EP0573980A1

EP0573980A1 - Three-way cutoff unit particularly for sanitary distribution systems

Info

Publication number: EP0573980A1
Application number: EP93109287A
Authority: EP
Inventors: Renato Galetti
Original assignee: BRANDONI SpA
Current assignee: BRANDONI S.P.A.
Priority date: 1992-06-12
Filing date: 1993-06-09
Publication date: 1993-12-15
Also published as: ITMI921459A0; ITMI921459A1; IT1258989B

Abstract

Three-way cutoff unit particularly for sanitary-water distribution systems, including a valve body (1) which can be connected on a water pipe and which forms a central chamber (2) delimited by a directional inlet valve (3) connected to an inlet (4) for potable water, and by a directional outlet valve (5) arranged on an outlet (6) for the distribution of potable water. A shutter element (7) is provided within the chamber, for engaging a discharge hole (8) so as to close it tightly, and is connected to a membrane (9) which is arranged within, and sealingly divides, a cavity (10) which is superimposed on the central chamber, delimiting a control chamber which is connected to the inlet by a duct (11). The shutter is elastically loaded by a contrast spring (13), and the shutter is internally provided with a control element (18-20) for controlling a smaller port (15) having a smaller cross-section than the discharge hole.

Description

The present invention relates to a three-way cutoff unit particularly for sanitary-water distribution systems.
A cutoff unit is a safety valve meant to avoid the return of water into the public potable-water distribution system, when the pressure in this system is temporarily lower than the pressure in the possibly contaminated (private) system.
Various devices have been provided in the course of time to perform this task; their common elements are a water inlet which is provided with a one-way valve and which is connected to a middle chamber provided with a discharge valve leading into an outlet provided with a one-way valve.
Statutory provisions prescribe that when the difference between the internal pressure of the middle chamber and the pressure in the water inlet is smaller than a certain preset ΔP, the discharge valve must be opened in order to prevent any problem of contamination of the potable water.
Various problems are posed by these statutory provisions: attempts have generally been made to solve them by using a cavity into which a supply duct transfers the pressure of the inlet in a half-chamber by compressing an elastically loaded membrane. The loading of the membrane, which is sealingly crossed by a stem for actuating the discharge valve which is rigidly coupled to said membrane, is such as to cause the opening of the discharge valve in the absence of pressure in the inlet and is linked to the above mentioned pressure differential ΔP. The load, which is calibrated for the different operating situations, is produced by a spring acting on the membrane or on the stem.
The technical problems of these solutions are numerous: in order to achieve quick opening, the membrane must be highly sensitive to minimal pressure changes, and this is achieved with membranes which are much larger than the port of the discharge valve. However, it is not practically possible to produce cutoff units with membranes having an excessively large diameter, due both to the sizes of the valve bodies and to economical reasons. It is thus necessary to seek the best compromise which allows to comply with the applicable technical prescriptions.
Some solutions currently used are briefly analyzed hereafter.
French Patent No. 2544832 relates to a valve body with one-way elements having an arrangement which can be defined as classic, with a membrane which is arranged above the middle chamber and which forms an upper half-chamber connected to the water system upstream of the inlet one-way valve. Said valve is a typical example of typical construction, which has sensitivity problems in detecting the pressure differential.
European Patent No. 0084754, with respect to the preceding solution, provides for a hollow stem which constitutes an air venting opening which can facilitate the emptying of the middle chamber, i.e. to make it quicker by facilitating the flow of air into the middle chamber.
German Patent No. 431407 has a particularly complicated valve structure, but substantially remains a classic structure with a solid and monolithic stem.
U.S. Patent No. 3906987 eliminates the actuation membrane, but provides for a venting piston which acts if a pressure differential lower than the preset value is detected; said piston is arranged on the upstream one-way valve to open the discharge valve.
Other patents, such as German Patent No. 2854003, German Patent No. 2925179, British Patent No. 2023776, Canadian Patent No. 1101303, U.S. Patent 4518006, Italian Patent No. 68554/BE/86, European Patent No. 002600, Canadian Patent No. 1030423, European Patent No. 0029387, European Patent No. 0183909 and European Patent No. 0130306 teach other structures, both classic and non-classic, which however have the usual problem linked to sensitivity in detecting the pressure differential.
Other problems not solved by the statutory provisions are linked to the maintenance of the one-way valves and of the discharge valve, due to the fact that the discharge valve must be opened in case of breakages of the cutoff unit; other problems are also variously mentioned but not conclusively taught in any of the above mentioned patents.
A principal object of the present invention is to eliminate or substantially reduce the drawbacks described above by providing a three-way cutoff unit particularly for sanitary-water distribution systems which considerably increases the sensitivity of said cutoff unit to pressure changes, even to instantaneous ones.
Another object of the present invention is to provide a cutoff unit which allows simple and rapid access to the valves for their maintenance.
A further object of the present invention is to provide a highly reliable cutoff unit which is relatively easy to manufacture and at competitive costs.
With these and other objects in view, there is provided, according to the invention, a three-way cutoff unit particularly for sanitary-water distribution systems, comprising: a valve body connectable to a water pipe and forming a central chamber delimited by a directional inlet valve, which is arranged at a fluid inlet, and by a directional outlet valve, which is arranged at a fluid outlet; and a shutter element provided within said chamber for engaging a discharge hole so as to close it tightly, said shutter element being connected to a membrane which is arranged within, and sealingly divides, a cavity which is superimposed on said central chamber, forming a control chamber which is connected to said inlet by a duct, said shutter being elastically loaded by a contrast spring, and said shutter being internally provided with a control element for controlling a smaller port having a smaller cross-section than the discharge hole.
Further characteristics and advantages of the present invention will become apparent from the following detailed description of a preferred but not exclusive embodiment thereof, illustrated only by way of non-limitative example in the accompanying drawings, wherein:

figure 1 is a sectional lateral elevation view of a cutoff unit according to the present invention in normal operating position;
figure 2 is a sectional lateral elevation view of a cutoff unit according to the invention in the position for discharge through a smaller port; and
figure 3 is a sectional lateral elevation view of a cutoff unit according to the invention in the position for discharge through the discharge hole.

With reference to the above figures, a three-way cutoff unit particularly for sanitary-water distribution systems comprises a valve body, generally designated by the reference numeral 1, which can be interposed on a water pipe and which forms a central chamber 2 delimited by a directional inlet valve, generally designated by the reference numeral 3, which is connected to a potable water inlet 4, and by a directional outlet valve, generally designated by the reference numeral 5, which is arranged on a potable water distribution outlet 6.
A shutter element, generally designated by the reference numeral 7, is provided within the chamber 1, acts on a discharge hole 8 so as to close it tightly, and is connected to a membrane 9 which is arranged within, and sealingly divides, a cavity 10 superimposed on and connected to the central chamber.
The membrane 9 forms a control chamber 10a, which is connected to the inlet 4 by means of a duct 11; a first threaded seat 12 for accommodating a pressure gauge is formed on the duct 11.
The shutter is elastically loaded by a contrast spring 13. Another pressure gauge can be arranged within a second threaded seat 14 located on the distribution outlet 6.
The shutter 7 is internally provided with a control element for controlling a smaller port 15 having a smaller cross-section than the discharge hole 8.
The shutter element 7 comprises a sheath 16, having an elongated longitudinal extension, being sealingly inserted in the central chamber 1 and sealingly entering the cavity 10, and a valve 17 for closing the discharge hole 8. The control element, comprising a stem 18 connected to the closure valve 17, is inserted in the sheath 16.
The sheath 16 selectively controls the opening and closure of the smaller port 15 formed within the closure valve 17. Connection is obtained by means of a pin 21 which, by means of slots 23, enters and is connected to a portion 20 which controls the port 15 by means of a point 19.
The smaller port 15 is connected to the central chamber 2, when it is open, for water discharge, by means of an opening 24 formed in the valve 17.
The sheath 16 is fixed to the membrane 9 by means of a pair of disks 25 and 26 and of an annular presser 27. The disks 25 and 26 are arranged respectively upstream and downstream of the membrane 9, and the contrast spring 13 engages against the disk 26, abutting with its other end against the end wall of a cylindrical portion 10b of the cavity 10.
The stem 18 protrudes from the valve body 1 on the side opposite to the discharge port 8 within an element 28 for compensating the hydrostatic load of the closure valve.
The discharge hole 8 is formed in a wall 29 of the valve body 1 which can be fully removed from said valve body in order to allow access to the central chamber 2 and to the directional inlet and outlet valves 3 and 5. The wall 29 is fixed to the remaining part of the valve body 1 by means of screws 46.
Each directional valve 3 (5) has a conical element 30 (31) which is rigidly coupled to a shaft 32 (33) which is slidingly arranged within a hollow conical body 34 (35) having a flanged end 36 (37) against which a cylindrical spring 38 (39) abuts; the other end of said spring 38 (39) engages against an internal face of the conical element 30 (31). Said conical element 30 (31) slides freely and engages against an annular raised portion 40 (41) to close the inlet 4 or the outlet 6 respectively. The hollow conical body 34 (35) is fixed to the valve body 1 by means of a respective flange 42 (43) the respective fixing screws 44 (45) whereof can be accessed from the opening of the removable wall 29.
Operation is as follows: during normal operation, figure 1, the valves 3 and 5 are open, allowing the flow of potable water for distribution, and the shutter element 7 keeps the valve 17 and the stem 18 in closed position. In this situation, the pressure transferred into the control chamber 10a through the duct 11 fully contrasts the contrasting opening action applied to the membrane 9 by the spring 13.
If, figure 2, there is a sudden pressure variation, i.e. if the pressure differential is violated even slightly, the pressure in the control chamber 10a which acts on the membrane 9 decreases, and thus the contrast spring 13 raises the sheath 16 until the smaller port 15 opens. Considering the different sizes of the membrane 9 and of the smaller port 15, the improvement in terms of sensitivity introduced by the present invention is understandable. When the smaller port 15 is open, dripping occurs initially and ceases if pressure conditions according to the applicable statutory provisions are restored, the pressure acting on the membrane 9 compresses the spring 13, and the smaller port 15 is closed again.
If instead the pressure differential increases, the spring 13 moves until it reaches its maximum stroke; by means of the stem, said spring moves the valve 17 into its open position (figure 3), fully opening the discharge hole 8 and thus allowing the water present in the central chamber 2 to discharge. In both of the above described situations, the one- way valves 3 and 5 are in closed position.
It should be noted that advantageously, when the pressure differential occurs, the stem 18 is raised immediately, producing an immediate discharge of water from the central chamber and thus causing a pressure decrease in the chamber 2.
Furthermore, conveniently, if the membrane 9 should fail, the spring 13 would immediately open the valve 17, thus preventing any possible contamination of the upstream potable water with water which has already flowed into the distribution system.
Furthermore, advantageously, the wall 29 allows, by means of its removal, direct intervention inside the central chamber 2, furthermore allowing rapid replacement of both the shutter element 7 and the valves 3 and 5, the respective fixing screws 44 and 45 whereof, as previously mentioned, directly face the opening left by the wall 29.
Practical tests have shown that the present invention achieves the intended objects, providing a cutoff unit which is extremely sensitive to pressure variations by virtue of the difference in diameter between the control membrane 9 and the smaller port 15.
The invention thus conceived is susceptible to numerous modifications and variations, all of which are within the scope of the inventive concept. All the details may furthermore be replaced with other technically equivalent elements.
Thus, it is possible to provide the inlet 4 and the distribution outlet 6 on elements which are associated with the valve body; in this manner it is possible to vary the diameters and dimensions of the connections without modifying the valve body.
In practice, the materials employed, as well as the dimensions, may be any according to the requirements.
Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims

Three-way cutoff unit particularly for sanitary-water distribution systems, comprising: a valve body (1) connectable to a water pipe and forming a central chamber (2) delimited by a directional inlet valve (3), which is arranged at a fluid inlet (4), and by a directional outlet valve (5), which is arranged at a fluid outlet; and a shutter element (7) provided within said chamber for engaging a discharge hole (8) so as to close it tightly, said shutter element being connected to a membrane (9) which is arranged within, and sealingly divides, a cavity (10) which is superimposed on said central chamber, forming a control chamber which is connected to said inlet by a duct (11), said shutter being elastically loaded by a contrast spring (13), and said shutter being internally provided with a control element (18) for controlling a smaller port (15) having a smaller cross-section than the discharge hole.
Cutoff unit according to claim 1, characterized in that said shutter element comprises a sheath (16) having an elongated longitudinal extension, being sealingly inserted in said central chamber, and sealingly entering said cavity, and a valve (17) for closing said outlet, said control element being inserted in said sheath and being constituted by a stem (18) suitable to selectively control the opening and closure of said smaller port, said sheath being connected to an expanded portion (20) by means of a pin (21) which enters said sheath, said expanded portion controlling said smaller port.
Cutoff unit according to the preceding claims, characterized in that said smaller port (15) is connected to said central chamber (2), for the discharge of fluid, by means of an opening (24) formed in said valve (17).
Cutoff unit according to one or more of the preceding claims, characterized in that said sheath (16) is fixed to said membrane (9) by means of a pair of disks (25,26) and of an annular presser (27), said disks being arranged respectively upstream and downstream of said membrane, said contrast spring engaging against one of said disks and abutting against a wall of said cavity.
Cutoff unit according to one or more of the preceding claims, characterized in that said stem (18) protrudes from said valve body on the side opposite to said discharge port within a compensation element of the discharge valve.
Cutoff unit according to one or more of the preceding claims, characterized in that said discharge hole (8) is formed in a wall (29) of said valve body which can be completely removed from said valve body to allow access to said central chamber and to said directional inlet and outlet valves.
Cutoff unit according to one or more of the preceding claims, characterized in that each directional valve is fixed to said valve body by means of a respective flange (42,43) accessible from said removable wall.