Fluid handling – With leakage or drip collecting
Reexamination Certificate
2000-06-26
2001-02-13
Lee, Kevin (Department: 3753)
Fluid handling
With leakage or drip collecting
C137S614180, C251S063500, C251S063600
Reexamination Certificate
active
06186163
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is directed to a double seat valve with means for preventing leakage, particularly for the food and beverage industry, which has in its housing two valve disks (
6
,
7
) that cooperate with one another and define a leakage space (
10
) which customarily opens out into the open via lines (
11
). A shared drive unit is provided for the actuation of the two valve disks (
6
,
7
). This drive unit contains a cylinder (
17
) with a first work piston (
18
) which is loaded at both sides by pressure springs (
29
,
22
) and is fixedly connected with the valve stem or valve shaft (
13
) of the lower valve disk (
7
), this valve disk (
13
) penetrating the upper valve disk (
6
) and its tubular shaft (
14
) in a telescoping manner, the shaft, in turn, projecting into the cylinder (
17
) by its upper end and having an abutment (
31
) at that location for the lower pressure spring (
29
) which presses the upper valve disk (
6
) into its seat (
8
), and a second work piston (
36
) which acts on the tubular shaft and is movable on the tubular shaft is arranged under the first work piston (
18
) in the cylinder (
17
), and a third work piston (
30
) which acts on the lower valve disk is arranged above the first work piston.
A blocking valve of the type described above is known from DE-A1 30 05 329.
The seat faces of the two valve disks are constructed so as to be conical and are aligned in such a way that the two valve disks move into the seat face in the same direction. A leakage space which customarily discharges into the open via a line is formed between the valve disks.
Further, DE 42 36 464 A1 discloses a double seat valve in which the lower valve disk continues downward into a balance piston which has approximately the same diameter as the lower valve disk in order to prevent the lower valve disk from lifting due to pressure shocks and to prevent medium from entering the leakage space. Pressure shocks in the pipeline accordingly act on the balance cylinder and valve disk with the same force, so that the pressure forces are balanced in the axial direction.
The known valves can carry out three functions. To open the valve, both valve disks are lifted; to clean the valve seats, the lower or upper valve disk can each be individually moved out of its seat face slightly in order to clean the seat face.
For this purpose, drive units are provided for the valves, these drive units having cylinders which are arranged in series and in which the required pistons are arranged. The pistons act on the two valve disks via two concentric valve shafts.
For opening, a first work piston which is connected with the lower valve disk via a valve shaft is acted upon by compressed air. Accordingly, the first piston is moved upward against the force of a first spring while carrying along the lower valve disk, this spring being further pretensioned until the lower valve disk abuts against the upper valve disk. The leakage space is then closed. When lifted further, the two valve disks move jointly upward, so that the valve is opened.
In the opened state, a second spring which is supported against stops at the valve shaft and at the tubular valve shaft press the two valve disks together.
The closing of the valve proceeds in the reverse order; but the first work piston is moved by the force of the first spring in the pressureless state. As soon as the upper valve disk has reached its seat, the two valve disks separate and the lower valve disk moves into its seat. In so doing, the second spring is further compressed.
To clean the valve seats, the valve disks must be lifted individually. A second and a third piston are provided for this purpose. These pistons act individually, via the valve shafts, on the lower and upper valve disks, respectively.
The second piston for the cleaning lift of the lower valve disk is located in its own cylinder above the cylinder for the first piston. The valve shaft for the lower valve disk is guided in this second cylinder. As soon as its underside is acted upon by compressed air, it lifts the associated valve shaft via a suitable stop and, along with the valve shaft, lifts the lower valve disk out of its seat. A suitable cleaning medium can penetrate into the leakage chamber through an annular gap formed in this way between the valve disk and valve seat.
To clean the upper valve seat, the third piston which is arranged in the cylinder between the first piston and the lower housing wall, is acted upon from below by compressed air. The piston is lifted until it abuts against an abutment arranged at the tubular valve shaft. The upper valve disk is accordingly also lifted from its seat somewhat via the valve shaft. The associated valve seat is rinsed by the penetrating cleaning medium.
The construction of the drive unit turns out to be quite costly due to the large number of switching functions.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a double seat valve of the type mentioned above with a drive unit which is beneficial with respect to manufacturing technique and which consumes a small amount of air when switching, responds quickly to switching command, and safely prevents mixing of media in all conceivable operating states.
This object is met in that the first spring is arranged so as to be supported at the third piston. In this way, a special cylinder for the piston for lifting the lower valve disk can be dispensed with for cleaning the lower valve seat. Instead, the piston is arranged in the same cylinder as the rest of the pistons. The drive unit for the valve is therefore favorably designed with respect to manufacturing technique. In contrast to the drive units formerly used for double seat valves, the double seat valve according to the invention needs no additional cylinders in order to reliably carry out all desired functions, namely, opening, closing and cleaning the valve seats. At the same time, the overall height of the cylinders is advantageously reduced.
Air consumption during the cleaning lift of the lower valve disk is reduced advantageously when a stop limiting the lift of the third piston is provided in the cylinder.
A spring cage can be dispensed with in an advantageous manner in that the first spring has a length defined by stops.
The position of the second radially sealing valve disk in the cylindrical seat face is secured in that the first spring is arranged so as to hold the valve disks at a distance under pretensioning.
Settling phenomena in the upper seal can be advantageously compensated because the spacing of the valve disks is adjustable.
When an intermediate space is provided between the drive unit and valve housing, in which intermediate space a preferably adjustable stop is arranged on the tubular valve rod for limiting the path of the upper valve disk, the amount of lift can be conveniently adjusted from the outside.
The construction of the drive unit, according to the invention, can be used particularly advantageously in a valve in which the lower valve disk is provided with a radially acting seal which cooperates with a cylindrical seat face of the valve housing.
An advantageously precise centering of the valve disks in the sealing seat results in combination with an upper valve disk which is constructed so as to cooperate with a conical seat face of the valve housing.
In an alternative construction, the upper valve disk can also be constructed so as to cooperate with an axial seat face of the valve housing.
When the upper valve disk has a cylindrical recess for tightly receiving the lower valve disk, the valve advantageously switches without leakage.
The seals are treated gently during switching in that the upper valve disk has a surface which is arranged so as to form a throttle gap with a counter-face of the valve housing along a partial lift path.
Pressure shocks do not result in leakage because the lower valve disk has a hydraulic compensating surface. This compensating surface is realized by a balance piston which is guided in the housing and connected with the lower valve disk
Alfa Laval LKM APS
Lee Kevin
Striker Michael J.
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