BACKGROUND

[0001] The present invention relates to pumps having variable output characteristics for selectively dispensing a fluid at different volumetric flow rates. In some aspects, the invention relates to pumps within a chemical dosing system operable to dispense one or more chemicals at different rates to be mixed with a diluent to achieve a user-selected chemical solution.

SUMMARY

[0002] Many industries rely on systems that mix one or more chemicals and water or another suitable fluid. These systems require a means of consistently and accurately providing doses of chemicals to the appropriate amount of water to create a correctly diluted solution. The goal is for the system to create effective solutions without wasting chemical. These and other systems may benefit from a reciprocating piston pump, the capacity of which is variable simply and reliably with few steps of user intervention.

[0003] In one aspect, the invention provides a reciprocating piston pump assembly comprising a driven crank wheel, a crank arm coupled to and driven by the crank wheel, the crank arm terminating at a wrist pin, a pump housing, and a piston. The pump housing defines a pump chamber. The piston includes a plunger provided within the pump chamber and configured to reciprocate along a pumping axis with respect to the pump chamber. A drive slot is formed in one of the piston and the pump housing, and the drive slot receives the wrist pin such that the one of the piston and the pump housing having the drive slot is configured to be driven relative to the other one of the piston and the pump housing to drive the reciprocation of the plunger with respect to the pump chamber. The drive slot is provided as a variable-length drive slot so that lost motion can be selectively incurred, in accordance with a length of the drive slot, between a motion of the crank arm and a retraction of the plunger with respect to the pump chamber. Variation of the length of the drive slot is configured to change both a stroke length of the plunger reciprocation and the volume of the pump chamber through which the plunger reciprocates so that a capacity of the reciprocating piston pump assembly can be varied without affecting priming performance and without changing a rate at which the crank wheel is driven.

[0004] In another aspect, the invention provides a reciprocating piston pump assembly comprising a pump housing defining a pump chamber, and a piston including a plunger provided within the pump chamber and configured to reciprocate along a pumping axis with respect to the pump chamber. A drive slot is formed in the piston for receiving a driving input such that the one of the piston and the pump housing having the drive slot is configured to be driven relative to the other one of the piston and the pump housing to drive the reciprocation of the plunger with respect to the pump chamber in response to the driving input. A valving arrangement is configured to provide two-stage pumping action between the pump chamber and a secondary pump chamber behind the plunger such that the reciprocating piston pump assembly is configured to draw fluid into the pump chamber on a retracting direction of the plunger reciprocation and to discharge fluid from the secondary pump chamber on both the retracting direction and an advancing direction of the plunger reciprocation. An adjustment member is configured to change both a stroke length of the plunger reciprocation and the volume of the pump chamber through which the plunger reciprocates by altering a length of the drive slot so that a capacity of the reciprocating piston pump assembly can be varied without affecting priming performance and without changing a rate of the driving input.

[0005] In yet another aspect, the invention provides a reciprocating piston pump assembly comprising a first pump housing portion defining a first pump chamber therein, the first pump housing portion configured for reciprocating movement along the pumping axis. A first plunger is positioned along the pumping axis within the first pump chamber to form a first pumping unit with the first pump chamber. A second pump housing portion defines a second pump chamber therein, the second pump housing portion configured for reciprocating movement with the first pump housing portion along the pumping axis. A second plunger is positioned along the pumping axis within the second pump chamber to form a second pumping unit with the second pump chamber. The second plunger defines an advancing stroke direction in the second pump chamber that is opposite an advancing stroke direction defined by the first plunger in the first pump chamber. A drive slot is formed cooperatively by respective portions of the first and second pump housing portions. An adjustment member is operable to alter a spacing distance along the pumping axis between the first and second pump chambers to simultaneously alter a plunger stroke distance and a chamber volume for both the first and second pumping units so that a capacity of the reciprocating piston pump assembly can be varied without affecting priming performance and without changing a rate at which the first and second pump housing portions are reciprocated. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 is a perspective view of an exemplary reciprocating piston pump assembly according to a first embodiment of the present disclosure.

[0007] FIG. 2 is a cross-section view of the reciprocating piston pump assembly taken along line 2-2 of FIG. 1.

[0008] FIG. 3 is a cross-section view of the reciprocating piston pump assembly taken along line 3-3 of FIG. 1.

[0009] FIG. 4A is a cross-section view of the reciprocating piston pump assembly of FIG. 1 at a fully retracted piston position while set at a maximum capacity stroke configuration.

[0010] FIG. 4B is a cross-section view of the reciprocating piston pump assembly of FIG. 1 at a fully advanced piston position while set at the maximum capacity stroke configuration.

[0011] FIG. 5 A is a cross-section view of the reciprocating piston pump assembly of FIG. 1 at a fully retracted piston position and a minimum capacity stroke configuration.

[0012] FIG. 5B is a cross-section view of the reciprocating pump assembly of FIG. 1 at a fully advanced piston position while set at the minimum capacity stroke configuration.

[0013] FIG. 6 is a graphical plot of pump discharge volume versus crank angle for the reciprocating piston pump assembly of FIG. 1.

[0014] FIG. 7A is a schematic view illustrating an advancing discharge stroke of the piston.

[0015] FIG. 7B is a schematic view illustrating a retracting charge and discharge stroke of the piston.

[0016] FIG. 7C is a schematic view illustrating a spring ball check valve for use in a reciprocating piston assembly.

[0017] FIG. 7D is a schematic view illustrating a spring ball check valve for use in a reciprocating piston assembly.

[0018] FIG. 8 is a graphical plot of pump discharge volume versus crank angle for a conventional single chamber reciprocating pump assembly as shown in FIGS. 9A and 9B. [0019] FIG. 9A is a schematic view of a conventional single chamber reciprocating piston pump assembly on an advancing discharge stroke of the piston.

[0020] FIG. 9B is a schematic view of a conventional single chamber reciprocating piston pump assembly on a retracting charging stroke of the piston.

[0021] FIG. 10A is a cross-section view illustrating a first piston valve construction for selectively coupling primary and secondary pumping chambers of the reciprocating piston pump assembly of FIG. 1.

[0022] FIG. 10B is a cross-section view illustrating a second piston valve construction for selectively coupling primary and secondary pumping chambers of the reciprocating piston pump assembly of FIG. 1.

[0023] FIG. 10C is a cross-section view illustrating a third piston valve construction for selectively coupling primary and secondary pumping chambers of the reciprocating piston pump assembly of FIG. 1.

[0024] FIG. 10D is another cross-section view of the third piston valve construction of FIG. 10C.

[0025] FIG. 10E is a cross-section view illustrating a fourth piston valve construction for selectively coupling primary and secondary pumping chambers of the reciprocating piston pump assembly of FIG. 1.

[0026] FIG. 10F is another cross-section view of the fourth piston valve construction of FIG. 10E.

[0027] FIG. 11 is a perspective view showing an exemplary dosing machine including the reciprocating piston pump assembly for dispensing a metered quantity of product from the reciprocating piston pump assembly, which is formed in conjunction with a dosing engine that dispenses a diluent.

[0028] FIG. 12 is a perspective view of the dosing machine of FIG. 11, with the reciprocating piston pump assembly at a fully advanced position. [0029] FIG. 13 is a perspective view of the dosing machine of FIG. 11 , with the reciprocating piston pump assembly remaining at the fully advanced position during a first retraction motion of the crank and crank arm.

[0030] FIG. 14 is a perspective view of the dosing machine of FIG. 11, with the reciprocating piston pump assembly retracted to a fully retracted position following a suction stroke during a further retraction motion of the crank and crank arm.

[0031] FIG. 15 is a perspective view of the dosing machine of FIG. 11, with the reciprocating piston pump assembly remaining at the fully retracted position during a first advancing motion of the crank and crank arm.

[0032] FIG. 16 is a perspective view illustrating adjustment of the adjustment member to change the stroke and volume of the reciprocating piston pump assembly.

[0033] FIG. 17 is a perspective view of another exemplary reciprocating piston pump assembly according to the present invention.

[0034] FIG. 18 is a perspective view illustrating an adjustment member removed from the piston assembly of the pump of FIG. 17.

[0035] FIG. 19 is a perspective view of the adjustment member of FIG. 18.

[0036] FIG. 20 is a side view of the reciprocating piston pump assembly of FIG. 17, in which a first gear train is established with the crank wheel for rendering high speed operation with a first drive gear.

[0037] FIG. 21 is a side view of the reciprocating piston pump assembly of FIG. 17, in which a second gear train is established with the crank wheel for rendering low speed operation with an another drive gear.

[0038] FIG. 22 is a perspective view of another exemplary reciprocating piston pump assembly according to the present invention.

[0039] FIG. 23 is a cross-section view of the reciprocating piston pump assembly taken along line 23-23 of FIG. 22. [0040] FIG. 24A is a front view of the reciprocating pump assembly of FIG. 22 at a first limit position while set at a maximum capacity stroke configuration.

[0041] FIG. 24B is a front view of the reciprocating pump assembly of FIG. 22 at a second limit position while set at the maximum capacity stroke configuration.

[0042] FIG. 25 A is a front view of the reciprocating pump assembly of FIG. 22 at a first limit position while set at a minimum capacity stroke configuration.

[0043] FIG. 25B is a front view of the reciprocating pump assembly of FIG. 22 at a second limit position while set at the minimum capacity stroke configuration.

[0044] Before any embodiments of the present invention are explained in detail, it should be understood that the invention is not limited in its application to the details or construction and the arrangement of components as set forth in the following description or as illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. It should be understood that the description of specific embodiments is not intended to limit the disclosure from covering all modifications, equivalents and alternatives falling within the spirit and scope of the disclosure. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

DETAILED DESCRIPTION

[0045] FIGS. 1-3 illustrate an exemplary reciprocating piston pump assembly 100 for producing an output fluid flow rate that can be varied among multiple settings without changing the input drive to the pump assembly 100. The pump assembly 100 includes a piston assembly 102 that is mounted for reciprocating movement along a pumping axis A within a pump housing or chamber housing 104. The chamber housing 104 defines at its interior a pump chamber 106, along with a fluid inlet 108 and a fluid outlet 110. The chamber housing 104 can take the form of a single (e.g., molded) element, or a multi-piece assembly. The fluid inlet 108 and the fluid outlet 110 are both in fluid communication with the pump chamber 106 for admitting fluid into the pump chamber 106 and directing pumped fluid out of the pump chamber 106, respectively. The fluid inlet 108 is provided in direct or indirect fluid communication with a fluid source SF, such as a reservoir, to draw fluid therefrom into the pump chamber 106. Likewise, the fluid outlet 110 can be provided in direct or indirect fluid communication with a further fluid device or output mechanism, represented schematically as

111 in FIG. 1 (e.g., a sprayer, nozzle, mixer, etc.). The device 111 can optionally receive one or more additional fluids to be combined with the fluid from the pump assembly 100. For example, FIG. 1 illustrates that a diluent source SD can be connected to the device 111 to deliver a diluent, which may be water, an additional chemical, or an alternate fluid to the device 111.

[0046] A framework 112 of one or more frame elements supports the chamber housing 104 in a fixed position. For example, the chamber housing 104 can be fastened to the framework

112 at one or a plurality of fastener joints. As shown, the chamber housing 104 is formed with a plurality of bosses, each of which receives a respective fastener (e.g., screw) that extends perpendicular to the pumping axis A to secure the chamber housing 104 to the framework 112. The framework 112 can be defined at least in part by a flat plate. The plate defines a plane extending parallel to the pumping axis A, but the framework 112 can take a variety of other forms in other constructions.

[0047] The framework 112 also defines a guide slot 114 for guiding sliding movement of a wrist pin 116. The guide slot 114 is formed through the framework 112 in a direction perpendicular to the pumping axis A, and the guide slot 114 is elongated in a direction parallel to the pumping axis A. The wrist pin 116 is provided at one end of a crank arm 118 and defines a crank-slider mechanism that at least partially operates as a drive assembly of the pump assembly 100. The drive assembly includes the crank arm 118 that extends between the wrist pin 116 and a crank wheel 120, which is coupled to the crank arm 118 by a crank pin 122. When the crank wheel 120 is rotated (e.g., by a drive wheel 124 meshed with the crank wheel 120 (both of which are gear wheels provided with complementary of teeth and gaps between the teeth), the wrist pin 116 is driven to reciprocate within the bounds of the guide slot 114. As shown, the framework 112 provides a single guide slot 114 on one side of the piston assembly 102, although, the framework 112 can have an additional, parallel guide slot(s) and/or the guide slot 114 may be disposed at another position adjacent the piston assembly 102.

[0048] The crank wheel 120 is supported for rotation about a central axis Al on one or both of the framework 112 and the pump housing 104. Likewise, the additional drive wheel 124 meshed to drive the crank wheel 120 can also be supported for rotation about a central axis A2 on one or both of the framework 112 and the pump housing 104. As spur gears, the axes Al, A2 of the crank and drive wheels 120, 124 are parallel to each other and perpendicular to the pumping axis A. However, other arrangements and other types of drive members, both gear types and non-gear types, are envisioned. As shown schematically in FIG. 1, the pump assembly 100 (and particularly the drive wheel 124 in the illustrated embodiment) is driven by a rotary engine 125 of an appropriate type, such as an electric motor or a fluid-driven motor for example. The rotary engine 125 can be integrated as part of the pump assembly 100 (e.g., supported on the framework 112, or maintained separately therefrom but coupled therewith to form an overall system). In some embodiments, the drive wheel 124 includes a coupling structure such as a hub pocket 124A that is adapted to drivingly couple (e.g., by mating of complementary non-circular shapes) with an output member 125A of the rotary engine 125, which may be provided as a shaft. As illustrated, each of the hub pocket 124A and the output shaft 125A has a D-shaped cross-section. In some constructions, the crank wheel 120 is driven by the rotary engine 125 directly, without an intermediate drive wheel 124 or other transmission device. It is also noted here that, notwithstanding the ability for the rotary engine 125 to change its speed, the power transmission path between the rotary engine 125 and the crank arm 118 is fixed to a single setting and not adapted to provide multiple switchable drive ratios during use. Thus, when the rotary engine 125 operates at a given fixed speed, the result is that the wrist pin 116 traverses a fixed distance between two limit positions within the guide slot 114 with a consistent speed profile relative to the given fixed speed. Despite such limitations, pumping capacity (volumetric fluid delivery rate) from the pump assembly 100 can be altered as described further below.

[0049] In addition to being guided along the guide slot 114, the wrist pin 116 is coupled to the piston assembly 102 to drive the piston assembly 102. The wrist pin 116 is engaged with a tail portion 126 of the piston assembly 102 that is axially joined with a piston head portion or “plunger” 128. More particularly, the wrist pin 116 extends perpendicularly through a drive slot 130 of the tail portion 126 of the piston assembly 102. The tail portion 126 and the plunger 128 can be separately formed and securely fixed together (e.g., by fastener(s), adhesive, staking welding, etc). In some constructions, the tail portion 126 and the plunger 128 are integrally or monolithically formed (e.g., molded or cast) as a single piece. The plunger 128 resides at least partially within the pump chamber 106 at all times when assembled and operational. The tail portion 126 resides at least partially outside the pump chamber 106 at all times when assembled and operational. [0050] The drive slot 130 has a length L that is defined along the pumping axis A. The wrist pin 116 is entrapped within the drive slot 130 and the wrist pin 116 is only allowed to move within the drive slot 130 by an amount by which the length L exceeds the corresponding dimension D of the wrist pin 116. Furthermore, the length L of the drive slot 130 is configured to be adjustable to a variety of values. At one limit, the length L may be adjustable so that there is substantially no excess clearance between the length and the wrist pin dimension D. At an opposite limit, the length L may be adjustable so that the length L is at least 1.5 times the wrist pin dimension D, at least 2.0 times the wrist pin dimension D, at least 3.0 times the wrist pin dimension D, or at least 4.0 times the wrist pin dimension D. Adjustment of the drive slot length L can be accomplished by an adjustment member 132 that is engaged with or forms part of the piston tail portion 126. The adjustment member 132 can be configured to adjust the length L by a single input (e.g., rotation) that is accessible externally relative to the framework 112 (e.g., via a tool or by hand). Disassembly and multi-step operations are not required for adjustment. The adjustment member 132 can provide infinite or step-wise adjustment of the length L within the total range of adjustment and is positionable along the drive slot 130 to change the effective length thereof. A distal end surface 172 of the adjustment member 132 can set the rear end of the drive slot 130, such that the drive slot 130 is formed in part by the piston tail portion 126 and on the opposite end by the adjustment member 132. In effect, the movement of the adjustment member 132 can block from use a portion of the available slot length in the tail portion 126. As illustrated, the adjustment member 132 is a threaded set screw that provides infinite adjustment between the minimum and maximum stroke settings. Other adjustment members are contemplated, some of which are described further in detail below.

[0051] FIGS. 4A and 4B illustrate the plunger 128 in the fully retracted and fully advanced positions, respectively, with the adjustment member 132 set at a maximum capacity stroke configuration. As can be seen in these views, the piston assembly 102 moves directly with the wrist pin 116 because the adjustment member 132 is set to a depth that takes up all available clearance and pinches the wrist pin 116 to the plunger 128. Thus, the drive slot length L matches the dimension D of the wrist pin 116, and the piston assembly 102 is driven with a reciprocating path length that matches the reciprocating path length of the wrist pin 116.

[0052] FIGS. 5 A and 5B illustrate the plunger 128 in the fully retracted and fully advanced positions, respectively, with the adjustment member 132 set at or near a minimum capacity stroke configuration. As can be seen in these views, the adjustment member 132 is set to a depth that leaves a clearance between the inner side of the adjustment member 132 and the wrist pin 116 such that the piston assembly 102 moves only after the wrist pin 116 contacts the plunger 128 or the adjustment member 132. Thus, the drive slot length L does not match, but rather exceeds, the dimension D of the wrist pin 116. As such, the piston assembly 102 is driven with a reciprocating path length that does not match, but rather is less than, the reciprocating path length of the wrist pin 116 due to the free or lost-motion travel therebetween. As can be seen from FIGS. 4A to 5B, the piston assembly 102 is driven to the same fully advanced position regardless of the setting of the adjustment member 132. Thus, changing stroke of the piston assembly 102 also changes the effective chamber volume accordingly (i.e. the pumping chamber volume is reduced proportionally when the stroke is reduced by the adjustment member 132). Due to this feature, the reciprocating piston pump assembly 100 can effectively self-prime even when set to a short stroke.

[0053] Attention is now turned to the pumping mechanics of the reciprocating piston pump assembly 100. In particular, FIG. 6 illustrates an exemplary plot of pump discharge volume versus crank angle that shows how the reciprocating piston pump assembly 100 produces a discharge from the outlet 110 on both the advancing and retracting strokes. With additional reference to FIG. 7A, it can be seen that, during the advancing stroke, the plunger 128 advances into the pump chamber 106 toward the inlet 108 such that a one-way valve 136 at the inlet 108 is closed as the pump chamber 106 shrinks in volume. Fluid inside the pump chamber 106 is pressurized and directed through a one-way “interstage” valve 138 on the plunger 128. Opening the interstage valve 138 opens a passage through the plunger 128 from the pump chamber 106 to a secondary or rear pump chamber IO62. The cross-sectional area of the rear pump chamber IO62 is less than that of the pump chamber 106 by half due to being occupied partly by the body of the plunger 128. As the plunger 128 continues the advancing stroke to shrink the volume of the pump chamber 106 while expanding the volume of the secondary pump chamber IO62, the rate of volume reduction of the pump chamber 106 exceeds the rate of volume increase in the secondary pump chamber IO62 (by the cross-sectional area ratio of 2: 1), and the transfer of fluid from the pump chamber 106 into the secondary pump chamber IO62 demands that (for an incompressible liquid) a corresponding fluid volume be discharged from the outlet 110. In FIG. 6, this is represented by the first half of the first “pump cycle” covering the first 180 degrees of crank rotation. Then, turning to FIG. 7B, retraction of the plunger 128 is described. During retraction or the “suction” stroke, the volume of the pump chamber 106 is increased, which produces suction and opens the one-way valve 136 at the inlet 108 for the admittance of fluid from the fluid source SF into the pump chamber 106. At the same time, movement of the plunger 128 leads to reduction in the volume of the secondary chamber IO62, such that the interstage valve 138 is closed. As such, during admittance of new fluid into the pump chamber 106, the fluid already contained in the secondary chamber IO62 is discharged from the outlet 110. In FIG. 6, this is represented by the second half of the first pump cycle covering the crank rotation of 180 degrees to 360 degrees. The process then repeats for additional pumping cycles as shown in FIG. 6. Smaller, more precise discharges are generated from the pump 100 as compared to a conventional pump (see FIGS. 9A and 9B) of matching volumetric capacity that has finite, separate suction and discharge strokes as shown in FIG. 8.

[0054] According to certain embodiments, the one-way valve 136 may comprise an umbrella valve or a spring ball check valve. According to certain embodiments, the interstage valve 138 may comprise an umbrella valve or a spring ball check valve. FIGS. 7C and 7D illustrate the principle of operation for a spring ball check valve. Spring ball check valve 400 comprises a fluid inlet 402, a fluid outlet 404, a ball valve 406, a spring 408, and reverse flow restrictor 410. During normal flow conditions, fluid enters fluid inlet 402 and creates a positive pressure on ball valve 406 towards fluid outlet 404. The resultant positive pressure on ball valve 406 allows spring 408 to compress. As the fluid maintains positive pressure on ball valve 406, fluid flows around the ball valve 406, around the spring 408, and into the fluid outlet 404.

[0055] Turning to FIG. 7D, shown is an illustrative instance when the fluid supply may be interrupted, or a temporary spike in fluid pressure in the fluid outlet 404 arises. Where the pressure differential between the fluid inlet 402 and fluid outlet 404 reduces below the spring force of spring 408, ball valve 406 will forced back towards fluid inlet 402, and spring 408 will release compression and expand towards fluid inlet 402. Ball valve 406 will contact reverse flow restrictor 410, and prevent any fluid flow from reversing into fluid inlet 402. The contact between ball valve 406 and fluid restrictor 410 creates a seal that prevents reverse flow through the assembly.

[0056] The dual pumping stage action described with reference to FIGS. 6 to 7D can be accomplished through several different physical valving arrangements on or in the plunger 128. FIG. 10A illustrates an exemplary valving arrangement for the plunger 128 of the pump 100. The sealing and valving functions for the plunger 128 are provided by separate structures. In addition to a peripheral seal 140 on the plunger 128 (e.g., a quad ring as shown) for sealing to the chamber wall 141, the plunger 128 includes an umbrella valve 138 that serves as the interstage valve. The umbrella valve 138 fits into an opening 142 exposed to the distal end of the plunger 128. The flexible, peripheral portion of the umbrella valve 138 overlies, and selectively exposes, one or more fluid passages 144 extending between the primary and secondary pump chambers 106, IO62. The umbrella valve 138 seals the passage(s) 144 against flow from the secondary pump chamber IO62 to the primary pump chamber 106. Thus, fluid passing through the passage(s) 144 to get from the primary pump chamber 106 to the secondary pump chamber IO62 passes through the plunger 128. The opening 142 and passage(s) 144 can extend, respectively, along and parallel to the axis A, or in another alternate orientation.

[0057] FIG. 10B illustrates another exemplary embodiment in which a peripheral lip seal or skirt seal 138A is provided around the periphery of the plunger 128A to simultaneously act as both the plunger seal and the interstage valve. The skirt seal 138A is a one-way or non-retum valve having a portion (i.e., the skirt or lip) that elastically deflects radially inward toward the axis A in the presence of a positive net pressure differential between the primary pump chamber 106 and the secondary pump chamber IO62 in order to establish fluid flow around the periphery of the plunger 128A. As such, sealing of the plunger 128A to the chamber wall 141 is transient or selective, and not maintained through the full pumping cycle. The plunger 128A forms a solid body dividing the primary and secondary pump chambers 106, IO62, without any flow passage extending therethrough to connect the primary and secondary pump chambers 106, IO62.

[0058] In yet another example, illustrated by FIGS. 10C and 10D, the interstage valve can be provided as a sliding or “floating” peripheral seal 138B that is retained in an axially oversized pocket or groove 148 on the plunger 128B. As shown, the floating peripheral seal 138B is defined by a ring having a square cross-section. A radial inner side of the floating peripheral seal 138B is provided with clearance to the plunger 128B, or at least relatively less friction than between the radially outer side of the floating peripheral seal 138B where the floating peripheral seal 138B contacts the chamber wall 141. As such, the floating peripheral seal 138B is generally biased to stay at a fixed orientation with respect to the chamber wall 141 so that it provides relative movement on the plunger 128B when the plunger 128B changes direction. Only when the floating peripheral seal 138B is slid away from the distal end of the plunger 128B, as shown in the drawings (i.e. by positive pressure differential between the primary and secondary pump chambers 106, IO62), does the floating peripheral seal 138B expose a fluid passage formed by recesses 152 provided along the outer surface(s) of the plunger 128B. Thus, the floating peripheral seal 138B assumes the illustrated position only on the advancing stroke, and slides toward the distal end of the plunger 128B to close the fluid passages provided by the plunger recesses 152 on the retracting/ suction stroke.

[0059] According to certain embodiments and in yet another example, illustrated by FIGS. 10E and 10F, the peripheral seal 138B may be removed altogether. In embodiments where the peripheral seal 138B is not present, a spring ball check valve 113 may be installed in fluid communication with outlet 110. The spring ball check valve 113 may be constructed and operate similar to the spring ball check valve 400 depicted in FIGS. 7C and 7D. A fluid passage formed by recesses 152 provided along the outer surface(s) of the plunger 128B allows the flow of fluid along the outer surface of plunger 128B. The fluid may then pass towards outlet 110, where along outlet 110 the fluid will communicate with spring ball check valve 113.

[0060] It was unexpectedly discovered that the assembly may function without the inclusion of peripheral seal 138B. The addition of spring ball check valve 113 in outlet 110 allows for the pump assembly to discharge fluid at least once per cycle. The spring ball check valve 113 prevents siphoning of product into the air gap when the pump is static. Further, the spring ball check valve acts to prevent overdosing at high reciprocating pump speeds.

[0061] FIGS. 11-16 illustrate an exemplary use of the reciprocating piston pump assembly 100 as part of a rotary dosing engine 125 in a commercial fluid dosing system 156. The fluid dosing system 156 is operable to output a metered quantity of product (e.g., chemical concentrate or another product mixable with a diluent) from the reciprocating piston pump assembly 100 in conjunction with the delivery of diluent. The product and diluent can form a combined output from the fluid dosing system 156 to make a solution or dilution according to a prescribed concentration to be used at a point of use or collected in a receptacle. FIG. 12 shows the fluid dosing system 156 with the reciprocating piston pump assembly 100 at the fully advanced position. As can be seen, the adjustment member 132 is set to a position that reduces the pump stroke from its available maximum stroke. In other words, FIG. 12 illustrates that the wrist pin 116 is spaced from the adjustment member 132 when in the fully advanced position. FIG. 13 shows the reciprocating piston pump assembly 100 after an initial retraction motion of the crank wheel 120 and crank arm 118. Despite substantial travel of the wrist pin 116 along the guide slot 114 (a first portion of the total retraction distance of the crank arm 118 and wrist pin 116), the piston assembly 102 remains at the fully advanced position (see that the tail portion 126 has not moved from FIG. 12). FIG. 13 shows the free or lost-motion travel of the wrist pin 116 toward the adjustment member 132 on the retraction/suction stroke.

[0062] FIG. 14 shows the next phase of retraction motion of the crank wheel 120 and crank arm 118 in which the retraction/suction stroke of the piston assembly 102 takes place. After the take-up of the lost-motion distance between the wrist pin 116 and the adjustment member 132, the piston assembly 102 is driven to retract in-sync with the wrist pin 116 toward the fully retracted position (see that the tail portion 126 has retracted from the position of FIG. 13 and the wrist pin 116 has reached the rear end of the guide slot 114). Thus, the piston assembly 102 moves a retraction distance equal to only a second portion of the total retraction distance of the crank arm 118 and wrist pin 116. Although the crank arm 118 is somewhat obscured, it will be appreciated that FIG. 14 represents the maximum rearward throw of the crank assembly, including the crank wheel 120 and crank arm 118, and thus also that of the piston assembly 102. FIG. 15 shows the reciprocating piston pump assembly 100 remaining at the fully retracted position during a first advancing motion of the crank wheel 120 and crank arm 118. As can be seen by comparing FIGS. 14 and 15, the wrist pin 116 advances along the guide and drive slots 114, 130 in the forward direction away from the adjustment member 132, and the tail portion 126 does not move. After the wrist pin 116 reaches the forward end of the drive slot 130, the piston assembly 102 is driven in-sync with the wrist pin 116 until the crank assembly reaches the forward throw limit. Thus, as with the retracting stroke, the piston assembly 102 moves an advancing distance equal to only a second portion of the total advancing distance of the crank arm 118 and wrist pin 116, following a first advancing distance in which there is lost motion between the crank arm 118 and the piston assembly 102.

[0063] FIG. 16 is a perspective view illustrating a user adjusting the adjustment member 132 to change the stroke and volume of the reciprocating piston pump assembly 100. As shown, the adjustment can be accomplished by insertion of a tool 160 (e.g., hex key, screwdriver, etc.) into the tail portion 126 of the piston assembly 102 to establish a rotation-driving coupling with the adjustment member 132. The end of the tail portion 126 is thus open to facilitate access to the adjustment member 132. Manipulation of the adjustment member 132 can enable variation of the pump capacity at the factory assembly stage and/or adjustment at a point of sale or point of use. In the illustrated example, the fluid dosing system 156 is user-configurable to adjust the reciprocating piston pump assembly 100 so that solutions containing a plurality of different concentrations of the pumped product can be obtained from the output of the fluid dosing system 156. Although the tool 160 is illustrated in FIG. 16, the adjustment member 132 can include an exposed portion that provides a grip for tool-less adjustment by hand. A reference scale may be provided along the drive slot 130 to provide an indication of pump capacity corresponding to position of the adjustment member 132 so that the user has a visual guide for moving the adjustment member 132. It is also reiterated here that the adjustment member 132 can take other forms besides a threaded screw. For example, the adjustment member 132 can be provided with a plurality of detent positions along the tail portion 126 of the piston assembly 102 so that there are a prescribed number of individual discrete settings available. In yet other embodiments, described below, the adjustment member 132 is a swappable member among a plurality of available adjustment members, each one providing the drive slot 130 with a different drive slot length L.

[0064] FIGS. 17-19 illustrate another embodiment of a reciprocating piston pump assembly 200 that has many similarities to that of the preceding drawings and description, which are referenced for the further explanation of features not repeated below. The reciprocating piston pump assembly 200 includes a piston assembly 202 mounted for reciprocating movement along a pumping axis A within a chamber housing 204. The chamber housing 204 defines a pump chamber, along with a fluid inlet 208 and a fluid outlet 210. A framework (not shown) may be provided similar to the framework 112 shown in the preceding figures, including a guide slot to guide the wrist pin 216. The wrist pin 216 is provided at one end of a crank arm 218 so as to define a crank-slider mechanism that operates as at least part of a drive assembly of the pump assembly 200. The drive assembly includes the crank arm 218 extending between the wrist pin 216 and a crank wheel 220, which is coupled to the crank arm 218 with a crank pin 222. The crank wheel 220 is rotated by a drive wheel 224 meshed with the crank wheel 220, both of which are gear wheels provided with complements of teeth. The crank wheel 220 is supported for rotation about a central axis Al, and the additional drive wheel 224 is supported for rotation about a central axis A2, which can be parallel to axis Al and perpendicular to the pumping axis A. In a configuration in which the drive wheel 224 rotates at a fixed speed, the crank arm 218 is likewise fixed to a constant speed, the power transmission path between the drive wheel 224 and the crank arm 218 being fixed to a single setting. The result is that the wrist pin 216 traverses a fixed distance between two limit positions with a consistent speed profile relative to the given fixed speed. Despite these limitations, pumping capacity (volumetric fluid delivery rate) from the pump assembly 200 can be altered. [0065] The wrist pin 216 is coupled to the piston assembly 202 to drive the piston assembly 202. The wrist pin 216 is engaged with a tail portion 226 of the piston assembly 202 that is axially joined with a piston head portion or “plunger” 228. More particularly, the wrist pin 216 extends perpendicularly through a drive slot 230 of the tail portion 226 of the piston assembly 202. The drive slot 230 has a length L that is defined along the pumping axis A. The wrist pin 216 is entrapped within the drive slot 230 and only allowed to move within the drive slot 230 by an amount by which the length L exceeds the corresponding dimension D of the wrist pin 216. Furthermore, the length L of the drive slot 230 is configured to be adjustable to a variety of values. Adjustment of the drive slot length L can be accomplished by an adjustment member 232 that is engaged with or forms part of the piston tail portion 226.

[0066] As best shown in FIGS. 18 and 19, a locking interface is defined between the adjustment member 232 and the piston tail portion 226. The locking interface fixes the adjustment member 232 and the piston tail portion 226 to a single, predetermined relative axial position. The locking interface is defined by one or more sets of complementary bayonet connection structures, including a protrusion 266 and a slot 268. As illustrated, the protrusions 266 are formed on the outer periphery of the piston tail portion 226, and the slots 268 are provided on the adjustment member 232, although these may be reversed in other embodiments. The locking interface is defined separately from an insertion portion 270 of the adjustment member 232 that extends into the piston tail portion 226 to set the length L of the drive slot 230. In other embodiments a locking interface can be incorporated with the insertion portion 270. As will be appreciated, the illustrated embodiment locks the locking interface by axial joining of the adjustment member 232 and the piston tail portion 226, followed by a relative rotation (e.g., less than 90 degrees). The locking interface is unlocked by a relative rotation in the opposite direction from the locking rotation, followed by axial separation.

[0067] The length L270 of the insertion portion 270 of the adjustment member 232 is measured to a distal end surface 272 of the insertion portion 270 and sets the rear end of the drive slot 230 in which the wrist pin 216 is contained, either with or without clearance. As such, and consistent with other constructions of the invention described herein, the adjustment member 232 limits both the stroke of the plunger 228 and the pump chamber volume. The pumping stroke and volume are proportionally set together as a function of the length L270 of the insertion portion 270. Unlike the adjustment member 132, the adjustment member 232 provides a single setting, and different settings for stroke and volume are achieved through replacement of the adjustment member 232 with another adjustment member like the adjustment member 232 but for a prescribed variance in the length L270 of the insertion portion 270. Two or more adjustment members 232 are thus required and exchanged to change the pump stroke and volume. This can be accomplished at the factory assembly stage and/or reconfiguration of a product at a point of sale or point of use. It is also noted that the tail portion 226 of the piston assembly 202 can optionally be threaded to accept a threaded adjustment member like that of the preceding embodiment. Likewise, the tail portion 126 of the preceding embodiment may be used with one or more adjustment members 232 of a construction like that of FIGS. 17 to 19.

[0068] FIGS. 20 and 21 illustrate another feature of the reciprocating piston pump assembly 200 for varying the reciprocation speed of the piston assembly 202 without changing the input speed of the drive wheel 224. FIG. 20 shows that the drive wheel 224 has a first tooth count (e.g., 30). The drive wheel 224 is engaged with a first gear portion 220A of the crank wheel 220, which has two stacked, integrally-rotatable first and second gear portions 220A, 220B defining a compound gear. The first gear portion 220A is the smaller of the two gear portions 220A, 220B and may have a tooth count (e.g., 15) that is less than the tooth count of the drive wheel 224. As assembled in FIG. 20, the crank wheel 220 rotates (and thus drives the crank arm 218) at a speed that is stepped up from the speed of the drive wheel 224 (e.g., double). The larger second gear portion 220B of the crank wheel 220 can be inactive in this configuration.

[0069] Turning now to FIG. 21, the drive wheel 224 is removed and replaced with another drive wheel 224’ that has an alternate tooth count (e.g., 15) compared to that of the drive wheel 224, with the tooth count of the alternate drive wheel 224’ being reduced (e.g., by half). The drive wheel 224’ is meshed with the larger second gear portion 220B (e.g., tooth count 30) rather than the first gear portion 220A of the crank wheel 220. The crank wheel 220 can thus be driven at a speed that is stepped down from the speed of the drive wheel 224’ (e.g., half). Of course, the description of the illustrated embodiment refers to tooth counts of gears meshed together, although it will be understood that drive speed ratios can be accomplished similarly with other structures (e.g., with friction wheels or pulleys of different diameters). Thus, the reciprocating piston pump assembly 200 has the capability of speed adjustment by gear swapping so that the remainder of the assembly has common parts that enable two or more different versions to be assembled with swappable gear components. The gear swapping or selection among the drive wheels 224, 224’ can enable variation at the factory assembly stage and/or reconfiguration of a product at a point of sale or point of use. In either case, the compound crank wheel 220 includes both of the first and second gear portions 220 A, 220B, only one of which is utilized for a particular construction of the reciprocating piston pump assembly 200. In this way, the crank wheel 220 can be configured to rotate at at least two different speeds where the input rotational speed at the upstream drive wheel (224 or 224’). In the illustration of FIGS. 20 and 21, respectively, the crank wheel 220 is driven at double the input speed or half the input speed. This feature is particularly useful where the reciprocating piston pump assembly 200 is part of a larger assembly, e.g., with other driven components tied to the same drivetrain or drive source, wherein the rotational speed of the component(s) driving the crank wheel 220 cannot simply be changed without adversely affecting other components of the assembly.

[0070] FIGS. 22-25B illustrate yet another reciprocating piston pump assembly 300 having many similarities to that of FIGS. 1-7 and 10-21 and the related description, which are referenced for the further explanation of features not repeated below. Briefly, the reciprocating piston pump assembly 300 includes a stroke and a chamber volume that are adjustable in unison via a variable length drive slot 330. It should be appreciated that the reciprocating piston pump assembly 300 differs fundamentally from those of the preceding embodiments of the present invention in that the piston assembly 302 is not mounted for reciprocating movement along a pumping axis A. Instead, the reciprocating action is accomplished by a driven chamber housing 304 that reciprocates along the pumping axis A with respect to a non-driven piston assembly 302. The chamber housing 304 includes two opposed chamber housing parts or portions 304A, 304B providing separate, opposite pump chambers 306A, 306B (FIG. 23) that communicate with two opposing plungers 328A, 328B of the piston assembly 302. The housing 304, rather than the piston assembly 302, is driven by a crank arm 318, which in turn is driven by a crank wheel 320, details of which are similar to the preceding embodiments. As discussed in further detail below, a wrist pin 316 at one end of the crank arm 318 is arranged in an adjustable length drive slot 330 to drive the pump. The two plungers 328A, 328B form a unitary structure (whether monolithically formed or not) on which the chamber housing 304 moves with the effect that each plunger 328A, 328B reciprocates in a respective one of the pump chambers 306A, 306B. By configuring the pump assembly 300 in this way, discharge of the product is possible on both opposite stroke directions. On one stroke direction, product discharge is produced from one pump chamber 306A, and on the opposite stroke direction, product discharge is produced from the opposite pump chamber 306B. Divergent fluid flow paths are established through the two separate pump chambers 306 A, 306B.

[0071] In the reciprocating piston pump assembly 300, an inlet 308 is formed to establish fluid communication with first internal passages 376 extending through the respective plungers 328A, 328B. As shown in FIG. 23, the internal passages 376 intersect with each other at the end of the passage forming the inlet 308, which may be formed integrally as a single piece with the plungers 328A, 328B or otherwise fixedly secured and sealingly coupled. Likewise, a separate passage forms an outlet 310 extending from second internal passages 378 in the respective plungers 328A, 328B. The passage forming the outlet 310 may be formed integrally as a single piece with the plungers 328A, 328B fixedly secured and sealingly coupled. As illustrated, the second internal passages 378 extend along the central pumping axis A, while the first internal passages 376 are radially offset therefrom, although other arrangements are contemplated. The two first internal passages 376 form a shared inlet chamber for the two pumping units, and the two second internal passages 378 form a shared outlet chamber for the two pumping units. A seal 340 is provided at each interface between one of the plungers 328A, 328B and the respective pump chamber housing portion 304A, 304B. Flow from the first internal passages 376 (and thus, from the inlet 308) into the corresponding pump chambers 306A, 306B is enabled through a first one-way valve, while flow from the pump chambers 306A, 306B into the corresponding second internal passages 378 is enabled through a second one-way valve. Both of the one-way valves can be integrated into a single valve member 380 to minimize part count and assembly difficulty, although other arrangements are optional. For example, the valve member 380 may be a two-way duckbill/umbrella valve member. In such a valve member 380, the umbrella portion can open on the suction stroke for a given plunger 328A, 328B when the pressure is higher in the first internal passage 378 than in the corresponding one of the pump chambers 306A, 306B (while the duckbill portion remains closed). Conversely, on the compression stroke of a given plunger 328A, 328B, the pressure is higher in the pump chamber 306A or 306B than in the corresponding second internal passage 378, and this causes the duckbill portion to open (while the umbrella portion remains closed). Thus, rather than multiple pumping stages for a fluid passing through the pump, the reciprocating piston pump assembly 300 acts as a pair of separate pumping units that have conjoined structure and fluid paths.

[0072] As with the preceding embodiments, the drive slot 330 has a length L that is defined along the pumping axis A, while the wrist pin 316 is entrapped within the drive slot 330 and only allowed to move within the drive slot 330 by an amount by which the length L exceeds the corresponding dimension D of the wrist pin 316. The wrist pin dimension D and the drive slot length L are labeled in FIGS. 24A and 25 A, respectively, with the understanding that the drive slot length L is adjusted down to match the wrist pin dimension D in FIG. 24 A. Thus, the length L of the drive slot 330 is configured to be adjustable to a variety of values to change the pump capacity, simultaneously changing the pumping stroke and chamber volume. FIGS. 24A and 24B illustrate one limit in which there is substantially no excess clearance between the length L and the wrist pin dimension D. At an opposite limit, the length L may be adjustable so that the length L is at least 1.5 times the wrist pin dimension D, at least 2.0 times the wrist pin dimension D, at least 3.0 times the wrist pin dimension D, or at least 4.0 times the wrist pin dimension D. Adjustment of the drive slot length L can be accomplished by an adjustment member 332 that is engaged with or forms part of the pump chamber housing 304. The adjustment member 332 can be configured to adjust the length L by a single input (e.g., rotation) from an external operator means, for example by a tool or by hand. Disassembly and multi-step operations are not required for adjustment. The adjustment member 332 can provide infinite or step-wise adjustment of the length L within the total range adjustably positionable along the drive slot 330 to change the effective length thereof. In the illustrated embodiment, the adjustment member 332 is a threaded member (e.g., screw) that extends between and couples the two separate housing portions 304A, 304B such that adjustment of the adjustment member 332 varies an amount of axial overlap between adjacent proximal portions of the respective housing portions 304 A, 304B including the separate portions that make up the drive slot 330. Adjusting the housing portions 304A, 304B nearer together as in FIGS. 25A and 25B increases the amount of overlap and increases the drive slot length L, while adjusting the housing portions 304A, 304B further apart as in FIGS. 24A and 24B decreases the amount of overlap and decreases the drive slot length L. As such, the adjustment member 332 provides infinite adjustment between the minimum and maximum stroke settings, however, alternate adjustment members are contemplated, some of which adjust stepwise.

[0073] FIGS. 24A and 24B illustrate the pump housing 304 in the two limit positions according to the fixed throw of the wrist pin 316 from the crank arm 318 and crank wheel 320. Because the drive slot 330 is adjusted to match the wrist pin 316, without excess clearance, the entire housing 304 moves in-sync with the back-and-forth travel of the wrist pin 316. This results in a first or maximum stroke Xi for each plunger 328A, 328B. The first and second plungers 328A, 328B are shown in the fully retracted and fully advanced positions, respectively, in FIG. 24A and this is reversed in FIG. 24B. FIGS. 25A and 25B illustrate how the pump housing 304 moves between restrained limit positions due to the excess length L of the drive slot L. The first and second plungers 328A, 328B are shown in the fully retracted position (FIG. 25 A) and fully advanced position (FIG. 25B, which is reversed). Although the wrist pin 316 travels the same distance as in FIGS. 24A and 24B, the setting of FIGS. 25A and 25B introduce lost motion by which the movement of the wrist pin 316 is not directly followed by the housing 304 during part of the travel. Instead of causing full stroke of the plungers 328A, 328B, a reduced stroke X2 is provided. As can be seen from observance of FIGS. 24A to 25B, each plunger 328A, 328B achieves the same fully advanced position, regardless of whether the overall stroke is reduced by the setting of the adjustment member 332. Thus, changing the stroke of the piston assembly 102 also changes the effective chamber volume accordingly (i.e., the pumping chamber volume is reduced proportionally when the stroke is reduced by the single adjustment member 332). Described another way, stroke reduction occurs by eliminating the bottom of the stroke rather than the top of the stroke where the plunger 328A, 328B comes closest to the end of the corresponding chamber 306A, 306B. Due to this feature, the reciprocating piston pump assembly 300 can effectively self-prime even when set to a short stroke.

[0074] In any of the preceding embodiments, it may be useful for an electronic controller to determine the current setting of the variable pump. As will be appreciated from the foregoing, the pump setting for stroke and volume can be varied by a human interaction, rather than directly under electronic control from the controller. This can be used for informational (data collection, calculation, logging, etc.) purposes or as an input for responsively controlling other parameters of an associated dosing system or overall system in which the pump is included. Implementation for determining the pump setting may desirably use existing hardware (e.g., sensor(s)) minimizing or eliminating the requirement for new hardware such as a dedicated sensor designed to directly monitor the movement of the adjustment member 132, 232, 332. In this regard, FIG. 1 illustrates an exemplary controller 1000 in communication with a drivetrain sensor such as an encoder 1004. As shown, the encoder 1004 is provided on or integrated with the rotary engine 125. However, the encoder 1004 can be placed elsewhere along the drivetrain, e.g., on the crank wheel 120 or the drive wheel 124. Regardless of the drive slot length L, the drivetrain will move continuously and predictably throughout its operation, unlike the piston assembly 102. The encoder 1004 is configured to detect and report to the controller 1000 the angular position, for example by counting prescribed angular steps magnetically, optically, or other means. Information from the encoder 1004 can be utilized by the controller 1000 to determine at what time during the drivetrain motion the retraction of the piston assembly begins following reaching the fully advanced stroke position. Detecting the position of the piston assembly 102 at fully advanced stroke can be accomplished by another sensor 1006 (e.g., a magnetic sensor operable to detect a magnet secured to the piston assembly 102, or a momentary switch actuated by an exposed portion of the piston assembly 102). When the pump setting is high or maximum, the retraction will begin nearly immediately after reaching the fully advanced stroke position. On the other hand, various amounts of delay at this juncture in the drive motion correspond to various amounts of reduction of the pump capacity by the adjustment member 132 as clearance in the drive slot 130 is taken up by initial movement of the wrist pin 116. While shown and described with principal reference to the reciprocating piston pump assembly 100 of the first embodiment, this principle is also applicable to the other embodiments as well.

[0075] Various aspects of the invention are set forth in the following claims.