Acoustic filter.

p0001The present invention relates to an acoustic filter comprising a body having an inlet port and an outlet orifice, a tube pierced with orifices connecting the inlet to the body of the outlet and intended for the circulation a liquid, a bladder made of a flexible and deformable material, the said bladder surrounding the tube and delimiting a chamber for a pressurized gas.

p0002These devices have drawbacks. Firstly there are clogging risks. In addition, they involve the risk of rupture of the bladder by extrusion of the elastomer through the holes of the central pipe when the hydraulic circuit is depressurized.

p0003The invention solves the problem of creating a filter in which the risk of rupture of the membrane are eliminated.

p0004This result is obtained thanks to the fact that the entire diffuser-holder mounted around the tube is made of a neighboring flexible material than the bladder and comprises orifices having a large passage cross section relative to that of the orifices of the tube.

p0005Preferably, the diffuser-holder assembly consists of diffuser rings fitted on the tube with a spacing determined so as to leave an annular passage for a fluid between two successive diffuser rings.

p0006The advantages obtained through this invention consist essentially in that the bladder does not deteriorate when in contact with the holder assembly diffusers. On the other hand, a large passage cross section is provided for the liquid.

p0007Furthermore, according to a particular characteristic of the invention, the diffuser rings are shaped such that the annular passages existing between two successive rings are open when the pressure inside the tube exceeds the pressure outside bladder and closed otherwise.

p0008More preferably, each diffuser consists of a metal frame externally surrounded by an elastomer ring.

p0009According to a first particular embodiment, the reinforcement has a male cone section, the elastomer ring having a shaped portion of female cone of larger diameter than that of the male cone.

p0010According to a second particular embodiment, each diffuser ring comprises a cylindrical metal reinforcement surrounded externally by an elastomeric ring having lips likely to get closer to those of the neighboring diffuser when a hydraulic pressure is exerted from outside on said rings.

p0011The invention is described below in more detail using drawings representing only one embodiment.<ul><li>- Figure 1 is an overall view, partly in section of an acoustic filter constructed in accordance with the invention.</li><li>- Figure 2 shows an enlarged sectional view of an end portion of the acoustic filter of the invention shown in Figure 1.</li><li>- Figure 3 is a perspective view, on an enlarged scale, of rings forming part of the embodiment of Figures 1 and 2. </li><li>- Figure 4 shows a sectional view of an end portion of a second embodiment of an acoustic filter in accordance with the invention.</li></ul>

p0012Figure 1 shows an acoustic filter constructed in accordance with the invention. This filter is intended to be mounted in line on a pipe. It is used to dampen the pressure waves caused for example by piston pumps or other equipment. It comprises for example a body 2 consists of a cylinder 2a to relatively thick walls, each end of which are mounted two screw fastening 2b. A slotted nut is screwed onto each of the fastening screws. A locking ring is mounted in a recess of each of the fastening screws. Inside the coupling rings are connections for connecting the filter to a pipe.

p0013At each end, a knurled cap 6 is screwed onto a thread of the cylinder 2a. A tube called a diffuser-holder tube connects the fitting located on the left end of the figure to the fitting at the right end. Distributors of rings according to the invention are mounted on the tube 7.

p0014Is shown in Figure 2 a sectional view of the acoustic filter of Figure 1. The tube 7 is pierced with orifices 13. Distributors, designated by reference 20a, are constituted by a frame 21a surrounded externally by a ring 23a in elasticity meter. Each armature 21a has a cylindrical shape of circular section. It is centered on the tube 7 from external polygonal section. It has at one of its ends a spacer consisting, in the embodiment described, four projections formed on the frame 21a. Of course, these spacers may also be formed by inserts.

p0015Is shown in Figure 3 a perspective view partially in section of three superimposed diffusers. Broadcasters rings 20a shown in the upper part of Figure 3 are longitudinal sectional views. We particularly note the slots 29 formed at the end of the frame 21a. In the embodiment described, there are four slots 29 that determine four passages 31 for the liquid. Of course, this number could be different according to another embodiment. One example would provide only three slots 29. Note also that the orientation of two consecutive rings relative to one another is irrelevant.

p0016The lower diffuser ring 20a shown in the lower part of Figure 3 is seen from the outside. Note the left free passage between two consecutive rings.

p0017In order to establish communication between openings 13 made in the tube 7 with the passage openings between two successive diffusers 20a, it is necessary to construct a manifold surrounding the diffuser-holder tube. The tube 7 has a polygonal external cross section, for example square. This form allows to identify four passages 33 between the sides of the square and the inner bore of the frame 21a. Four ports 13 located at 90 ° to one another are drilled in each of the square faces. Each hole 13 opens into a passage 33. It is noted that the orientation of the diffuser ring 20a relative to the square of the diffuser-holder tube is immaterial. Indeed, whatever the orientation, there is a sufficient relief area for the liquid. The tube 7 also ensures centering broadcasters rings 20a on the vertices of the square.

p0018The outer rings 23a (Figures 2 and 3) have a generally cylindrical shape of circular section. They have a shallow groove 23b of rounded profile on its outer surface. The upper and lower faces 23c of the ring 23a form with the axis of the tube 7, and therefore with the axis of the diffusers, an inside corner, that is to say less than 90 °. For example, this angle may be 75 °. Thus the faces of two successive rings 23a going towards and allow the fluid to an outlet space which is narrower than the input space as can be seen in Figures 2 and 3. These ridges thus form a type lip.

p0019The rings 23a are made of a material which is compatible with that of the bladder, so that it does not wear out or does not deteriorate when it is applied on the outer circumference of the rings. They are made of the same material as the latter, namely elastomer.

p0020In the embodiment of Figures 2 and 3, the space left free for the fluid closes when gas pressure-against is applied to the bladder. The nature of the materials present avoids puncturing the bladder so that it can withstand a fluid against pressure / fluid than 250 bars.

p0021According to the embodiment of Figure 4, elastomer rings 23a are molded directly onto the tube 7, thus forming a tube in one piece could also be made entirely of elastomeric for low pressure applications.

p0022According to the embodiment shown in Figure 5, the frame 21b has a tapered male portion 25 connected by a rounded portion. The outer ring 23b has an inner cone 27 whose diameter is larger than the diameter of the male taper 25 so as to leave a space between the two cones when the rings are mounted on the tube 7. The spacing between two successive rings is ensured by means of slots 29 made on the end part of the frame. The liquid flows through the space left free between the spacers 29.

p0023The advantages of the present invention are:     the tube 7 causes a low pressure loss. It is non-blocking. It does not filter the impurities that may be contained in the liquid, because of the large passage cross section offered to the fluid. It causes the fluid in the bladder 9 at reduced speed; he does not play the role of filter or oil trap; it supports without permanent deformation and without degradation of the fluid against pressures / fluid above 250 bars; it does not cause any deterioration in the bladder when it is applied to the tube under the effect against a pressure greater than 250 bars.