Patent Application
20070178000
The present invention relates to a plunger pump in which the interior of the bellows structure is substantially at atmospheric pressure.
U.S. Pat. No. 4,436,494 teaches a plunger pump having a bellows surrounding a plunger. The bellows is constructed of flourine plastics and the like. When the pump operates, the bellows extends and contracts within the housing of the pump, and separates the fluid to be pumped from the plunger. To offset the pressure exerted on the outer surface of the bellows by the fluid being pumped through the pump, the bellows is filled with a liquid such as oil and the like. The extension and contraction of the bellows changes the volume within the bellows, which either forces oil out of the bellows or draws oil into the bellows. Variations in the volume in the bellows is matched with a variation of volume in a liquid filled portion of an upper case portion due to the simultaneous movements of a socket constituting a part of the plunger.
The present invention provides an improvement over the plunger pump disclosed in U.S. Pat. No. 4,436,494. The prior art bellows is constructed of a material that does not have predictable fatigue characteristics. Maintenance is made difficult by the unpredictable failure of the prior art bellows. Also, should there be a failure of the prior art bellows, there is a risk of contamination of the fluid being pumped with the oil in the bellows. The present invention utilizes a plunger pump having a bellows that communicates with atmospheric air and is not filled with oil. This enables a plunger pump to be constructed without a variable volume accumulator to handle oil displaced from the inside of the bellows during operation.
In one embodiment, the invention provides a pump comprising a housing defining an inner cavity and having an inlet port, an outlet port, and a bellows port. A first valve permits one-way flow of fluid into the inner cavity through the inlet port. A drive rod is supported for reciprocal movement within the inner cavity. A bellows within the inner cavity surrounds a portion of the drive rod, and extends and contracts in response to the reciprocal movement of the drive rod. A second valve is interconnected with the drive rod for reciprocal movement within the inner cavity and permits one-way flow of fluid from a first side of the second valve to a second side of the second valve. The inner cavity is divided into an inlet portion on the first side of the second valve, an outlet portion between the second side of the second valve and an outer surface of the bellows, and an atmospheric portion within the bellows. The inlet port is adapted for communication between the inlet portion and a source of fluid to be pumped, the outlet port is adapted for communication between the outlet portion and a receptacle for pumped fluid, and the bellows port is adapted for communication between the atmospheric portion and the atmosphere. The bellows is substantially airtight and separates the outlet portion of the inner cavity from the atmospheric portion. Air is drawn into and displaced from the atmospheric portion of the inner cavity in response to respective extension and contraction of the bellows.
Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings, respectively. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.
With reference to
A first check valve 46 is disposed on the primer shaft 28 and a second check valve 48 is disposed on the intermediate shaft 30. Both of the first and second valves 46, 48, are one-way valves that, in the illustrated embodiment, permit the flow of fluid only upwardly through the pump 10. A valve stop 50 is mounted to the bottom flange 18, and the first check valve 46 is movable between abutment with the valve stop 50 (as in
The housing 12 defines an inner cavity that is divided into three portions: an inlet portion 54 on one side of the second check valve 48, an outlet portion 56 on the other side of the second check valve 48 and around the outside of the bellows 42, and an atmospheric portion 58 within the bellows 42. The inlet portion 54 communicates with the container of fluid through the inlet port 20 and through the aperture 21 in the wiper 19, the outlet portion 56 communicates with a receptacle into which the fluid is pumped through the outlet port 22, and the atmospheric portion 58 communicates with the atmosphere through the bellows port 24.
In operation, an external downward force is applied to the pump 10. The downward force may come from a hydraulic cylinder, one or more biasing members, or any other mechanism capable of applying constant controllable force to the entire pump 10. The downward force will force the wiper 19 into the container of fluid. Since the wiper 19 extends across the container and forms a fluid-tight sliding seal with the inner surface of the container of fluid, fluid rises through the aperture 21 to the inlet port 20. In some embodiments, the bottom flange 18 is coupled to a source of fluid under sufficient pressure that the fluid is forced to the inlet port 20 without having to use a wiper 19.
Also during operation, the prime mover 17 is interconnected with an end of the drive shaft 34 and causes cyclical reciprocation of the plunger assembly 26. On the upward stroke (i.e. movement of the plunger assembly 26 from the position illustrated in
On the downward stroke (i.e., movement of the plunger assembly 26 from the position illustrated in
When in abutment with the bottom flange 18, the first check valve 46 blocks the inlet port 20 to prevent the flow of fluid out of the inlet port 20. However, when the first check valve 46 lifts off the bottom flange 18 and abuts the valve stop 50, a flow path 62 for fluid from the container of fluid into the inlet portion 54 of the inner cavity of the housing 12 is opened. When the second valve 48 abuts the conical surface 52 of the intermediate shaft 30, it prevents the flow of fluid from the outlet portion 56 of the inner cavity into the inlet portion 54. However, when the second valve 48 lifts off the conical surface 52, it opens a flow path 64 around an end 36 of the intermediate shaft 30, through the second check valve 48, and into the outlet 56 portion of the inner cavity.
During operation, the bellows 42 extends and contracts as the prime mover 17 inserts and retracts the drive shaft 34 with respect to the housing 12. Because the interior of the bellows 42 (i.e., the atmospheric portion 58 of the inner cavity of the housing 12) communicates with the atmosphere through the bearing 40 in the bellows port 24, any air drawn into or displaced from the atmospheric portion 58 is sucked in from or exhausted to the atmosphere. No separate accumulator or other device is required to hold fluid displaced from the interior of the bellows 42. Also, should the bellows 42 develop small cracks but continue to pump fluid out of the outlet 22 (albeit less efficiently), there is no fluid (other than air) in the bellows 42 that would leak into and contaminate the pumped fluid prior to discovery of the flaw in the bellows 42.
The bellows 42 is constructed of a material that has sufficient rigidity to maintain its shape while forcing fluid into and out of the outlet portion 56, but that has sufficient flexibility to be formed into a bellows 42 shape. The material should be chemically non-reactive with the fluids being pumped. Also, the material should have fatigue characteristics that enable its cycles to failure to be accurately predicted, so the bellows 42 can be replaced prior to failure. One example of a material that may be used for the bellows 42 is stainless steel.
Various features of the embodiments are set forth in the following claims.
