A valve assembly for heating plants

Abstract: A valve assembly comprising a three-way valve and an associated control valve of mechanical type that are fitted on top of each other, wherein the control valve comprises a pan (25) and a flexible diaphragm (24) axially urged upward by a first helical spring (23) and an axially movable central stop member (31) carrying a stem (29) projecting upward to actuate the overlying three-way valve (1). The pan (25) carries a laterally opened central projection (30) that houses a plunger member (33) having an axial hole (34) and a second helical spring (35) that realize tha bypass, and the central projection (30) further has a stem (26) protruding downward for actuating additional electric devices.

Description: The present invention concerns a valve assembly of the type comprising a three-way valve with an associated flexible diaphragm control valve, particularly for heating plants that generate also sanitary or domestic hot water. In these type of plants the hot water for heating purposes, obtained from a gas-fired boiler or of other kind, is also used for heating (through a water-water heat exchanger) the domestic hot water that is drawn from taps, showers, washing machines and the like. The heating water circuit is separated from the domestic supply water circuit and in order to divert the heating hot water to the heat exchanger when this is required, a three-way valve is used which in turn is controlled or operated by another valve alreadt present in the domestic water supply plant. Such control valve generates a command for the three-way valve and in case for the boiler, when the domestic hot water starts to be drawn. When the three-way valve is of the mechanically actuated type, the two valves can be mechanically arranged together to form a single valve assembly or unit. There are known valve assemblies of this type in which the control valve uses the Venturi effect to actuate or drive a rod or a piston opening or closing the three-way valve, but such devices have large load losses in the domestic water supply plant. There are further known valve assemblies (or double valves) using a flexible diaphragm valve for operating the three-way valve, that nevertheless have some shortcomings. Namely in these devices the command rod or stem is quite long and this makes the centering difficult with a resulting difficult and irregular working of the valve assembly. Moreover the flexible diaphragm is rigidly connected to a steel pan and also accomplishes a bypass function together with a disk having thin slots that are easily subjected to be clogged. This valve assembly moreover provides for complicated seal systems to ensure that the heating water circuit and the domestic supply water circuit are kept rigorously separated. The present invention aims to provide a valve assembly of the above mentioned kind that overcomes the above mentioned shortcomings and limitations of the prior art. Such objects are achieved through the invention that consists of a valve assembly comprising a three-way valve and an associated control valve of mechanical type that are fitted on top of each other, characterized in that such control valve comprises: a discoid-shaped body provided with an inlet duct and an outlet duct; a pan and a flexible diaphragm having a central opening, both located within control valve and axially urged upward by a first helical spring; an axially movable central stop member carrying a first stem projecting upward from said valve body to actuate the overlying three-way valve; the lower portion of said pan carrying a laterally opened central projection that houses a plunger member having an axial hole and a second helical spring urging said plunger member to obstruct said pan opening, said central projection further having a second stem protruding downward from the valve body for actuating additional electric devices. The invention will be described in details with reference to a preferred embodiment illustrated in the attached drawings, in which: Fig. 1 is a transverse cross section of a valve assembly according to the present invention; and Fig. 2 shows an enlarged portion of the control valve of Fig. 1. As it is clearly seen in the transverse cross section of Fig. 1, the valve arrangement according to the invention comprises two portions that are mechanically coupled together, but hydraulically separated, that is an upper three-way valve 1 in which heating hot water flows, and a lower control valve 2 of the diaphragm type in which the domestic water flows. The two valves are arranged on top of each other thanks to a collar 50 provided with a flared portion 51 radially projecting from the valve 2 and housed within a lower cylindrical end 54 of the valve 1 having one or more holes 52 for receiving conical fastening screws 53. The actuating mechanical connection is realized by means of a stem or rod 29 projecting from the lower valve 2 and vertically movable, that interacts with a command stem 18 projecting downward from the upper valve 1, as will be explained with more details later on. Sealing rings 55 and 56 (O rings) ensure the separation and the seal between the two valves. The upper three-way valve comprises two inlet and outlet ducts 11 and 12 respectively, for the heating water circulating through the heating plant, and a third duct 13 along which the hot water from duct 11 can be directed, the duct being connected to a heat exchanger (not shown) in which the heating water can transfer heat to the domestic water before this latter is delivered. Within the three-way valve 1 a command member is slidably fitted which comprises two stems 14 and 18 with a plunger 15 and 16 carried at each end, respectively, such plungers being provided with guide and reinforcing axially extending members, e.g. located at 120°, and designated with 45 and 48, respectively. The two stems 14 and 18 are axially aligned so that an axial force applied to one of them is axially transmitted to the other. The plungers 15, 16 are of plastic material, integer with the members 45, 48, and each of them is equipped with a peripheral groove for housing a rubber sealing ring (O ring), designated by 61 and 62, respectively. Te lower command stem 18 is actuated by the underlying diaphragm valve 2 by means of a command stem 29 as will be explained with more details later on, whereas a helical spring 19 housed in a spring retainer within the duct 12 urges downwardly the plunger 15. In the position illustrated in Fig. 1, the two plungers 15, 16 are kept in a raised position by the force applied by the stem 29 overcoming the resistance of the spring 19, and the heating water from the duct 11 passes through the members 45 and then through the duct 12, whereas the plunger 16 obstructs the passage to the duct 13. This situation corresponds to the rest condition when no domestic water is drawn and therefore the heating water circulates through the heating plant. With reference now also to Fig. 2, the lower valve 2 comprises a discoid-shaped body or casing made up by two portions 20A and 20B, respectively, provided with an inlet duct 21 and an outlet 22 duct both connected to the domestic water circuit. Within the upper valve 2, between the inlet duct 21 and tha outlet duct 22, there is interposed a flexible diaphragm 24 of plastic or elastomeric material. Such flexible diaphragm has a circular shape, with a central hole, and is clamped along its peripheral edge between the edges of the valve portions 20A and 20B. The inner space of the valve 2 is thus divided into two chambers by the diaphragm 24, namely an upper chamber 2A and a lower chamber 2B. A pan 26 with a central opening is secured to the flexible diaphragm 24 on the side facing the lower chamber 2B. A brass bush 63 is fitted to the pan opening 37 and provided with an outer groove 64 in the upper portion housing the inner lip of the flexible diaphragm 24. The pan 25 has a lower central projection 30 laterally opened or formed with axially extending studs, e.g. by four of such studs located at 90°. Preferably the pan and the central projection 30 are formed as a single moulded piece of plastic material. From the bottom of the seat 30 a central rod 26 projects for actuating a switch 66 (shown with phantom lines) e.g. for starting the boiler. The lower surface of the pan 25 is biased by a helical spring 23 having the lower end housed in a spring retainer 28 formed at the bottom of the body portion 2B. The force of the spring 23 is properly selected so that in the rest conditions the spring urges upward the pan 25 and the overlying diaphragm 24 until they abut a central stop member 31 provided with openings 32 for the water passage. The upper portion of the central stop member 31 carries the actuating stem 29 projecting from the collar 50 and capable to act on the stem 18 of the three-way valve. Within the pan central projection 30 there is located a plunger member 33 urged by an additional helical spring 35 against the opening 37 of the pan. This additional spring 35 has a smaller size and strength than those of the spring 23. The plunger carries a peripheral seal ring 36 and upper guide means 38, and is further equipped with an axial passage hole 34 communicating the chamber 2A with the chamber 2B, and therefore the duct 21 with the duct 22, even when the opening 37 is ostructed by the plunger 33 (position illustrated in the Figures). This hole 34 is calibrated in accordance with the requested flow rate by suitably selecting its diameter. Preferably the plunger 33 is formed as a moulded plastic component integral with the guide means 38. The working of the valve assembly according to the invention is as follows. In the rest condition shown by the Figures, no domestic hot water is drawn through the valve 2 and therefore the helical spring 23 keeps the pan 25 and the flexible diaphragm 24 raised so that the stem 29 of the central stop member 31 is raised and pushes upward the stem 18 and consequently the associated stem 14, thus keeping the two plungers 16 and 15 in the raised position allowing for the communication between the ducts 11 and 12, and closing the communication to the duct 13 leading to the heat exchanger. Under these conditions, the heating water circulates according to a preestablished setting only in the heating plant. When one or more taps in the domestic water supply system are turned on, the domestic hot water passes through the lower valve 2 through the axial hole 34 and comes out from the outlet duct 22. This way a depression or pressure difference is created between the chamber 2B and the chamber 2A, and a force is applied to the flexible diaphragm 24 that overcomes the force of the spring 23. The spring 19 is no longer opposed and let the two plungers 15, 16 descend so as to divert the hot water from the duct 11 to the duct 13 (the one of the heat exchanger), at the same time closing the passage toward the duct 12 (the one of the heating plant). This causes also the lowering of the central stop member 31 and as a consequence also the stem 26 acting on an electric microswitch 66 (shown in phantom lines) is lowered. Such microswitch 66 can start, for example, a gas-fired boiler or by other means enable the boiler working in case thi is requested to meet the demand of domestic hot water (through temperature sensors of the heating water). Later on, once the pressure has reached a value greater than the minimum one requested to carry the pan 25 to the end of its stroke, any pressure increase will further overcome the resistance of the spring 37 in the pan, so as to increase the water flow and accomplish the water bypass. This way, the domestic hot water can circulate without appreciable losses after the transient stage. The plunger member 33 opens against the force of the spring 35 when the pressure increases and beside working as a flow limiter (by changing the hole size) it also accomplishes the bypass function of the control valve. The assembly according to the invention, which employs two guided short command stems does not have centering problems and the actuation results in being quite smooth. Moreover, when using an assemply according to the invention, it is possible to repair a malfunction affecting the domestic water supply without the need of emptying the heating plant and viceversa.

Claims: A valve assembly comprising a three-way valve (1) and an associated control valve (2) of mechanical type that are fitted on top of each other, characterized in that such control valve comprises: a discoid-shaped body (20A, 20B) provided with an inlet duct (21) and an outlet duct (22); a pan (25) and a flexible diaphragm (24) having a central opening (37), both located within control valve (2) and axially urged upward by a first helical spring (23); an axially movable central stop member (31) carrying a first stem (29) projecting upward from said valve body (2) to actuate the overlying three-way valve (1); the lower portion of said pan (25) carrying a laterally opened central projection (30) that houses a plunger member (33) having an axial hole (34) and a second helical spring (35) urging said plunger member (33) to obstruct said pan opening (37), said central projection (30) further having a second stem (26) protruding downward from the valve body for actuating additional electric devices (66). A valve assembly as claimed in claim 1, characterized in that said central stop member (31) is provided with openings (32) for water passage. A valve assembly as claimed in claim 1 or 2, characterized in that said plunger member (33) carries a peripheral seal ring (36) and upper guide means (38). A valve assembly as claimed in claim 3, characterized in that said valve pan (25) is a moulded plastic component integral with said central projection (30), and provided with a bush (63) at the central opening (37) thereof, said bush being provided with a groove (64) for housing the inner lip (65) of said flexible diaphragm (24). A valve assembly as claimed in claim 4, characterized in that said flexible diaphragm (24) is of an elastomeric or plastomeric material. A valve assembly as claimed in claim 5, characterized in that said flexible diaphragm (24) has a circular shape with a central opening, and the peripheral edge thereof is clamped between the edges of two portions (20A, 20B) making up said discoid-shaped valve body (2) so as to divide said body into an upper chamber (2A) and a lower chamber (2B). A valve assembly as claimed in claim 6, characterized in that said laterally opened central projection (30) is made up by axially extending studs with the stem (26) for actuating a boiler starting switch fixed at the center thereof. A valve assembly as claimed in any of claims 1 to 7, characterized in that said two valves (1, 2) are releasebly fastened together by a collar (50) having a flared portion (51) projecting from the control valve (2) that is housed within the cylindrical lower end (54) of the three-way valve (1) having at least one hole (52) for tightening conical screws (53) A valve assembly as claimed in any of the preceding claims, characterized in that within said three-way valve (1) there is slidably mounted a command member comprising two plunger members (15, 16) at the ends of two axially aligned stems (14, 18), that work together under the action of said first stem (29) at one end, and of a helical spring (19) at the other end. A valve assembly as claimed in claim 9, characterized in that said two plunger members (15, 16) are provided with projecting reinforcing and guide members (45, 48) and with grooves housing seal rings, and in that said two plunger members (15, 16) are of plastic material moulded as a single piece with said guide and reinforcement members (45, 48).

Inventors: FUGAZZA GIUSEPPE, FUGAZZA, GIUSEPPE
Applicants: FUGAZZA GIUSEPPE, FUGAZZA, GIUSEPPE
Application year: 1991
Main classification: F16K11
IPC codes: F24D19