Abstract:
An automatic bleed unit for a fuel filter used particularly in diesel engines includes a filter chamber  5  for accumulating water present in the fuel. Sensors  220, 230  and associated floats  24, 25  are provided for determining the level of water in the chamber. Upon reaching a predetermined level, a microprocessor activates a withdrawal device  7  to drain water from the chamber. The device is only activated when the vehicle engine is at rest and the ignition key is in first switch position that makes the relevant electrical system live. A system that verifies the compatibility between the withdrawal device casing  70  and a base part  20  of the sensing system can also be included.

Description:
TECHNICAL FIELD 
     This invention relates to improvements in the automatic bleed unit for a disposable filter fully described in PCT/IB00/01527 Published as WO01/33069 A1 in the name of the same Applicant, the text of which is to be considered an integral part of the present description for suitable reference. 
     BACKGROUND ART 
     Essentially, the device of said document comprises a sensor means associated with the chamber of the filter for the vehicle fuel (such as diesel oil) in which the water present in said fuel accumulates, a withdrawal device provided for discharging said water when it reaches a predetermined maximum level, and a microprocessor (or electronic card) which is connected to said sensor means and to said withdrawal device such as to activate this latter, with the vehicle engine at rest and the relative electrical system live, when the water reaches said predetermined maximum level. 
     In particular with said vehicle electrical system there is associated a visual indicator which is activated by the sensor means via the microprocessor, the said microprocessor being arranged to maintain the withdrawal device deactivated when the vehicle engine rotates and said visual indicator is energized. Said sensor means also comprises two mutually movable elements, of which one is permanently associated with the shell of the filter in which the water collects, and which is disposable, whereas the other is positioned inside a casing which contains said microprocessor and said withdrawal device, is removably connected to said shell, and is permanently associated with the vehicle. 
     For further details reference should be made to the text of the application cited in the introduction. 
     A problem which has been encountered in using the aforedescribed unit derives from the fact that the sensor means may sometimes not intervene due to its two component elements being unable to move relative to one another, and the difficulties resulting therefrom. Investigations have shown that said lack of intervention is mainly due to at least one of the following reasons. 
     Materials such as impurities, dirt or adhesive lumps can deposit on the element permanently associated with the vehicle, to hinder sliding of the element associated with the filter, even when this is new and clean. 
     In addition, as one of the two elements is replaced when the filter is replaced, dimensional inaccuracies can occur between these elements, particularly if the used and new filters pertain to different batches or originate from different operating lines. In this case coupling inaccuracies and/or misalignments thereof can occur when the shell of the new filter is connected to said water withdrawal device. 
     The main object of the present invention is to obviate the aforesaid problem within the context of a simple, rational, reliable and economical construction. 
     DISCLOSURE OF THE INVENTION 
     Said object is attained by virtue of the characteristics indicated in the claims. 
     In attaining said object, according to the invention said sensor means of the known unit cited in the introduction is made to consist of a differential water level reading and monitoring system comprising two measurement members, each sensitive to a level between the maximum predetermined level and the depth of said accumulation chamber, said two measurement members being connected to the unit microprocessor such that, with the vehicle engine at rest and the relative electrical system live, it energizes said withdrawal device in response to the signal received from one or other of said two members. 
     Moreover, apart from the respective external electric cabling, and as will be apparent hereinafter, the constituent elements of said two measurement members are advantageously permanently positioned in the lower part of the accumulation chamber of the disposable filter. 
     Finally, means described hereinafter are interposed between said differential reading and monitoring system and that part of the bleed unit permanently associated with the visual indicator, to verify the compatibility between the filter and the bleed unit. By virtue of the aforegoing, all the objects of the invention are attained. 
     In this respect, the danger of non-intervention of the sensor means is reduced to a minimum in that on the one hand the activation signal for the bleeding stage is generated even if the reading member is disabled by the presence of excessive deposits of foreign material, and on the other hand a filter having characteristics different from those required by the bleed unit cannot be mounted. 
     The constructional and operational characteristics and merits of the invention will be apparent from the ensuing detailed description, given with reference to the figures of the accompanying drawings, which show two preferred embodiments thereof by way of non-limiting example. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an overall scheme showing the main components of the unit. 
     FIG. 2 is an axial section showing the discharge port of the disposable filter of FIG. 1, said filter being of the type operating with its cartridge under pressure. 
     FIG. 3 is a view similar to the preceding, where the filter shown is of the type operating with its cartridge under vacuum. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Said figures, and in particular FIG. 1, show a filter  1  of the disposable cartridge type, known overall, comprising, starting from the top downwards, a conduit  2  through which the fuel (such as diesel oil) to be filtered arrives, a conduit  3  through which the filtered fuel leaves, a filtering diaphragm  4 , a chamber  5  for collecting the water separated from said fuel, and a discharge port  6  for said water. 
     In said port  6  there is housed a differential reading and monitoring system, described hereinafter, for the level  10  of the water present in the chamber  5 , below the port  6  there being a water withdrawal device  7  from which there branches a conduit  8  leading to an accumulation vessel  9 . 
     The device  7  is permanently installed on the vehicle provided with the filter  1 , and is incorporated in the respective electrical system. It is connected to the battery  11  by the cable  13  via the switch  12 . 
     The switch  12  is controlled by the microprocessor or electronic card  14 , which is connected to the ignition switch  15  of said vehicle. 
     In the usual manner, by means of the key  16  said ignition switch  15  can assume three positions indicated by A, B and C respectively, in the first A of which the vehicle engine is stationary and the respective electrical system is switched off, in the second B the engine is at rest and the electrical system is energized, and in the third C the engine rotates and the electrical system is live. 
     According to a first embodiment of the invention, in the vehicle passenger compartment, typically on the dashboard, there is a warning lamp  17 , usually present on most vehicles, typically those with a diesel engine. 
     Said lamp  17  is connected to a differential reading and monitoring system for the level  10  by the cable  170 , and is controlled by the card  14 . Said cable  170  presents a branch  177 , also connected to said differential level reading and monitoring system, the purpose of said branch being apparent hereinafter. 
     Said differential level reading and monitoring system comprises, as shown in FIGS. 2 and 3, a cup-shaped member  19  the base part  20  of which is centrally provided with a threaded through hole  33  and is sealed inside the port  6  of the filter  1 . 
     The wall of said cup-shaped member is defined by three (or more) angularly equidistant salient fins  21  each presenting two inwardly projecting shoulders, namely a lower  22  and an upper  23 . 
     The shoulders  22  and  23  define the upward travel limit of respective floats  24  and  25  contained within the member  19  with a certain radial slack. 
     Said floats  24  and  25  have a specific gravity between that of water and that of the fuel. 
     The lower float  24  is shaped as a cup, in the base of which there is a central hole coaxial with the hole  33  in the base of the member  19 . 
     The upper float  25  is shaped in the manner of a mushroom the stem of which is contained, with a certain radial slack, in the cavity of the underlying float  24 . 
     When the level  10  of the water present in the filter collection chamber  5  is insufficient to raise the floats, as shown in FIGS. 2 and 3, the head of said mushroom shape rests against the upper circumferential edge of the lower float  24 , and the stem of said mushroom shape is slightly spaced from the base of said lower float  24 . 
     This is to prevent any inconvenient sticking between the two floats, seeing that the foreign material separated from the fuel tends to accumulate in the lowest part of the chamber  5 . Respective sensors  220  and  230  are positioned at said shoulders  22  and  23 . 
     In a first embodiment said sensors  220  and  230  are magnetic proximity microswitches, in which case the floats  24  and  25  are suitably magnetized, for example by means of a thin metal strip wrapped about their end. 
     Alternatively said sensors  220  and  230  can consist of optical sensors sensitive to the colour, the same or different, of the respective floats  24  and  25 . 
     Said sensors  220  and  230  are electrically powered via a recognition system arranged to identify compatibility between the disposable filter  1  and that part of the bleed unit permanently associated with the vehicle, which in the illustrated example is the withdrawal device  7 . 
     This latter comprises a casing  70  presenting at its top an externally threaded hollow stem  71  screwed into the hole  33  in the base part  20  with a gasket  44  therebetween. 
     Concentrically to said stem  71 , on the lower face of the base part  20 , there are embedded four electrically conductive annular tracks  55 , external to which there is an annular gasket  66  clamped between the casing  70  and the port  6 . 
     The outer pair of tracks  55  is electrically connected to the sensor  220 , the inner pair being connected to the sensor  230 . Against said two pairs of tracks  55  there rest respective pairs of underlying electrically conductive push rods  77  which are slidingly mounted on the upper wall of the casing  70  via suitable interposed elastic thrust means, not shown in the figures, for example in the form of leaf springs. 
     The aforedescribed electrical connection of interface type forms said system for identifying compatibility between the disposable filter  1  and that part of the bleed unit associated with the vehicle. 
     Said push rods  77  are electrically connected to the card  14  positioned in the casing  70  and connected in its turn to the vehicle electrical system by the push-on connector  72 . 
     To the side of the connector  72  there is a water discharge spout  73  which at its bottom is connected to the conduit  8  (see FIG. 1) and at its top communicates with the stem  71  via the following interposed means. 
     In the case of a filter  1  with a vacuum cartridge (see FIG.  3 ), said means comprise a micropump  74  interposed between said spout  73  and stem  71 , and driven by an electrical micromotor  75  powered by the battery  11  when enabled by the card  14 , said micropump, micromotor and card being housed in the casing  10 . 
     In the case of a filter with a pressure cartridge (see FIG.  2 ), said means consist of a normally closed solenoid valve. 
     This comprises a tube  76  sealedly clamped between said stem  71  and spout  73 , to form the core of a coil  78  electrically connected to the card  14 . 
     Inside said tube  76  there are provided, from the bottom upwards, a gasket  79 , a valving element  80 , a compressed spring  81  for maintaining the visual indicator constantly urged elastically towards the closure position, and a jacket  82  wrapping the upper part of the spring  81  to define the extent of opening travel of the visual indicator  80 . 
     The invention operates as follows. 
     With reference to FIG. 1, in which it can be seen that the sensors  220  and  230  are connected in parallel with the lamp  17 , when the level of the water  10  is below the predetermined value the lamp  17  remains extinguished whatever the position of the ignition switch  15 , and the floats  24  and  25  adapt to said level. Under normal operating conditions the lower float  24  rises carrying with it the upper float  25 . 
     When the water  10  exceeds said predetermined level, and the vehicle electrical system is energized, the sensor  220  senses the presence of the lower float  24  and emits a signal causing the lamp  17  to light. The lamp  17  could for example remain lit continuously, for the reason given hereinafter. 
     If the vehicle engine rotates, the card  14  inhibits intervention of the withdrawal device  7 , whereas if the engine is at rest the card  14  energizes the device  7  for a predetermined period sufficient for all the water present in the chamber  5  to be discharged, with simultaneous extinguishing of the lamp  17 . 
     If the lower float  24  is unable to rise, for example because it adheres to the soiled face of the base part  20 , only the upper float  25  rises, the procedure being repeated identically when the upper sensor  230  senses the presence of said upper float  25 . 
     The electronic card  14  is preferably provided with means for selecting the energization time of the withdrawal device  7  depending on the specific sensor activated. 
     This is because activation of the sensor  230  means that there is a greater accumulation of water  10  than that associated with activation of the sensor  220 . Consequently in the former case the period of energization of the device  7  is correspondingly greater. Advantageously, according to the invention the electronic card  14  is provided with means for indicating possible lack of energization of the withdrawal device  7  when the water has reached the predetermined level, which may be due either to non-raising of the lower float  24  as already stated, or non-intervention of the lower sensor  220 , for example due to a fault. 
     Said means are typically arranged to energize the warning lamp  17  in a different manner depending on which sensor has emitted the overfull signal. 
     For example the lamp  17  may as stated emit continuous light when the lower sensor  220  is activated, and the same lamp  17  emit intermittent light when the upper sensor  230  is activated. Preferably the lamp  17  is energized in the said intermittent manner starting from the second activation of the upper sensor  230 . 
     By this means the vehicle driver is warned that the unit is operating abnormally. 
     The merits and advantages of the invention are apparent from the aforegoing and from an examination of the accompanying figures. The invention is not limited to that illustrated and described, but covers all the technical equivalents of the invention and their combinations, if implemented within the context of the following claims.