LIQUID DISPENSING PUMP
Technical Field
This invention pertains to fluid dispensing apparatus.
In particular, it pertains to a pump especially designed for the accurate and repeatable dispensing of small to medium quantities of liquid.
Background Art
There are numerous commercial, industrial, and research applications that require the ability to repetitively deliver liquid in accurately metered amounts. For instance, food and drug processing, cosmetic packaging, biochemical procedures, and industrial chemistry applications often require the rapid and repetitive delivery of liquid into viles, jars, or other containers.
Some applications require the repeat accuracy (that is, the variance of volume delivered in successive deliveries), to be as great as .01 percent at volumes of .5 milliliters. Additionally, when handling unusually viscous liquids such as toothpaste and cosmetics, there is a need to forcibly separate the individual portions of dispensed fluid from the pump nozzle after delivery of the portion from the pump.
U.S. Patents 4,755,113, 4,690,310, and 4,648,533, all assigned to the same assignee as the present application, describe pumps especially designed to dispense fluids in small amounts and with high accuracy. While such pumps are particularly well suited to certain applications, the machining and manufacturing costs of such pumps are not always justified by particular applications.
Moreover, the inventors of the present invention are not aware of any suitable apparatus for separating dispensed, highly viscous liquids from the nozzle of a dispensing pump.
A fluid dispensing pump designed for the rapid, repetitive dispensing of liquid in carefully metered amounts, that was especially designed to reduce machining and assembly costs in its manufacture, and which incorporated a means for rapidly and positively separating highly viscous liquids from the nozzle of the pump, would present decided advantages.
Summarv of the Invention
The present invention incorporates the ability to rapidly and repetitively dispense fluid in accurately metered amounts into a pump structure specially designed to reduce machining and assembly requirements in the manufacture of the pump. Moreover, the invention hereof incorporates the ability to rapidly, and positively separate highly viscous liquids from the pump nozzle as they are dispensed by the pump.
The liquid dispensing pump in accordance with the present invention includes a pump body having an axially oriented, valve spool receiving internal chamber, a generally cylindrical valve spool shiftably received within the chamber, and a piston barrel detachably coupled to the pump body and oriented transversely to the axis of the valve spool. In one embodiment, the valve spool includes an internal, axial outlet channel for dispensing fluid in the direction of the path of travei of the shiftable valve spool. A specially designed nozzle provides for introduction of pressurized air into the stream of dispensed fluid to forcibly separate the dispensed fluid from the nozzle.
Brief Description of the Drawings
Fig. 1 is a fragmentary, sectional, front elevational view of the fluid dispensing pump in accordance with the present invention, with the valve spool and piston oriented for entry of liquid into the pump;
Fig. 2 is similar to Fig. 1 but with the valve spool and piston oriented for discharge of liquid;
Fig. 3 is a fragmentary, sectional, front elevational view of a fluid dispensing pump in accordance with a second embodiment of the present invention with the valve spool and piston oriented for entry of liquid into the pump;
Fig. 4 is similar to Fig. 3 but with the valve spool and piston oriented for discharge of liquid;
Fig. 5 is a fragmentary, sectional, front elevational view of the liquid dispensing pump nozzle in accordance with the present invention;
;
Fig. 6 is similar to Fig. 5, but with the nozzle pressurized with compressed air so as to separate the dispensed liquid from the pump nozzle.
Detailed Description of the Drawings
Referring to the drawings, a liquid dispensing pump 10 in accordance with the present invention broadly includes pump body 12, shiftable valve spool 14, piston barrel 16, piston 18, and spool drive 20.
Pump body 12 includes spool receiving axial channel 22, radially oriented inlet channel 24, and radially oriented transfer channel 26. The axial channel 22 includes lower portion 28 having a first diameter, and an upper portion 30 having a second, larger diameter.
Valve spool 14 is shiftably received within the pump body axial channel 22. The valve spool 14 includes upper, middle, and lower sealing portions 32, 34, 36, each having a diameter just slightly smaller than the diameter of the axial channel 22. Upper recessed valve spool portion 38 is interposed between the upper and middle sealing portions 32, 34. Lower recessed portion 40 is interposed between middle and lower sealing portions 34, 36. The upper and lower recessed portions 38, 40 each present a diameter smaller than the diameter presented by the sealing portions 32, 34, 36. Frustoconical nozzle portion 42 extends downwardly from the lower sealing portion 36 of the valve spool 14. Fluid discharge channel 44 extends generally axially along the center axis of the valve spool 14 from the tip of the nozzle portion 42 upwardly to a generally radial fluid receiving channel 48.
Upper sealing portion 32 of valve spool 14 includes first and second annular grooves 50, 52. The uppermost annular groove 50 retains a fluorocarbon resin guiding washer 54. The lower annular groove 52 retains a sealing O-ring 56. Similarly, lower sealing portion 36 of valve spool 14 include first and second annular grooves 58, 60. The lower annular groove 60 retains a fluorocarbon resin guiding washer 62, and the upper groove 58 retains sealing Onng 64. The middle sealing portion 34 of the valve spool 14 includes first and second annular grooves 66, 68 which each retain a sealing Gring-70, 72.
Piston barrel 16 is oriented with its longitudinal axis generally perpendicular to the spool receiving, axial channel 22 of pump body 12. The piston barrel 16 is detachably retained on the pump body 12 by threadable engagement, a bayonet lock, or some other suitable arrangement. Sealing Onng 74 provides a fluid tight fit between the piston barrel 16 and the pump body 12. Piston 18 includes piston head 76 and piston rod 78. The piston head 76 includes leading and trailing annular grooves 80, 82. Sealing O-ring 84 is received within the leading annular groove 80, and fluorocarbon resin guiding washer 86 is received within the trailing annular groove 82.
Spool drive 20 is detachably coupled to the valve spool 14. The spool drive 20 advantageously comprises a shuttle cylinder such as the D-7-Bl-X model cylinder manufactured by Fabco Air, Inc.
of Gainesville, Florida. The spool drive 20 includes an adjustment lever 88 for variably controlling the stroke length of valve spool 14.
Referring to Figs. 3 and 4, a liquid dispensing pump 100 in accordance with the second embodiment of the present invention is depicted. Pump 100 includes a pump body 102, valve spool 104, piston barrel 106, piston 108, and spool drive 110.
Pump body 102 includes spool receiving channel 112, radial inlet channel 114, radial outlet channel 116, and radial transfer channel 118. The spool receiving channel 112 includes lower portion 120 having a generally uniform diameter, and upper axial channel portion 122 having a generally uniform diameter that is less than the diameter of the lower channel portion 120.
The valve spool 104 of the second embodiment of the pump 100 is similar in most respects to the valve spool 14 described above in conjunction with the pump 10 in accordance with the first embodiment of the invention. Accordingly, the structure of the valve spool 104 can be understood with reference to the description of the valve spool 14. As will be apparent from viewing Figs. 3 and 4, however, the valve spool 110 does not include an axial, internal channel, or a nozzle. Similarly, the structure of the piston barrel 106, piston 108, and spool drive 110 can be understood with reference to the descriptions of the piston barrel 16, piston 18, and spool drive 20 of the pump 10 in accordance with the first embodiment of the invention.
Referring to Figs. 5 and 6, a nozzle 150 in accordance with the present invention for providing positive separation of dispensed, highly viscous liquids is depicted. The nozzle 150 is shown in conjunction with the outlet of a pump body 12'. Nozzle 150 broadly includes nozzle body 152 and valve plug 154.
The nozzle body 152 includes fluid dispensing channel 156 aligned with and in communication with the fluid outlet channel of the pump body 12'. The nozzle body 152 further includes valve plug receptacle 158 and pressure channel 160 communicating the valve plug receptacle 158 with dispensing channel 156. The pressure channel 160 is orientated generally perpendicular to the dispensing channeL156.
Valve plug 154 is detachably received within the valve plug receptacle 158 by a threaded connection, bayonet lock, or some similar retaining arrangement. The valve plug 154 includes a seating portion 162 and an internal portion 164. The seating portion 162 forms a seal with the valve plug receptacle 158. The internal portion 164 has a diameter less than the diameter of the valve plug receptacle 158, to allow for fluid flow around the internal portion 164 within the receptacle 158. Valve plug 154 also includes an internal channel 166 having an axial portion 168 and a radial portion 170. Conduit 172 is in fluid communication with the valve plug channel 166, and extends outwardly away from the seating portion 162 of the valve plug 154.
The internal portion 164 of valve plug 154 includes leading and trailing annular grooves 174, 176 on either side of the outlet 178 of the axial portion 168 of channel 166. The leading groove 174 retains a U-shaped in cross section, annular valving ring 180. The trailing groove 176 retains sealing O-ring 182.
Operation of the pump 10 in accordance with the first embodiment of the invention can be understood with reference to
Figs. 1 and 2.
Referring to Fig. 1, the valve spool 14 is depicted retracted into the spool receiving channel 22 of pump body 12 to the fluid intake position. The inlet channel 24 and transfer channel 26 are in fluid communication across the lower recessed portion 40 of the valve spool 14. Shifting of the piston 18 away from the pump body 10, with the valve spool 14 in the fluid intake position of Fig.
1, will draw fluid into the chamber of piston barrel 16.
Once the piston 18 is fully retracted away from the pump body 10, the valve spool 14 is shifted downwardly to the fluid discharge position of Fig. 2. Referring to Fig. 2, it will be seen that the inlet channel 24 is now isolated from the transfer channel 26.
The discharge channel 44 of the valve spool 14, however, is in fluid communication with the transfer channel 26. Shifting of the piston 18 towards the pump body 10, with the valve spool 14 in the fluid discharge position of Fig. 2, forces fluid out of the chamber of piston barrel 16 and into the discharge channel 44 of valve spool 14. The fluid is subsequently discharged from the nozzle portion 42 of the valve spool 14. After fluid has been completely discharged, the valve spool 14 is again retracted to the fluid intake position of Fig. 1, and the cycle is repeated.
As described above, the diameter of the upper portion 30 of the spool receiving, axial channel 22 is of a larger diameter than the lower portion 28 of the axial channel 22. Accordingly, as the valve spool 14 is retracted upwardly within the pump body 10, the volume displaced as the upper sealing portion 32 transits upwardly within the upper axial portion 30 of channel 22 is greater than the volume replaced as the middle sealing portion 34 transits upwardly through the lower portion 28. Accordingly, a suction is created within the discharge channel 44 that sucks the residual liquid within the discharge channel 44 upwardly so as to prevent dripping of fluid from nozzle 42. The amount of suck-back of residual fluid can be controlled by adjusting the stroke length of the valve spool 14 with adjustment lever 88.
Fluorocarbon resin guiding washers 54 and 62 center and guide the valve spool 14 as it shifts upwardly and downwardly within the pump body axial channel 22. The valve spool 14 is thereby prevented from coming into damaging contact with the surface of the axial channel 22, and the wear on the sealing O-rings 56, 60, 70, 72 is reduced. Similarly, the fluorocarbon resin guide ring 86 centers and guides the piston head 76 of piston 18 within the piston barrel 16.
Operation of the pump 100 in accordance with the second embodiment of the invention can be understood with reference to Figs. 3 and 4.
Referring to Fig. 3, the valve spool 104 is depicted in its extended, fluid intake position. Inlet channel 114 of pump body 102 is in fluid communication with transfer channel 118 across the upper recessed portion of valve spool 104. Shifting of the piston 108 away from the pump body 102, with the valve spool 104 in the fluid intake position, accordingly draws fluid into the chamber of pump barrel 106.
Once the piston 108 has completed its stroke away from the pump body 102, the valve spool 104 is retracted to -the fluid discharge position depicted in Fig. 4. The middle sealing portion of the valve spool 104 isolates the inlet channel 114 from the transfer channel 118, with the valve spool 104 in the fluid discharge position. Outlet channel 116, however, is now in fluid communication with transfer channel 118 across the lower recessed portion of the valve spool 104. Shifting of the piston 108 towards the pump body 102 accordingly forces the fluid within the chamber of piston barrel 106 through the transfer channel 118 and into the outlet channel 116. Once the piston 108 has completed it stroke towards the pump body 102, the valve spool 104 is again extended to the fluid intake position depicted in Fig. 3, and the cycle is repeated.
As described above, the lower axial channel portion 120 of axial channel 112 is of a greater diameter than the diameter of the upper axial portion 122. Shifting of the valve spool 104 downwardly from the fluid discharge position depicted in Fig. 4 to the fluid intake position depicted in Fig. 3, will accordingly draw residual fluid within the outlet channel 116 into the pump body 110, thereby preventing dripping of the fluid from the pump body.
Operation of the nozzle 150 in accordance with the present invention can be understood with reference to Figs. 5 and 6.
Fig. 5 depicts a viscous fluid F being discharged from the pump body 12' and nozzle 150 in the downwardly direction indicated by the arrows. The valve plug 154 is not pressurized in
Fig. 5, and the U-shaped in cross section, annular valve ring 180 prevents entry of the fluid F into the valve plug receptacle 158.
Fig. 6 depicts the nozzle 150 at the end of a discharge cycle of the pump. Pressurized air is introduced into the valve plug receptacle 158 through conduit 172. The valving ring 180 collapses radially inwardly under the force of the pressurized air, and the burst of pressurized air separates the discharged fluid F at the point where pressure channel 60 intersects dispensing channel 156. Once the pressurized air is removed from the valve plug 154, the resilient valving ring 180 will return to its sealing position as depicted in Fig.
5, and the fluid can again be discharged from the nozzle without entry of the fluid into the plug receptacle 158.