Patent Application
20050051382
This application claims priority to German Utility Model Application Number 203 14 134.2 filed Sep. 10, 2004.
The present invention relates to a silencer for the damping of noises occurring in pneumatic pressure systems as a result of pressure blow-off flows from a pressure side to an atmosphere side. The silencer consists of a housing surrounding an expansion space with a pressure-side inlet for the blow-off flow and an opposite atmosphere-side outlet.
Such a silencer is known by the term “expansion tube”. Silencing is based on the known principle of “double cross-sectional jump”, in that the inlet first widens into the expansion space (cross-sectional enlargement) and the latter transitions into the narrowed outlet (cross-sectional reduction). In addition, in the known expansion tube, a disc-shaped air filter (foam filter or sintered filter cartridge) corresponding to the inner cross section of the expansion space is arranged in front of and near the outlet for the purpose of filtering air sucked in from the atmosphere side via a compressor through the silencer. The known expansion tube is still not satisfactory where silencing is concerned.
The object on which the invention is based is to improve a silencer of the type mentioned in such a way that markedly more effective silencing is achieved.
To achieve this object, several novel inventive measures may be employed individually (alternatively) or else in a specific combination.
In a first measure according to the invention, a damping element is arranged within the expansion space in the vicinity of the inlet, specifically preferably directly in the connection to the inlet. This damping element consists of a dimensionally stable, but porous material through which a flow is therefore capable of passing. Thus, the blow-off flow flows through the damping element before, during or immediately after the first cross-sectional jump, thus bringing about highly effective silencing by the amount of at least 5 dB.
In addition to the special arrangement of the damping element in the region of the inlet, according to the invention, there may be provision, if appropriate, but also alternatively (irrespective of this), for the damping element to have a flow area through which a flow is capable of passing, which is larger than the inner cross-sectional area of the expansion space. Owing to this enlargement of the area available for the throughflow, effective silencing can likewise be achieved.
As a further solution according to the invention for achieving the above object, an insulating material, such as wadding or similar soft stuffable fibre material, may be arranged within the expansion space. This measure likewise leads to an improvement in silencing, specifically even without the damping element according to the invention or with a known disc-shaped filter element.
Finally, the ratio of the inner cross section of the expansion space to the cross section of the outlet should be in the range of between 2:1 and at most 30:1, and in this case it was recognized that, surprisingly (since it is contrary to theoretical considerations), it is precisely lower ratios, particularly in the region around 8:1, which lead to optimum damping. This may be achieved, for example, if a specific inner cross section (diameter) of the expansion space is accompanied by an enlargement of the cross section or diameter of the outlet.
Further advantageous design features of the invention are contained in subclaims and in the following description.
The invention will be explained in more detail with reference to a preferred exemplary embodiment illustrated in the drawing.
A silencer 1 according to the invention is to be arranged in an intake line (not illustrated) of a pneumatic pressure system. The silencer 1 consists of a cartridge-like housing 2 which surrounds an expansion space 4 and which has an inlet 6 located on one side and an opposite outlet 8. As illustrated, the expansion space 4 has an inner cross section A1 widened with respect to the inlet 6 and the outlet 8, according to the “double cross-sectional jump” principle. The inlet 6 is connected via a switching-valve arrangement, not illustrated, to a compressor 10 which builds up a pressure “p” in any pneumatic assembly 12. For this purpose, the compressor 10 sucks in air from an atmosphere side through the silencer 1, this being illustrated by broken arrows 14. For this intake flow 14, the outlet 8 actually forms an inlet and the inlet 6 actually forms an outlet. In specific operating states of the pneumatic pressure system, however, it is necessary at least partially to discharge the pressure p from the assembly 12, thus giving rise to a reverse blow-off flow, illustrated by unbroken arrows 16, which, on account of a flow velocity which is relatively high as a consequence of pressure, causes pronounced noises which are to be damped by the silencer 1. The blow-off flow (arrows 16) thus takes place from the pressure-side inlet 6 through the expansion space 4 to the atmosphere-side outlet 8.
As illustrated, furthermore, the inlet 6 and the outlet 8 may in each case be designed as connection pieces for the connection of pipelines or hose lines, not illustrated.
According to the invention, within the expansion space 4, a damping element 18 consisting of a porous material through which a flow is therefore capable of passing is arranged in such a way that the blow-off flow 16, and, of course, also the reverse intake flow 14, can flow through it. The damping element 18 thereby additionally also has a filter function. According to the invention, the damping element 18 is arranged directly in the connection to the inlet 6. In this case, the damping element 18 has a flow area through which a flow is capable of passing, which, in any event, is larger than the inner cross-sectional area A1 of the expansion space 4. For this purpose, in the exemplary embodiment illustrated, the damping element 18 is designed as an elongate hollow body with a porous body wall 20, the hollow body projecting freely from the inlet 6 into the expansion space 4. The hollow body, on its side facing the inlet 6, has an inflow orifice and opposite it has a closed bottom. The body wall 20 consists of a porous, but dimensionally stable plastic, in particular from the group of polyolefins, preferably of a porous high-density polyethylene (HDPE).
In the exemplary embodiment illustrated, a soft, flexible, stuffable insulating material 22, such as wadding or suchlike fibre material is additionally arranged within a region of the expansion space 4 which is adjacent to the damping element 18. By the damping element 18 being arranged accordingly to the invention on the side adjacent to the inlet 6, the insulating material 22 is consequently arranged in the region between the damping element 18 and the outlet 8, but may also be arranged at least partially within the outlet 8.
As a further measure according to the invention, there is provision for the ratio of the inner cross-sectional area A1 of the expansion space 4 to the cross-sectional area A2 of the outlet 8 to be at most 30:1. For especially effective damping, this ratio should, in particular, lie approximately in the range of 2:1 to 10:1, in particular around about 8:1. If, for example, the housing 2 or the expansion space 4 is a cylinder with a circular inner cross section and the outlet 8 likewise has a circular inner cross section, a diameter ratio of the inside diameter of the expansion space 4 to the inside diameter of the outlet 8 of between 1.5:1 and 6:1, in particular around about 3:1, is obtained.
The cartridge-like housing 2 expediently consists of two housing parts 2a, 2b, preferably made from plastic which are preferably connected via a latching connection 24 (snappable, in particular circumferentially closed positive or non-positive/positive connection). The damping element 18 is preferably connected via a threaded connection, not illustrated, to one housing part 2a in such a way that the blow-off flow 16 flows out of an inlet 6 directly to the hollow body of the damping element 18, and then through the wall 20 further on into the expansion space 4. An additional highly effective silencing is thereby achieved precisely in the region of the first cross-sectional jump. The large flow-through flow area of the damping element 18 also contributes to this. The damping element 18 may also be connected in one piece to the housing part 2a, for example in a materially integral manner by two-component injection, adhesive bonding, welding or the like.
The invention is not restricted to the exemplary embodiment illustrated and described, but also embraces all versions having an identical effect within the meaning of the invention. Thus, all the individual features of the invention may be provided alternatively or in any desired combination.
While the above description constitutes the preferred embodiment of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 203 14 134.2 | Sep 2003 | DE | national |
