EP1734260B1 - Silencer for pneumatic drive - Google Patents

Abstract

The muffler has a casing body (2) linked with an exhaust port of a control valve. The body exhibits a porous, air-permeable base structure and includes a cavity. The casing body has a pressure sensor (6), pressure sensor that produces warning signal and switches off pneumatic drive when impact pressure within cavity increased due to increased contamination of muffler reaches a predetermined limit pressure.

Description

The invention relates to a muffler for damping the exiting at pneumatic control valves of a pneumatic actuator sound pressure consisting of a housing-like body which is coupled to the vent port of the control valve, wherein the body has a porous, air-permeable basic structure and includes a cavity, wherein the body with a Pressure sensor is provided, which causes a warning signal and / or a shutdown of the pneumatic actuator with increasing contamination of the muffler and the concomitant increase of the dynamic pressure within the cavity at a pre-definable limit pressure.

For pneumatic actuators in the form of double-acting pneumatic cylinders, pneumatic control valves are used to control them. Such double-acting pneumatic cylinders are characterized in that they can be activated in both directions of movement. For this purpose, a piston is provided in the cylinder tube of the pneumatic cylinder, from which a piston rod is guided in the axial direction outward from the cylinder tube. This piston divides the cylinder tube into two pressure chambers, so that when alternating pressurization the pressure chambers of the pistons in one or the other

Direction is adjusted.

It is known to apply by appropriate control valves via a pressure line, first, the first pressure chamber with pressure and at the same time to vent the second pressure chamber via the pressure line. This vent is also switched by the control valve. If now the pneumatic cylinder or its piston to move in the opposite direction, the control valve is reversed and the second pressure line of the second pressure chamber pressurized, while the pressure line of the first pressure chamber for venting the first pressure chamber is "unlocked". Since this reversal takes place abruptly and thus abruptly degrades the pressure to be released in the respective pressure line, this is always connected by the sudden pressure reduction with a higher noise level. In this case, a vent port is provided on the control valve for each pressure line, to which the respective pressure line is switched when their "activation". To dampen the noise level, it is known to provide these exhaust ports with mufflers to achieve quieter operation of the pneumatic actuator.

Such mufflers usually have a box-like body, which is connected to the vent port. In this case, this body may for example be provided with a connection thread and screwed directly into the vent port. In order to dampen the pressure reduction and at the same time as possible to the air flow flowing from the pressure chamber to be vented To counteract low flow resistance, the body has a porous and air-permeable basic structure, which usually includes a cavity. Thus, when the pressure line is disconnected, the air pressure contained therein can be dissipated via the vent connection and the silencer, sound-damping being effected.

It has now been found that during prolonged operation of such a pneumatic drive such mufflers are added in particular from the inside by contamination. Since this clogging occurs essentially from the cavity, this is barely visible to the outside. With increasing degree of contamination thus the air permeability of the muffler is reduced, so that always builds up in the muffler when venting an ever-increasing backpressure. By this counter-pressure, however, the movement speed of the pneumatic cylinder is considerably reduced. As a rule, this results in the operator increasing the operating pressure for operating the pneumatic cylinder in order to be able to maintain or restore the desired working speed of the pneumatic cylinder. In order to perform an increase in pressure, it is therefore necessary to size the air compressor larger in order to maintain just this operating speed can. This is on the one hand constructively related to the compressor with higher costs and on the other hand with higher operating costs, since this compressor has to generate a higher operating pressure.

Only when the operating pressure can not be increased, so the silencer is changed. Only after changing the muffler can then be used again with the original, lower operating pressure.

By expressly referring to Article 54 (3) EPC, reference should be made to EP 1 555 400 A1 which discloses a silencer for pneumatic machines. In this article, a cylindrical, outer filter element is provided, which is fixedly connected to a connecting piece. This connection piece is used to connect the silencer with a corresponding outlet of the machine. The outer filter element consists of a porous, air-permeable material and is accordingly flowed through by damping the sound pressure from the air stream flowing out of the machine. In this outer filter element, an inner filter element is inserted adjustable. Increases now the "dynamic pressure", for example, due to contamination in the outer filter element, the inner filter element is moved out of the outer filter element, so that the "filter surface" of the outer filter element increases and the "back pressure" is reduced again. This process is repeated until the inner filter element has been pushed out to a maximum from the outer filter element. After the last adjusting movement, a subarea of the filter surface of the outer filter element was likewise released again. after this part has "clogged up" due to soiling, the filter must be cleaned or replaced. Although the adjustment of the inner filter element to the outer filter element is visible to the outside, but not when the muffler after execution the last setting movement is actually so far polluted that a cleaning or replacement is required.

From the GB 1 297 228 A1 Further, an "exhaust muffler" is known, which consists of two "dome-shaped" interconnected, a cavity enclosing damper elements. These damper elements are made of a porous material and are used tightly in an outer end region of an actuating cylinder. This actuating cylinder is in turn arranged adjustably in an outer cylinder. In this case, the actuating cylinder is in an inner starting position in close communication with an air inlet, through which the sound pressure of an air flow is supplied to the muffler. This air flow flows through the two damper elements to the outside. Increases now the back pressure in the actuating cylinder due to increasing contamination of the two damper elements, the actuating cylinder is adjusted relative to the outer cylinder to the outside. The outer cylinder has in its lying towards the air inlet end region breakthroughs, which lead directly into the atmosphere. These breakthroughs are released by the actuating movement of the actuating cylinder, so that the air flow passes directly from the air inlet through the openings to the outside into the atmosphere. Due to the increased noise level and the outward recognizable adjusting movement of the actuating cylinder is thus indicated that the damper element to be cleaned or replaced. This device is characterized in particular by an extremely complicated structure, so that the disassembly for the purpose of the exchange or the Cleaning the two damper elements is very complicated to accomplish.

The invention is accordingly an object of the invention to design a muffler of the generic type such that with a simple structure, at least from the outside easily recognizable, at which time this muffler is added by pollution and must be replaced.

The object is achieved in that the pressure sensor consists of a housing arranged in a pressure piston, which is deflected when exceeding the limit pressure and that the pressure piston is coupled to a signal pin, which is pressed visible in the deflection of the plunger from the housing.

The embodiment according to the invention provides a silencer, in which it can be seen in the simplest manner when it is to be exchanged or cleaned. For this purpose, an existing from a pressure piston pressure sensor is provided which causes a warning signal with increasing pollution at a predetermined limit pressure. This warning signal can be optical, acoustic or otherwise. By this recognizability of the state of the muffler, the operator can replace it early and / or clean, so that you do not have to work with increased operating pressures. Furthermore, it can also be provided that the pneumatic drive is switched off. In this case, the pressure piston is arranged in a housing and is deflected when the limit pressure is exceeded. This pressure piston is further coupled to a signal pin, which is visibly pushed out of the housing when the pressure piston is deflected. In this simple embodiment, the operator can thus easily detect an inadmissible degree of contamination or an unacceptable pressure increase in the cavity formed by the muffler and replace the muffler.

In order to keep the pressure piston in a non-deflected position, can be provided according to claim 2, that a return spring is provided for adjusting the limit pressure in the housing. Against the spring force of this return spring, the pressure piston is deflected when the limit pressure is exceeded. Thus, this solution variant is extremely simple and inexpensive to manufacture.

However, according to claim 3, the pressure piston can also be held in the housing by friction, which can be achieved for example by an appropriate choice of the material for the pressure piston. When a certain limit pressure is exceeded, this static friction is now overcome and the pressure piston deflected. This solution variant is extremely simple and inexpensive to produce.
In particular, this solution variant can also be embodied as an injection-molded component. This solution variant has the advantage that the pressure piston and thus also the signal pin, remains in its deflected position.

According to claim 4 it can be provided that an electronic monitoring device can be activated by the signal pin, which optionally emits an additional visual or audible warning signal. This configuration is always one for controlling the pneumatic Control valve existing electronic control device with einbeziehbar.

This electronic control device can also be controlled according to claim 5 such that an electronic monitoring device can be activated by the signal pin, by which the control valve is deactivated. This means that when the limit pressure is exceeded, the control valve and thus the pneumatic drive is switched off, so that the operator must inevitably change the muffler. Such a configuration may be necessary in manufacturing processes in which it is absolutely necessary that the pneumatic drive is always to operate at the maximum speed.

Due to the configuration according to claim 6, the coupling of the muffler to the control valve is extremely easy to carry out. For this purpose, the body is tubular and can be tightly coupled by means of a threaded connector with the vent port. Further, the pressure sensor with the tubular body or a receiving housing, in which the body is interchangeable inserted by a press or threaded connection to be removably connected. This in turn has the advantage that even a defective pressure sensor can be replaced in the simplest way.

In summary, it should therefore be stated that the operating state of the silencer according to the invention can be checked in the simplest manner and this silencer can be exchanged if necessary in the case of an appealing pressure sensor. This is the operational safety of the pneumatic actuator significantly improved, but in particular an increase in pressure during operation is not necessary, since clogging by contamination of the muffler is always recognizable by the operator.

Fig. 1

einen Vertikalschnitt durch ein erstes Ausführungsbeispiel eines erfindungsgemäßen Schalldämpfers mit Drucksensor in seiner Ausgangsstellung;

Fig. 2

den Drucksensor aus Fig. 1 im Vertikalschnitt in seiner ausgelösten Position;

Fig. 3

einen Vertikalschnitt durch ein zweites Ausführungsbeispiel eines erfindungsgemäßen Schalldämpfers mit Drucksensor in seiner Ausgangsstellung;

Fig. 4

den Schalldämpfer aus Fig. 3 im Vertikalschnitt in seiner ausgelösten Stellung;

Fig. 5

eine schematische Prinzipdarstellung eines Pneumatikantriebes mit einem Steuerventil und einem doppelseitig wirkenden Pneumatikzylinder.

Reference to the drawing, the invention is explained in more detail by way of example below. It shows:

Fig. 1

a vertical section through a first embodiment of a muffler according to the invention with pressure sensor in its initial position;

Fig. 2

the pressure sensor off Fig. 1 in vertical section in its triggered position;

Fig. 3

a vertical section through a second embodiment of a muffler according to the invention with pressure sensor in its initial position;

Fig. 4

the silencer off Fig. 3 in vertical section in its tripped position;

Fig. 5

a schematic diagram of a pneumatic actuator with a control valve and a double-acting pneumatic cylinder.

Fig. 1 shows a silencer 1 according to the invention in vertical section. This silencer has a body 2, which is tubular and consists of a porous, air-permeable material. This body 2 defines a cavity 3 and causes a sound attenuation when venting a pressure line of a pneumatic drive. At the lower end of the tubular body 2 is provided with a, this body 2 occlusive connection element 4, which has a coupling thread 5. By means of this coupling thread 5, the muffler 1 according to the invention, for example, with a vent port of a control valve directly coupled.

The tubular body 2 is closed at its end opposite the connecting element 4 by means of a pressure sensor 6. This pressure sensor 6 has a housing part 7, which in the present embodiment is pressed onto the tubular body 2 via a slight press fit. This interference fit is designed such that the housing part 7 in case of need, for example in case of defect of the pressure sensor 6, from the tubular body 2 is manually removable.

The housing part 7 has a central through-bore 8, in which a signal pin 9 of a pressure piston 10 is inserted axially displaceable. To limit the stroke of this pressure piston 10 and the signal pin 9 in the through hole 8 is in the present embodiment a guide pin 11 is provided, which engages in a guide slot 12 of a guide cylinder 13 of the housing part 7 positively and axially adjustable. The maximum travel of the pressure piston 10 is thus precisely defined over the length of the guide slot 12 in the guide cylinder 13. To the pressure piston 10 in his in Fig. 1 To keep the initial position shown, a return spring 14 is provided, the spring forces are dimensioned such that the pressure piston 10 is deflected upon reaching a certain, acting in the cavity 3 limit pressure in the direction of arrow 15 upwards.

Due to the deflection of the pressure piston 10, this passes into the in Fig. 2 shown, deflected upwards end position. In this end position, the signal pin 9 protrudes beyond the outer end face 16 of the housing part 7, so that it is visible from the outside by the operator. Thus, the operator is able to recognize that the tubular body 2 is added by contamination and thus the flow of air is hindered such that in the cavity 3, at least for a short time, the pressure when venting a pressure line of a pneumatic actuator on the limit has risen.

It can be seen that this pressure sensor 6 is extremely simple and has an extremely high reliability. The pressure piston 10 is slightly smaller in its diameter than the inner diameter of the tubular body 2, so that between the pressure piston 10 and the body 2, an annular gap 17 is formed. Thus, the pressure piston 10 with its signal pin 9 is approximately frictionless both in the guide cylinder thirteenth as well as received in the tubular body 2, so that a limit pressure on the spring force of the return spring 14 is relatively precisely adjustable.

Fig. 3 shows a vertical section of a second embodiment of a muffler 20. In this muffler 20, the sound-absorbing, porous and air-permeable body 21 is formed as a cylinder tube and interchangeable inserted into a receiving housing 22.
This receiving housing 22 has in its side walls in the axial region of the tubular body 21 a plurality of radial, approximately over the entire length of the body 21 extending openings 23.

Furthermore, the receiving housing 22 is also provided in the region of its lower end with a coupling thread 24, via which the receiving housing 22 with a corresponding vent port of a control valve is tightly coupled. Also, the tubular body 21 includes a cavity 25, which communicates via a corresponding vent hole 26 with the pressure line to be vented of a pneumatic drive.

According to the embodiment Fig. 3 is in the receiving housing 22 on its, the coupling thread 24 opposite end, a pressure sensor 27 screwed interchangeable via a threaded connection 28. This pressure sensor 27 has an outer end wall 29, which is provided with a central through-bore 30 into which a signal pin 31 of a pressure piston 32 protrudes suitably. In this embodiment, the housing 33 of the pressure sensor 27 and the pressure piston 32 with be made a signal pin 31 as a plastic injection molded part.

In the embodiment according to the 3 and 4 it is provided that the pressure piston 32 is held by friction in the housing 33. Now increases with increasing contamination of the tubular body 21 when venting a pressure line of a pneumatic actuator, the pressure in the cavity 25 over a predetermined limit pressure, which is determined by the static friction of the pressure piston 32 in the housing 33, the pressure piston 32 from the in Fig. 3 illustrated starting position in the in Fig. 4 pressed end position shown. That is, the pressure piston 32 at a corresponding limit pressure is exceeded in the direction of arrow 15 from the in Fig. 3 illustrated starting position in the in Fig. 4 shown end position is pressed.

It can be seen that also in this case the signal pin 31 protrudes from the outer end face 34 of the housing 33, so that the exceeding of the limit pressure for the operating personnel is recognizable. In the embodiment according to the 3 and 4 Thus, when this limit pressure is reached, the body 21 can be replaced by a new body 21, so that the muffler 20 in turn receives its optimal permeability.

Fig. 5 shows a schematic representation of a pneumatic actuator 40, which is formed from a double-acting pneumatic cylinder 41 and a, this pneumatic cylinder 41 controlling control valve 42. The pneumatic cylinder 41 has, as from the prior art is known, a cylinder tube 43, in which a pressure piston 44 is received axially adjustable. With this pressure piston 44 is a piston rod 45 in communication, via which an actuating movement of the pressure piston 44 is transmitted to the outside. It can be seen that the pressure piston 44 divides the cylinder tube 43 into a first pressure chamber 46 and a second pressure chamber 47.

The first pressure chamber 46 is connected via a first pressure line 48 to a first pressure port 49 of the control valve 42 in connection. The second pressure chamber 47 is in turn connected via a second pressure line 50 with a second pressure port 51 of the control valve 42 in connection.

Next is out Fig. 5 it can be seen that the control valve 42 has a first vent connection 52 and a second vent connection 53. With these venting ports 52 and 53, a muffler 1/1 and 1/2 respectively coupled, wherein the muffler 1/1 and 1/2 in Fig. 5 are shown only schematically. Next, a pressure line 54 is connected to the control valve 42, via which the control valve 42 and the control valve 42 to the pneumatic cylinder 41, the corresponding operating pressure is supplied alternately.

In the in Fig. 5 shown first functional position of the control valve 42 is supplied via the control valve 42 of the supplied via the pressure line 54 system pressure via the first pressure port 49 and the first pressure line 48 of the first pressure chamber 46 of the pneumatic cylinder 41. The second pressure line 50 of the pneumatic cylinder 41 is via the second pressure port 51 via the control valve 42 switched to the second vent port 53.

In this functional position, the pressure chamber 46 is thus subjected to system pressure, so that the pressure piston 44 is displaced in the direction of the arrow 55. At the same time, the operating pressure applied in the second pressure chamber 47 is reduced via the second pressure line 50, the second pressure port 51 and via the control valve 42 to the second venting port 53 via the silencer 1/2.

After the pressure piston 44 of the pneumatic cylinder 41 has moved into its right end position in the direction of the arrow 55, the control valve 42 can now be reversed for the return movement. In this second functional position, the second pressure chamber 47 is acted upon by the second pressure line 50 and the second pressure port 51 with operating pressure. At the same time, the first pressure chamber 46 is connected via the first pressure line 48 and the first pressure port 49 to the first vent port 52, so that the previously applied operating pressure in the first pressure chamber 46 is reduced via the silencer 1/1 at the first vent port 52. Since the switching operations of the control valve 42 are substantially abrupt, there is also a sudden pressure reduction in the respective pressure chamber 46 and 47 when switching the control valve 42. This sudden pressure reduction leads to a certain sound pressure, which by the two silencers 1/1 and 1 / 2 is degraded, so that here on this silencer 1/1 and 1/2 a corresponding sound attenuation is effected.

Instead of purely mechanical pressure sensors, as exemplified in the Fig. 1 to 4 are shown, also electronic pressure sensors may be provided, which control a corresponding control device (not shown in the drawing) such that this control device emits or causes a corresponding audible or visual warning signal. Furthermore, it can also be provided that the entire pneumatic drive 40 is switched off when the adjustable limit pressure is exceeded when the warning signal is present.

It can also be provided that by the signal pins 9 and 31 on the respective pressure sensor 6 and 27 attached microswitch is actuated, by which in turn a corresponding control signal for delivering a warning signal is delivered to an electronic monitoring device, which in turn an acoustic or optical Warning signal and / or a shutdown of the pneumatic actuator 40 causes.

It can be seen that the functioning of the respective muffler 1, 1/1, 1/2 or 20 can be checked in a simple manner by the mufflers according to the invention with their pressure sensors 6 and 27.

Claims (6)

1. A silencer (1, 20) for silencing the sound emanating from the pneumatic control valves (42) of a pneumatic drive (40), consisting of a housing-like body (2, 21), which can be coupled with the air outlet connection (52, 53) of the control valve (42), wherein the body (2, 21) has a porous, air-permeable basic structure and encloses a cavity (3, 25), wherein the body (2, 21) is provided with a pressure sensor (6, 27), which upon increasing levels of dirt in the silencer (1, 20) and with the associated increase in stagnation pressure inside the cavity (3, 25) at a predeterminable limit pressure triggers a warning signal and/or switches off the pneumatic drive,
   characterised in that
   the pressure sensor (6, 27) consists of a pressure piston (10, 32) arranged in a housing (7, 33), which pressure piston is displaced when the limit pressure is exceeded, and in that the pressure piston (10, 32) is coupled to a signal pin (9, 31), which upon the displacement (arrow 15) of the pressure piston (10, 32) is pushed visibly out of the housing (7, 33).
2. The silencer according to claim 1, characterised in that for the adjustment of the limit pressure in the housing (7) a restoring spring (14) is provided, against the spring force of which the pressure piston (10) is displaced when the limit pressure is exceeded.
3. The silencer according to claim 1, characterised in that the pressure piston (32) in the housing (33) is held by static friction, and in that on exceeding the limit pressure the static friction is overcome and the pressure piston (32) is displaced (arrow 15).
4. The silencer according to claim 1, 2 or 3, characterised in that by means of the signal pin (9, 31) an electronic monitoring device can be activated which optionally emits an additional optical or acoustic warning signal.
5. The silencer according to claim 1, 2 or 3, characterised in that by means of the signal pin (9, 31) an electronic monitoring device can be activated, by means of which the control valve (42) is deactivated.
6. The silencer according to one of claims 1 to 5, characterised in that the body (2, 21) is designed to be tubular and can be tightly coupled with the air outlet connection (52, 53) by means of a thread connection (4, 5, 24), and in that the pressure sensor (6, 27) is connected removably with the tubular body (2) or a mounting housing (22), in which the body (21) inserted replaceably, by means of a press or thread connection (28).

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