Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
1999-09-13
2001-05-01
Walberg, Teresa (Department: 3742)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
C417S460000, C417S557000
Reexamination Certificate
active
06224347
ABSTRACT:
TECHNICAL FIELD
This invention relates to a positive displacement pump particularly suited for delivering low volumes of a fluid with high precision. More specifically, this invention relates to such a pump whereby the precise amount of fluid to be delivered may be adjusted, and the accurate delivery of fluid is assured by the elimination of dead space in the pump.
BACKGROUND ART
Pumps are often utilized to meter or otherwise deliver small quantities of fluid with a required high precision. Such accurate and repeatable dispensing of a fluid is often required in laboratory instrumentation environments such as the photographic processing industry or in the medical field such as in the metering and delivery of a low volume, precise amount of reagent to test blood.
Many pumps used for this purpose are of the positive displacement type which normally include poppet valves or check valves at the inlets and outlets thereof. However, such valves are usually, most conveniently, made of rubber material which can be the subject of attack by many chemicals. As a result, such valves will deteriorate causing the pump to lose its accuracy and eventually resulting in the need for replacement.
Thus, valveless, positive displacement, piston pumps are more suited for this application. However, known of such pumps may not consistently provide the accuracy required for many applications. For example, the positive displacement piston pump shown in U.S. Pat. No. 3,168,872 is typical of those that are available today. The problem with these types of pumps is that there is some dead space in the piston chamber where a small amount of fluid can remain after each piston stroke. Since most all fluids contain entrapped gas, such may also tend to accumulate in that dead space and form a small gas bubble. Eventually, the piston which is intended to deliver fluid will be compressing gas and not dispensing the correct amount of fluid. In effect then, the stroke of the piston is compressing and uncompressing the gas bubble to the detriment of accurate volume fluid dispensing.
The need exists, therefore, for a pump which will repeatedly deliver a precise amount of fluid, even in small microliter volumes.
DISCLOSURE OF THE INVENTION
It is thus an object of the present invention to provide a pump which can deliver low volumes of fluid with high precision.
It is another object of the present invention to provide a pump, as above, which is valveless and utilizes a piston moveable in a chamber to deliver the fluid.
It is an additional object of the present invention to provide a pump, as above, in which essentially all dead space in the pump is eliminated.
It is yet another object of the present invention to provide a pump, as above, in which the stroke of the piston is easily adjustable to provide a wide range of control over the precise, minute amount of fluid to be dispensed.
These and other objects of the present invention, as well as the advantages thereof over existing prior art pumps, which will become apparent from the description to follow, are accomplished by the improvements hereinafter described and claimed.
In general, a fluid pump made in accordance with the present invention includes a rotating cylinder having a piston capable of reciprocating therein. A plate is positioned adjacent to the cylinder, the plate having a fluid intake port communicating with an intake groove formed in the plate, and a fluid discharge port communicating with a discharge groove formed in the plate. The grooves and the ports communicate with the cylinder such that upon rotation of the cylinder and reciprocation of the piston, the piston sequentially draws fluid from the intake groove and the intake port into the cylinder and then discharges that fluid from the cylinder into the discharge groove and through the discharge port.
In accordance with another aspect of the present invention, a fluid pump includes a motor and a pumping assembly rotated by the motor. The pumping assembly includes a face plate having a port therein, a cylinder associated with the plate and communicating with the port, and a piston capable of reciprocating in the cylinder. A manifold plate is positioned adjacent to the face plate and includes a fluid intake port, an intake groove communicating with the intake port, a fluid discharge port, and a discharge groove communicating with the discharge port. Upon rotation of the pumping assembly and reciprocation of the piston, the piston sequentially draws fluid from the intake groove and the intake port through the port of the face plate and into the cylinder and then discharges that fluid through the port of the face plate and into the discharge groove and through the discharge port.
In accordance with yet another aspect of the present invention, a fluid pump includes a stationary plate having a fluid intake area and a fluid discharge area. A second plate is positioned adjacent to the stationary plate, and means are provided to rotate the second plate. A cylinder is associated with the second plate and selectively communicates with the fluid intake area and the fluid discharge area. A piston is positioned in the cylinder, and means are provided to reciprocate the piston in the cylinder to selectively draw fluid from the intake area into the cylinder and discharge that fluid from the cylinder into the discharge area.
A preferred exemplary pump incorporating the concepts of the present invention is shown by way of example in the accompanying drawings without attempting to show all the various forms and modifications in which the invention might be embodied, the invention being measured by the appended claims and not by the details of the specification.
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Clark George A.
Hayes Robert J.
Campbell Thor
Renner Kenner Greive Bobak Taylor & Weber
The Gorman-Rupp Company
Walberg Teresa
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