Drying and gas or vapor contact with solids – Apparatus – Vacuum
Patent
1997-08-26
2000-06-20
Bennett, Henry
Drying and gas or vapor contact with solids
Apparatus
Vacuum
F26B 504
Patent
active
06076273&
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a stabilized vacuum apparatus for industrial hide driers with multiple evaporation beds, of the type that includes a main vacuum source that can be connected to a series of evaporation beds and is suitable to produce a negative pressure having a preset value in the beds, when the system is running in the steady state, so as to facilitate evaporation and condensation of the moisture contained in the hides applied to the beds.
A vacuum system of the above mentioned type is disclosed for example, in the Italian patent application No. VI93A000041, the contents of which are considered as reference in the present invention.
As is known, the beds of vacuum driers have covers that can be opened to load and unload the hides to be dried. Once a bed has been opened, it is disconnected from the vacuum source and is reconnected to it after placing the hides and closing the cover again. During this step, the pressure produced in the remaining beds, which are still closed, rises suddenly because the beds are simultaneously connected to the same vacuum source, which is normally constituted by one or more vacuum pumps and/or blowers.
Accordingly, a cyclic variation of the pressure occurs in the beds, increasing the time required to stabilize the pressure at its normal operating value. This negatively affects the productivity and quality of the hides, which are accordingly stressed in a cyclic manner and can have unevenly dried regions at the end of the treatment.
The aim of the present invention is to eliminate this drawback by providing a vacuum apparatus that in steady-state running conditions can produce in the beds a negative pressure whose value is substantially constant, independently of the opening and closing of each bed during the unloading and loading of the hides from it.
This aim is achieved by virtue of a secondary vacuum source which is suitable to create, in one bed at a time, after the bed has closed, a negative pressure which is close to the steady-state pressure, a valve means being provided to selectively connect each bed, which is initially at ambient pressure, first to the secondary vacuum source and then to the main vacuum source.
This arrangement allows to gradually reduce the pressure in each bed that is initially at atmospheric pressure without affecting at all the remaining beds and eliminates pressure variations in all the beds when the bed that is initially at atmospheric pressure is connected to the main vacuum source.
Further characteristics and advantages will become apparent from the detailed description of a preferred embodiment, illustrated only by way of non-limitative example in the accompanying drawings, wherein:
FIG. 1 is a diagram of a system according to the invention, applied to a three-bed drier;
FIGS. 2 to 5 illustrate successive steps of the operation of the system shown in FIG. 1.
With reference to FIG. 1, this figure schematically illustrates a drier with three evaporation beds, respectively designated by the reference numerals 1, 1', 1", which are connected to a main vacuum source, generally lines 2, 2', 2".
The vacuum source P.sub.A can be of the "high-vacuum" type, as described in the above mentioned application, i.e. it can be constituted by a vacuum pump P.sub.V which is arranged in series to a blower S which is parallel-connected to a bypass valve V. With this layout it is possible to create a vacuum of approximately 10 mbar. Of course, it is possible to use just a vacuum pump P.sub.V without altering the inventive concept.
According to the invention, the beds 1, 1', 1" may be connected, by virtue of respective lines 3, 3', 3", to a secondary vacuum source, generally designated by P.sub.B, which for example is constituted by a single vacuum pump which is similar to P.sub.V but has a lower power rating and capacity and can accordingly be termed "low-vacuum" pump.
A valve means is also associated with each bed and is suitable to connect each bed either to the main vacuum source P.sub.A or to the secondary one P.sub.B. Since the valve means i
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Bennett Henry
Coleman Henry D.
Officine Di Cartigliano, S.p.A.
Sudol R. Neil
Wilson Pamela A.
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