Valve-device for gradually putting under pressure pneumatic systems

Abstract

 A device for gradually putting under pressure pneumatic systems, in particular for automatic starting up of presses, pneumatic actuators and pneumatic power-consuming machines in general.
The device comprises a valve casing (1) defining a passage for the fluid, between an inlet port (2) and an outlet port (3); a pneumatically-operated pressure-reducing valve (8,9) is arranged in the fluid passage and operates in order to substantially reduce the pressure of the fluid fed in, each time the system is started up, said valve (8,9) opening instantaneously and making it possible to feed the fluid at full pressure value, as soon as the pressure of the fluid in the system reaches a pre-established value. The valve device also comprises a single-acting valve (27,30) for rapid exhaust of the system.

Description

[0001] This invention refers to a valve device for gradually and automatically putting under pressure pneumatic systems and equipment, such as systems for controlling pneumatically-operated large presses, pneumatic actuators and power-consuming machines in general, and for gradually putting under pressure the chamber of pneumatic cylinders.

[0002] As is known, at the end of each daily work cycle of a power-consuming machine, it is customary to exhaust the compressed air from the system, thereby enabling all the moving parts of the machine connected to operating pistons, to return to the normal or resting position. During the subsequent work cycle, it is necessary to supply the system once more with compressed air, feeding it in gradually until the working pressure is reached in order to prevent any sharp increases in the pressure from causing a rapid movement of the mechanical parts of the machine, thereby damaging the machine itself.

[0003] Known devices do not adequately resolve the problems connected with the various types of pneumatic machinery and systems which, at times, call for an adequate adjustment of the initial feeding pressure of the fluid.

[0004] Therefore, a scope of this invention is to provide a valve device, for the described purposes, which is unaffected by pressure peaks which may occur during operation, thus avoiding unnecessary repairs or stoppage of the machine under still acceptable operating conditions, and intervening only when the pressure of the fluid fed to the pneumatic circuit drops below a pre-established value, usually below the value of the initial limited feeding pressure.

[0005] A further scope of this invention is to provide a valve-device by which it is possible to slowly put the system under pressure, at a limited or lower pressure than the normal working pressure of the system, thanks to the use of a pressure-reducing valve which is automatically piloted by the pressure within the pneumatic system, this piloting being achieved by means of a differential control of the pressure upstream and, respectively, downstream from the reducing valve.

[0006] A still further scope of this invention is to provide a valve-device for the described purposes, which is simple in construction, compact and also embodies a single-acting rapid exhaust valve, which operates automatically in order to allow the reverse flow of the air under pressure, from the inlet to the outlet of the valve-device itself.

[0007] A still further scope of this invention is to provide a valve-device for gradually and progressively starting up pneumatic systems, which is of universal use, namely that it can be used in systems and machines of different types, due to the fact that it is provided with a device for adjusting the pressure-reducing valve.

[0008] These and other scopes and features of this invention are achieved by means of a valve-device comprising a valve casing having an inlet and an outlet port connected by means of a pressure-reducing valve, said reducing valve comprising a poppet member, also referred to as "poppet" mounted on a spool axially movable from a completely open to a partially closed position of the reducing valve; a first chamber to one side of the poppet, communicating with the fluid inlet, and a second chamber on the opposite side of the poppet, communicating with the fluid outlet, and a balancing spring acting upon the poppet to push it towards a valve seat, in the second position of the supporting spool; the device comprising moreover, pneumatic pilot means for piloting the reducing valve, comprising a front piston and, respectively, a back piston connected to the aforesaid spool, said front piston being movable within a third chamber communicating with the fluid inlet, said back piston being, in turn, movable within a fourth chamber communicating with the fluid outlet through a pressure picking-up passage in the spool, which opens out downstream from the pressure-reducing valve.

[0009] The invention will be described in greater detail hereunder, by reference to the examples of the accompanying drawings, in which:

Fig. 1 shows a cross-sectional view of a first embodiment of the valve-device according to the invention;

Fig. 2 shows a longitudinal cross-section of a modified embodiment of the device.

[0010] With reference to figure 1, the valve-device comprises a casing 1 provided with an inlet port 2 for the fluid under pressure, and an outlet port 3 situated on the opposite side, and in a different plane to the inlet port 2. The fluid inlet 2 is in communication with the outlet 3 through an internal passage comprising a pressure-piloted reducing valve.

[0011] In particular, as shown in the cross-sectional view, inside the valve casing 1 is a tubular extension or sleeve 4 spaced apart from the inner surface of the casing and defining, together with the latter, an annular chamber the purpose of which will be described in detail further on. The tubular extension or sleeve 4, presents radial apertures 5 through which the inlet 2 communicates with an internal chamber 6, hereinafter referred to as first chamber, and respectively, with another internal chamber 7, coaxial to and above the first, referred to as third chamber.

[0012] The end of the sleeve 4 inside the valve casing 1, defines an annular valve seat 8 towards which is pushed a flow control member or poppet 9 fixed to the shank of a spool 10, said spool 10 being able to slide axially in the sleeve 4, from a forward or fully open position of the pressure-reducing valve 8,9, to a backward or partially closed position of the aforesaid reducing valve. Consequently, the poppet 9 of the reducing valve is movable within a chamber 11, referred to as second chamber, communicating directly with the outlet 3 of the valve-device. A biasing spring 12 acts upon the poppet to push it towards the valve seat 8 or second condition of the spool 10; said biasing spring 12 is housed in a lower extension of the second chamber and rests directly between the disc 9A of the poppet and a plug 13 on the bottom of the chamber 11, possibly provided with a connecting aperture for a pressure switch.

[0013] The device comprises moreover, pilot means for piloting the reducing valve, capable of opening said reducing valve rapidly whenever a pressure equal to a pre-established percentage of the working pressure of the system is reached downstream from the reducing valve. The reducing valve piloting device is based on the principle of sensing a pressure difference between the pressure upstream and the pressure downstream from the reducing valve, and of rapidly opening the valve whenever this difference is balanced or has merely changed the sense.

[0014] According to the embodiment shown, the spool 10 supporting the plug or poppet 9, is connected to a pair of opposing pistons upon which different pressures are exerted; in particular, the pilot means comprises a first or front piston 14 consisting of a portion having a greater diameter than the spool 10, provided with a lip seal 15 which slides in contact with the internal wall of the chamber 7 having a greater diameter and opening out on the chamber 6, upstream from the reducing valve. A second piston in the form of a sleeve 17, acting in the opposite way to the first one and therefore referred to as back piston, consists of a sleeve tightly sliding on a neck portion 18 of the spool 10; here too, the second piston 17 is provided with a lip seal 19 tightly sliding in a fourth chamber 20 situated at the opposite end of the described valve casing 1. The sleeve 17 of the second piston is movable with regard to the spool 10, and presents an annular flange 21 which stops against an annular ledge surface 22 on the internal wall of the casing 1. The chamber 20 of the back piston 17 is in connection with the pressure upstream from the reducing valve; consequently, in the embodiment shown, the spool 10 presents an axial duct 23, of limited diameter, which opens out, on one side, into the chamber 20 of the back piston, whereas, on the other side, it opens out on the chamber 11 situated downstream from the valve 8,9, through a passage in the supporting plate of the poppet.

[0015] The described valve-device moreover comprises an adjustable stop member against which the spool 10 comes to rest, in order to prevent the reducing valve 8,9 from closing completely. This stop member is in the form of a threaded dowel 24 which is screwed tight into an extension 25 of the casing 1; the internal end of the threaded dowel 24 comprises a flat head 26 against which the end of the' spool 10 comes to rest. Adjusting the position of the stop dowel 24, consequently adjusts the position of the poppet of the reducing valve and, therefore, the value of the reduced pressure fed through the outlet 3 of the device, to a system or power-consuming machine.

[0016] The device is completed by a single-acting or rapid-exhaust valve, for connecting the outlet 3 and the inlet 2 of the device, by-passing the reducing valve 8,9, whenever the pneumatic system must be exhausted or turned off at the end of a daily work cycle. This has been made possible, in a two-way valve-device, by using an annular-type valve arranged coaxially to the reducing valve; as shown, the single acting valve comprises an annular seal 27, made of rubber or other elastic material, hinged to a ring 28 of the same material, which fits into a circular seat on the outer surface of the sleeve 4. The annular seal 27 is subjected to the pressure of the incoming fluid existing in the annular chamber 29 which surrounds the sleeve 4 and which communicates with the chambers 6 and 7 through the passages 5 in the sleeve itself; the aforesaid seal 27 is consequently pushed shut against an annular seat 30 inside the casing 1, by the pressure of the incoming fluid itself, and is raised and opened by the downstream pressure, whenever the feeding of the pneumatic fluid is interrupted and the system is exhausted.

[0017] The device operates as follows: from the side of the first chamber 6 of the poppet, the compressed air or pneumatic fluid is fed in at a first pressure value P1, whereas the internal diameter of the chamber 6, apart from negligible differences, corresponds with the diameter of the internal surface of the poppet 9 sealing against the seat 8; the external diameter of the poppet 9, on the side of the chamber 11 situated downstream from the pressure-reducing valve is greater than the internal diameter of chamber 6. Moreover, the diameter of the piston 14 is greater than that of the previous chambers, and the diameter of the back piston 17 or of the relative chamber 20, is greater than the diameter of the front piston. It is also assumed that the stop dowel 24 for the spool supporting the poppet is situated in a position so that the reducing valve 8,9 allows the fluid to flow through with a maximum pressure drop equivalent to 30% of the working pressure P1 fed in at the inlet 2 of the valve-device; in other words, it is assumed that the maximum downstream pressure provided by the reducing valve is P2 - 70% 91.

[0018] Initially, that is to say, when the system has yet to be started up, it is empty and the pistons which operate the moving parts of a power-consuming machine are in their resting position. Therefore, as soon as the pneumatic fluid begins to be fed in, the pistons start to slide slowly in their cylinders without any substantial pressure increase occurring in the system, until the pistons reach the end of their stroke. Under these conditions, the pressure downstream from the reducing valve and, therefore, the pressure in the chamber 20 of the back piston, will remain considerably lower than the operating pressure P2 of the device. The sum of the thrust exerted by the pressure on either side of the poppet 9 and on the pistons 14, 17, will be such as to push the poppet 9 towards the seat 8, however the stop'dowel 24 will prevent this valve from closing completely. Meanwhile the single-acting valve 27 remains closed due to the fact that the pressure exerted on the upper side of the annular seal 27 is greater than that exerted on the opposite side.

[0019] As soon as the system is saturated, at the end of the piston strokes of the machine, there is a sudden sharp increase in the pressure downstream from the reducing valve 8,9 which is transmitted to the chamber 20 through the duct 23 in the spool 10. This signal is sensed by the back piston, the thrust of which now prevails over that of the balancing piston 15, and the poppet 8 of the reducing valve is pushed open; however, as soon as the poppet starts to open, the annular flow area of the fluid increases, consequently causing an increase in the downstream pressure, resulting in the sudden rapid opening of the reducing valve, which now allows the fluid to be fed at the full working pressure P1 of the system. The valve-device remains in this operating condition throughout the entire working period of the machine or pneumatic system in which it is installed. Any pressure variations or peaks which may occur will not affect the valve-device, which will continue to remain open, even if the value of the inlet pressure should accidentally drop below its rated value P1, to the reducing valve-operating value P2. Hence, the system will continue to remain in operation; the rapid-exhausting valve 27 will only open when the inlet pressure drops substantially below the pressure P2, for example, when exhausting the system upstream from the above-described valve-device, due to the lack of pressure P1, whilst the pressure-reducing valve will close, that is to say, it will return to its initial operating condition without, consequently, affecting the exhausting of the pneumatic fluid.

[0020] It will be clear, from the foregoing description and that shown in figure 1, that a two-way valve-device is provided, for gradually putting under pressure pneumatic systems, which is absolutely new and original in conception, due to the particular system of pneumatically piloting the pressure-reducing valve, and to the presence of a single-acting rapid-exhaust valve which utilizes the same inlet and the same outlet as the fluid, without affecting the reducing valve.

[0021] A signal is sometimes requested to indicate that the system or machine is working at full pressure, or for carrying out other tasks. This signal can easily be obtained by providing a contact or switch 31 operated by a tongue 32 screwed onto the lower end of the spool 10, as shewn in the modified embodiment of figure 2, in which the same numerical references indicate parts corresponding to the example of figure 1. The tongue 32 is screwed or otherwise secured to the spool 10, without closing the channel 23, and slides through a sealing device provided at the end of the casing 1, as shown. As far as the rest is concerned, the valve of figure 2 is constructed in the same way and operates identically to'the valve of fig. 1; hence, the same device, without any substantial modifications, carries out two distinct or correlated functions, acting both as a device for gradually putting pneumatic systems under pressure, and as a pressure switch.

Claims

1. Valve-device for automatically and gradually putting under pressure pneumatic systems and apparatuses, characterized by the fact that it comprises a valve casing (1) having an inlet port (2) and an outlet port (3) connected by means of a pressure-reducing valve (8,9), said reducing valve (8,9) comprising a flow control member (9) mounted on a spool (10) axially movable from a first operating position with said member (9) close to a valve seat (8); a first chamber (6) on one side of the flow control member (9) communicating with the fluid inlet (2), a second chamber (11) on the opposite side of the aforesaid member (9) communicating with the outlet (3), and a spring (12) acting on said control member (9,9a) to push it towards said valve seat (8); the device comprising moreover, pneumatic pilot means (14,17) for piloting the reducing valve (8,9), acting to keep the reducing valve (8,9) in its'second operating condition until a pre-established pressure is reached downstream from the reduction valve itself; the valve-device further comprising a single-acting rapid exhaust valve (27,29) between the outlet port (3) and inlet port (2).

2. Device as claimed in claim 1, characterized in that said pneumatic pilot means (14,17) for piloting the reducing valve (8,9) comprise a front piston (14) movable within a third chamber (7) communicating with said first chamber (6) and the fluid inlet (2), and a back piston (17), acting in the opposite direction upon said spool (10) supporting the flow control member (9,9a) of the reducing valve (8,9), said back piston (17) being movable in a fourth chamber (20) connected by means of a duct (23) with a point (11) downstream from the reducing valve (8,9).

3. Device as claimed in claim 2, characterized in that said fourth chamber (20) of the back piston (17) is connected to an axial duct (23) made in the spool (10), which opens into the second chamber (11) downstream from the flow control member (9,9a).

4. Device as claimed in claim 2, characterized in that said back piston (17) has a diameter greater than that of the aforesaid front piston (14).

5. Device as claimed in claim 2, characterized in that said back piston (17) is movable with respect to the supporting spool (10).

6. Device as claimed in claim 5, characterized in that said back piston (17) comprises a sleeve sliding along an end portion (18) of the spool (10), said sleeve (17) having a seal member (19) sliding along the wall of the piston chamber (20).

7. Device as claimed in claim 6, characterized in that the sleeve (17) of the back piston comprises a peripheral flange (21), and an annular stop surface (22) for said flange (21) being provided inside the casing (1) of the device.

8. Device as claimed in claim 1, characterized in that said seat (8) of the reducing valve (8,9) is situated at the end of a tubular extension (4) inside the casing (1), said tubular extension (4) defining, together with the internal wall of the casing (1), an annular chamber (29) for said single-acting valve (27) and being provided with apertures (5) for the passage of the fluid, which open out onto the first (6) and the third (7) of the aforementioned chambers.

9. Device as claimed in claim 8, characterized in that said single-acting valve (27) comprises a pressure-actuated flow control annular member, said member being pushed by the pressure of the incoming fluid, against an annular seat (30) inside the casing (1).

10. Device as claimed in claim 9, characterized in that said flow control member (27) consists of an annular seal member of elastomeric material, externally disposed on the aforesaid tubular extension (4) inside the casing (1) of the device.

11. Device as claimed in claim 1, characterized in that means (26) are provided for stopping the spool (10), at the end opposite to the reducing valve (8,9) and means (24,25) for adjusting the position of the aforesaid stopping means (26).

12. Device as claimed in claim 11, characterized in that said means for stopping the spool (10) comprise a threaded dowel (24) having a flat head (26) for stopping the spool (10).

13. Device as claimed in claim 1, characterized in that it comprises a spool-operated control device (31) in the first operating condition, for providing a control signal.

14. Device as claimed in claim 13, characterized in that said device (31) comprises an electric switch operated by an axial extension (32) of the spool (10).

Drawing