Fire hydrant with check valve

Abstract: A fire hydrant comprising a standpipe (1) with closable top outlet (2) and with an underside in communication with a pressure pipe for water or the like, a valve seat (9) arranged in the standpipe and at the underside thereof, a main valve (10), a valve stem (11) carried upward through the standpipe and control means arranged above the standpipe for moving the valve stem (11) up or down in order to release the main valve (10) and to respectively lift from and press it against the seat (9). Dirt collected in the standpipe (1) may, after use of the hydrant, enter the water supply pipe to which the hydrant is connected, endangering public health. To avoid this drawback the fire hydrant according to the invention comprises a check valve (20), freely movable and guided in the passage (5) of the standpipe between valve seat and pressure pipe. Preferably the check valve (20) is provided with an upper surface, being parallel the bottom of the main valve (10), the valve body is provided with one or more guiding members, like pins (21) protruding into the passage (5).

Description: The invention relates to a fire hydrant comprising a standpipe with closable top outlet and with an underside in communication with a pressure pipe for water or the like, a valve seat arranged in the standpipe and at the underside thereof, a main valve, a valve stem carried upward through the stand pipe and control means arranged above the standpipe for moving the valve stem up or down in order to release the main valve and to respectively lift from and press it against the seat, and a freely movable check valve arranged and guided in the passage of the standpipe between valve seat and pressure pipe. Fire hydrants of the type described in the preamble and disclosed in EP-A-0 113 913 are typically arranged in the ground and connect to an underground pipe system. The danger that occurs here is that dirt collects in the standpipe if the fire hydrant is not used. When the main valve is lifted from the seat and the top outlet is closed or no water is taken off, liquid from the pressure pipe system will first be pressed upward into the standpipe and compress the air in the standpipe. After the flow in the water has stopped, the dirt carried upward will sink downward and can enter the mains network via the open valve and thus pollute the water, which involves a danger to public health if this water is used as drinking water. The invention has for its object to ameliorate the working of the check valve and provides to this end a fire hydrant which is distinguished in that the check valve is provided with an upper surface, being parallel to the pressure surface of the bottom of the main valve, said lower surface of the main valve and the top surface of the check valve are embodied with co-acting complementary centering means, for example an annular groove having annular ribs fitting therein and wherein the check valve body is provided with one or more guiding members, like pins protruding into the passage. Due to the upper surface of the check valve being parallel to the bottom of the main valve, and the guide pins protruding into the passage, an upright guiding of the check valve is herewith ensured and resonating of the valve, which can cause water hammer pressure, is prevented. In order to cause the check valve to open without friction, it is recommended to widen the peripheral edge of the disc-shaped valve towards the top, which peripheral edge co-acts with a complementary annular surface in the passage. It is recommended for good closing to embody the peripheral edge of the check valve with a groove recessed therein for receiving an O-ring, which co-acts with the annular surface. In order to prevent a great flow speed pulling the O-ring out of the groove when the check valve is half opened and also to obtain a small enclosed dirty water volume between the check valve and the main valve the invention proposes having the annular surface in the passage connect directly to the head end surface of this passage embodied as valve seat. Because of the relatively sharp transition between the annular surface and the valve seat a "dead" space is created with respect to flow along the O-ring, so that the flow forces acting thereon are small. According to a prefered further proposition of the invention the main valve is covered with a jacket of elastic material. In addition the main valve can be guided in ridges or cams arranged in the standpipe in order to keep the guiding of the main valve purely axial, which contributes to better guiding of the check valve and thereby to preventing the resonance phenomenon with the "loose" check valve. It is finally proposed to connect the main valve to the valve stem or said pressure member via a universal joint. Above mentioned and other features will be further elucidated in the following figure description. In the annexed drawing: Fig. 1 shows an upright section through the fire hydrant according to the invention, fig. 2, 3 and 4 each show an upright section corresponding with fig. 1 of the underside of the standpipe having accommodated therein main and check valve in three different positions, fig. 5 shows an alternative embodiment of the guiding of the check valve in the passage of the standpipe, Designated in the figures with the reference numeral 1 is the standpipe, which is provided at its top end with a closable passageway 2. Arranged on the passageway 2 is a coupling 3 for connecting a counter coupling which is attached to a hose or the like. The passageway 2 is closed off by means of a cover 4. The standpipe 1 is provided on the underside with a passage 5 and a connecting flange 6 which can be fixed by means of bolts 7 onto a flange 8 of a pressure pipe (not shown) of a mains network. Extending on the top of the passage 5 is an annular horizontal head end surface 9 which serves as seat for a main valve 10 to be pressed thereon. The main valve 10 is coupled via a control rod or valve stem 11 to a control mechanism arranged outside the standpipe 1 at the top side adjacent to the passageway 2. The control mechanism has a support 12 wherein a threaded rod 13 is rotatably mounted at 14. The threaded rod 13 is provided at the top end with a coupling pin 15, whereon a bush 16 with square head can be mounted with clamping fit. The threaded rod 13 co-acts with a nut 17 which is received non-rotatably in the top end of the valve stem 11. The valve stem is provided at the top end 18 with an axial blind bore for receiving the bottom end of the threaded rod 13. It will be apparent that the per se known operating method of the valve stem 11 provides for lifting of the valve 10 from and the pressing thereof onto the seat 9 by setting the threaded rod 13 into rotation with a suitable hand tool. This rotation ensures an up and downward movement of the nut 17 and therefore of the valve stem 11 with the main valve 10 coupled thereto. In this way the standpipe 1 can be filled with water from the mains network on the underside of the flange 8 by lifting the valve 10, and otherwise closed off therefrom by replacing the valve 10 on the seat 9. Any water present in the standpipe 1 can be discharged via a dewatering opening 19, so that no danger of freezing can occur. It is noted that when the valve 10 is lifted the dewatering opening 19 is enclosed by the side thereof, see fig. 3, 4, so that when the fire hydrant is used there are no losses due to leakage. The above described fire hydrant forms part of the prior art and the operation and the function thereof are further assumed to be known to a person skilled in the art. Arranged according to the invention under the main valve 10 is a check valve 20 which is embodied here as a disc-shaped body with three of four guide pins 21 along the periphery on the bottom surface thereof. These guide pins lie flat against the inner wall of the passage 5. The peripheral edge of the disc-shaped check valve 20 widens towards the top, in other words, is slightly conical and connects to an annular, upwardly widening surface of the passage 5, which surface connects to the head end surface 9 which serves as seat for the main valve 10. Recessed into the peripheral surface 22 of the check valve 20 is a groove wherein an O-ring 23 is received. This O-ring rests in the position according to fig. 1 against the annular surface of the passage 5. The main valve 10 consists of a core of rigid material that is covered with a jacket of elastic material 25. It is noted that the core of the main valve is embodied on the underside with an outwardly protruding radial flange 26 which protrudes over the seat 9. Above the flange 26 the core initially extends in a cylindrical part which extends upward over a determined height such that in co-action with the adjacent jacket 25 the opening of the discharge channel 19 debouching into the standpipe 1 is closed off if the valve lies in the position according to fig. 3, 4. The core extends further in a frusto-conical portion wherein a blind bore 27 is received. The blind bore had at a determined height above the bottom thereof an annular channel 28 that serves to receive an annular ring 29. The valve stem 11 is provided on the underside with a narrowed portion 30 likewise provided with an annular channel 31 wherein the annular ring 29 fits. The bottom end of the narrowed portion 30 is rounded off and can press on the bottom of the blind bore 27 when the valve stem is mounted in the valve 10 as shown in fig. 1. It is noted that the covering of elastic material 25 can be provided on the shoulder between the transition of the valve stem to the narrowed portion 30 with an integrally moulded O-ring 32 in order to seal the blind bore 27 against the water standing in the standpipe 1. In the assembled situation this O-ring 32 also functions to orient the valve body 10 axially relative to the centre line of the valve stem 11. For a good guiding of the valve 10 in the standpipe 1 at least three ridges 33 are cast on the inside of the standpipe 1, the contact surface of these ridges with the valve 10 being machined. The ridges 33 are arranged as shown in a widened part of the standpipe 1, necessary to realize sufficient passage for the water to be carried through. It is finally noted that the bottom surface of the valve 10, in particular the covering 25, has an annular ridge 35, which co-acts with an annular groove 36 recessed in the upper surface of the check valve 20. Said ridge and groove act like centering means in order to retain the free-movable check valve in the center of the main valve. Other embodiments are possible. The above described fire hydrant operates as follows. Starting from the situation drawn in fig. 1, the user can raise the main valve 10 by turning the threaded rod 13 in the correct direction, whereby the valve stem 11 is moved upward taking with it the valve 10. If there is pressure in the mains network on the underside of the check valve 20, this valve is immediately moved upward and, if there is sufficient pressure, will remain lying against the main valve 10. The water flow is such that all the dirt which could possibly have collected in the standpipe 1 can be carried along with the water flow via the outlet opening 2 of the standpipe 1. This position is shown in fig. 4. If the valve 4 is closed, and therewith the outlet opening 2, the air in the standpipe 1 will be compressed and the flow in the water in the passage 5 will stop. Under the influence of gravity the check valve 20 will sink back such that the peripheral edge 22 comes into contact with the annular surface in the passage 5, whereby the passage is closed off. Any downward sinking dirt cannot therefore enter the pressure pipe of the mains network. It is noted here that the dropping back of the check valve 20 can take place accurately due to the guiding of the pins 21 in the passage 5 so that the closing off is perfect all round. As soon as the pressure is increased in the pressure pipe and as soon as there is any upward flow through the passage 5, the check valve 20 is lifted and, depending on the strength of the flow, this valve can remain floating in an intermediate position as shown in fig. 3. The flow is immediately carried in a fan shape in the widened portion of the standpipe 1, so that any collected dirt is also immediately set into turbulence and carried upward in the standpipe 1. As soon as the pressure fall reverses or the flow stops the check valve 20 drops back onto the seat again faster than the dirt situated in the standpipe and closes the standpipe off from the mains network. The fire hydrant can be closed again by carrying the valve stem 11 downward by turning the threaded rod 13 in opposing direction, whereby the main valve 10 is pressed with its bottom surface onto the top surface of the check valve 20 until the edge of the main valve rests on the seat 9. The guiding of the main valve 10 is ensured because of the ridges 33 so that the bottom surface remains precisely parallel to the top surface of the check valve 20. Owing to the universal joint between valve stem 11 and valve body 10 a setting of the valve on the seat is possible without problem. It is further noted here that the pressure force of the valve stem 11 can be transmitted directly onto the valve body 10 by the contact between the bottom end of the valve stem and the bottom of the blind bore in the valve. Fig. 5 shows an alternative embodiment of the valve guiding for the check valve 20. The valve body thereof is embodied for this purpose with a central pin 40 which is received in a bush 41 which is connected to the wall of the passage 5 via radially directed arms 42. The pin 40 can therefore ensure an upright guiding of the check valve 20 in accordance with the pins 21 of the foregoing embodiment.

Claims: Fire hydrant comprising a standpipe (1) with closable top outlet (29) and with an underside in communication with a pressure pipe for water or the like, a valve seat (9) arranged in the standpipe (1) and at the underside thereof, a main valve (10), a valve stem (11) carried upward through the stand pipe and control means (16) arranged above the standpipe for moving the valve stem up or down in order to release the main valve and to respectively lift from and press it against the seat, and a freely movable check valve (20) arranged and guided in the passage of the standpipe between valve seat (9) and pressure pipe, characterized in that the check valve is provided with an upper surface, being parallel to the pressure surface of the bottom of the main valve (10) said lower surface of the main valve (10) and the top surface of the check valve (20) are embodied with co-acting complementary centering means (35, 36), for example an annular groove having annular ribs fitting therein and wherein the check valve body is provided with one or more guiding members, like pins protruding into the passage (5). Fire hydrant as claimed in claim 1, characterized in that at least three guide pins (21) are arranged, extending at a distance to the inner wall of the passage. Fire hydrant as claimed in claim 1 or 2, characterized in that the disc-shaped upper part of the check valve (20) is embodied with a peripheral edge (22) widening towards the top which co-acts with a complementary annular surface (23) in the passage (5). Fire hydrant as claimed in claim 3, characterized in that a groove is recessed in the peripheral edge of the check valve for receiving an O-ring. Fire hydrant as claimed in any of the preceding claims, characterized in that the wall of the passage continues directly into a head end surface (9) of the passage (5) embodied as valve seat. Fire hydrant as claimed in any of the preceding claims, characterized in that the main valve (10) is covered with a jacket (25) of elastic material. Fire hydrant as claimed in claim 6, characterized in that the jacket (25) is embodied at the transition between valve stem and valve body with an O-ring (28) integrally formed thereon. Fire hydrant as claimed in any of the preceding claims, characterized in that the main valve is connected to the valve stem (11) by means of a universal joint (30). Fire hydrant as claimed in claim 8, characterized in that the universal joint is formed by an annular ring (28) which is received fitting with clearance in a groove of the valve stem (11) and an opposite groove in a blind bore (27) of the valve body (10). Fire hydrant as claimed in claim 8 or 9, characterized in that the valve body (10) is held between three or more inwardly protruding ribs (33) in the standpipe (1).

Inventors: VAN DIESSEN HENRICUS MATHEUS C, VAN DIESSEN,HENRICUS MATHEUS CORNELIA
Applicants: RMI HOLLAND BV, RMI HOLLAND B.V.
Application year: 1991
Main classification: E03B9
IPC codes: E03B9