JP7469752B2 - Metering Pump - Google Patents

Description

The present invention relates to a metering pump that can draw fluid from a source and dispense small amounts of fluid to a sink. The metering pump may dispense a predetermined amount of fluid ranging from a few microliters to about 100 μL.

In the prior art, piston pumps are known to those skilled in the art. A piston pump is capable of drawing fluid from a source and passing the fluid to a sink. At the inlet of the piston pump, an inlet check valve is connected to a chamber in which the piston reciprocates. At the outlet of the chamber, an outlet check valve is provided.

Prior art piston pumps have the disadvantage that the vacuum at the outlet valve draws fluid from the source. Because of this, the amount of fluid dispensed by the piston pump cannot be precisely determined.

Also, prior art piston pumps have a large amount of clearance and cannot bleed the conduit connected between the inlet check valve and the supply.

Furthermore, dosing systems are known in the prior art. These dosing systems comprise a pusher which opens an opening through which the fluid is dispensed. As soon as the set amount of fluid has been dispensed, the opening is closed by the pusher. These systems require a pressurized source or a pump between the fluid source and the pusher. These systems are undesirable, since a pressurized source or an additional pump increases the complexity and volume of the metering system.

Dispensing systems equipped with a pusher that closes an opening are known, for example, from U.S. Pat. No. 5,393,431, U.S. Pat. No. 5,493,431, U.S. Pat. No. 5,523,311, and U.S. Pat. No. 5,523,431.

International Patent Application Publication No. 1988/003052A1 European Patent Application Publication No. 1674163A2 European Patent Application Publication No. 1721681A2 European Patent Application Publication No. 1802191A1

The object of the present invention is to provide a metering pump that can reproducibly dispense a predetermined amount of fluid drawn from a supply.

The object of the present invention is achieved by a metering pump according to claim 1 and a metering system according to claim 15. The dependent claims relate to embodiments of the invention.

The present invention discloses a metering pump comprising a chamber having a proximal portion and a distal portion, and a piston housed in the chamber and movable from the proximal portion to the distal portion and vice versa. The metering pump further comprises a drive portion for driving the piston reciprocally within the chamber from a proximal dead center to a distal dead center. The distal dead center is located at the distal portion of the chamber. The proximal dead center is located at the proximal portion of the chamber. An outlet valve is located adjacent to the distal portion of the chamber. The outlet valve may be located opposite the chamber. The outlet valve allows fluid flow out of the chamber when the piston moves in a distal direction and prevents fluid flow into the chamber when the piston moves in a proximal direction.

The metering pump further comprises a seal located at a distal portion of the chamber, the seal located at the distal portion sealing the chamber when the piston is located at the distal portion. The metering pump further comprises an inlet valve, the inlet valve allowing fluid flow into the chamber when the piston moves in a proximal direction and preventing fluid flow out of the chamber when the piston moves in a distal direction. The piston may contact the seal located at the distal portion at its distal dead center position.

The piston may elastically engage the seal located at the distal portion at its distal dead center. In particular, the piston may elastically compress the seal located at the distal portion at its distal dead center.

Metering pumps have the advantage that they can draw fluid, e.g., liquid, from a source and bleed and vent the conduits connected between the source and the inlet valve, respectively. Furthermore, a vacuum in the conduit connected to the outlet valve will not draw fluid from the chamber and the source.

The inlet valve may include an inlet opening and an outlet opening. The inlet valve permits fluid flow from the inlet opening to the outlet opening when the pressure at the outlet opening is less than the pressure at the inlet opening and when the pressure at the inlet opening is less than or equal to the pressure in the metering pump environment.

Metering pumps do not require a pressurized source or a pump between the source and the injection opening of the inlet valve. This reduces the complexity of the metering pump.

The inlet channel of the metering pump may be connected to the inlet valve and the chamber, with the inlet channel juxtaposed to a seal located distal to the chamber. This allows a small amount of clearance to be achieved, allowing the pump to quickly and reliably bleed and vent, respectively, the inlet conduit and the conduit connected between the source and the inlet valve.

The drive may be provided adjacent to the proximal portion of the chamber. The drive may comprise a stepper motor, a linear drive, a solenoid, a servo drive or a linear motor, etc. This allows the piston to be positioned as desired. Furthermore, the piston travel can be adapted as desired.

The metering pump may include a first sub-controller. The first sub-controller is configured to receive a command indicative of a set amount of fluid to be dispensed by the metering pump. The first sub-controller is further configured to calculate a set value of a reciprocating stroke such that, when the metering pump dispenses the set amount of fluid, the set amount of fluid is dispensed by the metering pump and the piston is located within the seal and/or seal located at the distal portion of the chamber. The first sub-controller is further configured to control the drive unit such that the drive unit reciprocates the piston a set value of a reciprocating stroke. The first sub-controller is also configured to position the piston within the seal and/or seal located at the distal portion of the chamber when the piston reciprocates a set value of a reciprocating stroke. In particular, the first sub-controller is also configured to position the distal end of the piston within the seal and/or seal when the piston reciprocates a set value of a reciprocating stroke. In this embodiment, the control unit may control the drive unit such that the piston reciprocates a maximum piston stroke.

Because the piston is located in the seal and/or seal located at the distal portion of the chamber after dispensing of fluid, the vacuum in the conduit connected to the outlet valve does not draw fluid out of the chamber and/or source. This ensures that the set amount of fluid is dispensed.

The metering pump may further include a second sub-controller. The second sub-controller is configured to receive a command indicative of an amount of fluid to be dispensed. The second sub-controller is configured to calculate a piston travel of the piston such that when the metering pump dispenses a set amount of fluid, the set amount of fluid is dispensed and the piston is located within the seal and/or seal located at the distal portion of the chamber. The second sub-controller is further configured to control the drive unit to reciprocate the piston in the proximal and distal directions by the set piston travel. The second sub-controller is also configured to position the piston within the seal and/or seal located at the distal portion of the chamber when the piston has reciprocated by the set piston travel and the set numerical value of the reciprocating stroke. In particular, the second sub-controller is also configured to position the distal end of the piston within the seal and/or seal located at the distal portion of the chamber when the piston has reciprocated by the set piston travel and the set numerical value of the reciprocating stroke. In this embodiment, the control unit may control the drive unit to reciprocate less than the maximum piston stroke.

An advantage of the present invention is that the piston travel can be adapted so that after reciprocation of the piston, the piston is located in the seal and/or seal located in the distal part of the chamber. This allows an amount less than the piston travel to be dispensed by the metering pump after dispensing a predetermined amount of fluid without sacrificing the sealed position of the piston. Regardless of the amount of fluid to be dispensed, the piston may be positioned in contact with the seal and/or seal located in the distal part of the chamber. When an amount of fluid less than the maximum piston stroke or piston travel is dispensed, the piston is again positioned in the seal and/or seal located in the distal part of the chamber.

In one embodiment, the control unit may include a first sub-control unit and a second sub-control unit. The control unit is configured to receive a command indicative of an amount of fluid to be dispensed. The control unit is further configured to calculate a set value of the reciprocating stroke and a set piston travel of the piston such that when the metering pump dispenses a set amount of fluid, the set amount of fluid is dispensed and the piston is positioned within the seal and/or seal located at the distal portion of the chamber. The control unit is configured to control the drive unit such that the drive unit reciprocates the piston in the proximal and distal directions by the set piston travel and the set value of the reciprocating stroke. The control unit is further configured to position the piston in contact with the seal and/or seal located at the distal portion of the chamber when the piston has reciprocated by the set piston travel and the set value of the reciprocating stroke.

In this embodiment, the controller can adapt the piston travel to ensure that after dispensing a set amount of fluid through multiple strokes, the piston is located in or against the seal and/or seal located in the distal portion of the chamber. This can ensure that fluid is not drawn from the chamber and/or source due to the vacuum and negative pressure, respectively, in the conduits connected to the outlet valve.

The controller may be configured to vary the piston travel between the two strokes. In other words, the controller may be configured to control the actuator such that the actuator reciprocates the piston a first piston travel during a first stroke and the actuator reciprocates the piston a second piston travel during a second stroke, the second piston travel being shorter than the first piston travel. This allows for a high flow rate to be achieved by dispensing a large volume of fluid by having all piston strokes have a long piston travel except for the last piston stroke, which has a shorter piston travel to ensure that an accurate volume is dispensed and that the piston is located at the seal located at the distal portion of the chamber after dispensing the set volume.

The inlet and outlet valves may be check valves.

The cylinder clearance may be less than 5% of the piston displacement, preferably less than 2% of the piston displacement, and more preferably less than 1% of the piston displacement. The clearance is located at the distal part of the chamber, in particular between the distal dead center and the opening of the outlet valve that faces the chamber.

The amount metered by a single stroke at maximum piston displacement is in the range of about 5 μL to about 0.02 mL, preferably about 4 μL to about 0.04 mL, and more preferably greater than about 0 μL to about 0.1 mL.

The control may be configured to control the minimum piston travel such that a single stroke of the piston meters a volume of fluid in the range of about 2 μL to about 5 μL, preferably about 1 μL to about 3 μL, and more preferably less than about 1 μL to about 5 μL. The minimum piston travel is the minimum step range or minimum commandable drive range of the drive.

The set volume dispensed by the micro metering pump of the present invention may range from about 1 μL to about 125 μL. The micro metering pump may dispense the set volume within a period of about 1 to 15 seconds, preferably about 1 to 10 seconds, and more preferably about 1 to about 5 seconds.

The outlet valve comprises a valve seat housed in the body of the metering pump and a valve member movable within and/or relative to the valve seat. In one embodiment, when the valve member of the outlet valve is in its closed position, the piston contacts the valve member of the outlet valve at its distal position (distal dead center). This can further reduce dead space. The valve seat of the outlet valve can be softer than the valve member of the outlet valve. The valve member of the outlet valve can be a valve plunger, a valve piston, or a valve disc, etc.

In one embodiment, the outlet valve seat and the seal located in the distal portion of the chamber are integrally formed (as one piece). In this embodiment, the outlet valve seat is softer than the outlet valve member.

The present invention also discloses a metering system comprising the above-mentioned metering pump. The metering system comprises a fluid container coupled to the injection opening of the inlet valve. The fluid container is a fluid source. The fluid container is filled with the fluid to be metered by the metering pump. The pressure in the fluid container corresponds to the pressure in the environment of the metering pump.

The present invention has the advantage that the fluid in the container does not need to be pressurized. The fluid container further comprises a vent opening in fluid communication with the environment of the fluid container. Because the fluid to be dispensed does not need to be pressurized in the fluid container, the pressure in the environment of the fluid container matches the pressure in the environment of the metering pump.

The fluid to be metered may be a liquid, for example drinking water.

The present invention will now be described with reference to the accompanying drawings, which show non-limiting exemplary embodiments of the invention.
1 shows a schematic cross-sectional view of a metering pump according to the present invention. 1 shows a schematic diagram of a weighing system according to the present invention; 3 shows a flow diagram of a method of operating a metering pump according to the present invention. 2 shows a second embodiment of a valve arrangement according to the invention. 3 shows a third embodiment of a valve arrangement according to the invention.

The figures are not drawn to scale and merely serve the purpose of understanding the principles of the invention. Geometric relationships, such as up and down, are merely used to describe the principles of the invention and should not be considered as limitations.

Refer to FIG. 1, which shows a schematic cross-sectional view of a micro-metering pump 100 according to the invention. The pump 100 comprises an essentially cylindrical chamber 102 in which a piston 104 is provided. The piston is shown at its distal dead center position 108. The piston 104 may reciprocate between the distal dead center 108 and the proximal dead center 106. The piston 104 is driven by a drive 130 which is coupled to the piston 104 by an arm 128. The arm 128 is guided in a guide 126.

The pump 100 further comprises an inlet opening 110 in the chamber 102 connected to the outlet opening 114b of the inlet valve 114. The injection opening 114a of the inlet valve 114 is connected to the inlet conduit 118. The inlet valve 114 and the inlet opening 110 are formed adjacent to the distal dead center 108. An inlet channel 113 is formed between the outlet opening 114b of the inlet valve 114 and the inlet opening 110.

At the distal dead center 108, an outlet opening 112 is formed in the chamber 102. The outlet opening 112 is formed adjacent to an inlet opening 116a of an outlet valve 116. An outlet opening 114b of the outlet valve 116 is connected to an outlet conduit 120. The inlet valve 114 and the outlet valve 116 may be check valves.

At the distal dead center 108, a first seal 122 is provided in the chamber 102. In the embodiment shown in FIG. 1, the first seal 122 is formed by an O-ring. When the piston 104 is located at the distal dead center 108 such that the distal part of the piston 104 is provided in the first seal 122 and/or in contact with the first seal 122 and/or in elastic compression of the first seal 122, the vacuum and negative pressure of the outlet conduit 120, respectively, will not allow fluid to be pumped from the chamber 102, the inlet valve 114 and the inlet conduit 118 connected to a fluid source, e.g. a tank, in particular a tank filled with liquid.

In the embodiment shown in FIG. 1, the first seal 122 is provided in a cylindrical recess 123 formed around the cylindrical chamber 102 at the distal dead center 108 of the piston 104. The recess 123 extends in the axial direction of the chamber 102 a sufficient distance to accommodate the first seal 122. The first seal 122 must not have any play in the recess 123 in the axial direction of the chamber 102. Preferably, the first seal 122 is elastically compressed by the recess 123 in the axial direction of the chamber 102. When the piston 104 is located at the distal dead center 108 of the first seal 122 and/or in the first seal 122, the first seal 122 is compressed in the radial direction of the chamber 102 between the piston 104 and the radial outer surface of the recess 123.

At the distal dead center 108 of the piston 104 shown in FIG. 1, the piston 104 contacts the first seal 122. At the distal dead center 108 of the piston 104, the piston elastically compresses the first seal 122. In particular, at the distal dead center 108 of the piston 104, the piston elastically compresses the first seal 122 radially of the chamber 102. In the embodiment shown in FIG. 1, the piston 104 is located at the distal dead center 108 within the O-ring that forms the first seal 122.

The second seal 124 is located at the near dead center 106 of the chamber 102, where the second seal 124 contacts the piston 104. The second seal 124 is received in a second recess 125. The second seal 124 prevents the piston 104 from leaking fluid into the housing of the pump 100 or from pumping fluid from the inside of the housing of the pump 100.

The first seal 122 and/or the second seal 124 may be an O-ring or an X-ring.

The inlet opening 110 is located as close as possible to the first sealing material 122 and/or the distal dead center 108 of the piston 104 reciprocating within the chamber 102.

Between the first sealant 122 and the inlet opening 110, a separation member 136 is provided to separate the first sealant 122 from the inlet opening 110 of the chamber 102 in the axial direction of the chamber 102. The separation member 136 may extend about 0.1 to about 2 mm, preferably about 0.1 to about 1 mm, and most preferably about 0.1 to about 0.5 mm in the axial direction of the chamber 102.

The inlet opening 110 is located as close as possible to the outlet opening 112, allowing the pump 100 to quickly and reliably bleed and vent the chamber 102, inlet valve 114 and/or inlet conduit 118, respectively.

The pump 100 further includes a control unit 132 connected to the drive unit 130 and the position sensor 134.

The position sensor 134 may determine the position of the piston 104. The sensor 134 may be, for example, an optical sensor. This allows the control unit 132 to monitor proper movement of the piston 104 and detect potential blockages of the piston 104. In one embodiment, the pump 100 may include a travel or path sensor that determines the actual position of the piston 104 and/or the piston stroke traveled by the piston in a given period of time. This allows for more precise control of piston travel and allows for a feedback loop to control the movement of the drive unit 130 and the piston 104.

The control unit 132 may be connected to the dispenser control unit via an interface 138 that supplies electrical energy to the control unit 132.

The drive 130 may comprise a stepper motor, a linear drive, a solenoid, a servo drive, a linear motor and/or any drive capable of positioning the piston 104 in any desired manner. This allows the piston travel of the reciprocating piston 104 to be adjusted in a predetermined manner. Furthermore, the reciprocating speed can be adjusted in a predetermined manner. The minimum step range or minimum commandable travel range of the drive 130 determines the minimum travel of the piston 104 during one stroke.

The maximum displacement of the piston 104 may be within the range of about 5 μL to about 0.02 mL, preferably about 4 μL to about 0.04 mL, and more preferably about 2 μL to about 0.1 mL.

The control unit 132 is configured to control the minimum piston travel so that a single stroke of the piston 104 meters a volume in the range of about 2 μL to about 5 μL, preferably about 1 μL to about 3 μL, and more preferably about 1 μL to about 5 μL.

The cylinder clearance is less than 5% of the piston displacement, preferably less than 2% of the piston displacement, and more preferably less than 1% of the piston displacement. The clearance is essentially formed by the distance between the distal surface of the piston 104 at its distal dead center 108 and the distal surface of the chamber 102 and the inlet valve 114 and the outlet valve 116.

Refer to FIG. 2, which shows a schematic diagram of a metering system according to the present invention. The metering pump 100 is connected to a fluid reservoir 202 filled with a liquid 206. The fluid reservoir 202 is provided with a vent opening. Thus, the pump 100 and the liquid 206 are subjected to the same environmental pressure.

During operation, the piston 104 reciprocating within the cylinder 102 can bleed air from the chamber 102, the inlet valve 114, the inlet conduit 118, and the conduit 205 that connects the pump 100 and the fluid tank 202. Once the bleeding of air within the fluid supply is complete, the reciprocating piston 104 dispenses fluid into the outlet conduit 209.

2 also shows the application of the metering system 200 in a beverage dispenser 300. The beverage dispenser 300 may include a water source 310, e.g. a tap. A filter 312 is connected to the water source 310. The filter 312 filters the water from the water source 310 and reduces the minerals in the water. A mineralizer 314 is connected to the filter 312. The mineralizer 314 adds minerals to the filtered water. After the water passes through the mineralizer 314, the beverage is dispensed into a user's container 316, e.g. a glass.

The beverage dispenser 300 also includes a dispenser control 308. The dispenser control 308 communicates to the control 132 of the pump 100 the amount of liquid 206 to be metered to the mineralizer 314. The liquid 206 may be a mineral liquid that adds minerals to deionized water so that the water dispensed by the mineralizer 314 is suitable for human consumption. Alternatively or in addition, the liquid 206 may include trace elements. The beverage 206 dispensed by the beverage dispenser 300 may be water.

Refer to FIG. 3, which illustrates an exemplary embodiment in which the metering pump and/or metering system of the present invention may be used in an exemplary application.

In step 402, the dispenser control unit 308 communicates to the control unit 132 of the pump 100 the amount of liquid to be dispensed by the pump 100.

In step 404, the control unit 132 calculates the number of piston strokes and the required piston movement required to dispense the set amount of liquid instructed by the dispenser control unit 308. In one embodiment, the control unit 132 may calculate the required number of piston strokes by instructing the piston 104 to reciprocate through the maximum piston movement and a final stroke that is shorter than the maximum piston movement to dispense the remaining amount. The number of piston strokes and the set amount may be calculated based on the following formula: Dispensing set amount = (number of piston strokes - 1) x amount dispensed by maximum piston movement + amount dispensed by final piston stroke.

In other embodiments, the control unit 132 may instruct the drive unit 130 to reciprocate the piston 104 at a constant piston travel until the set amount is dispensed.

In step 406, the method verifies whether a fixed piston travel should be used for each stroke. If a fixed piston travel should be applied for each stroke, the method proceeds to step 408, where it instructs the drive unit 130 to reciprocate the piston 104 the set piston travel and the set number of strokes. The method then ends.

If the method determines in step 406 that the piston 104 should reciprocate as many times as possible at the maximum piston travel, the method proceeds from step 406 to step 410. In step 410, the method determines whether the set amount has been dispensed.

If the set amount was not dispensed, the method proceeds from step 410 to step 412. In step 412, the method determines whether the difference in the set amount to be dispensed is greater than the actual amount dispensed.

If the method determines that the difference in the set amount to be metered is greater than the actual amount to be metered, the method proceeds from step 412 to step 414. In step 414, the control unit 132 instructs the drive unit 130 to reciprocate the piston 104 through the maximum available piston travel.

The method returns to step 410 to verify whether the set amount has been metered by the pump 100. If the method determines that the set amount has been metered by the pump 100, the method ends. If the set amount has not been metered, the method proceeds to step 412 to determine whether the difference between the set amount to be metered and the actual metered amount is greater than the amount that can be metered with the maximum piston travel. If the difference is greater, the method continues with step 414 above and the loop formed by steps 410, 412 and 414.

As soon as the method detects in step 412 that the difference between the set amount to be metered and the actual amount metered is less than the amount that can be metered by the maximum piston travel, the method proceeds to step 416. In step 416, the control unit 132 instructs the drive unit 130 to reciprocate the piston 104 in the chamber 102 with a stroke having a piston travel that is less than the maximum piston travel. The method then ends.

The amount metered by the stroke of the reciprocating piston 104 is the product of the cross-sectional area of the piston 104 and the actual piston movement. If the piston 104 has a cylindrical shape, the actual metered fluid amount is the product of the actual piston movement multiplied by the cylindrical base surface of the piston 104. This allows the control unit 132 to determine the number of strokes and/or the required piston movement required to meter a set amount of fluid.

Note that if a set amount smaller than the maximum piston travel needs to be measured, the method shown in FIG. 3 may be applied. In this case, the piston 104 needs to reciprocate only a single stroke with a piston travel smaller than the maximum piston travel.

Referring now to FIG. 4, a second embodiment of the valve according to the invention is shown in detail. The second embodiment corresponds generally to the first embodiment, with corresponding features identified by corresponding reference numerals and an addend of 400 added to the reference numerals of FIG. 1. A piston 504 is housed in a cylinder 502. The piston is sealed by a first seal 522 and a second seal 524 in the cylinder 502. The first seal 522 and the second seal 524 may be O-rings or X-rings.

The inlet valve 514 is connected to a conduit 518 which is connected to a liquid source. The outlet of the inlet valve 514 is connected to the chamber 502 by a conduit 513. The movable valve member 514f is biased by a spring 514d against a valve seat 514e in a closed position.

As soon as the piston 504 moves from the distal position shown in FIG. 4 to the proximal position, the movable valve member 514f is moved away from the valve seat 516e against the bias of the spring 514d and fluid flows through the conduits 518, 513 into the chamber 502. As soon as the piston 504 moves in the proximal direction, the fluid presses the movable valve member 514f against the valve seat 514e. In the embodiment shown in FIG. 4, the movable valve member 514f includes a circumferential groove in which the O-ring 514c is received. In the embodiment shown in FIG. 4, the O-ring 514c has a higher elasticity than the valve seat 514e.

The outlet valve 516 includes a linear movable valve member 516f biased against a valve seat 516e in a closed position by a spring 514d. In the closed position shown in FIG. 4, the linear movable valve member 516f of the outlet valve 516 contacts the distal end of the piston 504 when the piston moves to distal dead center. This prevents any fluid from passing through the first seal 522, the valve seat 516e, and the linear movable valve member 516f.

In the embodiment shown in FIG. 4, the linear movable valve member 516f includes a circumferential groove in which the O-ring 516c is received. In this embodiment, the O-ring 516c has a higher elasticity compared to the valve seat 516e.

Reference is now made to FIG. 5, which shows a third embodiment of a valve according to the present invention. The third embodiment corresponds generally to the first embodiment, with like features identified by like reference numerals and an addend of 500 added to the reference numerals of FIG. 1. The inlet valve 614 comprises a movable valve member 614f biased against a valve seat 614e by a spring 614d. The movable valve member 614f has a lower elasticity compared to the valve seat 614e.

When the piston 604 is moved distally within the chamber 602, the movable valve member 614f is released from the valve seat 614e and fluid can flow through the conduit 613 and the opening 610 into the chamber 602. When the piston 604 is moved distally, the fluid presses the movable valve member 614f against the valve seat 614e.

The outlet valve 616 includes a movable valve member 616f biased against a seat 616e by a spring 616d. When the piston 604 is moved distally within the chamber 602, the fluid within the chamber 602 presses against the movable valve member 616f, disengaging the movable valve member 616f from the valve seat 616e against the bias of the spring 616d, allowing fluid to exit the chamber 602 and enter the conduit 620. At the distal end (distal dead center), the distal end of the piston 604 contacts the surface of the movable valve member 616f that faces the piston 604. This prevents fluid flow from the chamber 602 through the outlet valve 616 and into the conduit 620.

In the embodiment shown in FIG. 5, the first seal 622' housed around the distal end of the piston 604 is integrally (formed as one piece) with the seat 616e of the outlet valve 616.

In this embodiment, the valve seat 616e has a higher elasticity compared to the movable valve member 616f.

The valve seat 616e and the first seal 622' around the distal portion of the piston are formed as one piece, reducing manufacturing costs and preventing fluid leakage from the chamber 602.

An advantage of the present invention is that the vacuum at the outlet of the pump 100 does not draw liquid 206 out of the chamber 102, the inlet valve 114, the inlet conduit 118 and the liquid 206. Furthermore, the present invention allows the pump 100 and any equipment connected at the inlet side of the pump 100 to be quickly and reliably bled, even though the pump 100 is actually configured to precisely dispense small amounts of liquid 206.

100 Pump 102, 602 Chamber 502 Cylinder 104, 504, 604 Piston 106 Proximal dead center 108 Distal dead center 110, 610 Inlet opening 112 Outlet opening 113 Inlet channel 114, 514, 614 Inlet valve 114a Inlet opening 114b Discharge opening 116, 516, 616 Outlet valve 116a Inlet opening of outlet valve 118, 518 Inlet conduit 120 Outlet conduit 122, 522, 622 First sealing material 123 First recess 124, 524 Second sealing material 125 Second recess 126 Guide 128 Arm 130 Drive unit 132 Control unit 134 Position sensor 136 Separation member 138 Interface 200 Metering system 202 Liquid tank 206 Liquid 209 Conduit 300 Beverage dispenser 308 Dispenser control 310 Water source 312 Filter 314 Mineralizer 316 Container 514c, 516c O-ring 514d, 614d, 616d Spring 514e, 614e, 516e Valve seat 514f, 516f, 614f, 616f Movable valve member 513, 613, 620 Conduit

Claims (17)

a chamber having a proximal portion and a distal portion;
a piston contained within the chamber and movable within the chamber;
a drive unit that reciprocates the piston within the chamber from a proximal dead point to a distal dead point, the distal dead point being located at the distal portion of the chamber and the proximal dead point being located at the proximal portion of the chamber;
an outlet valve located adjacent the distal portion of the chamber, the outlet valve permitting fluid flow out of the chamber when the piston moves in a distal direction and preventing fluid flow into the chamber when the piston moves in a proximal direction;
a seal located at the distal portion of the chamber, the seal sealing the chamber when the piston is in a sealing position contacting the seal ;
an inlet valve that allows fluid flow into the chamber when the piston moves in a proximal direction and prevents fluid flow out of the chamber when the piston moves in a distal direction;
Equipped with
A metering pump , wherein the inlet valve is connected to the chamber at a position proximal to the sealing position and the outlet valve is connected to the chamber at a position distal to the sealing position . the inlet valve includes an inlet opening and an outlet opening connected to the chamber , the inlet opening being in fluid communication with a fluid source;
the pressure in the fluid source is equal to the pressure in the environment in which the metering pump is installed;
2. The metering pump of claim 1, wherein the inlet valve allows fluid flow from the inlet opening to the outlet opening when the pressure at the outlet opening is less than the pressure at the inlet opening and when the pressure at the inlet opening is equal to or less than the pressure in the installation environment of the metering pump. The metering pump of claim 1 or 2 , further comprising an inlet channel connected to the inlet valve and the chamber, the inlet channel being aligned with the sealant. The drive unit is
Stepping motor,
Linear drive unit,
solenoid,
Servo drive unit,
Linear motor,
The metering pump according to any one of claims 1 to 3, comprising at least one of: A first sub-control unit is further provided,
The first sub-control unit is
Accepting a command indicating a set amount of fluid to be dispensed;
calculating a set value of a reciprocating stroke such that when the metering pump dispenses a set amount of fluid, the set amount of fluid is dispensed and the piston is positioned at the sealing position in contact with the seal;
Controlling the drive unit so that the drive unit reciprocates the piston by a reciprocation stroke of the set value;
5. The metering pump according to claim 1, wherein the piston is configured to be positioned at the sealing position when the piston has reciprocated by the set numerical value of the reciprocating stroke. Further comprising a second sub-controller,
The second sub-control unit is
Accepting a command indicating an amount of fluid to be dispensed;
calculating a piston travel of the piston such that the piston is positioned at the seal when the metering pump has dispensed a set amount of fluid;
Controlling the drive unit so that the drive unit reciprocates the piston in the proximal and distal directions by a set piston movement amount;
The metering pump according to any one of claims 1 to 5, configured to position the piston at the sealing position in which the piston contacts the sealant when the piston reciprocates by the set piston travel and a set numerical value of the reciprocating stroke. A control unit including the first sub-control unit and the second sub-control unit is further provided,
The control unit is
Accepting a command indicating an amount of fluid to be dispensed;
calculating a set value of a reciprocating stroke and a set value of piston travel for the piston such that when the metering pump dispenses a set amount of fluid, the set amount of fluid is dispensed and the piston is in the sealed position ;
Controlling the drive unit so that the drive unit reciprocates the piston in the proximal and distal directions by the set piston movement amount and the set numerical reciprocation stroke,
When the piston reciprocates by the set piston movement amount and the reciprocating stroke of the set numerical value,
The metering pump of claim 5 configured to position the piston in the sealing position in contact with the seal. 8. The metering pump of claim 7, wherein the controller is configured to control the driver such that the driver reciprocates the piston a first piston travel during a first stroke and the driver reciprocates the piston a second piston travel during a second stroke, the first stroke and the second stroke dispensing the set amount of fluid , the second piston travel being less than the first piston travel. The metering pump according to any one of claims 1 to 8, wherein at least one of the inlet valve and the outlet valve is a check valve. 9. The metering pump of claim 1, wherein the amount of clearance in the chamber between the distal portion of the chamber and an injection opening of the outlet valve located adjacent to the distal portion is less than 5% of piston displacement. The amount measured by a single stroke at maximum piston displacement is
5 μL to 0.02 mL,
4 μL to 0.04 mL,
2 μL to 0.1 mL,
The metering pump according to any one of claims 1 to 10, wherein the metering pump is within one of the ranges of: The control unit is configured to control the single stroke of the piston to:
2 μL to 5 μL,
1 μL to 3 μL,
1 μL to 5 μL,
A metering pump according to any one of claims 7 to 11, configured to control minimum piston travel so as to meter an amount in one of the ranges: the metering pump comprises a body having the chamber and containing the sealant;
the outlet valve includes a valve seat received in the body portion and a valve member movable relative to the valve seat;
A metering pump according to any preceding claim, wherein the piston contacts the valve member of the outlet valve at its distal position when the valve member of the outlet valve is in its closed position. the metering pump comprises a body having the chamber and containing the sealant;
the outlet valve including a valve seat received in the body of the metering pump and a valve member movable relative to the valve seat;
A metering pump according to any preceding claim, wherein the valve seat of the outlet valve and the seal located in the distal portion of the chamber are integrally formed. The metering pump according to any one of claims 1 to 14,
a fluid container coupled to the injection opening of the inlet valve;
the fluid container is filled with a fluid to be metered by the metering pump;
A metering system, wherein the pressure in the fluid container matches the pressure in the environment of the metering pump. the fluid enclosure further comprising a vent opening in fluid communication with an environment of the fluid enclosure;
the pressure in the fluid container environment is equal to the pressure in the metering pump environment;
16. The weighing system of claim 15. 17. A metering system according to claim 15 or 16, wherein the fluid to be metered is a liquid.