CA1066255A

CA1066255A - Vacuum operated check valve for vacuum conduits

Info

Publication number: CA1066255A
Application number: CA291,182A
Authority: CA
Inventors: Harald Michael
Original assignee: Electrolux GmbH
Current assignee: Dometic GmbH
Priority date: 1976-11-20
Filing date: 1977-11-18
Publication date: 1979-11-13
Also published as: GB1538820A; DE2652878C3; NO148757B; AU508916B2; DE2652878B2; FI68111B; SE7712885L; CH624748A5; DE2652878A1; SE431784B; FI773501A; JPS5380826A; NL7712406A; FR2371622A1; NO773950L; DK512977A; NO148757C; FR2371622B1; AU3075077A

Abstract

Abstract of the Disclosure A diaphragm-type check valve for vacuum pipes is provided which enables opening of the valve using substantially less operating force than is required in conventional valves of the same size and type. The valve includes a flexible diaphragm which is disposed in the pipe and is held in its closed position by the vacuum in the pipe. A mechanical operator such as a vacuum-actuated piston causes opening of the valve. A cavity located on the side of the diaphram opposite that which is exposed to the pipe vacuum is selectively connected to a source of suction or vacuum (preferably that provided by the pipe itself) so as to substantially equalize the pressure on both sides of the diaphragm and thereby enable opening of the valve with a less bulky operating mechanism that provides only the reduced operating force referred to above.

Description

The present invention relates to an improved diaphragm check valve for vacuum conduits of the type comprising a flexible diaphragm which is moved into the closed position by the vacuum in the conduit and into the open posi-tion by means of an operating mechanism connected to the diaphragm. ~-A check valve of the type referred to above is described in German Patent 1,609~245, and can be utilized in such devices as vacuum waste water conduits. In such prior art valves, the drive force of the opening mechanism must be relatively powerful in order to overcome the constant, oppositely acting force on the diaphragm provided by the vacuum in the line or conduit.
Thus, if the drive mechanism is a cylinder-piston unit adapted to be connected to vacuum to provide the opening force, the surface area of the piston must necessarily be larger than the effective surface area of the diaphragm. Thus, such valve units are large and bulky in relation to the cross section of the conduit.
Two patents of possible interest were cited against the German application on which this application is based, viz., United States Patent No. 3,451,423 and German Offenlengungsschrift 1,947~396. The former discloses two coaxially intereonnected pistons, one of which mechanically engages a valve diaphragm. The latter discloses a valve diaphragm which is acted upon directly by a pressure medium.
Generally speaking, the invention is concerned with the problem of producing a check valve of the type specified wherein the operating or drive mechanism need only provide a relatively weak operating force and hence can be correspondingly small in size.
According to the invention there is provided a diaphragm check valve for vacuum pipes or conduits comprising a diaphragm which is movable into a first position, wherein the valve is closed, by the pressure difference between the ambient atmospheric pressure and the suction pressure within the pipe in ;
which the check valve is located and an operating mechanism connected ~o said diaphragm for moving said diaphragm to a second position wherein the valve is - ~_ -, .
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open, the improvement wherein a cavity is provided on the side of the dia~
phragm opposite to that which is exposed to the suction pressure within the pipe and means are provided for selectively supplying suction pressure to said cavity.
Supplying the cavity with suction or vacuum reduces the pressure ~ :
across the diaphragm and decreases the operating force required to open the valve. Stated differently, providing for opening of the valve by vacuum or suction applied to the cavity, enables the effect of the pipe vacuum on the diaphragm to be wholly or partly - la -B
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~066255 counterbalanced so that only a slight additional force need be exerted by the operating mechanism to overcome the existing frictional and deformation forces (as well as any gravitational or spring biasing forces in the direction of -`
closure~ and thereby to move the diaphragm into the open position. Thus, in valves of this type wherein the operating mechanism is a control piston acted on by suction or vacuum forces, the piston can have a substantially smaller diameter than heretofore. In addition, the mounting and retaining devices for the piston cylinder can be of corresponding small dimensions.
Because the additional opening force that is to be applied by the operating mechanism in the check valve of the invention is largely independent of the size of the diaphragm, the same operating mechanism can be used for check valves with conduits of different sized cross sections. It will be ,~
appreciated that substantial advantages with respect to production and stock inventories accrue from such standardization of the operating mechanism.
A further advantage of the valve of the invention results from the fact that the valve can open more rapidly because of the comparatively greater operating force that can be produced by the simplified operating mechanism, - -thus avoiding the danger of having solids in the waste water clog the valve.
The invention is basically independent of the form of the diaphragm and the seat cooperating therewith, as well as independent of the type of operating mechanism and whatever biassing arrangement in the direction of closure is provided. For practical reasons, a piston, such as a vacuum opera-ted diaphragm piston, is preferably utilized as the operating mechanism be-cause a vacuum is available from the conduit itself right at the location of the valve. Thus, only a branch line is needed in order to simultaneously provide the suction forces for both the cavity and the drive piston of the operating mechanism. In such an embodiment a vacuum control line or conduit is connected to the waste water conduit downstream of the valve and to the ;~
cavity and the drive piston cylinder. This control line preferably includes a suitable additional control means provided for a specific purpose, e.g., a

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manual valve or an automatic control valve that responds to the limiting level of a liquid reser~oir that is to be sucked off through the valve, such as it described for example in German OS 2,455,551. Moreover, a delay in the clos-ing movement of the valve may be provided so as to, for example, admit a specific volume of air into the waste water conduit after the liquid is drawn off. This can be achieved by means of an adjustable choke in the control conduit which is operated when the check valve is closed.
In a preferred embodiment of the check valve of the invention, the connecting rod between the piston and the diapragm passes through the wall of outer cavity or recess to which a vacuum is selectively applied and conse~-quently a seal is disposed between the rod and this wall of the cavity.
Advan~ageously, a diaphragm seal is used. While it is true that such a seal reduces the force acting in the direction of opening in proportion to the size of the check valve diaphragm, such diaphragm seals, as opposed to sliding seals, afford the advantage of being less likely to malfunction.
Other features and advantages of the invention will be set forth in, or apparent from, the de~ailed description of the preferred embodiments found hereinbelow.
The single figure in the drawings is a side elevational view, largely in cross section, of a check valve constructed in accordance with a preferred embodiment of the invention.
Referring to the drawings, a vacuum pipe or conduit is indicated at 10. Conduit 10 is, for example, a waste water conduit which must normally be kept closed by a check valve at the external connections theretol e.g., at the toilet bowls or a waste water collecting point. Such check valves are briefly opened by a special control mechanism so as to suck the waste water that has collected at the connection, as well as a specific amount of air, into the vacuum conduit. Diaphragm valves are advantageous for this purpose. `
Such valves include a diaphragm, denoted 12 in the drawings, which

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is held securely in the closed position thereof by the vacuum in ~he line or conduit 10. In order to open the diaphragm valve, a driving force is employed which advantageously makes use of a vacuum in conduit 10. Similarly to the diaphragm valve disclosed in German Patent 1,609,245 referred to above, the ;
valve illustrated in the drawings includes a vacuum operated cylinder-piston unit 14 comprising a fixedly mounted cylinder 16 and a piston 20 connected therewith by means of a flexible sleeve or diaphragm 18. As is conventional, drive piston 20 can be biassed by a weight 22 in the direction o~ closure.

A spring (not shown) can also be used for this purpose. nrive piston 20 is fixedly connected to diaphragm 12 by a piston rod 24 and suitable fastening means such as the pin connectors indicated at 26. -As discussed above, in prior art systems drive pistons corresponding to piston 20 would supply all of the necessary force for moving the diaphragm -12 into the open position, and thus the piston would have ~o be relatively large. However, in the check valve of the invention drive piston 20 is com-paratively much smaller than that normally utili~ed. According to the inven-tion, a cavity 28 is provided which is tightly sealed from the ambient by an external wall 30, and which is selectively subjected to a vacuum or suction pressure. In this way, the suction force provided by the vacuum in conduit 10, and acting on diaphragm 12 in the direction of closure, is substantially balanced.
To prevent loss of vacuum in cavity 28, a seal is provided between wall 30 and piston 24. Two different embodiments of such a seal are illustra-ted. On the lefthand side of the drawings a lip seal 32 is illustrated which provides for a sliding motion on piston rod 24. On the righthand side, a diaphragm seal 32 is illustrated which, in the application in question, should have the smallest possible surface area in order to keep frictional forces at a minimum.
In the illustrated embodiment of the invention, a cylinder 16 and cavity 28 are connected through a pair of branch conduits 36, 38 to a common :

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`~6~ 55 vacuum conduit 40 in which a control valve 42 is connected. Valve 42 includes a connection to ambient indicated at 44. In the position of the valve body ~`
illustrated, the valve 42 connects cylinder 16 and cavity 28 to connection 44, and thus to the ambient pressure. Under these circumstances, there is no ~-connection between conduit 10 and cavity 28 or cylinder 16 and thus the vacuum in conduit 10 holds the check valve in the closed position illustrated. If the rotary valve body of control valve 42 is rotated clockwise about 45 in the example illustrated, cylinder 16 and cavity 28 will both be connected with the vacuum or suction pressure in conduit 10 by means of common control conduit 40 and thus piston 20 will act to open the valve.
It should be pointed out that cylinder 16 and cavity 28 do not neces-sarily have to be placed under vacuum simultaneously, or connected simultane-ously with the ambient, as is provided for in the illustrated embodiment. For example, the speed up the valve opening operation, cavity 28 could be initially connected to vacuum conduit 10, whereby the overall check valve, because of biassing provided by weight 22 and other internal forces, would remain closed.
If thereafter drive piston 20 is then put under vacuum, diaphragm 12 will be drawn very rapidly into the open position thereof.
Although the invention has been described relative to examplary -~
embodiments thereof, it will be understood that other variations and modifica-tions can be effected in these embodiments without departing from the scope and spirit of the invention.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A diaphragm check valve for vacuum pipes or conduits comprising a diaphragm which is movable into a first position, wherein the valve is closed, by the pressure difference between the ambient atmospheric pressure and the suction pressure within the pipe in which the check valve is located and an operating mechanism connected to said diaphragm for moving said diaphragm to a second position wherein the valve is open, the improvement wherein a cavity is provided on the side of the diaphragm opposite to that which is exposed to the suction pressure within the pipe and means are provided for selective-ly supplying suction pressure to said cavity.

2. A check valve as claimed in claim 1 wherein the operating mechanism comprises a piston which is movable responsive to suction pressure, said piston being connected to said diaphragm by a connecting rod, said valve further comprising means for selectively communicating said piston with suction pressure or the ambient pressure and for selectively communicating said cavity with suction pressure or the ambient pressure.

3. A check valve as claimed in claim 2 wherein said cavity and said piston are simultaneously placed in communication with the same suction pressure.

4. A check valve as claimed in claim 2 wherein said communicating means includes a connecting conduit including a control valve which is open during the closing movement of said diaphragm.

5. A check valve as claimed in claim 4 wherein said control valve is adjustable.

6. A check valve as claimed in claim 1 wherein the outer wall of the said cavity is integral with the wall of the conduit in which said valve is located.

7. A check valve as claimed in claim 1 wherein said operating mechanism comprises a piston and cylinder unit, the cylinder being mounted on the outer wall of said cavity.