| Pump apparatus and method for continuously conveying a viscous material -> Monitor Keywords |
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Pump apparatus and method for continuously conveying a viscous materialRelated Patent Categories: Pumps, Expansible Chamber Type, Plural Pumping Chambers, Including Valved PistonPump apparatus and method for continuously conveying a viscous material description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060193738, Pump apparatus and method for continuously conveying a viscous material. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCES TO RELATED APPLICATIONS [0001] This application claims the priority of German Patent Applications, Serial Nos. 10 2005 008 938.0, filed Feb. 26, 2005, and 10 2005 031 194.6, filed Jul. 1, 2005, pursuant to 35 U.S.C. 119(a)-(d), the subject matter of which are incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] The present invention relates in general to a pump apparatus, and method for conveying a viscous material. [0003] Nothing in the following discussion of the state of the art is to be construed as an admission of prior art. [0004] Pumps of a type involved here are used in the field of concrete conveyance for almost 80 years and operate mechanically by means of crank mechanism, i.e. crankshaft and connecting rod, with a single cylinder. The cubic capacity attainable by this type of crank mechanism is slight because of the very limited piston stroke, when applied for piston diameters of about 200 mm that are still predominantly being used to date. As a consequence, the so-called pump gate, i.e. the valve system, which alternatingly connects the pump cylinder(s) with a concrete reservoir and a delivery pipeline, wear off substantially. Even today, the gate mechanism still represents the most important and most critical component of the concrete pump, save for the typical concrete distributor booms which increasingly become longer in size, thereby increasing manufacturing costs which depending on the boom length can significantly surpass the costs for the actual concrete pump. [0005] The gate mechanism still represents the single most wearing part of the concrete pump. In view of the ever increasing demand for greater stroke volumes at piston strokes of up to 2500 mm that became feasible through application of respective hydraulic drives as early as about 1950, the switching frequency per conveyed cubic meter of concrete dropped off to a fraction. The gates which necessarily also assumed the function of rock crusher so as to be able to reach their end position, wear off predominantly during the switching operation and less during the subsequent throughflow of concrete. [0006] U.S. Pat. No. 5,316,453 to Schwing describes a slurry pump having two main delivery cylinders driven by a hydraulic cylinder for alternatingly conducting concrete via a transfer tube to a delivery pipeline. The transfer tube includes a through channel which creates a fluid communication between the outlet of one main delivery cylinder and the delivery pipeline in a first switching mode and a fluid communication between the outlet of the other main delivery cylinder and the delivery pipeline in a second switching mode. Disposed in a movement plane of the inlet port of the transfer tube on both sides thereof are gate valve disks which bar a return flow of concrete into the reservoir during the switch-over phase from pumping phase to intake phase of the respective main delivery cylinder. The gate valve disks also permit a compression stroke for compacting concrete in a main delivery cylinder against the gate valve disks at the start of the pump stroke. A compensating cylinder maintains a flow in the delivery pipeline during the switching phase. Practice has shown that the surfaces of the gate mechanism which slide on one another undergo substantial wear and the forces necessary to overcome the friction resistance during switching operation are high. [0007] U.S. Pat. No. 6,450,779 to Schwing discloses a pump which prevents a differential pressure on the sliding sealing surfaces during switch-over. The parts of the switching system are subjected during shifting motion either to no load by the concrete pressure (zero pressure at a shut-off valve in the suction line) or are acted upon all-round (outside and inside) by the concrete pressure (balanced pressure in intake swivel pipe in the pressure housing). This type of pump has many shortcomings. The housing must be sized large enough to accommodate the swivel pipe together with the entire concrete content and to allow their rotation, and moreover must be heavy enough because it is under the delivery pressure. In addition, there is only little space available for the flow paths of pumped concrete past the concrete under pressure at the swivel pipe. Thus, on its way from both ports of the delivery cylinders through the housing until exiting into the delivery pipeline, the concrete flow has to undergo several directional changes that are defined by narrow radii of curvature. Depending on the coarseness of concrete, there is a risk of encountering very high flow resistance which could lead to stoppage. This is especially true, as is the case here, when concrete has to flow past standing concrete. When deflected, substantial friction is caused compared to a flow along a pipe wall. Another drawback is the fact that the swivel pipe cannot be sealed against the cylinder ports by a so-called self-adjusting ring which is constructed to automatically compensate for wear. [0008] In addition, the center distance of the main delivery cylinders is too great for a typical installation between length beams of a truck frame, or a substantial swivel angle of e.g. 250.degree. must be accepted instead of about 70.degree. in the case of discontinuous pumps. A hydraulic drive for such a great angle is bulky, heavy, and expensive and consumes much energy and time for the switching operation so that the already brief time available for the intake operation is even further shortened. [0009] It would therefore be desirable and advantageous to provide an improved pump apparatus which obviates prior art shortcomings and which is universally applicable for viscous materials to produce a continuous product flow while subjecting moving parts to little wear. SUMMARY OF THE INVENTION [0010] According to one aspect of the present invention, a pump apparatus for conveying a viscous material includes at least two main delivery cylinders for conveying a viscous material, a delivery pipeline for conducting the viscous material in a flow direction, a switchable gate mechanism moveable between a first position to establish a connection between an outlet port of a first one of the delivery cylinders and the delivery pipeline, and a second position to establish a connection between an outlet port of a second one of the delivery cylinders and the delivery pipeline, a compensating cylinder disposed downstream of the gate mechanism and having an outlet port for discharge of the viscous material into a section of the delivery pipeline, and a shut-off valve disposed in the delivery pipeline in flow direction upstream of the outlet port of the compensating cylinder and constructed in the form of a two-port rotary gate valve. [0011] The present invention resolves prior art problems by using a compensating cylinder to decrease the drop of the delivery pressure and the delivery flow in the downstream delivery pipeline to the compensating cylinder during the switching operation or to maintain the delivery pressure and delivery flow. The provision of the shut-off valve in the delivery pipeline upstream of the outlet port of the compensating cylinder enables the pump apparatus to prevent a return flow of viscous material pumped by the compensating cylinder into the delivery pipeline so that the viscous material pumped into the delivery pipeline effectively maintains the delivery pressure and delivery flow. [0012] To ensure clarity, it is necessary to establish the definition of several important terms and expressions that will be used throughout this disclosure. [0013] The term "viscous material" is used here in a generic sense and the principles described in the following description with respect to concrete are equally applicable to any other type of viscous material, in particular those used in the food industry. [0014] The term "gate mechanism" is used here in a generic sense and may involve even a system in the absence of an actual slider in a conventional sense so long as the switching modes or connection modes are realized. Thus, a gate mechanism may also include transfer tubes, for example. [0015] The term "zone of spherical shape" relates to any surface configuration which resembles at least a surface part of a sphere, including conical configuration. [0016] The term "two-port rotary gate valve" as used in the disclosure relates to a shut-off valve with two switching modes (open/closed) and has a flow cross section which can be opened or closed by turning a swivel body. The rotary motion can suitably be implemented via a sealed stem from outside the valve housing. The swivel body may also have the shape of a disk (rotary flat gate valve). [0017] The provision of a two-port rotary gate valve as shut-off valve enables realization of a constant volume of the flow rate in the delivery pipeline, even during switch-over of the shut-off valve. Thus, the swivel body does not execute a positive or negative pump function as a result of its switching operation. Another advantage of the application of a two-port rotary gate valve is the complete disposition of the swivel body in the delivery pipeline in the absence of any movement to a lateral space. There is no translatory motion out of the delivery pipeline. Sealing of the rotary motion of a drive shaft can be realized without any problem. In addition, the two-port rotary gate valve is easy to manufacture and has only few components that can easily be controlled. [0018] A pump apparatus according to the present invention enables a change of the pressure level upstream of the closed shut-off valve in relation to the delivery pressure downstream of the shut-off valve. As a result, the switching operation of the gate mechanism can be implemented in relation to the delivery pressure in the delivery pipeline at a different, preferably lower, pressure level of the viscous material. The pressure level of the viscous materials between a reservoir and the main delivery cylinders and the upstream part of the delivery pipeline between the main delivery cylinders and the shut-off valve can thus be equalized. Normally, the viscous materials surround components of the switching gate mechanism or are situated within the components of the gate mechanism. When realizing a like pressure level of the viscous materials or even lowering the pressure level of the viscous materials, these components of the gate mechanism can be moved easily. Likewise, the shut-off valve can be operated easily. As the concrete volume upstream of the shut-off valve is suitably compressed, to a same pressure level anteriorly of the port of the shut-off valve as in the delivery pipeline downstream of the shut-off valve, equalized pressure is realized during switching operation. Thus, switching takes place under similar favorable condition as the operation of the gate mechanism which is able to switch absent any pressure in the flow medium. This is realized by the shut-off valve and there is no risk of return flow of viscous material from the delivery pipeline when the pressure drops. [0019] The use of two main delivery cylinders is currently preferred and is applicable in concrete pumps installed on trucks because the two main delivery cylinders can be arranged in inclined relationship to the horizontal and guided through the carrier frame of the truck. Thus, existing trucks can be retrofitted, allowing even the use of existing components such as main delivery cylinders, existing gate mechanism, and the essential parts of the delivery pipeline and the distributor boom. Of course, a pump apparatus according to the present invention may also be constructed with more than two main delivery cylinders. [0020] According to another feature of the present invention, the gate mechanism may be constructed to connect the second delivery cylinder with a reservoir, when assuming the first switching position, and to connect the first delivery cylinder with the reservoir, when assuming the second switching position. Thus, as a result of the alternating operation, in the first switching mode the first main delivery cylinder feeds viscous material into the delivery pipeline, while the second main delivery cylinder draws viscous material from the reservoir, whereas in the second switching mode the second main delivery cylinder feeds viscous material into the delivery pipeline, while the first main delivery cylinder draws viscous material from the reservoir. The gate mechanism may hereby be constructed in the form of a transfer tube. As a consequence of this construction, the one main delivery cylinder that is not in pumping mode is able to draw viscous material from the reservoir while the other main delivery cylinder is in pumping mode to feed viscous material into the delivery pipeline. [0021] The gate mechanism may be constructed of several parts. For example, the gate system may include separate slides which respectively open the connection of the first main delivery cylinder to the delivery pipeline, while closing the respective port of the second main delivery cylinder. A further slide closes the connection of the first main delivery cylinder to the reservoir at the same time and opens its connection to the delivery pipeline. Currently preferred is however a gate mechanism using a transfer tube. An example of a transfer tube is described in U.S. Pat. No. 4,373,875 to which reference is made herewith and the entire specification and drawings of which are expressly incorporated herein by reference. Other possible constructions of a gate mechanism for incorporation in a pump apparatus according to the present invention are described in German Offenlegungsschriften DE 26 32 816, DE 21 62 406 and DE 1 278 247, to which reference is also made herewith. Of course, any of the gate systems used in discontinuously operating pump devices for viscous materials, such as concrete, may be used as well. Continue reading about Pump apparatus and method for continuously conveying a viscous material... Full patent description for Pump apparatus and method for continuously conveying a viscous material Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Pump apparatus and method for continuously conveying a viscous material patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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