Pumps – Correlated pump and motor or clutch control – Pump distributor control
Reexamination Certificate
2000-02-02
2002-09-17
Freay, Charles G. (Department: 3746)
Pumps
Correlated pump and motor or clutch control
Pump distributor control
C417S518000, C417S519000, C417S531000, C417S532000, C417S900000
Reexamination Certificate
active
06450779
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a two-cylinder thick-matter pump according to the preamble of claim
1
.
Two-cylinder thick-matter pumps consist of two single pumps which are linked by circuit technology and synchronized in their motion sequence in such a way that while one cylinder (Z
1
) pumps the other cylinder (Z
2
) executes a suction stroke. Usually, the reciprocating speeds of the pistons are equal in both cylinders so that the ending times of the cylinder strokes (suction stroke and pumping stroke) coin-cide. The direction of motion of the cylinder pistons is reversed at the end of each stroke so as to effect constant alternation between pumping and suction strokes.
The suction stroke serves to convey thick matter such as concrete from a priming tank to the particular sucking cylinder. In the subsequent pumping stream the previously sucked-in material is urged out of the now pumping cylinder into the delivery pipe. To ensure that this process always takes place properly one usually provides one or more controllers or reversing valves—for example diverter valves or flat slide valves—which move back and forth between two end positions in order to establish the right connection between the cylinder openings, the delivery pipe connection and the priming tank.
Diverters, the currently most common controllers, are generally so disposed as to swivel back and forth between two end positions in which they establish the necessary connection between the cylinder openings, the delivery pipe connection and the priming tank. The diverter is constantly connected at one end with the delivery pipe while the other end covers the cylinder opening of the particular pumping cylinder. The cylinder opening of the sucking cylinder is thus open to the priming tank.
Since the reversing process of the diverter from one cylinder opening to the other cannot be effected at any desired speed, the flow of material in the delivery pipe is interrupted upon a change of stroke. This necessarily results in a discontinuous flow of material with problematic consequences such as acceleration shocks, surges, high mechanical loads on the components, oscillations in a possibly connected distributing boom, increased wear, etc.
Further adverse effects can prolong the flow interruptions further. For example one often observes the effect that the sucked-in thick matter is compressible because of its air or gas content. At the onset of the pumping stroke the thick matter must thus first be precompressed to the operating pressure prevailing in the delivery pipe before the flow of material commences. Depending on the kind of concrete and in accordance with the other operating conditions, however, the necessity of precompression can also be negligibly small.
Another kind of flow interruption is especially problematic, however. It results from the fact that diverters of the above-described kind and arrangement do not completely cover the delivery cylinder openings at the same time in the center position during their shifting motion (this effect being known as “negative cover”). The thick matter pressurized and prestressed in the delivery pipe can thereby flow back into the cylinder filled with as yet uncompressed thick matter, or past its opening into the priming tank (this effect being known as a “short circuit”).
Altogether, the above-described effects lead to a considerable temporal interruption of the flow of material in the delivery pipe and possibly also to a considerable reduction of output due to return flow out of the delivery pipe. One can lessen the adverse effects by accelerating the shifting motion, but not completely eliminate them.
There is thus a desire to avoid interruptions in the flow of material and to deliver concrete continuously. The prior art already shows several attempted solutions for this but they are either insufficiently operable or involve unreasonable constructional effort making the pumps too expensive and uneconomical.
According to one idea, the piston speeds in the delivery cylinders are dimensioned differently, e.g. the suction speed is selected so much greater than the pumping speed that the suction stroke is ended early enough for the diverter to swivel as far as the center position between the two cylinders in the remaining time until the end of the pumping stroke. A plurality of phases are thereby passed through, in the first of which the cylinder opening of the previously sucking cylinder is closed by means of a shut-off element so that the pressurized concrete cannot flow back into the priming tank in any phase. Closing the cylinder opening additionally permits thick matter located in the cylinder to be precompressed to the operating pressure prevailing in the delivery pipe. In a further swivel phase the opening of the previously sucking cylinder is likewise connected with the delivery pipe, while the pumping stroke of the other cylinder is still ongoing. The cylinder filled with pre-compressed thick matter remains in this position (pump standby position) up to the end of the pumping stroke and then starts its own pumping stroke without a time delay and without a pressure drop in the delivery pipe, while in a third phase the opening of the previously pumping cylinder is initially closed by means of a further shut-off element (to avoid a short circuit). in a fourth and last phase the opening of said cylinder to the priming tank is released and the cylinder, or the piston of this cylinder, begins its suction stroke, again at a higher speed than that of the ongoing pumping stroke. The end of the suction stroke is followed by a new reversing process of the diverter, again while the pumping stroke in the reverse direction is still ongoing.
According to a furtherknown solution from the applicant, described in DE 29 09 964 to Schwing, each delivery cylinder is assigned its own diverter for controlling the suction and pumping stream while avoiding back flow and permitting precompression. A shut-off plate integrally formed as a shut-off element laterally on the inlet opening of the diverter prevents back flow and permits the precompression stroke. The outlet ends of the diverters open into a forked pipe whose outlet communicates with the delivery pipe. This pump is particularly worthy of improvement with respect to its overall width, constructional expense (two diverters, i.e. double material expense) and energy consumption (double expenditure of energy for the two swivel drives of the diverters).
The generic U.S. Pat. No. 3,663,129 proposes realizing the control of the thick-matter stream of a continuous-flow two-cylinder thick-matter pump with only one diverter. In contrast to DE 29 09 964, the pump of U.S. Pat. No. 3,663,129 has only one diverter passed by the pressurized stream, but its outsized inlet opening is problematic. It extends in an oblong shape over the arc of the swivel radius and must have a length corresponding to at least three times the diameter of the delivery cylinder openings since both cylinders must be connected with the delivery pipe in an intermediate phase (pump standby position of the previously sucking cylinder).
The high forces occurring at the usual high operating pressures cannot be absorbed by this diverter and the priming tank receiving the diverter, except with extremely great wall thickness. This is exacerbated by the fact that very high inertia forces and moments also result from the necessary short swivel times over the long shifting paths. From a static point of view as well, the excess weight of the usually mobile pumps resulting from the great wall thickness is unacceptable, as are the high costs.
The invention therefore aims to provide a continuous-flow two-cylinder thick-matter pump with low constructional expense.
The invention achieves this goal by the subject of claim
1
.
Continuous-flow thick-matter pumps known from the prior art have in common that their development has long kept to disposing the diverter in the bottom area of the priming tank in the usual way and giving the diverter the function of guiding the pumpi
Freay Charles G.
Kinney & Lange , P.A.
Schwing GmbH
Solak Timothy P.
LandOfFree
Two-cylinder thick matter pump does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Two-cylinder thick matter pump, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Two-cylinder thick matter pump will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2853983