Agitating – Having specified feed means – Adjustable mixing ratio control
Patent
1998-09-16
2000-12-19
Cooley, Charles E.
Agitating
Having specified feed means
Adjustable mixing ratio control
3661623, 222134, B01F 1504
Patent
active
061619566
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a process for the synchronous conveying of flowable materials. The invention relates furthermore to a device for implementing such a process. More specifically, the invention relates to a process for the synchronous conveying of flowable materials with conveyor pumps in a mixing device, from which the mixture of these materials can be fed to a consumer, for example a spray-paint pistol, whereby the conveyor pumps are each operated by means of a hydraulic adjusting unit, in which one operating piston is guided in an operating cylinder, and whereby the adjusting units lie in a hydraulic circuit of a drive fluid loading the operating pistons. The invention relates furthermore to a device for implementing such a process.
BACKGROUND OF THE INVENTION
A process of this type and an associated device are already known from the Patent Application EP 0 644 025 A1, in which two dosing conveyor pumps convey the individual materials into one single mixing device in such a manner that a drive member of a first conveyor pump is loaded with a constant flow pressure and the flow pressure of the drive fluid loading a second drive member are each controlled by adjusting commands of a control device such that the through-flow measured values of the conveyor streams fed by the conveyor pumps have a predetermined relationship, which can be superimposed onto the control device as a desired value.
During a relatively slow conveying of the materials such a control indeed assures their homogeneous mixing. It is possible, at relatively high conveying speeds, for inhomogeneities to occur in the conveyed mixed goods, which can cause difficulties during technical use.
Moreover, the operating efficiency of the control depends essentially on the pressure measurements and controls in the circuit of the drive fluid, which demand measuring devices for the occurring pressures. The demand measuring devices can be calibrated and operate reliably over long periods of time. The measured values from these pressure measurements must thereby be connected with measured values for the travel paths covered by the operating pistons, for the determination of which distance sensors are mounted on the operating cylinders, which are controlled by the operating pistons themselves or by back and forth moving structural parts connected to these. The measured values of pressure and travel distance must then in addition be mathematically connected in order to obtain therefrom the actual values for the conveyor streams out of the conveyor pumps and, therefrom the actual mixture ratio of the materials fed to the mixer. Time delays must be expected in particular for mechanical measurement of the pressures. It is therefore not certain that the materials are continuously processed into a homogeneous mixture, which at all times has the desired mixture ratio. Rather local heterogeneities and deviations from the mixture ratio can, at times, not be avoided in the finished mixture.
It is also already known to carry out the conveying of the materials by means of conveyor pumps, each single one of which is driven by a hydraulic adjusting unit, and in which the flow of the drive fluid active in the adjusting unit can each be adapted by a control valve, which is controlled by a proportional governor. Even though high conveying pressures and performances can be easily handled here, the arrangement often cannot accomplish a mixing of homogeneous goods, which mixing is constant in a wide conveying range, because the adjusting units cannot be synchronized with one another in such a manner that the conveying directions correspond always in various adjusting units, especially when a reversal in direction of the operating piston movement takes place at the same time.
Therefore one obvious solution already used is to enable the drive of several adjusting units to be carried out only by one single drive unit so that the conveyor pumps are now operated simultaneously and one indeed achieves a homogeneous distribution of the conveyed m
REFERENCES:
patent: 3908862 (1975-09-01), Chandra et al.
patent: 4079861 (1978-03-01), Brown
patent: 4312463 (1982-01-01), Daby
patent: 4832499 (1989-05-01), Fiorentini
patent: 4881820 (1989-11-01), Luckhoff
patent: 5556007 (1996-09-01), Breitsprecher
Cooley Charles E.
WiWa Wilhelm Wagner GmbH & Co. KG
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