Valves and valve actuation – With means to increase head and seat contact pressure – With positive reduction
Patent
1987-01-30
1988-09-13
Walton, George L.
Valves and valve actuation
With means to increase head and seat contact pressure
With positive reduction
251177, 251215, 251227, 251229, 251250, 251251, 251263, 251303, 251308, F16K 2500, F16K 122, F16K 31524, F16K 3153
Patent
active
047703920
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a shut-off device for pipes according to the introductory part of claim 1.
2. Description of the Prior Art
The inventive shut-off device differs from a simple valve flap which constitutes a double lever with respect to the driving shaft and swivels on the seat on the housing side with each flap half from different sides regarded in the axial direction. This known valve flap necessitates a spherical contour of the sealing surfaces on the flap and housing sides, which must therefore be precisely fitted to each other. The tight flap seat must have a press fit between the valve flap and its seat on the housing side due to the pressure differences in the tubular housing. When the valve flap is opened or closed this necessitates a high driving torque. Due to the friction between the valve flap and the housing there is very great wear on the sealing surfaces in particular in the case of abrasive flow media. This wear initially causes a reduction of imperviousness. Therefore, the entire shut-off device must be frequently replaced.
In the inventive shut-off device, however, the sealing effect is maintained for long periods of time and in spite of frequent operation. There is also a small driving torque when the flap is opened and closed.
SUMMARY OF THE INVENTION
The point of departure for the invention is a known shutoff device (German Offenlegungsschrift No. 31 43 843). In this device, the valve flap can be swivelled out of the flow position completely into a position perpendicular to the axis of flow at first without touching the housing, so that the driving torque must only overcome the flow forces of the flow medium.
The valve flap is pressed onto the housing seat by a set of gears which acts only in one direction and therefore onesidedly between the driving shaft and the valve flap. This avoids frictional stress on its edges. However, it is disadvantageous that the ring wheel mounted loosely on the driving shaft must be pressed off the valve flap by disk springs in order to ensure the engagement of a gear cam on the driving shaft when the ring wheel and the valve flap are jointly swivelled onto the housing seat, or to ensure a ring wheel stop fixed on the housing. For, on the one hand, this makes it much more difficult for the axial movement of the valve flap toward the housing seat to be initiated due to the high frictional forces of the gearing. On the other hand, the valve flap can be lifted from its housing seat only by the force of the disk springs which are compressed in the process, after the gear cam has released the valve flap due to the driving shaft being rotated back. If the high shutting pressure of the shut-off device acts on the same side of the valve flap, the spring force, which cannot be increased at will, generally does not suffice to lift it.
The invention is based on the problem of providing a valve flap capable of being lifted off its seat independently of the direction of the pressure in the pipe acting on the valve plate located in the shutting position, in the shut-off device assumed as being known, which runs smoothly during swivelling and during the axial movement of the valve flap.
This problem is solved by the invention with the features of claim 1. Expedient embodiments of the invention are the object of the subclaims.
According to the invention, the gearing built in between the driving shaft and the valve flap acts compulsorily in both axial directions. Consequently, no springs are required to lift the valve flap off the seat fixed on the housing. This gearing constitutes the only connection between the valve flap and the driving shaft according to the invention. This makes it possible to give the gearing a smooth-running design because the forces which hold the ring wheel and the valve flap together during swivelling are not transmitted via the gearing elements. For jointly swivelling the ring wheel and the valve flap the forces of a self-locking gearing generally suffice to prevent the ri
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VanOphem Remy J.
Walton George L.
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