US3461805A - Reciprocating piston metering pump - Google Patents

Description

United States Patent O U.S. Cl. 103-38- 6 Claims ABSTRACT F THE DISCLOSURE A piston type pump which expels iluid from :a central cavity through a rst check valve during the movement into the cavity of the piston and rells the central cavity through a second check valve during the'withdrawal of thepiston from thecavity, piston stroke length being'used to control the volume of uid displaced.

Background of the invention" The present invention relates to adjustable output metering pumps and, more particularly, to improved hydraulic pressure pumps having single acting reciprocating pistons and provided with seated type inlet and outlet valvesV and capable of adjustment to repeatably deliver extremely precise determinable volumes of lluid.

The pharmaceutical industry is increasingly moving from individual local pharmacy compounded drugs and remedies toward prepackaged products delivered in a form essentiallycompletely ready for dispensing. This trend toward prepackaging is in part dueto difficulties in handling and storing the newer drugs some of which are even radio-active. As a result, more drugs are packaged at central locations, than were formerly, ,thus` raising a need for types of dispensing apparatus not needed in local pharmacies where high speed did,.I.1ot necessarily have to accompany accuracy and antiseptic procedures. .i

Among the types of dispensingapparatus foundnecessary for mass prepackaging of drugs, is means forJ filling ampules, syringes and vials with preciselymeasured quantities of Various liquid ,formspf drugs. Since for antiseptic reasons Yalone it isusually desirable to remove human participation from the lling process, .and since such removal'is ofte'nvmandatory where the human-would be exposed to radio-active drugs,I it becomes necessary that the dispensing apparatus be capable of very reliably dispensing exact amounts ofV fluid without humanintervention of any kind-including monitoring.

It is accordingly a principal object of. the invention to provide a new and improved metering pump capable, once adjusted, of reliably delivering a dose'of exactly the requiredl size or volume to an ampule or other package. The pump necessarily must be adjustable to admit of varying thedoze size andzmust be so constructed that it can be repeatedly subjected to the autoclave process associated with antiseptic procedures.

In keeping with these problems and objects, the inventive pump comprises a cavity containingl block tted with one or more pistons' reciprocable into and out of the cavity. The cavity has inlet and outlet passages eachhaving a check valve therein.The piston stroke is precisely adjustable by means of a micrometer type screw' which positions a piston stroke limiting stop. For a better undern Patented Aug. 19, 1969 FIGURE 2 is a partial perspective View in the direction of arrows 2-2 in FIGURE 1;-further illustrating the stroke adjusting. means; and

FIGURE 3 is a partial perspective View illustrating an alternative stroke adjusting means.

A pump body 10 comprises an interior cavity 12. The pump body is further provided with two bored passages 14 and 16 to receive piston guides 18 and 20 respectively. Each of the piston guides contains a passage bored therethrough for a close fitting but free relationship with a piston; guide 18 having piston 22 fitted therein and guide 20, piston 24. Each of the pistons 22 and 24 has an enlarged diameter of collar-like appearance, 26 and 28 respectively. Between these collars and the upstanding flanges 30 and 32 of their respective guides, are positioned compression - springs 34 and 36 respectively. Each spring tends to push its associated piston outwardly from the interior cavity'12.

Piston guides 18 and 20 are each secured in position by an end cap, cap 38 for guide 18 and cap 40 for guide 20. Each end cap is -threadedly engaged into pump body 10 to press upon the flange of its associated guide and thereby retain it in position. Simultaneously the flanges 30 and 32 compress resilient sealing means, such as an O ring, 92 and 94, into chambers at the entrance to bored passages 14 and 16, thereby sealing the guides to the pump body.

It is a feature of the invention that each of the end caps in turn has a stroke limiting stop threadedly engaged in the outermost portion of its bore to thereby retain the associated piston and fixed the outermost limit of piston travel byblocking movement of the piston collar. Thus, by screwing the stop inward or outward, maximum travel of the piston 22 is thereby decreased and increased proportionally. Similarly, positional adjustment of stroke limiting stop 44 etects corresponding changes inthe stroke of piston 24. The manner of adjusting stops 42 and 44 is described further in connection with FIGURES 2 and 3.

To insure a tight t of pistons 22 and 24 in their respective guides, there is provided packing ring means 46 and 48. For embodiments constructed to date, the packing means has taken the form of a high temperature ionizingl radiation resistant material with sufficient resilience to effect the required seal and has been in the form of an O ring retained in an annular groove in the bore of the piston guide. For more severe service, more such packing ring can be provided in each guide.

Cooperating with the operation of the pistons to enable pumping action are seated type inlet andoutlet check valves 50 and 52,v respectively. Valve S0 is constrained to operation in a` valve chamber 54 communicating with y valve seat of bonnet 56 by form factors, gravity and standing of vthe' invention and its advantages, reference should be made to the accompanying drawing and descriptive matter in which are illustrated and described specific inventive embodiments. f

In the drawings: FIGURE 1 is a cross-sectional view of the adjustable output metering pump embodying the present invention;

the pressure within cavity 12 exerted by pistons 22 and 24. While this construction is preferred for its mechanical simplicity, in some embodiments a compression spring inserted between valve 50 and body 10 has been used to advantage to maintain the proper seating relationship. A suction tube 62'secured to bonnet 56l extends away from the pump and,` during pump operation, is normally submerged in the supply of liquid to be pumped.

' To facilitate mounting of the pump to the supply vessel and thus enhance sterility, bonnet 56 can be variously configured. As shown the outer surface 96 of bonnet 56 has been given a" standard v24-40 Flask Taper to permit mating contact with the ground surface of a glass laboratory flask. Since this contact can be and often is airtight, a drilled bypass 98 for makeup air is provided in the bonnet and microporous iilter 100 is inserted therein to block the passage of micro-organisms carried with the air. Still other exterior contigurations of bonnet 56, such as a bayonet or screw shape, has proven useful.

Valve 52 operates similarly to valve 50. However, valve seat 64 is formed in pump body 10 and valve chamber 66 is closed to the pump exterior by bonnet `68 and gasket 70. Discharge tube 72 is shown truncated but is normally tted at its outermost extremity with an output adapter particularly suited for iilling the desired special container.

In Operation the pump ejects precise increments of fluid from the discharge line 72 upon the reciprocation of either or both of pistons 22 and 24, either individually or simultaneously in combination. As the pistons are moved in the direction of arrows 74 and 76 into the interior cavity of the pump, pressure therein increases, opening outlet valve 52 and further seating inlet valve 50, and, a volume of uid equal to total piston displacement is ejected from the cavity into the outlet tube 72. Piston inward travel is limited when piston collars 26 and 28 engage their respective guides 18 and 20.

When the driving force represented by arrows 74 and 76 is released, the pistons move outwardly in their respective guides due to the action of springs 34 and 36 until the piston collars 26 and 28 limit piston travel upon engaging stops 42 and 44. The outward movement of the pistons lowers pressure in cavity 12 thus seating outlet valve 52, unseating inlet valve 50, and causing the ingestion uid into the cavity through the supply suction tube 62 from the supply vessel.

No particular method of actuating pistons 22 and 24 is shown, since such means are generally conventional and outside the scope of this invention. Obviously however, it is desirable that the piston drive means be capable of more travel than piston maximum and, the drive means is then preferably coupled by a resilient connection of any suitable type that allows for the necessary over-travel.

For economy of operation and antiseptic reasons, it is desirable that the volume of fluid retained in the pump cavity be made as small as possible considering the maximum delivery volume. It is a feature of the invention that this m-atching of cavity size to maximum output volume is facilitated by providing a recess 78 in the innermost tip of piston 22. By proportioning recess 78 to surround the top of piston 24 when either or both of pistons 22 and 24 are moved inwardly, volume of cavity 12 is minimized.

Since the inventive pump is primarily intended for the very accurate metering of various volumes of fluids, it has been found that output volume adjustment is enhanced by utilizing pistons of substantially diterent diameter and hence displacement. In the embodiment shown and preferred, piston 22 displaces ten times the volume of piston 24 for substantially equal axial movement.

A further inventive feature is micrometric adjustment of pump displacement and output. The means for achieving such adjustment are stops 42 and 44. By positioning the stops through screwing them in or out of their respective caps 38 and 49 piston travel, and hence displacement, is adjusted. As best shown in FIGURE 2, cap38 bears an index mark 80. Cooperating therewith are numerous indicia 82 radially disposed about the face of stop 42, one mark for each decimal increment in fluid displacement of the associated piston; e.g., if maximum piston displacement is one hundred (100) cc., threads 84 are chosen and indicia 82 disposed so that moving from one indicium 82 to the next adjacent indicium will vary displacement by one (l) cc. Stop 44 is similarly configured except that total displacement of piston 24 is normally a small fraction of that of piston 22 with a consequential corresponding reduction inthe value of each indicium on the stop. It is an additional inventive feature that by using holes as `indicia A8 2, the use of a spannerwrenchfor adjusting stop position is facilitated.

Another and advantageous variation of the method for achieving micrometric adjustment of pump Output iS shown in FIGURE 3. As there illustrated, a conventional type of micrometer thimble 90. bearing decimal calibrations 86 is selectively adjusted'relative to index mark 80, aknurled grip '88 being provided for effecting thimble rotation. Although the variation of `FIGURE 3 is advantageous in some circumstances, for economy 0f manufacture, the combination embodied in FIGURES l and 2 is preferred. However, it should be understood thatfurther modifications and variations may be employed by those skilled in the pump art without departing from the spirit and scope of the invention. What is claimed is: Y v 1. A metering pump for dispensing a precise preset volume of fluid comprising a pump body comprising an interior cavity, inlet and outlet valve chambers opening upon said cavity and communicating with the exterior of said body, and at least one stepped diameter piston operating passage opening upon said cavity and extending to the exterior of said body,

piston means positioned for reciprocation in said cylinder operating passage, said piston having a collar affixed thereto,

spring means acting upon said collar to thereby 'urge said piston outwardly from-said cavity,

adjustably positioned stop means for limiting the outward travel of said pistonmeans, and

inlet and outlet check valves positioned in said inlet and outlet `valve chambers respectively, whereby reciprocation of said piston between contact with said stop andV said stepped diameter ejects fluid from said cavity through said outlet valve-equal in volume to piston displacement.

2. A metering pump in accord with claim 1 wherein said piston means comprises two horizontally opposed pistons of substantially diiferent diameter, the larger diameter piston having a recess in its working surface proportioned to surround the tip of the smaller piston when both pistons are operated simultaneously. t

3. A metering pump in accord with claim 1 wherein said inlet valve chamber is closed by bonnet means, said bonnet means comprising an outer surface having a standard flask taper and makeup air bypass means including lter means.

4. A metering pump in accord with claim 1 wherein said stepped diameter piston operating passage comprises anged piston guide means inserted in said pump body.

5. A metering pump in accord with claim 4 wherein said adjustably positioned stop means comprisesv cap means secured to said valve body and a stop threadedly engaged with said cap.

46. A metering pump in accord with claim 4 wherein said adjustably positioned stop means comprises cap means secured to said valve body and a micrometer thimble type stop threadedly engaged withsaid stop. p

References Cited UNITED STATES PATENTS 3,116,648 1/1964 Arenhold 103-l-38 X 3,258,175 6/1966 Taylor 222-380 `3,327,900 6/1967 Goda 222-309X 3,343,539 9/1961 Moorhouse 222-309` X LEONARD H. GERIN, Primary Examiner U.S. Cl. X.R.

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