Pumps – Successive stages – Stages driven by relatively movable motor working members
Reexamination Certificate
2001-07-27
2003-05-06
Freay, Charles G. (Department: 3746)
Pumps
Successive stages
Stages driven by relatively movable motor working members
C417S244000, C417S400000, C417S401000, C417S539000, C417S053000
Reexamination Certificate
active
06558134
ABSTRACT:
TECHNICAL FIELD
The present invention relates to fluid pumping and, more particularly, to intensifier pumping.
BACKGROUND
Hydraulic intensifier pumps are widely used in applications requiring the delivery of a high pressure jet of fluid. An intensifier pump includes a pump cylinder, a hydraulic working piston, a product intensifier piston, inlets for the hydraulic working fluid to both advance and retract the piston, an inlet for the product fluid to be pressurized, and an outlet for the pressurized fluid. In operation, lower pressure hydraulic fluid is applied to the comparatively large working piston. The working piston, in turn, drives the smaller intensifier piston. The ratio of the hydraulic and product piston areas is the intensification ratio. The hydraulic pressure is multiplied by the intensification ratio to produce an increase in pressure.
The fluid to be intensified typically is delivered to the intensifier via an inlet check valve from a low pressure fluid supply pump. The fluid supply pump generally is able to generate sufficient pressure to overcome the tension of an internal poppet spring within the check valve, opening the check valve when the intensifier is in the retraction cycle and allowing product fluid to be delivered to the intensifier cylinder. When the piston begins its advance cycle to expel the pressurized fluid, the higher pressure of the intensified product fluid overcomes the lower supply pressure, closing the inlet check valve and thereby preventing backflow of the intensified fluid into the low pressure supply side of the pump. Many intensifier systems incorporate two or more intensifier pumps that advance and retract on an alternating basis to provide a substantially continuous fluid jet. When one product intensifier piston retracts, the other advances. The relative timing of the advance and retraction cycles is carefully controlled to provide a substantially constant fluid pressure.
For industrial applications requiring precise fluid delivery, pressure fluctuation can be highly undesirable. For example, in processing of dispersions, emulsions, liposomes, and the like, the total amount of work, or energy, being applied is a function of both the mechanical power, or shear, and the time the product is in the shear zone. Further, in order to effectively process dispersions, the energy level must be sufficiently high and uniform to disperse agglomerate structure. A gradient of energy levels being applied to a dispersion, as a result of the processes having pulsation, will result in some of the product being subjected to insufficient processing. Continued processing of the product, under conditions where pulsations exist, cannot compensate for the gradient of energy levels that is less than the energy level required. Other applications that suffer from pulsation include the processing and pumping of coating solutions to a coating process such as a coating die where pulsation will cause product caliper variation.
Other considerations for intensifier pump systems include the overall size of the pumps, the configuration of the equipment to both advance and retract the intensifier pumps and the speed at which the intensifier pumps can be cycled. Intensifier pumps having hydraulic advance and retract cycles need to be appropriately configured, thereby increasing their overall size. Furthermore, the hydraulic retraction cycle can be relatively slow, thereby increasing the length of each cycle. For example, the intensifier pump has a hydraulic retraction cycle, during which the low pressure supply pump fills the intensifier barrel. Thus, the hydraulic retraction cycle must provide a sufficiently long period of time to allow the conventional check valves to open and the supply pump to fill the barrel. To provide this extended time period, the conventional intensifier pump has a relatively long piston length, thus increasing both the overall size of the intensifier pump and the delay imparted through the operation of the intensifier pump. Further complicating this problem is the need to precompress the product prior to advancing. That is, the intensifier pump typically must be filled to capacity and then advanced to a point where the product is raised to a predetermined pressure. Only then is the outlet opened and the product is delivered at pressure. These processes further increase the cycle time of the intensifier
SUMMARY
The present invention is generally directed to a hydraulic intensifier system useful in the delivery of fluid material under pressure. The intensifier system gains efficiencies through the use of a charge intensifier pump that delivers a supply of material under a relatively high pressure to one or more product intensifier pumps. The charge intensifier pump functions at a pressure level sufficient to cause a piston in a receiving product intensifier pump to retract, thus allowing the product intensifier pump barrel to fill with product. After filling, the charge intensifier pump can continue to increase the pressure within the filled product intensifier pump barrel, thus reducing the amount of preloading required by the product intensifier pump prior to beginning its advance cycle.
A system and method, in accordance with the present invention, preferably make use of a low pressure supply pump to deliver material into the system. The low pressure supply pump feeds into a charge intensifier pump through a controllable check valve. The charge intensifier pump then delivers the material at a much higher pressure to one of multiple product intensifier pumps. The product intensifier pumps are configured so that some of the pumps are essentially out of phase with one another. That is, in a system having two product intensifier pumps, one is advancing (and hence delivering product) while the other is retracting and preloading. During the retraction of the product intensifier pump, it is being filled with product so that during a subsequent advance stroke, material is expelled.
At the end of an advance cycle, material is allowed to enter the product intensifier pump from the charge intensifier pump. The material is delivered at a relatively high pressure that is sufficient to cause the product intensifier pump to retract at a relatively high speed. Thus, the charge intensifier pump can increase the speed of the retraction stroke of the product intensifier pump. The charge intensifier pump has a larger product displacement per stroke than that of the product intensifier pumps. Thus, the charge intensifier pump fully fills one (or more) of the product intensifier pumps with each stroke. Furthermore, the charge intensifier pump fills the product intensifier pumps without introducing air, thus aiding in the control and elimination of pulsation. Even after fully retracting, material is still delivered from the charge intensifier pump to the barrel of the product intensifier pump, causing the material within the product intensifier pump to further increase in pressure. This reduces the amount of time the product intensifier pump will need to preload or precompress the material before the advance stroke begins to deliver product. The product intensifier pump then begins its advance cycle, delivering product. At or near the same time, the other product intensifier pump (in a two product pump system) is retracted by the delivery of product from the charge intensifier pump.
In this manner, material is substantially constantly and consistently delivered by the product intensifier pumps. The product intensifier pump pistons are retracted quickly with the aid of the charge intensifier pump. The preload period is greatly reduced. Thus, efficiency is increased through a reduction in the required time duration for each cycle. Further, because the charge intensifier pump causes the retraction of each of the product intensifier pumps, there is no need to provide a hydraulic retraction cycle for any of the product intensifier pumps. Rather, in some embodiments, the hardware and fittings necessary for delivery of working fluid for retraction can be eliminated. Thu
Erickson LeRoy C.
Serafin Mark
Freay Charles G.
Imation Corp.
Levinson Eric D.
Solak Timothy P.
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