GB2050503A

GB2050503A - Noise Mufflers for Valves in Compressed Air Equipment

Info

Publication number: GB2050503A
Application number: GB8008465A
Authority: GB
Original assignee: Wabco Fahrzeugbremsen GmbH
Current assignee: Wabco Fahrzeugbremsen GmbH
Priority date: 1979-03-15
Filing date: 1980-03-13
Publication date: 1981-01-07
Also published as: DE2910209A1; FR2451530A1; SE8001929L; IT8067345A0

Abstract

A housing containing sound- deadening material 3 bounding an expansion region 5 has an inlet 2 at one end and an outlet at the other end and at least one passage 4 extends longitudinally through the sound- deadening material to connect the expansion region 5 to the outlet. The end of the, or each, passage 4 is offset with respect to the, or each, inlet aperture. <IMAGE>

Description

SPECIFICATION Noise Muffler for Valve Devices in Compressed Air Equipment The invention relates to noise mufflers for valve devices in compressed air equipment, especially in vehicle braking systems.

Noise mufflers of this type are intended to reduce the blow-off noise which is produces, for example, when superfluous compressed air is discharged into the atmosphere from compressed air brake systems) to a sound level prescribed by the authorities. The noise muffler is generally fitted to a valve device built into or attached to a compressed air line system of the braking equipment, which valve device discharges into the atmosphere as part of its function.

In particular, it is the pressure regulators and relay valves (intended to regulate the operating pressure in compressed air braking systems) which are equipped with noise mufflers, since the sudden discharging into the atmosphere when a particular tank pressure is reached causes loud noises to be produced.

Noise mufflers are known which, in order to damp the flow of air, consist of resistance or deadening elements arranged in hollow bodies and deflecting the air flow as a result of their transverse position with respect to the air flow.

A noise muffler of this type, for compressed air braking systems, is described in German Offenlegungsschrift 22 53 995. This noisedamping device consists of a closed hollow body with sound-deadening elements composed of resilient material and with lateral air outlet channels leading out through the walls of the hollow body.

Noise mufflers constructed in this way only achieve an adequate effect, however, if they are of comparatively large volume. Moreover, although impurities and moisture from the braking system are eliminated by means of a separation apertuere in an end wall of the hollow body, dirt can penetrate through the lateral air outlet channels from outside and may block up the muffler. The same disadvantage applies to another form of noise muffling device which is open on all sides and composed of sinter material, while a still further form of noise muffler which is constructed on the exhaust principle (i.e. which consists of a body containing perforated metal plates connected in series and provided with central holes) has the disadvantage that it must be of relatively long construction in order to achieve adequate sound deadening.

An object of the present invention is to make it possible to provide a noise muffler which is not readily dirtied by impurities and moisture from the compressed air system, or in which dirtying is reduced to a minimum, and which is so designed that the penetration of dirt from outside can easily be prevented. In view of the limited space which is usually available to accommodate noise mufflers, a further object is to provide a muffler which can be manufactured with comparatively small dimensions. It is also desirable that a noise muffler should not affect substantially the operation of the valves and apparatus with which it is associated or produced an undesirable deterioration in the venting times.

The present invention provides a noise muffler for valve devices in compressed air equipment, comprising a housing with an inlet and an outlet in respective, opposed, end walls of the housing and a sound-deadening material arranged within the housing, there being an expansion area within the housing adjacent the inlet and limited by the sound-deadening material, and at least one passage running through the sound-deadening material substantially longitudinally of the housing to connect the expansion area with the outlet in the second end wall of the housing, the or each passage being so arranged that the end of the passage nearest to the inlet is offset with respect to the or each inlet aperture.

The invention will now be described in greater detail, with reference to two exemplary embodiments which are illustrated in the drawings, in which Figure 1 shows a noise muffler for valve devices which have a bunched central outlet, and Figure 2 shows a noise muffler for valve devices with outlets which are not bunched together but are distributed over a certain radius.

The noise muffler shown in Figure 1 is for valve devices of a braking system and consists of a cylindrical housing 1 which is open at one end and has a central inlet 2 at the other end, and the cavity of which contains sound-deadening material 3. In principle, any porous and air permeable material may be used as the sound deadening material 3, for example rock wool, spun glass (heat-resistant) or reticulated polyurethane foam (very high permeability to air).

Outside the central air entry region, i.e. near the walls of the cylinder, several passages 4 are provided which penetrate longitudinally through the sound-deadening material 3, with the diameter of the passages and the nature of the sound-deadening material 3 being so selected that the venting times and/or the operation of the braking system remain unaffected by the presence of the muffler. A free space remaining in the housing at the inlet end above the sound deadening material 3 acts as an expansion area 5 for the expansion of compressed air flowing in by way of the inlet 2. The open end of the housing (the outlet end) is closed by a cover acting as a non-return valve 6 which prevents the penetration of spray and dirt.

The operation of the noise muffler which has been described with reference to Fig. 1 is as follows: Compressed air flowing out of a valve device of the braking system is first led by way of the inlet 2 and inlet aperture 8 into the expansion area 5 and then onto the upper baffle surface 7 formed by the sound-deadening material 3. The expansion area 5 produces a uniform distribution of pressure over the sound-deadening material 3.

An addition air-permeable baffle plate 7a which is provided in the expansion area 5 protects the baffle surface 7 from overloading.

The air flow is discharged through both the sound-deadening material 3 and the free passages 4 out into the atmosphere by way of the non-return valve 6.

The housing 1 which is completely sealed by means of the non-return valve 6 ensures that the noise muffler operates effectively without being affected by outside influences.

The sound energy is substantially absorbed as a result of the incoming air flow being aimed directly onto the baffle plate 7a and/or baffle surface of the sound-deadening material 3, and the calming effect achieved by the simultaneous free expansion of the air in the expansion area 5 and the uniform diffusion through the sound deadening material, and also by the deflection and friction of the part streams of the air flow led through the free passages 4.

The configuration of the various features of the noise muffler, namely baffle surface 7 and additional baffle plate 7a (when present), expansion area 5, sound-deadening material 3 and free passages 4, allow moisture and impurities produced in the braking system to flow readily through the muffler: at the same time, the closure 6 at the outlet end prevents impurities entering from outside and, in this way, the noise muffler is protected against becoming blocked.

In Fig. 2 of the drawings, the reference numerals used correspond, where possible to those used in Fig. 1. In the muffler shown in Fig.

2, due to the form of the connecting flange of the valve device for the mounting of the muffler, the inlet 2 has several inlet openings 9. As a consequence, following the principle of the impact of inflowing air on baffle surface 7 of the sound-deadening material 3 (according to Figure 1), there is a single free passage 10 through the material 3, set in the centre of the muffler.

In this case, the passage 10 is lined by a plate 11 which could be omitted but which, when present, is perforated to allow the penetration of air from the sound-deadening material 3 into the passage 10, this being necessary for effective operation of the device. Similar perforated plates could be used to line the passages 4 in the Figure 1 embodiment.

A non-return valve (not shown) of appropriate form, corresponding to the non-return valve 6 of Figure 1, would be associated with the outlet 12 in Figure-2 to prevent impurities entering the muffler from outside.

The operation of this embodiment is the same as that described with reference to Figure 1 and, although only a single passage 10 is shown through the sound-deadening material 3, several passages could be provided if appropriate having regard to the positions of inlet openings 9.

In each of the embodiments described above, due to the introduction of longitudinal channel(s) 10, 4 running through the air-permeable material 3 contained in the housing 1 (in contrast to lateral air passages used in prior art mufflers), there is only the lower discharge aperture 12 to be protected from the action of impurities and moisture from the outside. At the same time the, of each, vertical passage 10, 4 allows any moisture and impurities produced in the braking system to flow out through the muffler, and the position chosen for the passage(s), which allows only an indirect inflow of the compressed air coming from the valve, ensures an optimum damping effect.

Finally, mufflers in accordance with the invention can be used for noise reduction generally, in any system in which air is blown off into the atmosphere, and are not restricted to use on braking systems.

Claims

1. A noise muffler for valve devices in compressed air equipment, comprising a housing with an inlet and an outlet inrespective, opposed, end walls of the housing and a sound-deadening material arranged within the housing, there being an expansion area within the housing adjacent the inlet and limited by the sound-deadening material, and at least one passage running through the sound-deadening material substantially longitudinally of the housing to connect the expansion area with the outlet in the second end wall of the housing, the of each passage being so arranged that the end of the passage nearest to the inlet is offset with respect to the or each inlet aperture.

2. A noise muffler according to claim 1, in which the outlet end wall of the housing is provided with a non-return valve opening to the exterior of the housing.

3. A noise muffler according to claim 1 or claim 2, in which the inlet comprises a single inlet aperture and there are a plurality of passages running through the sound-deadening material.

4. A noise muffler according to claim 1 or claim 2 in which the inlet comprises a plurality of inlet apertures and a single passage runs through the sound-deadening material.

5. A noise muffler according to claim 1, in which the inlet comprises a plurality of inlet apertures and there are a plurality of passages running through the sound-deadening material.

6. A noise muffler according to any one of claims 1 to 3, in which an air-permeable baffle plate is arranged in the expansion area between the inlet and the sound-deadening material.

7. A noise muffler substantially as described herein with reference to, and as shown in, Fig. 1 or Fig. 2 of the accompanying drawings.