DE3923530A1 - Pressure compensator between machine housing and ambient atmos. - includes liq.-tight, but gas permeable membrane supported on less resilient grid - Google Patents

Abstract

The pressure compensator (2) comprises a breathing element (3) which covers an opening (4) in the housing (1) and a breathing passage (8) for alternate flow directions with a gas permeable device, which retains a lubricant. The device is a plastics membrane (10) which is gas permeable, but liq-tight in the operating pressure range. The membrane has a support grid (13) of less elastic material. The membrane and grid are pressed together sealingly against an elastic backing (12) by a hold-down member (9) at their edges, and can swing about a rest position. ADVANTAGE - Self-cleaning effect, reduced maintenance, and oil mist formation.

Description

The invention relates to a pressure equalizer according to the Preamble of claim 1 and is based on the pressure equalization Oil ejection from the housing to prevent air bleeding Filter cartridges for dirty environments. Such z. B. known from the FR 24 14 849 pressure equalizer Filter inserts have the disadvantage that there is no blow-off without any lubricant ejection and no suction without gradual penetration of dirt is possible. Therefore need they are actually a very frequent maintenance. Mostly knows such pressure equalizers than in the wall of machine housings screw-in insert body, in which felt or fabric under held a cover plate leaving a breathing gap is.

Blown off when heated and then in the surrounding area Precipitation oil mist not only often deceives one Leak before. In the oil-soiled, sticky greasy There will soon be strong dirt accumulations in the environment, and the respiratory gap can eventually become completely blocked. The associated breakdown of the ventilation function then to a certain overpressure in the machine housing and in the Consequences to the destruction of the filter or to intolerable real ones greater oil losses through other openings in the housing. Light then it happens that shaft seals etc. act like valves, since they are not designed for overpressures.

With such conventional pressure equalizers, whose Internals consist of separator internals and filter material also achieved no reliable water resistance, as z. B. when using tractors in rice fields or in others machines to be used under water is required to Exclude water ingress into the machine housing. Wrong or lack of maintenance often leads to the failure of such itself pressure compensators that appear simple.  

Avoiding liquid spills under Maintaining breathability is now possible a device for venting pipes, fermentation tanks etc., with the help of a known one liquid-tight membrane material the leakage of liquid can be prevented, shows EP-A-01 55 115. Thereby becomes a filter that is a gas permeable waterproof Plastic membrane with a gas and water permeable Support base commonly used to protect the membrane against overpressure to protect on the liquid side. As materials for this the base immediately after the membrane is mentioned Plastic fleece, foam and fabric, sintered metal, ceramic as well as wire screens. It also suggests membrane and To connect the base to each other using a plastic edge.

However, this type of ventilation is not yet suitable for Machine housing. The constipation problems outlined above continue to exist because it is still too or dust accumulation with which the pressure compensator sucking back clean air, e.g. B. when cooling from Machine housings etc., is prevented. Especially the one alone provided rigid arrangement of membrane and base in Breathing body is not suitable, the membrane is maintenance-free Keep clear of blockages even if the air side of the Pressure equalizer is heavily contaminated.

The object of the invention is seen in it, really liquid-tight and no more oil mist draining To create pressure equalizers for machine housings, which in rough outdoor use and with heavy dirt outside have significantly longer usability and normally none Maintenance efforts require more by doing one thing with little construction effort permeable to air or gas in both directions, but if possible no longer permeable to oil or water are, but also clean themselves.  

The solution to this problem is the pressure equalizer essentially according to the characterizing part of claim 1 achieved that now known from water pipe fans, etc. Material to a functional design Lubricant outflow preventer is used. The liquid-tight but highly gas-permeable membrane wafer-thin, microporous plastic film under one or double-sided assembly with flexible but more flexible Backing material (such as glass fiber fleece, perforated film, Plastic fiber fabric etc.) so flexible and all-round bendable clamped by the respiratory duct that they both against mechanical damage from dirt accumulation is protected as also so far due to pollution-related pressure differences dentable remains that when changing the contamination-related pressure differences flutter or vibrate can, creating a self-cleaning effect with shaking and Breaking as well as blow-off of the membrane coverings is achieved without that the membrane tears itself or its liquid-sealing Loses effect.

For this purpose, the film has at least one on the lubricant side Freedom of movement in the housing of the pressure compensator, in which into it can bulge in and out with relatively little resistance. The associated alternating deformations are wanted, thus any deposits on the outside of the membrane be prevented from caking.

Further advantages are given in the subclaims specified embodiments achieved.

• - The free space is particularly effective by two to each other spaced and flexibly supported membranes provided are where the inner is the oil from the space keeps away. The outer membrane prevents water from entering and protects the space from dust etc.  
• - Depending on the direction of printing, their circumference can differ an elastomer ring elastically clamped membranes bulge outside or inside, and again and again if necessary automatically periodically free of deposits by they also repel or break open incrustations.
• - With the spaced clamping of two membranes at least one of its own support bases can be one further increase in tool life can be achieved.
• - Leave with the membrane's own physical values particularly favorable functional properties Achieve pressure equalizers according to the invention.
• - When using one also for high and low temperatures suitable plastic, such as. B. PTFE, will be a very long lifespan with good ventilation performance too achieved under extreme conditions. The are preferred Films of the membrane with a thickness of approx. 0.01 to 0.10 mm with a pore size of approx. 0.2 to 2.0 µm and one Porosity of about 80 to 100% and then remain Oil-tight up to approx. 2 bar inlet pressure. The preferred used plastic PTFE has a very high Chemical resistance between -240 ° C to + 270 ° C.
• - By using a pre-assembled and the membrane Protective insert body can be different Machine housing with pressure equalizer of the same design and Equip arrangement options.
• - If a dirt deflector in the insert body immediately is integrated, so is the dirt content to be kept controllable as little as possible.
• - If the dirt deflector is arranged in the housing jacket a damage-protected inclusion in the Housing contour relieved.
• - When arranging a breathing opening within a bell-shaped cover, preferably around the top Fifth of the same, the membrane comes into the area lowest air flow velocities and is thereby also through the cover against possible mechanical  Damage and immediate blockages from Deposits and ice formations are well protected, as these can be done outside the cover.
• - With a resilient textile membrane on an elastic Sealing ring press-on snap lid as a hold-down in addition to a simple, damage-proof installation also z. B. changes in flow direction or others Reasons sufficient for changing sealing force direction compliant self-sealing achieved.
• - By in parts of the lower edge of the cover Sieken made you get next to a row slot-shaped passage cross-sections not only on the circumference good shock resistance, but also a fuse against unauthorized or incorrect opening and Reinstall the membrane.
• - Insert body in the form of screw-in nipples similarly known Refinements can be made with a circular membrane be provided to z. B. in tapped holes from Machine housings to be used.
• - By designing the insert body as a ring cassette and Use an annular membrane in radial Arrangement can be the pressure equalizer Allocate shaft seal axially or radially. With the radial allocation would save construction length and the cassette only in an enlarged bearing bore with the Shaft seal used together. With axial assignment a small diameter would be possible.
• - Thanks to the good elasticity of the textile membrane, the same can with double use of the installation space also in one Sealing element made of elastomer material immediately e.g. B. be fitted by gluing, so that in such No separate pressure compensation element at all is more necessary.  
• - A particularly favorable placement of the textile membranes results when using the same in a parallel to Shaft provided and this at a distance outside enclosing shell-shaped sealant part, in which the textile membranes in centrifugal direction in appropriate window is glued, with an axial Covering the windows by a housing collar or a Socket causes advantageous dirt repellency.

The invention opens up the physical advantages of special membrane material now also for Special applications in the ventilation or degassing of Oil-carrying machine housings, which cause considerable pollution from inside and outside and the ongoing change of Are exposed to environmental conditions. So far they were technical Applications of the proposed membrane materials only for large coverage of sensitive electronic elements and in biotechnology with membranes loaded on one side become known and their use as a combination of overpressure and ventilation valve, oil separator and water intrusion protection on machine housings that are also exposed to external pollution has not yet taken place or was suggested and was one Self-cleaning in rough use has not yet been achieved.

The invention is not based on the combination of features Claims limited. There are more for the person skilled in the art reasonable combinations of claims and individual Claim characteristics from the task.

The invention will now be described more schematically Drawings of exemplary embodiments explained in more detail.

Fig. 1 shows a pressure equalizer with two membranes in an insert body shaped as a screw-in nipple;

Fig. 2 shows an enlarged section of membranes clamped between a clamping cover and an O-ring serving as a spacer with a space that remains free of dirt and oil;

Fig. 3 shows the pressure equalizer in the form of an insert body designed as a ring cassette, which encloses a shaft seal radially on the outside;

Fig. 4 shows a pressure compensator, also designed as a ring cassette, which is arranged axially upstream of a shaft seal;

FIG. 5 shows a pressure equalizer which is designed directly as a sealing element and has windows which are embedded in the sealing elastomer and are closed by the membrane.

In FIG. 1, the pressure compensator 2.1 is inserted in a machine housing 1 by means of a complete insert body 3.1 designed as a nipple into a housing opening 4 , in which it is fastened by thread 5 while compressing the housing seal 6 . The insert body 3.1 is covered by a bell-shaped cover as a dirt deflector 7 on the outside such that an air gap remains free by a distance A approximately corresponding to the free cross section of the breathing channel 8 penetrating the insert body 3.1 . The breathing channel 8 is closed off from this air gap under the cover 7 by means of a holding-down device 9 clamped on the insert body 3.1 by two membranes 10 A + 10 B serving as dirt trap and lubricant outflow preventers, made of liquid-tight but gas-permeable membrane material known per se. The inner membrane 10 B must be oil-tight and the outer 10 A at least watertight, so that the space remains free of oil and water and the outer membrane 10 A offers space for bulging. The hold-down device 9 here has one or more bores 11 above the breathing channel 8 in order to allow air or gas, which can pass through the membrane 10 in both directions, to enter and exit. The membranes 10 are pressed against their outer circumference under prestress against elastomer bases 12 , which are provided here as O-rings. The material of the membrane 10 can be protected against mechanical damage on one or both sides by perforated support films 13 or fleece-like or lattice-like support material to protect against excessive bulging, but it must retain its ability to bulge. To protect against mechanical damage, the inner edges of the opening 11 of the hold-down device 9 and also the documents 12 are provided with rounded edges. The outer membrane 10 A is supported by an elastomer base 12 A with a round edge profile supporting it under its outer edge in the intermediate space 14 with a round edge profile from the upper end face of the spacer sleeve 17 to a sufficient safe distance for the vibrations of the membrane 10 that the O-ring The elastomer base 12 A is thicker than an annular collar of the spacer element 17 which supports it radially towards the center of the breathing channel 8 . This results in a larger area for the outer membrane 10 A by approximately the annular collar of the spacer element 17 than for the inner membrane 10 B , which with the help of the lower end face of the spacer sleeve 17 and the lower elastomer pad 12 B placed thereon on an approximately the same Corresponding thickness of the insert body 3 is pressed. The surface differences and different porosities or elasticities make it possible to trigger the vibrations of the membranes 10 A and 10 B when blowing off air, etc., by means of the different pressure relief stages then brought about, which contributes to keeping the surfaces free.

In FIG. 2 a variant of the above-mentioned pressing of the membranes is 10 A, 10 B by means of a holding-down device 9 to the elastomeric pad 12 is shown, in which over the front by a certain radial projection of the O-ring used as the elastomer pad 12 Front side of the insert body results in a free space 14 , in which the membrane 10 and a support film or a grid 13, possibly combined with it, can carry out oscillatory movements without causing harmful shear forces on sharp edges. If a second membrane is used on the oil side, which securely holds back oil, the outer membrane 10 A can be safely protected against internal adhesion by oil.

In the further figures only one membrane 10 with base 13 is indicated. However, here too, preferably spaced double membranes are used in the same arrangement as in FIGS. 1 + 2.

In Fig. 3 an example of the pressure equalizer 2.3 according to the invention is shown with an annular configuration. The outer edge 15 of the cover 7 can here similar to the basic principle of Fig. 1 axially parallel to the breathing channel 8 through the elastomer pad 12 about the same distance as the edge of the blank holder 9 are bent. In order to stiffen the edge 15 and to fix certain air inflow or outflow openings, elongated sieves 16 can be incorporated into the edge 15 , which also ensure the radial distance of the cover 7 from the hold-down device 9 . Instead of an insert body inserted separately into the machine housing 1 , a corresponding neck 17 is screwed here directly into a machine housing 1 with a corresponding assignment to respiratory channels 8 . For additional protection against loosening, the covers 7 can be pressed onto the hold-down device 9 by means of screws 18 if, for example, a corresponding knob 19 or a spacer is provided in the cover above the hold-down device 9 . Such an annular pressure equalizer 2.3 can be easily installed in an annular groove 20 , which for example surrounds a shaft 21 with a shaft sealing ring 22.3 encompassing it with a small axial intermediate wall 23 , which results in a radial assignment with corresponding space savings in the axial direction.

In FIG. 4 is a schematic same configuration of pressure balancer 2.4 is shown when this is a shaft seal arranged upstream of 22.4 outside apart by a axial distance 24th Here too, similar to FIG. 3, an annular insert body 3.4 was used, which, however, is sealed off from the shaft 21 and the machine housing 1 by means of ring seals 25 .

FIG. 5 shows the use of a pressure compensator 2.5 according to the invention directly in an additional sealing element 26 which is arranged axially on the outside of a shaft seal 22.5 . This sealing element 26 , which can be implemented as desired, has the task here of making certain axial movements with the shaft 21.5 , by means of which the space in front of the actual shaft seal 22.5 varies, that is to say it has to be ventilated or vented on its own. For this purpose, a breathing channel 8 was cut out in several places in an approximately axially parallel central part 27 of the sealing element 26 , which is covered on the inside by an annular or several small membrane (s) 10 , which could be glued or vulcanized. Thanks to the ventilation, the sealing element 26 with its outer collar 28 and its inner collar 29 is always equally strong radially on the shaft 21.5 or the machine housing 1 , even if certain deformations occur as a result of the axial movements in the middle of the axially parallel central part 27 durable attachment of the membrane 10 reached. In the sealing element 27 shown as an example, the sealing pressure is ensured to the outside by a spreading spring 30 and inwards by a support ring 31 while maintaining a sufficiently large inner annular groove 32 under an outer radial gap 33 in such a way that the membrane 10 is not deformed by any type of deformation of the sealing element 26 could be blocked. In the example, the breathing channel 8 is covered axially at a distance by a special wear-resistant bushing 35 , so that dust and dirt cannot reach the breathing channel 8 directly.

With these arrangement options a long one Lifespan of the breathing elements of the pressure compensators Cost-effective producibility possible, with modifications correspondingly different installation conditions than in the area of the idea of the invention are considered lying.

Thanks to the valve-like peculiarities of the textile material used for the membrane 10 , with the pressure equalizer according to the invention, effective gearbox or machine protection measures are possible in the long run with little material and assembly or maintenance effort. Oil vapor can no longer be deposited in the area of the breathing channel. Water cannot enter the machine housing via breather. The ventilation is no longer hindered by dirt blockages in the breathing channel and overpressures that could endanger the shaft seals are eliminated.

Reference numerals

1 machine housing
2 pressure equalizers
2.1 Pressure equalizer with 3.1
2.2 pressure equalizer with 3.2
2.3 Pressure equalizer with 3.3
3 insert bodies
3.1 Insert body as a nipple
3.2 Insert body as a cassette
3.3 Insert body as a sealing element
4 housing opening
5 threads in 4
6 housing seal
7 cover (dirt deflector)
8 respiratory channel (bore)
9 hold-down device
9 A spacer sleeve
10 A , 10 B diaphragms (lubricant outflow preventers)
11 opening in 9
12 A , 12 B O-rings (elastomer pad for 10 )
13 A , 13 B support foils or grids
14 space or vibration space for 10 with only one membrane
15 edge of 7
16 wins in 7
17 spacer or sleeve
18 screws for 7
19 knobs in 7
20 ring groove in 1
21 wave
22 bearing bore
22.4 Shaft seal
23 partition from 1
24 axial distance from 3.4 and 22.4
25 seals from 3.4 in 1
26 sealing element with 7 and 8
27 axially parallel central part of 26
28 outer fret of 26
29 inner waistband of 26
30 spreading spring for 26
31 support ring for 26
32 inner ring groove of 26
33 Outer radial gap on 26
34 inner radial gap at 26
35 bushing in 1
A distance from 3.1 and 7 for 8

Claims (11)

1. Pressure equalizer ( 2 ) between the machine housing ( 1 ) and the environment, consisting essentially of:

• - a breathing element ( 3 ) covering an opening ( 4 ) of a housing ( 1 ),
• - With a breathing channel ( 8 ) for changing flow directions, in which a gas-permeable, lubricant-retaining device is located,

thereby featured,

• - that the device is a liquid-tight but gas-permeable plastic membrane ( 10 ) in the operating pressure range with a support grid ( 13 ) made of a low elastic material,
• - Which are pressed together by a hold-down device ( 9 ) on their edge sealing against an elastic base ( 12 ) and can oscillate around a rest position.

2. Pressure equalizer according to claim 1, characterized in

• - That two membranes ( 10 A , 10 B ) are provided with an intermediate space ( 14 ),
• - Which are combined at least on one side with a support grid ( 13 ) so clamped against the base ( 12 ) that the space ( 14 ) through the inner membrane ( 10 B ) lubricant-free and through the outer membrane ( 10 A ) dust and water free is held.

3. Pressure equalizer according to claim 2, characterized in

• - That the distance between the membranes ( 10 A and 10 B ) is formed by spacers ( 12 , 17 ),
• - Which consist of a sleeve ( 17 ) surrounding the breathing channel ( 8 ) and displaceably guided in the hold-down device ( 9 ), each with elastomer pads ( 12 ) centered on the end face in front of the same, against which the edge areas of the two membranes ( 10 A and 10 B ) together with any associated support grids ( 13 ) are pressed tightly.

4. Pressure equalizer according to claim 3, characterized in

• - That the inner edges of the opening ( 11 ) of the hold-down device ( 9 ) are rounded off by the membrane ( 10 )
• - And that documents ( 12 ) and spacers ( 17 ) have round edge profiles in the area of their inner diameter.

5. Pressure equalizer according to claim 1, characterized in that the outer membrane ( 10 A ) is a perforated film and the inner membrane ( 10 B ) is a non-woven material as a support grid ( 13 ) each directly on the side facing away from the housing. 6. Pressure equalizer according to claim 1, characterized in that the insert body ( 3.1 or 3.2 or 3.3 ) of the machine housing ( 1 ) is adapted and with membrane ( 10 ) etc. are completely interchangeable. 7. Pressure equalizer according to claim 1, characterized in that an outer dirt deflector ( 7 ) for the insert body ( 3.1 or 3.2 or 3.3 ) is provided. 8. Pressure equalizer according to claim 7, characterized in that the dirt deflector ( 7 ) on the machine housing ( 1 ) is attached. 9. Pressure equalizer according to claim 1, characterized in that the dirt deflector ( 7 ) consists of a bell-shaped cover ( 7 ) of the insert body ( 3.1 or 3.2 or 3.3 ), to which a free distance ( A ) corresponding to the cross section of the breathing channel ( 8 ) is provided. 10. Pressure equalizer according to claim 6, characterized in that the insert body ( 3.3 ) itself consists directly of a sealing element ( 26 ), in which breathing channels ( 8 ) are provided on the circumference, which are closed by means of glued-in or welded-in membranes ( 10 ).