EP0149386B1 - Urgent-venting device for pneumatic actuators - Google Patents

Description

• une entrée d'alimentation de fluide sous pression, qui est reliée directement ou indirectement à un distributeur pneumatique,
• une sortie de fluide, qui est reliée à une chambre du vérin,
• et une entrée de commande, qui reçoit un signal de commande agissant sur un organe de commutation interne apte à relier ou non la sortie de fluide à l'atmosphère, l'entrée et la sortie étant en communication lorsque ce signal est absent (FR-A-1 400 535).

The invention relates to an emergency purge device for a pneumatic cylinder, which is intended to cause the latter to stop and which comprises:

• a pressurized fluid supply inlet, which is connected directly or indirectly to a pneumatic distributor,
• a fluid outlet, which is connected to a chamber of the jack,
• and a control input, which receives a control signal acting on an internal switching device capable of connecting the fluid outlet to the atmosphere or not, the input and the output being in communication when this signal is absent (FR- A-1 400 535).

Such devices can be used in all pneumatic installations, either to stop the displacement of the rods of jacks, for example when a danger appears, or to make possible manual actuation of the rod of this jack, in order execute a verification or adjustment operation.

There are already known rapid purge circuits for cylinders which, to obtain the purge possibility mentioned above, use a 3/2 monostable distributor (FR-A-2 352188); this 3/2 distributor is placed between a cylinder chamber and a normal pneumatic distributor so that, in the presence of a control signal, the cylinder chamber is connected to the distributor, while, in the absence of this signal, the chamber is connected to the exhaust, and that the pipe coming from the normal distributor is closed.

We cannot really speak here of a device particularly suited to the desired function insofar as this 3/2 distributor is studied for more general functions, and has a shape adapted to these.

The assembly and the implementation of such a distributor have the disadvantage, on the one hand, of requiring a significant time and, on the other hand, of leading to bulky assemblies. When the aforementioned assembly is completed, the presence of this 3/2 distributor in the vicinity of the jack is not appreciated by users insofar as this results in a stack of organs which, obviously, were not designed to this end.

Furthermore, the mounting of these 3/2 distributors, which is justified when one associates the speed regulators with the cylinder, implies that these are placed between the cylinders and said regulators. As a result of the modern trend to generalize the use of speed regulators incorporated in fittings located directly on the cylinder body, the use of these 3/2 distributors for the purposes mentioned above has become obsolete.

The concern of instantaneously stopping a jack or that of making it maneuverable by hand occurs frequently in industrial installations where it is either essential to limit the damage and the risks that can cause faulty operations, or is still necessary to perform before a start-up or after a repair.

A cylinder can only be stopped and placed in an indifferent state if the pressures exerted on the two faces of its piston disappear after having decreased simultaneously.

As the cylinders are supplied via pipes which connect them to distributors and these are themselves connected to a source of compressed air, often distant, by a general line and to an exhaust manifold, it is sometimes difficult to quickly empty or purge the cylinder by interrupting the arrival of the fluid on the general line and by purging the latter.

Such a symmetrical emptying is even longer and more difficult to obtain if, as is the case frequently, air escapes from the jack to the distributor through one or more flow limiting members. In the latter case, it is observed that the masses of compressed air contained on either side of the piston escaping at different speeds, continue to exert on this piston different pressures which prolong the movement thereof after the opening of the pneumatic disconnector.

It is also known that a 3/2 modular pneumatic disconnector can be used to operate the venting of a pressure supply line serving a multiplicity of distributors, each associated with a respective jack; such a disconnector, which simultaneously operates the interruption of the arrival of the pressurized fluid from the source in the general line and connects the latter to the atmosphere, is always placed at the head of this line, so that one must take into account the purge time from the line lengths, distributors and flow limiters mentioned above.

The invention therefore proposes to provide an inexpensive and space-saving simple purge device for an actuator which is capable of rapidly evacuating the air which it contains when, exceptionally, a signal of opening, controlling the interruption of the supply of compressed air is applied to an installation, and in particular when this opening signal which switches a pneumatic switch capable of connecting the general distribution line to an exhaust after having disconnected it of the compressed air source, is represented by the disappearance of a pressure.

According to the invention, the aim is achieved thanks to the fact that this device has fixing means which are screwed directly onto the body of the jack and comprises an internal channel connected to the supply inlet, to the fluid outlet and to an orifice communicating with an exhaust, this orifice being closed by a valve placed opposite when a closing force is exerted on it created by the pressure of the fluid on the control input and this orifice being opened by the fluid escaping from the chamber when the control pressure and the supply pressure disappear simultaneously.

Rapid purge devices have already been used between the cylinders and the distributors to accelerate the movement of a cylinder when the circuit which supplies it does not have a sufficient size to ensure rapid displacement of the fluid, or when the distributor is located away from the jack; such a device which is located near the cylinder, connects the chamber of the cylinder, discharging its fluid, directly to the exhaust as soon as the distributor operates its switching; these devices use a valve which is placed opposite an orifice communicating with the atmosphere, and which is either applied against the latter when the cylinder is supplied with pressure, or lifted by the fluid of the cylinder when the latter is being evacuated. Such a rapid purge device therefore operates continuously.

The objective sought by these rapid purge devices, as well as its embodiment, have nothing in common with those of the invention.

• La figure 1a représente schématiquement une installation pneumatique mettant en oeuvre le dispositif de purge selon l'invention dans une phase de fonctionnement normal.
• La figure 1b montre une partie des organes de la figure 1a lors de l'apparition d'une panne.
• La figure 2 illustre dans une coupe par un plan PP' une vue en élévation d'un premier mode de réalisation du dispositif de purge.
• La figure 3 représente en coupe par un plan QQ' de la figure 2 une vue de dessus du dispositif selon cette figure.
• La figure 4 illustre un détail du clapet utilisé à la figure 2.
• La figure 5 représente en coupe une vue en élévation d'un second mode de réalisation du dispositif de purge.

Other features of the invention and a system for stopping the operation of a pneumatic installation implementing the device of the invention will be better understood on reading the description below and on examining appended figures among which:

• FIG. 1a schematically represents a pneumatic installation implementing the purge device according to the invention in a normal operating phase.
• Figure 1b shows part of the bodies of Figure 1a when a fault occurs.
• Figure 2 illustrates in a section through a plane PP 'an elevational view of a first embodiment of the purge device.
• 3 shows in section through a plane QQ 'of Figure 2 a top view of the device according to this figure.
• Figure 4 illustrates a detail of the valve used in Figure 2.
• Figure 5 shows in section an elevational view of a second embodiment of the purge device.

In the installation 1 visible in FIG. Ia, the compressed air source 2 of pressure “P is connected by the pipe 3 to a general pneumatic disconnector 4 which is represented here in its on state, where it allows the fluid to circulate towards a general distribution pipeline 5.

This passing state of the disconnector, which is maintained when a pressure control signal “P is applied to its control input 6, is switched when this signal disappears so that a connection is established between line 5 and a vent 7 opening atmosphere A (see Figure 1b, in a non-conducting state).

The general distribution line, the length of which can be significant, is connected at certain points to distributors such as 8 and 9 which are also connected to an exhaust manifold 10. The first 8 of these distributors supplies for example a first cylinder 11, without one or more speed adjustment devices being placed on one of the supply lines 12 or 13 so that the speed of movement of the piston of this cylinder is essentially determined by the characteristics of the load 14 that it displaces, and by the pressure P.

The second distributor 9 is connected to a second jack 17 by lines 15 and 16 which have speed regulators 18 respectively 19 on their path. These each comprise at least one throttle of adjustable value, such as 21, which is frequently placed in parallel on a one-way valve such as 20.

It is recalled that the function of such a speed regulator is to allow the fluid to move, either without hindrance from the distributor towards the cylinder, or with a certain slowing down when the fluid escapes from the cylinder towards the distributor.

In the state of the distributor illustrated in FIG. 1a, the piston tends to move to the left because a fluid enters the right chamber 22.

Between the left chamber 23 and / or right 22 of the cylinder and the speed regulator 18 and / or 19, is placed directly on the jack, a purge device according to the invention 24, 24 'whose internal constitution is described below. below and whose function is to connect the chamber 23, respectively 22, either to the speed regulator 18 respectively 19 in its active state, or to a vent 25 respectively 25 'opening to the atmosphere in its passive state. The pipe portion 15 'shown in FIG. 1a between the chamber 23 and the purge device is therefore as short as the material embodiment allows. The active state of the purge device 24 represented in FIG. 1a, is obtained by the application to an input 26 of a pressure control signal "P •, which is conveyed by the same line 27 as that leading to the input 6 of the general disconnector.

When the installation is operating normally, the displacement speed of the piston belonging to the jack 17 is determined not only by the nature of the load 28 but also by the speed regulators 18 and 19 which impose restrictions on the passage of fluids from the chambers and going to the exhaust manifold 10.

If an incident occurs in the installation, and it is necessary to interrupt its supply, the control pressure "PjL On line 27 is interrupted, and becomes" P for example using d 'A pneumatic emergency stop switch not shown, and the main disconnector 4 connects the pipe 5 to the atmosphere. Given the immediate proximity of the distributor 8, the disconnector 4, and the jack 11, the latter very quickly purges its chambers through the pipes 12, 10 and 13, 5 so that the movement of the piston is stopped in practice instantly.

On the other hand, if we examine the operation of the jack 17 which is distant from the disconnector 4, we note that the mere fact of connecting the line 5 to the atmosphere through the general disconnector 4 would not be sufficient in the absence of the device purge 24, to cause an instantaneous stop of the corresponding piston, on the one hand due to the existence of pressure drops in line 5, and on the other hand due to the presence of speed regulators 18 and 19. Indeed, the fluid which is enclosed in the chamber 22 is compressed to a value much higher than that which exists in the chamber 23 and, if these pressures do not decrease while preserving identical values, which is rarely the case due different speeds that must take the cylinders to go and return, it follows that the piston continues to move due to the difference in these pressures after the distribution line has been connected to the atmosphere.

Thanks to the installation directly at the inlet or at the inlets of the jack of one or two purge devices such as 24, 24 ', a short connection to the atmosphere of line 5 and rooms 22 and 23; it follows that the piston stops almost instantaneously in the position which is hers at the moment when the pressure of the control signal "P disappears, see figure 1 b.

It can also be seen that the state of rapid purging of the jack does not impose slow circulation on the air contained in the chambers 22 and 23 through the speed regulator (s) 20, 21 when the piston rod 29 must be actuated by hand, for example to carry out an adjustment or a verification of the positions that this rod can take, because on the one hand, the aspiration towards a chamber takes place in the direction of passage of the non-return valve , and on the other hand, the backflow coming from the other chamber escapes directly to the atmosphere.

It is clear that the pneumatic circuit of the installation which has just been described retains its interest if only one flow regulator is used and even if, in the absence of flow regulators, one or both pipes 15, 16 have a length such that the own pressure drops added to those of the line 5 and of the manifold 10 significantly slow down the emptying speed of the jack.

A purge device, in accordance with a first embodiment such as 24, is in particular visible in FIG. 2 where, to reduce as much as possible the length of pipe 15 'mentioned above, a controlled valve 30 for setting The exhaust has been combined with a known type swivel fitting 31 which is fixed directly to the wall of the cylinder 32 of a jack 17.

The swivel fitting essentially comprises a body 33 having a first through bore 34 of axis XX 'and a second bore 35 of perpendicular axis YY' which communicates internally with the first and which presents externally association means 36 with a pipe such that 15, or such as 15 ", if a speed regulating device (not shown) is placed between it and the distributor 9. The bore 34 is traversed by a hollow bolt 37 which cooperates with the bore in leaktight manner thanks to seals 38, 39 and one end 40 of which has a thread 41 capable of cooperating in leaktight manner with a corresponding thread 42 of the wall 32, for example by means of a seal 45 or a conical thread, while an opposite end 43 has a clamping head 44, for example polygonal.

The bolt has an axial through channel XX '46 connected by openings 47 to an annular space 48 placed between it and the bore 34. The region of this channel 46 opposite the thread 41 opens out through an orifice 49 in a cylindrical housing 50a, 50b which is hollowed out in the head 44 and which receives a part of revolution 51. The latter has an internal housing 52 which is placed opposite the orifice 49 and which receives a valve 30 capable of closing the latter by axial sliding XX ' in the housing 52. The external surface 53 of this part 51 circulates parallel to the housing 50a and has radial extensions 54 which are centered in the housing 50b to make the axis of the part 51 coaxial with XX ', see FIG. 3.

_. A first annular space 55 existing between the bottom of the housing 50a and the part 51 as well as a second annular space 56 existing between the housing 50a and the part 51 make it possible to connect the orifice 49 to the atmosphere 63 through radial spaces 57 placed between the radial extensions, see Figure 3.

The region of the part 51 opposite the housing 52 has a second housing 58 which is connected to the latter and which receives a small orientable connector 60 materializing the inlet 26 visible in FIG. 1a; this connector 60 is therefore connected to an external pipe 27 taking, for example, the form of a flexible plastic tube.

The operation of the rapid purge device results from the chosen arrangement, the presence or absence of pressures in the lines 27 and 15, 15 "respectively in the chamber 23 of the jack 17 and the ratio of the diameters of the orifice 49 and housing 52.

If it is assumed, which is the most frequent case, that during filling of the chamber 23 the pressure present in the pipe 27 is equal to the pressure in this chamber, one will obtain a closure of the orifice 49 by the choice of a diameter of the housing 52 greater than the diameter of this orifice. Under these conditions, the purge device behaves like a conventional connector.

If, in accordance with the operating principle set out above, the supply of fluid to the line 15, 15 "is interrupted and the pressure on the control line 27 is simultaneously interrupted, a purge of the fluid present in the chamber 23 will take place towards the atmosphere through the spaces 55, 56, 57 by lifting the valve 30 out of the orifice 49 which served as its seat.

In order to reduce the intensity of the noises during a purge and the penetration of foreign bodies into the purge device through the passages 55, 56 and 57, it is possible to place in this last passage a filter 61 having a very low loss of charge for the purge fluid. If this pressure drop should be even lower, an annular protective valve 62 could replace the filter and be placed above the outlet 63 of the passage 57. Such a valve, which can be produced from a elastomer sheet, is advantageously fixed in a groove 64 of the part 51, so as to bear elastically on the periphery 65 of the head 44 and to move away therefrom when the purge fluid comes to lift it.

The displacements of the free valve 30 which, in the embodiment of FIG. 2, are guided only by its elastic skirt, could also be guided by a rod 66 of cruciform section secured to the valve 30 'and movable in the channel 46, see figure 4.

It should be understood that to reduce the external dimensions of the device, there are preferably a number of its elements in the rod 67 of the bolt 37; the space aside, the advantages of the device remain the same if, for example the valve 30 is placed axially at the level of the head 44; the direction of the bolt head must therefore be understood as the region opposite to that which presents the thread.

In a second embodiment, visible in FIG. 5, the purge device 70 comprises a body 72 and a fixing bolt 73, on which a bent connection 71 can appear, containing, for example, a one-way flow regulator 100 , 101.

The body 72 has, in a tab 72 ', a bore 74 of axis XX' which passes right through it, and in a lateral extension 72 ", a bore 110 of axis YY ', perpendicular to XX', which opens out on the one hand, in the first bore and, on the other hand, through an orifice 76, towards a concentric housing 77 communicating with the outside.

In this housing is fixed a cylindrical part 79, for example by means of radial projections 89, which are applied to the internal surface 77 of the housing, and which leave between them and the external surface 80 of this part passages 81, 91.

This part has an internal end 85, which is located at a certain distance from the bottom 78 of the housing, and which has a cylindrical housing 83 in which is housed in a sliding and sealed manner, a valve 84 made of elastomer.

An internal channel 82 of the part 79 communicates with the housing 83 and with a quick pneumatic connector 86, which is fitted at the opposite end 90 to receive a pipe 27, for example flexible.

The bore 74 is crossed by a hollow fixing bolt 73 which has an internal channel 111 concentric with XX '. This channel, which communicates by lateral openings 95 with an annular space 96 situated between the bore 74 and the external surface of the bolt placed opposite, has a thread 92 at a first upper end.

The bolt has an upper head 94, for example provided with hexagonal flaps 93 for a tightening tool, and an end 99 carrying a thread 98.

Thanks to the interposition of seals such as 97 ′, 97 ″, the bolt can be tightly tightened in an opening 42 in the wall 32 of a jack 17. The bores 110 and 111 respectively represent portions 75 ′ and 75 "of an internal channel 75 of the purge device.

The points mentioned in 15 ", 15 'and 26 correspond to those of FIG. 1a, and correspond respectively to the pressure inlet, the pressure outlet and the control inlet.

A conventional elbow fitting 71 itself having a hollow connecting bolt 71 ′ can be screwed and tightly fixed by the latter in the thread 92 of the bolt 73.

These connections frequently present today, a flow regulator such as 101, adjusted by the adjustment button 102 and a one-way valve 100, these members being here represented symbolically.

A pipe 112 is connected to this connection at a point 15, which corresponds to that mentioned in FIG. 1a, and which is therefore supplied by a pneumatic distributor such as 9.

As in the previous embodiment, a filter 62 ′ can be placed between the passages 81, 91 and the exhaust 89; alternatively, the exhaust 89 can be protected, as in the previous mode, by a flexible annular part 88, similar to 62.

The operation of the second embodiment is identical to the previous one, namely that, when a control signal pressure is applied to point 26, the valve 84 closes the orifice 76 due to the fact that the diameter of the housing 83 has been chosen large enough compared to that of the orifice, to resist the force applied to it on the surface of the orifice.

A pressure applied at 15 therefore flows through the unidirectional valve 100 and passes through points 15 "and 15 'to supply the jack; when to obtain a reverse movement of the piston of the jack, point 15 is connected to the exhaust, the chamber 113 of the cylinder is emptied by 15 'and 15 "through the speed regulator 101.

If the pressure of the control signal and that present at 15 disappear simultaneously, the fluid present in the chamber 113 cannot escape quickly through the speed regulator, or due to any other pressure drop on the line 112 and on its extensions, its pressure raises the valve 84 and therefore connects this chamber to the atmosphere by the shortest route 25.

Claims (6)

1. An emergency drain device (24, 70) for a pneumatic cylinder (17) for causing this latter to stop and comprising a pressurized fluid supply inlet (15") which is connected to a pneumatic distributor (9), a fluid outlet (15') which is connected to a chamber (23) of the cylinder (17) and a control inlet (26) which receives a fluid acting on an internal pneumatic member (30, 84) adapted for connecting the fluid outlet (15') to the atmosphere or not, wherein said drain device (24, 70) has fixing means (37, 73) screwed directly to the body (32) of the cylinder (17) and comprises an internal channel (46, 75) connected to the supply inlet (15"), to the fluid outlet (15') and to an orifice (49, 76) communicating with an exhaust (25), this orifice being closed by an oppositely placed valve (30, 84) when a closing force is exerted thereon created by the pressure of the fluid at the control inlet (26), whereas this orifice (49, 76) is opened by the fluid escaping from the chamber (23) when the control pressure disappears.

2. The drain device as claimed in claim 1, characterized in that said fixing means are formed by a hollow bolt (37, 73) which passes through a bore (34, 74) in a body (33, 72) extending perpendicular to the axis XX' of the bolt and has a tightening head (44, 93) for, on the one hand, applying said body sealingly to the cylinder (17) body (32) and, on the other hand, receiving a pneumatic connector (60, 71).

3. The drain device as claimed in claim 2, characterized in that said pneumatic connector (60) receives the control signal at its inlet (26), whereas the bolt (37) comprises a valve (30) which is movable between an orifice (49) formed at one end of a channel (46) in this bolt and an added piece (51), this latter being disposed concentrically to the axis XX' of the bolt, so as to leave an annular space (55, 56, 57) free, going to the exhaust (25), the supply inlet (15") being placed in a body (33) which communicates with said channel (46).

4. The drain device as claimed in claim 2, characterized in that said pneumatic connector (71) receives the supply inlet (15") placed in the head (93) of a bolt (73) through which passes axially a channel (111), whereas the valve (84) is movable between an orifice (76) placed in said body (72), in communication with said channel and a piece (79) which is fixed in said body, while leaving in existence therewith an annular space (91) leading to the exhaust (89), said piece having a connector (86) which receives the input (26) of the control signal.

5. The drain device as claimed in one of claims 3 or 4, characterized in that the outlets (63, 89) to the exhaust (25) of the annular spaces are protected either by a filter (61) with a very low pressure loss or by means of a cover (62, 88) which moves away or is elastically deformed when the drain fluid flows.

6. The pneumatic installation using a drain device (24, 70) such as claimed in one of claims 1 to 5, characterized in that the control inlet (26) of said drain device is activated at the same time as the control inlet (6) of a general pneumatic isolating switch (4) adapted to connect a general supply duct (5) of this installation either to a pressurized fluid source (2) or to the atmosphere (A).

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