Liquid dispensing systems and methods

Information

  • Patent Grant
  • 6302662
  • Patent Number
    6,302,662
  • Date Filed
    Thursday, March 9, 2000
    24 years ago
  • Date Issued
    Tuesday, October 16, 2001
    22 years ago
Abstract
The present invention provides systems and methods of dispensing liquids. In one embodiment, the system includes a pump with a removable pump module with at least one displacement piston and at least one piston valve. A motor and base assembly provides the supporting components of the pump, which can be used in environments where precise small volumes of ultra-pure liquids must be transferred from a reservoir to a point of use. The preferred embodiment of the system prevents contaminants and air bubbles from being introduced into the liquid to be dispensed by placing a filter across the discharge line downstream from the pump, and providing a separate drawback line for performing the drawback of the liquid in the dispensing nozzle.
Description




BACKGROUND OF THE INVENTION




This invention relates to dispensing liquids in precise volumes and more particularly to the transfer of liquid from a reservoir to a point of use by a pump having a displacement piston and a rotating piston valve communicating with one of a plurality of liquid ports.




The ability to deliver precise small volume amounts of liquids without introduction of contaminants is quite important in the manufacture of many products, especially in the electronics industry. A semiconductor foundry has several principal areas-metrology, lithography, and track where resist and developer must be rapidly and precisely dispensed. More specifically, photolithography requires precise repeatable delivery of photoresist and developer at different rates such as volumes of 0-10 ml±0.1%, repeatable to within ±0.1 volume % with substantially no contaminants or air bubbles. If these requirements cannot be met consistently, it adversely impacts the yield of the process. See, e.g., Chang & Sze,


ULSI Technology


(1996) hereby incorporated by reference.




The semiconductor industry provides, for example, different pumps such as piston pumps, diaphragm pumps, and peristalic pumps to transfer liquid from a liquid reservoir to a dispense nozzle above a silicon wafer in a spin station. After the liquid is dispensed any residual liquid left in the tip of the nozzle is drawn back slightly so that the resulting meniscus force prevents uncontrolled drips on the wafer and the wafer is rotated at high rpm to spread the liquid uniformly over the wafer.




The liquid dispensing system must also provide a filter to capture contaminants which might be introduced in the liquid dispensed. When the filter is upstream of the pump, it captures the contaminants generated for example at the reservoir and/or the reservoir line leading to the pump but will be ineffective at capturing contaminants generated in the pump which then enter the liquid dispensed on the wafer. When the filter is downstream of the pump, the filter may capture pump generated contaminants but may still release air bubbles and contaminants into the dispensing system during draw back mode when the liquid reverses direction through the filter, which tends to dislodge some of the particles caught in the filter.




SUMMARY OF THE INVENTION




The invention provides systems and methods of rapid delivery of liquids in precise volumes and with accuracy. The systems include a pump operating under the positive displacement principle. The pump includes at least one displacement piston, and at least one piston valve with a fluid slot, where the pistons in a cylinder define a pumping chamber. In general the displacement piston travels back and forth in the cylinder, producing suction, and discharging pumping action. The distance traveled by the displacement piston determines the dispensing volume of the pumping chamber and the direction of travel determines the direction of flow through any cylinder port. The piston valve rotates to align the fluid slot with a given cylinder port to communicate with the pumping chamber.




In refill mode, the piston valve rotates until the slot aligns with the intake port of the cylinder so the pumping chamber can communicate with the reservoir. The displacement piston retracts in the cylinder, expanding the pumping chamber, and drawing liquid from the reservoir though the intake port and into the pumping chamber. In dispense mode, the piston valve rotates closing the intake port so that the pumping chamber no longer communicates with the reservoir until the piston valve slot aligns with the discharge port out of the pumping chamber. The displacement piston slides forward, reducing the volume of the pumping chamber, expelling liquid through the discharge port.




In one embodiment, the piston valve includes a plurality of ports, such as an intake port, a discharge port, and a drawback port to permit precise delivery of liquids through a dispense nozzle without introducing contaminants, air bubbles, or liquid dripping. In drawback mode, in this embodiment, after the discharge step, the piston valve rotates closing the discharge port and the piston valve slot aligns with the drawback port, then the displacement piston slides back, expanding the volume of the pumping chamber, drawing liquid back in the dispense nozzle. The embodiment of the system also prevents contaminants and air bubbles from being introduced into the liquid to be dispensed from the nozzle by placing a filter across the discharge line downstream from the pump, and providing a separate drawback line for performing the drawback of the liquid in the dispensing nozzle so that drawback does not occur through the filter. This embodiment has special advantage in the precise control of semiconductor equipment used in dispensing liquid chemicals in ULSI technology.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a perspective drawing of an embodiment of the pump, and illustrates the assembled pump including the pump module and the motor and base assembly.





FIG. 2

is a partial cross-section taken along A—A of

FIG. 5 and a

perspective drawing of an embodiment of the pump module.





FIG. 3

is an exploded view of the components of the pump module shown in FIG.


2


.





FIG. 4

is an exploded perspective view illustrating a preferred universal coupling for the piston valve.





FIG. 5

is an end view of the port fitting case, the valve bearing ball, the three ports of the port fitting case, and a clamp band around the port fitting case.





FIG. 6

is a schematic diagram illustrating the basic components of one embodiment of the precision liquid dispensing system.





FIG. 7

is an exploded perspective view with partial cross-sections of a ratchet-actuator assembly. The ratchet housing is on the left and the pneumatic actuator on the right.





FIG. 8

illustrates another view of the ratchet-actuator assembly of FIG.


7


. The pneumatic actuator now is on the left and the ratchet housing on the right.





FIG. 9

is a perspective view of the inner parts of the ratchet-actuator.





FIG. 10

is an exploded perspective view of the ratchet-actuator assembly.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS





FIG. 1

illustrates an embodiment of a pump


1


capable of transferring precise small volumes, e.g., 0-10 ml, of a liquid from a liquid reservoir to a dispense nozzle. The pump


1


can be used in a system such as that depicted in

FIG. 6

to deliver resist and developer to semiconductor wafers. As shown in

FIG. 6

, the components of the system include a liquid supply reservoir


143


, a liquid supply line


144


, a three-port pump


1


, an upstream discharge line


148


, a filter


149


, a downstream discharge line


150


, a dispense line


151


, a dispense nozzle


152


, and a drawback line


147


. The liquid reservoir


143


can be a variety of well known reservoirs, the liquid lines are preferably of Teflon, the tube hardware and fittings can be Parker, Parabound Adaptor, Paraflare x Pipe BA-4F4, one suitable filter


149


is the Pall model no. MCD9116UFTEH, and the materials of the pump


1


will be described in detail below.




In operation, the pump


1


and the liquid lines are preferably charged with liquid. In dispensing mode, the pump


1


displaces liquid through the upstream discharge line


148


, the filter


149


, the downstream discharge line


150


, the dispense line


151


, and out of the dispense nozzle


152


onto the wafer. In drawback mode, occurring preferably a short time after the dispense mode, the three-port pump


1


valve is actuated to communicate with the drawback line


147


and the displacement piston in the cylinder of pump


1


reverses direction to enable drip-free dispense by drawing the liquid back inside the nozzle


152


through the drawback line


147


avoiding the need to reverse the flow through the filter


149


. This feature helps to prevent contaminants from being dislodged from the filter


149


. In purge mode, the system can use the drawback line


147


to prime any air out of the nozzle


152


also without going through the filter


149


. This feature reduces air bubbles from being introduced into the liquid dispensed. Alternatively, the pump


1


might add a fourth port to allow purge of air from entering into the liquid supply reservoir


143


through a liquid purge back line (not shown) to conserve resist.




Referring again to the embodiment shown in

FIG. 1

, the pump


1


includes a pump module, a motor and base assembly, and an electronic controller (not shown), and operates by the positive displacement principle. As shown in

FIG. 2

, the displacement piston


80


pumps the liquid by traveling back and forth in a cylinder liner


30


, as indicated by the arrows, producing suction and discharging action. The distance traveled by the displacement piston


80


in the cylinder liner


30


is proportional to the volume of the pumping chamber


87


. For liquid intake the piston valve


81


rotates so that the fluid slot


82


aligns with an intake port


85


(

FIG. 5

) so that the pumping chamber


87


communicates with the liquid reservoir


143


(FIG.


6


). The displacement piston


80


retracts in the cylinder liner


30


, expanding the pumping chamber


87


, drawing liquid from the reservoir


143


(

FIG. 6

) though the intake port


85


(

FIG. 5

) and into the pumping chamber


87


. The piston valve


81


rotates closing the intake port


85


(

FIG. 5

) so that the pumping chamber


87


no longer communicates with the reservoir


143


(FIG.


6


).




To discharge the liquid drawn into the pumping chamber


87


, the piston valve


81


rotates to align the fluid slot


82


with the discharge port


83


, and the displacement piston


80


extends into the cylinder liner


30


, expelling liquid from pumping chamber


87


through the discharge port


83


. To draw back liquid in the discharge line, the displacement piston


80


can retract immediately after the discharge step. However, in the preferred embodiment, the pump


1


draws back the liquid in the dispense nozzle


152


(

FIG. 6

) by rotating the piston valve


81


to align the fluid slot


82


with a drawback port


90


, and then retracting the displacement piston


80


.





FIG. 3

is an exploded view of the parts making up the pump module


10


. A valve bearing ball


96


is attached on a neck


35


(

FIG. 1

) of the piston valve


81


by a cone point socket set screw


161


. To form a liquid seal the pump module


10


preferably provides a cylinder end cap


160


, a Teflon thrust washer


158


, a flange


157


on the piston valve


81


, a Teflon thrust washer


163


, and a lip seal


162


. A conventional clamp band


43


is provided to hold a port fitting case


31


on the cylinder liner


30


. As shown in

FIG. 1

, a support


172


, preferably including a spacer


171


, is located under the port fitting case


31


to prevent rotation of the port fitting case


31


from torque produced by rotation of the motor


14


. The port fitting case


31


is preferably made of Teflon. Another liquid seal is provided by assembly of a cylinder end cap


79


, a lip seal


89


, and a cylinder liner


30


. A socket head cap screw


53


is provided which is inserted into a spherical bearing retainer


54


and a spherical bearing


75


with a race


154


(

FIG. 2

) and into the end of the displacement piston


80


to hold the retainer


54


, the bearing


75


, and the displacement piston


80


in fixed relationship with each other.




When the various parts shown in

FIG. 3

are assembled, the pump module


10


appears as shown in FIG.


2


.

FIG. 2

illustrates that the fluid seal includes a cylinder end cap


79


holding a lip seal


89


against the cylinder liner


30


and a contact surface


78


of the displacement piston


80


.

FIG. 2

illustrates when the fluid slot


82


described earlier is aligned with the drawback port


90


. The clamp band


43


holds the port fitting case


31


to the cylinder liner


30


so that the drawback port


90


aligns with the L-shaped port


91


of the port fitting case


31


. Similarly, the clamp band


43


holds the port fitting case


31


to the cylinder liner


30


so that the discharge port


83


aligns with the L-shaped port


84


. The L-shaped port


91


narrows to a passage


92


in a male connector


94


, and threads


93


engage a twist tight collar


33


(FIG.


1


). Likewise, the L-shaped port


84


narrows to a passage


99


of a male connector


101


and threads


100


engage a twist tight collar


32


(FIG.


1


). Again, the fluid seal at the valve bearing ball


96


end preferably uses the parts discussed earlier in connection with FIG.


3


. The piston valve


81


includes a relief band


156


, which is slightly smaller in diameter than the rest of piston valve


81


to permit liquid to enter in the gap to prevent the curing of the liquid under the pressures and temperatures created by the tight fit and movement of the piston valve


81


. The piston valve


81


also includes an inner neck


159


, an outer neck


35


and is attached to the valve bearing ball


96


which has two slots


98


and


164


and a flat surface


97


for reasons discussed below.





FIG. 2

also shows that the spherical bearing


75


is held to a piston end cap


76


preferably made of stainless steel


316


. The piston end cap


76


is heat shrunk or glued on the end of the displacement piston


80


as shown in

FIGS. 2-3

. The displacement piston


80


, the piston valve


81


, and the cylinder liner


30


are preferably made of aluminum oxide or polished zirconia (YTZP) but can be also made of another suitable ceramic, a stainless steel, Delrin™, Tefzel™, or Kynar™. The advantage of aluminum oxide is it may not require lubrication beyond that provided by the liquid being dispensed or metered, it is extremely hard and resists abrasion, it exhibits little wear after many cycles, it is chemically stable, and it allows precision machining and diamond tooling with close running fits (100 millionths of an inch). Aluminum oxide's properties of low friction, hardness, and stability allow the pump module


10


to be primarily sealed by close clearance of the pistons


80


,


81


, and the cylinder liner


30


. This means no compliant seals may be needed which eliminates a set of parts which frequently fail and require replacement in conventional pumps.




As shown in

FIGS. 1-2

, the pump


1


includes motors


14


and


22


for driving the pump module


10


. First, a stepper motor


22


drives the displacement piston


80


by rotating a bottom pulley


65


coupled by a drive belt


23


to a set of pulleys


24


and


64


. In alternative embodiments, the motor


22


can be a servo motor or another suitable positioning motor. The pulleys contact the drive belt


23


with sufficient friction and tension to prevent slippage between the pulleys and the belt. One suitable drive belt is the Breco-flex 10T5/390. A suitable pulley is the LS21T


5/20-2


made by Breco-flex. The tension of the drive belt


23


can be adjusted by loosening bolts


71


-


74


residing in the vertical slots of rigid plate


70


so that the pulley


65


can move up to reduce or down to increase the tension of the drive belt


23


. Thus, the rigid plate


70


provides an adjustable support structure for mounting the pulley


65


and the stepper motor


22


.




In a preferred embodiment if the stepper motor


22


rotates, the drive belt


23


transfers that force to the pulleys


24


and


64


, which rotate precision lead screws


44


and


19


. Eastern Air Devices, Inc., motor series LH2318 together with Intelligent Motion Systems, Inc. Model IM483 drive electronics provide a compatible motor and controller combination for this purpose. One end of precision lead screw


44


attaches to the pulley


24


and the other end rotates in a lead screw and linear shaft bearing block


29


. One end of precision lead screw


19


attaches to the pulley


64


and the other end rotates in a lead screw and linear shaft bearing block like block


29


but not shown to expose other parts to view.




Spacers


63


and


62


space pulleys


24


and


64


from triangular shaped lead nuts


58


and


25


. Lead nut


58


is fixed to a displacement slide block


46


by bolt


57


hidden by drive belt


23


in

FIG. 1

, a bolt


55


partially hidden by spacer


63


in

FIG. 1

, and a bolt


56


. The lead nut


25


is bolted to a displacement slide block


21


by bolt


61


hidden by the spacer


62


, a bolt


59


, and a bolt


60


. A pair of parallel linear bearing shafts


17


and


45


guides the displacement slide blocks


21


and


46


. A piston coupling


28


is attached by bolts


51


and


52


to the displacement slide blocks


21


and


46


and to the displacement piston


80


by the socket head cap screw


53


, the retainer


54


, and the bearing


75


described earlier. Thus, the piston coupling


28


, and the displacement slide blocks


21


and


46


move as a unit to drive the displacement piston


80


in and out of the cylinder liner


30


as the precision lead screws


44


and


19


rotate and engage the threads of the lead nut


58


and the lead nut


25


, respectively. Preferably, the displacement slide blocks


21


and


46


have holes, which are not threaded and therefore do not engage either the threads of the precision lead screw or bind the linear bearing shafts.




An adjustable flag


20


is held by bolts


49


and


50


to the displacement slide block


21


and overlaps an adjacent piston extended position sensor


15


when the displacement piston


80


fully extends into the cylinder liner


30


. Similarly, an adjustable flag


27


is held by bolts


47


and


48


to the displacement slide block


46


and overlaps an adjacent piston retracted position sensor


26


when the displacement piston


80


fully retracts in the cylinder liner


30


. One suitable sensor uses the Hall effect to detect when the metal flag interrupts a magnetic field emanating from the sensor. Another uses the photoelectric effect where an object fixed to the displacement block serves to partially or fully interrupt a light beam aimed at a photo detector. The Honeywell Microswitch 4AV series is suitable for performing this function.





FIGS. 1-2

illustrate that the pump


1


also includes a motor


14


for driving the piston valve


81


of the pump module


10


by rotating a pulley


38


coupled by a belt


13


to a pulley


12


. The pulleys


12


and


38


have sufficient friction with the belt


13


to avoid slippage. The motor


14


is preferably an air-powered rotary indexer because it quickly rotates the fluid slot


82


into alignment with a port when commanded by a conventional controller. In such a motor such as that manufactured by SMC, for example, the NCRBI-W30-1805 series motor, pneumatic air enters input


18


and a well known ratchet-gear mechanism converts the 180 degree movements of the motor


14


into the desired angular increment, e.g., 120 degrees for a three-port embodiment as shown in FIG.


1


. After an angular increment occurs the air is relieved at air exhaust


16


. In alternative embodiments, the motor


14


can be a servomotor or another suitable positioning motor. Preferably, a conventional controller using advanced solid-state electronics with microprocessor technology and sensors can be used to control the pump


1


, including the motors


22


and


14


to actuate the movement of the displacement piston


80


and the piston valve


81


at appropriate velocities, distances, and times.





FIG. 7

is a partially exploded cross-sectional view of an embodiment of the ratchet-actuator assembly


200


. The ratchet-actuator assembly


200


includes a ratchet housing


202


, a pneumatic actuator


204


, and an adapter ring


242


. The adapter ring


242


locates the pneumatic actuator


204


on the ratchet housing


202


. The assembly


200


is held together by socket cap screws


206


,


208


, and


210


in the following manner. Screw


210


, for example, butts against a counterbore


220


in the ratchet housing


202


, travels through a ratchet hole


222


, then into a hole in an adapter ring


242


, and into a threaded hole


244


in the pneumatic actuator


204


. Screws


206


and


208


are similarly inserted and/or threaded through their respective holes in the same parts. In a preferred arrangement, the three screws


206


,


208


, and


210


are spaced apart from each other 120 degrees. The screws


206


,


208


, and


210


are held in the assembly


200


by internal threads in the pneumatic actuator


204


. Screws


206


,


208


, and


210


use the leftover thread on the backside of cap screws


255


and


257


(FIG.


8


).




Ratchet housing


202


houses a ratchet


234


integral or fixed to a ratchet shaft


214


. The shaft


214


has a groove


212


, functioning as a key seat. The ratchet


234


/shaft


214


rotate within the housing


202


, via a roller clutch/bearing assembly


218


press-fit into a collar


216


of the housing


202


. As shown in

FIG. 8

, the opposite end of the ratchet


234


has three teeth


223


,


224


, and


225


, spaced 120 degrees apart from each other. The ratchet housing


202


includes a pawl


226


held to the ratchet housing


202


by a pin


227


. The pin


227


is fixed to the pawl


226


. Socket cap screws


232


and


235


shown in

FIG. 10

hold a spring plunger block


230


to the ratchet housing


202


. The spring plunger block


230


laterally supports a spring plunger


228


, which biases the pawl


226


against a cam


240


as discussed below.




The pneumatic actuator


204


is a conventional pneumatic vane type actuator such as the SMC NCRB1BW30, including a vane blade


246


fixed and extending from a vane hub


249


attached or integral with a vane shaft


248


. A vane shaft collar


251


locates the vane shaft


248


axially in the pneumatic actuator


204


. A cam


240


preferably attached to the vane shaft


248


raises and lowers the pawl


226


off the ratchet


234


depending on the rotational position of the cam


240


.





FIG. 8

illustrates the same ratchet-actuator assembly


200


shown in

FIG. 7

, with a better view of the pneumatic actuator


204


and the internal parts of the ratchet housing


202


. In particular,

FIG. 8

shows the end of the vane shaft


253


and the collar


251


holding the vane shaft


253


, the socket cap screws


255


and


257


holding the pneumatic actuator together, the location of port


18


, and the three ratchet teeth


223


,


224


, and


225


.




Air pressure (e.g., 100 psi max) is applied through a conventional four-way solenoid valve (not shown) into the port


16


against the vane blade


246


. This rotates the vane blade


246


until it runs into a mechanical stop as shown in

FIG. 8

in the pneumatic actuator


204


such that the lobe


241


of the cam


240


raises the pawl


226


off the ratchet


234


. This is the ratchet-gear actuator's normal pressurized state. When the air pressure switches into the port


18


and exhausts air through the port


16


, the vane blade


246


rotates forward as indicated by the arrow above the camshaft


238


shown in FIG.


8


. During this rotation the cam


240


lowers the pawl


226


back onto the ratchet


234


, which shortens the rotation of the vane shaft


248


from 180 degrees to 120 degrees when the pawl


226


engages one of the teeth


223


,


224


, or


225


, spaced 120 degrees apart. Thus, as the ratchet


234


rotates, each ratchet tooth consecutively catches on the pawl


226


, which is swiveled axially about the pin


227


(shown FIGS.


8


-


10


).




A roller clutch


259


such as a Torrington, type DC roller clutch transfers rotational motion from the cam


240


to the ratchet


234


(FIG.


8


). The roller clutch


259


engages the camshaft


238


when the cam


240


and the camshaft


238


rotate forward as shown by arrow, which rotates the ratchet


234


in the same direction. During a reverse rotation, the roller clutch


259


disengages and acts as a bearing to the camshaft


238


, which allows the cam


240


, the camshaft


238


, and the vane shaft


248


, all fixed together, to rotate back to the normal position. To prevent reverse rotation on the ratchet


234


, a roller clutch/bearing assembly


218


such as Torrington, type DC roller clutch and bearing assembly, FCBL-8-K, is press-fit into the ratchet housing


202


, and acts on the ratchet shaft


214


. In a preferred embodiment, one alternation (i.e., forward rotation) of the pneumatic actuator shaft


248


produces one increment of direct rotation of the ratchet shaft


214


.





FIG. 9

is a perspective view of the inner parts of the ratchet-actuator assembly. It shows the vane shaft


248


having an end


253


, a hub


249


, and a vane blade


246


. It shows the cam


240


attached to the vane shaft


248


, and the lobe


241


at peak rotation to raise the pawl


226


around the pin


227


against the biasing force being applied by the spring plunger


228


at a contact point


231


. The plunger block


230


laterally holds the spring plunger


228


so that it can move up and down in response to the rotation of the cam


240


. A screw


201


is turned to adjust the amount of biasing force being applied to the pawl


226


. When the cam


240


raises the pawl


226


, the pawl


226


disengages from the ratchet tooth, here shown as tooth


224


. Rotation of the ratchet shaft


248


has the same affect with respect to the other teeth


223


and


225


.





FIG. 10

is an exploded view of the ratchet-actuator assembly


200


shown in

FIGS. 7-9

. The same parts shown in

FIGS. 7-10

have the same part numbers. Roller clutch/bearing assembly


218


is shown before it is press-fit into ratchet housing


202


. The spring plunger block


230


is shown before a set of screws


232


and


235


are inserted in holes


221


and


233


of the spring plunger block


230


, and into the threaded holes


229


and


203


of the ratchet housing


202


. The ratchet housing


202


includes a notch to give access to the pawl and to secure the spring plunger block


230


to the ratchet housing


202


.

FIG. 10

shows the ratchet


234


, the ratchet shaft


214


apart from the ratchet housing


202


and before the ratchet shaft


214


is inserted into the bearing


218


. The pin


227


fixed to the pawl


226


has two ends, including shown end


217


, both of which extend beyond the edges of the pawl


226


.

FIG. 10

shows the camshaft


238


before insertion into the bearing


259


where the camshaft


238


contacts the inner bearing surface


258


. In this embodiment, the cam


240


is attached to the pneumatic actuator shaft


248


by socket cup point set screw


243


, being inserted into the camshaft


238


, and tightened against a flat surface


260


of the pneumatic actuator shaft


248


. The adapter ring


242


includes holes


245


,


256


, and


262


, which correspond to the socket cap screws


206


,


208


, and


210


, which in turn, are inserted into holes


268


,


266


, and


270


in the pneumatic actuator


204


. An adapter ring dowel pin


247


is later force-fit in the adapter ring


242


and orients the ratchet housing


202


.




A suitable drive belt


13


is the Breco-flex 10T5/390 and one suitable pulley is the LS21T5/20-2 made by Breco-flex. The tension of the drive belt


13


can be easily adjusted by loosening bolts such as bolts


40


-


41


in the vertical slots at corners of a rigid plate


39


and moving the rigid plate


39


supporting the pulley


38


up to reduce the tension or down to increase the tension of the drive belt


13


. Thus, the rigid plate


39


provides an adjustable support structure for mounting the pulley


38


and the motor


14


. A L-shaped bracket


37


includes a conventional sealed bearing for supporting the shaft of the pulley


12


and an universal coupling


11


shown in FIG.


1


.




The universal coupling


11


eliminates the problem of how to exactly align the axis of the pulley


12


with that of the piston valve


81


. The location of the universal coupling


11


in the pump


1


is best shown in

FIG. 1

, but the details are in FIG.


4


. As shown in

FIG. 4

, an exploded view, the universal coupling


11


includes a coupling body


8


with a receptacle for the valve bearing ball


96


, and a set of pins


2


and


9


to hold the valve bearing ball


96


in the receptacle. Pin


2


engages slot


98


and pin


9


engages slot


164


on valve bearing ball


96


to provide a positive rotational coupling. Thus, the pump module


10


is held by the universal coupling


11


on one end and by the piston coupling


28


on the other. This permits the pump module


10


to be quickly removed from the rest of the pump


1


for cleaning or autoclaving. For example, to remove the pump module


10


, one would remove piston coupling


28


, then pivot the pump module


10


approximately 90 degrees with respect to the operational axis on pins


2


and


9


to the dofted line position shown in FIG.


4


. When slots


98


and


164


are aligned perpendicular to coupling


8


, the pump module


10


can be removed. To assist in that removal, the flat surface


97


of the valve bearing ball


96


provides clearance to the button


5


in universal coupling


11


when the pump module


10


is pivoted 90 degrees.




A biasing means holds the valve bearing ball


96


in place during operation and includes a button


5


biased by a Belleville washer


6


(i.e., domed shaped for spring action) and held by a retainer washer


7


. To install the biasing means in the coupling body


8


the following steps are taken. The Belleville washer


6


is inserted in the retainer washer


7


, the button


5


is placed on the washer


6


, and preferably three dowel pins such as dowel pin


3


are partially inserted in holes 120 degrees apart to protrude in the coupling body


8


to guide the retainer washer


7


along corresponding slots


174


,


176


, and


178


. When each pin hits the end of its slot, where a hole exists, the pin can be driven into the hole of the retainer washer


7


. Because of the tight fit and flared shape of the pins, this technique firmly attaches the retainer washer


7


in the coupling body


8


. A cone point set screw


4


travels through the larger top hole in coupling body


8


and engages in threaded hole


180


in the retainer washer


7


, acting to fix the coupling body


8


to the shaft of the pulley


12


. As shown in

FIG. 1

, conventional spacers (not shown) maintain pulleys


12


and


38


at an appropriate distance from respectively the L-shaped bracket


37


and the plate


39


.





FIG. 5

is a detail end view of one embodiment of a three-port case fitting


31


. It shows where the cross-section A—A is taken in the embodiment illustrated in FIG.


2


and can be understood in conjunction with embodiments illustrated in

FIGS. 1-2

. In those embodiments, the top port dedicated to a drawback line, includes a male connector


94


defining a passage


92


and having threads


93


. The bottom right port, almost completely hidden in

FIG. 2

, and dedicated to an intake line, includes a male connector


168


defining a passage


167


and with threads


169


. The bottom right port communicates with the fluid slot


82


by the port


85


represented by dotted lines. The bottom left port, dedicated to a discharge line, includes a male connector


101


defining a passage


99


and with threads


100


.

FIG. 5

also illustrates an embodiment for the valve bearing ball


96


including the flat surface


97


as well as the slots


98


and


164


for engaging pins


2


and


9


of the universal coupling


11


as discussed earlier.




Any given port can function as an intake or a discharge liquid depending on whether the displacement piston


80


retracts or extends into the cylinder liner


30


after alignment. Further, the port fitting case


31


is not limited to three ports as illustrated but could be a plurality of ports depending on the application. Accordingly, the pump module


10


could have multiple outputs and/or multiple inputs and/or multiple drawbacks and/or purge lines. In addition, a pump


1


could have a plurality of pump modules


10


disposed in parallel each having a stepper motor


22


or driven by the same stepper motor


22


and each having their own piston valve


81


and motor


14


or driven by the same motor


14


. Of course, this permits the compact pumping of different liquid chemicals with isolation between the chemicals. The design of the piston valve


81


dispenses and meters liquid without any secondary mechanism such as check valves which allows for longer life, higher reliability, and greater accuracy.



Claims
  • 1. A liquid dispensing pump system, comprising:a pump module including a displacement piston and a piston valve disposed in a cylinder and defining a pumping chamber, wherein the displacement piston travels back and forth in the cylinder, producing suction, and discharging pumping action, a port case fitting with a plurality of ports able to communicate one at a time with a fluid slot in the piston valve based on rotation of the piston valve, and the direction of travel of the displacement piston determines the direction of flow out of any port; a motor for driving the displacement piston back and forth in the cylinder; a ratchet-actuator assembly for rotating the piston valve so that the fluid slot of the piston valve communicates with one of the plurality of ports in the port case fitting; and a motor and base assembly for supporting the pump module, the motor for driving the displacement piston, and the ratchet-actuator assembly for rotating the piston valve.
  • 2. The system of claim 1, wherein the ratchet-actuator assembly includes:an actuator for rotating an actuator shaft, a cam and camshaft extending from the actuator shaft, and a ratchet extending from a ratchet shaft, wherein the actuator shaft rotates back and forth causing the cam to lower or lift a pawl to engage or disengage with a ratchet tooth and a roller clutch transfers forward rotation of the camshaft to the ratchet when the pawl is not engaged with the ratchet tooth.
  • 3. The system of claim 2, wherein the actuator is a pneumatic actuator with a vane blade.
  • 4. The system of claim 1, wherein the ratchet-actuator assembly transfers the forward and reverse rotation of an actuator shaft to forward rotation of a ratchet shaft coupled to the piston valve.
  • 5. The system of claim 1, wherein the ratchet-actuator assembly includes:a ratchet in a housing and having ratchet teeth, wherein the ratchet is integral with or fixed to a ratchet shaft and coupled to a roller clutch, an actuator shaft with a cam and camshaft coupled to the roller clutch, and a pawl adjacent the cam, wherein the rotational position of the cam determines whether the pawl engages or disengages the ratchet teeth, and wherein the roller clutch engages when the camshaft rotates forward and disengages when the camshaft rotates back.
  • 6. An apparatus for pumping fluid, comprising:a pump module, including a cylinder liner with a plurality of ports, a displacement piston slidably disposed in the cylinder liner, a piston valve with a fluid slot rotatably disposed in the cylinder liner, wherein the displacement piston and the piston valve and cylinder liner define a pumping chamber; a first motor operably driving the displacement piston back and forth; a second motor operably rotating the piston valve to align the fluid slot with each of the liner ports; and a motor and base assembly supporting the pump module, the first motor, and the second motor.
  • 7. The apparatus of 6, further comprising a controller coupled to the first motor and the second motor during refill, discharge, and drawback modes to actuate:the displacement piston to expand the volume of the pumping chamber and the piston valve to rotate the fluid slot so the pumping chamber only communicates with an intake port, the displacement piston to reduce the volume of the pumping chamber and the piston valve to rotate the fluid slot so the pumping chamber only communicates with a discharge port, and the displacement piston to reduce the volume of the pumping chamber and the piston valve to rotate the fluid slot so the pumping chamber only communicates with a drawback port.
  • 8. The apparatus of claim 6, wherein the first motor is coupled to a plurality of lead screws supported by the motor base assembly and disposed parallel to the pump module.
  • 9. The apparatus of claim 8, further comprising a plurality of displacement slide blocks, each displacement slide block having a lead screw hole parallel to the pump module, a member joining the displacement slide blocks holding the pump module, and wherein each of the plurality of lead screw resides in a lead screw hole in one of the displacement slide blocks.
  • 10. The apparatus of claim 8, wherein the first motor is coupled to a motor pulley, wherein each of the plurality of leads screws is coupled to a lead screw pulley, and wherein a belt couples the first motor pulley and each of the lead screw pulleys to drive the displacement piston back and forth.
  • 11. The apparatus of claim 9, further comprising a plurality of linear bearing shafts, wherein each of the plurality of linear bearing shafts resides in a linear bearing shaft hole in one of the displacement slide blocks.
  • 12. The apparatus of claim 6, wherein the second motor includes a ratchet-actuator assembly for rotating a cam actuator shaft forward or back and a ratchet assembly converting the forward or reverse rotation to forward rotation of the piston valve.
  • 13. The apparatus of 12, wherein the ratchet-actuator assembly includes:a ratchet, in a housing, having ratchet teeth, a shaft, and supporting a roller clutch, an actuator shaft with a cam, and a pawl biased to engage the ratchet teeth, wherein the rotation of the cam raises and lowers the pawl with respect to the ratchet teeth, wherein each ratchet tooth catches on the pawl.
  • 14. A ratchet-actuator assembly, comprising:a ratchet, in a housing, having ratchet teeth, a shaft, and supporting a roller clutch; an actuator shaft with a cam and camshaft; a pawl biased to engage the ratchet teeth; and wherein the actuator shaft rotates the cam back and forth so as to engage and disengage the pawl with respect to the ratchet teeth and the camshaft engages the roller clutch to rotate the ratchet forward.
  • 15. A ratchet-actuator assembly, comprising:an actuator shaft with a cam and camshaft; an actuator for rotating the actuator shaft back and forth; and a ratchet with one or more teeth, a housing, a shaft, a pawl, a spring, and a roller clutch, wherein the housing rotatably supports the ratchet, the pawl, and the spring to bias the pawl against the ratchet, wherein the ratchet supports the roller clutch to engage and disengage the camshaft depending on the direction of rotation of the camshaft and the pawl selectively engages the teeth depending on the position of the cam with respect to the pawl.
  • 16. The ratchet-actuator assembly of claim 15, wherein the actuator is a pneumatic actuator, including a vane blade extending from a vane shaft and directing pressurized gas for rotation of a vane shaft back and forth.
  • 17. A ratchet-actuator assembly comprising:an actuator for rotating an actuator shaft; a cam and camshaft extending from the actuator shaft; and a ratchet extending from a ratchet shaft, wherein the actuator shaft rotates back and forth causing the cam to lower or lift a pawl to engage or disengage a ratchet tooth and a roller clutch transfers forward rotation of the camshaft to the ratchet when the pawl is not engaged with the ratchet tooth.
Parent Case Info

This application is a continuation-in-part of application Ser. No. 09/360,851, filed Jul. 24, 1999, which is incorporated herein by reference.

US Referenced Citations (4)
Number Name Date Kind
5044889 Pinkerton Sep 1991
5312233 Tanney et al. May 1994
5863187 Bensley et al. Jan 1999
5996620 Bensley Dec 1999
Continuation in Parts (1)
Number Date Country
Parent 09/360851 Jul 1999 US
Child 09/522249 US