WO2005035985A1

WO2005035985A1 - Device for automatically controlling a hydraulic pump

Info

Publication number: WO2005035985A1
Application number: PCT/IT2004/000415
Authority: WO
Inventors: Mirian Ronchi
Original assignee: Mac 3 S.P.A.
Priority date: 2003-10-17
Filing date: 2004-07-29
Publication date: 2005-04-21
Also published as: ITFI20030264A1; EP1678424A1

Abstract

Device for controlling a hydraulic pump comprising flow detection means making use of an elastically hindered check valve (3), pressure detection means arranged downstream with respect to the flow detection means; and switch means (12, 23) for switching on and off the electrical power supply to the pump, operated in parallel by flow and pressure detection means. The flow detection means comprise magnetic means (9, 10, 11) integral with the check valve (3), and means (27) responsive to the displacement of the magnetic means (9, 10, 11), for operating the relative switch means (12) as a function of said displacement. Preferably, the pressure detection means comprise a pressure detection system (14) for operating the relative switch means (23) at a predetermined minimum pressure detection, to turn the pump on, and at a predetermined maximum pressure detection, to turn the pump off, a maximum pressure detection delay mechanism (15) being also provided.

Description

TITLE DEVICE FOR AUTOMATICALLY CONTROLLING A HYDRAULIC PUMP DESCRIPTION Field of the invention The present invention refers to the field of hydraulic pumps. More specifically, it concerns a device for automatically controlling a motor-driven pump. Background of the invention In any water distribution network in which water is supplied through a motor-driven pump, the same must be switched on, supplying pressurized water, and switched off, stopping the flow of water, in response to the demand of the users of the network. The transmission of on/off control signals to the motor-driven pump represents one of the main problems in the design and management of water distribution networks, with such a pump having to ensure the supply to users at a substantially constant pressure, while keeping a working pace compatible with its specifications: in this respect, it is well known the fundamental requirement of avoiding too frequent start- stop cycles of the pump. The problem has up to now been tackled by making use of essentially two types of systems. In a first system, commonly known as "surge tank system" , a pressure-triggered switch turns the pump on and off, respectively at a minimum and a maximum pressure value detected in the network. The switch is built-in with a liquid storage tank comprising an air-loaded membrane, having the task of delaying the stop of the pump once started. The drawbacks of such a system are known and can mainly be summarized in terms of a considerable bulk, high manufacturing and maintenance costs, lack of general- purpose characteristics, noteworthy pressure variations that are in any case suffered by the user. In a second type of system, devised more recently but very widely used, the control is carried out by a CPU electronic device, built-in with a water-tight casing having a water inlet and outlet, for being installed directly on the delivery side of the motor-driven pump. Many devices of such kind are available on the market, having substantially similar basic characteristics: compact construction; detection of the minimum and maximum pressure through a device that reads the position of a spring loaded membrane; flow detection through a check valve; electronic components for processing the pressure and flow signals and, in response thereto, for transmitting on/off operation signals to the pump. The CPU has, among others, the task of delaying the stop signal sent to the pump by a time that can be predetermined, mainly to avoid the occurrence of harmful cycling phenomena . It is the very presence of the electronic components to be the source of significant problems, both as far as reliability and costs are concerned. Regarding the costs, it should be noted that, in practice, the cost of the electronic components is often greater than the overall cost of the mechanical parts, and therefore causes a substantial increase of the sale price of the device. Summary of the invention The object of the present invention is to overcome such problems, by providing a control device that can ensure a working efficiency comparable to that of the above mentioned devices of the prior art, doing without CPU electronic components, i.e. using purely electromechanical solutions, and without impairing the compactness of the construction. This object is achieved with the device for automatically controlling a hydraulic pump according to the present invention, the essential characteristics of which are defined in the first of the attached claims. Brief description of the drawings Characteristics and advantages of the device for automatically controlling a hydraulic pump according to the present invention will be apparent from the following description of an embodiment thereof, given purely as an example and not limitative, with reference to the attached drawings, in which: - figure 1 is a simplified perspective view (i.e. with some parts schematized and others omitted) of the device according to the present invention; figure 2 is a top plan view, once again simplified, of the device of figure 1; - figure 3 is a sectional view taken along line III-

III of figure 2; - figure 4 is a sectional view taken along line IV-

IV of figure 2; - figure 5 is an enlarged sectional view taken along line V-V of figure 4; - figure 6 is a partial and enlarged sectional view taken along line VI-VI of figure 2; - figure 7 is a sectional view taken along line VII- VII of figure 6; and - figure 8 shows in top plan view the head of a valve of a maximum pressure detection delay mechanism used in the device . Description of a preferred embodiment With reference to the above figures, the device according to the invention comprises a frame 1 integrally defining a duct 2 for the passage of water downstream of the ^' motor-driven pump to be controlled. The device is therefore to be arranged at the delivery side of the same pump (not shown) . The duct 2 has an inlet 2a and an outlet 2b, defined by respective end portions projecting outwards from the frame 1. A cartridge filter 6 is arranged within the duct 2 immediately downstream of the inlet 2a (figure 1) , and is provided with a magnetic element to intercept possible metallic dross transported by the liquid flow. With particular reference to figures 4 and 5, a check valve 3 is slidably arranged in correspondence to a slight enlargement of the duct 2. The valve 3 comprises a disc-shaped head 3a integral with a stem 3b sliding on two supports 24, 25 (the support 25 being represented only in figure 5) . An internal sleeve 5 integrally departs from the inner side surface of the duct 2 in correspondence to the same enlargement. The sleeve 5 projects axially towards the outlet 2b, thus being spaced apart from the inner side surface of the duct in the enlarged section. The head 3a of the valve 3 is elastically urged against the free edge of the sleeve 5, as shall be seen in detail hereinafter, so as to be able to sealably block off the passage of water. More specifically, the head 3a, being substantially cup-shaped, comprises a deep peripheral groove 7 for engagement with the sleeve 5. The groove 7 is formed in the upstream side, between the central part of the head 3a and an outer skirt 3c. An 0- ring 26 is arranged on the bottom of the groove 7, as shown in figure 5. In the sealing position, i.e. of the flow being blocked, as is the case in figures 4 and 5, the groove 7 receives the sleeve 5 almost completely, with the skirt 3c that becomes arranged on the outside of the sleeve itself. It is also clear that, further to a displacement of the valve 3 towards the outlet 2b, as a result of the occurrence of a flow of water, the same flow is deviated by the groove 7, from the inside to the outside of the sleeve 5, following a substantially S-shaped path (as seen in longitudinal section like in figure 4 and 5) . Downstream of the head 3a, the stem 3b of the valve 3 integrally supports a T-shaped member 8, urged by a helical spring 36 (figure 5) in order to exert the aforementioned elastic action on the head. In fact, the spring 4 is compressed between the member 8 and the adjacent stem supporting element 25. The T-shaped member 8 comprises two sideways arms which are slidably supported by longitudinal guides 2c formed along two diametrically opposite generatrices of the duct 2. A central arm of the T-shaped member 8 is indicated at 8a and has a free end face 8b that extends axially in the immediate vicinity of the inner surface of the duct 2. Three magnets 9, 10, 11 are embedded in the arm 8a, mounted substantially flush with the end surface 8b and aligned along the longitudinal direction. The first magnet, i.e. the one nearest to the outlet 2b, indicated at 9, has inverse polarity with respect to the other two. . At the outside of the duct 2, in a position corresponding to the T-shaped member 8 of the valve 3, the frame 1 supports a microswitch 12 with an actuation lever 12a (figures 2 and 5) . The microswitch 12 is electrically connected to the pump through suitable wiring, coming out from the frame 1 through raceway portions 20 and to be fixed to a terminal board 13, also mounted on the frame 1. An actuation lever 12a for actuating the microswitch 12 in turn carries a magnet 27 (figure 5) , having an inverse polarity with respect to the first magnet 9 and with the same polarity as the other two magnets 10 and 11. The mutual arrangement between the lever 12a of the microswitch 12 with the relative magnet 27, and the magnets 9, 10 and 11 is such that, when the check valve 3 is closed, the first magnet 9 exactly corresponds to the magnet 27 of the lever 12a and, due to the mutual magnetic attraction, drives the same lever to a switch-off position of the pump. On the other hand, when the check valve 3 is open, i.e. in the presence of a water flow, the two magnets 10, 11 with inverse polarity are brought to face the lever 12a of the microswitch 12. The repulsive force thus created causes a displacement of the lever 12a, so that the pump is switched on. With particular reference now to figures 1, 2, 3, 6, 7 and 8, downstream of the valve 3 the duct 2 there is arranged a pressure detection system 14, combined with a maximum pressure detection delay mechanism 15 for delaying the transmission of the relative switch-off signal to the pump. The detection delay mechanism 15 comprises a cylindrical water stagnation chamber 16 arranged so as to be substantially tangent to the duct 2, and to form an aperture 17 for deviating the water radially from the duct 2 to the chamber 16. A tubular filter 18 is arranged precisely in the chamber 16, for filtering the flow through the aperture 17. The chamber 16 is closed at one end - the lower end if reference is made to the view of figure 3 - by a fixed diaphragm 16a, whereas in the opposite (upper) end a through seat 16b is formed. The seat 16b is flared towards the inside of the chamber 16 and is reversibly closed by the frusto-conical head 19b of a poppet valve 19, arranged coaxially within the chamber 16. A stem 19a of valve 19 is slidably supported by a guide 16c projecting integrally from the fixed diaphragm 16a. As can be seen in figure 8, A distribution of small radial grooves 19c is formed in the side surface of the frusto-conical head 19b of the poppet valve 19, i.e. the surface that comes into contact with the flared surface of the seat 16b. When the valve 19 is kept in a closed position by means of a spring (not represented in the drawings) , the radial grooves 19b make for the leakage of a certain water flow rate out of the chamber 16. Through the seat 16b the chamber 16 opens at the bottom of a bowl 21 having a greater bore than the chamber 16 and slightly off-center with respect to the same. The bowl 21 represents the base of the pressure detection system 14, being surmounted coaxially by a cylinder 22 closed at the upper end by a lid 37 and obstructed immediately above the bowl 21 by a membrane 28 (figure 3) . The displacement upwards of the membrane 28 is elastically hindered by a spring (not shown) . The bowl 21 in practice realizes a liquid expansion tank, this expansion being responded to by a displacement of the membrane 28. The displacement is transferred to the outside by a piston 29, slidably arranged in the cylinder 22 above the membrane, controlled by a guide 37a projecting from the lid 37. The piston 29 comprises a head 29a that is reactive to the displacement of the membrane and a prong 29b projecting radially on the outside of the cylinder 22 through an axial slit 22a formed in it. The prong 29b is engaged, with a certain play, in a slot 30b (figure 3) formed in a slider 30 carrying an actuation cam 30a for actuating a second microswitch 23, supported by the frame 1 (figures 2, 3, 6 and 7) and in turn electrically connected to the pump by means of wiring introduced into the raceway portions 20 and fixed at the terminal board 13. The play between the prong 29b and the slot 30b of the slider 30 is such as to cause the displacement of the slider - and consequently the engagement/disengagement between the cam 30a and the microswitch 23 in order to turn the pump on/off - in response to displacements of the membrane corresponding, respectively, to predetermined minimum and maximum water pressure values. A third microswitch 31 is arranged adjacent to the microswitch 23 and controlled, vi the cam 30a, by the prong 29b. As can be understood from figures 6 and 7, the cam 30a is shaped in such a way as to actuate the third microswitch 31 following a further downward displacement with respect to the displacement required for the actuation of the microswitch 23. Thanks to a suitable calibration of the spring loading the membrane 28, said further displacement occurs only in case of lack of water in the duct 2 , a circumstance in which the third microswitch 31 turns the pump off, preventing failures from idling. A fourth microswitch 32, shown in figure 2, connected in parallel with the safety microswitch 31, is used to restore the normal work condition when water is once again available. For such a purpose, the fourth microswitch 32 can be actuated manually by means of a screwdriver or the like, to be inserted in a hole 33 suitably formed in a cover of the frame 1. Also the third microswitch 31 and the fourth microswitch 32 are obviously connected to the pump through wiring that, through the raceway portions 20, is fixed to the terminal board 13. Optionally, the device can be prearranged for the connection with a pressure gauge. As shown in figures 2 to 4, a tube 34 can be provided, projecting upwards from the duct 2 substantially at the section enlargement. The possible communication between the duct 2 and the tube 34 is obstructed by a breakable diaphragm. The free (upper) end of the tube 34 is suitable for supporting the gauge, the bulk of which is outlined with a broken line in figure 2 and indicated at 35. The arrangement of the manometer must obviously be preceded by the breaking of the aforementioned diaphragm. The general working of the control device according to the present invention will be apparent from the above, being in any case similar to that of the electronic devices according to the prior art . The two microswitches 12 and 23 are electrically arranged in parallel, for which reason the pump starts up and/or remains in operation at a "low" pressure or in the presence of a water flow. On the other hand, the stop of the pump shall occur only with "high" pressure and in the absence of flow. Regarding this, it must be noted that the S-shape of the passage between sleeve 5 and groove 7 ensures that the valve 3 is displaced appreciably from the closed position, thereby turning the pump on, even when the water flow is a minimal one . As far as the pressure detection delay mechanism 15 is specifically concerned, the delay in the detection of maximum pressure derives from the fact that the filling of the expansion tank, i.e. of the bowl 21, and the consequent upwards displacement of the membrane 28 when the valve 19 is in a closed condition (i.e. with pressure in a "high" or pump switch-off status) , occurs slowly, the water leaking through the grooves 19c in the side surface of the frusto-conical head 19b. This prevents the occurrence of a pump start-stop cycle, which would on the other hand have been triggered by the immediate entry into

"high" pressure of the bowl 21 in conditions of zero flow

(or in any case a flow not detected by the check valve 3) . With a bowl 21 such as to require about 20÷25 cm³ of liquid to reach the maximum pressure, and based upon standard working conditions, it is possible to obtain a delay of 8÷10 seconds (sufficient to protect the pump from damage) with an overall passage section, defined by the grooves 19c in the side surface of the frusto-conical head 19b, in the range of a few hundredths of a square millimeter. On the other hand, although it is important that the filling of the bowl 21 occurs slowly, it is equally important for the discharge to be immediate, since the water contained therein must be immediately available to the user upon the opening of a supply tap. This result, clearly unachievable with a simple rigid narrowing in section, is obtained thanks to the opening of the seat 16b by the sliding poppet valve 19. Moreover, a rigid narrowing would rapidly become blocked by clogging phenomena. According to the invention, clogging is prevented by the abundant flow which, each time the water supply is required by the user, flushes the head 19b of the valve 19 and thus carries out a regular and frequent cleaning of the relative grooves 19c. As far as the check valve 3 is concerned, the transmission of the command through magnetic means is safe and constructively simple. The repulsive magnetic field

(magnets 10 and 11) allows the actuation of the microswitch 12 to be made immediate, following even a minimal displacement of the check valve 3, whereas the attractive magnet 9 assists the action of the spring in closing the valve itself. The presence of a double repulsive magnet increases the field size, and therefore the reliability of operation. The device according to the invention has the same effectiveness as the prior art CPU electronic control devices, with purely electro-mechanical means and therefore with greater reliability and lower costs. The construction is in any case simple and very compact . Variants and/or modifications can be brought to the device for automatically controlling a hydraulic pump according to the present invention without for this reason departing from the scope of protection of the invention itself as defined by the appended claims.

Claims

1. Device for controlling a hydraulic pump comprising: a duct (2) with an inlet (2a) and an outlet (2b) , to be connected to the delivery side of said pump; flow detection means (3) for detecting the flow in said duct (2) , comprising an elastically hindered check valve (3) ; pressure detection means (14, 15) for detecting the pressure in said duct (2) , arranged downstream of said flow detection means; and switch means (12, 23) for switching on and off the electrical power supply to said pump, arranged outside of said duct (2) and operated in parallel by said flow and pressure detection means, characterized in that said flow detection means (3) comprise magnetic means (9, 10, 11) integral with said check valve (3) , means (27, 12a) responsive to the displacement of said magnetic means (9, 10, 11) being arranged outside of said duct (2) for operating the relative switch means (12) as a function . of said displacement .

2. The device according to claim 1, wherein said magnetic means (9, 10, 11) comprise two magnets (9, 10) with mutually opposite polarity, supported in a longitudinally aligned manner at the radial periphery of said valve (3) , said responsive means (27, 12a) comprising a further magnet (27) integral with an actuation lever (12a) of a first microswitch (12) , said further magnet (27) having an opposite polarity with respect to a downstream magnet (9) of the valve (3) , the mutual arrangement between said magnets (9, 10) of the valve (3) and the actuation lever (12a) with the further magnet (27) being such that when the check valve (3) is in a closed position said downstream magnet (9) of said valve (3) is radially aligned with said further magnet (27) of the lever (12a) and, due to the mutual magnetic attraction, drives the same lever (12a) into a pump turn-off position; and such that, on the other hand, when said valve (3) is open in a flow detection position, an upstream magnet (10) of the same valve (3) becomes radially aligned with said further magnet (27) of the lever (12b) , thereby the magnetic repulsive force causes the displacement of the lever (12b) into a pump turn-on position.

3. The device according to claim 2 , wherein a third magnet

(11), is supported by said valve, arranged upstream of, and longitudinally aligned with, the other two magnets (9, 10) of the valve (3) , said third magnet (11) having an inverse polarity with respect to said magnet (27) of said lever (12a) .

4. The device according to claim 2 or 3 , wherein said valve (3) comprises a check head (3a) and a T-shaped member (8) integral with said head, downstream of it, said T-shaped member (8) comprising two side arms which slidably engage with longitudinal guides formed along two diametrically opposite generatrices of said duct (2) , and a central arm (8a) in which said magnets (9, 10, 11) of the valve are embedded.

5. The device according to claim 4, wherein said central arm (8a) of said member (8) has a free end face (8b) that extends longitudinally in the immediate vicinity of the inner surface of the duct (2) and in which said magnets (9, 10, 11) are embedded.

6. The device according to claim 4 or 5, wherein said head (3a) of said valve (3) has, on the side arranged upstream, a deep peripheral groove (7) formed axially between a central portion of the head (3a) and an outer skirt (3c) thereof, said groove (7) engaging with a sleeve (5) formed coaxially inside said duct (2) , spaced apart from the inner side surface of the same duct (2) , thereby the flow of water is deviated by said groove (7) between the inside and the outside of said sleeve (5) along a substantially S-shaped path.

7. The device according to claim 6, wherein an O-ring seal (26) is arranged at the bottom of said groove (7) of said head (3a) .

8. The device according to any of the previous claims, wherein said pressure detection means (14) comprise: a liquid expansion tank (21) communicated with said duct (12) and closed by a spring loaded membrane (28) ; means (29, 30) for operating the relative switch means (23) in response to the displacement of said membrane (28) at a predetermined minimum pressure detection, to turn said pump on, and at a predetermined maximum pressure detection, to turn said pump off; and a maximum pressure detection delay mechanism (15) comprising a stagnation chamber (16) for the liquid, placed between said duct (2) and said expansion tank (21) , a seat (16b) communicating said chamber (16) with said tank (21) , and a check valve (19) placed within said chamber (16) , slidable with elastic hindrance between a closed position in which said seat (16b) is obstructed, and an open position displaced towards the inside of said chamber (16) , in said closed position the engagement between said check valve (19) and said seat (16b) being such as to allow the leakage of a certain flow rate of liquid towards said expansion tank (21) .

9. The device according to claim 8, wherein said check valve (19) of said stagnation chamber (16) is a poppet IS valve comprising a head (19b) defining a contact surface with said seat (16b) communicating said chamber (16) and said expansion tank, a distribution of radial grooves (19c) being formed in said contact surface for permitting said leakage when the valve (19) is in the closed position.

10. The device according to claim 9, wherein said contact surface of said head (19b) of said poppet valve (19) has a frusto-conical shape, said seat (16b) communicating said chamber (16) with said expansion tank (21) being correspondingly flared to accommodate said head (19b) .

11. The device according to any of claims 8 to 10, wherein said stagnation chamber (16) is cylindrical in shape and is arranged so as to be substantially tangent to said duct (2) , and to form an aperture (17) for deviating the liquid radially from the duct (2) to the chamber (16), said expansion tank comprising a bowl (21) that coaxially surmounts said chamber (16) , said seat (16b) being formed in the bottom of said tank (21) .

12. The device according to claim 11, wherein a tubular filter (18) is arranged in said stagnation chamber (16) for filtering the flow through said aperture (17) .

13. The device according to any one of claims 8 to 12, comprising a piston (29) slidably arranged in a cylinder (22) arranged coaxially to said expansion tank (21) , outside of said membrane (28) , said piston (29) comprising a head (29a) that is reactive to the displacement of the membrane (28) and a prong (29b) projecting radially on the outside of said cylinder (22) through an axial slit (22a) formed in it, transmission means (30) being arranged between said prong (29b) and a second microswitch (23) to operate the same at said minimum and maximum pressure i& detections .

14. The device according to claim 13, wherein said transmission means (30) comprise a slider (30) in which a slot (30b) is formed for engagement with said prong (29b) with a certain play, and a cam (30a) integral with said slider (30) for engaging/disengaging with said second microswitch (23) , respectively to turn said pump on and off, said play being such as to control the displacement of the slider (30) , and consequently the engagement/disengagement with said second microswitch (30a) , following displacements of said membrane (28) respectively corresponding to said minimum and maximum pressure detections.

15. The device according to claim 14, wherein a third microswitch (31) for switching on/off the electrical power supply to said pump is arranged adjacent to said second microswitch (23) , said cam (30a) driven by said prong

(29b) being shaped in such a way as to operate said third microswitch (31) , to turn the pump off, following a further displacement with respect to the displacement required to operate said second microswitch (23) , said further displacement occurring only in the case of absence of water in said duct (2) , a manually operatable fourth microswitch (32) being connected in parallel to said third microswitch (31) , to restore the normal working of the pump when water is once again available.

16. The device according to any of the previous claims, comprising a tube (34) projecting from said duct (2) downstream of said flow detection means (3) , the communication between the tube (34) and the duct (2) being blocked by a breakable diaphragm, the free end of said tube (34) being prearranged for supporting a pressure gauge .

17. The device according to any of the previous claims, wherein a cartridge filter (6) is arranged within said duct (2) upstream of said pressure and flow detection means, provided with a magnetic element to intercept possible metallic dross transported by the liquid flow.