tank having heating means and a concentrate tank having refrigerating means, the water tank and concentrate tank each connected to one of the measuring chamber portions, common supply and return passage means connected with the operating chamber portion, a water supply line for supplying water under pressure, and a fluid valve alternatively connecting the common supply and return passage means to the water supply line and the water tank for alternately supplying water under pressure to the operating chamber portion to drive the pumping members into discharged position and for returning spent water to the water tank responsive to the pumping members moving into loaded position, whereby the spent water is heated for subsequent discharge.

18. The apparatus of claim 17 wherein a part of the body surrounding at least a portion of the water-measuring chamber portion is received within the water tank in good heat-conducting relation to its heated contents, the concentrate-measuring chamber portion being positioned in its entirety outside the confines of the water tank.

19. An apparatus for simultaneously dispensing different fluids in a blended beverage of measured proportions and comprising a body having a chamber, a pumping member movable in the chamber between loaded and discharged positions, the pumping member dividing the chamber into a plurality of fluid-measuring chamber portions and an operating chamber portion, the measuring chamber portions each having inlet and outlet means for simultaneously admitting different fluids to the measuring chamber portions and discharging the different fluids simultaneously from the measuring chamber portions respectively, a conditioning tank for treating one of the fluids and supplying the same for subsequent discharge, a pressurized source of supply for said one fluid, a passage between the operating chamber portion and the conditioning tank, and a valve in said passage alternatively connecting the operating chamber portion to the pressurized source ofsupply for said one fluid and the conditioning tank to respectively drive the pumping member into discharged position and, upon its return to loaded position, to discharge said one fluid to the conditioning tank to be treated for discharge in a subsequent dispensing operation.

20. An apparatus for dispensing a plurality of different fluids in a beverage of measured proportions and comprising a body having a chamber, pumping means movable in the chamber between loaded and discharged positions and dividing the chamber into a plurality of fluid compartments including an operating compartment, a tank, and heating means for heating the fluid in the tank, the tank being connected between the operating compartment and one of the other fluid compartments for receiving fluid from the operating compartment while additionally providing a source of heated fluid for said one fluid compartment for subsequent discharge in a beverage, the operating compartment having a maximum volume less than that of said one fluid compartment to compensate for fluid expansion upon heating the fluid received in the tank from the operating compartment, thereby promoting a constant fluid level in the tank.

21. The apparatus of claim 20 wherein a fluid displacement member is fixed within the operating compartment for establishing the volume differential between the operating compartment and said one fluid compartment.

22. The apparatus of claim 20 further including a fluid supply passage connected to the tank, and a fluid level control including valve means in said passage and control means for opening and closing the valve means responsive to the height of the fluid level in the tank between predetermined minimum and maximum levels of fluid in the tank.

23. The apparatus of claim 22 wherein the fluid level control includes magnetically actuated switch means for controlling the valve means, and a float controlled magnet for actuating the switch means.

24. The apparatus of claim 20 wherein the chamber extends longitudinally of the body and its fluid compartments are coaxially aligned, the pumping means being reciprocable in unison within the chamber between said loaded and discharged positions, and wherein a fluid displacement member is coaxially fixed within the body for providing the maximum volume differential between the operating compartment and said one fluid compartment.

25. The apparatus of claim 24 wherein throw adjustment means is releasably secured in a selected adjusted position on the fluid displacement member to provide a stop for the pumping means upon its return movements from discharged position to loaded position.

26. The apparatus of claim 20 further including throw adjustment means releasably fixed to the body in a selected adjusted position and providing a stop limiting movement of the pumping means between its loaded and discharged positions.

27. The apparatus of claim 26 wherein the stop provided by the throw adjustment means is positioned within the chamber for limiting return movements of the pumping means from its discharged position to its loaded position, permitting uninterrupted travel of the pumping means to a fully discharged position at an end of at least one of the fluid compartments for ensuring self-purging of said one fluid compartment irrespective of the adjusted position of the throw adjustment means.

28. The apparatus of claim 1 further including throw adjustment means providing a variable stop limiting movement of the pumping member between its loaded and discharged positions and adjusting the stroke of the pumping member therebetween for selectively adjusting the maximum volume of fluid discharged from the fluid compartments, the throw adjustment means permitting uninterrupted travel of the pumping means to a fully discharged position at an end of at least one of the fluid compartments for ensuring self-purging of said one fluid compartment irrespective of the adjusted stroke of the pumping means.

29. The apparatus of claim 28 wherein the throw adjustment means provides a stop for return movements of the pumping means from its discharged position to its loaded position.

30. An apparatus for simultaneously dispensing a plurality of different fluids in a blended beverage of measured proportions and comprising a body having a chamber, pumping means movable in the chamber in unison between loaded and discharged positions and dividing the chamber into a plurality of fluid compartments, fluid circuit means in communication with the fluid compartments for admitting fluids to and discharging them from the compartments, a fluid tank, a passage connecting the tank to one of the fluid compartments, and a valve in the passage for connecting the tank to said one compartment, the valve establishing an open passage after the pumping means is in discharged position but before return movement of the pumping means to loaded position.

31. The apparatus of claim 30 wherein the valve is operable independently of the pumping means.

32. The apparatus of claim 30 further including throw adjustment means providing a variable stop limiting movement of the pumping means between its loaded and discharged positions and adjusting the travel of the pumping means therebetween for selectively adjusting the maximum volume of fluid discharged from the fluid compartments.

33. The apparatus of claim 30 wherein electrically actuated solenoid means are provided for operating the valve.

34. The apparatus of claim 30 wherein the chamber extends longitudinally of the body, wherein the pumping means is reciprocable in the chamber and divides the chamber into three different fluid-measuring compartments and an operating compartment, the fluid-measuring compartments each having separate fluid inlet and outlet means, and the operating compartment having a common supply and return passage connected to the fluid tank.

35. The apparatus of claim 1 wherein the elongated pumping member includes at least two piston portions joined by a rod of reduced diameter reciprocable within the chamber and dividing it into separate fluid-measuring chamber portions, wherein the fluids dispensed from the fluid-measuring chamber portions are at different temperatures, one of the fluidmeasuring chamber portions having a maximum volume establishing a preselected measured quantity of fluid for discharge in a blended beverage, one of the piston portions corresponding to said one fluid-measuring chamber portion having a length greater than its stroke and minimizing thermal conduction between adjacent fluid-measuring chamber portions to promote discharge of the fluid from said one fluiddimensioned to provide a preselected maximum clearance between the said one piston portion and the chamber wall, and

wherein fluid from one of the fluid-measuring portion is received within said clearance to provide a thin lubricating fluid film for the said one piston portion.

37. The apparatus of claim 35 wherein a maximum clearance in the order of 0.00S-inch thickness exists between the said one piston portion and the chamber wall.

38. A metering pump usable in a beverage dispenser for simultaneously dispensing two different fluids in a two stroke cycle and comprising a body having a longitudinally extending chamber, a pair of coaxially aligned pistons reciprocable in the chamber and connected in longitudinally spaced relation for simultaneous movement between loaded and discharged positions, a flexible rolling diaphragm secured to the body and supporting one of the pistons for radially self-centering frictionless movement in the chamber, the diaphragm and said one piston jointly forming a movable partition within the chamber, the movable partition and the other of the pistons dividing the chamber into a pair of fluid-measuring chamber portions and an operating chamber portion, a guide tube coaxially mounted in the chamber between the pistons, said one piston being of U-shaped half-section having an elongated hub portion slidably received in the guide tube, the measuring chamber portions each having inlet and outlet means formed in the body for simultaneously admitting two different fluids to and exhausting them from the measuring chamber portions respectively, and a return spring in the chamber portions respectively, and a return spring in the chamber continuously urging the pistons toward loaded position, the return spring being coiled about the guide tube and urging said one piston into loaded position, whereby the guide tube assists in maintaining the pistons in radially self-centering alignment in the chamber while additionally supporting the spring to prevent excessive radial movement thereof.

39. A metering pump usable in a beverage dispenser for simultaneously dispensing two different fluids in a two-stroke cycle and comprising a body having a longitudinally extending chamber, a pair of pistons reciprocable in the chamber and connected in longitudinally spaced relation for simultaneous movement between loaded and discharged positions, a flexible rolling diaphragm secured to the body and supporting one of the pistons for radially self-centering frictionless movement in the chamber, the diaphragm and said one piston jointly forming a movable partition within the chamber, the movable partition and the other of the pistons dividing the chamber into a pair of fluid-measuring chamber portions and an operating chamber portion, the measuring chamber portions each having inlet and outlet means formed in the body for simultaneously admitting two different fluids to and exhausting them from the measuring chamber portions respectively, and a return spring in the chamber continuously urging the pistons toward loaded position, said one piston being of U-shaped half-section opening toward the spring and having an annular end wall, the rolling diaphragm being secured to a side of said end wall opposite the spring, and a ball bearing assembly being mounted on an opposite side of said end wall with a thrust plate interposed between the spring and the ball bearing assembly, whereby said one piston is free to rotate relative to the spring for ensuring minimal twisting ofthe rolling diaphragm.

Claims

1. An apparatus for simultaneously dispensing different fluiDs in a blended beverage of measured proportions and comprising a body having a chamber, a pumping member reciprocable in the chamber between loaded and discharged positions and dividing the chamber into a plurality of fluid-measuring chamber portions and an operating chamber portion, fluid circuit means in communication with the measuring chamber portions for admitting different fluids to and discharging them simultaneously from the measuring chamber portions respectively, the fluid circuit means including a pressurized source of supply for one of the fluids, means for holding said one fluid for discharge, and a common inlet and outlet passage connected to the operating chamber portion and serving to communicate the operating chamber portion alternately to the source of supply, for driving the pumping member to discharged position, and to the holding means for conveying said one fluid thereto from the operating chamber portion for subsequent discharge.

2. The apparatus of claim 1 wherein said chamber portions are in coaxial alignment, and wherein the pumping members comprises a pair of coaxially spaced pistons and a connecting rod joining the pistons to form a one-piece operating unit.

8. The apparatus of claim 7 wherein said tanks include a water tank and a concentrate tank in isolated relation to the water tank, wherein heating means is provided for the water tank and heat absorbing means is provided for the concentrate tank, and wherein heated water and refrigerated concentrate are independently conducted to the measuring chamber portions of the pump, respectively, through the separate inlet connections thereto responsive to piston movement from discharged to loaded position.

10. The apparatus of claim 8 wherein the fluid valve in the supply and return passage means is normally closed to the fluid supply line and normally open to the water tank, and wherein a second fluid valve is provided in the inlet connection to the water measuring chamber portion of the pump, the second fluid valve normally being open to permit communication between the water tank and the water-measuring chamber portion for charging the same with a supply of heated water to be discharged, said fluid valves being simultaneously operable to effect reversal of their operative positions for supplying raw water to the operating chamber portion while closing the water tank to both the operating and water measuring chamber portions during piston movement from loaded to discharge position.

13. An apparatus for simultaneously dispensing two different fluids in a blended beverage of measured proportions and comprising a metering pump including a body having a longitudinally extending chamber, a pair of coaxially spaced pistons and a connecting rod joining the pistons to form a one-piece operating unit longitudinally reciprocable in the chamber in unison between a loaded limit position and a discharged limit position, the pistons dividing the chamber into coaxial chamber portions including a pair of fluid-measuring chamber portions and an operating chamber portion, a return compression spring in the chamber continuously urging the pistons toward said loaded limit position, one of the pistons being of U-shaped half-section opening toward the spring and receiving the same in concentric relation thereto, fluid circuit means in communication with the measuring chamber portions for simultaneously admitting two different fluids to and discharging them from the measuring chamber portions respectively, the fluid circuit means including a fluid valve and a common supply and return passage connecting the fluid valve with the operating chamber portion for controlling longitudinal movement of the pistons, the common supply and return passage being in permanently open communication with the operating chamber portion and providing a highly responsive pumping action with minimal time delay.

16. An apparatus for simultaneously dispensing two different fluids in a blended beverage of measured proportions and comprising a metering pump including a body having a longitudinally extending chamber, a pair of coaxially spaced pistons and a connecting rod joining the pistons to form a one-piece operating unit longitudinally reciprocable in the chamber in unison between loaded and discharged positions, the pistons dividing the chamber into coaxial chamber portions including a pair of fluid-measuring chamber portions and an operating chamber portion, a guide tube coaxially mounted in the chamber between the pistons, one of the pistons being of U-shaped half-section having an elongated hub portion slidably received in the guide tube for maintaining the pistons in radially self-centering alignment in the chamber, and fluid circuit means in communication with the measuring chamber portions for simultaneously admitting two different fluids to and discharging them from the measuring chamber portions respectively, the fluid circuit means including a fluid valve and a common supply and return passage connecting the fluid valve with the operating chamber portion for controlling longitudinal movement of the pistons, the common supply and return passage being in permanently open communication with the operating chamber portion and providing a highly responsive pumping action with minimal time delay.

19. An apparatus for simultaneously dispensing different fluids in a blended beverage of measured proportions and comprising a body having a chamber, a pumping member movable in the chamber between loaded and discharged positions, the pumping member dividing the chamber into a plurality of fluid-measuring chamber portions and an operating chamber portion, the measuring chamber portions each having inlet and outlet means for simultaneously admitting different fluids to the measuring chamber portions and discharging the different fluids simultaneously from the measuring chamber portions respectively, a conditioning tank for treating one of the fluids and supplying the same for subsequent discharge, a pressurized source of supply for said one fluid, a passage between the operating chamber portion and the conditioning tank, and a valve in said passage alternatively connecting the operating chamber portion to the pressurized source of sUpply for said one fluid and the conditioning tank to respectively drive the pumping member into discharged position and, upon its return to loaded position, to discharge said one fluid to the conditioning tank to be treated for discharge in a subsequent dispensing operation.

35. The apparatus of claim 1 wherein the elongated pumping member includes at least two piston portions joined by a rod of reduced diameter reciprocable within the chamber and dividing it into separate fluid-measuring chamber portions, wherein the fluids dispensed from the fluid-measuring chamber portions are at different temperatures, one of the fluid-measuring chamber portions having a maximum volume establishing a preselected measured quantity of fluid for discharge in a blended beverage, one of the piston portions corresponding to said one fluid-measuring chamber portion having a length greater than its stroke and minimizing thermal conduction between adjacent fluid-measuring chamber portions to promote discharge of the fluid from said one fluid-measuring chamber portion at a preselected generally uniform temperature.

36. The apparatus of claim 35 wherein the said one piston portion has a low-friction fluid seal extending about its periphery, the fluid seal being formed of a material of low thermal conductivity, wherein the said one piston portion is dimensioned to provide a preselected maximum clearance between the said one piston portion and the chamber wall, and wherein fluid from one of the fluid-measuring portion is received within said clearance to provide a thin lubricating fluid film for the said one piston portion.

37. The apparatus of claim 35 wherein a maximum clearance in the order of 0.005-inch thickness exists between the said one piston portion and the chamber wall.

38. A metering pump usable in a beverage dispenser for simultaneously dispensing two different fluids in a two stroke cycle and comprising a body having a longitudinally extending chamber, a pair of coaxially aligned pistons reciprocable in the chamber and connected in longitudinally spaced relation for simultaneous movement between loaded and discharged positions, a flexible rolling diaphragm secured to the body and supporting one of the pistons for radially self-centering frictionless movement in the chamber, the diaphragm and said one piston jointly forming a movable partition within the chamber, the movable partitIon and the other of the pistons dividing the chamber into a pair of fluid-measuring chamber portions and an operating chamber portion, a guide tube coaxially mounted in the chamber between the pistons, said one piston being of U-shaped half-section having an elongated hub portion slidably received in the guide tube, the measuring chamber portions each having inlet and outlet means formed in the body for simultaneously admitting two different fluids to and exhausting them from the measuring chamber portions respectively, and a return spring in the chamber continuously urging the pistons toward loaded position, the return spring being coiled about the guide tube and urging said one piston into loaded position, whereby the guide tube assists in maintaining the pistons in radially self-centering alignment in the chamber while additionally supporting the spring to prevent excessive radial movement thereof.

39. A metering pump usable in a beverage dispenser for simultaneously dispensing two different fluids in a two-stroke cycle and comprising a body having a longitudinally extending chamber, a pair of pistons reciprocable in the chamber and connected in longitudinally spaced relation for simultaneous movement between loaded and discharged positions, a flexible rolling diaphragm secured to the body and supporting one of the pistons for radially self-centering frictionless movement in the chamber, the diaphragm and said one piston jointly forming a movable partition within the chamber, the movable partition and the other of the pistons dividing the chamber into a pair of fluid-measuring chamber portions and an operating chamber portion, the measuring chamber portions each having inlet and outlet means formed in the body for simultaneously admitting two different fluids to and exhausting them from the measuring chamber portions respectively, and a return spring in the chamber continuously urging the pistons toward loaded position, said one piston being of U-shaped half-section opening toward the spring and having an annular end wall, the rolling diaphragm being secured to a side of said end wall opposite the spring, and a ball bearing assembly being mounted on an opposite side of said end wall with a thrust plate interposed between the spring and the ball bearing assembly, whereby said one piston is free to rotate relative to the spring for ensuring minimal twisting of the rolling diaphragm.