Patent Application
20250223958
The invention concerns systems, methods, and mechanisms for adjusting the effective stroke-length of a positive-displacement pump.
Delivery of fluids in precise flowrates is sometimes called metering. A metering pump is a pump that moves a set volume of fluid during each cycle of the pump in order to deliver an accurate volumetric flow rate over a specified time period. The term “metering pump” is based on the application or use rather than the exact kind of pump used, although some types of pumps are far more suitable than most other types of pumps for such purposes, depending on the application.
Although metering pumps can pump water, they are often used to pump chemicals, solutions, or other fluids, and are often used to pump such chemicals, solutions, or other fluids into pressurized volumes or into systems in which other material is already flowing (e.g. oil and gas pipelines). They are typically made to meter at flow rates which are practically constant (when averaged over time) within a wide range of discharge (outlet) pressures.
Certain pumping situations, such as when a pump is injecting the fluid into a high-pressure environment or when there is a need to pump fluids with higher viscosities, accurate metering generally necessitates the use of a positive displacement pump. This class of pump moves a fluid by repeatedly enclosing a fixed volume, with the aid of seals or valves, and moving it mechanically through the system. Such pumps have the inherent ability to maintain a consistent flow rate over a wide and varying pressure range. The pumping action is typically cyclic and driven by operation of a motor, diaphragm, or pneumatic or hydraulic piston. By controlling the speed or stroke length of the pumping action, a specific delivery rate or accurate single dose may be achieved.
The design of reciprocating diaphragm pumps generally requires the use of flexible membranes the materials for which (e.g., rubber, silicone, etc.) tend to be less robust, and therefore more susceptible to wear and tear and the increased maintenance that naturally flows therefrom, than the corresponding components of reciprocating positive displacement pumps that employ plungers or pistons, which are frequently made of metal.
In many modern applications, positive displacement pumps, and especially those used for metering, have pump head driven by a motor. In such pumps, the motor drives the actuation of the components of the pump head in a reciprocating manner which is used to create pressure differentials that force the fluid through the system.
Piston-type metering pumps generally include a piston, (sometimes called plunger), which is typically cylindrical, which can go in and out of a correspondingly shaped chamber in the pump head. The inlet and outlet lines are joined to the piston chamber. There are two check valves, often ball check valves, attached to the pump head, one at the inlet line and the other at the outlet line. The inlet valve allows flow from the inlet line to the piston chamber, but not in the reverse direction. The outlet valve permits fluid to flow from the chamber to the outlet line, but not in reverse. The operation of driving side of the pump (e.g., a motor) repeatedly moves the piston/plunger into and out of the piston chamber, causing the volume of said chamber to repeatedly become smaller and larger. When the piston moves out of the piston chamber, a vacuum is created. Low pressure in the chamber causes fluid to enter and fill the piston chamber through the inlet check valve, but higher pressure at the outlet causes the outlet check valve to shut. Then when the piston strokes back into the piston chamber, it pressurizes the now fluid-filled piston chamber. High pressure in the piston chamber causes the inlet check valve to shut, the outlet check valve to open, and forces the fluid from inside of the piston chamber past the outlet check valve and into the outlet line. As the motor operates, these alternating suction and discharge strokes are repeated over and over to meter the fluid.
Assuming the piston chamber remains a constant volume, the metering rate can be adjusted by (i) varying the distance that the piston travels during a cycle of the pump (a.k.a. the “stroke-length” of the piston/pump), (ii) varying the frequency of the pump's cycling, which is generally achieved by varying the speed of the motor's operation, or (iii) controlling the duration of the pump's operation. As some motors operate at only one or more set speeds, or are otherwise unable to finely control the speed of their operation; and the action of controlling the amount of time that the motor is operating requires some level of active control of the motor itself and results in an uneven distribution of fluid being injected into the system over time, there are advantages that may be achieved by the providing for and use of a mechanism that allows for the varying of the stroke-length of such a reciprocating piston-driven pump.
Additionally, while a single motor may be used to drive a single pump head, at times it may be more efficient to operate multiple pump heads off a single motor. Generally, such multi-head metering pump systems have two pump heads disposed on opposite sides of the motor, opposing one another such that when the motor drives the first head's position forward the second head's piston is being pulled backward, and vice versa. By paring multiple pump heads to a motor, an operator may both increase the efficiency of the pumping operation by reducing the number of motors it requires and thereby reducing the physical footprint of the pumping equipment, while also loading the motor more evenly throughout its cycling (allowing it to operate more efficiently while also reducing the dynamic loading and unloading that can cause stresses in its materials).
For such multi-head metering pump systems, there are means known in the art to change their stroke-length, such as by adjusting the attachment between the camshaft and the crosshead in order to create lost motion therebetween, and thereby changing the stroke-length of a pump head attached thereto; however, this affects the travel of the crosshead and therefore it would affect each pump head attached to the motor in a consistent manner.
There are scenarios in which it may be desirous to change the flowrate of one or more pump heads attached to a single motor without affecting the flowrate of the one or more other pump heads attached to the motor. As varying the speed or time of the motor's operation would affect the flowrate of all pump heads attached to the motor, and so to would varying the stroke-length of the pump heads' pistons, by the means described above, such methods would not be suitable for this purpose. Accordingly, it would be advantageous to have a mechanism that provides for the ability to adjust the piston stroke-length of pump head independently from those of any other pump heads driven by a common motor.
Furthermore, while many applications require metering pumps to function at relatively high flowrates (e.g., gallons per minute), wherein small changes to the stroke-length may result in relatively minimal changes to the head's flowrate, some applications may require metering pumps to function at much lower flowrates (e.g., quarts per day), wherein even small changes to stroke-length could result in a, proportionally, much larger effect on the flowrate. Therefore, there would be advantages for mechanisms that provide for fine, rather than gross, adjustments to piston stroke-length; and further, ones which may be relatively continuous rather than having discrete increments.
This disclosure describes systems, methods, and mechanisms which provide for an improved means for adjusting the stroke-length of positive displacement pumps, including, for the pump heads of piston-driven metering pumps.
More specifically, this disclosure concerns the means for altering the effective stroke-length of a positive displacement pump by introducing a mechanism between the crosshead and the piston which causes the piston to remain stationary during a portion of the cycling of the pump. Such a mechanism causes a loss of motion between the crosshead and the piston during the cycling of the pump. This lost motion may occur on one or more of the positive-displacement (forward) stroke of the crosshead, or during the negative-displacement (backward) stroke of the crosshead.
By enabling the piston to remain stationary during a portion of the crosshead's cycling, the adjustment mechanism may facilitate an effective reduction in the stroke-length of the position during said cycle. This may allow an operator of the pump to reduce the volume of fluid being pumped per cycle by that specific pump head.
The adjustment mechanisms discussed herein provide various means for varying the distance that the crosshead must travel, while the piston remains stationary, before the crosshead engages with the piston, causing it to travel with the crosshead for the remainder of the stroke. This provides not only for the creation of lost motion between the crosshead and the piston, but for the magnitude of such lost motion to be easily varied by the operator of the pump.
By setting the magnitude of the motion loss between the crosshead and the piston to a particular level, the pump operator may be able to reduce the volume of fluid being pumped during each cycle of the pump to tailor the pump's flowrate to a desired level, which may be suitable, or preferable, for various pumping applications.
The foregoing has outlined rather broadly certain aspects of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.
For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
The present invention is directed to improved systems, methods, and mechanisms for, among other things, adjustment of effective stroke-length of a plunger positive displacement pumps. The configuration and use of the presently preferred embodiments are discussed in detail below. It should be appreciated, however, that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of contexts other than those specifically touched on in this document. Accordingly, the specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention. In addition, the following terms shall have the associated meaning when used herein:
“axis of travel” or “axis of motion” means the linear axis in which the component(s) of a piston-based pump head move responsive to rotation of the camshaft;
Referring now to the FIGs,
Adjustment mechanism 100 may be operable to change the effective stroke-length of the plunger by causing there to be lost motion along the axis of travel by selectably altering the point at which a plunger is mechanically engaged by the adjustment mechanism 100 and is thereby urged forward by the motion of a crosshead. The magnitude of the lost motion caused by the adjustment mechanism 100 may be varied based on the selection of which of the holes 104A-C through which pin 106 is inserted and secured to the plunger. The use of a hole closer to the proximal end of the adjustment mechanism 100 (e.g., hole 106A) results in a reduction of lost motion and therefore a corresponding increase in the amount of fluid displaced per cycle of the pump, while the use of a hole closer to the distal end of the adjustment mechanism 100 (e.g., hole 104C) results in an increase in the amount of lost motion and therefore a corresponding decrease in the amount of fluid displaced per cycle of the pump.
In
This positioning of pump 200 shows piston chamber 205 at a point of maximum retraction of plunger 208 for the setting of the adjustment mechanism 210. This point of the retraction of plunger 208 is reduced from the true point of maximum retraction of plunger 208 due to the lost motion caused by adjustment mechanism 210. At the point depicted in the figure, a low pressure has been generated in piston chamber 205 such that fluid will have been drawn past inlet check valve 207 and into piston chamber 205. In this position outlet check valve 509 is closed, preventing fluid from piston chamber 205 from exiting therefrom.
This positioning of pump 200 shows piston chamber 205 at a point of maximum extension of plunger 208. At this position high pressure has been generated in piston chamber 205 due to forward motion of plunger 208 such that inlet check valve 207 will be forced closed, preventing additional fluid from entering piston chamber 205, and the fluid that was previously drawn into piston chamber 205 has been forced past outlet check valve 209 and downstream out of head 204.
When comparing the configurations depicted in
Further, this difference between the configurations of adjustment mechanism 210 depicted in
In other words, in order to change the effective stroke-length pump head using the embodiment of an adjustment mechanism depicted in
As can be seen in
For example, the duplex pump embodiment depicted in
Sleeve 402 may be open on its ends, defining channel 406. Channel 406 may be configured to permit at least a portion of a plunger to pass therethrough and to allow the plunger to travel freely relative to adjustment mechanism 400, along their common axis.
In the embodiment depicted in
Adjustment mechanism 400 may be operable to change the effective stroke-length of the plunger during a cycle by causing there to be lost motion along the axis of travel. The magnitude of the lost motion caused by adjustment mechanism 400 may be varied based on how far adjustment mechanism 400 is screwed into the crosshead, the amount of lost motion may be decreased by increasing the degree to which adjustment mechanism 400 and crosshead are screwed together; and, correspondingly, the amount of lost motion may be increased by decreasing the degree to which adjustment mechanism 400 and crosshead are screwed together.
To achieve such a configuration, the distal end of plunger/plunger sleeve 508/516 comprising flange 518 may be inserted into crosshead 506 and then the distal end of plunger/plunger sleeve 508/516 may be inserted into and through the channel defined by adjustment mechanism 510. The proximal end of adjustment mechanism 510 may then be screwably engaged with crosshead 506 while flange 518 is positioned therebetween. This may provide for flange 518 to be captured by the combination of crosshead 506 and adjustment sleeve 510 such that the end of plunger/plunger sleeve 508/516 comprising flange 518 may not escape therefrom. Locking nut 522 may be screwed onto the threading of adjustment mechanism 510 before adjustment mechanism 510 is screwed into crosshead 506. Once adjustment mechanism 510 has been screwed on/into crosshead 506 to a desired degree, locking nut 522 may be screwed down until it abuts a distal end of crosshead 506, thereby locking adjustment mechanism 510 in position relative thereto.
In embodiments, flange, such as flange 518, may comprise a snap ring, clip, pair of half-collars, or other structure suitable for preventing the egress of the end of the plunger/plunger sleeve 508/516 from its position inside of crosshead 506 when adjustment mechanism 510 is engaged therewith.
As, in
This positioning of pump 500 shows piston chamber 505 when at the top of a stroke, whereby plunger 508 is at a maximum level of displacement. When pump 500 is in the position depicted, low pressure has been generated in piston chamber 505 such that fluid will have been drawn past inlet check valve 507 and into piston chamber 505. In this position outlet check valve 509 is closed, preventing fluid from piston chamber 505 from exiting therefrom.
Additionally, it should be noted that while the embodiment of the screw-based adjustment mechanism depicted in
As a cycle of the pumping is performed, pump 500 starts its forward stroke causing camshaft 500 to push crosshead 506 forward along the pump's axis of motion. As adjustment mechanism 510 is screwably engaged with crosshead 506 and locking nut 522 is screwably engaged with adjustment mechanism 510 and abutting the distal surface of crosshead 506, the forward motion of crosshead 506 pushes both adjustment mechanism 510 and locking nut 522 forward as well. As plunger 508, and if present plunger sleeve 516, are floating relative to adjustment mechanism 510 and crosshead 506, during the forward stroke of pump 500, crosshead 506 must first traverse the length of first volume 520 (i.e., d2) before its receiving surface engages the proximal end of plunger/plunger sleeve 508/516. This forward motion of crosshead 506 during which plunger 508 remains stationary is what provides the loss of motion that shortens the stroke-length of plunger 508. Once the receiving surface of crosshead 506 abuts the proximal end of plunger/plunger sleeve 508/516, further forward motion of crosshead 506 is imputed to plunger/plunger sleeve 508/516, thereby beginning the effective stroke of plunger 508.
While in the associated figures embodiments of screw-based adjustment mechanisms comprising locking nuts, such as locking nut 522, are presented, alternate locking mechanisms known in the art, such as but not limited to set screws, elastic members, clamp rings, retaining clips, or any other suitable locking mechanism may be used without departing from the scope of this disclosure.
Embodiments, of screw-based adjustment mechanisms, such as that depicted in
This positioning of pump 500 shows piston chamber 505 at a state of maximum compression wherein high pressure has been generated in piston chamber 505 due to forward motion of plunger 508 such that inlet check valve 507 will be forced closed, preventing additional fluid from entering piston chamber 505, and the fluid that was previously drawn into piston chamber 505 has been forced past outlet check valve 509 and downstream out of head 504.
Once the forward stroke of pump 500 reaches a maximum (as is depicted in
As the amount of motion loss in pump 500 is determined by the distance between the receiving surface of crosshead 506, the proximal end of adjustment mechanism 510, and the width of flange 518; then, assuming that flange 518 maintains a constant width, the amount of motion loss in pump 500 may be adjusted by screwing adjustment mechanism 510 on/into crosshead 506 and thereby increasing or decreasing the distance between such surfaces. The farther out that adjustment mechanism 510 is unscrewed from crosshead 506 the greater the distance that crosshead 506 adjustment mechanism 510 system must travel during a forward stroke before the receiving surface of crosshead 506 abuts and pushes forward plunger/plunger sleeve 508/516, and the greater the distance that crosshead 506 adjustment mechanism 510 system must travel during a backwards stroke before the proximal end of adjustment mechanism 510 abuts flange 518 and pushes plunger/plunger sleeve 508/516 backwards. Correspondingly, the more that adjustment mechanism 510 and crosshead 506 are screwed together, the lesser the distance that crosshead 506 adjustment mechanism 510 system must travel during a forward stroke before the receiving surface of crosshead 506 abuts and pushes forward plunger/plunger sleeve 508/516, and the lesser the distance that crosshead 506 adjustment mechanism 510 system must travel during a backwards stroke before the proximal end of adjustment mechanism 510 abuts flange 518 and pushes plunger/plunger sleeve 508/516 backwards.
In the embodiment depicted in
Pump 600 further comprises head 604′, which comprises adjustment mechanism 610′ which is screwed all the way into crosshead 606′, whereby there is no play between the receiving surface of crosshead 606′, flange 618′, and the proximal end of adjustment mechanism 610′, resulting in no lost motion being created in head 604′. Screwing adjustment mechanism 601′ further into crosshead 606′ results in a reduction of the volume 620′ through which camshaft 602 and crosshead 606′ must travel before engaging plunger/plunger sleeve 608′/616′ to actuate them forwards. This configuration of adjustment mechanism 610′ mirrors that of the adjustment mechanism depicted in
As can be seen in
A potential benefit of the screw-based embodiment of an adjustment mechanism, as depicted in
While the present apparatuses, systems, and methods of their use have been disclosed according to several preferred embodiments of the invention, those of ordinary skill in the art will understand that other embodiments have also been enabled. Even though the foregoing discussion has focused on particular embodiments, it is understood that other configurations are contemplated. In particular, even though the expressions “in one embodiment” or “in another embodiment” are used herein, these phrases are meant to generally reference embodiment possibilities and are not intended to limit the invention to those particular embodiment configurations. These terms may reference the same or different embodiments, and unless indicated otherwise, are combinable into aggregate embodiments. The terms “a”, “an” and “the” mean “one or more” unless expressly specified otherwise. The term “connected” means “communicatively connected” unless otherwise defined.
While embodiments discussed herein focus on plunger-based reciprocating pumps, it should be understood by a person having ordinary skill in the art that the teachings herein may be applied to at least piston-based pumps as well, and accordingly such should be considered as being within the scope of the present disclosure.
When a single embodiment is described herein, it will be readily apparent that more than one embodiment may be used in place of a single embodiment. Similarly, where more than one embodiment is described herein, it will be readily apparent that a single embodiment may be substituted for that one device.
In light of the wide variety of methods for adjusting the effective stroke-length of a piston/plunger-based pump known in the art, the detailed embodiments are intended to be illustrative only and should not be taken as limiting the scope of the invention. Rather, what is claimed as the invention is all such modifications as may come within the spirit and scope of the following claims and equivalents thereto.
None of the description in this specification should be read as implying that any particular element, step or function is an essential element which must be included in the claim scope. The scope of the patented subject matter is defined only by the allowed claims and their equivalents. Unless explicitly recited, other aspects of the present invention as described in this specification do not limit the scope of the claims.
