Compressed-air supply device and valve housing

A compressed air-supply device for a utility vehicle includes a valve housing and an exchangeable air-drying cartridge. The air-drying cartridge has a filter device which cleans the air flowing from the valve housing into the air-drying cartridge. The filter device separates the pre-filter area facing the valve housing from the post-filter area that faces the air-drying cartridge and in which foreign particles captured by the filter device are collected. A non-return valve is provided parallel to the filter device, which prevents air flowing from the pre-filter area to the post-filter area but allows the air flow from the post-filter area to the pre-filter area. The non-return valve is arranged in the valve housing.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a compressed-air supply device for a utility vehicle, with a valve housing and with an exchangeable air drier cartridge. The air drier cartridge having a filter device which purifies air flowing out of the valve housing into the air drier cartridge. The filter device separates a pre-filter region facing the valve housing from a post-filter region which faces the air drier cartridge and in which foreign particles picked up by the filter device are collected. Parallel to the filter device, a non-return valve is provided, which prevents an air flow from the pre-filter region into the post-filter region and allows an air flow from the post-filter region into the pre-filter region.

The invention relates, furthermore, to a valve housing for a compressed-air supply device with an exchangeable air drier cartridge. The air drier cartridge has a filter device which purifies air flowing out of the valve housing into the air drier cartridge. The filter device separates a pre-filter region facing the valve housing from a post-filter region which faces the air drier cartridge and in which foreign particles picked up by the filter device are collected. Parallel to the filter device, a non-return valve is provided, which prevents an air flow from the pre-filter region to the post-filter region and allows an air flow from the post-filter region into the pre-filter region.

Such compressed-air supply devices with a valve housing and with an air drier cartridge are used in order to supply compressed-air consumers of a utility vehicle with dry and purified air. What may be considered as compressed-air consumers are, for example, the brake system or a pneumatic spring installation. The drying of the air in this case takes place by means of a desiccant present mostly as a granulate. Moreover, it is useful to remove foreign substances, for example compressor oil, from the compressed air.

This oil is supplied to the compressed-air supply device, together with the air, in a partially vaporous state of aggregation, and, because of the high temperatures and high pressures, it is in multiple cracked form. The substances therefore present are harmful to the components of a compressed-air installation. For example, cracked oils seriously lower the service life of sealing elements.

One example of a compressed-air supply device in which these foreign substances are removed from the compressed air supplied is disclosed in DE 103 29 401 A1. Here, a coalescence filter is provided, which purifies the compressed air flowing into the filter cartridge, the foreign particles extracted from the air accumulating in a post-filter region. So as to be able to empty the post-filter region from time to time, a non-return valve is provided parallel to the coalescence filter. This non-return valve makes it possible, by a discharge valve in the valve housing being opened, for the foreign particles to flow out and to be ejected into the atmosphere.

The non-return valve therefore comes into intensive contact with the collected foreign particles, thus making it necessary to manufacture the non-return valve from comparatively costly materials. This would be manageable per se in light of the overall costs of a compressed-air supply device. The problem, however, is that the air drier cartridge has to be exchanged from time to time. Consequently, the production of the non-return valve from costly material is not only reflected in the procurement costs of the compressed-air supply device, but especially also in the costs of the exchangeable drier cartridge. In terms of the overall costs of the air drier cartridge, however, the costs of the non-return valve constitute an appreciable proportion.

The object on which the invention is based is to make available a compressed-air supply device, so that the costs associated with the exchange of the air drier cartridge are reduced.

The invention builds on the generic compressed-air supply device in that the non-return valve is arranged in the valve housing. The non-return valve is thus preserved even in the event of a cartridge change. It therefore does not contribute to the costs incurred when the filter cartridge is exchanged.

Expediently, there is provision for the post-filter region to have a collecting duct for the foreign particles picked up by the filter device, at least one portion of the collecting duct defining a horizontal plane when the compressed-air supply device is in the installed uninclined state, and for the non-return valve to lie below the plane. This ensures that, at least when the utility vehicle is standing horizontally, a complete emptying of the collecting duct via the non-return valve can take place.

It is especially useful in this respect that, in the event of an inclination of the compressed-air supply device of up to 15 degrees with respect to the horizontal plane about any axis, the non-return valve lies on a lower vertical coordinate than the lowest point of the at least one portion, defining the horizontal plane, of the collecting duct. The collecting duct is thus emptied even when the utility vehicle is in an oblique position, for example when traveling up or down a hill.

The invention is developed in a particularly useful way in that the air drier cartridge has a cartridge housing receiving a desiccant box, and in that the cartridge housing is connected to the valve housing directly via a seal. Such compressed-air supply devices are also designated as open systems. In particular, the air drier cartridge is not equipped with a foot flange, via which closed systems are connected to the valve housing.

The invention is especially suitable for open systems, since a scavenging duct for transferring the foreign substances which have accumulated in the collecting duct of the drier cartridge into the valve housing can be implemented without any obstruction, that is to say, in particular, without a bypass or drilling through of a foot flange.

The invention builds on the generic valve housing in that the non-return valve is arranged in the valve housing.

DETAILED DESCRIPTION OF THE DRAWINGS

In the following description of the drawings, the same reference symbols designate identical or comparable components.

FIG. 1shows a perspective sectional view of a compressed-air supply device according to the invention. The compressed-air supply device10illustrated comprises a valve housing12and an air drier cartridge14. The air drier cartridge14or a housing28of the air drier cartridge14is connected directly to the valve housing12via a seal30. In particular, the air drier cartridge14is not equipped with a foot flange which delimits the air drier cartridge14in the direction of the valve housing. The sealing force acting on the seal30is made available by a bayonet ring32. A desiccant box26is arranged inside the housing28of the air drier cartridge14.

When the compressed-air supply device10is in use, compressed air flows through an inlet34of the valve housing12into the latter. The compressed air is conducted through a pre-filter36, in order subsequently to flow, in an interspace between the outsides of the desiccant box26and the inside of the housing28, into a free space38above the desiccant box. Provided in the top side of the desiccant box are a multiplicity of orifices40which connect the free space38above the desiccant box to the interior of the latter. In particular, the compressed air flows out of the free space38via the orifices40and a first labyrinth region42of the desiccant box into the lower region of the desiccant box26, where the air is then deflected in order to flow into a second labyrinth region44. The compressed air, conducted upward there, is once again deflected in the upper region, in order then to flow through a central labyrinth region46downward in the direction of the valve housing12again. The dried compressed air is thus available in the air routes of the valve housing, so that it can be supplied from there to the compressed-air consumers. The desiccant box26is filled with granulate for the purpose of drying the compressed air. The pre-filter36serves for purifying the compressed air in terms of coarser impurities. A further filter device, which is not illustrated inFIG. 1, follows the pre-filter36in the flow direction of the compressed air, in order then also to free the compressed air of further impurities, in particular of oil and the like. The oil accumulates in the region of the air drier cartridge in a collecting duct, not illustrated inFIG. 1. With suitable pressure conditions in the compressed-air supply device, the oil can then flow from there via a scavenging duct48and a non-return valve22into the valve housing and from there out to a discharge. The non-return valve22is advantageously designed as a diaphragm valve, in which case the diaphragm should be manufactured from a material which for a long period of time withstands the chemical loading of the foreign substances to be repelled.

FIG. 2shows a diagrammatic illustration of the interface between an air drier cartridge and a valve housing of a compressed-air supply device according to the invention. Here, the arrangement of the components involved in the purification of the compressed air and in the ejection of the foreign particles is illustrated diagrammatically. The compressed air50first flows through the pre-filter36in order then to flow thereafter through the filter device16. The filter device16is preferably designed as a coalescence filter, the foreign particles separated by the coalescence filter16accumulating downstream of the coalescence filter16in the flow direction in a collecting duct24. Within the framework of the present description, the entire region which is located upstream of the filter device16in the flow direction of the compressed air is designated as the pre-filter region, while the region downstream of the filter device16is designated as the post-filter region20. In the valve housing12, a scavenging duct48is provided, which is connected to the collecting duct24via a seal. The end of the scavenging duct48is sealed off by means of a non-return valve22. The latter closes the scavenging duct48during the compressed-air conveyance phase in which the pressure in the pre-filter region18usually overshoots the pressure in the post-filter region20. If, however, a discharge valve is opened, thus leading to the pressure drop in the pre-filter region18, the pressure in the post-filter region20overshoots the pressure in the pre-filter region18. The non-return valve22consequently opens, with the result that the foreign particles which have accumulated in the collecting duct24are ejected via the non-return valve22. The scavenging duct48may be arranged entirely in the valve housing, in which case the scavenging duct48adjoins the collecting duct24via a seal52. There may likewise be provision for part of the scavenging duct to be provided inside the air drier cartridge14. It is essential merely that a pressure-tight connection between the collecting duct24and the valve housing is made available, so that, with corresponding pressure conditions, the described ejection of foreign particles can take place. This can easily be implemented in open systems, since a foot flange sealing off the drier cartridge is not present and therefore can be ignored in the design.

Expediently, the non-return valve22is arranged at a markedly lower level than the collecting duct24. Thus, even an oblique position of the compressed-air supply device is permitted, without a complete emptying of the collecting duct24thereby being ruled out. In particular, inclinations of the vehicle of up to 15 degrees should still not impede a complete emptying of the collecting duct24.