Pump

Details Pump Pump

2001-02-13

2002-07-02

Denion, Thomas (Department: 3748)

Rotary expansible chamber devices

With mechanical sealing

Seal element between stationary cylinder parts

C418S015000, C092S086000

Reexamination Certificate

active

06413064

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a pump for delivering a fluid, in particular a rotary vane pump, of the type having a delivery device accommodated in a casing, a casing cover on one end face, and a bearing flange adjoining the casing on the opposite side of the casing cover. The delivery device serves to displace the fluid from a suction side to a delivery side of the pump.
The pump of the described type may further have a feed channel for the fluid, which is formed in the casing and extends into the suction side of the delivery device, and an injector device serving to deliver the fluid, wherein the injector device injects the fluid under high pressure into the fluid exiting from the feed channel into an upstream jet chamber, thereby entraining or accelerating same.
Pumps of the kind under discussion, for example rotary vane pumps, are adequately known from practice, for example from DE 39 28 029 A1, DE 41 22 433 C2, and DE 41 38 516 A1.
Pumps of the described type are used, for example in power steering systems, and they deliver a special oil for purposes of assisting the steering force being applied to the steering wheel of an automobile. Preferably, the pumps are rotary vane pumps, which take in oil from a reservoir provided outside of the pump, preferably an external tank. Normally, such pumps are equipped with a flow control valve, which permits directing oil from the high-pressure or delivery side, to the suction side of the pump. Effective a certain rotational speed of pump and with a constantly adjustable delivery, the flow control valve opens a discharge bore, through which oil under high pressure is allowed to leave. The oil enters the suction chamber of the delivery device.
On the delivery side of the pump, leakages occur constantly, so that special measures are needed for removing the leakage oil. To this end, leakage paths leading to the suction side are provided in pumps of the art, so that the leakage oil is again supplied to the oil directed from the tank into the pump. Measures realized so far with respect to leakage paths or leakage oil channels involve a significant manufacturing expenditure and, consequently, represent quite a relevant cost factor in the manufacture of the pump.
U.S. Pat. No. 5,496,152 discloses a rotary vane pump, which comprises for purposes of realizing as much as possible a cavitation-free operation, a very special arrangement for delivering the tank oil, namely an injector device, which operates similarly to a water jet pump. The injector device receives fluid under high pressure, which is supplied to the injector device from the high-pressure side. The injector device injects this high-pressure fluid into the stagnant fluid from the feed channel, namely in the region of a jet chamber upstream of the delivery device. As a result, the fluid coming from the tank is entrained or accelerated, and enters from there, via a further channel system, the suction side of the delivery device.
However, the technique disclosed in U.S. Pat. No. 5,496,152 and relating to the use of an injector device is problematic in that this injector device operates only on one side of the casing with a jet nozzle, from where it must deliver the fluid coming from the tank to both sides of the casing, in the respective suction zone, for purposes of making the fluid available in an adequate amount on both sides of the casing to the suction chambers associated to both sides of the delivery device or rotary group. Due to the differently long flow paths to the suction chambers arranged on both sides, different pressure conditions occur in the fluid, which results again in a varying supply of fluid to the suction chambers on both sides. This leads to cavitation or damage resulting from cavitation, in particular in the case of high delivery rates of the pump. Furthermore, a uniform filling of the suction zones on both sides is questionable.
It is the object of the present invention to improve and further develop a pump of the described type such that it enables a reliable removal of the leakage oil on the delivery side, while simultaneously reducing constructional and manufacturing measures. Furthermore, it is desired to ensure a uniform admission of fluid to the cells of the delivery device. Damage due to cavitation is to be prevented effectively.
SUMMARY OF THE INVENTION
The above and other objects and advantages of the invention are achieved by the provision of a pump of the described type wherein a seal is disposed between at least one of (1) the casing cover and one end face of the casing and (2) the bearing flange and the other end face of the cover. The fluid leakage path extends between the delivery side and the suction side, with at least a portion of the leakage path extending along the inner side of the seal.
In accordance with the invention, it has been recognized that it is possible to design and construct the leakage path, so that it extends at least in sections parallel to the seal. The arrangement of the leakage path close to the seal relieves the seal on the delivery side. Consequently, the arrangement of the seal achieves not only a reliable removal of the fluid or leakage oil, but also a reliable relief of the seal, thereby assisting the sealing effect in the long run. The leakage path is provided wherever leakage oil emerges, which is to be removed on the delivery side. Consequently, the leakage path extends at least in sections parallel to the seal, namely on the inner side or media side of the seal.
From manufacturing aspects, it will be quite especially advantageous, when a groove that is anyway provided for the seal, is used as leakage path. This groove is formed either in the casing cover or, if present, in the bearing flange or in the respective end face of the casing, and it is actually used for inserting or receiving the seal. For example, the groove may be made integral with the respective component.
To use this groove as leakage path, the groove is made at least in part wider than the seal toward the inner side of the seal or media side, so that the groove forms on the inner side of the seal the leakage path that extends parallel to the seal directly adjacent thereto.
Within the scope of such a constructional measure, the seal is directly relieved only on its inner side. At the same time, it is lubricated on its inner side and cooled, if need arises. In the case of a wide construction of the groove, the later has a double function, namely, on the one hand, the accommodation of the seal, and on the other hand, the arrangement of a leakage path or leakage channel. Since the groove is needed anyway for receiving the seal, manufacturing expenditure is reduced quite considerably. Furthermore, this measure reduces the overall space needed as a whole, so that it assists a miniaturization of the pump.
Very advantageously, the groove is designed and constructed as a self-contained, peripheral annular groove, so that a gasket is is suitable for use as a seal. As previously stated, the groove may be widened over its entire length, so that the leakage path extends over the entire length of the seal on the inner side of the seal or media side. Likewise, it is possible to extend the leakage path as a widening of the groove only in part over the length of the groove, namely wherever leakage oil emerges that is to be removed.
Concretely, the groove could be made as a simple groove with a substantially widened groove bottom (at any rate wider than the normal groove for receiving the seal), so that the seal or gasket can be positioned in the outer region of the groove in contact with the outer groove wall. This results automatically from the dimensioning of the groove on the one hand and the gasket on the other.
It is likewise possible to make the groove stepped toward the groove bottom, with the seal being arranged in the outer step of the groove. Advantageously, the outer groove portion that receives the seal is submerged. Furthermore, it is possible to make the groove as a kind of double groove, with a partition extending between the

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