US 3810716 A
Novel check valves for use in precision pumping systems and particularly in a novel liquid chromatography pumping system incorporating the valves. The novel check valve comprises a filter compartment and a quick-responding ball check member which is protected by a filter element. The ball check member is constrained to have a minimal movement between its open and closed positions. A chromatography system is described which comprises a positive displacement pump incorporating such a valve on each of the inlet and outlet sides of the pump. On each side of the pump, a filter is used to avoid contamination of the ball seal chamber by pump seal debris.
Claims available in
Description (OCR text may contain errors)
United States Patent [1 1 Abraharns et al.
11 3,810,716 45] May 14, 1974 CHECK VALVE AND SYSTEM CONTAINING SAME  Assignee: Waters Associates Inc.,
 Filed: Oct. 27, 1972  Appl. No.: 301,358
 US. Cl. 417/313, 417/559, 137/533.1l,
7 137/544 I  Int. Cl. F04b 21/02, F04b 39/10  Field of Search 137/544-550;
 References Cited UNITED STATES PATENTS 1,927,582 9/1933 Denk 137/549 X 3,073,256 111963 Browne et a1 417/559 X 7/1970 Busse et a1 417/559 X 11/1971 Phillips 417/571 X Primary ExaminerWilliam L. Freeh Assistant ExaminerRichard E. Gluck Attorney, Agent, or FirmCesari and McKenna [5 7] ABSTRACT 'Novel check valves for use in precision pumping systems and particularly in a novel liquid chromatography pumping system incorporating the valves. The novel check valve comprises a filter compartment and a quick-responding ball check member which is protected by a filter element. The ball check member is constrained to have a minimal movement between its open and closed positions. A chromatography system is described which comprises a positive displacement pump incorporating such a valve on each of the inlet and outlet sides of the pump. On each side of the pump, a filter is used to avoid contamination of the ball seal chamber by pump seal debris.
11 Claims, 5 Drawing Figures PATENTEUIAY 14 \914 L.C. COLUMN l REFRAC.
k RESERVOIR PRE-FILTER BACKGROUND OF THE INVENTION Liquid chromatography is a well-known technique in chemical analysis work wherein a mobile liquid phase, usually consisting of a carrier liquid and material to be analyzed, is contacted with an immobile phase in a contact zone, and, as a consequence of the contact, some components of the liquid phase are preferentially retarded in their passage through the contact zone. This preferential retardation, usually combined with an analytical process, such as spectrometry, is the basis for a chemical evaluation of the liquid phase.
Liquid chromatography has important utility in medical research and other fields in which only very small samples of the material to be analyzed are available.
The performance of such apparatus is often limited by a phenomenon known as peak spreading." Peak spreading obtains its name from the result witnessed on a recording chart whereby a given chemical constituent which enters a liquid chromatography system over a relatively short period of time is sensed by the analytical instrument (and the recorder) over a significantly longer period of time. Thus the recording chart has a peak less sharply distinguishable than is theoretically possible were there no peak spreading. This lack of sharpness or spreading of the peak is a material limitation in interpreting the data obtained by liquid chromatographic processes. Peak spreading often makes necessary the use of larger samples, different passes using different carrier. fluids, slower throughput rates and other such manipulative procedures to avoid the masking effect of the peak spreading. Even then, many analyses remain impossible or impractical because of the peak spreading phenomenon.
Thus, a great deal of attention has been given to providing means to minimize peak spreading between the time a sample enters the apparatus and the time it is analyzed. For example, see U.S. Pat. No. 3,674,373 to Waters et al. wherein a refractometer heat exchanger is constructed to minimize the problem as a sample enters the refractometer. Another example of such inventive work relating to avoiding excessive peak spreading is disclosed in commonly-owned and co-pending U.S. Ser. No. 232,128 filed on Mar. 6, 1972, by Abrahams et al. and entitled Pumping System for Liquid Chromatography.
It has been a problem to provide liquid chromatography pumping systems which are highly accurate, i.e., produce a minimum of fluctuation in flow output and a minimum of this peak spreading. Moreover, in liquid chromatography, one of the most time consuming procedures is trying to find the ideal set of conditions of column and mobile phase to effect a desired separation/Very often the chromatographer is faced with changing the mobile phase several times before he is successful in separating a new sample. Thus it is highly desirable that he be able to change from one solvent to another quickly. A quick, thorough flushing of the system would be of tremendous advantage.
Thus far, the pumping system which most nearly achieves the ideal flow output and smallest amount of peak spreading is believed to be that of which is available under the trade designation Model 6000 Delivery System from Waters Associates of Framingham, Massachusetts, U.S.A. This pumping system comprises two piston-type pumping chambers which are operated out of phase with one another with such precise relative timing that a constant flow rate is achieved. Moreover, a surprisingly small amount of peak spreading takes place in the aforesaid pumping system. Nonetheless, the continued high efficiency of such a system depends in part on the prompt precise on-off sealing action of the check valves mounted at the inlet and outlet of each pump. Without such sealing an undesirable amount of mixing would necessarily occur as a consequence of fluid movement in the vicinity of the check valves.
It has been the problem faced by applicants to provide a chromatography system incorporating check valve means which so cooperate with the pumping action as to minimize flow movement in the vicinity of the check valves as the liquid in the valves tends to change direction during each pumping cycle, and to achieve this without interfering with the reliability of the pumping system over an extended operating life.
SUMMARY OF THE INVENTION Therefore it is an object of the invention to provide an improved valving system to be used in conjunction with a positive displacement pump in a novel liquid chromatography system to minimize peak spreading.
Another object of the invention is to provide improved check valve assemblies characterized by quick on-off action and a dependable ball seating action.
Still another object of the invention is to provide a check valving system for use with positive displacement pumps that is dependably protected from dirt contamination.
It is a particular object of the invention to provide a pumping system using a plurality of pistons operating out of phase with one another to provide a steady flow output which is provided with dependable flow checking valves that operate with little or no interference with flow for extended periods of time.
Other objects of the invention will be obvious to those skilled in the art on reading this application.
The above objects have been substantially accomplished by construction of a novel and improved check valve wherein the ball travels but a very short distance between its fully open and fully closed positions.
Most of the solid or semi-solids debris'which interferes with such check valves has been found to come from incidental wearing of the pump seals, in the pump. Therefore it has been discovered to be important to place filter units between the pump and the aforesaid check valves. This is particularly true because the valves of the invention, as a consequence of the relatively small clearances about the ball, have a number of surfaces, beside those of the valve seat itself, which should be maintained free of contamination to avoid malfunctioning of the valve.
ILLUSTRATIVE EXAMPLE OF THE INVENTION In this application and accompanying drawings there is shown and described a preferred embodiment of the invention and suggested various alternatives and modifications thereof, but it is to be understood that these are not intended to be exhaustive and that other changes and modifications can be made within the scope of the invention. These suggestions are selected and included for purposes of illustration in order that others skilled in the art will more fully understand the invention and the principles thereof and will be able to modify it and employ it in a variety of forms, each as may be best suited in the condition of a particular case.
IN THE DRAWINGS FIG. 1 is a schematic diagram of a liquid chromatography system incorporating the invention.
FIG. 2 is a fragmentary view of a pump head showing The relationship thereto of the check valve system of the invention to a piston. It should be kept in mind that the illustrated system will employ at least two pistons operating so phased as to provide at least an approximation of a constant flow.
FIG. 3 is a perspective view, partly in section of check valve elements.
FIG. 4 is a plan view of a fenestrated ball-restraining ring.
FIG. 5 is a section of the ring of FIG. 4.
Referring to FIG. 1, it is seen that liquid is supplied from a reservoir through a pre-filter 22 and then fed to a double piston pump represented by piston chambers 24. On each side of the piston chambers are inlet check valve assemblies 26 and outlet check valve assemblies 28. After passing through valves 28, the flow is consolidated and passed, usually at pressures from 20 to 6000 psi, through a liquid chromatography column 27 and thereupon through an analytical device such as refractometer 29. The problem is to supply the column with a liquid supply profile which has been subjected to as little distortion by mixing or the like as is possible.
In FIG. 2, in view of the fact that the inlet valve assembly 26 and outlet valve assembly 28 shown therein are substantially similar in construction, the corresponding elements of the outlet valve assembly, i.e., the upper valve assembly, are marked with corresponding numerals except that the suffix a is used with respect to the parts on the outlet valve assembly.
With reference to FIG. 2, it is seen that a positive displacement pump 30 comprises a cylinder head 32 comprising a bore 34 in which a piston 36 reciprocates. As piston 36 moves to the right, liquid is drawn into bore 34 through inlet port 38 and, as piston 36 moves to the left, the liquid is forced out of the bore along the annulus between piston 36 and the bore wall and thence outward through outlet port 39. The unidirectional flow pattern through the pump depends on the presence of another check valve means 28 mounted in head 32. These valves prevent backflow, thereby forcing the liquid being pumped to advance in the desired direction. It is the means by which the efficient operation of the check valves is assured that is an important aspect of the invention.
Each check valve is mounted in a check valve housing 42 and comprises, in series, a ball-check compartment 44 and a filter compartment 46 each contained in housings 48 and 50 respectively. Housings 48 and 50 are separated by a washer-shaped seal 52 formed of an elastomeric material such as that sold under the trademark RULONID by Dixon Corporation. A projecting portion of housing 48 forms a cylinder 54 which is a means for supporting seal 52 against excessive radial distension.
A sapphire ball element 56 of valve means 40 takes up the major portion of space available in compartment 44 and seats on a sapphire ring seat 58 when in closed position and against a fenestrated restraining insert 60 when in open position. Its compartment 44 is lined with an elastomeric sleeve 62 which is constructed of a material sold under the trade designation KEL-F by 3M Company.
Housing 50 for filter compartment 46 is similar to housing 48 of ball compartment 44 in that it too comprises a restraining cylinder 64 for resisting the distension of a circular seal 66 separating housing 50 from the cylinder head 32. Compartment 46 houses a filter element 68 which provides means to stop particulate material.
The function of the valve system in conjunction with a pump is as follows: Assume the pump has been primed with a liquid supplied to conduit 72. On the backward (to the right) stroke of pump piston 36, ball 56 rises from seat 58 until it is supported against insert 60 and liquid is sucked upwardly through compartment 44 and 46 into that portion of bore 34 which is evacuated by piston 36. During this stroke, filter 68 is not intended to do any significant filtering. It is situated on the low pressure side of the pump and a preliminary filter (not shown in FIG. 2 but provided as a matter of course upstream of conduit 72 as shown in FIG. 1) has provided a clean inlet fluid. When filter 68 is used with the illustrated pump system, dirt collected on the upstream side of the filter could unduly interfere with flow of liquid through the filter into the pump.
On the other hand, as liquid is pushedout of bore 34 on the advance stroke of piston 36, it is expelled outwardly through valve assembly 28 and filter 68a does perform a stream filtering function by collecting particulate matter such as seal debris from elastomeric pump seals 74 and the like on the upper surface thereof.
It is to be noted that in such positive displacement pumping systems are being described, the collection of small particulate matter on the pump side filter 68a does not usually interfere with flow: the high output pressure of the pump easily overcomes any small pressure drop contributed by such particles. As piston 36 stops its rightward, or suction, stroke and starts its leftward stroke, the function of filter 68 also becomes apparent: It collects on its pump side surface any particulate material which has been displaced forwardly in bore 34 by piston 36 and tends to settle downwardly through conduit 76 during those periods of the pumps cycle when no liquid is being pulled upwardly through conduit 76.
The movement of the ball 56 between (a) its open position in which it contacts disc 60 and (b) its closed position in which it seals against seat 56 should be less than 0.010 inch in liquid chromatography systems of the type generally used in analytical work. The illustrated embodiment of the invention has a ball seat diameter of about 0.09 inches, a ball of about 0.125 inches diameter. Thus, there is only a short movement of the ball from seat 58 to the disk 60. When the valve is open, the ball rests against the center portion 78 of the disk and the liquid flows around the disk through openings 80 therein.
It will be noted the travel of the ball is not more than about 0.010 inches or, in larger embodiments of the invention, not more than about 10 percent of the diameter of the ball. This short travel facilitates the quick open-shut action of the valve. Those skilled in art will understand that check valves other than ball valves can be utilized in the broadest aspect of the invention when the valve element is of appropriately short mean travel. A so-called flapper valve is one such check valve.
Thus it is seen that the entire function of the filter elements is to cooperate with the ball-check valves by making it impossible for pump-generated debris to interfere with the proper seating of the ball, this proper seating being absolutely required to assure a constant flow pattern.
It is to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which might be said to fall therebetween.
What is claimed is:
1. In a pumping system comprising a piston-type posifive-displacement pump, a plurality of cylinder having pistons mounted for reciprocal motion therein and adapted to provide a liquid input and output from said pump through inlet and outlet ports ofeach said cylinder, and ball check valves on each of said inlet and said outlet ports, said check valves having a ball valving element enclosed in a compartment with a ball seat member at one end thereof, the improvement wherein said system comprises a filter element positioned between each of said ball check valves and the inlet side and outlet side of each cylinder.
2. Apparatus as defined in claim 1 wherein travel of each said ball valving element between open and shut positions is less than about percent of the diameter of the ball.
3. Apparatus as defined in claim 1 wherein travel of each said ball valving element between open and shut positionsis less than about 0.010 inches.
4. Apparatus as defined in claim 1 wherein said filter element is adapted to filter particles larger than microns in average diameter.
5. Apparatus as defined in claim 3 wherein said filter element is adapted to filter particles larger than 15 microns in average diameter.
6. In liquid chromatography apparatus of the type comprising a chromatographic column and a positivedisplacement pump of the type comprising a plurality of pump cylinders each with a piston adapted for reciprocal motion therein and ball check valving means on each of the inlet and outlet sides of each pump cylinders, the improvement wherein a filter element is positioned between each said inlet and outlet side of each said pump cylinder and said check valving means.
7. Apparatus as defined in claim 6 wherein an additional filter is provided at the inlet side of the pump to provide a clean inlet liquid to said ball check valving means on the inlet side of the pump and to maintain the filter surface nearest said check valving means in substantially clean condition.
8. In a pumping system comprising a piston-type positive-displacement pump, a plurality of cylinders having pistons mounted for reciprocal motion therein and adapted to provide a liquid input and output from said pump, through inlet and outlet ports of each said cylinder and check valves on each of said inlet and said outlet ports, said check valves having a valving element enclosed in a compartment with a seat member at one end thereof, the improvement wherein said system comprises a filter element positioned between each of said check valves and the inlet side and outlet side of each cylinder.
9. Apparatus as defined in claim 8 wherein said filter element is adapted to filter particles larger than 15 microns in average diameter.
10. In a liquid chromatograhpy apparatus of the type comprising a chromatographic column and a positivedisplacement pump of the type comprising a plurality of pump cylinder each with a piston adapted for reciprocal motion therein and check valving means on each of the inlet and outlet sides of each pump cylinder, the improvement wherein a filter element is positioned between each said inlet and outlet side of each said pump and said check valving means.
11. Apparatus as defined in claim 10 wherein an additional filter is provided at the inlet side of the pump to provide a clean inlet liquid to said check valving on the inlet side of the pump and to maintain the filter surface nearest said check valve in substantially clean con dition.