FILTER FOR HYDRAULIC SYSTEMS HAVING PACKING WITH CONSTANT SIDE ACTION FOR THE SCREW-ON CARTRIDGE UNIT AND HAVING A GLOGGING INDICATOR RESPONDING TO DIFFERENTIATED PRESSURE

Abstract: Filter for hydraulic systems, consisting of a holder (26) of a disposable cartridge (25), that can be screwed onto the head (10) to mount on piping serving the system, comprising an annular packing (15), between the head (10) and the holder (26) of the cartridge (25), having a transversal action in relation to the direction of screwing, and a clogging detector (40) sensitive to differences in pressure upstream and downstream of the head (10).

Description: FILTER FOR HYDRAULIC SYSTEMS HAVING PACKING WITH CONSTANT SI ACTION FOR THE SCREW-ON CARTRIDGE UNIT AND HAVING A CLOGGING INDICATOR RESPONDING TO DIFFERENTIATED PRESSURE Well known objects are filters with replaceable cartridges for hydraulic purposes. The packing between cartridge holder and the head fixed to pipes supplying the system is generally placed at the front in relation to coupling surfaces and its action therefore gen¬ erally takes place in the same direction as that in which the cartridge is screwed on. This means that the packing is squeezed and that its pressure is in practice conditioned by the force applied to screwing on the cartridge with the need for very small tolerances. The filters at present in use are therefore costly, though operating pressure is not high, while lubricating action is subject to limitation. Devices for detecting and announcing cartridge clogging are difficult to operate as, though pressure variations upstream of the filter can theoretically serve for such detection,fre quent leaks or seeping through in the above mentioned packing prevents such devices from functioning properly. The above invention avoids these drawbacks as will be explain below. Subject of the invention is a filter for hydraulic systems, consisting os a replaceable cartridge whose holder is screwed onto the head to be mounted on the down piping, comprising an annular packing acting transversally in relation to the screw ing direction, and a clogging detector .sensitive to differen¬ ces in pressure upstream and downstream of the head. Due to its independence from screwing play and from any irre¬ gularity in this process, packing so placed avoids leaks and passage of fluid between head and cartridge holder, also en¬ suring precision in operation of the detector. The head comprises an annular seat communicating with the fluid input aperture and an internal threaded connector , coaxial to the annular seat, communicating with the fluid out let aperture. The container comprises a small axial head having a cylindri- neck matching with the above annular head, and a central threaded hole for fluid outflow, coaxial to said neck, made to allow the head .connector to be screwed on. Round the c ' entral outlet hole there are a number of holes for entry of fluid. The above invented annular packing is placed between the in- ner cylindrical face of the annular seat of the head, and the outer cylindrical faces of the neck on the small head of the container. The container is made of steel and is fixed to the small head by its edge being bent back, preferably * to form an over- turned "U", round the outer raised rim of the small head so as to create a hermetic, stable and secure seal. The small head is die-cast and is preferably of aluminium or aluminium alloys. The clogging detector comprises a cylindrical body in whose cylindrical seat on the head there are two chambers, a front one communicating by a small channel with the outlet aper¬ ture of the head, and an inner annular chamber communicating by another small channel with the inlet aperture of the head. A piston sliding inside said cylindrical body also creates two chambers, a front one communicating with the front cham ber of the detector's cylindrical seat, and an inner annu¬ lar one communicating by means of a small channel with the annular chamber of said cylindrical seat. A spring, or equivalent means, pushes the piston towards the back end of the detector. Therefore, when clogging causes the pressure of fluid .en¬ tering the head to exceed a certain value corresponding to calibration of the spring, said piston moves forward com- pressing the spring and making it possible for a warning to be given to announce that the cartridge is clogged. The warning is made by means of a slider moving freely in a longitudinal direction outside the body of the detector to which a permanent magnet is fixed. There is another permanent magnet inside the piston. Polarities of said magnets, on the opposing faces, are equal. When, therfore, the filter is clogged and the piston moves forward from its starting position, magnetic repulsion pushes the slider magnet in the opposite direction moving it to its back end-stroke position and causing a clogged filter warn¬ ing to be given outside. This is noted, through a window in the detector, by seeing one half or the other half of the slider respectively indicating its normal position or that assumed when the filter becomes clogged. One half of the slider is green and the other half red. When moved to its end-stroke position, denoting a clogged filter, the slider works a switch that closes the electric circuit operating a visual or an acoustic warning. Characteristics and purposes of the invention will be made still clearer by the examples of its application here fol¬ lowing illustrated by drawings. Fig. 1 Side view of the head, partially exposed. Fig. 2 Replaceable cartridge with container. Fig. 3 The filter mounted and in a clogged condition. The head (10) is connected to the hydraulic system by .means of the inflow aperture (11) and outflow aperture (12). Aperture (11) communicates with the annular seat (13) pro¬ vided with the channel (14) for the packing (15). Aperture (12) communicates with the outer threaded connec¬ tion (16), axial to the seat (13) and concentric to it. The cartridge (25), Figs. 2, 3, is mounted in the cylindri cal steel container (26) with small die-cast discoid head (27).- " having an axial neck (28), a series of circular holes (29) set radially for fluid inflow, and a central internal¬ ly threaded hole (30) for screwing onto the connection (16) of the head. The steel container (26) is fixed to the small head (27) by said container's edge (31) being bent back, to form an over turned "IT", all round the outer upward facing rim (32) of said small head, thus creating a hermetic, stable and se¬ cure seal. When the cartridge container is screwed onto the connection (16) of the head, so as to fit closely against the flat sur face (34) of the seat (13), the vertical cylindrical faces (33) of the neck (28) are counterposed against the packing (15) ensuring a hermetic seal. At the top (17) of the head there is a threaded seat (22) for the detector (40) which creates the front chamber (19) and the inner one (18). The aperture (11) in the head communicates with chamber(18) by means of the channel (20) while aperture (12) communi- cates with the chamber (19) by means of channel (21). The detector (40) comprises the cylindrical body (41 ) with its threading (42) to allow it to screw on to the threaded seat (22) of the top (17) of the head, with its tubular end (43) and packing (44). The piston (45) slides inside the cylindrical body and is held down on the bottom of the body (41) by the calibrated compression spring (46) which at the front connects to the locking ring (47) . The permanent magnet (48) is fixed to the back end of the piston. An annular slider can. slide axially on the outer cylindri¬ cal surface of the body (41) , a permanent annular magnet being fixed to said slider which consists of two halves, one red (50) and the other green (49). The magnets (48) and (51) lie opposite one another and their polarities .are of the same sign. There is a cylindrical collar (52) outside the slider, ha¬ ving a transparent part (53) held by the cap (54) fixed by the screw (55) to the body (41). Inside the cap there is a microswitch (56) with button switch (57) connected by electric cables (58) and the connector(59) to the source of electricity, and to an acoustic or visual warning device not shown in the figures. The annular packing ( 60 ) on the piston (45) creates the front chamber (43) communicating with the chamber (19) in the cylindrical seat (22) of the head, and the annular in¬ ner chamber (61) communicating by means of the small chan¬ nel (62) with the annular chamber (18) in the above seat. The head (10) is installed by connecting the apertures (11) and (12) respectively with the delivery and return pipes. The container (26) with cartridge (25) is mounted on the head by screwing the threaded hole (30) onto the connector (16). The packing (1 ) is placed to fit against the outer faces (33) of the neck (28) of the container ensuring its seal. Under normal filtering- conditions, pressure A in the cham¬ ber (61) communicating through the small tube (62) with the chamber (18), which in turn communicates with the fluid upstream of the filter, is less than overall pressure B which includes the pressure of fluid in chamber (19), com¬ municating with the fluid downstream of the filter, plus the tension of the spring (46) . The green half (49) of the slider lies in view behind the transparent window '' (53) of the ring (52). When, due to the cartridge being clogged, the resistence given by the filter to the fluid reaches a certain value (Fig. 3), pressure A exceeds pressure B and the piston is pushed towards its front end which leads to compression of the spring (46) and passage of the magnet (48) beyond the halfway point of the annular magnet (51). Due to the effect of repulsion set up by equality of oppo¬ sing polarities, the magnet (51) moves to the back end of the detector pulling the slider with it whose red half (50; then is seen through the window (53) giving warning that the filter is clogged. Simultaneously part (49) of the slider presses against .he button switch (57) putting into effect the electric visual or acoustic warning. Advantages These are evident. Seal pressure is independent both of the force applied to screwing on the cartridge holder and of its axial position. Working pressure can therefore reach values many times higher than that obtainable with ordinary filters having packing squeezed frontally. The differentiated pressure clogging detector indicates values that are perfectly correct in relation to calibra- tion of the spring, since the packing between cartridge holder and the head ensures a constant seal being affected neither by any play nor by irregularities in the way the holder is screwed on. As applications of the invention have been described as examples only not limited to these, it is understood that any equivalent applications of the inventive concepts ex¬ plained and any product manufactured and/or in operation according to the charac eristics of the invention, will be covered by its field of protection.

Claims: Claims 1. Filter for hydraulic systems consisting αf a disposable cartridge placed in a holder that is screwed onto a head to be mounted on the piping serving the ' system, characterized in that it comprises an annular packing (l5) f between the head (10) and the holder (26) of the cartridge (25) » acting transversally in relation to the direction of screwing and therefore exerting a constant seal pressure irrespective of play and irregularities of said screwing process, and a clogging detector (40) sensitive to differences in pressure upstream and downstream of the head (10),. precision of said detector being assured by constancy of said seal pressure. 2. Filter for hydraulic systems as in claim 1, character¬ ized in that the head (10) comprises an annular seat (13) communicating with the inflow aperture (11) of the fluid ' and an inner threaded connector (16) coaxial to the annu¬ lar seat (13) communicating with the outflow aperture(l2) of the fluid while the holder (26) comprises a small head (27) having a cylindrical neck (28) matching the above an- nular seat (13) and a central threaded hole (30),for fluid outflow, coaxial to said neck (28) into which the connector (16) of the head (10) is screwed, the annular packing (15) being set in a channel (14) in the inner cylindrical face of the annular seat (13) of the head (10) to establish a seal against the outer cylindrical faces of the neck (28) of the small head (27) on the holder (26). 3. Filter for hydraulic systems as in claim 2, character¬ ized in that the holder (26.). is made of steel sheeting and is fixed to the small head (27) by its edge (31) beingbent back in the form of an overturned "U" round the raised rim (32) of the small head (27) die-cast preferably in alumi¬ nium and its alloys. 4. Filter for hydraulic systems as in claim 1, character¬ ized in that when the cylindrically shaped clogging detec- tor (40) is inserted into its cylindrical seat (22) on the - 8 - head (10) it creates two chambers, a front chamber (19) communicating by means of a small channel (2l) with the outflow aperture (12) of the head (10) and an inner an¬ nular chamber (18) communicating by means of a small chan- nel (20) with the inflow aperture (11) of the head (10), said detector (40). comprising an internal piston (45) which also creates two chambers, a front chamber (43) di rectly in communication with the chamber (19) of the above cylindrical seat (22) and an annular chamber (61 situated further back, communicating by means of a small channel (62) with the annular chamber (18) of said seat (22), a spring (46), or equivalent means, pushing the piston (45) towards the back of the detector (40) so that when, on ac¬ count of clogging, pressure of the fluid entering the head (10) exceeds pressure exerted by the calibrated spring(46), said piston (45) is pushed forward compressing the spring (46) and enabling a warning of clogging to be given. 5. Filter for hydraulic systems as in claim 4, character¬ ized in that the warning of clogging is given by means of a slider, composed of two joined halves (49) and (50),free to move longitudinally outside the detector to which a per manent magnet (51) is fixed, there being inside the piston (45) another permanent magnet (48) with equal polarity in the face opposite the first magnet (51) so that when on a count of the filter being clogged, the piston (45) is pushed forward,the magnet(5l)on the slider (49)-(50) operates by magnetic repulsion in the reverse direction pulling the slider (49)-(50) to its back end-stroke position and so giving an external warning that the filter is clogged. 6. Filter for hydraulic systems as in claim 5, character¬ ized in that warning of clogging is given, 'through a window (53),and the like, in the detector, by the view of one half (49) of the slider in its resting position or of the other half (50) in the position it assumes when the filter is clogged, the first half (49) being preferably green and - 9 - and the second half (50) red. 7. Filter for hydraulic systems as in claim 5, character¬ ized in that, when in its end-stroke position signifying clogging, the slider (49) -(5 . 0) works the press button(57) of the switch (56) that closes the circuit (58) electri¬ cally operating a visual or acoustic warning.

Inventors: PASOTTO BRUNO, PASOTTO, BRUNO
Applicants: MP FILTRI SRL, PASOTTO BRUNO, MP FILTRI S.R.L., PASOTTO, BRUNO
Application year: 1986
Main classification: B01D35
IPC codes: B01D27, B01D35