This invention relates to the field of pressurized gas feeding systems, in particular compressed air feeding systems provided with one or more air re¬ ceivers and more specifically the pneumatic systems used for the operation of heavy industrial vehicles. As well known, a considerable amount of water pro¬ duced by condensation of the humidity always present in the atmospheric air deposits on the bottom of air receivers. Such water deposit is undesirable as it may cause even very serious damages both to the receivers and the systems using compressed air. For example, water on the bottom of the air recei¬ vers can cause the oxidation and then the corrosion of the air receiver walls. Furthermore, water can be entrained into the con¬ duits in which it may freeze in case of a low outer temperature, thus causing the conduits to be occluded and broken with the tragic event which may result when said conduits are connected to the braking sy- stem of a heavy vehicle.

It follows that the drainage of water deposit from the air receivers, which is very expedient in case of stationary compressed air systems, becomes an absolute necessity in case of systems designed for heavy vehicles and mainly in case of braking systems. Unfortunately there is at the time being no efficient apparatus carrying out automatically and with the desired frequency drainage of condensate deposits

existing in the air receivers of industrial vehicles. In most case, however, each air receiver of an indu¬ strial vehicle -it should be noted that each heavy vehicle has typically more than one air receiver, e.g. there are vehicles having six or more air re¬ ceivers- is provided with' a manual condensate drai¬ nage apparatus, typically a snifting valve. This rather primitive solution, which is not able for certain by itself to -ssure that the necessary drai- nage of the condensate deposits is carried out with the due reliability, is further impaired by the pla¬ cement of the various air receivers under the frame of the vehicle in hardly accessible positions. It follows that the manual condensate drainage operation is usually carried out in case the vehicle is stopped for repair or maintenance reasons.

Therefore, the gravity of the danger inherent to the lack of a periodic and frequent condensate drainage of the air receivers, which heavy vehicles are equip- ped with, caused such vehicles to be necessarily pro¬ vided with an automatic apparatus providing for such an operation. It should be noted that, since the con¬ densate drainage causes necessarily the outlet of compressed air, the operation of such an automatic apparatus has to provide for the opening of the val¬ ve devices being limited to the time strictly neces¬ sary for the drainage of the condensate in order to avoid the total leakage of the compressed air con¬ tained in the air receiver or most of it. Failing this feature, i.e. the possibility of cau¬ sing a very short opening of the condensate drainage

valve in order to avoid loss of compressed air from the air receiver, the automatic condensate drainage apparatus available on the market are less efficient, the best of them causing a leakage of 70% of the compressed air contained in the air receivers.

Therefore, this invention seeks to provide an appa¬ ratus able to cause the condensate to be drained from all air receivers of an industrial vehicle with an optimized frequency and in an automatic manner when the motor of the vehicle is stopped, which is a typical and frequent operation of the vehicle. Another object of the invention is to provide an apparatus causing a short opening of the valves such as to reduce the leakage of compressed air from the air receivers to that which is strictly necessary. According to a preferred embodiment the apparatus includes: a pneumatic valve, in the casing of which first and second chambers are provided, both cham¬ bers being connected by a cylindrical passageway provided with a first valve seat and a second valve seat at the ends thereof, respectively; a pipe con¬ necting said first chamber to the air compressed re¬ ceiver from which condensate has to be drained; a pipe connecting a compressed air source to the se- cond chamber, which also communicates with the at¬ mosphere; a pneumatic pl-nger having two heads of different area, one for each chamber, respectively, and first and second valve members, one for each head of the plunger, cooperating with the first and second valve seat, respectively; a two-position electrovalve placed in the conduit connecting the

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compressed air outlet to the outside of the second chamber with respect to the plunger head.

In operation, the position of the electrovalve controls the position of the plunger carrying the valve members within, yhe valve casing, so that the change of such a position will cause the first valve member to move from its seat and the passageway between both chambers to be opened, and then the condensate to be drained into the atmosphere through the second chamber, the passageway to be closed again by the second valve member and then to be opened again and finally closed by the first valve seat.

The pneumatic valve is provided also with a manual safety driving knob.

An embodiment and the operation of the apparatus according to the invention will now be described in detail with reference to the accompanying drawing, wherein: Fig. 1 is a section of a pneumatic valve in the first closed position;

Fig. 2 is a section of the valve in the middle opened position; and

Fig. 3 is a section of the valve in the second closed position.

Shown in Fig. 1 is one of the valves of the apparatus designed for the drainage of an air receiver of a compressed air supplying system such as for example that installed in heavy industrial vehicles including up to six receivers.

Such a pneumatic valve includes:

a cylindrical valve casing 10 provided with cooling fins 11; a first chamber 12 placed in the left (in the figure) portion of the valve casing 10; a second chamber 13 placed in the right (in the figure) portion of the valve casing 10; an axial passageway 14 connecting chamber 12 to chamber 13; a first conical valve seat 15 formed at one end of the passageway 14 to chamber 13; a threaded pipe fitting Ϊ8 con- nected to the first chamber 12, a first threa¬ ded pipe fitting designated by 19 and a second threaded pipe fitting designated by 20 connec¬ ted to the second chamber 13.

As readily apparent a plunger 21 having a rod 22 easily sliding into the passageway 14 is placed i, the valve casing 10.

As the diameter of rod 22 is considerably lower than that of passageway 14, a sufficiently large hollow space is formed between the former and the inner wall of the latter.

Rod 22 carries at its left end a head 23, the cylindrical surface of which is provided with axial splines 24 and slides towards the inner wall of the first chamber 12. Furthermore, for- med at the base of head 23 about rod 21 is a conical valve member 25 adapted to cooperate with the conical valve seat 15 formed at the end of passageway 14 to the chamber 12 in order to seal said passageway. Rod 22 carries at its right end a head 26 having a diameter larger than that of the head 23 which

is provided with an O-ring 27 about its circum¬ ference so as to sealingly slide in the second chamber 13, thus forming an embolus. Furthermore, a conical valve member 29 is for- med within head 26 at the inner end of collar 28 connected to head 26 about rod 22, said val¬ ve member being adapted to cooperate with the conical valve seat 16 formed at the end of pas¬ sageway 14 to the chamber 13 in order to seal said passageway.

Screwed on the threaded pipe fitting 18 of the chamber 12 is the end 30 of pipe 31 leading to the air receiver (not shown) from which the con¬ densate has to be drained. Screwed on the threaded pipe fitting 19 is the end 32 of a pipe 33, the other end 34 of which is connected to a pipe fitting 35 of an electro- valve 36 which is supplied with compressed air by a pipe 47 through pipe fitting 37, said com- pressed air being at the same pressure as the air receiver from which the condensate has to be drained under operating condition. Electrovalve 36 has a rest position in which it connects pipe 33 to atmosphere, and an ope- rative position in which it supplies the compres¬ sed air of pipe 37 to pipe 33 and then to the right portion 13B of chamber 13 outside the sur¬ face 39 of the embolus. With such a construction of the valve the opera- tion is as follows:

During the normal operation of the vehicle each

electrovalve 36 associated to the air receiver from which condensate has to be drained through pipe 31 coming from the bottom thereof is under rest or de-energized condition, chamber 13 being at the atmospheric pressure because of its con¬ nection to the outer environment through pipe 33 and the opening 38 of electrovalve 36. Therefore plunger 21 takes the position shown in Fig. 1 in which the conical member 25 seals the valve seat 15.

Under normal operative condition, for example, during either the turning off or on of the mo¬ tor or at automatically preselected time inter¬ vals or under control in the stationary systems, the electrovalve will receive by known means commercially available here not illustrated nor described an energizing electric pulse from the battery B and will pass to the condition illustrated in Figs. 2 and 3, in which co pres- sed air at the same pressure as in the air re¬ ceiver -rom which condensate has to be drained will arrive to chamber 13B through pipes 47 and 33. For example, pipe 47 supplying comprressed air to electrovalve 36 comes out from the upper part of the same receiver as condensate draining pipe 31.

Owing to the larger area of the surface 39 of _. head 26 with respect to the surface 42 of head 23, plunger 21 is displaced to the left in Fig. 1 and during such a displacement will take in

particular the position depicted in Fig. 2, in which the condensate present in the air re¬ ceiver and in pipe 31 coming from the bottom of the receiver itself is conveyed into cham- ber 12 and then through the splines 24 in the head 23 and passageway 14 arrives to chamber 13 and is drained outside through the drainage pipe fitting 20. In the meantime the stronger thrust of head 26 under such conditions carries plunger 21 to the position illustrated in Fig. 3, in which the conical valve member 29 seals the valve seat 16. This is the second tempora¬ ry closed position of the valve. It should be noted that an elastic ting 40 is applied to the end wall 41 of chamber 12. The outer surface 42 of head 23 abuts against such * a ring, thus cushioning the end of the stroke ' of plunger 21 and then decreasing the force of abutment of the valve member 29 against the valve seat 16 so that the wear of these parts is reduced.

When the electrical energizing pulse is switched off, electrovalve 36 turns to the position shown in Fig. 1, in which plunger 21 is forced to the position shown in Fig. 1 as chamber 12 is at a pressure greater than the atmospheric pressure of chamber 13B. Of course, during the second stroke of the plunger the same condition depic¬ ted in Fig. 2 is repeated, i.e. the condensate is drained from pipe 31 through the splines 24, passageway 14 and fitting 20.

It should be noted that the end of stroke of the plunger is cushioned by the compressed air from pipe 31 that after passing through the splines 24 forms an air cushion between the annular wall of chamber _. 12 about the valve seat 16 and the annular inner surface of head

23 about the valve member 25.

It should be appreciated that in the valve according to the invention the screwed knob 46 has a rod 43 with a thread 44 which screws in the sleeve 48 and engages the protruding member 45 i.ntegral with head 26 so as to force plunger 21 to take the closed position of Fig.

3. Knob 46 therefore is a manually operated safety closure means.

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