APPARATUS FOR CONTROLLING START UP AND STOP DOWN OF A HYDRAULIC PUMP

Abstract: The apparatus is of the kind comprising a flow detector supplying, in the absence of flow, a stop down signal for the pump, a pressure detector supplying, for a predetermined minimum value of the pressure, a start up signal for the pump, and impeller means for the pressure detector, and is featured by the fact that the pressure detector comprises a movable part (1,2) which is integral with a membrane (3) closing a cavity (3b) communicating with the hydraulic network, and a fixed part (4,5) ar­ ranged in the apparatus body at the displacement position of the movable part (1,2), the impeller means for the mov­ able part of the pressure detector are constituted of a spring (8) mounted between the said movable part (1,2) and the apparatus body (9), the flow detector comprising a part (6,7) which is movable in the vertical direction and performs the function of gravity closing valve, and a fixed part (4,5) which is arranged in the apparatus body.

Description: The present invention relates to an apparatus for controlling start up and stop down of a hydraulic pump. BACKGROUND OF THE INVENTION In some hydraulic networks wherein a liquid is supplied under the action of a pump, such as, for example, house water installations including a pressure water tank and water pump generally powered by an electric motor, the pump must be stopped down and started up according to the needs. In short, the matter is with the fact that the pump is to be started up when a valve or cock is opened, in order to hold a pressure in the tank and associated network, and stopped down when the cock is closed, in order to prevent a pressure rise over a desired value. There are nowadays several apparatus for controlling the stop down and start up of such a pump. The most used kind of apparatus consist of a pressure controlled switch connecting and disconnecting the pump within maximum and minimum pressure limits. In order to damp the hydraulic surge and also to act as a liquid accumulator thus lengthening the periods between the pump start up and stop down operations, the apparatus is provided with a so called "hydrosphere", a sphere shaped receptacle in the inside of which a movable membrane receives on one side the network liquid pressure and encloses at the other side a given volume of pressure air, the volume of which is variable according to the network pressure. A safety detector must be installed together with the above apparatus, acting on the basis of a minimum level in the tank, in order to prevent the pump from burning down when it is sucking with no liquid in the network. Besides, this kind of apparatus are subject to several drawbacks. In first place, the hydrosphere is usually made of steel, which rusts thus causing impairment of the membrane and frequent replacement of this latter. In second place, the hydrosphere is very bulky, thus making difficult the installation thereof. Owing to the constructive features of the apparatus, there is always a pressure variation between a minimum value and a maximum value, which is governed by a pressure controlled switch. This pressure variation may be rather high, for example of 2 to 3 Kg/cm², and has a negative influence on the use of some apparatus such as the gas operated water heaters in which the lighting is controlled by the water pressure. There is known also other kind of apparatus disclosed in EP-A-0 219 360 which essentially comprises a flow detector providing, in the absence of flow, the stop down signal for the pump, and a pressure detector providing, for a predetermined value of the pressure, the start up signal for the pump, and impeller means for the pressure detector, consisting of the hydrosphere membrane upon which the inner air acts. In this case, some of the problems are solved because of the pump being started up by the flow detector, so that the pressure surge effect is considerably reduced. However, a hydrosphere is still present, though it may be smaller owing to the surge pressure effect being reduced. Some of the drawbacks which are inherent with the use of the hydrosphere are thus remaining: the air pressure within the hydrosphere is not easily adjustable, and there is always some pressure loss with time, which claims for a periodic air replenishment. The hydrosphere membrane closes a cavity communicating with the hydraulic network and the pressure detector comprises a movable part pushed by the membrane and a fixed part arranged in the apparatus body at the displacement position of the movable part. The flow detector comprises also a movable part and a fixed part which is arranged in the apparatus body. On the other hand, the flow detector is associated with a valve which is operated by the liquid flow and provided with a return spring, and this latter performs closure somewhat abruptly, thus enhancing the pressure surge effect. There is also another apparatus disclosed in DE-A-2 238 799 where the flow detector is movable in vertical direction performing the function of gravity closing valve. In this particular arrangement no spring is necessary as it is the valve weight which counteracts the push of the liquid flow. However in this document the pressure detector in the network is a conventional presostat independent from the apparatus. DESCRIPTION OF THE INVENTION The apparatus according to the invention achieves solving of the above noted drawbacks and provides other advantages to be described. The apparatus for controlling start up and stop down of a hydraulic pump making the subject of the invention, is featured in that the movable part of the pressure detector and the movable part of the flow detector are aligned; the membrane is integral with the movable part of the pressure detector; the impeller means for the movable part of the pressure detector are constituted of a spring mounted between the said movable part and the apparatus body; and the fixed part of the pressure detector and the fixed part of the flow detector are constituted of a single magnetic detector connected to an amplifier network. The apparatus of the invention thoroughly dispenses with the hydrosphere, thus removing all of the problems related with the use of same. Further to reducing the membrane maintenance problems, a stable pressure is achieved because such pressure no longer depends on the air pressure. Furthermore, the movable part of the pressure detector has a longer stroke which permits to have a plurality of positions in the same pressure detector. The alignment of the movable parts of the detectors provides a constructional simplification of the apparatus. Finally, the apparatus has a single magnetic detector which makes it more simple, especially as to the electronic circuitry associated with the detector. Preferably, the movable part of the pressure detector is a permanent magnet, and the fixed part of the same is a magnetic detector connected to an amplifier network. This detector provides a great accuracy and fast response. It is also noticeable the service reliability of the magnetic detector as regards other detectors usually employed, such as photoelectric cells. To advantage, the impeller spring tension is adjustable, thus providing for a regulation of the minimum pressure for starting up the pump. This kind of regulation is by far more comfortable and faster that the regulation used in the known apparatus provided with hydrosphere, in which a pneumatic pump needs to be resorted to. An important feature to be underlined resides in that the movable part of the pressure detector is located, in its lower position, under the zone corresponding to the detection of a minimum pressure in the detector. In this position the detector is not activated and acts as a minimum liquid level detector. Therefore, the movable part of the pressure detector has three different positions: an upper position in which the detector is not activated, an intermediate position in which the detector is activated, and a lower position in which the detector is again not activated. When in the lowest position it is not a simple minimum pressure detector, but it acts as a level detector, thus avoiding operation of the pump when the network carries no liquid, and the corresponding impairment. It is also preferable that the movable part of the flow detector is a permanent magnet, and the fixed part of the flow detector a magnetic detector connected to an amplifier network. As indicated above in connection with the pressure detector, this flow detector achieves as well a great accuracy and fast response. On the other side, it is to remark the service reliability of the magnetic detector as regards other kinds of used detectors, such as photoelectric cells. Finally, it is important to note that the amplifier network is provided with a push button to manually emulate the magnetic detector signal. This feature is specially useful for manually starting up the pump when there is no water in the tank. The pump is manually set on after the tank has been filled. BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the above, a drawing is enclosed showing a diagrammatic and non restrictive example of a practical embodiment. In the said drawings: Figure 1 is a view in longitudinal section of the apparatus of the invention, showing the position corresponding to no liquid flow and no liquid in the tank; Figure 2 shows a detail of the valve, and Figure 3 shows the apparatus of Figure 1 in the position corresponding to the start of a liquid flow. DESCRIPTION OF A PREFERRED EMBODIMENT As indicated in Figure 1, the apparatus of the invention comprises a pressure detector having a movable part formed of a magnet 1 mounted in a body 2 which is joined to a membrane 3, in turn mounted in a cavity of the body 9 such that it defines an atmospheric chamber 3a in communication with the outside, and a pressure chamber 3b connected through means not shown with the pressure water network. The fixed part of the said detector is formed of a magnetic detector 4 connected to an amplifier network 5 in turn connected with the control switch of the pump motor through conventional measures not requiring to be further described. The apparatus comprises also a flow detector, the movable part of which is slidable in a vertical direction, includes a magnet 6, and is arranged to perform the function of a closing valve 7, while its fixed part is constituted of the same magnetic detector 4 and amplifier network 5. A spring 8 mounted between the body 2 and the apparatus body 9, loads the membrane 3 of the pressure detector. The load of the spring 8 can be adjusted by mean of the screw 10. As can be seen in Figure 1, the amplifier network is provided with a push button 11 to manually emulate the signal of the magnetic detector 4. Figure 2 shows a detail of the valve 7 with the closing gasket 12 fitting onto the shoulder 13 of the body 9. It is an example of embodiment as, obviously, any such other kind of suitable closure may be used. The working of the apparatus of the invention is as follows: When there is no water in the network, the apparatus is in the position shown in Figure 1. When there is water in the network and the cock is closed the water is under pressure and the movable part 1,2 is in its upper position as shown in figure 3. When, with the ensemble of the network filled with water in working condition, a cock (not shown) is opened to supply an amount of water for use, water begins to circulate along the hydraulic network and enters the apparatus of the invention through the inlet 14 and drags together the movable part 7 of the flow detector until this part comes to the position of Figure 3, wherein the magnetic detector 4 sends a signal, through the amplifier network 5, to the motor driving the pump, in order to start up this latter. When the pump is operated, the hydraulic pressure goes down but maintaining the membrane 3 in an intermediate position against the action of the spring 8 and dragging with it the body 2 of which the magnet 1 is integral. The pump remains operated while the magnet 6 is facing the detector 4. When the cock is closed, water stops flowing and the movable part 7 of the flow detector falls under gravity to the position of Figure 1. In this position, magnet 6 has moved apart from the detector 4, the pressure has risen and the movable part 1,2 of the pressure detector is in its upper position thus causing a stop down signal to be sent to the pump. As long as a pressure exists in the network, the membrane remains in the position of Figure 3. In the case where no water is present in the network, the membrane 3 comes to the position indicated in Figure 1, and thus the magnet 1 is located under the zone corresponding to the detection of a minimum pressure by the detector 4, wherein the said detector 4 is not activated and operates as a liquid minimum level detector. In order that the pump may be started up, the push button 11 must be depressed. As explained above, the tension of spring 8 is adjustable, thus regulating the minimum pressure for starting up the pump.

Claims: Apparatus for controlling start up and stop down of a hydraulic pump, of the kind comprising a flow detector supplying, in the absence of flow, a stop down signal for the pump; a pressure detector supplying, for a predetermined minimum value of the pressure, a start up signal for the pump; a membrane (3) which closes a cavity (3b) communicating with the hydraulic network; impeller means for the pressure detector; the pressure detector comprising a movable part pushed by the membrane and a fixed part (4,5) arranged in the apparatus body at the displacement position of the movable part (1,2); the flow detector comprising a part (6,7) which is movable, and a fixed part (4,5) which is arranged in the apparatus body, characterized in that the movable part (1,2) of the pressure detector and the movable part (6,7) of the flow detector are aligned; the movable part of the flow detector is movable in the vertical direction and performs the function of gravity closing valve; the membrane is integral with the movable part of the pressure detector; the impeller means for the movable part of the pressure detector are constituted of a spring (8) mounted between the said movable part (1,2) and the apparatus body (9); and the fixed part of the pressure detector and the fixed part of the flow detector are constituted of a single magnetic detector (4) connected to an amplifier network (5). Apparatus according to claim 1, characterized by the fact that the movable part of the pressure detector is a permanent magnet (1), and the fixed part is a magnetic detector (4) connected to an amplifier network (5). Apparatus according to claim 1, characterized by the fact that the load of the impeller spring (8) is adjustable, thus providing for a regulation of the minimum pressure for starting up the pump. Apparatus according to claim 2, characterized by the fact that the movable part (1,2) of the pressure detector is located, in its lower position, under the zone corresponding to the detection of a minimum pressure by the detector, in which position the detector is not activated and acts as a minimum liquid level detector. Apparatus according to claim 1, characterized by the fact that the movable part (6,7) of the flow detector is a permanent magnet (6), and the fixed part of the flow detector is a magnetic detector (4) connected to an amplifier network (5). Apparatus according to claim 5, characterized by the fact that the amplifier network (5) is provided with a push button (11) to manually emulate the magnetic detector signal.

Inventors: BANUS GARCIA, FERNANDO
Applicants: BANUS GARCIA, FERNANDO
Application year: 1988
Main classification: F04B49
IPC codes: G01L9, F04B49